摘要:

Vibrotactile thresholds were determined for non‐Pacinian (SA and RA) and Pacinian (PC) mechanoreceptive units innervating the foot pad of the cat with vibratory stimuli of varying frequency (20, 80, and 240 Hz) and duration (100, 400, and 800 ms). Both the absolute (1 impulse/stimulus train) and the tuning (1 impulse/cycle) thresholds of SA and RA units were elevated and those of PC units were decreased as a function of increasing vibration frequency. PC units had the lowest thresholds at 80 and at 240 Hz whereas RA units had the lowest thresholds at 20 Hz. Larger atonal intervals (the range between the absolute and the tuning thresholds) were obtained for all unit types with increasing vibration frequency and PC units had the smallest atonal intervals at all frequencies. The absolute thresholds of all unit types were independent of stimulus duration. The tuning thresholds of SA and RA units were elevated with increasing stimulus duration whereas the tuning thresholds of PC units were independent of stimulus duration. Consequently, larger atonal intervals were obtained for RA and SA but not for PC units with increasing stimulus duration. The results indicate that there are both differences (effect of frequency) and similarities (effect of stimulus duration and the width of atonal intervals) in response characteristics of non‐Pacinian mechanoreceptors innervating the hairy skin and the glabrous foot pad of the

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1984.tb07390.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Both propranolol and the electron donors ascorbate plus phenazine methosulfate increase the K+‐permeability of the red blood cell membrane. The present investigation examined whether these effects were additive. Contrary to expectations, propranolol added after electron donors sharply inhibited the K+(86Rb) efflux induced by such donors, without forming new K+channels analogous to those induced by propranolol in intact red blood cells. The inhibitory effect of propranolol may be due to generalized disturbances of membrane structures necessary for the functioning of the K+channels organized in the presence of reducing agents. In contrast, the electron donors added after propranolol caused a further stimulation of the86Rb loss from the propranolol‐treated red cells. The combined effect of these drugs therefore depends on the order of their addition. The possible mechanism of their interaction is briefly discus

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1984.tb07391.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

The effect of adenosine and some related compound was studied on blood flow in feline oral mucosa. Changes in the rate of disappearance of125Iodide (k‐value) from a local depot in the oral mucosa was used to determine changes in the mucosal blood flow. Infusion of adenosine caused a dose‐dependent increase of blood flow. Two stable adenosine analogues, adenosine 5′‐ethylcarboxamide (NECA) andl‐phenylisopropyl‐adenosine (l‐PIA), were 20 and 10 times more potent than the parent compound. Dipyridamole (2 mg/kg), which blocks adenosine uptake, significantly enhanced the potency of adenosine. Theophylline (10 mg/kg) inhibited the vasodilatory effect of adenosine and of the adenosine analogues. The result suggest that adenosine may be involved in the regulation of blood flow in th

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1984.tb07392.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

The activation of human platelet monoamine oxidase (MAO) and rat brain mitochondrial MAO (RBM‐MAO) by human plasma were studied. The deamination of two different substrates, tyramine and phenethylamine (PEA) was investigated. The increase in MAO activity in the presence of human plasma can be explained by the observed decrease in the apparent Kmfor the amine (tyramine, PEA). This activation pattern was the same both for human platelet MAO and RBM‐MAO. The activating properties of human plasma were recovered in high molecular weight fractions after gel filtrat

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1984.tb07393.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Differences in skeletal muscle characteristics between smokers and non‐smokers have been demonstrated in a previous study (Örlander, J. et al. 1979, Acta Physiol Scand 107: 39–46). In order to decide whether these differences had a genetical background, six pairs of smoking‐discordant monozygous twins were studied with respect to muscle (vastus lateralis) morphology, metabolism and function. The percentage type I fibres was lower in the smokers, who also had smaller diameters of this fibre type. Cytochrome oxidase activity was decreased in the smokers. No differences were seen for other enzymes of energy metabolism, capillary density, isometric or dynamic strength, or short‐term muscular endurance. The non‐smokers tended to be more physically active. In four ex‐smoker/non‐smoker pairs, no significant differences were found for the investigated parameters. It was concluded, that the difference in fibre type distribution is not due to a hereditary predisposition to take up smoking. Furthermore, the small difference in physical activity level is an unlikely cause. Thus, smoking per se appears to be the most plausible explanation for the difference in fibre type distribution and associated muscle characteristics. No definitive conclusion regarding the reversibility of the smoking‐related differences can be drawn from the

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1984.tb07394.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Species differences concerning the effects of alpha‐and beta‐receptor stimulation on glucagon release and carbohydrate metabolism have been reported. The aim of the present study was to investigate how the subtypes of alpha‐and beta‐receptors regulate the plasma levels of glucagon, insulin, glucose and free fatty acids in fasted rabbits. Epinephrine‐induced 1) hyperglucagonaemia, 2) hypoinsulinaemia and 3) hyperglycaemia were significantly inhibited by alpha‐2 receptor blockade (yohimbine), and not influenced by alpha‐1 receptor blockade (prazosin). Isoproterenol‐induced 1) hyperglucagonaemia was not affected by beta‐1 or beta‐2 receptor blockade, 2) hyperinsulinaemia was inhibited by a lower dose of beta‐2 (ICI 118.551) than beta‐1 receptor blockade (metoprolol), 3) hyperglycaemia was inhibited by beta‐2 receptor blockade and 4) increases in the plasma levels of free fatty acids were blocked by beta‐1 receptor blockade. It is concluded that in fasted rabbits: 1) plasma levels of glucagon are mainly increased by alpha‐2 receptor stimulation, 2) plasma levels of insulin are decreased by alpha‐2 receptor stimulation, and increased more by beta‐2 than by beta‐1 receptor stimulation, 3) plasma levels of glucose are increased by alpha‐2 and beta‐2 receptor stimulation and 4) the plasma levels of free fatty acids are i

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1984.tb07395.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

In these experiments the effects of α1‐adrenoceptor agonism and antagonism were studied on the stages of the sleep‐waking cycle of the cat, in order to determine optimal levels of α1‐adrenergic transmission for these stages. Polygraphic 16‐h recordings showed that prazosin, an α1‐adrenoceptor antagonist, at 1 mg/kg i.p., increased paradoxical sleep (PS) time from 15.3% to 26.4% (p<0.001) of total time, and the number of PS episodes from 30.4 to 43.6 (p<0.001). The effect was prompt, reaching a maximum during the first 4 h with a shortening of PS latency from 40.4 min to 11.0 min (p<0.001). Prazosin at doses of 0.5 and 3.0 though not at 10.0 mg/kg also slightly, but significantly, increased PS. Methoxamine, an α1‐adrenoceptor agonist, at doses of 0.5 and 3.0 mg/kg, increased aroused waking time (low voltage mixed frequency EEG) during the first 4 h from 23.5% to 33.3% (p<0.05) and to 50.3% (p<0.01), and decreased PS. Prazosin potentiated dose‐dependently clonidine‐induced drowsiness (hypersynchronized 4–8 Hz EEG), whereas the decrease in deep slow wave sleep and PS were potentiated only at the largest dose of it. These results indicate that moderate inhibition of cerebral α1‐adrenergic transmission facilitates paradoxical sleep in the cat. Furthermore, they suggest that the level of cerebral α1‐adrenergic transmission is high during aroused waking a

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1984.tb07396.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

In the present study we have investigated the presence of radioimmunoassayable neurotensin‐like immunoreactivity (NTLI) in extracts of adrenal glands from hen, guinea‐pig, rat, cat, dog and man. In addition, gel filtration chromatography and studies on the storage site of NTLI, using subcellular fractionation techniques, were performed. Finally, NTLI release in relation to noradrenaline (NA) from cat adrenal glands upon splanchnic nerve activation was studied in vivo. In all species investigated except guinea‐pig and man, the NTLI levels in the adrenal glands were higher than the levels in the heart (control tissue) but lower than in the ileum. Gel filtration of NTLI from cat adrenal glands revealed presence of roughly equal amounts of the whole neurotensin molecule, i.e. NT(1–13), and its main metabolite the N‐terminal octapeptide NT(1–8), while in plasma from the adrenal vein almost exclusively NTd‐13) was revealed after electrical stimulation of the splanchnic nerve. The release of NTLI and NA upon splanchnic stimulation was antagonized by hexamethonium. Subcellular fractionation of cat adrenal glands indicated that NTLI was stored in a large subcellular organelle, co‐migrating with chromaffin granules. We suggest that NT may be a new adrenal gland hormone or transmitter, possibly co‐stored with NA in chromaffin cells. However, at the present stage it cannot be distinguished whether NT exerts its actions locally within the adrenal gland or after release into the sys

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1984.tb07397.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

The influence of renal nerve stimulation on the tubuloglomerular feedback mechanism was studied on anaesthetized rats. The analyses was made by comparing the single‐glomerular filtration rate (SNGFR) measured from late proximal tubules with SNGFR measured from distal tubules in the same nephron. In the former situation the flow to the macula densa cells is interrupted and in the latter the macula densa is influenced by the flow passing by. In the control situation the SNGFR measured proximally was 47.7 ± 2.2 nl · min‐1(mean ± SE) and 40.1 ± 1.8 measured distally indicating an activated tubuloglomerular feedback. During renal nerve stimulation (2–3 Hz), the SNGFR fell to 38.5 ± 2.3 and 33.5 ± 1.7 when measured proximally and distally, respectively. The results indicate that the tubuloglomerular feedback mechanism is unaffected by renal nerve

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1984.tb07398.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Acute hypertension impairs the function of biological barriers, e.g. that of blood‐brain barrier. We tested the hypothesis that chronic hypertension might influence the penetration of compounds through blood‐brain and blood‐testis barriers. With this in mind, the penetration of relatively small radioactive compounds (14C‐2‐methyl‐4‐chlorophenoxyacetic acid = 14C‐MPA, 14C‐sucrose and 14C‐antipyrine, 5 μCi/kg intravenously) into the brain, liquor space and testis was compared in male normotensive (Wistar and chronically hypertensive SH rats (11–22 months old). In chronic hypertension after 14C‐MCPA and 14C‐sucrose administration the penetration of radioactivity into the brain, cerebrospinal fluid and testis had significantly decreased or showed evidence of decrease, while after 14C‐antipyrine administration the penetration remained unchanged. Penetration of Evans blue‐albumin complex into the brain was studied by giving intravenous injection of Evans blue (5% solution) which is firmly bound to serum albumin. Extravasation of dye‐protein complex into the brain showed no difference between Wistar and SH rats. The results suggest that chronic hypertension does not increase the penetration of compounds into the brain a

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1984.tb07399.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY