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PubMed1997

Easy Procedure for Milk Collection in Lactating Rats.

Procedures have been developed for easy collection of milk samples without oxytocin injection. Dams were separated from their pups for 24 h, then were hand-milked with or without aspiration. During the lactation period, the collected milk volume increased up to day 10 of lactation, reached a plateau between days 10 and 18 (range, 2.49 1.49 to 4.27 1.26 g/dam/15 min), then was lower on day 21 (2.12 1.32 g/dam/15 min). We validated our method by administering estradiol (E2) from days 10 to 17 of lactation. Treatment with E2 was associated with a dose-related reduction in the number of dams giving milk at sampling on day 18 of lactation (controls: 14/14; E2 at 0.05 mg/kg/d of body weight/d 10/15; E2 at 0.10 mg/kg/d 5/15) and a severe dose-related reduction in milk volume collected (controls: 3.75 1.40 g/dam/15 min; E2 at 0.05 mg/kg/day: 0.80 1.03 g/dam/15 min; E2 at 0.10 mg/kg/d 0.38 0.68 g/dam/15 min). Our results suggest that days 10 to 18 of lactation appear to be the most suitable period for milk collection in lactating rats in regulatory reproductive toxicologic studies; within this period, we recommend either day 16 or day 18 for milk collection.

Journal Article↗
PubMed1999

Ultrastructure and lectin cytochemistry of the cloacal pelvic glands in the male newt Triturus marmoratus marmoratus.

The cloacal organ of Salamandridae species contains four glands: pelvic, dorsal, ventral, and Kingsbury's glands. Pelvic glands have been studied only by light microscopy with conventional methods, and consist of multiple tubular serous glands with a prismatic epithelium which contains numerous PAS positive secretory granules. The present report is an ultrastructural and lectin cytochemistry characterization of the pelvic glands of Triturus marmoratus marmoratus throughout the reproductive cycle. Our methods consisted of conventional electron microscopy, and colloidal-gold lectin cytochemistry of the following lectins: WGA, ConA, LcA, UEA-I, PNA, SBA, and HPA. In the prereproductive period, the glands showed a tall epithelium which consisted of two cell types, dark and clear cells, surrounded by elongated, myoepithelial cells. Both dark and clear cells showed the ultrastructural characteristics of secretory cells, and exhibited many secretory granules in the apical cytoplasm. Areas showing densely packed, degenerating cell organelles--which were not surrounded by membrane--were observed in the dark cells whereas the clear cells showed large heterolysosomes. In the postreproductive period the number of secretory granules decreased, the rough endoplasmic reticulum was less developed, and areas of degenerating organelles were absent. In addition, small basal cells appeared. The results of the lectin histochemistry study were similar in both reproductive periods. In the epithelial cells, the rough endoplasmic reticulum, the Golgi complex, and secretory granules exclusively labeled to ConA. In all cell types, the nuclei reacted to all lectins while the cytosol only reacted to LcA lectin. The ultrastructural and histochemical characteristics of the pelvic glands of T. marmoratus suggest that these glands could be homologous to the mammalian seminal vesicles and prostate.

Animals↗
PubMed1985

Effect of breed of sire on growth of gilts and on subsequent reproductive performance.

This study was conducted to determine the effect of breed of sire on performance of crossbred gilts during the growing-finishing period and on subsequent reproductive performance for three consecutive parties. Average daily gain of gilts sired by Yorkshire boars was greater (P less than .05) than average daily gain of gilts sired by Landrace boars. Average daily gain of gilts sired by Duroc boars was between that of Yorkshire and Landrace sired gilts, but was not significantly different from either. Birthweight of Duroc and Landrace-sired pigs was heavier (P less than .05) than that of Yorkshire-sired pigs. Landrace-sired pigs were heavier at weaning (35 days of age) than were Duroc and Yorkshire-sired pigs. Sows sired by Yorkshire boars were heavier (P less than .05) when pigs were weaned, at 110 days of gestation and one day post-farrowing than sows sired by Duroc boars. Weight of Landrace-sired sows was intermediate between Yorkshire and Duroc-sired sows and was not significantly different from either. Survival traits were not affected by breed of sire.

Animal Husbandry↗
PubMed2000

[Investigation on growth and development of Tussilago farfara L. in Beijing].

OBJECTIVE: To provide a scientific basis for the introduction and harvest of T. farfara in Beijing. METHOD: Random sampling in late growing period. RESULT: T. farfara reached the peak of vegetation growth in early September and concurrently began its reproductive growth. During this period its bud and rhizome began to form and develop and kept growing until the period of freezing weather. CONCLUSION: There are two optimum the times for reaping T. farara bud: one is around the fifteenth day before the period of freezing weather, and the other is around the tenth day after the thawing season in the next year.

Asteraceae↗
PubMed1984

Exploring the presence of imitation during early infancy.

2 investigations of early imitative ability were conducted with cross-sectional samples of infants between 4 and 21 weeks. Study 1 involved 2 rounds of modeling 5 gestures to infants. In Study 2, the number of modeled gestures was reduced to 3, but each one was modeled many more times--for the duration of the infant's attention over a 3-min period. When frequencies of reproduction of a modeled act were compared against baseline frequencies and against average frequencies of the act during periods when other actions were modeled, several main results were obtained. First, the most general finding was that imitative-like matching of modeled gestures was the exception, not the rule, at all ages. Second, even where significantly greater frequencies of a gesture occurred during modeling than during control periods, it was always a partial and incomplete version of the modeled act that was reproduced, not a well-formed copy of the adult's gesture. Finally, where results were consistent with an interpretation of imitation, as with responses to tongue protrusion modeling, the effect was restricted to the youngest ages: 4-6 weeks. Given the restricted evidence for imitation, and the fact that neither linear nor curvilinear growth trends were apparent, the most appropriate explanation for the reproduction of tongue protrusions at the youngest age is to be sought in terms of a reflexive or fixed action pattern type of response.

Child Development↗
PubMed2005

Opportunistic mothers: female marmosets (Callithrix kuhlii) reduce their investment in offspring when they have to, and when they can.

All female primates incur energetic costs associated with producing and caring for offspring, but females belonging to the New World primate family Callitrichidae, the marmosets and tamarins, appear to face even further demands. In fact, the energetic demands of rearing callitrichid infants are thought to have led to the evolution of cooperative infant care in these species. If this explanation is true, then one might expect that natural selection should also have shaped patterns of maternal behavior to be sensitive to the costs of reproduction and equipped females to reduce their investment in offspring under certain conditions. Therefore, we examined the maternal effort and postpartum endocrine profiles of individual female marmosets (Callithrix kuhlii) across conditions that represented two hallmarks of callitrichid reproduction-conception during the early postpartum period and alloparental assistance. When females conceived during the early postpartum period and faced the upcoming demands of caring for their newly conceived litters (Study 1), they significantly reduced their caregiving effort and had significantly higher postpartum levels of estradiol relative to breeding attempts in which conception occurred later in the postpartum period. Postpartum estradiol was negatively correlated with maternal carrying effort. When experienced alloparents were present (Study 2), females again reduced their caregiving effort relative to breeding attempts in which experienced alloparents were not present. Postpartum cortisol, however, did not vary as a function of experienced alloparental assistance. The results of these studies suggest that female marmosets have been subjected to similar selection pressures as females of other primate taxa--to maximize their reproductive success by reducing their investment in offspring under the worst and best of conditions--and suggest that hormones may mediate within-female variation in maternal care. These studies also provide support for the notion that mothers are "flexible opportunists" when it comes to providing care to their young.

Animals↗
PubMed2001

The effects of deleterious mutations in cyclically parthenogenetic organisms.

Cyclically parthenogenetic organisms experience benefits of both sexual and asexual reproductive modes in a constant environment. Sexual reproduction generates new genotypes and may facilitate the purging of deleterious mutations whereas asexuality has a two-fold advantage and enables maintenance of well-fitted genotypes. Asexual reproduction can have a drawback as increased linkage may lead to the accumulation of deleterious mutations. This study presents the results of Monte Carlo simulations of small and infinite diploid populations, with deleterious mutations occurring at multiple loci. The recombination rate and the length of the asexual period, interrupted by sexual reproduction, are allowed to vary. Here I show that the fitness of cyclical parthenogenetic population is dependent on the length of the asexual period. Increased length of the asexual period can lead both to increased segregational load following sexual reproduction and to a stronger effect of deleterious mutations on variation at a linked neutral marker, either by reducing or increasing the variation.

Animals↗
PubMedDate not supplied

[Phasic changes in reproductive potential, intracellular polyamines and antilysozyme activity in Escherichia coli in periodic culture].

Growth-phase associated changes in and relationships between the specific growth rate (mu) characterizing the reproductive capacity of the cells, the contents of intracellular biogenic polyamines (BPA), such as putrescine (P), cadaverine (C), and spermidine (S), and antilysozyme activity (ALA) were studied in 37 strains of Escherichia coli grown in batch culture on solid medium. A decrease in mu upon the transition of the culture to the stationary growth phase was accompanied by a decrease in the pool of free BPA, mainly P and C, and by the appearance of ALA. The interrelations between the parameters studied were described as a complex of direct and negative correlations; the combination of low initial P and C contents, reduced P/S and C/S ratios, and a high level of ALA was designated as a factor of slight inhibition of E. coli reproduction. It is argued that BPA and ALA are integrated in a system controlling both the metabolism and stability of peptidoglycan in E. coli.

Biogenic Polyamines↗
PubMed2002

Long-day inhibition of reproduction and circadian photogonadosensitivity in Zembra Island wild rabbits (Oryctolagus cuniculus).

We investigated the effects of photoperiod on testicular activity in wild rabbits (Oryctolagus cuniculus) captured on Zembra Island (North Tunisia) and maintained in experimental photoperiodic conditions. Sexually inactive animals were subjected to alternate 3-mo periods of short days (8L:16D) and long days (16L:8D) for 1 yr. Testicular activity increased significantly and then decreased to levels equivalent to or lower than those measured during sexual quiescence after 1 mo of 8L:16D or 16L:8D, respectively. Eight groups of sexually active animals were also exposed to 8L:16D for 60 days. The light phase was divided into two photofractions (7.5 and 0.5 h). The short photofraction interrupted the dark phase 9.5-18.5 h after the beginning of the main photofraction. Testicular activity was inhibited if the short photofraction interrupted the dark phase 12.5 h or more after the beginning of the main photofraction. These results clearly confirm that photoperiod affects reproduction in this species: Short days stimulate reproduction, whereas long days inhibit it. The asymmetric pattern of skeleton photoperiods used demonstrated the existence of a circadian rhythm for photogonadosensitivity, with the photosensitive phase beginning 12.5 h after dawn. In this species, photoperiod length controls both the beginning and the end of the reproductive period. These results differ from those obtained with continental populations of wild rabbits, in which reproduction is inhibited by short day length. This difference may reflect genetic drift linked to the geographic isolation of this population, which is known to have been present on this small island for more than 2000 yr.

Animals↗
PubMed2001

Can we abandon routine evaluation of serum estradiol levels during controlled ovarian hyperstimulation for assisted reproduction?

OBJECTIVE: To assess whether abandoning measurement of serum estradiol (E2) and spacing ultrasound evaluations at greater intervals had an effect on the results of assisted reproduction technology (ART). DESIGN: A retrospective comparison of two consecutive periods. SETTING: Division of Assisted Reproduction Technology, Department of Obstetrics and Gynecology, Ha'Emek Medical Center, Afula, Israel. PATIENT(S): One thousand nine hundred and eighty-five controlled ovarian hyperstimulation (COH) cycles for ART were initiated during the years 1996 to 1999. INTERVENTION(S): During the first 2 years an intensive follow-up protocol was used that included E2 blood levels measurements. In the next 2 years a less intensive protocol was adopted that did not use E2 measurements. MAIN OUTCOME MEASURE(S): ART results and the rate of ovarian hyperstimulation syndrome (OHSS). RESULT(S): The patients' background characteristics did not differ between the two periods. The cancellation rate was not different (9.8% vs. 7.2%). There was no difference in the duration of stimulation or the amount of gonadotropins used. The number of oocytes retrieved (12.1 +/- 9.3 vs. 9.6 +/- 6.3), fertilization rates (74% vs. 75%), and clinical pregnancy rates (26.2% vs. 27.9%) did not differ. The incidence of severe ovarian hyperstimulation syndrome was not significantly different between the two periods. CONCLUSION(S): Controlled ovarian hyperstimulation for ART can be done reliably without routine, serial serum E2 measurements without compromising the treatment results.

Estradiol↗
PubMed1999

Intraspecific brood parasitism: a strategy for floating females in the European starling.

In many bird species, there is a floating population of females that are excluded from breeding because of competition for limited breeding resources. Female floaters may enhance their reproductive success by engaging in intraspecific brood parasitism. We studied female floaters in a population of European starlings, Sturnus vulgaris, in order to determine their identity and potential parasitic behaviour. Females were caught after being attracted to nestboxes with artificial nests during 1993-1995. None of the females was known to have a nest of her own at capture but 47% of the females either laid an egg in the nest or carried a fully developed egg within the reproductive tract, indicating that they were intraspecific brood parasites. The floating females were significantly younger and smaller than breeding females. Of 13 females equipped with radiotransmitters and followed daily, all but one started a breeding attempt of their own after 3-8 days and the majority settled as secondary females or mated with males where the original female had disappeared. This suggests that females that are unable to compete successfully for nest sites or males early in the breeding season may use intraspecific brood parasitism to enhance reproductive success during the period that they are constrained from breeding. The importance of settling rapidly because of a seasonal decline in reproductive success may also promote the evolution of intraspecific brood parasitism in the starling. The relative reproductive success of combining egg dumping with breeding compared with traditional breeding will depend on the costs of delaying breeding as well as the probability of finding a mate later in the breeding season. Copyright 1999 The Association for the Study of Animal Behaviour.

Journal Article↗
PubMed1990

Effect of some drugs, experimental stress and estrus on unstable and fixed conditioned alimentary motor reflexes in cats. Reproduction and stress. Part V.

Reproduction of fixed conditioned alimentary motor reflexes in long-time laboratory kept cats in the course of the year is remarkably influenced by the sexual cycle. Estrus, anestrus, gestation and deliveries act upon the reflex reproduction in a similar way like deliberate application of experimental stress of various intensity. The study of the antistress efficacy of drugs modifying psychological functions and mental states in the method of reproduction of fixed alimentary motor reflexes under stress must specify the actual effect of experimental stress. Experimental sensory stress represented by intermittent sound of 98 dB and intermittent light (0.6 joules) acting with simultaneous frequency of 6 Hz was found to generally impair reflex reproduction over the whole period of twelve months. Correct response latencies were significantly prolonged and incorrect motor reactions significantly increased. If reflex reproduction was impaired due to the sexual cycle, simultaneous sensory stress still aggravates the impairment. The definition of the actual efficacy of experimental stressing thus necessarily requires regular control experiments in the course of the year with reproduction influenced neither by stress nor drugs at least at forthightly intervals.

Animals↗
PubMed2000

Survival and production in variable resource environments.

A dynamic energy budget (DEB) model describes the rates at which organisms assimilate and utilize energy from food for maintenance, growth, reproduction and development. We study the dynamic behavior of one particular DEB model, Kooijman's kappa-rule model, whose key assumption is that somatic and reproductive tissues are competing for energy. We assume an environment in which the food density fluctuates either periodically or stochastically (pink noise). Both types of fluctuations stimulate growth; the magnitude of the (average) increase in size depends on both the strength and duration of the fluctuations. In a stochastic environment, the risk of mortality due to starvation increases with increasing fluctuation intensity. The mean lifespan is also a function of the model parameter kappa characterizing the partitioning of energy between somatic and reproductive tissues. Organisms committing a large fraction of resources to reproduction endure periods of food shortage relatively well. The effects of food fluctuations on reproduction are complex. With stochastic food, reproduction in survivors increases with increasing fluctuation intensities, but lifetime reproduction decreases. Periodic fluctuations may enhance reproduction, depending on the value of kappa. Thus, a variable food supply stimulates growth, increases mortality and may enhance reproduction, depending on life history.

Animals↗
PubMed2003

Juvenile hormone agonists affect the occurrence of male Daphnia.

The water flea Daphnia magna reproduces primarily by cyclic parthenogenesis. Environmental stimuli that signal a change to adverse conditions induce the organisms to switch from parthenogenesis to gamogenetic reproduction. During the gamogenetic period, they produce male daphnids and dormant resting eggs, which can survive prolonged periods of environmental adversity. However, little is known about the mechanisms associated with the switch from parthenogenesis to gamogenetic reproduction. We investigated the effects of several juvenoids on sex determination in Daphnia. Females less than 24 h old were exposed to various concentrations of the test substance and were observed for 21 days. It was found that they can trigger the appearance of male daphnids: the percentage of males in the population increases to a level greater than what occurs under ordinary environmental conditions. We found that methylfarnesoate, juvenile hormone III, methoprene, and the phenoxyphenoxy derivatives pyriproxyfen and fenoxycarb (both insecticides) reduced the production of offspring and produced sex ratios dominated by male daphnids. Pyriproxyfen and fenoxycarb showed striking effects at low concentrations. Exposure to either of these chemicals at a concentration of 330 ngl(-1) caused adult females to produce almost all male neonates. Methylfarnesoate, juvenile hormone III, and methoprene showed an effect in inducing male production at higher concentrations (3.7 x 10(3), 3.3 x 10(5), and 1.3 x 10(5) ngl(-1), respectively). Our findings suggest that juvenile hormone agonists, including some insecticides, affect the chemical signaling responsible for inducing the production of male offspring.

Animals↗