Search PubMed⌕ Search

Biomedical subjects

J Warberg

Publications and source records attributed to J Warberg.

At least 127 records · Page 7Linked to original sources
PubMed1987

Organ extraction of atrial natriuretic peptide (ANP) in man. Significance of sampling site.

Arterial plasma immunoreactivity of endogenous human alpha-atrial natriuretic peptide (ANP) underwent mean 54%, 28% and 40% extraction during one passage through the circulation in the kidney (n = 12), liver-intestine (n = 14) and lower limb (n = 8), respectively, in supine fasting subjects with no detectable disease or subjects with cardiovascular or hepatic disorders of minor degree undergoing a haemodynamic investigation. No extraction was identified across the lungs as evaluated by the same concentration of ANP in pulmonary and femoral arteries (n = 7). The concentration of ANP in a superficial arm vein relative to the femoral artery varied considerably and extractions from 0% up to 58% were identified (mean 18%). The results suggest a high degree of, but only to some extent selective, extraction of ANP, which may account for its proposed short plasma half-life. Due to the different concentrations of ANP in various vascular beds, sampling site should be thoroughly specified.

Adult↗
PubMed1987

Progressive central hypovolaemia in man--resulting in a vasovagal syncope? Haemodynamic and endocrine variables during venous tourniquets of the thighs.

Hypotensive functional haemorrhage induced by venous pooling of blood in the legs has been reported to be characterized by a vasovagal reaction. In the present study these observations were extended by determination of the hormonal profile developed during progressive central hypovolaemia and an emotionally induced vasovagal syncope. In six subjects venous pooling resulted in normotensive central hypovolaemia, in one subject hypotensive central hypovolaemia was induced, and one subject experienced an emotionally induced vasovagal syncope. During normotensive central hypovolaemia heart rate increased from 58 +/- 4 to 76 +/- 4 beats min-1 (P less than 0.05) and cardiac output fell from 6.1 +/- 0.4 to 4.1 +/- 0.2 1 min-1. Pulse pressure and central venous pressure decreased from 64 +/- 4 to 53 +/- 4 mmHg, and from 8 +/- 2 to 3 +/- 2 mmHg, respectively. Adrenaline and noradrenaline increased from 87 +/- 10 to 120 +/- 20 pg/ml and from 196 +/- 33 to 370 +/- 50 pg/ml, respectively. Angiotensin II increased from 13 +/- 4 to 36 +/- 6 pg/ml and aldosterone from 63 +/- 9 to 180 +/- 27 pg/ml. In hypotensive central hypovolaemia the decrease in mean arterial pressure was accompanied by a decrease in heart rate and increments in the plasma concentrations of pancreatic polypeptide, indicating increased vagal activity and beta-endorphin, while plasma noradrenaline was unchanged. In emotionally induced syncope heart rate decreased to cardiac arrest for 13 s, associated with increments in the plasma concentrations of pancreatic polypeptide and beta-endorphin. It is concluded that normotensive functional haemorrhage in man is associated with increased sympathetic activity and that the qualitatively similar observations obtained during an emotionally and a hypovolaemic-induced hypotensive episode indicate that the hypotensive functional haemorrhage is characterized by a vasovagal reaction.

Adult↗
PubMed1987

Central venous pressure--a physiological stimulus for secretion of atrial natriuretic peptide in humans?

A sensitive radio-immunoassay (RIA) for the measurement of human alpha-atrial natriuretic peptide (ANP) in extracted plasma was developed and used in a study of the possible effect of posture on the concentration of ANP in plasma. The least detectable quantity was less than 2 pg per tube equivalent to 5 pg ml-1 plasma. In the middle sensitivity range (approximately 50 pg per tube), the within-assay and between-assay coefficients of variation were 4.0 and 2.8%, respectively. The recovery of ANP added to plasma prior to extraction was 95-101%. High pressure liquid chromatography (HPLC) of plasma extracts revealed that endogenous ANP was eluted in the same fractions as synthetic ANP. In order to investigate the effect of posture on the concentration of ANP in plasma six healthy volunteers were exposed to five positions in the following sequence: supine, standing, sitting, supine and 10 degrees head-down tilt on a tilt-table. The concentration of ANP was lower in the standing and sitting position than in the supine and head-down tilted position. In another study six healthy volunteers were subjected to passive tilting on a tilt-table in order to evaluate the effect of tilting on blood pressure (BP), heart rate, central venous pressure (CVP) and the concentration of ANP in plasma. It was found that a fall in CVP was accompanied by a significant decrease in the concentration of ANP and that a rise in CVP was accompanied by a rapid increase in the concentration of ANP in plasma. The results are in agreement with the hypothesis that CVP is a physiological stimulus for the secretion of ANP.

Atrial Natriuretic Factor↗
PubMed1987

Plasma arginine vasopressin during neck suction in upright sitting man.

In order to examine the influence of carotid baroreceptor stimulation on arginine vasopressin secretion, 8 normal healthy males were subjected to static neck suction of -3.3 kPa for 20 min in the upright sitting position after overnight food and fluid restriction. The plasma concentration of arginine vasopressin did not change significantly during neck suction. However, in 3 subjects the termination of neck suction induced large increases in plasma arginine vasopressin from 1.8 to 63.7 ng/l, from 0.7 to 34.3 ng/l and from 2.1 to 19.0 ng/l, respectively. Two subjects experienced symptoms such as nausea and paleness during neck suction. Systolic arterial pressure increased slightly but significantly during neck suction from 15.3 +/- 0.3 to 15.7 +/- 0.4 kPa (N = 7, P less than 0.05), whereas mean arterial pressure, diastolic arterial pressure, central venous pressure, heart rate, plasma osmolality, plasma sodium and potassium were unchanged. Haemoglobin concentration in blood and haematocrit increased significantly during and after neck suction, whereas plasma volume decreased. We conclude that neck suction with a negative pressure of 3.3 kPa in upright sitting man does not significantly affect plasma arginine vasopressin. However, termination of the stimulation induces large increases in some subjects. This may be explained by a direct effect on the vagus nerve or by a selective deloading of carotid baroreceptors.

Adult↗
PubMed1987

Effects of H2-receptor antagonists on prolactin secretion: specificity and mediation of the response.

The effects on prolactin secretion of histamine H2-receptor antagonists infused intracerebroventricularly were studied in urethane anaesthetized male rats. A dose of 1.6 mumol cimetidine stimulated basal prolactin secretion and did not affect the histamine-induced release, whereas 0.4 mumol cimetidine inhibited basal and histamine-stimulated prolactin secretion. 0.1 mumol cimetidine had no effect. The more potent H2-receptor antagonist ranitidine at doses of 0.1, 0.4, 1.6 mumol had no effect on basal prolactin secretion, whereas 0.4 and 1.6 mumol inhibited the histamine-stimulated secretion completely. SKF-92408, a compound resembling cimetidine in chemical structure but devoid of H2-receptor antagonist activity, stimulated basal prolactin secretion at a dose of 1.6 mumol, but had no effect on the histamine-induced release or at a dose of 0.4 mumol. The H2-receptor antagonists metiamide and oxmetidine (1.6 mumol) stimulated basal prolactin secretion and did not prevent the response to histamine. A dose of 0.4 or 1.6 mumol imidazole (the ring structure contained in cimetidine, SKF-92408, metiamide, and oxmetidine) had no effect on basal or histamine-stimulated prolactin secretion. The findings indicate that cimetidine stimulates prolactin secretion by a non-specific action when infused centrally at high doses. In contrast, when infused at lower doses cimetidine inhibits the basal and histamine-stimulated secretion by blockade of H2-receptors. The prolactin-stimulatory action of cimetidine was not due to an H2-agonist effect, since ranitidine did not prevent the response. Cimetidine did not stimulate prolactin secretion via an effect on the dopaminergic system, since the drug had no effect on the dopamine concentration in hypophysial portal blood or in hypothalamic tissue and since inhibition of the dopamine synthesis by alpha-methyl-p-tyrosine did not prevent the cimetidine-induced prolactin release.

Animals↗
PubMed1987

Effect of anaesthetics on PRL and LH secretion in rats. Importance of pre-anaesthetic adaptation and involvement of monoaminergic neurons.

General anaesthesia has been reported to interact with neuroendocrine functions leading to large variations in basal and stimulated plasma levels of several hormones, but the findings are often contradictory. In the present investigation we have attempted to clarify the importance of the experimental procedure when evaluating the influence of anaesthetics on the secretion of PRL and LH in male rats. One group of rats (non-adapted) were anaesthetized (ip) with pentobarbital (P), urethane (U), ketamine (A), or althesin (A) without being accustomed to the laboratory environment prior to anaesthesia. Another group of rats (adapted) were kept for 90 min in their individual cages before induction of anaesthesia with P or U. In non-adapted rats the plasma concentration of PRL declined rapidly during the first 30 min following administration of all anaesthetics or saline (controls) and attained a steady level after 60 min. Except for a brief rise following U injection, the LH concentration was not affected by anaesthesia in the non-adapted rats. In adapted rats, the concentration of both PRL and LH declined markedly during the pre-anaesthetic adaptation period and had stabilized at the end of that period. Following administration of U, P or saline, no further changes in the hormone concentrations were observed. Injection of the dopamine receptor antagonist pimozide prevented the decrease in plasma PRL during the adaptation period, but had no effect on LH secretion. In pimozide-treated rats, U caused a 5-fold increase in the PRL concentration. This effect of U was inhibited by the serotonin receptor antagonist methysergide. The PRL response to 30 micrograms of histamine was similar in conscious and U-anaesthetized rats, whereas P anaesthesia caused a reduction in the response.(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptation, Physiological↗
PubMed1986

Vagal slowing of the heart during haemorrhage: observations from 20 consecutive hypotensive patients.

Heart rate and arterial blood pressure were monitored in 20 consecutive patients during resuscitation from haemorrhagic shock. The mean blood loss (2.3 (SEM 0.3) 1) corresponded to 36(4)% of their estimated mean blood volume. During shock the mean blood pressure was 81/55 (3/2) mm Hg and heart rate 73 (3) beats/min. Administration of blood and crystalloids resulted in immediate increases to 111/72 (2/2) mm Hg and 102 (3) beats/min followed by steady state values of 131/79 (6/3) mm Hg and 82 (2) beats/min. In three otherwise healthy patients plasma concentrations of the vagally regulated hormone pancreatic polypeptide rose from resting values of 64-77 pmol/l (272-327 pg/ml) to 198-280 pmol/l (842-1190 pg/ml). These findings suggest that reversible hypotensive hypovolaemic shock is characterised by a decrease in heart rate conceivably reflecting an increase in vagal tone.

Adult↗
PubMed1986

Central transmural venous pressure and plasma arginine vasopressin during negative pressure breathing in man.

After overnight food and fluid restriction, 8 normal healthy males were examined in the upright sitting position before (prestudy), during and after (recovery) negative pressure breathing (NPB) with a pressure (P = difference between airway pressure and barometric pressure) of -9.6 +/- 0.5 to -10.4 +/- 0.4 mm Hg for 30 min. Plasma arginine vasopressin (pAVP) did not change significantly comparing prestudy with 10 and 30 min of NPB or comparing recovery with NPB at 10, 20 or 30 min. However, at 20 min of NBP, pAVP was slightly lower than at prestudy (p less than 0.05). Central venous pressure (CVP) decreased significantly during NPB, and central transmural venous pressure (CVP-P) increased significantly from -0.9 +/- 0.8 mm Hg to 3.8 +/- 0.7, 4.3 +/- 0.7 and 4.5 +/- 0.6 mm Hg (p less than 0.001) after 10, 20 and 30 min, respectively. Systolic, diastolic and mean arterial pressure and heart rate did not change significantly during NPB. Diuresis, natriuresis, kaliuresis, osmotic excretion and clearance were slightly increased during the recovery hour after NPB compared to prestudy, while urine osmolality decreased during NPB (n = 6). However, none of these changes were significant. There was no significant correlation between CVP-P and pAVP. In conclusion, -10 mm Hg NPB for 30 min in upright sitting subjects did not change pAVP consistently, while CVP-P was significantly increased and HR and arterial pressures were unchanged. This lends support to the concept that arterial baroreceptors and not cardiopulmonary mechanoreceptors are of importance in regulating AVP secretion in man.

Adult↗
PubMed1986

Central venous pressure and plasma arginine vasopressin in man during water immersion combined with changes in blood volume.

To investigate the influence of central venous pressure (CVP) changes on plasma arginine vasopressin (pAVP), 8 normal male subjects were studied twice before, during and after immersion to the neck in water at 35.1 degrees +/- 0.1 degrees C (mean +/- SE) for 6 h. After 2 h of immersion, blood volume was either expanded (WIEXP) by intravenous infusion of 2.0 1 of isotonic saline during 2 h or reduced by loss of 0.5 1 of blood during 30 min (WIHEM). The two studies were randomised between subjects. WIEXP increased CVP, systolic arterial pressure (SAP), diuresis, natriuresis, kaliuresis and osmolar clearance compared to WIHEM while haematocrit, haemoglobin concentration and urine osmolality decreased. Heart rate, mean arterial (MAP) and diastolic arterial pressure, plasma osmolality, plasma sodium, plasma potassium and free water clearance did not differ significantly in the two studies. pAVP was significantly higher after 6 h in WIHEM than after 6 h in WIEXP (2.0 +/- 0.2 vs. 1.6 +/- 0.2 pg X ml-1, mean +/- SE; P less than 0.05). pAVP values were corrected for changes in plasma volume due to infusion in order properly to reflect AVP secretion. In conclusion, there was a weak, but significant, negative correlation between CVP and pAVP during the two studies, while during recovery from WIHEM and WIEXP decrements in SAP and MAP correlated significantly and strongly with increases in pAVP. It is therefore concluded that it is the arterial baroreceptors rather than the cardiopulmonary mechanoreceptors which are of importance in AVP regulation in man.

Adult↗
PubMed1986

Sympathoadrenal and parasympathetic responses to exercise.

Exhaustive exercise is associated with a persistent sensation of weakness and sometimes nausea suggesting abdominal vagal activity. We measured plasma indices of sympathoadrenal (adrenaline, noradrenaline, dopamine) and vagal (pancreatic polypeptide) activity before, during and after submaximal and maximal exercise in healthy young subjects. Plasma adrenaline, noradrenaline and dopamine increased to 8.5 (range 7.4-40.5), 48.0 (32.3-100.5) and 1.8 (1.2-6.6) nmol 1-1 respectively (n = 5), during maximal exercise and decreased towards control values within 15 min of rest. Pancreatic polypeptide (n = 10) increased only during maximal exercise and reached its highest value, 48 (21-145) pmol 1-1, after exertion. The results conform to an increase in sympathetic activity during exercise and a persistent vagal activity after intense exercise which could contribute to the sensation of weakness.

Adult↗
PubMed1986

Circulating atrial natriuretic peptide (ANP) and central blood volume (CBV) in cirrhosis.

Endogenous alpha-atrial natriuretic peptide (ANP) in plasma is elevated in various hypervolaemic conditions. Possible relationships between circulating immunoreactive ANP and cardiovascular and splanchnic haemodynamics were therefore studied in patients with cirrhosis (n = 16) and controls (n = 12). Arterial plasma concentration of ANP in supine patients was (mean +/- SEM) 33 +/- 4 vs 41 +/- 10 pg/ml (9.9 +/- 1.2 vs 12.3 +/- 3.0 fmol/l) in controls (n.s.), and there was a weak direct correlation with right atrial pressure (r = 0.36, P = 0.05). There was no relationship with the presence of ascites or diuretic treatment. Central blood volume (CBV, i.e. the blood volume in the heart cavities, lungs, and aorta), determined from the mean transit time of 125I-labelled of 125I-labelled albumin and cardiac output, was significantly reduced in cirrhotics compared to controls (1.45 +/- 0.12 vs. 1.83 +/- 0.10 l, P less than 0.02) and inversely correlated with portal pressure (r = 0.42, P less than 0.05), whereas total plasma volume was somewhat increased (3.51 +/- 0.2 vs. 3.19 +/- 0.2, 0.05 less than P less than 0.1). A high arterio-venous extraction of ANP was found in the splanchnic system (extraction ratio 0.44 vs 0.28), kidney (0.45 vs 0.54), lower limb (0.53 vs 0.40), and forearm (0.27 vs 0.18) in patients and controls, respectively (n.s.). Our results suggest that the lack of elevation of circulating ANP in cirrhosis, even in the presence of actual fluid retention, may be explained by central hypovolaemia in these patients. Turnover and degradation of ANP is rapid and normal, as evaluated from the tissue extraction ratios.

Adult↗
PubMed1986

Effects of synthetic human atrial natriuretic peptide (hANP) in conscious dogs.

The effects of synthetic human atrial natriuretic peptide (hANP) on arterial blood pressure, heart rate, and renal functions were evaluated in conscious trained dogs in moderate sustained water diuresis. Synthetic hANP was given i.v. over 3 min at doses of 0.27-2.16 micrograms kg-1 body wt. It did not cause significant changes in blood pressure or heart rate. The rate of sodium excretion increased 20-fold following 2.16 micrograms kg-1 and 2.5-fold after 0.54 micrograms kg-1. Natriuresis was immediate and vanished after 10 min, regardless of dose. The concomitant increase in diuresis was less than 50%, but significant for a longer period of time. Increases in potassium excretion were significant, but small, that is, by a factor of 1.5-2.8. All natriuretic doses of hANP increased PAH clearance (at constant blood pressure), but some did so without measurably affecting creatinine clearance.

Animals↗
PubMed1986

Cardiovascular and endocrine responses to head-up tilt and vasopressin infusion in humans.

The effects of passive tilt on arterial and central venous pressures (MAP and CVP), heart rate (HR), arterial concentrations of vasopressin (AVP) and aldosterone (ALDO), osmolality, and hematocrit were studied in eight healthy young men. Tilting was performed at 30 degrees/min to 20 or 40 degrees and maintained for 45 min. The 20 degrees tilt did not change MAP while CVP fell by 5.9 mmHg (P less than 0.01) and HR increased by 5 beats/min (51-56 beats/min, P less than 0.05). AVP and ALDO concentrations were unchanged. At 40 degrees, MAP increased by 5.7 mmHg (86.0-91.7 mmHg, P less than 0.01), CVP decreased by 7.4 mmHg (P less than 0.01), HR rose by 8 beats/min (55-63 beats/min, P less than 0.01), and pulse pressure fell by 6 mmHg (P less than 0.05). ALDO increased fivefold (P less than 0.05), but AVP did not change. Infusions of AVP at 0.25 or 1.0 ng X min-1 X kg body wt-1 elevated plasma AVP to 11 +/- 1 and 52 +/- 8 pg/ml. Only the larger dose caused a small increase in MAP while CVP and HR remained unchanged; however, washout of a subcutaneous depot of Xe was reduced greater than 60% even by the lower dose. It is concluded that small-angle nonhypotensive passive tilt does not affect AVP measurably despite substantial reductions of CVP and a marked increase in ALDO. Elevations of AVP elicit marked subcutaneous vasoconstriction also in the absence of changes in CVP, HR, and MAP.

Adult↗
PubMed1986

Hypotension induced by passive head-up tilt: endocrine and circulatory mechanisms.

Circulatory changes and arterial plasma hormone concentrations were measured in seven healthy young adults during 30 and 60 degrees passive head-up tilt with the subjects supported by a saddle. The 30 degrees tilt induced a decrease in pulse pressure (Pp) from 45 +/- 2 to 35 +/- 4 (mean +/- SE) mmHg concomitant with an increase in heart rate (HR) from 58 +/- 4 to 78 +/- 8 beats/min and a marginal increase in mean arterial pressure (MAP). Norepinephrine increased from 180 +/- 20 to 310 +/- 40 pg/ml, aldosterone increased fivefold, and angiotensin II increased from 8 +/- 2 to 22 +/- 7 pg/ml. The 60 degrees tilt initially produced changes, which were qualitatively similar to the 30 degrees tilt. However, after 19 +/- 3 min sudden decreases were seen in MAP (94 +/- 3 to 50 +/- 8 mmHg), in Pp (38 +/- 5 to 18 +/- 4 mmHg), and in HR (90 +/- 7 to 57 +/- 6 beats/min). Concomitantly, epinephrine doubled while norepinephrine remained unchanged; the vagally controlled hormone pancreatic polypeptide increased from 29 +/- 3 to 51 +/- 8 pmol/l, vasopressin from 4 +/- 1 to 126 +/- 58 pg/ml, and angiotensin II from 23 +/- 9 to 35 +/- 12 pg/ml. The hypotensive bradycardiac episode was immediately reversible on termination of the head-up tilt.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1986

Arginine vasopressin, circulation, and kidney during graded water immersion in humans.

Ten normal males rested sitting upright at an air temperature of 28 degrees C for 5.5 h (control, C) and underwent 4 h of graded water immersion (WI) to the umbilicus (UI), to the chest (CI), and to the neck (NI), respectively (water temperature = 34.5 degrees C), on different experimental days. Plasma arginine vasopressin (PAVP) was suppressed during WI compared with C and maximally so during NI. However, there was no change in PAVP comparing CI with UI even though central venous pressure (CVP) increased. CVP increased during CI and NI compared with C but was unchanged during UI, whereas cardiac output (rebreathing method), stroke volume, and plasma volume increased to approximately the same level during all three steps of WI compared with C. Heart rate and total peripheral vascular resistance decreased during UI, CI, and NI. Systolic arterial pressure (SAP) and pulse pressure (PP) were increased gradually from prestudy related to the degree of WI. Also diuresis, natriuresis, kaliuresis, osmotic excretion, and clearance were increased gradually compared with C, whereas free water clearance (CH2O) gradually decreased. There were weak negative but statistically significant correlations between PAVP and CVP and between changes in PAVP from prestudy and corresponding changes in SAP and PP. Furthermore, a statistically significant and negative correlation between CH2O and natriuresis could be established. We conclude that graded immersion gradually increases central blood volume and decreases PAVP. However, not only cardiopulmonary mechanoreceptors but also arterial baroreceptors may play a role in AVP suppression during WI in humans. In hydropenic subjects the suppression of PAVP during WI is apparently not effective in counteracting the decrease in CH2O induced by increased solute excretion.

Adult↗