Book Reviews

Die hartJou Harl en Lewe. Deur A. J. Brink. Bl. 248. Gemustreer. RI6,95. Pretoria: Femina. 1982.The physiology of digestionExperiments and Observations on the Gastric Juice and the Physiology of Digestion. By William Beaumonr. 1st ed. 1&33. Reprinted in facsimile for the Classics ofMedicine Library, Division of Gryphon Editions Ltd, Birmingham, Alabama, 1980.Bone in Clinical Orthopaedics: A Study in ComparativeOsteology. Ed. by G. Sumner-Smith. Pp. xvi + 435. Illustrated. R94,25. Philadelphia: W. B. Saunders. 1982.Tamoxifen in breast cancerThe Role of Tamoxifen in Breast Cancer. Ed. by S. Iacobelli, M. E. Lippman and G. R. Della Cuna. Pp. xii + 124. Illustrated. 523,12. New York: Raven Press. 1982.Under the Influence. A History ofNitrous Oxide and OxygenAnaesthesia. By W. D. A. Smith. Pp. xxviii + 188. Illustrated. R33,50. London: Macmillan. 1982.Clinical internal medicine in the agedClinical Internal Medicine in the Aged. By R. W. Schrier. Pp. vii + 324. Illustrated. R61,-. Philadelphia: W. B. Saunders. 1982.Genital Infection by Chlamydia Trachomatis (Current Topicsin Infection, No. 2). By J. D. Oriel and G. L. Ridgway. Pp. viii + 144. Illustrated. R32,20. London: Edward Arnold. 1982.Placental Function Tests. By T. Chard and A. Klopper. Pp. viii + 94. Illustrated. DM42,-. Berlin: Springer-Verlag. 1982.Therapeutic Heat and Cold. 3rd ed. Ed. by J. F. Lehmann. Pp. xiv + 641. Illustrated. Baltimore: Williams & Wilkins. 1982

The Expression of PHOSPHO1, nSMase2 and TNAP is Coordinately Regulated by Continuous PTH Exposure in Mineralising Osteoblast Cultures

Sustained exposure to high levels of parathyroid hormone (PTH), as observed in hyperparathyroidism, are catabolic to bone. The increase in the RANKL/OPG ratio in response to continuous PTH, resulting in increased osteoclastogenesis is well established. However, the effects of prolonged PTH exposure on key regulators of skeletal mineralisation has yet to be investigated. This study sought to examine the temporal expression of PHOSPHO1, TNAP and nSMase2 in mineralising osteoblast-like cell cultures and to investigate the effects of continuous PTH exposure on the expression of these genes in vitro. PHOSPHO1, nSMase2 and TNAP expression in cultured MC3T3-C14 cells significantly increased from day 0 to day 10. PTH induced a rapid downregulation of Phospho1 and Smpd3 gene expression in MC3T3-C14 cells and cultured hemi-calvariae. Alpl was differentially regulated by PTH, displaying upregulation in cultured MC3T3-C14 cells and downregulation in hemi-calvariae. The effects of PTH on Phospho1 expression were mimicked with the cAMP agonist forskolin, and blocked by the PKA inhibitor PKI (5-24), highlighting a role for the cAMP/PKA pathway in this regulation. The potent down-regulation of Phospho1 and Smpd3 in osteoblasts in response to continuous PTH may provide a novel explanation for the catabolic effects on the skeleton of such an exposure. Furthermore, our findings support the hypothesis that PHOSPHO1, nSMase2 and TNAP function cooperatively in the initiation of skeletal mineralisation

Geophysical Observations of Taliks Below Drained Lake Basins on the Arctic Coastal Plain of Alaska

Lakes and drained lake basins (DLBs) together cover up to ∼80% of the western Arctic Coastal Plain of Alaska. The formation and drainage of lakes in this continuous permafrost region drive spatial and temporal landscape dynamics. Postdrainage processes including vegetation succession and permafrost aggradation have implications for hydrology, carbon cycling, and landscape evolution. Here, we used surface nuclear magnetic resonance (NMR) and transient electromagnetic (TEM) measurements in conjunction with thermal modeling to investigate permafrost aggradation beneath eight DLBs on the western Arctic Coastal Plain of Alaska. We also surveyed two primary surface sites that served as nonlake affected control sites. Approximate timing of lake drainage was estimated based on historical aerial imagery. We interpreted the presence of taliks based on either unfrozen water estimated with surface NMR and/or TEM resistivities in DLBs compared to measurements on primary surface sites and borehole resistivity logs. Our results show evidence of taliks below several DLBs that drained before and after 1949 (oldest imagery). We observed depths to the top of taliks between 9 and 45 m. Thermal modeling and geophysical observations agree about the presence and extent of taliks at sites that drained after 1949. Lake drainage events will likely become more frequent in the future due to climate change and our modeling results suggest that warmer and wetter conditions will limit permafrost aggradation in DLBs. Our observations provide useful information to predict future evolution of permafrost in DLBs and its implications for the water and carbon cycles in the Arctic

Remote sensing-based statistical approach for defining drained lake basins in a continuous Permafrost region, North Slope of Alaska

Lake formation and drainage are pervasive phenomena in permafrost regions. Drained lake basins (DLBs) are often the most common landforms in lowland permafrost regions in the Arctic (50% to 75% of the landscape). However, detailed assessments of DLB distribution and abundance are limited. In this study, we present a novel and scalable remote sensing-based approach to identifying DLBs in lowland permafrost regions, using the North Slope of Alaska as a case study. We validated this first North Slope-wide DLB data product against several previously published sub-regional scale datasets and manually classified points. The study area covered \u3e71,000 km2, including a \u3e39,000 km2 area not previously covered in existing DLB datasets. Our approach used Landsat-8 multispectral imagery and ArcticDEM data to derive a pixel-by-pixel statistical assessment of likelihood of DLB occurrence in sub-regions with different permafrost and periglacial landscape conditions, as well as to quantify aerial coverage of DLBs on the North Slope of Alaska. The results were consistent with previously published regional DLB datasets (up to 87% agreement) and showed high agreement with manually classified random points (64.4–95.5% for DLB and 83.2– 95.4% for non-DLB areas). Validation of the remote sensing-based statistical approach on the North Slope of Alaska indicated that it may be possible to extend this methodology to conduct a comprehensive assessment of DLBs in pan-Arctic lowland permafrost regions. Better resolution of the spatial distribution of DLBs in lowland permafrost regions is important for quantitative studies on landscape diversity, wildlife habitat, permafrost, hydrology, geotechnical conditions, and high-lat-itude carbon cycling

Climate Change Drives Widespread and Rapid Thermokarst Development in Very Cold Permafrost in the Canadian High Arctic

Climate warming in regions of ice‐rich permafrost can result in widespread thermokarst development, which reconfigures the landscape and damages infrastructure. We present multisite time series observations which couple ground temperature measurements with thermokarst development in a region of very cold permafrost. In the Canadian High Arctic between 2003 and 2016, a series of anomalously warm summers caused mean thawing indices to be 150–240% above the 1979–2000 normal resulting in up to 90 cm of subsidence over the 12‐year observation period. Our data illustrate that despite low mean annual ground temperatures, very cold permafrost (<−10 °C) with massive ground ice close to the surface is highly vulnerable to rapid permafrost degradation and thermokarst development. We suggest that this is due to little thermal buffering from soil organic layers and near‐surface vegetation, and the presence of near‐surface ground ice. Observed maximum thaw depths at our sites are already exceeding those projected to occur by 2090 under representative concentration pathway version 4.5

Statistical mechanics of voting

Decision procedures aggregating the preferences of multiple agents can produce cycles and hence outcomes which have been described heuristically as `chaotic'. We make this description precise by constructing an explicit dynamical system from the agents' preferences and a voting rule. The dynamics form a one dimensional statistical mechanics model; this suggests the use of the topological entropy to quantify the complexity of the system. We formulate natural political/social questions about the expected complexity of a voting rule and degree of cohesion/diversity among agents in terms of random matrix models---ensembles of statistical mechanics models---and compute quantitative answers in some representative cases.Comment: 9 pages, plain TeX, 2 PostScript figures included with epsf.tex (ignore the under/overfull \vbox error messages

MEPE is a novel regulator of growth plate cartilage mineralization

Matrix extracellular phosphoglycoprotein (MEPE) belongs to the SIBLING protein family which play key roles in biomineralization. Although the growth plates of MEPE-overexpressing mice display severe morphological disruption, the expression and function of MEPE in growth plate matrix mineralization remains largely undefined. Here we show MEPE and its cleavage product, the acidic serine aspartate-rich MEPE-associated motif (ASARM) peptide, to be localised to the hypertrophic zone of the growth plate. We also demonstrate that the phosphorylated (p)ASARM peptide inhibits ATDC5 chondrocyte matrix mineralization. Stable MEPE-overexpressing ATDC5 cells also had significantly reduced matrix mineralization in comparison to the control cells. Interestingly, we show that the addition of the non-phosphorylated (np)ASARM peptide promoted mineralization in the ATDC5 cells. The peptides and the overexpression of MEPE did not affect the differentiation of the ATDC5 cells. For a more physiologically relevant model, we utilized the metatarsal organ culture model. We show the pASARM peptide to inhibit mineralization at two stages of development, as shown by histological and ?CT analysis. Like in the ATDC5 cells, the peptides did not affect the differentiation of the metatarsals indicating that the effects seen on mineralization are direct, as is additionally confirmed by no change in alkaline phosphatase activity or mRNA expression. In the metatarsal organ cultures, the pASARM peptide also reduced endothelial cell markers and vascular endothelial growth factor mRNA expression. Taken together these results show MEPE to be an important regulator of growth plate chondrocyte matrix mineralization through its cleavage to an ASARM peptide

Impact of facial conformation on canine health: Brachycephalic Obstructive Airway Syndrome

The domestic dog may be the most morphologically diverse terrestrial mammalian species known to man; pedigree dogs are artificially selected for extreme aesthetics dictated by formal Breed Standards, and breed-related disorders linked to conformation are ubiquitous and diverse. Brachycephaly–foreshortening of the facial skeleton–is a discrete mutation that has been selected for in many popular dog breeds e.g. the Bulldog, Pug, and French Bulldog. A chronic, debilitating respiratory syndrome, whereby soft tissue blocks the airways, predominantly affects dogs with this conformation, and thus is labelled Brachycephalic Obstructive Airway Syndrome (BOAS). Despite the name of the syndrome, scientific evidence quantitatively linking brachycephaly with BOAS is lacking, but it could aid efforts to select for healthier conformations. Here we show, in (1) an exploratory study of 700 dogs of diverse breeds and conformations, and (2) a confirmatory study of 154 brachycephalic dogs, that BOAS risk increases sharply in a non-linear manner as relative muzzle length shortens. BOAS only occurred in dogs whose muzzles comprised less than half their cranial lengths. Thicker neck girths also increased BOAS risk in both populations: a risk factor for human sleep apnoea and not previously realised in dogs; and obesity was found to further increase BOAS risk. This study provides evidence that breeding for brachycephaly leads to an increased risk of BOAS in dogs, with risk increasing as the morphology becomes more exaggerated. As such, dog breeders and buyers should be aware of this risk when selecting dogs, and breeding organisations should actively discourage exaggeration of this high-risk conformation in breed standards and the show ring