• Testosterone regulates mitochondrial aspartate aminotransferase gene expression in rat ventral prostate

      Qian, Kaifeng; Franklin, Renty B.; Costello, Leslie (1991)
      One of the physiological functions of the rat ventral prostate, like human prostate, is to secrete an extraordinarily high quantity of citrate. This unique characteristic is under the influence of testicular androgen. The continuous secretion of citrate from prostate results in loss of a 6-carbon compound from the metabolic pool which must be replenished. Citrate is synthesized from the concentration of acetyl-CoA and oxaloacetate. Acetyl-CoA may come from various sources. However, recent studies indicated that the possible available source for oxaloacetate is the transamination of aspartate. Mitochondrial aspartate amino-transferase (mAAT) is an important enzyme which regulates citrate production in rat ventral prostate. Testosterone, as a major testicular androgen, stimulates citrate production and mAAT activity in a similar pattern. The hypothesis in this dissertation is that the ability of testosterone to increase citrate production and mAAT activity is the result of stimulation of mAAT gene expression. To verify this hypothesis, numerous in vivo and in vitro studies were utilized to analyze the steady-state level of mAAT mRNA in response to testosterone depletion and repletion. The rats were castrated, followed by testosterone or oil vehicle injection. Twenty-four (or forty-eight) hours later all animals were killed, prostates removed, RNA and nuclei isolated. In vitro studies were performed using primary cultured pig prostate cells. The quantity of mAAT mRNA was measured using northern hybridization. The rates of transcription and degradation of mAAT mRNA were determined by in vitro transcription assay and pulse chase labeling assay, respectively. Results show that castration caused a significant decrease in the content of mAAT mRNA and the transcription rate of the mAAT gene. However, testosterone administration reversed these hormonal depletion effects. Moreover, testosterone administration also prolonged the half life of mAAT mRNA. These results support the hypothesis that one of the major physiological functions of testosterone is to stimulate mAAT mRNA gene expression, which in turn enhances citrate production in rat ventral prostate. Furthermore, these results confirm that the increase in the steady-state level of mAAT mRNA in response to testosterone administration results from stimulation of mAAT gene transcription and inhibition of mAAT mRNA degradation.
    • The optimal size range of particulate demineralized bone matrix for osteoinduction

      Desverreaux, Robert William; Hiatt, James L., 1934- (1991)
      There have been several investigations to determine the optimal particle size range of demineralized bone matrix (DBM) for osteoinduction. Results from these investigations have not been in agreement. Particulate bone matrix preparations can be combined with biodegradable delivery systems to treat ablative bony wounds. Therefore, an optimization of the particle size range is important. The purpose of this study was to determine the optimal size range of particulate DBM for osteoinduction at both a heterotopic and an orthotopic site. DBM was prepared according to the method of Reddi-Huggins and sieved to 13 different size ranges. In the first phase of the experiment DBM (20 mg) was placed in gelatin capsules, sealed in nylon mesh baskets, and implanted in the pectoralis muscle of 210 Long-Evans male and female rats (27 to 35 days old). In the second phase DBM (20 mg) was implanted in an 8 mm critical sized calvarial defect in an additional 210 Long-Evans male and female rats. There were 15 animals per treatment group in each phase of the study. Specimens were retrieved at 28 days post surgery, and embedded, undecalcified in plastic, sectioned, and stained using von Kossa stain. Bone formation was quantitated by radiomorphometry and histomorphometry using a Quantimet 520 Image Analysis System. Moreover, alkaline phosphatase and calcium were quantitated by atomic absorption spectrophotometry in the heterotopic site. All implants demonstrated a high degree of biocompatibility and no significant inflammatory cell infiltrates were observed in any of the specimens. Results indicate that the 590-710 um range particles produced significantly more new bone than all other size ranges (p {dollar}<{dollar} 0.05). These results further narrow those obtained by Reddi and Huggins, who found the optimum size range for particles to be 420-850 um.
    • Pain, coping, and depression following burn injury

      Ulmer, Janice Fitzgerald; Gift, Audrey G. (1991)
      Pain, coping, and depression were examined in a convenience sample of 32 burn injured men and women. Subjects were interviewed 3 times at approximately weekly intervals. The first and third interviews focused on coping, the second interview focused on how burn pain is described and rated by burn injured subjects and their care providers. Three criterion variables, pain intensity, pain distress, and depression were used to measure coping outcome. Five variables, severity of injury, surgical intensity, baseline depression, duration of pain, and level of analgesic drug were predicted to influence coping. Although the burn wound was identified as the source of worst pain, when subjects were asked to rate wound, donor, and skin graft pain using the short form McGill Pain Questionnaire (MPQ-SF), no significant differences were found. Average pain intensity, average pain distress, and level of depression decreased significantly over time. Pain with routine activity and pain worst continued to be rated moderate to severe by most patients at the third interview. No changes were noted in coping strategy use when coping was measured using the Coping Strategies Questionnaire. Subjects' perceptions of their ability to control pain increased significantly over the three measurement sessions. Subjects' perceptions of their ability to decrease their pain increased but did not achieve significance. Significant correlations between predictor and criterion variables were found for severity of injury, duration of pain, level of analgesic drug, baseline depression, and perceptions of ability to control and decrease pain. Significant correlations were also found between the criterion variables and beliefs related to personal control and the tendency to catastrophize. A significant positive correlation was found between care provider estimates of pain distress today and the average self-reported pain distress score. Care provider estimates of pain intensity today did not correlate with the average self-reported pain intensity score. When t-test comparisons were made between care provider and patient ratings no significant differences were found.
    • The relationship between child sexual abuse and self-concept in adult women: A community survey study

      Gibbons, John Joseph; Vassil, Thomas V. (1991)
      The relationship between Child Sexual Abuse (CSA) and Self-Concept was investigated using subjects from a community survey study conducted in Baltimore, Maryland. Regression and Step-wise regression analysis were employed to (1) identify CSA as a statistically significant predictor of self-concept, i.e. self-esteem and locus of control, (2) to control for extraneous variables, and (3) to rank order predictor variables in terms of their effect on the dependent variables. Several situational variables, i.e. variables inherent in the abuse event and a possible intervening variable, i.e. perceived social support were also controlled for. Statistically significant relationships were found between (1) CSA and self-esteem and locus of control, (2) CSA with intercourse and self-esteem and locus of control, and (3) Perceived Social Support and self-esteem and locus of control. Findings are discussed with implications for social work research, practice and policy.
    • Minority student success in predominantly white schools of nursing: Cognitive and noncognitive factors

      Rodgers, Shielda Glover; Holt, Frieda M. (1991)
      The purpose of this study was to examine the nature of the relationship of selected cognitive and noncognitive factors to academic success of minority nursing students enrolled in predominantly white schools of nursing. In this study, the relationship between academic success (college grade point average) and the cognitive factors of high school grade point average and SAT score and the noncognitive factors of social isolation, self concept of ability, and self esteem was investigated. The theoretical framework for the study was based on Tracey and Sedlacek's model for predicting college success using noncognitive factors. Students from five NLN accredited baccalaureate schools of nursing in Virginia and Maryland participated in the study. A four part questionnaire was administered to the students which consisted of the Rosenberg Self Esteem Scale, the modified Brookover Self Concept of Ability Scale, the social isolation subscale of the UCLA Loneliness Scale and a demographic/academic data questionnaire. The student's cumulative grade point average at the end of the semester in which data collection occurred was obtained from university officials and all other academic data was self reported on the questionnaire. There were 40 black students, 33 other minority students and 117 white students in the study. Data were analyzed using regression analysis, discriminant analysis, frequency distributions, Chi Square and Pearson Product Moment Correlation. Results indicated that for the total sample of nursing students, those factors which were predictive of success were self concept of ability, self esteem, and SAT scores. For black nursing students, those factors which were predictive of success were self concept of ability and high school grade point average. For other minority students the only factor predictive of success was high school grade point average. The three groups of students (Blacks, Whites, Other minorities) included in this study differed significantly on their scores on ratings of self esteem, social isolation and college grade point average. Black students had higher levels of self esteem and social isolation, but lower college grade point averages than either whites or other minorities. No demographic characteristic correlated significantly with college grade point average for either group of minority students. Black students were significantly older and more likely to be employed than either of the other two groups. The findings from this study suggest that a combination of cognitive and noncognitive factors should be explored when attempting to predict success for black students.
    • The characterization of heterogeneous surfaces using modified immersional calorimetry

      Demarest, Dudley Alvin, Jr.; Hollenbeck, R. Gary (1991)
      The present work describes the development and validation of a sensitive modified immersional calorimeter for assessing the integral interfacial energetics and wettability of tablet surfaces by aqueous dispersions of hydroxypropyl methylcellulose and its usefulness in predicting film coating results. Tablets manufactured from microcrystalline cellulose, dibasic calcium phosphate, lactose, and magnesium carbonate gelatin granulations were analyzed. Tablet surfaces were modified by varying the tablet porosity (by changing compression force) and specific surface energy (by adding various levels of magnesium stearate). A thermal gravimetric technique utilizing first derivative plots of drying curves of coating droplets on tablets as well as a kinematic assessment of tablet wettability are also described. Coating of tablets manufactured from the same excipient was performed in a 30 cm diameter Hi-Coater{dollar}\sp{lcub}\rm R{rcub}{dollar} side-vented coating apparatus using a competitive coating operation. The coating parameters were set to a level in which overwetting occurred thus "stressing" the coatability of the tablets. Tablet coating success was assessed by visual analysis, diametrical hardness increases, and with a size exclusion chromatographic (SEC) technique. This technique allowed the amount of coat applied to individual tablets to be determined at coat amounts of less than 1 mg. Immersional results were directly related to the surface area of interaction which depended not only on the porosity and penetration of the coating dispersion but, with low energy tablets, on the relative surface area of the immediate tablet surface. It was hypothesized that an immersional response "window" exists within which tablets will ultimately coat well. Those with larger immersional results will show rapid wetting of the tablet by the coating droplets which will dehydrate the droplets too rapidly for the coating to coalesce, and those with low responses will not allow enough spreading of the droplets to allow adequate coalescence. The comparison of the immersional results with the results of the tablet coating operation to some extent support such an hypothesis although the measurement of the surface area of interaction is essential in estimating the true surface energies of the interface from immersional results.
    • Zero-order release through nonuniform drug distribution in a noneroding diffusional matrix: Theoretical design and actual manufacture

      Scott, Douglas Craig; Hollenbeck, R. Gary (1991)
      The theoretical design and actual manufacture of a non-eroding matrix pellet dosage form was undertaken. Non-uniform drug distribution in a non-eroding matrix can be used as a technique to achieve zero-order release. Flat slab and spherical geometry were examined through the development of a mathematical model to verify that it is theoretically possible to achieve zero-order release. Traditional non-eroding matrices, which contain drug uniformly distributed, do not yield zero-order release due to a constantly increasing barrier thickness which develops as drug diffuses from the matrix. Non-uniform drug distribution in a porous non-eroding matrix, in which drug is more concentrated in deeper matrix layers, creates an increasing depletion zone porosity as drug is leached from the matrix. This increasing porosity compensates for the increasing barrier thickness to achieve constant rate release. A common pelletization technique was employed to manufacture pellets. Previous investigations of this approach are few and have never combined a theoretical approach with a practical manufacturing process. An automated modified suspension layering technique was developed to create pellets containing drug non-uniformly distributed. A gradient pumping system used in conjunction with a specially fabricated Wurster column was used to produce these pellets. To examine the feasibility of this process, an investigation of the behavior of a water soluble drug, chlorpheniramine maleate, and a water insoluble drug, haloperidol, was undertaken. The model drugs and non-eroding matrices were characterized and actual release profiles were compared to theoretical profiles. In the case of the water soluble drug, an alternate release mechanism appears to predominate and the system does not behave as predicted by theory. In the case of the water insoluble drug the model fits well. A slight burst of drug is observed and is due to an initial porosity which exists in the matrix. The differing performance of these drugs appears to be due to their physico-chemical character. The water insoluble drug conforms to the assumptions and conditions of the model and demonstrates that non-uniform drug distribution in theory and actuality can be used to achieve zero-order release.
    • Correlates of nursing faculty scholarly productivity in colleges and universities in Taiwan, Republic of China

      Hsu, Man-Ying Fang; Holt, Frieda M. (1991)
      The purpose of this exploratory-descriptive study was to determine and to describe predictors of nursing faculty scholarly productivity (NFSP) in higher education in Taiwan of Republic of China. A systems model was developed based on the Andreoli & Musser's (1984) systems model of nursing faculty productivity to determine selected variables of the study. Cultural impacts on NFSP are considered. The Nursing Faculty Scholarly Productivity (NFSP) Inventory was developed to measure the phenomena of nursing faculty scholarly productivity in Taiwan. A weighting scheme used as a standard index was established by nursing committee members to increase the reliability of the measurement of NFSP. Test-retest reliability and content validity were tested and are acceptable at a predetermined level. A nationwide sample of 242 respondents (all female) had a response rate of 52.4%. All subjects worked full-time in one of sixteen colleges and universities across the northern, middle and southern regions in Taiwan, republic of China. The survey was done by mail. The deans/directors of the subjects were invited to provide organizational data. Two hundred twenty-eight usable questionnaires were included in the data analysis. Data analysis procedures included descriptive statistics, oneway ANOVA, and multiple regression analysis. Findings suggested that the systems model was a useful framework to determine variables of the NFSP. Significant predictors of NFSP in three subsystems were identified. Both teaching and research role are preferred with teaching as their primary concern, length of nursing teaching career, associate professor, teaching assistant, and aged 46-50 in human subsystem are significant predictors of NFSP. Resource support match, printed policy and being employed at a private senior college in organizational subsystem are significant predictors of NFSP. Number of persons cared for in family subsystem is a significant predictor of NFSP. Of three subsystems, the human subsystem predictors were found to have the most explanatory power of variance in NFSP in this study. Methodological issues in this study are discussed, recommendations are made for future research, and implications for improving nursing faculty scholarly productivity are also addressed.
    • Mechanisms of thioether conjugate toxicity

      Brown, Paul Charles; Jones, Thomas W. (1991)
      Glutathione conjugation is widely recognized as an important detoxification mechanism for a variety of electrophilic xenobiotics. However, several pathways have been defined by which glutathione conjugates may be toxic. One proposed route of toxicity occurs when glutathione conjugation does not completely eliminate the toxicity of a xenobiotic. The toxicity of thioether conjugates of quinones was investigated as an example of toxicity by this route. The N-acetylcysteine conjugate of the quinone menadione (2-methyl-1,4-naphthoquinone) was found to damage isolated rat renal epithelial cells primarily by inducing oxidative stress. Interestingly, the glutathione conjugate of menadione was not toxic to isolated rat renal epithelial cells because a novel intramolecular cyclization reaction destroys the quinone nucleus. Another route of glutathione conjugate toxicity involves metabolism to the cysteine conjugate followed by activation to a reactive intermediate by cysteine conjugate {dollar}\beta{dollar}-lyase. Halogenated alkenes are examples of compounds toxic through this route. The toxicity of S-(1,2,3,4,4-pentachlorobutadienyl)-L-cysteine (PCBC), the cysteine conjugate of hexachlorobutadiene, is associated with a rise in cytosolic calcium. Work presented here suggests that this rise is important in the toxicity since buffering this rise with cell permeant Ca{dollar}\sp{lcub}2+{rcub}{dollar} chelators is protective. The toxicity was not associated with an activation of catabolic enzymes; however, it did appear to be associated with oxidative damage. In addition, the oxidative damage appeared to be related to deregulation of cytosolic Ca{dollar}\sp{lcub}2+{rcub}{dollar}. Mitochondria have been proposed to be a critical target of haloalkene thioether conjugates. In isolated rat renal mitochondria these conjugates induced an inner membrane permeability transition characterized by collapse of the membrane potential, release of Ca{dollar}\sp{lcub}2+{rcub}{dollar}, and oxidation of pyridine nucleotides. All of these effects were blocked by treatments known to inhibit the induction of the permeability transition. However, a nonmetabolisable form of PCBC also induced the same effects, suggesting that this process does not require the activation of the conjugates to a reactive electrophile through the {dollar}\beta{dollar}-lyase pathway.
    • A study of family life education experiences among Chewa grandmothers, mothers, and daughters in Malawi

      Banda, Eta Elizabeth; Ruth, M. Virginia; Kreider, Mildred Sherk, 1936- (1991)
      A significant problem in adolescent health care in Malawi is a lack of information about family life education. The purpose of this descriptive and correlational study was to describe family life education experiences of Chewa grandmothers, mothers and daughters as a means of identifying the nature of the organization and type of educational programme/learning experiences that traditionally have been offered for developmental task readiness for adult life. The subjects for preliminary interviews were limited to three sets of grandmothers, mothers and daughters, i.e. nine participants. This data was used to develop the tool utilized for data collection in the study. The sample size for this study was 300. Data analysis was carried out using descriptive statistics, chi-square, analysis of variance and content analysis. Family life education organization was primarily perceived to be either the responsibility of the family or a shared responsibility between the family, village and other social organizations. Family life education was mainly informally conducted within the family, although multiple resources were utilized for teaching. Music in combination with verbal communication played an important role in instruction and reading was observed to be almost absent as a method of teaching across all generations. Although mostly of the teaching was done didactically there was some practical experience in the sex education component where a female adolescent was given a male partner to learn and this male was called a 'fisi'. Significant differences were found in virtually all organizational variables, by generation and area of residence. Ten categories of family life education learning experiences were identified and tested for differences on the basis of generation and area of residence. The results revealed statistically significant intergenerational as well as geographic differences in learning experiences in sex education, menstruation and sanitary towel care, anatomy and physiology of the female reproductive system, socialization into adulthood, relationships with parents, elders, peers of the same and opposite sex, and disabled persons, traditional practices, psychological and spiritual issues. In addition analysis of variance to examine differences in traditional values between grandmothers, mothers and daughters revealed a statistically significant main effect for generation on traditional family values. (Abstract shortened with permission of author.)
    • A study of maternal employment and family contexts: Influences on maternal health and mother-infant interaction

      Wendt, Linda Elaine; Parks, Peggy L. (1991)
      The purpose of this study was to examine relationships between selected employment, family, mother and infant characteristics, and mother-infant interaction in a sample of 81 mothers who were employed by three-months postpartum. The goal of the study was to identify family and employment variables that indirectly predicted mother- infant interaction through maternal health. A longitudinal design was used to test the Lerner-Galambos model of maternal employment. Family context variables included family social support, spousal support, and child care arrangements. Employment context variables included reasons for working, employment incongruence, hours worked and employment changes. Maternal health variables included depressive symptomatology, general health status, and number of health conditions. Mother-Infant interaction was measured by the Clark ERA dyad subscales. Variables were measured at three times: in the hospital following birth, at three-months postpartum, and at six-months postpartum. Employment context, family context, and mother and infant health variables were factor analyzed for purposes of data reduction. The factor scores were entered into hierarchical regressions. Neither employment context, nor family context, nor a combination of employment context and family context variables predicted mother-infant interaction through maternal health at six months. Maternal and infant health did not predict mother-infant interaction at six months. Family context at three months and at six months predicted maternal employment at three and six months. Exploratory analyses indicated that family context factors at three months predicted maternal health at six months. Employment context at three months predicted maternal health at six months. These findings are important for nurses who work with employed mothers during the perinatal period.
    • Hospital social workers and AIDS patients: Stressors, potency, burnout and physical symptoms

      Egan, Marcia; Oktay, Julianne S. (1991)
      This study examined a model of stress and cognitive appraisal as it applies to burnout in hospital social workers providing services to AIDS patients. The research was done in response to reports of the stresses on healthcare workers presented by the AIDS epidemic, and to calls in the burnout literature to examine coping responses in specific practice areas. Questionnaires were mailed to social workers in hospitals of over 350 beds in the ten states with the highest incidence of AIDS. The sample was comprised of 128 social workers who had provided services to 10 or more AIDS patients within the previous six months. The questionnaire measured background variables (demographic variables, work and practice characteristics), independent variables (stressors of practice with AIDS patients, potency and how difficult the social workers found their practice with AIDS patients) and dependent variables (burnout and physical symptoms). The research was guided by the theories of Lazarus, Maslach and Ben Sira. Univariate, bivariate and multivariate analyses were used to test hypothesized relationships between the dependent and independent variables. Background variables were used as controls. The analyses supported the hypotheses that stressors of practice with AIDS patients and difficulty in practice were correlated, and that potency interacts with stressors as they relate to difficulty. That is, in persons with high potency, the relationship between stressors and difficulty is lower than is the case in persons with low potency. The three measures of burnout were related to difficulty. Potency also had a strong direct effect on burnout and physical symptoms. The results suggest that potency is an important factor in burnout, and should be studied further. If substantiated in further research, the results imply that employers and educators need to develop strategies to increase the sense of mastery, self-confidence and faith in societal justness (potency) if they hope to decrease burnout in social workers who practice with AIDS patients.
    • Trophic influences on embryonic chicken spinal motor neurons

      Jeong, Soo Jeong; Oh, Tae H. (1991)
      Embryonic spinal motor neurons are generated in excess. Superfluous neurons are subsequently eliminated by a process of naturally occurring cell death which coincides with the innervation of the target tissue, skeletal muscle. From extensive in vivo and in vitro studies, motor neurons have been shown to depend upon a target-derived trophic factor in order to survive the period of cell death. However, such a trophic factor for motor neurons has not been identified and characterized as yet. To investigate the trophic influences of skeletal muscle and of other cells interacting with motor neurons, purified motor neuron cultures were established from 6-day-old chicken embryos using metrizamide step-gradient centrifugation. One of the cell fractions was enriched in spinal motor neurons since it contained cells with a high specific activity of choline acetyltransferase (CAT), a high percentage of retrogradely labeled cells, and which had a large average cell diameter. Our laboratory has isolated a neurite-promoting protein from striated muscles. This protein has been further characterized by various biochemical, biological, and immunological assays. when the protein was tested in neuronal cultures including spinal motor, sensory, and autonomic neurons, it supported survival and neuritic growth of all neurons tested but it was not able to promote CAT activity or choline uptake by motor neurons. Although the biological effect of the protein is not specific for motor neurons, it does promote survival and growth of the neurons in culture. Additional trophic influences on spinal motor neurons were studied using media conditioned by skeletal muscle, heart muscle, sensory neurons, astrocytes, and Schwann cells. These conditioned media promoted the survival, neuritic growth, and CAT activity of the cultured motor neurons. Motor neurons especially exhibited distinct neuritic arborization in different conditioned media. These data suggest that the cells interacting with motor neurons in situ may affect the survival and development of the motor neuron. The present study provides some basic properties of the trophic interactions between motor neurons and their environment. Further characterization of the neurite-promoting protein should help in better understanding the nature of trophic interactions at the molecular level.
    • Detecting critical on-line information: The relationship between nurse characteristics, computer screen designs, and computer interaction measures during laboratory results retrieval tasks

      Staggers, Nancy; Mills, Mary Etta C. (1991)
      This study focused on the match between nurse characteristics and computer interface designs during critical information detection tasks and examined: (1) which of three computer screen density levels promoted the fastest, most accurate target detection performance and greatest subjective screen satisfaction among clinical nurses, and (2) which of a set of selected cognitive and demographic nurse characteristics were related to nurses' practiced performance speed, accuracy, and subjective screen satisfaction. A conceptual framework for research in nurse-computer interaction was developed by integrating concepts from human-computer interaction, nursing informatics, and developmental psychology. The study sample was 110 randomly selected clinical nurses from an East-coast university medical center. A two-factor within subjects repeated measures analysis was used for the study's screen design section. Overall and for practiced tasks, nurses found information targets significantly more quickly on high density than moderate or low density screens during practiced tasks. Also, nurses found information more quickly on moderate versus low density screens. Nurses' mean accuracy and subjective screen satisfaction scores were essentially the same for all screen types. These results suggest increases in screen information density can result in faster performance speeds without sacrificing nurses' accuracy or screen satisfaction. Using step-wise multiple regression analyses, nurses' age, spatial memory, and spatial visualization explained 35.9% of overall performance speed and 21.5% of accuracy variance. Younger nurses with higher spatial memory and visualization abilities had faster performance speeds and higher accuracy rates. Nurses' previous computer experience represented a basement effect. Nurse characteristic predictors explained 27.8% of high density screen performance speed, 10.9% for moderate, and 22.5% for low density screens. During step-wise regression, age emerged as a significant predictor for all three screen types, and spatial memory was a significant predictor for high and low density screens. Spatial visualization emerged as a significant predictor for performance speed on high and moderate screens but not low. The set of predictors explained little accuracy during practiced tasks, 12.4%, and virtually none of the screen design satisfaction variance, 6%. These results suggest nurse educators and system designers may need to design visual aids and/or computer training to accommodate nurses' age and cognitive individual differences.
    • Modulation of microbial growth and antimicrobial activity of aminoglycosides by oxygen tensions in gram-negative bacteria

      Park, Matthew Kihoon; Marzella, Louis (1991)
      Oxygen tensions alter microbial growth, antimicrobial activity, and host responses to infections. In particular, hyperoxia is bactericidal for microorganisms with deficient antioxidant defenses and influences the activity of several classes of antimicrobial agents. I hypothesized that hyperoxia can augment the bacteriostatic and bactericidal effects of protein synthesis inhibitors by increasing the generation of reactive oxygen species. To test this hypothesis, I have characterized the interactions between hyperoxia and aminoglycosides on the growth of gram-negative bacteria. Growth inhibition was quantitated by determining the postantibiotic effect (PAE; the period of bacterial growth suppression that follows a brief exposure to an antibiotic) under normoxic and hyperoxic conditions. I found that hyperoxia (100% O{dollar}\sb2{dollar}, 101.3 kPa) enhanced the PAE of tobramycin against P. aeruginosa. The delay in growth recovery was associated with reduced rates of protein synthesis. Hyperbaric oxygen (100% O{dollar}\sb2{dollar}, 274.5 kPa) further suppressed the growth recovery of P. aeruginosa. I next examined the effects of hyperoxia on bacterial growth and killing by aminoglycosides in the family Enterobacteriaceae. While hyperoxia did not influence bacterial growth, hyperoxia markedly influenced the bactericidal activity of aminoglycosides in a strain-specific manner. This finding extends the range of oxygen tensions that are known to influence the bactericidal activity of tobramycin. Finally, I investigated the role of reactive oxygen species in the hyperoxic enhancement of the tobramycin-induced PAE in P. aeruginosa. Hyperoxia is known to increase the intracellular flux of reactive oxygen species. I found that hyperoxia induced antioxidant defenses and that tobramycin blocked this induction. However, antioxidants did not decrease the susceptibility of tobramycin-exposed P. aeruginosa to hyperoxia. I conclude that hyperoxia influences the bacteriostatic and bactericidal activities of aminoglycosides against gram-negative bacteria. These findings have potential implications for the treatment of infections in patients exposed to high fractional inspired oxygen concentrations.
    • Role of Vibrio cholerae neuraminidase in the binding and penetration of cholera toxin

      Galen, James Eugene; Kaper, James B. (1991)
      Vibrio cholerae neuraminidase (NANase) is hypothesized to act synergistically with cholera toxin (CT) and increase the severity of a secretory response by increasing the binding and penetration of CT to enterocytes. To test this hypothesis, the neuraminidase gene (nanH) from V. cholerae Ogawa 395 was first cloned and sequenced. Isogenic wildtype and NANase V. cholerae 395 strains were then constructed using suicide vector-mediated mutagenesis. The influence of NANase on CT binding and penetration was examined in vitro using culture filtrates from these isogenic strains. Fluorescence due to binding of fluorescein-conjugated CT(CT-FITC) to C57BL/6 and C3H mouse fibroblasts exposed to NANase{dollar}\sp+{dollar} filtrates increased 5-fold and 8-fold respectively, relative to NANase{dollar}\sp-{dollar} filtrates. In addition, NANase{dollar}\sp+{dollar} filtrates increased the short-circuit current measured in Ussing chambers 65% relative to NANase{dollar}\sp-{dollar} filtrates, although this difference decreased as production of CT increased. The role of NANase in V. cholerae pathogenesis was examined in vivo by intragastric inoculation of the isogenic strains into CD1 suckling mice. No difference in fluid accumulation (FA) ratios was seen at doses from 10{dollar}\sp4{dollar} to 10{dollar}\sp8{dollar}, but NANase{dollar}\sp+{dollar} strains produced 18% higher FA ratios at 10{dollar}\sp9{dollar} than NANase{dollar}\sp-{dollar} strains when inoculated into non-fasted suckling mice. It is concluded that NANase plays a subtle but significant role in the binding and uptake of CT by susceptible cells under defined conditions.
    • Origins of infantile Tay-Sachs disease alleles in a Cajun population

      McDowell, Geraldine A. Edgell; Blitzer, Miriam G. (1991)
      The mechanisms responsible for the origin and maintenance of Tay-Sachs disease (TSD) alleles in the Ashkenazi Jewish population and others in which the occurrence of TSD is increased have yet to be delineated satisfactorily. As a model for studying these mechanisms, we evaluated five apparently unrelated Cajun families having members affected with TSD. The occurrence of TSD is elevated among Cajuns and preliminary studies suggest that the carrier frequency in the Cajun population may be increased over that of the general population. DNA sequence analysis revealed that, contrary to expectation, two different TSD alleles are present in the Cajun population: a {dollar}\beta{dollar}-hexosaminidase A {dollar}\alpha{dollar}-chain exon 11 insertion which is common among Jewish TSD carriers and an mRNA-negative allele which has not been described previously. Evaluation of pedigrees of 28 TSD carriers, identified by enzymatic and molecular screening of 95 relatives of the probands, revealed that the exon 11 insertion mutation has existed in the Cajun population since its establishment in the mid-1700's and most likely was introduced by members of a single family whose geographic origin is in France. Examination of these pedigrees for evidence of both increased fertility or survival among carriers of the insertion mutation compared to controls and preferential inheritance of this TSD allele produced no suggestion of heterozygote advantage. The presence of common ancestors among most of the exon 11 insertion carriers suggests that founder effect is responsible for the proliferation of this mutation among the Cajuns. The novel mutation has been in the Cajun population no more than four generations and appears confined to a single family. The Cajun population may well serve as a model for how founder effect and random genetic drift can result in the presence of two TSD alleles in a single population, one allele being found in the majority of carriers. This distribution of TSD alleles is similar to that seen in the Ashkenazi Jewish population. Of practical importance to the Cajun community is the likelihood that the exon 11 insertion mutation is widely distributed in southwest Louisiana and presents a significant public health problem within this community.
    • The relationships among psychological hardiness, faculty practice involvement, and perception of role stress of nurse educators

      Lambert, Clinton E., Jr.; Ruth, M. Virginia (1991)
      The primary purpose of this descriptive cross-sectional survey of nurse educators, employed full-time by a NLN accredited baccalaureate and higher degree granting school of nursing with both a graduate and an undergraduate program, was to identify if the variables, psychological hardiness, faculty practice involvement, and perceived role stress, were inter-related. An additional purpose was to determine whether there were differences between those involved in faculty practice and those not involved in faculty practice. It was predicted that: (1) the nurse educators perception of role stress would be negatively related to the level of psychological hardiness, (2) the perception of role stress by nurse educators involved in faculty practice would be greater than the perception of role stress by nurse educators not involved in faculty practice, and (3) the level of psychological hardiness of nurse educators involved in faculty practice would be greater than the level of psychological hardiness of nurse educators not involved in faculty practice. Each of 1345 identified nurse educators, whose name had been provided by the deans of 34 randomly selected schools of nursing, was requested to anonymously respond to a mailed, self-administered, pencil and paper questionnaire comprised of three instruments (Demographic Data Questionnaire, Personal Views Survey, and Role Conflict and Role Ambiguity Scale). A 66.5% subject response rate was obtained. Data from 871 of the respondents' questionnaires were analyzed using descriptive statistics and inferential statistics. The nurse educators perception of role stress was found to be significantly negatively correlated to the level of psychological hardiness. No significant difference was found between those involved in faculty practice and those not involved in faculty practice with respect to perception of role stress or to level of psychological hardiness. The results of this study suggest that faculty practice involvement of nurse educators in NLN accredited baccalaureate and higher degree granting schools of nursing with both a graduate and an undergraduate program is a self-selective process.
    • Characterization of the intrinsic protein kinase activity and the kinase catalytic motifs of the large subunit of the herpes simplex virus type 2 ribonucleotide reductase

      Luo, Jianhua; Aurelian, Laure (1991)
      The large subunit of Herpes Simplex Virus type 2 (HSV-2) ribonucleotide reductase (ICP10) is a chimera protein consisting of a serine/threonine protein kinase (PK) domain at the amino-terminus and a ribonucleotide reductase (RR) domain at the carboxyl-terminus. Like growth factor receptor PKs, ICP10 is myristylated, it has features of a signal peptide and putative transmembrane (TM) segment, and its PK activity is modulated by basic proteins and by antibodies to amino acid residues upstream of the TM. To further characterize this PK domain, we constructed a bacterial expression vector (pJL11) containing DNA sequences encoding ICP10 amino acid residues 1-445. Bacteria containing pJL11 were induced to express a 29 KDa protein (designated pp29{dollar}\sp{lcub}\rm la1{rcub}){dollar} that represents a truncated portion of the ICP10 PK domain as demonstrated by immunoprecipitation with antibodies that recognize different antigenic domains, competition studies with extracts of ICP10 positive eukaryotic cells, and peptide mapping. pp29{dollar}\sp{lcub}\rm la1{rcub}{dollar} has autophosphorylating and transphosphorylating activity for calmodulin. The enzyme is activated by Mn{dollar}\sp{lcub}2+{rcub}{dollar} but not by Mg{dollar}\sp{lcub}\rm 2+{rcub}{dollar} ions, and autophosphorylation is inhibited by histone. It differs from the authentic ICP10-PK in that phosphorylation is specific only for threonine. To determine the significance of ICP10 PK catalytic motifs, site-directed and deletion mutants in PK motifs I and II, the putative signal peptide and the TM segment were used to determine the role of these elements in ICP10-PK activity. PK activity was lost by deletion of the putative TM segment (amino acid residues 85-106). However, mutation of the central Gly in PK catalytic motif I (Gly{dollar}\sp{lcub}106{rcub}{dollar}) or of the invariant Lys in PK catalytic motif II (Lys{dollar}\sp{lcub}176{rcub}{dollar}) or deletion of both of these catalytic motifs (amino acid residues 106-178) did not abolish the kinase activity as determined both in auto- and transphosphorylation assays. PK activity of the mutant deleted in domains I and II was 4-fold lower than that of the wild type ICP10 and it was insensitive to Mn{dollar}\sp{lcub}2+{rcub}{dollar}, suggesting that these motifs are involved in Mn{dollar}\sp{lcub}2+{rcub}{dollar} activation of kinase activity. The result of immunoblotting demonstrated that ICP10 complexes with GTPase activating protein (GAP). Ras GTPase activity is significantly inhibited in ICP10 transformed (JHLa1) cells. These results suggested that ICP10 may constitutively activate ras activity by blocking its down-regulation process, implying a potential signal transduction mechanism for ICP10 induced transformation.
    • Role of cytokines in Campylobacter jejuni infection and immunity in mice

      Baqar, Shahida; Rollwagen, Florence M.; Falkler, William A., Ph.D. (1991)
      Cytokines incorporated into agarose blocks and implanted subcutaneously into mice established an in vivo gradient which can be used to mimic a local inflammatory process. A model was developed in which cellular influx into cytokine impregnated blocks paralleled the normal cellular reaction to infections or wounds. Agarose blocks containing antigens of the intestinal pathogen, C. jejuni, were implanted in normal and infected mice. Kinetics of cellular influx into the blocks showed an early influx of lymphocytes in infected mice only. The two groups showed similar but discrete patterns of cytokine secretion within the blocks. Infected, but not normal mice, were actively synthesizing antibodies to C. jejuni at the local site (within the blocks), whereas the levels of total immunoglobulin were similar for the two groups. The results suggested that the agarose block model can be successfully applied to study local cytokine production and the role of various cells in infectious diseases. The primary infection with C. jejuni in mice resulted in the generation of sensitized B and T cells which could be boosted by rechallenge with homologous bacteria. These results indicated the presence of a functional immunity to C. jejuni challenge in mice. An antibody secreting cell assay allowed the early detection of specific antibody producing cells in circulation. In addition, data suggested a homing pattern of B cells to spleen as well as Peyer's patches. The profile of cytokine production at a local site (intestine) and in the circulation is suggestive of a role of local IL-1 and local as well as systemic IL-6 in immunity and in the pathogenesis of Campylobacter. Crude cytokine suspensions, when fed orally before challenging with C. jejuni, reduced the bacterial load from the gut and also augmented both humoral and cellular immune responses to the bacterial antigens. Oral treatment of mice with rIL-6 had an immediate effect in reducing the bacterial load whereas this effect was delayed in mice treated with rIL-5. Although IL-6 and IL-5 enhanced local as well as systemic antibodies to C. jejuni, these provided only a partial protection from rechallenge with homologous bacteria. On the other hand, mice treated with rIL-2 before challenge had better protection and a faster clearance of bacteria from their guts. In none of the groups could DTH to bacterial antigens be demonstrated, however, the lymphocytes responded to in vitro by stimulation with the same antigens. The data suggested that various cytokines have potential for use as immune modifiers to enhance the immune response to various enteric pathogens. (Abstract shortened with permission of author.)