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排序方式: 共有140条查询结果,搜索用时 15 毫秒
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PM Visscher 《遗传、选种与进化》1995,27(4):335-345
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PM Cala 《The Journal of general physiology》1977,69(5):537-552
The nucleated high K, low Na red blood cells of the winter flounder demonstrated a volume regulatory response subsequent to osmotic swelling or shrinkage. During volume regulation the net water flow was secondary to net inorganic cation flux. Volume regulation the net water flow was secondary to net inorganic cation flux. Volume regulation after osmotic swelling is referred to as regulatory volume decrease (RVD) and was characterized by net K and water loss. Since the electrochemical gradient for K is directed out of the cell there is no need to invoke active processes to explain RVD. When osmotically shrunken, the flounder erythrocyte demonstrated a regulatory volume increase (RVI) back toward control cell volume. The water movements characteristic of RVI were a consequence of net cellular NaCl and KCl uptake with Na accounting for 75 percent of the increase in intracellular cation content. Since the Na electrochemical gradient is directed into the cell, net Na uptake was the result of Na flux via dissipative pathways. The addition of 10(-4)M ouabain to suspensions of flounder erythrocytes was without effect upon net water movements during volume regulation. The presence of ouabain did however lead to a decreased ration of intracellular K:Na. Analysis of net Na and K fluxes in the presence and absence of ouabain led to the conclusion that Na and K fluxes via both conservative and dissipative pathways are increased in response to osmotic swelling or shrinkage. In addition, the Na and K flux rate through both pump and leak pathways decreased in a parallel fashion as cell volume was regulated. Taken as a whole, the Na and K movements through the flounder erythrocyte membrane demonstrated a functional dependence during volume regulation. 相似文献
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Erica G. Tierney Garry P. Duffy Sally-Ann Cryan Caroline M. Curtin Fergal J. O’Brien 《Organogenesis》2013,9(1):22-25
One solution to the shortage of human organs available for transplantation envisions growing new organs in situ. This can be accomplished by transplantation of developing organ anlagen/primordia. Allotransplantation of embryonic day 15 metanephroi into the omentum of adult hosts is followed by differentiation, growth, vascularization and function of the implants. Here we show that survival of rats with all native renal mass removed can be increased by prior metanephros transplantation and ureteroureterostomy. Excretion of urine formed by metanephroi is prerequisite for enhanced survival. This is the first demonstration that life can be extended following de novo renal organogenesis. 相似文献
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Uxmal and Tulum are two important Mayan sites in the Yucatan peninsula. The buildings are mainly composed of limestone and grey/black discoloration is seen on exposed walls and copious greenish biofilms on inner walls. The principal microorganisms detected on interior walls at both Uxmal and Tulum were cyanobacteria; heterotrophic bacteria and filamentous fungi were also present. A dark‐pigmented mitosporic fungus and Bacillus cereus, both isolated from Uxmal, were shown to be acidogenic in laboratory cultures. Cyanobacteria belonging to rock‐degrading genera Synechocystis and Gloeocapsa were identified at both sites. Surface analysis previously showed that calcium ions were present in the biofilms on buildings at Uxmal and Tulum, suggesting the deposition of biosolubilized stone. Apart from their potential to degrade the substrate, the coccoid cyanobacteria supply organic nutrients for bacteria and fungi, which can produce organic acids, further increasing stone degradation. 相似文献
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Angela D. Luis David T. S. Hayman Thomas J. O'Shea Paul M. Cryan Amy T. Gilbert Juliet R. C. Pulliam James N. Mills Mary E. Timonin Craig K. R. Willis Andrew A. Cunningham Anthony R. Fooks Charles E. Rupprecht James L. N. Wood Colleen T. Webb 《Proceedings. Biological sciences / The Royal Society》2013,280(1756)
Bats are the natural reservoirs of a number of high-impact viral zoonoses. We present a quantitative analysis to address the hypothesis that bats are unique in their propensity to host zoonotic viruses based on a comparison with rodents, another important host order. We found that bats indeed host more zoonotic viruses per species than rodents, and we identified life-history and ecological factors that promote zoonotic viral richness. More zoonotic viruses are hosted by species whose distributions overlap with a greater number of other species in the same taxonomic order (sympatry). Specifically in bats, there was evidence for increased zoonotic viral richness in species with smaller litters (one young), greater longevity and more litters per year. Furthermore, our results point to a new hypothesis to explain in part why bats host more zoonotic viruses per species: the stronger effect of sympatry in bats and more viruses shared between bat species suggests that interspecific transmission is more prevalent among bats than among rodents. Although bats host more zoonotic viruses per species, the total number of zoonotic viruses identified in bats (61) was lower than in rodents (68), a result of there being approximately twice the number of rodent species as bat species. Therefore, rodents should still be a serious concern as reservoirs of emerging viruses. These findings shed light on disease emergence and perpetuation mechanisms and may help lead to a predictive framework for identifying future emerging infectious virus reservoirs. 相似文献
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Pathophysiology of white-nose syndrome in bats: a mechanistic model linking wing damage to mortality
Lisa Warnecke James M. Turner Trent K. Bollinger Vikram Misra Paul M. Cryan David S. Blehert Gudrun Wibbelt Craig K. R. Willis 《Biology letters》2013,9(4)
White-nose syndrome is devastating North American bat populations but we lack basic information on disease mechanisms. Altered blood physiology owing to epidermal invasion by the fungal pathogen Geomyces destructans (Gd) has been hypothesized as a cause of disrupted torpor patterns of affected hibernating bats, leading to mortality. Here, we present data on blood electrolyte concentration, haematology and acid–base balance of hibernating little brown bats, Myotis lucifugus, following experimental inoculation with Gd. Compared with controls, infected bats showed electrolyte depletion (i.e. lower plasma sodium), changes in haematology (i.e. increased haematocrit and decreased glucose) and disrupted acid–base balance (i.e. lower CO2 partial pressure and bicarbonate). These findings indicate hypotonic dehydration, hypovolaemia and metabolic acidosis. We propose a mechanistic model linking tissue damage to altered homeostasis and morbidity/mortality. 相似文献
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Burris TP Pelton PD Zhou L Osborne MC Cryan E Demarest KT 《Molecular endocrinology (Baltimore, Md.)》1999,13(3):410-417
Peroxisome proliferator-activated receptor-gamma (PPARgamma), a member of the nuclear hormone receptor superfamily, plays an essential role in the mediation of the actions of antidiabetic drugs known as thiazolidinediones (TZDs). PPARgamma activates many target genes involved in lipid anabolism including the adipocyte fatty acid binding protein (aP2). In this study, induction of aP2 gene expression by PPARgamma agonists was examined in both cultured cells and diabetic mice using branched DNA (bDNA)-mediated mRNA quantitation. bDNA technology allows for the direct measurement of a particular mRNA directly within cellular lysate using a 96-well plate format in a time frame comparable to a reporter gene assay. In cultured human subcutaneous preadipocytes, the TZDs, troglitazone and BRL-49653, both rapidly induced aP2 mRNA as detected with the bDNA method. In these cells, the effect of BRL-49653 on aP2 mRNA levels was detectable as early as 30 min after treatment (47% increase) and was maximal after 24 h of treatment (12-fold increase). The effects of troglitazone on aP2 mRNA induction were similar to those of BRL-49653 except that the maximal level of induction was consistently lower (e.g. 24 h treatment = 4-fold increase). Dose-response relationships for both of the TZDs were also determined using the 24-h treatment time point. EC50s for both BRL-49653 and troglitazone were estimated to be 80 nM and 690 nM, respectively. A natural PPARgamma ligand, 15-deoxy-delta12,14-PGJ2, was also active in this assay with a maximal induction of aP2 mRNA of approximately 5-fold when tested at 1 microM. Since the PPARgamma:retinoid X receptor (RXR) heterodimer has been characterized as a permissive heterodimer with respect to RXR ligands, the ability of 9-cis-retinoic acid (9-cis-RA) to induce aP2 mRNA was examined. Although 9-cis-RA had very low efficacy (2-fold induction), the maximal effect was reached at 100 nM. No synergism or additivity in aP2 mRNA induction was detected when 9-cis-RA was included with either of the TZDs used in this study. Significant induction of aP2 mRNA in bone marrow of db/db mice treated with either troglitazone or BRL-49653 was also detected, indicating that the bDNA assay may be a simple method to monitor nuclear receptor target gene induction in vivo. 相似文献