Gastrin in fetal and neonatal pigs

1. The concentration and molecular profile of gastrin were examined in plasma and tissue extracts of fetal and neonatal pigs from 93 days gestation up to 12 weeks of age and also in the fetal gastric contents. 2. Gastrin was present in the gastrointestinal tract and plasma of fetal pigs at 93 days gestation. The concentration in both plasma and antral extracts increased progressively up to birth and continued to rise postnatally, reaching a peak at about 3 weeks of age in plasma and 6 weeks in the antrum. 3. In blood the major molecular form of gastrin was G34 (up to 80%), while in the antrum the major form was G17 (66-91%). The percentage of G34 in the antrum was highest in later gestation (21%), and reached adult proportion by 8 weeks of age (4%). 4. A considerable amount of gastrin, chiefly G17, was detected in the fetal gastric contents. Synthetic human G17 was stable in fetal gastric contents when incubated at 37 degrees C for 60 min, although, when incubated with gastric contents from a sow, it disappeared within 5 min. 5. It is suggested that the presence of gastrin in fetal gastric contents may be important in stimulation of fetal gut development.     

Renal Excretion of N4-Acetyl Sulphanilamide and N4-Acetyl Sulphadimidine in Goats

The renal excretion of N4-acetyl sulphanilamide and N4-acetyl sulphadimidine was studied in 19 experiments with 6 goats during continuous intravenous administration of the 2 sulphonamide derivatives. Deacetylation of both compounds takes place to a small extent only. Further it is shown that both sulphonamide derivatives are bound to plasma proteins to a greater extent than sulphanilamide and sulphadimidine. The excretion of the N4-acetylated sulphonamides is compared with the renal excretion of creatinine. The non-protein-bound fraction of the 2 N4-acetylated sulphonamides is excreted by filtration and active tubular secretion. The renal clearances of the acetyl derivatives are higher than those of the parent compounds.     

Plasma prostaglandin levels during early neonatal life following term and pre-term delivery

The concentrations of prostaglandin E (PGE), prostaglandin F (PGF) and 13,14-dihydro-15-oxo-PGF (PGFM) have been measured by sensitive and specific radioimmunoassays in neonatal plasma after term and pre-term delivery. Blood samples were taken in the term delivery group from the umbilical artery at birth and on the sixth post-natal day and after pre-term delivery at 2–4 days, on the sixth day, at 2–4 weeks and at 5–8 weeks after birth. The levels of prostaglandins circulating during the first month of life were far greater than those found in normal adults. In neonates delivered at term the plasma concentration of PGE was significantly lower six days after delivery compared with the concentration at delivery whereas the concentrations of PGF and PGFM were essentially unchanged. Following pre-term delivery prostaglandin concentrations declined with increasing neonatal age although only levels of PGE at 5–8 weeks of age were within the normal range of adult values. Comparison of prostaglandin levels six days after delivery between neonates born at term and pre-term showed no significant differences. These results suggest that prematurity is not associated with marked abnormalities in the ability of the neonate to synthesize or metabolize prostaglandins.     

Free radicals, lipid peroxidation and the antioxidant system in the blood of cows and newborn calves around calving

The oxidative stress of birth in cattle (Bos taurus) was evaluated by measuring steady state concentration of free radicals in whole blood, rate of lipid peroxidation and activity of antioxidant enzymes in erythrocytes, antioxidant capacity of blood plasma in 14 calves at birth and four times after birth until 3 weeks of age and also in their mothers at calving. The same parameters were also measured in 58 dairy cows before calving, at parturition and after calving. Free radical concentration in the blood of newborn calves was higher than in cows confirming that birth means oxidative stress for calves. Red blood cell malondialdehyde in calves was the highest at birth and following the first solid feed intake at the third week. Superoxide dismutase activity increased in calves during the first three weeks of life. Ferric reducing ability of plasma was higher in calves at birth than in cows and decreased thereafter. Higher superoxide dismutase activity in red blood cells and lower ferric reducing ability of plasma in dairy cows was found at calving compared to the average of all pre- and post-calving results. We conclude that the blood of newborn calves is well prepared to deal with the oxidative stress of birth, and that such a stress is present even when some fingerprint markers of redox imbalance show no apparent alterations. Stress of calving has minor effects on the antioxidant system of cows.     

Simultaneous observations of iodothyronine content in the thyroid gland, serum and thyroxine 5'- and 5-monodeiodinase activity in liver, during the neonatal period of the pig

Serum T4 and rT3 were high at about 4-12 h after birth, then they decreased to a nadir on day 3 (rT3) and day 7 (T4). Serum T3 concentration fell immediately after birth but then increased to a relatively stable level during the next 2-6 weeks, then fell after weaning. Reciprocal concentration profiles of T4, T3 and rT3 in the thyroid were found. The thyroidal iodothyronine content increased significantly after weaning. In the liver, 5'-monodeiodinating activity, low after birth, rose until day 3 and then decreased concomitantly with T3 in serum. The 5-monodeiodinating activity, high at birth, fell to a nadir at about 3 weeks. No changes in 5- and 5'-deiodinase activity after 3 weeks were observed. Opposite to the variations in absolute content, the iodothyronine relative proportion in thyroid tissue was practically unchanged until weaning time (6 weeks), when they rose. Serum T3/T4 and rT3/T4 ratios increased with age until weaning. The post-weaned pigs had T3/T4 and rT3/T4 ratios about two times smaller than 6-weeks-old pigs. Serum rT3/T3, high after birth, decreased with age. Summarizing, the results indicate that neither changes in the thyroid iodothyronine content nor in the liver T4-monodeiodinating activity can solely account for variations in serum TH during the early neonatal period in the pig. It is suggested that the rapid variations in serum TH levels can reflect changes in the thyroidal secretory activity in preferential T3 secretion and/or blood disappearance rates.     

Rate of disappearance of glycerol from plasma of fetal and newborn sheep

The disappearance of glycerol from plasma was studied after a single intravenous injection to estimate its volume of distribution (Vdist), plasma clearance rate, and rate constant for irreversible loss (kd). Studies were repeated before and after birth of the lamb to test whether loss of the placenta could account for rapidly increasing plasma concentrations in the newborn. The disappearance of glycerol was closely described by a double-exponential model in each instance. In fetal sheep Vdist averaged 0.41 +/- 0.15 (SD) 1/kg fetal wt (n = 15). This volume decreased to 0.33 +/- 0.11 l/kg (n = 8) soon after functionally removing the placenta (by snaring the umbilical cord and maintaining the fetus with intrauterine ventilation), but the change was not significant. In newborn lambs 1-3 days of age, Vdist averaged 0.45 +/- 0.11 l/kg (n = 5, NS). Plasma clearance rate also did not change significantly, averaging 7.9 +/- 2.9, 7.9 +/- 3.8, and 9.0 +/- 5.9 ml.min-1.kg-1 in the fetus, after simulated birth, and in the newborn lamb, respectively, kd also was not altered measurably and averaged 0.020 +/- 0.006, 0.024 +/- 0.007, and 0.019 +/- 0.007 min-1 during the same time periods. Similar results were obtained by using three widely different amounts of infused glycerol. The results indicate that removal of glycerol does not depend on placental function to an appreciable extent. It is concluded that plasma glycerol concentration reflects principally glycerol turnover and, hence, lipolysis before and after birth.     

Glucose metabolism in the newborn rat. Hormonal effects in vivo

1. The concentrations of liver glycogen and plasma d-glucose were measured in caesarian-delivered newborn rats at time-intervals up to 3h after delivery after treatment of the neonatal rats with glucagon, dibutyryl cyclic AMP, cortisol or cortisol+dibutyryl cyclic AMP. Glycogenolysis was promoted by glucagon or dibutyryl cyclic AMP in the third hour after birth but not at earlier times. Cortisol and dibutyryl cyclic AMP together (but neither agent alone) promoted glycogenolysis in the second hour after birth, but no hormone combination was effective in the first postnatal hour. 2. The specific radioactivity of plasma d-glucose was measured as a function of time for up to 75 min after the intraperitoneal injection of d-[6-(14)C]glucose and d-[6-(3)H]glucose into newborn rats at delivery and after treatment with glucagon or actinomycin D. Glucagon-mediated hyperglycaemia at this time was due to an increased rate of glucose formation and a decreased rate of glucose utilization. Actinomycin D prevented glucose formation and accelerated the rate of postnatal hypoglycaemia. 3. The specific radioactivity of plasma l-lactate and the incorporation of (14)C into plasma d-glucose was measured as a function of time after the intraperitoneal injection of l-[U-(14)C]lactate into glucagon- or actinomycin D-treated rats immediately after delivery. The calculated rates of lactate formation were unchanged by either treatment, but lactate utilization was stimulated by glucagon administration. Glucagon stimulated and actinomycin D diminished (14)C incorporation into plasma d-glucose. 4. The factors involved in the initiation of glycogenolysis and gluconeogenesis in the rat immediately after birth are discussed.     

Ontogeny and kinetics of carnitine palmitoyltransferase in liver and skeletal muscle of the domestic felid (Felis domestica)

The ontogeny of carnitine palmitoyltransferase (CPT) was examined in liver and muscle throughout growth and development of the domestic felid. Homogenates from animals in six age categories (newborn, 24-h, 3-, 6- and 9-week-old, and adult) were examined. Hepatic CPT specific activity increased progressively from birth to 6 weeks and then declined slightly into adulthood, with maximal values for animals greater than 24 h of age [171 nmol/(min g wet tissue)] being 70% higher than for newborns [99 nmol/(min g wet tissue)] (P<.05). Specific activity in adults was similar to that in 6- and 9-week-old juveniles. Total hepatic CPT activity [nmol/(min liver)] increased linearly with age, but the activity expressed per kg body weight [nmol/(min kg BW)] declined after 3 weeks. In contrast, skeletal muscle CPT-specific activity remained unchanged from birth to 3 weeks and then increased significantly, with maximal values at 9 weeks being 90% greater than those for young animals (newborn to 3 weeks; P<.05), whereas specific activity in adults was 50% lower than that observed in 9-week-old animals (P<.05). Hepatic and muscle apparent Km's for carnitine averaged 440 microM and did not vary with age. Hepatic carnitine concentrations remained relatively constant during development, but were lower in adult lactating females, whereas skeletal muscle concentrations increased markedly with age. Hepatic concentrations were 20-50% higher than apparent Km's for carnitine in young and growing animals, but concentrations were similar to the apparent Km at 6 weeks and significantly lower than the apparent Km in adults. Carnitine concentrations in skeletal muscle were 37% lower than apparent Km during the neonatal period, but significantly higher in cats >3 weeks of age. We conclude that postnatal increases in CPT activity support increased capacity for fatty acid oxidation in the developing felid and that dietary carnitine may be required to maximize enzyme activity.     

Biphasic effect of methadone on hepatic drug metabolism

When methadone HCl (30 mg/kg, po) was given acutely to mice, it was found to inhibit drug metabolism as evidenced by a prolongation of hexobarbital sleeping time and zoxazolamine paralysis time. Pharmacokinetic studies revealed that this acute dose of the narcotic analgesic could also prolong the plasma half-life of aminopyrine without any change in its volume of distribution. When added to the incubation mixture containing 10,000 g mouse liver supernatant fraction and a complete system for measuring aminopyrine N-demethylase or aniline hydroxylase, methadone showed a dose-dependent inhibition of the enzymes; the former enzyme was inhibited to a greater extent than the latter one. However, subacute treatment of mice with methadone HCl (30 mg/kg, po, twice daily for 3 days) resulted in increases in liver weight, microsomal protein, and cytochrome P-450 content in consonant with the increased activities of four hepatic drug-metabolizing enzymes: aminopyrine N-demethylase, aniline hydroxylase, p-nitroanisole, O-demethylase, and benzphetamine N-demethylase. Moreover, both hexobarbital sleeping time and zoxazolamine paralysis time were shortened. The plasma half-life of aminopyrine was decreased. These changes were prevented by simultaneous administration of puromycin diHCl (80 mg/kg, ip). Methadone thus seems to act in a manner very similar to that of propoxyphene or SKF-525A, acting as a potent inhibitor of hepatic drug metabolism when given acutely and as an inducer when given subacutely.     

Effect of sex hormones on plasma T-kininogen in the rat

The influence of sex hormones on rat plasma T-kininogen concentration was examined. The level of T-kininogen in the post-pubertal female rat is about 3-times that of the male animal. Female rats castrated as adults or 15 days after birth, had low T-kininogen concentrations, near those of male rats. In contrast, castration of mature or immature male animals induced no change in T-kininogen. Treatment of castrated female or male rats with 17 alpha-ethinylestradiol significantly increased the T-kininogen level, whereas administration of testosterone or progesterone had no effect. The influence of estrogen was specific for T-kininogen, since plasma HMW kininogen concentration was the same in male and female rats and was not affected by castration or sex hormone treatment. T-kininogen concentration was not significantly changed in pregnant rat between the 12th and the 20th day of pregnancy, but increased after parturition. It was high in the newborn rat at birth and then decreased similarly over the next 3 weeks in males and females. It continued to decrease in the males, reaching the level of the adult rat, but it increased in the female from 3-4 weeks of age and reached the adult level at about 6-8 weeks. These data indicate that natural estrogens have a physiological influence on the plasma level of T-kininogen in female rats whereas testosterone had no effect on either male or castrated female rats. HMW kininogen is not physiologically dependent on sex hormones.     

Amino acids and insulin are regulators of muscle protein synthesis in neonatal pigs

The stage of development between birth and weaning in mammals is a period of very rapid growth that is crucial for the long-term well-being of the animal. The rate of protein deposition in neonatal animals is very high because dietary protein is efficiently utilized to increase body protein mass. Our studies in neonatal pigs have shown that this high efficiency of protein deposition is largely due to the marked increase in protein synthesis after feeding, and this response is particularly profound in the skeletal muscle. The enhanced stimulation of muscle protein synthesis in neonates after feeding is independently mediated by the rise in insulin and amino acids and this response declines with age. Intracellular signaling components that respond to the postprandial rise in amino acids and insulin have been identified and their activation has been shown to be elevated in skeletal muscle of neonatal pigs after a meal and to decrease with development. The enhanced activation of these components in the amino acid and insulin signaling pathways in neonatal muscle contributes to the high rate of muscle protein synthesis and rapid gain in skeletal muscle mass in newborn pigs, which are essential determinants of efficient growth during development.     

The Metabolism of Serum Proteins in Neonatal Rabbits

1. Incorporation of S³⁵-labeled amino acids into serum proteins has been studied in neonatal and developing rabbits. It was found that, per unit weight, neonatal rabbits synthesized only about 1/36 of the gamma globulin, 1/7 of the beta globulin, ½ of the alpha globulin, and ⅛ of the albumin that an adult synthesized. The growing rabbit developed the ability to synthesize various serum proteins at different times. 2. Plasma volumes and serum protein concentrations were determined at different times during the growth period of the rabbit. Plasma volumes were found to be 1 and ½ times larger in newborn animals than in adults, with a gradual decline to the adult level. The total serum protein concentration at birth was about 60 to 65 per cent of the adult value and gradually increased with growth as the plasma volume decreased. 3. Half-lives of homologous albumin and gamma globulin were studied. The half-life of albumin in neonates was nearly twice as long as the half-life in adults, the latter value being reached at 1 month of age. The half-life of gamma globulin in neonates was more than twice as long as the half-life in adults and reached adult values at 2 to 3 months. 4. Attempts were made to alter serum protein metabolism. Gamma globulin synthesis early in life was augmented with antigen injections.     

Production and excretion of nitrate by human newborn infants: neonates are not little adults.

Endothelium-derived relaxing factor, identified as nitric oxide or its adducts, is metabolized to nitrate and excreted in the urine. Since blood pressures are lower in newborn infants compared to adults, we hypothesized that newborn infants would have increased excretion of nitrate on the day of birth. Neonatal urine was collected before 24 h of age when exogenous intake of nitrate was low. Two different analytical methods showed that nitrate accounted for >99% of nitrogen oxides in urine of healthy neonates and adults. The absolute micromolar concentration of nitrate in urine from infants was significantly below that of adults. When nitrate content was standardized for the reduced renal function in the newborn infant (creatinine content) and body mass (kilogram weight), the concentration of nitrate in neonatal urine was significantly higher than that of adults. Nitrate concentrations in the urine of prematurely born infants were twice that of nitrate measured in urine from term infants. These findings suggested that nitric oxide is produced in larger intravascular quantities in newborn infants versus adults. Thus, we postulated that nitric oxide released from a nitrosothiol would be metabolized to nitrate more readily by neonatal erythrocytes compared to red blood cells obtained from adults. Neonatal erythrocytes, suspended at concentrations of 8, 12, or 16 g per deciliter of hemoglobin, produced 1.7- to 2.1-fold more nitrate than equivalent hemoglobin concentrations of adult erythrocytes that were each incubated with S-nitroso-N-acetylpenicillamine (100 microM) over a 2-h period. Taken together, the studies of urinary nitrate in newborn infants and the ability of neonatal erythrocytes to generate nitrate are consistent with a robust production of nitric oxide immediately after birth.     

Metabolic and hormonal response to acute cold exposure in newborn pig

Glucose metabolism and changes in plasma insulin, glucagon and catecholamines were studied in unfed newborn pigs during acute cold exposure immediately after birth. When newborn pigs are exposed to a moderate cold external temperature (20 degrees C), they exhibit a transient thermoregulatory response characterized by an increased liver glycogenolysis, an enhanced blood glucose clearance rate (+35%) and a rise in plasma catecholamine concentrations. When the newborn pigs are exposed to a cold external temperature (12 degrees C), they become rapidly (10-12 h after birth) hypothermic and hyperglycaemic. This results from a fall in blood glucose clearance rate (-40%). Muscle glycogenolysis is low in normothermic animals during the 12 h following birth. Muscle glycogenolysis increases after a delay of 6 h in animals exposed to an external temperature of 20 degrees C or 12 degrees C. These data demonstrate that the failure in the thermoregulatory response in the newborn pig exposed to a cold temperature is not the consequence of a lack of mobilization of energy stores, but results from a defect in glucose utilization.     

Asphyxia-induced release of alpha-melanocyte-stimulating hormone in newborn pigs.

Asphyxia and reperfusion induced changes in the plasma and cerebrospinal fluid (CSF) concentrations of alpha-melanocyte-stimulating hormone (alpha-MSH) were studied in newborn pigs using a specific radioimmunoassay technique. Cardiovascular and metabolic failure induced by neonatal asphyxia resulted in a 3-fold, significant (P < 0.05) increase in plasma alpha-MSH levels, whereas the hormone concentration in CSF was significantly (P < 0.05) reduced by 50% during postasphyxial reperfusion. Our data indicate an asphyxia-induced release of alpha-MSH, and suggest a discordant regulation of plasma and CSF concentrations in newborn pigs.     

Enzymes of glycerolipid synthesis in small-intestinal mucosa of foetal and neonatal guinea pigs.

1. The activities of some enzymes of glycerolipid synthesis were measured in homogenates obtained from the intestinal scrapings of 62-66-day foetuses and 2- and 8-day-old guinea pigs. 2. The ratio of protein concentration/DNA concentration was significantly higher (P greater than 0.001) in homogenized tissue from the neonatal compared with the foetal guinea pigs. Enzyme activities were therefore expressed relative to both protein and to DNA. 3. The specific activities (relative to DNA) of palmitoyl-CoA synthetase, glycerol phosphate acyltransferase and phosphatidate phosphatase were higher in homogenized tissues from neonatal than in those from the foetal guinea pigs. These activities are probably involved more in cell proliferation than in the absorption and transport of triacylglycerol. Its activity was not significantly different in the foetal and neonatal guinea pigs when expressed relative to DNA but it was lower in the neonatal guinea pigs when expressed relative to protein. The entry of food into the intestine after birth is therefore not necessary for its activity.     

ONTOGENESIS OF DOPAMINERGIC-CHOLINERGIC INTERACTIONS IN THE RAT STRIATUM: A NEUROCHEMICAL STUDY

Abstract— In the striatum of the newborn rat, the activity of tyrosine hydroxylase, the concentration of dopamine and the activity of the synaptosomal high-affinity uptake process for dopamine is 10% of that of the adult; there is a linear and closely associated increase in all three parameters during maturation, achieving 75% of adult levels by 4 weeks after birth. In contrast, the specific activity of choline acetyltransferase exhibits a more delayed developmental rise commencing 1 week after birth; the concentration of acetylcholine is disproportionately high in the neonatal striatum and precedes the developmental increase in the activity of choline acetyltransferase. At birth, the specific activity of dopamine-sensitive adenylate cyclase is 20% of that of the adult striatum and achieves adult activity by 4 weeks after birth. Pretreatment with the neuroleptic, fluphenazinc. does not reduce the striatal content of acetylcholine until 8 days after birth. It is postulated that dopaminergic influences on cholinergic neuronal activity appear when the cholinergic neurons in the striatum cease dividing and start differentiating.     

The effect of neonatal estrogen treatment on plasma hormone levels and behaviour in pre- and post-pubertal bulls

Plasma testosterone, androstenedione and LH concentrations were measured at regular intervals from birth to 500 days of age in bulls; bulls treated with estradiol for 3 weeks after birth; steers and heifers. Behavioural observations were conducted at various periods over 12 months. Apart from a possible quietening effect at 4 months of age, neonatal estrogen administration had no effect on the aggressive behaviour of young bulls. There were no differences among the groups in testosterone levels for the first 60 days but by day 100 the levels in the normal and estrogenized bulls had risen significantly. No differences in androstenedione concentration occurred among the groups. Plasma LH decreased for the first 7 days in the bulls, steers and heifers then rose gradually, however a marked rise occurred in the steers from day 28. The neonatal decline in plasma LH was extended during the period of estrogen administration.     

Thyroid function in the newborn lamb. Physiological approach of the mechanisms inducing the changes in plasma thyroxine, free thyroxine and triiodothyronine concentrations

Several experiments were performed to study the mechanisms inducing the neonatal rises in plasma iodothyronine concentrations in lambs. TSH levels rose during the first 4 to 8h of life, whereas plasma T4 an T3 concentrations increased only from birth to respectively 2 and 1h; the rise in free T4 levels was longer and more important than the rise in total T4. Only T4 changes were strongly related to the extent of TSH increase. The neonatal TSH surge was inhibited by delaying the first milk intake, indicating a great importance of the early nutritional status; in these conditions, the neonatal T4 rise did not occur, whereas the T3 increase was not affected; therefore, in contrast to T4, the T3 increase occurring at birth is not TSH-dependent. As in thyroidectomized lambs continuously infused with T4, plasma T3 concentrations did not increase at birth, it appears that the neonatal T3 surge probably has a thyroidal origin. These results raise the possibility of the existence of a specific stimulator of thyroidal T3 secretion, at least in the newborn lamb. In addition, comparison of the respective T4 increases, at birth or after TSH stimulation in 24 h-old animals, suggests that the ability of the thyroid to respond to a sustained stimulation is strongly reduced at birth. Lastly, neonatal changes in the affinity and/or capacity of carrier proteins for T4, perhaps partly induced by the observed simultaneous rise in free fatty acid levels, could explain that plasma T3 concentrations remained elevated despite a decrease in total T4 levels from 2 h after birth.     

Ontogeny of erythropoietin mRNA expression in liver, kidneys and testes of the foetal and the neonatal pig

Erythropoietin (EPO) mRNA expression in kidneys, liver and testes of foetal and neonatal pigs was analysed using a competitive RT-PCR assay. The results indicate that in the foetal pig, erythropoietin expression is greatest in the liver, at birth; hepatic and renal expression are nearly identical, and by 5 weeks of age there is mainly renal expression. The dynamics of the renal expression of EPO mRNA in the perinatal period provide a correlate for observations made earlier of plasma EPO concentrations. Early in foetal life (30 days after artificial insemination), the mesonephroi contained large amounts of EPO mRNA. As in the rat, the testes produced EPO mRNA in amounts comparable to the liver on a per gram tissue basis, though much less on a per organ basis.