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Biomedical subjects

S Y Lin

Publications and source records attributed to S Y Lin.

At least 361 records · Page 20Linked to original sources
PubMed1977

Mechanism of anticholinesterase activities of cardiotoxin, protamine and polylysine.

Cardiotoxin, protamine and polylysine are potent inhibitors of various cholinesterases. CaCl2 and MgCl2 overcome the inhibition. The order of addition of the inhibitor and the protecting agent (MgCl2) influences the final degree of the inhibition observed. These findings suggest that cardiotoxin, protamine and polylysine inhibit cholinesterases by the ionic binding of their basic groups with the anionic sites of cholinesterase molecules.

Animals↗
PubMed1976

The binding of lac repressor and the catabolite gene activator protein to halogen-substituted analogues of poly[d(A-T)].

We have measured the binding of two regulatory proteins to the complete halogen-substituted series of poly[d(A-T)] analogues. Both the lac repressor and the catabolite gene activator protein were found to bind more strongly to all of the halogen-substituted DNAs than they do to poly[d(A-T)]. For both proteins, the order of binding preference is poly[d(A-ioU)] is greater than poly[d(A-brU)] is greater than or equal to poly[d(A-clU)] is greater than poly[d(A-flU)] is greater than poly[d(A-T)]. Quantitative data on the binding of these proteins to poly[d(A-U)] is also given. The significance of these results for the mechanism of protein-DNA interaction is discussed. This is the first report that an activator protein binds more strongly to a halogen-substituted DNA; we discuss this result with regard to the mechanism of action of bromodeoxyruidine and other halogen-substituted base analogues on the inhibition and induction of differentiation in eucaryotic cells.

Bacterial Proteins↗
PubMed1975

Comparative studies on the biological activities of cardiotoxin, melittin and prymnesin.

The actions of cardiotoxin (CTX), melittin and prymnesin were compared on dog erythrocytes, chicken biventer cervicis muscle, rabbit conjunctiva, acetylcholinesterase, succinate-cytochrome c reductase and turbidity of the rat liver mitochondrial suspension. 1. CTX and melittin were approximately equipotent in the various biological activities, while prymnesin was not. 2. The rate of direct ehmolysis induced by CTX was slow, while that induced by either melittin or prymnesin was fast. 3. Phosphate ions, 10mM Ca++, as well as 1 mM reduced glutathione, considerably inhibited the CTX-induced hemolysis, but only slightly inhibited that induced by melittin or prymnesin. 4. CTX, melittin and prymnesin caused contracture of the chicken biventer cervicis muscle. Prymnesin was much less active in this preparation as compared with its hemolytic potency. The CTX contracture was completely inhibited by high Ca++ (10mM) medium, while the melittin contracture was not. 5. The rate of CTX contracture to reach the peak tension was increased when the concentration of CTX was increased, while the rate of melittin contracture did not change very much as the concentrations varied. 6. All three toxins caused a local irritation of the conjunctival sac of the rabbit eye. 7. Both CTX and melittin inhibited acetylcholinesterase and succinate-cytochrome c reductase activities, and also increased the turbidity of the rat liver mitochondrial suspension, while prymnesin was totally inactive in these respects. It is concluded that the mechanism of actions of these toxins may be different at the molecular level. The role of the detergent properties of these toxins in their biological activities is discussed.

Acetylcholinesterase↗
PubMed1974

Photochemical attachment of lac repressor to bromodeoxyuridine-substituted lac operator by ultraviolet radiation.

The transducing phage lambdah80dlac carries the lac operator, whereas wild-type lambdah80 does not. We find that in high salt (0.18 M KCl), ultraviolet radiation causes the formation of a very stable complex between repressor and 5-bromodeoxyuridine (BrdU)-substituted lambdah80dlac but not to BrdU-lambdah80 DNA. Studies with inducers of the lac operon confirm the specificity of attachment. In low slat (0.01 M KCl), ultraviolet radiation will also attach repressor nonspecifically to BrdU-lambdah80 DNA. The stability of the complex suggests that covalent bonds are formed. We also report that another regulatory protein, the catabolite gene activator protein, can be attached similarly to DNA.

Binding Sites↗
PubMed1973

Seasonal infection of Culex mosquitos and swine with Japanese encephalitis virus.

A year-round study of the infection rates of JE virus in Culex mosquitos was made during 1970-71 in 2 hamlets in Taoyuan County, China (Province of Taiwan). JE virus was recovered from 5 of 314 pools of C. annulus, and from 1 of 22 pools of C. tritaeniorhynchus; these recoveries occurred during a 14-day period in July 1971. None of the 288 pools of C. p. fatigans, which had been collected between October and April, was positive. In addition, sentinel swine were assessed for antibody and virus. All the pigs became highly immune by 23 July; in each hamlet all the pigs had become infected within 1 week, virus being detected in them for only 1-2 weeks. Virus-positive mosquitos appeared to have obtained their infections at about the time that viraemia was occurring in the sentinel swine. These observations illustrate once again the lower infection rate and shorter duration of virus-positive mosquitos in China (Province of Taiwan) as compared with Japan.

Animals↗
PubMed1972

Lac operator analogues: bromodeoxyuridine substitution in the lac operator affects the rate of dissociation of the lac repressor.

As measured by a decreased rate of dissociation, lac repressor binds 10-times tighter to 5-bromodeoxyuridine-substituted lac operator than it does to normal lac operator. This result is obtained both in the absence and in the presence of isopropylthiogalactoside, an inducing ligand. These data are significant with regard to the mechanism of sequence-specific protein-DNA interaction, and also suggest a possible explanation for the effects of bromodeoxyuridine on the expression of differentiated functions in eukaryotic cells.

Bacterial Proteins↗
PubMed1972

The effect of vaccination with a live attenuated strain of Japanese encephalitis virus on stillbirths in swine in Taiwan.

Since an excellent candidate strain (M) for live virus vaccination of swine against Japanese encephalitis was developed, a number of large vaccination programmes have been implemented in Japan with the aim of controlling Japanese encephalitis epidemics in man by reducing the population size of nonimmune swine. Encouraging results have been obtained but no studies have been made on the benefits of live-virus vaccination to the industry. In order to determine the effect of vaccination upon the number of stillbirths occurring in the Japanese encephalitis post-emergence season, a total of 74 vaccinated, and subsequently mated, gilts at a large breeding farm in subtropical Taiwan were subjected to follow-up observations in comparison with a control group. The total incidence of litter stillbirths in the vaccinated group (1/74) was significantly lower than that in the control group (21/68). Over 92% of the newborn piglets from the vaccinated gilts were healthy, while 31.6-54.1% of the newborn piglets in the control groups were stillborn. The litter size of vaccinated gilts was larger than that of the control gilts. The vaccine was shown by tests in 22 swine to have an adequate degree of safety. Four weeks after vaccination with either 10(5.6) or 10(8.0) smicLD(50) of virus, all the swine developed an adequate level of antibody. The results indicate that live virus vaccination could benefit the industry in addition to achieving the main aim of controlling Japanese encephalitis viraemia in swine.

Animals↗