Alberta Northern Field Work, 1966: Rheumatic Heart Disease in LaCrete and Paddle Prairie

A sociologic and medical study was undertaken of the incidence of rheumatic heart disease in an isolated Mennonite colony in Northern Alberta, Canada. A group of Métis in a nearby settlement was used as a control. A total of 1294 individuals were examined, and evidence of carditis was found in 42 Mennonites.This project is one of a series of student summer research programs sponsored by the Department of Community Medicine, University of Alberta, and supported by grants from the Provincial Department of Health during the past three summers.The students - medical and dental - receive in Edmonton a seven- to 10-day orientation and indoctrination course dealing with the sociological, anthropological and medical problems likely to be met with in the North. Research protocol and methodological techniques are prepared and devised with student participation. A minimum of supervision is given in the field to encourage the undergraduates to adapt and adjust to a changed environment. Student response to this type of learning experience has been most encouraging.     

Evidence for the involvement of metalloendoproteases in the acrosome reaction in sea urchin sperm

An essential initial step in fertilization in the sea urchin Strongylocentrotus purpuratus is an intracellular membrane fusion event in the sperm known as the acrosome reaction. This Ca2+-dependent, exocytotic process involves fusion of the membrane of the acrosomal vesicle and the plasma membrane. Recently, metalloendoproteases requiring divalent metals have been implicated in several Ca2+-dependent membrane fusion events in other biological systems. In view of the suggested involvement of Zn2+ in the sea urchin sperm acrosome reaction (Clapper, D.L., Davis, J.A., Lamothe, P.J., Patton, C., and Epel, D. (1985) J. Cell Biol. 100, 1817-1824) and the fact that Zn2+ is a metal cofactor for metalloendoproteases, we investigated the potential role of this protease in the acrosome reaction. A soluble metalloendoprotease was demonstrated and characterized in sperm homogenates using the fluorogenic protease substrate succinyl-alanine-alanine-phenylalanine-4-aminomethylcoumarin. The protease was inhibited by the metal chelators EDTA and 1,10-phenanthroline, and activity of the inactive apoenzyme could be reconstituted with Zn2+. The metalloendoprotease substrate and inhibitors blocked the acrosome reaction induced either by egg jelly coat or by ionophore, but had no effect on the influx of Ca2+. These observations suggest that inhibition occurs at a step independent of Ca2+ entry. Overall, the results of this study provide strong indirect evidence that the acrosome reaction requires the action of metalloendoprotease.     

Allogeneic leukocyte and germ cell-induced murine immunodeficiency

Immune deficiency, as defined by significant decreases in lymphocyte Con A and allo-reactivity and in natural killer (NK) function, was induced in normal adult mice by i.p. injections of combinations of allogeneic testicular germ cells and splenic leukocytes over 3 wk. This immune deficiency was evident at 8 wk after initial injection, and profound by 12 wk. Neither leukocytes nor testicular cells, given alone, were able to induce similar immune deficiency. These findings suggest the possibility that allogeneic germ cells and leukocytes of semen, on repeated administration, may induce immune deficiency and may act as co-factors to viral agents in the development of clinical AIDS in humans.     

Genetic analysis of hybridization and introgression between wild mongoose and brown lemurs

Background  

Hybrid zones generally represent areas of secondary contact after speciation. The nature of the interaction between genes of individuals in a hybrid zone is of interest in the study of evolutionary processes. In this study, data from nuclear microsatellites and mitochondrial DNA sequences were used to genetically characterize hybridization between wild mongoose lemurs (Eulemur mongoz) and brown lemurs (E. fulvus) at Anjamena in west Madagascar.     

Potent inhibition of heterotopic ossification by nuclear retinoic acid receptor-γ agonists

Heterotopic ossification consists of ectopic bone formation within soft tissues after surgery or trauma. It can have debilitating consequences, but there is no definitive cure. Here we show that heterotopic ossification was essentially prevented in mice receiving a nuclear retinoic acid receptor-γ (RAR-γ) agonist. Side effects were minimal, and there was no significant rebound effect. To uncover the mechanisms of these responses, we treated mouse mesenchymal stem cells with an RAR-γ agonist and transplanted them into nude mice. Whereas control cells formed ectopic bone masses, cells that had been pretreated with the RAR-γ agonist did not, suggesting that they had lost their skeletogenic potential. The cells became unresponsive to rBMP-2 treatment in vitro and showed decreases in phosphorylation of Smad1, Smad5 and Smad8 and in overall levels of Smad proteins. In addition, an RAR-γ agonist blocked heterotopic ossification in transgenic mice expressing activin receptor-like kinase-2 (ALK2) Q207D, a constitutively active form of the receptor that is related to ALK2 R206H found in individuals with fibrodysplasia ossificans progressiva. The data indicate that RAR-γ agonists are potent inhibitors of heterotopic ossification in mouse models and, thus, may also be effective against injury-induced and congenital heterotopic ossification in humans.     

Molecular population genetics of the melanic plumage polymorphism in Arctic skuas (Stercorarius parasiticus): evidence for divergent selection on plumage colour

The Arctic skua (Stercorarius parasiticus) is a classic example of an avian plumage polymorphism, with variation in melanin‐based ventral plumage coloration defining pale, intermediate and dark morphs in adults of both sexes. However, despite several decades of field research, there is an incomplete understanding of how the polymorphism in ventral plumage colour is maintained and the selective forces involved. Here, we investigate selection on a locus (MC1R) that is strongly associated with plumage colour variation in Arctic skuas using patterns of nucleotide variation and comparison to neutral loci (nuclear introns and mtDNA). We find that three linked nonsynonymous mutations in MC1R, including the single mutation described previously, are associated with plumage colour in the Arctic skua. The position of nonsynonymous mutations on a MC1R haplotype network implies that divergent selection drove the initial evolution of the colour morphs. Comparisons of F_STs of MC1R vs. nuclear introns among five skua populations differing in proportion of dark morphs along an approximate north–south cline reveal a signature of divergent selection on MC1R. In contrast, we find limited evidence for balancing selection on MC1R within populations, although the power is low. Our results provide strong evidence for both past and ongoing selection on MC1R, and, by implication, plumage colour in Arctic skuas. The results suggest that a fruitful avenue for future ecological studies will be analysis of selection on morphs in colonies at the extremes along the morph ratio cline.     

Spatial and temporal variation of photosynthetic parameters in natural phytoplankton assemblages in the Beaufort Sea, Canadian Arctic

During summer 2008, as part of the Circumpolar Flaw Lead system study, we measured phytoplankton photosynthetic parameters to understand regional patterns in primary productivity, including the degree and timescale of photoacclimation and how variability in environmental conditions influences this response. Photosynthesis–irradiance measurements were taken at 15 sites primarily from the depth of the subsurface chlorophyll a (Chl a) maximum (SCM) within the Beaufort Sea flaw lead polynya. The physiological response of phytoplankton to a range of light levels was used to assess maximum rates of carbon (C) fixation (P _m^*), photosynthetic efficiency (α ^*), photoacclimation (E _k), and photoinhibition (β ^*). SCM samples taken along a transect from under ice into open water exhibited a >3-fold increase in α ^* and P _m^*, showing these parameters can vary substantially over relatively small spatial scales, primarily in response to changes in the ambient light field. Algae were able to maintain relatively high rates of C fixation despite low light at the SCM, particularly in the large (>5 μm) size fraction at open water sites. This may substantially impact biogenic C drawdown if species composition shifts in response to future climate change. Our results suggest that phytoplankton in this region are well acclimated to existing environmental conditions, including sea ice cover, low light, and nutrient pulses. Furthermore, this photoacclimatory response can be rapid and keep pace with a developing SCM, as phytoplankton maintain photosynthetic rates and efficiencies in a narrow “shade-acclimated” range.