Guanylate cyclase activity was assayed in homogenates, in particulate and soluble fractions from retina, cerebellum, cerebral cortex and adrenal gland of adult C3H/HeJ mice with a dystrophic retinopathy. In comparison to control mice (DBA/1J), in C3H/HeJ strain a significant decrease in guanylate cyclase activity occurred in homogenates from retina, cerebellum and adrenal gland. In particular a significant decrease was found in particulate fraction of retina, in the soluble fraction of cerebral cortex and cerebellum and in both fractions of the adrenal gland. In contrast to the retina and cerebellum where guanylate cyclase activity in homogenates was found significantly decreased both in the male and female, in the cerebral cortex guanylate cyclase decreased in both sexes although in female this was more marked.

Adrenal Glands↗

PubMedDate not supplied

Thyroxine effects on polyamine metabolism in rat cerebellum and brain cortex during postnatal development.

Polyamine content, ODC and SAMDC activities have been assayed in cerebellum and brain cortex of hyperthyroid rats during postnatal development. Daily thyroxine treatment induced ODC and SAMDC biosynthesis in early periods of postnatal life in both cerebellum and brain cortex. In addition, in comparison to controls an increase in spermidine and spermine content was shown to occur in hyperthyroid rats. A functional correlation between polyamine content and nucleic acids could explain a correlation between polyamine biosynthesis and morphofunctional maturative processes in the brain.

Animals↗

PubMedDate not supplied

Effects of estrogens and progesterone on GABA system in ovariectomized rat retina.

In an attempt to characterize the effect of estrogens and progesterone on retinal GABA metabolism, female Wistar Nossan rats were ovariectomized and treated for three days with 17 beta-estradiol (1 microgram/day), estrone (2 micrograms/day), estriol (200 micrograms/day) and progesterone (500 micrograms/day) or vehicle. After 3 days of steroid hormones treatment, GAD, GABA-T activities and GABA content were measured in retina homogenate. Progesterone did not reduce GAD, GABA-T activities and GABA content from ovariectomized levels. 17 beta-estradiol, estrone and estriol decreased the GAD activity. Furthermore the decrease in GAD activity was maximal for 17 beta-estradiol whereas the estrogens treatment was ineffective on GABA-T. GABA content was significantly decreased only by 17 beta-estradiol. Estrogens reduced the Vmax of GAD for glutamate as a substrate without changing the Km.

4-Aminobutyrate Transaminase↗

PubMedDate not supplied

Cysteic and cysteine sulphinic acid decarboxylase activity in rat tissues during postnatal growth.

1) Cysteic and cysteine sulphinate decarboxylase activities have been determined in rat retina, brain, liver, kidney, lung and spleen during postnatal growth. 2) The two enzymic activities increase as function of age in retina, brain and liver. 3) In contrast the cysteic and cysteine sulphinate decarboxylase activities decrease with age in kidney, lung and spleen. 4) The rate of decarboxylation of cysteine sulphinate is higher than cysteic acid and the ratio of the two decarboxylating activities for each tissue is constant; this uniformity may exclude the existence of two separate enzymes.

Aging↗

PubMedDate not supplied

Putrescine, polyamines, and N1-acetylpolyamine levels in retina, visual cortex and cerebellum of free-running mice kept under continuous light or darkness.

Putrescine, spermidine and spermine levels were detected in the retina, visual cortex, cerebellum and parietal cortex of CD1 mice exposed to 36h continuous light or darkness. Retinal putrescine and polyamine concentrations were found to be highest in dark-adapted mice, and the stimulation of dark-adapted retina with flicker illumination was also accompanied by a significant decrease in putrescine, spermidine and spermine levels. In visual cortex as well as in cerebellum spermidine and spermine contents were higher in dark-adapted mice in comparison to light-exposed animals, while in parietal cortex no significant change was found neither in spermidine nor spermine levels. In the brain areas studied flicker illumination produced no significant decreases in putrescine and polyamine contents. The total polyamines expressed as putrescine equivalents were noticeably decreased in retina, visual cortex and cerebellum of light-adapted mice. In the retina spermine/spermidine molar ratio was significantly higher than in dark-adapted mice. The administration of N1, N2-bis-(2,3-butadienyl)-1,4-butanediamine (MDL 72527) produced a strong decrease of retinal putrescine and spermidine concentrations in both dark-adapted and light-exposed mice, and in the retina of mice exposed to continuous light a significant decrease in the spermine level was also observed. According to the influence on polyamine reutilization, after the irreversible inhibition of polyamine oxidase by MDL 72527, in the retina N1-acetylspermidine and N1-acetylspermine accumulation was highest in light-adapted mice. On the contrary in visual cortex, cerebellum and parietal cortex the MDL 72527 administration produced a more marked decrease of putrescine and spermidine contents in mice kept in continuous darkness.

Animals↗

PubMedDate not supplied

Methionine activating enzyme in various human platelet populations.

Human platelets have been separated into four populations by a discontinuous sucrose gradient. MAE activity has been determined in the various platelet populations and significant differences were obtained with respect to platelet size, the large-heavy platelets showing a higher enzymatic activity than the small-light ones. These data suggest that higher MAE activity in the younger and large-heavy platelets may be responsible for a much higher biochemical and functional efficiency.

Blood Platelets↗