Home About us Contact
|
Home About us Contact | ||
|
|
||
Mammalian Systems (mammalian + system)
Selected AbstractsDifferential growth and multicellular villi direct proepicardial translocation to the developing mouse heartDEVELOPMENTAL DYNAMICS, Issue 1 2008Laurel S. Rodgers Abstract In the mammalian system the proepicardium (PE) arises from mesothelium of the septum transversum before translocation to the heart where it forms the epicardium and progenitor cells of the coronary vessels. Despite its importance, the process in which PE cells translocate to the myocardium in mammals is not well defined. The current paradigm states that cellular cysts of PE float across the pericardial space and contact the outer surface of the myocardium. This mechanism does not provide a satisfactory explanation for the directionality or localization of PE migration. To better define PE migration, we performed a detailed study of mouse PE development. We provide thorough documentation that redefines the size of the PE migratory field and the mechanism of migration. Our new model incorporates differential growth and direct contact between multicellular PE villi and the myocardium as mechanisms in formation of the epicardium. Developmental Dynamics 237:145,152, 2008. © 2007 Wiley-Liss, Inc. [source] Effects of the androgenic growth promoter 17-,-trenbolone on fecundity and reproductive endocrinology of the fathead minnow,ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 6 2003Gerald T. Ankley Abstract Trenbolone acetate is a synthetic steroid that is extensively used in the United States as a growth promoter in beef cattle. The acetate is administered to livestock via slow-release implants; some is converted by the animal to 17-,-trenbolone, a relatively potent androgen receptor agonist in mammalian systems. Recent studies indicate that excreted 17-,-trenbolone is comparatively stable in animal waste, suggesting the potential for exposure to aquatic animals via direct discharge, runoff, or both. However, little is known concerning the toxicity of trenbolone to fish. Our goal was to assess the effects of 17-,-trenbolone on reproductive endocrinology of the fathead minnow (Pimephales promelas). An in vitro competitive binding study with the fathead minnow androgen receptor demonstrated that 17-,-trenbolone had a higher affinity for the receptor than that of the endogenous ligand, testosterone. Male and female fish were exposed for 21 d to nominal (target) concentrations of 17-,-trenbolone ranging from 0.005 to 50 ,g/L. Fecundity of the fish was significantly reduced by exposure to measured test concentrations , 0.027 ,g/ L. The 17-,-trenbolone was clearly androgenic in vivo at these concentrations, as evidenced by the de novo production in females of dorsal (nuptial) tubercles, structures normally present only on the heads of mature males. Plasma steroid (testosterone and ,-estradiol) and vitellogenin concentrations in the females all were significantly reduced by exposure to 17-,-trenbolone. The 17-,-trenbolone also altered reproductive physiology of male fathead minnows, albeit at concentrations much higher than those producing effects in females. Males exposed to 17-,-trenbolone at 41 ,g/L (measured) exhibited decreased plasma concentrations of 11-ketotestosterone and increased concentrations of ,-estradiol and vitellogenin. Overall, our studies indicate that 17-,-trenbolone is a potent androgen and reproductive toxicant in fish. Given the widespread use of trenbolone acetate as a growth promoter, and relative stability of its metabolites in animal wastes, further studies are warranted to assess potential ecological risk. [source] Expression of an Aedes aegypti cation-chloride cotransporter and its Drosophila homologuesINSECT MOLECULAR BIOLOGY, Issue 4 2003V. Filippov Abstract Insects maintain haemolymph homeostasis under different environmental conditions by modulating the concentrations of Na+, K+ and Cl, ions. One group of proteins involved in ion transport across cell membranes consists of cation-chloride cotransporters that form a family of structurally similar proteins. Although much is known about these proteins in mammalian systems, our understanding of them in insects is lacking. The recent sequencing of two insect genomes, Drosophila and Anopheles, enabled us to identify globally members of the family of cation chloride cotransporters in these insects. Using RT-PCR we monitored the transcription of members of this family in development and in several tissues. Our analyses showed that transcription of these genes differ considerably from the ubiquitously and highly expressed CG5594 gene to the almost silent gene CG31547. Comparison of Drosophila CG12773 and its Aedes homologue AaeCG12773 showed that they have similar transcript expression profiles. Immunohistochemical analysis of AaeCG1277 gene expression revealed that it is highly expressed in the gut of larvae and female adults but not in Malpighian tubules. A more detailed analysis showed that this protein is localized predominantly in the basolateral membrane of these tissues. This expression pattern confirmed the results of RT-PCR analysis. We also created a mutant for one of the genes, CG10413, in Drosophila using P-element excision. Analysis of this mutant showed this protein does not appear to be essential for development. [source] Yeast Programmed Cell Death: An Intricate PuzzleIUBMB LIFE, Issue 3 2005P. Ludovico Abstract Yeasts as eukaryotic microorganisms with simple, well known and tractable genetics, have long been powerful model systems for studying complex biological phenomena such as the cell cycle or vesicle fusion. Until recently, yeast has been assumed as a cellular 'clean room' to study the interactions and the mechanisms of action of mammalian apoptotic regulators. However, the finding of an endogenous programmed cell death (PCD) process in yeast with an apoptotic phenotype has turned yeast into an 'unclean' but even more powerful model for apoptosis research. Yeast cells appear to possess an endogenous apoptotic machinery including its own regulators and pathway(s). Such machinery may not exactly recapitulate that of mammalian systems but it represents a simple and valuable model which will assist in the future understanding of the complex connections between apoptotic and non-apoptotic mammalian PCD pathways. Following this line of thought and in order to validate and make the most of this promising cell death model, researchers must undoubtedly address the following issues: what are the crucial yeast PCD regulators? How do they play together? What are the cell death pathways shared by yeast and mammalian PCD? Solving these questions is currently the most pressing challenge for yeast cell death researchers.IUBMB Life, 57: 129-135, 2005 [source] Ischemia,reperfusion injury pathophysiology, part IJOURNAL OF VETERINARY EMERGENCY AND CRITICAL CARE, Issue 4 2004DACVECC, Maureen McMichael DVM Abstract Objective: To review the current scientific literature on ischemia,reperfusion (IR) injury in both human and veterinary medicine. To describe the normal antioxidant defense mechanisms, the pathophysiology of IR injury, and the role of neutrophils in IR injury. Data sources: Data sources include scientific reviews and original research publications in both human and veterinary medicine. Summary: IR injury is a complex pathophysiological process involving numerous pathways and body systems. Normal antioxidant defense mechanisms function to limit oxidative injury during times of health. Ischemia is the period that occurs before oxygenated blood is re-introduced and the severity of injury has been shown to correlate with the magnitude and length of ischemia in dogs. During ischemia, there is a buildup of substances (i.e., xanthine oxidase, hypoxanthine, etc.) that, upon re-introduction of oxygen, form reactive oxygen species (ROS). ROS, produced in large part upon reperfusion, can cause extensive damage to DNA, proteins, carbohydrates, and lipids. Although mammalian systems are endowed with abundant antioxidant defenses, the generation of large amounts of ROS can overwhelm these mechanisms leading to cell dysfunction and death. Neutrophils play a critical role in IR injury and may mediate the majority of mucosal and microvascular injury that occurs by releasing ROS and proteolytic enzymes. Although experimental studies have been carried out on cats, dogs, and horses there are few clinical studies on companion animals. Conclusions: The pathophysiology of IR injury is complex and involves damage by ROS to all biological membranes. Neutrophils play a major role in IR injury and initiate and propogate much of the damage. This article is intended as a review of the pathophysiology of IR injury. [source] The unique value of primate models in translational researchAMERICAN JOURNAL OF PRIMATOLOGY, Issue 9 2009Carol A. Shively Abstract This special issue of AJP is focused on research using nonhuman primates as models to further the understanding of women's health. Nonhuman primates play a unique role in translational science by bridging the gap between basic and clinical investigations. The use of nonhuman primates in biomedical research challenges our resolve to treat all life as sacred. The scientific community has responded by developing ethical guidelines for the care and the use of primates and clarifying the responsibility of investigators to insure the physical and psychological well-being of nonhuman primates used in research. Preclinical investigations often involve the use of animal models. Rodent models have been the mainstay of biomedical science and have provided enormous insight into the workings of many mammalian systems that h ave proved applicable to human biological systems. Rodent models are dissimilar to primates in numerous ways, which may limit the generalizability to human biological systems. These limitations are much less likely in nonhuman primates and in Old World primates, in particular, Macaques are useful models for investigations involving the reproductive system, bioenergetics, obesity and diabetes, cardiovascular health, central nervous system function, cognitive and social behavior, the musculoskeletal system, and diseases of aging. This issue considers primate models of polycystic ovary syndrome; diet effects on glycemic control, breast and endometrium; estrogen, reproductive life stage and atherosclerosis; estrogen and diet effects on inflammation in atherogenesis; the neuroprotective effects of estrogen therapy; social stress and visceral obesity; and sex differences in the role of social status in atherogenesis. Unmet research needs in women's health include the use of diets in nonhuman primate studies that are similar to those consumed by human beings, primate models of natural menopause, dementia, hypertension, colon cancer, and frailty in old age, and dedicated colonies for the study of breast cancer. Am. J. Primatol. 71:715,721, 2009. © 2009 Wiley-Liss, Inc. [source] Sequence-specific gene silencing in murine muscle induced by electroporation-mediated transfer of short interfering RNATHE JOURNAL OF GENE MEDICINE, Issue 1 2004Tsunao Kishida Abstract Background Post-genomic biomedical research requires efficient techniques for functional analyses of poorly characterized genes in living organisms. Sequence-specific gene silencing in mammalian organs may provide valuable information on the physiological and pathological roles of predicted genes in mammalian systems. Here, we attempted targeted gene knockdown in vivo in murine skeletal muscle through the electroporation-mediated transfer of short interfering RNA (siRNA). Methods siRNA duplexes corresponding to the firefly luciferase (Luc), green fluorescent protein (GFP), or glyceraldehyde-3-phosphate dehydrogenase (GAPD) genes were delivered by electroporation into the tibial muscle of normal or enhanced GFP (EGFP) transgenic mice. Plasmid vectors carrying the Luc, hRluc or ,-galactosidase (,-gal) reporter genes were also delivered. The Luc and hRluc activities in the muscle lysates were assayed. The EGFP and GAPD expression was detected by fluorescence microscopic observation and RT-PCR, respectively. Results When Luc-specific siRNA was co-delivered with the Luc expression vector into the tibial muscle, the reporter gene expression was markedly suppressed (less than 1% of the control level) for 5 days. As little as 0.05 µg of siRNA almost completely blocked the reporter gene expression from 10 µg of the plasmid. To examine whether siRNA can also suppress expression of an endogenous gene, transgenic mice carrying the EGFP gene received intramuscular transfection of a mixture of ,-gal plasmid and GFP-specific siRNA. ,-Gal-positive cells failed to express detectable levels of EGFP, while EGFP expression was not inhibited in control mice that received nonspecific siRNA. Expression of GAPD was also suppressed by the specific siRNA. Conclusions The present system may provide a useful means of phenotypic analysis of genetic information in mammalian organs for basic research as well as therapeutic molecular targeting in the post-genomic era. Copyright © 2003 John Wiley & Sons, Ltd. [source] Identification of genes encoding N -glycan processing ,- N -acetylglucosaminidases in Trichoplusia ni and Bombyx mori: Implications for glycoengineering of baculovirus expression systemsBIOTECHNOLOGY PROGRESS, Issue 1 2010Christoph Geisler Abstract Glycoproteins produced by non-engineered insects or insect cell lines characteristically bear truncated, paucimannose N -glycans in place of the complex N -glycans produced by mammalian cells. A key reason for this difference is the presence of a highly specific N -glycan processing ,- N -acetylglucosaminidase in insect, but not in mammalian systems. Thus, reducing or abolishing this enzyme could enhance the ability of glycoengineered insects or insect cell lines to produce complex N -glycans. Of the three insect species routinely used for recombinant glycoprotein production, the processing ,- N -acetylglucosaminidase gene has been isolated only from Spodoptera frugiperda. Thus, the purpose of this study was to isolate and characterize the genes encoding this important processing enzyme from the other two species, Bombyx mori and Trichoplusia ni. Bioinformatic analyses of putative processing ,- N -acetylglucosaminidase genes isolated from these two species indicated that each encoded a product that was, indeed, more similar to processing ,- N -acetylglucosaminidases than degradative or chitinolytic ,- N -acetylglucosaminidases. In addition, over-expression of each of these genes induced an enzyme activity with the substrate specificity characteristic of processing, but not degradative or chitinolytic enzymes. Together, these results demonstrated that the processing ,- N -acetylglucosaminidase genes had been successfully isolated from Trichoplusia ni and Bombyx mori. The identification of these genes has the potential to facilitate further glycoengineering of baculovirus-insect cell expression systems for the production of glycosylated proteins. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2010 [source] Conditional gene silencing utilizing the lac repressor reveals a role of SHP-2 in cagA -positive Helicobacter pylori pathogenicityCANCER SCIENCE, Issue 5 2004Megumi Higuchi RNA interference (RNAi) is a newly described biological phenomenon mediated by small interfering RNA (siRNA) that targets mRNA for degradation by cellular enzymes and has become a powerful method for studying gene functions in mammalian systems. The development of systems for inducing siRNA expression should enable examination of acute loss-of-function phenotypes in a cell of interest without the need to consider lethality or epigenetic adaptation of cells. We describe in this report an inducible siRNA expression system made by combined utilization of the RNA polymerase III-dependent promoter H1 and the bacterial lac repressor. Using this system, we established AGS gastric epithelial cells in which expression of SHP-2, a cellular tyrosine phosphatase known to specifically bind the Helicobacter pylori virulence factor CagA, is conditionally and reversibly silenced by the lactose analog isopropyl-1-thio-,-D-galactopyranoside (IPTG). Upon expression in AGS cells, CagA provoked a morphological transformation, termed the hummingbird phenotype, which is associated with CagA virulence. This morphogenetic activity of CagA was totally abolished when SHP-2 expression was silenced by inducible siRNA expression in AGS cells. Our results indicate that SHP-2 is a critical downstream effector of H. pylori CagA. The conditional gene silencing system described here should become a powerful tool for investigating the roles of cancer-related genes through a reversed genetic approach. [source] | |||||||||||||