摘要:

Response habituation in pekin ducks was observed during a study of the early phase of the dive response. This is interpreted as the orienting response and strongly suggests higher CNS influence in the initial phase of the forced immersion heart rate response. Repeated forced dives (20–30 s) of restrained ducks were performed with 40 s recovery period between dives. During the first dives, the ducks' heart rates fell 69% (272 ± 8 to 83 ± 32 beatsmin‐1, x̄± SE) of pre‐dive values. The extent of this bradycardia decreased progressively as the dives were repeated. After 60 dives, the heart rates dropped by only 29% (248 ± 3 to 177 ± 25 beats min‐1for pre‐dive value). Voluntary diving of the ducks, lasting 5–20 s, caused no diving bradycardia. They showed breathing tachycardia which caused a 25% increase in heart rates above diving level (160 ± 5 to 200

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1985.tb07562.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Exhaled air temperature (Te), respiratory frequency (f), and rectal temperature (Tb) were measured in two reindeer before, during and after running for 45 min at a constant speed of 9.2 km‐hr‐1on a level treadmill at different ambient temperatures (Ta), in summer with fur insulation at a minimum and in winter with fur insulation at its prime. Before and immediately after the 45‐min running period, skin temperature (Tsk) and radiative surface temperature (Tr) were also measured.Te,TskandTrdecreased at rest with decreasingTaboth summer and winter.Tbwas elevated during running except at lowTain summer. During runningTsk,Teandfwere higher in winter than in summer, whileTrwas higher in summer than in winter. The changes inTrandTskin response to running were more pronounced on the legs than on the trunk. It is suggested that in the running reindeer the body surface is an effective avenue of heat loss during summer, while heat dissipation by way of the respiratory tract attains increased importance in winter, when fur insulation is at its

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1985.tb07563.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Functional β‐adrenoceptor populations in the human heart were studiedin vitroin electrically‐paced strips of the right auricular and ventricular myocardium. The relative potency of selected agonists in producing inotropic responses (Tmax,T′max) in the presence of blockers for neuronal and extraneuronal uptakes was found to be as follows: isoprenaline>noradrenaline = adrenaline = salbutamol>dobutamine. Prenalterol had a negative inotropic effect in these preparations. The selective β1‐(practoloI) and β2‐(H 35/25) blockers reduced inotropic responses to adrenaline (Tmax,T′max) and noradrenaline (T′max) in the auricular strips. These results indicate the participation of β2‐adrenoceptors in inotropic responses in the human auricular and ventricular myocardium. For comparison, inotropic responses of electrically‐paced rat myocardium to β‐adrenergic agonists in the presence of blockers for neuronal and extraneuronal uptakes were likewise studied. The relative potencies forTmaxwere: noradrenaline = adrenaline>prenalterol>dobutamine = salbutamol. Given the high relative potency of salbutamol in the human myocardial strips (analogous to that previous shown in the β2‐dominated atria of the frog and trout) and the low relative potency of salbutamol in the rat tissue, these findings indicate a greater population of functionally active β2‐adrenoceptors in the hu

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1985.tb07564.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

The effects of insulin on pancreatic kallikrein secretion were studied in streptozotocin diabetic rats and after acute administration of insulin to normal rats. Studies on total protein and amylase secretion were included for comparison. In diabetic rats, the concentration of amylase in pancreatic tissue as well as basal and CCK‐stimulated amylase exocrine secretion were significantly reduced. Insulin treatment restored pancreatic tissue concentration and exocrine release of amylase to normal. Insulin deficiency did not induce any change in the concentration of kallikrein or trypsin‐like activity in pancreatic tissue. However, basal kallikrein secretion was higher in diabetic rats than in controls. Insulin treatment of diabetic rats did not alter basal kallikrein secretion but potentiated CCK‐stimulation of kallikrein release. In normal rats, CCK induced an increase of pancreatic protein, amylase, and kallikrein secretion but not pancreatic juice flow. Additional administration of insulin potentiated the CCK‐induced secretory rate of pancreatic juice, protein, and kallikrein but not amylase. A 1.6 times higher concentration of kallikrein was found in the portal vein than in arterial blood, indicating an endocrine release of pancreatic kallikrein. No difference in the concentration of circulating kallikrein was observed between the control and the insulin‐trea

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1985.tb07565.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Arctic reindeer exhibit marked seasonal changes in fat deposition and mobilization. At intervals throughout the year, therefore, we have measured feed intake of both Svalbard (SR) and Norwegian reindeer (NR) together with the seasonal changes in size, lipogenic and lipolytic capacity of isolated adipocytes from both sub‐species. Feed intake of both NR and SR was maximal in August, but declined thereafter, reaching minimum values in January (NR) and March (SR), 55 and 69% below the August value, respectively. NR and SR adipocyte volume changed in parallel and were reduced to the same extent (69%) from their maximum in August to their minimum in May. Adipocyte lipogenic capacity, measured as acetate incorporation into cellular lipid at saturated acetate concentrations, was lowest in January (NR adipocytes) and March (SR adipocytes), 92 and 90%, respectively, below the maximum values, which were obtained in August. Lipolytic capacity, measured as maximum adrenaline‐stimulated glycerol release, was high in SR adipocytes from March through to October and in NR adipocytes from July through to January. Minimum lipolytic capacity, on the other hand, was found in January (SR adipocytes) and March (NR adipocytes). The present findings may be explained by alterations in lipogenic enzyme activity and in the lipolytic activation sys

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1985.tb07566.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

The effects of thyroidectomy (4 weeks) on dopamine (DA) and noradrenaline (NA) turnover rates were determined by means of regression analysis. The disappearance of catecholamine (CA) fluorescence (using quantitative histofluorimetry) after tyrosine hydroxylase inhibition (α‐methyl‐DL‐p‐tyrosine methyl ester) has been investigated in discrete hypothalamic and forebrain DA and NA nerve terminal systems of the male rat. A time‐dependent monophasic CA fluorescence disappearance was observed in all CA nerve terminal systems of the sham‐operated and thyroidectomized rats. In the thyroidectomized rat, DA turnover in the anterior nucleus accumbens and in the medial and lateral palisade zones of the median eminence (ME) was reduced while DA turnover in the posterior nucleus accumbens was increased as compared to control rats. Furthermore, NA turnover was increased in the paraventricular hypothalamic nucleus (PA) and reduced in the dorsomedial hypothalamic nucleus (DM) and in the ‘border zone’ (lateral hypothalmus). Radoimmunoassay of hormones in serum demonstrated marked increases in TSH levels and reduced concentrations of GH, prolactin, corti‐costerone, triiodothyronine and thyroxine. The reduced DA turnover in the external layer of the ME and the increased NA turnover in the PA may indicate an inhibitory dopaminergic mechanism in the ME and a facilitatory noradrenergic mechanism in the PA in the regulation of TSH secretion. These mechanisms seem to interact with thyroid hormones. The reduced NA turnover demonstrated in the DM and in the border zone may be related to the lowering of growth hormone levels and pulsatility caused by thyroidectomy. Finally, the DA nerve terminal systems in the anterior and posterior parts of the nucleus accumbens are differently regulated by changes in the brain‐pi

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1985.tb07567.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

The electrical resistance of the vascular endothelium was determined on single microvessels in the hamster cheek pouch in order to obtain information about this variable in a mammalian preparation. So far, the technique has only been applied to frog microvessels. The technique consists of injection of current into the vascular lumen via a microelectrode and recording of the ensuing intravascular potential distribution by a second microelectrode. Cable theory was used for the analysis. The average diameter of the vessels under study was 41 μm for arterioles and 28 μm for venules. The average resistance of the vessel wall at 37oC was 19 ωcm2and 3.3 ωcm2, respectively. For the venules this is somewhat lower than what has been recorded on muscle capillaries (Olesen&Crone 1983) in the frog at room temperature, whilst the values on arterioles are rather similar. The calculated sodium permeabilities,PNa+, were for arterioles 4 ± 10‐5cm. s‐1and for venules 23 × 10‐5cms‐1. The high permeability values for arterioles and venules indicate that the vascular exchange function may not be limited to cap

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1985.tb07568.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY