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Biomedical subjects

M Tamura

Publications and source records attributed to M Tamura.

At least 19 recordsLinked to original sources
PubMed1992

Effects of 1,3-chelation induced by cis-diamminedichloroplatinum(II) on the stability of DNA duplexes.

Several 1,3-intra-strand cross-linked decadeoxynucleotide duplexes, modified with cis-diamminedichloroplatinum(II) (cis-DDP), and their base substitution analogues at the complementary site to the intervening base of the coordination sites, were synthesized and measured for UV-melting profiles to determine melting temperature (Tm) values. The results indicated the thermal stability of the oligonucleotide duplexes containing Pt-induced 1,3-intra-strand cross-linking did not depend on the kind of intervening base of the coordination site but rather on its complementary base. These results may explain the mutagenicity of cis-DDP from a chemical aspect.

Base Sequence↗
PubMed1992

Reduction of alpha-tocopherolquinone to alpha-tocopherolhydroquinone in rat hepatocytes.

The contents of alpha-tocopherolhydroquinone (TQH2), alpha-tocopherolquinone (TQ) and alpha-tocopherol (Toc) in isolated rat hepatocytes and liver homogenates were determined by HPLC under anaerobic conditions, because TQH2 easily autoxidizes to TQ under aerobic conditions. The viable hepatocytes were used for the determination without homogenization. The hepatocytes contained 3.1, ND and 5.0, 3.1-9.0, and 31.3-63.2 nmol of TQH2, TQ and Toc/g liver, respectively. However, TQH2 was not detected in liver homogenates because endogeneous TQH2 autoxidizes to TQ during preparation of homogenates under aerobic conditions. The homogenates contained 2.0-23.5 and 36.5-54.9 nmol of TQ and Toc/g liver, respectively. Addition of TQ showed that TQ was reduced and converted into TQH2 in isolated hepatocytes. The TQH2 formation from TQ was also observed in liver homogenates in the presence of either NADPH or NADH. The formation was further analysed and confirmed by HPLC and mass spectrometry. The formation of TQH2 was also found to occur in mitochondria, microsomes and cytosol. The specific activity of NADPH-dependent TQ reductase activity was in the order of mitochondria greater than or equal to microsomes greater than cytosol. Furthermore, NADPH-cytochrome P450 reductase was found to catalyse TQH2 formation from TQ.

Animals↗
PubMed1992

Stabilization of human neutrophil NADPH oxidase activated in a cell-free system by cytosolic proteins and by 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide.

The superoxide-generating respiratory burst oxidase (NADPH oxidase) from human neutrophils can be activated in a cell-free system consisting of plasma membrane and cytosol by anionic amphiphiles such as sodium dodecyl sulfate and arachidonate (McPhail, L. C., Shirley, P. S., Clayton, C. C., and Snyderman, R. (1985) J. Clin. Invest. 75, 1735-1739; Curnutte, J. T. (1985) J. Clin. Invest. 75, 1740-1743; Bromberg, Y., and Pick, E. (1984) Cell. Immunol. 88, 213-221). Herein, the activity thus obtained is shown to be very labile at 37 degrees C. The rate of inactivation varied inversely with cytosol concentration. The stabilizing factor(s) was destroyed by heat and trypsin, indicating that it is protein in nature. Whereas cytosol from normal cells and from a chronic granulomatous disease patient lacking p67phox stabilized the oxidase activity, that from a chronic granulomatous disease patient lacking p47phox did not. Also, dialdehyde NADPH-treated cytosol showed no stabilizing effect, indicating that p47phox and a putative NADPH-binding component both participate in stabilization. The mechanism of inactivation was further explored by examining the stabilizing effect of agents that can act as chemical cross-linkers. Of several tested, 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) was the most effective, but others that utilize different chemical mechanisms were also partially effective. EDC extended the half-life at 37 degrees C from 2 to 120 min, protected against the inactivating effects of Triton X-100 and high salt, and did not affect the Km for NADPH. Stabilization required prior activation in the presence of both cytosol and membrane; and EDC treatment of cytosol, membrane, or a mixture of the two prior to the addition of sodium dodecyl sulfate failed to induce stabilization. EDC eliminated the requirement for the continuous presence of cytosol and activator. Dialysis did not cause a loss in activity, whereas control activity was diminished with dialysis and was largely restored with added sodium dodecyl sulfate. In the absence of EDC, the separation of cytosol from the membrane fraction resulted in a significant loss of activity, which was largely restored by the addition of cytosol. However, EDC treatment allowed the isolation of a nearly fully active oxidase in the membrane fraction, the activity of which was not influenced by added cytosol. These results support a model in which the active NADPH oxidase consists of a dissociable complex among membrane and cytosolic components and indicate that the longevity of the activated state requires continuous association of these components.

Cell Membrane↗
PubMed1992

Spermine down-regulates superoxide generation induced by fMet-Leu-Phe in electropermeabilized human neutrophils.

Effect of spermine, a naturally occurring polyamine, was investigated on superoxide generation in intact and electropermeabilized human neutrophils. Spermine suppressed N-formyl-methionyl leucyl phenylalanine (fMLP)-induced superoxide generation in permeabilized cells by reducing the rate and shortening the duration time. The inhibition was specific for spermine comparing with its precursor amines, spermidine and putrescine. The inhibition was not observed when cells were preincubated with spermine without permeabilization. Concanavalin A-induced superoxide generation was also down-regulated by spermine in permeabilized cells, but the activation induced by non receptor-mediated agonist (dioctanoylglycerol, phorbol myristate acetate, and arachidonate) was not affected by spermine. On the other hand, GTP-gamma-S-induced activation of superoxide generation was substantially suppressed by spermine. These results indicate that spermine inhibition occurs at a step prior to protein kinase C in signal transduction or in a pathway which is independent of the kinase.

Cell Membrane Permeability↗
PubMed1992

The simultaneous measurement of the redox state of cytochrome oxidase in heart and brain of rat in vivo by NIR.

The mutual relationship of the redox state of cytochrome oxidase in both cardiac and brain tissues were examined by the simultaneous optical measurement. The oxygenation states of cardiac and brain tissues behaved in a same manner during progressive hypoxia. We concluded that the oxygenation state of brain completely depends on the oxygenation state of cardiac tissue which determines the cardiac output.

Animals↗
PubMed1992

Cerebral oxygenation state in chemically-induced seizures in the rat--study by near infrared spectrophotometry.

The hemoglobin oxygenation state and the redox state of Cyt.ox. in the rat brain during and after seizure induced by PTZ were measured by using near-infrared spectrophotometry. PTZ administration caused transient reduction of Cyt.ox. in the brain, which might be a trigger for the increase of CBF during seizure. In postictal phase, although BP remained high, Cyt.ox. was in the certain reduced state, which might be due to A-V shunt. Hypoxic loading during seizure caused more reduction of Cyt.ox. than under non-epileptic conditions, which meant that seizure even under mild hypoxic conditions could cause severe hypoxic brain damage.

Animals↗
PubMed1992

Suprasellar germinomas; relationship between tumour size and diabetes insipidus.

The clinical and neuro-endocrinological aspects of 17 suprasellar germinoma patients treated between 1972-1991 are reported. Surgical extirpation was not initially attempted, but all patients received irradiation with or without a biopsy. Sixteen of those have led useful lives with appropriate hormonal replacement therapy during a mean follow up of 8 years. Seven tumours at diagnosis were less than 2 cm in diameter (type 1), nine tumours more than 2 cm (type 2), and one double midline tumour was of unknown size. All 7 type 1 patients required 1-deamino-8-D-arginine-vasopressin (DDAVP) to control diabetes insipidus (DI), but only 2 of the 9 type 2 patients have needed DDAVP since completion of the treatment. Patients with smaller tumours required more DDAVP following tumour disappearance, than those with larger tumours. The prognostic indicators for the post-treatment course of DI and retarded growth appeared to be the tumour size and the age at diagnosis. We also emphasize the absence of metastasis in unoperated cases and the use of tumour markers as a diagnostic criterion which obviates surgical acquisition of tissue to make the diagnosis. Possible reasons are discussed and the literature reviewed.

Adolescent↗
PubMed1992

The additive effect of alpha-difluoromethylornithine (DFMO) and radiation therapy on a rat glioma model.

The effects of alpha-difluoromethylornithine (DFMO), radiation and the therapy of their combination were investigated in rats bearing G-XII glioma. DFMO treatment as well as radiation therapy prolonged the survival period when compared to the results in non-treated control rats. The combination therapy showed a greater effect on the survival rate than the single therapies, the effect being additive. The concentration of putrescine, spermidine, and N1-acetylspermidine in tumor tissue was lowered by DFMO, while that of spermine was slightly elevated. Radiation decreased the concentration of all the polyamines, putrescine, spermidine, spermine and N1-acetylspermidine. The concomitant treatment with DFMO and radiation further decreased the concentrations of putrescine and N1-acetylspermidine in tumor tissues. The survival period of glioma-bearing rats is inversely correlated with the tissue levels of putrescine plus N1-acetylspermidine.

Animals↗
PubMed1992

Mediastinitis caused by odontogenic infection associated with adult respiratory distress syndrome.

A case of descending mediastinitis resulting from dental infection and complicated by adult respiratory distress syndrome (ARDS) is reported. The patient had a long history of heavy drinking. His condition was so serious that he died despite some successful therapies. The cause of ARDS appeared to be aspiration pneumonia. It is extremely rare for oral and maxillofacial surgeons to encounter a patient with ARDS.

Alcoholism↗
PubMed1992

Collagenous deposits on explanted intraocular lenses.

An immunohistochemical study of type I collagen in deposits on the surface of two intraocular lenses (IOLs) explanted from human eyes was conducted. Type I collagen-immunoreactive proteinaceous deposits with cells were found around the haptics of an iris-supported IOL. A few such deposits and what appeared to be macrophages were observed on the optic. A few cells (presumably macrophages and giant cells) were observed on a posterior chamber IOL, whereas proteinaceous deposits that reacted positively to the antibody were not identified. Type I collagen-immunoreactive deposits on the iris-supported IOL were thought to be the products of fibroblastic cells, originating from iris tissue, that attached directly to the haptics and helped stabilize the implant.

Aged↗
PubMed1992

Effects of recombinant human granulocyte colony-stimulating factor on neutrophil functions in aged animals.

We have studied the effects of recombinant human granulocyte colony-stimulating factor (rG-CSF) on granulopoiesis and neutrophil functions in aged rats and aged mice. We subcutaneously injected rG-CSF or control vehicle into aged rats (22 months old and 25 months old) for 7 consecutive days, counted the peripheral neutrophils and evaluated the functions of neutrophils isolated from venous blood. The peripheral neutrophil count in aged rats tended to be increased as compared with that in young rats (11 weeks old). However, the neutrophils in aged rats exhibited a decline of superoxide anion (O2-) release and phagocytic activity as compared with young rats. The peripheral neutrophil count in aged rats was significantly increased 5-6-fold as many as the control value by rG-CSF treatment, which was accompanied by a significant enhancement of O2- release and of phagocytic activity being restored to normal levels or better. In another series of experiments, we subcutaneously injected rG-CSF or control vehicle into aged mice (24-28 months old) or young mice (8 weeks old) for 7 consecutive days, and evaluated the functions of neutrophils isolated from peritoneal cavity. The peritoneal exudate neutrophils from the aged mice exhibited a decline of phagocytic and chemotactic activity as compared with the young mice. These functions in both young and aged mice were significantly enhanced by rG-CSF-treatment, and these functions in rG-CSF-treated aged mice were restored to a level higher than the level in control young mice. These findings demonstrate that rG-CSF is capable of enhancing granulopoiesis and restoring the age-related decline of neutrophil functions.

Aging↗
PubMed1992

Clinical experience in using a new type of nasal prong for administration of N-CPAP.

Nasal continuous positive airway pressure (N-CPAP) has been used in infants with decreased lung compliance for increasing the functional residual capacity (FRC), decreasing the work of breathing and improving the PaO2/PAO2 (arterial-alveolar PO2 ratio) without intubation. However, the currently available nasal prongs for administration of N-CPAP have presented some problems in fixation, and lesions to the nasal septum or nostrils might be induced by aggressive pressure intended to fix them. We would therefore like to report our experience in using a new type of nasal prong for administration of N-CPAP therapy. The nasal prongs we used were provided by Dr. Wung of Columbia University in New York, who first designed them, and have been used safely, effectively and without any complications.

Apnea↗
PubMed1992

Comparison of the incidence of intracranial hemorrhage following conventional mechanical ventilation and high frequency oscillation in beagle puppies.

Controversy exists as to whether high frequency oscillation (HFO) increases the risk of intraventricular hemorrhage (IVH) compared with conventional mechanical ventilation (CMV). We compared the risk of intracranial hemorrhage after phenylephrine-induced hypertension, combined with a hypovolemic, hypotensive insult followed by rapid volume replacement in two groups of newborn beagle puppies (one group on a piston pump HFO and the other on CMV). A total of 12 beagle puppies (6 on HFO and 6 on CMV) survived the protocol. Arterial blood gas analysis and arterial blood pressures through the study were of the same magnitude in both groups. The length of time for which the puppies remained hypertensive and hypotensive also did not vary significantly between the groups. Intraventricular hemorrhages were observed in two of six CMV puppies and two of six HFO puppies. One animal in each group had a white matter hemorrhage. Subarachnoid hemorrhages were seen in 4 animals on CMV and 3 on HFO. This study indicated that HFO does not increase the risk of any kind of intracranial hemorrhage, including IVH, in beagle puppies.

Animals↗