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Biomedical subjects

K Takakura

Publications and source records attributed to K Takakura.

At least 235 records · Page 13Linked to original sources
PubMed1991

The expression of c-kit protein during oogenesis and early embryonic development.

The c-kit proto-oncogene encodes a transmembrane tyrosine kinase receptor and was shown to be allelic with the white-spotting locus (W) of the mouse. Mutations at the W locus have pleiotropic effects on the development of hematopoietic stem cells, melanoblasts, and primordial germ cells. In order to elucidate the role of c-kit protein in gametogenesis and oocyte maturation, we have examined immunohistochemically the expression of c-kit in the ovaries of mice at late fetal and postnatal stages, and in early embryos. By the avidin-biotin-peroxidase (ABC) method using rat anti-mouse c-kit monoclonal antibody, the c-kit protein was detected in ovaries after the time of birth, but not before. The expression of c-kit was observed mainly on the surface of oocytes, but not in granulosa cells nor in interstitial regions. Oocytes of primordial to fully grown Graafian follicles showed the c-kit protein. When ovulation was induced by hCG, the expression of c-kit in ovulated unfertilized oocytes was weaker than in oocytes of Graafian follicles. In 1-cell embryos the c-kit protein was still observed, but with cell division its expression further decreased, and it was not detected in embryos of 4-cell, 8-cell, and morula stages. In summary, the highest expression of c-kit was observed on the surface of oocytes arrested in the diplotene stage of meiotic prophase. With ovulation and the resumption of meiotic maturation, its expression declined. These results suggest that the c-kit protein may play some role in meiotic arrest, oocyte growth, and oocyte maturation.

Animals↗
PubMed1991

The role of cerebral microvessel endothelium in regulation of cerebral blood flow through production of endothelin-1.

We have previously reported the production of endothelin-1 (ET-1) by the cerebral microvessel endothelia and suggested an important role of ET-1 and microvessel endothelia in the regulation of local blood flow within the brain. In the present study, radioimmunoassay of ET-1 revealed that ET-1, produced by cultured cerebral microvessel endothelia grown on a filter, is released mainly to the basal side (corresponding to the basement membrane side), not to the apical side (corresponding to the vascular lumen side). This might indicate that ET-1 constricts arterioles locally at the same place where it is produced by endothelia. The present results also show that cultured cerebral microvessel endothelia produce less ET-1 under low oxygen pressure and that they produce more ET-1 under low carbon dioxide pressure. Taken together, our results may suggest that the negative feedback regulation of cerebral blood flow through oxygen and carbon dioxide pressure is mediated by ET-1 produced locally by cerebral microvessel endothelia.

Capillaries↗
PubMed1991

Open surgery assisted by the neuronavigator, a stereotactic, articulated, sensitive arm.

A new computed tomographic-stereotactic device that translates the operating point onto preoperative computed tomographic (CT) images, the Neuronavigator, has been developed. We have applied this system to various neurosurgical procedures to examine its usefulness. The system consists of a 6-joint sensing arm and a 16-bit personal computer. It projects the location of the arm tip onto a corresponding CT slice with a cursor that guides the surgeon toward the intracranial target during open surgery. The system also projects the location of the tip onto angiograms, and when used in conjunction with echography or a transcranial Doppler (TCD) flow meter, the surgeon's ability to navigate is enhanced. Sixty-eight patients underwent operation with the Neuronavigator. The navigation system worked as the core of a multimodal three-dimensional data base that proved to be useful during surgery. The maximum detection error was 2.5 mm, which was considered sufficient for open microsurgery. It also proved useful in designing the position of a craniotomy, in targeting deep-seated mass lesions, and in tracing the tumor edge, which had been identified on a CT scan. When the angiogram was combined with the navigator, it became easy to identify key vessels within a small operating field. The system was also combined with a TCD flow meter. This combination makes it possible to translate the measuring point of the TCD directly into CT coordinates, improving the precision of location of the TCD probe. The Neuronavigator combines various diagnostic images into one database and effectively guides the surgeon during surgery.

Adolescent↗
PubMed1991

Immunohistochemical demonstration of protein kinase C isozymes in human brain tumors.

Immunohistochemical studies of the expression of protein kinase C isozymes were done in 38 human brain tumors using monoclonal antibodies to three major isozymes: Type I, Type II, and Type III. The brain tumors, with the exception of 3 medulloblastomas and 2 of 6 pituitary adenomas, showed strong immunoreactivity for the Type III isozyme. Astrocytomas, anaplastic astrocytomas, and glioblastomas also showed weak immunostaining for Type II, whereas other tumors lacked this staining. Immunoreactivity for Type I was present, although weak, in some astrocytic gliomas. There was no correlation between the presence of immunoreactivity for protein kinase C isozymes or the intensity of staining for the Type III isozyme and the pathological grade of malignancy. In normal human brain tissue, Type I is localized mainly in neuronal cells, Type II in the neuropil of the cerebral cortex and the molecular and granular layers of the cerebellum, and Type III almost exclusively in astrocytes. The presence of immunoreactivity for the Type III isozyme in varying tumor cells, including those of non-astrocytic tumors and the presence of the Type II and/or Type I isozymes in astrocytic gliomas demonstrate that the expression of protein kinase C isozymes differs between normal and transformed cells.

Antibodies, Monoclonal↗
PubMed1991

Suppression by human placental protein 14 of natural killer cell activity.

Human decidua of early pregnancy contains considerable numbers of CD3-CD56+ natural killer (NK) cells. In this study, two major protein products of the decidua, placental protein 14 (PP14) and placental protein 12 (PP12), were tested for the ability to regulate human NK cell activity. In vitro overnight exposure to PP14 of blood lymphocytes or purified large granular lymphocytes (LGL) resulted in suppression of cytotoxicity against K562 target cells in a 4-h 51Cr release assay. The NK inhibition was dependent on concentrations of PP14, being detectable at 5 micrograms/ml and reaching maximum at 50 micrograms/ml. Manifestation of PP14-induced NK suppression required 18-h contact with NK cells. The suppression of NK activity by PP14 was not abolished by indomethacin. In a target binding assay the number of PP14-treated LGL binding to K562 was comparable to that of untreated ones. By contrast with PP14, PP12 produced no effects on NK cells. These results indicate that PP14 suppresses the function of NK cells, which might be involved in prevention of maternal immune rejection of fetus at the fetomaternal interface.

Cells, Cultured↗
PubMed1991

Luteinizing hormone induces progesterone receptor gene expression in cultured porcine granulosa cells.

We have examined the effect of LH on the regulation of the progesterone receptor (PR) in cultured porcine granulosa cells. In this study we used the RNase protection assay to evaluate the PR mRNA levels with a porcine cDNA clone isolated by the polymerase chain reaction (PCR) method. This clone was regarded as part of the porcine PR cDNA because of its 98.3% and 95.7% homology to the hormone-binding domain of human PR cDNA in amino acid and nucleotide sequences, respectively. Treatment with LH (500 ng/ml) increased porcine PR mRNA to a maximum level of 8.6 +/- 1.1-fold (mean +/- SE) after 3-h exposure. This induction was mimicked by (Bu)2cAMP as well as by FSH and hCG, and the increased PR caused by LH and (Bu)2cAMP occurred in a dose-dependent manner. Basal and LH-induced PR mRNA levels were not affected by progesterone (100 ng/ml), estrogen (100 ng/ml), and RU 486 (10 ng/ml) at 3 h. The mechanism of the increased PR mRNA levels was studied in the presence of actinomycin-D and cycloheximide. While inhibition of RNA synthesis with actinomycin-D blocked LH-induced PR mRNA expression, inhibition of protein synthesis with cycloheximide increased basal and LH-induced PR mRNA levels. These results indicate that the expression of PR mRNA is positively regulated by LH, and this induction does not require ongoing protein synthesis. There may be a cycloheximide-sensitive mechanism that modulates PR mRNA stability. From our results we suspect that progesterone modulates ovarian function through LH-induced PR in granulosa cells.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1991

Interleukin-1 inhibits in vitro decidualization of human endometrial stromal cells.

Interleukin-1 (IL-1), a critical cytokine for the initiation of the immune response to infection or antigenic challenge, is known to also possess a variety of biological functions outside the immune system. We examined whether IL-1 could affect the decidualization of human endometrial stromal cells (ESC), a conspicuous part in the process of implantation, by assessing PRL production and morphological transformation in an in vitro system. Purified human ESC were cultured in the presence of progesterone (P) with or without the addition of IL-1. IL-1 markedly suppressed the induction of PRL production by P in a dose-dependent manner. The morphological decidualization of ESC in response to P was also inhibited by IL-1. This report demonstrates for the first time the possibility that IL-1 blocks decidualization, the functional differentiation of human endometrial stromal cells in response to ovarian steroids.

Cell Count↗
PubMed1991

Improvement of postoperative hypocalcemia by repeated allotransplantation of parathyroid tissue without anti-rejection therapy.

Long lasting postoperative hypocalcemia, an uncomfortable complication of a thyroid operation for hyperthyroidism, was treated with allotransplantation of parathyroid tissue. Small pieces of the parathyroid tissue offered from two unrelated donors were transplanted to an 18-year-old male with severe postoperative hypoparathyroidism. Prednisolone was given for 2 days, but no other immunosuppressive drugs were used. The remaining tissue was stored in frozen for the repeat transplantation. The functional activity of the frozen tissue was determined by the production of parathyroid hormone in the tissue culture medium adjusted to appropriate concentration of calcium. Loss of the graft function, probably due to rejection, was supplemented with repeated grafting. Hypocalcemia was improved by three times of transplantation using frozen tissue (once) and fresh tissue (twice). This preliminary trial demonstrates that the tissue transplantation of the parathyroid gland is effective to lessen the symptoms and medication of postoperative hypoparathyroidism.

Adolescent↗
PubMed1991

Effect of high-dose methylprednisolone on vasospasm after subarachnoid hemorrhage.

The effects of high-dose methylprednisolone (MP) on vasospasm following subarachnoid hemorrhage (SAH) were investigated. In a double hemorrhage canine model, administration of high-dose MP (10 mg/kg, every 12 hours) reduced angiographic narrowing of the basilar artery and prevented morphological changes in the arterial wall. In addition, increased platelet aggregation observed from days 4 to 7 in untreated SAH dogs was inhibited by the MP treatment. An in vitro experiment showed that MP inhibited platelet aggregation dose-dependently. High-dose MP had a nonspecific vasodilatory effect on the smooth muscle of the basilar artery. In another SAH model with dysautoregulation of cerebral blood flow (CBF), intravenous MP administration markedly attenuated the decrease in both blood pressure and CBF caused by exsanguination. These results indicate that MP has beneficial effects in normalizing CBF dysautoregulation following SAH. High-dose MP has several advantages for preventing and improving the multiple pathological status in cerebral vasospasm following SAH.

Animals↗
PubMed1991

Reversibility of cerebral function assessed by somatosensory evoked potentials and its relation to intracranial pressure--report of six cases with severe head injury.

The critical value and duration of intracranial pressure (ICP) causing cerebral function damage was evaluated in six head injury patients by monitoring the first negative cortical component (N20) of the somatosensory evoked potential (SEP). The SEP was elicited by stimulating the median nerve, and N20 (C3' or C4'-Fz on the affected side) and N13 (C2S-Fz) were monitored serially with a signal processor. The auditory brainstem response (ABR) was simultaneously recorded on the affected side (A1 or A2-Cz). A reversible loss of N20 occurred 7 times in six cases. In all cases, the N20 was restored by emergency decompression or hyperosmolar therapy. The minimum ICP at which N20 disappeared was 30 mmHg, and the N20 was restored when decompression was performed within 4.5 hours. However, when the disappearance persisted for more than 1.5 hours, the N20 latency was markedly prolonged after restoration. These changes appeared before the ABR showed definite abnormalities. These results show that the cerebral function may be damaged when ICP exceeds 30 mmHg, and that emergency decompression is required within 4.5 hours, preferably within 1.5 hours, to restore cerebral function. This critical ICP and duration should be of clinical value in patient management.

Adolescent↗
PubMed1991

Effect of intracisternal injection of endothelin-1 on regional cerebral blood flow in cats.

The effect of endothelin-1 on regional cerebral blood flow (rCBF) was investigated in adult mongrel cats. Endothelin-1 was injected into the cisterna magna and rCBF was measured by the hydrogen clearance method before and every 30 minutes for 180 minutes after the injection. Endothelin-1 (10(-11) mol and 10(-9) mol) induced a significant decrease in rCBF and an increase in arterial pressure. The effects of endothelin-1 on rCBF and arterial pressure were mediated, at least in part, by Ca2+, because pretreatment with intracisternally injected nicardipine prevented the changes. Cerebral angiograms obtained before and after endothelin-1 injection demonstrated severe constriction of the basilar artery, but constriction of the internal carotid and middle cerebral arteries was mild. Since the rCBF measured was in the territory of the middle cerebral artery, the decrease in blood flow was probably not solely due to the artery constriction. Other mechanisms such as arteriole constriction and/or regulation of rCBF by the central nervous system may also occur.

Animals↗
PubMed1991

Delayed traumatic intracerebellar hematoma: correlation between the location of the hematoma and the pre-existing cerebellar contusion--case report.

A rare case of delayed traumatic intracerebellar hematoma (DTIC1H) in a 54-year-old male achieved an excellent outcome without surgery. Analysis of this case and other reported cases suggests that DTIC1H occurs in two types: Group I with hematoma developing in previously contused areas, and Group II with hematoma developing in areas appearing normal on the initial computed tomographic scan. Group I hematomas occurred in the cerebellar cortex, but Group II hematomas occurred in the subcortical region or vermis where direct impact is less likely to have an effect. This suggests different mechanisms of development for DTIC1H.

Brain Concussion↗
PubMed1991

Treatment of severe intraventricular hemorrhage by intraventricular infusion of urokinase.

Six patients with severe intraventricular hemorrhage were treated with direct intraventricular infusion of urokinase. In each case, hemorrhage extended into all ventricular chambers, and a cast formation and expansion of the third and fourth ventricles were found. Immediately after the therapy was started (within 7 days from onset of symptoms), reduction of intraventricular hematoma volume was observed on computerized tomography. On average, both the third and fourth ventricles became clear on the third day after hemorrhage; there was one exception, a case of ruptured aneurysm. Five of the six patients showed excellent or good outcome, although two developed delayed hydrocephalus. No infection or rebleeding was observed. The outcome in a retrospectively studied group of five patients not treated with urokinase is also reported. The authors conclude that this relatively easy method of treatment will greatly improve the prognosis of severe intraventricular hemorrhage.

Adolescent↗
PubMed1991

[Magnetoencephalographic studies on spike foci using a 37-channel biomagnetometer system].

We report the results of a clinical trial of Magnetoencephalography (MEG) on spike foci in patients with epilepsy, which was performed from December 1990 to June 1991 at The University of Tokyo Hospital. Fifty patients with focal epilepsy; 26 primary epilepsy, 24 secondary epilepsy (7 brain tumor, 4 arteriovenous malformation, 4 encephalitis, 3 porencephaly, 2 arachnoid cyst, 1 brain abscess, 1 hemimegaloencephaly, 1 Lance-Adams syndrome, 1 hygroma), and ten normal subjects were enrolled in this study. MEG data were recorded using a 37-channel biomagnetometer system SMI-1001 (BTi Magnes, Biomagnetic Technologies, Inc., San Diego). A simultaneous 19-channel EEG recording with linked-ear reference was also obtained. The overall study was completed safely and none of the normal subjects showed abnormal paroxysmal MEG activity. Two patients showed interictal EEG spikes which would not have been noticed without first noting the presence of corresponding prominent MEG spikes. On the whole, the MEG signal seemed to have a wider frequency bandwidth than EEG. In most cases, the source localization predicted by MEG corresponded well with the EEG findings. The relative accuracy of MEG spike source localization was estimated to be within a cubic centimeter from the cases which showed tightly clustered localization of individual spikes. High-pass filtering reduced interference by superimposed slow wave activity, thereby improving the localization of spike sources. These results demonstrate that 37-channel biomagnetometer system could be a useful tool for analyzing epileptic spike sources.

Adolescent↗
PubMed1991

[Restoration of circadian rhythmicity after transplantation of the suprachiasmatic nucleus in the rats--its conditions for functional recovery and long-term survival].

Whole tissue grafts of day 1 neonatal or day 21 embryonic suprachiasmatic nuclei (SCN) in rats transplanted into host's third ventricle restored circadian rhythmicity in 8 cases out of 18 SCN-lesioned arrhythmic rats. Restored circadian rhythmicity had been observed for maximum 14 months after the transplantation. Immunohistochemical staining (Vasoactive intestinal polypeptide: VIP and vasopressin) confirmed the survival of the transplanted SCN tissues within the host's third ventricle. This may be the case of the longest-term survival of functioning SCN grafts which connected with the host's brain by neurites after transplantation. This finding may be a promising support for clinical application of neural tissue transplantation. In contrast, rhodamine-labeled SCN cell suspension transplanted into host's third ventricle did not restore circadian rhythmicity in 24 cases. Histological analysis revealed aggregated donor cells attached to the third ventricle and immunocytochemically stained with both VIP and vasopressin. Furthermore, rhodamine within the host brain suggested the fiber connections between the host and the donor cells. This result indicated that the circadian oscillator in SCN may function only based on the structural integrity of the SCN.

Animals↗
PubMed1991

[Magnetoencephalographic localization of epileptic foci using a 37-channel biomagnetometer].

The magnetoencephalography (MEG) and electroencephalography (EEG) were recorded simultaneously from 10 normal subjects using a 37-channel biomagnetometer. No paroxysmal spikelike waveform was observed in MEG at rest with eyes closed. The MEG and EEG were recorded also from 16 patients with primary epilepsy and 24 patients with secondary epilepsy. The examination proved to be safe for both normal subjects and patients with epilepsy. Interictal spikes were observed in 27 cases during the examination. The percentage of spikes identified in MEG but not in EEG was found to be 2. 3% of all spikes. The foci of the spikes identified in MEG were localized and determined in 20 cases. In 10 patients with secondary epilepsy, the localization of the foci were compared with the lesion demonstrated by magnetic resonance imaging (MRI) or computerized tomography (CT) and with the findings of EEG. In 6 cases, the foci by MEG were consistent. In the 4 cases where the MEG foci did not correspond to the MRI or CT findings, MEG foci were supported by the findings of EEG. MEG allows three-dimensional localization and enables us to elucidate the propagation of paroxysms. MEG was very useful in diagnosing epilepsy.

Adolescent↗