Deletion of PKBα/Akt1 Affects Thymic Development

BACKGROUND: The thymus constitutes the primary lymphoid organ for the majority of T cells. The phosphatidyl-inositol 3 kinase (PI3K) signaling pathway is involved in lymphoid development. Defects in single components of this pathway prevent thymocytes from progressing beyond early T cell developmental stages. Protein kinase B (PKB) is the main effector of the PI3K pathway. METHODOLOGY/PRINCIPAL FINDINGS: To determine whether PKB mediates PI3K signaling in the thymus, we characterized PKB knockout thymi. Our results reveal a significant thymic hypocellularity in PKBalpha(-/-) neonates and an accumulation of early thymocyte subsets in PKBalpha(-/-) adult mice. Using thymic grafting and fetal liver cell transfer experiments, the latter finding was specifically attributed to the lack of PKBalpha within the lymphoid component of the thymus. Microarray analyses show that the absence of PKBalpha in early thymocyte subsets modifies the expression of genes known to be involved in pre-TCR signaling, in T cell activation, and in the transduction of interferon-mediated signals. CONCLUSIONS/SIGNIFICANCE: This report highlights the specific requirements of PKBalpha for thymic development and opens up new prospects as to the mechanism downstream of PKBalpha in early thymocytes

Breeding on the leading edge of a northward range expansion: differences in morphology and the stress response in the arctic Gambel's white-crowned sparrow

Individuals at the forefront of a range shift are likely to exhibit phenotypic traits that distinguish them from the population breeding within the historic range. Recent studies have examined morphological, physiological and behavioral phenotypes of individuals at the edge of their range. Several studies have found differences in the hypothalamic-pituitary-adrenal (HPA) axis activity in response to acute restraint stress in individuals at the range limits. HPA axis activation leads to elevations in glucocorticoids that regulate physiology and behavior. Here we compare the hormonal profiles and morphometrics from Gambel's white-crowned sparrows (Zonotrichia leucophrys gambelii) breeding at the northern limit of the population's range to those birds breeding within the historic population range. Birds breeding at the northern limit experienced a harsher environment with colder temperatures; however, we found no differences in arthropod prey biomass between the northern limit and more southern (historic) sites. Males at the northern limit had higher body condition scores (mass corrected for body size) compared to individuals within the historic range, but no differences were found in beak and tarsus lengths, wing chord, muscle profile or fat stores. In males during the pre-parental stage, before breeding commenced, HPA axis activity was elevated in birds at the northern limit of the range, but no differences were found during the parental or molt stages. Females showed no differences in HPA axis activity during the parental stage. This study suggests that "pioneering" individuals at the limits of their breeding range exhibit physiology and morphology that are distinct from individuals within the historic range

New Record For Ixodes texanus (Acarina, Ixodidae) Banks In Mississippi, With A New Host Record

Volume: 94Start Page: 139End Page: 14

Notes On The Geographical distribution Of The Gulf coast Tick, Amblyomma maculatum (Koch) [Acari, Ixodidae]

Volume: 94Start Page: 103End Page: 10

Ultrastructure of the venom gland of the brown recluse spider, Loxosceles reclusa gertsch and mulaik (Araneae: Loxoscelidae)

Studies were conducted to describe the histology and fine structure of the venom gland of the brown recluse spider, Loxosceles reclusa, and to provide information about venom production and secretion. The L. reclusa venom glands are paired bulbous structures, located in the cephalothoracic cavity; the glands diminish proximally into cuticle-lined ducts that lie within the cheliceral fangs. The secretory epithelium is surrounded by a thick, striated musculature composed of irregularly shaped muscle bundles and is ensheathed by a basement membrane. The venom-producing cells of the gland are pyramidal epithelial cells which extend into the central portion of the gland. The secretory products of the venom gland are produced in the basal area of the epithelial cells as Golgi-associated, membrane-bounded packets of different electron densities and subsequently fuse with a large apical vacuole. Morphological evidence of neuroglandular control of the apical venom release is presented. Evacuation of the gland, following venom release, is subsequently promoted by the constriction of the large musculature. Comparison of venom glands from electrically depleted and normalbiting situations reveals no morphological differences. This study provides the first description of the L. reclusa venom gland in addition to supporting the use of venom obtained from spiders by electrical stimulation. © 1979