Ablation of cyclase-associated protein 2 (CAP2) leads to cardiomyopathy

Cyclase-associated proteins are highly conserved proteins that have a role in the regulation of actin dynamics. Higher eukaryotes have two isoforms, CAP1 and CAP2. To study the in vivo function of CAP2, we generated mice in which the CAP2 gene was inactivated by a gene-trap approach. Mutant mice showed a decrease in body weight and had a decreased survival rate. Further, they developed a severe cardiac defect marked by dilated cardiomyopathy (DCM) associated with drastic reduction in basal heart rate and prolongations in atrial and ventricular conduction times. Moreover, CAP2-deficient myofibrils exhibited reduced cooperativity of calcium-regulated force development. At the microscopic level, we observed disarrayed sarcomeres with development of fibrosis. We analyzed CAP2’s role in actin assembly and found that it sequesters G-actin and efficiently fragments filaments. This activity resides completely in its WASP homology domain. Thus CAP2 is an essential component of the myocardial sarcomere and is essential for physiological functioning of the cardiac system, and a deficiency leads to DCM and various cardiac defects.     

The implications of viral reservoirs on the elite control of HIV-1 infection

The mechanisms by which a small percentage of HIV-1 infected individuals known as elite suppressors or controllers are able to control viral replication are not fully understood. Early cases of viremic control were attributed to infection with defective virus, but subsequent work has demonstrated that infection with a defective virus is not the exclusive cause of control. Replication-competent virus has been isolated from patients who control viral replication, and studies have demonstrated that evolution occurs in plasma virus but not in virus isolates from the latent reservoir. Additionally, transmission pair studies have demonstrated that patients infected with similar viruses can have dramatically different outcomes of infection. An increased understanding of the viral factors associated with control is important to understand the interplay between viral replication and host control, and has implications for the design of an effective therapeutic vaccine that can lead to a functional cure of HIV-1 infection.     

An addition to the amphibian fauna of California

A population of salamanders of the genus Ambystoma has been found at Grass Lake, Siskiyou County, in Northern California. A five - year study has established that the salamanders are reproducing successfully and may represent a relictual population of native amphibians. The Grass Lake area has a sparse human population, which may help to explain how this secretive amphibian could have escaped notice. Attempts to determine the taxonomic position of the Grass Lake salamander, through comparisons of body measurements and coloration with those of other western ambystomatids, were inconclusive. These comparisons suggest, however, a close relationship with the geographically most proximate subspecies, A.t. californiense Gray and A.t. melanostictum Baird. Grass Lake is near the midpoint of a gap area of approximately 800 km that separates these subspecies. Regardless of the origin of the population, it must now be listed as an established addition to the amphibian fauna of California.     

Selenium geochemical relationships of some northern Nevada soils

Soil samples, one from each of 10 locations in northern Nevada, were evaluated for redox potential, total and extractable selenium, phosphate, free iron oxide, total and ferrous iron. Mole fractions for extractable selenium species were calculated from redox potentials. Data were used to extrapolate general geochemical relationships for soil selenium at the sample sites. Results obtained from one sample per location allowed only the most general conclusions to be drawn. Soil phosphate levels, which affect the adsorption of selenite species on iron oxide by competing for adsorption sites, were not correlated with levels of extractable selenium in this study. This would suggest that selenium would exist in solution, having been displaced from adsorption sites by phosphorous. Ferrous iron, iron oxides, and redox potential had a combined effect on the level of extractable selenium at all sites. Soils in this study support selenite species that are not readily available to plants and therefore could not support vegetation adequate in Se.     

宇宙学与战略"大思维"

宇宙学在近当代获得了长足发展,而这一发展正是孕育于强大而极富创造性的思维母体。从一般系统理论的角度来说,公司或政府机构等大型商业或政治组织的领导人可以利用宇宙学及其思维方法,进行战略性“大思维”,从而做出正确的决策。在本文中,作者不仅对宇宙学的具体理论和原则进行了归纳总结,而且还提出具体实例,以为这些领导人运用宇宙学进行战略高度的“大思维”提供佐证,从而进一步证明,“大思维”对于在复杂的现代组织中取得成功具有重要意义。     

RIM1alpha is required for presynaptic long-term potentiation.

Two main forms of long-term potentiation (LTP)-a prominent model for the cellular mechanism of learning and memory-have been distinguished in the mammalian brain. One requires activation of postsynaptic NMDA (N-methyl d-aspartate) receptors, whereas the other, called mossy fibre LTP, has a principal presynaptic component. Mossy fibre LTP is expressed in hippocampal mossy fibre synapses, cerebellar parallel fibre synapses and corticothalamic synapses, where it apparently operates by a mechanism that requires activation of protein kinase A. Thus, presynaptic substrates of protein kinase A are probably essential in mediating this form of long-term synaptic plasticity. Studies of knockout mice have shown that the synaptic vesicle protein Rab3A is required for mossy fibre LTP, but the protein kinase A substrates rabphilin, synapsin I and synapsin II are dispensable. Here we report that mossy fibre LTP in the hippocampus and the cerebellum is abolished in mice lacking RIM1alpha, an active zone protein that binds to Rab3A and that is also a protein kinase A substrate. Our results indicate that the long-term increase in neurotransmitter release during mossy fibre LTP may be mediated by a unitary mechanism that involves the GTP-dependent interaction of Rab3A with RIM1alpha at the interface of synaptic vesicles and the active zone.     

Reproductive biology and prospects for conservation ofCaldesia parnassifolia (Alismataceae)—A threatened monocot in China

Caldesia parnassi folia (Bassi ex Linn.) Parl. in China has declined in number in recent years and is increasingly faced with the risk of extirpation arising from anthropogenic changes associated with rapid urbanization and expansion of both agriculture and infrastructure. To aid in provision of the data needed for effective conservation of the species, studies on the habitat, pollination ecology, and breeding system ofC. parnassi folia were carried out on natural populations occurring in Southeastern China. Flowering in the study populations extended for more than eighty days beginning in early summer. Floral anthesis occurred in the morning hours and proceeded rapidly, lasting about 45 min. Flowers lasted ca. 8 h.Caldesia parnassi folia is self-compatible; however autogamy resulted in lower seed set than geitonogamy and xenogamy as well as free pollination. The data on pollen/ ovule (P∶O) ratio is consistent with a partially selfing and outcrossing mating system. Interpopulational crosses yielded similar seed set to within-population crosses. Agamospermy did not occur in the study populations. Propagation is achieved through seeds as well as through turions which commonly occur in the inflorescences. Flies (Insecta; Diptera) were the most frequent visitors to the flowers ofC. parnassi folia; however bees (Insecta; Hymenoptera) composed a larger proportion of effective pollinators. The Syrphidae speciesSphaerophoria indiana (Bigot) presents evidence of oligolectic foraging behavior. Recommendations are made on the immediate steps necessary for conservation ofCaldesia species in China. Foundation item: Supported by the State Key Basic Research and Development Plan of China (973) (G2000046805) and the National Natural Science Foundation of China (30070055) Biography: Robert Wahiti, Gituru (1967-), male, Kenya, Ph. D., research direction: plant biosystematics.