Gamma- and UV-induced DNA synthesis in neurons of the rat neocortex

Nuclear DNA synthesis in neocortex neurons of neonatal 14- and 60-day rats after in vitro irradiation of isolated sections was estimated by the incorporation of a labeled precursor into DNA. gamma- and UV-radiation increased the rate of DNA synthesis in the cells of animals of all studied age groups. However, the level of the UV-induced synthesis sharply dropped during the postnatal ontogenesis while gamma-radiation-induced synthesis decreased slightly. The peculiarities revealed in the repair DNA synthesis seem to be influenced by the process of postnatal differentiation of a neuron accompanied by the nucleosome length shortening and the decrease in the DNA-polymerase alpha content.     

DNA repair in mammalian nerve cells. I. DNA synthesis in the neocortex of rats induced by gamma irradiation

A study was made of the DNA synthesis in cerebral cortex of rats, aged 14 and 60 days, after gamma-irradiation in vivo in a dose of 7 Gy, the 3H-thymidine incorporation into DNA being determined.137 Cs-radiation induces additional DNA synthesis in the neocortex tissue and in neurons. In the cortex of 14 day-old rats, the induced DNA synthesis stops 2 hours after irradiation, whereas in the cortex of 60 day-old rats and in neurons of rats of both the age groups DNA synthesis is proceeding for 3-3.5 hours. Specificity of DNA reparation processes in non-dividing cells is discussed.     

DNA synthesis in the Purkinje neurons

(3H) Thymidine is incorporated into some cerebellar Purkinje cells of 6- to 30-day-old rats. The frequency of labelled neuronal nuclei was higher in the 12- to 30-day old rats than in the 6- to 10-day-old animals. The grain distribution pattern in autoradiographs was mostly nucleolar amounting to three to ten grains. Some other local labels were revealed, too. Only six Purkinje cells among 42,000 studied in 21 rats possessed heavy label (25 to 50 grains) distributed throughout the nucleus. Control estimations with deoxyribonuclease, hot perchloric acid and covering the autoradiographs again established that the Purkinje cells synthesize DNA perhaps for the purpose of DNA surplus accumulation and/or DNA repair in the neurons.     

Iron metabolism and erythropoiesis in the prenatal and early postnatal periods of the rat

Spectrophotometric studies have been made on iron balance in the liver, spleen, bone marrow, and blood serum of 15-, 17- and 20-day rat embryos, as well as 1-90 days old rats. It was shown that foetal period is the main one for the formation of iron-accumulating function of the liver. Anaemic period in 14-28-day rat puppies results from insufficient hemoglobin synthesis, rather than from iron deficiency in the organism. The latter is observed in 35-60-days old rats. Maturation of the spleen as the organ involved in reutilization of iron was noted in 42-60-day rats.     

DNA content of the mitochondria of the developing rat brain

Studies have been made on the content of DNA in the mitochondria from the brain of 1, 5, 10, 15, 21, 60, and 400 days old rats. Isolated DNA preparations contained 7% of RNA and 3% of proteins. It was shown that the amount of DNA in 21- and 60-day rats is 4 times higher that than in newborn ones. DNA content of the mitochondria increases during the first 3 weeks of postnatal life of rats.     

Age-dependent changes of the autonomic neurons expressing vanilloid TRPV1 receptors

Expression of vanilloid receptors in sympathetic and afferent ganglionic neurons was studied in rats of different ages (newborn, 10-day old, 20-day old, 30-day old, 60-, 180-day old) using immunohistochemical methods. The results obtained indicate that the majority of the afferent neurons in the nodose ganglion of vagus nerve (GNVN) and in the spinal ganglia (SG) were TRPV1-positive from birth onwards. The percentage of neurons containing TRPVT receptors in SG slightly increased with age up to 30 days postnatally. In the GNVN, the percentage of TRPV1-positive neurons was higher in comparison with the SG in all age groups. The vast majority of the sympathetic neurons were TRPV1-positive from birth onwards, and the percentage of TRPV1-immunoreactive neurons substantially decreased during further development. In 20-day old and older animals, we observed only few TRPV1-immunoreactive neurons in sympathetic ganglia. Finally, the percentage of neurons containing these types of neurons, become similar to adult animals to the end of the first month of life.     

克隆鸭乙型肝炎病毒DNA双体体内转染的研究

用一种含头尾相连DHBVDNA双体的质粒体内转染2日龄芙蓉鸭,大多数鸭（86％）产生了短暂病毒血症。血清DHBs／preSAg和DHBVDNA于转染后第9天出现,第12～14天达峰值,第28天时多数转阴;少数鸭的病毒血症可持续50天以上。转染鸭肝组织中也检测到复制中间型DHBVDNA的存在。用转染鸭病毒血症期的血清作磷钨酸负染电镜观察,找到了完整的DHBV病毒颗粒,并且用此血清腹腔注射1日龄鸭,60％的鸭被感染成功,证明体内转染后有生物活性的DHBV病毒颗粒的产生。该研究方法的建立．对于研究DHBV变异株．DHBV基因结构与功能的关系等,均有一定理论意义及应用价值。     

Appearance and differentiation of NADPH-D-neurons in ontogeny of the cerebral cortex in rats

The appearance of presumptive NO-ergic nerve cells and their differentiation in the rat neocortex were studied. For this purpose, a comparative analysis of the development and differentiation of NADPH-D-positive neurons in the neocortex transplants taken from the embryos of different ages and transplanted in the occipital cortex of adult rats and in the normally developing cerebral cortex. The nervous tissue was stained histochemically for NADPH-D. The results we obtained suggest that no NADPH-D-containing neurons were found in the transplants from 15-day embryos, while they developed in those from 18-day embryos. Hence, precursors of NO-ergic neurons were still absent in the presumptive neocortex of 15-day embryos and appeared only on day 16-18 of embryogenesis. Expression of NADPH-D begins in them only within four to five days, but the neurons are differentiated during a relatively short period of time. Most NADPH-D-positive neurons reach their structural-functional maturity already by the end of the first week of postnatal development, while their complete maturation takes place by the end of the second week of postnatal development.     

The age specifics of the neurotransmitter composition of the stellate ganglion neurons

The stellate ganglion neurons' transmitter composition in the rat siblings of different age (newborn, 10-, 20-, 30-, 60-day old) revealed that the greatest amount of the neurons in all the rats contained thyrosinhydroxylase. Most cholinacetyltransferasepositive. In 30- and 60-day old rats, just a few cells contained both above enzymes. Since birth, the percentage of cells containing thyrosinhydroxylase and neuropeptide Y has been growing. Along with that, the share of somatostatin-positive neurons was decreasing. The percentage of the VIP-positive cells and the neurons containing cholinacetyltransferase was increasing until the 10th day of life and then dropped again. The somatostatin-positive neurons in all the rat siblings were represented by small cells, whereas the neurons containing cholinacetyltransferase were represented by large cells. The maturation of the neurotransmitter set in the rat stellate ganglion terminates by the end of the second month of life.     

Variable effect of ghrelin administration on pancreatic development in young rats. Role of insulin-like growth factor-1.

Ghrelin, an endogenous ligand of the growth hormone secretagogue receptor, has been primarily isolated from the human and rat stomach. Ghrelin has been shown to stimulate appetite and fat deposition in adult rats and humans. The aim of this study was to investigate the effect of ghrelin administration on pancreatic growth in suckling, weaned and peripubertal seven week old rats. Rats were treated with saline or ghrelin (4, 8 or 16 nmol/kg/dose) intraperitoneally twice a day: suckling rats were treated for 7 or 14 days starting from the first postnatal day, three week old weaned rats and seven weeks old rats were treated for 5 days. Treatment with ghrelin did not affect animal weight in suckling or weaned rats, whereas in young seven week old rats, ghrelin caused a significant increase in body weight. Ghrelin decreased food intake in weaned rats; whereas in seven week old rats, food intake was enhanced. In suckling rats, ghrelin decreased the pancreatic weight, pancreatic amylase content, DNA synthesis and DNA content. In contrast, ghrelin increased pancreatic weight, DNA synthesis, DNA content and amylase content in weaned or young seven week old rats. Pancreatic blood flow was not affected by ghrelin in any group of rats tested. Ghrelin increased serum level of growth hormone in all rats. This effect was weak in suckling rats, higher in weaned and the highest in seven week old animals. Ghrelin did not affect serum level of insulin-like growth factor-1 (IGF-1) in suckling rats. In weaned and in seven week old rats, treatment with ghrelin caused increase in serum level of IGF-1. We conclude that ghrelin reduces pancreatic growth in suckling rats; whereas in weaned and young seven week old animals, treatment with ghrelin increases pancreatic growth. This biphasic effect of ghrelin in young animals on pancreatic growth seems to be related to age-dependent changes of the release of anabolic IGF-1.     

Fidelity of DNA Polymerase-β in Neurons from Young and Very Aged Mice

Abstract: Neurons do not divide during adult life and thus they provide a unique system to study the effects of age-accumulated damage to DNA in the absence of DNA replication. We have analyzed DNA polymerase activity in neurons isolated from young adult and very aged mice. The predominant catalytic activity is DNA polymerase-β and it is present in similar amounts in neurons from young and old mice. This polymerase is highly errorprone in copying φX174 DNA, the error frequency being about 1/7,000 and not significantly different when obtained from young and old animals. This high infidelity is considered with respect to DNA repair and the protein synthesis error catastrophe theory of aging.     

Fluctuations in DNA synthesis by mammary tissue from the pregnant hamster, rat and three strains of mice

1. DNA synthesis was determined at midnight and noon in mammary tissue from 13-day pregnant mice (C3H, C57B110 and BALB/c) and 14-day pregnant golden hamsters and Sprague-Dawley rats. 2. Mammary tissue from the hamster and the three mouse strains had elevated DNA synthesis at midnight compared with noon. 3. In contrast, DNA synthesis in mammary tissue from the rat was not different at these two time periods.     

Acute effect of human chorionic gonadotropin (hCG) on 17 alpha-hydroxylase and C17,20-lyase activity in neonatal or prepubertal rat testis

In contrast to the situation in adults, desensitization of androgen production, secondary to loss of enzyme activity, was not found in testes of neonatal rats exposed to human Chorionic Gonadotropin (hCG). In the present study attention was given to the acute effects of a single injection of hCG upon the activity of testicular 17 alpha-hydroxylase, C17,20-lyase and the concentration of testosterone in the serum of 5, 10 or 28-30 day old rats was investigated. Tritiated H2O from 17 alpha-[3H]progesterone and 14CH3COOH from 21-[14C]progesterone were the products measured to evaluate hydroxylase and lyase activities respectively. Large increases in hCG in the serum were detected within 2 h of a subcutaneous injection. Testosterone, which was highest in 5 day animals, increased quickly in all animals given hCG. In 28-30-day old animals, the concentration of this steroid began to fall 24 h after injection of hCG. 17 alpha-Hydroxylase activity decreased in the testes of all animals given hCG, but only after a brief increase. Activity returned to the starting level, or above, within 24 h in 5 or 10-day old animals. In 28-30-day old rats the activity of both enzymes decreased dramatically to a nadir at 24 h, but increased thereafter. The results indicate that desensitization of testicular androgen synthesizing enzymes occurs in neonatal as well as older testes stimulated with hCG, but the desensitization was very brief in neonatal animals and no desensitization of lyase was found in 5-day old rat testes.     

Perinatal methadone exposure and brain development: a biochemical study

Abstract— The neurochemical effect of maternally administered methadone (5 mg/kg, DL-methadone-HCI) on the brain (including the olfactory bulbs, cerebellum, and brain stem) and cerebellum of offspring exposed during gestation and/or lactation was studied in 10-, 21-, and 60-day old rats. Brain weights were significantly reduced in all methadone-exposed groups at 10 days of age, while only those rats subjected to methadone during gestation or lactation had deficits in brain weights at day 21; no differences were found at 60 days. Brain DNA content was significantly reduced in all opiate-exposed offspring at every age examined, but RNA/DNA and protein/DNA ratios were only consistently increased in rats of the gestation group. Cerebellar weight was reduced at 10 days in the gestation-lactation pups, at 21 days in rats of the gestation and lactation groups, and at 60 days in animals of the gestation and gestation-lactation groups. Cerebellar DNA content was significantly decreased in pups of the gestation group at every age investigated, but only reduced at 21 days in the lactation group and at 60 days in the gestation-lactation group. Rats in the lactation group had the greatest number of alterations in terms of RNA and protein, with the most noticeable being decreases in mean cellular RNA content on days 21 and 60 and a reduction in the mean cellular protein content on day 60. These data suggest that prenatal and/or postnatal methadone treatment affects the biochemical maturation of the central nervous system; deficits in neurons and/or glia, as well as a reduction in myelination, might be reflected in these changes.     

大鼠老化过程大脑皮层及小脑神经元染色质构象分析

 本文在前文~[2]的基础上进一步以MCN和DNaseⅠ为探针研究大鼠脑神经元终末分化后不同生理时期染色质构象,结果表明:MCN酶解DNA产物PAGE显示脑老化过程大脑皮层及小脑神经元染色质核小体单体DNA分别保持在176bp和215bp水平,核小体连接DNA长度存在组织差异,但不受老化影响;<2>DNaseⅠ酶解DNA产物PAGE显示各年龄组大脑皮层及小脑神经元染色质DNA存在10bp间隔重复结构和相同的泳动区带分布特征,提示脑老化中染色质具有稳定的B型双螺旋结构和一致的螺线管卷曲形式。染色质DNaseⅠ降解率随年龄增加而降低,提示老化导致活性染色质区域减少,老化过程脑神经元染色质构象改变成为其转录功能减退的结构基础。     

Age-related loss of DNA repair synthesis in isolated rat myocardial cells

Singly isolated beating heart cells from newborn rats performed unscheduled DNA synthesis (‘repair’ synthesis) when irradiated with ultraviolet light in vitro. Repair synthesis could not be induced in beating cardiac cells isolated from adult animals (3–12 months old).     

Cholecystokinin-8 activates myenteric neurons in 21- and 35-day old but not 4- and 14-day old rats

Cholecystokinin (CCK) activates the myenteric neurons of adult rats. The goal of this work is to determine the ontogeny of this activation by CCK-8 in the myenteric plexus of the duodenum (2 cm immediately following the pyloric sphincter aborally) and compare it with that of the dorsal vagal complex (DVC) - which occurs in 1-day old pups. Despite the existence of both of the CCK receptors, CCK₁ and CCK₂, in 4, 14, 21 and 35 day old rats, CCK-8 (0, 5, 10, 20 and 40 μg/kg, i.p.) increased Fos-like immunoreactivity (Fos-LI, a marker for neuronal activation) in the myenteric neurons of 21- and 35-day old rats but in the DVC of all age groups. As such, this belated activation of myenteric neurons by CCK-8 compared to the DVC may reflect a delayed role for these neurons in CCK-related functions.     

Inhibition of mitosis and tritiated DNA precursor uptake in human leucocyte cultures by rat lymph node extract.

A water soluble extract was prepared from the lymph nodes of rats of different age groups. This extract, when added to human peripheral blood leucocyte cultures, inhibits DNA synthesis and mitosis when added in different concentrations for varying lengths of time in culture. Also, it was observed that the extract from old rats was not as effective as that from younger animals.     

The short-term and long-lasting changes in DNA and RNA synthesis in the cerebral cortex cells of animals subjected to hypoxia and nerve tissue transplantation]

The DNA and RNA synthesis in the cells of the brain cortex of intact rats and animals subjected to hypoxia, hypoxia with subsequent transplantation or by the local brain injury has been investigated. The DNA synthesis changes insignificantly in the case of hypoxia, it enhances slightly in the area of the injury and increases much more after transplantation. The RNA synthesis decreases considerably immediately after hypoxia and decreases much more 120 days later. Using the ultracentrifuge method it has been found that under the effect of hypoxia the number of nervous cells decreases, the number of glial cells does not change. The local injury in the nervous tissue enhances abruptly the synthesis in neurons and glial cells in the hypoxia-exposed animals, the embryonic nervous tissue transplantation normalizes the number of neurons in the specimens under study and the RNA synthesis in the neurons and glial cells.     

Appearance and Differentiation of NADPH-D-Neurons in Ontogeny of Cerebral Cortex in Rats

The appearance of presumptive NO-ergic nerve cells and their differentiation in the rat neocortex were studied. For this purpose, a comparative analysis of the development and differentiation of NADPH-D-positive neurons in the neocortex transplants taken from the embryos of different ages and transplanted in the occipital cortex of adult rats and in the normally developing cerebral cortex was undertaken. The nervous tissue was stained histochemically for NADPH-D. The results we obtained suggest that no NADPH-D-containing neurons were found in the transplants from 15-day embryos, while they developed in those from 18-day embryos. Hence, precursors of NO-ergic neurons were still absent in the presumptive neocortex of 15-day embryos and appeared only on day 16–18 of embryogenesis. Expression of NADPH-D begins in them only within four to five days, but the neurons are differentiated during a relatively short period of time. Most NADPH-D-positive neurons reach their structural–functional maturity already by the end of the first week of postnatal development, while their complete maturation takes place by the end of the second week of postnatal development.