Term Rat Fetuses Research Articles

Glutamate Promotes Contraction of the Rat Ductus Arteriosus.

Extremely preterm infants frequently have patent ductus arteriosus (PDA). Recent recommendations include immediately beginning amino acid supplementation in extremely preterm infants. However, the effect of amino acids on closure of the ductus arteriosus (DA) remains unknown.Methods and Results:Aminogram results in human neonates at day 2 revealed that the plasma glutamate concentration was significantly lower in extremely preterm infants (<28 weeks' gestation) with PDA than in those without PDA and relatively mature preterm infants (28-29 weeks gestation). To investigate the effect of glutamate on DA closure, glutamate receptor expression in fetal rats was examined and it was found that the glutamate inotropic receptor, α-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) type subunit 1 (GluR1), mRNA was highly expressed in the DA compared to the aorta on gestational day 19 (preterm) and gestational day 21 (term). GluR1 proteins were co-localized with tyrosine hydroxylase-positive autonomic nerve terminals in the rat and human DA. Intraperitoneal administration of glutamate increased noradrenaline production in the rat DA. A whole-body freezing method demonstrated that glutamate administration induced DA contraction in both preterm (gestational day 20) and term rat fetuses. Glutamate-induced DA contraction was attenuated by the calcium-sensitive GluR receptor antagonist, NASPM, or the adrenergic receptor α1 blocker, prazosin. These data suggest that glutamate induces DA contraction through GluR-mediated noradrenaline production. Supplementation of glutamate might help to prevent PDA in extremely preterm infants. (Circ J 2016; 80: 2388-2396).

Neonatal sensitization to ethanol-induced breathing disruptions as a function of late prenatal exposure to the drug in the rat: Modulatory effects of ethanol's chemosensory cues

Preclinical and clinical studies have systematically demonstrated abrupt changes in fetal respiratory patterns when the unborn organism is exposed to the effects of maternal ethanol intoxication. In subprimates, chronic exposure to this drug during gestation and infancy results in marked alterations of the plasticity of the respiratory network. These alterations are manifested in terms of an early incapability to overcome deleterious effects of hypoxic events as well as in terms of sensitization to ethanol's depressant effects upon breathing patterns. It has also been demonstrated that near term rat fetuses process ethanol's chemosensory cues when the drug contaminates the amniotic fluid and that associative learning processes occur due to the temporal contiguity existing between these cues and different ethanol-related physiological effects. In the present study during the course of late gestation (gestational days 17–20), pregnant rats were intragastrically administered with either 0.0 or 2.0g/kg ethanol. Seven-day-old pups derived of these dams were evaluated in terms of respiration rates (breaths/min) and apneas when subjected to different experimental conditions. These conditions were defined by postnatal exposure to the drug (intragastric administrations of either 0.0, 0.5, 1.0 or 2.0g/kg ethanol), postadministration time of evaluation (5–10 or 30–35min) and olfactory context at test (no explicit ambient odor or ethanol ambient odor). The results, obtained via whole body plethysmography, indicated that brief prenatal experience with the drug sensitized the organisms to ethanol's depressant effects particularly when employing the higher ethanol doses. In turn, presence of ethanol odor at test potentiated the above mentioned respiratory alterations. Prenatal treatment with ethanol was not found to alter pharmacokinetic profiles resulting from postnatal exposure to the drug or to affect different morphometric parameters related with lung development. These results indicate that even brief exposure to the drug during late gestation is sufficient to sensitize the organism to later disruptive effects of the drug upon breathing responsiveness. These deficits are potentiated through the re-exposure to the olfactory context perceived in utero which is known to be associated with ethanol's unconditioned effects. As a function of these observations it is possible to suggest a critical role of fetal sensory and learning capabilities in terms of modulating later ethanol-related breathing disruptions.

Morpho-functional characteristics of rat fetal thyroid gland are affected by prenatal dexamethasone exposure

Thyroid hormones (TH) and glucocorticoids strongly contribute to the maturation of fetal tissues in the preparation for extrauterine life. Influence of maternal dexamethasone (Dx) administration on thyroid glands morpho-functional characteristics of near term rat fetuses was investigated applying unbiased stereology. On the 16th day of pregnancy dams received 1.0mg/Dx/kg/b.w., followed by 0.5mg/Dx/kg/b.w. on the 17th and 18th days of gestation. The control females received the same volume of saline. The volume of fetal thyroid was estimated using Cavalieri’s principle; the physical/fractionator design was applied for the determination of absolute number of follicular cells in mitosis and immunohistochemically labeled C cells; C cell volume was measured using the planar rotator. The functional activity of thyroid tissue was provided from thyroglobulin (Tg) and thyroperoxidase (TPO) immunohistochemical staining. Applying these design-based modern stereological methods it was shown that Dx treatment of gravid females led to a significant decrease of fetal thyroid gland volume in 19- and 21-day-old fetuses, due to decreased proliferation of follicular cells. The Tg and TPO immunohistochemistry demonstrated that intensive TH production starts and continues during the examined period in control and Dx-exposed fetuses. Under the influence of Dx the absolute number of C cells was lower in both groups of near term fetuses, although unchanged relation between the two populations of endocrine cells, follicular and C cells suggesting that structural relationships within the gland are preserved. In conclusion maternal glucocorticoid administration at the thyroid gland level exerts growth-inhibitory and maturational promoting effects in near term rat fetuses.

Does Selenium Ameliorate Toxic Effects of Prenatal Aluminium on Brain of Full Term Rat Fetuses?

Does Selenium Ameliorate Toxic Effects of Prenatal Aluminium on Brain of Full Term Rat Fetuses?

428: Acute hypoxic stress-induced in utero meconium passage in near term rat fetuses is mediated by a novel myenteric neuronal CRF-R1/R2 receptor system

428: Acute hypoxic stress-induced in utero meconium passage in near term rat fetuses is mediated by a novel myenteric neuronal CRF-R1/R2 receptor system

406: Mechanisms of fetal meconium passage: Anatomical and biochemical localization of CRF-R1 receptors in fetal rat gastrointestinal tract

Hypoxic-stress is a potent stimulator of in utero meconium passage in term human and rat fetuses. Together with known corticotrophin releasing factor (CRF) gastrointestinal (GI) stimulatory effects and elevated CRF levels in hypoxic rat fetuses, we propose that CRF is a key mediator of hypoxia-induced fetal meconium passage. As CRF action is mediated by binding to GI stimulatory R1 receptors, we sought to determine the presence of CRF-R1 in the GI tracts of term rat fetuses by anatomical and biochemical techniques.

Development of pituitary ACTH and GH cells in near term rat fetuses

This study describes the development of ACTH and GH cells in 19- and 21-day-old rat fetuses using immunohistochemistry and morphometric measurements. Between days 19 and 21 of pregnancy, the total volume of fetal ACTH cells was unchanged, while their volume density and number per unit of area decreased significantly. ACTH-like immunopositivity in the pars intermedia increased during the examined period. The cell volume, volume density and number of GH cells per unit of area all markedly increased in parallel with fetal development, i.e., from gestational days 19 to 21. GH-like immunopositivity is demonstrated in the pars intermedia of 21-day-old fetuses for the first time.

Intrauterine hyperglycemia increases insulin binding sites but not glucose transporter expression in discrete brain areas in term rat fetuses.

Diabetic pregnancy results in several metabolic and hormonal disorders, both in the embryo and the fetus of different species, including humans. Insulin is a potent modulator of brain development and is suggested to promote the differentiation and maturation of hypothalamic or related extrahypothalamic structures, which are directly involved in neural inputs to the pancreas. Because these structures are known to be specifically responsive both to insulin and glucose, we examined the effects of 48-h hyperglycemic clamps in unrestrained pregnant rats on insulin binding and glucose transporter expression in hypothalamic and extrahypothalamic-related areas of their fetal offspring. The main result was an increase in insulin binding in the ventromedial hypothalamic nucleus (VMH), the arcuate nucleus (AN), and the lateral hypothalamus (LH), and in the nucleus of the tractus solitarius (NTS) for extrahypothalamic areas (+30% in the VMH, +37% in the AN, +25.8% in the LH, and +37.3% in the NTS). The deleterious effect of brain hyperinsulinism during the late gestational stage does not seem to act through glucose transporter (GLUT) expression, inasmuch as no relationship between GLUT level and hyperinsulinism in brain areas could be observed. The specific increase in insulin binding in areas involved in the nervous control of metabolism could be a factor in the increased glucose intolerance and impairment of insulin secretion that was previously observed in the adult rats from hyperglycemic mothers.

Asymmetrical development of the dopamine system in the fetal rat as indicated by lateralized administration of SKF-38393 and SCH-23390

The dopamine D 1 agonist SKF-38393 and the D 1 antagonist SCH-23390 were administered into the left or right cerebral hemisphere of the rat fetus on E21 of gestation. Intrahemispheric (IH) injection of the agonist promoted a large-magnitude increase in fetal motor behavior, which involved movements of the head, limbs, and body trunk. Although no lateral asymmetries were evident in left or right injections of the agonist, IH injection of the antagonist into the fetus's left hemisphere produced more pronounced effects on oral behavior, including mouth, lick, and facial wipe movements. Administration of SCH-23390 into the same hemisphere as SKF-38393 was effective in reversing the behavioral effects of the agonist, with left IH injections showing more immediate and complete blockade of agonist-induced behavioral activation. These data provide evidence for functional asymmetries in D 1 receptors of the dopamine system in the term rat fetus.

Intracisternal administration of SKF-38393 and SCH-23390: Behavioral effects in the rat fetus

The dopamine D 1 agonist SKF-38393 and the D 1 antagonist SCH-23390 were administered into the central nervous system of the E21 rat fetus via intracisternal (IC) injection. IC injection of SKF-38393 promoted a dose-dependent increase in fetal motor activity, principally including movements of the forelimbs, head, and body trunk. IC injection of SCH-23390 did not affect overall activity, but selectively suppressed forelimb, rearlimb, and head movements and promoted an increase in mouthing, licking, and facial wiping. Administration of SCH-23390 after IC injection of SKF-38393 was effective in completely reversing the behavioral effects of the D 1 agonist. These findings suggest that central manipulation of dopamine D 1 receptors can have direct and potent behavioral effects in the term rat fetus.

Modulation of dopamine binding in the fetal rat: Effects of milk and exogenous opioid manipulation

Presentation of milk to the newborn rat promotes changes in sensory and motor behavior and concomitant changes in both endogenous opioid and dopamine systems. The present study employed an in vivo binding technique with a tritiated ligand for the D 2 receptor ([ 3H]raclopride) to examine the effects of intraoral milk infusion and opioid manipulations on dopamine activity in the term rat fetus (E21). In Experiment 1, fetuses received a series of milk infusions, which resulted in decreased occupancy at D 2 receptors by the endogenous ligand, dopamine, in striatal, septal, and hypothalamic brain regions. In Experiment 2, fetuses were pretreated with morphine, the μ-agonist [D-Ala 2,NMe-Phe 4,Gly 5-ol]-enkephalin (DAMGO), the κ-agonist U50,4488, or salin. Opioid manipulations had no effect on binding at D 2 receptors. These results confirm that intraoral milk infusion can modulate activity in the dopamine system of the near-term fetal rat.

Effects of Ethanol on Hexose Uptake by Cultured Rat Brain Cells

The effects of ethanol on hexose uptake by glial cells was investigated using primary cultures prepared from term rat fetuses. Specific 3H 2-deoxy-D-glucose (2DG) uptake was significantly reduced by a 4-hr exposure to ethanol at concentrations of 25, 50, and 100 mM, but not 200 or 300 mM. The inhibitory effect of 50 mM ethanol increased with the duration of exposure, with 2DG uptake inhibited by 36% after 18 hr. Astrocytes cultured from the brains of term fetuses of rats fed ethanol during pregnancy showed essentially the same 2DG uptake response to in vitro ethanol treatment. Kinetics of 2DG uptake showed a significant decrease of Vmax in the presence of ethanol. No interaction was found between ethanol and insulin, which stimulated 2DG uptake and protein content of the cultures. The data suggest that ethanol can modulate hexose uptake by astrocytes cultured from fetal rat brain. However, insulin actions on glial cells were not affected by ethanol.

Functional teratogens of the rat kidney: I. Colchicine, dinoseb, and methyl salicylate

Substances known or suspected to cause subtle or transient anatomical alterations in renal development were administered prenatally or neonatally to rats in order to determine whether they are capable of altering renal functional development. Colchicine alters mitotic activity and cytoskeletal structure and is teratogenic in many species. Since the kidney of the newborn rat undergoes extensive cellular proliferation and nephron differentiation, it is possible that neonatal administration of colchicine may affect nephron development. Dinoseb and methyl salicylate have previously been reported to produce a high incidence of dilated renal pelvis in the term rat fetus. Colchicine was injected sc, at 75 μg/kg, to Postnatal Day (PD) 1 Sprague-Dawley rats. Dinoseb was administered ip to pregnant Sprague-Dawley rats on Gestation Days 10–12 at doses of 8 or 10.5 mg/kg/day, and methyl salicylate was administered ip at doses of 200, 250, or 300 mg/kg/day on Gestation Days 11–12. Renal function was examined in pups from immediately after birth through weaning. Maximal urine concentrating ability was measured after DDAVP (desmopressin acetate, a vasopressin analog) injection in suckling rats, and after 24 hr of water deprivation in weanlings. Proximal tubule transport was measured in renal cortical slices. Basal urinary parameters, including urine flow, osmolality, pH, and chloride content, were measured. Colchicine treatment had no effect on body weight or kidney weight. There was a significant decrease in maximal urine osmolality in PD 30 rats measured after 24 hr of water deprivation. The urine concentrating deficit detected in functionally mature PD 30 rats suggests that colchicine treatment during renal histogenesis causes a latent deficit in medullary function in the absence of any gross morphological effects. The 10.5 mg/kg/day dose of dinoseb caused a weight reduction in neonates which persisted after weaning. Urine volume after DDAVP challenge was increased over controls in both dose groups on PD 6, but maximal urine concentration was unaffected. On PD 14, maximal urine concentration after DDAVP injection was decreased in the 10.5 mg/kg/day group. By PD 30, urine concentrating ability was comparable to controls. Renal cortical slices from the 10.5 mg/kg/day dose group had an enhanced ability to accumulate organic anions on PD 3 and 31, but opposite effects were observed in the low-dose group. No other renal functional parameters were altered. Urine osmolality after DDAVP challenge was decreased over controls in the 250 mg/kg/day methyl salicylate group on PD 6, and urine volume was increased in this group after DDAVP injection on PD 14. Urine flow was also increased in this group on PD 2 after 4 hr of isolation from the dam, a significant water deprivation to neonatal rats. By PD 30, urine concentrating ability was comparable to controls. The results indicate that there is a temporary delay in the maturation of urine concentrating ability in rats transplacentally exposed to methyl salicylate or dinoseb.

Ontogenesis of gastric acid secretion in fetal rat.

The pH of gastric fluid was measured in rat fetuses during the last 3 days of gestation. On day 19, the gastric pH was close to neutral. During the night of day 20, the pH was clearly lowered (6.11 +/- 0.15 units), this decrease becoming more marked on the following day. At birth (day 22), just before the first feeding, the pH of gastric fluid reached the mean value of 2.98 +/- 0.14 units. This drop in gastric pH was concomitant with an increase in chloride concentration whereas the gastric PCO2 remained constant. These results imply that in term rat fetuses, the gastric mucosa secretes fixed acid, very likely hydrochloride acid. The administration of acetazolamide (inhibitor of carbonic anhydrase) to 20-day-old fetuses did not suppress the spontaneous acidification of gastric fluid, although the enzyme activity was reduced by approximately 80%. Moreover, the gastric pH in acetazolamide-injected fetuses was markedly lower than in the noninjected littermates. The administration of NaCl solution (acetazolamide vehicle) had no effect on the carbonic anhydrase activity but clearly decreased the pH of gastric fluid. Thus, the drop of gastric pH produced by injection of acetazolamide or saline solution alone probably results from a stress effect of puncture. In fetuses from adrenalectomized, metopirone-treated mothers, the injection of NaCl solution no longer had effect on the pH of gastric fluid whereas triamcinolone injection produced a clear decrease in the gastric pH 3 hr latter.

Hormonal control of glucose-6-phosphatase and phosphoenolpyruvate carboxykinase activities in the fetal rat kidney.

Triamcinolone (20 microgram per fetus) administered in utero to term rat fetuses (day 21 of gestation) increases the activities of renal G-6-Pase and PEPCK. The absence (or marked decrease) of circulating corticosteroids in fetuses from adrenalectomized, metopirone-treated mothers has, however, no clear effect on the enzyme activities. Therefore, it is doubtful that corticosteroids play a role in the development of G-6-Pase and PEPCK activities during the fetal period of life. In 21-day-old fetuses entirely decapitated on day 18, both enzyme activities are lower than intact fetuses of the same litter (G-6-Pase, -48%; PEPCK, -36%). In partially decapitated fetuses, the activity of G-6-Pase remains at the control level, whereas the PEPCK activity is clearly reduced (-39%). These results strongly suggest that on the last day of gestation the hormone group of parathormone, calcitonin, or thyroxine controls the G-6-Pase activity, whereas the hypothalamo-hypophysis system is implied in the development of PEPCK activity. Parathormone (1 unit per fetus) administered to decapitated fetuses completely restores the G-6-Pase activity. Neither rat growth hormone, synacthene, nor arginine vasopressin has significant effects on the activity of PEPCK in the kidneys of decapitated fetuses. The administration of 0.5 mumole of dibutyryl-cAMP or cyclic adenosine 3':5'-monophosphate (cAMP) to decapitated fetuses completely restores the activity of renal PEPCK, suggesting that the development PEPCK is controlled by cAMP-dependent hormone. The same dose of dibutyryl-cAMP has no effect on the activity of G-6-Pase; cAMP produces a slight but significant increase of this enzyme activity.

A metallothionein-like protein in the hepatic cytosol of the term rat fetus

Endogenous zinc levels in the cytosol of normal fetal rat liver were found to be 4.5- to 7-fold higher than levels found in the cytosol of the corresponding maternal liver. When the fetal cytosol was subjected to gel-filtration, 50 to 60% of the zinc was found to be associated with a peak not present in maternal cytosol. In vitro addition of CdCl 2 to fetal cytosol prior to gel-filtration caused a displacement of zinc from the peak and an accumulation of cadmium. Pretreatment of the pregnant female with CdCl 2 48 hr prior to term led to the appearance of a peak in the maternal hepatic cytosol with an elution volume similar to the fetal peak. The peak contained both cadmium and zinc which is characteristic of metallothionein. The results suggest the presence of a metallothionein-like protein in the cytosol of term fetal liver which is not normally found in maternal liver and which appears to function as a storage depot for endogenous zinc.

Postmaturity in the Rat: Phosphorylase, Glucose-6-Phosphatase and Phosphoenolpyruvate Carboxykinase Activities in the Fetal Liver

Liver glucose-6-phosphatase and phosphoenolpyruvate carboxykinase activities were increased in the postmature rat fetus (23.5 day old) when compared to term rat fetus (21.5 day old). Postmaturity was without effect on liver phosphorylase activity. The three liver enzyme activities were also determined in normal 2 day old neonates. These results are correlated with the mobilisation of fetal liver glycogen occuring during postmaturity in the rat and are discussed in relation to the secretory pattern of the pancreatic hormones.

Effect of Cortisone or &lt;i&gt;L&lt;/i&gt;-Triiodothyronine Administration to Pregnant Rats on the Activity of Fetal Intestinal Disaccharidases and Lysosomal Acid β-Galactosidase

Activities of maltase, sucrase, lactase and acid-beta-galactosidase were studied in jejunum and ileum of term rat fetuses obtained by cesarian section. Female rats were either untreated or injected daily in the last (3rd) week of pregnancy with cortisone acetate (10 or 50 mg/100 g body weight) or L-triiodothyronine (20 or 50 microgram/100 g body weight). Two other control groups were injected with appropriate solvents. Cortisone or T3 treatment to mothers increased sucrase and maltase activity in jejunum and ileum of the offspring. Generally, higher doses of hormone were more effective. Lactase activity was increased by 25% in the jejunum by the higher dose of cortisone. Both doses of cortisone increased ileal lactase. Jejunal acid-beta-galactosidase activity was decreased in fetuses of T3-treated mothers.

Studies on Experimental Hypotrophy in the Rat III. Plasma Insulin and Glucagon

Insulin and glucagon have been measured in the plasma of rats with intrauterine growth retardation (IUGR) and their littermate controls. A lower plasma insulin and a higher plasma glucagon were observed in IUGR term rat fetuses. After birth there was no difference in the circulating level of insulin and glucagon in IUGR rats and their littermate controls. It is concluded that postnatal hypoglycemia of IUGR rat did not result from an impaired glucagon secretion or an increased insulin secretion.

Factors affecting the secretion of insulin and glucagon by the rat fetus.

Insulin (IRI) and glucagon (IRG) increased in the plasma of the rat fetus from 18½ to 20½ days of gestation and decreased on day 21½. The demonstrated failure of insulin and glucagon to cross the placenta of the rat allowed the conclusion that fetal rat pancreas secreted IRI and IRG in the plasma of the fetus at the end of gestation. Fetal hyperglycemia induced by perfusing pregnant rats with glucose for one hour produced a marked increase in fetal plasma IRI but did not modify plasma IRG. Fetal hypoglycemia induced by perfusing pregnant rats with insulin for one hour produced a fall in fetal plasma IRI but no rise in fetal plasma IRG. Chronic fetal hypoglycemia produced by fasting pregnant rats for ninety-six hours or by intrauterine growth retardation of fetuses increased fetal plasma IRG and decreased fetal plasma IRI. Norepinephrine injection in term rat fetus increased plasma IRG and decreased plasma IRI. Acetylcholine injection increased both plasma IRI and IRG, whereas serotonin remained without effect. These data suggest that IRI and IRG secretion by the fetal rat pancreas is controlled by both the blood glucose level and autonomic nervous system activity. Lower blood glucose levels and higher plasma IRI and IRG levels in pregnant than nonpregnant rats are also reported.