首页 | 本学科首页   官方微博 | 高级检索  
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   12篇
  完全免费   1篇
  2016年   1篇
  2013年   1篇
  2012年   1篇
  2011年   1篇
  2010年   1篇
  2009年   1篇
  2003年   1篇
  2002年   1篇
  2000年   1篇
  1997年   1篇
  1994年   1篇
  1990年   1篇
  1980年   1篇
排序方式: 共有13条查询结果,搜索用时 31 毫秒
Abstract: Catechol- O -methyltransferase (COMT) activity in the liver and kidneys of adult Fischer-344 (F-344) rats is only half of that in the same organs of Wistar-Furth (W-F) rats. The trait of low COMT activity in these animals is inherited in an autosomal recessive fashion. A comprehensive study of patterns of change in COMT activity during growth and development was performed to determine whether "temporal gene" effects might play a role in the inherited differences in enzyme activity present in adult animals. The COMT activity expressed per mg protein in liver and kidneys of newborn F-344 rats is only 50–60% of that in the same organs of W-F animals. The liver and the kidneys of newborn rats of both strains have COMT activity an order of magnitude higher than those in brain, heart, or blood. In addition, in both strains there are much larger increases in liver and kidney COMT activities during growth and development (5–10 fold) than in blood, brain, or heart (one- to twofold). Immunotitration with antibodies against rat COMT demonstrates that differences in immunoreactive COMT parallel differences in COMT activity, both between strains and within strains during growth and development. However, when the temporal patterns of change in enzyme activities in the liver and the kidneys of the two strains of rat are compared at multiple times during growth and development, no differences in the patterns are present. These results make it unlikely that temporal gene effects can explain the inherited differences in COMT activity in liver and kidneys of F-344 and W-F rats.  相似文献
It is often assumed that otolith growth is in some way dependent on somatic growth (i.e. that the two processes are coupled). We examined the relationships between sagitta radius and fork length in 0+ Atlantic salmon parr that would subsequently smolt aged 1 + (UMG fish) or 2+ (LMG fish). Repeated measurements of fork lengths of individually marked parr, taken over a 211-day period from first feeding, were compared to sagitta radii on the same measuring dates (obtained by analysis of daily increments). The results showed that there was a linear relationship between fork length and otolith radius in UMG parr. However, this was not true for LMG parr. These fish enter a state of natural anorexia in their first autumn (despite excess food), but their otoliths continued to grow at the same rate despite the virtual cessation of somatic growth; they had therefore developed disproportionately large otoliths by the end of the study period. The relative growth rates of soma and otoliths first changed in LMG fish in late July/early August; this is the most precise estimate yet obtained of the timing of divergence in the developmental pathways of UMG and LMG parr. The rate of sagitta accretion was consistently lower in LMG parr, possibly indicating a lower metabolic rate in these fish. The results are discussed in relation to previous theories of the relationship between otolith and somatic growth.  相似文献
皖南花猪11种血液生化指标的发育性变化及性别差异   总被引:1,自引:0,他引:1  
随机选择出生30、45、90、180日龄的皖南花猪公母各5头,测定了11项血清生化指标.结果显示:血糖(GLU)、总胆固醇(TC)、高密度脂蛋白胆固醇(HDL-C)、游离脂肪酸(FFA)、脂联素(ADP)、瘦素(leptin)和IgG有极显著的发育性变化(P<0.01);而甘油三酯(TG)、低密度脂蛋白胆固醇(LDL-C)、Iga和IgM等没有明显的发育性变化.母猪的TG、TC、HDL-C和IgM极显著或显著大于公猪(P<0.01或P<0.05),其他血清生化指标虽在总体上没有性别差异,但在有些日龄差异明显.大多表现为母猪在90或180日龄大于公猪.结果表明:皖南花猪血液生化指标有特定的发育性模式.并存在不同程度的性别差异.  相似文献
木霉对草酸耐受和消除作用的初步分析   总被引:1,自引:0,他引:1       下载免费PDF全文
【目的】草酸(Oxalic acid,OA)是灰霉菌(Botrytis cinerea)等植物致病菌的致病因子,一些木霉(Trichoderma spp.)生防菌可消除草酸并降低植物发病率,但其消除草酸防治病害的途径和机制尚未研究透彻。【方法】首先从42株木霉菌株中筛选出一株在30 mmol/L草酸胁迫下耐受性最强的哈茨木霉T. harzianum LTR-2,通过形态学方法观察和原位分析了不同浓度草酸胁迫下LTR-2的发育特征变化,并测定了草酸消除水平、滤液pH和菌丝干重,分析了LTR-2在草酸为唯一碳源的生长情况。通过Real-time PCR分析了OXDC基因LTR_4445在草酸处理下的表达水平。【结果】在PDA固体培养基中,25 °C半光照条件下培养5 d,在草酸浓度为50?80 mmol/L时,LTR-2可存活,但无正常菌落形态;在30?50 mmol/L浓度下,LTR-2先萌发厚垣孢子,而后再次萌发菌丝形成菌落;在<30 mmol/L浓度下,LTR-2发育正常,仅生长速度减缓。25 °C、160 r/min振荡培养5 d,LTR-2可消除草酸。在20 mmol/L浓度时,草酸消除率最高,为66.50%;10 mmol/L浓度中的消除率次之,为55.06%。草酸浓度>50 mmol/L时,消除能力下降为6.75%?38.94%。相应地,培养液pH被不同程度地提高,在10、20 mmol/L草酸浓度下提高的幅度更大。当草酸浓度<20 mmol/L时,木霉的菌丝干重有不同程度的提高。将草酸作为唯一碳源进行液体培养5 d时,在10、20 mmol/L浓度下,LTR-2可形成肉眼可见的绿色菌丝球,但高于50 mmol/L条件下无法生长。草酸处理下,LTR_4445表达水平上调。【结论】通过分析LTR-2在草酸胁迫条件下的形态特征变化及消除草酸的特性,暗示在木霉消除草酸作用中除了已知的草酸降解代谢途径,还存在响应草酸胁迫模式的转变、将草酸作为前体转化为营养物质的途径等其他消除途径。  相似文献
The larval patterns of marine invertebrates pose intriguing questions for both evolutionary and developmental biologists. However, combined investigations have been rare. Quantitative models analyze the selective factors that drive evolutionary change in larval nutrition and timing of metamorphosis. Developmental studies describe the morphogenesis characterizing ancestral and derived larval patterns. Rigorous evolutionary analysis of the transition to derived modes of development is lacking and detailed developmental and ecological data are needed to test and refine theoretical models. A major challenge facing studies of life cycle evolution is the elucidation of the genetic structure and covariance of important developmental and larval traits.  相似文献
Developmental patterns of embryonic heart rate were measured non-invasively in two procellariiform seabirds, the Laysan albatross (Diomedea immutabilis) and wedge-tailed shearwater (Puffinus pacificus), during prepipping and after pipping. The O2 pulse, defined as the O2 consumption per single heart beat, was calculated using the previously reported O2 consumption for these species. The embryonic heart rate of the albatross was not changed by internal pipping (initial pipping event in this species), remained unchanged during the prolonged internal pipping period and tended to increase, although insignificantly, with the initiation of external pipping (second pipping event). Heart rate in the shearwater remained unchanged during the late prepipping stages, did not change with external pipping (initial pipping event), but increased during the prolonged internal pipping period (second pipping event) and reached a maximum on the last day of incubation. The developmental pattern of heart rate in the shearwater was very similar to that reported previously for the brown noddy, a member of the order Charadriiformes but with the same pipping sequence. Developmental patterns of embryonic O2 pulse were also different between the two procellariiform seabirds. However, those of the shearwater and the noddy were similar. The sequence of access to atmospheric O2 during development and hatching may be an important factor determining the developmental patterns of embryonic heart rate and O2 pulse.Abbreviations A-VO2 difference, arteriovenous oxygen difference - BCG ballistocardiogram of egg - CV coefficient of variation - EP external pipping - HR heart rate - IP internal pipping - mass mass of freshly laid egg - SD standard deviation  相似文献
Ledermanniella (c. 44 species) is the largest podostemoid genus in Africa. This paper deals with the structure and development of the Ghanaian species Ledermanniella bowlingii (J.B. Hall) C. Cusset (subgenus Ledermanniella). Characters typical for L. bowlingii include: green ribbon-like roots with exogenous lateral roots and endogenous shoots up to 120 cm; most leaves 3–7 times forked, with intrapetiolar stipules; flowers solitary or in clusters, borne on elongate stems or directly on roots; each flower bud inverted within a spathella; flowers unistaminate; tricolpate pollen in dyads; ovary mainly unilocular but bilocular at the base due to a rudimentary septum; mature capsule with eight ribs, 1.0–1.8 mm long, containing 12–34 seeds, dehiscing by two equal valves; capsule stalk with pedicel (10 mm) and gynophore (2 mm); silica bodies absent in all plant parts. Several characters of L. bowlingii are described here for the first time. The paper shows that accurate morphological analyses of African Podostemaceae are badly needed. Received September 30, 2002; accepted November 20, 2002 Published online: March 24, 2003  相似文献
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号