Clinical features and prognosis of acute aortic intramural hemorrhage compared with those of acute aortic dissection: a single center experience

The clinical manifestations and natural history of acute aortic intramural hemorrhage are not well characterized. Therefore, we have evaluated the differences in the clinical features and prognosis between acute intramural hemorrhage and acute classic aortic dissection. One hundred two consecutive patients with acute aortic syndrome were diagnosed between November 1994 and May 1999. The clinical features, treatment modalities and survival of these patients were analyzed. Thirty one of the 102 patients (30%) had intramural hemorrhage and 71 (70%) had aortic dissection. Patients with intramural hemorrhage were older than those with aortic dissection (mean ages 67 and 55 years, respectively) (p < 0.001), and intramural hemorrhage showed a lower proportion of type A than did aortic dissection (32% and 58%, respectively) (p = 0.018). The incidence of severe complications was significantly lower in patients with intramural hemorrhage than in those with aortic dissection (19% and 27%, respectively) (p < 0.001). Mean follow-up duration was 23.1+/-16.0 months. The overall death rate for patients with intramural hemorrhage (2 / 31; 6%) tended to be lower than those with aortic dissection (14 / 71; 20%) (p = 0.104). The Stanford classification and treatment modalities were not correlated with death. Late follow-up imaging studies in intramural hemorrhage showed partial to complete resolution of intramural hematoma (9 / 15; 60%). In this study, intramural hemorrhage was fairly common, more frequent among older patients, had a lower proportion of type A, and showed a lower incidence of severe complications and a more favorable prognosis in terms of mortality, than aortic dissection.

Effect of repeated seizure experiences on tyrosine hydroxylase immunoreactivities in the brain of genetically epilepsy-prone rats

The genetically epilepsy-prone rat (GEPR) is a model of generalized tonic/clonic epilepsy, and has functional noradrenergic deficiencies that act as partial determinants for the seizure predisposition and expression. The present study investigated the effect of repeated seizure experiences by acoustic stimulation (110 dB, 10 times) on the immunoreactivities of tyrosine hydroxylase (TH), a rate-determining enzyme in the synthesis of norepinephrine, in brain regions of GEPRs. TH immunoreactivity in locus coeruleus, the major noradrenergic nucleus in brain, was lower in GEPRs than control Sprague-Dawley rats. It was also decreased in several regions including inferior colliculus of GEPRs. Repeated experiences of audiogenic seizures further decreased TH immunoreactivities in locus coeruleus and inferior colliculus of GEPRs. The results from the present study suggest that the lower immunoreactivities of TH in locus coeruleus and inferior colliculus contribute, at least in part, to the noradrenergic deficits in GEPRs, and repeated seizure experiences further intensified these noradrenergic deficits, which may be related to the altered seizure expression by repetitive audiogenic seizure in GEPRs.

Immunocytochemical study on the distribution of p53 in the hippocampus and cerebellum of the aged rat

A role for p53-mediated modulation of neuronal viability has been suggested by the finding that p53 expression is increased in damaged neurons in models of ischemia and epilepsy. P53 gene upregulation precedes apoptosis in many cell types, and a potential role for this molecule in apoptosis of neurons has already been demonstrated in Alzheimer's disease. Recent studies suggest that p53-associated apoptosis may be a common mechanism of cell loss in several important neurodegenerative diseases. In the present study, we examined changes in p53-immunoreactive (IR) neurons in the brains of aged rats for the first time employing immunocytochemical and in situ hybridization methods. P53-IR neurons were found in the CA1 region of hippocampus, septal region and cerebellum in the aged rats, but there was no p53-IR cell in the brains of adult rats. In the hippocampus of the aged rat, p53-IR cells predominated in the stratum oriens and pyramidal layers, while the molecular layer contained relatively few p53-IR cells. The most prominent population of immunoreactive labeling in cerebellar cortex was localised within the cell bodies of Purkinje cells and dendrites in molecular layers. Upregulation of p53 in the Purkinje cells observed in this study suggests that significant loss of Purkinje cells with aging may be regulated with several apoptosis-controlling factors including p53 and oxidative stress mechanism. Further investigations are required to establish whether direct functional relations exist between p53 and the apoptotic neuronal death in normal aging or Alzheimer brains.

Self-assembled hydrogel nanoparticles from curdlan derivatives: characterization, anti-cancer drug release and interaction with a hepatoma cell line (HepG2)

Self-assembled hydrogel nanoparticles were synthesized from carboxymethylated (CM)-curdlan, substituted with a sulfonylurea (SU) as a hydrophobic moiety for self-assembly. The degree of SU substitution was 2.4, 5.6, or 7.2 SU groups per hundred anhydroglucose units of curdlan. The physicochemical properties of the self-assembled hydrogel nanoparticles (DS 2.4, DS 5.6, and DS 7.2) in aqueous media were characterized by dynamic light scattering, transmission electron microscopy, and fluorescence spectroscopy. The mean diameter of all samples was less than 300 nm with a unimodal size distribution. The critical aggregation concentrations (CAC) of self-assembled hydrogel nanoparticles in distilled water were 4.2 x 10(-2), 3.1 x 10(-2) and 1.9 x 10(-2) mg/ml for DS 2.4, 5.6 and 7.2, respectively. The loading and release of all-trans retinoic acid (ATRA) was studied. The ATRA loading efficiencies and loading contents of CM-curdlan/SU nanoparticles increased as the degree of SU substitution increased. The ATRA release rate was controlled by the degree of substitution and drug-loading. For specific interaction with a hepatic carcinoma cell line (HepG2), CM-curdlan was additionally conjugated with lactobionic acid (LBA; galactose moiety) (5.5 LBA molecules per hundred glucose units). HepG2 was strongly luminated by ligand-receptor interactions with fluorescence-labeled LBA/CM-curdlan/SU hydrogel nanoparticles. The luminescence was not observed for other control cases. It is concluded that LBA/CM-curdlan/SU hydrogel nanoparticles are a useful drug carrier for the treatment of liver cancer, because of the potential immunological enhancement activities of CM-curdlan in the body, the ligand-receptor mediated specific interactions, and the controlled release of the anti-cancer drug.

Identification of two novel frame shift mutations of the NF1 gene in Korean patients with neurofibromatosis type 1

Neurofibromatos is type 1 (NF1) is one of the most common inherited disorders and is characterized by abnormalities in multiple tissues derived from the neural crest. The NF-1 gene has been cloned and mapped to human chromosome 17q11.2. The NF-1 gene has an open reading frame that predicts a protein consisting of 2,818 amino acids, known as neurofibromin. Here, we report two kinds of novel frame shift mutations of the NF1 gene from 2 out of 56 unrelated Korean NF1 patients. These mutations were detected using polymerase chain reaction and single strand conformational polymorphism analysis. Sequencing analysis revealed four base pair insertion at codon 1270 of exon 22, and a base pair deletion at codon 1398 of exon 24. These mutations resulted in premature termination of the mutant alleles and may encode truncated forms of neurofibromin.

Selective involvement of reactive oxygen intermediates in platelet-activating factor-mediated activation of NF-kappaB

Although it has been suggested that some biological activities of platelet-activating factor (PAF) are mediated by, at least in part, reactive oxygen intermediates (ROI), the precise mechanisms underlying the interaction between the two remains to be elucidated. Antioxidants, such as alpha-tocopherol acid succinate, N-acetyl-L-Cysteine, pyrrolidinedithiocarbamate failed to inhibit PAF-induced immediate systemic reactions such as lethality, symptoms of disseminated intravascular coagulation, and histological changes such as pulmonary edema and hemorrhage in renal medullae 10 min following PAF injection. In contrast. antioxidants significantly inhibited both the in vivo and in vitro PAF-induced NF-kappaB activation and NF-kappaB-dependent TNF-alpha expression. The effects of the antioxidants were due to their inhibition of PAF-induced degradation of IkappaBalpha, a protein responsible for keeping NF-kappaB in an inactive form. A protein tyrosine kinase and N-tosyl-L-phenylalanine chloromethyl ketone sensitive serine protease were involved in both PAF- and H2O2-induced NF-kappaB activation. Collectively, these data indicate that the PAF-induced NF-kappaB activation is selectively mediated through the generation of ROI.

Local structural elements in the mostly unstructured transcriptional activation domain of human p53

DNA transcription is initiated by a small regulatory region of transactivators known as the transactivation domain. In contrast to the rapid progress made on the functional aspect of this promiscuous domain, its structural feature is still poorly characterized. Here, our multidimensional NMR study reveals that an unbound full-length p53 transactivation domain, although similar to the recently discovered group of loosely folded proteins in that it does not have tertiary structure, is nevertheless populated by an amphipathic helix and two nascent turns. The helix is formed by residues Thr(18)-Leu(26) (Thr-Phe-Ser-Asp-Leu-Trp-Lys-Leu-Leu), whereas the two turns are formed by residues Met(40)-Met(44) and Asp(48)-Trp(53), respectively. It is remarkable that these local secondary structures are selectively formed by functionally critical and positionally conserved hydrophobic residues present in several acidic transactivation domains. This observation suggests that such local structures are general features of acidic transactivation domains and may represent "specificity determinants" (Ptashne, M., and Gann, A. A. F. (1997), Nature 386, 569-577) that are important for transcriptional activity.

Management of Kikuchi's disease using glucocorticoid

Histiocytic necrotizing lymphadenitis, or Kikuchi's disease, is a self-limiting cervical lymphadenitis of unknown origin. Since no specific treatment has been reported for Kikuchi's disease to date, once a diagnosis of Kikuchi's disease has been established, the role of the physician has been limited only to treating the symptoms. Sometimes, however, the clinical manifestations of the disease can be very distressing for the patients. Thus, a more aggressive form of treatment may be required for the patients who suffer from severe and persisting symptoms and recurrence. We present three cases of Kikuchi's disease that benefited significantly from systemic administration of prednisone.

Cyclooxygenase-derived products, rather than nitric oxide, are endothelium-derived relaxing factor(s) in the ventral aorta of carp (Cyprinus carpio)

In some fish blood vessels, the existence of a NO (nitric oxide) system has been reported. We examined the possibility that this NO system acts as an endothelium-derived relaxing factor (EDRF) in carp aorta using the carp aorta alone and in a combined carp-rat aorta donor-detector system. Use of the typical NO stimulating agent in mammal acetylcholine (ACh) only induced constriction of the carp aorta. This response was not modified by denudation or by NO synthesis inhibition with N-nitro-L-arginine methyl ester. Neither the indirect NO stimulating agents bradykinin and histamine nor the direct NO releasers sodium nitroprusside (SNP) and SIN-1 induced vasorelaxation. Both SNP and ACh elevated the cGMP concentration in rat aorta, but not in carp aorta. In the aorta combination set-up, where carp served as a NO donor and rat aorta served as a NO detector, no relaxation of the rat aorta was observed. The calcium ionophore A23187, a known EDRF producer in mammals, induced relaxation of carp aorta through an endothelium- and cyclooxygenase-dependent mechanism. These results indicate that carp aorta does not produce NO as an EDRF nor does it respond to exogenously supplied NO. The major EDRF in carp is apparently a product(s) of cyclooxygenase metabolism.

Differentiation of Borrelia burgdorferi sensu lato on the basis of RNA polymerase gene (rpoB) sequences

We determined the nucleotide sequences (329 bp) of the rpoB DNAs from 22 reference strains of Borrelia. No insertions or deletions were observed. Deduced amino acid sequences of amplified rpoB DNA comprised 109 amino acid residues (N(450) to M(558) [Escherichia coli numbering]). All amino acid sequences were identical with the exception of those of Borrelia lusitaniae PotiB2 (T(461)-->A) and B. bissettii DN127 (I(498)-->V). Each species of B. burgdorferi sensu lato was differentiated as a distinct entity in the phylogenetic tree constructed by a neighbor-joining method. B. burgdorferi sensu lato could be distinguished from B. turicatae and B. hermsii, which are associated with relapsing fever. Seventeen Korean isolates could be identified by PCR-linked direct sequencing and restriction analysis of the rpoB DNA. These results suggest that rpoB DNA is useful for identification and characterization of Borrelia. In addition, we developed the rapid species identification method using the species-specific primer sets based on rpoB gene sequences.

Role of the glutamate 332 residue in the transglycosylation activity of ThermusMaltogenic amylase

A sequence alignment shows that residue 332 is conserved as glutamate in maltogenic amylases (MAases) and in other related enzymes such as cyclodextrinase and neopullulanase, while the corresponding position is conserved as histidine in alpha-amylases. We analyzed the role of Glu332 in the hydrolysis and the transglycosylation activity of Thermus MAase (ThMA) by site-directed mutagenesis. Replacing Glu332 with histidine reduced transglycosylation activity significantly, but enhanced hydrolysis activity on alpha-(1,3)-, alpha-(1,4)-, and alpha-(1,6)-glycosidic bonds relative to the wild-type (WT) enzyme. The mutant Glu332Asp had catalytic properties similar to those of the WT enzyme, but the mutant Glu332Gln resulted in significantly decreased transglycosylation activity. These results suggest that an acidic side chain at position 332 of MAase plays an important role in the formation and accumulation of transfer products by modulating the relative rates of hydrolysis and transglycosylation. From the structure, we propose that an acidic side chain at position 332, which is located in a pocket, is involved in aligning the acceptor molecule to compete with water molecules in the nucleophilic attack of the glycosyl-enzyme intermediate.

Immunohistochemical study on the distribution of the voltage-gated calcium channel alpha(1B) subunit in the mature rat brain

Many neuronal processes are regulated by calcium influx through voltage-gated calcium channels. Among these calcium channels, the N-type channel has been shown to play a significant role in the regulation of neurotransmitter release. This present report has demonstrated the distribution of the alpha(1B) subunit of the N-type calcium channel in the mature rat brain. The most striking findings were the highest immunoreactivity in the CA1 region of the hippocampus and the clear demarcation in the thalamus. Characteristic patterns of distribution were noted in the cerebral cortex, hippocampus, caudate-putamen, thalamus, and cerebellum. In the cerebral cortex, strong staining was seen in layers II-III and V. In the basal ganglia, the staining intensity was high in the caudate-putamen, whereas there was no immunoreactivity in the globus pallidus. Although the staining intensity was relatively low compared to that of the forebrain, moderate alpha(1B)-IR was found in the dorsal cochlear nucleus and mesencephalic trigeminal nucleus. The detailed features of this study will extend our current knowledge of alpha(1B) subunit distribution in terms of the number of neuroanatomical areas examined, by investigating alpha(1B) subunit protein expression, for the first time.

Diastereoselective synthesis of hydantoin- and isoxazoline-substituted dispirocyclobutanoids

Synthetic strategies for constructing novel achiral cyclobutanoid isoxazolidinoimidazolidinedione heterocycles, with a generalized structure of II, have been developed via 1,3-dipolar cycloaddition and carbanilide cyclization transformations from methylenecyclobutane 13. The exo methylene cyclobutane system has made the realization of some diasteroselectivity possible, such that the H-bond (Boc-NH) directed product (i.e., 14) was obtained with 3:1 selectivity relative to the non-H-bond directed product (i.e., 15).

Immunohistochemical study on the distribution of neuronal voltage-gated calcium channels in the rat cerebellum

Many neuronal processes are regulated by calcium influx through voltage-gated calcium channels (VGCCs), including protein phosphorylation, gene expression, neurotransmitter release, and firing patterns of action potential. In the present study, we have used anti-peptide antibodies directed against a unique sequence in rat alpha(1A), alpha(1B), alpha(1C) and alpha(1D) subunits of VGCCs to determine their cellular distribution in normal rat cerebellum. Throughout the molecular layer, immunoreactivity for alpha(1B) and alpha(1D) subunits were found in the cell bodies of basket and stellate cells as well as in the neuropil. In the Purkinje cells, only alpha(1C)-IR was observed in the dendritic branches of Purkinje cells, whereas immunoreactivity for alpha(1B) and alpha(1D) subunits were rarely found in the cell bodies of Purkinje cells. Immunoreactivity for the alpha(1A), alpha(1B,) and alpha(1D) subunits were strong in the granule cell bodies, whereas alpha(1C)-IR was not prominent in the cell bodies. In the cerebellar nuclei, a distinct band of punctate immunoreactivity for the alpha(1A), alpha(1B), alpha(1C), and alpha(1D) subunits were observed. The overall results of the above localization study showed clearly that the alpha(1A), alpha(1B,) alpha(1C) and alpha(1D) pore forming subunits of VGCCs have differential distribution in the rat cerebellum. The present studies may provide useful data for such future investigations to understand the role of calcium channels in neurological pathways.

Molecular characterization of a dimeric intracellular maltogenic amylase of Bacillus subtilis SUH4-2

An additional amylase besides the typical alpha-amylase was detected in the cytoplasm of Bacillus subtilis SUH4-2, an isolate from Korean soil. The corresponding gene encoded a maltogenic amylase, which hydrolyzed cyclodextrin or starch to maltose and glucose; pullulan to panose; acarbose to glucose and acarviosine-glucose. Maltogenic amylase of B. subtilis SUH4-2 transferred sugar molecules to form various branched oligosaccharides upon the hydrolysis of substrates. The enzyme existed in a monomer-dimer equilibrium with a molar ratio of 3:2 in 50 mM KH(2)PO(4)-NaOH buffer (pH 7.0). The maltogenic amylase is most likely to be associated with carbohydrate metabolism in the cytoplasm, since the nucleotide sequence of the gene was highly homologous to the yvdF gene of B. subtilis 168, which is located in a gene cluster involved in maltose/maltodextrin utilization.

Structure, specificity and function of cyclomaltodextrinase, a multispecific enzyme of the alpha-amylase family

Cyclomaltodextrinase (CDase, EC 3.2.1.54), maltogenic amylase (EC 3. 2.1.133), and neopullulanase (EC 3.2.1.135) are reported to be capable of hydrolyzing all or two of the following three types of substrates: cyclomaltodextrins (CDs); pullulan; and starch. These enzymes hydrolyze CDs and starch to maltose and pullulan to panose by cleavage of alpha-1,4 glycosidic bonds whereas alpha-amylases essentially lack activity on CDs and pullulan. They also catalyze transglycosylation of oligosaccharides to the C3-, C4- or C6-hydroxyl groups of various acceptor sugar molecules. The present review surveys the biochemical, enzymatic, and structural properties of three types of such enzymes as defined based on the substrate specificity toward the CDs: type I, cyclomaltodextrinase and maltogenic amylase that hydrolyze CDs much faster than pullulan and starch; type II, Thermoactinomyces vulgaris amylase II (TVA II) that hydrolyzes CDs much less efficiently than pullulan; and type III, neopullulanase that hydrolyzes pullulan efficiently, but remains to be reported to hydrolyze CDs. These three types of enzymes exhibit 40-60% amino acid sequence identity. They occur in the cytoplasm of bacteria and have molecular masses from 62 to 90 kDa which are slightly larger than those of most alpha-amylases. Multiple amino acid sequence alignment and crystal structures of maltogenic amylase and TVA II reveal the presence of an N-terminal extension of approximately 130 residues not found in alpha-amylases. This unique N-terminal domain as seen in the crystal structures apparently contributes to the active site structure leading to the distinct substrate specificity through a dimer formation. In aqueous solution, most of these enzymes show a monomer-dimer equilibrium. The present review discusses the multiple specificity in the light of the oligomerization and the molecular structures arriving at a clarified enzyme classification. Finally, a physiological role of the enzymes is proposed.

Squamous differentiation downregulates Muc1 mucin in hamster tracheal surface epithelial cell

To investigate whether the squamous differentiation of primary hamster tracheal epithelial cell, which is induced by retinoic acid deficiency or chronic PMA treatment, regulates Muc1 expression, we first produced and characterized a monoclonal antibody against hamster tracheal Muc1 mucin using pGEX-Muc1 fusion protein as an antigen and the changes of Muc1 mucin expression was determined by Western blot. Squamous differentiation downregulated the expression of Muc1 mucin from HTSE cells. The decrease in the immunoreactivity of Muc1 mucin was parallel to the decrease in the immunoreactivity of high molecular weight mucin, which is secreted from HTSE cells. The data from the present study implicate a possible role of Muc1 mucin in squamous differentiation of HTSE cells.

A nonsense mutation at Arg-1947 in the NF1 gene in a case of neurofibromatosis type 1 in a Korean patient

We report a case of neurofibromatosis (NF) 1 presenting as a C-to-T transition changing an Arg-1947 codon to a stop codon. Because this mutation has been described in multiple Caucasian and Japanese families, the codon CGA for Arg-1947 in the NF1 gene is considered to be a hotspot for mutation in neurofibromatosis type 1 in all ethnic groups.

Role of metabolic activation by cytochrome P450 in thioacetamide-induced suppression of antibody response in male BALB/c mice

Effects of thioacetamide on antibody response to sheep red blood cells were investigated in male BALB/c mice. When mice were treated intraperitoneally with thioacetamide once, the antibody response was significantly suppressed at 200 mg/kg with hepatotoxicity. When mice were treated intraperitoneally with thioacetamide for 7 consecutive days, the antibody response was suppressed at 50 mg/kg without hepatotoxicity. To determine the possible role of metabolic activation by cytochrome P450 in thioacetamide-induced suppression of antibody response, mice were pretreated with phenobarbital intraperitoneally for 3 days, followed by intraperitoneal administration of 100 mg/kg of thioacetamide for 3 days. The elevated activities of serum aspartate aminotransferase and alanine aminotransferase by thioacetamide were potentiated by phenobarbital pretreatment. The suppression of antibody response by thioacetamide was potentiated by phenobarbital. In liver microsomes, the activities of P450 2B-specific enzymes were induced by phenobarbital. Our present results suggest that thioacetamide may require metabolic activation by P450 to its immunosuppressive form(s).

Effects on Rb(+)(K+) uptake of HeLa cells in a high K(+) medium of exposure to a switched 1.7 Tesla magnetic field

Effects of a switched, time-varying 1.7 T magnetic field on Rb(+)(K+) uptake by HeLa S3 cells incubated in an isosmotic high K(+) medium were examined. The magnetic flux density was varied intermittently from 0.07-1.7 T at an interval of 3 s. K(+) uptake was activated by replacement of normal medium by high K(+) medium. A membrane-permeable Ca(2+) chelating agent (BAPTA-AM) and Ca(2+)-dependent K(+) channel inhibitors (quinine, charibdotoxin, and iberiotoxin) were found to reduce the Rb(+)(K+) uptake by about 30-40%. Uptake of K(+) that is sensitive to these drugs is possibly mediated by Ca(2+)-dependent K(+) channels. The intermittent magnetic field partly suppress ed the drug-sensitive K(+) uptake by about 30-40% (P < 0.05). To test the mechanism of inhibition by the magnetic fields, intracellular Ca(2+) concentration ([Ca(2+)]c) was measured using Fura 2-AM. When cells were placed in the high K(&plus;) medium, [Ca(2+)]c increased to about 1.4 times the original level, but exposure to the magnetic fields completely suppressed the increase (P < 0.01). Addition of a Ca(2+) ionophore (ionomycin) to the high K(+) medium increased [Ca(2+)]c to the level of control cells, regardless of exposure to the magnetic field. But the inhibition of K(+) uptake by the magnetic fields was not restored by addition of ionomycin. Based on our previous results on magnetic field-induced changes in properties of the cell membrane, these results indicate that exposure to the magnetic fields partly suppresses K(+) influx, which may be mediated by Ca(2+)-dependent K(+) channels. The suppress ion of K(+) fluxes could relate to a change in electric properties of cell surface and an inhibition of Ca(2+) influx mediated by Ca(2+) channels of either the cell plasma membrane or the inner vesicular membrane of intracellular Ca(2+) stores.

Elevated glutamate levels in the vitreous body of an in vivo model of optic nerve ischemia

OBJECTIVE

To explore the possibility that an elevation of glutamate levels in the vitreous might be associated with the microvascular compromise of the optic nerve.

MATERIALS AND METHODS

Endothelin-1, 0.1 microg/d (5 rabbits), or balanced salt solution (4 rabbits) was delivered to the perineural region of the anterior optic nerve by osmotically driven minipumps for 2 weeks. Vitreous specimens were obtained, and their amino acid contents were determined by high-performance liquid chromatography.

RESULTS

There was a statistically significant elevation in the mean +/- SEM vitreous concentrations of glutamate (264% +/-41%; P = .04), aspartate (269% +/-31%; P = .04), and glycine (232% +/-26%; P = .04) in the eyes subjected to endothelin-1 when compared with the fellow control eyes.

CONCLUSION

Administration of endothelin-1 to the microvasculature of the optic nerve leads to elevation of glutamate, aspartate, and glycine concentrations in the vitreous.

CLINICAL RELEVANCE

The increase of excitatory amino acids in the vitreous might be associated with various ischemic processes of the optic nerve, including glaucomatous optic neuropathy, and may play a role in the neuronal damage that is seen in these diseases.

Nuclear magnetic resonance solution conformation of alpha-conotoxin AuIB, an alpha(3)beta(4) subtype-selective neuronal nicotinic acetylcholine receptor antagonist

The neuronal nicotinic acetylcholine receptors constitute a highly diverse group, with subtypes consisting of pentameric combinations of alpha and beta subunits. alpha-Conotoxins are a homologous series of small peptides that antagonize these receptors. We present the three-dimensional solution structure of alpha-conotoxin AuIB, the first 15-residue alpha-conotoxin known to selectively block the alpha(3)beta(4) nicotinic acetylcholine receptor subtype. The pairwise backbone and heavy-atom root mean square deviation for an ensemble of 20 structures are 0.269 and 0.720 A, respectively. The overall fold of alpha-conotoxin AuIB closely resembles that of the alpha4/7 subfamily alpha-conotoxins. However, the absence of Tyr(15), normally present in other alpha4/7 members, results in tight bending of the backbone at the C terminus and effectively renders Asp(14) to assume the spatial location of Tyr(15) present in other neuronal alpha4/7 alpha-conotoxins. Structural comparison of alpha-conotoxin AuIB with the alpha(3)beta(2) subtype-specific alpha-conotoxin MII shows different electrostatic surface charge distributions, which may be important in differential receptor subtype recognition.

Characterization of Borrelia burgdorferi strains isolated from Korea by 16S rDNA sequence analysis and PCR-RFLP analysis of rrf (5S)-rrl (23S) intergenic spacer amplicons

Haenam strains of Borrelia burgdorferi, which had been isolated from Ixodes granulatus and Apodemus agrarius in Haenam, Korea, were characterized by PCR-RFLP analysis of rrf (5S)-rrl (23S) intergenic spacer amplicons and by sequence analysis of the 16S rRNA gene (rDNA). The Msel and Dral restriction patterns of the 5S-23S intergenic spacer amplicons of Haenam strains differed from those of other B. burgdorferi sensu lato strains. Furthermore, in the phylogenetic tree based on the 16S rDNA sequences, Haenam strains formed a distinctive cluster, clearly separated from the other members of B. burgdorferi sensu lato. These results suggest that, apart from Borrelia garinii and Borrelia afzelii, other genotypes of B. burgdorferi sensu lato exist in Korea and the Haenam strain is a newly identified one.

Transglycosylation of neohesperidin dihydrochalcone by Bacillus stearothermophilus maltogenic amylase

Neohesperidin dihydrochalcone (NHDC), a sweet compound derived from citrus fruits, was modified to a series of its oligosaccharides by transglycosylation activity of Bacillus stearothermophilus maltogenic amylase (BSMA). Maltotriose as a donor was reacted with NHDC as an acceptor to glycosylate for the purpose of increasing the solubility of NHDC. Maltosyl-NHDC was a major transglycosylation product among the several transfer products by TLC analysis. The structure of the major transglycosylation product was determined to be maltosyl-alpha-(1,6)-neohesperidin dihydrochalcone by MALDI-TOF/MS and (1)H and (13)C NMR. Maltosyl-NHDC was 700 times more soluble in water and 7 times less sweet than NHDC.