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Biomedical subjects

K Kitamura

Publications and source records attributed to K Kitamura.

At least 1,459 records · Page 81Linked to original sources
PubMed1977

Excitation-contraction coupling in the smooth muscle cells of the rabbit main pulmonary artery.

1. Increasing the external K concentration depolarizes the smooth muscle cells of the main pulmonary artery, and this depolarization reaches a maximal slope of 58 mV for a tenfold change of [K](o). The threshold depolarization for inducing contraction is at 4 mV and the maximal contraction is reached at a [K](o) of 58 mM.2. Noradrenaline concentrations between 2 x 10(-8)M and 10(-7)M induce tension without depolarizing the cells, but at higher concentrations noradrenaline not only elicits a large tension response but also depolarizes the cells in a dose-dependent way.3. The effect of noradrenaline on the pulmonary artery is appreciably modified by substituting sucrose for NaCl: the cells are slightly hyperpolarized and the tension response is very much reduced.4. By studying the tension response to noradrenaline in other experimental conditions which cause a small hyperpolarization of the cells, such as 5 mM-[Ca](o), 2.9 mM-[K](o) or a small depolarization, such as 11.9 mM-[K](o), it was found that a slight modification of the membrane potential can exert an important effect on the noradrenaline response.5. A simultaneous decrease of [Ca](o) and [Na](o) reduces the tension response to all noradrenaline concentrations. It was found that a reduction of [Na](o) exerts a more depressing effect than a reduction of [Ca](o). In interpreting these results we have to take into account changes of the membrane potential, of availability of Ca, and some competition between external Ca and Na.6. A study of the effect of different concentrations of noradrenaline in Krebs solutions and Ca-free solution has shown that concentrations up to 2.5 x 10(-7)M elicit contraction by increasing the Ca influx, while higher concentrations also induce a release of cellular Ca.7. Caffeine depolarizes the cells and reduces the membrane resistance. It modifies the K, Cl and Ca fluxes in the same way as noradrenaline, but it suppresses the mechanical response induced by noradrenaline.

Animals↗
PubMed1977

Human chorionic gonadotropin produced by ectopic pinealoma in a girl with precocious puberty. Case report.

A case is reported in which a human chorionic gonadotropin (HCG-)-producing ectopic pinealoma was found in a 5-year-old girl with precocious puberty. Physical examination revealed abnormal breast enlargement. Endocrinological study disclosed a high plasma HCG concentration of 1192 ng/ml with a normal follicular stimulating hormone (FSH) level. The HCG content of the tumor was as high as 400 ng/mg of acetone dried tissue, but no FSH was detectable. This is the first reported case of precocious puberty associated with pineal tumor in a female.

Cerebral Ventricle Neoplasms↗
PubMed1977

[A case of multiple anomalies of cerebral vessels--fenestration of the middle cerebral artery aneurysm of the anterior communicating artery and arteriovenous malformation on the frontopolar region (author's transl)].

A case associated with multiple cerebral vascular anomalies, which consisted of fenestration of the middle cerebral artery, arteriovenous malformation and aneurysm of the anterior communicating artery, was reported. A 48 year-old male has been suffering from the left paralysis and mental disorder after the initial attack of subarachnoid hemorrhage, and the second attack resulted in the deterioration of the symptoms. He was admitted to our clinic on October 28, 1974. On neurological examination, mental disorders, such as disorientation, emotional incontinence, amnesia and acalculia, hemiplegia on the left and meningeal irritation signs were observed in admission period. Physical examination was negative. Cerebral angiographic findings were as follows: 1) Moderate vasospasm of the right internal carotid artery at the terminal segment, mild bowing of the anterior cerebral artery and stretching of the frontparietal opercular branches of the middle cerebral artery were observed. 2) Right frontpolar arteriovenous malformation fed by the frontobasal artery and the frontopolar artery, and drained via the aberrant cortical vein into the superior sagittal sinus. 3) Aneurysm of the anterior communicating artery was opacified by left carotid angiography. 4) An abnormal vessel derived from the terminal segment of the right internal carotid artery and terminated at the portion of the sphenoidal segment of the middle cerebral artery. Complete loop was formed between genuine middle cerebral artery and this abnormal artery. He was operated with dissecting microscope on November 11, 1974. The arteriovenous malformation at right frontopolar region was totally removed and aneurysm of the anterior communicating artery was clipped. According to the operative findings, the arachnoid membrane over the right frontopolar region was turbid and adhered to the adjacent tissues. On the contrary, no abnormal findings suggestive of previous subarachnoid hemorrhage were observed around the region of the anterior communicating artery aneurysm. These findings showed that subarachnoidal bleeding was caused by rupture of the arteriovenous malformation of right frontopolar region, but not by the aneurysm on the anterior communicating artery. The postoperative course was uneventful and during the hospitalization the patient starts on rehabilitation therapy. The authors discussed the genesis of fenestration of the middle cerebral artery and relation among these combined vascular anomalies. We inferred that fenestration of the middle cerebral artery arose from the in complete fusion of procursor vascular network in embryonic stage. Additionally, we emphasized that it was necessary to make a distinction between these two terms "fenestration" and "duplication".

Cerebral Angiography↗
PubMed1977

[Computerized transverse axial tomography in intracerebral, intracerebellar and intraventricular hemorrhage (author's transl)].

Computerized transverse axial tomography (CT) of the brain is a recently developed method which allows non-invasive roentgenologic evaluation of intracranial diseases. The advent of CT represents a great advance in the diagnosis of a very wide variety of intracranial lesions, including cerebrovascular diseases. Especially, CT was found to be extremely informative in evaluating intracerebral, intracerebellar and intraventricular hemorrhage. The purpose of this report is to evaluate the clinical usefulness of CT in the diagnosis of intracranial hemorrhage. From the seven hundreds cases of various intracranial diseases hitherto examined by the EMI-scanner (160 X 160 matrix), twenty-three cases of nontraumatic intracranial hemorrhage were selected for the present study. Fifteen cases of fresh hemorrhage consisted of hypertensive cerebrovascular disease, arterio-venous malformation, aneurysm and unknown etiology, number of cases being six, three, four and two, respectively. All cases were examined within fifteen days after the ictus and the positive findings were obtained in all cases. The characteristic feature of the hematoma is the circumscribed and increased density area surrounded by the decreased density zone probably representing the accompanied brain edema. The sequential CT studies revealed that the hematoma area was gradually decreased in its density and finally transformed into the rather low density one in four weeks or so after the ictus. The smallest hematoma detected by CT was the cerebellar hematoma about five grams in weight, which was failed to be recognized by the angiography. In cases of the old hemorrhage, besides the decreased density area of the hematoma, such findings were obtained as cerebral atrophy, ventricular dilatation and porencephalic change. It would be concluded that CT study is the most useful aid at present available in the diagnosis of intracranial hemorrhage. The precise anatomic extent of the hematoma, associated brain edema, ventricular deformity and displacement and hydrocephalus are all readily assessed by CT.

Adolescent↗
PubMed1977

[A case of HCG-producing ectopic pinealoma in a girl with precocious puberty (author's transl)].

HCG-producing ectopic pinealoma of two cell pattern type was demonstrated in a 5-year old girl who presented precocious puberty and bilateral choked discs. The tumor was localized at the anterior third ventricle and suprasellar region. Endocrinological findings are as following: Plasma basal LH was markedly elevated to 306 mIU/ml and HCG was elevated to 1,192 ng/ml. Provocative test of hypophyseal function revealed low response. Plasma estrogen was not detectable. HCG content of resected tumor tissue was elevated to 400 ng/mg. FSH, however, was not detectable. Histological findings of this tumor showed atypical teratoma, so-called two cell pattern pinealoma. Electron microscopic findings revealed two types of cells, dark and clear cells. Many secreting granules were found in the dark cells. In this case, HCG in plasma, CSF and tumor tissue was remarkably elevated. In addition, plasma FSH was also elevated to 8.9 mIU/ml. Precocious puberty associated with tumor in the pineal-suprasellar region has been seen only in boys. There has been no case report of precocious puberty in girls. This case is the first female case is which HCG-producing ectopic penealoma is caused in precocious puberty.

Brain Neoplasms↗
PubMed1977

[A study of excitability changes in DSCT neurons of the cat (author's transl)].

Excitability changes in the dorsal spinocerebellar tract (DSCT) neurons of the cat were extracellularly studied with correlation analysis. Most of the interval histograms were classifed as normal distribution, and occasionally bimodal distributions were observed, which resulted from an occasional "double spiking" in the spontaneous background discharge (BD). The conduction velocity was measured in 72 DSCT fibers. The histogram showed a peak at 40-50 M/S. The majority of the units had BD with coefficient of variation less than 0.2, which suggest BD with regular firing. Based on cross-correlelograms, DSCT responses to electrical stimulation of the muscle nerves of the hind leg were classified into at least three types. Type 1 response, constituted approximately one-fifth of the total, is monosynaptic activation. Type 2 response, observed most frequently (47%), is inhibition of DSCT cells with a short latency. Type 3 responses, observed nearly as often as type 2 (34%), is a long latency excitation, undoubtedly polysynaptic. Changes in stimulation intensity showed complex changes in the pattern of response. Type 1 and 2 responses were unaffected by increasing stimulus rate. Peak correlations in type 3 response were reduced by increase in stimulus rate. There were no data demonstrating feedback circuitry associated with collaterals of DSCT axons. This suggest that axon collaterals have no direct effect on the activity of Dsct cells.

Afferent Pathways↗