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Biomedical subjects

S Snyder

Publications and source records attributed to S Snyder.

At least 37 records · Page 2Linked to original sources
PubMed1999

Lipopolysaccharide bilayer structure: effect of chemotype, core mutations, divalent cations, and temperature.

Lipopolysaccharide (LPS), the primary lipid on the surface of Gram-negative bacteria, is thought to act as a protective and permeability barrier. X-ray diffraction analysis of osmotically stressed LPS multilayers was used to determine the structure and interactive properties of LPSs from strains containing the minimum number of sugars necessary for bacterial survival (Re chemotype) to the maximum number of sugars found in rough bacteria (Ra chemotype). At 20 degrees C in the absence of divalent cations, LPS suspensions gave a sharp wide-angle reflection at 4.23 A and a broad low-angle band centered at 50-68 A depending on the chemotype, indicating the presence of gel phase bilayers separated by large fluid spaces. As osmotic pressure was applied, the apposing bilayers were squeezed together and lamellar diffraction at 6 A resolution was obtained. At low applied pressures (<10(6) dyn/cm2), the total repulsive pressure between bilayers could be explained by electrostatic double layer theory. At higher applied pressures, there was a sharp upward break in each pressure-distance relation, indicating the presence of a hydrophilic steric barrier whose range depended strongly on the LPS chemotype. The positions of these upward breaks, along with electron density profiles, showed that the sugar core width systematically increased from 10 A for the Re chemotype to 27 A for the Ra chemotype. In excess buffer, the addition of divalent cations brought the bilayers into steric contact. Electron density profiles were used to determine the locations of cation binding sites and polar substituents on the LPS oligosaccharide core. The area per hydrocarbon chain was approximately 26 A2 in liquid-crystalline LPS bilayers, an indication of an acyl chain packing that is much tighter than that found in bilayers composed of typical membrane lipids. This unusually tight packing could be a critical factor in the permeability barrier provided by LPS.

Barium↗
PubMed1999

Resistance to Coccidioides immitis in mice after immunization with recombinant protein or a DNA vaccine of a proline-rich antigen.

Two inbred strains of mice (BALB/c and C57BL/6) were vaccinated with either recombinant expression protein of a Coccidioides immitis spherule-derived proline-rich antigen (rPRA) in monophosphoryl lipid A-oil emulsion adjuvant or a DNA vaccine based on the same antigen. Four weeks after vaccination, mice were infected intraperitoneally with arthroconidia. By 2 weeks, groups of mice receiving saline or plasmids with no PRA insert exhibited significant weight loss, and quantitative CFUs in the lungs ranged from 5.9 to 6.4 log10. In contrast, groups of mice immunized with either rPRA or DNA vaccine had significantly smaller pulmonary fungal burdens, ranging from 3.0 to 4.5 log10 fewer CFUs. In vitro immunologic markers of lymphocyte proliferation and gamma interferon (IFN-gamma) release after splenocytes were stimulated with rPRA correlated with protection. Also, plasma concentrations of rPRA-specific total immunoglobulin G (IgG), IgG1, and IgG2a showed increases in vaccinated mice. These studies expand earlier work by demonstrating protection in mice which differ in H-2 background, by using an adjuvant that is potentially applicable to human use, and by achieving comparable protections with a DNA-based vaccine. Our in vitro results substantiate a Th1 response as evidenced by IFN-gamma release and increased IgG2a. However, IgG1 was also stimulated, suggesting some Th2 response as well. PRA is a promising vaccine candidate for prevention of coccidioidomycosis and warrants further investigation.

Animals↗
PubMed1998

Idealization in the liver transplant setting.

Liver transplant patients in psychotherapy may often be relatively silent about their new organs but intensely preoccupied with their medical and psychosocial caregivers. An important challenge for the liver transplant recipient is to preserve positive relationships with caregivers, and to ward off frightening feelings of anger and mistrust that may threaten to emerge. Idealization of caregivers is common, and may be ego-enhancing. Any threat to the idealization may be hazardous. Three liver transplant cases from the author's psychotherapy practice are presented which illustrate this paradigm. The ideas developed are readily applicable to current problems involving both psychotherapy and selection of transplant recipients.

Adaptation, Psychological↗
PubMed1998

Occupational exposure to HIV: experience at a tertiary care center.

We examined our hospital-based occupational health clinic's experience with combination antiretroviral therapy for postexposure prophylaxis for human immunodeficiency virus (HIV). Over a 12-month period, 68 workers started postexposure prophylaxis: 23 with zidovudine and lamivudine and 45 with zidovudine, lamivudine, and indinavir. Fifty-one (75%) of the 68 workers starting postexposure prophylaxis reported one or more side effects. Side effects were more common among those taking three drugs. Many workers failed to complete the recommended 28-day regimen because of the side effects of the various treatments. The estimated mean cost for evaluations, prophylaxis, and monitoring of exposed workers was $669 per reported exposure. In our experience, major challenges in carrying out the current HIV postexposure prophylaxis guidelines include expeditious source testing, improved staff education and prevention measures, and scrupulous monitoring of workers taking combination antiretroviral drugs for postexposure prophylaxis, with consideration of alternate regimens for intolerant workers.

Anti-HIV Agents↗
PubMed1997

Workshop on schizophrenia.

On November 29-30, 1995, the National Academy of Sciences and the Institute of Medicine brought together experts in schizophrenia and specialists in other areas of the biological sciences in a workshop aimed at promoting the application of the latest biological information to this clinical problem. The workshop paid particular attention to evidence of pathology in the brains of people with schizophrenia, and to the possibility that this reflects an abnormality in brain development that eventually leads to the appearance of symptoms. The participants were impressed with the complexity of the problem, and felt that multiple approaches would be required to understand this disease. They recommended that a major focus should be on the search for predisposing genes, but that there should be parallel research in many other areas.

Brain↗
PubMed1997

Regional fat distribution in women and risk of cardiovascular disease.

Improvements in technology have allowed more precise measurements of regional fat distribution and also present the opportunity to make a systematic evaluation of the various fat depots, including intraabdominal adipose tissue (IAF), subcutaneous adipose tissue (SAF), trunk fat, arm fat, and leg fat. The purpose of this study was to determine which of the fat distribution variables (arm fat, leg fat, trunk fat, IAF, or SAF) may have independent relations with cardiovascular (CVD) risk factors [serum triacylglycerol, serum cholesterol, high-density-lipoprotein (HDL) cholesterol, HDL2 cholesterol, HDL3 cholesterol, low-density-lipoprotein (LDL) cholesterol, very-low-density-lipoprotein (VLDL) cholesterol, VLDL3 cholesterol, lipoprotein(a), and systolic and diastolic blood pressure] in women after adjusting for age, menopause status, and other fat-distribution variables. Two hundred twenty-four (138 premenopausal and 86 postmenopausal) white females ranging in age from 17 to 77 y were sampled. Percentage body fat ranged from 8.8% to 48.1% and IAF cross sections ranged from 9.2 to 335 cm2. Simple zero-linear correlations and partial correlations were calculated. IAF and trunk fat were consistently positively related to CVD risk factors, whereas leg fat was consistently negatively related to CVD risk, indicating that IAF and trunk fat may put women at increased risk of developing CVD.

Absorptiometry, Photon↗
PubMed1997

The neurological basis of attention deficit hyperactivity disorder.

Attention deficit hyperactivity disorder (ADHD) is a serious disability with long-term consequences. At present the disorder is considered organic in pathology, particularly in regard to central nervous system functioning. This paper reviews research on ADHD. The role of neurochemical stimulation is discussed, and the signs of neurological deficits are explored. Nearly 600,000 young people in the United States receive medication daily for ADHD, and these drugs mimic brain neurotransmitters. The chemical action of these drugs and the cognitive, affective, and behavioral effects are discussed. Side effects and dosage levels are also examined. Basic behavior modification with ADHD children and how these techniques can be combined with effective drug treatment are elaborated.

Attention Deficit Disorder with Hyperactivity↗
PubMed1996

Intra-abdominal adipose tissue cut-points related to elevated cardiovascular risk in women.

Intra-abdominal adipose tissue (IAF) seems to be the primary fat depot putting individuals at risk for cardiovascular disease (CVD). The purpose of this study was to determine IAF cut-points for identifying CVD risk in pre- and post-menopausal women. Age ranged from 18 to 77 y and percentage fat ranged from 9 to 48%. Computed tomography (CT), IAF, DEXA determined regional fat and blood lipid profiles were obtained on 220 Caucasian women. Student's t-tests were run to determine differences between pre- and post-menopausal women. Receiver-operating characteristic (ROC) analysis was used to develop IAF cut-points associated with elevated CVD risk. Post-menopausal women had higher percentage fat, greater proportion IAF and higher CVD risk. Menopausal status was not consistently independently related to CVD risk after adjusting for IAF, but IAF was after adjusting for menopausal status. The same cut-points for CVD risk were found with both 4- and 6-CVD risk factor analysis and for both pre- and post-menopausal as well as pooled data. 4-CVD risk factor analysis comprised cholesterol (C), HDL-C, systolic blood pressure and diastolic blood pressure. 6-CVD risk factor analysis comprised the 4-CVD risk factors plus triglycerides and cholesterol : HDL-C ratio. ROC L positive values indicate levels of IAF above which metabolic disturbances will be increased and were determined to be 110 cm2. ROC L negative values indicate levels of IAF below which CVD risk will not be affected and were determined to be 40 cm2. False positives were 3% and false negatives were 9%. ANOVA comparing women with IAF cross-sections less than 40 cm2, between 40 and 110 cm2 and more than 110 cm2 demonstrate large differences in CVD risk profile. It is suggested women who have IAF values above 110 cm2 are in jeopardy of possessing elevated CVD risk.

Abdomen↗
PubMed1996

Anthropometric equations for estimating abdominal adipose tissue distribution in women.

OBJECTIVES: (1) to develop multiple regression equations for predicting computed tomography (CT) derived intra-abdominal (IAF), subcutaneous (SCF) and total (TOTF = IAF + SCF) abdominal adipose tissue areas from anthropometric measures and (2) to validate the equations. DESIGN: Cross-sectional study. SUBJECTS: 204 healthy Caucasian females subjects with a large range of age (17-76 years) and percentage body fat (8.8%-48.1%). Fifty-one subjects served as an independent sub-sample for the validation of the equations. MEASUREMENTS: Various fatness and fat distribution parameters (hydrodensitometry, single CT scan, skinfold and circumference measures). RESULTS: Multiple regression equations were developed to estimate IAF, SCF and TOTF. R2 for IAF, SCF and TOTF was 0.75, 0.81 and 0.85, respectively. The equations were validated on an independent sub-sample of 51 subjects. All three equations met validation criteria with R2 validations of 0.79, 0.71 and 0.84 for IAF, SCF and TOTF, respectively. CONCLUSION: These equations might be used as an inexpensive estimation of IAF, SCF and TOTF in adult Caucasian females varying greatly in age and percentage body fat.

Abdomen↗
PubMed1995

Movie portrayals of juvenile delinquency: Part 1--Epidemiology and criminology.

Movies chronicling the phenomenology of juvenile delinquency have been produced since the 1930s. These films have become part of American culture and are at once a representation of and possible etiologic factor in causing delinquency. This paper reviews aspects of the epidemiology and criminology of delinquency and how they have been reflected in American films. Movies of historical and sociopsychological significance are examined in more detail, and the following questions are addressed: As the ethnicity of the United States changes, to what extent are American films dealing with juvenile delinquency reflecting this evolution? How are such films symbolizing the theme of "law and order," pervasive in U.S. approaches to crime for a quarter century? When these movies come close to mimicking certain aspects of the environment of the viewer, an interactive or "resonating" effect may occur such that the youth who view such films may be more likely to commit delinquent acts. A countervailing utility of these movies may be their prosocial potential in educating and rehabilitating youth.

Adolescent↗
PubMed1995

Movie portrayals of juvenile delinquency: Part II--Sociology and psychology.

The visual media, especially movies, are appealing to youth with their rapid presentation of visual images of immediate gratification and unbridled pursuit of materialism. As social class differences in America widen, movies may serve both as a reflection of the social psychology of juvenile delinquency and as an etiologic factor in the development of such wayward youth. This paper examines some current aspects of the sociology and psychology of juvenile delinquency, and presents the historical significance of movies since the 1930s as both a visual representation and causative factor in the social psychology of delinquent youth.

Adolescent↗
PubMed1994

Beta/A4-evoked degeneration of differentiated SH-SY5Y human neuroblastoma cells.

beta/A4 peptides are known to induce neurodegeneration in cultures of rat brain cells and rat neural cell lines (Yankner et al: Science 250:279-282, 1990; Behl et al: Biochem Biophys Res Commun 186:944-950, 1992). The current data show that these peptides induce similar neurodegeneration in SH-SY5Y neuroblastoma cells, extending characterization of beta/A4 toxicity to a human nerve cell line. Human SH-SY5Y cells respond to aggregated beta/A4 with changes in cell shape, membrane blebbing, antigenic modification, loss of attachment to the substrate, and cell death. beta/A4 peptides require aggregation for maximum toxic effects, as cellular degeneration is evoked by aggregated beta/A4 1-42 and 4-41 cysteine but not by monomeric beta/A4 1-40. Aged (pre-aggregated) beta/A4 1-40 also evoked neurodegeneration. Antigenic changes comprise upregulation of Alzheimer's-type tau epitopes, recognized by the PHF-1 and Alz-50 monoclonals. These particular changes in tau support the connectivity between this in vitro model and mechanisms leading to neurodegeneration in Alzheimer's disease. A significant feature of the SH-SY5Y response is that cells must be differentiated before they become sensitive to the degeneration evoked by beta/A4. Signaling pathways leading to beta/A4-evoked neurodegeneration thus are under experimental control, becoming complete only when proliferating cells withdraw from the cell cycle and develop a postmitotic phenotype.

Alzheimer Disease↗
PubMed1994

Development and validation of computed tomography derived anthropometric regression equations for estimating abdominal adipose tissue distribution.

The purpose of this study was twofold: (1) to develop multiple regression equations for predicting computed tomography (CT) derived intra-abdominal (IAF), subcutaneous (SCF), and total (TOTF= IAF+SCF) abdominal adipose tissue areas from anthropometric measures in adult white males with a large range of age (18-71 years) and percent body fat (2.0-40.6); and (2) to validate the new and existing equations that used similar Hounsfield Units (HU) for determining IAF for estimating these fat depots. One hundred fifty-one white male subjects had IAF, SCF, and TOTF determined by a single CT scan, skinfold and circumference measures taken and body density determined. Linear intra-correlations and factor analysis procedures were used to identify variables for inclusion in stepwise multiple regression solutions. IAF was estimated from age, waist circumference, the sum of mid-thigh and lower thigh circumferences, and vertical abdominal skinfold. SCF was estimated from age, umbilicus circumference, chest and suprailiac skinfolds. TOTF was estimated from age, body mass index (BMI), chest skinfold, and umbilicus circumference. R2 for IAF, SCF, and TOTF was .73, .77, and .86 respectively. The existing and the new equations were validated on an independent sub-sample of 51 subjects. The only existing equation that met validation criteria had a validation R2 = .67 for IAF. All three new equations met validation criteria with R2 validations of .75, .79, and .85 for IAF, SCF, and TOTF respectively. It is concluded that the new equations might be used as an inexpensive estimation of IAF, SCF, and TOTF in adult white males varying greatly in age and percent body fat.

Abdomen↗
PubMed1994

Challenges and barriers to managing quality in an end-stage renal disease facility.

The End-Stage Renal Disease Program is underfunded and overregulated. Objective parameters of end points of care do not correlate to specific clinical practice patterns. We do not have consensus between payers, providers, and patients as to what the objectives of the End-Stage Renal Disease Program are or should be. This report will address the need for an integrated health care delivery system that would benefit the end-stage renal disease patient and the barriers to designing such a system. The quality improvement program of a five-unit dialysis system will be described. The deficiencies of the quality improvement program and the limitation of the facilities to improve outcome will be discussed, and constructive alternatives to achieve an integrated health care delivery system that promotes improvement in patient outcomes will be suggested.

Hemodialysis Units, Hospital↗