Epigenetic change in IGF2R is associated with fetal overgrowth after sheep embryo culture

Manipulation or non-physiological embryo culture environments can lead to defective fetal programming in livestock. Our demonstration of reduced fetal methylation and expression of ovine IGF2R suggests pre-implantation embryo procedures may be vulnerable to epigenetic alterations in imprinted genes. This highlights the potential benefits of epigenetic diagnostic screening in developing embryo procedures.     

Human Genome and Diseases:¶The molecular pathogenesis of the Marfan syndrome

The Marfan syndrome (MFS) is an autosomal dominant heritable disorder of connective tissue with highly variable clinical manifestations including aortic dilatation and dissection, ectopia lentis, and a range of skeletal anomalies. Mutations in the gene for fibrillin-1 (FBN1) cause MFS and other related disorders of connective tissue collectively termed type-1 fibrillinopathies. Fibrillin-1 is a main component of the 10- to 12-nm extracellular microfibrils that are important for elastogenesis, elasticity, and homeostasis of elastic fibers. Mutations in fibrillin-1 are hypothesized to exert their effects by dominant negative mechanisms, but recent work has also emphasized the potential role of proteases and disturbances in tissue homeostasis in the pathogenesis of the MFS. This article provides an overview of the clinical aspects of the MFS and current thinking on the pathogenesis of this disorder.     

Kin selection and eusociality

Arising from M. A. Nowak, C. E. Tarnita & E. O. Wilson 466, 1057-1062 (2010); Nowak et al. reply. Hamilton described a selective process in which individuals affect kin (kin selection), developed a novel modelling strategy for it (inclusive fitness), and derived a rule to describe it (Hamilton's rule). Nowak et al. assert that inclusive fitness is not the best modelling strategy, and also that its production has been "meagre". The former may be debated by theoreticians, but the latter is simply incorrect. There is abundant evidence to demonstrate that inclusive fitness, kin selection and Hamilton's rule have been extraordinarily productive for understanding the evolution of sociality.     

Spatial learning impairments in PLB1Triple knock-in Alzheimer mice are task-specific and age-dependent

We recently generated an advanced mouse model of Alzheimer’s disease (AD) by targeted knock-in of single-copy mutated human amyloid precursor-protein (APP) and tau genes, crossed with a non-symptomatic presenilin (PS1A246E) over-expressing mouse line. These PLB1_Triple mice presented with age-dependent and AD-relevant phenotypes. Homozygous PLB1_Triple mice aged 4–12 months were assessed here in a battery of spatial learning tasks: Exp.1 radial-arm water maze (spatial reference and working memory) Exp.2 open-field water maze (spatial reference memory); Exp.3 home cage observation system with spatial learning (IntelliCage); Exp.4 spontaneous object recognition (SOR; novel object and spatial object shift). A separate test with high-expression transgenic APP mice matching the design of experiment 1 was also performed. Spatial deficits in PLB1_Triple mice were confirmed at 12, but not 4 months in both water maze tasks. PSAPP mice, by contrast, presented with severe yet non-progressive spatial learning deficits already at 4 months. During tests of spatial learning in SOR and IntelliCage, PLB1_Triple mice neither acquired the location of the water-rewarded corner, nor recognize novel or spatially shifted objects at 4 months, indicating these protocols to be more sensitive than the water maze. Collectively and in line with AD symptomatology, PLB1_Triple mice present with a graded and progressive age-dependent loss of spatial memory that can be revealed by the use of a battery of tasks. With the emergence of subtle deficits progressively increasing in severity, PLB1_Triple mice may offer a more patho-physiologically relevant model of dementia than aggressive expression models.     

Survey indicators for pygmy rabbits: temporal trends of burrow systems and pellets

Obtaining estimates of absolute abundance for rare or cryptic species can be challenging. In these cases,methods using indirect indicators such as sign might offer useful indices of population size. Pygmy rabbits ( Brachylagus idahoensis ) are small, burrowing lagomorphs for which methods for population assessment and monitoring are needed. Current tools for estimating relative abundance rely on detecting and assessing fecal pellets and burrow systems. We evaluated temporal changes in each of these indicators to gauge their potential usefulness as indicators of relative and absolute abundance of pygmy rabbits. Pellet persistence was strongly influenced by environmental exposure, and based on our data, we estimated that maximum persistence of fecal pellets would be 24–34 months. Pellet appearance (color) was affected by both time and exposure. Burrow systems were remarkably resilient over the course of the study. Probability of burrow systems transitioning between activity classes (active, recent, and old) did not vary detectably by study site, season, or year. We suggest that 2 protocols currently used for classification of pygmy rabbit burrow systems are most useful for different applications. Further work is needed, however, to link such assessments to quantitative estimates of population size.     

Movement, distribution, and predation: Lepidomeda vittata and nonnative salmonids in eastern Arizona

Nonnative rainbow trout ( Oncorhynchus mykiss ) are stocked into several reservoirs in the range of federally threatened Little Colorado spinedace ( Lepidomeda vittata ), and so have the opportunity to negatively impact Little Colorado spinedace populations. We examined rainbow trout escapement from Nelson Reservior into Nutrioso Creek, critical habitat for L. vittata . We also examined movements of L. vittata and incidence of predation by rainbow trout on L. vittata . We detected no movement of rainbow trout out of Nelson Reservoir over 4 years of study. Lepidomeda vittata marked in 3 streams did not move much; but sample sizes were too small to make any meaningful conclusions regarding movement. Most L. vittata we captured during surveys subsequent to marking were unmarked, suggesting movement out of the study area, low tag retention, mortality, or failure to capture marked fish. Lepidomeda vittata co-occurred with O. mykiss , Salmo trutta , and Salvelinus fontinalis and were typically less than half the size of the sympatric nonnative salmonids. Consequently, they are potential prey fish for these species. We found fish remains in stomachs of 33% of S. trutta , 6% of O. mykiss and 25% of S. fontinalis examined, but remains of L. vittata were found only in a single S. trutta . Because S. fontinalis are rare in the streams examined, they probably do not pose a great threat to L. vittata . Salmo trutta , which are no longer stocked, had the highest piscivory level and may thus pose more of a threat to L. vittata than O. mykiss .     

Asian tapeworm ( Bothriocephalus acheilognathi ) in native fishes from the Little Colorado River, Grand Canyon, Arizona

Examination of gastrointestinal tracts of native cyprinids from the Little Colorado River (LCR) in Grand Canyon, Arizona, 1990-1994, revealed varying rates of prevalence and infrapopulation levels of Asian tapeworm ( Bothriocephalus acheilognathi ). Mean prevalence was 28% (range 0-78%) in humpback chub ( Gila cypha ) and 8% (range 0-46%) in speckled dace ( Rhinichthys osculus ), with infrapopulations as high as 46 and 28, respectively. We also note Asian tapeworm infection of nonnatives common carp ( Cyprinus carpio ), fathead minnow ( Pimephales promelas ), and plains killifish ( Fundulus zebrinus ) from the LCR. Reported pathogenic and chronic effects of this cestode to its definitive hosts add concern for the status of the Grand Canyon population of the federally endangered humpback chub. The rapidity which Asian tapeworm has spread to different drainages of the Colorado River Basin likely portends an eventual cosmopolitan basin distribution in lower elevations suitable to the parasite's thermophilic life history. Such biotic changes must be considered among the most serious threats to conservation and recovery of native fish populations.     

Persistence of added retinoids in organ culture media during induction of mucous metaplasia and glandular morphogenesis in hamster cheek pouches

The retinoid concentration (determined colorimetrically) did not change significantly in retinyl acetate-supplemented (6 micrograms/ml) Eagle's Minimal Essential Medium containing 10% fetal calf serum when stored at -20 or 4 degrees C over 7 days. After the medium was incubated at 37 degrees C for 48 h, 37-49% of the retinoid remained, whether or not tissue (neonatal Syrian hamster cheek pouch) was present, and irrespective of explant age. The normal retinoid level in the tissue was approximately 0.25 micrograms per gram. Therefore, neonatal hamster cheek pouches, incubated in medium with the addition of 6 micrograms of retinyl acetate per ml of medium and undergoing mucous metaplasia and some mucous gland morphogenesis, were continually being exposed to retinoid levels which, though gradually decreasing, remained well above their normal physiological level.