Biomedical subjects

B Yang

Publications and source records attributed to B Yang.

At least 91 records · Page 5Linked to original sources

PubMed2001

[The clinical characteristics of adhesive type cholesteatoma].

OBJECTIVE: To study the clinical characteristics of adhesive type cholesteatoma. METHODS: Fifty-two cases (52 ears) of adhesive type cholesteatomas were reviewed. Of the 52 cases there were 30 males and 22 females; 24 left ears and 28 right ears. The age of the patients ranged from 8 to 70 years. All of the patients were treated by tympanoplasty, and the open and close methods were performed in 37 ears and 10 ears, respectively. Other methods were employed in the remaining 5 cases. Nine ears underwent tympanoplasty type "O" without ossicular re-construction for an increase in the threshold of the bone conduction. Types I, III and IV tympanoplasties were performed in 1, 16 and 26 ears, respectively. RESULTS: The structures of the upper parts of the stapes had disappeared in 25 ears, which was significantly higher in this series than that in the attic type cholesteatoma. The over-all recovery rate of hearing was 69.8%, while 75.9% and 55.6% in the open and closed tympanoplasties, respectively. Postoperative complications of perforations and re-adhesions of the tense part of the tympanic membrane were observed in 3 and 4 ears, respectively. CONCLUSIONS: Adhesive type cholesteatoma is not uncommon. The cause of this disease may be the functional defects in the pharynotympanic tube. A thorough and effective treatment for the secretory otitis media is crucial for the prevention of adhesive type cholesteatomas. The open method tympanoplasty was considered as the first choice for adhesive type cholesteatoma while the closed method must be great careful.

Adolescent↗

PubMed2001

[Studies on original plant of traditional Chinese drug "bai zhi" (radix Angelicae Dahuricae) and its closely related wild plants. III. Comparison of coumarins of "bai zhi" with those of closely related wild plants].

OBJECTIVE: To provide chemical data for confirming the original plant of traditional Chinese drug "Bai Zhi". METHOD: Coumarins of 4 cultivated breeds of "Bai Zhi" and 3 closely related wild plants, together with other 2 Angelica plants were compared by HPLC. RESULT: According to coumarin patterns, 4 cultivated breeds of "Bai Zhi" and 3 closely related wild plants could be divided into 3 groups: 1. 4 cultivated breeds of "Bai Zhi" ("Chuan Bai Zhi", "Hang Bai Zhi", "Qi Bai Zhi" and "Yu Bai Zhi") and Angelica dahurica var. formosana; 2. A. dahurica; 3. A. porphyrocaulis. CONCLUSION: In point of the coumarin components, A. dahurica var. formosana is closer to traditional Chinese drug "Bai Zhi" than the others.

Angelica↗

PubMed2001

[Studies on original plant of traditional Chinese drug "bai zhi" (radix Angelicae Dahuricae) and its closely related wild plants. IV. Discussion on original plant and cultivation history of traditional Chinese drug "bai zhi" and evolution of its closely related wild plants].

OBJECTIVE: To confirm the original plant of traditional Chinese drug "Bai Zhi" and to inquire into the cultivation history of "Bai Zhi" and evolution of closely related wild plants of "Bai Zhi". METHOD: Various research results obtained were synthesized and discussed according to historical and current data. RESULT: Obtained research results, historical and current data showed almost no difference. CONCLUSION: 1. Angelica dahurica var. formosana must be the original plant of traditional Chinese drug "Bai Zhi". 2. A. porphyrocaulis should be treated as a variety of A. dahurica, named as A. dahurica var. porphyrocaulis. 3. 4 sorts of Chinese traditional drug "Bai Zhi" (Chuang Bai Zhi, Hang Bai Zhi, Qi Bai Zhi and Yu Bai Zhi) should not be taxonomically distinguished. The history of utilization and cultivation of "Bai Zhi", and the evolutional relation of the closely related wild plants of "Bai Zhi" (A. dahurica, A. dahurica var. formosana, and A. dahurica var. porphyrocaulis) were also discussed.

Angelica↗

PubMed2001

The management of epithelial ingrowth after laser in situ keratomileusis.

OBJECTIVE: . To investigate the treatment of corneal epithelial ingrowth with flap melt after LASIK. PATIENTS AND METHOD: Thirteen eyes of 13 patients with corneal epithelial ingrowth and flap melt after LASIK were treated based on the thickness and the extent of melting of the flap. Nine eyes were treated by lifting the flap and scraping the epithelium in the interface. Three eyes underwent allogenic keratomileusis. The flap was removed in one eye. RESULTS: Recurrence occurred in 2 eyes treated by lifting the flap. The flaps, however, healed normally after retreatment. The grafts healed normally in the allogenic keratomileusis group, except for one eye in which the flap was lost. The corneal epithelium healed over the stromal bed after the flap was removed. Corneal haze of grade 2 was present at 6 months. The uncorrected visual acuity was between 0.3 and 1.0, and the best-corrected visual acuity lost 1 to 3 lines. CONCLUSIONS: Corneal epithelial ingrowth with flap melt is a severe complication after LASIK. However, with proper treatment, vision can be salvaged in most cases.

Corneal Diseases↗

PubMed2000

Quantitation of basic fibroblast growth factor by immunoassay using BIAcore 2000.

A sensitive, accurate, and efficient immunoassay using a BIAcore 2000 biosensor instrument for the quantitation of basic fibroblast growth factor (bFGF) in HEPES-buffered saline containing 100 microg/ml heparin (HHBS) has been developed and validated. In this method, anti-bFGF monoclonal antibody 48.1 (MAb 48.1) was selected as a binding ligand and immobilized to the matrix surface of Sensor Chip CM5 by amine coupling. A high immobilization level of MAb 48.1 (12643+/-816 RU, mean +/- S.D., n = 5) was achieved with high reproducibility (i.e. coefficient of variation (CV) was 6.5%). This immobilized MAb 48.1 sensor surface was used to detect and quantity bFGF. This assay has a range of reliable BIAcore response from 5.65 to 1440 ng/ml bFGF in HHBS. which was well fitted with a sigmoidal model. The immobilized MAb 48.1 was found to be stable for at least 150 regeneration cycles and for at least 9 days at room temperature. Intra- and interassay CVs ranged from 0.9 to 5.9%, and from 2.7 to 8.5%, respectively. Matrices such as serum, bovine serum albumin (BSA), and two pharmaceutical excipients (Pluronic F127 surfactant and sodium carboxymethylcellulose) did not interfere with bFGF analysis over the sensor surface. Therefore, this validated assay has good precision, accuracy and specificity, and has been found useful in quantifying bFGF in several research and development studies.

Antibodies, Monoclonal↗

PubMed2000

Identification of sequence determinants that direct different intracellular folding pathways for aquaporin-1 and aquaporin-4.

Homologous aquaporin water channels utilize different folding pathways to acquire their transmembrane (TM) topology in the endoplasmic reticulum (ER). AQP4 acquires each of its six TM segments via cotranslational translocation events, whereas AQP1 is initially synthesized with four TM segments and subsequently converted into a six membrane-spanning topology. To identify sequence determinants responsible for these pathways, peptide segments from AQP1 and AQP4 were systematically exchanged. Chimeric proteins were then truncated, fused to a C-terminal translocation reporter, and topology was analyzed by protease accessibility. In each chimeric context, TM1 initiated ER targeting and translocation. However, AQP4-TM2 cotranslationally terminated translocation, while AQP1-TM2 failed to terminate translocation and passed into the ER lumen. This difference in stop transfer activity was due to two residues that altered both the length and hydrophobicity of TM2 (Asn(49) and Lys(51) in AQP1 versus Met(48) and Leu(50) in AQP4). A second peptide region was identified within the TM3-4 peptide loop that enabled AQP4-TM3 but not AQP1-TM3 to reinitiate translocation and cotranslationally span the membrane. Based on these findings, it was possible to convert AQP1 into a cotranslational biogenesis mode similar to that of AQP4 by substituting just two peptide regions at the N terminus of TM2 and the C terminus of TM3. Interestingly, each of these substitutions disrupted water channel activity. These data thus establish the structural basis for different AQP folding pathways and provide evidence that variations in cotranslational folding enable polytopic proteins to acquire and/or maintain primary sequence determinants necessary for function.

Amino Acid Sequence↗

PubMed2000

The mammalian sodium channel BNC1 is required for normal touch sensation.

Of the vertebrate senses, touch is the least understood at the molecular level The ion channels that form the core of the mechanosensory complex and confer touch sensitivity remain unknown. However, the similarity of the brain sodium channel 1 (BNC1) to nematode proteins involved in mechanotransduction indicated that it might be a part of such a mechanosensor. Here we show that disrupting the mouse BNC1 gene markedly reduces the sensitivity of a specific component of mechanosensation: low-threshold rapidly adapting mechanoreceptors. In rodent hairy skin these mechanoreceptors are excited by hair movement. Consistent with this function, we found BNC1 in the lanceolate nerve endings that lie adjacent to and surround the hair follicle. Although BNC1 has been proposed to have a role in pH sensing, the acid-evoked current in cultured sensory neurons and the response of acid-stimulated nociceptors were normal in BNC1 null mice. These data identify the BNC1 channel as essential for the normal detection of light touch and indicate that BNC1 may be a central component of a mechanosensory complex.

Animals↗

PubMed2000

Neonatal mortality in an aquaporin-2 knock-in mouse model of recessive nephrogenic diabetes insipidus.

Hereditary non-X-linked nephrogenic diabetes insipidus (NDI) is caused by mutations in the aquaporin-2 (AQP2) water channel. In transfected cells, the human disease-causing mutant AQP2-T126M is retained at the endoplasmic reticulum (ER) where it is functional and targetable to the plasma membrane with chemical chaperones. A mouse knock-in model of NDI was generated by targeted gene replacement using a Cre-loxP strategy. Along with T126M, mutations H122S, N124S, and A125T were introduced to preserve the consensus sequence for N-linked glycosylation found in human AQP2. Breeding of heterozygous mice yielded the expected Mendelian distribution with 26 homozygous mutant offspring of 99 live births. The mutant mice appeared normal at 2-3 days after birth but failed to thrive and generally died by day 6 if not given supplemental fluid. Urine/serum analysis showed a urinary concentrating defect with serum hyperosmolality and low urine osmolality that was not increased by a V2 vasopressin agonist. Northern blot analysis showed up-regulated AQP2-T126M transcripts of identical size to wild-type AQP2. Immunoblots showed complex glycosylation of wild-type AQP2 but mainly endoglycosidase H-sensitive core glycosylation of AQP2-T126M indicating ER-retention. Biochemical analysis revealed that the AQP2-T126M protein was resistant to detergent solubilization. Kidneys from mutant mice showed collecting duct dilatation, papillary atrophy, and unexpectedly, some plasma membrane AQP2 staining. The severe phenotype of the AQP2 mutant mice compared with that of mice lacking kidney water channels AQP1, AQP3, and AQP4 indicates a critical role for AQP2 in neonatal renal function in mice. Our results establish a mouse model of human autosomal NDI and provide the first in vivo biochemical data on a disease-causing AQP2 mutant.

Animals↗

PubMed2000

Nicotine is a potent blocker of the cardiac A-type K(+) channels. Effects on cloned Kv4.3 channels and native transient outward current.

BACKGROUND: Nicotine is a main constituent of cigarette smoke and smokeless tobacco, known to increase the risk of sudden cardiac death. This study aimed at establishing ionic mechanisms underlying potential electrophysiological effects of nicotine. METHODS AND RESULTS: Effects of nicotine on Kv4.3 and Kv4.2 channels expressed in Xenopus oocytes were studied at the whole-cell and single-channel levels. The effects of nicotine on the transient outward K(+) current (I:(to)) were studied by use of whole-cell patch-clamp techniques in canine ventricular myocytes. Nicotine potently inhibited Kv4 current. The concentration for half-maximal inhibition (IC(50)) was 40+/-4 nmol/L, and the current was abolished by 100 micromol/L nicotine. The IC(50) for block of native I:(to) was 270+/-43 nmol/L. The steady-state activation properties of Kv4.3 and I:(to) were unaltered by nicotine, whereas positive shifts of the inactivation curves were observed. Of the total inhibition of Kv4.3 and I:(to) by nicotine, 40% was due to tonic block and 60% was attributable to use-dependent block. Activation, inactivation, and reactivation kinetics were not significantly changed by nicotine. Nicotine reduced single-channel conductance, open probability, and open time but increased the closed time of Kv4.3. The effects of nicotine were not altered by antagonists to various neurotransmitter receptors, indicating direct effects on I:(to) channels. CONCLUSIONS: Nicotine is a potent inhibitor of cardiac A-type K(+) channels, with blockade probably due to block of closed and open channels. This action may contribute to the ability of nicotine to affect cardiac electrophysiology and induce arrhythmias.

Animals↗

PubMed2000

The virulence factor AvrXa7 of Xanthomonas oryzae pv. oryzae is a type III secretion pathway-dependent nuclear-localized double-stranded DNA-binding protein.

AvrXa7 is a member of the avrBs3 avirulence gene family, which encodes proteins targeted to plant cells by a type III secretion apparatus. AvrXa7, the product of avrXa7, is also a virulence factor in strain PXO86 of Xanthomonas oryzae pv. oryzae. Avirulence and virulence specificities are associated with the central repeat domain, which, in avrXa7, consists of 25.5 direct repeat units. Mutations in three C-terminal nuclear localization signal motifs eliminated avirulence and virulence activities in rice and severely reduced nuclear localization in a yeast assay system. Both pathogenicity functions and nuclear localization were restored on the addition of the sequence for the nuclear localization signal motif from SV40 T-antigen. The loss of avirulence activity because of mutations in the acidic transcriptional activation domain was restored by addition of the activation domain from the herpes simplex viral protein VP16. The activation domain was also required for virulence activity. However, the VP16 domain could not substitute for the endogenous domain in virulence assays. In gel shift assays, AvrXa7 bound double-stranded DNA with a preference for dA/dT rich sequences. The results indicate that products of the avrBs3-related genes are virulence factors targeted to host cell nuclei and have the potential to interact with the host DNA and transcriptional machinery as part of their mode of action. The results also suggest that the host defensive recognition mechanisms are targeted to the virulence factor site of action.

Amino Acid Motifs↗

PubMed2000

Influence of the N-1 alkyl chain length of cannabimimetic indoles upon CB(1) and CB(2) receptor binding.

The N-1 alkyl side chain of the aminoalkylindole analogues (AAI) has been implicated as one of a three-point interaction with the cannabinoid CB(1) receptor. In this study, the morpholinoethyl of WIN 55,212-2 was replaced with carbon chains of varying lengths ranging from a methyl to heptyl group. Additional groups were added to the naphthoyl and the C2 positions of the molecule. These structural changes revealed that high affinity binding to the CB(1) and CB(2) receptors requires an alkyl chain length of at least three carbons with optimum binding to both receptors occurring with a five carbon side chain. An alkyl chain of 3-6 carbons is sufficient for high affinity binding; however, extension of the chain to a heptyl group results in a dramatic decrease in binding at both receptors. The unique structure of the cannabimimetic indoles provides a useful tool to define the ligand-receptor interaction at both cannabinoid receptors and to refine proposed pharmacophore models.

Animals↗

PubMed2000

Determination of catechins in human urine subsequent to tea ingestion by high-performance liquid chromatography with electrochemical detection.

The title determination was conducted by HPLC with electrochemical detection using an ODS column and a mobile phase of acetonitrile: 0.1 M phosphate buffer (pH 2.5) (15:85, v/v). The eight catechins, gallocatechin (GC), epigallocatechin (EGC), catechin (C), epicatechin (EC), epigallocatechin gallate (EGCg), gallocatechin gallate (GCg), epicatechin gallate (ECg), and catechin gallate (Cg), were detected at 0.6 V vs Ag/AgCl. Good linear relationships between current and amount were noted for 0.5-250 pmol of each catechin, with a correlation coefficient of 0.999 in each case. The detection limit for any one was 0.5 pmol (signal to noise ratio, S/N = 3). After the ingestion of 340 ml canned green tea, GC, EGC, C, and EC, mostly in conjugated form, were determined in urine samples. Conjugated catechins were hydrolyzed by enzymes using sulfatase and beta-glucuronidase. The time courses of the above four catechins showed a maxima at 1-3 h after tea ingestion. (+), (-)-EC and (+), (-)-C were present in canned tea.

Acetonitriles↗

PubMed2000

Novel syntheses of hexahydro-1H-pyrrolo[1,2-a]ĭmidazoles and Octahydroimidazo[1,2-a]pyridines.

1-Phenyl-5-(benzotriazol-1-yl)hexahydro-1H-pyrrolo[1,2-a]ĭmidazole (18) and 1-phenyl-5-benzotriazolyloctahydroimidazo[1,2-a]pyridine (27) were readily prepared from succindialdehyde or glutaraldehyde, benzotriazole, and N-phenylethylenediamine. Synthons 18 and 27 reacted with Grignard reagents, allylsilanes, silyl ethers, and triethyl phosphite to produce 1-phenyl-5-substituted-hexahydro-1H-pyrrolo[1,2-a]ĭmidazoles 20a-f, 22, 24a,b, and 25 and 1-phenyl-5-substituted-octahydroimidazo[1, 2-a]pyridines 28a-e, 32, 33a,b, and 34 in good to excellent yields. The configurations of 20, 22, 24, and 25 were determined to be cis isomers by NOE experiment, while the configurations and conformations of 28a-e, 32, 33a,b, and 34 were elucidated by (1)H-(1)H COSY and (1)H-(13)C COSY.

Imidazoles↗

PubMed2000

[Clinical analysis of 29 cases of hounglass spinal tumor].

We analysed retrospectively 29 cases with hounglass tumor in spinal canal from March 1990 to November 1998 in our hospital. Hounglass tumors in all patients were successfully diagnosed by CT scanning and magnetic resonance imaging(MRI). Microsurgery was carried out in 27 cases(27/29). Sixteen out of 27 cases were followed up from 8 months to 7 years. The result showed that 12 cases got complete healing, and 3 cases incomplete healing. The paper has stress discussion on the clinical features, CT, MRI examination and operation of the disease.

Adolescent↗

PubMed2000

Nephrogenic diabetes insipidus in mice lacking aquaporin-3 water channels.

Aquaporin-3 (AQP3) is a water channel expressed at the basolateral plasma membrane of kidney collecting-duct epithelial cells. The mouse AQP3 cDNA was isolated and encodes a 292-amino acid water/glycerol-transporting glycoprotein expressed in kidney, large airways, eye, urinary bladder, skin, and gastrointestinal tract. The mouse AQP3 gene was analyzed, and AQP3 null mice were generated by targeted gene disruption. The growth and phenotype of AQP3 null mice were grossly normal except for polyuria. AQP3 deletion had little effect on AQP1 or AQP4 protein expression but decreased AQP2 protein expression particularly in renal cortex. Fluid consumption in AQP3 null mice was more than 10-fold greater than that in wild-type litter mates, and urine osmolality (<275 milliosmol) was much lower than in wild-type mice (>1,200 milliosmol). After 1-desamino-8-d-arginine-vasopressin administration or water deprivation, the AQP3 null mice were able to concentrate their urine partially to approximately 30% of that in wild-type mice. Osmotic water permeability of cortical collecting-duct basolateral membrane, measured by a spatial filtering optics method, was >3-fold reduced by AQP3 deletion. To test the hypothesis that the residual concentrating ability of AQP3 null mice was due to the inner medullary collecting-duct water channel AQP4, AQP3/AQP4 double-knockout mice were generated. The double-knockout mice had greater impairment of urinary-concentrating ability than did the AQP3 single-knockout mice. Our findings establish a form of nephrogenic diabetes insipidus produced by impaired water permeability in collecting-duct basolateral membrane. Basolateral membrane aquaporins may thus provide blood-accessible targets for drug discovery of aquaretic inhibitors.

Amino Acid Sequence↗

PubMed2000

Purification, cloning, and characterization of the CEL I nuclease.

CEL I, isolated from celery, is the first eukaryotic nuclease known that cleaves DNA with high specificity at sites of base-substitution mismatch and DNA distortion. The enzyme requires Mg(2+) and Zn(2+) for activity, with a pH optimum at neutral pH. We have purified CEL I 33 000-fold to apparent homogeneity. A key improvement is the use of alpha-methyl-mannoside in the purification buffers to overcome the aggregation of glycoproteins with endogenous lectins. The SDS gel electrophoresis band for the homogeneous CEL I, with and without the removal of its carbohydrate moieties, was extracted, renatured, and shown to have mismatch cutting specificity. After determination of the amino acid sequence of 28% of the CEL I polypeptide, we cloned the CEL I cDNA. Potential orthologs are nucleases putatively encoded by the genes BFN1 of Arabidopsis, ZEN1 of Zinnia, and DSA6 of daylily. Homologies of CEL I with S1 and P1 nucleases are much lower. We propose that CEL I exemplifies a new family of neutral pH optimum, magnesium-stimulated, mismatch duplex-recognizing nucleases, within the S1 superfamily.

Amino Acid Sequence↗

PubMed2000

Direct block of inward rectifier potassium channels by nicotine.

Nicotine has been shown to depolarize membrane potential and to lengthen action potential duration in isolated cardiac preparations. To investigate whether this is a consequence of direct interaction of nicotine with inward rectifier K(+) channels which are a key determinant of membrane potentials, we assessed the effects of nicotine on two cloned human inward rectifier K(+) channels, Kir2.1 and Kir2.2, expressed in Xenopus oocytes and the native inward rectifier K(+) current I(K1) in canine ventricular myocytes. Nicotine suppressed Kir2.1-expressed currents at varying potentials negative to -20 mV, with more pronounced effects on the outward current between -70 and -20 mV relative to the inward current at hyperpolarized potentials (below -70 mV). The inhibition was concentration dependent. For the outward currents recorded at -50 mV, the IC50 was 165 +/- 18 microM. Similar effects of nicotine were observed for Kir2.2. A more potent effect was seen with I(K1) in canine myocytes. Significant blockade ( approximately 60%) was found at a concentration as low as 0.5 microM and the IC50 was 4.0 +/- 0.4 microM. The effects in both oocytes and myocytes were partially reversible upon washout of nicotine. Antagonists of nicotinic receptors (mecamylamine, 100 microM), muscarinic receptors (atropine, 1 microM), and beta-adrenergic receptors (propranolol, 1 microM) all failed to restore the depressed currents, suggesting that nicotine acted directly on Kir channels, independent of catecholamine release. This property of nicotine may explain its membrane-depolarizing and action potential duration-prolonging effects in cardiac cells and may contribute in part to its ability to promote propensity for cardiac arrhythmias.

Animals↗

PubMed2000

Partial correction of the urinary concentrating defect in aquaporin-1 null mice by adenovirus-mediated gene delivery.

The feasibility of water channel gene delivery to kidney tubules and microvessels was evaluated by delivery of an adenovirus encoding aquaporin 1 (AQP1-Ad5) to transgenic AQP1 null mice. In wild-type mice, AQP1 is expressed in kidney proximal tubule, thin descending limb of Henle, and descending vasa recta, where urine osmolality (Uosm) increases from 1000-1500 mOsm (before) to 2500-3500 mOsm after 36 hr of water deprivation. Uosm in AQP1 null mice remains nearly fixed at 650-750 mOsm. AQP1-Ad5 (with a CMV promoter) was generated and purified. Infection of CHO cells gave strong uniform AQP1 expression with plasma membrane localization and eightfold increased water permeability over noninfected cells. AQP1-Ad5 was delivered to 20 to 25-g AQP1 null mice by tail vein infusion (0-10(10) PFU). At 3-7 days, AQP1 protein expression was strongest in liver (approximately 20 microg of AQP1 protein per liver) and next strongest in kidney, with expression in proximal tubule apical and basolateral membranes, and renal microvessels. Functional analysis showed increased water permeability in apical membrane vesicles from proximal tubule. AQP1 expression was not detected in glomerulus, limb of Henle, or collecting duct. In water-deprived null mice receiving 5 x 10(9) PFU of AQP1-Ad5, Uosm increased by up to 510 mOsm (mean increase, 225 +/- 24 mOsm; n = 33 mice). Whereas the control null mice became lethargic and lost 34.2 +/- 0.6% body weight, the virus-treated mice remained relatively active and lost 32.3 +/- 0.7% body weight. Viral DNA and AQP1 transcript were detected in kidney and liver of null mice up to 17 weeks after virus infusion; partial correction of the urinary concentrating defect persisted for 3-5 weeks. These results demonstrate partial functional correction of a urinary concentrating defect by adenoviral delivery of the AQP1 gene.

Adenoviridae↗