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Biomedical subjects

W Yang

Publications and source records attributed to W Yang.

At least 361 records · Page 20Linked to original sources
PubMed1997

Crystal structure of the complex of diphtheria toxin with an extracellular fragment of its receptor.

We describe the crystal structure at 2.65 A resolution of diphtheria toxin (DT) complexed 1:1 with a fragment of its cell-surface receptor, the precursor of heparin-binding epidermal-growth-factor-like growth factor (HBEGF). HBEGF in the complex has the typical EGF-like fold and packs its principal beta hairpin against the face of a beta sheet in the receptor-binding domain of DT. The interface has a predominantly hydrophobic core, and polar interactions are formed at the periphery. The structure of the complex suggests that part of the membrane anchor of the receptor can interact with a hinge region of DT. The toxin molecule is thereby induced to form an open conformation conducive to membrane insertion. The structure provides a basis for altering the binding specificity of the toxin, and may also serve as a model for other EGF-receptor interactions.

Binding Sites↗
PubMed1997

Enhanced survival of glioma bearing rats following boron neutron capture therapy with blood-brain barrier disruption and intracarotid injection of boronophenylalanine.

Boronophenylalanine (BPA) has been used for boron neutron capture therapy (BNCT) of brain tumors in both experimental animals and humans. The purpose of the present study was to determine if the efficacy of BNCT could be enhanced by means of intracarotid (i.c.) injection of BPA with or without blood-brain barrier disruption (BBB-D) and neutron irradiation using a rat brain tumor model. For biodistribution studies, F98 glioma cells were implanted stereotactically into the brains of Fischer rats, and 12 days later BBB-D was carried out by i.c. infusion of 25% mannitol (1.373 mOsmol/ml), followed immediately by i.c. administration of 300, 500 or 800 mg of BPA/kg body weight (b.w.). At the 500 mg dose a fourfold increase in tumor boron concentration (94.5 micrograms/g) was seen at 2.5 hours after BBB-D. compared to 20.8 micrograms/g in i.v. injected animals. The best composite tumor to normal tissue ratios were observed at 2.5 hours after BBB-D, at which time the tumor: blood (T: Bl) ratio was 10.9, and the tumor: brain (T:Br) ratio was 7.5, compared to 3.2 and 5.0 respectively for i.v. injected rats. In contrast, animals that had received i.c. BPA without BBB-D had T : Bl and T:Br ratios of 8.5 and 5.9, respectively, and the tumor boron concentration was 42.7 micrograms/g. For therapy experiments, initiated 14 days after intracerebral implantation of F98 glioma cells, 500 mg/kg b.w. of BPA were administered i.v. or i.c. with or without BBB-D, and the animals were irradiated 2.5 hours later at the Brook-haven Medical Research Reactor with a collimated beam of thermal neutrons delivered to the head. The mean survival time for untreated control rats was 24 +/- 3 days, 30 +/- 2 days for irradiate controls, 37 +/- 3 days for those receiving i.v. BPA, 52 +/- 15 days for rats receiving i.c. BPA without BBB-D, and 95 +/- 95 days for BBB-D followed by i.c. BPA and BNCT. The latter group had a 246% increase in life span (ILS) compared to untreated controls and a 124% ILS compared to that of i.v. injected animals. These survival data are the best ever obtained with the F98 glioma model and suggest that i.c. administration of BPA with or without BBB-D may be useful as a means to increase the efficacy of BNCT.

Animals↗
PubMed1997

Homologous segments in three subunits of the guanine nucleotide exchange factor eIF2B mediate translational regulation by phosphorylation of eIF2.

eIF2B is a five-subunit guanine nucleotide exchange factor that is negatively regulated by phosphorylation of the alpha subunit of its substrate, eIF2, leading to inhibition of translation initiation. To analyze this regulatory mechanism, we have characterized 29 novel mutations in the homologous eIF2B subunits encoded by GCD2, GCD7, and GCN3 that reduce or abolish inhibition of eIF2B activity by eIF2 phosphorylated on its alpha subunit [eIF2(alphaP)]. Most, if not all, of the mutations decrease sensitivity to eIF2(alphaP) without excluding GCN3, the nonessential subunit, from eIF2B; thus, all three proteins are critical for regulation of eIF2B by eIF2(alphaP). The mutations are clustered at both ends of the homologous region of each subunit, within two segments each of approximately 70 amino acids in length. Several mutations alter residues at equivalent positions in two or all three subunits. These results imply that structurally similar segments in GCD2, GCD7, and GCN3 perform related functions in eIF2B regulation. We propose that these segments form a single domain in eIF2B that makes multiple contacts with the alpha subunit of eIF2, around the phosphorylation site, allowing eIF2B to detect and respond to phosphoserine at residue 51. Most of the eIF2 is phosphorylated in certain mutants, suggesting that these substitutions allow eIF2B to accept phosphorylated eIF2 as a substrate for nucleotide exchange.

Amino Acid Sequence↗
PubMed1997

[Observation on surface characters of particles emitted from gasoline and diesel motor vehicle].

Surface compositions and morphological features of particles emitted from gasoline and diesel motor vehicle in Taiyuan were observed by scanning electron microscopy equipped with an energy dispersive X-ray spectrometer. The results showed that the surface of particles from gasoline motor vehicle contained larger amount of lead, amounting to 22.5% (average) among 15 elements measured; whereas the particles from diesel motor vehicle contained less lead, amounting to only 8%. But the size from diesel motor vehicle particle was smaller than those from gasoline motor vehicle, < or = 2 microns particles amounted to 73% and 62% of the total particles, respectively. The shapes of particles were irregular, with rough multiple-porous surface. The morphological features of particles from both motor vehicles were similar.

Particle Size↗
PubMed1997

[Prevalence of diabetes and its risk factors in China 1994. National Diabetes Prevention and Control Cooperative Group].

We studied the prevalence of diabetes and impaired glucose tolerance (IGT) and their risk factors in the population of China. It was a population-based, cross-sectional study of 224,251 residents aged 25 years and over in 19 provinces and areas, including cities and rural areas of the North, South, East, West and central China. Using 1985 WHO criteria, We found the prevalence of diabetes and IGT were 2.51% and 3.20% respectively in 213,515 subjects aged 25 to 64 years. 70.33% of the subjects had newly recognised diabetes. The prevalence of diabetes in China is about 3 times higher than it was ten years ago, and the rate is increasing faster in the countryside than in cities. On average, subjects with diabetes are older, have higher personal annual incomes, and have more frequently a family history of diabetes. They also have higher mean body mass index (BMI), ratio of circumference of the waist to hip, systolic blood pressure, diastolic blood pressure and a greater prevalence of hypertension. They perform less physical activity and receive less education than persons with normal OGTT. Multiple logistic, stepwise regression analysis shows that age, BMI (or WHR), family history of diabetes, hypertension, less physical activity and higher annual income are independent risk factors of NIDDM, and that low education is also an independent risk factor of NIDDM in people with higher personal annual income.

Adult↗
PubMed1997

[Clinical characteristics and main diagnostic points of latent autoimmune diabetes mellitus in adults].

To understand latent autoimmune diabetes mellitus in adults (LADA), we compared the clinical characteristics, fasting plasma glucose and C-peptide level, genetic frequency of HLA-DQA1, -DQB1 chain in 25 patients with LADA, 57 patients with insulin-dependent diabetes mellitus (IDDM, 21 patients with children-onset IDDM, 36 patients with adult-onset IDDM with ketosis), 38 patients with NIDDM (mild and moderate 30 patients and severe 8) and 42 normal persons. The onset of age was 20-48 years old associated with obvious polyphagia, and weight loss. Body mass index (BMI) was < or = 25 and fasting plasma glucose was > or = 16.5 mmol/L (297 mg/dl). Fasting and 1, 2 hour post prandial C-peptide level showed low and flatter curve (0.4, 0.8 and 0.8 nmol/L respectively). Glutamate decarboxylase (GAD) antibody was positive. HLA-DQ beta chain substitution of aspartate molecule was at position 57 (susceptic gene). LADA could be diagnosed if a patient has the first point and any point of the second to the fourth point. Patients with LADA should take diet, exercises, especially insulin as early as possible in order to control fasting and post prandial plasma glucose, and prevent from further destroy of residue islet B cells and reduce diabetic complications of eye, kidney and nerve.

Adult↗
PubMed1997

[A preliminary ultrasound biomicroscopic study of anterior segment structures in normal human eyes].

OBJECTIVE: We investigated anterior segment structures in normal human eyes by ultrasound biomicroscopy (UBM). METHOD: UBM high frequency transducer (50-100mHz) was used to measure the anterior segment of normal human eyes. RESULT: Cornea, sclera, iris, lens, ciliary body, anterior chamber, posterior chamber and extraocular muscles can be visualized by UBM. CONCLUSION: UBM is a new noninvasive method for imaging the anterior segment structures under living condition, and supplementary to the present existing imaging methods that have shortcomings in dynamic observation of the anterior ocular structures under such condition. As the frequency of the transducer is rather high, the imaging depth is limited to 4-5 mm, thus only the anterior ocular structures can be viewed.

Adult↗
PubMed1997

[Color Doppler imaging diagnosis of ocular tumor].

OBJECTIVE: To study the characteristics of color Doppler imaging (CDI) of ocular tumors for the diagnosis and differential diagnosis of the tumors. METHODS: 92 cases with ocular tumor (105 eyes) were examined by CDI to observe the vasculature of ocular tumors, and the various parameters of blood vessels and blood flow in the lesions were measured. SAS software was used to analyze the results. RESULTS: Blood flow signal can be found in retinoblastoma, melanoma of choroid, angioma of choroid, angioma of optic nerve papilla, Coats disease, persistent hyperplastic primary vitreous (PHPV) and metastatic tumors of choroid, but we can not find any blood flow signal in choroid osteoma and melanocytoma of optic nerve papilla. The blood flow parameters of central retinal artery in choroidal melanoma and that of ophthalmic artery, central retinal artery and posterior ciliary artery in angioma of choroid are lower than normal (P < 0.05). In the comparison of the blood velocity in the posterior ciliary artery between choroidal melanoma and choroidal angioma, it was found that the former is much higher than the latter (P < 0.05). CONCLUSION: CDI is very important in the diagnosis and differential diagnosis of ocular tumors.

Adolescent↗
PubMed1997

[Sudden hearing loss in acoustic neuroma].

To avoid misdiagnosis and mistherapy of acoustic neuroma, 104 cases of acoustic neuroma treated between 1986 and 1995 were retrospectively reviewed. Among them, 23 patients (24 ears, 23%) presented with sudden hearing loss as the starting symptoms. The clinical and audiological analysis demonstrated that 54.2% of the ears showed hearing loss over 71 dB HL, and all ears had deteriorated ABRs. -SP/AP was measured in nine ears, seven showed -SP/AP greater than 0.4. Acoustic reflex was negative in all 11 ears tested, and 94.4% of the ears showed abnormal ENG. The rate of positive CT scan was 88.8%. The diagnosis was made with CT pneumo-encephalography or MRI in those with negative CT result. It was concluded that for patients with sudden deafness, ABR should be used as a routine test. When ABR was abnormal, CT scan of the internal auditory meatus was needed.

Adolescent↗
PubMed1997

[Diagnosis and management of Mondini malformation].

Owing to the development of imaging technology and audiology, some of the sensorineural hearing loss cases that were previcusly considered to be of unknown cause have been found to be inner ear malformation. Five cases of Mondini malformation are reviewed in this paper. CSF otorhinorrhea occurred in four cases, Klippel-Feil syndrome in three, and concurrent otosclerosis in one patient. In discussion, the authors point out that: 1) CT scanning is an supplement to audiologic tests for such patients; 2) perilymph fistula in Mondini malformation is often found at the oval window and its vicinity, the foot plate and the round window; 3) the fistula can be treated by plugging with fascial tissue via tympanoplastic approach with endaural incision. The mucosa around the fistula should be stripped away and the plugging tissue should be of dumb-bell shape.

Adolescent↗
PubMed1997

[Fermentation conditions of engineering strain utilizing starch for production of alkaline proteinase].

The highest activity of alkaline proteinase produced by Bacillus pumilus c172(pBX 96) transformant was 9,000 U/ml in shaking flask where corn meal and bean cake meal were carbon and nitrogen sources, respectively. The enzyme activity was raised under the conditions of initial pH 7.0, MgCl2 instead of MgSO4, and glucose (0.1%) in the substrate. The fermentation of c172(pBx 96) transformant was carried out with parameters of pH, reducing sugar, total sugar and enzyme activity.

English Abstract↗
PubMed1997

[Simultaneous determination of matrine and oxymatrine in jieeryin and fuyanshuan by RP-HPLC].

Matrine and oxymatrine in Jieeryin and Fuyanshuan were separated and determined by Reversed Phase High Performance Liquid Chromatography, A chromatographic method for the separation and determination of matrine and oxymatrine in these preparations was established. Chromatographic coditions: ODS column with methanol-water-triethylamine(55:45:0.02) as the mobil phase, and UV detection at 215 nm. The method is simple, sensitive and accurate. This study provides the scientific basis for quality evaluation and quality control in making these preparations.

Alkaloids↗
PubMed1997

[Detection of desmosine in elastin by high performance liquid chromatography (HPLC)].

An assay of desmosine (DES) in elastin hydrolysate was performed by HPLC. Desmosine alone or its mixture with tyrosine and phenylalanine as well as elastin hydrolysate was separated on a C18 column eluted with a mobile phase of MeOH:H2O (2:8, V/V) and detected at UV-280nm. The results showed that the time of DES eluted in all cases mentioned above was comparable. The ratio of peak area (CA) and peak height (CH) between DES and Tyr is 1.4% and 3.4% resectively. It could be as a reliable measure to evaluate the quantity of DES in elastin. The correlation coefficient r was 0.9956 in the range of 0.16-0.64mg/L for a calibration curve of DES concentration vs peak area. In conclusion, this method could be used as a biochemical indication to detect the degradation level of elastin in the pathological state.

Chromatography, High Pressure Liquid↗
PubMed1997

[Recent advances in absolute analysis by graphite furnace atomic absorption spectrometry].

This paper summarizes recent advances in absolute analysis by graphite furnace atomic absorption spectrometry, including the developments of absolute analysis in atomic absorption spectrometry, the theoretical calculation of characteristic mass, the study of the stability of experimental characteristic mass and the applications of standardless analysis in various samples.

English Abstract↗