摘要:

In vitroeffects of two bioactive forms of pituitary adenylate cyclase activating polypeptide (PACAP): PACAP–38 and PACAP–27 were studied on rabbit vascular and non–vascular smooth muscle. Segments of the ovarian artery and muscle strips from the fallopian tube were used. Two series of experiments were performed on vessels: the dose–response relationship of PACAP–38 (10–10–7 M) was established on noradrenaline– (NA, 10–6 M) contracted vessels. In the other set of experiments the contractile effect of 10–8–10–4 M NA added cumulatively, was studied on arterial segments incubated with PACAP–38 (10–7 M), PACAP–27 (10–7 M) or VIP (10–7 M). The effect of PACAP–38, PACAP–27 and VIP (10–10–10–6M) was investigated on spontaneously contracting smooth muscle of the fallopian tube. Longitudinally as well as transversally cut specimens were investigated. PACAP–38 produced a significant dose–related relaxation on the NA–precontracted vessels. However, pre–incubation of the vessels with 10–7 M PACAP–38, PACAP–27 and vaso active intestinal polypeptide (VIP) did not induce a general rightward shift of the NA concentration–response curves, although a tendency to inhibition in the low–dose interval was observed. The peptides caused a significant, dose–dependent inhibition of both frequency and amplitude on the fallopian tube smooth muscle activity. The effects of the three peptides on l

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1994.tb09792.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Acetylcholine (ACh) induces an Nω–nitro–L–arginine (L–NOARG)–resistant relaxation and hyperpolarization in the rat isolated hepatic artery. The possibility that carbon monoxide (CO) produced by haem oxygenase (HO) is an endogenous mediator of this response was investigated. Exogenously applied CO evoked a concentration–dependent relaxation, and the CO ‘scavenger’ oxyhaemoglobin (10μM) reduced the maximum ACh–induced relaxation by 25%. The HO inhibitor zinc protoporphyrin IX (ZnPP, 10 μMvirtually abolished the ACh–induced relaxation in experiments carried out under ordinary light conditions. However, ZnPP did not affect the ACh–induced relaxation under dark conditions, even after exposure of ZnPP to intense light before the preincubation period. Biliverdin (0.1 mM), a feedback inhibitor of HO, was also inactive under dark conditions, and the HO substrate haematin (0.1 mM) did not facilitate the ACh–induced relaxation. The relaxation induced by the nitric oxide (NO) donor 3–morpholino–sydnonimin was not affected by ZnPP in the presence of light. However, ZnPP inhibited the relaxation evoked by the potassium channel opener levcromakalim and the tonic component of the contractile response to 60 mM potassium, indicating that ZnPP has effects distinct from HO inhibition in the presence of light. ZnPP should therefore be protected from light when used to inhibit HO–mediated CO formation. The results do not suggest that CO generated by HO mediates the endothelium–dependent, L–NOARG–resistant relaxation in

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1994.tb09793.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

The present study was undertaken to examine the influence of transmural pressure on vasomotion and to determine if any such influence was endothelium–dependent. Responses to changes in intravascular pressure of cannulated mesenteric small arteries were investigated under no–flow conditions. Both intact and endothelium–denuded arteries dilated passively when intravascular pressure was increased stepwise from 20 to 140 mmHg. When tone was induced by noradrenaline, pressure increase resulted only in dilatation, independent of endothelium. The sensitivity to noradrenaline was significantly increased in vessels without endothelium, indicating a relaxing influence of the endothelium. Rhythmic contractions in response to noradrenaline occurred in all intact arteries, but were absent when the endothelium was removed. The amplitude of the rhythmic contractions decreased significantly when transmural pressure was elevated. The frequency increased when pressure was elevated from 20 to 80 mmHg and then remained rather constant during further pressure increases. As shown previously in non–pressurized arteries, exogenous cyclic GMP induced oscillations in endothelium–denuded arteries. Pressure–related effects on vasomotion were not dependent on an intact endothelium. Ryanodine, ouabain or verapamil inhibited the rhythmic activity, confirming previous results in non–pressurized arteries.Thus, changes in transmural pressure can modulate vasomotion, but this effect does not appear to be mediated by the endothelium. Generation of vasomotion may depend on release of Ca2+from intracellular stores, the activity of the Na+, K+–pump and transmembrane Ca2+inflow in a pressurized artery as shown previously in these arteries under isome

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1994.tb09794.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

The effects of the non–peptide NK, receptor antagonists, CP96,345 and RP–67,580, were investigated in a model using anaesthetized pigs. Both the blood flow in the internal maxillary and the bronchial artery (ultrasonic flowmetry) and the superficial blood flow in nasal mucosa and the skin (laser–Doppler flowmetry) were monitored simultaneously. Vasodilation induced by substance P administered i.v. systemically was blocked by pretreatment with CP–96,345, 3 mg kg1but not by RP–67,580. CP–96,345 had no effects on the vasodilationo induced by calcitonin gene–related peptide or vasoactive intestinal polypeptide. The capsaicin–induced vasodilation in the superficial blood flow of the nasal mucosa and the skin, was reduced after the CP–96,345 pretreatment. The vasodilation induced by capsaicin infusion in the internal maxillary or the bronchial artery was not affected by the CP–96,345 pretreatment. Electrical stimulation of the vagal nerve induced a vasodilation in the bronchial circulation which was not attenuated by pretreatment with CP–96,345.In the nasal mucosa and the skin NK1receptors seem to be involved in the vasodilation in the superficial small vessels, due to chemical activation of sensory C–fibre afferents. Furthermore, CP–96,345 is a useful tool in the evaluation of NKXreceptor–mediated responses. RP–67,580 which has been shown to have NK1antagonistic properties in the rat has no suc

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1994.tb09795.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Single fibres from the anterior tibialis muscle ofRana temporaria(temperature, 2–3oC) were moderately fatigued at a prestretched sarcomere length (approximately 3.6 μm) by reducing the intervals between 2 s tetani from 240 to 20 s. Changes in length of marked segments along the muscle fibre were monitored during fixed–end tetani using a photoelectric recording system. In contrast to the situation at 2.2 μm sarcomere length, the central region of the fibre was elongated during tetanus at the prestretched fibre length, whereas the segments next to the fibre–tendon junctions (end segments) shortened correspondingly. These length changes were associated with a slow climb of force (tension creep). During development of fatigue, the maximum tetanic tension was reduced to about 78% of the control value and the time course of the tetanus was markedly changed. The tension creep observed in control tetanus was greatly reduced during fatigue, the tetanic tension remaining nearly constant after an initial rising phase. The change in shape of the force myogram during fatigue was associated with a considerable reduction in the amplitude of segment movements along the fibre. The results are explainable by assuming that the end segments (having shorter sarcomeres) become more fatigued than other parts in series along the fibre. At the same time the central segments are likely to have acquired a higher ability to resist stretch by the end s

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1994.tb09796.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Neuronal cultures were made from the 8–d–old embryonic chick telencephalon. The primary culture model was further improved, the medium composition was modified, and the cells grown for 10 d, which allowed the development of relatively differentiated neurones. A superfusion protocol was developed and applied to study the release of [3H]–γ–aminobutyric acid ([3H]GABA). High endogenous activity levels of glutamate decarboxylase (GAD) and of a Ca–dependent potassium stimulated [3H]GABA release were used as criteria for GABAergic differentiation. The influence of the non–substrate inhibitor of GABA transport, SKF 89976–A, on the GABA release, was studied using the primary neuronal culture. The release was found to be inhibited by SKF 89976–A at higher concentra

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1994.tb09797.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

In contrast to mammalian erythrocytes which fulfil their energy requirements via anaerobic glycolysis, fish erythrocytes obtain most of their energy aerobically via the Krebs cycle. This enables them to use various substrates, including monocarboxylic acids, glucose and amino acids. This review discusses the membrane permeability of these substrates, and their relative importance in the energy production of fish erythrocytes. Agnathans are characterized by a high permeability to all of the potential substrates, glucose, monocarboxylic and amino acids. In contrast, teleost erythrocytes are often characterized by low glucose permeability. It appears that monocarboxylic acids and certain amino acids such as glutamine may be more important in energy production of teleost erythrocytes than glucose.

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1994.tb09798.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

It is becoming increasingly evident that many teleost fish use hormones and their metabolites as sex pheromones. Although hormonal pheromone systems of several species of fish have now been characterized, that of the goldfish is the best understood. Reproductively–active female goldfish sequentially release derivatives of three steroidal hormones and two prostaglandins which have specific and potent actions on the goldfish olfactory sense and subsequently conspecific reproductive behaviour and physiology. Three goldfish hormonal pheromones are unmodified sex hormones which are also found in the blood of many other species offish and are therefore unlikely to be species–specific. This scenario evokes two related questions. First, how did these systems evolve? Second, do hormonal pheromones represent specialized signals used for communication or rather simple metabolites which fish have evolved the ability to detect because of their intrinsic meaning (‘spying’)? Here we review hormonal pheromone function in fish and then describe a study of the goldfish which tests whether hormonal pheromones are specialized communicatory signals by comparing the profile of steroids released by goldfish with their olfactory responsiveness to these compounds. Little correlation between signal production and detection was found and we conclude that the goldfish hormonal pheromone system most likely exemplifies

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1994.tb09799.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Living in an aquatic environment, often devoid of light but rich in dissolved compounds, fish have highly developed chemosensory and chemical signalling systems. The olfactory and gustatory systems comprise the major chemosensory pathways. Despite considerable variations in structural organization of the peripheral olfactory organ throughout fish species, ultrastructural organization of the olfactory sensory epithelium is extremely consistent. The olfactory receptor cell is a bipolar neurone which is directly exposed to the external environment and sends information to the brain by its own axon (cranial nerve I). Four major classes of chemicals have been identified as specific olfactory stimuli and their stimulatory effectiveness characterized: amino acids, sex steroids, bile acids/salts and prostaglandins. Olfactory signals such as those involved in reproduction and feeding may be processed independently through two distinct subsystems: the lateral and medial olfactory systems. The taste buds constitute the structural basis of the gustatory organ. Taste buds may occur not only in the oropharyngeal cavity, but on the whole body surface. Chemical information detected by specialized epithelial cells, gustatory cells, is transmitted to the central nervous system by cranial nerve VII (facial), IX (glossopharyngeal), and X (vagal). Besides diverse sensitivities and specificities for amino acids, fish gustatory receptors detect various organic acids, nucleotides and bile salts. Putative receptors, molecular mechanisms of transduction and the role played by olfaction and gustation in feeding, reproduction, migration and other fish behaviours are discussed.

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1994.tb09800.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Functional and structural aspects of the vascular endothelium were studied in major blood vessels from two distantly related species, the Atlantic salmon(S. salar)and the cod (G.morhua.) The ventral aorta (VA) of both teleosts and the dorsal aorta (DA) and the coeliaco mesenteric artery (CMA) of the cod and the salmon respectively were examined for endothelium dependent and independent responses to acetylcholine (ACh), adrenaline (A) and endothelin–1 (ET–1).In the salmon, endothelial probing resulted in reduced contractile responses to high K+in both VA and CMA while the responses to ACh and A were reduced only in CMA. Indomethacin, but not L–NMMA, enhanced vasoconstrictions to high K+, ACh and A in the unprobed CMA.In the cod vessels the endothelial probing caused reduced contractile responsestothe two effective vasoconstrictors in both vessels, to high K+and A in VA and to high K+and ET–1 in DA. Both indomethacin and L–NMMA enhanced contractile tension to A in VA, while indomethacin, but not L–NMMA, enhanced the constrictions by high K+in VA and by ET–1 in DA.These experiments have revealed heterogeneous patterns of endothelial function in blood vessels of two teleosts, reflecting differences in endothelial morphology and in production of potent endothelial derived contracting factors as well as prostanoic and non–prostanoic endothelium–derived

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1994.tb09801.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY