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81.
A variety of soil studies were carried out along a 920-km transect running SE to NW from near the border with northern Nepal,
through the Western Tibet Highlands (soils sampled at six locations at an elevation of about 4200 m), to the Takla Makan Desert.
This transect, which parallels the China-India border, covers a range of aridities. Annual precipitation decreased exponentially
(from 169 mm to ca. 50 mm) north-westwards along the transect. The humidity index also decreased exponentially to the desert
zone in the Western Tibet Highlands, and decreased further in the Takla Makan Desert because of the high temperature in the
latter area. Vegetation changed fromCaragana thorn-bush steppe, throughArtemisia sparse steppe, to desert. Soil properties were studied in relation to the humidity index. Organic C, total N, cation exchange
capacity, and very low C/N ratio values (a maximum of 12.8) of soils decreased with the decrease in humidity index. In contrast,
carbonate, pH (KCl), and sulfate increased exponentially. Available P and ammonia content were inversely related to the abundance
of carbonate, whereas nitrate increased where carbonate was abundant. Illite was the most abundant of the clay minerals, followed
in order by kaolinite and montmorillonite. 相似文献
82.
在颈七水平横断大鼠脊髓以诱发急性胃溃疡。结果表明:(1)脊髓横断动物的体温随环境温度而下降,体温的下降可能是诱发溃疡的重要原因之一;(2)注射肾上腺素可减轻溃疡和防止体温下降,且两者均呈剂-效关系;(3)切除肾上腺可使脊髓横断诱发的溃疡明显减轻,如补充注射地塞米松则可使之重新加重,但体温的下降在以上情况下均不受影响;(4)脊髓横断后胃粘膜泌酸和内分泌功能的改变可能与溃疡生成有关。 相似文献
83.
S. P. Kidambi J. R. Mahan A. G. Matches J. J. Burke R. R. Nunna 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1990,80(4):433-436
Summary Understanding polymorphism at the enzyme level is basic to its use in population and genetic studies. However, no such information is available on the variability among different sainfoin (Onobrychis) species. Therefore, our objective was to study the existence of genetic polymorphism for esterase in 17 Onobrychis species and three cultivars of O. viciifolia Scop. Three regions of banding were observed in all the materials tested, with the number of bands varying from 0 to 3, 3 to 14, and 1 to 2 bands in each of these zones, which have been designated EST1, EST2, and EST3 respectively. All the materials studied had unique banding patterns, the only common feature being that all of them, except one species, had isozyme 1. Identification was possible only for four species (O. iberica, O. kachetica, O. transcaucasica, and O. bieberstenii) and one cultivar (Nova) based on the banding patterns. Large diversity was evident from the wide range of percent similarity values (0%–79%). Subsequent studies should be directed in using these isozyme banding patterns as markers to the desirable agronomic and quality traits of different germplasm lines.This work was supported by USDA Specific Cooperative Agreement No. 58-7MN1-8-143 from the Plant Stress and Water Conservation Unit, USDA-ARS, Lubbock, Texas. Joint contribution of the Texas Tech University, Lubbock, Texas and the USDA-ARS. TTU Journal no. T-4-302 相似文献
84.
Roger A. Hoffman Peter Habeeb Gerald R. Buzzell 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1990,160(3):269-275
Summary Long-term increased or decreased circulating levels of thyroid hormones significantly modify porphyrin concentrations and morphology in the Harderian glands of male and female hamsters. Administration of T3 reduced porphyrin concentrations in females; this treatment or decreasing thyroid hormone levels with KClO4 suppressed the post-castration rise of porphyrins in males. Hypophysectomy led to increased porphyrins in the Harderian glands of males; this rise was suppressed in hypophysectomized males by T3 or T4. In females, hypophysectomy reduced porphyrins which were further reduced by daily administration of T3 or T4. These modifications in the normal females were identical in castrated males. Mitotic activity in the Harderian glands of females was stimulated by KClO4 and by hypophysectomy with or without exogenous T3. In males, castration increased mitotic activity which was suppressed by T3 and exacerbated by KClO4. Increased mitotic activity seemingly follows loss of tissue mass. The data show that thyroid hormones act directly on the Harderian glands rather than indirectly through modification of TSH synthesis/release. Female type glands in males are a consequence of loss of gonadal androgens by castration, or by suppression or loss of thyroid hormones by hypophysectomy or by treatment with KClO4. However, male type glands in females are the result of androgen treatment, and/or increased levels of thyroid hormones via reduced ambient temperatures or of photic input. We conclude that regulation of the Harderian gland appears to be different in the two sexes.Abbreviations
T
3
Triiodothyronine
-
T
4
Thyroxine
-
TSH
Thyroid Stimulating Hormone
-
KClO
4
Potassium Perchlorate
-
h
hours
-
ml
milliliter
-
mg
milligram
-
g
gram
-
male
-
female
-
castrated male
- AP
hypophysectomized
-
CON
Control
-
ALA
delta aminole-vulenic acid
-
HG
Harderian Gland 相似文献
85.
86.
西双版纳热带季节雨林植物种类多样性的一种研究方法 总被引:11,自引:1,他引:10
一、方法1.样地的选择样地分别选取热带干性季节雨林的典型代表——以箭毒木(Antiaris toxicaria)、龙果(Pouteria grandifolia)为标志的群落,以千果榄仁(Terminalia myriocarpa)、番龙眼 相似文献
87.
植物种群的空间分布型是生物在特定的条件下形成的,它反映了植物种群个体的散布状态以及对环境的适应性和生境对植物影响的生态反映的生态学关系,是一条可以了解凭种类组成研究演替的研究途径 森下正明(Morisita,1959)提出了扩散指数Io(Morisita's index);美国的Lloyd,(1967)提出了平均拥挤度(Mean crowding,m)这个颇有兴趣 相似文献
88.
Secretogranin II: Relative Amounts and Processing to Secretoneurin in Various Rat Tissues 总被引:2,自引:0,他引:2
Bernd Leitner Reiner Fischer-Colbrie Gerhard Scherzer Hans Winkler 《Journal of neurochemistry》1996,66(3):1312-1317
Abstract: Secretoneurin is a 33-amino-acid peptide produced in vivo from secretogranin II. An antiserum raised against this peptide recognizes both the free peptide and its precursors. By HPLC and radioimmunoassay we characterized the immunoreactive molecules and determined the levels of immunoreactivity in various rat organs. In adrenal medulla and to a lesser degree in the anterior pituitary processing of secretogranin II to secretoneurin was very limited, whereas in all other organs studied (brain, intestine, endocrine pancreas, thyroid gland, and posterior pituitary) a high degree of processing was apparent. Thus, practically all of the immunoreactivity was present as free secretoneurin. This was also true for serum. When the total amount of secretoneurin immunoreactivity was calculated for the various organs, the largest pools in descending order were in the intestine, CNS, anterior pituitary, pancreas, and adrenal gland. This makes it likely that secretoneurin in serum is mainly derived from the intestine. The high degree of processing of secretogranin II in most organs is consistent with the concept that this protein acts as a precursor of a functional peptide, i.e., secretoneurin. 相似文献
89.
AP-1-Related Proteins Bind to the Enkephalin CRE-2 Element in Adrenal Chromaffin Cells 总被引:1,自引:0,他引:1
Linda MacArthur 《Journal of neurochemistry》1996,67(6):2256-2264
90.
164 taxa were identified in the net zooplankton of the pelagial of L. Peipsi-Pihkva in 1909–1987, including 3 species of protozoans, 74 species of rotifers, 58 species of cladocerans, 28 species of copepods and 1 mollusc. One rotifer species, Ploesoma peipsiense Mäemets et Kutikova, has been described as new for science here. The zooplankton of L. Peipsi-Pihkva is remarkably rich in species including rarities in Estonia: Limnosida frontosa, Drepanothrix dentata, Bythotrephes longimanus, B. cederstroemi etc. Due to its large surface area, L. Peipsi-Pihkva provides a large scale of biotopes of a diverse trophic state and humic content, which support species with different ecological requirements. Most of the aquatory of the lake has lately been mesotrophic, favouring the coexistence of indicators of oligo- and mesotrophic state and species preferring a higher trophic state. The occurrece of 10 species of the genus Bosmina including B. berolinensis, B. gibbera, B. lilljeborgi, B. thersites and B. crassicornis, sparse in Estonian lakes, is the most noteworthy feature of the zooplankton of L. Peipsi-Pihkva. The coexistence of B. coregoni and B. berolinensis, B. gibbera, B. lilljeborgi etc. which were earlier regarded as subspecies of B. c. coregoni proves that they are different species producing usually no hybrids. The species composition was subjected to certain changes during the years under consideration. Larvae of Dreissena were first found in zooplankton in 1962. The oligo-mesotrophic indicator Holopedium gibberum occurred in the lake in 1909–1964, but was lacking in later samples. 相似文献