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Biomedical subjects

T Nakata

Publications and source records attributed to T Nakata.

At least 19 recordsLinked to original sources
PubMed1995

Young borderline hypertensives are hyperreactive to mental arithmetic stress: spectral analysis of R-R intervals.

To investigate whether sympathetic tone and its reactivity to stress are increased in borderline hypertension, we compared pressor and autonomic nervous responses to mental arithmetic stress in male borderline hypertensives (BH) and normotensive volunteers (NT). Three age groups, 30, 40 and 50-year-old groups, which included 30 to 39, 40 to 49 and 50 to 59-year-old subjects, were studied. Fractional LF (%LF), fractional HF (%HF) and L/H, obtained from the power spectrum of R-R intervals, were used as indices of autonomic nervous function. Baseline autonomic nervous indices did not differ between NT and BH of any age group. Blood pressure rose higher during mental arithmetic stress in 50 than in 30-year-old NT but not in comparable age groups of BH. Pressor responses were augmented in BH compared to NT only in the 30-year-old group. However, the differences were not significant when pressor responses were expressed as percent increases in blood pressure. Both %L and L/H increased during arithmetic stress. The increase in %L did not differ between NT and BH but that in L/H (% delta L/H) was larger in 50 than in 30-year-old NT. % delta L/H was larger in BH than in NT only in the 30-year-old group. These findings suggest that both pressor and autonomic nervous responses to metal arithmetic stress were altered by aging and augmented in BH compared to NT in the 30-year-old group.

Adult↗
PubMed1995

The functional role of 55- and 75-kDa tumour necrosis factor receptors in human polymorphonuclear cells in vitro.

The expression and biological role of 55- and 75-kDa tumour necrosis factor-receptors (TNF-RI and TNF-RII) in human polymorphonuclear cells (PMN) in vitro were studied using agonistic rabbit polyclonal anti-TNF-R antibodies. PMN express TNF-RII predominantly, and release the superoxide anion on stimulation by human recombinant lymphotoxin (LT) in vitro. Anti-TNF-RI but not anti-TNF-RII antibody stimulated the superoxide release mimicking LT. Release of the elastase from azurophilic granule of PMN was augmented by LT in vitro. Anti-TNF-RI but not anti-TNF-RII antibody augmented the elastase release. Release of the lactoferrin from the specific granules of PMN was enhanced by LT in vitro. Anti-TNF-RI but not anti-TNF-RII antibody augmented the elastase release. Release of the lactoferrin from the specific granules of PMN was enhanced by LT in vitro. Anti-TNF-RI but not anti-TNF-RII antibody enhanced the lactoferrin release. These antibodies failed to co-stimulate these PMN functions. The adhesiveness of PMN to a plastic plate and the expression of Mac-1 on PMN were upregulated by LT in vitro. Anti-TNF-RI but not anti-TNF-RII antibody upregulated the adhesiveness and Mac-1 expression of PMN mimicking LT. Though anti-TNF-RII antibody by itself did not alter the adhesiveness and marginally suppressed Mac-1 expression, it maintained the adhesiveness and adhesion molecule expression in the presence of anti-TNF-RI antibody. In summary, PMN predominantly express TNF-RII, the signalling of LT (and TNF) in PMN is mediated mainly by TNF-RI, and the adhesion function can be modulated also by TNF-RII when TNF-RI is stimulated.

Antibodies↗
PubMed1995

KIF3A/B: a heterodimeric kinesin superfamily protein that works as a microtubule plus end-directed motor for membrane organelle transport.

We cloned a new member of the murine brain kinesin superfamily, KIF3B, and found that its amino acid sequence is highly homologous but not identical to KIF3A, which we previously cloned and named KIF3 (47% identical). KIF3B is localized in various organ tissues and developing neurons of mice and accumulates with anterogradely moving membranous organelles after ligation of nerve axons. Immunoprecipitation assay of the brain revealed that KIF3B forms a complex with KIF3A and three other high molecular weight (approximately 100 kD)-associated polypeptides, called the kinesin superfamily-associated protein 3 (KAP3). In vitro reconstruction using baculovirus expression systems showed that KIF3A and KIF3B directly bind with each other in the absence of KAP3. The recombinant KIF3A/B complex (approximately 50-nm rod with two globular heads and a single globular tail) demonstrated plus end-directed microtubule sliding activity in vitro. In addition, we showed that KIF3B itself has motor activity in vitro, by making a complex of wild-type KIF3B and a chimeric motor protein (KIF3B head and KIF3A rod tail). Subcellular fractionation of mouse brain homogenates showed a considerable amount of the native KIF3 complex to be associated with membrane fractions other than synaptic vesicles. Immunoprecipitation by anti-KIF3B antibody-conjugated beads and its electron microscopic study also revealed that KIF3 is associated with membranous organelles. Moreover, we found that the composition of KAP3 is different in the brain and testis. Our findings suggest that KIF3B forms a heterodimer with KIF3A and functions as a new microtubule-based anterograde translocator for membranous organelles, and that KAP3 may determine functional diversity of the KIF3 complex in various kinds of cells in vivo.

Amino Acid Sequence↗
PubMed1995

Point mutation of adenosine triphosphate-binding motif generated rigor kinesin that selectively blocks anterograde lysosome membrane transport.

In the study of motor proteins, the molecular mechanism of mechanochemical coupling, as well as the cellular role of these proteins, is an important issue. To assess these questions we introduced cDNA of wild-type and site-directed mutant kinesin heavy chains into fibroblasts, and analyzed the behavior of the recombinant proteins and the mechanisms involved in organelle transports. Overexpression of wild-type kinesin significantly promoted elongation of cellular processes. Wild-type kinesin accumulated at the tips of the long processes, whereas the kinesin mutants, which contained either a T93N- or T93I mutation in the ATP-binding motif, tightly bound to microtubules in the center of the cells. These mutant kinesins could bind to microtubules in vitro, but could not dissociate from them even in the presence of ATP, and did not support microtubule motility in vitro, thereby indicating rigor-type mutations. Retrograde transport from the Golgi apparatus to the endoplasmic reticulum, as well as lysosome dispersion, was shown to be a microtubule-dependent, plus-end-directed movement. The latter was selectively blocked in the rigor-mutant cells, although the microtubule minus-end-directed motion of lysosomes was not affected. We found the point mutations that make kinesin motor in strong binding state with microtubules in vitro and showed that this mutant causes a dominant effect that selectively blocks anterograde lysosome membrane transports in vivo.

Adenosine Triphosphate↗
PubMed1995

Role of basic and acidic fragments in delicious peptides (Lys-Gly-Asp-Glu-Glu-Ser-Leu-Ala) and the taste behavior of sodium and potassium salts in acidic oligopeptides.

The role of the acidic fragment (Asp-Glu-Glu) in delicious peptides was investigated in detail by using the Na+ or K+ salts of acidic oligopeptides so that amount of Na+ or K+ intake of peptides composed of acidic amino acids could be varied by changing their sequences. The taste of these peptides was confirmed to vary with Na+ or K+ intake. Additionally, in order to study the role of basic (Lys-Gly) and acidic (Asp-Glu-Glu) fragments in delicious peptides for producing the taste, five delicious peptide analogs, Ser-Leu-Ala-Lys-Gly-Asp-Glu-Glu, Ser-Leu-Ala-Asp-Glu-Glu-Lys-Gly, Lys-Gly-Ser-Leu-Ala-Asp-Glu-Glu, Lys-Gly-Asp-Glu-Glu, and Glu-Glu-Asp-Gly-Lys, were synthesized. The intensity of the umami and/or salty taste of these peptides and their Na salts was almost the same, despite their chemical structures being different. These results indicate that the acidic fragment as well as the basic fragment plays an important role in the taste production and intensity of delicious peptides, and that an umami or salty taste can be produced by the localization of the cation of the basic fragment and the anion of the acidic fragment.

Amino Acid Sequence↗
PubMed1995

[Prediction of left ventricular functional recovery in patients with acute myocardial infarction using single photon emission computed tomography with thallium-201 and iodine-123-beta-methyl-p-iodophenyl-pentadecanoic acid].

The relationships between myocardial perfusion, fatty acid metabolism, and cardiac function were investigated using dual single photon emission computed tomography (SPECT) with thallium and iodine-123-beta-methyl-p-iodophenyl-pentadecanoic acid (123I-BMIPP) during the acute (10 +/- 1 days) and recovery (60 +/- 14 days) phases in 29 patients with acute myocardial infarction. There were 18 patients who underwent successful primary coronary angioplasty (PTCA group) and 11 patients who received conservative therapy (non PTCA group). Thallium and BMIPP uptakes were scored visually by a 4-point system and left ventricular ejection fraction (LVEF) was calculated by radionuclide ventriculography. Although significant positive correlations between thallium and 123I-BMIPP scores were observed during both phases, BMIPP scores were significantly lower than thallium scores in both acute and recovery phases in the PTCA group. No significant difference in thallium and 123I-BMIPP scores was observed at the recovery phase in the non PTCA group. LVEF significantly correlated with thallium and 123I-BMIPP scores in both phases in the PTCA group. Furthermore, the difference between thallium and 123I-BMIPP scores during the acute phase significantly correlated with the improvement of LVEF during the follow-up period in the PTCA group (y = 0.92x-0.77, r = 0.65, p < 0.005). These findings suggest that mismatch of perfusion and metabolism in infarcted myocardium assessed by thallium and 123I-BMIPP SPECT is increased by reperfusion therapy and persists at least until the recovery phase of myocardial infarction. The recovery of left ventricular function depends on the extent of the mismatched uptake, indicating a predictor for functional recovery following acute myocardial infarction.

Adult↗
PubMed1995

Cardiac sympathetic denervation in transthyretin-related familial amyloidotic polyneuropathy: detection with iodine-123-MIBG.

In familial amyloidotic polyneuropathy (FAP), the peripheral nervous system is predominantly impaired. Cardiac sympathetic function has not been directly assessed. A 65-yr-old man with severe peripheral neuropathy due to primary systemic amyloidosis was studied. Echocardiograms and scintigraphic examinations with 20Tl and 99mTc-pyrophosphate demonstrated highly thickened but normally perfused left ventricular walls with intense diffuse amyloid deposits. No definite myocardial activity of [123I]metaiodobenzylguanidine (MIBG) was detected in any cardiac region, indicating lack of sympathetic nerve endings. Despite maintained cardiac contractility, left ventricular diastolic performance and heart rate variability assessed by power spectral analysis were markedly depressed. Thus, the myocardial defect of MIBG activity may provide direct evidence of impaired cardiac sympathetic nerve endings due to amyloid deposits in FAP.

3-Iodobenzylguanidine↗
PubMed1995

[Quantitative assessment of myocardial viability by thallium-201 reinjection with SPECT: comparative studies with resting image in myocardial infarction].

Exercise-stress thallium (Tl) scintigraphy is a reliable diagnostic tool for evaluating the reversibility of injury to the myocardium; however, overestimation of infarcted volume has been considered as a clinical limitation, both in recent and in old myocardial infarctions. To reveal the clinical efficacy of reinjection modification, infarcted and ischemic myocardium were quantitatively evaluated by stress, reinjection, and resting image with 201Tl SPECT in 43 patients with myocardial infarction. A quite significant correlation was found in severity scores from reinjection and resting images (87 +/- 12 vs. 81 +/- 10, r = 0.85, p < 0.001), these were significantly lower than the scores from post-exercise (124 +/- 13) and 4-hour delayed (103 +/- 11) images. The fractions of reversible ischemic myocardium predicted by reinjection and resting images also correlated with each other (r = 0.55, p < 0.05) and were significantly larger than those from 4-hour delayed images. Furthermore, the degree of redistribution of myocardial perfusion observed in reinjection image showed a significant positive linear correlation with improved myocardial perfusion after coronary revascularization (r = 0.80, p < 0.001), while that from the 4-hour delayed image did not. These results suggest that the severity score of thallium reinjection method is useful for quantifying both labile and non-labile myocardium after myocardial infarction and contributes to predicting the effect of coronary revascularization therapy.

Adult↗
PubMed1994

KIF3A is a new microtubule-based anterograde motor in the nerve axon.

Neurons are highly polarized cells composed of dendrites, cell bodies, and long axons. Because of the lack of protein synthesis machinery in axons, materials required in axons and synapses have to be transported down the axons after synthesis in the cell body. Fast anterograde transport conveys different kinds of membranous organelles such as mitochondria and precursors of synaptic vesicles and axonal membranes, while organelles such as endosomes and autophagic prelysosomal organelles are conveyed retrogradely. Although kinesin and dynein have been identified as good candidates for microtubule-based anterograde and retrograde transporters, respectively, the existence of other motors for performing these complex axonal transports seems quite likely. Here we characterized a new member of the kinesin super-family, KIF3A (50-nm rod with globular head and tail), and found that it is localized in neurons, associated with membrane organelle fractions, and accumulates with anterogradely moving membrane organelles after ligation of peripheral nerves. Furthermore, native KIF3A (a complex of 80/85 KIF3A heavy chain and a 95-kD polypeptide) revealed microtubule gliding activity and baculovirus-expressed KIF3A heavy chain demonstrated microtubule plus end-directed (anterograde) motility in vitro. These findings strongly suggest that KIF3A is a new motor protein for the anterograde fast axonal transport.

Animals↗
PubMed1994

Direct visualization of the microtubule lattice seam both in vitro and in vivo.

Microtubules are constructed from alpha- and beta-tubulin heterodimers that are arranged into protofilaments. Most commonly there are 13 or 14 protofilaments. A series of structural investigations using both electron microscopy and x-ray diffraction have indicated that there are two potential lattices (A and B) in which the tubulin subunits can be arranged. Electron microscopy has shown that kinesin heads, which bind only to beta-tubulin, follow a helical path with a 12-nm pitch in which subunits repeat every 8-nm axially, implying a primarily B-type lattice. However, these helical symmetry parameters are not consistent with a closed lattice and imply that there must be a discontinuity or "seam" along the microtubule. We have used quick-freeze deep-etch electron microscopy to obtain the first direct evidence for the presence of this seam in microtubules formed either in vivo or in vitro. In addition to a conventional single seam, we have also rarely found microtubules in which there is more than one seam. Overall our data indicates that microtubules have a predominantly B lattice, but that A lattice bonds between tubulin subunits are found at the seam. The cytoplasmic microtubules in mouse nerve cells also have predominantly B lattice structure and A lattice bonds at the seam. These observations have important implications for the interaction of microtubules with MAPs and with motor proteins, and for example, suggest that kinesin motors may follow a single protofilament track.

Animals↗
PubMed1994

Alcohol norms, expectancies, and reasons for drinking and alcohol use in a U.S. versus a Japanese college sample.

Two hundred eighty-two students at Arizona State University in the U.S. and 339 students at Okayama University in Japan completed a questionnaire on their alcohol use, expectancies of the effects of alcohol on their own and others' moods and behaviors, the desirability of these effects, norms of significant others for levels of alcohol use and the subject's desire to comply with these norms, and reasons for drinking and not drinking alcohol. Although frequencies of current drinkers versus abstainers did not differ between the two samples, the U.S. students began regular alcohol use at a significantly earlier age, currently drank more alcohol, had higher alcohol expectancies for emotional responses, and endorsed more celebratory reasons for drinking than their Japanese counterparts. U.S. students, however, had lower expectancies for flushing and lower perceived norms for drinking. Hierarchical multiple regressions performed using data from the current drinkers indicated that expectancies of disinhibition and especially aggressiveness after alcohol use, alcohol norms, celebratory (but not pathological) reasons for drinking, and reasons for not drinking were more predictive of reported levels of alcohol use among the U.S. students as compared with the Japanese students.

Adolescent↗
PubMed1994

Redistribution of synapsin I and synaptophysin in response to electrical stimulation in the rat neurohypophysial nerve endings.

To understand the dynamics of synaptic vesicles and synapsin I, we have studied the localization of synapsin I and synaptophysin in resting and stimulated nerve endings by ultracryomicrotomy and colloidal gold-immunocytochemistry. First, we characterized microvesicles in resting nerve endings of the rat neurohypophysis, which was chosen as the model of nerve ending in this study. Synaptophysin was localized in microvesicles that were clustered beneath the plasma membrane. Quick-freeze deep-etching electron microscopy showed that short strands cross-linked microvesicles to each other, which highly resemble the structures observed in our studies of the presynaptic nerve terminals of central and peripheral nervous system and in vitro reconstitution of synapsin I and synaptic vesicles. Immunocytochemistry showed that synapsin I was localized to the region of cluster of microvesicles. Second, using this system, we examined localization of synapsin I and synaptophysin in nerve endings after electrical stimulation. Besides release of neurosecretory granules, clusters of microvesicles dissappeared and both microvesicles and synaptophysin were scattered over nerve endings. These changes were also confirmed by quick-freeze, freeze-substitution. Immunocytochemistry of the stimulated sample revealed that synapsin I was also scattered. The results show that microvesicles in neurohypophysis have similar characteristics of typical synaptic vesicles and synapsin I has a role as a scaffold to cross-link microvesicles to be clustered in resting nerve endings. This scaffold of synapsin I was disengaged after stimulation to redistribute microvesicles and synapsin I itself, which may be the mechanism of synapsin I to regulate the availability of synaptic vesicles for release.

Animals↗
PubMed1994

Intrapulmonary lymph nodes.

We report two cases of intrapulmonary lymph nodes detected by a chest roentgenogram or CT scan. The first patient was a 61-year-old fisherman referred complaining of cough and hemosputum. Chest roentgenogram showed a subpleural small nodular shadow at the superior segment of the right lower lobe. Thoracotomy showed a small anthracotic lymph node. The other case was a 68-year-old female patient admitted for further examination of a subpleural small nodular shadow at the latero-basal segment of the left lower lobe detected on a chest CT scan. Thoracoscopic surgery revealed that the black nodule was an anthracotic lymph node. The appearance of an intrapulmonary lymph node on radiological examination is rare, however, it should be considered in the differential diagnosis of a solitary or multiple peripheral pulmonary nodules in adults. A small nodular shadow should be resected if malignancy is suspected though not proven. Subpleural intrapulmonary lymph node warrants thoracoscopic surgery.

Aged↗
PubMed1994

Effect of an angiotensin II receptor antagonist, TCV-116, on cardiac hypertrophy and coronary circulation in spontaneously hypertensive rats.

To determine whether an angiotensin II receptor antagonist (AT antagonist) could improve the impaired coronary circulation as well as induce regression of cardiac hypertrophy in the hypertensive heart, and to elucidate whether the nitric oxide system in the coronary artery was involved in this mechanism, the AT1 antagonist, TCV-116 (10 mg/kg), was administered orally to spontaneously hypertensive rats (SHR) and Wistar Kyoto rats (WKY), and coronary flow was measured in the isolated hearts. High systolic blood pressure in SHR was significantly reduced by a 2-week treatment with TCV. Left ventricular (LV) hypertrophy in SHR regressed after TCV treatment, while LV weight in WKY was not reduced. Total minimum coronary vascular resistance (MCVR) obtained with adenosine (10(-5) M) infusions in a Langendorff apparatus was significantly greater in SHR than in WKY. Increased MCVR in SHR was reduced after TCV treatment. Coronary perfusion with NG-monomethyl-L-arginine monoacetate (L-NMMA) increased coronary vascular resistance (CVR) in WKY, while it failed to increase CVR in SHR. TCV treatment restored the responses to L-NMMA in SHR. These findings suggest that the AT1 antagonist, TCV-116, lowered the high blood pressure in SHR, concomitantly improving the impaired coronary circulation, and that it induced regression of the cardiac hypertrophy. The suppressed nitric oxide (NO) system in the coronary vessels in SHR appeared to be activated by TCV treatment.

Angiotensin Receptor Antagonists↗
PubMed1993

The primary structure of rat brain (cytoplasmic) dynein heavy chain, a cytoplasmic motor enzyme.

Overlapping cDNA clones encoding the heavy chain of rat brain cytoplasmic dynein have been isolated. The isolated cDNA clones contain an open reading frame of 13,932 bp encoding 4644 aa (M(r), 532,213). The deduced protein sequence of the heavy chain of rat brain dynein shows significant similarity to sea urchin flagellar beta-dynein (27.0% identical) and to Dictyostelium cytoplasmic dynein (53.5% identical) throughout the entire sequence. The heavy chain of rat brain (cytoplasmic) dynein contains four putative nucleotide-binding consensus sequences [GX4GK(T/S)] in the central one-third region that are highly similar to those of sea urchin and Dictyostelium dyneins. The N-terminal one-third of the heavy chain of rat brain (cytoplasmic) dynein shows high similarity (43.8% identical) to that of Dictyostelium cytoplasmic dynein but poor similarity (19.4% identical) to that of sea urchin flagellar dynein. These results suggested that the C-terminal two-thirds of the dynein molecule is conserved and plays an essential role in microtubule-dependent motility activity, whereas the N-terminal regions are different between cytoplasmic and flagellar dyneins.

Amino Acid Sequence↗
PubMed1993

Thermal drift is enough to drive a single microtubule along its axis even in the absence of motor proteins.

One-dimensional diffusion of microtubules (MTs), a back-and-forth motion of MTs due to thermal diffusion, was reported in dynein motility assay. The interaction between MTs and dynein that allows such motion was implicated in its importance in the force generating cycle of dynein ATPase cycle. However, it was not known whether the phenomenon is special to motor proteins. Here we show two independent examples of one-dimensional diffusion of MTs in the absence of motor proteins. Dynamin, a MT-activated GTPase, causes a nucleotide dependent back-and-forth movement of single MT up to 1 micron along the longitudinal axes, although the MT never showed unidirectional consistent movement. Quantitative analysis of the motion and its nucleotide condition indicates that the motion is due to a thermal driven diffusion, restricted to one dimension, under the weak interaction between MT and dynamin. However, specific protein-protein interaction is not essential for the motion, because similar back-and-forth movement of MT was achieved on coverslips coated with only 0.8% methylcellulose. Both cases demonstrate that thermal diffusion could provide a considerable sliding of MTs only if MTs are restricted on the surface appropriately.

Animals↗