Biomedical subjects

Y Tan

Publications and source records attributed to Y Tan.

At least 91 records · Page 5Linked to original sources

PubMed1999

Calbindin-D 28kD immunofluorescence in ventral mesencephalic neurons labeled following injections of Fluoro-Gold in nucleus accumbens subterritories: inverse relationship relative to known neurotoxin vulnerabilities.

The shell and core of the nucleus accumbens exhibit different vulnerabilities to neurotoxins. Calcium binding proteins are reported to offer some neuroprotection against excitotoxicity by suppressing or buffering intracellular calcium. Differences in the distributions of the calbindin-D 28kD (CB) and calretinin (CR) might be related to the different vulnerabilities to neurotoxins of dopaminergic neurons in the ventral mesencephalon that project to the core and medial shell of the nucleus accumbens. To address this possibility, Fluoro-Gold (FG) was injected into accumbens subterritories and numbers of retrogradely labeled neurons in the ventral tegmental area containing CB and CR immunoreactivities (ir) were expressed as a percentage of total numbers of labeled neurons. The perikaryal diameters and lengths of the immunoreactive dendrites of FG labeled neurons were also measured. About 70% and 35% of retrogradely labeled cells observed following core and medial shell injections, respectively, exhibited CB immunoreactivity. Differences were not observed in the percentages of FG labeled cells exhibiting CR immunoreactivity following medial shell (13%) and core (15%) injections. The mean perikaryal diameters and median summed lengths of dendrites of retrogradely labeled neurons containing CB were smaller than in labeled neurons lacking CB following injections in both core and medial shell of the nucleus accumbens. The data indicate that the different 6-hydroxydopamine (6-OHDA) vulnerabilities of ventral mesencephalic dopaminergic neurons are not obviously related to the presence of CB and CR.

Animals↗

PubMed1999

The inhibitory role of CpG immunostimulatory motifs in cationic lipid vector-mediated transgene expression in vivo.

We have previously reported that intravenous administration of cationic lipid-protamine-DNA complexes (LPD) induces production of large quantities of proinflammatory cytokines that are toxic and cause inhibition of transgene expression. Cytokine induction appears to be mediated by the unmethylated CpG sequences since methylation of plasmid DNA significantly decreases the cytokine levels. In this study, the inhibitory role of CpG in lipid-mediated gene transfer was further investigated using chemically well-defined, CpG-containing oligodeoxynucleotides (ODNs). Injection (intravenous) of ODNs formulated in LPD into mice triggered production of proinflammatory cytokines including interferon gamma and TNF-alpha. The potency of CpG-containing ODNs in cytokine induction was affected by its flanking sequences and was significantly reduced when CpG was methylated. Preinjection of ODN-containing LPD led to inhibition of transgene expression in lungs after a subsequent injection of LPD containing plasmid expression vector with luciferase gene. The degree of inhibition correlated with the levels of ODN-triggered cytokines. Finally, intraperitoneal injection of dexamethasone suppressed LPD-induced cytokine production, and led to significantly higher levels of transgene expression on both first and second injection. These studies suggest that mutation of potent CpG motifs in plasmid DNA together with the use of immune suppression agent may represent an effective approach to improve cationic lipid-mediated gene transfer to the lung.

Animals↗

PubMed1999

Carnosine and taurine protect rat cerebellar granular cells from free radical damage.

Carnosine and taurine have been suggested to protect excitable tissues against oxidative stress. We have investigated the protection of cerebellar granule cells (neurons) by these compounds against free radicals generated by kainic acid (KA), and 3-morpholinosydnonimine hydrochloride (SIN-1) treatment. Carnosine decreased free radical levels in KA and SIN-1 treated cells, and increased cell viability. The KA effect, but not that of SIN-1, was dependent on the presence of external Ca2+ ions. Taurine increased cell viability, but did not decrease free radical levels. These results suggest that there are multiple pathways leading to cell death, not all of which involve decreases in intracellular free radical levels, and also indicate that multiple mechanisms of cellular defense exist against oxidative stress.

Animals↗

PubMed1999

Metallothionein expression and nuclear size in benign, borderline, and malignant serous ovarian tumours.

Metallothioneins (MTs) are low-molecular-weight proteins involved in metalloregulatory functions such as cell proliferation, growth, and differentiation. In recent years, MT expression has been linked with carcinogenesis, resistance to cancer therapy, and tumour progression. However, the significance of MT expression in ovarian cancers is at present inadequately documented. In this study, MT immunohistochemistry was performed in 12 benign, 14 borderline, and eight malignant serous tumours of the ovary. The intensity of the immunostaining was evaluated by image analysis. There was a significantly higher number of MT-immunopositive cells in the multilayered epithelial cells of borderline serous tumours (atypical proliferative serous tumours) than in the single layered epithelial cells within the same tumour, and in the single cell layer of benign serous tumours. There was no difference in the expression of MTs in the single layered tumour cells of benign and borderline serous tumours. Significantly higher numbers of MT-immunopositive cells were observed in both the single and the multilayered epithelial cells of serous carcinomas, the highest number being observed in the multiple layers of serous carcinomas. The positively stained malignant tumour cells in both single and multiple layers were larger than the negatively stained cells in benign, borderline, and malignant serous ovarian tumours. There was moderate to intense staining. These findings indicate that there is increased expression of MTs in the progression of malignancy, which could be used as a marker in grading the three groups of ovarian serous tumours and for determining prognosis.

Adult↗

PubMed1999

Single nucleotide polymorphism determination using primer extension and time-of-flight mass spectrometry.

The high frequency of single nucleotide polymorphisms (SNPs) in the human genome makes them a valuable source of genetic markers for identity testing, genome mapping, and medical diagnostics. Conventional technologies for detecting SNPs are laborious and time-consuming, often prohibiting large-scale analysis. A rapid, accurate, and cost-effective method is needed to meet the demands of a high-throughput DNA assay. We demonstrate here that analysis of these genetic markers can now be performed routinely in a rapid, automated, and high-throughput fashion using time-of-flight mass spectrometry and a primer extension assay with a novel cleavable primer. SNP genotyping by mass spectrometry involves detection of single-base extension products of a primer immediately adjacent to the SNP site. Measurement of the mass difference between the SNP primer and the extension peak reveals which nucleotide is present at the polymorphic site. The primer is designed such that its extension products can be purified and chemically released from the primer in an automated format. The reduction in size of the products as a result of this chemical cleavage allows more accurate identification of the polymorphic base, especially in samples from a heterozygotic population. All six possible heterozygotes are resolved unambiguously, including an A/T heterozygote with extension products differing by only 9 Da. Multiplex SNP determination is demonstrated by simultaneously probing multiple SNP sites from a single polymerase chain reaction (PCR) product as well as from multiplexed PCR amplicons. Samples are processed in parallel on a robotic workstation, and analyzed serially in an automated mass spectrometer with analysis times of only a few seconds per sample, making it possible to process thousands of samples per day.

DNA Primers↗

PubMed1999

Immunocytochemical characterization of catecholaminergic neurons in the rat striatum following dopamine-depleting lesions.

It is possible either permanently or transiently to deplete the rat striatum of dopamine. Following such depletions, striatal neurons immunoreactive for tyrosine hydroxylase (TH), aromatic L-amino acid decarboxylase (AADC) or dopamine appear. The presence of dopamine-producing neurons in the striatum has relevance for the treatment of Parkinson's disease, but whether these catecholaminergic phenotypes all produce dopamine is unclear. In the present study we establish that after unilateral 6-hydroxydopamine lesions or methamphetamine administration, striatal TH-immunoreactive neurons differ in size, morphology and location from those that are immunopositive for AADC or dopamine. The TH-positive cells which were localized either to ventral parts of the striatum or to the central and dorsal areas of the caudate-putamen generally have the morphological features of projection neurons, whereas those containing AADC or dopamine were confined to subcallosal positions in the dorsal medial quadrant of the caudate-putamen and resemble small, local-circuit neurons. The fact that AADC-immunoreactive neurons overlap in size, morphology and location with the cells that produce dopamine suggests strongly that this population is dopaminergic. However, the simultaneous appearance of neurons that contain the TH enzyme but clearly do not make dopamine raises questions about the functional role of these cells and the cellular mechanisms responsible for their induction following striatal dopamine loss.

Animals↗

PubMed1999

Fat distribution in HIV-infected patients reporting truncal enlargement quantified by whole-body magnetic resonance imaging.

BACKGROUND: Antiretroviral therapy has improved the prospects for people infected with HIV, but some develop a syndrome of profound body habitus and metabolic alterations that include truncal enlargement. OBJECTIVE: The purpose of this study was to define the body-composition changes associated with this syndrome by using techniques with the power to estimate regional body composition. DESIGN: We compared whole-body and regional skeletal muscle and adipose tissue contents measured by magnetic resonance imaging and dual-energy X-ray absorptiometry (DXA) in 26 HIV-infected patients and 26 matched control subjects. Twelve of the HIV-infected patients had evidence of truncal enlargement. RESULTS: HIV-infected men and women who noted truncal enlargement had similar amounts of skeletal muscle and subcutaneous adipose tissue but greater visceral adipose tissue than HIV-infected patients without truncal enlargement; these values were larger in men (P < 0.001) than in women (P = 0.08). The ratio of visceral to subcutaneous adipose tissue was greater in both men (P < 0.02) and women (P = 0.05) with truncal enlargement. Two subjects with MRI-confirmed visceral adiposity syndrome (VAS) were not taking protease inhibitors. CD4+ lymphocyte counts were higher (P < 0.001) and plasma viral burdens tended to be lower (P = 0.08) in HIV-infected patients with VAS. CONCLUSIONS: There was significantly more visceral adipose tissue in the subgroup of HIV-infected patients with truncal enlargement than in those without this sign. VAS occurs in both men and women, is associated with higher CD4+ lymphocyte counts and lower plasma HIV viral burdens, and is not limited to those receiving protease inhibitor therapy.

Absorptiometry, Photon↗

PubMed1999

Expression of metallothionein and nuclear size in discrimination of malignancy in mucinous ovarian tumors.

Metallothioneins (MTs) are low molecular weight proteins that control cell proliferation via their metalloregulatory function. Several studies in various tumors have shown their influence in determining response to chemotherapy and prognosis. Because there has been no such study pertaining to ovarian tumors, we investigated MT expression and nuclear size in mucinous ovarian neoplasms (12 benign, 6 borderline, and 8 malignant). The percentage of MT-positive stained cells was significantly higher in the borderline than in the benign tumors, but lower than in the malignant tumors. Single layers of cells in the borderline tumors showed mild immunostaining in 50% of the cells and moderate staining in the remaining 50%, while 83.3% of cells within multilayered epithelium showed moderate to strong immunostaining. In the carcinomas, 87.5% of tumors showed moderate to strong staining in single-layered epithelium and moderate to strong staining of all the cells in multilayered epithelium. Morphometry measurements showed that the mean nuclear area of cells in the carcinomas was significantly larger than in the borderline or benign tumors. The nuclear area of cells in the carcinomas with early recurrence or metastasis was also significantly larger than in carcinomas without recurrence or metastasis. It is concluded that MT protein expression and nuclear size are possible markers for the evaluation of the progression of malignancy in mucinous ovarian tumors.

Cell Nucleus↗

PubMed1999

Survival- and death-promoting events after transient cerebral ischemia: phosphorylation of Akt, release of cytochrome C and Activation of caspase-like proteases.

Release of cytochrome c (cyt c) into cytoplasm initiates caspase-mediated apoptosis, whereas activation of Akt kinase by phosphorylation at serine-473 prevents apoptosis in several cell systems. To investigate cell death and cell survival pathways, the authors studied release of cyt c, activation of caspase, and changes in Akt phosphorylation in rat brains subjected to 15 minutes of ischemia followed by varying periods of reperfusion. The authors found by electron microscopic study that a portion of mitochondria was swollen and structurally altered, whereas the cell membrane and nuclei were intact in hippocampal CA1 neurons after 36 hours of reperfusion. In some neurons, the pattern of immunostaining for cyt c changed from a punctuate pattern, likely representing mitochondria, to a more diffuse cytoplasmic localization at 36 and 48 hours of reperfusion as examined by laser-scanning confocal microscopic study. Western blot analysis showed that cyt c was increased in the cytosolic fraction in the hippocampus after 36 and 48 hours of reperfusion. Consistently, caspase-3-like activity was increased in these hippocampal samples. As demonstrated by Western blot using phosphospecific Akt antibody, phosphorylation of Akt at serine-473 in the hippocampal region was highly increased during the first 24 hours but not at 48 hours of reperfusion. The authors conclude that transient cerebral ischemia activates both cell death and cell survival pathways after ischemia. The activation of Akt during the first 24 hours conceivably may be one of the factors responsible for the delay in neuronal death after global ischemia.

Animals↗

PubMed1999

Genomic structure of the rat major AP endonuclease gene (Apex) with an adjacent putative O-sialoglycoprotease gene (Prsmg1/Gcpl1) and a processed Apex pseudogene (Apexp1).

Genomic sequencing and chromosomal assignment of the gene encoding rat APEX nuclease, a multifunctional DNA repair enzyme, were performed. An active Apex gene and a processed pseudogene were isolated from a rat genomic library. The active Apex gene consists of 5 exons and 4 introns spanning 2.1 kb. The putative promoter region of the Apex gene lacks the typical TATA box, but contains CAAT boxes and a CpG island having putative binding sites for several transcription factors, such as Sp1, AP-2, GATA-1 and ATF. A putative O-sialoglycoprotease (a homologue of Pasteurella haemolytica glycoprotease, gcp; abbreviated as Prsmg1/Gcpl1) gene consisting of 11 exons and 10 introns spanning 7.3 kb lies immediately adjacent to the Apex gene in a 5'-to-5' orientation. The Apex gene locus was mapped to rat chromosome 15p12 using in situ hybridization. The processed pseudogene (designated as rat Apexp1) has a nucleotide sequence 87.1% identical to that of the rat Apex cDNA, although several stop codons interrupting the coding sequences and multiple nucleotide deletions were observed. The Apexp1 is located in an inactive LINE sequence. Calculation of nucleotide substitution rates suggests that the immediate, active progenitor of Apexp1 arose 23 million years ago and that the non-functionalization occurred 15 million years ago.

Animals↗

PubMed1999

Efficacy of recombinant methioninase in combination with cisplatin on human colon tumors in nude mice.

The present treatment of colon cancer is based on 5-fluorouracil (5-FU). Despite promising results of combining leucovorin or levamisole with 5-FU, the 5-year survival rate of patients with advanced colon cancer has not increased significantly. Colon tumors in vitro have been shown previously to have an elevated requirement for methionine, suggesting a new therapeutic target. In this study, targeting the methionine dependence of colon tumors is effected by recombinant methioninase (rMETase), alone and in combination with cisplatin (CDDP). In vitro results demonstrated that CDDP and rMETase act synergistically on the human colon cancer cell line SW 620, with a combination index (CI) of 0.45, as well as on the human colon cancer cell line Colo 205 with a CI of 0.7. Human colon cancer lines HCT 15, HT 29, Colo 205, and SW 620 growing in nude mice were treated with rMETase to determine an effective dose for depletion of tumor methionine. rMETase at 15 units/g/day for 5 days depleted tumor methionine in all four tumor types to approximately 30% of untreated control. rMETase alone arrested growth of HCT 15 and HT29 in nude mice for 1 week after treatment termination. Colo 205 and SW 620 were partially arrested by rMETase. However, CDDP in combination with rMETase resulted in tumor regression of Colo 205 and growth arrest of SW 620 in nude mice. The ratio of the treated:control group (T:C) tumor weights for Colo 205 was 8% when CDDP was given on day-5, followed by treatment on days 5-9 with rMETase. This treatment schedule resulted in two of the six animals having no detectable tumor when the experiment was terminated on day 16. SW620 was resistant to CDDP alone and only partially sensitive to rMETase alone. However, when SW 620 was treated with rMETase from days-5 to -9 and CDDP on day-5, tumor growth was arrested. The results demonstrate that rMETase used simultaneously in combination with CDDP had significant antitumor efficacy in colon cancer in vitro and in vivo. The data suggest a novel and promising therapeutic approach by targeting the elevated methionine dependence of colon cancer.

Animals↗

PubMed1999

Treatment of epigastralgia by external application of huweigao at shenque point.

140 cases of epigastralgia were divided into two groups at random. The 100 cases in the treatment group were treated with Huweigao externally applied at Shenque (Ren 8), and the 40 cases in the control group by oral administration of Weinaian capsule. After a one-month treatment, the total symptom-relieving rate and the gastroscopy-proved effective rate were 94.0% and 52.6% respectively in the treatment group, much superior to those in the control group.

Acupuncture Points↗

PubMed1999

[Quantitative detection of Mycobacterium tuberculosis DNA in peripheral blood from patients with pulmonary tuberculosis by AmpliSensor-PCR technique].

OBJECTIVE: To evaluate the clinical value of the quantitative detection of Mycobacterium tuberculosis DNA by Amplisensor-PCR in peripheral blood from patients with pulmonary tuberculosis. METHODS: The model of Mycobacterium tuberculosis DNA in blood was made by QIAamp and AcuPure methods, quantitative detection of Mycobacterium tuberculosis DNA by AmpliSensor-PCR technique and the results were compared with IS6110 single-tube nested PCR (SN-PCR). RESULTS: The peripheral blood from 200 patients with pulmonary tuberculosis were detected respectively by using AmpliSensor-PCR and IS6110 SN-PCR methods. The positive rates of Mycobacterium tuberculosis DNA were 60.5% and 63.5% respectively, and that from 85 patients with non-pulmonary tubeculosis were 4.7%, 8.2%. CONCLUSIONS: AmpliSensor-PCR method showed higher sensitivity and specificity in detecting the Mycobacterium tubeculosis DNA from peripheral blood. The variation of the TB-DNA may be useful in evaluating the prognosis of the patients.

DNA, Bacterial↗

PubMed1999

[Usefulness of CYFRA21-1 as a tumor marker of non-small-cell lung cancer].

OBJECTIVE: To evaluate the clinical usefulness of CYFRA21-1 as a serum tumor marker in diagnosis, evaluation of clinical status and prognosis of patients with non-small-cell lung cancer (NSCLC). METHODS: CYFRA21-1 in 126 serum samples of NSCLC patients was measured by radioimmunoassay. Of the 126 samples, 71 were collected before treatment, 29 at two weeks after operation, and 26 after 15-18 months follow-up. RESULTS: CYFRA21-1 was positive in 49.3% of the NSCLC patients who had not received any treatment. The positive rate was 69.2% for squamous-cell carcinoma, and 25.0% for adenocarcinoma. The serum level of CYFRA21-1 was significantly higher in squamous-cell carcinoma than in adenocarcinoma (P < 0.0001). The serum level of CYFRA21-1 well correlated and increased with TNM staging (P = 0.0001). The level decreased significantly within two weeks after surgical operation in 29 cases (P = 0.0005). On follow up for 15-18 months, no change in CYFRA21-1 level was observed in 16 patients whose disease was stable, while there was significant increase in 10 patients with progressive disease. CONCLUSION: CYFRA21-1 is a soluble fragment of cytokeratin 19 in serum of patients with NSCLC. It can be used as a useful tumor marker of NSCLC.

Adolescent↗

PubMed1999

[Effects of cytokines and umbilical cord blood preserved at 4 degrees C on the growth of CFU-GM and HPP-CFC].

We studied the effects of different cytokine combinations and umbilical cord blood preserved at 4 degrees C for 4 days on the growth of CFU-GM and HPP-CFC. The results showed that the growth of umbilical cord blood CFU-GM was markedly different when various combinations of cytokines were used. After 2 weeks culturing with IL-3 alone or plus GM-CSF, the number of umbilical cord blood CFU-GM was increased when compared with GM-CSF group; upon stimulation with GM-CSF plus IL-3 plus IL-6 plus Epo, a significant increase of umbilical cord blood CFU-GM was seen. After umbilical cord blood being preserved 4 days at 4 degrees C, the number of umbilical cord blood CFU-GM and HPP-CFC was decreased.

Blood Preservation↗

PubMed1999

[Research on anti-thrombosis effect of ethanol extract from beheaded leech (EEBL)].

OBJECTIVE: To study the anti-thrombosis effect of EEBL and its possible mechanism. METHOD: Using a thrombosis model induced by collagen-adrenaline in mice and an artery-vein bypass in rats. The effect of EEBL on erythrocyte membrane and thrombocyte membrane fluidity were measured by fluorescence polarization. RESULT: EEFL inhibited the thrombosis induced by collagen-adrenaline in mice and the thrombosis in artery-vein bypass in rats significantly. EEBL also enhanced in vitro erythrocyte membrane fluidity and thrombocyte membrane fluidity markedly. CONCLUSION: The anti-thrombosis effect of EEBL may possibly be associated with the enhancement of fluidity of erythrocyte membrane and thrombocyte membrane. There exist anti-thrombosis chemical constituents in the body of beheaded leech.

Animals↗

PubMed1999

[Experimental study on antiendotoxin effect of extracts from Artemisia annua L].

OBJECTIVE: To explore the antiendotoxin effect of extracts from Artemisia annua (AA) and qinghaosu (QHS). METHOD: LPO and SOD in chondriosome, ACP in lysosomes, tumor nicrosis factor-alpha(TNF-alpha) and endotoxin in plasma, and P450 concentration in hepatic microsome of rats were determined. Mortality of endotoxemic mice and histomorphology were observed. RESULT: LPO, ACP, endotoxin, TNF-alpha and P450 content were decreased with AA and QHS. SOD activity was increased with AA and QHS. At the same time, mortality was decreased. Histomorphology of lysosomes and chondriosome of rats were protected from endotoxin. CONCLUSION: AA and QHS possess an antiendotoxin effect.

Animals↗

PubMed1999

[Effect of IL-6 on the multiplication of Toxoplasma gondii].

AIM: To observe the effect of IL-6 on the multiplication of Toxoplasma gondii. METHODS: Peritoneal macrophages from C57BL/6 mouse were incubated with 3H-uracil-labelled T. gondii in vitro. RESULTS: Pretreatment (but not post-treatment) of Mphi with IL-6 enhanced T. gondii multiplication in a dose-dependent manner. Pretreatment with IFN gamma resulted in active killing of parasites whereas the addition of IL-6 resulted in a partial reversal of IFN gamma-mediated toxoplasmacidal activity. Combining TNF alpha with IL-6 and IFN gamma pretreatment resulted in restoration of toxoplasmacidal activity. Addition of polyclonal anti-TNF alpha antibodies to IL-6 and IFN gamma pretreatment resulted in enhancement in the IL-6-mediated impairment of IFN gamma function. CONCLUSION: IL-6 could enhance intraperitoneal multiplication of T. gondii and reverse IFN gamma-mediated toxoplasmacidal activity.

Animals↗