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Biomedical subjects

J Chin

Publications and source records attributed to J Chin.

At least 163 records · Page 9Linked to original sources
PubMed1983

A monoclonal antibody with ability to distinguish between NH2-terminal fragments derived from fibrinogen and fibrin.

A stable hybridoma secreting homogeneous antibody (immunoglobulin class IgG2a) has been prepared by fusion using cells of immunoglobulin non-secreter myeloma (P3X63Ag8.653) and spleen cells of mice which had previously been immunized with the NH2-terminal CNBr fragment of human fibrinogen, the so-called N-DSK [(A alpha 1-51, B beta 1-118, gamma 1-78)2]. In competitive ELISA or radioimmunoassay this antibody (MAb/1-8C6) cross-reacted with intact fibrinogen, N-DSK, a des fibrinopeptide A (des FPA) variant of N-DSK, the so-called (B)N-DSK, as well as the intact B beta chain (B beta 1-118) obtained from N-DSK. Also, and mot importantly, cross-reactivity was observed with fibrinogen-free ethanol extracts of plasma obtained from patients known to contain high levels of fibrinogen or fibrin degradation products. In vitro thrombin digestion of any of these competitors resulted in complete loss of cross-reactivity. MAb/1-8C6 did not react with the A alpha or gamma-chains of N-DSK, free fibrinopeptide B(FPB), free B beta 15-42, as well as equimolar mixtures of the latter two peptides. These results suggest that MAb/1-8C6 may be to an epitope in or around the thrombin-susceptible B beta 14 Arg-25 Gly bond. Furthermore, due to its reactivity with patient plasma extracts, this antibody may be useful in clinical investigations dealing with fibrino(geno)lysis.

Antibodies, Monoclonal↗
PubMed1983

Evidence for the general base mechanism in carboxypeptidase A-catalyzed reactions: partitioning studies on nucleophiles and H2(18)O kinetic isotope effects.

Methanol does not detectably compete with water in carboxypeptidase-catalyzed cleavage of any substrate, although it is preferentially reactive in a model for the proposed nucleophilic mechanism for the enzyme that involves an anhydride intermediate. To test for such a common intermediate in the cleavage of related peptide and ester substrates, a method has been developed to examine H2(16)O-H2(18)O kinetic isotope-partitioning effects. The finding that benzoylglycylphenylalanine has an isotope effect of 1.019 +/- 0.002 while benzoylglycyl-beta-L-phenyl-lactate shows a small inverse isotope effect excludes most versions of a nucleophilic mechanism having a common anhydride intermediate. The bulk of the available evidence strongly favors the previously proposed general base mechanism.

Carboxypeptidases↗
PubMed1983

An unusual strain of Venezuelan encephalitis virus existing sympatrically with subtype I-D strains in a Peruvian rain forest.

In 1971, an unusual strain of Venezuelan encephalitis (VE) virus (71D1252) was recovered from the same small area of a rain forest in the western Amazon basin of South America near Iquitos, Loreto, Peru, from which strains of subtype I-D were recovered. The marker characteristics of this strain resembled most closely those of VE subtype III (Mucambo) and were distinctly different from coexisting I-D strains. Thus the concurrent presence of two different VE virus subtypes in one place was a striking exception to the usual geographic allopatry of VE virus subtypes. Strain 71D1252 also contained temperature sensitive (ts) (37 degrees C versus 39 degrees C) virions in the original mosquito suspension and first suckling mouse passage brain tissue suspensions. It thus represents one of the few so-far-reported ts strains of viruses found in nature, and the only natural ts strain of VE virus.

Animals↗
PubMed1982

Protective role of human milk against sudden death from infant botulism.

We examined the possibility that human milk and formula milk might differentially affect the severity of the infant botulism because they differ in immunologic composition and in influence on the normal intestinal microflora against which Clostridium botulinum must compete. A beneficial effect of human milk was suggested by the different feeding experiences of the moderate, hospitalized patients and the sudden death cases. Of patients hospitalized in California, 66% (33/50) were still being nursed at onset of illness, a percentage significantly greater than that of matched controls (P less than 0.01). In contrast, all ten California cases of sudden infant death attributable to C. botulinum infection were being fed iron-supplemented formula milk at death) unlike their controls, P less than 0.02) and had received no human milk within ten weeks of death. A beneficial effect of human milk was also observed in differences in mean age at onset; hospitalized breast-fed patients were almost twice as old (13.8 +/- 6.7 weeks) as were hospitalized formula-fed patients (7.6 +/- 2.9 weeks) (P less than 0.01). Human milk (or possibly other factors associated with breast-feeding) appeared to have moderated the severity at onset of infant botulism, allowing time for hospital admission, whereas for some infants with this illness, formula milk (or possibly other factors associated with formula feeding) was linked to sudden unexpected death.

Botulism↗
PubMed1982

Public health implications of rubella antibody levels in California.

Rubella hemaggluttination inhibition (HI) antibody determinations were performed in 1977 on a sample of California school children and in 1977-1979 on young women who were about to be married or who were pregnant. Among the pupils, 66 per cent reported prior rubella immunization; immunization history was more common in younger pupils. Seventy-seven per cent had detectable antibody, with little trend of greater seropositivity at older ages. Over 86 per cent of those with a written record of immunization had detectable antibody. There was no consistent indication of loss of seropositivity with increasing time since immunization. Children immunized at 12-14 months of age tended to have a lower seropositivity rate than those immunized at older ages. Among young women, the prevalence of detectable antibody was 80-83 per cent. Comparison with data obtained in 1968-1969 indicates that rubella immunization has had a marked impact on antibody levels in children but less impact on levels in teenagers and adults. The pool of rubella-susceptibles entering secondary schools will probably not decrease soon, so that rubella outbreaks may continue in high school and college-age populations. Ultimately, school entry immunization requirements should drastically curtail disease activity. In the interim, programs to immunize teenagers and young adult females must be strengthened. (Am J Public Health 1982; 72:167-172.)

Adolescent↗
PubMed1981

Evidence for coordinate expression of 3-hydroxy-3-methylglutaryl coenzyme A reductase ad low density lipoprotein binding activity.

A Chinese hamster ovary cell mutant that requires both cholesterol and unsaturated fatty acids for growth (Limanek, J. S., Chin, J., and Chang, T. Y. (1978) Proc. Natl. Acad. Sci. U. S. A. 75, 5452-5456) has been further characterized with respect to its dependence on cholesterol. Upon removal of serum lipids from the growth medium, the activity of the important cholesterogenic enzyme 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase and the low density lipoprotein (LDL) binding activity both increase significantly in the normal cell. Both these increases were much less in the mutant cell. Studies in vitro with NaF indicate that the differences in reductase activities between normal and mutant cells are not due to differences in activation by a dephosphorylation mechanism. Heat inactivation profiles and Km for HMG-CoA of both cell reductases were found to be identical, thus reducing the possibility that the mutant cell contains a mutation in the polypeptide chain of reductase. The fact that in lipid-deficient medium both reductase and LDL binding activities are low in the mutant strongly suggests that the expression of these activities is controlled in a coordinate manner. This conclusion is supported by parallel studies on a spontaneous revertant of the mutant in which the expression of reductase and LDL binding activities have both reverted to normal. These results indicate that the phenotypic abnormalities seen in the mutant are probably caused by a single mutation. A common factor is postulated to mediate this coordinate expression, and the function of such a factor is altered in the mutant cell.

Animals↗
PubMed1981

Application of immunoperoxidase staining to more rapid detection and identification of rubella virus isolates.

Efforts were made to shorten the time required for detection of rubella virus in clinical materials through the use of immunoperoxidase (IP) staining. Comparative studies were performed in which specimens were inoculated in parallel into BHK-21 hamster kidney cells, which were examined by IP staining at 5 days, and into BK-13 and BS-C-1 cells, which were examined in two ways, viz., by subpassage at 7 days into BHK-21 cells and IP staining 3 days later and by subpassage at 7 days into BS-C-1 cells followed by interference testing and immunofluorescence (IF) staining on positive materials (standard method). Direct inoculation into BHK-21 cells with IP staining at 5 days permitted detection and identification of 59% of the 63 positive specimens. Toxicity of some specimens preserved with sorbitol and of certain tissue specimens reduced the number of satisfactory examinations which could be performed in this system. Virus detection and identification by IP staining on subpassaged RK-13 and BS-C-1 materials, requiring a total of 18 days, was comparable to the longer interference-IF method, requiring 17 days. Results obtained by IP staining and interference-IF showed 98% correlation on RK-13 materials and 97% correlation on BS-C-1 materials. IP staining on inoculated BHK-21 cells can be a useful method for rapid identification of a relatively high proportion of rubella-positive specimens, particularly if sorbitol-preserved specimens are avoided, and IP staining on subpassaged RK-13 and BS-C-1 materials is a highly satisfactory alternative to the longer interference-IF method.

Animals↗
PubMed1981

Sensitivity of Toxorhynchites amboinensis mosquitoes versus chicken embryonic cell cultures for assays of Venezuelan encephalitis virus.

Toxorhynchites amboinensis mosquitoes inoculated intrathoracically with Venezuelan encephalitis virus and tested for infectious virus 12 to 19 days later by inoculation of primary chicken embryonic cell cultures yielded approximately the same titers of virus as did direct inoculation of cultures, with counting of plaques 3 days thereafter. Titers were slightly higher in T. amboinensis for three virus strains, equal for two virus strains, and slightly lower for two virus strains. Comparative titers of four strains were similar, whether virus suspensions came from infectious vertebrate cells or infected invertebrate (T. amboinensis) cells. Each of the seven strains of Venezuelan encephalitis virus reached virus concentrations of 10(4.2) to 10(5.1) plaque-forming units in individual T. amboinensis mosquitoes after extrinsic incubation periods of 12 to 19 days. No temperature-sensitive (29 versus 37 degrees C) virus was detected in T. amboinensis mosquitoes infected by six strains of Venezuelan encephalitis virus.

Animals↗