bluuebunny/crossref_metadata_2025 huggingface dataset:
Fetal and Adult Hemoglobin in the Chronically Catheterized Sheep Fetus
Authors: Jansen C.A.M. , Lowe K.C. , Beck N.F.G. , Thomas A.L. , Tucker E.M. , Nathanielsz P.W.
Published: September 2009

The switch from fetal to adult hemoglobin (Hb) has been investigated in fetal and newborn lambs. In the period between 125 and 145 days gestation, the proportion of fetal cells containing adult Hb increased significantly in catheterized fetuses. This increase paralleled the rise in fetal plasma cortisol under several different experimental conditions. However, infusion of synthetic adrenocorticotropin (ACTH1–24) into the fetus, which increased fetal plasma cortisol concentrations to levels slightly higher than observed at term, did not bring about any increase in the proportion of cells containing adult Hb. Increasing fetal plasma prolactin (PRL) concentration either by infusion of PRL or by stimulating endogenous PRL release with thyrotropin-releasing hormone (TRH) did not influence the time or rate of the switch. The fetal reticulocyte count was significantly higher in blood samples taken at the time of catheterization in fetuses of 103–115 days gestation than at 116–128 days gestation. In one repeatedly sampled fetus of adult type Hb AB, Hb C was observed at the time when the fetus was anemic. At birth the number of cells containing adult Hb was significantly higher in catheterized lambs than in nonoperated controls.
Depression of Respiration Induced by Metabolic Acidosis in Newborn Lambs
Authors: Bureau M.A. , Bégin R.
Published: September 2009

The present study evaluates the strength of the drive to breathe and the respiratory response of newborns to metabolic acidosis. The study consisted in a HCl mild and severe acidosis induced in 30 unanesthetized newborn lambs aged from 2 to 90 days. During mild acidosis (pHa = 7.20), all lambs experienced an increase in the minute ventilation (VE) associated with an increase in the neuromuscular drive of breathing which was measured by the occlusion pressure (PO.1). However, with severe acidosis (pHA = 7.10) both VE and PO.1 decreased towards the preacidotic level in the 2- and 10-day-old lambs but continued to increase in older lambs. It is concluded that newborn lambs have an immature drive of breathing and a blunted respiratory output to metabolic acidosis.
Plasma Renin Activity during Acute Ventilatory Hypoxia in the Ewe and Fetal Lamb
Authors: Drummond Willa H. , Lindheimer Carmen A.
Published: September 2009

Plasma renin activity (PRA) was determined during ventilatory hypoxia (n = 6) or normoxia (n = 5) in chronically catheterized ewes and fetuses. Compared to identically studied controls, hypoxemic ewes (PaO2 = 34.2 ± 3 Torr, p < 0.01) developed significant tachycardia (103 vs. 125 ± 6, p < 0.05) without change in blood pressure. Hypoxemic (PaO2 = 9.1 ± 0.7 Torr, p < 0.01) fetuses developed hypertension (39.3 vs. 44 ± 2 mm Hg, p < 0.05), tachycardia (182 ± 2 vs. 202 ± 5, p < 0.05), and elevated hematocrit (34 ± 1.5 vs. 38.5 ± 1.8%, p < 0.02) during hypoxemia. Fetal plasma renin levels increased from 0.26 ± 0.05 to 7.6 ± 2.8 ng/ml/h (p < 0.06) and to 14.7 ± 5.6 ng/ml/h (p < 0.05) after 60 and 120 min of hypoxia, respectively. Fetal PRA returned to baseline after 60 min of recovery. Ewe PRA did not change in either group. From these data, we conclude that differences exist between fetal and adult plasma renin levels during hypoxia. The mechanism of this response remains to be clarified.
A Useful Correlation between Blood and Brain N-Acetylneuraminic Acid Contents
Authors: Morgan Brian L.G. , Boris Gayle L. , Winick Myron
Published: September 2009

A study was conducted to determine if serum N-acetylneuraminic acid (NeuAc) levels correlate with brain NeuAc levels. Sprague-Dawley rats were given either a diet containing 100 g casein/kg or one with 200 g casein/kg throughout pregnancy and lactation. At 12, 16 and 21 days’ postpartum, litters of pups from each of the groups were killed. Their serum was assayed for NeuAc and their brains for total ganglioside and glycoprotein NeuAc. It was found that brain wet weight, ganglioside and glycoprotein NeuAc contents all correlate with serum NeuAc levels. It is suggested that serum NeuAc levels might represent a new method of measuring functional development of the brain.
Inhibition of Lymphocyte Transformation by Serum from Pregnant Women: Lack of Correlation with Levels of Alpha-Fetoprotein
Authors: Papiha S.S. , Wajner M. , Wagstaff T.I.
Published: September 2009

Lymphocytes from pregnant and non-pregnant women were stimulated with optimal doses of phytohaemagglutinin (PHA) in order to detect any possible suppression of the maternal cellular immune capabilities. No major differences were observed. Similar cultures using lymphocytes from normal healthy individuals were exposed to sera from pregnant and non-pregnant women. A consistent inhibitory influence, more pronounced at the end of gestation, was identified in the sera from pregnant women. No correlation was found between the levels of alpha-fetoprotein in the pregnant sera and the degree of inhibition observed in the cultures.
α1-Acid Glycoprotein in the Neonate with and without Infection
Authors: Philip Alistair G.S. , Hewitt Jean R.
Published: September 2009

In a study of early neonatal infection, 278 babies had a blood culture and an α1-acid glycoprotein (α1-AGP) determination. There were significant differences between the mean (± SEM) levels of α1-AGP in infants who were noninfected (26 ± 1.3 mg/dl, n = 244), infected (81 ± 11 mg/dl, n = 12) and proved to have sepsis (66 ± 10 mg/dl, n = 22). In the ‘noninfected’ group, α1-AGP levels increased with postnatal age. Increasing levels were seen on the 1st day with both increasing gestational age (15–34 mg/dl from < 30 to ≥ 38 weeks) and birth weight (17–42 mg/dl from < 1,000 to ≥ 4,000 g), irrespective of the infant’s sex. Among the sepsis group, infants who died had lower levels than those who survived (19 mg/dl vs. 90 mg/dl).
Functional Residual Capacity and Sleep States in the Premature Newborn
Authors: Moriette Guy , Chaussain Michèle , Radvanyi-Bouvet Marie-France , Walti Hervé , Pajot Nicole , Relier Jean-Pierre
Published: September 2009

Functional residual capacity (FRC) variations in relation to sleep state changes were studied in 11 premature infants with birth weights of 1.68 ± 0.48 kg and gestational ages of 32.7 ± 2.2 weeks (mean ± SD). Helium dilution was used to measure FRC, and sleep states were identified using neurophysiologic criteria. No significant difference in FRC could be demonstrated between data collected during active sleep (AS) and quiet sleep. However a relationship was shown between AS and paradoxical breathing (p < 0.02) and between AS and irregular breathing (p < 0.05). Several factors are discussed which might explain the discrepancy between the present data in premature infants and the previously published data in term infants. (1) Neurophysiologic identification of sleep states does not include breathing pattern whereas behavioral identification does. It is therefore possible that lung volume changes are related to breathing pattern changes and not to sleep state changes per se. (2) Maturational changes may occur among the mechanisms which control FRC, leading to a progressive stabilisation of FRC, the variation of which could become related to sleep state changes.
Effects of GABA and Some GABA Analogues on Respiratory Regulation in the Preterm Rabbit
Authors: Hedner Thomas , Hedner Jan , Bergman Boinge , Iversen Knut , Jonason Jan
Published: September 2009

Preterm neonatal rabbits (gestational age 29 days) were given GABA (750 mg/kg) or the GABA-like drugs muscimol (2 mg/kg) and GHBA (375 mg/kg) intraperitoneally. Basal respiration and the ventilatory response to 10% CO2 were studied, before and after drug administration, in a whole body plethysmograph during halothane anesthesia. The three drugs tested all caused a decrease in minute volume. The decrease in minute volume was mainly due to a decrease in tidal volume after GABA and muscimol, while GHBA reduced minute volume due to a decrease in respiratory frequency. A decrease in respiratory frequency was also seen after muscimol administration. Changes in the respiratory time intervals were seen after muscimol and GHBA both causing significant increases in expiratory and respiratory time. ‘Inspiratory drive’ and ‘respiratory timing mechanisms’ were evaluated by Vτ/TI and Tι/TTOT, respectively. GABA and muscimol reduced both VT/TI and Tι/TTOT while GHBA only reduced TI/TTOT Addition of 10% CO2 to the inhalation gas caused an increase in tidal volume and minute volume during control conditions. This response to CO2 was abolished by GABA and GHBA treatment. Our findings demonstrate that GABA and GABA-like drugs cause respiratory depression in the preterm neonate. Central mechanisms are most likely involved in this response. These findings may be relevant to the irregular or apneic breathing sometimes seen in the preterm human infant.
Effects of Continuous Positive Airway Pressure on Renal Function in Prematures
Authors: Tulassay T. , Machay T. , Kiszel J. , Varga J.
Published: September 2009

The effects of continuous positive airway pressure respiratory therapy – used in centrencephalic apnea in premature infants – has been investigated at a value of + 6 cm H2O end-expiratory pressure. The results showed a significantly decreased glomerular filtration rate, decreased sodium and hydrogen ion excretion and urine output, without changes in systemic blood pressure, pulse rate, and blood gas values. At + 3 cm H2O end-expiratory pressure no changes were observed.
Functional Development of Adrenergic Uptake Mechanisms in the Human Fetal Heart
Authors: Saarikoski Seppo
Published: September 2009

The uptake of 3H-NA into human fetal heart tissue was low during the first half of gestation, only one-fifth of that observed in the mouse heart. A gradual increase in uptake was seen during the second trimester of gestation. A drop in temperature resulted in inhibition of 3H-NA uptake in all samples, but most distinctly in the mouse heart and in the human fetal heart at 14–20 weeks of gestation. Cocaine and desipramine reduced the uptake of 3H-NA in human fetal atria after 14 weeks of gestation but not before that. Nialamide showed no such effect. The functional development of the noradrenergic nervous system in the human fetal heart was found to be very slight during the first trimester of pregnancy. After that a gradual maturation of noradrenergic mechanisms was seen. At the end of the first half of gestation the noradrenergic neurons in the human fetal heart may be held to function qualitatively similarly to those in the mature mouse heart.
Basal Insulin Secretion and Erythrocyte Insulin Binding in Preterm and Term Newborn Infants
Authors: Knip M. , Puukka Raija , Lautala P. , Leppilampi Marjatta , Puukka M.
Published: September 2009

To study the ontogeny of the insulin secretion and the erythrocyte insulin receptor we measured plasma immunoreactive insulin and C-peptide concentrations and the binding of [125I]-insulin to the erythrocytes in cord blood from 16 preterm and 16 term infants. 20 normal-weight adults were also studied. The C-peptide concentrations and the molar ratio of C-peptide to insulin were lower in the newborn infants than in the adults. The immunoreactive insulin correlated positively with birth weight in the term infants. The insulin binding to erythrocytes from the newborn infants was increased when compared to the adults. Erythrocytes from the preterm infants bound more insulin than the cells from the term infants. There was a strong negative correlation between insulin binding and gestational age. In the term infants, plasma C-peptide correlated negatively with the insulin binding. The increased binding to erythrocytes from the term infants was due to an increase in the receptor concentration. The high insulin binding in the preterm infants was a result of both an increased receptor concentration and affinity. These data suggest that the basal insulin secretion is similar in preterm and term infants and that the clearance of insulin is decreased in newborn infants. The increased insulin binding in newborn infants may be a mechanism by which the growth stimulatory effect of insulin in fetal life is mediated.
Skeletal Muscle Fatty Acid Oxidation during Early Postnatal Development in the Rat
Authors: Carroll James E. , Shumate Jack B. , Villadiego Aida , Choksi Rati M. , Morse Daniel P.
Published: September 2009

(1-14C)-palmitate oxidation in rat skeletal muscle homogenates increased only minimally from birth until 15 days of age and then increased more than five times between 15 days and adulthood. In contrast, liver oxidation of palmitate reached adult levels by 4 days of age. Although muscle carnitine concentration, carnitine palmityl transferase activity, and total muscle protein increased during the neonatal period, these changes did not completely parallel the rise in muscle palmitate oxidation. Palmityl-CoA synthetase and palmityl-CoA dehydrogenase activities also did not parallel the rise in overall palmitate oxidation.
Respiratory Distress Syndrome in the Newborn: Relationship to Serum Prolactin, Thyroxine, and Sex
Authors: Dhanireddy R. , Smith Y.F. , Hamosh M. , Mullon D.K. , Scanlon J.W. , Hamosh P.
Published: September 2009

Prolactin and thyroxine levels were measured by radioimmunoassay in cord blood of 61 premature infants of 26–36 weeks gestation. 30 of the infants subsequently developed respiratory distress syndrome (RDS). The infants who developed RDS had a mean cord prolactin level of 174.5 ± 24.5 ng/ml and a mean cord thyroxine level of 5.9 ± 0.4 μg/dl. In the 31 healthy infants, the mean cord prolactin and thyroxine levels were significantly higher (226.3 ± 25.8 ng/ml and 7.1 ± 0.4 μg/dl, respectively). The correlation coefficient between prolactin and thyroxine was r = 0.56 in infants with RDS (p < 0.0008). Both prolactin and thyroxine correlated with gestational age in the RDS group (r = 0.71 and 0.47, respectively). Discriminant analysis shows that the correlation between prolactin and thyroxine is independent of gestational age (r2 = 0.32, p < 0.05). There was no correlation between the levels of prolactin and thyroxine in infants without RDS. In the healthy group, the cord prolactin levels were significantly higher (p < 0.01) in female (335.8 ± 47.7 ng/ml) than in male infants (209 ± 17.2 ng/ml). Premature infants who develop RDS have significantly lower thyroxine and prolactin levels in cord blood than infants who remain healthy.
Cerebrospinal Fluid Concentration of Biogenic Amine Metabolites in Idiopathic Apnea of Prematurity
Authors: Bhat Abdul M. , Scanlon John W. , Lavenstein Bennett , Chuang L. , Karoum Farouk
Published: September 2009

The concentration of homovanillic acid and 3-methoxy-4-hydroxyphenylglycol (MHPG), the major metabolites of dopamine and norepinephrine, respectively, were studied in the cerebrospinal fluid (CSF) of 34 newborn infants. No significant difference was found in the levels of MHPG and homovanillic acid between preterm and term infants. Apneic preterm infants had significantly higher levels of MHPG than nonapneic prematures. Theophylline did not change the levels of these metabolites in CSF. There was a progressive rise of MHPG levels in CSF in preterm infants as their postnatal age increased. We suggest that idiopathic apnea of prematurity is not associated with depletion of catecholamine stores in the central nervous system. Theophylline does not seem to relieve apnea by stimulation of the central adrenergic system.
Effects of Maternal Diabetes on the Development of Carbohydrate-Metabolizing Enzymes, Glycogen Deposition and Surface Active Phospholipid Levels in Fetal Rat Lung
Authors: Singh Malathy , Feigelson Muriel
Published: September 2009

Streptozotocin-induced maternal diabetes has been shown to alter developmental patterns of carbohydrate-metabolizing enzyme activities, glycogen deposition and surfactant levels in late fetal rat lung in a tissue-specific manner, as follows: (a) marked reduction in glycogen synthase a activity, due to aberrant interconversion between active and inactive forms of the enzyme; less glycogen was thus accumulated; (b) lowered activities of hexokinase, phosphofructokinase and pyruvate kinase at term; (c) reduced disaturated phosphatidylcholine (surfactant) concentrations. The diminished synthesis and accumulation of glycogen and glycolytic capacity in the lungs of fetuses of diabetic mothers has been related to reduction in surfactant level, which underlies respiratory distress syndrome frequently encountered in neonates of diabetic pregnancies.
Effects of Acute Preload and Afterload Stress on Myocardial Function in Newborn and Adult Sheep
Authors: Berman William , Christensen Deborah
Published: September 2009

Unanesthetized, chronically instrumented newborn and adult sheep were subjected to acute circulatory preload stress (rapid administration of 30·ml kg––1 isotonic saline) and afterload stress (intravenous administration of 0.2 mg·kg––1 methoxamine). Variables of circulatory status and myocardial function were monitored continuously during experimental manipulations. Preload stress elevated arterial and venous pressures, reduced the preejection period (PEP) to left ventricular ejection time (LVET) ratio (PEP/LVET), and increased the rate of left ventricular pressure rise (dp/dt) to a comparable extent in newborn and adult subjects. Afterload stress increased arterial and venous pressures to a comparable extent in newborns and adults; the percent changes in PEP (25), LVET (16), PEP/LVET (12) and dp/dt (––21) in newborns were more pronounced than those in adults.
Effects of Excess Amounts of Synthetic Amino Acid Preparations on Hypothalamus of Mice and Kittens
Authors: Tanaka Kazuhiko , Shimada Morimi , Nakao Koji , Kosugi Akiko , Yamamoto Hisashi , Oya Noriaki
Published: September 2009

The relationship between the neurotoxicity caused by excess amounts of synthetic amino acid preparations and serum levels of a certain amino acid was examined using suckling mice and kittens. Three preparations, two of which contained aspartic acid and glutamic acid, were injected intraperitoneally into neonatal mice. Almost all the animals which were treated with the preparations containing aspartic acid and glutamic acid at a dosage of more than 40 μl/g body weight (b.w.) showed hypothalamic lesions. The severity of these increased according to each dose increment. On the other hand, none of the animals treated with the preparation containing neither aspartic acid nor glutamic acid sustained hypothalamic lesions. All kittens injected intravenously with the preparation containing aspartic acid and glutamic acid at dosages of more than 20 μl/g b.w. also showed hypothalamic lesions, but none of the kittens treated with dosages of less than 10 μl/g b.w. did. Serum levels of each amino acid reached their highest values as early as 5 min after injection and then returned abruptly to the control value within 3 h.
Ontogenesis and Sex Differences in Rabbit Fetal Adrenal Phenylethanolamine N-Methyltransferase
Authors: Padbury James F. , Hobel Calvin J. , Gonzalez Fred A. , Fisher Delbert A.
Published: September 2009

The development of the sympatho-adrenal system is important for neonatal adaptation to extrauterine life. On the basis of previous studies suggesting relatively accelerated adrenal maturation in the female rabbit fetus, we conducted an ontogenetic study of male-female differences in adrenal levels of phenylethanolamine N-methyltransferase (PNMT), the terminal enzyme in epinephrine biosynthesis. Geometric mean adrenal PNMT activities increased significantly from 5.1 ± 0.07 pmol/pair adrenals/h for females and 3.3 ± 1.21 for males at 24 days gestation to 32.1 ± 1.07 for females and 29.2 ± 1.08 for males at 31 days gestation. These increases with gestational age were highly significant (p < 0.001). Analysis of variance showed significantly increased activity in female versus male littermates (p < 0.025). No significant differences were noted among the female fetuses grouped according to their numbers of male neighbors. These results demonstrate that adrenal PNMT increases significantly with advancing gestational age and that female fetuses have significantly increased activity relative to their male littermates. The near neighbor fetal data do not suggest that this effect is mediated by a humoral agent which is transferable by the uterine vasculature or by interamniotic diffusion. We speculate that sex differences in sympatho-adrenal development may explain the lower neonatal morbidity and mortaliy in female infants.
Capacity of Cyclic Urea Synthesis in Neonatal Rat Liver
Authors: Kadowaki Hiroko , Bibb Philip C. , Knox Eugene
Published: September 2009

The optimal conditions for the measurements of the capacity of cyclic urea formation was determined using tissue homogenate. Under these conditions, the capacity of cyclic urea synthesis in adult rat liver was 1.10 μmol/min/g wet tissue. On the other hand, the capacity of fetal liver was very low. After parturition, the capacity increased rapidly in 24 h to one-quarter of the adult level, and by weaning age it reached one-half the adult level.
Hormonal Control of Postnatal Development of Heal Neuraminidase and Acid Beta-Galactosidase
Authors: Leeper Lucy L. , Henning Susan J.
Published: September 2009

This study examines the effect of changes of thyroid and glucocorticoid status on the development of ileal neuraminidase and acid β-galactosidase. Thyroxine (T4) administration on postnatal days 6–13 had no effect on the activity of either enzyme. In contrast, a single injection of cortisone acetate on day 6 caused a precocious reduction of the activities of both enzymes. Hypothyroidism delayed the usual developmental decline of neuraminidase activity and prevented the decline of acid β-galactosidase activity. This was probably due to an effect of T4 on endogenous glucocorticoids because cortisone acetate was just as effective as T4 in restoring enzyme activities to control levels. Adrenalectomy delayed the decline of both enzyme activities whereas glucocorticoid replacement in these same animals depressed enzyme activities to, or below, control levels. It is likely that glucocorticoids act as the primary cue in the maturation of these enzymes, but with T4 interaction necessary for the normal pattern to be elicited.
Hyperammonemia in Hypoglycemic Preterm Neonates
Authors: Sann L. , Dellamonica C.
Published: September 2009

Plasma glucose, blood urea nitrogen, and ammonia were measured simultaneously in 44 newborns a few hours after birth. When the concentration of plasma glucose was below 30 mg/dl, plasma ammonia concentration was significantly higher (129 ± 67 μmol/l) than in normoglycemic infants (74 ± 33 μmol/l; p < 0.01). Blood urea nitrogen was slightly lower in hypoglycemic infants (3.65 ± 0.7 mmol/l) than in the control group (4.5 ± 1 mmol/l) but the difference was not significant. These data show that hyperammonemia can be associated to hypoglycemia in low birth weight infants. Therefore, further investigations are required to determine the link between urea and glucose production rates in hypoglycemic newborns and whether hyperammonemia participates in the deleterious effects of hypoglycemia on the neonatal brain.
Method for the Study of Metabolite Transfer from Rat Mother to Fetus
Authors: Lasunción Miguel A. , Testar Xavier , Palacín Manuel , Chieri Ramón , Herrera Emilio
Published: September 2009

Infusion medium containing a tracer was introduced through the left uterine artery to 20.5-day pregnant rats. In this way, the left uterine horn received the tracer directly while it reached the right horn after dilution in the mother’s circulation. When U-14C-D-glucose or U-14C-L-alanine was infused, radioactivity in fetal blood from the left uterine horn was 3 or 8 times higher respectively than in the right horn and 2 or 6 times higher than in maternal blood. When the infusion was carried out with 125I-labelled growth hormone, which is known not to cross the placental barrier, very little radioactivity was found in fetuses compared with that in the mother’s plasma and no differences were observed in blood radioactivity levels of fetuses from either horn. After infusion of U-14C-D)-glucose through the maternal jugular vein instead of the left uterine artery, radioactivity was the same in fetuses from the left and right horns, indicating that manipulations of the left uterine side did not greatly affect its circulation. These findings, together with the determination of specific radioactivity of the tracer used in both maternal and fetal plasma, validate the technique as a semiquantitative means to determine the direct transfer of any product through the placental barrier in the rat.
Management of the Antenatal Preterm Fetal Lung in the Prevention of Respiratory Distress Syndrome in Lambs
Authors: Solca Maurizio , Kolobow Theodor , Huang Harry , Pesenti Antonio , Buckhold Delwin , Pierce Joseph E.
Published: September 2009

We have explored change in pulmonary compliance before, and after, repeated deep insufflation of the lungs to a pressure of 35 cm H2O, in 130-days gestation fetal lambs delivered by cesarean section, and while still connected to the intact umbilical cord and the ewe. As a group, all 15 out of 28 fetal lambs that had a rise in total compliance to above 0.2 ml (cm H2O)-1 kg-1 after the first inflation, tolerated 24 h of mechanical ventilation with excellent health and good lung function; only 3 animals out of 13 that showed no similar initial rise in compliance after the first inflation, ultimately survived. We believe the first deep insufflation is an important therapeutic intervention and a useful index to rapidly assess chance of survival in a high-risk fetal lamb population.
Somatomedin Activity and Cartilage [35S]Sulphate Incorporation in the Growth-Retarded Neonatal Rat
Authors: Fekete M. , Hill D.J. , Milner R.D.G.
Published: September 2009

Plasma somatomedin activity, cartilage metabolism and the levels of insulin and growth hormone were studied during relative neonatal malnutrition in the rat, produced by the small and large litter method. In growth-retarded rats reduced somatomedin activity and raised growth hormone concentration were found. Neither basal cartilage activity nor cartilage responsiveness to somatomedin was altered in the growth-retarded animals.
Plasma Levels of Catecholamine Metabolites in the Newborn Period
Authors: Gabriel M. , Hunneman D.H. , Gahr M.
Published: September 2009

Plasma levels of homovanillic acid (HVA) and vanillylmandelic acid (VMA) were measured mass fragmentographically in 37 healthy preterm infants and 62 healthy infants born at term during the postnatal period. HVA and VMA levels increased after birth and declined steadily afterwards. Infants with various clinical problems showed marked elevations of HVA and VMA during episodes of clinical deterioration. The results indicate a readily functioning sympathoadrenal system in newborns.
Endocrine Reactivity (T3, T4, Cortisol) during Cold Exposure in Preterm and Full-Term Lambs
Authors: Cabello G.
Published: September 2009

The endocrine reactivity to a short-term cold exposure (+ 4 °C during 1 h 30 min) was studied in 8 full-term (FT) and 12 preterm (PT) Limousin × Romanov lambs, obtained by oestrogen injections to the ewes; 4 PT animals died (PTD) during the observation period and 8 remained alive (PTA). The plasma cortisol, T4 and T3 levels were lower in PT lambs (particularly in PTD for T4 and T3) during the first hours of life. Moreover, rectal temperature decreased sharply between birth and 30 min postpartum in the PT group; at this time, plasma T3 levels and rectal temperature were positively related. During cold exposure, the plasma cortisol levels increased in FT lambs, but did not change in the PT group. Moreover, the plasma T4 levels rose slightly in FT animals (+ 12%), increased sharply in PTA lambs (+ 137%), or showed a small decrease in the PTD group (––5%) in which a marked hypothermia occurred; the relative changes in the circulating T4 levels were positively related to the algebraic variations of rectal temperature in PT lambs. However, the changes in the plasma T3 levels did not parallel that of T4 in the three groups of animals, but a positive relationship was observed, in all lambs, between the circulating T3 levels and the rectal temperatures at the end of the cold exposure. These results suggest a reduced sensitivity of the adrenal cortex to stressful conditions in PT lambs. Moreover, they underline the importance of thyroid function for thermoregulation in the newborn lamb, particularly in PT animals.
Developmental Pattern of DNA and Proteins in Brain, Liver, Lung and Heart of Rats Given Excess Vitamin A Postnatally
Authors: Shukla R.R. , Joshi Harish C. , Misra U.K.
Published: September 2009

The effect of an excessive dose of vitamin A (1,000 IU) to rat pups on 4, 6, 8 and 10 days of age was studied on growth and organ weights. The effects on the amounts of DNA and proteins and incorporation of 3H-thymidine into DNA and 3H-leucine into proteins of brain, liver, lung and heart was studied on 11, 17 and 23 days of age. Excess vitamin A administration affected the postnatal development of DNA and protein metabolism of these organs differently.
Hypotension in Fetal and Newborn Lambs; Different Patterns of Reflex Heart Rate Control Revealed by Autonomic Blockade
Authors: Walker Adrian M. , Cannata J.P. , Ritchie B.C. , Maloney J.E.
Published: September 2009

Reflex heart rate (HR) responses to hypotension were studied in chronically instrumented fetal and newborn lambs. Studies spanned 106–141 days of gestation and 1–22 days after birth. Brief hypotensive stimuli (10 s) were produced by inflation of a cuff implanted around the inferior vena cava; HR and mean arterial pressure (MAP) were recorded from a carotid arterial catheter. Autonomic nervous control of HR was examined using selective sympathetic beta-adrenergic blockade (propranolol 1 mg/kg), cholinergic blockade (atropine 0.2–0.3 mg/kg), and total autonomic blockade (propranolol plus atropine). In newborn lambs (n = 4) HR increased progressively as MAP was reduced in the range 5–50%. Tachycardia during mild hypotension (< 15% MAP fall) was due to sympathetic activation as it was abolished by propranolol. During severe hypotension ( > 30% MAP fall) tachycardia was reduced by selective beta-adrenergic blockade and by cholinergic blockade, and totally abolished by total autonomic blockade; thus withdrawal of vagal tone plus augmentation of sympathetic activity contribute to the increase of HR in response to large MAP falls in the newborn. Fetal lambs (n = 4) responded with tachycardia in mild hypotension (< 15% MAP fall) but this was reversed when hypotension was severe (> 30% MAP fall). The primary tachycardia was due to sympathetic activation and was indistinguishable from the newborn response. Reversal of the tachycardia in severe hypotension was due to increased vagal activity which counteracted the sympathetic acceleration. This pattern of simultaneous activation of the opposing autonomic pathways prevents tachycardia and appears to be a characteristic fetal response to severe hypotensive and hypoxemic stress.
Heart Rate Response to Tilting in Newborns in Quiet and Active Sleep
Authors: Finley John P. , Hamilton Robert , MacKenzie Mary Gordon
Published: September 2009

The heart rate response to tilting was investigated in active and quiet sleep in 19 normal newborns (age 1–7 days) and 11 healthy premature infants (age 2–19 days). RR intervals were determined by computer from the ECG for 30–60 s periods immediately before and after each tilt. Term infants had a significant (p < 0.005) decrease in RR interval for head-up tilting and significant (p < 0.005) increase in RR with head down tilts. There was no significant difference in the magnitude of RR change between upward and downward tilt or between active and quiet sleep. For premature infants, the response to tilting was similar to that of the term infants, especially with allowance for the faster heart rates of the former. Respiratory rate changes were an important source of variability in the heart rate response to tilting and are likely the source of previous inconsistencies. Our results indicate that healthy newborns have a well-developed heart rate response to tilting, suggesting considerable maturity of neural control of heart rate.
Thyroid Hormone Effects on Skin and Hepatic Epidermal Growth Factor Concentrations in Neonatal and Adult Mice
Authors: Hoath Steven B. , Lakshmanan J. , Fisher Delbert A.
Published: September 2009

Tissue concentrations of mouse epidermal growth factor (skin, submandibular gland and liver) are compared in control and thyroxine-treated neonatal and adult animals. The results identify an early onset thyroid-induced augmentation of EGF levels in neonatal skin with continuation of hormone responsiveness into adult life. Hepatic EGF levels are shown to be low and, unlike skin and submandibular gland, are not augmented by T4. The significance of hormonal modulation of nonsalivary growth factor concentrations is discussed.
The Effect of Hematin on Bilirubin Binding in Bilirubin-Enriched Neonatal Cord Serum
Authors: Kirk James J. , Ritter Dorothy A. , Kenny John D.
Published: September 2009

It has been suggested that the serum of infants with ABO hemolytic disease contains hematin which might interfere with bilirubin binding to albumin, increasing the risk of kernicterus. Using the horseradish peroxidase assay, we investigated this possibility. Cord serum from healthy term infants was enriched with bilirubin to a bilirubin/albumin molar ratio of 0.6, and then varying amounts of hematin were added. Hematin had a significant adverse effect on bilirubin binding when present in half to equimolar ratios with bilirubin. This high concentration of hematin does not appear to be present in serum from infants with ABO hemolytic disease and no difference was seen when comparing the dilute and the undilute peroxidase assays. These data suggest that hematin can alter bilirubin binding in neonatal serum but is not of physiologic importance for infants with ABO-isoimmune hemolysis.
Brainstem Auditory Evoked Responses in the Newborn Lamb
Authors: Ashwal Stephen , Staddon Thearon , Geller Mark , Longo Lawrence D.
Published: September 2009

Brainstem auditory evoked responses (BAER) have been studied in several species and have provided a neurophysiologic ‘window’ into brainstem function. We have pursued further studies in the newborn lamb and adult sheep. BAER amplitude increased as the stimulus intensity increased from 45 to 95 dB and as the click frequency decreased from 88.8 to 22.2 Hz. BAER latency increased as both the stimulus intensity decreased and the click frequency increased. Developmental studies were performed between the 2nd and 35th day of life in the newborn lamb. No significant change in either latency, amplitude, or wave morphology was noted in contrast to other species where developmental changes are prominent. This was due to both the prenatal maturation of the lamb’s brain and to the relatively short interval of the postnatal studies. We also studied the effect of prolonged severe hypoxia and acidosis on the BAER in the newborn lamb and found no significant change in either the amplitude or latency of the response.
Cardiovascular and Renal Effects of Isoproterenol Infusions in Young Swine
Authors: Buckley N.M. , Brazeau P. , Charney A.N. , Cabili S. , Feldman G. , Garvey M. , Frasier I.D.
Published: September 2009

The cardiovascular and renal effects of intravenous (i.v.) and intra-arterial (i.a.) infusions of isoproterenol (ISP, 0.1–0.2 μg/kg/min) were evaluated in 17 two-week-old swine anesthetized with pentobarbital. The glomerular filtration rate (GFR) of each kidney and blood flow and vascular resistance (RVR) of the left kidney were determined in all animals. In the 8 animals given ISP i.v., right ventricular pressure and dP/dtmax were also determined via a thoracotomy. In 9 animals, ISP was given i.a. after stabilization of constant-flow perfusion of the left kidney in situ. During i.v. infusion of ISP, the positive inotropic and chronotropic effects and the decrease in arterial pressure were maintained; renal blood flow and GFR increased and RVR decreased. During i.a. infusion of ISP in the constant-flow perfused kidney, similar changes in RVR and GFR were observed despite the higher effective concentrations of drug reaching the kidney. We conclude that, at this stage of postnatal renal development, the infusion of cardiotonic doses of ISP lowers RVR and produces a small increase in GFR.
Glucose Homeostasis in Fasted Neonatal Rats Treated with High Doses of L-Thyroxine
Authors: Escrivá F. , Pascual-Leone A.M.
Published: September 2009

A neo-T4 syndrome was induced by subcutaneous administration of high doses of L-thyroxine (T4) to neonatal rats. These doses produced important alterations in carbohydrate metabolism: hypoglycemia, hypoinsulinemia and increased levels of blood lactate, pyruvate and ketone bodies. T4-treated and control rats were subjected to fasting. In contrast to controls where glycemia decreased to 60% of basal values, in 11-day-old neo-T4 rats blood glucose levels decreased to only 90% of basal values. These different adaptations to fasting are discussed with regard to endocrine equilibrium in neo-T4 rats.
Serum Angiotensin I-Converting Enzyme Activity in Premature and Full-Term Infants
Authors: Maury Martine , Walti Hervé , Richer Christine , Francoual Christine , Relier Jean-Pierre , Giudicelli Jean-François
Published: September 2009

Serum angiotensin I-converting enzyme activity (SCEA) was investigated in 15 healthy premature (gestational age ranging from 30 to 36 weeks) and in 14 healthy full-term (gestational age ranging from 37 to 41 weeks) newborns as well as in 16 healthy adults (32.0 ± 2.6 years). SCEA mean values in the three groups, respectively, 23.3 ± 1.3, 24.4 ± 1.6 and 23.2 ± 1.7 nM·min––1·ml––1, did not differ significantly from each other and in the newborns there was no correlation between SCEA values and gestational age.
Cardiovascular and Catecholamine Responses to Successive Episodes of Hypoxemia in the Fetus
Authors: Lewis Alan B. , Wolf Wendy J. , Sischo William
Published: September 2009

The cardiovascular and plasma catecholamine responses to successive episodes of hypoxemia were evaluated in 5 fetal lambs in utero (≥ 0.7 gestation). Fetal heart rate (HR) and blood pressure (BP) were monitored continuously and specimens obtained for arterial blood gases, plasma norepinephrine (NE) and epineprine (E) during a baseline control period, during each of 5 hypoxemic episodes and during 4 intervening recovery periods. Hypoxemia (PO2 = 9.8–13.7 Torr) was produced by gradual, controlled constriction of the umbilical cord by a silicone rubber cuff. HR fell from 176 ± 9 beats/min (x ± SE) to between 105 ± 11 and 119 ± 5 (p < 0.01) and BP increased from 71 ± 2/49 ± 1 mm Hg to between 79 ± 2/55 ± 2 and 90 ± 3/66 ± 3 (p < 0.01) during the hypoxic periods. There was no evidence of waning in the magnitude of the hypertensive response over the course of successive hypoxemic episodes. Baseline plasma NE and E rose from 278 ± 65 and 28 ± 8 pg/ml, respectively, to between a mean of 4,982 and 17,060 pg/ml for NE and 2,217 to 9,471 pg/ml for E. No attenuation in the rise of NE and E was observed throughout the 5 hypoxic periods. Thus, the late gestation fetus appears capable of sustaining appropriate cardiovascular and catecholamine responses to multiple successive episodes of hypoxemia.
Lecithin-Cholesterol Acyltransferase Activity in Children in the Early Neonatal Period
Authors: Dobiášová M. , Stožický F. , Kopecká J.
Published: September 2009

Changes in the rate of plasma cholesterol esterification occurring shortly after birth were followed by determining the activity of lecithin-cholesterol acyltransferase (EC 2.3.1.43) in newborn children, and at the age of 3 days and 3 months. The radioassay method using ‘common’ substrate was applied. The molar esterification rate (MER) in umbilical cord serum was about half of the values found in the sera of 3-day-old and 3-month-old children, or adult subjects. Because of a positive correlation between MER and the plasma concentration of unesterified cholesterol, the values of fractional esterification rate in children were in good agreement with those characteristic for healthy adults.
Effect of Maternal Progesterone Exposure on Fetal Testosterone in Mice
Authors: Pointis G. , Latreille M.T. , Richard M.O. , D’Athis P. , Cedard L.
Published: September 2009

The effect of maternal exposure to progesterone on plasma testosterone levels was studied in fetal mice. A daily subcutaneous injection of 2 mg progesterone to mice from day 14 to 17 of pregnancy resulted in a significant decline of circulating testosterone levels in male fetuses (p < 0.05). A single injection of progesterone to mothers on day 18 of pregnancy leads to the same effect in male fetuses but increased significantly plasma testosterone levels in female ones (p < 0.01). The testes of fetuses from progesterone-exposed mothers produced in vitro less testosterone than those of controls (p < 0.01). These results show that both long- and short-term maternal exposure to pharmacological concentrations of progesterone reduce testosterone production in the male fetus. The nature of this mechanism is yet unknown, but it is suggested that the change of plasma testosterone levels may result from a local inhibition of the fetal testicular function.
Serum and Urine Amino Acid Patterns during the First Month of Life in Small-for-Date Infants
Authors: Robles R. , Gil A. , Faus M.J. , Periago J.L. , Sánchez-Pozo A. , Pita M.L. , Sánchez-Medina F.
Published: September 2009

Prenatal nutrition is impaired in small-for-gestational-age infants. Serum amino acids may show some biochemical features related to the nutritional state of these children. We have carried out a study on serum and urine amino acids in 12 small-for-date infants (SFD) and 14 healthy newborns from birth to 1 month of life. SFD infants showed a high serum level of alanine and decreased concentrations of branched chain amino acids, aspartate, cystine and tryptophan at birth. The results are compatible with a protein malnutrition state. Levels of serum amino acids in SFD infants showed no differences in relation to normal infants after 1 month of rehabilitation with a diet consisting of an adapted milk formula.
Effect of Phototherapy on Plasma 25(OH)-Vitamin D in Neonates
Authors: Gillies D.R.N. , Hay A. , Sheltawy M.J. , Congdon P.J.
Published: September 2009

The possibility that phototherapy may increase plasma levels of 25 (OH)-vitamin D was assessed by measuring levels before and after 48 h continuous phototherapy using a standard phototherapy unit (Vickers, Basingstoke, England). There was no significant increase in plasma 25(OH)-vitamin D after 48 h phototherapy and it is concluded that such treatment does not stimulate photobiosynthesis of vitamin D.
Development of the Gastrointestinal Mucosal Barrier
Authors: Udall John N. , Bloch Kurt J. , Vachino Gloria , Feldman Paula , Walker Allan
Published: September 2009

Prior to weaning, young rabbits take up increased amounts of macromolecules across the intestine and into the circulation. The increased macromolecular uptake may be due in part to decreased intestinal proteolysis in these animals. To assess the effect of intestinal proteolysis on macromolecular uptake, we initially tested the basal level of intestinal trypsin-like activity in newborn and 4-week-old weaned animals. The newborn rabbits had significantly less trypsin-like activity in their small intestinal rinse fluid compared to the 4-week-old animals. Subsequently, we tested the effect of the protease inhibitor, aprotinin, on small intestinal rinse fluid trypsin-like activity and the intestinal uptake of bovine serum albumin (BSA). Newborn and 2-week-old rabbits were force-fed with aprotinin or phosphate-buffered saline (PBS) followed after several hours by BSA. Animals pretreated with aprotinin had significantly decreased levels of small intestinal rinse fluid trypsin-like activity and increased concentrations of immunoreactive BSA (iBSA) in plasma compared to PBS-pre-treated control animals. 4-week-old weaned rabbits force-fed with equivalent amounts (on the basis of body weight) of aprotinin and BSA had significantly decreased trypsin-like activity in small intestinal rinse fluid compared to control animals. However, plasma iBSA was not significantly different from that of PBS-pretreated controls. These findings suggest that the inhibition of intestinal proteolytic activity is associated with increased macromolecular uptake in young rabbits prior to weaning. At weaning, suppression of proteolytic activity was not associated with increased macromolecular uptake detectable with the same assay procedures used successfully in the newborn animals. Thus, processes which act to limit macromolecular uptake in the older animals were not reversed by an inhibitor of proteolysis.
Ontogeny and Neonatology of Circulating Endogenous Inhibitor(s) of Prostaglandin Synthase in the Human
Authors: Brennecke S.P. , Kirkham F.J. , Morton K.E. , MacKenzie I.Z. , Wilkinson A.R. , Mitchell M.D.
Published: September 2009

To further understand the mechanism by which in vivo prostaglandin synthesis may be orchestrated, plasma levels of endogenous inhibitor(s) of prostaglandin synthase (EIPS) in the human fetus, neonate and adult have been measured. In general, a reciprocal relationship was found between plasma EIPS levels and previously reported plasma prostaglandin concentrations. This result supports a role for EIPS in the control of prostaglandin biosynthesis in the human.
Oxygen Consumption of Infants with Respiratory Distress Syndrome
Authors: Richardson Peter , Bose Carl L. , Bucciarelli Richard L. , Carlstrom Jeffrey R.
Published: September 2009

The objective of this research was to determine the oxygen consumption of newborn infants with respiratory distress syndrome in the first 4 days of life. Serial determinations of oxygen consumption were made in 14 infants with respiratory distress syndrome receiving positive end-expiratory pressures. The mean ( ± SE) oxygen consumption determined at 24, 48, 72, and 96 h postnatal age were 8.3 ± 0.9, 6.5 ± 0.8, 5.5 ± 0.5, and 5.3 ± 0.6 ml/min/kg, respectively. The level of oxygen consumption at 24 h postnatal age was significantly greater than the levels determined at 48, 72, and 96 h (p < 0.03). The oxygen levels found at 72 and 96 h of age were comparable to those determined for healthy preterm infants. A linear regression of serial oxygen consumption and weight loss yielded a ‘fair’ (r = 0.5) correlation with a significant inference (p < 0.01).
Pre- and Postnatal Developmental Changes in Hypothalamic and Pituitary Content of α-Melanocyte-Stimulating Hormone and Somatostatin in the Rat
Authors: Khorram O. , McCann S.M.
Published: September 2009

The developmental pattern of hypothalamic and pituitary somatostatin and α-melanocyte-stimulating hormone (α-MSH) was studied in the rat by radioimmunoassay (RIA). Prenatally hypothalamic somatostatin was low and the first increase in content occurred on day 5 of the postnatal period. Pituitary somatostatin was undetectable prenatally and was first detected on day 6 postnatally. Pituitary somatostatin showed the same development pattern as hypothalamic somatostatin. Whole pituitaries were analyzed from the fetuses and neonates. Analysis of anterior and posterior lobes from adults revealed that all the somatostatin was in the posterior lobe. Therefore, it is believed that the somatostatin found in the glands of the younger animals was in the neural lobe. α-MSH was detected in the fetal hypothalamus as early as day 16, with a marked increase occurring on day 19 prenatally and a further increase on day 10 postnatally. Pituitary α-MSH content, readily detectable on the first day examined, i.e. day 16 of the fetal period, increased throughout development. The effect of α-MSH on the release of growth hormone in vitro from pituitaries of rats of various ages was tested. α-MSH had no effect on growth hormone release.