Search PubMed⌕ Search

Biomedical subjects

K Nitta

Publications and source records attributed to K Nitta.

At least 55 records · Page 3Linked to original sources
PubMed2001

Evaluation of prognostic factors for myeloperoxidase anti-neutrophil cytoplasmic antibody- (MPO-ANCA) associated glomerulonephritis.

AIMS: To identify prognostic factors for myeloperoxidase anti-neutrophil cytoplasmic antibody- (MPO-ANCA) associated glomerulonephritis. MATERIALS: We analyzed the relations between the clinical and histological features of MPO-ANCA-associated glomerulonephritis and clinical outcome in 14 patients with the disease. The patients were divided into two groups: group 1 consisted of 5 patients with progressive deterioration of renal function leading to end-stage renal disease or chronic dialysis, group 2 consisted of 9 patients in whom the initial deterioration of renal function had improved by the time of the final examination. RESULTS: Creatinine clearance at the time of biopsy was significantly lower in group 1 than in group 2, and urinary protein was higher. The mean interval between onset of symptoms and biopsy in both groups was almost the same. Recovery of renal function was correlated with the percentage of global sclerosis, but patients who had severe crescent formation did not always have a poor response to steroid therapy. There was no statistical difference between the two groups in treatment regimens. Four patients required hemodialysis at the time of biopsy (3 in group 1 and 1 in group 2). Plasmapheresis was performed in 5 patients (1 in group 1 and 4 in group 2). CONCLUSIONS: Degree of proteinuria and renal dysfunction are indicators of a poor prognosis in MPO-ANCA-associated glomerulonephritis. Global sclerosis is a histological feature that is an indicator of a poor prognosis, whereas cellular crescent formation is a predictor of a good response to steroid therapy.

Adult↗
PubMed2001

Tubular osteopontin expression in patients with ANCA-associated glomerulonephritis.

OBJECTIVE: To elucidate the role of osteopontin (OPN) in monocyte recruitment in crescentic glomerulonephritis, we investigated immunohistochemical localization of OPN in the kidney and its correlation with clinical and histopathologic parameters in biopsy specimens of patients with myeloperoxidase antineutrophil cytoplasmic autoantibody- (MPO-ANCA) associated glomerulonephritis. METHODS: Twelve patients with MPO-ANCA-associated glomerulonephritis were enrolled in this study. Clinical parameters such as creatinine clearance and urinary protein excretion of each patient were obtained at the time of biopsy. Paraffin-embedded sections were used for immunohistochemical staining using the LSAB method. Five cortical interstitial fields randomly selected at original magnification x 200 were assessed using a computer-assisted color image analyzer. Tubular OPN expression was assessed as the percentage of positive area in the tubulointerstitium. Double immunofluorescent staining using antibodies against OPN and alpha(v)beta3 was performed. RESULTS: In all of the cases studied, OPN was occasionally localized within the glomeruli, and expressed slightly in proximal tubular epithelium and significantly in distal tubular epithelium. Tubular OPN expression tended to be promoted in the interstitium infiltrating by numerous monocytes/macrophages. The extent of tubular OPN expression was positively correlated with serum ANCA titers and urinary OPN concentrations. Enhanced alpha(v)beta3 expression appeared in the distal tubular epithelium expressing OPN. CONCLUSION: These results suggest that inducible expression of OPN and alpha(v)beta3 in the tubular epithelium seems to be associated with interstitial moncyte infiltration and subsequent tubulointerstitial changes in human MPO-ANCA-associated glomerulonephritis.

Adult↗
PubMed2001

[Renal dysfunction and hyperphosphatemia--role of hyperphosphatemia on vascular calcification].

Coronary-artery calcification was present in 14 of 16 hemodialysis patients who were 20 to 30 years old by electron-beam computed tomography. Bone matrix protein, such as osteopontin produced by infiltrating macrophages into the atherosclerotic arterial lesions, is thought to be associated with vascular calcification. Therefore, it is required to recognize the interaction between abnormal bone metabolism and vascular calcification. Control of serum phosphorus levels is likely to be most important for the prevention and treatment of vascular calcification in patients with end-stage renal diseases.

English Abstract↗
PubMed2000

Hydrogen exchange study of canine milk lysozyme: stabilization mechanism of the molten globule.

The native state (1)H, (15)N resonance assignment of 123 of the 128 nonproline residues of canine milk lysozyme has enabled measurements of the amide hydrogen exchange of over 70 amide hydrogens in the molten globule state. To elucidate the mechanism of protein folding, the molten globule state has been studied as a model of the folding intermediate state. Lysozyme and alpha-lactalbumin are homologous to each other, but their equilibrium unfolding mechanisms differ. Generally, the folding mechanism of lysozyme obeys a two-state model, whereas that of alpha-lactalbumin follows a three-state model. Exceptions to this rule are equine and canine milk lysozymes, which exhibit a partially unfolded state during the equilibrium unfolding; this state resembles the molten globule state of alpha-lactalbumin but with extreme stability. Study of the molten globules of alpha-lactalbumin and equine milk lysozyme showed that the stabilities of their alpha-helices are similar, despite the differences in the thermodynamic stability of their molten globule states. On the other hand, our hydrogen exchange study of the molten globule of canine milk lysozyme showed that the alpha-helices are more stabilized than in alpha-lactalbumin or equine milk lysozyme and that this enhanced stability is caused by the strengthened cooperative interaction between secondary structure elements. Thus, our results underscore the importance of the cooperative interaction in the stability of the molten globule state.

Amides↗
PubMed2000

Chitin-binding proteins in invertebrates and plants comprise a common chitin-binding structural motif.

Tachycitin, a 73-residue polypeptide having antimicrobial activity is present in the hemocyte of horseshoe crab (Tachypleus tridentatus). The first three-dimensional structure of invertebrate chitin-binding protein was determined for tachycitin using two-dimensional nuclear magnetic resonance spectroscopy. The measurements indicate that the structure of tachycitin is largely divided into N- and C-terminal domains; the former comprises a three-stranded beta-sheet and the latter a two-stranded beta-sheet following a short helical turn. The latter structural motif shares a significant tertiary structural similarity with the chitin-binding domain of plant chitin-binding protein. This result is thought to provide faithful experimental evidence to the recent hypothesis that chitin-binding proteins of invertebrates and plants are correlated by a convergent evolution process.

Amino Acid Sequence↗
PubMed2000

Partially unfolded equilibrium state of hen lysozyme studied by circular dichroism spectroscopy.

Equilibrium unfolding of hen egg white lysozyme as a function of GdnCl concentration at pH 0.9 was studied over a temperature range 268.2-303.2 K by means of CD spectroscopy. As monitored by far- and near-UV CD at 222 and 289 nm, the lack of coincidence between two unfolding transition curves was observed, which suggests the existence of a third conformational species in addition to native and unfolded states. The three-state model, in which a stable intermediate is populated, was employed to estimate the thermodynamic parameters for the GdnCl-induced unfolding. It was found that the transition from the native to intermediate states proceeds with significant changes in enthalpy and entropy due to an extremely cooperative process, while the transition from the intermediate to unfolded states shows a low cooperativity with small enthalpy and entropy changes. These results indicate that the highest energy barrier for the GdnCl-induced unfolding of hen lysozyme is located in the process from the native state to the intermediate state, and this process is largely responsible for the cooperativity of protein unfolding.

Animals↗
PubMed2000

Local and long-range interactions in the molten globule state: A study of chimeric proteins of bovine and human alpha-lactalbumin.

The molten globule state of alpha-lactalbumin has ordered secondary structure in the alpha-domain, which comprises residues 1 to 34 and 86 to 123. In order to investigate which part of a polypeptide is important for stabilizing the molten globule state of alpha-lactalbumin, we have produced and studied three chimeric proteins of bovine and human alpha-lactalbumin. The stability of the molten globule state formed by domain-exchanged alpha-lactalbumin, in which the amino acid sequence in the alpha-domain comes from human alpha-lactalbumin and that in the beta-domain comes from bovine alpha-lactalbumin, is the same as that of human alpha-lactalbumin and is substantially greater than that of bovine alpha-lactalbumin. Therefore, our results show that the stability of the molten globule state of alpha-lactalbumin is determined by the alpha-domain and the beta-domain is not important for stabilizing the molten globule state. The substitution of residues 1 to 34 of bovine alpha-lactalbumin with those of human alpha-lactalbumin substantially increases the stability of the molten globule state, while the substitution of residues 86 to 123 of bovine alpha-lactalbumin with those of human alpha-lactalbumin decreases the stability of the molten globule state. Therefore, residues 1 to 34 in human alpha-lactalbumin is more important for the stability of the human alpha-lactalbumin molten globule state than residues 86 to 123. The stabilization of the molten globule state due to substitution of both residues 1 to 34 and 86 to 123 is not identical with the sum of the two individual substitutions, demonstrating the non-additivity of the stabilization of the molten globule state. This result indicates that there is a long-range interaction between residues 1 to 34 and 86 to 123 in the molten globule state of human alpha-lactalbumin. The differences in the stabilities of the molten globule states are well correlated with the averaged helical propensity values in the alpha-domain when the long-range interactions are negligible, suggesting that the local interaction is the dominant term for determining the stability of the molten globule state. Our results also indicate that the apparent cooperativity is closely linked to the stability of the molten globule state, even if the molten globule state is weakly cooperative.

Allosteric Site↗
PubMed2000

Structure and thermodynamics of the extraordinarily stable molten globule state of canine milk lysozyme.

Here, we show that an unfolded intermediate of canine milk lysozyme is extraordinarily stable compared with that of the other members of the lysozyme-alpha-lactalbumin superfamily, which has been studied previously. The stability of the intermediate of this protein was investigated using calorimetry, CD spectroscopy, and NMR spectroscopy, and the results were interpreted in terms of the structure revealed by X-ray crystallography at a resolution of 1.85 A to an R-factor of 17.8%. On the basis of the results of the thermal unfolding, this protein unfolds in two clear cooperative stages, and the melting temperature from the intermediate to the unfolded states is about 20 degrees C higher than that of equine milk lysozyme. Furthermore, the (1)H NMR spectra of canine milk lysozyme at 60 degrees C, essentially 100% of which exists in the intermediate, showed that small resonance peaks that arise from ring-current shifts of aliphatic protons are still present in the upfield region from 0 to -1 ppm. The protein at this temperature (60 degrees C) and pH 4.5 has been found to bind 1-anilino-naphthalene-8-sulfonate (ANS) with enhancement of the fluorescence intensity compared with that of native and thermally unfolded states. We interpret that the extraordinarily stable intermediate is a molten globule state, and the extraordinary stabilization of the molten globule state comes from stronger protection around the C- and D-helix of the aromatic cluster region due to the His-21 residue. The conclusion helps to explain how the molten globule state acquires its structure and stability.

Amino Acid Sequence↗
PubMed2000

Acetyl-seryl-aspartyl-lysyl-proline is a novel natural cell cycle regulator of renal cells.

A natural tetrapeptide, acetyl-seryl-aspartyl-lysyl-proline (AcSDKP) is a physiological negative regulator of hematopoiesis. The precursor of AcSDKP, thymocin beta 4, is expressed in many tissues including kidney. The present study examined the antiproliferative effect of AcSDKP in two renal cell lines, namely, renal interstitial fibloblasts cell line (NRK 49F) and renal proximal tubular epitherial cells (LLC-PK1). An addition of AcSDKP for 48 hours in theses cells resulted in a concentration-dependent attenuation in the proliferation rate (significant difference to non-treated cells was observed at 10(-9) to 10(-5) M AcSDKP) determined by a colorimetry of alamer blue oxidation. The cell cycle analysis of NRK 49F cells treated with AcSDKP showed that AcSDKP significantly reduced the ratio of S-phase to G2/M-phases. Thus, physiological concentrations of AcSDKP is capable of altering cell cycle to inhibit the proliferation of renal cells.

Animals↗
PubMed2000

Cold denaturation of alpha-lactalbumin.

We have investigated the thermal unfolding of bovine alpha-lactalbumin by means of circular dichroism spectroscopy in the far- and near-ultraviolet regions, and shown that the native alpha-lactalbumin undergoes heat and cold denaturation. The guanidine hydrochloride-induced unfolding of alpha-lactalbumin was also investigated by circular dichroism spectroscopy at various temperatures from 261 to 318 K. It is shown that the population of the molten globule state is strongly dependent on temperature and that the molten globule state does not accumulate during the guanidine hydrochloride-induced unfolding transition at 261 K. Our results indicate that the molten globule state of alpha-lactalbumin undergoes cold denaturation as the native alpha-lactalbumin does, and that the heat capacity change of unfolding from the molten globule to the unfolded state is positive and significant. The present results further support the idea that the molten globule and the unfolded states do not belong to the same thermodynamic state, and that the native, molten globule and unfolded states are sufficient for interpreting the guanidine hydrochloride-induced unfolding behavior of alpha-lactalbumin.

Animals↗
PubMed2000

Localization of Smad6 and Smad7 in the rat kidney and their regulated expression in the anti-Thy-1 nephritis.

Under normal conditions, kidney expresses Smad6 and Smad7 most abundantly among the organs of the body. To understand the physiological roles of these Smad expressions in the kidney, we first identified the sites of Smad6 and Smad7 expression in the rat kidney by in situ hybridization. The expression of Smad7 in the rat kidney was only observed in the glomeruli, while Smad6 was expressed in both the glomeruli and thick ascending limb of Henle's loop. In order to investigate whether Smad6 and 7 are also involved in the negative feedback loop of TGF-beta signaling in vivo, we examined the changes of mRNA levels of these Smads in the glomeruli of rat anti-Thy1 (1-22-3) nephritis, a model where the expression of TGF-beta in the glomeruli has been shown to be most up-regulated from day 4 to 14 after the antibody injection. Unexpectedly, 7 days after injection, the levels of Smad6 and Smad7 did not increase but rather decreased to approximately 70% of the levels on day 0. During that period, Smad7 immunostaining was observed in the glomerular endothelial cells (GEN) where Smad3 immunostaining was also observed. This suggested that Smad7 expression was not augmented by the TGF-beta signal in GEN in vivo in anti-Thy-1 nephritis. The absence of up-regulation of these inhibitory Smads may be involved in the pathogenesis of anti-Thy-1 nephritis.

Animals↗
PubMed2000

A comparison between low-flow leak test and oxygen flush leak test.

PURPOSE: The clinical efficacy of two methods of preanesthetic leak test,namely the oxygen flush leak test (OFLT) and the low-flow leak test (LFLT), was compared regarding their ability to detect leakage in the anesthesia circuit and their accuracy. METHODS: Examinees comprised 16 staff anesthesiologists and 7 physicians undergoing anesthesia training at our institution. They performed the two leak tests on anesthesia machines with some intentional leaks (0.1-1.0 l.min(-1)). The leakage detection rates (LDR) were analyzed by the chi(2)-test. The ability to detect leaks was measured by recording how many leaks were detected by 50% (LDR(50)) and 95% (LDR(95)) of the examinees. RESULTS: The LDRs in the two tests were significantly different (chi(2)- analysis, P < 0.0001). Both LDR(50) and LDR(95) for the LFLT (0.23 and 0.41 l.min(-1), respectively) were smaller than the values for the OFLT (0.37 and 0.82 l.min(-1), respectively). The sensitivity and specificity of the LFLT (0.97 and 0.84, respectively) were higher than those of the OFLT (0.78 and 0.80, respectively). CONCLUSION: The LFLT was found to be superior to the OFLT regarding leak detection and reliability. We therefore recommend the LFLT for preanesthetic leak testing.

Journal Article↗
PubMed2000

Integration test project of CEEF--a test bed for Closed Ecological Life Support Systems.

CEEF (Closed Ecology Experiment Facilities) were installed at Rokkasho village in northern Japan, for the purpose of clarifying life-support mechanisms in a completely closed space, such as a Lunar or Mars base. An integration test using the Closed Plantation Experiment Facility and Closed Animal Breeding & Habitation Experiment Facility is needed before conducting an entire closed experiment including plants, animals and humans. These integration tests are planned to be conducted step by step from fiscal 2001 to 2008.

Air Conditioning↗
PubMed2000

Stability of the molten globule state of a domain-exchanged chimeric protein between human and bovine alpha-lactalbumins.

A domain-exchanged chimeric alpha-lactalbumin (alpha-LA), which consisted of the alpha-domain of human alpha-LA and the beta-domain of bovine alpha-LA, was constructed. Like native alpha-LA, the chimeric protein was in a molten globule state in the absence of Ca(2+) at neutral pH and low salt concentration. The stability of the molten globule state of the constructed chimeric protein was identical to that of the recombinant human protein and was higher than that of the recombinant bovine protein. The stability of the molten globule state of alpha-LA is defined by the stability of the alpha-domain.

Amino Acid Sequence↗
PubMed2000

CD28 knockout mice as a useful clue to examine the pathogenesis of chronic graft-versus-host reaction.

BACKGROUND: Injection of BALB/c or DBA/2 spleen cells into F1 C57BL/6 (B6) hybrids induces a graft-versus-host reaction (GVHR) of a chronic stimulatory type that results in clinical and pathologic manifestations that resemble the human systemic lupus erythematosus (SLE). The aim of the present study was to examine the role of a major T-cell costimulatory signal receptor, CD28, in the production of autoantibody and the development of an immune complex glomerulonephritis, which are common in SLE pathology. METHODS: For this purpose, CD28-deficient (CD28KO) mice were used for the source of donor lymphocytes. Chronic GVHR was induced by an injection of BALB/c or BALB. CD28KO donor cells into normal BCF1 mice. Serum titers of anti-dsDNA antibodies were assessed by enzyme-linked immunosorbent assay (ELISA) and major histocompatibility complex (MHC) class II antigen expression on B cells were tested by flow cytometry. In addition, depositions of immunoglobulin (Ig) were examined by direct immunofluorescence staining on frozen kidney sections. RESULTS: When (BALB/c x B6)F1 mice were injected with parental BALB/c lymphocytes, serum anti-dsDNA titer was significantly increased in association with nonspecific B-cell activation and IgG deposition in the glomerular basement membrane. In sharp contrast, none of these signs were observed in F1 mice, which were injected with CD28KO spleen cells. CONCLUSION: The CD28-mediated T-cell costimulatory pathway plays a pivotal role in the development of polyclonal B-cell activation, autoantibody production, and an immune complex glomerulonephritis. We propose that CD28KO mice are useful clues in examining the pathogenesis of experimental lupus nephritis.

Animals↗
PubMed2000

In vitro antimicrobial properties of recombinant ASABF, an antimicrobial peptide isolated from the nematode Ascaris suum.

ASABF is a CSalphabeta-type antimicrobial peptide that contains four intramolecular disulfide bridges (Y. Kato and S. Komatsu, J. Biol. Chem. 271:30493-30498, 1996). In the present study, a recombinant ASABF was produced by using a yeast expression system, and its antimicrobial activity was characterized in detail. The recombinant ASABF was active against all gram-positive bacteria tested (7 of 7; minimum bactericidal concentration [MBC], 0.03 to 1 microg/ml) except Leuconostoc mesenteroides, some gram-negative bacteria (8 of 14; MBC, >0.5 microg/ml), and some yeasts (3 of 9; MBC >3 microg/ml). Slight hemolytic activity (4.2% at 100 microg/ml) against human erythrocytes was observed only under low-ionic-strength conditions. Less than 1 min of contact was enough to kill Staphylococcus aureus ATCC 6538P. The bactericidal activity against S. aureus was inhibited by salts.

Amino Acid Sequence↗