Comparisons of blood viscosity between amphibians and mammals at 3°C and 38°C

(1) The range of temperature exposure of endotherms is narrow compared to ectotherms that can experience daily and seasonal temperature fluxes. (2) Comparison of the blood viscosity of amphibians (bullfrog, Woodhouse's toad, and marine toad) and mammals (horse, dog, and rat) at 3°C and 38°C was undertaken to determine if the effect of temperature on blood viscosity was diminished in amphibians relative to mammals. (3) Mammals did not consistently show greater changes in blood viscosity, plasma viscosity, or relative viscosity with decreasing temperatures relative to the amphibians in this study. (4) These data do not support our hypothesis that blood viscosity of amphibians is less affected by temperature than mammalian blood.     

Water lecithin binding in lecithin-water lamellar phases at 20°C

¹H and ³¹P continuous wave and spin-echo NMR measurements have been made on lecithin-water mixtures as a function of water content at 20 °C. An analysis of the data demonstrates the existence of two water environments, lecithin bound and free. Conclusions are presented concerning the stoichiometry and kinetics of the binding. The results indicate that six molecules of water are bound to one lecithin molecule and the lifetime of the bound water is 6·10⁻⁵±3·10⁻⁵ s.     

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).     

Bcl‐xL overexpression does not enhance specific erythropoietin productivity of recombinant CHO cells grown at 33°C and 37°C

Overexpression of bcl‐xL in recombinant Chinese hamster ovary (rCHO) cells has been known to suppress apoptotic cell death and thereby extend culture longevity during batch culture. However, its effect on specific productivity (q) of rCHO cells is controversial. This study attempts to investigate the effect of bcl‐xL overexpression on q of rCHO cells producing erythropoietin (EPO). To regulate the bcl‐xL expression level, the Tet‐off system was introduced in rCHO cells producing EPO (EPO‐off‐bcl‐xL). The bcl‐xL expression level was tightly controlled by doxycycline concentration. To evaluate the effect of bcl‐xL overexpression on specific EPO productivity (q_EPO) at different levels, EPO‐off‐bcl‐xL cells were cultivated at the two different culture temperatures, 33°C and 37°C. The q_EPO at 33°C and 37°C in the presence of 100 ng/mL doxycycline (without bcl‐xL overexpression) were 4.89 ± 0.21 and 3.18 ± 0.06 μg/10⁶cells/day, respectively. In the absence of doxycycline, bcl‐xL overexpression did not affect q_EPO significantly, regardless of the culture temperature, though it extended the culture longevity. Taken together, bcl‐xL overexpression showed no significant effect on the q_EPO of rCHO cells grown at 33°C and 37°C. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009     

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.     

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.

Hamster oocyte fertilizability after 4°C storage

The purpose of the present work was to study the feasibility of using hamster oocytes stored at 4°C in M-2 culture medium for 24 and 48 hours in the evaluation of human sperm fertilizability. A total of 1,394 oocytes were stored for 24 hours and 1,234 were stored for 48 hours. After the storage period all the ooctyes were stained with fluorescein diacetate, proving the physical integrity of the egg plasma membrane. Twenty-five and 22 semen samples were used to compare their ability to penetrate freshly ovulated and 24-and 48-hour-stored hamster oocytes. Freshly ovulated and 24-hour-stored oocytes were penetrated at percentages that in more than 95% of the cases showed no significant differences. The same experiments carried out with oocytes stored for 48 hours showed that in 75% of the cases no significant differences were found. The use of oocytes preserved at 4°C when large numbers of semen samples are to be tested for fertilizability is recommended.     

Thermodynamic interaction between urea and the peptide group in aqueous solutions at 25°C

Isopiestic vapor pressure measurements of the ternary systems water + triglycine + urea and water + glycine-L-alanine + urea were made and used to calculate the Gibbs free energy of these systems. Together with recently published analogous results on systems, in which the first solute was glycine or alanine or diglycine, and measurements of the excess enthalpy of all these solutions, it is possible to calculate the Gibbs free energy of transfer and the enthalpy of transfer of the peptide group from water to aqueous urea solutions. The transfer can be described as a binding of urea to the peptide group with ΔG = ?1.85 kJ mol^?1 and ΔH = ?18.7 kJ mol^?1 at 298.1 K.     

Improved fluorometric assay of histamine: Condensation with O-phthalaldehyde at −20°C

Histamine reacts with OPT at an alkaline pH giving rise to fluorescent conjugation products. Optimum fluorophore formation was observed at pH 12.5 after 10 hr under nitrogen at −20°C, i.e., in the frozen state. After acidification with sulfuric acid to pH 2.5 the resulting fluorescence, read at room temperature, was stable for hours. The procedure now measures as little as 1 ng histamine/ml and is much more specific than the conventional fluorometric assay. Spermidine did not interfere with the assay of histamine, and histidine only if present in great excess over histamine. It could be shown that with deproteinized extracts of rat gastric mucosa, histamine could be estimated without further purification, which means saving a lot of time and labor.     

Developmental competence of domestic cat oocytes from ovaries stored at various durations at 4 °C temperature

Temporal storage of ovaries can provide opportunity to rescue oocytes from ovaries of endangered felids. The objective of the study was to examine the effect of different storage periods (2, 24 and 48 h) of ovaries at 4 °C for maturation of cat oocytes in vitro. Ovaries were collected from 25 domestic cats at various stages of the estrous cycle by routine ovariohysterectomy following anesthesia at different local veterinary clinics, and maintained in physiological saline at 4 °C for 2, 24 or 48 h until oocytes recovery. Selected COCs were maturated at 38 °C for 48 h in four-well petri dishes, which included 500 μL modified synthetic oviduct fluid (mSOF) medium under mineral oil in a humidified 5% CO₂, 5% O₂, and 90% N₂ atmosphere incubator. After the in vitro maturation period, there were no differences between the rate of oocytes matured at MII stages in 2 and 24 h storage groups (50.7% and 48.2% respectively, p > 0.05). However, the same result for the 48 h group was significantly lower than the 2 and 24 h groups (28.0%, p < 0.001).Our results suggest that while 2 or 24 h storage of ovaries at 4 °C does not affect the meiotic competence of oocytes in vitro, 48 h storage of ovaries decrease the results dramatically.     

Myelin basic protein ability to organize lipid bilayers: structural transition in bilayers of lysophosphatidylcholine micelles

Myelin basic protein isolated by a single step with the cationic detergent cethyltrimethylammonium bromide in a lipid-bound form is able to induce structural transition of lysophosphatydilcholine micelles into multi-laminar vesicles. This finding, observed through electron microscopy, is discussed in the light of the assumed ability of the basic protein to organize myelin lipids.     

Effects of metabolic rate on thermal responses at different air velocities in −10°C

The effects of exercise intensity on thermoregulatory responses in cold (−10°C) in a 0.2 (still air, NoWi), 1.0 (Wi1), and 5.0 (Wi5) m s⁻¹ wind were studied. Eight young and healthy men, preconditioned in thermoneutral (+20°C) environment for 60 min, walked for 60 min on the treadmill at 2.8 km/h with different combinations of wind and exercise intensity. Exercise level was adjusted by changing the inclination of the treadmill between 0° (lower exercise intensity, metabolic rate 124 W m⁻², LE) and 6° (higher exercise intensity, metabolic rate 195 W m⁻², HE). Due to exercise increased heat production and circulatory adjustments, the rectal temperature (T_re), mean skin temperature (T_sk) and mean body temperature (T_b) were significantly higher at the end of HE in comparison to LE in NoWi and Wi1, and T_re and T_b also in Wi5. T_sk and T_b were significantly decreased by 5.0 m s⁻¹ wind in comparison to NoWi and Wi1. The higher exercise intensity was intense enough to diminish peripheral vasoconstriction and consequently the finger skin temperature was significantly higher at the end of HE in comparison to LE in NoWi and Wi1. Mean heat flux from the skin was unaffected by the exercise intensity. At LE oxygen consumption (V ₂) was significantly higher in Wi5 than NoWi and Wi1. Heart rate was unaffected by the wind speed. The results suggest that, with studied exercise intensities, produced without changes in walking speed, the metabolic rate is not so important that it should be taken into consideration in the calculation of wind chill index.