Effects of chorionic gonadotropin on the hematopoietic stem cells

It was shown on the exogenic colony-forming unit (CFU) assay that the chorionic gonadotropin (CG) administration to female mice CBA in doses correlating with its concentration in different stages of woman pregnancy stimulated (depending upon the doses) the CFU formation of bone marrow, but not spleen origin. Injections of CG to the ovariectomized mice has the opposite (inhibited) effect on the CFU contents in bone marrow and spleen. CG-administration in the dose of 40 U1 to the ovariectomized and non-castrated irradiated recipients bone marrow cells stimulates (statistically significant) colonies formation. As for 200 U1 dose hormone has the similar effect only on the non-castrated animals.     

Modulation of the neutrophil functional activity by chorionic gonadotropin]

The functions of nonpregnant woman neutrophils in the presence of chorionic gonadotropin (CG) have been studied, as well as possible mechanisms of intracellular hormone signaling. Expression of adhesion molecule CD18 and phagocyte activity of the cells are shown to be inhibited by a high dose of CG (100 IU/ml). Oxygen metabolite production by activated neutrophils decreases almost in a half in the presence of hormone, irrespective of the dose. Synthesis of nitric oxide, an oxidant and effective regulator molecule, is also suppressed by CG. Neutrophil incubation with hormone induces a dose-dependent modulation of intracellular cAMP level. The effect of CG is most strongly expressed for a low hormone dose (10 IU/ml), implying the presence of high affinity hormone-binding structures on the cell membrane. Judging from the correlation of data obtained, the functional effects of CG cannot be attributed to the regulation of adenylatcyclase activity and suggests that this is not the major mechanism of hormone signal transduction. Neutrophil sensitivity to suppressive CG effects is one of the ways of regulating nonspecific defence reactions in different physiological and/or pathological states connected with the presence of this hormone in the organism.     

The significance of chorionic gonadotropin in regulating the antigen-independent differentiation of immunocompetent splenic cells]

The functional activity of fractionated splenocytes were investigated in the syngeneic transfer system. Chorionic gonadotrophin (CG) was injected to ovariectomized and noncastrated lymphocyte donors, the T or B lymphocytes being isolated on a column with a nylon fiber and by means of anti-BaO-serum accordingly. In some series CG was introduced only into recipients before their being irradiated and before syngeneic cells transferring. CG has been stated to be capable of influencing either independently or by means of ovarian hormones splenic B lymphocytes without exhibiting a significant effect on T helper precursors as well as radioresistant cells of the splenic stroma. The character of immunoregulating effect was completely dependent on the presence of ovaries in mice and on the hormone dose.     

Role of cAMP and Neutrophil Cyclooxygenase in Gonadotropin-Dependent Regulation of T Lymphocyte Proliferation

The effect of the main pregnancy hormone, chorionic gonadotropin (CG), on proliferation of peripheral blood mononuclear cells (PBMC) was studied in the presence of autologous neutrophils; also, hormone-dependent regulation of the cAMP levels in T lymphocytes and neutrophils was evaluated. PBMC proliferation in response to a mitogen is suppressed by physiological doses of CG (10, 50, and 100 IU/ml). Autologous neutrophils enhance the suppression induced by the low dose of CG (10 IU/ml), but when cyclooxygenase was inhibited this effect was not observed; this suggests that the anti-proliferative effects of the low dose of CG can be mediated by the products generated by neutrophil cyclooxygenase. The effect of CG was associated with increased cAMP levels in T lymphocytes and neutrophils. Comparison of functional and cAMP-related effects of CG in both cell populations indicates that cAMP is involved in the anti-proliferative effects of CG.     

Effects of thyroid hormones on the receptor level in estrogen target organs

The influence of thyroid hormones on the turnover of cytoplasmic estrogen receptors in the liver, kidney and uterus of intact and ovariectomized female rats was studied under in vivo conditions. Thyroidectomy had no significant effect on the receptor level in the uterus but caused a substantial reduction of the receptor content in the liver and kidney. In livers of intact and ovariectomized animals receptor values were reduced with 70 and 80%, respectively, 30 days after thyroidectomy. Substitution with triiodothyronine (T3) restored the hepatic estrogen receptor concentration in thyroidectomized rats to the preoperative level. If rats that had been both ovariectomized and thyroidectomized were substituted with thyroid hormone for the same time period, the receptor level was increased but did not reach the level seen in animals that had been ovariectomized only. The effects of thyroid hormone substitution was found to be dose dependent and paradoxical. Thus, a high dose of 50 micrograms/day of triiodothyronine given to intact animals for nine days caused a 30% reduction in the hepatic receptor content. The same level of reduction was seen in the ovariectomized rat given a hormone dose of only 1 micrograms/day. When this type of rats was treated with the higher dose of triiodothyronine the reduction in hepatic estrogen receptors was 50%. These results are discussed in relation to existing information concerning the multihormonal regulation of estrogen receptor concentration in the rat liver.     

Assessment of luteal rescue and desensitization of macaque corpus luteum brought about by human chorionic gonadotrophin and deglycosylated human chorionic gonadotrophin treatment

The objective of the current study was to investigate the mechanism by which the corpus luteum (CL) of the monkey undergoes desensitization to luteinizing hormone following exposure to increasing concentration of human chorionic gonadotrophin (hCG) as it occurs in pregnancy. Female bonnet monkeys were injected (im) increasing doses of hCG or dghCG beginning from day 6 or 12 of the luteal phase for either 10 or 4 or 2 days. The day of oestrogen surge was considered as day ‘0’ of luteal phase. Luteal cells obtained from CL of these animals were incubated with hCG (2 and 200 pg/ml) or dbcAMP (2.5,25 and 100 M) for 3h at 37°C and progesterone secreted was estimated. Corpora lutea of normal cycling monkeys on day 10/16/22 of the luteal phase were used as controls. In addition thein vivo response to CG and deglycosylated hCG (dghCG) was assessed by determining serum steroid profiles following their administration. hCG (from 15–90 IU) but not dghCG (15-90 IU) treatment in vivo significantly (P < 0.05) elevated serum progesterone and oestradiol levels. Serum progesterone, however, could not be maintained at a elevated level by continuous treatment with hCG (from day 6–15), the progesterone level declining beyond day 13 of luteal phase. Administering low doses of hCG (15-90 IU/day) from day 6–9 or high doses (600 IU/day) on days 8 and 9 of the luteal phase resulted in significant increase (about 10-fold over corresponding control P < 0.005) in the ability of luteal cells to synthesize progesterone (incubated controls) in vitro. The luteal cells of the treated animals responded to dbcAMP (P < 0.05) but not to hCC added in vitro. The in vitro response of luteal cells to added hCG was inhibited by 0,50 and 100% if the animals were injected with low (15-90 IU) or medium (100 IU) between day 6–9 of luteal phase and high (600 IU on day 8 and 9 of luteal phase) doses of dghCG respectively; such treatment had no effect on responsivity of the cells to dbcAMP. The luteal cell responsiveness to dbcAMP in vitro was also blocked if hCG was administered for 10 days beginning day 6 of the luteal phase. Though short term hCG treatment during late luteal phase (from days 12—15) had no effect on luteal function, 10 day treatment beginning day 12 of luteal phase resulted in regain ofin vitro responsiveness to both hCG (P < 0.05) and dbcAMP (P < 0.05) suggesting that luteal rescue can occur even at this late stage. In conclusion, desensitization of the CL to hCG appears to be governed by the dose/period for which it is exposed to hCG/dghCG. That desensitization is due to receptor occupancy is brought out by the fact that (i) this can be achieved by giving a larger dose of hCG over a 2 day period instead of a lower dose of the hormone for a longer (4 to 10 days) period and (ii) the effect can largely be reproduced by using dghCG instead of hCG to block the receptor sites. It appears that to achieve desensitization to dbcAMP also it is necessary to expose the luteal cell to relatively high dose of hCG for more than 4 days     

Cellular requirements for the expression of IgM. Immunological memory in vitro

In vitro culture techniques have been used to compare the direct (IgM) plaqueforming cell (PFC) response to heterologous erythrocytes (RBC) by normal mouse spleen cells and spleen cells from mice injected intravenously with 5 × 10⁴ RBC ten days previously [low dose primed (LDP)]. Although LDP mice fail to undergo a significant primary PFC response, their spleen cells are capable of a secondary or enhanced PFC response in vitro. The secondary PFC response is shown to be a function of: (A) an increase in the frequency of immunocompetent cells or units (IU) due to in vivo priming, and (B) an increased number of PFC generated per IU subsequent to in vitro stimulation. The latter increase is shown to be mediated through a shorter PFC doubling-time during logarithmic expansion of the PFC population. Analysis of nonadherent spleen cell dose response experiments indicate that two nonadherent cell types interact in the secondary response. Subsequent cocultivation experiments suggested that both of these cell types must be “primed” to allow induction of a secondary response. Although adherent cells are required for the secondary response, normal splenic adherent cells serve as equivalent substitutes for LDP adherent cells.     

Selective effect of irradiation on responses to thymus-independent antigen

Low doses of ionizing radiation have a selective immunosuppressive effect on in vivo B cell responses to thymus-independent (TI) antigens. The B cell response, assayed as direct anti-trinitrophenyl (TNP)-specific plaque-forming cells (PFC), induced by type 2, TI antigens (TNP-Ficoll or TNP-Dextran), was reduced, on the average, by 10-fold in animals exposed to 200 rad of ionizing radiation 24 hr before antigen challenge. In contrast, PFC responses to type 1, TI antigens (TNP-lipopolysaccharide or TNP-Brucella abortus) are unaffected in mice exposed to the same dose of radiation. Adoptive transfers showed that this selective immunosuppression is a result of the specific inactivation of the B cell subpopulation responding to type 2, TI antigens. These experiments suggest that physiologic differences exist in the B cell subpopulations of normal mice which respond to type 1, or type 2, TI antigens.     

Effect of chorionic gonadotropin on the cooperative interrelations of splenocytes involved in the primary immune response

The influence of chorionic gonadotropin (CG) on the interaction of spleen T- and B-cells has been studied in adoptive transfer system. It has been established that CG increases the primary immune response in non-ovariectomized mice. This effect reversely depended on the hormone concentration and was independent of prostaglandins (PG). In the experiments on ovariectomized mice the influence of CG was opposite and the immune response was decreased. This action was completely abolished by Voltren-induced blockade of UG-synthetase. In spleen cell culture of female mice CG suppresses the synthesis of interleukin-2 (IL-2). It is suggested that CG may have an independent immunosuppressive action, the mechanism of which consists of disturbed cell-to-cell communications on the level of short-acting mediators of the immunity--PG and IL-2.     

Studies on the control of antibody synthesis. XIV. Role of T cells in regulating antibody affinity.

The effect of limiting the number of helper T cells on the affinity of the primary antibody response to a T-dependent antigen (DNP-BGG) was evaluated in a cell transfer system. Lethally irradiated, thymectomized mice were reconstituted with either bone marrow or anti-brain θ antiserum plus complement-treated spleen as the source of B cells. In addition, they received various numbers of thymus cells as a source of helper T cells. The animals were immunized with DNP-BGG 1 day after cell transfer and their splenic anti-DNP PFC response was assayed for magnitude and affinity 3 weeks later. A marked restriction in helper T-cell activity resulted in a primary response which was of low magnitude, which lacked indirect PFC, and which had a very low affinity and restricted heterogeneity. When sufficient thymus cells were given to permit a switch to indirect plaque formation, a highly heterogeneous, high-affinity primary response was elicited. Further increase in the number of thymic cells resulted in a progressive increase in the magnitude of the primary response but had no effect on affinity. Thus, a reduction of 50% in the magnitude of the response as a consequence of limiting the number of T-helper cells had no effect on the affinity of the PFC. The results are consistent with the interpretation that the effect of restriction in T-cell help on antibody affinity is not due to a direct effect on precursors of high-affinity PFC but is secondary to inefficient selection for high-affinity cells when the degree of cell proliferation is markedly reduced.     

Human chorionic gonadotropin and luteinizing hormone-releasing hormone reverse the blockade of ovulation in pregnant mare's serum gonadotropin-primed immature rats by the anti-androgenic drug, hydroxyflutamide

The present study was designed to examine mechanism(s) of the anti-ovulatory action of the anti-androgen, hydroxyflutamide (OH-F). Prepubertal rats were treated with 4 IU pregnant mare's serum gonadotropin (PMSG) (day -2) to induce first estrus and ovulation. They received OH-F in sesame oil or oil alone at 08:00 and 20:00 h on day 0 (the day of proestrus) and ovulations were assessed on the morning of day 1. Eighty-three percent of control animals ovulated with a mean of 7.7 +/- 1.1 corpora lutea per rat. Hydroxyflutamide blocked ovulation in all but 2 of the 12 rats receiving this drug alone. All of OH-F treated rats that received 5 and 25 IU human chorionic gonadotropin (hCG) ovulated with means +/- SEM of 9.1 +/- 0.1 and 7.3 +/- 1.4 corpora lutea per rat, respectively. The dose of 0.2 IU hCG was essentially ineffective, while the effect of 1.0 IU hCG was intermediate. At the dose of 20 ng and above (100 and 500 ng) luteining hormone-releasing hormone (LHRH) completely overcame the ovulation blockade in the OH-F treated animals, while a 4-ng dose was ineffective. At 18:00 h on the day of proestrus, serum LH levels in control animals were 17.56 +/- 2.60 ng/mL, which were 920% above basal levels (1.90 +/- 0.13) indicating a spontaneous LH surge. This surge was suppressed in OH-F treated rats. Injection of LHRH, at the dose of 20 ng and above, reinstated the LH release in OH-F treated animals. Thus, the anti-androgen, OH-F, inhibits ovulation in PMSG-treated immature rats through its interference with the preovulatory LH surge; the inhibition can be reversed by hCG or LHRH. Hydroxyflutamide does not appear to interfere at the level of the pituitary, but may have direct action at the hypothalamic and (or) extrahypothalamic sites involved in the generation of positive feedback signals that control LH release.     

Relationship between luteinizing hormone and decidual luteotropin in the maintenance of luteal steroidogenesis

Between Days 6-11 of pregnancy or pseudopregnancy, the decidual tissue of the rat produces a prolactin-like hormone, decidual luteotropin, which can sustain luteal progesterone production when prolactin is suppressed. However, this effect is dependent upon the presence of the pituitary. The present investigation was undertaken to determine whether decidual luteotropin and luteinizing hormone (LH) act together to sustain luteal steroidogenesis and if so, to find out whether the need for LH is due to the inability of the decidual tissue to produce LH-like material and/or whether LH affects decidual luteotropin production. Pseudopregnant rats with or without decidual tissue were hypophysectomized on Day 8 and treated with either 1.5 IU human chorionic gonadotropin (hCG)/day or with vehicle. Within 24 h, serum progesterone dropped in both vehicle-treated groups and decidual luteotropin levels declined by 80% in the decidual tissue. Human CG administration had no effect on progesterone production in the control group. Yet in rats with decidual tissue, hCG stimulated progesterone production for at least 48 h and maintained the decidual tissue content of decidual luteotropin. Progesterone, but not hCG treatment, maintained decidual luteotropin concentrations in ovariectomized rats. To compare the luteotropic activity of the decidual tissue with that of the placenta, pregnant or pseudopregnant rats with decidual tissue were hypophysectomized on Day 8 and treated with 1.5 IU hCG. Control groups had decidual tissue or placentas removed and were similarly treated. Human CG stimulated progesterone production only in rats with placental or decidual tissue.(ABSTRACT TRUNCATED AT 250 WORDS)     

Bimodal effects of luteinizing hormone and role of androgens in modifying superovulatory responses of rats to infusion with purified porcine follicle-stimulating hormone

Prepubertal (28-30 days old) female rats were infused s.c. over a 60-h period with a purified porcine pituitary follicle-stimulating hormone (FSH) preparation having FSH specific activity 8.4 times that of NIH-FSH-S1 and luteinizing hormone (LH) specific activity less than 0.005 times that of NIH-LH-S1, based on radioreceptor assays. When the FSH infusion rate of this preparation was increased over the range of 0.5-2 units/day (mg NIH-FSH-S1 equivalent), an all-or-none response was observed, with the threshold dose for superovulation being between 1 and 2 units/day. Eleven of twelve rats receiving the 2 units/day dose ovulated a mean +/- SEM of 67 +/- 8 oocytes on the morning of the third day after the beginning of FSH infusion. Addition of human chorionic gonadotrophin (hCG), as a source of LH activity, to a subthreshold (1 U/day) FSH infusion rate resulted in 20% of rats ovulating at an hCG dosage of 50 mIU/day; increasing the hCG infusion to 200 mIU/day concomitant with the subthreshold FSH infusion rate increased ovulation rate to a mean of 69 +/- 8/rat, with 100% of rats ovulating. To determine the effect of varying both FSH infusion rates and LH:FSH ratios, FSH was infused at several rates, with hCG added to give varying hCG:FSH ratios for each FSH infusion rate. Administration of hCG alone was ineffective in causing ovulation except at the highest infusion rates. Adding hCG to FSH to reach a ratio of 0.2 IU hCG/U FSH significantly increased the superovulatory response to an intermediate, 1 U/day FSH dose, but not to the low, 0.5 U/day dose.(ABSTRACT TRUNCATED AT 250 WORDS)     

Comparative characteristics of the antitumor and immunodepressive activity of carminomycin on the L-1210 experimental model]

The antitumor activity of carminomycin was estimated by the number of lymphoma colonies formed in the spleen of DBA/2 mice on their inoculation with the bone marrow cells from mice with transplantable leukemia L-1210. The immunodepressive properties of carminomycin were determined by the number of the antibody forming cells in the spleen of CBA and DBA/2 mice with leukemia L-1210 after immunization with sheep red blood cells. It was found that in a single dose of 1.5 mg/kg carminomycin inhibited the lymphoma colonies by 50 per cent. The maximum immunodepressive effect was observed when carminomycin was used in a single dose of 1.5 mg/kg 48 hours after the antigen stimulation. In this case the number of the antibody forming cells in DBA/2 mice with leukemia L-1210 was lower than that in CBA mice without leukemia.     

The differential effect of atrazine on luteinizing hormone release in adrenalectomized adult female Wistar rats

High doses of atrazine (ATR), administered for 4 days, suppress luteinizing hormone (LH) release and increase adrenal hormones levels. Considering the known inhibitory effects of adrenal hormones on the hypothalamo-pituitary-gonadal axis, we investigated the possible role the adrenal gland has in mediating ATR inhibition of LH release. To determine the extant and duration of adrenal activation, ovariectomized Wistar rats were given a single dose of ATR (0, 50, or 200 mg/kg), and corticosterone (CORT) levels were assayed at multiple time points posttreatment. CORT levels were increased within 20 min and remained elevated over 12 h postgavage in 200-mg/kg animals. To determine the effects of adrenalectomy on ATR inhibition of the LH surge and pulsatile LH release, adrenalectomized (ADX) or sham-operated ovariectomized rats were treated for 4 days with ATR (0, 10, 100, or 200 mg/kg), and an LH surge was induced with hormone priming. In the afternoon following the last dose of ATR, blood was sampled hourly for 9 h. Another cohort of ovariectomized rats was examined for pulsatile patterns of LH secretion after ATR (0, 50, or 200 mg/kg) and sampled every 5 min for 3 h. ADX had no effect on ATR inhibition of the LH surge but prevented the ATR disruption of pulsatile LH release. These data indicate that ATR selectively affects the LH pulse generator through alterations in adrenal hormone secretion. Adrenal activation does not play a role in ATR's suppression of the LH surge, and therefore ATR may work centrally to alter the preovulatory LH surge in female rats.     

Validation of the mechanisms proposed for the stimulatory and inhibitory effects of progesterone on gonadotropin secretion in the estrogen-primed rat: a possible role for adrenal steroids.

The stimulatory and inhibitory effects of progesterone on luteinizing hormone (LH) and follicle-stimulating hormone (FSH) secretion were found to be dependent on the length of estrogen exposure in ovariectomized estrogen-primed rats. Progesterone suppressed LH and FSH secretion when administered 16 hours after a single injection of estradiol to ovariectomized rats. If the estradiol treatment was extended over 40 hours by two injections of estradiol 24 hours apart, progesterone administration led to a highly significant elevation of both serum LH and FSH levels 6 hours later. In addition to the direct stimulatory effect on LH and FSH release, progesterone, when injected 1 hour before, was able to antagonize the suppressive effect of a third injection of estradiol on LH and FSH release. In the immature ovariectomized estrogen-primed rat, 10 IU of ACTH brought about a release of progesterone and corticosterone 15 minutes later and LH and FSH 6 hours later. Progesterone, but not corticosterone, appeared to be responsible for the effect of ACTH on gonadotropin release. The synthetic corticosteroid triamcinolone acetonide brought about LH and FSH release in the afternoon, while cortisol, similar to corticosterone, was unable to do so. Nevertheless, triamcinolone acetonide and cortisol brought about increased secretion of FSH the following morning.     

Influence of arginine vasotocin on the estrogen-induced surge of LH and FSH in adult ovariectomized rats

The effects of arginine vasotocin (AVT) on the estrogen-induced surge of LH and FSH were examined in ovariectomized adult rats. Two and one-half weeks after ovariectomy, animals that were treated with a single subcutaneous (s.c.) dose of 5 μg of estradiol benzoate (EB) exhibited a surge of LH and FSH at 1700 and 1900 hours, respectively, two days after the administration of the EB. AVT, antidiuretic hormone (ADH) and oxytocin (OT) were administered s.c. in 1 μg dose every 4 hours beginning at 1500 hours on day 1 after EB treatment and then every 2 hours beginning at 1200 hours on day 2 after EB treatment. AVT completely prevented the LH surge at 1700 hours but was without effect on the FSH surge at 1900 hours on the day 2 after steroid treatment. Neither ADH nor OT had any significant effect on the afternoon surge of these hormones. It is postulated that AVT may interfere with the mechanisms mediating the estrogen-induced afternoon surge of LH in ovariectomized rats.     

Comparative study of blocking effects of various retinoids on the occurrence of permanent proliferation of vaginal epithelium in mice treated neonatally with estrogen

Neonatal injections of 20 micrograms 17 beta-estradiol (E2) induced persistent proliferation and cornification of the vaginal epithelium in adult ovariectomized C57 Black/Tw mice. However, permanent vaginal changes were prevented by various retinoids when, simultaneously with E2 treatment, the animals were given injections of 100 micrograms daily dose of retinol, retinol acetate, retinal or of 200 micrograms daily dose of retinol palmitate (RoP). Neonatal injections of a 100 micrograms daily dose of RoP had no preventive effect on the occurrence of E2-induced permanent vaginal changes. This finding suggests that the preventive effect of RoP is weaker than that of other retinoids showing approximately the same degree of prevention. Combined treatment with E2 plus retinoic acid (even a small dose of 20 micrograms) had such a toxic effect on newborn mice that they died within 7 days after birth, while the animals given neonatal injections of 20 micrograms retinoic acid alone survived until the termination of the experiment.     

Preimplantation embryo development and serum steroid levels in immature rats induced to ovulate or superovulate with pregnant mares' serum gonadotropin injection or follicle-stimulating hormone infusions

Follicular stimulation protocols using pregnant mares' serum gonadotropin (PMSG) or a follicle-stimulating hormone (FSH) preparation were compared to evaluate the yield and quality of embryos obtained from immature rats. Rats received a superovulatory dose of PMSG (401U), a nonsuperovulatory dose of the same gonadotrophin (4 IU), or a continu ous s.c. infusion over a 72-h period with a purified FSH preparation containing an opti mum ratio of luteinizing hormone (LH): FSH (FSH-hCG). The females were caged with fertile males on the evening of the 3rd day of gonadotropin treatment and scored for the occurrence of mating on the next morning; subgroups were killed on days 1–4 of preg-nancy. High fertilization rates were observed in rats treated with 4 IU PMSG (84.1%) and in rats infused with FSH-hCG (91.0%); however, a much lower fertilization rate was observed following treatment with 40 IU PMSG (41.5%). From median ovulation rates of 9 and 79 in rats treated with 4 IU PMSG and in rats infused with FSH-hCG, medians of 8 and 69 embryos, respectively, were recovered from reproductive tracts flushed on day 4 of pregnancy, from which 75% were morulae or blastocysts; in contrast, from a median ovu lation rate of 42.5, a median of only 12 embryos was recovered on day 3 of pregnancy following superovulation with 40 IU PMSG of which 80% were degenerate ova. Serum steroid profiles during the first 4 days of pregnancy differed significantly among treatment groups, the major differences being in substantially elevated levels of estradiol and andro-gens on days 1–3 in rats receiving the high (40 IU) dose of PMSG. Levels of these steroids in rats superovulated with the FSH-hCG infusion regimen were only marginally elevated above levels observed in rats treated with the low (4 IU) nonsuperovulatory dose of PMSG. Consistent with high ovulation rates, serum progesterone levels rose to considera bly higher levels during the period in both superovulated groups than in animals receiving the low, nonsuperovulatory dose of PMSG. This work describes a novel method to superovulate rate (FSH-hCG) leading to high yields of normally developing embryos at all preimplantation stages and illustrates the close association between high yield of emyryos and low levels of circulating andorgens and estradiol-17β during the preimplantation period.     

Modulation of mouse anti-SRBC antibody response by placental extracts

Mouse placental extracts (PE) and corresponding Sephadex G-200 fractions were administered to isogeneic CBA mice along with an optimal immunizing dose of SRBC. Spleen cells were harvested 8 days later and transferred to CBA recipients, subsequently immunized with SRBC. The immunoregulatory activity of spleen cells from PE-treated donors was compared to cells from liver extract (LE)-treated controls or from mice immunized with SRBC only, using Cunningham's PFC direct and indirect tests. Within the dose range used, selective modulatory activities were obtained with cells from PE, but not from LE, treated mice, the latter being comparable to cell transfer effects from donors immunized with SRBC only. Spleen cells from animals injected with low doses of PE (0.25 to 4 mg per mouse) added to immunizing SRBC had a suppressive effect on the primary IgM response of recipients immunized against SRBC. In contrast, when SRBC were given to donor animals with higher doses of PE (8 to 13 mg), transferred spleen cells potentiated the IgM response of the recipients. These opposite suppressive and potentiating activities were found in distinct Sephadex G-200 fractions of 40 and 60 kDa, respectively. When the effect of PE treatment was tested within the same animal, the indirect secondary PFC response following a challenge with SRBC was significantly modified. We observed an overall suppression of the different isotypes after treatment with lower doses of PE or with its 40-kDa fraction. PE doses of 0.5 to 2 mg resulted in a stronger inhibition of IgM than IgG₁ production. This phenomenon was also obtained with the 40 KDa fraction. IgG₂ responses were significantly reduced by all doses of this fraction. In contrast, all doses of the 60-kDa fraction gave a strong stimulation of IgG₂ and IgM responses and a constant suppression of the IgG₁ response. This shows a clear dissociation between IgG₁ and C'-fixing (IgM, IgG₂) antibody classes as far as the influence of placental substances is concerned in their regulation. These data emphasize the relevance of isogeneic placental products as a useful physiological material capable of modulating xenogeneic immune responses (as well as allogeneic systems).