A fluorescence depolarization study of the orientational distribution of crossbridges in muscle fibres

A fluorescence depolarization study of the orientational distribution of crossbridges in dye-labelled muscle fibres is presented. The characterization of this distribution is important since the rotation of crossbridges is a key element in the theory of muscle contraction. In this study we exploited the advantages of angle-resolved experiments to characterize the principal features of the orientational distribution of the crossbridges in the muscle fibre. The directions of the transition dipole moments in the frame of the dye and the orientation and motion of the dye relative to the crossbridge determined previously were explicitly incorporated into the analysis of the experimental data. This afforded the unequivocal determination of all the second and fourth rank order parameters. Moreover, this additional information provided discrimination between different models for the orientational behaviour of the crossbridges. Our results indicate that no change of orientation takes place upon a transition from rigor to relaxation. The experiments, however, do no rule out a conformational change of the myosin S 1 during the transition. Correspondence to: Y. K. Levine     

Characterization of Low pH-induced Catecholamine Secretion in the Rat Adrenal Medulla

Abstract: Catecholamine (CA) secretion was evoked when the isolated rat adrenal gland was perfused with HEPES-buffered Krebs solution acidified by the addition of HCI or by gassing with 95% O₂/5% CO₂. The secretion was detectable at pH 7.0 and increased with decreasing pH until at ～6.4. The low pH-induced CA secretion consisted of two phases, an initial transient response followed by a sustained phase. An intracellular Ca²⁺ antagonist, 3,4,5-trimethoxybenzoic acid 8-(N,N-diethylamino)octyl ester, selectively inhibited the initial phase of secretion. Both of the responses were resistant to nifedipine, a blocker of voltage-gated Ca²⁺ channel, but were completely inhibited in Ca²⁺-free (1 mM EGTA containing) solution. Adrenaline was an exclusive component in CAs released by low pH. The time course and extent of intracellular acidification caused either by low pH in the external medium or by the offset of a transitory NH₄CI application had no correlation with those of the secretory responses in the corresponding period. These results suggest that extracellular acidification preferentially activates adrenaline secretive cells to evoke CA secretion and that this low pH-induced CA secretion may be mediated by dihydropyridine-insensitive Ca²⁺ influx. Furthermore, the initial transient phase of the low pH-induced CA secretion might be caused by a Ca²⁺ release from intracellular stores, which is also induced by the Ca²⁺ influx.     

New technique in optical resolutions

The present paper illustrates the development of an advanced technique in optical resolution. Both of the amphetamine enantiomers can be obtained by a two-step distillation in nearly quantitative yield without any loss of the resolving agent. It is proved that the second-order interactions (H-bond) are sufficient for separation of enantiomers by distillation. © 1994 Wiley-Liss, Inc.     

Effect of exchangeable aluminium on the reduction of potato scab

The severity of the incidence of the fungal disease, potato scab, varies with different soil groups at the same soil pH. At a soil pH of 5.3, potato scab is easily controlled in soils of western Hokkaido (soil group A) by simply decreasing soil pH, but in soils from eastern Hokkaido (soil group B) it is not so easily controlled. The difference appears to be due to higher levels and exchangeable aluminium in Group A.Addition of sufficient aluminium or ferrous sulfate to a group B soil decreased the incidence of potato scab in a field experiment. Higher levels of aluminium sulfate depressed crop production. It is concluded that aluminium ions control the incidence of potato scab in acid soils. It is suggested that, in soils with low exchange acidity Y1, potato scab can be controlled by adding sufficient aluminium to increase their exchange acidity Y1 to above 7–8.     

Dynamics of the immune system response in cerebrospinal fluid and blood of SIVmac-infected rhesus monkeys

Paired sera and CSF samples were collected from SIV_mac-infected macaques. Animals infected with SIV_mac251 maintained low gag and high env-specific antibody levels in plasma. Increasing env-specific antibody titers in CSF were associated in one animal with strong intrathecal synthesis. SIV_mac239-infected monkeys revealed high antibody titers of gag and env-specificity, in one animal accompanied by weak intrathecal synthesis of virus-specific antibodies. In all animals, the CD4/CD8 ratio in CSF decreased faster compared to blood.     

Annual survival rate and age structure of habu,Trimeresurus flavoviridis (Viperidae), on Minna island,Japan: Estimation from removal trapping

A population of a viperid snake,Trimeresurus flavoviridis, was studied over 10 years by removal trapping on a small subtropical island in Japan. The sex ratio of trapped individuals changed seasonally, but was not biased to either sex in the whole sample of 258 individuals. The age of each individual was estimated through the size structure and the age-size relationship. The minimum number of individuals at the beginning of the study was estimated through accumulating older individuals trapped in the subsequent years. By assuming an annual natural survival rate in the course of this accumulation, an age structure was simulated which led to calculate a resulted natural survival rate. The assumed rate of 0.62 fitted best to the resulted one. The annual trapped proportion estimated on the simulated absolute number of individuals was higher in older individuals than in younger ones with the overall mean of 16%.     

Normalization of electromyogram in the neck-shoulder region

Linear and curvilinear electromyogram (EMG) normalization methods were compared among ten healthy men during a simulated work cycle demanding attention and static holding of the arm (Solitaire test). Maximal voluntary contractions (MVC) and gradually increasing contractions up to 70% of MVC were used for normalization in different arm postures. The test contractions studied included inward and outward rotations, abduction, shoulder elevation, and flexion in different arm positions. The shoulder load moment was calculated for the flexion tests using a simple two-dimensional model. The effect of arm posture on the EMG versus shoulder load moment relationship was studied on the following muscles: supraspinatus, infraspinatus, trapezius (three parts), deltoid (two parts) and pectoralis major. All muscles participated in the MVC tests performed, and its was not possible to suggest a single recommended test for each muscle. Differences in normalized EMG median values ranging up to 30% of MVC were found between linear and curvilinear normalization methods. Short-term repeatability of normalization based on a contraction with gradually increasing force was good. Arm posture affected the relationships between shoulder load moment and EMG activity of all muscles studied. Arm posture did not, however, have a significant effect on the estimated amplitude probability distribution functions during the simulated work task. Therefore, at least for the tasks studied, the principle of normalizing in the middle position of the range of movement was deemed acceptable.     

Mediterranean juvenile bluefin tuna: life history patterns

As there is a lack of information on the growth and migrations of bluefin tuna, information about them was gathered using the structural and chemical characteristics of their otoliths and mercury levels in body tissues as indicators of physiological and habitat characteristics. The otoliths of juvenile tuna caught in the Spanish Mediterranean littoral were studied. Otolith increments, assumed to be formed daily, were enumerated. Measurements by wavelength dispersive electron microprobe confirmed the presence of strontium in otolith tissue, and an inverse relationship between strontium/calcium (Sr/Ca) concentration ratio and temperature is suggested. Electron microprobe analyses combined with daily increment analyses of otoliths provided life history profiles for individual fish. Additional Sr/Ca concentration ratio data on fish supported the idea that Sr/Ca ratios can provide information on the environmental history of individual fish. Body concentrations of mercury were related to otolith analyses to suggest age structure, critical life history periods, growth environment, stock structure, food web position, and migration history. The techniques applied present an innovative approach to management-related problems, and the combination of chemical analyses with structural analyses promises to expand our knowledge of the life history of migratory fishes.     

Transpiration and drought resistance of Douglas-fir seedlings exposed to excess ammonium

 In a pot trial growth and transpiration of 3-year-old Douglas-fir seedlings on an acid, sandy soil was examined at a deficient (30 kg N ha^{–  1} year^{–  1}) and an excessive level (120 kg N ha^{–  1} year^{–  1}) of NH₄ application. Dissolved ammonium sulphate was applied to the pots weekly for two growing seasons. In half of the pots a complete set of other nutrients was applied in optimal proportions to the applied nitrogen. Water supply was optimal and transpiration was recorded. At the end of the second treatment season irrigation was stopped for 2 weeks during dry and sunny weather. Both high application of NH₄ and additional nutrients increased shoot growth and transpiration demand in the first treatment year. The root system was smaller at higher N level and this reduced water uptake accordingly. In the second year the combination of high NH₄ ⁺ and additional nutrients affected root functioning predominantly due to salinity effects and this seriously decreased water uptake capacity and shoot water potentials, finally resulting in tree death. Without addition of other nutrients the high NH₄ ⁺ application resulted in a high degree of soil acidification, which damaged the roots, that showed a decrease in water uptake capacity. At the low NH₄ supply level soil acidification was lower, and root functioning was not affected, and the trees recovered quickly from the imposed drought. Higher needle K and P status depressed transpiration rates at the low NH₄ application rate. Received: 9 January 1995 / Accepted: 18 September 1995     

Site-specific isotope fractionation of hydrogen in the biosynthesis of plant fatty acids

The overall deuterium content of plant lipids has been investigated by isotope ratio mass spectrometry (IRMS), and the site-specific natural isotope fractionation of hydrogen has been studied by ²H-NMR at natural abundance (SNIF-NMR). An analytical strategy has been developed in order to exploit the isotopomeric composition determined in clusters associated with different chemical sites of one or several fatty acid components. The method, which combines spectrometric and chromatographic data, enables isotopic criteria to be directly derived from raw vegetable oils containing in general two saturated and two unsaturated fatty acids. These results provide new information on isotopic fractionation caused by biochemical, physiological and natural environmental effects. Some alternation in the molecular deuterium distribution has been detected which may be related to the mechanism of fatty acid elongation. The successive methylene groups introduced through malonyl CoA are the subjects of different kinetic isotope effects since one of them is exclusively derived from NADH whereas the other has a contribution from pyruvate. A discriminant analysis of the cluster isotopic parameters enables several kinds of botanical precursors to be distinguished. The authenticating performances can be improved by taking into account the influence of climatic effects related to the region in which the plant grew.