摘要:

Isolated hearts from adult spontaneously hypertensive rats (SHR; Okamoto 1969), with established hypertension, were investigated in an antegrade perfusion apparatus where preload and afterload could be varied independently. Frank‐Starling curves were constructed at constant afterloads ranging from 50 mmHg to 150 mmHg. As earlier reported, the SHR hearts exhibited a rightward shift of their Frank‐Starling relationships compared to those from the normotensive control hearts, though visible only at afterloads up to about 100 mmHg. At higher afterloads the SHR hearts performed significantly better then the NCR ones as their maximal stroke volume was significantly greater compared to that of controls. Thus, left ventricular hypertrophy obviously increases the work capacity of the heart, though at the cost of an altered Frank‐Starling relation dependent on the reduced diastolic compliance. For such reasons the myocardial hypertrophy in established SHR hypertension must be considered a physiologic adaptation and not a degenerative phenomenon, though naturally degenerative processes may later become superim

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1979.tb06435.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

The left atrial pressure in adult spontaneously hypertensive rats (SHR) of the Okamoto strain and normotensive control rat (NCR) was measured via chronically implanted catheters. In SHR left atrial pressure in end‐expiration was more than twice as high (10.3±0.4 mmHg) as in NCR (4.6±0.3 mmHg). There was no difference in the intrapleural pressure between the two groups of rats, therefore the enhanced left atrial pressure in SHR represents a real rise in the diastolic filling pressure of its left ventricle. This is considered to be the most important compensation for the earlier reported rightward shift of the Frank‐Starling curve in SHR (Hallbäck, Isaksson&Noresson 1975, Noresson et al. 1979a). Without this compensation the stroke volume would have been drastically reduced for the hypertrophied

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1979.tb06436.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

The characteristics of 11 left atrial receptors in 9 adult male spontaneously hypertensive rats (SHR) were investigated. All the receptor afferents were non‐medullated with conduction velocities from 0.5 to 1.5 m/s. Elevation of left atrial pressure during graded aortic occlusion always induced a marked increase in receptor discharge with maximal frequencies ranging from 29 to 70 Hz. The threshold for activation was from 7.5 to 13 mmHg in mean left atrial pressure (mean ± S.E., 10.2±0.6 mmHg). Upon atrial distension all the receptors displayed a clear rhythmicity and the discharge correlated mainly with the v‐wave, indicating distension as the cause of receptor activation. The relationship between the mean left atrial pressure and the frequency of discharge was constructed for all the receptors and compared with similar data obtained from normotensive control rats (NCR) (Thorén et al. 1979). It was then obvious that the left atrial receptors are reset in SHR probably secondarily to a decreased distensibility of the left

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1979.tb06437.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

The importance of carbohydrate availability during exercise for metabolism and plasma hormone levels was studied. Seven healthy men ran on a treadmill at 70% of individual maximal oxygen uptake having eaten a diet low (F) or high (CH) in carbohydrate through 4 days. At exhaustion the subjects were encouraged to continue to run while glucose infusion increased plasma glucose to preexercise levels. Forearm venous blood, biopsies from vastus muscle and expiratory gas were analyzed. Time to exhaustion was longer in CH‐(106±5 min (S.E.)) than in F‐expts. (64±6). During exercise, overall carbohydrate combustion rate, muscular glycogen depletion and glucose and lactate concentrations, carbohydrate metabolites in plasma, and estimated rate of hepatic glucose production were higher, fat metabolites lower, and the decrease in plasma glucose slower in CH‐than in F‐expts. Plasma norepinephrine increased and insulin decreased similarly in CH‐and F‐expts., whereas the increase in glucagon, epinephrine, growth hormone and Cortisol was enhanced in F‐expts. Glucose infusion eliminated hypoglycemic symptoms but did not substantially increase performance time. During the infusion epinephrine decreased markedly and glucagon even to preexercise levels. Infusion of insulin (to 436% of preexercise concentration) in addition to glucose in F‐expts. did not change the plasma levels of the other hormones more than infusion of glucose only but reduced fat metabolites in plasma. At exhaustion muscular glycogen depletion was slow, and the glucose gradient between plasma and sarcoplasma as well as the muscular glucose 6‐phosphate concentration had decreased. Conclusions: The preceding diet modifies the energy depots, the state of which (as regards size, receptors and enzymes) is of prime importance for metabolism during prolonged exercise. Plentiful carbohydrate stores favor both glucose oxidation and lactate production. During exercise norepinephrine increases and insulin decreases independent of plasma glucose changes whereas receptors sensitive to glucose privation but not to acute changes in insulin levels enhance the exercise‐induced secretion of glucagon, epinephrine, growth hormone and Cortisol. Abolition of cerebral hypoglycemia does not inevitably incrase performance time, because elimination of the hypoglycemia may not abolish

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1979.tb06438.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

The influence of muscle temperature (Tm) on maximal muscle strength, power output, jumping, and sprinting performance was evaluated in four male subjects. In one of the subjects the electromyogram (EMG) was recorded from M. vastus lateralis, M. biceps femoris, and M. semitendinosus.Tmranged from 30.0°C to 39°. Maximal dynamic strength, power output, jumping, and sprinting performance were positively related toTm.The changes were in the same order of magnitude for all these parameters (4–6%× C‐1) Maximal isometric strength decreased by 2%× C‐1with decreasingTm.The force‐velocity relationship was shifted to the left at subnormalTm.Thus in short term exercises, such as jumping and sprinting, performance is reduced at lowTmand enhanced atTmabove normal, primarily as a result of a variation in maximal dynam

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1979.tb06439.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Smokers and nonsmokers of a homogeneous population of sedentary men have been compared with respect to skeletal muscle (vastus lateralis) morphological, metabolic and functional characteristics. The percentage type I fibres was lower and that of type IIB fibres higher in the smokers. Fibre areas were almost equal in the two groups. Muscle oxidative capacity was lowered in the smokers, as judged from decreased mitochondrial enzyme activities and a lowered fibrillar space mitochondrial volume fraction. Isometric and dynamic strengths were lower in the smokers, except at the highest velocity of movement studied. Dynamic strengths expressed in relation to isometric strength were similar at all velocities except the highest, where the smokers were relatively stronger. Muscular endurance, measured in short‐term isometric and dynamic tests, was not different. It is suggested that the lowered muscle oxidative capacity and strength in the smokers may be partly a consequence of the different fibre type distribution. A possibly lower physical activity level, and tobacco smoke constituents (e.g. carbon monoxide) may also be instrumental. It is not clear whether the different fibre type distribution in the smokers is an effect of smoking per se, or if background factors are responsibl

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1979.tb06440.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Plantar flexion strengths were studied in 30 right‐handed males. Static and dynamic maximum plantar flexion torques were recorded, knees fully extended (0°) and in 90° flexion. In five of the subjects the soleus and gastrocnemius muscle structure were studied by light microscopy and enzyme histochemistry. Specimens were obtained by needle biopsy, usually bilaterally. Intraindividual declines of force were found to be a function of angular motion velocity. Static and dynamic torques correlated significantly. Peak torques were significantly greater (mean 15%) at the 0° than at the 90° knee angle and left maximum plantar flexion torques at 0° were greater (mean 10%) than right. Mean morphometric data on the m. soleus suggested right‐left symmetry, which could not be demonstrated for the m. gastrocnemius. Fibres with low stainability for myofibrillar ATPase (Type 1 fibres) had smaller diameters, but constituted the major part of the cross‐sectional areas. In these five non‐athletes no significant correlation between data on plantar flexion strength and morphometric data on triceps surae structure could be demonstrated. On the other hand, strength covariated with calf c

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1979.tb06441.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Blastocysts recovered from mice in a state of delay of implantation were incubated for 10 h with either α‐aminoisobuturic acid (AIB) or 2,4‐diaminobuturic acid (DAB), two non‐metabolizable amino acids. The incubation medium was composed so as to maintain growth arrest of the inactive, delayed blastocysts in vitro. The blastocysts were then transferred to a complete outgrowth medium without the two non‐metabolizable amino acids to test the capacity for trophoblast outgrowth. AIB, which displays saturation kinetics, was harmless to the blastocysts even at a high concentration, while DAB at a low concentration irreversibly damaged the trophoblast cells and prevented outgrowth, probably due to nonsaturation kinetics resulting in a high intracellular accumulation. The harmful effect of DAB could be abolished by concomitant incubation withl‐alanine andl‐methionine, which compete with DAB for the same transport system, while thed‐forms of the same amino acids had little or no effect. The results suggest the presence of transport System A in mouse blastocysts growth arrested in vitro, indicating an operative carrier mechanism already during delay o

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1979.tb06442.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

The tissue/blood partition coefficient, Λtb, defined as the amount of blood having the same tracer content as one unit of tissue at diffusion equilibrium, was determined for125I‐iodoantipyrine (I‐Ap) and tritiated water (THO) in the dog kidney cortex. Measurements were made afterin vivoequilibration for 75 to 300 s and with liver circulation excluded. In 18 kidneys, Λtbfor I‐Ap averaged 1.38 (S.D. 0.13) w/w (weight/weight), without significant correlation to hematocrit (range: 23–43) or to urine pH (range 5.5–8.6). The Λtbfor THO averaged 0.97 (S.D. 0.06) v/w (volume/weight), close to the relative water contents. Erythrocyte/plasma partition for I‐Ap was 0.82 w/w, compared to a water partition of 0.72. Thus, at diffusion equilibrium the apparent I‐Ap concentration in renal cortical and red cell water exceeds that of plasma water by 14 and 60%, respectively. It follows that I‐Ap cannot be used as a general indicator for total tissue water content. When used for measurement of local blood flow and modum Kety, Λtbmust be determined for each

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1979.tb06443.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Disparate reports on intrarenal blood flow distribution prompted a direct comparison between microspheres (Ms) and inert diffusible tracers (DT). The “tissue sampling technique” for estimating local flow with DT (Kety) was adapted for the dog kidney, using125I‐iodoantipyrine (I‐Ap) and tritiated water (THO). Ms (15 μm) were injected 2–3 min prior to 10–15 s DT infusion made during continuous 1 s arterial blood sampling. Tracers were measured in 7 to 20 samples from each of the following zones: Outer, middle and inner cortex (C1, C2, C3), outer and inner halves of outer medulla (OM1, OM2), and inner medulla (IM).I‐Apand THO gave closely similar flow distributions, and average total renal blood flow (RBF) of 3.90 and 3.78 as compared to 3.94 ml/min g with Ms. Flow in C2(ml/min g) was similar with all tracers, and in per cent thereof average local flows were: C1102, C370, OM134, OM212, and IM 2 with DT versus 117, 53, 12, 3, and 0 with Ms. Zonal flow fractions of total RBF obtained with DT were: C10.41, C20.33, and C3+medulla 0.26 versus 0.51, 0.33 and 0.16 with Ms. Thus, a Ms surplus in C1relative to DT flow, representing 10% of total RBF, matched a Ms deficit in C3+medulla. This disparity might result from: (1) Failure of Ms to enter deep afferent arterioles in proportion to blood flow, (2) diffusion of DT from deep portions of the interlobular arteries, and/or (3) postglomerular inward flow o

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1979.tb06444.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY