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

Follicle stimulating hormone (FSH) in rat serum is successfully measured by a radioreceptor assay system employing PMS-treated immature rat ovary. The non-specific inhibitory effect of serum was partially overcome by the addition of merthiolate to every component, while the residual effect was compensated for by using FSH-free serum which was prepared by passing the pooled female diestrous rat sera through an immunoadsorbent column packed with anti-ovine FSH-coupled Sepharose 4B. The assay system consisted of 100 microliter of Tris-MgCl2-BSA or standard, 100 microliter of FSH-free serum or sample, 100 microliter of the receptor preparation and 100 microliter of 125I-FSH. The incubation was carried out for 4 hr at 37 degrees C and 500 microliter of cold Tris-MgCl2-BSA was used for the termination. Serum FSH could be measured within a range of 0.125-16 ng NIAMDD rat FSH I-3/tube. The mean within-assay coefficient of variation was 10.5%. The mean between-assay coefficient of variation was 11.0%. The assay values obtained by RRA showed a good correlation to those by RIA under the same physiological states of the animals. The ratio of the assay values, RRA/RIA, was found to change according to the sex and the physiological states, e.g. around 1.3 in normal males and 1.7 in orchiectomized animals and 2.21 in female rats. Serum FSH levels in female rats obtained by RRA and RIA changed almost in parallel until 20 : 00 (hr) of proestrous day, but after the first surge of serum FSH they were not parallel. These facts seem to indicate possible changes in the affinity of FSH with its receptor according to the state of animals and lead to the problem of the heterogeneity of FSH.
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PMID:Measurement of rat serum FSH by radioreceptor assay and comparison with radioimmunoassay. 679 Feb 68

Polymyxin-resistant pmrA mutants of Salmonella typhimurium differed from their parents in that they were resistant to tris(hydroxymethyl)aminomethane-ethylenediaminetetraacetate-lysozyme, tris(hydroxymethyl)aminomethane-ethylenediaminetetraacetate-deoxycholate, and tris(hydroxymethyl)aminomethane-ethylenediaminetetraacetate-bacitracin. Tris(hydroxymethyl)aminomethane-ethylenediaminetetraacetate released about 50% less lipopolysaccharide from the pmrA strains than from the parental strains when the bacteria were grown in L-broth containing 2 mM Ca2+. Protamine, polylysine, octapeptin, benzalkonium chloride, cold NaCl, cold MgCl2, or cold tris(hydroxymethyl)aminomethane hydrochloride (pH 7.2) caused no leakage or markedly less leakage of periplasmic beta-lactamase from a pmrA mutant than from its parent strain. pmrA mutants were more resistant than their parent strains to protamine and polylysine but not to octapeptin or benzalkonium chloride, as measured by the ability of these agents to kill the bacteria or to sensitize them to deoxycholate-induced lysis. The pmrA strains did not differ from their parent strains in sensitivity to several antibiotics, in porin function (as measured by cephaloridine diffusion across the outer membrane), or in outer membrane-associated phospholipase A activity.
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PMID:Increased outer membrane resistance to ethylenediaminetetraacetate and cations in novel lipid A mutants. 679 77

We have studied the kinetics of the gelation process that occurs upon warming cold extracts of Acanthamoeba using a low-shear falling ball assay. We find that the reaction has at least two steps, requires 0.5 mM ATP and 1.5 mM MgCl2, and is inhibited by micromolar Ca++. The optimum pH is 7.0 and temperature, 25 degrees-30 degrees C. The rate of the reaction is increased by cold preincubation with both MgCl2 and ATP. Nonhydrolyzable analogues of ATP will not substitute for ATP either in this "potentiation reaction" or in the gelation process. Either of two purified or any one of four partially purified Acanthamoeba proteins will cross-link purified actin to form a gel, but none can account for the dependence of the reaction in the crude extract on Mg-ATP or its regulation by Ca++. This suggests that the extract contains, in addition to actin-cross-linking proteins, factors dependent on Mg-ATP and Ca++ that regulate the gelation process.
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PMID:Viscometric analysis of the gelation of Acanthamoeba extracts and purification of two gelation factors. 689 18

In this paper we obtain thermodynamic and molecular information about the specific complexes formed between Escherichia coli RNA polymerase holoenzyme and a restriction fragment of T7 D111 DNA carrying the A1 and D promoters. Specific binding was observed at both 0 and 37 degrees C over a side range of pH values and ion concentrations [Strauss, H. S., Burgess, R. R., & Record, M. T., Jr. (1980) Biochemistry (first paper of four in this issue)]. The specific complexes formed at these two temperatures may correspond to the closed and open promoter complexes discussed by Chamberlin [Chamberlin, M. J. (1976) RNA Polymerase (Losick, R., & Chamberlin, M., Eds.) pp 159-161, Cold Spring Harbor Laboratory, cold Spring Harbor, NY]. Promoter binding constants KobsdRP are obtained from competition filter binding data by using a statistical analysis and previously determined values of the nonspecific holoenzyme-DNA binding constant KobsdRD. From the magnitudes of KobsdRP at 0 and 37 degrees C, and the dependences of these binding constants on pH and ion concentrations, we conclude that, under physiological ionic conditions, both the 0 and the 37 degrees C complexes are stabilized to a large extent by the formation of ionic interactions and the accompanying release of counterions and that one or two protonation events (pK approximately 7.4) are required for complex formation in both cases. However, the 0 and 37 degrees C complexes differ in their sensitivity to ion concentrations as well as in the magnitude of KobsdRP, and we conclude that the two complexes are distinct. (More counterion release accompanies formation of the 37 degrees C complex). Comparisons of the two complexes with one another and with nonspecific holoenzyme-DNA complexes are drawn from the binding data. We have also examined the equilibrium selectivity ratio (KobsdRP/DobsdRD) and find it to be a sensitive function of temperature and ionic conditions. Selectivity of holoenzyme for promoter sites on the promoter-containing fragment is higher at 37 degrees C than at 0 degrees C under the conditions investigated. Selectivity at either temperature is increased by reducing the pH (in the range 6.1-8.6). At 37 degrees C, selectivity is increased by reducing the salt concentration. Under approximately physiological conditions (0.2 M NaCl and 0.003 M MgCl2, pH 7.4, 37 degrees C), the equilibrium selectivity ratio is found to be of order of magnitude 10(4).
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PMID:Binding of Escherichia coli ribonucleic acid polymerase holoenzyme to a bacteriophage T7 promoter-containing fragment: evaluation of promoter binding constants as a function of solution conditions. 699 5

The metabolic consequences of low-temperature kidney preservation by pulsatile perfusion and cold storage were evaluated in canine kidneys by serial adenosine triphosphate (ATP) determinations. Serial cortical ATP levels were determined (1) after optimal harvest, (2) after 60 minutes of warm ischemia, and (3) after 60 minutes of warm ischemia followed by an intra-aortic infusion of ATP-MgCl2. After 24 hours of preservation, cortical ATP levels were significantly greater when pulsatile perfusion was used-both after optimal harvest and after 60 minutes of warm ischemia. Cortical ATP levels were significantly greater at 24 hours in both perfused and cold-storage kidneys when an intra-aortic infusion of ATP-MgCl2 was used following ischemia. These results may explain the 24-hour limitation of cold storage as well as its inferior results following ischemia injury. Furthermore, since ATP is critical in cellular metabolism, the technique of intra-aortic ATP-MgCl2 infusion warrants further investigation in the field of organ preservation.
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PMID:Renal cortical levels of adenosine triphosphate: restoration after prolonged ischemia by in situ perfusion of ATP-MgCl2. 700 46

New cytochemical method, based on biochemical experiments, was elaborated for the ultrastructural localization of phospho(enol)pyruvate carboxylase (EC 4.1.1.31). The procedure was used to study the saprophytic submerged mycelium of the ascomycetous fungus Claviceps purpurea Tul. producing clavine alkaloids. The pelleted mycelium was fixed in ice cold 3% glutaraldehyde in 50 mM cacodylate buffer pH 7.2 and washed repeatedly in the same cold buffer The reaction mixture contained 100 mM Tris-HCl buffer pH 9.0, 10 mM phospho(enol)pyruvate, 30 mM sodium potassium tartrate, 3 mM Pb(NO3)2, 60 mM MgCl2 and 30 mM NaHCO3. Enzyme activity was localized in vacuoles, particularly inside lipid globules (spherosomes) and less frequently in membranous vesicles. Acetyl-CoA activated PEP-carboxylase both in cell free extracts and in the cytochemical staining. Aspartate inhibited the enzyme in the biochemical assay with coupled malate dehydrogenase system; the cytochemical reaction was not influenced, probably due to the interference of asparagine synthase (EC 6.3.1.1).
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PMID:Electron-cytochemical localization of phospho(enol)pyruvate carboxylase (EC 4.1.1.31) in fungal cells. 739 80

Eukaryotic Y-box proteins are reported to interact with a wide variety of nucleic acid structures to act as transcription factors and mRNA masking proteins. The modular structure of Y-box proteins includes a highly conserved N-terminal cold-shock domain (CSD, equivalent to the bacterial cold-shock proteins) plus four basic C-terminal domains containing arginine clusters and aromatic residues. In addition, the basic domains are separated by acidic regions which contain several potential sites for serine/threonine phosphorylation. The interaction of Y-box proteins, isolated from Xenopus oocytes (FRGY2 type), with RNA molecules has been studied by UV crosslinking and protein fragmentation. We have identified two distinct binding activities. The CSD interacts preferentially with the polypurines poly(A,G) and poly(G) but not poly(A), this activity being sensitive to 5 mM MgCl2 but not to 5 mM spermidine. In the presence of 1 mM MgCl2 or 1 mM spermidine, the basic domains interact preferentially with poly(C,U), this activity being sensitive to 0.5 M NaCl. Binding of the basic domains is also sensitive to low concentrations of heparin. The basic domains can be crosslinked individually to labelled RNA. These results are discussed with reference to the various specificities noted in the binding of Y-box proteins to RNA and DNA.
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PMID:Binding of Y-box proteins to RNA: involvement of different protein domains. 753 Aug 42

A metabolite of estradiol, 2-methoxyestradiol (2ME), inhibits angiogenesis in the chicken embryo chorioallantoic membrane assay. Since 2ME causes mitotic perturbations, we examined its interactions with tubulin. In our standard 1.0 M glutamate system (plus 1.0 mM MgCl2 at 37 degrees C), superstoichiometric concentrations (relative to tubulin) of 2ME inhibited the nucleation and propagation phases of tubulin assembly but did not affect the reaction extent. Although polymer formed in the presence of 2ME was more cold-stable than control polymer, morphology was little changed. Under suboptimal reaction conditions (0.8 M glutamate/no MgCl2 at 26 degrees C), substoichiometric 2ME totally inhibited polymerization. No other estrogenic compound was as effective as 2ME as an inhibitor of polymerization or of the binding of colchicine to tubulin. Inhibition of colchicine binding was competitive (Ki, 22 microM). Thus, a mammalian metabolite of estradiol binds to the colchicine site of tubulin and, depending on reaction conditions, either inhibits assembly or seems to be incorporated into a polymer with altered stability properties.
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PMID:2-Methoxyestradiol, an endogenous mammalian metabolite, inhibits tubulin polymerization by interacting at the colchicine site. 817 Oct 20

Helicobacter pylori cells cultured on solid medium were quantitatively tested for haemolytic activity against erythrocytes of man, sheep, the guinea pig and rabbit. Using 4-day and 8-day cultures of two standard strains (ATCC 43504, IMMi 676), human erythrocytes were not lysed by 10% bacterial suspensions. Rabbit erythrocytes were the most sensitive to 8-day cultures. Hot-cold incubation yielded the highest haemolysis titres. The extent of haemolysis strongly correlated with the number of bacterial cells. Supplementation of the test medium (PBS, pH 7.4) with L-cysteine, dithiothreitol, MgCl2, EDTA, cholesterol, lecithin or sphingomyelin did not influence the haemolysis titres. They were significantly reduced in the presence of pronase E, human serum, bovine serum albumin or CaCl2, and by heat treatment of the bacteria. Supplementation of the test medium with cardiolipin strongly increased the haemolysis titres. Comparing the cell-associated haemolytic activity of 18 strains, the titres ranged from < 2 to 64, with a median titre of 16. No correlation was found between the haemolytic activity and phospholipase C activity of the cell suspensions. It was concluded that the formation of lysophosphatides and non-enzymatic factors rather than a sulphydryl-activated cytolysin or phospholipase C are responsible for the cell-associated haemolytic activity. This property may be involved in the pathogenicity and virulence of Helicobacter pylori.
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PMID:Cell-associated haemolytic activity of Helicobacter pylori. 850 Apr 89

The oral poliovaccine strains lose infectivity when they are stored above refrigerator temperatures. These losses increase rapidly at the high temperatures encountered in tropical countries, thus causing problems if the cold chain is inadequate. Attempts to minimise these losses have generally relied on the addition of salts such as MgCl2. In this paper we show that the fall in infectivity, which is due to the hydrolysis of the genomic RNA by the RNA polymerase within the virus particle, can be greatly inhibited by the suppression of this enzymatic activity. This can be achieved simply by reducing the pH below 7.
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PMID:Stabilising oral poliovaccine at high ambient temperatures. 857 21


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