The association between acanthosis nigricans and dysglycemia in an ethnically diverse group of eighth grade students

Objective:

The purpose of this study was to describe the prevalence of acanthosis nigricans (AN) and to quantify its association with dysglycemia in an ethnically diverse group of eighth‐grade students.

Design and Methods:

Data were collected in 2003 from a cross‐sectional study of students from 12 middle schools in three US states. Sex, race/ethnicity, and pubertal status were self‐reported. Anthropometric measures were recorded. Trained staff identified the presence and severity of AN by inspection of the back of the neck. Fasting and 2 h blood samples were analyzed for impaired fasting glucose (IFG), impaired glucose tolerance (IGT), and high‐risk glycated hemoglobin (A1C), respectively, defined as ≥100 mg/dl, ≥140 mg/dl, and ≥ 5.7‐6.4%.

Results:

Overall, 25.0%, 58.2%, and 16.8% were Black, Hispanic, and White, respectively. AN was present among 406/1,438 (28.2%) of students: 39% among Black, 30% among Hispanic, and 5.4% among White. IGT and high‐risk A1C were present among 2.1%, and 12.4%, respectively. In multivariate logistic modeling after adjusting for gender, family history of diabetes, BMI percentile, and pubertal staging, the presence (vs. absence) of AN was associated with a 59% increased likelihood of high‐risk A1C: (P = 0.04), twice the likelihood of IGT (P = 0.06), and 47% greater likelihood of IGT/IFG combined (P < 0.0001). Adjustment for insulin attenuated the ORs by 25‐70%.

Conclusion:

In a racially/ethnically diverse sample of US adolescents, AN was common, occurring in 28% of the sample. AN was associated with a 50‐100% increased likelihood of dysglycemia even after consideration of established diabetes risk factors.     

Induction of suppressor cells by a tumor-derived suppressor factor

Murine fibrosarcomas produce a factor that activates suppressor cells to inhibit expression of delayed-type hypersensitivity (DTH) responses to dinitrochlorobenzene (DNCB). This tumor-derived suppressor factor (TDSF) was partially purified by preparative isoelectric focusing of spent medium and 3 M KCl extracts of cultured methylcholanthrene-induced and spontaneous fibrosarcomas of C3H/He mice. Incubation of 1 micrograms/ml of a fraction, isoelectric pH less than 2.9, with normal syngeneic spleen cells for 1-6 hr at 37 degrees C induced suppressor cells that inhibited the primary DTH response to DNCB upon intraperitoneal transfer to normal C3H/HeJ mice. TDSF was not present in extracts of either syngeneic embryonic fibroblasts or normal spleen cells or in medium conditioned by normal peritoneal exudate cells but was present in 3 M KCl extracts of and the spent medium from four different cultured murine fibrosarcomas. TDSF activity was not restricted at the major histocompatibility complex. The suppressor cells inhibited the efferent limb of the DTH response because (1) hyporesponsive recipients of TDSF-treated spleen cells had splenic effector T cells capable of transferring DTH to DNCB into naive secondary recipients and (2) the ability of Lyt 1+,2- effector Tdth cells to transfer a secondary DTH response to DNCB was inhibited by co-incubation with macrophages or Lyt 1-,2+ T cells treated with TDSF. Preliminary biochemical analysis suggested that TDSF was an RNA- protein complex. Thus, several murine fibrosarcomas produced a soluble factor that activated splenic suppressor cells to depress the immune response to nonneoplastic antigens. These suppressor factors represent a novel group of regulatory molecules which may be ribonucleoprotein complexes.     

A novel evolutionary lineage of carbonic anhydrase (epsilon class) is a component of the carboxysome shell

A significant portion of the total carbon fixed in the biosphere is attributed to the autotrophic metabolism of prokaryotes. In cyanobacteria and many chemolithoautotrophic bacteria, CO(2) fixation is catalyzed by ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO), most if not all of which is packaged in protein microcompartments called carboxysomes. These structures play an integral role in a cellular CO(2)-concentrating mechanism and are essential components for autotrophic growth. Here we report that the carboxysomal shell protein, CsoS3, from Halothiobacillus neapolitanus is a novel carbonic anhydrase (epsilon-class CA) that has an evolutionary lineage distinct from those previously recognized in animals, plants, and other prokaryotes. Functional CAs encoded by csoS3 homologues were also identified in the cyanobacteria Prochlorococcus sp. and Synechococcus sp., which dominate the oligotrophic oceans and are major contributors to primary productivity. The location of the carboxysomal CA in the shell suggests that it could supply the active sites of RuBisCO in the carboxysome with the high concentrations of CO(2) necessary for optimal RuBisCO activity and efficient carbon fixation in these prokaryotes, which are important contributors to the global carbon cycle.     

Vegetation dynamics in a Quercus‐Juniperus savanna: An isotopic assessment

Abstract. Woody plants are increasing in many grassland and savanna ecosystems around the world. As a case in point, the Edwards Plateau of Texas, USA, is a vast region (93 000 km²) in which rapid woody encroachment appears to be occurring. The native vegetation (prior to the Anglo‐European settlement 150–200 yr ago) and the biogeochemical consequences of woody encroachment in this region, however, are poorly understood. To assess these matters we measured plant and soil δ¹³C, soil organic C and soil N content from grasslands and two important woody patch types (mature Quercus virginiana clusters and Juniperus ashei woodlands) in this region. Soil δ¹³C values showed that relative productivity of C₃ species has increased in grassland and both woody habitats in recent times. δ¹³C of SOC in grasslands and Q. virginiana clusters increased with depth from the litter layer to 30 cm (grasslands =?21 to ?13‰Q. virginiana clusters =?27 to ?17‰) and were significantly different between habitats at all depths, indicating that Q. virginiana has been a long‐term component of the landscape. In J. ashei woodlands, soil δ¹³C values (at 20–30 cm depth) near the woodland edge (‐13‰) converged with those of an adjacent grassland (‐13‰) while those from the woodland interior (‐15‰) remained distinct, indicating that the woodland has been present for many years but has recently expanded. Concentrations and densities of SOC and total N were generally greater in woody patches than in grasslands. However, differences in the amount of SOC and N stored beneath the two woody patch types indicates that C and N sequestration potentials are species dependent.     

Clinical pathology and assessment of pathogen exposure in southern and Alaskan sea otters

The southern sea otter (Enhydra lutris nereis) population in California (USA) and the Alaskan sea otter (E. lutris kenyoni) population in the Aleutian Islands (USA) chain have recently declined. In order to evaluate disease as a contributing factor to the declines, health assessments of these two sea otter populations were conducted by evaluating hematologic and/or serum biochemical values and exposure to six marine and terrestrial pathogens using blood collected during ongoing studies from 1995 through 2000. Samples from 72 free-ranging Alaskan, 78 free-ranging southern, and (for pathogen exposure only) 41 debilitated southern sea otters in rehabilitation facilities were evaluated and compared to investigate regional differences. Serum chemistry and hematology values did not indicate a specific disease process as a cause for the declines. Statistically significant differences were found between free-ranging adult southern and Alaskan population mean serum levels of creatinine kinase, alkaline phosphatase, alanine aminotransferase, aspartate aminotransferase, calcium, cholesterol, creatinine, glucose, phosphorous, total bilirubin, blood urea nitrogen, and sodium. These were likely due to varying parasite loads, contaminant exposures, and physiologic or nutrition statuses. No free-ranging sea otters had signs of disease at capture, and prevalences of exposure to calicivirus, Brucella spp., and Leptospira spp. were low. The high prevalence (35%) of antibodies to Toxoplasma gondii in free-ranging southern sea otters, lack of antibodies to this parasite in Alaskan sea otters, and the pathogen's propensity to cause mortality in southern sea otters suggests that this parasite may be important to sea otter population dynamics in California but not in Alaska. The evidence for exposure to pathogens of public health importance (e.g., Leptospira spp., T. gondii) in the southern sea otter population, and the na?veté of both populations to other pathogens (e.g., morbillivirus and Coccidiodes immitis) may have important implications for their management and recovery.     

Rates and patterns of mitochondrial DNA sequence evolution in fringilline finches (fringilla spp.) and the greenfinch (Carduelis chloris)

Rates and patterns of evolution in partial sequences of five mitochondrial genes (cytochrome b, ATPase 6, NADH dehydrogenase subunit 5, tRNA(Glu), and the control region) were compared among taxa in the passerine bird genera Fringilla and Carduelis. Rates of divergence do not vary significantly among genes, even in comparisons with the control region. Rate variation among lineages is significant only for the control region and NADH dehydrogenase subunit 5, and patterns of variation are consistent with the expectations of neutral theory. Base composition is biased in all genes but is stationary among lineages, and there is evidence for directional mutation pressure only in the control region. Despite these similarities, patterns of substitution differ among genes, consistent with alternative regimes of selective constraint. Rates of nonsynonymous substitution are higher in NADH dehydrogenase subunit 5 than in other protein-coding genes, and transitions exist in elevated proportions relative to transversions. Transitions appear to accumulate linearly with time in tRNA(Glu), and despite exhibiting the highest overall rate of divergence among species, there are no transversional changes in this gene. Finally, for resolving phylogenetic relationships among Fringilla taxa, the combined protein-coding data are broadly similar to those of the control region in terms of phylogenetic informativeness and statistical support.      

Blood gas and catecholamine levels in capture stressed desert bighorn sheep.

Forty-seven bighorn sheep (Ovis canadensis nelsoni) were captured within a 3-day period in December, 1989 as part of a California Department of Fish and Game effort to repopulate historic ranges in California. They were captured on the Mojave Desert in the Kelso Mountains near Old Dad Peak, San Bernardino County, California. Venous blood gases measured at the site of capture demonstrated a severe metabolic acidosis (base deficit, 23 mEq/liter), with no evidence of respiratory acidosis. There were moderately elevated plasma epinephrine (1.25 ng/ml), norepinephrine (2.60 ng/ml), and dopamine (114 pg/ml) levels. These data appear to reflect animals that have been moderately stressed. These acid-base-catecholamine values differ from values in resting domestic sheep, and are similar to those reported in greyhounds after brief strenuous exercise.