The accessory olfactory system and its role in the pheromonally mediated suppression of oestrus in grouped mice

Mice were grouped to induce suppression of oestrus and subjected to removal of the vomeronasal organs or treatment with CB 154 which lowers prolactin levels. Both treatments overcame the suppression of oestrus after 72 h. Oestrus suppression was induced in lesioned mice by haloperidol treatment which raises plasma prolactin, and oestrus returned some 72 h after withdrawal of haloperidol treatment.     

Effects of prostaglandin and prolactin on luteolysis and parturient behaviour in the non-pregnant tammar, Macropus eugenii

In Exp. 1 non-pregnant female tammars were injected, on Day 26 (the day parturition would normally occur) after removal of pouch young, with saline, 200 micrograms ovine prolactin or 5 mg PG and changes in plasma concentrations of progesterone, prolactin, PGF-2 alpha metabolite (PGFM), oestradiol-17 beta and LH were determined. Luteolysis occurred in females treated with prolactin alone, while treatment with PG first induced a rapid rise in prolactin and subsequently a significant decrease in plasma progesterone. After prolactin treatment the oestradiol peak, oestrus and the LH surge were advanced significantly compared to the saline-treated females. In Exp. 2 the effects of the same treatments as used in Exp. 1 were determined on Day 23 and again on Day 26 after removal of pouch young in non-pregnant females. On Day 23 both prolactin and PG induced significant elevations in plasma progesterone, but luteolysis did not occur. On Day 26 the treatments initially induced significant elevations in plasma progesterone but these were followed by luteolysis within 8-12 h after treatment. PG treatment induced parturient behaviour in the non-pregnant females within 3-21 min and this persisted during the period that plasma concentrations of PGFM were elevated. The results show that PG induces birth behaviour and the release of prolactin, while prolactin first induces an elevation of plasma progesterone concentrations and, in the mature CL on Day 26, subsequently induces luteolysis.     

Fetal role in the control of parturition in the tammar, Macropus eugenii

When female tammars carrying dormant blastocysts were injected with progesterone at the time of removal of their pouch young the development of the fetus was advanced and parturition occurred 5 days earlier than in the control tammars. In these tammars the prolactin pulse was also advanced by 5 days but the usually concomitant fall in progesterone was not. In non-pregnant tammars similar injections of progesterone did not advance the subsequent fall in progesterone, oestrus, or the LH pulse. In non-pregnant tammars injected with ovine prolactin on Day 26, to mimic the prolactin pulse, plasma progesterone was reduced to basal levels within 12 h, significantly earlier than in controls. Conversely, in 5 pregnant and 1 non-pregnant tammar injected with ovine prolactin on Day 23, to mimic the condition induced by advancing the time of parturition with progesterone, the decline in plasma progesterone was not advanced and the endogenous prolactin pulse, parturition, post-partum ovulation and the LH pulse all occurred after intervals similar to those of controls. The results support the view that the fetus is associated with the pre-partum prolactin pulse in maternal plasma and that a prolactin pulse at this stage is luteolytic in non-pregnant tammars.     

Intermittent stimulation and delay of puberty by urinary chemosignals and social contact in wild stock female house mice (Mus Domesticus)

A sequence of six experiments using wild stock house mouse (Mus domesticus) tested the effects of intermittent stimulation with either the urinary chemosignal released by grouped female mice or social contact from grouped females on the age of first vaginal oestrus in young females. Weanling female mice were exposed to bedding soiled by grouped females or cages containing grouped females for 15 min periods, then removed for a prescribed period, and placed again in a cage with soiled bedding or grouped females. The nature of the exposure to the puberty delaying effect, the number of total exposures each day, the total length of exposure to the stimulus, and the total time period over which the exposures occurred were varied. None of the treatment regimes employed here with soiled bedding from grouped females resulted in delays in the onset of first oestrus in test females. Young females exposed to grouped females for 6 or 8 exposures in a 4 h period, 6 or 8 exposures in an 8 h period, or 8 exposures in a 12 h period were significantly delayed in attaining puberty relative to control females that were exposed to cages containing clean bedding. These results are in contrast to earlier findings involving chemosignals that accelerate first oestrus wherein young females exhibited the capacity to accumulate the exposures to the urinary chemosignals from males, females in oestrus and pregnant or lactating females. Direct exposure to the grouped females on an intermittent basis can provide stimulation that is cummulative and results in delays in the onset of first oestrus.     

Serum prolactin concentrations and the initiation of maternal behavior in the rat

Maternal behavior and serum prolactin were measured in pregnant and virgin female rats. Pregnant rats were either ovariectomized or shamovariectomized on Day 17 of pregnancy, while virgin females were ovariectomized at the same age. Two days after surgery nests were rated and the three treatment groups were tested for responsiveness to rat pups. Both pregnant treatment groups built superior nests compared to the virgin group and also responded more frequently to rat pups within a 1 hr test period than the virgin controls. In addition, significantly more ovariectomized pregnant subjects responded to pups than did intact pregnant females. Serum prolactin levels did not differ among the three treatments nor did exposure to pups affect serum prolactin levels. In each treatment group serum prolactin was less than 15 ng/ml, well below the 139.7 ng/ml mean found on Day 23 of pregnancy. These data suggest that high levels of serum prolactin during late pregnancy are not essential for the initiation of maternal behavior in the rat.     

Effects of ovariectomy on clock-timed daily gonadotropin rhythms in prepubertal golden hamsters

Daily rhythms of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) are measurable in the serum of prepubertal female golden hamsters by 17 days after birth. These rhythms, which are characterized by peak levels at 1700 h, persist until they are replaced by a 4-day rhythm as ovulatory cycles begin, approximately 3 wk later. We have tested the proposition that the ovaries are required for the onset and maintenance of clock-timed gonadotropin release by removing the ovaries and measuring the levels of LH and FSH in prepubertal hamsters. Ovariectomy was performed both before and after the onset of the rhythm and the effect of removal was determined by subsequent collection of blood samples during the mid- to late-prepubertal period. Ovariectomy on 7, 10 or 13 days after birth results in tonic levels of LH and FSH in blood samples collected at 1400, 1700 and 2000 h on Days 17 through 29. Sham-operated or intact controls had significantly elevated levels of these hormones at 1700 h. Ovariectomy on Day 21 and killing on Day 25 at the same times of day abolished the rhythm of serum LH measured in sham-ovariectomized controls. Ovariectomy on Day 21 and killing on Days 26, 28 or 30 at hourly intervals resulted in variable but nonrhythmic patterns of circulating LH. Thus, ovariectomy before the initiation of clock-timed gonadotropin release prevented its initiation; ovariectomy after its initiation abolished the rhythm. These results show that the ovary provides an essential "message" to the brain-pituitary axis for the initiation and maintenance of clock-timed gonadotropin release in prepubertal females.     

Role of photoperiod and temperature in production of the oestrus-inducing pheromone in male wild mice

Ninety adult males divided in six equal groups were exposed to different photoperiods for 21 days. Exposures included natural light (ca 11 hr), long photoperiod (16L:8D) and short photoperiod (8L:16D). The first three groups received these exposures at room temperature (13-20 degrees C) while the remaining three at raised temperature (36-38 degrees C). Soiled bedding of the above males was introduced in the cages of unisexually housed noncyclic females and their potentiality to induce oestrus was assessed. It was noticed that the bedding of all the males proved to be a stimulus inducing oestrus in the majority of the females during the 7 day exposure. There was no significant difference in the number of females returning to oestrus following exposure to soiled bedding of different males. These results elucidate that environmental factors, especially light and temperature do not influence the production/release of the oestrus-inducing pheromone in wild mice.     

Infertility in a line of mice with the high growth mutation is due to luteal insufficiency resulting from disruption at the hypothalamic-pituitary axis.

Animals with extreme body growth frequently experience poor reproductive performance, but the cause for this association has not been clearly established. A line of mice homozygous for the high growth (hg) mutation, a mutation that has a major effect on post-weaning growth, exhibits several reproductive deficits including an abnormally high incidence of luteal failure. The objective of the present study was to investigate luteal failure in high-growth (HG) mice during pregnancy and to determine whether the cause of the apparent luteal failure resides in the ovary or the hypothalamic-pituitary unit. In HG females with a demonstrated history of infertility, progesterone injections (1 mg s.c. daily) beginning on Day 1 postcoitum (p.c.) increased the proportion of animals pregnant at Day 17 of gestation. Twice-daily injections of 100 microgram of ovine prolactin (PRL) in alkaline saline given to another group of females beginning on Day 1 p.c. increased the proportion of HG females that were pregnant on Day 6 of gestation compared with saline-injected HG females, although PRL did not increase the pregnancy rate in HG females when compared with a group of noninjected control females. When ovaries from HG females were transplanted into ovariectomized congenic C57 hosts, the C57 graft hosts displayed normal estrous cycles, and upon mating the majority of graft hosts became pregnant. In contrast, when ovaries from C57 females were transplanted into ovariectomized HG hosts, the HG graft hosts displayed normal estrous cycles, but upon mating most were unable to maintain pregnancy. These results suggest that the hypothalamic-pituitary unit of the HG female provides an inadequate signal to the ovaries to maintain pregnancy. Luteal failure in HG females may be due to insufficient PRL as required for establishment and early maintenance of the CL during pregnancy in mice.     

Ovulation rate in induced oestrous cycles of anoestrous ewes given bromocriptine

The suppression of prolactin in anoestrous ewes by daily injections of bromocriptine reduced the average number of corpora lutea on Day 8 after induced oestrus from 2.8 to 1.6 (P less than 0.02). There was a significant correlation (r = 0.87, P less than 0.05) between the preovulatory peak values for prolactin and ovulation rate in treated but not in control ewes. Bromocriptine failed to prevent the ewes from returning to anoestrus after the induced oestrus.     

Reproductive inhibition and serum prolactin concentrations in laboratory populations of the prairie deermouse

Radioimmunoassay (RIA) of prolactin in the prairie deermouse was established and validated. Serum samples were taken from reproductively inhibited animals grown in experimental populations and compared with reproductively capable control animals of both sexes. At the time of assay, serum prolactin concentrations was unaffected by the length of time a control female was exposed to the olfactory stimulation of bedding soiled by her mate or the stage of the estrous cycle as indicated by vaginal cytology. The reproductively inhibited males and females had significantly reduced reproductive organ weights, body weights, and serum prolactin concentrations compared with their respective controls. Also, the relative mean adenohypophysial weight was greater in the inhibited males. Several significant correlations between prolactin and various gravimetric measures are reported for both males and females. Possible relationships between prolactin and other endocrine systems are discussed.     

Multiple causes of pregnancy failure in hamsters precociously ovulated by human chorionic gonadotropin

Cycling adult female hamsters can be induced to mate and ovulate 24 h early by the injection of 20 IU human chorionic gonadotropin (hCG) at 1500 h on Day 3 (day before proestrus), but pregnancy is not established. Although there is evidence of decreased sperm transport in precociously ovulated females, this does not appear to be the primary cause of infertility. Reduced size and vascularity of corpora lutea (CL) in treated females suggests incomplete or failed CL activation. Control and hCG-treated females were killed by exsanguination under ether anesthesia at intervals for the first 5 days after mating. Serum luteinizing hormone (LH), follicle-stimulating hormone (FSH), prolactin, estradiol, and progesterone were measured by radioimmunoassay. Luteinizing hormone in treated animals was very high at 2200 h on Day 1 after mating (31 h after the hCG injection), due to endogenous release, and dropped below control levels thereafter. Follicle-stimulating hormone, by contrast, was significantly lower than controls at 2200 h on Day 1 and remained low until 2200 h on Day 3 after mating. Prolactin in treated animals was not different from that in controls, except for 1000 h on Day 4, when it showed a significant dip. Estradiol in treated animals was significantly higher than in controls at 2200 h on Day 1 (when LH was also high and FSH was low), and remained high at 1000 h and 2200 h on Day 2, dropping thereafter to control levels. Progesterone was initially at control levels but had dropped significantly by 1000 h on Day 2 and remained low for the next 24 h. These results suggest that pregnancy failure is due to inadequate activation of corpora lutea. This may be due to: 1) immaturity of follicles at the time of ovulation; 2) inappropriate timing of preovulatory events; 3) the luteolytic effects of high levels of LH or estradiol or both; 4) the low level of FSH in the early stages of corpus luteum development; or 5) a combination of the above. Abnormalities of prolactin secretion were not investigated in detail but cannot be ruled out at this time.     

Pheromones from males of different familiarity exert divergent effects on adult neurogenesis in the female accessory olfactory bulb

Pheromones from urine of unfamiliar conspecific male animals can reinitiate a female's estrus cycle to cause pregnancy block through the vomeronasal organ (VNO)‐accessory olfactory bulb (AOB)‐hypothalamic pathway. This phenomenon is called the Bruce effect. Pheromones from the mate of the female, however, do not trigger re‐entrance of the estrus cycle because an olfactory memory toward its mate is formed. The activity of the VNO‐AOB‐hypothalamic pathway is negatively modulated by GABAergic granule cells in the AOB. Since these cells are constantly replenished by neural stem cells in the subventricular zone (SVZ) of the lateral ventricle throughout adulthood and adult neurogenesis is required for mate recognition and fertility, we tested the hypothesis that pheromones from familiar and unfamiliar males may have different effects on adult AOB neurogenesis in female mice. When female mice were exposed to bedding used by a male or lived with one, cell proliferation and neuroblast production in the SVZ were increased. Furthermore, survival of newly generated cells in the AOB was enhanced. This survival effect was transient and mediated by norepinephrine. Interestingly, male bedding‐induced newborn cell survival in the AOB but not cell proliferation in the SVZ was attenuated when females were subjected to bedding from an unfamiliar male. Our results indicate that male pheromones from familiar and unfamiliar males exert different effects on neurogenesis in the adult female AOB. Given that adult neurogenesis is required for reproductive behaviors, these divergent pheromonal effects may provide a mechanism for the Bruce effect. © 2013 Wiley Periodicals, Inc. Develop Neurobiol 73: 632–645, 2013     

Proliferative response of seminal vesicle cells to androgen and estrogen in neonatally castrated mice

Proliferation and death of androgen- and estrogen-responsive cells in seminal vesicles were compared between neonatally and adult (on Day 60 after birth) castrated mice. Daily injections of either testosterone propionate (TP) or estradiol-17 beta (E2) were started on Day 90 after birth; the incorporation of 5-[125I]iodo-2'-deoxyuridine ([125I]IdUrd) into the whole seminal vesicles was used as an index for proliferation. Although the peak of [125I]IdUrd uptake was observed 3 days after starting TP injections in both neonatally and adult castrated mice, the peak was lower and the period of proliferation was much longer in the former than in the latter. When TP injections were stopped, the fraction of surviving cells that synthesized DNA on Day 3 of TP injections was much larger in neonatally than adult castrated mice. The difference was attributed to the presence of TP-induced proliferation of fibromuscular cells in the neonatally castrated mice but not in the adult castrated mice; only the fibromuscular cells but not epithelial cells survived after stopping TP injections. Although injections of E2 increased the proliferation of epithelial cells but did not the weight of seminal vesicles in adult castrated mice, the same procedure increased the proliferation of both epithelial and fibromuscular cells and the weight in neonatally castrated mice. The E2-induced fibromuscular cells seemed to survive in the presence or absence of E2. The present results seem to indicate that androgen- and estrogen-induced proliferation of fibromuscular cells is irreversible in seminal vesicles of neonatally castrated mice and that the depletion of androgen in the seminal vesicle during neonatal and prepubertal periods is at least in part compensated by the administration of androgen, even after 90 days of age.     

Serum concentrations of prolactin, oestrogen and LH during the perioestrous period in prepubertal gilts induced to ovulate and mature gilts

The temporal relationships of serum prolactin, oestrogen and LH concentrations during the perioestrous period were compared in prepubertal gilts induced to ovulate by PMSG and hCG and in mature gilts. In Exp. 1, 2 sustained prolactin surges, beginning 4 days and 1 day before the preovulatory LH surge, occurred in all mature gilts. A single preovulatory prolactin surge occurred in 3 prepubertal gilts, starting just before the preovulatory LH surge, but 4 prepubertal gilts had neither a prolactin nor an LH surge. A status (prepubertal or mature) versus time interaction (P less than 0.01) was detected for serum prolactin concentrations. A preovulatory oestrogen surge occurred in all gilts but was of lesser magnitude (P less than 0.01) and duration (P less than 0.05) in the prepubertal gilts without prolactin and LH surges compared to mature gilts and of lesser magnitude (P less than 0.01) compared to prepubertal gilts with prolactin and LH surges. The relative timing of the oestrogen surge in prepubertal gilts corresponded with that of mature gilts when adjusted to the LH surge (if present) but was delayed (P less than 0.01) in all prepubertal gilts if standardized to the hCG injection. In Exp. 2, mature gilts were examined to determine whether 2 perioestrous prolactin surges were characteristic of all cycling gilts. Of 9 gilts, 8 exhibited an initial prolactin surge 4-5 days before oestrus and 5/9 gilts exhibited a periovulatory prolactin surge. The presence of 2 perioestrous serum prolactin surges was not a requirement for subsequent pregnancy maintenance.(ABSTRACT TRUNCATED AT 250 WORDS)     

Synchronization of oestus and timed insemination of mares.

Oestrus was synchronized in 116 mares by means of an i.m. injection of prostaglandin F-2 alpha (Day 0) and of fluprostenol (a PG analogue) on Day 16. Mares were then randomly divided into three groups. Group A mares (N = 30) were given 2500 i.u. hCG I.M. ON Day 20 and artificially inseminated on Day 21 without detection of oestrus. Group B mares (N = 32) were given 2500 i.u. hCG i.m. on Day 20 and inseminated on Days 21 and 23, also without oestrus detection. Group C mares (N = 54) were teased on Days 18, 19, 21, 23 and 25 and inseminated on Days 19, 21, 23 and 25 while they were in oestrus. Semen was collected by artificial vagina from 3 stallions. One-third of the mares in each group were assigned to each stallion at random. The gel-free fraction was divided equally among the mares, and used within 1 h of collection. Pregnancy rates at about 60 days of gestation were not significantly different. A high rate of synchronization of oestrus (80%) was attained within 48 h of treatment with fluprostenol.     

Appearance of a nocturnal peak of leptin secretion in the pubertal rat

Whether leptin is involved in the timing of puberty remains highly controversial in the rat. Daytime leptin secretion shows little change during the transition into adulthood. Because leptin exhibits a diurnal variation in the adult, it is possible that the ontogeny of such a rhythm provides important information for the timing of puberty. To begin to evaluate this hypothesis, we determined the development of the diurnal leptin secretion in the rat. The young females were raised in a light-controlled environment (12L, 0700 h light on). A cannula was placed in the right atrium on the previous day, and blood samples were collected every 4 h on Days 21, 24, 28, 32, 36 (1 day after vaginal opening), and 48 (adult, diestrus of estrous cycle). In addition to vaginal opening, plasma prolactin levels were determined as an endocrine index of puberty. Changes in food intake were monitored because nocturnal food intake has been considered to be a synchronizer for the leptin rhythm. This pattern of food intake was clearly evident throughout the ages studied. By contrast, there was no leptin rhythm at 21 and 24 days of age. Beginning at 28 days, leptin secretion exhibited a significant nocturnal peak (2300 h); this nocturnal peak increased in amplitude at 32 and 36 days and was still apparent in the cycling adult at Day 48. Plasma prolactin did not exhibit a diurnal rhythm but it increased from Days 32 to 48. The present findings indicate that in the rat, both the appearance of the nocturnal leptin rhythm and the nocturnal increase in circulating leptin levels during development carry information for timing the onset of puberty.     

Olfactory contribution to Fos expression during mating in inexperienced male hamsters

Male hamsters are very dependent on chemosensory cues for normal mating behavior. We have previously reported that central, vomeronasal pathways are intensely and selectively activated during mating or pheromonal stimulation. The contribution of main olfactory sensory input to the patterns of c-fos activation was investigated in this study. Sexually inexperienced male hamsters were either made anosmic by intranasal infusion of zinc sulfate or remained intact. Fos protein immunoreactivity was analyzed in main olfactory and vomeronasal pathways of the zinc sulfate-treated, anosmic animals after mating with receptive females for 45 min, and compared with Fos patterns seen in intact mating animals, some of which have been described in a previous publication. The zinc sulfate-treated anosmic males described here all mated when given access to receptive females. Whether mated or unstimulated, anosmic males had little or no Fos expression in main olfactory pathways; significantly less even than in unstimulated intact animals. Mating did not increase Fos expression in main olfactory pathways of intact animals over that of unstimulated intact controls. However, Fos expression in central vomeronasal pathways was significantly higher in mating anosmic males, as in intact males, compared with appropriate non-mating controls. Fos expression was significantly different between intact and zinc sulfate-treated anosmic mating males in only one area studied. The rostral anterior medial amygdala, known to receive a small olfactory terminal field, had significantly lower Fos expression in zinc sulfate-treated anosmic males that mated when compared with intact-mating animals. Thus, functional main olfactory input to the rostral vomeronasal amygdala can be demonstrated but does not appear to be critical for mating behavior in previously inexperienced male hamsters with intact vomeronasal organs. Other main olfactory input appears to have a negligible contribution to Fos-patterns in such animals.      

Intraspecific communication through chemical signals in female mice: reinforcing properties of involatile male sexual pheromones

In rodents, social and reproductive behaviors critically depend on chemical signals, including sexual pheromones that have been suggested (but not demonstrated) to be rewarding. In this work, we analyze this issue by studying the chemoinvestigatory behavior of adult female mice (without experience with male-derived chemicals) toward 1) the synthetic odorant citralva, 2) bedding soiled by different conspecifics (females, males, and castrated males), and 3) volatiles derived from bedding soiled by males and castrated males (confronted in 2-choice tests). We also study whether these chemical signals are able to induce conditioned place preference, a reliable test for rewarding properties of stimuli. The results show that involatile, male-derived chemicals elicit an intense and sustained chemoinvestigation and, more importantly, are the only tested chemical signals that induce conditioned place preference. In contrast, volatile, male-derived chemicals are not significantly chemoinvestigated. Bedding soiled by castrated males induces a transient chemoinvestigation, likely directed to steroid-independent, biologically relevant chemical signals, whereas the intense chemoinvestigation of female-soiled bedding shows a slow habituation. Finally, females did not explore significantly citralva-odorized bedding. The present work constitutes the first demonstration of the unconditioned reinforcing properties of involatile (likely detected by the vomeronasal organ) steroid-dependent chemical signals in mammals.     

Changes in serum immunoreactive inhibin and follicle-stimulating hormone during gonadal development in male and female rats.

We have measured serum and ovarian immunoreactive inhibin alpha (irI alpha) and serum FSH in fetal and neonatal rats from 20 days of gestation until 40 days of age. For animals aged 10 days or older, serum measurements were made on intact and gonadectomized animals. Serum irI alpha was detectable in intact male and female rats at all ages studied. In females, irI alpha levels were low until Day 5 and then increased steadily to peak at Day 25. Thereafter they declined until Day 35 to reach levels typical of adult females. There was a significant decrease in irI alpha levels 24 h after ovariectomy at all ages. Serum FSH levels in females were low until Day 7, then increased rapidly to plateau from Days 10-15. The levels then declined until Day 25 and were generally unchanged after that time. There was a significant increase in FSH 24 h after ovariectomy in rats aged 20 days and older, and in younger rats by 48 h after ovariectomy. In male rats, serum irI alpha levels were significantly higher than females until Day 7. The levels increased at Day 7 and then remained relatively constant until Day 20, after which they declined to reach typical adult male levels. Serum irI alpha levels were significantly lower in males than females from Days 25-40. There was a significant decrease in serum irI alpha 24 h after castration at all ages studied. Serum FSH levels in males were low until Day 20, increased at Day 25, and thereafter remained relatively unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)     

Influence of SLA haplotype on preimplantation embryonic cell number in miniature pigs

Embryonic cell number in miniature pigs inbred for specific SLA haplotypes (a, c, and d) was determined on Day 6 by nuclear staining and, on Days 9 and 11, by DNA analyses (first day of oestrus = Day 0). Pigs exhibiting first behavioural oestrus at 08:00 h were hand-mated to an SLA homozygous boar 12 and 24 h later. Numbers of embryos flushed from uteri at 08:00-10:00 h on Days 6, 9 and 11 were greater (P less than 0.05) for SLAd females than for SLAa or SLAc females, which did not differ (8.2 vs 6.8 and 6.2, respectively). Recovery rates (embryos recovered/CL number) were similar, averaging 75.8% for all three SLA haplotypes. Embryos from SLAd dams contained fewer blastomeres (23 cells) on Day 6 than did embryos from SLAa (89 cells) or SLAc (79 cells) females. The reduced cell numbers of SLAd vs SLAa or SLAc embryos continued to Day 9 (28 vs 107 and 67 ng DNA/embryo) and Day 11 (167 vs 674 and 586 ng DNA/embryo). These results suggest an effect of the SLA complex on preimplantation embryonic development.