Anatomic variations of anterior cerebral artery cortical branches.

The anterior cerebral artery (ACA) is a major vessel responsible for the blood supply to the interhemispheric region. The ACA segment after the anterior communicating artery (AComA) origin is called the distal ACA and has central and cortical branches. The cortical branches are distributed in the different regions of the orbital and medial part of the brain. The objects of this study are the anatomical variations found in the distal ACA. In 76 hemispheres the ACA distal branches were injected with latex and dissected under microscope magnification. Vessel diameters and distances between vessel origins and anterior communicating artery were recorded and analyzed. Microsurgical dissection was carried out to demonstrate anatomic variations of these vessels. Average diameter of ACA at origin was 2.61 +/- 0.34 mm and average diameter of cortical branches diameter ranged from 0.79 +/- 0.27 mm to 1.84 +/- 0.3 mm. Distances between vessel origin and AComA ranged from 7.68 +/- 3.91 mm (orbitofrontal) to 112.6 +/- 11.63 mm (inferior internal parietal). This study found anatomical variations: a single (azygos) ACA was present in one case and three in three cases. Crossing branches of the distal ACA to the contralateral hemisphere were present in 26% of the cases. In some cases a single ACA may supply the posterior hemispheric region through crossing branches. This calls attention to potential bilateral brain infarcts due to a single unilateral ACA occlusion.

Regionalization of oviducts in Boophilus microplus (Canestrini, 1887) (Acari: Ixodidae) and its potential significance for fertilization.

The structural analysis of oviducts in Boophilus microplus (Canestrini, 1887) in different stages of ingurgitation has indicated that they are constituted primarily of an internal cylinder and an external cylinder with different cell types being found between them. Copulated females in active ingurgitation process show typical variations along the internal cylinder, and three regions can be defined: anterior, ring-like and transitional. Based on such regionalization, hypotheses were raised about where and how fertilization takes place, a process yet to be clarified for the acari.

Anatomy of Liliequist's membrane.

The anatomy of Liliequist's membrane was studied in seven adult human cadavers by a technique that preserves the cisternal shape, stains arachnoid membranes violet, and fills the arteries with red gelatin. Our findings suggest the following about Liliequist's membrane: it is located between the interpeduncular cistern posteriorly, the carotid cisterns anterolaterally, and the chiasmatic cistern anteromedially; it is attached laterally to the mesial surface of the temporal lobe above the tentorial edge; it lies posterior to the infundibulum; and it presents a free edge between the optic tract and the temporal uncus.

Acetylcholinesterase activity in the human subfornical organ.

The acetylcholinesterase activity (AChE) in the human subfornical organ (SFO) was detected by the method of Koelle and Friedenwald in 16 human brains collected between 6 and 12 hrs postmortem. The only AchE-positive structures found were neuronal cell bodies and processes, morphologically classified as stellate and fusiform neurons of large, medium and small size. Large ones prevailed in the dorsal zone. The neurons were homogeneously distributed in the rostral area of the SFO. The penetration and ramification of large blood vessels produced a decreasing neuronal density in the medium-caudal area. The architecture of the SFO in sagittal sections comprised a central zone with neurons juxtaposed to the walls of the vascular plexus, whose dendritic and axonal processes showed an intricate pattern without a special arrangement. This neuronal zone of the SFO was surrounded by a peripheral layer of neurons with axonal projections to the rostral area. This layer was thicker in the dorsal zone of the SFO, where axonal fibers "climbing-up" from the central perivascular neurons could be demonstrated. In coronal sections some neurons with prolongations of arcuate distribution connected the dorsal and ventral zones.

Anatomoradiological correlation of the intersection of the carotid siphon with the dura mater.

In order to obtain frames of reference to determine the place of intersection of the carotid siphon with the dura mater in conventional arteriograms, a debated topic lacking general agreement in the literature, 34 cadaveric sphenoids were prepared with the injection of radiopaque medium in both internal carotid arteries. After having marked the dura mater with steel wire, the pieces were radiographed in lateral view. The points of intersection of the clinoclinoid line and the sphenoidal line with the internal carotid artery as well as the emergence of the ophthalmic artery and its posterior projection were marked on the radiographs obtained. The distances between the various points were measured and submitted to statistical treatment. The results showed multiple regressions with a strong correlation coefficient in two equations. A table was built in which, knowing the distances between the points of the clinoclinoid and the sphenoidal plane lines and those of the ophthalmic artery and its projection, the position of the dura mater which covers the cavernous sinus may be estimated in arteriograms.