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At least 919 records · Page 51Linked to original sources
PubMed1990

[Tumor control-significance of the stem cell number].

The stem cell number is one of the important factor determining tumor control radiation dose. It is now clear that 50% tumor cell doses in various rodent tumors inversely related to their tumor control radiation doses. Roles of radiation-sterilized cells on the clonogenicity of survived stem cells are controversial, and should be explored by future research. Methodological innovations are also desirable to measure the stem cell number in human tumors.

Animals↗
PubMed2005

Role of the pineal gland and melatonin in the photoperiodic control of hypothalamic gonadotropin-releasing hormone in the male jerboa (Jaculus orientalis), a desert rodent.

The neuroendocrine mechanism underlying seasonal changes in gonadal activity of the jerboa, a desert hibernating rodent adapted to harsh climatic conditions, are poorly understood. We investigated the role of the pineal gland and melatonin in the photoperiodic control of hypothalamic gonadotropin-releasing hormone (GnRH). Intact and pinealectomized male jerboas were subjected to short photoperiod, while others were kept under long photoperiod and injected daily with melatonin or vehicle. Testes activity was monitored by evaluating the testes volume during 10 weeks. GnRH immunoreactivity was investigated quantitatively with image analysis. Following melatonin administration, the hormone peaked in plasma after 30 min, with return to control levels 2.5 h later. Exposure to short photoperiod and melatonin resulted in marked increase in the number of GnRH-containing cells in the preoptic area and mediobasal hypothalamus, whereas GnRH immunoreactivity of fibers and terminals in the median eminence decreased under these conditions. The findings indicate that in the jerboa short photoperiod induces testicular regression by prolonging the duration of melatonin as an endocrine signal. This mechanism probably involves inhibition of GnRH release in the median eminence, with consequent accumulation of GnRH in perikarya of the preoptic area and mediobasal hypothalamus. Interestingly, GnRH cells of the median eminence did not appear to be influenced by the photoperiod and pineal melatonin, whereas their number was increased by exogenous melatonin. The latter data suggest for the first time the involvement of an extrapineal melatonin, whose origin remains to be identified, in the modulation of the GnRH regulatory system in rodents.

Analysis of Variance↗
PubMed1999

Altered expression of bone sialoproteins in vitamin D-deficient rBSP2.7Luc transgenic mice.

Bone sialoprotein (BSP) and osteopontin (OPN) are two major noncollagenous matrix proteins in mineralized connective tissue that have discrete roles in bone matrix formation, mineralization, and remodeling. The osteotropic secosteroid, 1,25-dihydroxyvitamin D3, a potent regulator of bone remodeling required for normal bone development, has been shown to exert differential effects on OPN and BSP expression by bone cells in vitro. To investigate these effects in vivo, we induced vitamin D3 deficiency in a transgenic mouse line (rBSP2.7Luc) that has a 2.7 kb rat BSP promoter linked to a luciferase reporter gene in its genome. Pregnant rBSP2.7Luc mice were fed vitamin D3-deficient food and demineralized water for 6 weeks. Their offspring were weaned at 3 weeks of age and then fed vitamin D-deficient food for an additional week. The control group were fed normal rodent pellets and water during the entire experimental procedure. Bone tissues from 40, 4-week-old offspring in each group were analyzed for BSP, OPN and luciferase expression. Vitamin D3-deficient mice displayed a rachitic phenotype that included reduced size and malformation of bones. Assays of the BSP promoter transgene in calvariae, mandibles, and tibiae of the rachitic mice showed increases in luciferase activity of 3.1-, 1.9-, and 4.6-fold, respectively, when compared with control littermates. Semiquantitative reverse transcriptase polymerase chain reaction assays of BSP mRNA revealed increases of 7-, 74-, and 66-fold, respectively, in the same rachitic bones, while OPN mRNA was reduced 12.5-fold in calvariae and 2-fold in tibiae and mandibles. In situ hybridization using mouse cRNA probes revealed that the increased BSP expression and decreased OPN expression in the vitamin D3-deficient mice was primarily in osteoblastic cells on the surface of calvariae and endosteal spaces of alveolar bone, on newly formed epiphyseal bone, and in cementoblasts and in hypertrophic chondrocytes. These studies are the first to show that BSP and OPN are differentially regulated by vitamin D3 in vivo, reflecting the diverse roles of these protein in bone remodeling. Moreover, the increased expression of the BSP transgene in the rachitic mice demonstrates that vitamin D3 regulation of BSP expression is mediated, in part, by element(s) within the 2.7 kb promoter region.

Animals↗
PubMed1987

Induction of liver microsomal epoxide hydrolase, UDP-glucuronyl transferase and cytosolic glutathione transferase in different rodent species by 2-acetylaminofluorene or 3-methylcholanthrene.

Control activities vary 12-fold for microsomal epoxide hydrolase, two-fold for UDP-glucuronyl transferase and five-fold for cytosolic glutathione (GSH) transferase among the different rodents (rat, hamster, guinea-pig, mouse) examined. For all three enzymes the activities in rat liver are towards the lower values. In these rodents, except for a 100% increase in microsomal epoxide hydrolase in guinea-pig liver, 2-acetylaminofluorene induces the three phase 2 enzymes only in rat. Treatment with 3-methylcholanthrene also produces the largest effects on these three enzyme activities in rat liver; exceptions are its failure to induce microsomal epoxide hydrolase in female rat and the large induction of cytosolic GSH transferase in hamster liver. Quantitatively, hepatic microsomal epoxide hydrolase, UDP-glucuronyl transferase and cytosolic GSH transferase activities, and their inducibility by 2-acetylaminofluorene or 3-methylcholanthrene, in male Sprague-Dawley rats are not representative for other rodent species or even, in all cases, for female rat.

2-Acetylaminofluorene↗
PubMed2004

Prevalence of hantavirus antibody in patients with chronic renal disease in Egypt.

In Egypt, the etiology of chronic renal failure (CRF) is not well defined. A hospital-based case-control study was initiated in February 1998, to determine whether hantavirus infection is involved in chronic renal disease (CRD) in Egypt. The study enrolled 350 study patients with a history of CRF and 695 matched controls with CRD due to renal calculus or renal cancer, but with normal renal functions. Sera from cases and controls were tested for anti-hantavirus IgG using ELISA with a cell-lysate antigen from Hantaan virus prototype strain 76-118. A demographic questionnaire was completed for each study participant. Five of the 350 cases (1.4%), and seven of the 695 controls (1.0%) were antibody-positive to hantavirus, with a titer > or =1:400. The difference in antibody prevalence between the study cases and the control cases was not statistically significant (P = 0.48). All antibody-positive study cases and controls had been exposed to rodents. Data indicated that in Egypt, hantavirus seroprevalence in CRD patients is low, and hantavirus infections do not appear to be a significant cause of CRF.

Adult↗
PubMed2005

Polymorphisms at codons 108 and 189 in murine PrP play distinct roles in the control of scrapie incubation time.

Susceptibility to transmissible spongiform encephalopathies (TSEs) is associated strongly with PrP polymorphisms in humans, sheep and rodents. In mice, scrapie incubation time is controlled by polymorphisms at PrP codons 108 (leucine or phenylalanine) and 189 (threonine or valine), but the precise role of each polymorphism in the control of disease is unknown. The L108F and T189V polymorphisms are present in distinct structural regions of PrP and thus provide an excellent model with which to investigate the role of PrP structure and gene variation in TSEs. Two unique lines of transgenic mice, in which 108F and 189V have been targeted separately into the endogenous murine Prnp(a) gene, have been produced. TSE inoculation of inbred lines of mice expressing all allelic combinations at codons 108 and 189 has revealed a complex relationship between PrP allele and incubation time. It has been established that both codons 108 and 189 control TSE incubation time, and that each polymorphism plays a distinct role in the disease process. Comparison of ME7 incubation times in mouse lines that are heterozygous at both codons has also identified a previously unrecognized intramolecular interaction between PrP codons 108 and 189.

Animals↗
PubMed2000

Historical vehicle and positive control micronucleus data in mice and rats.

The rodent bone marrow micronucleus (MN) assay has been widely used as part of an in vivo genotoxicity test battery in product safety evaluation. In this assay, the historical vehicle and positive control data form an important component in the assay performance and data interpretation. Also, in light of minimizing animal use in research and still obtain required data from a study, the routine use of positive control in every MN assay has been questioned by the scientific community, especially in laboratories which have demonstrated assay reproducibility and conduct studies under Good Laboratory Practice regulations. In this paper, mouse and rat vehicle and positive control MN data, collected manually, are described as a reference for a period of 12 years (1987-1998) in our laboratory. The vehicles generally included a variety of aqueous solutions and suspensions and cyclophosphamide dosed intraperitoneally at 20mg/kg (rats) or 40 mg/kg (mice) served as positive control, in all studies. Based on combined sex data (430 animals), for CD(1) mice, the vehicle control MN polychromatic erythrocyte (PCE) range was 0.9-3.1 with a mean of 1.75 per 1000 PCE and the positive control range (220 animals) was 8.8-42.1 with a mean of 23.1 MNPCE per 1000 PCE. Similarly, for Wistar rats, the vehicle control range (360 animals) was 1.3-5.3 with a mean of 2.6 MNPCE per 1000 PCE and the positive control range (240 animals) was 10.4-33.8 MNPCE per 1000 PCE. Vehicle control ranges reported here are comparable to the literature database and the positive control response was > or = 4-fold over vehicle control, in all studies. These data demonstrate the reproducibility of positive control response in MN assay in our laboratory and support the MN Assay Expert Panel's view that the use of positive control may not be necessary in every study.

Animals↗
PubMedDate not supplied

FDA points-to-consider documents: the need for dietary control for the reduction of experimental variability within animal assays and the use of dietary restriction to achieve dietary control.

Standard protocols for conducting chronic toxicity and carcinogenicity studies have been refined over the years to carefully control for many variables. Nevertheless, over the last 2 decades, there has been a steady increase in variability, a decrease in survival, an increase in tumor incidence rates, and an increase in the average body weight of control animals among the various rodent species and strains used for toxicity testing. These observations have prompted an evaluation of chronic study designs to determine what factor(s) may be responsible for such confounding changes. Ad libitum feeding and the selection of successful breeders with rapid offspring growth is believed to be at least partially responsible for the heavier, obese rodents with which many laboratories are coping today. As a result of these changes, some studies used for the evaluation of safety have been deemed inconclusive or inadequate for regulatory purposes and either additional supportive studies have been requested and/or studies per se have been repeated. Research on the molecular mechanisms of caloric restriction and agent-induced toxicity at the Food and Drug Administration (FDA) National Center for Toxicological Research stimulated the first international conference on the biological effects of dietary restriction in 1989; this was followed in 1993 by an FDA workshop exploring the utility of dietary restriction in controlling reduced survival in chronic tests and an international conference in 1994 exploring the implications for the regulatory community of using dietary restriction in toxicity and carcinogenicity studies used in support of a sponsor's submission or in risk assessments. The outcome of that conference was the FDA's commitment to develop Points-to-Consider documents that address the issue of dietary control in chronic toxicity and carcinogenicity studies.

Animal Feed↗
PubMed2006

Fluorescent in situ hybridization as a tool to retrospectively identify Cryptosporidium parvum and Giardia lamblia in samples from terrestrial mammalian wildlife.

Fecal samples of five terrestrial mammalian wildlife species stored at 4 degrees C or at -20 degrees C for up to 36 months have been tested for human zoonotic enteric parasites (i.e., Cryptosporidium parvum and Giardia lamblia) using combined fluorescent in situ hybridization (FISH) and direct fluorescent antibody techniques. The prevalence of C. parvum and G. lamblia varied from 20 to 63% (mean, 45.8%) and from 13 to 100% (mean, 53.2%), respectively. The prevalence of C. parvum and G. lamblia infections was higher in small rodents (mean, 68.5%) than in other wildlife (mean, 21%). Overall, 31.1% of animals were coinfected, and coinfections were more prevalent in small rodents (mean, 52%) than in other wildlife species (mean, 13.2%). The present study has shown that the FISH assay can be retrospectively applied to fecal samples for the identification of C. parvum oocysts, but is less suitable for the identification of G. lamblia cysts in such samples. Terrestrial mammalian wildlife, particularly small rodents, can contribute to watershed contamination with C. parvum oocysts and G. lamblia cysts. To control contamination, the management of pristine watersheds used for drinking water purposes should incorporate control measures for terrestrial wildlife, especially field rodents residing within such watersheds.

Animals↗
PubMed1998

Gonadal steroids and hypothalamic galanin and neuropeptide Y: role in eating behavior and body weight control in female rats.

The neuropeptides, galanin (GAL) and neuropeptide Y (NPY), based on studies in male rodents, are believed to have a role in controlling energy balance, both nutrient ingestion and metabolism. Whereas these peptides are also involved in reproduction, little is known about their specific function in energy balance in females. In rats consuming lab chow or macronutrient diets, measurements across the estrous cycle were taken of hypothalamic GAL and NPY, using RIA and immunohistochemistry; of the circulating hormones, estradiol, progesterone, and LH; and also of food intake and body weight. Levels of GAL and NPY peak during the proestrous phase of the female cycle when circulating estradiol and progesterone also rise. As previously reported for GAL, this peak is detected in two areas, the medial preoptic area (MPOA; +110%; P < 0.05) and the external zone of the median eminence (+57%; P < 0.05). In addition, this proestrous peak is seen in the paraventricular nucleus (PVN), specifically the anterior parvocellular portion (+35%; P < 0.05). Similarly, NPY rises during proestrous in the medial region of the PVN (+21%; P < 0.05) in addition to the MPOA (+78%; P < 0.05) and arcuate nucleus (+35%; P < 0.05). This peak in peptide levels is accompanied by an increase in caloric intake in rats receiving the lab chow diet and a specific increase in preference for fat in rats receiving macronutrient diets. Animals showing a preference for a fat-rich diet exhibit higher levels of GAL in the MPOA as well as the PVN and median eminence and also of NPY specifically in the MPOA. These peptides in the MPOA are similarly enhanced in animals with greater body fat, independent of diet. This evidence suggests that in the female rat, both GAL and NPY in the MPOA may contribute to the overeating and increased weight gain that occur during a fat-rich diet.

Animals↗
PubMed2006

Control of cellular proliferation by modulation of oxidative phosphorylation in human and rodent fast-growing tumor cells.

The relationship between cell proliferation and the rates of glycolysis and oxidative phosphorylation in HeLa (human) and AS-30D (rodent) tumor cells was evaluated. In glutamine plus glucose medium, both tumor lines grew optimally. Mitochondria were the predominant source of ATP in both cell types (66-75%), despite an active glycolysis. In glucose-free medium with glutamine, proliferation of both lines diminished by 30% but oxidative phosphorylation and the cytosolic ATP level increased by 50%. In glutamine-free medium with glucose, proliferation, oxidative phosphorylation and ATP concentration diminished drastically, although the cells were viable. Oligomycin, in medium with glutamine plus glucose, abolished growth of both tumor lines, indicating an essential role of mitochondrial ATP for tumor progression. The presumed mitochondrial inhibitors rhodamines 123 and 6G, and casiopeina II-gly, inhibited tumor cell proliferation and oxidative phosphorylation, but also glycolysis. In contrast, gossypol, iodoacetate and arsenite strongly blocked glycolysis; however, they did not affect tumor proliferation or mitochondrial metabolism. Growth of both tumor lines was highly sensitive to rhodamines and casiopeina II-gly, with IC(50) values for HeLa cells lower than 0.5 microM, whereas viability and proliferation of human lymphocytes were not affected by these drugs (IC(50) > 30 microM). Moreover, rhodamine 6G and casiopeina II-gly, at micromolar doses, prolonged the survival of animals bearing i.p. implanted AS-30D hepatoma. It is concluded that fast-growing tumor cells have a predominantly oxidative type of metabolism, which might be a potential therapeutic target.

Adenosine Triphosphate↗
PubMed2006

Involvement of PDX-1 in activation of human insulin gene transcription.

Islet beta cell-specific transcription of the insulin gene is mediated through the binding of the islet-enriched PDX-1, BETA2, and MafA transcription factors to conserved 5'-flanking region regulatory elements. However, additional non-conserved sequences within this region are also significant in regulating expression. Thus, PDX-1 binds to and activates the GG2 element located between nucleotides -145 and -140 of the human gene, while the corresponding, but non-identical, site in the rodent insulin genes are negatively regulated by the Nkx2.2 transcription factor. Here, we show that despite binding PDX-1 approximately 20-fold less effectively than the conserved insulin A3 and A1 sites in gel mobility shift assays, human GG2 appears to be more important for the activation of transfected human insulin enhancer-driven reporter constructs in beta cell lines. Furthermore, functional interaction analysis in non-islet cell lines demonstrated that PDX-1 binding to GG2, A1, and A3 contributes to synergistic activation of insulin gene expression with MafA. Our analysis also illustrated the requirement of poorly conserved human sequences between -293 and -251 in mediating activity through the more upstream A3 binding site. Collectively these experiments have revealed distinct features in control of the human and rodent insulin genes by PDX-1, processes that may be involved in regulating insulin expression under both normal and diabetic conditions in humans.

Animals↗
PubMed1999

BHA diet enhances the survival of mice exposed to phosgene: the effect of BHA on glutathione levels in the lung.

Phosgene-induced pulmonary edema formation has been under investigation for many years. One mechanism of protection may involve the use of antioxidants. Previously, it has been shown that butylated hydroxyanisole (BHA) treatment can enhance glutathione (GSH) levels. The present study focused on dietary supplementation in mice using BHA, a phenolic compound used in food preservation. Three groups of male CD-1 mice were studied: group 1, control animals fed with Purina rodent chow 5002; group 2, fed 0.75% BHA (w/w) in 5002; and group 3, fed 1.5% BHA (w/w) in 5002. Mice were fed for 22 days. On day 23 mice were exposed to 32 mg/m(3) phosgene for 20 min in a whole-body exposure chamber. Survival rate (SR) and odds ratio (OR) were determined at 12 and 24 h. In mice that died within 12 h, the lungs were removed immediately and lung wet weights (WW), dry weights (DW), lung wet weight/body weight ratio (LWW/BW), and lung tissue total glutathione (GSH) were assessed. For 12-h data, 6 mice from the 1.5% BHA group were sacrificed for lung tissue measurements. The SR for 0.75% BHA was 80% at 12 h and 55% at 24 h, compared with 36% and 23%, respectively, for controls. For 1.5% BHA, the 12- and 24-h SR were 100% and 92%, respectively. Odds ratios of 6.9 for 0.75% BHA and 46.6 for 1.5% BHA at 12 h and 4.0 and 42 for 0. 75% and 1.5% BHA, respectively, at 24 h were significantly (chi2) higher than control diet phosgene-exposed mice. Dietary pretreatment with 0.75% and 1.5% BHA significantly enhanced lung tissue GSH, 1.8-fold (p < or =.01) and 5.8-fold (p < or =.01), respectively, compared with phosgene-exposed control diet. Both BHA-supplemented diets significantly reduced WW. Only 1.5% BHA reduced DW, a measure of lung hyperaggregation. and LWW/BW compared with control diet. In air-exposed controls, BHA induced a dose-responsive decrease in WW, DW, LWW/BW ratio, and GSH. In conclusion, dietary pretreatment with BHA at the two dose levels reduced lung edema and lethality by enhancing lung tissue GSH in mice exposed to phosgene.

Animals↗
PubMed1995

New frontiers in heart transplantation. Clinical applications of basic research and new surgical approaches.

The growing understanding of alloimmune responses may help elucidate the mechanisms a novel immunomodulatory strategies, affording insights into new single or combination regimens. These insights are currently elusive because of the number of immuno-suppressive agents and techniques, the array of possible organ transplants, and the variety of experimental in vitro and in vivo models in diverse species. These possibilities add a bewildering level of complexity to the usual therapeutic problems of selecting drug doses, vehicles, routes, and schedules of administration. Although the results of in vitro assays have been used as indices of alloreactivity, they show only inconsistent correlations with clinical events. Only stringently controlled in vivo studies in rodents, large animals models, and humans will determine which agents or procedures represent real improvements over conventional therapy. The results of preclinical transplantation models and initial clinical trials suggest that immunosuppression for transplant patients is likely to evolve into various combination regimens. It appears now that there will be a choice between cyclosporine and FK506 as baseline immunosuppression because clinical experience has shown that these two drugs cause excessive nephrotoxicity when used in combination. Ideally the combination of additional new agents will enable the doses of cyclosporine and FK506 to be lowered to levels that are nonnephrotoxic and at the same time minimize or completely eliminate the need for corticosteroids and anti-T cell antibody therapy. The diverse mechanisms of immunosuppressive action of the new drugs under investigation certainly offer the hope for creative and effective strategies for the control of many forms of graft rejection in the near future.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2003

Variable tissue expression of transferrin receptors: relevance to acute respiratory distress syndrome.

Acute respiratory distress syndrome (ARDS) is associated with altered plasma and lung iron chemistry. Iron can promote microbial virulence and catalyse pro-oxidant reactions, thereby contributing to the oxidative stress that characterises the syndrome. Therefore, the expression of ferritin and transferrin receptors (TfR) were sought in the lungs and hearts of rodents treated with lipopolysaccharide (LPS), and measurements of TfR and ferritin protein expression were taken from lung biopsy specimens from patients with ARDS and appropriate controls. TfR messenger ribonucleic acid (mRNA) was significantly upregulated in the lungs and significantly downregulated in the hearts of rats 4 h after LPS. Ferritin mRNA levels (light and heavy chains) remained unaltered. Protein TfR levels were significantly upregulated in lungs and downregulated in hearts 4 h post-LPS. Ferritin protein levels were significantly downregulated in lungs compared to baseline values but were unaltered in hearts. Nonhaem iron levels were increased in lungs and decreased in hearts, and iron-regulatory-protein activity increased in hearts but not lungs. TfR protein levels were significantly increased in lung biopsies from patients with ARDS compared to controls. Transferrin receptors are upregulated in rodent lungs during inflammation but are downregulated in the heart. Transferrin receptor protein levels were significantly increased in the lungs in clinical acute respiratory distress syndrome. These findings have implications for the pathogenesis of acute respiratory distress syndrome, especially in relation to the role of iron as a mediator of oxidative stress.

Adult↗
PubMed1990

Macrophage secretory activity and atherosclerosis during chronic renal failure.

Accelerated atherosclerosis is a serious complication of chronic renal failure (CRF) treated by peritoneal dialysis. In order to study the pathological mechanisms underlying its development we are using an animal model, namely the C57BL/6J mouse, which develops foam cell-type atherosclerotic lesions after surgical induction of CRF. During atherogenesis, monocyte/macrophages move from the circulation to the blood vessel wall, migrate through the endothelium, imbibe lipid and transform into foam cells. Migration through the endothelium involves proteolysis by plasminogen activator (PA) and uptake of lipids involves hydrolysis of lipoproteins by lipoprotein lipase (LPL). Both of these enzymes are secreted by macrophages. In this paper we report the results of studies on the effect of uremia on the secretion of PA and LPL by macrophages from C57BL/6J mice. The secretion of PA and LPL by macrophages from uremic mice (as defined by BUN levels) was higher than that by cells from control animals. Furthermore, whereas macrophage secretion of PA and LPL was significantly less in normal mice fed a high fat diet than in mice fed rodent chow, it was increased above control levels in uremic animals fed the atherogenic diet. We conclude that increased secretion of PA and LPL by macrophages may contribute to atherogenesis in uremic C57BL/6J mice.

Animals↗
PubMed1996

Retardation by restricted feeding of age-related changes in steroidogenic activity of rat pre- and post-ovulatory follicles.

Reproductive ageing in female rodents is accompanied by changes in circulating peptide and steroid hormones leading to irregular, lengthened oestrous cycles prior to loss of fertility. In this study, the effect of ageing is reported on steroid hormone synthesis within individual ovarian follicles and its retardation by restricted feeding for two groups of ad libitum fed animals (114 and 350 days) and two groups of diet-restricted animals (350 and 600 days). Follicles from ad libitum fed animals of 350 days showed a transition in follicular steroid hormone synthesis to release elevated amounts of oestradiol-17beta on all days of the cycle. This age-related change in follicle steroid release was significantly delayed by maintaining animals on a restricted feeding regime, and was not complete even by 600 days of age. This effect of diet as a means to manipulate ageing of the follicular steroidogenic pathways provides a useful system for investigating the control of reproductive ageing in rodents.

Aging↗