利血平和丘脑下部促黄体素释放激素类似物(LHRH-A)对大鳞副泥鳅促性腺激素细胞的分泌活动和排卵的促进作用

利血平能使神经分泌细胞的儿茶酚胺贮存量减少甚至消耗殆尽,导致多巴胺作为GRIF的作用减弱,从而显著增强LHRH-A促进GtH分泌和诱导排卵的效应。对大鳞副泥鳅,利血平和LHRH-A同时注射或者利血平比LHRH-A提前3小时注射,都能激活GtH细胞,显著增强其分泌活动并诱导排卵。利血平的最低有效剂量为1—5微克/克体重。利血平(25微克/克体重) LHRH-A(0.05微克/克体重)的催产效果和多巴胺拮抗物pimozide(1微克/克体重) LHRH-A(0.05微克/克体重)的催产效果一样,排卵率都达到了100％。     

Histological,Biochemical, and Ultrastructural Studies on Hyperpigmented Human Skin Xenografts

The mechanisms for hyperpigmentation observed in human cutaneous xenografts placed on athymic nude mice was investigated. Histologic, biochemical, histochemical, and ultrastructural examinations were performed on human skin prior to grafting and at various times ranging from 2 weeks to 30 weeks post-grafting (PG). Hyperpigmentation was macroscopically visible on the graft as early as 4–6 weeks. The number of Dopa-positive melanocytes per unit area was increased at 2 weeks PG and remained elevated until 20 weeks PG. The surface area of the melanocytes, a measure of the activity of the cells, also increased significantly and remained above the pre-grafting size throughout the study. Western blot analysis using tyrosinase specific antibody (αTy-SP) revealed the presence of tyrosinase exclusively in the grafted skin from 2 weeks to 12 weeks PG tested. Histological and ultrastructural observations revealed the presence of numerous dendritic melanocytes, indeterminant clear cells suggestive of Langerhans cells, and dermal melanophages. The results of this study suggest that the observed hyperpigmentation in grafted tissue is caused by an increase in the number of Dopa-positive melanocytes and probably from enhanced melanin production. Extracts of proteins from the xenografts exhibited prominent differences in low and high molecular proteins between pre- and post-grafted skin. Among them, the exclusive appearance of a protein doublet with apparent mw ～14 kDa was found in grafted skin, and subsequent studies indicate it has potent effects on melanocyte function.     

Secretion of Hexosaminidase Isozymes by Tetrahymena*

SYNOPSIS. Tetrahymena pyriformis strain HSM secrete large quantities of lysosomal acid hydrolases into the medium. The finding that 2 isozymes of β-N-acetylhexosaminidase (2-acetamido-2-deoxy-β-D-glucoside acetamidodeoxyglucohydrolase; EC 3.2.1.30) could be resolved by DEAE ion exchange chromatography and of possible differences between the secreted mixture and the intralysosomal hexosaminidase activity suggested that Tetrahymena might prove useful for studies of the control of lysosomal hydrolase isozyme secretion. In the present paper, we report a considerable purification of these isozymes and describe a number of their kinetic properties. Four isozymes were isolated into 2 major forms, A₁ and B₁, and 2 minor forms, A₂ and B₂, which were similar to the respective major forms in all kinetic properties tested. Hexosaminidase B₁ has a molecular weight of ?93,000 daltons and is inhibited by high concentrations of p-nitrophenyl-N-acetyl-β-D-glucosaminide. The inhibition is reversed by ethanol. Hexosaminidase A₁ has a molecular weight of ?170,000 and is not inhibited by high concentrations of substrate. The A forms are relatively less active against p-nitrophenyl-N-acetyl-β-D-galactosaminide than the B forms. Neither hexosaminidases A₁ or B₁ has any endo-β-N-acetylhexosaminidase activity. Comparison of the properties of the 2 major isozymes suggested that measurements of activity obtained under different assay conditions could be used to quantitate the amount of each isozyme in a mixture of the two. Log- and early stationary-phase cells secrete ?20% of isozyme A and 80% of isozyme B into the medium or into a dilute salt solution. With increasing culture age the fraction of isozyme A secreted rises to over 90%. Supplementation of the proteose-peptone growth medium with glucose causes a decrease in total hexosaminidase subsequently secreted but with no change in proportion of each isozyme. Cells suspended in a dilute salt solution containing 0.1 mM L-propranolol secrete slightly more isozyme A than do control cells suspended without L-propranolol. Phenoxy-benzamine (0.2 mM) causes a slight decrease in the proportion of isozyme A released.     

Phase Change in Hedera helix: Induction of the Mature to Juvenile Phase Change by Gibberellin A3

A sensitive and reproducible method to obtain GA₃ induced morphological reversion of mature Hedera helix to the juvenile form has been developed. Dose response experiments indicate that GA₃ stimulates reversion over a 50–100 fold range with a half maximal response at approximately 0.5 μg GA₃ per plant. The individual characteristics involved in phase change revert to the juvenile form in a sequential manner as GA₃ dose is increased. Variations in light intensity from 1.2–3.6 × 10⁴ lux and temperature from 15 to 26°C do not affect this hormonal response. Other growth regulators including indoleacetic acid, kinetin, abscisic acid and (2-chloroethyl)phosphonic acid (Ethephon) are inactive but other gibberellins (GA₁ and a mixture of A₄–A₇) are active in stimulating reversion. Therefore, the response is specific for gibberellins as a class of hormones but non-specific for a particular form of gibberellin. The significance of this response in relation to juvenility in woody plants is discussed.     

Unravelling mitochondrial retrograde regulation in the abiotic stress induction of rice ALTERNATIVE OXIDASE 1 genes

Mitochondrial retrograde regulation (MRR) is the transduction of mitochondrial signals to mediate nuclear gene expression. It is not clear whether MRR is a common regulation mechanism in plant abiotic stress response. In this study, we analysed the early abiotic stress response of the rice OsAOX1 genes, and the induction of OsAOX1a and OsAOX1b (OsAOX1a/b) was selected as a working model for the stress‐induced MRR studies. We found that the induction mediated by the superoxide ion (O_2·^‐)‐generating chemical methyl viologen was stronger than that of hydrogen peroxide (H₂O₂). The addition of reactive oxygen species (ROS) scavengers demonstrated that the stress induction was reduced by eliminating O_2·^‐. Furthermore, the stress induction did not rely on chloroplast‐ or cytosol‐derived O_2·^‐. Next, we generated transgenic plants overexpressing the superoxide dismutase (SOD) gene at different subcellular locations. The results suggest that only the mitochondrial SOD, OsMSD, attenuated the stress induction of OsAOX1a/b specifically. Therefore, our findings demonstrate that abiotic stress initiates the MRR on OsAOX1a/b and that mitochondrial O_2·^– is involved in the process.     

Effects of light heterogeneity on growth of a submerged clonal macrophyte

Many studies have examined the effects of spatial heterogeneity in light supply on clonal plants in terrestrial environments, but few have examined those in aquatic conditions. In a greenhouse experiment, we grew the rhizomatous submerged macrophyte Vallisneria spiralis L. in containers in three homogeneous light treatments (100%, 65%, and 30% of ambient light coded as high, medium, and low light, respectively) and two heterogeneous ones differing in patch scale (small and large patch). The growth of V. spiralis decreased significantly with decreasing light availability. In the low light conditions, V. spiralis allocated greater biomass to shoots and developed elongated leaves. In the patchy treatments, ramets distributed in the light‐rich patches had significant costs in the large patch treatment, but not in the small patch treatment, while both small and large patch treatments had no significant benefits in the light‐poor patches. We conclude that V. spiralis could escape from adverse habitats and occupy the favorable habitats. Providing the same amount of light, responses of V. spiralis to different patch scales were different at the patch level, but not at the whole clone level. Together, growth of V. spiralis could not benefit from different patch scales in heterogeneous environments at the patch as well as the whole clone level.     

Overexpression and Immunological Characterization of the Serine Protease AgSp24D from the Malaria Mosquito, Anopheles gambiae

ABSTRACT Serine proteases are a class of proteolytic enzymes that play regulatory roles in protein processing and degradation. Previous molecular characterization of a mosquito serine protease, AgSp24D , indicated that it is a nondigestive chymotrypsin-like enzyme that is developmentally regulated, and is strongly expressed during the adult stage. Since the biological role of AgSp24D is unknown, we were interested in further characterizing the gene product. Thus, a polyclonal antibody against an AgSp24D fusion protein was produced. The antiserum recognizes two polypeptides of 50 kDa and 60 kDa in immunoblots of whole body homogenates from adult mosquitoes. Western blot analysis showed the strongest signal in a homogenate of thoraces. The signal was also detected in the head, midgut, cuticle plus fat body, ovary, and Malpighian tubules. No signal was detected in the hemolymph. A comparison of Anopheles gambiae, Aedes aegypti, Armigeres subalbatus, Drosophila melanogaster, Acheta domesticus, Manduca sexta , and bovine cardiac muscle and skeletal muscle showed that the polyclonal antibody cross-reacted to similarly sized polypeptides in all samples.     

Data-Mining Discovery of Pattern and Process in Ecological Systems

ABSTRACT Most ecologists use statistical methods as their main analytical tools when analyzing data to identify relationships between a response and a set of predictors; thus, they treat all analyses as hypothesis tests or exercises in parameter estimation. However, little or no prior knowledge about a system can lead to creation of a statistical model or models that do not accurately describe major sources of variation in the response variable. We suggest that under such circumstances data mining is more appropriate for analysis. In this paper we 1) present the distinctions between data-mining (usually exploratory) analyses and parametric statistical (confirmatory) analyses, 2) illustrate 3 strengths of data-mining tools for generating hypotheses from data, and 3) suggest useful ways in which data mining and statistical analyses can be integrated into a thorough analysis of data to facilitate rapid creation of accurate models and to guide further research.     

Geographical and seasonal gradients in hatching failure in Eastern Bluebirds Sialia sialis reinforce clutch size trends

Eggs untended during the laying phase can lose viability if exposed to high temperatures, such as those common at lower latitudes and late in the nesting season. The egg‐viability hypothesis states that constraints on viability during the laying phase could account for latitudinal and seasonal gradients in clutch size. We used 7 years’ worth of data collected by volunteers (The Birdhouse Network, co‐ordinated by the Cornell Laboratory of Ornithology) to look simultaneously at populations across the temperate breeding range of Eastern Bluebirds Sialia sialis in order to test three predictions of the egg‐viability hypothesis: the probability of hatching failure decreases at higher latitude and increases later in the season, and that these trends are strongest among large clutches. The overall average number of unhatched eggs relative to the total number of eggs laid was similar to that found by other studies (7.8%; range 6.8–8.9% annually; n = 32 567 eggs from 7231 nests from 530 study sites). Using generalized linear mixed models that controlled for the non‐independence of eggs within a clutch, we found that the ‘per‐egg’ probability of hatching failure was highest late in the season, highest at lower latitudes, and highest for both small (three‐egg) and large (six‐egg) clutches. The seasonal and geographical gradients in egg hatching failure reinforce documented seasonal and geographical trends in clutch size. Loss of egg viability prior to incubation currently provides the most parsimonious and consistent explanation of the observed patterns of hatching failure. However, alternative explanations for large‐scale patterns, particularly those not consistent with the egg‐viability hypothesis, warrant further research into other causes of hatching failure, such as microbes and infertility (related to extra‐pair mating). Our results demonstrate that investigating causes of variation in demography among local populations across a geographical gradient provides a potential means of identifying selection pressures on life‐history traits.