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

A simple and rapid gas-liquid-solid chromatographic method for the analysis of trace concentrations of acetaldehyde in urban air (in the Nagoya area) was developed, with the use of cold trapping with liquid oxygen. In the analytical main column the conditions were: stationary phase, Triton X-100 (0.4%); support, Carbopack B (60-80 mesh); glass column, 1.5 m X 3 mm I.D.; column temperature, 75 degrees; carrier gas (nitrogen) flow-rate, 50-80 ml/min. In the cold trapping pre-column the conditions were: stationary phase, Tris (2-cyanoethoxy) propane (25%); support, Shimalite (AW, DMCS) (60-80 mesh); glass column, 31 cm X 4 mm I.D.; operating temperature for the trapping, -183 degrees (liquid oxygen temperature); operating temperature for injection of the condensed sample into the gas chromatograph, increased from -183 degrees to +100 degrees for 2 min. The acetaldehyde peak was identified by the disappearance method with a 2,4-dinitrophenylhydrazine-orthophosphoric acid-glass beads column. The ranges and average concentrations of acetaldehyde detected in 13 urban air samples were 1.5-9.6 and 4.7 ppb, respectively.
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PMID:Simple and rapid gas-liquid-solid chromatographic analysis of trace concentrations of acetaldehyde in urban air. 88 63

Impedance plethysmography was used to measure resting cardiac stroke volume (SV) and thoracic conductive volume (TCV) in four divers at intervals during a prolonged dry saturation dive (17 days at 18.6 ATA and 7 days' decompression). Resting heart rate (HR), blood pressure (BP), and pulmonary minute ventilation (VE) were measured 4 times per day for the duration of the 30-day experiment. The vital capacity (VC) and its subdivisions IC and ERV were measured by spirometry every 3 days. In nonsmokers, VC fell significantly with time (r = 0.64), while VC in smokers increased nearly 400 ml during the first week at pressure before tending to fall with time. Compared to predive, the mean ERV was increased 629 ml at pressure, while VE and respiratory rate were not changed. The increased ERV did not persist postdive and was probably the result of the increased work of breathing a dense gas (4.1 g/liters). Residual volume (RV) measured by nitrogen dilution before and after the dive increased 38% and remained significantly increased (22%) even after one year in 4 divers. It is suggested that hyperoxia (0.3 ATA PO2) combined with increased gas flow resistance caused the VC to fall and RV to increase. The major cardiovascular findings were a transient bradycardia associated with increased stroke volume leading to a significant increase in resting cardiac output associated with an increased rate of rapid ventricular filling, TCV, and BP at depth. Lowering the ambient temperature for 3 days did not re-establish the bradycardia, suggesting that hyperbaric bradycardia is not due to a subtle cold stress.
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PMID:Hana Kai II: a 17-day dry saturation dive at 18.6 ATA. IV. Cardiopulmonary functions. 91 Mar 17

Male rats were exposed chronically to cold (5 degrees C air), hypoxia (12% oxygen in nitrogen), and both combined. Intake of water and food, as well as urinary excretion, were measured during both a 5-d pretreatment control period and throughout the first 3 weeks of the treatment period. Regression analysis of water intake on urine output revealed that, at a given water intake, all three treated groups excreted significantly more urine than controls. No significant differences occurred among treated groups. Serum osmolalities of all three treated groups, measured at the end of the 48-d treatment period, were elevated significantly above the level of the control group. All treated groups also manifested a thirst immediately following return to control environment (26 degrees C, 20.9% oxygen). Water intakes of all three treated groups were significantly greater than that of the control group during the first 2 h after return to control environment. Thus, the three treated groups appeared to be dehydrated relative to the control group. The results further suggest that the effect of combined cold (5 degrees C) and hypoxia (12% oxygen) on water exchange is not a summation of that occurring separately during cold and hypoxia. The factors inducing dehydration in cold and hypoxia are apparently related to increased evaporative water loss and to alterations in thirst and renal mechanisms.
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PMID:Water exchange in rats exposed to cold, hypoxia, and both combined. 93 95

1. Six closely shorn sheep were given brome grass (Bromus inermis) pellets at 1 h intervals and maintained at ambient temperatures of --I to Idegree and 18--21degrees for 28 d. Measurements of digestion were made during the last 10 d of temperature exposure. 2. Cold exposure resulted in a reduction in apparent dry matter (DM) digestibility from 0-482 to 0-450, and of apparent digestibility of organic matter (OM) from 0-511 to 0-477. Neither apparent digestibility nor retention of nitrogen was affected. 3. Apparent digestibility of OM in the rumen decreased from 0-300 to 0-242 with cold exposure, and was highly correlated with turnover time in the rumen of 103Ru, which was used as a particulate marker. 4. The efficiency of microbial synthesis (g N incorporated into microbial cells/kg OM apparently digested) was correlated with the dilution rate of the solute marker (51Cr) and with the turnover time of the particulate marker (103Ru) in the rumen. 5. Digestion in the intestine of DM and OM accounted for significantly more of apparent digestion in the whole gastrointestinal tract for sheep kept in the cold than for sheep kept in the warm. The apparent digestibilities of DM and OM entering the intestine were similar in sheep on both treatments, but significantly more non-ammonia-N was digested in the intestines of cold-exposed sheep. 6. The influence of dilution rate of rumen fluid on the efficiency of synthesis of microbial cells in the rumen is discussed.
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PMID:The effect of cold exposure of sheep on digestion, rumen turnover time and efficiency of microbial synthesis. 95 36

Papain (EC 3.4.22.2) is a proteolytic enzyme, the three-dimensional structure of which has been determined by x-ray diffraction at 2.8 A resolution (Drenth, J., Jansonius, J.N., Koekoek, R., Swen, H. M., and Wothers, B.G. (1968), Nature (London) 218, 929-932). The active site is a groove on the molecular surface in which the essential sulfhydryl group of cysteine-25 is situated next to the imidazole ring of histidine-159. The main object of this study was to determine by the difference-Fourier technique the binding mode for the substrate in the groove in order to explain the substrate specificity of the enzyme (P2 should have a hydrophobic side chain (Berger and Schechter, 1970) and to contribute to an elucidation of the catalytic mechanism. To this end, three chloromethyl ketone substrate analogues were reacted with the enzyme by covalent attachment to the sulfur atom of cysteine-25. The products crystallized isomorphously with the parent structure that is not the native, active enzyme but a mixture of oxidized papain (probably papain-SO2-) and papain with an extra cysteine attached to cysteine-25. Although this made the interpretation of the difference electron density maps less easy, it provided us with a clear picture of the way in which the acyl part of the substrate binds in the active site groove. The carbonyl oxygen of the P1 residue is near two potential hydrogen-bond donating groups, the backbone NH of cysteine-25 and the NH2 of glutamine-19. Valine residues 133 and 157 are responsible for the preference of papain in its substrate splitting. By removing the methylene group that covalently attaches the inhibitor molecules to the sulfur atom of cysteine-25 we obtained acceptable models for the acyl-enzyme structure and for the tetrahedral intermediate. The carbonyl oxygen of the P1 residue, carrying a formal negative charge in the tetrahedral intermediate, is stabilized by formation of two hydrogen bonds with the backbone NH of cysteine-25 and the NH2 group of glutamine-19. This situation resembles that suggested for the proteolytic serine enzymes (Henderson, R., Wright, C. S., Hess, G. P., and Blow, D. M. (1971), Cold Spring Harbor Symp. Quant. Biol. 36, 63-70; Robertus, J. D., Kraut, J., Alden, R. A., and Birktoft, J. J. (1972b), Biochemistry 11, 4293-4303). The nitrogen atom of the scissile peptide bond was found close to the imidazole ring of histidine-159, suggesting a role for this ring in protonating the N atom of the leaving group (Lowe, 1970). This proton transfer would be facilitated by a 30 degrees rotation of the ring around the C beta-Cgamma bond from an in-plane position with the sulfur atom to an in-plane position with the N atom. The possibility of this rotation is derived from a difference electron-density map for fully oxidizied papain vs. the parent protein.
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PMID:Binding of chloromethyl ketone substrate analogues to crystalline papain. 95 85

Rats were exposed to 4 or 25 degrees C for 6, 12, and 24 h or for longer periods up to 2 wk, then eviscerated. The hourly changes in plasma alpha-amino nitrogen were followed for 4 h after operation, which because of functional removal of the liver allows amino acids released from the extrahepatic tissues to accumulate in the blood. Although cold exposure of tissues to accumulate in the blood. Although cold exposure of 24-h-fasted rats for 6 h before eviscerated resulted in an increased rate of rise of plasma alpha-amino nitrogen postoperatively, the rise was not significantly greater than warm controls until after 12 h of exposure. Thereafter, similar results were obtained whether cold was 12, 24, or 48 h or 14 days duration. Fasting in the cold produced an immediate sharp rise after evisceration so that the concentration was 2 times the control value in 2 h. By contrast, animals allowed to eat adlibitum showed the rise after evisceration but it was progressively smaller in amount as the exposure extended beyond the 1st day. After 5 days there were no longer significant differences from control values. The reduction in rate of rise in plasma alpha-amino nitrogen coincided with cold-induced increases in food intake. The findings support the view that protein metabolism of muscle, the predominant extrahepatic tissue, may participate in thermogenesis when other sources of energy in the body have been depleted.
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PMID:Rise in plasma alpha-amino nitrogen concentration in rats eviscerated after colure regulation. 96 57

Effects of high-fat and high-protein diets on cold tolerance in fasted rats were investigated. High-fat diets caused significant increases in body weight, blood-free fatty acids (FFA), ketone bodies and glucose, while high-protein diet did not modify any of these parameters. Rats on high-fat diets that were exposed to cold after clipping exhibited an intermediate cold tolerance as assessed by the rate of fall in colonic temperature between control rats on a standard diet and cold-acclimated rats. The extent of increase of blood FFA and decrease of blood glucose due to cold exposure was less in the high-fat diet group than in control group, but greater than in cold-acclimated group. The lower fall in colonic temperature due to cold exposure was signifcantly associated with less increase in blood FFA and less decrease in blood glucose. In this relation the high-fat diet group was also intermediate between the control and cold-acclimated groups. The high-protein diet did not make any difference in cold tolerance and cold-induced changes in blood metabolites as compared with those in control standard diet, although it resulted in a marked increase in urinary nitrogen excretion. These results indicate that a high-fat diet could exert a significant favorable effect on cold tolerance in fasted rats, but the effect would not be as much as as in cold acclimated rats.
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PMID:Effects of diets on cold tolerance and metabolic responses to cold in fasted rats. 96 2

The state of the regional haemodynamics was studied in 216 patients with vibration disease kept on balneologic therapy. Vibration disease was the result of "local" vibration in 104 patients, and that of combined vibration -- in 112. Rheographic studies of the peripheral blood flow demonstrated disorders of the regional haemodynamics in 76% of the patients, their severity depending on the stage of the pathological process. Rheogrammes recorded during spontaneous attacks of angiospasm or following a cold test revealed a distinct, sometimes complete levelling of the rheographic elements predetermined by the angiospastic state of the peripheral vessesl. The revealed changes in the functional state of the regional flow were of a similar angiospastic nature and reflected the severity of the pathological syndrome, as well as the site of the prevailing vibration effect. Dynamic rheographic studies conducted in patients following balneological treatment (nitrogen-thermal or bromiodine baths) revealed positive changes in the qualitative and quantative rheographic parameters indicating normalization or improvement of the peripheral circulation in vibration disease cases. A comparative assessment of the immediate therapeutic effect of the balneological treatment demonstrated more distinct positive shifts in the rheographic parameters of the regional haemodynamics following a course of nitrogen-thermal baths.
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PMID:[State of regional hemodynamics in patients with vibration disease during sanatorium treatment (reographic studies)]. 101 49

A rapid method for preparing cell-free extracts of Aspergillus ochraceus was developed. Mycelial mats were prefrozen in liquid nitrogen, ground to a fine powder in a cold mortar, and homogenized in an all-glass mechanical homogenizer. This method provided preparations averaging 43.0 mg of protein per g of mycelium (wet weight). The method was fast, efficient, and did not subject the extract to temperatures above 1 C or to heavy metals. The preparation method was suitable for studying a variety of in vitro fungal enzyme systems. Amylase, acid phosphate dehydrogenase, beta-glucosidase, beta fructofuranosidase, and trehalase activities were measurable in the preparations.
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PMID:Rapid method for preparing cell-free extracts of Aspergillus ochraceus. 111

There is need for a storable cryogen suitable for use in dermatological cryosurgery as an alternate for the standard nonstorable cryogen now used (liquid nitrogen). Argon gas was tested and found satisfactory, but has not proved to be commercially feasible. Nitrous oxide apparatus is now available but is of limited usefulness. Various freons (fluorinated hydrocarbons) present possibilities for our use. Although they are incapable of producing the degree of cold and depth of penetration attainable with liquid nitrogen apparatus, they can be used to treat the vast majority of lesions now treated by cryosurgery in an office-based dermatological practice. Freons 12, 22 and 13, alone or mixed with other gases, have been tested. Freon 22 seems the most practical for general dermatologic cryosurgery. Although these gases are considered relatively non-toxic, at this time we really do not know their total noxious capabilities.
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PMID:Alternate cryogens for cryosurgery. 122 54


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