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Biomedical subjects

K Nishikawa

Publications and source records attributed to K Nishikawa.

At least 199 records · Page 11Linked to original sources
PubMed1997

Evaluation of XD/A Plus and ST8G films for cephalometric radiography with Grenex G8 and BH-III screens.

OBJECTIVES: Sensitometric properties, clinical image quality, and patient dose requirements are important considerations when selecting film for cephalometrics. Two recently released films, XD/A Plus and ST 8G green sensitive films, were studied. METHODS: The films were each combined with Grenex G8 (Fuji Medical) green-fluorescing matched and BH-III (Kasei Optonix) blue-fluorescing mismatched intensifying screens. The density response and resolution for each screen-film combination were evaluated by use of the characteristic curve and modulation transfer function. The kilovoltage settings providing clinically acceptable images were assessed individually by 12 observers. Clinically acceptable images for each combination were also compared, and the skin entrance doses in the temporomandibular joint region were determined. RESULTS: The average contrast at the most effective density range was found to be slightly higher for the BH-III group than for the G8 group. The modulation transfer function for the BH-III group was inferior to that for the G8 screens. There were no significant differences in diagnostically acceptable image quality among the four combinations; nevertheless the BH-III screen group required two to three times more exposure than the G8 screen group. CONCLUSIONS: XD/A Plus and ST8G films provide acceptable image detail for cephalometrics. To minimize the patient dose they should be used with green-emitting screens.

Analysis of Variance↗
PubMed1997

Requirement of fibroblast growth factor signaling for regeneration of epiphyseal morphology in rabbit full-thickness defects of articular cartilage.

The involvement of fibroblast growth factor-2 (FGF-2) during the repair process in rabbit full-thickness defects of articular cartilage was studied. Fibroblast growth factor-2 (50 pg/h) was administered for 2 weeks in a 5 mm defect of articular cartilage, which is large enough not to repair spontaneously. The administration of FGF-2 resulted in the regeneration of the articular cartilage and the subchondral bone within 8 weeks. In these defects, undifferentiated mesenchymal cells initiated chondrogenic differentiation coupled with replacement by subchondral bone, resulting in the resurfacing of the defects with hyaline cartilage and the recovery of subchondral bone up to the original bone-articular cartilage junction. In rabbits, full-thickness defects are capable of regenerating articular cartilage as long as the defect size is limited to < or = 3 mm in diameter. In the defects, strong immunoreactivity for FGF-2 was observed in the granulation tissue filling the defects in the early stage of repair, in association with the expression of FGF-2 mRNA shown by in situ hybridization. Once the undifferentiated mesenchymal cells had differentiated into chondrocytes, both the immunoreactivity and the in situ hybridization signal declined significantly. Upon the local administration of a monoclonal antibody against FGF-2 (bFM-1, 50 ng/h), the defects were filled with fibrous tissue and no resurfacing hyaline cartilage was formed. Compared to the non-treated defects, there were marked increases in FGF-2 immunoreactivity and the overexpression of FGF-2 mRNA in the reparative tissue in the bFM-1-treated defects. This rebound phenomenon indicates that the autocrine FGF-2 signaling is critically important for the regeneration of articular cartilage.

3T3 Cells↗
PubMed1997

Prediction of protein secondary structure using the 3D-1D compatibility algorithm.

A new method for the prediction of protein secondary structure is proposed, which relies totally on the global aspect of a protein. The prediction scheme is as follows. A structural library is first scanned with a query sequence by the 3D-1D compatibility method developed before. All the structures examined are sorted with the compatibility score and the top 50 in the list are picked out. Then, all the known secondary structures of the 50 proteins are globally aligned against the query sequence, according to the 3D-1D alignments. Prediction of either alpha helix, beta strand or coil is made by taking the majority among the observations at each residue site. Besides 325 proteins in the structural library, 77 proteins were selected from the latest release of the Brookhaven Protein Data Bank, and they were divided into three data sets. Data set 1 was used as a training set for which several adjustable parameters in the method were optimized. Then, the final form of the method was applied to a testing set (data set 2) which contained proteins of chain length < or = 400 residues. The average prediction accuracy was as high as 69% in the three-state assessment of alpha, beta and coil. On the other hand, data set 3 contains only those proteins of length > 400 residues, for which the present method would not work properly because of the size effect inherent in the 3D-1D compatibility method. The proteins in data set 3 were, therefore, subdivided into constituent domains (data set 4) before being fed into the prediction program. The prediction accuracy for data set 4 was 66% on average, a few percent lower than that for data set 2. Possible causes for this discrepancy are discussed.

Algorithms↗
PubMed1997

Evolution of pulmonate gastropod mitochondrial genomes: comparisons of gene organizations of Euhadra, Cepaea and Albinaria and implications of unusual tRNA secondary structures.

Complete gene organizations of the mitochondrial genomes of three pulmonate gastropods, Euhadra herklotsi, Cepaea nemoralis and Albinaria coerulea, permit comparisons of their gene organizations. Euhadra and Cepaea are classified in the same superfamily, Helicoidea, yet they show several differences in the order of tRNA and protein coding genes. Albinaria is distantly related to the other two genera but shares the same gene order in one part of its mitochondrial genome with Euhadra and in another part with Cepaea. Despite their small size (14.1-14.5 kbp), these snail mtDNAs encode 13 protein genes, two rRNA genes and at least 22 tRNA genes. These genomes exhibit several unusual or unique features compared to other published metazoan mitochondrial genomes, including those of other molluscs. Several tRNAs predicted from the DNA sequences possess bizarre structures lacking either the T stem or the D stem, similar to the situation seen in nematode mt-tRNAs. The acceptor stems of many tRNAs show a considerable number of mismatched basepairs, indicating that the RNA editing process recently demonstrated in Euhadra is widespread in the pulmonate gastropods. Strong selection acting on mitochondrial genomes of these animals would have resulted in frequent occurrence of the mismatched basepairs in regions of overlapping genes.

Animals↗
PubMed1997

Assignment of imino proton signals of G-C base pairs and magnesium ion binding: an NMR study of bovine mitochondrial tRNA(SerGCU) lacking the entire D arm.

The mammalian mitochondrial tRNA(SerGCU) (mt tRNA[SerGCU]) has a unique structure in that it lacks the whole D arm. To elucidate its higher-order structure, we synthesized unmodified bovine mt tRNA(SerGCU) using T7 RNA polymerase and measured its 1H-NMR spectrum in the imino proton region. Although the imino proton signals heavily overlapped, we succeeded in assigning all the seven imino proton signals of the G-C base pairs by a combination of base replacement and 15N-labeling of the G residues of a whole tRNA molecule or of the 3'-half fragment. The results indicate that the tRNA possesses the secondary structure that has been supposed on the basis of biochemical studies. Analysis of the effect of the magnesium concentration on the G-C pairs suggests that the acceptor and T stems do not form a co-axial helix, and that the core region of the tRNA does not interact with magnesium ions. These features are significantly different from those of canonical tRNAs. Despite this, it is very likely that the tRNA as a whole takes a nearly L-shape tertiary structure.

Animals↗
PubMed1997

Assessment of pseudo-energy potentials by the best-five test: a new use of the three-dimensional profiles of proteins.

We propose a new assessment, called the best-five test, for the pseudo-energy potential empirically derived from the protein structural database. The object of the test is the three-dimensional (3D) profiles of proteins, which are directly connected to the pseudo-energy potentials. In the 3D profile, the fitness of each amino acid type is ranked at each residue site of a protein. A site whose native residue type is ranked within the best-five out of 20 amino acids is regarded as satisfactory and the ratio of the satisfactory sites over all the sites of all the proteins examined is indicative of the efficiency of the pseudo-energy potential employed. We applied the test to our potential function consisting of four terms; side-chain packing, hydration, backbone hydrogen-bonding and local conformation, by setting various kinds of definitions for each term. Through this test, the validity of the minus average operation is confirmed, where the energy level of potential functions is adjusted by referring to the random-environmental state of the proteins. Especially in the side-chain packing function, the success ratio increases from about 30 to 50% with this operation. Failure without the operation is ascribed to bulky hydrophobic residues, which almost always occupy higher ranking positions in the 3D profile table. A maximum success ratio of 55.6% was attained with the final potential set consisting of the above four terms. The efficiency of the final set was further checked in the fold-recognition test for distantly related proteins. The best-five test is a new use of the 3D profile table for assessing the ability of the pseudo-energy potentials.

Amino Acid Sequence↗
PubMed1997

Studies on gastric mucosal cell injury induced by Helicobacter pylori.

The cause of gastric cell injury induced by Helicobacter pylori was investigated in vitro using gastric mucosal cells derived from male Japanese white rabbits. To evaluate the contribution of the potent urease activity of H. pylori to gastric mucosal cell injury, the supernatant of the H. pylori bacterial pellet, solubilized with N-octyl-glucoside, was added to the gastric mucosal cell suspension. Cell injury was assessed by lactate dehydrogenase (LDH) release into the extracellular fluid. Treatment of cells with H. pylori extracts together with urea resulted in high levels of LDH release, suggesting definite gastric mucosal cell injury, and elevation of ammonia concentration was also observed. In contrast, incubation with H. pylori extracts alone or urea solution alone did not result in increased LDH release or elevated ammonia concentrations. The degree of LDH release from gastric mucosal cells due to H. pylori extracts in the presence of urea was similar to that induced by administration of the same amount of exogenous ammonia. The addition of acetohydroxamic acid, a potent specific urease inhibitor, remarkably inhibited ammonia production, the elevation of pH of extracellular fluid, and LDH release in a dose-dependent manner. These results suggest that ammonia produced by potent urease activity of H. pylori in the presence of urea plays an important role in the pathogenesis of gastric mucosal cell injury.

Ammonia↗
PubMed1997

Bupivacaine does not suppress cardiac sympathetic nerve activity during halothane anesthesia in the cat.

BACKGROUND: The finding that i.v. lidocaine suppresses cardiac sympathetic nerve activity during 1 MAC halothane, but not during 2 MAC or 3 MAC halothane, suggests that the neurally mediated circulatory effects of i.v. local anesthetics may vary with background autonomic activity. This study aimed to compare the effects of i.v. lidocaine and bupivacaine on cardiac sympathetic nerve activity (CSNA) during normal and high levels of CSNA. METHODS: Cats were anesthetized with halothane and allocated to three groups. In groups I-L and I-B, sympathetic hyperactivity was induced by electrical stimulation of the posterior hypothalamus. CSNA, heart rate and mean arterial pressure were then measured before and after administration of lidocaine 2 mg.kg BW-1 i.v. (Group I-L, n = 7) or bupivacaine 0.5 mg.kg BW-1 i.v. (Group I-B, n = 7) during 1% halothane anesthesia. In Group II (n = 7), following administration of bupivacaine 0.5 mg.kg BW-1 i.v., CSNA, sinus cycle length (SCL), and subintervals of atrioventricular conduction time (A-H, H-V, and H-S) at pacing were measured during 0.8%, 1.6% and 2.4% halothane anesthesia without sympathetic hyperactivity. RESULTS: Lidocaine suppressed CSNA hyperactivity and tachycardia significantly in Group I-L, but bupivacaine did not do so in Group I-B. In Group II, bupivacaine did not affect CSNA at any concentrations of halothane, but lengthened SCL, A-H, H-V and H-S intervals significantly at each concentration of halothane. CONCLUSIONS: We conclude that i.v. bupivacaine, unlike i.v. lidocaine, does not suppress CSNA during either normal or high CSNA under halothane anesthesia although i.v. bupivacaine has stronger depressive effects on cardiac conduction than does i.v. lidocaine during deep halothane anesthesia.

Anesthesia, General↗
PubMed1997

Human urinary macrophage colony-stimulating factor reduces the incidence and duration of febrile neutropenia and shortens the period required to finish three courses of intensive consolidation therapy in acute myeloid leukemia: a double-blind controlled study.

PURPOSE: To determine whether macrophage colony-stimulating factor (M-CSF) reduces the incidence and duration of febrile neutropenia during three courses of intensive consolidation therapy and whether it shortens time to complete consolidation therapy. PATIENTS AND METHODS: In 198 adult patients with acute myeloid leukemia (AML) in complete remission (CR), M-CSF (8 x 10(6) U/d) or placebo was administered from 1 day after the end of each consolidation chemotherapy for 14 days. RESULTS: The duration and incidence of febrile neutropenia was significantly reduced by 34% (P = .00285) and 17% (P = .02065), respectively, in 88 assessable patients in the M-CSF group compared with those in 94 assessable patients in the placebo group. Patients in the M-CSF group had 565 days and 133 episodes of febrile neutropenia during 7,901 days at risk, while patients in the placebo group had 977 days and 185 episodes during 9,077 days at risk. The median period required to finish the three courses of consolidation therapy was 93 days in the M-CSF group, which was significantly shorter than 110 days in placebo group (P = .0050). In the M-CSF group, the recovery of neutrophils and platelets was significantly faster (P = .0348 and P = 0.0364, respectively), the administration of systemic antimicrobial agents tended to be less (P = .0839), and the frequency of platelet transfusion (P = .0259) and the total volume of transfused platelets (P = .0292) were significantly less. However, there was no significant difference in the disease-free survival. CONCLUSION: M-CSF significantly reduced the incidence and duration of febrile neutropenia during the intensive consolidation therapy, and shortened the time to complete consolidation chemotherapy in AML.

Acute Disease↗
PubMed1997

Activation of phorbol ester responsive form of protein kinase C zeta in association with Ca(2+)-induced differentiation of primary cultured mouse epidermal cells.

In primary cultured mouse epidermal cells, protein kinase C (PKC) zeta consists of multiple forms: a low salt-eluted PKC zeta (1-PKC zeta, 79 and 85 kDa) and a high salt-eluted PKC zeta (h-PKC zeta, 79 and 85 kDa) by anion-exchange column chromatography (K. Nishikawa et al., Cell. Signal. 7, 491-504, 1995). In the present study, PKC isozyme-specific responses during terminal differentiation of epidermal cells, which were induced by the increase of Ca(2+)-concentration in culture medium, were examined. After 24 hr-treatment with 1.8 mM Ca2+, 79-kDa 1-PKC zeta in the particulate fraction was apparently shifted to the 85-kDa form. The phosphatidylserine-dependent kinase activity of this 1-PKC zeta was increased in association with the shift. These results suggest the pivotal role of 1-PKC zeta in the particulate fraction in the Ca(2+)-induced epidermal cell differentiation processes.

Amino Acid Sequence↗
PubMed1997

Purification of characterization of soybean allergen Gly m Bd 28K.

At least 15 allergenic proteins have been found in soybean using the sera of soybean-sensitive patients with atopic dermatitis [T. Ogawa et al., J. Nutr. Sci. Vitaminol., 35, 555-565 (1991)]. In the present study, a monoclonal antibody (mAb) against Gly m Bd 28K, one of the major allergens of soybean, was prepared, and Gly m Bd 28K was purified from defatted soybean flakes by five purification steps, including immunoaffinity chromatography with the mAb as a ligand. The purified allergen was found to be a glycoprotein with a molecular mass of 26 kDa. During the purification process the allergen was converted to more acidic proteins with the same molecular mass, suggesting that the allergen is unstable. The sugar composition and amino acid sequence of Gly m Bd 28K suggest that the allergen is a new glycoprotein with an Asn-linked sugar moiety. The distribution of the allergen in soybean products was examined by an immunoblotting technique with the mAb.

Allergens↗
PubMed1997

The role of complement in the pathogenesis of tubulointerstitial lesions in rat mesangial proliferative glomerulonephritis.

Persistent proteinuria and tubulointerstitial lesions are important signs of progressive renal disease. The purpose of this study was to assess the role of complement in the development of tubulointerstitial lesions in rats with proteinuria due to primary glomerulonephritis. Mesangial proliferative glomerulonephritis was induced in mononephrectomized rats by intravenous injection of monoclonal antibody (mAb) 1-22-3 (Clin Exp Immunol 102: 181-185, 1995). As early as 24 h after the injection, proteinuria became evident, persisted throughout the observation period, and was associated with mesangial cell proliferation and tubulointerstitial lesions when examined at 7 and 14 d after mAb administration. Deposition of rat C3 and C5b-9 was observed at the luminal surface of proximal tubules and in cellular debris present in the tubular lumen (group I). Rats injected with mAb 1-22-3 and depleted of complement by injections of cobra venom factor starting at day 3 developed glomerulonephritis and proteinuria comparable to rats of group I, but complement deposition in the tubules and the tubulointerstitial lesions were markedly reduced (group II). Rats in group III were injected with mAb and, from day 3, with soluble complement receptor type 1, which became detectable at the luminal surface of proximal tubules and in the urine. Deposition of C5b-9 in tubular cells was not detectable, and the severity of tubulointerstitial lesions was reduced compared with rats in group I. These results indicate that, in this model of primary mesangial proliferative glomerulonephritis with proteinuria, the development of tubulointerstitial lesions is associated with activation of serum complement at the level of tubular brush border, and tubulointerstitial lesions can be reduced by inhibition of complement activity.

Animals↗
PubMed1997

Permeation of organic cations and ammonium through the glutamate receptor channel in Drosophila larval muscle.

The inside-out configuration of the patch-clamp technique was used to study the effects of large organic cations on the single-channel current through the glutamate receptor channel in muscles of Drosophila larvae. Control experiments with symmetrical Na+ showed slightly supra-linear I-V curves. When external Na+ was equiosmolarly replaced with either arginine+ or N-methyl-D-glucamine+ (NMDG+), the reversal potential changed almost according to VNa, suggesting that both these ions are only slightly permeant through the channel. However, both ions strongly reduced the current amplitude in a voltage-dependent manner, the effect being most pronounced for the inward current. Tris+ had similar effects on the Na+ current, although the reversal potential indicated that this ion is somewhat permeant. All of these results could be fitted with a "one-ion" Eyring model for the channel with internal binding sites. The ion-channel dissociation constants for arginine+, NMDG+, and Tris+ were found to be 17, 27, and 23 mM, respectively. In order to acquire evidence for the "one-ion" hypothesis used in the model, I-V data were taken with different mixtures of Na+ and a comparably permeant ion, NH4+. All of the data could be accurately fitted with the results of the Eyring theory for singly occupied channels.

Animals↗
PubMed1997

Protective effects of candesartan cilexetil (TCV-116) against stroke, kidney dysfunction and cardiac hypertrophy in stroke-prone spontaneously hypertensive rats.

The effects of chronic treatment with an angiotensin II receptor antagonist, candesartan cilexetil (TCV-116, 0.1, 1, 10 mg/kg), and an angiotensin converting enzyme inhibitor, enalapril maleate (enalapril, 10 mg/kg), on the development of end-organ damage were examined in stroke-prone spontaneously hypertensive rats (SHRSP). The control SHRSP developed severe hypertension with stroke signs and increased urinary protein excretion. TCV-116 (0.1 mg/kg) reduced the stroke incidence and urinary protein excretion without affecting the blood pressure. TCV-116 (1 and 10 mg/kg) and enalapril reduced blood pressure, the stroke incidence, the urinary indices and left ventricular weight. Circulating renin-angiotensin system (RAS) and renal renin mRNA expression were significantly accelerated or tended to be accelerated in the control SHRSP with end-organ damages. A low dose of TCV-116 tended to reduce the RAS indices in plasma by improving the damages, whereas a high dose (10 mg/kg) increased them by the reflexes with blocking RAS. The present results indicate that chronic All blockade reduces the increase in blood pressure, end-organ damages and RAS related to the damages in SHRSP.

Angiotensin Receptor Antagonists↗
PubMed1997

[Prognostic implication of DNA contents on long-term outcome of childhood acute lymphoblastic leukemia].

Prognostic value of cellular DNA content was evaluated in 189 children with acute lymphoblastic leukemia. Treatment outcome of the three different DNA index (DI) groups (Group A, DI = 1.0 vs. Group B, DI 1.01-1.15 vs. Group C, DI > or = 1.16) was compared between the two treatment risk groups (standard-risk and high-risk groups) stratified by the initial leukocyte count and age. In the standard-risk group, these groups had 10-year event free survival (EFS) rate (SE) of 62% (6%), 40% (21%) and 87% (6%), respectively (p < 0.05). In the high risk group, they had 10-year EFS rate of 30% (5%), 33% (27%) and 60% (19%), respectively (p < 0.01). Use of the DI, leukocyte count and age may be sufficient to distinguish the patients with an extremely low risk of failing to the standard ALL therapy from the patients with a relatively high-risk of treatment failure.

Child↗