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Biomedical subjects

S Ramanathan

Publications and source records attributed to S Ramanathan.

At least 163 records · Page 9Linked to original sources
PubMedDate not supplied

Possible role of phosphorylation-dephosphorylation in the regulation of calcium metabolism in cardiovascular tissues of SHR.

Spontaneously hypertensive rats (SHR) and Wistar-Kyoto normotensive rats (WKY) were compared for phosphorylation-dephosphorylation mechanism(s) in aorta, caudal artery, inferior vena cava, and right and left ventricles. Reduction of cAMP-induced phosphorylation of microsomes and cAMP-dependent protein kinase activity was significant in the aorta and caudal artery of SHR compared with WKY. These changes were not observed in the vena cava of SHR. Phosphoprotein phosphatase activity was significantly increased (p less than 0.05) in the soluble fraction of arterial smooth muscle. No changes were observed, however, in the myocardium or vein. Furthermore, the extent of phosphorylation, and Ca2+ uptake ability and the protein kinase activity in the soluble and the microsomal fractions were not reduced in the myocardium of SHR compared with WKY. These data suggest that phosphorylation-dephosphorylation mechanisms are altered in the microsomal fraction of the aorta and caudal artery of SHR, which may result in reduced Ca2+ uptake by the intracellular organelle. The changes observed could have a significant effect on vasodilatation of arteries in the hypertensive state. The lesion appears specific to the arterial smooth muscle in the cardiovascular tissues.

Animals↗
PubMedDate not supplied

Thermometric estimation of carbon dioxide output in the anesthetized patient.

A thermometer reaching the center of an experimental thermally-insulated lime container, placed in the exhalation limb of a Foregger circle system, was used to measure the carbon dioxide (C02) output of a paralyzed anesthetized patient. Fresh gas inflow, ventilatory rate, and tidal volume were standard. Temperature rise in the canister was found closely related to CO2 output, which was calculated, after a period of stabilization, with the help of a nomogram. The results with this simple instrument coincided with those of more complex procedures.

Anesthesia, Inhalation↗
PubMedDate not supplied

Rebreathing characteristics of the Bain anesthesia circuit.

The humidity output and CO2 elimination of the Bain circuit were tested on a simulated adult patient. The moisture content of inspired gases was found to be adequate when the circuit was used with a minute volume of 8.4 L/min and a fresh gas inflow of 4.9 L/min (65 percent relative humidity at room temperature at the onset of experimentation, rising to 100 percent after 80 minutes). However, the mean inspired CO2 concentration increased from 0.8 percent to 5.5 percent when the fresh gas inflow was decreased from 8 L/min to 3.5 L/min. It is recommended, therefore, that the circuit should not be used for long periods of time without measuring arterial CO2 tension or in situations where intentional hypocarbia is desired.

Adult↗
PubMedDate not supplied

Accidental needlesticks: do anesthesiologists practice proper infection control precautions?

Anesthesiologists as well as patients are at risk for acquiring blood-borne infections such as hepatitis and AIDS. We surveyed 2,530 anesthesiologists, a 10% random sample of the members of the American Society of Anesthesiologists, with a response rate of 57.1%, to determine the incidence of accidental needlestick exposure among anesthesia personnel and whether anesthesiologists are adhering to infection control guidelines to protect themselves and their patients from exposure to infectious diseases. Eighty-eight percent of respondents reported at least 1 accidental needlestick in the past 10 years; 21% received a needlestick from a high-risk patient and 4.5% a needlestick from a known HIV-positive patients. Residents reported significantly more accidental needlesticks from known HIV-positive patients (8.5%). Mucous membrane, open cut, eye, or other significant exposure to HIV-contaminated blood or body fluids was sustained by 8.34% of respondents in the past 10 years. Sixty percent of respondents reported they almost never reuse common syringes now compared with a 40.8% non-reuse rate (P < 0.001) in a similar survey on infection control practices conducted in 1990. Sixty-three percent reported they almost never reuse a vasopressor syringe compared with the 1990 non-reuse rate of 52.5% (P < 0.001). In the current survey, 39% of anesthesiologists reported reusing syringes from one patient to another and 36% reported reusing the same vasopressor syringes for different patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesiology↗
PubMedDate not supplied

The intestinal absorption of camptothecin, a highly lipophilic drug, across Caco-2 cells is mediated by active transporter(s).

The intestinal transport properties and kinetics of camptothecin (CPT) through Caco-2 cell monolayers were characterized by determining concentration-, temperature-, and ATP-dependence as well as the effect of selected inhibitors. The absorptive permeability (Peff) of CPT was found to be concentration dependent and saturable (K(m) = 31.2 +/- 6.9 microM) indicating the involvement of a high affinity, low capacity transport system. CPT transport was also temperature dependent and inhibited by sodium azide plus 2-deoxyglucose, which deplete cellular ATP, further suggesting that an active, carrier-mediated transport system contributes to CPT absorption. Based on inhibition studies, the involvement of organic anion and cation transporters was implicated but not conclusively demonstrated. Total CPT transport decreased four fold with increasing pH from 5.5 to 8.5 indicating that CPT lactone contributed more significantly to overall CPT transport than CPT carboxylate. The results of these studies suggest that CPT absorption is mediated by multiple mechanisms including significant passive diffusion and active transport components. Since typical substrates for intestinal carriers are hydrophilic and charged, the involvement of putative absorptive carriers in the transport of CPT is a novel finding that may give insight into the erratic oral bioavailability of CPTs observed in the clinic.

Adenosine Triphosphate↗
PubMedDate not supplied

The hypothermic action of epidural and subarachnoid morphine in parturients.

Sublingual body temperatures were measured before and at 0.5, 1, 2, 3, 4, 8, 12, and 24 hours after administration of epidural or subarachnoid morphine in four groups of patients (n = 15 in each group) undergoing cesarean delivery with regional anesthesia. All patients were acutely hydrated with 1200 ml warmed lactated Ringer's solution. Group 1 received 5 mg epidural morphine; Group 2, 5 ml epidural saline; Group 3, 0.5 mg subarachnoid morphine, and Group 4, 0.5 ml subarachnoid saline. The results were expressed as means +/- SEM and analyzed using analysis of variance at p less than 0.05. Body temperature decreased significantly in all the four groups after anesthesia. The maximum decreases in Groups 1, 2, 3, and 4, respectively, were 0.95 +/- 0.1, 0.9 +/- 0.1, 1.4 +/- 0.2, and 0.8 +/- 0.13 degrees C and occurred at 0.5, 1, 2, and 1 hour, respectively. The decrease was greater in the subarachnoid morphine group than in the other groups (p less than 0.03). At any of the measurement periods, the temperatures in the two epidural groups did not differ from each other. However, the temperature in the subarachnoid morphine group remained significantly lower than the corresponding temperature in the control group for up to 24 hours. It is concluded that subarachnoid morphine intensifies the hypothermic action of spinal anesthesia in parturients.

Adult↗