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Biomedical subjects

S Levy

Publications and source records attributed to S Levy.

At least 163 records · Page 9Linked to original sources
PubMed1991

Perceptions and knowledge about the acquired immunodeficiency syndrome among students in university residences.

Using an anonymous questionnaire to obtain baseline data on sexual behaviour and knowledge of the acquired immunodeficiency syndrome (AIDS) among students in university residences, the following information was obtained: Knowledge of AIDS was found to be high, although misconceptions regarding transmission of the virus were prevalent. Mosquito bites (15%) and the donating of blood (31%) were incorrectly identified as methods of transmission of the virus. Deep kissing was recognised by only 27% of the students as a possible method of transmission while 22% and 13% of the students, respectively, failed to identify the sharing of razor blades and blood transfusions as possible means of contracting HIV infection. The students' knowledge had not greatly affected sexual behaviour. Two-thirds of the respondents had previously had sexual contact; 38% were sexually active at the time of the study, and of these 74% had engaged in unprotected intercourse with casual partners in the previous 6 months. There was a negative attitude towards condom use and over 80% of sexually active students did not perceive themselves to be at risk of contracting AIDS. Campus Health (82%), State health services (51%), and public advertisements (60%) were preferred sources of AIDS information. Newspapers/magazines (80%) and leaflets (69%) were identified as the preferred media. In reality, significantly fewer students obtained their information from Campus Health (15%; P less than 0.05), State health services (19%, P less than 0.05) and leaflets (44%; P less than 0.05). It can be concluded that education programmes should be developed by credible organisations to ensure that an awareness of AIDS results in appropriate sexual behaviour.

Acquired Immunodeficiency Syndrome↗
PubMed1991

Modulation of the oxidative burst in trout myeloid cells by adrenocorticotropic hormone and catecholamines: mechanisms of action.

The oxidative burst of rainbow trout (Oncorhynchus mykiss) phagocytes was previously found to be differentially modulated by adrenocorticotropic hormone (ACTH) and the catecholamine receptor agonists phenylephrine and isoproterenol. From data obtained using both luminol-enhanced chemiluminescence (LECL) and ferricytochrome C (cyt C) reduction to measure oxidative burst kinetics, we postulated that the observed modulation was mediated by affects on enzymes responsible for the production and metabolism of superoxide anion. Using exogenous superoxide dismutase (SOD) and catalase as scavengers, nitroprusside to poison endogenous SOD, and an assay for hydrogen peroxide, we have tested our postulates by exploiting the differences with which various reactive oxygen intermediates influence LECL and cyt C reduction. The ability of ACTH to potentiate both assays of the oxidative burst appears due to its enhancing influence on the production of superoxide. Phenylephrine, an alpha-adrenergic receptor agonist, appears to enhance the activity of endogenous SOD, whereas isoproterenol, a beta-adrenergic receptor agonist, may suppress SOD activity. This work reveals how components of the natural immune system may be regulated by products of the neuroendocrine system. Also, lymphocyte-derived ACTH may provide a novel pathway for lymphoid regulation of inflammation.

Adrenocorticotropic Hormone↗
PubMed1991

Effects of nicardipine on pulmonary and systemic vascular reactivity to oxygen in patients with pulmonary hypertension secondary to chronic obstructive lung disease.

We compared the acute effects of nicardipine and a placebo on the response of pulmonary and systemic circulation to different inspiratory fractional concentrations of O2 (FiO2) in 10 patients with pulmonary hypertension secondary to chronic obstructive lung disease. After catheterization of the pulmonary and femoral arteries, gas mixtures containing 15, 21, and 30% O2 were randomly administered for 20 min each during infusion of saline and then nicardipine (0.06 mg/kg/min). Plasma nicardipine level was maintained at 30 ng/ml. During nicardipine infusion, cardiac index (CI) was significantly higher (+20%, p less than 0.05) than during placebo infusion, with no change in mean pulmonary artery pressure (MPAP). Pulmonary resistances also decreased significantly (-20%) during nicardipine. No change in arterial or mixed venous O2 contents was noted. Mean arterial pressure (MAP) and systemic resistances decreased significantly with nicardipine. Inhaling a hyperoxic mixture was followed by a significant decrease in arterial pressure during placebo infusion; this was not observed during nicardipine. In contrast with systemic circulation, the response of the pulmonary circulation to different FiO2 levels was unaffected by nicardipine.

Blood Gas Analysis↗
PubMed1991

Use of a triaxial magnetometer for respiratory measurements.

We describe a triaxial magnetometer (Tri-mag) system, which consists of a transmitter, four sensors, a processing unit, and a personal computer (PC). The Tri-mag processing unit outputs the position of each sensor relative to the transmitter in three orthogonal coordinates, and this information is communicated to the PC. First, we demonstrated that within a defined octant of a sphere in which the center is the transmitter, we can measure radial distances with an accuracy of +/- 1 mm over a range extending from 10 to 70 cm from the transmitter. Second, we recorded the three-dimensional movement of sensors on the anterior and posterior surfaces of the chest wall during maximum voluntary ventilation in four normal men; all sensors were placed in the midsagittal plane of the body. Anterior sensors were located on the sternum at the level of the third intercostal space and at 2 cm above the umbilicus, whereas posterior sensors were located on the posterior spine at the same vertical levels as the anterior sensors. In all subjects the following was found. 1) Both anterior sensors moved anterior and cephalad during inspiration. The anterior thoracic sensor showed greater vertical than anteroposterior (A-P) movement, whereas the anterior abdominal sensor showed greater A-P than vertical movement. 2) Inspiration was associated with spinal extension, whereas expiration was associated with spinal flexion. Third, we used Tri-mag information to 1) measure tidal volume (VT) over a range extending from 500 ml to inspiratory capacity and 2) measure the change in end-expiratory lung volume (EELV) over a range extending from FRC to FRC plus a minimum of 1.5 liters. Our results indicate that greater than 96% of the changes in VT and greater than 82% of the changes in EELV can be accounted for by changes in A-P, vertical, and lateral dimensions of the chest wall.

Adult↗
PubMed1991

The value of oral amiodarone in the treatment of ventricular arrhythmias in heart disease.

The antiarrhythmic properties of amiodarone at the ventricular level were discovered in the early 1970s. The unanimously recognised efficacy of amiodarone includes a weak negative inotropic effect and compensatory vasodilatory properties, making amiodarone particularly suitable for treating the potentially malignant arrhythmias associated with organic disease. In a review of 611 hospitalised patients on amiodarone, and 353 patients in whom the drug had been prescribed, over a 52-month period in our 60-bed department, we noted that amiodarone was prescribed in 53% of patients for arrhythmias and in 47% of patients for coronary insufficiency. Ventricular arrhythmias represented 13% of the rhythmic indications. These indications differ from those in the USA. The efficacy (70 to 90%) of amiodarone in ventricular extrasystoles has been shown in open studies. In coronary patients, the antiarrhythmic activity of amiodarone is superior to that of propranolol. However, there has been no controlled study because the need for a loading dosage, and the electrocardiographic effects render such studies difficult. After myocardial infarction, ventricular arrhythmias constitute a significant risk factor independently of prognosis; amiodarone may be useful in this indication, and studies of the European Myocardial Infarction Amiodarone Trial (EMIAT) type will examine its value here. Since 1973, it has been recognised that amiodarone can prevent ventricular tachycardia in 55 to 89% of patients in the clinical situation. After a long-standing controversy, the positive predictive value of programmed stimulation has finally been agreed on. In hypertrophic cardiomyopathy, retrospective studies suggest a reduction in mortality in patients treated with amiodarone. By contrast, the value of amiodarone in dilated cardiomyopathy requires more intensive investigation. We consider amiodarone to be indicated in ventricular arrhythmic complexes, particularly if they are associated with an ejection fraction of less than 35% and/or atrial fibrillation. The value of amiodarone in arrhythmias associated with heart failure needs to be evaluated. In conclusion, amiodarone is a powerful antiarrhythmic agent but, because of the possibility of dose- and duration-dependent side effects, evaluation of the risk: benefit ratio in each indication is needed.

Administration, Oral↗
PubMed1991

[Observation of cellular communication in the corneal endothelium using a small molecular weight fluorescent dye].

The metabolic and functional connection between corneal endothelial cells is thought to depend on the transfer of small molecules via gap junctions, as has been reported for other tissues. Cell-to-cell communication in the corneal endothelium was studied by monitoring the spread of fluorescence following the direct injection of Lucifer Yellow CH into single endothelial cells of the excised rabbit cornea. The image of the endothelial cells was observed during the injection and post-injection periods using specular microscopy and fluorescence microscopy. In the fresh cornea, the dye transferred readily from the injected endothelial cell to its neighbors. In damaged cells, dye transfer was slower or did not occur. After 5 hours of incubation in tissue culture medium 199, the specular microscopic image degraded, lowered cell membrane potential and decreased dye transfer rate were measured. This study showed that in normal corneal endothelial cells there were efficient cell communication channels between neighboring cells, and as the endothelium becomes less viable, cell communication is inhibited.

Animals↗
PubMed1991

A seroepidemiological study of hepatitis B amongst Fiji health care workers.

Hepatitis B immunization for health care workers is common policy in many countries where they constitute a particular at risk group. A seroepidemiological study of hepatitis B virus (HBV) in Fiji health care workers was conducted to determine whether this occupational group (or subgroups thereof) were at higher risk of infection than the general Fiji population. The purpose of this study was to ascertain whether health staff should be immunized, or whether it would be more productive to focus resources on neonatal immunization. Blood samples were obtained from 2,639 health workers and the sera analysed by radio-immunoassay for hepatitis B surface antigen (HBsAg), and hepatitis B surface antibody (anti-HBs). Prevalence rates of HBV markers of infection were compared with those observed in the general population, from a previous population-based cluster sample survey. Approximately 70% of the health care staff participated in the study. Prevalence of total HBV markers was 24%. The rate of HBsAg was 5%. Sex and ethnic group specific prevalence rates varied. Male subjects, Fijians and "other" Pacific Islanders all experienced higher rates of infection. Rural/urban and age related trends were also observed. Rates of infection in health staff were lower than those reported in the general population. Previous studies have indicated that most of the transmission of hepatitis B in hyperemdemic Pacific populations occurs at birth or within the next few years. There was no consistent pattern of hepatitis B infection in different occupational groups of health care workers. Certain relatively socially homogeneous subgroups of health workers were analysed separately, and among these health workers there was evidence for increased risk of infection due to exposure to blood or used hypodermic syringes, but not due to patient contact. Until health staff assume a higher risk of infection than the general Fijian population, efforts directed at community-wide control of hepatitis B continue to be the most appropriate use of resources.

Adolescent↗
PubMed1991

Simulations of the static and dynamic molecular conformations of xyloglucan. The role of the fucosylated sidechain in surface-specific sidechain folding.

The hemicellulosic polysaccharide xyloglucan binds with a strong affinity to cellulosic cell wall microfibrils, the resulting heterogeneous network constituting up to 50% of the dry weight of the cell wall in dicotyledonous plants. To elucidate the molecular details of this interaction, we have performed theoretical potential energy calculations of the static and dynamic equilibrium conformations of xyloglucan using the GEGOP software. In particular, we have evaluated the preferred sidechain conformations of hexa-, octa-, deca- and heptadecasaccharide model fragments of xyloglucan for molecules with a cellulose-like, flat, glucan backbone, and a cellobiose-like, twisted, glucan backbone conformation. For the flat backbone conformation the determination of static equilibrium molecular conformations revealed a tendency for sidechains to fold onto one surface of the backbone, defined here as the H1S face, in the fucosylated region of the polymer. This folding produces a molecule that is sterically accessible on the opposite face of the backbone, the H4S face. Typically, this folding onto the H1S surface is significantly stabilized by favorable interactions between the fucosylated, trisaccharide sidechain and the backbone, with some stabilization from adjacent terminal xylosyl sidechains. In contrast, the trisaccharide sidechain folds onto the H4S face of xyloglucan fragments with a twisted backbone conformation. Preliminary NMR data on nonasaccharide fragments isolated from sycamore suspension-cultured cell walls are consistent with the hypothesis that the twisted conformation of xyloglucan represents the solution form of this molecule. Metropolis Monte Carlo (MMC) simulations were employed to assess sidechain flexibility of the heptadecasaccharide fragments. Simulations performed on the flat, rigid, backbone xyloglucan indicate that the trisaccharide sidechain is less mobile than the terminal xylosyl sidechains. MMC calculations on a fully relaxed molecule revealed a positive correlation between a specific trisaccharide sidechain orientation and the 'flatness' of the backbone glucosyl residues adjacent to this sidechain. These results suggest that the trisaccharide sidechain may play a role in the formation of nucleation sites that initiate the binding of these regions to cellulose. Based on these conformational preferences we suggest the following model for the binding of xyloglucan to cellulose. Nucleation of a binding site is initiated by the fucosylated, trisaccharide sidechain that flattens out an adjacent region of the xyloglucan backbone. Upon contacting a cellulose microfibril this region spreads by step-wise flattening of successive segments of the backbone. Self-association of xyloglucan molecules in solution may be prevented by the low frequency of formation of these nucleation sites and the geometry of the molecules in solution.

Carbohydrate Sequence↗
PubMed1991

[Oral propranolol in Wolff-Parkinson-White syndrome. Electrophysiological data].

The effects of oral propranolol were studied in 24 patients with the WPW syndrome. The average daily dose of propranolol was 130 +/- 24 mg administered in 3 doses over a period of 48 to 72 hours. Endocavitary electrophysiological study was performed 2 to 4 hours after the last dose. The effective anterograde refractory periods (EARP) of the accessory and normal pathways were measured before and after propranolol (and, in both studies, before and after isoproterenol). The EARP of the accessory pathway was not affected by the propranolol. However, in the 9 patients in whom its value was less than 270 ms, it increased significantly (p = 0.01). The EARP of the accessory pathway measured after administration of isoproterenol increased significantly in all patients with oral propranolol (p = 0.001). Sustained reciprocating tachycardia could be induced in 19 patients and non-sustained reciprocating tachycardia in 5 other patients during base line electrophysiological study. Oral propranolol prevented the induction of the tachycardias in 18 patients (75%), even after isoproterenol. The shortest R-R interval between two pre-excited complexes in atrial fibrillation increased after propranolol (283 +/- 45 to 343 +/- 95 ms). These results show that oral propranolol increases the EARP of the accessory pathway and the shortest R-R interval between two pre-excited complexes in atrial fibrillation in patients with short anterograde refractory periods of their accessory pathways, and is effective in preventing reciprocating tachycardia. Oral propranolol may be useful and can be used safely in patients with the Wolff-Parkinson-White syndrome.

Administration, Oral↗
PubMed1991

[Pulmonary hypertension secondary to talc microemboli in a HIV seropositive heroin-addict woman].

Severe pulmonary hypertension presenting as acute cor pulmonare was observed in a HIV positive heroin addict. The usual aetiological investigations were negative. The apparently primary pulmonary hypertension was resistant oxygen and vasodilator therapy and was fatal in 6 months. Anatomopathological examination revealed the presence of talc microemboli in the pulmonary arterioles, severe medial hypertrophy and fibrous subendothelial thickening. The presence of the talc suggests that the pulmonary hypertension in this case was due to obstruction of the pulmonary vascular bed by the obstructive arterial lesions, despite the context of HIV infection.

Adult↗
PubMed1990

TAPA-1, the target of an antiproliferative antibody, is associated on the cell surface with the Leu-13 antigen.

A murine mAb, 5A6 (IgG1), has been isolated by immunization with a human B lymphoma cell line and screening for growth inhibition. The antibody immunoprecipitated a single chain protein of 26 kDa from cell lysates made with Triton X-100 but additional proteins were precipitated when cell lysates were made with the milder detergent CHAPS (3-[3-cholamidopropyl)dimethylammonio)-1-propane sulfate). We have identified one of these coprecipitated molecules as the 16-kDa Leu-13 Ag. 5A6 and anti-Leu-13 showed similar, although not identical, reactivity, growth inhibition and temperature-dependent aggregation effects among hematolymphoid cell lines. The aggregation induced by 5A6 and anti-Leu-13 was not dependent on LFA-1 (lymphocyte function-associated Ag-1). The cell-surface expression of both TAPA-1 (target of an antiproliferative antibody-1) and Leu-13 could be down-modulated by binding to their respective antibodies and they could be reciprocally comodulated. These results suggest that TAPA-1 and Leu-13 form a complex on the cell surface and play a role in growth control through a common pathway.

Antibodies, Monoclonal↗
PubMed1990

Diverse VH and VL genes are used to produce antibodies against a defined protein epitope.

mAb secreting hybridomas were produced from mice hyperimmune to the model Ag tobacco mosaic virus protein. Six mAb were selected for their ability to bind synthetic peptides corresponding to amino acid residues 103-112 and 97-107 of tobacco mosaic virus protein. These mAb were analyzed for their fine specificity by measuring binding to synthetic analogs of the decapeptide, and cDNA sequences encoding the mAb V regions were determined. These analyses revealed that a wide range of different V regions are capable of binding with the same decapeptide epitope, and that these antibody sequence differences generally coincided with different binding fine specificities. This diverse antibody response with specificity for the same epitope demonstrates both the breadth of potential of the immune system and the lack of exclusivity in specific protein:protein interactions.

Amino Acid Sequence↗
PubMed1990

Idiotypic variation in a human B lymphoma cell line.

The Ig Id of a B cell lymphoma serves as a distinct marker of the malignant clone and thus as a tumor-specific target for antibody therapy. Somatic variation of the Ig genes expressed by B cell tumors can lead to loss of reactivity with anti-Id antibodies and escape of tumors from the therapeutic effects of such antibodies. In our study, we have used anti-Id antibodies to screen for variants within a cell line derived from a patient with a large cell lymphoma of the B cell type. Cells were simultaneously stained on their surface for idiotypic and for isotypic Ig determinants using reagents labeled with different fluorochromes. Tumor cells expressing intact Ig molecules with alteration of their idiotypic determinants were isolated with the fluorescence activated cell sorter. Idiotypic variation was an ongoing process in vitro with Id- variants being generated at a rate of 2.7 x 10(-4)/cell per generation and Ig- cells being produced at a rate of 1.31 x 10(-5)/cell per generation. Subcloned variants expressed subtle differences in reactivity with a panel of three non-cross-blocking anti-Id antibodies. Analysis of Ig gene rearrangements by the Southern blotting technique using a JH probe established that the variants and the original tumor cells were all clonally related. Immunoprecipitation of surface labeled Ig molecules from the variant subclones disclosed major alterations of the lambda-L chains with no gross alterations of the mu-H chains. Related studies have established that the tumor cells undergo rearrangement and expression of new lambda-L chain genes.

Antibodies, Anti-Idiotypic↗
PubMed1990

Ethnobotanical inventory of medicinal plants used by the Guaymi Indians in western Panama. Part II.

A list of newly identified plants is presented to supplement Part I (Joly et al. (1987) Journal of Ethnopharmacology 20, 145-171). A comparative analysis is made between our work and two other recent inventories of plants used by the Guaymi Indians of Panama and Costa Rica. As in Part I, the results of a literature survey are also provided, including medicinal uses, known constituents and pharmacological effects.

Medicine, Traditional↗
PubMed1990

Analysis of spinal and muscular activity during flexion/extension and free lifts.

Detailed measurements of the relative contributions of spine motion and pelvic motion during flexion-extension and free lifts (squat-type) are examined. The results are consistent with the conclusion that passive stretching of the ligamentous tissues transmits significant extensor moment in these activities, the power being supplied by the hip extensor complex acting on the pelvis. In addition, certain injuries result in measurable changes in the kinematic parameters that determine the ligamentous involvement, and these changes can be used to help evaluate spinal condition.

Biomechanical Phenomena↗
PubMed1990

TAPA-1, the target of an antiproliferative antibody, defines a new family of transmembrane proteins.

A murine monoclonal antibody was identified by its ability to induce a reversible antiproliferative effect on a human lymphoma cell line. Immunoprecipitation studies revealed that the antibody reacted with a 26-kilodalton cell surface protein (TAPA-1). A diverse group of human cell lines, including hematolymphoid, neuroectodermal, and mesenchymal cells, expressed the TAPA-1 protein. Many of the lymphoid cell lines, in particular those derived from large cell lymphomas, were susceptible to the antiproliferative effects of the antibody. TAPA-1 may therefore play an important role in the regulation of lymphoma cell growth. A cDNA clone coding for TAPA-1 was isolated by using the monoclonal antibody to screen an expression library in COS cells. Analysis of the deduced amino acid sequence indicated that the protein is highly hydrophobic and that it contains four putative transmembrane domains and a potential N-myristoylation site. TAPA-1 showed strong homology with the CD37 leukocyte antigen and with the ME491 melanoma-associated antigen, both of which have been implicated in the regulation of cell growth.

Amino Acid Sequence↗
PubMed1990

[Complex ventricular extrasystole. Value of programmed electric stimulation for evaluating the risk of sudden death].

A prospective study was carried out from May 1984 to July 1987 to determine the prognostic value of the results of programmed electrical stimulation (PES) in patients with complex ventricular ectopy. The study population comprised 118 patients, 80 with and 38 without apparent underlying cardiac disease. The PES consisted in at most 3 extrastimuli delivered to the right ventricular apex during 2 imposed basal rhythms. Two groups of patients were identified: Group I (n = 35; 29.6%) in which a significant ventricular arrhythmia was induced (sustained ventricular tachycardia (11 cases), non-sustained VT (21 cases) and ventricular fibrillation (3 cases); and Group II (n = 83; 70.3%) in which no significant arrhythmia could be induced. During follow-up (average 28.7 +/- 11.7 months, range 6 to 48 months) there were 10 cardiac deaths, 8 of which occurred suddenly. Sudden death only occurred in patients with cardiac disease and usually with LV ejection fraction of less than 0.40; the prevalence of sudden death in Group I (11.5%) was higher than in Group II (4.8%) but the difference was not statistically significant. The prognosis of patients in Group II was the same as that of the general population. The results of this study suggest that PES enables identification of a subgroup of patients with complex ventricular ectopy in which ventricular tachyarrhythmias cannot be induced and the risk of sudden death is low; the management of patients with inducible ventricular tachyarrhythmias and normal LV function has to be determined case by case.

Adolescent↗