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Biomedical subjects

K Shimada

Publications and source records attributed to K Shimada.

At least 307 records · Page 17Linked to original sources
PubMed1999

A new cytochrome subunit bound to the photosynthetic reaction center in the purple bacterium, Rhodovulum sulfidophilum.

The nucleotide sequence of the puf operon, which contains the genes encoding the B870 light-harvesting protein and the reaction center complex of the purple photosynthetic bacterium, Rhodovulum sulfidophilum, was determined. The operon, which consisted of six genes, pufQ, pufB, pufA, pufL, pufM, and pufC, is a new variety in photosynthetic bacteria in the sense that pufQ and pufC coexist. The amino acid sequence of the cytochrome subunit of the reaction center deduced from the pufC sequence revealed that this cytochrome contains only three possible heme-binding motifs; the heme-1-binding motif of the corresponding tetraheme cytochrome subunits was not present. This is the first exception of the "tetraheme" cytochrome family in purple bacteria and green filamentous bacteria. The pufC sequence also revealed that the sixth axial ligands to heme-1 and heme-2 irons were not present in the cytochrome either. This cytochrome was actually detected in membrane preparation as a 43-kDa protein and shown to associate functionally with the photosynthetic reaction center as the immediate electron donor to the photo-oxidized special pair of bacteriochlorophyll. This new cytochrome should be useful for studies on the role of each heme in the cytochrome subunit of the bacterial reaction center and the evolution of proteins in photosynthetic electron transfer systems.

Amino Acid Sequence↗
PubMed1999

A light-harvesting antenna protein retains its folded conformation in the absence of protein-lipid and protein-pigment interactions.

The first study by nmr of the integral membrane protein, the bacterial light-harvesting (LH) antenna protein LH1 beta, is reported. The photosynthetic apparatus of purple bacteria contains two different kinds of antenna complexes (LH1 and LH2), which consist of two small integral membrane proteins alpha and beta, each of approximately 6 kDa, and bacteriochlorophyll and carotenoid pigments. We have purified the antenna polypeptide LH1 beta from Rhodobacter sphaeroides, and have recorded CD spectra and a series of two-dimensional nmr spectra. A comparison of CD spectra of LH1 beta observed in organic solvents and detergent micelles shows that the helical character of the peptide does not change appreciably between the two milieus. A significantly high-field shifted methyl signal was observed both in organic solvents and in detergent micelles, implying that a similar three-dimensional structure is present in each case. However, the 1H-nmr signals observed in organic solvents had a narrower line width and better resolution, and it is shown that in this case organic solvents provide a better medium for nmr studies than detergent micelles. A sequential assignment has been carried out on the C-terminal transmembrane region, which is the region in which the pigment is bound. The region is shown to have a helical structure by the chemical shift values of the alpha-CH protons and the presence of nuclear Overhauser effects characteristic of helices. An analysis of the amide proton chemical shifts of the residues surrounding the histidine chlorophyll ligand suggests that the local structure is well ordered even in the absence of protein-lipid and protein-pigment interactions. Its structure was determined from 348 nmr-derived constraints by using distance geometry calculations. The polypeptide contains an alpha-helix extending from Leu19 (position of cytoplasmic surface) to Trp44 (position of periplasmic surface). The helix is bent, as expected from the amide proton chemical shifts, and it is similar to the polypeptide fold of the previously determined crystal structure of Rhodopseudomonas acidophila Ac10050 LH2 beta (S. M. Prince et al., Journal of Molecular Biology, 1997, Vol. 268, pp. 412-423). It is concluded that the polypeptide conformation of this region may facilitate assembly of the LH complex.

Amino Acid Sequence↗
PubMed1999

Interaction site for high-potential iron-sulfur protein on the tetraheme cytochrome subunit bound to the photosynthetic reaction center of Rubrivivax gelatinosus.

We have recently demonstrated, using site-directed mutagenesis, that soluble cytochromes interact with the Rubrivivax gelatinosus photosynthetic reaction center (RC) in the vicinity of the low-potential heme 1 (c-551, Em = 70 mV) of the tetraheme cytochrome subunit, the fourth heme from the special pair of bacteriochlorophyll [Osyczka, A., et al. (1998) Biochemistry 37, 11732-11744]. Although the mutations generated in that study did not show clear effects on the electron transfer from high-potential iron-sulfur protein (HiPIP), which is the major physiological electron donor to the RC in this bacterium, we report here that other site-directed mutations near the solvent-exposed edge of the same low-potential heme 1, V67K (valine-67 substituted by lysine) and E79K/E85K/E93K (glutamates-79, -85, and -93, all replaced by lysines), considerably inhibit the electron transfer from HiPIP to the RC. Thus, it is concluded that HiPIP, like soluble cytochromes, binds to the RC in the vicinity of the exposed part of the low-potential heme 1 of the cytochrome subunit, although some differences in the configurations of the HiPIP-RC and cytochrome c-RC transient complexes may be postulated.

Bacterial Proteins↗
PubMed1999

Homocysteine increases nitric oxide synthesis in cytokine-stimulated vascular smooth muscle cells.

BACKGROUND: Elevated plasma homocysteine levels have been reported to be an independent risk factor for vascular disease. However, there have been no reports concerning the effects of homocysteine on the production of nitric oxide (NO), another modulator of vascular function and proliferation, by the vascular smooth muscle. METHODS AND RESULTS: We investigated the effects of homocysteine on NO synthesis by measuring the production of nitrite, a stable metabolite of NO, in cultured rat vascular smooth muscle cells (VSMCs). Incubation of cultures with interleukin (IL)-1beta 10 ng/mL for 24 hours caused a significant increase in nitrite generation. The IL-1beta-induced nitrite production by VSMCs was significantly increased by homocysteine in a dose-dependent manner. This effect of homocysteine was significantly inhibited in the presence of NG-monomethyl-L-arginine or actinomycin D. The homocysteine-induced nitrite production was accompanied by increased inducible NO synthase mRNA and protein accumulation. Cysteine, glutathione, or hydrogen peroxide also increased nitrite accumulation in IL-1beta-stimulated VSMCs. Coincubation with the radical scavenger catalase or superoxide dismutase markedly reduced homocysteine-induced nitrite accumulation. CONCLUSIONS: Homocysteine enhances NO synthesis in IL-1beta-stimulated VSMCs, and oxidative products are involved in the effect of homocysteine.

Animals↗
PubMed1999

Augmented proliferation of human alveolar macrophages after allogeneic bone marrow transplantation.

After allogeneic bone marrow transplantation (allo-BMT), recipient alveolar macrophages (AM) are gradually replaced by AM of the donor origin. An influx of mononuclear phagocytes of donor origin to the lung is responsible for the repopulation, but the detailed kinetics remain unclear. We therefore studied 24 BMT recipients who underwent bronchoalveolar lavage (BAL) from 24 to 83 days after BMT. AM cell number, size, morphology, proliferating ability, and genotype of AM were measured. Before day 50, the number and size of AM in BAL fluid were similar to those of normal nonsmokers. However, after day 50, the mean number of AM increased threefold and the mean cell size decreased due to the increase of small AM. These small cells are presumably of donor origin based on DNA fingerprinting analysis and based on fluorescence in situ hybridization for the Y chromosome in a sex-mismatched case. Immunohistochemistry and cell cycle analysis demonstrated that the increase in AM number coincided with a remarkable increase of AM expressing proliferating cell nuclear antigen, suggesting that small AM are proliferating. This is the first report representing that augmented proliferation of donor AM in situ may contribute to the reconstitution of AM population after BMT.

Adolescent↗
PubMed1999

Dopamine and serotonin in the larval CNS of a drosophilid fly, Chymomyza costata: are they involved in the regulation of diapause?

Developmental profiles of dopamine (DA) and serotonin (5-hydroxytryptamine, 5-HT) in the larval CNS of Chymomyza costata were measured by HPLC using electrochemical detection. Larvae of two strains, wild-type (W) and nondiapause mutant (M), were maintained either under long-day (LD, inducing pupariation) or short-day (SD, inducing diapause in W-strain) photoperiods. The levels of DA ranged from 10 fmol/CNS (early 3rd instar larvae) to 60 fmol/CNS (150-day-old diapausing larvae); the range for 5-HT was from 10 fmol/CNS to 75 fmol/CNS in the same larvae. During the 3rd larval instar, which is the decisive stage for photoperiodic induction of diapause, no differences were found in DA developmental profiles between different strains or conditions. Some differences were found in 5-HT developmental profiles, but only after the end of sensitive stage, and were therefore regarded as insignificant for regulation of developmental mode. Similarly, no clear correlations between the developmental profiles of DA and 5-HT and the course of developmental changes during the maintenance and termination of a few-month-long larval diapause were observed. Furthermore, the DA and 5-HT levels in the CNS were pharmacologically manipulated by feeding the larvae with either precursors or enzyme inhibitors of DA and 5-HT biosynthesis. Although retardations of growth and development were observed, the treated larvae retained full capacity for the photoperiodic response, irrespective of the level of DA or 5-HT in their CNS. Larvae with their 5-HT depleted to trace levels survived and were capable of diapause induction, maintenance, and termination. Depletion of DA to trace levels resulted in 100% mortality. Collectively, the present study indicates that 5-HT in the CNS is dispensable for the photoperiodic response in C. costata. More information is needed to elucidate the potential role of DA.

5-Hydroxytryptophan↗
PubMed1999

Intravascular ultrasound-guided balloon angioplasty for treatment of in-stent restenosis.

We investigated the usefulness of intravascular ultrasound (IVUS)-guided balloon angioplasty for in-stent restenosis in 37 lesions of 34 consecutive patients. We divided these patients into two groups: a group in which the balloon size was determined by quantitative coronary angiography (QCA group; 17 patients, 19 lesions) and a group in which the balloon size was determined by IVUS (IVUS group; 17 patients, 18 lesions). We compared short-term and 6-month outcomes for these groups. In the IVUS group, we used a balloon of a size equal to 95% of the media-to-media diameter at the distal to the stent, as determined by IVUS. No significant differences were observed in patient or lesion characteristics between the two groups. The clinical success rate was 100% in both groups, and no clinical events were observed in either of the groups. The balloon/artery ratio was larger in the IVUS group than in the QCA group (1.33 +/- 0.35 vs. 1.16 +/- 0.13, P < 0.05), and the recurrent restenosis rate was lower (17% vs. 53%, P < 0.05). These results suggest that repeat balloon angioplasty using a balloon size determined by IVUS is useful for in-stent restenosis. Cathet. Cardiovasc. Intervent. 47:298-303, 1999.

Angioplasty, Balloon, Coronary↗
PubMed1999

Usefulness of newly designed pigtail catheter with multiple side holes by reducing incidence of ventricular ectopy.

This study was designed to determine whether a newly designed 5 Fr pigtail catheter of Jet Balance with multiple side holes reduces the incidence of ventricular ectopy during left ventriculography. To examine the catheter movement in vitro, we injected a colored glycerin solution by an injector through 5 Fr Jet Balance catheter and 6 Fr conventional pigtail catheter suspended in a water filled, glass container. A recoil of the catheter caused by injection was observed for a 6 Fr conventional catheter; however, no catheter movement was observed when a 5 Fr Jet Balance was used. To evaluate clinical usefulness of the 5 Fr Jet Balance, we compared the number of incidence of ventricular ectopy during left ventriculography between 5 Fr Jet Balance and 6 Fr conventional pigtail catheters. In 104 consecutive patients who underwent left ventriculography, a 5 Fr Jet Balance was used in 55 patients (5 Fr Jet Balance group), and a 6 Fr conventional pigtail in 49 patients (6 Fr conventional pigtail group). The 5 Fr Jet Balance group had a significantly lower incidence of VPB (21.8% vs. 42.9%, P = 0.02), ventricular tachycardia (1.9% vs. 14.3%, P = 0.02), and multiple VPB (9.0% vs. 34.7%, P = 0.001), respectively, than the 6 Fr conventional pigtail group. In conclusion, a 5 Fr Jet Balance pigtail catheter is useful and safe as regard to the incidence of ventricular ectopy during left ventriculography. Cathet. Cardiovasc. Intervent. 48:220-225, 1999.

Aged↗
PubMed1999

Pharmacokinetics of ezlopitant, a novel non-peptidic neurokinin-1 receptor antagonist in preclinical species and metabolite kinetics of the pharmacologically active metabolites.

The pharmacokinetics of ezlopitant were determined in the rat, gerbil, guinea pig, ferret, dog and monkey after intravenous and oral administration. In general, ezlopitant is marked by high clearance values that approach or exceed hepatic blood flow values, moderate to high values for steady-state volume of distribution (3. 9-28 L/kg), and terminal phase half-life values ranging from 0.6 h in the guinea pig to 7.7 h in the rat. Oral bioavailability ranged from <0.2% (guinea pig) to 28% (dog). Data from portal vein cannulated dogs suggested that 37% of an oral dose of ezlopitant enters the portal vein as an unchanged drug in this species. Ezlopitant is metabolized to two pharmacologically active metabolites, an alkene (CJ-12 458) and a benzyl alcohol (CJ-12 764). After administration of the parent compound, CJ-12 764 was found in greater abundance than CJ-12 458 in all species examined. Ezlopitant and CJ-12 458 were highly protein bound in plasma (or serum), whereas the protein binding of CJ-12 764 was somewhat lower. Measurement of the kinetics of ezlopitant, CJ-12 458 and CJ-12 764 in the cerebrospinal fluid (CSF) of dogs demonstrated that all three compounds can partition into the CSF, and thereby, be capable of contributing to centrally mediated pharmacological effects. Thus, these data suggest that the pharmacological activity exhibited by ezlopitant in preclinical species in vivo is likely a result of the parent compound plus the active metabolites. Furthermore, the contributions of ezlopitant and the active metabolites to pharmacological activity probably varies with the identity of the model species, as well as the dose and route of ezlopitant administration.

Animals↗
PubMed1999

Myotonic dystrophy associated with QT prolongation and torsade de pointes.

A rare case of myotonic dystrophy (MD) with congestive heart failure, associated with QT prolongation and torsade de pointes (TdP) is reported. A 53-year-old woman was admitted to the hospital because of congestive heart failure. Electrocardiograph (ECG) showed first-degree atrioventricular block and QT prolongation. During hospitalization, TdP appeared but returned to sinus rhythm spontaneously. As the patient had quadriplegia, a myopathic face, cataracts, diabetes mellitus, and an increased number of cytosine-thymineguanine (CTG) repeats (760 repeats), she was diagnosed as having MD. Electrocardiographic analysis of her family also revealed abnormal QT(U) prolongation in her daughter and brother who both had MD, while ECG findings of other family members without MD were normal. Thus, the presence of QT(U) prolongation was associated with MD in this family.

Cardiotonic Agents↗
PubMed1999

Effects of naloxone on neurohypophyseal peptide release by hypertonic stimulation in chicks.

The effects of opioid peptides on the osmotic release of neurohypophyseal hormones, arginine vasotocin (AVT) and mesotocin (MT), were determined in 2-day-old chicks. Experiment 1 examined the effect of a variety of doses of naloxone, an opioid antagonist, on chicks administered isotonic or hypertonic solution. Plasma osmolality in chicks administered hypertonic solution was significantly higher than that in groups administered isotonic solution. None of the doses of naloxone affected plasma osmolality in response to isotonic and hypertonic solution. Plasma levels of AVT increased in hypertonic solution and this response was further enhanced by naloxone injection as the doses increased. The hypertonic solution alone did not affect plasma levels of MT, but additional treatment with naloxone slightly increased plasma levels of MT. Experiment 2 examined the effect of DAMGO ([d-Ala(2), N-Me-Phe(4),Gly-ol]-enkepha lin), a specific mu receptor agonist. Relatively high plasma osmolality caused by hypertonic solution was not affected by additional treatment with DAMGO. Plasma levels of AVT in response to hypertonic solution and to additional treatment with naloxone were reduced by higher doses of DAMGO. Experiment 3 examined the effect of naloxone on chicks administered different concentrations of NaCl. Administration of hypertonic solution resulted in an increase in plasma osmolality and plasma levels of AVT. Naloxone administration enhanced the increase in plasma AVT levels in response to hypertonic solution. Experiment 4 examined the effect of naloxone on different kinds of hypertonic solution, 0.15 M NaCl, 1.5 M NaCl, 2.55 M urea, and 1.95 M sucrose. The increases in plasma osmolality resulting from the administration of the urea and sucrose solutions were the same as those in the chicks injected with 1.5 M NaCl. In sucrose-treated chicks, plasma levels of AVT increased in chicks administered naloxone but not in chicks injected with normal saline. In contrast, no significant changes in plasma levels of AVT were observed in urea treatment with or without naloxone. In Experiments 3 and 4, plasma levels of MT after administration of hypertonic solutions did not change. However, naloxone administration enhanced plasma levels of MT in osmotically stimulated chicks. The results of the present study suggest that opioid peptides attenuate the increase in plasma AVT and MT in hypertonic states.

Analgesics, Opioid↗
PubMed1999

Endomyocardial biopsy findings in patients with atrioventricular block in the absence of apparent heart disease.

The purpose of this study was to examine the histopathological findings of right ventricular endomyocardial biopsies from ten patients less than 60 years of age (47 +/- 9.8 (mean +/- SD) years) with documented atrioventricular block but without apparent heart disease. They underwent electrophysiological testing, echocardiography, coronary angiography, and right ventricular endomyocardial biopsy. Biopsy specimens were assessed for morphologic changes in myocyte diameter, fibrosis, disarray, and degeneration. Electrophysiological testing demonstrated atrioventricular nodal block in 2, intra-His bundle block in 2, and infra-His bundle block in 6 patients. Histology revealed evidence of myocardial fibrosis with either myocyte hypertrophy or disarray in 7 of the 10 patients. The results of electrophysiological testing did not correlate with the histopathological findings or severity. In one patient, heart failure appeared during the follow-up period. We conclude that patients with atrioventricular block of unknown etiology have histological abnormalities of the ventricular endomyocardium in addition to the conduction system disturbances. We consider such cases as constituting one of the disease groups of cardiomyopathy, and suggest that it is necessary to follow up the clinical course in these patients.

Adult↗
PubMed1999

Pheophytinization of bacteriochlorophyll c and energy transfer in cells of Chlorobium tepidum.

Bacteriochlorophyll (BChl) c in whole cells of Chlorobium tepidum grown at 46 degrees C changed into bacteriopheophytin (BPhe) c within 10 days after reaching full growth. When a small amount of C. tepidum cells in which BChl c had been completely pheophytinized were transferred to a new culture medium, normal growth was observed after a short lag phase, and the absorption spectrum of the growing cells showed the presence of a normal amount of BChl c. During the growth of C. tepidum in the new culture, the BChl c concentration was nearly proportional to the cell density measured by turbidity (OD640). These results indicate that C. tepidum can survive even when BChl c has been completely pheophytinized and that BChl c is newly synthesized in such cells when transferred to a new culture medium. In partly pheophytinized cells, upon excitation of BPhe c at 550 nm the fluorescence emission spectrum showed maxima at 775 and 810 nm, which correspond to emissions from BChl c and BChl a, respectively. This indicates energy transfer from BPhe c to BChl c and BChl a. In cells in which BChl c was completely pheophytinized, fluorescence measurements were indicative of direct energy transfer from BPhe c to baseplate BChl a. These findings suggest that when BChl c in C. tepidum cells is pheophytinized, the product (BPhe c) remains in the chlorosomes and continues to work as a light-harvesting pigment.

Bacteriochlorophylls↗