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PubMed1989

Tolerance of corneas to multimolar dimethyl sulfoxide at 0 degrees C. Implications for cryopreservation.

Attempts to improve current methods of cryopreservation of corneas, whether by conventional freezing and thawing or by vitrification in the absence of ice, will require the use of high concentrations of cryoprotectants. In this study we extend our previous investigation of the tolerance of rabbit corneas to multimolar concentrations of the cryoprotectant dimethyl sulfoxide (Me2SO) added and removed at 0 degrees C in CPTES, a hyperkalaemic preservation solution containing the impermeant anionic buffer N-Tris(hydroxymethyl)methyl-2-aminoethane sulphonate (TES). Isolated corneas were exposed to 1, 2 or 3 mol/l Me2SO at 0 degrees C to minimize any effect due to temperature-dependent chemical toxicity and attention was given to the procedure for diluting Me2SO from the tissue in order to minimize osmotic stress to the endothelium. Endothelial integrity following these procedures was assessed both by the ability to control stromal hydration during perfusion on the specular microscope and by the structural integrity when examined by light and electron microscopy. The presence of an active endothelial pump and good morphology were demonstrated in corneas exposed to 1 and 2 mol/l Me2SO; serial dilution of the cryoprotectant was more beneficial than a single-step direct dilution. Corneas immersed directly into 3 mol/l Me2SO were irreparably damaged irrespective of the method of dilution. Sequential addition of 1 M, then 2 M and finally 3 M cryoprotectant followed by serial dilution was, however, tolerated by the endothelium and minor alterations to the structural integrity of the endothelial layer were rapidly repaired. The osmotic nature of these observations are analyzed and discussed.

Animals↗
PubMed1995

Influence of glucose load on cardiovascular and humoral responses to a cold pressure test.

To investigate the relationship between insulin and reactivity to the cold pressure test four groups of mildly obese patients (12 per group: normotensive, essential hypertensive, normotensive (N-NIDD) and hypertensive non-insulin-dependent diabetics (H-NIDD)) underwent a standardised oral glucose tolerance test. During the test, BP and heart rate were monitored and venous blood samples were obtained at 0, 60 and 120 minutes to determine serum levels of glucose, insulin (microU/ml), sodium, potassium (mEq/I), renin activity (ng/ml/hour), aldosterone, noradrenaline and adrenaline. The cold pressure tests were performed before glucose ingestion (I-CPT) and again at 60 minute after ingestion (II-CPT). As expected, glucose ingestion caused a significant increase in glycaemia and serum insulin; the latter rose significantly more at 60 minutes in normotensives (85 +/- 6) and essential hypertensives (83 +/- 5) than in N-NIDD (30 +/- 4) and H-NIDD (29 +/- 3). Plasma K significantly decreased in normotensives (4.4 +/- 0.1 vs. 3.6 +/- 0.1, P < 0.05) and essential hypertensives (4.3 +/- 0.1 vs. 3.5 +/- 0.1, P < 0.05) but did not change in either N-NIDD or H-NIDD. PRA significantly increased in normotensives (0.6 +/- 0.1 vs. 1.2 +/- 0.1, P < 0.01) and essential hypertensives (0.8 +/- 0.1 vs. 1.5 +/- 0.2, P < 0.05) but did not change in N-NIDD or H-NIDD. Plasma sodium and catecholamines did not change in any group. I-CPT induced similar reactivity in all the groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed1977

Pilot studies on recombinant cold-adapted live type A and B influenza virus vaccines.

Recombinant live attenuated type A and B influenza virus vaccines derived from standardized cold-adapted parent strains were given singly and in combination to volunteers. The vaccine viruses were well tolerated, functioned as good antigens, and failed to spread to intimate household contacts. Thirty-nine isolates that were recovered after a single passage in humans appeared genetically stable. The results of histopathologic studies in ferrets encourage development of an animal model for attenuation of the virus.

Animals↗
PubMed2005

Cold, salinity and drought stresses: an overview.

World population is increasing at an alarming rate and is expected to reach about six billion by the end of year 2050. On the other hand food productivity is decreasing due to the effect of various abiotic stresses; therefore minimizing these losses is a major area of concern for all nations to cope with the increasing food requirements. Cold, salinity and drought are among the major stresses, which adversely affect plants growth and productivity; hence it is important to develop stress tolerant crops. In general, low temperature mainly results in mechanical constraint, whereas salinity and drought exerts its malicious effect mainly by disrupting the ionic and osmotic equilibrium of the cell. It is now well known that the stress signal is first perceived at the membrane level by the receptors and then transduced in the cell to switch on the stress responsive genes for mediating stress tolerance. Understanding the mechanism of stress tolerance along with a plethora of genes involved in stress signaling network is important for crop improvement. Recently, some genes of calcium-signaling and nucleic acid pathways have been reported to be up-regulated in response to both cold and salinity stresses indicating the presence of cross talk between these pathways. In this review we have emphasized on various aspects of cold, salinity and drought stresses. Various factors pertaining to cold acclimation, promoter elements, and role of transcription factors in stress signaling pathway have been described. The role of calcium as an important signaling molecule in response to various stress signals has also been covered. In each of these stresses we have tried to address the issues, which significantly affect the gene expression in relation to plant physiology.

Acclimatization↗
PubMed1988

Transformation of the cryobehavior of rye protoplasts by modification of the plasma membrane lipid composition.

The freezing tolerance of protoplasts isolated from nonacclimated rye leaves (Secale cereale L. cv Puma) was significantly altered by using a pH-induced protoplastliposome fusion technique to modify the lipid composition of the plasma membrane. The increase in freezing tolerance was elicited by fusion with liposomes composed of either the total phospholipid fraction isolated from the plasma membrane of cold-acclimated leaves or single mono- or diunsaturated species of phosphatidylcholine (PtdCho). Of the PtdCho species tested, dilinoleoylphosphatidylcholine ([Lin(2)]PtdCho) and dilinolenoylphosphatidylcholine ([Lnn(2)]PtdCho) liposomes were the most effective; 1-palmitoyl-2-oleoylphosphatidylcholine, 1-palmitoyl-2-linoleoylphosphatidylcholine, or dioleoylphosphatidylcholine liposomes were somewhat less effective; dimyristoylphosphatidylcholine or dipalmitoylphosphatidylcholine liposomes had no effect. The increased freezing tolerance was the result of a transformation in the cryobehavior of the plasma membrane during freeze-induced osmotic contraction. In control nonacclimated protoplasts, osmotic contraction resulted in endocytotic vesiculation of the plasma membrane which was irreversible and resulted in lysis during osmotic expansion after melting of the suspending medium. In nonacclimated protoplasts fused with mono- or diunsaturated species of PtdCho, osmotic contraction resulted in the reversible formation of exocytotic extrusions of the plasma membrane-as normally occurs in protoplasts isolated from cold-acclimated leaves (acclimated protoplasts). In scanning electron micrographs, the morphology of the extrusions of nonacclimated protoplasts fused with [Lin(2)]PtdCho was virtually indistinguishable from that of the extrusions formed in acclimated protoplasts. These studies provide direct evidence that changes in the lipid composition of the plasma membrane are causally related to one facet of the cold-acclimation process.

Journal Article↗
PubMed2002

Elements of cold hardiness in a littoral population of the land snail Helix aspersa (Gastropoda: Pulmonata).

The land snail Helix aspersa can be considered partially tolerant to freezing, in the sense it can survive some ice formation within its body for a limited time, and possesses a limited ability to supercool. This study aimed at understanding what factors are responsible for the variation of the temperature of crystallization ( Tc) in a littoral temperate population. The ability to supercool was maximal (ca. -5 degrees C) during dormancy periods (hibernation and aestivation) and minimal (ca. -3 degrees C) during spring and autumn, in relation with the decrease of water mass and the increase of osmolality. Tc decreased in October to remain stable through late autumn and winter; it increased quickly with the awakening of animals in April. Snails with an epiphragm had a significantly higher ability to supercool (ca. -4.8 degrees C) than snails which did not form an epiphragm (ca. -4.2 degrees C). The animals' size had a weak but significant influence on the realization of the Tc. It appeared that there was not a real cold-hardiness strategy in this population; rather a sum of parameters, varying in consequences of the external conditions and of the activity cycle, which are responsible for the enhancement of the supercooling ability during winter.

Acclimatization↗
PubMed1987

Pain threshold and tolerance in women with syndrome X and women with stable angina pectoris.

A recent report showed that during Holter monitoring of patients with syndrome X (typical anginal pain, positive exercise test response [at least 0.1 mV of ST-segment depression], no evidence of coronary spasm and angiographically normal coronary arteries), 50% of episodes of ischemic ST-segment depression were painful. This proportion is considerably higher than that in patients with chronic stable angina, which is about 30%. A significantly lower threshold and tolerance to painful stimuli was seen in a group of patients with chronic stable angina in whom 50% of episodes were painful compared with a group in whom only 5% of episodes were silent. Hence, patients with syndrome X may have enhanced sensitivity to painful stimuli. To investigate whether this difference was due to a lower threshold for painful stimuli in general, 12 patients with syndrome X and 10 (age- and sex-matched) with chronic stable angina were studied using the same battery of painful stimuli. Patients with syndrome X had a significantly lower threshold and tolerance for forearm ischemia (-36%, p less than 0.05, and -40%, p less than 0.001) and electrical skin stimulation (-37%, p less than 0.01, and -35%, p less than 0.001); the cold pressor test did not show significant differences (-7%, p = 0.391, and -1%, p = 0.818). Thus, patients with syndrome X in this study had significantly lower threshold and tolerance values for forearm ischemia and for electrical skin stimulation. These differences in sensitivity to pain may partly explain a higher incidence of painful ischemic episodes detected by ambulatory electrocardiographic monitoring during unrestricted daily life.

Angina Pectoris↗
PubMed2004

On the nature of pre-freeze mortality in insects: water balance, ion homeostasis and energy charge in the adults of Pyrrhocoris apterus.

Three acclimation groups [i.e. non-diapause (LD), diapause (SD) and diapause, cold-acclimated (SDA)] of the adult bugs Pyrrhocoris apterus differed markedly in their levels of chill tolerance. Survival time at a sub-zero, but non-freezing, temperature of -5 degrees C (Lt50) extended from 7.6 days, through 35.6 days, to >60 days in the LD, SD and SDA insects, respectively. The time necessary for recovery after chill-coma increased linearly with the increasing time of exposure to -5 degrees C, and the steepness of the slope of linear regression decreased in the order LD>SD>SDA. The capacity to prevent/counteract leakage of Na(+) down the electrochemical gradient (from haemolymph to tissues) during the exposure to -5 degrees C increased in the order LD<SD<SDA. As a result, the rates of counteractive outward movement of K(+), and of the E(K) dissipation, decreased in the same order. The least chill-tolerant insects (LD) showed the highest rate of body-water loss. Most of the water was lost from the haemolymph compartment. The ability to regulate a certain fraction of ion pools into the hindgut fluid was the highest in the SDA group, medium in the SD group and missing in the LD group. The adenylate energy charge in the fat body cells was constant in all three groups. The total pools of ATP, ADP and AMP, however, decreased in the SD and SDA groups but remained constant in the LD group. The inability of insects to maintain ion gradients at sub-zero temperature is discussed as an important cause of pre-freeze mortality.

Acclimatization↗
PubMedDate not supplied

Physiological ecology of overwintering in the hatchling painted turtle: multiple-scale variation in response to environmental stress.

We integrated field and laboratory studies in an investigation of water balance, energy use, and mechanisms of cold-hardiness in hatchling painted turtles (Chrysemys picta) indigenous to west-central Nebraska (Chrysemys picta bellii) and northern Indiana (Chrysemys picta marginata) during the winters of 1999-2000 and 2000-2001. We examined 184 nests, 80 of which provided the hatchlings (n=580) and/or samples of soil used in laboratory analyses. Whereas winter 1999-2000 was relatively dry and mild, the following winter was wet and cold; serendipitously, the contrast illuminated a marked plasticity in physiological response to environmental stress. Physiological and cold-hardiness responses of turtles also varied between study locales, largely owing to differences in precipitation and edaphics and the lower prevailing and minimum nest temperatures (to -13.2 degrees C) encountered by Nebraska turtles. In Nebraska, winter mortality occurred within 12.5% (1999-2000) and 42.3% (2000-2001) of the sampled nests; no turtles died in the Indiana nests. Laboratory studies of the mechanisms of cold-hardiness used by hatchling C. picta showed that resistance to inoculative freezing and capacity for freeze tolerance increased as winter approached. However, the level of inoculation resistance strongly depended on the physical characteristics of nest soil, as well as its moisture content, which varied seasonally. Risk of inoculative freezing (and mortality) was greatest in midwinter when nest temperatures were lowest and soil moisture and activity of constituent organic ice nuclei were highest. Water balance in overwintering hatchlings was closely linked to dynamics of precipitation and soil moisture, whereas energy use and the size of the energy reserve available to hatchlings in spring depended on the winter thermal regime. Acute chilling resulted in hyperglycemia and hyperlactemia, which persisted throughout winter; this response may be cryoprotective. Some physiological characteristics and cold-hardiness attributes varied between years, between study sites, among nests at the same site, and among siblings sharing nests. Such variation may reflect adaptive phenotypic plasticity, maternal or paternal influence on an individual's response to environmental challenge, or a combination of these factors. Some evidence suggests that life-history traits, such as clutch size and body size, have been shaped by constraints imposed by the harsh winter environment.

Adaptation, Physiological↗
PubMed1987

Learning processes in the persistence behavior of chronic low back pain patients with repeated acute pain stimulation.

Twenty-one chronic low back pain (CLBP) patients and 20 control subjects participated in 8 successive cold pressor tests (CPT). The hypotheses were that: (1) CLBP patients would demonstrate poorer acute pain tolerance and report higher acute pain, and (2) CLBP patients would become sensitized during 8 successive CPT trials, while control subjects would habituate, resulting in increasing differences in test behavior between both groups. The results show that the first hypothesis was confirmed. The second hypothesis requires modification, as the control group both habituated and became sensitized, while within the CLBP group no learning or training effect was found. These findings lead one to conclude that the deviant acute pain behavior of CLBP patient may be regarded either as a consequence of CLBP or as an important risk factor in the development of CLBP. Patients with relatively high CLBP levels performed poorly on the CPT as compared with patients with relatively low CLBP levels.

Acute Disease↗
PubMed1997

Using asymmetric jaws to junction with previously treated areas.

The feasibility of employing asymmetric jaws to match previously irradiated portals has been investigated. According to the isodose plot of one treatment planning system a near perfect match can be obtained by exactly matching the beam divergence of the initial port. However, another treatment planning system shows a cold junction. Films taken at 6 cm depth show a 6% cold spot when matching at the inferior border of the previously irradiated port and a 7% hot spot when matching at the superior border. As long as one is aware of the limitations of computer planning and collimator setting tolerance, junctioning with asymmetric jaws may still be preferred over the conventional method of gapping on the skin, because it avoids larger hot and cold spots below and above the matchpoint.

Computer Simulation↗
PubMed1984

Acute hemodynamic and humoral effects of metoclopramide on blood pressure control improvement in subjects with diabetic orthostatic hypotension.

Metoclopramide (MCP), a dopaminergic antagonist, is effective in postural hypotension, but the mechanisms of action have not been well defined. We studied responses of mean arterial pressure (MAP), heart rate, cardiac output (CO), and total peripheral resistance (TPR) after 5 min of increasing degrees of head tilt (15 degrees to 90 degrees) before and after MCP (20 mg IV) in seven subjects with diabetic postural hypotension. Plasma renin activity (PRA) and plasma aldosterone levels (PA) were determined at each degree of tilt; responses to the cold pressor test were also assessed before and after MCP. Before MCP, the maximal degree of tilt tolerated was 75 degrees, while after MCP four subjects were able to support 90 degrees tilt. At 45 degrees tilt, the decreases in MAP were smaller after than before MCP (-7.6 +/- 3.3 and -28.1 +/- 8.5 mm Hg; means +/- SE). This was associated with responses of TPR to tilt after (from 18.6 +/- 2.6 to 24.0 +/- 3.9 arbitrary units [AU]) but not before (from 22.9 +/- 4.0 to 25.6 +/- 4.5 AU) MCP. Reductions in CO were of the same order before and after MCP. PRA responded to tilt better after than before MCP. Supine PA levels increased with MCP (delta PA = 5.4 +/- 0.7 ng/dl), but its response to tilt was unaltered. There were significant rises in MAP and HR during the cold pressor test after but not before MCP. Our data suggest that vasoconstriction is the main mechanism of MCP improvement in blood pressure response to an orthostatic stimulus in diabetic postural hypotension, possibly because of its antidopaminergic property.

Adult↗
PubMed1968

Resistance of organisms to extreme influences in relation to some exobiological problems.

The conditions to which organisms have not been able to adapt in the process of evolution are called extreme influences or extreme conditions. The experiments show that organisms and cells have a potential for resistance; among animals, there are forms that are able to stand extremely low temperatures (from -80 to -269 degrees) when the water content of their tissues is large enough. Some species of protozoa can tolerate ionizing radiation in doses (500-1800 kr) of many orders exceeding those existing on the Earth and out in space. There are different ways of obtaining "protection" against ultraviolet (UV) shortwave sun radiation detained by the ozone layers of the Earth's atmosphere (photoreactivation, biological screens non-permeable for UV light, etc.). Many insects, especially alpine species, do not require as much oxygen as is contained in lower layers of the Earth's atmosphere. Hence, earth organisms possess some "margins of safety", enabling us to suggest the existence of similar biological systems in conditions different from the Earth's. The resistance to the action of extreme factors is probably connected with the resistance of biopolymers, protein complexes of cells and also with the capability of the organism to recover from damage.

Animals↗
PubMed1990

Clinical and histologic effects of extreme intraocular hypothermia.

Rabbit eyes in which vitrectomy was performed underwent three hours of hypothermic perfusion with either 22 C or 2 C lactated Ringer's solution. Clinical, electroretinographic, fluorescein angiographic, histologic, and ultrastructural examinations were performed. No changes were noted in eyes cooled with 22 C fluid. Reversible lens opacities, equivocal electroretinographic changes, and subclinical retinal detachments were found in the eyes cooled with 2 C fluid. Extreme cooling of eyes is not advisable, although temperatures of 22 C are well tolerated.

Animals↗
PubMed2000

Dehydration in dormant insects.

Many of the mechanisms used by active insects to maintain water balance are not available to dormant individuals. Physiological and biochemical mechanisms of dehydration tolerance and resistance in dormant insects and some other invertebrates are reviewed, as well as linkages of dehydration with energy use and metabolism, with cold hardiness, and with diapause. Many dormant insects combine several striking adaptations to maintain water balance that-in addition to habitat choice-may include especially reduction of body water content, decreased cuticular permeability, absorption of water vapour, and tolerance of low body water levels. Many such features require energy and hence that metabolism, albeit much reduced, continues during dormancy. Four types of progressively dehydrated states are recognized: water is managed internally by solute or ion transport; relatively high concentrations of solutes modify the behaviour of water in solutions; still higher concentrations of certain carbohydrates lead to plasticized rubbers or glasses with very slow molecular kinetics; and anhydrobiosis eliminates metabolism.

Journal Article↗
PubMed1992

Intravesical lidocaine: topical anesthesia for bladder mucosal biopsies.

The intravesical instillation of lidocaine solution has been used as a topical form of anesthesia for bladder biopsies. We performed 63 ambulatory procedures in which multiple cold-cup biopsies were obtained during cystoscopy. There was no need for electrocautery. All patients tolerated the procedure well and were discharged from the office immediately thereafter. There were no changes in heart rate or blood pressure during the procedures. Serum concentrations of lidocaine were measured in 10 patients at 5, 10 and 30 minutes, and they were clinically insignificant. This simple office procedure can be used for the diagnosis and followup of patients with carcinoma in situ of the bladder.

Administration, Intravesical↗
PubMed2002

Brain antioxidant regulation in mammals and anoxia-tolerant reptiles: balanced for neuroprotection and neuromodulation.

Reactive oxygen species (ROS) generated by mitochondrial respiration and other processes are often viewed as hazardous substances. Indeed, oxidative stress, defined as an imbalance between oxidant production and antioxidant protection, has been linked to several neurological disorders, including cerebral ischemia-reperfusion and Parkinson's disease. Consequently, cells and organisms have evolved specialized antioxidant defenses to balance ROS production and prevent oxidative damage. Research in our laboratory has shown that neuronal levels of ascorbate, a low molecular weight antioxidant, are ten-fold higher than those in much less metabolically active glial cells. Ascorbate levels are also selectively elevated in the CNS of anoxia-tolerant reptiles compared to mammals; moreover, plasma and CSF ascorbate concentrations increase markedly in cold-adapted turtles and in hibernating squirrels. Levels of the related antioxidant, glutathione, vary much less between neurons and glia or among species. An added dimension to the role of the antioxidant network comes from recent evidence that ROS can act as neuromodulators. One example is modulation of dopamine release by endogenous hydrogen peroxide, which we describe here for several mammalian species. Together, these data indicate adaptations that prevent oxidative stress and suggest a particularly important role for ascorbate. Moreover, they show that the antioxidant network must be balanced precisely to provide functional levels of ROS, as well as neuroprotection.

Animals↗
PubMed1997

The unique hetero-oligomeric nature of the subunits in the catalytic cooperativity of the yeast Cct chaperonin complex.

The structural and functional organization of the Cct complex was addressed by genetic analyses of subunit interactions and catalytic cooperativity among five of the eight different essential subunits, Cct1p-Cct8p, in the yeast Saccharomyces cerevisiae. The cct1-1, cct2-3, and cct3-1 alleles, containing mutations at the conserved putative ATP-binding motif, GDGTT, are cold-sensitive, whereas single and multiple replacements of the corresponding motif in Cct6p are well tolerated by the cell. We demonstrated herein that cct6-3 (L19S), but not the parolog cct1-5 (R26I), specifically suppresses the cct1-1, cct2-3, and cct3-1 alleles, and that this suppression can be modulated by mutations in a putative phosphorylation motif, RXS, and the putative ATP-binding pocket of Cct6p. Our results suggest that the Cct ring is comprised of a single hetero-oligomer containing eight subunits of differential functional hierarchy, in which catalytic cooperativity of ATP-binding/hydrolysis takes place in a sequential manner different from the concerted cooperativity proposed for GroEL.

Amino Acid Sequence↗