Factor analysis of rat behavior in the open-field test

Method of major components, a variety of factor analysis, was used for evaluation of rats behaviour motivational structure in the open field test. 40 outbred rats of Wistar line (20 males and females) were examined in which 22 behaviour characteristics were studied. It was shown that a greater part (60%) of rats individual behaviour variability in the open field test was determined by the action of three major components (factors), which were defined as "investigation", "fear" and "shifted activity". Factor structure was studied of main characteristics of behaviour, recorded in the open field test. The use of factor analysis allowed to carry out animals classification on the basis of their disposition in coordinates of the obtained major components.     

Ovarian hormones,copulatory stimuli,and female sexual behavior in the Mongolian gerbil

The effects of repeated estradiol benzoate (1.0 or 3.3 μg) and progesterone (0.5 mg) injections and mating experiences (10 min or 4 hr) were examined in ovariec-tomized female Mongolian gerbils (Meriones unguiculatus) paired with sexually vigorous but unfamiliar males. Estradiol benzoate alone for 2 days did not elicit female sexual responses. Estradiol benzoate for 2 days followed by progesterone facilitated lordosis in the female. In females injected daily with 1.0 μg estradiol benzoate, progesterone exposure for approximately 1 day produced a significant inhibition in subsequent lordosis, although these females continued to respond to the male with lordosis quotients of approximately 60. A 4-hr mating experience produced a nearly complete elimination of sexual activity in tests observed 24 hr later with a fresh male. Footstomping was positively associated with sexual activity in both sexes, although females footstomped more often in the 1.0 rather than the 3.3-μg estradiol benzoate condition. Fighting was most frequent in tests in which lordosis quotients were low. Interactions among copulatory experiences and inhibitory effects of progesterone summed to terminate female sexual receptivity and alter other social interactions in the gerbil.     

Differential effects of testosterone metabolites in the neonatal period on open-field behavior and lordosis in the rat

Two experiments were done to compare the effects of neonatal exposure to testosterone and its major metabolites, dihydrotestosterone (DHT) and estradiol (E₂), on the development of sex differences in open-field behavior in the rat. In Experiment 1 female rats administered either testosterone propionate (TP), DHT, or estradiol benzoate (EB) were found as adults to have low activity scores, more typical of adult males, when compared to the high scores of oil-treated females. In Experiment 2 the adult open-field behavior of female rats treated neonatally with testosterone or the metabolites was compared to that of male rats treated from Day 1 to 10 of life with the aromatizing enzyme inhibitor, androst-1,4,6-triene-3,17-dione (ATD). These same animals were later tested for lordotic behavior after gonadectomy and priming with EB and progesterone. All male animals and female animals exposed neonatally to testosterone or to either of the metabolites had suppressed open-field activity scores compared to oil-treated females. However, the lordotic behavior of females exposed to DHT and of males exposed to ATD was not defeminized and was comparable to that of oil-treated females. These observations were discussed in terms of a role for the androgenic actions of testosterone in establishing sex differences in nonreproductive behavior in the rat.     

Ovarian hormones inhibit the release of prostacyclin-like material from isolated rat uterus

The influence of sex steroids on the production of prostacyclin (PGI₂) like material by the isolated rat uterus incubated in a buffer medium was explored by monitoring its ability to inhibit ADP-induced platelet aggregation. Chopped uterine strips from rats in natural estrus can generate an unstable substance that inhibits platelet aggregation and suggest to be prostacyclin. This capacity was significantly enhanced in preparations from spayed animals. The injection of 17-beta estradiol; progesterone or both diminished the production of the prostacyclin-like material by the uterus from ovariectomized rats. The already existing notion that ovarian steroids are able to regulate the synthesis of stable prostaglandins is discussed together with the present results suggesting in addition a depressive effect of sex hormones on the uterine PGI₂ synthetase system.     

tip genes act in parallel pathways of early Dictyostelium development

Analysis of Dictyostelium strains carrying null mutations in tipA showed a primary defect in cell sorting and the formation of tips on the developing mound. To study the process affected in tipA^– mutants further, other mutants with a similar phenotype were isolated and characterized. These studies showed three new Dictyostelium genes: tipB, tipC, and tipD. All the tip mutants aggregate into larger than average mounds, which split up and form many tips on their surfaces. Furthermore, each mutant exhibits reduced or aberrant cell‐sorting behavior, never makes migrating slugs, and has severely reduced fruiting body and spore production. The mRNA of each tip gene is present in vegetative cells and does not vary significantly with development. Prespore and prestalk gene expression is reduced or delayed in the tip mutants indicating cell type differentiation is dependent on the function of these genes. Developing mutant cells in chimeric mixtures with wild‐type cells demonstrated that the defects in each tip mutant behave cell autonomously. The overexpression of TipA in a tipB^– background and the overexpression of TipB in a tipA^– background significantly improved the morphogenesis of these mutants. These were the only situations in which the expression of one tip gene could compensate for the lack of a different tip gene. Except for the tipA^–/tipB^– strain, double mutations in the tip genes have additive effects, causing a more severe mutant phenotype with defects earlier in development than single mutants. The tipA^–/tipB^– double mutant does not show additive effects and is very similar to the tipA^– single mutant. Analysis of the effects of double mutations and overexpression indicates that members of this class of genes appear to act through parallel pathways of differentiation and tip formation in early Dictyostelium development. Furthermore, TipA and TipB appear to have some overlapping functions or are involved in the same pathway. The multitipped phenotype observed in all the mutants may be a general result of perturbing early developmental events such as cell type differentiation and cell type proportioning. Dev. Genet. 25:64–77, 1999. © 1999 Wiley‐Liss, Inc.     

Darkness during early postnatal development is required for normal circadian patterns in the adult rat

Early light experience influences the brain during development. Perinatal light exposure has an important effect on the development of the circadian system, although the role of quantity versus quality of light in this process is still unclear. We tested the development of the circadian rhythm of locomotor activity under constant bright light from the day of weaning, of six groups of rats raised under different light conditions during suckling. Results indicated that when rats received daily darkness during suckling (rats reared under constant darkness or light-dark cycles with dim or bright light) became arrhythmic when exposed to continuous bright light after weaning. However, those rats reared in the absence of darkness (constant dim or bright light, or alternating dim and bright light) developed a circadian rhythm, which was stronger and had a shorter period depending on the quantity of light received during suckling. Vasointestinal polypeptide immunoreactivity in the suprachiasmatic nucleus (SCN) was higher in those rats with weaker rhythms. However, no apparent differences among these groups were found in the melanopsin-expressing retinal ganglion cells, which provide the SCN with light input in the photoentrainment process. When bright light was shifted to dim light in three of the groups on day 57 after weaning, all of them generated a circadian rhythm with a longer period in those rats previously arrhythmic. Our results indicate the importance of the amount of light received at the early stages of life in the development of the circadian system and suggest that darkness is needed for the normal development of circadian behaviour.     

Ovarian response to exogenous hormones in six-week-old lambs.

Crossbred lambs 5--6 weeks old were treated with human chorionic gonadotrophin (hCG) (500 or 1500 i.u.) alone, hCG plus pregnant mare serum gonadotrophin (PMSG) (1000 or 2000 i.u.), 1000 i.u. PMSG alone, or were untreated. PMSG alone and PMSG + hCG increased ovarian weight and uterine weight. PMSG alone stimulated growth and luteinization of follicles but PMSG + hCG induced ovulations and formation of corpora lutea. hCG alone did not change any of the characteristics which were measured. PMSG had a significant effect on the number of vesicular follicles but none of the treatments affected the number of growing follicles.     

Thyroid hormones alter the adenine nucleotide hydrolysis in adult rat blood serum

The effects of ATP, ADP, and adenosine in the processes of platelet aggregation, vasodilatation, and coronary flow have been known for many years. The sequential hydrolysis of ATP to adenosine by soluble nucleotidases constitutes the main system for rapid inactivation of circulating adenine nucleotides. Thyroid disorders affect a number of biological factors including adenosine levels in different fractions. Then, we intend to investigate if the soluble nucleotidases responsible for the ATP, ADP, and AMP hydrolysis are affected by variations in the thyroid hormone levels in blood serum from adult rats. Hyperthyroidism was induced by daily intraperitoneal injections of L-thyroxine (T4) (2.5 and 10.0 μg/100 g body weight, respectively) for 7 or 14 days. Hypothyroidism was induced by thyroidectomy and methimazole (0.05%) added to their drinking water during 7 or 14 days. The treatments efficacy was confirmed by determination of hemodynamic parameters and cardiac hypertrophy evaluation. T4 treatment predominantly inhibited, and hypothyroidism (14 days after thyroidectomy) predominantly increased the ATP, ADP, and AMP hydrolysis in rat blood serum. These results suggest that both excess and deficiency of thyroid hormones can modulate the ATP diphosphohydrolase and 5'-nucleotidase activities in rat blood serum and consequently modulate the effects mediated by these enzymes and their products in vascular system.     

Ovarian hormones after postnatal day 20 reduce neuron number in the rat primary visual cortex

Previous work from our lab has documented a sex difference in neuron number in the binocular region of the adult rat primary visual cortex (Oc1B), with males having 19% more neurons than females. In the present study, the role of developmental steroid hormones in the formation of this difference was explored. Male and female rats underwent neonatal hormone manipulation (female + testosterone or dihydrotestosterone; male + flutamide) followed by gonadectomy on postnatal day 20. Animals that did not undergo hormone manipulation were either gonadectomized or sham operated at day 20. Neuron number was quantified in the monocular (Oc1M) and binocular (Oc1B) subfields of the adult rat primary visual cortex using the optical disector technique. As adults, day 20 gonadectomized females, as well as females + testosterone and females + dihydrotestosterone, had significantly more neurons than intact females. There was no difference in neuron number between postnatal day 20 gonadectomized males, males + flutamide, and intact males. Also, intact males had significantly more neurons than intact females in both in Oc1M and Oc1B. It appears that ovarian steroids after day 20 are the primary cause of the lower number of neurons in the primary visual cortex of the female rat.     

Individual typologic characteristics of the open-field behavior of rats

By means of ethograms record and analysis, connection has been studied between the properties of rats behaviour organization in the open field, determining the level of behaviour entropy in this test, and the speed of conditioned reflexes formation in the Skinner chamber. According to behaviour entropy level the rats are significantly divided into four groups; the lowest speed of conditioned reflexes formation in the Skinner's chamber is observed in the animals of the first (low entropy) group, the highest--in the fourth (high entropy) group. The obtained data are discussed according to Pavlov's concepts on the characteristics of the basic nervous processes, determining individual-typological characteristics of the higher nervous activity of the animal. Conclusion is made that division according to the level of behaviour entropy in the open field test may serve as a safe method of express-estimation of the animals abilities to conditioned habits formation.     

CHLOROPLAST BIOGENESIS genes act cell and noncell autonomously in early chloroplast development

In order to identify nuclear genes required for early chloroplast development, a collection of photosynthetic pigment mutants of Arabidopsis was assembled and screened for lines with extremely low levels of chlorophyll. Nine chloroplast biogenesis (clb) mutants that affect proplastid growth and thylakoid membrane formation and result in an albino seedling phenotype were identified. These mutations identify six new genes as well as a novel allele of cla1. clb mutants have less than 2% of wild-type chlorophyll levels, and little or no expression of nuclear and plastid-encoded genes required for chloroplast development and function. In all but one mutant, proplastids do not differentiate enough to form elongated stroma thylakoid membranes. Analysis of mutants during embryogenesis allows differentiation between CLB genes that act noncell autonomously, where partial maternal complementation of chloroplast development is observed in embryos, and those that act cell autonomously, where complementation during embryogenesis is not observed. Molecular characterization of the noncell autonomous clb4 mutant established that the CLB4 gene encodes for hydroxy-2-methyl-2-(E)-butenyl 4-diphosphate synthase (HDS), the next to the last enzyme of the methylerythritol 4-phosphate (MEP) pathway for the synthesis of plastidic isoprenoids. The noncell autonomous nature of the clb4 mutant suggests that products of the MEP pathway can travel between tissues, and provides in vivo evidence that some movement of MEP intermediates exists from the cytoplasm to the plastid. The isolation and characterization of clb mutants represents the first systematic study of genes required for early chloroplast development in Arabidopsis.     

Cholecystokinin tetrapeptide,proglumide and open-field behavior in rats

The effect of cholecystokinin tetrapeptide (CCK-4) was studied in an open field situation. CCK-4 increased locomotion and rearing and the effect was enhanced by proglumide, a selective antagonist of CCK-8. This is in sharp contrast to our earlier findings that CCK-8 decreased the open-field behavior and that proglumide completely blocked the effect. Thus, the effects of CCK-4 and CCK-8 appear to be opposite to each other in that one is excitatory and the other inhibitory to open-field responses.     

Functional development of oligodendrocytes and open-field behavior in developing rats: an approach using monoclonal antibody to immature oligodendrocytes.

To examine the relation between functional development of oligodendrocytes and open-field behavior during the postnatal period, a mouse monoclonal antibody termed 14F7, which predominantly labels stage-specific immature oligodendrocytes, was employed. Antibody 14F7 was administered intraperitoneally into male pups on day 3 and 4 after birth. The open-field test was performed on days 12 and 18 of the postnatal period. Horizontal activity increased remarkably with the growth of pups. On day 18, horizontal activity in the group with 14F7 was significantly higher than the control, while there was no significant difference between treatments on day 12. In contrast to the horizontal activity, the frequency of hind leg rearing, vertical activity, in the group with 14F7 was significantly lower than that in the control. On day 12, choline acetyltransferase (ChAT) and acetylcholinesterase (AChE) activities in the cerebral cortex were similar between the groups. These activities increased with the growth of pups in both groups. In the 14F7 group on day 18, ChAT activity was the same as the control, whereas AChE activity was significantly lower compared with the control. These results suggest that neonatal exposure to 14F7 induces abnormal neurotransmission by reducing the degradation of acetylcholine and alters the spontaneous activities in developing rats.     

Superovulation and early embryo development in the adult mouse after prenatal exposure to diethylstilboestrol

Pregnant mice were injected subcutaneously with diethylstilboestrol (DES: 10 micrograms/kg body weight in 0.1 ml corn oil) or corn oil alone on Day 15 or 16 of gestation (Day 1 = day of copulatory plug) and allowed to give birth. Female progeny from control and DES-exposed animals were superovulated with exogenous gonadotrophins at 6-8 weeks of age. In-vivo results indicated that the total number of ovulated ova, 2-cell embryos and blastocysts were significantly increased in DES-exposed progeny but that there was a decline in developmental potential from the ovulated ova stage to the blastocyst stage in these animals. However, there was no significant difference in the in-vitro development of 2-cell embryos to the blastocyst stage between control and DES-exposed animals. These results indicate that the ovaries of mice exposed in utero to DES are capable of responding to exogenous gonadotrophins and that second generation progeny have the potential for normal development to the early postblastocyst stage of embryogenesis. The in-vivo decline in developmental potential may be attributable to reproductive tract abnormalities rather than ova/embryo defects.     

Prenatal and early postnatal dietary sodium restriction sensitizes the adult rat to amphetamines

Acute sodium deficiency sensitizes adult rats to psychomotor effects of amphetamine. This study determined whether prenatal and early life manipulation of dietary sodium sensitized adult offspring to psychomotor effects of amphetamine (1 or 3 mg/kg ip) in two strains of rats. Wistar-Kyoto (WKY) and spontaneously hypertensive (SHR) dams were fed chow containing low NaCl (0.12%; LN), normal NaCl (1%; NN), or high NaCl (4%; HN) throughout breeding, gestation, and lactation. Male offspring were maintained on the test diet for an additional 3 wk postweaning and then fed standard chow thereafter until testing began. Overall, blood pressure (BP), total fluid intake, salt preference, and adrenal gland weight were greater in SHR than in WKY. WKY LN offspring had greater water intake and adrenal gland weight than did WKY NN and HN offspring, whereas WKY HN offspring had increased BP, salt intake, and salt preference compared with other WKY offspring. SHR HN offspring also had increased BP compared with other SHR offspring; all other measures were similar for SHR offspring. The low-dose amphetamine increased locomotor and stereotypical behavior compared with baseline and saline injection in both WKY and SHR offspring. Dietary sodium history affected the rats' psychomotor response to the higher dose of amphetamine. Injections of 3 mg/kg amphetamine in both strains produced significantly more behavioral activity in the LN offspring than in NN and HN offspring. These results show that early life experience with low-sodium diets produce long-term changes in adult rats' behavioral responses to amphetamine.