Age Of Pups Research Articles

Proper micro-environment alleviates mortality in laboratory mouse breeding induced by litter overlap and older dams

The ongoing worldwide effort to reduce animal numbers in research often omits the issue of pre-weaning mortality in mouse breeding. A conservative estimate of 20% mortality would mean approximately 1.1 M mice die annually in the EU before scientific use. We hypothesize that pre-weaning mortality in laboratory mouse breeding is associated with cage social and macro/micro-environment conditions. Here we count pups from 509 C57BL/6J litters daily for accurate detection of mortality, and monitor cage micro-environment for 172 C57BL/6J litters. Probability of pups to die increases with the increase in dam age, number and age of older pups in the cage (of overlapped/cohabitating litters), and in small (<6 pups) and large (>11 pups) focal litters. Higher temperatures (>23.6 °C) and nest scores (>3.75) compensate for some of the socially-associated risks for pup death. These findings can be implemented in strategies for reducing pre-weaning mouse mortality, a more welfare-friendly and sustainable approach for science.

Prey targeted by lactating Weddell seals (Leptonychotes weddellii) in Erebus Bay, Antarctica

AbstractFemale Weddell seals (Leptonychotes weddellii) display a mixed capital-income breeding strategy, losing up to 40% of their body mass between birthing and weaning their pups. How and when they regain energy stores, however, remains to be fully explored. To better understand the foraging by lactating Weddell seals, we fitted time-depth recorders and head-mounted cameras on 26 seals in Erebus Bay, Ross Sea, for ~ 5 days in November and December 2018 and 2019. We aimed to (1) identify prey species and foraging depth and (2) investigate relationships between seal physiology and demographics and probability of foraging. We recorded 2782 dives, 903 of which were &gt; 50 m, maximum depth was 449.3 m and maximum duration was 31.1 min. Pup age likely contributes to the probability of a lactating Weddell seal foraging (Est. = 1.21 (SD = 0.61), z = 1.97, p = 0.0484). Among 846 prey encounters, the most frequent prey items were crustaceans (46.2%) and Antarctic silverfish (Pleuragramma antarcticum, 19.0%); two encounters were observed with juvenile Antarctic toothfish (Dissostichus mawsoni, 0.2%). We identified substantial variability in foraging behaviour, individually and between locations, and found that lactating seals target many species and some may specialise on certain prey groups.

From land to ocean: One month for southern elephant seal pups to acquire aquatic skills prior to their first departure to sea

Weaned southern elephant seals (SES) quickly transition from terrestrial to aquatic life after a 5- to 6-week post-weaning period. At sea, juveniles and adult elephant seals present extreme, continuous diving behaviour. Previous studies have highlighted the importance of the post-weaning period for weanlings to prepare for the physiological challenges of their future sea life. However, very little is known about how their body condition during this period may influence the development of their behaviour and brain activities. To characterise changes in the behavioural and brain activity of weanlings prior to ocean departure, we implemented a multi-logger approach combining measurements of movements (related to behaviour), pressure (related to diving), and brain electrical activity. As pups age, the amount of time allocated to resting decreases in favour of physical activity. Most resting (9.6 ± 1.2 h/day) takes place during daytime, with periods of slow-wave sleep representing 4.9 ± 0.9 h/day during the first 2 weeks. Furthermore, an increasing proportion of physical activity transitions from land to shore. Additionally, pups in poorer condition (lean group) are more active earlier than those in better condition (corpulent group). Finally, at weaning, clear circadian activity with two peaks at dawn and dusk is observed, and this pattern remains unchanged during the 4 weeks on land. This circadian pattern matches the one observed in adults at sea, with more prey catches at dawn and dusk, raising the question of whether it is endogenous or triggered by the mother during lactation.

Nest-building in breeding mice: Impact of macro- and micro-environment.

The housing conditions of laboratory mice must be strictly controlled in order to reduce the impact of pathophysiological changes that affect animal health and welfare, possibly resulting in increased variability within experimental results. One way to improve the activity and survival of laboratory mice is to provide nesting material. The objective of this study was to determine if nest-building quality could be used to detect changes in murine mating behaviour in a rodent facility under controlled conditions. Nesting scores of 847 cages with monogamous pairs from three different genetic backgrounds (129, B6 and BALB/c) of both sexes were correlated with 18 predefined variables. The effects on nest quality were evaluated using descriptive data analysis, correspondence analysis and ordinal logistic model fitting. The results showed a strong relationship between nest quality and nest position. Humidity, genetic background, cage change and the number and age of pups in the cage affected the nest-building scores. The most important indicators were cage change and relative humidity, both of which exerted significant negative effects on nest-building quality. Even though the criteria were well defined, the observer could still influence nest score appraisal. However, in a long-term observational study, observers could improve their assessment by training and acquiring greater experience in score assignment. Nest-building scores are easy to assess in the cage, with little discomfort to the animal. Moreover, the nest score is a valid indicator of the health and well-being of laboratory mice and can provide valuable support in the management of animal facilities.

CNSC-39. GENERATION AND CHARACTERIZATION OF LIVING ORGANOTYPIC BRAIN SLICE CULTURES AS A NOVEL PRE-CLINICAL MODEL FOR BRAIN CANCER

Abstract A challenge in cancer research is developing reproducible, reliable, and practical models which can capture the complexity of cancer development and treatment. The development of functional precision medicine platforms is emerging as a promising strategy for improving pre-clinical drug testing and guiding clinical decisions. We have developed an organotypic brain slice culture (OBSC) technology composed of intact multicellular tissue which can be rapidly used for spatiotemporal drug response testing. OBSCs are reproducibly generated from Sprague-Dawley rat pups and used as living tissue substrates to culture treat different tumor cell lines and uncultured patient brain tumor resection tissue. We evaluated OBSC quality and reproducibility throughout the study by using a propidium iodide nuclear permeability assay. This technique enabled a broad dynamic range to distinguish between healthy and unhealthy slices. In these studies, the rat pup age at the time of generation had an impact on OBSC quality and quantity, indicating that OBSCs should be generated from eight-day-old pups. We also found that optimal OBSCs were generated using improved methods for brain dissection and OBSC culture conditions, establishing our robust, standardized procedure for OBSC generation. Following this optimization period, we continued to conduct quality control analysis with 6 OBSCs per batch for reproducibility. We also conducted immunohistochemistry analysis immediately after slicing and concluded that morphology of neurons in OBSCs remained unchanged between day 0 and 4. In addition, the activation of astrocytes attenuates by day 4 but persists in macrophages/microglia, suggesting that the myeloid cells can phagocytose dead cells and debris in OBSCs. In summary, these results indicate that the OBSC platform may be an effective model that accelerates preclinical drug testing and directs drug development towards clinical evaluation.

Cypermethrin Toxicity-induced Infertility: An Assessment of Longitudinal Transfer of Protective Potentials of Date Fruit Extracts in Wister Rats.

There is a potential for longitudinal and horizontal transfer of the cytotoxic effects of cypermethrin, and evidence suggests that date fruit extracts can ameliorate these cytotoxic effects. Thus, the current study evaluated female Wister rats' fertility and pup parameters after mating males treated with cypermethrin and date fruit (Phoenix dactylifera) extract. Adult Wistar rats (n = 74; 140 - 207 g) were used to conduct this experiment in two phases: The first phase was a single dose toxicity study (n = 18), while the second phase (n = 56) evaluated female Wister rats' reproductive and pup development parameters after mating with male Wistar rats exposed to date fruit extract and cypermethrin. Male rats were distributed randomly into four groups (n = 7 per group) and administered distilled water (Group I); 60 mg/kg cypermethrin (Group II) to simulate infertility; 250 mg/kg date fruit extract alone (Group III); and date fruit extracts plus 60 mg/kg cypermethrin (Group IV). Treated males were then mated with healthy female rats at a ratio of 1:1. Successfully mated females were appraised for conception and pregnancy rates, gestation length, litter size, and weights at birth, and on days 5, 10, 15, and 21 post-partum, an anogenital distance at day-20, sex ratio, and age of pup when hair growth was evident. Significant differences (p < 0.05) were observed in litter size and male anogenital distance but not in reproductive performance. Also, the study demonstrated that date fruit extract skewed the sex ratio of offspring to more female than male pups when female Wister rats were mated with males that received date fruit extracts alone or cypermethrin and date fruit extracts. The body weight gain did not differ significantly between the control and cypermethrin-treated groups. This evidence suggested a longitudinal transfer of the protective effects of date fruit extracts following a weekly exposure of male rats to cypermethrin at 60 mg/kg.

REARING RODENT PUPS IN FOSTER FAMILIES OF TNEIR OWN OR ANOTHER MAMMAL SPECIES: SURVIVAL AND THE CAUSES OF MORTALITY

Conditions of rearing pups at an early age render a significant impact on subsequent development, reproduction and certain features of the behavior of mammals including rodents. Parents, mostly lactating females, are the main component of the social environment of pups at the early period of postnatal ontogenesis in most mammal species. Therefore, rearing pups in foster families of their own (in-fostering) or another, even taxonomically distant species (cross-fostering) is one of the main methods of assessing the impact of early experience and maternal environment on the development of animal behavior. Cross-fostering or in-fostering is also used for the conservation of valuable animal species. Therefore, more effective fostering methods that provide the maximum survival of the young are necessary to be developed. According to this, we investigated the survival and possible causes of the mortality of rodent pups representing several species in foster families of their own or another mammal species. We conducted a series of experiments on the cross-fostering and in-fostering of house (Mus musculus) and mound-building (Mus spicilegus) mice, yellow steppe lemmings (Eolagurus luteus) and brown rats (Rattus norvegicus), and on rearing rat pups in foster families of the European polecat (Mustela putorius). The proportion of successfully cross-fostered pups (0–68.4) was lower compared to the in-fostered (93.3–100) ones. This result is presumably explained by more significant differences in the maternal environment when reared by a heterospecific female. According to the literature data, the age of foster and recipient female pups, species-specific differences of odor, the presence or absence of a male and the level of paternal care, the level of stress of the mother and offspring, the expression of maternal instinct, the previous female experience in rearing its own and foster pups, the duration of lactation and the nutritional value of maternal milk are the factors that seem to affect the survival and mortality of foster pups.

Plasticity in parental behavior and vasopressin: responses to co-parenting, pup age, and an acute stressor are experience-dependent.

The impact of variation in parental caregiving has lasting implications for the development of offspring. However, the ways in which parents impact each other in the context of caregiving is comparatively less understood, but can account for much of the variation observed in the postnatal environment. Prairie voles (Microtus ochrogaster) demonstrate a range of postnatal social groups, including pups raised by biparental pairs and by their mothers alone. In addition to the challenges of providing parental care, prairie vole parents often experience acute natural stressors (e.g., predation, foraging demands, and thermoregulation) that could alter the way co-parents interact. We investigated how variation in the experience of raising offspring impacts parental behavior and neurobiology by administering an acute handling stressor on prairie vole families of single mothers and biparental parents over the course of offspring postnatal development. Mothers and fathers exhibited robust behavioral plasticity in response to the age of their pups, but in sex-dependent ways. Pup-directed care from mothers did not vary as a function of their partner's presence, but did covary with the number of hypothalamic vasopressin neurons in experience-dependent ways. The relationship between vasopressin neuron numbers and fathers' behaviors was also contingent upon the stress handling manipulation, suggesting that brain-behavior associations exhibit stress-induced plasticity. These results demonstrate that the behavioral and neuroendocrine profiles of adults are sensitive to distinct and interacting experiences as a parent, and extend our knowledge of the neural mechanisms that may facilitate parental behavioral plasticity.

Advancing surrogate-rearing methods to enhance southern sea otter recovery

Recovery of wildlife and their ecosystems may require enhancement of vulnerable populations through human intervention. As a southern sea otter (Enhydra lutris nereis) enhancement strategy, surrogate rearing and releasing of stranded orphans provides these individuals with another opportunity of life in the wild, promotes species-specific development of behaviors necessary for survival and reproduction after release, and may bolster targeted populations and resiliency of nearshore ecosystems. To further advance surrogacy as a viable recovery strategy for this threatened subspecies, we comprehensively describe our methods and use a machine learning algorithm to monitor and evaluate program success. Specifically, we model 20 years (2002−2021) of rehabilitation outcomes for 64 pups (i.e., success or failure reacclimating to the wild) based on 34 parameters representing three release sites and five treatment stages: stranding, stabilization, surrogacy, pre-release, and release. We find that surrogacy is a successful rehabilitation method (75%), robust to all measured factors through release preparation, including idiosyncrasies in pup origin, age, early development, and pairings with female sea otters. Instead, key performance indicators of successful outcomes in the wild are environmental conditions experienced during release, such as favorable sea conditions and weather, localized dispersal, and minimal competition from local populations. Most importantly, success requires optimal values among all environmental conditions at chosen release sites because a decline in any one factor may result in failure. Our findings highlight the importance of continuously evaluating rehabilitation methods to enhance species recovery and may have broader application to restoring other threatened species and their ecosystems.

Gut microbiota of endangered Australian sea lion pups is unchanged by topical ivermectin treatment for endemic hookworm infection.

The gut microbiota is essential for the development and maintenance of the hosts' immune system. Disturbances to the gut microbiota in early life stages can result in long-lasting impacts on host health. This study aimed to determine if topical ivermectin treatment for endemic hookworm (Uncinaria sanguinis) infection in endangered Australian sea lion (Neophoca cinerea) pups resulted in gut microbial changes. The gut microbiota was characterised for untreated (control) (n = 23) and treated (n = 23) Australian sea lion pups sampled during the 2019 and 2020/21 breeding seasons at Seal Bay, Kangaroo Island. Samples were collected pre- and post-treatment on up to four occasions over a four-to-five-month period. The gut microbiota of untreated (control) and treated pups in both seasons was dominated by five bacterial phyla, Fusobacteria, Firmicutes, Proteobacteria, Actinobacteria and Bacteroidetes. A significant difference in alpha diversity between treatment groups was seen in pups sampled during the 2020/21 breeding season (p = 0.008), with higher richness and diversity in treated pups. Modelling the impact of individual pup identification (ID), capture, pup weight (kg), standard length (cm), age and sex on beta diversity revealed that pup ID accounted for most of the variation (35% in 2019 and 42% in 2020/21), with pup ID, capture, and age being the only significant contributors to microbial variation (p < 0.05). There were no statistically significant differences in the composition of the microbiota between treatment groups in both the 2019 and 2020/21 breeding seasons, indicating that topical ivermectin treatment did not alter the composition of the gut microbiota. To our knowledge, this is the first study to characterise the gut microbiota of free-ranging Australian pinniped pups, compare the composition across multiple time points, and to consider the impact of parasitic treatment on overall diversity and microbial composition of the gut microbiota. Importantly, the lack of compositional changes in the gut microbiota with treatment support the utility of topical ivermectin as a safe and minimally invasive management strategy to enhance pup survival in this endangered species.

Non-essential heavy metals and protective effects of selenium against mercury toxicity in endangered Australian sea lion (Neophoca cinerea) pups with hookworm disease

The endangered Australian sea lion, Neophoca cinerea, faces ongoing population decline. Identification of key threats to N. cinerea population recovery, including disease and pollutants, is an objective of the species’ recovery plan. Previous studies have identified Uncinaria sanguinis, an intestinal nematode, as a significant cause of disease and mortality in N. cinerea pups. Given the impact of heavy metals on the immune response, investigation of these pollutants is critical. To this end, the concentrations of arsenic (As), total mercury (Hg), cadmium (Cd), chromium (Cr), lead (Pb) and selenium (Se) were determined in blood collected from N. cinerea pups sampled during the 2017/18, 2019 and 2020/21 breeding seasons at Seal Bay Conservation Park, South Australia.Significant differences (p < 0.05) in Hg, As, Cr, and Se concentrations and molar ratio of Se:Hg were seen between breeding seasons. Pup age, maternal parity and inter-individual foraging behaviour were considered factors driving these differences. The concentrations of Hg (357, 198 and 241 µg/L) and As (225, 834 and 608 µg/L) were high in 2017/18, 2019 and 2020/21 respectively with Hg concentrations in the blood of N. cinerea pups above toxicological thresholds reported for marine mammals. The concentration of Se (1332, 647, 763 µg/L) and molar ratio of Se:Hg (9.47, 7.98 and 6.82) were low compared to other pinniped pups, indicating potential vulnerability of pups to the toxic effects of Hg. Significant (p < 0.05) negative associations for Pb and Cd with several red blood cell parameters suggest they could be exacerbating the anaemia caused by hookworm disease. Temporal (age-related) changes in element concentrations were also seen, such that pup age needs to be considered when interpreting bioaccumulation patterns.Further investigation of the role of elevated heavy metal concentrations on N. cinerea pup health, disease and development is recommended, particularly with respect to immunological impacts.

Maternal responses to pup calls in a high-cost lactation species.

Bonding between mothers and their young is fundamental to mammalian reproductive behaviour and individual fitness. In social systems where the risk of confusing filial and non-filial offspring is high, mothers should demonstrate early, strong and consistent responses to their kin throughout the period of offspring dependence, irrespective of maternal traits. We tested this hypothesis through playback experiments in the northern elephant seal Mirounga angustirostris, a phocid species that breeds in high-density colonies. We found that mothers recognized their offspring throughout lactation and as early as 1-2 days after parturition. Measures of experience (age) and temperament (aggressivity) did not predict their response strength to filial playback treatments, nor did pup age or sex. Some mothers showed great consistency in behavioural responses throughout the lactation period, while others were less predictable. The strength of a female's response did not influence her pup's weaning weight; however, more consistent females weaned pups of higher mass. This is a rare demonstration of individual recognition among phocid mothers and their offspring, and suggests that consistency in maternal responsiveness may be an important social factor influencing the pup's growth and survival.

A break from the pups: The effects of loft access on the welfare of lactating laboratory rats.

Rats (Rattus norvegicus) bred for research are typically confined with their litters until weaning, but will spend time away from pups when given the opportunity. We aimed to assess how dam welfare is affected by the ability to escape from their pups. Rat dams (n = 16) were housed in cages either with or without an elevated loft. We measured time dams spent in lofts, time spent nursing, and affective states using elevated plus maze and anticipatory behavior testing. We predicted that 1) dams housed with lofts would use them increasingly as pups aged, 2) dams without a loft would spend more time passively nursing (i.e. initiated by pups rather than the dam) and more total time nursing as pups aged, and 3) dams housed with lofts would show evidence of a more positive affective state. Dams housed with lofts spent more time in the loft with increasing pup age; dams spent on average (mean ± SE) 27 ± 5% of their time in the loft when pups were 1 wk old, increasing to 52 ± 5% of their time at 3 wks. When pups were 3 wks old, dams with lofts spent less time passively nursing (10 ± 2% of total time, compared to 27 ± 4% for dams without a loft) and less time nursing overall (36 ± 4% of time versus 59 ± 2% for dams without a loft). Rats without loft access showed increased anticipatory behavior potentially indicative of negative affective state (24.5±1.8 behaviors per minute in wk 3 compared to 18.8±1.0 in wk 1). These findings indicate that rat dams in laboratories choose to spend time away from their pups when provided the opportunity, particularly later in lactation; an inability to do so is associated with increased passive nursing and negative affect.

Effects of rapamycin and OSI-027 on α-SMA in lung tissue of SD rat pups with hyperoxic lung injury

ObjectiveTo investigate the effect and significance of mammalian target of rapamycin (mTOR) inhibitors on the expression of α-SMA in lung injury induced by high volume fraction of inspired oxygen (hyperoxygen) in SD rat pups. MethodsSeventy-two Sprague-Dawley rat pups (age: 3 weeks) were randomly divided into air + saline, hyperoxia + saline, hyperoxia + OSI-027, and hyperoxia + rapamycin groups. Animal models were constructed (n = 18). Hyperoxia was induced by continuous administration of 90% oxygen. Normal saline, OSI-027, and rapamycin are administered by intraperitoneal injection on 1d, 3d, 6d, 8d, 10d, 13d of the observation period, respectively. Following assessments were made on the 3rd, 7th, and 14th day of modeling: pathological changes in lung tissues, lung injury score, Western Blot to assess the distribution and expressions of mTOR, pS6K1, and α-SMA protein in lung tissues. ResultsIn terms of time factors, the protein expressions of mTOR, pS6K1, and α-SMA increased with time. Except for the air group, the lung injury scores of the other groups increased with time, In terms of grouping factors, lung injury score in the air group was significantly lower than that in the other groups. In the hyperoxia group, the protein expressions of mTOR, PS6K1, and α-SMA were significantly higher than those in the other groups. The lung injury score in the hyperoxia group was significantly higher than that in the other groups. The lung injury score in the hyperoxia OSI group was significantly lower than that in the hyperoxia rapamycin group. ConclusionIn hyperoxia lung injury, inhibiting the activation of mTOR signaling pathway can effectively reduce the expression of α-SMA; however, only mTORC1/2 dual inhibitor OSI-027 exhibited an anti-proliferative effect, and alleviated hyperoxia-induced lung injury and fibrosis in SD rat pups.

Fetal exposure to dichloroacetic acid and impaired cognitive function in the adulthood.

IntroductionDichloroacetic acid (DCA), a by‐product of disinfection in drinking water, is a multiple organ carcinogen in humans and animals. Still, little research on its neurotoxicity and its underlying mechanism has not been elucidated.MethodsSprague Dawley rats were intragastrically treated with DCA at 10, 30, 90 mg/kg body weight from pregnancy till delivery. At eight weeks of age of pups, we assessed cognitive performance using the standard behavioral tests. And the hippocampus structure and ultrastructure were evaluated using light and electron microscope. The oxidative stress indicators and neuroinflammation factors were measured with the corresponding kits. The mRNA and protein of synaptic factors were detected using RT‐PCR and Western blot.ResultsThe results indicated that maternal weight gain and offspring birthweight were not significantly affected by DCA. However, behavioral tests, including morris water maze and step down, showed varying degrees of changes in DCA‐treated pups. Additionally, we found significant differences in hippocampal neurons by histomorphological observation. Biochemical analysis results indicated superoxide dismutase (SOD) and catalase (CAT) activities, as well as reactive oxygen species (ROS), nitric oxide (NO), and reduced glutathione (GSH) levels, were affected by DCA accompanying with DNA damage. Moreover, the results showed that the neuroinflammation factors (TNF‐α, IL‐6, IL‐1β) in DCA treatment groups increased significantly compared with the control pups. And we also found that DCA treatment caused a differential modulation of proteins (BDNF, cAMP‐response element‐binding protein1 (CREB1), p‐CREB1, postsynaptic density‐95 (PSD‐95), synapsin I, p‐synapsin I), and mRNA (BDNF, PSD‐95).ConclusionsTaken together, these results above showed that oxidative stress, neuroinflammation response, and weakened synaptic plasticity in pups hippocampus induced by fetal exposure to DCA could damage the function of memory and cognition in the adulthood.

Environmental and social factors influencing wolf (Canis lupus) howling behavior

AbstractAnimals communicate in a variety of ways and calls are used for a number of important behaviors. Temperature, wind, time of day, and human activities can affect animals’ use of calls, particularly over long distances. Effects of group size on the use of calls can be particularly influential in territorial social carnivores. Where gray wolves (Canis lupus) are hunted by humans, for example, howling may make it easier for hunters to locate individuals and ultimately increase mortality. We hypothesized that a suite of factors would affect wolves’ responses to simulated howling. Specifically, we predicted that howling behavior would increase with (a) group size, (b) pup age, and (c) during crepuscular time periods and howling behavior would decrease (a) where wolves were harvested and (b) when it was hot or windy. Contrary to our prediction, larger groups did not respond as quickly to simulated wolf howls as smaller groups did and minimum and maximum daily temperatures were not good predictors of wolf howling response rates. Individuals in small litters of pups may have responded more quickly to howls than those in large litters because they are eager to seek safety from and have socialization with adults returning from foraging bouts. Although harvest did not appear to affect vocal communication by wolves, group size, pup age, time of day, wind, and number of howls emitted greatly affected wolves’ behavior and responses during howling surveys. Howling responses did not change because of harvest; response rates from wolves were nearly identical with (2.2%) and without (2.3%) harvest. The year‐round benefits of long‐distance vocal communication may outweigh the costs of increased mortality arising from howling during harvest season.

Reproductive and Pup Parameters of Female Wistar Rats (Rattusnorvegicus) Mated by Males Treated with Date Fruit Extract and Cypermethrin

The work was designed to study the effect on fertility and pup parameters of female Wistar rats mated to male Wistar rats that were treated with Date fruit extract and Cypermethrin. A total of 48 mature Wistar rats (Rattusnorvegicus) comprising of 24 males and 24 females were randomly distributed into four groups (I, II, III, and IV) of 12 animals per group of which six were males and six were females. The six males in groups I, II, III and IV received distilled water; Cypermethrin at 60mg/kg body weight; Date fruit extract (DFE) at 250 mg/kg body weight; and a mixture of Cypermethrin (60 mg/kg body weight) and DFE (250mg/kg body weight) respectively. Treatment was given once weekly per os for eight weeks after which treated males were mated with the females at a ratio of 1: 1. Conception and pregnancy rates; gestation length; litter size; litter weights at birth, day‐5, day‐10, day‐15 and day‐21 post‐partum; anogenital distance at day‐10; sex ratio and age of pup at hair growth were measured. Results showed that there were no significant differences (p&gt;0.05) in all parameters measured except sex ratio. More female than male offsprings were born to the Date fruit treated male groups. It was concluded that Cypermethrin at 60 mg/kg body weight did not alter the fertility of male Wistar rats while Date fruit extract at 250 mg/kg body weight favored the birth of more female off springs. Further investigation is required to unravel the potential of Date fruit extract in sex selection.

Efficiency of timed pregnancies in C57BL/6 and BALB/c mice by mating one male with up to four females.

For a wide range of biomedical approaches, an accurate estimate of the age of embryos or pups is important. Overnight mating is the method that is mostly used to establish timed pregnancies. The oestrus cycle in mice repeats every four to five days. So, not all females will get pregnant because they are not in oestrus. Therefore, the aim of this study was to analyse whether polygamous mating could increase the rate of timed pregnancies per breeding cage and female. We compared overnight timed mating regimes with up to four females per male, using C57BL/6 and BALB/c mice as well as F1 hybrids of these two strains. The number of vaginal plugs, number of females that gave birth and weaned litter (including size and weaning weight) were recorded. Our results showed that the plug and pregnancy rate decreased, but the productivity per breeding cage increased for polygamous mating regimes. The proportion of females with vaginal plugs and females that gave birth was significantly higher in monogamous mating. The proportion of plugged females that gave birth, as well as litter size and weaning weight, were not influenced by the mating regime. After analysing 513 breeding cages with a total of 1090 females, we found that polygamous mating with up to three females per male can increase the number of timed pregnancies. However, in the mating regime with more than three females, the rate of timed pregnancy as well as number of pups per female declined.

Prenatal intermittent hypoxia sensitizes the laryngeal chemoreflex, blocks serotoninergic shortening of the reflex, and reduces 5-HT3 receptor binding in the NTS in anesthetized rat pups

We tested the hypothesis that exposure to intermittent hypoxia (IH) during pregnancy would prolong the laryngeal chemoreflex (LCR) and diminish the capacity of serotonin (5-hydroxytryptamine; 5-HT) to terminate the LCR. Prenatal exposure to IH was associated with significant prolongation of the LCR in younger, anesthetized, postnatal day (P) rat pups age P8 to P16 compared to control, room air (RA)-exposed rat pups of the same age. Serotonin microinjected into the NTS shortened the LCR in rat pups exposed to RA during gestation, but 5-HT failed to shorten the LCR in rat pups exposed to prenatal IH. Given these observations, we tested the hypothesis that prenatal hypoxia would decrease binding to 5-HT3 receptors in the nucleus of the solitary tract (NTS) where 5-HT acts to shorten the LCR. Serotonin 3 receptor binding was reduced in younger rat pups exposed to IH compared to control, RA-exposed rat pups in the age range P8 to P12. Serotonin 3 receptor binding was similar in older animals (P18-P24) regardless of gas exposure during gestation. The failure of the 5-HT injected into the NTS to shorten the LCR was correlated with a developmental decrease in 5-HT3 receptor binding in the NTS associated with exposure to prenatal IH. In summary, prenatal IH sensitized reflex apnea and blunted processes that terminate reflex apneas in neonatal rat pups, processes that are essential to prevent death following apneas such as those seen in babies who died of SIDS.

The neuroprotective role of melatonin in a gestational hypermethioninemia model

Elevated levels of methionine in blood characterize the hypermethioninemia, which may have genetic or non-genetic origin, as for example from high protein diet. Born rats from hypermethioninemic mothers presented cerebral oxidative stress, inhibition of Na+,K+-ATPase, memory deficit and ultrastructure cerebral changes. Melatonin is a hormone involved in circadian rhythm and has antioxidant effects. The aim of this study was to verify the possible neuroprotective effects of melatonin administration in hypermethioninemic pregnant rats on damage to biomolecules (Na+,K+-ATPase, sulfhydryl content and DNA damage index) and behavior (open field, novel object recognition and water maze tasks), as well as its effect on cells morphology by electron microscopy in offspring. Wistar female rats received methionine (2.68 μmol/g body weight) and/or melatonin (10 mg/kg body weight) by subcutaneous injections during entire pregnancy. Control rats received saline. Biochemical analyzes were performed at 21 and 30 days of life of offspring and behavioral analyzes were performed only at 30 days of age in male pups. Results showed that gestational hypermethioninemia diminished Na+,K+-ATPase activity and sulfhydryl content and increased DNA damage at 21 and 30 days of life. Melatonin was able to totally prevent Na+,K+-ATPase activity alteration at 21 days and partially prevent its alteration at 30 days of rats life. Melatonin was unable in to prevent sulfhydryl and DNA damage at two ages. It also improved DNA damage, but not at level of saline animals (controls). Regarding to behavioral tests, data showed that pups exposed to gestational hypermethioninemia decreased reference memory in water maze, spent more time to the center of the open field and did not differentiate the objects in the recognition test. Melatonin was able to prevent the deficit in novel object recognition task. Electron microscopy revealed ultrastructure alterations in neurons of hypermethioninemic at both ages of offspring, whose were prevented by melatonin. These findings suggest that melatonin may be a good neuroprotective to minimize the harmful effects of gestational hypermethioninemia on offspring.