Assembly of lipoprotein (a) in transgenic rabbits expressing human apolipoprotein (a)

The study of human lipoprotein (a) [Lp(a)] has been hampered due to the lack of appropriate animal models since apolipoprotein (a) [apo(a)] is found only in primates and humans. In addition, human apo(a) in transgenic mice can not bind to murine apoB to form Lp(a) particles. In this study, we generated three independent transgenic rabbits expressing human apo(a) in their plasma at 1.8-4.5 mg/dl. In the plasma of transgenic rabbits, unlike the plasma of transgenic mice, about 80% of the apo(a) was covalently associated with rabbit apo-B and was contained in the fractions with density 1.02-1.10 g/ml, indicating the formation of Lp(a). These results suggest that transgenic rabbits expressing human apo(a) exhibit efficient assembly of Lp(a) and can be used as an animal model for the study of human Lp(a).

Upregulated expression of cardiac endothelin-1 participates in myocardial cell growth in Bio14.6 Syrian cardiomyopathic hamsters

OBJECTIVES

The purpose of this study is to investigate the role of endogenous endothelin-1 (ET-1) in myocardial growth in Bio 14.6 Syrian cardiomyopathic hamsters (Bio).

BACKGROUND

While ET-1, as a growth-promoting peptide, has been implicated in the development of secondary cardiac hypertrophy, the role of endogenous ET-1 in cardiac growth in primary myocardial disease is unknown.

METHODS

We measured left ventricular ET-1 levels by a specific sandwich enzyme-linked immunosorbent assay. Furthermore, we examined the chronic effect of T0201, an ET type A receptor-specific antagonist.

RESULTS

The ET-1 levels in the left ventricles were 1.8-fold higher (p < 0.0005) at 20 weeks and 6.4-fold higher (p < 0.0001) at 35 weeks in the Bio compared to age-matched control F1B hamsters (F1B). The Bio ET-1 levels in the lungs exhibited an only 1.3-fold elevation at 35 weeks. Immunohistochemistry demonstrated the localization of ET-1 mainly in the cardiac myocytes. The treatment with T0201 significantly reduced the heart weight/body weight ratio in the Bio, but did not affect the heart weight/body weight ratio in the F1B. Histologically, T0201 reduced the myocyte diameter of Bio to a level similar with that of F1B. However, T0201 did not affect the extent of fibrosis in Bio or F1B.

CONCLUSIONS

The ET-1 level in the heart of cardiomyopathic hamsters increases in stage-dependent and organ-specific manners. Though myocyte degeneration and subsequent replacement fibrosis do not require an ET-1 pathway, the accelerated synthesis of ET-1 in the heart may contribute to the pathological growth of remaining myocytes in this animal model.

Antioxidant function of the mitochondrial protein SP-22 in the cardiovascular system

The mitochondrial protein SP-22 has recently been reported to be a member of the thioredoxin-dependent peroxide reductase family, suggesting that it may be one of the antioxidant systems in mitochondria, which are the major site of reactive oxygen intermediate generation. The aim of this study was to examine whether SP-22 is involved in mitochondrial antioxidant mechanisms and whether its expression is induced by oxidative stresses, particularly those in mitochondria. The expression of SP-22 protein was enhanced by about 1.5-4.6-fold when bovine aortic endothelial cells (BAEC) were exposed to various oxidative stresses, including mitochondrial respiratory inhibitors which increased the superoxide generation in BAEC mitochondria. The expression of SP-22 mRNA increased 2.0-3.5-fold with a peak at 3-6 h after exposure to Fe2+/dithiothreitol or a respiratory inhibitor, antimycin A. BAEC with an increased level of SP-22 protein caused by pretreatment with mild oxidative stress became tolerant to subsequent intense oxidative stress. On the other hand, BAEC that had been depleted of SP-22 with an antisense oligodeoxynucleotide against SP-22 mRNA became more labile to oxidative stress than control BAEC. The induction of SP-22 protein by oxidative stress in vivo was demonstrated in an experimental model of myocardial infarction in rat heart. These findings indicate that SP-22 functions as an antioxidant in mitochondria of the cardiovascular system.

The role of endothelin-converting enzyme-1 in the development of alpha1-adrenergic-stimulated hypertrophy in cultured neonatal rat cardiac myocytes

BACKGROUND

Accumulating evidence suggests that the local synthesis of endothelin-1 (ET-1) plays a role in the development of heart failure in vivo. We investigated the role of endothelin-converting enzyme-1 (ECE-1), which mediates the conversion of big ET-1 to mature ET-1, in the development of alpha1-adrenergic-stimulated hypertrophy in cultured neonatal rat cardiac myocytes.

METHODS AND RESULTS

Phenylephrine (PE) induced the expression of ET-1 in rat cardiac myocytes and accelerated the conversion of big ET-1 to ET-1. The ECE-1 mRNA levels were markedly increased 3 hours after PE stimulation (3.6-fold compared with saline stimulation, P<0.005). A specific ECE-1 antagonist, FR901533, inhibited the PE-stimulated increase in protein synthesis rate by 45% (P<0.05). As genetic markers for the hypertrophic response, FR901533 inhibited the PE-stimulated transcriptional activities of the 3.5-kb beta-myosin heavy chain promoter by 79% (P<0.01) but did not affect that of the 3.4-kb atrial natriuretic factor (ANF) promoter. In Bio14.6 Syrian cardiomyopathic hamsters, ventricular ET-1 and ANF mRNA levels did not correlate at 2 different stages.

CONCLUSIONS

ET-1-independent pathways may mediate activation of the ANF gene program in ventricular myocytes both in vitro and in vivo. These results also indicate that the conversion of big ET-1 to ET-1 in rat cardiac myocytes is required for the development of alpha1-adrenergic-stimulated hypertrophy and beta-myosin heavy chain gene transcription.

Blockade of ATP-sensitive K+ channels attenuates preconditioning effect on myocardial metabolism in swine: myocardial metabolism and ATP-sensitive K+ channels

OBJECTIVE

We investigated if blockade of ATP-sensitive K+ channels (KATP) abolishes the protective effect of ischemic preconditioning (IP) on myocardial metabolism and ischemia-induced reactive hyperemia (RH) in pigs.

METHODS

IP was elicited by a single cycle of 5 min occlusion and 5 min reperfusion of coronary artery, followed by 15 min of test ischemia and 120 min of reperfusion. Vehicle or the ATP-sensitive K+ channels (KATP) blocker, glibenclamide (3 or 6 mg/kg; G3 or G6) was administered before IP (groups; IP, G3+IP, G6+IP). As respective controls, the same treatment was performed in groups without IP (groups; C, G3, G6). Tissue levels of ATP, creatine phosphate (CP) and intracellular pH (pHi) in the area at risk were measured by 31P-nuclear magnetic resonance spectroscopy. RH after 5 min of preconditioning ischemia was assessed by regional myocardial blood flow.

RESULTS

ATP and pHi were preserved after 15 min of ischemia in the IP group [C/IP; ATP=57+/-4/76+/-10% of baseline, pHi=6.18+/-0.08/6.66+/-0.03, P<0.05, C vs. IP]. Both doses of glibenclamide completely abolished the ATP sparing effect of IP. The high dose completely abolished pHi preservation (G6+IP=6.33+/-0.06), while the low dose showed only a partial effect (G3+IP=6.48+/-0.03). Glibenclamide did not adversely affect myocardial metabolism in groups without IP. Glibenclamide attenuated RH after 5 min of ischemia by 30% in both subendocardium and subepicardium.

CONCLUSIONS

Blockade of KATP abolished the preconditioning effect on myocardial metabolism, and partially attenuated post-ischemic reactive hyperemia in pigs. These results indicate that KATP activation might be involved in the mechanisms of these phenomena, reactive hyperemia is not sufficient to induce IP protection.

Localization of Six4/AREC3 in the developing mouse retina; implications in mammalian retinal development

The Six4/AREC3 gene was originally isolated as a regulatory factor which bound to the positive regulatory region of the Na, K-ATPase alpha 1 subunit. It is a murine homologue of the Drosophila sine oculis (so) gene, which is essential for the development of the entire insect visual system. In this study, we attempted to determine the localization of the Six4/AREC3 gene product in the developing mouse retina in order to examine its role in retinal cell differentiation. Immunohistochemistry with anti-SIX4/AREC3 and anti-Na, K-ATPase alpha 1 subunit antisera was performed on developing mouse retinas, and immunoblotting analysis with anti-SIX4/AREC3 was also performed. The localization of Six4-like immunoreactivity (Six4-LI) showed a temporally regulated pattern: During embryonic development, Six4-LI was found in the nuclei of cells located at the inner neuroblastic layer of the retina as early as on ED12, nearly corresponding to the onset of retinal cell differentiation. In the PD1 retina, Six4-LI was observed in the nuclei of the ganglion cells, and increased its intensity until PD4, and thereafter kept its intensity until PD7 when Six4-LI was often found in the cytoplasm. On PD4, the presumptive amacrine cells found in the inner portion of the inner nuclear layer appeared to be immunostained in their nuclei. On PD7, the presumptive bipolar cells located in the outer portion were immunostained in the nuclei. After that, Six4-LI gradually decreased, and in the mature retina no detectable Six4-LI was observed in the nuclei. This pattern of Six4-LI localization during retinal development seemed to correlate with retinal cell differentiation, but did not correlate with the distribution pattern of Na, K-ATPase alpha 1 subunit protein-like immunoreactivity. These results suggest that the Six4 gene may play a role in the differentiation of neural retinal cells during mouse retinal development, rather than regulating the expression of the Na, K-ATPase alpha 1 subunit gene.

Cardiac endothelin-1 plays a critical role in the functional deterioration of left ventricles during the transition from compensatory hypertrophy to congestive heart failure in salt-sensitive hypertensive rats

BACKGROUND

To investigate whether endogenous ET-1 participates in an adaptive process of left ventricular hypertrophy (LVH) or a maladaptive process from LVH to congestive heart failure (CHF), we used a Dahl salt-sensitive (DS) rat model, in which systemic hypertension caused compensated concentric LVH at the age of 11 weeks followed by marked LV dilatation and global hypokinesis at the age of 17 weeks.

METHODS AND RESULTS

By specific sandwich enzyme immunoassay, serum and myocardial ET-1 levels at the LVH stage were not elevated compared with age-matched Dahl salt-resistant (DR) rats, despite the marked increase of LV/body weight ratio (LV/BW). However, at the CHF stage, serum and LV ET-1 levels increased by 3. 8-fold and 5.4-fold, respectively. LV ET-1 contents had close relationships with the fractional shortening (r=0.763) and the systolic wall stress (r=0.858) measured by in vivo transthoracic echocardiography. Immunohistochemistry demonstrated that the remarkably increased ET-1 in LV is located mainly in cardiomyocytes. By competitive reverse transcriptase-polymerase chain reaction, LV prepro-ET-1 mRNA levels increased by 4.1-fold in CHF rats. We randomized 11-week-old LVH rats to chronic treatment with the endothelin receptor antagonist bosentan (Bos, 100 mg. kg-1. d-1, n=14), the alpha1-receptor antagonist doxazosin (Dox, 1 mg. kg-1. d-1, n=12), or vehicle (Cont, n=14). Bos treatment did not alter the LV geometry and function at 15 weeks; however, it attenuated the decrease of LV fractional shortening by 51% (P<0.01) without reducing the LV/BW at 17 weeks. Conversely, Dox, which decreased the blood pressure to the same extent as Bos, did not affect the progression of LV dysfunction. Bos (93%; P<0.0001 versus Cont) but not Dox (42%; P=0.8465 versus Cont) ameliorated the survival rate at 17 weeks (Cont; 36%).

CONCLUSIONS

The accelerated myocardial synthesis of ET-1 contributes directly to LV contractile dysfunction during the transition from LVH to CHF. Unelevated levels of LV ET-1 at the established LVH stage and lack of effects on LV mass by chronic bosentan treatment suggest that myocardial growth is mediated through alternative pathways. These studies indicate that chronic ET antagonism may provide an additional strategy for heart failure therapy in humans.

Microwave Spectrum of the SD+3 Ion: Molecular Structure

The J = 1-0 to 4-3 spectral lines of SD+3 were measured in the 152-610 GHz region using a source-modulated microwave spectrometer. The SD+3 ion was generated in a free space absorption cell by a hollow-cathode discharge in a gas mixture of D2S and D2. The rotational constant B0 and the centrifugal distortion constants DJ and DJK were determined from the measured frequencies. A vibration-rotation analysis was carried out and the rz structures of SH+3 and SD+3 were derived from their zero point averaged rotational constants, expressed as SH+3: rz = 1.36512(22) Å and thetaz = 94.098(26) degrees, and SD+3: rz = 1.36086(16) Å and thetaz = 94.1211(195) degrees, where the difference between thetaz(HSH) and thetaz(DSD) was assumed to be the same as that between thetaz(HPH) of PH3 and thetaz(DPD) of PD3. From the shift between the rz structures of SH+3 and SD+3, the re structure of SH+3 was estimated to be re = 1.35001(113) Å, thetae = 94.181(135) degrees. Copyright 1998 Academic Press.

Allosteric regulation of a ribozyme activity through ligand-induced conformational change

An allosteric ribozyme has been designed using the hammerhead ribozyme as the active site and aflavin-specific RNA aptamer as a regulatory site. We constructed six variants with a series of base pairs in the linker region (stem II). Under single turnover conditions, kinetic studies were carried out in the absence and presence of flavin mononucleotide (FMN). Interestingly, FMN addition did not influence the cleavage rate of constructs with a 5-6 bp linker but stimulated the catalytic activity of those bearing a shorter linker. In particular, the apparent k cat of Rz3 increases by approximately 10-fold upon addition of saturating amounts of FMN. To determine the rate constants( K m4and k cat), the ribozyme regulated most effectively by FMN was further investigated. FMN mainly affected the k cat value, reflecting the rate limiting conformational change step of the overall cleavage reaction, depending on helix formation in stem II. Probably, FMN influences the orientation of structures necessary for the cleavage reaction through stem II formation. The result of chemical modification revealed that binding of FMN to the aptamer domain induced the helix formation in stem II required for catalytic activity. Therefore, a specific FMN-mediated allosteric interaction seems to promote a conformational alteration from an open to a closed structure in stem II. The concept of conformational modification in the allosteric effect is consistent with other allosteric enzymes, suggesting that such a conformational change is a fundamental feature of allosteric enzymes in biological systems.

A family with Liddle's syndrome caused by a new missense mutation in the beta subunit of the epithelial sodium channel

Liddle's syndrome is an autosomal dominant form of salt sensitive hypertension caused by mutations in the beta or gamma subunit of the epithelial sodium channel. Systematic mutagenesis studies revealed that a conserved PPPXY sequence (PY motif) of the C-terminus of the alpha, beta, or gamma subunits might be involved in the regulation of the channel activity. However, only two missense mutations in the PY motif of the beta subunit have been reported to cause Liddle's syndrome. We sequenced the C-termini of the beta and gamma subunits of the epithelial sodium channel in a Japanese family clinically diagnosed as having Liddle's syndrome and found a new missense mutation in the PY motif of the beta subunit, P615S. Expression studies with P615S mutant in Xenopus oocytes resulted in an about 3-fold increase in the amiloride-sensitive sodium current compared to the wild type (p = 0.001). These findings provide further clinical evidence for the hypothesis that a conserved PY motif may be critically important for the regulation of the epithelial sodium channel.

Evidence for involvement of two isoforms of Syk protein-tyrosine kinase in signal transduction through the high affinity IgE receptor on rat basophilic leukemia cells

Recent evidence suggests a critical role for Syk in mast cell activation upon high affinity IgE receptor (FcepsilonRI) aggregation. A rat basophilic leukemia cell line, RBL-2H3, expresses similar levels of two Syk isoforms that differ with respect to the presence of a 23-amino acid insert within the "linker" region located between the second Src homology 2 and the catalytic domain. Although they exhibit comparable intrinsic enzymatic activity, functional differences between the two isoforms are unknown. Here we report that the deleted Syk isoform can mediate signal transduction in RBL-2H3 cells. Aggregation of chimeric kinase, consisting of either form of Syk fused to the transmembrane and extracellular domains of guinea pig type II IgG Fc receptor, on RBL transfectants resulted in degranulation, release of leukotrienes, and enhanced gene expression of tumor necrosis factor-alpha. The chimeras as well as phospholipase C-gamma1 and Vav became tyrosine-phosphorylated upon aggregation of chimeras. We also found that both Syk isoforms from transiently transfected COS-7 cells were capable of binding to phosphorylated FcepsilonRI, and their kinase activities were similarly up-regulated in the presence of tyrosine-phosphorylated synthetic peptides based on the sequence of the gamma subunit of FcepsilonRI. Thus, these results establish that both isoforms of Syk can mediate signal transduction in mast cells and suggest that the 23-amino acid insert in the linker region of Syk may not be obligatory for FcepsilonRI signaling.

Use of temporary vena cava filters after catheter-directed fragmentation and thrombolysis in patients with acute pulmonary thromboembolism

Acute pulmonary thromboembolism is a life-threatening disease and in almost all cases originates from deep venous thrombosis in the proximal deep venous system of the legs. In order to prevent further episodes of thromboembolism in 2 patients with acute pulmonary thromboembolism, we inserted an Antheor temporary vena cava filter after catheter-directed fragmentation and thrombolysis. No complications occurred during the insertion of the filters and our results suggest that this filter device may be clinically safe and effective for temporary protection against pulmonary thromboembolism.

Spinal meningeal melanocytoma presenting with superficial siderosis of the central nervous system. Case report and review of the literature

Meningeal melanocytoma is a benign melanocytic tumor that originates most frequently from the melanocytes in the posterior fossa or along the spinal cord. This tumor generally occurs as an extraaxial mass that compresses adjacent neural structures to produce various neurological signs. The authors describe an unusual case in which a patient with a meningeal melanocytoma located at the thoracic spinal cord presented with superficial siderosis of the central nervous system (CNS). Extensive neuroradiological studies identified the presence of a spinal cord tumor, and postsurgical histological examination revealed the meningeal melanocytoma as a bleeding source. After surgery, lumbar puncture demonstrated normalization of the patient's cerebrospinal fluid; however, no neurological improvement occurred. The neurological deficits seem irreversible. Meningeal melanocytoma is biologically benign and can be cured by complete surgical resection; therefore, this tumor should be included in the differential diagnosis of pigmented lesions of the CNS. The authors reviewed 14 cases of well-documented meningeal melanocytoma in the literature and discuss the clinical, radiological, and pathological features of the present case to emphasize the importance of early diagnosis and identification of the source of bleeding in patients with superficial siderosis.

Early embryonic interaction of retinal pigment epithelium and mesenchymal tissue induces conversion of pigment epithelium to neural retinal fate in the silver mutation of the Japanese quail

The neural retina and retinal pigment epithelium (RPE) diverge from the optic vesicle during early embryonic development. They originate from different portions of the optic vesicle, the more distal part developing as the neural retina and the proximal part as RPE. As the distal part appears to make contact with the epidermis and the proximal part faces mesenchymal tissues, these two portions would encounter different environmental signals. In the present study, an attempt has been made to investigate the significance of interactions between the RPE and mesenchymal tissues that derive from neural crest cells, using a unique quail mutant silver (B/B) as the experimental model. The silver mutation is considered to affect neural crest-derived tissues, including the epidermal melanocytes. The homozygotes of the silver mutation have abnormal eyes, with double neural retinal layers, as a result of aberrant differentiation of RPE to form a new neural retina. Retinal pigment epithelium was removed from early embryonic eyes (before the process began) and cultured to see whether it expressed any phenotype characteristic of neural retinal cells. When RPE of the B/B mutant was cultured with surrounding mesenchymal tissue, neural retinal cells were differentiated that expressed markers of amacrine, cone or rod cells. When isolated RPE of the B/B mutant was cultured alone, it acquired pigmentation and did not show any property characteristic of neural retinal cells. The RPE of wild type quail always differentiated to pigment epithelial cells. In the presence of either acidic fibroblast growth factor (aFGF) or basic FGF (bFGF), the RPE of the B/B mutant differentiated to neural retinal cells in the absence of mesenchymal tissue, but the RPE of wild type embryos only did so in the presence of 10-40 times as much aFGF or bFGF These observations indicate that genes responsible for the B/B mutation are expressed in the RPE as well as in those cells that have a role in the differentiation of neural crest cells. They further suggest that development of the neural retina and RPE is regulated by some soluble factor(s) that is derived from or localized in the surrounding embryonic mesenchyme and other ocular tissues, and that FGF may be among possible candidates.

Analysis of the murine Hoxa-9 cDNA: an alternatively spliced transcript encodes a truncated protein lacking the homeodomain

Hoxa-9 is one of the homeo box (Hox) genes exhibiting similarity to the Drosophila Abdominal B gene. So far, only partial nucleotide sequences have been reported for mouse Hoxa-9 cDNA (Rubin et al., (1987) Mol. Cell. Biol. 7, 3836-3841). Here, we have determined the nucleotide sequence of the 5'-region of mouse Hoxa-9 cDNA and its genomic structure. Mouse Hoxa-9 cDNA contains a complete ORF encoding a protein of 271aa exhibiting 96.7% identity to its human counterpart. Interestingly, an alternatively spliced transcript (Hoxa-9T) was identified by RT-PCR. Sequence analysis revealed that 173bp within the Hoxa-9 ORF was missing from the Hoxa-9T cDNA. This additional splicing would potentially result in a frameshift, leading to the production of a truncated protein lacking the homeobox. Northern blot analysis revealed that the probe containing the homeodomain hybridized to two major transcripts (2.5 and 1.9kb) in the trunk region of 12.5 dpc embryos, and adult kidney and large intestine. On the other hand, the probe containing the additional intron detected only 2.5kb transcript in the same tissues, indicating that 1.9kb transcript corresponds to Hoxa-9T mRNA. We have also determined the transcriptional start site of Hoxa-9T.

Region-specific expression of murine Hox genes implies the Hox code-mediated patterning of the digestive tract

BACKGROUND

Hox genes encode transcription factors which are involved in the establishment of regional identities along the anteroposterior (AP) body axis. To elucidate the AP patterning of the digestive tract, we have systematically examined the expression patterns of Hox genes belonging to paralogue groups 6, 7, 8 and 9 by whole-mount in situ hybridization and by section in situ hybridization analyses.

RESULTS

The expression patterns of these genes showed co-linearity along the wall of the digestive tract, thereby yielding the Hox code of the gut. The expression boundaries of the Hox genes at later stages (12.5 d.p.c.) corresponded to the morphological boundaries of individual gut subdomains.

CONCLUSIONS

The visceral mesoderm-restricted expression suggested that the Hox code primarily functions in the mesenchymal specification which eventually leads to the regional differentiation of gut subdomains as the result of epithelial-mesenchymal interactions. Overlapping expression patterns were found among the paralogous Hox genes, indicating that the paralogues may have redundant functions in the specification of the gut.

Diffusible factors produced by cultured neural retinal cells enhance in vitro differentiation of pineal cone photoreceptors of developing quail embryos

The avian pineal is a photoreceptive organ and is believed to function as a circadian clock. Avian pineal cells are secretory rudimentary photoreceptors, and previous studies have demonstrated that there are two types of photoreceptors in developing quail pineals, one of which is rhodopsin-like immunoreactive and the other iodopsin-like immunoreactive. Much larger number of rhodopsin-like immunoreactive cells than of iodopsin-like immunoreactive cells were found in quail pineals, both in vivo and in vitro. In the present study we co-cultured pineal cells of embryonic quails with retinal cells but separated the two with a bio-membrane filter. We found that diffusible material produced by the cultured retinal cells intensely promotes the appearance of pineal iodopsin-like immunoreactive cells in vitro. This effect of retina-derived factor(s) is cell-type specific, since there is no effect on the differentiation of pineal rhodopsin-like immunoreactive cells. Retinal cell cultures had much more intensive iodopsin-promoting effect than other embryonic brain cultures such as cerebral cell cultures. The production of the retinal factor(s) seems to be developmentally regulated, since retinal cells from older embryos (E13 and older) did not have such effects. The factor(s) possibly act on pineal precursor cells by stimulating the expression of the iodopsin-like immunoreactive phenotype. Preliminary characterization of conditioned medium obtained from cultured retinal cells shows that the factor is a stable polypeptide, probably of low molecular weight. The pineal-retina culture system will provide a good experimental system to analyze the effect of extrinsic environments on cell differentiation.

Identification and characterization of XPC-binding domain of hHR23B

hHR23B was originally isolated as a component of a protein complex that specifically complements nucleotide excision repair (NER) defects of xeroderma pigmentosum group C cell extracts in vitro and was identified as one of two human homologs of the Saccharomyces cerevisiae NER gene product Rad23. Recombinant hHR23B has previously been shown to significantly stimulate the NER activity of recombinant human XPC protein (rhXPC). In this study we identify and functionally characterize the XPC-binding domain of hHR23B protein. We prepared various internal as well as terminal deletion products of hHR23B protein in a His-tagged form and examined their binding with rhXPC by using nickel-chelating Sepharose. We demonstrate that a domain covering 56 amino acids of hHR23B is required for binding to rhXPC as well as for stimulation of in vitro NER reactions. Interestingly, a small polypeptide corresponding to the XPC-binding domain is sufficient to exert stimulation of XPC NER activity. Comparison with known crystal structures and analysis with secondary structure programs provided strong indications that the binding domain has a predominantly amphipathic alpha-helical character, consistent with evidence that the affinity with XPC is based on hydrophobic interactions. Our work shows that binding to XPC alone is required and sufficient for the role of hHR23B in in vitro NER but does not rule out the possibility that the protein has additional functions in vivo.

Effects of lecithin addition in oil or water phase on the stability of emulsions made with whey proteins

The effects of lecithin addition in oil or water phase on the stability of oil-in-water emulsions made with 0.1 wt% whey protein and 10 wt% n-tetradecane at neutral and acidic pH were studied by monitoring the gravitational creaming and phase separation. The effects of lecithin addition on the interfacial behavior of beta-lactoglobulin were also studied to compare with the results of emulsion stability. At neutral pH, crude phosphatidylcholine (PC) from egg yolk or soybean increased the stability of the emulsion made with protein and lowered the interfacial tension of protein films more effectively than pure egg PC. A more remarkable effect on both the emulsion stability and the interfacial tension was found when crude PC was added in the oil phase rather than in the water phase. The purity of lecithins and the way to add them are suggested to be very important to make a stable emulsion with protein. On acidic pH (4.5 or 3.0), the increased creaming or phase separation in a whey protein-stabilized emulsion, but the lowered interfacial tension of beta-lactoglobulin films, were found upon the addition of pure or crude PC in oil or water phase. These results suggest that in acidic pH, densely packed films may be formed on a planar oil-water interface, but not on adsorbed layers around oil droplets in an emulsion.

Neurohumoral and hemodynamic mechanisms of diuresis during atrioventricular nodal reentrant tachycardia

Thirty-two consecutive patients with paroxysmal supraventricular tachycardias, with previously defined mechanisms of the tachycardias, were interviewed by noninvestigators about whether they experienced symptoms of diuresis during or at the termination of the tachycardias, to test the hypothesis that patients with AV nodal reentrant tachycardia would have a feeling of diuresis, polyuria, or both during or at the termination of the tachycardia. Twelve of the 13 patients with AV nodal reentrant tachycardia (92%), two of the 15 patients with AV reentrant tachycardia (13%), and one of the 4 patients with atrial flutter associated with 2:1 AV conduction (25%) felt diuresis during or at the termination of the tachycardias (AV nodal reentrant tachycardia vs other forms of tachycardia; P < 0.001). In 14 of the 32 patients, the right atrial pressure and plasma atrial natriuretic peptide (ANP) concentration were measured during both the tachycardias and sinus rhythm. The mean right atrial pressure during AV nodal reentrant tachycardia was significantly elevated compared to that during other forms of tachycardia (P < 0.01). The plasma ANP concentration during AV nodal reentrant tachycardia was also elevated significantly compared to that during other forms of tachycardias (P < 0.001). There were no significant differences in the cycle lengths of the tachycardias, age, left atrial dimensions, or the left ventricular ejection fraction between the AV nodal reentrant tachycardia and the other forms of tachycardia. We concluded that the feeling of diuresis during or at the termination of tachycardia was a more common symptom in patients with AV nodal reentrant tachycardia. The higher secretion of plasma ANP from the right atrium might be involved in the mechanism of this symptom.

Radiofrequency catheter ablation of an accessory pathway in dextrocardia

A 60-year-old woman with situs inversus and paroxysmal supraventricular tachycardias utilizing an AV accessory pathway underwent successful, uncomplicated RF ablation. Using biplane fluoroscopy, accessory pathway catheter ablation in dextrocardia is as safe, easy, and useful as that for normal heart structure cases, and does not require a lengthy procedure.

[A patient with bronchial asthma and mucoid impaction who presented with a high concentration of carcinoembryonic antigen in serum]

We encountered a patient with bronchial asthma and mucoid impaction who presented with a high concentration of carcinoembryonic antigen (CEA) in serum. The patient was a 46-year-old woman. One year after resection of a uterine myoma and an ovarian cyst, examination of serum revealed a high concentration of CEA (24.1 ng/ml). Further examination revealed no evidence of malignant disease, but an abnormal shadow was seen on a chest X-ray film, and was thought to be compatible with mucoid impaction. Fiberoptic bronchoscopy revealed mucoid impaction in the right lower-lobe bronchus. The concentration of CEA in bronchoalveolar lavage fluid was also high (6100 ng/ml). Lavage was done five times and the impaction was removed completely. The concentrations of CEA in serum and in bronchoalveolar lavage fluid decreased to 3.4 ng/ml and 621.9 ng/ml, respectively.