ThermoSpots to Detect Hypothermia in Children with Severe Acute Malnutrition

Introduction

Hypothermia is a risk factor for increased mortality in children with severe acute malnutrition (SAM). Yet frequent temperature measurement remains unfeasible in under-resourced units in developing countries. ThermoSpot is a continuous temperature monitoring sticker designed originally for neonates. When applied to skin, its liquid crystals are designed to turn black with hypothermia and remain green with normothermia.

Aims

To (i) estimate the diagnostic accuracy of ThermoSpots for detecting WHO-defined hypothermia (core temperature <35.5°C or peripheral temperature <35.0°C) in children with SAM and (ii) determine their acceptability amongst mothers.

Methods

Children with SAM in a malnutrition unit in Malawi were enrolled during March-July 2010. The sensitivity and specificity of ThermoSpots were calculated by comparing the device colour against ‘gold standard’ rectal temperatures taken on admission and follow up peripheral temperatures taken until discharge. Guardians completed a questionnaire to assess acceptability.

Results

Hypothermia was uncommon amongst the 162 children enrolled. ThermoSpot successfully detected the one rectal temperature and two peripheral temperatures recorded that met the WHO definition of hypothermia. Overall, 3/846 (0.35%) temperature measurements were in the WHO-defined hypothermia range. Interpreting the brown transition colour (between black and green) as hypothermia improved sensitivities. For milder hypothermia definitions, sensitivities declined (<35.4°C, 50.0%; <35.9°C, 39.2%). Specificity was consistently above 94%. From questionnaires, 40/43 (93%) mothers reported they were 90–100% happy with the device overall. Free-text answers revealed themes of “Skin Rashes”, “User-satisfaction” and “Empowerment".

Conclusion

Although hypothermia was uncommon in this study, ThermoSpots successfully detected these episodes in malnourished children and were acceptable to mothers. Research in settings where hypothermia is common is needed to determine performance with certainty. Instructing users to act when the device’s transition colour appears could improve accuracy. If reliable, ThermoSpots may offer simple, acceptable and continuous temperature measurement for high-burden areas and reduce the workload of over-stretched staff.     

Thermal,Metabolic, Blood,and Circulatory Adjustments in Prolonged Outdoor Exercise

Thermal, metabolic, and circulatory responses were studied in six hill-walkers taking part in a 28-mile (45-km.) walk in rough country in autumn and winter, air temperatures being 6 to 12° C. and –2 to 2° C., respectively.Though they were an apparently well-matched party, the walkers had to split into three pairs to avoid exhaustion. They adjusted their clothing so that mean skin temperatures were similar in both warm and cold conditions, the average value being 30·5° C. compared with the resting comfort range of 33 to 34·5° C. When, on the winter trial, skin temperatures were lowered by reduction of clothing, mean skin temperatures fell to 26·5 to 27·8° C., one subject showing a value of 21·3° C. These temperatures were associated with moderate discomfort from cold.Gut temperatures during exercise, measured with a radio pill, averaged 38·7 to 37·9° C. on the autumn exercise. Slightly lower values were observed in winter, but this was associated with slower walking rather than cold stress. A fat and a thin subject walking together with minimal clothing showed widely different temperature responses, the fatter subject having a lower skin temperature and higher gut temperature than his companion. These results were compared with other results on extreme cold stress and discussed in relation to hypothermia. Heart rate and blood pressure findings were unremarkable, except for increased post-exercise heart rates and standing/lying heart rate differences, and a tendency to postural hypotension associated with exhaustion. Blood volume was not reduced in exhaustion and there were no significant changes in blood electrolytes or other constituents apart from a small rise in potassium. Ketonuria developed in all subjects.     

Modeling the Recovery of Heat-Treated Bacillus licheniformis Ad978 and Bacillus weihenstephanensis KBAB4 Spores at Suboptimal Temperature and pH Using Growth Limits

The apparent heat resistance of spores of Bacillus weihenstephanensis and Bacillus licheniformis was measured and expressed as the time to first decimal reduction (δ value) at a given recovery temperature and pH. Spores of B. weihenstephanensis were produced at 30°C and 12°C, and spores of B. licheniformis were produced at 45°C and 20°C. B. weihenstephanensis spores were then heat treated at 85°C, 90°C, and 95°C, and B. licheniformis spores were heat treated at 95°C, 100°C, and 105°C. Heat-treated spores were grown on nutrient agar at a range of temperatures (4°C to 40°C for B. weihenstephanensis and 15°C to 60°C for B. licheniformis) or a range of pHs (between pH 4.5 and pH 9.5 for both strains). The recovery temperature had a slight effect on the apparent heat resistance, except very near recovery boundaries. In contrast, a decrease in the recovery pH had a progressive impact on apparent heat resistance. A model describing the heat resistance and the ability to recover according to the sporulation temperature, temperature of treatment, and recovery temperature and pH was proposed. This model derived from secondary mathematical models for growth prediction. Previously published cardinal temperature and pH values were used as input parameters. The fitting of the model with apparent heat resistance data obtained for a wide range of spore treatment and recovery conditions was highly satisfactory.     

The efficacy of pre-warming on reducing intraprocedural hypothermia in endovascular coiling of cerebral aneurysms

Background

The anesthetic management of patients undergoing endovascular treatment of cerebral aneurysms in the interventional neuroradiology suite can be challenged by hypothermia because of low ambient temperature for operating and maintaining its equipments. We evaluated the efficacy of skin surface warming prior to induction of anesthesia to prevent the decrease in core temperature and reduce the incidence of hypothermia.

Methods

Seventy-two patients were randomized to pre-warmed and control group. The patients in pre-warmed group were warmed 30 minutes before induction with a forced-air warming blanket set at 38°C. Pre-induction tympanic temperature (Tpre) was measured using an infrared tympanic thermometer and core temperature was measured at the esophagus immediately after intubation (T0) and recorded at 20 minutes intervals (T20, T40, T60, T80, T100, and T120). The number of patients who became hypothermic at each time was recorded.

Results

Tpre in the control and pre-warmed group were 36.4 ± 0.4°C and 36.6 ± 0.3°C, whereas T0 were 36.5 ± 0.4°C and 36.6 ± 0.2°C. Core temperatures in the pre-warmed group were significantly higher than the control group at T20, T40, T60, T80, T100, and T120 (P < 0.001). Compared to T0, core temperatures at each time were significantly lower in both two groups (P = 0.007 at T20 in pre-warmed group, P < 0.001 at the other times in both groups). The incidence of hypothermia was significantly lower in the pre-warmed group than the control group from T20 to T120 (P = 0.002 at T20, P < 0.001 at the other times).

Conclusion

Pre-warming for 30 minutes at 38°C did not modify the trends of the temperature decrease seen in the INR suite. It just slightly elevated the beginning post intubation base temperature. The rate of decrease was similar from T20 to T120. However, pre-warming considerably reduced the risk of intraprocedural hypothermia.

Trial registration

Clinical Research Information Service (CRiS) Identifier: KCT0001320. Registered December 19th, 2014.     

Factors influencing seed germination of medicinal plant Salvia aegyptiaca L. (Lamiaceae)

Salvia aegyptiaca is a xerophytic perennial herb belongs to the Lamiaceae family commonly used for medicinal purposes. Laboratory experiments were carried out to assess the effects of temperature and salinity on seed germination and recovery responses after transferring to distilled water. Temperatures between 10 and 40 °C seem to be favourable for the germination of this species. Germination was inhibited by either an increase or decrease in temperature from the optimum (30 °C). The highest germination percentages were obtained at 0 mM NaCl; however, the increase of solution osmolalities progressively inhibited seed germination. The germination rate decreased with an increase in salinity for most of tested temperatures, but comparatively higher rates were obtained at 30 °C. Salt stress decreased both the percentage and the rate of germination. An interaction between salinity and temperature yielded no germination at 300 mM NaCl. By experimental transfer to distilled water, S. aegyptiaca seeds that were exposed to moderately saline conditions recovered and keep their ability to germinate mostly at low temperatures. At 300 mM NaCl, germination recovery decreased with increasing temperature and it was completely inhibited at 40 °C.     

Hypothermia Activates Adipose Tissue to Promote Malignant Lung Cancer Progression

Microenvironment has been increasingly recognized as a critical regulator of cancer progression. In this study, we identified early changes in the microenvironment that contribute to malignant progression. Exposure of human bronchial epithelial cells (BEAS-2B) to methylnitrosourea (MNU) caused a reduction in cell toxicity and an increase in clonogenic capacity when the temperature was lowered from 37°C to 28°C. Hypothermia-incubated adipocyte media promoted proliferation in A549 cells. Although a hypothermic environment could increase urethane-induced tumor counts and Lewis lung cancer (LLC) metastasis in lungs of three breeds of mice, an increase in tumor size could be discerned only in obese mice housed in hypothermia. Similarly, coinjections using differentiated adipocytes and A549 cells promoted tumor development in athymic nude mice when adipocytes were cultured at 28°C. Conversely, fat removal suppressed tumor growth in obese C57BL/6 mice inoculated with LLC cells. Further studies show hypothermia promotes a MNU-induced epithelial-mesenchymal transition (EMT) and protects the tumor cell against immune control by TGF-β1 upregulation. We also found that activated adipocytes trigger tumor cell proliferation by increasing either TNF-α or VEGF levels. These results suggest that hypothermia activates adipocytes to stimulate tumor boost and play critical determinant roles in malignant progression.     

Promotion of Viral IRES-Mediated Translation Initiation under Mild Hypothermia

Internal ribosome entry site (IRES)-mediated translation is an essential replication step for certain viruses. As IRES-mediated translation is regulated differently from cap-dependent translation under various cellular conditions, we sought to investigate whether temperature influences efficiency of viral IRES-mediated translation initiation by using bicistronic reporter constructs containing an IRES element of encephalomyocarditis virus (EMCV), foot-and-mouth disease virus (FMDV), hepatitis C virus (HCV), human rhinovirus (HRV) or poliovirus (PV). Under mild hypothermic conditions (30 and 35°C), we observed increases in the efficiency of translation initiation by HCV and HRV IRES elements compared to translation initiation at 37°C. The promotion of HRV IRES activity was observed as early as 2 hours after exposure to mild hypothermia. We also confirmed the promotion of translation initiation by HRV IRES under mild hypothermia in multiple cell lines. The expression levels and locations of polypyrimidine tract-binding protein (PTB) and upstream of N-Ras (unr), the IRES trans-acting factors (ITAFs) of HCV and HRV IRES elements, were not modulated by the temperature shift from 37°C to 30°C. Taken together, this study demonstrates that efficiency of translation initiation by some viral IRES elements is temperature dependent.     

Physiology and Pharmacology of Hypothermia

Homoiothermic organisms react to hypothermia by shivering and thermogenesis to retain their euthermic state. This reactive homeostatic mechanism recruits a strong sympathetic response, which must be suppressed by anesthesia and adjuvants during induced hypothermia. Below 30° C there is significant neural and organ depression associated with cold narcosis. Cardiac arrhythmias and ventricular fibrillation are grave developments when the core temperature is below 28° C. Proper cardiopulmonary support must be instituted in a patient who has induced or accidental hypothermia at these severely hypothermic levels.Although clinical hypothermia is used to protect the brain and the heart from ischemic insults during an operation, it induces a complex array of physiologic changes in the body that must be appreciated so that optimal care may be provided to a patient.     

Enhancing Protein Expression in HEK-293 Cells by Lowering Culture Temperature

Animal cells and cell lines, such as HEK-293 cells, are commonly cultured at 37°C. These cells are often used to express recombinant proteins. Having a higher expression level or a higher protein yield is generally desirable. As we demonstrate in this study, dropping culture temperature to 33°C, but not lower, 24 hours after transient transfection in HEK-293S cells will give rise to ~1.5-fold higher expression of green fluorescent protein (GFP) and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors. By following the time course of the GFP-expressing cells growing at 37°C and 33°C from 24 hours after transfection (including 19 hours recovery at 37°C in the normal growth medium), we found that a mild hypothermia (i.e., 33°C) reduces the growth rate of HEK-293S cells, while increasing cellular productivity of recombinant proteins. As a result, green cells remain undivided in a longer period of time. Not surprisingly, the property of a recombinant protein expressed in the cells grown at 33°C is unaffected, as shown by the use of AMPA receptors. We further demonstrate with the use of PC12 cells that this method may be especially useful when a recombinant protein is difficult to express using a chemical-based, transient transfection method.     

Combination Treatment of Hypothermia and Mesenchymal Stromal Cells Amplifies Neuroprotection in Primary Rat Neurons Exposed to Hypoxic-Ischemic-Like Injury In Vitro: Role of the Opioid System

This study was designed to reveal the therapeutic regimen and mechanism of action underlying hypothermia treatment in combination with stem cell transplantation for ameliorating neonatal hypoxic-ischemic-like injury. Primary rat neurons were exposed to oxygen-glucose deprivation (OGD), which produced hypoxic-ischemic-like injury in vitro, then incubated at 25°C (severe hypothermia), 34°C (moderate hypothermia), and 37°C (normothermia) with or without subsequent co-culture with mesenchymal stromal cells (MSCs). Combination treatment of moderate hypothermia and MSCs significantly improved cell survival and mitochondrial activity after OGD exposure. The exposure of delta opioid human embryonic kidney cells (HEK293) to moderate hypothermia attenuated OGD-mediated cell alterations, which were much more pronounced in HEK293 cells overexpressing the delta opioid receptor. Further, the addition of delta opioid peptide to 34°C hypothermia and stem cell treatment in primary rat neurons showed synergistic neuroprotective effects against OGD which were significantly more robust than the dual combination of moderate hypothermia and MSCs, and were significantly reduced, but not completely abolished, by the opioid receptor antagonist naltrexone altogether implicating a ligand-receptor mechanism of neuroprotection. Further investigations into non-opioid therapeutic signaling pathways revealed growth factor mediation and anti-apoptotic function accompanying the observed therapeutic benefits. These results support combination therapy of hypothermia and stem cells for hypoxic-ischemic-like injury in vitro, which may have a direct impact on current clinical trials using stand-alone hypothermia or stem cells for treating neonatal encephalopathy.     

Differential Effect of Culture Temperature and Specific Growth Rate on CHO Cell Behavior in Chemostat Culture

Mild hypothermia condition in mammalian cell culture technology has been one of the main focuses of research for the development of breeding strategies to maximize productivity of these production systems. Despite the large number of studies that show positive effects of mild hypothermia on specific productivity of r-proteins, no experimental approach has addressed the indirect effect of lower temperatures on specific cell growth rate, nor how this condition possibly affects less specific productivity of r-proteins. To separately analyze the effects of mild hypothermia and specific growth rate on CHO cell metabolism and recombinant human tissue plasminogen activator productivity as a model system, high dilution rate (0.017 h⁻¹) and low dilution rate (0.012 h⁻¹) at two cultivation temperatures (37 and 33°C) were evaluated using chemostat culture. The results showed a positive effect on the specific productivity of r-protein with decreasing specific growth rate at 33°C. Differential effect was achieved by mild hypothermia on the specific productivity of r-protein, contrary to the evidence reported in batch culture. Interestingly, reduction of metabolism could not be associated with a decrease in culture temperature, but rather with a decrease in specific growth rate.     

Variation among Species in the Temperature Dependence of the Reappearance of Variable Fluorescence following Illumination

The relationship between the thermal dependence of the reappearance of chlorophyll variable fluorescence following illumination and temperature dependence of the apparent Michaelis constant (K_m) of NADH hydroxypyruvate reductase for NADH was investigated in cool and warm season plant species. Brancker SF-20 and SF-30 fluorometers were used to evaluate induced fluorescence transients from detached leaves of wheat (Triticum aestivum L. cv TAM-101), cotton (Gossypium hirsutum L. cv Paymaster 145), tomato (Lycopersicon esculentum cv Del Oro), bell pepper (Capsicum annuum L. cv California Wonder), and petunia (Petunia hybrida cv. Red Sail). Following an illumination period at 25°C, the reappearance of variable fluorescence during a dark incubation was determined at 5°C intervals from 15°C to 45°C. Variable fluorescence recovery was normally distributed with the maximum recovery observed at 20°C in wheat, 30°C in cotton, 20°C to 25°C in tomato, 30 to 35°C in bell pepper and 25°C in petunia. Comparison of the thermal response of fluorescence recovery with the temperature sensitivity of the apparent K_m of hydroxypyruvate reductase for NADH showed that the range of temperatures providing fluorescence recovery corresponded with those temperatures providing the minimum apparent K_m values (viz. the thermal kinetic window).     

THE EFFECT OF TEMPERATURE UPON FACET NUMBER IN THE BAR-EYED MUTANT OF DROSOPHILA : PART III.

Three strains of the bar-eyed mutant of Drosophila melanogaster Meig have been reared at constant temperatures over a range of 15–31°C. The mean facet number in the bar-eyed mutant varies inversely with the temperature at which the larvæ develop. The temperature coefficient (Q₁₀) is of the same order as that for chemical reactions. The facet-temperature relations may be plotted as an exponential curve for temperatures from 15–31°. The rate of development of the immature stages gives a straight line temperature curve between 15 and 29°. Beyond 29° the rate decreases again with a further rise in temperature. The facet curve may be readily superimposed on the development curve between 15 and 27°. The straight line feature of the development curve is probably due to the flattening out of an exponential curve by secondary factors. Since both the straight line and the exponential curve appear simultaneously in the same living material, it is impractical to locate the secondary factors in enzyme destruction, differences in viscosity, or in the physical state of colloids. Differential temperature coefficients for the various separate processes involved in development furnish the best basis for an explanation of the straight line feature of the curve representing the effect of temperature on the rate of physiological processes. Facet number in the full-eyed wild stock is not affected by temperature to a marked degree. The mean facet number for fifteen full-eyed females raised at 27° is 859.06. The mean facet number for the Low Selected Bar females at 27° is 55.13; for the Ultra-bar females at 27° it is 21.27. A consistent sexual difference appears in all the bar stocks, the females having fewer facets. This relation may be expressed by the sex coefficient, the average value of which is 0.791. The average observed difference in mean facet number for a difference of 1°C. in the environment in which the flies developed is 3.09 for the Ultra-bar stock and 14.01 for the Low Selected stock. The average proportional differences in the mean for a difference of 1°C. are 9.22 per cent for Ultra-bar, and 14.51 for Low Selected. The differences in the number of facets per °C. are greatest at the low and least at the high temperatures. The difference in the number of facets per °C. varies with the mean. The proportional differences in the mean per °C. are greatest at the lower (15–17.5°) and higher (29–31°) temperatures and least at the intermediate temperatures. Temperature is a factor in determining facet number only during a relatively short period in larval development. This effective period, at 27°, comes between the end of the 3rd and the end of the 4th day. At 15°, this period is initiated at the end of 8 days following a 1st day at 27°. At 27° this period is approximately 18 hours long. At 15° it is approximately 72 hours long. The number of facets and the length of the immature stage (egg-larval-pupal) appear related when the whole of development is passed at one temperature. That the number of facets is not dependent upon the length of the immature stage is shown by experiments in which only a part of development was passed at one temperature and the remainder at another. Temperature affects the reaction determining the number of facets in approximately the same way that it affects the other developmental reactions, hence the apparent correlation between facet number and the length of the immature stage. Variability as expressed by the coefficient of variability has a tendency to increase with temperature. Standard deviation, on the other hand, appears to decrease with rise in temperature. Neither inheritance nor induction effects are exhibited by this material. This study shows that environment may markedly affect the somatic expression of one Mendelian factor (bar eye), while it has no visible influence on another (white eye).     

Effects of Visible Light and UV Radiation on Photosynthesis in a Population of a Hot Spring Cyanobacterium, a Synechococcus sp., Subjected to High-Temperature Stress

Assays of photosynthesis were conducted with a biofilm population of a cyanobacterium, a Synechococcus sp., growing at ~70°C in a Yellowstone National Park hot spring to test whether cells growing near the upper temperature limit of photosynthetic life are optimally adapted to their mean environmental temperature. Cell suspensions were assayed at 70, 65, and 55°C while being simultaneously exposed to modified solar environments, including reduction of total irradiance and exclusion of UV radiation. Carbon fixation was greatest at 65°C, while 70 and 55°C were always supraoptimal and suboptimal for photosynthesis, respectively. The degree of temperature stress was dependent upon light intensity, and this light-dependent temperature effect may involve both reduced quantum efficiency at subsaturating irradiances and a lower saturating irradiance at both supraoptimal and suboptimal temperatures. The Synechococcus sp. was also more susceptible to UV inhibition of photosynthesis at nonoptimal temperatures. These results suggest that this population is persisting at a nearly lethal temperature and is consequently subject to greater damage by both visible and UV radiation, but it is speculated that these cells may be avoiding competition with other photoautotrophs under these nonoptimal conditions. In separate experiments monitoring diurnal patterns of photosynthesis, cells exhibited peak productivity during the morning, followed by an afternoon decline. No recovery of photosynthesis was observed during the remaining daytime, and carbon fixation was always UV inhibited under conditions of photosynthetically saturating light.     

Out of the frying pan into the air—emersion behaviour and evaporative heat loss in an amphibious mangrove fish (Kryptolebias marmoratus)

Amphibious fishes often emerse (leave water) when faced with unfavourable water conditions. How amphibious fishes cope with the risks of rising water temperatures may depend, in part, on the plasticity of behavioural mechanisms such as emersion thresholds. We hypothesized that the emersion threshold is reversibly plastic and thus dependent on recent acclimation history rather than on conditions during early development. Kryptolebias marmoratus were reared for 1 year at 25 or 30°C and acclimated as adults (one week) to either 25 or 30°C before exposure to an acute increase in water temperature. The emersion threshold temperature and acute thermal tolerance were significantly increased in adult fish acclimated to 30°C, but rearing temperature had no significant effect. Using a thermal imaging camera, we also showed that emersed fish in a low humidity aerial environment (30°C) lost significantly more heat (3.3°C min⁻¹) than those in a high humidity environment (1.6°C min⁻¹). In the field, mean relative humidity was 84%. These results provide evidence of behavioural avoidance of high temperatures and the first quantification of evaporative cooling in an amphibious fish. Furthermore, the avoidance response was reversibly plastic, flexibility that may be important for tropical amphibious fishes under increasing pressures from climatic change.     

Body Temperatures in the Elderly: A National Study of Physiological,Social, and Environmental Conditions

Two large-scale surveys of body temperatures in elderly people living at home were carried out in the winter of 1972. Most of the homes visited were cold with room temperatures below the minimum recommended by the Department of Health. Deep body temperatures below 35·5°C were found in 10% of those studied, and the difference between the skin temperature and the core temperature was also reduced in this group. Such individuals are at risk of developing hypothermia since they show evidence of some degree of thermoregulatory failure. Further research is needed, but meanwhile there are practical measures that could be taken to reduce the risk of hypothermia in the elderly.     

Operative Treatment of Terrible Triad of the Elbow via Posterolateral and Anteromedial Approaches

The aim of the study was to explore the clinical outcome of posterolateral and anteromedial approaches in treatment of terrible triad of the elbow. The study involved 12 patients with closed terrible triad of the elbow treated by posterolateral and anteromedial approaches between January 2010 and June 2012. The mechanism of injury included fall from height in 9 patients and traffic accident in 3. According to O’Driscoll classification for fractures of the ulnar coronoid, there were 11 patients with type Ⅰ and 1 with type Ⅱ fractures. According to Mason classification for fractures of the radial head, there were 3 patients with type Ⅰ, 7 with type Ⅱ and 2 with type Ⅲ fractures. All patients were followed up for 12-27 months (average 15.5 months), which showed no pain or severe pain in all patients except for 2 patients with mild pain. At the last follow-up, the mean flexion was for 125°(range, 90°-140°), the mean extension loss for 20°(range, 0°-70°), the mean pronation for 66°(range, 20°-85°) and the mean supination for 60°(range, 30°-85°). The bony union time was 8-14 weeks (average 11 weeks) and the elbows were stable in flexion-extension and varus-valgus in all patients. The elbows maintained a concentric reduction of both the ulnotrochlear and the radiocapitellar articulation. Mild heterotopic ossification of the elbow occurred in 3 patients at 6 months after operation and mild degenerative change in 1 patient at 18 months after operation. The Broberg and Morrey elbow performance score was 82 points (range, 58-98 points). The results were excellent in 6 patients, good in 4, fair in 1 and poor in 1, with excellence rate of 83.3%. The results showed that the combined posterolateral and anteromedial approaches can facilitate the reduction and fixation of terrible triad of the elbow. Repair of radial head, coronoid, medial and lateral collateral ligaments can sufficiently restore the elbow stability, allow early postoperative motion and enhance the functional recovery.     

Temperature Dependence of Vasopressin Action on the Toad Bladder

Toad bladders were challenged with vasopressin at one temperature, fixed on the mucosa with 1% glutaraldehyde, and then subjected to an osmotic gradient at another temperature. Thus, the temperature dependence of vasopressin action on membrane permeability was distinguished from the temperature dependence of osmotic water flux. As the temperature was raised from 20° to 38°C, there was a substantial increase in the velocity of vasopressin action, but osmotic flux was hardly affected. In this range of temperature the apparent energy of activation for net water movement across the bladder amounted to only 1.2 kcal/mole, a value well below the activation energy for bulk water viscosity. It is suggested that osmotic water flux takes place through narrow, nonpolar channels in the membrane. When the temperature was raised from 4° to 20°C, both vasopressin action as well as osmotic water flux were markedly enhanced. Activation energies for net water movement were now 8.5 kcal/mole (4°–9°C) and 4.1 kcal/mole (9°–20°C), indicating that the components of the aqueous channel undergo conformational changes as the temperature is lowered from 20°C. At 43°C bladder reactivity to vasopressin was lost, and irreversible changes in selective permeability were observed. The apparent energy of activation for net water movement across the denatured membrane was 6.6 kcal/mole. Approximately 1 µosmol of NaCl was exchanged for 1 µl of H₂O across the denatured membrane.