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排序方式: 共有373条查询结果,搜索用时 536 毫秒
361.
In a preliminary study, cryosurgery of the prostate in patients with prostatic cancer has been observed to possess a biphasic effect on the proliferative responsiveness of peripheral blood lymphocytes (PBL) to the plant mitogen, phytohaemagglutinin. Phytohaemagglutinin-stimulated PBL cultured in autologous serum obtained up to 1 week postoperatively showed reduction from their preoperative levels. In contrast, cultures in homologous serum showed increased responsiveness following cryosurgery. Although depression of lymphocyte proliferation in autologous serum was transitory, gradually returning to approximate or exceeding levels of lymphocytic reactivity observed preoperatively, such depression may facilitate reduced host surveillance to potential infectious agents and to metastatic tumour cells, leading to an alteration of tumour-host homeostasis. Further studies will be required to delineate the possible clinical significance of the present observations.  相似文献   
362.
The in vitro stimulation of human and rabbit erythrocyte membrane Ca2+-ATPase activity by physiological concentrations of thyroid hormone has recently been described. To extend these observations to a nucleated cell model, Ca2+-ATPase activity in a membrane preparation obtained from rabbit myocardium has been studied. Activity of 5'-nucleotidase in the preparation was increased 26-fold over that of myocardial homogenate, consistent with enrichment by sarcolemma. Mean basal enzyme activity in membranes from nine animals was 20.8 +/- 3.3 mumol Pi mg membrane protein-1 90 min-1, approximately 20-fold the activity described in rabbit red cell membranes. Exposure of heart membranes in vitro to L-thyroxine (T4) (10(-10)M) increased Ca2+-ATPase activity to 29.2 +/- 3.8 mumol Pi (P less than 0.001). Dose-response studies conducted with T4 showed that maximal stimulatory response was obtained at 10(-10) M). Hormonal stimulation was comparable for L-T4 and triiodo-L-thyronine (T3) (10(-10) M). Tetraiodothyroacetic acid was without biological activity, whereas triiodothyroacetic acid and D-T4, each at 10(-10) M, significantly decreased enzyme activity compared to control (basal) levels. The action of L-T4 on myocardial membrane Ca2+-ATPase activity was inhibited by trifluoperazine (100 microM) and the naphthalenesulfonamide W-7 (50-100 microM), compounds that block actions of calmodulin, the protein activator of membrane-associated Ca2+-ATPase. Radioimmunoassay revealed the presence of calmodulin (1.4 micrograms/mg membrane protein-1) in the myocardial membrane fraction and 0.35 micrograms/mg-1 in cytosol. Myocardial Ca2+-ATPase activity, apparently of sarcolemmal origin, is thus thyroid hormone stimulable. The hormonal responsiveness of this calcium pump-associated enzyme requires calmodulin.  相似文献   
363.
刘迪  陈海  马羽赫  史琴琴  白晓娟 《生态学报》2023,43(8):3079-3089
厘清乡村振兴视角下农户生态系统服务依赖度及其多层次影响因素对落实乡村振兴措施、改善农户福祉具有一定实践意义。以生态脆弱区陕西省米脂县为例,基于价值法评估农户生态系统服务依赖度,同时分析乡村振兴视角下服务依赖度的村庄差异和农户差异,最后利用多层次模型揭示服务依赖度的影响因素。结果如下:(1)农户的服务依赖度均值为0.673;农户主要依赖供给服务,对调节和文化服务依赖较低;供给服务中主要依赖作物收益,对水果和牲畜依赖度较低。(2)示范村农户的服务依赖度高于非示范村,且各类服务依赖度存在较强村庄异质性。“作物+牲畜+调节服务”“作物+水果+调节服务”与“作物+调节服务”类型农户占比约80%,依赖度分别为0.690、0.835、0.410;服务类型多样化指数为2.882,且示范村多样化指数高于非示范村。(3)环境变量中,土壤保持能力较高的村庄,农户对作物与牲畜的依赖度越高;政府资金投入较多的村庄,农户对水果和文化服务的依赖度越高;海拔与水果依赖度呈现显著正相关,人口密度与调节服务呈显著负相关。  相似文献   
364.
识别生态保护关键区域,优化新疆县域生态空间结构,对促进绿洲区域经济与生态环境和谐发展,提升人类福祉具有重要意义。以拜城县为研究区,通过生态系统服务价值综合评定结果确定生态保护的核心"源"区,利用最小阻力模型,结合GIS空间分析技术及CA-Markov模型,识别拜城县生态安全格局,分析其发展变化趋势,探究生态空间布局调整策略,完善县域生态空间网络体系,结果表明:(1)研究期内,拜城县生态系统服务价值总量逐年上升,其中水源涵养、废物处理价值量增长最高,不同服务类型增长率差异较小。(2)分析2009、2016、2019拜城县生态安全格局特征发现,县域生态安全布局整体存在"源"地分布不均、廊道结构破碎且网络化程度低、生态脆弱区面积较大的现状特征。(3)基于2009、2016、2019年生态保护格局,同时依据生态"源"地及生态保护重要性用地的变化趋势,模拟2029年生态"源"地及其重要性等级区域分布,结合县域自然地理特征及总体发展规划,提出构筑"两带、三功能、四区、多中心、十廊道"的拜城县生态空间布局体系,为绿洲地区生态安全及区域生态文明建设提供参考。  相似文献   
365.
366.
石飞  杨庆媛  王成  江娟丽  胡蓉 《生态学报》2021,41(14):5747-5763
区域耕地休耕规模测算是耕地休耕空间配置的重要组成部分,从资源承载力视角理解,其本质是将休耕空间布局于耕地资源承载力相对较低的区域。立足于从区域耕地生态经济系统探索耕地休耕规模,运用能值分析方法和生态足迹方法,以生态严重退化地区、国家第一批休耕试点县的贵州省松桃县为案例区,修正了耕地能值生态足迹改进模型(ECEF,简称"修正模型")与耕地能值可持续指数(ESIcl),测算了松桃县2016年休耕面积范围值。结果表明:(1)耕地能值生态盈亏可以作为乡镇是否应该休耕的判定标准,基于此测算的最大休耕面积关键在于测算生态耕地面积。总体来看,全县耕地能值生态赤字,应该安排耕地休耕;从分乡镇来看,有3个乡镇可以不休耕、25个乡镇应该休耕。按照全县平均统计(SCAL)和按照分乡镇统计(STL),全县最大休耕面积分别19558.62hm2和17673.83hm2。最大休耕面积中等及以上等级的乡镇散布于4个区域的8个乡镇。(2)ESIcl可以作为休耕乡镇时序的判定标准,其优先休耕乡镇的最大休耕面积之和即为全县最小休耕面积。全县ESIcl偏低,应该适度休耕。优先休耕、适度休耕和暂不休耕的乡镇分别有2个、23个和3个。全县最小休耕面积1396.10hm2,占耕地面积的1.88%。按照全县平均统计(SCAL),全县休耕面积范围值1396.10-19558.62hm2,占总耕地面积的1.88%-26.34%;按照分乡镇统计(STL),全县休耕面积1396.10-17673.83hm2,占总耕地面积的1.88%-23.8%。修正模型和ESIcl为测算区域休耕规模提供了更加科学的技术方法,以期为其他类似区域开展休耕实践提供借鉴。  相似文献   
367.
R J Ablin 《Cryobiology》1974,11(5):416-422
The intensity and specificity of the immune response developed following each of three independent in situ freezing insults of the coagulating gland (anterior prostate) of immature male rabbits have been compared to that obtained following similar cryostimulation of the coagulating gland of mature bucks by the methods of tanned cell haemagglutination and gel diffusion precipitation. Results of this study offer confirmation to the previously demonstrated secondary or anamnestic immune response observed following multiple freezing of the rabbit coagulating gland and indicate further that the size and physiological status of the coagulating gland, i.e., the concentration of coagulating gland secretory autoantigens, are among the important variables in determining the cryosensitivity of a given animal. This cryosensitivity may be of particular significance in the prospective treatment of patients with prostatic cancer by cryoimmunotherapy. That is, the development of an immune response in such patients may reasonably be related to the concentration and subsequent release of prostatic tumourspecific or tumour-associated antigens.  相似文献   
368.
Recent studies suggested that prostaglandins (PGs) may play a role in the pathogenesis of retinopathy of prematuriry (ROP). To evaluate if PGs inhibitor, indomethacin, would affect the incidence or severity of the ble-blind controlled study of indomethacin for the closure of PDA. Twenty-three were in the control group and 24 in the indometchin group. Indirect ophthalmospic examinations wee performed from about 4 weeks of postnatal age and onward and needed. There was no significant differences between the groups with respect to birth weight, gestational age, postnatal age, Apgar score, and cardiopulmonary status shortly after birth and at the time of study.Six in the control and 2 in the indomethacin group (p=0.58) developed active ROP; one in each group developed cicatricial ROP. It appears that with current doses of therapy, indomethacin does not increase the incidence or severity of ROP.  相似文献   
369.
Abstract. Data from more than 900 vegetation plots surveyed in the evergreen shrublands of southern California were used to develop predictions of the distributions of eight dominant shrub species for a 3880 km2 region. The predictions, based on classification tree (CT) models, were validated using independent field data collected during a vegetation survey conducted in the 1930s. Presence and absence were correctly predicted an average of 75% of the time for the eight species. At the same time, these models minimized false positives, so that presence was predicted in the correct proportion of the cases for most species. The areal proportion of the landscape on which the species were predicted to occur was in the same rank order, and of the same magnitude, as their frequency (proportion of plots in which they occurred) within the field data sets. Predictive maps of species presence were overlaid and combined with an existing regional vegetation map. The shrub species ‘assemblages’ that resulted from this procedure had analogs with vegetation series defined using field data in previous studies. The resulting multiple species map will be used in a landscape simulation model of fire disturbance and succession.  相似文献   
370.
记述了江西省上高县发现的一窝不完整蛋窝的恐龙蛋。根据恐龙蛋宏观形态和蛋壳显微结构特征将其归入石嘴湾珊瑚蛋(Coralloidoolithus shizuiwanensis)。该窝恐龙蛋为近圆形球体,平均长径11.8 cm,平均赤道直径9.8 cm,蛋壳厚度可达2.5 mm;蛋壳由锥体层与柱状层组成,锥体层较薄,柱状层可分为内层、中间层和外层,内层发育致密的水平生长纹,中间层结构松散,含有大量暗色物质,中间层和外层发育次生壳单元。依据新标本的观察,明确珊瑚蛋属在石笋蛋科中以柱状层中间层结构松散为主要分类特征。上高新标本的发现,丰富了石嘴湾珊瑚蛋的古地理分布,同时也为上高地区晚白垩世含恐龙蛋红层的对比提供了新的证据。  相似文献   
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