Changes in regenerated and normal liver in rats during the lactation period

Summary In female rats weighing 160–200 g two-thirds of the liver were excised after Higgins' and Andersen's technique. A month after the operation, upon completion of the regeneration process, a study was made of the influence of functional load (pregnancy and lactation) on the regenerated and normal liver in the rats.(Presented by Academician N. A. Kraevskii) Translated from Byulleten' Éksperimental'noi Bioligii i Meditsiny, Vol. 59, No. 5, pp. 93–96, May, 1965     

Behavioral insensitivity to progesterone during lactation in female rats

Lactating female rats failed to display sexual receptivity after receiving 50 μg of estradiol benzoate followed by 1 mg of progesterone. Lactating rats appear to be insensitive to progesterone, based on several experiments. In ovariectomized control rats receiving moderate estrogen priming (1 μg EB for 3 days), progesterone greatly facilitated sexual receptivity; similarly estrogen-primed lactating females showed no responsiveness to progesterone injections, even at a high dose of progesterone (10 mg). Consistent with this reduced behavioral responsiveness to progesterone, lactating females had significantly reduced nuclear progestin receptor levels after an injection of 1 mg progesterone compared to ovariectomized controls. On the other hand, both ovariectomized controls and lactating rats responded with high levels of receptivity to 3 days of priming with 10 μg of estradiol benzoate (without progesterone). Lactating females treated for 3 days with a moderate dose (1 μg) of estradiol benzoate showed slightly reduced receptivity compared to ovariectomized controls; this result could reflect a reduced sensitivity to estrogen but is more likely related to the somewhat lower serum levels of estradiol and consequently lower nuclear estrogen receptors in lactating females compared to ovariectomized controls. The possibility of reduced sensitivity to estrogen leading to a reduced sensitivity to progesterone cannot be eliminated (since animals respond to progesterone only after estrogen priming); however, the reported results favor the idea that lactating females are primarily refractory to progesterone and do not have a generalized insensitivity to estrogen.     

Quantitative alteration of grooming behavior in aged male rats

Novelty-induced grooming was studied in aged male rats (24 months old) compared to young animals (3 months old). When put in a novel environment, aged rats exhibited a grooming activity markedly higher than that shown by young rats. Such an excessive grooming did not disappear over a 30 min observation. Furthermore, no significant difference between old and young rats was found in ambulation, rearing and defecation, as observed in an open field. It may be suggested that increased grooming activity in aged rats involves a disability to adapt to a novel environmental situation.     

Impairment of inflammatory response in adult rats submitted to maternal undernutrition during early lactation: Role of insulin and glucocorticoid

Objective: Early nutritional environment may program permanent metabolic alterations, predisposing to later diseases. We have investigated the interference of maternal malnutrition during lactation with the development of acute inflammation in adult rats. Materials and methods: Adult rats, offspring of dams fed with either protein-free diet (UN group) or 22% protein diet (C group) during the first 10 days of lactation, were submitted to pleurisy with carrageenan (500 g/cavity). Pleural edema, neutrophil migration and ICAM expression, were evaluated 4 h after and correlated with alterations in plasma insulin and corticosterone. Leukocyte-endothelium interactions were evaluated by intravital microscopy 1 h after inflammation. Results: Compared to controls, UN rats showed a decrease in pleural edema formation (50%), neutrophil migration (50%), endothelial ICAM-1 expression on pulmonary tissue, and impairment in leukocyte adhesion (50%) and migration (80%) through endothelium. Circulating insulin was lower (42%) and corticosterone was higher (34%) in UN, compared to controls. Pre-treatment of UN with insulin (5 IU/day) or RU486 (20 mg/kg/day), inhibitor of glucocorticoid receptor, restored leukocyte functions and ICAM-1 expression. Conclusion: Postnatal maternal malnutrition, programming for permanent alterations in insulin and glucocorticoid secretion in progeny, that were unable to properly mount an inflammatory response, probably predisposes to chronic diseases in adult life.Received 5 December 2002; returned for revision 6 June 2003; accepted by I. Ahnfelt-Rønne 28 June 2003     

Increased susceptibility to malaria during the early postpartum period

BACKGROUND: Pregnancy is associated with increased susceptibility to malaria. It is generally agreed that this increased risk ends with delivery, but the possible persistence of increased susceptibility during the puerperium had not been investigated. METHODS: From June 1, 1990, to December 31, 1998, we monitored exposure to malaria, parasitemia, and morbidity among the residents of a village in Senegal in which the rate of transmission of malaria was high. In this population we analyzed 71 pregnancies in 38 women from the year before conception and through one year after delivery. RESULTS: Among the 38 women, there were 58 episodes of clinical Plasmodium falciparum malaria during 61,081 person-days of observation. The incidence of malaria was 20.2 episodes per 1000 person-months during the year preceding conception and 12.0 episodes per 1000 person-months during the period from 91 to 365 days after delivery. The incidence of episodes of malaria increased significantly during the second and third trimesters of pregnancy and reached a maximum of 75.1 episodes per 1000 person-months during the first 60 days after delivery. The adjusted relative risk of an episode of malaria was 4.1 (95 percent confidence interval, 1.8 to 9.5) during the first 60 days post partum, as compared with the year preceding pregnancy. The duration of fever during the episodes of malaria was longer and the prevalence and density of asymptomatic malarial parasitemia were significantly higher during pregnancy and the early postpartum period than during the other periods. CONCLUSIONS: Among women who live in areas with high rates of transmission of malaria, the susceptibility to malaria is highest during the second and third trimesters of pregnancy and the early postpartum period.     

Cerebrovascular and cerebral metabolic responses of aged rats to changes in arterial PCO2

—Cerebrovascular and cerebral metabolic responses to changes in arterial PCO₂ were tested in young (4 month) and aged (24 month) Sprague-Dawley rats. Rats were anesthetized with 70% nitrous oxide and 30% oxygen, paralyzed with tubocurare and artificially ventilated. Cerebral blood flow (CBF) was measured with radioactive microspheres and cerebral oxygen metabolism (CMRO₂ was analyzed from arterial and sagittal sinus oxygen content differences. CBF increased in both young and aged rats with increasing arterial PCO₂. Aged rats had significantly depressed cerebrovascular reactivity to changes in CO₂ compared to young rats (p<0.05). CMRO₂ was not significantly different between young and aged rats and did not significantly change with changes in arterial PCO₂.     

Complex maze performance in young and aged rats: response to glucose treatment and relationship to blood insulin and glucose.

In aged rats and humans, impaired glucose regulation has been correlated with poor memory performance, and glucose treatment can result in improved performance. We tested this glucose hypothesis with rats in a 14-unit T-maze that has provided robust evidence of age-related performance decline. Aged (24-25 month) and young (6-7 month) male F-344 rats were pretrained for one-way active avoidance before receiving complex maze training (4 daily trials over 5 days) with the contingency of moving through each of 5 segments to avoid footshock. Ten min before daily training, aged rats received either saline or glucose in doses of 10, 100, or 500 mg/kg IP, while young rats received saline. Significant (ps less than 0.05) age-related increases in errors, runtime, and shock duration were observed. Glucose treatment had no significant effect on the number of maze errors committed; however, performance variables such as runtime and shock duration appeared to be reduced in rats receiving glucose. About 4-6 weeks later, a sample of these rats was fasted overnight, injected IP with glucose (150 mg/kg), and bled at various postinjection intervals to obtain estimates of blood glucose and insulin levels. Significant correlations (ps less than 0.05) were observed between maze errors and baseline glucose levels, r(21) = -.62, and peak glucose response, r(19) = .49. However; within the aged group, significant correlations (ps less than 0.01) with maze errors emerged only for baseline glucose, r(13) = -.69, and peak insulin response, r(13) = -.65. Thus, regulation of insulin, but not glucose, appeared related to learning abilities among aged rats.(ABSTRACT TRUNCATED AT 250 WORDS)     

Learning and memory impairment in adult rats due to severe zinc deficiency during lactation

In a series of three experiments, adult rats who suffered severe zinc deficiency and/or undernutrition during lactation were tested in a 17-arm radial maze for working memory, reference memory, forgetting and learning. In Experiment 1, eight out of 17 arms were baited. The zinc deficient (ZD) and undernourished (PF) rats revealed a learning deficit when compared to adequately nourished rats (AL). ZD rats also appeared to display a loss of working memory. No evidence of loss of reference memory was observed among any of the groups. A reverse learning procedure was used in Experiment 2 to test the same rats used in Experiment 1. ZD rats were significantly inferior in performance of the reverse learning task compared to the AL and PF rats. No significant differences in performance were noted between the AL and PF rats. Although all groups displayed forgetfulness from Experiment 1 to Experiment 2, no significant differences in forgetfulness were evidenced among the groups. In Experiment 3, all 17 arms were baited. The ZD rats displayed a significant working memory deficit as compared to the AL and PF rats. No significant differences in working memory between the AL and PF rats occurred. The possibility that the differences in performance were due to differences in food motivation or attention was considered and rejected. It was concluded that ZD rats experienced a severe learning deficit and some working memory deficit while the PF rats experienced a mild learning deficit as compared to the AL rats.     

Aerobic exercise training induces metabolic benefits in rats with metabolic syndrome independent of dietary changes

OBJECTIVES:

We evaluated the effects of aerobic exercise training without dietary changes on cardiovascular and metabolic variables and on the expression of glucose transporter Type 4 in rats with metabolic syndrome.

METHODS:

Twenty male spontaneously hypertensive rats received monosodium glutamate during the neonatal period. The animals were allocated to the following groups: MS (sedentary metabolic syndrome), MS-T (trained on a treadmill for 1 hour/day, 5 days/week for 10 weeks), H (sedentary spontaneously hypertensive rats) and H-T (trained spontaneously hypertensive rats). The Lee index, blood pressure (tail-cuff system), insulin sensitivity (insulin tolerance test) and functional capacity were evaluated before and after 10 weeks of training. Glucose transporter Type 4 expression was analyzed using Western blotting. The data were compared using analysis of variance (ANOVA) (p<0.05).

RESULTS:

At baseline, the MS rats exhibited lower insulin sensitivity and increased Lee index compared with the H rats. Training decreased the body weight and Lee index of the MS rats (MS-T vs. MS), but not of the H rats (H-T vs. H). There were no differences in food intake between the groups. At the end of the experiments, the systolic blood pressure was lower in the two trained groups than in their sedentary controls. Whole-body insulin sensitivity increased in the trained groups. Glucose transporter Type 4 content increased in the heart, white adipose tissue and gastrocnemius muscle of the trained groups relative to their respective untrained groups.

CONCLUSION:

In conclusion, the present study shows that an isolated aerobic exercise training intervention is an efficient means of improving several components of metabolic syndrome, that is, training reduces obesity and hypertension and increases insulin sensitivity.     

慢性代谢性酸中毒显著诱导大鼠系膜细胞的增殖

目的：研究慢性代谢性酸中毒对大鼠肾小球体积、系膜细胞增殖、基质表达的影响及分子机制。 方法： 采用0.28 mol/L NH4Cl喂饲大鼠构建大鼠慢性代谢性酸中毒模型。采用光镜结合图像分析软件观察和分析大鼠肾小球结构。从肾皮质分离大鼠肾小球，肾小球增殖细胞核抗原(PCAN)和p27的表达采用免疫组化和/或Western blotting检测。肾皮质纤维连接蛋白(FN)ｍRNA的表达采用荧光定量RT-PCR检测。分别采用［3H］-TdR掺入法和ELISA方法检测了慢性酸负荷对体外培养的大鼠系膜细胞增殖及FN合成的影响。 结果： 各时点实验组大鼠动脉血pH、［HCO3-］均显著低于对照组(P<0.01)。第3、7、14 d实验组大鼠肾重及肾/体重比值均显著大于对照组，而绝对体重与对照相比无显著差异；平均肾小球面积、肾小球丝球体面积、球内细胞总数以及系膜区细胞数均大于对照组（P<0.05），第14 d大鼠肾小球系膜区面积与肾小球丝球体面积比值高于对照组（P<0.05）；第3、7、14 d Western blotting检测实验组大鼠肾小球PCNA表达增加，p27表达下调，免疫组织化学检测显示肾小球内阳性PCNA细胞主要位于系膜区；第7 d、14 d大鼠肾皮质FN mRNA的表达显著高于对照组（P<0.01）。体外系膜细胞［3H］-TdR掺入量随酸负荷强度而增高，酸负荷24 h和48 h，系膜细胞上清中FN含量显著增高。 结论： 慢性代谢性酸中毒能够诱导大鼠肾小球肥大、系膜细胞增生及细胞外基质增多，其机制与系膜细胞周期调控蛋白P27的表达下调有关。本研究为慢性代谢性酸中毒参与慢性肾小球疾病的硬化提供了体内和体外证据。     

A gene knockout approach in mice to identify glucose sensors controlling glucose homeostasis

A key aspect of glucose homeostasis is the constant monitoring of blood glucose concentrations by specific glucose sensing units. These sensors, via stimulation of hormone secretion and activation of the autonomic nervous system (ANS), regulate tissue glucose uptake, utilization or production. The best described glucose detection system is that of the pancreatic beta-cells which controls insulin secretion. Secretion of other hormones, in particular glucagon, and activation of the ANS, are regulated by glucose through sensing mechanisms which are much less well characterized. Here I review some of the studies we have performed over the recent years on a mouse model of impaired glucose sensing generated by inactivation of the gene for the glucose transporter GLUT2. This transporter catalyzes glucose uptake by pancreatic beta-cells, the first step in the signaling cascade leading to glucose-stimulated insulin secretion. Inactivation of its gene leads to a loss of glucose sensing and impaired insulin secretion. Transgenic reexpression of the transporter in GLUT2/beta-cells restores their normal secretory function and rescues the mice from early death. As GLUT2 is also expressed in other tissues, these mice were then studied for the presence of other physiological defects due to absence of this transporter. These studies led to the identification of extra-pancreatic, GLUT2-dependent, glucose sensors controlling glucagon secretion and glucose utilization by peripheral tissues, in part through a control of the autonomic nervous system.     

Lack of influence of glucagon on glucose homeostasis after prolonged exercise in rats

Summary The significance of glucagon for post-exercise glucose homeostasis has been studied in rats fasted overnight. Immediately after exhaustive swimming either rabbit-antiglucagon serum or normal rabbit serum was injected by cardiac puncture. Cardiac blood and samples of liver and muscle tissue were collected before exercise and repeatedly during a 120 min recovery period after exercise. During the post-exercise period plasma glucagon concentrations decreased but remained above pre-exercise values in rats treated with normal serum, while rats treated with antiglucagon serum had excess antibody in plasma throughout. Nevertheless, all other parameters measured showed similar changes in the two groups. Thus after exercise the grossly diminished hepatic glycogen concentrations remained constant, while the decreased blood glucose concentrations were partially restored. Simultaneously concentrations in blood and serum of the main gluconeogenic substrates, lactate, pyruvate, alanine and glycerol declined markedly. During the post-exercise period NEFA concentrations in serum and plasma insulin concentrations remained increased and decreased, respectively, while plasma catecholamines did not differ from basal values. Muscle glycogen concentrations decreased slightly. These findings suggest that in the recovery period after exhaustive exercise the increased glucagon concentrations in plasma do not influence gluconeogenesis.     

The acetylcholine release enhancer linopirdine induces Fos in neocortex of aged rats

Centrally acting cholinergic agents induce the immediate early gene c-fos in the rat brain resulting in transient increases of Fos protein, most notably in the cerebral cortex. In this study we have monitored by Fos immunohistochemistry the effect of the acetylcholine release enhancer linopirdine (DUP996) on the immediate early gene c-fos in brains of 3 months and 30 months old rats. In young rats linopirdine had only a marginal effect on Fos expression. In contrast, in aged rats linopirdine caused widespread expression of Fos throughout neocortex. In somatosensory cortex, the induction of the c-fos gene by linopirdine was nearly completely blocked by atropine and scopolamine and strongly attenuated by the NMDA receptor blockers CPP and MK-801. The results suggest that the age-related decline in acetylcholine release in rodents can be partially compensated for by administration of linopirdine.     

Elucidation of thrifty features in adult rats exposed to protein restriction during gestation and lactation

Since the introduction of the thrifty phenotype hypothesis, the potential traits of thrift have been described in increasingly broad terms but biochemical and behavioral evidence of thrift has not been well demonstrated. The objective of our studies was to use a rodent model to identify features of thrift programmed by early life protein restriction. Robust programming of thrifty features requires a thrifty nutritional environment during the entire window of developmental plasticity. Therefore, pregnant rats were exposed to a low protein diet throughout the window of developmental plasticity spanning the period of gestation and lactation and its effects on energy acquisition, storage and expenditure in the adult offspring were examined. Maternal protein restriction reduced birth weight and produced long term reductions in body and organ weights in the offspring. Low protein offspring demonstrated an increased drive to seek food as evidenced by hyperphagia that was mediated by changes in plasma leptin and ghrelin levels. Hyperphagia was accompanied by increased efficiency in converting caloric intake into body mass. The higher feed efficiency was mediated by greater insulin sensitivity. Energy expenditure of low protein offspring in locomotion was not affected either in the light or dark phase. However, low protein offspring exhibited higher resting and basal metabolic rates as evidenced by higher core body temperature in the fed and fasted states. The increased thermogenesis was not mediated by thyroid hormones but by an increased sympathetic nervous system drive as reflected by a lower areal bone mineral density and bone mineral content and lower plasma adiponectin and triglyceride levels. Elevated thermogenesis in the low protein offspring possibly offsets the effects of hyperphagia, minimizes their chances of weight gain, and improves survivability. This constellation of metabolic features in the low protein offspring will maximize survival potential in a post natal environment of nutritional scarcity and constitute a thrifty phenotype.     

Micronucleus frequency in spleen lymphocytes from severely malnourished rats during lactation

The purpose of this ex vivo study was to determine if severe malnutrition increases the frequency of micronuclei in spleen lymphocytes of experimentally malnourished rats during lactation. Micronucleus frequencies were analyzed in binucleate cells produced by the cytokinesis block method. The overall micronucleus frequency was significantly higher in binucleate cells from malnourished rats (21.3%‰) as compared to that observed in control rats (11.5%‰). The number of binucleate cells with more than one micronucleus was also higher in malnourished rats than in controls (3.1%‰ vs. 1.2%‰). These results indicate that severe malnutrition produces cellular damage in vivo, as was evidenced by the increased micronucleus frequency in rat spleen lymphocytes in vitro. This damage may produce negative effects for the further development of the organism, since the spleen is an important lymphopoietic organ in rodents. © 1995 Wiley-Liss, Inc.     

Hypoxia during early developmental period induces long-term changes in the dopamine content and release in a mesencephalic cell culture.

The present study was conducted to elucidate the long-term effects of exposure to hypoxia of dopaminergic neurons during the early developmental period. Primary mesencephalic cell cultures prepared from fetal rats and containing 0.5-2% of dopaminergic neurons were exposed to hypoxia between in vitro days 1 and 6, the putative critical developmental period. Changes in the content, release and uptake of dopamine were found to depend on the degree of hypoxia and on the duration of exposure. Following moderate hypoxia (7 h, 5% O2) on two consecutive days between in vitro days 1 and 3, the cultures showed a small increase in the dopamine levels, by 16%. After severe hypoxia (0% O2/95% N2 for 24 h), during the same time window, the cellular dopamine content was elevated by 100%. Moreover, severe hypoxia produced long-lasting modulations of the dopaminergic system. On in vitro day 14, cells exhibited increased levels of 3,4-dihydroxyphenylacetic acid and homovanillic acid (by 34% and 55%, respectively), and elevations of both the spontaneous and potassium-stimulated dopamine release by 70%. The dopamine transport and metabolism of cells exposed to hypoxia between in vitro days 4 and 6 remained unchanged with regard to long-term effects. The present study provides strong evidence for the induction of long-term changes in dopaminergic cells due to hypoxia during the critical developmental period in mesencephalic culture. The developmental period capable of inducing long-lasting changes in dopamine metabolism is restricted to in vitro days 1-3.     

Regional cerebral glucose utilization rates in rats during asymptomatic period of exposure to 1, 2 and 3 atmospheres absolute of oxygen

A previous study has shown an increase in regional cerebral metabolic rate for glucose prior to the onset of central nervous system oxygen toxicity in rats exposed to 5 atmospheres absolute of oxygen. The present study was designed to measure regional cerebral glucose utilization rates at pressures used for oxygen therapy and prolonged exposures during which rats are known to be asymptomatic. The regional metabolic rate for glucose in 26 brain structures and in gray and white matter of the thoracic and lumbar spinal cord was autoradiographically measured in awake unrestrained rats using the autoradiographic [14C]2-deoxyglucose technique. Femoral artery and vein cannulae were inserted 3 days before the experiment. Rats were divided into four groups of 15: (a) air control; (b) 6 h at 1 atmosphere absolute oxygen; (c) 4 h at 2 atmospheres oxygen; and (d) 2 h at 3 atmospheres oxygen. Statistically significant increases in glucose utilization (p less than 0.05) are seen only in lateral thalamus at 3 atmospheres oxygen, in superior olivary nucleus and inferior colliculus at 2 atmospheres oxygen and in superior olivary nucleus at 1 atmosphere oxygen. The combination of our previous data at 5 atmospheres oxygen and the present results at prolonged and safe exposures to lower pressures indicated that increased glucose utilization in some neuronal structures precedes the onset of the central nervous system manifestations of oxygen toxicity.