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

The method given earlier for predicting the thermodynamics of protein unfolding from the x-ray structure of a protein is applied here to the poly(L-alanine) helix. First, the fitting parameters derived earlier from a data base of 10 proteins were used to predict the unfolding thermodynamics of 4 other proteins. The agreement between the observed and predicted values is comparable to that found for the 10 proteins studied initially. Next, the temperature dependences of the Gibbs energy and enthalpy changes for unfolding of bacteriophage T4 lysozyme were predicted and compared with data in the literature. The predicted and observed temperature dependences are similar and the predicted results indicate that cold denaturation should be observed at low temperatures, as observed recently for a T4 lysozyme mutant. The fitting parameters derived from thermodynamic data for protein unfolding and for hydration of model compounds were used to predict the unfolding thermodynamics of the poly(L-alanine) helix. The results predict that helix formation is enthalpy-driven, and the predicted enthalpy change for unfolding (0.86 kcal per mol per residue) is close to the value found in a recent calorimetric study of a 50-residue alanine-rich helix.
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PMID:Prediction of the thermodynamics of protein unfolding: the helix-coil transition of poly(L-alanine). 201 95

It is known that cellular edema and functional impairment develop during anaerobic cold storage of organs. The extent of both is related to the storage time and the composition of the preservation solution used. We studied hypothermia-induced cell swelling and its effect on liver function after cold storage preservation with either Eurocollins (EC), a number of modified EC solutions in which glucose was replaced by various concentrations of raffinose, or UW solution. After 24 h storage, tissue swelling as determined by total tissue water (TTW) in rat liver tissue slices was most pronounced in slices incubated in Eurocollins, whereas the TTW was only moderately increased in slices stored in modified Eurocollins containing 90 to 120 mM raffinose. In contrast, slices incubated in UW solution had a TTW equal to normal rat liver tissue. Furthermore, intact rabbit livers preserved with Eurocollins had an increase in the whole organ weight, while there was no weight change after preservation with the modified solution containing 120 mM raffinose (M120). In contrast, a pronounced weight loss was observed after preservation with UW solution. After cold storage, the livers were reperfused for 2 h at 38 degrees C in an isolated perfusion circuit (IPL) with an acellular perfusate. Bile flow was significantly greater in livers preserved in M120 than in those preserved with the conventional Eurocollins. However, the bile flow in the livers stored in M120 was inferior to that in the livers preserved with UW solution, which in turn was equal to that in control livers. The release of alanine-aspartate-aminotransferase into the perfusate was higher in livers preserved with Eurocollins, with or without modification, than in the livers preserved with UW solution.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:The functional effects of suppression of hypothermia-induced cell swelling in liver preservation by cold storage. 207 Jun 17

The in vitro oxidation to CO2 and tissue incorporation of alanine label by pieces of rat interscapular brown adipose tissue (IBAT) has been investigated. Insulin increased both uptake and oxidation of alanine, as well as the incorporation of alanine label into tissue. This effect only was observed in the presence of glucose in the incubation medium. Noradrenaline hampered alanine incorporation, not affecting its rate of oxidation. IBAT from 4-h cold-exposed rats showed a higher alanine utilization than that of controls; however, IBAT pieces from both 36-h starved and 30-day cold-exposed rats presented lower rates of alanine utilization. The main fate of alanine taken up by the IBAT pieces was its oxidation to CO2. Part of the label was also incorporated into the fatty acid fraction of lipids. The results obtained in this study agree with a possible role of alanine as alternative energetic substrate for IBAT.
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PMID:In vitro alanine utilization by rat interscapular brown adipose tissue. 212 Dec 75

We have identified by differential screening a novel Arabidopsis thaliana gene, called kin1, which is induced at +4 degrees C. The nucleotide sequences of both the genomic clone and the corresponding cDNA were determined. The deduced 6.5 kDa polypeptide has an unusual amino acid composition being rich in alanine, glycine and lysine. The gene belongs to a family of at least two genes. Northern blot analysis revealed that the level of kin1 mRNA is increased 20-fold in cold-treated plants. In addition to being expressed in cold, kin1 is also induced by water stress and the plant hormone abscisic acid (ABA) which has been suggested to be a common mediator for osmotic stress responses and cold acclimation in plants. Sequence comparisons showed that the kin1 gene product has similarities to fish antifreeze proteins (AFPs).
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PMID:Cloning and characterization of a cold- and ABA-inducible Arabidopsis gene. 215 30

A mutagenic oligonucleotide cassette was used to introduce single and tandem amino acid substitutions into the proteinase 3C coding region of an infectious poliovirus type 1 cDNA. The sites targeted for mutagenesis, residues 60, 61, and 66, are located within a putative helical loop structure which may be involved in substrate recognition by the enzyme. Fourteen viable 3C proteinase mutants were isolated. A Lys----Arg substitution at position 60 resulted in cold sensitivity for growth at 33 degrees. Replacement of Lys 60 with Ile, either singly or in combination with substitutions at position 61, resulted in viruses that produced three- to fivefold more 3D RNA polymerase than wild-type poliovirus. 3C-mediated processing of the remaining sites within the polyprotein was not noticeably affected. The overproduction of 3D is a consequence of more efficient processing of the carboxy-terminal Gln-Gly amino acid pair of 3C. Together with a previous report in which substitution of Val 54 with an Ala residue results in a poliovirus that produces decreased levels of 3D, these observations provide evidence that the putative loop region (residues 51-66) may be a functional domain involved in recognition of the carboxy-terminal Gln-Gly cleavage site of 3C.
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PMID:A genetic locus in mutant poliovirus genomes involved in overproduction of RNA polymerase and 3C proteinase. 215 85

To assess the validity of determining the origin of plasma lactate from the ratio of lactate and glucose specific activities (SA) during infusion of labeled glucose, normal subjects received infusions of [6-3H]- and [6-14C]glucose for 4 h after a 12 h fast, and, on another day, cold glucose labeled with both tracers during 4-6 h of hyperinsulinemia (approximately 650 microU/ml). Basally, less lactate was derived from plasma glucose when measured with [6-3H]glucose (27 +/- 2%) than with [6-14C]glucose (40 +/- 2%, P less than 0.001). Insulin did not increase the percent of lactate derived from plasma glucose when measured with [6-3H]glucose (29 +/- 2%) but did increase when measured with [6-14C]glucose (60 +/- 4%). The arterialized blood (A) [3H]lactate SA was 30-40% higher (P less than 0.01) than deep venous blood (V) [3H]lactate SA, whereas A and V [14C]lactate SA were similar. During conversion of alanine to lactate with glutamic-pyruvic transaminase (GPT) and lactate dehydrogenase (LDH) in vitro, 32 +/- 2% of 3H in [3-3H]alanine was found in water and 68 +/- 2% in lactate. During infusion of [6-3H]- and [6-14C]glucose, the ratio of [14C]alanine to lactate SA (0.88 +/- 0.05) was less than the ratio of [3H]alanine to lactate SA (0.31 +/- 0.03, P less than 0.001). In conclusion 1) loss of 3H relative to 14C from position 6 in glucose occurs during lactate formation in extrahepatic tissues possibly due to the GPT reaction (alanine conversion to pyruvate), and 2) even under supraphysiologic hyperinsulinemic conditions not all of plasma lactate originates from plasma glucose.
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PMID:Measurement of lactate formation from glucose using [6-3H]- and [6-14C]glucose in humans. 220 8

The activities of alanine-, aspartate- and branched-chain amino-acid transaminases, glutamine synthetase, glutamate dehydrogenase and adenylate deaminase in white adipose tissue of adult male rats have been determined in animals submitted to 12-h cold exposure (4 degrees C) or to 24-h food deprivation. Starvation resulted in small changes in glutamate dehydrogenase and alanine transaminase when expressed per unit of protein weight, inducing an increase in branched-chain amino-acid transaminase and glutamine synthetase. Cold exposure showed the same effects as starvation with respect to glutamate dehydrogenase and alanine transaminase, but induced increases in glutamine synthetase and aspartate transaminase. It is concluded that starvation increases the handling of some amino acids by white adipose tissue and the detoxification of the ammonia thus evolved. The changes observed suggest a different pattern of amino-acid metabolism enzyme changes with either cold or starvation.
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PMID:Amino-acid metabolism enzyme activities in rat white adipose tissue. 243 May 32

Previously we reported that chymotryptic fragments of bovine adrenal 190-kDa microtubule-associated proteins (27-kDa fragment) and bovine brain tau (14-kDa fragment) contained microtubule-binding domain (Aizawa, H., Murofushi, H., Kotani, Hisanaga, S., Hirokawa, N., and Sakai, H. (1987) J. Biol. Chem. 262, 3782-3787; Aizawa, H., Kawasaki, H., Murofushi, H., Kotani, S., Suzuki, K., and Sakai, H. (1988) J. Biol. Chem. 263, 7703-7707). In order to study the structure of microtubule-binding domain of the two microtubule-associated proteins, we analyzed the amino acid sequence of the 27-kDa fragment and compared the sequence with that of the 14-kDa fragment. This revealed that 190-kDa microtubule-associated protein and tau contained at least one common sequence of 20 amino acid residues in their microtubule-binding domains. A synthetic polypeptide corresponding to the common sequence (Lys-Asn-Val-Arg-Ser-Lys-Val-Gly-Ser-Thr-Glu-Asn-Ile-Lys- His-Gln-Pro-Gly-Gly-Gly-Arg-Ala-Lys) was bound to microtubules competitively with the 190-kDa MAP. The apparent dissociation constant (KD) for the binding of the polypeptide to microtubules was estimated to be 1.8 x 10(-4) M, and the maximum binding reached 1.2 mol of the synthetic polypeptide/mol of tubulin dimer. This synthetic polypeptide increased the rate and extent of tubulin polymerization and decreased the critical concentration of tubulin for polymerization. The polypeptide-induced tubulin polymers were morphologically normal microtubules and were disassembled by cold treatment. The common sequence (termed assembly-promoting sequence) was thus identified as the active site of 190-kDa microtubule-associated protein and tau for the promotion of microtubule assembly. The reconstitution system of microtubules with this synthetic polypeptide with assembly-promoting sequence may be useful to elucidate detailed molecular mechanism of the promotion of microtubule assembly by microtubule-associated proteins.
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PMID:A common amino acid sequence in 190-kDa microtubule-associated protein and tau for the promotion of microtubule assembly. 249 69

This study pursued the isolation and partial characterization of the enzyme polyphenoloxidase from apple (Malus domestica Anna variety), grown in the Hermosillo Coast (State of Sonora, Mexico). The effects of pH and temperature as well as its specificity towards substrates, and its behavior under conditions of hydrophobic chromatography, were studied. The enzyme was isolated from a residual powder obtained from ripe apples homogenized with cold acetone. The extract thus prepared was used to characterize the enzyme, and it showed an optimum pH of 5.36 and an optimum temperature of 35 degrees C. The substrate specificity proved to decrease from 4-methyl catechol, chlorogenic acid, catechol, and caffeic acid, to 3,4-dihydroxiphenyl alanine (DOPA). The enzyme resulted to be more thermostable (temperature range: 35 degrees C to 60 degrees C) than the rest of oxidases of plant origin. When the extract was eluted under conditions of hydrophobic chromatography separation, it appeared as a single peak resulting in a 300 fold purification. The phenolase activity characteristics found in the present study were similar to those observed in other apples from temperate climates; however, this particular polyphenoloxidase is more thermostable under natural conditions. This explains why apples of the Anna variety, at the high harvesting temperature, show a very fast formation of brown spots even when there is a minor damage. The content of compounds with phenolic group was high (1.16 g/100 g fresh weight). Further increase of the velocity of fruit enzymatic browning was due to this reason.
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PMID:[Isolation and partial characterization of phenoloxidase from apples (Malus domestica, var. Anna)]. 251 28

In preparation for functional analyses, a study of the binding of H-2Kb-specific monoclonal antibodies (mAb) to formaldehyde (FOR)-fixed H-2b spleen or tumor cells revealed that three of nine mAb tested had lost reactivity with the FOR-fixed cells, whereas the reactivity of the other mAb generally did not diminish. Comparison of the reactivity of these mAb on untreated H-2Kbm mutant cells and on FOR-treated H-2Kb cells suggests that for three mAb the total loss of reactivity on the latter could be a consequence of the alteration by FOR of lysine 89, which is substituted by alanine in mutant bm3. H-2Kb-specific alloreactive polyclonal or monoclonal CTL, all of which had retained reactivity with bm3 target cells, had also retained reactivity with FOR-fixed H-2b cells as indicated by cold target inhibition studies. The H-2Kb-specific CTL were probably reactive with "conformational" determinants of H-2Kb, which are dependent on the integrity of both the alpha 1 and the alpha 2 domains of the H-2Kb molecule. Results are compatible with FOR treatment selectively affecting a serological determinant in the alpha 1 domain without affecting conformational-type CTL determinants.
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PMID:Selective destruction by formaldehyde fixation of an H-2Kb serological determinant involving lysine 89 without loss of T-cell reactivity. 258 Jul 85


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