Isolation and structure of a 4-O-methyl-glucuronoarabinogalactan from Boswellia serrata.
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Carbohydrate Conformation↗
Biomedical subjects
A K Sen
Publications and source records attributed to A K Sen.
A comparative study on the immune response of sheep to foot and mouth disease virus vaccine type Asia-1 prepared with different inactivants and adjuvants.
Foot and mouth disease virus type Asia-1 was inactivated either with formaldehyde or binaryethylenimine (BEI). Inactivated vaccines were prepared incorporating aluminium hydroxide gel or mineral oil as an adjuvant. The antibody response to the adult sheep was studied by ELISA and SN test for a period of 6 months. There was no difference in the antibody response between vaccines inactivated with formaldehyde or BEI. Whereas significant difference in the antibody response was observed between gel and oil vaccines. The high titres of antibody stimulated by oil vaccines persisted longer than those of gel vaccines within the period of study.
Animals↗
Endogenous substrates of rat heart protein kinase C type I, II, and III isozymic forms in cardiac sarcolemma.
The endogenous substrate proteins of rat cardiac protein kinase C type I, II, and III isozymic forms were studied in rat cardiac sarcolemma. The 19-, 21-, 29-, 35-, and 95-kDa proteins were phosphorylated by both types II and III, but not type I. The extent of phosphorylation by individual protein kinase C isozymic forms was additive and equal to the extent of phosphorylation observed when a mixture of isozymic forms was employed. The extent of phosphorylation of the 21-kDa protein by type III was much higher than that by type II. These results suggest that the protein kinase C isozymes have preferences for specific endogenous substrate proteins. The phosphorylation of these endogenous substrate proteins by protein kinase C isozymes probably plays a role in cardiac cell functions.
Animals↗
Protein kinase C mediated activation and phosphorylation of Ca(2+)-pump in cardiac sarcolemma.
The effects of purified protein kinase C (PKC) on the Ca(2+)-pumping ATPase of cardiac sarcolemma were investigated. The addition of PKC to sarcolemmal vesicles resulted in a significant increase in ATP-dependent Ca2+ uptake, by increasing the calcium affinity by 2.8-fold (Km 0.14 vs. 0.4 microM for control) and by increasing Vmax from 5 to 6.8 nmol.mg protein-1.min-1. The addition of PKC also stimulated Ca2+ ATPase activity in sarcolemmal preparations. This activity was increased further upon the addition of calmodulin. These results suggest that PKC stimulates Ca2+ ATPase through a kinase-directed phosphorylation. The addition of PKC to a purified preparation of Ca2+ ATPase in the presence of [gamma-32P]ATP resulted in a 100% increase in phosphorylation that was dependent on the presence of Ca2+, phosphatidylserine, and phorbol 12,13-dibutyrate. These results demonstrate that the Ca2+ ATPase of canine cardiac muscle can be phosphorylated by PKC in vitro, resulting in increased affinity of the Ca2+ ATPase for Ca2+ and increase in the Ca2+ pump pumping rate. The results suggest that the Ca(2+)-pumping ATPase in heart tissue can be stimulated by PKC, thereby regulating the intracellular Ca2+ levels in whole heart.
Adenosine Triphosphate↗
A study on the immune response of sheep to foot and mouth disease virus vaccine type 'O' prepared with different inactivants and adjuvants.
Foot and mouth disease virus (FMDV) type 'O' was inactivated either with formaldehyde or binaryethyleneimine (BEI). Vaccines were prepared with inactivated virus incorporating aluminum hydroxide gel or mineral oil as an adjuvant. The antibody response in sheep was monitored by serum neutralization and ELISA test for a period of six months. Significant difference in antibody response was not observed between vaccines inactivated with formaldehyde or BEI. On the other hand significant difference in the antibody response was noticed between alhydrogel and oil vaccines. The high titer of antibodies stimulated by oil adjuvant vaccines persisted longer than those of alhydrogel vaccines within the period of study.
Adjuvants, Immunologic↗
Calculation of control coefficients of metabolic pathways. A flux-oriented graph-theoretic approach.
Within the premises of the flux-oriented theory of Crabtree & Newsholme [(1987) Biochem. J. 247, 113-120], I have used a graph-theoretic approach for calculating the Control Coefficients of metabolic pathways. It is shown that a directed graph representing the control structure of a metabolic pathway can be constructed in a heuristic manner directly from the reaction diagram of the pathway, without the necessity of writing down the governing equations for the Control Coefficients. The Control Coefficients are derived from an analysis of the topology of the directed graph. The graph-theoretic approach also provides a visual framework for analysing the functional relationships of the individual enzymes. The control structures of the following pathways are examined here: (a) a simple unbranched pathway with four enzymes, (b) a simple branched pathway with three enzymes, and (c) a branched pathway with both carbon and energy (ATP) fluxes.
Metabolism↗
Purification and characterization of protein kinase C isozymes from rat heart.
A calcium-sensitive, phospholipid-dependent protein kinase (protein kinase C) and its three isozymes were purified from rat heart cytosolic fractions utilizing a rapid purification method. The purified protein kinase C enzyme showed a single polypeptide band of 80 KDa on SDS-polyacrylamide gel electrophoresis, and was totally dependent on the presence of Ca2+ and phospholipid for activity. Diacylglycerol was also found to stimulate enzymatic activity. Autophosphorylation of the purified PKC showed an 80 KDa polypeptide. The identity of the purified protein was also verified with monoclonal antibodies specific for PKC. Further fractionation of the purified PKC on a hydroxylapatite column yielded three distinct peaks of enzyme activity, corresponding to type I, II and III based on similar chromatographic behaviour as the rat brain enzyme. All three forms were entirely Ca2+ and phosphatidylserine dependent. Type II was found to be the most abundant. Type I was found to be highly unstable. PKC activity studies demonstrate that types II and III isozymic forms are different with respect to their sensitivity to Ca2+.
Animals↗
Quantitative analysis of metabolic regulation. A graph-theoretic approach using spanning trees.
A graph-theoretic technique using spanning trees is described for the evaluation of Flux Control Coefficients of metabolic pathways. The technique is illustrated by investigating a linear pathway (a) in the absence of feedback and feedforward regulation. (b) with its first enzyme inhibited by the end product and (c) with multiple feedback loops. It is shown that the Flux Control Coefficients of a linear pathway with one or more feedback loops can be derived in a systematic manner by superimposing the effect of the feedback loop(s) on the expressions pertaining to the Flux Control Coefficients of the unregulated pathway.
Enzymes↗
Meibomian gland carcinoma in a 20-year-old patient.
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Adenocarcinoma↗
Carbachol-stimulated phosphorylation of a 170-kDa endogenous protein in avian salt gland cells.
The effect of cholinergic stimulation of cellular protein phosphorylation was studied using an intact cell preparation isolated from the avian salt gland. Isolated cells were allowed to incorporate 32Pi into the cellular ATP pool and then challenged with compounds known to induce ion secretion in this tissue. Addition of carbachol resulted in a time- and concentration-dependent (EC50 = 500 nM) increase in 32Pi content of a 170-kDa protein (pp170). The stimulated phosphorylation could be blocked by the inclusion of atropine (100 microM). Subcellular fractionation studies localized pp170 to the plasma membrane fraction of the tissue. The integral nature of this protein was demonstrated by detergent-solubilization experiments with Triton X-100. The possibility that carbachol stimulates phosphorylation of pp170 via activation of protein kinase C (PKC) was investigated. Incubating salt gland cells with 4 beta-phorbol 12-myristate 13-acetate (PMA; 1 microM) or carbachol (100 microM) resulted in a translocation of soluble PKC from the cytosol to a plasma membrane fraction. Addition of either PMA (1 microM) or ionomycin (1 microM) alone did not enhance phosphorylation of pp170. A 4.5-fold increase in the phosphorylation state of pp170 was only observed when PMA and ionomycin were added concurrently. Preincubation of salt gland cells with PKC inhibitors H-7 (50 microM) or staurosporine (10 microM) inhibited the carbachol-stimulated phosphorylation of pp170. These findings suggest that carbachol mediates its secretomimetic effects via activation of PKC and that pp170 may represent a novel integral membrane PKC substrate protein.
1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
Application of electrical analogues for control analysis of simple metabolic pathways.
I have used electrical analogues for calculating the Flux Control Coefficients of metabolic pathways. An analogue circuit consists of resistances that are connected in series (or parallel) with a voltage (or current) source. In constructing the analogues, each of the enzymes in the pathway is associated with a resistance whose magnitude depends on the Elasticity Coefficients of the enzymes. These circuits can be designed in a heuristic fashion directly from the configuration of the pathway, without the necessity of writing down the governing equations with the use of Summation and Connectivity Theorems. The Flux Control Coefficients of the enzymes are represented by voltages across (or currents through) the resistances and are determined by an application of Ohm's Law. Results are given for (a) a simple linear pathway without feedback or feedforward regulation, and (b) a linear pathway with feedback inhibition. The analogue circuits are also convenient for assessing the relative importance of the various enzymes in flux control, and for simplifying the structure of a given pathway.
Electricity↗
Metabolic control analysis. An application of signal flow graphs.
In this paper the method of signal-flow graphs is used for calculating the Control Coefficients of metabolic pathways in terms of enzyme elasticities. The method is applied to an unbranched pathway (a) without feedback or feedforward regulation and (b) with feedback inhibition of the first enzyme by the last variable metabolite. It is shown that, by using a signal-flow graph, the control structure of a metabolic pathway can be represented in a graphical manner directly from the configuration of the pathway, without the necessity of writing the governing equations in a matrix form. From a signal-flow graph the various Control Coefficients can be evaluated in an easy and straightforward fashion without recourse to matrix inversion or other algebraic techniques. A signal-flow graph also provides a visual framework for analysing the cause-effect relationships of the individual enzymes.
Chemical Phenomena↗
Lipid A mutants of Vibrio cholerae: isolation and partial characterization.
Vibrio cholerae mutants resistant to common antibiotics and neutral and anionic detergents were isolated. Analysis of isolated outer membranes revealed a significant deficiency in the acylation of lipid A in the resistant strains. The content of amide-linked and ester-bound fatty acids in the lipid A of the mutant strains compared to that of the wild type was about 50-56% and 29-37% respectively. This defect was specific for lipid A as there was no change in the acylation of phospholipids. The reduction in fatty acid content of lipid A was reflected in the altered endotoxic properties in the mutant strains.
Drug Resistance, Microbial↗
Topological analysis of metabolic control.
A topological approach is presented for the analysis of control and regulation in metabolic pathways. In this approach, the control structure of a metabolic pathway is represented by a weighted directed graph. From an inspection of the topology of the graph, the control coefficients of the enzymes are evaluated in a heuristic manner in terms of the enzyme elasticities. The major advantage of the topological approach is that it provides a visual framework for (1) calculating the control coefficients of the enzymes, (2) analyzing the cause-effect relationships of the individual enzymes, (3) assessing the relative importance of the enzymes in metabolic regulation, and (4) simplifying the structure of a given pathway, from a regulatory viewpoint. Results are obtained for (a) an unbranched pathway in the absence of feedback the feedforward regulation and (b) an unbranched pathway with feedback inhibition. Our formulation is based on the metabolic control theory of Kacser and Burns (1973) and Heinrich and Rapoport (1974).
Enzymes↗
Metabolic control theory: a graph-theoretic approach.
The regulatory properties of metabolic pathways are investigated using a graph-theoretic approach. Applying concepts from classical graph theory, analytical expressions are derived for the flux control coefficients of a linear pathway subject to feedback inhibition. It is shown that the relative importance of the various enzymes in the control of flux can be easily established with the aid of this graphical procedure. Another advantage of this technique is that it can be implemented in a step-by-step fashion for simplifying the pathway structure. The graph-theoretic method can also be used for studying the cause-effect relationships of the individual enzymes in a given pathway.
Enzymes↗
Herniation of RAE tube through split Boyle Davis gag.
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Adenoidectomy↗
Milk whey as a serum supplement for the growth of FMD virus in BHK-21 cells.
Two batches of experimental media containing 10% milk whey (sweet or sour) and 1% bovine serum supported the growth of BHK-21 cells in serial passages. The cell yield was greater than 2 x 10(6)/ml at 48 h. The cells were susceptible to inoculation with foot and mouth disease (FMD) virus type 'A' and the virus titres obtained were comparable with those in Eagle's MEM-G with 10% serum. The use of milk whey could reduce the consumption of serum required for the growth of FMD virus in BHK-21 cells by up to 90%.
Animals↗
Effects of product inhibition in metabolic pathways: stability and control.
The effect of product inhibition in metabolic pathways is examined using (a) an unbranched pathway in the absence of endproduct inhibition and (b) an unbranched pathway with endproduct inhibition. It is shown that product inhibition may be considered an alternative mechanism to endproduct inhibition for reducing the overall logarithmic gain of an unregulated pathway. When product inhibition and endproduct inhibition are both present, they act in concert with each other to lower the overall logarithmic gain and alleviate parameter sensitivities. Product inhibition is also found to exert a stabilizing influence that competes with the destabilizing effect of endproduct inhibition in controlling the dynamic behavior.
Kinetics↗