Journal articles: 'Fetal lamb'

1

Rajion, MA, JG McLean, and R. NP Cahill. "Essential Fatty Acids in the Fetal and Newborn Lamb." Australian Journal of Biological Sciences 38, no. 1 (1985): 33. http://dx.doi.org/10.1071/bi9850033.

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The concentrations of linoleic and linolenic acids and their metabolites in the liver, kidney, brain, erythrocytes and plasma of fetal lambs at various stages of gestation, and of newborn and 2-week-01d suckled lambs was determined. Throughout gestation the fetal tissues, erythrocytes and plasma all contained low levels of linoleic and linolenic acids together with consistently high levels of their long-chain polyunsaturated metabolites. The triene : tetraene (eicosa-5,8, 11-trienoic acid/arachidonic acid) ratio was always 0 . 4 or less except at birth when it reached 0 . 6 in liver and 0 . 9 in plasma. Milk intake significantly increased the linoleic and linolenic acid levels in the lamb by 2 weeks after birth. These results show that the developing fetal lamb should not be regarded as being deficient in essential fatty acids, as suggested by previous investigators. It is proposed that the total metabolites of linoleic and linolenic acids are the most appropriate measure of the essential fatty acid status of the fetal lamb.

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Brown, Erin G., Benjamin A. Keller, Lee Lankford, Christopher D. Pivetti, Shinjiro Hirose, Diana L. Farmer, and Aijun Wang. "Age Does Matter: A Pilot Comparison of Placenta-Derived Stromal Cells for in utero Repair of Myelomeningocele Using a Lamb Model." Fetal Diagnosis and Therapy 39, no. 3 (July 7, 2015): 179–85. http://dx.doi.org/10.1159/000433427.

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Introduction: Fetal amniotic membranes (FM) have been shown to preserve spinal cord histology in the fetal sheep model of myelomeningocele (MMC). This study compares the effectiveness of placenta-derived mesenchymal stromal cells (PMSCs) from early-gestation versus term-gestation placenta to augment FM repair to improve distal motor function in a sheep model. Methods: Fetal lambs (n = 4) underwent surgical MMC creation followed by repair with FM patch with term-gestation PMSCs (n = 1), FM with early-gestation PMSCs (n = 1), FM only (n = 1), and skin closure only (n = 1). Histopathology and motor assessment was performed. Results: Histopathologic analysis demonstrated increased preservation of spinal cord architecture and large neurons in the lamb repaired with early-gestation cells compared to all others. Lambs repaired with skin closure only, FM alone, and term-gestation PMSCs exhibited extremely limited distal motor function; the lamb repaired with early-gestation PMSCs was capable of normal ambulation. Discussion: This pilot study is the first in vivo comparison of different gestational-age placenta-derived stromal cells for repair in the fetal sheep MMC model. The preservation of large neurons and markedly improved motor function in the lamb repaired with early-gestation cells suggest that early-gestation placental stromal cells may exhibit unique properties that augment in utero MMC repair to improve paralysis.

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Morin, F. C., E. A. Egan, W. Ferguson, and C. E. Lundgren. "Development of pulmonary vascular response to oxygen." American Journal of Physiology-Heart and Circulatory Physiology 254, no. 3 (March 1, 1988): H542—H546. http://dx.doi.org/10.1152/ajpheart.1988.254.3.h542.

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The ability of the pulmonary circulation of the fetal lamb to respond to a rise in oxygen tension was studied from 94 to 146 days of gestation. The unanesthetized ewe breathed room air at normal atmospheric pressure, followed by 100% oxygen at three atmospheres absolute pressure in a hyperbaric chamber. In eleven near-term lambs (132 to 146 days of gestation), fetal arterial oxygen tension (PaO2) increased from 25 +/- 1 to 55 +/- 6 Torr (mean +/- SE), which increased the proportion of right ventricular output distributed to the fetal lungs from 8 +/- 1 to 59 +/- 5%. In five very immature lambs (94 to 101 days of gestation), fetal PaO2 increased from 27 +/- 1 to 174 +/- 70 Torr, but the proportion of right ventricular output distributed to the lung did not change, 8 +/- 1 to 9 +/- 1%. In five of the near-term lambs, pulmonary blood flow was measured. It increased from 34 +/- 3 to 298 +/- 35 ml.kg fetal wt-1.min-1, an 8.8-fold increase. We conclude that the pulmonary circulation of the fetal lamb does not respond to an increase in oxygen tension before 101 days of gestation; however, near term an increase in oxygen tension alone can induce the entire increase in pulmonary blood flow that normally occurs after the onset of breathing at birth.

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Walther, F. J., R. David-Cu, E. I. Mehta, D. H. Polk, A. H. Jobe, and M. Ikegami. "Higher lung antioxidant enzyme activity persists after single dose of corticosteroids in preterm lambs." American Journal of Physiology-Lung Cellular and Molecular Physiology 271, no. 2 (August 1, 1996): L187—L191. http://dx.doi.org/10.1152/ajplung.1996.271.2.l187.

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Although administration of exogenous corticosteroids accelerates the late gestational rise in fetal rat and lamb lung antioxidant enzyme activity, the effect of dosing intervals on these responses remains uncertain. We studied the persistence and efficacy of the antioxidant response in fetal lamb lung to a single fetal dose of corticosteroids injected between 121 and 127 days gestational age. Fetal lambs received 0.5 mg/kg of betamethasone (n = 35) or saline (n = 26) by fetal intramuscular injection 24 h, 48 h, 4 days, or 7 days before preterm delivery at 128 days gestation (term = 150 days). After delivery, the lambs were ventilated for 40 min and killed. Total superoxide dismutase, catalase, glutathione peroxidase activities, and lipid hydroperoxide levels were measured, using homogenized lung. The saline-injected controls were similar at all time points. Lung antioxidant enzyme activity was consistently higher and lipid hydroperoxide presence was lower in the betamethasone-treated groups. We conclude that the positive effect of a single fetal dose of betamethasone on lung antioxidant enzyme activity occurs within 24 h after exposure, persists over a period of 7 days without a major change in the magnitude of the response, and leads to a reduction in lipid hydroperoxide formation during immediate postdelivery oxygen exposure.

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5

Binder, N. D., and D. F. Anderson. "Plasma renin activity responses to graded decreases in renal perfusion pressure in fetal and newborn lambs." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 262, no. 3 (March 1, 1992): R524—R529. http://dx.doi.org/10.1152/ajpregu.1992.262.3.r524.

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We examined the relationship between acute reductions in renal perfusion pressure, as approximated by femoral arterial blood pressure, and plasma renin activity in the uninephrectomized fetal lamb. Renal perfusion pressure was reduced and maintained at a constant value by controlled partial occlusion of the aorta above the renal artery. After 15 min of reduced blood pressure, blood samples were taken for determination of plasma renin activity. This protocol was performed 22 times in 11 fetal lambs. Additionally, three of the fetuses were delivered by cesarean section and studied as newborns for the first week of life. In the fetus, there was a linear relationship between log plasma renin activity and femoral arterial blood pressure (P less than 0.01). After birth, the relationship still existed, although it was shifted to the right (P less than 0.0001). We conclude that there is a significant relationship between plasma renin activity and renal perfusion pressure in the fetal lamb, and as early as 1 day after birth, this relationship shifts to the right in the newborn lamb.

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6

Rosenkrantz, T. S., I. Knox, E. L. Zalneraitis, J. R. Raye, P. J. Porte, R. Cramer, R. Smoloski, and A. F. Phillipps. "Cerebral metabolism and electrocortical activity in the chronically hyperglycemic fetal lamb." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 265, no. 6 (December 1, 1993): R1262—R1269. http://dx.doi.org/10.1152/ajpregu.1993.265.6.r1262.

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Previous studies in the fetal lamb have demonstrated that hyperglycemia stimulates the fetal metabolic rate. The present study examined the effects of chronic fetal hyperglycemia on fetal cerebral metabolic rate and electrocortical activity. Nine chronically instrumented fetal lambs had measurements of cerebral blood flow and cerebral uptake/excretion of oxygen, glucose, lactate, and beta-hydroxybutyrate taken before and during a 48-h fetal glucose infusion. Electrocortical activity was also recorded. The fetal arterial glucose concentration was 19.8 +/- 2.0 mg/dl before glucose infusion and 48 +/- 4.5 to 54.6 +/- 6.6 mg/dl during the infusion period. Cerebral blood flow and cerebral glucose and oxygen uptake increased by 219, 209, and 171%, respectively, by the end of the infusion period. There was a linear relationship between the fetal arterial glucose concentration and cerebral blood flow and cerebral glucose and oxygen uptakes. The electroencephalogram showed significant slowing with increases in the cerebral metabolic rate. These findings suggest that fetal hyperglycemia is associated with significant metabolic stimulation of the brain.

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7

Gilbert, R. D., H. Schroder, T. Kawamura, P. S. Dale, and G. G. Power. "Heat transfer pathways between fetal lamb and ewe." Journal of Applied Physiology 59, no. 2 (August 1, 1985): 634–38. http://dx.doi.org/10.1152/jappl.1985.59.2.634.

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Heat produced by the fetus exists to the mother by one of two principal routes: by fetal-maternal exchange in the placenta or through the fetal skin to the amniotic fluid and uterine wall. We measured heat conductances along each pathway to estimate the fraction of total heat exiting each route. Thermistors were placed in the fetal aorta, two different sites in the amniotic fluid, and in a maternal artery. Five days after surgery we injected a total of 280 ml of ice-cold saline into the two separate amniotic fluid sites during a 45-s interval and measured the temperature response for the next hour. After one or two such injections the fetus was killed to cut off umbilical blood flow, and the experiment was repeated to measure the heat fluxes in the absence of placental heat exchange. Experimentally obtained temperature curves were compared with the predictions of a mathematical model. Heat conductances of the skin and uterine wall, as well as the fetal heat production, were estimated in the model using least-squares parameter optimization. In 10 fetal lambs, weighing 3.73 +/- 0.40 (SE) kg, total fetal heat production averaged 3.75 +/- 0.33 W X kg-1. The heat conductance of the uterine wall, 6.6 +/- 0.8 W X degrees C-1, was lower than that of the fetal skin, 10.2 +/- 1.0, and of the placenta, 25.7 +/- 2.9 W X degrees C-1, temperature gradient. We estimated that 84.5% of total fetal heat production exists by fetal-maternal exchange in the placenta with the remaining 15.5% exiting through the fetal skin.

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8

Moores, R. R., B. S. Carter, G. Meschia, P. V. Fennessey, and F. C. Battaglia. "Placental and fetal serine fluxes at midgestation in the fetal lamb." American Journal of Physiology-Endocrinology and Metabolism 267, no. 1 (July 1, 1994): E150—E155. http://dx.doi.org/10.1152/ajpendo.1994.267.1.e150.

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Plasma serine disposal rate (DR), decarboxylation, and conversion to fetal plasma glycine by the placenta were measured in six fetal lambs at 72 +/- 1 days gestation. L-[1-13C]serine, L-[U-14C]serine, and 3H2O were infused over 3 h into the fetal circulation, the latter for measurement of uterine and umbilical blood flow. The fetal plasma serine DR was 8.7 +/- 1.0 mumol/min or 61.8 +/- 4 mumol.min-1.kg fetus-1. Approximately 90% of the DR represented placental uptake of fetal serine. There was no detectable release of fetal serine into the maternal circulation. The fetal arterial plasma glycine-to-serine enrichment ratio was approximately 0.30. The conversion rate of fetal serine to fetal plasma glycine by the placenta was 5.8 +/- 0.7% of the serine DR. Fetal and placental CO2 production from fetal plasma serine carbon was 1.9 +/- 0.4 and 1.2 +/- 0.4 mumol/min, respectively. Thus, at midgestation, there is a rapid fetoplacental serine exchange that constitutes most of the fetal plasma serine turnover. Placental conversion of serine to fetal glycine and serine oxidation together account for only 10% of the placental uptake of fetal serine.

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9

Martin, Ana Carranza, and Alejandro E. Relling. "PSXIII-33 Polyunsaturated fatty acid and their fetal programming effect on the FFARs from ewe lambs’ ovaries." Journal of Animal Science 97, Supplement_3 (December 2019): 364–65. http://dx.doi.org/10.1093/jas/skz258.728.

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Abstract Free fatty acids (FA) receptors (FFAR) are critical for metabolic functions and energy homeostasis. The FFAR1 and FFAR4 are activated by long-chain polyunsaturated FA, but FFAR2 and FFAR3 join to short-chain FA. There is no evidence fetal programming on nutritional effects on those receptors, insulin receptor (INS-R) and stereological enzyme in lambs’ ovaries. The objective of this study was to evaluate the effect of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) supplementation to ewes during late gestation on finishing lamb ovary gene expression. Lambs born from ewes supplemented with Ca salts of EPA and DHA (PUFA), or palm FA distillate (PFAD) high in palmitic and oleic acid at 0.39% DM during the last 50d of gestation were used. After weaning and high concentrate diet adaptation (45d), 14 Hampshire x Dorset cross females lambs were blocked by initial BW and used in a 2x2 factorial arrangement of treatments using the factors of dam supplementation and lamb diets (PUFA or PFAD at 1.5% DM). At day 42, lambs were euthanized and ovary samples were obtained for FFARs, INS-R and steroid acute regulatory protein (STAR) mRNA concentration analysis. There was a dam diet effect on the abundance of FFAR4 mRNA (P = 0.05); lambs born from PUFA dams showed greater concentration than PFAD. Also, PUFA lambs tend to have greater concentration of FFAR4 (P = 0.07). The abundance of FFAR2, INS-R, and STAR mRNA was not significant for dam or lamb diet effect (P > 0.1). The mRNA of FFAR1 and FFAR3 were no found in the samples. However, mRNA concentration of FFAR2 and STAR were positively associated (r = 0.74 P < 0.05). In conclusion, dam and lamb diets modified FFAR4 mRNA concentration; and there might be a functional association between FFAR2 and STAR.

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10

Rurak, Dan, and Natalee W. Bessette. "Changes in fetal lamb arterial blood gas and acid-base status with advancing gestation." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 304, no. 10 (May 15, 2013): R908—R916. http://dx.doi.org/10.1152/ajpregu.00430.2012.

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To determine whether there are changes in blood gas and acid-base status with advancing gestation in the fetal lamb, similar to that reported in the human fetus, blood gas, acid-base, and blood metabolite values were measured in 447 control, arterial blood samples from 108 chronically instrumented fetal lambs between 103 and 146 days gestation. With advancing gestation, Po2, pH, O2saturation, and O2content fell significantly, while Pco2and hemoglobin concentration increased. Blood glucose and lactate concentrations were unchanged, although the lactate level increased with decreasing Po2, particularly when below ∼13 mmHg. Multiple linear regression indicated that increasing fetal number was associated with decreased Po2and glucose level and increased pH, HCO3−, base excess, and lactate concentration. Hemoglobin concentration was higher in female than male lambs. Overall, there was a linear relationship between glucose concentration and birth weight. It is concluded that in fetal lambs as in the human fetus, there are changes in blood gas and acid-base status with advancing gestation. This may be due to the decrease in fetal weight-normalized uterine and umbilical blood flows than occurs in these and other species as gestation proceeds. In addition, the reduced birth weight in twin and triplet lambs may be due to hypoglycemia rather than hypoxemia.

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11

Wakatsuki, Akihiko, Yuji Murata, Yuko Ninomiya, Naoki Masaoka, James G. Tyner, and Krishna K. Kutty. "Physiologic baroreceptor activity in the fetal lamb." American Journal of Obstetrics and Gynecology 167, no. 3 (September 1992): 820–27. http://dx.doi.org/10.1016/s0002-9378(11)91596-8.

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12

Longaker, Michael T., Brent R. W. Moelleken, Joseph C. Cheng, Russell W. Jennings, Scott N. Adzick, Jan Mintorovich, David G. Levinsohn, Leonard Gordon, Michael R. Harrison, and David J. Simmons. "Fetal Fracture Healing in a Lamb Model." Plastic and Reconstructive Surgery 90, no. 2 (August 1992): 161–71. http://dx.doi.org/10.1097/00006534-199208000-00001.

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13

Longaker, Michael T., Brent R. W. Moelleken, Joseph C. Cheng, Russell W. Jennings, Scott N. Adzick, Jan Mintorovich, David G. Levinsohn, Leonard Gordon, Michael R. Harrison, and David J. Simmons. "Fetal Fracture Healing in a Lamb Model." Plastic and Reconstructive Surgery 90, no. 2 (August 1992): 161–71. http://dx.doi.org/10.1097/00006534-199290020-00001.

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14

Andrew, M., H. O'Brodovich, and L. Mitchell. "Fetal lamb coagulation system during normal birth." American Journal of Hematology 28, no. 2 (June 1988): 116–18. http://dx.doi.org/10.1002/ajh.2830280211.

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Andrew, M., H. O'Brodovich, and L. Mitchell. "Fetal lamb coagulation system during birth asphyxia." American Journal of Hematology 28, no. 3 (July 1988): 201–3. http://dx.doi.org/10.1002/ajh.2830280317.

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16

Sato, Atsuyasu, Angelica Schehr, and Machiko Ikegami. "Leptin does not influence surfactant synthesis in fetal sheep and mice lungs." American Journal of Physiology-Lung Cellular and Molecular Physiology 300, no. 3 (March 2011): L498—L505. http://dx.doi.org/10.1152/ajplung.00418.2010.

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In the fetus, leptin in the circulation increases at late gestation and likely influences fetal organ development. Increased surfactant by leptin was previously demonstrated in vitro using fetal lung explant. We hypothesized that leptin treatment given to fetal sheep and pregnant mice might increase surfactant synthesis in the fetal lung in vivo. At 122–124 days gestational age (term: 150 days), fetal sheep were injected with 5 mg of leptin or vehicle using ultrasound guidance. Three and a half days after injection, preterm lambs were delivered, and lung function was studied during 30-min ventilation, followed by pulmonary surfactant components analyses. Pregnant A/J mice were given 30 or 300 mg of leptin or vehicle by intraperitoneal injection according to five study protocols with different doses, number of treatments, and gestational ages to treat. Surfactant components were analyzed in fetal lung 24 h after the last maternal treatment. Leptin injection given to fetal sheep increased fetal body weight. Control and leptin-treated groups were similar in lung function (preterm newborn lamb), surfactant components pool sizes (lamb and fetal mice), and expression of genes related to surfactant synthesis in the lung (fetal mice). Likewise, saturated phosphatidylcholine and phospholipid were normal in mice lungs with absence of circulating leptin (ob/ob mice) at all ages. These studies coincided in findings that neither exogenously given leptin nor deficiency of leptin influenced fetal lung maturation or surfactant pool sizes in vivo. Furthermore, the key genes critically required for surfactant synthesis were not affected by leptin treatment.

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17

Philipps, A. F., T. S. Rosenkrantz, M. L. Grunnet, M. E. Connolly, P. J. Porte, and J. R. Raye. "Effects of Fetal Insulin Secretory Deficiency on Metabolism in Fetal Lamb." Diabetes 35, no. 9 (September 1, 1986): 964–72. http://dx.doi.org/10.2337/diab.35.9.964.

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18

Bloch, Clifford, and Mark Sperling. "Sources and Disposition of Fetal Glucose: Studies in the Fetal Lamb." American Journal of Perinatology 5, no. 04 (October 1988): 344–52. http://dx.doi.org/10.1055/s-2007-999721.

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19

Holcomb, RobertG, and RandallB Wilkening. "Fetal Hepatic Oxygen Consumption under Normal Conditions in the Fetal Lamb." Neonatology 75, no. 5 (1999): 310–18. http://dx.doi.org/10.1159/000014109.

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20

Philipps, A. F., T. S. Rosenkrantz, M. L. Grunnet, M. E. Connolly, P. J. Porte, and J. R. Raye. "Effects of fetal insulin secretory deficiency on metabolism in fetal lamb." Diabetes 35, no. 9 (September 1, 1986): 964–72. http://dx.doi.org/10.2337/diabetes.35.9.964.

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21

Coulter, C. L., H. M. Mulvogue, I. R. Young, C. A. Browne, and I. C. McMillen. "Effect of fetal hypophysectomy on the localization of the catecholamine biosynthetic enzymes and enkephalins in the adrenal medulla of the fetal sheep." Journal of Endocrinology 121, no. 3 (June 1989): 425—NP. http://dx.doi.org/10.1677/joe.0.1210425.

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ABSTRACT We have investigated the effect of fetal hypophysectomy on the localization of dopamine B-hydroxylase (DBH), phenylethanolamine N-methyltransferase (PNMT) and enkephalin-containing peptides in the fetal sheep adrenal, using immunocytochemical techniques. Staining with anti-DBH was observed throughout the adrenal medulla in the intact (140–146 days of gestation) and hypophysectomized fetal sheep (147–164 days of gestation) and the newborn lamb (10–12 days after birth). In the adrenal medulla of the lategestation intact fetal sheep and newborn lamb, positive staining with anti-PNMT was observed in the peripheral rim of medullary cells adjacent to the adrenal cortex. After hypophysectomy, there was intense positive staining with anti-PNMT in the peripheral adrenal medullary cells and a small and variable proportion of central adrenal medullary cells were stained with anti-PNMT. In the adrenal gland of the intact fetal sheep and the newborn lamb, there was intense staining with anti-enkephalin in the peripheral rim of adrenal medullary cells. Staining with antienkephalin was less intense in the central medullary cells of the adrenal gland of the intact fetal sheep and the 10- to 12-day-old newborn lamb, and many unstained central medullary cells were present. After hypophysectomy, intense positive staining with antienkephalin was observed throughout the entire fetal adrenal medulla. Therefore, the fetal pituitary, either directly or indirectly through the adrenal cortex, plays a role in regulating the pattern of localization of both PNMT and enkephalin in the fetal sheep adrenal. Journal of Endocrinology (1989) 121, 425–430

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22

Dunbar Ivy, D., Timothy D. le Cras, Thomas A. Parker, Jeanne P. Zenge, Malathi Jakkula, Neil E. Markham, John P. Kinsella, and Steven H. Abman. "Developmental changes in endothelin expression and activity in the ovine fetal lung." American Journal of Physiology-Lung Cellular and Molecular Physiology 278, no. 4 (April 1, 2000): L785—L793. http://dx.doi.org/10.1152/ajplung.2000.278.4.l785.

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Mechanisms that regulate endothelin (ET) in the perinatal lung are complex and poorly understood, especially with regard to the role of ET before and after birth. We hypothesized that the ET system is developmentally regulated and that the balance of ETAand ETB receptor activity favors vasoconstriction. To test this hypothesis, we performed a series of molecular and physiological studies in the fetal lamb, newborn lamb, and adult sheep. Lung preproET-1 mRNA levels, tissue ET peptide levels, and cellular localization of ET-1 expression were determined by Northern blot analysis, peptide assay, and immunohistochemistry in distal lung tissue from fetal lambs between 70 and 140 days (term = 145 days), newborn lambs, and ewes. Lung mRNA expression for the ETA and ETB receptors was also measured at these ages. We found that preproET-1 mRNA expression increased from 113 to 130 days gestation. Whole lung ET protein content was highest at 130 days gestation but decreased before birth in the fetal lamb lung. Immunolocalization of ET-1 protein showed expression of ET-1 in the vasculature and bronchial epithelium at all gestational ages. ETA receptor mRNA expression and ETB receptor mRNA increased from 90 to 125 and 135 days gestation. To determine changes in activity of the ETA and ETBreceptors, we studied the effect of selective antagonists to the ETA or ETB receptors at 120, 130, and 140 days of fetal gestation. ETA receptor-mediated vasoconstriction increased from 120 to 140 days, whereas blockade of the ETBreceptor did not change basal fetal pulmonary vascular tone at any age examined. We conclude that the ET system is developmentally regulated and that the increase in ETA receptor gene expression correlates with the onset of the vasodilator response to ETA receptor blockade. Although ETB receptor gene expression increases during late gestation, the balance of ET receptor activity favors vasoconstriction under basal conditions. We speculate that changes in ET receptor activity play important roles in regulation of pulmonary vascular tone in the ovine fetus.

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Ibe, Basil O., Fred C. Sander, and J. Usha Raj. "Platelet-activating factor receptors in lamb lungs are downregulated immediately after birth." American Journal of Physiology-Heart and Circulatory Physiology 278, no. 4 (April 1, 2000): H1168—H1176. http://dx.doi.org/10.1152/ajpheart.2000.278.4.h1168.

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Platelet-activating factor (PAF) is a phospholipid with diverse biological functions mediated by a G protein-coupled receptor. We determined PAF receptor binding in lung membranes of four groups of perinatal lambs. Membrane protein (100 μg/ml) was incubated for 60 min at 30°C with 0.5–24 nM of acetyl-[3H]PAF in 30 mM Tris buffer, pH 7.2, containing 0.25% BSA, 10 mM MgCl2, and 125 mM choline chloride. PAF bound to membrane was isolated and quantified by scintillation spectrometry, followed with Scatchard analysis for receptor density (Bmax). The Bmax (means ± SE, fmol/mg protein) were 445.8 ± 12.3, 244.2 ± 3.3, 250.6 ± 3.6, and 419.9 ± 8.6 for the fetal, 90-min-old, <1-day-old, and 6- to 12-day-old lambs, respectively. The Bmax for the 90-min-old and <1-day-old lambs were not different but were significantly lower than those of either the term fetal or 6- to 12-day-old lambs. These data show a significant decrease in PAF binding to its receptor and in PAF Bmax in lung membranes of immediate newborn lambs. The dissociation constants ( K D, nM) were 7.7 ± 0.52, 11.5 ± 0.34, 6.9 ± 0.48, and 5.0 ± 0.53 for fetal, 90-min-old, <1-day-old, and 6- to 12-day-old newborn lamb lungs, respectively. The K D of the 90-min-old lamb was the highest of all. PAF receptor gene measured by RT-PCR showed a significant downregulation of PAF receptor gene mRNA in lungs of lambs <1 day old, suggesting a transcriptional regulation of PAF receptor gene expression in the immediate newborn period. We speculate that decreased PAF receptor binding immediately after birth will facilitate the fall in pulmonary vascular resistance in the immediate newborn period.

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Allworth, M. B., H. A. Wrigley, and A. Cowling. "Fetal and lamb losses from pregnancy scanning to lamb marking in commercial sheep flocks in southern New South Wales." Animal Production Science 57, no. 10 (2017): 2060. http://dx.doi.org/10.1071/an16166.

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Perinatal lamb mortality is a major challenge for sheep producers worldwide. Lamb losses from ultrasound pregnancy scanning to lamb marking were assessed in 125 mobs of ewes sourced predominantly from sheep flocks in southern New South Wales. In total, 103 086 lambs were marked from100 165 ewes present at joining. Despite the majority of producers undertaking best-practice ewe management, including ultrasound scanning for pregnancy and preferential feeding of multiple bearing ewes, losses were similar to those reported previously (11% and 29% for singles and twins respectively). Non-Merino ewes had significantly lower losses than did Merino ewes, irrespective of ram type (13% versus 21%, P < 0.001). There was a tendency for mob size in twin-bearing ewes to influence survival, with a lower mob size (<200) having lower losses (29% versus 33%, P = 0.07). These results are discussed in the context of existing extension advice about ewe management and perinatal lamb mortality.

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Clarke, Lynne, David Pam Yakubu, and Michael E. Symonds. "Influence of maternal bodyweight on size, conformation and survival of newborn lambs." Reproduction, Fertility and Development 9, no. 5 (1997): 509. http://dx.doi.org/10.1071/r97016.

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Although body condition score was not significantly different between light (<55 kg, n = 6) and heavy (≥60 kg, n = 70 ewes at mating, it declined between Day 30 and Day 90 of gestation in light but not heavy ewes, and remained lower up to term. All ewes bore twins, delivered near term (Days 144–146) by Caesarean section. One lamb was immediately placed into a warm (30°C; WD) and its twin into a cool (15°C; CD) ambient temperature, and tissues were sampled at 0·5 h or 6 h. All CD lambs born to light ewes exhibited hypothermia and/or respiratory failure and did not survive longer than 30 min; these symptoms were not observed in their WD twins or any lamb born to heavy ewes. Total lamb birth weight, placental weight and fetal cotyledonary weight were lower with light than with heavy ewes. Lambs born to light ewes had less perirenal adipose tissue and smaller liver, heart, kidneys, brain, adrenals and thyroid, although their heart, brain and pancreas represented a larger proportion of total bodyweight; pancreas weight was similar to that in lambs born to heavy ewes. Hence, maternal bodyweight critically influences placental weight and lamb size and survival after birth.

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Baker, B. W., P. A. Dailey, S. C. Hughes, S. M. Shnider, D. B. C. Cheek, R. Field, J. T. Parer, and J. Johnson. "EFFECTS OF ISOFLURANE ON THE ASPHYXIATED FETAL LAMB." Anesthesiology 65, Supplement 3A (September 1986): A395. http://dx.doi.org/10.1097/00000542-198609001-00393.

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27

Rawashdeh, N. M., J. C. Rose, and D. R. Kerr. "Renin secretion by fetal lamb kidneys in vitro." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 258, no. 2 (February 1, 1990): R388—R392. http://dx.doi.org/10.1152/ajpregu.1990.258.2.r388.

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We studied the content and secretion of renin by renal cortical slices obtained from ovine fetuses at 0.62-0.77 gestation (n = 5 immature) and at 0.84-1.00 gestation (n = 5 mature). Renin content of fresh slices and renin secretion after the incubation of slices in Robinson's medium with or without isoproterenol or dibutyryl (DB) adenosine 3',5'-cyclic monophosphate (cAMP) (10(-4)-10(-8) M) were measured. Renin content of immature fetal kidneys (ng.ml homogenate-1.h-1.mg-1) and basal renin secretion rate [ng (ANG I/h).mg tissue-1.h incubation-1] were 24.3 +/- 3.0 and 1.4 +/- 0.4, respectively. Both of these values were significantly lower (P less than 0.02) than the corresponding results obtained with mature fetal kidneys (67.0 +/- 4.5 and 3.4 +/- 0.5). Renin content and basal secretion rates were strongly correlated (r = 0.78, P less than 0.01). The addition of isoproterenol or DBcAMP induced a significant increase in renin secretion only when incubated with slices from mature fetuses. We conclude that there is a deficit in the beta-adrenoceptor-mediated renin release distal to cAMP formation in immature fetuses, which may be related to low renal content of renin at this stage of development.

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28

Luks, Francois I., Jan Deprest, Marco Marcus, Kamiel Vandenberghe, Jan D. Vertommen, Toni Lerut, and Ivo Brosens. "Carbon Dioxide Pneumoamnios Causes Acidosis in Fetal Lamb." Fetal Diagnosis and Therapy 9, no. 2 (1994): 105–9. http://dx.doi.org/10.1159/000263916.

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Longaker, Michael T., D. Andrew R. Burd, Allen M. Gown, T. S. Benedict Yen, Russell W. Jennings, Brian W. Duncan, Michael R. Harrison, and N. Scott Adzick. "Midgestational excisional fetal lamb wounds contract in utero." Journal of Pediatric Surgery 26, no. 8 (August 1991): 942–48. http://dx.doi.org/10.1016/0022-3468(91)90841-g.

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30

de Haan, Harmen H., Jos L. H. Van Reempts, Johan S. H. Vles, Jelte de Haan, and Tom H. M. Hasaart. "Effects of asphyxia on the fetal lamb brain." American Journal of Obstetrics and Gynecology 169, no. 6 (December 1993): 1493–501. http://dx.doi.org/10.1016/0002-9378(93)90424-h.

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31

SCAGLIOTTI, DANIEL, DENISE D. SHIMOKOCHI, and KEVIN C. PRINGLE. "Permanent Cardiac Pacemaker Implant in the Fetal Lamb." Pacing and Clinical Electrophysiology 10, no. 6 (November 1987): 1253–61. http://dx.doi.org/10.1111/j.1540-8159.1987.tb04961.x.

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32

Papadakis, Konstantinos, François I. Luks, Jan A. Deprest, Veerle E. Evrard, Hélène Flageole, Marc Miserez, and Toni E. Lerut. "Single-port tracheoscopic surgery in the fetal lamb." Journal of Pediatric Surgery 33, no. 6 (June 1998): 918–20. http://dx.doi.org/10.1016/s0022-3468(98)90674-1.

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Weil, Sharon R., Pierantonio A. Russo, James L. Heckman, Rohinton K. Balsara, Valarie Pasiecki, and Jeffrey M. Dunn. "Pressure-volume relationship of the fetal lamb heart." Annals of Thoracic Surgery 55, no. 2 (February 1993): 470–75. http://dx.doi.org/10.1016/0003-4975(93)91021-e.

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34

Bouayad, Asmàa, Hiroki Kajino, Nahid Waleh, Jean-Claude Fouron, Gregor Andelfinger, Daya R. Varma, Amanda Skoll, et al. "Characterization of PGE2 receptors in fetal and newborn lamb ductus arteriosus." American Journal of Physiology-Heart and Circulatory Physiology 280, no. 5 (May 1, 2001): H2342—H2349. http://dx.doi.org/10.1152/ajpheart.2001.280.5.h2342.

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Although the role of PGE2 in maintaining ductus arteriosus (DA) patency is well established, the specific PGE2 receptor subtype(s) (EP) involved have not been clearly identified. We used late gestation fetal and neonatal lambs to study developmental regulation of EP receptors. In the fetal DA, radioligand binding and RT-PCR assays virtually failed to detect EP1 but detected EP2, EP3D, and EP4 receptors in equivalent proportions. In the newborn lamb, DA total density was one-third of that found in the fetus and only EP2 was detected. Stimulation of EP2 and EP4 increased cAMP formation and was associated with DA relaxation. Though stimulation of EP3 inhibited cAMP formation, it surprisingly relaxed the fetal DA both in vitro and in vivo. This EP3-induced relaxation was specifically diminished by the ATP-sensitive K+ (KATP) channel blocker glibenclamide. In conclusion, PGE2 dilates the late gestation fetal DA through pathways that involve either cAMP (EP2 and EP4) or KATP channels (EP3). The loss of EP3 and EP4receptors in the newborn DA is consistent with its decreased responsiveness to PGE2.

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35

Revell, D. K., S. T. Morris, Y. H. Cottam, J. E. Hanna, D. G. Thomas, S. Brown, and S. N. McCutcheon. "Shearing ewes at mid-pregnancy is associated with changes in fetal growth and development." Australian Journal of Agricultural Research 53, no. 6 (2002): 697. http://dx.doi.org/10.1071/ar01140.

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This study investigated the effect of mid-pregnancy shearing (at Day 70 of pregnancy, P70) on herbage intake of grazing single- and twin-bearing ewes, lamb birth weight, and cold resistance of new-born lambs. At pregnancy diagnosis on P50, 30 single-bearing and 30 twin-bearing ewes were allocated either to be shorn at P70 (n = 15 for each pregnancy rank) or to remain unshorn to serve as controls (n = 15 for each pregnancy rank). All ewes were mated over a 3-day period with synchronisation of their oestrus. Herbage intake was measured indirectly from in vitro pasture digestibility and faecal output of grazing ewes, with the use of intra-ruminal chromium slow-release capsules, over six 5-day periods from P64 to P105. The weights of placental and fetal tissues were assessed in a subgroup of 16 ewes at P140 and P141. In the remaining sheep, lamb liveweight at birth and during lactation until weaning at 103 days of age was measured, and cold-resistance of new-born lambs was assessed by measuring summit metabolic rate (SMR) by indirect calorimetry. Ewe liveweight (corrected for fleece weight), condition score, and herbage intake during pregnancy were not affected by shearing treatment. Mid-pregnancy shearing did not affect placental weight, but increased the relative weights (i.e. g/kg liveweight) of fetal thyroid gland and lungs and reduced the relative weight of adrenal glands and heart. The ratio of secondary to primary wool follicles in near-term fetal skin was about 10% higher in offspring of shorn than of unshorn ewes. The metabolic rate of fetal hepatic tissue was increased by mid-pregnancy shearing, particularly in twin fetuses, possibly indicative of an increase in placental transport of nutrients to the fetuses. This conclusion is supported by the greater birth weight (average response 0.5 kg) of lambs born to ewes shorn at mid-pregnancy. Mid-pregnancy shearing also increased the SMR of new-born twin lambs by 16%, but decreased the SMR of singleton lambs by 26%. These results indicate that mid-pregnancy shearing can increase lamb birth weight without increasing ewe herbage intake or placental weight. An increase in the efficiency of nutrient uptake by the placenta is implied, and possible effects on the activity of thermogenic tissues are discussed.

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36

Yamashiro, Kaeli, Laura A. Galganski, Jamie Peyton, Kalie Haynes, Victoria Vicuna, Priyadarsini Kumar, Benjamin Keller, et al. "Surviving Lambs with Myelomeningocele Repaired in utero with Placental Mesenchymal Stromal Cells for 6 Months: A Pilot Study." Fetal Diagnosis and Therapy 47, no. 12 (2020): 912–17. http://dx.doi.org/10.1159/000510813.

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Background: Fetal repair of myelomeningocele (MMC) with placental mesenchymal stromal cells (PMSCs) rescues ambulation in the ovine model up to 48 h postnatally. Outcomes past 48 h are unknown as MMC lambs have not been survived past this timepoint. Objective: We aimed to survive lambs for 6 months following the fetal repair of MMC with PMSCs. Methods: Fetal MMC lambs were repaired with PMSCs. Lambs received either no additional treatment or postnatal bracing and physical therapy (B/PT). Motor function was assessed with the sheep locomotor rating (SLR). Lambs with an SLR of 15 at birth were survived for 6 months or until a decline in SLR less than 15, whichever came first. All lambs underwent a perimortem MRI. Results: The lambs with no postnatal treatment (n = 2) had SLR declines to 7 and 13 at 29 and 65 days, respectively, and were euthanized. These lambs had a spinal angulation of 57° and 47°, respectively. The B/PT lamb (n = 1) survived for 6 months with a sustained SLR of 15 and a lumbar angulation of 42°. Conclusion: Postnatal physical therapy and bracing counteracted the inherent morbidity of the absent paraspinal muscles in the ovine MMC model allowing for survival and maintenance of rescued motor function of the prenatally treated lamb up to 6 months.

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Bell, A. W., J. M. Kennaugh, F. C. Battaglia, E. L. Makowski, and G. Meschia. "Metabolic and circulatory studies of fetal lamb at midgestation." American Journal of Physiology-Endocrinology and Metabolism 250, no. 5 (May 1, 1986): E538—E544. http://dx.doi.org/10.1152/ajpendo.1986.250.5.e538.

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Uterine and umbilical blood flows, the placental clearance of 3H2O, uterine and umbilical uptakes of oxygen, glucose, and lactate were measured in conscious, pregnant sheep at 71-81 days gestation. Fetal weight was 210 +/- 20 g and less than half placental weight. In relation to fetal weight, umbilical flow was 468 +/- 57 ml X min-1 X kg-1, more than double normal values for the mature fetus. Clearance of 3H2O was approximately 12% of the late pregnancy value but high in relation to fetal weight (280 +/- 23 ml X min-1 X kg-1). Fetal oxygen uptake was 10.9 +/- 0.6 ml X min-1 X kg-1, approximately 40% greater than in late gestation. Umbilical uptake of glucose was also relatively high, whereas lactate uptake was low. Uteroplacental tissues consumed more than 80% of the oxygen and glucose taken up by the pregnant uterus. However, uteroplacental utilization rates of oxygen and glucose as well as net lactate production were lower (approximately 50, 30, and 25%, respectively) than in late pregnancy, despite a larger placental mass (486 +/- 22 vs. 302 +/- 12 g).

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38

Black, Stephen M., Lucienne S. Sanchez, Eugenia Mata-Greenwood, Janine M. Bekker, Robin H. Steinhorn, and Jeffrey R. Fineman. "sGC and PDE5 are elevated in lambs with increased pulmonary blood flow and pulmonary hypertension." American Journal of Physiology-Lung Cellular and Molecular Physiology 281, no. 5 (November 1, 2001): L1051—L1057. http://dx.doi.org/10.1152/ajplung.2001.281.5.l1051.

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Utilizing aortopulmonary vascular graft placement, we established a lamb model of pulmonary hypertension that mimics congenital heart disease with increased pulmonary blood flow. We previously demonstrated that endothelial nitric oxide synthase (eNOS) is increased in lambs at age 4 wk. However, these lambs display a selective impairment of endothelium-dependent pulmonary vasodilation that is suggestive of a derangement downstream of NO release. Thus our objective was to characterize potential alterations in the expression and activity of soluble guanylate cyclase (sGC) and phosphodiesterase type 5 (PDE5) induced by increased pulmonary blood flow and pulmonary hypertension. Late-gestational fetal lambs ( n = 10) underwent in utero placement of an aortopulmonary vascular graft (shunt). Western blotting analysis on lung tissue from 4-wk-old shunted lambs and age-matched controls showed that protein for both subunits of sGC was increased in shunted lamb lungs compared with age-matched controls. Similarly, cGMP levels were increased in shunted lamb lungs compared with age-matched controls. However, PDE5 expression and activity were also increased in shunted lambs. Thus although cGMP generation was increased, concomitant upregulation of PDE5 expression and activity may have (at least partially) limited and accounted for the impairment of endothelium-dependent pulmonary vasodilation in shunted lambs.

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39

Guyton, T. S., H. De Wilt, P. V. Fennessey, G. Meschia, R. B. Wilkening, and F. C. Battaglia. "Alanine umbilical uptake, disposal rate, and decarboxylation rate in the fetal lamb." American Journal of Physiology-Endocrinology and Metabolism 265, no. 3 (September 1, 1993): E497—E503. http://dx.doi.org/10.1152/ajpendo.1993.265.3.e497.

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Fetal plasma alanine disposal rate (DR) and decarboxylation rate were measured at 132 +/- 1 days gestation in nine fetal lambs infused with L-[1-14C]alanine via a brachial vein. In five experiments, L-[1-13C]alanine was added to the infusate. Using L-[1-14C]alanine, we found mean DR to be 15.5 +/- 1.8 mumol.min-1 . kg-1. DR was significantly correlated to both arterial plasma alanine and whole blood lactate concentrations. Placental uptake of fetal plasma alanine accounted for 19 +/- 4% of DR. Fetal and placental production of CO2 from the first carbon of alanine were 61 +/- 2 and 16 +/- 2% of DR, respectively, for a total uterine excretion of 77 +/- 3%. Net alanine flux from placenta to fetus was 5.2 +/- 0.5 mumol.min-1 x kg-1, which was less than fetal plasma alanine decarboxylation (9.4 +/- 1.2 mumol.min-1 x kg-1) plus fetal alanine accretion (2.4 mumol.min-1 x kg-1). Utilizing L-[1-13C]alanine, we found DR to be 14.2 +/- 0.8 mumol.min-1 x kg-1, not significantly different from the 14C data. We conclude that both the umbilical uptake of alanine from the placenta and fetal alanine synthesis contribute to fetal alanine supply and that oxidation is the main route of fetal plasma alanine disposal.

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40

MEARS, G. J. "RELATIONSHIP BETWEEN LAMB BIRTH WEIGHTS AND FETAL PLASMA GROWTH HORMONE AND INSULIN CONCENTRATIONS." Canadian Journal of Animal Science 66, no. 4 (December 1, 1986): 995–1001. http://dx.doi.org/10.4141/cjas86-109.

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Plasma concentrations of growth hormone (GH) and insulin were monitored in 11 chronically cannulated ovine fetuses and their mothers during the last month of gestation to obtain information on the role that these hormones have in determining fetal growth rate. Maternal plasma GH and insulin concentrations were independent of stage of gestation and lamb birth weights. Fetal plasma insulin concentrations were episodic in nature, independent of stage of gestation, and tended to be higher in fetuses that were heavier at birth. Fetal plasma GH concentrations were only slightly episodic in nature, were tenfold higher than maternal levels at 116–124 d gestation and increased by approximately another 25% prior to parturition. Fetal plasma GH concentrations were negtively correlated with lamb birth weights. In twin preparations, fetal plasma GH concentrations were significantly lower in the twin that was heaviest at birth. The lower GH concentrations found in faster growing fetuses are suggestive of a more rapid metabolic clearance of GH by the tissues of these animals. The results indicate that circulating fetal GH and, possibly, insulin are involved in determining the rate of ovine-fetal growth. Key words: Ovine birth weights, fetal GH, fetal insulin, fetal growth

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41

Bartelds, Beatrijs, Jan-Willem C. Gratama, Hennie Knoester, Janny Takens, Gioia B. Smid, Jan G. Aarnoudse, Hugo S. A. Heymans, and Jaap R. G. Kuipers. "Perinatal changes in myocardial supply and flux of fatty acids, carbohydrates, and ketone bodies in lambs." American Journal of Physiology-Heart and Circulatory Physiology 274, no. 6 (June 1, 1998): H1962—H1969. http://dx.doi.org/10.1152/ajpheart.1998.274.6.h1962.

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No information is available on perinatal changes in myocardial metabolism in vivo. We measured myocardial supply and flux of fatty acids, carbohydrates, and ketone bodies in chronically instrumented fetal, newborn (1–4 days), and juvenile (7 wk) lambs, by measuring aorta-coronary sinus concentration differences and blood flow. In the fetal lambs, myocardial supply and flux of fatty acids were zero. In the newborn lambs, the supply of fatty acids increased tenfold, but there was no flux of fatty acids. Carbohydrates were the major energy source in fetal and newborn lambs, accounting for 89 and 69% of myocardial oxygen consumption, respectively. In the juvenile lambs, the flux of fatty acids was increased threefold. The supply and flux of carbohydrates were decreased (by 31 and 82%, respectively). The supply and flux of ketone bodies gradually increased with age. We show that the myocardium of the lamb in vivo does not switch immediately after birth from carbohydrates to fatty acids. The mechanisms involved in the development of myocardial fatty acid oxidation remain to be elucidated.

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42

Landau, S., Z. Zoref, Z. Nitsan, and Z. Madar. "The influence of extruding corn grain in diets fed to Finn × Awassi crossbred ewes during late pregnancy on birth weight of lambs." Canadian Journal of Animal Science 77, no. 1 (March 1, 1997): 141–47. http://dx.doi.org/10.4141/a94-132.

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As part of a program aimed at increasing lamb survival by maximizing lamb birth weight, the relationship between corn starch degradability in late pregnancy diets and lambing performance was studied in 60 Finn–Awassi ewes fed diets supplemented with 500 g d−1 of whole (WC), extruded (EC) or ground corn (GC). Lamb birth- weights ranked as follows: single lambs: EC > WC > GC (NS at 2nd parity, P < 0.10 at 3rd and higher parities); twin lambs: EC > WC = GC (P < 0.02 at 2nd, P < 0.07 at 3rd and higher parities). The ratio between birth weight of twin lamb litters and maternal weight measured 4 d postpartum in ewes at 3rd and higher parities was 25% greater in EC-fed ewes than in their WC- or GC-fed counterparts (P < 0.03). Colostrum accumulation prepartum was not affected by litter size or diet, but was higher (P < 0.04) in ewes from 3rd and higher parities compared with 2nd parity. Plasma NEFA (positive correlation) and insulin (negative correlation) concentrations on day 23 pre-partum, or plasma NEFA (positive correlation), insulin and glucose (negative correlations) concentrations on day 9 pre-partum, and ewe body weight at day 4 post-partum (positive correlation) explained 78% of variance in lamb birth weight (P < 0.0001). In conclusion 1) in prolific ewes at late pregnancy, highly degradable corn starch promotes better fetal growth than moderately degradable corn starch; 2) the positive correlation between NEFA and lamb birth weight, even in "overfed" ewes carrying single lambs indicates that maximal lamb birth weight is not likely to be maximized without some degree of maternal lipolysis. Key words: Sheep, birth weight, pregnancy, nutrition, starch, prolificacy

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43

Gao, Yuansheng, Jean-Francois Tolsa, Michael Botello, and J. Usha Raj. "Developmental change in isoproterenol-mediated relaxation of pulmonary veins of fetal and newborn lambs." Journal of Applied Physiology 84, no. 5 (May 1, 1998): 1535–39. http://dx.doi.org/10.1152/jappl.1998.84.5.1535.

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β-Adrenergic agonists are important regulators of perinatal pulmonary circulation. They cause vasodilation primarily via the adenyl cyclase-adenosine 3′,5′-cyclic monophosphate (cAMP) pathway. We examined the responses of isolated fourth-generation pulmonary veins of term fetal (145 ± 2 days gestation) and newborn (10 ± 1 days) lambs to isoproterenol, a β-adrenergic agonist. In vessels preconstricted with U-46619 (a thromboxane A2 analog), isoproterenol induced greater relaxation in pulmonary veins of newborn lambs than in those of fetal lambs. The relaxation was eliminated by propranolol, a β-adrenergic antagonist. Forskolin, an activator of adenyl cyclase, also caused greater relaxation of veins of newborn than those of fetal lambs. 8-Bromoadenosine 3′,5′-cyclic monophosphate, a cell membrane-permeable analog of cAMP, induced a similar relaxation of all vessels. Biochemical studies show that isoproterenol and forskolin induced a greater increase in cAMP content and in adenyl cyclase activity of pulmonary veins in the newborn than in the fetal lamb. These results demonstrate that β-adrenergic-agonist-mediated relaxation of pulmonary veins increases with maturation. An increase in the activity of adenyl cyclase may contribute to the change.

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Murata, Yuji, Yoshiaki Miyake, Tatsuo Yamamoto, Motokazu Higuchi, John Hesser, Satoshi Ibara, Takefumi Bessho, and James G. Tyner. "Experimentally produced sinusoidal fetal heart rate pattern in the chronically instrumented fetal lamb." American Journal of Obstetrics and Gynecology 153, no. 6 (November 1985): 693–702. http://dx.doi.org/10.1016/s0002-9378(85)80262-3.

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45

Bard, Harry, and Jean-Claude Fouron. "The increase in fetal hemoglobin synthesis in the fetal lamb during hyperglycemic hypoxemia." American Journal of Obstetrics and Gynecology 159, no. 5 (November 1988): 1269–72. http://dx.doi.org/10.1016/0002-9378(88)90462-0.

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46

Thomas Kisker, C., David P. Bohlken, and William R. Clarke. "Effects of Acidosis on Fetal and Maternal Blood Coagulation: A Fetal Lamb Model." Pediatric Research 19, no. 1 (January 1985): 78–82. http://dx.doi.org/10.1203/00006450-198501000-00021.

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47

Fong, Daniel D., Kaeli J. Yamashiro, Michael Austin Johnson, Kourosh Vali, Laura A. Galganski, Christopher D. Pivetti, Diana L. Farmer, Herman L. Hedriana, and Soheil Ghiasi. "Validation of a Novel Transabdominal Fetal Oximeter in a Hypoxic Fetal Lamb Model." Reproductive Sciences 27, no. 10 (June 15, 2020): 1960–66. http://dx.doi.org/10.1007/s43032-020-00215-5.

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48

Muylder, Xavier De, Jean-Claude Fouron, Harry Bard, and Josée S. Lafond. "Physiologic modulations of the systolic time intervals in the fetal lamb." Canadian Journal of Physiology and Pharmacology 63, no. 7 (July 1, 1985): 893–97. http://dx.doi.org/10.1139/y85-146.

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To examine the modulation of fetal systolic time intervals of the ovine fetus in relation to fetal maturation, heart rate, respiratory activity, and circadian rhythm, studies were carried out on 13 fetal–maternal sheep preparations. The data obtained showed that there was a significant correlation between the ejection time (ET) and the RR intervals of the electrocardiogram. The pre-ejection period (PEP) and PEP/ET increased in relation to the fetal maturation (38 ms and 0.25 at 120 days to 52 ms and 0.33 at 145 days of gestation, respectively). When the circadian rhythmicity was analyzed, a relative tachycardia was in evidence during the 21- to 03-h period but systolic time intervals remained unchanged. Except for some tachycardia and cardiac rhythm variability, respiratory activity also had no influence on the systolic time intervals.

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49

Shaul, P. W., I. S. Yuhanna, Z. German, Z. Chen, R. H. Steinhorn, and F. C. Morin. "Pulmonary endothelial NO synthase gene expression is decreased in fetal lambs with pulmonary hypertension." American Journal of Physiology-Lung Cellular and Molecular Physiology 272, no. 5 (May 1, 1997): L1005—L1012. http://dx.doi.org/10.1152/ajplung.1997.272.5.l1005.

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Nitric oxide (NO), produced by endothelial (e) NO synthase (NOS), is critically involved in the cardiopulmonary transition from fetal to neonatal life. We have previously shown that NO-dependent relaxation is attenuated in intrapulmonary arteries from fetal lambs with pulmonary hypertension (PHT) created by prenatal ligation of the ductus arteriosus. In the present study, we determined whether this is due to altered pulmonary eNOS expression. eNOS and neuronal NOS (nNOS) protein expression were assessed in lungs from near-term control lambs and PHT lambs that underwent ductal ligation 10 days earlier. eNOS protein expression was decreased 49% in PHT lung. In contrast, nNOS protein abundance was unchanged. NOS enzymatic activity was also diminished in PHT vs. control lung (60 +/- 3 vs. 110 +/- 7 fmol.mg protein-1.min-1, respectively). Paralleling the declines in eNOS protein and NOS enzymatic activity, eNOS mRNA abundance was decreased 64% in PHT lung. Thus pulmonary eNOS gene expression is attenuated in the lamb model of fetal PHT. Because NO modulates both vasodilation and vascular smooth muscle growth, diminished eNOS expression may contribute to both the abnormal vasoreactivity and the excessive muscularization of the pulmonary circulation in fetal PHT.

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50

Berry, L. M., D. H. Polk, M. Ikegami, A. H. Jobe, J. F. Padbury, and M. G. Ervin. "Preterm newborn lamb renal and cardiovascular responses after fetal or maternal antenatal betamethasone." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 272, no. 6 (June 1, 1997): R1972—R1979. http://dx.doi.org/10.1152/ajpregu.1997.272.6.r1972.

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The optimal dose, route of administration, and treatment-to-delivery interval necessary to induce beneficial extrapulmonary effects of glucocorticoids are not known. Pregnant ewes (127 days gestation) were randomized to receive maternal or fetal intramuscular injections of betamethasone (0.2 or 0.5 mg/kg body wt) or saline 24 h before cesarean delivery of their lambs. Three hours after delivery, low-dose maternal vs. control lamb mean arterial pressure [64 +/- 4 vs. 47 +/- 2 (SE) mmHg], glomerular filtration rate (1.7 +/- 0.2 vs. 0.7 +/- 0.1 ml.min-1.kg-1), and total renal sodium reabsorption (219 +/- 31 vs. 85 +/- 12 mueq.min-1.kg-1) were increased. Comparable increases were observed in the high-dose maternal and fetal groups without effects in the low-dose fetal group. This study provides the first quantitative data demonstrating that even short-term (24-h) antenatal betamethasone exposure alters preterm newborn cardiovascular and renal functions. These responses are route and dose dependent and are comparable to glucocorticoid-induced maturational effects after longer-term antenatal exposure.

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Journal articles on the topic 'Fetal lamb'

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