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Biomedical subjects

H Will

Publications and source records attributed to H Will.

At least 217 records · Page 12Linked to original sources
PubMed1984

Cloned duck hepatitis B virus DNA is infectious in Pekin ducks.

Approximately 10% of German-bred Pekin ducks were found to be chronically infected with duck hepatitis B virus (DHBV). The genomes of three German DHBV isolates analyzed were closely related but showed substantial restriction site polymorphism compared with U.S. isolates. We tested the infectivity of three sequence variants of cloned DHBV DNA by injecting them into the liver of virus-free ducklings. Most of these animals injected with double-stranded closed-circular or plasmid-integrated dimer DHBV DNA developed viremia, demonstrating the infectivity of all three cloned DHBV DNA variants. The cloned viruses produced were indistinguishable from those from naturally infected animals, implying that our experimental approach can be used to perform a functional analysis of the DHBV genome.

Animals↗
PubMed1984

HBV-DNA in sera of patients with HBsAg-positive primary liver cell carcinoma.

Sera of ten patients with HBsAg-positive primary liver carcinoma were tested for anti-HBc-IgM and HBV-DNA. Five patients were positive for anti-HBc-IgM and six for HBV-DNA. There was no correlation between the presence of anti-HBc-IgM and HBV-DNA. Our study suggests that complete viral replication exists in some HBsAg-positive primary liver carcinomas.

Aged↗
PubMed1983

Early presence of phospholamban in developing a chick heart.

Phosphorylation of phospholamban and development of reticular Ca2+ transport were studied in crude membrane preparations of embryonic, newborn and adult chick heart. Maximal phosphorylation of phospholamban by added catalytic subunit of cyclic AMP-dependent protein kinase increases from embryonic day 4-15. It decreases with further development. In the same membrane preparations active Ca2+-uptake into vesicles of sarcoplasmic reticulum rises from day 4-7 and decreases then slightly until day 20. A several-fold increase in Ca2+-transport activity occurs at the time of hatching. The data indicate separate genetic control for synthesis of phospholamban and sarcoplasmic reticulum Ca2+-ATPase.

Aging↗
PubMed1983

Detection of an element of the SV40 late promoter in vectors used for expression studies in COS cells.

Plasmids containing hepatitis B virus (HBV) DNA and a 232-bp SV40 DNA fragment encoding the origin of replication were constructed. When introduced by transfection into COS cells, these plasmids directed the synthesis of hepatitis B surface antigen. S1 mapping of the mRNAs covering the S gene showed that transcriptional initiation was promoted by the interaction of HBV sequences with an SV40 promoter element: transcription started on HBV DNA but had several properties of SV40 late transcription. The detection of a promoter element in an SV40 origin fragment commonly used in the COS system is important for the interpretation of data deriving from expression studies in COS cells.

Animals↗
PubMed1983

Characterization of endogenous phosphorylation in isolated cardiac sarcolemma.

The cardiac sarcolemma contains kinases which catalyze the incorporation of 32P-phosphate into acid stable and acid precipitable membrane components of low molecular weight. The phosphorylation is not influenced by cyclic AMP or calmodulin. Analysis of phosphorylation products using proteolytic digestion, organic solvent extraction, thin layer chromatography and gel filtration reveals both polypeptides and lipids as kinase substrates. Polypeptides are phosphorylated at their serine and threonine residues, while lipid phosphorylation gives rise to 32P-labelled phosphatidylinositol phosphates and some nonidentified compounds. Phosphorylated polypeptides and phosphorylated lipids do not separate in SDS polyacrylamide gel electrophoresis. On the basis of the fast time course of 32P-phosphate incorporation, it may be supposed that endogenous phosphorylation may play a role in the short term regulation of the cardiac sarcolemmal function.

Animals↗
PubMed1983

Hepatitis B after infection of a chimpanzee with cloned HBV DNA.

Transfection of chimpanzee liver cells in vivo or in vitro with cloned HBV DNA induced typical hepatitis B in the inoculated animal. Intravenous inoculation of a 1000-fold greater dose of the same cloned HBV DNA did not induce infection or disease. The experiment proved that cloned HBV DNA is fully functional and that the nick gap structure, proteins covalently linked to the HBV genome, or any other HBV particle associated protein are not needed for initiation of virus replication.

Animals↗
PubMed1982

Potentiating effect of calmodulin and catalytic subunit of cyclic AMP-dependent protein kinase on ATP-dependent Ca2+-transport by cardiac sarcolemma.

Highly purified sarcolemmal membranes were prepared from pig heart homogenates by differential and density gradient centrifugations. The membrane fragments exhibit ATP-dependent Ca2+-transport and Na+/Ca2+-exchange activities. ATP-dependent Ca2+-transport (K0.5Ca2+ = 0.3 microM; Vmax = 4.6 nmol Ca2+.mg protein-1.min-1) is not stimulated by oxalate. Ca2+-uptake is also not supported by p-nitro-phenylphosphate. Preincubation of sarcolemma with MgATP, calmodulin and catalytic subunit of cyclic AMP-dependent protein kinase stimulates active Ca2+-transport 1.8-fold. The effects of calmodulin and catalytic subunit are potentiating rather than additive. A large portion of the Ca2+ additionally accumulated after prephosphorylation of membranes is exchangeable for Na+ via the Na+/Ca2+-exchange system.

Adenosine Triphosphate↗
PubMed1982

Isolation of cell surface membranes from cultured C6 glioblastoma cells.

Plasma membranes were isolated from C6 glioblastoma cells by two methods. In the first method cells were treated with concanavalin A and lysed in hypotonic medium. After partial separation of plasma membranes from other cell material, the lectin was displaced with alpha-methyl-D-mannoside. In the second method untreated cells or cells iodinated in a lactoperoxidase-catalyzed reaction were homogenized in isotonic medium. Membrane fractions obtained by either homogenization procedure were further purified by rate zonal and equilibrium centrifugations into linear density gradients. Disruption of the glioblastoma cell membrane gives rise to heterogeneous assemblies of membrane fragments. Two populations of plasma membranes were isolated from untreated and from iodinated cells: a "lighter" membrane fraction characterized by relatively lower sedimentation velocity and buoyant density, and a "heavier" membrane fraction of relatively faster sedimentation velocity and higher buoyant density. Both fractions showed electrophoretic patterns similar to those of 125I-labeled cell surface proteins. Their specific (Na+ + K+)-ATPase activity was seven- to eightfold the homogenate activity (recovery, 13.1%). Both fractions were, however, still contaminated by smooth endoplasmic reticulum, as judged from the activity of NADPH-dependent cytochrome c reductase (recovery, 2.4%). It is suggested that plasma membrane fragments present in the two fractions might differ in the organization of their structures, e.g., membrane vesicle intactness and membrane orientation.

Animals↗
PubMed1982

Structure and function of the hepatitis B virus genome.

A preliminary map of the hepatitis B virus genome has been derived from the nucleotide sequence of cloned human hepatitis virus (HBV) DNA. The genes for two viral antigens were identified and their expression was studied using SV40 vector systems. HBV DNA cloned and amplified in bacteria induces hepatitis in chimpanzees demonstrating that the cloned HBV DNA is functionally intact.

Base Sequence↗
PubMed1980

Monoclonal antibody directed against RNA polymerase II of Drosophila melanogaster.

Monoclonal antibodies were raised against purified RNA polymerase II ( or B) from Drosophila melanogaster. The antibody produced by one hybridoma cell clone was found to be directed against the two large subunits of the enzyme. The absence of antibodies directed against proteins possibly contaminating the antigens used for immunization allowed us to identify RNA polymerase unequivocally in interbands and puffs of polytene chromosomes. Within a single heat shock puff (87C1) RNA polymerase was found to be clustered in two separate areas suggesting two distinct regions of RNA polymerase activity in this puff.

Animals↗
PubMed1980

Monoclonal antibodies against chromosomal proteins of Drosophila melanogaster: establishment of antibody producing cell lines and partial characterization of corresponding antigens.

Total nuclear protein from the embryonic D. melanogaster cell line Kc and crude hydroxyapatite fractions thereof were used for immunization of mice. From the spleen cells of these mice we established 755 permanent lymphoid cell lines using the hybridoma technique originally developed by Köhler and Milstein (1975). Radioimmunoassay showed 455 of these cell lines secreted antibodies which bound to component(s) contained in the antigen mixtures used for immunization. Screening of 311 cell lines using indirect immunofluorescence revealed 58 lines whose antibodies showed a highly selective staining pattern on polytene chromosomes from the salivary glands of D. melanogaster third instar larvae. Eight of these cell lines were cloned and further characterized. We were able to order the staining patterns into three distinct classes based on the staining behaviour of the monoclonal antibodies: staining of active regions, staining of phase dark bands or staining of most interbands. The molecular weight of those antigens against which the monoclonal antibodies were directed was determined in SDS polyacrylamide gels.

Animals↗
PubMed1980

Subcellular distribution and some properties of particulate guanylate cyclase of pigeon myocardium.

Most of the particle-bound guanylate cyclase of pigeon heart muscle, which is the predominant form of the enzyme in this tissue, co-purified with calcium pump system of the sarcoplasmic reticular fraction. Specific enzyme activity at 37 degrees C ranged up to 0.67 nmol/mg of protein/min. The K0.5 values for MnCl2, Mn2+ free, and GTP were found to be 0.72, 0.076, and 0.057 mM, respectively. Mg2+ activates and Ca2+ inhibits the enzyme in the presence of Mn2+, whereas carbamylcholine was without effect. The ratio of guanylate cyclase to adenylate cyclase activity was found to be 12:1 in the sarcoplasmic reticulum fraction and 0.5:1 in the sarcolemal fraction. Our findings suggest that the major portion of guanylate cyclase in pigeon myocardium is not directly activated by the interaction of hormones and neurotransmitters with their receptors in the cell surface membrane.

Adenylyl Cyclases↗
PubMed1979

Mass isolation of cell surface membrane fragments from pigeon heart.

Cell surface membrane fragments were isolated and purified by successive rate zonal and isopycnic centrifugation of calcium oxalate-loaded pigeon heart microsomes in sucrose density gradients. The most highly purified cell membrane fraction sediments at a buoyant density of 1.105 g/ml. Some of the membrane pieces are present as open fragments and leaky vesicles, while others form tightly sealed vesicles of both inside-in and inside-out membrane orientation. The pigeon heart cell membrane preparation exhibits high (Na+ + K+ + Mg2+)-ATPase and adenylate cyclase activities. Additional activity of these enzymes is uncovered by sodium dodecyl sulfate and alamethicin, respectively. Electron microscopic inspection of the cell surface membrane preparation revealed (a) a predominance of thick-walled vesicles with smooth surfaces on negative staining and (b) binding of concanavalin A to the bulk of isolated membrane pieces following their incubation with the lectin.

Adenylyl Cyclases↗
PubMed1979

[Function of the rabbit myocardium sarcoplasmic reticulum and the resting potentiation of isolated trabeculae following cholesterol-oil feeding].

It is assumed that the resting potentiation of contraction corresponds to the Ca accumulating activity of the sarcomplasmic reticulum (SR). To test this supposition, resting potentiation and Ca transport by isolated microsomes of the heart were compared. The experiments were done in isolated trabeculae and in hearts of rabbits which had received a lipid-rich diet for 12 weeks. Preparations of control animals were used for comparison. Resting potentiation of the isometric contraction as well as Ca binding and Ca uptake were enhanced by the lipid-rich diet. The results confirm the strong relation between the resting potentiation of contraction and the Ca accumulating activity of the SR. The increased Ca transport may be related to differences in the lipid content of SR membranes.

Animals↗