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Biomedical subjects

A Sakamoto

Publications and source records attributed to A Sakamoto.

At least 181 records · Page 10Linked to original sources
PubMed1995

Generator locations of movement-related potentials with tongue protrusions and vocalizations: subdural recording in human.

Movement-related potentials (MRPs) associated with tongue protrusions and vocalizations were recorded from chronically implanted subdural electrodes over the lower perirolandic area in 7 patients being evaluated for epilepsy surgery. In 3 patients, tongue protrusions elicited a clearly defined, well localized slow negative Bereitschaftspotential (BP) at the motor tongue area, and a positive BP at the sensory tongue area. At the motor tongue area the negative BP was followed by a negative slope (NS') and a motor potential (MP), and at the sensory tongue area the positive BP and a positive reafferent potential (RAP) were seen but no NS' and MP could be identified. In the other 4 patients, tongue protrusions elicited positive BP, NS' and MP at the motor and sensory tongue area, and positive RAP at the sensory area. It was concluded that BPs, NS' and MPs are mainly generated in the motor cortex involving the crown as well as the anterior bank of the central fissure. The sensory cortex (areas 3a and 3b) also participated in the generation of BPs but to a lesser degree. Different degree of involvement of these multiple generators most likely explains the interindividual variability of polarity and distribution of the MRPs. RAPs most likely arise from primary sensory areas 1 and 2. Brain potentials were also recorded at the motor (2 patients) and sensory (2 patients) language areas, but no specific language-related potentials could be identified. Evoked potentials to lip stimulation were investigated in 4 patients. In 3 patients, the responses at the sensory tongue area (P16, N21 and P30) had the same latency but opposite polarity to those at the motor tongue area. In the other patient, the responses (P16, N21 and P30) at the motor and sensory tongue areas were of the same polarity. The MRPs to tongue protrusions in those 4 patients revealed the same polarity relationship between the pre- and postcentral potentials. However, the maximal amplitude of evoked potentials and MRPs was seen at almost the same electrodes, suggesting that the main generators for these MRPs and evoked potentials must be located at contiguous areas in the anterior and posterior bank, respectively, of the central fissure.

Adolescent↗
PubMed1995

N-ras mutation of thyroid tumor with special reference to the follicular type.

Using the method of polymerase chain reaction-single strand conformation polymorphism, the point mutations of the ras oncogenes in a total of 33 thyroid tissues, including 12 follicular adenomas, 6 follicular carcinomas, 11 papillary carcinomas, and 4 undifferentiated carcinomas, were examined. The frequency of the mutation was 3% (1/33) in codon 12, 13 of Ki-ras and 18% (6/33) in codon 61 of N-ras, including 17% (2/12) in follicular adenoma, 50% (3/6) in follicular carcinoma, 0% (0/11) in papillary carcinoma and 25% (1/4) in undifferentiated carcinoma. In follicular adenoma, positivity was observed in microfollicular or trabecular subtypes. Furthermore, the mutation of ras, was examined in histologically different parts, coexisting in the same tumor in a total of four cases. Both the undifferentiated carcinoma and coexisting follicular adenoma, and both the microfollicular adenoma and trabecular nodule growing in the tumor, had the same N-ras (61) mutation. Direct sequencing analysis showed that all mutations were CAA (Gln) to CGA (Arg) transition of codon 61, except for CAA to AAA transversion in one case of follicular carcinoma. A similar genetic abnormality of N-ras genes at codon 61 between follicular adenoma and follicular carcinoma suggests that the mutation of N-ras at codon 61 might play a part in oncogenesis in follicular tumors.

Adenocarcinoma, Follicular↗
PubMed1995

Long-lasting activation of cation current by low concentration of endothelin-1 in mouse fibroblasts and smooth muscle cells of rabbit aorta.

1. Recombinant human ETA receptors were expressed in a mouse fibroblast cell line (Ltk- cell) and functional coupling of the receptors with Ca2+ permeable channels at low concentrations of endothelin-1 (ET-1) was investigated using whole-cell recordings and monitoring the changes in intracellular free Ca2+ concentrations ([Ca2+]i) with a Ca2+ indicator, fluo-3. A similar type of coupling was investigated in freshly dispersed vascular smooth muscle cells (VSMCs) of rabbit thoracic aorta by use of whole-cell recordings. 2. In Ltk- cells expressing recombinant human ETA receptors, concentrations of ET-1 (10(-8) M, 10(-9) M) evoked an initial transient peak and a subsequent sustained elevation in [Ca2+]i whereas a lower concentration of ET-1 (10(-10) M) evoked only a sustained elevation of [Ca2+]i. After removal of extracellular Ca2+, ET-1 evoked only an initial peak without a sustained elevation of [Ca2+]i. The sustained elevation induced by 10(-10) M ET-1 was blocked by 300 microM mefenamic acid (a cation channel blocker) but not by 10 microM nifedipine (a blocker of voltage-operated Ca2+ channel). 3. In whole-cell recordings with Ltk- cells, a brief (3-5 min) application of ET-1 (10(-10) M) induced a sustained inward current at a holding potential of -60 mV. The current-voltage relationship revealed that the reversal potential of the ET-1-induced current was close to 0 mV (1.9 mV) and was not altered by reducing the concentration of Cl- in the bath solution, indicating that the current is carried by cations. The current was reversibly blocked by 300 microM mefenamic acid, and it persisted after all cations in the bath solution had been replaced by Ca2+ (5 or 30 mM) and nonpermeant cation N-methyl-D glucamine,indicating that the ET-1-activated channel is permeable to Ca2+. Activation of the current was independent of membrane potential and the current was induced even after addition of a high concentration (10 mM) of a Ca2+ chelator, EGTA, to the pipette solution.4. In whole-cell recordings from rabbit aortic VSMCs, ET-l (101-10 M) induced a sustained inward current at a holding potential of -60 mV. The reversal potential was - 12 mV and was not altered when the concentration of Cl- in the pipette solution was decreased, indicating that the current is carried by cations. Again activation of the current was independent of membrane potential and was observed even after addition of a high concentration (10 mM) of a Ca2+ chelator, EGTA to the pipette solution. The current was reversibly blocked by 300 microM mefenamic acid and was permeable to Ca2+,showing marked similarities to ET-1-induced cationic current in Ltk- cells.5. These results indicate that in Ltk- cells transfected with cDNA for recombinant ETA receptors andVSMCs, ETA receptors can functionally couple with a nonselective cation channel permeable to Ca2+.Thus the present data suggest that the cation channel plays an essential role in the sustained elevation of[Ca2+]i at low concentrations of ET-l by causing Ca2+ entry through the channel.

Aniline Compounds↗
PubMed1995

[A case of fulminant psittacosis necessitating mechanical ventilation diagnosed by chlamydial isolation form BALF].

A 51-year-old female was admitted with complaints of fever and general fatigue. Chest X-ray showed diffuse bilateral fine nodular shadows and infiltrates. Complication of hepatic and muscular injury was suspected from increased levels of GOT, GPT and CPK in the serum. Arterial blood gas analysis revealed hypoxemia. Because hypoxemia aggravated despite treatment with intravenous minocycline (200 mg/day), corticosteroids and mechanical ventilation were started, and the administration of minocycline (400 mg/day) and sparfloxacin was added. Consequent, chest X-rays and several laboratory data improved gradually. The final diagnosis was established with a significant rise of both IgG and IgM antibody against Chlamydia psittaci with MIF and identification of Chlamydia with the cell culture method. Chlamydia was successfully isolated from BALF of this patient obtained 5 days after commencement of minocycline treatment. Psittacosis should be considered as a possible cause of severe respiratory failure necessitating emergency care including mechanical ventilation.

Bronchoalveolar Lavage Fluid↗
PubMed1995

Negative chronotropic effect of endothelin 1 mediated through ETA receptors in guinea pig atria.

Endothelins exert potent excitatory cardiac effects by acting on specific receptors on myocytes. In this study, we have examined the signal transduction mechanism for the chronotropic effect of endothelins in guinea pig atria. A competition binding of [125I]endothelin 1 ([125I]ET-1) using the recently developed ETA receptor-selective antagonist BQ123 showed the presence of almost equal populations of ETA (44%) and ETB (56%) receptors in the guinea pig right atria. In a concentration-response study, endothelin 3 (ET-3), an agonist with higher affinity to ETB receptors than to ETA receptors, and sarafotoxin S6c (STXS6c), an ETB receptor-selective agonist, increased the rate of spontaneous beating at all concentrations tested (10 pmol/L to 100 nmol/L). In contrast, ET-1, a nonselective agonist, increased the heart rate at lower concentrations (10 pmol/L to 10 nmol/L) but decreased it at higher concentrations (30 to 100 nmol/L). When ET-1 (100 nmol/L) was applied in a single amount, heart rate was strongly increased; however, this increase was followed by a rapid decline in the response. ET-1 (100 nmol/L) but not ET-3 or STXS6c significantly reduced the heart rate when it was raised by isoproterenol (ISO, 300 nmol/L) either in the absence or presence of a phosphodiesterase inhibitor, 3-isobutyl-1-methylxanthine (IBMX). Correspondingly, ET-1 significantly reduced the ISO-induced elevation of cAMP accumulation (19.1 +/- 1.7 pmol/mg protein [n = 8] and 12.6 +/- 1.2 pmol/mg protein [n = 7] in the absence and presence of ET-1, respectively; P < .01), which was also observed even in the presence of IBMX.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Amnesia of the epileptic aura.

In a prospective study lasting 6 months, we recorded on video 108 seizures with aura of 23 patients in an attempt to evaluate the mechanisms involved in the encoding of memories. In 88 of those seizures, we also recorded an EEG. The percentage of auras remembered decreased significantly with increasing severity of the seizures. The recollection of auras was also significantly dependent on the ictal EEG changes during the aura. Ninety-seven percent of the auras without EEG changes, 94% of the auras with unilateral EEG changes, and 73% of the auras with bilateral EEG changes during the aura were remembered. The spread of the ictal EEG pattern during the aura also showed a significant correlation with the severity of the ensuing seizure. Three patients with bitemporal epilepsy made up a considerable proportion of those who never remembered their aura before secondary generalized tonic-clonic seizures (2 of 3) and of those who had a transient postictal amnesia of their aura (2 of 3). The only patient who failed to remember a previously documented isolated aura also suffered from bitemporal epilepsy. During the second part of the study, we questioned whether information provided during the history could be helpful in defining the type of epilepsy syndrome or localizing the EEG seizure pattern of the 80 patients who had been admitted for presurgical epilepsy diagnosis. Localized (regional, unilateral, and independent left and right lateral) EEG seizure patterns occurred in 82% of the 51 patients with auras in their history as compared with 24% of the 17 patients who did not have auras in their history (p < 0.01).

Amnesia↗
PubMed1995

[Mutagenesis study of pharmacological receptors: approach to their structure-function relationships].

Recent cDNA cloning of pharmacological receptors revealed their primary structures, and the following functional studies with those cloned receptors enabled us to discover the existence of various receptor subtypes. Each receptor has three characteristics properties: 1) ligand binding, 2) effector coupling and 3) desensitization. Delineation of precise domains of a receptors involved in these functions is now an important matter. The molecular mapping of receptors would give us not only a rationale for designing selective drugs, but also new insight about the genotype-phenotype relationships of a certain kinds of hereditary diseases caused by a mutation of receptor genes. A mutagenesis study is a powerful approach for elucidating the structure-function relationships of pharmacological receptors. In contrast to a peptide, a protein is impossible to engineer in vitro. However, modulation of a specific codon in a given cDNA could bring about a substitution of a corresponding amino acid in the protein expressed in vivo. In this article, the popular strategies for generating artificially mutated receptors are discussed. This review will focus on three types of mutant receptors: 1) point mutation, 2) chimeric and 3) truncated receptors. The annotated bibliographies will also come in handy when devising experimental protocols.

Animals↗
PubMed1995

[Pulmonary endometriosis with recurrent catamenial hemoptysis].

A 32-year-old woman with a history of dilation and curettage for missed abortion at 31 years old had sudden hemoptysis during menstruation on May 25, 1993. She had catamenial hemoptysis again, and was admitted to our hospital on July 21, 1993. After admission, catamenial hemoptysis occurred, and a nodular shadow was noted in the right S4 area on chest roentgenogram and computed tomogram. A few days after menstruation, hemoptysis and the abnormal shadow on chest roentgenogram disappeared. Pulmonary endometriosis was diagnosed by clinical course, past history, and chest roentgenographic findings. During the next menstruation, hemoptysis and a nodular shadow in the right S4 area on chest roentgenogram recurred, so transbronchial lung biopsy and laparoscopy were done. TBLB specimens revealed macrophages with phagocytosed hemosiderin, and laparoscopy revealed pelvic endometriosis. She was treated with buserelin acetate. Catamenial hemoptysis and the nodular shadow on the chest roentgenogram disappeared after treatment.

Adult↗
PubMed1995

[Simultaneous production of parathyroid hormone-related protein (PTHrP) and granulocyte colony-stimulating factor (G-CSF) in lung cancer patients with hypercalcemia and leukocytosis].

Hypercalcemia and leukocytosis are often associated with primary lung cancer as a paraneoplastic syndrome. Recently, parathyroid hormone-related protein (PTHrP) and granulocyte colony stimulating factor (G-CSF) have been identified as major causative peptides for hypercalcemia and leukocytosis, respectively. We studied four men with advanced primary lung cancer (stages from IIIA to IV) who presented with hypercalcemia (corrected serum calcium levels: 10.5 mg/dl) and leukocytosis (WBC > 10,000 per mm3). The age of the patients ranged from 59 to 79 years old. The pathological subtypes were squamous cell carcinoma in three and adenocarcinoma in one. The mean serum calcium levels and leukocyte counts were 15.8 +/- 1.4 mg/dl (mean +/- SE) and 24,800 +/- 3,253 cells/mm3 (mean +/- SE), respectively. Abnormally high serum levels of PTHrP and G-CSF were found in three patients (mean +/- SE: 137 +/- 68 pg/ml; normal range in human serum, < 16 pg/ml), and in all four (mean +/- SE: 72 +/- 7.7 pg/ml; normal range in human serum, < 20 pg/ml), respectively. Immuno-histochemical examination of cancerous tissue obtained from these patients showed positive staining for both PTHrP and G-CSF within the cytoplasm of all the cancerous tissue. These results suggest that the association of hypercalcemia and leukocytosis in patients with advanced primary lung cancer is caused by production of both PTHrP and G-CSF by cancerous tissue.

Aged↗
PubMed1995

KMD-3213, a novel, potent, alpha 1a-adrenoceptor-selective antagonist: characterization using recombinant human alpha 1-adrenoceptors and native tissues.

alpha 1-Adrenoceptors (ARs) comprise a heterogeneous family, and subtype-selective ligands are valuable for studying the functional role of each receptor subtype. We characterized a newly synthesized, alpha 1-AR antagonist, KMD-3213, by using Chinese hamster ovary cells stably expressing the three cloned human alpha 1-ARs (alpha 1a, alpha 1b, and alpha 1d), as well as native rat and human tissues. KMD-3213 potently inhibited 2-[2-(4-hydroxy-3-[125I]iodophenyl)ethylaminomethyl]-alpha-tetralone binding to the cloned human alpha 1a-AR, with a Ki value of 0.036 nM, but had 583- and 56-fold lower potency at the alpha 1b- and alpha 1d-ARs, respectively. KMD-3213 inhibited norepinephrine-induced increases in intracellular Ca2+ concentrations in alpha 1a-AR-expressing Chinese hamster ovary cells with an IC50 of 0.32 nM but had a much weaker inhibitory effect on the alpha 1b- and alpha 1d-ARs. Using pharmacologically well characterized native rat tissues [submaxillary gland (alpha 1A-AR-expressing tissue), liver (alpha 1B-AR-expressing tissue), and heart (mixed alpha 1A- and alpha 1B-AR-expressing tissue)], binding studies showed that inhibition curves for KMD-3213 in submaxillary gland and liver best fit a one-site model (with Ki values of 0.15 and 16 nM, respectively), whereas KMD-3213 had high and low affinity sites in heart membranes. Chloroethylclonidine treatment of rat heart membranes completely eliminated the low affinity sites for KMD-3213. Furthermore, in human liver and prostate KMD-3213 could identify high and low affinity sites, the Ki values of which corresponded well to those for the cloned human alpha 1a- and alpha 1b-ARs, respectively. Moreover, the affinity of KMD-3213 was found to be approximately 10-fold higher at the cloned human alpha 1a-AR than at the cloned rat alpha 1a-AR. KMD-3213 is a potent and highly selective antagonist for the human alpha 1a-AR and would be useful for studying the physiological roles of human alpha 1-AR subtypes.

Adrenergic alpha-1 Receptor Antagonists↗
PubMed1995

[Efficacy of epidural neurolysis].

Forty-one patients were treated with epidural neurolysis using 50 % ethyl alcohol 2 ml. Thirty eight patients were suffering from cancer pain and three patients were complaining of chronic benign pain. Alcohol block was repeated 2.3 times (mean) in the same patient. Thirty patients were followed after the treatment. Forty-seven percent of the patients reported 70 % or greater pain relief and 20 % of the patients reported about 50 % pain relief. Duration of pain relief was from 9 days to 203 days with a mean duration of 54 days. Adverse effects were reported 43 % of the patients. There is no miserable adverse effect. Adverse effect reported most was pain with epidural injection of drugs after the alcohol block had been performed.

Adult↗
PubMed1995

[Correlation between pulmonary vascular changes and hemodynamic parameters during exercise before and after mitral valve surgery].

Sixteen cases with mitral valvular disease were studied with regard to the correlation between pathological changes in the pulmonary vasculature and pulmonary hemodynamics during exercise before and after surgery. In muscular pulmonary arteries obtained by open lung biopsy, medial wall thickness (MWT) was 13.8 +/- 3.2% and intimal thickness (IT) was 37.3 +/- 13.5%. MWT was correlated with IT (r = 0.60, p < 0.05). Wall thickness in pulmonary veins was 8.21 +/- 1.8%. Preoperative mean pulmonary arterial pressure (MPAP) during exercise was 45.9 +/- 9.4 mmHg, and decreased significantly to 38.1 +/- 11.3 mmHg postoperatively. However, in 4 patients, MPAP during exercise increased after surgery. Pulmonary vascular resistance (PVR) during exercise was unchanged before and after surgery (2.74 +/- 1.90 U.M2-->2.69 +/- 1.3 U.M2). MWT was significantly correlated with preoperative MPAP at rest only. In patients showing an increase of MPAP during exercise postoperatively, mean MWT was 16.2% and mean IT was 47.4%. In conclusion our data suggest that postoperative pulmonary hemodynamics does not improve in patients whose MWT exceeds 15% and IT exceeds 40% and that irreversibility may be due to pulmonary vascular lesions.

Adult↗
PubMed1995

Functional coupling of ETA receptor with Ca(2+)-permeable nonselective cation channel in mouse fibroblasts and rabbit aortic smooth-muscle cells.

Endothelin-1 (ET-1) induces persistent vasoconstriction via a sustained increase in intracellular free Ca2+ concentrations ([Ca2+]i). The mechanisms of the elevation of [Ca2+]i operating at physiologically low concentrations of ET-1 are controversial. Here we report that both native ETA receptors in vascular smooth-muscle cells and recombinant ET(A) receptors expressed in mouse fibroblasts (Ltk cells) are functionally coupled with a non-selective cation channel, which is permeable to Ca2+ and is blocked by mefenamic acid. The channel is persistently activated by a low concentration of ET-1 (10(-10) M) without stimulation of inositol triphosphate (IP3) formation and mediates sustained vasoconstriction.

Animals↗
PubMed1995

Paraquat tolerance of transgenic Nicotiana tabacum with enhanced activities of glutathione reductase and superoxide dismutase.

Transgenic tobacco with enhanced cytosolic activities of glutathione reductase and superoxide dismutase were generated by cross-fertilization. Leaves of the hybrids exhibited further increased tolerance to a O2-.-generating herbicide paraquat than those of their parents. This result indicates the efficiency of manipulating more than one gene in improving resistance of plants to photooxidative stress.

Drug Resistance↗
PubMed1994

Endothelin-A receptor mediates cardiac inhibition by regulating calcium and potassium currents.

Voltage-sensitive ion channels play fundamental roles in the regulation of cardiac function by various neurotransmitters. Endothelins have strong positive inotropic and chronotropic effects, for which recent studies have implicated various intracellular mechanisms. However, very little is known about the underlying ion-channel regulation by the peptide. We report here that endothelin-1 consistently hyperpolarizes the membrane and shortens the duration of the action potential in mammalian atrial myocytes, leading to suppression of electrical excitability of the heart. Endothelin-1, but not endothelin-3, inhibited the L-type calcium current by decreasing cyclic AMP accumulation and activated the muscarinic potassium current by stimulating a pertussis toxin-sensitive GTP-binding protein. Consistent with these results, endothelin-1 strongly reduced the heart rate when it was increased by beta-adrenoceptor stimulation. These effects were blocked by an ETA (endothelin-1-selective) receptor-selective antagonist, BQ123 (refs 8-11). The ETA receptor-mediated regulation of cardiac ion channels gives new insight into our understanding of the physiological and pathophysiological roles of endothelins in the control of cardiac function.

Action Potentials↗
PubMed1994

Increased UV-induced SCEs but normal repair of DNA damage in p53-deficient mouse cells.

UV-induced sister chromatid exchanges (SCEs) in p53-deficient mouse cells were studied to obtain more evidence regarding the involvement of p53 protein in the DNA repair pathway as a checkpoint protein. After 5 J/m2 UV irradiation, mutant-type homozygous cells for p53-deficiency showed the same number of SCEs as the heterozygous and wild-type homozygous cells. In the heterozygous and wild-type homozygous cells, no further increase of SCEs was observed after 10 J/m2 UV irradiation. In contrast, in mutant-type homozygous cells about twice as many SCEs were induced by 10 J/m2 UV as by 5 J/m2 UV. In mutant-type homozygous cells, fractions of S-phase cells decreased just after 10 J/m2 UV irradiation, but recovered to higher than control levels within a short time, while in heterozygous and wild-type homozygous cells, the decrease in S-phase cells was prolonged by more than 6 hr and no increase above control levels was observed. Although no difference in UV sensitivity and repair of UV-induced DNA damage was found among the 3 genotypes, which were determined by the relative colony-forming ability after UV irradiation and removal of thymine dimers and (6-4) photoproducts from cellular DNA, our data strongly suggest an impaired checkpoint function in p53-deficient cells when DNA is damaged.

Animals↗