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Biomedical subjects

D V Shah

Publications and source records attributed to D V Shah.

At least 19 recordsLinked to original sources
PubMed2003

Chronic thromboembolic pulmonary hypertension--diagnosed on spiral CT angiography.

Chronic thromboembolic pulmonary hypertension (CTEPH) is a part of the spectrum of venous thromboembolism in which pulmonary thrombus fails to resolve, resulting in occlusion of the major pulmonary artery. Diagnosis of this disease is important as it is potentially curable by pulmonary thromboendarterectomy. A case of CTEPH diagnosed non-invasively on spiral computerized (CT) pulmonary angiography is reported.

Angiography↗
PubMed1999

Echinaforce and other Echinacea fresh plant preparations in the treatment of the common cold. A randomized, placebo controlled, double-blind clinical trial.

The aim of this randomized, double-blind, placebo controlled study was to investigate the efficacy and safety of different doses and preparations of Echinacea purpurea in the treatment of common cold. 246 of 559 recruited healthy, adult volunteers caught a common cold and took 3 times daily 2 tablets of either Echinaforce (Echinacea purpurea-preparation from 95% herba and 5% radix), Echinacea purpurea concentrate (same preparation at 7 times higher concentration), special Echinacea purpurea radix preparation (totally different from that of Echinaforce) or placebo until they felt healthy again but not longer than 7 days. The primary endpoint was the relative reduction of the complaint index defined by 12 symptoms during common cold according to the doctor's record. Echinaforce and its concentrated preparation were significantly more effective than the special Echinacea extract or placebo. All treatments were well tolerated. Among the Echinacea groups the frequency of adverse events was not significantly higher than in the placebo group. Therefore, Echinacea concentrate as well as Echinaforce represent a low-risk and effective alternative to the standard symptomatic medicines in the acute treatment of common cold.

Adjuvants, Immunologic↗
PubMed1993

Vitamin K-dependent carboxylase activity, prothrombin mRNA, and prothrombin production in two cultured rat hepatoma cell lines.

The presence of under-gamma-carboxylated forms of plasma prothrombin is a marker for human primary hepatocellular carcinoma. A rat hepatoma cell line (7777) which was previously shown to secrete undercarboxylated prothrombin when grown as a solid tumor has now been grown in monolayer culture. This cell line has a decreased activity of the microsomal vitamin K-dependent carboxylase when compared to a control (H4IIEC3) hepatoma line, does not increase intracellular prothrombin concentrations in response to vitamin K depletion, and secretes undercarboxylated prothrombin even when grown in vitamin K supplemented media. Prothrombin gene expression in the 7777 cell line, as measured by prothrombin mRNA levels, was not altered in the 7777 cell line. This cell line appears to be a model for assessing the cellular alterations responsible for undercarboxylated prothrombin excretion by human hepatocellular tumors.

Alkylation↗
PubMed1993

Prothrombin synthesis in rat hepatoma H4IIEC3 cells: response to the proposed "coagulopoietin factor".

Based on studies in intact animals, the presence of humoral factors, "coagulopoietins", which regulate the synthesis of vitamin K-dependent plasma proteins has been proposed. These proposed factors are produced in response to vitamin K deficiency, coumarin treatment, or specific antibody depletion of vitamin K-dependent clotting factors. The production of prothrombin by rat hepatoma H4IIEC3 cells has now been shown to be dependent on the source of bovine serum in the media. Cells grown in serum from cows treated with dicoumarol produce about 20% more prothrombin in 24 h than those cells grown in control serum. The humoral factor causing this response is present early in the course of dicoumarol treatment, and the increase in prothrombin production is dependent on the amount of serum from a dicoumarol-treated cow in the media. Based on membrane filtration studies, the factor appears to be associated with the protein fraction of serum.

Animals↗
PubMed1988

Vitamin K deficiency from dietary vitamin K restriction in humans.

Vitamin K is required for the maintenance of normal hemostatic function. Ten college-aged male subjects chose diets restricted in vitamin K content for 40 d. Median phylloquinone intakes based on analysis of food composites dropped from 82 micrograms/d during the prestudy period to 40 and 32 micrograms/d at d 9 and 27 of dietary restriction, respectively. Serum phylloquinone concentrations fell from a mean of 0.87 to 0.46 ng/mL during a 21-d period of vitamin K restriction. Supplementation with 50 micrograms phylloquinone/d for 12 d increased serum phylloquinone to 0.56 ng/mL, and supplementation with 500 micrograms phylloquinone/d increased serum phylloquinone to 1.66 ng/mL. Vitamin K restriction resulted in alterations in a functional clotting assay that detects undercarboxylated prothrombin species in plasma and in a decrease in urinary gamma-carboxyglutamic acid. Supplementation with either 50 or 500 micrograms of phylloquinone restored both these indices to near normal values. These data are consistent with a human dietary vitamin K requirement of approximately 1 microgram/kg body wt/d.

Adult↗
PubMed1987

Abnormal prothrombin in the plasma of rats carrying hepatic tumors.

Vitamin K is required for the posttranslational formation of gamma-carboxyglutamyl residues in a number of plasma clotting factors. Interference with vitamin K action results in the appearance of abnormal (des-gamma-carboxy) forms of prothrombin in human plasma. Vitamin K-sufficient patients with primary hepatocellular carcinoma also secrete significant quantities of abnormal prothrombin; this response has now been studied in a rat model. Normal Buffalo strain rats had 9 micrograms/mL of circulating plasma abnormal prothrombin, whereas Buffalo strain rats carrying the transplantable Morris hepatoma tumor no. 7777 had 33 micrograms/mL at 3 weeks after transplant. Vitamin K-dependent carboxylase activity was normal in the liver of these rats, but very low in the tumor tissue. Rats carrying Morris hepatoma tumors no. 9618A and 5123D did not secrete significant amounts of abnormal prothrombin. Carboxylase activity in these tumors was 15 times that of the 7777 tumor. The data suggest that the secretion of abnormal prothrombin by hepatocellular tumors is the result of normal expression of the prothrombin gene by those tumors and a failure of the tumor to express the carboxylase gene.

Adsorption↗
PubMed1985

Coagulopoietin activity in rat plasma: influence of degree of hypoprothrombinemia and reproducibility of the response.

Injection of plasma from a vitamin K-deficient hypoprothrombinemic rat into a normal rat causes an increase in plasma prothrombin activity in the recipient rat. Maximum concentrations of the factor responsible for this response (coagulopoietin) are present in the plasma of rats fed a vitamin K-deficient diet for 7 days and do not increase as the period of deficiency is increased. The coagulopoietin activity of plasma from individual rats is variable, but similar activity was observed when multiple recipient rats received the same donor plasma.

Animals↗
PubMed1984

Abnormal prothrombin in the vitamin K-deficient rat.

Vitamin K is required for the post-translational formation of gamma-carboxyglutamyl residues in the vitamin K-dependent plasma clotting factors. Interference with vitamin K action results in the appearance of undercarboxylated, "abnormal," forms of prothrombin in bovine and human plasma, but the extent of this response in the rat has been controversial. Development of amidolytic and immunochemical assays for rat prothrombin have now shown that plasma from vitamin K-deficient or Warfarin-treated rats contains a non-BaSO4 adsorbable (undercarboxylated) pool of prothrombin that is equivalent to between 5 and 10% of the normal plasma prothrombin concentration.

Animals↗
PubMed1983

Vitamin K-dependent carboxylase: effect of detergent concentrations, vitamin K status, and added protein precursors on activity.

Activity of the rat liver microsomal vitamin K-dependent carboxylase has been studied at various concentrations of detergent. The activity which could be solubilized by 0.25% Triton X-100 was low but could be greatly increased if vitamin K-deficient rats were given vitamin K a few minutes before they were killed. At higher concentrations of Triton, more activity was solubilized and this effect was not seen. In vitro carboxylation of endogenous microsomal proteins was decreased by 80-90% if vitamin K was administered 1 min before rats were killed, but the amount of assayable prothrombin precursor was decreased by only 20%. Decarboxylated vitamin K-dependent rat plasma proteins were not substrates for the carboxylase and did not influence peptide carboxylase activity significantly. Purified microsomal prothrombin precursors did, however, stimulate carboxylation of peptide substrate and were used as a substrate for the carboxylase in a preparation from precursor depleted vitamin K-deficient rats.

Animals↗
PubMed1983

Vitamin K-dependent carboxylase: effect of endogenous microsomal protein precursors on the rate of exogenous substrate carboxylation.

Rat liver microsomes contain a Triton X-100 solubilizable vitamin K-dependent carboxylase activity that converts specific glutamyl residues of a microsomal prothrombin precursor to gamma-carboxyglutamyl residues. This activity has been studied in partially (0.25% Triton X-100) and completely (1.0% Triton X-100) solubilized rat liver microsomal preparations. The rate of vitamin K-dependent carboxylation of endogenous microsomal protein precursors was very rapid in the completely solubilized liver microsomal preparation, and carboxylation of an exogenous peptide substrate (Phe-Leu-Glu-Glu-Leu) proceeded at the same time. In the partially solubilized liver microsomal preparation, the rate of protein carboxylation was greatly reduced, and a lag in carboxylation of the exogenous substrate was observed. When microsomal preparations which were depleted of endogenous precursors were used, this lag was eliminated. These data suggest that both substrates utilize the same microsomal pool of carboxylase and that the fraction of the carboxylase bound to the endogenous precursors is not immediately available to exogenous substrates.

Animals↗
PubMed1978

Metabolism and transport of gamma-carboxyglutamic acid.

gamma-Carboxyglutamic acid residues have beeh shown to be present in prothrombin, the other vitamin K-dependent clotting factors, and more recently in bone and kidney proteins. This amino acid is formed by a posttranslational vitamin K-dependent carboxylation of glutamyl residues in polypeptide precursors of these protens. It has now been demonstrated that this amino acid, either in the free or peptide-bound form, is not metabolically degraded by the rat, but is quantitatively excreted in the urine. In nephrectomized rats, the tissue concentration of intravenously administered gamma-carboxyglutamic acid is increased, but there is still no evidence of any oxidative metabolism of this amino acid. These amino acid is transported by kidney slices against a concentration gradient, but does not accumulate in liver, intestinal or brain tissues. Preliminary data suggest that gamma-carboxyglutamic acid may be concentrated by a carrier system different from that utilized by other amino acids.

Aminoisobutyric Acids↗
PubMed1975

Plasma abnormal prothrombin and microsomal prothrombin precursor in various species (38492).

Abnormal, biologically inactive forms of prothrombin have previously been shown to appear in the plasma of cows or humans given coumarin anticoagulants. We have previously shown that a protein with similar properties increases in the liver of rats given these vitamin K antagonists, and have postulated that this protein represents the liver precursor to plasma prothrombin. Eight species, rats, mice, guinea pigs, hamsters, rabbits, calves, dogs, and chickens, have now been surveyed for both plasma abnormal prothrombin and liver precursor activity. Large amounts of plasma abnormal prothrombin were found in the bovine, substantial amounts were seen in the chick, and small amounts in rat and mouse plasma. With the exception of the bovine, all anticoagulant treated animals showed elevated levels of liver precursor activity in microsomal preparations. The relationship of these observations to the mechanism of action of vitamin K is discussed.

Animals↗
PubMed1975

Vitamin K requirement and warfarin tolerance in the hamster.

A dietary deficiency of vitamin K has been demonstrated in the Syrian hamster. This species has also been shown to be relatively resistant to the action of the indirect anticoagulant Warfarin, and very sensitive to the anticoagulant action of the vitamin K antagonist chloro-K. These observations, and the hamster's apparently high requirement for the vitamin, indicate that it responds to vitamin K and vitamin K antagonists in the same fashion as Warfarin-resistant strains of rats.

Animals↗