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PubMed1998

Comparison of blood viscosity in red-eared sliders (Trachemys scripta) adapted to cold and room temperature.

Red-eared sliders (Trachemys scripta) in their northern range undergo hibernation at temperatures of about 5 degrees C, which may result in a profound bradycardia and a drop in blood pressure leading to very slow blood flows. Blood viscosity increases with decreasing temperature and at low shear rates associated with slow blood flows. To investigate the effects of temperature on the blood viscosity of these animals, 20 red-eared sliders were randomly assigned to each of two groups, cold environment (5 degrees C) or room-temperature environment (25 degrees C). At the end of 5 months treatment, hematocrit values, plasma protein concentration, and whole-blood viscosity values were determined for each turtle. Blood viscosity measurements were determined at five shear rates (3.75, 15, 30, 75, and 150 s-1) at 5 degrees C and 25 degrees C for all animals. No significant differences were found in hematocrit or plasma protein values between cold-adapted and room temperature-adapted animals. Whole-blood viscosity between groups at any shear rate at a temperature of 5 degrees C was also nonsignificant. The only significant difference in blood viscosity between turtles adapted to cold and room temperature occurred at a shear rate of 3.75 s-1 at 25 degrees C. The whole-blood viscosity of red-eared sliders, whether adapted to cold or to room temperature, tended to be lower as compared to other vertebrates under similar conditions of temperature, shear rate, and hematocrit. This innate lower blood viscosity may compensate for the potential detrimental effects on blood viscosity brought about by the low temperatures and decreased shear rates that occur in these animals during hibernation.

Adaptation, Physiological↗
PubMed1986

The effect of melatonin administration and short exposures to cold on body temperature of the blind subterranean mole rat (Rodentia, Spalax ehrenberghi, Nehring).

Improvement of the cold resistance capacity of the mole rat (Spalax ehrenbergi, Nehring), a blind subterranean rodent, was achieved following subcutaneous melatonin administration. Melatonin-treated mole rats exhibited reduction both in initial body temperature (Tbo) and in the decrease of body temperature (delta Tb) after 6 hours of exposure to cold. The tested mole rats were acclimated to and kept during the experiment, under long (16L/8D) photoperiod schedule while the effects of melatonin administration on body temperature simulated the effects of short photoperiod conditions. These results suggest that in mole rats, melatonin biochemically mediates photoperiodic information into body temperature physiological response. As a byproduct of the original experiment, it was found that frequently repeated short (6 hours) exposure to cold (Ta = 5 +/- 1 degrees C) can in itself initiate an improvement of cold resistance capacity similar to the effect of melatonin administration. This supports the idea that mole rats may improve their cold resistance in response to either photoperiodic or climatic changes.

Animals↗
PubMed2006

Winter forest soil respiration controlled by climate and microbial community composition.

Most terrestrial carbon sequestration at mid-latitudes in the Northern Hemisphere occurs in seasonal, montane forest ecosystems. Winter respiratory carbon dioxide losses from these ecosystems are high, and over half of the carbon assimilated by photosynthesis in the summer can be lost the following winter. The amount of winter carbon dioxide loss is potentially susceptible to changes in the depth of the snowpack; a shallower snowpack has less insulation potential, causing colder soil temperatures and potentially lower soil respiration rates. Recent climate analyses have shown widespread declines in the winter snowpack of mountain ecosystems in the western USA and Europe that are coupled to positive temperature anomalies. Here we study the effect of changes in snow cover on soil carbon cycling within the context of natural climate variation. We use a six-year record of net ecosystem carbon dioxide exchange in a subalpine forest to show that years with a reduced winter snowpack are accompanied by significantly lower rates of soil respiration. Furthermore, we show that the cause of the high sensitivity of soil respiration rate to changes in snow depth is a unique soil microbial community that exhibits exponential growth and high rates of substrate utilization at the cold temperatures that exist beneath the snow. Our observations suggest that a warmer climate may change soil carbon sequestration rates in forest ecosystems owing to changes in the depth of the insulating snow cover.

Bacteria↗
PubMed2006

Basal metabolic rate and organ size in Brandt's voles (Lasiopodomys brandtii): Effects of photoperiod, temperature and diet quality.

This study examined the effects of photoperiod (long day [16 Light:8 Dark] and short day [8 Light:16 Dark]), temperature (cold [5 degrees C] and warm [23 degrees C]), and diet quality (high-fiber diet [36% neutral-detergent fiber (NDF)] and low-fiber diet [23% NDF]) on basal metabolic rate (BMR), digestible energy intake, and organ size in the Brandt's vole (Lasiopodomys brandtii). Cold increased BMR and showed a significant interaction with diet quality. Cold and short photoperiod increased intake of food and digestible energy. The high-fiber diet increased food intake, but decreased digestibility, and had no effects on digestible energy intake. Voles housed in the cold had heavier liver, kidneys and gastrointestinal segments but a lighter carcass. Segments of the gastrointestinal tract tended to be heavier when voles were fed the high-fiber diet. Voles housed in short photoperiod had lighter heart and kidneys but heavier gut segments. With the effects of body mass on BMR and organs was removed, BMR was significantly related to the dry mass of heart, liver, kidneys and cecum. Digestible energy intake was significantly related to the dry mass of kidneys and stomach. These significant relationships were also detected after removing the effects of body mass, temperature, photoperiod and diet quality. There was also a significant correlation between BMR and digestible energy intake. Our results suggest that variations in BMR reflected the evolution of metabolic machinery that induces higher energy intakes. The data also support the assimilation capacity model of endothermy.

Animals↗
PubMed1989

Monoclonal antibody to microtubule-associated STOP protein: affinity purification of neuronal STOP activity and comparison of antigen with activity in neuronal and nonneuronal cell extracts.

Microtubules, ordinarily cold-labile structures, are made entirely resistant to cold temperature by the presence of substoichiometric amounts of STOP (stable tubule only polypeptide), a microtubule-associated protein. We have produced a monoclonal antibody which specifically recognizes a 145-kDa protein previously implicated in STOP activity in rat brain extracts. An antibody affinity column removes both the 145-kDa protein and STOP activity from solution. A urea eluate from the affinity column contains the 145-kDa protein and exhibits substantial STOP activity. We conclude the 145-kDa protein accounts for all measurable STOP activity in rat neuronal extracts. For this work, we have developed an assay of microtubule cold stability which is generally applicable to the detection of STOP activity in various tissues. Using this assay, we show STOP activity is most abundant in neuronal tissue but is detectable in all tissues tested, with the exception of heart muscle. In all tissues that we have examined, STOP activity elutes as a single peak from heparin affinity columns, and in common with brain STOP, all activity is Ca2+-calmodulin sensitive. The monoclonal antibody recognizes the 145-kDa STOP in rat neuronal extracts but reacts with no protein in active fractions from other tissue. A similar, but not identical, analogue of brain STOP thus appears to be widespread in mammalian tissues.

Animals↗
PubMed1996

Model experiments to establish behaviour of Yersinia enterocolitica O: 9 strains in various types of fresh dry sausage.

In model experiments different kinds of raw sausages were inoculated with liquid cultures of virulent-plasmid-carrying clinical Yersinia (Y.) enterocolitica (e.) strains of the O: 9 serotype, doses being between 10(4) and 10(5) cfu g-1. The sausage samples were stored at 3-5 degrees C and 13-16 degrees C. During the first 10 d of storage the Y.e. plate count was detected with Desoxycholate-Citrate-Lactose-Sucrose Agar every day, later on in addition to it with phosphate buffer-enrichment and with enrichment according to Schiemann (1982) in intervals of several days' duration. The pH and aw values, the contents of salt and water were detected. The multitude of complexly acting factors and substances prevents obviously the proliferation of Y.e. in fresh dry sausages. Decay dynamics of Y.e. were found to be considerably affected by storage temperature. Cold storage, basically, had a conservation effect and thus delayed the dying process of model strains. Yersinia enterocolitica-contaminated fresh dry sausage may cause potential danger to consumers, because of relatively extended survival periods of the pathogen. Therefore, manufacturers are expected to observe most stringent hygienic rules of Good Manufacturing Practice.

Animals↗
PubMed1994

Retinal adhesiveness in surgically enucleated human eyes.

PURPOSE: Retinal adhesion in rabbits and monkeys has been shown to involve the interphotoreceptor matrix and depend on environmental factors, such as temperature, pH, and calcium concentration. This study was designed to see whether these same factors modulate retinal adhesiveness in humans. METHODS: Four surgically enucleated human eyes were studied. Strips of eyecup were placed in experimental baths shortly after enucleation to evaluate environmental conditions. Retinal adhesive strength was quantified by the amount of retinal pigment epithelial pigment adherent to retina peeled from strips of eyecup. Cone and rod sheaths of the interphotoreceptor matrix were studied by microscopic examination of samples stained with the lectins peanut and wheat germ agglutinin. RESULTS: Retinal adhesiveness fell to 0 approximately 40 minutes after enucleation. Adhesive strength was maintained by cold temperature and was weakened by low pH or low calcium in the bath. Cone and rod matrix sheaths became stretched (indicating a bond) as outer segments and retinal pigment epithelium were peeled apart. CONCLUSION: Retinal adhesion in humans appears to involve similar mechanisms as in rabbits and monkeys.

Adhesiveness↗
PubMedDate not supplied

Seasonal variations in the temperature acclimation response of the channel catfish, Ictalurus punctatus.

Channel catfish were collected on 11 different dates from October 1991 to July 1993 and acclimated in the laboratory to 7 degrees C, 15 degrees C, or 25 degrees C for 6 wk. Hepatosomatic index, mg protein mg-1 DNA, total liver DNA and protein, and the activities of liver glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, lactate dehydrogenase, and malate dehydrogenase were measured to examine seasonal variation in the acclimation response. Liver and muscle cytochrome oxidase and lactate dehydrogenase activities were measured to compare tissue-specific responses. Hepatosomatic indexes of fall and winter channel catfish were highest at 7 degrees C, with values at 15 degrees C higher than at 25 degrees C, while spring and summer fish had the highest values at 15 degrees C, with values at 7 degrees C higher than those at 25 degrees C. Acclimation patterns for total liver protein and DNA, mg protein mg-1 DNA, and glycogen were generally higher in cold temperatures but varied seasonally in an unpredictable manner. Glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, and malate dehydrogenase demonstrated positive acclimation in the fall and winter; fish collected in the spring and summer showed little or inverse acclimation. Liver lactate dehydrogenase activity showed little or no positive compensation at any time of the year. Cytochrome oxidase activity showed positive acclimation in muscle but not liver. All liver enzymes, even those that showed marginal acclimation on a protein basis, showed positive acclimation when activity was expressed on a whole-liver basis.

Acclimatization↗
PubMed1968

Abscisic Acid levels and seed dormancy.

Dormant seeds from Fraxinus species require cold-temperature after-ripening prior to germination. Earlier, we found that abscisic acid (ABA) will inhibit germination of excised nondormant embryos and that this can be reversed with a combination of gibberellic acid and kinetin. Using Milborrow's quantitative "racemate dilution" method the ABA concentration in 3 types of Fraxinus seed and pericarp were determined. While ABA was present in all tissues, the highest concentration was found in the seed and pericarp of dormant F. americana. During the chilling treatment of F. americana the ABA levels decreased 37% in the pericarp and 68% in the seed. The ABA concentration of the seed of the nondormant species, F. ornus, is as low as that found in F. americana seeds after cold treatment. Experiments with exogenously added ABA solutions indicate that it is unlikely that the ABA in the pericarp functions in the regulation of seed dormancy. However, the ABA in the seed does seem to have a regulatory role in germination.

Journal Article↗
PubMed1986

Biochemical responses to temperature in the contractile protein complex of striped bass Morone saxatilis.

The effects of acute and long-term changes in temperature upon catalytic and calcium regulatory function of red (slow oxidative) and white (fast glycolytic) muscle from striped bass (Morone saxatilis) were determined. Acclimation to 5 degrees C or 25 degrees C had no significant effect on catalytic function (ATPase activity) or regulatory sensitivity (Ca++-activation) of myofibrils from either muscle type. Substantial differences between red and white muscle were found in the intrinsic thermal sensitivity of maximally-activated Mg++-Ca++ myofibrillar ATPase. Arrhenius plots of myofibrillar ATPase from white muscle show one significant breakpoint at 29 degrees C, with activation energies (Ea) of 2.3 and 23.4 kcal mole-1 at temperatures above and below this transition, respectively. Arrhenius plots of myofibrillar ATPase from red muscle show two transitions occurring at 22 and 9 degrees C, with Ea of 7.6 kcal mole-1 above 22 degrees C and 18.3 kcal mole-1 between 9 and 22 degrees C. Activation energies for myofibrils from red muscle increase substantially to approximately 107.3 kcal mole-1 below the 9 degrees C breakpoint. Differences in the intrinsic thermal sensitivity of red and white muscle catalytic function are apparently due to interaction of actomyosins and calcium regulatory proteins which are specific to each muscle type. The results suggest that capacity for sustained swimming in striped bass, which is powered exclusively by red muscle, will be severely impaired at cold temperature unless compensations occur above the level of contractile proteins.

Actomyosin↗
PubMed1982

Optimal myocardial protection with fluosol cardioplegia.

An oxygenated perfluorocarbon cardioplegic solution was examined, utilizing a blood-perfused canine model. Twenty-one animals were divided into three equal groups, and each animal received Fluosol cardioplegia at one of three infusion temperatures: 20 degrees C, or 4 degrees C. All hearts underwent 90 minutes of ischemia, during which time 150 ml of the cardioplegic solution was infused every 30 minutes. Myocardial oxygen and carbon dioxide tensions (PmO2 and PmCO2) were monitored continually using mass spectrometry, and myocardial oxygen consumption was calculated with each cardioplegic injection. The mean increase in PmO2 was 7.1 +/- 0.9 mm Hg with 20 degrees C Fluosol infusions, 31.1 +/- 4.7 mm Hg with 10 degrees C Fluosol injections, and 22.2 +/- 4.7 mm Hg with infusions of 4 degrees C Fluosol. Average myocardial oxygen consumptioN, expressed as cubic centimeters of oxygen per 100 gm of left ventricle (wet weight), was 21.2 +/- 0.5 with 20 degrees C Fluosol, 22.8 +/- 1.3 for 10 degrees C Fluosol, and 19.6 +/- 1.0 for 4 degrees C Fluosol. Mean myocardial temperatures with infusions of 20 degrees C, 10 degrees C, and 4 degrees C solutions were 21.4 +/- 0.1 degree C, 16.9 +/- 0.4 degree C, and 15.9 +/- 0.5 degree C, respectively. After 45 minutes of reperfusion, maximum rate of rise of left ventricular pressure, expressed as percentage of preischemic control, was 70.9 +/- 3.9% for 20 degrees C Fluosol, 90.9 +/- 3.2% for 10 degrees C Fluosol, and 90.4 +/- 2.3% for 4 degrees C Fluosol (p less than 0.005, 20 degrees C versus 10 degrees C, 4 degrees C Fluosol). In addition, the 10 degrees C and 4 degrees C Fluosol hearts had essentially normal structure by light and electron microscopy. These data demonstrate tht Fluosol cardioplegia results in near optimal myocardial protection when infused at cold temperatures (4 degrees C to 10 degree C). The increases intramyocardial oxygen and myocardial oxygen consumption with each injection demonstrate that there is enhanced oxygen delivery and utilization, which may account for the improved functional recovery observed in these hearts.

Animals↗
PubMed1985

Studies on the eye lens in poikilothermal animals. I. Comparative studies on cation maintenance systems in rainbow trout and rat lenses.

The response of the poikilothermal lens to various incubation temperatures in vitro was compared with that of the homothermal lens. The rainbow trout lens was used as the poikilothermal lens and the rat lens as the homothermal lens. In contrast to rat lenses, cataract developed at 37 degrees C in rainbow trout lenses, which was called 'warm cataract'. Warm cataract developed not only when lenses were incubated in vitro but also when rainbow trout were kept in water at 37 degrees C. Water, Na+, Ca2+ and insoluble protein increased and K+ and Mg2+ decreased in warm cataract lenses, but GSH and soluble protein sulfhydryl levels did not change. This cataract was irreversible after only 5 min incubation at 37 degrees C. On the other hand, rainbow trout lenses remained transparent without the change of cation balance at 0-25 degrees C while cold cataract developed in rat lenses. Na,K-ATPase activity was detected at 0 degrees C in rainbow trout lens homogenates, but not in rat lens homogenates. Na+-K+ ratio (Na+/K+) increased when the rainbow trout lens was treated with ouabain at 0 degrees C. In the rainbow trout lens, lactic acid was produced continuously for 30 days at 0 degrees C while it was not in the rat lens between 1 hr and 10 days after. These results strongly suggest that Na,K-ATPase acts as a cation pump at 0 degrees C and that ATP is supplied by glycolysis in the rainbow trout lens in order to maintain the transparency. The above results also suggest that enzymes and membrane structures in rainbow trout lens are adapted to a cold-temperature habitat and that Na,K-ATPase and anaerobic glycolysis are important for the maintenance of lens transparency at low temperatures.

Animals↗
PubMed2005

Thermal stability of proteins.

Protein stability is critical to the outcome of nearly all thermally mediated applications to biomaterials such as thermal therapies (including cryosurgery), burn injury, and biopreservation. As such, it is imperative to understand as much as possible about how a protein loses stability and to what extent we can control this through the thermal environment as well as through chemical or mechanical modification of the protein environment. This review presents an overview of protein stability in terms of denaturation due to temperature alteration (predominantly high and some low) and its modification by use of chemical additives, pH modification as well as modification of the mechanical environment (stress) of the proteins such as collagen. These modifiers are able to change the kinetics of protein denaturation during heating. While pH can affect the activation energy (or activation enthalpy) and the frequency factor (or activation entropy) of the denaturation kinetics, many other chemical and mechanical modifiers only affect the frequency factor (activation entropy). Often, the modification affecting activation entropy appears to be linked to the hydration of the protein. While the heat-induced denaturation of proteins is reasonably well understood, the heat denaturation of structural proteins (e.g., collagen) within whole tissues remains an area of active research. In addition, while some literature exists on protein denaturation during cold temperatures, relatively little is known about the kinetics of protein denaturation during both freezing and drying. Further understanding of this kinetics will have an important impact on applications ranging from preservation of biomaterials and pharmaceutics to cryosurgery. Interestingly, both freezing and drying involve drastic shifts in the hydration of the proteins. It is clear that understanding protein hydration at the molecular, cellular, and tissue level will be important to the future of this evolving area.

Animals↗
PubMed1983

Temperature of the portio uteri in cryosurgical treatment.

The cryosurgical treatment of various benign changes in the uterine cervix has gained wide acceptance [4, 8, 15, 16, 17, 29]. The application of cryosurgery has widened the range of gynaecologic therapeutic methods. As all new methods, it could not entirely fulfil all expectations. The results of initial attempts at curing cancer or various precancerous diseases of the cervix were not wholly satisfying and, according to our present knowledge, the application of cryosurgery in such cases is not advisable except under certain specific circumstances [2, 3, 5, 7, 10, 12, 13, 14, 18, 24, 28, 33, 35]. The method promises excellent results in the treatment of chronic inflammation of the cervix resistant to conservative therapy, of condyloma acuminatum, ectopium, etc. [4, 8, 15, 17, 29, 30]. The present studies were undertaken in order to determine the relationship between the cooling velocity attained in cryosurgery and using Erbokryo-Amoils 40/a type device and nitric oxide. The extent of tissue destruction depends namely first of all on the velocity of cooling and then thawing. The thawing time is given as a function of the blood in the tissue. The cold temperature is not negligible causing tissue damage either.

Body Temperature↗
PubMed2004

Raynaud's phenomenon of the nipple: a treatable cause of painful breastfeeding.

Maurice Raynaud first described the vasospasm of arterioles in 1862, and Raynaud's phenomenon is now felt to be common, affecting up to 20% of women of childbearing age. Raynaud's phenomenon has been reported to affect the nipples of breastfeeding mothers and is recognized by many lactation experts as a treatable cause of painful breastfeeding. In 1997, Lawlor-Smith and Lawlor-Smith reported 5 women with Raynaud's phenomenon associated with breastfeeding, but there are few other case reports, and none report the possible relationship between Raynaud's phenomenon of the nipple and previous breast surgery. We report 12 women who breastfed 14 infants, all of whom were seen in 1 pediatric practice and 1 lactation consultation center in San Francisco, California, within the past 3 years. Of the 12 women, 11 were seen between June 2002 and May 2003. All women suffered from extremely painful breastfeeding, with symptoms precipitated by cold temperatures and associated with blanching of the nipple followed by cyanosis and/or erythema. Poor positioning and poor attachment or latch may cause blanching of the nipple and pain during breastfeeding, but 10 of the 12 mothers were evaluated by experienced lactation consultations, who were sure that inappropriate breastfeeding techniques were not contributing factors. Because the breast pain associated with Raynaud's phenomenon is so severe and throbbing, it is often mistaken for Candida albicans infection. It is not unusual for mothers who have Raynaud's phenomenon of the nipple to be treated inappropriately and often repeatedly for C albicans infections with topical or systemic antifungal agents. Eight of our 12 mothers and their infants received multiple courses of antifungal therapy without relief before the diagnosis was made. To diagnose Raynaud's phenomenon accurately, additional symptoms such as precipitation by cold stimulus, occurrence of symptoms during pregnancy or when not breastfeeding, and biphasic or triphasic color changes must be present. All our mothers experienced precipitation of symptoms by cold stimuli and demonstrated biphasic or triphasic color changes, and 6 of the 12 experienced symptoms during pregnancy. Interestingly 3 of 12 mothers also reported a history of breast surgery, including 1 mother who had a fibroadenoma removed and 2 who had breast-reduction surgery. The association between breast surgery/implants and autoimmune disease, including Raynaud's phenomenon, has been discussed extensively, but the association of Raynaud's phenomenon of the nipple during breastfeeding has not been reported previously. Given the small numbers in the study, it is uncertain as to whether this may be a precipitating factor in developing Raynaud's phenomenon. Treatment options include methods to prevent or decrease cold exposure, avoidance of vasoconstrictive drugs/nicotine that could precipitate symptoms, and pharmacologic measures. There are reports in the lay press of the use of herbal medicines, aerobic exercise, and dietary supplements, but because most women with painful breastfeeding require immediate relief of the pain to continue breastfeeding successfully, it is important to offer a treatment plan that will alleviate the pain quickly. Nifedipine, a calcium channel blocker, has been used to treat Raynaud's phenomenon because of its vasodilatory effects. Very little of the medication can be demonstrated in breast milk and thus is safe to use in breastfeeding mothers. Of the 12 mothers in our series, 6 chose to use nifedipine, and all had prompt relief of pain. Only 1 mother developed side effects from nifedipine. Pediatricians and lactation consultants should be aware of this treatable cause of painful breastfeeding and should specifically question their patients, because most mothers will not provide this information to the breastfeeding consultant. Prompt treatment will allow mothers to continue to breastfeed pain free while avoiding unnecessary antifungal therapy.

Adult↗
PubMed1990

Adaptation to temperature: phospholipid synthesis in hepatocytes of rainbow trout.

De novo phospholipid biosynthesis was assayed in isolated hepatocytes of rainbow trout (Oncorhynchus mykiss) both fully acclimated to 5 or 20 degrees C and undergoing acclimation from one temperature extreme to the other. Incorporation of [14C]choline, [3H]ethanolamine, and [3H]serine into phosphatidyl-choline (PC), phosphatidylethanolamine (PE), or both, was followed to assess metabolic capacity. PE biosynthesis rates exceeded those for PC four- to fivefold. Methylation of PE accounted for 10 (20 degrees C)-17% (5 degrees C) of the synthetic capacity for PC, whereas 6 (20 degrees C-acclimated)-27% (5 degrees C-acclimated) of PE synthesis was derived from phosphatidylserine (PS) decarboxylation. Several factors may contribute to the altered proportions of PE and PC or unsaturated molecular species of phospholipids characteristic of thermally acclimated animals. 1) Activities of choline and ethanolamine phosphotransferase pathways were significantly higher, and decarboxylation activity lower, in 20 degrees C than in 5 degrees C-acclimated trout, resulting in maintained PE synthesis despite a general depression of lipid biosynthesis at cold temperatures. 2) PC biosynthesis depended more on temperature (Q10 = 2.6-3.0) than that of PE (Q10 = 1.8-2.2), causing the ratio of PC/PE synthesis to be positively correlated with temperature. 3) Contribution of methyltransferase pathway to the synthesis of PC was higher at 5 than 20 degrees C. 4) The percentage of ethanolamine incorporation recovered in PC increased threefold in the early stages of warm acclimation. However, not all adjustments in biosynthetic capacity (most notably a 10-fold stimulation of PC synthesis 2 days after transfer of warm-acclimated trout to 5 degrees C) influence membrane lipid composition, implicating other processes in the regulation of this parameter.

Acclimatization↗
PubMed1998

Prevention of cellular edema directly caused by hypothermic cardioplegia: studies in isolated human and rabbit atrial myocytes.

OBJECTIVES: This study tested the hypothesis that edema during hypothermic cardioplegia is caused by the hypotonicity of the perfusate at cold temperatures. METHODS: The volume of isolated human and rabbit atrial myocytes was measured by video microscopy under nonischemic conditions. Each cell served as its own control. RESULTS: After equilibration in 37 degrees C physiologic buffer (Tyrode's solution), exposure to 9 degrees C St. Thomas' Hospital solution for 20 minutes caused human atrial cells to swell by 20% and rabbit atrial cells to swell by 10%. Cell volume fully recovered on rewarming in 37 degrees C physiologic solution. Cell swelling was due to the composition of St. Thomas' Hospital solution rather than hypothermia alone. Exposure to 9 degrees C physiologic solution did not significantly affect cell volume. Swelling of myocytes was largely prevented by replacing most of the Cl- in St. Thomas' Hospital solution with an impermeant anion so that the product of the concentrations of K+ and Cl- were the same as in the physiologic solution. CONCLUSIONS: This study suggests that cell swelling during hypothermic cardioplegia is caused in part by the composition of the cardioplegic solution. The volume of cardiac myocytes appears to follow a Donnan equilibrium in the cold, and the perfusate KCl product determines water movement. Thus, the tonicity of hyperkalemic cardioplegic solutions can be adjusted to a physiologic value by replacing most Cl- by an impermeant anion. Following this simple principle, a reformulation of cardioplegic solutions may be able to minimize iatrogenic myocardial edema.

Adult↗