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Biomedical subjects

J M Weber

Publications and source records attributed to J M Weber.

At least 163 records · Page 9Linked to original sources
PubMed1984

Pulmonary surfactant.

The mammalian lung is stabilized by a specialized material, the pulmonary surfactant, which acts by reversibly reducing the surface tension at the air-liquid interface of the lung during breathing. Pulmonary surfactant contains approximately 90% lipid and 10% proteins. Dipalmitoyl phosphatidylcholine, the major lipid component, appears to be primarily responsible for the ability to reduce surface tension to near 0 dyn/cm (1 dyn = 10 microN). The other components of pulmonary surfactant promote the adsorption and spreading of this disaturated lecithin at the air-liquid interface. Surfactant activity can be accessed by physical and biological assays. Apparent discrepancies between the results obtained with the Wilhelmy plate surface balance and the pulsating bubble surfactometer have led to the suggestion that separate "protein-facilitated" (catalytic type) and "protein-mediated" (chemical type) processes may be involved in adsorption and (or) spreading at the different surfactant concentrations used with these two techniques. Artificial surfactants, which mimic the essential properties of the natural product with the pulsating bubble surfactometer, can be produced with synthetic lipids. Treatment of prematurely delivered infants suffering from the neonatal respiratory distress syndrome with lipid extracts of pulmonary surfactant leads to a marked improvement in gaseous exchange.

Animals↗
PubMed1984

Grower diets and bird density effects on growth and cannibalism in ring-necked pheasants.

The effects of bird density and dietary protein and energy level on growth rate and feather pecking in Ring-Necked pheasants were investigated in two experiments. After brooding, pheasants in Experiment 1 were housed at densities of .19, .38, or .74 m2/bird and fed grower diets containing 16, 19, or 22% protein. Experiment 2 pheasants were housed at .4 m2/bird and fed diets containing 16 or 22% protein with energy levels of 2530, 2750, 2970, or 3190 kcal/kg. Body weight was not affected by bird density differences, but feather pecking was significantly reduced by increasing floor space per bird. Body weight, cannibalism, and feed conversion were poorer in groups fed the 16% protein diet than those fed the 19 or 22% protein diets. Body weight gains, feed efficiency, and feather pecking scores improved as the energy content of grower diets increased. Significant interactions existed between dietary protein and bird density and between dietary protein and energy for feather picking in pheasants. Total performance was best for groups fed a grower diet of 22% protein and 2970 kcal/kg metabolizable energy level with a floor space of .38 m2 or greater per bird.

Animals↗
PubMed1983

The role of phosphorylation and core protein V in adenovirus assembly.

The role of phosphorylation and the minor core protein V in adenovirus type 2 assembly was examined. Comparison of the phosphoprotein composition of top components (TC), young virions and mature virions of wild-type and assembly mutants showed specific changes related to virus assembly and maturation. TC were identified as precursors of young virions which contain two molecular weight forms of core protein V, one of which is phosphorylated. Conversion of TC into young virions by DNA encapsidation resulted in the loss of the unphosphorylated form of protein V, and subsequent maturation to old virions resulted in the dephosphorylation of the core protein. This last step is blocked by the tsl mutation which inactivates the viral endoproteinase.

Adenoviridae↗
PubMed1983

Single radial hemolysis test for rubella immunity and recent infection.

The single radial hemolysis (SRH) test was compared with the hemagglutination inhibition (HI) test for establishing rubella immune status and diagnosing recent infection. Correlation between mean SRH diameters and HI titers greater than or equal to 1:8 was high (R = 0.99). It is suggested that a level of greater than or equal to 5 IU represents low-level antibody and that greater than or equal to 15 IU is a conservative threshold for designation of immunity. Of 343 sera tested, only 1 false-positive was found by SRH with the 5 IU cutoff level. The SRH test could detect serum antibody levels as low as 2.5 IU, whereas 15 IU was generally the limit of resolution of the HI test. Data from sucrose density gradient fractionation of serum demonstrated that neither rubella-specific immunoglobulin M (IgM) nor early postinfection HI-reactive IgG was detected by SRH. However, diagnostic changes in antibody titer measured by SRH were in general greater than those measured by HI. The SRH test showed diagnostic titer changes in some sera containing specific IgM for which no such changes were detected by the HI test. A 2.5-mm difference in hemolytic zone diameters (a fourfold rise in international units) between acute- and convalescent-phase serum pairs was chosen as being of diagnostic significance. This difference was less than the minimum observed difference of 2.9 mm from 59 serum pairs showing diagnostic changes by HI and far exceeded (greater than 3.6 standard deviations) the within-test and individual variability seen for 95 pregnant women from whom samples were obtained during each trimester.

Antibodies, Viral↗
PubMed1983

Persistence of naturally acquired cell-mediated immunity to rubella virus during the first trimester of pregnancy.

We studied the persistence of naturally acquired cell-mediated immunity to rubella during early pregnancy. We compared lymphocyte transformation responses to phytohemagglutinin and rubella virus in 35 naturally immune women aged 17-37 years, in the first trimester of pregnancy, with 49 naturally immune age-matched nonpregnant controls. A significant lower lymphocyte transformation response to phytohemagglutinin was observed during the first trimester of pregnancy (P = 0.008), but lymphocyte transformation responses to rubella virus were not significantly different (P = 0.901). These data indicate that, in naturally immune women, cell-mediated immunity to rubella virus is not significantly altered by the physiological changes in early pregnancy.

Adult↗
PubMed1982

The effect of reverse protein and low protein feeding regimens in the rearing period on pullet growth, subsequent performance, and liver and abdominal fat at end of lay.

Four brown egg strains were used to study the effect of rearing diets on growth and performance. The treatments were arranged in a 4 x 3 factorial with two replicates of 45 birds. The control diet was formulated and fed to National Research Council recommendations. Birds on reverse protein (RP) were fed diets with 13, 16, and 19% protein and those on low protein (LP) regimen received a 13.5% protein diet with amino acids adjusted on a megacalorie basis to approximate the control diet. At 20 weeks of age pullets were caged and fed a standard layer diet. Logistic curves were fitted to the growth data by a nonlinear least squares method and the parameters of each curve analyzed. No significant strain x diet interactions were observed. There were significant differences among strains in weight gain and feed intake. Dietary regimens had no significant effect on total gain and feed intake. However, diets significantly altered age at one-half maximum growth or inflection point (alpha) and mean growth rate (rho). Inflection point of the growth curve was significantly delayed in birds fed RP and LP diets. Although apparent conversion was not affected by diets, the partition coefficients at any time (t) for maintenance (beta mt) and gain (beta gt) were altered. Neither strain nor dietary regimens affected abdominal fat or organ weights at the end of the rearing period. No significant effect of rearing dietary regimens was detected in age at 50% production or peak production, feed conversion, feed intake, livability, liver fat, abdominal fat, or shell strength. The reverse-protein regimen significantly depressed egg weight. The results of the study indicate that 1) the rearing dietary regimens were adequate for strains of different body weight and egg output characteristics; 2) dietary alteration of growth curve parameters failed to influence production, feed intake, mortality, shell strength, livability, liver fat, or abdominal fat during the production period.

Abdomen↗
PubMed1981

Persistence of humoral and cell-mediated immunity to rubella virus in cloistered nuns and in schoolteachers.

Humoral and cell-mediated immunity to rubella virus after naturally acquired infection were compared in 19 cloistered nuns (29-79 years of age), 18 female schoolteachers (21-61 years of age), and 21 female control subjects (20-30 years of age), who were all seropositive for rubella virus, by use of a hemagglutination-inhibition test, a passive hemagglutination test, a hemolysis-in-gel test, a radioimmunoassay, an enzyme-linked immunosorbent assay, and lymphocyte transformation tests. No significant differences were found among the groups by the radioimmunoassay, the hemolysis-in-gel test, and the enzyme-linked immunosorbent assay. The cloistered nuns had significantly lower cell-mediated immunity to rubella virus than did the teachers and the control subjects but nonetheless showed protective levels of antibody to rubella virus and significant lymphocyte transformation responses, which persisted until age 79 in the probable absence of reinfection.

Adult↗
PubMed1981

The nature of the DNA associated with incomplete particles of adenovirus type 2.

The nature of the DNA in incomplete particles (IP) synthesized by adenovirus type 2 and the ts4 mutant which accumulates such particles were analysed by agarose gel electrophoresis, restriction endonuclease cleavage and blot hybridization techniques. IP DNA consisted of a heterogeneous population of subgenomic-size DNA (IPSD1) and smaller molecules ranging from about 1000 base pairs to 200 base pairs (IPSD2). IPSD1 from ts4 was more heterogeneous than that from wild-type (wt), but both contained sequences from all parts of the viral genome. IPSD2 contained heterogeneous cellular sequences and viral sequences from the left 4.4% of the genome. An endonuclease activity associated with IP and virions was capable of digesting viral or cellular DNA to IPSD2-like fragments suggesting a possible origin for these molecules.

Adenoviruses, Human↗
PubMed1976

Factors influencing the production of interferon from L cells.

The production of interferon from Newcastle disease virus-infected mouse L929 cells was investigated in relation to superinduction procedures, cell density, cellular cyclic adenosine 3',5'-monophosphate (cAMP) levels, and rate of incorporation of 14C-labeled protein hydrolysate into trichloroacetic acid-precipitable material. Densely populated cultures did not have their interferon production enhanced through "superinduction" using cycloheximide, actinomycin D, or the two antimetabolites in combination. These dense cultures produced more interferon per cell than less dense cultures, even though the interferon production from the latter cells could be enhanced two- to threefold by cycloheximide or combined cycloheximide and actinomycin D. Cells in densely populated cultures relative to those from sparsely populated cultures were smaller in volume, had a correspondingly reduced protein content and a lower concentration of cAMP, and were less able to concentrate 14C-labeled protein hydrolysate, although proportionally they were just as efficient in incorporating labeled precursors into trichloroacetic acid-precipitable polypeptides.

Animals↗
PubMed1975

Cyclic AMP potentiation of interferon antiviral activity and effect of interferon on cellular cyclic AMP levels.

Treatment of L cells with 3 to 10 mM 3':5'-cyclic adenosine monophosphate (cAMP) in the presence of interferon was found to potentiate the development of antiviral activity. The dose response of interferon activity at various time periods in the presence and absence of cAMP indicated that potentiation of interferon activity by cAMP occurred at an early stage in the development of antiviral activity. Among the analogues of cAMP tested for interferon-potentiating activity, only the acylated derivatives were found to be active. Combined L-epinephrine and theophylline treatment of cells elevated cellular cAMP levels and also potentiated interferon-mediated antiviral activity. Interferon was also found to elevate cAMP levels in L cells. This activity was limited to biologically active interferon and antagonized the depression of cAMP associated with vesicular stomatitis virus (VSV) infection of L cells. These observations suggest that some aspects of interferon's biological activity is associated with an alteration in cellular levels of cAMP.

Animals↗