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Biomedical subjects

T M Lee

Publications and source records attributed to T M Lee.

161 records · Page 9Linked to original sources
PubMed1980

Measurement of the internal pH of yeast spores by 31P nuclear magnetic resonance.

The asci and single spores of the yeast Pichia pastoris were examined by using 31P NMR. The pH within the spores was determined from the pH-dependent chemical shifts of the internal orthophosphate (Pi) peaks. In spectra of asci, two internal Pi peaks corresponding to two compartments were observed. Only small variations in the internal pH values were found upon incubation of the asci in buffers ranging in pH from 3 to 10. For this range in external pH, the internal pH values calculated from the Pi chemical shifts were 5.5-6.3 and 5.1-5.9. The two internal Pi peaks, which have line widths of approximately 60 Hz, have been assigned to spore and epiplasmic compartments, respectively. Spectra of single spores revealed only one Pi peak, and, upon germination of either the single spores or asci, only this Pi peak disappeared. Peaks corresponding to ATP were not found in the dormant spores and asci but did appear upon germination. These NMR studies show the yeast spore to have a mobile and relatively acidic interior.

Adenosine Triphosphate↗
PubMed1976

Effects of diphenylhydantoin on cardiac arrhythmias induced by carotid occlusion in the cat.

The effects of diphenylhydantoin (DPH) on cardiac arrhythmias induced by occlusion of the common carotid arteries were studied in vagotomized cats under light chloralose anesthesia. It was found that the mean effective dose of DPH via the i.v. route was 11.0 mg/kg. When DPH was injected into the vertebral artery, the carotid artery or the 4th cerebral ventricle, the mean effective dose was 0.8, 1.2 and 0.32 mg/kg, respectively, When DPH was injected directly into the posterior hypothalamic regions, the mean effective dose was even smaller, i.e., 0.14 mg/kg. On the other hand, when DPH was injected into the left ventricle of the heart, the mean effective dose was 1.7 mg/kg and the dose was significantly increased to 4.4 mg/kg when cerebral circulation was temporarily occluded. The data suggest that DPH exerts a potent antiarrhythmic effect through its action on the central nervous system. For the cardiac arrhythmias induced by occlusion of the common carotid arteries, it appears likely that DPH acts on the posterior hypothalamus.

Animals↗
PubMedDate not supplied

Relationship of circadian activity and social behaviors to reentrainment rates in diurnal Octodon degus (Rodentia).

Previous experiments with female Octodon degus showed that entrained males (donors) inhibited and entrained females accelerated female phase-shifters' teentrainment rates of temperature and activity rhythms following 6-h advances. In this experiment, entrained males were housed with other entrained males or with phase-shifting females (experiencing a phase advance of the light-dark (LD) cycle) and entrained females were housed with other entrained females or with phase-shifting females. Pairs separated by a barrier were videotaped for 66 h to identify the behavioral interactions that underlie the opposite effects of donor social cues on reentrainment rates in females. As reported previously, female phase-shifters housed with entrained females reentrained faster than those "housed with entrained males following 6-h advances. Despite accelerated reentrainment, the timing or total durations of general activity, sleep, cage investigation, barrier investigation, and scent marking did not differ between female phase-shifters housed with male or female donors, although all phase-shifters increased investigatory behaviors compared to entrained animals. In contrast, male and female donors housed with female phase-shifters increased the frequency of scent marking and the duration of cage and barrier investigation compared with those housed with entrained same-sex conspecifics. Changes in scent marking and sniffing investigation suggest olfactory cues, not alterations in sleep or other daily rhythms, supply the critical social influence necessary to alter reentrainment rates in females. Daily and/or specific phase increases in motor activity did not correlate with accelerated reentrainment. We suggest that the salience of social cues perceived by female phase-shifters, female phase-shifters' sensitivity to cues and/or the strength of emitted donor cues may contribute to differential responses of the circadian system in females housed with male vs. female donors.

Animals↗
PubMedDate not supplied

Effect of visceral afferent activation on leg extension induced by sciatic afferent stimulation.

In cats under light chloralose and sodium pentobarbital anesthesia the effects of electrical stimulation of various visceral afferent nerves on leg extension induced by sciatic afferent stimulation were studied. Stimulation of the central end of the cervical vagus and stellate ganglion produced inhibition of induced leg extension while stimulation of the distal end of the thoracic vagus, coeliac ganglion, and splanchnic nerves produced facilitation. Decortication slightly reduced the inhibitory effect and greatly reduced the facilitatory effect. Additional decerebration greatly reduced the inhibitory effect and almost abolished the facilitatory effect. Spinal transection at C1 completely abolished the inhibitory and facilitatory effects on induced leg extension. These results suggest that visceral afferents facilitate sciatic induced leg extension principally through the cortex while they inhibit extension through the midbrain and hypothalamus.

Afferent Pathways↗
PubMedDate not supplied

Role of transesophageal echocardiography in the management of metastatic tumors invading the left atrium.

Two patients with metastatic tumors invading the left atrium are described. One is a 52-year-old woman with osteosarcoma; the other is a 77-year-old man with lung cancer. The first patient presented with severe dyspnea 1 year after treatment for a primary tumor. Cardiac metastasis was suspected, then documented by transesophageal echocardiography. The study of pulmonary vein flow showed decreased systolic forward and increased diastolic components of pulmonary venous flow. The second patient presented with chronic cough without dyspnea. Although a huge tumor invaded the left atrium, as in the first patient, a normal pattern of pulmonary vein flow with higher systolic than diastolic velocities was shown by transesophageal echocardiography. Thus, transesophageal echocardiography is not only a useful tool to diagnose left atrial metastatic tumors, but also the study of pulmonary venous flow patterns can delineate causes of dyspnea in patients with metastatic tumors invading the left atrium.

Adenocarcinoma↗
PubMedDate not supplied

Efficacy and safety of barnidipine compared with felodipine in the treatment of hypertension in Chinese patients.

The efficacy and safety profiles of barnidipine in the treatment of hypertension were evaluated in an open parallel-group study. Fifty-nine Chinese patients with mild-to-moderate essential hypertension were randomized to receive either barnidipine or felodipine (5 mg once daily, titrated to 10 mg or 15 mg once daily, as indicated) for 12 weeks. Both drugs reduced blood pressures significantly with > or = 68% of cases obtaining marked or moderate blood pressure reduction. Mean reductions in systolic and diastolic blood pressure for barnidipine treatment were 23.7 +/- 13.5 mmHg and 12.7 +/- 7.9 mmHg, and for felodipine, 24.3 +/- 18.4 mmHg and 14.5 +/- 10.0 mmHg, respectively. There was no significant difference between these two drugs in anti-hypertensive effect, heart rate, laboratory measurements or incidence of adverse events. The only difference was that more patients taking felodipine experienced palpitations. We conclude that barnidipine has similar efficacy and a similar safety profile to felodipine in the treatment of mild-to-moderate essential hypertension in Chinese patients.

Adolescent↗
PubMedDate not supplied

Effect of anti-hypertensive drug dose frequency on the clinic-home blood pressure difference in patients with stage 1 treated hypertension.

Clinic blood pressure (CBP) is generally used for diagnosis and treatment monitoring in hypertension, but target organ damage correlates more closely with home blood pressure (HBP). Eliminating the clinic-home blood pressure difference (CHBPD) would make conventional CBP a more accurate alternative to HBP. This prospective, randomized, open trial compared the effect of a once-daily versus a twice-daily regimen of anti-hypertensive therapy on CHBPD. After a 2-week wash-out period, 85 confirmed stage 1 hypertensive patients were randomized to receive 2 mg trichlormethiazide daily in one (40 subjects) or two (45 subjects) daily doses for 3 weeks. CBP and HBP measurements were taken during the third week of treatment and the CHBPD calculated. After treatment, the systolic and diastolic CHBPD values were significantly greater in the once-daily regimen than in the twice-daily regimen. Conventional CBP should not be used as an alternative to HBP for evaluating prognosis and monitoring anti-hypertensive therapy when using a once-daily regimen.

Adult↗