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At least 109 records · Page 6Linked to original sources
PubMed2002

Diversity of Anisoptera (Odonata): infering speciation processes from patterns of morphological diversity.

With roughly 2500 described species Anisoptera are among the species-poor suborders within insects. However, morphological and ecological variability are truly impressive. Anisoptera are classified into about 15 families of variable species richness. In this analysis phylogenetic research is integrated with comparative approaches to investigate possible explanations of differential speciation rates within this suborder. A short review of phylogenetic work based on morphological characters is compared to published molecular phylogenies. Sistergroup comparisons are used to elucidate whether a) sexual selection, b) duration of life cycles, or c) differentiation in body size, have had a detectable effect on speciation rate. In all three analyses effects of distributional range and latitudinal distribution were controlled. These analyses suggest sexual selection promotes speciation and an increase in body size is positively correlated with speciation rate. The evolutionary significance of these results is discussed and experimental approaches that should advance our understanding of anisopteran diversity are suggested.

Journal Article↗
PubMed1986

A joining-diversity-joining complex generated by inversion mechanism and a variable-diversity complex in the beta-chain gene of the human T-cell receptor.

We have analysed an inactive allele of the beta-chain gene of the T-cell receptor in a human T-cell line HPB-ALL. Comparison with germline sequences showed that HPB-ALL has a joining (J)-diversity (D)-J complex recombined in head-to-head configuration and a variable (V)-D complex in tail-to-tail configuration. These results demonstrate that the inversion mechanism functions in the beta-chain gene of the T-cell receptor. The presence of the V-D complex suggests that V-D recombination could occur prior to D-J recombination although there is no definite proof that the V-D complex is an intermediate to form the V-D-J complex.

Base Sequence↗
PubMed1996

Ryanodine receptor Ca2+ release channels: does diversity in form equal diversity in function?

Complexities in calcium signaling in eukaryotic cells require diversity in the proteins involved in generating these signals. In this review, we consider the ryanodine receptor (RyR) family of intracellular calcium release channels. This includes species, tissue, and cellular distributions of the RyRs and mechanisms of activation, deactivation, and inactivation of RyR calcium release events. In addition, as first observed in nonmammalian vertebrate skeletal muscles, it is now clear that more than one RyR isoform is frequently coexpressed within many cell types. How multiple ryanodine receptor release channels are used to generate intracellular calcium transients is unknown. Therefore, a primary focus of this review is why more than one RyR is required for this purpose, particularly in a tissue, such as vertebrate fast-twitch skeletal muscles, where a relatively simple and straightforward change in calcium would appear to be required to elicit contraction. Finally, the roles of the RyR isoforms and the calcium release events they mediate in the development of embryonic skeletal muscle are considered.

Animals↗
PubMed1998

[Diverse effects of glucocorticoids on diverse leucocytes apoptosis].

OBJECTIVE: To observe effects of glucocorticoids on the process of apoptosis in main inflammatory cells related to pulmonary inflammation. METHOD: Human peripheral blood neutrophil(PMN), eosinophil (EOS) and T lymphocyte(TLC) were cultured in vitro under glucocorticoids condition. In situ end-labeling technique of fragmented DNA was used to detect the dynamic fesatures of apoptosisin experimental collected cell. The peripheral PMN apoptosis in acute respiratory distress syndrome(ARDS) and EOS, TLC apoptosis in bronchial asthma were determined by the same method before and after treatment with glucocorticoids. RESULT: PMN, EOS and TLC showed signs of apoptosis spontaneously and no signs of surviving cells after 12 h/43 h, 15 h/65 h and 65 h/128 h of culture respectively. Dexamethasone accelerated EOS and TLC apoptosis, while inhibited PMN apoptosis. The PMN apoptosis in ARDS and EOS, TLC apoptosis in bronchial asthma were in various degreof inhibitory state. The above time of PMN, EOS and TLC apoptosis were 41.5 h/92.6 h,29.3 h/100 h,92.4 h/152.2 h respectively. The inhibitory state of PMN apoptosis was not influenced by glucocorticoids therapy, but the EOS and TLC apoptosis were relieved from their inhibitory state. CONCLUSION: Effects of glucocorticoids are different in diverse leucocyte apoptosis. This could have an differential significance in pulmonary inflammation.

Adolescent↗