Death signals from the B cell antigen receptor target mitochondria, activating necrotic and apoptotic death cascades in a murine B cell line, WEHI-231

B cell antigen receptor (BCR)-mediated cell death has been proposed as a mechanism for purging the immune repertoire of anti-self specificities during B cell differentiation in bone marrow. Mitochondrial alterations and activation of caspases are required for certain aspects of apoptotic cell death, but how the mitochondria and caspases contribute to BCR-mediated cell death is not well understood. In the present study, we used the mouse WEHI-231 B cell line to demonstrate that mitochondrial alterations and activation of caspases are indeed participants in BCR-mediated cell death. The peptide inhibitor of caspases, N-benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone (z-VAD-fmk), blocked cleavage of poly(ADP-ribose) polymerase and various manifestation of nuclear apoptosis such as nuclear fragmentation, hypodiploidy and DNA fragmentation, indicating that signals from the BCR induced the activation of caspases. In addition, z-VAD-fmk delayed apoptosis-associated changes in cellular reduction-oxidation potentials as determined by hypergeneration of superoxide anion, as well as exposure of phosphatidylserine residues in the outer plasma membrane. By contrast, although z-VAD-fmk retarded cytolysis, it was incapable of preventing disruption of the plasma membrane even under the same condition in which it completely blocked nuclear apoptosis. Mitochondrial membrane potential loss was also not blocked by z-VAD-fmk. Bongkrekic acid, a specific inhibitor of mitochondrial permeability transition pores, suppressed not only the mitochondrial membrane potential but also the change of plasma membrane permeability. Overexpression of Bcl-xL prevented mitochondrial dysfunction, nuclear apoptosis and membrane permeability cell death triggered by BCR signal transduction. These observations indicate that death signals from BCR may first cause mitochondrial alterations followed by activation of both necrotic and apoptotic cascades.

[Evaluation of child-rearing environmental factors that affect the occurrence of sudden infant death syndrome: interview conducted by public health nurses]

PURPOSE

We examined the child-rearing environmental factors that affect the occurrence of sudden infant death syndrome (SIDS) by using a nation-wide survey.

METHOD

Infants who died due to SIDS between January 1996 and June 1997 in Japan were identified from death certificates. Controls of the same sex, birthplace, and birth months as the corresponding SIDS were chosen from birth certificates. Interviews of both cases and controls were undergone in January and February 1998 by public health nurses.

RESULTS

The following Child-rearing factors exhibited a significant relationship with the occurrence of SIDS: 1. Concerning the sleeping position, the prone position was associated with increased risk compared to the supine position, with an odds ratio of 3.02 (95% c.i. 2.07-4.65). 2. Regarding the feeding method, artificial feeding only demonstrated a higher risk than breast feeding only, with an odds ratio of 4.92 (95% c.i. 2.78-9.63). 3. With regard to smoking, infants with both parents who smoked exhibited a higher risk than infants where neither parents smoked, with an odds ratio of 3.50 (95% c.i. 1.74-8.32).

Evaluation of endoscopic injection sclerotherapy with and without simultaneous ligation for the treatment of esophageal varices

For more effective and simple endoscopic injection sclerotherapy (EIS) for esophageal varices, we developed an EIS procedure with ligation (EISL) that is non-invasive, in which EIS and endoscopic variceal ligation (EVL) are performed simultaneously. In this study, we compared EISL and EIS in a randomized sample of patients (n = 14 for each procedure). For EISL, EVL was performed, including the injection site, after the injection of 5% ethanolamine oleate with iopamidol (EOI) into a varix. The mean number of treatment sessions required for eradication of esophageal varices was 2.3+/-0.5 for EISL and 3.9+/-0.8 for EIS (P < 0.001); the mean number of treatment sites was 6.2+/-2.2 for EISL and 14.0+/-5.0 for EIS (P < 0.001); the mean total amount of EOI used was 13.8+/-5.2ml for EISL and 26.3+/-9.8ml for EIS (P < 0.001). There were no significant differences in rates of recurrence of varices or in bleeding between the two groups. For EISL, fewer treatment sessions and less sclerosant were sufficient, probably because the sclerosants were more effective due to the blockage of variceal blood flow by the ligation. This method should provide a novel modification of EIS.

Characterization of plasmid DNA binding and uptake by peritoneal macrophages from class A scavenger receptor knockout mice

PURPOSE

Plasmid DNA (pDNA) has become an important class of macromolecular agent suitable for non-viral gene therapy as well as DNA vaccination. Our recent study has suggested that pDNA is taken up by mouse peritoneal macrophages via a specific mechanism mediated by a receptor similar to the scavenger receptor (SR). This study was designed to further characterize the pDNA uptake by macrophages in order to elucidate the mechanism.

METHODS

The binding and uptake of pDNA labeled with 32P or a fluorescent marker were studied in vitro using cultured Chinese hamster ovary (CHO) cells expressing the class A scavenger receptor (SRA) and peritoneal macrophages from SRA-knockout mice.

RESULTS

pDNA binding and uptake by CHO(SRA) cells were minimal and almost identical to that by wild-type CHO cells. Macrophages from the knockout mice showed pronounced pDNA binding and uptake as did the control macrophages. In both types of macrophage, pDNA binding was significantly inhibited by cold pDNA, polyinosinic acid and dextran sulfate but not by polycytidylic acid or Ac-LDL. These results provide direct evidence that SRA is not responsible for the significant binding and subsequent uptake of pDNA by mouse peritoneal macrophages. Further binding experiments revealed that, in addition to polyinosinic acid and dextran sulfate, heparin was a potent inhibitor among a variety of polyanionic compounds such as polynucleotides, anionic polysaccharides and modified proteins including Ox-LDL.

CONCLUSIONS

The present study suggest that pDNA binding and uptake by mouse peritoneal macrophages are mediated by a specific mechanism to some defined polyanions not by scavenger receptors. The finding would be an important basis for further studies to elucidate the mechanism(s) of pDNA uptake by macrophages.

Optical recording of membrane potential on isolated spiral ganglion cells of newborn mice using a voltage-sensitive dye

Optical imaging methods make monitoring of the membrane potential feasible. With this technique, one can observe different optical signals depending on optical properties, in response to membrane potential, using voltage-sensitive dyes. We used the multiple-site optical imaging system to investigate membrane potentials of the isolated, cultured spiral ganglion cells (SCGs) from newborn mice. We used a voltage-sensitive absorption dye. With high potassium (150 mM K+) exposure, the absorbency of SGCs stained with voltage-sensitive dye increased temporarily under a 700-nm interference filter at approximately 0.3%. This detection of the depolarization of SGCs using an optical recording technique with a voltage-sensitive dye is important because it shows that the simultaneous measurement of activity in a variety of regions is possible, as is the exploring of the intercellular signalling pathway.

Interactions of endothelin receptor subtypes A and B with Gi, Go, and Gq in reconstituted phospholipid vesicles

To understand the biochemical basis for the functional divergence of the human endothelin receptor subtypes A (ETAR) and B (ETBR), they were expressed, purified from insect Sf9 cells, and reconstituted into phospholipid vesicles with the Go, Gq, and Gi proteins. For each G protein, a unique pattern of reactivity was observed with the different receptor subtypes. Both ETAR and ETBR activated Go to a similar maximal extent, and both subtypes activated Gq with similar EC50 values; however, the ETAR displayed a 2-3-fold higher maximal extent of activation. In contrast, both subtypes activated Gi to a similar maximal extent, but the ETAR displayed a 4-fold higher EC50 value as compared to the ETBR. To test whether these coupling specificities are influenced by C-terminal palmitoylation of the receptor, we mutated a cluster of cysteine residues near the end of the seventh transmembrane helix in both receptors. While the cysteine mutations in the ETBR resulted in a partially palmitoylated receptor, the replacement of these cysteine residues in the ETAR yielded a mostly palmitoyl-deficient receptor and had no effect on Go activation, but caused a reduction in the extents of Gi and Gq stimulation. Together, these studies provide important insights into the specificity of G protein coupling in the endothelin receptors. The ability to discriminate between the different G proteins under various physiological conditions may be a key element in the selection of distinct signal transduction pathways by the two receptor subtypes.

White matter hyperintensities on MRI in a patient with corticobasal degeneration

We describe a patient who presented with the clinicopathological features of corticobasal degeneration (CBD). Over the course of 8 years, the patient developed myoclonus, dystonia, and supranuclear gaze palsy associated with an akinetic-rigid syndrome. To our knowledge, no previous report of a patient with CBD has described clear-cut regional white matter changes as revealed by magnetic resonance imaging (MRI) scans. In our patient, a T2-weighted MR image of the brain showed focal atrophy of the bilateral frontal cortex and asymmetric regional hyperintensities of the subjacent white matter. These signal changes seemed to primarily reflect the progression of neuronal degeneration, especially the demyelination secondary to axonal loss or change.

Oligonucleotide aggregates bind to the macrophage scavenger receptor

We have prepared a model receptor containing a Lys cluster (320-340) in the collagen-like domain of the bovine macrophage scavenger receptor, and have shown that it has a similar binding specificity to the native scavenger receptor. The native scavenger receptor is reported to bind the quadruplex structure of nucleotides. In this study, we analyzed the model receptor binding of nucleotides with various structures, random, parallel or antiparallel quadruplex and aggregate forms. This was carried out by direct binding assays using labeled oligonucleotides or surface plasmon resonance, and by an inhibition assay using Chinese hamster ovary (CHO) cells expressing the scavenger receptor. The results showed that the nucleotides forming the quadruplex structure did not exhibit any binding. Only the aggregate forms of the nucleotide could bind to the model receptor. They also inhibited the degradation of acetylated low density lipoprotein by CHO cells expressing the native scavenger receptor, whereas nucleotides that did not bind to the model receptor had no effect on cellular acetylated low density lipoprotein degradation. Our results suggest that the quadruplex structure is not essential but may be required for the formation of the nucleotide aggregates, which can interact with the scavenger receptor.

Immunohistochemical study of some cytoskeletal proteins in hereditary myopathy of the diaphragmatic muscles in Holstein-Friesian cattle

We have investigated the expression, using immunohistochemical and Western blot methods, of some cytoskeletal proteins including desmin, vimentin, actin, alpha-actinin, and ubiquitin in hereditary myopathy of the diaphragmatic muscles in Holstein-Friesian cattle (the histochemical and electron microscopical aspects have been previously reported). Immunohistochemically, the expression of desmin was observed strongly in the subsarcolemmal regions, but was lacking or faint in the area corresponding to the core-like structures. Vimentin showed almost the same localization as desmin, but no activity could be observed in the core-like structures. In addition, the core-like structures showed strong immunoreactivity for actin and ubiquitin, but no immunoreactivity for alpha-actinin. F-actin stained with phalloidin-tetramethyl-rhodamine was strongly positive in irregular spots that corresponded to the core-like structures, but was negative for desmin-positive regions. Western blot analysis of the diseased muscles revealed a significant increase in the amount of desmin and vimentin immunoreactivities and similar amounts of actin and alpha-actinin compared with the control muscles. Two-dimensional electrophoresis revealed no isoforms of desmin, suggesting the absence of abnormal phosphorylated forms of desmin. Since the co-localization of desmin and vimentin and the absence of phosphorylated desmin suggest that the overexpression of desmin may be reflected in the reactive change or regenerating process, the present myopathy should be regarded as an entity separate from desmin-storage myopathy or desmin-related myopathies. We also discuss the possibility that the present myopathy could be considered as myofibrillar myopathy, a recently proposed nosological entity.

Immunohistochemical and electron microscopical studies of myocardial inclusions in hereditary myopathy of the diaphragmatic muscles in Holstein-Friesian cattle

In hereditary myopathy of the diaphragmatic muscles in Holstein-Friesian cattle, the largest number of acidophilic intracytoplasmic inclusions was found in the myocardium. These inclusions, which were oval and measured 12-15 microm in the transverse sections, were characterized by a dense, amorphous zone, and a relatively hyalinized sarcous substance in paraffin-embedded hematoxylin and eosin (H & E)-stained sections. Histochemically, each inclusion was stained intense red and dark green with H & E and Gomori's trichrome, respectively. NADH-TR activity was absent. The region surrounding the inclusions was less acidophilic with H & E, and showed an increased activity with NADH-TR. The inclusions showed no immunoreactivity for desmin, vimentin, actin or alpha-actinin, while strong desmin immunoreactivity was observed in the region surrounding the inclusion. Some inclusions showed strong immunoreactivity for ubiquitin, but others reacted only faintly. Ultrastructurally, the inclusion had a dense core composed of myofibrillar aggregations. The periphery of this dense core was surrounded by thin or intermediate-sized filaments, which corresponded to the desmin-positive area. This alteration was sometimes found to be continuous with the Z disk, which showed streaming or disintegration or with the desmosome of the intercalated disk. We discuss here the similarity between this specific inclusion and the other alternative organelles that have been reported previously in cardiomyopathy or in cardiac lesions associated with various myopathies.

Effect of amino acids and glucose on exercise-induced gut and skeletal muscle proteolysis in dogs

The effect of amino acid and/or glucose administration before and during exercise on protein metabolism in visceral tissues and skeletal muscle was examined in mongrel dogs. The dogs were subjected to treadmill running (150 minutes at 10 km/h and 12% incline) and intravenously infused with a solution containing amino acids and glucose (AAG), amino acids (AA), glucose (G) or saline (S) in randomized order. The infusion was started 60 minutes before exercise and continued until the end of the exercise period. An arteriovenous-difference technique was used to estimate both tissue protein degradation and synthesis. When S was infused, the release of leucine (Leu) from the gut and phenylalanine (Phe) from the hindlimb significantly increased during exercise, thus indicating that exercise augmented proteolysis in these tissues. The balance of Leu across the gut during exercise demonstrated a net uptake with both AAG and AA, whereas a net release was observed for G and S. In addition, Leu uptake in the gut during the last 90 minutes of the exercise period tended to be greater with AAG versus AA (P = .06). Phe balance across the hindlimb during the late exercise period showed a significant release with S, AA, and G, whereas the balance with AAG did not show a significant release. These results suggest that exercise-induced proteolysis in the gut may be reduced by supplementation with AA, and this effect may be enhanced by concomitant G administration. However, in skeletal muscle, both AA and G may be required to prevent net protein degradation during exercise. G provided without AA did not achieve net protein synthesis in either tissue.

Properties of cationic liposomes composed of cationic lipid YKS-220 having an ester linkage: adequate stability, high transfection efficiency, and low cytotoxicity

Cationic lipid N-[3-[2-(1,3-dioleoyloxy)propoxy-carbonyl]propyl]-N,N,N-trimethyla mmonium iodide (YKS-220) having a symmetrical and biodegradable structure was employed for the preparation of cationic liposomes with dioleoylphosphatidylethanolamine (DOPE). The stability, transfection activity in several cell lines and cytotoxicity of YKS-220 cationic liposomes were studied. It was found the YKS-220 cationic liposomes were very stable and their transfection activity remained even after storage at 4 degrees C for 12 months. The transfection activity of these liposomes was assayed using CHO, COS, and HepG2 cells and found to be comparable with, or better than, that of other cationic liposomes, such as N-[1-(2,3-dioleoyloxy)propyl]-N,N,N-trimethylammonium methylsulfate (DOTAP) liposome, N-[1-(2,3-dioleyloxy)propyl]-N,N,N-trimethylammonium chloride (DOTMA) liposome (Lipofectin), and 2,3-dioleyloxy-N-[2-(sperminecarboxamido)ethyl]-N,N-dimethyl -1-propanaminium trifluoroacetate (DOSPA) liposome (LipofectAMINE). In addition, the cytotoxicity of YKS-220 cationic liposomes was far lower than that of other cationic liposomes.

Clinical significance of plasma vascular endothelial growth factor in gastrointestinal cancer

Circulating vascular endothelial growth factor (VEGF) was measured in gastric and colorectal cancer patients using an enzyme-linked immunosorbent assay (ELISA). Firstly, serum and plasma samples were collected from 20 normal controls to compare the values of VEGF and to determine which specimen type was most suitable for detecting circulating VEGF. Seventeen of 20 normal controls had plasma VEGF levels under the limit of detection (15 pg/ml) and the levels of the remaining three controls were 21, 22 and 38 pg/ml. In contrast, all serum samples indicated high levels of VEGF (mean 238 pg/ml), ranging from 44 to 450 pg/ml. In a time-course test of two normal controls serum VEGF values increased markedly between 30 and 60 min and remained high, whilst plasma VEGF values were low up to 480 min. Thus, plasma samples are more suitable for the measurement of circulating VEGF. Next, plasma VEGF levels were examined in 44 patients with gastric cancer (8 early, 7 advanced without remote metastasis and 29 metastatic), 13 with colorectal adenoma (2 with focal cancer) and 26 with colorectal carcinoma (8 advanced without metastasis and 18 metastatic) before treatment. An extremely high plasma concentration of VEGF was seen in some cancer patients with metastasis. To discriminate these patients, a cut-off level was determined, considering both the distribution of the sample concentration and the upper limit of 95% confidence area of VEGF in the cancer patients without metastasis. The cut-off value was 108 pg/ml and most cancer patients without metastases had VEGF levels below the cut-off value. In 11 of 29 metastatic gastric cancer patients (38%) and 9 of 18 metastatic colorectal cancer patients (50%), plasma VEGF levels were higher than the cut-off value. Survival was also analysed in the patients with metastasis. It was significantly longer in the patients with low VEGF levels (below the cut-off) than in those with high VEGF levels (logrank test, P = 0.042). 34 patients with metastasis (19 gastric cancer and 15 colorectal cancer) were treated with systemic chemotherapy, and their pretreatment levels of plasma VEGF and conventional tumour markers (CEA and CA19-9) were evaluated in relation to response. The response to chemotherapy was significantly higher in patients with low VEGF levels (< or = 108 pg/ml) than in those with high VEGF levels (P = 0.047). Such a difference was not observed with CEA/CA19-9. In conclusion, plasma VEGF is a useful marker for tumour metastasis and patient survival, and a possible predictive factor for the response of patients with gastrointestinal cancer to chemotherapy.

DNA cleaving activities of 9-membered masked enediyne analogues possessing DNA intercalator and sugar moieties

The DNA cleaving properties of various enediyne analogues possessing sugar moieties and DNA-intercalators were investigated. The DNA cleaving experiments show that these hybrids analogues induced sequence-selective DNA cleavage and the simple sugars in the enediyne serve as a DNA recognition element for DNA cleavage.

Synthesis of 9-membered masked enediyne analogues possessing DNA intercalator and sugar moieties

Syntheses of hybrid DNA cleaving molecules which have the 9-membered enediyne structure of kedarcidin with the DNA intercalator of NCS and/or the sugar moieties were accomplished. Introduction of the sugar moieties to the masked enediyne was achieved via S-alkylation of a bromoacetate derivative with a sugar-containing thiol without the need for protection of the sugar moiety.

[Simultaneous cholecystectomy and CABG for acute cholecystitis and post-infarction angina]

A 71-year-old man was admitted to our hospital with massive GI bleeding and followed by acute myocardial infarction. Severe three vessel coronary artery disease with poor left ventricular performance (EF: 40%) was demonstrated by coronary angiography. He was referred for CABG. He had also cholecystitis, which needed surgical treatment simultaneously. Combined CABG and cholecystectomy were performed without using gastroepiploic artery as a bypass graft, and through separate median sternotomy and through right upper transrectal laparotomy. Postoperative course was uneventful. This combined procedure is beneficial for the patients with acute cholecystitis and unstable angina.

Both Ets-1 and GATA-1 are essential for positive regulation of platelet factor 4 gene expression

In the rat platelet factor 4 (PF4) promoter, Ets motifs and GATA motifs are located at positions -880, -75 and -135, -30, respectively, and their motifs are found in the promoter region of most megakaryocyte protein genes. In order to investigate how the Ets and GATA motifs affect PF4 promoter activity, we constructed Ets and/or GATA motif mutant genes. A single disruption of either -75Ets, -135GATA, or -30GATA significantly reduced PF4 promoter activity, and double disruptions involving these motifs completely abolished it. Furthermore, gel-retardation assays revealed that Ets-1 and GATA-1 proteins from HEL and MEG-01 cells bound to the Ets motifs and GATA motifs, respectively. Co-transfection experiments showed that the overexpression of Ets-1 and/or GATA-1 enhanced the expression of the PF4 promoter reporter gene. These effects of Ets-1 and GATA-1 on PF4 promoter activity are additive. When HEL cells were treated with dimethylsulfoxide in order to induce differentiation into megakaryocytes, the mRNA level of ets-1 increased 10-fold, which might be directly correlated with the significant increase in PF4 mRNA level induced by dimethylsulfoxide. All these results strongly suggest that both Ets-1 and GATA-1 play key roles in the positive regulation of PF4 gene expression.

A multifunctional transcription factor (A1p145) regulates the smooth muscle phenotype in mesangial cells

A1p145, a novel DNA binding protein for type IV collagen gene (COL4), has multiple functions including DNA replication factor C and DNA binding for several other genes. To elucidate the mechanisms underlying the differentiation process of mesangial cells (MCs), we investigated the effects of A1p145 on rat MCs. Cells in the early passages showed a smooth muscle-like phenotype such as low cell turnover, high levels of expression for COL4, and smooth muscle alpha-actin (SMA). Cells in the late passages lost their phenotype. The amount of binding activity to COL4 promoter was inversely correlated with the level of COL4 mRNA. Introduction of antisense for A1p145 into late passage cells enhanced the levels of mRNA for COL4 and SMA. The levels of proliferating cell nuclear antigen mRNA were also suppressed. These results suggest that A1p145 is a negative transcription factor for COL4 and may be a phenotypic modulator.

Effect of glucose on ureagenesis during exercise in amino acid-infused dogs

The purpose of this study was to investigate the effect of glucose administered with amino acids before and during exercise on hepatic ureagenesis. Eight mongrel dogs subjected to treadmill running for 150 minutes at 10 km/h on a 12% incline were intravenously infused with either a mixture of amino acids and glucose (AAG) or amino acids alone (AA). The infusion was started 60 minutes before exercise and continued until the end of exercise. The rate of urinary urea excretion increased after infusion of both AAG and AA. However, the rate of urinary urea excretion was significantly lower in the AAG group versus the AA group during the first 1.5 hours of the recovery period ([R0 to R90] 514+/-24 v 637+/-24 mg/h, mean+/-SE, P < .05). Moreover, hepatic urea output was decreased during AAG versus AA infusion (229+/-62 v 367+/-55 microg/kg/min, P < .05). Hepatic glucose production during exercise was also significantly lower in AAG versus AA infusion (354+/-54 v 589+/-56 mg/kg, P < .05). On the other hand, no difference was observed in hepatic total amino acid uptake between the groups. Thus, these results indicate that AAG administered before and during exercise appears to reduce hepatic ureagenesis due to reduced hepatic gluconeogenesis as compared with administration of AA alone. These findings also suggest that nitrogen retention is enhanced by glucose administered during exercise.

Axially chiral N-benzyl-N,7-dimethyl-5-phenyl-1, 7-naphthyridine-6-carboxamide derivatives as tachykinin NK1 receptor antagonists: determination of the absolute stereochemical requirements

A potent and orally active NK1 antagonist, trans-N-[3, 5-bis(trifluoromethyl)benzyl]-7,8-dihydro-N, 7-dimethyl-5-(4-methylphenyl)-8-oxo-1,7-naphthyridine-6-carboxamide (1t), was shown to exist as a mixture of separable and stable (R)- and (S)-atropisomers (1t-A and 1t-B) originating from the restricted rotation around the -C(6)-C(=O)- bond; the antagonistic activities of 1t-A were ca. 6-13-fold higher than those of 1t-B. Analogues of 1t (3), which have (S)- and (R)-methyl groups at the benzylic methylene portion of 1t, were prepared and separated into the diastereomeric atropisomers, 3a-A, 3a-B and 3b-A, 3b-B, in enantiomerically pure forms. Among the four isomers of 3, the (aR, S)-enantiomer (3a-A) exhibited the most potent antagonistic activities with an IC50 value of 0.80 nM (in vitro inhibition of [125I]BH-SP binding in human IM-9 cells) and ED50 values of 9.3 micrograms/kg (iv) and 67.7 micrograms/kg (po) (in vivo inhibition of capsaicin-induced plasma extravasation in guinea pig trachea), while the activity of the (aS,R)-enantiomer (3b-B) was the weakest with an IC50 value of 620 nM. The structure-activity relationships in this series of antagonists indicate that the (R)-configuration at the axial bond and the stacking (or stacking-like) conformation between the two phenyl rings as shown in 1t-A and 3a-A are essential for high-affinity binding and suggest that the amide moiety functions as a hydrogen bond acceptor in the interaction with the receptor.

Implantation of a mechanical valve within the orifice of a mitral bioprosthesis in a case with severely calcified left atrium--a case report

The case of a 61-year-old woman with deterioration of mitral bioprosthesis and severe left atrial calcification is presented. Although the implantation of a mechanical valve within the orifice of a mitral bioprosthesis was tried, we found a major pitfall in this method was exact orifice matching.

The sodium channel has four domains surrounding a central pore

The voltage-gated sodium channel generates the action potential. This 300-kDa protein has four homologous regions, which are also homologous to the voltage-sensitive tetrameric potassium channel. We isolated sodium channels from Electrophorus electricus electroplax by detergent solubilization and immunoaffinity chromatography and studied their structure by electron microscopy of negatively stained specimens. Different projections were aligned, classified, and averaged. In side view, the channel protein exhibits the shape of a truncated cone, 14 nm in height. One end has a diameter of 12 nm and is asymmetric, while the other is more symmetric and has a diameter of 7-10 nm. In top views, the sodium channel appears to consist of four domains of different size and to have a stain-filled pore in the center.