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Biomedical subjects

S L White

Publications and source records attributed to S L White.

At least 109 records · Page 6Linked to original sources
PubMed1982

Sperm specific antigen(s) in detergent extract of rhesus monkey spermatozoa.

Sperm surface antigens were prepared by detergent extraction (Hyamine-Triton, Rohm and Haas Co., Philadelphia, PA) of spermatozoa from rhesus monkeys. Heterologous antisera against the extracts were produced in female New Zealand White (NZW) rabbits by hyperimmunization. The antiserum was absorbed initially with sperm-free monkey seminal plasma and then with lyophilized tissue homogenates of liver, kidney, spleen, and pancreas from male rhesus monkeys. The unabsorbed antiserum produced at least three precipitin lines against detergent extract in double immunodiffusion tests and possessed sperm immobilization and sperm agglutination antibody activity. The absorbed antiserum showed one precipitin line against the detergent extract and retained sperm agglutination antibody activity only. The sperm agglutination antibody in the absorbed antiserum was completely removed by either epididymal or washed ejaculated rhesus monkey spermatozoa. The same results were obtained with ammonium-sulfate-precipitated immunoglobulin preparations. Immunoelectrophoresis revealed only one precipitation line with the absorbed immunoglobulin preparation. It is concluded that Hyamine-Triton extract of rhesus monkey spermatozoa contains a component which can be characterized as sperm-specific by immunoabsorption techniques and is apparently associated with sperm agglutination but not with immobilization.

Animals↗
PubMed1981

The impact of mental health services on medical care utilization: economic and organizational implications.

A wealth of studies support the assertion that patients seen by medical doctors for physical complaints can often be helped by psychotherapeutic intervention. Many physical ailments have been linked to emotional problems, and practitioners are beginning to understand that emotional and physical health are highly interrelated. Even very brief mental health intervention can reduce the number of visits for medical care, the studies show. Despite some obvious methodological shortcomings, past studies and literature reviews strongly endorse the development of a closer working relationship between mental health and physical health professionals. The need for extensive additional research with sound methodological design is discussed. The economic and organizational implications of this relationship are also explored from the perspectives of physical and mental health practitioners, patients, group health plans, and third-party payers.

Adolescent↗
PubMed1981

Effect of ionophores on survival, penetration, and development of Eimeria tenella sporozoites in vitro.

Free Eimeria tenella sporozoites were exposed to the anticoccidial ionophores monensin, lasalocid, narasin, or salinomycin for 4 hr at 40 C, whereupon the drugs were removed by dilution centrifugation and the parasites inoculated into cultures of chick kidney cells. Cultures were fixed and stained at 4 and 96 hr postinoculation to determine the effect of ionophore uptake by the extracellular sporozoites on invasion and development. Pretreatment with each of these antibiotics significantly reduced the number of intracellular sporozoites and dramatically inhibited asexual development. These effects were dose-dependent. Exposure of free (extracellular) sporozoites to monensin at 40 C caused a significant decline in the number of surviving organisms over time as compared to nontreated sporozoites. This response also appeared to be dose-dependent. Scanning and transmission electron microscopy revealed that the surface of the treated sporozoites was very irregular and the organisms often exhibited a gross swelling. These results indicated that free Eimeria tenella sporozoites may incorporate a potentially lethal concentration of the polyether ionophorous antibiotics and that a coccidiocidal activity may be expressed whether or not penetration of host's cells occurs.

Animals↗
PubMed1977

Electron microscopy of fibers and discs of hemoglobin S having sixfold symmetry.

Aggregated forms of deoxyhemoglobin S were examined with a field emission transmission electron microscope. Images of isolated helical fibers were obtained from sickled cell lysates stained directly on the electron microscope grid. Optical and digital analyses of the electron micrographs showed that the fibers are similar to those characterized by J. T. Finch, M. F. Perutz, J. F. Bertles, and J. Döbler [(1973) Proc. Natl. Acad. Sci. USA 70, 718-722] in that they consist of stacked discs each composed of six hemoglobin molecules. The fibers exhibit an outer diameter of 160-170 A and an inner diameter of about 60 A with an axial spacing of 58 A per disc. The fiber can be described as a helix consisting of 56 discs per helical turn. We observed discs of six hemoglobin molecules, which may be stable substructural components of the fibers. They were observed in preparations of hemoglobin fibers and exhibited 6-fold symmetry by power spectrum analysis. A reconstructed image of a disc digitally filtered for 6-fold symmetry has a maximum external diameter of approximately 170 A and a central hole of 60 A diameter and is similar to the axial projection of a single disc from a low-resolution, three-dimensional reconstructed model of a fiber.

Computers↗
PubMed1976

Titration of the carboxyhemoglobin tetramer-dimer equilibrium by inositol hexaphosphate.

The results of a series of light scattering experiments of the reaction of inositol hexaphosphate (at pH 7.0) over 6 orders of magnitude of concentration (10(-8) to 10(-2) M) with carboxyhemoglobin indicates that there is a shift in the tetramer-dimer equilibrium towards the tetramer, reaching a maximum effect at 0.1 mM inositol hexaphosphate. Raising the phosphate concentration beyond this latter value promotes dissociation to dimers. However, in this range some of the dissociation of carboxyhemoglobin was undoubtedly due to the increase in ionic strength from the inositol hexaphosphate ion. If the effect of ionic strength is allowed for by classical Debye-Hückel theory, one- and possibly two-phosphate binding sites per dimer can be detected. (Approximate association constant is 8000 M-1 for a single site at 0.1 ionic strength). The location of such sites is considered to lie near the dissociable plane of the hemoglobin tetramer and possibly to include half of the residues that bind inositol hexaphosphate in the tetramer.

Binding Sites↗
PubMed1976

A comparison of the prophylactic and therapeutic effects of poly I:C and endotoxin in mice infected with Mengo virus.

We have compared the protective effect in AKR mice of poly I:C and bacterial endotoxins against lethal doses of Mengo virus. Administered intravenously or intraperitoneally, both interferon inducers protected mice to about the same extent from virus challenges of 2-3 LD50's. Endotoxin, however, was unable to protect the mice effectively against higher challenge doses of virus. Evidence is presented that the level of protection afforded by both inducers is related to the level of circulating interferon produced. We have also shown that a single intravenous dose of poly I:C results in the appearance of two distinct bursts of interferon activity, with maxima at about 2 h and 9 h post injection. Endotoxin, on the other hand, produced only one peak of activity, at 2 h post injection.

Animals↗
PubMed1975

The molecular dissociation of ferrihemoglobin derivatives.

Measurement of the dissociation constants of ferrihemoglobin by light scattering indicates that the quaternary structure is altered by the type of heme ligand. Fluoromethemoglobin and aquomethemoglobin, high spin derivatives with weak ligands, have tetramer-dimer dissociation constants of 80 and 50 muM, respectively. For low spin cyanmethemoglobin the dissociation constants were 1 muM (pH 6.0) and 3 muM (pH 9.0) under the general conditions of 0.1 ionic strength and 25 degrees. Of the ferrihemoglobins studied, alkaline methemoglobin (pH 9.0) has the lowest dissociation constant (0.2 muM). Dissociation constants of mixtures of alkaline and fluoromethemoglobin were significantly higher than that of the alkaline form alone. At pH 9.0 the 55 and 78% fluoride-bound derivatives had tetramer-dimer dissociation constants of 0.7 and 2 muM, respectively. The cyanmethemoglobin quaternary conformation was found to be less affected by pH than the fluoromethemoglobin and aquomethemoglobin conformations. Measurement of the dissociation constant (0.2 muM) for aquomethemoglobin-inositol hexaphosphate indicates stabilization of the tetramer by this organic phosphate. The extent of stabilization by inositol hexaphosphate does not appear to be that found for deoxyhemoglobin as suggested by Perutz (Perutz, M. F. (1972) Nature 237, 495-499) even though inducement of higher spin and iron-heme plane displacement may occur.

Calorimetry↗
PubMed1975

A microplaque reduction assay for human and mouse interferon.

A microplaque reduction assay for human and mouse interferons is described, using plastic disposable multicompartmental plates with flat-bottomed wells of 6 mm in diameter. The procedure is rapid and reproducible and lends itself to a considerable degree of automation. Its potential application in other areas of virology, such as rapid screening of samples for virus content or assay of neutralizing antibodies, is also discussed.

Cell Line↗
PubMed1975

Expression of congenital defects in the haemopoietic micro-environment. Erythroid and granulocyte-macrophage progenitor cells in pre-natal 'steel' (Slj/Slj) anaemic mice.

The erythropietin sensitivities of dissociated cell cultures and explanted fragments of fetal livers of congenitally anaemic Slj/Slj mice, and their normal littermates, have been compared. The erythropoietin responsiveness of Slj/Slj foetal liver cells is deficient in both types of culture. The maximum liver complement of erythroid colony forming cells (CFUe) occurs on the 16th day of development when 'normal' livers contain approximately 6 X 10(5) erythroid colony forming cells/liver. In Slj/Slj fetuses the maximum reached is only 1 X 10(5). Granulocyte-macrophage colony forming cells (CFUc) in Slj/Slj fetal livers are also reduced to approximately 60% of normal numbers. Erythroid colony forming cells are also reduced in the spleen and femoral bone marrow of Slj/Slj mice in the 2-3 days preceding birth. Granulocyte-macrophage colony forming cells are rare in the femoral marrow of pre-natal Slj/Slj mice, but their production in the Slj/Slj pre-natal spleen appears unaffected.

Anemia↗
PubMed1975

The relationship between erythropoietin-dependent cellular differentiation and colony-forming ability in prenatal haemopoietic tissues.

Levels of haem synthesis achieved by foetal liver erythroblasts responding to erythropoietin in vitro are similar in dissociated cell cultures and in cultures of organized tissues. Erythroid colony-forming cells reach maximum numbers on the sixteenth day of gestation. Their presence in foetal liver is associated with the period of most rapid production of erythrocytes, and with in vitro sensitivity to erythropoietin measured as enhanced haem synthesis. It is concluded that at least a proportion of erythroid colony-forming cells in the foetal liver are dependent on erythropoietin in situ and that these cells are separated from the earliest recognizable pro-erythroblast by 1-2 cell divisions. Populations of granulocyte-macrophage colony-forming cells change independently of erythroid colony-forming cell numbers.

Animals↗