PubMed Health⌕ Search

Biomedical subjects

A M Das

Publications and source records attributed to A M Das.

50 records · Page 3Linked to original sources
PubMed1991

Control of mitochondrial ATP synthase in rat cardiomyocytes: effects of thyroid hormone.

Activities of the mitochondrial ATP synthase and the electron transfer chain were investigated in cultured cardiomyocytes prepared from untreated and thyroxine-treated rats. Quiescent cells from the thyroxine-treated animals showed a 33% increase in mitochondrial ATP synthase capacity, but no change in respiratory chain capacity, relative to those from control animals. This increase was attributable largely to (a) a 25% increase in F1 content in these mitochondria, and partly to (b) a 10% stimulation in ATPase activity due to raised intramitochondrial Ca2+. Both types of cell showed a normal ATP content of 38-40 nmol/mg cell protein. In control cells, the mitochondrial ATP synthase responded to increased energy demand (by electrical stimulation and/or by positive inotropic agents) with an increase in its capacity of up to 2-fold. This response was absent in cells from thyroxine-treated animals. In addition, cellular ATP levels fell significantly after 2 min electrical stimulation of cells from thyroxine-treated animals, while those of control cells were constant. It was concluded that regulation of the mitochondrial ATP synthase was defective in heart cells from thyroxine treated rats, leading to an energy deficit when energy demand on the cells was increased. Animals treated with thyroxine, but allowed to recover for 17 days after treatment, showed responses indistinguishable from the control cells. Thus, the effects of thyroxine on mitochondrial activities were reversible.

Adenosine Triphosphate↗
PubMed1990

Regulation of the mitochondrial ATP synthase in intact rat cardiomyocytes.

The ATP synthase capacity of rat heart myocytes can be measured in sonicated cell suspensions and in sonicated preparations of cultured cardiomyocytes. This procedure allows the rapid measurement of mitochondrial function in response to changes in the metabolic status of the cell. In cultured myocytes, transitions in ATP synthase capacity (with no detectable change in cellular ATP concentration) accompany a change to anoxia or electrically stimulated contraction (rise of 70%). These changes are reversed on returning to the original conditions. Exposure of myocytes to low pH has little effect on basal ATP synthase capacity (down to values less than pH 6), but markedly affects cellular ATP levels and the response of the cells to anoxia and reoxygenation, possibly mimicking changes seen in ischaemic heart. Similar effects are seen in suspensions of freshly prepared myocytes, but these preparations are less stable and more pH-sensitive than are cells in culture. It is proposed that mitochondria in vivo are directly regulated at the level of the ATP synthase, and that a regulator protein, the naturally occurring inhibitor protein from mitochondria, may be responsible for this regulation.

Adenosine Triphosphate↗
PubMed1990

Control of mitochondrial ATP synthase in heart cells: inactive to active transitions caused by beating or positive inotropic agents.

STUDY OBJECTIVE - The aim of the study was to measure variations in ATP synthase capacity in cultured cardiomyocytes under conditions of metabolic stimulation. DESIGN - ATP synthase activity was measured in cultured rat cardiomyocytes using a procedure which allowed rapid measurement of mitochondrial function during changes in metabolic state. EXPERIMENTAL MATERIAL - Calcium tolerant cardiomyocytes were prepared from male Wistar rats, weight 250-300 g, n = 6-22 per experiment. MEASUREMENTS AND MAIN RESULTS - Electrical stimulation of cardiomyocytes led to an approximate doubling of ATP synthase capacity within 1-2 min, and was rapidly reversible. Activation was reduced when extracellular calcium was lowered and abolished in presence of the calcium entry blocker ruthenium red. Exposure of cardiomyocytes to isoprenaline or to an inhibitor of phosphodiesterase III also led to a large increase in ATP synthase capacity, which was abolished in presence of ruthenium red. However, the response of cells to isoprenaline depended on their pretreatment: activation of ATP synthase was abolished after 20 min anoxia prior to isoprenaline treatment but regained after a subsequent 30 min reoxygenation. This may reflect down regulation of beta receptors on the cell surface during anoxia. CONCLUSIONS - ATP synthase is directly controlled in vivo by a non-allosteric mechanism. Activation of ATP synthase is a response to intramitochondrial Ca2+ concentration.

Animals↗
PubMed1990

Defects in regulation of mitochondrial ATP synthase in cardiomyocytes from spontaneously hypertensive rats.

Control of mitochondrial ATP synthase capacity was investigated in cultured cardiomyocytes from normotensive (Wistar-Kyoto) and spontaneously hypertensive (SHR) rats. The basal ATP synthase capacity in quiescent cardiomyocytes was raised in the hypertensive rats (2.9 +/- 0.1 mumol.min-1.mg protein-1) compared with normotensive rats (2.2 +/- 0.1 mumol.min-1.mg-1). However, this high value is restored to normal after treatment of the cells with verapamil or ruthenium red; agents that do not affect ATP synthase capacity in normal cells. It is concluded that abnormally high intramitochondrial Ca2+ levels, or an abnormal mitochondrial response to Ca2+ concentration, are responsible for ATP synthase activation in quiescent SHR cells. Cardiomyocytes from normotensive rats respond to increased energy demand (caused by electrical stimulation or treatment with positive inotropic agents) by increasing their ATP synthase capacity up to twofold. Cells from SHR rats are unable to control their ATP synthase in this way. It is concluded that some defect in regulation of the mitochondrial ATP synthase occurs in myocytes from hypertensive rats.

Adenosine Triphosphate↗
PubMed1990

Aeromonas sobria in bubaline (water buffalo) abortion: growth requirement, biochemical characters, antibiotic susceptibility, experimental pathogenicity and serology.

A. sobria was isolated unexpectedly on Campylobacter selective medium from abortion specimens of 16 buffaloes. All strains (AS1-AS16) required Campylobacter growth supplement (sodium pyruvate, sodium metabisulphate and ferrous sulphate) and 10% C02 atmosphere on primary isolation. They were unusually sensitive to bile salt and failed to grow on MacConkey's agar. Biochemically, these strains were homogeneous but antibiogram profile and physiological/other characters revealed a moderate heterogeneity. In vitro antibiotic sensitivity pattern showed a number of antibiotics effective whereas only a few (penicillin and co-trimoxazole) ineffective against these strains. It took 9 days for 3 x 10(8) A. sobria organisms/ml in 5 ml quantity to terminate the pregnancy in an experimentally infected buffalo via iv route. Foetal and placental lesions were classical as that of field cases. The infection evoked serum antibody response. Apparently disease-free buffalo sera were devoid of such antibodies.

Abortion, Veterinary↗
PubMed1989

Reversible modulation of the mitochondrial ATP synthase with energy demand in cultured rat cardiomyocytes.

The ATP synthase capacity of rat heart myocytes can be measured in sonicates of cultured cardiomyocytes. In these cells, transitions in ATP synthase capacity occur on changing to the anoxic or uncoupled state (drop in ATP synthase capacity of over 40%) or on electrically stimulating the cells to contract (rise of 70%). These changes occur rapidly (half time less than 1 min) and are completely reversed on returning to the original conditions. It is proposed that mitochondria in vivo are directly regulated at the level of the ATP synthase. The naturally occurring inhibitor protein from mitochondria may be responsible for this regulation.

Adenosine Triphosphatases↗
PubMed1988

Serratia marcescens infection associated with early abortion in cows and buffaloes.

Serratia marcescens was isolated in pure culture from cases of septic abortion in 4 cows on one farm and 10 buffaloes on two other farms. A reddish vaginal discharge was observed after abortion in all animals and in the internal organs of the aborted fetuses. All but two of the isolates produced prodigiosin, and two of the isolates from buffaloes were atypical in that they fermented raffinose. O-serological, bacteriophage and bacteriocin typing revealed four different strains. All cows were infected by the same strain, and this strain was also isolated from the semen of a breeding bull on the same farm. In another farm a strain of serotype O 14 was isolated from 6 of 10 buffaloes, and two other distinct strains were isolated from the remainder. The strain from the cattle was sensitive to gentamicin and so were two of the buffalo isolates. The infected cows were treated with intra-uterine gentamicin and the organism disappeared from cervical mucus after 3 days. Each animal after abortion showed a raised titre of agglutinating antibody to their respective isolate. A survey of 1172 healthy buffaloes and cattle gave an incidence of 1.8% with raised titres towards S. marcescens.

Abortion, Septic↗
PubMed1986

Yersinia enterocolitica associated with third trimester abortion in buffaloes.

A group of buffaloes aborted at the third trimester of their gestational period. Yersinia enterocolitica was isolated from all cases. All aborted animal sera had high antibody titres against Y. enterocolitica antigen which crossreacted significantly with Brucella abortus antigen. All animals were culturally negative after intrauterine infusion of gentamycin sulphate (160 mg/day) for three consecutive days.

Abortion, Veterinary↗
PubMedDate not supplied

Seventeen novel mutations that cause profound biotinidase deficiency.

We report 17 novel mutations that cause profound biotinidase deficiency. Six of the mutations are due to deletions, whereas the remaining 11 mutations are missense mutations located throughout the gene and encode amino acids that are conserved in mammals. Our results increase the total number of different mutations that cause biotinidase deficiency to 79. These additional mutations will undoubtedly be helpful in identifying structure/function relationships once the three-dimensional structure of biotinidase is determined.

Amidohydrolases↗