Microanatomical study of the recurrent artery of Heubner.

The purpose of this study has been to describe the microanatomy of the recurrent artery of Heubner (RAH) in detail, to deepen anatomical knowledge and aid neurosurgeons in their work. The material was obtained from cadavers (ages 31-75 years) at routine autopsy. A total of 70 human brains (39 male and 31 female) were examined. People who died due to neurological disorders were not included in the study. Right after dissection, the arteries were perfused with acrylic paint emulsion, through the Circle of Willis or electively through the RAH. Brains were fixed in a 10% solution of formaldehyde, sectioned and placed in methyl salicylate for tissue transparency. To obtain corrosion-casts, the vessels were perfused with polyvinyl chloride or Mercox CL-2R resin and corroded using concentrated potassium chloride. The obtained material was analyzed using a stereoscopic light microscope. The RAH was present in 138 hemispheres with a mean of 1.99 RAH per hemisphere (275 RAH in total). The mean RAH length was 25.2 mm and the mean RAH diameter, in its place of origin, was 1 mm. Two to 30 branches (mean=9.4) originated from the stem of the RAH. The number of RAHs showed a negative correlation to the number of arteries from the medial group of lenticulo-striate arteries (LSA) (R=-0.62; p < 0.0001) which branch off the middle cerebral artery (MCA). This study further supports the RAH embryologic theory by Abbie. The RAH, in its extra- and intracerebral course, may join with the middle group of the LSA or directly with the MCA.

Analysis of microvascular trees by means of scanning electron microscopy of vascular casts and 3D-morphometry.

Arterial and capillary trees form by consecutive branching (mostly bifurcations) from a stem vessel, venous trees form by repeated merging of blood vessels. Diameters of stem (parent, mother) vessels and daughter vessels (branches), interbranching distances and branching angles between stem and daughter vessels lastly define the overall three-dimensional structure of the vascular network as well as the basic transport capacity of the system. Here we use scanning electron microscopy and 3D-morphometry to measure these variables from stereo paired images of vascular corrosion casts of the anterior cerebral artery and its main branches and from arteriolar bifurcations of the mesencephalic optic tectum in the actinopterygian fish, Acipenser ruthenus. We then calculate bifurcation indices, area ratios, asymmetry ratios and test for the optimality principles underlying the bifurcations studied. Our results show that arteriolar bifurcations in the optic tectum are in favor of the principles of minimum pumping power and minimum volume rather than the principles of minimum surface and minimum drag. We conclude that scanning electron microscopy of vascular corrosion casts in conjunction with 3D-morphometry is an excellent tool to thoroughly analyze vascular trees in healthy and diseased tissues and organs, as well as on an ontogenetic and phylogenetic scale.

Morphological changes of dendrites in the human edematous cerebral cortex. A transmission electron microscopic study.

The structural pathology of dendritic processes has been examined in 38 patients with clinical diagnosis of brain trauma, brain tumours and congenital malformations. Cortical biopsies of frontal, parietal, temporal and occipital cortex were conventionally processed for transmission electron microscopy. Isolated ultrathin sections and montages of electron micrographs were used to trace the intracortical dendritic course. Swollen and beaded dendrites were observed in all cases examined, which exhibited fragmentation of limiting plasma membrane and cytoskeletal structures. The swollen dendrites showed vacuolization, dense residual bodies, enlarged rough and smooth endoplasmic reticulum, edematous clear and dark mitochondria, a decreased synaptic density of shaft synapses, edematous and dystrophic changes of spine apparatus and a partial loss of dendritic spines. A wide variety of dendritic spine shapes were observed: mushroom-type, stubby, gem-like filiform spine, and megaspine, considered as spine dysgenesis in the congenital malformations and spine pathology and spine plasticity in brain traumatic injuries and brain tumours. The multifactorial processes associated with brain edema and brain ischemia, such as calcium overload, activation of calcium-dependent proteolytic enzymes, protein aggregation, glutamate-induced neurotoxicity, release of lysosomal enzymes, deficit of ATP, stress oxidative and lipid peroxidation have been considered in relation with the pathological dendritic changes. Dendrotoxicity due to brain edema and brain ischemia seems to be the fundamental pathogenetic mechanism.