Vestured pits and vestured vessel member walls in some Indian dicotyledonous woods

NAIR, M. N. B. AND MOHAN RAM, H. Y., 1989. Vestured pits and vestured vessel member walls in some Indian dicotyledonous woods. The woods of 144 taxa belonging to 38 families of angiosperms were examined for vestured pits and vestured vessel member walls using scanning electron microscopy. Vestured pits are present in 66 taxa (belonging to ten families) and vestured vessel member walls occur in only six taxa (belonging to three families). In Ehretiaceae and Euphorbiaceae vestures are present only in certain vessel members. In Wrighlia tinctoria , perforation plates containing vestures have been observed in addition to the presence of vestured pits. A classification of vestured pits based on their morphology and distribution is proposed by us. In all the types of vestured pits, vestures are present on the margin of the outer pit aperture or on the pit chamber wall. Occasionally, they are present in the pit canal, on the margin and in the vicinity of the inner pit aperture and rarely over the inner walls of the vessel members. The functions of vestured pits are not clear, although several suggestions are made. Whether or not these structures affect wood processing is not presently understood. It appears that vestured pits and vestured vessel member walls have diagnostic rather than phylogenetic value.     

斜胸叶蝉属一新种（同翅目：叶蝉总科：耳叶蝉科）

本文记述耳叶蝉科斜胸叶蝉属一新种:黄缘斜胸叶蝉Epiclinata flavomarinata sp.nov.。标本采自我国西藏。文中描述了新种的外部形态及雄性外生殖器构造特征,并与近似种进行比较,附有主要特征图。模式标本保存于中国科学院动物研究所。     

皖南、赣北奥陶纪笔石立体标本形成环境的初步研究*

皖南、赣东北和赣西北地区奥陶纪笔石地层发育良好,笔石化石丰富。宁国组和胡乐组均为笔石相地层,但笔石的保存特点并不相同。立体保存的黄铁矿化笔石标本主要见于宁国组,而胡乐组的笔石几乎均为薄膜标本。在比较宁国组和胡乐组在岩性、颜色、化石、矿物和元素等方面的特点后发现,两者有较明显的差异。这表明宁国组和胡乐组形成时的环境是不同的,前者为弱还原环境,后者为较强的还原环境,而在研究区内影响笔石体立体保存的主要因素为还原环境和较高的铁含量。在还原环境下,铁可呈Fe~(2+)存在,笔石体内含有硫,死亡后经降解作用可生成H_2S;H_2S和Fe~(2+)结合可使笔石体黄铁矿化,从而使笔石体硬化而呈立体保存下来。宁国组的铁含量明显高于胡乐组,这似可以解释宁国组产有较多笔石立体标本的原因。     

爪蟾(Xenopus laevis)的四倍体及其子一代

在爪蟾受精卵第一次有丝分裂中期进行静液压处理,抑制细胞质分裂从而得到四倍体。实验中获得三只存活了三年以上的四倍体雌性爪蟾。其中一只雌性与二倍体雄性爪蟾作人工催青得到受精卵。现已产卵三批,发育的胚胎400余,经检查子代染色体为三倍体。     

Lithium in drinking water and the incidences of crimes,suicides, and arrests related to drug addictions

Using data for 27 Texas counties from 1978-1987, it is shown that the incidence rates of suicide, homicide, and rape are significantly higher in counties whose drinking water supplies contain little or no lithium than in counties with water lithium levels ranging from 70-170 micrograms/L; the differences remain statistically significant (p less than 0.01) after corrections for population density. The corresponding associations with the incidence rates of robbery, burglary, and theft were statistically significant with p less than 0.05. These results suggest that lithium has moderating effects on suicidal and violent criminal behavior at levels that may be encountered in municipal water supplies. Comparisons of drinking water lithium levels, in the respective Texas counties, with the incidences of arrests for possession of opium, cocaine, and their derivatives (morphine, heroin, and codeine) from 1981-1986 also produced statistically significant inverse associations, whereas no significant or consistent associations were observed with the reported arrest rates for possession of marijuana, driving under the influence of alcohol, and drunkenness. These results suggest that lithium at low dosage levels has a generally beneficial effect on human behavior, which may be associated with the functions of lithium as a nutritionally-essential trace element. Subject to confirmation by controlled experiments with high-risk populations, increasing the human lithium intakes by supplementation, or the lithiation of drinking water is suggested as a possible means of crime, suicide, and drug-dependency reduction at the individual and community level.     

Consequences of the iron-dependent formation of ferredoxin and flavodoxin on photosynthesis and nitrogen fixation on Anabaena strains

Iron-dependent formation of ferredoxin and flavodoxin was determined in Anabaena ATCC 29413 and ATCC 29211 by a FPLC procedure. In the first species ferredoxin is replaced by flavodoxin at low iron levels in the vegetative cells only. In the heterocysts from Anabaena ATCC 29151, however, flavodoxin is constitutively formed regardless of the iron supply.Replacement of ferredoxin by flavodoxin had no effect on photosynthetic electron transport, whereas nitrogen fixation was decreased under low iron conditions. As ferredoxin and flavodoxin exhibited the same K_m values as electron donors to nitrogenase, an iron-limited synthesis of active nitrogenase was assumed as the reason for inhibited nitrogen fixation. Anabaena ATCC 29211 generally lacks the potential to synthesize flavodoxin. Under iron-starvation conditions, ferredoxin synthesis is limited, with a negative effect on photosynthetic oxygen evolution.     

Temperature-dependent changes in Photosystem II heterogeneity support a cycle of Photosystem II during photoinhibition

High light treatments were given to attached leaves of pumpkin (Cucurbita pepo L.) at room temperature and at 1°C where the diffusion- and enzyme-dependent repair processes of Photosystem II are at a minimum. After treatments, electron transfer activities and fluorescence induction were measured from thylakoids isolated from the treated leaves. When the photoinhibition treatment was given at 1°C, the Photosystem II electron transfer assays that were designed to require electron transfer to the plastoquinone pool showed greater inhibition than electron transfer from H₂O to paraphenyl-benzoquinone, which measures all PS II centers. When the light treatment was given at room temperature, electron transfer from H₂O to paraphenyl-benzoquinone was inhibited more than whole-chain electron transfer. Variable fluorescence measured in the presence of ferricyanide decreased only during room-temperature treatments. These results suggest that reaction centers of one pool of Photosystem II, non-Q_B-PS II, replace photoinhibited reaction centers at room temperature, while no replacement occurs at 1°C. A simulation of photoinhibition at 1°C supports this conclusion.Abbreviations BSA bovine serum albumin - Chl chlorophyll - DCMU 3-(3,4,-dichlorophenyl)-1,1,-dimethylurea - DCPIP dichlorophenol-indophenol (2,6-dichloro-4((4-hydroxyphenyl)imino)-2,5-cyclohexadien-1-one) - DPC diphenyl carbazide (2,2-diphenylcarbonic dihydrazide) - FeCN ferricyanide (hexacyanoferrate(III)) - _app apparent quantum yield of photosynthetic oxygen evolution - MV methyl viologen (1,1-dimethyl-4,4-bipyridinium dichloride) - PPBQ phenyl-p-benzoquinone - PPFD photosynthetic photon flux density - PQ pool plastoquinone - Q_B secondary quinone acceptor of PS II - RT room temperature - WC whole chain electron transfer     

A short history of nuclear activation analysis

The major developments in the field of nuclear activation analysis, from 1936 to 1989, are discussed. The developments are grouped into five consecutive time periods. The impact of various scientists on the development of the field in the first 35 years is also discussed.     

Anaerobic energy metabolism in the oligochaeteLumbriculus variegatus Müller

Summary Anoxia tolerance, glycogen degradation, free amino acid pool, adenylate energy charge and the accumulation and excretion of end products were monitored inLumbriculus variegatus Müller throughout 48 h of anoxia. A transition period lasting about 4 h could be distinguished from subsequent events during which malate, present in high amounts in the resting animals, is utilized, probably by conversion to succinate. Up to the 12th hour of anoxia there is an increase in concentration of free amino acids, except aspartate. Glutamate increases rapidly during the first half hour but decreases thereafter. Beginning with the second hour of anoxia the alanine concentration increases at the same rate glutamate concentration decreases, but the source of nitrogen during the first hour is unknown. It is argued that the nitrogen required for the synthesis of some of the amino acids is ultimately derived from proteolysis. After about 3 h of anoxia propionate and acetate are synthesized. At first these acids accumulate in the tissues, but after 4–6 h they are excreted into the surrounding medium. Acetate is excreted over the whole experimental period at a constant rate, whereas the excretion rate of propionate decreases slowly with time. The propionate/acetate ratio is in excess of 2. Classic malate dismutation is by far the most important mechanism in the maintenance of redox balance. Depletion of glycogen stores appears to play an important role in determining anoxic survival time. Due to extremely low activity of PEPCK the ratio of the specific activities of PK and PEPCK is very high. Further, the kinetic properties of pyruvate kinase do not support the assumption of a shift of the glycolytic carbon flow at the PEP level.Abbreviations PK Pyruvate kinase - PEPCK phosphoenolpyruvate carboxykinase - PEP phospho(enol)pyruvate - FBP fructose-1,6-bisphosphate - AEC adenylate energy charge - EMP-scheme Embden-Meyerhof-Parnas scheme of glycolysis - f _w fresh body weight - dw dry body weight     

Modeling in the museum: On the role of remnant models in the work of Joseph Grinnell

Accounts of the relation between theories and models in biology concentrate on mathematical models. In this paper I consider the dual role of models as representations of natural systems and as a material basis for theorizing. In order to explicate the dual role, I develop the concept of a remnant model, a material entity made from parts of the natural system(s) under study. I present a case study of an important but neglected naturalist, Joseph Grinnell, to illustrate the extent to which mundane practices in a museum setting constitute theorizing. I speculate that historical and sociological analyses of institutions can play a specific role in the philosophical analysis of model-building strategies.