Estradiol does not influence strategy choice but place strategy choice is associated with increased cell proliferation in the hippocampus of female rats

Adult neurogenesis occurs in the hippocampus of most mammals. While the function of adult hippocampal neurogenesis is not known, there is a relationship between neurogenesis and hippocampus-dependent learning and memory. Ovarian hormones can influence learning and memory and strategy choice. In competitive memory tasks, higher levels of estradiol shift female rats towards the use of the place strategy. Previous studies using a cue-competition paradigm find that 36% of male rats will use a hippocampus-dependent place strategy and place strategy users had lower levels of cell proliferation in the hippocampus. Here, we used the same paradigm to test whether endogenous or exogenous ovarian hormones influence strategy choice in the cue-competition paradigm and whether cell proliferation was related to strategy choice. We tested ovariectomized estradiol-treated (10 μg of estradiol benzoate) or sham-operated female rats on alternating blocks of hippocampus-dependent and hippocampus-independent versions of the Morris water task. Rats were then given a probe session with the platform visible and in a novel location. Preferred strategy was classified as place strategy (hippocampus-dependent) if they swam to the old platform location or cue strategy (hippocampus-independent) if they swam to the visible platform. All groups showed a preference for the cue strategy. However, proestrous rats were more likely to be place strategy users than rats not in proestrus. Female place strategy users had increased cell proliferation in the dentate gyrus compared to cue strategy users. Our study suggests that 78% of female rats chose the cue strategy instead of the place strategy. In summary the present results suggest that estradiol does not shift strategy use in this paradigm and that cell proliferation is related to strategy use with greater cell proliferation seen in place strategy users in female rats.     

Chronic lithium enhances hippocampal long-term potentiation,but not neurogenesis,in the aged rat dentate gyrus

We investigated the hippocampal long-term potentiation (LTP), neurogenesis, and the activation of signaling molecules in the 20-month-old aged rats following chronic lithium treatment. Chronic lithium treatment produced a significant 79% increase in the numbers of BrdU(+) cells after treatment completion in the dentate gyrus (DG). Both LTP obtained from slices perfused with artificial cerebrospinal fluid (ACSF-LTP), and LTP recorded in the presence of bicuculline (bicuculline-LTP) were significantly greater in the lithium group than in the saline controls. Our results show that as with young rats, chronic lithium can substantially increase LTP and the number of BrdU(+) cells in the aged rats. However, neurogenesis, assessed by colocalization of NeuN and BrdU, was not detected in the aged rat DG subjected to chronic lithium treatment. Therefore, it is concluded that the increase in LTP and the number of BrdU(+) cells might not be associated with increases in neurogenesis in the granule cell layer of the DG. Lithium might has a beneficial effects through other signaling pathways in the aged brain.     

Differential effects of corticosterone and dexamethasone on hippocampal neurogenesis in vitro

Prenatal stress during fetal development results in the blockade of neurogenesis in the dentate gyrus in adulthood. Present study was undertaken to investigate the dominant role of the glucocorticoid receptors in corticosterone actions on the neurogenesis of fetal hippocampal progenitor cells. For that purpose, expressions of key molecules affected by corticosterone and dexamethasone were compared during proliferation and differentiation of the hippocampal progenitor cells. Corticosterone (2 microM) significantly decreased the number of bromodeoxyuridine-labeled cells (about 50%) and caused the dendritic atrophy in microtubule-associated protein 2-labeled cells. The expressions of NeuroD, BDNF, and NR1 mRNA levels and protein levels of p-ERK and p-CREB were remarkably decreased by corticosterone in a dose-dependent manner. In contrast, dexamethasone, a glucocorticoid receptor (GR) specific agonist, had an inhibitory effect on proliferation, but not differentiation. It is concluded that corticosterone elicits its effects on neurogenesis including proliferation and differentiation whereas stimulation of the glucocorticoid receptor is sufficient to decrease only proliferation.     

Evidence for cell proliferation in the sheep brain and its down-regulation by parturition and interactions with the young

Production of new neurons continues throughout life in the subventricular zone (SVZ) and the dentate gyrus (DG) of the hippocampus and is influenced by both endocrine and social factors. In sheep parturition is associated with the establishment of a selective bond with the young based on an olfactory learning. The possibility exists that endocrine changes at parturition together with interactions with the young modulate cell proliferation in the neurogenic zones. In the present study, we first investigated the existence of cell proliferation in sheep. Newly born cells labeled by the cell proliferation marker 5-bromo-2′-deoxyuridine (BrdU) were found in the SVZ, the main olfactory bulb (MOB) and the DG and completely co-localized with Ki-67, another mitotic marker. Forty to 50% of the BrdU-labeled cells contained GFAP suggestive of the presence of neural stem cells. Secondly, parturition with or without interactions with the lamb for 2 days, down-regulated the number of BrdU-labeled cells in the 3 proliferation sites in comparison to no pregnancy. An additional control provided evidence that this effect is specific to early postpartum period: estrus with interactions with males did not affect cell proliferation. Our results provide the first characterization of neural cell proliferation in the SVZ, the DG and unexpectedly in the MOB of adult sheep. We hypothesize that the down-regulation of cell proliferation observed in the early postpartum period could facilitate the olfactory perceptual and memory demands associated with maternal behavior by favouring the survival and integration of neurons born earlier.     

Increased cell proliferation in the adult mouse hippocampus following chronic administration of group II metabotropic glutamate receptor antagonist, MGS0039

We have previously reported that MGS0039, a novel antagonist of group II metabotropic glutamate receptors (mGluRs), exerts antidepressant-like effects in experimental animal models. Recent studies suggest that the behavioral effects of chronic antidepressant treatment are mediated by the stimulation of neurogenesis in the hippocampus. In the present study, we examined the effects of MGS0039 on cell proliferation in the adult mouse hippocampus. MGS0039 (5 or 10mg/kg) or fluvoxamine was administered chronically to male ICR mice over a period of 14 days. Multiple bromodeoxyuridine (BrdU) administrations were performed after the last drug injection to label dividing cells. Immunohistochemical analyses after BrdU injections revealed that chronic MGS0039 treatment enhanced BrdU-positive cells in the dentate gyrus ( approximately 62% increase) in the same manner as chronic fluvoxamine treatment. This is the first in vivo study to demonstrate an increase in cell proliferation following a blockade of group II mGluRs. These findings raise the possibility that MGS0039 may exert antidepressant-like effects by modulating cell proliferation in the hippocampus.     

Effects of a new synthetic butyrylcholinesterase inhibitor, HBU-39, on cell proliferation and neuroblast differentiation in the hippocampal dentate gyrus in a scopolamine-induced amnesia animal model

In this study, we synthesized [1-(4-(benzo[d][1,3]dioxol-5-ylmethyl)piperazin-1-yl)-5-(1,2-dithiolan-3-yl)pentan-1-one, HBU-39], a (α)-lipoic acid derivative, and found this compound strongly inhibited butyrylcholinesterase (BuChE) in an in vitro experiment. We also examined the effects of HBU-39 on cell proliferation and neuroblast differentiation using the specific markers Ki67 and doublecortin (DCX), respectively, in the hippocampal dentate gyrus of a rat model of scopolamine-induced amnesia. For this, scopolamine was subcutaneously administered for 28 days by an ALzet osmotic minipump (44 mg/mL delivered at 2.5 μL/h). HBU-39 (1 mg/kg per day) and galantamine (an acetylcholinesterase inhibitor used as a control; 5 mg/kg per day) were intraperitoneally administered for 28 days. The administration of scopolamine significantly decreased the mean number of Ki67- and DCX-immunoreactive cells in the dentate gyrus. However, treatment with both HBU-39 and galantamine significantly ameliorated the reductions in cell proliferation and neuroblast differentiation. In particular, the mean number of Ki67- and DCX-immunoreactive cells was prominently abundant in the HBU-treated group compared to that in the galantamine-treated group. These results suggest that the BuChE inhibitor, HBU-39, can ameliorate the scopolamine-induced reductions of cell proliferation and neuroblast differentiation, and HBU-39 may be applicable to amnesia patients to promote memory functions.     

The effects of Rhodiola rosea extract on 5-HT level, cell proliferation and quantity of neurons at cerebral hippocampus of depressive rats

The purpose of this study was to investigate the effects of Rhodiola rosea extract and depression on the serotonin (5-HT) level, cell proliferation and quantity of neurons at cerebral hippocampus of depressive rats induced by Chronic Mild Stress (CMS). Seventy male Sprague-Dawley rats were divided into seven groups (10 per group): normal control group, untreated depressive rat model group, negative control group, positive control group, low dosage Rhodiola rosea extract (1.5 g/kg) group, medium dosage Rhodiola rosea extract (3 g/kg) group and high dosage Rhodiola rosea extract (6 g/kg) group. After the depressive rats induced by CMS had received Rhodiola rosea extract for 3 weeks, the 5-HT levels at cerebral hippocampus were detected by high performance liquid chromatography. Bromodeoxyuridine (BrdU) was injected in vivo to label the proliferating cells at hippocampus, and morphometry was used to count the hippocampal neurons. The results showed that the 5-HT level of the three experimental groups had recovered to normal status. The immunohistochemistry of hippocampus BrdU positive cells had returned to the normal level in the group of depressive rats with low dosage Rhodiola rosea extract. In conclusion the results demonstrated that Rhodiola rosea extract could improve 5-HT level in hippocampus in depressive rats, and low dosage Rhodiola rosea could induce neural stem cell proliferation at hippocampus to return to normal level, repairing the injured neurons at hippocampus.     

Chronic corticosterone during pregnancy and postpartum affects maternal care, cell proliferation and depressive-like behavior in the dam

Stress during pregnancy and the postpartum can influence the well-being of both the mother and her offspring. Prolonged elevated levels of glucocorticoids are associated with depression and we developed an animal model of postpartum depression/stress based on high levels of corticosterone (CORT) during the postpartum. Gestational stress is a risk factor for postpartum depression and prenatal and/or postnatal high levels of CORT may have differential effects on the mother. Thus the present study was conducted to investigate the effects of low (10 mg/kg) or high levels of CORT (40 mg/kg) given to dams either during gestation, postpartum or across both gestation and postpartum on maternal care, depressive-like behavior and hippocampal cell proliferation in the dam. Only the high dose of CORT administered during the postpartum increased depressive-like behavior in the dam. Furthermore the high dose of CORT altered maternal care (reduced time spent on the nest and nursing) regardless of whether administration of CORT was during gestation or postpartum. Gestational and/or postpartum treatment with high CORT and postpartum low CORT reduced cell proliferation in the dentate gyrus of postpartum dams compared to oil-treated controls. Thus prolonged treatment with high levels of CORT postpartum reduced maternal care, hippocampal cell proliferation and induced depressive-like behavior in the dam and therefore might be considered an animal model of postpartum depression. More research is needed to understand the effects of stress hormones during different phases of reproduction and how they affect the brain and behavior of the mother and her offspring.     

Armet, a UPR-upregulated protein, inhibits cell proliferation and ER stress-induced cell death

The accumulation of misfolded proteins in the endoplasmic reticulum (ER) causes ER stress that initiates the unfolded protein response (UPR). UPR activates both adaptive and apoptotic pathways, which contribute differently to disease pathogenesis. To further understand the functional mechanisms of UPR, we identified 12 commonly UPR-upregulated genes by expression microarray analysis. Here, we describe characterization of Armet/MANF, one of the 12 genes whose function was not clear. We demonstrated that the Armet/MANF protein was upregulated by various forms of ER stress in several cell lines as well as by cerebral ischemia of rat. Armet/MANF was localized in the ER and Golgi and was also a secreted protein. Silencing Armet/MANF by siRNA oligos in HeLa cells rendered cells more susceptible to ER stress-induced death, but surprisingly increased cell proliferation and reduced cell size. Overexpression of Armet/MANF inhibited cell proliferation and improved cell viability under glucose-free conditions and tunicamycin treatment. Based on its inhibitory properties for both proliferation and cell death we have demonstrated, Armet is, thus, a novel secreted mediator of the adaptive pathway of UPR.     

Evidence for the Colocalization of Parvalbumin and Glutamate, but Not GABA, in the Perforant Path of the Gerbil Hippocampal Formation: A Combined Immunocytochemical and Microquantitative Analysis

Abstract: Gerbils ( Meriones unguiculatus ) are known for their seizure sensitivity, which is dependent on an intact perforant path from the entorhinal cortex to the hippocampus. In contrast with other species, the perforant path in gerbils contains parvalbumin, a cytosolic high-affinity calcium-binding protein. Parvalbumin is known to be present in a subpopulation of GABA-containing neurons and is thought to be responsible for their physiological characteristics of fast spiking activity and lack of spike adaptation. Therefore, the question arose of whether this projection in gerbils is GABAergic or glutamatergic as in other species. In a first approach to this question, the effect of lesioning the origin of the perforant path, the entorhinal cortex, on levels of GABA and glutamate was determined by enzymatic-luminometric assay in single layers of the dentate gyrus of lyophilized brain sections. Parallel sections were cryofixed using an acidified acetone-formaldehyde mixture at -20°C for 48 h, and subsequently stained for parvalbumin immunocytochemistry. Seven days after ablation of the entorhinal cortex, parvalbumin staining was undetectable in the termination zone of the perforant path, the outer two-thirds of the stratum moleculare. In parallel, glutamate content was reduced to 80% of controls (and of the unoperated contralateral side) but unchanged in the inner third of the stratum moleculare and in stratum granulare. GABA content was not significantly altered by the lesion. From these results, we conclude that in the gerbil as in other species, the perforant path contains glutamate. The association of glutamate with parvalbumin suggests, however, that in the gerbil the calcium-dependent release of the transmitter is carefully controlled in the entorhinal perforant path.     

Effects of rGM-CSF on leukemia cell proliferation and on the incorporation of cytosine arabinoside into DNA.

In vitro studies of the effects of recombinant granulocyte macrophage-colony stimulating factor (rGM-CSF) on freshly obtained human leukemia cells were conducted to determine if there is a relationship between the effects of this growth factor on the proliferative characteristics of leukemia cells and on their incorporation of cytosine arabinoside (araC) into DNA. While rGM-CSF was found to be able to stimulate both leukemia cell proliferation and araC incorporation, for individual leukemia specimens there was no consistent relationship among these effects. In some specimens proliferation was stimulated without an increase in araC incorporation. The reverse was also observed. These studies demonstrate the difficulty in identifying assays capable of predicting the clinical effects of growth factors on leukemia cells in patients since the effect in vitro vary with the assay.     

The mouse pubic symphysis as a remodeling system: morphometrical analysis of proliferation and cell death during pregnancy, partus and postpartum

Marked changes in mice pubic symphysis occur by the end of pregnancy. Tissue remodeling involves a dynamic balance between cell proliferation and programmed cell death as well as changes in the extracellular matrix components. Therefore, it is important to consider both of these cellular behaviors when investigating the mechanism that regulates interpubic tissue remodeling, growth during late pregnancy and partus ensuring involution during the postpartum period. Proliferating and programmed death cells were identified by immunohistochemistry (proliferating cell nuclear antigen and TUNEL detection, respectively) and the rates at which these processes occurred were determined by morphometric analysis. The results demonstrated that cellular proliferation was intense during the period of ligament formation, from D15 to D18, thereafter abruptly declining on D19. From parturition (D19) onwards, an ever-increasing decline in the cellular proliferation levels could be observed. The quantitative analyses of cellular death showed opposite results when compared to cellular proliferation. During early pregnancy the cycle of cellular renovation was clearly proliferative and during late mouse pregnancy the cycle was directed by programmed cellular death. Although the high levels of cellular death during postpartum involution could be shown by the TUNEL-positive cells, we were unable to observed picnotic nucleus at the light microscopy.     

Mitotic activity of the pars intermedia in the female mouse: age-associated variations in proliferation rate and circadian periodicity

We previously reported daily variations in the mitotic activity of the endocrine cells in the pars intermedia of 21- and 28-day-old male mice. Since cellular proliferation might be affected by factors such as sex and age, we undertook the present experiments to study the mitotic activity of the pars intermedia from 14-, 28-, and 150-day-old female mice. Inbred C3H/S mice, grouped according to age, were housed under standard conditions (12h each of light and dark [LD 12:12]) for periodicity analysis and were killed in lots of 5-11 animals every 4h over a single 24h cycle, with each mouse receiving 2 μg/g of colchicine 4h before decapitation. Pituitaries were excised, extracted, fixed in buffered formaldehyde, embedded in celloidin-paraffin, sectioned at 5 μm, and stained with hematoxylin and eosin. We counted the total number of nuclei to estimate the total number of cells monitored and then calculated the mitotic index (metaphases/1000 nuclei). Differences were analyzed for statistical significance by the Student t test. While the 14-day-old animals manifested no significant changes in mitotic activity during the 24h cycle, the 28- and 150-day-old mice showed higher mitotic indices during the period of darkness. The average mitotic activity over the entire cycle, however, was higher in the two groups of younger animals than in the 150-day-old mice. Moreover, the averages for the 28-day-old females were higher than the corresponding values previously reported by us for male mice of the same age. (Chronobiology International, 17(6), 751-756, 2000)     

Effect of extension of the heparin binding pocket on the structure,stability, and cell proliferation activity of the human acidic fibroblast growth factor

Acidic human fibroblast growth factor (hFGF1) plays a key role in cell growth and proliferation. Activation of the cell surface FGF receptor is believed to involve the glycosaminoglycan, heparin. However, the exact role of heparin is a subject of considerable debate. In this context, in this study, the correlation between heparin binding affinity and cell proliferation activity of hFGF1 is examined by extending the heparin binding pocket through selective engineering via charge reversal mutations (D82R, D84R and D82R/D84R). Results of biophysical experiments such as intrinsic tryptophan fluorescence and far UV circular dichroism spectroscopy suggest that the gross native structure of hFGF1 is not significantly perturbed by the engineered mutations. However, results of limited trypsin digestion and ANS binding experiments show that the backbone structure of the D82R variant is more flexible than that of the wild type hFGF1. Results of the temperature and urea-induced equilibrium unfolding experiments suggest that the stability of the charge-reversal mutations increases in the presence of heparin. Isothermal titration calorimetry (ITC) data reveal that the heparin binding affinity is significantly increased when the charge on D82 is reversed but not when the negative charge is reversed at both positions D82 and D84 (D82R/D84R). However, despite the increased affinity of D82R for heparin, the cell proliferation activity of the D82R variant is observed to be reduced compared to the wild type hFGF1. The results of this study clearly demonstrate that heparin binding affinity of hFGF1 is not strongly correlated to its cell proliferation activity.     

二甲双胍对人脐带间充质干细胞形态、增殖、表面标志及细胞周期的影响

目的探讨不同浓度二甲双胍（METF）对人脐带间充质干细胞（hUC-MSC）形态、增殖、表面标志及细胞周期的影响。 方法取健康足月新生儿脐带在体外分离出hUC-MSC进行传代培养,至第3代（流式细胞仪分析）对细胞进行鉴定,取第6代处于对数生长期的hUC-MSC （相对老化）,将对照组与不同浓度METF （0.1,1,5,10,20?mmol/L）干预的细胞进行比较,观察不同浓度METF干预对细胞的形态、增殖率（MTT法分别于24、48、72?h检测）、及细胞表面标志和细胞周期的影响,采用One-Way ANOVA,及LSD-t检验进行统计学分析。 结果（1）METF为0.1?mmol/L、1?mmol/L,细胞形态无显著改变,当药物浓度为5?~?20?mmol/?L时,随着药物浓度增加、培养时间延长,细胞形态改变越显著。（2）METF为0.1?mmol/L（24?h：101.28±0.98,24?h：104.06±1.76,24?h：101.51±0.67）促进hUC-MSC增殖,药物浓度为1?~ 10?mmol/L在培养初期可增加间充质干细胞的增殖率,随着培养时间的延长,细胞的增殖逐渐被抑制。METF为20?mmol/L（24?h：86.64±0.66,48?h：58.38±2.52,72?h：17.75±1.35）抑制细胞增殖,抑制作用随着时间延长而增强（P?< 0.05）。（3）当METF浓度为5,10,20?mmol/L时,随着药物浓度的增加,CD105的表达逐渐减弱（F?= 17.539,P?< 0.05）。METF未对CD44、CD90产生影响。（4）METF为0.1?mmol/L时降低G0/G1期的比例（64.16±1.20,P?< 0.05）,促进间充质干细胞的增殖,随着药物浓度的增加,细胞增殖逐渐被抑制。 结论METF浓度在0.1mmol/?L促进hUC-MSC增殖,而在浓度5 ~ 20?mmol/L时抑制人脐带间充质干细胞的增殖及表面标志CD105的表达,不同浓度的METF均未对CD44、CD90的表达产生影响。     

Down-regulation of the expression of O-acetyl-GD3 by the O-acetylesterase cDNA in hamster melanoma cells: effects on cellular proliferation, differentiation, and melanogenesis

The composition of the gangliosides of hamster melanoma cells is closely related to their cellular growth and degree of differentiation, with slow-growing, highly differentiated melanotic melanoma MI cells expressing GM3 and fast-growing, undifferentiated amelanotic Ab melanoma cells having a preponderance of GD3 and O-acetyl-GD3. To study the putative function of O-acetyl-GD3, we established stably transfected AbC-1 amelanotic hamster melanoma cells with O-acetylesterase gene from influenza C virus to hydrolyze the O-acetyl group from O-acetyl-GD3. The content of O-acetyl-GD3 in the transfected cells expressing O-acetylesterase gene was reduced by >90%. These O-acetyl-GD3-depleted cells differed from the parental ones in their cellular morphology, growth behavior, and melanogenesis activity. The absence of O-acetyl-GD3 in the transfected cells was accompanied by increased thick dendrite formation with an enlarged cell body, which is in striking contrast to the control cells, which were rounded and flattened, with few processes. Their growth was significantly slower than that of the control cells. They also demonstrated significantly lower tyrosinase activity and melanogenic potential. We suggest that the enhanced expression of melanoma-associated O-acetyl-GD3 ganglioside may stimulate cellular growth and suppress certain differentiated phenotypes such as dendrite formation but not melanogenesis.     

Leptin stimulates human osteoblastic cell proliferation, de novo collagen synthesis, and mineralization: Impact on differentiation markers, apoptosis, and osteoclastic signaling

Anabolic hormones, mechanical loading, and the obese protein leptin play separate roles in maintaining bone mass. We have previously shown that leptin, as well as its receptor, are expressed by normal human osteoblasts. Consequently, we have investigated how leptin affects proliferation, differentiation, and apoptosis of human osteoblasts. Iliac crest osteoblasts, incubated with either leptin (100 ng/ml), calcitriol (1,25(OH)(2)D(3); 10(-9) M) or 1-84 human parathyroid hormone (PTH; 10(-8) M), were cultured for 35 consecutive days and assayed for expression of various differentiation-related marker genes (as estimated by RT-PCR), de novo collagen synthesis, proliferation, in vitro mineralization, and osteoclast signaling. The effects of leptin on protection against retinoic acid (RA; 10(-7) M) induced apoptosis, as well as transition into preosteocytes, were also tested. Leptin exposure enhanced cell proliferation and collagen synthesis over both control condition and PTH exposure. Leptin inhibited in vitro calcified nodule production after 1-2 weeks in culture, however, subsequent to 4-5 weeks, leptin significantly stimulated mineralization. The mineralization profile throughout the entire incubation period was almost undistinguishable from the one induced by PTH. In comparison, 1,25(OH)(2)D(3) generally reduced proliferation and collagen production rates, whereas mineralization was markedly enhanced. Leptin exposure (at 2 and 5 weeks) significantly enhanced the expression of TGFbeta, IGF-I, collagen-Ialpha, ALP, and osteocalcin mRNA. Leptin also protected against RA-induced apoptosis, as estimated by soluble DNA fractions and DNA laddering patterns subsequent to 10 days of culture. The expression profiles of Bax-alpha and Bcl-2 mRNAs indicated that leptin per se significantly protected against apoptosis throughout the entire incubation period. Furthermore, the osteoblast marker OSF-2 was diminished, whereas the CD44 osteocyte marker gene expression was stimulated, indicating a transition into preosteocytes. In terms of osteoclastic signaling, leptin significantly augmented the mRNA levels of both interleukin-6 (IL-6) and osteoprotegerin (OPG). In summary, continuous leptin exposure of iliac crest osteoblasts, promotes collagen synthesis, cell differentiation and in vitro mineralization, as well as cell survival and transition into preosteocytes. Leptin may also facilitate osteoblastic signaling to the osteoclast.     

Factors controlling cell proliferation and antibody production in mouse hybridoma cells: I. Influence of the amino acid supply

To investigate the influence of medium amino acid resources on hybridoma cell proliferation and monoclonal antibody secretion, we first determined, in two different cell lines, the pattern of amino acid consumption. We then showed that complementation of each cell line by an amino acid solution prepared to cover its needs led in both cases to a marked increase in cell density and monoclonal antibody production. This observation suggests that the amino acid supply is one of the factors limiting cell growth and productivity in typical batch processes, and we demonstrated that a similar limitation occurs in a semicontinuous culture. Finally, we showed that the cell decline observed after a period of amino acid deficiency is not irreversible and that proliferation could be resumed if the required amino acids were added.     

Prenatal stress on the kinetic properties of Ca2+ and K+ channels in offspring hippocampal CA3 pyramidal neurons

Prenatal stress is known to cause neuronal loss and oxidative damage in the hippocampus of offspring rats. To further understand the mechanisms, the present study was undertaken to investigate the effects of prenatal stress on the kinetic properties of high-voltage-activated (HVA) Ca(2+) and K(+) channels in freshly isolated hippocampal CA3 pyramidal neurons of offspring rats. Pregnant rats in the prenatal stress group were exposed to restraint stress on days 14-20 of pregnancy three times daily for 45 min. The patch clamp technique was employed to record HVA Ca(2+) and K(+) channel currents. Prenatal stress significantly increased HVA Ca(2+) channel disturbance including the maximal average HVA calcium peak current amplitude (-576.52+/-7.03 pA in control group and -702.05+/-6.82 pA in prenatal stress group, p<0.01), the maximal average HVA Ca(2+) current density (-40.89+/-0.31 pA/pF in control group and -49.44+/-0.37 pA/pF in prenatal stress group, p<0.01), and the maximal average integral current of the HVA Ca(2+) channel (106.81+/-4.20 nA ms in control group and 133.49+/-4.59 nA ms in prenatal stress group, p<0.01). The current-voltage relationship and conductance--voltage relationship of HVA Ca(2+) channels and potassium channels in offspring CA3 neurons were not affected by prenatal stress. These data suggest that exposure of animals to stressful experience during pregnancy can exert effects on calcium ion channels of offspring hippocampal neurons and that the calcium channel disturbance may play a role in prenatal stress-induced neuronal loss and oxidative damage in offspring brain.