Chronic maternal dietary iodine deficiency but not thiocyanate feeding affects maternal reproduction and postnatal performance of the rat

Iodine deficiency disorders affect reproductive performance in the afflicted populations. Environmental iodine deficiency (ID) and goitrogens are important in their aetiology. We observed earlier that chronic maternal dietary ID but not goitrogen feeding altered the blood-brain barrier nutrient transport in adult rats. Whether similar differences exist in their effects on reproduction of dams and postnatal performance of the offspring has been assessed. Inbred, female, weaning WNIN rats were rendered hypothyroid by feeding for 8-12 weeks, a low iodine test diet or a control diet with added potassium thiocyanate (KSCN) (@ 25 mg/rat/day). Following mating with control males, they continued on their respective diets till their pups were weaned. Indices of reproductive performance such as percentage of conception, mortality of dams during pregnancy and parturition, litter size, and survival of pups till weaning were affected markedly by ID but not thiocyanate feeding. Neither ID nor thiocyanate feeding from conception or parturition affected their reproductive performance. Nevertheless, postnatal weight gain of pups was less in all the three ID groups but not thiocyanate fed dams. Rehabilitation of chronically ID pregnant dams from conception or parturition did not improve their pregnancy weight gain, litter size or birth weight of pups but decreased abortion and mortality of mothers during pregnancy and parturition. Rehabilitation improved the pups' postnatal weight gain but the effect was only moderate. Based on the results of the present study it may be suggested that maternal ID but not thiocyanate feeding affects reproductive performance and postnatal performance of their offspring.     

Body weight deficit in the absence of reduction in cerebrum weight and nucleic acid content in progeny of swine restricted in protein intake during pregnancy

Fifty-six castrated male progeny of crossbred (Chester White x Landrace x Large White x Yorkshire) dams fed an adequate diet (control, C), a control diet fed at one-third of C (restricted, R), or diets severely deficient in protein (PF) or restricted in nonprotein calories (RCal) were killed at age 25 weeks. Dams were fed their respective diets in the following regimens: C, 1.8 kg (6000 kcal daily) throughout pregnancy; R, 0.6 kg of C diet daily for 70 days, then 1.8 kg of C daily to parturition at about 114 days; PF, 1.8 kg of a "protein-free" diet (less than 0.2% protein) throughout pregnancy; RCal, 0.6 kg daily (2000 kcal) of a diet containing three times the concentration of protein, minerals, and vitamins provided by the C diet for 70 days, then 1.8 kg of C daily to parturition. All dams were fed an adequate diet ad libitum through a 28-day lactation. Castrated male progeny were assigned to one of two replicates based on birth date and fed a corn-soybean meal diet ad libitum from weaning to age 25 weeks, supplemented from age 10 to 12 weeks with 0, 110, or 220 mg/kg of thyroprotein (iodinated casein). Cerebrum weight was unaffected by maternal diet, despite a significant (P less than 0.001) reduction in body weight of progeny of PF dams compared with other groups, resulting in a higher relative cerebrum weight in progeny of PF dams than in progeny of C, R, and RCal dams. Absolute and relative weights of RNA, DNA, and total protein in cerebrum were unaffected by maternal diet. Thyroprotein supplementation to the diet of the progeny had no effect on cerebrum weight or its protein or nucleic acid content. It is concluded that maternal protein deprivation but not restriction of feed or nonprotein calorie intake to one-third of recommended allowance during gestation results in stunting of body weight in young adult progeny but does not affect cerebrum weight, cerebrum cell number (DNA), or protein synthetic activity (RNA), or RNA-to-protein ratio.     

Onset of puberty in CD-1 mouse pups exposed prenatally through weaning to endophyte-infected tall fescue seed

This study was undertaken to investigate the effects of feeding endophyte - infected (Acremonium coenophialum ) tall fescue seed to CD-1 mouse dams (P(1)) during gestation and lactation, and on the subsequent growth and sexual maturity (onset of puberty) of their male and female offspring (F(1)). Forty-eight 21 d old pups (24 male and 24 female F(1) mice) were weaned from dams fed one of two diets containing 50% rodent chow (w/w) and 50% KY-31 tall fescue (Festuca arundinacea ) seed. The seed in Diet 1 was noninfected, while the seed in Diet 2 was 80% endophyte-infected. At weaning (21 d), the F(1) pups were fed rodent chow, ad libitum throughout the remaining experimental period. At 24 d, they were paired with sexually mature non-treated virgin CD-1 mice (fed 100% rodent chow) for one parturition cycle. Male F(1) mice were sacrificed at 84 d to determine testicular development. The age at the birth of the first litter for Diet 2 F(1) male (76.8 +/- 2.2 d) and female (58.4 +/- 2.1 d) was significantly greater (P<0.05) than the age at parturition for Diet 1 male and female F(1) test mice (64.1 +/- 1.8 and 51.9 +/- 1.2 d, respectively). At parturition, the female F(1) mice showed no significant differences (P>0.05) in either mean parturition weight or number of F(2) pups born per litter. However, total F(2) litter wight (11.38 +/- 1.14 g) and mean weight per F(2) pup (1.40 +/- 0.04 g) for Diet 2 female F(1) mice litters were lower (P<0.05) when compared with Diet 1 females (14.53 +/- 0.57 g and 1.66 +/- 0.02 g, respectively). No significant differences were observed between the two male F(1) treatment groups, for total F(2) litter weight or the number of pups born per F(2) litter. Although Diet 2 F(1) males weighed significantly less (P<0.05) at weaning and at pairing, final body weights at sacrifice (84 d) were not different (P>0.05) from the Diet 1 males.     

Relationships of maternal nesting to thermoregulatory nesting in house mice (Mus musculus) at warm and cold temperatures

Thermoregulatory and maternal nesting in Mus musculus (indexed as weight of cotton pulled into the cage) was measured at 5 C and 22 C on mice representing lines from a bidirectional selection experiment for nest size at room temperature. The effects of both selection and temperature were significant across the entire experiment. Nesting on the day of parturition correlated highly with thermoregulatory nesting, and with the number of offspring that survived to weaning, indicating a common genetic basis for maternal and thermoregulatory nesting and a direct correlation of these traits with Darwinian fitness. Amount of cotton used increased soon after mating and remained high with a large amount of variability until about 10 days after parturition, and then decreased sharply. The pattern of changes in nest size during pregnancy resembled changes in progesterone levels reported previously in the literature for mice, and contrasted with models of a smooth symmetric curve peaking at parturition.     

A reproductive study of Weiser-Maples guinea pigs]

The Weiser-Maples (WE) guinea pig strain was introduced by Backshire Co., Ltd. (USA) in 1977. We have been breeding WE strain guinea pigs for skin melanization research. The WE guinea pig colony produced 1271 pups in 417 litters from May 1978 through December 1983. Breeding date are shown below. The mean litter size was 3.05, the stillborn rate was 15.2%, the weaning rate for live-born pups was 93.5% and the sex ratio was 1.01. The average age at first vaginal membrane rupture was 31.4 days at which time body weight was 290.5g. The mean length of the first 7 estrous cycles was about 17 days, with no cyclical variation in length. The mean duration of gestation was 67.9 days. Duration of pregnancy varied with litter size. There was an inverse relationship between litter size and duration of pregnancy. Most of the pups were delivered alive in mid-pregnancy with a parturition range of 56 to 76 days. The probability of pup death depends on gestational length: the lowest incidence of mortality was seen in litters born at 70 days. The mortalities were related to litter size but not to parity. There was an inverse relationship between birth weight and litter size. In WE guinea pigs, the mean weight for a litter of 1 was 120 g; for a litter of 5, the mean body weight was 58g. Male body weights were slightly heavier than female at birth and at weaning age. The mean body weights are shown below, date of birth: female 88.3g, male 93.3g, weaning age (2 weeks): female 181.1g, male 198.8g and 30 weeks: female 758.7g, male 1018.0g. These date for WE guinea pigs are comparable to those of other strains.     

Problems in the genetics of stress. II. Genetic analysis of endocrine gland weight in mice under normal conditions and during exposure to stress]

Relative weight of adrenals, thymus, hypophysis and gonads was studied in female mice after 21 days after parturition and in intact males. One group of females was stressed during pregnancy, and another group was intact. All these animals were a progeny of the full diallele cross of 4 inbred mice strains (BALB/c, C3H/He, C57BL/6, AKR/J). On the basis of analysis of general and specific combining ability the conclusion is drawn that the relative weight of the endocrine glands is inherited additively in females of both experimental groups. However, it was found that the size of additive genetic variation for these characters in the population of females, which had been stressed during their pregnancy was larger, than in the control population. A significant role of non-additive genes in the determination of these characters was observed in males. The degree of hypertrophy of adrenals and lysis of thymus in stressed females corresponded to their emotional reactivity. Significant genotypic correlations between the weight of some endocrine glands, on one hand, and the emotional reactivity and the rate of sexual maturation, on the other hand, were found in both experimental groups of females. In the stressed group these correlations were higher.     

Urine-marking by female mice throughout their reproductive cycle.

It is commonly believed that the scent-marking activity of female mammals is elevated when they are sexually receptive, yet urine-marking by female mice does not vary in relation to their estrous cycles. We examined the marking behavior of female mice during their reproductive cycle with attention to their postpartum period of sexual receptivity. In the first experiment, females were allowed to mark prior to mating, during gestation, on the evening of parturition, during lactation, and after weaning their pups. They were exposed to a male or female mouse or nothing at each testing period in a counter-balanced fashion. Overall, the subjects marked most frequently in the presence of a male stimulus; their marking rates did not differ when they were exposed to another female or to nothing. The females' marking remained relatively steady through gestation, declined dramatically at parturition, then gradually returned to the levels observed prior to mating. In the second experiment, multiparous females were allowed to mark while they were simultaneously lactating and pregnant. Compared to unmated females, the subjects' marking frequency was low at parturition, declined further to its lowest level about 1 week later, then regained the preceding low level prior to weaning the initial litter and delivering the next. Together these results demonstrate that urine-marking by female mice is diminished just after parturition. Thus, in contrast to some other species, the marking behavior of female mice apparently is not enhanced around the time they are sexually receptive. Because female mice generally mark most frequently when males are nearby, we postulate that a major function of this behavior is to evoke endocrine and behavioral responses in proximate males rather than to attract distant males.     

Thiocyanate effects on thyroid function of weaned mice

The aim of this study was to determine the effects of thiocyanate on thyroid function in weaned mice. At this developmental period, induction and reversibility of thiocyanate effects have not yet been studied. In the present work, adult female mice were given thiocyanate [SCN(-) (1 g L(-1))] in their drinking water from the 15(th) day of pregnancy until either the 25(th) (group B) or the 15(th) day (group C) after parturition. During five days after weaning, water and food consumptions of treated mice (group B) were 42.2+/-1.2% and 56.4+/-0.9%, respectively, less than those of the controls (group A). On the sacrifice day (the 25(th) day after birth), body weight, thyroid iodine content and thyroid hormone levels (FT(4) and FT(3)) decreased by 10.4+/-3.0%, 40.6+/-2.3%; 18.7+/-2.3% and 18.1+/-1.3%, respectively. Plasma TSH increased by 30.6+/-1.7% along with the hypertrophy of thyroid glands (52.6+/-3.1%). We have observed a hypertrophy of follicle cells and a decrease in colloid volume within histological slides. After SCN(-) withdrawal (group C), partial or total recovery were noted in all parameters studied. We concluded that hypothyroidism effects added to the weaning event affected greatly thyroid function and behaviour of mice; these would be largely reversed by withdrawing thiocyanate treatment for a period of ten days.     

Effect of mild stress in mice latently infected pseudorabies virus.

Stress is one of the important factors that induces reactivation of pseudorabies virus (PrV) in latently infected pigs. We established a murine model of latent PrV infection and examined the effects of mild stress treatment in order to demonstrate that this model simulates natural infection in the pig. Latently infected mice excreted PrV from the nasal cavity under stress treatments consisting of restraint, exposure to cold or transport. Similar reactions have been observed upon treatment with acetylcholine and dexamethasone. The present findings demonstrate that these kinds of mild stress reactivate the virus in murine latent infection models in a manner similar to the induction of latent infection in pigs in the field.     

Role of IL-6 and IL-1beta in reactivation by acetylcholine of latently infecting pseudorabies virus.

We previously reported that the latently infecting Pseudorabies virus (PrV) could be reactivated by injection of swine or mice with acetylcholine. However, the mechanism of the reactivation was not clear yet. In this study, we analyzed the kinetics of cytokines related to stress to clarify the relationship between virus reactivation by acetylcholine and the immune system. IL-6 and IL-1beta were detected in mice after stimulation with acetylcholine. This shows that acetylcholine induced physiological stress conditions. However, there seemed to be no relationship between the kinetics of the cytokine levels and PrV excretion. Moreover, neither IL-6 nor IL-1beta alone could reactivate latently infecting PrV. Thus, acetylcholine causes the reactivation of latent PrV via a mechanism not involving these immunological factors.     

Role of essential glycoproteins gII and gp50 in transneuronal transfer of pseudorabies virus from the hypoglossal nerves of mice.

The propagation of pseudorabies virus (PrV) mutants deficient in essential glycoproteins gp50 and gII was studied after inoculation of transcomplemented gp50- and gII- PrV into the motor hypoglossal (XII) nerves of mice. In this model, viral spread from the infected XII motoneurons involves specific transneuronal transfer to connected cells and local, nonspecific transfer. For comparison, a PrV mutant lacking the nonessential nonstructural glycoprotein gX was included. Although the efficiencies of first-cycle replication were similar for the three viruses, only gX- and gp50- progeny mutants could spread from XII motoneurons via transneuronal and local transfer. The extents of transfer of gX- and gp50- PrV were comparable. The results show that the absence of gp50 does not alter the pattern of transneuronal or local spread of PrV, whereas gII is essential for both processes.     

Effects of multiple, chronic and early hashish exposure on mating behavior, nest-building and gestation in mice

1. The effects of hashish extract on social behavior were investigated in pairs of mice living together from mating to parturition. The drug was administered orally to both animals at a dose of 20 mg delta 9-tetrahydrocannabinol/kg three times a week, either (I) during the 3 weeks from mating to parturition, (II) during the 12 weeks from weaning to mating and parturition, or (III) only during the 3 weeks after weaning. 2. In the mating tests, an acute administration (I) caused a general sedation. Chronically treated animals (II) showed decreased sexual behavior and lower social investigations despite significantly more non-social activities. Early drug treatment (III) had no effect on mating behavior. In all three series of experiments the females had conceived by the next morning. 3. The nest-building behavior during pregnancy was suppressed after multiple (I) and chronic (II) drug administration. In early drug-treated animals (III) the transport of nesting material was only slowed down. Non-social activities were normal or increased in all three series. 4. Parturition was significantly delayed by one day after multiple (I) and chronic (II) drug administration. The birth weight was not affected, but the litter size was decreased after chronic drug treatment. Early drug administration (III) had no effects on these parameters. 5. In conclusion, whereas tolerance to the sedative effects of hashish developed very rapidly, the drug influences on social behavior were stable. Therefore, discussions on legalization of cannabis should pay attention to the drug effects on social behavior.     

Induction of parturition in pigs by intravaginal application of the prostaglandin analog cloprostenol

Cloprostenol was deposited in the vaginal lumen of sows on Day 111 of pregnancy at dosages of 100, 125 or 175 g and volumes of 1, 2 or 5 ml, respectively. A control group was treated with physiological saline. In 92 out of 93 prostaglandin-treated sows, parturition commenced approximately 22 h after application, with no significant differences between dose levels or volumes. There were also no differences in the average size and weight of litters born, weaning weight, frequency of postpartum complications or post-weaning fertility. Intravaginal application of cloprostenol is thus a simple and efficient means of inducing parturition in sows.     

Effects of feeding endophyte infected tall fescue seed on reproductive performance of female CD-1 mice via competitive breeding

This study was conducted to determine the effects of feeding endophyte-infected (Acremonium coenophialum ) tall fescue (Festuca arundinacea ) seed on the growth and reproductive performance of female CD-1 mice via competitive breeding. One hundred sixty female mice were randomly allocated to groups of ten and fed one of two diets. Diet 1 consisted of 50% mouse chow and 50% noninfected Ky-31 tall fescue seed (w/w). Diet 2 contained 50% chow and 50% tall fescue seed that was 80% infected with A. coenophialum . After 50 d of preconditioning on their respective diets, a single male was introduced into each group of 10 females and allowed to cohabitate for 96 h. The males were removed after the cohabitation period and the females continued through gestation on their respective diets. Body weight of dams and litter weights were recorded at parturition. There were no differences (P>0.05) in pregnancy rates between dietary Treatments 1 and 2 (50% vs 48.8%, respectively). However, the average number of pups born per litter (11.10 pups) and average total litter weight (17.21 g) was greater for those females consuming Diet 1 than for females consuming Diet 2 (9.33 pups per litter and 13.97 g total litter weight). The incidence of dead and cannibalized pups was more frequent with Diet 2 than Diet 1 (0.13 vs 0.0 dead; 0.21 vs 0.03 cannibalized, respectively). The obtained data suggest that although the pregnancy rate was similar between the two dietary treatments, the reproductive capacity (litter size and litter weight) of female CD-1 mice was affected by the consumption of endophyte infected fescue seed.     

水貂妊娠与泌乳期的能量代谢

孕貂摄入日粮比孕前高8.03%,即摄入总能量高11.70%。产后,母貂摄入日粮与总能量的变化,近似S型曲线。孕貂体重与妊娠时间呈正相关,与泌乳时间呈负相关。妊娠期,孕貂每天摄入总能量超过呼吸量与粪便排出量之总和,则体重增加。泌乳期,母貂每天摄入总能量少于呼吸量、粪便排出量及泌乳量之总和,故体重减轻。     

Effects of prenatal and postnatal exposure to vitamin A on the development of the murine immune system

Vitamin A and its derivatives are known to enhance the immune system and affect embryogenesis. In this study, five daily subcutaneous injections of retinol palmitate (0.001 mg/kg body weight) were administered to eight female SW mice before mating. Six more weekly injections of retinol palmitate were given during pregnancy and lactation. Eight controls were similarly treated with saline. Four of the eight vitamin-A-treated females had litters, whereas seven of the eight saline-treated females had litters. Resultant litters did not differ in size or appearance. At 12 weeks of age, serum IgM and IgG1 levels were significantly higher in the progeny of vitamin-A-treated mothers before but not after immunization with a test antigen, sheep red blood cells (SRBC). This difference was not seen when other progeny were tested at the age of one year. Anti-SRBC titers did not differ in the two groups of progeny at the age of 12 weeks or one year. One-year-old progeny of vitamin-A-treated mothers weighed significantly more than did control progeny; significant enlargement of the heart, spleen, and kidneys was observed. However, organ-to-body-weight ratios did not differ significantly. In a separate experiment, adult female mice treated with varying doses of vitamin A (five daily doses of 0.0001, 0.0005, or 0.001 mg/kg body weight) showed a dose-dependent reduction of serum IgG1 and hematocrits, but no change in serum IgM levels or leukocyte counts. Resting untreated mice had IgM levels which were one-half those seen in saline-treated controls. These studies indicate that large doses of vitamin A can affect some aspects of the developing and mature murine immune system.     

Influence of daylength experienced by dams on post-natal development of young meadow voles (Microtus pennsylvanicus)

Meadow voles born to dams kept in short days (SD) beginning 5 or 11 weeks before parturition (SD-5, SD-11) had less developed testes, gained weight more slowly and built larger nests than did young gestated and maintained in long days (LD). Pelage development was greater in SD than in LD young at 21 and 45 days of age. At weaning, SD-5 young had less dense fur and shorter guard hairs than did SD-11 young, indicating that the photoperiodic history of dams before insemination affects the post-natal pelage development of their progeny. Short daylengths experienced by dams before mating may facilitate winter preparedness of their offspring.     

Developmental aluminum toxicity in mice can be modulated by low concentrations of minerals (Fe,Zn, P,Ca, Mg) in the diet

Female Swiss Webster mice were fed diets containing 7 (control) or 1000 μg Al/g diet from conception to weaning. Pregnancy weight gain, brith weight, litter size, postnatal mortality, and weaning weight were measured. In different groups, diets low in Fe, Zn, P, or Ca and Mg (CaMg) were used as basal diets, to which Al was added. Relative to controls, who received NRC recommended levels of these nutrients, all diets with marginal essential trace elements impacted development, as demonstrated by effects on birth weight (CaMg, Fe) or weaning weight (Fe, Zn, P). Compared to diets low in Al, the 1000-mg Al/g diet led to reduced weaning weight regardless of the essential element content of the diet. Other end points were influenced by Al only within the basaldiet group; pregnancy weight gain with the low-P diet, litter size with the low-Fe diet, pregnancy completion with the low-Zn diet, and postnatal mortality with the low-CaMg or low-Zn diet. Thus, diets marginal in selected minerals can differentially alter the toxicological profile of developmental Al exposures. A basal diet was also used in which the NRC diet was supplemented with ascorbic acid, which promotes Al absorption. No modification of Al toxicity was seen with ascorbic acid supplementation.     

Infant vocalization, adult aggression, and fear behavior of an oxytocin null mutant mouse

Previous studies have shown that oxytocin (OT)-deficient female mice produced by homologous recombination fail to lactate but exhibit normal parturition and reproductive behaviors. We examined the ultrasonic vocalizations of infant mice and the subsequent aggressive and fear behavior of adult male OT knockout (OT-KO) mice. Infant OT-KO mice were less vocal than wild-type (WT) control mice during separations from the mother and peers. Adult OT-KO males were generally more aggressive in isolation-induced and resident-intruder tests of aggression and less fearful in the plus maze and acoustic startle reflex tests than WT controls. Although the increase in tests of aggression was robust for OT-KO males from obligate litters (progeny of homozygous x homozygous crossings), the increase in aggression was reduced during tests for OT-KO males derived from nonobligate mating (progeny of heterozygous x heterozygous crossings), suggesting that the OT-KO genotype was not, by itself, responsible for the changes in adult behavior. We conclude that the absence of exposure to OT during development was associated with abnormalities in the development of emotional behavior.