Search PubMed⌕ Search

Biomedical subjects

Y Yao

Publications and source records attributed to Y Yao.

At least 253 records · Page 14Linked to original sources
PubMed1990

Coordinate and discoordinate accumulation of protein constituents in chicken breast muscle.

Accumulation of protein constituents in developing chicken breast muscle was examined by two-dimensional gel electrophoresis. Quantitative analysis of the two-dimensional gels showed a moderate coordination in accumulation among contractile proteins (actin, tropomyosin and myosin light chains) during postnatal development in spite of their isoform transition. Creatine kinase was also accumulated coordinately with contractile proteins during development. In contrast, accumulation kinetics of glycolytic enzymes (glyceraldehyde-3-phosphate dehydrogenase, aldolase and enolase) showed discoordination with those of contractile proteins. These findings suggest that there are two distinct phases in muscle maturation: (1) structural maturation and (2) metabolic maturation.

Animals↗
PubMed1990

Two distinct ferredoxins from Rhodobacter capsulatus: complete amino acid sequences and molecular evolution.

Two distinct ferredoxins were purified from Rhodobacter capsulatus SB1003. Their complete amino acid sequences were determined by a combination of protease digestion, BrCN cleavage and Edman degradation. Ferredoxins I and II were composed of 64 and 111 amino acids, respectively, with molecular weights of 6,728 and 12,549 excluding iron and sulfur atoms. Both contained two Cys clusters in their amino acid sequences. The first cluster of ferredoxin I and the second cluster of ferredoxin II had a sequence, CxxCxxCxxxCP, in common with the ferredoxins found in Clostridia. The second cluster of ferredoxin I had a sequence, CxxCxxxxxxxxCxxxCM, with extra amino acids between the second and third Cys, which has been reported for other photosynthetic bacterial ferredoxins and putative ferredoxins (nif-gene products) from nitrogen-fixing bacteria, and with a unique occurrence of Met. The first cluster of ferredoxin II had a CxxCxxxxCxxxCP sequence, with two additional amino acids between the second and third Cys, a characteristics feature of Azotobacter-[3Fe-4S] [4Fe-4S]-ferredoxin. Ferredoxin II was also similar to Azotobacter-type ferredoxins with an extended carboxyl (C-) terminal sequence compared to the common Clostridium-type. The evolutionary relationship of the two together with a putative one recently found to be encoded in nifENXQ region in this bacterium [Moreno-Vivian et al. (1989) J. Bacteriol. 171, 2591-2598] is discussed.

Amino Acid Sequence↗
PubMed1989

An atypical heme-binding structure of cytochrome c1 of Euglena gracilis mitochondrial complex III.

Complex III was purified from submitochondrial particles prepared from Euglena gracilis. The purified complex consisted of 10 subunits and lost antimycin sensitivity. The Euglena complex III showed an atypical difference absorption spectrum for cytochrome c1 with its alpha-band maximum at 561 nm. The pyridine ferrohemochrome prepared from covalently bound heme in the Euglena complex III had an alpha-peak at 553 nm. This wavelength is the same as that of pyridine ferrohemochrome prepared from Euglena mitochondrial cytochrome c (c-558), the heme of which is linked to only a single cysteine residue through a thioether bond. Cytochrome c1 which was a heme-stained subunit with a molecular mass of 32.5 kDa was isolated from the purified complex III and its N-terminal sequence of 46 amino acids was determined. On the basis of apparent homologies to cytochromes c1 from other sources, this sequence included the heme-binding region. However, the amino acid at position 36, corresponding to the first cysteine involved in heme linkage in other cytochromes c1, was phenylalanine. Position 39, corresponding to the second cysteine, was not identified despite the treatment for removal of the heme and carboxymethylation of the expected cysteine. The unidentified amino acid is assumed to be a derivative of cysteine to which the heme is linked through a single thioether bond. The histidine-40 corresponding to the probable fifth ligand for heme iron was conserved in Euglena cytochrome c1.

Amino Acid Sequence↗
PubMed1989

Ferredoxin and rubredoxin from Butyribacterium methylotrophicum: complete primary structures and construction of phylogenetic trees.

Complete amino acid sequences of ferredoxin and rubredoxin from Butyribacterium methylotrophicum, a methylotrophic hetero-acetogen, were determined by combination of protease digestion, Edman degradation, carboxypeptidase digestion, and/or partial acid hydrolysis. The ferredoxin was composed of 55 amino acids with a molecular weight of 5,732 excluding iron and sulfur atoms and showed a typical 2[4Fe-4S]-type ferredoxin sequence with an internal repeat at the 14-23 and 42-51 positions. The rubredoxin was composed of 53 amino acids with a molecular weight of 5,672 excluding iron atom and showed a sequence similar to those of other anaerobic rubredoxins. The sequences were compared to those of corresponding proteins from six different bacteria to construct phylogenetic trees, which showed essentially the same topology. The relationships between the ferredoxin sequences from this bacterium and those of Clostridium thermoaceticum and Methanosarcina barkeri, both of which possess a carbonyl-dependent acetyl-CoA metabolic system, are also discussed.

Amino Acid Sequence↗
PubMed1989

The tremorigen aflatrem is a positive allosteric modulator of the gamma-aminobutyric acidA receptor channel expressed in Xenopus oocytes.

Aflatrem, a mycotoxin from Aspergillus flavus, potentiates the gamma-aminobutyric acid (GABA)-induced chloride current. This positive allosteric regulatory action of aflatrem was quantitatively studied on the GABAA receptor channel expressed in Xenopus oocytes after injection with chick brain mRNA under voltage-clamp conditions. In this model system, aflatrem potentiates the current induced by 5 microM GABA in a concentration-dependent manner. Half-maximal potentiation was obtained with 2.4 microM aflatrem and maximal stimulation of the GABA (5 microM) response was more than 10-fold. The potentiation was not associated with a change of the reversal potential of the GABA-induced current. In the presence of 2 microM aflatrem, the GABA dose-response curve shifted to lower concentrations, with the Ka decreasing from 28 to 7 microM and the Hill coefficient, n, from 1.5 to 0.8, as measured at a membrane potential of -100 mV. At saturating concentration of GABA (250 microM), aflatrem (10 microM) was still able to enhance the current by about 21%. Further experiments suggest that the site of action of aflatrem on the GABAA receptor channel complex is different from that of benzodiazepines, pentobarbital, and picrotoxin. Aflatrem (10 microM) had no significant effect on the coexpressed voltage-dependent sodium and calcium channels and on the kainate channel. The potentiating action of aflatrem on the GABAA receptor channel may explain the initial symptoms of intoxication caused by aflatrem in vivo, i.e., diminished activity or immobility of the affected animal.

Allosteric Regulation↗
PubMed1989

[Clinical significance of competitive protein binding assay of 25-hydroxyvitamin D concentration].

The level of serum 25-hydroxyvitamin D (25-OH-D3) was determined in 94 cases of healthy volunteers and 98 patients with various diseases. The mean level of the controls was 16.2 +/- 4.6 ng/ml (x /- S). The patients were divided into 5 groups, 1) Osteomalacia and rickets 42 cases, showing typical changes of bone in X-ray films. In 12 of them the disease was caused by vitamin D deficiency. The mean value of 25-OH-D3 was 3.3 +/- 2.0 ng/ml, being much lower than that of controls (P less than 0.001). In 14 cases of hypophosphatemia, 8 cases of renal tubular acidosis and 8 cases of renal insufficiency all complicated with osteomalacia the mean value of 25-OH-D3 was 17.9 +/- 11.4, 18.2 +/- 9.6 and 19.2 +/- 5.6 ng/ml (P greater than 0.05) respectively. 2) Intestinal malabsorption 18 cases. The mean level of 25-OH-D3 was 4.5 +/- 3.2 ng/ml (P less than 0.001). Some of them had hypocalcemia and/or secondary hyperparathyroidism. 2 showed osteoporosis and 1 osteomalacia. 3) Chronic liver disease 24 cases, the mean value of 25-OH-D3 was 6.2 +/- 5.6 ng/ml, being much lower than that of the controls (P less than 0.001). 4) 10 cases after taking anti-epileptic drugs had a mean level of 25-OH-C3 6.9 +/- 5.8 ng/ml (P less than 0.001). 1 had X-ray evidence of osteomalacia. 5) 4 cases of overdosage of vitamin D had a mean value of 110.3 +/- 22.5 ng/ml, being much higher than that of the controls (P less than 0.001). Competitive protein binding assay for measuring 25-OH-D3 is a simple and economic method. It is sensitive and specific as it provides distinct discrimination between healthy controls and patients with vitamin D deficiency or overdosage.

Adult↗
PubMed1988

Colorectal cancer detection with the 60 cm flexible sigmoidoscope in a solo general internist's office.

Emphasis is placed on the importance of early detection of colorectal cancer by the primary care physician using the 60 cm flexible sigmoidoscope. A training format for this procedure is proposed. The author, trained according to this format, found 49 polyps and three carcinomas among his first 365 randomly chosen patients. Of these 317 (87%) were asymptomatic, having no risk factors. The average distance of insertion was 53 cm and the average examination time was 20 minutes. The calculated cost for these 365 patients was approximately +60,000, and the estimated average cost for a potentially curable colorectal cancer detection was approximately +20,000. Although a relatively long examination time may be necessary for the beginner, the author concludes that the primary care physician can be readily trained to handle the 60 cm flexible sigmoidoscope safely and cost effectively.

Adult↗
PubMed1985

The sulfhydryl groups of ferredoxin-NADP+ oxidoreductases: is a disulfide bond really present?

The sulfhydryl groups of three ferredoxin-NADP+ oxidoreductases [EC 1.18.1.2] (FNR) two from blue-green algae, Spirulina sp. and Synechococcus sp., respectively, and one from spinach, were analyzed by carboxymethylation and titration with sulfhydryl reagents under different conditions. Five sulfhydryl groups in Spirulina and spinach enzymes and four in Synechococcus enzyme were found to be in reduced forms. There was no disulfide bond in any FNR tested. The results in the present experiment contradict those reported by Karplus et al. [Biochemistry 23, 6576-6583 (1984)].

Amino Acids↗
PubMed1985

Intestinal anisakiasis: clinical and radiologic features.

We report the clinical and radiologic features of 12 patients with acute intestinal anisakiasis. Diagnosis of anisakiasis was made immunologically by positive antibody to Anisakis larvae and a recent history of raw fish intake. Severe abdominal pain was a major symptom in these patients-half experienced fluid levels indicating ileus on plain x-ray films of the abdomen. Radiologic findings included irregular thickening of the jejunum, ileum, or colon, with mucosal edema and luminal narrowing with dilatation of the proximal intestine. In two cases a thread-like filling defect suggesting a worm was visualized on the x-ray film. These findings were interpreted as anisakiasis. Although ileus developed in some patients, all were treated and cured completely without surgery.

Adult↗
PubMed1984

Characterization of the bovine prolactin gene.

The gene coding for bovine prolactin was shown to exist as a single copy per haploid genome. Three restriction fragment polymorphisms were detected in the prolactin gene by Southern blot analysis of DNA obtained from the semen of pedigreed bulls representing eight breeds. The organization of the bovine prolactin gene was determined by restriction mapping of a clone isolated from a genomic library and by genomic blots. The 5'-flanking region and two exons were sequenced and the transcription start site mapped by primer extension. Comparison of the bovine prolactin sequence reported here with the published sequence of the rat prolactin gene revealed extensive homology (79%), extending 360 nucleotides upstream from the cap site, after which the sequences diverge. The homology exceeds that of the coding regions. A possible alternate intron-exon splice site was noted within the sequence coding for the signal peptide.

Amino Acid Sequence↗
PubMed1984

Spirulina ferredoxin-NADP+ reductase. The complete amino acid sequence.

The amino acid sequence of ferredoxin-NADP+ oxidoreductase [EC 1.18.1.2, FNR] from Spirulina sp., a blue-green alga, was determined. Spirulina ferredoxin-NADP+ oxidoreductase was composed of 294 amino acid residues and the molecular weight of the holoenzyme was 34,135. An apparent homology of the amino(N)-terminal region was found between ferredoxin-NADP+ reductases from Spirulina and spinach. We also found some sequence similarities in human erythrocyte glutathione reductase and p-hydroxybenzoate hydroxylase from Pseudomonas fluorescens, both of which are NADPH-dependent FAD enzymes.

Amino Acid Sequence↗
PubMed1977

Thyroid nodules--benign or malignant? 1. Diagnosis.

Radioisotope scanning is an invaluable aid in determining whether a palpable thyroid nodule is benign or malignant. In many cases, however, precise diagnosis is impossible without needle biopsy or surgical exploration.

Adenoma↗