Vasospastic Phenomena on the Luminal Replica of Rat Brain Vessels

Strikingly localized ring-like constrictions (other than sphincters, cushions and offshoot furrows) have appeared on the casted vessels of some of our preparations. Morphology of the phenomena reveals diverse degree of active contraction of the vessel wall, ranging from corrugation of the luminal surface to near severance of the acrylic cast. Distribution of the vasospastic phenomena reveals as particularly affected the arteries in the diameter range between 25 and 75 μm, that belong either to intra-arterial anastomoses between the branches of each of the three major cerebral arteries or to their terminal junctions in the border zones (inter-arterial anastomoses). Among the possible causes for the occurrence of the observed vasospasms, we indicate the susceptibility to raised intraluminal pressure during injection, producing contraction of the smooth muscle cell. Reactivity appears heightened in the anastomotic districts of the circulation. The evidence of so-called plastic strips clinging to constricted sections of affected vessels prompts re-examination of their proposed origin as plastic wrapping . Rather, they appear to be remnants of dynamic elements of the vascular wall (smooth muscle cells) that resisted corrosion

The Capillary Bed in the Choroid Plexus of the Lateral Ventricles: A Study of Luminal Casts

Micro-angioarchitecture of the choroid plexus of the lateral ventricles is investigated in microcorrosion casts of animal and human preparations studied with the scanning electron microscope. The capillary bed in the diverse regions of the tissue belongs to one of three patterns: (1)-a network of capillary meshes that envelop the larger arteries and veins predominates in the central segment. (2)-in the villous regions a leaf-like organization of sinusoids is found together with (3)-fronds of glomerular formations. Glomeruli are formed when arterial afferents and venous efferents converge in a quasi hilar structure before branching in arterio-venous loops. Nodular thickenings are observed on glomerular capillaries The preparations studied (rat, dog, human) are remarkably similar and differ mostly in degree of occurrence of common architectural patterns. Arterio-venous communications are found at the hilus of human glomerular formations

Microsurgical anatomy of the hypoglossal nerve

WOS: 000241596700007PubMed: 16935514The aim of the present study was to review the surgical anatomy of the hypoglossal nerve (HN), to reveal its relationships on its course and to provide some landmarks to its identification. Ten cadaveric head dissections (20 sides) were performed using microsurgical techniques. The anatomical relationships between the HN and other nerves, muscles, arteries and veins were carefully recorded, and some measurements were made between the HN and related structures. Thus, various landmarks were determined for the easy identification of the HN. In addition, the hypoglossal triangle, which containes major vascular structures, is described. The HN is divided into three main parts: cisternal. intracanalicular and extracranial. The HN arises from the medulla as a line of rootlets situated along the anterior margin of the lower two-thirds of the olive in the preolivary sulcus. It is the newly described 'hypoglossal' triangle in the anterior neck that is bordered by the descending hypoglossus laterally, transverse hypoglossus inferiorly and inferior border of the stylohyoid muscle superiorly. In our specimens, we determined that the HN was 3-7 mm (mean 5 mm) inferior to the digastric tendon, as well as mostly superficial. The occipital artery arose from the posterior surface of the external carotid artery (ECA) 6-9 mm (mean 7 mm) above the carotid bifurcation. There is also an important 'cross' between the occipital artery and the HN. In all cadavers, this crossing point was 7-9 mm (mean 8 mm) superior to the emergence of the occipital artery from the ECA. In conclusion, understanding the detailed anatomy of the HN and using landmarks to identify the nerve are crucial for surgery in the region. (c) 2006 Elsevier Ltd. All rights reserved

A Case History of Glioma Progression

Low-grade diffuse astrocytomas have an intrinsic tendency for malignant progression but the factors determining the kinetics of this process are still poorly understood. We report here the case of a male patient who developed a fibrillary astrocytoma at the age of 33 years and who underwent six surgical interventions over a period of 17 years without radiotherapy or chemotherapy. The first three biopsies spanned a period of 11 years and led to the diagnosis of low-grade, diffuse astrocytoma (WHO grade II), with a growth fraction (MIB-1 labeling index) of 2.3-3.7%. The fourth to sixth biopsies showed histological features of anaplastic astrocytoma (WHO grade III), with growth fractions between 5.0 and 10.5%. The fraction of gemistocytic neoplastic astrocytes also increased, from 0.3% in the first biopsy to 17.5% in the last biopsy and preceded the increase in proliferative activity and transition to anaplastic astrocytoma. The fraction of tumor cells immunoreactive to BCL-2 increased from 0.3% to 8.2%. A p53 mutation in codon 273 (CGT→TGT, Arg→Cys) was identified in the first biopsy and persisted throughout the course of the disease. However, the fraction of cells with p53 protein accumulation increased significantly during progression, from 3.2% in the first biopsy to 13.7% in the last. The absence of additional genetic alterations (PTEN mutations, loss of chromosome 10 and 19q) may be responsible for the slow progression and lack of glioblastoma features even after a 17-year disease duration

Mechanisms underlying the generation of autonomorespiratory coupling amongst the respiratory central pattern generator, sympathetic oscillators, and cardiovagal premotoneurons

The respiratory rhythm and pattern and sympathetic and parasympathetic outflows are generated by distinct, though overlapping, propriobulbar arrays of neuronal microcircuit oscillators constituting networks utilizing mutual excitatory and inhibitory neuronal interactions, residing principally within the metencephalon and myelencephalon, and modulated by synaptic influences from the cerebrum, thalamus, hypothalamus, cerebellum, and mesencephalon and ascending influences deriving from peripheral stimuli relayed by cranial nerve afferent axons. Though the respiratory and cardiovascular regulatory effector mechanisms utilize distinct generators, there exists significant overlap and interconnectivity amongst and between these oscillators and pathways, evidenced reciprocally by breathing modulation of sympathetic oscillations and sympathetic modulation of neural breathing. These coupling mechanisms are well-demonstrated coordinately in sympathetic- and respiratory-related central neuronal and efferent neurogram recordings and quantified by the findings of cross-correlation, spectra, and coherence analyses, combined with empirical interventions including lesioning and pharmacological agonist and antagonist microinjection studies, baroloading, barounloading, and hypoxic and/or hypercapnic peripheral and/or central chemoreceptor stimulation. Sympathetic and parasympathetic central neuronal and efferent neural discharge recordings evidence classic fast rhythms produced by propriobulbar neuronal networks located within the medullary division of the lateral tegmental field, coherent with cardiac sympathetic nerve discharge. These neural efferent nerve discharges coordinately evidence slow synchronous oscillations, constituted by Traube Hering (i.e., high frequency), Mayer wave (i.e., medium or low frequency), and vasogenic autorhythmicity (i.e., very low frequency) wave spectral bands. These oscillations contribute to coupling neural breathing, sympathetic oscillations, and parasympathetic cardiovagal premotoneuronal activity. The mechanisms underlying the origins of and coupling amongst, these waves remains to be unresolved