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Biomedical subjects

R Kishore

Publications and source records attributed to R Kishore.

At least 55 records · Page 3Linked to original sources
PubMed1993

Stereochemical constraints in peptide design: analysis of the influence of a disulfide bridge and an alpha-aminoisobutyryl residue on the conformation of a hexapeptide.

The competing effects of a disulfide bridge and an alpha-aminoisobutyryl residue (Aib) in determining the conformation of a hexapeptide have been investigated, by comparing the cyclic disulfide [sequence: see text] and the acylic peptide Boc-Cys (SBzl)-Val-Aib-Ala-Leu-Cys (SBzl)-NHMe (2). Previously published nmr and crystallographic studies [R. Kishore, S. Raghothama, and P. Balaram (1987) Biopolymers, Vol. 26, pp. 873-891; I. L. Karle, R. Kishore, S. Raghothama, & P. Balaram, (1988) Journal of the American Chemical Society Vol. 110, pp. 1958-1963] have established an antiparallel beta-hairpin structure for 1 with a central Aib-Ala beta-turn. A comparison of nmr data for 1 and 2 in chloroform and dimethylsulfoxide reveals that the acyclic peptide is conformationally labile. Evidence for a 3(10)-helical conformation in CDCl3 is obtained from sensitivity of NH chemical shifts to temperature and solvent perturbation and low JHNC alpha H values. Studies in solvent mixtures establish a conformational transition on going from CDCl3 to (CD3)2SO. The changes in NH nmr parameters, together with the observation of several interresidue C alpha i H-Ni+1H nuclear Overhauser effects support a conformation having a central beta-turn with extended arms in (CD3)2SO. A single Aib residue appears to stabilize a helix in apolar solvents, for the acyclic hexapeptide, while the disulfide bridge serves to lock the beta-hairpin conformation.

Amino Acid Sequence↗
PubMed1992

Photo and Nutritional Regulation of the Light-Harvesting Chlorophyll a/b-Binding Protein of Photosystem II mRNA Levels in Euglena.

In Euglena gracillis var bacillaris, light exposure increases the level of mRNA encoding the light-harvesting chlorophyll a/b-binding protein of photosystem II (LHCPII) approximately twofold. LHCPII mRNA levels increased in the dark upon either malate or ethanol addition. LHCPII mRNA is present but LHCPII is not synthesized in the bleached mutants W(3)BUL and W(10)BSmL, which lack protochlorophyll(ide) and most if not all of the chloroplast genome. Light exposure increased LHCPII mRNA levels in W(3)BUL but not in W(10)BSmL. Carbon availability and light acting through a nonchloroplast photoreceptor appear to regulate LHCPII mRNA levels. A chloroplast photoreceptor and/or a product produced by the chloroplast appear to regulate LHCPII mRNA translation.

Journal Article↗
PubMed1989

Cystine peptides. Antiparallel beta-sheet conformation of the cyclic biscystine peptide [Boc-Cys-Ala-Cys-NHCH3]2.

The crystal structure analysis of the cyclic biscystine peptide [Boc-Cys1-Ala2-Cys3-NHCH3]2 with two disulfide bridges confirms the antiparallel beta-sheet conformation for the molecule as proposed for the conformation in solution. The molecule has exact twofold rotation symmetry. The 22-membered ring contains two transannular NH...OC hydrogen bonds and two additional NH...OC bonds are formed at both ends of the molecule between the terminal (CH3)3COCO and NHCH3 groups. The antiparallel peptide strands are distorted from a regularly pleated sheet, caused mainly by the L-Ala residue in which phi = -155 degrees and psi = 162 degrees. In the disulfide bridge C alpha(1)-C beta(1)-S(1)-S(3')-C beta(3')-C alpha(3'), S--S = 2.030 A, angles C beta SS = 107 degrees and 105 degrees, and the torsional angles are -49, -104, +99, -81, -61 degrees, respectively. The biscystine peptide crystallizes in space group C2 with a = 14.555(2) A, b = 10.854(2) A, c = 16.512(2) A, and beta = 101.34(1) with one-half formula unit of C30H52N8O10S4.2(CH3)2SO per asymmetric unit. Least-squares refinement of 1375 reflections observed with magnitude of F greater than 3 sigma(F) yielded an R factor of 7.2%.

Amino Acid Sequence↗
PubMed1988

Synthetic peptide models for the redox-active disulfide loop of glutaredoxin. Conformational studies.

Two cyclic peptide disulfides (Sequence: see text). (X = L-Tyr or L-Phe) have been synthesized as models for the 14-membered redox-active disulfide loop of glutaredoxin. 1H NMR studies at 270 MHz in chloroform solutions establish a type I beta-turn conformation for the Pro-X segment in both peptides, stabilized by a 4----1 hydrogen bond between the Cys(1) CO and Cys(4) NH groups. Nuclear Overhauser effects establish that the aromatic ring in the X = Phe peptide is oriented over the central peptide unit. In dimethyl sulfoxide solutions two conformational species are observed in slow exchange on the NMR time scale, for both peptides. These are assigned to type I and type II beta-turn structures with -Pro-Tyr(Phe)- as the corner residues. The structural assignments are based on correlation of NMR parameters with model 14-membered cyclic cystine peptides with Pro-X spacers. Circular dichroism studies based on the -S-S- n-omega* transition suggest a structural change in the disulfide bridge with changing solvent polarity, establishing conformational coupling between the peptide backbone and the disulfide linkage in these systems.

Bacterial Proteins↗
PubMed1986

Autoradiolysis of iodinated monoclonal antibody preparations.

We investigated the effects of ionizing radiation on the immunointegrity of antibody fragments (Fab) because large amounts of high specific activity 131I may damage the proteins. We found that 1000 Gy of external 137Cs gamma radiation was sufficient to destroy 80-90% of the immunointegrity of the initial preparation. This effect was also produced by internally added [131I]NaI in a quantity sufficient to provide the same radiation absorbed dose. Since radioiodinated monoclonal antibodies labeled to high specific activity are being evaluated for radioimmunotherapy, the above observation is significant since high levels of internal radiation occur with therapeutic doses of 131I-labeled antibody. Human serum albumin in low concentration (2%) added to the iodinated antibody solutions was successful in preventing loss of immunoreactivity and can be used to protect and stabilize therapeutic quantities of radiolabeled monoclonal antibody preparations.

Antibodies, Monoclonal↗
PubMed1986

Immunoreactivity assay for labeled anti-melanoma monoclonal antibodies.

A convenient, rapid, and reproducible assay was developed to evaluate the immunoreactivity of radiolabeled monoclonal antibodies against three different human melanoma-associated antigens, p97, a proteoglycan and a GD3 ganglioside. A cloned melanoma cell line (M 2669 CL 13) was selected as the target and, when fixed with paraformaldehyde, showed binding as good as or better than that obtained with live cells for the three antigens. Fixed cells retained good binding properties stored at 4 degrees C for over 6 mo. This assay has general applicability to other antigen-antibody systems for testing chemically modified monoclonal antibodies or fragments during the development of a radiopharmaceutical or as a routine quality control measure for clinical agents.

Antibodies, Monoclonal↗
PubMed1984

Allergic disease in children. Guide to diagnosis and treatment.

Allergy is responsible for many problems in the pediatric age-group. At times the most difficult job for the physician is to determine if the patient is indeed allergic and, if so, to what. Allergy skin testing remains the first choice for diagnostic study. Treatment consists of avoiding the offending allergen if possible, controlling symptoms with appropriate medication, and using immunotherapy if indicated.

Adolescent↗
PubMed1984

Intraabdominal pressure and ascitic fluid volume in decompensated liver cirrhosis.

Tense ascites is a widely used clinical concept lacking a quantitative correlate. In 13 patients with tense cirrhotic ascites we measured total intraabdominal pressure (IAP), hydrostatic pressure (HP), and tension. HP was defined as the level of ascitic fluid determined by percussion of the abdominal wall, and tension was the fluid level in the manometer above the HP. The total IAP is the sum of HP and tension. At a later, second measurement 11 patients significantly decreased their IAP. As expected in early stages of ascites resolution, major changes were found to be due to the reduction of the tension component, which accounted for 68% of the decrease in IAP. The HP seemed to show a definite decline only at a late stage of resolving ascites. Five patients, two with an essentially unchanged IAP and three with declining IAP, increased their ascitic fluid volume at the second study. The most probable explanation of this phenomenon is in the transfer of fluid from the edematous splanchnic organs into the peritoneal cavity in the early phase of ascites mobilization.

Abdominal Muscles↗
PubMed1984

Intraabdominal pressure and resorption of ascites in decompensated liver cirrhosis.

We determined the levels of total intraabdominal pressure and the tension resulting from the distention of the abdominal wall in 12 patients with ascites resulting from alcoholic cirrhosis of the liver. The measurements were performed first when ascites was tense, and were repeated later when ascites became non-tense with treatment. Using intraperitoneal injections of 131I-labeled human serum albumin, we measured the ascites volume and the resorption of albumin from the ascitic compartment at the same time as the pressure studies. Reduction in intra-abdominal pressure from 29.5 +/- 4.1 to 21.7 +/- 6.0 cm H2O (p less than 0.001) and in tension from 8.3 +/- 2.7 to 2.9 +/- 1.6 cm H2O (p less than 0.001) did not result in significant changes in resorption of albumin from the peritoneal cavity. Lowering of intra-abdominal pressure was not associated with any change in the volume of the resorbed ascitic fluid or the amount of albumin resorbed. We conclude that the ascites resorption rate in cirrhosis is not linearly related to intra-abdominal pressure and that in tense ascites, the decreased permeability of the parietal peritoneum counteracts the effects of the increased intra-abdominal pressure on albumin resorption. Cirrhotic ascites is associated with a changing permeability of the peritoneal membrane.

Abdomen↗
PubMed1976

A micromethod for evaluating the phagocytic activity of human macrophages by ingestion of radio-labelled polystyrene particles.

Studies in vitro of human macrophage function in health and disease have been impeded by the difficulty of obtaining such cells in sufficient number. Unlike animal species, the only readily available source of human macrophages are circulating monocytes. Herein, a method is described whereby the phagocytic rate of small numbers of glass-adherent mononuclear cells can be accurately measured. The method utilizes the ingestion by macrophages of technetium labelled polystyrene particles; both the radiolabel and ingestible substrate are readily available and the labelling process simple and efficient. The phagocytic rate can be expressed as radioactive counts per microgram of cell protein; data is also presented showing that the number of particles ingested per cell can be accurately derived.

Blood Cell Count↗
PubMed1972

Mercury concentrations in museum specimens of tuna and swordfish.

The mercury levels of museum specimens of seven tuna caught 62 to 93 years ago and a swordfish caught 25 years ago have been determined by instrumental neutron activation analysis. These levels are in the same range as those found in specimens caught recently.

Activation Analysis↗