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排序方式: 共有83条查询结果,搜索用时 15 毫秒
1.
The metabolism and hormonal responses of human eccrine sweat glands isolated by collagenase digestion.
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T Kealey 《The Biochemical journal》1983,212(1):143-148
1. Collagenase digestion of biopsies of human skin yields eccrine sweat glands that can be picked out under binocular light microscopy. The glands are viable as determined by the exclusion of Trypan Blue, the uptake of Methylene Blue, electron microscopy, the rate of lactate dehydrogenase release, ATP content and the rates of glucose oxidation and lactate release. 2. It is proposed that eccrine sweat glands engage in aerobic glycolysis, which accounts for the high content of lactate in sweat (15--60 mM) and the high lactate/pyruvate ratio (100: 1) [Emrich & Zwiebel (1966) Pfluegers Arch. 290, 315--319]. 3. Acetylcholine causes a 4-fold increase in cyclic GMP content, dilatation of the intercellular canaliculi and a reversible, atropine-sensitive, 2-fold increase in the rates of glucose oxidation and lactate release. 4. Isoprenaline causes a 2.5-fold increase in cyclic AMP content. Phenylephrine does not significantly alter cyclic nucleotide metabolism. 相似文献
2.
Calcium content and distribution as a function of growth and transformation in the mouse 3T3 cell
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Total Ca content and that fraction of Ca sensitive to removal by the chelator ethylene glycol-bis(β-aminoethyl ether)N,N,N',N'-tetraacetate (EGTA) have been investigated in the mouse 3T3 cell as a function of growth stage, transformation with SV40 virus, and serum levels of the media. Cells were allowed to grow through several doublings in media containing (45)Ca. The cellular content of (45)Ca was used to access total cell Ca. That fraction of (45)Ca removed by EGTA was presumed to represent primarily surface-localized Ca. The data are expressed on a per cell volume basis to compensate for size differences as a function of growth stage and transformation. During exponential growth phase, the 3T3 cell contains 525pmol Ca/μl cell volume. Of this, approx. 457 pmol/μl is not removable by EGTA and, presumably, is cytoplasmically located. This value is in close agreement with previous studies on the HeLa cell (470 pmol Ca/μl cell water after the removal of the surface Ca). The low level of EGTA- removable Ca present in the 3T3 cell during early exponential growth (68 pmol Ca/μl cell volume) increases progressively with increasing cell density, and upon quiescence it is sevenfold greater. In contrast, SV40- transformed 3T3 cells growing exponentially possess total levels of Ca which are approximately two-thirds the levels of the normal 3T3 cell. However, their EGTA-sensitive Ca is not significantly different from that of exponentially growing, normal 3T3 cells. As the transformed cells continue to grow at high density, their total ca and their sensitivity to EGTA do not change, in contrast to the normal 3T3 cell. Thus, an increase in Ca associated with the cell surface appears to be correlated with growth inhibition. This has been investigated further by regulating growth of the normal and transformed cell with alterations in the serum level of the media. In 4 percent calf serum the normal cell is stopped from continued proliferation. Growth stoppage under these conditions is characterized by a nearly fourfold increase in EGTA-removable Ca, similar to the increase observed upon quiescence in depleted 10 percent serum. Similar treatment of the transformed cell does not reduce its growth rate, nor does it significantly alter Ca distribution. However, at 0.5 percent medium serum levels, the SV40 3T3 growth rate is substantially reduced and, under these conditions, EGTA-removable Ca increases twofold. 相似文献
3.
Lai CM Yu MJ Brankov M Barnett NL Zhou X Redmond TM Narfstrom K Rakoczy PE 《Genetic vaccines and therapy》2004,2(1):3
Background
Leber's congenital amaurosis (LCA) is a severe form of retinal dystrophy. Mutations in the RPE65 gene, which is abundantly expressed in retinal pigment epithelial (RPE) cells, account for approximately 10–15% of LCA cases. In this study we used the high turnover, and rapid breeding and maturation time of the Rpe65 -/- knockout mice to assess the efficacy of using rAAV-mediated gene therapy to replace the disrupted RPE65 gene. The potential for rAAV-mediated gene treatment of LCA was then analyzed by determining the pattern of RPE65 expression, the physiological and histological effects that it produced, and any improvement in visual function. 相似文献4.
l-Aspartate-alpha-decarboxylase (PanD) catalyzes the decarboxylation of aspartate to produce beta-alanine, a precursor of Coenzyme A (CoA). The pyruvoyl-dependent enzyme from Escherichia coli is activated by self-cleavage at serine 25 to generate a 102-residue alpha subunit with the pyruvoyl group at its N terminus and a 24-residue beta subunit with a hydroxy at its C terminus. A mutant form of the panD gene from E. coli in which serine 25 was replaced with an alanine (S25A) was constructed. Assays conducted in vitro and in vivo confirmed that the mutant version was completely inactive and was incapable of undergoing self-cleavage to generate the active form of the enzyme. The S25A panD mutant was used to replace the chromosomal copy of panD in BAP1, a strain of E. coli modified for polyketide production. Comparison of this strain with panD2 mutant strains derived from E. coli SJ16 showed an equivalent dependence on exogenous beta-alanine for growth in liquid medium. Unlike the undefined and leaky panD2 mutation, the panD S25A mutation is defined and tight. The panD S25A E. coli strain enables analysis of intracellular acyl-CoA pools in both defined and complex media and is a useful tool in metabolic engineering studies that require the manipulation of acyl-CoA pools for the heterologous production of polyketides. 相似文献
5.
Stacy L. Schmidt Kristin A. Harmon Teresa A. Sharp Elizabeth H. Kealey Daniel H. Bessesen 《Obesity (Silver Spring, Md.)》2012,20(11):2186-2193
Despite living in an environment that promotes weight gain in many individuals, some individuals maintain a thin phenotype while self‐reporting expending little or no effort to control their weight. When compared with obesity prone (OP) individuals, we wondered if obesity resistant (OR) individuals would have higher levels of spontaneous physical activity (SPA) or respond to short‐term overfeeding by increasing their level of SPA in a manner that could potentially limit future weight gain. SPA was measured in 55 subjects (23 OP and 32 OR) using a novel physical activity monitoring system (PAMS) that measured body position and movement while subjects were awake for 6 days, either in a controlled eucaloric condition or during 3 days of overfeeding (1.4× basal energy) and for the subsequent 3 days (ad libitum recovery period). Pedometers were also used before and during use of the PAMS to provide an independent measure of SPA. SPA was quantified by the PAMS as fraction of recording time spent lying, sitting, or in an upright posture. Accelerometry, measured while subjects were in an upright posture, was used to categorize time spent in different levels of movement (standing, walking slowly, quickly, etc.). There were no differences in SPA between groups when examined across all study periods (P > 0.05). However, 3 days following overfeeding, OP subjects significantly decreased the amount of time they spent walking (?2.0% of time, P = 0.03), whereas OR subjects maintained their walking (+0.2%, P > 0.05). The principle findings of this study are that increased levels of SPA either during eucaloric feeding or following short term overfeeding likely do not significantly contribute to obesity resistance although a decrease in SPA following overfeeding may contribute to future weight gain in individuals prone to obesity. 相似文献
6.
Background
Long-lasting insecticidal nets (LLINs) reduce malaria transmission by protecting individuals from infectious bites, and by reducing mosquito survival. In recent years, millions of LLINs have been distributed across sub-Saharan Africa (SSA). Over time, LLINs decay physically and chemically and are destroyed, making repeated interventions necessary to prevent a resurgence of malaria. Because its effects on transmission are important (more so than the effects of individual protection), estimates of the lifetime of mass distribution rounds should be based on the effective length of epidemiological protection.Methods
Simulation models, parameterised using available field data, were used to analyse how the distribution's effective lifetime depends on the transmission setting and on LLIN characteristics. Factors considered were the pre-intervention transmission level, initial coverage, net attrition, and both physical and chemical decay. An ensemble of 14 stochastic individual-based model variants for malaria in humans was used, combined with a deterministic model for malaria in mosquitoes.Results
The effective lifetime was most sensitive to the pre-intervention transmission level, with a lifetime of almost 10 years at an entomological inoculation rate of two infectious bites per adult per annum (ibpapa), but of little more than 2 years at 256 ibpapa. The LLIN attrition rate and the insecticide decay rate were the next most important parameters. The lifetime was surprisingly insensitive to physical decay parameters, but this could change as physical integrity gains importance with the emergence and spread of pyrethroid resistance.Conclusions
The strong dependency of the effective lifetime on the pre-intervention transmission level indicated that the required distribution frequency may vary more with the local entomological situation than with LLIN quality or the characteristics of the distribution system. This highlights the need for malaria monitoring both before and during intervention programmes, particularly since there are likely to be strong variations between years and over short distances. The majority of SSA's population falls into exposure categories where the lifetime is relatively long, but because exposure estimates are highly uncertain, it is necessary to consider subsequent interventions before the end of the expected effective lifetime based on an imprecise transmission measure. 相似文献7.
Marcos G Godoy Alejandra Aedo Molly JT Kibenge David B Groman Carmencita V Yason Horts Grothusen Angelica Lisperguer Marlene Calbucura Fernando Avendaño Marcelo Imilán Miguel Jarpa Frederick SB Kibenge 《BMC veterinary research》2008,4(1):1-13
Background
Several forms of progressive retinal atrophy (PRA) segregate in more than 100 breeds of dog with each PRA segregating in one or a few breeds. This breed specificity may be accounted for by founder effects and genetic drift, which have reduced the genetic heterogeneity of each breed, thereby facilitating the identification of causal mutations. We report here a new form of PRA segregating in the Border Collie breed. The clinical signs, including the loss of night vision and a progressive loss of day vision, resulting in complete blindness, occur at the age of three to four years and may be detected earlier through systematic ocular fundus examination and electroretinography (ERG). 相似文献8.
9.
Sanjay Agarwalla James T Kealey Daniel V Santi Robert M Stroud 《The Journal of biological chemistry》2002,277(11):8835-8840
An Escherichia coli open reading frame, ygcA, was identified as a putative 23 S ribosomal RNA 5-methyluridine methyltransferase (Gustafsson, C., Reid, R., Greene, P. J., and Santi, D. V. (1996) Nucleic Acids Res. 24, 3756-3762). We have cloned, expressed, and purified the 50-kDa protein encoded by ygcA. The purified enzyme catalyzed the AdoMet-dependent methylation of 23 S rRNA but did not act upon 16 S rRNA or tRNA. A high performance liquid chromatography-based nucleoside analysis identified the reaction product as 5-methyluridine. The enzyme specifically methylated U1939 as determined by a nuclease protection assay and by methylation assays using site-specific mutants of 23 S rRNA. A 40-nucleotide 23 S rRNA fragment (nucleotide 1930--1969) also served as an efficient substrate for the enzyme. The apparent K(m) values for the 40-mer RNA oligonucleotide and AdoMet were 3 and 26 microm, respectively, and the apparent k(cat) was 0.06 s(-1). The enzyme contains two equivalents of iron/monomer and has a sequence motif similar to a motif found in iron-sulfur proteins. We propose to name this gene rumA and accordingly name the protein product as RumA for RNA uridine methyltransferase. 相似文献
10.
Arthur V. Peterson Jr. Patrick M. Marek Kathleen A. Kealey Jonathan B. Bricker Evette J. Ludman Jaimee L. Heffner 《PloS one》2016,11(2)