Louis W. Holm

Failure of initiation of parturition after electrocoagulation of the pituitary of the fetal lamb

Abstract Electrocoagulation lesions were made in the pituitaries of fetal lambs between the ninety-third and one hundred and forty-third day of gestation. Initiation of parturition failed to occur in 9 ewes operated on before 134 days in which the fetal pituitary lesion involved more than 70 per cent of the gland. Operation at the one hundred and forty-third day was followed by spontaneous delivery as was also the case in 3 ewes in which the fetal pituitary lesion involved less than 60 per cent of the gland. Four multiple pregnancies, with one fetus spared operation in each, and 4 shamoperated pregnancies terminated spontaneously at term. Pregnancy was prolonged in 2 ewes carrying fetuses with intact pituitaries; in one, the fetal hypothalamus was extensively damaged and, in the other, the pituitary stalk had been coagulated at the one hundred and forty-first day of gestation. It is concluded that the integrity of the fetal pituitary and probably of the hypothalamus is essential to the initiation of parturition in the sheep.

Hemodynamic Changes in Fetal Lamb in Utero in Response to Asphyxia, Hypoxia, and Hypercapnia

The effects of hypoxia (administration of 10 per cent O2 in N2 and constriction of the uterine arteries), of hypercapnia (administration of 8 per cent CO2 in air), and of asphyxia (obstruction of the umbilical circulation) were studied on the fetus in utero in near-term pregnant ewes under spinal anesthesia. Hypoxia and hypercapnia produced increases in the maternal arterial pressure, maternal heart rate, and uterine blood flow. Fetal arterial pressure and carotid and umbilical blood flows increased, while the fetal heart rate decreased. Fetal femoral flow decreased during hypoxia and increased during hypercapnia. There was a delay of five to six minutes between the initiation of hypoxia or hypercapnia and the appearance of fetal circulatory changes. Transient reduction of uterine blood flow evoked insignificant hemodynamic alterations in the mother and fetus. A reduction of flow greater than 50 per cent of control values produced a fetal bradycardia along with increases in fetal arterial pressure, carotid and umbilical flows. Constriction of the umbilical veins with the umbilical arteries intact produced a prompt bradycardia together with a decrease in fetal arterial pressure and regional blood flows. Constriction of the umbilical arteries alone also produced a bradycardia with an initial rise in arterial pressure and carotid flow. Similar changes were observed after cutting the umbilical cord. Elimination of the low resistance of the placenta played a major role in these changes. Placing the lamb in the head-down position caused a marked increase in carotid blood flow without greatly modifying arterial pressure.

Systemic and Regional Hemodynamic Alterations in Toxemia

THE NATURE of the vascular disorder which underlies acute toxemia of pregnancy has been controversial. In human toxemia, because of the elevated arterial pressure, total systemic vascular resistance is thought to be increased. In toxemia in sheep, on the other hand, the blood pressure is normal or subnormal and the status of the systemic vascular resistance is unknown. The object of this paper is to present data on the changes in systemic and regional circulation in human and sheep toxemia and to discuss the significance of these changes in terms of the etiopathogenesis of this disease.

THE HISTOLOGY OF THE POSTTERM BOVINE PLACENTA.

Abstract Placentomes from 8 cases of prolonged pregnancy in Holstein and Guernsey cows were examined histologically and compared with those from normal term pregnancies. In all specimens studied there was fibrosis of the maternal ridges, atrophy of the small trophoblast cells, and pyknosis of their nuclei. There was slight to moderate vacuolization of the binucleated fetal giant cells, with loss of reaction to the P.A.S. reagent. The chorionic villi were shrunken in some areas and there were varying degrees of cytoplasmic vacuolar degeneration of the trophoblast cells. In most instances there was some degree of vacuolar degeneration of the chorionic epithelium. In general, the degree of vacuolization of both ordinary trophoblast and giant cells was increased with the age of the placenta; whereas at term most giant cells stained intensely with the P.A.S. negative, and especially so in the villi in which the ordinary trophoblast cells were undergoing vacuolar degeneration. Neutral lipid as revealed by oil red O was distributed in the maternal cryptal epithelium in all cases, and visual estimation of the amount in the epithelium indicated that there was a decrease in the crypts which exhibited denuded epithelium. In all the early postterm placentas alkaline phosphatase was demonstrated in the trophoblast giant cells, cryptal epithelium, walls of the maternal blood vessels, and intercotyledonary membrane. Except in the crypts where there was a demonstrable loss of maternal epithelium, there was no apparent increase or decrease in the amount or distribution of the enzyme in any postterm placenta. In one instance there was evidence of sclerosis of the endometrial arterioles with small foci of placental infarction. Among the postterm specimens examined, there was a diminution of the number of maternal blood vessels in the septa; although quantitative estimations could not be made with any degree of accuracy, the impression was gained that the older placentas possessed fewer maternal vessels than did those in the first postterm month. In general, the Guernsey placentas exhibited more retrogressive and widespread changes than did those of the Holstein-Friesians.

Estrogens in the peripheral plasma of cows during normal and prolonged gestations

Abstract Estimations were made of the concentrations of estrone and estradiol in the jugular vein plasma of Holstein cows during term and through postterm pregnancies. The analytical procedure consisted of hydrolysis, separation of estrogens from interfering chromogens and fluorescent materials in the extract by means of ascending paper chromatography, further partitioning by means of column chromatography, and estimation of estrone and estradiol in the eluted fractions by fluorimetry. In two of the cows destined to have prolonged pregnancies, the midpregnancy level of estrone plus estradiol was measurably greater than the levels during term pregnancy, and in two prolonged gestations peak plasma concentrations were measured at 25 to 40 days prior to calculated term, after which there was a steep decline. This contrasts with the general finding in term pregnancies of peak concentrations at term. These findings are considered in relation to the normal decline in progesterone at term and a sustained level of progesterone during prolonged gestation and are discussed in relation to the endocrine factors which may be operative at parturition.

Renal Hemodynamics, Electrolyte Excretion and Water Metabolism in Pregnant Sheep Before and After the Induction of Toxemia of Pregnancy

Renal hemodynamics, electrolyte excretion and plasma level of glucorticoids were studied in pregnant sheep before and after the experimental induction of toxemia. Marked renal ischemia occurred in the animals which developed toxemia. This abnormality occurred concomitantly with an increase in plasma corticoids. Despite the renal ischemia, arterial pressure remained the same. There are some similarities between the toxemia of the sheep and that of human pregnancy.

Preliminary observations on free amino acids in cow and calf plasma in prolonged gestation

Abstract Preliminary observations have been made on the free amino acids in maternal and fetal plasma in prolonged gestation in the Guernsey cow, with the following findings: (1) Jugular venous plasma amino acid levels were the same in normal cows-and those with postterm dysmature calves. (2) Amino acid levels in umbilical vein plasma were higher than maternal in both normal and postterm fetuses: these differences were most marked in the normal calf plasma. (3) The low levels of some of the amino acids in the postterm fetal plasma suggest a degree of placental insufficiency during prolonged gestation and support previous evidence of impaired placental function.