EFFECTS OF BACTERIAL ENDOTOXIN ON HEMOPOIETIC COLONY-FORMING CELLS IN THE SPLEENS OF NORMAL MICE AND MICE OF GENOTYPE S1/S1

Multiple doses of S. typhosa endotoxin caused an increase in the number of hemopoietic stem cells present in mouse marrow and spleen that could be detected using the spleen-colony assay. This increase was inhibited by Colcemid, and by the genetically-determined defect in hemopoiesis in mice of genotype S1/S1^d. However, the defect in S1/S1^d hosts did not prevent an endotoxin-induced increase in the number of cells capable of forming colonies in cell culture. The results support the view that bacterial endotoxin acts, via a genetically-controlled regulatory mechanism, to stimulate the proliferation of hemopoietic stem cells in the spleen.     

U-series evidence for widespread reef development in Shark Bay during the last interglacial

Field observations and U-series ages reveal that Shark Bay, Western Australia (WA) has been inundated by the sea on at least three occasions during the Late Pleistocene/Holocene, resulting in a succession of marine deposits around the Bay. The exact age of these deposits has until now been problematic due to a lack of reliable and accurate age data. This study reports 16 new U-series coral dates from emergent reef deposits around Shark Bay, and point to an extended period of coral reef development during the peak of the last interglacial, marine isotope stage (MIS) 5e. This is attributed to enhancement of marine circulation within the reaches and basins, a result of higher sea levels and an absence of major sill and bank structures. Stromatolites are absent from the geological record within Shark Bay until the late Holocene, suggesting that sea levels and marine sedimentary processes that have operated during the present sea-level highstand are unique to this period. There is little direct evidence of fossil reef development occurring during interglacials of the middle/late Pleistocene (MIS 9/11).     

Psychiatric Seminars for the General Practitioner

A program of case-centred seminars in psychiatry designed for general practitioners was begun in Ontario during 1965. It came into being as the result of the cooperative endeavour of the Ontario Chapter, College of General Practice, the Ontario Psychiatric Association and the Division of Postgraduate Medicine, University of Toronto. The program was conducted on a regional rather than on a centralized basis. No general practitioner had to travel more than 30 miles to his seminar, thus ensuring regular weekly attendance for an average of 12 weeks. The Ontario Chapter recruited the general practitioners, the Psychiatric Association selected appropriate regional psychiatrists, and the University gave a brief preliminary course for these psychiatrists. Nineteen separate groups were formed in 13 different Ontario cities, with an average total weekly attendance of 120. A review conference of participating psychiatrists and general practitioners, held in November 1965, developed plans for renewal and extension of the program for 1966. This approach seems especially appropriate for large geographic regions with scattered populations.     

PKA Phosphorylation of Cardiac Troponin I Modulates Activation and Relaxation Kinetics of Ventricular Myofibrils

Protein kinase A (PKA) phosphorylation of myofibril proteins constitutes an important pathway for β-adrenergic modulation of cardiac contractility and relaxation. PKA targets the N-terminus (Ser-23/24) of cardiac troponin I (cTnI), cardiac myosin-binding protein C (cMyBP-C) and titin. The effect of PKA-mediated phosphorylation on the magnitude of contraction has been studied in some detail, but little is known about how it modulates the kinetics of thin filament activation and myofibril relaxation as Ca²⁺ levels vary. Troponin C (cTnC) interaction with cTnI (C-I interaction) is a critical step in contractile activation that can be modulated by cTnI phosphorylation. We tested the hypothesis that altering C-I interactions by PKA, or by cTnI phosphomimetic mutations (S23D/S24D-cTnI), directly affects thin filament activation and myofilament relaxation kinetics. Rat ventricular myofibrils were isolated and endogenous cTn was exchanged with either wild-type cTnI, or S23D/S24D-cTnI recombinant cTn. Contractile mechanics were monitored at maximum and submaximal Ca²⁺ concentrations. PKA treatment of wild-type cTn or exchange of cTn containing S23D/S24D-cTnI resulted in an increase in the rate of early, slow phase of relaxation (k_REL,slow) and a decrease in its duration (t_REL,slow). These effects were greater for submaximal Ca²⁺ activated contractions. PKA treatment also reduced the rate of contractile activation (k_ACT) at maximal, but not submaximal Ca²⁺, and reduced the Ca²⁺ sensitivity of contraction. Using a fluorescent probe coupled to cTnC (C35S-IANBD), the Ca²⁺-cTn binding affinity and C-I interaction were monitored. Ca²⁺ binding to cTn (pCa₅₀) was significantly decreased when cTnI was phosphorylated by PKA (ΔpCa₅₀ = 0.31). PKA phosphorylation of cTnI also weakened C-I interaction in the presence of Ca²⁺. These data suggest that weakened C-I interaction, via PKA phosphorylation of cTnI, may slow thin filament activation and result in increased myofilament relaxation kinetics, the latter of which could enhance early phase diastolic relaxation during β-adrenergic stimulation.     

Anthropogenic evolution in an insect wing polymorphism following widespread deforestation

Anthropogenic environmental change can underpin major shifts in natural selective regimes, and can thus alter the evolutionary trajectories of wild populations. However, little is known about the evolutionary impacts of deforestation—one of the most pervasive human-driven changes to terrestrial ecosystems globally. Absence of forest cover (i.e. exposure) has been suggested to play a role in selecting for insect flightlessness in montane ecosystems. Here, we capitalize on human-driven variation in alpine treeline elevation in New Zealand to test whether anthropogenic deforestation has caused shifts in the distributions of flight-capable and flightless phenotypes in a wing-polymorphic lineage of stoneflies from the Zelandoperla fenestrata species complex. Transect sampling revealed sharp transitions from flight-capable to flightless populations with increasing elevation. However, these phenotypic transitions were consistently delineated by the elevation of local treelines, rather than by absolute elevation, providing a novel example of human-driven evolution in response to recent deforestation. The inferred rapid shifts to flightlessness in newly deforested regions have implications for the evolution and conservation of invertebrate biodiversity.     

Phosphorylation of SHP-2 regulates interactions between the endoplasmic reticulum and focal adhesions to restrict interleukin-1-induced Ca2+ signaling

Interleukin-1 (IL-1)-induced Ca2+ signaling in fibroblasts is constrained by focal adhesions. This process involves the proteintyrosine phosphatase SHP-2, which is critical for IL-1-induced phosphorylation of phospholipase Cgamma1, thereby enhancing IL-1-induced Ca2+ release and ERK activation. Currently, the mechanisms by which SHP-2 modulates Ca2+ release from the endoplasmic reticulum are not defined. We used immunoprecipitation and fluorescence protein-tagged SHP-2 or endoplasmic reticulum (ER)-protein expression vectors, and an ER-specific calcium indicator, to examine the functional relationships between SHP-2, focal adhesions, and IL-1-induced Ca2+ release from the ER. By total internal reflection fluorescence microscopy to image subplasma membrane compartments, SHP-2 co-localized with the ER-associated proteins calnexin and calreticulin at sites of focal adhesion formation in fibroblasts. IL-1beta promoted time-dependent recruitment of SHP-2 and ER proteins to focal adhesions; this process was blocked in cells treated with small interfering RNA for SHP-2 and in cells expressing a Y542F SHP-2 mutant. IL-1 stimulated inositol 1,4,5-trisphosphate receptor-mediated Ca2+ release from the ER subjacent to the plasma membrane that was tightly localized around fibronectin-coated beads and was reduced 4-fold in cells expressing Tyr-542 SHP-2 mutant. In subcellular fractions enriched for ER proteins, immunoprecipitation demonstrated that IL-1-enhanced association of SHP-2 with the type 1 inositol 1,4,5-trisphosphate receptor was dependent on Tyr-542 of SHP-2. We conclude that Tyr-542 of SHP-2 modulates IL-1-induced Ca2+ signals and association of the ER with focal adhesions.