摘要:

AbstractKittens weighing 0.5 to 1 kg, corresponding to an age of 5 to 10 weeks, were subjected to immersion hypothermia to 17.4–16.2oC rectal temperature. Blood pressure, ECG, respiration, and rectal temperature were continuously recorded. Metaraminol was administered intermittently to maintain an adequate blood pressure at lower temperatures, and the animals were respirated mechanically when necessary. Only 1 out of 12 kittens developed ventricular fibrillation; the remaining animals could be re‐warmed without major complications. Under similar conditions, adult animals have previously been found to develop ventricular fibrillation constantly. Fluorescence microscopy revealed a low degree of development of cardiac adrenergic nerves compared with adult animals, in agreement with a lower concentration of cardiac noradrenaline. The possibility is discussed that the not yet fully developed adrenergic innervation of the heart in young animals may account for the higher resistance to reduction of the body temperature as compared with adult anim

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1969.tb04445.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractTo examine whether renal autoregulation was abolished by vasoconstriction and vasodilatation, experiments were performed on anesthetized dogs with intact renal circulation and nervous supply. Angiotensin or noradrenaline was infused into the renal artery at a constant rate that reduced renal blood flow (RBF) to less than half of control values. By mechanical constriction of the renal artery, perfusion pressure could be reduced to averages of 69 and 80 mm Hg respectively (74 mm Hg during control conditions), before RBF dropped more than 5%. Normal autoregulation was also obtained during intravenous infusion of angiotensin and noradrenaline. during stimulation of renal nerves, and after development of tachyphylaxis to angiotensin. At normal and low arterial pressures, but at similar RBF, noradrenaline or angiotensin was injected into the renal artery. RBF was least reduced at low perfusion pressure, indicating that autoregulation did not compensate for the vasoconstrictive effect of noradrenaline and angiotensin. By acetylcholine infusion. RBF could be doubled, and a curvilinear relationship between RBF and perfusion pressure was obtained. Similar curves could be constructed by the application of Poiseuille's law on the premise that vasoactive agents act mainly on muscle elements other than those participating in autoregulation. It is concluded that autoregulation is essentially independent of nervous and humoral stimuli.

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1969.tb04446.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractThe effects of large urine flow and high tubular pressure on renal blood flow (RBF) and glomerular filtration rate (GFR) were studied in dogs. In unanesthetized animals, ethacrynic acid and furosemide infused during hypotonic saline or mannitol diuresis increased urine flow to more than half of the filtered load without reducing GFR, whereas clearance of paraamino‐hippurate (CI’.VH) rose. In anesthetized dogs, ethacrynic acid and furosemide increased RBF. By stepwise renal artery constriction RBF was reduced in proportion to perfusion pressure, indicating abolished autoregulation. A similar moderate increase in RBF and abolition of autoregulation were also obtained by ureteral obstruction. In contrast, autoregulation was maintained until RBF was nearly doubled during infusion of saline or mannitol. During infusions of hypotonic solutions, CPAHincreased despite reductions in serum osmolality which in renal perfusion experiments led to a fall in RBF.Conclusion: High tubular or intestitial pressure acts on the autoregulating mechanism which dilates afferent arterioles until the hydrostatic pressure difference over the glomerular membrane is reestablished. By this mechanism, RBF is increased and GFR maintained at high urine flow. Vasodilating factors may be elicited during expansion of extracellular volume, but do not affect autoregulation and are without distinct effect on

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1969.tb04447.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractStudies of K42and Na24movements during the cardiac cycle were made on right ventricle from the rat and guinea‐pig, on frog atrium and on frog ventricular strips. The methods used in these studies have been described in earlier papers cited in the text. The K42study showed a cyclic leakage of radioactive potassium from the rat ventricle: no such leakage was observed in ventricle from the guinea‐pig. Both frog preparations showed an increase of K42efflux during the electrical activity. The Na24study showed a slight decrease in the radioactive sodium efflux from the rat and guinea‐pig ventricle at the depolarization phase and the first part of the action potential; in frog preparations a large increase in the activity efflux preceded by a slight decrease was observed. The possibility of mechanical artifacts is discussed and an interpretation of the results is proposed which is based on a different pattern of potassium permeability between the species, the guinea‐pig and frog showing a “rectangular” action potential and the rat a “sigmoid” action potential. The slight decrease in Na24activity preceding the mechanical systole could reflect the basic ionic mechanisms of the

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1969.tb04448.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractFetuses of guinea‐pigs, rabbits, rats and mice were obtained by caesarean section in late pregnancy. They were immediately sacrificed, and fixed by whole‐body freezing, after which transverse cryostat sections of the ductus arteriosus were prepared for morphological observations. The inner diameter and wall thickness of the ductus were measured at its narrowest part. The descending thoracic aorta of full‐term rat fetuses was treated in the same way as the ductus.In all species, the mean inner diameter of the ductus increased with fetal age, and was accompanied in the guinea‐pig and rabbit by a gain in thickness of the media. The development of an intima was most evident in rabbit fetuses. In all species, the structure of the ductal wall was comparable in the youngest and oldest fetuses.The inner diameter and wall thickness of rat and mouse fetuses near term corresponded well to values in newborns. The divergent values between fetuses and newborns of the guinea‐pig and rabbit are discussed. The relation recorded between the cross‐sectional areas of the ductus arteriosus and thoracic aorta is in agreement with the present concepts of prenatal circulation.The similarities in ductal morphology between full‐term fetuses and newborns might justify the use of full‐term fetuses in experiments on the physiology of the du

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1969.tb04449.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractFull‐term guinea‐pigs were delivered by caesarean section. Living fetuses with intact, or interrupted umbilical circulation were allowed to breathe, for periods of 5 min, air or nitrogen, or air followed by nitrogen. Animals sacrificed immediately on birth served as controls. Sacrifice was performed in liquid nitrogen.–Spontaneously delivered rats were either sacrificed immediately on birth or kept up to 4 hrs at 37° C in air or 8c/cO2 in N2, before sacrifice in isopentane. cooled by dry ice. In addition, the heart rate of newborn rats, kept at the same temperature and in the same atmospheres, was recorded. – Changes in ductal inner diameter and wall thickness were measured in cryostat sections of both species. Oxygen caused marked constriction of the ductus in the guinea‐pig. Further constriction was found in animals with a clamped umbilical cord. No evidence was obtained of an effect of nitrogen inhalation, neither on the open nor on the constricted ductus. In the rat, reduced atmospheric oxygen concentration caused a delay in ductal closure rate. Lowering of the heart rate was also observed. The present results–obtainedin vivoin the guinea‐pig and rat–show that oxygen is essential for closure of the ductus arteriosus, independent of the rat

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1969.tb04450.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractThe external pancreatic secretion of fluid, bicarbonate and protein in 4 dogs with Thomas type fistulae, has been studied in response to secretin (1 U/kg b.w.), gastrin (2 U/kg b.w.) and combined secretin–gastrin stimulation. Gastrin exerted a stimulating effect on the pancreatic secretion of fluid, bicarbonate and protein and increased the bicarbonate concentration in the juice significantly above basal level. The combined effect of secretin and gastrin on the secretion of fluid, bicarbonate and protein did not differ from the summarized effect of the two agents given separately. Potentation between secretin and gastrin was not demonstrate

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1969.tb04451.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

Abstract17 adult cats were subjected to cardiac sympathectomy under nembutal anesthesia by bilateral excision of the cervical sympathetic chains between and including the superior cervical and stellate ganglia. Immediately after operation, the anesthetized animals were cooled by submersion in an ice‐water bath. Blood pressure, ECG, rectal temperature and respiration were continuously observed. Angiotensin was administered intermittently to maintain the blood pressure at an adequate level at the lower body temperatures. Artificial respiration was applied when indicated. Under these conditions, only 2 out of 17 denervated animals died in ventricular fibrillation, at 23 and 18.4oC rectal temperature. The remaining animals were cooled to 17.7–15oC and subsequently re‐warmed to normothermia without complications. All of 17 unoperated control animals subjected to hypothermia in the same way developed ventricular fibrillation. Cardiac noradrenaline determined fluorimetrically at the end of the experiments did not differ significantly between the two experimental groups. The results of the present and earlier investigations indicate that hypothermia activates the sympathetic system through a central mechanism and that the cardiac sympathetic nerves represent an important factor for the spontaneous development of ventricular fibrillation, a characteristic complication of induced deep hypothermia in homeothermic ma

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1969.tb04452.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractIn 16 normal human subjects a study was made of averaged responses in the occipital regions to monochromatic flashes of 15 different wavelengths with equal energy. The responses to monochromatic flashes were found to have the same principal components as those previously shown in responses to white light. With low intensity flashes of equal energy, the latencies of all components were shortest in the middle range (514–576mix), longer in the blue, and longest in the red end of the spectrum. With high intensity stimuli, the latencies were in general shorter, and did not vary with wavelength. The high variability of the amplitudes of the evoked responses made it difficult to correlate amplitude with wavelength. However, some individual curves, as well as the average amplitude/wavelength curve for the whole group of 16 subjects, showed partly significant peaks at 453–475, 551 and at 615mix, a finding which appears to support the existence of a trichromatic colour receptor mechanism in man. One group of the subjects showed a strikingly stable form of the evoked responses, but varying amplitudes of separate components at different wavelengths. Another group showed very stable forms of the responses which appeared specific to wavelen

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1969.tb04453.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractThe elimination of iodine‐labelled fibrinogen was followed in 3 groups of dogs after: 1. thromboplastin infusion, 2. simultaneous infusions of thromboplastin and epsilon aminocaproic acid (EACA), and 3. simultaneous infusions of thromboplastin and Trasylol. Platelet count, fibrinogen concentration, radioactivity in plasma and in fibrinogen as well as hematocrit were determined. Thromboplastin caused changes of the same type as those previously obtained with thrombin, indicating the development of a fibrinolytic process, secondary to intravascular coagulation. The secondary changes were effectively blocked by pretreatment with EACA and Trasylol. The incidence of and mortality in thromboembolism suggest some anticoagulant effect of Trasylol. The antifibrinolytic activity of Trasylol is much stronger than the anticoagulant one. EACA too, seems to give some protection against thromboplastin‐induced coagulat

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1969.tb04454.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY