A Three-Dimensional Study of the Morphology and Topography of Pericytes in the Microvascular Bed of Skeletal Muscle

Digested tissue specimens and corrosion casts of rat soleus and tibialis anterior muscles were employed for this Scanning Electron Microscopy (SEM) study. The shape, morphology, and position of pericytes were compared to corresponding imprints on the cast surfaces. Pericytes, observed in digested tissue specimens, showed a typical morphological pattern: a central body with two primary processes that run along the capillary in opposite directions. From these primary processes, secondary ones arise and often encircle the vessel almost completely. On the surface of corrosion casts, roundish imprints were found in the microvascular tree at the same level where digested tissue specimens showed the presence of pericyte bodies. Along and around the cast surface, shallow grooves reproduced the course of the primary and secondary processes. The peculiar tridimensional arrangement of pericytes at the level of capillary bifurcations underlines their role in red cell flow regulation. However, if the mechanical linkage of the pericytes to the endothelium and their contractability is taken into account, additional roles of these perivascular cells may be hypothesized

Multiple negative carbon-isotope excursions during the Carnian Pluvial Episode (Late Triassic)

The Carnian Pluvial Episode was a phase of global climatic change and biotic turnover that occurred during the early Late Triassic. In marine sedimentary basins, the arrival of huge amounts of siliciclastic sediments, the establishment of anoxic conditions, and a sudden change of the carbonate factory on platforms marked the Carnian Pluvial Episode. The sedimentary changes are closely associated with abrupt biological turnover among marine and terrestrial groups as, for example, an extinction among ammonoids and conodonts in the ocean, and a turnover of the vertebrate fauna and the flora on land. Multiple negative carbon-isotope excursions were recorded during the Carnian Pluvial Episode in both organic matter and marine carbonates, suggesting repeated injection of 13C-depleted CO2 into the ocean–atmosphere system, but their temporal and causal links with the sedimentological and palaeontological changes are poorly understood. We here review the existing carbon-isotope records and present new data on the carbon-isotope composition of organic carbon in selected sections of the western Tethys realm that record the entire Carnian Pluvial Episode. New ammonoid, conodont and sporomorph biostratigraphic data were collected and coupled to an extensive review of the existing biostratigraphy to constrain the age of the sampled sections. The results provide biostratigraphically constrained composite organic carbon-isotope curves for the Carnian, which sheds light on the temporal and causal links between the main carbon-isotope perturbations, and the distinct environmental and biotic changes that mark the Carnian Pluvial Episode. The carbon-isotope records suggest that a series of carbon-cycle perturbations, possibly recording multiple phases of volcanic activity during the emplacement of the Wrangellia Large Igneous Province, disrupted Carnian environments and ecosystems repeatedly over a remarkably long time interval of about 1 million years

Anatomy of the superficial veins

Veins arise from capillaries and transport blood away from the tissues towards the heart. In contrast to arteries which branch, they form a network which merges repeatedly to form larger veins. They are named according to their calibre and position as venous capillaries, venules, tributaries and saphenous trunk

Segmental hypoplasia of the great saphenous vein and varicose disease

Objectives. Primitive narrowing of great saphenous vein segments (saphenous hypoplasia) has been described in healthy limbs. The aim of the present study was to detect great saphenous vein segmental hypoplasia in limbs with varicose veins and to evaluate the local anatomical and haemodynamic patterns. Materials and Methods. The incidence of saphenous hypoplasia and the local haemodynamic rearrangement were evaluated by duplex ultrasonography in 676 normal limbs and in 320 limbs with varicose veins. Results. Segmental hypoplasia was demonstrated in 84 normal limbs and in 79 limbs with saphenous reflux. In the latter, the retrograde flow leaves the GSV at the proximal end of the hypoplastic segment to feed tributary veins. Conclusions. Saphenous hypoplasia occurs in varicose limbs more frequently than in healthy ones (p = > 0.001). It greatly influences the path of the reflux and the anatomy of the varicose veins. GSV segmental hypoplasia can be detected preoperatively by duplex ultrasonography. Its occurrence may influence surgical management for two main reasons: in about 68% of varicose limbs with segmental hypoplasia, the distal GSV is competent. If the distal GSV is varicose, its size and flow direction is normalised by treating the accessory vein that bypasses the hypoplastic segment