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Biomedical subjects

K Ramanathan

Publications and source records attributed to K Ramanathan.

At least 19 recordsLinked to original sources
PubMed1995

Single kinesin molecules stressed with optical tweezers.

Using the optical tweezers to pull on microtubules, we have stretched and twisted single kinesin molecules adsorbed to glass surfaces. Preliminary measurements suggest that the mechanical system is very compliant, with an apparent stretch of 120 nm with < 2 pN of force. Although measurements of the series compliance of the bead-microtubule structure are still in progress, the kinesin attachment site does not slip with stretch. However, under torsional stress, kinesin appears to slip. With torques < 2 pN-microns approximately 1 Hz in 2 mM AMP-PNP, there is no apparent limit to the number of revolutions that the microtubule can rotate around the kinesin attachment site (n = 44). Preliminary data from other nucleotide conditions are similar. Although there are rare instances of torsional elasticity where the attachment site unwinds, the restoring forces are not constant with angular position, also indicating slippage. Mechanisms of mechanochemical transduction must account for linear force generation in the presence of angular "slippage."

Adenylyl Imidodiphosphate↗
PubMed1986

Sperm granuloma.

Explore the source record for details and available documents.

Adult↗
PubMed1986

Sonographic demonstration of simultaneous intrauterine and extrauterine gestation.

Simultaneous intrauterine and ectopic pregnancies are extremely rare. The diagnosis is usually made by laparoscopy and/or laparotomy. Three cases are presented in which the diagnosis was made during sonographic examinations by simultaneous demonstration of fetal cardiac motion in both the intrauterine and extrauterine fetuses. Early diagnosis of this condition significantly reduces the morbidity and mortality of both the mother and the intrauterine gestation.

Adult↗
PubMed1985

Squamous cell carcinoma of the oral mucosa in Malaysia--any change?

The prevalence rate of 749 cases of oral squamous cell carcinomas (SCC) recorded between 1978-1984 was studied. Results showed that the Indians formed the dominant group (63.8%) followed by the Malays (19.6%) and Chinese (16.6%). The peak incidences were generally located between the sixth and eighth decades. Only in the Chinese group a male preponderance was noted. In the Indians, the buccal mucosa was the most prevalent site; in the Malays and Chinese males, the gingiva and alveolus; and the Chinese female, the tongue. In all three groups, the well-differentiated SCC was the commonest type and the poorly differentiated least common.

Adult↗
PubMed1985

Oral candidiasis--its pleomorphic clinical manifestations, diagnosis and treatment.

Up to 60% of the population carry Candida albicans as part of the oral flora without having evidence of candidiasis. The pleomorphic clinical manifestations of oral candidiasis viz. thrush, denture stomatitis, angular cheilitis, median rhomboid glossitis, speckled leukoplakia, and chronic mucocutaneous candidiasis and its variants are briefly discussed. Current diagnostic techniques of oral candidiasis (OC) are reviewed. A simple and quick method of helping the clinician in the diagnosis of OC by taking a direct smear of the lesion is emphasized. OC is a 'disease of the diseased'. As a routine a full blood picture, serum iron and serum folate levels should be looked at. Several predisposing causes of OC need to be investigated. An up-date on the treatment of OC with nystatin, amphotericin B lozenges, clotrimazole and miconazole is made.

Candidiasis, Oral↗
PubMed1981

Natural history of contractile abnormalities after acute myocardial infarction in man: severity and response to nitroglycerin as a function of time.

The natural history of contraction abnormalities and their response after acute myocardial infarction in man were studied using radionuclide angiography. Sixteen patients were studied before and after sublingual nitroglycerin within 24 hours, 5-7 days and 4-6 weeks after the onset of chest pain. Within 24 hours, central chord shortening in the zone of infarction was reduced to 13.1 +/- 9.8%, but improved 27.2 +/- 18.4% (p less than 0.001) after nitroglycerin. After 5-7 days, central chord shortening improved similarly, but less markedly, from 12.9 +/- 9.2% to 24.4 +/- 13.2% (p less than 0.001). After nitroglycerin 4--6 weeks after the acute myocardial infarction, the central chord showed no response to nitroglycerin; it was 13.9 +/- 10.9% before and 13.4 +/- 2.5% after nitroglycerin. Changes in the lateral chords paralleled changes in the central chords in the three studies. Nonischemic zone improvement after nitroglycerin in all three studies. Global ejection fraction improved and end-diastolic and end-systolic volumes decreased in all three studies after nitroglycerin. These data indicate that after acute myocardial infarction, there is a significant reduction in hemiaxis shortening in the central and lateral chords that remains essentially unchanged over 4-6 weeks. However, the asynergic ischemic area improves considerably after nitroglycerin within 24 hours and 5-7 days, but fails to improve after 6 weeks.

Acute Disease↗
PubMed1981

Effect of progressive pressure reduction with nitroprusside on acute myocardial infarction in humans. Determination of optimal afterload.

The effect of nitroprusside-induced progressive systemic pressure reduction on segmental function in patients with acute myocardial infarction is unclear. In 15 patients control radionuclide angiograms were obtained at control within 24 hours of the onset of chest pain and during the administration of intravenous nitroprusside. The initial study showed a significant reduction in hemiaxial shortening in the zone of myocardial infarction. With nitroprusside, systolic pressure was decreased from a mean of 133 mm Hg to an intermediate pressure of 116 mm Hg (p less than 0.001). At this pressure central chord hemiaxial shortening increased in eight of 15 zones with an average increase from 10.1% to 27.8% (p less than 0.006). After further reduction in pressure to 87.1 mm Hg, an additional five of the seven remaining zones of acute infarction improved. However, of the eight zones that improved initially, four deteriorated at the lowest pressure. Similar changes were seen in the lateral chords. Thus, afterload reduction can improve hemiaxial shortening of the infarct zone. However, the degree of reduction in systemic pressure must be individualized to avoid adverse effects of an excessive decrease in perfusion pressure.

Adult↗