摘要:

Receptor activation on the cell surface is coupled through a guanine nucleotide regulatory protein to polyphosphoinositide phosphodiesterase. The activation of this enzyme catalyses the hydrolysis of phosphatidylinositol biphosphate. One of the products of this hydrolysis is diacylglycerol, which activates protein kinase C. It can also be activated by tumour‐promoting phorbol esters. The synthetic diacylglycerol, 1‐oleoyl‐2‐acetyl‐rac‐glycerol (OAG) and the phorbal ester 12‐O‐tetradecanoylphorbol 13‐acetate (TPA) have been used to stimulate protein kinase C in a pure population of rat peritoneal mast cells. Both of them caused histamine release, but the rate of release with TPA or OAG alone was slow. The release was inhibited by blocking the oxidative energy metabolism with antimycin A, and was associated with progressive exocytosis, showing that it is a secretory process. Studies on the interaction between the stimulation of protein kinase C by OAG/TPA and the secretagogues showed a dual effect, both potentiation and inhibition. Antigen (in sensitized cells) and compound 48/80 showed this pattern of response. With the calcium ionophore, A23187, potentiation was the dominant effect, although some inhibition could be shown with TPA. This is possibly related to the large calcium influx which causes translocation of protein kinase C to the membranes and enhances its activity. The potentiation suggests that protein kinase C is involved in the secretion process by the secretagogues, while the inhibition reflects a regulatory function, which is apparently exerted through an inhibition of phosphatidylinositol breakdown.Calcium uptake was enhanced by both TPA and OAG. Protein kinase C may thus contribute to the replenishment of the intracellular calcium stores after the s

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1990.tb08930.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

The circulatory effects of morphine abstinence have recently been found to involve decreased renal sympathetic nerve activity and increased mean arterial pressure, induced by vasoconstriction. A direct influence of morphine withdrawal on the peripheral vasculature could possibly contribute to the increased resistance. Therefore, contractile responses to transmural nerve stimulation and to applied noradrenaline of peripheral arteries from morphine‐dependent and untreated rats were examinedin vitrounder paired conditions.No increase in contractile response was observed after chronic morphine treatment, either on nerve stimulation or on applied noradrenaline. Instead the smooth muscle sensitivity to adrenergic stimulation was reduced. Consequently, the present study does not support a peripheral adrenergic origin of the vasoconstriction during naloxone‐precipitated morphine abstine

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1990.tb08931.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

The effect of a carbohydrate‐rich meal on subcutaneous adipose tissue blood flow was studied with and without continuous i. v. infusion of propranolol in healthy volunteers.The subcutaneous adipose tissue blood flow was measured with the133Xe washout method in three different locations: the forearm, the thigh and the abdomen. The subjects were given a meal consisting of white bread, jam, honey and apple juice (about 2300 kJ). The meal induced a twofold increase in blood flow in the examined tissues. Propranolol abolished the flow increase in the thigh and the abdomen and reduced it in the forearm. This indicates that the mechanism for the flow increase is elicited by a stimulation of vascular β‐adrenoceptors in the subcutaneous adipose tissue, since the β‐adrenoceptor inhibition did not affect the overall metabolic and hormonal responses to t

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1990.tb08932.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

The markers, bovine IgG (BIgG, mol. wt = 150000 Da) and bovine serum albumin (BSA, mol. wt = 67000 Da) together with I‐deamino‐cysteine‐8‐D‐arginine vasopressin (dDAVP, mol. wt = 1067 Da), were intratracheally instilled into young and adult rats and their passages via the respiratory tract were assessed as immunoreactive marker levels in blood serum.In the adult rats (100–120 days old) the BSA serum levels peaked 16–24 h after instillation and with a calculated transferred amount (bioavailability) of 4.3 ± 1.7 to 5.6 ± 1.4% of the dose given (five resp. 50 mg kg‐1body wt). BIgG passed via the respiratory tract with a maximum at 16 h, and with a transferred amount of 1.5 ± 0.3%, while dDAVP serum levels peaked at I h and with a transferred amount of 20 ± 4%. For the 30‐day‐old rats, similar passage time curves were obtained as for the adult, but the transferred amount was lower for BIgG (0.7 ± 0.3%), similar for BSA (4.1 ± 1.1%) and higher for dDAVP (45 ± 16%). The serum levels of BSA increased linearly with increasing dose instilled (2.5–200 mg kg‐1body wt), indicating a passive transepithelial transport route.The results show that macromolecules pass via the respiratory tract into the circulation of the rat in mainly intact forms and in high amounts, compared with passage via the GI tract. There appears to exist an inverse relationship between the molecular weights of instilled molecules and the transferred amount, a relationship affected

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1990.tb08933.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

The present study documents the effects of hypophysectomy and the effects of dexamethasone substitution on the NaCl‐stimulated release and on the basal secretion rates of ANP from the rat atriain vitro. We also measured the concentration of mRNA in the atria after hypophysectomy. Rats (n= 12) were subjected to hypophysectomy by a parapharyngeal approach. One group of rats (n= 6) received dexamethasone 0.2 mg s. c. daily for 4 weeks, while the other group was left unsubstituted. After 4 weeks, the atrial block (n= 10) was excised, placed in an organ bath (field stimulation 4 s‐1, 20 V, I ms; resting tension = 5 mN) and superfused (7 ml min‐1) either with a physiological buffer solution (295 mosmol kg‐1) or with a hyperosmotic NaCl solution (330 mosmol kg‐1). The atria from the hypophysectomized rats did not respond to the stimulus: the concentration of ANP in the I‐min samples of the perfusate was under 100 pg ml‐1. Dexamethasone treatment significantly (P<0.05) increased the ANP concentration to a maximum of 165 ± 17 (mean ± SEM) pg ml‐1during the superfusion while the control concentration was 110±19 pg ml‐1. The ANP mRNA/18 S RNA ratios did not differ between the atria of hypophysectomized and control rats.In conclusion, glucocorticoids are required in the stimulus‐induced release of ANP and the impaired release of ANP after hypophysectomy does not depend on an imp

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1990.tb08934.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Grey seal pups (Halichoerus grypus) were collected at the time of weaning (mid‐October) and fasted for 52 days at thermoneutrality in separate cages. Body weight decreased exponentially, while metabolic rate dropped 45% from an average of 2.95 ± 0.15 (SEM) W kg‐1at day 2 of fasting to a stable level of 1.62 ± 0.06 (SEM) W kg‐1from day 10 to day 47 of fasting. Respiratory quotient was low, indicating extensive catabolism of triglycerides, while plasma cortisol was fairly stable at 110 ± 8 (SEM) nmol 1‐1throughout the fasting period. Daily urinary output decreased from 236 ± 20 (SEM) ml day‐1at day 2 to a stable value of 87 ± 6 (SEM) ml day‐1between days 8 and 50 of fasting. The urine was analysed for urea, uric acid, creatinine, ammonia, total nitrogen and osmolality. Urea was always the principal excretory end‐product, amounting to between 70 and 80% of the total excreted nitrogen. The urine was moderately concentrated (range 770–1300 mosmol kg‐1). Total excreted urinary nitrogen decreased by 68% from 3.7±0.7 (SEM) g day‐1to 1.2 ± 0.4(SEM) g day‐1between days 2 and 50. The urinary nitrogen was used to calculate the daily amount of protein being oxidized and its energy content was compared with the measured basal metabolic rate of individual animals. Approximately 6% of the energy expended by grey seal pups during the post‐weaning fast is derived from oxidation of protein. It is concluded that a rapid depression of basal metabolic rate and extensive blubber catabolism enable grey seal pups to endure prolonged periods of fasting without any apparent

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1990.tb08935.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

In order to find out whether damage of the visual cortex (area 17) of the brain results in a functional reorganization of the motor cortex, experiments were carried out with freely moving rabbits performing a food acquisition task in an experimental cage. Two rabbits served as controls, while in three rabbits the visual cortex was bilaterally damaged. Analysis of the activity of 575 neurons in the control and operated rabbits after the recovery of the original instrumental food acquisition behaviour revealed a marked difference in the behavioural specialization of the neurons in the motor cortex of two operated rabbits compared with the control animals. Although the same types of units as in the control rabbits could be found in the operated rabbits (M neurons activated in relation to body and limb movements, S neurons activated in relation to food seizure and L neurons activated in relation to learned food acquisition task), the number of S units was about half of that in the controls and the number of L units about double. The relative number of activations of the neurons in the operated rabbits was significantly less frequent during the food seizure and more frequent during the learned behaviour. This difference indicates a change in the pattern of behavioural specialization of the neurons in the motor cortex due to the damage of the visual cortex. In this reorganization, the motor cortex became more like (but not identical to) visual and limbic cortices that normally contain noticeably more L neurons than the motor cortex. The number of neurons activated in relation to the behaviour in the operated rabbits, as compared with the control animals, was smaller in the upper and larger in the lower layers of the motor cortex. This may indicate recruitment of new neurons from the lower cortical layers.

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1990.tb08936.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1990.tb08937.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1990.tb08938.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1990.tb08939.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY