Cloning of the gene and cDNA for mammalian beta-adrenergic receptor and homology with rhodopsin

The adenylate cyclase system, which consists of a catalytic moiety and regulatory guanine nucleotide-binding proteins, provides the effector mechanism for the intracellular actions of many hormones and drugs. The tissue specificity of the system is determined by the particular receptors that a cell expresses. Of the many receptors known to modulate adenylate cyclase activity, the best characterized and one of the most pharmacologically important is the beta-adrenergic receptor (beta AR). The pharmacologically distinguishable subtypes of the beta-adrenergic receptor, beta 1 and beta 2 receptors, stimulate adenylate cyclase on binding specific catecholamines. Recently, the avian erythrocyte beta 1, the amphibian erythrocyte beta 2 and the mammalian lung beta 2 receptors have been purified to homogeneity and demonstrated to retain binding activity in detergent-solubilized form. Moreover, the beta-adrenergic receptor has been reconstituted with the other components of the adenylate cyclase system in vitro, thus making this hormone receptor particularly attractive for studies of the mechanism of receptor action. This situation is in contrast to that for the receptors for growth factors and insulin, where the primary biochemical effectors of receptor action are unknown. Here, we report the cloning of the gene and cDNA for the mammalian beta 2AR. Analysis of the amino-acid sequence predicted for the beta AR indicates significant amino-acid homology with bovine rhodopsin and suggests that, like rhodopsin, beta AR possesses multiple membrane-spanning regions.     

Ecology: ultraviolet reflectance by the skin of nestlings

Birds can perceive the reflectance of ultraviolet light by biological structures. Here we show that the skin of the mouth and body of starling nestlings substantially reflects light in the ultraviolet range and that young in which this reflectance is reduced will gain less mass than controls, despite low background levels of ultraviolet and visible light in the nest. We suggest that this ultraviolet reflectance from starling nestlings and its contrast with surrounding surfaces are important for parental decisions about food allocation.     

Maternal nodal and zebrafish embryogenesis

In fish and amphibians, the dorsal axis is specified by the asymmetric localization of maternally provided components of the Wnt signalling pathway. Gore et al. suggest that the Nodal signal Squint (Sqt) is required as a maternally provided dorsal determinant in zebrafish. Here we test their proposal and show that the maternal activities of sqt and the related Nodal gene cyclops (cyc) are not required for dorsoventral patterning.     

Deficiencies in DNA damage repair limit the function of haematopoietic stem cells with age

A diminished capacity to maintain tissue homeostasis is a central physiological characteristic of ageing. As stem cells regulate tissue homeostasis, depletion of stem cell reserves and/or diminished stem cell function have been postulated to contribute to ageing. It has further been suggested that accumulated DNA damage could be a principal mechanism underlying age-dependent stem cell decline. We have tested these hypotheses by examining haematopoietic stem cell reserves and function with age in mice deficient in several genomic maintenance pathways including nucleotide excision repair, telomere maintenance and non-homologous end-joining. Here we show that although deficiencies in these pathways did not deplete stem cell reserves with age, stem cell functional capacity was severely affected under conditions of stress, leading to loss of reconstitution and proliferative potential, diminished self-renewal, increased apoptosis and, ultimately, functional exhaustion. Moreover, we provide evidence that endogenous DNA damage accumulates with age in wild-type stem cells. These data are consistent with DNA damage accrual being a physiological mechanism of stem cell ageing that may contribute to the diminished capacity of aged tissues to return to homeostasis after exposure to acute stress or injury.     

Partial revision of the Indo-Australian braconine wasp genus Gammabracon Quicke (Hymenoptera: Braconidae) with descriptions of new species from Indonesia (Mollucas), Malaysia,Philippines and Thailand

Ten distinctive new species of the taxonomically difficult braconine wasp genus Gammabracon Quicke, 1984 are described: G. apicoluteus sp. nov. from Malaysia (Negri); G. curticornis sp. nov. from Malaysia (Negri); G. philippinensis sp. nov. from the Philippines; G. siamensis sp. nov. from Thailand; G. striatus sp. nov. from West Malaysia; G. strandorum sp. nov. from Indonesia (Java), G. subvena sp. nov. from Malaysia (Negri and Sabah); G. townesorum sp. nov. from the Philippines; G. variipennis sp. nov. from Thailand; and G. wegeneri sp. nov. from Indonesia. Myosoma forticarinata Cameron, 1902 is transferred to Gammabracon, hence Gammabracon forticarinata comb. nov. A lectotype is designated for Gammabracon erythroura (Cameron). The status of Cratobracon strandiellus (Cameron) is discussed and a new combination proposed, Shelfordia strandiellus Cameron, 1910 comb. nov. (=Bracon strandiellus Cameron). Paucity of discrete morphological variation makes separation of most of the species with orange-red mesosoma, black metasoma and conspicuous back setae currently unrealistic and it may be that there is a single widespread and morphologically variable species.

http://zoobank.org/urn:lsid:zoobank.org:pub:56B8884E-99C8-4B53-9747-D011F552312D     

C 3 and C 4 Species Changes Identified by δ 13 C values of soil organic matter in a Colorado prairie

We measured carbon isotope signatures (δ 13 C) from 0-10 cm and 10-20 cm soil depth intervals for grassland soils near Boulder, Colorado. These grasslands included tall-, short-, and mixed-grass prairies that were grazed, ungrazed, or hayed. Soils exhibited δ 13 C signatures consistent with observations that current sites are a mix of C 3 and C 4 species, with C 3 plants more abundant in mixed-grass than in native tall- or shortgrass prairies. The δ 13 C signatures were not significantly different for grassland types; however, management treatments (grazing, no grazing, haying) significantly influenced changes in soil δ 13 C signatures from the 0-10 cm to 10-20 cm soil depth intervals. We observed a correlation ( r = 0.63) between isotopic values of surface soils and percent native species in total vegetation cover. Overall, the community type with the lowest percentage of nonindigenous species cover had the most enriched δ 13 C signature. Sites currently grazed by prairie dogs, cattle, or both herbivores had stronger C 3 signatures, indicating that grazing may have increased C 3 plant productivity in these communities at the expense of C 4 grasses. This finding differs from studies of native shortgrass steppe where grazing has the opposite effect on the relative abundance of these 2 functional groups of plants. This result, along with the correlation between C 3 isotopic values and nonnative vegetation abundance, provides evidence that management practices that maintain dominance of C 4 grasses should be encouraged.