Synthesis of nitrodiazirinyl derivatives of neurotoxin II from Naja naja oxiana and their interaction with the Torpedo californica nicotinic acetylcholine receptor

Five singly modified nitrodiazirine derivatives of neurotoxin II (NT-II) from Naja naja oxiana were obtained after NT-II reaction with N-hydroxysuccinimide ester of (2-nitro-4-[3-(trifluoromethyl)-3H-diazirin-3yl]phenoxy)acet ic acid followed by chromatographic separation of the products. To localize the label positions, each derivative was first UV-irradiated and then subjected to reduction, carboxymethylation, and trypsinolysis. Tryptic digests were separated by reversed phase-HPLC, the labeled peptides being identified by mass spectrometry. The derivatives containing the photolabel at the position Lys 25, Lys 26, Lys 44, or Lys 46 were [125I]iodinated by the chloramine T procedure. Each iodinated derivative was found to form photoinduced cross-links with the membrane-bound nicotinic acetylcholine receptor (AChR) from Torpedo californica. The pattern of labeling the receptor's alpha, beta, gamma, or delta subunits was dependent on the photolabel position in the NT-II molecule and differed from that obtained earlier with an analogous series of p-azidobenzoyl derivatives of NT-II. The results obtained indicate that (i) different sides of the neurotoxin molecule are involved in the AChR binding, and (ii) fragments of the different AChR subunits are located close together at the neurotoxin-binding sites.

Hepatocellular carcinoma in cirrhotic livers: detection with unenhanced and iron oxide-enhanced MR imaging

PURPOSE

To evaluate diagnostic accuracy with unenhanced and superparamagnetic iron oxide (SPIO)-enhanced magnetic resonance (MR) imaging for detection of hepatocellular carcinoma (HCC) in cirrhotic livers.

MATERIALS AND METHODS

Fifteen patients with 26 histologically proved HCCs associated with liver cirrhosis underwent imaging with T1-, T2-, and proton-density-weighted spin-echo (SE) and fast low-angle shot (FLASH) sequences. Lesion-to-liver contrast-to-noise ratios were measured in all sequences. Diagnostic performance of the imaging techniques was assessed by using receiver operating characteristic analysis.

RESULTS

Enhanced SE and FLASH sequences were significantly more accurate (P < .005) for the detection of small HCCs. Among the unenhanced pulse sequences, the accuracy of tumor localization was highest with the T2-weighted SE sequences; however, 25% of the lesions were located incorrectly. Compared with unenhanced images, lesions were correctly located more often when SPIO-enhanced SE and FLASH sequences were used.

CONCLUSION

SPIO-enhanced MR imaging with proton-density-weighted or FLASH sequences was more accurate in the detection of small HCCs in cirrhotic livers.

Insulin resistance associated with decreased levels of insulin-receptor messenger ribonucleic acid: evidence of a de novo mutation in the maternal allele

Mutations in the insulin receptor gene may lead to insulin resistance and diabetes mellitus in some patients. We have studied an insulin-resistant patient with leprechaunism. Insulin binding to the patient's fibroblasts was markedly decreased. Determination of the nucleotide sequence of the patient's insulin receptor gene revealed heterozygosity for a 2-basepair deletion in exon 15. If the premessenger ribonucleic acid (pre-mRNA) is spliced normally, it causes a replacement of codon 970 in the beta-subunit with a premature chain termination codon, thereby deleting most of the intracellular domain of the receptor. The mRNA transcribed from the allele with a 2-base-pair deletion is likely to be unstable because mRNA transcripts from this allele could not be detected by complementary DNA sequencing. Northern blot analysis showed that the patient's insulin receptor mRNA was decreased by 90% compared with that of a control subject, thus suggesting that the patient is a compound heterozygote for two mutations that decrease levels of insulin receptor mRNA. This deletion mutation in exon 15 seems to be a de novo mutation, because it was not detected in either parent. Investigation of the inheritance of a silent sequence polymorphism in exon 17 provided that the deletion occurred in the maternal allele. Furthermore, linkage analysis suggests that the second mutation is derived from the patient's father, although we could not directly identify it by sequencing the coding region of the insulin receptor gene. Therefore, it is possible that this mutation is present in a regulatory domain of the insulin receptor gene, acting in cis-dominant fashion to reduce the levels of insulin receptor mRNA. Analyses of the hypervariable region in the myoglobin and pMCT118 loci were consistent with the assumption that the father and mother studied here are indeed the biological parents of the diseased patient. We hereby conclude that the patient is a compound heterozygote for two mutant alleles, both of which are responsible for the reduced levels of insulin receptor mRNA and insulin binding.

Adnexal masses: accuracy of characterization with transvaginal US and precontrast and postcontrast MR imaging

PURPOSE

To determine the accuracy of transvaginal ultrasound (TVUS) and of precontrast and contrast material-enhanced magnetic resonance (MR) imaging in the differentiation of adnexal masses.

MATERIALS AND METHODS

Five blinded readers analyzed images of 80 masses in 72 patients. MR and TVUS images were interpreted in separate sessions. Findings were confirmed at surgery or laparoscopy.

RESULTS

Higher diagnostic accuracy was attained with MR imaging in mature cystic teratomas and endometriomas. However, better accuracy was achieved with contrast-enhanced MR imaging and TVUS in simple cysts, cystadenomas, and malignant tumors because internal details could be visualized. Receiver operating characteristic study indicated that observer confidence was significantly higher with contrast-enhanced MR imaging than with precontrast MR imaging (P = .011) or TVUS (P = .002) in the differentiation of benign and malignant masses.

CONCLUSION

Contrast-enhanced MR imaging is superior to precontrast MR and TVUS imaging in the characterization and differentiation of adnexal masses.

Binding of pig sperm receptor in the zona pellucida to the boar sperm acrosome

Pig zona pellucida (ZP) contains three families of glycoproteins: PZP2, PZP3 alpha and PZP3 beta. PZP3 alpha mediates the binding of the ZP to spermatozoa. In this study, the binding site of pig ZP on boar spermatozoa and the zona-binding proteins of boar spermatozoa were studied using chemically modified zona glycoproteins or anti-pig ZP antiserum. Endo-beta-galactosidase-digested PZP3 alpha (E beta G-PZP3 alpha), which is deficient in sulfated N-acetylpolyactosamine, as well as solubilized ZP, bound to the acrosomal region of acrosome-damaged or partially acrosome-reacted spermatozoa. However, they did not bind to acrosome-intact or fully acrosome-reacted spermatozoa. Solubilized ZP did bind to the acrosomal cap released upon acrosome reaction. In western blot analyses, E beta G-PZP3 alpha bound to the sperm proteins with molecular masses similar to proacrosin-acrosin and the binding was inhibited by fucoidan and anti-pig acrosin antiserum. These results suggest that the binding site of solubilized pig ZP and E beta G-PZP3 alpha on spermatozoa is located mainly in the acrosomal matrix and on the membranous compartments in the acrosome and suggest that E beta G-PZP3 alpha binds to proacrosin-acrosin. The binding of E beta G-PZP3 alpha to proacrosin-acrosin may be involved in the binding of the ZP to the acrosome of partially acrosome-reacted spermatozoa.

A novel biotinylated heterobifunctional cross-linking reagent bearing an aromatic diazirine

The synthesis of a p-[(3-trifluoromethyl)diazirine-3-yl]benzoic acid derivative is described as a new carbene generating heterobifunctional cross-linking reagent. The cross-linker carries a biotin moiety in order to make use of avidin-biotin technology for specific manipulation of cross-linked components. To evaluate the ability of this reagent, the inter-subunit cross-linking of egg-white avidin tetramer was investigated. As a typical application of avidin-biotin technology for cross-linking experiments, a chemiluminescent detection method was examined to identify photobiotinylated components. A cross-linked dimeric product with an apparent molecular mass of 38 kDa was clearly visualized by the combined use of a horseradish peroxidase-streptavidin conjugate and a luminol-based chemiluminescent system.

Differential diagnosis of focal liver lesions: role of spin-echo and contrast-enhanced dynamic MR imaging

PURPOSE

To evaluate the role of spin-echo (SE) and contrast material-enhanced dynamic magnetic resonance (MR) imaging in the differential diagnosis of focal liver lesions.

MATERIALS AND METHODS

Conventional T1- and T2-weighted SE and fast low-angle shot dynamic MR imaging were performed in 300 focal liver lesions on a 1.5-T MR imager. Findings at both SE and dynamic imaging were analyzed by means of univariate and multivariate analysis.

RESULTS

Although considerable overlap existed, signal intensity on T2-weighted images, tumor margin, and internal architecture were significant factors for SE imaging. For dynamic imaging, the hemodynamics and pattern of enhancement were significant factors. A logistic regression analysis revealed 86% of lesions were correctly categorized with these parameters.

CONCLUSION

A specific diagnosis of liver lesions can be obtained in most cases by combining parameters obtained from SE and dynamic MR images.

Mature cystic teratomas of the ovary without fat in the cystic cavity: MR features in 12 cases

OBJECTIVE

The diagnosis of mature cystic teratoma may be overlooked in the small number of cases that do not contain fat in the lumen of the cyst. The purpose of this study was to evaluate the MR appearance of mature cystic teratomas containing little or no fat and to determine the value of gradient-echo MR imaging for detection of small amounts of fat.

MATERIALS AND METHODS

In a review of pathologic specimens of 78 mature cystic teratomas, we found 12 tumors without fatty fluid (sebum) in their cystic cavity. Histologically, a small amount of fat was present in the wall of the cyst in each case. We retrospectively reviewed MR images of these tumors. In seven tumors with small amounts of hyperintense tissue on T1-weighted MR images, opposed-phase and in-phase gradient-echo MR images were obtained in order to verify the presence of fat.

RESULTS

All 12 lesions were hypointense on T1-weighted MR images and markedly hyperintense on T2-weighted images, indicating that the cystic cavity contained aqueous fluid. Fatty tissue was not identified in the lumen or wall of the cyst on MR images in five of the 12 tumors. In seven tumors, MR images showed small hyperintense areas in the walls of the cysts. These hyperintense signals were canceled on opposed-phase gradient-echo images. Characteristic MR findings for mature cystic teratoma, such as reversed chemical-shift artifact, gravity-dependent layering, or dermoid plug, were not observed in any of the lesions.

CONCLUSION

MR images in some cases of mature cystic teratomas may show aqueous fluid within the lumen of the cyst. In such cases, detection of fat in the cyst wall, especially with gradient-echo MR imaging, may help to establish the diagnosis.

Intracortical regionality represented by specific transcription for a novel protein, latexin

The monoclonal antibody (mAb) PC3.1 recognizes a subset of neurons distributed in the infragranular layers of the lateral neocortex of the rat. Immunoaffinity chromatography with mAb PC3.1 showed that this antibody specifically binds a peptide epitope on a 29 kDa protein named latexin. To study the molecular details of the protein, we isolated four independent cDNA clones for latexin from cDNA libraries of the rat cerebral cortex and whole brain using the amino acid sequences of latexin fragments. Analysis of these cDNA clones showed that the predicted primary structure of latexin consists of 223 amino acids, and has no strict homology to any sequences so far known. Western and Northern blots demonstrated that the latexin and its mRNA were expressed predominantly in neural tissues with some expression in non-neural tissues. The gene that encodes latexin in the rat appeared to have homologues in other mammalian species and in the chick. In situ hybridization showed that latexin mRNA is synthesized in a subset of neurons in the lateral but not the dorsal neocortex, and that the distribution profile of these neurons is quite similar to that of neurons expressing latexin. These results indicate that latexin is a novel class of neuronal protein which represents intracortical regionality, and suggest that the regional specification of the neocortex involves selective parcellation of neurons which express a particular gene.

Value of phase-shift gradient-echo MR imaging in the differentiation of pelvic lesions with high signal intensity at T1-weighted imaging

PURPOSE

To assess the value of phase-shift gradient-echo magnetic resonance (MR) imaging with the fast low-angle shot (FLASH) technique in the differentiation of hemorrhagic tumors and teratomas.

MATERIALS AND METHODS

T1- and T2-weighted spin-echo imaging and phase-shift MR imaging were performed in 60 patients. On T1-weighted images, the signal intensity of lesions was compared with that of intraperitoneal fat. Findings at MR imaging were compared with the surgical findings. The diagnostic performance of each pulse sequence was analyzed with receiver operating characteristic curves.

RESULTS

Sixty high-signal-intensity lesions were identified in 45 patients at T1-weighted imaging. Hemorrhagic lesions and teratomas had similar signal intensities on both T1- and T2-weighted images. Lesions were detected more decisively with FLASH imaging than with T1- and T2-weighted imaging.

CONCLUSIONS

Phase-shift gradient-echo imaging is a readily available method for the differential diagnosis of lesions with high signal intensity at T1-weighted MR imaging.

pH-sensitive dissociation and association of beta-N-acetylhexosaminidase from boar sperm acrosome

beta-N-Acetylhexosaminidase (beta-Hex, EC, 3.2.1.52) was released from cauda epididymal boar sperm by treatment with ionophore A23187, indicating that this enzyme is localized in the acrosome. beta-Hex was extracted on a large scale, with 2% acetic acid containing 0.2% Brij 35, from washed ejaculated sperm. By gel filtration chromatography, beta-Hex was separated into a high-molecular-weight fraction (beta-Hex I) and a low-molecular-weight fraction (beta-Hex I). beta-Hex I, which is predominant under acidic conditions (pH 6.5), dissociated into beta-Hex II under alkaline conditions (pH 7.4). beta-Hex II, converted from beta-Hex I, associated again to form beta-Hex I under acidic conditions. By sequential chromatography on ion-exchange, lectin, gel filtration, and ion-exchange HPLC columns, beta-Hex I and II were purified 1200-fold and 4000-fold, respectively, with a combined recovery of 23% as measured with synthetic substrate. An inhibitor of beta-Hex, O-(2-acetamido-2-deoxy-D-glucopyranosylidene) amino N-phenyl-carbamate (PUGNAC), reduced the in vitro fertilization rate in porcine cumulus-enclosed eggs, but barely changed the rate when cumulus-free eggs were used. beta-Hex I was shown to possess cumulus dispersion activity, suggesting that beta-Hex plays a role in the passing by sperm through cumulus cells before they bind to the zona pellucida.

Hyperechoic renal tumors: anechoic rim and intratumoral cysts in US differentiation of renal cell carcinoma from angiomyolipoma

To determine whether angiomyolipomas (AMLs) and renal cell carcinomas (RCCs) can be differentiated at ultrasonography (US), the authors retrospectively evaluated the sonographic appearances of 31 AMLs and 38 RCCs. Sonograms were evaluated by three radiologists without knowledge of histologic findings, with respect to the echogenicity of the tumor, predominant echotexture, and whether an anechoic rim was present. All patients had also undergone computed tomography (CT) to check for tumoral fat. Intratumoral fat was evident at CT in 28 of the 31 AMLs. RCCs had no fat at CT or histologic evaluation. An anechoic rim was evident in 32 of 38 (84%) RCCs, and 10 RCCs had small anechoic areas with back echo enhancement, which corresponded to intratumoral cysts or cystic necrosis at histologic evaluation. The anechoic rim and areas indicative of cysts were not found in AMLs. Demonstration of an anechoic rim and/or intratumoral cysts in a hyperechoic mass at US suggests that the tumor is an RCC.

A glycine-1008 to valine mutation in the insulin receptor in a woman with type A insulin resistance

We examined the insulin receptor gene in a Japanese woman with type A insulin resistance. Acanthosis nigricans and polycystic ovary were present. A 75-g oral glucose tolerance test showed a diabetic pattern, and fasting insulinemia was 780 pmol/L. Insulin binding was normal, but autophosphorylation and tyrosine kinase activity were reduced in partially purified insulin receptors from Epstein-Barr virus-transformed lymphocytes. The nucleotide sequence for all 22 exons of the insulin receptor gene was determined by direct sequencing of genomic DNA amplified with the polymerase chain reaction. Substitution of valine for glycine at codon 1008 in the tyrosine kinase domain was identified in one allele. This was the same mutation found in another patient, but there was no relationship between the two families. The father had the same mutation in one allele and impaired glucose tolerance with mild hyperinsulinemia, but the mother and two brothers had normal glucose tolerance. We conclude that a single mutant allele in the tyrosine kinase domain caused the insulin resistance.

[Infusion therapy for acute superior mesenteric artery occlusion]

We performed transcatheter fibrolytic therapy using a coaxial microcatheter in two cases of acute superior mesenteric artery occlusion in the early stage. The tip of the microcatheter was introduced into the clot of the superior mesenteric artery. Urokinase was infused at a rate of 10,000 IU/min. The clots dissolved immediately after the infusion of 240,000 IU and 480,000 IU, respectively, without any complications. This infusion technique is promising for the treatment of acute superior mesenteric artery occlusion.

Urinary neopterin as a predictive marker of coronary artery abnormalities in Kawasaki syndrome

We investigated whether urinary neopterin concentrations respond to the pathological conditions (especially coronary artery dilatation) of Kawasaki syndrome. All of 29 children with Kawasaki syndrome had very high urinary neopterin concentrations. Increased urinary neopterin concentrations coincided with fever and with monocytosis in peripheral blood. The urinary neopterin excretion peaking within the first 8 days after onset correlated with the development of coronary artery dilatation. Increased urinary neopterin concentrations indicate that cell-mediated immunity is activated in patients with Kawasaki syndrome. Endogenous interferon-gamma and activation of monocytes/macrophages may play a role in the pathogenesis of Kawasaki syndrome. Not only do neopterin concentrations correlate with symptoms in the acute phase of Kawasaki syndrome, they also act as a predictive marker of coronary artery abnormalities in affected patients.

Urinary neopterin as a predictive marker of coronary artery abnormalities in Kawasaki syndrome

We investigated whether urinary neopterin concentrations respond to the pathological conditions (especially coronary artery dilatation) of Kawasaki syndrome. All of 29 children with Kawasaki syndrome had very high urinary neopterin concentrations. Increased urinary neopterin concentrations coincided with fever and with monocytosis in peripheral blood. The urinary neopterin excretion peaking within the first 8 days after onset correlated with the development of coronary artery dilatation. Increased urinary neopterin concentrations indicate that cell-mediated immunity is activated in patients with Kawasaki syndrome. Endogenous interferon-gamma and activation of monocytes/macrophages may play a role in the pathogenesis of Kawasaki syndrome. Not only do neopterin concentrations correlate with symptoms in the acute phase of Kawasaki syndrome, they also act as a predictive marker of coronary artery abnormalities in affected patients.

Clinico-pathological studies on a transitional type between extrahepatic biliary atresia and paucity of the interlobular bile ducts

Among the neonatal and infantile cases of obstructive jaundice seen at Niigata and Yamagata University Hospitals between 1976 and 1990, extrahepatic bile ducts were visualized in 19 cases by either preoperative endoscopic retrograde cholangiopancreaticography (ERCP) or intraoperative cholangiography. Neonatal hepatitis was diagnosed in 3 of these cases by clear images of the bile duct system extending from the common bile duct to the intrahepatic bile duct. In 7 cases, the common bile duct was able to be seen, while the common hepatic duct was only slightly visualized. Four of these 7 cases were consistent with paucity of the interlobular bile ducts (PILBD) based on hepatic histology, while the remaining 3 showed fibrosis, bile ductular proliferation, and many bile plugs in the bile ductuli of the portal areas, concurrent with histological changes in extrahepatic biliary atresia (EHBA), not PILBD. In 9 cases, only the common bile duct was visualized while the common hepatic duct was not seen, 7 of these 9 cases being consistent with type III-a1 EHBA. In 2 cases, neither fibrosis nor proliferation of the bile ductuli was observed in the portal areas, and portal areas without any bile ductuli were also seen, in accordance with findings for PILBD. Three cases which showed similar hepatic histological findings to EHBA despite the presence of patent extrahepatic bile ducts, and 2 cases which had obstructed extrahepatic bile ducts and hepatic histological findings similar to PILBD, were thought to be of a transitional type between EHBA and PILBD.(ABSTRACT TRUNCATED AT 250 WORDS)

Circular dichroic evidence for regulation of enzymatic activity by nonsubstrate hydrophobic ligand on glutathione S-transferase P

1-Anilinonaphthalene-8-sulfonic acid (ANS) noncompetitively inhibited enzyme activity of glutathione S-transferase P for both glutathione and 1-chloro-2,4-dinitrobenzene (Ki = 30 microM). Dissociation constant for ANS.GST-P complex calculated from the binding study was 15 microM. From the similar values of the inhibition constant and the dissociation constant, it was concluded that specific ANS binding caused the loss of enzyme activity. In the protein structural analysis by circular dichroism, the secondary structures remarkably changed by ANS binding in accordance with the decrease of enzymatic activities. The conformational change of the protein and the decrease in enzymatic activity were reversed by dissociation of ANS. This fact strongly suggested that the enzymatic activity was regulated by a nonsubstrate hydrophobic ligand.

Characterization of saccharide moiety in the electroplax sodium channel

Carbohydrate chains on the large peptide of the voltage-sensitive sodium channel from Electrophorus electricus electroplax have been partially characterized by the lectin-blotting technique combined with digestion using three glucosidases: neuraminidase, endo-beta-N-acetylglucosaminidase H, and peptide: N-glycosidase F. The results show that both N-linked oligosaccharides and O-linked (mucin-type) oligosaccharides are present. In N-linked oligosaccharides, the results suggest the presence of complex- and hybrid-type oligosaccharides which contain bisecting N-acetylglucosamine(s), as well as the complex-type oligosaccharides with the alpha-Fuc-GlcNAc-(Asn) residue(s). In O-linked oligosaccharides, they must carry Gal beta1----3GalNAc- moieties which contain NeuNAc residues in the terminal.

Characterization of cysteine residues of glutathione S-transferase P: evidence for steric hindrance of substrate binding by a bulky adduct to cysteine 47

Glutathione S-transferase P (GST-P) lost the enzymatic activity by 7-fluoro-4-sulfamoyl-2, 1, 3-benzodiazole (ABD-F), a thiol-group chemical modifier, but did not by methylmethanethiol-sulfonate. Both ABD-F and methylmethanethiolsulfonate reacted with Cys47 and Cys101. These two cysteine residues were site-directedly mutated with serine residues. Only the Cys101Ser lost the enzymatic activity by the treatment of ABD-F. On carbon 13 NMR experiments, a NMR signal of S-[13C]CH3 adduct to Cys47 did not show any change by the addition of S-hexylglutathione. These facts revealed that Cys47 did not locate at the active site, and a bulky adduct to Cys47 hindered the binding of substrates to the active site.