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Biomedical subjects

C P Sharma

Publications and source records attributed to C P Sharma.

At least 91 records · Page 5Linked to original sources
PubMed1989

Influence of steroid hormones on protein-platelet interaction at the blood-polymer interface.

To develop artificial materials for prolonged use in the vascular system, the complicated process of surface-induced thrombosis needs to be better understood. Steroidal hormones have a profound role in thrombosis and haemostasis, although adequate studies are not available to demonstrate their part in the thromboembolic phenomena that occur at the blood-foreign material interface. We studied the interfacial phenomena of five steroid hormonal drugs, Sustanon, Menstrogen, Mixogen, Durabolin and Ovral and their interaction with proteins and platelets toward an artificial surface using contact angle, polyacrylamide gel electrophoresis, trace labelling methods, etc. This study demonstrates the effect of these hormones to modulate platelet-surface attachment in the presence of platelet inducers. The addition of steroid hormones to the polymer-protein system can inhibit the level of surface-bound albumin where the fibrinogen binding to an artificial surface has been enhanced or unaltered. Steroids also increase platelet-surface attachment to variable degrees. Prolonged use of steroids or the oestrogen-containing oral contraceptive agents may not be advisable for patients having an artificial implant in contact with blood.

Adsorption↗
PubMed1989

The effect of antihypertensive drugs on protein adsorption, platelet adhesion, and blood coagulation toward an artificial surface.

Protein adsorption and platelet adhesion are two important biological processes arising at the blood-prosthetic interface. The ability of certain antihypertensive and anticholesterol drugs, namely, clonidine, hydralazine, sembrina, frusemide, clofibrate, sorbitrate, thyroxine, etc., to modulate the surface-induced platelet adhesion to polycarbonate substrate was investigated using washed calf platelets in the presence and absence of fibrinogen. This study also demonstrated the changes in protein-surface binding with these drugs using electrophoretic techniques. It seems that the addition of these drugs to the polymer-protein system increased the level of surface-bound albumin variably. These drugs also reduced the fibrinogen surface concentration and inhibited the surface-induced platelet adhesion to variable degrees. Therefore, it may be possible that the enhanced albumin-surface concentration, or reduced fibrinogen-surface binding, in the presence of these drugs may be one of the parameters for a reduced platelet-surface attachment, which may also improve the blood compatibility of the substrate. A better understanding of the mechanism of these drugs under in vivo conditions is needed to correlate these findings.

Adsorption↗
PubMed1989

The preparation of a urokinase-AT-III-PGE1-methyldopa complex, and its effects on platelet adhesion, coagulation times, protein adsorption, and fibrinolysis.

Modifications of urokinase by substances possessing useful therapeutic activity permit combined action preparations to be obtained. Here an attempt was made to develop a complex having combined action for therapeutic activity. The possibility of repeatedly modified urokinase with antithrombin-III-methyldopa-prostaglandin E1 had been experimentally demonstrated. The complex was immobilized on albuminated substrate, which showed fibrinolytic, anticoagulant, and antiplatelet effects simultaneously, in addition to the normal antihypertensive action of methyldopa. The complex immobilized substrate also demonstrated an increase in albumin-surface attachment and a reduction in fibrinogen binding. This may be one of the parameters for a reduced platelet-surface attachment, which may also improve the blood compatibility of the substrate. The approaches suggested indicate the possible new ways of creating nonthrombogenic surfaces with wider applications. A better understanding of the mechanism of these complexes are needed in in vivo conditions to correlate these findings.

Animals↗
PubMed1989

Permeability of PEUU membranes: their modification towards blood compatibility.

An attempt was made to develop haemodialysis membranes using polyether urethane urea synthesised in our laboratory. It was observed that the processing parameters such as precipitation medium, precipitation temperature etc. can influence the porosity of the membrane and subsequently the permeability property. It was also noted that the permeability of the dried membrane was negligible even though it was kept in distilled water overnight before use. The effect of pH on permeability through the membrane was studied by dialysis experiment using mixtures of various components such as urea, creatinine, uric acid, inulin, albumin, NaCl and KCl at various pH. Standard cellulose acetate (CA) membrane was used for comparison. Membranes were also prepared using biomer solution by precipitating in distilled water at room temperature and the monomer, 2-hydroxy ethyl methacrylate (HEMA) was grafted onto it by glow discharge technique. It was found that the permeability was increased by HEMA grafting with some loss of tensile strength and strain. A comparative study of fibrinogen adsorption during dialysis and adsorption by direct exposure of samples to a mixture containing urea, uric acid, creatinine, dextran, fibrinogen and electrolytes like sodium and potassium ions was also done with 125I labelled fibrinogen. Platelet adhesion studies indicated that the number of adhered platelets was less on the HEMA grafted samples which may enhance blood compatibility. Finally, the membranes were subjected to different sterilization processes possible under wet conditions such as glutaraldehyde treatment and autoclaving. The contact angle, permeability, mechanical property and platelet adhesion studies indicated that the sterilization method can affect the performance of the membrane.

Adsorption↗
PubMed1988

Changes in albumin/platelet interaction with an artificial surface--due to a antibiotics, pyridoxal phosphate, and lymphocytes.

Protein adsorption and platelet adhesion are two important biological processes arising at the blood prosthetic interface. The effect of certain antibiotics, namely, neomycin, gentamicin, ampicillin, penicillin-G, and streptomycin to modulate the albumin polycarbonate surface interaction was investigated using 125I albumin from a protein mixture in the presence and absence of isolated calf lymphocytes. This study also demonstrated the changes in platelet-surface adhesion with these antibiotics. The effect of pyridoxal phosphate to modulate the red blood cell-mediated platelet-surface attachment was also attempted. It appears from pyridoxal phosphate studies that pyridoxal 5'-phosphate (PLP) could modify the surface-platelet attachment. It also inhibited the fibrinogen-induced platelet adhesion. It seems, the addition of antibiotics to the polymerprotein system increased the level of surface-bound albumin variably whereas lymphocytes incubated in the medium did not affect the surface-albumin concentration with time course. These antibiotics also inhibited the surface-induced platelet adhesion to variable degrees. Our earlier studies have indicated that certain antibiotics or antiplatelet drugs can inhibit the fibrinogen binding to an artificial surface. Therefore, it may be possible that the enhanced albumin-surface concentration or reduced fibrinogen-surface binding, in the presence of these antibiotics, may itself be one of the parameter for a reduced platelet-surface attachment, which may also improve the blood compatibility of the substrate. A better understanding of the mechanism of antibiotics is needed in in vivo conditions to correlate these findings.

Animals↗
PubMed1987

Effect of vitamin B6 on the synthesis and degradation of aspartate aminotransferase in chicken embryo fibroblasts.

The effect of pyridoxal depletion and supplementation on the intracellular level of mitochondrial and cytosolic aspartate aminotransferase in cultured chicken embryo fibroblasts was examined. No apoenzyme was detected in cells grown in the presence of pyridoxal, and the specific activity of total enzyme did not vary profoundly from primary to quaternary cultures. Under pyridoxal depletion, up to 40% apoenzyme was found in tertiary cultures which was entirely due to the mitochondrial isoenzyme. Cytosolic apoenzyme was never detected. Total aspartate aminotransferase relative to total protein was increased 2-fold in secondary cultures; only the mitochondrial isoenzyme contributed to the increased specific activity. The cytosolic isoenzyme decreased steadily and was below the limit of detection in quaternary cultures. The changes are attributed to an increased and decreased synthesis of mitochondrial and cytosolic isoenzyme, respectively. No induction of either isoenzyme was observed after incubating the cells with different hormones and substrates. In secondary cultures, no degradation of mitochondrial isoenzyme could be detected under pyridoxal deficiency or supplementation during 4.4 days, an interpassage duration. The cytosolic aspartate aminotransferase was degraded initially with an apparent half-life of approximately 0.9 day under both sets of conditions. The pronounced stability of mitochondrial aspartate aminotransferase, even though one-third of it was present as apoenzyme, excludes the formation of the apoform to be the rate-limiting step in its degradation. The present results show that pyridoxal affects the synthesis of mitochondrial and cytosolic aspartate aminotransferase, but differently.

Animals↗
PubMed1987

Prostacyclin immobilized albuminated surfaces.

The adhered platelets on artificial surfaces play a crucial role in inducing thrombosis. Therefore, it is very much desirable to have surfaces which can effectively retard platelet adhesion and aggregation. Prostaglandins like PGE2, PGE1 and PGD2 possess potent antiplatelet activity, but have very short half life. A chemically stable prostacyclin analog, 10,10-difluoro-13-dehydroprostacyclin (DF2-PGI2) seems to be promising. Polyelectrolyte (PE) synthesized from natural poly cis-1,4 isoprene has also been found to possess outstanding anticoagulant and antiplatelet activity. Modification of polyetherurethane urea (PEUU) by immobilizing DF2-PGI2 and poly-electrolyte in various combinations using glow discharge technique has been attempted. Surfaces thus modified showed negligible platelet adherence. The inhibition of platelet adherence in presence of inducing agents like fibrinogen, thrombin and ADP was also remarkable. The interactions of albumin and fibrinogen with the modified surfaces were studied using 125I labelled proteins.

Adenosine Diphosphate↗
PubMed1987

Influence of L-ascorbic acid, blood cells and components on protein adsorption/desorption on polycarbonate.

In a previous study we have shown that vitamin C has some effect on the polymer surface by adsorption to it, which would probably affect the protein adsorption and platelet adhesion. The present work has been extended to demonstrate the influence of vitamin C on the kinetics of protein-polymer interaction, using labeled proteins, in the presence and absence of red blood cells, platelets and white blood cells. It appears that vitamin C causes an increase in albumin surface concentration compared to bare substrate which seems to decrease slightly in the presence of blood cells. On the other hand, the infusion of vitamin C to the fibrinogen blood cells system dramatically inhibits the fibrinogen surface binding. The role of L-ascorbic acid to reduce the protein adsorption in the presence of blood cells is discussed by taking into account the interaction of vitamin C with the polymer surface, the interaction of vitamin C with the proteins and cellular membrane, and the interaction of proteins and cells with the polymer itself. The effect of various blood components also seems to be important, and slight differences in the adsorption pattern of proteins are observed in the presence of urea, creatinine, bilirubin, Fe ion and zinc at normal blood levels.

Adsorption↗
PubMed1987

Inhibition of platelet adhesion to glow discharge modified surfaces.

Plasma glow technique has created much interest in the field of surface modification of polymers due to its versatility of generating active polar groups on the surface without affecting the bulk properties. Here an attempt is made to inter-relate the surface properties and platelet adhesion on various polymeric substrates due to plasma treatments. Initially, a critical review of the process and development of thrombosis upon contact of an artificial surface with blood, has been provided, which has been extended with the need for surface modifications to improve their blood compatibility and the versatility of plasma treatments for such modifications have been emphasized. Phospholipids like phosphoryl choline, phosphatidyl choline and phosphoryl ethanolamine were attached to Angioflex surface by plasma glow. The role of such modified substrates to interact with platelets were investigated using Tyrode washed calf platelets. It seems, glow discharge modified phosphoryl choline bilayers dramatically inhibited the platelet-surface binding, which may be due to their biochemical resemblance with thromboresistant surfaces of human blood cells. Further, the behaviour of all phospholipids towards bloodpolymer interaction is not similar and may change depending on the nature of their functional groups, net charge of the phospholipid adsorbed surface and their interaction with platelets and its activation. It is possible to chemically immobilize lipid bilayers on standard polymers, using plasma glow, to improve their biological performance; by suitably selecting the phospholipid combinations.

Adhesiveness↗
PubMed1987

Introduction of surface functional groups onto biomaterials by glow discharges.

An attempt was made to graft the monomer HEMA to the polymer surface by "Glow discharge" technique. Experiments were carried out for different surfaces varying the exposure times of samples to HEMA and also as a function of glow discharge time. It was found that as the percentage of grafting increases the hydrophilicity also increases. Contact angle measurements were performed on these substrates, which confirmed the hydrophilic nature of the grafted samples compared to the controls. The role of protein adsorption and their effects to modulate the blood polymer interaction is briefly discussed. When a foreign material comes in contact with blood, the initial event is the adsorption of plasma proteins in parallel with the adhesion of platelets to the material. Albuminated surfaces discourage platelet adhesion while fibrinogen enhances the platelet attachment and thrombosis. Hence a decreased ratio of fibrinogen to albumin on a substrate can be correlated as an indication to its improved blood compatibility. Fibrinogen to albumin ratios of the grafted samples showed a reduction, indicating that albumin adsorption is high; which may make the modified surfaces non-thrombogenic.

Acrylates↗
PubMed1986

A low molecular weight growth inhibitor secreted in cultures of chicken embryo fibroblasts.

We report evidence for the occurrence of a novel type of growth inhibitor in conditioned medium of chicken embryo fibroblasts which inhibits both DNA synthesis and cell proliferation. The inhibitor does not compete with the growth factors present in the serum and its effect on the target cells is non-cytotoxic and reversible. The kinetics of the inhibition of thymidine incorporation indicate that the inhibitor acts in the S-phase of the cell cycle. Comparison of the chemical and physico-chemical properties of the inhibitor with other, recently described growth inhibitors of fibroblasts has demonstrated that it is different in many respects. The inhibitor has a Mr of less than 2000, is protease resistant, and acid- and heat-stable.

Animals↗
PubMed1986

The precursor of mitochondrial aspartate aminotransferase is translocated into mitochondria as apoprotein.

Mitochondrial aspartate aminotransferase is synthesized on free polysomes as a higher molecular weight precursor (Sonderegger, P., Jaussi, R., Christen, P., and Gehring, H. (1982) J. Biol. Chem. 257, 3339-3345). The present study examines whether the coenzyme pyridoxal phosphate or pyridoxamine phosphate is required for the uptake of the precursor into mitochondria. Chicken embryo fibroblasts were cultured in medium prepared with and without pyridoxal. In cells grown in the presence of pyridoxal only holoform of aspartate aminotransferase and no apoenzyme was detected. Cells cultured under pyridoxal deficiency contained about 30% of apoenzyme in secondary cultures. All of this apoform was identified as mitochondrial isoenzyme. In order to differentiate whether this apoenzyme corresponded to newly synthesized protein or originated from pre-existing holoenzyme, double isotope-labeling experiments were performed. Secondary cultures of chicken embryo fibroblasts grown under pyridoxal depletion were labeled with [3H]methionine, and then pulsed with [35S]methionine. In another series of experiments, the 3H-labeled cells were pulsed with [35S]methionine in the presence of the protonophore carbonyl cyanide m-chlorophenylhydrazone in order to accumulate the precursor. Subsequently, the accumulated precursor was chased into the mitochondria by addition of the carbonyl cyanide m-chlorophenylhydrazone antagonist cysteamine. The holo- and apoenzyme from the ultrasonic extract of the double-labeled cells were separated by affinity chromatography on a phosphopyridoxyl-AH-Sepharose column, immunoprecipitated, and analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and fluorography. Under both experimental conditions, the 3H/35S ratio of the apoenzyme was less than half of that of the holoenzyme. Therefore, the apoenzyme and not the holoenzyme is the first product of the precursor in the mitochondria. Apparently, the precursor of mitochondrial aspartate aminotransferase is transported into mitochondria as apoprotein and is processed there independently of the coenzyme.

Animals↗
PubMed1986

Protein/platelet interaction with an artificial surface: effect of vitamins and platelet inhibitors.

Protein adsorption and platelet adhesion are two important biological processes arising at the blood-prosthetic interface. The effect of Vitamins and antiplatelet drugs to modulate the surface induced platelet adhesion to polycarbonate was investigated using washed calf platelets in presence and absence of fibrinogen. This study also demonstrated the effects of Vitamins and antiplatelet drugs towards protein adsorption to an artificial surface. It seems Vitamin B6, Vitamin E, combinations of Aspirin-Persantine, Aspirin-Vitamin C, a synthetic Polyelectrolyte and Galactosamine reduced the fibrinogen (fg) surface concentration from a mixture of proteins. These antiplatelet agents also enhanced the albumin surface concentration. This itself may be one of the parameters to reduce the platelet adhesion towards an artificial surface. A combination of Aspirin-Vitamin C-Vitamin B6-Vitamin E inhibited the fibrinogen surface binding, which might be beneficial to improve the blood compatibility of an artificial surface.

Adsorption↗
PubMed1986

Molybdenum nutrition of isolates of four Aspergillus species.

The molybdenum requirement for growth and conidial formation by Aspergillus flavus, A. terreus, and A. sulphureus was found to be 0.2 ppb, which was one-fifth that of an A. niger isolate. Molybdenum deficiency depressed growth, conidial formation, dry weight, soluble protein, and the specific activities of nitrate reductase, succinic dehydrogenase, and aconitase in all the isolates of Aspergillus studied, but the specific activities of catalase and peroxidase were depressed only in isolates of A. niger, A. terreus, and A. flavus. Also, molybdenum deficiency stimulated the specific activities of acid phosphatase and ribonuclease in the A. flavus isolate, although the specific activities of these enzymes decreased in other isolates. Eighteen hours after the addition of molybdenum (5 ppb) to molybdenum-deficient (0.02 ppb) cultures of A. niger, the specific activities of catalase, peroxidase and succinic dehydrogenase were restored in the absence of cycloheximide, while the specific activity of nitrate reductase was recovered even in the presence of the inhibitor. There was no effect on the specific activities of aconitase and acid phosphatase following the addition of molybdenum to molybdenum-deficient cultures of A. niger.

Acid Phosphatase↗
PubMed1985

Changes in protein adsorption on polycarbonate due to L-ascorbic acid.

When a synthetic material is introduced into blood, plasma proteins are rapidly adsorbed on to its surface, followed by the attachment of formed elements of blood, leading to thrombus formation. Previous research reported that vitamin C (L-ascorbic acid) prolongs the clotting time due to the formation of vitamin C-calcium complexes, which reduce the availability of Ca2+ ions for the clotting mechanism in in vitro conditions. Contact angle and platelet adhesion studies have indicated that vitamin C modifies the surface-protein interaction and surface-platelet binding at the interface. In this paper an increased thickness of protein layer deposited on the polycarbonate substrate has been observed in the presence of vitamin C (approximately 50 A) using ellipsometric measurements. Further polyacrylamide gel electrophoresis (PAG) and infrared attenuated total reflection spectroscopy (IR-ATR) techniques have provided a better understanding of the interfacial phenomena. It seems, that the adsorption of albumin is increased, relatively, in the presence of vitamin C, when compared with that of fibrinogen and gamma-globulin from an equal amount of protein mixture.

Adsorption↗
PubMed1984

Structural relevance of adsorbed aminosugars on polycarbonate - antithrombogenicity.

The effects of glucosamine, galactosamine, and mannosamine on platelet adhesion and coagulation induced by an artificial surface were investigated. Glucosamine and galactosamine showed both antiplatelet and anticoagulant effects, but in case of mannosamine none of the above effects was found significant. The three analogs studied were having the same molecular weight and common molecular structure, however from our preliminary observations it could be suggested, that the spatial arrangement of functional groups in the glucopyranose ring at C2, C4 positions were important for it's activity.

Animals↗