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Biomedical subjects

N Patel

Publications and source records attributed to N Patel.

At least 343 records · Page 19Linked to original sources
PubMed1977

Fetal metabolism during recovery from surgical stress.

10 fetal lambs prepared with sampling catheters in the common umbilical vein and distal aorta were studied at 2 h, 2 and 4 days postoperatively. Umbilical blood flow was measured by a diffusion equilibrium method. Oxygen, lactate, pyruvate, glucose and alpha-amino nitrogen concentrations were determined on umbilical arterial (UA) and umbilical vein (UV) blood. Fetal oxygen consumption averaged 10.4, 10.6 and 1.0 ml.kg-1.min-1 for the three study periods. Lactate/pyruvate ratios were higher in UV than in UA in 17 of 20 experiments. Significant reductions (p less than 0.05) in (1) maternal mixed venous-UA glucose concentration difference, and (2) UA glucose concentrations occurred at 2 and 4 days compared to the 2-hour period. Fetal alpha-amino nitrogen balance was negative at the 2-hour period, but positive 2 days and 4 days postoperatively.

Animals↗
PubMed1976

Restoration of leukemia virus-suppressed immunocytes in vitro by peritoneal exudate cells.

Depressed antibody responsiveness to sheep erythrocytes in mice infected with Friend leukemia virus continued in vitro when spleen cell cultures from infected animals were cultured in the presence of antigen. Addition of PE cells from normal donor mice to the immunologically depressed splenocyte cultures resulted in a marked restoration of antibody responsiveness. Restoration of the immune response was PE cell dose-dependent; a ratio of 1 PE cell per 10 splenocytes resulted in the largest numbers of PFC's. These results suggest that impaired antibody responsiveness by spleen cell cultures from FLV-infected mice may be due, in part, to effects on antigen-processing macrophages, since restoration of immune responsiveness occurs by PE cell supplements.

Animals↗
PubMed1975

Xanthosine-5'-phosphate amidotransferase from Escherichia coli.

The purified enzyme xanthosine-5'-monophosphate (XMP) aminase from Escherichia coli strain B-96 is shown to possess catalytic activity with either glutamine or ammonia as a substrate. This enzyme, which possesses identical subunits, has the following properties: (a) a pH optimum of 8.3 for both aminase and amidotransferase; (b) an apparent K-m for both glutamine and NH3 of 1 mM; (c) an amidotransferase that is approximately 2 times more active than the aminase; (d) a linear relationship between velocity and enzyme concentrationfor both activities; (e) inhibition of both activities by the glutamine analogue 6-diazo-5-oxo-L-norleucine, but the amidotransferase is more sensitive than the aminase; and (f) inhbiition of both activities by the adenosine analogue, psicofuranine, but again the amidotransferase activity is more sensitive than the aminase. The so-called XMP aminase from the E. coli mutant B-24-1 also has been examined in both crude extracts nad ammonium sulfate fractions and the following data have been obtained: (a) both preparations of enzyme contain aminase and amidotransferase activity; (b) both activities have the same substrate requirements; (c) the pH optima for both activities in the crude extract are identical with those found with the purified enzyme preparation; and (d) the amidotransferase activity in the crude extract and the ammonium sulfate fractions is 2- to 3-fold more active than the aminase. These data demonstrate that this enzyme from E. coli is not strictly a XMP aminase but is, in fact, an amidotransferase capable of utilizing either glutamine or NH3 as a substrate.

Aminohydrolases↗
PubMed1975

Restoration of in vitro immune responsiveness of mastocytoma-suppressed splenocytes by activated T cells.

Spleen cells from normal DBA/2 mice pretreated with a soluble factor from mastocytoma cells or from ascitic fluid of mastocytoma-bearing mice were markedly impaired in terms of antibody formation to SRBC in vitro. Such immunosuppression by mastocytoma homogenates or ascitic fluid was reversed when syngeneic T cells activated to SRBC were added to the cultures, but not when peritoneal exudate cells or anti-theta-treated normal splenocytes were used. Activated T cells, as well as normal B lymphocytes prepared from spleens of lethally irradiated mice reconstituted with bone marrow cells, were less sensitive to the immunosuppressive factor than non-activated T cells. The ability of educated T cells to restore immunocompetence of suppressed spleen cells in vitro suggests that the target of the immunosuppressive factor from mastocytoma cells may be non-activated T cells, especially those involved in T cell helper function.

Animals↗
PubMed1974

Homologous and hybrid complexes of anthranilate synthase from Bacillus species.

The subunits of anthranilate synthase were separated and partially purified by Sephadex G-100 gel filtration from the following six species of Bacillus: Bacillus subtilis, Bacillus licheniformis, Bacillus alvei, Bacillus coagulans, Bacillus pumilus, and Bacillus mascerans. Our data suggest that the enzyme from B. alvei is unique among these species. First, the anthranilate synthase complexes are readily dissociated during gel filtration in the absence of glutamine into a large component (aminotransferase), subunit E, and a small component subunit X (glutamine-binding protein), whereas a higher salt concentration is required to dissociate the complex from B. alvei. Second, the aminotransferase activity from all six species is stimulated by glycerol and inhibited by tryptophan; however, only the large component from B. alvei is stimulated by 2-mercaptoethanol. Finally, the large component can be titrated with the small component to yield a complex which can utilize glutamine as a substrate (amidotransferase). The homologous complexes have an amidotransferase to aminotransferase ratio of 1.4 to 2.3, but the B. alvei complex has a ratio of 0.9. Except for complexes that involve the large component from B. alvei, hybrid complexes can be formed which have ratios as good as the homologous complexes. These data are consistent with the hypothesis that B. alvei is unique among the bacilli with respect to some enzymes in the aromatic amino acid biosynthetic pathway.

Amides↗
PubMed1973

Intergeneric complementation of anthranilate synthase subunits.

Partially purified subunits of anthranilate synthase were prepared from Bacillus subtilis and Pseudomonas aeruginosa. The large component from B. subtilis (I(B)) complements well with the small component from P. aeruginosa (II(P)) to reconstitute a glutamine-reactive anthranilate synthase. This interaction can be demonstrated with crude extracts from a B. subtilis trpX mutant and a P. aeruginosa trpA mutant. Complementation was also observed with the large component from P. aeruginosa (I(P)) and the small subunit from B. subtilis (II(B)). At saturation the heterologous complex I(B)II(P) has 93% of the activity of the homologous complex I(B)II(B), whereas the hybrid I(P)II(B) is only 22% as active as the homologous complex I(P)II(P).

Ammonia↗