日本落叶松引种区林地棕壤肥力的多变量分析

本研究从日本落叶松引种区林地棕壤9个主要理化性状及与之配套的17株优势木材料入手,采用多变量分析方法筛选出影响该地区日本落叶松生长的主要肥力因子为氮及磷,並据此将该林地棕壤划分为9个肥力类型。在进行聚类分析时,本研究的创新在于以任意二样本点在各主成份上的坐标值为变量,以各主成份的贡献率为权重,重新定义欧氏距离公式,对主成份坐标值聚类,使其更为合理、直观。同时采用回归分析拟合出理化性状间的多个回归方程。此研究为该林地科学施肥、速生丰产、永续利用提供了可靠的数量依据。     

Phagocytosis of Intravenously Administered Particles by Leukocytes Adhered to the Aortic Endothelium of the Rat

Phagocytosis has been used to characterize on a functional basis leukocytes adhered to the aortic endothelium of the rat. After intravenous administration of particles, phagocytosis was observed microscopically in esterase-positive leukocytes adhered to the endothelium in whole mounts of aorta. Polybead^R blue and red, 0.5 and 1 μm particle size, were inadequate because they were insufficiently colored to be identified individually at 400. Fluoresbrite^tm YG 0.25 and 0.50 μm at doses of 0.2 and 2 ± 0.3 m1/100 g, respectively, produced endothelial lesions. The same occurred with Monastral blue B^R (MbB) at 0.3 ml/100 g, red iron at 2 ± 16 mg/100 g and India ink at different concentrations depending on the supplier. At lower particle doses, lesions were not found. Deferoxamine mesylate 1.5 mg/100 g intravenous and allopurinol 5 mg/100 g intraperitoneal administered before the particles diminished the number and intensity of lesions. In none of the cases studied was the percentage of phagocytic cells greater than 50%. Clearance curves of MbB and Fluoresbrite^tm indicated rapid disappearance of particles from the blood. Results indicate that administration of particulate suspensions is not a good method for characterizing the phagocytic leukocytes adhering to the aortic endothelium because low doses produce rapid clearance of particles, thus impeding sufficient leukocyte loading, and higher doses produce endothelial lesions that often impair reliable counting of the adhering leukocytes.     

Clonal growth in woody plants: A review

Bulkiness, longevity and solidity of the body in woody plants enable the successive development of accessory shoots and adventitious roots in (1) both proximal and distal positions on organs, (2) both the above-ground and below-ground space, (3) both the aerial and soil environments. In monocotyledons, woody rhizomes play an essential role in the basic growth habit and architectural models. In dicotyledonous and a few gymnospermous trees, attached and successively disconnected ramets play a multilateral role in the pertinent life strategies. The majority of sprouts, coppice shoots and root suckers behave as opportunistic organs (a) serving as means of vegetative reproduction, (b) securing colonization of unoccupied ground, (c) increasing competitive power of the species within the community, (d) increasing survival rate of the stressed/disturbed genet in marginal habitats, (e) forming replacement for ageing or damaged organs, and (f) enabling reiteration of the genet's entire architectural model.     

Physico-chemical characteristics of a permanent Spanish hypersaline lake: La Salada de Chiprana (NE Spain)

La Salada de Chiprana Lake, located in the Ebro River basin, northeastern Spain, is the only permanent and deep water hypersaline ecosystem in all of western Europe. With a total surface of 31 ha and a maximum depth of 5.6 m, it has several basins bounded by elongated sandstone-bodies or ribbons which are paleochannels of Miocene age. Its salinity varied from 30 to 73 g 1^–1 during the 1989 hydrological cycle and the most abundant ions were magnesium and sulphate. Depth-time distributions of major physico-chemical variables demonstrated that the lake was stratified in two distinctive layers during most of the year. The chemocline disappeared only in October, with the complete overturn of the water column. In the deep water, three conditions occurred which allowed development of green sulphur bacteria populations: (1) oxygen depletion, (2) presence of hydrogen sulphide and (3) presence of light. Benthic microbial mats covered the sediments of shallow shores of moderate slope.     

Ammonium Injection Induces an N-Methyl-d-Aspartate Receptor-Mediated Proteolysis of the Microtubule-Associated Protein MAP-2

Abstract: We have shown previously that chronic hyperammonemia increases, in brain, the polymerization of microtubules that is regulated mainly by the level and state of phosphorylation of microtubule-associated protein 2 (MAP-2). Activation of the N -methyl- d -aspartate (NMDA) receptor dephosphorylates MAP-2. Because we have found that acute ammonia toxicity is mediated by the NMDA receptor, we have tested the effect of high ammonia levels on MAP-2 in brain. Microtubules isolated from rats injected intraperitoneally with 6 mmol/kg ammonium acetate showed a marked decrease of MAP-2. Also, the amount of MAP-2 in brain homogenates, determined by immunoblotting. was markedly reduced, presumably by proteolysis. The content of MAP-2 was decreased by ∼75% 1-2 h after ammonium injection and returned to normal values after 4 h. Proteolysis of MAP-2 was prevented completely by injection of 2 mg/kg MK-801, a specific antagonist of the NMDA receptor, suggesting that proteolysis is mediated by activation of this receptor. l -Carnitine, which protects rats against ammonia toxicity, also prevented MAP-2 degradation. Because activation of the NMDA receptor increases [Ca²⁺]_i, we determined whether rat brain contains a Ca²⁺-dependent protease that selectively degrades MAP-2. We show that there is a cytosolic Ca²⁺-dependent protease that degrades MAP-2, but no other brain proteins. The protease has been identified tentatively as calpain I, for it is inhibited by a specific inhibitor of this protease. Our results suggest that ammonium injection activates the NMDA receptor, leading to an increase in [Ca²⁺]_i, which activates calpain I. This, in turn, selectively degrades MAP-2. Possible implications in chronic hyperammonemic states and in the mechanism of ammonia toxicity are discussed.     

Regulation of ammonium ion assimilation enzymes inNeurospora crassa nit-2 andms-5 mutant strains

InNeurospora crassa thenit-2 andnmr-1 (ms-5) loci represent the major control genes encoding regulatory proteins that allow the coordinated expression of various systems involved with the utilization of a secondary nitrogen source. In this paper we examine the effect of thenit-2 andms-5 (nmr-1 locus) mutations on the regulation of the ammonium assimilation enzymes, glutamine synthetase and glutamate dehydrogenase, which are regulated by the products of these genes; however, glutamate synthase is not so regulated. Glutamine synthetase and glutamate dehydrogenase levels are also regulated by the amino nitrogen content. We present evidence that thems-5 andgln ^r strains, which behave very similarly in their resistance to glutamine repression, are different and map in different loci.     

Agave studies in Yucatan,Mexico. II. Nutritional value of the inflorescence peduncle and incipient domestication

Recent ethnobotanical exploration of henequen (Agave fourcroydes) in the Peninsula of Yucatan, Mexico, finds that inflorescence peduncles are used as emergency food and in the preparation of a fermented drink. Bromatological analysis and determination of total carbohydrates were made for the two length classes (ca. 3.30 m and ca. 0.60 m) which are consumed. The analysis of both the cultivated plant and its putative wild ancestor (Agave angustifolia) suggests that utilization of the inflorescence peduncles as food may have been involved in the initial stages of the history of its evolution under artificial selection, because the wild and the cultivated plants have similar palatability. The subsequent agricultural prevalence of annual crop species in the region was possibly responsible for the abandonment of henequen in the local diet. No significant differences are observed between the bromatological and total carbohydrate values of domesticated and wild plants. The preference for small inflorescence peduncles as a vegetable is a consequence of its significantly minor content of raw fiber and its larger content of total carbohydrates. As a fermented drink, longer peduncles are preferred because they provide more substrate material and because fiber can be eliminated by filtering. This agricultural byproduct, almost totally wasted, has potential value as a source of carbohydrates and raw fiber.