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Biomedical subjects

J H Jean

Publications and source records attributed to J H Jean.

11 recordsLinked to original sources
PubMed1991

Fusion of sphingomyelin vesicles induced by proteins from Taiwan cobra (Naja naja atra) venom. Interactions of zwitterionic phospholipids with cardiotoxin analogues.

Egg sphingomyelin vesicles were used to assay aggregation/fusion activities of proteins from Taiwan (Naja naja atra) venom to avoid the problem of phospholipase A2 contamination during protein purification. It led to the identification of a new cardiotoxin (CTX) analogue protein (CTX V) with major aggregation/fusion, but few hemolysis, activities. On the contrary, cardiotoxin (CTX III) induced significant hemolysis of human red blood cells but exhibited few aggregation/fusion activities. To study the structure/activity relationship of these CTX-induced processes, the amino acid sequence of CTX V was determined and its aggregation/fusion activity was compared with that of CTX III by transmission electron microscopy, quasielastic laser light scattering, differential scanning calorimetry, and fluorescence spectroscopy. The results show that the CTX-induced fusion process at temperatures slightly above that of the gel to liquid-crystalline phase transition of sphingomyelin vesicles can ultimately convert small sonicated vesicles into large fused vesicles with sizes of 1-2 microns. The abilities of CTX V to induce the leakage of sphingomyelin vesicles content and to cause the fusion of vesicles are approximately 10-fold higher than those of CTX III. Based on the CTX structures determined in the present and other studies, it is suggested that the amino acid residue X within the well conserved sequence of -Cys-Pro-X-Gly-Lys-Gln-Leu-Cys- plays a role in the interaction of CTX with lipid molecules. The lipid phase transition could further enhance the protein-lipid interaction in the process leading to the fusion of vesicles.

Amino Acid Sequence↗
PubMed1979

Chronically persistent infection with human cytomegalovirus in human lymphoblasts.

Cells from a line of human lymphocytes originating from a leukemic patient were persistently infected with human cytomegalovirus. Assays of infectious centers and fluorescent antigen staining indicated that 1%--10% of the cells were infected. It appears that persistent infection is due to an equilibrium between the release of virus by infected host cells and the growth of uninfected cells rather than to defective virus or temperature-sensitive mutants.

Antigens, Viral↗
PubMed1978

Characterization of the replicative structures of the DNA of a herpesvirus (pseudorabies).

The replication of PRV DNA occurs in two phases, early and late. During the early stages of infection newly synthesized DNA is associated with molecules sedimenting with an S-value up to two-fold greater than that of mature viral DNA. These molecules represent unit-size linear or circular molecules, as well as small concatemers in the process of replication. Initiation of replication occurs at a site situated 20 micron from one of the ends as well as at or near the end of the molecules. At later times, newly synthesized DNA is associated with large, "tangled" concatemers containing single-stranded segments of DNA. Our results indicate that at least some of the single-stranded DNA may be produced during the extraction procedure. Analysis of the large, "tangled" concatemers with restriction enzymes shows that they consist of linear arrays of viral DNA molecules.

Centrifugation, Density Gradient↗
PubMed1976

Appearance in vivo of single-stranded complementary ends on parental herpesvirus DNA.

Intracellular forms of pseudorabies virus parental DNA were examined before and after the onset of viral DNA synthesis. Before initiation of synthesis, parental viral DNA acquires single-stranded ends. Circular and concatemeric molecules are also observed, indicating that the single-stranded ends are complementary. Viral DNA replication is initiated at an internal site within the DNA molecule, giving rise to characteristic replicative loops with single-stranded regions in the trans position. Such replicative loops were seen in unit-size (and smaller than unit-size) linear molecules as well as in circular and concatemeric molecules. These results show that the parental viral DNA molecules that acquire single-stranded ends, and consequently are able to form circles and concatemers, proceed to replicate.

DNA Replication↗