Morphological variability of geographically distinct populations of the estuarine copepod Acartia Tonsa

Variations in the number of spines on the left and right posterior dorsal and posterior margins of the prosome as well as the length of the prosome of Acartia tonsa from three estuaries, the upper western side of the Chesapeake Bay, Montauk Bay near the eastern end of Long Island Sound and the coast of Peru were determined. The length of the prosome and number of spines in each of the four locations were used as an indication of morphological similarity between the populations.     

Competition between electron acceptors in photosynthesis: Regulation of the malate valve during CO2 fixation and nitrite reduction

For maximal rates of CO₂ assimilation in isolated intact spinach chloroplasts the generation of the adequate NADPH/ATP ratio is achieved either by cyclic electron flow around photosystem I or by linear electron transport to oxaloacetate, nitrite or oxygen (Mehler-reaction). The interrelationships between these poising mechanisms turn out to be strictly hierarchical. In the presence of antimycin A, an inhibitor of ferredoxin-dependent cyclic electron transport, the reduction of both, oxaloacetate and nitrite, but not that of oxygen restores CO₂ fixation. When oxaloacetate and nitrite are added at low concentrations simultaneously during steady-state CO₂ fixation, the reduction of nitrite is clearly preferred over the reduction of oxaloacetate, but CO₂ fixation is not influenced. Nitrite reduction is not decreased upon addition of oxaloacetate, but vice versa. This is due to the regulation of NADP-malate dehydrogenase activation by electron pressure via the ferredoxin/thioredoxin system on the one hand, and by the NADPH/(NADP+NADPH) ratio (anabolic reduction charge, ARC) on the other hand. Thus the closing of the malate valve prevents drainage of reducing equivalents from the chloroplast (1) when a low ARC indicates a high demand for NADPH in the stroma and (2) when nitrite reduction reduces the electron pressure at ferredoxin. The malate valve is opened when cyclic electron transport is inhibited by antimycin A. Under these conditions the rate of malate formation is higher than in the absence of the inhibitor even in the presence of oxaloacetate, thus indicating that the regulation of the malate valve functions at various redox states of the acceptor side of Photosystem I.Abbreviations ARC anabolic reduction charge (NADPH/(NADP+NADPH)) - Chl chlorophyll - DTT dithiothreitol; Fd-ferredoxin - NADP-MDH NADP-malate dehydrogenase - OAA oxaloacetate - PS photosystem - qN non-photochemical quenching - qP photochemical quenching - _E quantum efficiency of PS II Dedicated to Prof. Dr. Hans Walter Heldt on the occasion of his 60th birthday.     

Transpiration measurements on apple trees with an improved stem heat balance method

Since the late eighties a handy and user-friendly sap flow meter (Dynagage®) is on the market which can quantify 0205 the sap flow through intact plant stems, based on the stem heat balance method. The documentation about its accuracy and reliability, however, is still too limited to use it as a standard method in field experiments with apple trees. We therefore tested this commercial system on potted apple trees (Malus domestica L.; cv. Red Elstar and Jonagold; on rootstock M9 vf) with stem diameters of 1.8 to 4 cm. The measured sap flow was compared with mass loss measured by an automated balance, supposing the total mass loss of the trees was equal to the water loss by transpiration. The results revealed three major problems:

Developmental changes in the diurnal water budget of the grape berry exposed to water deficits

The diurnal water budget of developing grape (Vitis vinifera L.) berries was evaluated before and after the onset of fruit ripening (veraison). The diameter of individual berries of potted ‘Zinfandel’ and ‘Cabernet Sauvignon’ grapevines was measured continuously with electronic displacement transducers over 24 h periods under controlled environmental conditions, and leaf water status was determined by the pressure chamber technique. For well-watered vines, daytime contraction was much less during ripening (after veraison) than before ripening. Daytime contraction was reduced by restricting berry or shoot transpiration, with the larger effect being shoot transpiration pre-veraison and berry transpiration post-veraison. The contributions of the pedicel xylem and phloem as well as berry transpiration to the net diurnal water budget of the fruit were estimated by eliminating phloem or phloem and xylem pathways. Berry transpiration was significant and comprised the bulk of water outflow for the berry both before and after veraison. A nearly exclusive role for the xylem in water transport into the berry was evident during pre-veraison development, but the phloem was clearly dominant in the post-veraison water budget. Daytime contraction was very sensitive to plant water status before veraison but was remarkably insensitive to changes in plant water status after veraison. This transition is attributed to an increased phloem inflow and a partial discontinuity in berry xylem during ripening.     

Pleural Fluid Adenosine Deaminase and Lymphocyte Proportion: Clinical Usefulness In the Diagnosis of Tuberculosis

Adenosine deaminase (ADA) and lymphocyte proportion are known to be independently elevated in tuberculous effusions, but are non-specific, and false positive results are frequent. to overcome this problem the combined use of both parameters was prospectively studied in 276 patients with pleural effusion seen at Porto Alegre, Brazil. Using a cut-off level of 40 U/l at 37°C (method of Giusti¹⁹) for ADA activity and lymphocyte proportion of more than 50%, the correct diagnosis of tuberculosis (sensitivity) was made in 90.7% (CI 87.3–94.1%) of 54 patients. A specificity of 97.7% (CI 95.9–99.5%) was recorded. Five false positive diagnoses of tuberculous effusion were made. Five false negative diagnoses were made: three cases with haematogenous tuberculous dissemination with low ADA levels, and two other patients with low lymphocyte proportion. the combined use of ADA activity determination and lymphocyte proportion is a highly efficient diagnostic strategy of low cost, that merits wider use.     

The impact of hybrids between genetically modified crop plants and their related species: biological models and theoretical perspectives

Forces affecting the rate of spread and increase of hybrids between genetically modified crop plants and their related species remain qualitatively similar, irrespective of whether genetic modification was achieved using traditional methods, those of biotechnology or as a result of the natural evolutionary process. However, the precise magnitude of the forces and, consequently, the likely environmental impact of such hybrids, may depend strongly on the nature of the gene or genes introduced into the native species. While many classes of transgenes are similar to those manipulated by conventional breeding techniques or evolution, biotechnology offers the potential to introduce genes into crops which are novel both from the point of view of function and origin. The qualitative similarity between transgenes and the products of conventional or evolutionary modification suggests that a historical view of the environmental impact of hybrids between traditionally produced crops or exotic species and their relatives would be of use in estimating the probable fate of hybrids containing transgenes in the environment. However, with certain classes of transgenes for which there are no existing analogues, there will need to be greater care in assessing the possible risks associated with release into the environment.     

棉田生态系统能流经济阈值的初步研究

系统能流经济阈值（ＥＥＴ）为本项研究提出的新概念。它是指系统的初级生产者－作物向其它亚系统输出能量的允许临界值,由此产生的期望收益最大,系统能流经济阈值是一条仅与作用现丰量相关的动态曲线,与其他亚系统无直接关系,本文以末施药棉田为系统,提出能流经济阈值的研究方法为：建立能流动态模型;确定害虫防治代价,计算期望产出,运用计算机仿真语言对作物的能流输出参数进行优化并建立系统能流经济阈值模型。     

Wild pearl millet population (Pennisetum glaucum,Poaceae) integrity in agricultural Sahelian areas. An example from Keita (Niger)

Morphometric and isozymic analyses of adjacent cultivated and spontaneous populations of pearl millet in Niger revealed in the field a unique continuous distribution of phenotypes ranging from the most cultivated one to a typical cultivated × wild hybrid. The natural population was subdivided into a major wild group and a hybrid wild × cultivated group. Cultivated millet displayed an equilibrium state between recombined domesticated and wild genes. The natural population, in spite of a high rate of immigration by pollen from cultivated plants, retained its structure by apparently reproducing itself exclusively from the major wild group.     

Modulation of fibroblast response to maitotoxin along the cell division cycle

Maitotoxin (MTX) induces an increase of [Ca²⁺]_i and of phosphoinositide breakdown in various cell types. The [Ca²⁺]_i increase followed with fluorescent probes on cell suspensions has been described as slow and lasting, in contrast to the signal induced by calcium ionophores such as ionomycin. MTX effects have been studied on two fibroblastic cell lines, BHK21 C13 and FR 3T3, synchronized by serum deprivation treatment performed in an isoleucine-free medium for BHK21 C13 cells. In BHK21 C13 cells, flow cytometry analysis showed that two stages, G1/S and G2/M, were particularly susceptible to MTX treatment. Scanning laser cytometry demonstrated that calcium response of FR 3T3 fibroblasts followed with Indo-1 varied during the cell division cycle. The [Ca²⁺]_i increase was almost always vertical, but its delay after MTX addition lasted from zero (S and G2/M transition) to 10–20 min (G1) or more (G2). No [Ca²⁺]_i change could be detected during mitosis. The [Ca²⁺]_i response at the S phase was biphasic. These observations suggest that (1) the lasting response described in the literature represents a global cell population effect, and (2) cells are more sensitive to MTX at specific stages of the cell division cycle, which could correspond to periods when calcium signals have been detected in different cell types.Abbreviations MTX maitotoxin - [Ca²⁺]_i intracellular calcium concentration - IP₃ inositol triphosphate     

Determination of ammonium and L-Glutamine in hybridoma cell cultures by sequential flow injection analysis

A flow injection anlytical system based on a gas diffusion membrane module for ammonia and an ammonium flow-through potentiometric detector has been set up for measurement of L-glutamine and ammonium ions in hybridoma cell cultures. The main feature of the system is that the same basic analytical concept and equipment is used in both measurements, the only difference being for the determination of L-glutamine, in which the sample flows through an immobilized glutaminase cartridge. The conditions to enable the performance of both analysis consecutively, avoiding potential interferences by unwanted deamination of other compounds in the samples, have been determined. Finally, the proposed system has been compared with reference analytical methods for batch hybridoma cell culture experiments.