Cryptic female choice favours sperm from major histocompatibility complex-dissimilar males

Cryptic female choice may enable polyandrous females to avoid inbreeding or bias offspring variability at key loci after mating. However, the role of these genetic benefits in cryptic female choice remains poorly understood. Female red junglefowl, Gallus gallus, bias sperm use in favour of unrelated males. Here, we experimentally investigate whether this bias is driven by relatedness per se, or by similarity at the major histocompatibility complex (MHC), genes central to vertebrate acquired immunity, where polymorphism is critical to an individual''s ability to combat pathogens. Through experimentally controlled natural matings, we confirm that selection against related males'' sperm occurs within the female reproductive tract but demonstrate that this is more accurately predicted by MHC similarity: controlling for relatedness per se, more sperm reached the eggs when partners were MHC-dissimilar. Importantly, this effect appeared largely owing to similarity at a single MHC locus (class I minor). Further, the effect of MHC similarity was lost following artificial insemination, suggesting that male phenotypic cues might be required for females to select sperm differentially. These results indicate that postmating mechanisms that reduce inbreeding may do so as a consequence of more specific strategies of cryptic female choice promoting MHC diversity in offspring.     

Going Where the Grass Is Greener: On the Study of Pastoral Mobility in Ferlo, Senegal

Based on a case study from Ferlo in Senegal, this paper discusses how pastoral mobility can be studied and understood with special emphasis on the use of GPS data. It has a dual objective: first, to investigate the methodological potential of using GPS data; second, to discuss the analytical use of GPS data for understanding mobility. The methodological potential for using GPS data is related to quantifying mobility and characterizing mobility patterns in space and time. Analytically, GPS data can be used in combination with qualitative information to make method triangulation. The GPS data can be used both prior to qualitative interviews to make informed questions about mobility and they can be used after qualitative investigations to illustrate points made or to reveal inconsistencies. The study shows that cattle walk about 5000 km per year (excluding night grazing) and different mobility patterns occur depending on the season. Issues such as the cattle complex and the notion of the independent, nomadic pastoralist are discussed in relation to pastoral mobility. Although cattle are of major importance to the Fulani, it is not important for them to walk with their animals, which are left to roam freely or supervised by paid herders. It is necessary to take into account all these issues if we want to go beyond the simple understanding of mobility as a means to find pasture and water.     

The protein-tyrosine phosphatase CD45 reaches the cell surface via golgi-dependent and -independent pathways

CD45 is a receptor protein-tyrosine phosphatase essential for T cell development and lymphocyte activation. It is highly glycosylated, with multiple isoforms and glycoforms expressed on the cell surface depending on the cell type and stage of differentiation. Interestingly, we found two pools of newly synthesized CD45 expressed on plasma membrane, one of which arrived by 5 min after synthesis. The remaining pool of CD45 was fully glycosylated and began to arrive at the cell surface at approximately 15 min. The rapidly expressed population of CD45 possessed exclusively endoglycosidase H-sensitive N-linked carbohydrate. Additionally, this rapidly expressed pool of CD45 appeared on the cell surface in a brefeldin A (BFA)-insensitive manner, suggesting that it reached the cell surface independent of the Golgi complex. The remaining CD45 trafficked through the Golgi complex, and transport proceeded via a BFA-sensitive mechanism. These data suggest that CD45 is able to reach the cell surface via two distinct routes. The first is a conventional Golgi-dependent pathway that allows fully processed CD45 to be expressed. The second utilizes an ill defined mechanism that is independent of the Golgi, is BFA-resistant, and allows for the expression of CD45 with immature carbohydrate on the cell surface.     

Apoptosis in activated rat pancreatic stellate cells

Proliferation and matrix synthesis by activated pancreatic stellate cells (PSC) participate in the development of chronic pancreatitis. Apoptosis of PSC may terminate this process but has not yet been studied in this particular cell type and was the aim of the present study. PSC were isolated from rat pancreas and characterized for expression of glial fibrillary acidic protein, alpha-smooth muscle actin, CD95, and tumor necrosis factor-alpha-related apoptosis-inducing ligand (TRAIL) receptors. Apoptosis was determined by TdT-UTP nick end-labeling reaction, annexin V binding, and caspase-8 activation. Both CD95L and TRAIL induced apoptosis in PSC. The apoptotic response was minor in PSC cultured for 7 days but increased markedly thereafter. Sensitization of PSC with culture duration was accompanied by increased expression of CD95 and TRAIL receptor 2 and no alterations of Flip expression or protein kinase B phosphorylation but was paralleled by the appearance of a COOH-terminal cleavage product of receptor-interacting protein. PSC apoptosis was also induced by PK-11195, a ligand of the peripheral benzodiazepine receptor. PSC apoptosis may be important in terminating the wound-healing response after pancreas injury and exhibits features distinct from apoptosis induction in hepatic stellate cells.     

Allatostatins of the tiger prawn,Penaeus monodon (Crustacea: Penaeidea)

More than 40 peptides belonging to the -Y/FXFGL-NH(2) allatostatin superfamily have been isolated and identified from the central nervous system (CNS) of the tiger prawn, Penaeus monodon (Crustacea: Penaeidea). The peptides can be arranged in seven sub-groups according to the variable post-tyrosyl residue represented by Ala, Gly, Ser, Thr, Asn, Asp, and Glu. Two of the residues (Thr and Glu) have not been observed in this position previously in either insects or crustaceans. Also reported for the first time for allatostatins, two of the peptides are N-terminally blocked by a pyroglutamic acid residue. The yields of certain peptides with similar amino acid sequences to each other were, in some instances, very different. As an example, the yield of ANQYTFGL-NH(2) was 2pmol, compared with ASQYTFGL-NH(2), with a yield of 156 pmol. There are several possibilities to account for this. If, as in all species so far investigated, there is a single allatostatin gene in P. monodon, then it would appear that different sub-populations have contributed mutant forms of particular peptides to the extract. Another, less likely possibility is that this species has more than one allatostatin gene, producing a variable array of peptides albeit in different molar ratios. Several peptides were present apparently as a result of the loss of one or more residues at the N-terminus of a larger form, either due to N-terminal degradation or specific post-translational processing. The number of peptides identified exceeds that for any other insect or crustacean species previously investigated. None is identical to any of the 60-70 insect allatostatins so far identified, and only three are common to other crustaceans. Immunohistochemical study of the CNS of P. monodon, with the same antisera as used to monitor the purification, confirms the widespread nature and complexity of allatostatinergic neural pathways in arthropods. Thus, all neuromeres of the brain, and all except one of the ventral cord ganglia, possess allatostatin neurons and extensive areas of allatostatin-innervated neuropile. In addition to the cytological evidence that the allatostatins act as neurotransmitters, associated with tissues as varied as eyes and legs, their presence in neurohemal areas such as the sinus gland and the perineural sheath of the thoracic ganglia suggests a neuroendocrine function. As well as posing a challenge to physiologists assigning specific functions to the allatostatins, their extensive intra-species multiplicity, linked to their inter-species variability, also presents a complex problem to geneticists and evolutionists.     

Crystal structure of human dipeptidyl peptidase IV/CD26 in complex with a substrate analog

Dipeptidyl peptidase IV (DPP-IV/CD26) is a multifunctional type II transmembrane serine peptidase. This enzyme contributes to the regulation of various physiological processes, including blood sugar homeostasis, by cleaving peptide hormones, chemokines and neuropeptides. We have determined the 2.5 A structure of the extracellular region of DPP-IV in complex with the inhibitor valine-pyrrolidide. The catalytic site is located in a large cavity formed between the alpha/beta-hydrolase domain and an eight-bladed beta-propeller domain. Both domains participate in inhibitor binding. The structure indicates how substrate specificity is achieved and reveals a new and unexpected opening to the active site.     

Characterization of a novel Eph receptor tyrosine kinase, EphA10, expressed in testis

In mammals, 14 members of the Eph receptor tyrosine kinase family have been described so far. Here we present a not yet described member of this family denoted EphA10. We report the identification of three putative EphA10 isoforms: one soluble and two transmembrane isoforms. One of the latter isoforms lacked the sterile alpha motif commonly found in Eph receptors. The gene encoding EphA10 is located on chromosome 1p34 and expression studies show that EphA10 mRNA is mainly expressed in testis. Binding studies to ephrin ligands suggests that this receptor belongs to the EphA subclass of Eph receptors binding mainly to ephrin-A ligands.     

Mapping of a milk production quantitative trait locus to a 420-kb region on bovine chromosome 6

A QTL affecting milk production traits was previously mapped to an interval of 7.5 cM on chromosome 6 in Norwegian dairy cattle. This article aimed to refine this position by increasing the map density in the region by a set of single-nucleotide polymorphisms and analyzing the data with a combined linkage and linkage disequilibrium approach. Through a series of single- and multitrait and single- and multipoint analyses, the QTL was positioned to an interval surrounded by the genes ABCG2 and LAP3. As no recombinations were detected in this interval, physical mapping was required for further refining. By using radiation hybrid mapping as well as BAC clones, the bovine and human comparative maps in the region are resolved, and the QTL is mapped within a distance of 420 kb.     

Identification of critical active-site residues in angiotensin-converting enzyme-2 (ACE2) by site-directed mutagenesis

Angiotensin-converting enzyme-2 (ACE2) may play an important role in cardiorenal disease and it has also been implicated as a cellular receptor for the severe acute respiratory syndrome (SARS) virus. The ACE2 active-site model and its crystal structure, which was solved recently, highlighted key differences between ACE2 and its counterpart angiotensin-converting enzyme (ACE), which are responsible for their differing substrate and inhibitor sensitivities. In this study the role of ACE2 active-site residues was explored by site-directed mutagenesis. Arg273 was found to be critical for substrate binding such that its replacement causes enzyme activity to be abolished. Although both His505 and His345 are involved in catalysis, it is His345 and not His505 that acts as the hydrogen bond donor/acceptor in the formation of the tetrahedral peptide intermediate. The difference in chloride sensitivity between ACE2 and ACE was investigated, and the absence of a second chloride-binding site (CL2) in ACE2 confirmed. Thus ACE2 has only one chloride-binding site (CL1) whereas ACE has two sites. This is the first study to address the differences that exist between ACE2 and ACE at the molecular level. The results can be applied to future studies aimed at unravelling the role of ACE2, relative to ACE, in vivo.     

Functional role of centrosomes in spindle assembly and organization

The centrosome is the main MT organizing center in animal cells, and has traditionally been regarded as essential for organization of the bipolar spindle that facilitates chromosome segregation during mitosis. Centrosomes are associated with the poles of the mitotic spindle, and several cell types require these organelles for spindle formation. However, most plant cells and some female meiotic systems get along without this organelle, and centrosome‐independent spindle assembly has now been identified within some centrosome containing cells. How can such observations, which point to mutually incompatible conclusions regarding the requirement of centrosomes in spindle formation, be interpreted? With emphasis on the functional role of centrosomes, this article summarizes the current models of spindle formation, and outlines how observations obtained from spindle assembly assays in vitro may reconcile conflicting opinions about the mechanism of spindle assembly. It is further described how Drosophila mutants are used to address the functional interrelationships between individual centrosomal proteins and spindle formation in vivo. © 2004 Wiley‐Liss, Inc.