热应激对小鼠精液品质的影响及其在全球变暖背景下的生态意义

为了研究全球变暖和局部极端高温气候对雄性小型啮齿类动物繁殖能力的影响,建立小鼠热应激模型,设立5个温度组28、31、34、37和40℃,其中28℃组为对照组。在14d内分别在第1天—第3天、第5天、第7在、第10天和第14天检测小鼠的精子活力、精子顶体完整率、精子畸形率。结果显示,温度越高,精液质量下降越快;温度在较温和的范围内变动时,精液质量随温度的升高而呈现下降的趋势,但经过一段时间的适应,有所回升;在极端温度(40℃)胁迫下,小鼠的精液质量持续下降而不能得到恢复。这说明,高温影响下,雄鼠的繁殖能力存在适应性生理调节过程,但影响是相当明显的,至少在短期内不能恢复到原来水平。由此可以推断,自然界中,较长的精液品质下降期和恢复期可能打破了与雌鼠发情周期的同步化(如果高温对雌鼠影响不大),在自然界中可能对雌鼠的受孕率产生明显影响。此外,即使雌鼠能在雄鼠精液品质恢复期之前受孕,精子损伤也会明显降低受孕率,还可能产生活力低下、畸形或存在其他生理缺陷的后代,进而影响成活率。     

球磨杠柳木质素化学结构特性

对球磨的杠柳(Periploca sepium)采用含有0.05mol/L HCl的80%液体二氧六环在85℃处理4h、二甲基亚砜在85℃处理4h,以及8% NaOH在50℃处理3h,得到86%的原本木质素.采用FTIR、UV、液态1H和13C-NMR研究了酸性二氧六环、二甲基亚砜和碱溶性木质素组分的结构特征.结果表明:温和条件下,球磨与酸水解对分离的木质素大分子结构破坏不大.其中,温和酸水解使半纤维素和木质素之间醚键发生显著断裂,并使半纤维素发生部分降解.由于酸性二氧六环溶解的木质素主要来自初生壁,而碱溶性木质素主要来自次生壁,导致酸性二氧六环溶解的木质素与二甲基亚砜和碱溶性木质素结构不同.     

温度对水曲柳种子萌发过程中物质转化和内源激素含量的影响

以经过层积处理解除休眠的水曲柳(Fraxinus mandshurica Rupr.)种子为材料,在两种不同温度条件下进行萌发试验,探讨温度对种子萌发过程中物质转化和内源激素含量的影响.结果表明:与适宜温度下萌发相比,较高温度(25 ℃)下萌发时,种胚中GA3和ZT含量降低,种胚和胚乳中ABA含量升高,种胚中GA3/ABA、IAA/ABA、ZT/ABA的比值降低.内源激素向利于种子休眠的方向发展,从而使种子中脂肪酶和β-淀粉酶活性受抑制,脂肪和淀粉的分解缓慢,可溶性蛋白和糖的进一步代谢受到不同程度的抑制,导致种子不能正常萌发.     

Experimental separation of sensory and motor functions in pea tendrils

When illuminated pea tendrils from light-grown plants are rubbed on their abaxial side, they rapidly coil in a spiral fashion. If similar tendrils are held in the dark for 3 days and then rubbed, however, they will not coil until they are subsequently illuminated. They can remain uncoiled in the dark for as long as 2 hours after stimulation, and will still coil immediately when they are illuminated. Tendrils that are rubbed and held at 25 degrees C will coil, but those treated at 5 degrees or 10 degrees C will not. However, tendrils rubbed at 25 degrees C and kept from coiling for an hour at 5 degrees C, will immediately coil when restored to the higher temperature. These observations are interpreted to imply separation of sensory and motor functions.     

Microorganisms in the accreted ice of Lake Vostok, Antarctica

Analysis of a portion of Vostok ice core number 5G, which is thought to contain frozen water derived from Lake Vostok, Antarctica (a body of liquid water located beneath about 4 kilometers of glacial ice), revealed between 2 x 10(2) and 3 x 10(2) bacterial cells per milliliter and low concentrations of potential growth nutrients. Lipopolysaccharide (a Gram-negative bacterial cell biomarker) was also detected at concentrations consistent with the cell enumeration data, which suggests a predominance of Gram-negative bacteria. At least a portion of the microbial assemblage was viable, as determined by the respiration of carbon-14-labeled acetate and glucose substrates during incubations at 3 degrees C and 1 atmosphere. These accreted ice data suggest that Lake Vostok may contain viable microorganisms.     

Tongue Cooling during Drinking: A Regulator of Water Intake in Rats

Rats that had been deprived of water for 23(1/2) hours were presented with water for 30 minutes per day. As the temperature of the water was increased from 12 degrees to 36 degrees C (body temperature), the total water intake for 30 minutes increased 71 percent. Tongue cooling during drinking appears to suppress drinking in anticipation of extracellular hydration.     

48,000 years of climate and forest change in a biodiversity hot spot

A continuous 48,000-year-long paleoecological record from Neotropical lower montane forest reveals a consistent forest presence and an ice-age cooling of approximately 5 degrees to 9 degrees C. After 30,000 years of compositional stability, a steady turnover of species marks the 8000-year-long transition from ice-age to Holocene conditions. Although the changes were directional, the rates of community change were no different during this transitional period than in the preceding 30,000-year period of community stability. The warming rate of about 1 degrees C per millennium during the Pleistocene-Holocene transition was an order of magnitude less than the projected changes for the 21st century.     

Thermoperiodic control of diapause in an insect: theory of internal coincidence

Females of the parasitic wasp Nasonia vitripennis raised from the egg stage in the total absence of light but subjected to daily temperature cycles (13 degrees to 23 degrees C), are able to distinguish a "short-day" thermoperiod ( 13 hours at 23 degrees C per day) from a "long-day" thermoperiod ( 13 hours at 23 degrees C per day) and produce diapausing or developing progeny accordingly.     

Interferon binding: the first step in establishment of antiviral activity

Chick cells incubated at 1 degrees C with interferon fail to develop antiviral activity, but this activity appears subsequent to a 7-hour incubation at 37 degrees C after removal of interferon by repeated washings. Treatment with actinomycin D blocks the development of the latter activity. Cells incubated with interferon at 1 degrees C for up to 1 hour and then washed and incubated for 2 hours at 37 degrees C develop a degree of antiviral activity proportional to the concentration of interferon at initial incubation; at any concentration, the antiviral activity increased with the duration of initial incubation at 1 degrees C, but a maximal response was reached at 10 or 20 minutes. Treatment with trypsin after incubation with interferon at 1 degrees C inhibited development of antiviral activity. Interferon is rapidly bound to a superficial cell site, and this binding is necessary for development of antiviral activity in chick cells.     

Male sterility induced in tomato by sodium 2, 3-dichloroisobutyrate

Increasing the pH from 3.0 to 10.8 increased the uterine weight three-fold and the number of positive vaginal smears from 0 to 78 percent in immature rats injected with chorionic gonadotropin in aqueous solution. Activity of a solution held at pH 2.6 and 5 degrees C for 24 hours was restored by neutralization.     

Io: an intense brightening near 5 micrometers

Spectrophotometric observations of the jovian satellite Io on 20 and 21 February 1978 (Universal Time) were made from 1.2 to 5.4 micrometers. Io's brightness at 4.7 to 5.4 micrometers was found to be three to five times greater at an orbital phase angle of 68 degrees than at orbital phase angles of 23 degrees (5.5 hours before the brightening) and 240 degrees (20 hours after the brightening). Since the 5-micrometer albedo of Io is near unity under ordinary conditions, the observed transient phenomenon must have been the result of an emission mechanism. Although several such mechanisms were examined, the actual choice is not clear.     

Regulation of body temperature in the blue-tongued lizard

Lizards (Tiliqua scincoides) regulated their internal body temperature by moving back and forth between 15 degrees and 45 degrees C environments to maintain colonic and brain temperatures between 30 degrees and 37 degrees C. A pair of thermodes were implanted across the preoptic region of the brain stem, and a reentrant tube for a thermocouple was implanted in the brain stem. Heating the brain stem to 41 degrees C activated the exit response from the hot environment at a colonic temperature 1 degrees to 2 degrees C lower than normal, whereas cooling the brain stem to 25 degrees C delayed the exit from the hot environment until the colonic temperature was 1 degrees to 2 degrees C higher than normal. The behavioral thermoregulatory responses of this ectotherm appear to be activated by a combination of hypothalamic and other body temperatures.     

Lactate dehydrogenase Isozymes: substrate inhibition in various human tissues

The total lactate dehydrogenase (LDH) in whole homogenates of various human tissues reacts more similarly toward pyruvate and lactate at 25 degrees C than expected from the marked differences in substrate inhibition at this temperature between isolated, purified LDH-1, and LDH-5. At 37 degrees C, LDH-5 closely resembles LDH-1 in extent of inhibition by substrate. These results are incompatible with the theory that differences in degree of isozyme inhibition by substrate have resulted in predominance of LDH-5 in aerobic tissues and predominance of LDH-1 in aerobic tissues.     

Weakening of dunite by serpentine dehydration

A shear press has been used to determine the mechanical behavior of serpentinized dunite and forsterite at normal pressures to 50 kilobars, temperatures to 900 degrees C; and strain rates from 10(-1) to 10(-4) per second. The shear strength of dunite, containing less than 5 percent by volume of serpentine, is reduced by at least 30 percent as the temperature is raised from 300 degrees to 520 degrees C. Abundant kink bands develop at normal pressures above 35 kilobars at 27 degrees C and at lower pressures as the temperature is increased.     

Forebrain temperature activates behavioral thermoregulatory response in arctic sculpins

Arctic sculpins of the genus Myoxocephalus adapted to water at 5 degrees C escaped from warm water at 20 degrees , 16 degrees , and 12 degrees C when their deep-body temperatures increased from an initial 5 degrees C to about 8 degrees C. Heating parts of the forebrain with water at 25 degrees C circulating through a pair of thermodes astraddle rostral parts of the forebrain shortened the time spent in the warm water and lessened the incease in deep-body temperature before exit from the warm water. Cooling the forebrain to about -1 degrees C caused a large increase in the body temperature and sometimes suppressed the escape from the warm water.     

温度和叶表化学物质对松杨栅锈菌夏孢子萌发的影响

松杨栅锈菌夏孢子萌发适宜温度范围为10～24℃,最适温度20℃左右。供试的2菌株对温度有不同的依赖性。TH菌株温度适应性范围较宽,GL菌株较窄。在最适温度范围内,供试的2个菌株呈现相同的萌发动力学模式,萌发最大速率出现在4～12h,温度越高,最大萌发速率出现时间越晚,并随时间的延长,萌发速率逐渐减小。在5、30℃,萌发速率有2～3个峰值,第1峰值最大,第2、第3峰值逐渐减小或消失。26℃下峰值呈现过渡型状态,有1个较小的次高峰。供试的2菌株,TH的萌发速率较GL稍高并在出现时间上略前。最适萌发条件下,石油醚、乙醚、乙酸乙酯、正丁醇、水的卜氏杨和毛白杨提取物对松杨栅锈菌夏孢子萌发有不同的影响。毛白杨所有提取物在接种12h内,均抑制夏孢子的萌发,而卜氏杨乙醚提取物则促进夏孢子萌发,其余则抑制夏孢子萌发。所有水提取物在接种12h均表现为抑制作用。接种12～24h,2种杨树叶片正丁醇萃取物对夏孢子萌发速率均有一定程度的促进作用。     

Hemoglobin Kinetics of the Galapagos Rift Vent Tube Worm Riftia pachyptila Jones (Pogonophora; Vestimentifera)

Kinetics of the reactions of Riftia pachyptila hemoglobin with oxygen were followed spectrophotometrically by stopped-flow and laser flash photolysis techniques. The rate of oxygen dissociation increases eightfold over the range of 5 degrees to 20 degrees C (k = 2.2 sec(-1)at 10 degrees C). Oxygen recombination after flash photolysis was biphasic. The rates of both slow and fast phases of the reaction were independent of temperature from 0 degrees to 20 degrees C(k'fast = 7 x 10(6); k'slow = 1 x 16(6) liter mole (-1) sec(-1)). As the oxygen affinity is relatively temperature independent, analysis in terms of the two-state model of cooperativity requires that the conformational equilibrium constant L decrease by about 50-fold between 3 degrees and 15 degrees C.     

Oxygen consumption of red and white muscles from tuna fishes

Metabolic rates of unstimulated, minced preparations of red and white muscles from two species of Pacific tuna fishes (Katsuwonus pelamis and Thunnus obesus) were determined from respirometric measurements of oxygen consumption. Ratios of mean metabolic rates for red muscles to those of white muscles averaged 6.2 at five temperatures over the range of 5 degrees to 35 degrees C. Temperature coefficients (Q10's) for mean metabolic rates for both types of muscle were between 1.0 and 1.2 over the entire temperature range. Metabolic rates of tuna red muscles were equal to those of preparations of mixed red and white muscle from the white rat at 25 degrees and 35 degrees C, and were higher than the mammalian rates at lower temperatures.     

Prevention of protein denaturation during exposure to sterilization temperatures

Firefly luciferase exposed to a temperature of 135 degrees C for 36 hours re tained up to 40 percent of its original activity. Prerequisites for heat stability were the use of a molecular sieve (Seph adex G-25 or Biogel P-300) and a high vacuum (5 x 10(-4) mm-Hg). These studies present a possible solution to the problem of sterilization for exobiologi cal experiments.     

Glacial-postglacial temperature difference deduced from aspartic Acid racemization in fossil bones

The magnitude of the temperature increase that occurred in continental regions following the termination of the last glaciation has been determined from the degree of racemization of aspartic acid in fossil bones of known age. The results indicate an increase of 4 degrees C for the Mediterranean coast and 5 degrees to 6 degrees C for East Africa. These estimates are believed to be reliable within 1 degrees C.