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Biomedical subjects

K Kitamura

Publications and source records attributed to K Kitamura.

At least 1,243 records · Page 69Linked to original sources
PubMed1982

Intracranial venous angiomas.

Publications in the scientific literature are controversial in regard to the clinical significance of intracerebral venous angiomas. The present study of 11 patients with venous angiomas underscores the clinical importance of these lesions as potential causes of cerebral hemorrhage and obstructive hydrocephalus. The clinical and radiographic manifestations in 9 of these 11 patients correlated well. In cases of venous angiomas, the venous phase of angiography must be carefully scrutinized, particularly in patients with subarachnoid or intracerebral hemorrhage. Some diagnostic problems related to the angiography of venous angiomas are discussed.

Adolescent↗
PubMed1982

Paraventricular cerebral cyst in an infant.

The case of a paraventricular cerebral cyst with a partial defect of the corpus callosum is reported. The cyst wall was studied using light and electron microscopy. Electron microscopy revealed that the lining of the cyst consisted by a single layer of epithelial cells. The cells of the cyst wall, which rested on a basement membrane, had microvilli and abnormal cilia, and there were desmosomes between the cells, In accordance with the pathological findings, the cyst was classified as a type transitional between a choroidal epithelial cyst and an ependymal cyst.

Agenesis of Corpus Callosum↗
PubMed1982

Cells constituting cerebellar hemangioblastomas. Ultrastructural study.

Five capillary hemangioblastomas exhibiting a range of histologic variations common to this tumor were studied using electron microscopy. The capillary hemangioblastoma were composed commonly of three cell lines -- stromal cells, endothelial cells and pericytes. In addition, extramedullary hematopoietic foci were seen in the tissue of one case. We regarded all these cellular elements as neoplastic components. The interconvertibility among them was not confirmed. The capillary hemangioblastomas were highly organized by those multiple cell lines. The histologic pattern of growth was arbitrarily subgrouped into stromal cell prominent type and capillary prominent type. Intermediate features between the two types were observed. These different types would depend on relative proportions and the degree of maturity of the constituting cell elements. From the histogenetic point of view, we considered capillary hemangioblastomas as being a hamartomatous tumor.

Adult↗
PubMed1982

Neuritogenic determinant of bovine P2 protein in peripheral nerve myelin.

Experimental allergic neuritis (EAN) is an experimentally produced demyelinating disease of peripheral nervous system. Several peptides of bovine P2 protein were tested for neuritogenic activity in Lewis rats. The hexacosapeptide CiT4 (residues 53--78 of bovine P2 protein) showed the highest neuritogenic activity among the peptides tested. The nonapeptide (residues 70--78) and the tridecapeptide (residues 66--78) were synthesized using the liquid phase peptide synthesis technique. The tridecapeptide showed mild, but definite activity in inducing EAN in the rats, while the nonapeptide was inactive. The localization of the neuritogenic determinant of bovine P2 protein in Lewis rats is discussed.

Animals↗
PubMed1982

The complete amino acid sequence of human P2 protein.

The complete amino acid sequence of P2 protein from human peripheral nerve myelin was determined from nine staphylococcal protease peptides and four cyanogen bromide peptides. Human P2 protein is composed of 131 amino acids and has a molecular weight of 14,818. Compared to bovine P2 protein, there are replacements at nine positions (human in equilibrium bovine): 18(Asp in equilibrium Glu), 39(Thr in equilibrium Arg), 56(Thr in equilibrium Pro), 83(Ile in equilibrium Thr), 87(Gln in equilibrium Ala), 96(Arg in equilibrium Lys), 100(Lys in equilibrium Asn), 115(Ala in equilibrium Val), and 121(Gly in equilibrium Asp).

Amino Acid Sequence↗
PubMed1982

Roles of stored calcium on the mechanical response evoked in smooth muscle cells of the porcine coronary artery.

Effects of acetylcholine (ACh), caffeine and procaine on the membrane and mechanical properties of the intact and skinned muscle cells of the porcine coronary artery were investigated using the micro-electrode and isometric tension recording methods.1. ACh (10(-8)-10(-5)m) had no effect on the membrane potential and membrane resistance, as assessed from the current-voltage relationship.2. Caffeine possessed dual actions on the membrane property, i.e. a low concentration (0.3-1 mm) hyperpolarized and a high concentration (over 1 mm) depolarized the membrane, while caffeine (over 0.3 mm) consistently increased the ionic conductance of the membrane. Procaine (over 1 mm) depolarized the membrane and decreased the ionic conductance of the membrane.3. The spike and contraction evoked by outward current pulses in the presence of 10 mm-TEA were suppressed by treatment with caffeine (5 mm) or procaine (3 mm), but the spike was slightly and the electrically induced contraction was significantly suppressed by ACh (10(-6)m) due to the marked increase in resting tension.4. In Ca-free 2 mm-EGTA containing solution, the K-induced contraction (118 mm) rapidly ceased, but not the contraction evoked by ACh (10(-5)m) or caffeine (5 mm). The ACh-induced contraction rapidly ceased in the presence of 1 mm-procaine; however, over 5 mm-procaine was required to abolish the caffeine-induced contraction.5. The pCa-tension relationship was measured in saponin-treated skinned muscles. The minimum concentration of free Ca required to produce contraction was 2 x 10(-7)m, while maximum contraction was observed at 10(-5)m-free Ca. The maximum amplitude of Ca-induced contraction observed in skinned muscles was larger or the same as that evoked by ACh in the intact muscle. ACh (10(-5)m), caffeine (5 mm) and procaine (5 mm) had no effect on the pCa-tension relationship.6. After Ca has been loaded in skinned muscles, caffeine and replacement of K with choline (116 mm) in the Ca-free EGTA containing solution produced the contraction. However, the application of ACh did not result in a release of the stored Ca, and procaine suppressed the release of Ca activated by caffeine.7. The present results indicate that ACh activates the muscarinic receptor distributed on the plasma membrane, thus releasing the stored Ca. However, this mechanism may not be a prerequisite for direct action of ACh on the Ca releasing site. The possible mechanism of ACh action on the Ca releasing site, mainly sarcoplasmic reticulum, was discussed in relation to actions of caffeine and procaine, particularly with regard to the functional relations between plasma membrane and sarcoplasmic reticulum.

Acetylcholine↗
PubMed1982

Factors modifying contraction-relaxation cycle in vascular smooth muscles.

Contraction-relaxation cycles in vascular smooth muscles are largely dependent on the regulation of free Ca2+ in the myoplasm, as is the case in skeletal and cardiac muscles. In this article we describe the varieties of contraction-relaxation cycles of vascular smooth muscles determined at cellular and subcellular levels. To discuss the excitation-contraction and pharmacomechanical coupling mechanisms in vascular tissues, passive and active membrane properties and ionic movements measured by various procedures are briefly introduced. In vascular smooth muscles the sources of Ca2+ contributing to the activation of contractile proteins are extra- and intracellular. Influxes of Ca2+ across the membrane are enhanced by the calcium spike and electrical and chemical depolarizations or activations of autonomic receptors.l However, the Ca2+ influx during the generation of action potential does not directly increase the free Ca2+ in the cell; rather, this ion is sequestered in the storage site and activates the calcium-induced calcium-release mechanism in the storage sites with a subsequent increase in the levels of free Ca2+. In some vascular tissues depolarizations induced by activations of autonomic receptors are not a prerequisite for generation of the contraction, as these mechanical responses appear with hyperpolarization of the membrane or without a change in the membrane potential. Possible functional links between the myoplasmic membrane where the receptors are distributed and the Ca2+ storage and releasing sites (mainly sarcoplasmic reticulum) in the cell are discussed. In addition, small arteries possess possibly more than three subtypes of alpha-adrenoceptors, including the presynaptic alpha 2-adrenoceptor. The roles of sarcoplasmic reticulum and the calcium receptor of contractile proteins (calmodulin or leiotonin C) from the chemically skinned muscles of vascular tissues were compared with those of intact muscles. The relaxation of vascular tissues as induced by activations of beta-adrenoceptors, nitrites, and other chemicals is also briefly introduced.

Action Potentials↗
PubMed1982

Somatotopic arrangement of lateral spinothalamic tract in percutaneous cervical cordotomy.

As a new clinical approach for the purpose of mapping a lamina analysis, the present report deals with another landmark for insertion of the spinal needle in man other than the usual dentate ligament when performing a percutaneous cordotomy. Electrophysiological studies were made on 19 patients in order to determine the effect of electrostimulation with a bipolar concentric electrode, as well as to corroborate the position of the electrode radiologically. A new apparatus has been devised so that one can locate the target insertion point easily.

Cordotomy↗
PubMed1982

Finger blood flow decrease in leg exercise.

Finger blood flow (FBF) was measured with mercury-in-silastic strain gauge venous occlusion plethysmography before, during and after 2-min leg exercise on a Monark bicycle ergometer at exercise intensities of 0, 60, 90 and 120 watts. The FBF rapidly decreased in all subjects immediately after the onset of exercise, and was as maintained at low levels during exercise. The amount of decrease in FBF observed during exercise seemed to be independent of exercise intensity.

Adult↗
PubMed1982

The ultrastructure of the geniculate ganglion.

The ultrastructure of the geniculate ganglion was studied in the guinea pig and monkey. Two cytologically distinct colonies of ganglion cells were seen and identified as light and dark cells. All neurons were unmyelinated and most were unipolar, although a few bipolar cells were seen. The axons, upon leaving the cell bodies, followed convoluted courses in the vicinity of the cells bodies before becoming invested by myelin sheaths. Two types of nerve terminal were identified on the small light cells. The first type contained predominantly agranular and spherical vesicles and had synaptic contact with the cell body. The second type did not show synaptic contacts but contained many ellipsoidal vesicles. This study provided no information on the functional significance of these nerve terminals.

Animals↗
PubMed1982

Ventricular and subarachnoid seeding of intracranial tumors of neuroectodermal origin--a study of 26 consecutive autopsy cases with reference to focal ependymal defect.

In a series of 26 consecutive autopsy cases of intracranial tumors of neuroectodermal origin, tumor seeding on the ventricular surface and in the subarachnoid space was studied. Five cases of glioblastoma multiforme, six of malignant astrocytoma, six of medulloblastoma, one mixed glioblastoma-fibrosarcoma, one unclassified glioma, and one ependymoma showed ventricular and/or subarachnoid seeding of tumor. The incidence of tumor seeding in our series (76.9%) is much higher than in other series. This discrepancy is probably due to the inclusion of a large number of very small tumor metastases that may have been overlooked in other series. In all cases where metastases were observed the primary tumor extended into the cerebrospinal fluid (CSF). Tumor seeding via the cerebrospinal pathway was more frequently associated with malignant tumors. The distribution of tumor metastases correlated with CSF flow and with the site of focal ependymal defects, which were present in normal brains but occurred more frequently and widely in hydrocephalus.

Adolescent↗