Influence of food size and food quantity on the feeding of the mussel Dreissena polymorpha

Summary In common with many other suspension feeders, the freshwater mussel Dreissena polymorpha has a maximum filtration rate at low food concentrations and a maximum ingestion rate at high food concentrations. These high rates, which reflect the potential maximum food uptake of the animal, are called the filtration capacity and the ingestion capacity respectively. The ingestion capacity was attained without forming pseudofaeces with Chlamydomonas reinhardii as food. The incipient limiting level could be calculated as the quotient of these two values. A decrease of the filtration rate at high food concentrations was correlated with changes in pumping activity, which showed more frequent interruptions, or a lower level of water transport. Dreissena can filter out particles of diameter greater than 0.7 m from the water. Retention reaches a plateau at about 5 m particle diameter. Scanning electron micrographs of the arrangement of the cilia on the gill filaments are given.     

Initiation of morphogenic cell-suspension and protoplast cultures of barley (Hordeum vulgare L.)

Cell-suspension cultures were initiated from embryogenic calli of various barley cultivars. Seven fast-growing suspension lines were obtained from four different cultivars (cvs. Dissa, Emir, Golden Promise and Igri). Two of these cell suspensions showed morphogenic capacity. From a cell suspension of cv. Dissa, albino plantlets were regenerated when aggregates were cultured on solid medium. Aggregates of cv. Igri usually stopped differentiation at the globular stage, but occasionally formed scutellum-like structures. Five suspension lines were used for protoplast isolation and culture. Dividing protoplasts were obtained from all lines, but with cv. Igri a few divisions only and no further development were observed. Protoplasts from the various lines differed in the time of first division (2–14 d), division frequency (0.09–70.9%) and efficiency of colony formation (0.09–7.3%). Protoplasts isolated from the morphogenic cell suspension of cv. Dissa developed compact calli which sporadically regenerated albino plantlets.Abbreviations CC, MS, N6, SH, Kao8p culture media; see Material and methods - cv chltivar - dicamba 3,6-dichloro-o-anisic acid - 2,4-D 2,4-dichlorophenoxyacetic acid - picloram 4-amino-3,5,6-trichloropicolinic acid     

大剂量~(60)Co照射后造血干细胞潜在的残留损伤

本文对受到临界全致死剂量——8.5Gy~(60)Co照射后的小鼠造血干细胞(HSC)的自我更新力进行了测试,并对照射后4个月,造血功能业已恢复的小鼠HSC的造血重建功能进行了研究。结果表明:应用骨髓连续移植实验所测得的照后3个月中骨髓CFU_s的自我更新潜能明显衰退了。用照射后造血恢复小鼠的CFU_s给全致死剂量照射的受体进行移植治疗,发现其移植效力比正常的显著减弱。在受体存活30天时,CFU_s的再生速率只有正常的1/17。通过对性染色体追踪观察的资料分析,此种小鼠的??造血细胞在受体中难以形成长期稳定的嵌合体。以上事实反映出,照射后小鼠的HSC的造血重建功能大大削弱了,揭示出残存干细胞质量上的缺陷。对于这种潜在的残留损伤的机制,从“干细胞增殖力耗竭学说”和“基因自我修整假说”的角度进行了讨论。     

The acute effect of 30 min of moderate exercise on high density lipoprotein cholesterol in untrained middle-aged men

Fifteen middle-aged, untrained (defined as no regular exercise) men (mean age 49.9 years, range 42-67) cycled on a cycle ergometer at 50 rpm for 30 min at an intensity producing 60% predicted maximum heart rate [(fc,max), where fc,max = 220 - age]. Total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C) and triglyceride (Tg) concentrations were measured from fasting fingertip capillary blood samples collected at rest, after 15 and 30 min of exercise, and at 15 min post-exercise. The mean HDL-C level increased significantly from the resting level of 0.85 mmol.l-1 to 0.97 mmol.l-1 (P < 0.05) after 15 min of exercise, increased further to 1.08 mmol.l-1 (P < 0.01) after 30 min of exercise and remained elevated at 1.07 mmol.l-1 (P < 0.01) at 15 min post-exercise. These increases represented changes above the mean resting level of 14.1%, 27.1% and 25.9% respectively. The HDL-C/LDL-C ratio increased significantly from a resting ratio of 0.20 to 0.26 after 30 min of exercise (P < 0.01) and to 0.24 at 15 min post-exercise (P < 0.05). The mean Tg level increased significantly from a resting level of 0.88 mmol.l-1 to 1.05 mmol.l-1 after 15 min, and to 1.06 mmol.l-1 after 30 min of exercise (P < 0.05 at each time). The TC/HDL-C ratio decreased significantly (P = 0.05) after 30 min of exercise and at 15 min post-exercise by 18.8% and 14%, respectively. No significant changes were observed in the levels of TC or LDL-C over time.(ABSTRACT TRUNCATED AT 250 WORDS)     

Scaling physiological measurements for individuals of different body size

This paper examines how selected physiological performance variables, such as maximal oxygen uptake, strength and power, might best be scaled for subject differences in body size. The apparent dilemma between using either ratio standards or a linear adjustment method to scale was investigated by considering how maximal oxygen uptake (l.min-1), peak and mean power output (W) might best be adjusted for differences in body mass (kg). A curvilinear power function model was shown to be theoretically, physiologically and empirically superior to the linear models. Based on the fitted power functions, the best method of scaling maximum oxygen uptake, peak and mean power output, required these variables to be divided by body mass, recorded in the units kg 2/3. Hence, the power function ratio standards (ml.kg-2/3.min-1) and (W.kg-2/3) were best able to describe a wide range of subjects in terms of their physiological capacity, i.e. their ability to utilise oxygen or record power maximally, independent of body size. The simple ratio standards (ml.kg-1.min-1) and (W.kg-1) were found to best describe the same subjects according to their performance capacities or ability to run which are highly dependent on body size. The appropriate model to explain the experimental design effects on such ratio standards was shown to be log-normal rather than normal. Simply by taking logarithms of the power function ratio standard, identical solutions for the design effects are obtained using either ANOVA or, by taking the unscaled physiological variable as the dependent variable and the body size variable as the covariate, ANCOVA methods.     

Coexistence of Tetranychus urticae (Acarina: Tetranychidae) with different capacities for diapause: comparative life-history traits

Summary Individuals of the two-spotted spider mite, Tetranychus urticae Koch (Acarina: Tetranychidae), with and without a capacity for diapause, coexist in central Japan. Diapause appears to be adaptive because females in diapause suffered less mortality than non-diapausing individuals when frozen at –24°C for more than 4 h. However non-diapausing females showed good survival up to 4 h of freezing. Active non-diapausing mites survived on rose leaves in Kyoto (35°N) throughout the winters of 1988–1989 and 1989–1990. Cultures of mites with low (LD) and high (HD) diapause capacities at 18°C and 9L-15D photoperiod were successfully selected from the rose population and from a population on chrysanthemum in Nara (34.4°N). Their life-history traits at 15, 20, 25 and 30°C were characterized. HD and LD mites from both populations were of similar ages at first reproduction at 15–30° C. However, at temperatures 20° C, HD individuals produced more eggs than LD individuals, resulting in higher fecundity and intrinsic rate of natural increase. These traits allow HD individuals, which stop breeding between October and April, to increase faster in summer than LD individuals. This provides a mechanism, together with climatic fluctuations, in maintaining the coexistence of diapausing and non-diapausing T. urticae in Kyoto where winter conditions are rarely lethal to the non-diapausing individuals.     

Dry matter production and photosynthetic capacity in Gossypium hirsutum L. under conditions of slightly suboptimum leaf temperatures and high levels of irradiance

Summary Gossypium hirsutum L. var. Delta Pine 61 was cultivated in controlled-environment chambers at 1000–1100 mol photosynthetically active photons m^-2 s^-1 (medium photon flux density) and at 1800–2000 mol photons m^-2 s^-1 (high photon flux density), respectively. Air temperatures ranged from 20° to 34°C during 12-h light periods, whereas during dark periods temperature was 25° C in all experiments. As the leaf temperature decreased from about 33° to 27° C, marked reductions in dry matter production, leaf chlorophyll content and photosynthetic capacity occurred in plants growing under high light conditions, to values far below those in plants growing at 27° C and medium photon flux densities. The results show that slightly suboptimum temperatures, well above the so-called chilling range (0–12° C), greatly reduce dry matter production in cotton when combined with high photon flux densities equivalent to full sunlight.Abbreviations DW dry weight - F _v variable fluorescence yield - F _M maximum fluorescence yield - PFD photon flux density (400–700 nm)     

带有隐含神经元的单层神经网络模型

提出了一种带有隐含神经元的单层神经网络模型。把网络的记忆容量区分为信息记忆容量和物理记忆容量。新模型能记忆相关图样,其信息容量α_i(最大记忆图样数/表达神经元数)首次超过了1。所作出的计算机模拟结果,表明了理论分析的正确性,证实了由5×5个显神经元组成的点阵能记住包含26个英文字母和4个任选图样的30个图样,因此该模型为神经网络的广泛应用提供了一条重要途径。     

Thermodynamics of the disproportionation of adenosine 5'-diphosphate to adenosine 5'-triphosphate and adenosine 5'-monophosphate. I. Equilibrium model

The thermodynamic treatment of the disproportionation reaction of adenosine 5′-diphosphate to adenosine 5′-triphosphate and adenosine 5′-monophosphate is discussed in terms of an equilibrium model which includes the effects of the multiplicity of ionic and metal bound species and the presence of long range electrostatic and short range repulsive interactions. Calculated quantities include equilibrium constants, enthalpies, heat capacities, entropies, and the stoichiometry of the overall reaction. The matter of how these calculations can be made self-consistent with respect to both calculated values of the ionic strength and the molality of the free magnesium ion is discussed. The thermodynamic data involving proton and magnesium-ion binding data for the nucleotides involved in this reaction have been evaluated.     

Maximal exercise capacity in adolescent European and Amerindian high-altitude natives

Forty-seven highland natives were given maximal exercise tests on a treadmill ergometer at 3,600 m. The subjects were grouped into four subsamples on the basis of ethnicity (European vs. Aymara) and age (young vs. old adolescent). Two-way ANOVA indicated that VO2max adjusted for body size did not differ significantly between ethnic groups but was significantly larger in older than younger boys within each ethnic group (p less than .05). This finding does not support the hypothesis that Amerindian highland natives have adapted genetically to hypoxia but is consistent with the hypothesis that the relatively high VO2max's of highlanders are acquired by developmental adaptation. Several measures of ventilation and oxygen transport capacity differed significantly between ethnic groups, suggesting that growing European and Aymara boys may respond somewhat differently to the stress of high-altitude hypoxia. However, despite these differences, VO2max, an integrated measure of the overall functional capacity of the oxygen transport system, did not differ significantly between ethnic groups, suggesting that both groups are equally capable of meeting the body's oxygen requirements during maximal exercise at high altitude.