Systematics within Gyps vultures: a clade at risk

Background  

Populations of the Oriental White-backed Vulture (Gyps bengalensis) have declined by over 95% within the past decade. This decline is largely due to incidental consumption of the non-steroidal anti-inflammatory veterinary pharmaceutical diclofenac, commonly used to treat domestic livestock. The conservation status of other Gyps vultures in southern Asia is also of immediate concern, given the lack of knowledge regarding status of their populations and the continuing existence of taxonomic uncertainties. In this study, we assess phylogenetic relationships for all recognized species and the majority of subspecies within the genus Gyps. The continuing veterinary use of diclofenac is an unknown but potential risk to related species with similar feeding habits to Gyps bengalensis. Therefore, an accurate assessment of the phylogenetic relationships among Gyps vultures should aid in their conservation by clarifying taxonomic uncertainties, and enabling inference of their respective relatedness to susceptible G. bengalensis.     

Phosphorylation of membrane-bound guanylate cyclase of sea urchin spermatozoa

When Arbacia punctulata spermatozoa are incubated in seawater containing ammonium hydroxide (pH 8.8), the sperm plasma membrane-bound guanylate cyclase is dephosphorylated, its electrophoretic mobility increases (from an apparent molecular mass of 160 to 150 kD), and its enzymatic activity decreases 3.5-fold. Transfer of these cells into ammonium-free seawater (pH 7.4) results in the rephosphorylation of the cyclase, its reconversion to 160 kD, and recovery of the enzymatic activity lost upon dephosphorylation. This is the first direct demonstration that the activity of membrane-bound guanylate cyclase can be regulated by phosphorylation. A plasma membrane preparation is described that specifically supports the in vitro phosphorylation of the guanylate cyclase. This preparation will be useful in more detailed studies on the relationship between phosphorylation state and enzymatic activity of membrane-bound guanylate cyclase.     

Acquired drug resistance is accompanied by modification in the karyotype and nuclear matrix of a rat carcinoma cell line

A Walker 256 breast carcinoma cell line (WR) exhibiting a greater than 20-fold resistance to alkylating agents has been selected from a parent cell line (WS). Karyotypic heterogeneity was apparent, with a number of differences evident between WR and WS cells. The modal chromosome number for WS is 62; for WR, 54; double minutes were found only in WR, whereas spontaneous chromosomal aberrations were present in approx. 40% of the WS cells. No similar aberrations were observed in WR. Using SDS-gel electrophoresis and subsequent silver staining, differences in the profile of nuclear matrix proteins in WR and WS were observed. A diffuse band at approx. 70 kD in the WS was absent in WR cells. This protein was phosphorylated, together with a number of the other major matrix polypeptides. Levels of phosphorylated matrix proteins were approximately equivalent in both WR and WS cell lines, but matrix protein phosphorylation levels were approx. 2-fold higher than corresponding values for bulk nuclear proteins. Selective pressure of drug exposure has resulted in enhanced genetic stability in WR cells and observed karyotype differences are accompanied by modifications in the structural proteins of the nuclear matrix. Whether the observed differences are the cause or result of drug resistance remains to be established.     

Patterns of divergence during evolution of alpha 1-proteinase inhibitors in mammals

alpha 1-Proteinase inhibitor (alpha 1-PI), a member of the serine proteinase inhibitor superfamily, has a primary role in controlling neutrophil elastase activity within the mammalian circulation. Several studies have indicated that the reactive center region of alpha 1-PI, the amino acid sequence of which is critical to recognition of and binding to target proteinases, is highly divergent within and among species. This appears to be a consequence of accelerated rates of evolution that may have been driven by positive Darwinian selection. In order to examine this and other features of alpha 1-PI evolution in more detail, we have isolated and sequenced cDNAs representing alpha 1- PI mRNAs of the mouse species Mus saxicola and Mus minutoides and have compared these with a number of other mammalian alpha 1-PI mRNAs. Relative to other mammalian mRNAs, the extent of nonsynonymous substitution is generally high throughout the alpha 1-PI mRNA molecule, indicating greater overall rates of amino acid substitution. Within and among mouse species, the 5'-half of the mRNA, but not the 3'-half, has been homogenized by concerted evolution. Finally, the reactive center is under diversifying or positive Darwinian selection in murid rodents (rats, mice) and guinea pigs yet is under purifying selection in primates and artiodactyls. The significance of these findings to alpha 1-PI function and the possible selective forces driving evolution of serpins in general are discussed.      

Mitochondrial DNA polymorphisms in subterranean mole-rats of the Spalax ehrenbergi superspecies in Israel, and its peripheral isolates

Patterns of mitochondrial DNA (mtDNA) variation were examined in 133 mole-rats constituting all four chromosomal species (2n = 52, 2n = 54, 2n = 58, and 2n = 60) of the Spalax ehrenbergi superspecies in Israel, as well as the peripheral isolates of 2n = 60. In the main range of the complex, a total of 28 mtDNA haplotypes were found in 64 mole-rats, with most haplotypes being unique to either a single chromosomal species or population. mtDNA divergence increased from low to high diploid number in a north-to-south direction in Israel. Overall levels of mtDNA diversity were unexpectedly the highest in the 2n = 60, the youngest species of the complex. The mtDNA haplotypes can be separated into two major groups, 2n = 52-54 and 2n = 58-60, and a phylogenetic analysis for each group revealed evidence of a few haplotypes not sorted by diploid number. The overall patterns of mtDNA divergence seen within and among the four chromosomal species are consistent with the parapatric mode of speciation as suggested from previous studies of allozyme and DNA hybridization. In a separate data set the patterns of mtDNA variation were examined across the main geographic range and across peripheral semi-isolates and isolates of the 2n = 60 chromosomal species. Fifteen haplotypes were found in 69 mole-rats. High levels of mtDNA diversity characterized the main range, semi-isolated, and even some desert isolated populations. The peripheral isolates contain much mtDNA diversity, including novel haplotypes.      

Oxide-Based Solid-State Batteries: A Perspective on Composite Cathode Architecture

The garnet-type phase Li₇La₃Zr₂O₁₂ (LLZO) attracts significant attention as an oxide solid electrolyte to enable safe and robust solid-state batteries (SSBs) with potentially high energy density. However, while significant progress has been made in demonstrating compatibility with Li metal, integrating LLZO into composite cathodes remains a challenge. The current perspective focuses on the critical issues that need to be addressed to achieve the ultimate goal of an all-solid-state LLZO-based battery that delivers safety, durability, and pack-level performance characteristics that are unobtainable with state-of-the-art Li-ion batteries. This perspective complements existing reviews of solid/solid interfaces with more emphasis on understanding numerous homo- and heteroionic interfaces in a pure oxide-based SSB and the various phenomena that accompany the evolution of the chemical, electrochemical, structural, morphological, and mechanical properties of those interfaces during processing and operation. Finally, the insights gained from a comprehensive literature survey of LLZO–cathode interfaces are used to guide efforts for the development of LLZO-based SSBs.     

The cytolytic isolation of the cortex of the sea urchin egg

When the vitelline layer of sea urchin eggs (Lytechinus pictus) is disrupted by trypsin or dithiothreitol and the eggs are placed in an isosmotic medium devoid of Ca²⁺, cytolysis of the eggs occurs. During lysis the entire egg cortex peels off in one piece. Lysis is temperature and pH dependent and is inhibited by cytochalasin B. Cortices from unfertilized eggs contain seven major macromolecular components. A 42K-dalton component is believed to be actin, representing between 12 and 27% of the total protein. Cortices from fertilized eggs may contain between 50 and 65% actin. The actin appears to increase the strength of its attachment to the cortex after fertilization. This method of isolating the entire cortex may be useful for studying structural and enzymatic changes which may occur in the cortex during the cell cycle.     

The accessory function of murine intercellular adhesion molecule-1 in T lymphocyte activation. Contributions of adhesion and co-activation.

These studies demonstrate that the murine intercellular adhesion molecule-1 (ICAM-1) performs at least two roles in enhancing T cell activation. These two roles are evident in both of our experimental systems: with ICAM-1 expressed on the surface of transfected fibroblast cells, and with purified ICAM-1 immobilized on plastic. First, as has been documented by many investigators, ICAM-1 mediates adhesion between ICAM-1- and lymphocyte function-associated Ag-1 (LFA-1)-bearing cells. This adhesive interaction occurs even in the absence of T cell stimulation, although it is increased by addition of phorbol ester and calcium ionophore. Although ICAM-1 expression does markedly increase intercellular adhesion, the increase is significantly less than the improvement ICAM-1 expression makes in the Ag-presenting ability of MHC class II-transfected fibroblast cells. We have investigated whether this difference is due to LFA-1-mediated signaling, and we present data that demonstrates that although ICAM-1 does not deliver costimulatory signals required for T cell activation, the interaction of LFA-1 with ICAM-1 does synergize with TCR-transduced signals. This synergy is observed for ICAM-1 on live and on chemically fixed accessory cells, and for purified ICAM-1 molecules, but in all cases occurs only when the ICAM-1 and the TCR ligands are on the same surface. Finally, when the ICAM-1 is present on the surface of accessory cells, it enhances T cell activation by changing the Ag dose-dependence of the T cell, but when ICAM-1 and CD3 mAb are co-immobilized, ICAM-1 increases the peak response of the T cell without affecting the dose dependence of the response.