摘要:

The effects of exposure to hyperoxic conditions (>95 kPa at normobaric pressure) on bronchial wall dimensions and lung mechanics were examined in adult rats. Measurements of baseline pulmonary resistance and changes in pulmonary resistance following acetylcholine aerosol inhalation were made in rats exposed to hyperoxia for 48 and 60 h and in control rats exposed to air. Exposures for 48 h were carried out in humid (80% relative humidity) or dry (35–40% relative humidity) conditions. Morphometric measurements of airway wall thickness in lobar bronchi were made in separate groups of similarly exposed rats. Exposure to hyperoxia was associated with an increase in baseline pulmonary resistance (control rats 0.043 (0.016) cmH2O ml‐1s‐1, 60 h exposed rats 0.125 (0.042) cmH2O ml‐1s‐1) but hyper‐responsiveness to acetylcholine inhalation did not occur. Thickness of the airway wall and its subdivisions, epithelium, lamina propria and muscularis, was not altered by hyperoxic exposure in humid conditions. However, epithelial thickening in the lobar bronchi was observed in rats exposed for 48 h to hyperoxia in dry conditions compared to rats exposed in humid conditions (mean (SD) thickness 13.2 (3.3)μm for controls, 14.5 (1.5)μm for humid exposed rats and 16.5 (3.3)μm for dry exposed rats). The increase in pulmonary resistance caused by hyperoxic exposure is unlikely to be due to airway damage as airway hyper‐responsiveness did not occur, and is more likely to be associated with the development of alveolar oedema. Environmental humidity may modulate lung damage induced by hyperoxia, as exposure in dry conditions was associated with significant epith

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1993.tb09571.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Tracheal gas density breathing heliox at 31.3 atmospheres absolute (O2at 0.42 ATA) is 6.287 g 1‐1, or approximately 5.5 times greater than air at 1 ATA. This constitutes a significant respiratory load, previously shown to induce respiratory adaptation. During a saturation dive to 31.3 ATA, five divers were exposed to this load for 16 days. This project aimed at investigating possible hysteresis in pulmonary function during dive compression, adaptation and decompression phases. Pulmonary function tests were performed at the surface in air, and at four pressure stops during compression and decompression, with divers breathing the helium‐oxygen gas mixture. Significant hysteresis patterns were observed for pooled maximal voluntary ventilation, forced expired volume at 1 s, peak expiratory flow, and maximum expiratory flows (P<0.05), with post‐adaptation flows consistently exceeding those observed during compression. Two mechanisms may explain these observations. Differences may be attributable to positive effort‐dependence in the forced expiratory flow; or it is possible the subjects adapted to the respiratory load by modifying neural input to airway smooth muscle, thereby modifying airway res

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1993.tb09572.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Lower limbs show acute fluid shift in response to transition from upright to supine body position. It is hypothesized that this would affect tomographic estimations of muscle mass and composition. Seven healthy subjects were investigated during the initial 120 min of bed rest, using repeated computerized tomography (CT) and continuous bioelectrical impedance analysis (BIA). Thigh and calf muscle cross‐sectional area (CSA) decreased (P<0.05) by 1.9 and 5.5% whereas fat CSA decreased (P<0.05) by 4.1 and 4.4%, respectively. Radiological density (RD) of muscle showed a simultaneous increase (P0.05) in muscle or fat CSA or muscle RD in either thigh or calf between the first and second hour of bed rest. Fluid shift, as estimated by BIA, showed an exponential decay in thigh (τth= 30 min) and calf (τc2= 37 min) by 2.5 and 8.7%, respectively, from first to 120 min of bed rest. Moreover, the calf showed an initial rapid (τc1= 8 s) 2.2% decrease. The demonstrated short‐term changes in leg CSA were more pronounced in the calf than in the thigh. They were similar in muscle and subcutaneous fat. These fluid shifts merit consideration when tomographic imaging techniques are used to estimate muscle mass and compo

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1993.tb09573.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

The possible involvement of tachykinins in the nervous reflex activated by exposing the intestinal mucosa to cholera toxin was investigated in cats and rats. Three types of experiments were performed. In cats the release of tachykinins into blood was followed after placing cholera toxin in the intestinal lumen. In rat experiments a tachykinin receptor antagonist (Spantide II) was given close i.a. and its effect on cholera toxin‐evoked fluid secretion was studied. Finally, in rats the effect of cholera toxin on the SP contents in the intestinal mucosa was studied. No release of tachykinins could be demonstrated. Spantide II did not change the rate of cholera toxin induced secretion. The SP content in the intestinal mucosa was not influenced by placing the toxin in the intestinal lumen. Hence, no experimental evidence was obtained for the involvement of a tachykinin neuron in the intestinal secretory nervous reflex activated by cholera toxin. Based on observations reported in the literature the involvement of an acetylcholine/tachykinin neuron in the reflex is tentatively discusse

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1993.tb09574.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

The permeation of intravenously administered51Cr‐EDTA and [14C]mannitol to the perfused intestinal lumen was measured in anaesthetized rats together with the net intestinal fluid. Net fluid secretion was induced by cholera toxin or by intravenous infusion of vasoactive intestinal polypeptide (VIP). The plasma clearance of Cr‐EDTA and mannitol was 0.9 ± 0.1 and 1.4 ± 0.2μl min‐1g‐1intestine during the control period prior to the secretion and the net fluid absorption was about 7 ± 5μl min‐1g‐1. Cholera toxin induced a net fluid secretion of about 30 ± 7μl min‐1g‐1but the clearance did not rise but decreased significantly. The findings for VIP‐induced secretion were similar. No indication of solvent drag was seen. Thus it is concluded that the fluid was secreted in channels which were smaller than the probes and we propose that the secreted fluid entered the intestinal lumen through the epithelial cells and not by the paracellular route. The decreased permeation of Cr‐EDTA and mannitol from plasma to lumen during volume secretion suggest that there was a decreased mucosal permeability during the secretion. The decrease in permeability was consistent with a decrease in pore size. One explanation of the data is that the pore radius contracted from about 35 to 15 Å during cholera if we assume a homogenous pore population. However, the data indicated that there was not a uniform size of the pore. A more plausible alternative is the presence of a small number of large pores (100 Å or more) which could decrease in size while the majority of pores had a c

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1993.tb09575.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

In the gall bladder of a fasting subject, a decline in the pH of the contents occurs due to secretion of H+from the mucosa. In this study in anaesthetized cats, the gall bladder lumen was perfused with a bicarbonate buffer bubbled with 4% CO2in air. During basal conditions, thePco2always rose while the pH and [HCO‐3] fell in the buffer when passing through the gall bladder lumen, indicating a continuous secretion of H+by the mucosa. This H+secretion was enhanced by stimulation of the respective sympathetic nerves and was blocked by intraluminal amiloride. Intravenous infusion of vasoactive intestinal peptide (VIP) raised the pH and [HCO‐3] in the buffer during the passage through the gall bladder lumen, indicating a secretion of bicarbonate from the mucosa. In view of the presence of sympathetic and VIP immunoreactive nerve fibres in the gall bladder wall and VIP receptors on the luminal epithelial cells, the study demonstrates that there are functional grounds for physiological variations in the secretion of H+and HCO‐3by the gall bladder mucosa. These variations may be important for the solubility of calcium salts in the gall bladder con

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1993.tb09576.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

The effects of 24 h of fasting and refeeding on the release of oxytocin, prolactin, insulin and LH in three lactating sows were investigated. The sows were starved, but supplied with waterad libitum, from 09.00 h on day 27 of lactation until 15.00 h on day 28 of lactation, when they were refed. Blood samples were collected continuously, using an automatic collection system, at a rate of 1 ml min‐1from 09.00 to 21.00 h on day 28 (P1 = 6 h period after the 24 h fast, P2 = 6 h period after refeeding). For both P1 and P2 the mean number of nursings was 7.0 ± 1.0. Plasma insulin and glucose decreased to very low levels during fasting and increased (P<0.001) after refeeding (insulin, 2.5 ± 0.7 vs. 28.9 ± 0.7 mU 1‐1; glucose, 2.6 ± 0.3 vs. 6.4 ± 0.3 mmol 1‐1). Following fasting, levels of prolactin were low (2.8 ± 0.1μg 1‐1), and sucking did not induce significant release of prolactin. However, prolactin increased rapidly after refeeding (5.4 ± 0.1μg 1‐1,P<0.001). Neither the 24 h fast nor refeeding had a marked effect on basal levels of oxytocin, the percentage of sucklings with an oxytocin peak or the size of oxytocin peak. LH release (average and basal levels and number of pulses/6 h) during fasting was similar to that measured after refeeding. Plasma CCK increased significantly after feeding. The results indicate that the release of prolactin is also regulated by feed intake. Consequently the 24 h fast in lactating sows may alter milk production via an inhibition of prolactin release. Neither a stimulatory effect of insulin nor an inhibitory effect of prolactin on LH re

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1993.tb09577.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Antibodies were raised in rabbits against C‐ or N‐terminal fragments of a cloned nitric oxide synthase (NOS) enzyme from rat cerebellum, and used for demonstration of NOS‐immunoreactive (NOS‐IR) nerves in different tissues from the rat (colon, duodenum, adrenal gland, aorta, caval vein, penis and urethra). Both antisera demonstrated the same neuronal elements, although with differences in intensity in the immunoreaction in some tissues. Sections incubated with antisera preabsorbed with excess of the antigens showed no NOS immunoreactivity. In duodenum and colon, NOS‐immunoreactivity was found in the cytoplasm of numerous cell bodies in myenteric ganglia and in some nerve cell bodies in the submucosa. NOS‐IR nerve fibres were numerous in the circular muscle layer, while few were found in the longitudinal layer or the mucosa and submucosa. In the penis, strong NOS immunoreactivity was found in nerves surrounding the deep penile and dorsal arteries, and in nerves in the stroma of the cavernous tissue. In the urethra, NOS immunoreactivity was found in nerves in the mucosa. No NOS immunoreactivity was found in the urothelium. The adrenal medulla, and occasionally the cortex, contained nerve cell bodies with strong cytoplasmic NOS immunoreactivity as well as scattered nerve fibres. No NOS immunoreactivity was found in the abdominal aorta or inferior caval vein. Combined NOS immunostaining and NADPH diaphorase staining showed that virtually all NOS‐IR nerve structures were also NADPH diaphorase‐positive. However, thin nerve fibres and cell linings were sometimes better visualized by NOS‐immunohistochemistry. Furthermore, the adrenal cortex, which only occasionally showed NOS immunoreactivity, was strongly NADPH diaphorase‐positive. A positive NADPH diaphorase reaction, but a negative NOS immunoreactivity, was also found in other structures, such as urothelium, epithelial cells in duodenum and colon, and endothelium of some vessels. It is concluded that the antibodies raised against the synthesized sequences of neuronal NOS are highly specific and may be used in immunohistochemistry in order to

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1993.tb09578.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

A non‐adrenergic, non‐cholinergic (NANC)‐mediated relaxation has been demonstrated in the female rabbit urethral lamina propria, both in response to electrical stimulation and after administration of acetylcholine. The present study was performed to investigate if these relaxations are mediated via thel‐arginine/nitric oxide (NO) pathway. In the lamina propria of the female rabbit urethra, numerous NADPH diaphorase‐positive, fine varicose nerve fibres were observed both around arteries, in and around smooth muscle bundles, and in arterial endothelium. Since NADPH diaphorase histochemistry may be a marker of NO synthase‐containing neurons, this finding suggests the occurrence of NO synthase in this tissue. Isolated preparations of the rabbit urethral lamina propria, contracted by noradrenaline, produced frequency‐dependent NANC relaxations in response to electrical field stimulation, and concentration‐dependent NANC relaxations in response to acetylcholine. Electrically induced relaxations were possible to evoke even in preparations where acetylcholine‐induced relaxation was poor or absent. Pretreatment with the NO synthase inhibitor, NG‐nitro‐l‐arginine (l‐NOARG) reduced the maximum relaxation obtained at 30 Hz to 12% of the control response. NG‐nitro‐d‐arginine (d‐NOARG) had no effect. The effects ofl‐NOARG were antagonized by the addition ofl‐arginine. Acetylcholine relaxed noradrenaline‐precontracted strips by 36%; vasoactive intestinal polypeptide (VIP) reduced the contraction by 95%.l‐NOARG, but notd‐NOARG, abolished or reversed acetylcholine‐induced relaxations, but failed to reduce the relaxations produced by VIP.The results demonstrate the occurrence of NADPH diaphorase‐positive nerve fibres in the lamina propria of the female rabbit urethra. NANC‐mediated relaxations, sensitive to inhibition of NO synthase, were produced both by electrical stimulation and by acetylcholine. The fact that NANC nerve‐mediated relaxation was demonstrated also in preparations where no relaxant response to acetylcholine could be detected suggests that the NO which produces relaxation can be

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1993.tb09579.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

In 10 subjects, laser Doppler flowmetry was used to study whether cholinergic orβ‐adrenergic pathways are involved in the control of tooth pulp blood flow (PBF) in response to isometric hand grip and the cold pressor test. We also examined if differences exist between the regulation of blood flow in the tooth pulp and the nearby gingiva (GBF). Isometric hand grip (35% of maximum force, 2 min) and the subsequent ischaemia (2 min) induced a brief rise in PBF and a more long‐lasting rise in GBF. Atropine increased heart rate about by 40% and changed the pulpal response to a fall in flow, without altering gingival flow. Propranolol, causing a 20% reduction in heart rate, had no effect on either flow during the actual test, but induced a rise in GBF after the ischaemic period. The cold pressor test (2 min at 0.5 °C) resulted in a reduction in PBF and GBF, unaffected by the blocking drugs. With atropine, however, PBF increased immediately after this test. The relative changes in arterial pressure and heart rate were unaffected by the drugs. Our study has demonstrated the existence of cholinergic nervous vasodilation in vessels serving the tooth pulp. Non‐adrenergic non‐cholinergic mechanisms probably contribute to the evoked rise in GBF during exercise.β‐adrenoceptors are involved in the control of GBF immediately after isometric exercise. While the two tests under control conditions evoked mostly parallel changes in PBF and GBF, the use of blocking agents showed that blood flow is controlled by different mechanisms in the two adjacent v

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1993.tb09580.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY