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J T Lanman

Publications and source records attributed to J T Lanman.

At least 37 records · Page 2Linked to original sources
PubMed1975

Ovarian and placental origins of plasma progesterone following fetectomy in monkeys (Macaca mulatta).

Fetectomy, either alone or combined with ovariectomy, was performed in 17 monkeys. Following fetectomy alone in 8 animals, progesterone values were maintained at normal pregnancy levels (1.0 ng/cc plasma or more), until expulsion of the placenta, which frequently occurred at a time well past normal term. Values declining toward but not reaching the nonpregnancy range were observed in some animals in the 2 to 6 weeks preceding expulsion; no similar decline occurs preceding normal labor. In all cases, after the placenta was expelled, progesterone values fell below 1 ng/cc plasma within 2 days. When ovariectomy was superimposed on 3 animals previously fetectomized, plasma progesterone values fell abruptly to nonpregnancy levels, and the placenta was expelled in an average of 6.3 days. The source of the progesterone in these fetectomized animals was, therefore, the ovaries, not the placenta damaged by a preceding fetectomy. However, the ovarian progesterone production after fetectomy was dependent on the continued presence of the placenta. In 6 animals following ovariectomy, and with an intact fetus and placenta, plasma progesterone levels were usually maintained at normal pregnancy levels. When fetectomy was superimposed in these animals with a preceding ovariectomy, plasma progesterone levels fell into the nonpregnancy range in an average of 4.8 days, and placental expulsion occurred after an average of 30.8 days. We believe this reflected a deteriorating ability of the fetectomized placenta to produce progesterone, which was capable only transiently of maintaining plasma values, but later of exerting sufficient local effect to maintain uterine quiescence for a longer time.

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PubMed1975

Metabolic clearance rates (MCR) and production rates (PR) plasma progesterone in pregnant and pseudopregnant rabbits.

Our studies were designed to determine whether changing peripheral progesterone levels in rabbits reflected changing metabolic clearance rates (MCR) or changing production rates (PR), or both. Plasma progesterone concentrations rise from nonpregnancy levels to peak values at the end of the first third of gestation and at midpseudopregnancy. In the pregnant rabbit, these decline slowly during the second third of gestation and then more rapidly until near nonpregnancy values are reached at term. Progesterone levels decline sharply during the second half of pseudopregnancy. During pregnancy and pseudopregnancy, we found only small variations in MCRs which cannot account for the approximately 10-fold increase in plasma progesterone concentrations. The increases can, however, be accounted for by changes in PRs which rose sharply after conception of hCG injection to 14-fold the nonpregnancy level on day 16 of gestation and 11-fold on day 7 of pseudopregnancy. These results indicate that changes in ovarian PRs are the major factor for the variations in peripheral progesterone levels during pregnancy and pseudopregnancy. The rabbit differs in this respect from the guinea pig, in which changing progesterone concentrations during pregnancy were shown to reflect sharply reduced MCRs. After a single injection of progesterone in 20-day pregnant rabbits, the disappearance of the steroid from the circulation consisted of two components; an initial phase during which progesterone disappeared rapidly (t1/2 = 2.4 +/- 0.2 min) followed by a slower rate of disappearance (t1/2 = 21.5 +/- 2.2 min).

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PubMed1965

Homograft immunity in pregnancy. The placental transfer of cytotoxic antibody in rabbits.

The mammalian fetus affixed to the uterine wall in some ways resembles a homograft, but maternal homograft immunity even when specifically directed against her fetuses fails to destroy them. The placental barrier appears to be critical in protecting the fetus against maternal immunologic attack. In order to evaluate the means by which it affords protection, we have measured in rabbits the transfer of cytotoxic antibody from mother to fetus. When the offspring were not the specific targets for maternal antibody, we found titers of cytotoxic antibody in the newborn animals at or near maternal levels in 16 of 18 cases (89 per cent), demonstrating the ability of this antibody to cross the rabbit placenta. When the offspring were appropriate targets for antibody, however, 11 of 18 newborn animals (61 per cent) had no demonstrable titer. We believe that in these latter cases, antibody had become fixed to antigenic sites and thereby had been removed from the fetal circulation. There was, however, no evidence of harm to any of the fetuses, either in survival (as demonstrated in a previous study) or in spleen or thymus weights or peripheral leukocyte and mononuclear cell counts. Cytotoxic antibody appears to reach the embryo early in gestation, since we found antibody in 8-day-old blastocyst fluid in each of 2 trials. We conclude that the fetus neither receives nor requires protection against cytotoxic antibody, and believe that fetal protection against maternal homograft immunity is afforded by a placental barrier to maternal mononuclear leukocytes.

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