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Biomedical subjects

T Thien

Publications and source records attributed to T Thien.

At least 217 records · Page 12Linked to original sources
PubMed1989

Decreased rectal body temperature induced by different vasodilatory drugs.

In three patients with either hypertension or Raynaud's phenomenon who were treated with different types of vasodilatory drugs, i.e. prazosin, nifedipine and prostacyclin, a decrease in rectal body temperature was measured. Overt hypothermia occurred in one patient. Because we found a pronounced improvement of arteriovenous shunt flow within the skin vessels in two of these patients, increased heat loss seems the most reasonable explanation for the observed decrease in body temperature. These observations point to an adverse effect of vasodilatory drugs. One should be aware of this possibility in patients being treated with these drugs who have complaints suggestive of hypothermia.

Adult↗
PubMed1989

Disparate effects of mental stress on plasma noradrenaline in young normotensive and hypertensive subjects.

The response of blood pressure, heart rate and plasma catecholamines to a mental arithmetic and a cold pressor test was studied in 70 patients with mild essential hypertension and in 41 age- and sex-matched normotensives. Each group consisted of three prospectively stratified age classes: 20-29, 30-39 and 40-55 years. During mental arithmetic, hypertensives showed only a higher increment of systolic blood pressure (+17-19%) than normotensives (+12-15%). Plasma noradrenaline in the youngest normotensives (20-29 years) showed a small but significant decrease (-0.20 +/- 0.07 nmol/l) whereas the youngest hypertensives showed a small but significant increase of plasma noradrenaline (+0.14 +/- 0.04 nmol/l). The difference between both groups was highly significant (P less than 0.001). In the two older age classes there was no difference in plasma noradrenaline response between normo- and hypertensives. During the cold pressor test both the cardiovascular and plasma noradrenaline response were of the same magnitude in normo- and hypertensives. These data reinforce the concept that the increased sympathetic reactivity to mental stress in hypertensives may be restricted to the younger age.

Adult↗
PubMed1989

Occlusion of unilateral stenosed renal arteries--relation to medical treatment.

In 78 patients we studied retrospectively the occurrence of occlusion in unilateral renal artery stenosis during antihypertensive drug treatment. Complete occlusion occurred in 14 patients (18%). In a multivariate analysis the following characteristics were included: blood pressure, aetiology of the stenosis, serum creatinine, the degree of the stenosis, anti-hypertensive medication, standing renal vein renin ratio and age. In this analysis the combination of a diuretic and an ACE-inhibitor, during the observation period, showed an independent relation to the development of an occlusion (P less than 0.05). Also the ACE-inhibitor alone showed a relation (P = 0.06). In the 14 patients who developed an occlusion only three showed a significant rise in serum creatinine. We conclude that special attention should be given to the follow-up of patients with renal artery stenosis who have ACE-inhibitors in their treatment regimen, especially when in combination with a diuretic.

Adolescent↗
PubMed1989

Caffeine reduces dipyridamole-induced myocardial ischemia.

The mechanism of action of coronary vasodilation after dipyridamole may be based on inhibition of cellular uptake of circulating endogenous adenosine. Since caffeine has been reported to be a competitive antagonist of adenosine we studied the effect of caffeine on the outcome of dipiridamole-201Tl cardiac imaging in one patient. During caffeine abstinence dipyridamole induced myocardial ischemia with down-slope ST depressions on the ECG, and reversible perfusion defects on the scintigrams. When the test was repeated 1 wk later on similar conditions, but now shortly after infusion of caffeine (4 mg/kg), the ECG showed no, and the scintigrams only slight signs of ischemia. We conclude that when caffeine abstinence is not sufficient, the widespread use of coffee and related products may be responsible for false-negative findings in dipyridamole-201Tl cardiac imaging.

Caffeine↗
PubMed1988

Comparison of blood pressure response to exogenous epinephrine in hypertensive men and women.

This study investigated possible differences between hypertensive men and hypertensive women concerning the hemodynamic effects of incremental doses of exogenous epinephrine. The study population comprised 38 men (37 +/- 10 years) (standard deviation) and 25 women (33 +/- 9 years) with mild essential hypertension (mean blood pressure 147/90 and 147/93 mm Hg, respectively). Body mass index was slightly higher in men (25 +/- 3 kg/m2) than in women (23 +/- 2 kg/m2). Both groups received an intravenous infusion with epinephrine of 15 and 30 ng/kg/min for 8 minutes each. Despite the similar doses of epinephrine infused in both groups, the increase of venous plasma epinephrine in men was nearly twice that in women (1.04 +/- 0.09 vs 0.67 +/- 0.09 nmol/liter, p less than 0.01), suggesting that women cleared the infused epinephrine more efficiently than men. At the highest infusion dose, the increase of systolic blood pressure was larger in men than in women (5.3 +/- 1.2 vs 1.7 +/- 1.1 mm Hg, p less than 0.05). Conversely, the decrease of diastolic blood pressure was also larger in men than in women (-8.8 +/- 1.0 vs -5.8 +/- 1.0 mm Hg, p less than 0.05). The heart rate increased to the same extent in both groups (11.5 +/- 0.8 and 13.7 +/- 1.2 beats/min). If the blood pressure responses were corrected for the increase of plasma epinephrine, the difference between men and women disappeared.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Pressure↗
PubMed1988

Dose-response study of prazosin in Raynaud's phenomenon: clinical effectiveness versus side effects.

In a dose-response study of prazosin in 24 patients with Raynaud's phenomenon, the clinical effectiveness and side effects of 3, 6, and 12 mg prazosin administered daily were compared. Diary analysis and measurement of finger skin blood flow and temperature before, during, and after cold challenge showed no major differences among these three dose regimens. Standing systolic blood pressure decreased significantly during the 12-mg period in comparison with the 6-mg (P less than .05) and with the 3-mg period (P less than .02), whereas heart rate increased in the 6-mg and 3-mg periods (P less than .05). In the higher dosage ranges, spontaneous mentioned side effects were noticed most often, which was in accordance with the results of a checklist analysis on adverse effects. Three patients withdrew from the study because of complaints that might be due to orthostatic hypotension. Most patients that wanted to continue prazosin after this study (n = 13) did so on a 3-mg basis (n = 10). Because prazosin 3 mg daily is more effective in treating of Raynaud's phenomenon than is placebo, the study shows that in a dosage of 3 mg daily, the best balance between clinical effectiveness and side effects is obtained.

Adolescent↗
PubMed1988

Blood pressure and both venous and urinary catecholamines after cerebral infarction.

Blood pressure, both venous and urinary catecholamines and plasma renin activity (PRA) were studied in 10 patients (6 men and 4 women, mean age 70 +/- 10 years) on the first three days after cerebral infarction. Blood pressure fell significantly (p less than 0.02) on the second and third day after stroke. There was a small but significant (p less than 0.01) decrease in plasma epinephrine concentration on the third day. The norepinephrine values remained constant on the three days. The PRA showed a significant (p less than 0.01) rise on the third day. No significant correlation was detected between the course of the blood pressure and the plasma catecholamines or PRA. When blood pressure was correlated with the urinary catecholamines, however, a significant correlation with epinephrine (r = 0.45; p less than 0.05) and with norepinephrine (r = 0.44; p less than 0.05) was found. We conclude that the changes in blood pressure after stroke are at least partly mediated by the changes in catecholamine production.

Aged↗
PubMed1988

Impaired vasodilation during long-term beta 1-selective beta-blockade in hypertensive patients.

In eight patients with essential hypertension the effect of 50 mg atenolol, once daily for 6 months, on vasodilation during epinephrine infusion and submaximal dynamic exercise was studied. The normal decrease of diastolic blood pressure during bicycle exercise, reflecting a decrease in total peripheral resistance not mediated by circulating epinephrine, disappeared during atenolol treatment. Low-dose infusion of epinephrine had no influence on systolic blood pressure both before and after atenolol. However, the decrease of diastolic blood pressure occurring before atenolol was abolished and the increase in heart rate was attenuated during atenolol treatment. Forearm vascular resistance decreased before and during atenolol to the same extent. So the normal physiologic vasodilation during submaximal dynamic exercise seems impaired during long-term treatment with atenolol. In addition the normal vasodilating response to an increase of circulating epinephrine to levels occurring during daily life stress seems impaired even with the low dose of this beta 1-selective beta-blocker.

Adult↗
PubMed1988

Reproducibility of haemodynamic and plasma catecholamine responses to isometric exercise and mental arithmetic in normo- and hyper-tensive subjects.

1. To determine the reproducibility of a mental arithmetic stress test and a handgrip exercise test, we studied the responses of blood pressure, heart rate, forearm blood flow and plasma catecholamines on two occasions, with an interval of at least 1 week, in 24 normotensive and 22 hypertensive subjects. 2. The SE of a single observation of the percentage changes of blood pressure ranged from 3.9 to 9.3% in normotensive subjects and from 3.9 to 7.4% in hypertensive subjects in both tests. For heart rate, these values were 4.9-12.3% in the normotensive subjects and 4.8-5.7% in the hypertensive subjects. However, there was a wide individual scatter of these haemodynamic responses during both tests. The forearm blood flow, only measured during mental arithmetic, had an SE of a single observation of 33.7%. 3. In 10 normotensive subjects the SE of a single observation of the change in plasma noradrenaline was 0.16 nmol/l during handgrip exercise and 0.09 nmol/l during mental arithmetic. The corresponding values for plasma adrenaline were 0.04 and 0.05 nmol/l. 4. In conclusion, although both tests showed a rather low SE of a single observation for the blood pressure and heart rate responses in normo- and hyper-tensive subjects, there was a considerable individual variability. If related to the mean forearm blood flow responses, the SE of a single observation of the forearm blood flow response was of similar magnitude. The limited intra-individual reproducibility of both tests should be borne in mind when interpreting pharmacological intervention studies or studies evaluating sympathoadrenal reactivity in cardiovascular disorders.

Adolescent↗
PubMed1988

Deleterious effects of anabolic steroids on serum lipoproteins, blood pressure, and liver function in amateur body builders.

The effects of self-administered anabolic steroids (AS) on lipoproteins, liver function, and blood pressure were studied in male amateur body builders. Twenty body builders were studied at the end of a course of AS (group 1) and 42 body builders were studied after discontinuation of the AS for a mean of 5 months (group 2). Sixteen body builders were studied after discontinuation of AS for at least 2 months and at the end of a 9-week course of AS (group 3). A group of 13 body builders who never used AS served as a control group. Both groups 1 and 2 showed higher levels of transaminas and a higher systolic blood pressure than the controls (P less than 0.05). Group 3 showed an increase of the transaminases an a slight but significant increase of systolic blood pressure (+3 mm Hg) and heart rate (+7 bts/min) after one course of AS (P less than 0.05). Group 1 showed a considerably lower high-density lipoprotein cholesterol (HDLC) (P less than 0.001), a higher low-density lipoprotein cholesterol (LDLC) (P less than 0.05), and a lower apoprotein A-l/B ratio (Apo A-l/ApoB) (P less than 0.001) than the controls and group 2. The ratio of LDLC/HDLC in group 1 was fourfold higher than in the controls (P less than 0.01). In group 3 HDLC decreased from 1.18 +/- 0.05 to 0.60 +/- 0.08 mmol/l (P less than 0.001) and LDLC increased from 3.97 +/- 0.39 to 5.74 +/- 0.71 mmol/l (P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

The effects of caffeine on the postprandial fall of blood pressure in the elderly.

In a double-blind placebo-controlled study, we examined the effect of caffeine pretreatment on the haemodynamic and humoral changes after a standardized breakfast in 15 healthy elderly subjects (mean age 75.4 +/- 6.6 years). After placebo, the preprandial blood pressure did not change and the postprandial blood pressure declined by a maximum of 6.1%. After oral ingestion of 250 mg caffeine, 60 min before breakfast, the preprandial blood pressure increased by 12.5%. Although the decrease of the postprandial blood pressure was not altered, blood pressure remained above its basal value. The increase in plasma noradrenaline after the meal was similar in the placebo and the caffeine tests. Plasma adrenaline decreased after placebo (-19%) but did not change after caffeine. Thus, despite the unchanged decrease of the postprandial blood pressure, the preprandial pressor effect of caffeine prevented the decline of the postprandial blood pressure below its baseline value. The clinical relevance of this finding has still to be determined.

Aged↗
PubMed1988

Patients with congenital dopamine beta-hydroxylase deficiency. A lesson in catecholamine physiology.

We recently described a case of congenital dopamine beta-hydroxylase (DBH) deficiency. The syndrome is characterized by noradrenergic denervation, adrenomedullary failure, but intact baroreflex afferents, cholinergic innervation, and adrenocortical function. Norepinephrine, epinephrine, and their degradation products were undetectable in plasma, urine, and cerebrospinal fluid, whereas dopamine and its degradation products were elevated. Plasma DBH was not detectable. Studies in this novel syndrome showed evidence for the peripheral production of dopamine from sympathetic nerve terminals noradrenergic in nature. Tyrosine hydroxylase is probably induced in this syndrome, since plasma levels of L-DOPA were also elevated. Absence of hemodynamic effects of sympathicolytic agents in the face of an increase in blood pressure after dopamine antagonists suggest that intrasynaptic concentrations of dopamine are in the range of its plasma concentrations. Hypoprolactinemia, reduced REM sleep, increased slow wave sleep and sodium loss, despite low blood pressure, are further evidence for the biological role of dopamine in man.

Adult↗
PubMed1988

Role of adrenaline in the short-term upregulation of beta-adrenoceptors in essential hypertensive and adrenalectomized females.

The effect of mental arithmetic on beta 2-adrenoceptors on lymphocytes, as measured by (-)125I-iodocyanopindolol binding, was studied in normotensive and essential hypertensive females. To determine the role of adrenaline, mental arithmetic was also carried out in bilaterally adrenalectomized females. There were no significant differences in the blood pressure and heart rate responses to mental arithmetic among the three groups. Baseline values or changes in adrenaline levels during mental arithmetic were similar in normotensives and hypertensives, whereas levels of adrenaline remained undetectable throughout the test in adrenalectomized females. Baseline values of beta 2-adrenoceptors did not differ among the three groups. In normotensive and hypertensive females the increase in beta 2-adrenoceptor density was, respectively, 27 and 20%. Baseline values of beta 2-adrenoceptors were not related to the percentage changes in the receptor densities. In adrenalectomized females, in contrast to normotensives and hypertensives, there was no change in receptor density. These findings suggest that adrenaline plays a role in the short-term upregulation of beta 2-adrenoceptors after mental arithmetic.

Adrenalectomy↗
PubMed1988

Intravenous nicardipine in Raynaud's phenomenon: a controlled trial.

The hemodynamic effects of intravenously administered nicardipine (5 mg/h during 85 min) were investigated in 12 Raynaud patients and in 12 healthy volunteers in a double-blind placebo-controlled cross-over study. In both groups we found no change in systolic blood pressure, but a significant fall in diastolic blood pressure of 7 mm Hg (p less than 0.001). Heart rate increased 14 beats/min (p less than 0.001) and forearm blood flow increased 1.0 ml/100 ml/min (p less than 0.01) with a concomitant decrease of 10 arbitrary units (AU) in forearm vascular resistance (p less than 0.001). In healthy volunteers the recovery of the finger skin temperature after cold challenge improved significantly (p less than 0.05). In patients with primary Raynaud's phenomenon we observed a significant (p less than 0.001) increase in skin temperature of 4.6 degrees C before cooling, together with a better recovery after cold induced vasospasm (p less than 0.001). In secondary Raynaud's patients, nicardipine caused no vasodilatation within the skin vessels. There were no significant correlations between the plasma nicardipine concentration and any of the observed pharmacological effects.

Adult↗
PubMed1988

Hemodynamic effects of prostacyclin infusions in healthy volunteers.

The selective hemodynamic effects of an intravenous infusion of prostacyclin on skin and on forearm blood flow during increasing doses up to 6 ng.kg.-1 min.-1 were evaluated in 12 healthy volunteers. The highest dose raised total skin blood flow (p = 0.0001) as measured by laser Doppler with a concomitant rise in finger skin temperature (p = 0.02). Capillary perfusion as measured by transcutaneous oxygen monitoring remained relatively unaffected (p = 0.25). Cold-induced vasoconstriction and the recovery thereafter were not influenced. Diastolic blood pressure tended to decrease (p = 0.06), but there was no change in systolic blood pressure, forearm blood flow, and calculated forearm vascular resistance. The authors conclude that prostacyclin may have dissimilar vasoactive potencies in different vascular beds as shown by a pronounced increase in total skin blood flow, owing to vasodilation of shunt vessels, simultaneously with an insignificant change in nutritional skin blood flow and forearm muscle blood flow.

Adult↗
PubMed1988

Hemodynamic reactivity to sympathoadrenal stimulation in adrenalectomized women.

To determine the extent to which circulating epinephrine (E) mediates the cardiovascular effects of sympathoadrenal stimulation, we studied the blood pressure (BP), heart rate, forearm vascular resistance, and plasma catecholamine responses to a mental arithmetic test, head-up tilt test, and cold pressor test in 10 adrenalectomized women and 10 age-matched normotensive women. The mean basal diastolic BP was slightly higher in the adrenalectomized women (80 vs. 68 mm Hg; P less than 0.05). During mental arithmetic, the adrenalectomized women had a smaller heart rate increase than the normal women [6 +/- 1% (+/- SE) vs. 16 +/- 4%; P less than 0.05], but the BP response was not different. During the head-up tilt and cold pressor tests the hemodynamic responses were similar in the adrenalectomized and normal women. As expected, plasma E was undetectable in the adrenalectomized women. Plasma norepinephrine (NE) did not change in either group during mental arithmetic. In the adrenalectomized women the plasma NE increases during the head-up tilt and cold pressor test were not significantly different from those in the normal women. Thus, the adrenalectomized women had a normal pressor response during all 3 types of adrenergic stimulation, apparently independent of plasma E. Together with the normal plasma NE responses to head-up tilt and cold exposure, we challenge the contention that the E-mediated presynaptic beta-adrenergic stimulation of NE release plays a pivotal physiological role during short term adrenergic stress.

Adrenal Glands↗
PubMed1988

Kinetics of (-)125iodocyanopindolol binding to intact human mononuclear cells.

In association experiments of (-)125Iodocyanopindolol (125ICYP) with human mononuclear cells (MNC) at 70 pM and a temperature of 37 degrees C equilibrium was reached within 30 min. However, when the same experiments were performed at a concentration of 4 pM 125ICYP, equilibrium was only reached after 3 hours. The consequences of incomplete equilibrium for the interpretation of binding experiments under the incorrect assumption that equilibrium has been reached, was investigated at equilibration times of one, two and three hours. The dissociation constant, Kd, decreased from 7.4 +/- 0.2 pM after one hour to 2.5 +/- 0.4 pM after three hours of incubation while the receptor density, RO, decreased from 970 +/- 170 to 713 +/- 58 sites/cell. Analysis of computer simulated binding curves confirmed the decrease in Kd and RO at prolonged incubations. We conclude that in 125ICYP binding in intact MNC one hour of incubation is not sufficient to obtain equilibrium at the lower concentrations. This leads to an overestimation of Kd- and to a lesser extent of RO-values. Extending the incubation time to three hours on the other hand may lead to a loss of cells and therefore to an underestimation of RO.

Humans↗