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Query: UMLS:C0009443 (cold)
 92,137 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Tomato, Lycopersicon esculentum L. cv. RX-335, and watermelon plants, Citrullus lanatus [Thom.] Mansf. cv. F-90 were grown under controlled conditions at three different temperatures (10 degrees, 25 degrees and 35 degrees C) for 30 days. The aim of the experiment was to analyse the effect of the different temperatures on Fe uptake and distribution, as well as the behaviour of the main bioindicators of this element. Thus, we analysed the total and free Fe concentrations and H2O2 concentrations, as well as enzymatic activities of Fe-chelate reductase (FeCH-R), aconitase (Aco), guaiacol peroxidase (GPX), catalase (CAT), and Fe-superoxide dismutase (FeSOD), and the dry weight of the plants. The effect caused by each temperature varied according to the species of plant. Our results indicate that heat stress appears in tomato plants when grown at 35 degrees C (above the optimal temperature for growth), while in watermelon plants, which need more heat than do tomatoes, cold stress appears at 10 degrees C (below the optimal temperature for growth). Despite these differences between the two species, the results under conditions of thermal stress were the same: 1) decreased shoot weight, 2) reduced Fe uptake, 3) depressed activities of FeCH-R, Aco, GPX, CAT and 4) boosted SOD activity. In short, our results appear to indicate that, whether heat in tomato plants or cold stress in watermelon plants, Fe uptake was diminished, as were the enzymatic activities related to the levels of this micronutrient in the plant. The high FeSOD activity in these plants could be explained by a defensive response to heat or cold stress.
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PMID:Influence of temperature on biomass, iron metabolism and some related bioindicators in tomato and watermelon plants. 1459 8

Xanthine dehydrogenase from the plant Arabidopsis thaliana was analyzed on molecular and biochemical levels. Whereas most other organisms appear to own only one gene for xanthine dehydrogenase A. thaliana possesses two genes in tandem orientation spaced by 704 base pairs. The cDNAs as well as the proteins AtXDH1 and AtXDH2 share an overall identity of 93% and show high homologies to xanthine dehydrogenases from other organisms. Whereas AtXDH2 mRNA is expressed constitutively, alterations of AtXDH1 transcript levels were observed at various stresses like drought, salinity, cold, and natural senescence, but also after abscisic acid treatment. Transcript alteration did not mandatorily result in changes of xanthine dehydrogenase activities. Whereas salt treatment had no effect on xanthine dehydrogenase activities, cold stress caused a decrease, but desiccation and senescence caused a strong increase of activities in leaves. Because AtXDH1 presumably is the more important isoenzyme in A. thaliana it was expressed in Pichia pastoris, purified, and used for biochemical studies. AtXDH1 protein is a homodimer of about 300 kDa consisting of identical subunits of 150 kDa. Like xanthine dehydrogenases from other organisms AtXDH1 uses hypoxanthine and xanthine as main substrates and is strongly inhibited by allopurinol. AtXDH1 could be activated by the purified molybdenum cofactor sulfurase ABA3 that converts inactive desulfo-into active sulfoenzymes. Finally it was found that AtXDH1 is a strict dehydrogenase and not an oxidase, but is able to produce superoxide radicals indicating that besides purine catabolism it might also be involved in response to various stresses that require reactive oxygen species.
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PMID:Tandem orientation of duplicated xanthine dehydrogenase genes from Arabidopsis thaliana: differential gene expression and enzyme activities. 1472 15

Applying calcium oxide into soil could improve the ability of rice seedlings in low temperature-and damping-off disease resistance. After treated with calcium, the active oxygen eliminating enzyme activities of rice seedlings increased significantly. Compared with control, the SOD activity in seedling's root and shoot increased. The POD activity in rice seedling's root also increased, but decreased in shoot. The CAT activities decreased at the early stage, but increased at late stage. The soluble protein content in seedling's root and shoot was higher than that of the control. In the PAGE pattern of isoperoxidase, the band number of shoot increased, but that of root decreased. AU these changes were part of reasons that applying calcium oxide into soil improved the resistance of rice seedlings to cold and damping-off disease.
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PMID:[Physiological mechanism of rice seedlings in low temperature-and damping-off disease resistance induced by calcium application into soil]. 1532 Mar 89

The DnaA protein is the initiator of Escherichia coli chromosomal replication. In this study, we identify a novel DnaA-associating protein, DiaA, that is required for the timely initiation of replication during the cell cycle. DiaA promotes the growth of specific temperature-sensitive dnaA mutants and ensures stable minichromosome maintenance, whereas DiaA does not decrease the cellular DnaA content. A diaA::Tn5 mutation suppresses the cold-sensitive growth of an overinitiation type dnaA mutant independently of SeqA, a negative modulator of initiation. Flow cytometry analyses revealed that the timing of replication initiation is disrupted in the diaA mutant cells as well as wild-type cells with pBR322 expressing the diaA gene. Gel filtration and chemical cross-linking experiments showed that purified DiaA forms a stable homodimer. Immunoblotting analysis indicated that a single cell contains about 280 DiaA dimers. DiaA stimulates minichromosome replication in an in vitro system especially when the level of DnaA included is limited. Moreover, specific and direct binding between DnaA and DiaA was observed, which requires a DnaA N-terminal region. DiaA binds to both ATP- and ADP-bound forms of DnaA with a similar affinity. Thus, we conclude that DiaA is a novel DnaA-associating factor that is crucial to ensure the timely initiation of chromosomal replication.
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PMID:DiaA, a novel DnaA-binding protein, ensures the timely initiation of Escherichia coli chromosome replication. 1532 79

1-Aminocyclopropane-1-carboxylate synthase (ACS) catalyzes the rate-limiting step in the ethylene biosynthetic pathway in plants. The Arabidopsis genome encodes nine ACS polypeptides that form eight functional (ACS2, ACS4-9, and ACS11) homodimers and one nonfunctional (ACS1) homodimer. Transgenic Arabidopsis lines were constructed expressing the beta-glucuronidase (GUS) and green fluorescence protein (GFP) reporter genes from the promoter of each of the gene family members to determine their patterns of expression during plant development. All genes, except ACS9, are expressed in 5-d-old etiolated or light-grown seedlings yielding distinct patterns of GUS staining. ACS9 expression is detected later in development. Unique and overlapping expression patterns were detected for all the family members in various organs of adult plants. ACS11 is uniquely expressed in the trichomes of sepals and ACS1 in the replum. Overlapping expression was observed in hypocotyl, roots, various parts of the flower (sepals, pedicle, style, etc.) and in the stigmatic and abscission zones of the silique. Exogenous indole-3-acetic acid (IAA) enhances the constitutive expression of ACS2, 4, 5, 6, 7, 8, and 11 in the root. Wounding of hypocotyl tissue inhibits the constitutive expression of ACS1 and ACS5 and induces the expression of ACS2, 4, 6, 7, 8, and 11. Inducers of ethylene production such as cold, heat, anaerobiosis, and Li(+) ions enhance or suppress the expression of various members of the gene family in the root of light-grown seedlings. Examination of GUS expression in transverse sections of cotyledons reveals that all ACS genes, except ACS9, are expressed in the epidermis cell layer, guard cells, and vascular tissue. Similar analysis with root tip tissue treated with IAA reveals unique and overlapping expression patterns in the various cell types of the lateral root cap, cell division, and cell expansion zones. IAA inducibility is gene-specific and cell type-dependent across the root tip zone. This limited comparative exploration of ACS gene family expression reveals constitutive spatial and temporal expression patterns of all gene family members throughout the growth period examined. The unique and overlapping gene activity pattern detected reveals a combinatorial code of spatio-temporal coexpression among the various gene family members during plant development. This raises the prospect that functional ACS heterodimers may be formed in planta.
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PMID:Unique and overlapping expression patterns among the Arabidopsis 1-amino-cyclopropane-1-carboxylate synthase gene family members. 1546 21

The role of nitric oxide (NO) in cardio-vascular homeostasis is now known to include allosteric redox modulation of cell respiration. An interesting animal for the study of this wide-ranging influence of NO is the cold-adapted Antarctic icefish Chionodraco hamatus, which is characterised by evolutionary loss of hemoglobin and multiple cardio-circulatory and subcellular compensations for efficient oxygen delivery. Using an isolated, perfused working heart preparation of C. hamatus, we show that both endogenous (L-arginine) and exogenous (SIN-1 in presence of SOD) NO-donors as well as the guanylate cyclase (GC) donor 8Br-cGMP elicit positive inotropism, while both nitric oxide synthase (NOS) and sGC inhibitors, i.e. L-NIO and ODQ, respectively, induce significant negative inotropic effects. These results therefore demonstrate that under basal working conditions the icefish heart is under the tonic influence of a NO-cGMP-mediated positive inotropism. We also show that the working heart, which has intracardiac NOS (shown by NADPH-diaphorase activity and immunolocalization), can produce and release NO, as measured by nitrite appearance in the cardiac effluent. These results indicate the presence of a functional NOS system in the icefish heart, possibly serving a paracrine/autocrine regulatory role.
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PMID:No hemoglobin but NO: the icefish (Chionodraco hamatus) heart as a paradigm. 1547 16

The effects of 1-MCP (1-methylcyclo-propene) at 0.5, 1 and 2 muL/L on senescence and quality attributes in edible podded pea (Pisum sativum L.var.Saccharatum) during cold storage at 1 degrees C were investigated. The results indicated that treatments with 1 and 2 microL/L 1-MCP significantly inhibited respiratory rate, ethylene production and superoxide production, maintained higher levels of SOD, AsA-POD activities and chlorophyll and AsA contents, reduced the increases in MDA and fiber contents and decay index, thereby delayed the senescence process and quality deterioration. Treatment with 0.5 microL/L 1-MCP showed no significant effects on senescence and quality changes in harvested edible podded pea.
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PMID:[Effect of 1-MCP on senescence and quality in cold-stored edible podded pea]. 1559 42

Changes of activity antioxidant enzymes and of levels of isoflavonoids were studied in the roots and hypocotyls of the etiolated soybean (Glycine max (L.) Merr. var. Essor) seedlings, submitted to cold. Prolonged exposure to 1 degrees C inhibited hypocotyl and root elongation and limited their growth after seedlings were transferred to 25 degrees C. Roots were more sensitive to chilling than hypocotyls. At 1 degrees C a gradual increase in MDA concentration in roots but not in hypocotyls was observed. An increase in catalase (CAT, EC 1.11.1.6) and superoxide dismutase (SOD, EC 1.15.1.1) activity in hypocotyls was observed both at 1 degrees C and after transfer of plants to 25 degrees C. In roots, CAT activity increased after 4 days of chilling, while SOD activity only after rewarming. L-Phenylalanine ammonia-lyase (PAL, EC 4.3.1.5) activity decreased in roots of chilled seedlings, but did not change in hypocotyls until activity increased after transfer to 25 degrees C. The content of genistein and daidzein increased after 24 h of treatment by low temperature and then decreased with prolonged chilling in hypocotyls and remained high in roots. However, it should be noted that genistin level (genistein glucoside) in chilled hypocotyls is 10 times higher than in roots, despite falling tendency. The role of antioxidant enzymes and isoflavonoids in preventing chilling injury in hypocotyls and roots of soybean seedlings is discussed.
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PMID:Antioxidant enzymes and isoflavonoids in chilled soybean (Glycine max (L.) Merr.) seedlings. 1590 Aug 82

Living conditions for plants in the mountains become increasingly less favorable with increasing altitude. In the alpine region, the plants are commonly exposed to daily rather than seasonal temperature fluctuations and by frequent freezing temperature. To elucidate the freezing tolerance mechanism of alpine plants, Saussurea laniceps Hand.-Mazz. was used as a model plant. It is a perennial herbal plant distributed in alpine regions of Yunnan and Tibet of China. It can survive on mountains with elevations over 4000 m. Wild S. laniceps plants are propagated only by seeds in the alpine areas. Micropropagation of S. laniceps through seed was a desirable method to get enough seedlings for freezing research. Micropropagation through plantlets derived from germinated S. laniceps seeds collected from Tibet was achieved successfully. Activities of antioxidant enzyme and solute contents were investigated in plantlets of S. laniceps. Freezing tolerance in plantlets increased after 7 or 15 d of cold-hardening (Table 1). Cold-hardening (2 degrees C) increased the activities of SOD, peroxidase, and catalase (Fig.1) in plantlets. A similar increase was also observed in the protein and proline content (Fig.1), whereas soluble carbohydrates changed little (Fig.1). These results obtained suggest that the higher activities of SOD, peroxidase, and catalase, as well as the higher protein and proline content may be biochemical adaptation for freezing toleranc in cold-hardened S. laniceps plantlets. Interestingly, deacclimation was slow; even after the plants were placed again under a temperature of 21-23 degrees C for 5 d, the higher freezing hardiness, enzyme activities, protein and proline content acquired after cold acclimation remained. In conclusion, our plantlet cultures have proved to be good materials for experimentation on freezing resistance in study of freezing-resistance mechanism in the alpine plant S. laniceps.
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PMID:[Effects of cold-hardening on freezing tolerance and antioxidant enzyme activities in plantlets of Saussurea laniceps Hand.-Mazz]. 1612 Oct 17

Marinomonas sp. NJ522, isolated from Antarctic sea ice, produces a cold-active iron superoxide dismutase (SOD; EC 1.15.1.1). The purified SOD was dimeric and had an approx. Mr of 48 kDa. Highest activity was detected from pH 8 to 10 and at 40 degrees C (assayed over 10 min). Activity at 0 degree C was nearly 35% of the maximum activity.
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PMID:Purification and characterization of a cold-active iron superoxide dismutase from a Psychrophilic Bacterium, Marinomonas sp. NJ522. 1636 90


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