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Biomedical subjects

T Thien

Publications and source records attributed to T Thien.

At least 199 records · Page 11Linked to original sources
PubMed1990

Beta 2-adrenoceptor up-regulation in relation to cAMP production in human lymphocytes after physical exercise.

The effect of isotonic bicycle exercise on beta 2-adrenoceptors and cAMP production in lymphocytes was studied. The origin of the newly exposed receptors was studied by measuring radioligand binding in the presence of hydrophylic or lipophylic 'cold' ligands. During exercise beta 2-adrenoceptor density increased from 1207 +/- 144 to 1776 +/- 152 sites/cell (56 +/- 14%). Isoprenaline induced an increase in cAMP synthesis, which was 68 +/- 15% higher than those values measured before the test. Forskolin did not induce a higher increase in cAMP production after exercise. The increase in receptor density seems not to be due to a transfer of internalized receptors to the membrane surface. We conclude that physical exercise induces an up-regulation of beta 2-adrenoceptors on lymphocytes and that these adrenoceptors are functional.

Adult↗
PubMed1990

The relationship between adrenaline and beta 2-adrenoceptors on human lymphocytes.

To study the relation between plasma adrenaline (AD) and noradrenaline (NA) and the beta 2-adrenoceptor number (Bmax) on lymphocytes these variables were measured in the following three groups: a) In 67 normotensive volunteers after a rest period of at least 15 min. b) In 10 essential hypertensive (HT) and 10 age and sex matched normotensive (NT) subjects before and after a standardized bicycle exercise test (BE). c) In 10 bilaterally adrenalectomized females (AF) and 10 healthy age matched females (NF) before and after a mental arithmetic test (MA). Significant correlations were found between AD and Bmax in NT (r = 0.30, P = 0.015) and between the proportional increase in AD and the proportional increase in Bmax after BE (r = 0.60, P less than 0.005). The MA induced elevation of Bmax was blunted after adrenalectomy. All these findings point to a relation between AD and beta 2-adrenoceptor regulation.

Adrenalectomy↗
PubMed1990

The diagnostic value of clinical signs and symptoms in patients with Raynaud's phenomenon. A cross-sectional study.

Patients presenting with Raynaud's phenomenon pose differential diagnostic problems. The question is whether the discolorations are a symptom of the benign primary type or a symptom of an underlying disease, mostly a connective tissue disease or an atherosclerotic occlusive disease, both having major prognostic implications. To evaluate whether Raynaud patients can be classified properly in the above-mentioned categories on clinical grounds we evaluated 225 patients using a checklist dealing with signs and symptoms supposed to be specific for primary Raynaud's phenomenon or the two major types of the secondary form. Complaints that started before the age of 20, reactive hyperaemia at the end of an attack and discolorations of the earlobes and the nose have a high predictive value for primary Raynaud's phenomenon. Trophic skin disturbances are rare in the latter but are rather specific for connective tissue diseases. In the case of arterial obstructive disease, the feet are always involved and risk factors associated with atherosclerosis are often present, whereas this type is specifically encountered in men in whom the complaints started over the age of 50 [corrected], and in whom signs of atherosclerotic vessel wall disease were seen elsewhere. In conclusion, in most patients who present with a Raynaud's phenomenon a complete history and physical examination are sufficient for a correct diagnosis. Supplementation with determination of anti-nuclear antibodies, measurements of the capillary perfusion and of the finger skin systolic pressure completes the diagnostic classification.

Adult↗
PubMed1990

The captopril test in the detection of renovascular disease in hypertensive patients.

A number of reports share the conclusion that the captopril test is an adequate screening procedure for the detection of renovascular disease among hypertensive patients. Therefore, we prospectively studied the value of this test in 149 consecutive hypertensive patients. The test was considered positive if plasma renin activity, after an oral dose of 25 mg of captopril, rose by more then 4.44 ng.L-1.s-1 (16.0 ng/mL per hour). The sensitivity of the test was 39%, the specificity was 96%, the positive predictive value was 81%, and the negative predictive value was 79%. No clinically important cutoff point identifying patients with renal artery stenosis could be detected in the values of baseline and stimulated plasma renin activity nor in baseline blood pressure or changes after captopril testing. The low sensitivity makes the captopril test unfit to be used as a screening procedure in an unselected hypertensive population.

Captopril↗
PubMed1989

Cardiovascular responsiveness to norepinephrine in mild essential hypertension.

The responses of blood pressure, heart rate and forearm vascular resistance to exogenous norepinephrine (NE) were measured in 40 normotensive and 65 mildly hypertensive subjects (mean blood pressure 117/72 and 146/92 mm Hg, respectively). Both groups received low incremental doses of NE: 15, 30 and 60 ng/kg/min for 8 minutes each. In contrast to previous studies that compared the dose-response curves in normo- and hypertensive subjects, this study corrected the cardiovascular responses for the increment of plasma NE to account for differences in metabolic clearance of NE. Although age and sex appeared to play a role, the corrected cardiovascular responses did not differ significantly between normo- and hypertensive subjects. Thus, an increased cardiovascular sensitivity to exogenous NE was not demonstrated in mildly hypertensive subjects. This finding confirms some but not all previous studies of the dose-response relation.

Adult↗
PubMed1989

[Hypotension following a one-time (initial) dose of captopril].

In a group of 269 untreated hypertensive patients the effect of a single oral dose of captopril (25 mg) on blood pressure was studied for 90-120 minutes. The systolic blood pressure decreased by more than 20% in 9.5% and by more than 30% in 1.1% of the patients. In 22.6% the diastolic blood pressure decreased by more than 20%; in 4.5% it fell more than 30%. The calculated mean arterial pressure (MAP) was reduced by more than 20% in 12.3% of the patients and by more than 30% in 3%. Three patients showed transient neurological deficits. Factors related to a strong blood pressure drop were: renal artery disease and resistant hypertension. However, a potentially dangerous fall in blood pressure, i.e. an acute fall of MAP of over 30%, was also observed in the absence of these risk factors. Therefore not all patients at risk can be identified in advance, and treatment with ACE-inhibitors has to be started under well-controlled circumstances especially in elderly patients.

Adult↗
PubMed1989

A comparison of the hypotensive effects of captopril and atenolol in the treatment of hypertension in diabetic patients.

In a double-blind, randomized, cross-over study in 23 diabetic patients, insulin treated (N = 11) or noninsulin treated (N = 12), with mild to moderate hypertension, the hypotensive effects of captopril and atenolol were compared. Five patients had overt diabetic nephropathy. All patients received 50 mg twice daily of either drug. Treatment periods lasted 6 weeks and were preceded and separated by a placebo period. Two patients dropped out, one because of intermittent claudication during atenolol, one with cardiac arrhythmia during placebo. Blood pressure was reduced from 165 +/- 5/96 +/- 1 to 154 +/- 5/89 +/- 2 mmHg (mean +/- SEM: P less than 0.01) during captopril and from 171 +/- 5/98 +/- 1 to 159 +/- 6/89 +/- 2 mmHg (P less than 0.01) during atenolol. These antihypertensive effects are not significantly different. There was a wide inter- and intraindividual variation in hypotensive response to both drugs, which may have important consequences for treatment strategies. No consistent differences between insulin and noninsulin treated patients were seen. Parameters of glycemic control did not change during any therapy, neither in insulin treated nor in non-insulin treated patients. Albuminuria and renal function did not change. During captopril treatment one patient complained of a non-productive cough. Two patients experienced a severe hypoglycemic reaction during atenolol. No other major side-effects were seen. In conclusion, this study showed equal hypotensive effectivity of 100 mg captopril and 100 mg atenolol daily in hypertensive diabetics, without evident effect on glycemic control.

Adult↗
PubMed1989

Postocclusive reactive hyperemia of fingertips, monitored by laser Doppler velocimetry in the diagnosis of Raynaud's phenomenon.

Measurement of laser Doppler flow on the fingertip was evaluated before and after occlusion of the fingerbase for 5 min by suprasystolic compression in normal control subjects and in patients with several types of Raynaud's phenomenon (RP). Baseline flow values differed significantly (P less than 0.002) between the 24 normals and the 29 primary Raynaud patients but there was a considerable overlap between the primary and the secondary Raynaud group. The postocclusive reactive hyperemia parameters showed an improved discrimination between the patients with primary RP and the 38 patients with secondary RP. The patients with scleroderma and those with arterial obstructive disease of the finger had the lowest increase in flow. Of all the indices analyzed none showed an optimal discrimination among the several subtypes of finger ischemia. The parameters that represent the increase in laser Doppler values after occlusion differentiated best between primary and secondary types (P less than 0.02). Time variables after the peak were more suitable to differentiate scleroderma patients from those with arterial obstructive disease (P less than 0.002). The reproducibility of the laser Doppler-monitored postocclusive response in normals was found to be only moderate (standard error of a single observation varies between 7 and 43% for different parameters). In conclusion postocclusive reactive hyperemia may be useful in determining the degree of obstructive vascular disease in groups of patients presenting with RP. It is not sensitive enough to discriminate adequately among individuals in the several subgroups.

Arterial Occlusive Diseases↗
PubMed1989

Nicotine enhances the circulatory effects of adenosine in human beings.

A randomized, double-blind, and placebo-controlled study was performed in 10 healthy volunteers to evaluate a possible interaction between adenosine and nicotine in human beings. The infusion of adenosine alone (0.07 mg/kg/min) induced an increase in heart rate of 4.7 beats/min versus 0.2 beats/min after placebo administration (p less than 0.02). The infusion of adenosine alone induced a decrease in finger skin temperature compared with placebo administration (-1.0 degrees versus 0.0 degrees C, p less than 0.01). When compared with baseline values, nicotine gum chewing increased systolic and diastolic blood pressures by 6.2 and 7.0 mm Hg, respectively (p less than 0.001), heart rate by 5.5 beats/min (p less than 0.01), and plasma adrenaline levels by 0.03 nmol/L (p less than 0.025), whereas skin temperatures fell by 1.3 degrees C (p less than 0.001). The nicotine-induced increase in heart rate was larger during adenosine infusion than during placebo administration (14.9 versus 5.5 beats/min, p less than 0.001), whereas the increment of diastolic blood pressure was lower (1.1 versus 4.0 mm Hg, p less than 0.05). The increment in systolic blood pressure was not altered by concomitant adenosine infusion. The rise in plasma noradrenaline levels during the combined administration of nicotine and adenosine differed significantly from the response to nicotine alone (+ 0.23 versus -0.05 nmol/L, p less than 0.02). We concluded that, in human beings, the characteristic hemodynamic response to adenosine infusion is enhanced by nicotine.

Adenosine↗
PubMed1989

Cardiovascular effects of two xanthines and the relation to adenosine antagonism.

We hypothesize that the hemodynamic effects of xanthine derivatives depend on their ability to antagonize the vasodilating effects of endogenous adenosine. In a randomized, double-blind, and placebo-controlled study of 10 normotensive volunteers caffeine, a xanthine with in vitro adenosine antagonistic properties, increased mean arterial pressure by 5.6 +/- 0.9 mm Hg and lowered heart rate by 5.3 +/- 1.1 beats/min. After administration of enprofylline, a xanthine without adenosine antagonism, forearm vascular resistance decreased by 5.6 +/- 3.4 IU, heart rate increased by 10.6 +/- 2.6 beats/min, and plasma adrenaline, plasma noradrenaline, and renin activity increased by 178 +/- 86%, 14 +/- 8%, and 36 +/- 13%, respectively. Adenosine infusion alone induced a dose-related increase in pulse pressure and heart rate, and it increased plasma adrenaline and noradrenaline by 186 +/- 77% and 132 +/- 55%, respectively. This response to adenosine was reduced by pretreatment with caffeine but not enprofyline. Thus opposite circulatory responses to caffeine and enprofylline occurred, with signs of vasoconstriction and vasodilation, respectively. In addition, caffeine, but not enprofylline, reduced the cardiovascular response to exogenous adenosine.

Adenosine↗
PubMed1989

Adrenoceptors on blood cells in patients with essential hypertension before and after mental stress.

The effect of mental arithmetic (MA) on alpha 2- and beta 2-adrenoceptors on platelets and lymphocytes, respectively, and on plasma catecholamines was studied in normotensive (NT) and essential hypertensive (HT) subjects. There were no significant differences in responses of blood pressure, forearm blood flow (FBF) and heart rate to MA between the two groups. Baseline values and changes in adrenaline and noradrenaline levels during MA were similar in NT and HT. Alpha 2-adrenoceptor density and antagonist affinity did not differ between NT and HT and was not influenced by MA. Baseline values of beta 2-adrenoceptor density also did not differ between NT and HT and increased similarly after MA in both groups. Antagonist affinity to the beta 2-adrenoceptors under baseline conditions was lower in HT and did not change during MA in either group. Our results indicate that there are no differences between NT and HT in alpha 2- and beta 2-adrenoceptor density, either under baseline conditions or after mental stress.

Adult↗
PubMed1989

Effects of isometric exercise on blood cell adrenoceptors in essential hypertension.

The effect of handgrip (HG) isometric exercise on plasma catecholamines, alpha 2-adrenoceptors on platelets and beta 2-adrenoceptors on lymphocytes was studied in normotensive subjects (NT) and essential hypertensive subjects (HT). Whereas systolic blood pressure (SBP) increases were similar in NT and HT subjects, diastolic blood pressure (DBP) and heart rate (HR) increased more in the former group. Baseline values and changes in plasma epinephrine (E) and norepinephrine (NE) did not differ between both groups. No differences were apparent in alpha 2-adrenoceptor density and affinity between NT and HT subjects before or after the test. HG isometric exercise induced a similar increase in beta 2-adrenoceptors on lymphocytes of 22 +/- 7 and 13 +/- 5% in NT and HT subjects, respectively. Affinity to the beta 2-adrenoceptors under baseline conditions was somewhat lower in HT (8.1 +/- 0.4 pM) than in NT subjects (6.5 +/- 0.5 pM), and this difference persisted during the test. Our results indicate that there are no differences in alpha 2- and beta 2-adrenoceptor densities either at baseline conditions or after HG isometric exercise between NT and HT subjects. Small differences noted in affinity to the beta 2-adrenoceptors require further investigation.

Adult↗
PubMed1989

The diagnostic value of several immunological tests for anti-nuclear antibody in predicting the development of connective tissue disease in patients presenting with Raynaud's phenomenon.

One-hundred-and-one patients referred because of Raynaud's phenomenon (RP) were prospectively followed for a mean period of 42 months. At presentation they were screened for signs and symptoms of connective tissue disease (CTD) according to a detailed protocol. At presentation 37 patients had primary RP (PRP), nine had RP in combination with vascular occlusive disease (RP-VOD), 25 had one symptom of a CTD (questionable PRP), 13 had two or more symptoms (undifferentiated CTD, UCTD) and 17 had definite CTD. Progression from one of these groups to another was seen in 24 patients and from PRP, RP-VOD or questionable PRP towards a (U)CTD was seen in 19 patients. Patients with one sign of CTD showed a high tendency (56%) to develop CTD. The presence of ANA as detected by immunofluorescence and by immunoblotting at the start of the study was associated with the future development of symptoms of CTD; positive predictive value 65% and 71% and negative predictive value 93% and 83%, respectively. ANA-testing by immunoblotting was of special help in predicting the development of scleroderma, the CREST syndrome and mixed connective tissue disease. In conclusion, testing for ANA by indirect immunofluorescence helps to discriminate between patients with persisting PRP and those who will develop a CTD, while testing for ANA by the immunoblotting technique helps to predict the development of a specific CTD.

Adolescent↗
PubMed1989

The interaction between indomethacin and captopril or enalapril in healthy volunteers.

In this study eight healthy volunteers were involved in a randomized, cross-over trial in which they were treated with either 25 mg of captopril b.i.d. or 20 mg of enalapril o.i.d. alone or in combination with 50 mg of indomethacin b.i.d. in order to detect a difference between both converting enzyme inhibitors when interacting with indomethacin. Before and after each 4-d treatment period, blood pressure (determined by random zero sphygmomanometer), body weight, plasma renin activity, angiotensin converting enzyme, plasma potassium, serum creatinine and the 24-h urinary excretion of 6-keto-prostaglandin F1 alpha were measured. Indomethacin attenuated the decrease of supine diastolic blood pressure during treatment with captopril, but not with enalapril. However, the initial decrease of blood pressure on captopril was greater than on enalapril. Both converting enzyme inhibitors had no effect on the urinary excretion of 6-keto-prostaglandin F1 alpha, while indomethacin reduced it. The results suggest a difference between captopril and enalapril in interaction with indomethacin.

Adult↗
PubMed1989

The influence of age and blood pressure on the hemodynamic and humoral response to head-up tilt.

It has been reported that postural hypotension in the elderly is common. However, these studies included institutionalized and more or less disabled persons. Furthermore, postural hypotension may be related to baseline blood pressure. In this study, the influence of age and blood pressure on the hemodynamic and plasma catecholamine responses to orthostatic stress was investigated in young and old normotensive and hypertensive healthy subjects. In normotensive and hypertensive elderly persons, the percentage blood pressure responses during tilt were not significantly different from that seen in young normotensives. We measured a slight decrease of systolic blood pressure and a slight increase of diastolic blood pressure. The hypertensive young patients showed an enhanced diastolic blood pressure response with no fall in systolic blood pressure, in contrast to the normotensive young subjects. Both elderly groups had a lower increase of heart rate than the young subjects. The percentage increase in norepinephrine after tilting was significantly lower in elderly hypertensives than in elderly normotensives and young hypertensives. The presence of hypertension was associated with a decrease in blood pressure, but age had no influence on the change in blood pressure during tilt. In this group of healthy elderly subjects, there was no significant orthostatic hypotension when the blood pressure course of the entire tilt test was taken into account.

Adult↗
PubMed1989

Effect of decaffeinated versus regular coffee on blood pressure. A 12-week, double-blind trial.

The effect of decaffeinated versus regular coffee on blood pressure and heart rate was investigated. In a randomized double-blind, crossover trial, 45 healthy volunteers (23 women and 22 men, 25-45 years old) with a habitual intake of 4-6 cups coffee/day received 5 cups of regular coffee each day for a period of 6 weeks, and 5 cups of decaffeinated coffee for the next 6 weeks or vice versa. The background diet was kept constant. The total amount of caffeine ingested was 40 mg during the decaffeinated coffee period and 445 mg during the regular coffee period. Use of decaffeinated coffee led to a significant but small decrease in systolic (mean +/- SEM, -1.5 +/- 0.4 mm Hg; p = 0.002) and diastolic (-1.0 +/- 0.4 mm Hg; p = 0.017) ambulant blood pressure and to a small increase in ambulant heart rate (+1.3 +/- 0.6 beats/min; p = 0.031). Individual differences in rate of caffeine metabolism did not explain differences in long-term response of blood pressure to caffeine. We conclude that in normotensive adults replacement of regular by decaffeinated coffee leads to a real but small fall in blood pressure. However, it remains to be established whether a mass switch from regular to decaffeinated coffee would significantly reduce the total incidence of hypertension-related disorders.

Adolescent↗