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Biomedical subjects

R Weil

Publications and source records attributed to R Weil.

At least 199 records · Page 11Linked to original sources
PubMed1973

Dansyl-galactoside, a fluorescent probe of active transport in bacterial membrane vesicles.

A fluorescent galactoside, 2-(N-dansyl)-aminoethyl beta-D-thiogalactoside (dansyl-galactoside), competitively inhibits lactose transport by membrane vesicles of Escherichia coli, but is not actively transported. An increase in dansyl-galactoside fluorescence is observed upon addition of D-lactate. The fluorescence increase is not observed in membrane vesicles lacking the beta-galactoside transport system, and is blocked or rapidly reversed by addition of beta-galactosides, sulfhydryl reagents, inhibitors of D-lactate oxidation, or uncoupling agents. The fluorescence increase exhibits an emission maximum at 500 nm and excitation maxima at 345 nm and at 292 nm. The latter excitation maximum is absent unless D-lactate is added, indicating that the bound dansyl-galactoside molecules are excited by energy transfer from the membrane proteins. Titration of vesicles with dansyl-galactoside in the presence of D-lactate demonstrates that the beta-galactoside carrier protein represents about 3.3% of the total membrane protein. The data indicate that D-lactate oxidation leads to binding of the fluorescent galactoside to the beta-galactoside carrier protein in such a manner that the dansyl group is transferred to a hydrophobic environment within the membrane.

Binding Sites↗
PubMed1973

"Early" virus-specific RNA may contain information necessary for chromosome replication and mitosis induced by Simian Virus 40.

Simian Virus 40 (SV40) induces in "contact-inhibited" tissue culture cells of mouse kidney an abortive infection that leads to the appearance of intra-nuclear SV40-specific tumor (T-) antigen, followed by replication of the mouse-cell chromatin and mitosis, while no viral progeny DNA or capsid protein is produced. Synthesis of "early" SV40-specific RNA ("19S RNA") begins a few hours before the appearance of T-antigen and appears to be switched off after the onset of chromatin replication. As the most simple working hypothesis that can account for the experimental results available, we assume that early SV40 RNA contains information necessary for production of T-antigen and that this antigen (or an unknown early virus-specific function that would simply parallel the appearance of T-antigen) activates or de-inhibits a cellular regulatory element that governs chromosome replication and mitosis. The experimental results agree with the idea that SV40 acts primarily as a mitogen.

Animals↗
PubMed1973

Interferon: evidence for its glycoprotein nature.

In an attempt to understand the structure of rabbit interferon, the possibility of carbohydrate being part of the molecule was tested. Interferon incubated with neuraminidase from Vibrio cholera is homogeneous in charge as revealed by isoelectric focusing. Treatment of "asialointerferon" with galactose oxidase (EC 1.1.3.9) from Dactylium dendroides and subsequent reduction with tritiated sodium borohydride yields labeled material with unimpaired antiviral activity. Enzymic incorporation of N-[(14)C]acetylneuraminic acid into tritiated asialointerferon restores the original charge heterogeneity. The newly generated sialointerferon contains both (3)H and (14)C activity. Asialointerferon is retained by an affinity column containing phytohemagglutinin from Phaseolus vulgaris and can be displaced from the adsorbent by a glycoprotein of known structure. It is concluded that rabbit interferon is a glycoprotein containing the terminal oligosaccharide sequence sialic acid --> galactose.

Animals↗
PubMed1971

Analysis of the events leading to SV40-induced chromosome replication and mitosis in primary mouse kidney cell cultures.

Abortive infection with simian virus 40 in confluent, "contact-inhibited", mouse kidney cell cultures was studied. The sequential events, in individual cells, are tentatively represented by the simplified scheme: (a) transcription of early virus-specific (messenger) RNA; (b) appearance of T-antigen; (c) [psychrosensitive event(s)]; (d) chromosome replication; (e) normal or abnormal mitosis. No evidence for the replication of viral progeny DNA was obtained. The sequence of the events (a)-(d) is analogous to that observed in contact-inhibited mouse kidney tissue culture cells during lytic infection with polyoma virus.

Animals↗
PubMed1971

Transcription of the polyoma virus genome: synthesis and cleavage of giant late polyoma-specific RNA.

The size of virus-specific RNA synthesized in cultured mouse kidney cells infected with polyoma virus was estimated by electrophoresis and sedimentation analysis of RNA extracts from whole cells. Newly synthesized "late" polyoma-specific RNA appears as "giant" molecules of heterogeneous size, up to several times larger than a strand of polyoma DNA (1.5 x 10(6) daltons). Treatment with dimethylsulfoxide or urea showed that the large size of these molecules is not due to aggregation. Giant polyoma-specific RNA is strikingly similar in size distribution to "nuclear messenger-like" RNA ("heterogeneous nuclear" RNA) of the host cell. Subsequent to its synthesis, some of the giant polyoma-specific RNA appears to be cleaved to at least three smaller species.

Animals↗