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Biomedical subjects

J K Collins

Publications and source records attributed to J K Collins.

At least 145 records · Page 8Linked to original sources
PubMed1979

Effects of cell culture and laboratory conditions on type 2 dengue virus infectivity.

The stability of type 2 dengue virus to exposure to a variety of laboratory conditions was determined. Suckling mouse brain passage virus was adapted for growth in BHK-21 cells, and plaque assays were performed using a tragacanth gum overlay. A three- to fourfold increase in plaque size could be obtained if monolayers were subconfluent at time of inoculation. Incubation of virus for 24 h at 37 degrees C, pH 6.5, or in buffer containing 1 mM ethylenediaminetetraacetate considerably reduced virus infectivity as compared with virus incubated for the same period at 4 degrees C, pH 8.0, or in buffer with or without 1 mM CaCl2 and 1 mM MgCl2. Multiple freezing and thawing of virus tissue culture medium containing 10% fetal calf serum did not reduce virus infectivity.

Animals↗
PubMed1978

Purification of the influenza hemagglutinin glycoprotein and characterization of its carbohydrate components.

Hemagglutinin from influenza A/PR8 virus was purified after treatment of the virus with sodium deoxycholate followed by extraction with tri-n-butyl phosphate. This fully disrupted the virus while preserving hemagglutinating activity. The hemagglutinin was obtained in the form of small aggregates that could be separated from other viral components. Purified hemagglutinin was hydrolyzed to determine carbohydrate composition and digested with Pronase to analyze oligosaccharide structures. Sugars present in the hemagglutinin were galactose, mannose, fucose, and glucosamine in molar rates of about 6:11:2:5, and these comprised 16% of the hemagglutinin glycoprotein. Oligosaccharides obtained from virus included a major component of a molecular weight of 2,800, composed of glucosamine, galactose, mannose, and fucose, and a minor heterogenous component of a molecular weight of 1,500 to 2,000, containing predominantly mannose. The 2,800-molecular-weight oligosaccharide was a constituent of the hemagglutinin, and treatment of this large oligosaccharide with specific exo-glycosidases demonstrated the presence of terminal galactose and fucose and allowed the deduction of a general structure for this component.

Carbohydrates↗
PubMed1978

Removal of carbohydrate from influenza A virus and its hemagglutinin and the effect on biological activities.

Treatment of influenza virus and its purified hemagglutining with glycosidases from Diplococcus pneumoniae, which included beta-galactosidase, beta-N-acetylglucosminidase, and endoglycosidase D, released amino and neutral sugars from the virus and these as well as large oligosaccharides from the purified hemagglutinin. The released glucosamine-containing oligosaccharides were of one discrete size. Large oligosaccharides not removed by the glycosidases were found on the virus as well as the hemagglutinin. Some oligosaccharides on the virus were inaccessible to the enzymes, since they could be removed only from the purified hemagglutinin. Approximately 50% of the hemagglutinin carbohydrates could be removed without effect on hemagglutinating activity. Similarly, removal of 20 to 25% of the carbohydrates from intact virus particles did not alter infectivity.

Carbohydrates↗
PubMed1977

A developmental study of the effects of instructions on visual shape judgements.

Previous developmental studies of visual shape judgements have failed to instruct subjects clearly as to the type of shape judgements required. Using the method of adjustment 180 subjects in five age groups, 6, 8, 10, 12 and 19 years, were instructed to judge either the real or projected shape of an elliptical standard slanted 39, 57 and 72 degrees from the fronto-parallel. No age changes were found in the tendency towards shape constancy. Objective shape judgements exhibited a significantly greater degree of constancy than projective judgements and there was no decline in constancy with increasing slant of the standard under objective instructions, in contrast to a marked decline under projective instructions. Female subjects consistently manifested a greater tendency towards shape constancy than males.

Adolescent↗
PubMed1977

Identification of simian virus 40 protein A.

A large simian virus 40 (SV40)-specific protein can be efficiently immunoprecipitated from infected cell extracts with antisera obtained from hamsters bearing SV40-induced tumors. The protein has an apparent molecular weight of 88,000 to 100,000 with respect to markers with known molecular weights, but behaves anomalously on sodium dodecyl sulfate (SDS)-polyacrylamide gels. Cell lines infected by two different strains of SV40 synthesize immunoreactive proteins that differ slightly in mobility during SDS-polyacrylamide gel electrophoresis, evidence that the protein is coded for by the virus. These differences in protein size correlate with differences in the electrophoretic mobility of viral DNA fragments obtained by digestion with HindII and III restriction enzymes. The size of the viral capsid proteins VP2 and VP3 also varies with the strain of virus. dl-1001, a constructed deletion mutant that lacks part of the SV40A gene, directs the synthesis of a 33,000-dalton polypeptide that is not detected in cells infected with wild-type virus. The deletion fragment, like the larger protein, is phosphorylated. Maps of tryptic peptides from the 88,000- to 100,000-dalton protein and the 33,000-dalton fragment show common peptides and provide strong direct evidence that the proteins are products of the SV40 A gene. The deletion fragment reacts with antitumor sera and binds to double-stranded DNA in the presence of the complete A protein.

Capsid↗
PubMed1977

Modification of simian virus 40 protein A.

The A protein of simian virus 40 is phosphorylated in both productive and transforming infection. The phosphorylated amino acid has been identified as serine and has been localized in a single tryptic peptide of the protein. Because the A protein synthesized in infection by A mutants is phosphorylated to the same extent and in the same peptide as in infection by wild-type virus, the functional defect of the A mutants is apparently unrelated to phosphorylation. At least three distinct forms of the A protein with apparent molecular weights of 85,000, 88,000, and 100,000 can be identified in extracts of cells infected by wild-type virus. After exposure of cells to Nonidet P-40, the 85,000- and 88,000-dalton proteins were found in varying amounts in extracts of permissive cells but not in extracts of transformed cells. This finding raised the question of the possible functional importance of the smaller proteins in productive infection. However, the virtual absence of the 85,000- and 88,000-dalton proteins in some extracts of the fully permissive CV-1 cell line indicates that a conversion of the larger to the smaller forms of the A protein is not required in significant quantity for productive infection. Furthermore, a study of extraction conditions shows that the smaller proteins are easily generated during extraction and provides an explanation for the appearance of these proteins in some cells after extraction under unfavorable conditions.

Cell Line↗
PubMed1976

Regulation of arginine and pyrimidine biosynthesis in Pseudomonas putida.

Repression of biosynthetic enzyme synthesis in Pseudomonas putida is incomplete even when the bacteria are growing in a nutritionally complex environment. The synthesis of four of the enzymes of the arginine biosynthetic pathway (N-acetyl-alpha-glutamokinase/N-acetylglutamate-gamma-semialdehyde dehydrogenase, ornithine carbamoyltransferase and acetylornithine-delta-transaminase) could be repressed and derepressed, but the maximum difference observed between repressed and derepressed levels for any enzyme of the pathway was only 5-fold (for ornithine carbamoyltransferase). No repression of five enzymes of the pyrimidine biosynthetic pathway (aspartate carbamoyltransferase, dihydro-orotase, dihydro-orotate dehydrogenase, orotidine-5'-phosphate pyrophosphorylase and orotidine-5'-phosphate decarboxylase) could be detected on addition of pyrimidines to minimal asparagine cultures of P. putida A90, but a 1-5- to 2-fold degree of derepression was found following pyrimidine starvation of pyrimidine auxotrophic mutants of P. putida A90. Aspartate carbamoyltransferase in crude extracts of P. putida A90 was inhibited in vitro by (in order of efficiency) pyrophosphate, CTP, UTP and ATP, at limiting but not at saturating concentrations of carbamoyl phosphate.

Aldehyde Oxidoreductases↗
PubMed1976

Failure of complex supplementation of minimal cultures to elicit a shift-up response in Pseudomonas putida.

The addition of complex supplements (particularly amino acids) to cultures of Pseudomonas putida growing on a good carbon source did not result in a substantial increase in the growth rate. Amino acids entered the cells within 30 s of addition and reached significant internal pool concentrations. Endogenous amino acid biosynthesis was quickly inhibited (about 75%), with a substantial sparing of the original carbon source. Within 20 min of supplementation significant respiration of added amino acids was detected, yet the ATP pool size did not increase and the bacteria did not grow faster. The RNA content of P. putida growing in complex medium differed from that of enteric bacteria in that, although it varied with growth rate, it was not substantially larger than the RNA content of bacteria grown in a minimal medium with a good carbon and energy source. The rate of RNA accumulation on shift-up remained substantially unchanged on supplementation if the minimal medium had a carbon source producing fast growth, and did not increase for about 30 min if the carbon source was relatively poor. In other respects RNA synthesis was similar to that of the enteric bacteria, being stringently controlled, inhibited by trimethoprim and continuing in the presence of chloramphenicol. It is proposed that growth of P. putida in complex media is limited by the rate of synthesis of stable RNA.

Adenosine Triphosphate↗
PubMed1975

Regulation of tumor antigen synthesis by simain virus 40 gene A.

Simian virus 40 gene A has previously been shown to promote the replication of viral DNA and the transcription of late viral RNA in productive infection and to maintain the growth characteristics of some transformed cells. The present study examines the effect of the A function on proteins synthesized during productive and transforming infections. Under restrictive conditions, temperature-sensitive A mutants induce the overproduction of a 100,000-dalton protein both in productively infected monkey cells and in transformed rabbit cells. Immunoprecipitation of the induced protein with antisera, prepared against simian virus 40-induced tumors in hamsters, was used to identify the induced protein as tumor antigen. The same protein can be precipitated from extracts of cells infected by wild-type virus but not from uninfected cells. Furthermore, the mutant-induced protein is more rapidly degraded in vivo and is less tightly bound to intranuclear components than the protein induced by wild-type virus. The presence of the same virus-induced protein in infected cells from different species and the altered behavior of that protein in mutant infection strongly suggest that the protein is virus coded. Because the protein is large enough to account for the entire coding capacity in the early region of the simian virus 40 genome, the 100,000-dalton protein may well be the primary product of the only early gene identified by complementation studies, the A gene. If the 100,000-dalton protein that is overproduced in mutant infection is the A protein and the only early protein, then functional wild-type A protein must regulate its own synthesis in both productive and transforming infections.

Animals↗