摘要:

Male weanling Wistar rats were castrated or sham‐operated and followed for 12 weeks without substitution or with large (2 mg‐ 14 days‐1) or small (0.2 mg 14 days‐1) intramuscular dose of testosterone enantate. Castration without substitution was associated with lower body weight and smaller fat cell sizes in different adipose tissue depots. The epididymal and caudal subcutaneous depots were the most sensitive to castration. The percentage of fast‐twitch high‐oxidative (type II A) muscle fibers decreased in the non‐substituted castrated animals. There was a decrease in phosphorylase and lactate dehydrogenase activities in the white portion of the gastrocnemius muscle of the castrates. These changes were reversed by the large dose of testosterone. Removal of testosterone by castration thus seems to “feminize” male rats with respect to body composition and

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1980.tb06592.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

The cytoplasmic form of human renal carbonic anhydrase, CA‐C (carbonate dehydratase, EC 4.2.1.1), purified by affinity chromatography, was characterized kinetically at 37°C in 25 mM N‐methyl imidazole buffer, 1=0.15, pH 7.1, using a pH‐indicator stopped‐flow technique. Under these conditions the rate constants for the uncatalyzed hydration of CO2and dehydration of H2CO3were 0.12 s‐M1and 0.60‐s‐1, respectively. The kinetic parameters for CA‐C were found to be: Hydration reaction, Km=11.8 mM, V/[E]0=10.6 × 105· s‐1, dehydration reaction, Km=70 mM, V/[E]0=5×105· s‐1. In the hydration reaction CA‐C was non‐competitively inhibited by acetazolamide, Ki= 16 nM, sulfanilamide, Ki=8 μM, and chlorothiazide, Kil μM. The levels of immunoassayable CA‐C in cortex, medulla and papilla of perfused donor kidneys were 1.3, 1.0 and 0.6 mg enzyme protein/g tissue protein respectively which corresponded well with the levels measured catalytically. The erythrocyte form, HCA‐B, was also detected immunochemically (˜0.1 mg/g protein) but is thought to be a contaminant. Calculations indicated that the uncatalyzed hydration of CO2in the tubular cells can support 17 or 0.7% of the rate of urine acidification, dependent on whether the cellular alkaline pH‐disequilibrium during acid secretion is 0.1 or 0.01 pH units, respectively. CA‐C accelerates the hydration rate 6800‐fold which enables the cell to sustain high rates of proton generation, while maintaining near CO2‐equilibrium and maximal buffering capacity. Even at an assumed pH‐disequilibrium of only 0.01 pH‐unit, CA‐C is present in 50‐fold excess of apparent physiological needs. When the enzyme is inhibited the rate of the uncatalyzed reaction increas

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1980.tb06593.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

Pial arterial vessels were inspected in hypercapnia (PaCO297±9 (S.E.) mmHg) and in acute hypertension induced by 5 μg kg‐1noradrenaline i.v. (mean arterial pressure 210±5 mmHg) by means of a cranial window. The diameter of arterial vessels with a resting diameter of 10 to 150 μm was measured either from photographs or by aid of an image splitting eyepiece. Arterioles with a resting diameter ≫30 μm exhibited the highest degree of dilatation both in hypercapnia and acute hypertension. The mean dilatation was higher in hypertension than in hypercapnia in vessels of all sizes, the difference being statistically significant in arterioles up to 50 μm resting

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1980.tb06594.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

The effect of bilateral hindlimb occlusion on the distribution of renal cortical blood flow was investigated in anesthetized dogs. Local blood flow in outer cortex (OCF) and in inner cortex (ICF) was measured by 6 platinum electrodes recording hydrogen gas clearance. Renal blood flow fell unsignificantly while hematocrit (Hct) rose from 37 to 47% during the 4 h tourniquet period. After the release of the tourniquets average arterial blood pressure fell to about 75% of control, whereas OCF and ICF were proportionately reduced towards 30—40% of control. Hct increased to 58%. Patchy, intermittent ischemia in outer and inner cortex was irregularly observed after release of the tourniquets when Hct had increased markedly, as previously found during dehydration and endotoxin shock. The sudden shifts in washout rates from single electrodes were not accompanied by corresponding variations in total renal blood flow. Heparinization or α‐receptor blocking did not suppress the appearance of abrupt flow changes in this period. However, sudden shifts in local flow were also seen shortly after application of the tourniquets, before Hct had increased, in this phase possibly induced by an increased renal nervous tone. In conclusion: OCF and ICF fell to the same degree during tourniquet shock. Patchy, intermittent ischemia was observed in the renal cortex, most frequently at high Hct, but also before Hct did

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1980.tb06595.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

It was recently reported that administration of sulphonylureas may lead to a stimulation of the release of glucagon and a gastrin‐like peptide. These peptides may then eventually influence the insulin releasing action of the sulphonylureas. Therefore, the effects of glucagon and pentagastrin on basal and glibenclamide‐induced insulin secretion were studied. It was found that at a dose of 4.25 nmol/kg the two peptides induced a significant stimulation of basal insulin secretion. However, pentagastrin at the dose of 4.25 nmol/kg did not influence the insulin release induced by glibenclamide, whereas an equimolar dose of glucagon potentiated the insulin secretory response to this sulphonylurea drug by about 40%. Glucagon in contrast to pentagastrin thus positively modulates the insulin secretory pathway stimulated by the sulphonylurea drug glibenclam

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1980.tb06596.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

The relationships between capillary diffusion capacity (PS) for Cr‐EDTA respective capillary filtration capacity (CFC) and vascular resistance during graded intraarterial infusions of NA and 5‐HT into the artificially constant flow perfused rat hindquarter vascular bed were investigated. During maximal vasodilatation PS for Cr‐EDTA was some 5.5‐5.7 m//min × 100 g, CFC some 0.04 ml/min × mmHg × 100 g, while vascular resistance was 2.8 mmHg × ml‐1× min × 100 g (PRU100) and isogravimetric capillary pressure 12.8 mmHg on an average. Setting out from maximal vasodilatation, increasing doses of NA and 5‐HT produced graded reductions in capillary surface area as reflected by progressive decreases in both PS for Cr‐EDTA and CFC. These changes occurred simultaneously with progressive increases in both pre‐ and postcapillary resistances, causing elevations in both arterial and capillary hydrostatic pressures and hance in capillary fluid filtration at constant flow. Capillary hydrostatic pressure increased maximally to 45 mmHg (calculated for NA) and vascular resistance to some 21 mmHg × ml‐1× min × 100 g on an average. PS for Cr‐EDTA decreased maximally to some 0.7‐1 ml/min × 100 g for both NA and 5‐HT and, furthermore, the relationships between PS for Cr‐EDTA and PRU100for NA respective 5‐HT were almost identical. This was taken to indicate that capillary surface area for nutritional exchange is affected similarly by both drugs. However, the CFC‐PRU100relationship was shifted towards some 30–50% higher CFC values for 5‐HT than for NA at almost every level of vasoconstriction. This might suggest that 5‐HT besides reducing capillary surface area also induces moderate increases in capillary permeability through increases in number and/or radius of large pores (gaps) (cf. Rippe, Kamiya&Folkow 1978). Even during NA‐induced vasoconstriction, when virtually no changes in capillary permeability occurred, PS for Cr‐EDTA was reduced to a relatively greater extent than CFC, the discrepancy being most pronounced during marked vasoconstricti

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1980.tb06597.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

Two alkaline RNases, designated RNase 1 and RNase 2, were isolated from the culture media of silica‐treated and non‐treated macrophages. The yield of RNase from the medium of silica‐treated macrophages was 30% of that from the non‐treated control. The effects of these RNases on cultured granuloma fibroblasts and on granulation‐tissue nuclei were studied. RNase 1 inhibited thymidine incorporation into fibroblasts except at low concentrations, where it was observed to be stimulatory. RNase 1 also inhibited the protein synthesis of fibroblasts. The incorporation of cytidine into RNA in cultured fibroblasts was not affected by RNase 1, but the incorporation into isolated nuclei was decreased. In pulse chase experiments RNase 1 increased the release of cytidine, but not that of thymidine, from the cells. RNase 2 had no effect on the protein or nucleic acid metabolism of the fibroblasts or on the RNA metabolism of isolated nuclei, perhaps because of impermeability. These experiments confirm that macrophage RNase activity is able to regulate the metabolism of granulation‐tissue fibroblasts by increasing RNA degradation. Through this action it also regulates DNA and protein synthesis and other metabolic functions of

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1980.tb06598.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

The development of ectopic n.m.j.s. between the transplanted superficial fibular nerve and the soleus muscle has been studied in adult rats. Impulse conduction in the sciatic nerve was blocked chronically and synapse formation between the blocked fibular nerve and the paralysed soleus was compared with synapse formation between non‐blocked fibular nerves and denervated soleus muscles. Nerves with conduction block readily made new n.m.j.s. Thus 6 and 10–14 days after the onset of the block the number of newly innervated muscle fibres, the percentage of innervated fibres responding with action potentials and the frequency of m.e.p.p.s. at new junctions were comparable to that observed during innervation by non‐blocked nerves. Muscle fibres innervated by both the original soleus nerve and the foreign fibular nerve were regularly encountered in the impulse blocked preparations. Junctions formed by impulse blocked fibular nerves had either no or very little AChE activity 10–15 days after the onset of the block. The evidence for this was 1) weak staining for ChE; 2) prolonged rise time and ½ decay time of m.e.p.p.s.; 3) positive correlation between m.e.p.p. amplitude and ½ decay time and 4) insensitivity to anticholinesterases. In contrast, junctions formed by non‐blocked fibular nerves had strong AChE activity by these criteria at corresponding times. AChE activity at the original soleus endplates was much reduced 10–15 days after the onset of con

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1980.tb06599.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

Autonomic nervous alterations have generally been held responsible for the bradycardia of the endurance athlete. In order to determine whether there is also a non‐autonomic component in the bradycardia of long‐term training, we compared the intrinsic heart rate (HR) of highly trained bicyclists (heart volume: 995±155 ml) with that of untrained men (heart volume: 805±195 ml) at rest and during bicycle ergometer exercise at 50, 75 and 100% of maximal oxygen uptake (VO2max.) Intrinsic HR was achieved by combined vagal and beta‐adrenergic blockade with atropine and propranolol or metoprolol (cardioselective) injected intravenously. Intrinsic HR was significantly lower in trained (T) than in untrained (UT) at rest and at all levels of exercise. The chronotropic reserve from resting HR to maximal HR was identical in the two groups. Nearly identical intrinsic HRs were achieved with atropine and either beta‐adrenergic antagonist. HR differences between T and UT were very similar in magnitude—approximately 13 beats/min—at rest and during exercise at a given percentage of VO2max, with and without autonomic blockade. Evidence is thus provided for a non‐autonomic component in the bradycardia of well‐trained men which may be responsible for a parallel downward shift in the relationship between HR and percentage of VO2max. The lower intrinsic HR in well‐trained men might be explained by, i.a. the

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1980.tb06600.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

In order to assess the influence of severe hypoglycemia on local cerebral blood flow (1‐CBF) artificially ventilated rats, maintained on 70% N2O, were injected with insulin to provide either an EEG pattern of slow‐wave poly spikes, or cessation of spontaneous EEG activity for 5, 15, or 30 min (“coma”). In other animals, glucose was injected at the end of a 30 min period of “coma” and 1‐CBF was measured after recovery periods of 5, 30, 90, or 180 min. Local CBF was measured autoradiographically with14C‐iodoantipyrine as the diffusible tracer. In the slow‐wave poly spike period 1‐CBF was increased in most of the structures studied, and reached values that were 1.4 to 3.2 times greater than control. In many structures, cessation of EEG activity was accompanied by a further increase in 1‐CBF, with some structures (thalamus, hypothalamus, pontine gray, and cerebellar cortex) showing flow rates of 400–500% of control. The increase in 1‐CBF was unrelated to arterial hypertension, hypercapnia, or hypoxia. 5 min after glucose injection the hyperemia persisted in only some of the structures studied; in others, the 1‐CBF were close to, or below, control values. During the subsequent recovery period 1‐CBF was markedly reduced with some structures (cerebral cortical areas, hippocampus, and caudate‐putamen) showing flow rates of only 20–35% of control. In others, notably pontine gray and cerebellar cortex, secondary hypoperfusion was never observed. The hypoperfusion was unrelated to arterial hypotension, hypocapnia, or increase in intracranial pressure. It is concluded that, like hypoxia and ischemia, substrate deficiency due to hypoglycemia is accompanied by vasodilatation in the brain. Furthermore, like long‐lasting ischemia, severe hypoglycemia is followed by a delayed hypoperfusion syndrome that, by restricting oxygen supply, may well contribut

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1980.tb06601.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY