Kunihiko Harada

Pediatric acoustic schwannoma showing rapid regrowth with high proliferative activity

Abstract Acoustic schwannoma is a slow-growing tumor and usually occurs in adult patients. We report a rare pediatric case of acoustic schwannoma with high proliferative potential. A 10-year-old boy was diagnosed as having a right cerebellopontine angle tumor. The tumor was subtotally resected. Histological examination revealed a typical acoustic schwannoma with a few mitotic figures. Chromosomal analysis showed no abnormality on the long arm of chromosome 22 associated with neurofibromatosis type 2. The lesion regrew rapidly as an acoustic schwannoma, necessitating subtotal resection on three occasions and CyberKnife radiosurgery. The immunohistochemical MIB-1 staining indices of the specimens obtained at the first, second, and third operations were 2.3%, 4.6% and 14.7%, respectively. The immunohistochemical proliferative potential of acoustic schwannoma is discussed.

Acetylcholinesterase-containing neurons in the striatum, septum and hippocampus of the rat in embryonic culture and adult in situ

Neurons of the rat brain, of either adult in situ or embryonic culture, have been studied by using a sensitive method for acetylcholinesterase (AChE) histochemistry. In the culture system, incubated for 6-18 days, AChE-positive neurons were found in tissues originating from the striatum and septum, but not in those from the hippocampus. These positive somata were morphometrically analyzed in terms of the cell size, i.e. the lengths of the major axis (Lmax) and the minor axis (Lmin) in cultured dishes of the striatum and septum; the mean Lmax was 20 and 22 microns, respectively. In in situ adult brain sections, a similar morphometric examination of AChE-positive neurons gave comparable results to those obtained in the culture system. An evaluation of both in vitro and in vivo through the histogramatical analysis revealed that the striatum contained more than two populations of AChE-positive cells differing in cell size. In contrast, a major single peak of Lmax was detected in the histogram of the septum. In both cases of striatum and septum in in situ adult brain, sagittal sections show larger size of Lmax, indicating that AChE-positive neurons are arranged in the sagittal direction. In studies on electrophysiological properties of large striatal cells in culture, both acetylcholine and glutamate induced changes in the membrane potential and/or the frequency of excitatory postsynaptic potential, while dopamine induced much smaller responses.

Relationship between resting cytosolic Ca2+ and responses induced byN-methyl-d-aspartate in hippocampal neurons

Cytosolic calcium concentrations ([Ca2+]i) in cultured hippocampal neurons from rat embryos were measured using fura-2. Neurons with higher resting [Ca2+]i showed greater [Ca2+]i responses to N-methyl-D-aspartate (NMDA) and K+ depolarization. There was a strong relationship between resting [Ca2+]i and the maximal changes in [Ca2+]i (delta[Ca2+]i), which fit the our proposed equation to describe this relationship.

The microvascular architecture of human malignant glioma

SummaryThe three-dimensional microvascular architecture of human glioma was investigated. The results of the study, the first of its kind, suggested that the process of vascularization in glioma is based on two patterns. In a large proportion of the glioma, one pattern is similar to the vascularization observed in normal developing fetal and newborn rat brain, while in a small proportion of the glioma, another pattern including complicated vascular protrusion and spiral running, is seen.

Cerebral endothelial regeneration following experimental brain injury

SummaryIt is still unknown when and in which area endothelial regeneration occurs after brain injury, and to what extent such changes depend on the severity of the injury. We have, therefore, studied bromodeoxyuridine (BrdU) uptake by regenerating endothelial cells in two different groups of rats given cold lesions using immunohistochemistry employing anti-BrdU monoclonal antibody, anti-factor VIII-related antigen antibody and anti-glial fibrillary acidic protein antibody. The earliest evidence for the presence of BrdU-positive endothelial cells (BrdU+end) was observed at 2 days after injury, the injured endothelial cells regenerating from the edge toward the center of the lesion in both groups. We considered that edema fluid could act as an important factor, since at 2 days post-injury BrdU+end were not in contact with macrophages and were always found in Evans blue-stained areas. Study of endothelial cell kinetics also confirmed that the repair of injured endothelial cells was intimately involved in the reconstruction of the blood-brain barrier, since the time of disappearance of BrdU+end coincided with the disappearance of Evans blue-stained areas. The difference in the process of endothelial regeneration was first apparent on the 3rd day, there being no difference at 2 days.

Hippocampal neurotrophic factors influence the perikaryal size of septal acetylcholinesterase-containing neurons in culture.

The septal neurons were cultured under the following conditions: (1) treated with 7S nerve growth factor (NGF) (50 ng/ml); (2) grown with hippocampal cell-conditioned medium supernatant; (3) cocultivated with hippocampal cells; (4) cocultivated with cerebellar cells; (5) no treatment. Acetylcholinesterase histochemistry was used to identify cholinergic cells after pretreatment with diisopropylfluorophosphate. The mean values of the perikaryal major axis and minor axis at day 14 of culture were significantly larger in septal cells cocultivated with hippocampal cells than in septal cells grown under other conditions. NGF-treated septal cells showed a smaller, but significant, increase in the mean value of the major axis of these neurons.

The dose-response relationship for N-methyl-d-aspartate currents in cultured rat septal neurons: effects of magnesium ions and 2-amino-5-phosphonovaleric acid

Dose-response relations of the peak ionic current induced by N-methyl-D-aspartate (NMDA) under Mg-free vs normal saline (1.2 mM Mg) conditions were obtained in cultured neurons dissociated from septa of fetal rat brains using the single electrode voltage clamp method. The effect of D,L-2-amino-5-phosphonovalerate (APV) on the dose-response relationship was also studied. In the Mg-free condition, the response to NMDA increased progressively with dose up to 0.2 mM, at which point the response saturated up to 1 mM NMDA (ED50 was about 70 microM). At larger doses (1-3 mM) the response increased sharply. In normal saline the response increased up to doses of 10 mM, and there was no apparent plateau. In a comparison between the depressant effects of APV and Mg ions on the peak current value, the depression caused by APV (10-30 microM) at higher NMDA concentrations was larger than that caused by Mg.

Regeneration of Cerebral Microvessels After Cold Injury: Biological Significance of Edema Fluid

Brain edema is a frequent and serious problem in man. Many investigators have performed morphological studies on various aspects of brain edema, including blood-brain barrier (BBB) damage and vascular permeability, for which they have often employed the cold-lesion model of vasogenic edema. In this cold-injury model, it has been clearly established that edema fluid passes into the brain tissue and accumulates within the abnormally distended extracellular space [1]. Many neurons as well as all other cellular elements are separated from each other by the hematogenous edematous fluid, and eventually begin to float freely in the fluid. However, it seems that little attention has been paid to the biological significance of the edema fluid. Mitosis of astrocytes is observed in edematous tissue. By cinematography, it has also been noted that many cells showing ruffle movement swim about feverishly in the edematous tissue [2]. Obviously, many cells in the edematous tissue will take part in lesion repair, under conditions where the vascular network in the edematous tissue is sparse [3]. However, it is still unknown from where and how many cells receive the energy for lesion repair. In the present study, by revealing sequential changes in endothelial cell kinetics following different types of cold injury using immunohistochemical techniques, we intended to verify if edematous fluid is an important factor for lesion repair. In addition, it was considered important to observe if transferrin receptors (Tf-R) are present when transferrin in edematous fluid is needed. Transferrin is the major serum iron-transport protein and, along with iron, plays an important role in cell growth and metabolism. Key reactions in energy metabolism and DNA synthesis are catalyzed by iron-containing enzymes. The first step in the delivery of iron to cells by transferrin involves its binding to a specific cell-surface receptor [4]. However, synthesis of transferrin does not occur in the brain [5]. In the normal brain, transferrin receptors are expressed on brain capillaries, facilitating transport of transferrin into brain tissues [6].

Cerebral Endothelial Regeneration Following Brain Injury

It has not been determined when and in which area regeneration of the cerebral endothelium occurs after brain injury (Orita et al. 1988). We therefore studied bromodeoxyuridine (BrdU) uptake by regenerating endothelial cells in two different groups of rats given cold lesions using immunohistochemistry employing anti-BrdU monoclonal antibody, anti-factor VIII-related antigen antibody and anti-glial fibrillary acidic protein antibody.