Search PubMed⌕ Search

Biomedical subjects

Y Yu

Publications and source records attributed to Y Yu.

At least 523 records · Page 29Linked to original sources
PubMed1994

Energetics of ribonuclease T1 structure.

The energetics of thermal denaturation of two isoforms of ribonuclease T1 (Gln25 and Lys25) in various solvents have been studied by differential scanning calorimetry. It has been shown that the thermal transition of both forms of RNase T1 is strongly affected by slow kinetics, which cause an apparent deviation of the transition from a simple two-state model. By decreasing the heating rate or increasing the transition temperature, the denaturation of RNase approaches an equilibrium two-state transition. This permits determination of the thermodynamic parameters characterizing unfolding of the native structure. These thermodynamic parameters were correlated with the structural features of protein. Analysis of different contributions to the stability of RNase T1 shows that van der Waals interactions and hydrogen bonding are the major contributors to the conformational stability of the protein.

Aspergillus oryzae↗
PubMed1994

Respiratory chain of the lung fluke Paragonimus westermani: facultative anaerobic mitochondria.

The respiratory chain of adult Paragonimus westermani, a lung fluke, was characterized in isolated mitochondria. The fluke mitochondria exhibited cyanide- and antimycin A-sensitive succinate oxidase activity at a rate of 16.8 nmol O2 min-1 mg-1 protein. The succinate oxidation was shown to be stimulated by ADP and linked to the formation of membrane potential. The specific activities of oxidoreductases composing the succinate oxidase system, i.e., succinate-ubiquinone and succinate--cytochrome c oxidoreductase (complex II and complex II-III, respectively) and cytochrome c oxidase (complex IV), were compared in mitochondria from adult Paragonimus, bovine heart (an aerobic tissue), and muscle of adult Ascaris suum which possesses an anaerobic respiratory chain. The activity values of complex II-III and complex IV were high, middle, and low for bovine heart, Paragonimus, and A. suum, respectively, whereas the activity of complex II was comparable among the three sources. The cytochrome contents of Paragonimus mitochondria as determined by difference absorption spectrophotometry ranged between those in Ascaris and bovine mitochondria for types c and aa3 cytochromes. Paragonimus mitochondria exhibited a high activity of NADH-fumarate reductase; the specific activity was about 18-fold higher in fluke submitochondria than in bovine heart submitochondria. Quinone analysis by HPLC and mass spectrometry showed that the fluke mitochondria contain both rhodoquinone-10 and ubiquinone-10 at concentrations of 0.572 and 0.321 nmol mg-1 mitochondrial protein, respectively. These data clearly show that mitochondria from adult P. westermani, unlike adult Ascaris mitochondria, possess both cyanide-sensitive succinate oxidase and NADH-fumarate reductase systems, indicating that the fluke mitochondria are facultatively anaerobic.

Adaptation, Physiological↗
PubMed1994

Effect of infection with the 139H scrapie strain on the number, area and/or location of hypothalamic CRF- and VP-immunostained neurons.

Scrapie is a transmissible neurodegenerative disease which shares some characteristics with Alzheimer disease (AD). Recent studies show abnormal enlargement of the adrenal glands and kidneys in 139H-affected hamsters. Using immunocytochemical techniques with antibodies to corticotropin-releasing factor (CRF) and vasopressin (VP), we observed the following: (1) a significantly higher number of CRF-immunostained neurons in the preoptic nucleus of hypothalamus of 139H-affected hamsters than controls; (2) the area of VP-immunostained (ir-VP) neurons in the lateral hypothalamus, which includes the internuclear group of magnocellular neurons and the nucleus circularis, was significantly lower for 139H-affected hamsters than for controls; and (3) no significant difference between 139H-affected and control hamsters with regard to the number of ir-VP neurons in the dorsal-medial hypothalamus (DMH), including the paraventricular hypothalamus, or the supraoptic nuclei. However, the population of ir-VP neurons in the DMH shifted to the anterior part of the hypothalamus in 139H-affected hamsters. Three-dimensional models of the immunostaining were prepared and these provide clear depictions of the changes noted. The changes in the CRF and VP systems in 139H-affected hamsters suggest that the neuroendocrine system can be affected by unconventional slow infections.

Animals↗
PubMed1994

Adriamycin induces large deletions as a major type of mutation in CHO cells.

Adriamycin (ADR), a commonly used cancer chemotherapy antibiotic, exhibits a variety of genotoxicities. In this study, we have examined the mutagenicity of ADR at the hypoxanthine-guanine phosphoribosyltransferase gene (hprt) in Chinese hamster ovary (CHO) cells and the xanthine-guanine phosphoribosyltransferase locus (gpt) in a pSV2gpt-transformed CHO cell line, AS52. Although ADR induced a dose-dependent increase of mutant frequency at both loci, it was more mutagenic to the gpt gene than to the hprt locus. Multiplex PCR analysis revealed that 35% of the 103 independent ADR-induced HPRT-deficient mutants carried large deletions. Among these deletion mutants, 33% were total gene deletions, 22% affected multiple exons, and 42% involved a single exon, of which most (9/15) were exon 1. The majority (63%) of ADR-induced AS52 mutants had a total deletion of the gpt gene. These observations indicate that ADR induces large deletions as a major type of gene mutation in mammalian cells, suggesting the involvement of reactive oxygen species as one mutagenic pathway in the mutagenesis of ADR.

Animals↗
PubMed1994

Evidence for nontargeted mutagenesis in a monkey kidney cell line and analysis of its sequence specificity using a shuttle-vector plasmid.

Intact pZ189 DNA was allowed to replicate in monkey kidney vero cells that had been pretreated with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). The E. coli MBM7070 was transfected with replicated plasmid, and those with mutations in the supF gene were identified. The frequency of mutants that did not contain recognizable changes in the electrophoretic mobility of the plasmid DNA was scored. The frequency of such mutants was 12.2 x 10(-4) (43/35376) and 6.2 x 10(-4) (22/35712) in mutants derived from cells pretreated with 0.2 mumoles/l and 2 mumoles/l MNNG respectively; these values represent an increase of 5.8- and 2.9-fold over the spontaneous mutation frequency of 2.1 x 10(-4) (10/47741) (p < 0.01). Sequence analysis of the supF genes of these mutants showed that 89% (24/27) of base substitutions occurred at G.C base pairs; 59% of the base substitutions (16/27) were transversions, and 41% (11/27) were transitions. The types of base substitutions were predominantly G.C-->T.A and G.C-->A.T. 48% of base substitutions occurred at 6 sites of the supF gene; 4 of these sites consist of 5'-TTNN where N is G or C. Base substitutions never previously reported were found, namely, T-->C at 61, G-->T at 70, G-->T at 99, and G-->C at 103 were found; these have never been reported up to now. In addition, 2 of the 5 frameshifts occurred in the region 99-105 of the supF gene (GGTGGGG), suggesting that this region is a hot spot for nontargeted frameshifts. These results strongly suggest that nontargeted mutagenesis can occur in mammalian cells and shows that the spectrum of mutations induced differs from that of spontaneous and targeted mutations.

Animals↗
PubMed1994

Paramyxovirus mediated cell fusion requires co-expression of both the fusion and hemagglutinin-neuraminidase glycoproteins.

Syncytia formation in either CV-1 or HeLa T4+ cells required recombinant expression of both fusion (F) and hemagglutinin-neuraminidase (HN) glycoproteins from the human parainfluenza virus type 3 (HPIV3), human parainfluenza virus type 2 (HPIV2), and simian virus 5 (SV5). In this system, recombinant T7 transcription vectors (pT7-5 or pGEM) containing F or HN, were transfected individually or in combination into cells previously infected with a recombinant vaccinia virus expressing T7 RNA polymerase (vTF7-3). While both proteins were processed and expressed at the cell surface, syncytia formation occurred only when both glycoproteins were co-expressed. The function of HN in the fusion process could not be replaced using lectins or by co-expression of heterologous F and HN proteins. Further, cell fusion was not observed when experiments were performed using individually expressed F and HN proteins in adjacent cells. The data presented in this report support the notion that a specific interaction between both paramyxoviral glycoproteins is required for the formation of syncytia in tissue culture monolayers.

Animals↗
PubMed1994

Hyperplasia and hypertrophy of B cells in the islets of Langerhans in hamsters infected with the 139H strain of scrapie.

Previous studies showed that in hamsters the 139H, but not the 263K, scrapie strain caused a marked increase in pancreatic size and led to obesity, hypoglycaemia and striking hyperinsulinaemia. In the preceding paper (Ye et al., 1994), the islets of Langerhans in 139H-affected hamsters showed cellular atrophy, fibrosis, cytoplasmic vesicles and nuclear pathological changes. In the present study, the profiles of pancreatic islets were classified into three sizes with an image analyzer. The number and total area covered by "small" islet profiles were less in 139H-affected than in normal hamsters. In contrast, the number and the area of "medium" and "large" islet profiles were significantly greater in 139H than in normal hamsters. With antibodies to insulin, glucagon, somatostatin and pancreatic polypeptide, the proportions of B, A, D and F cells were determined. With somatostatin-positive cells arbitrarily given a value of 1, the ratio of B:A:D:F cells in the islets was 27:5:1:0.04 in normal hamsters and 122:7:1:0.04 in 139H-affected hamsters. The increase in B cells would account for the islet enlargement and the hypoglycaemia-hyperinsulinaemia seen in 139H-affected hamsters.

Animals↗
PubMed1994

Epistasis analysis of suppressor mutations that allow HO expression in the absence of the yeast SW15 transcriptional activator.

We have examined mutations which overcome the requirement for SW15-dependent transcriptional activation of the Saccharomyces cerevisiae HO gene. We show that the RPD3 gene is the same as SDI2, and that SIN4 is the same as the TSF3 and SDI3 genes. We have also identified a new swi5 suppressor, RGR1. The RGR1 gene was identified originally as a negative regulator of SUC2. Epistasis analysis indicates that six swi5 suppressor genes function in four distinct pathways, with RPD3 and SIN3 in one pathway, RGR1 and SIN4 in a second pathway, and SDI4 and SIN5 each in distinct pathways. Finally, we show that complete suppression of the swi5 defect in HO expression by sin5 requires the wild-type ACE2 gene. This suggests that one function of SIN5 is to prevent ACE2, a SWI5 homolog, from activating HO expression.

Epistasis, Genetic↗
PubMed1994

Multiplex polymerase chain reaction-based deletion analysis of spontaneous, gamma ray- and alpha-induced hprt mutants of CHO-K1 cells.

Independent Chinese hamster ovary (CHO)-K1 cell mutants at the hypoxanthine-guanine phosphoribosyltransferase (hprt) locus were isolated from untreated, 60Co gamma ray- and 212Bi alpha-exposed cells and the genetic changes underlying the mutation determined by multiplex polymerase chain reaction (PCR)-based exon deletion analysis. In the 71 spontaneous mutants analyzed, 77.5% of the clones showed no change in exon number or size, 15.5% showed a loss of a single exon, 4.2% showed a loss of 2-8 exons, and 2.8% showed loss of all nine hprt exons (total gene deletion). Exposure to 6 Gy of gamma rays, which reduced survival levels to 10%, produced a significantly different deletion spectrum that was shifted toward deletions with 45% of the 20 mutants analyzed showing a loss of a single exon and 30% showing a loss of all nine exons. Exposure to 2 Gy alpha radiation from 212Bi, a 220Rn daughter, a dose which also reduced survival levels to about 10%, resulted in a deletion spectrum similar to the gamma-ray spectrum in that more than 75% of the 49 mutants analyzed were deletions. The alpha spectrum, however, was significantly different from both the spontaneous and gamma spectra with 55.1% of the alpha mutants showing a loss of all nine exons, 10.2% showing loss of a single exon, and 14.3% showing loss of 2-8 exons. Thus, alpha-radiation appears to produce larger intragenic deletions than gamma radiation. The results suggest that intragenic deletion size should be considered when low- and high linear energy transfer (LET) mutation spectra are compared.

Alpha Particles↗
PubMed1994

Analysis of the C-polyhedrin genes from different geographical isolates of a type 5 cytoplasmic polyhedrosis virus.

The C-polyhedrin genes of two different geographic isolates of a type 5 cytoplasmic polyhedrosis virus (CPV) were cloned. A CPV infecting Orgyia pseudotsugata (OpCPV), isolated in the Pacific Northwest of the U.S.A., and a CPV infecting Heliothis armigera, isolated in South Africa, were studied. Both genes were found to be 883 nucleotides in length and encoded a predicted protein of 246 residues (M(r) of 28,890). Comparison of the nucleotide sequences of these two viruses with another type 5 geographic isolate, infecting Euxoa scandens (EsCPV; isolated in Eastern Canada), showed that there were only 17 nucleotide differences among the three genes. The only nucleotide variation that had an effect on the encoded protein was a deletion of nucleotide 774 in the gene of EsCPV. The deletion introduces a frameshift mutation resulting in the alteration of the carboxyl-terminal amino acid sequence. Sequence alignment of the OpCPV C-polyhedrin showed little homology to a type 1 CPV (infecting Bombyx mori) or with analogous proteins (N-polyhedrins) from two baculoviruses infecting O. pseudotsugata. Interestingly, most of the conserved residues between the N- and C-polyhedrins were either basic or aromatic amino acids.

Amino Acid Sequence↗
PubMed1994

Similar cytokine but different coagulation responses to lipopolysaccharide injection in D-galactosamine-sensitized versus nonsensitized rats.

To compare cytokine release and coagulation disturbances induced by administration of high versus low doses of endotoxin (lipopolysaccharide [LPS]), we used two endotoxin test systems similar in mortality but different in the degree of endotoxemia. One group of rats (n = 11) randomly received endotoxin (15.0 mg/kg of body weight intraperitoneally [i.p.]) and 1 ml of Ringer's solution (nonsensitized animals). The second group (n = 11) received 1 ml of D-galactosamine (500 mg/kg i.p.) and endotoxin (100 micrograms/kg i.p.) simultaneously (sensitized animals). Endotoxin levels in the plasma of nonsensitized rats were 1,000-fold higher than those in the plasma of sensitized rats (69.33 x 10(3) +/- 22.42 x 10(3) versus 75.8 +/- 27.08 ng of LPS per ml), leading to a mortality of 91% in nonsensitized rats versus 82% in the sensitized-rat model within 48 h postendotoxemia. Serum transaminase activity increased up to 100-fold in sensitized rats as a sign of hepatocyte damage. Despite the large difference in LPS levels in plasma, the time courses of the plasma tumor necrosis factor (TNF) increase were similar in the two groups, with a peak at 2 h (54 +/- 12 ng/ml in nonsensitized rats versus 43 +/- 12 ng/ml in sensitized rats), and also similar to that of a group of nonsensitized rats (n = 5) that received a low dose of LPS (100 micrograms/kg) only (52 +/- 21 ng/ml), while D-galactosamine alone did not induce TNF release. Despite similar TNF levels, a more pronounced coagulation disorder was observed at 4 h in nonsensitized rats (with the high LPS dose) as measured by platelet counts, plasma fibrinogen levels, and activated partial thromboplastin time prolongation (191 x 10(3) +/- 107 x 10(3) cells per microliter, 40 +/- 24 mg/dl, and 53 +/- 15 s, respectively) than in rats with the low LPS dose either sensitized (495 x 10(3) +/- 153 x 10(3), 95 +/- 49, and 38 +/- 16, respectively) or nonsensitized (439 x 10(3) +/- 62 x 10(3), 170 +/- 18, and 35 +/- 11, respectively).(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1994

Cloning of Entamoeba genes encoding proteolipids of putative vacuolar proton-translocating ATPases.

Molecular cloning techniques were used to identify genes encoding the proteolipids of putative vacuolar proton-transporting ATPases (V-ATPases; EC 3.6.1.35) of Entamoeba histolytica (Ehvma3) and Entamoeba dispar. The Ehvma3 gene encoded a 177-amino-acid peptide, with an M(r) of 18,110, which showed extensive positional identities with peptides of E. dispar (92%), Schizosaccharomyces pombe (58%), and humans (56%).

Amino Acid Sequence↗
PubMed1994

Physicochemical damage to liposomal membrane induced by iron- or copper-mediated lipid peroxidation.

A carboxyfluorescein (CF)-enveloping soybean phosphatidylcholine liposome was used as a model of physicochemical damage of biomembranes. The liposomes were exposed to a metal-chelate complex [2 mM of ferric nitrilotriacetate (FeNTA) or cupric nitrilotriacetate (CuNTA)] plus a reductant (2 mM of ascorbate or various concentrations of reduced glutathione), and CF release from damaged liposomal membranes and the generation of thiobarbituric acid-reactive substances (TBARS) were measured. In the presence of a reducing agent, both FeNTA and CuNTA stimulated markedly CF release and an increase in the TBARS level, while in the absence of a reducing agent both of the chelate complexes showed little CF release and TBARS. The effects of H2O2 addition to the reaction system containing liposome with FeNTA or CuNTA plus ascorbate were also examined. The CF release was slightly increased by the addition of a smaller dose (0.5 mM) of H2O2 and it was inhibited by 8 mM of H2O2. A similar result was obtained in the TBARS test. These results suggest that FeNTA- or CuNTA-mediated lipid peroxidation can damage liposomal membranes physicochemically, and the redox reaction of the chelated metal itself is more important than a Fenton-type reaction in the process.

Ferric Compounds↗
PubMed1994

Growth and carcass characteristics of beef steers fed silage and different levels of energy with or without protein supplementation.

Fifty-six large-framed crossbred steers averaging 227 kg were used in an experiment including a growing period (24 wk) and a finishing period ending when the steers had approximately 4 to 10 mm of fat thickness (Canadian grade A1). Steers were individually fed and assigned to a completely randomized design with seven treatments for the growing period. From the end of the growing period until slaughter, all steers received the same basal diet. Half of the steers from each treatment used in the growing period received a supplement containing protein and the other half a supplement containing protein and fat. Treatments during the growing phase consisted of 1) timothy silage alone or mixed (on a DM basis) with 2) 7.5% molasses, 3) 15% molasses, 4) 7.5% canola meal, 5) 5.5% canola meal and 7.5% molasses, 6) 3.6% canola meal and 15% molasses, or 7) 15% canola meal. The total N intake from supplements 2, 5, or 6 was similar. Compared with silage fed alone, canola meal supplementation increased (P < .05) ADG, whereas molasses had no effect. Combining molasses and canola meal did not improve ADG compared with feeding only canola meal on an isonitrogenous basis. Canola meal supplementation compared with feeding only silage during the growing phase reduced (P < .05) days on feed, and molasses tended (P = .059) to reduce it. Carcass data were generally similar among treatments.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

[Study on phagocytosis of human neutrophils in diabetics].

Infection is one of the most common complications in diabetes mellitus (DM). The neutrophil plays an important role in the anti-infection mechanism. A comparative study on phagocytosis of P. Aeruginosa by human neutrophils in diabetic patients and healthy volunteers was carried out by means of the monolayer of neutrophils and ultrastructural observation in electronic microscopy. The results showed that the rates of phagocytosis, index of phagocytosis and rates of microbe lysis in DM group were much lower than those in normal controls (P < 0.01). The ultrastructure of neutrophils in diabetic patients became apparently abnormal during the process of neutrophil phagocytosis. The results demonstrated that the impairment in phagocytosis of neutrophils may be one of the causes of severe and repeated infection in diabetics.

Aged↗
PubMed1994

[Restrictive fragment length polymorphism analysis of gamma-crystallin in congenital cataract families].

Using gamma-crystallin gene probe P5G1, we investigated the RFLP in two large families of congenital cataracts and normal people, calculated the allelic gene frequency and defined the haplotypes by genetic linkage analysis. In accordance with foreign reports, TaqI/p5G1 detected 3 polymorphic sites, and the allelic gene frequency was close to that in foreign reports. However, foreign reports claimed that the haplotype P was linked to Coppock cataracts, but we did not find such linkage by haplotype analysis. The result suggests that not all the inherited cataracts are linked to gamma-crystallin gene, and the haplotype P should not be simply regarded as genetic marker in prenatal diagnosis.

Cataract↗