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Biomedical subjects

O Prakash

Publications and source records attributed to O Prakash.

At least 127 records · Page 7Linked to original sources
PubMed1982

Effects of fentanyl, and the antagonism by naloxone, on regional blood flow and biochemical variables in conscious rabbits.

Effects of fentanyl (cumulative doses: 25, 75 and 125 micrograms.kg-1, i.v.) on respiratory, systemic and regional haemodynamic and biochemical variables were studied in the conscious rabbit. The initial dose of fentanyl (25 micrograms.kg-1) produced a rise in blood pressure and a decrease in heart rate but, on subsequent doses, smaller effects were observed. The drug produced changes in arterial blood gases which were due to a severe decrease in respiratory frequency and an increase in muscular rigidity of chest and neck muscles. The blood flow to skin, stomach, mesentery plus pancreas, bones and fat was decreased by fentanyl. These changes resemble those obtained during alpha-adrenergic stimulation and, thus, may be related to a release of catecholamines during respiratory depression. On the contrary, however, hepatic arterial blood flow was increased and this effect may be responsible for the rapid metabolism and a short duration of action of fentanyl. Fentanyl also caused an increase in the concentration of glucose, lactate and inorganic phosphates in the arterial blood. These changes are probably due to hypoxia. Administration of naloxone not only reversed the residual effects of previous fentanyl administration but also antagonized the respiratory, haemodynamic and biochemical responses to the morphinomimetic drug.

Animals↗
PubMed1981

Cardiovascular effects of etomidate with emphasis on regional myocardial blood flow and performance.

The effects of 30-min infusions of etomidate 0.03, 0.12 and 0.24 mg kg-1 min-1 on systemic and regional haemodynamic variables and cardiac performance and metabolism were studied in pigs. The drug caused moderate, but dose-dependent, decreases in the cardiac output, arterial pressure and LVdP/dt max. Myocardial wall thickening, measured by echographic analysis, was decreased by the drug. However, heart rate, myocardial blood flow distribution and myocardial metabolism of lactate, glucose and free fatty acids remained unchanged. Cerebral blood flow was decreased substantially. However, renal blood flow changed only slightly.

Animals↗
PubMed1981

Small reovirus particle composed solely of sigma NS with specificity for binding different nucleic acids.

We reported previously that polycytidylate [poly(C)]-dependent RNA polymerase activity was a property of small spherical or triangular reovirus-specific particles which sedimented at 13 to 19S and were composed solely of the reovirus protein, sigma NS. Depending on the fraction of cellular extracts from which they were obtained, these particles exhibited marked differences in stability. Most 13 to 19S particles from a particular fraction repeatedly disaggregated into smaller 4 to 5S subunits with no enzymatic activity. Disruption of many particles could be prevented and polymerase activity retained after these particles had bound different single-stranded (ss) RNAs. Our previous results indicated that there was heterogeneity among the 13 to 19S particles in that possession of poly(C)-dependent RNA polymerase activity was a property of only some. Support for this heterogeneity was derived from the demonstration in this report that there were at least three types of binding sites present within particles in any purified preparation: (i) those binding only poly(C); (ii) those binding only reovirus ss RNAs; and (iii) those binding one or the other, but not both at the same time. It is suggested that only those particles able to bind either poly(C) or reovirus ss RNAs had poly(C)-dependent RNA polymerase activity, as reovirus ss RNAs markedly inhibited the polymerase activity. All three size classes of reovirus ss RNAs were equally effective in binding, but once bound, they were not copied. It is possible that heterogeneity in binding capacity of different particles comprised of only one protein, sigma NS, could result from the ability of subunits containing this protein to assemble into slightly different 13 to 19S particles with specificity of binding or polymerase activity conferred by the configuration of the assembled particles. The high capacity of sigma NS to bind many different nucleic acids with some specificity suggests that these particles may act during infection as condensing agents to bring together 10 reovirus ss RNA templates in preparation for double-stranded RNA synthesis.

DNA-Directed RNA Polymerases↗
PubMed1981

Cardiorespiratory monitoring during open heart surgery.

Thirty-three patients underwent extensive cardiorespiratory monitoring during cardiac surgery. Recordings of measurements, with derived variables, were made preoperatively, postoperatively, and after extubation approximately 3 h after operation. The data provide a reference that allows decisions on whether the condition of a patient after cardiac surgery deviates from the ordinary course. Details are given of the spontaneous ventilation test which taken together with monitored data provided criteria for successful early extubation in uncomplicated cases.

Adult↗
PubMed1980

Haemodynamic and biochemical variables after induction of anaesthesia with fentanyl and nitrous oxide in patients undergoing coronary artery by-pass surgery.

The effects on the haemodynamic and biochemical parameters of three different anaesthetic induction regimes, namely fentanyl (4.1 micrograms.kg-1 or 15 micrograms.kg-1) plus 60 per cent nitrous oxide with oxygen and fentanyl 15 micrograms.kg-1 plus 60 per cent nitrogen with oxygen, were studied in patients undergoing coronary artery surgery. Fentanyl 15 micrograms.kg-1 with nitrous oxide and oxygen produced simultaneous reductions in oxygen uptake, cardiac index and left ventricular stroke work with an unaltered oxygen extraction. Diastolic blood pressure (an index of coronary artery perfusion) was only slightly reduced, and there were no changes in arterial lactate, glucose and free fatty acids. The lower dose of fentanyl (4.1 micrograms.kg-1) with nitrous oxide produced no haemodynamic changes but decreased the oxygen uptake and extraction. The patients receiving fentanyl 15 micrograms.kg-1 with nitrogen and oxygen showed increases in heart rate, blood pressure, cardiac index and left ventricular stroke work, together with a significant fall in oxygen extraction. Moreover, in the patients who received fentanyl 4.1 micrograms.kg-1 with nitrous oxide and oxygen and fentanyl 15 micrograms.kg-1 with nitrogen and oxygen there were significant increases in blood lactate, glucose and free fatty acids, indicating increased sympathetic activity. We conclude that fentanyl 15 micrograms.kg-1, together with 60 per cent nitrous oxide with oxygen provides a satisfactory haemodynamic and biochemical state during induction of anaesthesia in patients with myocardial function prejudiced by coronary artery insufficiency.

Adult↗
PubMed1980

Clinical studies of gas exchange during ventilatory support--a method using the Siemens-Elema CO2 analyzer.

We describe a new portable infra-red analyses for use with the Siemens-Elema Servo ventilator. The sensor head constitutes a Y-piece connecting the patient to the ventilator tubing, and gives instant carbon dioxide determination. It is based upon simple principles that can be realized with modern techniques, offering for instance freedom from interference by anaesthetic gases, and eliminating the need for calibration. A non-zero inspired carbon dioxide concentration interferes with the measurements. Integration of the carbon dioxide signal with the flow signal from the Servo ventilator yields data about carbon dioxide excretion, and additional calculation yields VD/VT if PaCO2 is known. The accuracy of determination of end-tidal carbon dioxide and carbon dioxide elimination was found to be adequate for research purposes, and that of VD/VT for clinical purposes. The device is considered to be of value in the operating theatre and intensive care unit, for monitoring, as a guide to ventilatory needs, and for the investigation of the magnitude and causes of increased deadspace.

Aged↗
PubMed1979

Biotinyl 5'-adenylate: corepressor role in the regulation of the biotin genes of Escherichia coli K-12.

A DNA filter-binding technique was used to study the interaction of the biotin repressor and operator site. From a biotin saturation curve, the concentration for half-maximal binding (K0.5) was calculated to be 1 microM. However, in a similar study with the in vitro coupled transcription-translation system in which biotin served as the corepressor, the K0.5 for repression was 7.1 nM. This marked difference of over 2 orders of magnitude was attributed to the activation of biotin by the partially purified repressor preparation in the in vitro system. The activated product formed from biotin, ATP, and repressor preparation was identified as biotinyl 5'-adenylate by paper chromatography and hydroxamic acid formation. Synthetic biotinyl 5'-adenylate was as effective as biotin in the in vitro system (K0.5, 10 nM) and much more effective than biotin in the DNA-binding assay (K0.5 1.1 nM versus 1 microM). These studies indicate that biotinyl 5'-adenylate has a more direct role in the regulation of the biotin genes than does biotin per se.

Adenosine Monophosphate↗
PubMed1979

A study of D-glucose uptake by small intestine of rats following in vivo vinblastine treatment.

The pharmacokinetics of tritiated vinblastine in rats has indicated a considerable excretion of the alkaloid through bile into the intestinal lumen. The present study was undertaken to find out whether the presence of the alkaloid in the lumen of small intestine alters the normal transport of nutrients across the small intestine. This was done by measuring the in vitro D-glucose uptake by slices of small intestine of rats pretreated with vinblastine. Vinblastine pretreatment was done by filling the lumen of in vivo segments of small intestine of rats with different concentrations of the alkaloid for 30 and 60 min before uptake was measured. A significant dose-dependent reduction in D-glucose uptake was observed.

Animals↗
PubMed1979

A study of small intestinal dipeptidases of rats: effect of vinblastine treatment.

Activities of L-glycyl-L-valine and L-glycyl-L-leucine dipeptidase were studied in the mucosa of the small intestine of rats following intraperitoneal administration of vinblastine sulfate (1.0 mg/kg). Activities of these dipeptidases were depressed significantly; the effect was maximal between 4 and 5 h after the injection and lasted for more than 16 h. The depression in the enzyme activities reached even up to 95% when the alkaloid was administered repeatedly in 4-hourly intervals. The present results, showing a dose-dependent inhibitory effect on these dipeptidases, suggest a toxic effect on the enzymes in addition to simple inhibition resulting from a blockade of cell division. The former possibility was examined by incubating mucosal homogenates with various concentrations of the alkaloid for 30 min. Subsequent measurement of the activities showed a significant depression when the alkaloid concentration was raised to 10 microgram/mg wet mucosa. It is concluded that vinblastine sulfate not only arrests the mitosis of the crypts but influences, additionally, the enzymatic complements of the enterocytes.

Animals↗
PubMed1979

A study of intestinal dipeptidases of rats: effect of in vivo mucosal exposure to vinblastine.

The mucosal population of small intestine of rats was exposed in vivo to various concentrations of vinblastine sulfate for 30 and 60 min and the activities of glycyl-L-valine and glycyl-L-leucine hydrolase were measured in the treated mucosa of the upper jejunal segment. A significant depression in the activity of these dipeptidases was observed which was further found to be dose dependent.

Animals↗
PubMed1978

In vitro synthesis and and regulation of the biotin enzymes of Escherichia coli K-12.

The synthesis and regulation of two of the enzymes of the biotin operon of Escherichia coli, 7,8-diaminopelargonic acid aminotransferase and dethiobiotin synthetase, were studied in vitro in a coupled transcription-translation system. These enzymes are encoded by genes located on opposite strands of the divergently transcribed operon (A. Guha, Y. Saturen, and W. Szybalski, J. Mol. Biol. 56:53-62, 1971). The kinetics of synthesis of both the enzymes were determined and the efficiency of the system was 0.3 to 0.4% that of the in vivo rate of synthesis in derepressed cells. Guanosine 3'-diphosphate 5'-diphosphate at 0.2 mM concentration stimulated the synthesis of 7,8-diaminopelargonic acid aminotransferase two- to threefold but had no effect on dethiobiotin synthetase synthesis. Biotin, which was most effective as the corepressor in vivo, also functioned in vitro at physiological concentrations in conjunction with a crude repressor protein isolated from a lysogen carrying the bioR gene. However, the two strands showed differential repression. At a repressor concentration where 7,8-diaminopelargonic acid aminotransferase synthesis was completely repressed, the repression of dethiobiotin synthetase was only 20% and did not exceed 50% with increasing repressor concentrations. Although the exact reason for the partial repression remains to be resolved, our data clearly suggest that the biotin operon is regulated from two separate operators.

Biotin↗
PubMed1978

Cardiovascular monitoring with special emphasis on mixed venous oxygen measurements.

With the advent of complicated surgical procedures the need for invasive hemodynamic monitoring has taken a prominent place in the management of patients. This has resulted in improved morbidity and mortality in overall patient care. Along with conventional monitoring of heart rate, arterial pressure and central venous pressure, the information about the function of the left heart is essential. This paper describes the usefulness of Swan-Ganz catheter (SG catheter) during intensive care. The purposes of the study is to determine the relationship between mixed venous oxygen saturation measurement, peripheral skin temperature and volume replacement in the immediate postoperative period, as well as the need for prolonged mechanical ventilation in shocked patients.

Blood Pressure↗