摘要:

The effect of glucagon on exocrine pancreatic secretion stimulated by a test meal was studied in three dogs with a chronic gastric fistula and a modified Thomas duodenal fistula which allows easier collection of pure pancreatic juice after a meal. Glucagon was given by continuous intravenous infusion in doses of 5, 10, 15, or 30 μg/kg per hour, before and during a test meal. At each dose level glucagon significantly reduced the water and electrolyte secretion of the pancreas. At 15 and 30 μg/kg per hour glucagon inhibited protein output; this effect was absent at lower doses. These findings demonstrate a dose-dependent inhibition by glucagon of the pancreatic bicarbonate and protein response to a meal. Inhibition of bicarbonate output was more sensitive to glucagon than that of protein output.

ISSN:0008-4212    

DOI:10.1139/y78-001

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Intracellular recordings from neurones, receiving monosynaptic contacts from a dopamine-containing (DA-containing) neurone in the central ganglia of the gastropod molluscPlanorbis corneus, revealed that there are at least three DA-mediated responses. These are 'fast' excitatory postsynaptic potentials (EfPSPs) (200 ms), 'slow' excitatory postsynaptic potentials (EsPSPs) (900 ms), and inhibitory postsynaptic potentials (IPSPs) (200–900 ms). Various combinations of these synaptic potentials were recorded from postsynaptic neurones: EsPSPs, EfPEPs, EsEfPSPs, or EfIPSPs. Neurones receiving such connections also responded appropriately to iontophoresized DA with a 'fast' depolarization (EfPSPs), a 'slow' depolarization (EsPSPs), or a hyperpolarization (IPSPs). These responses could be distinguished on the basis of function (excitation or inhibition), duration, rate of desensitization, and sensitivity to apomorphine,D-LSD, and tubocurarine. The neuroleptic drugs (DA antagonists) haloperidol, fluphenazine, and metoclopramide reduced both excitatory and inhibitory DA transmission. This investigation strongly supports the hypothesis that DA is the transmitter mediating multiple synaptic responses inPlanorbis.

ISSN:0008-4212    

DOI:10.1139/y78-002

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Evidence has recently been presented indicating that muscle stretch reflexes have a large supraspinal component. This finding introduces the possibility that stretch reflex parameters may be modifiable by stimuli involving other modalities besides stretch. In this investigation, the effects of a visual cue on the reflex portions of the EMG activity following a sudden muscle stretch were examined. The results, obtained from the flexor carpi radialis muscles of six normal awake subjects, failed to show any significant change in the EMG parameters as a result of visual cues occurring at the instant of onset of muscle stretch. This was interpreted as indicating that visual inputs do not reach the areas of brain involved in the supraspinal reflex in sufficient time to modify the reflex.

ISSN:0008-4212    

DOI:10.1139/y78-003

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The critical opening pressure (COP) of small vessels in the tails of conscious rats was measured by the spectroscopic technique as an index of arteriolar smooth muscle contraction force. In 11 rats acute intramuscular injection of clonidine (15 μg/kg) decreased systolic blood pressure (SBP) and COP by 13.7 ± 1.7 (SEM) and 7.6 ± 1.1 mmHg, respectively, in intact rats but increased SBP by 30.4 ± 2.6 and COP by 25.9 ± 3.5 mmHg in six ganglion-blocked rats. Reactivity of arteriolar muscle was measured as the increase in COP of the vessels in response to intravenous infusion at three or four dose levels of angiotensin II (2–12 ng kg−1 min−1), noradrenaline (30–120 ng kg−1 min−1), or lysine-8-vasopressin (0.085–0.34 mU kg−1 min−1). The dose–response relationship was considered to be essentially linear and increases in COP in clonidine-treated and control rats were compared directly. Acute administration of clonidine (1, 3, or 10 μg/kg, im) decreased vascular reactivity to each of these agents in both the intact and ganglion-blocked rat. For example, in ganglion-blocked rats total increases in COP were as follows: (1) during infusion of angiotensin (8 ng kg−1 min−1), 22.3 ± 1.3 (SEM) mmHg in clonidine-treated rats and 40.3 ± 3.7 in controls (p< 0.01); (2) during infusion of noradrenaline (120 ng kg−1 min−1), 8.4 ± 1.7 mmHg in clonidine-treated rats and 30.0 ± 2.6 in controls (p< 0.001); and (3) during infusion of vasopressin (0.34 mU kg−1 min−1), 24.8 ± 0.3 mmHg in clonidine-treated rats and 47.8 ± 0.9 in controls (p< 0.001). Chronic treatment of rats with clonidine (20 μg kg−1day−1) for 7 or more days had a similar effect on vascular reactivity. This apparently nonspecific reduction of vascular reactivity could play an important part in the antihypertensive effect of clonidine hydrochloride.

ISSN:0008-4212    

DOI:10.1139/y78-004

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The present study was undertaken to assess the effect of renal vein pressure on sodium and bicarbonate transport under two opposite conditions of bicarbonate filtered loads. Unilateral partial occlusion of the renal vein (RVO) was induced in 17 mongrel dogs: renal vein pressure rose from 9 to 20, 25, and 30 mmHg in a stepwise fashion. Seven of these animals (group I) were studied during bicarbonate loadingand six others (group II) were studied during metabolic acidosis, induced with ammonium chloride. In the four remaining dogs (group III), administered bicarbonate in the manner described for group I, acetazolamide was given in a bolus and sustained infusion to inhibit the carbonic-anhydrase-mediated fraction of bicarbonate reabsorption while renal vein pressure was being kept at 30 mmHg. PlasmapCO2was maintained at constant levels in all studies.In group I, urinary sodium(UNaV) decreased from 203 ± 32 to 110 ± 17 μEquiv./min, and bicarbonaturiafrom 131 ± 21 to 79 ± 18 μEquiv./min during RVO. In group II,UNaV) dropped from 132 ± 32 to 81 ± 20 μEquiv./min whileremained at 2 μEquiv./min. Urinary ammonium and titratable acid decreased from 12.6 ± 1.7 to 8.7 ± 1.2 and from 8.0 ± 1.6 to 5.5 ± 1.1 μEquiv./min, respectively, during RVO. In group III,UNaVaveraged 208 ± 42, 132 ± 29, and 203 ± 37 μEquiv./min during control, RVO, and RVO plus acetazolamide, respectively. During these same periods,was 144 ± 22, 72 ± 23, and 155 ± 30 μEquiv./min. All the above changes observed in the experimental kidney were significant (p< 0.05). In contrast, the same parameters measured in the opposite control kidney remained unaffected. Glomerular filtration and renal plasma flow remained stable in group I but decreased slightly in groups II and III. Filtration fraction was unaffected, however.The data indicate that RVO influences Na and HCO3excretion through mechanisms not obviously related to peritubular physical forces. Since acetazolamide abolishes the effect of RVO, the mechanism(s) of antinatriuresis could be related to renal carbonic anhydrase activity.

ISSN:0008-4212    

DOI:10.1139/y78-005

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The purpose of this work was twofold: (a) to develop a muscle preparation of the rabbit aorta free of adventitia and endothelium, and (b) to measure the metabolism of angiotensin II (ATII) in this preparation. The muscle was prepared by 'shucking-off' the adventitia layer and by eliminating the endothelium. Concentration–response curves to ATIIand noradrenaline (NA) measured in the muscle preparation provided pD2values for ATIIand NA not significantly different from those observed in the intact aortic strip. However, the maximal tension developed by the two agonists averaged 20–30% of the maximal tension of the intact strips. Apparent diffusion of ATII, in and out of the tissue, was faster in the muscle while NA diffusion was not significantly different. Metabolism of ATIIwas measured at the plateau of contraction and after complete relaxation in both the muscle and the intact strip. Ten percent of ATIIwas metabolized at the plateau of the contraction and 50% after complete relaxation. Heptapeptide 1–7 was the metabolite found in both preparations. 1-β-Asp ATIIwas also broken down to heptapeptide 1–7 while 1-β-Asp,8-Phe-OMe-ATIIresisted the degradation and was found unchanged even after 90 min of incubation. It is suggested that the enzyme which inactivates ATIIis located in the smooth muscle cells and that it is a carboxypeptidase.

ISSN:0008-4212    

DOI:10.1139/y78-006

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The concentrations of a somatostatin-binding protein, found in the cytosol of a number of rat tissues, are similar in both sexes, and hypophysectomy has little or no effect on the level of binding protein in tissue extracts. On the other hand, streptozotocin-induced diabetes mellitus causes a modest decrease. The somatostatin-binding proteins obtained from extracts of several rat tissues are not only similar in molecular weight but also exhibit a similar isoelectric point and electrophoretic mobility. Agents that block thiol groups or prevent the formation of disulfide bridges markedly decrease the binding of somatostatin to the cytoplasmic protein. Studies using thiol reagents and gel filtration suggest that free thiol groups in somatostatin-binding protein are important for the binding of somatostatin.

ISSN:0008-4212    

DOI:10.1139/y78-007

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The effect of an intravenous infusion of ethanol was examined on the rates of hepatic glucose production (Ra) and overall glucose utilization (Rd) in conscious dogs in the postabsorptive state under basal conditions and in insulin-induced hypoglycaemia, after a 4-day fast or in diabetes. The rates were calculated by a tracer infusion method with3H-labelled glucose as the tracer. The concentrations of glucose, lactate, insulin, and ethanol in plasma or blood were determined, and the rate of ethanol utilization estimated. The infusion of 0.04 or 0.24–0.29 mmol ethanol/kg per minute did not change the concentration of glucose in normal or diabetic dogs in the postabsorptive state, whereas a small decrease in fasted dogs was observed especially when ethanol was infused at the lower rate. Plasma lactate levels were increased; insulin levels did not change.Rawas transiently decreased in fasted dogs, but not in the postabsorptive state in normal or diabetic animals. Ethanol had no effect on the magnitude of the increase inRaduring insulin-induced hypoglycaemia. The estimated rate of ethanol utilization was reduced by fasting but not in diabetes. In conclusion, ethanol did not decrease the elevated rate of gluconeogenesis in diabetic dogs, nor did it interfere with the hepatic response to hypoglycaemia.

ISSN:0008-4212    

DOI:10.1139/y78-008

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The administration ofL-cycloserine to mice resulted in a dramatic decrease in the activities of 4-aminobutyrate:2-oxoglutarate aminotransferase (GABA-T) andL-alanine:2-oxoglutarate aminotransferase (ALA-T) in both brain and liver,L-Aspartate:2-oxoglutarate aminotransferase was inhibited only slightly, and brain glutamic acid decarboxylase not at all. Liver ALA-T activity returned to near normal levels within 24 h ofL-cycloserine administration whereas liver GABA-T and brain ALA-T activities had returned only halfway to normal levels in the same time period. The recovery in the activity of brain GABA-T was even slower. A consequence of the inhibition of brain GABA-T activity was an elevation in the GABA content of the tissue which was maximal 3 h afterL-cycloserine administration and which was still noticeable 8 h after the drug treatment.L-cycloserine was also a potent in vitro inhibitor of brain GABA-T activity. The inhibition was competitive with respect to GABA, theKivalue being 3.1 × 10−5 M. The prior administration ofL-cycloserine to mice significantly delayed the onset of isonicotinic acid hydrazide induced convulsions.

ISSN:0008-4212    

DOI:10.1139/y78-009

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

This study presents theory, operation, and evaluation of a new earpiece method for measurement of cardiac output using the multichannel fiberoptic system recently described. The system includes an earpiece of simple design and small size suitable for applications in all subjects regardless of their age or size. The method requires no withdrawal and analysis of blood samples for calibration. Compared with earlier techniques the present method, based on measurements in three distinct absorption bands in the infrared, provides an increase in accuracy of the estimations.This accuracy was tested in children undergoing routine cardiac catheterization. Comparisons were made in 39 instances (25 subjects) between simultaneously carried out determinations by the earpiece and cuvette densitometer methods. The agreement was good (r = 0.97,p< 0.001), with a standard deviation of the differences of 0.479 ℓ/min, or 10.2% of the mean values derived from the cuvette curves. The regression equation describing the values derived from ear curves in terms of values from the cuvette curves differed only slightly from unity (Y = 0.167 + 0.985X).The usefulness of the fiberoptic earpiece technique both in clinical investigations and cardiovascular diagnosis was demonstrate

ISSN:0008-4212    

DOI:10.1139/y78-010

出版商:NRC Research Press    

年代:1978

数据来源: NRC