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[Effect of bacterial physiological state and heavy metals on the hyperactive reaction of tobacco leaf].

It has been shown that the initiation and proceeding of hypersensitive reaction on the tobacco leaf under the bacterial effect are influenced by the infectious loading of the pathogen, physiological state of bacteria, their viability, temperature of the environment and heavy metal salts. It has been established that the hypersensitive reaction is most distinctly manifested when 1-3 days bacterium cultures are used. Their activity decreases essentially with age, and 10-14 days old cultures are not able to evoke the hypersensitive reaction. The bacterial cells being inactivated with temperature and UV-irradiation lose the ability to evoke the hypersensitive reaction. The reaction of hypersensitive is inhibited by salts of heavy metals in concentrations 0.1-1% and by high temperature of the environment (30 degrees C).

Dose-Response Relationship, Drug↗
PubMed1998

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

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

Adaptation, Physiological↗
PubMed1996

High temperature ecosystems and their chemical interactions with their environment.

Phototrophic thermal ecosystems consist of microbial mats whose composition is largely determined by water temperature, dissolved oxygen, sulfide and pH. Mats exposed to sunlight consist of an upper zone of phototrophic bacteria and cyanobacteria and an undermat of heterotrophic bacteria. There is little or no net accumulation of reduced carbon and a quasi-equilibrium is established between the synthesis and oxidation of reduced carbon. The flux of carbon and other metabolites induces chemical change in the interstitial water which may assist the deposition of hydrothermal minerals. Uptake of carbon dioxide by phototrophs is favourable to calcium carbonate (travertine) deposition. Thermal systems also contain a range of chemolithotrophs and sulfate reducers potentially capable of depositing carbonate. Acid production by sulfate reducers may have the ability to precipitate silica from alkaline thermal waters but has not yet been demonstrated in vivo. Deposition of thermal ochre is also possible via bacterial oxidation of reduced iron and manganese. It appears that bacteria play a minor role in the deposition of hydrothermal minerals through chemical interaction. However, they may play a more important physical role by providing a large surface are suitable for mineral nucleation. If hydrothermal deposits occur on Mars, the distribution of travertine is likely to be restricted if there is a lack of pre-existing sedimentary carbonate. Less biologically interactive deposits of silica and ochre may predominate.

Archaea↗
PubMed1997

Do sperm cells age? A review of the physiological changes in sperm during storage at ambient temperature.

In a liquid environment, at high dilutions, fertility of bull sperm is maintained for 3-5 days when stored at ambient temperatures (10-21 degrees C), after which time it steadily declines at a rate of 3-6% per day. This decline in fertility occurs irrespective of whether the sperm are stored at 5 degrees C or at 15 degrees C, but the rate is greater once storage temperatures exceed 25 degrees C. Sperm motility can be maintained for extended periods in an environment where the extracellular oxidative stress is minimized by reducing the oxygen tension, by addition of antioxidants and chelating agents; however, this will not prevent a significant drop in fertility after five days of storage at ambient temperature. The requirement of energy by the sperm-motility apparatus demands a high level of respiratory activity. This system is very active and the free radicals produced in vivo during this process could lead to chromatin damage. As no internal repair mechanism exists in sperm, an extraneous supply of protectants, or an environment where damage is minimized, is essential to maintain its fertilizing potential. The lack of extended storage potential of sperm, even in the presence of antioxidants, seems to suggest that although oocyte-penetrating ability of the sperm could still be intact, the high rate of intracellular metabolic activity could lead to mitochondrial DNA damage and chromosomal abnormalities that would compromise the viability of the resulting conceptus.

Animals↗
PubMed2006

Drink temperature influences fluid intake and endurance capacity in men during exercise in a hot, dry environment.

The effect of different drink temperatures on the perception of exertion and exercise endurance has not been extensively investigated. Consequently, the purpose of the present study was to examine the effect of drink temperature on fluid intake and endurance during cycling in the heat. Eight healthy, non-acclimated males (26 +/- 7 years; maximum oxygen uptake, 54 +/- 5 ml kg(-1) min(-1); mean +/- S.D.) cycled to exhaustion at 34 degrees C and at 65% of their peak aerobic power, consuming a drink at either 19 degrees C (CON) or 4 degrees C (COLD). Six of the eight subjects cycled for longer during COLD, with exhaustion occurring at 62 +/- 4 min, compared to 55 +/- 4 min for CON (P < 0.05; mean +/- S.E.M.). Subjects consumed significantly more fluid during COLD compared to CON (1.3 +/- 0.3 l h(-1) compared to 1.0 +/- 0.2 l h(-1); P < 0.05). Heart rate tended to be lower by approximately 5 beats min(-1) during COLD, and rectal temperature during the second half of the exercise period was approximately 0.25 degrees C lower during the COLD trial; however, these trends were not significant (P = 0.08 and P = 0.07, respectively). No differences were observed between trials for ventilation, concentrations of prolactin, glucose and lactate or perceived exertion. It is concluded that a drink at 4 degrees C during exercise in the heat enhances fluid consumption and improves endurance by acting as a heat sink, attenuating the rise in body temperature and therefore reducing the effects of heat stress.

Adult↗
PubMed2026

Maternal and developmental temperature modulate adult response to temperature in Drosophila melanogaster.

Beyond inherited genes and environmentally induced changes in gene expression, phenotypes can also be shaped by parental effects-an effect from a parental phenotype that causes modifications in offspring traits, which cannot be solely explained by the parental or offspring genomes. Such effects may prepare offspring for future environmental conditions and contribute to phenotypic plasticity, including responses to temperature. While temperature-induced plasticity has been extensively studied, the relative contributions of parental versus direct environmental cues remain poorly understood. The fruit fly Drosophila melanogaster is a powerful model for studying physiological and behavioral adaptation to temperature. Flies inhabit environments spanning broad thermal ranges and show evidence of parental effects, such as increased heat tolerance in offspring from warm-reared parents. Here, we exposed mothers to two experimental temperatures and split their broods between the same two temperatures to estimate the relative importance of maternal and developmental effects on adult physiological and developmental responses to temperature. We find that the reaction norms of locomotor activity under gradually increasing temperatures, responses to heat-shock and cold-shock, and fecundity are mostly governed by direct plastic responses to developmental environment. We detected comparatively weak maternal effects in the response to heat-shock, fecundity, and grand-offspring survival where matched environments counteracted the effects of direct offspring experience. We conclude that thermal experience during development is the primary determinant of phenotypic plasticity in D. melanogaster, while maternal experience contributes a small but non-negligible component.

Animals↗
PubMed2006

Selection and inbreeding depression: effects of inbreeding rate and inbreeding environment.

The magnitude of inbreeding depression in small populations may depend on the effectiveness with which natural selection purges deleterious recessive alleles from populations during inbreeding. The effectiveness of this purging process, however, may be influenced by the rate of inbreeding and the environment in which inbreeding occurs. Although some experimental studies have examined these factors individually, no study has examined their joint effect or potential interaction. In the present study, therefore, we performed an experiment in which 180 lineages of Drosophila melanogaster were inbred at slow and fast inbreeding rates within each of three inbreeding environments (benign, high temperature, and competitive). The fitness of all lineages was then measured in a common benign environment. Although slow inbreeding reduced inbreeding depression in lineages inbred under high temperature stress, a similar reduction was not observed with respect to the benign or competitive treatments. Overall, therefore, the effect of inbreeding rate was nonsignificant. The inbreeding environment, in contrast, had a larger and more consistent effect on inbreeding depression. Under both slow and fast rates of inbreeding, inbreeding depression was significantly reduced in lineages inbred in the presence of a competitor D. melanogaster strain. A similar reduction of inbreeding depression occurred in lineages inbred under high temperature stress at a slow inbreeding rate. Overall, our findings show that inbreeding depression is reduced when inbreeding takes place in a stressful environment, possibly due to more effective purging under such conditions.

Animals↗
PubMed1984

[Effect of bombesin, its various fragments and their analogs on thermoregulation in rabbits].

Out of synthetic tetradecapeptide bombesin, its fragments C-terminal nonapeptide and N-terminal pentapeptide and their analogues ( Val7 , D- Ala11 ), ( Ala7 , D- Ala11 ), (Leu7, D- Ala11 ) and ( Pro6 , Gly7 , D- Ala11 ), the first two, being injected into the lateral ventricle of the brain in rabbits, affected the body temperature in cold environment (+ 10 degrees C). The analogues exerted a lesser effect on the body temperature. N-terminal pentapeptide was ineffective both in cold (+ 10 degrees C) and warm (+ 30 degrees C) environment.

Animals↗
PubMed1976

Effects of various ambient temperatures and of heating and cooling the hypothalamus and cervical spinal cord on antidiuretic hormone secretion and urinary osmolality in pigs.

1. Plasma ADH concentration, urinary and plasma osmolality and haematocrit were measured in young pigs placed in cold, thermoneutral, warm and hot ambient temperatures. In some experiments a thermode placed in the hypothalamus or over the cervical spinal cord was heated or cooled at various ambient temperatures. 2. Plasma ADH concentration remained at a low level (0-5--5 muu. ml.-1) over 2 hr or 3 hr periods when the pigs were in cold, thermoneutral or warm ambient temperatures. A hot environment, which caused a marked rise in the pigs' rectal temperature, was associated with a large rise in plasma ADH level. 3. The rise in plasma ADH level which occurred during an increase in body temperature was consistently and completely suppressed by simultaneous cooling of the thermode in the pre-optic region to 5 to 10 degrees C. When the thermode was in the region of the supraoptic nucleus the rise in ADH was only partly suppressed, and when it was over the cervical cord it was only sometimes suppressed. 4. Cooling the thermodes in any position at a cold or thermoneutral ambient temperature, or heating them at a thermoneutral or warm ambient temperature, caused no consistent change in ADH. 5. A diuresis, with a urinary flow-rate of at most 1 ml. min-1 and minimal urinary osmolality of 53 m-osmole kg-1, was observed on only three occasions, twice during cooling of a thermode in the hypothalamus and once after the end of a period when the thermode was heated. In each case, the plasma ADH was less than 2 muu. ml.-1. 6. A slight rise of haematocrit in cold ambient conditions and a slight fall in the warm were observed. Otherwise changes in haematocrit were trivial, and a shift of water between vascular system and interstitium could not be invoked to account for changes in ADH levels. Observed variation of plasma osmolality was also slight.

Animals↗
PubMed1992

Overshoot and high equilibrium in body temperature responses of rats to ambient heat: relation to thermoregulatory ability and improvement in estimation of survival time in a hot environment.

Physiological significance of body temperature responses to ambient heat (BTRAH) with high overshoot or a high equilibrium phase was studied in relation to thermoregulatory ability. Subsequently, an attempt was made to predict survival time (ST) by measuring the period required to attain a colonic temperature (Tco) of 42.0 degrees C (t42.0), whereas ST hitherto having been calculated on the basis of a period until Tco attains 42.5 degrees C (t42.5). Tco of rat was monitored continuously with a Cu-Co thermocouple during exposure to an ambient temperature (Ta) of 42.5 degrees C. The lower the overshoot temperature (Tos) or the equilibrium temperature (Teq), the longer the rats survived in a hot environment. The present findings further suggest that these two types of BTRAH are immature variations of the typical triphasic BTRAH which is characteristic of heat resistant individuals. A new regression line of ST (Y) as a function of the t42.0 (X) was obtained for most rats as follows: Y = 0.963X + 43.85 (male); and Y = 0.973X + 39.10 (female). This equation enabled to calculate ST without thermal death. However, the former approach based on t42.5 must be applied yet in small number of rats which showed the irregular BTRAHs with Tos or Teq higher than 42.0 degrees C. Delayed influence on survival and fecundity at a Ta of 24 degrees C were not found during one year following this hyperthermia up to 42.5 degrees C.

Animals↗
PubMed1994

Temperature-dependent sex determination in the snapping turtle: manipulation of the embryonic sex steroid environment.

In certain reptiles with temperature-dependent sex determination (TSD), estrogens act as a signal for female differentiation. Because aromatase produces estrogens from androgens, this enzyme plays a pivotal role in TSD. Whether androgens act as the signal for male differentiation in TSD species in not yet clear. We manipulated the hormonal environment in eggs of the common snapping turtle (Chelydra serpentina) to determine the effects of an estrogen (estradiol 17-beta), an aromatase inhibitor (fadrozole; CGS 16949A), and androgens (testosterone and dihydrotestosterone) on sex determination in this TSD species. Test solutions were applied topically to representative eggs (total tested = 1054 from 27 clutches) and incubated at two male-producing temperatures (24 and 26.5 degrees) and at a predominantly female-producing temperature (29 degrees). In this species, application of an estrogen induced female development at all temperatures tested. In contrast, the aromatase inhibitor had no effect at the male-producing temperatures, but induced male development at the predominantly female-producing temperature. At this temperature, aromatase inhibitor plus testosterone had a similar male-producing effect, but when applied alone, testosterone failed to augment male production. Dihydrotestosterone had a similar effect, in contrast to its reported androgenic effects in other TSD species. In the snapping turtle, male differentiation may not be androgen dependent; rather, it may proceed in the absence of female differentiation. In this species, female development is clearly estrogen-dependent and is altered by aromatase inhibition at female-producing temperatures. Our results not only provide additional evidence that sex steroids mediate gonadal differentiation in TSD species, but also suggest caution with respect to generalizations about the proximal mechanisms of TSD in reptiles.

Androgens↗
PubMed1999

Effect of low temperature on microbial growth: lowered affinity for substrates limits growth at low temperature.

The effect of environmental temperature on the affinity of microorganisms for substrates is discussed in relation to measurements of affinity by either K(s) values or specific affinity (a(A)). It can be shown for psychrophiles, mesophiles and thermophiles that when a(A) is used as the measure of affinity, affinity decreases consistently as temperature drops below the optimum temperature for growth. This effect may be because of stiffening of the lipids of the membrane below the temperature optimum, leading to decreased efficiency of transport proteins embedded in the membrane. The lower temperature limit for growth is, therefore, that temperature at which an organism is no longer able to supply the maintenance requirement of the growth rate-limiting nutrient because of loss of affinity for that substrate. This linking of temperature and affinity for substrates taken up by active transport (a temperature-modulated substrate affinity model) includes uptake of both organic and inorganic substrates. This effect of decreased substrate affinity at low temperature may have profound implications on the availability of substrates in the natural environment as environmental temperatures change. At temperatures below their optimum for growth microorganisms will become increasingly unable to sequester substrates from their environment because of lowered affinity, exacerbating the anyway near-starvation conditions in many natural environments.

Journal Article↗
PubMed2002

Developmental differences in temporal patterns and potentiation of isolation-induced ultrasonic vocalizations: influence of temperature variables.

The present study examined the relationship between the thermal environment and core body temperature in producing age-related patterns of ultrasonic vocalizations (USVs). Implanted telemetry devices allowed on-line measurement of core body temperature during an extended period of isolation and after maternal contact, both as a function of age and thermal environment. At 12 or 17 days of age, rat pups were isolated for 30 min in either a cool or a warm environment, returned home for 5 min, and then re-isolated for 10 min. Number of USVs, body temperature, and behavioral activity were measured. During initial isolation in a cool environment, 12-day-olds displayed relatively stable patterns of ultrasounding and body temperature across time whereas older animals showed a time-dependent increase in USV calling and in core temperature. During re-isolation, 12-day-olds potentiated their USV calling at both ambient temperatures while 17-day-olds did not. The overall results suggest a strong dependence between USV calling, core body temperature, and ambient temperature during initial isolation at both ages-a finding in agreement with interpretations of USVs as an acoustic by-product of thermal challenge. In contrast, during re-isolation, USV calls, core body temperature, and ambient temperature functioned independently-a finding in agreement with interpretations of USVs as a representation of an emotional state.

Animals↗
PubMed2006

Scanning tunneling spectroscopy in an ionic liquid.

Molecular redox levels can be used to modulate tunneling currents through single or small numbers of molecules and induce molecular electronic device function. While most of these devices require cryogenic conditions, room temperature operation has been demonstrated by using electrochemical gating in aqueous environments. The latter have, however, serious shortcomings with a view on their relatively high volatility and narrow stability ranges in terms of potential. Here we report the first-time use of an ionic liquid, 1-butyl-3-methylimidazoliumhexafluorophosphate (BMI), as an electrochemical gate in a Scanning Tunneling Microscope (STM) configuration. Ionic liquids are known to have a very low vapor pressure, and accessible potential ranges are in principle large, up to 6 V. In a proof-of-principle experiment, we show how a heteroleptic redox-active Os bisterpyridine complex (Ossac) can be brought to exhibit both transistor and diode function in this novel environment at room temperature. This renders ionic liquids an attractive gating medium for configurations where back-gating is difficult to implement (e.g., break-junction techniques) or experimental conditions prohibit the use of aqueous or organic electrolyte media (vacuum or high temperatures). From an applied perspective, they represent a step toward solid-state molecular electronics with electrochemical gating.

Journal Article↗
PubMed1984

Activity of rat blood cholinesterases following exposure of the animals to increased environmental temperature.

The acetylcholinesterase activity of erythrocytes was investigated and compared with cholinesterase activity of the blood plasma in rats exposed to elevated temperature of the environment. The rats were kept in a thermic chamber with regulated temperature, forced air flow and controlled moisture of 55-19%. The applied temperatures were 21 degrees C (control) and 28 degrees C or 37 degrees C. The rats were exposed once for 3, 6, 12 or 24 hours and repeatedly for six successive days, for six hours each day. Experiments were also performed to find whether previous exposure of the rats to raised temperature "sensities" acetylcholinesterase to the action of typical cholinesterases inhibitor (DFP). Arrhenius plots were determined for erythrocyte acetylcholinesterase of rats subjected for 6 hours to raised temperature. It was found that the activities of both enzymes undergo only slight changes in dependence on the temperature applied and the time of exposure. More pronounced changes in this activity were observed when the rats were subjected to 37 degrees C. This may have been connected with disturbance of the lipoprotein structure and with an increase of osmotic fragility of the erythrocytes. It was also noted that earlier exposure of the animals to raised environmental temperature "sensitises" the acetylcholinesterase of the erythrocytes to the action of the organophosphorus inhibitor in vivo.

Acetylcholinesterase↗
PubMed1982

Survival under heat stress of lines selected for fast and slow growth at two temperatures.

Two replicates of four lines of White Leghorn chickens previously selected for fast and slow gain from 5 to 9 weeks of age in a hot (32.2 C) and cold (21.1 C) selection environment were grown from 5 to 9 weeks in the hot and cold temperature environments and then subjected to high temperature stress at 40.6 C. Four different experiments were run. The percent mortality was analyzed when approximately 50% of the birds had died. Birds reared in the cold environment were heavier and consistently had higher mortality than those reared in the hot environment when both were subjected to acute heat stress (40.6 C). The importance of acclimation to mild heat stress on response to acute heat stress was demonstrated by the mortality difference. No significant differences in survival under heat stress were found between lines selected in the hot and the cold selection environments. Lines selected for fast growth had significantly higher mortality rates under high temperature stress than lines selected for slow growth in replicate 1 but not in replicate 2. Estimates of the genetic correlation between weight gain from 5 to 9 weeks of age and percent mortality under heat stress after two generations of selection in replicate 2 was -.004, and after three generations of selection in replicate 1 was +.076.

Animals↗