摘要:

AbstractIn neurones of the ventral ganglion ofHelix pomatiaan adaptation type is demonstrated, where the impulses contribute to the adaptation, as if a slowly changing outward current were associated to every impulse. The current appears to be accumulated from impulse to impulse and the accumulated current to decrease towards zero in the interval between the impulses. This type of adaptation is calledimpulse dependent.A method to distinguish between impulsedependentadaptation and impulseindependentadaptation is described. Typical adaptation curves for the impulse dependent adaptation are shown. With a strong adaptation there is a linear relation between the steady state frequency and the applied stimulus. When stimuli of short duration are applied repetitively, neurones with impulse dependent adaptation respond with spikes on an increasing fraction of the stimuli as the stimulus strength is increased. A simplified model of the adaptation is proposed, and the firing pattern of the cells is compared with that of the model. In this way numerical values of the model parameters have been estimated.

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1977.tb06020.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractBy conventional voltage clamp methods an increase in membrane conductance after a depolarizing pulse is demonstrated in neurones ofHelix pomatia.This increase decays exponentially with a time constant in the range of 5–20 s. The rise of the conductance during the depolarization can be represented by 3 exponentials with time constants from 12 ms to 1 s. The steady state value of the conductance depends on the membrane potential in a sigmoid manner. The conductance gives rise to an outward current, which appears to be carried by potassium ions. The firing pattern of the cell is governed by the conductance. A short, rectangular potential change, a pulse clamp, is used to disturb the firing pattern of the freely firing cell. The effect on the firing pattern depends on the height and duration of the clamp pulse in the same manner as the conductance increase. The normal firing produces similar changes in the membrane conductanc

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1977.tb06021.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractExperiments were designed to test the hypothesis that angiotensin II, in its action on receptor sites in vascular smooth muscle and the proximal tubule, acts homeostatically to stabilize hydrostatic pressure in the proximal tubule, and as a consequence, maintains a constant flow of fluid to the distal tubule. Infusion, at 20 n1 min‐1, of Ileu5‐angiotensin II [(Ileu5)‐A II] (20 ng m1‐1) into peritubular capillaries adjacent to a proximal tubule was found to be accompanied by an increase in hydrostatic pressure in both the infused capillaries and the proximal tubule and by a decrease in the rate of proximal fluid reabsorption (RPFR). RPFR was derived from timed quantitative collections of tubular fluid from the last superficial proximal segments. Tubular pressure before infusion and pressures in noninfused capillaries were not related to plasma renin activity (PRA). 1‐Sarcosine, 8‐alanine‐angiotensin II [(Sar1, Ala8)‐A II] is known to be a competitive antagonist to the action of angiotensin II on vascular smooth muscle and on adrenocortical zona glomerulosa cells. Infusion, at 20 n1 min‐1, of (Sar1, Ala8)‐A II (333 ng m1‐1) into peritubular capillaries caused a decrease in hydrostatic pressure in the peritubular capillaries and adjacent proximal tubules. The most striking fall in pressure (‐4 cmH2O) occurred in rats with high levels of PRA. No pressure change resulted from infusion with a mixture of (Ileu5)‐A II and (Sar1, Ala8)‐A II. (Sar1, Ala8)‐A II in this mixture blocked the inhibitory effect of (Ileu5)‐A II on RPFR, but infusion of the angiotensin antagonist alone did not influence RPFR. It is concluded that angiotensin II is a physiological regulator of hydrostatic pressure in both the proximal tubule

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1977.tb06022.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractCortical and striatal turnover rates of acetylcholine TRAchwere estimated by applying steady‐state tracer kinetics in rats killed by microwave irradiation following a constant i.v. infusion of3H‐Ch. In control rats TRAChwas 3.6 nmol · g‐1· min‐1in the cortex and 23.8 nmol · g‐1· min‐1in the striatum. When steady‐state plasma concentrations of Ch were increased from 17 to 140 μmol · 11by a 15‐min infusion of unlabeled Ch the corresponding TRAChwere 3.6 nmol · g‐1· min‐1and 21.4 nmol · g‐1· min‐1, respectively. These results indicate that increased plasma levels of Ch are not accompanied by

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1977.tb06023.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractThe effect of a variation in the preceding day's dietary energy intake‐4, 10 and 18 MJ‐on the oxygen consumption and respiratory quotient at rest and at work before and after a test meal (4 MJ) was investigated. 7 normal male subjects were studied at 3 different experimental situations. During the first day the subjects had an energy intake of 10 MJ and normal activity. The following morning measurements of V̇o2and V̇co2were performed atrest andat workona bicycle ergometer (36 W) before and after the test meal. The same measurements were performed on the following day but the dietary intake between the two sets of measurement was then either 6, 0 or 14 MJ. No significant effect was found of the preceding day's dietary energy intake on the oxygen consumption or on the energy transformed during rest, during exercise before and after the test meal. The results do no support the conclusions of previously published studies, proposing a significant feed‐back mechanism tending to control the body energy content by regulation of the energy expenditure through chemical or mechanical unc

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1977.tb06024.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractA new technique has been developed to make deep renal cortical structures in rats accessible for micro‐puncture: The left kidney is dissected free and immobilized in a lucite cup. A lense‐shaped slice, 1–2 mm thick and about 5×5 mm wide, is cut off from the dorsal aspect of the kidney. Blood oozing from the cut surface is removed by flushing with saline and suction by microsponges. The bleeding stops in 1–3 min and causes none or only transient fall in arterial pressure (PA). Up to 40 glomeruli become visible and remain circulated for several hours, as shown by injection of dye or silicone rubber. Glomerular capillary pressures (PG), measured with servocontrolled counter pressure (Wiederhielm), showed no consistent change with time and no correlation to PA. Average PG± S.E. in mmHg (number of glomeruli in parantheses) were: Wistar rats (WR), Inactin anesthesia, 57.8 ± 1.4 (41), Membumal anesthesia, 58.1 ± 1.3 (13). Sprague Dawley rats, Inactin, 58.1 ± 1.7 (14). In WR, PGwas lower in deep than in midcortical glomeruli: ≤ 0.4 mm below kidney surface, 57.9 ± 1.8 (20); 0.5‐0.9 mm: 60.5+1.5 (20) and ≥ 1.0 mm: 53.8 ± 2.5 (13). Pressure in Bowman's capsule: 11.2 ± 0.6 (30). The observed PGis higher than previously reported on the Munich mutant strain of WR, and suggests that glomerular filtration equil

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1977.tb06025.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractThe importance of autonomic nervous activity for the pancreatic hormonal response to exercise in man was studied. 7 men ran at 58% of V̇o2max (determined without administration of drugs) to exhaustion during a‐adrenergic blockade with phentolamine (P), during parasympathetic blockade with atropine (A), or without drugs (C). At rest phentolamine increased the plasma concentrations of both insulin and norepinephrine. During exercise norepinephrine concentrations increased and were in P experiments 3 times the concentrations in C experiments. Insulin always declined during exercise but in P experiments never decreased below basal levels. At identical times neither glucagon nor glucose differed significantly in the different expts. Thus during exercise α‐adrenergic blockade increased insulin concentrations but did not diminish the glucagon response. Nor was this response increased when β‐receptor stimulation in P experiments was intensified by the particularly high catecholamine concentrations. The concentrations of FFA, glycerol and lactate were highest in P experiments and identical in A and C experiments. These findings indicate that during prolonged moderate exercise in man insulin secretion is depressed by stimulation of α‐adrenergic receptors whereas glucagon secretion is not influenced by adrenergic receptors. Stimulation of β‐adrenergic receptors enhances lipolysis but neither lipolysis nor pancreatic hormonal secretion is influenced by cholinergic activity d

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1977.tb06026.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractThe K+‐permeability of the blood‐brain barrier at the capillary level was estimated from determinations of brain extracellular K+‐concentration in response to an isotonic bolus containing KC1 injected into the carotid artery. A very low permeability appeared from the fact that the extracellular K+‐concentration—measured by aid of K+‐sensitive microelectrodes—remained unchanged during the passage of the bolus. An upper limit for the blood‐brain barrier K.+‐permeability in the rat was estimated to be 2.8 7ti

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1977.tb06027.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractThe function of the suggested hypothalamic osmoreceptors was re‐examined in dogs during light chloralose anesthesia. The body weight of the dogs was increased to—and maintained at—102.0% of the initial value by i.v. infusion of a hypo‐osmolar solution of glucose and urea. During the water diuresis renal free water clearance (CH2O) remained approximately constant for more than 3 h during which infusion of physiological amounts of vasopressin (5 or 10 μU/(kg b.wt. · min)) was associated with a dose‐dependent, reversible decrease in CH2O. Infusion of hyper‐osmolar sodium chloride solution (90μmol/(kg b.wt. · min) for 60min) was performed either through a central venous catheter or through needles placed in both common carotid arteries. After an initial increase in CH2Othese infusions elicited antidiuresis (negative CH2O) and increase in the rates of excretion of sodium (100‐fold) and potassium (3‐fold). Left atrial pressure and renal clearance of inulin and PAH did not change significantly. The renal effects of NaCl infusion were independent of the mode of infusion. It is concluded that the results are inconsistent with the hypothesis that the area supplied by the common carotid arteries includes an osmoreceptor which is capable of changing —within seconds—the rate of secretion of vasopressin, although they support the view that the renal excretion of water is strongly influenced by a receptor which is sensitive to osmolality or concentration of sodium. In addition it appeared that an increase of a few per cent in the concentration of sodium in plasma was associated with a substantial increase in the rate of excretion of sodium without measurable changes in central venous pressure or in glo

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1977.tb06028.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractThe heterogeneity of nutritive skeletal muscle blood flow during shock was studied in terms of cellular transmembrane potential variations. Shock was induced in dogs by exteriorization of the small intestine for 3 h, whereafter the intestine was replaced and the dogs were studied for another 3–4 h. Transmembrane potentials of single skeletal muscle cells were recorded by the use of modified Ling‐Gerard microelectrodes. The mean resting transmembrane potential in control animals was ‐90.4 mV ± 0.7. The variation in transmembrane potential between adjacent fibers was small. During shock there was a significant decrease in the mean transmembrane potential and at the same time there was an increasing variation of up to 29 mV in the values between adjacent fibers. To exclude metabolic differences between red and white fibers as the main reason for this increasing heterogeneity of transmembrane potentials of adjacent fibers, complete tourniquet ischemia was also studied. The total tissue ischemia resulted in a marked reduction of the transmembrane potential in all cells with only small differences between adjacent fibers. After release of the tourniquet a marked spread of resting membrane potentials, with variations of 17–25 mV between adjacent fibers, occurred. This variation was similar to that observed during shock. It is concluded that repeated transmembrane potential registrations may reveal the variable state of adjacent cells subjected to a heterogeneous nutritive blood flow

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1977.tb06029.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY