Induction and Rejoining of DNA Single-Strand Breaks in Relation to Cellular Growth in Human Cells Exposed to Three Hydroperoxides at 0°C and 37°C

There was a 5-fold increase in cytotoxicity for cumene hydroperoxide, 10-fold for tert-butyl hydroperoxide and 25-fold for hydrogen peroxide, under metabolizing conditions (37°C) in comparison to nonmetabolizing conditions (0°C), when human P31 cells were exposed for 60 min. The induction of DNA single-strand breaks correlated poorly with cytotoxicity. Hydrogen peroxide was by far the most effective agent inducing single-strand breaks irrespective of temperature. Cumene hydroperoxide produced fewer strand breaks than tert-butyl hydroperoxide despite its greater cytotoxicity at either 37°C or at 0°C. The pattern of single-strand break induction did not change with temperature. The number of breaks, however, increased when the cells were exposed at 37°C. The pattern of rejoining was similar for hydrogen peroxide- and tert-butyl hydroperoxide-induced breaks at both temperatures whereas the rejoining of cumene hydroperoxide-induced breaks deviated somewhat from this pattern. The results indicate that there is no clear-cut relationship between induction of DNA single-strand breaks and cytotoxicity after hydroperoxide exposure.     

Finger temperatures during military field training at 0 to −29 °C

1. Skin and rectal temperatures were recorded continuously in 70 measurements during typical tasks of infantry and artillery training at 0 to −29 °C. The duration of the measurements varied from 55 min to 9.5 h.

2. The distribution of finger skin temperatures was quite similar at ambient temperature ranges 0 to −10 °C and −10 to −20 °C, while at −20 to −30 °C the finger temperatures were clearly lower.

3. At different ambient temperature ranges, 20–69% of finger temperatures were low enough to cause cold thermal sensations.

4. Sensation of cold was experienced at a finger temperature of 11.6±3.7 °C (mean±SD).     

Improved Control of Otiorhynchus sulcatus at 9°C by Cold-stored Heterorhabditis megidis UK211

The effect of storage temperature (9 and 20°C) on North West European Heterorhabditis megidis isolate UK211 for control of Otiorhynchus sulcatus larvae at 9°C is assessed. O. sulcatus mortality increased from -5.3% (corrected mortality) using freshly produced nematodes, to 27.1% using nematodes that had been cold-stored for 12 weeks. The number of nematodes invading the insect larvae increased almost 27-fold. Nematode storage at 9°C for 11 to 12 weeks weeks resulted in significantly higher O. sulcatus mortality (41%) than storage at 20°C for 2 to 3 weeks (12%). Thus, cold storage does enhance nematode infectivity for O. sulcatus larvae.     

Thermal responses during and after whole-body cryotherapy (−110°C)

The effect of whole-body cryotherapy (WBC) on rectal and skin temperatures was measured in healthy subjects before, during and after WBC exposure. WBC did not cause any significant change in rectal temperature. The lowest local skin temperatures were recorded in the forearm, 5.2 (2.8)°C, and in the calf, 5.3 (3.0)°C. WBC involves no risk for frostbites. After WBC, all skin temperatures recovered rapidly, indicating that the analgetic effects of WBC only occur during a limited period after the exposure.     

Light-induced changes of fluorescence and absorbance in spinach chloroplasts at −40 °C

1. 1. Spinach chloroplasts were stored in the dark for at least 1 h, rapidly cooled to −40 °C, and illuminated with continuous light or short saturating flashes. In agreement with the measurements of Joliot and Joliot, chloroplasts that had been preilluminated with one or two flashes just before cooling showed a less efficient increase in the yield of chlorophyll a fluorescence upon illumination at −40 °C than dark-adapted chloroplasts. The effect disappeared below −150 °C, but reappeared again upon warming to −40 °C. Little effect was seen at room temperature in the presence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), added after the preillumination.

2. 2. Light-induced absorbance difference spectra at −40 °C in the region 500–560 nm indicated the participation of two components, the socalled 518-nm change (P518) and C-550. After preillumination with two flashes the absorbance change at 518 nm was smaller, and almost no C-550 was observed. After four flashes, the bands of C-550 were clearly visible again.

3. 3. The fluorescence increase and the absorbance change at 518 nm showed the same type of flash pattern with a minimum after the second and a maximum at the fourth flash. In the presence of 100 μM hydroxylamine, the fluorescence response was low after the fourth and high again after the sixth flash, which confirmed the hypothesis that the flash effect was related to the so-called S-state of the electron transport pathway from water to Photosystem 2.

4. 4. The kinetics of the light-induced absorbance changes were the same at each wavelength, and, apart from the size of the deflection, they were independent of preillumination. Flash experiments indicated that the absorbance changes were a one-quantum reaction. This was also true for the fluorescence increase in dark-adapted chloroplasts, but with preilluminated chloroplasts several flashes were needed to approximately saturate the fluorescence yield.

5. 5. The results are discussed in terms of a mechanism involving two electron donors and two electron acceptors for System 2 of photosynthesis.

Effect of low temperature (−30 to −60°C) on the reoxidation of the Photosystem II primary electron acceptor in the presence and absence of 3(3,4-dichlorophenyl)-1,1-dimethylurea

The fluorescence yield has been measured on spinach chloroplasts at low temperature (−30 to −60°C) for various dark times following a short saturating flash. A decrease in the fluorescence yield linked to the reoxidation of the Photosystem II electron acceptor Q is still observed at −60°C. Two reactions participate in this reoxidation: a back reaction or charge recombination and the transfer of an electron from Q⁻ to Pool A. The relative competition between these two reactions at low temperature depends upon the oxidation state of the donor side of the Photosystem II center:

1. (1) In dark-adapted chloroplasts (i.e. in States S₀+S₁ according to Kok, B., Forbush, B. and McGloin, M. (1970) Photochem. Photobiol. 11, 457–475), Q, reduced by a flash at low temperature, is reoxidized by a secondary acceptor and the positive charge is stabilized on the Photosystem II donor Z. Although this reaction is strongly temperature dependent, it still occurs very slowly at −60°C.

2. (2) When chloroplasts are placed in the S₂+S₃ states by a two-flash preillumination at room temperature, the reoxidation of Q⁻ after a flash at low temperature is mainly due to a temperature-independent back reaction which occurs with non-exponential kinetics.

3. (3) Long continuous illumination of a frozen sample at −30°C causes 6–7 reducing equivalents to be transferred to the pool. Thus, a sufficient number of oxidizing equivalents should have been generated to produce at least one O₂ molecule.

4. (4) A study of the back reaction in the presence of 3(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) shows the superposition of two distinct non-exponential reactions one temperature dependent, the other temperature independent.

Fluorescence spectra of chlorella in the 295–77°K range

A relation of fluorescence spectra of Chlorella (in the 295–77°K range) to the changes in the phase of the ice is suggested in this paper.

When Chlorella cells are first cooled to 77°K and then warmed slowly, the change of the fluorescence intensity as a function of temperature is different for different bands as earlier reported in spinach chloroplasts. In the 80–150°K range, the F698 decreases rapidly, F687 remains almost unchanged, and f680 increases; above 150°K (the temperature at which ice changes from vitreous to cubic phase), F687 decreases more rapidly than any other band. The F725, that decreases smoothly in the 77–295°K range, is composed of several bands (F717 and F725).

If Chlorella cells are first cooled to 77°K, and then warmed to 260°K, and recooled to 77°K before melting, f685, f698 and f730 — but not f717 — are lowered; this fluorescence decrease is not due to changes in the reabsorption of fluorescence or to major changes in the cellular structure due to freezing.

The F698 band is greatly influenced by the aqueous environment; the phase of the ice and the addition of polar solvents (10% dimethylsulfoxide) greatly influence it. These data are consistent with the hypothesis that F698 is from an energy trap (at low temperatures) of System II.     

Melting behaviour of schizophyllan extracellular polysaccharide gels in the temperature range between 5 and 20°C

Gels of the glucan schizophyllan, consisting of a 1,3-β- -linked backbone of glucose residues with 1,6-β- -glucosyl side groups, were found to show melting behaviour in the temperature range between 5 and 20°C, depending on the glucose concentration in the solvent (0–50 wt% glucose). While the qualitative features of the modulus-versus-concentration and modulus-versus-temperature rheological data for the gels can be modelled using modified cascade theory (which implicitly assumes that no sub-level of organisation exists in the gel structure), a consistent quantitative fit cannot be achieved. The inconsistencies found are consistent with the idea that the gel is composed of bundles (consisting of many triple helices of schizophyllan) with strong intra-bundle attraction and weak inter-bundle forces. Transmission Electron Microscopy (TEM) micrographs of diluted samples indicate that schizophyllan polymers engage in lateral aggregation of triple helical strands at temperatures below the melting temperature, suggesting that indeed bundles of polymers will be present in the gel state.     

Stereological analysis of mitochondria from brains of temperature acclimated goldfish, Carassius auratus L. (5 and 30°C)

1. 1.|The mitochondrial population in hypothalamic and hypophysial brain tissue from warm (30°C) and cold (5°C) acclimated goldfish (Carassius auralus L.) was analyzed using sterological techniques.

2. 2.|It was revealed that there is a significantly larger volume density (Vv) in the cold acclimated tissue, with no significant difference in either of the surface densities (Svext and Svint) from either of the brain areas.

3. 3.|The hypothalamic brain tissue has a significantly lower specific surface (S/V) in the cold acclimated tissue but there is not a significant difference in this parameter for the hypophysial brain tissue.

4. 4.|The values for these three parameters (Vv, Svext and SVint, and S/V) indicate that mitochondria from acclimated brain tissue undergo shape changes in response to thermal stress.

5. 5.|We suggest that the shape changes may be related to the change in the phospholipid composition of the inner mitochondrial membrane with acclimation temperature.

Isometric contractile properties and instantaneous stiffness of amphibian skeletal muscle in the temperature range from 0 to 20 degrees C

The isometric contractile properties of frog (Rana pipiens) and toad (Bufo bufo) sartorii have been studied over the temperature range from 0 to 20 degrees C. The isometric twitch tension was found to vary considerably between these two species and between muscles in the same species. Between 0 and 4 degrees C there was very little change in maximum isometric twitch tension. Between 4 and 12 degrees C several muscles from frog or toad showed a potentiation of twitch tension whereas others showed a decline. Over this temperature range the toad sartorii consistently demonstrated a greater potentiation. By 12 degrees C a steady decline in twitch tension in both muscles was seen as the temperature range the toad sartorii consistently demonstrated a greater potentiation. By 12 degrees C a steady decline in twitch tension in both muscles was seen as the temperature approached 20 degrees C. The maximum isometric tetanic tension recorded between 18 and 20 degrees C increased fractionally to an average of 1.504 +/- 0.029 (n = 4) for frog sartorii and to 1.377 +/- 0.008 (n = 5) for toad sartorii. The time to peak twitch tension and the half-relaxation time decreased markedly with an increase in temperature. Moreover, the half-relaxation time was reduced by a greater proportion than the time to peak twitch tension. Measurements of instantaneous stiffness by controlled velocity releases from the plateau of isometric tetani revealed that the large increase in isometric tetanus tension as the muscle was warmed was not accompanied by a corresponding increase in the total number of active cross-bridges. The possibility that a decreased availability of intracellular Ca2+ ions at the contractile sites contributing to the fall of isometric twitch tension at elevated temperatures is discussed. The possibility exists that at elevated temperatures a change inthe intrinsic contractile ability of the muscle occurs which produces an increased tension per cross-bridge.     

Exhalant air temperatures in the Virginia opossum

1. 1.Nasal exhalant air temperature in the adult Virginia opossum averages 20.9°C at ambient temperatures near 20.8°C (relative humidity: 47%) and 15.1°C at ambient temperatures near 9.2°C (RH: 78%). Exhalant air temperature is well below deep body temperature (34.5–35.6°C), indicating counterecurrent cooling of the exhalant air in the nasal passages.

2. 2.The extent of cooling of exhalant air is similar in juvenile (15-week-old) and adult opossums.

3. 3.As judged from exhalant air temperature, the effectiveness of countercurrent cooling is similar in the opossum to that seen in small and medium-sized placental mammals. The question is discussed of whether cooling of the exhalant air in these animals represents an adaptation or a physically inevitable, fortuitous effect.

The influence of pH on the viscous behavior of starch-poly(ethylene-co-acrylic acid) complexes

Starch-poly (ethylene-co-acrylic acid) (EAA) complexes were prepared by jet-cooking mixtures of either cornstarch, waxy cornstarch or high amylose cornstarch with aqueous ammonia dispersions of EAA (4% EAA based on the weight of starch). Viscosities (η) were determined at temperatures ranging from 80°C to 22°C, and plots of log η versus 1/T (K⁻¹) were prepared. When cooked with EAA, cornstarch and waxy cornstarch showed major changes in viscous behavior between 50°C and 60°C. Above 50–60°C, viscosity increased markedly with a reduction in temperature; however, viscosity increased slowly below 50–60°C with an apparent activation energy for the process approximating that of water itself. The temperature dependence of the measured viscosity from 80°C to 60°C could be attributed to the large increase in size and complexity of the flowing particles as individual amylopectin molecules were bound together by complexed EAA. Apparently, complexing is essentially complete at 50°C. When high amylose cornstarch was cooked in the absence of EAA, retrogradation produced a sharp increase in log η at temperatures below about 50°C. However, if EAA is present, association between amylose molecules apparently takes place via complex formation rather than retrogradation, since log η increases sharply at about 70–80°C. Also, in contrast to cornstarch and waxy cornstarch, log η versus 1/T plots for high amylose cornstarch did not level off at low temperatures. In general, viscosities increased with the pH of the system, particularly when η was measured at high temperatures. This could result from improved complexing ability of EAA under high pH conditions, possibly due to reduced micelle size and maximum extension of polymer chains from micelle surfaces.     

Stability of xanthan in aqueous sodium chloride at elevated temperature

Aqueous NaCl solutions of dimerized Na xanthan with salt concentrations of 0.005, 0.01 and 0.1 were exposed to 80°C for different time periods t, and their viscosities were determined as a function of t. The measured relative viscosities decreased markedly with t, suggesting that Na xanthan denatured at 80°C undergoes some conformation changes or degradation. The molecular weights of the test samples recovered at different t were estimated by viscometry in cadoxen, a single-coil solvent for xanthan, and were found to decrease monotonically with t. Thus, it was concluded that the observed decreases in relative viscosity are due primarily to degradation of Na xanthan.     

Free Radicals Appear to Affect Survival of Hepatocytes at 4°C

1) Rat hepatocytes, stored in a simple salts medium for 24 h at 4°C, retain more than 80% of their capacity to synthesize glucose from lactate.

2) The combination of NH₄Cl with oleate is cytotoxic during storage and during subsequent incubation of hepatocytes from 48 h starved rats, but not to hepatocytes from fed rats.

3) Protection against cytotoxicity is afforded by albumin and by a number of other compounds, notably polyols and glycerol.

4) These compounds appear to exert their effects by scavenging free radicals and, in the case of polyols and glycerol, by supplying reducing equivalents to maintain the redox state of the cell in the face of increased flux through glutathione peroxidase.     

Muscle temperature and muscle metabolism during short-term exercise in the goat

1. 1.|External heat exchangers acting on lower aortal blood temperature were used to dissociate hindleg muscle temperature (T_hlm) from general internal temperature (T_int) during short-term exercise of moderate intensity.

2. 2.|In series 1 39°C T_hlm was combined with 40.6°C T_int, and in series II 42°C T_hlm was combined with 39.8°C T_int.

3. 3.|At constant work rates, the 3°C difference in muscle temperature did not result in significantly different concentrations of muscle metabolites.

4. 4.|It is concluded that high local muscle temperature without general hyperthermia does not influence muscle metabolism during short-term moderate excercise.

Thermoregulatory responses to manipulations of photoperiod in wood mice Apodemus sylvaticus from high latitudes (57°N)

1. 1. The thermoregulatory responses to manipulations of photoperiod in wood mice (Apodemus sylvaticus), which were drawn from a population living at a high latitude (57°N) were studied.

2. 2. Mice captured in spring were acclimated to two different photoperiod regimes 16L:8D and 8L:16D at a constant ambient temperature of 24°C, for 3 weeks.

3. 3. Daily rhythms of body temperature, oxygen consumption and body temperature at various ambient temperatures, nonshivering thermogenesis (the response to a noradrenaline injection) and body mass were measured. Minimal overall thermal conductance was calculated for both groups.

4. 4. Acclimation to long photophase increased the thermoregulatory abilities at relatively high ambient temperatures while that of long-scotophase increased thermoregulatory abilities at low ambient temperatures.

5. 5. Changes in photoperiod may therefore be used as cues for seasonal acclimatization of thermoregulatory mechanisms in this population of wood mice.

     

The effects of erythrocythemia on blood viscosity,maximal systemic oxygen transport capacity and maximal rates of oxygen consumption in an amphibian

Graded erythrocythemia was induced by isovolemic loading of packed red blood cells in the toad, Bufo marinus. Blood viscosity, hematocrit, hemoglobin concentration, maximal aortic blood flow rate and maximal rates of oxygen consumption were determined after each load. Blood viscosity was related to hematocrit in the expected exponential manner; ln eta = 0.43 + 0.035 Hct. Maximal blood flow rates in the dorsal aorta were inversely proportional to blood viscosity and fit predictions of the Poiseuille-Hagen flow formula. The effect of increased blood viscosity was to reduce aortic pulse volume, but not maximal heart rate. Maximal systemic oxygen transport capacity (aortic blood flow rate X hemoglobin concentration X O2 binding capacity of hemoglobin) was linearly correlated with the maximal rate of oxygen consumption. These date indicate that optimal hematocrit theory is applicable for maximal blood flow rates in vivo, and that systemic oxygen transport is the primary limitation to aerial VO2 max in amphibians.     

The effect of cryopreservation at −196°C on the viability of fowl and Turkey spermatozoa assessed in vitro

The effect of storing fowl and turkey spermatozoa at −196°C in a glycerol-based diluent on post-thawing levels of motility, ATP content, morphology and leakage of lactate dehydrogenase was investigated. Compared to those of freshly-diluted spermatozoa, these parameters were reduced to 24, 26, 55 and 61% respectively, for fowl spermatozoa and to 22, 26, 34 and 60%, respectively, for turkey spermatozoa, immediately after thawing and the removal of glycerol. On subsequent incubation for 3 h at 40°C, the ATP content and morphological integrity of frozen/thawed spermatozoa of both species fell to less than 5% of the levels of similarly-incubated non-frozen spermatozoa. Only after prolonged incubation of fowl and turkey spermatozoa could these parameters be shown to reflect, and, therefore, be of use as monitors of the reduction of fertilizing ability caused by freezing.     

Circadian modulation of starvation-induced hypothermia in sheep and goats

Prolonged food deprivation is known to cause a fall in the core body temperature of homeotherms. In various species of small birds and mammals (body mass up to 2-3 kg), it has been shown that starvation-induced hypothermia is modulated by the circadian system, in the sense that hypothermia is observed primarily during the inactive phase of the daily activity cycle (i.e., during the night for diurnal animals and during the day for nocturnal animals), whereas relatively normal temperatures are recorded during the active phase. To investigate whether this modulation occurs also in larger animals, we investigated the effects of 4d food deprivation on the body temperature rhythm of goats and sheep (body mass 30-40 kg). In goats, the body temperature rhythm was found to have a mean level of 39.0°C with a mean daily range of excursion of 0.42°C. The daily oscillation in body temperature persisted during the first day of fasting, but the rhythm was drastically damped, if not eliminated, over the next 3 d as body temperature descended from the baseline level of 39.0 to 38.2°C. In sheep, the rhythm was found to have a mean level of 39.3°C with a mean daily range of excursion of 0.34°C. The daily oscillation in body temperature persisted through the 4 d of food deprivation, even though the mean level of body temperature gradually fell. Temperature fell more during the third and fourth nights than during the third and fourth days. Thus, circadian modulation of starvation-induced hypothermia was observed in sheep but not in goats.     

A structural transition in egg lecithin-cholesterol bilayers at 12 °C

The thermal coefficient of expansion of egg lecithin bilayer thickness, αd₁, was measured as a function of its cholesterol content up to mole ratio lecithin/cholesterol of 1:1, and over the temperature range 0–40 °C. At all cholesterol contents αd₁ changes abruptly at approximately 12 °C indicating a structural transition at this temperature. Above 12 °C, αd₁ decreases monotonically from −2·10⁻³ for pure egg lecithin to −1·10^–3 at mole ratio 1:1. Below 12 °C αd₁ is walways higher than above 12 °C and shows a sharp, anomalously high value of −6·10⁻³ at the mole ratio 2:1. The results have been interpreted as the movement of cholesterol into the bilayer or the formation of lecithin-cholesterol “complexes” at temperatures below 12 °C. Similar studies with phosphatidylinositol containing cholesterol showed no structural transition and lysolecithin containing cholesterol behaved differently giving two lamellar phases in equilibrium.