Transverse tubule remodelling: a cellular pathology driven by both sides of the plasmalemma?

Transverse (t)-tubules are invaginations of the plasma membrane that form a complex network of ducts, 200–400 nm in diameter depending on the animal species, that penetrates deep within the cardiac myocyte, where they facilitate a fast and synchronous contraction across the entire cell volume. There is now a large body of evidence in animal models and humans demonstrating that pathological distortion of the t-tubule structure has a causative role in the loss of myocyte contractility that underpins many forms of heart failure. Investigations into the molecular mechanisms of pathological t-tubule remodelling to date have focused on proteins residing in the intracellular aspect of t-tubule membrane that form linkages between the membrane and myocyte cytoskeleton. In this review, we shed light on the mechanisms of t-tubule remodelling which are not limited to the intracellular side. Our recent data have demonstrated that collagen is an integral part of the t-tubule network and that it increases within the tubules in heart failure, suggesting that a fibrotic mechanism could drive cardiac junctional remodelling. We examine the evidence that the linkages between the extracellular matrix, t-tubule membrane and cellular cytoskeleton should be considered as a whole when investigating the mechanisms of t-tubule pathology in the failing heart.     

Karyotypes and DNA values for members of the suborder Esocoidei (Osteichthyes: Salmoniformes)

Karyotypes prepared from tissues of gills, gonads, fins, liver, and spleen, yielded the following diploid numbers: all Esox spp. 50, all Umbra spp. (excluding U. krameri) 22, Novumbra hubbsi 48, Dallia pectoralis 78. DNA measurements from Feulgen stain content of erythrocytes, indicated that the species could be divided into two categories: 30–39% of human-Esox spp., Dallia pectoralis, Novumbra hubbsi: 70% of human-Umbra spp. Chromosomal polymorphism was not observed among the various tissues examined nor was it observed among specimens from different habitats. Both the karyotypes and the DNA values indicated that the present tendency to combine the genera Umbra, Novumbra, and Dallia in the single family Umbridae may be ill advised.This work was supported by grants from the Fisheries Research Board of Canada and the National Research Council of Canada.     

Systematic landscape restoration in the rural–urban fringe: meeting conservation planning and policy goals

Many landscapes that straddle the rural/urban divide suffer from low levels of species diversity following extensive clearing and fragmentation of native vegetation communities and conversion of land to agriculture. Further pressures are placed on remnant vegetation by encroaching urban expansion. These landscapes now exhibit a mosaic of small, patchy vegetation remnants that are under considerable pressure from housing and light-industrial development. Furthermore, agriculture in these landscapes tends to be of high economic value from uses such as intensive horticulture. Concerted and well-planned efforts are needed to balance the many conflicts of interest and competing demands for land with the need to restore landscapes for the protection of biodiversity. There has been a recent move in Australia toward regional biodiversity planning and goal setting, however specific detail on how to plan for achieving targets in complex landscapes is lacking. This paper applies a systematic landscape restoration model to a mixed-use, peri-urban landscape on the northern fringes of Adelaide, South Australia. The region contains fragments of remnant vegetation amongst a mosaic of high-value horticulture, light industry and urban development. Models produce maximally efficient solutions that meet comprehensive, adequate and representative conservation targets. Further constraints are added to the model to take into account the value of agricultural output, the biodiversity value of remnants, and property size and tenure. The effects on solution efficiencies as the number of constraints increase are investigated. This paper demonstrates the flexibility found in applying a systematic landscape restoration methodology. The process we present can be transferred to any rural–urban fringe region.