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161.
Lassen N Bateman JB Estey T Kuszak JR Nees DW Piatigorsky J Duester G Day BJ Huang J Hines LM Vasiliou V 《The Journal of biological chemistry》2007,282(35):25668-25676
ALDH3A1 (aldehyde dehydrogenase 3A1) is abundant in the mouse cornea but undetectable in the lens, and ALDH1A1 is present at lower (catalytic) levels in the cornea and lens. To test the hypothesis that ALDH3A1 and ALDH1A1 protect the anterior segment of the eye against environmentally induced oxidative damage, Aldh1a1(-/-)/Aldh3a1(-/-) double knock-out and Aldh1a1(-/-) and Aldh3a1(-/-) single knock-out mice were evaluated for biochemical changes and cataract formation (lens opacification). The Aldh1a1/Aldh3a1- and Aldh3a1-null mice develop cataracts in the anterior and posterior subcapsular regions as well as punctate opacities in the cortex by 1 month of age. The Aldh1a1-null mice also develop cataracts later in life (6-9 months of age). One- to three-month-old Aldh-null mice exposed to UVB exhibited accelerated anterior lens subcapsular opacification, which was more pronounced in Aldh3a1(-/-) and Aldh3a1(-/-)/Aldh1a1(-/-) mice compared with Aldh1a1(-/-) and wild type animals. Cataract formation was associated with decreased proteasomal activity, increased protein oxidation, increased GSH levels, and increased levels of 4-hydroxy-2-nonenal- and malondialdehyde-protein adducts. In conclusion, these findings support the hypothesis that corneal ALDH3A1 and lens ALDH1A1 protect the eye against cataract formation via nonenzymatic (light filtering) and enzymatic (detoxification) functions. 相似文献
162.
Gregg A. Kormanik James N. Cameron 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1981,141(4):457-462
Summary A series of experiments was conducted to investigate whether ammonia is excreted across the seawater-acclimated blue crab's gills as ionized NH
4
+
or as the free base, NH3. The net excretion rate of ammonia was not changed by transfer of the crabs to reduced (150 mM) Na+ solutions, by transfer to Na+- and K+-free artificial sea water, or by the sodium transport inhibitor amiloride. Ammonia excretion, therefore, does not appear to be linked to Na+ uptake in these animals, and appears to take place by passive diffusion. Since ammonia could diffuse either as NH
4
+
or NH3, we examined two other kinds of evidence. The trans-epithelial potential was measured in sea water and the various artificial media. In spite of a 10 mV more negative potential in Na+-, K+-free medium, the ammonia excretion was not reduced. Also, in alkalinized seawater in which the partial pressure gradient of NH3 was reduced, but the concentration gradient of NH
4
+
increased, ammonia excretion was reduced by about 70%. These results are consistent with the conclusion that ammonia excretion takes place by diffusion of the free base, NH3.Abbreviations
SW
sea water
-
ASW
artificial sea water
-
t.e.p.
transepithelial potential
The University of Texas Marine Science Institute Contribution No. 461Supported by NSF Grant PCM77-24358 相似文献
163.
Gregg T. Nagle 《Developmental neurobiology》1981,12(6):599-611
Ganglia of the marine mollusk Macrocallista nimbosa were pooled, homogenized, and subjected to differential centrifugation. The neuropeptide Phe-Met-Arg-Phe-NH2 (FMRFamide) was concentrated in the microsomal pellet. When the medium-speed supernatant was centrifuged in a discontinuous sucrose gradient, three separate peaks of activity were detected and identified as acetylcholine, 5-hydroxytryptamine, and FMRFamide. The relative concentration of FMRFamide in each fraction was determined by bioassay and by radioimmunoassay (RIA). Both determinations revealed a peak of peptide in the middle of the sucrose gradient. Electron micrographs of each of the gradient interfaces were analyzed. The interface containing the peak of biological FMRFamide activity was enriched two- to fivefold in neurosecretory granules with a mean diameter of 104 nm and various electron densities. Morphologically similar vesicles were also seen in intact ganglia. These findings support the notion that FMRFamide is a neurosecretory product. But the physiological function of the peptide in bivalve ganglia remains unknown. 相似文献
164.
Baronas-Lowell D Lauer-Fields JL Borgia JA Sferrazza GF Al-Ghoul M Minond D Fields GB 《The Journal of biological chemistry》2004,279(42):43503-43513
Tumor cell binding to components of the basement membrane is well known to trigger intracellular signaling pathways. Signaling ultimately results in the modulation of gene expression, facilitating metastasis. Type IV collagen is the major structural component of the basement membrane and is known to be a polyvalent ligand, possessing sequences bound by the alpha1beta1, alpha2beta1, and alpha3beta1 integrins, as well as cell surface proteoglycan receptors, such as CD44/chondroitin sulfate proteoglycan (CSPG). The role of alpha2beta1 integrin and CD44/CSPG receptor binding on human melanoma cell activation has been evaluated herein using triple-helical peptide ligands incorporating the alpha1(IV)382-393 and alpha1(IV)1263-1277 sequences, respectively. Gene expression and protein production of matrix metalloproteinases-1 (MMP-1), -2, -3, -13, and -14 were modulated with the alpha2beta1-specific sequence, whereas the CD44-specific sequence yielded significant stimulation of MMP-8 and lower levels of modulation of MMP-1, -2, -13, and -14. Analysis of enzyme activity confirmed different melanoma cell proteolytic potentials based on engagement of either the alpha2beta1 integrin or CD44/CSPG. These results are indicative of specific activation events that tumor cells undergo upon binding to select regions of basement membrane collagen. Based on the present study, triple-helical peptide ligands provide a general approach for monitoring the regulation of proteolysis in cellular systems. 相似文献
165.
Marino DiFranco Marbella Qui?onez Perry Shieh Gregg C. Fonarow Daniel Cruz Mario C. Deng Julio L. Vergara Holly R. Middlekauff 《PloS one》2014,9(10)
Background
Exercise intolerance in chronic heart failure (HF) has been attributed to abnormalities of the skeletal muscles. Muscle function depends on intact excitation-contraction coupling (ECC), but ECC studies in HF models have been inconclusive, due to deficiencies in the animal models and tools used to measure calcium (Ca2+) release, mandating investigations in skeletal muscle from HF patients. The purpose of this study was to test the hypothesis that Ca2+ release is significantly impaired in the skeletal muscle of HF patients in whom exercise capacity is severely diminished compared to age-matched healthy volunteers.Methods and Findings
Using state-of-the-art electrophysiological and optical techniques in single muscle fibers from biopsies of the locomotive vastus lateralis muscle, we measured the action potential (AP)-evoked Ca2+ release in 4 HF patients and 4 age-matched healthy controls. The mean peak Ca2+ release flux in fibers obtained from HF patients (10±1.2 µM/ms) was markedly (2.6-fold) and significantly (p<0.05) smaller than in fibers from healthy volunteers (28±3.3 µM/ms). This impairment in AP-evoked Ca2+ release was ubiquitous and was not explained by differences in the excitability mechanisms since single APs were indistinguishable between HF patients and healthy volunteers.Conclusions
These findings prove the feasibility of performing electrophysiological experiments in single fibers from human skeletal muscle, and offer a new approach for investigations of myopathies due to HF and other diseases. Importantly, we have demonstrated that one step in the ECC process, AP-evoked Ca2+ release, is impaired in single muscle fibers in HF patients. 相似文献166.
Dawn R. D. Bignell José C. Huguet-Tapia Madhumita V. Joshi Gregg S. Pettis Rosemary Loria 《Antonie van Leeuwenhoek》2010,98(2):179-194
Plant pathogenicity is rare in the genus Streptomyces, with only a dozen or so species possessing this trait out of the more than 900 species described. Nevertheless, such species
have had a significant impact on agricultural economies throughout the world due to their ability to cause important crop
diseases such as potato common scab, which is characterized by lesions that form on the potato tuber surface. All pathogenic
species that cause common scab produce a family of phytotoxins called the thaxtomins, which function as cellulose synthesis
inhibitors. In addition, the nec1 and tomA genes are conserved in several pathogenic streptomycetes, the former of which is predicted to function in the suppression
of plant defense responses. Streptomyces scabies is the oldest plant pathogen described and has a world-wide distribution, whereas species such as S. turgidiscabies and S. acidiscabies are believed to be newly emergent pathogens found in more limited geographical locations. The genome sequence of S. scabies 87-22 was recently completed, and comparative genomic analyses with other sequenced microbial pathogens have revealed the
presence of additional genes that may play a role in plant pathogenicity, an idea that is supported by functional analysis
of one such putative virulence locus. In addition, the availability of multiple genome sequences for both pathogenic and nonpathogenic
streptomycetes has provided an opportunity for comparative genomic analyses to identify the Streptomyces pathogenome. Such genomic analyses will contribute to the fundamental understanding of the mechanisms and evolution of plant
pathogenicity and plant-microbe biology within this genus. 相似文献
167.
168.
Efficient transmission of circular plasmids in Streptomyces spp. proceeds by an uncharacterized mechanism that requires a cis-acting locus of transfer (clt) and often only a single plasmid-encoded protein. For circular plasmids from other bacteria, site- and strand-specific nicking takes place at the cis-acting oriT locus via the plasmid-encoded relaxase protein prior to single-strand transfer. Using an assay originally designed to demonstrate that conjugative transfer of plasmids containing tandem oriT loci results in the formation of a single composite oriT locus, we show here that an analogous construct involving the pIJ101 clt locus apparently does not undergo such a conjugation-mediated event during plasmid transfer. Our results, which imply that streptomycete plasmids are transferred by a functionally distinct mechanism compared to oriT-containing plasmids, are complementary to other recent evidences that support a novel double-stranded model for streptomycete circular plasmid transfer. 相似文献
169.
The response of an established line of non-transformed adult rat liver epithelial cells (ARL 15) to thyroid hormone (T3) (3,5,3'-triiodothyronine) was characterized. Exposure of confluent monolayers to 1.10(-8) M T3 for 3 days increased O2 consumption (QO2) between 14-58%, ouabain-sensitive Rb+ uptake 26%, (Na+ + K+)-ATPase activity 32%, alpha-glycerophosphate dehydrogenase activity 103% and cytochrome oxidase activity 208%. The ARL 15 cells, maintained in continuous culture, therefore, exhibit the hallmarks of an authentic physiological response to thyroid hormone. 相似文献
170.