摘要:

SUMMARY1. A method is described which allows the determination of liquid junction potentials between biological fluid samples of less than 1 nL with a reproducibility of 10%. This was achieved by use of a micro‐method and the use of 3% agarose added to the electrolyte in the measuring electrodes.2. Validation was performed with a modified flowing boundary method and the system was also tested using a solution containing divalent ions. Liquid junction potential between surface fluid from rat kidneys and harvested renal proximal tubular fluids was‐0.62 ± 0.11 mV (mean ± s.d.,n

ISSN:0305-1870    

DOI:10.1111/j.1440-1681.1989.tb01605.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SUMMARY1. The actions of angiotensin II, bradykinin, oxytocin, arginine vasopressin, relaxin, serotonin and the prostaglandins E2and F2αwere examined on preparations of costo‐uterine muscle from stilboestrol‐treated rats.2. All the agonists, except relaxin, when used in concentrations which contract the rat uterus, also produced contractions of costo‐uterine muscles. Concentration‐response curves were steep and maximal responses to the agonists were comparable. The negative log molar EC50values were: serotonin, 6.5; angiotensin II, 8.8; bradykinin, 8.4; PGE2, 8.3; PGF2α, 7.1. The EC50values (units/L) for oxytocin and vasopressin were 4.4 and 2.7 respectively.3. Indomethacin (2.8 or 5 μmol/L) did not decrease the contractile effects of the peptides or serotonin. The effects of serotonin were reduced, but not reversed, by methysergide (0.94 μmol/L).4. Porcine relaxin inhibited field stimulation‐induced contractions of costouterine muscle and uterine horns from immature rats pretreated with oestradiol cypionate and from stilboestrol‐treated mature rats. It was much less potent, and its effects were less clearly concentration‐related, on costo‐uterine muscle.5. The inhibitory effects of relaxin on the uterus were unaffected by propranolol (1 μmol/L), confirming that on this tissue relaxin acts independently of the release of catecholamines. Progesterone (30 μmol/L) was also without effect on the action of relaxin on the uterus.6. These results taken together indicate that the costo‐uterine muscle of the rat: (i) contracts in response to serotonin and the peptides angiotensin II, arginine vasopressin, bradykinin and oxytocin independently of the release of the contractile prostaglandins F2αand E2; and (ii) in contrast to the uterus, may lack a significant population of receptors for relaxin. These differences from the whole uterine horn of this species may reflect the absence of endometrial tissue, and/or of sensitivity of the smooth muscle cells of the costo‐u

ISSN:0305-1870    

DOI:10.1111/j.1440-1681.1989.tb01606.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SUMMARY1. Anaesthetized homozygous Brattleboro (DI) rats were used to study the renal response to iso‐oncotic blood volume expansion.2. With the same degree of hypervolaemia DI rats had exaggerated diuresis, natriuresis, and chloriuresis, but not kaliuresis, compared with heterozygous control rats. This increased excretion resulted in negative water balance by the end of the experiment in DI rats, whereas the controls showed restoration of normal balance. The control rats retained significant amounts of sodium and chloride, the Brattleboro rats, however, did not.3. The lithium clearance method was used to localize the defect in sodium reabsorption. As judged from this method, there was a significantly lower sodium reabsorption in the proximal tubules as well as in the distal parts of the nephron of DI rats.4. Plasma immunoreactivity of atrial natriuretic factor (ANF) was not different between groups before volume expansion. ANF levels rose and fell similarly in both groups during and after the iso‐oncotic infusion.5. Our results demonstrate that DI rats respond to acute hypervolaemia with an exaggerated diuresis and saluresis. The mechanism of the increased salt excretion may involve inhibition of sodium transport in the proximal tubules as well as in the distal parts of the nephron. These transport defects are not dependent on differing plasma ANF lev

ISSN:0305-1870    

DOI:10.1111/j.1440-1681.1989.tb01607.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SUMMARY1. Isometric contractile responses and caffeine sensitivity were studied in isolated mouse hemidiaphragm (HD), extensor digitorum longus (EDL) and soleus muscles.2. The maximum twitch and tetanic tensions developed by the EDL showed a greater temperature dependence than the soleus. The rates of force development and relaxation were more temperature sensitive in the soleus.3. For the HD, Q10values for all contractile parameters were intermediate between those of the EDL and the soleus but closer to those of the EDL.4. The soleus was significantly more sensitive to caffeine than the EDL while the HD showed a response closer to that of the EDL than the soleus.5. Costal segments of the HD developed force more rapidly but were less caffeine sensitive than the vertebral or sternal segments.6. The results indicate that the mouse HD exhibits isometric contractile characteristics and caffeine sensitivity more closely resembling the EDL than the soleus but there is a variation in these properties between the different parts of the HD.

ISSN:0305-1870    

DOI:10.1111/j.1440-1681.1989.tb01608.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SUMMARY1. The effects of reserpine treatment on the myocardial contents of catecholamines and enkephalins and the incidence of ventricular arrhythmias during ischaemia and reperfusion in the isolated rat heart were studied.2. Reserpine treatment almost completely depleted the heart of noradrenaline (NA). It also significantly depleted the heart of adrenaline and dopamines. It did not, however, alter the myocardial contents of enkephalins.3. Reserpine‐treatment attenuated significantly, but did not abolish, cardiac arrhythmias induced by ischaemia and reperfusion in the isolated heart preparation.4. The results of the present study indicate that myocardial catecholamines especially NA are a contributing factor to arrhythmogenesis during ischaemia and reperfusio

ISSN:0305-1870    

DOI:10.1111/j.1440-1681.1989.tb01609.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SUMMARY1. Aggregation of diluted whole blood (impedance method) and thromboxane B2production during aggregation were measured in cigarette smokers and non‐smokers, aged 41–68 years, with (n= 14) and without (n= 15) major symptomatic peripheral vascular disease. The plasma level of the lyso derivative of platelet activating factor (lyso‐PAF) was also measured using a bioassay with14C‐serotonin labelled rabbit platelets, after extraction and acetylation to active PAF.2. Aggregation to ADP and collagen was significantly less in non‐smokers without vascular disease (n= 8) than in the other three groups (P<0.01; ANOVA). Thromboxane B2production was not significantly different between the groups. There was no significant difference in plasma lyso‐PAF between groups. No change was found in any variable after smokers smoked two cigarettes.3. In these older age subjects, both vascular disease and the smoking habit were associated with greater whole blood aggregation. However, current smoking and the smoking of two cigarettes did not affect aggregation in subjects with vascular disease and plasma lyso‐PAF levels were not consistently related to either smoking or vas

ISSN:0305-1870    

DOI:10.1111/j.1440-1681.1989.tb01610.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SUMMARY1. Adrenocorticotrophin (ACTH) administration to sheep produces a rapid adrenally dependent hypertension which is maximal after 3 days and associated with increased cardiac output (CO) and heart rate (HR), while calculated total peripheral resistance remains unchanged.2. This study investigated the proposal that a centrally mediated increase in sympathetic activity is important in the development of ACTH‐induced hypertension.3. Concomitant intravenous infusions of either clonidine (60 μg/kg per day) or methyldopa (60 mg/kg per day) with ACTH (5 μg/kg per day) failed to inhibit the increase in mean arterial pressure (MAP) observed with ACTH.4. In a separate experiment clonidine abolished the increase in CO and HR but not the pressor response associated with ACTH administration.5. These results do not support a role for centrally mediated increase in sympathetic activity in the genesis of ACTH‐induced hyperte

ISSN:0305-1870    

DOI:10.1111/j.1440-1681.1989.tb01611.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Textbook of Physiology.By D. Emslie‐Smith, C. R. Paterson, T. Scratcherd and I. W. Rea

ISSN:0305-1870    

DOI:10.1111/j.1440-1681.1989.tb01612.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY