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Biomedical subjects

T Tabata

Publications and source records attributed to T Tabata.

At least 91 records · Page 5Linked to original sources
PubMed1998

Plasma leptin level and its relationship with body composition in hemodialysis patients.

Leptin is a newly found hormone secreted by adipocytes that regulates food intake, thermogenesis, and body fat. We measured plasma leptin levels in 103 patients with chronic renal failure treated by hemodialysis and 167 age- and gender-matched healthy control subjects to examine the impact of renal failure on plasma leptin levels and the influence of leptin on body composition measured by dual-energy X-ray absorptiometry. Hemodialysis patients showed a significant decrease in both body fat mass and lean body mass compared with those of the control subjects. Plasma leptin was significantly elevated in the hemodialysis group over the controls. In both groups, leptin was higher in female than male subjects, and it correlated positively with percent body fat. The subjects were divided into six categories according to percent body fat, and plasma leptin levels were compared between the two groups in the same category. Leptin of hemodialysis patients was significantly higher than that of the control subjects in the percent body fat categories of 30 or greater, whereas there was no statistically significant difference in leptin concentrations in the lower percent body fat categories. This was also true in the comparison in each gender, and leptin levels in female subjects showed a more remarkable difference between the hemodialysis and control groups in obese categories. Multiple regression analysis in all subjects indicated that plasma leptin levels were independently affected by percent body fat, plasma insulin concentration, gender, and renal failure. The positive impact of renal failure on leptin remained significant in the subjects with percent body fat of 30 or greater in the multiple regression model, whereas it was no longer significant in the remaining lean subjects. In multiple regression analysis of factors affecting fat mass index and lean mass index, leptin level was selectively associated with fat mass index, but not with lean mass index, regardless of percent body fat ranges. These results indicate that renal failure is an important factor affecting plasma leptin levels, especially in obese female subjects, and that hyperleptinemia was closely related to fat mass but not to lean body mass in hemodialysis patients.

Body Composition↗
PubMed1998

Interplay of signal mediators of decapentaplegic (Dpp): molecular characterization of mothers against dpp, Medea, and daughters against dpp.

Decapentaplegic (Dpp) plays an essential role in Drosophila development, and analyses of the Dpp signaling pathway have contributed greatly to understanding of the actions of the TGF-beta superfamily. Intracellular signaling of the TGF-beta superfamily is mediated by Smad proteins, which are now grouped into three classes. Two Smads have been identified in Drosophila. Mothers against dpp (Mad) is a pathway-specific Smad, whereas Daughters against dpp (Dad) is an inhibitory Smad genetically shown to antagonize Dpp signaling. Here we report the identification of a common mediator Smad in Drosophila, which is closely related to human Smad4. Mad forms a heteromeric complex with Drosophila Smad4 (Medea) upon phosphorylation by Thick veins (Tkv), a type I receptor for Dpp. Dad stably associates with Tkv and thereby inhibits Tkv-induced Mad phosphorylation. Dad also blocks hetero-oligomerization and nuclear translocation of Mad. We also show that Mad exists as a monomer in the absence of Tkv stimulation. Tkv induces homo-oligomerization of Mad, and Dad inhibits this step. Finally, we propose a model for Dpp signaling by Drosophila Smad proteins.

Amino Acid Sequence↗
PubMed1998

Differences in transmitral flow velocity pattern during increase in preload in patients with abnormal left ventricular relaxation.

Changes in transmitral flow (TMF) and pulmonary venous flow (PVF) velocities during increases in preload were compared in patients with a higher peak atrial systolic velocity than peak early diastolic velocity (A/E > 1) for the TMF velocity to determine differences in hemodynamic response. Fifteen patients with dilated hearts, 22 with hypertrophied hearts and 15 control patients were studied. TMF and PVF velocities were recorded by transesophageal pulsed Doppler echocardiography before and during application of lower body positive pressure. The value for peak early diastolic velocity increased, while the isovolumic relaxation time decreased with increases in preload in all groups. The value for peak atrial systolic velocity decreased in the dilated-heart group, but increased in the hypertrophied-heart and control groups. The peak second systolic and early diastolic PVF velocities increased in the dilated- and hypertrophied-heart groups, but did not change in the control group. The peak atrial systolic PVF velocity and the difference in duration of the atrial systolic PVF and TMF velocities increased in the dilated- and hypertrophied-heart groups, and its changing rate was highest in the group with dilated hearts. These results suggest that both peak early diastolic and atrial systolic TMF velocities increase during increases in preload through the Frank-Starling mechanism in hypertrophied hearts. Furthermore, the left ventricular functional reserve was lower in the dilated-heart group. Thus, TMF and PVF velocities respond differently during increases in preload, depending on the underlying heart disease.

Blood Flow Velocity↗
PubMed1998

Xenopus Smad8 acts downstream of BMP-4 to modulate its activity during vertebrate embryonic patterning.

Bone morphogenetic proteins (BMPs) participate in the development of nearly all organs and tissues. BMP signaling is mediated by specific Smad proteins, Smad1 and/or Smad5, which undergo serine phosphorylation in response to BMP-receptor activation and are then translocated to the nucleus where they modulate transcription of target genes. We have identified a distantly related member of the Xenopus Smad family, Smad8, which lacks the C-terminal SSXS phosphorylation motif present in other Smads, and which appears to function in the BMP signaling pathway. During embryonic development, the spatial pattern of expression of Smad8 mirrors that of BMP-4. We show that an intact BMP signaling pathway is required for its expression. Overexpression of Smad8 in Xenopus embryos phenocopies the effect of blocking BMP-4 signaling, leading to induction of a secondary axis on the ventral side of intact embryos and to direct neural induction in ectodermal explants. Furthermore, Smad8 can block BMP-4-mediated induction of ventral mesoderm-specific gene expression in ectodermal explants. Overexpression of Smad8 within dorsal cells, however, causes patterning defects that are distinct from those reported in BMP-4-deficient embryos, suggesting that Smad8 may interact with additional signaling pathways. Indeed, overexpression of Smad8 blocks expression of Xbra in whole animals, and partially blocks activin signaling in animal caps. In addition, Smad8 inhibits involution of mesodermal cells during gastrulation, a phenotype that is not observed following blockade of activin or BMPs in Xenopus. Together, these results are consistent with the hypothesis that Smad8 participates in a negative feedback loop in which BMP signaling induces the expression of Smad8, which then functions to negatively modulate the amplitude or duration of signaling downstream of BMPs and, possibly, downstream of other transforming growth factor-beta (TGF-beta) family ligands.

Activins↗
PubMed1998

Difference in systolic motion velocity of the left ventricular posterior wall in patients with asymmetric septal hypertrophy and prior anteroseptal myocardial infarction. Evaluation by pulsed tissue Doppler imaging.

The left ventricular (LV) posterior wall in patients with asymmetric septal hypertrophy or prior anteroseptal myocardial infarction (A-MI) frequently demonstrates normal or supernormal motion to compensate for hypokinesis of the interventricular septum. This study evaluated the systolic motion velocity of the posterior wall in these conditions using a pulsed tissue Doppler imaging system. The study population consisted of 30 patients with hypertrophic cardiomyopathy (HC) and asymmetric septal hypertrophy, 25 with prior A-MI and 30 normal controls. The systolic excursion of the posterior wall was obtained by M-mode echocardiography. The endocardial motion velocities of the posterior wall were obtained by pulsed tissue Doppler imaging. The systolic excursion of the posterior wall was significantly greater in the A-MI and HC groups than in the control group, and was significantly greater in the A-MI group than in the HC group. The peak systolic velocity of the posterior wall was significantly lower in the HC group than in the control and A-MI groups, and the time from the electrocardiographic Q wave to the peak of the systolic wave of the posterior wall was significantly longer in the HC group than in the other groups. There were rough negative and positive correlations between the LV end-diastolic pressure and the peak systolic velocity and time from the Q wave to the peak of the systolic wave, respectively. In conclusion, LV myocardial contractility in HC patients was impaired when compared to A-MI patients despite similar posterior wall motion on the M-mode echocardiogram. Pulsed tissue Doppler imaging method may provide new insights and allow further evaluation of myocardial dysfunction.

Cardiac Catheterization↗
PubMed1998

Right heart flow dynamics after tricuspid valve annuloplasty. Characteristics and time course.

To evaluate the effect of tricuspid annuloplasty (TAP) on right heart flow dynamics, we analyzed tricuspid inflow velocity pattern, jugular venous pulse and color Doppler flow signal of tricuspid regurgitation (TR) before and after surgery in 16 patients who underwent TAP (TAP group). Cardiac rhythm was atrial fibrillation in all patients. Twelve patients with lone atrial fibrillation served as controls (AF group). Patients in the TAP group were studied before and serially after surgery with a mean follow-up period of 2.7 years. TAP was performed according to the modified De Vega technique in all patients. In a comparison of the most recent data in the TAP group and the data in the AF group, the maximum tricuspid inflow velocity was significantly increased, and both the deceleration time of the tricuspid inflow velocity wave and the y-h interval of the jugular venous pulse were significantly prolonged in the TAP group compared to the AF group. Immediately after surgery, in the TAP group, the area of the TR jet was markedly decreased, and the deceleration time of the tricuspid inflow velocity wave was significantly prolonged compared to those before surgery. The area of the TR jet was dramatically decreased and remained small during the follow-up period. Thus, TAP may produce mild tricuspid stenosis but may also confer sustained preventive effects against TR.

Adult↗
PubMed1998

Intermediate-density lipoprotein as an independent risk factor for aortic atherosclerosis in hemodialysis patients.

Patients with chronic renal failure often show accumulation of intermediate-density lipoprotein (IDL). Because recent studies have emphasized the atherogenicity of IDL in the general population, we evaluated the relationship between this lipoprotein and aortic atherosclerosis in uremic patients treated with hemodialysis. Aortic pulse wave velocity (PWV) was measured as a noninvasive index of sclerotic change of aorta in 205 hemodialysis patients and 184 age- and gender-matched healthy subjects. Fasting plasma lipoproteins were fractionated by ultracentrifugation into very low-density lipoprotein (VLDL), IDL, LDL, and HDL. Plasma lipoprotein (a) (Lp(a)) was measured by a latex immunoturbidimetric assay. Aortic PWV was significantly higher in the hemodialysis patients than in the control subjects. The hemodialysis group showed a significant increase in VLDL and IDL cholesterol, whereas their LDL and HDL cholesterol were lower than the control levels. Lp(a) levels did not differ between the two groups. In the hemodialysis population, VLDL, IDL, and LDL cholesterol correlated positively with aortic PWV adjusted for age, gender, smoking, and BP, whereas Lp(a) did not. Multiple regression analyses indicated that plasma triglycerides, independent of HDL cholesterol, had a significant association with aortic PWV in the hemodialysis patients but not in the control subjects. Further analyses revealed that aortic PWV in the hemodialysis patients had a significant and independent association with IDL cholesterol, whereas aortic PWV in the control subjects had significant and independent associations with HDL cholesterol and Lp(a). These results demonstrate that IDL is the lipoprotein fraction most closely associated with aortic PWV in the hemodialysis patients.

Adult↗
PubMed1998

Cerebrospinal ascites developed 3 years after ventriculoperitoneal shunting in a hydrocephalic patient.

We report a 23-year-old woman who developed ascites 3 years after ventriculoperitoneal shunting. Revision of the shunt to ventricular drainage followed by ventriculo-atrial shunting was required for resolution of ascites. In our patient the pathophysiology of this rare shunt complication most likely involved impaired absorption of fluid within the peritoneum associated with multiple shunt reconstructions and tube extensions resulting in chronic inflammation. Cerebrospinal ascites must be suspected irrespective of post-shunt intervals in similar patients.

Adult↗
PubMed1998

[Preoperative endovascular ultrasonography in lung cancer patient for detecting aortic wall invasion: a case report].

A 69-year-old man was admitted to our hospital because of left primary lung cancer. As tumor invasion to the descending artery was suspected, preoperative endovascular ultrasonography was performed. Part of the wall lacked respiratory movement. However, the wall of the descending artery was visualized as three layers, i.e., hyper-, hypo- and hyperechoic layers by sonography, so tumor invasion to the descending artery was diagnosed as negative. Although inflammatory tumor adhesion to the descending artery was found, left upper lobectomy was safely performed. Endovascular ultrasonography was considered to be useful in marking an accurate diagnosis of tumor invasion to the descending artery.

Aged↗
PubMed1998

[Increase in pulmonary vascular permeability caused by increased adhesiveness of polymorphonuclear leukocytes and superoxide].

We report that mechanical stimulation of human neutrophils results in their accumulation in isolated rat lungs and in an increase in pulmonary vascular permeability. To determine whether reactive oxygen species were involved in this increase and, if so, whether it is mediate by xanthine oxidase metabolites, we assessed the effect of stimulated and unstimulated neutrophils, and of a superoxide scavenger, superoxide dismutase (SOD), and a xanthine oxidase inhibitor, allopurinol (ALLO) on pulmonary vascular permeability in isolated perfused lungs from Sprague-Dawley rats. Pulmonary vascular permeability in isolated rat lungs was assessed using a filtration coefficient determined by gravimetry. To quantify neutrophil accumulation in the lung, we measured myeloperoxydase (MPO). Neutrophils were stimulated by gentle agitation in a glass container for 10 s and Mac-1 was subsequently upregulated on the surface of the neutrophils. In lungs that received stimulated neutrophils, the pulmonary vascular filtration coefficient was about 5 times higher than in lungs that received unstimulated neutrophils. An increase in filtration coefficient was almost completely blocked by pretreatment with SOD or ALLO. However, the accumulation of stimulated neutrophils was not, or only partly, blocked by SOD or ALLO, respectively. We conclude that the increase in pulmonary vascular permeability caused by mechanically stimulated neutrophils was partly mediated by reactive oxygen species generated via the xanthine oxidase system.

Animals↗
PubMed1997

Daughters against dpp modulates dpp organizing activity in Drosophila wing development.

The family of TGF-beta signalling molecules play inductive roles in various developmental contexts. One member of this family, Drosophila Decapentaplegic (Dpp) serves as a morphogen that patterns both the embryo and adult. We have now isolated a gene, Daughters against dpp (Dad), whose transcription is induced by Dpp. Dad shares weak homology with Drosophila Mad (Mothers against dpp), a protein required for transduction of Dpp signals. In contrast to Mad or the activated Dpp receptor, whose overexpression hyperactivates the Dpp signalling pathway, overexpression of Dad blocks Dpp activity. Expression of Dad together with either Mad or the activated receptor rescues phenotypic defects induced by each protein alone. Dad can also antagonize the activity of a vertebrate homologue of Dpp, bone morphogenetic protein, as evidenced by induction of dorsal or neural fate following overexpression in Xenopus embryos. We conclude that the pattern-organizing mechanism governed by Dpp involves a negative-feedback circuit in which Dpp induces expression of its own antagonist, Dad. This feedback loop appears to be conserved in vertebrate development.

Amino Acid Sequence↗
PubMed1997

Clinical application of pulsed Doppler tissue imaging for assessing abnormal left ventricular relaxation.

Conventional assessment of left ventricular (LV) relaxation by calculating the time constant of LV pressure decay during the isovolumic diastole requires an invasive approach. Conversely, noninvasive parameters obtained by measuring isovolumic relaxation time and transmitral flow velocity often give inaccurate information. Using LV pressure curve, pulsed Doppler echocardiography, and pulsed Doppler tissue imaging in 38 patients with heart disease and 12 control subjects, we calculated the time constant and recorded transmitral flow velocity and motion velocities at the endocardial portions of the ventricular septum and LV posterior wall. Compared with the controls, patients exhibited a prolonged time constant, a decreased peak early diastolic velocity of the LV posterior wall, and a prolonged time interval from the second heart sound to the peak of the early diastolic wave. The time constant correlated well with the isovolumic relaxation time and various parameters calculated from the transmitral flow velocity, except in patients with elevated LV end-diastolic pressure. In all subjects, the time constant correlated negatively with the peak early diastolic velocity of the posterior wall and positively with the time from the second heart sound to the peak of the early diastolic wave. Thus, early diastolic parameters derived from the motion velocity of the LV posterior wall by pulsed Doppler tissue imaging were closely related to the time constant. This technique may allow noninvasive evaluation of abnormal LV relaxation in patients with various heart diseases.

Blood Flow Velocity↗
PubMed1997

Evaluation of left atrial appendage function by measurement of changes in flow velocity patterns after electrical cardioversion in patients with isolated atrial fibrillation.

We investigated temporary changes in left atrial appendage (LAA) flow velocity patterns in patients undergoing electrical cardioversion for chronic isolated atrial fibrillation, and evaluated the role of active LAA contraction in directing blood flow to the left atrial main chamber and left ventricle. The study consisted of 26 patients with chronic isolated atrial fibrillation treated with electrical cardioversion and 20 normal controls in sinus rhythm. Using transthoracic and transesophageal Doppler echocardiography, we recorded transmitral, pulmonary venous, and LAA flow velocity patterns before, 24 hours, and 1 week after cardioversion in all subjects. In the 15 patients who underwent successful cardioversion, the maximal LAA area 24 hours after cardioversion was smaller than the area before cardioversion, whereas LAA ejection fraction during atrial systole and peak atrial systolic emptying velocity of the LAA flow were lower 24 hours after cardioversion than those in the control group. One week after cardioversion, maximal LAA area and LAA peak atrial systolic emptying velocity were restored to levels approximately equivalent to those in the control group, although LAA ejection fraction was lower than in the control group. Maximal LAA area and LAA peak atrial systolic emptying velocity correlated negatively and positively with LAA ejection fraction, respectively, 24 hours and 1 week after cardioversion. These results suggest that LAA and the left atrial main chamber show stunning 24 hours after cardioversion, and the atrial systolic emptying wave of LAA flow is generated by active LAA contraction.

Adult↗
PubMed1997

Transesophageal pulsed Doppler echocardiographic evaluation of left atrial systolic performance in hypertrophic cardiomyopathy: combined analysis of transmitral and pulmonary venous flow velocities.

BACKGROUND: Hypertrophic cardiomyopathy (HC) is characterized by impaired left ventricular (LV) diastolic function due to an increase in LV wall thickness. The severity of this disease varies depending on the localization and extent of the hypertrophied myocardium and the presence and extent of myocardial disarray or fibrosis. HYPOTHESIS: The purpose of this study was to examine the background of hemodynamic abnormalities between the left atrium and the left ventricle during atrial systole in patients with HC using pulsed Doppler echocardiography. METHODS: Hemodynamic abnormalities between the left atrium and left ventricle during atrial systole were evaluated in patients with HC using transmitral flow (TMF) and pulmonary venous flow (PVF) velocities obtained by transesophageal pulsed Doppler echocardiography. The study population included 50 patients with HC, including 39 with asymmetric septal hypertrophy and 11 with apical hypertrophy, and showing fractional shortening of the left ventricle > or = 30%. They were classified into three groups: (1) Group A (n = 11): the ratio of the late to early TMF velocity < 1, and peak atrial systolic PVF velocity (PVA) < 25 mm/s; (2) Group B (n = 13): their ratio < 1, and PVA > or = 25 mm/s; and (3) Group C (n = 26): their ratio > or = 1. The mean age of patients in Group A was lower than that in Groups B and C. RESULTS: Left atrial dimension in Group B was significantly greater than that in the other HC groups and the control group. Furthermore, left atrial volume changes during atrial systole in Group B were significantly smaller than those in the other HC groups and the control group. Peak atrial systolic PVF velocity in Group B was significantly higher than that in the control group and in Group C. The duration of the atrial systolic waves of the TMF and PVF in Group B was significantly shorter and longer, respectively, than that in Group A. Left ventricular end-diastolic pressure (LVEDP) decreased in descending order with Group B > Group C > Group A. In all patients there was a significant positive correlation between the LVEDP and peak atrial systolic PVF velocity or the difference in duration between the atrial systolic waves of PVF and TMF. Plots of these values shifted toward the left and inferiorly in Group A, and toward the right and superiorly in Group B. CONCLUSION: Peak velocity and duration of TMF and PVF during atrial systole by transesophageal pulsed Doppler echocardiography are useful indices of hemodynamic abnormalities between the left atrium and the left ventricle during atrial systole, particularly a forceful atrial contraction mismatched to the left atrial afterload and severity of LV diastolic dysfunction, in HC.

Adult↗
PubMed1997

Echocardiographic characteristics and causal mechanism of physiologic mitral regurgitation in young normal subjects.

BACKGROUND: It has become evident that mitral regurgitation (MR) is not uncommon in healthy subjects, and Doppler color flow mapping is a technique that imparts important information relevant to its detection. HYPOTHESIS: Using transthoracic echocardiography, this study evaluated the mechanism of physiologic MR in young normal subjects using transthoracic echocardiography. METHODS: The study population consisted of 48 young normal subjects (mean 21 +/- 5 years) with MR (physiologic MR group), 40 age-matched young normal subjects (mean 20 +/- 5 years) without MR (control group), 45 patients (mean 41 +/- 15 years) with mitral valve prolapse with MR (MVP group), and 27 patients (mean 59 +/- 13 years) with ruptured chordae tendineae (rupture group). RESULTS: Men were predominant in the rupture group, whereas there were no significant gender differences in the other three groups. Left ventricular end-diastolic dimension and left atrial systolic dimension were slightly smaller in the physiologic MR group than in the control group, but were significantly smaller than those in the MVP and rupture groups. The ratio of the maximum anteroposterior diameter to the maximum transverse diameter on chest radiography and the ratio of the short- to long-axis diameter of the left ventricular cavity at end diastole, determined from two-dimensional short-axis echocardiogram, were significantly lower in the physiologic MR group than in the other three groups. Mitral regurgitation occurred more frequently at the posteromedial commissural site in the physiologic MR and MVP groups, whereas there was no preference for location in the rupture group. Early systolic MR was often observed in the physiologic MR group, whereas pansystolic MR was common in the MVP and rupture groups. CONCLUSION: As a causal mechanism for physiologic MR detected in young normal subjects, "flattening" of the thorax during growth may cause morphologic abnormalities of the left atrial and ventricular cavities, resulting in spatial imbalance of the mitral complex and resulting in malcoaptation of the valve.

Adult↗
PubMed1997

Atherogenic lipoprotein changes in the absence of hyperlipidemia in patients with chronic renal failure treated by hemodialysis.

We compared plasma lipid and lipoprotein parameters between 210 chronic renal failure patients treated by hemodialysis and 223 age- and sex-matched healthy control subjects to examine whether atherogenic lipoprotein changes were present in hemodialysis patients in the absence of hyperlipidemia. The hemodialysis group showed higher levels of plasma triglycerides, very low density lipoprotein (VLDL) cholesterol, and intermediate density lipoprotein (IDL) cholesterol and a lower level of high density lipoprotein (HDL) cholesterol. Low density lipoprotein (LDL) cholesterol of the hemodialysis group was not elevated but their LDL was significantly more triglyceride-enriched than that of controls. Subjects were then divided into five categories according to their plasma triglyceride levels at an interval of 50 mg/dl, and comparison was made between the two groups in the same range of plasma triglycerides. Hemodialysis patients again showed higher levels of VLDL- and IDL-cholesterol, and lower levels of HDL-cholesterol than the control group even in the plasma triglycerides-matched comparisons. Similarly, higher VLDL- and IDL-cholesterol levels in hemodialysis patients were significant in plasma total cholesterol-matched subgroup comparisons. Multiple regression analysis indicated that the relationship between plasma lipid concentrations and individual lipoprotein levels were substantially altered in uremic state. The 95th percentile level of IDL-cholesterol in the nonuremic controls was 15 mg/dl, and 45% of hemodialysis patients exceeded this level. Decreased HDL-cholesterol levels < or = 35 mg/dl were seen in 6% of the control and 38% of the hemodialysis group. Elevated IDL-cholesterol and decreased HDL-cholesterol were persistently found in hemodialysis patients with normal lipid levels. It is concluded that hemodialysis patients exhibited more atherogenic lipoprotein profile than nonuremic subjects with comparable levels of plasma triglycerides and total cholesterol. Especially, increased IDL- and decreased HDL-cholesterol levels in hemodialysis patients persisted even at very low levels of plasma lipids. Since elevated IDL and decreased HDL-cholesterol are implicated in the progression of atherosclerosis, these findings are of clinical importance in the diagnosis of lipoprotein disorder in chronic renal failure.

Arteriosclerosis↗