摘要:

The literature on the classical mechanical properties of geometrically simple mammalian smooth muscle preparations is analyzed in an attempt to characterize the contractile system. Although the physiological behavior of smooth muscle is diverse, indices of contractile system function suggest there is considerable uniformity at this level. Compared to vertebrate striated muscles, smooth muscle tissues and possibly individual cells (i) often develop equal or greater maximum isometric force/cell cross-sectional area, with (ii) low and fairly uniform maximum shortening velocities, and (iii) operate over a range of lengths which may be no greater than the potential in striated muscle. Few details are known of filament structure, organization, interactions, and of force transmission in comparison with the extensive information on the contractile unit (sarcomere) for striated muscle. Consequently, tissue or cellular mechanical parameters may not be directly proportional to the output of the myofilamental contractile unit in smooth muscle. A sliding filament mechanism involving actin-myosin interactions qualitatively similar to those in striated muscle seems probable. However, there are important quantitative differences in the contractile apparatus which may be related to functional properties.

ISSN:1018-1172    

DOI:10.1159/000158076

出版商:S. Karger AG    

年代:1976

数据来源: Karger

摘要:

The literature concerned with studies of the occurrence and function of the cyclic nucleotides in blood vessels is reviewed. Emphasis is placed on the critical evaluation of the evidence which relates to the hypothesis that cyclic nucleotides mediate the effects of drugs and neurotransmitters on vascular contractility. The hypothesis that cyclic AMP mediates vasodilation, especially that induced by β-adrenergic relaxation, is supported by many experimental approaches, but it is concluded that the evidence remains unconvincing based on the criteria established for such a mediator role. Possible sites of action of cyclic AMP are discussed. The demonstrated action of cyclic AMP on vascular membrane electrophysiology and calcium ion pumps are reviewed as possible causes of relaxation. The role of both nucleotides in vascular disease, especially hypertension is discussed. Finally the needs for further research in this area are suggested

ISSN:1018-1172    

DOI:10.1159/000158077

出版商:S. Karger AG    

年代:1976

数据来源: Karger

摘要:

In the present study, both of the major enzymes, monoamine oxidase and catechol-o-methyltransferase, involved in the degradation of norepinephrine were examined indirectly in segments of rabbit aorta by exposure of tissues to 14C-norepinephrine and subsequent isolation of metabolites from homogenates by chromatographic techniques. Segments of aorta were preincubated with vasodilators to examine their influence on accumulation and metabolism of 14C-noreρinephrine. The accumulation of labeled norepinephrine by aortae was enhanced after pre-incubation with hydrochlorothiazide or diazoxide, and reduced after preincubation with sodium nitroprusside or nitroglycerin. However, the fraction of accumulated 14C-norepinephrine which was degraded was significantly reduced after exposure to all four vasodilators. These results suggest that a decrease in degradation of norepinephrine in vascular smooth muscle can be observed (1) in vitro and (2) fairly rapidly after exposure to vasodilators

ISSN:1018-1172    

DOI:10.1159/000158078

出版商:S. Karger AG    

年代:1976

数据来源: Karger

摘要:

Digital artery blood flows were compared with digital pad opacity pulse amplitudes in dogs during vasoconstrictor responses. A high correlation between digital artery flow and opacity pulse amplitudes occurred during infusions of epinephrine and sciatic and tibial nerve stimulations, but not during superficial fibular nerve stimulation. The results confirmed earlier findings that tibial nerve stimulation produced predominantly precapillary constriction, and that superficial fibular nerve stimulation produced predominantly postcapillary constriction. Events in precapillary vessels appeared to be responsible for the opacity pulse. This fact probably forms the basis for the close relationship between opacity pulse amplitude and blood flow.

ISSN:1018-1172    

DOI:10.1159/000158079

出版商:S. Karger AG    

年代:1976

数据来源: Karger

摘要:

Thoracic aortic histamine synthesis has been examined in rats rendered hypertensive for periods ranging from ¼ to 8 days through ligation of the abdominal aorta between origins of the renal arteries, in a preliminary attempt to establish whether activity of the aortic nonmast-cell histidine decarboxylase system is increased in experimental hypertension. Results indicate that aortic histamine synthesis is increased 66, 75, 96 and 55% at postsurgical intervals of ¼, ½, 1 and 8 days. These data suggest at least one biochemical explanation for both increased arterial wall permeability and the arterial inflammation consistently associated with both clinical and experimental hypertension by resolving these into those associated with the prolonged inflammatory respon

ISSN:1018-1172    

DOI:10.1159/000158080

出版商:S. Karger AG    

年代:1976

数据来源: Karger

摘要:

The purpose of this work was to test the hypothesis that stress relaxation (SR) in vascular smooth muscle is related to the amount of contractile activity (developed stress) and perhaps a property of the contractile element (CE). Using medial-intimal strips from the hog carotid artery, a strain (Δ1/l0, where l0 equals optimal length for force development) of 2% was applied at two different rates in the presence of various levels of developed or passive stress. Developed stress was altered either by changing the extracellular K-ion concentration with the strip length equal to l0 or by stimulating with a salt solution containing 30 mil KCl at various strip lengths. Passive stress was altered by varying strip length. At each level of developed or passive stress the magnitude of the increment in stress due to the strain (induced stress) and the SR were noted. SR varied directly with the magnitude of the developed stress, but there was a small and relatively unchanging amount of SR when passive stress was varied. At a given level of developed stress, the magnitude of SR was greater at a strain rate of 0.016 than at 0.001 l0/sec. When developed stress was altered, the magnitude of SR was essentially equal to the amount of induced stress; however, when passive stress was varied, SR was always less than induced stress. These observations are consistent with the hypothesis that, in the presence of developed stress, a large fraction of the SR represents the lengthening of the CE. This increased CE length allows a reequilibration of stress between the series elastic element and the contractile element. In the absence of developed stress, SR may represent a passive, physical property of this heterogeneous tissue

ISSN:1018-1172    

DOI:10.1159/000158081

出版商:S. Karger AG    

年代:1976

数据来源: Karger

摘要:

Experiments were performed to investigate whether local cooling facilitates adrenergic neurotransmission in the cutaneous vein of the dog. Helical strips of saphenous veins were incubated with 3H-noreρineρhrine and mounted for isometric tension recording and superfusion. The superfusate was collected for measurement of total radioactivity or for chromatographic analysis. Electrical stimulation (2 Hz) caused contraction and augmented the efflux of 3H-norepinephrine and metabolites. Cooling (from 37 to 28 °C) imposed during electrical stimulation caused a further increase in tension, but decreased the amount of 3H-norepinephrine and metabolites overflowing into the superfusate. These experiments demonstrate that the potentiating effect of cooling on the response of cutaneous veins to sympathetic nerve stimulation is not associated with facilitation of adrenergic neurotransmission. It probably is due to an altered sensitivity of the vascular smooth muscle to the transmitt

ISSN:1018-1172    

DOI:10.1159/000158082

出版商:S. Karger AG    

年代:1976

数据来源: Karger

摘要:

Following partial constriction of the abdominal aorta, the increase in arterial pressure in vessels proximal to the ligature at 3, 6, 14, 21 and 28 days was correlated with pathological changes and with proliferation of cells in the arterial wall measured by 3H-thymidine labeling indices and mitotic counts. The time course of arterial pressure rise and vascular smooth muscle cell proliferation were similar. Patterns of proliferation of cells of the artery wall varied in distribution with time, the presence or absence of traumatic changes seen by light microscopy, and the histological structure of the vessel. Arteries not subject to hypertension did not differ from sham-operated animals.

ISSN:1018-1172    

DOI:10.1159/000158083

出版商:S. Karger AG    

年代:1976

数据来源: Karger