Biomedical subjects
Publications and source records attributed to S Hiraga.
The partition-proficient mini-F plasmid pXX325 was stably maintained in the mukB null mutant, which is defective in chromosome partitioning into the two daughter cells. In the null mutant, the plasmid was partitioned into both nucleate and anucleate daughter cells, independently of host chromosomes.
In order to examine a role of extracellular matrix (ECM) components in the process of glioma cell invasion, we investigated the immunohistochemical localization of fibronectin (FN), laminin(LN) and FN-receptor (FN-R) in human malignant gliomas. The surgical specimens were obtained from 15 patients with malignant gliomas. Tumor tissue and adjacent brain tissue including tumor infiltration were frozen at -80 degree C immediately after the resection. Ten microns thick frozen tissue was cut out on a cryostat and divided into three different parts on the histology stained with HE, ie, the tumor region(T), brain tissues with tumor infiltration(I), and the border region between these two parts(B). These sections were air-dried, and fixed with cold acetone (-4 degrees C) for 5min. Adjacent sections were immunohistochemically stained by ABC method, using monoclonal antibody for FN-R and polyclonal antibodies for FN and LN. FN, LN and FN-R were all stained at the vascular and pial-glial basement membranes intensely in all gliomas. In immunostain for FN, fine networks of FN were observed in the extracellular space in all three parts. Some tumor cells were clustered around such networks of FN in brain tissues with tumor infiltration. Immunostain for LN demonstrated that the vascularity in the border between the tumor and the brain with tumor infiltration was much higher than that in other parts. LN was not stained in the extracellular space in all these gliomas. FN-R was expressed in some tumor cells, especially in the clustered tumor cells in the brain with tumor infiltration.(ABSTRACT TRUNCATED AT 250 WORDS)
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We report a case of arteriovenous malformation (AVM) which recurred as a giant AVM 19 years after resection. At the age of 23, the patient underwent craniotomy for a small AVM with surrounding old hematoma in the right parietal lobe. The AVM was judged to have been removed completely on postoperative angiography, while abnormal small vessels were noted retrospectively. He did well until 19 years later when he had seizures. Repeated angiography showed huge recurrent AVM at the operative site. Considering the risk involved in surgery, he was discharged from the hospital with anticonvulsants. Recurrence of AVM after removal is rare, but patients with AVM surgery should be followed up with CT and angiography for a long period of time.
Intra-arterial infusion chemotherapy has been applied for the treatment of malignant brain tumors to increase the distribution of the drug into the tumor. MX2, a new morpholinoanthracycline, is a lipophilic compound, and has a strong antineoplastic effect against human and rat glioma cells. In this report, the acute toxicity and distribution of MX2 after intracarotid injection were studied using female Wistar rats weighing 150 g. To test the acute toxicity, various doses ranging 1.5 to 6 mg/kg was administered. All rats died within 4 days when received more than 3 mg/kg of intra-arterial or intravenous MX2. No rats died if the dose was reduced to less than 2 mg/kg. For the purpose to examine distribution in the brain, rats which received 2 mg/kg of intra-carotid MX2 were killed 5 to 120 min. after injection. The level of MX2 in the ipsilateral brain tissue reached to the maximum 5 min. after injection, and then rapidly decreased. The maximum concentration of MX2 in the ipsilateral brain was 25-fold higher than that in the contralateral brain, and 20-fold higher than that after intravenous injection of the same dose. The AUC (area under the curve) in the ipsilateral brain after intra-carotid injection was 8.0-fold higher than that in the contralateral brain, and 7.3-fold higher than that after intravenous injection of the same dose. These results indicate that intra-carotid administration can increase the distribution of MX2 in the normal brain.
The nucleotide sequence of the parC gene essential for chromosome partition in E. coli was determined. The deduced amino acid sequence was homologous to that of the A subunit of gyrase. We found another new gene coding for about 70 kd protein. The gene was sequenced, and the deduced amino acid sequence revealed that the gene product was homologous to the gyrase B subunit. Mutants of this gene were isolated and showed the typical Par phenotype at nonpermissive temperature; thus the gene was named parE. Enhanced relaxation activity of supercoiled plasmid molecules was detected in the combined crude cell lysates prepared from the ParC and ParE overproducers. A topA mutation defective in topoisomerase I could be compensated by increasing both the parC and the parE gene dosage. It is suggested that the parC and parE genes code for the subunits of a new topoisomerase, named topo IV.
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The hopE mutants of Escherichia coli, which cannot stably maintain a mini-F plasmid during cell division, have mutations in the recD gene coding for subunit D of the RecBCD enzyme (exonuclease V). A large amount of linear multimer DNA of mini-F and pBR322 plasmid accumulates in these hopE mutants. The linear multimers of plasmid DNA in the hopE (recD) mutants accumulate in sbc+ genetic backgrounds and this depends on the recA+ gene function. Linear plasmid multimers also accumulated in a recBC xthA triple mutant, but not an isogenic xth A mutant or an isogenic recBC mutant. The recBC xth A mutant is defective in the conjugative type of recombination. Linear plasmid multimers were not detected in the recBC strain. We propose models to account for linear multimer formation of plasmids in various mutants.
Complementation and sequencing analyses revealed that the hopD mutants, which could not support stable maintenance of mini-F plasmids (Niki et al. 1988), had mutations in the hupB gene, and that the hopD410 mutation was an ochre mutation at the 5th Gln position of HU-1. Maintenance and stability of various plasmids, mini-P1 plasmids, mini-F plasmids, and oriC plasmids, were studied in the hupA and hupB mutants (HU mutants), and himA and hip mutants (IHF mutants). Mini-P1 plasmids and mini-F plasmids could not be introduced into the delta hupA-delta hupB double deletion mutant. Replication of mini-F plasmids was partially inhibited in the hupB mutants, including the delta hupB and hopD(hupB) mutants, whereas replication of oriC plasmids was not significantly affected even in the delta hupA-delta hupB double deletion mutant. The mini-P1 plasmid was slightly unstable in the himA-hip mutant, whereas the mini-F plasmid was stable.
The seg-3 mutant Escherichia coli does not support the maintenance of mini-F plasmid at 42 degrees C. We cloned the chromosomal DNA segment of the wild-type strain W3110 that complements the Seg- phenotype of this mutant. Cleavage mapping of this segment showed that it was derived from the 76-min region of the E. coli chromosome map. Complementation tests using plasmids carrying subcloned DNA segments suggested that the seg-3 mutant carried two mutations that additively affected the maintenance of mini-F plasmid; one was in the ugpA gene and the other was presumably in the rpoH gene. We generated a disrupted ugpA null mutant and found that the mini-F plasmid was unstable in this ugpA null mutant even at 30 degrees C. This suggests that the ugpA gene product is required for the stable maintenance of mini-F plasmid.
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Radioiodinated R- and S-Quinuclidinyl derivatives of RS-benzilate (R- and S-125IQNB) have been synthesized for quantitative evaluation of muscarinic acetylcholine receptor binding in vivo. Two sets of experiments were performed in rats. The first involved determining the metabolite-corrected blood concentration and tissue distribution of tracer R-IQNB (active enantiomer) and S-IQNB (inactive enantiomer) in brain 1 min to 26 h after intravenous injection. The second involved the measurement of brain tissue washout over a 2-min period after loading the brain by an intracarotid artery injection of the ligands. Various pharmacokinetic models were tested, which included transport across the blood-brain barrier (BBB), nonspecific binding, low-affinity binding, and high-affinity binding. Our analysis demonstrated that the assumptions of rapid equilibrium across the BBB and rapid nonspecific binding are incorrect and result in erroneous estimates of the forward rate constant for binding at the high-affinity receptor sites (k3). The estimated values for influx across the BBB (K1), the steady-state accumulation rate in cerebrum (K), and the dissociation rate constant at the high-affinity site (k4) of R-IQNB were independent of the specific compartmental model used to analyze these data (K1 approximately 0.23 ml/min/g, K approximately 0.13 ml/min/g, and k4 approximately 0.0019 min-1 for caudate). In contrast, the estimated values of k3 and the efflux rate constant (k2) varied over a 10-fold range between different compartmental models (k3 approximately 2.3-22 min-1 and k2 approximately 1.6-16 min-1 in caudate), but their ratios were constant (k3/k2 approximately 1.4). Our analysis demonstrates that the estimates of k3 (and derived values such as the binding potential) are model dependent, that the rate of R-IQNB accumulation in cerebrum depends on transport across the BBB as well as the rate of binding, and that uptake in cerebrum is essentially irreversible during the first 360 min after intravenous administration. Graphical analysis was consistent with compartmental analysis of the data and indicated that steady-state uptake of R-IQNB in cerebrum is established within 1-5 min after intravenous injection. We propose a new approach to the analysis of R-IQNB time-activity data that yields reliable quantitative estimates of k3, k4, and the nonspecific binding equilibrium constant (Keq) by either compartmental or graphical analysis. The approach is based on determining the free unbound fraction of radiolabeled ligand in blood and an estimate of K1.(ABSTRACT TRUNCATED AT 400 WORDS)
The positioning of replicated chromosomes at one-fourth and three-fourths of the cell length was inhibited when protein synthesis was inhibited by chloramphenicol or rifampin or by starvation for amino acids. Under these conditions, the progress of chromosome replication continued and replicated chromosomes were located close to each other as one nucleoid mass at midcell. Cells which already had two separate daughter chromosomes located at the cell quarters divided into two daughter cells under these conditions. When protein synthesis resumed, daughter chromosomes moved from midcell to the cell quarters, respectively, before any detectable increase in cell length was observed. The chromosome positioning occurred even under inhibition of the initiation of chromosome replication and under inactivation of DNA gyrase. The chromosome positioning presumably requires new synthesis of a particular protein(s) or translation itself.
hopA mutants, which have been suggested to be defective in mini-F plasmid partitioning (H. Niki, C. Ichinose, T. Ogura, H. Mori, M. Morita, M. Hasegawa, N. Kusukawa, and S. Hiraga, J. Bacteriol. 170:5272-5278, 1988), were found to carry mutations in the gyrB gene, coding for the B subunit of DNA gyrase. In gyrB(HopA) mutants, relaxation of the superhelicity of plasmids, increased IncG incompatibility, and increased SopB protein production were observed. It is suggested that altered expression of the sop genes, which is due to relaxation of the mini-F plasmid DNA, causes both defective partitioning of the mini-F plasmids and increased IncG incompatibility in gyrB(HopA) mutants.
The transport rate constants across rat brain capillaries of a muscarinic acetylcholine receptor antagonist, [125I]quinuclidinyl benzilate (IQNB), an opiate receptor antagonist, [3H]cyclofoxy (CF), and a highly diffusible blood flow indicator, [14C]iodoantipyrine (IAP), were determined by the indicator-diffusion technique and a model that includes a distribution of capillary transit times and a homogeneous distribution of the test compound in the tissue parenchyma. The mean influx extraction ratio (E1) of IAP was greater than 0.91, and E1 for CF and IQNB was 0.56-0.79 and 0.34-0.46, respectively. The order of lipid solubility was IQNB greater than IAP greater than CF; the apparent discrepancy (high lipid solubility and low permeability) of IQNB was partly due to intravascular binding to plasma protein and red blood cells. The observed initial tissue distribution volumes (lambda 1, ml/g brain) for IQNB (0.09-0.17), CF (0.51), and IAP (0.71) were compared with those estimated for the unbound free ligand in blood (lambda a, ml/g brain; IQNB = 1.3-2.3, CF = 0.88, and IAP = 1.4). These findings suggest that the binding of lipid-soluble radioligands and drugs to plasma proteins and red blood cells can be a major determinant of transport across the blood-brain barrier and the apparent distribution volume of the ligand in brain tissue.
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Congenital neurogenic bladder dysfunction with spina bifida and sacral dysgenesis manifested itself at middle age is reported. A 48-year-old male who had urinary retention and suprapubic cystostomy one year and a half before in another hospital was seen, asking for removal of the cystostomy. He had never had any neurologic or bladder dysfunction in his childhood and adulthood. X-ray examination revealed a bifid spine and sacral dysgenesis, bilateral hydronephrosis, bilateral VUR and urethral stricture. Uroflowmetry showed a severe dysuric pattern (voided volume 5 ml, residual urine 230 ml) and the cystometrogram revealed a hyperactive bladder. Optical urethrotomy for stricture yielded some improvement i.e. recovery of voluntary voiding with large amount of residual urine. TUR of the bladder neck resulted in almost complete voiding. Cohen's antireflux operation yielded favorable improvement of hydronephrosis. The bladder and renal function remained favorable in the follow-up period of about two years. The clinical course of this patient suggested that his bladder dysfunction was due to late manifestation of congenital neurogenic bladder.