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Biomedical subjects

P Baron

Publications and source records attributed to P Baron.

At least 91 records · Page 5Linked to original sources
PubMed1988

[A study of the literature on the concentrations of arsenic, lead, cadmium and mercury in body fluids and tissues to define normal values and detection of overload. 1. Description of analytical methods and arsenic].

The present review covers 208 papers dealing with determination of the metals arsenic, cadmium, lead and mercury in human biologic material. A comprehensive data bank survey of the literature from January 1980 to April 1984 was conducted and supplemented by review of some earlier publications. As shown by comparison of the results from a number of papers, the various state-of-the-art methods for determining metal content in biologic materials (e.g., atomic absorption spectrophotometry, neutron activation analysis, and x-ray fluorescent analysis) appear to be equally sensitive and reliable. These detection methods are suited to determination of the above metals in the following media: arsenic in urine, hair; cadmium in blood, urine, hair, renal cortex; lead in blood, hair; mercury in blood, urine, hair. To permit better comparison of the results presented in various publications, agreement must be reached on use of uniform concentration units and participation in quality control programs. Safe levels of chronic biological exposure overlap with concentrations which cause health effects or measurable impairment of body function over a wide range. Individual sensitivity to biological exposure varies. In a number of studies, metal concentrations are measured in symptom-free persons which cause symptoms in persons examined in other studies. Due to differences in the sensitivity of detection of symptoms, the range of minimum levels of biological exposure considered to be associated with deleterious health effects (levels of critical exposure) is unacceptably broad. Minimum levels of critical exposure should protect against development of early symptoms of toxicity. If the lowest published critical levels of biological exposure are taken as a cutoff, then a sizable portion of the persons currently revealing metal exposure in any of the reported media exceeds such levels. Symptoms of detrimental effects should be detectable in such persons and should be investigated. In establishing and evaluating current minimum levels of critical chronic metal exposure, there is a general need for a quantitative increase in determinations and for a qualitative increase in the sensitivity of detection of symptoms and other health effects--in order to avoid dependence on reports of acute toxicity. When detected levels of a given metal are in a range held to be normal, exclusion of toxic effects and poisoning requires additional consideration of clinical findings.

Arsenic↗
PubMed1988

[A review of the literature on the concentration of arsenic, lead, cadmium and mercury in body fluids and tissues for the localization of normal values and the detection of body burden. 2. Cadmium].

The 2nd of 4 communications on metal concentrations in human body media deals with cadmium. Publications obtained from a comprehensive data bank search from January 1980 to April 1984 are listed in tables; study groups have been assigned to the following categories: normal; exposed; and exposed, exhibiting adverse health effects. Quality and strength of evidence of analytical procedures and reported data are discussed, particularly in light of adverse health effects. General methods and individual analytical procedures were presented in the 1st communication, a summary of mean exposure levels, critically elevated levels, and references will be published in the 4th communication.

Body Burden↗
PubMed1987

Respirable dust control in grinding gray iron castings.

High speed grinding of gray iron castings long has been associated with excessive exposure to crystalline silica. Not all workers engaged in these operations are protected by conventional ventilation techniques. Dust in the air that has been entrained by the spinning grinding wheel and not captured in the grinder hood has been postulated to be a major exposure source. A pilot grinding operation was constructed, and the size distribution and concentration of airborne particles were measured with the aerodynamic particle sizer (APS). Various control measures proved effective in reducing the respirable dust concentration: increased exhaust ventilation, and installation of baffles and/or the use of an air jet to deflect the entrained air stream. The concentration of respirable dust is the breathing zone was reduced approximately 20-fold through the combined use of increased ventilation, interior baffles, and an air jet. The air jet and baffle utilized at the base ventilation rate reduced the respirable dust concentration by a factor of three to four, whereas the baffle alone halved the concentration.

Air Pollutants, Occupational↗
PubMed1986

S-100 protein and laminin: immunocytochemical markers for human Schwann cells in vitro.

Human fetal and adult Schwann cells, which had been maintained in culture for 5 weeks according to an explant-reexplantation technique, were labeled by immunoperoxidase using antibodies directed against S-100 protein and laminin in order to find specific antigenic markers. Immunocytochemical analysis of the distribution of both proteins showed that they were expressed in long-term cultures. The localization of S-100 protein and laminin in long-term cultures indicated that the expression of these proteins by human Schwann cells was not axon-dependent and also occurred in absence of myelin synthesis.

Cells, Cultured↗
PubMed1986

Size and concentration measurement of an industrial aerosol.

Several real-time particle sizing instruments were evaluated for measuring the size distribution and concentration of the aerosol produced during the high speed grinding of gray iron castings. Aerosol was sampled in the airstream entrained by the motion of a spinning grinding wheel in a pilot grinding operation. Measurement methods based on differing physical principles were selected for evaluation and compared: particle inertia (aerodynamic particle sizer and quartz crystal microbalance cascade impactor); light scattering (laser aerosol spectrometer); and projected-area microscopy (scanning electron microscope). Inferences of aerodynamic diameter based on measurements by the laser aerosol spectrometer consistently undersized that determined by the aerodynamic particle sizer by a factor of 1.5. Estimates of aerodynamic diameters from projected area diameters determined by scanning electron microscopy differed from those obtained by the aerodynamic particle sizer by a factor of 2. Differences appeared to be a non-linear function of particle diameter. Estimates of respirable mass determined from mass-weighted particle size spectra varied by a factor of 6 between the largest estimate (scanning electron microscope) and the smallest estimate (laser aerosol spectrometer).

Aerosols↗
PubMed1986

Opportunistic infections in acquired immune deficiency syndrome result from synergistic defects of both the natural and adaptive components of cellular immunity.

We evaluated the cellular immunity of 408 clinically stratified subjects at risk for acquired immune deficiency syndrome (AIDS), to define the role of interferon-alpha production deficits in the pathogenesis of opportunistic infections (OI). We followed 115 prospectively for up to 45 mo. Onset of OI was associated with, and predicted by, deficiency both of interferon-alpha generation in vitro, and of circulating Leu-3a+ cells. Interferon-alpha production is an index of the function of certain non-T, non-B, large granular lymphocytes (LGL) that are independent of T cell help. Leu-3a+ cell counts are a marker of T cell function. OI did not usually develop until both of these mutually independent immune functions were simultaneously critically depressed, leading to a synergistic interaction. These data suggest that the AIDS virus affects a subset of LGL, and that cytokine production by these cells is an important component of the host defense against intracellular pathogens that becomes crucial in the presence of severe T cell immunodeficiency.

Acquired Immunodeficiency Syndrome↗
PubMed1985

Antibodies to proteus in rheumatoid arthritis.

Antibodies to proteus species were measured in patients with rheumatoid arthritis (RA) and ankylosing spondylitis (AS) and in healthy controls by a Coombs agglutination method. The titres to Proteus mirabilis were higher in 30 RA patients being treated with gold than in 24 patients with active AS (p less than 0.001), 28 patients with inactive AS (p less than 0.001), and 41 healthy control subjects (p less than 0.001). Control studies with Klebsiella pneumoniae var oxytoca showed high antibody titres only in active AS patients.

Adult↗
PubMed1985

Binding of latamoxef (moxalactam) and its decarboxylated derivative to Escherichia coli and Pseudomonas aeruginosa penicillin-binding proteins.

The binding of latamoxef (moxalactam) and of a decarboxylated derivative to Escherichia coli and Pseudomonas aeruginosa penicillin-binding proteins (PBPs) was measured by competition experiments with 125I-radiolabelled penicillin X. Latamoxef and the decarboxylated derivative were highly bound to most of the PBPs, with the exception of PBP-2. As the two compounds possess a phenolic side-chain, they also could be radiolabelled with 125I. The proteins thus labelled by these derivatives were qualitatively the same as those labelled by 125I-penicillin X, except for PBP-2 which was not labelled by the iodo derivatives of latamoxef and its decarboxylated derivative, and PBP-1c (in E. coli) which is labelled only poorly by the radioactive penicillin. No important difference between latamoxef and its decarboxylated derivative was found, and the same observation was made for penicillin G and carbenicillin. Thus, it was concluded that the carboxylic group of latamoxef does not play an important role in affinity for the targets.

Bacterial Proteins↗
PubMed1984

Affinity of temocillin for Escherichia coli K-12 penicillin-binding proteins.

Temocillin is a 6 alpha-methoxy penicillin which shows poor affinity for the penicillin-binding proteins (PBPs) of Escherichia coli K-12 when tested by competition with [14C]penicillin G or [125I]penicillin X. When the reaction conditions for the radiolabeled penicillin used in this procedure were modified by lowering the temperature (2 degrees C) and reducing the incubation time (3 min), temocillin showed a much higher affinity for PBP-3 and improved affinity for the other PBPs, with the exception of PBP-2. Direct labeling procedures with [14C]temocillin also showed that the compound had affinity for PBPs 1a and 3. These results are more consistent with the effects of temocillin on the morphology of E. coli than the poor affinity values obtained by the classical competitive procedure. Reasons for the disparity between these assay systems are discussed.

Anti-Bacterial Agents↗
PubMed1984

Do patients with low tension glaucoma have particular cardiovascular characteristics?

It has been suggested that low tension glaucoma (LTG) could be the consequence of a hemodynamic crisis or chronic occlusive disease. The purpose of the present study was to test this hypothesis by comparing three groups of patients matched for age and sex: 51 patients with LTG, 51 patients with open angle glaucoma (OAG) and 46 control patients. Clinical symptoms and history of occlusive arterial disease and conditions which could be associated with or were the consequence of acute blood pressure lowering were not more frequent in the LTG group. The prevalence of rhythm and conduction abnormalities on the ECG was two times more frequent in the glaucoma groups, but the differences were not statistically significant. Mean cardiovascular risk factor levels were not higher in the LTG group than in the two other groups. But the mean difference of blood pressure between the standing and lying positions was significantly greater in the LTG group (systolic blood pressure: -6.9 mm Hg) than in the OAG group (-1.2 mm HG) and the control group (-1.5 mm Hg). These results suggest that postural hypotension could play a role in the pathogenesis of LTG.

Aged↗