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Biomedical subjects

K Sakai

Publications and source records attributed to K Sakai.

At least 505 records · Page 28Linked to original sources
PubMed1996

cDNAs encoding spinach stromal and thylakoid-bound ascorbate peroxidase, differing in the presence or absence of their 3'-coding regions.

Two cDNA clones encoding stromal (SAP28) and thylakoid-bound (SAP22) ascorbate peroxidase were isolated from a spinach cDNA library constructed by greening cotyledons. The SAP22 and SAP28 contained an open reading frame encoding mature protein of 295 and 345 amino acids with calculated molecular mass of 32239 Da and 37710 Da, respectively, preceded by the common transit peptides of 70 amino acid residues. Interestingly, the N-terminal 364 amino acids of SAP22 were 100% identical with SAP28 except for one C-terminal amino acid residue (Asp-365), and the C-terminal of SAP22, which is the putative transmembrane segment, was 50 amino acids longer than that of SAP28.

Amino Acid Sequence↗
PubMed1996

Activity of primate inferotemporal neurons related to a sought target in pair-association task.

Visual long-term memory in primates has been assessed by using the pair-association (PA) task, in which a subject retrieves and chooses the paired associate of a cue picture. Our previous studies on single neurons in the anterior inferotemporal (AIT) cortex suggested their roles in representing paired associates in the mind. To test the possibility that the delay activity of AIT neurons is related to a particular picture as a sought target, we devised the PA with color switch (PACS) task. In the PACS task, the necessity for memory retrieval and its initiation time were controlled by a color switch in the middle of the delay period. A control task, in which there is no color switch, corresponds to the conventional delayed matching-to-sample (DMS) task where the monkey chooses the same picture as a cue. We found that AIT neurons started to respond just after the color switch in the PACS task, when the cue-optimal picture's associate was presented as a cue. In contrast, they showed no response change in the DMS task. We confirmed that this effect is not due to the visual response to colors. Furthermore, when the cue-optimal picture was presented as a cue, these neurons showed suppression after the color switch in the PACS task. These results suggest that the activity of AIT neurons mediates gating mechanisms that preferentially pass information about a sought target, even when the sought target is retrieved from long-term memory.

Animals↗
PubMed1996

Solution X-ray scattering data show structural differences between yeast and vertebrate calmodulin: implications for structure/function.

We present here the first evidence, obtained by the use of solution X-ray scattering, of the solution structure of yeast calmodulin, a poor activator of vertebrate enzymes. The radius of gyration of yeast calmodulin decreased from 21.1 to 19.9 angstroms when excess Ca2+ ions were added. The profiles of the pair-distribution function suggested that yeast calmodulin without Ca2+ has a dumbbell-like shape which changes toward a rather asymmetric globular shape, from its dumbbell shape, by the binding of Ca2+. In the presence of a calmodulin binding peptide such as MLCK-22 (a synthetic peptide corresponding to residues 577-598 of skeletal myosin light chain kinase), the radius of gyration of yeast calmodulin decreased by 1.6 angstroms, and the molecular shape of it estimated from the profile of the pair-distribution function was globular but less compact than that of vertebrate calmodulin. These results for the structure of yeast calmodulin complexed with Ca2+ and with Ca(2+)-peptides are quite different from those of vertebrate calmodulin. Thus, the functional differences between yeast and vertebrate calmodulin which we reported previously [Matsuura, I., et al. (1993) J. Biol. Chem. 268, 13267-13273] have been interpreted on the basis of the structural differences between them. Moreover, the structural studies on chimeric proteins of chicken and yeast calmodulin suggest that Ca2+ binding at site IV is essential to form the full active dumbbell structure, which is characteristic of vertebrate-type calmodulin.

Amino Acid Sequence↗
PubMed1996

A novel heparin-dependent processing pathway for human tryptase. Autocatalysis followed by activation with dipeptidyl peptidase I.

Tryptase is the major protein constituent of human mast cells, where it is stored within the secretory granules as a fully active tetramer. Two tryptase genes (alpha and beta) are expressed by human mast cells at the level of mRNA and protein, each with a 30 amino acid leader sequence. Recombinant precursor forms of human alpha- and beta-tryptase were produced in a baculovirus system, purified, and used to study their processing. Monomeric beta-protryptase first is shown to be intermolecularly autoprocessed to monomeric beta-pro'tryptase at acid pH in the presence of heparin by cleavage between Arg-3 and Val-2 in the leader peptide. The precursor of alpha-tryptase has an Arg-3 to Gln-3 mutation that precludes autoprocessing. this may explain why alpha-tryptase is not stored in secretory granules, but instead is constitutively secreted by mast cells and is the predominant form of tryptase found in blood in both healthy subjects and those with systemic mastocytosis under nonacute conditions. Second, the NH2-terminal activation dipeptide on beta-pro'tryptase is removed by dipeptidyl peptidase I at acid pH in the absence of heparin to yield an inactive monomeric form of tryptase. Conversion of the catalytic portion of beta-tryptase to the active homotetramer at acid pH requires heparin. Thus, beta-tryptase homotetramers probably account for active enzyme detected in vivo. Also, processing of tryptase to an active form should occur optimally only in cells that coexpress heparin proteoglycan, restricting this pathway to a mast cell lineage.

Amino Acid Sequence↗
PubMed1996

Histaminergic descending inputs to the mesopontine tegmentum and their role in the control of cortical activation and wakefulness in the cat.

We have demonstrated previously the importance of histaminergic neurons in arousal mechanisms. In addition to their ascending axons, these neurons also send heavy descending inputs to the mesopontine tegmentum (MPT), which plays a key role in cortical activation during wakefulness (W). This anatomical link suggests histaminergic control of the mechanisms of the MPT relevant to behavioral states. In this study, we sought to demonstrate, at the light microscopy level, hypothalamotegmental histaminergic pathways and their topographical interaction with MPT neurons in the cat and to explore further their involvement in sleep-wake control. Using immunohistochemistry of histamine (HA), either alone or together with that of choline-acetyltransferase or tyrosine hydroxylase, a large number of very fine, short and varicose HA-positive fibers and terminal-like dots were detected in the MPT, including the laterodorsal tegmental nucleus, locus coeruleus (LC), LC alpha, and peri-LC alpha. Furthermore, these fibers and terminal-like structures were found in close proximity to a great number of cholinergic or noradrenergic neurons. We also investigated the effects of microadministration of HA agonists and antagonist into the mediodorsal pontine tegmentum on the cortical electroencephalogram (EEG) power spectra and the sleep-wake cycle in freely moving cats. Microinjection of HA or 2-thiazolylethylamine (an H1-receptor agonist) caused a long-lasting suppression of cortical slow activity and an increase in quiet wakefulness (W). Paradoxical sleep, however, was less affected. The effects of HA were attenuated by systemic or in situ pretreatment with mepyramine (an H1-receptor antagonist), which when injected alone produced an increase in slow wave sleep. Microinjection of impromidine (an H2-receptor agonist) into the same area had no effect on either the cortical EEG or W. Because MPT ascending and presumed cholinergic neurons discharge tonically during cortical activation of W and because HA causes excitation of MPT cholinergic neurons via H1 receptors, we hypothesize that the histaminergic descending afferents in the MPT would promote cortical desynchronization and W, at least partially, via activation of H1 receptors situated on cholinergic neurons and that the interactions between histaminergic and cholinergic neurons constitute an important circuit in cortical activation during W.

Animals↗
PubMed1996

Autocrine/paracrine mechanism of insulin-like growth factor-1 secretion, and the effect of insulin-like growth factor-1 on proteoglycan synthesis in bovine intervertebral discs.

The present study was undertaken to investigate the effect of insulin-like growth factor-1 on proteoglycan synthesis and the autocrine/paracrine mechanism involving insulin-like growth factor-1 in the bovine coccygeal intervertebral disc. Insulin-like growth factor-1 stimulated proteoglycan synthesis in cultured cells of the nucleus pulposus of bovine intervertebral discs in a dose-dependent manner, and the effect was inhibited by an anti-insulin-like growth factor-1 monoclonal antibody. In situ hybridization histochemistry revealed the expression of insulin-like growth factor-1 mRNA in the cultured cells, and its production in these cells was demonstrated by radioimmunoassay. Insulin-like growth factor-1 receptor in the cultured cells was also demonstrated immunohistochemically. Scatchard analysis using an [125I]insulin-like growth factor-1 binding assay showed that the cells cultured in monolayer had a single type of insulin-like growth factor-1 receptor, whose affinity and number were estimated to be 7.38 x 10(8)/M and 9.27 x 10(4)/cell, respectively. These results suggest that insulin-like growth factor-1 stimulates proteoglycan synthesis in cells of the nucleus pulposus and that these cells in culture have an insulin-like growth factor-1 autocrine/paracrine mechanism. The expressions of insulin-like growth factor-1 mRNA and insulin-like growth factor-1 receptor in disc tissue were greater in cells of the nucleus pulposus of fetal bovine intervertebral discs than in those of the adult discs. These findings suggest that the action of autocrine/paracrine insulin-like growth factor-1 is more active in cells of the young nucleus pulposus than in cells of mature subjects.

Age Factors↗
PubMed1996

Endometrial carcinoma associated with hyperplasia.

The aim of this study was to clarify the relationship of endometrial hyperplasia to endometrial carcinoma. From 1979 through 1990, 115 cases of stage I-IV endometrial carcinomas treated initially by hysterectomy were reviewed histologically. Forty-two of 115 (36.3%) patients had hyperplasia in the endometrium adjacent to the carcinoma. Women with both endometrial carcinoma and hyperplasia were significantly younger than those with carcinoma without hyperplasia (P < 0.05). In a comparison of patients with carcinoma without hyperplasia, those with hyperplasia were better differentiated (P = 0.0072), and lacked deep myometrial invasion (P < 0.0001), cervical involvement (P = 0.0192), lymph-vascular space invasion (P = 0.0102), and para-aortic lymph node metastases (P = 0.0434). The presence of endometrial metaplasia (P = 0.0001). The estimated 5-year survival rates for patients with carcinoma with hyperplasia and those with carcinoma without hyperplasia were 96.55 and 73.33%, respectively (P = 0.0016). In endometrial carcinomas, the presence of endometrial hyperplasia may demonstrate a more favorable prognosis.

Adult↗
PubMed1996

Beneficial effects of angiotensin I converting enzyme inhibitor on post-ischemic contractile function of perfused rat heart.

The present study was undertaken to determine whether trandolaprilat, an active form of angiotensin I converting enzyme (ACE) inhibitor, may improve ischemia/reperfusion-induced contractile dysfunction and metabolic derangement of isolated rat hearts. Ischemia (25 min) and subsequent 60-min reperfusion resulted in a small recovery of post-ischemic left ventricular developed pressure (LVDP), a sustained increase in left ventricular end-diastolic pressure, an increase in the release of creatine kinase and ATP metabolites from the perfused heart, and changes in myocardial sodium, potassium, calcium and magnesium contents. Treatment with 10-100 microM of trandolaprilat for the last 10 min of pre-ischemia recovered approximately 50-90% of pre-ischemic LVDP during reperfusion, whereas that with 30-100 microM of enalaprilat restored approximately 55-65% of the pre-ischemic LVDP. Treatment with either trandolaprilat or enalaprilat at these concentrations attenuated the release of creatine kinase and ATP metabolites into the perfusate during reperfusion. Treatment with 30 microM trandolaprilat suppressed ischemia/reperfusion-induced changes in myocardial ion content. Treatment with bradykinin during the last 10 min of pre-ischemia also resulted in a post-ischemic contractile recovery with a degree similar to that of the trandolaprilat-treated hearts. E4177, an AT1-antagonist, showed no effect on ischemia/reperfusion-induced changes in cardiac parameters. The enhancement of post-ischemic contractile recovery by the ACE inhibitor was abolished by treatment with either Hoechst 140, a bradykinin (BK2) antagonist, or diclofenac, a cyclooxygenase inhibitor. These results suggest that trandolaprilat is capable of attenuating ischemia/reperfusion injury of isolated perfused hearts and altered BK metabolism is, at least in part, involved in this effect.

Adenosine Triphosphate↗
PubMed1996

Expression and purification of recombinant human tryptase in a baculovirus system.

B2 is a mAb that recognizes a conformational determinant on the active form of native tryptase, but does not recognize native tryptase that spontaneously loses activity in physiologic buffer. Precursor forms of recombinant human (rh) alpha- and rh beta-tryptase have been expressed in a baculovirus system. In each case, multiple electrophoretic forms were detected in both culture media and cell lysates of infected insect cells by Western blots developed with the G3 mAb made against native human tryptase. Although only 4 of 30 amino acids in the leader sequences of alpha- and beta-tryptase differ, rh alpha-tryptase appeared predominantly in the cell lysates, rh beta-tryptase predominantly in the culture media. B2 recognized rh alpha-tryptase and rh beta-tryptase found in the culture media of infected Sf-9 cells, but not that in cell lysates. Secreted forms of tryptase were purified to homogeneity by B2-immunoaffinity chromatography. From 1 liter of culture fluid 1.5 to 3 mg of rh-tryptase could be purified. Each rh-tryptase precursor was enzymatically inactive with synthetic substrates. Analysis of the N-terminal amino acid sequences of purified rh alpha- and rh beta-tryptase precursors (APAPVQA and APAPGQA, respectively) indicated that the initial 18 amino acids of the 30-amino-acid leader sequence had been removed. Differential N-glycosylation was found in both rh alpha-tryptase (one or two carbohydrate groups per molecule) and rh beta-tryptase (zero or one carbohydrate group per molecule). Thus, the baculovirus expression system is a useful tool for generation of rh alpha- and rh beta-tryptase precursors that exhibit a conformational epitope also present on natural tryptase and that are preferentially secreted into the culture media of infected cells.

Amidohydrolases↗
PubMed1996

Overproduction of D-aminoacylase from Alcaligenes xylosoxydans subsp. xylosoxydans A-6 in Escherichia coli and its purification.

We constructed the high-expression plasmid for D-aminoacylase from Alcaligenes xylosoxydans subsp. xylosoxydans A-6. The appropriate Shine-Dalgarno sequence (AAGGAG) was introduced to the eight bases upstream of start codon (ATG) of D-aminoacylase structural gene by site-directed mutagenesis, and then the 1.75-kb DNA fragment including the open reading frame was inserted into the downstream of the tac promoter of plasmid vector pKK223-3. The resultant plasmid, which was named pKNSD2, showed a high D-aminoacylase activity in Escherichia coli JM109 cells transformed with it. The enzyme was purified to homogeneity in only two steps with a final yield of 24% (sp act, 2023 U/mg).

Alcaligenes↗
PubMed1996

Aggressive angiomyxoma occurring in the scrotum: report of a case.

The authors recently treated a case of aggressive angiomyxoma occurring in the left scrotum. A 61-year-old Japanese man was diagnosed as having an inguinal irreducible hernia that descended to the bottom of the scrotum preoperatively. However, during the operation a large tumor was found between the spermatic fascia and the skin pressing the testis upward. The tumor measured 20 x 15 x 15 cm, was yellowish with a smooth surface encapsulated by a membrane similar to the pleura, and the cut surface was gelatinous. The histological findings indicated that the tumor had thick-walled vessels which had prominently increased in size, delicately waved collagen fibers, and stromal cells in a myxoid background. The patient has remained recurrence-free as of 11 months after surgery.

Capillaries↗
PubMed1996

Inhibitory effect of pulmonary surfactant on Sendai virus infection in rat lungs.

Intranasal infection of rats with active (infectious) Sendai virus enhances secretion of tryptase Clara, a Sendai virus-activating protease, into the bronchial lumen by Clara cells of the bronchial epitheliums, and inversely suppresses secretion of pulmonary surfactant, an inhibitor of the protease, into the lumen [Kido H et al. (1993) FEBS Lett 322: 115-119]. A trypsin-resistant mutant, TR-2, showed similar effects, although its replication was restricted to a single cycle in the lungs. In contrast, neither nonactive (noninfectious) wild-type virus possessing receptor-binding activity and lacking envelope fusion activity nor UV-inactivated virus retaining receptor binding and envelope fusion activities altered the mode of secretions. These results indicate that viral replication is required for producing a condition in the bronchial lumen for proteolytic activation of progeny virus, thereby infection is extended to a fatal pneumonia. On the other hand, intranasal administration of infected rats with pulmonary surfactant suppressed activation of progeny virus and pathological changes in the lungs, suggesting a therapeutic use of pulmonary surfactant for influenza pneumonia.

Animals↗
PubMed1996

A randomized trial comparing ftorafur alone with ftorafur plus tamoxifen in postoperative adjuvant therapy for breast cancer. Kinki Area Research Group for Postoperative Adjuvant Therapy for Breast Cancer.

A randomized study was performed in 35 centers in the Kinki area of Japan to determine the effectiveness of ftrorafur (FT) plus tamoxifen (TAM) compared with FT monotherapy in postoperative adjuvant therapy for breast cancer. Patients were randomized by the envelope method to receive either FT 600 mg/day or FT 600 mg/day plus TAM 20 mg/day orally for 1 year, starting on day 7 after mastectomy. Between April 1982 and January 1985, 628 patients were assigned to treatment with FT alone and 626 to treatment with FT + TAM. Of these, 571 (90.9%) and 539 (86.1%) patients, respectively, met the eligibility requirements for this study. There were no significant differences in major background factors between the two groups of eligible patients. Five-year survival rates were 91.4% for FT alone and 91.1% for FT+TAM (not significantly different). Five-year disease-free survival rates showed a tendency towards a better prognosis (P = 0.090) in the FT + TAM group, with observed rates of 83.0% for FT alone and 86.7% for FT + TAM. Stratified analysis showed that disease-free survival with FT + TAM is better than with FT alone for patients aged 50 years or more ( P = 0.048) and for patients with from one to three positive nodes (P = 0.064).

Adult↗
PubMed1996

Dermoid cyst within an upper thoracic meningocele.

A case of dermoid cyst within an upper thoracic meningocele is reported. The incidental feature of this combination is extremely rare. As upper thoracic meningocele is often associated with other spinal and intracranial abnormalities, close observation and radiologic evaluation of the craniospinal axis are necessary to obtain an exact diagnosis and to achieve an appropriate treatment.

Comorbidity↗
PubMed1996

Ontogeny of striatal dopamine release in rats after acute administration of methamphetamine.

In the present study, we examined the effects of acute MAP administration on striatal extracellular levels of dopamine (DA) and its metabolites in groups of rats on postnatal days (PNDs) 14, 21, 28, and 56. A single injection of 4 mg/kg MAP (IP) induced increase in extracellular DA and decrease in extracellular 3,4-dihydroxyphenylacetic acid (DOPAC) in the striatal perfusates of rats on all PNDs examined. The magnitude of increase in DA concentrations at 20 min after the MAP injection was significantly smaller on PND 14 than PNDs 21, 28, and 56, whereas the magnitude of decrease in DOPAC concentrations after the MAP injection was significantly smaller on PND 14 than PNDs 21, 28, and 56. After the MAP injection, homovanillic acid levels decreased on PNDs 21, 28, and 56, but increased on PND 14. These results suggest that rats on PND 14 differ from those thereafter in MAP-induced DA release and changes in its metabolites, and that such developmental effect on MAP-induced DA release may be involved in the ontogeny of MAP-induced behavioral sensitization.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1996

Clinical utility of magnetic corticospinal tract stimulation at the foramen magnum level.

We applied magnetic stimulation of the corticospinal tract at the foramen magnum level to 19 patients with various neurological disorders. Results were consistent with our previous speculation that activation occurs at the foramen magnum level. This method was clinically useful for the following conditions. (1) Detection of subclinical lesion: one patient who had transient ischemic attack that caused no clinical symptoms at examination was shown to have dysfunction of the corticospinal tract. (2) Multiple lesions: our method disclosed at least one lesion above and below the foramen magnum in two patients with multiple sclerosis. (3) Unmasking of dysfunction of the corticospinal tract masked by peripheral neuropathy: magnetic stimulation showed conduction delay in the corticospinal tract in two patients in whom no pyramidal signs were evident because of muscular atrophy due to neuropathy. One patient had multiple sclerosis and chronic inflammatory demyelinating polyradiculoneuropathy, the other had degenerative ataxia and neuropathy. (4) Association of disorders: conduction delay rostral to the foramen magnum, which should not occur in patients with only cervical myelopathy, was shown in a patient with cervical myeloradiculopathy and amyotrophic lateral sclerosis. We conclude that this magnetic stimulation method which is less painful than electrical stimulation has extensive clinical usefulness.

Adult↗