The human Ia system: Definition and characterization by xenogeneic antisera

The production of xenogeneic anti-Ia serum against Ia antigens in serum has been previously described in the mouse and we now describe the production of xenogeneic anti-human Ia antisera using similar methods. With an indirect resetting technique, Ia-like antibodies were shown to react with the majority of B cells (95%), a subpopulation of T cells, with carbonyl iron adherent cells, and with some E^–Ig^– null cells, but there was no reaction with red cells and platelets. These reactions were the same as those obtained with DRW antisera using cytotoxicity testing. In addition, antigens detected with xenogeneic antisera were also found in serum, where they were found to exist in a low molecular weight, dialyzable form. By the selective removal of different cell surface markers by cocapping, no association could be found with the specifities detected with the xenogeneic anti-Ia antisera and with surface Ig, ₂-microglobulin, or HLA-A and B specificities. Alloantibodies to DRW specificities (but not HLA-A, B specificities) were able to specifically block the binding of the rabbit anti-Ia antibodies to B cells, and reciprocal blocking of rabbit antisera by DRW antibodies was also observed. Several xenogenic antisera were produced by immunizing rabbits with the serum of different individuals. Each antiserum was shown to contain a number of different specificities, as they gave different reaction patterns with different individuals when testing was done both directly and by absorption. These xenogeneic anti-la sera also segregated in a family with HLA-A and B specificities. The detection of a polymorphic antigenic system segregating with the HLA complex, distinct from HLA-A and B specificities, and whose antigens occur predominantly on B cells is therefore described. Because of the similarity of the reactions of the xenogeneic antisera in man to those found in the mouse, and because of the close relationship to the DRW specificities, the system has been provisionally called the H.Ia system.Abbreviations used in this paper AET 2-aminoethyl isothiouronium bromide - ₂-M -2 microglobulin - BSA Bovine serum albumin - H.Ia Human Ia - HuRBC Human red blood cells - Ig Immunoglobulin - Ir Immune response - MHC Major histocompatibility complex - MLR Mixed lymphocyte reaction - NHS Normal human serum - NMS Normal mouse serum - PBL Peripheral blood lymphocytes - PBS Phosphate-buffered saline - RAHIg Rabbit anti-human immunoglobulin - RASIg Rabbit anti-sheep immunoglobulin - RFC Rosette-forming cells - SAHIg Sheep anti-human immunoglobulin - SARIy Sheep anti-rabbit immunoglobulin - SRBC Sheep red blood cells     

Endothelial FAK is essential for vascular network stability, cell survival, and lamellipodial formation

Morphogenesis of a vascular network requires dynamic vessel growth and regression. To investigate the cellular mechanism underlying this process, we deleted focal adhesion kinase (FAK), a key signaling mediator, in endothelial cells (ECs) using Tie2-Cre mice. Targeted FAK depletion occurred efficiently early in development, where mutants exhibited a distinctive and irregular vasculature, resulting in hemorrhage and lethality between embryonic day (e) 10.5 and 11.5. Capillaries and intercapillary spaces in yolk sacs were dilated before any other detectable abnormalities at e9.5, and explants demonstrate that the defects resulted from the loss of FAK and not from organ failure. Time-lapse microscopy monitoring EC behavior during vascular formation in explants revealed no apparent decrease in proliferation or migration but revealed increases in cell retraction and death leading to reduced vessel growth and increased vessel regression. Consistent with this phenotype, ECs derived from mutant embryos exhibited aberrant lamellipodial extensions, altered actin cytoskeleton, and nonpolarized cell movement. This study reveals that FAK is crucial for vascular morphogenesis and the regulation of EC survival and morphology.     

Antiprogestins as a model for progesterone withdrawal

The key physiological function of the endometrium is preparation for implantation; and in the absence of pregnancy, menstruation and repair. The withdrawal of progesterone is the initiating factor for breakdown of the endometrium. The modulation of sex steroid expression and function with pharmacological agents has provided an invaluable tool for studying the functional responses of the endometrium to sex steroids and their withdrawal. By administration of the antiprogestin mifepristone, it is possible to mimic progesterone withdrawal and study local events in early pregnancy decidua that may play a role in the process of early pregnancy failure. Our data indicate that antagonism of progesterone action at the receptor level results in an up-regulation of key local inflammatory mediators, including NF-kappaB, interleukin-8 (IL-8), monocyte chemotactic peptide-1 (MCP-1), cyclooxygenase 2 (COX-2) and others in decidua. Bleeding induced by mifepristone in the mid-luteal phase of the cycle is associated with changes in the endometrium similar to those that precede spontaneous menstruation including up-regulation of COX-2 and down-regulation of PGDH. Administration of antagonists of progesterone provide an excellent model to study the mechanisms involved in spontaneous and induced abortion as well as providing information which may help devise strategies for treating breakthrough bleeding associated with hormonal contraception.     

Germline and somatic mosaicism in a female carrier of Duchenne muscular dystrophy

The family of a male with Duchenne muscular dystrophy (DMD) and a deletion within the dystrophin gene has been studied. Polymerase chain reaction analysis of ectopic mRNA from peripheral blood T+B lymphocytes and the use of (CA) _n repeat polymorphisms in and around the deleted region showed the proband's mother to be both a germline mosaic and a somatic mosaic for the deletion seen in her son. The mutation therefore occurred as a mitotic event early in embryogenesis.     

Microbial community composition in sediments resists perturbation by nutrient enrichment

Functional redundancy in bacterial communities is expected to allow microbial assemblages to survive perturbation by allowing continuity in function despite compositional changes in communities. Recent evidence suggests, however, that microbial communities change both composition and function as a result of disturbance. We present evidence for a third response: resistance. We examined microbial community response to perturbation caused by nutrient enrichment in salt marsh sediments using deep pyrosequencing of 16S rRNA and functional gene microarrays targeting the nirS gene. Composition of the microbial community, as demonstrated by both genes, was unaffected by significant variations in external nutrient supply in our sampling locations, despite demonstrable and diverse nutrient-induced changes in many aspects of marsh ecology. The lack of response to external forcing demonstrates a remarkable uncoupling between microbial composition and ecosystem-level biogeochemical processes and suggests that sediment microbial communities are able to resist some forms of perturbation.     

Integration of RNA processing and expression level control modulates the function of the Drosophila Hox gene Ultrabithorax during adult development

Although most metazoan genes undergo alternative splicing, the functional relevance of the majority of alternative splicing products is still unknown. Here we explore this problem in the Drosophila Hox gene Ultrabithorax (Ubx). Ubx produces a family of six protein isoforms through alternative splicing. To investigate the functional specificity of the Ubx isoforms, we studied their role during the formation of the Drosophila halteres, small dorsal appendages that are essential for normal flight. Our work shows that isoform Ia, which is encoded by all Ubx exons, is more efficient than isoform IVa, which lacks the amino acids coded by two small exons, in controlling haltere development and regulating Ubx downstream targets. However, our experiments also demonstrate that the functional differences among the Ubx isoforms can be compensated for by increasing the expression levels of the less efficient form. The analysis of the DNA-binding profiles of Ubx isoforms to a natural Ubx target, spalt, shows no major differences in isoform DNA-binding activities, suggesting that alternative splicing might primarily affect the regulatory capacity of the isoforms rather than their DNA-binding patterns. Our results suggest that to obtain distinct functional outputs during normal development genes must integrate the generation of qualitative differences by alternative splicing to quantitative processes affecting isoform protein expression levels.     

A role for the androgen receptor in the endometrial antiproliferative effects of progesterone antagonists

In women and nonhuman primates, treatment with progesterone antagonists suppresses estrogen-dependent mitotic activity in the endometrial glands. This antiproliferative effect is paradoxical, because progesterone antagonists do not bind to the estrogen receptor (ER). While this phenomenon has been termed a "functional noncompetitive antiestrogenic effect," it does not occur in all species or in all regions of the primate reproductive tract, so is best referred to as an "endometrial antiproliferative effect." Recent studies of ours in both women and macaques revealed that the endometrial androgen receptor (AR) was increased by progesterone antagonist treatment. Because androgens are known to suppress estrogen-dependent endometrial proliferation, we hypothesized that the AR was involved in the antiproliferative effects induced by progesterone antagonists. In a test of this hypothesis, we administered the antiandrogen, flutamide, along with progesterone antagonists to ovariectomized, estrogen-treated macaques. Flutamide counteracted the suppressive effects of the progesterone antagonists on endometrial wet weight, thickness, stromal compaction, and mitotic index. Hyaline degeneration of the spiral arteries was also blocked by flutamide. These data implicate the AR as a functional component of the mechanism through which progesterone antagonists induce endometrial antiproliferative effects in the presence of estrogens.     

Passive acoustic monitoring predicts daily variation in North Atlantic right whale presence and relative abundance in Roseway Basin,Canada

North Atlantic right whale monitoring in Roseway Basin, Canada, is primarily based on short‐term (<14 d) visual surveys conducted during August–September. Variability in survey effort has been the biggest limiting factor to studying changes in the population's occurrence and habitat use. Such efforts could be enhanced considerably using passive acoustic monitoring (PAM). We sought to determine if variation in whale presence, relative abundance, demography, and/or behavior (estimated through visual surveys) could be explained by variation in three right whale call types in this habitat. A generalized linear model was fit to 23 d of concurrent PAM and visual monitoring during four summers within the Roseway Basin Right Whale Critical Habitat boundaries. The model revealed significant positive relationships between relative abundance, call counts and presence of surface‐active group behavior. PAM can refine daily right whale presence estimates. While visual observations (n = 23 d) implied a 40% decline in right whale presence during 2014–2015 relative to 2004–2005, PAM data (n = 211 d) showed right whales were present between 71%–85% of survey days throughout all years analyzed. We demonstrate that PAM is a useful tool to extend periods of right whale monitoring, especially in areas where visual monitoring efforts may be limited.     

Ca2+ and Mg2+-binding and a putative calmodulin type Ca2+-binding site in Synechococcus Photosystem II

Thylakoids and Photosystem II particles prepared from the cyanobacterium Synechococcus PCC 7942 washed with a HEPES/glycerol buffer exhibited low rates of light-induced oxygen evolution. Addition of either Ca²⁺ or Mg²⁺ to both thylakoids and Photosystem II particles increased oxygen evolution independently, maximal rates being obtained by addition of both ions. If either preparation was washed with NaCl, light induced O₂ evolution was completely inhibited, but re-activated in the same manner by Ca²⁺ and Mg²⁺ but to a lower level. In the presence of Mg²⁺, the reactivation of O₂ evolution by Ca²⁺ allowed sigmoid kinetics, implying co-operative binding. The results are interpreted as indicating that not only Ca²⁺, but also Mg²⁺, is essential for light-induced oxygen evolution in thylakoids and Photosystem II particles from Synechococcus PC 7942. The significance of the reactivation kinetics is discussed. Reactivation by Ca²⁺ was inhibited by antibodies to mammalian calmodulin, indicating that the binding site in Photosystem II may be analogous to that of this protein.Abbreviation HEPES n-2-Hydroxyethylpiperazine--2-ethane sulphonic acid