Revision of the digger wasps of the Ampulicidae and Heterogynaidae (Hymenoptera) of Saudi Arabia,with the description of a new species of the enigmatic genus Heterogyna Nagy

The apoid wasps of the families Ampulicidae and Heterogynaidae of Saudi Arabia are revised. In Ampulicidae, four species in three genera are reported, of which three species are recorded for the first time from Saudi Arabia (Al-Baha, Asir and Riyadh regions): Ampulex assimilis Kohl, Dolichurus arabicus Ohl and Trirogma caerulea Westwood. Additionally, the family Heterogynaidae is reported for the first time from Saudi Arabia (Asir and Riyadh regions), and a new species, Heterogyna saudita sp. nov., is described, diagnosed and illustrated. An illustrated key to the species of Heterogyna from the Arabian Peninsula is provided.

www.zoobank.org/urn:lsid:zoobank.org:pub:C23C70A7-AA1C-47C0-951A-D164E7B20001     

Change in pattern of ongoing cortical activity with auditory category learning

Humans are able to classify novel items correctly by category; some other animals have also been shown to do this. During category learning, humans group perceptual stimuli by abstracting qualities from similarity relationships of their physical properties. Forming categories is fundamental to cognition and can be independent of a 'memory store' of information about the items or a prototype. The neurophysiological mechanisms underlying the formation of categories are unknown. Using an animal model of category learning, in which frequency-modulated tones are distinguished into the categories of 'rising' and 'falling' modulation, we demonstrate here that the sorting of stimuli into these categories emerges as a sudden change in an animal's learning strategy. Electro-corticographical recording from the auditory cortex shows that the transition is accompanied by a change in the dynamics of cortical stimulus representation. We suggest that this dynamic change represents a mechanism underlying the recognition of the abstract quality (or qualities) that defines the categories.     

Empty MHC class I molecules come out in the cold

Major histocompatibility complex (MHC) class I molecules present antigen by transporting peptides from intracellularly degraded proteins to the cell surface for scrutiny by cytotoxic T cells. Recent work suggests that peptide binding may be required for efficient assembly and intracellular transport of MHC class I molecules, but it is not clear whether class I molecules can ever assemble in the absence of peptide. We report here that culture of the murine lymphoma mutant cell line RMA-S at reduced temperature (19-33 degrees C) promotes assembly, and results in a high level of cell surface expression of H-2/beta 2-microglobulin complexes that do not present endogenous antigens, and are labile at 37 degrees C. They can be stabilized at 37 degrees C by exposure to specific peptides known to interact with H-2Kb or Db. Our findings suggest that, in the absence of peptides, class I molecules can assemble but are unstable at body temperature. The induction of such molecules at reduced temperature opens new ways to analyse the nature of MHC class I peptide interactions at the cell surface.     

Balanced responsiveness to chemoattractants from adjacent zones determines B-cell position

B lymphocytes re-circulate between B-cell-rich compartments (follicles or B zones) in secondary lymphoid organs, surveying for antigen. After antigen binding, B cells move to the boundary of B and T zones to interact with T-helper cells. Despite the importance of B--T-cell interactions for the induction of antibody responses, the mechanism causing B-cell movement to the T zone has not been defined. Here we show that antigen-engaged B cells have increased expression of CCR7, the receptor for the T-zone chemokines CCL19 and CCL21, and that they exhibit increased responsiveness to both chemoattractants. In mice lacking lymphoid CCL19 and CCL21 chemokines, or with B cells that lack CCR7, antigen engagement fails to cause movement to the T zone. Using retroviral-mediated gene transfer we demonstrate that increased expression of CCR7 is sufficient to direct B cells to the T zone. Reciprocally, overexpression of CXCR5, the receptor for the B-zone chemokine CXCL13, is sufficient to overcome antigen-induced B-cell movement to the T zone. These findings define the mechanism of B-cell relocalization in response to antigen, and establish that cell position in vivo can be determined by the balance of responsiveness to chemoattractants made in separate but adjacent zones.