Long-term effects of stress in critical periods of development on reactivity of adult female rats

Effects of stress during different periods of ontogeny, namely, the prenatal, prepubertal, or their combination (prenatal+prepubertal), on the indices of psychoemotional and tonic pain-related behaviors, as well as corticosterone reactivity after pain behavior were investigated in adult 90-day-old female Wistar rats. Our data show for the first time, the similarity of effects of prenatal (immobilization stress of a rat dam during the last week of pregnancy) and prepubertal (forced swimming, pain-related response in the formalin test) stresses on the indices under study, an increase in the time of immobility and in licking duration, but the difference between effects of combined stress on these indices. Pain-related response increased corticosterone in prepubertally stressed rats while in prenatally stressed rats, decreased it. In rats experienced combined stress, formalin-induced pain increased corticosterone as compared with that in prenatally, but not in prepubertally stressed rats. A positive correlation between pain-related reaction and stressed hormonal response was revealed in prepubertally stressed animals. So, long-term effects of stress during critical periods of ontogeny determine stress reactivity of behavioral and hormonal responses in adult female rats.     

Intestinal microbiocenosis at the critical periods of child development

The bacteriological study of fecal specimens obtained from 595 children at different critical periods of the development of their immune system was carried out. The comparison of intestinal microflora in children at the critical periods of the development of their immune system revealed that in children under 1 year considerable changes in the microflora composition were observed during the first 6 months of life. These changes, most pronounced in children aged 1 month and 3-6 months, were characterized by decreased level of indigenous microflora and an increase in the qualitative and quantitative content of aerobic microflora with the representatives of the family Enterobacteriaceae playing the dominating role. In boys such disturbances were manifested to a greater extent than in girls.     

Developmental regulation of water uptake in wheat

The discovery of aquaporins has provided a new basis for studying and interpreting water relations in plants. However, slow progress has been made in elucidating the functional facets of the aquaporin-mediated water pathway in whole plant systems. While increasing experimental evidence suggests that these proteins are directly involved in mediating water homeostasis at varying environmental conditions, only a few attempts have been made to understand their contribution to overall water transport at different developmental stages. By using a chemical inhibitor (HgCl(2)) of aquaporins function, here we present in planta evidence for both diurnal and developmental regulation of aquaporin activity in wheat. We demonstrate that the greatest sensitivity of water flux to pharmacological blockage occurs at the stage of ear emergence and does not coincide with the phenological stage at which the greatest plant water uptake occurs (milky ripeness). The relationship transpiration flux (Q) vs. soil-leaf water potential difference (DeltaPsi(soil-leaves)) revealed a gradual decrease of plant resistance to water flux from tillering to milky ripeness, both in HgCl(2)-treated and untreated control plants. However, the mercury-inhibition of water flux began to gradually increase at ear emergence, suggesting that a larger portion of water moves through aquaporins from this developmental stage on. Although the intercept of the DeltaPsi(soil-leaves)/Q regression line, i.e. the DeltaPsi required to initiate the water flux through the soil-plant-air continuum, was generally not affected by mercury treatment, a significant mercury effect on the intercept was observed at the stage of ear formation. These findings may have important implications for predicting which strategy plants utilize to optimize water use during their life cycle.     

Gravity-related critical periods in vestibular and tail development of Xenopus laevis

Sensory systems are characterized by developmental periods during which they are susceptible to environmental modifications, in particular to sensory deprivation. The experiment, XENOPUS, on Soyuz in 2008 was the fourth space flight experiment since 1993 to explore whether tail and vestibular development of Xenopus laevis has a gravity-related critical period. During this flight, tadpoles were used that had developed either the early hindlimb (stage 47) or forelimb bud (stage 50) at launch of the spacecraft. The results revealed (1) no impact of microgravity on the development of the roll-induced vestibuloocular reflex (rVOR) in both stages and (2) a stage-related sensitivity of tail development to microgravity exposure. These results were combined and compared with observations from space flights on other orbital platforms. The combined data revealed (1) a narrow gravity-related critical period for rVOR development close to the period of the first appearance of the reflex and (2) a longer one for tail development lasting from the early tail bud to the early forelimb bud stage.     

Motor reactions in rats during critical growth periods in the early postnatal age

Within the first days after birth, the sleeping rats demonstrate the high rate of motor reactions (RMR) of the jerk type. With advancing age the RMR diminishes. However during a sudden change in the growth, the 25-day-old rats show an increase in the RMR of the jerk type. This is manifested by the return of the functions to the state marking the first days of life. The catecholaminergic mechanisms of the growth and development of rats are discussed.     

Factors affecting the development of isolation-induced hypertension in rats

Rats were housed either individually in separate metabolic cages or in pairs in two connecting metabolic cages and systolic blood pressure was measured before and after a 5 day period over which the animals were left undisturbed. After the 5 day period isolated rats were hypertensive whereas paired rats were not. A further study compared the Na+, K+ and water balances of pairs of normotensive rats with those of isolated rats over the 5 days during which the latter became hypertensive. There was no evidence of any renal Na+ and water retention in isolated, hypertensive rats and thus it is unlikely that mineralocorticoids could have caused a plasma volume expansion and thereby contributed to the hypertension.     

Protein synthesis in the critical periods of early postnatal ontogeny: its role in the development of the interspecific aggressive behavior of rats

Chronic administration of cycloheximide to young rats from 15-th to 30-th postnatal day before daily 3-hour seances of their contacts, disturbed the formation of animals intraspecies aggressivity. In adults it was manifested by hyperaggressivity and by changes of proportions of different reactions in the integral act of aggressive behaviour. By their character these disturbances were close to those observed in the young rats completely deprived of social contacts in this period of ontogenesis.     

Dietary sodium manipulation during critical periods in development sensitize adult offspring to amphetamines

This study examined critical periods in development to determine when offspring were most susceptible to dietary sodium manipulation leading to amphetamine sensitization. Wistar dams (n = 6-8/group) were fed chow containing low (0.12% NaCl; LN), normal (1% NaCl; NN), or high sodium (4% NaCl; HN) during the prenatal or early postnatal period (birth to 5 wk). Offspring were fed normal chow thereafter until testing at 6 mo. Body weight (BW), blood pressure (BP), fluid intake, salt preference, response to amphetamine, open field behavior, plasma adrenocorticotropin hormone (ACTH), plasma corticosterone (Cort), and adrenal gland weight were measured. BW was similar for all offspring. Offspring from the prenatal and postnatal HN group had increased BP, NaCl intake, and salt preference and decreased water intake relative to NN offspring. Prenatal HN offspring had greater BP than postnatal HN offspring. In response to amphetamine, both prenatal and postnatal LN and HN offspring had increased locomotor behavior compared with NN offspring. In a novel open field environment, locomotion was also increased in prenatal and postnatal LN and HN offspring compared with NN offspring. ACTH and Cort levels 30 min after restraint stress and adrenal gland weight measurement were greater in LN and HN offspring compared with NN offspring. These results indicate that early life experience with low- and high-sodium diets, during the prenatal or early postnatal period, is a stress that produces long-term changes in responsiveness to amphetamines and to subsequent stressors.     

Critical periods in the development of spurs in light of the theory of phylembryogenesis]

Two critical periods have been established in the development of spurs representing a derivative of the corneous squama. During the first period the exposure to x-rays results in the development of the corneous squama instead of the spur, and the same exposure during the second critical period completely suppresses the development of the spur. These periods seem to correspond to the truning-points in the chain of morphogenetical processes of the spur formation associated with phylembryogeneses. Department of Embryology, Institute of Experimental Medicine, USSR Acad. Med. Sci., Leningrad.     

The gastrin-secreting effects of the salt components of naftusia water]

Intragastric administration of certain salt components of mineral water naftusia in minimal concentrations (1-5 mmol/l) changes intensity and direction of hypergastrinemic reaction in the rats. The effect is determined by the anionic composition of salts rather than by the cationic one and depends on the initial concentration of gastrin in blood.     

Ethanol alters astrocyte development: A study of critical periods using primary cultures

Using astrocytes obtained from 21-day-old rat fetuses, in primary culture, we have analyzed the effect of prenatal alcohol consumption on DNA and protein synthesis of astrocytes during their development. The variation in sensitivity of astrocytes to ethanol in vitro during the proliferation and maturation periods was also assessed. Control astrocytes showed peaks of DNA and protein synthesis at 8 and 15 days, respectively. A significant decrease in both DNA and protein synthesis was found in astrocytes from fetuses prenatally exposed to ethanol. This effect on DNA synthesis was also observed when control astrocytes were exposed to ethanol (100mM) in vitro during the entire culture period. The effects on astrocytes of short term (48h) exposure to ethanol during the proliferation or differentiation periods on the above mentioned parameters and on the cell cycle as well as the possible recovery from these effects were also evaluated. Decreases in DNA and protein synthesis were found in both periods. However, DNA synthesis and content were more affected in astrocytes exposed to ethanol during the proliferation period. This effect correlates with an accumulation of cells in the G_o/G₁ phase of the cell cycle. On the other hand, when cells exposed to ethanol were cultured in alcohol-free medium to assess recovery, only cells exposed to ethanol during days 4 to 6 still showed DNA ethanol-induced effects at 21 days. In conclusion, our results show that ethanol consumption during gestation induces serious damage to cortical astrocyte progenitor cells. Our results further demonstrate that although astrocytes are more sensitive to the toxic effect of alcohol during the proliferation period, exposure to ethanol during glial maturation also alters their normal development.     

The effect of a salt water regimen on the development of the salt glands of domestic ducklings

Commencing on the fourth day after hatching and continuing for 2 weeks, 84 experimental ducklings were given drinking water containing 1 or 1.2% sodium chloride for 12 hours daily and fresh tap water for the remainder of each day; 39 control birds drank only tap water. During the third day of the experiment, salt gland effluent, high in sodium content, appeared at the external nares of the ducklings. After 5 days of the salt water treatment the salt glands of experimental birds weighed significantly more than those of the control birds, while the body weights of the experimental ducklings increased more slowly than those of the controls.The salt water regimen evoked a rapid increase in the size of the secretory cells, an apparent increase in the number of secretory cells, an elongation of the secretory tubules, and an increase in the size of the secretory lobules, with concomitant dilution of the connective tissue.Histochemical differences between the salt glands of experimental and control birds, evident by the end of the third day, were intensified during the remainder of the experiment. In addition to their rich complement of phospholipid, the large secretory cells in the salt glands of the experimental birds contained abundant succinic dehydrogenase and cytochrome oxidase activity. Smaller but similar cells in the glands of control birds of the same age bore little phospholipid and were only slightly reactive for these enzymes. In addition, the secretory cells of the experimental birds gave moderate reactions for nonspecific esterase, monoamine oxidase, and acid phosphatase. The onset of the secretory competence of the salt gland coincided with the appearance of abundant phospholipid and strong oxidative enzyme activity in the secretory cells.In the secretory lobules of both experimental and control birds, two distinct cell types could be distinguished by their enzyme content. The principal secretory cells were acidophilic; they contained no alkaline phosphatase, but abounded in succinic dehydrogenase and cytochrome oxidase. The terminal or peripheral cells at the blind ends of the secretory tubules were basophilic; they reacted for alkaline phosphatase, but contained little succinic dehydrogenase or cytochrome oxidase. The position, as well as the relatively undifferentiated state of the peripheral cells, suggests that they have a generative function.The pattern of innervation, revealed by the cholinesterase technique, was more elaborate in the salt glands of experimental birds than in the controls. This observation, when correlated with available physiological data, suggested that the salt water regimen might not directly influence the growth and differentiation of the salt gland but that the effect might be mediated by the nervous system.     

Effect of agents affecting water structure on the uptake of saccharides by agar and polyacrylamide gels

Uptake of D -xylose, D -glucose, lactose, and dextran 10 was studied in 3% and 12.5% polyacrylamide gels in the presence of 2 M LiCl, 2 M NaCl, 2 M KCl, 2 M RbCl, 2 M CsCl, 2 M MgCl₂, 2 M CaCl₂, 1 M NaF, 1 M NaI, 0.5 M guanidine thiocyanate, 0.5 M guanidine sulphate, and 0.5 M N,N′-diethylurea. With the exception of N,N′-diethylurea and, in some cases, LiCl, which had an accelerating effect, the compounds retarded considerably the uptake of saccharides by agar gel but had only a slight effect in polyacrylamide. The nature of the gel is thus of primary importance in interactions of this type. According to the magnitude of their effect on saccharide uptake, the salts used were arranged into several series. An attempt was made to correlate the effects of individual salts with their hydration properties. The strongest effect was found to be exerted by KCl, RbCl, and CsCl, i.e., by chlorides of cations possessing negative hydration shells.     

Proliferation of piriform neurons in the rat cerebellar cortex in the pre- and postnatal periods of development]

The method of histoautoradiography with the use of H3-thymidine was applied to the study; there were established the periods of appearance in the cerebellar anlage of albino rats of neuroblasts differentiated into the piriform neurones of the cerebellar cortex; dynamics of the proliferative activity of these cellular elements in the course of the pre- and postnatal periods of development of the experimental animals was investigated. On the basis of the material obtained a conclusion was drawn that the last cell divisions (the result of cell differentiation were Purkinje's cells of the cerebellar cortex) stopped by the 13th--15th day of the embryonic development. No incorporation of the labeled precursor into the DNA of the nuclei of the differentiating piriform neurons occurred later.     

Effect of salt loading on the body water compartments in rats of different ages

In acute experiments on anaesthetized rats from three age groups (15-20, 25-30 days of postnatal life, adult ones), studies have been made on water basins of the organism after peroral injection of hypertonic (2.5-5%) solutions of NaCl (5 and 10 ml per 100 g of the body weight). It was demonstrated that during ontogenesis, total content of water decreases mainly at the expense of extracellular fluid. Infusion of saline solutions into the stomach of rats decreases fluid content in all water basins, especially in the interstitial one. The level of changes depends on the volume of the injected solution and, to a greater extent, on the concentration of the latter and the age of animals. The described response is due to osmotic transport of water into the alimentary tract, as suggested by the decrease of water content in this tract. The role of the digestive tract in osmotic and volume regulation during peroral salt loading is discussed.