Gridlock signalling pathway fashions the first embryonic artery.

Arteries and veins are morphologically, functionally and molecularly very different, but how this distinction is established during vasculogenesis is unknown. Here we show, by lineage tracking in zebrafish embryos, that angioblast precursors for the trunk artery and vein are spatially mixed in the lateral posterior mesoderm. Progeny of each angioblast, however, are restricted to one of the vessels. This arterial-venous decision is guided by gridlock (grl), an artery-restricted gene that is expressed in the lateral posterior mesoderm. Graded reduction of grl expression, by mutation or morpholino antisense, progressively ablates regions of the artery, and expands contiguous regions of the vein, preceded by an increase in expression of the venous marker EphB4 receptor (ephb4) and diminution of expression of the arterial marker ephrin-B2 (efnb2). grl is downstream of notch, and interference with notch signalling, by blocking Su(H), similarly reduces the artery and increases the vein. Thus, a notch-grl pathway controls assembly of the first embryonic artery, apparently by adjudicating an arterial versus venous cell fate decision.     

Prediction from the One‐Way Error Components Model with AR(1) Disturbances

In this paper we extend the works of Baillie and Baltagi (1999, in Analysis of Panels and Limited Dependent Variables Models, Hsiao C et al. (eds). Cambridge University Press: Cambridge, UK; 255–267) and generalize certain results from the Baltagi and Li (1992, Journal of Forecasting 11 : 561–567) paper accounting for AR(1) errors in the disturbance term. In particular, we derive six predictors for the one‐way error components model, as well as their associated asymptotic mean squared error of multi‐step prediction in the presence of AR(1) errors in the disturbance term. In addition, we also provide both theoretical and simulation evidence as to the relative efficiency of our alternative predictors. The adequacy of the prediction AMSE formula is also investigated by the use of Monte Carlo methods and indicates that the ordinary optimal predictor performs well for various accuracy criteria. Copyright © 2011 John Wiley & Sons, Ltd.     

The nuclear envelope: emerging roles in development and disease

The chromosomes of eukaryotic cells are separated from the cytoplasm by the nuclear envelope. The nuclear envelope includes two riveted membranes, plus embedded pore complexes that mediate nuclear import and export. In this sense, the nuclear envelope is truly a border zone. However, the envelope also links directly to chromosomes, and anchors two major infrastructures--the nuclear lamina and Tpr filaments--to the nuclear perimeter. Proteins of the nuclear envelope mediate a variety of fundamental activities, including DNA replication, gene expression and silencing, chromatin organization, cell division, apoptosis, sperm nuclear remodeling, the behavior of pronuclei, cell fate determination, nuclear migration and cell polarity. Furthermore, mutations in nuclear lamins and lamin-binding proteins cause tissue-specific inherited diseases. This special issue of Cell and Molecular Life Sciences is devoted to recent major advances in the characterization of nuclear envelope proteins and their roles. We offer here an overview of the topics covered in this issue of CMLS, and also discuss the emerging recognition that the nuclear envelope is an organelle critical for a wide range of genetic and developmental activity in multicellular organisms.     

Deep levels,transport and THz emission properties of SiGe/Si quantum-well structures

In coal mines in such countries as China and Russia,most of the coal mine methane(CMM) generated during mining is emitted to the atmosphere without any effective usage,because the methane concentration of CMM is relatively low and not allowed to be used as fuel for safety reasons.Methane is one of the greenhouse gases.Therefore,if it becomes possible to concentrate CMM to an acceptable level for use as fuel,this will greatly contribute to reduction of greenhouse gas emissions.With the aim of gaining approva...     

Characteristics of natal and non-natal kit fox dens in the northern Chihuahuan Desert

We studied kit fox den characteristics of the northern McGregor Range of Fort Bliss Military Reservation, New Mexico, during 1994 to 1995. Twenty radio-collared kit foxes used 132 different dens, including 16 natal dens. Kit fox dens were located primarily in creosote-dominated habitat found in relatively flat, well-drained terrain. Natal dens were virtually indistinguishable from non-natal dens; however, natal den entrances were taller than non-natal den entrances. Entrances found at all dens were oriented more frequently toward the northwest and southwest. Kit foxes used more dens during the breeding (January-February) and pup-rearing season (May-July) than during gestation.     

Breeding biology of the Double-crested Cormorant on Utah Lake

Research on the nesting of the Double - crested Cormorant ( Phalacrocorax auritus auritus ) was undertaken to determine the breeding biology of the bird on Utah Lake, Utah County, and the possible effects that diking Provo Bay would have on the cormorants breeding there. In 1973, two colonies in Provo Bay were visited weekly to determine laying dates, incubation period, clutch size, and hatching dates. Another colony, located on the dike of the Geneva Steel Works Reservoir near Orem, was visited daily during the spring and summer of 1973. At this colony egg-laying occurred from 13 April to 17 May. The average clutch size was 3.8, and the egg length and width averaged 60.50 mm x 39.05 mm. The average period of incubation was 28 days, and 29.5 percent of the eggs hatched, beginning on 20 May and ending on 9 June. The young weighed an average of 36 gm at hatching with a beak length of 17 mm and tarsometatarsal length of 11 mm. These measurements increased to 1543 gm, 73 mm, and 58 mm, respectively, in 23 days. The cormorant population on Utah Lake may be severely reduced by the proposed diking of Provo Bay.     

Recovery of Gambel oak after fire in central Utah

The height of oak ( Quercus gambelii Nutt.) stems was measured on several fire scars within the Uinta National Forest and vicinity and compared with the height of oak stems on adjacent, nonburned areas. A significant relationship exists between the recovery rate of oak after fire and elevation, with the recovery rate being greatest at low elevations. A trend also exists showing that recovery tends to be greater on south to westerly exposures than on north to easterly exposures.     

Pilfering of stored seeds and the relative costs of scatter-hoarding versus larder-hoarding in yellow pine chipmunks

Yellow pine chipmunks ( Tamias amoenus ) scatter-hoard food during summer and autumn but must form a larder as a winter food source before winter begins. Yellow pine chipmunks do not larder-hoard large quantities of food during the summer, apparently because a summer larder could not be defended from pilferers. We tested the assumption that the rate of pilferage from an unguarded larder would be significantly greater than the rate of pilferage from surface caches (which are also unguarded by yellow pine chipmunks) during the summer and autumn. Buried plastic buckets were used as artificial nests containing larders of 1000 sunflower seeds or 200 Jeffrey pine ( Pinus jeffreyi ) seeds. The pilferage of larder contents was monitored daily and compared to pilferage of surface caches. Animals (yellow pine chipmunks and deer mice, Peromyscus maniculatus ) removed sunflower seeds from caches much faster than from larders, but caches of Jeffrey pine seeds disappeared much more slowly than pine seeds in larders. Further, animals removed pine seeds from larders more quickly than they did sunflower seeds from larders. The difference between seed species was probably because sunflower seeds have much stronger odors, which rodents readily detect, and because chipmunks prefer pine seeds over sunflower seeds. Yellow pine chipmunks must spend a considerable portion of their time foraging for seeds and may not be able to defend a large larder during summer.     

Temperature-mediated changes in seed dormancy and light requirement for Penstemon palmeri (Scrophulariaceae)

Penstemon palmeri is a short-lived perennial herb colonizing disturbed sites in semiarid habitats in the western USA. In this study seed was harvested from six native and four seeded populations during two consecutive years. In laboratory germination trials at constant 15 C, considerable between-lot variation in primary dormancy and light requirement was observed. Four weeks of moist chilling (1 C) induced secondary dormancy at 15 C. Cold-induced secondary dormancy was reversed by one week of dark incubation at 30 C. This warm incubation treatment also reduced the light requirement of unchilled, after-ripened seed. Fluctuations in dormancy and light requirement of buried seeds have been linked to seasonal changes in soil temperature. Penstemon palmeri germination responses to temperature appear to be similar to those of facultative winter annuals.     

Lahontan sagebrush ( Artemisia arbuscula ssp. longicaulis ): a new taxon

A new subspecies of Artemisia arbuscula is described, A. arbuscula ssp. longicaulis Winward & McArthur, ssp. Nov. This taxon is a landscape dominant in portions of northwestern Nevada and adjacent California and Oregon at elevations from 1050 to 2000 m on shallow or argillic (clayey) soils. It differs from A. arbuscula ssp. arbuscula in its long floral stalks and large leaves. Morphological, chemical, ecological, and cytological data suggest that it is of hybrid origin. It is hexaploid (6x). We hypothesize that 2x A. arbusucla ssp. arbusucla and 4x A. tridentata ssp. wyomingensis are its parents.