Archivio di scienze biologiche最新文献

Rat thymocytes were stimulated with phytohaemagglutinin (PHA), Concanavalin A (Con A), pokeweed mitogen (PWM) and lipopolysaccharide (LPS) or with mixtures of two of these mitogens, added simultaneously to in vitro cultures. Four-five concentrations of first mitogen were matched with four-five concentrations of second mitogen, in all possible combinations. Synergistic effects were observed with LPS plus PHA and LPS plus PWM and inhibitory effects with PHA plus Con A and LPS plus Con A. The hypothesis is discussed that an inhibitory effects occurs when two mitogens react with identical or very similar receptors on the lymphocyte surface, while a synergistic effect is produced by two mitogens reacting with different receptors.

The activity of several acid hydrolases in different sections of the C.N.S. of various mammalian has been evaluated. The enzymes which have been studied are: beta-glucosidase, beta-galactosidase, beta-N-acetylglucosaminidase, beta-N-acetylgalactosaminidase, beta-glucuronidase, alpha-mannosidase. The enzymes show a higher activity in the gray matter than in the white matter. The results are interpreted on the assumption that glyco-lipoprotein turnover is higher in the gray matter than in the white matter, since myelin, which is the major component of the white matter, is a relatively stable structures.

Isometric contraction time (CT), half relaxation time (1/2 RT), tetanus fusion frequency (TFF) and tetanus: twitch ratio (T : t ratio) were measured in the denervated (D) and tenotomized-denervated (TD) Soleus muscle of the rat. In D muscle there was an apparent speeding effect at the 2nd day after denervation, with a significant decrease of CT, which was followed by the usual slowing process of denervated muscle. In TD muscle, denervation was performed a week after tenotomy. Tenotomy "per se" was ineffective in modifying dynamic properties of muscle, but it accentuated the early shortening of CT caused by denervation, while reducing and delaying the subsequent slowing process. The results are discussed in the light of the hypothesis that muscle disuse has a speeding effect which counteracts the slowing effect of denervation, and/or that tenotomy modifies the effects of denervation by changing the pattern of fibrillation development.

The concentrations of gamma-amino-n-butyric acid in brains of rats intoxicated with half intraperitoneal LD50 ethanol were determined at various times and found increased at early times (10 min) and decreased later (1 to 3 hours). The concentration tended to be restored to normal values upon administration of n-dipropylacetate (400 mg/kg) or L-glutamine (340 mg/kg). The treatment with both substances showed a positive interaction with an overall positive effect greater than the sum of each.

Xenopus laevis adult specimens were exposed to environmental changes simulating those undergone by these animals in their natural "habitat". After keeping groups of animals under dry conditions, some of them were returned to water. In both cases some parameters were compared with those of control animals kept in water. A lower activity in the Na+/K+-dependent ATPase of the epidermis and striated muscle was detected in "dry" animals with respect to the control ones or those rehydrated whereas the same ATPase activity in the kidney was higher in "dry" animals than in those from the other groups.

Daily variations of serum and urine calcium and phosphate were determined in young and adult rats of both sexes. The animals were maintained in natural conditions of illumination and feeding ad libitum. The twenty-four hour rhythm of the serum levels and urinary excretion of these electrolytes in male rats is confirmed. This rhythm is markedly modified in young females and less in adult females. Evidence for a circadian rhythm of the Ca/PO4 ratio appears in all groups of rats. The rhythms of serum and urine Ca/PO4 rations are similar in all experimental groups.

The lipid and protein composition and the metabolic turnover of myelin in the C.N.S., are briefly reported. For a better understanding, it seemed useful to introduce some historical data on the discovery of myelin and to give a morphological description at structural and ultrastructural level.

Density gradient centrifugation analysis has been used to study rat kidney receptors for dexamethasone. Density gradients performed with cytosol incubated with 3H-dexamethasone in a Tris 10 mM, EDTA 1.5 mM, glycerol 5%, monothioglycerol 12 mM (pH 7.5) buffer never gave any good evidence of a 85 radioactivity peak probably due to instability of the complex. The stability of the complex for at least 30 h was achieved by homogenizing the tissue and incubating cytosol in a distilled water, glycerol 5% monothioglycerol 12 mM solution. Density gradient centrifugation analysis in this way showed radioactivity peak at the bottom of the tube probably due to the aggregation of the complex. Since this drawback is inherent in the technique it must be concluded that density gradient centrifugation analysis cannot be used to study the dexamethasone-receptor complex of the kidney.