Effects of L-triiodothyronine on tubulin content in developing male and female rat brain

The tubulin content and biochemical components were determined in the cerebrum, cerebellum and hypothalamus from intact and T3-treated male and female rats during early life. T3-treatment between 0 and 9 days of age increased soluble protein, RNA DNA and tubulin content (mg per g tissue) in the 10-day-old male cerebellum but not in the cerebrum and hypothalamus except for soluble protein and tubulin (mg per g tissue), respectively. Intracellular tubulin content (mg per mg DNA) was increased by the T3-treatment in the 10-day-old male hypothalamus but not the other regions. When T3 was administered between 10 and 19 days, there was little effect of the treatment; increased tubulin (mg per g tissue) in the cerebrum and decreased RNA (mg per g tissue) and a ratio of tubulin to protein in the cerebellum from 20-day-old males. Less response to T3-treatment was observed in female cerebrum and hypothalamus but not in the cerebellum, compared with the male. These results suggest that the effect of T3-treatment on brain is modified by several factors such as tissue specificity, age-dependency and sexual differences. Modification by these factors might depend, at least in part, on changes in the number of T3-receptors due to the hormone treatment.     

DNA,RNA, protein and DNases in developing rat cerebellum: Effects of early postnatal nutritional deprivation

The effect of early postnatal undernutrition and subsequent rehabilitation on wet weight, DNA, RNA, protein and the activities of acid and alkaline DNases in the cerebellar region of rat brain was studied. The cerebellar region was found to be affected significantly during early undernutrition. Further, earlier the initiation of nutritional rehabilitation the better was the recovery and in some cases timely nutritional rehabilitation resulted in better than normal biochemical composition of the brain. The specific activities of acid and alkaline DNases were not affected by early undernutrition. However, the total activities of these enzymes were significantly low in undernourished rats (R1₁₅ and R₂₁) Rehabilitation of these deprived groups upto 150 days resulted in higher amounts of these enzymes as compared to those of age-matched controls. It is concluded that the two DNases, are synthesized in a preferential manner during rehabilitation, It is further concluded that cerebellar region, in terms of development schedule and response to imposed calorie restriction, is intermediary between grey and white matter regions.     

Mitochondrial DNA,RNA, and protein synthesis in different regions of developing rat brain

In vivo and in vitro (tissue slices) incorporation of labeled precursors into DNA, RNA, and proteins was measured in mitochondria obtained from cerebral hemispheres, cerebellum, and brain stem of rats at different days of postnatal development. To compare the synthesis of macromolecules in mitochondria with that in other subcellular fractions, the incorporation of labeled precursors into DNA, RNA, and proteins extracted from nuclei and into RNA and proteins extracted from microsomes and cytoplasmic soluble fractions was also measured.The results obtained showed that the incorporation of [³H]thymidine into DNA and of [¹⁴C]leucine into proteins of nuclei and mitochondria from the various brain regions examined decreased during postnatal development, however, at 30 days of age the specific radioactivity of mitochondrial DNA was higher than that of nuclear DNA. [³H]Uridine incorporation into RNA decreased from 10 to 30 days of age in nuclei while in mitochondria it was quite similar at both ages. This result may be due to a faster turnover of mitochondrial RNA compared to that of mitochondrial DNA and proteins. The results obtained suggest an active biosynthesis of macromolecules in brain mitochondria and might indicate an intense biogenesis of these organelles in rat brain during postnatal development.Preliminary reports of these results were presented at the XI FEBS Meeting, Copenhagen, August 14–19, 1977, Poster number A2-2-155-3, and at III Meeting of Italian Biochem. Soc., Siena, October 3–5, 1977, Abstract C6.     

Mitochondrial DNA, RNA and protein synthesis in normal and hypothyroid developing rat liver

Mitochondrial DNA, RNA and protein synthesis in normal and hypothyroid rat liver between the ages of -3 and 21 days were followed. In normal rats DNA polymerase activity and protein synthesis behaved similarly, showing two peaks of activity, one at -3 and the other at 21 days of age. RNA polymerase activity did not change between days -3 and 14, whereas it increased by 21 days of age. Hypothyroidism delayed the developmental pattern of DNA polymerase activity, affected RNA polymerase activity only at 21 days, whereas it inhibited protein synthesis at birth and in the third week of life. The cytochrome aa3 content appeared to be affected by hypothyroidism at birth and at 21 days of age.     

Elevated corticosterone levels in stomach milk,serum, and brain of male and female offspring after maternal corticosterone treatment in the rat

Early influences such as maternal stress affect the developmental outcome of the offspring. We created an animal model of postpartum depression/stress based on giving high levels of corticosterone (CORT) to the rat dam, which resulted in behavioral and neural changes in the offspring. This study investigated whether highly elevated levels of maternal CORT during pregnancy or the postpartum result in higher levels of CORT in the stomach milk, serum, and brain of offspring. Dams received daily injections of CORT (40 mg/kg) or oil (control) either during pregnancy (gestational days 10–20) or the postpartum (Days 2–21). Pups that were exposed to high gestational maternal CORT had higher CORT levels in serum, but not in stomach milk or brain, on postnatal day (PND) 1. However, on PND7, pups that were exposed to high postpartum maternal CORT had higher CORT levels in stomach milk and brain, but not in serum. Conversely on PND18, pups that were exposed to high postpartum maternal CORT had higher CORT levels in serum, but not in brain (prefrontal cortex, hypothalamus, or hippocampus). Moreover, 24 h after weaning, there were no significant differences in serum CORT levels between the groups. Thus, CORT given to the dam during pregnancy or the postpartum results in elevated levels of CORT in the offspring, but in an age‐ and tissue‐dependent manner. Developmental exposure to high CORT could reprogram the HPA axis and contribute to the behavioral and neural changes seen in adult offspring. © 2010 Wiley Periodicals, Inc. Develop Neurobiol 70: 714–725, 2010     

Thyroxine-induced changes of hepatic glucose-6-phosphatase activity and glycogen, protein, RNA and DNA contents in the rat

Thyroxine (T4) in a dose of 0.1 microgram per g body weight caused in the rat a significant increase in hepatic glucose-6-phosphatase activity, while a reduction of this enzyme activity was observed after 1 microgram of T4 per g. The hepatic glycogen content was found to be depleted and a marked elevation in protein, RNA and DNA contents were observed after both doses of T4.     

Changes in DNA,RNA, protein and the activities of acid and alkaline DNases in developing and aging rat cerebellum

The content of DNA, RNA and protein in cerebellum at different stages of the life span of rat as well as the ratios of protein to DNA, showed-that in this region extensive cell proliferation occurs between the 1st and 7th day after birth and once again between the ages of 225 and 750 days. The putative DNA degrading enzymes, acid and alkaline DNases, showed a positive correlation with the rapid DNA accretion noticed during developmental stages as well as during old age. From these results, it could be presumed that there was a second bout of glial cell multiplication in aging cerebellum and that DNases must be playing some important role in the process.     

Effects of corticosterone on connectin content and protein breakdown in rat skeletal muscle

We examined the effects of a glucocorticoid, corticosterone, on calpain activity, connectin content and protein breakdown in rat muscle. The results indicated that calpain activity was increased by corticosterone and thus breakdown of connectin was stimulated followed by increased breakdown of skeletal muscle protein.     

Changes in RNA,DNA, protein contents and growth of turbot Scophthalmus maximus larvae and juveniles

The growth potential of turbot Scophthalmus maximus larvae and juveniles was studied using nucleic acid‐based indices and protein variables. The experiment was carried out from 4 to 60 days post hatching (dph). A significant increase in instantaneous growth rate during metamorphosis and retarded growth rate during post‐metamorphic phase were observed. Ontogenetic patterns of DNA, RNA and protein all showed developmental stage‐specific traits. The RNA:DNA ratio decreased up to 12 dph, then increased rapidly till 19 dph and fluctuated until 35 dph followed by a decline to the end. The RNA:DNA ratio was positively correlated with growth rate of juveniles during the post‐metamorphic phase, whereas this ratio was not a sensitive indicator of growth during the pre‐metamorphic phase and metamorphosis. The protein:DNA ratio showed a similar tendency to the RNA:DNA ratio. Changes of DNA content and protein:DNA ratio revealed that growth of S. maximus performed mainly by hyperplasia from 4 to 12 dph and hypertrophy until 21 dph during the pre‐metamorphic larval phase. Growth was dominantly hypertrophical from the early‐ to mid‐metamorphosing phase and hyperplastic thereafter. The results show that the DNA content and protein:DNA ratio can evaluate growth rates of larval and juvenile S. maximus on a cellular level.     

Effects of chronic hypogonadism on corticosterone secretion and cyclic AMP production in male rat adrenocortical cells

AIM: To determine the secretion of corticosterone (CCS) both in vivo and in vitro during different intervals after orchidectomy in male rats. METHODS: Three- and 12-month-old rats had been orchidectomized 0, 3, 6, or 9 months before decapitation. RESULTS: Orchidectomy increased the concentrations of plasma CCS, the basal release of CCS, and the adenosine 3', 5'-cyclic monophosphate (cAMP) production in rat zona fasciculata reticularis (ZFR) cells. The forskolin/3-isobutyl-l-methylxanthine-stimulated releases of CCS and cAMP production by ZFR cells were higher in rats with chronic hypogonadism. The CCS release from ZFR cells of orchidectomized rat was not altered by 8-bromo-cAMP treatment. Orchidectomy enhanced the stimulatory effect of deoxycorticosterone on CCS release in ZFR cells. CONCLUSION: These results suggest that orchidectomy-related increases of CCS secretion in rats are associated with an increase of adenylate cyclase activity, cAMP generation, and 11-beta-hydroxylase activity in ZFR cells.     

Quantitation of mitochondrial DNA,RNA, and protein in starved and starved-refed rat liver

The purpose of this study was to investigate the problem of mitochondrial biogenesis in rat liver. The approach consisted of isolating mitochondria from control, 6 day starved and 6 day starved-5 day refed rats and comparing their DNA, RNA and protein content. This was performed by isolating the mitochondria by reorienting rate zonal centrifugation in sucrose gradients. It was found that six days of starvation resulted in a loss of 30% of the body weight, 55% of the liver weight, 40% of the mitochondrial protein, 60% of the mitochondrial RNA, but only 20% of the mitrochondrial DNA. It was also shown that refeeding of the rats for five days resulted in a restoration to normal or near normal levels in all the parameters measured. Further experiments employing the incorporation of ³H-TTP into isolated mitochondria indicated that the maintenance of mitochondrial DNA was not the result of continuous DNA synthesis.     

Effects of corticosterone on the negative feedback action of testosterone, 5 alpha-dihydrotestosterone and estradiol in the adult male rat

Corticosterone acetate (10 mg/day) was administered to gonadectomized and adrenalectomized male rats bearing 5, 10 or 15 mm long testosterone filled silicone elastomer capsules. It was found that the serum testosterone levels induced by these capsules were not influenced by corticosterone treatment and that the weights of the prostates in the corticosterone treated rats were not different from their controls. In contrast, corticosterone acetate increased markedly the LH and FSH inhibitory effects of testosterone. Since several brain structures are able to convert testosterone into 17-beta-hydroxy-5-alpha-androstan-3-one (5-alpha-dihydrotestosterone) and/or estradiol, and these metabolites are probably involved in mechanisms controlling gonadotropin secretion, we studied also the effects of corticosterone on the feedback action of dihydrotestosterone and estradiol. 5 alpha-Dihydrotestosterone was administered by 5, 10 or 20 mm long elastomere capsules whereas estradiol was given by daily s.c. injections of 0.125, 0.25 or 0.50 micrograms estradiol benzoate. In the presence of corticosterone acetate the gonadotropin inhibitory action of testosterone, 5 alpha-dihydrotestosterone and estradiol increased more than 2 times.     

Effects of water deprivation on corticosterone production in the male Brattleboro rat genetically deprived of vasopressin

Effects of 72 h water-deprivation on plasma corticosterone concentration have been investigated in male Brattleboro rats homozygous for hypothalamic diabetes insipidus (DI) and in male Long-Evans rats (LE), as controls. To determine the global effect of water deprivation, drinking water deprived rats were compared with hydrated animals. Because water deprived rats showed a depressed food intake, to elucidate the specific effect of dehydration alone, drinking water deprived rats were compared with similar food-restricted but water supplied animals. Increases in adrenal weights and in plasma corticosterone content, following 72 h water-deprivation, were greater in DI than in LE rats. In LE rats, they seemed to be the result of both dehydration and denutrition. Conversely in DI rats lacking vasopressin, dehydration alone increased neither adrenal weights nor plasma concentration of corticosterone; the whole plasma corticosterone content was reduced. So, in DI rats, the global response to drinking water deprivation was essentially due to food restriction, whose effect was partly suppressed by dehydration. Whatever the circumstances, plasma concentrations of corticosterone were higher in DI than in LE rats. Interrelationships between water deprivation, stress, vasopressin and glucocorticoids are discussed.     

Consequences of artificial and natural chromosome doubling on DNA,RNA and protein contents inCochlearia (Brassicaceae)

The effects of chromosome doubling on macromolecular composition, i.e. DNA, RNA and protein, were examined in diploidCochlearia pyrenaica DC., its established natural autotetraploidC. officinalis L., and their newly colchicine-induced autotetraploid and autooctoploid derivatives. DNA, RNA and protein contents increase from lower to higher ploidy levels (2x > 4x > 8x). The established natural autotetraploids and newly induced autotetraploids also differ, as DNA, RNA and protein have been reduced during the course of establishment. Net synthesis of RNA and protein per unit DNA does not change significantly neither from lower to higher ploidy levels nor between the autotetraploids of newly induced and established natural origins.     

Diazepam: endocrine effects and hypothalamic binding sites in the developing male and female rat

The ontogeny of diazepam's endocrine effects in male and female rats, and of 3H-diazepam binding in the hypothalami of both sexes was studied. Diazepam inhibited basal prolactin levels in 38 day-old male rats and, if prolactin levels were stimulated by Haloperidol the inhibition occurred in 28 day-old males, indicating that the hypoprolactinemic effect of the drug could be evidenced earlier if prolactin titers were high. The prolactin inhibition in females did not reach statistical significance at any studied age. Diazepam significantly released LH only in male rats at 12 days, showing thus, a period of special sensitivity of LH release to the drug. Benzodiazepine-hypothalamic binding sites increased in number from birth to puberty, reaching a plateau at 20 days of age. No sexual differences or changes in affinity were found throughout the studied period. These results suggest that the maturation of diazepam's hypoprolactinemic effect could be partially related to the increase in hypothalamic binding sites, whereas the sexual differences observed in diazepam's endocrine actions could be due to sexual differentiation of endocrine control mechanisms.