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Biomedical subjects

D Bennett

Publications and source records attributed to D Bennett.

At least 235 records · Page 13Linked to original sources
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↗
PubMed1983

Abnormalities of cells and extracellular matrix of T/T embryos.

The dominant mutation T, (Brachyury), of the T/t-complex in the mouse causes severe disorganization in neural tube, notochord, and somites in homozygotes. The use of scanning electron microscopy to investigate the relationships of cells to one another and to the extracellular matrix in the three axial organs and in the head mesenchyme reveals that cells in all areas examined are abnormal in size, shape, and arrangement in T/T embryos. Cells of T/T head mesenchyme and somites are arrayed in flat sheets of broadened cells with fewer cytoplasmic processes than those of normal littermates. The notochord is discontinuous and its surface is exposed rather than covered by a dense matrix as in the normal. Likewise the sheath of the T/T neural tube is less dense than normal. Cell size and shape are very irregular whereas normal neural tube cells are all about the same size. Extracellular matrix in T/T embryos is greatly decreased in all areas.

Animals↗
PubMed1983

Characterization of an antigen present on testicular cells and preimplantation embryos whose expression is modified by the t12 haplotype.

In attempts to identify cell surface molecules specified by lethal genes in the T/t-complex, we prepared a rabbit antiserum that has cytotoxic activity against testicular cells from males heterozygous for t12, but not against wild type cells. However, anti-t12 serum immunoprecipitates the same major component, a glycoprotein of mol. wt. 87,000 daltons, from galactose-labelled C3H. +/t12 testicular cell lysate and from congenic C3H. +/+ lysate, although the gp87 molecule precipitated from +/t12 cells appears to be more highly galactosylated than the +/+ form. The antigen is heavily glycosylated in both genotypes, since when testicular cells are treated with tunicamycin before immunoprecipitation, a protein of 40,000-42,000 daltons is obtained. Gp87 is also present on pre-implantation embryos, and on teratocarcinoma cells, but is barely detectable on any adult somatic cells examined. Its expression is developmentally regulated during pre-implantation stages, but the temporal pattern of its expression appears to be different between wild type and t12 embryos. Thus, we believe we have identified a molecule that may play a role in the differentiation of testicular cells and pre-implantation embryos, and that is either specified by genes in the t12 haplotype, or responsive in some way to the effects of t12.

Animals↗