摘要:

To examine further the role of the oral receptors in the masticatory–salivary reflex, a study with eight subjects was performed. The influence on mean parotid salivation of combined alterations in frequency and force of chewing and length of the chewing object was evaluated by group comparison. Salivary flow rate was recorded using a sensitive micromanometer, and the frequency (12, 60 and 90 cycles min‐1) and force of chewing (to and 40% of maximum) were controlled by a metronome and masseter muscle EMG, respectively. The maximum instantaneous flow and the latency of the masticatory‐salivary reflex were examined in three subjects. For comparison with mean salivation rate during chewing, gustatory stimulation was performed with 0.5 or 5.0% citric acid. The masticatory–salivary reflex was mainly ipsilateral, and depended upon having an object between the teeth. Salivation increased with increases in frequency and force of chewing and with the number of teeth involved, each parameter of chewing having the greatest influence when increased from a low level of action. The salivation response to chewing showed two phases; the first, presumably due to contraction of the myoepithelial cells, had a latency of 0.2–0.4 S, while the second phase occurred about r s later. Our results support the hypothesis that the periodontal mechanoreceptors have a major role in the parotid response to chewing. Application of 0.5 and 5.0% citric acid on the back of the tongue induced dose‐dependent parotid secretions, significantly higher than those of chewing. A negative correlation was found between the maximum fluid outputs during chewing and 5.0% citric acid

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1987.tb08223.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Parotid ducts were ligated unilaterally in rats for periods from 6 h to 5 months. A slight increase in gland weight was observed during the first 24 h; thereafter, the weight gradually fell, being less than 5o% of controls at 5 months. The activity of the putrescine‐forming enzyme, ornithine decarboxylase (ODC), increased with peak values by 3 days and 3 weeks. However, the putrescine content had already reached its highest value by 24 h. A notably marked reduction of spermidine and spermine contents was observed by 1 day after ligation and throughout the whole time of observation. The results suggest that an inverse polyamine metabolism occurred, that is, spermine converts to spermidine which in turn converts to putrescin

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1987.tb08224.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

The purpose of the present study was to examine the effect of changes in arterial pH and PCO2on biliary HCO‐3secretion. This was done in order to further characterize the various ion transport mechanisms considered responsible for biliary HC3secretion in the pig. Experiments were performed on two groups of six pigs. In both groups arterial pH was varied in steps from pH 7.40 to 7.40, both at PCO25.5 PCO2and PCO2, 10 kPa. In group I (n= 6), data were obtained on the effect of arterial pH and PCO2on ductular PCO2secretion in bile acid depleted (cholestyramine pretreated), secretin‐infused pigs. In group II (n= 6), the effect of pH and PCO2on canalicular HCO‐3secretion was studied in ursodeoxycholic acid (UDCA)‐infused pigs (3 μml min‐1kg‐1body wt). In group I, biliary HCO‐3secretion exhibited PCO2‐ dependent, positive straight line relationships to arterial pH. An increment in biliary HCO‐3secretion of 17 (11–24)% was seen during high PCO2at pH 7.40. In group II, biliary HCO‐3secretion exhibited PCO2‐dependent, positive curvilinear relationships to arterial pH. A median increment in HCO‐3secretion of 37 (20–62)% was seen during elevated PCO2at arterial pH 7.40. The linear dependence of ductular HCO‐3secretion on arterial pH and the effect of elevated HCO‐3on PCO2secretion fit well with findings in other epithelia, where proton transport is thought be driven by a proton pump. A computer simulation provided evidence suggesting that secretin‐dependent HCO‐3secretion does not involve the action of a Na+/H+ion exchanger—in contrast to UDCA‐dependent HCO‐3secretion. It is concluded that ductular and canalicular HCO‐3secretion could be mediated by a proton pump and a Na+/H+ion exchanger in addition to canalicular HCO‐3secretion d

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1987.tb08225.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

The distribution of histochemically identified muscle fibre types was studied in biopsy samples from the two main muscles in the lumbar region of the human erector spinae, the multifidus and the longissimus, in 16 healthy subjects (nine males and seven females, age 20–30 years). Muscle fibres were classified as types I, IIA, IIB or IIC on the basis of the pH lability of their myofibrillar ATPases. There were no differences between the multifidus and the longissimus muscles in the relative occurrence of type I (62vs. 57%), type IIA (20 vs. 22%) or type IIB fibres (18vs. 22%), or in the absolute size of fibres (range of mean least diameters 58–66μm). The oxidative potential (NADH‐diaphorase staining intensity) was high in type I and low in type II fibres, irrespective of subgroups, in both muscles. In the females, the type I fibres occupied a relatively larger area (70–75vs. 54–58% for the males) although the relative number of type I fibres was the same in both sexes. This was due to smaller type II fibres in the females resulting in higher type I/type II area ratios (1.70–1.90vs. 0.88–0.92 for males). This suggests a difference in functional capacity of lumbar back muscles between males and females. On the other hand, the similarity in histochemical fibre‐type distribution between the multifidus and the longissimus muscles does not give support for a functional differentiation between these two anatomically different parts of the lumbar erect

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1987.tb08226.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

At three occasions during a year, the ratio of contractional work (output)/integrated electromyographic activity (input), that is, CW/iEMG, was measured during repetitive maximum isokinetic manoeuvres for m. quadriceps and m. triceps surae in male elite orienteers. Running velocity at the onset of blood lactate accumulation (Vobla), which was considered as a measure of running performance, and maximal oxygen uptake (VO2max) were analysed at each test. Type and amount of training were continuously registered. For m. quadriceps there was a decline in CW/iEMG during the first 30 manoeuvres, followed by an unchanged plateau level. In contrast, m. triceps surae showed a plateau level of virtually unaltered CW/iEMG ratio from the start to the end of the experiment. The differences might be explained by structural causes, but also by local muscle adaptation to training. The plateau level of CW/iEMG of m. quadriceps was positively correlated to VO2max. An increase in the plateau level of CW/iEMG was found for both tested muscle groups after the winter training period (mainly low intensity road running) when bothVoblaand VO2OBLA increased. During the competition period (mainly high intensity forest running), the whole group increased while some orienteers lowered theirVobla. During this period, no changes in the plateau level of CW/iEMG of any muscle group or in VO2OBLA occurred. The changes in the plateau level of CW/iEMG might express local muscle adaptations to changes in running technique and aerobic/anaerobic demands during low intensity road runningversushigh intensity forest running.

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1987.tb08227.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

The transition speed between walking and running was determined in 18 healthy males (23–38 years) of various statures (range of leg length 0.86–1.09 m) during acceleration and deceleration of different magnitudes (0.05‐0.11 m s‐2) on a motor‐driven treadmill. The speed of the treadmill belt and the duration of the stance phases of each foot were recorded. A transition step was identified and the speed of transition was taken as the average speed value of the stance phase of that step. The overall mean value for the transition speed was 1.88 m s‐1(range 1.30–2.55). Deceleration resulted in a somewhat lower speed of transition than acceleration. There was a tendency towards increasing values for transition speed with increasing leg length. This could partly be explained by differences in natural frequency. The reasons for the switch between walking and running at a speed which is not extreme for either mode of progression are unclear. The subjective feeling that a transition will lead to a more comfortable situation might be based on previous experience combined with information from peripheral receptors and activity in central networks controlli

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1987.tb08228.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Respiration and shivering were measured in unanaesthetized, cold‐exposed pigeons using pneumotachography and electromyography, respectively. The instantaneous intensity of shivering in the pectoral muscle varied in phase with respiration. Power spectral analysis showed that the main frequency components of respiration and demodulated EMG coincided exactly. The intensity of shivering was highest during end‐expiration and lowest at end‐inspiration. This was confirmed by cross‐correlation analysis of respiration and demodulated EMG. The absolute level of modulation remained constant (c. 10μV peak‐to‐peak) despite changes in the general intensity of shivering. On the other hand, the relative depth of modulation was highest during incipient shivering. These facts indicate that only a part of the motor units recruited for shivering is susceptible to respiratory modulation and that this part is first recruited during incipient shivering. Inhalation of 5% CO2did not affect the interaction between respiration and shivering although respiration frequency varied from 25 to 6o min‐1. Thus, pulmonary chemoreceptors do not mediate this effect. It is suggested that the interaction between respiration and shivering occurs directly in the CNS. The question whether the interaction is adaptive for the animal or merely reflects a common evolutionary history of the underlying neural circuit

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1987.tb08229.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

The aim of the present investigation was to explore whether in isolated frog skin there should be different pathways for K+absorption and secretion. Therefore, the unidirectional fluxes of42K+and the K+‐like isotope86Rb+were measured. By using various transport inhibitors, separate pathways for active K+absorption and secretion were detected. The data obtained indicate that the transepithelial K+and Rb+transport across isolated frog skin is made up of four different components: one passive and three active. One of the active components is directed from the apical to the basolateral solution, whereas the other two are in the opposite direction. The direction of the net K+transport depends on the activities of these three active transport components. The active uptake mechanism, which is present in the epithelial cells, discriminates between K+and Rb+. The ratio between the K+and Rb+influxes, K/Rb, is about 3. The presence of Ba2+, furosemide or ouabain in the apical solution had no effect on the K+influx. The active secretion of K+takes place via two different pathways, namely the skin glands and the epithelial cells. The K+secretion via the glands is inhibited by furosemide (basolateral), but is unaffected by Ba2+(apical) and does not discriminate between K+and Rb+. The active K+secretion via the epithelial cells is blocked by apical Ba2+, and it discriminates between K+and Rb+. The ratio between the K+and Rb+effluxes is about z. The data presented show that the K+channels in the apical and the basolateral membrane of the epithelial cells discriminate between K+and Rb+. The K+flux via these channels can be blocked by Ba2

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1987.tb08230.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Rat pancreaticβandα2cells were purified by autofluorescence‐activated cell sorting and used for electrophysiological patch clamp studies and measurements of the initial uptake of45Ca. Bothβandα2cells were electrically active, the action potentials of the latter cells also were detected in the absence of glucose. Furthermore,α2cells differed fromβcells in lacking a glucose‐sensitive K+channel with a single channel conductance of 50–60 pS (in symmetric 140 mmK+solutions). The rate of Ca2+entry into theα2cells was slower than that into theβcells, being equivalent to 0.2 mmol, kg‐1dry wt min‐1. Whereas raising the glucose concentration to 20 mmsignificantly increased the amount of Ca2+entering theβcells, the sugar was without effect on Ca2+ent

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1987.tb08231.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

The aim of the study was to test the hypothesis that extrinsic adrenergic neurons modulate electrogenic ion transport in the jejunum by inhibition of intramural secretory nerve activity. Isolated pieces of rat jejunum were mounted in the Ussing chamber. Noradrenaline (NA) was released from sympathetic nerve endings in the tissue by electrical stimulation of the mesenteric nerves or by the indirect sympathomimetic agent tyramine. Intramural neurons were activated by electrical field stimulation (EFS). Mesenteric nerve stimulation induced a frequency‐related decrease in the transepithelial potential difference (PD) and short circuit current (SCC), effects which were abolished by theα‐adrenergic antagonist phentolamine. A similar response was induced by the serosal application of tyramine and by exogenous NA. Tetrodotoxin (TTX), a nerve conduction inhibitor, had no significant effect on the response to NA, but attenuated the response to tyramine. Both NA and tyramine markedly attenuated the secretory response to EFS, but there was no significant effect of catecholamines on the secretory response to serosal theophylline. The results suggest at least two mechanisms behind the adrenergic modulation of electrogenic chloride secretion: (1) a ganglionic or presynaptic modulation of secretory nerve activity via innervatedα‐receptors, and (2) a modulation at the level of the enterocytes via non‐innervatedα‐receptors. The latter effect does not seem to be mediated by the

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1987.tb08232.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY