摘要:

[3H]adenine was taken up by a crude hypothalamic synaptosomal fraction and incorporated into mainly nucleotides. The synaptosomes were superfiTsed and after the initial washout a steady fractional release rate of 0.5‐1 % of the content/min was found. Electrical pulses (2 ms, 50 Hz, 10–20 mA, 4 min) and veratridine (10 μM, 4 min) induced a Ca++‐dependent increase in purine release rate. K+(30 mM, 4 min) caused a largely Ca++independent increase. Most of the released material co‐chromatographed with adenosine, inosine and hypoxanthine, while little or no nucleotide material was detected. Release of endogenous adenosine, inosine and hypoxanthine was detected by high performance liquid chromatography. However, following hypo‐osmotic shock most of the released material was in nucleotides. The removal of glucose from the medium increased the fractional release rate 2–3 fold. Histamine, acetylcholine and glutamate were without effect. High amounts of noradrenaline caused an EGTA‐inhibited release of purines, which was un‐af‐fected by propranolol or phentolamine. It is suggested that purines are released from neuronal structures and that the release reflects increased energy consumption and/or decreased

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1979.tb06377.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

The effect of an increase in vascular transmural pressure upon the blood flow in two subcutaneous vascular beds, maximally dilated by papaverine was studied in 6 healthy humans. Blood flow was measured on the dorsum of the hand and at the lateral malleolus by the local133Xe washout technique. Increase in vascular transmural pressure was induced by lowering the labelled area various distances below heart level. Lowering the area caused an increase in blood flow. The increase was less pronounced in the legs than in the hand. As arterial perfusion pressure head remained constant during lowering, this indicates that the relative decrease in vascular resistance was smaller in the leg than in the hand. Experimental edema did not influence the relative decrease in vascular resistance. The results suggest that ‘distensibility’ of the resistance vessels is smaller in the leg than in the hand. This might be due to a structural adaptation of the vascular wall in vessels often subjected to increased hydrostatic press

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1979.tb06378.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

The aim of this study has been to examine the utility of the washout of a freely diffusible radioactive indicator as a measure of regional myocardial blood flow in open‐chest anesthetized dogs. The method employed was direct intramyocardial injection of Xenon‐133 followed by measurement of its gamma‐radiation. The experimental washout curves show, after a short acceleration period, monoexponential washout of the indicator over two decades. We found indications of insignificant veno‐arterial shunting by diffusion of the blood flow level measured, insignificant arterial recirculation of the indicator, and minimal radioactive contribution to precordial residue versus time curves arising from right heart or non‐myocardial tissue. We suggest that diffusion equilibrium between the tissue in the counting field and the blood leaving it is maintained during the linear down slope of two decades of the clearance curve, and that local blood flow can be calculated from washout rate constant obtained from this part of the curve. The method employing intramyocardial injection of Xenon‐133 was found to give the same results as atraumatic epicardial labelling indicating negligible effect of the injection trauma and supporting the validity of the local injection method using small volume

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1979.tb06379.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

The cardiac output and regional blood flow have been simultaneously determined in the anesthetized rat by using the reference organ method.99Tcmlabelled dextran 15 μm microspheres were injected in the left ventricle while simultaneously an arterial reference sample was drawn at constant known rate. The values calculated regarding cardiac output agree well with previously recorded series. Regional organ blood flow in the rat is presented as ml. min‐1. g‐1tissue and values do agree with those reported by others. The results indicate that the reference organ method can be used in the rat for the study of cardiac output and regional blood

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1979.tb06380.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

In a comparative study the isometric twitch tension and the latency relaxation were correlated to the sarcomere length in frog and mammalian muscle, the latter only in the length range from 2.4 to 3.1 μm since at higher degrees of stretch the sarcomere lengths became increasingly non‐uniform along the fibres. The location of the triads in mammalian muscle fibres was examined by means of electron microscopy. During stretch the location of the triads was gradually changed from the overlap zone at sarcomere lengths below 2.6 to 2.7 jim to the I‐band at sarcomere lengths above 3.0 to 3.1 μm, their centres (T‐tubules) being equally distributed between the overlap zone and the I‐band at sarcomere lengths around 2.9 μm. In both types of muscle the maximum amplitude of the latency relaxation (of about equal relative size) occurred at a sarcomere length of about 3.1 μm; and both twitch tension and latency relaxation were dependent upon the presence of a zone of overlap between the thin and thick filaments. In neither of the two types of muscles did the time,t1, from stimulation to the onset of tension drop depend upon the sarcomere length. At room temperature (22oC)t1was about 1 ms in mammalian muscle and 2 ms in frog muscle. In mammalian muscle the time,t2, from the stimulus to the maximum drop in tension and the time,t3, to positive tension development were both substantially uninfluenced by changes in sarcomere length in the range 2.4 to 2.9 μm, whereas in frog muscle botht2andt3increased linearly with increasing sarcomere length in the above range. These findings are discussed in the light of the different locations of the triads in frog and mammalian muscle. It is concluded that the theory of Sandow (1966)–extended by Mulieri (1972)–and that of Haugen&Sten‐Knudsen (1976), which both have the virtue of being able to account for the increase of the latent period with stretch in frog muscle, also would be applicable to mammalian muscle provided that a time lag of 0.5 to 1.0 ms exists from the time of the binding of Ca2+‐ions to the troponin molecules inside the zone of overlap until the attached cross bridges start to move

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1979.tb06381.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

4, 14 and 28 days old rats were exposed to a hypoxic environment of 6% O2‐94% N2for 30 min. Tyrosine hydroxylase and tryptophan hydroxylase acivity was studied in different brain regions (hemispheres, striatum, midbrain and brainstem) in vivo by measuring the accumulation of dihydroxyphenylalanine (Dopa) and 5‐hydroxytryptophan (5‐HTP) respectively, after inhibition of aromatic L‐amino acid decarboxylase with NSD 1015. Tyrosine and tryptophan levels in the different brain regions were measured simultaneously. The tyrosine and tryptophan levels in the various brain parts were generally not influenced during exposure to hypoxia. Tyrosine hydroxylase activity decreased in most areas in the 4 and 14 days old rats, and all brain areas studied in the 28 days old rats. Tryptophan hydroxylase activity decreased markedly in all brain areas at all ages studied. It is concluded that the enzymes tyrosine hydroxylase as well as tryptophan hydroxylase seem to be equally affected during hypoxia in the different brain regions

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1979.tb06382.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Carbonic anhydrase is found in the cytoplasm and brush border membranes of renal proximal tubular cells. Both the soluble and the membrane‐bound enzyme have been assigned roles for the secretion of hydrogen ions into the tubular fluid and hence also for the reabsorption of bicarbonate. Attempts were made to differentiate between the roles of these enzymes for the rate of proximal tubular acidification. Proximal tubules of rats were instilled and perfused with bicarbonate solutions containing carbonic anhydrase inhibitors, especially designed to be impermeable to cell membranes. The acidification rate was measured with an antimony micro‐electrode system–the only instantly responding micro‐pH electrode. The membrane impermeable inhibitors had no effect on this rate in contrast to acetazolamide, which markedly inhibited the acidification rate when administered in‐traluminally. It is therefore concluded that the cytoplasmic carbonic anhydrase is the important enzyme for the proximal tubular acidification rate, and hence the rate of bicarbonate reabsorption. The function of the brush border enzyme remains an outstandin

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1979.tb06383.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Na+transport across frog skin, measured as short‐circuit current (SCC) shows perfect temperature compensation in frogs acclimated to 6°, 12°, and 23°C as SCC values observed at the acclimation temperatures are equal (about 13 μA/cm2). Reacclimation experiments show that this is not a starvation effect. While very little temperature compensation is seen in the activity of Na+, K+‐ATPase in epidermal homogenates from frog skins, the activity of Mg2+‐ATPase shows inverse compensation at assay temperatures from 4oto 48oC. This ATPase is apparently activated either by Mg2+or by Ca2+and it probably controls the passive permeability of epidermal cells. It is suggested that the inverse temperature compensation in the activity of this enzyme is the main mechanism by which the observed perfect temperature compensation of Na+transport across frog sk

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1979.tb06384.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Five to six weeks after bilateral stellate ganglionectomy, noradrenaline (NA) levels in cats' atria were reduced to ∽ 20% of controls. In vivo uptake of3H‐NA and of35S‐sulphate into gradient fractions containing noradrenergic vesicles from the atria decreased to ∽30% and ∽40%, respectively. The uptakes of3H‐NA and35S‐sulphate were significantly correlated in both control and ganglionectomized cats, and the distributions of3H and35S on the gradients were parallel. The findings suggest that sulphomucopolysaccharides (SMPSs) may be localized in noradrenergic vesicles, possibly participating in the storage of NA. In 10‐week‐old rats treated neonatally with either 6‐hydroxydopamine (6‐OH‐DA) or guanethidine, levels of NA in the heart, spleen and salivary glands were decreased to<10% and to 10–20%, respectively; in the seminal ducts to 33% and 45%, respectively.3H‐NA uptake into noradrenergic‐vesicle‐enriched subcellular fractions from the heart, spleen and salivary glands of 6‐OH‐DA treated rats decreased almost to the extent of NA depletion but in the seminal ducts the decrease was less marked. Guanethidine treatment left the uptake unaffected, except for the spleen. The discrepancy between storage and uptake suggests that surviving neurons display during their outgrowth into tissues a high uptake capacity but lack full NA synthesis.35S‐sulphate incorporation into non‐lipid compounds, presumably SMPSs, in the noradrenergic‐vesicle‐enriched fractions appeared unaffected or increased over corresponding control levels, possibly due to hig

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1979.tb06385.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Cardiovascular ‘reactivity’ to graded splanchnic nerve stimulations was compared in adult spontaneously hypertensive rats (SHR) and normotensive controls (NCR), during abolished adrenal medullary secretion and neurogenic cardiac control and depressed reflex vascular adjustments. Arterial pressure, heart rate and cardiac output were measured, and total peripheral resistance (TPR) and stroke volume (SV) computed before, during and after nerve stimulation. The neurogenic resistance increases in the major gastrointestinal‐renal‐hepatic circuits expressed themselves as TPR elevations, which were much accentuated in SHR. This reflects an increasedw/r1of SHR resistance vessels rather than any altered effector sensitivity, since the responses were particularly accentuated at high discharge rates when noradrenaline junction concentrations approach maximal levels. The splanchnic capacitance responses expressed themselves as SV increases, being the most relevant aspect of capacitance control. SV increased less in SHR, mainly reflecting the reduced diastolic compliance of the hypertrophied SHR left ventricle and the consequent rightward shift of its Frank‐Starling curve. The results indicate that an elevated resistance may well be maintained by a normal sympathetic discharge in established SHR hypertension. There seems, however, to be an increasing need for accentuated discharge to the capacitance side to maintain proper cardiac filling of the hypertrophied left

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1979.tb06386.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY