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Biomedical subjects

Y Xu

Publications and source records attributed to Y Xu.

At least 919 records · Page 51Linked to original sources
PubMed1996

Estrogen regulates somatostatin receptor subtype 2 messenger ribonucleic acid expression in human breast cancer cells.

Somatostatin (SRIF) and its analogs exhibit antiproliferative effects that are mediated by SRIF receptors (sst) present in responsive normal and neoplastic tissue including breast cancer. However, information regarding regulation of sst gene expression in cancer cells and modulation of SRIF binding is limited. In the present study we have determined the pattern of sst subtype messenger RNA (mRNA) expression in human breast cancer cells. Furthermore, we investigated the effect of 17beta-Estradiol (E2) treatment on steady state levels of sst mRNA by solution hybridization/nuclease protection analysis and on SRIF binding to membranes of treated cells by receptor binding assay. sst2 mRNA was highly expressed in T47D, ZR75-1, and MDA MB231 cells. Transcripts for sst1 were also detected at very low levels in ZR75-1 cells, whereas sst5 mRNA was expressed at low levels in MCF-7 cells. No sst subtype was detected in MDA MB 435s cells. When the estrogen receptor (ER)(+) cell lines T47D and ZR75-1 were cultured in phenol red-free media plus CS-FCS, sst2 mRNA levels decreased by 60-80% compared with complete serum controls. Adding E2 restored sst2 mRNA levels to control in both cell lines. Moreover, the effect of E2 on sst2 gene expression in T47D and ZR75-1 cells was dose- and time-dependent. In contrast, neither culturing in phenol red-free media plus CS-FCS nor E2 influenced sst2 expression in the ER(-) cell line MDA MB231. E2-induced regulation of SRIF binding and sst2 mRNA expression occurred in a parallel manner in T47D cells but were dissociated in ZR75-1 cells. The pure antiestrogen ICI 182 780 inhibited E2-induced sst2 expression in both cell lines. The antiestrogen 4OH tamoxifen showed strong estrogen-like effects on sst2 mRNA expression in T47D cells, while acting as a potent antiestrogen in ZR75-1 cells. Thus, these data suggest that E2 regulates sst2 expression in human breast cancer cell lines through the ER. The human breast cancer cell lines provide a useful model to examine the molecular mechanisms involved in E2 regulation of sst2 expression.

Breast Neoplasms↗
PubMed1996

Molecular cloning and nucleotide sequence of the groEL gene from the alkaliphilic Bacillus sp. strain C-125 and reactivation of thermally inactivated alpha-glucosidase by recombinant GroEL.

The groEL gene of the alkaliphilic Bacillus sp. strain C-125 was cloned in Escherichia coli and sequenced. The groEL gene encoded a polypeptide of 544 amino acids and was preceded by the incomplete groES gene, lacking its 5'-end. The sequence of the derived amino acids was 87.5% identical to that of B. subtilis, 85.4% identical to that of B. stearothemophilus, and 60.9% identical to that of E. coli. The GroEL protein was expressed in E. coli. Purified GroEL protected yeast alpha-glucosidase from irreversible aggregation at a high temperature and the addition of Mg-ATP was essential for reactivation of the alpha-glucosidase. The addition of E. coli GroES increased recovery of the enzyme activity, indicating that C-125 GroEL could function in coordination with E. coli GroES.

Alkalies↗
PubMed1996

Antileukemic activity of recombinant humanized M195-gelonin immunotoxin in nude mice.

A leukemia-selective immunotoxin was constructed by linking recombinant gelonin (rGel), a single chain ribosome inhibitory protein, to recombinant humanized M195 antibody (HuM195), which recognizes the cell-surface protein designated CD33. CD33 is an antigen found on myeloid leukemia blasts as well as myeloid progenitor cells but it is not expressed in detectable amounts on the ultimate hematopoietic progenitor stem cell. Our previous studies indicated that a non-recombinant humanized immunotoxin displayed specific, potent toxicity towards CD33-positive cells but not to CD33-negative cells in vitro. In the current study, a recombinant humanized immunotoxin, HuM195-rGel, was evaluated in vivo in a nude mouse model of human myeloid leukemias. HuM195-rGel was found to target leukemia cells rapidly in vivo and was subsequently internalized into the cells. For trials in vivo, nude mice were injected (ip) with 10(7) log-phase HL60 human leukemia cells 10 days prior to the start of i.p. HuM195-rGel treatments. HuM195-rGel demonstrated significant tumor suppressive activity in this model. While all mice treated with either saline, rGel alone, or HuM195 plus unconjugated rGel (at 10 or 14 days after transplantation) had rapid tumor growth or early deaths, 50% of mice treated with HuM195-rGel failed to develop leukemic tumors for 5 months and the 50% had significantly retarded tumor growth after treatment with HuM195-rGel. Mice treated at later times (28 days after transplantation of leukemia cells) also showed delayed leukemia cell growth, but no cures. These data show that HuM195-rGel can target leukemia cells in vivo and can result in pronounced anti-leukemic effects.

Animals↗
PubMed1996

Stereotactic intratumour irradiation with nuclide for craniopharyngiomas.

OBJECTIVE: Craniopharyngiomas is a kind of intractable tumor in neurosurgery. Since the radical excision is very difficult and occasionally hazardous because of its deep location and close neighbouring to critical cerebral structures, it is necessary to look for a simple and effective method. PATIENTS AND METHODS: Stereotactic intratumour irradiation with instillation of nuclide colloid was performed in 220 patients with craniopharyngiomas (altogether 265 times), of whom, 130 were male and 90 female. Their ages ranged from 5 to 69 years. The syndromes of optic path's impairment were present in all of the patients. CT or MRI scan showed cystic tumour in 125 patients, solid and cystic in 80 and solid in 15. No severe complications and death were related to the operation. RESULTS: 150 patients were followed up for 2 months to 7 years (average 3.5 years). Tumours disappeared in 92 patients (61.4%), decreased dramatically in 20 (13.4%), decreased less than 50% in 19 (12.6%), and increased in 15 (10%); and there were 4 deaths (2.6%). CONCLUSIONS: Stereotactic intratumour irradiation with instillation of nuclide colloid is effective in the patients with craniopharyngiomas. Beta-emitting isotopes (P-32 and Y-90) are the preferred internal radiation source because of their limited penetration of the energy released and the greater ease of handling. A calculated dose of 20 000 rads to the cyst wall is recommended.

Adolescent↗
PubMed1996

[A clinical investigation on scleral reinforcement for treatment of high myopia].

OBJECTIVE: The study was designed to observe the therapeutic effects of scleral reinforcement in treatment of high myopia. METHOD: 86 patients (109 eyes) with high myopia were treated by scleral reinforcement using silicone sponge and heterogeneous sclera. RESULTS: Postoperatively, the naked visual acuity increased in 71.9% of all the eyes in 1-4 years of follow-up. 69.9% of them had a stable axial length, and the volume of blood flow in ophthalmic artery increased in some eyes. CONCLUSION: Scleral reinforcement has therapeutic effects in treatment of high myopia. The surgical techniques applied were mentioned.

Adolescent↗
PubMed1996

Secretory expression of a single-chain insulin precursor in yeast and its conversion into human insulin.

A synthetic single-chain porcine insulin precursor (PIP) gene and an alpha-mating factor leader sequence (alpha MFL) gene obtained by the PCR method are inserted between the promoter and 3'-terminating sequence of the alcohol dehydrogenase gene ADH1 in plasmid pVT102-U to form plasmid pVT102-U/alpha MFL-PIP. The single-chain insulin precursor is expressed and secreted to the culture medium by Saccharomyces cerevisiae transformed by pVT102-U/alpha MFL-PIP. The precursor is purified and converted into human insulin by tryptic transpeptidation. The purified human insulin is fully active and can be crystallized. The overall yield of human insulin is 25 mg per liter of culture medium.

Base Sequence↗
PubMed1996

Gene prediction by pattern recognition and homology search.

This paper presents an algorithm for combining pattern recognition-based exon prediction and database homology search in gene model construction. The goal is to use homologous genes or partial genes existing in the database as reference models while constructing (multiple) gene models from exon candidates predicted by pattern recognition methods. A unified framework for gene modeling is used for genes ranging from situations with strong homology to no homology in the database. To maximally use the homology information available, the algorithm applies homology on three levels: (1) exon candidate evaluation, (2) gene-segment construction with a reference model, and (3) (complete) gene modeling. Preliminary testing has been done on the algorithm. Test results show that (a) perfect gene modeling can be expected when the initial exon predictions are reasonably good and a strong homology exists in the database; (b) homology (not necessarily strong) in general helps improve the accuracy of gene modeling; (c) multiple gene modeling becomes feasible when homology exists in the database for the involved genes.

Algorithms↗
PubMed1996

Inhibition of capacitative Ca2+ entry into cells by farnesylcysteine analogs.

Capacitative Ca2+ influx, which occurs in response to mobilization of intracellular Ca2+ stores, is a general feature of many cell types. Although the mechanism of capacitative Ca2+ entry is not known, evidence suggests the involvement of small G proteins that are prenylated on a cysteine residue near their carboxyl termini. We have investigated the actions of farnesyl-cysteine analogs on capacitative Ca2+ influx. Using human embryonic kidney 293 cells, we found that S-farnesylthioacetic acid, N-acetyl-S-farnesyl-L-cysteine, N-pivaloyl-S-farnesyl-L-cysteine, and N-acetyl-S-gernylgernyl-L-cysteine blocked the activation of capacitative Ca2+ influx, whereas N-benzoyl-S-farnesyl-S-cysteine had no effect on capacitative Ca2+ entry. Inhibition by S-farnesylthioacetic acid was concentration dependent (5-20 microM) and specific for Ca2+ influx through non-voltage-gated Ca2+ channels. A single protein band of 26-28 kDa was labeled specifically with a photoaffinity analog of farnesylcysteine. GTP binding to the photoaffinity-labeled band was demonstrated. These findings suggest, but do not prove, that a prenylated substrate, possibly a small G protein, is linked functionally to capacitative Ca2+ entry in human embryonic kidney 293 cells.

Affinity Labels↗
PubMed1996

Construction of a stable and non-resistant bivalent vaccine candidate strain against Shigella flexneri 2a and Shigella sonnei.

The E. coli cs3 gene coding for CFA/II antigen was site-specifically integrated into the asd gene locus of S. flexneri 2a vaccine strain T32, resulting in the inactivation of the asd gene. Meanwhile, the gene cluster for S. sonnei O antigen was cloned into a non-resistant expression vector pXL378 to construct the plasmid pXL390. By transforming the asd-mutant of the T32 strain with pXL390, the bivalent vaccine candidate strain FS01 against S. flexneri 2a and S. sonnei was finally obtained. Experiments showed that the recombinant plasmid pXL390 was very stable in the asd-T32 strain without the use of any antibiotics; the FS01 strain was genetically stable and expressed two kinds of Shigella LPS-O antigens on the surface without any enhancement of its toxicity. Animal tests demonstrated that FS01 strain, when administered subcutaneously in mice, could provide 100% protection against the intraperitoneal challenges of virulent S. flexneri 2a and S. sonnei.

Animals↗
PubMed1996

Emergency percutaneous transluminal coronary angioplasty in acute myocardial infarction complicated with cardiogenic shock.

OBJECTIVE: To approach the efficacy of emergency percutaneous transluminal coronary angioplasty (PTCA) in Chinese patients with acute myocardial infarction (MI) complicated by cardiogenic shock. METHODS: Twelve patients with cardiogenic shock treated by emergency PTCA in this institution from January 1990 to May 1994 were retrospectively reviewed. There were anterio-lateral MI in 4 cases, inferio-posterial MI in 7, anterial and inferial MI in I, of which triple vessel disease in 4 cases, double vessel disease in 6, single vessel disease in I and left main coronary artery (LM) disease in 1. PTCA was performed under assistance of IABP in 7 cases and of centrifugal pump in 1. Only infarct-related Coronary artery (IRCA) was dilated during acute phase. Direct PTCA was done in 7 cases and rescue PTCA after failure of thrombolytic therapy in 5. RESULTS: PTCA was successful in 11 (91.7%) of the 12 cases, in 1 case with failure of PTCA the IRCA was reperfused by intracoronary thrombolytic therapy. Cardiogenic shock was reverted in 7 (63.6%) of the 11 cases reperfused by PTCA, among whom 6 (54.5%) survived. Four died of irreversible shock after 3 hours-9 days and 1 case with reversed shock died of cardiac rupture after 4 days. During a period of 13-55 months follow-up, long-term survivals were obtained in 4 cases. CONCLUSIONS: Emergency PTCA can achieve a high success rate and significantly decrease the mortality rate to less than 50% in Chinese patients with acute MI complicated with cardiogenic shock. The patients tolerate the PTCA procedure very well under the assistance of intra-aortic balloon counterpulsation (IABP) even in very severe condition.

Aged↗
PubMed1996

Re-evaluation of the mechanism and treatment of angina decubitus.

30 patients with angina decubitus (AD) were studied during hospitalization. These patients were found to have severe coronary artery obstructive lesions and an increase of myocardial oxygen consumption (MOC) before the onset to AD, indicating that AD belongs to the category of effort angina. 18 patients were investigated by continuous hemodynamic monitoring. Three patients had significant increase in pulmonary artery diastolic pressure (PADP) before the onset. In the other 15 patients, PADP increased slightly in 12 and remained unchanged in 3 cases before the onset. Left ventriculography showed ejection fraction (EF) > 45% in 25 of the 27 patients. These results indicate that left ventricular (LV) systolic dysfunction is not a major factor in the pathogenesis of AD. The patients with LVEDP > 12 mmHg constituted 60% of 25 patients with EF > 45%, suggesting that these patients had obvious LV diastolic dysfunction, which may be the major factor in the pathogenesis of AD. According to the results of our treatment, beta blockers may be used as the major form of treatment in the patients with AD.

Adult↗
PubMed1996

[A study on acute multiple sclerosis].

With the purpose of investigating the clinicopathological changes and the criterion for differential diagnosis, ten cases of Acute multiple sclerosis (AMS) were analysed. The data suggested that its clinical course was an acute neurologic event characterized by psychic syndrome, paralysis and incontinence of bowel movement and urination. Pathologically, the demyelination lesion consisted of three patterns, i.e.: vascullar or spongy lesions, shadow plaques and liquefaction or necrosis. One of the above forms could exist individually or coexist with the others. The accurate diagnosis was made only after autopsy. Criterion for the differential diagnosis between AMS and ADEM were discussed.

Acute Disease↗
PubMed1996

Spike waves and synaptic ultrastructure in human epileptic brains.

OBJECTIVE: To find morphological changes of synapses related to the spike discharge by observation on ultrastructures of the EEG spike foci of cerebral cortexes. MATERIAL AND METHODS: The cerebral cortexes were obtained surgically from the EEG spike (recorded by flaky silver electrodes on the surface of cortexes) foci and nonspike areas within the limits of the brain tissue that would be removed in 20 cases of human epilepsy, and were processed for transmission electron microscopic (TEM) observation. RESULTS: In the spike foci, presynaptic terminals of axospinal asymmetric synapses were obviously swollen but postsynaptic spines were relatively unaffected. In these synapses, the synaptic vesicles remarkably decreased in number and accumulated predominantly at the presynaptic membranes or aggregated. Similar changes were observed in the presynaptic terminals of the axospinal asymmetric synapses in the nonspike areas but were of milder degree than in the spike foci. CONCLUSION: Axospinal asymmetric synapses may release a large quantity of excitatory neurotransmitters, which may result in epileptic abnormal electric activities during seizure.

Adolescent↗
PubMed1996

[Acute toxicity and anti-inflammatory effect of processed products of gamboge].

The acute toxicity and anti-inflammatory effect of processed and raw Gamboge were compared. The results showed that the acute toxicity of processed Gamboge was less than that of the raw one, while both had significant anti-inflammatory effect alike. Among the differently processed products, those boiled with lotus leaf juice and steamed by high pressure were better.

Animals↗
PubMed1996

Left ventricular diastolic dysfunction in patients with angina decubitus.

OBJECTIVE: To investigate the relationship between left ventricular diastolic dysfunction and episodes of angina decubitus. METHODS: The study population consisted of three groups, groups I (20 controls) had no cardiovascular diseases. Group II (20 patients) had coronary artery disease (CAD) without angina decubitus. Group III (24 cases with ejection fraction (EF) > 45%) were selected from 26 patients with angina decubitus. RESULTS: Left ventriculography (LVG) showed that left ventricular (LV) first 1/3 filling fraction (1/3FF) was significantly reduced in groups III as compared with groups II and I (P < 0.01). Left ventricular end-diastolic pressure (LVEDP) significantly increased in patients with angina decubitus after LVG as compared with that before LVG (P < 0.01). However, there were no statistically differences in LVEDP, before and after LVG in both groups II and I. CONCLUSIONS: Patients with angina decubitus have abnormalities of LV diastolic filling and decrease in LV compliance.

Adult↗