Behavior and serotonergic disorders in rats exposed prenatally to valproate: A model for autism

In order to explore whether some aspects of the autistic phenotype could be related to impairment of the serotonergic system, we chose an animal model which mimics a potential cause of autism, i.e. rats exposed to valproate (VPA) on the 9th embryonic day (E9). Previous studies have suggested that VPA exposure in rats at E9 caused a dramatic shift in the distribution of serotonergic neurons on postnatal day 50 (PND50). Behavioral studies have also been performed but on rats that were exposed to VPA later (E12.5). Our aim was to test whether VPA exposure at E9 induces comparable behavioral impairments than at E12.5 and causes serotonergic impairments which could be related to behavioral modifications. The results showed significant behavioral impairments such as a lower tendency to initiate social interactions and hyperlocomotor activity in juvenile male rats. The serotonin levels of these animals at PND50 were decreased (−46%) in the hippocampus, a structure involved in social behavior. This study suggests that VPA could have a direct or indirect action on the serotonergic system as early as the progenitor cell stage. Early embryonic exposure to VPA in rats provides a good model for several specific aspects of autism and should help to continue to explore pathophysiological hypotheses.     

Effect of the hydra peptide morphogen on posthypoxic disorders in rats exposed to prenatal hypoxia

Lipid peroxidation in the lungs and blood are activated while DNA synthesis in the tracheal epithelium and hepatocytes is inhibited during the first five days of postnatal life in rat pups after severe prenatal hypoxia. Intraperitoneal injection of the undecapeptide pGlu-Pro-Pro-Glu-Glu-Ser-Lys-Val-Ile-Leu-Phe, a peptide morphogen isolated from the hydra, before hypoxia normalizes lipid peroxidation in the lungs and blood of the five-day-old pups. A compensatory activation of DNA synthesis occurs in tracheal epithelium and hepatocytes. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 123, No. 3, pp. 269–272, March, 1997.     

Developmental patterns of macronutrient intake in female and male rats from weaning to maturity

Male and female Sprague-Dawley rats had available pure macronutrient diets, protein, carbohydrate and fat, from birth to day 77 of age. Analyses of their intake of these nitrients, as a function of age, demonstrate that, in both sexes, daily protein intake and preference for this nutrient relative to the other macronutrients rise steadily from weaning and peak precisely at the time of puberty (day 37–44 for females and days 42–49 for males), when there is also a peak in body weight gain. This is in contrast to daily carbohydrate intake, which peaks 2 weeks after puberty in males, and also to the female and male rats' preference for carbohydrate, which remains relatively stable from weaning to maturity. These patterns also differ from those observed for daily fat intake and fat preference for females and males, which are relatively high during the first postweaning week and then decline and remain very low until shortly after puberty (day 54), when there occurs a sharp burst in fat intake. Comparisons between the females and males reveal a significantly stronger preference for carbohydrate in the females, exhibited as early as 23 days of age; a stronger preference for protein and fat in the males, evident after day 28; and greater light-period feeding of carbohydrate and fat by females compared to males, apparent after puberty. Correlational analyses demonstrate that body weight and total kcal intake are closely related to daily protein consumption, more strongly in females compared to males; are strongly related to daily fat intake only in males; and are unrelated to intake of carbohydrate, at any age and in either sex.     

Preferential nesting in lemon-scented environment in rats reared on lemon-scented bedding from birth to weaning

Newborn rats (males and females) were reared on lemon scented shavings from birth to weaning. The experienced rats (111 animals) and their controls (135 animals) were tested for lemon odor preference at 21, 51, 81, 111 and 141 days of age. The test box consisted of two preference chambers, containing wood shavings, interconnected by a starting compartment. Shavings of one of the preference chambers were sprinkled with natural lemon juice. The preference ratio was obtained on the basis of the chamber selected for nesting. The results clearly show that (1) sex differences occur in both experienced and control groups of rats and (2) rats reared on lemon scented bedding from birth to weaning acquire a permanent preference for nesting in the lemon scented chamber. The results are consistent with the hypothesis that an imprinting-like process takes place.     

Biomechanical properties of femoral shafts and bone tissue in protein-malnourished rats from weaning to adulthood

The present study was designed to estimate the bone biomechanical repercussion of protein restriction imposed to rats between the 26th and the 135th days of age. Female rats were placed on either a 4% (P4) or 20% (P20) protein diets. Body weight at the end of the study was 350.5?g (SD?31.0?g) in P20 rats and 87.5?g (19.4?g) in P4 ones. Femur weight and length were significantly reduced. The diaphyseal cross-sectional area and the cross-sectional moment of inertia were also diminished. Femoral calcium concentrations in ashes were similar in both groups. However, the femoral mass (calcium mass) was significantly lower in P4 than in P20 rats. When the femoral bone mass was normalized per 100-g femur, no significant difference between groups was found. The right femur of each animal was subjected to a three-point bending test in order to obtain the load/deformation curve. A significant weakening of bone beams, shown by a correlative impairment of diaphyseal ultimate strength and stiffness, was observed in P4 rats. However, when their values were normalized for body weight, the differences disappeared. The bone material quality indicators, or pre-yield bending stiffness (elastic modulus) and yielding stress were similar in P4 and P20 rats. In summary, we have described a number of alterations in bone morphometrical and biomechanical variables in rat femur shafts resulting from protein restriction from weaning to early adulthood. The clear differences in strength and stiffness of bone beams seemed to be the result of an induced subnormal gain in bone structural properties as a consequence of a correlative subnormal gain in bone growth and mass, yet not in bone material properties.     

Contribution of self-grooming to onset of puberty in male rats

Self-grooming was observed to increase during the prepubertal period of Long-Evans rats. Males were significantly more likely than females to engage in genital grooming during this period. To determine whether self-grooming contributes to the onset of puberty, males were fitted with collars that either prevented or allowed self-grooming of hindquarters or were left uncollared from 27 to 48 or 55 days of age when autopsied to determine weight of accessory organs. Ventral, dorsal, and lateral prostates and seminal vesicles were significantly lighter in those rats wearing collars that prevented self-grooming. It was concluded that self-grooming, probably of the genitals, contributes to accessory organ growth in males of this species.     

Early weaning predisposes rats to exacerbated activity-stress ulcer formation

Rats were weaned early (Day 15), normally (Day 21) or late (Day 27). When they reached 200 g (+/- 10) they were placed into the activity-stress paradigm. Half the rats in each weaning group were housed in activity-wheel cages and fed only 1 hr each day. The remaining rats served as food-yoked home cage controls and were fed only that amount of food eaten by their wheel-housed partners. Early weaned rats ran more than normally or late weaned animals. Early weaned rats also died at a faster rate and exhibited a significantly greater cumulative ulcer length than did normally or late weaned rats, although ulcer incidence did not differ between the groups. No ulcers occurred in home cage control rats. Early maternal deprivation may generally predispose rats to stress-induced gastrointestinal disease, whether or not such disease has an acid etiology.     

Wistar rats allowed to self-select macronutrients from weaning to maturity choose a high-protein,high-lipid diet

The aim of this work was to study the evolution of rat food choice in relation to their age and metabolic parameters. Eighty Wistar rats were studied from birth to 13 weeks of age. At weaning, six litters were fed on a macronutrient self-selecting diet and four on a standard diet. In self-selecting males, protein intake was maximal at Week 7 of age and then plateaued (Week 13), whereas in females, protein consumption peaked at Week 7 and then steadily decreased. Females showed a strong and early preference for fat, which increased continuously with age. Males and females ingested their total energy intake during the dark period (respectively, 79% and 70%). Simple meals (composed of one item) were mainly ingested during the light phase, while mixed meals (at least two items) were ingested during the night. In males, most mixed meals began with carbohydrate bouts and finished with proteins, while in females no particular choice was observed at the beginning of meals, but most of them ended with protein bouts. Body weights of either male and female self-selecting or control fed rats were not significantly different at the end of the experiment. Differences between dietary groups in body fat mass were not observed with the exception of higher subcutaneous fat found in self-selecting rats. Moreover, insulinemia was lower in both male and female self-selecting rats. The high-protein, high-fat diet chosen by the self-selecting rats could be linked to a prevention of the age-related insulin resistance.     

Effect of gossypol on the thyroid in young rats

The effect of gossypol on thyroid structure and function was examined. Groups of young male rats were subcutaneously injected daily with 0.2 ml gossypol acetic acid in doses of 1, 5, or 10 mg per kg body weight. Control rats were injected with vehicle only. At the end of the 15-day treatment, there was a dose-dependent decrease in the serum concentrations of thyroid hormones, i.e., free thyroxine, triiodothyronine, and reverse triiodothyronine. Histopathological examination revealed focal degeneration of thyroid follicles after a dose of 1 mg gossypol per kg body weight; widespread follicular atrophy occurred with 5 mg and 10 mg gossypol per kg body weight. The degenerating follicles were lined with discontinuous cuboidal or squamous follicular epithelium, some of which exfoliated into colloid.     

Newly exposed immunochemically cross-reactive epitopes in sperm-specific LDH after glucosylation and gossypol interaction

PROBLEM: In a previous study, mouse lactate dehydrogenase-C4 (LDH-C4) after chemical modifications with gossypol (Gossy-LDH-C4) and glucosylation with lactose (Glu-LDH-C4) was found to induce high immunological infertility in allogenic mice. In the present study, the characterization of antibodies and cross reactivity of the antisera produced against Gossy- and Glu-LDH-C4 with purified somatic isozymes are being reported. METHODS: Allo-antisera generated in Balb/c mice (i.r. route) against one primary (50 microg) and two secondary doses (30 x 2 microg) in Al(OH)3 were tested for cross-reactivity by ELISA and antibody avidity using Scatchard plot and Sip's plot. RESULTS: Results suggested that IgG against native LDH-C4 failed to recognize somatic isozyme, while antisera against chemically modified LDH-C4 consistently reacted with purified LDH from kidney and placenta. Scatchard plots and antibody saturation curves of native and complexed LDH supported the presence of heterogenous antibodies with a mean association constant (Ka) of the order of 10(6)-10(7) M(-1), whereas diversity of heterogeneity, defined by diversity constant (a), ranged between 0.89 and 1.23. In general, anti-Glu-LDH-C4 antiserum and native LDH-C4. reacted with higher Ka (low affinity) with a diversity constant of 0.89 compared with interaction between native LDH-C4 and it's antibodies. CONCLUSIONS: It is concluded that LDH-C4 is not an immunochemically sperm-specific protein, in which crossreactive epitopes are hidden within its conformation. Due to the large intake of cotton seed (a source of gossypol) by cattle, its unrefined oil by humans in various parts of the world, and the prevelance of diabetic state all the world over, the present study warns of immunological consequences in situ following gossypol interaction and glucosylation of LDH and conformationally related proteins in circulation.     

Cardiovascular defects in rat embryos cultured on serum from rats chronically exposed to phenytoin

Headfold-stage rat embryos were cultured for 48 hours on serum from rats chronically exposed to phenytoin for periods as long as from conception until 11 months of age. Serum from phenytoin-exposed rats caused approximately 50% of the cultured rat embryos to develop cardiovascular defects as compared to 12% for controls. These morphological abnormalities included hemorrhaging of blood vessels within the embryo, pericardial edema, and absence of yolk sac circulation. Neither serum glucose nor phosphate levels nor serum osmolality were appreciably affected by phenytoin treatment. However, serum protein concentration was reduced in rats exposed to phenytoin as compared to controls. An absence of the serum protein hemopexin was associated with the reduction in serum protein levels but did not appear to be responsible for the observed cardiovascular defects.     

Thermoregulatory behavior in rat pups from birth to weaning

One–19 day old rat pups were placed individually in a thermal gradient (floor temperatures 17–45°C) at either 45°, 30°, or 20°C. From the first day of life, pups placed at 45° or 30°C and given sufficient time (up to 2 hrs) oriented and moved along the gradient to an area of moderate temperatures (35°–40°C). The pups regulated their body temperatures by remaining in appropriate positions in the gradient. Most pups under a week old were immobilized when placed in the cold area. During the next two weeks, pups placed at 20°C moved up the gradient to the 35°–40°C area. Response latency was related to both starting temperature and age. Observations of the pups' behavior in different temperatures are discussed.     

Mesenteric lymph nodes in rats exposed to emotional stress

Structural and functional peculiarities of mesenteric lymph nodes were studied in 40 stressed August rats using micro anatomical methods. The stress was induced by limitation of any movement for 5 hrs every day. Peculiarities and intensity of modifications demonstrated was dependent on duration of stress actions. Significant decrease of cortical substance area, its lymphoid nodules length and width and germinal centre area, fraction of large, medium and small lymphocytes was observed following 5 hrs of the experiment, which was combined with expansion of the area, occupied by medullar substance. On the 2nd d of 5 hrs experiment cortical substance area was widened (on histological section), the number and sizes of lymphoid nodules grew up and lymphoid nodules appeared in medullar bands. On the 3rd experimental day mesenteric lymph node structure gradually restored. It showed control values on the 6th experimental day.     

Increased cardiac contractility in rats exposed to 5 bar

The left ventricular pressure, arterial blood pressure and heart rate were studied in three series of pentobarbital-anaesthetized rats exposed to 5-bar normoxic (PO2 = 0.2 bar) environments: nitrogen-oxygen (15 and 60 min) and helium-oxygen (15 min). The maximal left ventricular pressure (LVP max) and the maximal velocities of LVP rise (+ dP/dt max) and fall (- dP/dt) were significantly (P less than 0.01) increased immediately after reaching normoxic 5 bar (He, 13-28%; N2, 13-23%) and during the exposure at 5 bar (He, 22-44%; N2, 13-18%). The pulse pressure increased significantly (He, 50-62%; N2, 30-34%; P less than 0.01) during the hyperbaric exposure. No changes in heart rate or end-diastolic and mean arterial pressure were detected. The present findings indicate an enhanced cardiac contractility (+ dP/dt max) at 5 bar, with the greatest increase found when He was used as inert gas. The increased contractility was of significant duration (at least 60 min), and was not completely reversed until 5-10 min after decompression.