The platelet open canalicular system: a final common pathway.

Channels of the surface-connected, open canalicular system (OCS) of human platelets serve as the pathway for transport of substances into the cells and as conduits for the discharge of alpha granule products secreted during the platelet release reaction. The purpose of the present study was to determine if both functions of the OCS can take place simultaneously. Suspensions of washed platelets were exposed to thrombin at 1 U/ml for 5, 60, or 180 seconds in the presence of fibrinogen molecules coupled to particles of colloidal gold (Fgn/Au). The samples were fixed in a low concentration of glutaraldehyde and embedded in L.R. White resin to preserve antigenicity. Thin sections were exposed to a rabbit polyclonal antibody to human fibrinogen followed by an anti-rabbit IgG coupled to 5-nm gold beads. Thrombin caused Fgn/Au particles to bind to platelets and enter channels of the surface-connected OCS. Endogenous fibrinogen detected by immunogold 5-nm beads were localized to alpha granules in resting platelets and 5 seconds after thrombin stimulation. At 60 seconds and 3 minutes Fgn/Au particles were present in swollen alpha granules, as well as OCS channels. Fibrinogen gold beads were evident in alpha granules and OCS channels connected to the platelet surface. The 18- to 20-nm Fgn/Au particles were in the same channels of the OCS as fibrinogen gold beads. The OCS is a final common pathway for uptake of particulates and discharge of secretory products in thrombin-activated human platelets.     

Bone and glucose metabolism: A two-way street

Evidence from rodent models indicates that undercarboxylated osteocalcin (ucOC), a product of osteoblasts, is a hormone affecting insulin production by the pancreas and insulin sensitivity in peripheral tissues, at least in part through enhanced secretion of adiponectin from adipocytes. Clinical research to test whether this relationship is found in humans is just beginning to emerge. Cross-sectional studies confirm associations between total osteocalcin (OC), ucOC and glucose metabolism but cannot distinguish causality. To date, longitudinal studies have not provided a consistent picture of the effects of ucOC or OC on fasting glucose and insulin sensitivity. Further exploration into the physiological and mechanistic effects of ucOC and OC, in rodent models and clinical studies, is necessary to determine to what extent the skeleton regulates energy metabolism in humans.     

A two-way street: LSD1 regulates chromatin boundary formation in S. pombe and Drosophila

Two recent studies in Molecular Cell (Lan et al., 2007; Rudolph et al., 2007) implicate histone demethylation by LSD1 in the regulation of boundaries between silenced and active chromatin domains in both fission yeast and flies, but by distinct mechanisms.     

The intercellular canalicular system in the endocrine pancreas. A putative dynamic formation

A system of intercellular spaces in the islets of Langerhans of the rat pancreas was found after 6-hydroxydopamine treatment being absent in the control animals. Therefore, we propose that the intercellular canalicular system occurs in response to increased secretory activity of the islets.     

The human blood platelet: its derivation from the red blood cell. A morphologic study.

The blood platelet arises from the interior of the red blood cell when blood is either damaged or disturbed. The platelet body may be seen to form from an amorphous granular mass to a definite granular platelet body when blood is prevented from coagulating by the use of a retardant solution.     

Stabilization of blood platelet microtubular system by staurosporine

The stimulative effects of phorbol myristate acetate (PMA) on rabbit platelet shape change and platelet adhesion were completely inhibited by staurosporine (STS)-pretreatment. When the platelets were observed by whole mount immuno transmission electron microscopy (TEM), STS was found to stabilize platelet microtubular cytoskeleton. Electrophoretic analysis of the isolated marginal bundles of cytoskeleton after STS-PMA treatment revealed a newly formed 200 K high molecular weight protein band accompanied with heavy losses of tubulin monomers. These bundles of STS-treated platelets as observed in immuno TEM responded poorly to the anti alpha- or beta-tubulin antibody as compared with those of the control platelets. The results suggest that sts favour the specific assembly of tubulin bundles with a possible involvement of the microtubular associated proteins (MAPs). The resultant tight marginal bundles (MB) of cytoskeleton will stabilize the platelets and resist the effects of exogeneously added stimulants such as PMA.     

The human blood platelet: its derivation from the red blood cell. II. Instantaneous changes in form in the platelet and red cell. A morphologic study

The human blood platelet arises from the interior of the red cell instantaneously as blood is either damaged or disturbed. The platelet starts out as a fine granular structure that rather suddenly changes in form and function with the passage of a very small amount of time.     

The surface-connected canalicular system in the sinus endothelial cells of rat spleen

The existence of a surface-connected canalicular system in the splenic sinus endothelial cells of the rat has been demonstrated by transmission electron microscopy with lanthanum nitrate acting as a tracer for the extracellular space. In addition, the three-dimensional arrangement of the canaliculi has been revealed by computer-aided reconstruction. The surface-connected canalicular system of the sinus endothelial cells consists of slender canaliculi that are branched, anastomosed, and that show continuity with the plasma membrane. They twist in and out among the organelles and are often found in close apposition to the spherical invaginations of the plasma membrane and run alongside them. Canaliculi which are not infiltrated by lanthanum nitrate take the form of electron-lucent tubules and are accompanied by numerous spherical invaginations of the plasma membrane. From a computer-aided reconstruction, the canaliculi, which invaginate from various sites of the plasma membrane, have been found to be continuous with each other and to penetrate to the surface of the sinus endothelial cell; they also branch and anastomose to form a complex network in the cytoplasm. Although the surface-connected canalicular system in blood platelets and thrombocytes is believed to function as the main route for the discharge of granules and the uptake of foreign materials and also to take part in the storage and transport of calcium, it is unclear at present whether the network of the surface-connected canalicular system in splenic sinus endothelial cells has any physiological significance.     

The boylston street fishweir: Revisited

Excavations for the Boston subway system early in this century and later for building sites revealed the presence of waterlogged wood in the peat and silt deep beneath the present surface. Beginning more than 50 yr ago, the investigation of geological and biological materials recovered from these sites, especially the wood remains, believed to have been set in place by prehistoric Native Americans, became a benchmark for the multidisciplinary application of scientific methods in archaeology and environmental reconstruction. Recent excavations for building foundations in Boston have exposed additional wooden materials. We have analyzed 216 specimens recently recovered from an excavation at 500 Boylston Street where older office buildings were demolished to make way for a new commercial structure. Although some of our findings differ from those of the previous investigators we find support for the earlier supposition that the remains represent an ancient Native American fishweir, a fencelike barrier and trap for fish on an ancient shoreline.     

Use of a laser photometer to determine blood platelet shape and aggregation in a flowing system]

The paper treats of an original device for studies with the photometric method of the platelets shape and of their aggregation and disaggregation processes in the flow. Experiments on the stenosed vessel model showed that in the presence of ADP stenosis potentiated the platelets aggregation in the rabbit platelet-rich plasma.     

HaploSearch: a tool for haplotype-sequence two-way transformation

Comparison of available mitochondrial DNA data is some times hindered by the data presentation format. HaploSearch is a simple tool for transforming DNA sequences into haplotype data and vice versa, speeding up the manipulation of large datasets. Although designed for mitochondrial DNA, HaploSearch could be used with any kind of DNA type. HaploSearch program, detailed software instructions and example files are freely available on the web http://www.haplosite.com/haplosearch/.