Effects of lead and hyperthermia on prenatal brain growth of guinea pigs

The effects of lead at blood levels of 100 micrograms/100ml or less on the brains of young animals have not been clearly defined, and little is known of its effects and interactions with other agents on prenatal brain development. This study examined the effects of subclinical doses of lead acetate given to pregnant guinea pigs on the development of the embryo brain. At 9 A.M. on day 20 or 21 of pregnancy, guinea pigs were given 6, 12.5, or 25 mg/kg body weight of 0.5% lead acetate in distilled water by intraperitoneal injection. Some of the animals at each dose rate were also exposed to hyperthermia at 11 A.M. on the day of injection and the following day. Another group was exposed to hyperthermia without lead treatment. A saline-treated control group was used for comparison. Mean levels of lead in blood 1 hour after dosing ranged between 65 and 128 micrograms/100 ml and at 24 and 72 hours between 65 and 96 micrograms/100 ml. Brain weights of newborn guinea pigs in the 12.5- and 25-mg lead acetate group were significantly reduced compared with control values. Body weights of all groups receiving lead were not significantly different from those of controls. There was no indication of interaction between hyperthermia and lead acetate in doses of 6 or 12.5 mg/kg. At 25 mg/kg plus hyperthermia, there appeared to be a strong synergistic response, with an incidence of 88% micrencephaly compared with 5% in the group given 25 mg/kg without hyperthermia and 46% in the hyperthermia without lead group.(ABSTRACT TRUNCATED AT 250 WORDS)     

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.     

Influence of prenatal malnutrition on later body-weight gain in guinea pigs]

In prenatally underfed guinea pigs the following data were obtained: 1. On the 1st day of life the mean body weight of 18 underfed animals was significantly reduced as compared to that of 18 control animals. This difference was not compensated by postnatal feeding ad libitum but persisted up to the 36th week of life (day of sacrificing). 2. The mean food intake per day estimated over 10 days during the 5th month of life was also significantly diminished in the prenatally underfed animals. 3. A significant positive correlation was found between the body weight at birth and the adult body weight, adult body length and adult body weight/body length, when the parameters of the experimental plus control animals were evaluated together. These findings suggest that in guinea pigs, which are born in a relatively mature stage, the prenatal nutrition can influence body weight, body length and body weight/body length ratio as well as food intake in adulthood.     

Effects of growth and maturation on biliary structures of guinea pigs

The biliary system and major duodenal papilla of male guinea pigs were examined in vivo using intravital microscopy. Study of the photomicrographs and videotape recordings indicated that biliary organs changed with age and growth of the guinea pigs. Physiological data including the frequency of sphincteric contractions were recorded and efforts were made to correlate these data with changes in structure thought to be due to maturation. The volume of smooth muscle in the bile duct sphincter (measured using histological sections) increased with age as did surface area of the mucosa. The bile duct was separate from the pancreatic duct in each of 28 guinea pigs. Study of the guinea pig extrahepatic biliary system (EBS) allowed the isolated examination of effects of maturation on bile duct capacity. The anatomical reason for this is that the ampulla of the bile duct emptied into the duodenum (independently of the pancreatic duct) at the major duodenal papilla. The duct of the pancreas entered the duodenum distally (caudally) to the major duodenal papilla on the minor duodenal papilla. The separation of biliary and pancreatic ducts simplified the making of casts of the EBS. It is important to consider this feature in selection of a model for studies of bile duct function in living animals. Three anatomical techniques were selected to focus from differing perspectives on growth-related changes that occurred among the EBS of neonatal, juvenile and adult animals. These techniques were: The capacity (volume) of bile contained within the EBS was determined using plastic casts of the system.(ABSTRACT TRUNCATED AT 250 WORDS)     

Lung mechanics, cellularity, and surfactant after prenatal starvation in guinea pigs

Prenatal starvation in the guinea pig causes reduced pulmonary diffusing capacity and retarded alveolarization among neonates. To study the impact of such starvation on biochemical and mechanical properties of the neonatal lung, pregnant guinea pigs were fed ad libitum throughout gestation or starved with 50% rations during their last trimester. Neonatal body weight was 35% less due to starvation, and dry lung weight, DNA, and protein contents were decreased 26, 36, and 31%, respectively (P less than 0.001 for all). Hematological data indicated no anemia, hypoproteinemia, or altered glucocorticoid levels due to starvation. Total surfactant phospholipids in these neonates were reduced 61% in lavage and 35% in the neonatal lung tissue, although surfactant compositions were similar to controls. Specific lung compliance in the air-filled lungs was not altered, but the saline-filled lungs were more distensible over deflation pressures of 9-18 cmH2O (transpulmonary). Although starvation retarded both lung cellularity and surfactant, only that portion of lung elastic recoil attributable to tissue forces was affected.     

Sex-specific effects of dietary fatty acids on saliva cortisol and social behavior in guinea pigs under different social environmental conditions

Background

Unbalanced dietary intakes of saturated (SFAs) and polyunsaturated (PUFAs) fatty acids can profoundly influence the hypothalamic-pituitary-adrenal (HPA)-axis and glucocorticoid secretions in relation to behavioral performances. The beneficial effects of higher dietary PUFA intakes and PUFA:SFA ratios may also affect social interactions and social-living per se, where adequate physiological and behavioral responses are essential to cope with unstable social environmental conditions.

Methods

Effects of diets high in PUFAs or SFAs and a control diet were investigated in male and female guinea pigs after 60 days of supplementation. Plasma fatty acid patterns served as an indicator of the general fatty acid status. HPA-axis activities, determined by measuring saliva cortisol concentrations, social behaviors, and hierarchy ranks were analyzed during group housing of established single-sexed groups and during challenging social confrontations with unfamiliar individuals of the other groups.

Results

The plasma PUFA:SFA ratio was highest in PUFA supplemented animals, with female levels significantly exceeding males, and lowest in SFA animals. SFA males and females showed increased saliva cortisol levels and decreased aggressiveness during group housing, while sociopositive behaviors were lowest in PUFA males. Males generally showed higher cortisol increases in response to the challenging social confrontations with unfamiliar individuals than females. While increasing cortisol concentrations were detected in control and PUFA animals, no such effect was found in SFA animals. During social confrontations, PUFA males showed higher levels of agonistic and sociopositive behaviors and also gained higher dominance ranks among males, which was not detected for females.

Conclusions

While SFAs seemingly impaired cortisol responses and social behaviors, PUFAs enabled adequate behavioral responses in male individuals under stressful new social environmental conditions. This sex-specific effect was possibly related to a general sex difference in the n-3 PUFA bioavailability and cortisol responses, which may indicate that males are more susceptible to changing environmental conditions, and shows how dietary fatty acids can shape social systems.

     

Sex-specific effects of hybridization on reproductive fitness in Mytilus

Blue mussels of the genus Mytilus form extensive hybrid zones in the North Atlantic and elsewhere where the distributions of different species overlap. Mytilus species transmit both maternal and paternal mtDNA through egg and sperm, respectively, a process known as doubly uniparental inheritance (DUI), and some females produce offspring with extremely biased sex ratios. These two traits have been shown to be linked and maternally controlled, with sex determination involving nuclear–cytoplasmic interactions. Hybridization has been shown to disrupt DUI mitochondrial inheritance and sex ratio bias; however, the effect of hybridization on reproductive fitness has not previously been examined. We investigated this effect in M. edulis × M. trossulus crosses through histological examination of mature F1 progeny, and spawning of F1 hybrids to monitor survival of their progeny through to the D stage of larval development. For progeny produced from mothers with a strong bias toward female offspring (often 100%) in pure-bred crosses, there was a clear breakdown in female dominance of progeny and significantly more hermaphrodites in the hybrid crosses produced from sperm with the M-tr1 mitotype. We also found significant sex-specific differences among hybrid progeny, with females producing normal eggs while males and hermaphrodites evidenced impaired gonadal development with significantly greater numbers of Sertoli cells, phagocytic hemocytes, and degenerating germ cells, all associated with gonad resorption. Males from crosses where DUI was disrupted and where male progeny were homoplasmic for the female mtDNA were the most severely compromised. Allelic incongruity between maternal and paternal mitotypes in hybrid crosses was associated with significant disruption of male gonadal development.     

Effects of intracranial implants of dihydrotestosterone on the reproductive physiology and behavior of male guinea pigs

An experiment was conducted to determine whether the intracranial application of dihydrotestosterone (DHT), a nonaromatizable androgen, would stimulate male guinea pig mating. Of three castrate groups studied, one was a control group in which subjects were implanted both in the medial preoptic area (MPOA) and under the skin with cannulae containing cholesterol (NoDHT). Males in one of the experimental groups received implants of cholesterol in the MPOA plus subcutaneous implants containing DHT (ScDHT). Members of the other experimental group were subcutaneously implanted with cholesterol and simultaneously given intracranial implants of DHT (IcDHT). Compared to either the NoDHT control group of the ScDHT experimental group, greater numbers of males in the IcDHT group displayed mounts (P less than 0.01), intromissions (P less than 0.01), and ejaculations (P less than 0.001). Additionally, the hypothalamic implants of DHT had no significant effects on peripheral target tissues. These data indicate that androgenic stimulation of the guinea pig brain is sufficient to activate masculine sexual behavior in this species.     

Sex-specific, behavior-specific actions of dihydrotestosterone: Activation of aggression, but not mounting in ovariectomized guinea pigs

Adult ovariectomized guinea pigs were tested for aggressive behavior during treatments with estradiol benzoate (EB), testosterone propionate (TP), dihydrotestosterone propionate (DHTP), or with DHTP + EB. Aggression was not influenced by EB, but was augmented by all other steroid treatments. DHTP given by itself was not as effective as TP, but was significantly potentiated by the concurrent administration of EB. When tested for mounting behavior, ovariectomized guinea pigs were refractory to DHTP and to DHTP + EB, whereas they mounted when given TP. The findings suggest that the hormone-sensitive neural systems which mediate aggression in female guinea pigs have in part different steroid requirements from those subserving the activation of mounting. In addition, the findings emphasize that DHTP + EB administration does not always duplicate the effects of TP for behavioral endpoints, since DHTP + EB and TP had similar effects on aggression, but quite different effects on mounting in female guinea pigs. These results stand in contrast to those obtained with male guinea pigs, in which DHTP has been reported to be as effective as TP for the activation of mounting. It is hypothesized that both sex-specific and hormone-specific activational phenomena may be genetically regulated by factors separate from those responsible for the establishment of prenatal hormonal conditions.     

Fasting stress exacerbates classical conditioned histamine release in guinea pigs

To clarify the contribution of stress to classical conditioning-associated asthmatic responses, the effect of fasting stress on conditioned histamine release was investigated in a guinea pig model of asthma. The animals were randomly divided into 2 groups for Experiment 1 and 2, and received a conditioning procedure in which ovalbumin (OA) as an unconditioned stimulus (US) and dimethylsulfide (DMS, sulfur smelling) as a conditioned stimulus (CS) were simultaneously inhaled after fasting for 16 h. Then, one group was given food as a reward for respiratory distress, and the other group was denied it for more than 3 h, while being placed in front of the feeding group. After this procedure was repeated 5 times, the plasma histamine levels in response to the CS were measured in half of each group in Experiment 1, and the respiratory resistance (Rrs) was assessed similarly in the other half of each group in Experiment 2. The same experiments were again performed after exchanging assignments of feeding group or fasting group in both experiments. The control groups in both experiments received the CS and the US 10 times separately in a random order under 16 h fasting conditions and were provided food after the exposures. After these pseudo-conditioning presentations, the plasma histamine levels or the Rrs in response to the CS were measured. In Experiment 1, the plasma histamine levels in the fasting stress group after the first conditioning sessions were significantly higher than those of the other groups. This difference was not observed when the groups were exchanged. In Experiment 2, the fasting stress group showed higher values in the Rrs compared to the other groups, irrespective of the first or second conditionings; however, they were not significant. The present study indicates that fasting stress after the conditioning procedures exacerbates the following conditioned histamine release, although the stress effect on bronchoconstriction was not confirmed.     

短波长单色光对豚鼠眼屈光发育的影响

目的研究短波长单色光对豚鼠的屈光发育和眼生物学参数的影响。方法 20只出生约2周的健康雄性豚鼠,随机分成两组（n=10）,分别在蓝光（430 nm）和白光（色温5000 K）下进行饲养。蓝光组为实验组,白光组为对照组,实验周期为12周。两种光照的光量子数均为每秒3×10-4μmol/cm2,测量光强度蓝光为0.527mW/cm2,白光为0.247 mW/cm2。实验前后均进行屈光度、角膜曲率、眼轴各部分长度的测量。结果实验前两组测量参数差异无显著性（P〉0.05）。光照12周后,蓝光组屈光度增加（1.20±0.66）D,白光组减少（1.18±0.85）D,蓝光组与白光组相比平均形成约2.40 D远视,统计学差异显著（P〈0.0001）;蓝光组眼轴和玻璃体腔分别增长（0.77±0.12）mm与（0.05±0.10）mm,白光组分别增长（0.95±0.18）mm与（0.21±0.13）mm。蓝光组的眼轴和玻璃体腔长度增长较白光组慢（P〈0.05）。但实验后两组角膜曲率半径、前房深度和晶状体厚度的变化差异无显著性（P〉0.05）。结论 430 nm短波长单色光诱导豚鼠眼轴和玻璃体腔长度延长较慢,产生远视。     

Combined effect of ascorbic acid and selenium supplementation on alcohol-induced oxidative stress in guinea pigs

Oxidative stress is a key step in the pathogenesis of ethanol associated liver injury. Ethanol administration induces an increase in lipid peroxidation either by enhancing the production of oxygen reactive species or by decreasing the level of endogenous antioxidants. In this present study, four groups of male guinea pigs (Cavia porcellus) were maintained for 45 days as follows: Control group (1 mg ascorbic acid (AA)/100 g body wt./day); Ethanol group (1 mg AA/100 g body wt./day+900 mg ethanol/100 g body wt./day); Selenium+AA group (25 mg AA+0.05 mg sodium selenite/100 g body wt./day); Ethanol+Se+AA group (25 mg AA+0.05 mg sodium selenite/100 g body wt.+900 mg ethanol/100 g body wt./day). Malondialehyde (MDA), hydroperoxides (HP) and conjugated dienes (CD) were significantly increased, while the activities of scavenging enzymes superoxide dismutase (SOD) and catalase were reduced in the alcohol administered groups. Co-administration of Se+AA along with alcohol increased the activities of scavenging enzymes and reduced the lipid peroxidation products level in hepatic tissues of guinea pigs. Activities of glutathione peroxidase (GPX) and glutathione reductase (GR) were enhanced in co-administered group. gamma-Glutamyl transpeptidase (GGT), a marker enzyme of alcohol induced toxicity, was also reduced, as was the glutathione content. This study suggests that the combined effect of Se+AA, provides protection against alcohol-induced oxidative stress as evidenced from the decreased levels of lipid peroxidation products and enhanced activities of scavenging enzymes.