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Biomedical subjects

T Ban

Publications and source records attributed to T Ban.

At least 19 recordsLinked to original sources
PubMed1995

Prediction of reversible ischemia after revascularization. Perfusion and metabolic studies with positron emission tomography.

BACKGROUND: Accurate noninvasive determination of myocardial viability is of paramount importance for the clinical identification of patients who will benefit most from revascularization. The preserved metabolic activity in the myocardium, as studied with positron emission tomography (PET), has been considered a gold standard for this purpose. However, recent reports show that moderate hypoperfusion or stress-induced ischemia may represent reversible ischemia. The present study was undertaken to compare the value of perfusion and metabolic studies with PET for predicting improvement in wall motion after revascularization. METHODS AND RESULTS: Of 61 patients who had regional asynergy and underwent PET before revascularization, 43 patients who had successful revascularization were included in the study. Each patient underwent rest-stress 13N-ammonia perfusion scans and 18F-fluorodeoxyglucose (FDG) scan at rest while in a fasting state. Reversible ischemia was considered to be present when the resting perfusion was > or = 50% of the peak value, stress-induced hypoperfusion was present, or an increase in FDG uptake was observed. Of 130 asynergy segments, 51 segments had improved wall motion after revascularization. The positive and negative predictive values for improvement in asynergy were 48% and 87% by the rest perfusion study, 63% (P = .05 versus the rest value) and 87% by the rest-stress perfusion study, and 76% (P < .01 versus the rest value) and 92% by the FDG study. CONCLUSIONS: FDG PET provided the best predictive value for improvement in wall motion after revascularization. On the other hand, 13N-ammonia PET is useful for predicting nonreversible myocardial scarring when it shows severe hypoperfusion at rest or hypoperfusion without stress-induced ischemia.

Adult↗
PubMed1995

Right ventricular function evaluated by volumetric analysis during left heart bypass in a canine model of postischemic cardiac dysfunction.

Right ventricular function during left heart bypass was evaluated by volumetric analysis with a conductance catheter in 12 dogs with postischemic cardiac dysfunction. The conductance catheter was used to assess the volumetric status of the right ventricle and thereby allowed a right ventricular pressure-volume curve to be obtained, in which transient volume loading on the right ventricle was applied. The following right ventricular properties during left heart bypass were assessed and compared with properties measured without left heart bypass, by means of load-independent parameters: maximum elastance, stroke work/end-diastolic volume relation, end-diastolic pressure/volume relation, and stroke work/end-diastolic pressure relation. The stroke volume derived from the conductance catheter and the electromagnetic flow probe showed good linear correlation (r2 = 0.733 to 0.975). After initiation of left heart bypass, maximum elastance did not change significantly, although volume intercept significantly increased, from 1.2 +/- 7.3 to 3.6 +/- 7.9 ml (p < 0.05). End-diastolic pressure/volume relation was well fitted to the exponential curve (EDP = e(k1.EDV+k2)) and was shifted to the right and downward during left heart bypass; the slope k1 significantly decreased, from 0.12 +/- 0.06 to 0.10 +/- 0.07 (p < 0.01). Stroke work/end-diastolic volume relation and stroke work/end-diastolic pressure relation were closely fitted to the linear regression, and their slopes were significantly increased during left heart bypass, from 0.14 +/- 0.08 to 0.18 +/- 0.08 (p < 0.05) and from 0.22 +/- 0.15 to 0.34 +/- 0.19 (p < 0.01), respectively. These results suggest that the decompression of the left ventricle and septal shifting by left heart bypass provide good diastolic compliance and good systolic performance because of afterload unloading of the right ventricle. Thus the left heart bypass improved the overall right ventricular performance, particularly at higher end-diastolic pressures, in dogs with postischemic cardiac dysfunction.

Animals↗
PubMed1995

Immunoprecipitation isolates multiple TSH receptor forms from human thyroid tissue.

Attempts to purify the thyroid-stimulating hormone receptor (TSHR) have been complicated by its susceptibility to proteolysis and its low level of expression in thyrocytes and many transfected cells. Controversy exists over its size and structure. Multiple, single-polypeptide forms of the TSHR (230, 187, and 95-100 kDa) have been recently identified in immunoblots of crude plasma membranes prepared from COS-7 cells transfected with rat or human cDNA, but the relationship of these receptor species to the TSHR in human thyroid tissue has been heretofore unknown. We have developed a technique for immunoprecipitation of the TSHR which employed IgG purified from a polyclonal rabbit antiserum to TSHR residues 352-366. We have used immunoprecipitation to isolate the previously characterized 95-100 kDa TSH-holoreceptor, 187 kDa intermediate, and 230 kDa precursor forms of the TSHR from plasma membrane prepared from transfected COS-7 cells and human thyroid tissue. The presence of all three forms was not altered by the addition of reducing agent to the sample buffer, demonstrating the single polypeptide structure of the TSHR. This is, to our knowledge, the first report of the purification from transfected COS-7 cells of these TSHR species identified previously only in immunoblots of crude plasma membrane, and the first report of the identification by any means of these TSHR forms in human thyroid tissue. The isolation of TSHR from human thyroid tissue requires confirmation by direct means, but promises to make the receptor available in a soluble form for studies of its structure and function.

Cell Line↗
PubMed1995

Selective blockade of P-type calcium channels by lead in cultured hippocampal neurons.

The effects of lead ions (Pb2+) on neuronal calcium channels were examined in cultured hippocampal neurons. Pb2+ blocked calcium channels in a concentration-dependent manner. The current-voltage relationship of the inhibition suggested a selective blockade of high-threshold calcium channels by Pb2+ up to a concentration of 3 microM. Pb2+ (3 microM) preferentially suppressed the omega-agatoxin IVA-sensitive components of the calcium channels. These findings suggest that Pb2+ mainly affects the P-type calcium channels at low concentrations.

Animals↗
PubMed1995

[Surgical treatment of congenital aortic stenosis by aortoseptal approach].

Between 1975 and 1994, six patients under 15 years old with congenital aortic stenosis underwent relief of left ventricular outflow tract obstruction (LVOTO) by aortoseptal approach. Although we got satisfactory relief of LVOTO in all patients, there were two late deaths. In one patient with residual ventricular septal defect (VSD), intractable ventricular arrhythmia developed 12 years postoperatively. Although the residual VSD closure was performed, the patient died of the arrhythmia. The another one who was the youngest 4-year-old boy suddenly died 4 months postoperatively. The detail about his death was unknown, but we presumed ischemic heart attack as the cause of his death. In 3 of remaining survived 4 patients, we encountered a few complications. They were right ventricular outflow obstruction, coronary artery injury and conduction system injury. All complications and problems we encountered in this series were related to the incision and the reconstruction of aortoseptal approach. In conclusion, the aortoseptal approach is effective technique for relief of LVOTO, but on the other hand it is invasive and not so safe operation. So we should be cautious about these complications and problems.

Adolescent↗
PubMed1994

Pulmonary arterial changes in patients dying after a modified Fontan procedure following pulmonary artery banding.

Pulmonary arterial changes were histometrically analyzed in four cases of postoperative death following a modified Fontan procedure in which pulmonary artery banding had previously been performed because of pulmonary hypertension. Case 1 was a 3-year-old girl with corrected transposition of the great arteries (TGA), ventricular septal defect, and double-inlet left ventricle; case 2 was a 6-year-old girl with single ventricle (SV) and complete TGA; case 3 was a 25-month-old boy with SV and double-outlet right ventricle; and case 4 was a 21-year-old man with tricuspid atresia. The cause of death in cases 1, 2, and 3 was pulmonary hypertensive crisis due to postoperative vasoconstriction of the small pulmonary arteries. Medical hypertrophy remained in half of the preacinar small pulmonary arteries although it was not observed in all the intraacinar arteries in cases 1 and 2, even after banding. The postoperative course of case 4 was uneventful despite multiple thromboembolism in the small pulmonary arteries. However, the patient died due to a thrombosed artificial valve. The results suggest that residual medial hypertrophy of the small pulmonary arteries was a major risk factor in these cases. Lung biopsy is recommended to determine the indications for the Fontan procedure in these hemodynamically critical cases.

Adult↗
PubMed1994

Thyrotropin stimulation of the lutropin/choriogonadotropin receptor: different sites mediate agonist activity and high affinity binding.

Surprisingly, thyrotropin (TSH) can increase cAMP and inositol phosphate (IP) levels in Cos-7 cells transfected with the lutropin (LH)/choriogonadotropin (CG) receptor (LH/CGR) as well as LH or CG, as evidenced by similar EC50 and maximal stimulation values. Additionally surprising, TSH activation is evident, despite markedly reduced levels of high affinity TSH binding by comparison to CG (Hidaka A, et al. 1993 Biochem Biophys Res Commun 196:187-195). In this report, we questioned whether the unusual TSH activity, as well as the discrepancy between TSH activity and binding, might reflect the existence of distinct agonist and binding sites on the LH/CGR extracellular domain and the ability of TSH to interact with the former despite a minimal interaction with the latter. We evaluated this possibility by using two chimeras spanning the extracellular domain of the TSHR and the LH/CGR:Mc1 + 2, where residues 8-165 of the TSHR are substituted, and Mc2 + 3 + 4, where residues 90-370 are replaced with the corresponding peptide segment from the LH/CGR. After transfection in Cos-7 cells, Mc2 + 3 + 4 exhibits higher affinity for CG than wild-type LH/CGR, but has no CG agonist response in assays measuring cAMP or inositol phosphate (IP) levels. Conversely, the Mc1 + 2 chimera exhibits significantly decreased affinity for CG, but CG agonist activity is comparable to wild-type LH/CGR in cAMP and IP assays. These data show that the extracellular domain of the LH/CGR does have distinct sites for CG binding and agonist activity: the C-terminus in Mc2 + 3 + 4 is important for high affinity CG binding, whereas the N-terminus in Mc1 + 2 is able to exhibit a CG agonist response, despite low affinity binding. When evaluated using TSH, Mc1 + 2, with the C-terminus of the TSHR present, exhibits high affinity TSH binding comparable to wild-type TSHR. Unexpectedly, Mc1 + 2, with the substitution of the N-terminus of the extracellular domain of the LH/CGR, exhibits even better TSH agonist activity than wild-type TSHR, not a loss of activity. Thus, the N-terminus of the extracellular domain of the LH/CGR can couple TSH binding to signal transduction events even better than the N-terminus of the TSHR. This may, in part, explain why TSH has an unusual agonist activity in cells transfected with LH/CGR, despite relatively low affinity binding. Although distinct agonist and binding sites exist in the linear sequence of the extracellular domain, the activity of the two sites is interdependent.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1994

[Effects of volatile anesthetics on force interval relationships in guinea-pig atrial preparations].

Depressant effects of halothane, enflurane and isoflurane on isolated guinea-pig left atrial muscles bathed in Tyrode's solution at 30 degrees C were examined. Contractions were elicited by stimulation through external field electrodes while tension was recorded continuously. Frequency-force relationships at stimulation rates of 0.1, 0.2, 0.5 and 1 Hz were studied. The pD2 values of these volatile anesthetics at each stimulation rates were not different significantly, suggesting the frequency-independent depressions of these anesthetics. Interval-strength relationships at time intervals of 0.3-20 sec during 1 Hz-stimulation were also studied. Mechanical restitution curves after converting to logistic function reached a peak at 8-20 sec and were fitted well to double exponential functions with time constants of 200-600 msec (k1) and 2-6 sec (k2). All volatile anesthetics depressed the magnitude constants for fast response in a dose dependent manner. Accordingly, at high concentrations, mechanical resuscitation curves tended to fit single exponential function. Halothane and enflurane did not alter time constant k1, k2 significantly, while isoflurane increased k2 significantly. These results suggest that the mechanisms of myocardial depressant effects are different between these anesthetics.

Anesthetics, Inhalation↗
PubMed1994

A model study of time- and voltage-dependent effects of class I antiarrhythmic drugs in guinea-pig papillary muscles as related to external potassium concentration.

1. A piecewise exponential three-state model previously introduced by the authors in 5.4 mmol/l was intended to apply to states with different [K+]o and with a different drug. Using the conventional microelectrode technique the effects of 20 mumol/l mexiletine (MEX), 5 mumol/l aprindine (APR), 20 mumol/l quinidine (QUI), 5 mumol/l flecainide (FLE), 5 mumol/l E-0747 (dl-6-chloro-2,2'-dimethyl-1'-[3-(4-hydroxypiperizino)propyl]spiro [chroman-4,4'-imidazolidine]-2',5'-dione hydrochloride and 100 mumol/l QX-222, a quaternary derivative of lidocaine, on action potentials (APs) in guinea-pig papillary muscles were studied. Specific objects of the study were (1) steady state Vmax values at various frequencies (all drugs), (2) the recovery process of Vmax in premature responses (MEX) and (3) Vmax changes during a train of stimulation at 1 Hz after a rest period (all other drugs) in 2.7 and 10 mmol/l [K+]o. Further, those of APR alone and APR plus 1 mmol/l nicorandil (NIC), which shortened action potential durations (APDs) specifically, were investigated on the above items (1) and (3) in 5.4 mmol/l [K+]o. 2. All the drugs reduced the Vmax of APs frequency-dependently and, except QX-222, more markedly in 10 mmol/l [K+]o than in 2.7 mmol/l [K+]o at 1 Hz. 3. The rate constants estimated from the model fitting characterized MEX and APR and the other drugs as predominantly inactivated and activated channel blockers, respectively. The calculated rate of onset of block, lambda T, does not differ much between the three [K+]o levels. lambda T shows that APR belongs to class Ia rather than class Ib.(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗
PubMed1994

[Surgery of type A acute aortic dissection with gelatin-resorcin-formal (GRF) biological glue--study of six cases].

GFR (Gelatin-Resorcin-Formalin) glue consists of mixture of gelatin and resorcin. The mixture is hardened by the addition of medical form-aldehyde, creating tridimensional network. From August 1991 to February 1993, six patients of type A acute aortic dissection underwent repair of false lumen with GRF glue. Including one female, the mean age was 57.3 years old ranged 51 years old to 64 years old. The entry of aortic intima were found in the ascending aorta in 4 cases, in the greater curvature of aortic arch in one case, and in the lesser curvature of aortic arch in one case. We used GRF glue for adhesion of intimal and medial wall of dissecting aneurysm in all cases. In case 1, the ascending aorta was replaced with a ringed intraluminal graft, and in case 2, the ascending aorta was replaced with a graft. In case 3 and 4, the aortic wall was closed primarily using GRF glue after patch closure of an entry. In case 5 and 6, the ascending aorta including an aortic arch was replaced with a graft. We revealed that GRF glue could harden the thin wall of aorta in the acute phase.

Aortic Dissection↗
PubMed1994

[Effect of left heart bypass on right ventricular function in normal and acute heart failure dogs--an application of the conductance catheter to the right ventricle].

We investigated right ventricular function during left heart bypass (LHB) with 18 mongrel open-chest dogs, in normal and acute heart failure (AHF) dogs which underwent aortic cross clamp. Left ventricular unloading was completely accomplished with a centrifugal pump. For more accurate evaluation of right ventricular volume, conductance catheter was employed to assess right ventricular function. Analysis were performed with right ventricular pressure-volume curve which was changed by transient volume loading on right ventricle. And right ventricular properties with and without LHB were compared by the use of load independent parameters as follows. Right ventricular systolic property was evaluated by maximum elastance (Emax) and stroke work-end-diastolic volume relation (SW/EDVR), and its diastolic function was evaluated by end-diastolic pressure-volume relation (EDP/VR). Overall right ventricular performance was assessed by stroke work-end-diastolic pressure relationship (SW/EDPR). In the normal heart, only a parallel shift to the right in EDP/VR and SW/EDVR was noted without any significant changes in slope with LHB. On the other hand, in AHF dogs, the slope of SW/EDVR and SW/EDPR were increased from 0.14 +/- 0.08 to 0.18 +/- 0.08 (p < 0.05), from 0.22 +/- 0.15 to 0.34 +/- 0.19 (p < 0.01), respectively, and the curve of EDP/VR was shifted right and downward. These result suggested that decompression of the left ventricle and septal shifting by LHB provided good diastolic compliance and afterload unloading of the right ventricle, and these effects had a more significant role in acute heart failure than in the normal heart.

Acute Disease↗
PubMed1994

Fetal bovine serum is not necessary for the cryopreservation of aortic valve tissues.

The purpose of this study was to estimate the protective effects of fetal bovine serum on the cryopreservation of aortic valve tissues. Ten porcine aortic valves were divided into two groups according to the nutrient content of the medium used for sterilization and cryopreservation. Group A valves were preserved in Dulbecco's modified Eagle medium containing 10% fetal bovine serum, whereas group B valves were preserved in Dulbecco's modified Eagle medium alone. The fibroblast viability of the cryopreserved tissues was assessed autoradiographically with the use of tritiated proline at the following points: fresh control, after sterilization, and after storage for 1 week or 3 months. The proportion of viable fibroblasts decreased to a similar extent in both groups of tissues after 1 week of storage, 81.1% +/- 2.5% in group A and 80.4% +/- 3.3% in group B, and after 3 months of storage it decreased slightly to around 73% for both groups of tissues. No significant difference was observed between the two groups at any time. These result suggest that fibroblasts are adequately preserved even after 3 months of cryopreservation, and that the addition of fetal bovine serum to the medium does not further improve their viability. Thus, from a point of view of fibroblast viability, it is not necessary to use fetal bovine serum for the cryopreservation of aortic valve tissues.

Animals↗
PubMed1993

[Development and medical application of Er-YAG laser].

Result of developments of Er-YAG laser and its delivery system were reported. Er-YAG laser's wavelength is 2.94 microns, the beam absorption rate by water is higher than other laser beam. Er-YAG laser has repeated pulse oscillation, pulse width is 400 mu, sec, the repeat frequency is between 5 to 10 pulse per second. The mean power is 4 W maximum, 10 pps. The fibers of laser are made of zirconium-F-glass. We carried out a study on the possible application of the Er-YAG laser on the rabbit arteries and myocardium and human arteries were examined in vitro. Very clear cuts were observed on the histological examination. There were no evidence of thermal damage, no carbonization on the sharp cutting surface. Experimental result showed that Er-YAG lasers had good potential for angioplastic laser.

Angioplasty, Laser↗
PubMed1993

Decreased expression of DCC mRNA in human colorectal cancers.

The mRNA expression levels of DCC gene, which is cloned from the deleted region of chromosome 18q in colorectal cancers and thought to be a tumor-suppressor gene, was evaluated in tissue specimens surgically resected from patients with colorectal cancer by RT-PCR. This method was chosen as the expression level of DCC mRNA is below the detectable level for Northern-blot analysis. Semi-quantitative measurements of DCC mRNA were performed based on a standard curve defined by serial dilution of DCC cDNA. As a result, the expression level of DCC mRNA was found to be lower in 17 out of 30 colorectal cancers than in adjacent non-cancerous tissues. Inclusion of smooth muscle in tissue specimens was observed to have little disturbing effect on comparisons between cancerous and non-cancerous regions. In addition, all 4 specimens of colorectal cancer with liver metastasis showed the decreased expression level of DCC mRNA, suggesting that functional loss of DCC in cancerous tissues may play an important role in metastatic events.

Actins↗
PubMed1993

Use of thyrotropin receptor (TSHR) mutants to detect stimulating TSHR antibodies in hypothyroid patients with idiopathic myxedema, who have blocking TSHR antibodies.

Deletions of residues 295-306, 299-301, and 387-395 of the TSH receptor, as well as point mutations of cysteine 301 or 390 to serine, and tyrosine 385 to phenylalanine or alanine, markedly diminish the ability of a transfected receptor to measure the activity of blocking TSH receptor autoantibodies (TSHRAbs) in patients with idiopathic myxedema and hypothyroidism, but not stimulating TSHRAbs in Graves' patients. This has allowed us to use these mutants to detect stimulating TSHRAb activity in the sera of hypothyroid patients with idiopathic myxedema who have blocking TSHRAbs. In 7 such patients, we show that 50% or more have significant stimulatory activity in cells transfected with mutant receptors, as evidenced by the ability of the immunoglobulin G to directly increase cAMP levels or to enhance the ability of TSH or a Graves' stimulating TSHRAb to increase cAMP levels. Three of the TSH receptor mutants, deletions of residues 295-306 and 387-395 and the point mutation of cysteine 301 to serine, are shown to be particularly useful in these assays and may be useful to clarify the pathogenetic role and clinical significance of stimulating TSHRAbs in patients with autoimmune thyroid disease who also have blocking TSHRAbs.

Animals↗
PubMed1993

Receptor cross-talk can optimize assays for autoantibodies to the thyrotropin receptor: effect of phenylisopropyladenosine on adenosine 3',5'-monophosphate and inositol phosphate levels in rat FRTL-5 thyroid cells.

Immunoglobulins (IgG) from patients with Graves' disease increase inositol phosphate (IP) as well as cAMP production in rat thyroid FRTL-5 cells; IgGs from normal control subjects do not. Graves' IgG-and TSH-induced IP formation is inhibited by blocking TSH receptor (TSHR) antibodies from hypothyroid patients with primary myxedema, as is the cAMP response; this suggests that the Graves' IgG are acting through the TSHR to induce both the cAMP and phosphatidyl-inositol 4,5-biphosphate signal cascades in FRTL-5 thyroid cells as in cells with recombinant TSHR. Optimal conditions for measuring the Graves' IgG-induced IP increase include a NaCl-free Hanks' Balanced Salt Solution (HBSS) buffer system and a P1 purinergic receptor agonist; the action of each is additive. Optimization by NaCl-free HBSS is similar to that observed in cAMP assays and is specific for TSH or Graves' IgG; thus, NaCl-free HBSS did not affect ATP-induced, and actually inhibited norepinephrine-induced, IP production in FRTL-5 cells. The P1 purinergic receptor agonist acts via receptor cross-talk, which also allows further optimization of cAMP assays. Thus, adenosine deaminase improves Graves' IgG-induced cAMP production by removing adenosine from the medium. Although NaCl-free HBSS improved TSH- or Graves' IgG-induced IP and cAMP production in cells with recombinant TSHR; the modulatory action of phenylisopropyladenosine was lost.

Animals↗