Histological evaluations of organ tissues reveal sublethal effects in a freshwater mussel (Villosa iris) exposed to chloride and potassium concentrations below benchmark estimates

Salinization of freshwater ecosystems due to anthropogenic sources will increasingly impact biodiversity. An example of point-source industrial salinization has occurred from historical activities at a U.S. Environmental Protection Agency Superfund Site near Saltville, Virginia USA and its associated chemical waste ponds adjacent to the North Fork Holston River. These point source discharges are documented contributors to mussel declines, partially due to high concentrations of chloride (Cl^-, ≤ 26,000 mg Cl^-/L) and potassium (K⁺, ≤ 97 mg K⁺/L). During a chronic 61-day laboratory study, Rainbow mussels, Villosa iris, were exposed to concentrations of Cl- (0, 416, 831, and 1,663 mg/L) and K+ (0, 4, 8, and 17 mg/L) to determine effects on survival and organ tissues. All test mussels died by day-2 in the 1,663 mg Cl^-/L exposure, and 50% of mussels died by day-13 in the 17 mg K⁺/L concentration. Significantly greater abundances of tissue abnormalities were observed in digestive glands and kidneys with exposures to the 4 and 8 mg/L concentrations of K⁺ versus the control, and significantly greater abundances of lesions in kidneys were observed in the 416 and 831 mg Cl^-/L concentrations compared to the control. The sublethal effects to digestive glands and kidneys were below reported effect (EC_{50, 20, 10} and LOEC) concentrations. Significant histological differences between control and baseline (day-0 sample) mussels were observed, suggesting the need for further study on the effects of captivity during longer-term laboratory experiments.

Understanding the influence of multiple pollutant stressors on the decline of freshwater mussels in a biodiversity hotspot

The Clinch River watershed of the upper Tennessee River Basin of Virginia and Tennessee, USA supports one of North America's greatest concentrations of freshwater biodiversity, including 46 extant species of native freshwater mussels (Order Unionida), 20 of which are protected as federally endangered. Despite the global biological significance of the Clinch River, mussel populations are declining in some reaches, both in species richness and abundance. The aim of this study was to evaluate the exposure of adult resident mussels to a suite of inorganic and organic contaminant stressors in distinct sections of the Clinch River that encompassed a range of mussel abundance and health. To provide insight into the potential role of pollutants in the decline of mussels, including within a previously documented "zone of mussel decline", the mainstem Clinch River (8 sites) and its tributaries (4 sites) were examined over two consecutive years. We quantified and related metals and organic contaminant concentrations in mussels to their associated habitat compartments (bed sediment, suspended particulate sediment, pore water, and surface water). We found that concentrations of organic contaminants in resident mussels, particularly the suite of 42 polycyclic aromatic hydrocarbons (PAHs) analyzed, were related to PAH concentrations in all four habitat (media) compartments. Further, PAH concentrations in mussel tissue (range 37.8-978.1 ng/g dry weight in 2012 and 194.3-1073.7 ng/g dry weight in 2013) were negatively related to the spatial pattern in mussel densities (r_s = -0.64, p ≤ 0.05 in 2012 and r_s = -0.83, p ≤ 0.05 in 2013) within the river, and were highest in the "zone of mussel decline". In contrast, the suite of 22 metals analyzed in resident mussels were largely unrelated to the spatial pattern of variation of metals in the four habitat compartments except for Manganese (Mn; range 3630.5-23,749.2 μg/g dry weight in 2012 and 1540.4-12,605.8 μg/g dry weight in 2013) in surface water (r_s = 0.58, p < 0.1) and pore water (r_s = 0.76, p ≤ 0.05). This study revealed that PAHs and Mn are important pollutant stressors to mussels in the Clinch River and that they are largely being delivered through the Guest River tributary watershed. Accordingly, future conservation and management efforts would benefit by identifying, and ideally mitigating, the sources of PAHs, Mn, and other current or legacy mining-associated pollutants to the mainstem river and its tributaries.

Assessment of growth, survival, and organ tissues of caged mussels (Bivalvia: Unionidae) in a river-scape influenced by coal mining in the southeastern USA

The Clinch River contains one of the most diverse freshwater mussel assemblages in the United States, with 46 extant species, 20 of which are listed as federally endangered. In a 91 km section of the Clinch River, mussel densities have severely declined at key sites from 1979 to 2014 (zone of decline), compared to other river sections that support high density and stable mussel populations (zone of stability). Coal mining has occurred in tributary watersheds that drain to the zone of decline since the late nineteenth century. To determine differences in survival, growth, and organ (gills, digestive glands, kidneys, and gonads) tissue health between the river zones, laboratory-propagated mussels were deployed to cages for one year at four sites each within the zones of mussel stability and decline. Means of growth and survival of mussels in the zone of stability were significantly greater than in the zone of decline, and mean fractions of kidney lipofuscin in mussels in the zone of decline was significantly greater than in the zone of stability. Water concentrations of K⁺, Na⁺, Al, and Mn were significantly greater in the zone of decline than in the zone of stability. Statistical correlation results indicated that mussel survival was positively associated with concentrations of Mn in water, and kidney lipofuscin was negatively associated with concentrations of dissolved K⁺, SO₄^2-, and Mg²⁺. Most concentrations of contaminants were below published benchmark criteria, yet our results suggest that conditions continue to exist in the zone of decline that promote impacts to mussels that are at least partially associated with low concentration coal-related contaminants. More research is needed to determine the additive, synergistic, or antagonistic effects of these complex ionic mixtures on freshwater mussels from river environments, such as in the Clinch River, where constituent concentrations are relatively low.

Acclimation of Arabidopsis thaliana to the light environment: the role of photoreceptors

The regulation by light of the composition of the photosynthetic apparatus was investigated in photomorphogenic mutants of Arabidopsis thaliana (L.) Heynh. cv. Landsberg erecta. Leaf chlorophyll, photosynthesis, photosystem II function, and ribulose-1, 5-bisphosphate carboxylase-oxygenase and photosystem II contents were determined for plants grown under high- or low-irradiance growth regimes. Although certain mutant lines had altered chloroplast composition compared to the wild type, all photoreceptor mutants tested were capable of light-dependent changes in chloroplast composition and photosynthetic function, indicating that photoreceptors do not play a central role in the regulation of acclimation at the level of the chloroplast. However, the clear acclimation defect in a det1 signal transduction mutant indicates that photoreceptor-controlled responses either share regulatory components with acclimation, or are important in the expression of components which in turn regulate acclimation. We suggest that the COP/DET/FUS regulatory cluster is a focus for multiple signal transduction pathways, including some of the metabolic signals which form the basis for the acclimatory response.

Muscle morphogenetic protein induces myogenic gene expression in Swiss-3T3 cells

Myogenesis is thought to be regulated by the MyoD family of regulatory genes, which includes MyoD, myogenin, MRF- 4/myf-6, and myf-5. In situ hybridization studies of vertebrate skeletal muscle development have shown the colocalization of the MyoD family of regulatory genes to specific stages of muscle development. Although many studies have analyzed the regulatory role of these genes during myogenesis, there have been few reports dealing with the activation of these myogenic regulatory genes by exogenous agents. We have previously shown that muscle morphogenetic protein induces myogenesis in clonal populations of avian pluripotent stem cells. The current study was designed to examine the ability of muscle morphogenetic protein to induce myogenesis in a clonal population derived from the established fibroblastic Swiss-3T3 cell line. Swiss-3T3 cells were cloned to generate separate cell populations, tested for pluripotency, propagated through 690 cell doublings, retested for pluripotency, treated with muscle morphogenetic protein, and examined for the induction of gene expression using probes for the transcription products of MyoD and myogenin. Muscle morphogenetic protein induced the expression of mRNAs for MyoD and myogenin, suggesting a role for this compound as an exogenous activator of myogenesis.

Surgical clerkship performance of traditional and nontraditional students in a problem-based learning environment

BACKGROUND

To determine whether nontraditional students perform better than traditional students during surgical clerkships as reflected on the surgical clerkship final examination.

METHODS

Retrospective review of medical student records from the classes of 1986 through 1993. Students admitted soon after completing undergraduate training were identified as "traditional," and those having prior careers as "nontraditional."

RESULTS

There were 150 traditional and 72 nontraditional students. The ratio of men to women and admission MCAT scores were not significantly different. Traditional students were significantly younger and had higher admission grade point averages (GPAs). Nontraditional students were more likely to be married and have children. Final examination scores of traditional and nontraditional students were not significantly different. MCAT scores and college GPAs were the best predictors of final examination performance. Married students performed significantly better than single students.

CONCLUSIONS

There was no significant difference between nontraditional and traditional student performance on the surgical clerkship final examination.

Evaluating local public health performance at a community level on a statewide basis

As part of efforts to develop a surveillance system to evaluate local public health performance, six state health departments surveyed local health departments in their states. Overall, 370 respondents (94 percent) returned completed surveys. Based on responses to 26 indicators, the mean percent community performance of the three core functions of public health was 56 percent of the potential score. Scores were also calculated for perceived adequacy of performance and for each of 10 practices linked to the three core functions. Variations in performance were related to population size, state, and administrative relationship of local jurisdictions to the state. These results suggest local public health performance can be evaluated at a community level on a statewide basis using a relatively small number of indicators.

Assessing public health practice: application of ten core function measures of community health in six states

Factor analysis, combined with an evaluation of item difficulty and discrimination, can provide useful insights in questionnaire development. In 1993, as part of a study to develop a questionnaire to assess performance of the core functions of public health at a community level, 370 local health departments (LHDs) in six states completed a 26-item questionnaire (94% response). This study describes factor analysis results after controlling for item difficulty and discrimination. Fifteen items had intermediate difficulty and fair-to-good discrimination. Factor analysis of these 15 items identified four factors. Three of these factors included items from more than one of the core functions. These findings pose an interesting question for future research: are the core functions of public health better conceived as three discrete, distinguishable factors or as three interlocking factors that form a single, seamless unit?

Myelolipoma of the adrenal gland: a case report

Adrenal myelolipomas are rare benign neoplasms composed of mature fat and bone marrow elements. Most are asymptomatic tumors found incidentally at postmortem examinations. We report the natural history of an adrenal myelolipoma in a middle-aged man over a 6-year interval.

Trocar-site metastasis following laparoscopic cholecystectomy for unsuspected carcinoma of the gallbladder. Case report and review of the literature

Fifteen cases of trocar-size metastasis from unsuspected gallbladder carcinoma following laparoscopic cholecystectomy have been reported in the literature. We present the case of a 66-year-old woman who developed this complication 21/2 months postoperatively. We feel that carcinoma of the gallbladder is a contraindication to laparoscopic cholecystectomy. When unsuspected lesions are discovered, intraoperative frozen-section lesions will facilitate the surgical management.

Differentiation factors induce expression of muscle, fat, cartilage, and bone in a clone of mouse pluripotent mesenchymal stem cells

Growth factors have been used experimentally to accelerate wound healing by increasing scar tissue formation at a wound site. These studies suggest that stimulation of fibroblastic differentiation and proliferation are essential components of adult tissue repair. Recent studies report the presence of mesenchymal stem cells within granulation tissue and as connective tissue-resident stem cells. This suggests that mesenchymal stem cells as well as fibroblasts may contribute to wound healing and repair. To determine the potential for mesenchymal stem cells to contribute to nonfibrogenic tissue repair, a clonal population of murine mesenchymal stem cells was examined with dexamethasone, a general differentiation agent, and muscle morphogenetic protein, a specific differentiation-inducing agent. Dexamethasone induced the expression of phenotypic markers for fat, cartilage, and bone in the stem cells. Muscle morphogenetic protein induced the expression of mRNAs for the muscle specific regulatory genes MyoD1 and myogenin in these cells. These results suggest that pluripotent mesenchymal stem cells within connective tissue compartments and granulation tissue have the potential to contribute to functional tissue restoration, rather than contributing solely to fibrogenic scar tissue formation during tissue repair.

Thru-knee amputation: the operation of choice for non-ambulatory patients

Between 1983 and 1990, 32 consecutive patients had 35 thru-knee amputations for ischemia causing infection or gangrene of the lower leg. Twenty-seven patients were nonambulatory, five had limited mobility, and none were considered to be candidates for rehabilitation with a prosthesis after surgery. The average age was 73 years. Thirty-day hospital mortality was 3 per cent. The incidence of complications was low, and healing was achieved in 97 per cent of survivors. One patients required revision to an above-knee amputation. Average postoperative hospital stay was 8.7 days. It is concluded from this study that thru-knee amputation is the treatment of choice in patients with nonsalvageable ischemic legs and in whom ambulation is not planned after operation.

Variables discriminating residential placement of severely handicapped children

The relationship of 11 social and status variables to two placement groups of severely handicapped children (home and community-based residential facility). Using a multiple discriminant analysis, we found that 6 of these variables (child's age, parental feelings about the suggestion to institutionalize, religiosity, mother's age, child's age at first words, and child's age at school entry) contributed significantly to the discrimination between the two groups. When the resulting coefficient of discrimination was applied to a subsample, statistical classification agreed with known placement in 75.68% of the cases, indicating a high degree of discrimination between children residing at home and in residential settings on the variables studied.

Size Distributions of Sedimentary Populations

Separate sedimentary populations are not all characterized by lognormal size distributions. Populations of different sizes of material are produced by different mechanisms of abrasion: pebbles and gravel by singlestage crushing; sand by repeated abrasion; and silt and clay by chipping from larger grains. Each mechanism imposes a different size distribution on the product.