Search PubMed⌕ Search

Biomedical subjects

J C Bennett

Publications and source records attributed to J C Bennett.

At least 91 records · Page 5Linked to original sources
PubMed1981

Interleukin 1: production by P388D1 cells attached to microcarrier beads.

The murine macrophage-derived cell line P388D1 is commonly used for the production of Interleukin 1 (IL1) and other macrophage products. In order to circumvent the tendency of this cell line to undergo selection for a non-adherent subpopulation of cells which does not produce IL1, we have grown P388D1 cells attached to microcarrier beads. IL1 produced by these cells is indistinguishable from that elaborated by cells grown in monolayer or suspension culture. Moreover, several volumes of conditioned medium can be produced from one batch of cells suitable for the large-scale purification of this mediator.

Animals↗
PubMed1981

Comparative studies on dihydroorotate dehydrogenase from P. berghei and the mouse reticulocyte.

Kinetic parameters on dihydroorotate dehydrogenase (DHO-DHase) from the rodent malarial parasite, Plasmodium berghei, have been determined. This enzyme, the fourth in de novo pyrimidine biosynthesis, is particulate and is absent in the mature mammalian red cell. The Km of the substrate, dihydroorotate, was determined to be 23 microM and the Ki values for a number of substrate analogues have been determined. The most potent inhibitor was dihydroazaorotate (Ki, 3 microM), 5-azaorotate (Ki, 20 microM) and other pyrimidine analogues. The activity of the enzyme was also affected by a number of respiratory chain inhibitors. As the P. berghei infection is accompanied by reticulocytosis, a comparative study of DHO-DHase in mouse reticulocytes was also carried out. The general properties of the enzyme from these sources were similar to those of the parasite enzyme. However, significant differences in the response of the two enzymes to various inhibitors were observed and could provide a rational basis for the development of chemotherapeutic agents active against the parasite.

Animals↗
PubMed1980

Alignment of the peptides derived from acid-catalyzed cleavage of an aspartylprolyl bond in the major internal structural polypeptide of avian retroviruses.

The major internal structural polypeptide (p27) of Rous sarcoma virus (RSV), and the analogous polypeptide (P27(0)) OF Rous-associated virus-O (RAV-O), an endogenous virus released spontaneously by some chicken cells) have been cleaved selectively at a single aspartylprolyl peptide bond to yield two fragments. The NH2- and COOH-terminal amino acid sequences of p27 and p27(0) and their mild acid-cleavage fragments have been determined. These results show the existence of an identical cleavage site and a similar NH2- and COOH-terminal amino acid sequence in both the polypeptides. Furthermore they indicate that the difference in the molecular weights of p27 and p27(0) results from an insertion of amino acids in the COOH-terminal peptide of p27(0) rather than a shift in the scission site of the precursor molecule.

Amino Acid Sequence↗
PubMed1980

Partial amino acid sequence of human factor D:homology with serine proteases.

Human factor D purified to homogeneity by a modified procedure was subjected to NH2-terminal amino acid sequence analysis by using a modified automated Beckman sequencer. We identified 48 of the first 57 NH2-terminal amino acids in a single sequencer run, using microgram quantities of factor D. The deduced amino acid sequence represents approximately 25% of the primary structure of factor D. This extended NH2-terminal amino acid sequence of factor D was compared to that of other trypsin-related serine proteases. By visual inspection, strong homologies (33--50% identity) were observed with all the serine proteases included in the comparison. Interestingly, factor D showed a higher degree of homology to serine proteases of pancreatic origin than to those of serum origin.

Amino Acid Sequence↗
PubMed1980

Monoclonal and allospecific H-2Kk antisera precipitate a high molecular weight protein.

A protein with an apparent m.w. of 68,000 has been observed in immunoprecipitations of NP-40 solubilized BW5147 thymoma cells by using monoclonal or polyclonal allospecific H-2Kk antisera. By contrast, H-2Dk alloantisera precipitated a 45,000 m.w. protein from the same membrane preparations. The 68,000 m.w. protein is expressed on the plasma membrane as determined by vectoral labeling. Extensive clearing experiments and the use of monoclonal antibody demonstrate that the protein does not bear group-specific C-type viral determinants.

Animals↗
PubMed1979

Structure of the membrane protein of influenza virus. I. Isolation and characterization of cyanogen bromide cleavage products.

After cleavage of the membrane (M) protein of influenza A/WSN virus by using cyanogen bromide (CNBr), six peptide peaks representing approximate molecular weights of 6,000, 4,000, 2,200, 1,600, 1,200, and 1,000 were resolved by gel filtration on BioGel P6. Analysis by thin-layer chromatography indicates that the first, second, fourth, and fifth peaks contain single-peptide components, whereas the third and sixth peaks contain more than one peptide. By using Whatman CM52 ion-exchange chromatography in 5 M urea, four peptides were resolved from the third BioGel P6 peak. The amino acid composition of each of the purified peptides has been determined, and partial sequences were obtained for several peptides. Based on finding a blocked amino terminal residue, the 6,000-dalton fragment appears to contain the amino terminus of the M protein, whereas the carboxy terminal peptide was identified as a 2,000-dalton peptide.

Amino Acid Sequence↗
PubMed1978

The infectious etiology of rheumatoid arthritis. New considerations.

Several possible mechanisms of chronic inflammatory arthritis that might be initiated by infectious agents are discussed. Some recent information on mycoplasma infections, long-term virus infections, and shed bacterial components provides the bases for new experimental approaches. Currently, evidence of involvement of mycoplasma or viral agents in rheumatoid arthritis is tenuous. Chronic peptidoglycan-immune-complex formation is a consideration that has been discussed, but only recently pursued in depth. It may well be that experimental studies on the infectious etiology of rheumatoid arthritis will be revitalized through an appreciation of the bacterial antigen load in the gastrointestinal tract. The perimental vehicles for testing this possibility are available and should be directly applicable at the clinical level.

Animals↗
PubMed1978

Amino-terminal amino acid sequence of the major structural polypeptides of avian retroviruses: sequence homology between reticuloendotheliosis virus p30 and p30s of mammalian retroviruses.

The major structural polypeptides, p30 of reticuloendotheliosis virus (REV) (strain T) and p27 of avian sarcoma virus B77, have been compared with regard to amino acid composition. NH2-terminal amino acid sequence, and immunological crossreactions. The amino acid composition of the two polypeptides is distinct, and a comparison of the first 30 NH2-terminal amino acids of REV p30 with that for the first 25 of B77 p27 yields only three homologous residues. In competition radioimmunoassays the polypeptides show no crossreactivity. A comparison of the amino acid composition and NH2-terminal amino acid sequence of REV p30 with those reported for several mammalian retrovirus p30s shows remarkable similarities. Both REV and mammalian p30s contain a large number of polar residues in their amino acid composition and show approximately 40% homology in the first 30 NH2-terminal amino acids. No crossreactivity could be observed, however, in competition radioimmunoassays between Rauscher murine leukemia virus p30 and that of REV. The observations reported here suggest a close evolutionary relationship between REV and the mammalian retroviruses.

Amino Acid Sequence↗
PubMed1978

Bacterial leaching patterns on pyrite crystal surfaces.

Selected pyrite crystals were placed as a bacterial energy source into stationary cultures of Thiobacillus ferroxidans. Scanning electron microscope studies performed after a period of 2 years on these crystals revealed bacterial etching pits in characteristic patterns; they include pit arrangements in loose statistical disorder, in pairs, in clusters, and most remarkably in pearl-string-like chains. It has previously been confirmed that the chemical processes of bacterial leaching occur mainly in the region of contact between bacteria and the sulfide surface. The evidence presented in this experiment strongly suggests that the observed bacterial distributions are critically dependent on crystal structure and on deviations in the crystal order (fracture lines, dislocations) of the leachable substrate.

Crystallization↗
PubMed1977

Primary structure of human J chain: isolation and characterization of tryptic and chymotryptic peptides of human J chain.

Human J chain isolated from the plasma of a patient with Waldenstrom's macroglobulinemia was subjected to extended and limited digestion with trypsin and chymotrypsin. The digests were fractionated by combination of column chromatography and high voltage paper electrophoresis. Peptide purity was established by their amino acid analysis and a single amino terminal residue. All the necessary peptides which would provide the total primary structure of molecule were thus obtained.

Amino Acids↗