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Biomedical subjects

D Bennett

Publications and source records attributed to D Bennett.

At least 253 records · Page 14Linked to original sources
PubMed1984

Fate and biological effects of methyl parathion in outdoor ponds and laboratory aquaria. I. Fate.

Three outdoor ponds were treated with methyl parathion (MEP) applied beneath the water surface at a concentration of 100 micrograms liter-1. Laboratory aquaria containing either tap water, pond water, tap water plus plants, tap water plus sediment, or tap water plus sediment and plants were similarly treated. Samples of water, sediment, and fish were analyzed for residues of MEP. The rate of loss from water and concentrations found in sediment were compared with predictions based on a calculated rate of biodegradation and a sediment:water partition coefficient. The rate of loss of MEP from pond water isolated in an aquarium was similar to the predicted rate. However, the rate of loss from outdoor ponds, or from aquaria containing plants and sediment, was greater than predicted. MEP was not detected in sediment even though predicted concentrations far exceeded the limit of detection. These results are discussed and it is suggested that the rate of biodegradation in shallow bodies of water may be determined predominantly by bacteria attached to sediments and plants, rather than by planktonic bacteria. Bioaccumulation in fish was predicted from empirical equations based on the octanol:water partition coefficient. Observed values were in good agreement with predictions.

Animals↗
PubMed1984

Atrial fibrillation.

Atrial fibrillation is a common arrhythmia and one which may cause pilot incapacitation. In many cases there may be no more than one episode and there will be no organic heart disease. Prediction of the risk of recurrence is not possible. Atrial fibrillation in both paroxysmal and persistent forms should be disqualifying for Class I or unrestricted Class III certification. Individuals with a single episode of atrial fibrillation related to a reversible toxic cause but with no evidence of organic heart disease could be considered for restricted duty subject to echocardiographic and ambulatory electrocardiographic follow up. Atrial flutter and atrial tachycardia should disbar from aircrew duties.

Adult↗
PubMed1984

Generation of human C3a, C4a, and C5a anaphylatoxins by protein A of Staphylococcus aureus and immobilized protein A reagents used in serotherapy of cancer.

Protein A (SpA) alone or immobilized on bacteria (e.g., Cowan strain I), collodion charcoal, or on Sepharose have been used in serotherapy of cancer in humans and experimental animals. Because SpA forms complexes with IgG that can activate complement, and the physiologic response during treatment often involves hypocomplementemia and reactions that are similar to those induced by anaphylatoxins, we used sensitive and specific radioimmunoassays to test the ability of SpA reagents to generate C3a, C4a, and C5a from human serum. The yield of anaphylatoxins depended on the dose of SpA, with the maximum generation of C3a (47 to 55 micrograms/ml) and C5a (1.4 to 1.9 micrograms/ml) being produced with levels of SpA that were maximally precipitated from serum. Maximum C4a levels (up to 15 micrograms/ml) were obtained at concentrations of SpA equal to or greater than the dose required to give optimal precipitation. The maximum concentrations of anaphylatoxins correspond to essentially quantitative conversions of C3 to C3a, C4 to C4a, and 40% of C5 to C5a after correction for levels found in serum incubated in pyrogen-free saline. Preformed insoluble complexes prepared from either serum or monomeric IgG also were capable of generating anaphylatoxins in fresh whole serum up to levels approximately equal to those observed in serum treated directly with an optimal amount of SpA. The preformed complexes from serum or IgG generated similar high concentrations of anaphylatoxins when carried through four sequential incubations with fresh serum, and complexes that contained approximately 1 microgram SpA were still active. Preincubating the insoluble complexes with chicken anti-SpA serum did not alter their activity. Incubation of serum with collodion charcoal coated with SpA, in a system that models the perfusion technique used to treat cancer, produced complexes that generated significant levels of C3a compared with levels found in serum passaged over albumin charcoal or in untreated serum. The C3a levels in serum from the albumin collodion charcoal were not significantly different from those found in untreated serum. Similar amounts of C3a, C4a, or C5a were observed in serum incubated with differing numbers of bacteria representing a strain of S. aureus rich in cell bound SpA (Cowan strain I) or a strain (Wood 46) deficient in SpA. This suggests that in intact bacteria, cell wall factors other than SpA (e.g., peptidoglycan) are predominantly responsible for generating anaphylatoxins.(ABSTRACT TRUNCATED AT 400 WORDS)

Anaphylatoxins↗
PubMed1983

Radioimmunoassays for protein A of Staphylococcus aureus.

Radioimmunoassays have been developed that can detect nanogram amounts of protein A (SpA), a product generated by Staphylococcus aureus that binds selectively to the Fc region of IgG from most mammalian species. Competition assays for fluid phase SpA utilize antibodies produced in chickens, 125I-labeled SpA as the tracer molecule, and either F(ab')2 fragments of rabbit IgG anti-chicken IgG or 40% ammonium sulfate as the precipitating agent to separate antigen-antibody complexes from free antigen. The double antibody assay could be carried out in serum from species that form only soluble complexes with SpA (e.g., rabbit), that react poorly with SpA (e.g., rat), or under appropriate conditions in serum from species (e.g., dog) that show high reactivity with SpA and form precipitating complexes. Chicken antibodies prepared by affinity chromatography on SpA-Sepharose and labeled with 125I were used in a direct binding assay for SpA present either on the cell wall of Cowan strain I or Wood 46 bacteria, in insoluble complexes prepared from SpA and whole serum or purified IgG, or in Clq binding complexes that were formed by passage of serum from normal or tumor bearing humans or dogs over SpA-collodion charcoal. Since both types of assays could detect SpA even in the presence of serum or IgG, they offer advantages over other techniques in which the SpA-Fc interaction may interfere.

Animals↗
PubMed1983

Correlation between a learning disorder and elevated brain-reactive antibodies in aged C57BL/6 and young NZB mice.

Previous studies have indicated an increase in brain-reactive antibodies (BRA) in sera of aging mammals and an autoimmune disorder underlying senescence has been suggested. Since New Zealand Black (NZB) mice have a shorter lifespan and greater propensity for autoimmune diseases than C57BL/6 mice, various age groups from both strains of mice were investigated for simultaneous occurrence of BRA serum titer and deficits in learning. NZB mice exhibited a marked learning deficit as well as higher BRA levels at all ages. C57BL/6 mice showed increased BRA and a learning deficit only at advanced ages. The findings of "precocious" BRA titers along with marked learning deficits, both occurring at young ages in NZB mice and both similar to defects seen in the normal mice at senescence and in patients with senile-dementia, suggest that NZB mice may serve as a useful animal model of pre-senile dementia.

Aging↗
PubMed1983

A categorical analysis of the social attributions of learning-disabled children.

The social attributions of learning-disabled and control children with either similar or higher social acceptance ratings were assessed within an open-ended interview format. In addition, measures of social self-esteem and expectation of social success were obtained. The learning-disabled group used luck more frequently and personality interaction less frequently as explanations for social outcomes than did the other two groups. Learning-disabled children also had the lowest expectation of social success and, like the low acceptance group, had a poorer social self-image. Possible explanations for the development of these attributions and the implications for holding them were discussed.

Child↗
PubMed1983

A class of large polysaccharides contains the antigenic determinants for the cytotoxic antibodies in a conventional syngeneic anti-F9 serum as well as a monoclonal antibody prepared against F9 cells.

The molecular natures of the antigenic targets detected by cytotoxic antibodies in both a monoclonal antibody (ECMA-3) made against F9 cells and a conventional mouse anti-F9 serum were investigated. Both of the antibodies precipitated a class of high molecular weight polysaccharides from Nonidet P40 lysates of F9 cells. These molecules were labeled by radioactive galactose and fucose but only poorly by amino acids; in addition, they were fairly resistant to pronase and the digest still had a molecular weight of 70 K or more. Even after extensive pronase digestion the polysaccharides inhibited the cytotoxic activities of the antibodies, suggesting that the antigenic targets reside on the carbohydrate portion. This class of polysaccharides was shown to be a minor component of the characteristic large polysaccharides of F9 cells.

Animals↗
PubMed1983

Immunoscanning electron microscopy of antigenic determinants of T/t-complex (tw18) mouse embryos.

tw18 antigen(s) have been localized by immunoscanning electron microscopy in 7.5-day mutant embryos using a primary antiserum to tw18 made and defined on male germ cells and a secondary rabbit anti-mouse Ig antibody coupled to hemocyanin. Homozygotes (tw18/tw18) diagnosed on morphological grounds are more densely labeled primarily on those cell types affected by genetically caused dysfunction. Eight-celled tw18 embryos are not labeled. This finding of embryonic cell type specificity, together with the available evidence for stage specificity, implicate a function for t-antigens in embryonic development.

Animals↗
PubMed1983

Carbohydrate changes in pre- and peri-implantation mouse embryos as detected by a monoclonal antibody.

We have examined the tissue and embryonic distribution of an antigen on a large polysaccharide that is recognized by a monoclonal antibody, IIC3, prepared against F9 teratocarcinoma cells. By immunofluorescence the antigen is first detected on compacted morulae and early blastocysts. It is strongly expressed on the primary endoderm and trophoblast of expanded blastocysts, but then disappears from the trophoblast of attached blastocysts in vitro. The binding of the antibody is completely inhibited by D-galactose and N-acetylgalactosamine. Fluoresceinated lectins were used to study further the changes in cell surface carbohydrates on trophoblast during implantation. Ricinus I, specific for terminal galactose, binds to preimplantation stages but does not bind to the trophoblast of the attached blastocyst. On the other hand, wheat germ agglutinin, specific for N-acetylglucosamine and sialic acid, binds to all preimplantation embryos and also to attached blastocysts (embryo proper and trophoblast). Neuraminidase treatment of blastocyst outgrowths enhances binding of both IIC3 and Ricinus I to the trophoblast; conversely, the binding of wheat germ agglutinin is decreased by this treatment. The results obtained in this study show changes of cell surface carbohydrates during early mouse development and suggest that sialic acid may be masking molecules on the surface of the trophoblast at the time of implantation.

Animals↗
PubMed1983

Cis-trans test shows a functional relationship between non-allelic lethal mutations in the T/t-complex.

Recessive lethal mutations in the T/t-complex of the mouse characteristically show defective genetic complementation, even when they affect very different stages of embryogenesis and are known to be nonallelic. To address the question of their genetic or functional relationship, we have applied the cis-trans test, using several well defined recombinant t-chromosomes that carry two or more lethal mutations, and others that are devoid of specific lethals. We show here that the defective complementation that occurs between different t-lethals is a specific result of the trans configuration; thus these genes, which may map as much as 15 cM apart, constitute a functional unit. Some speculations are presented to interpret this enigma in terms of DNA plasticity.

Alleles↗
PubMed1983

Physical dosimetry of 125I seeds of a new design for interstitial implant.

The physical characteristics of a new 125I seed, consisting of radioactive iodine absorbed on a silver wire and contained in a sealed titanium shell, have been measured. Advantages of the new seed design are: increased radiopacity, possible determination of seed orientation in an implant for dosimetric calculations, and source strength specification traceable to the National Bureau of Standards. Spectroscopic analysis of the new seed using an intrinsic Ge detector revealed the 27.4, 31.4 and 35.5kev photons from the decay of 125I, and in addition, 22.1 and 25.2kev fluorescent X ray from the silver wire. Measured and calculated relative dose distribution along the perpendicular bisector of the new seed is similar to that of the existing seed, with a slightly more rapid fall-off due to the existence of the lower energy photons. The measured angular distributions of the seeds of the two designs are similar, exhibiting significant anisotropy. A protocol of source strength specification, choice of effective gamma constant value and dose calculation relative to 125I implants is suggested.

Brachytherapy↗
PubMed1983

Changes in body composition and muscle protein degradation during nutritional supplementation in nutritionally growth-retarded children with cystic fibrosis.

Changes in body composition and muscle protein degradation were studied in seven nutritionally growth-retarded children with cystic fibrosis (CF) before and after nutritional supplementation and in eight healthy children who served as controls. Supplemental feedings consisted of a peptide formula that increased dietary protein and energy intakes approximately 20-40% over a 6-month period, delivered either as oral supplement or overnight intragastric feeding. Body composition was assessed by anthropometric data and measurements of whole body potassium (40K) and creatinine excretion. Muscle protein degradation was measured by urinary 3-methylhistidine excretion, an index of myofibrillar protein catabolism. Compared with controls, CF children had significantly reduced body mass, body fat, and muscle mass, and a significantly increased rate of myofibrillar protein degradation. With nutritional supplementation, significant catch-up weight gain and improved linear growth were observed with evidence of accretion of lean body mass and muscle mass, and in all but one severely malnourished patient with progressive disease, there was normalization of the high rate of muscle protein degradation. Thus, this form of nutritional therapy has significant benefits in terms of body protein accretion and myofibrillar protein degradation.

Adolescent↗