Copulatory behavior of golden hamsters: effects on pregnancy.

Two experiments were conducted to study the role of male copulatory behavior in initiating physiological responses necessary for pregnancy in female hamsters. In Experiment 1, it was found that copulation beyond the first ejaculatory series is critical to attainment of maximal probabilities of pregnancy. Whereas all females became pregnant when mated to a criterion of sexual satiety, only 20 percent were pregnant after one ejaculatory series. The relationship between increased copulatory stimulation and increased probability of pregnancy was further refined in Experiment 2. Females required more than 4 ejaculatory series to maximize the probability of pregnancy. Mounts without intromission had no effect. Neither parturition number of ova shed, nor little size appeared affected by amount of copulatory stimulation. A coadaptation between the copulatory pattern of the males and the response systems of the females of several rodent species appears to have evolved and to aid successful reproduction.     

Pseudopregnancy in female rats: Effects of hormonal manipulations of the male

The stimulus determinants of pseudopregnancy were examined by mating female rats to castrated males maintained on estradiol benzoate (EB) or testosterone propionate (TP), or to intact males. Females were mated for five intromissions (5I), one ejaculatory series (1E), or three ejaculatory series (3E). Copulatory behavior was quite similar for males of all groups. Overall, females that copulated with EB males became pseudopregnant significantly less often than those females mated to TP or intact males. The amount of copulation (5I vs. 1E vs. 3E) received by females from functionally intact males influenced their probability of becoming pseudopregnant or pregnant. EB males had significantly lower body, penile, and seminal vesicle weights in addition to a greatly reduced complement of penile spines than either TP or intact males; adrenal weights did not differ. TP and intact males did not differ on any weight measure. These results indicate that some factor influenced by male hormonal status, possibly penile morphology, plays a role in the initiation of the functional luteal phase in laboratory rats.     

Antibodies to Borrelia burgdorferi in rodents in the eastern and southern United States.

Serologic studies were conducted to determine whether white-footed mice (Peromyscus leucopus) and cotton mice (Peromyscus gossypinus) contained serum antibodies to Borrelia burgdorferi, the causative agent of Lyme borreliosis. Enzyme-linked immunosorbent assays detected antibodies to this spirochete in 35.7 and 27.3% of 56 P. leucopus and 535 P. gossypinus serum samples, respectively, collected in Connecticut, North Carolina, South Carolina, Georgia, Florida, Alabama, and Mississippi. Antibody titers ranged from 1:160 to greater than or equal to 1:40,960. On the basis of adsorption tests, the antibodies detected appeared to be specific to Borrelia spirochetes. Seropositive rodents in the eastern and southern United States, areas where human cases of Lyme borreliosis have been reported, indicate a widespread geographic distribution of B. burgdorferi or a closely related spirochete.     

Postpartum copulation and induction of pregnancy in roof rats (Rattus rattus)

Two groups of 10 female roof rats were mated either in cycling or postpartum estrus to provide a quantitative comparison of copulatory behavior and to compare the stimulus requirements for the initiation of pregnancy. Animals in both estrous conditions were mated to one ejaculation, three ejaculations and to sexual satiety in repeated tests. The results indicate there were no differences between estrous conditions in the qualitative patterns of copulation but that males achieved more intromissions in the first series of postpartum tests than in cycling estrous tests. The stimulus requirements for pregnancy initiation were not found to vary as a function of estrous condition, however it was found that postpartum matings resulted in more pups per litter than did cycling estrous matings. The results were discussed with regard to the functional significance of species differences in copulatory behavior and in stimulus requirements for pregnancy.     

Complete Freund adjuvant treatment of pregnant females influences resorption rates in CBA/J x DBA/2 matings via progesterone-mediated immunomodulation.

Treatment of pregnant CBA/J females with CFA at day 0.5 and 7.5 of pregnancy significantly reduced the fetal resorption rates from 45% to 29% (P less than 0.05). Supernatants of progesterone-treated spleen cells from CFA treated CBA/J females pregnant of DBA/2 males significantly reduced natural cytotoxicity, while those of untreated identically pregnant mice had no effect. Supernatants of CFA-treated virgin mice blocked natural cytotoxicity to the same extent as those of CFA-treated pregnant mice. These data suggest that nonspecific immunostimulation induces progesterone receptors in spleen cells of CBA mice and that these receptors allow a progesterone dependent suppressive pathway to exert an antiresorptive effect.     

Possible influence of strain differences on pregnancy initiation in laboratory rats

Recent research in this laboratory has failed to replicate previous findings that the first ejaculatory series of the male is sufficient to induce a high incidence of pregnancy in female laboratory rats (Rattus norvegicus). The incidence of pregnancy and pseudopregnancy in albino and hooded females were compared in a standard experimental paradigm. Eight percent of Sprague-Dawley albino females exhibited a progestational response, while 45% of the Long-Evans hooded females became progestational. On the basis of these findings, and a lack of previous formal comparison of genetic strains, it is suggested that genetic differences among strains may be at least partially responsible for differences observed in the ability of a single ejaculatory series to impregnate female laboratory rats.     

Cytotoxic cell populations in normal and alloimmunized pregnant mice

Cytotoxic cell activity directed against paternal alloantigens was investigated in primiparous C57BL/10 and CBA/Ca mice using a microcytotoxicity assay. Most allogeneically or syngeneically mated females lacked effector cells in their spleens or paraaortic lymph nodes both during pregnancy and immediately postpartum. However, spleen, cells from 33% of C57BL/10 females mated to CBA/Ca males exhibited low levels of paternal target cell killing (P less than 0.05-0.01). Alloimmunization of virgin mice prior to mating resulted in only allogeneically mated females producing cytotoxic cells and alloantibody. These responses were not detectable during pregnancy but appeared immediately postpartum. The ability of pregnancy to induce memory cell formation was tested by allowing females one successful pregnancy before challenging them postpartum with allogeneic spleen cells. Kinetic studies of cytotoxic cell production showed that C57BL/10 females that had borne (C57BL/10 X CBA/Ca)F1 litters responded earlier than their syngeneically mated sisters giving a peak response at 4 days compared to 7 days after immunization. This indicates that a single allogeneic pregnancy can prime the mother against paternal alloantigens suggesting that the conceptus is weakly immunogenic.     

The effect of gestation and fetal mismatching on the development of autoimmune diabetes in non-obese diabetic mice

The impact of gestation and fetal-maternal interactions on pre-existent autoimmune beta cell destruction is widely unknown. The aim of this study was to investigate the influence of gestation per se and fetal mismatching on the onset of autoimmune diabetes in female non-obese diabetic (NOD) mice. We examined cumulative diabetes frequencies of NOD dams mated to syngeneic NOD, haploidentical CByB6F1/J and fully mismatched C57BL/6J male mice. Pregnancy from NOD males neither increased nor accelerated the diabetes onset of NOD dams (71% by age 28 weeks) compared to unmated female NOD mice (81% by age 28 weeks; P = 0·38). In contrast, delayed diabetes onset was observed when NOD dams were mated at 10 weeks of age with major histocompatibility complex (MHC) haploidentical CByB6F1/J male mice (38% at age 28 weeks; P = 0·01). Mating with fully MHC mismatched C57BL/6J male mice (72% diabetes by age 28 weeks; P = 0·22) or mating with the haploidentical males at the later time-point of age 13 weeks (64% versus 91% in unmated litter-matched controls; P = 0·13) did not delay diabetes significantly in NOD females. Because infusion of haploidentical male mouse splenocytes was found previously to prevent diabetes in NOD mice we looked for, but found no evidence of, persistent chimeric lymphocytes from haploidentical paternal origin within the dams' splenocytes. Gestation per se appears to have no aggravating or ameliorating effects on pre-existent autoimmune beta cell destruction, but pregnancy from MHC partially mismatched males delays diabetes onset in female NOD mice.     

Reproductive capacity of sperm obtained after germ cell transplantation in a mouse model

BACKGROUND: The testicular stem cell transplantation technique has become an established research model in the mouse. This technique may also become useful for clinical applications. Therefore, it is necessary to investigate whether sperm obtained after testicular stem cell transplantation retain their full functional capacity and whether they are able to produce normally-developing embryos. This study aimed at evaluating the fertilizing and developmental abilities of sperm obtained after stem cell transplantation. METHODS: First, transplanted male mice were mated with females in order to evaluate in-vivo conception. Subsequently, functionality of sperm obtained after testicular germ cell transplantation was investigated by performing both IVF and ICSI. RESULTS: After in-vivo conception we found that in the control group 90% of the mice with a copulating plug became pregnant. In the experimental group only 35% of the mice with a copulating plug became pregnant (P = 0.006). After IVF, fertilization and blastocyst developmental rates were significantly lower in the transplanted group (P < 0.0001). Fertilization and blastocyst developmental rates after ICSI were comparable with control sperm. CONCLUSIONS: Our study showed that in the mouse, sperm obtained after stem cell transplantation are able to fertilize oocytes on the basis of assisted reproduction. It is recommended to further investigate this method in the human, as well as to investigate the post-implantation development of the embryo.     

Deficiency in p57Kip2 expression induces preeclampsia-like symptoms in mice

p57Kip2, a potent inhibitor of several cyclin/cyclin dependent kinase complexes (CDK ), is a paternally imprinted gene in both humans and mice, and here we show that pregnant mice which are heterozygous for p57Kip2 deficiency display symptoms similar to preeclampsia. p57-/+ (heterozygotes for p57Kip2 ) female mice that were mated with p57-/+ males showed hypertension, proteinuria, thrombocytopenia, decreased anti-thrombin III activity, and increased endothelin levels during late pregnancy. In their kidneys, endotheliosis of glomeruli were recognized along with fibrinoid or hyalinoid deposits. These characteristics were also observed in pregnant p57-/+ females that were mated with wild type males, but not in pregnant wild type females mated with p57-/+ males or wild type males. The pregnant p57-/+ mice had conceptuses both with and without p57Kip2 expression. The conceptuses without p57Kip2 expression showed trophoblastic hyperplasia, which mimics the hallmark proliferation of intermediate trophoblasts in clinical preeclampsia. It is suggested that the preeclampsia-like symptoms of the pregnant p57-/+ mice might have been induced by the conceptus(es) without p57Kip2 expression. In addition, pregnant p57-/+ mice might serve as a new animal model for preeclampsia characterized by trophoblastic hyperplasia.     

Disruption of ejaculates by male copulation in deer mice (Peromyscus maniculatus)

Six experiments were conducted to analyze possible disruption of sperm transport occurring when one male deer mouse copulates soon after another male ejaculates. When a second male mated soon after the first, females had significantly fewer uterine sperm 1 hr later than when a delay of 7 or 15 min was imposed between males. However, it was impossible to detect any effect of such disruption on pregnancy initiation. Similarly, artificial stimulation soon after an ejaculation was ineffective in disrupting pregnancy initiation. No effect of a rapid resumption of copulation could be detected on litter composition in a sperm competition situation. Although it is clear, from these and other data, that the phenomenon of ejaculate disruption occurs in deer mice, technical difficulties may interfere with experimental analysis.     

Hippocampal lesions are without effect on olfactory memory formation in the context of pregnancy block

Female mice which have mated and are subsequently exposed to male urine odours (pheromones), which differ from those of the male that mated (stud male), undergo hormonal changes resulting in a block to pregnancy. Since the stud male's odour blocks the pregnancy of females other than those he mated, this would suggest that a memory specific for this male's odour is established at the time of mating. Hippocampal lesions, when made prior to mating, did not disrupt memory formation to the odour of the stud male. This male's odour did not block pregnancy, while changing odour to that of the strange male did block pregnancy. In order to establish the functional effectiveness of these hippocampal lesions, olfactory discriminations were examined in a modified T-maze. The odour discrimination was urine-soiled bedding taken from a cage of different strain males versus same strain bedding. After 35 trials, neither control nor lesioned females were performing above chance level (50% correct responses), indicating the difficulty in cognitively learning this discrimination. These female mice were therefore trained to distinguish a novel odour (butyl acetate) from familiar strain urine-soiled bedding. Hippocampal-lesioned females were slower to acquire this discrimination and did not perform above chance level after 35 trials, in contrast to the 70% success of sham-lesioned females. Hence, hippocampal lesions, while producing a deficit in olfactory learning in the maze test, are without effect on the formation or retrieval of the specific olfactory memory formed for the stud male at mating, as revealed from pregnancy block tests.     

Nest building in nulligravid,primigravid and primiparous C57BL/6J and DBA/2J mice (Mus musculus)

C57BL/6J (B6) and DBA/2J (D2) mice differ in maternal behavior and nest building, but previous observations on nest building appear to be contradictory. Lactating B6 females spent more time nest building than lactating D2 females [Physiol. Behav. 67 (1999) 599.]; however, pregnant D2 females have been reported to build better nests than pregnant B6 females [Physiol. Behav. 29 (1982) 153.]. To resolve this apparent discrepancy, virgin B6 and D2 females were mated, and the nest quality of nulligravid, primigravid and lactating primiparous females was compared between groups and with that of virgin females. There were no strain differences in the nest ratings of virgin or mated nulligravid females, nor did these groups differ within strains. Pregnant and lactating females of both strains built better nests than nonpregnant females. There was an increase in nest ratings in both strains on the day of parturition. The nest ratings of pregnant and lactating females were higher in B6 than D2 females. The largest strain differences were observed between pregnant B6 and D2 females. One hypothesis to account for these results is that females of these two strains differ in their levels of or sensitivity to hormones during pregnancy and parturition.     

Experimental analysis of the placental barrier permeability in toxoplasmosis under conditions of normal and pathological pregnancy

Summary The work was an attempt to elucidate the problem of placental barrier permeability in toxoplasmosis. Five series of experiments were set up on pregnant rabbits. The chief conclusion drawn was that during latent toxoplasmosis created by infection of pregnant rabbits which have been immunized before being mated, the placental barrier is impermeable to toxoplasma under conditions of normal pregnancy. In those cases with latent toxoplasmosis where the normal course of pregnancy was disturbed by stress (experimental neurosis, hypoxia), the placental barrier became permeable to toxoplasma.(Presented by Active Member of the AMN SSSR V. V. Parin) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 56, No. 12, pp. 44–48, December, 1963     

Effect of stevioside on growth and reproduction

The effect on growth and reproduction in hamsters of stevioside, which is extracted from stevia leaves (Stevia rebaudiana Bertoni) and is currently used as a non-caloric sweetener, was investigated. Four groups of 20 one-month-old hamsters (10 males and 10 females) were daily force-fed with stevioside (0.0, 0.5, 1.0 and 2.5 g/kg body wt/day, respectively). No abnormalities were found in growth and fertility in both sexes. All males mated females efficiently and successfully. Females showed normal 4-day oestrus cycles and became pregnant after mating. Each female was mated and allowed to bear three litters during the period of experiment. The duration of pregnancy, number of fetuses, as well as number of young delivered each time from females in the experimental groups were not significantly different from those in the control group. The young F1 and F2 hamsters continuously receiving stevioside via drinking water until one month old and daily force-fed afterwards at the same doses as their parents showed normal growth and fertility. Histological examinations of reproductive tissues from all three generations revealed no evidence of abnormality which could be linked to the effects of consuming stevioside. We conclude that stevioside at a dose as high as 2.5 g/kg body wt/day affects neither growth nor reproduction in hamsters.     

Maternal regulator cells during murine pregnancy

Helper and suppressor cells have been identified in lymph nodes of multiparous pregnant mice using one-way mixed lymphocyte reactions. Primiparous C57Bl and C57Bl/10ScSn females during pregnancy and immediately post-partum gave unaltered MLR reactivity compared to virgin controls when stimulated with paternal or third-party alloantigens. In contrast, multiparity produced strain-dependent alterations in responsiveness: C57Bl females being hyporesponsive while C57Bl/10ScSn mice were hyper-responsive to these antigens. To evaluate regulator activity, the cells were treated with mitomycin C and mixed with normal syngeneic MLR responder populations. Results showed that mixtures of para-aortic and inguinal lymph node cells from pregnant C57Bl females suppressed while those from pregnant C57Bl/10ScSn increased normal virgin MLR responses. Treatment of the regulator cells with anti-Thy-1.2 plus complement showed that suppressor activity was predominantly non-T cell in nature while C57Bl/10ScSn helper activity was wholly T cell-dependent. The regulator cells appeared to be non-specific since they were found in syngeneically as well as allogeneically mated females but covert specificity could not be totally excluded. Embryo resorption in the C57Bl strain was associated with helper rather than suppressor activity. These results suggest that suppressor cells are not essential for the maintenance of pregnancy and that the presence of regulator cells probably reflects the normal homeostatic mechanisms controlling the maternal immune response to the conceptus.     

Stress-Triggered Abortion: Inhibition of Protective Suppression and Promotion of Tumor Necrosis Factor-α (TNF-α) Release as a Mechanism Triggering Resorptions in Mice

PROBLEM: Stress adversely affects pregnancy outcome and has been implicated as an abortogen in both animals and humans. However, the mechanisms whereby stress aborts are largely unknown. Alloimmunization can prevent stress-triggered abortion, and immunization is known to increase transforming growth factor-β2 (TGF-(32)-related suppressive activity. METHOD: To investigate these mechanisms, DBA/2J males were mated to CBA/J or C3H/ HeJ females, and the pregnant females were exposed to ultrasonic sound stress for a period of 24 h between day 4.5 to 8.5 of pregnancy. RESULTS: Ultrasonic stress significantly elevated the resorption rate with a peak effect on day 5.5 in the CBA/J females and on day 4.5 in the LPS-resistant C3H/HeJ females. The tumor necrosis factor-α (TNF-α) release from the decidua was also elevated and the TGF-β2-mediated suppressive activity was significantly decreased. The resorption rate only increased when the TNF-α/TGF-β2 ratio was increased compared to the control. CONCLUSION: These data suggest that stress may inhibit protective suppressor mechanisms and promote secretion of abortogenic cytokines such as TNF-α. Possible mechanisms are discussed.     

Mice: progesterone and the regulation of strain differences in pregnancy-induced nest building

Pregnant DBA/2J females built significantly larger and more completely enclosed nests than did pregnant C57BL/6J mice. This strain difference was restricted to the last half of gestation and was not observed during either the virgin state or lactation. Genotype-based differences in pregnancy-induced nest building were not related to circulating levels of progesterone (P), core temperature, or body weight. Exposure to supplemented P during pregnancy elevated nest building exhibited by pregnant C57BL females but did not induce DBA-like levels of the behavior. Also, virgin DBA females built larger nests in response to P than did C57BL females. These findings suggest that differences in the sensitivity of central neural tissue to steroid hormones may account for genotypically determined variation in patterns of pregnancy-induced nest building.     

Impaired reproduction of histamine deficient (histidine-decarboxylase knockout) mice is caused predominantly by a decreased male mating behavior

PROBLEM: Histamine induces a Th2 shift. As successful allopregnancy is characterized by a peripheral Th2 dominance, we investigated the role of histamine in reproduction. METHOD OF STUDY: HDC knockout (HDC-/-) or wild-type (HDC+/+) mice kept on histamine-deficient or normal diet were mated. Appearance of vaginal plugs indicated day 0.5 of pregnancy. On day 10.5 uteri were inspected. Splenic IFN-gamma production and cytotoxic activity were determined. RESULTS: In HDC+/+ or HDC-/- females on normal diet, plugs appeared between 3 and 6 days. In 80% of the (HDC-/-)/(HDC-/-) matings on histamine-deficient diet, no vaginal plugs were observed for more than 1 month. After replacing males with the wild type, plugs appeared within 3 days. In HDC-/- mice, litter size was lower than in HDC+/+ animals. Cytotoxicity and IFN-gamma production were significantly increased in non-pregnant histamine-deficient mice, but not in pregnant mice. CONCLUSION: Histamine affects male mating behavior, but is not indispensable for successful pregnancy.     

Abnormal T-cell reactivity against paternal antigens in spontaneous abortion: adoptive transfer of pregnancy-induced CD4+CD25+ T regulatory cells prevents fetal rejection in a murine abortion model

Mammalian pregnancy is thought to be a state of immunological tolerance. The mechanisms underlying this phenomenon are still poorly understood. Here, we determined whether an inappropriate function of T regulatory (Treg) cells is involved in the pathogenesis of spontaneous abortion. We evaluated spleen and decidual lymphocytes from CBA/J mice undergoing immunological abortion (DBA/2J-mated) or having normal pregnancy (BALB/c-mated) on day 14 of gestation for ex vivo cytokine production after PMA or paternal antigen (alloantigen) stimulation. Treg activity was characterized by quantifying CD4(+)CD25(+) cells, foxp3 expression, and interleukin-10 secretion. Decidual lymphocytes from abortion CBA/J mice contained a significantly higher frequency of interferon-gamma-producing T cells specific for paternal antigens compared to those from normal pregnancy (7.8% versus 2.7%, P < 0.05). Compared to virgin CBA/J females, normal pregnant mice showed strongly elevated numbers of CD4(+)CD25(+) and interleukin-10(+) Treg cells in the thymus whereas significantly lower frequencies of Treg cells were observed in abortion mice. Very interestingly, CD4(+)CD25(+) Treg cells from normal pregnant and nonpregnant CBA/J mice could inhibit both proliferation and interferon-gamma secretion of lymphocytes from abortion mice in vitro whereas in vivo prevention of fetal rejection could only be achieved after adoptive transfer of Treg cells from normal pregnant mice. Our data suggest that pregnancy-induced Treg cells play a vital role in maternal tolerance to the allogeneic fetus.