Protecting the boundary: the sentinel role of host defense peptides in the skin

The skin is our primary shield against microbial pathogens and has evolved innate and adaptive strategies to enhance immunity in response to injury or microbial insult. The study of antimicrobial peptide (AMP) production in mammalian skin has revealed several of the elegant strategies that AMPs use to prevent infection. AMPs are inducible by both infection and injury and protect the host by directly killing pathogens and/or acting as multifunctional effector molecules that trigger cellular responses to aid in the anti-infective and repair response. Depending on the specific AMP, these molecules can influence cytokine production, cell migration, cell proliferation, differentiation, angiogenesis and wound healing. Abnormal production of AMPs has been associated with the pathogenesis of several cutaneous diseases and plays a role in determining a patient’s susceptibility to pathogens. This review will discuss current research on the regulation and function of AMPs in the skin and in skin disorders.     

Highly reactive oxygen species: detection, formation, and possible functions

The so-called reactive oxygen species (ROS) are defined as oxygen-containing species that are more reactive than O(2) itself, which include hydrogen peroxide and superoxide. Although these are quite stable, they may be converted in the presence of transition metal ions, such as Fe(II), to the highly reactive oxygen species (hROS). hROS may exist as free hydroxyl radicals (HO·), as bound ("crypto") radicals or as Fe(IV)-oxo (ferryl) species and the somewhat less reactive, non-radical species, singlet oxygen. This review outlines the processes by which hROS may be formed, their damaging potential, and the evidence that they might have signaling functions. Since our understanding of the formation and actions of hROS depends on reliable procedures for their detection, particular attention is given to procedures for hROS detection and quantitation and their applicability to in vivo studies.     

Distribution of Brechmorhoga clubskimmers (Odonata: Libellulidae) in the Grand Canyon region, southwestern USA

We examined the distribution of Brechmorhoga mendax and B. pertinax (Libellulidae) in northern Arizona and southern Nevada. Brechmorhoga mendax occurs widely throughout the Southwest and in Arizona up to the Mogollon Rim, and up the Colorado River from the west to at least River Mile 132 (downstream from Lees Ferry, Arizona) at elevations of 110-1460 m. In Grand Canyon it occurs along small to large tributaries and on the mainstream at elevations below 650 m. The only previously reported locality for B. pertinax in the United States is in southeastern Arizona, where it was presumed to be accidental. We report B. pertinax along 5 small, perennial tributaries emanating from Redwall Formation aquifer springs on the south side of central Grand Canyon. Those springs habitats may be threatened by regional groundwater depletion. Brechmorhoga pertinax appears to be somewhat more stenotolerant in its habitat requirements than B. mendax , a finding in keeping with these differences in range. The presence of isolated populations of B. pertinax in Grand Canyon is an example of a Neotropical influence on the fauna and indicates biogeographic corridor and refuge functions of this large, deep canyon.     

Effects of grazing exclusions on rangeland vegetation and soils, east central Idaho

Nineteen exclosures on sagebrush steppe and shadscale rangelands, varying in age from 18 to 38 years, were sampled for plant species richness, plant composition, indicators of soil erosion, ground cover, vegetative cover, and herb-low shrub layer screening cover. Features within the exclosures were compared with adjacent sites of the same size that were open to grazing by livestock and wildlife. Species richness typically was slightly greater inside exclosures than in adjacent grazed sites (median = 2 more species inside exclosures), but the difference was not significant ( P = 0.16). Similarity of plant community composition between exclosures and adjacent grazed sites ranged from 45% to 82%. Evidences of soil movement, soil pedestals, and soil flow patterns were all more pronounced outside exclosures than inside ( P ≤ 0.02), even though many sites were on flat to mild slopes (median slope = 12%). Meta-analysis of the 19 exclosure sites indicated that grazing exclusion resulted in less bare ground cover compared with adjacent grazed sites ( P ≤ 0.05). The effect of grazing exclusion on visible soil surface cryptogams was significant ( P ≤ 0.05), with generally greater cover inside exclosures. Cryptogam cover differences between grazed sites and exclosures tended to increase with the number of years of grazing exclusion ( r = 0.64, P = 0.046). Pseudoroegneria spicata , a principal livestock forage, averaged greater basal cover inside exclosures than outside on 4 of 10 sites where it occurred, although no exclosure sites had greater P. spicata cover on grazed sites. Meta-analysis of the 10 sites indicated that grazing exclusion resulted in greater P. spicata cover compared with adjacent grazed areas ( P ≤ 0.05). Poa secunda , a short-growing grass that initiates growth early in the spring and is not important livestock forage, averaged greater basal cover outside exclosures on 5 of 15 sites where it occurred. Meta-analysis of the 15 sites indicated a significant treatment effect ( P ≤ 0.05), with greater Poa secunda basal cover outside exclosures. Grazing exclusion resulted in greater screening cover in the herb-low shrub layer (0-0.5 m height; P ≤ 0.05). These results indicate that despite improved livestock grazing management over the past half century, livestock grazing still can limit the potential of native plant communities in sagebrush steppe ecosystems, and that the health of semiarid ecosystems can improve with livestock exclusion in the absence of other disturbances. A few exclosure sites were similar for the measured parameters, suggesting that these sites were ecologically stable and that exclusion of livestock grazing was not sufficient to move succession toward more pristine conditions, at least within the time periods studied. Managed disturbance such as fire or mechanical brush treatments may be necessary to restore herb productivity on these ecologically stable sites.     

Temperature and high salinity effects in germinating dimorphic seeds of Atriplex rosea

Atriplex rosea L. (Chenopodiaceae; tumbling orach), an annual herb, is a widely established weedy species of disturbed sites in all counties of Utah. Seeds of Atriplex rosea were collected from a salt marsh in Faust, Utah, and are dimorphic, light brown, and 2-2.5 mm wide, or black and 1-2 mm wide. Seed germination responses of the black and brown seeds were studied over a range of salinity and temperature. Both brown and black seeds germinated at 1000 mM NaCl, and the optimal temperature for germination of both types was 20°-30°C. Variation in temperature, however, affected germination of black seeds more than brown seeds. At lower thermoperiod only 40%-50% black seeds germinated in nonsaline control, and germination was almost completely inhibited with the inclusion of salinity. However, all brown seeds germinated in control at temperatures above 5°-15°C, and inhibition caused by salinity was comparatively lower. Brown seeds had a higher germination rate than black seeds at all temperature and salinity treatments. The highest rate of germination of both seeds occurred at the temperature regime of 5°-15°C. Recovery of germination for black seeds when transferred to distilled water after being in various salinity treatments for 20 days was quite variable. Recovery decreased with increase in salinity at lower temperature regimes, increased with salinity at optimal thermoperiod, and had no effect at 20°-30°C. Brown seeds recovered poorly from salinity at all thermoperiods except 5°-15°C, where recovery decreased with an increase in salinity. Brown seeds are adapted to germination in the early part of the growing season, whereas black seeds are capable of surviving harsher conditions and can germinate in later time periods. Characteristics of the dimorphic seeds increase chances for survival in the harsh saline desert environment.     

Biogeographic and taxonomic relationships among the mountain snails (Gastropoda: Oreohelicidae) of the central Great Basin

Described here are 4 species of mountain snails, Oreohelix , isolated on mountains in the central Great Basin of Nevada and Utah since the end of the Pleistocene. Forty-three mountains were searched during an 18-year period, resulting in 24 mountains found with no oreohelicids present. One population, Oreohelix loisae (19 mm to 23 mm in shell diameter), is described here as a new species related to, but geographically isolated from, the species Oreohelix nevadensis (17 mm to 22 mm diameter). Oreohelix loisae is present only in the Goshute Mountains while O. nevadensis is represented in 3 geographically adjacent ranges in the central Great Basin. These 2 species are possibly related to the Oreohelix haydeni group from the northern Wasatch Range. The subspecies Oreohelix strigosa depressa (15 mm to 21 mm diameter) is present on 11 ranges from western Utah west to east central Nevada. This subspecies is closely related to populations found today in the northern Wasatch Mountains of Utah. The smallest species in diameter (8 mm to 14 mm), Oreohelix hemphilli , is centered in the central Great Basin and found on 16 ranges often in sympatry with 1 or 2 of the larger conspecifics. Both qualitative and quantitative information on shell characters and soft anatomy is provided here for these 4 species. Shell characters, soft anatomy, geographical isolation, and statistical analysis suggest that 4 distinct species inhabit the central Great Basin today. Xeric and calciphilic species include O. hemphilli and O. loisae , while O. strigosa and O. nevadensis typically are associated with permanent water and both metamorphic and limestone mountains.     

Recurrence of Mexican long-tongued bats ( Choeronycteris mexicana ) at historical sites in Arizona and New Mexico

The Mexican long-tongued bat ( Choeronycteris mexicana ) is a nectar-eating species that seasonally inhabits the southwestern United States. Since 1906, fewer than 1500 individuals of C. mexicana have been documented throughout the range of the species. We conducted a field survey in Arizona and New Mexico during summer 1999 to check historically occupied areas for recurrence of C. mexicana . We observed C. mexicana occupying a majority (75%, n = 18) of visited sites. Multiple individuals were observed at many sites, including young-of-year. Choeronycteris mexicana roosted in lighted areas close to entrances within mine adits, abandoned buildings, wide rock crevices, and caves. All occupied sites in Madrean evergreen woodlands or semidesert grasslands where species of Agave were present. Most sites were located near a water source and, with the exception of a single site, near areas of riparian vegetation. Sites at which we did not encounter C. mexicana were frequently disturbed, difficult to search, or historically occupied by single individuals. Based on the relatively high rate of bat recurrence, we do not believe that populations of C. mexicana in the region have declined dramatically over the past several decades.     

Optimal temperatures for growth and upper thermal tolerance of juvenile northern leatherside chub

We examined optimal temperatures for growth and the upper thermal tolerance of juvenile northern leatherside chub ( Lepidomeda copei ). We conducted 2 experiments using the acclimated chronic-exposure method to estimate optimal temperature for growth of age-0 northern leatherside chub (range 12.8–28.3 °C). Upper thermal tolerance was estimated using the critical thermal maximum (CTM) and upper incipient lethal temperature (UILT) methods for fish acclimated at 15, 18, 23, and 28 °C. We also measured stream temperatures in Yellow Creek, Summit County, Utah, during July–August 2006 to compare our results to actual summer stream temperatures. Survival in growth tests was not significantly different between treatment temperatures in either experiment (P > 0.098). The optimal temperature for growth in the 1st trial estimated from the 2nd-order polynomial regression was 23.0 °C, falling outside the range of experimental temperatures (12.8–22.2 °C). The estimated optimal temperature for growth in the 2nd trial was 23.2 °C. In the upper thermal tolerance tests, juvenile northern leatherside chub had CTM values between 29.6 and 35.0 °C; CTM values increased as acclimation temperature increased. Upper incipient lethal temperatures (LT50) ranged from 26.5 to 30.2 °C, increasing with acclimation temperature. Summer stream temperatures in Yellow Creek had a lower mean (14.0–18.1 °C) than did the optimal temperature for growth determined in these studies, but these temperatures exhibited diel fluctuations as large as 15.7 °C.     

Pygmy rabbits in the Colorado River drainage

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