Effect of a single dose of some long-acting neuroleptics on the estrus cycle and the mammary gland of the rat]

The effects of two neuroleptics (pipotiazine and fluphenazine) and five long-acting neuroleptics (pipotiazine undecylenate and palmitate, fluphenazine enanthate and decanoate, fluopentixol decanoate) are tested in the rat, during an observation period of 20 to 40 days following only one injection of compound. The compounds administered at three different and non toxic doses, are showing effects, the intensity and duration of which are different according to the dose and the compound: diestrus of pseudo-gestation or more than 15 days, hypertrophy of mammary gland, decreasing of the uterine weight. Some long-acting neuroleptics are active during more than forty days.     

Evidence for a coupling of prolactin secretion and synthesis by rat pituitary cells in culture

The relationship between the release and the synthesis of prolactin by rat pituitary cells in culture was studied using a microtubule-disrupting drug, vinblastine. (1) Prolactin secretion was inhibited by vinblastine in short-term incubations. Vinblastine did not act via the dopamine pathway, since a potent anti-dopaminergic drug, fluphenazine, was unable to reverse the inhibiting action of the antimicrotubular agent. (2) Continuous treatment by vinblastine induced a progressive decrease of the rate of incorporation of [³H]leucine in prolactin. The half-inhibition time was about 2 days. This inhibition of prolactin synthesis was selective, since total protein synthesis remained unaffected. (3) Measurements of radioimmunoassayable prolactin showed that the inhibition of hormone release by vinblastine led to a transient increase of the intracellular content of prolactin. The phase of over-accumulation was followed by a progressive reduction of the total (cell + medium) prolactin. This result is in agreement with the observed inhibition of de novo synthesis of prolactin and indicates that a degradation process takes place in pituitary cells in culture. In conclusion, the use of vinblastine allows us to demonstrate that the rate of prolactin synthesis is dependent upon the secretory status of the cell.     

Calcium exerts an indirect effect on ATP-dependent proteolysis of rat liver mitochondria

The ATP-dependent proteolysis of rat liver mitochondria prepared in electrolyte-poor sucrose media requires the presence of Ca²⁺. Lanthanum, an inhibitor of Ca²⁺ uptake, inhibits the proteolysis. In contrast, proteolysis of mitochondria prepared in a salt medium does not require Ca²⁺, nor is it inhibited by lanthanum. It is concluded that Ca^a+ exerts its effect in an indirect manner, by causing swelling and thereby increasing the accessibility of the membrane proteins of the inner mitochondrial membrane.     

Protective effect of bilberry (Vaccinium myrtillus L.) on cisplatin induced ovarian damage in rat

Cisplatin is one of the most effective chemotherapeutic agents but injury may occur at higher doses. The aim of this study was to investigate the effect of bilberry on cisplatin induced toxic effects in rat ovary. Twenty-one female Wistar–Albino rats were utilized to form three groups: In group 1 (control group), each rat received intraperitoneal injection of 1 mL of 0.9 % NaCl saline solution during 10-days. In group 2 (cisplatin group), a single dose of 7.5 mg/kg b.w. cisplatin was given. In group 3 (cisplatin + bilberry group), a single dose of 7.5 mg/kg cisplatin and bilberry at 200 mg/kg b.w. were given for 10 days. Ovaries were surgically removed in all groups and prepared for biochemical and light microscopic investigations at the examination times. Malondialdehyde (MDA) levels and activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and glutathione-S-transferase (GST) of tissue samples were measured. Histopathological damages in cisplatin administrated rats were seen such as severe edema, vascular congestion, hemorrhage and follicular degeneration in the ovary tissue. Moderate pathological alterations were observed in rats treated with bilberry plus cisplatin. Cisplatin administration significantly increased MDA production and decreased SOD, CAT, GPx and GST activities in the ovarian tissue when compared to the control group (p < 0.05). Cisplatin + bilberry administration increased antioxidant enzymes activities and reduced MDA levels. Bilberry administration seems to reduce the cisplatin induced ovarian toxicity thus it alleviates free radical damage. But it dose not protect completely rat ovary tissues.     

The effect of thioglycolate on intermediate filaments and membrane translocation in rat urothelium during the expansion-contraction cycle

Summary The functional role of cytokeratin intermediate filaments in the translocation of asymmetric membrane plaques between cytoplasm and surface of apical urothelial cells was investigated during contraction and expansion of rat urinary bladders. A stereological investigation of electron micrographs provided estimations of surface area, volume, and number of discoidal vesicles and infoldings per unit volume of urothelial apical cell cytoplasm. Contracted and distended bladders incubated in 0.01 M sodium bicarbonate were compared to identical preparations experimentally incubated in 5 mM thioglycolic acid. The latter reagent disrupts the intermediate filament network by reducing sulfhydryl bridges. Densities of discoidal vesicles in cells contracted after incubation in thioglycolate were similar to density estimations in cells expanded under control conditions. Similarly, densities of vesicles in cells expanded after exposure to thioglycolate were comparable in number to those in normally contracted cells. Thus, membrane translocation to and from the luminal surface was blocked by thioglycolate treatment. The lack of normal membrane transfer at the luminal surface induces apical cells exposed to experimental conditions to undergo extraordinary adjustments in response to external pressures of bladder contraction and distension. During contraction, the apical-intermediate cell interface unfolded while the luminal surface ballooned out into the lumen. In distended bladders, large intercellular spaces formed between apical cells along their lateral margins. The results support a model published earlier implicating the filament network as a critical mediator of membrane translocation.     

Zinc protection against cadmium effect on estrual cycle of wistar rat

A single dose of cadmium chloride (2.2 mg/kg of body wt) increased the estrual cycle period about two times. This effect could be prevented by means of simultaneous administration of zinc at the same dose.     

Characteristics of retinal stem cells from rat optic cup at embryonic day 12.5 (tailbud stage)

Photoreceptor loss causes irreversible blindness in many retinal diseases. Repair of such damage by cell transplantation is one of the most feasible types of central nervous system treatment. Retinal stem cells (RSC) are a substrate for cell-replacement therapy, and previous studies have shown that RSCs from different developmental stages have distinct properties in proliferative capacity and differentiation potential. The tailbud stage is of special interest in retinogenesis, because RSCs commence differentiation after this period. However, no information about the characteristics of RSCs from the tailbud stage is available. In this study, the characteristics of cell cultures from the rat optic cup (referred to as optic-cup-derived RSCs; OC-RSCs) at embryonic day 12.5 (tailbud stage) were analyzed. OC-RSCs grew either as monolayers or as neurospheres in the presence of basic fibroblast growth factor and could be dissociated into a single cell suspension. Using the MTT assay, immunochemistry, cytogenetic analysis, and flow cytometry, we found that OC-RSCs were easily enriched to 92% by three passages, had a normal diploid karyotype, and exhibited no obvious differences in proliferative rate during eight passages (doubling time: 36 h). OC-RSCs produced retinal specific cells after the addition of serum to the medium, but the differentiation potential was affected by serum concentration. Preliminary results showed that transplanted OC-RSCs were incorporated into the degenerated retina of RCS rats and differentiated into rhodopsin-positive cells. Thus, OC-RSCs, after suitable enrichment, provide a population of stem cells with distinct growth and differentiation properties that make them suitable for research into RSC differentiation and transplantation.     

Toxicokinetics of a single intravenous dose of rac-propranolol versus optically pure propranolol in the rat

Conscious male Wistar SPF Riv:TOX rats were dosed intravenously with 2.5, 5, or 10 mg/kg rac-propranolol·HCl, or with 5 mg/kg of either (-)-(S)- or (+)-(R)-propranolol·HCl. Disposition of (-)-(S)- and (+)-(R)-propranolol after dosing of rac-propranolol was linear in the dose range examined. Total plasma clearance was not changed in animals dosed with the individual enantiomers compared to the animals that were dosed with rac-propranolol. However, for (-)-(S)-propranolol both volume of distribution and elimination half-life decreased, whereas for (+)-(R)-propranolol increases were observed for these characteristics, in animals dosed with the individual enantiomers. Our observations suggest that the (+)-(R)-enantiomer competes with (-)-(S)-propranolol for plasma protein binding sites, resulting in lower plasma protein binding of the (-)-(S)-enantiomer when the racemate is administered. From recent toxicological experiments, it was concluded that rac-propranolol is more toxic than the individual enantiomers in the rat, when dosed iv at the same total mass. It is concluded that the observed potentiation of toxic effects of propranolol enantiomers when administered as a racemate can at least partly be explained by a pharmacokinetic interaction. © 1995 Wiley-Liss, Inc.     

Contractile properties of the isolated rat soleus muscle and its single skinned soleus fibers at the early stage of gravitational unloading: Facts and hypotheses

The contractile properties of the postural soleus muscle were studied in rats at the early stage of gravitational unloading (three-day hindlimb suspension) with regard to different modes of muscle contraction (twitch and tetanic contraction of the isolated muscle and calcium-induced contraction of isolated skinned fibers). A significant (p < 0.01) enhancement of the peak twitch tension of the muscles of suspended rats without changes in time-dependent characteristics was observed, although the half-relaxation time tended to decrease. The fiber diameter did not change (42.37 ± 0.76 vs. 43.43 ± 1.15 μm in controls). The calcium-induced peak isometric tensions in control and unloaded soleus muscles were 37.6 ± 1.52 and 32.1 ± 1.05 mg, respectively (decrease significant at p < 0.05). No changes in threshold calcium concentration were recorded, but the pCa₅₀ value in unloaded muscles decreased from 6.05 ± 0.02 in controls to 5.97 ± 0.02 (p ≤ 0.05), indicating loss of myofibrillar calcium sensitivity. The cooperativity coefficient ηn in control animals was 3.46 ± 0.16, and in suspended ones it decreased to 3.08 ± 0.11 (p < 0.05). Analysis with the Fluo-4AM calcium probe demonstrated that the intracellular Ca²⁺ concentration increased significantly after hindlimb suspension, whereas the relative contents of titin or nebulin did not change.     

Action exerted by atropine sulfate on the luteinization phenomenon induced by a total gonadotropic preparation of prehypophysis at several stages of the estrus cycle in the rat

These experiments explored the effect of 70 mg atropine sulfate, and several doses of Gonadormone Byla, given at 1700 on diestrous I or at 1700 on diestrous II in the strains WI and WII rats derived in the authors' laboratory from Wistar rats. In Experiment 1 300 rats, 30 per group, received 2.5 or 5.0 mouse units of Gonadormone per 100 gm body weight at 1700 of diestrous I, with or without atropine, and were killed for serial ovarian sections at 1100 of proestrus. The 2.5 unit experime nt generated significant differences in frequency of luteinization between season of the year (p less than .001), between atropine and no atropine treatment (p less than .001), and season of atropine administration (p less than .05). Atropine decreased frequency of luteinization defined as proportion of a group having luteinized with or without retained ova. There were no differences in mean coefficients of ovulation, i.e., mean proportion of ovulated corpora lutea in each rat among all luteinized follicles, between rat strains or atropine treatments. The 5 unit dose of gonadotropin per 100 gm body weight increased luteinization 100% over the 2.5 unit dose. In the 2nd series of 180 rats, the frequency of luteinization induced by 1.25 units of gonadotropin was decreased by atropine (p less than .01), but the frequency of ovulation and response in the 2 rat strains did not differ. The results were interpreted as due in part to endogenous gonadotropin release, although atropine was thought to act directly on the ovary.     

Growth pattern switch of renal cells and expression of cell cycle related proteins at the early stage of diabetic nephropathy

Renal hypertrophy, partly due to cell proliferation and hypertrophy, has been found correlated to renal function deterioration in diabetes mellitus. We screened the up-regulated cell cycle related genes to investigate cell growth and the expression of cell cycle regulating proteins at the early stage of diabetic nephropathy using STZ-induced diabetic rats. Cyclin E, CDK(2) and P(27) were found significantly up-regulated in diabetic kidney. Increased cell proliferation in the kidney was seen at day 3, peaked at day 5, and returned to normal level at day 30. Cyclin E and CDK(2) expression also peeked at day 5 and P(27) activity peaked at day 14. These findings indicate that a hyperplastic growth period of renal cells is followed by a hypertrophic growth period at the early stage of diabetes. The growth pattern switch may be regulated by cell cycle regulating proteins, Cyclin E, CDK(2), and P(27).     

大鼠一次性力竭跑台运动模型的建立及动态评价

目的跑台急性运动疲劳动物模型的建立及评价。方法选取清洁级雄性Wistar大鼠24只(8周龄)作为实验对象。采用多级递增负荷跑台运动方案(跑台坡度为0°,负荷分为三级)建立一次性力竭跑台运动动物模型。尾静脉取血,分别测定大鼠在安静、运动30 min、运动90 min、力竭、恢复30 min、恢复90 min各时间点外周血葡萄糖(GLU)、乳酸(LD)、尿素(BU)、丙二醛(MDA)浓度和肌酸激酶(CK)、超氧化物歧化酶(SOD)活性。结果一次性力竭运动过程中大鼠行为能力和运动能力、血液代谢产物及能量物质呈现阶段性的动态变化。外周血LD、BU、MDA浓度及CK活性均较安静时显著性增高(P<0.01,P<0.05);GLU浓度、SOD活性较安静时显著降低(P<0.01,P<0.05)。各指标的变化特征说明大鼠已达到运动疲劳状态。结论建立了大鼠一次性力竭跑台运动模型,并客观动态评价了大鼠在运动疲劳产生、发展、恢复等不同阶段各指标的变化特点及规律。该模型可用于后续运动疲劳机制的相关研究。     

Primary culture of single ectodermal precursors of Drosophila reveals a dorsoventral prepattern of intrinsic neurogenic and epidermogenic capabilities at the early gastrula stage.

We have analyzed the development in vitro of individual precursor cells from the presumptive truncal segmental ectoderm of the Drosophila embryo to study the intrinsic component in the determination of cell fate. For each cultured cell, the original position within as well as the developmental stage of the donor embryo were known. Cells removed from the ventral neurogenic region develop neural clones. Cells from the dorsal ectoderm and from the dorsalmost part of the ventral neurogenic ectoderm develop epidermal clones. These two classes of clones differ with respect to their division pattern, adhesiveness, cell morphologies and the expression of cell-specific markers. Mixed neural/epidermal clones were obtained from a fraction of precursors at almost all dorsoventral sites. We conclude that, at the onset of gastrulation, precursor cells of the truncal segmental ectoderm already have the capability to develop as either neuroblasts or epidermoblasts in the absence of further cell interactions. At the same time, positional cues distributed along the dorsoventral axis equip precursors with intrinsic preferences towards the neural or epidermal fate, thus defining a prepattern of high neurogenic preferences ventrally, and high epidermogenic preferences dorsally. It is likely that this prepattern is involved in defining the extent of the ventral neurogenic and dorsal epidermogenic regions of the ectoderm. The roles of intrinsic capabilities versus extrinsic influences in the regulation of the characteristic pattern of segregation of the two lineages are discussed.     

Learned helplessness in the rat: effect of response topography in a within-subject design

Three experiments investigated learned helplessness in rats manipulating response topography within-subject and different intervals between treatment and tests among groups. In Experiment 1, rats previously exposed to inescapable shocks were tested under an escape contingency where either jumping or nose poking was required to terminate shocks; tests were run either 1, 14 or 28 days after treatment. Most rats failed to jump, as expected, but learned to nose poke, regardless of the interval between treatment and tests and order of testing. The same results were observed in male and female rats from a different laboratory (Experiment 2) and despite increased exposure to the escape contingencies using a within-subject design (Experiment 3). Furthermore, no evidence of helplessness reversal was observed, since animals failed to jump even after having learned to nose-poke in a previous test session. These results are not consistent with a learned helplessness hypothesis, which claims that shock (un)controllability is the key variable responsible for the effect. They are nonetheless consistent with the view that inescapable shocks enhance control by irrelevant features of the relationship between the environment and behavior.     

The effect of metabolites,papaverine, and probenecid on cyclic AMP efflux from isolated rat islets of Langerhans

The process of cyclic AMP efflux from rat islets of Langerhans has been studied. The dynamics of glucose-induced cyclic AMP efflux closely resembled the pattern of glucose-induced insulin release. Thus, both processes were dose-dependent for glucose having the same threshold concentrations (4–8 mmol/l glucose), with the time course of cyclic AMP efflux and insulin release from 0–60 min being very similar. Galactose did not affect insulin release, cyclic AMP efflux and intra-islet cyclic AMP accumulation. On the other hand, inosine, N-acetylglucosamine, α-ketoisocaproic acid, L-leucine and xylitol all promoted insulin release and cyclic AMP efflux. Except for L-leucine, all these substances enhanced the intracellular accumulation of cyclic AMP. The phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine, greatly augmented all these parameters in the presence of glucose whereas in the absence of glucose, insulin release was not enhanced, while both cyclic AMP efflux and cyclic AMP accumulation were elevated. The drug, probenecid, did not alter either insulin release or intra-islet cyclic AMP levels, while cyclic AMP efflux was markedly reduced (though not abolished). Papaverine inhibited both insulin release and cyclic AMP efflux, but was found to augment the intra-islet cyclic AMP levels. The efflux of cyclic AMP correlates more closely with insulin release than with the cyclic AMP accumulation in most instances. The efflux is independent of either insulin secretory granule extrusion or intracellular fluctuations of the nucleotide, though it is not yet known whether cyclic AMP efflux may have some regulatory significance in insulin release.