Search PubMed⌕ Search

Biomedical subjects

A Jain

Publications and source records attributed to A Jain.

At least 415 records · Page 23Linked to original sources
PubMed1987

Determination of aspirin by pre-column transacetylation reaction of 3-aminophenol and reversed-phase high-performance liquid chromatography: simultaneous determination of aspirin, acetaminophen, and caffeine.

The accuracy of the measurement of aspirin by high-performance liquid chromatography (HPLC) is reduced by its hydrolysis into salicylic and acetic acids during sample preparation. The ready and quantitative transacetylation of 3-aminophenol by aspirin, giving 3-hydroxyacetanilide (which is stable), has been utilized as a pre-column reaction for the determination of aspirin either alone or in the presence of acetaminophen and caffeine by reversed-phase HPLC.

Acetaminophen↗
PubMed1987

Role of polyamines in the synthesis of RNA in mycobacteria.

All three polyamines - putrescine, spermidine and spermine stimulated the activity of mycobacterial RNA polymerase in vitro although the concentration required for maximal stimulation was different for each of the amines. Spermidine and spermine showed a biphasic effect on the enzyme activity. Stimulation of RNA synthesis by spermidine occurs only at higher DNA template/enzyme ratio. Spermidine stimulates RNA synthesis by acting on the elongation phase of RNA synthesis but it had no effect on initiation phase. Addition of mycobacterial RNA to the assay mixture resulted in the inhibition of RNA polymerase activity and this inhibition could be reversed by spermidine suggesting that spermidine stimulates transcription by binding to nascent RNA and thus destabilizing the short DNA-RNA hybrid region.

DNA↗
PubMed1987

Dissociation between global and regional systolic and diastolic ventricular function during coronary occlusion and reperfusion.

Indexes of global ventricular function such as the ejection fraction (EF) and the peak diastolic filling rate (PDFR) are often used to assess the effects of coronary recanalization in patients with myocardial infarction. In this investigation we assessed the relationship between these global indexes and directly measured indexes of regional function during 15 minutes of coronary occlusion followed by 120 minutes of reperfusion in 22 open-chest dogs. A computerized nuclear cardiac probe was used to assess EF and PDFR. Indexes of regional function were measured by Doppler ultrasonic wall-thickening probes. During coronary occlusion, paradoxical systolic thinning occurred and the EF and PDFR decreased an average of 31.6% and 24.4%, respectively. During reperfusion the EF and PDFR improved rapidly and at 60 minutes were similar to baseline. Systolic wall thickening improved more gradually and remained abnormal throughout reperfusion. Likewise, indexes of diastolic function (mean rate to half end-diastolic thinning and late diastolic thinning fraction) recovered slowly and remained abnormal throughout reperfusion (78% and 69.7%, respectively). The correlation between the rate of change of global and regional function was poor during both coronary occlusion and reperfusion. Thus, during coronary occlusion the global and regional indexes of ventricular function undergo directionally similar changes. However, during coronary reperfusion the global indexes do not reflect the slow recovery of the stunned myocardium.

Animals↗
PubMed1987

Brief periods of myocardial ischemia followed by reperfusion: a model in the dog of sudden cardiac death in humans.

Most experimental interest has focused on the electrophysiologic mechanisms which may underlie sudden death. The purpose of the present study was to develop a model in the dog where ischemia would produce not just ventricular fibrillation but also histologic abnormalities similar to those previously reported in sudden death in humans. First, the collateral blood flow to a portion of the ventricle was surgically abolished and then the arterial blood supply to this region was interrupted for 15 minutes after which nutrient flow was restored for 30 minutes. If the animal survived, this cycle was repeated up to seven times. Thirty-six animals were studied: 15 controls (Group A) survived an average of 1.75 +/- 0.8 cycles (mean +/- SD); 11 others (Group B) received a loading dose of sodium verapamil and survived 3.7 +/- 1.8 cycles while 10 (Group C) received a continuous infusion as well as the loading dose of sodium verapamil and survived 4.4 +/- 2.6 cycles--the difference between each group being significant (p less than 0.05). Four animals in Group C survived all 7 cycles; out of the other 32, 27 fibrillated just after reperfusion and the rest during ischemia. Histological examination revealed small foci of contraction band necrosis widely interspersed amongst large areas of morphologically normal tissue. The beneficial effect of verapamil and the histologic findings suggest cellular calcium overload may be important in the genesis of the fatal arrhythmias produced by reperfusion.

Animals↗
PubMed1986

Effect of inflation pressures on coronary angioplasty balloons.

It is a common conception that the balloons used in percutaneous transluminal coronary angioplasty will inflate to a certain designated diameter and maintain this diameter over the wide range of inflation pressures. With use of an optical magnification system, the diameters of multiple angioplasty dilating catheters made of polyvinyl chloride (USCI) and polyethylene (Advanced Cardiovascular System, Inc.) were measured with designated balloon diameter sizes of 2.0 to 3.7 mm. All balloons had a linear increase in diameter over a range of pressures from 2 to 10 atm. The average increase in diameter over this pressure range was 15% (range 7 to 18%). Polyvinyl chloride balloons reached their specified diameter at less than 5 atm and exceeded it at higher inflation pressures. Polyethylene balloons reached their specified diameter at 8 to 10 atm, and were below specified diameters at lower pressures. There was slight variation in size and only a minimal difference in compliance between balloons of the same material and size. A given balloon achieved the same diameter at a given pressure even after multiple inflations and maintained a stable diameter during prolonged inflations.

Angioplasty, Balloon↗
PubMed1986

Spermine decreases peripheral vascular resistance in the dog and relaxes the isolated aorta of the guinea pig.

Polyamines, found in all nucleated cells, have been shown to relax uterine, gastrointestinal, and respiratory tract smooth muscle. When parenterally administered to the rat or dog they cause hypotension. To determine the range of the relaxing effect of polyamines on smooth muscle and the mechanism of the hypotensive effect anaesthetised dogs were infused with increasing intravenous bolus doses of spermine while cardiovascular measurements were made. At doses of greater than or equal to 2 mg X kg-1 spermine a reversible hypotensive effect was produced that is accounted for by changes in peripheral vascular resistance. It is unlikely that this effect was due to the known propensity of polyamines to release histamine because the hypotensive action of 2 mg X kg-1 spermine was unaltered by pretreatment with the H1 and H2 blockers, diphenhydramine and cimetidine. Evidence that the spermine effect is not mediated by circulating agents was shown by the ability of spermine to relax the precontracted guinea pig isolated aorta. These results in vascular smooth muscle may be added to those in other types of smooth muscle shown to be relaxed by polyamines; the polyamine effect on smooth muscle may be ubiquitous. These data also raise the possibility that changing concentrations of tissue polyamines may play a role in the regulation of tissue blood flow.

Animals↗
PubMed1986

Effectiveness of bevantolol in the treatment of hypertension: once-daily versus twice-daily evaluation of home blood pressure measurements.

Two multicenter, double-blind, placebo-controlled studies were conducted to determine in patients with hypertension the oral dose of bevantolol that would effectively reduce home diastolic blood pressure to less than 95 mm Hg. The two studies differed only in once-daily or twice-daily dose administration. In the 125 patients evaluated, the mean decreases in home diastolic blood pressure were significantly greater in patients receiving 100 to 400 mg/day of bevantolol (8 to 10 mm Hg) than in patients receiving placebo (2 to 3mm Hg) (p less than 0.05). Bevantolol administered once daily or twice daily was equally effective in the management of hypertension and was well tolerated in the doses studied.

Adrenergic beta-Antagonists↗