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Biomedical subjects

C Chang

Publications and source records attributed to C Chang.

At least 181 records · Page 10Linked to original sources
PubMed1998

Direct quantitation of HIV by flow cytometry using branched DNA signal amplification.

Adaptation of the branched DNA signal amplification technology to flow cytometry has resulted in a quantitative nuclei-acid assay with significant advantages over the microwell-based format. In this assay, microbeads, rather than microwell plates, are derivatized with nucleic-acid capture probes and the derivatized beads are used to capture single nucleic-acid targets, which then capture fluorescent reporter probes via branched DNA. The assay detects DNA or RNA targets, has a current lower sensitivity limit of 500 human immunodeficiency virus (HIV) RNA molecules and responds linearly to target level from 500 to at least 50,000 molecules. Since microbeads can easily interrogate large volumes, viral lysis and genomic RNA capture can proceed in one step from comparatively large volumes, and sample preparation is greatly simplified compared to the microwell-format bDNA assay.

Cell Line↗
PubMed1998

The molecular basis of C4 photosynthesis in sorghum: isolation, characterization and RFLP mapping of mesophyll- and bundle-sheath-specific cDNAs obtained by differential screening.

C4 photosynthesis depends upon the strict compartmentalization of the CO2-assimilatory enzymes of the C4 and Calvin cycle in two different cell types, mesophyll and bundle-sheath cells. A differential accumulation is also observed for enzymes of other metabolic pathways, and mesophyll and bundle-sheath chloroplasts of NADP-malic enzyme type C4 plants differ even in their photosynthetic electron transport chains. A large number of studies indicate that this division of labour between mesophyll and bundle-sheath cells is the result of differential gene expression. To investigate the extent of this differential gene expression and thus gain insight into the genetic basis of C4 photosynthesis, genes that are differentially expressed in the mesophyll and bundle-sheath cells were catalogued in the NADP-malic enzyme type C4 grass Sorghum bicolor. A total of 58 cDNAs were isolated by differential screening. Using a tenfold difference in transcript abundance between mesophyll and bundle-sheath cells as a criterion, 25 cDNAs were confirmed to encode mesophyll-specific gene sequences and 8 were found to encode bundle-sheath-specific sequences. Eight mesophyll-specific cDNAs showed no significant similarities within GenBank and may therefore represent candidates for the elucidation of hitherto unknown functions in the differentiation of mesophyll and bundle-sheath cells. The chromosomal location of 50 isolated cDNAs was determined by RFLP mapping using an interspecific sorghum cross.

Base Sequence↗
PubMed1998

Thyroid hormone direct repeat 4 response element is a positive regulatory element for the human TR2 orphan receptor, a member of steroid receptor superfamily.

We demonstrate that TR2 orphan receptor (TR2) may induce transactivation activities via an AGGTCA-like-direct-repeat-4 consensus thyroid hormone response element (DR4-TRE) system. TR2 showed a slightly greater binding affinity than thyroid hormone receptor alpha1 (TR alpha1)/retinoid X receptor alpha (RXR alpha) heterodimer with Kds 0.5 nM and 2.3 nM, respectively. These receptors, TR2 and TR alpha1/RXR alpha heterodimer, competed with each other on binding to limited amounts of DR4-TRE. TR2 canceled the suppression effect of unliganded-TR alpha1 on CAT reporter activity in a dose-dependent fashion. Estrogen receptor (ER) and 2P2 (a mutated TR2 with P box sequence of androgen receptor) failed not only to bind to DR4-TRE but also to recover this inhibitory effect of unliganded TRalpha1. However, when T3 was supplemented, estradiol-ER competed for a full CAT activity while TR2 showed an additive effect on the transcriptional activation. These results indicate that DNA binding is essential for TR2 to take action and fully functional liganded TR alpha1 may rely on common factors shared with ER but not TR2.

Carrier Proteins↗
PubMed1998

Anti-tumor effects of d-dicentrine from the root of Lindera megaphylla.

d-Dicentrine, a naturally occurring aporphine type isoquinoline alkaloid, isolated from the root of Lindera megaphylla Hemsl. (Lauraceae), was evaluated for its potential anti-cancer activity. We found d-dicentrine significantly inhibited the growth of human hepatoma cell line HuH-7 by delaying its doubling time in tissue culture. An in vitro colony forming assay showed that d-dicentrine decreased the colony formation efficiency in both hepatoma cell lines, HuH-7 and MS-G2, used in our study. Biosyntheses of the macromolecules DNA and RNA were also strongly inhibited. An MTT assay in 21 tumor cell lines also revealed that d-dicentrine was most cytotoxic to esophageal carcinoma HCE-6, lymphoma cell lines Molt-4 and CESS, leukemia cell lines HL60 and K562, and hepatoma cell line MS-G2. An in vitro tumor growing assay in the Severe Combined immunodeficiency (SCID) mice showed that intraperitoneal injection of d-dicentrine at the dose of 100 micrograms twice a week for 4 weeks significantly inhibited the tumor incidence of leukemia cell line K562 in SCID mice. All these data indicated that d-dicentrine has potential anti-tumor applications.

Animals↗
PubMed1998

Characterization of fibrous retrocorneal membrane by confocal microscopy.

PURPOSE: To study the appearance of a fibrous retrocorneal membrane as seen by confocal microscopy. METHODS: A 67-year-old white woman with a history of multiple ocular surgeries, including repeated penetrating keratoplasties for aphakic bullous keratopathy, developed a retrocorneal membrane in the right eye. The membrane was first noticed 3 years after the last corneal transplant and remained stable subsequently. The patient was examined by in vivo white light tandem-scanning confocal microscopy. RESULTS: At the level of the retrocorneal membrane, confocal microscopy disclosed the presence of a hyperreflective fibrous-appearing layer. Normal endothelial cells could not be found. Anterior to the hyperreflective layer, activated keratocytes were identified. CONCLUSION: Confocal microscopy may allow noninvasive diagnosis of fibrous retrocorneal membrane. Additionally, our data suggest that the posterior keratocytes might play a role in the production and deposition of fibrous tissue.

Aged↗
PubMed1998

Differential expression of Nur77 family members in human T-lymphotropic virus type 1-infected cells: transactivation of the TR3/nur77 gene by Tax protein.

We analyzed the differential expression and regulation of three members of the Nur77 transcription factor family by the human T-lymphotropic virus type 1 (HTLV-1) Tax protein. We have demonstrated that in both HTLV-1-infected cells and Tax-expressing JPX-9 cells, TR3/nur77 is highly expressed, whereas neither NOR-1 nor NOT expression is detectable. Transient transfection analysis further confirmed the Tax transactivation of the TR3/nur77 promoter but not the NOR-1 promoter in different cell types. Furthermore, expression of a luciferase reporter gene driven by the NGFI-B (rat homolog of TR3/Nur77) response element (NBRE) provided evidence that Tax-mediated transactivation resulted in the induction of a functional protein. Cotransfection assays with the TR3/nur77 promoter sequence or the NBRE binding motif together with a series of Tax mutants have shown that Tax-induced TR3/nur77 expression is mediated by CREB/ATF-related transcription factors.

Activating Transcription Factor 1↗
PubMed1998

Mononeuropathy multiplex in hemophilia: an electrophysiologic assessment.

Single nerve lesion or mononeuropathy caused by extrinsic compression of hematoma or hemarthrosis is consistently reported for hemophilic patients. To study the manifestation of peripheral nerve lesions, an extensive nerve conduction study of peripheral nerves and specific nerves in correlation with clinical involvement was carried out on 126 hemophilic patients. We found 24 patients with 34 peripheral nerve lesions. The frequency of nerve lesion positively correlated with the severity of hemophilia (p < 0.01) and increasing age (p < 0.05). Nerve lesions occurred more commonly in lower extremities than in upper extremities. The femoral nerve was most commonly involved. Seven patients were identified to have mononeuropathy multiplex with 2 or more nerve lesions involving more than one extremity. All of these patients had chronic condition. Our findings suggest that mononeuropathy multiplex may occur in hemophilic patients.

Adolescent↗
PubMed1998

Antisense TR3 orphan receptor can increase prostate cancer cell viability with etoposide treatment.

In androgen-responsive LNCaP human prostatic cancer cells, human TR3 orphan receptor, a member of the steroid receptor superfamily, can be rapidly induced by androgen. In contrast, ablation of androgen by castration can induce the expression of the TR3 orphan receptor gene in rat ventral prostate that has undergone apoptosis. This phenomenon prompted us to further analyze the potential role of human TR3 orphan receptor in prostate cancer cells in which apoptosis had been induced. Northern blot analysis shows that human TR3 orphan receptor expression can be induced rapidly after treatment of LNCaP and PC-3 prostate cancer cells with calcium ionophore or etoposide. Our data further demonstrate that a much higher concentration of etoposide was needed to kill the same number of cells in LNCaP and PC-3 cells transfected stably with antisense TR3 orphan receptor compared with that in control vector transfectants. Together, our data suggest that the human TR3 orphan receptor may play an important role in modulating drug-induced prostate apoptosis.

Androgens↗
PubMed1998

The genomic structure and chromosomal location of the human TR2 orphan receptor, a member of the steroid receptor superfamily.

Human TR2 orphan receptor, isolated from the testis and prostate, is a member of the steroid/thyroid hormone receptor superfamily. With the screening of a human genomic library and the combination of primer walking and PCR sequencing, we found that the entire TR2 orphan receptor gene coding region and 5'-untranslated region feature 13 introns and 14 exons, and that the consensus splice sequences (GT-AG) are present in all intron-exon boundaries. Within the region that codes for the DNA binding domain, TR2 orphan receptor gene has a distinct intron-exon junction. Whereas all other known steroid receptors have one splice site that separates their first and second zinc fingers in the DNA binding domain, TR2 orphan receptor has a rare splice site located in the middle of its first zinc finger. The identification of specific junction sequences for potential alternative splicing sites helps to explain the existence of multiple forms of TR2 orphan receptor cDNA (TR2-5, 7, 9, 11). The S1 nuclease protection assay for TR2 message revealed that there are multiple transcription initiations, and that the major cap site surrounded by an initiator-like sequence is located at the 104th nucleotide upstream from the translation start codon. Sequence analysis of a 2.7-kb DNA fragment upstream of the TR2 orphan receptor translation start codon unveiled several potential cis-acting elements, such as AP-1, HNF-5, GATA1 binding sites, and GC boxes. Using fluorescence in situ hybridization combined with a high-resolution G-banding technique, we found that the TR2 orphan receptor gene was mapped to human chromosome 12 at band q22, whereas the structurally closely related TR4 orphan receptor gene was mapped to human chromosome 3 at band q24.3.

Amino Acid Sequence↗
PubMed1998

TR4 orphan receptor crosstalks to chicken ovalbumin upstream protein-transcription factor and thyroid hormone receptor to induce the transcriptional activity of the human immunodeficiency virus type 1 long-terminal repeat.

Here we investigate the roles of human testicular orphan receptors, TR2 and TR4, on the gene regulation of the long-terminal repeat of the human immunodeficiency virus type 1 (HIV-LTR). In gel-retardation assays, a palindromic element at the 5'-end of HIV-LTR,5'-AGGGGTCAGATATCCACTGACCTTT-3',showed high affinity to TR2 and TR4 with an equilibrium dissociation constant (Kd) of 1.11 +/- 0.48 (n = 3) and 0.52 +/- 0.12 nM (n = 3), respectively. Interestingly, each half-site of the palindromic element is sufficient to compete with the binding of the labeled palindromic element to TR2 or TR4 with an equilibrium inhibition constant (ki) around 10 nM. However, the transiently expressed TR2 or TR4 in Chinese hamster ovary (CHO) cells or Japanese quail muscle myoblasts (QM7) cells showed no activity in regulating the transcriptional activity of the chloramphenicol acetyltransferase (CAT) reporter gene inserted downstream of the HIV-LTR promoter. Although both TR2 and TR4 showed no effect on CAT activity by itself, our data showed only the TR4 could crosstalk to the chicken ovalbumin upstream protein-transcription factor (COUP-TF1) and thyroid hormone receptor (TR alpha 1), and potentiated the transcriptional activity of HIV-LTR on the CAT reporter gene regulated by COUP-TF1 and TR alpha 1. These results indicate that TR4, but not TR2, may couple to other nuclear receptors in the upregulation of the HIV replication.

Animals↗
PubMed1998

Induction of an intronic enhancer of the human ciliary neurotrophic factor receptor (CNTFRalpha) gene by the TR3 orphan receptor.

A hormone response element, CNTFRalpha-NBRE (5'-AAAGGTCA-3') has been identified in the fifth intron of the alpha component of ciliary neurotrophic factor receptor gene (CNTFR-15) for the human TR3 orphan receptor (TR3). A specific binding between in vitro expressed TR3 and CNTFRalpha-NBRE was demonstrated by using electrophoretic mobility shift assay. A reporter gene assay using chloramphenicol acetyl-transferase (CAT) showed that CNTFR-15 has an enhancer activity that could be induced by TR3 in a dose-dependent manner. This induction was significantly reduced in the absence of CNTFRalpha-NBRE. Together, these results indicate CNTFRalpha-NBRE is sufficient to mediate TR3 action in inducing the enhancer activity of CNTFR-15. Our finding may, therefore, suggest CNTFRalpha is a target gene regulated by TR3 and expand the role of TR3 in the nervous system.

Ciliary Neurotrophic Factor↗
PubMed1998

Evaluation of RU58841 as an anti-androgen in prostate PC3 cells and a topical anti-alopecia agent in the bald scalp of stumptailed macaques.

The effect of androgen receptor transcriptional activation by RU58841, a nonsteroidal anti-androgen, was studied in the human prostate cancer PC3 cell line by cotransfection with wild-type androgen receptor (wt AR) and an androgen-responsive reporter (MMTV-ARE-CAT) construct. Anti-and rogens, hydroxyflutamide, and Casodex, and the antiestrogen, genistein, were studied in parallel for comparison with RU58841. The wt AR was activated only by the androgen dihydrotestosterone (DHT). Neither the anti-androgens nor antiestrogen can enhance AR transcriptional activity at 10(-11)-10(-7)M in PC3 cells. Hydroxyflutamide, RU58841, and Casodex, but not genistein, displayed competitively suppressive effects on DHT activation of wt AR. The potency of RU58841 was comparable to that of hydroxyflutamide. From this result, topical application of RU58841, which is considered to be a potential therapy for skin diseases, may induce systemic side effects. However, RU58841, on topical application, revealed a potent increase in density, thickening, and length of hair in the macaque model of androgenetic alopecia, whereas no systemic effects were detected. Together our results suggest that RU58841 may have potent antagonism to the wt AR and could be considered as a topically applied active anti-androgen for the treatment of androgen-dependent skin disorders, such as acne, androgenetic alopecia, and hirsutism.

Alopecia↗
PubMed1998

Ontogeny and autoregulation of androgen receptor mRNA expression in the nervous system.

Androgens and the androgen receptor (AR) both play critical roles for the development of the male phenotype. To investigate the roles of androgens in the developing nervous system, we examined the AR messenger RNA distribution by in situ hybridization. Our results indicate that AR transcripts were detectable in male mouse embryos at embryonic day 11 (E1111). Intensive AR labeling appears in the neuroepithelium of brain vesicles and spinal cord, as well as in the reproductive organs. During E1 5-E16, new and strong AR labeling appeared in the cortex of cerebrum and hippocampus. Specific AR signals were also present in the brain areas known for hormonal control of copulatory behavior and mediating sensory processing. Interestingly, many ganglia were found to express AR mRNA at E15-E16. These novel AR-expressing sites include the dorsal root, sympathetic, and celiac ganglia, as well as the ophthalmic nerve of trigeminal ganglion. Sex dimorphism of AR expression in brain was also observed during E15-E16. Postnatally, brain and spinal cord can respond to circulating androgen levels by modifying their AR gene expression, but the ganglia cannot. Together, these data suggest androgens may have a great influence on the development and maintenance of the nervous system through the AR.

Animals↗
PubMed1998

'Two-component' ethylene signaling in Arabidopsis.

The Arabidopsis ETR1 gene codes for an ethylene hormone receptor that has striking sequence similarity with bacterial two-component regulators. This finding predicts that the ETR1 receptor transduces the ethylene signal through the phosphotransfer mechanisms established for a number of the bacterial regulators. To test this hypothesis, we have performed in vitro assays for ETR1 autokinase activity as well as for transfer of phosphate to the ETR1 receiver. So far, we have not detected either of these activities. Another question we are focusing on is the identity of protein substrates of the ETR1 receptor. Using the yeast two-hybrid system, we have obtained several clones to be subsequently characterized as potential interactors with ETR1.

Arabidopsis↗
PubMed1998

[The evaluation of umbilical arterial Doppler spectrum fractal characterization in obstetrics].

OBJECTIVE: To evaluate the clinical value of fetal umbilical arterial Doppler spectrum fractal. METHODS: 104 cases with 22-41 gestational weeks were included, and divided into two groups: normal pregnant group, 59 cases; abnormal pregnant group, 45 cases. Umbilical arterial Doppler spectrum were obtained by color Doppler ultrasound, then Doppler signal were transformed into computer through sound-frequency, and fractal were calculated. RESULTS: The fractal was 1.83 +/- 0.03 in normal pregnant group. The frequency of abnormal fractal was significantly higher in abnormal pregnant group than that in normal pregnant group (P < 0.001). Compared with the ratio of peak systolic to lowest diastolic flow velocity (S/D), the fractal was more sensitive than S/D ratio in abnormal pregnancy (P < 0.05). There were significant correlation between fractal and gestational weeks (r = 0.266). CONCLUSION: Fractal responses to complexity of umbilical arterial blood flow, and it is a better parameter than S/D ratio in monitoring abnormal umbilical arterial blood flow.

Adult↗
PubMed1998

[Doppler echocardiographic studies on fetal cardiac function of diabetic mothers].

OBJECTIVE: To assess fetal cardiac function by Doppler echocardiography in diabetic pregnancies. METHODS: We investigated the changes of cardiac function in 54 normal fetuses and 23 fetuses of diabetic mothers. Cardiac anatomic datas were obtained by measuring the diameter of the aortic (AO), the pulmonary artery (PA), the mitral valve(MV), the tricuspid valve (TV) and interventricular septal thickness (IVS). Blood flow evlocity were obtained from the AO, PA, atrioventricular valves. The following variables were measured: peak flow velocity (PFV), accelerate time (ACT), systolic volume (SV) and ForceF. These indices respresented the systolic function. The peak early flow velocity (PFVe), peak late flow velocity (PFVa), PFVe/PFVa(E/A), mean velocity (V) of MV or TV respresented the diastolic function. RESULTS: The results revealed that in fetuses of diabetic mothers, IVS became thickness. The diameter of AO, PA, MV, TV were wider than that of normal fetases. The PFV, SV, ForceF of AO or PA increased significantly. There was no different in ACT between two groups. The PFVa of MV or TV increased significantly, whereas the E/A of both atrioventricular valves decreased. CONCLUSION: It showed that the fetal hyperinsulinemia triggered by maternal hyperglycemia result in fetal weight increasing, as well as hyperplasia and hypertrophy of myocardial cells. An iacreased contractility is compatible with relatively larger size of such fetuses. The intracardiac flow volume increased secondary to the more needs of fetal development. Abnormal thickenning IVS might impair ventricular diastolic function.

Adult↗
PubMed1998

[Effect of Salvia Miltiorrhiza injection on umbilical artery hemodynamics during fetal distress in ewe].

OBJECTIVE: To study the effect of Salvia Miltiorrhiza injection (SMI) on umbilical artery hemodynamics during fetal distress in ewe. METHODS: Intrauterine surgery were performed at 116-125 gestational days in 3 pregnancy sheep for insertion of vascular catheters at abdominal aorta from femoral artery and for implantation of a electromagnetic flowmetre probe around umbilical artery. Gelatin microsphere injection to abdominal aorta through vascular catheter for obstruction of placental-fetal circulation. 2 ml of SMI was used 6 times(2 times each sheep), and the signs of umbilical artery blood flow and wave forms of fetal abdominal aorta blood pressure were recorded before and after injections of gelatin microsphere or SMI. The fast Fourier translation (FFT) was used to turn signs in time domain into powers spectral of input impedance in frequency domain for resistance and characteristic impedance of umbilical artery. RESULTS: After the SMI was injected into fetal abdominal aorta, the resistance of umbilical artery was significantly reduced (P < 0.05), and the changes of resistance was significantly relative with the resistance before SMI injected (r = -0.85, P < 0.001). But there were no significantly different impedance between before and after SMI treatment (P > 0.05). CONCLUSIONS: The SMI to fetal abdominal aorta can decrease umbilical artery blood flow resistance and the changes of resistance was significantly relative to that before SMI treatment.

Animals↗