Biomedical subjects

T Nishinaka

Publications and source records attributed to T Nishinaka.

At least 19 recordsLinked to original sources

PubMed2001

Homologous genetic recombination as an intrinsic dynamic property of a DNA structure induced by RecA/Rad51-family proteins: a possible advantage of DNA over RNA as genomic material.

Heteroduplex joints are general intermediates of homologous genetic recombination in DNA genomes. A heteroduplex joint is formed between a single-stranded region (or tail), derived from a cleaved parental double-stranded DNA, and homologous regions in another parental double-stranded DNA, in a reaction mediated by the RecA/Rad51-family of proteins. In this reaction, a RecA/Rad51-family protein first forms a filamentous complex with the single-stranded DNA, and then interacts with the double-stranded DNA in a search for homology. Studies of the three-dimensional structures of single-stranded DNA bound either to Escherichia coli RecA or Saccharomyces cerevisiae Rad51 have revealed a novel extended DNA structure. This structure contains a hydrophobic interaction between the 2' methylene moiety of each deoxyribose and the aromatic ring of the following base, which allows bases to rotate horizontally through the interconversion of sugar puckers. This base rotation explains the mechanism of the homology search and base-pair switch between double-stranded and single-stranded DNA during the formation of heteroduplex joints. The pivotal role of the 2' methylene-base interaction in the heteroduplex joint formation is supported by comparing the recombination of RNA genomes with that of DNA genomes. Some simple organisms with DNA genomes induce homologous recombination when they encounter conditions that are unfavorable for their survival. The extended DNA structure confers a dynamic property on the otherwise chemically and genetically stable double-stranded DNA, enabling gene segment rearrangements without disturbing the coding frame (i.e., protein-segment shuffling). These properties may give an extensive evolutionary advantage to DNA.

Adenosine Triphosphate↗

PubMed2001

EGF receptor-ERK pathway is the major signaling pathway that mediates upregulation of aldose reductase expression under oxidative stress.

Acceleration of the polyol pathway and enhanced oxidative stress are implicated in the pathogenesis of diabetic complications. We and others recently reported that aldose reductase (AR), the rate-limiting enzyme in the polyol pathway, was upregulated by reactive oxygen and nitrogen species in vascular smooth muscle cells. To clarify the molecular mechanisms underlying these findings, we investigated the signal transduction pathways mediating AR expression using the rat vascular smooth muscle cell line A7r5. A selective epidermal growth factor (EGF) receptor kinase inhibitor, tyrphostin AG1478, significantly suppressed the hydrogen peroxide (H2O2)-induced increase in AR mRNA and enzyme activity. Activation of extracellular signal-regulated protein kinase (ERK) by H2O2 was blunted by AG1478. PD98059, a specific inhibitor of ERK kinase (MEK1), reduced H2O2-induced AR expression. EGF alone elicited activation of ERK and induction of AR expression. Increased level of AR transcript was demonstrated in cells treated with oxidized low-density lipoprotein, and this increase was also suppressed by AG1478. Inhibition of p38 MAP kinase by SB203580 also partially suppressed the H2O2-initiated AR induction. The presence of ponalrestat, an AR inhibitor, significantly accelerated H2O2-induced cell death. These results suggested that AR may act as a survival factor in these cells and that the EGF receptor-ERK pathway is the major signaling pathway involved in the upregulation of AR expression under oxidative stress.

Aldehyde Reductase↗

PubMed2001

Atomic force microscopy of RecA--DNA complexes using a carbon nanotube tip.

We report high resolution images of RecA-double stranded (ds) DNA complexes obtained by atomic force microscopy (AFM). When a carbon nanotube (CNT) tip was used, AFM images visualized the 10-nm pitch of RecA-dsDNA complexes and RecA filaments as three-dimensional surface topography without reconstruction analysis. The depth of the notch between two pitches was less than 1 nm. When adsorbed on a soft surface covered with proteins, naked DNA, RecA monomers, RecA hexamers, and short RecA filaments were all clearly resolved in one image. The high resolution images with a CNT tip provided valuable information on the initiation process of RecA-dsDNA complex formation.

DNA↗

PubMed2001

Familial amyotrophic lateral sclerosis with a novel Leu126Ser mutation in the copper/zinc superoxide dismutase gene showing mild clinical features and lewy body-like hyaline inclusions.

BACKGROUND: Mutations in the SOD1 gene are responsible for approximately 25% of all familial amyotrophic lateral sclerosis (ALS) cases. However, the correlation between the clinical and pathological features and the various SOD1 gene mutations has not been well characterized. OBJECTIVES: To screen the SOD1 gene in search of potential mutations and to obtain clinical and pathological data for 2 Japanese families with ALS. DESIGN: Clinical histories and neurological findings, gross and microscopic pathological features, and DNA analysis of the SOD1 gene. RESULTS: The 2 families with ALS showed a novel missense mutation in the SOD1 gene, which was heterozygous for point mutation TTG to TCG, causing substitution of leucine for serine at codon 126 (Leu126Ser) in exon 5. Clinically, patients showed slower disease progression and lack of upper motor neuron signs. Neuropathologically, the autopsied patient showed the form of familial ALS with posterior column involvement, and the pontocerebellar tract and the dentate nuclei of the cerebellum were also involved. Furthermore, abundant Lewy body-like hyaline inclusions were observed in the affected motor and nonmotor neurons. CONCLUSIONS: Familial ALS with a novel Leu126Ser mutation in the SOD1 gene showed mild clinical features and lack of upper motor neuron signs. We believe that Leu126Ser might be associated with the clinical features and that the mutation site in the SOD1 gene and disease duration might be associated with the formation of Lewy body-like hyaline inclusions.

Adult↗

PubMed2001

Distribution of basal ganglia lesions in generalized variant of Pick's disease: a clinicopathological study of four autopsy cases.

We investigated four Japanese autopsy cases of the generalized variant of Pick's disease ("basophilic inclusion body disease") both clinically and pathologically, and examined the degree and distribution of the basal ganglia lesions, including the amygdala, striatum, pallidum, and substantia nigra. The lesions in the amygdala, striatum, and pallidum were classified into three categories (slight, moderate, and severe). The lesions in the substantia nigra were qualitatively judged, compared with normal controls. Extrapyramidal signs, not noticed in the generalized variant of Pick's disease, were evident in all four cases, in addition to dementia. The degree and distribution of basal ganglia lesions in all four cases were uniform: the caudate nucleus showed severe lesions, the amygdala and putamen severe to moderate lesions, and the pallidum moderate to slight lesions. The substantia nigra in all our cases showed prominent neuronal loss, probably being one of the lesions responsible for extrapyramidal signs. In the generalized variant of Pick's disease, the degree and distribution of the alterations within the basal ganglia differs from those reported in Pick's disease with Pick bodies (PDPB) and corticobasal degeneration (CBD). In PDPB, severe lesions are present in the amygdala with relative sparing of the substantia nigra, compatible with rare extrapyramidal signs in PDPB, while in CBD, severe lesions are found in the pallidum and substantia nigra. These clinicopathological findings may contribute not only to the elucidation of clinicopathological hallmarks, but also to the progress of neuroimaging, in the generalized variant of Pick's disease.

Adult↗

PubMed2001

Change in vasoconstrictive function during prolonged nonpulsatile left heart bypass.

We investigated changes in vasoconstrictive function accompanying prolonged nonpulsatile left heart bypass (NLHB). After 2-week pulsatile left heart bypass (PLHB) in 11 goats, NLHB was conducted for another 4 weeks (Group N) in 6 goats. In the other 5 goats, PLHB was continued for another 4 weeks (Group P). Systemic vascular resistance at rest (rSVR) was measured on the last days of the second and sixth postoperative week (W2 and W6, respectively). Subsequently, phenylephrine was injected, and the maximum values (SVRmax) and the maximum increasing change in SVR (DeltaSVR) were measured. No significant difference was observed in rSVR between groups at W2 or W6. The SVRmax and the DeltaSVR at W2 were consistent in both groups. However, at W6, the SVRmax and the DeltaSVR of Group N were significantly lower than those of Group P. In conclusion, prolonged NLHB caused a significant decrease in the SVR response to phenylephrine, indicating a dimunition of vasoconstrictive function.

Animals↗

PubMed2001

Application of indirect flow rate measurement using motor driving signals to a centrifugal blood pump with an integrated motor.

The method of measuring the flow rate of a centrifugal blood pump from the input electric power, which will be indispensable for the long-term use of such devices, was developed and was applied to the direct-driven centrifugal blood pump that has been developed by our research group. The accuracy was evaluated in a chronic animal experiment using an adult goat. The results demonstrated that this method carries the sufficient potential of the instantaneous monitoring method, but errors due to electromagnetic and mechanical losses were not determined always precisely. The detection of adverse phenomena such as the obstruction of the inlet cannula was also possible from the estimated value of the flow rate and its waveform pattern.

Animals↗

PubMed2001

DNA rotation by a coordinated conformational change of RecA filaments.

RecA protein forms two types of filament structures in the presence or absence of nucleotide cofactors. We recently constructed two molecular models of the DNA structure, the unwound form (N-type structure) and the twisted form (S-type structure), which correspond to the helical pitches of the extended form (ATP form) and compressed form (non-nucleotide form) of the RecA filament, respectively. If ATP hydrolysis is unidirectional and cooperative, and if the extended and compressed forms of RecA filament are interconvertible, the coordinated conformational change travels along the filament. While the RecA filament undergoes this worm-like motion, the wave of conformational change between the unwound and the twisted forms of DNA travels as ATP hydrolyzes, which makes the DNA strands rotate.

Adenosine Triphosphate↗

PubMed2000

Induction of aldose reductase in cultured human microvascular endothelial cells by advanced glycation end products.

Accelerated formation and accumulation of advanced glycation end products, as well as increased flux of glucose through polyol pathway, have been implicated in the pathogenesis of diabetic vascular complications. We investigated effects of advanced glycation end products on the levels of aldose reductase mRNA, protein, and activity in human microvascular endothelial cells. When endothelial cells were cultured with highly glycated bovine serum albumin, aldose reductase mRNA in endothelial cells demonstrated concentration-dependent elevation. The increase in aldose reductase mRNA was accompanied by elevated protein expression and enzyme activity. Significant increase in the enzyme expression was also observed when endothelial cells were cultured with serum obtained from diabetic patients with end-stage renal disease. Pretreatment of the endothelial cells with probucol or vitamin E prevented the advanced glycation end products-induced increases in aldose reductase mRNA and protein. Electrophoretic mobility shift assays using the nuclear extracts of the endothelial cells treated with advanced glycation end products showed enhancement of specific DNA binding activity for AP-1 consensus sequence. These results indicate that accelerated formation of advanced glycation end products in vivo may elicit activation of the polyol pathway, possibly via augmented oxidative stress, and amplify endothelial cell damage leading to diabetic microvascular dysfunction.

Aldehyde Reductase↗

PubMed2000

An autopsy case of postencephalitic parkinsonism of von Economo type: some new observations concerning neurofibrillary tangles and astrocytic tangles.

An autopsied case of postencephalitic parkinsonism of von Economo type with a 71-year duration is reported. Several cases of postencephalitic parkinsonism of von Economo type have been reported in Japan but this is the first reported case from western Japan. The patient was a Japanese man who was 74 years of age at the time of death. He developed encephalitis of unknown etiology at the age of 3 years. The first symptom was antisocial behavior, which developed at 30 years of age. At the age of 40 years, the patient showed progressive parkinsonism. Neuropathological findings disclosed marked neuronal loss with gliosis in the substantia nigra, locus ceruleus, and raphe nuclei, as well as the appearance of neurofibrillary tangles in the aforementioned areas. There were also widespread tuft-shaped astrocytes (Tu-SA) in the central nervous system, including the thalamus. Tuft-shaped astrocytes are considered to represent non-reactive astrocytes because the distributions of neurofibrillary tangles (NFT) and Tu-SA are clearly different. Therefore, the primary astrocytic lesions in postencephalitic parkinsonism of von Economo type may be more widespread. Ultrastructurally, the Tu-SA consisted of straight filaments, 15 nm in width, which formed tight bundles. Ultrastructurally, NFF in this case revealed paired helical filaments but straight filaments, 15 nm in width, which were also found in the neurons of the substantia nigra.

Aged↗

PubMed2000

Preprimed artificial lung for emergency use.

We investigated the possibility of preprimed storage of an artificial lung (AL), aiming at facilitating its emergency use. Test ALs, consisting of a special microporous hollow fiber membrane made of polyolefin in which direct blood-gas contact was completely eliminated, were preprimed with saline solution, sterilized by gamma-ray irradiation, and evaluated after 1-3 months of storage at room temperature. A small amount of bubble was noted in the priming solution after storage in some ALs, which most likely originated from the air dissolved in the priming solution or persisted in the liquid compartment at priming. Although the preprimed solution contained several polyolefin-breakdown products due to irradiation, including ethyl alcohol, n- and t-butyl alcohol, acetone, and carbon dioxide, the levels of these substances were at concentrations known to be not toxic. Endotoxin concentration was negligible. In SEM observation, no perceptible microstructural change was observed in the hollow fibers after preprimed storage. Maximum tensile stress and ultimate elongation of the hollow fiber in the test ALs were reduced by approximately 20% and 3%, respectively, from those of the control AL. The influence of preprimed storage on gas-exchange function was examined in a venoarterial bypass animal study using a goat. Oxygen transfer function was well preserved whereas carbon dioxide removal function was slightly lowered according to the storage term in the stored ALs compared with those of a nonpreprimed control AL. On the basis of these results, we conclude that preprimed storage of the AL with gamma-ray sterilization is basically feasible and realistic.

1-Butanol↗

PubMed2000

Effects of reduced pulse pressure to the cerebral metabolism during prolonged nonpulsatile left heart bypass.

We investigated changes in the cerebral metabolism with long-term reduced pulse pressure. Nine goats underwent pulsatile left heart bypass (LHB) for 2 weeks while awake, and nonpulsatile LHB was subsequently conducted for 4 weeks. The average pulse pressure during nonpulsatile LHB (13, 10, 11, and 11 mm Hg at the 1st, 2nd, 3rd, and 4th nonpulsatile LHB week, respectively) was significantly lower than that during pulsatile LHB (36 mm Hg). There were no significant differences in either arterio-jugular venous oxygen differences (AJDO2) and cerebral oxygen extraction ratio between the 2nd pulsatile LHB week and the 1st, 2nd, 3rd, and 4th nonpulsatile LHB weeks. The arterio-jugular venous glucose differences, jugular venous-arterial lactate differences (JAD Lactate), and lactate oxygen indexes (JAD Lactate/AJDO2) also remained unchanged during the entire course of the experiments. In conclusion, the cerebral metabolism during nonpulsatile LHB did not change compared to that during pulsatile LHB.

Analysis of Variance↗

PubMed2000

RecA-double stranded DNA complexes studied by atomic force microscopy.

RecA-double stranded (ds) DNA complexes have been studied by atomic force microscopy (AFM). When the complexes were prepared in the presence of ATP gamma S, fully covered RecA-dsDNA filaments were observed by AFM. When the concentration of RecA proteins was lower, various lengths of filaments were found. The variation of the observed structures may directly reflect the real distribution of the intermediate complexes in the reaction mixture, as the mixture was simply deposited on a mica surface for AFM observation without special fixation or staining. The use of a carbon nanotube (CNT) AFM tip enabled high resolution to reveal the periodicity of RecA-dsDNA filaments. Our observations demonstrated the potential of the AFM method for the structural studies of the RecA-dsDNA complexes, especially their intermediate states.

Adenosine Triphosphate↗

PubMed2000

Nitric oxide up-regulates aldose reductase expression in rat vascular smooth muscle cells: a potential role for aldose reductase in vascular remodeling.

Acceleration of the polyol pathway under hyperglycemia is among the mechanisms implicated in the pathogenesis of diabetic complications. Although aldose reductase (AR), the rate-limiting enzyme in this pathway, is a target for pharmacological intervention of diabetic complications, the clinical efficacy of AR inhibitors has not been consistently proved. Because nitric oxide (NO) plays important roles in vascular hemodynamics and inflammatory responses that are affected under diabetic conditions, the interaction of NO with AR was investigated with rat aortic smooth muscle cells. Spontaneous NO donors, S-nitroso-N-acetylpenicillamine (SNAP) and 3-(2-hydroxy-1-methyl-2-nitrosohydrazino)-N-methyl-1-propanamin e, elicited a dose-dependent increase in AR mRNA to a maximum of 7-fold in 12 h. The activity of AR was elevated after 10 h of SNAP treatment. These effects of NO donors were suppressed by the addition of 2-(trimethylammoniophenyl)-4,4,5, 5-tetramethylimidazoline-1-oxy 3-oxide, a scavenger of NO. Induction of AR mRNA by SNAP was completely abolished by actinomycin D or cycloheximide, but unaffected by guanylate cyclase inhibitors or genistein, a tyrosine kinase inhibitor. Pretreatment of the cells with N-acetyl-L-cysteine significantly suppressed the SNAP-induced up-regulation of AR mRNA. Under normal glucose conditions, inclusion of the AR inhibitor ponalrestat augmented the cytotoxic effect of SNAP on the cells. The level of AR mRNA also was elevated in a murine macrophage cell line RAW 264.7 stimulated with lipopolysaccharide and interferon-gamma. Inhibition of NO synthesis completely abolished the increase in AR mRNA in the stimulated cells. The up-regulation of AR by NO in the vascular lesions may modulate NO-induced cell death and the ensuing vascular remodeling during inflammatory responses.

Aldehyde Reductase↗

PubMed2000

Biological activity of alkyl 2-(acylthio)benzoates.

Of a series of synthetic alkyl 2-(acylthio)benzoate (1-20), all the derivatives except for n-butyl 2-butyrylthiobenzoate (18) and n-butyl 2-n-valerylthiobenzoate (20) showed clear phytogrowth-inhibitory activity. All the compounds tested except for methyl 2-butyrylthiobenzoate (3) exhibited cytotoxic activity on mouse splenic T cells. Strong phytogrowth-inhibition and cytotoxic activity were found with 1, 6, 11 and 16 with an acetylthio group at C-2, suggesting that the acetyl group seems to play an important role in both activities of alkyl 2-(acylthio)benzoates. Among them, methyl 2-acetylthiobenzoate (1) was the strongest inhibitor. On the other hand, potent inhibition of prolyl endopeptidase was exhibited by 2, 7, 12 and 17 with a propionylthio group at C-2. These findings imply that a propionyl group might be useful for increasing the inhibitory activity against on prolyl endopeptidase.

Animals↗

PubMed1999

Recruitment of the retinoblastoma protein to c-Jun enhances transcription activity mediated through the AP-1 binding site.

The retinoblastoma susceptibility gene product (RB) is a transcriptional modulator. One of the targets for this modulator effect is the AP-1 binding site within the c-jun and collagenase promoters. The physical interactions between RB and c-Jun were demonstrated by co-immunoprecipitation of these two proteins using anti-c-Jun or anti-RB antisera, glutathione S-transferase affinity matrix binding assays in vitro, and electrophoretic mobility shift assays. The C-terminal site of the leucine zipper of c-Jun mediated the interaction with RB. Although the B-pocket domain of RB alone bound to c-Jun, a second c-Jun binding site in the RB was also suggested. Mammalian two-hybrid-based assay provided corroborative evidence that transactivation of gene expression by RB required the C-terminal region of c-Jun. We conclude that RB enhances transcription activity mediated through the AP-1 binding site. Adenovirus E1A or human papillomavirus E7 inhibits RB-mediated transcription activity. These data reveal that the interactions between these two distinct classes of oncoproteins RB and c-Jun may be involved in controlling cell growth and differentiation mediated by transcriptional regulation.

3T3 Cells↗

PubMed1999

In vivo evaluation of the national cardiovascular center electrohydraulic total artificial heart.

We have been developing an electrohydraulic total artificial heart system. The system comprises an intrathoracic pumping unit composed of diaphragm type ellipsoidal blood pumps and an energy converter in addition to an electronics unit. The in vivo performance of the pumping unit was evaluated in a series of animal implantations with 3 calves weighing 62-85 kg. An interatrial shunt 4.5 mm in diameter was made in the atrial septum to compensate left-right imbalance. Two calves died early postoperatively, one of external controller power failure and the other of interatrial shunt stenosis due to thrombus formation. One calf, however, survived over 10 days under stable circulatory conditions. No abnormality was found in the oxygen metabolic condition or in major organ functions. The generation and dissipation of heat from the device was acceptable. This animal died of device malfunction caused by energy converter bearing breakdown. The device demonstrated a good anatomic fit without compromising the great vessels and adjacent tissues. It is concluded that the pumping unit has a sufficient in vivo basic performance although appropriate countermeasures are to be implemented against the detected problems concerning mechanical durability and interatrial shunt patency.

Animals↗

PubMed1999

Cardiac autonomic nervous function during long-term nonpulsatile left heart bypass.

We investigated the changes in cardiac autonomic nervous activities during long-term nonpulsatile left heart bypass (NLHB) by analyzing heart rate variability. A pulsatile ventricular assist device was installed in 3 goats, and pulsatile left heart bypass (PLHB) was conducted for 2 weeks. Then, NLHB was maintained for the following 4 weeks. The segmental data of the R-R intervals (R-Rs) was analyzed by maximum entropy spectral analysis. Changes in evaluated parameters from the last week of PLHB to the 4th week of NLHB were as follows: the mean R-Rs increased from 511 ms to 692 ms; the coefficient of variation of R-R increased from 10.2 to 14.1%; the power of the low frequency band (LF) increased from 747 ms2 to 2,855 ms2; the power of the high frequency band (HF) increased from 512 ms2 to 1,270 ms2; and the ratio of LF to HF increased from 2.6 to 6.5. These results indicated that the cardiac autonomic nervous activity, both sympathetic and parasympathetic, increased during long-term NLHB.

Analysis of Variance↗