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)

Prognostic value of an increase in fluorine-18 deoxyglucose uptake in patients with myocardial infarction: comparison with stress thallium imaging

OBJECTIVES

This study was undertaken to evaluate the prognostic value of an increase in fluorine (F)-18 deoxyglucose uptake compared with clinical, angiographic and stress thallium findings in patients with myocardial infarction.

BACKGROUND

Positron emission tomography (PET) imaging using F-18 deoxyglucose has been applied to assess tissue viability in patients with coronary artery disease. We hypothesized that patients with a myocardial segment with augmented F-18 deoxyglucose uptake are at high risk for a future cardiac event.

METHODS

One hundred fifty-eight consecutive patients with myocardial infarction referred for F-18 deoxyglucose PET and stress thallium scans were studied. Follow-up was obtained in 84 patients at a mean interval of 23 months to investigate prognostic implications of radionuclide studies.

RESULTS

Seventeen patients had a cardiac event during the follow-up interval. Univariate analysis showed that an increase in F-18 deoxyglucose uptake was the best predictor of a future cardiac event (p = 0.0006), followed by the number of stenosed vessels (p = 0.008). In the multivariate analysis, when an increase in F-18 deoxyglucose uptake was entered into the model, only angiographic variables had an independent prognostic value, whereas no other radionuclide variables showed significant prognostic value. Among patients who did not show redistribution, a future cardiac event was observed more often in patients with than in those without an increase in F-18 deoxyglucose uptake (p < 0.05).

CONCLUSIONS

Thus, an increase in F-18 deoxyglucose uptake seemed to be the best predictor of a future cardiac event among all clinical, angiographic and radionuclide variables in this study of stable patients with myocardial infarction. Even when a stress thallium-201 scan does not show redistribution, those patients who have an increase in F-18 deoxyglucose uptake in a PET study may be at risk for a future cardiac event, and these patients may need aggressive treatment to prevent a future cardiac event.

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.

[Biosynthesis and secretion of vasopressin]

Oxytocin and vasopressin (AVP), which are octapeptides with a molecular mass of approximately 1.1 kd, are posterior pituitary hormones. AVP produced by magnocellular neurons in the supraoptic and paraventricular nuclei of the hypothalamus is in a form bound to the specific peptide neurophysin II, in the neurosecretory granula (NSG). Cleavage of this prohormone occurs within the NSGs during its transport via the axons to the neurohypophysis. Neurohypophyseal secretion of these peptides is believed to occur by exocytosis, which might be regulated by intracellular Ca++. The biosynthesis and secretion of AVP are mainly regulated by plasma osmolality (osmotic regulation) and blood pressure or blood volume (nonosmotic regulation). Some drugs, neurotransmitters, and other chemical agents modulate the regulation of AVP release.

[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.

[Quantitative assessment of fibroblast viability in cryopreserved aortic valve allografts]

The purpose of this study is to clarify whether serum (fetal bovine serum or human serum) is necessary or not for cryopreservation of aortic valve allografts. The protective effects of fetal bovine serum compared with human serum were evaluated by means of quantitative assessment of fibroblast viability. Porcine aortic valves were excised and rinsed immediately after death, followed by treatment with low concentration antibiotics. Valves were gradually frozen at a control-rate of -1 degree C/min and then stored in liquid nitrogen vapor-phase. The samples were classified into three groups by nutrient medium as follows. Group A (n = 5); Dulbecco's Modified Eagle Medium (DMEM), Group B (n = 5); DMEM containing 10% fetal bovine serum, Group C (n = 5); DMEM containing 20% human serum. At 1 week, 1 month, and 3 months after initiation of storage, the valves were thawed rapidly and examined for fibroblast viability, which was assessed quantitatively by means of autoradiography with tritiated proline. After 1 week storage, the fibroblast viability rate reduced from 98% to 80.7% in group A, 79.4% in group B and 79.2% in group C respectively, but there were no significant differences among three groups. The viability rate decreased with the passage of time, and remained around 72% in all groups after 3 months storage. The histological examination did not show any changes in the structure of the valves in all samples up to 3 months of storage. The results demonstrate that the fibroblasts are still viable after 3 months storage by cryopreservation. The addition of fetal bovine serum or human serum does not improve fibroblast viability.(ABSTRACT TRUNCATED AT 250 WORDS)

[Gating properties of cardiac Na channels: from the macroscopic Na current viewpoint]

The sodium channel plays essential roles in the initiation and propagation of action potentials (APs) in excitable tissues including the heart, nerves, and muscles. Na channels in these tissues undergo so-called activation and then inactivation upon step-depolarizations of the cell membrane. Hodgkin and Huxley, early in the 1950s, proposed a mathematical model to describe such events, which was based on voltage-clamp (V-C) data on axonal membranes. However, for the next 30 years or so since the pioneering work of the above workers, electrophysiological studies of the Na channel kinetics in the heart had relied exclusively on AP data (Vmax) as an indirect measure of the Na current instead of V-C data due to difficulty in determining V-C from the complex geometry of cardiac tissues. However, recent development of an isolation procedure for preparing single heart cells and the use of single patch-pipettes for high resolution V-C experiments on these cells have made direct recording of Na channel currents also possible in the heart. Voltage-clamp studies carried out for the last decade have provided several lines of evidence supporting the view that the Na channel properties in the heart of any animal species are somehow more complex than in the axonal membrane and hence showing that Hodgkin-Huxley model can not be directly applied to describe the Na channel behavior in the former type of tissues. Here, we review recent results from V-C studies on Na channel properties with special reference to the macroscopic Na current in cardiac tissues.

Substitutions of different regions of the third cytoplasmic loop of the thyrotropin (TSH) receptor have selective effects on constitutive, TSH-, and TSH receptor autoantibody-stimulated phosphoinositide and 3',5'-cyclic adenosine monophosphate signal generation

TSH and immunoglobulin G (IgG) preparations from patients with Graves' disease increase inositol phosphate as well as cAMP formation in Cos-7 cells transfected with rat TSH receptor (TSHR) cDNA. In a previous report, we mutated alanine 623 of the third cytoplasmic loop (residues 605-625) of the TSHR and showed it was critical for TSH and Graves' IgG initiation of phosphatidylinositol bisphosphate (PIP2) but not cAMP signaling. In this report, we substituted residues in the third loop of the TSHR with sequences from the N- and C-termini of the third loop of the alpha 1- and beta 2-adrenergic receptors (ARs), which computer analysis has identified as homologous to those in the TSHR. Alanine 623 is conserved in most ARs as well as in glycoprotein hormone receptors; there is, therefore, no change in alanine 623. After transfection of the mutant TSHR cDNAs into Cos-7 cells, we show that the mutant proteins are normally synthesized, processed, and incorporated into the membrane bilayer by Western blotting with a specific receptor antibody. We also show that the dissociation constant for TSH binding in all mutants is the same or lower than wild type TSHR. We then evaluated the ability of TSH or Graves' IgG to increase PIP2 and cAMP signals in each transfectant. Mutants A622 and B621 replace, respectively, residues 622-625 and 621-625 of the TSHR with alpha 1- and beta 2-AR residues from the C-terminus of the third cytoplasmic loop; mutants A607 and B605 replace, respectively, TSHR residues 607-609 and 605-609 with N-terminus residues from alpha 1- and beta 2-AR. All four mutants, like the alanine 623 mutant, result in transfected cells which lose TSH and Graves' IgG initiation of PIP2 but not cAMP signalling. Like the alanine 623 mutation to glutamic acid, the A607, B605, A622, and B621 mutants also result in decreased basal cAMP, but not inositol phosphate levels, relative to wild type receptor. In contrast to these results, mutants A610, B610, A617, and B617, which replace residues 610-613 or 617-620 of the TSHR with corresponding residues of the alpha 1- and beta 2-AR, retain TSH and Graves' IgG responsiveness in both inositol phosphate and cAMP assays. Mutation of residues 610-613, in fact, potentiates TSH-increased inositol phosphate production, despite having no effect on TSH-increased cAMP production.(ABSTRACT TRUNCATED AT 250 WORDS)

[Quantitative assessment of improvement in perfusion after coronary bypass grafting: assessed by thallium-201 bull's eye subtraction polar map method]

To assess redistribution (RD) and improvement in regional perfusion after coronary bypass grafting (CABG) on thallium-201 SPECT images quantitatively, the Bull's eye subtraction polar (BS) map was created. BS map was created after subtraction of a normalized bull's eye polar map from another normalized polar map. The quantitative assessment on this map was compared to the visual qualitative analysis in 23 patients (115 segments) who received CABG. All of the improved segments after CABG showed > or = 15% on the BS map. On the other hand, 60% of the non improved segments showed < 10% on the BS map. Furthermore, 67% of the RD segments showing > or = 15% on the BS map before CABG improved in perfusion by > or = 15% on the BS map after CABG. On the BS map, an excellent correlation was observed between the extent of redistribution before CABG and the extent of improvement after CABG. Thus, BS map permits quantitative assessment of improvement in perfusion on T1 SPECT imaging, and this technique seems to be valuable for predicting improvement in perfusion after CABG.

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.

Chimeric studies of the extracellular domain of the rat thyrotropin (TSH) receptor: amino acids (268-304) in the TSH receptor are involved in ligand high affinity binding, but not in TSH receptor-specific signal transduction

A series of chimeric TSH-LH/CG receptors were constructed by substituting homologous segments of the extracellular domain of the rat TSH receptor with corresponding segments of rat LH/CG receptor: C1 (amino acids 37-123 substituted), C2 (91-112), C3 (173-234), C4 (233-266), C5 (268-304), C6 (112-305) and C7 (36-404). After transfection in Cos-7 cell, TSH- and LH/CG-receptor activities of these chimeras were evaluated and compared with those of deletion mutants involving the same residues [Kosugi et al. Thyroid 1:321 (1991)]. Western blot analyses revealed that most of the chimeric receptor proteins were normally synthesized and integrated in the membrane of transfected Cos-7 cells: an antibody to a TSH receptor specific synthetic peptide (residues 352-366) identified 170-190kDa and 90-100kDa TSH receptor structures in the plasma membrane fractions of Cos-7 cells transfected with wild-type TSH receptor cDNA and the C1 to C6 chimeras, but not C7 or wild LH/CG receptor cDNA. Despite this, no receptor except C5 exhibited any significant TSH receptor activities either in [12I]TSH binding or in cAMP responses to TSH and thyroid-stimulating antibodies (TSAbs) from Graves' patients. The chimeric receptor C5 exhibited only low affinity TSH binding (Kd = 3.5 x 10(-8) M), as did its counterpart the M2C mutant with residues 268-304 deleted. However, unlike M2C, C5 demonstrated a significant cAMP response to TSH as well as to TSAbs. The cAMP increase in response to TSH in the wild type receptor was observed at 10(-11) M TSH. In C5 the response was first evident at 10(-10) M TSH, but the maximum cAMP stimulation by TSH and TSAbs in C5 (EC50 = 6.7 x 10(-10) M) was approximately the same as the wild type receptor (EC50 = 1.5 x 10(-10) M). Inhibition of either TSH- or TSAb- stimulated cAMP increase by thyroid-stimulating blocking antibodies (TSBAbs) was also preserved in C5. These results suggest that amino acids 268-304 do not include an important determinant required for signal transduction, since a significant cAMP response to TSH and TSAbs was observed in the C5 receptor with these residues substituted. Additionally, these residues appear to be involved in ligand high affinity binding because high affinity TSH binding was lost in the chimeric receptor C5.

[A new skeletal muscle powered ventricle (SMPV) designed to work under physiologic preload]

To maximize pumping function the SMPV has been highly preloaded (over 30 mmHg); but the effects of pump size and configuration on the required preload have never been determined. A new double barrel dual chamber single layered (DCSL) SMPV having two SL small pumps in parallel was compared with a single chamber double layered small pump (SCDL). Stroke volume (SV) and stroke work (SW) were determined in acutely constructed SMPV using mongrel dog untrained latissimus dorsi: 10 DCSL and 12 SCDL. Under physiologic afterload (120 mmHg) and preload (15 mmHg), the DCSL displayed a significantly (p < 0.05) larger SV (9.9 +/- 1.2 ml) and SW (0.84 +/- 0.15 x 10(6) ergs) than the SCDL pumps (SV = 6.9 +/- 0.6 ml, and SW = 0.55 +/- 0.07 x 10(6) ergs). The DCSL pumps, requiring less muscle mass for its construction, indicated better performance under physiologic pre and afterload conditions than SCDL pumps.

Relationship between resting cytosolic Ca2+ and responses induced by N-methyl-D-aspartate in hippocampal neurons

Cytosolic calcium concentrations ([Ca2+]i) in cultured hippocampal neurons from rat embryos were measured using fura-2. Neurons with higher resting [Ca2+]i showed greater [Ca2+]i responses to N-methyl-D-aspartate (NMDA) and K+ depolarization. There was a strong relationship between resting [Ca2+]i and the maximal changes in [Ca2+]i (delta[Ca2+]i), which fit the our proposed equation to describe this relationship.

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.

Identification of thyroid-stimulating antibody-specific interaction sites in the N-terminal region of the thyrotropin receptor

Using mutants of the N-terminal region (residues 30-76) of the rat TSH receptor (TSHR), which substitute corresponding segments of rat gonadotropin receptors or hydrophilic (serine) and hydrophobic (alanine) amino acids as appropriate, we show that residues 30-33, 34-37, 42-45, 52-56, and 58-61, in addition to threonine-40, are determinants for the interaction of thyroid-stimulating autoantibodies (stimulating TSHRAbs) with the TSHR. The most important, residues 34-37, 42-45, and 52-56, whose mutants lose stimulating TSHRAb activity with at least 11 of 12 (> 90%) of the Graves' immunoglobulins G tested, are, like threonine-40, in regions of the TSHR that are nonhomologous with gonadotropin receptors. These data establish at least in part, therefore, the basis for the thyroid-specific effects of stimulating TSHRAbs. In no case do the same mutants lose their reactivity with TSH or blocking-type TSHR autoantibodies (blocking TSHRAbs) from hypothyroid patients with idiopathic myxedema. Since the latter have been shown to interact with high affinity TSH-binding sites on the C-terminal portion of the external domain of the TSHR, stimulating TSHRAbs and blocking TSHRAbs react with different receptor determinants, which can be presumed to have different roles in receptor function. This can explain the hyper- or hypothyroidism of different thyroid autoimmune diseases with receptor antibodies. Residues 30-33, 42-45, and threonine-40 appear to be related to the agonist action of TSH, since in each case mutation results in low affinity TSH binding, but normal TSH-increased cAMP activity, similar, for example, to a beta-adrenergic agonist. Using a receptor antibody to identify different receptor forms in the membrane, we can also identify determinants in this N-terminal region (residues 30-76) whose mutation results in a loss of all activities without apparently altering receptor synthesis, processing, or integration within the bilayer. These are residues 38 and 39, cysteine-41, residues 46-51, leucine-57, threonine-62, and, within residues 66-76, serine-69, alanine-71, phenylalanine-72, serine-74, leucine-75, and proline-76. We suggest that these residues are at the very least important in the conformational array of receptor determinants necessary for interactions with TSH and stimulating TSHRAbs.

Skeletal muscle-powered ventricle. Effects of size and configuration on ventricular function

The optimal size and configuration of skeletal muscle-powered ventricles are still undetermined. This study was aimed at comparing three types of skeletal muscle-powered ventricle: (A) a small size (15 ml capacity) double-layered pump, (B) a small size (15 ml capacity) single-layered pump, and (C) a large size (40 to 60 ml capacity) single-layered pump constructed sequentially with the same untrained latissimus dorsi muscle of 12 mongrel dogs. The skeletal muscle-powered ventricle was connected to a mock circulation system, the stroke volumes against 40 to 160 mm Hg of afterload at 5 to 60 mm Hg of preload were measured, and the stroke work was computer analyzed on line. Raising the preload from 5 to 60 mm Hg increased the peak isovolumic developed pressure (A) from 91.3 +/- 11.0 to 215.6 +/- 26.1 mm Hg, (B) from 92.8 +/- 12.0 to 166.3 +/- 19.0 mm Hg, and (C) from 32.3 +/- 5.2 to 121.4 +/- 15.5 mm Hg (p < 0.05, C versus A and B). Similarly, the stroke volume (stroke work) against an afterload of 120 mm Hg increased (A) from 3.8 +/- 0.5 ml (0.22 +/- 0.04 x 10(6) ergs) to 14.5 +/- 1.1 ml (1.05 +/- 0.11 x 10(6) ergs), (B) from 4.5 +/- 0.7 ml (0.30 +/- 0.08 x 10(6) ergs) to 10.7 +/- 0.9 ml (0.63 +/- 0.08 x 10(6) ergs), and (C) from 1.8 +/- 0.5 ml (0.09 +/- 0.04 x 10(6) ergs) to 24.0 +/- 3.6 ml (1.94 +/- 0.41 x 10(6) ergs) (p < 0.05, C versus B at 5 mm Hg of preload; p < 0.05, C versus A and B at preloads > or = 30 mm Hg). At low preloads (5 to 15 mm Hg) both small pumps generated a significantly larger stroke volume (stroke work) than the large pump, whereas at high preloads (> or = 30 mm Hg) the large pump generated a significantly larger stroke volume (stroke work) than the small pumps. It is concluded that under physiologic preload, B (small single-layered pump) performs better than or at least as well as A (small double-layered pump) and C (large single-layered pump), despite being constructed with only one half of the muscle mass used for either A or C.

Role of cysteine residues in the extracellular domain and exoplasmic loops of the transmembrane domain of the TSH receptor: effect of mutation to serine on TSH receptor activity and response to thyroid stimulating autoantibodies

The extracellular domain of the thyrotropin (TSH) receptor is the primary site with which TSH and receptor autoantibodies interact. Cysteines 494 or 569 in the 1st and 2nd exoplasmic loops, respectively, of the transmembrane domain of the TSH receptor are important in this process or in coupling ligand binding to signal generation. Thus, when either is mutated to serine, a receptor results which has no detectable TSH binding and no cAMP response to TSH or thyroid stimulating autoantibodies after transfection, despite the fact the mutant receptor is normally synthesized, processed, and integrated in the membrane, as evidenced by Western blotting using a TSH receptor-specific antibody. Additional site directed mutagenesis studies are performed in order to identify cysteine residues in the extracellular domain of the receptor which, with cysteines 494 and 569, are important for tertiary structure and receptor bioactivity.

Mutation of alanine 623 in the third cytoplasmic loop of the rat thyrotropin (TSH) receptor results in a loss in the phosphoinositide but not cAMP signal induced by TSH and receptor autoantibodies

Thyrotropin (TSH) and IgG preparations from patients with Graves' disease increase inositol phosphate as well as cAMP formation in Cos-7 cells transfected with rat TSH receptor cDNA. Mutation of alanine 623 in the carboxyl end of the third cytoplasmic loop of the TSH receptor, to lysine or glutamic acid, results in the loss of TSH- and Graves' IgG-stimulated inositol phosphate formation but not in stimulated cAMP formation. There is no effect of the mutations on basal or P2-purinergic receptor-mediated inositol phosphate formation. The mutations do not affect transfection efficiency or the synthesis, processing, or membrane integration of the receptor, as evidenced by the unchanged amount and composition of the TSH receptor forms on Western blots of membranes from transfected cells. The mutations increase the affinity of the TSH receptor for [125I]TSH and decrease Bmax; however, cells with an equivalently decreased Bmax as a result of transfection with lower levels of wild type receptor do not lose either TSH-induced inositol phosphate formation or cAMP signaling activity. Thus, in addition to discriminating between ligand-induced phosphatidylinositol bisphosphate and cAMP signals, the mutation appears to cause an altered receptor conformation which affects ligand binding to its large extracellular domain.

Major histocompatibility complex class I gene expression in rat thyroid cells is regulated by hormones, methimazole, and iodide as well as interferon

Autoimmune thyroid disease is associated with enhanced expression of major histocompatibility complex class I antigens on thyrocytes. To better understand this phenomenon, we have studied the normal expression of class I genes in FRTL-5 rat thyroid cells. A variety of hormones and growth factors that regulate the growth and function of these thyroid cells were found to decrease class I RNA levels: serum, insulin or insulin-like growth factor-I (IGF-I), and hydrocortisone. Antibody preparations from Graves' patients (thyroid-stimulating antibodies), which increase cAMP levels and stimulate the thyroid, also decrease class I RNA levels. This is consistent with the fact that TSH, via its cAMP signal, reduces class I transcripts. The class I response to TSH, serum, insulin, IGF-I, or hydrocortisone is specific, in that the same agents do not similarly affect TSH receptor, thyroglobulin, thyroid peroxidase, malic enzyme, or beta-actin RNA levels. Both gamma- and alpha-interferon increase class I RNA levels in FRTL-5 cells, even in the presence of the serum, IGF-I, or hormones noted above, i.e. they overcome hormonal negative regulation in normal thyrocytes. In contrast, methimazole treatment of rat FRTL-5 thyroid cells, but not rat fibroblasts or rat FRT thyroid cells, which have no TSH receptor and no TSH-regulated function, results in reduced class I RNA levels. The action of methimazole can inhibit interferon action, is transcriptional, is duplicated by iodide, and is additive with the negative regulatory action of hormones and serum factors, including TSH.

In vitro closing behavior of the St. Jude Medical heart valve in the pulmonary position. Valve incompetence originating in the prosthesis itself

We examined the in vitro closing behavior of the St. Jude Medical heart valve, simulating (1) a low-pressure system, (2) the anatomic peculiarity of the right ventricular outflow tract and the main pulmonary artery, and (3) disturbed diastolic compliance of the right ventricle. The variables in the experiment were the load impedance to the pump and the valve orientation. The results were as follows. The sequence of closure of the two semidiscs was based on the valve orientation; reduction in impedance caused the semidisc that closed last to remain open, while the other semidisc continued its open-close motion; further reduction in impedance prevented the semidisc, which continued its open-close motion, from closing completely. These results highlight the forces involved in semidisc closure and the existence of a threshold of force for completion of semidisc closure. Further, the results demonstrate that under certain circumstances the threshold cannot be exceeded via those forces. Therefore this incompetence must originate in the prosthesis itself. In this regard, we suggest an urgent need to reconsider the indications for St. Jude Medical heart valve pulmonic implantation. Finally, we advocate the necessity for an in vitro assessment of valve prostheses in a low-pressure system, to evaluate the safety of right-sided placement.

Specific antibody to the thyrotropin receptor identifies multiple receptor forms in membranes of cells transfected with wild-type receptor complementary deoxyribonucleic acid: characterization of their relevance to receptor synthesis, processing, structure, and function

An antibody to a peptide of the TSH receptor, residues 352-366 which are not present in gonadotropin receptors, specifically identifies three major forms of the receptor on Western blots of detergent-solubilized membrane preparations from Cos-7 cells transfected with full-length rat and human TSH receptor cDNA: 230, 180, and 95-100 kilodaltons (kDa), based on simultaneously run protein standards. The 95- to 100-kDa protein is absent in cells transfected with a mutant receptor with no signal peptide and is sensitive to endoglycosidase-F. Its size is consistent with the sum of amino acids predicted from its cDNA sequence (84 kDa after subtracting the signal peptide) plus its carbohydrate content (14 kDa estimated from glycosylation mutants). It alone is absent in two deletion mutants that have lost TSH binding and activity after transfection: M1 missing residues 37-121 and M2 missing residues 110-307. It, thus, appears to be the processed glycosylated functional receptor on the cell surface. The 230-kDa protein is a nonprocessed form of the receptor, as evidenced by its insensitivity to endoglycosidase-F and its continued presence in cells transfected with a mutant receptor with no signal peptide. It is the primary form identified in rat FRTL-5 thyroid cells that have a functioning TSH receptor; it is not present in rat FRT thyroid cells with no functioning TSH receptor or receptor RNA. It appears, therefore, to be a early synthetic form of the functional TSH receptor. The 180-kDa protein is endoglycosidase-F sensitive and appears to be a processed intermediate between the 230-kDa early synthetic form and the 95- to 100-kDa functional receptor, rather than a dimer of the latter. Thus, with decreases in size appropriate to a receptor monomer, it remains present in membranes from the M1 and M2 deletion mutants that contain the 230-kDa protein but are missing the 95- to 100-kDa receptor form in association with lost TSH binding and activity after transfection. Minor receptor forms (54 kDa in rat receptor transfectants, 54 and 48 kDa in human receptor transfectants) appear to be degraded forms of the processed and glycosylated 95- to 100-kDa receptor. The presence or absence of reducing agents in the detergent solubilization mixture does not change the pattern or amount of the receptor forms recognized by the antibody, including the 54-kDa form; however, boiling does.(ABSTRACT TRUNCATED AT 400 WORDS)

Skeletal muscle powered pumps can work under low preload. Design considerations

Characteristics of a dual chambered, single layered skeletal muscle powered pump (DCSLP) and a single chamber, multilayered pump (SCMLP) made from similar masses of untrained latissimus dorsi muscle (LD) were compared. For the DCSLP, 16 canine LDs (51.5 +/- 1.6 g) were wrapped in a "figure eight" around two parallel mandrels, whereas for the SCMLP, LDs were made in 10 by wrapping the LD (54 +/- 8.5 g) twice around one mandrel. Chamber compliance and pump isovolumic peak developed pressure (PDP), stroke volume (SV), stroke work (SW), and ejection fraction (EF) of single contractions were measured. In six of the DCSLP dogs (LV), heart left ventricular stroke volume (LVSV) and left ventricular stroke work (LVSW) were determined. Stimulation parameters were the same for all. Student's t-test (* = p < 0.05) was used for statistical analysis. Dual chambered, single layered skeletal muscle powered pumps with a diastolic volume/mass ratio of 0.63 were more compliant than SCMLPs with a ratio of 0.37. Single chamber, multilayered pumps generated slightly higher PDP, but this was significant only at 60 mmHg preload. At a preload of 15 and an afterload of 120 mmHg, DCSLPs had higher SV (10.7 +/- 1.1 ml) and SW (0.98 +/- 0.14 x 10(6) ergs) than SCMLPs (6.8 +/- 0.7 ml* and 0.58 +/- 0.08 x 10(6) ergs*), or their LV counterparts (5.3 +/- 0.9 ml and 0.84 +/- 0.22 x 10(6) ergs).(ABSTRACT TRUNCATED AT 250 WORDS)

Modelling of frequency-dependent effects of lignocaine homologues on the maximum upstroke velocity of action potentials in guinea-pig papillary muscles

1. The effects of 14 lignocaine homologues on the maximum upstroke velocity (Vmax) of the action potentials (AP) were studied in guinea-pig papillary muscles. These drugs possess one, two or three methyl groups in different positions: an ortho-chloro, -carbomethoxy or -ethyl group instead of an ortho-methyl group; or an N-butyl group instead of an N-diethyl group in lignocaine molecules. 2. At 50-100 mumol/L, six drugs possessing two ortho substituents (but not the other eight) reduced Vmax more prominently at 2-4 Hz than at 1 Hz, and slowed the time courses of recovery of the premature responses. None of the drugs affected resting potential. 3. Besides the two-state piecewise exponential model (models I and II) frequently used, a time-dependent and time-independent, two-state model (model III) was formulated and applied to these experimental data. The above two groups were effectively distinguished by the difference of the estimated association and dissociation rate constants (model II) and equilibrium constants for phasic state (model III) and for resting (model II) or tonic (model III) states. 4. The equilibrium constants for resting or tonic state correlated well with log P (where P = the n-octanol: water partition coefficients), but correlated better with an indicator variable that denotes the existence of two ortho substituents, suggesting the importance of the contribution of steric factors to the activity.

Arterial ketone body ratio during and after cardiopulmonary bypass

This study is the first to investigate the alteration in hepatic function during and after cardiopulmonary bypass in 30 patients by measuring the arterial ketone body ratio, an index of mitochondrial redox potential (oxidized nicotinamide-adenine dinucleotide/reduced nicotinamide-adenine dinucleotide). Although the preoperative arterial ketone body ratio was within normal limits (1.24 +/- 0.63), it decreased markedly 5 minutes after the start of cardiopulmonary bypass to 0.35 +/- 0.12 and remained at this low level throughout bypass. After bypass it continued to rise in a time-dependent fashion, returning to its preoperative level by the morning of the second postoperative day in normal convalescent patients. However, the ratio recovered more slowly in patients who required prolonged circulatory or respiratory support than in other patients. Thus we suggest that cardiopulmonary bypass had deleterious effects on the hepatic mitochondrial redox potential, which may contribute to homeostatic derangements and metabolic abnormalities.

Effect of nebracetam on nicotinic and muscarinic acetylcholine receptors expressed in Xenopus oocyte by injecting exogenous mRNA

Using voltage- and current-clamp methods the effects of nebracetam 4-aminomethyl-1-benzylpyrrolidine-2-one hemifumarate, WEB 1881 FU, CAS 118607-07-1), a new agent with nootropic property, on the nicotinic (nAChRs) and muscarinic acetylcholine receptors (mAChRs) were studied, which were expressed in Xenopus oocytes by injecting E. electricus mRNA and rat brain mRNA, respectively. Simultaneous application of nebracetam (0.03-2 mmol/l) with acetylcholine (ACh) (0.01-1 mmol/l) inhibited the ACh-responses of both nAChRs and mAChRs, whereas preapplication of these concentrations of nebracetam for 30 s to 1 min potentiated such inhibition. A simple competitive inhibition model for the effects of both drugs simultaneously applied yielded the inhibition constant, K1 of 0.419 and 0.212 mmol/l for nAChRs and mAChRs, respectively, indicating that the action on mAChRs is a little more potent than on nAChRs. Nebracetam induced a concentration-dependent slight increase in inward currents on mAChRs but not on nAChRs. It is suggested that the direct effects of nebracetam on nAChRs and mAChRS, which were induced only by a rather high concentration, as compared with the clinically expected plasma level, may be a contributing factor to the clinical effectiveness of the drug only if there is some critical change in the sensitivity to the drug.

Identification of separate determinants on the thyrotropin receptor reactive with Graves' thyroid-stimulating antibodies and with thyroid-stimulating blocking antibodies in idiopathic myxedema: these determinants have no homologous sequence on gonadotropin receptors

Deletions, substitutions, or mutations of the rat TSH receptor extracellular domain between residues 20 and 107 (all residue numbers are determined by counting from the methionine start site) have been made by site-directed mutagenesis of receptor cDNA. After transfection in Cos-7 cells, constructs were evaluated for their ability to bind [125I]TSH or respond to TSH and thyroid-stimulating antibodies (TSAbs) from Graves' patients in assays measuring cAMP levels of the transfected cells. Assay results were compared to results from Cos-7 cells transfected with wild-type receptor constructs or vector alone. We identify threonine-40 as a TSAb-specific site whose mutation to asparagine, but not alanine, reduces TSAb activity 10-fold, but only minimally affects TSH-increased cAMP levels. We show that thyroid-stimulating blocking antibodies (TSBAbs), which block TSH or TSAb activity and are found in hypothyroid patients with idiopathic myxedema, continue to inhibit TSH-stimulated cAMP levels when threonine-40 is mutated to asparagine or alanine, suggesting that TSBAbs interact with different TSH receptor epitopes than the TSAb autoantibodies in Graves' patients. This is confirmed by the demonstration that these TSBAbs interact with high affinity TSH-binding sites previously identified at tyrosine-385 or at residues 295-306 of the extracellular domain of the TSH receptor. This is evidenced by a loss in the ability of TSBAbs to inhibit TSAb activity when these residues are mutated or deleted, respectively. Since the TSAb and TSBAb epitopes are in regions of the extracellular domain of the TSH receptor that have no homology in gonadotropin receptors, these data explain at least in part the organ-specific nature of TSH receptor autoantibodies in autoimmune thyroid disease. Data are additionally provided which indicate that residues 30-37 and 42-45, which flank the TSAb epitope at threonine-40, appear to be ligand interaction sites more important for high affinity TSH binding than for the ability of TSH to increase cAMP levels and that cysteine-41 is critical for TSH receptor conformation and expression on the surface of the cell. Thus, despite unchanged maximal values for TSH-increased cAMP levels, substitution of residues 42-45 or deletion of residues 30-37 results in receptors, which, by comparison to wild-type constructs, exhibit significantly worsened Kd values for TSH binding than EC50 values for TSH- or TSAb-increased cAMP activity.(ABSTRACT TRUNCATED AT 400 WORDS)

[Surgical therapy of aortic regurgitation due to aortitis syndrome--effectiveness and extended indication of Bentall's operation]

Fourteen patients with aortic regurgitation due to aortitis syndrome that underwent surgical therapy were studied with particular emphasis on the long term merits of Bentall's operations over the conventional valve replacement. They were divided into two groups; Group A: 6 aortic valve replacements (AVRs) and Group B: 8 Bentall's operations. Post operative complications related to aortitis syndrome developed in 3 cases; a case of paravalvular leakage (Group A) and two cases of aneurysm formation at the coronary artery anastomotic sites (Group B). We speculated that these complications were due to abnormal healing and recurrent inflammatory process of the disease. Therefore we think that conventional valve replacement is not suited to cope with these problems. Since 1984, we have adopted the policy to perform Bentall's operations for all patients with aortitis requiring valve replacement. Bentall's operation required longer aortic cross-clamp time (212.1 +/- 53.9 min) than AVRs (73.0 +/- 25.0) and was more aggressive. However no patients with our current technique to reimplant the coronary artery button and distal graft to aorta anastomosis, which has been used since 1984, has developed pseudoaneurysm or valvular leakage. We conclude that our modified Bentall's operation is effective even for patients who have active aortitis syndrome or need redo operations.

[A case report of successful repair of an aortopulmonary fistula with partial dissection of the pulmonary artery]

We experienced a case of aortopulmonary fistula due to true thoracic aortic aneurysm. Surgical repair was electively performed when we found coexisting pulmonary arterial dissection. Under extracorporeal circulation, dissected flap was excised and the fistula was closed with his own pericardium, and his aortic arch and innominate artery were replaced with a piece of vascular prosthesis. His intra and post operative condition was stable, and postoperative course was uneventful. Prior to this case 13 surgically treated cases had been reported, and 5 had been successful. Among them, only 2 had been electively operated and both successful. Our case is the second case of aortopulmonary fistula associated with pulmonary arterial dissection.

Hormonal regulation of major histocompatibility complex class I genes in rat thyroid FRTL-5 cells: thyroid-stimulating hormone induces a cAMP-mediated decrease in class I expression

Thyrocytes normally express major histocompatibility complex (MHC) class I, but not class II, cell surface antigens. A rat thyrocyte cell line, FRTL-5, also expresses MHC class I antigens, in addition to a variety of thyroid-specific genes. Treatment of FRTL-5 thyrocytes with physiological concentrations of thyroid-stimulating hormone (TSH) has been shown to induce increased expressed of thyroglobulin and thyroid peroxidase but to simultaneously decrease expression of the TSH receptor. The reduction in TSH receptor expression by TSH is cAMP mediated. In the present study, it is demonstrated that, in thyrocytes treated with TSH, MHC class I expression decreases concomitant with the decrease in TSH receptor expression. This decreased expression is evidenced by reduced cell surface levels of MHC class I antigens, by reduced steady-state RNA levels, and by reduced transcription of the class I genes. TSH-mediated reduction of MHC class I gene transcription in FRTL-5 cells was mapped to a region within 135 base pairs of the promoter.

Molecular basis for the autoreactivity against thyroid stimulating hormone receptor

The present report identifies an important immunogenic region of the TSH receptor and determinants on the TSH receptor for the two types of autoantibodies seen in hyperthyroid Graves' disease and hypothyroid idiopathic myxedema, TSAbs and TSBAbs, respectively. The immunogenic domain with no important functional determinants, is contained within residues 303-382 and involves residues 352-366 in particular. There are determinants flanking the immunogenic domain on the C-terminal portion of the receptor which are the TSBAb and high affinity TSH binding sites: residues 295-306, 387-395, and tyrosine 385. Determinants on the N-terminal portion of the external domain, centered on residues 38-45, are TSAb interactions linked to low affinity TSH binding important for signal generation: threonine 40 and residues 30-33, 34-37, 42-45, 52-56, and 58-61. These determinants are conserved in human and rat receptors, are not present in gonadotropin receptors, and are each related to separate actions of TSH: binding vs. signal generation. They can, therefore, account for organ specific autoimmunity and the different disease expression effected by TSBAbs vs TSAbs, i.e. hypo- vs. hyperthyroidism, respectively. It is proposed that, in the thyroid, hormonal (TSH, insulin, hydrocortisone, IGF-I) suppression of class I genes might be one means of preserving self-tolerance in the face of the hormone action to increase the expression of tissue specific genes such as thyroglobulin and thyroid peroxidase. Inappropriately high class I expression in the thyroid, i.e. if induced by interferon, viruses, or some as yet unknown agent, would contribute to the generation of autoimmune disease. Thus, it would result in increased antigen presentation to the immune system, particularly those autoantigens increased by TSH and its cAMP signal such as thyroglobulin or thyroid peroxidase, or whose turnover is increased by TSH and its cAMP signal, such as the TSH receptor. In the case of the latter, peptide 352-366, known to be near a protease sensitive site on the receptor [41,49], would now act as a potent self-antigen and induce the formation of receptor autoantibodies. It is further proposed that methimazole and high doses of iodide are therapeutically effective agents in thyroid autoimmune disease because they, in part, decrease MHC class I gene expression. Speculation is presented which suggests that elimination of negative regulation of MHC class I and the TSH receptor is an important factor in the development of autoimmune thyroid disease.(ABSTRACT TRUNCATED AT 400 WORDS)

Echocardiographic assessment of left ventricular function and wall motion at high altitude in normal subjects

To understand the effects of high-altitude hypoxia on cardiac function and the change in cardiac function during high-altitude acclimatization, precise studies were first performed at greater than 5,000 m of altitude in Himalaya by 2-dimensional echocardiography. In addition to examining well-known indexes of cardiac function, the centerline method was used to assess regional wall motion, which has not been examined under conditions of high-altitude hypoxia. The subjects were 11 climbing members (aged 21 to 43 years) of the Kyoto University Medical Research Expedition of Xixabangma (8,027 m) in 1990. Examinations were performed at sea level, at the base camp (5,020 m), and twice at the advanced base camp (5,650 m). Heart rate, left ventricular (LV) end-diastolic volume, cardiac output, mean rate of circumferential fiber shortening, ejection fraction, % fractional shortening, and regional LV wall motion were measured. At high altitude, heart rate increased to 136% of the sea level value, but gradually decreased in the degree of increment at the early and late advanced base camp measurements. LV end-diastolic volume decreased significantly by 70%. At base camp there were significant increases in ejection fraction, mean rate of circumferential fiber shortening, and % fractional shortening, which showed little change during the long-term stay at high altitude. Regional wall motion at high altitude (measured by the center-line method) decreased at the septal wall and increased at the posterolateral wall. These results demonstrate that: (1) LV cardiac performance at high altitude is enhanced significantly in spite of reduced preload. After good acclimatization, cardiac performance remains augmented, but there is a tendency to decrease the degree of augmentation. (2) In regional LV wall motion, septal wall motion is impaired, but LV posterolateral wall motion shows a compensatory increase.

[Doppler echographic evaluation of pressure gradients of Björk-Shiley valve in the aortic position at rest and with exercise]

Pressure gradient across the Björk-Shiley (B-S) valve in the aortic position was assessed by Doppler echocardiography at rest and with exercise. There was close correlation between peak pressure gradient and area index which is a ratio of geometric orifice area (cm2) to body surface area (BSA) (m2). The correlation coefficient was -0.70 at rest and -0.86 with exercise. High peak pressure gradients with exercise were observed in the patients with 19 mm size (71 mmHg) and 21 mm size (107 mmHg). To avoid residual left ventricular outflow obstruction with exercise, it is considered advisable to use a #19 B-S valve in patients with BSA smaller than 1.1 m2, a #21 B-S valve in patients with BSA smaller than 1.4 m2, a #23 B-S valve in patients with BSA smaller than 1.8 m2, and a #25 B-S valve in patients with BSA smaller than 2.3 m2. If proper size of B-S valve cannot be inserted, aortic or aortic-mitral patch annuloplasty or the use of bileaflet valve are recommended as procedures of choice for small aortic annulus.

Further characterization of a high affinity thyrotropin binding site on the rat thyrotropin receptor which is an epitope for blocking antibodies from idiopathic myxedema patients but not thyroid stimulating antibodies from Graves' patients

Cysteine 390 of the rat thyrotropin (TSH) receptor, when mutated to serine, results in a receptor with a reduced ability of TSH to bind and increase cAMP levels but a preserved ability of thyroid stimulating autoantibodies (TSAbs) from hyperthyroid Graves' patients to increase cAMP levels. The ability of receptor autoantibodies from hypothyroid patients with idiopathic myxedema to inhibit the TSAb activity which is preserved is, however, like TSH binding, significantly reduced. Cysteine 390, together with tyrosine 385, thus appears to be an important determinant in a high affinity TSH binding site which is an epitope for receptor autoantibodies which block TSH or TSAb action and cause hypothyroidism rather than TSAbs which increase cAMP levels and are associated with hyperthyroidism. Threonine 388 and aspartic acid 403 may contribute to this ligand interaction site.

Site-directed mutagenesis of a portion of the extracellular domain of the rat thyrotropin receptor important in autoimmune thyroid disease and nonhomologous with gonadotropin receptors. Relationship of functional and immunogenic domains

Residues 287 to 404 of the rat thyrotropin (TSH) receptor exhibit little homology to gonadotropin receptors. A large segment of this region, residues 303-382, has no determinants important for TSH to bind or elevate cAMP levels nor for the activity of thyroid-stimulating autoantibodies (TSAbs) from the sera of Graves' patients, i.e. deletions, substitutions, or mutations in this segment do not result in a loss of any of these activities in transfected Cos-7 cells. Critical residues for these activities do, however, flank both sides of this segment. Of particular interest, deletion or mutation of residues 299-301 and 387-395 results in a marked decrease in high affinity TSH binding but preserves the ability of a TSAb to increase cAMP levels. Tyrosine 385 is also of particular interest since its mutation to phenylalanine, alanine, threonine, or glutamine results in a receptor with a 20-fold decrease in the ability of TSH to bind or increase cAMP levels, but one whose TSAb activity is, once again, preserved. Because one activity is preserved, we can conclude that (a) the receptor must be fully integrated within the membrane of the cell without malfolding, (b) these sequences represent determinants involved in the high affinity TSH binding site, and (c) separate determinants exist for high affinity TSH binding and TSAb activity, consistent with the existence of autoantibodies in Graves' sera which inhibit TSH binding (TBIAbs) or which increase cAMP levels (TSAbs). Additionally, we show that a 16-mer peptide (residues 352-367), which reacts with the sera of greater than 80% of patients with Graves' disease, can induce the formation of antibodies to a peptide with no sequence homology, residues 377-397. This peptide flanks the region, residues 303-382, with no determinants important for TSH receptor binding or activity. As noted above, it contains residues involved in the high affinity TSH binding site but whose deletion or mutation has no effect on TSAb activity, i.e. residues which would appear to be required at an epitope important for TBIAb but not TSAb antibody activity.

Relation of change in wall motion and glucose metabolism after coronary artery bypass grafting--assessment with positron emission tomography

Regional myocardial glucose metabolism was assessed by positron emission tomography (PET) in stunned myocardium. PET perfusion and metabolic imaging using N-13 ammonia and F-18 deoxyglucose (FDG) was performed before and 5-7 weeks after coronary artery bypass grafting (CABG) in 23 patients with coronary artery disease. Of 22 asynergy segments showing increased FDG uptake preoperatively, the postoperative PET showed a decrease in FDG uptake in 16 segments (73%) and persistent uptake in 6 segments (27%). The improvement in asynergy was observed in all of the segments showing postoperative decrease in FDG uptake, while it was observed in only 50% of those with persistent FDG uptake (p less than 0.01). On the other hand, 4 of 5 segments showing a new FDG uptake postoperatively revealed deterioration of wall motion abnormality. These data suggest that an increase in exogenous glucose utilization may often persist in postischemic myocardium. Improvement in regional function seems to be associated with the improvement in metabolic abnormality after CABG.

[Voltage-dependent effects of lidocaine and its metabolite, monoethylglycine xylidide (MEGX), on maximum rate of rise (Vmax) of action potential upstroke in guinea-pig papillary muscles]

We studied the effects of lidocaine and MEGX on the sodium current, using Vmax as an indicator, at an extracellular potassium concentration ([K]o) of 10 mmol.l-1, and compared the present results with those obtained at 5.4 mmol.l-1 [K]o in our previous study. At 10 mmol.l-1 [K]o, both lidocaine (10 micrograms.ml-1) and MEGX (10 micrograms.ml-1) significantly decreased the Vmax at the steady-state of 1 Hz, caused a significant rate-dependent decrease in Vmax, and slowed the recovery kinetics of Vmax. These effects of both agents were more prominent than those obtained at 5.4 mmol.l-1 [K]o, suggesting that MEGX as well as lidocaine produce voltage-or [K]o-dependent blocking effects on Vmax.

Cortico-cortical projections from the prefrontal cortex to the superior temporal sulcal area (STs) in the monkey studied by means of HRP method

Cortico-cortical connections from the prefrontal cortex to the superior temporal sulcal cortex (STs area) were studied in the monkey by means of retrograde axonal transport of horseradish peroxidase (HRP). After injections of 0.15-0.6 microliter of 50% HRP into the STs area, labeled cells were found in various cortical regions. In the prefrontal-STs projections, main features of topographic correlation were revealed; the posterior part of the STs area receives fibers from the superior frontal convexity (areas dorsal to the principal sulcus) and areas 8 and 6, whereas the anterior part of the STs area receives fibers from the inferior frontal convexity (areas ventral to the principal sulcus) and the frontal pole (area FD). The principal sulcus sends fibers to the entire STs area except for its ventral wall of the posterior part. A small cortical area adjacent to the inferior ramus of the arcuate sulcus (area 45 of ref. 41) sends fibers to the entire STs area. In addition, the orbitofrontal cortex projects mainly to the rostral part of the STs area, and the parahippocampal gyrus (areas TF and TH) projects to the deeper part of the entire STs area.

Immunoglobulins from Graves' disease patients interact with different sites on TSH receptor/LH-CG receptor chimeras than either TSH or immunoglobulins from idiopathic myxedema patients

To examine the identity of binding sites for thyrotropin (TSH) and thyroid stimulating antibodies (TSAbs) associated with Graves' disease, we constructed eight human TSH receptor/rat LH-CG receptor chimeras. Substitution of amino acid residues 8-165 of the TSH receptor with the corresponding LH-CG receptor segment (Mc1 + 2) results in a chimera which retains high affinity TSH binding and the cAMP response to TSH but loses both the cAMP response to Graves' IgG and Graves' IgG inhibition of TSH binding. Two of three IgGs from idiopathic myxedema patients which contain thyroid stimulation blocking antibodies (TSBAbs) still, however, react with this chimera. Chimeras which substitute residues 90-165 (Mc2) and 261-370 (Mc4) retain the ability to interact with TSH, Graves' IgG, and idiopathic myxedema IgG. The data thus suggest that residues 8-165 contain an epitope specific for TSAbs and that TSH receptor determinants important for the activities of TSAbs and TSH are not identical. Further, binding sites for TSBAbs in idiopathic myxedema may be different from receptor binding sites for both Graves' IgG TSAb as well as TSH and may be different in individual patients.

Regional wall thickening of left ventricle evaluated by gated positron emission tomography in relation to myocardial perfusion and glucose metabolism

Regional wall thickening was assessed by electrocardiographically gated positron emission tomography (ECG-gated PET) in 26 patients with coronary artery disease. The standardized percent count increase from end-diastole to end-systole (S-percent Cl) was calculated as an index of wall thickening. The S-percent Cl was 77.8% +/- 28.9% in the segments with normal perfusion at rest, 51.9% +/- 29.5% in those with mild hypoperfusion, and 32.8% +/- 30.9% in those with severe hypoperfusion (p less than 0.001, each). Among the segments with resting hypoperfusion, the S-percent Cl was 38.9% +/- 31.5% in those without stress-induced ischemia and 48.7% +/- 30.9% in those with ischemia (p less than 0.05). Furthermore, among resting severe hypoperfusion, the S-percent Cl was 23.0% +/- 23.9% in the segments without fluorine-18-fluorodeoxyglucose (FDG) uptake and 37.8 +/- 32.9% in those with FDG uptake (p less than 0.05). These results suggest that stress-induced ischemia and FDG accumulation correlated with wall thickening. Thus, quantitative analysis of regional wall thickening seems to be useful for combined analysis of regional function, perfusion and metabolism in coronary patients.

Metabolic activity in the areas of new fill-in after thallium-201 reinjection: comparison with positron emission tomography using fluorine-18-deoxyglucose

Reinjection of thallium-201 after recording the 3-hr delayed scan often demonstrates improvement in areas of persistent abnormalities. To determine the metabolic activity of these areas, the changes seen on stress/redistribution/reinjection thallium SPECT were compared with PET using fluorine-18-fluorodeoxyglucose (FDG) in 18 patients with coronary artery disease. Of 48 segments showing no redistribution on the delayed scan, the reinjection scan identified new fill-in in 20 segments (42%), all of which demonstrated FDG uptake. In contrast, only 7 of the 28 segments (25%) showing no fill-in after reinjection were PET viable (p less than 0.01). Eleven patients had coronary bypass graft surgery after the radionuclide study. The majority of the segments showing redistribution (87%) and new fill-in after reinjection (65%) improved in wall motion, whereas only eight segments (25%) without new fill-in improved after surgery. Of those without new fill-in, two segments showing PET ischemia improved in wall motion, whereas the remaining six segments showing PET scar did not improve after surgery. Thus, the segments showing new fill-in after reinjection are PET viable myocardium. However, reinjection thallium imaging still underestimates the extent of tissue viability compared to PET imaging.

Reperfusion injury in dog hearts with permanent occlusion of a coronary artery, probably due to reperfusion via collateral vessels

To clarify whether or not reperfusion injury occurs in the permanent occlusion of a coronary artery, we analyzed quantitatively contraction band necrosis as an indicator of early recanalization, coagulation necrosis, infarct size and measured regional blood flow in dog hearts with collateral circulation. Fifty mongrel dogs were divided into four groups: 15 dogs with a 24-hour occlusion of the left anterior descending coronary artery just distal to the first diagonal branch (permanent occlusion group): 15 dogs a with 3-hour occlusion followed by 24-hour recanalization (recanalization group); 10 dogs with a 2-hour occlusion without recanalization (transient occlusion group); 10 dogs with a 4-hour occlusion without recanalization (transient occlusion group). The regional blood flow in the subepicardium and subendocardium determined by the generated hydrogen gas clearance method was greatly decreased 30 minutes after occlusion (14 + 8%/12 +/- 9%) and was relatively restored from 180 minutes (31 +/- 21%/21 +/- 14%) to 24 hours later (41 + 19%/26 + 16%) in spite of complete occlusion of the coronary artery. The percentage infarct area in the risk area was significantly greater in the permanent occlusion group (60 +/- 26%) than in the recanalization group (35 +/- 31%). Although most of the infarct was occupied by contraction band necrosis in the recanalization group (86 +/- 12%), contraction band necrosis was diffusely seen even in the permanent occlusion group (54 +/- 27%). In both the permanent and recanalization groups, contraction band necrosis was the main histological feature of small infarcts occupying less than 30% of the risk area, while coagulation necrosis was the main feature in very large infarcts occupying more than 80% of the risk area. In the occlusion groups without recanalization, the percentage area of contraction band necrosis in the risk area was 6 +/- 8% after the 2-hour occlusion, 23 +/- 17% after the 4-hour occlusion and 31 +/- 21% after permanent occlusion; the difference between the 4-hour and permanent occlusion groups was not significant. In the permanent occlusion group, the percentage infarct area in the risk area was inversely correlated with regional blood flow during occlusion, an indicator of collateral flow. It was concluded that reperfusion injury occurs even in hearts without recanalization. The pathogenesis may involve reperfusion in the risk area via collateral circulation. Protection against reperfusion injury is important to minimize the infarct size even in hearts with permanent occlusion, although the presence of collateral flow is an important factor in limiting infarct size.

Does atrial appendectomy aggravate secretory function of atrial natriuretic polypeptide?

The present study was designed to clarify how atrial appendectomy affects hemodynamics and secretory function of atrial natriuretic polypeptide in the failing heart. Eleven mongrel dogs were prepared for the experimental model of high-output heart failure by creation of arteriovenous fistulas between femoral arteries and veins. Two months after the first operation, effects of bilateral atrial appendectomies on basal and pacing-induced secretions of atrial natriuretic polypeptide were investigated in five dogs with simultaneous measurement of various hemodynamic indices. In the remaining six dogs, used as a control group, pacing-induced secretion of atrial natriuretic polypeptide was examined in the same way as in the appendectomy group. After excision of the atrial appendages, neither systolic blood pressure nor either atrial pressure changed, but plasma atrial natriuretic polypeptide level was decreased (292 +/- 54 to 188 +/- 47 pg/ml, p less than 0.01) and cardiac output fell (3.7 +/- 0.9 to 3.0 +/- 0.8 L/min, p less than 0.01). During pacing-induced tachycardia, the peak level of plasma atrial natriuretic polypeptide was lower in the appendectomy group than in the control groups (593 +/- 213 versus 1170 +/- 324 pg/ml, p less than 0.05), despite similar left atrial pressures in the two groups. The excised appendages contained approximately 30% of the total amount of atrial natriuretic polypeptide. These results demonstrate that atrial appendectomy decreases secretory function of atrial natriuretic polypeptide and reduces cardiac output in dogs with experimental high-output heart failure.

Skeletal muscle powered ventricle: comparison of double-layered small ventricle and single-layered large ventricle

Canine left latissimus dorsi (LD) muscles were used to construct two kinds of skeletal muscle powered ventricles (SMPV): a double layered small size (10-17 mL) SMPV (A), and a single-layered large size (40-70 mL) SMPV (B). The same muscle was used sequentially for the construction of both SMPV. A mock circulation system was used for testing. This allowed for change of the preload (10-60 mmHg) and afterload (40-160 mmHg) independently. The peak developed pressure (PDP) and stroke volume (SV) were measured, and the stroke work (SW) was analyzed on line by a computer. The isovolumic PDP was 93.3 +/- 11.8 mmHg at 10 mmHg preload, and 157.7 +/- 20.2 mmHg at 60 mmHg for A, and 37.8 +/- 5.5 mHg and 107.8 +/- 8.5 mmHg for B. The SV and SW at 50 mmHg preload and 80 mmHg afterload were 18.30 +/- 1.25 mL and 1.06 +/- 0.10 x 10(6) erg for A, and 34.18 +/- 2.36 mL and 2.51 +/- 0.28 x 10(6) erg for B. The SV and SW at 20 mmHg preload and 160 mmHg afterload were 2.65 +/- 0.31 mL and 0.27 +/- 0.05 x 10(6) erg for A, and 1.03 +/- 0.23 mL and 0.04 +/- 0.01 x 10(6) erg for (B). The SW generated by the large single-layered SMPV is similar to that reported for the canine left ventricle but requires a high preload. The large single-layered SMPV showed a higher dependence on pre- and afterload changes than the double layered small SMPV, which generates a higher pressure even at low preloads.

Co-expression of X-hapten-like antigen and antigen YH206 on mucin molecules

The asialocarbohydrate antigen YH206 is expressed on adenocarcinoma-associated mucin molecules which lack epitopes of CA19-9 and DU-PAN-2. To further characterize this molecule, the monoclonal antibody BM2 against the affinity-purified antigen YH206 was established. It was demonstrated by an inhibition test that antigen BM2 was an X-hapten-like structure, one of the representative oncodevelopmental antigens. Although the sensitivity of antigen BM2 in sera of stomach and pancreas cancer patients did not appear to be superior to that of antigen YH206, both antigens were complementary to each other resulting in the improvement of sensitivity. Interestingly, double-determinant enzyme immunoassays showed that antigen BM2 and YH206, both having a cryptic nature for neuraminidase, were co-expressed on the same mucin molecule in sera of patients with stomach cancer or liver cirrhosis. These data suggest that mucin molecules in serum might be classified into several groups based on the distribution of tumor-associated epitopes.

[Detection of the new tumor marker MUSE 11 antigen in sera of pancreatic cancer patients: a comparison with sialyl SSEA-I antigen]

Using sera from patients with pancreatic cancer and chronic pancreatitis, we measured the level of the adenocarcinoma-associated antigen MUSE 11. A comparative study between levels of MUSE 11 and levels of sialyl SSEA-1 antigen (SLX) was also carried out. With respect to the MUSE 11 antigen, positive incidence was found in 17 out of 26 pancreatic cancer patients (65%), and in 1 out of 13 chronic pancreatitis patients (8%). Similar results were obtained from the assay of SLX levels. However, no correlation was found between the two markers. Out of 9 samples which showed MUSE 11 negative, three were positive for SLX. Out of 13 samples showing SLX negative, seven were positive for MUSE 11. Twenty out of 26 (77%) cases showed positive results for either antigen. These data suggest that the MUSE 11 antigen may be useful for the diagnosis of pancreatic cancers.

Effects of ulinastatin in experimental acute arterial occlusion in rats

The effects of ulinastatin (human urinary trypsin inhibitor, UTI) were studied in experimental acute arterial occlusion in rats. The experimental model comprised concurrent cross-clamping of the abdominal aorta and bilateral femoral arteries for 4 hours. Blood was sampled for measurement of the enzymes 2 hours after release of the clamps. The rats were grouped according to method of infusing UTI and/or physiologic saline solution. When UTI was infused continuously from the start of clamping, the plasma creatine phosphokinase and plasma beta-glucuronidase levels were significantly lower than in the control rats (p less than 0.05). The results suggest that UTI prevents the destruction of the lysosomal membrane in acute arterial occlusion.

Significance of fill-in after thallium-201 reinjection following delayed imaging: comparison with regional wall motion and angiographic findings

To identify reversible defects, reinjection of a small amount of thallium-201 (201Tl) following 3-hr delayed imaging was performed in 60 patients with coronary artery disease who had perfusion abnormalities on their post-exercise 201Tl images. Thallium-201 uptake was visually scored and judged as normal (Group 1), reversible defect (Group II), new fill-in after reinjection (Group IIIa) and no fill-in even after reinjection (Group IIIb). New fill-in after reinjection was observed in 27 segments of the 85 segments (32%), showing persistent defect on the stress and delayed images. The wall motion in Group IIIa was worse than Group II but better than Group IIIb. Group IIIa showed Q-wave on ECG more often (69%) than Group II (27%) (p less than 0.01), but less often than Group IIIb (85%) (p less than 0.05). These data indicate that the reinjection 201Tl imaging often identifies new fill-in in the areas of no redistribution on the delayed images and it may hold promise for assessing tissue viability which the conventional imaging may underestimate.