摘要:

Glycogen depletion of muscle fibre types I, IIA, IIAB and IIB was studied using a histochemical method to quantify glycogen content in individual fibres. The reliability was examined in 29 muscle biopsies, in which total glycogen content was compared to average periodic acid Schiff (PAS) stain intensity in sections from the same samples. Over a wide range of glycogen content (1–252 mmole glucosyl units. kg‐1wet weight) a linear relationship (r=0.93) was found between the two methods for quantification of muscle glycogen. Glycogen depletion patterns in type I, IIA, IIAB and IIB fibres were studied in 5 subjects during exhaustive bicycle exercise at 75% of VO2max. At rest before exercise glycogen content was 16% higher in type II subgroups than in type I (p<0.05).From start of exercise the same glycogen depletion rate was observed in type I and IIA.Glycogen content of Type IIAB and IIB was unchanged during the first part of exercise. Later a decrease was observed, first in type IIAB and finally in IIB, suggesting a decrease in threshold force of these fibre types. The results indicate physiological differences between the 3 subgroups of type II fibres in man, whereas at the present exercise intensity type I and IIA fibres were recruited simultaneously from st

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1984.tb07531.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

The muskoxen (Ovibos moschatus), a native of Greenland and the Canadian North West Territories, give birth in late April, and the newborn calves are known to tolerate an ambient temperature (Ta) of ‐35°C.At birth the calves weigh about 8 kg, increasing in weight with 0.6 kg. day‐1for the first 30 days. With a deep body temperature (DBT) of 39.5°C (range 37.7–41.3°C) the newborn calves are consequently able to maintain a thermogradient of at least 70°C between body core and the environment. The calves use primarily two modes of thermal protection: High metabolic heat production and prime fur insulation. Metabolic rate was about 3.5 W.kg‐1at thermoneutrality in calves aged from 8 h to 7 days. Lower critical temperature at this age was about ‐7°C and a drop in Tato ‐30°C increased metabolism to about 5.3 W.kg‐1.Upper critical temperature at age 4–7 days is as low as 20°C, while it in calves aged only 18–24 h appears to be even lower. The calves possess great amounts of brown adipose tissue (BAT) at birth. Mitochondria from the BAT deposits were isolated and found to be in an extremely loose‐coupled state with a great capacity for thermogenesis. Skeletal muscle contained very few mitochondria and is hardly employed in aerobic non‐shivering thermogenesis. Calves shiver visibly while drying just after birth, but are normally not seen shivering thereafter. The conductance value for the dry pelt of newborn calves averaged 3.2 W.m‐2.°C‐1(n=4).Wetting of the pelt with ice‐water at a Taof 3°C increased conductance to 8.8 W.m‐2.°C‐1.The conductance of the pelt was also influenced by wind, being 10 W.m‐2.C‐1at a windspeed of 10 m. sec‐1.The legs of the newborn calves are heavily furred and countercurrent circulation is not present, subcutaneous temperature just above the hooves being +29.8°C at Taof ‐24°C as compared to 37.5°C on the back. The newborn calves could cope with a Taof ‐30°C without apparent problems under experimental conditions, but they suffered hypothermia when exposed to a Taof ‐33°C in combination with wind of 10 m. sec‐1.At birth these calves are, however, able to walk, albeit with difficulty, with a DBT of 31°C.Wetting of the intact newborn calf with ice‐water at a Taof +6°C was tolerated, but the calves will most certainly succumb to the

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1984.tb07532.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

The neuronal and extraneuronal uptake of adrenaline and noradrenaline in the isolated perfused spleen of the cod has been studied using radiolabelled amines. The neuronal uptake of adrenaline shows an optimum at 0.5 μg/ml, but is less efficient than for noradrenaline in the concentration range 0.01–2.5 μg/ml. The neuronal uptake of noradrenaline accounts for 60–70% of the total (neuronal plus extraneuronal) uptake in the concentration range 0.01–1.0 μg/ml. At higher concentrations (2.5–5.0 μg/ml) the importance of the extraneuronal uptake increases for both amines, to reach more than 90% of the total uptake at 5.0 μg/ml. The extraneuronal uptake shows equal efficiency for the two amines throughout the concentration range studied. It is concluded that the cod spleen possesses a neuronal uptake mechanism which shows a higher uptake efficiency for noradrenaline than for adrenaline, while the extraneuronal uptake mechanism shows n

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1984.tb07533.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

The concentration of immunoreactive calcitonin (iCT) in human milk was 10–40 times the serum level. Thus in milk samples collected from 29 mothers within one week and from 46 mothers three months post partum the levels of iCT were respectively 2.46±0.99 ng/ml (mean ± SD) and 0.58±0.08 ng/ml. Eight of the 29 mothers delivered milk at two occasions, 1–2 and 4–6 days after delivery. There was a significant decline of iCT with about 20% during this period. One mother delivered milk for two months. During the first week after delivery the iCT decreased from 1.4 to 0.5 ng/ml and after that the iCT content remained rather constant. The level of ionized calcium (Ca++) was correlated to iCT the first week post partum (r=0.72p<0.01) but not in milk samples obtained after three months. The concentration of magnesium was weakly correlated to iCT during the first week post partum (r=0.37p<0.05).There was no correlation between iCT and the total calcium level nor to the concentration of zinc. The high concentration of iCT in milk compared to serum suggests a local production of iCT within the mammary gland or a specific transport and concentration m

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1984.tb07534.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

The effect of phentolamine on the neurogenic contractile response in vasa deferentia from rat and guniea pig was studied during Wallerian degeneration. This response was also investigated after partial denervation (surgery or chemical sympathectomy by guanethidine treatment) in vasa deferentia from guinea pig. During Wallerian degeneration the response showed a gradual increase in sensitivity to phentolamine and was abolished in the late stages. The neurogenic contractile response of the partially denervated vas deferens was blocked by low concentrations of phentolamine. It is concluded that decreased intimacy of the neuroeffector junctions leads to increased susceptibility to α‐adrenoceptor blockade of the contractile response to nerve stimulation. It is further concluded that the motortransmission in the vas deferens is essentially adrenergic. The resistance to α‐adrenoceptor blockade of the initial phase of the contractile response to nerve stimulation of intact vasa deferentia from guinea pig and rat might well be explained by the “proximity theory” of Dale&Gaddum although participation of supplementary mediators cannot be

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1984.tb07535.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

The resistance to atropine or scopolamine of the neurogenic contractile response to field stimulation of intramural nerves of the rat detrusor was studied during the early phase of Wallerian degeneration in vitro and in vivo. The neurogenic contractile response to low frequency stimulation of control bladders was completely resistant to atropine or scopolamine in vitro. As a matter of fact the response was enchanced by the drugs. In vivo a transient shortening of the response could be seen.26–34 h after bilateral extirpation of the pelvic ganglia there was prominent degeneration activity in the bladders in vitro as well as in vivo. Atropine or scopolamine inhibited this activity in vivo but enhanced it in vitro. The neurogenic contractile response to field stimulation of the bladder nerves was blocked in vivo but not in vitro by the antimuscarinic drugs 26–34 h after neurectomy. The results support the concept that the excitatory neurotransmission in the detrusor is essentially cholinergic. An explanation of the difference between the in vivo and the in vitro results based on differencies in degree of blockade of pre‐ and post‐junctional muscarinic receptors and diffusion of the antimuscarinics in the tissue is p

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1984.tb07536.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

The effects of Ca2+removal, nifedipine, and La3+on contractions induced by 124 mM K+and 10 μM noradrenaline (NA) were investigated in small mesenteric arteries from rat. Ring segments of the arteries were suspended between two steel wires in a 2.5 ml muscle bath, and the mechanical activity recorded “isometrically”.The tonic components of the contractile responses to both K+and NA were critically dependent on the presence of Ca2+in the bath solution. Nifedipine effectively relaxed K+‐contracted arteries, whereas those activated by NA were considerably less affected by the drug. Application of NA to arteries depolarized by K+in the presence of nifedipine induced a sustained tonic contraction, which was only approximately 20% smaller than that elicited by NA in “standard” Krebs solution, implicating pharmacomechanical coupling. Unlike nifedipine, La3+inhibited K+‐ and NA‐induced contractions to approximately the same extent. Re‐application of Ca2+to “Ca2+‐depleted” preparations exposed to K+and/or NA induced concentration‐dependent contractions. The experimental results suggested that the effects of K+and NA on the membrane permeability to Ca2+were additive. The Ca2+‐induced contractions were more inhibited by nifedipine in K+‐depolarized than in NA‐exposed artereis. It is concluded that K+and NA utilize partly different Ca2+entry pathways to increase the myoplasmic Ca2+concentration in rat mesenteric arteries. Whereas K+seems to promote the influx Ca2+by activation of Ca2+channels sensitive to the membrane potential, the nature of the receptor‐operated Ca2+entry p

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1984.tb07537.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

A triple‐isotope technique was used to obtain albumin clearances and blood flow in DMBA induced mammary tumours, normal lactating mammary glands and various other tissues of the rat. Albumin clearance was high both in tumours (0.0337 ml/min/100 g) and in lactating mammary glands (0.0414 ml/min/100 g).Albumin extraction (defined as the ratio of clearance over plasma flow) was exceptionally high in tumours (23times10‐4) and lactating glands (18times10‐4) as compared to all other tissues (1‐7times10‐4).This probably reflects an increased capillary permeability to macromolecules and/or a change in the relation between blood flow and available capillary surface area, both in the physiological, hormonally induced gland and in the abnormal neoplasia derived from the same tissue. Increased extravasation of albumin, together with other changes (e. g.impaired lymph formation) may be important factors behind the production of increased tumour interstitial pressure, which tend to reduce nutritional blood flow i

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1984.tb07538.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

The influence of cyclic nucleotides on meiosis in isolated rat oocytes was studied. It is known that dbcAMP inhibits the spontaneous maturation of isolated rat oocytes. However, the effect of other cyclic nucleotide derivatives upon meiosis has been poorly investigated. The present study shows that 8‐BrcAMP is comparatively ineffective in inhibiting oocyte meiosis but exerts a potent stimulatory effect on progesterone production in cumulus cells. Neither dbcGMP nor 8‐BrcGMP were able to inhibit the spontaneous maturation of cumulus‐enclosed oocytes. On the other hand, 8‐BrcGMP dose‐dependently inhibited the meiosis of denuded oocytes. This indicates that the cumulus cells may be of importance for a possible regulatory role of cGMP.These results show the differences in meiotic response to various cyclic nucleotide de

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1984.tb07539.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

The volumes of human erythrocytes after rapid and gradual swelling in hypotonic NaCl media were measured using a Coulter Counter ZBat temperatures of +4°C and +20°C together with potassium leakage, the degree of hemolysis and the ‘returning volume’, i. e., the volume in an isotonic solution to which the cells will return from that in a hypotonic solution. The methodological and systematic errors in the volume measurements were corrected by taking into account the shape dependence of the Coulter Counter and the change in cell population during hemolysis, whereafter the measured cell volume values and the comparison between them become more reliable. The curves for cell volume as an inverse function of osmotic pressure appeared to be non‐linear. The slopes were small at first but shoed a rapid increase as the cells approached their maximal volume. The critical hemolytic volume was approx.8% higher at +20°C after both rapid and gradual swelling than at +4°C and approx.4% higher after a gradual swelling as compared with a rapid swelling both at +4°C and +20°C.A decrease in temperature resulted in an increase in the critical osmotic pressure both in rapid and gradual hemolysis, but did not greatly affect the amount of prelytic K+leakage. The critical osmotic pressure was smaller in gradual hemolysis than in rapid hemolysis and the prelytic K+leakage was doubled at both +4°C and +20°C.The shifts in osmotic fragility as a function of temperature may be due to differences in the visco‐elastic properties of the cell membrane, but the shifts in osmotic fragility as a function of swelling rate may be connected with differences in potassium leakage and m

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1984.tb07540.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY