Ataxin1L Is a Regulator of HSC Function Highlighting the Utility of Cross-Tissue Comparisons for Gene Discovery

Hematopoietic stem cells (HSCs) are rare quiescent cells that continuously replenish the cellular components of the peripheral blood. Observing that the ataxia-associated gene Ataxin-1-like (Atxn1L) was highly expressed in HSCs, we examined its role in HSC function through in vitro and in vivo assays. Mice lacking Atxn1L had greater numbers of HSCs that regenerated the blood more quickly than their wild-type counterparts. Molecular analyses indicated Atxn1L null HSCs had gene expression changes that regulate a program consistent with their higher level of proliferation, suggesting that Atxn1L is a novel regulator of HSC quiescence. To determine if additional brain-associated genes were candidates for hematologic regulation, we examined genes encoding proteins from autism- and ataxia-associated protein–protein interaction networks for their representation in hematopoietic cell populations. The interactomes were found to be highly enriched for proteins encoded by genes specifically expressed in HSCs relative to their differentiated progeny. Our data suggest a heretofore unappreciated similarity between regulatory modules in the brain and HSCs, offering a new strategy for novel gene discovery in both systems.     

Biology and Functional Ecology of Equisetum with Emphasis on the Giant Horsetails

Horsetails are unique survivors of a very ancient group of vascular plants, the Sphenophyta, which has a history reaching back to the Upper Devonian. Despite the striking conservatism of Equisetum architecture and anatomy and the small number of species (15) in the modern flora, their ability to thrive under a wide range of conditions is remarkable. This is due to a diverse suite of adaptations that allow tolerance of disturbance, soil anoxia, high metals, and salinity, along with efficient nutrient uptake and nitrogen fixation. The giant horsetails represent the largest living Sphenophyta and provide insights into how their larger ancestors lived and how this ancient lineage has managed to survive in tropical regions.     

Mapping sea level rise impacts to identify climate change adaptation opportunities in the Chesapeake and Delaware Bays,USA

Wetlands Ecology and Management - Salt marshes are at risk globally if they cannot keep pace with sea level rise. Along the United States Mid-Atlantic coast, high marsh has already declined, and is...     

Stable isotope analysis of vegetation history and land use change at Laguna Santa Elena in southern Pacific Costa Rica

Vegetation History and Archaeobotany - Laguna Santa Elena (8.9290° N, 82.9257° W, 1055 m a.s.l.) is a small lake in the Diquís archaeological sub-region of southern Pacific...     

Association between sexually selected traits and allelic distance in two unlinked MHC II loci in white-tailed deer (Odocoileus virginianus)

Evolutionary Ecology - Body size and secondary sexual characteristics are drivers of male reproductive success among polygynous species. A gene complex found to be associated with morphology in...     

966. CLAVIJA DOMINGENSIS

Clavija domingensis Urb. & Ekman was one of the many Haitian endemics that were described based on collections made by the great Swedish botanist Leonard Ekman between 1924 and 1928. The species is Critically Endangered sensu IUCN (criteria c2a(i); D) and it is currently the focus of conservation initiatives in Jardin Botanique des Cayes (Haiti), Jardín Botánico Nacional Dr. Rafael M. Moscoso (Dominican Republic), and Fairchild Tropical Botanic Garden (U.S.A.). Now known from only six localities from southern Haiti, each locality only represents a single individual. The species is illustrated based on plants grown in Fairchild Tropical Botanic Garden.     

The association of Amyloid P-Component (AP) With The Amyloid Fibril: An updated Method for Amyloid Fibril Protein Isolation

Abstract

An amyloid fibril isolation procedure is proposed which uses citrate as well as saline washes to dissociate the calcium dependent linkage of amyloid P-component (AP) from the amyloid fibril. In two amyloid rich tissues, the amount of AP was quantitated in each saline and citrate wash and totalled 13.8% and 20.8% of the amyloid fibrils isolated. The amount of AP removed from these and 22 additional amyloid rich tissues was greater than had previously been recognized.

AP protein was present in tissue only when amyloid fibrils were present. It could not be found in normal non-amyloidotic tissue, nor could it be found in tissue sediment after the fibrils were removed.     

Stage of the Estrous Cycle Does Not Influence Myocardial Ischemia–Reperfusion Injury in Rats (Rattus norvegicus)

Even though cardiovascular disease is the leading cause of death for men and women, the vast majority of animal studies use male animals. Because female reproductive hormones have been associated with cardioprotective states, many investigators avoid using female animals because these hormones are cyclical and may introduce experimental variability. In addition, no studies have investigated the specific effects of the estrous cycle on cardiac ischemic injury. This study was conducted to determine whether the estrous cycle stage influences the susceptibility to ischemic injury in rat hearts. Estrous cycle stage was determined by using vaginal smear cytology, after which hearts underwent either in vivo (surgical) or ex vivo (isolated) ischemia–reperfusion injury. For in vivo studies, the left anterior coronary artery was ligated for 25 min of ischemia and subsequently released for 120 min of reperfusion. Infarct sizes were 42% ± 6%; 49% ± 4%; 40% ± 9%; 47% ± 9% of the zone-at-risk for rats in proestrus, estrus, metestrus, and diestrus, respectively. For ex vivo studies, isolated, perfused hearts underwent global ischemia and reperfusion for 25 and 120 min, respectively. Similar to our in vivo studies, the ex vivo rat model showed no significant differences in susceptibility to infarction or extent of cardiac arrhythmia according to estrous stage. To our knowledge, these studies provide the first direct evidence that the stage of estrous cycle does not significantly alter cardiac ischemia–reperfusion injury in rats.Abbreviations: VF, ventricular fibrillation; VT, ventricular tachycardiaCardiovascular disease remains the leading cause of morbidity and mortality throughout the industrialized world, with ischemic heart disease being a major manifestation of cardiovascular disease. Many investigators use animal models to advance our understanding of the etiology and mechanisms involved. Although ischemic heart disease is the leading cause of death for both men and women, the overwhelming majority of studies use male animals. Perhaps the most common reason for this practice is that physiologic fluctuations in female reproductive hormones such as estrogen may be a confounding variable, given the influence of female reproductive hormones on various organ systems.²⁵ Despite the assertion that cyclical variations in female reproductive hormones may confound experimental studies, few data are available that support estrous-cycle–dependent variations in susceptibility to ischemic heart injury.Epidemiologic studies suggest that, compared with men, women have lower cardiac mortality prior to undergoing menopause.⁴⁰ Consistent with human studies, experimental models in several species commonly show that the degree of cardiac injury in young female animals is lower than that in male counterparts.^7,9,21,22,42 Exogenous administration of estrogen has a clear effect in reducing injury,^14,15 but whether endogenous cyclical variations in female reproductive hormones affect cardiac injury is not known.Rats and mice are commonly used species to examine cardiac ischemia–reperfusion injury. Unlike humans, rodents do not undergo menstruation, during which the uterine endometrium sloughs off and is expelled through the vagina, but rather the uterine lining of rodents is reabsorbed during an estrous cycle.²⁴ The rat estrous cycle is typically 4 to 5 d in length and is defined by 4 separate stages: proestrus, estrus, metestrus, and diestrus. Proestrus is characterized by increasing levels of estrogen. At the end of proestrus, ovulation (signaled by luteinizing hormone) occurs and marks the beginning of the estrus cycle. During metestrus and diestrus, the uterine lining regenerates, and the cycle starts again.^24,33 These stages induce changes in the composition of the epithelium of the vagina and the presence of inflammatory cells, which can easily be detected by using vaginal cytology.^18,35We conducted the current study to determine whether estrous cycle stage influences the susceptibility to ischemia–reperfusion injury in the rat heart. Because the stage of the estrous cycle may influence cardiac injury either directly (via a direct effect of circulating hormones), or indirectly (by inducing changes that are intrinsic to the heart), we used both in vivo and ex vivo models of injury.