Growth-retarded Pups Research Articles

Prenatal Ischemia and White Matter Damage in Rats

Ischemia/reperfusion injury to the developing brain is a major cause of neurologic abnormalities in preterm infants. To investigate the underlying mechanisms, we modified a previously described rat model of unilateral uterine-artery ligation on the 17th embryonic day (E17). Growth retardation was taken as an index of in utero ischemia, and pups born with a birth weight more than 2 standard deviations below that of controls were compared with the same-litter, normal-growth control pups born from the nonligated horn. Prenatal ischemia probably associated with hypoxia and followed by reperfusion at birth induced white matter damage at a developmental stage corresponding to extreme prematurity in humans. On P0 (day of birth), growth-retarded pups exhibited lesions in the cingular white matter and internal capsule with increased counts of activated microglial cells for 2 weeks compared with controls. Astrogliosis was detected in the injured white matter. On P3, increased apoptotic cell death was seen in O4-positive preoligodendrocytes, which were abnormally scarce on P7. Defective myelination, as assessed by myelin-binding-protein labeling, was detected until adulthood. The diffuse white matter damage in growth-retarded rats replicated the main features of white matter damage in human preterm infants.

Effect of early fetal irradiation on the postnatal development of mouse.

An earlier study has shown that irradiation at the late fetal stage of Swiss albino mice disturbed postnatal growth and appearance of physiological markers. The present study was done to determine the effect of irradiation at the early fetal stage on the postnatal development of mouse. Fourteen-day pregnant Swiss albino mice were exposed to 0.1-1.5 Gy of cobalt-60 gamma-rays. F1 pups were observed for < or = 6 weeks of age. Postnatal mortality, body weight and length, head length and width, tail length, and the time of appearance of physiological markers (pinna detachment, eye opening, fur development, vaginal opening and testes descent) were noted. There was no increase in congenital anomalies. Postnatal mortality and percentage of growth-retarded pups increased significantly at doses of 0.5-1.5 Gy. A significant delay in the appearance of all the physiological markers was also noted at these doses. Body length, head length, and tail length remained significantly lower than in the controls throughout the observation period at doses of 0.3-1.5 Gy, whereas body weight and head width showed such a persistent change only at > or = 0.5 Gy. The early fetal day 14 in mouse is sensitive to radiation-induced postnatal mortality and impairment of growth and temporal development of physiological markers, but not to induction of congenital anomalies. While mortality and physiological markers are not affected at <0.5 Gy, growth retardation appears to have a lower threshold of approximately 0.3 Gy.

Long-term effects of postovulatory aging of mouse oocytes on offspring: a two-generational study.

Aims of this study were to analyze the long-term effects of postovulatory aging of mouse oocytes on 1) reproductive traits of parental (F(0)) and first (F(1))-generation females (pregnancy rate, gestation length, litter size, perinatal death, and sex ratio of offspring) and 2) developmental and behavioral variables of F(1) and second-generation (F(2)) offspring (birth weight and weight gain during preweaning development, postnatal day of attainment of immediate righting, spontaneous motor activity, and passive and active conditioned learning ability). Hybrid (C57BL/6JIco x CBA/JIco) females were artificially inseminated at 13 h (control group) or 22 h (oocyte-aged group) after GnRH injection. Experimental (oocyte-aged group) F(0) females exhibited lower pregnancy rate, shortened gestation length, decreased litter size, higher perinatal death of their pups, and increased percentage of male offspring compared to control F(0) females. Postovulatory aging of oocytes was also associated with increased number of growth-retarded pups, delayed development of the righting reflex, and higher spontaneous motor activity and emotionality of F(1) offspring. Postovulatory aging of F(0) oocytes did not affect birth weight, weight gain during preweaning development, passive and active conditioned learning ability of F(1) offspring, or reproductive traits of F(1) females or developmental and behavior variables of F(2) offspring.

Influence of postnatal overnutrition and pregnancy on non-insulin dependent diabetes induced in Wistar rats by neonatal streptozotocin.

Wistar rats with non-insulin dependent diabetes induced by neonatal streptozotocin (STZ) administration were raised either in large or in small litters. The STZ-treated rats from small litters showed a higher body weight as well as increased blood glucose levels compared with vehicle- and STZ-treated rats reared in large nests at an age of 8 weeks. The higher body weight of these rats was maintained until an age of 15 weeks, whereas the basal blood glucose was normalized. However, both STZ-treated groups exhibited an impaired glucose tolerance. During pregnancy only the glucose tolerance of the STZ-treated animals from large nests was improved although not normalized. The STZ-treated rats from small nests failed to adapt to pregnancy because the blood glucose levels after glucose load were similar to values found in the virgin state. The body weight of pregnant STZ treated rats raised in small litters was significantly lower than in vehicle- or STZ-terated rats from large nests. The number of fetuses per litter was similar in all groups tested. Compared with the vehicle-treated rats from large litters the fetal body weight of STZ-treated rats from small nests was decreased and that of STZ rats raised in large litters was increased. These results suggest that the rats with the more impaired glucose tolerance produce growth-retarded pups and, conversely, rats with rather mild impairment have bigger fetuses than the vehicle-treated ones. In the present study we have examined for the first time the combined effects of postnatal overnutrition and pregnancy on glucose homeostasis of rats treated neonatally with STZ. Our data demonstrate that postnatal overnutrition is an aggravating factor in the development of a diabetic state in these rats, especially at times when the insulin requirement is higher such as puberty and pregnancy.

Effects of maternal protein malnutrition on fetal growth, plasma insulin-like growth factors, insulin-like growth factor binding proteins, and liver insulin-like growth factor gene expression in the rat.

We examined the effects of maternal dietary protein restriction on fetal growth and expression of IGF-I and -II, and IGF-binding proteins (IGFBP). We sought to dissociate the respective effects of maternal protein versus calorie restriction on growth indices and IGF synthesis by the neonates of protein-restricted dams. Pregnant Wistar rats (six to eight per group) fed a low (5%) protein diet throughout gestation had impaired body weight gain compared with controls fed a normal (20%) protein diet (by 45%, p < 0.001). Their serum and liver IGF-I concentrations and liver IGF-I mRNA concentrations were also reduced by 60, 80, and 50%, respectively. Serum IGFBP-3 was reduced by 60% in protein-restricted dams within 1 to 2 h after delivery (p < 0.001 versus controls), although IGFBP-1, -2, and -4 were not significantly affected by the dietary protein intake. In pups of protein-restricted dams, the mean body and liver weight at birth was 15-20% less than that observed in the progeny from normal protein-fed dams (p < 0.01). Their plasma and liver IGF-I concentrations were 30 and 60% lower, respectively, whereas liver IGF-I mRNA abundance was reduced by 50% (p < 0.01). In contrast, neonatal plasma IGF-II and liver IGF-II mRNA concentrations were not significantly affected by the maternal protein malnutrition. Also, the plasma levels of IGFBP were not altered in the growth-retarded pups. Maternal protein restriction did not affect fetal and placental growth, plasma and liver IGF-I levels, and liver IGF-I mRNA abundance in 20-d-old fetuses.(ABSTRACT TRUNCATED AT 250 WORDS)

Differential effects of short and long durations of insulin-induced maternal hypoglycemia upon fetal rat tissue growth and glucose utilization.

We studied the effects of short and long durations of insulin-induced maternal hypoglycemia upon in vivo glucose utilization of several fetal tissues in the rat. Osmotic minipumps filled with insulin were implanted in pregnant rats on d 15 or 18 of gestation (term 21.5 d), and radiolabeled 2-deoxyglucose was used to measure relative glucose utilization rates (rGU) of fetal liver, lung, muscle, kidney, heart, placenta, and brain on d 20 of gestation after 2 or 5 d of hypoglycemia. Maternal plasma glucose concentrations decreased within 24 h of pump placement and remained less than controls throughout gestation. Fetal plasma glucose and insulin concentrations on d 20 were equally reduced after 2 and 5 d of hypoglycemia. Both 2 and 5 d of hypoglycemia were associated with significant reductions in the rGU of fetal liver, lung, and muscle. Reductions in fetal kidney rGU also occurred after 2 and 5 d of hypoglycemia but to a smaller degree. rGU of fetal heart was reduced after 2 d of hypoglycemia, but was normal after 5 d of hypoglycemia. Both 2 and 5 d of hypoglycemia were associated with increased rGU of fetal brain. Five d, but not 2 d of hypoglycemia resulted in decreased fetal weight on d 20 of gestation. However, at term, newborn pups delivered of hypoglycemic mothers weighed significantly less than controls regardless of the timing of minipump placement. Liver, lung, and carcass of these growth-retarded pups weighed less than control tissues, whereas kidney, heart, and brain weights were not affected.(ABSTRACT TRUNCATED AT 250 WORDS)

Neonatal sympathoadrenal response to acute hypoxia: impairment after experimental intrauterine growth retardation.

Sympathoadrenal system function may be altered following intrauterine growth retardation (IUGR). We tested the hypothesis that the growth-retarded newborn rat pup has increased basal sympathoadrenal activity under normoxic conditions and a blunted sympathoadrenal response to acute hypoxia. IUGR was established by uterine artery ligation on d 18 of gestation in Sprague-Dawley rats. Growth-retarded pups were chosen as those whose birth wt was more than 2 x SD below the mean birth wt of control pups delivered to sham-operated dams. At 24 +/- 12 h of age cardiac sympathetic neuronal activity (CSNA) was determined by 3H-norepinephrine tracer and alpha-methyltyrosine techniques. Adrenal medullary catecholamine synthesis (CAT SYN) was measured by 14C-tyrosine precursor methods, and adrenal catecholamine release (CAT REL) was determined using alpha-methyl-tyrosine. IUGR and control pups were studied over a 120-min period of normoxia or hypoxia (FiO2 = 0.09). Under normoxic conditions, the IUGR pups had increased CSNA and increased adrenal CAT SYN and CAT REL compared to controls. Adrenal CAT REL in normoxic IUGR pups was selective for epinephrine. In response to acute hypoxia, control pups had increased CSNA and increased adrenal CAT SYN and CAT REL compared to normoxic controls, with the proportion of norepinephrine and epinephrine released mimicking the ratio of the two amines in the adrenal. In contrast, in hypoxic IUGR pups CSNA and adrenal CAT SYN did not increase, and norepinephrine alone was released from the adrenal medulla.(ABSTRACT TRUNCATED AT 250 WORDS)

Alterations of fasting glucose and fat metabolism in intrauterine growth-retarded newborn dogs.

Maternal nutritional deprivation resulted in reduced fetal weight at term gestation (251 +/- 7 vs. 277 +/- 7 g, P less than 0.01) in newborn dogs. Growth-retarded pups developed lower blood glucose levels after 3, 6, and 9 h of neonatal fasting, reduced plasma levels of free fatty acids (FFA) at 9 and 24 h, and lower ketone bodies at 24 h compared with age-matched newborn control pups. Systemic rates of palmitate and alanine turnover were not affected, but systemic glucose turnover was reduced for 3-9 h after birth. The rate of alanine incorporation into glucose from 3 to 9 h was also reduced in growth-retarded pups compared with timed controls. Paradoxically, the rate of incorporation of palmitate into triglycerides was augmented in the smaller growth-retarded pups. Hepatic glycogen content was reduced at every time in the study among growth-retarded pups, whereas the rates of glycogenolysis between birth and 24 h were equivalent in the two pup groups. In contrast, hepatic triglyceride levels were augmented throughout the study in pups with growth retardation. Maternal starvation and lower glucose levels resulted in a lower hepatic energy charge, and augmented cytoplasmic and mitochondrial NAD-to-NADH ratios in intrauterine growth-retarded pups. These data suggest that intrauterine growth retardation in dogs results in fasting neonatal hypoglycemia that is due in part to reduced systemic glucose production. We speculate that reduced rates of gluconeogenesis from alanine and reduced oxidation of alternate fuels such as FFA contribute to hypoglycemia. FFA recycling to triglyceride synthesis rather than oxidative pathways may contribute to the observed reduction of circulating glucose levels.

Cerebral Metabolic Response to Neonatal Hypoglycemia in Growth-Retarded Dogs

The cerebral metabolic effects of hypoglycemia due to intrauterine growth retardation were studied in newborn dogs. Intrauterine growth retardation was induced in newborn dogs after 3 days of maternal nutritional deprivation (birth weight 251 +/- 7 versus 227 +/- 7 g, p less than 0.01). After birth, growth retarded pups developed fasting neonatal hypoglycemia which lasted from 3 to 9 h of life. The cerebral arteriovenous differences for glucose, oxygen, and ketone bodies were not different between growth-retarded pups or those from age-matched controls. The cerebral venous efflux of lactate was reduced, whereas the extraction of glucose (relative to blood glucose) was enhanced among growth-retarded pups. Cerebral glycogen content was lower in pups with growth retardation whereas phosphoenolpyruvate and pyruvate concentrations were augmented among growth-retarded pups. The latter may reflect a more oxidized cytoplasmic redox state but may also be due to diminished lactate efflux from the brain. Cerebral ATP content was not affected during periods of reduced blood glucose levels. These results suggest that in newborn dogs hypoglycemia associated with intrauterine growth retardation alters cerebral metabolism by increasing cerebral extraction of glucose and decreasing CNS efflux of lactate. We speculate that the net effect is increased lactate utilization within oxidative pathways and preservation of cerebral oxygen uptake. Cerebral glucose utilization is directed away from glycogen synthesis and toward glycolysis. Lactate oxidation rather than release to the systemic circulation may maintain cerebral ATP production in growth-retarded hypoglycemic newborn dogs.

Effects of prenatal and postnatal exposure to gentamicin on renal differentiation in the rat

Pregnant rats were injected daily, from the 10th day of gestation to term, with 75 mg/kg of gentamicin. They gave birth about 15 h later than control pregnant rats injected with saline to pups with various degrees of growth retardation. In pups born of gentamicin-treated mothers, the number of nephrons present at birth, as well as the final number of nephrons, were reduced by at least 20%. Observation of the kidneys by light microscopy showed focal tubular lesions on the mature nephrons. The intrarenal concentration of gentamicin was higher in the severely growth retarded pups than in the others. In another series of experiments, rats were given 75 mg/kg of gentamicin daily from days 1 to 13 after birth. Although under these conditions the concentration of gentamicin reached in the postnatal kidney was higher than that reached after exposure in utero, no reduction of the final number of nephrons was observed. It is concluded that administration of gentamicin to pregnant rats caused focal tubular lesions in the developing kidney and a reduced rate of early nephrogenesis. The latter was probably due to growth retardation, though a more direct effect of gentamicin on early nephrogenesis may also have been involved.

Absence of effects of lead feedings and growth-retardation on mitochondrial and microsomal cytochromes in the developing brain

Heme-containing enzymes were measured by absorption spectroscopy in mitochondria and microsomes isolated from the brains of PbCO 3-fed rat pups. Brain mitochondrial cytochromes also were measured in lead-fed adult rats and in growth-retarded pups. In normal animals, brain mitochondrial and microsomal cytochrome levels increased about twofold from 1 week of age to adulthood. In pups fed lead from birth, the resulting encephalopathy occurred most frequently in the first 2 weeks. Cerebellar mitochondrial cytochromes were decreased but only after 4 weeks of feedings. In pups fed lead from 2 weeks of age, the encephalopathy occurred after 2 weeks of feedings. There were no decreases in cerebral or cerebellar mitochondrial cytochromes. In both groups of pups, brain microsomal cytochromes tended to be higher in lead-fed than in control animals. Lead-feedings did not alter adult brain mitochondrial cytochrome levels. Brain mitochondrial levels also were unchanged in growth-retarded compared to normal rat pups. We conclude that the cytochrome concentrations of mitochondria and microsomes from both the immature and adult rat brain are relatively unaffected by factors such as inorganic lead exposure, known to influence pathways of heme breakdown and synthesis in other tissues. Second, changes in brain mitochondrial cytochrome contents are not associated with the development of lead encephalopathy in the rat pup.