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Biomedical subjects

G S Jacob

Publications and source records attributed to G S Jacob.

50 records · Page 3Linked to original sources
PubMed1985

Solid-state 15N NMR studies of the effects of penicillin on cell-wall metabolism of Aerococcus viridans (Gaffkya homari).

Lyophilized whole cells and isolated cell walls from Aerococcus viridans (Gaffkya homari) grown on a synthetic medium containing benzylpenicillin, and either L-[epsilon-15N]lysine or 15N-ammonium ion as the only source of label, have been studied using cross-polarization magic-angle spinning 15N nuclear magnetic resonance. The lysine is incorporated directly into protein and cell-wall peptidoglycan and was used to measure cell-wall cross-links. The ammonium ion acts as a non-specific label monitoring general metabolism. Inhibition of cell-wall cross linking by penicillin occurs, but may not be the exclusive cause of cell death and lysis in this microorganism. Instead, the disruption of the mechanism for control of peptidoglycan synthesis probably is a contributing factor.

Cell Wall↗
PubMed1985

Primary gastrointestinal lymphoma in Kuwait. An 11-yr retrospective analysis of 108 cases.

One hundred and eight cases of primary gastrointestinal lymphoma from the files of Kuwait Cancer Control Center over a period of 11 yr were analysed retrospectively. The occurrence was 47 in the proximal small intestine, 38 in the stomach, 18 in the distal ileum and five in the colon and rectum. The majority of the patients were in stage III. Using a modified Rappaport's classification, lymphocytic lymphoma was the commonest histologic type (60%) as compared to histiocytic lymphoma (19%). Four patients had early IPSID (immunoproliferative small intestinal disease). The 'Western' type of lymphoma occurred in the fourth decade while the 'Mediterranean' type occurred in the third decade of life. The latter occurred more commonly among people of low socioeconomic background. Chemotherapy was the single most effective mode of treatment. Addition of surgery, radiotherapy or both did not improve the 2-yr survival but did improve the 5-yr survival.

Adolescent↗
PubMed1984

Rectocolonic calcification due to schistosomiasis. A clinicoradiologic study.

Four patients who had intravenous pyelography were found to have radiologically visible calcification of the rectocolon and urinary tract due to schistosomiasis. All four patients had mild proctocolitis colonoscopically and multiple calcified schistosomal ova were found in the submucosa histologically. The authors believe that radiologically visible rectocolonic calcification is more common than reported and that it is associated with a clinically mild or latent form of schistosomiasis.

Adult↗
PubMed1984

Inflammatory bowel disease in Kuwait.

Inflammatory bowel disease is considered to be rare or nonexistent in some Arab countries. During a period of 6 years, 91 patients with ulcerative colitis and 17 with Crohn's disease were seen for initial diagnosis in the Gastroenterology Department of Amiri Hospital, which serves 55% of the population of Kuwait. From this group, 43 patients with ulcerative colitis and 14 patients with Crohn's disease were followed up for an average of 30.9 months. In the remaining 51 patients, the diagnosis was established in the same manner as in this series, but these patients were sent back to the referring physicians and therefore were not available for follow-up. The severity of the disease in the majority of patients with ulcerative colitis was mild to moderate. Nine of 14 patients with Crohn's disease underwent surgery as a diagnostic procedure in an acute abdominal emergency or for treatment of complications. The duodenum was involved in two patients with Crohn's disease and the endoscopic picture and histology of these were initially interpreted as immunoproliferative small intestinal disease which is highly prevalent in this area. We suggest that the assumption that inflammatory bowel disease is uncommon in our population is wrong.

Adolescent↗
PubMed1983

Direct measurement of peptidoglycan cross-linking in bacteria by 15N nuclear magnetic resonance.

Cross-polarization magic angle spinning 9.12-MHz 15N nuclear magnetic resonance was used to measure the extent of peptidoglycan cross-linking within intact bacterial cells and isolated cell walls of Aerococcus viridans ATCC 10400 grown in the presence of L-[epsilon-15N]lysine. A value of 49% for the cross-linking index was found for normal cells, while for those grown in the presence of low levels of penicillin G (0.1 micrograms/ml), the cross-linking index was reduced to 35%.

Magnetic Resonance Spectroscopy↗
PubMed1983

Fiberoptic colonoscopy. A report of findings in 481 patients from Kuwait.

The authors report 481 colonoscopic examinations, performed in the Amiri Hospital, Kuwait. The objective of this paper is to demonstrate the pattern of colonic diseases in this region and to compare our findings with those reported from elsewhere. Although these are preliminary results, they suggest that colonic diseases, in general, are uncommon in this area. Ulcerative colitis was the most common pathology detected on colonoscopy. Polyps and diverticulosis were less common than those observed in the west. The frequency of Crohn's disease in Indians and Pakistanis in Kuwait was found to be high, although it is reported to be a very rare disease in their native countries.

Adolescent↗
PubMed1980

Interaction of bovine carbonic anhydrase with (neutral) aniline, phenol, and methanol.

We have investigated the interaction of bovine carbonic anhydrase with neutral aniline, phenol, and methanol molecules. The measurements are of optical spectra and solvent water and methanol proton magnetic relaxation rates of solutions of Co2+-substituted enzyme. We recently proposed a model [Koenig, S. H., Brown, R. D., & Jacob, G. S. (1980) Proceedings of the Symposium on Biophysics and Physiology of Carbon Dioxide, Springer-Verlag, West Berlin and Heidelberg], based on the interaction of enzyme with monovalent anions, that accounts for the pH dependences observed for a wide variety of phenomena, including the apparent pKa for enzymatic activity. We now extend the model to include the observed effects of neutral molecules. Aniline and phenol, though isoelectronic, shift the observed pKa values in opposite directions, and both appear to bind at the aromatic binding site to which sulfonamide inhibitors and aromatic esters are known to bind. The resulting binary complexes behave as altered enzymes, with different values of the pKa for activity, but otherwise are similar to the native enzyme. In terms of our model, aniline and phenol alter the relative affinities of water and anions for the same coordination position of the metal ion at the active site. The effect is opposite in sign for the two nolecules becuase of the differing proton affinities of the NH2 and OH moieties of the phenol ring in each case. By extension, our results indicate that data from experiments using aromatic buffers such as imidazole and lutidine should be analyzed with some care; effects previously attributed to buffer molecules to the aromatic binding site in the active region of the enzyme. The interaction of methanol with carbonic anhydrase is quite different, and very weak. Methanol does displace water at the metal, but to first order there is little, if any, preferential binding of methanol compared to water. Observations by others that alcohols inhibit esterase activity with inhibition constants on the order of 1 M are not attributable to binding of alcohol to enzyme but rather, in our view, result from the increased solubility of aromatic ester substrates in the alcohol-modified solvent.

Aniline Compounds↗
PubMed1978

Magnetic cross-relaxation among protons in protein solutions.

The magnetic spin-lattice relaxation rates of solvent water nuclei are known to increase upon addition of diamagnetic solute protein. This enhancement of the relaxation rate is a function of magnetic field, and the orientational relaxation time of the protein molecules can be deduced from analysis of the field-dependent relaxation rates. Although the nature of the interactions that convey information about the dynamics of protein motion to the solvent molecules is not established, it is known that there is a contribution to the relaxation rates of solvent protons that plays no role in the relaxation of solvent deuterons and 17O nuclei. We show here that the additional interaction arises from a cross-relaxation process between solvent and solute protons. We introduce a heuristic three-parameter model in which protein protons and solvent protons are considered as two separate thermodynamic systems that interact across the protein-solvent interface. The three parameters are the intrinsic relaxation rates of each system and a cross-relaxation term. The sign of the latter term must always be positive, for all values of magnetic field, in order for magnetization energy to flow from the hotter to the cooler system. We find that the magnetic field-dependence of the cross-relaxation contribution is much like that of the remaining solvent proton relaxation, i.e., about the same as the deuteron relaxation field dependence. This finding is not compatible with the predictions of expressions for the cross-relaxation that have been used by other authors, but not applied to data over a wide range of magnetic field strength. The model predicts that the relaxation behavior of both the protein protons and the solvent protons is the sum of two exponentials, the relative contributions of which would vary with protein concentration and solvent isotopic composition in a fashion suggestive of the presence of two classes of protein protons, when there is in reality only one. This finding has immediate implications for the interpretation of published proton relaxation rates in complex systems such as tissues; these data should be reexamined with cross-relaxation taken into account.

Alkaline Phosphatase↗