Effects of the plasticiser DEHP on lung of newborn rats: catalase immunocytochemistry and morphometric analysis

Experimental administration of di-(2-ethylexyl)-phthalate (DEHP), a plasticiser employed in the fabrication of polyvinyl chloride (PVC), causes increases in lipid metabolising enzymes along with marked peroxisomal proliferation. The effects are found in several mammalian tissues, of which the rodent liver is the most responsive target. Leakage of DEHP from PVC devices is favoured by high temperature and contact with lipid-containing biological fluids. Since preterm babies are currently ventilated through endotracheal PVC tubes, it seemed worthwhile to investigate DEHP effects on immature mammalian lung. In this research, female rats were fed with DEHP in the last week of pregnancy and after delivery, and lungs were excised from 2-day-old pups. At this age, in fact, rat lung histological features closely resemble those found in 24- to 36-week-old human fetuses. In treated animals, morphometric analysis of histological parameters revealed a dramatic decrease in the number of parenchymal airspaces, together with significant increases in their mean size. Moreover, cytochemical detection of the peroxisomal marker catalase revealed an increase in the number of type II pneumocytes. Our findings closely resemble abnormal histological features observed in autoptic lung specimens from children affected with chronic lung diseases.     

Peroxisomes in the rat brain and the effects of di-(2-ethylhexyl) phthalate during postnatal development. An electron-microscopic study

Peroxisomes were identified in the neurons of cerebral cortex of 12-day-old suckling rats from normal and plasticizer di-(2-ethylhexyl) phthalate (DEHP)-fed mothers. The study suggests that DEHP passed to the pups through the mother's milk during nursing can induce peroxisomal proliferation in neurons during postnatal development.     

The postnatal age of rat lung fibroblasts influences G1/S phase transition in vitro

Summary In the neonatal rat lung, alveolar development occurs from postnatal Days 4–13, during which time there is a fourfold increase in interstitial fibroblasts. Factors influencing emergence of new septa and cell proliferation associated with septal elongation have yet to be identified, in part because of difficulties inherent in studying this process in vivo. Using flow cytometric analysis of the DNA content of freshly isolated lung fibroblasts, we found that proliferation, as indicated by the percentage of cells in S plus G₂/M phases, peaked on postnatal Day 4 (P<0.04). By Days 9–10 the proliferation rate was lower than on Days 3, 4, 5, or 6 (P<0.005). We then evaluated rates of in vitro proliferation as a function of postnatal age in first passage fibroblasts and found that the proliferative phenotype expressed in vivo persists in vitro. Fibroblasts from 4–5-d-old pups increased in number and incorporated ³H-thymidine at a faster rate than did fibroblasts obtained from pups at other postnatal ages (P<0.0001). Age-dependent differences in cell cycle transit time were compared in fibroblasts synchronized by serum starvation and analyzed by flow cytometry at 2-h intervals from 13–21 h after release from serum starvation. A greater percentage of cells from 5-d-old pups entered S phase during this period than was seen for cells obtained from 2-, 9-, 13-, or 23-d-old rat pups (P=0.0001). Cells from 5-, 9-, and 13-d-old pups reentered G₀/G₁ by 21 h after release from serum starvation, in contrast to fibroblasts from 2- and 23-d-old rats which did not. Throughout the 15-h period after release from serum starvation, levels of cyclin E, which peaks at the G₁/S border, were highest in the 5-d-old cells (P<0.025). Synchronization with 2.5 mM hydroxyurea which inhibits DNA synthesis completely abolished age-related differences in cell cycle transit time, implying that age-dependent differences in lung fibroblast proliferation rates are the result of events occurring before S-phase entry.     

Comparative Effects of Ethanol and Malnutrition on the Development of Catecholamine Neurons: Changes in Neurotransmitter Levels

Abstract: The comparative effects of exposure to ethanol and malnutrition on the concentrations of tyrosine and catecholamines in whole brain and selected regions of brain have been studied in the developing rat. These animals were the offspring of optimally nourished rats (control pups), of rats fed a diet with 35% of the calories supplied by ethanol (ETOH pups), or of animals fed a diet calorically equivalent to the latter but lacking ethanol (iso-caloric, 1C pups). These diets were administered to dams either during the last week of gestation (prenatal) or during lactation (postnatal). Tyrosine levels were elevated prior to birth in the prenatal ETOH or IC pups or at 1 and 2 weeks of age in postnatal ETOH or 1C pups as compared with values found in the control offspring. Dopamine concentration in whole brain was significantly lower in prenatal ETOH pups than in prenatal IC pups at 3 weeks of age. Levels in the brains of postnatal ETOH pups were lower than control values, but not relative to animals exposed to 1C diet. Investigation of corpus striatum showed a significant decrease in dopamine concentration compared with control or IC pup values as a result of postnatal exposure to ethanol. Norepinephrine levels in the whole brain of prenatal ETOH pups were consistently 30–40% lower than either control or matched 1C pups during development. At 3 weeks of age, the norepinephrine levels in the hypothalamus of animals exposed to ethanol pre or postnatally were 30–60% lower than values in the corresponding region in either control or 1C pups. In the rat model described, ethanol caused a decrease in catecholamine levels, perhaps solely by affecting the norepinephrine neurons.     

Effect of harmaline on the complex spike shape and depression time in cerebellar Purkinje cell discharge in rat postnatal ontogenesis

Functional relationship between wave form of complex spike (CS) and depression time of simple spike (SS) in discharge of cerebellar Purkinje cells was studied after their activation with afferent climbing fiber at different terms of postnatal ontogenesis in norm and after treatment with harmaline. The experiments were carried out on three age groups of Wistar rats: rat pups (2 weeks), the adult (4–6 months), and the old animals (22–26 months). It was established that the SS duration in norm was approximately equal in rat pups, adult, and old animals, whereas it markedly decreased form the young to the old animals during the SS depression in the Purkinje cell discharge. Frequency of small action potential (lAP) and their number in the Purkinje cell discharge were approximately equal in young rat pups and adult animals, while in old animals these parameters were higher, on average, by 30%. After administration of harmaline, all CS parameters in rat pups and old animals increased in parallel with the depression time elongation. In adult rats, harmaline did not produce statistically significant changes of the mean values of CS parameters, but an increase of the simple spike depression time was observed. The obtained results allow concluding that the SS wave form and the simple spike depression time in norm are functionally coupled and change with age. The effect of harmaline on the CS wave forms as well as on interrelation of the CS duration and the CS depression time in the Purkinje cell discharge was more pronounced at the early and the late stages of Wistar rat postnatal ontogenesis.     

Suppression of cell proliferation and programmed cell death by dexamethasone during postnatal lung development

Prematurely born babies are often treated with glucocorticoids. We studied the consequences of an early postnatal and short dexamethasone treatment (0.1-0.01 microg/g, days 1-4) on lung development in rats, focusing on its influence on peaks of cell proliferation around day 4 and of programmed cell death at days 19-21. By morphological criteria, we observed a dexamethasone-induced premature maturation of the septa (day 4), followed by a transient septal immatureness and delayed alveolarization leading to complete rescue of the structural changes. The numbers of proliferating (anti-Ki67) and dying cells (TdT-mediated dUTP nick end labeling) were determined and compared with controls. In dexamethasone-treated animals, both the peak of cell proliferation and the peak of programmed cell death were reduced to baseline, whereas the expression of tissue transglutaminase (transglutaminase-C), another marker for postnatal lung maturation, was not significantly altered. We hypothesize that a short neonatal course of dexamethasone leads to severe but transient structural changes of the lung parenchyma and influences the balance between cell proliferation and cell death even in later stages of lung maturation.     

DEHP effects on retinal vessels in newborn rats: a qualitative and quantitative analysis

Di-(2-ethylhexyl)-phthalate (DEHP), employed in polyvinyl chloride fabrication and released by endotracheal tubes, is known to cause alterations to several mammalian tissues, markedly in immature animals. The high incidence and severity of bronchopulmonary dysplasia and retinopathy in preterm babies submitted to endotracheal intubation prompted us to investigate the effects of DEHP in lung and retina perinatal development. We previously demonstrated that in rats delivered and breast-fed by DEHP-treated mothers lung alveolarisation is severely impaired. In the present research, the maturation of retinal vessels was studied in (a) flat-mounted retinas obtained after intracardiac injection of FITC-conjugated dextran, (b) flat-mounted retinas incubated with FITC-conjugated Bandeira simplicifolia isolectin B₄, marker of vascular endothelial cells, and (c) eyecup sections incubated with biotinylated IB₄ and revealed by ABC. DEHP-induced vascular alterations mainly affected the superficial plexus, where the radial vessels showed non-perfused as well as remarkably dilated and branched segments, capillary net appeared coarsely arranged and locally absent; periarteriolar capillary-free regions were still found in 14-day-old animals. This extensive vascular remodelling and generally the high responsiveness to DEHP shown by the immature rat retina confirm previous hypothesis that the phthalate released by PVC medical devices remarkably affects perinatal development of several tissues in different body districts.     

Dexamethasone Treatment of Newborn Rats Decreases Cardiomyocyte Endowment in the Developing Heart through Epigenetic Modifications

The potential adverse effect of synthetic glucocorticoid, dexamethasone therapy on the developing heart remains unknown. The present study investigated the effects of dexamethasone on cardiomyocyte proliferation and binucleation in the developing heart of newborn rats and evaluated DNA methylation as a potential mechanism. Dexamethasone was administered intraperitoneally in a three day tapered dose on postnatal day 1 (P1), 2 and 3 to rat pups in the absence or presence of a glucocorticoid receptor antagonist Ru486, given 30 minutes prior to dexamethasone. Cardiomyocytes from P4, P7 or P14 animals were analyzed for proliferation, binucleation and cell number. Dexamethasone treatment significantly increased the percentage of binucleated cardiomyocytes in the hearts of P4 pups, decreased myocyte proliferation in P4 and P7 pups, reduced cardiomyocyte number and increased the heart to body weight ratio in P14 pups. Ru486 abrogated the effects of dexamethasone. In addition, 5-aza-2''-deoxycytidine (5-AZA) blocked the effects of dexamethasone on binucleation in P4 animals and proliferation at P7, leading to recovered cardiomyocyte number in P14 hearts. 5-AZA alone promoted cardiomyocyte proliferation at P7 and resulted in a higher number of cardiomyocytes in P14 hearts. Dexamethasone significantly decreased cyclin D2, but not p27 expression in P4 hearts. 5-AZA inhibited global DNA methylation and blocked dexamethasone-mediated down-regulation of cyclin D2 in the heart of P4 pups. The findings suggest that dexamethasone acting on glucocorticoid receptors inhibits proliferation and stimulates premature terminal differentiation of cardiomyocytes in the developing heart via increased DNA methylation in a gene specific manner.     

Early stress affects neurogenesis in the rat rostral migratory stream

Stressful experience during the early postnatal period may influence processes associated with neurogenesis (i.e. proliferation, cell death, appearance of astrocytes or cell differentiation) in the neonatal rat rostral migratory stream (RMS). To induce stress, pups were subjected to maternal deprivation daily for three hours, starting from the first postnatal day till the seventh postnatal day. Immunohistochemical methods were used to visualize proliferating cells and astrocytes; dying cells and nitrergic cells were visualized using histochemical staining. Quantitative analysis showed that maternal deprivation decreased the number of proliferating cells and significantly increased the number of dying cells in the RMS. Maternal deprivation did not influence the appearance of astrocytes in the RMS, but caused premature differentiation of nitrergic cells. In control rats, nitrergic cells can be observed in the RMS as early as the tenth postnatal day. In maternally deprived pups, these cells were detected as early as the seventh postnatal day. The observed earlier appearance of nitrergic cells in the RMS was associated with altered proliferation and increased cell dying and this observation supports the hypothesis that nitric oxide has an anti-proliferative role in the RMS. Our study demonstrates that maternal deprivation represents a stressful condition with a profound impact on early postnatal neurogenesis.     

Recombinant human VEGF treatment transiently increases lung edema but enhances lung structure after neonatal hyperoxia

Recent studies suggest that VEGF may worsen pulmonary edema during acute lung injury (ALI), but, paradoxically, impaired VEGF signaling contributes to decreased lung growth during recovery from ALI due to neonatal hyperoxia. To examine the diverse roles of VEGF in the pathogenesis of and recovery from hyperoxia-induced ALI, we hypothesized that exogenous recombinant human VEGF (rhVEGF) treatment during early neonatal hyperoxic lung injury may increase pulmonary edema but would improve late lung structure during recovery. Sprague-Dawley rat pups were placed in a hyperoxia chamber (inspired O(2) fraction 0.9) for postnatal days 2-14. Pups were randomized to daily intramuscular injections of rhVEGF(165) (20 microg/kg) or saline (controls). On postnatal day 14, rats were placed in room air for a 7-day recovery period. At postnatal days 3, 14, and 21, rats were killed for studies, which included body weight and wet-to-dry lung weight ratio, morphometric analysis [including radial alveolar counts (RAC), mean linear intercepts (MLI), and vessel density], and lung endothelial NO synthase (eNOS) protein content by Western blot analysis. Compared with room air controls, hyperoxia increased pulmonary edema by histology and wet-to-dry lung weight ratios at postnatal day 3, which resolved by day 14. Although treatment with rhVEGF did not increase edema in control rats, rhVEGF increased wet-to-dry weight ratios in hyperoxia-exposed rats at postnatal days 3 and 14 (P < 0.01). Compared with room air controls, hyperoxia decreased RAC and increased MLI at postnatal days 14 and 21. Treatment with VEGF resulted in increased RAC by 181% and decreased MLI by 55% on postnatal day 14 in the hyperoxia group (P < 0.01). On postnatal day 21, RAC was increased by 176% and MLI was decreased by 58% in the hyperoxia group treated with VEGF. rhVEGF treatment during hyperoxia increased eNOS protein on postnatal day 3 by threefold (P < 0.05). We conclude that rhVEGF treatment during hyperoxia-induced ALI transiently increases pulmonary edema but improves lung structure during late recovery. We speculate that VEGF has diverse roles in hyperoxia-induced neonatal lung injury, contributing to lung edema during the acute stage of ALI but promoting repair of the lung during recovery.     

Inhibition of apoptosis by 60% oxygen: a novel pathway contributing to lung injury in neonatal rats

During early postnatal alveolar formation, the lung tissue of rat pups undergoes a physiological remodeling involving apoptosis of distal lung cells. Exposure of neonatal rats to severe hyperoxia (≥95% O(2)) both arrests lung growth and results in increased lung cell apoptosis. In contrast, exposure to moderate hyperoxia (60% O(2)) for 14 days does not completely arrest lung cell proliferation and is associated with parenchymal thickening. On the basis of similarities in lung architecture observed following either exposure to 60% O(2), or pharmacological inhibition of physiological apoptosis, we hypothesized that exposure to 60% O(2) would result in an inhibition of physiological lung cell apoptosis. Consistent with this hypothesis, we observed that the parenchymal thickening induced by exposure to 60% O(2) was associated with decreased numbers of apoptotic cells, increased expressions of the antiapoptotic regulator Bcl-xL, and the putative antiapoptotic protein survivin, and decreased expressions of the proapoptotic cleaved caspases-3 and -7. In summary, exposure of the neonatal rat lung to moderate hyperoxia results in an inhibition of physiological apoptosis, which contributes to the parenchymal thickening observed in the resultant lung injury.     

Effects of maternal captopril treatment during late pregnancy on neonatal lung development in rats

The renin-angiotensin system (RAS) has been implicated in pulmonary hypertension and pulmonary fibrosis. In the present study, we examined the effects of maternal exposure to captopril (2.85 mg/kg/day) during late pregnancy (G13-G21) on postnatal rat lung development. Treatment with captopril during late pregnancy caused a significant decrease in ACE activity in P0 rats. Body weight decreased at P0 (p<0.001), P8 and P15 (p<0.01) in captopril-treated rats. Lung weight of P0 and P8 pups was lower in treated-animals (p<0.05). Lungs from captopril-treated animals showed impaired alveolar formation, with enlarged distal airway spaces at P8, P15 and P30. Interalveolar wall distance measured by mean linear intercept increased in treated vs. age-matched animals at P8, P15 (p<0.001) and P30 (p<0.05) resembling new bronchopulmonary dysplasia. In control animals, the proliferating cell nuclear antigen (PCNA) marker was higher at P0 and then drops gradually, while in captopril-treated animals PCNA marker remains higher at all stages studied. α-Smooth muscle actin (α-SMA), a marker of fibroblast differentiation into myofibroblasts, was higher at the tips of developing secondary septa in captopril-treated lungs at P8 and P15. The increased expression of PCNA and α-SMA in treated pups suggest that beyond the effect caused by captopril, the developing lungs have the capacity to recover once the treatment was stopped. Taking together the low weight, histomorphological changes and increased expression of cellular markers caused by ACE inhibition during late pregnancy, it appears that the RAS could be an intrinsic factor involved in secondary septa formation during lung development.     

In utero and early-life exposure of rats to a Wi-Fi signal: screening of immune markers in sera and gestational outcome

An experimental approach was used to assess immunological biomarkers in the sera of young rats exposed in utero and postnatal to non-ionizing radiofrequency fields. Pregnant rats were exposed free-running, 2 h/day and 5 days/week to a 2.45 GHz Wi-Fi signal in a reverberation chamber at whole-body specific absorption rates (SAR) of 0, 0.08, 0.4, and 4 W/kg (with 10, 10, 12, and 9 rats, respectively), while cage control rats were kept in the animal facility (11 rats). Dams were exposed from days 6 to 21 of gestation and then three newborns per litter were further exposed from birth to day 35 postnatal. On day 35 after birth, all pups were sacrificed and sera collected. The screening of sera for antibodies directed against 15 different antigens related to damage and/or pathological markers was conducted using enzyme-linked immunosorbent assay (ELISA). No change in humoral response of young pups was observed, regardless of the types of biomarker and SAR levels. This study also provided some data on gestational outcome following in utero exposure to Wi-Fi signals. Mass evaluation of dams and pups and the number of pups per litter was monitored, and the genital tracts of young rats were observed for abnormalities by measuring anogenital distance. Under these experimental conditions, our observations suggest a lack of adverse effects of Wi-Fi exposure on delivery and general condition of the animals.     

Nitric oxide synthase inhibition decreases tolerance to hyperoxia in newborn rats

We evaluated the effects of sustained perinatal inhibition of NO synthase (NOS) on hyperoxia induced lung injury in newborn rats. N(G)-nitro-Larginine-methyl-ester (L-NAME) or untreated water was administered to pregnant rats for the final 7 days of gestation and during lactation; followed by postnatal exposure to hyperoxia (>95% O(2)) or room air. The survival rate of L-NAME treated pups when placed in > 95% O(2) at birth was significantly lower than controls from day 4 (L-NAME, 87%; control pups, 100%, p < 0.05) to 14 (L-NAME, 0%; control pups, 53%, p < 0.05). Foetal pulmonary artery vasoconstriction was induced by L-NAME with a decrease in internal diameter from 0.88 +/- 0.03 mm to 0.64 +/- 0.01 mm in control vs. L-NAME groups (p < 0.05), respectively. We conclude that perinatal NOS inhibition results in pulmonary artery vasoconstriction and a decreased tolerance to hyperoxia induced lung injury in newborn rats.     

Expression of autotaxin and lysophosphatidic acid receptors 1 and 3 in the developing rat lung and in response to hyperoxia

Abstract

We sought to evaluate lysophosphatidic acid (LPA) signaling improvement in lung development by assessing the expression of autotaxin and LPA receptor 1 and 3 (LPAR1 and LPAR3) in the neonatal rat lung during normal perinatal development and in response to hyperoxia. In the developmental study, rats were sacrificed on days 17, 19, and 21 of gestation; on postnatal days 1, 4, and 7; and at adulthood (postnatal 9 weeks). In the hyperoxia study, 42 postnatal 4-day-old rat pups were divided into seven groups and exposed to either 85% O₂ for 24, 72, or 120 h or room air for 0, 24, 72, or 120 h. The rats were then euthanized after 0, 24, 72, and 120 h of exposure. Immunofluorescence demonstrated that autotaxin, LPAR1, and LPAR3 proteins were broadly colocalized in airway epithelial cells, but mainly distributed in vascular endothelial and mesenchymal cells during the first postnatal week. The expression of autotaxin, LPAR1, and LPAR3 were increased during late gestation and then decreased after birth. Autotaxin expression and enzymatic activity were significantly increased at 72 and 120 h after exposure to hyperoxia. LPAR1 and LPAR3 expression was also increased after 120 h of hyperoxic exposure. These findings suggest that LPA-associated molecules were upregulated at birth and induced by hyperoxia in the developing rat lung. Therefore, the LPA pathway may be involved in normal lung development, including vascular development, as well as wound-healing processes of injured neonatal lung tissue, which is at risk of neonatal hyperoxic acute lung injury.     

Reduced Hippocampal Dendritic Spine Density and BDNF Expression following Acute Postnatal Exposure to Di(2-Ethylhexyl) Phthalate in Male Long Evans Rats

Early developmental exposure to di(2-ethylhexyl) phthalate (DEHP) has been linked to a variety of neurodevelopmental changes, particularly in rodents. The primary goal of this work was to establish whether acute postnatal exposure to a low dose of DEHP would alter hippocampal dendritic morphology and BDNF and caspase-3 mRNA expression in male and female Long Evans rats. Treatment with DEHP in male rats led to a reduction in spine density on basal and apical dendrites of neurons in the CA3 dorsal hippocampal region compared to vehicle-treated male controls. Dorsal hippocampal BDNF mRNA expression was also down-regulated in male rats exposed to DEHP. No differences in hippocampal spine density or BDNF mRNA expression were observed in female rats treated with DEHP compared to controls. DEHP treatment did not affect hippocampal caspase-3 mRNA expression in male or female rats. These results suggest a gender-specific vulnerability to early developmental DEHP exposure in male rats whereby postnatal DEHP exposure may interfere with normal synaptogenesis and connectivity in the hippocampus. Decreased expression of BDNF mRNA may represent a molecular mechanism underlying the reduction in dendritic spine density observed in hippocampal CA3 neurons. These findings provide initial evidence for a link between developmental exposure to DEHP, reduced levels of BDNF and hippocampal atrophy in male rats.     

The influence of phenobarbitone on maternal and perinatal hepatic drug-metabolizing enzymes in the rat.

Phenobarbitone (PB) (75 mg/kg) was administered orally for three consecutive days to pregnant or lactating rats at different pre- and postnatal stages in order that the perinatal animals would receive the agent either by transplacental passage or via the milk. Control animals received equivalent volumes of saline. The dams, fetuses, and pups were killed 24 h after the last dose. Hepatic p-nitroanisole O-demetnylase (OD), carboxylesterase (CE), and bromosulfophthalein-glutathione (BSP-GSH) conjugating enzyme activities in a 12 100 g - 20 min supernatant of a 20% w/v homogenate were measured. The morphology of the developing rat liver in the absence and presence of PB was examined by electron microscopy. The results demonstrated that the transplacental passage of PB to rat fetuses at term or 3 days prepartum had no effect on either the hepatic drug-metabolizing enzyme activities or on the ultrastructural appearance of the liver. Increased hepatic OD activity was observed in the pregnant animal but no effect was observed in the lactating dam. Phenobarbitone received by the suckling rat had two distinct effects. Compared to control activities, twofold increases in hepatic OD activity were observed in rat pups as early as 4 days after birth, associated with a marked proliferation in hepatic smooth endoplasmic reticulum. In contrast, PB-related significant increases in neonatal hepatic CE and BSP-GSH conjugating enzyme activities were not observed until 21 days of age. In the 4-day-old treated pups, characteristic morphological changes included numerous small membrane whorls in addition to increased smooth endoplasmic reticulum and microbodies in the liver.     

Oxygen consumption and survival prediction in neonatal rats exposed to prenatal hypervitaminosis A

Fetal exposure to excess vitamin A results in a highly variable degree of lung pathology and high neonatal mortality in the Long-Evans rat. The present study evaluated O2 consumption in newborn of vitamin A-treated, vehicle-treated, and untreated pregnancies on five consecutive postnatal days beginning with the day of delivery (D0). Pregnant female rats were treated by gavage with 160,000 USP units of retinyl acetate dissolved in 0.5 ml corn oil on days 15 through 19 of gestation. Vehicle and undisturbed controls were run concurrently. All animals delivered spontaneously, and the pups were tattooed and individually tested in a closed system consisting of three chambers submerged within a thermostatically controlled water bath at 33 degrees C. Vitamin A-exposed pups, as a group, have significantly lower QO2 (ml O2 consumed/min/kg body weight) values than controls through postnatal day 2 (p less than 0.05). By days 3 and 4 of age, the mean QO2 values of surviving vitamin A-treated pups were similar to those of controls. A QO2 of 30 or greater on day 0 appears to be critical for early neonatal survival of vitamin A-exposed pups, as 87% of the pups with initial QO2 less than 30 died prior to day 4. Oxygen consumption rates in teratogen-exposed pups exhibiting low QO2 on day 0 rarely reached normal levels. In contrast, the occasional control pup with such low initial levels were well within normal limits (means +/- 1 SD) by the following day.(ABSTRACT TRUNCATED AT 250 WORDS)     

Delayed maturation and altered proliferation within the rat rostral migratory stream following maternal deprivation

The objective of this study was to investigate whether stressful experience during early postnatal period may influence morphological characteristics of the rat neurogenic pathway--the rostral migratory stream (RMS) and proliferation of neuronal precursors in three successive areas of the RMS: in the vertical arm, the elbow and the horizontal arm. To induce stress, the pups were subjected to repeated maternal deprivation during the first postnatal week after birth. Brains were analyzed at the seventh postnatal day. The controls matched the age of maternally deprived animals. Observation of hematoxylin-eosin stained sections showed that maternal deprivation did not affect the general morphological appearance of the RMS. The shape of the RMS of maternally deprived rats resembles the RMS of control animals. Maternal deprivation caused slight, not significant increase in the RMS thickness in comparison with control rats. Significant difference between the control and maternally deprived rats concerns the olfactory ventricle. While in seven days old control rats the olfactory ventricle is completely closed, in maternally deprived rats of the same age the olfactory ventricle was regularly visible as a narrow lumen at the axis of the RMS horizontal arm. This finding indicates delayed maturation of the migratory pathway as a consequence of stress. Proliferation activity has been assessed by immunoreactivity of the endogenous cell cycle protein Ki-67. The results of Ki-67 immunohistochemistry showed that seven days' maternal separation for 3 h daily induces significant quantitative changes in the number of proliferating cells within the RMS. The response of Ki-67-positive cells to stress differed in individual part of the RMS, with a marked decrease in the vertical arm and a significant increase in the elbow, suggesting heterogeneity of neural stem cells along the RMS; while in the RMS vertical arm the number of dividing cells significantly decreased, there was a marked increase of Ki-67-positive cells in the RMS elbow. This suggests heterogeneity of neural stem cells along the RMS.