Vascular endothelial growth factor in exercising humans under different environmental conditions

It was the aim of this study to investigate the time course of changes in the serum concentrations of vascular endothelial growth factor (VEGF) during a regular survival training programme combined with food and fluid deprivation and during a high altitude marathon run. We studied soldiers of the Austrian Special Forces performing survival training at sea-level and marathon runners of the Posta Atletica who crossed the border between Chile and Argentina at altitudes up to 4722 m. Baseline data collected before the 1-week of survival training showed that the soldiers had normal VEGF [n = 8, 246.7 (SD 118.5) pg.ml(-1)] serum concentrations which remained unchanged during the course of the study. Before the high altitude marathon the subjects showed normal VEGF serum concentrations [178 (SD 84.5) pg.ml(-1)]. After the run VEGF concentrations were found to be significantly decreased [41.0 (SD 41.6) pg ml(-1), P < 0.01]. It was concluded that prolonged physical stress during normobaric-normoxia did not alter the VEGF concentrations whereas during severe hypobaric-hypoxia decreased VEGF serum concentrations were measured, at least temporarily, after prolonged physical exercise which might have been due to changes in production, release, removal and/or binding of circulating VEGF.     

Routine oxygen consumption and characteristics of the myotomal muscle in tench: Effects of long-term acclimation to hypoxia

Summary Tench (Tinca tinca) were acclimated to either aerated (P _{O 2} 17.6 KPa) or hypoxic water (P _{O 2} 1.5 KPa) at 15° C. Fish acclimated to P _{O 2} 17.6 KPa had a routine oxygen consumption (mls O₂/Kg bodyweight/h) of 32.7 in aerated water. Upon acute exposure to P _{O 2} 1.5 KPa oxygen consumption decreased to 10.8 and 15.6 in fish acclimated to aerated and hypoxic water, respectively.On the basis of staining for glycogen and for the activities of myofibrillar ATPase and succinic dehydrogenase, three main fibre types can be differentiated in the myotomal muscle.Fibres have been classified as slow, fast aerobic and fast glycolytic. Fast aerobic fibres can be distinguished histochemically by their alkaline-stable Ca²⁺-activated myofibrillar ATPase activity and their intermediate levels of staining for glycogen and succinic dehydrogenase activity.The patterns of innervation of the fibre types have been investigated by staining neuromuscular endplates and peripheral axons for acetylcholinesterase activity. Motor axons to slow fibres branch extensively giving rise to a number of diffuse endplate formations on the same and adjacent fibres. Fast glycolytic fibres also have a complex pattern of innervation with 8–20 endplates per fibre. A large proportion of the endplates belonged to separate axons.Cross-sectional areas and perimeters of fibres, the number of capillaries/fibre and the lengths of contacts between capillaries and fibres were determined from low-magnification electron micrographs.Acclimation to hypoxia resulted in a decrease in the number of capillaries per fibre for both slow (1.8 to 1.0) and fast (0.8 to 0.2) muscles. The capillary perimeter supplying 1 m² of fibre cross-sectional area decreased by 43 % and 76 % for slow and fast fibres, respectively.     

The ultrastructure and vascular supply of the different fibre types in the axial muscle of the sturgeon Acipenser stellatus,Pallas

Summary The ultrastructure and vascular supply of the different fibre types in the lateral muscles of the sturgeon Acipenser stellatus were studied by light- and electron microscopy and morphometry. Three fibre types form separate layers without intermingling. The red fibres are superficial, the white fibres deep and the intermediate fibres between them. From morphometric analyses, the mitochondrial volume fraction in red fibres is 30%, in intermediate fibres 3.7% and in white fibres 0.7%. Z lines are most fuzzy in the red fibres. Triads of the sarcotubular system are always situated at the level of the Z discs. In red fibres the three elements are arranged in a series along the myofibrils, whereas in white fibres they are arranged transversely and in the intermediate fibres they are aligned obliquely. The number of capillaries surrounding each fibre is 2.3, 0.9 and 0.2 for the red, intermediate and white fibres, respectively. In red fibres 16% of the surface is directly covered by capillaries. The corresponding percentages for intermediate and white fibres are 5 and 1, respectively. Per unit volume of the fibre, the directly vascularised fibre surface in red fibres is about ten times larger than that of white fibres.The degree of vascularisation of the fibre types is directly related to the volume fraction of mitochondria, and thus to their aerobic capacities.     

Follicle growth in the ovary of the rabbit after ovulation-inducing application of human chorionic gonadotropin

Summary The growth of tertiary follicles, i.e., the proliferation of cells in the stratum granulosum and in the capillary network of the theca interna, after injection of ovulation-inducing human chorionic gonadotropin (HCG), was investigated in the rabbit by means of autoradiographic and morphometric methods.Based on the frequency distribution of follicles with different sizes and on the labeling index (LI) of granulosa cells as a function of follicle size and of time prior to and after HCG stimulation, two groups of tertiary tollicles can be distinguished: growing (250–900 m in diameter) and mature (>900 m in diameter) elements. The growth of both groups is influenced by the release of gonadotropins.After HCG stimulation, follicles belonging to the first group grow rapidly. During, and a short time after ovulation, almost all non-ruptured follicles larger than 600 m in diameter become atretic. Within 35–50 h the ruptured and atretic mature follicles (>900 m in diameter) are replaced by follicles out of the group of growing follicles.From these results the following concept for regulation of follicle growth is derived: In principle, all growing follicles possess the potential to develop into mature follicles. When a sufficient number of mature follicles is generated, these mature follicles determine the number of succeeding growing follicles. Follicles that are not required for providing mature follicles become atretic as soon as they reach a diameter of 700 m. When the majority of mature follicles is lost during ovulation (by rupture or atresia), this inhibition regulated by mature follicles is abolished, and all of the growing follicles again are capable to develop into mature follicles.The relative amount of capillaries in the theca interna of growing and mature follicles remains constant with increasing follicle size. This means that the capillary network grows parallel to the increasing size of follicles. No differences are found between intact and atretic follicles; advanced atretic follicles were excluded from this study.The labeling index (LI) of granulosa cells in the stratum granulosum and of endothelial cells in the theca interna, as a function of follicle size and of time after HCG stimulation, are closely correlated. A change in the LI of granulosa cells is usually followed with a certain delay by a similar alteration of the LI of endothelial cells in the theca interna. This suggests that granulosa cells have a certain regulatory function on capillary growth.     

Review: Development of clinically relevant scaffolds for vascularised bone tissue engineering

Clinical translation of scaffold-based bone tissue engineering (BTE) therapy still faces many challenges despite intense investigations and advancement over the years. To address these clinical barriers, it is important to analyse the current technical challenges in constructing a clinically relevant scaffold and subsequent clinical issues relating to bone repair. This review highlights the key challenges hampering widespread clinical translation of scaffold-based vascularised BTE, with a focus on the repair of large non-union defects. The main limitations of current scaffolds include the lack of sufficient vascularisation, insufficient mechanical strength as well as issues relating to the osseointegration of the bioresorbable scaffold and bone infection management. Critical insights on the current trends of scaffold technologies and future directions for advancing next-generation BTE scaffolds into the clinical realm are discussed. Considerations concerning regulatory approval and the route towards commercialisation of the scaffolds for widespread clinical utility will also be introduced.