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Biomedical subjects

T Yamazaki

Publications and source records attributed to T Yamazaki.

At least 235 records · Page 13Linked to original sources
PubMed1999

Is the difference in alpha-amylase activity in the strains of Drosophila melanogaster with different allozymes due to transcriptional or posttranscriptional control?

The alpha-amylase in Drosophila melanogaster is a highly polymorphic enzyme, at both the allozyme level and the specific activity level. This enzyme changes its specific activity drastically depending on both food conditions and developmental stages, and it has been suggested that the ability to change its activity depending on the source of food has positive correlation with fitness. But the cause of the difference of specific activity among strains and food compositions is not known. In order to investigate the cause of these differences, we measured both the specific activity of amylase and the relative amount of Amy mRNA in eight strains of D. melanogaster with different electromorphs, in two food environments and two developmental stages. We found the following. First, the food-dependent activity change is regulated at the transcription level. Second, there was a significant correlation between specific activity and mRNA level among strains. So 80 to 90% of the specific activity difference can be explained by differences in the level of mRNAs, but the remaining part cannot. Finally, there were significant differences in specific activity per mRNA both among strains and between developmental stages. This suggests that there are differences in the catalytic efficiency of each allozyme, strain- or stage-specific translation rate, enzyme stability, or differential use of two Amy loci.

Animals↗
PubMed1999

Evolution of the amylase isozymes in the Drosophila melanogaster species subgroup.

The relationship between the net charge of molecules and their mobility on electrophoresis was analyzed for Drosophila alpha-amylases. Most of the differences in electrophoretic mobility, 98.2%, can be explained by the charge state. Therefore five reference amino acid sites, which are informative residues for charge differences among amylase isozymes, were considered for the evolution of the isozymes in Drosophila melanogaster. The amylase isozymes in D. melanogaster can be classified into three groups, I (AMY1, AMY2, and AMY3-A), II (AMY3-B and AMY4), and III (AMY5, AMY6-A, and AMY6-B), based on the differences in the reference sites. The most primitive amylase in D. melanogaster was found to belong to Group I, most likely the AMY2 isozyme. Groups II and III could have been derived from Group I. These results were confirmed by the analysis of 38 amino acid sites with charge differences in Drosophila.

Amino Acid Sequence↗
PubMed1999

Role of tissue angiotensin II in myocardial remodelling induced by mechanical stress.

In an in vivo study, spontaneously hypertensive rats (SHR) were treated with an angiotensin II (Ang II) type 1 receptor antagonist of candesartan or hydralazine. Untreated SHR progressively developed severe hypertension, and treatment with candesartan or hydralazine decreased blood pressure. Candesartan reduced left ventricular (LV) weight, LV wall thickness, transverse myocyte diameter, the relative amount of V3 myosin heavy chain, and interstitial fibrosis, while treatment with hydralazine slightly prevented an increase in LV wall thickness, but did not exert a significant reduction on other parameters. In an in vitro study, neonatal rat cardiomyocytes were cultured on deformable silicone dishes. Stretching cardiomyocytes activated second messengers such as protein kinase C, Raf-1 kinase, and mitogen-activated protein (MAP) kinase, increasing protein synthesis, enhancing endothelin (ET)-1 release, activating the Na+/H+ ion exchanger. Moreover, pretreatment with candesartan diminished an increase in phenylalanine incorporation, MAP kinase activity, and c-fos gene expression induced by the stretching of cardiomyocytes. This suggests that the cardiac renin-angiotensin system is linked to the formation of pressure-overload hypertrophy and that Ang II increases the growth of cardiomyocytes by an autocrine mechanism. Finally, we examined the signalling pathways leading to MAP kinase activation both in cardiac myocytes and in cardiac fibroblasts. Ang II-evoked signal transduction pathways differed between cell types. In cardiac fibroblasts, Ang II activated MAP kinase through a pathway including the Gbetagamma subunit of Gi protein, Src, Shc, Grb2, and Ras, while Gq and protein kinase C were important in cardiac myocytes.

Angiotensin II↗
PubMed1999

A case of anaplastic large cell (Ki-1) lymphoma of B-cell phenotype, occurring in Waldenström's macroglobulinemia.

A case of anaplastic large cell (Ki-1) lymphoma of B-cell lineage occurred in a 59-year-old male with Waldenström's macroglobulinemia. Immunostaining of the lymphoma cells showed sporadic positivity for IgM and occasional positivity for kappa chain. This immunoglobulin specificity is the same as that of plasmacytoid lymphocytes in the bone marrow; therefore anaplastic transformation of Waldenström's macroglobulinemia was strongly suggested. This seems to be the first reported case of anaplastic large cell lymphoma, confirmed by CD30 expression, arising in Waldenström's macroglobulinemia.

Antigens, CD20↗
PubMed1999

Risk factors for the development of Escherichia coli O157:H7 associated with hemolytic uremic syndrome.

Verotoxin-producing Escherichia coli (VTEC) O157:H7 is a major cause of hemorrhagic colitis that is often associated with the development of hemolytic uremic syndrome (HUS). In July, 1996, a severe mass outbreak of VTEC O157 infection occurred in Sakai city, Osaka. The present study investigates the risk factors which may contribute to the development of HUS in the early stages of the VTEC O157 infection. There was no significant difference between HUS-developed and non-HUS-developed groups with respect to sex, age, rates of clinical manifestations, such as fever, abdominal pain and bloody stool, use of anti-diarrheal agents, anti-motility agents, and/or antibiotic agents, and serum sodium concentrations at the early stage of VTEC O157 infection. Thus, these factors did not appear to be risk factors associated with the development of HUS. In contrast, leukocyte counts and C-reactive protein levels in the early stage of VTEC O157 infection were significantly higher in the HUS-developed group (P < 0.001), suggesting that these are risk factors associated with the development of HUS.

Bacterial Toxins↗
PubMed1999

Characterization of ureteral lesions associated with impacted stones.

BACKGROUND: Few studies have addressed the various types of ureteral lesions apparent in patients treated for ureteral stones, especially in those with impacted stones. Macroscopic and microscopic analyses of ureteral lesions associated with impacted stones were therefore undertaken. METHODS: From May 1994 to October 1996, 36 patients with ureteral stones, 21 of whom showed stone impaction, were treated with transurethral ureterolithotripsy. After ureteroscopic examination, biopsied specimens were obtained from six patients with impacted stones and were examined microscopically by conventional hematoxylin and eosin staining. RESULTS: Ureteroscopy revealed two types of mucosal lesions in the patients with impacted stones: Type 1 lesions were defined as edematous or cystic hemispheric lesions and occurred in 18 patients, whereas type 2 lesions had a villous appearance and were present in three patients. Microscopically, type 1 lesions appeared as submucosal edema without specific findings, whereas type 2 lesions appeared as columnar mesenchymal tissue coated with several layers of transitional epithelium. With regard to factors that might contribute to lesion formation, duration of stone presence was significantly greater for patients with impacted stones than for those with-non-impacted stones. However, no differences in such parameters were apparent between patients with type 1 lesions and those with type 2 lesions. CONCLUSIONS: Two types of ureteral lesions associated with impacted stones were confirmed microscopically. The duration of stone presence is a potential contributing factor in the development of ureteral lesions, but factors that determine the type of ureteral lesion remain unclear.

Adult↗
PubMed1999

Intermolecular contacts between the lambda-Cro repressor and the operator DNA characterized by nuclear magnetic resonance spectroscopy.

The specific interaction between lambda phage Cro repressor and the DNA fragment bearing the consensus sequence of operators has been studied using nuclear magnetic resonance (NMR). Using both 15N- and 13C/15N- labeled lambda-Cro in complex with unlabeled DNA, chemical shift assignments of the lambda-Cro-DNA complex were obtained using heteronuclear NMR experiments. Inter-molecular contacts between the protein and DNA were identified using heteronuclear filtered NOESY experiments. The inter-molecular contacts were supplemented with intra-protein and intra-DNA NOE constraints to dock lambda-Cro to the bent B-form DNA using restrained molecular dynamics. The structure of one of the subunits of lambda-Cro in the complex is essentially the same as that of the unbound form. In the complex, inter-molecular NOEs were observed between the "helix-turn-helix" region comprising the alpha2 and alpha3 helices of the lambda-Cro protein and the major groove of the DNA. The methyl group of Thr17 forms a hydrophobic contact with the methyl group of the thymine at base pair 1 in the DNA, and Val25 and Ala29 make hydrophobic contacts with the methyl group of the thymine at base pair 5. The presence and the absence of these contacts can explain the difference in the affinity of lambda-Cro to several variants of the operator sequence.

Carbon Isotopes↗
PubMed1999

The guanosine binding mechanism of the Tetrahymena group I intron.

The Tetrahymena group I intron catalyzes self-splicing through two consecutive transesterification reactions, using a single guanosine-binding site (GBS). In this study, we constructed a model RNA that contains the GBS and a conserved guanosine nucleotide at the 3'-terminus of the intron (omegaG). We determined by NMR the solution structure of this model RNA, and revealed the guanosine binding mechanism of the group I intron. The G22 residue, corresponding to omegaG, participates in a base triple, G22 xx G3 x C12, hydrogen-bonding to the major groove edge of the Watson-Crick G3 x C12 pair. The G22 residue also interacts with A2, which is semi-conserved in all sequenced group I introns.

Animals↗
PubMed1999

Cloning of the RNA polymerase alpha subunit gene from Thermus thermophilus HB8 and characterization of the protein.

The region containing the RNA polymerase alpha subunit (RNAPalpha) gene (rpoA) and the ribosomal protein genes of a thermophilic eubacterial strain, Thermus thermophilus (Tt) HB8, was cloned from a genomic DNA library by Southern hybridization. The gene order in this region is rpl36-rps13-rps11-rps4-rpoA-rpl17, which is identical to that in some other eubacteria. The rpoA gene encodes a 315 amino acid residue protein with a molecular weight of 35,013, the amino acid sequence showing 42% identity to that of Escherichia coli (Ec). From the results of comparison of the amino acid sequence and the predicted secondary structure of the C-terminal domain of Tt RNAPalpha (Tt alphaCTD) with those of Ec, the overall folding is expected to be similar. However, amino acid residues Asn268 and Cys269 in Ec alphaCTD, which are essential for its interaction with DNA or regulatory proteins, were replaced by His and Ser, respectively, in Tt alphaCTD. By means of a T7-based expression system in Ec cells, Tt RNAPalpha was overexpressed and purified. The high thermostability of Tt RNAPalpha was demonstrated by the CD spectra.

Amino Acid Sequence↗
PubMed1999

EPR studies on the photo-induced intermediates of ferric NO complexes of rat neuronal nitric oxide synthase trapped at low temperature.

Rat neuronal nitric oxide synthase (nNOS) was expressed in Escherichia coli and purified. Although the nitric oxide (NO) complex of the ferric heme was EPR-silent, photo-illumination at 5 K to the NO complex of the ferric nNOS in the substrate-free form produced a new high spin EPR signal similar to that of the ferric heme of N(omega)-nitro-L-arginine-bound nNOS, suggesting that the photo-dissociated NO might move away from the heme. Low photo-dissociability of NO in this complex indicated less restricted movement of the dissociated NO in the distal region of the heme, which might result in the rapid rebinding of the NO to the ferric heme at 5 K. In the presence of substrate L-arginine, derivatives, or product L-citrulline, the photo-products from the ferric NO complexes exhibited large novel EPR signals with a spin-coupled interaction between the ferric heme (S = 5/2) and the photolyzed NO (S = 1/2), suggesting a stereochemically restricted interaction between the photo-dissociated NO and the guanidino- or the ureido-group of the substrate analogues at the distal heme region of nNOS. The photo-product from the NO complex produced from citrulline-bound nNOS might be the same intermediate species as that formed in the last step of the catalytic cycle.

Animals↗
PubMed1999

[Non-Hodgkin's lymphoma complicated by recurrent intractable generalized herpes zoster responsive to long-term acyclovir therapy].

A 34-year-old male with a history of chickenpox developed primary abdominal non-Hodgkin's lymphoma (diagnosed in August 1995). Treatment with cyclophosphamide, doxorubicin, vincristine, and prednisolone achieved a partial remission. In July 1996, the disease recurred, and the patient received chemotherapy with carboplatine, etoposide, mitoxantrone, and prednisolone, but no response was noted. Involvement of the central nervous system and meninges was diagnosed on September 12, 1997. Blast cells were detected in the peripheral blood on September 26. Based on these findings, he was diagnosed as having leukemia. On September 27, painless vesicles developed on the left gluteal region. On October 13, the patient was hospitalized because the vesicles had spread over his entire body. Pathologic examination of the roofs of the blisters showed masses of inclusion bodies. Based on this, a diagnosis of varicella-zoster infection was made. Treatment with acyclovir (750 mg/day) for seven days failed to form crusts. New vesicles developed after the drug was discontinued, but crusts formed after acyclovir therapy was resumed. He died of interstitial pneumonia on December 21. Autopsy could not be performed. Histopathologic examination of pulmonary tissue obtained by necropsy did not reveal the presence of inclusion bodies characteristic of herpes simplex or varicella-zoster infection. Varicella-zoster virus (VZV) antigen was negative by an immunochemical staining method using monoclonal antibodies against VZV. Continuous long-term administration of acyclovir has been reported to be effective for non-Hodgkin's lymphoma complicated by recurrent intractable herpes zoster.

Acyclovir↗
PubMed1999

sn-glycerol-1-phosphate-forming activities in Archaea: separation of archaeal phospholipid biosynthesis and glycerol catabolism by glycerophosphate enantiomers.

In Methanobacterium thermoautotrophicum, sn-glycerol-1-phosphate (G-1-P) dehydrogenase is responsible for the formation of the Archaea-specific backbone of phospholipids, G-1-P, from dihydroxyacetonephosphate (DHAP). The possible G-1-P-forming activities were surveyed in cell-free extracts of six species of Archaea. All the archaeal cell-free homogenates tested revealed the ability to form G-1-P from DHAP. In addition, activities of G-3-P-forming glycerol kinase and G-3-P dehydrogenase were also detected in four heterotrophic archaea, while glycerol kinase activity was not detected in two autotrophic methanogens. These results show that G-1-P is produced from DHAP by G-1-P dehydrogenase in a wide variety of archaea while exogenous glycerol is catabolized via G-3-P.

Dihydroxyacetone Phosphate↗
PubMed1999

Epidemiology of visceral mycoses: analysis of data in annual of the pathological autopsy cases in Japan.

The data on visceral mycoses that had been reported in the Annual of the Pathological Autopsy Cases in Japan from 1969 to 1994 by the Japanese Society of Pathology were analyzed epidemiologically. The frequency of visceral mycoses among the annual total number of pathological autopsy cases increased noticeably from 1.60% in 1969 to a peak of 4.66% in 1990. Among them, the incidences of candidiasis and aspergillosis increased the most. After 1990, however, the frequency of visceral mycoses decreased gradually. Until 1989, the predominant causative agent was Candida, followed in order by Aspergillus and Cryptococcus. Although the rate of candidiasis decreased by degrees from 1990, the rate of aspergillosis increased up to and then surpassed that of candidiasis in 1991. Leukemia was the major disease underlying the visceral mycoses, followed by solid cancers and other blood and hematopoietic system diseases. Severe mycotic infection has increased over the reported 25-year period, from 6.6% of the total visceral mycosis cases in 1969 to 71% in 1994. The reasons for this decrease of candidiasis combined with an increase of aspergillosis or of severe mycotic infection might be that (i) nonsevere (not disseminated) infections were excluded from the case totals, since they have become controllable by antifungal drugs such as fluconazole, but (ii) the available antifungal drugs were not efficacious against severe infections such as pulmonary aspergillosis, and (iii) the number of patients living longer in an immunocompromised state had increased because of developments in chemotherapy and progress in medical care.

AIDS-Related Opportunistic Infections↗
PubMed1999

Pregnenolone, pregnenolone sulfate, and cytochrome P450 side-chain cleavage enzyme in the amphibian brain and their seasonal changes.

To clarify whether the amphibian brain synthesizes de novo neurosteroids, we examined pregnenolone, pregnenolone sulfate ester, and cytochrome P450 side-chain cleavage enzyme (cytochrome P450scc), an enzyme converting cholesterol to pregnenolone, using amphibians. Pregnenolone and its sulfate ester in the brain, gonad, and plasma of Xenopus laevis were measured by a specific pregnenolone RIA. The concentrations of these two steroids in the female brain were significantly larger than those in the ovary and plasma. A similar tendency was evident in the male. In both sexes, pregnenolone and its sulfate ester were concentrated more highly in the cerebellum than in the telencephalon, diencephalon, or midbrain. An immunoreactive protein band of electrophoretic mobility in the proximity of bovine adrenal P450scc was detected in the Xenopus brain as well as the testis by Western blot analysis. Immunohistochemical analysis indicated that Purkinje cells in the Xenopus cerebellum were specifically immunostained with the P450scc antibody. P450scc-like immunoreactive cells were further found in several telencephalic and diencephalic regions, such as the pallium mediale and nucleus preopticus, in the Xenopus brain. A similar localization of P450scc-like immunoreactive cells was evident in Rana nigromaculata, a seasonally breeding amphibian. In the present study, seasonal changes in pregnenolone and its sulfate ester were further examined as a possible physiological change using R. nigromaculata. In both sexes, pregnenolone concentrations in the brain were almost constant during the seasonally breeding cycle. In contrast, the pregnenolone sulfate concentration in the brain was significantly lower in the hibernating quiescent phase and higher in the breeding and postbreeding active phases, independent of the plasma steroid level. These results taken together suggest that the amphibian brain possesses steroidogenic enzyme P450scc and produces pregnenolone and its sulfate ester. Pregnenolone sulfate may function well during the breeding and postbreeding active phases of the year in the seasonal breeder.

Amphibians↗
PubMed1999

Enzymatic characterization of human cytosolic sulfotransferases; identification of ST1B2 as a thyroid hormone sulfotransferase.

Sulfotransferases (ST) are contained as multiple forms in human tissues with overlapping substrate specificities. To identify a form which contributes to the metabolism of 3, 3',5-triiodothyronine (T3), the functional properties of human STs were compared using recombinant STs, ST1A3, ST1A5, ST1B2, ST1E4 and ST2A3. ST1B2 showed a high affinity (Km 46.2 microM) for T3 sulfation, whereas ST1A3, ST1A5, ST1E4 and ST2A3 showed high affinities to p-nitrophenol (Km 0.4 microM), dopamine (Km 7.1 microM), beta-estradiol (Km 0.3 microM) and dehydroepiandrosterone (Km 3.3 microM), respectively. In Western blotting using antibodies raised against an individual ST, hepatic absolute amounts of these STs were determined. The content of ST1B2 in human liver correlated well with T3 sulfation activities in human liver (r=0.96). These results indicate that ST1B2 is biochemically distinct from other forms of ST, and is involved in the metabolism of T3 in human. In addition, studies of thermal stability and 2,6-dichloro-4-nitrophenol (DCNP) inhibition showed that ST1B2 was thermostable and more DCNP resistant than other forms of ST. Affinities for a co-factor, phosphoadenosine 5'-phosphosulfate, also differed 9-fold among 5 different forms of ST.

Cytosol↗
PubMed1999

HPLC profile analysis of hepatoprotective oleanene-glucuronides in Puerariae Flos.

In order to confirm the constitution of hepatoprotective oleanene glucuronide (OG), HPLC profile analyses of the total OG fractions of both Puerariae Thomsonii Flos (the flowers of Pueraria thomsonii) and Puerariae Lobatae Flos (the flowers of P. lobata) were performed. No remarkable difference in the HPLC profiles with respect to OGs in the flowers was shown, in contrast to those of the roots. By repeated chromatography of the total OG fraction of Puerariae Thomsonii Flos, soyasaponin I (1), kaikasaponin III (2) and kakkasaponin I (3), which had been already isolated from Puerariae Lobatae Flos, were obtained. The hepatoprotective activity of 2 towards immunologically induced liver injury was significantly more effective than that of 1. This information supported previously obtained structure-hepatoprotective relationship data which was measured on another model. The structure-activity relationship information which suggested that the hydroxymethyl group of the galactosyl unit would enhance the hepatoprotective activity was also substantiated.

Animals↗
PubMed1999

Hypertrophic responses of cardiomyocytes induced by endothelin-1 through the protein kinase C-dependent but Src and Ras-independent pathways.

We have previously shown that endothelin-1 (ET-1) modulates mechanical stretch-induced hypertrophic responses such as extracellular signal-regulated protein kinase (ERK) activation in cardiac myocytes. This study was undertaken to elucidate the ET-1-evoked signal transduction pathways leading to ERK activation. ET-1 was added to cultured cardiac myocytes of neonatal rats with or without a variety of inhibitors. ET-1 activated ERKs, which were followed by an increase in protein synthesis, and inhibition of protein kinase C activities by calphostin C completely suppressed the ET-1-induced ERK activation. We next examined whether tyrosine kinases or Ras are involved in ET-1-induced signaling pathways in cardiomyocytes. Pretreatment with a receptor tyrosine kinase inhibitor did not attenuate ET-1-induced activation of ERKs. Also, co-transfection of the dominant-negative mutant of Ras or active mutant of C-terminal Src kinase, a tyrosine kinase which inhibits Src family tyrosine kinases, with hemagglutinin-tagged ERK2 had no effects on ET-1-induced ERK2 activation. On the other hand, blockade of Raf-1 kinase function by overexpression of the dominant-negative mutant of Raf-1 kinase completely inhibited ET-1-induced ERK2 activation. These results suggest that protein kinase C and Raf-1 kinase, but not Src or Ras, are critical to ET-1-induced ERK activation in cardiac myocytes.

Amino Acids↗