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C Chang

Publications and source records attributed to C Chang.

At least 19 recordsLinked to original sources
PubMed2026

Antimicrobial-resistant Staphylococcus aureus isolated from Australian wildlife admitted to a veterinary hospital.

Although antimicrobial resistance (AMR) is a growing One Health concern, little is known about AMR in Staphylococcus aureus from Australian wildlife. This study investigated the occurrence, phenotypic AMR profiles, and genetic characteristics of S. aureus from six representative Australian wildlife species admitted to a wildlife hospital in Western Australia, including the western grey kangaroo (Macropus fuliginosus), quenda (Isoodon fusciventer), pelican (Pelecanus conspicillatus), galah (Eolophus roseicapilla), shingleback skink (Tiliqua rugosa) and long-necked turtle (Chelodina colliei). Staphylococcus aureus was isolated from 11.7% (21/180, 95% CI: 7.4%-17.3%) of the animals on admission. Whole genome sequencing identified 13 multi-locus sequence types (STs) and various virulence factors, including the human-specific immune evasion cluster (IEC). Resistance to at least one antimicrobial class was observed in 63.6% of the isolates. The blaZ, erm(T), aac(6')-aph(2″), and tet(L) AMR genes were detected in 63.6%, 13.6%, 4.5%, and 4.5% of S. aureus, respectively. After 7 days of hospitalisation, S. aureus was isolated from 16.5% (16/97, 95% CI: 9.7%-25.4%) of the animals, including two methicillin-resistant S. aureus (MRSA) isolated from two pelicans. The two MRSA were identified as community-associated MRSA clones (mecA-positive ST1-IV and ST93-IV), suggesting direct or indirect transmission between humans and wildlife during hospitalisation may have occurred. This study highlighted Australian wildlife may be a potential reservoir for genetically diverse antimicrobial-resistant S. aureus. AMR surveillance including wildlife using a One Health approach may be required.

Animals↗
PubMed1995

Suppression of gene expression on the simian virus 40 major late promoter by human TR4 orphan receptor. A member of the steroid receptor superfamily.

The key expression of the simian virus 40 (SV40) major late promoter could be repressed by the human TR4 orphan receptor via the +55 region of the SV40 major late promoter (nucleotide numbers 368-389, 5' -GTTA-AGGTTCGTAGGTCATGGA-3'). Using the coupled in vitro transcribed and translated TR4 orphan receptor with a molecular mass of 67.3 kilodaltons, electrophoretic mobility shift assay showed specific binding with a dissociation constant of 1.09 nM between the TR4 orphan receptor and the SV40 +55 oligonucleotides. In addition, chloramphenicol acetyltransferase assay demonstrated that this SV40 +55 region can function as a repressor via the TR4 orphan receptor, suppressing the transcriptional activities of both SV40 early and late promoters. Together, our data suggest that the TR4 orphan receptor may play an important role for the suppression of the SV40 gene expression.

Base Sequence↗
PubMed1995

Multiple functions of the TR2-11 orphan receptor in modulating activation of two key cis-acting elements involved in the retinoic acid signal transduction system.

The testicular receptor 2 (TR2) orphan receptor binds to hormone response elements (HREs) consisting of two AGGTCA half-site direct repeat consensus sequences (DR) with various spacing in the following order: DR1 > DR2 > DR5 DR4 DR6 > DR3. When binding to natural HREs, TR2 orphan receptor remains flexible with higher binding affinities to (a) cellular retinol-binding protein II promoter region (CRBPIIp) (DR1), SV40 +55 region (DR2), and retinoic acid response element beta (RARE beta) (DR5) than to (b) NGFI-B response element (NBRE) and also to (c) the palindromic thyroid hormone response element (TREpal). This wide spectrum of HRE recognition sequences suggests possible versatility of the TR2 orphan receptor in cross-talking with other signal transduction systems. Chloramphenicol acetyltransferase (CAT) assay demonstrates that the TR2 orphan receptor competes with CRBPIIp- and RARE beta-CAT gene expression activated by retinoid X receptor alpha (RXR alpha) and retinoic acid receptor alpha (RAR alpha)/RXR alpha heterodimers, respectively. In addition, this suppression may not be mediated by the formation of heterodimers between TR2 orphan receptor and either RXR alpha or RAR alpha. Instead, a minimum of 100-fold higher affinity of the TR2 orphan receptor for CRBPIIp than RXR alpha may explain why the TR2 orphan receptor dominates RXR alpha in CRBPIIp-CAT activation. Together, our data suggest that the TR2 orphan receptor may be a master regulator in modulating the activation of two key HREs, RARE beta and CRBPIIp, involved in the retinoic acid signal transduction pathway.

Animals↗
PubMed1995

Ethylene insensitivity conferred by Arabidopsis ERS gene.

ERS (ethylene response sensor), a gene in the Arabidopsis thaliana ethylene hormone-response pathway, was uncovered by cross-hybridization with the Arabidopsis ETR1 gene. The deduced ERS protein has sequence similarity with the amino-terminal domain and putative histidine protein kinase domain of ETR1, but it does not have a receiver domain as found in ETR1. A missense mutation identical to the dominant etr1-4 mutation was introduced into the ERS gene. The altered ERS gene conferred dominant ethylene insensitivity to wild-type Arabidopsis. Double-mutant analysis indicates that ERS acts upstream of the CTR1 protein kinase gene in the ethylene-response pathway.

Amino Acid Sequence↗
PubMed1995

Molecular cloning of NKB1. A natural killer cell receptor for HLA-B allotypes.

The expression of certain MHC class I allotypes by potential target cells can inhibit NK cell-mediated cytotoxicity. We recently identified the NKB1 surface Ag, expressed on T and NK cell subsets, as a putative inhibitory receptor for HLA-B class I molecules possessing the Bw4 serologic epitope. NKB1 is a 70-kDa glycoprotein that after deglycosylation migrates as a 50-kDa protein as determined by SDS-PAGE. A cDNA encoding the NKB1 receptor was cloned from a NKB1+T cell cDNA library by expression in COS-7 cells using the anti-NKB1 mAb DX9. NKB1 is a member of the lg superfamily containing three lg-like domains in the extracellular region and is related to the recently identified family (p58/NKAT) of human NK and T cell surface molecules that appear to function as inhibitory receptors for HLA class I.

Amino Acid Sequence↗
PubMed1995

A critical assessment of brain metabolites: analysis of perchloric acid extracts using proton nuclear magnetic resonance.

A critical assessment of perchloric acid (PCA) brain tissue extracts for precise identification and quantitation of brain metabolites using in vitro proton nuclear magnetic resonance (1H NMR) spectroscopy was studied. One pulse with a presaturation NMR experiment was used. The chemical shifts and coupling networks of the major brain metabolites as a function of pH were characterized by using individual model compounds and a model mixture solution. We found that the conditions of the PCA solution are essential for accurate interpretation of NMR spectra of brain metabolites. The maximum spectral resolution was obtained at pH 4.92. Caution is necessary when using high resolution 1H NMR spectroscopy to identify and quantify brain metabolites.

Animals↗
PubMed1995

The expression of prostatic acid phosphatase is transcriptionally regulated in human prostate carcinoma cells.

The expression of prostatic acid phosphatase (PAcP) in three human prostate carcinoma cell lines including LNCaP, DU 145 and PC-3, was studied to explore its potential role as a marker in the progression of prostate cancer. Although Southern blot analysis suggested the presence of PAcP gene in all three prostate carcinoma cell lines, the Northern blot analysis and the reverse transcriptase-polymerase chain reaction (RT-PCR) assay showed that PAcP mRNA can be detected only in LNCaP cells. As one of the major differences between LNCaP cells and PC-3 as well as DU 145 cells is the androgen-sensitivity of LNCaP cells, we then focused on the influence of PAcP expression by the presence of androgen receptor (AR) in human AR cDNA-transfected PC-3 cells and high passages of LNCaP cells. The results demonstrated that the transfection of human AR cDNA into PC-3 cells did not have any detectable effect on the expression of PAcP. Further, in LNCaP cells, while the level of PAcP mRNA diminished upon passage, the AR mRNA level remained approximately the same. Together, these data suggested that the differential expression of PAcP in different prostate carcinoma cells including high passages of LNCaP cells may occur at the transcriptional level and may have little linkage to the expression of AR.

Acid Phosphatase↗
PubMed1995

Sequences in the preC region of duck hepatitis B virus affect pregenomic RNA accumulation.

The pregenomic RNA of hepadnaviruses serves as both the mRNA for the core and polymerase proteins and the RNA template for reverse transcription. We have identified a region in the duck hepatitis B virus pregenomic RNA transcription unit that is critical for the accumulation of this transcript. This 85-nt region, termed alpha, is located within the preC region; deletion of alpha results in drastically reduced steady-state levels of pregenomic RNA. This effect is not due to reduction in transcription initiation or to enhancement of premature polyadenylation at the 5' copy of the viral poly(A) signal. However, this phenotype is suppressed by deletion of a second, larger region (beta) located ca. 1 kb downstream. The activity of the alpha element is tissue- and species-nonspecific; however, it displays absolute orientation-dependence and its activity is influenced by its position within the transcript. Models for its action are discussed.

Animals↗
PubMed1995

Identification of a new enhancer in the promoter region of human TR3 orphan receptor gene. A member of steroid receptor superfamily.

Human TR3 orphan receptor is a member of the steroid/thyroid hormone receptor superfamily and is the human homologue of the proteins encoded by the rat NGFI-B and mouse nur77 genes. These genes are induced rapidly by androgens/growth factors and may have functions related to cell proliferation, differentiation, and apoptosis. To investigate the TR3 orphan receptor gene transcriptional regulation, a 2.3-kilobase genomic DNA fragment containing the TR3 orphan receptor gene promoter region was isolated, sequenced, and characterized. Sequence homology search within this promoter region revealed some potential cis-acting elements such as cAMP response element, interleukin-6 response element, estrogen response element, and GC box. Deletion analysis and chloramphenicol acetyltransferase assay also showed a novel cis-acting element of TR3 orphan receptor gene (NCAE-TR3), 200-181 base pairs upstream of the transcriptional start site. Gel retardation assay further demonstrated that some nuclear factors can bind to this NCAE-TR3. Together, our data suggest that NCAE-TR3 could be a new enhancer element associated with the transcription of an early response gene for mitogenesis and apoptosis.

Animals↗
PubMed1995

Identification of human TR2 orphan receptor response element in the transcriptional initiation site of the simian virus 40 major late promoter.

A DNA response element (TR2RE-SV40) for the TR2 orphan receptor, a member of the steroid-thyroid hormone receptor superfamily, has been identified in the simian virus 40 (SV40) +55 region (nucleotide numbers 368-389, 5'-GTTAAGGTTCGTAGGTCATGGA-3'). Electrophoretic mobility shift assay, using in vitro translated TR2 orphan receptor with a molecular mass of 67 kilodaltons, showed a specific binding with high affinity (dissociation constant = 9 nM) for this DNA sequence. DNA-swap experiments using chloramphenicol acetyl-transferase assay demonstrated that androgen can suppress the transcriptional activities of SV40 early promoter via the interaction between this TR2RE-SV40 and the chimeric receptor AR/TR2/AR with the DNA-binding domain of the TR2 orphan receptor flanked by the N-terminal and androgen-binding domains of the androgen receptor. In addition, this TR2RE-SV40 can function as a repressor to suppress the transcriptional activities of both SV40 early and late promoters. Together, these data suggest the TR2RE-SV40 may represent the first identified natural DNA response element for the TR2 orphan receptor that may function as a repressor for the SV40 gene expression.

Animals↗
PubMed1995

Magnetic resonance microscopy of hamster olfactory bulb: a histological correlation.

BACKGROUND: Magnetic Resonance Imaging (MRI) has been widely used as a noninvasive diagnostic tool for obtaining morphological, metabolic, and functional information from tissue. However, its potential application in observing detailed structure comparable to that of the light microscope has not yet been fully explored. In order to evaluate the usefulness of MR microscopy, a high resolution three-dimensional (3-D) technique was applied to observe the laminar structure of the mammalian olfactory bulb (OB). METHODS: Adult male hamsters (Mesocrecitus auratus) were used as an animal model. Hamster OB and the attached anterior olfactory nucleus were removed from the skull for the MRI examinations. The images were performed with a Bruker AMX-400 system equipped with microimaging accessories. T2 weighted 3-D spin echo sequence was used with a field of view of 9 mm and data matrix of 128*128*128. The in-plane resolution was 70*70*70 microns. Histological preparation, including vibratome sectioning at 40 microns and Nissl staining, were used for light microscopic evaluations and comparisons. RESULTS: Five distinct layers from the superficial to the center of the OB were distinguished in the MR images of coronal, sagittal and horizontal slices. As compared to the histological sections at the corresponding cutting planes, the laminar structure of the OB displayed in the MR microscopic images correlated well with its counterparts. CONCLUSIONS: MR microscopy is capable of detecting cellular variation of unsectioned and unstained tissue. It can also be easily applied to obtain spatial information with good resolution. It appears to provide a great potential for diagnostic pathology.

Animals↗
PubMed1995

Molecular characterization of human CD94: a type II membrane glycoprotein related to the C-type lectin superfamily.

Natural killer (NK) cells preferentially express several genes of the C-type lectin superfamily which have been implicated in the regulation of NK cell function. We demonstrate that CD94 is a type II membrane protein encoded by a unique gene of the C-type lectin superfamily. While homology of CD94 with the NK cell-associated NKR-P1 and NKG2 C-type lectin genes is limited to the structural motifs conserved in the carbohydrate recognition domain, all of these genes are on human chromosome 12, the syntenic of mouse chromosome 6, where genes of the NK complex (NKR-P1 and Ly-49) are located. An unexpected feature of CD94 is the essential absence of a cytoplasmic domain, implying that association with other receptors may be necessary for the function of this molecule.

Amino Acid Sequence↗
PubMed1995

Crystallization, molecular replacement solution, and refinement of tetrameric beta-amylase from sweet potato.

Sweet potato beta-amylase is a tetramer of identical subunits, which are arranged to exhibit 222 molecular symmetry. Its subunit consists of 498 amino acid residues (Mr 55,880). It has been crystallized at room temperature using polyethylene glycol 1500 as precipitant. The crystals, growing to dimensions of 0.4 mm x 0.4 mm x 1.0 mm within 2 weeks, belong to the tetragonal space group P4(2)2(1)2 with unit cell dimensions of a = b = 129.63 A and c = 68.42 A. The asymmetric unit contains 1 subunit of beta-amylase, with a crystal volume per protein mass (VM) of 2.57 A3/Da and a solvent content of 52% by volume. The three-dimensional structure of the tetrameric beta-amylase from sweet potato has been determined by molecular replacement methods using the monomeric structure of soybean enzyme as the starting model. The refined subunit model contains 3,863 nonhydrogen protein atoms (488 amino acid residues) and 319 water oxygen atoms. The current R-value is 20.3% for data in the resolution range of 8-2.3 A (with 2 sigma cut-off) with good stereochemistry. The subunit structure of sweet potato beta-amylase (crystallized in the absence of alpha-cyclodextrin) is very similar to that of soybean beta-amylase (complexed with alpha-cyclodextrin). The root-mean-square (RMS) difference for 487 equivalent C alpha atoms of the two beta-amylases is 0.96 A. Each subunit of sweet potato beta-amylase is composed of a large (alpha/beta)8 core domain, a small one made up of three long loops [L3 (residues 91-150), L4 (residues 183-258), and L5 (residues 300-327)], and a long C-terminal loop formed by residues 445-493. Conserved Glu 187, believed to play an important role in catalysis, is located at the cleft between the (alpha/beta)8 barrel core and a small domain made up of three long loops (L3, L4, and L5). Conserved Cys 96, important in the inactivation of enzyme activity by sulfhydryl reagents, is located at the entrance of the (alpha/beta)8 barrel.

Amino Acid Sequence↗
PubMed1995

Plasticity of craniomandibular muscle function: 31P magnetic resonance spectroscopy of the rabbit masseter muscle.

The masseter muscle was studied during postnatal development of the rabbit from the juvenile to adult stage in which the oral function was altered during maturation by modifying the diet to soft food. The muscle was assessed using phosphate magnetic resonance (31P NMR) spectroscopy with a single-turn copper surface coil to study potential changes in phosphate metabolism. The 31P NMR spectra consisted of five peaks related to unbound forms of inorganic phosphate (Pi), creatine phosphate (PCr), and three peaks related to the adenosine triphosphate (ATP). The masseter was assessed in one group of five rabbits at 8 weeks postnatally (juvenile) and after 4 months of this experimental group masticating on soft food. They were compared with a control group of five rabbits raised on a normal hard diet. The Pi/PCr ratio increased in the adult masseter much higher during twitching, tetany, and periodic contraction than in the juvenile regardless as to whether the adult animal had been raised from the juvenile period on soft or hard diet. There were relatively few differences between the experimental adult animals raised on a soft diet and the normal adult animals despite the soft diet animals demonstrating a significantly lower weight and smaller muscle mass. These findings suggest that chronic underuse of the masseter muscle by decreasing the masticatory loads has a minimal effect on the phosphate metabolism of the maturing masseter.

Adaptation, Physiological↗
PubMed1995

Age-dependent neurotoxicity of striatal lesions produced by aminooxyacetic acid: quantitative in vitro 1H NMR spectroscopic studies.

Aminooxyacetic acid, a potent inhibitor of the mitochondrial malate-aspartate shunt, was used to assess the role of mitochondrial energy metabolism in damaged brain of rats of different age groups. Three age groups--juvenile (< 1 month), young adult (3-4 months), and adult (7 months)--were subjected to examine the age-related aminooxyacetic acid effect. We measured the absolute concentrations of metabolites in perchloric acid extracts of rat striatum after intraperitoneal administration of aminooxyacetic acid using 1H NMR spectroscopy. Among aminooxyacetic acid-treated groups, a twofold increase of GABA concentration was observed in juveniles and young adults, and a threefold elevation of GABA level was observed in adults, whereas there were no significant differences of alanine and glutamate levels in all three aminooxyacetic acid-treated groups as compared with the age-matched controls. Statistically significant decreases of N-acetylaspartate, glutamine, and creatine levels were detected in treated adults. A statistically significant elevation of lactate concentration was found in the adult treated group. These data have demonstrated that the impairment of energy metabolism in rat striatum induced by aminooxyacetic acid can be revealed by quantitative in vitro 1H NMR spectroscopy and that aminooxyacetic acid produces age-dependent striatal abnormalities.

Aging↗
PubMed1995

Expression of nuclear hormone receptors in the rat supraoptic nucleus.

To investigate the role of nuclear hormone receptors on neuropeptide gene expression in the hypothalamo-neurohypophyseal system (HNS) of the rat, a survey was made of members of the nuclear hormone receptor superfamily that are expressed in the supraoptic nucleus (SON). A polymerase chain reaction cloning strategy based on homologies in the DNA-binding domain of AGGTCA-binding factors was devised for the identification of receptors in microdissected SON tissue. Cloning of the amplified products led to the identification of five true receptors, thyroid hormone receptor-alpha (THR alpha), retinoic acid receptor-alpha, retinoic acid receptor-gamma, retinoid X receptor-alpha, and retinoid X receptor-gamma, as well as four orphan receptors, apolipoprotein AI regulatory protein (ARP-1), chicken ovalbumin upstream promoter transcription factor I (COUP-TF I), estrogen-related receptor 2, and testis receptor 4 (TR4). Dot-blot screening of amplified gene fragment analysis showed that THR alpha, ARP-1, TR4, and COUP-TF I were the most abundant factors expressed in the SON region, in the order THR alpha > ARP-1 > TR4 approximately COUP-TF I. THR alpha has previously been localized to HNS neurons. In situ hybridization analysis showed that ARP-1, COUP-TF I, and TR4 were not expressed in magnocellular neurons at appreciable levels, but rather in surrounding structures. Furthermore, in lactating female rats there were no significant differences in the composition of the nine identified nuclear hormone receptors in the SON region compared with control animals. From these experiments, it is concluded that there is a multitude of hypothalamically expressed nuclear hormone receptors, but that only THR alpha is expressed at relatively high abundance in HNS neurons. This indicates that the peptide-producing magnocellular neurons of the SON express a specific set of transcription factors of the nuclear hormone receptor family.

Amino Acid Sequence↗