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Biomedical subjects

T Walker

Publications and source records attributed to T Walker.

At least 91 records · Page 5Linked to original sources
PubMed1989

The specificity of a mouse monoclonal antibody to human aorta proteoglycans.

Mouse monoclonal antibodies to human aorta proteoglycans have been raised. A sensitive radioimmunoassay which can be employed to measure binding of proteoglycans to these antibodies is described. It offers advantages of simplicity and speed over other immunoassays currently employed for proteoglycan determination. One of the monoclonal antibodies, 6D2/B5, recognizes keratan sulfate-bound antigens (e.g. cartilage proteoglycans). Further work has indicated that this antibody is not specific for keratan sulfate, as brain sulfatide and the seaweed polysaccharide, fucoidan, also possess its epitope. The 6D2/B5 antibody can be of value in localizing and estimating keratan sulfate if additional biochemical criteria for keratan sulfate recognition are utilized.

Antibodies, Monoclonal↗
PubMed1989

Use of electron microscopy to characterize the surfaces of flocculent and nonflocculent yeast cells.

The surfaces of flocculent and nonflocculent yeast cells have been examined by electron microscopy. Nonextractive preparative procedures for scanning electron microscopy allow comparison in which sharp or softened images of surface details (scars, etc.) are the criteria for relative abundance of flocculum material. Asexually flocculent budding-yeast cells cannot be distinguished from nonflocculent budding-yeast cells in scanning electron micrographs because the scar details of both are well resolved, being hard and sharp. On the other hand, flocculent fission-yeast cells are readily distinguished from nonflocculent cells because fission scars are mostly soft or obscured on flocculent cells, but sharp on nonflocculent cells. Sexually and asexually flocculent fission-yeast cells cannot be distinguished from one another as both are heavily clad in "mucilaginous" or "hairy" coverings. Examination of lightly extracted and heavily extracted flocculent fission-yeast cells by transmission electron microscopy provides micrographs consistent with the scanning electron micrographs.

Flocculation↗
PubMed1987

Primary prevention of behavior problems in Mexican-American children.

A primary prevention program, the Houston Parent-Child Development Center, directed towards infants and their parents, has effectively reduced the frequency of behavior problems for these children 5 to 8 years after the program's completion. Teacher ratings showed significantly fewer acting-out, aggressive behaviors for program children. Ratings of classroom behaviors found program children significantly less hostile and more considerate than control boys. This appears to be the first primary prevention program to have demonstrated effectiveness in reducing behavior problems over such a long time.

Aggression↗
PubMed1985

Antibody response against schistosomulum surface antigens and protective immunity following immunization with highly irradiated cercariae of Schistosoma mansoni.

The production of antibodies against the schistosomulum surface antigens of Schistosoma mansoni in response to immunization with highly irradiated cercariae was followed. Four antigens were reproducibly identified by 125I surface labelling using Iodogen and immunoprecipitation; they had mol. wts of 38, 32, 20 and 15 kD. In addition a 92 kD antigen was also evident in most experiments. It was demonstrated that the 20 kD antigen was the same as that recognized by the monoclonal antibody NIMP/M.47 and that this antigen like the 38 and 32 kD antigens was thus identified during both chronic infection and following vaccination with irradiated cercariae. Two weeks following immunization with irradiated cercariae antibody was produced only against the 15 kD antigen but at 4 weeks the major response was against the 32 kD antigen. A second immunization with irradiated cercariae boosts the antibody response so that all four antigens were strongly precipitated. Further vaccinations did not lead to the identification of further antigens. Immunization of rats with highly irradiated cercariae also resulted in antibody production against the 38, 32, 20 and 15 kD antigens. Surface labelling of schistosomula transformed from irradiated cercariae resulted in the same four antigens being precipitated as from normal cercariae indicating that irradiation did not affect transformation nor antigen expression on 3h schistosomula. Furthermore, antibodies against the same surface antigens were detectable 4 weeks after immunization with equal numbers of cercariae irradiated with 0, 5, 25 or 50 krad. Vaccination of mice with irradiated, cloned cercariae resulted in identical antibody production and similar levels of immunity directed at both an homologous or heterogeneous challenge. Thus all parasites within our laboratory population appear to express the same antigens and there was no evidence for a genetically defined variation that could account for the partial resistance to reinfection exhibited by mice vaccinated with irradiated cercariae.

Animals↗
PubMed1984

The modulation of expression of polypeptide surface antigens on developing schistosomula of Schistosoma mansoni.

Five low m.w. polypeptide antigens are expressed on the surface of freshly transformed schistosomula of Schistosoma mansoni, and were reproducibly identified by surface labeling with 125I by using IODOGEN and immunoprecipitating with immune mouse sera. These molecules have approximate m.w. of 38,000, 32,000, 20,000, 17,000, and 15,000. They correspond to antigens recognized previously by lactoperoxidase-catalyzed iodination. Analysis of the surface of developing schistosomulum demonstrated that the 38,000 and 17,000 dalton antigens were lost from the parasite surface during 48 hr of in vitro culture. This process was not dependent on the presence of host serum. The two antigens were not lost due to shedding into the culture medium but were apparently sequestered to a site where they were no longer available for surface labeling. The 32,000, 20,000, and 15,000 dalton antigens, however, remained exposed on the schistosomulum surface for up to 2 days of in vitro culture. The expression of two new antigens was also induced by culture in vitro: a doublet of approximately 45,000 daltons and an antigen of approximately 11,000 daltons. The expression of the former was dependent on the presence of serum. These results demonstrate that the development of the schistosomula surface is a complex process, with events both dependent and independent of the presence of serum. In addition, the expression of polypeptide antigens is not coordinated, and antigens are lost, retained, or appear on the schistosomulum surface during the early stages of maturation.

Animals↗
PubMed1983

Comparison of platelet-derived growth factor prepared from release products of fresh platelets and from outdated platelet concentrates.

Platelet-derived growth factor was isolated from the release products of washed, human platelets and from freeze-thawed outdated platelet concentrates. On the basis of sodium dodecyl sulphate polyacrylamide gel electrophoresis and amino acid sequence determination we conclude that platelet derived growth factor released from platelets by the agonist thrombin (EC 3.4.4.13) is structurally similar to that isolated from lysed platelets and from platelet concentrates stored for more than 72 hr at room temperature.

Amino Acid Sequence↗
PubMed1983

Phosphorylation sites for ribosomal S6 protein kinases in mouse 3T3 fibroblasts stimulated with platelet-derived growth factor.

Platelet release products and purified platelet-derived growth factor stimulated the phosphorylation of ribosomal protein S6 in cultured mouse Balb/c 3T3 fibroblasts. The post-nuclear fraction of the stimulated cells was enriched in S6 kinase activity specific for sites resembling those phosphorylated within intact cells in response to PDGF as determined by tryptic peptide mapping. 3T3-S6 sites closely resembled those phosphorylated in S6 of rat hepatocytes stimulated with insulin and included sites for both cAMP-dependent and independent kinases.

Animals↗
PubMed1983

The relative effectiveness of guanidinium and some biguanide salts as denaturants. Assessment against penicillinase.

Penicillinase (penicillin amido-beta-lactamhydrolase, EC 3.5.2.6) has been used as a model for quantitating the effectiveness of several guanidine-derived denaturants. It was chosen because the mechanism of its denaturation by urea and guanidinium chloride has been worked out in detail, because it has a low thermodynamic stability bringing it in the range of weak denaturants, and because its denaturation can readily be followed by enzyme activity as well as by spectroscopic probes. Contrary to previous reports, biguanide HCl is found to be no more effective than guanidinium chloride. The denaturant effectiveness of the various compounds studied is found to increase in the order: guanidinium chloride identical to biguanide HCl less than propylbiguanide HCl less than hexylbiguanide HCl much less than n-decylbiguanide HCl. n-Decylbiguanide HCl is a particularly powerful denaturant, unfolding penicillinase at a concentration of less than 0.015 M.

Biguanides↗
PubMed1982

Sexual development in a homothallic fission yeast: synthesis of readiness proteins resolved by gel electrophoresis.

Sexual development of a homothallic strain of Schizosaccharomyces pombe was monitored by radiolabelling and sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis. Of more than 60 bands detected by Coomassie brilliant blue and by autoradiography, about 30 bands synthesized during development were discrete enough for experimental analysis. About a dozen bands are preferentially vegetative, another dozen preferentially developmental. However, vegetative bands as a group are also synthesized during development. Their synthesis is relatively unaffected by low concentrations of cycloheximide or by chloramphenicol and is not temperature sensitive at 37 degrees C nor catabolite repressible. Only band 40 (ca. 40 000 daltons) seems to be exclusively vegetative. The synthesis of developmental bands 13, 18, 24, 30, and alpha, all of which first appear during late-log phase, is catabolite repressible. Developmental band 51 is also synthesized throughout the vegetative phase. The synthesis of bands 24, 30, 51, and alpha is temperature sensitive at 37 degrees C during the development, but that of band 18 is not. The synthesis of band 13 during development is not temperature sensitive, but its earlier synthesis during late-log phase is. The synthesis of all these six developmental bands is immediately inhibited by cycloheximide, but not by chloramphenicol. Their appearance as a group of radioactive bands is greatly diminished in cultures grown in cycloheximide, in chloramphenicol, or in ethidium bromide. Developmental bands 13, 18, 24, and 30 may be called readiness proteins. They first appear prior to the earliest morphological signs of sexual activity. Their developmental synthesis is inhibited by conditions that inhibit sexual development. Such inhibitory conditions include anaerobiosis, restrictive temperature, aging in stationary phase, the presence of inhibitors of cytoplasmic protein synthesis and of mitochondrial function, and catabolite repression. Readiness proteins may be regulating the switch from vegetative metabolism.

Ascomycota↗
PubMed1978

Leukemic reticuloendotheliosis: polyclonal surface immunoglobulin on "hairy" cells.

The cytochemistry, surface markers and functional properties of purified mononuclear cells obtained from the peripheral blood and spleen of a patient with leukemic reticuloendotheliosis were studied. Nonspecific esterase activity, a monocyte marker, was demonstrable in 83% of the peripheral blood mononuclear cells and 84% of the splenic mononuclear cells. Rosetting techniques failed to detect T or B lymphocyte surface markers on the majority of the cells. Direct immunofluorescence revealed capped, noncytophilic surface immunoglobulin on the cells with all immunoglobulin classes being detectable. Since noncapping conditions ahd been used during immunofluorescence staining, the observed caps were attributed to in vivo binding of autoantibodies to the "hairy" cells. This conclusion was supported by the demonstration of susceptibility of the "hairy" cells to lysis mediated by normal allogeneic lymphocytes. It is postulated that the "hairy" cells in this patient are leukemic monocytes which bear autoantibodies directed against leukemia associated antigens.

Antibodies, Neoplasm↗