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991.
Role of peroxidase inhibition by insulin in the bovine thyroid cell proliferation mechanism. 总被引:1,自引:0,他引:1
León Krawiec Ramón A Pizarro Paula Aphalo Elena M V de Cavanagh Mario A Pisarev Guillermo J Juvenal Lucía Policastro Laura V Bocanera 《European journal of biochemistry》2004,271(13):2607-2614
Monolayer primary cultures of thyroid cells produce, in the presence of insulin, a cytosolic inhibitor of thyroid peroxidase (TPO), lacto peroxidase (LPO), horseradish peroxidase (HRPO) and glutathione peroxidase (GPX). The inhibitor, localized in the cytosol, is thermostable and hydrophylic. Its molecular mass is less than 2 kDa. The inhibitory activity, resistant to proteolytic and nucleolytic enzymes, disappears with sodium metaperiodate treatment, as an oxidant of carbohydrates, supporting its oligosaccharide structure. The presence of inositol, mannose, glucose, the specific inhibition of cyclic AMP-dependent protein kinase and the disappearance of peroxidase inhibition by alkaline phosphatase and alpha-mannosidase in purified samples confirms its chemical structure as inositol phosphoglycan-like. Purification by anionic interchange shows that the peroxidase inhibitor elutes like the two subtypes of inositol phosphoglycans (IPG)P and A, characterized as signal transducers of insulin action. Insulin significantly increases the concentration of the peroxidase inhibitor in a thyroid cell culture at 48 h. The addition of both isolated substances to a primary thyroid culture produces, after 30 min, a significant increase in hydrogen peroxide (H2O2) concentration in the medium, concomitantly with the disappearance of the GPX activity in the same conditions. The presence of insulin or anyone of both products, during 48 h, induces cell proliferation of the thyroid cell culture. In conclusion, insulin stimulates thyroid cell division through the effect of a peroxidase inhibitor, as its second messenger. The inhibition of GPX by its action positively modulates the H2O2 level, which would produce, as was demonstrated by other authors, the signal for cell proliferation. 相似文献
992.
BACKGROUND: Granulocytic sarcoma is an extramedullary tumor that is composed of granulocytic precursor cells. We report an unusual case of granulocytic sarcoma of the liver that arose in the background of myeloid metaplasia. Fine needle aspiration cytology (FNAC) was instrumental in making the diagnosis in absence of previously known Hematlogic abnormality. CASE: A 65-year-old woman presented with multiple nodules in the liver. USG-guided FNAC was performed on them. The aspirates showed many myeloid blasts, myelocytes, metamyelocytes, erytbroid precursors and lympboglandular bodies. We considered a differential diagnosis of granulocytic sarcoma and myeloid metaplasia. The presence of erytbroid precursors prompted us to consider myeloid metaplasia as a differential diagnorsis of granulocytic sarcoma. Peripberal smear showed a leukoerytbroblastic reaction. The patient died, and necropsy from the liver revealed extensive infiltration by undfferentiated blast cells with areas of myeloid metaplasia showing maturing erytbroid, myeloid and megakaryocytic elements. CONCLUSION: When a dual population of predominant myeloid blasts and normoblarts is encountered, a suspicion of granulocytic sarcoma arising in a background of myeloid metaplasia must be kept. Cells of all 3 lineages may not be always seen in myeloid metaplasia, and 1 cell line may predominate, causing a diagnostic dilemma. 相似文献
993.
Effects of elevated CO2 on the tolerance of photosynthesis to acute heat stress in C3, C4, and CAM species 总被引:3,自引:0,他引:3
Wang D Heckathorn SA Barua D Joshi P Hamilton EW Lacroix JJ 《American journal of botany》2008,95(2):165-176
Determining the effect of elevated CO(2) on the tolerance of photosynthesis to acute heat stress (AHS) is necessary for predicting plant responses to global warming because photosynthesis is heat sensitive and AHS and atmospheric CO(2) will increase in the future. Few studies have examined this effect, and past results were variable, which may be related to methodological variation among studies. In this study, we grew 11 species that included cool and warm season and C(3), C(4), and CAM species at current or elevated (370 or 700 ppm) CO(2) and at species-specific optimal growth temperatures and at 30°C (if optimal ≠ 30°C). We then assessed thermotolerance of net photosynthesis (P(n)), stomatal conductance (g(st)), leaf internal [CO(2)], and photosystem II (PSII) and post-PSII electron transport during AHS. Thermotolerance of P(n) in elevated (vs. ambient) CO(2) increased in C(3), but decreased in C(4) (especially) and CAM (high growth temperature only), species. In contrast, elevated CO(2) decreased electron transport in 10 of 11 species. High CO(2) decreased g(st) in five of nine species, but stomatal limitations to P(n) increased during AHS in only two cool-season C(3) species. Thus, benefits of elevated CO(2) to photosynthesis at normal temperatures may be partly offset by negative effects during AHS, especially for C(4) species, so effects of elevated CO(2) on acute heat tolerance may contribute to future changes in plant productivity, distribution, and diversity. 相似文献
994.
995.
Carey Philip G. Sargent Angela J. Taberner Antoni Martínez Ramón Guillem Moyà Gabriel 《Hydrobiologia》2001,448(1-3):193-201
On the island of Mallorca, anchihaline lagoons, meromictic in character, are common in the flooded coastal karst. These subterranean lagoons, containing important populations of crustacea, maintain a connection, albeit tenuous, to the sea. Thus, the first truly quantitative study of marine ciliates inhabiting anchihaline lagoons was undertaken between April 1996 and April 1997. Physical and chemical measurements were taken in-situ, together with water samples for faunal analysis in each of four stratified lakes. These lagoons typically displayed a temperature inversion, an increase in conductivity and a decrease in dissolved oxygen concentration with depth. Ciliates were present in all lagoons studied, with a total of nine species recorded. All were assigned to known taxa. Spatial distribution of the trophic cells was noteworthy with populations clearly stratified within the water column, most being found at the waters surface, sometimes in association with rafts of floating calcite crystals, or in the sediment. Only on one occasion were ciliates recorded in mid-water. Abundance was very low, typically <1 ciliate cm–3. The floating calcite crystals may form a delimitable biotope for ciliate populations. The role of the cyst in maintaining populations of ciliates in these cave waters is discussed. 相似文献
996.
In many shallow, eutrophic subtropical ponds, brachionid rotifers are common prey of the predatory copepod Mesocyclops thermocyclopoides. The predatory rotifer Asplanchna intermedia, which is itself a potential prey of the copepod, also feeds preferentially on brachionids. We studied in the laboratory the population dynamics of two mutually competing prey species, Brachionus angularis and B. calyciflorus, in the presence of the two predators A. intermedia and M. thermocyclopoides. The experimental design included separate population dynamics studies with one prey–one predator, two prey–one predator, one prey–two predator, and two prey–two predator systems. These combinations were compared with controls, in which both the prey species (B. angularis and B. calyciflorus) were grown separately and in combination with each other. In the absence of any predator, B. angularis generally eliminated the larger B. calyciflorus. Selective predation by the copepod allowed B. calyciflorus to persist longer in competition with B. angularis. Feeding by M. thermocyclopoides on A. intermedia reduced the predation pressure on B. calyciflorus. However, given enough time, the cyclopoid copepod was able to eliminate both the brachionids as well as the predatory Asplanchna. 相似文献
997.
998.
Hydrocortisone modulates the effect of estradiol on endothelial nitric oxide synthase expression in human endothelial cells. 总被引:2,自引:0,他引:2
The interaction between hydrocortisone and estradiol on the regulation of endothelial nitric oxide synthase (eNOS) expression was investigated in human umbilical vein endothelial cells (HUVECs). Following incubation in medium containing dextran-coated-charcoal-stripped serum (DCC-stripped medium) for 4 days, incubation of HUVECs with 0.1 nM estradiol for 24 hr in the absence of hydrocortisone increased levels of eNOS mRNA measured by ribonuclease protection assay above control (0 nM estradiol). 2 microM hydrocortisone applied for 24 hr preceding and during estradiol application inhibited the estradiol-elicited increase in eNOS mRNA levels, reducing mRNA levels from 134% +/- 14% of control to 85% +/- 5% of control. Significant (ANOVA, p<0.01) reductions of estradiol-mediated increases of mRNA levels occurred over a range of hydrocortisone concentrations (10 nM, p<0.05; 2 microM, p<0.05; n=3-12). In the presence of 2 microM hydrocortisone, 10 nM estradiol significantly reduced eNOS mRNA levels to 59% +/- 3% of control. The ability of hydrocortisone to block or reverse the estradiol-mediated increase in eNOS mRNA levels may provide a link between elevated hydrocortisone levels and decreased NO production, potentially contributing to the development of hypertension and cardiovascular disease in vivo and antagonizing cardioprotective effects of estrogens. 相似文献
999.
S. Gómez-Arroyo J. Cortés-Eslava R.M. Bedolla-Cansino R. Villalobos-Pietrini M.E. Calderón-Segura Y. Ramírez-Delgado 《Biologia Plantarum》2001,44(4):591-594
The induction of sister chromatid exchanges (SCE) by chloride and nitrate salts of nickel, cobalt, cadmium and zinc were studied in meristematic root cells of Vicia faba. Salts of nickel, cobalt and cadmium significantly increased the frequency of SCE, whereas chloride and nitrate salts of zinc did not increase the frequency of SCE significantly above the spontaneous level. The reported data demonstrate that the induction of SCE in Vicia faba may represent a valuable bioindicator for detecting the cytogenetic damage of heavy metals. 相似文献
1000.
B. R. Choudhary P. Joshi 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2001,102(6-7):1123-1128
The crossability between Brassica tournefortii (TT, 2n = 20) and Brassica rapa (AA, 2n = 20) and the cytomorphology of their F1 hybrids were studied. Hybrids between these two species were obtained only when B. tournefortii was involved as a female parent. The hybrid plants were intermediate for most of the morphological attributes and were found
to be free from white rust under field conditions. The F1 plants showed poor pollen fertility, although occasional seed set was achieved from open pollination. Self-pollination or
backcrosses did not yield any seeds in these plants. The occurrence of chromosome association ranging from bivalents (0–7),
trivalents (0–2) to a rare quadrivalent (0–1) in the dihaploid hybrids indicates pairing between the T and A genomes. The
homoeologous pairing coupled with seed set in the F1 plants offer an opportunity for interspecific gene transfers from B. tournefortii to B. rapa and vice-versa through interspecific hybridization.
Received: 3 July 2000 / Accepted: 22 September 2000 相似文献