Outcomes for Pressure Ulcer Trials (OUTPUTs) project: review and classification of outcomes reported in pressure ulcer prevention research.

In order to overcome inconsistencies in the reporting of outcomes in clinical trials, core outcome sets (COSs) have been developed in many clinical areas and the awareness of this concept is growing steadily. The Outcomes for Pressure Ulcer Trials (OUTPUTs) project aims to improve the quality of evidence from pressure ulcer prevention trials by developing a COS. As an initial step in the COS process we aimed to identify and classify both outcomes and concepts that represent potential outcomes for future trials that have been reported in pressure ulcer prevention research. A review was conducted in 12 major databases covering the literature indexed until 2016. Outcomes and relevant concepts reported in primary studies and/or reviews on pressure ulcer prevention in adult patients were extracted as presented in the articles, and afterwards inductively grouped into outcome domains. The domains were then categorized according to the outcome domain taxonomy recently proposed by the COMET group. In total 332 studies were included and 68 outcome domains were identified, covering multiple aspects of pressure ulcer prevention. Pressure ulcer occurrence was reported in 71% of all included studies, representing the most frequent outcome, followed by costs (22% of all studies) and acceptability of intervention and comfort (18% of all studies). A plethora of different outcomes are applied in pressure ulcer prevention research and substantial variations in definitions and reporting of similar outcomes were observed. A COS for pressure ulcer prevention trials is needed to overcome the noncomparability of outcomes.

Establishing the Maximum Collectivity in Highly Deformed N=Z Nuclei.

The lifetimes of the first excited 2^{+} states in the N=Z nuclei ^{80}Zr, ^{78}Y, and ^{76}Sr have been measured using the γ-ray line shape method following population via nucleon-knockout reactions from intermediate-energy rare-isotope beams. The extracted reduced electromagnetic transition strengths yield new information on where the collectivity is maximized and provide evidence for a significant, and as yet unexplained, odd-odd vs even-even staggering in the observed values. The experimental results are analyzed in the context of state-of-the-art nuclear density-functional model calculations.

Temporal Trends in Polybrominated Diphenylethers (PBDEs) in Blubber of Ringed Seals (Pusa hispida) from Ulukhaktok, NT, Canada Between 1981 and 2015.

Blubber taken from ringed seals (Pusa hispida) during a subsistence hunt at Ulukhaktok, NT (formerly Holman, NWT) at intervals between 2002 and 2015 was analysed for polybrominated diphenyl ether (PBDE) congeners. Results from these analyses were combined with others previously published to yield a data set of 18 tri- to hepta-substituted PBDE congeners in 102 animals sampled over a span of 19 year (females) and 34 year (males). In females, mean total PBDE concentrations increased between 1996 and 2015 by approximately 50%, from 1940 to 2780 pg/g wet wt., although not significantly so (p > 0.05) by one-way ANOVA. In males, concentrations ranged from 376 to 6470 pg/g wet wt. between 1981 and 2015 (p < 0.05). In males, the most rapid increase in PBDE concentrations occurred before 2000, but between 2002 and 2015 mean total PBDE concentrations increased by a further 50%. ANCOVA showed PBDE concentrations in females to be correlated (p < 0.05) with sampling year but not with age or condition (as measured by blubber thickness); in males, PBDE concentrations were strongly correlated (p < 0.01) with year, age and condition. The relative proportions of tetra-bromo- congeners declined weakly in both sexes over the sampling period, with a compensatory increase in penta-bromo-congener distribution. Overall, the results show no evidence yet of a decline in PBDE concentrations in western Arctic ringed seals in response to voluntary and regulated restrictions on PBDE use in the early 2000s.

Brown bullhead at the St. Lawrence River (Cornwall) Area of Concern: health and endocrine status in the context of tissue concentrations of PCBs and mercury.

The St. Lawrence River, at Cornwall Ontario, has accumulated sediment contaminants, mainly mercury (Hg) and polychlorinated biphenyls (PCBs), from industrial point sources over many years. Although those sources are past, the river at Cornwall remains an Area of Concern (AOC). Because of remediation and other changes in the AOC, improved knowledge of contaminants in wild-fish and their putative links to health effects could help decision makers to better assess the AOC's state. Thus, we compared tissue concentrations of Hg, PCBs, morphometric measures of health, and biomarkers of exposure, metabolic-, and reproductive health in native brown bullhead (Ameiurus nebulosus) from the AOC to those of upstream reference fish. Linear discriminant analysis separated the adult fish of both sexes among upstream and downstream sites without misclassification. Burdens of total-Hg (all sites) and PCB toxic equivalents (downstream sites) exceeded the guidance for the protection of wildlife consumers. There were subtle effects of site on physiological variables, particularly in female fish. Total-Hg in tissue correlated negatively to plasma testosterone and 17ß-estradiol in female fish at Cornwall: moreover, concentrations of both hormones were lower within the AOC compared to reference site fish. A similar effect on vitellogenin, which was uncorrelated to E2/T at the downstream sites, indicated the potential for reproductive effects. Downstream fish also had altered thyroidal status (T3, TSH, and ratio of thyroid epithelial cell area to colloid area). Despite spatial and temporal variability of the endocrine-related responses, these subtle effects on fish health within the AOC warrant further study.

Drivers of Mercury Cycling in the Rapidly Changing Glacierized Watershed of the High Arctic's Largest Lake by Volume (Lake Hazen, Nunavut, Canada).

Across the Arctic, glaciers are melting and permafrost is thawing at unprecedented rates, releasing not only water to downstream aquatic systems, but also contaminants like mercury, archived in ice over centuries. Using concentrations from samples collected over 4 years and calibrated modeled hydrology, we calculated methylmercury (MeHg) and total mercury (THg) mass balances for Lake Hazen, the world's largest High Arctic lake by volume, for 2015 and 2016. Glacial rivers were the most important source of MeHg and THg to Lake Hazen, accounting for up to 53% and 94% of the inputs, respectively. However, due to the MeHg and THg being primarily particle-bound, Lake Hazen was an annual MeHg and THg sink. Exports of MeHg and THg out the Ruggles River outflow were consequently very low, but erosion and permafrost slumping downstream of the lake increased river MeHg and THg concentrations significantly before entering coastal waters in Chandler Fjord. Since 2001, glacial MeHg and THg inputs to Lake Hazen have increased by 0.01 and 0.400 kg yr-1, respectively, in step with dramatic increases in glacial melt. This study highlights the potential for increases in mercury inputs to arctic ecosystems downstream of glaciers despite recent reductions in global mercury emissions.

Cerebrospinal fluid HIV RNA in persons living with HIV.

OBJECTIVES: Despite adequate suppression of plasma HIV RNA, viral escape in cerebrospinal fluid (CSF) is widely reported. Rates of CSF HIV RNA escape vary in the literature. In persons living with HIV (PLWH) undergoing lumbar puncture examination for clinical reasons, we assessed rates of CSF HIV RNA escape. METHODS: Persons living with HIV attending a designated HIV neurology service undergoing CSF assessment for clinical reasons between January 2015 and April 2017 were included in the study. CSF HIV RNA escape was defined as HIV RNA ≥ 0.5 log10 HIV-1 RNA copies/mL higher than plasma HIV RNA or detectable CSF HIV RNA when plasma HIV RNA was < 20 copies/mL. Clinical factors associated with CSF HIV RNA were assessed using logistic regression modelling. RESULTS: Of 38 individuals, 35 were receiving antiretroviral therapy, 30 were male and their mean age was 51 years. Clinical reasons for CSF assessment included investigation for cognitive decline (n = 25), early syphilis (n = 4) and other central nervous system (CNS) conditions (n = 9). HIV RNA was detectable in plasma and CSF in seven and six individuals, respectively, with two individuals (5.3%) meeting the definition of CSF escape. Detectable CSF HIV RNA was associated with a detectable plasma HIV RNA (P < 0.001) and a history of known antiretroviral drug resistance mutations (P = 0.021). CONCLUSIONS: The prevalence of CSF viral escape in PLWH undergoing lumbar puncture examination for clinical reasons is lower than previously reported.

Using cognitive pre-testing methods in the development of a new evidenced-based pressure ulcer risk assessment instrument.

BACKGROUND: Variation in development methods of Pressure Ulcer Risk Assessment Instruments has led to inconsistent inclusion of risk factors and concerns about content validity. A new evidenced-based Risk Assessment Instrument, the Pressure Ulcer Risk Primary Or Secondary Evaluation Tool - PURPOSE-T was developed as part of a National Institute for Health Research (NIHR) funded Pressure Ulcer Research Programme (PURPOSE: RP-PG-0407-10056). This paper reports the pre-test phase to assess and improve PURPOSE-T acceptability, usability and confirm content validity. METHODS: A descriptive study incorporating cognitive pre-testing methods and integration of service user views was undertaken over 3 cycles comprising PURPOSE-T training, a focus group and one-to-one think-aloud interviews. Clinical nurses from 2 acute and 2 community NHS Trusts, were grouped according to job role. Focus group participants used 3 vignettes to complete PURPOSE-T assessments and then participated in the focus group. Think-aloud participants were interviewed during their completion of PURPOSE-T. After each pre-test cycle analysis was undertaken and adjustment/improvements made to PURPOSE-T in an iterative process. This incorporated the use of descriptive statistics for data completeness and decision rule compliance and directed content analysis for interview and focus group data. Data were collected April 2012-June 2012. RESULTS: Thirty-four nurses participated in 3 pre-test cycles. Data from 3 focus groups, 12 think-aloud interviews incorporating 101 PURPOSE-T assessments led to changes to improve instrument content and design, flow and format, decision support and item-specific wording. Acceptability and usability were demonstrated by improved data completion and appropriate risk pathway allocation. The pre-test also confirmed content validity with clinical nurses. CONCLUSIONS: The pre-test was an important step in the development of the preliminary PURPOSE-T and the methods used may have wider instrument development application. PURPOSE-T proposes a new approach to pressure ulcer risk assessment, incorporating a screening stage, the inclusion of skin status to distinguish between those who require primary prevention and those who require secondary prevention/treatment and the use of colour to support pathway allocation and decision making. Further clinical evaluation is planned to assess the reliability and validity of PURPOSE-T and it's impact on care processes and patient outcomes.

Trophic Magnification of Organic Chemicals: A Global Synthesis.

Production of organic chemicals (OCs) is increasing exponentially, and some OCs biomagnify through food webs to potentially toxic levels. Biomagnification under field conditions is best described by trophic magnification factors (TMFs; per trophic level change in log-concentration of a chemical) which have been measured for more than two decades. Syntheses of TMF behavior relative to chemical traits and ecosystem properties are lacking. We analyzed >1500 TMFs to identify OCs predisposed to biomagnify and to assess ecosystem vulnerability. The highest TMFs were for OCs that are slowly metabolized by animals (metabolic rate kM < 0.01 day(-1)) and are moderately hydrophobic (log KOW 6-8). TMFs were more variable in marine than freshwaters, unrelated to latitude, and highest in food webs containing endotherms. We modeled the probability that any OC would biomagnify as a combined function of KOW and kM. Probability is greatest (∼100%) for slowly metabolized compounds, regardless of KOW, and lowest for chemicals with rapid transformation rates (kM > 0.2 day(-1)). This probabilistic model provides a new global tool for screening existing and new OCs for their biomagnification potential.

Cadmium and other elements in tissues from four ungulate species from the Mackenzie Mountain region of the Northwest Territories, Canada.

Tissue samples from four ungulate species from the south Mackenzie Mountain region of the Northwest Territories (NT), Canada, were analysed for stable and radioactive elements and (15)N and (13)C stable isotopes. Elevated Cd concentrations in moose (Alces americanus) kidney have been observed in the region and are a health care concern for consumers of traditional foods. This study examined the factors associated with, and potential renal effects from, the accumulation of cadmium, and interactions with other elements in four sympatric ungulate species. Mean renal Cd concentration was highest in moose (48.3mg/kg ww), followed by mountain caribou (Rangifer tarandus caribou) (13.9mg/kg ww) and mountain goat (Oreamnos americanus) (5.78mg/kg ww). No local sources of Cd were evident and the elevated levels in moose are considered to be natural in origin. Conversely, total Hg concentration was significantly higher in mountain caribou kidney (0.21mg/kg ww) than in moose (0.011mg/kg ww). (134)Cs (t½=2.1 y) in mountain goat and Dall's sheep (Ovis dalli) muscle is evidence of deposition from the Fukushima reactor accident in 2011. (137)Cs (t½=30.2 y) in all four ungulates is primarily a remnant of the nuclear weapons tests of the 1960s. The levels of both nuclides are low and the risk to the animals and people consuming them is negligible. Stable isotope δ(15)N and δ(13)C signatures in muscle showed a separation between the mountain caribou, with a lichen-dominated diet, and moose, which browse shrubs and forbs. Isotope signatures for mountain goat and Dall's sheep showed generalist feeding patterns. Differences in elemental and radionuclide levels between species were attributed to relative levels of metal accumulation in the different food items in the diets of the respective species. Kidneys from each species showed minor histological changes in the proximal tubule and glomerulus, although glomerular changes were rare and all changes were rare in mountain goat kidney. Kidney function was not expected to be affected in any species. Provisional Monthly Intake recommendations from the WHO indicate that Cd in moose organs will continue to be a public health care concern. However, traditional foods continue to be an important nutritional component of northern diets, particularly in consideration of the shift towards store-bought food.

Losses of sexual dichromatism involve rapid changes in female plumage colors to match males in New World blackbirds.

Differences in coloration between the sexes (sexual dichromatism) can increase or decrease in a species through evolutionary changes in either or both sexes diverging or converging in their colors. Few previous studies, however, have examined the relative rates of such changes, particularly when dichromatism is lost. Using reflectance data from 37 species of the New World blackbird family (Icteridae), we compared evolutionary rates of plumage color change in males and females when dichromatism was either increasing (colors diverging) or decreasing (colors converging). Increases in dichromatism involved divergent changes in both sexes at approximately equal rates. Decreases in dichromatism, in contrast, involved changes in females to match male plumage colors that were significantly more rapid than any changes in males. Such dramatic changes in females show how selection can differ between the sexes. Moreover, these evolutionary patterns support the idea that losses of dimorphism involve genetic mechanisms that are already largely present in both sexes, whereas increases in dimorphism tend to involve the appearance of novel sex-specific traits, which evolve more slowly. Our results have broad implications for how sexual dimorphisms evolve.

PAH fluxes to Siskiwit revisted: trends in fluxes and sources of pyrogenic PAH and perylene constrained via radiocarbon analysis.

Trends in concentrations and radiocarbon content of pyrogenic PAHs and perylene were determined 20 years after a previous study by Mcveety and Hites (1988). Pyrogenic PAH fluxes to sediments were observed to continue to decrease over the period from 1980 to 2000 at this remote site in contrast to observations in more urban areas. Radiocarbon analysis of pyrogenic PAHs showed a 50% decrease in the proportion of pyrogenic PAH derived from fossil fuel combustion over the past 50 years, consistent with decreasing emissions from regional coal-fired power-generating plants. Fluxes of pyrogenic PAHs related to biomass burning were consistent over this same period and found to exceed fossil fuel sources in the most recent samples. Fluxes of biomass-derived pyrogenic PAHs were similar in magnitude to total pyrogenic PAH fluxes in early 1900, suggesting that these fluxes may represent wildfire inputs. Not only did perylene concentrations in these sediments increase with depth as previously observed but also concentrations from the same sedimentary layers analyzed 20 years previously showed large increases in perylene concentrations. Radiocarbon analysis of perylene indicated that 70-85% of perylene observed in the deeper sediments could be explained by production from total organic carbon.

Chemical fingerprinting of naphthenic acids and oil sands process waters-A review of analytical methods for environmental samples.

This article provides a review of the routine methods currently utilized for total naphthenic acid analyses. There is a growing need to develop chemical methods that can selectively distinguish compounds found within industrially derived oil sands process affected waters (OSPW) from those derived from the natural weathering of oil sands deposits. Attention is thus given to the characterization of other OSPW components such as oil sands polar organic compounds, PAHs, and heavy metals along with characterization of chemical additives such as polyacrylamide polymers and trace levels of boron species. Environmental samples discussed cover the following matrices: OSPW containments, on-lease interceptor well systems, on- and off-lease groundwater, and river and lake surface waters. There are diverse ranges of methods available for analyses of total naphthenic acids. However, there is a need for inter-laboratory studies to compare their accuracy and precision for routine analyses. Recent advances in high- and medium-resolution mass spectrometry, concomitant with comprehensive mass spectrometry techniques following multi-dimensional chromatography or ion-mobility separations, have allowed for the speciation of monocarboxylic naphthenic acids along with a wide range of other species including humics. The distributions of oil sands polar organic compounds, particularly the sulphur containing species (i.e., OxS and OxS2) may allow for distinguishing sources of OSPW. The ratios of oxygen- (i.e., Ox) and nitrogen-containing species (i.e., NOx, and N2Ox) are useful for differentiating organic components derived from OSPW from natural components found within receiving waters. Synchronous fluorescence spectroscopy also provides a powerful screening technique capable of quickly detecting the presence of aromatic organic acids contained within oil sands naphthenic acid mixtures. Synchronous fluorescence spectroscopy provides diagnostic profiles for OSPW and potentially impacted groundwater that can be compared against reference groundwater and surface water samples. Novel applications of X-ray absorption near edge spectroscopy (XANES) are emerging for speciation of sulphur-containing species (both organic and inorganic components) as well as industrially derived boron-containing species. There is strong potential for an environmental forensics application of XANES for chemical fingerprinting of weathered sulphur-containing species and industrial additives in OSPW.

Rapid phenotypic evolution during incipient speciation in a continental avian radiation.

Adaptive radiations have helped shape how we view animal speciation, particularly classic examples such as Darwin's finches, Hawaiian fruitflies and African Great Lakes cichlids. These 'island' radiations are comparatively recent, making them particularly interesting because the mechanisms that caused diversification are still in motion. Here, we identify a new case of a recent bird radiation within a continentally distributed species group; the capuchino seedeaters comprise 11 Sporophila species originally described on the basis of differences in plumage colour and pattern in adult males. We use molecular data together with analyses of male plumage and vocalizations to understand species limits of the group. We find marked phenotypic variation despite lack of mitochondrial DNA monophyly and few differences in other putatively neutral nuclear markers. This finding is consistent with the group having undergone a recent radiation beginning in the Pleistocene, leaving genetic signatures of incomplete lineage sorting, introgressive hybridization and demographic expansions. We argue that this apparent uncoupling between neutral DNA homogeneity and phenotypic diversity is expected for a recent group within the framework of coalescent theory. Finally, we discuss how the ecology of open habitats in South America during the Pleistocene could have helped promote this unique and ongoing radiation.

Associations between complex OHC mixtures and thyroid and cortisol hormone levels in East Greenland polar bears.

The multivariate relationship between hair cortisol, whole blood thyroid hormones, and the complex mixtures of organohalogen contaminant (OHC) levels measured in subcutaneous adipose of 23 East Greenland polar bears (eight males and 15 females, all sampled between the years 1999 and 2001) was analyzed using projection to latent structure (PLS) regression modeling. In the resulting PLS model, most important variables with a negative influence on cortisol levels were particularly BDE-99, but also CB-180, -201, BDE-153, and CB-170/190. The most important variables with a positive influence on cortisol were CB-66/95, α-HCH, TT3, as well as heptachlor epoxide, dieldrin, BDE-47, p,p'-DDD. Although statistical modeling does not necessarily fully explain biological cause-effect relationships, relationships indicate that (1) the hypothalamic-pituitary-adrenal (HPA) axis in East Greenland polar bears is likely to be affected by OHC-contaminants and (2) the association between OHCs and cortisol may be linked with the hypothalamus-pituitary-thyroid (HPT) axis.

Age-growth relationships, temperature sensitivity and palaeoclimate-archive potential of the threatened Altiplano cactus Echinopsis atacamensis.

The tall (>4 m), charismatic and threatened columnar cacti, pasacana [Echinopsis atacamensis (Vaupel) Friedrich & G.D. Rowley)], grows on the Bolivian Altiplano and provides environmental and economic value to these extremely cold, arid and high-elevation (~4000 m) ecosystems. Yet very little is known about their growth rates, ages, demography and climate sensitivity. Using radiocarbon in spine dating time series, we quantitatively estimate the growth rate (5.8 and 8.3 cm yr-1) and age of these cacti (up to 430 years). These data and our field measurements yield a survivorship curve that suggests precipitation on the Altiplano is important for this species' recruitment. Our results also reveal a relationship between nighttime temperatures on the Altiplano and the variation in oxygen isotope values in spines (δ18O). The annual δ18O minimums from 58 years of in-series spine tissue from pasacana on the Altiplano provides at least decadal proxy records of temperature (r = 0.58; P < 0.0001), and evidence suggests that there are longer records connecting modern Altiplano temperatures to sea-surface temperatures (SSTs) in the Atlantic Ocean. While the role of Atlantic SSTs on the South American Summer Monsoon (SASM) and precipitation on the Bolivian Altiplano is well described, the impact of SSTs on Altiplano temperatures is disputed. Understanding the modern impact of SSTs on temperature on the Altiplano is important to both understand the impact of future climate change on pasacana cactus and to understand past climate changes on the Altiplano. This is the best quantitative evidence to date of one of the oldest known cactus in the world, although there are likely many older cacti on the Altiplano, or elsewhere, that have not been sampled yet. Together with growth, isotope and age data, this information should lead to better management and conservation outcomes for this threatened species and the Altiplano ecosystem.

Tissue contaminants and wild fish health in the St. Clair River Area of Concern - Part 2: Spatial trends and temporal declines in organics.

We explored tissue concentrations of polychlorinated biphenyls (PCBs), chlorinated pesticides, and relevant organochlorines and fish health in the following adult wild fish in the St. Clair River Area of Concern (Ontario, Canada): shorthead redhorse (Moxostoma macrolepidotum), yellow perch (Perca flavescens), and emerald shiner (Notropis atherinoides). We collected adult fish from sites within the river's industrial zone (Stag Island), a downstream site adjacent to Walpole Island (Chenal Écarte), and an upstream reference site in Lake Huron in 2002/2003 and 2014. We tested for trends in tissue concentrations of organic contaminants across sites and over time; we assessed the potential effects of contaminants on morphological indicators of fish health across sites by year. Over the 12-year period, the tissue concentrations of most PCBs declined at the river sites, except for some non-legacy PCBs (PCB11 and 185), which increased in yellow perch at Stag Island, a new observation for fish in the St. Clair River AOC. There was little difference between the concentrations of calculated toxic equivalents (TEQs) of the Lake Huron and the St. Clair River fish in 2014, except for emerald shiners from Stag Island which had elevated ΣPCB and TEQs. Each fish species at all sites exceeded the Canadian tissue residue guideline for PCBs for the protection of mammalian wildlife consumers of aquatic biota, but fish-derived TEQs indicated little potential health risk to fish. Over time, hexachlorobutadiene and hexachlorobenzene concentrations increased in some fish at Stag Island by about 8- and 4-fold, respectively, whereas they decreased at other sampling locations. Principal Component Analysis followed by Linear Discriminant Analysis of the 2014 SHRH data suggested that although the fish separated by site, tissue concentrations of PCB and organochlorine contaminants did not have consistent relationships to the morphological health indicators, including egg production in females, which implied the absence of causative relationships.

Renal trace elements in barren-ground caribou subpopulations: Temporal trends and differing effects of sex, age and season.

Caribou (Rangifer tarandus) are a culturally significant food resource for communities in northern Canada and Greenland. Many barren-ground caribou subpopulations are currently in decline, some dramatically; understanding the influence of stressors, such as toxic trace metals, is important. These contaminants enter Arctic terrestrial environments via atmospheric transport from industrialized areas and from local sources, accumulating there in the environment. Understanding how trace element concentrations interact and are influenced by caribou sex, age and season of collection is essential to evaluating trends in these elements over time and differences among subpopulations. We used path analysis to model the direct and indirect relationships between these variables in the Porcupine subpopulation and in barren-ground caribou from the Canadian Arctic and Greenland. Renal cadmium (Cd), copper (Cu) and mercury (Hg) varied significantly among subpopulations. Hg was positively correlated with Cd, Cu and selenium (Se) in female Porcupine caribou whereas Cd and Cu were negatively correlated in male Porcupine caribou. Age, season and sex influenced all three element concentrations and should be considered when comparing elements among caribou subpopulations or years. Renal Cd decreased slightly from the Canadian Western Arctic to Greenland and increased slightly over time, possibly reflecting patterns of atmospheric deposition. Renal Hg did not change significantly over time, and differences among subpopulations did not follow specific geographical patterns. Renal Cu declined over time, the changes being markedly different among subpopulations, sexes and seasons. This temporal decline is likely due to changes in diet, which could be driven by various environmental factors. Declining Cu concentrations in caribou is of concern as low levels could negatively affect reproductive success and therefore caribou at a population level. Continuing to monitor element concentrations in caribou is essential to better comprehend potential threats facing the species, and to promote food security in communities harvesting this important resource.

Stromelysin generates a fibronectin fragment that inhibits Schwann cell proliferation.

Our previous report (Muir, D., S. Varon, and M. Manthorpe. 1990. J. Cell Biol. 109:2663-2672) described the isolation and partial characterization of a 55-kD antiproliferative protein found in Schwann cell (SC) and schwannoma cell line-conditioned media and we concluded that SC proliferation is under negative autocrine control. In the present study the 55-kD protein was found to possess metalloprotease activity and stromelysin immunoreactivity. The SC-derived metalloprotease shares many properties with stromelysin isolated from other sources including the ability to cleave fibronectin (FN). Furthermore, limited proteolysis of FN by the SC-derived protease generated a FN fragment which itself expresses a potent antiproliferative activity for SCs. The active FN fragment corresponds to the 29-kD amino-terminal region of the FN molecule which was also identified as an active component in SC CM. Additional evidence that a proteolytic fragment of FN can possess antiproliferative activity for SCs was provided by the finding that plasmin can generate an amino-terminal FN fragment which mimicked the activity of the SC metalloprotease-generated antiproliferative FN fragment. Both the 55-kD SC metalloprotease and the 29-kD FN fragment could completely and reversibly inhibit proliferation of SCs treated with various mitogens and both were largely ineffective at inhibiting proliferation by immortalized or transformed SC lines. Normal and transformed SC types do secrete the proform of stromelysin, however, transformed cultures do not produce activated stromelysin and thus cannot generate the antiproliferative fragment of FN. These results suggest that, once activated, a SC-derived protease similar to stromelysin cleaves FN and generates an antiproliferative activity which can maintain normal SC quiescence in vitro.

Schwann cell proliferation in vitro is under negative autocrine control.

In healthy adult peripheral nerve, Schwann cells are believed to be generally quiescent. Similarly, cultures of isolated rat sciatic nerve Schwann cells hardly proliferate in serum-supplemented medium. The possibility that Schwann cells negatively regulate their own proliferation was supported by the demonstration that conditioned media from Schwann cell cultures inhibited the proliferation of mitogen-stimulated test cultures. The inhibition could be complete, was dose dependent, and was exhibited when the test Schwann cells were under the influence of different types of mitogens such as cholera toxin, laminin, and living neurons. The inhibition of proliferation was completely reversible and a rapid doubling of cell number resulted when treatment with conditioned medium was withdrawn from mitogen-stimulated Schwann cells. Conditioned medium from cholera toxin-stimulated and immortalized Schwann cell cultures contained less antiproliferative activity than that found in medium from quiescent Schwann cell cultures. However, media conditioned by two actively proliferating rat Schwannoma cell lines were rich sources of antiproliferative activity for Schwann cells. Unlike the mitogen-stimulated Schwann cells, whose proliferation could be inhibited completely, the immortalized and transformed Schwann cell types were nearly unresponsive to the antiproliferative activity. The antiproliferative activity in Schwann and Schwannoma cell conditioned media was submitted to gel filtration and SDS-PAGE. The activity exists in at least two distinct forms: (a) a high molecular weight complex with an apparent molecular mass greater than 1,000 kD, and (b) a lower molecular weight form having a molecular mass of 55 kD. The active 55-kD form could be derived from the high molecular weight form by gel filtration performed under dissociating conditions. The 55-kD form was further purified to electrophoretic homogeneity. These results suggest that Schwann cells produce an autocrine factor, which we designate as a "neural antiproliferative protein," which completely inhibits the in vitro proliferation of Schwann cells but not that of immortalized Schwann cells or Schwannoma lines.

Schwannoma cell-derived inhibitor of the neurite-promoting activity of laminin.

During the purification of laminin-proteoglycan complexes from rat RN22 Schwannoma cell-conditioned medium, a laminin-rich fraction was obtained which lacked neurite-promoting activity. Since laminin from several sources is known to have potent neurite-promoting activity, this result suggested that either this laminin was inactive or its activity was somehow masked by associated molecule(s). The latter possibility was supported by the demonstration that the inactive laminin-containing fraction inhibited active laminin-containing fractions. This inhibitory activity was partially purified by using ion exchange chromatography and isopycnic centrifugation. The purified material contained proteoglycan based on its high affinity for cationic resin, high buoyant density, large heterodisperse appearance on electrophoretic gels, ability to label with inorganic sulfate, sensitivity to trypsin and glycosaminoglycan lyases, and heat stability. A quantitative in vitro bioassay was used to monitor the inhibitor after treatments aimed at defining its activity. The isolated Schwannoma-derived inhibitor (a) inhibits the neurite-promoting activity of purified rat, mouse, and human laminin; (b) is active whether presented to laminin in solution or after either the inhibitor or laminin is first bound to the culture substratum; (c) does not act by displacing laminin from the substratum; (d) can be prevented from binding to neurite-promoting laminin substrates by polyclonal and monoclonal anti-laminin or polyclonal anti-entactin antibodies; and (e) is abolished by proteases or glycosaminoglycan lyases but not by heat. The above results suggest that the neurite-promoting activity of laminin is subject to regulation through association with a proteoglycan and entactin.