Endocrinologia experimentalis最新文献

Infusion of 0.5 ml kg-1 min-1 20% glucose i.v. failed to suppress the stimulatory effect of 0.25 microgram kg-1 min-1 epinephrine dissolved in and infused together with the above glucose solution on the activity of liver glycogen phosphorylase in adult male rats. However, 40% glucose solution administered in the same way abolished the effect of the epinephrine infusion completely. An i.v. pulse of 1 g kg-1 glucose in the form of a 40% solution immediately before the infusion of the same dose of epinephrine in saline had only a temporary inhibitory effect on epinephrine induced increase of phosphorylase activity. Finally, i.p. administration of 10 mg kg-1 phentolamine 60 min before epinephrine infusion in saline completely blocked the increasing effect of the latter on both liver phosphorylase and serum glucose, while that of 4 mg propranolol 30 min before the hormone failed to exert any influence. This reconfirmed the well known mediation of the glycogenolytic effect of catecholamines in adult male rats by alpha type adrenergic receptors.

The effect of natural Met-enkephalin and its analogues Tyr-D-Ala-Gly-Phe-Cys(Et) (I) and Tyr-D-Ala-Gly-Phe-Cys(Bu) (II) on serum rat prolactin and rat growth hormone levels in male rats has been studied. Met-enkephalin and both analogues increased serum growth hormone and prolactin concentration, analogue I being the most potent. Enkephalin analogue I, with isosteric isomer of methionine in Met-enkephalin, and analogue II with butyl residue showed a lower stimulatory effect than natural Met-enkephalin. Stimulatory effect of analogues I and II on prolactin and growth hormone release was found to be reversed by a simultaneous treatment with the opiate antagonist naloxone.

Growth hormone secretion after L-dopa administration (1000 mg p.o.) was investigated in young adult normal and blind volunteers. The average increment of plasma growth hormone after L-dopa stimulation in the blind was below the criterion for a positive response (less than 5 ng ml-1). The control volunteers showed normal response. After L-dopa stimulation there was a significantly diminished growth hormone response in the young adult blind compared to control volunteers.

The subject of the study was the determination of the content of vasopressin (AVP) in the cerebrospinal fluid (CSF) and of the release of this neurohormone into the fluid perfusing the cerebral ventricles. The content of AVP in CSF taken from the cerebellomedullary cistern of rats under urethane anesthesia was 27 +/- 2.97 pg/ml. AVP was released into the fluid perfusing the cerebral ventricles at the rate of 6.83 +/- 0.7 pg/ml per 30 min. Electric stimulation of preganglionic fibres to the superior cervical ganglia did not cause any alterations in AVP release into the fluid perfusing the cerebral ventricles, which evidences lack of effect of the sympathetic system on the release of this neurohormone into the cerebral ventricles.

Nuclear receptor affinity (Ka) and maximal binding capacity (MBC) for 3,5,3'-triiodothyronine (T3) in rat liver was estimated at 1, 12, 24, 48 and 120 hours after partial hepatectomy and 1, 24, 30, 40 and 120 hours after bilateral adrenalectomy and related to serum T4, T3 levels. Soluble T3 receptor fraction was prepared from purified rat liver nuclei and the values of Ka and MBC were calculated by Scatchard plot analysis from the saturation curves. As compared to sham operated rats a significant diminution in MBC for T3 (P less than 0.05) in the remaining about one third of liver tissue at 12, 24 and 48 hours after partial hepatectomy was observed. The thyroxine (T4) level in serum was diminished (with P ranging from less than 0.001 to less than 0.01) at 12, 24 and 48 hours after partial hepatectomy, while no changes in T3 serum level were found at all indicated time intervals. In contrast, no changes in Ka or MBC for T3 in rat liver nuclear receptor as well as in serum T4 and T3 levels were demonstrated 1, 24, 30, 40 and 120 hours after adrenalectomy. The data reflect an appreciable relation between nuclear receptor occupancy for T3 and serum T4 level after partial hepatectomy, serum T3 level and Ka for T3 of nuclear receptor remaining unchanged.

Twenty-four hour patterns of lutropin and progesterone pulsatile secretion base line were studied in six postpartum dairy cows. The base line of lutropin showed three peaks within 24 hours. The base line of progesterone showed two peaks which coincided in the time with the nadirs of lutropin base line. These peaks show up clearly irrespective of the stage of puerperium.

Protein--prednisolone adducts were detected by semiquantitative radioimmunoassay in both water- and urea soluble fractions of homogenates from lenses of chicken embryos, given systemically single doses (100 microliters each) of four prednisolone esters. The findings were correlated with macroscopic changes of lens transparency. The highest concentrations of protein-associated immunoreactive material were found after prednisolone sulphate application, associated with the most apparent loss of transparency.

A simple technique of chronic intraperitoneal cannulation in small laboratory animals has been described. It can be used for repeated i.p. administration of drugs without causing any remarkable disturbance to the animal as demonstrated by significantly less increase of corticosterone level compared to usual i.p. injection procedure. A simple device for producing a fixative ring on the cannula in order to hold the cannula in the proper place is described as well.

In several experiments the rats were subjected to immobilization stress (IMO) for 150 min daily for 7 to 38 days and after each IMO they were placed into individual metabolism cages. A considerable decrease of food and water intake was found even after the first IMO and lasted up to the 7th IMO. This resulted in a decrease of body weight and of diurnal urine output, while the osmolality of urine increased. However, the expected corresponding increase in urinary excretion of vasopressin (AVP) did not occur. In contrast, AVP excretion after 6th and 7th IMO decreased by about 50 per cent. In some experiments the urine was collected during the period of IMO. It was found that the total urine output sharply increased and its osmolality decreased. Moreover, the excretion of AVP decreased and the excretion of calcium and Na :K ratio in urine were elevated. After repeated IMO (i. e. after 7th, 16th and 38th IMO) all mentioned changes were still more expressed. Thus, the urine output increased more than two fold. However, the administration of dDAVP (synthetic analogue of AVP) prior to IMO resulted either in the normalization of urine output or anuria, respectively, depending on the dose administered. When 30 min portions of urine excreted during 150 min IMO were collected, it was found that during the first period, when the level of AVP in plasma was increased, the urine output was almost zero. During the second period of IMO the level of AVP in plasma decreased even bellow the control values which was accompanied by water diuresis. Similar biphasic changes were found even previously. It is suggested that the increased AVP release during the first period might be due to the physical stress stimuli (manual squeezing of animals, pain etc.), while the inhibition of AVP release during the second period may be caused by a simultaneous activation of other endocrine mechanisms (endogenous opioids, steroids, catecholamines, atrial natriuretic peptides etc.).

The effects of acetylsalicylic acid (ASA) at a dose of 800 micrograms/day per rat for 7 days on some androgenic parameters such as organ weights, succinate dehydrogenase, acid phosphatase, fructose, cholesterol and protein of testis, epididymis, vas deferens and accesory glands in adolescent male rats were investigated. The semen characteristics and scanning electron microscopy (SEM) study on sperm morphology of cauda epididymis were also carried out. The results revealed that the treatment manifested a marked effect in altering the metabolism of testis, cauda epididymis, seminal vesicle and vas deferens. The androgen antagonistic and antianabolic effects were by and large transient and reversible by ascorbic acid administration.