缺氧促进热休克蛋白70在肺动脉平滑肌细胞中的表达

缺氧性肺动脉高压中肺动脉结构重组,中膜平滑肌细胞增殖并迁移,但机制不明。本研究观察缺氧对肺动脉平滑肌细胞（ＰＡＳＭＣ）细胞周期、ＤＮＡ合成及细胞增殖的影响,并通过观察缺氧对ＰＡＳＭＣ热休克蛋白７０（ＨＳＰ７０）表达的影响,初步探讨缺氧的作用是如何介导的。结果表明缺氧可直接或协同内皮质－１促进ＰＡＳＭＣ ＤＮＡ合成及细胞增殖,并可增加ＨＳＰ７０在ＰＡＳＭＣ中的表达。     

沿海防护林体系热效应的遥感分析

沿海防护林体系热效应的遥感分析王述礼,金昌杰,关德新（中国科学院沈阳应用生态研究所１１００１５）ＲｅｍｏｔｅＳｅｎｓｉｎｇＡｎａｌｙｓｉｓｏｎｔｈｅＨｅａｔＥｆｆｅｃｔｓｏｆＣｏａｓｔａｌＳｈｅｌｔｅｒｂｅｌｔＳｙｓｔｅｍ．￥ＷａｎｇＳｈｕｌｉ;Ｊｉ...     

Influence of elevated ambient temperature after breeding on plasma corticoids, estradiol and progesterone in gilts

Thirty Yorkshire gilts were used to determine the influence of elevated ambient temperature during days 8 to 16 after breeding on concentrations of progesterone, corticoids and estradiol in plasma. Gilts were mated to a boar between 0800 and 1000 hr of the first day (day 0) and each subsequent day of estrus. On day 5 or 6, 22 gilts were anesthetized and a cannula was placed in the anterior vena cava. Gilts were randomly allotted to either control (23+/-1 C) or hot (35+/-1 C for 12 hr and 32+/-1 C for 12 hr daily) environmental chambers on day 8. Gilts were bled twice daily (0800 and 2000 hr) on days 9 through 16, then once daily until day 28. A third group of noncannulated gilts was bred and assigned to the control chamber. All cannulated gilts were injected intravenously with 25 IU of ACTH on day 16, and frequent blood samples were collected. Concentrations of progesterone in plasma were similar for heat-stressed and control gilts that were pregant. However, progesterone in plasma was reduced during days 13 to 19 in nonpregnant heat-stressed gilts compared to the pregnant and nonpregnant control gilts. Concentrations of estradiol in plasma were greater in nonpregnant heat-stressed gilts than in nonpregnant control and all pregnant gilts on days 10, 11 and 12 after estrus. Concentrations of corticoids and progesterone in plasma after infusion of ACTH on day 16 after breeding were reduced in heat-stressed nonpregnant gilts compared to heat-stressed pregnant, control pregnant and control nonpregnant gilts. These data indicate that reduced reproductive performance which occurs after exposure of gilts to increased ambient temperature during days 8 to 16 after breeding may be related to altered endocrine function.     

Small population instability and island settlement patterns

A model of extinction probability, based on the general theory of island biogeography [MacArthur and Wilson, 1967], is proposed for humans on oceanic islands; extinction probability is determined by island carrying capacity, frequency and amplitude of fluctuations in resources determining carrying capacity, and the net costs of contact and exchange between population units. The model predicts that extinction probability will determine island settlement patterns within an island group resulting in nonsettlement of islands with low carrying capacities and settlement of all islands with high carrying capacities. Data examined from the Marshall Islands tend to support the model. The model is extended to initial atoll colonization patterns. Possible requirements for initial settlement are suggested.Deceased.     

Species richness and endemism in the Usambara mountain forests,Tanzania

The East Usambara Mountain forests constitute what is probably one of the richest biological communities in Africa in terms of plant and animal species numbers and endemic taxa. This review presents brief accounts of the flora and of three invertebrate and four vertebrate groups and shows the percentage endemic taxa to vary from 2% (mammals) to 95% (millipedes) as a proportion of the true forest species. Notes are given on the geology, soils, climate and present land use of the Usambaras. Biological richness is considered to be due to long periods of isolation and geological stability coupled with periods of species immigration during times of re-establishment of a continuous forest cover. The nature of the endemic elements is briefly discussed. Evidence is given to show that the forests are subject to increasing pressure from legal and illegal encroachment due to agriculture (tea, cardamon, subsistence) and forestry timber operations. Air photograph analysis shows a forest decrease of some 50% in the vicinity of Amani from 1954 to 1976. The low conservation status of most forest reserves and the lack of detailed knowledge on the distribution, status and biology of the endemic species means present conservation efforts are poor and haphazard. This review calls for greatly increased research inputs and a complete halt to all exploitation of natural forest areas until a long term conservation land use plan can be implemented.     

State of water in extremely halophilic bacteria: Heat of dilution ofHalobacterium halobium

Summary Heat of dilution ofHalobacterium halobium was measured when thick pastes of the bacteria, harvested throughout a complete growth cycle, were lysed by mixing with 40 times their volume of water in a microcalorimeter. A series of comparative measurements was made with pastes of bacteria previously disrupted by freezing and thawing but otherwise identical to the pastes of whole bacteria. The frozen-thawed pastes gave endothermic values some 18% greater than those obtained with intact bacteria; the difference was highly significant. Evidence was obtained that the mechanical component of bursting did not contribute to the difference between whole and lysed bacteria. On the other hand, when a correction was applied for heat of mixing of intracellular salts with extracellular NaCl, such as occurs when the bacteria lyse, the difference between whole and disrupted organisms was largely eliminated from exponential phase halobacteria but not from those harvested in stationary phase. It is concluded that there is no evidence, as reflected in heat of dilution, of abnormal solution properties of the cytosol of young halobacteria, which are rich in potassium. On the other hand, and paradoxically, some doubt remains about stationary phase organisms whose cytosol has a much higher Na⁺ content (and Na/K⁺ ratio) than the cytosol of exponential phase bacteria.     

The pteridophytes of Mauritius (Indian Ocean): ecology and distribution

A survey of the pteridophytes of Mauritius is presented, including a summary of their habitats, ecology, and phytogeographical affinities. Of the 186 infrageneric taxa recorded from the island, 8 are adventive or naturalized, and 27 are presumed rare or extinct. Major ecological groupings are presented and species are listed for both indigenous and secondary plant communities.     

Heat-transfer relations of avian nestlings

1. 1.|To determine the thermoregulatory prowess of altricial nestlings, we conducted both equilibrium and transient analyses of white-crowned sparrow nestings, a representative fringillid.

2. 2.|For an individual nestling at thermal equilibrium, feather development is the major factor reducing heat loss after 2 days of age; tissue- and boundary-layer resistances are of minor importance.

3. 3.|The nest substantially reduces wind speeds near the nestlings. Heat transfer through the nest material is of only moderate importance. Evaporation also appears to be a small proportion of total heat loss during hypothermia in natural environments.

4. 4.|Net long-wave radiant exchange is also minor, but short-wave radiation is potentially a major component of the nestling's energy budget, approaching the magnitude of maximal metabolic heat production.

5. 5.|When nestlings cool, their body mass and metabolic rate are also major importance in determining the rate of cooling, and (for metabolism) the equilibrium temperature as well.

6. 6.|The huddling together of nestlings is perhaps the single most important factor affecting heat transfer.

7. 7.|An older brood actually has more insulation than does an adult in the same microclimate.