Biomedical subjects

A Hirata

Publications and source records attributed to A Hirata.

At least 163 records · Page 9Linked to original sources

PubMed1994

Structural modification of spindle pole bodies during meiosis II is essential for the normal formation of ascospores in Schizosaccharomyces pombe: ultrastructural analysis of spo mutants.

In order to characterize the morphological steps defined by sporulation (spo) genes during the formation of ascospores in the fission yeast Schizosaccharomyces pombe, we performed an electron microscopic study of the ultrastructure of the spindle pole body (SPB) and of the development of the forespore membrane during the second meiotic division (meiosis II) in sporulation-deficient (spo) mutants (spo4, spo5, spo14 and spo18). No difference was found in terms of the function and the structure of the SPB during the first meiotic division (meiosis I) between the four mutants and wild-type cells. However, during meiosis II, the spo4 and spo18 mutants underwent nuclear division but in neither case were the SPBs modified nor were forespore membranes formed. The SPBs of the spo18 mutant diminished in size after meiosis II and eventually disappeared after 18 h in sporulation medium. By contrast, the SPBs of the spo4 mutant remained unchanged even after an 18-h incubation. The outer plaques of SPBs of spo5 and spo14 mutants were sufficiently modified to allow them to initiate development of the forespore membrane, but the membrane had an abnormally expanded lumen and did not enclose the nuclei during meiosis II. The spo5 mutant produced anucleate spore-like bodies while the spo14 mutant formed unorganized structures with irregular peripheries which, presumably, contained spore-wall precursors, instead of anucleate spore-like bodies. We conclude that the modification of the SPB is essential for the formation of ascospores and at least two genes (spo5 and spo14) participate in the development of the forespore membrane. The defective phenotypes define discrete steps in the development of ascospores, which proceeds via steps defined by the mutant spo4, spo18, spo14 and spo5 genes respectively. Our observations provide further substantial evidence that the SPB plays a pivotal role in the normal development of ascospores in yeasts.

Meiosis↗

PubMed1994

Predominant localization of non-specific lipid-transfer protein of the yeast Candida tropicalis in the matrix of peroxisomes.

PXP-18 is a 14-kDa major peroxisomal protein of the yeast Candida tropicalis and a homologue of the non-specific lipid-transfer protein (nsLTP) of mammals. Mammalian nsLTP is thought to facilitate the contact of membranes, to stimulate lipid-transfer between them. If PXP-18 functions like nsLTP, it must be present on organelle membranes. Immunoelectron microscopy of C. tropicalis cells indicated that gold particles, which visualized PXP-18, localized exclusively in the matrix of peroxisomes. Subcellular fractionation followed by Western blotting revealed the association of PXP-18 with peroxisomes in C. tropicalis cells. An enzyme-linked immunosorbent assay revealed that almost all the PXP-18 associated with peroxisomes was detectable after the solubilization of the organelle but not before, implying the predominance of PXP-18 inside peroxisomes. This differential assay was applied to the intracellular import of the intact and truncated PXP-18s expressed in Saccharomyces cerevisiae cells. Most of the intact PXP-18 was shown to be imported into the matrix of host-cell peroxisomes, whereas the truncated PXP-18, which lacked the C-terminal tripeptide Pro-Lys-Leu, no longer targeted peroxisomes. These results are consistent with the view that PXP-18 is the matrix protein of peroxisomes and must function in a system other than that of lipid transfer.

Amino Acid Sequence↗

PubMed1994

Interaction of marine toxin dolastatin 10 with porcine brain tubulin: competitive inhibition of rhizoxin and phomopsin A binding.

Dolastatin 10, a cytostatic peptide containing several unique amino acid subunits, was isolated from the marine shell-less mollusk Dolabella auricularia. It inhibits microtubule assembly at concentrations below 5.0 microM (IC50, 3.0 microM) and causes formation of tubulin aggregates at higher (> 10 microM) concentrations in a somewhat different manner from that caused by vinblastine. Electron microscopical analysis showed irregular aggregates of microtubule proteins in the presence of 10 microM dolastatin 10. Dolastatin 10 inhibited the binding of both radiolabeled rhizoxin and phomopsin A to tubulin with inhibition constants (Ki) of 7 x 10(-8) M and 1 x 10(-7) M, respectively. The results suggest that at least one of the binding sites of dolastatin 10 on tubulin is the rhizoxin binding site.

Animals↗

PubMed1994

Inhibition of endoplasmic reticulum (ER)-to-Golgi transport induces relocalization of binding protein (BiP) within the ER to form the BiP bodies.

Immunofluorescence staining of yeast cells with anti-binding protein (BiP) antibodies shows uniform staining of the endoplasmic reticulum (ER). We have found that overproduction of Sec12p, an ER membrane protein, causes a change of BiP distribution within the cell. Upon induction of Sec12p by the GAL1 promoter, the staining pattern of BiP turns into bright dots scattering in the cell, whereas the staining of Sec12p remains to be the typical ER figure. Overproduction of other ER membrane proteins, HMG-CoA reductase or Sed4 protein, does not induce such relocalization of BiP. Pulse-chase experiments and electron microscopy have revealed that the overproduction of Sec12p inhibits protein transport from the ER to the Golgi apparatus. When the transport is arrested by one of the sec mutations that block the ER-to-Golgi step at the restrictive temperature, the BiP staining also changes into the punctate pattern. In contrast, the sec mutants that block later or earlier steps of the secretory pathway do not induce such change of BiP localization. These observations indicate that relocalization of BiP is caused by the inhibition of ER-to-Golgi transport. Using immunoelectron microscopy, we have found that the punctate staining is because of the accumulation of BiP in the restricted region of the ER, which we propose to call the "BiP body." This implicates existence of ER subdomains in yeast. A vacuolar protein, proteinase A, appears to colocalize in the BiP body when the ER-to-Golgi transport is blocked, suggesting that the BiP body may have a role as the site of accumulation of cargo molecules before exit from the ER.

Base Sequence↗

PubMed1994

Cytoplasmic axial filaments in Escherichia coli cells: possible function in the mechanism of chromosome segregation and cell division.

Overproduction of CafA caused formation of chained cells and minicells. The cafA gene is located downstream from the mre region at 71 min on the Escherichia coli chromosome map and was previously called orfF. A long axial structure running through the chained cells, consisting of bundles of filaments assembled in a long hexagonal pillar several micrometers long and about 0.1 to 0.2 micron in diameter, was visible in both phase-contrast micrographs of the lysozyme-treated cells and electron micrographs of ultrathin sections. The CafA protein displays 34% amino acid similarity with the N terminus of the Ams protein of E. coli, which cross-reacts with antibody to a nonmuscle myosin heavy chain.

Bacterial Proteins↗

PubMed1994

Insulin sensitivity and the effects of insulin on renal sodium handling and pressor systems in essential hypertensive patients.

Insulin resistance and hyperinsulinemia are linked with essential hypertension. To clarify insulin sensitivity in Japanese essential hypertensive patients and the role of insulin resistance in these patients, a euglycemic hyperinsulinemic glucose clamp was applied in 17 essential hypertensive patients and 12 normotensive subjects. The mean glucose infusion rate was used as an indicator of insulin sensitivity (M value). This study revealed a significantly lower M value in essential hypertensive patients than in normotensive subjects. Increased plasma norepinephrine, renin activity, and aldosterone levels were observed after hyperinsulinemia for 120 minutes after glucose clamp in normotensive subjects and essential hypertensive patients. Urinary sodium excretion and fractional excretion of sodium were decreased in essential hypertensive patients as well as normotensive subjects during glucose clamp compared with the period before glucose clamp. No difference in the percent change was observed between essential hypertensive patients and normotensive subjects. These results indicate that selective insulin resistance with respect to glucose metabolism exists in essential hypertensive patients and that insulin action on renal sodium handling and pressor systems was maintained in these patients.

Aldosterone↗

PubMed1994

An improved sandwich ELISA method for the determination of immunoreactive schizophyllan (SPG).

As it is important to determine the optimal serum concentration of schizophyllan (SPG) when it is used as an anti-cancer drug, we devised a solid-phase ELISA. We also developed a sandwich ELISA using murine anti-SPG monoclonal antibody as the first antibody and rabbit anti-SPG serum as the second antibody in order to improve the detection sensitivity. This assay was able to determine SPG concentrations over 1.0 ng/ml and the absorbance at 490 nm was directly proportional to the SPG concentration. SPG in rabbit serum, obtained after intravenous and intramuscular injection (SPG; 10 mg/kg), was determined by this sandwich ELISA. Furthermore, the sensitivity of this ELISA method was compared with that of the Limulus test. The Limulus test is able to detect SPG in physiological saline (pH 6.3) at concentrations greater than 1.0 microgram/ml, but the sensitivity increased when SPG was dissolved in alkaline solution (pH 12.0), enabling SPG to be measured almost down to 1.0 ng/ml. These data suggest that our sandwich ELISA may be used for the measurement of SPG in blood or tissue.

Animals↗

PubMed1994

Monoclonal antibody to proteoglycan derived from Grifola frondosa (Maitake).

A murine monoclonal antibody (MAb) was prepared by immunizing BALB/c mice with a proteoglycan fraction derived from Grifola frondosa (Maitake mushroom), followed by the hybridization of spleen cells with mouse myeloma cells. The MAb (subclass; Ig G2b), designated MPG2, reacted with schizophyllan (SPG), curdlan, scleroglucan, laminarin and lentinan, but not with dextran, pullulan, mannan and xylan. Immunohistochemistry (ABC-GO method) showed that MAb MPG2 reacted with lysosomal proteoglycan and (1-->6)-beta-branched laminaritriose taken up by rabbit peritoneal macrophages. These results suggest that this MAb may recognize mainly (1-->3)-beta-D-glucan, and may be useful for determining the immunological properties of Grifola frondosa-derived proteoglycan.

Animals↗

PubMed1994

The inhibitory effect of sulfated schizophyllans and related oligosaccharides on coagulation and fibrinolysis.

Sulfated schizophyllans and sulfated oligosaccharides were prepared and their inhibitory effects on coagulation and fibrinolysis were examined. Some sulfated schizophyllans, which had a sulfur content of more than 10%, prolonged prothrombin time (PT) and thrombin time (TT). Interestingly, some sulfated schizophyllans and related oligosaccharides were able to inhibit plasmin toward fibrinolysis and amidolysis.

Amino Acid Sequence↗

PubMed1994

[Characteristics of blood pressure regulating endocrinological factors in elderly essential hypertensives].

Plasma renin activity (PRA) was lower in elderly normotensive subjects and essential hypertensives (EHT), and a significant negative correlation was found between PRA and age in both groups. In EHT, the proportion of the low renin group to total EHT increased with aging. There was a significantly positive correlation between plasma norepinephrine (PNE) and age in NT, but not in EHT. The mean value of PNE in young subjects was significantly higher in EHT than in NT, but not in the middle-aged and elderly groups, suggesting the important role of PNE in young EHT. Power spectral analysis revealed a significant reduction of both sympathetic and parasympathetic activity with aging in NT and EHT, indicating much caution may be required if sympathetic nerve activity is evaluated only by PNE levels in elderly EHT. The expanded plasma volume was another characteristic in elderly EHT, and suppressed activity of renal kallikrein-kinin, prostaglandin and dopamine may be involved with its mechanisms. Regarding insulin sensitivity in elderly EHT, it was shown that 1) the reduction of insulin sensitivity plays some role in age related acceleration of hypertension and glucose intolerance, 2) selective insulin resistance with respect to glucose metabolism already exists at lower ages in EHT, and 3) both Na retention and pressor system activation via insulin action might be a cause of blood pressure elevation in EHT.

Adult↗

PubMed1994

Does insulin resistance participate in an impaired glucose tolerance in primary aldosteronism?

It has been reported that glucose intolerance is occasionally found in primary aldosteronism. In this study, we measured insulin sensitivity by the euglycaemic hyperinsulinaemic glucose clamp technique and ability to release insulin by 75 g oral glucose tolerance test (OGTT) in primary aldosteronism. Seven patients with primary aldosteronism (PA) (53.7 +/- 3.4 years; mean +/- SEM) and eight normotensive subjects (NS) (57.5 +/- 2.6 years) were employed in this study. The two-hour euglycemic hyperinsulinaemic glucose clamp technique was performed in seven PA before adrenalectomy, six PA after adrenalectomy and eight NS. The 75 g OGTT was also done in five PA before and after adrenalectomy and eight NS. The mean rate of glucose infusion to maintain euglycemia for the last 30 minutes of the clamp technique was used as an indicator of insulin sensitivity (M-value). The total blood glucose levels during 75 g OGTT (area under the curves) (sigma blood glucose) were significantly higher in PA than those in NS, and the total insulin levels during 75 g OGTT (area under the curves) (sigma IRI) were significantly lower in PA than those in NS. After adrenalectomy in PA, blood glucose levels were significantly decreased and IRI were significantly increased compared with the normal range. There was a significant positive correlation (P < 0.05, r = 0.71) between serum potassium levels and IRI in PA which were determined before and after adrenalectomy. In PA, M-values (240.7 +/- 14.6 mg/m2/min) were significantly higher than those in NS (199.0 +/- 12.3 mg/m2/min).(ABSTRACT TRUNCATED AT 250 WORDS)

Female↗

PubMed1994

[Sick sinus syndrome discovered after induction of general anesthesia in a patient with normal preoperative Holter ECG].

We reported a case of 50-year-old male who was found to have SSS after induction of general anesthesia though his preoperative cardiac function studies including Holter ECG were normal. He was scheduled to have anterior transposition of ulnar nerve for idiopathic ulnar nerve palsy. He had suffered from lung edema during the same operation about 10 months previously at another hospital and the cause had been unknown. We monitored direct radial artery pressure continuously before induction of general anesthesia. About 5 minutes after the induction, ECG showed bradycardia of less than 40.min-1 and systolic blood pressure decreased to 40 mmHg. Intravenous injection of atropine increased heart rate to 60.min-1 only transiently. We began continuous infusion of isoproterenol. It was effective and no bradycardia and hypotension occurred afterwards throughout the operation. About 2 months later, he showed severe dizziness and Holter ECG revealed sinus arrest for 5 seconds. Therefore, a permanent pacemaker was implanted.

Anesthesia, General↗

PubMed1994

Alteration of G protein levels in antigen-challenged guinea pigs.

To elucidate the mechanism(s) of altered responses of various receptors observed in asthma, we examined levels of G proteins in lung membranes isolated from guinea pigs at various stages of experimental asthma. We found that levels of Gi2 alpha and Gq alpha increase after multiple exposures to aerosolized antigen but not after a single exposure. Levels of Gi1 alpha, Gs alpha and G beta did not change under these experimental conditions. Tracheas from these animals exhibited hyperresponsive muscarinic bronchoconstriction and hyporesponsive beta adrenoceptor-mediated relaxation of endothelin-preconstricted tracheas as measured by an ex vivo isometric assay. No changes in numbers or affinities of membrane M3 muscarinic and beta-2 adrenergic receptors were detected as measured by binding of [3H]QNB and [125I]CYP, respectively. The impairment of beta adrenoceptor-mediated relaxation of tracheas isolated from animals treated by multiple challenges was reversed by the pretreatment of tracheas with pertussis toxin. On the other hand, the carbamylcholine-stimulated GTPase activity was higher in lung membranes isolated from animals in the multiple challenge group and was blocked by anti-Gq alpha protein antibody. Taken together, our present observations suggest that an underlying mechanism of altered receptor responses associated with asthma is in part due to increased expression of Gi2 alpha and Gq alpha proteins, leading to altered coupling of receptors to effector systems.

Acetylcholine↗

PubMed1994

[A case of vertical gaze palsy associated with a unilateral infarct in the thalamo-mesencephalic junction on MR imaging].

We report a case of a 54-year-old man with sudden-onset double-vision. On admission, neurological examination showed upward and downward gaze palsy on voluntary and smooth pursuit movements, and vertical oculocephalic maneuver elicited a full upward and downward response. Bell's phenomenon, horizontal eye movements and convergence were not impaired. Based on these findings, supranuclear dissociated vertical gaze palsy was diagnosed. T1-weighted MR images revealed low intensity on the medial side of the right thalamo-mesencephalic junction, which impaired the rostral interstitial nucleus of the medial longitudinal fasciculus (riMLF). T2-weighted MR images revealed a high-intensity area. The posterior commissure was spared. The clinical signs gradually improved, and the vertical gaze palsy almost disappeared one month after onset. Based on these findings, unilateral infarct in the thalamo-mesencephalic junction in the distribution of the right paramedian thalamic artery was diagnosed. Only two cases of upward and downward gaze palsy in association with unilateral upper midbrain lesion without posterior commissure have been previously reported. Since we did not perform a pathological examination, we cannot deny that there may have been some denervation of fibers at the posterior commissure. Cases of upward and downward gaze palsy in association with unilateral upper midbrain lesion without posterior commissure are rare, and it is very interesting that the lesion in our patients, like that seen in the two pathological reports, was right-sided.

Cerebral Infarction↗

PubMed1993

Is intracytoplasmic membrane structure a generic criterion? It does not coincide with phylogenetic interrelationships among phototrophic purple nonsulfur bacteria.

The 16S rRNA or rRNA gene sequences of the type strains of 5 species of Rhodobacter, Rhodopseudomonas blastica and Paracoccus denitrificans were determined. The sequence analysis revealed that Rhodobacter species, whose intracytoplasmic membrane systems were characteristically vesicular, composed a sole cluster. Rhodopseudomonas blastica, whose intracytoplasmic membrane system was lamellar, was included in the cluster of Rhodobacter. The phylogenetic co-clustering of these bacteria conformed to their possessing of the identical types of carotenoids. Paracoccus denitrificans, which is nonphototrophic, is a right member of the Rhodobacter cluster. Rhodobacter species, Rhodopseudomonas blastica and Paracoccus denitrificans are apart from the other phototrophic bacteria and have the common deletions of 21 bases at the positions 1258 to 1278 (Escherichia coli numbering system). It was demonstrated that the morphological character "intracytoplasmic membrane structure", that has been regarded as a generic criterion does not reflect the phylogeny in the phototrophic bacteria. The transfer of Rhodopseudomonas blastica to the genus Rhodobacter is proposed.

Base Sequence↗

PubMed1993

Possible advantages of aluminum-chloro-tetrasulfonated phthalocyanine over hematoporphyrin derivative as a photosensitizer in photodynamic therapy.

The potency of aluminum-chloro-tetrasulfonated phthalocyanine (AlS4Pc) as a photosensitizer in photodynamic therapy was evaluated in in vitro and in vivo studies. Compared with hematoporphyrin derivative (HpD), the following advantages of AlS4Pc were revealed: (1) AlS4Pc was less toxic than HpD in vitro without light irradiation. (2) AlS4Pc showed more photodynamic-dependent cytotoxicity and anti-tumor effect in the red area of the spectrum (> 660 nm) at which tissue penetration is high. (3) AlS4Pc appeared to be removed more rapidly from normal tissues such as muscle and skin. (4) AlS4Pc showed less photodynamic-dependent cytotoxicity in vitro and milder cutaneous phototoxicity in vivo with UVA irradiation. On the basis of these observations, AlS4Pc shows considerable promise as a photosensitizer for PDT.

Animals↗

PubMed1993

Differential properties of type I and type II benzodiazepine receptors in mammalian CNS neurones.

1. The effects of benzodiazepine receptor (BZR) partial agonists, Y-23684 and CL218,872, were compared with its full agonist, diazepam, on gamma-aminobutyric acid (GABA)-induced Cl- current (ICl) in acutely dissociated rat cerebral cortex (CTX), cerebellar Purkinje (CPJ) and spinal ventral horn (SVH) neurones, by the whole-cell mode patch-clamp technique. 2. The GABA-induced responses were essentially the same in both SVH and CPJ neurones, but the KD value of the GABA response in CTX neurone was lower than those in the other two brain regions. 3. Enhancement of the GABA response by the two partial agonists was about one-third of that by diazepam in the SVH neurones (where type II subtype of BZR, BZ2, is predominant), whereas these partial agonists potentiated the GABA response as much as diazepam in CPJ neurones (where the type I subtype of BZR, BZ1, is predominant). In CTX neurones where both type I and II variants are expressed, the augmentation ratio of the GABA response by diazepam was between the values in CPJ and SVH neurones. 4. In concentration-response relationships of BZR partial agonists, the threshold concentrations, KD values and maximal augmentation ratio of the GABA response were similar in all CTX, CPJ and SVH neurones. Also, in all preparations, the threshold concentration and KD values of diazepam action were 10 fold less than those induced by partial agonists. 5. All BZR agonists shifted the concentration-response relationship for GABA to the left without changing the maximum current amplitude, indicating that activation of both BZ1 and BZ2 increase the affinity of the GABAA receptor for GABA. 6. The results are important in clarifying the mechanism of anxiety and might explain the anxioselectivity of BZR partial agonists.

Aging↗

PubMed1993

Temperature-sensitive sporulation caused by a mutation in the Bacillus subtilis secY gene.

A thermosensitive sporulation mutant of Bacillus subtilis containing a mutation in the secY gene was isolated and characterized. No asymmetric septum specific to the sporulation was detected by electron microscopy at the nonpermissive temperature, indicating that the block occurred at a very early stage of sporulation. Furthermore, competence development in the mutant cell was affected even at the sporulation-proficient temperature. It is assumed that the SecY protein of B. subtilis has multiple roles both in the regulation of spore formation and in stationary-phase-associated phenomena.

Bacillus subtilis↗