Reduced MHC variation in a threatened tuatara species

The relationship between neutral and adaptive genetic diversity is important to understand in assessing the implications of a population bottleneck. Fitness-related genes, such as those of the major histocompatibility complex (MHC), may be influenced by selection, and so retain diversity even when it is lost at neutral markers. We measured MHC class I variation in an archaic reptile species Sphenodon guntheri [North Brother Island (NBI) tuatara], which naturally occurs on one 4 ha island in Cook Strait, New Zealand, and has low levels of microsatellite diversity. MHC variation in S. guntheri was compared with microsatellite DNA variation, and with MHC variation in a large population of Sphenodon punctatus (Cook Strait tuatara) on Stephens Island. The NBI population shows significantly decreased levels of genetic diversity compared with the Stephens Island population. Only three different MHC sequences and three genotypes were found on NBI, compared with 15 sequences and 21 genotypes in a similar sample size from Stephens Island. Two sequences appear to be unique to the NBI population. The assortment of sequence variants into genotypes suggests strong gametic disequilibrium between two MHC class I loci in S. guntheri , and only two haplotypes that were present in Hardy–Weinberg proportions were identified. MHC diversity in NBI tuatara appears to be largely influenced by genetic drift, consistent with a recent population bottleneck. This may compromise the ability of this population to respond to novel disease threats.     

Student perceptions of mistreatment and harassment during medical school. A survey of ten United States schools.

Senior students at 10 medical schools in the United States responded to a questionnaire that asked how often, if ever, they perceived themselves being mistreated or harassed during the course of their medical education. Results show that perceived mistreatment most often took the form of public humiliation (86.7%), although someone else taking credit for one''s work (53.5%), being threatened with unfair grades (34.8%), and threatened with physical harm (26.4%) were also reported. Students also reported high rates of sexual harassment (55%) and pervasive negative comments about entering a career in medicine (91%). Residents and attending physicians were cited most frequently as sources of this mistreatment. With the exception of more reports of sexual harassment from women students, perceived mistreatment did not differ significantly across variables such as age, sex, religion, marital status, or having a physician parent. Scores from the 10 schools also did not vary significantly, although the presence of a larger percentage of women in the class appeared to increase overall reports of mistreatment from both sexes.     

Citrullus lanatus ‘sentinel’ (watermelon) extract reduces atherosclerosis in LDL receptor-deficient mice

Watermelon (Citrullus lanatus or C. lanatus) has many potentially bioactive compounds including citrulline, which may influence atherosclerosis. In this study, we determined the effects of C. lanatus, provided as an extract of the cultivar ‘sentinel,’ on hypercholesterolemia-induced atherosclerosis in mice. Male low-density lipoprotein receptor-deficient mice at 8 weeks old were given either C. lanatus ‘sentinel’ extract (2% vol/vol; n= 10) or a mixture of matching carbohydrates (2% vol/vol; n= 8) as the control in drinking water while being fed a saturated fat-enriched diet for 12 weeks ad libitum. Mice consuming C. lanatus ‘sentinel’ extract had significantly increased plasma citrulline concentrations. Systolic blood pressure was comparable between the two groups. Consumption of C. lanatus ‘sentinel’ extract led to lower body weight and fat mass without influencing lean mass. There were no differences in food and water intake and in urine output between the two groups. C. lanatus ‘sentinel’ extract administration decreased plasma cholesterol concentrations that were attributed to reductions of intermediate-/low-density lipoprotein cholesterol. Plasma concentrations of monocyte chemoattractant protein-1 and interferon-gamma were decreased and those of interleukin-10 were increased in mice consuming C. lanatus ‘sentinel’ extract. Intake of C. lanatus ‘sentinel’ extract resulted in reductions of atherosclerosis in both aortic arch and thoracic regions. In conclusion, consumption of C. lanatus ‘sentinel’ extract led to reduced body weight gain, decreased plasma cholesterol concentrations, improved homeostasis of pro- and anti-inflammatory cytokines, and attenuated development of atherosclerosis without affecting systolic blood pressure in hypercholesterolemic mice.     

PD123319 Augments Angiotensin II-Induced Abdominal Aortic Aneurysms through an AT2 Receptor-Independent Mechanism

Background

AT2 receptors have an unclear function on development of abdominal aortic aneurysms (AAAs), although a pharmacological approach using the AT2 receptor antagonist PD123319 has implicated a role. The purpose of the present study was to determine the role of AT2 receptors in AngII-induced AAAs using a combination of genetic and pharmacological approaches. We also defined effects of AT2 receptors in AngII-induced atherosclerosis and thoracic aortic aneurysms.

Methods and Results

Male AT2 receptor wild type (AT2 +/y) and deficient (AT2 -/y) mice in an LDL receptor −/− background were fed a saturated-fat enriched diet, and infused with either saline or AngII (500 ng/kg/min). AT2 receptor deficiency had no significant effect on systolic blood pressure during AngII-infusion. While AngII infusion induced AAAs, AT2 receptor deficiency did not significantly affect either maximal width of the suprarenal aorta or incidence of AAAs. The AT2 receptor antagonist PD123319 (3 mg/kg/day) and AngII were co-infused into male LDL receptor −/− mice that were either AT2 +/y or −/y. PD123319 had no significant effect on systolic blood pressure in either wild type or AT2 receptor deficient mice. Consistent with our previous findings, PD123319 increased AngII-induced AAAs. However, this effect of PD123319 occurred irrespective of AT2 receptor genotype. Neither AT2 receptor deficiency nor PD123319 had any significant effect on AngII-induced thoracic aortic aneurysms or atherosclerosis.

Conclusions

AT2 receptor deficiency does not affect AngII-induced AAAs, thoracic aortic aneurysms and atherosclerosis. PD123319 augments AngII-induced AAAs through an AT2 receptor-independent mechanism.     

A Smartphone Ecological Momentary Assessment/Intervention “App” for Collecting Real-Time Data and Promoting Self-Awareness

We have designed a flexible ecological momentary assessment/intervention smartphone (EMA/EMI) “app”. We examine the utility of this app for collecting real-time data, and assessing intra-subject variability, by using it to assess how freshman undergraduates spend their time. We also explore whether its use can promote greater self-awareness. Participants were randomly divided into an experimental group, who used the app, and a control group, who did not. We used the app to collect both randomized in-the-moment data as well as end-of-day data to assess time use. Using a posttest survey we asked participants questions about how they spent time throughout the school semester. We also asked the experimental group about their experience with the app. Among other findings, 80.49% participants indicated that they became more aware of how they spent their time using the app. Corroborating this report, among the experimental group, end-of-semester self-assessment of time spent wasted, and time spent using electronics recreationally, predicted semester GPA at a strength comparable to high school GPA and ACT score (two of the best single predictors for first semester college GPA), but had no correlation among controls. We discuss the advantages and limitations of using apps, such as ours, for EMA and/or EMI.     

Daily age estimation reveals rapid growth of age‐0 alligator gar in the wild

We estimated the daily age and growth of wild age‐0 alligator gar (Atractosteus spatula) from Choke Canyon Reservoir and the Guadalupe and Trinity rivers, Texas, USA. Growth rates of wild age‐0 alligator gar were compared across systems, as well as to alligator gar reared in a Texas hatchery. Estimated ages of alligator gar ranged from 7 to 80 days in Choke Canyon Reservoir (n = 140), 11–73 days in the Guadalupe River (n = 16), and 4–115 days in the Trinity River samples (n = 245). Alligator gar growth was faster in the Trinity and Guadalupe rivers than growth in Choke Canyon Reservoir. Growth of alligator gar in Choke Canyon Reservoir (3.60 ± 0.08 mm/day), the Guadalupe River (4.76 ± 0.35 mm/day), and the Trinity River (5.13 ± 0.07 mm/day) was faster than growth of hatchery reared fish (3.41 ± 0.08 mm/day). This study represents the first account of early growth of age‐0 alligator gar in the wild, and documents some of the fastest growth of age‐0 fish among freshwater fishes. We attribute the rapid growth of wild alligator gar to their quick transition to piscivory at early stages, and their effective use of habitat and resources on inundated floodplains during flood pulses. Future studies should explore the effects of environmental factors on the hatching success, growth, and survival of age‐0 alligator gar.     

Have the Harmful Effects of Introduced Rats on Islands been Exaggerated?

Introduced rats are now being eradicated from many islands. Increasingly, these eradications are contested by activists claiming moral, legal, cultural, historic or scientific reasons and poorly documented evidence of effects. We reviewed the global literature on the effects of rats on island flora and fauna. We then used New Zealand as a case study because of its four-decade history of rat eradications and many detailed and innovative studies of how rats affect native species. These include use of exclosures, local manipulations of rat populations, video surveillance, and measurements of responses following eradications. The most intensive studies have been on the Pacific rat (Rattus exulans), a small South-East Asian species spread by Polynesians throughout the Pacific. These and the more recently introduced Norway rat (R. norvegicus) and ship (roof) rat (R. rattus) suppress some forest plants, and are associated with extinctions or declines of flightless invertebrates, ground-dwelling reptiles, land birds, and burrowing seabirds. On islands off France, Norway rats are also implicated in declines of shrews. Globally, ship rats were associated with declines or extinctions of the largest number of indigenous vertebrate species (60), including small mammals such as deer mice and bats. Effects of rats on forest trees and seabird populations are sufficiently pervasive to affect ecosystem structure and function. However, the data are patchy. Deficiencies in our knowledge would be reduced by documenting distribution and abundance of indigenous species before and after eradications. Comprehensive measurements of the responses of indigenous species to rat eradications would enable the development of testable models of rat invasion effects.     

Subcellular localization of silicon and germanium in grass root and leaf tissues by SIMS: evidence for differential and active transport

Silicon transport and incorporation into plant tissue is important to both plant physiological function and to the influence plants have on ecosystem silica cycling. However, the mechanisms controlling this transport have only begun to be explored. In this study, we used secondary ion mass spectrometry (SIMS) to image concentrations of Si in root and shoot tissues of annual blue grass (Poa annua L.) and orchard grass (Dactylis glomerata L.) with the goal of identifying control points in the plant silica uptake pathway. In addition, we used SIMS to describe the distributions of germanium (Ge); the element used to trace Si in biogeochemical studies. Within root tissue, Si and Ge were localized in the suberized thick-walled region of endodermal cells, i.e. the proximal side of endodermal cells which is in close association to the casparian strip. In leaves, Si was present in the cell walls, but Ge was barely detectable. The selective localization of Si and Ge in the proximal side of endodermal cell walls of roots suggests transport control is exerted upon Si and Ge by the plant. The absence of Si in most root cell walls and its presence in the cell walls of leaves (in areas outside of the transpiration terminus) suggests modifications in the chemical form of Si to a form that favors Si complexation in the cell walls of leaf tissue. The low abundance of Ge in leaf tissue is consistent with previous studies that suggest preferential transport of Si relative to Ge.