Biomedical subjects

Min Liu

Publications and source records attributed to Min Liu.

At least 127 records · Page 7Linked to original sources

PubMed2004

Diurnal changes in intestinal apolipoprotein A-IV and its relation to food intake and corticosterone in rats.

To further investigate the role of intestinal aplipoprotein A-IV (apo A-IV) in the management of daily food intake, we examined the diurnal patterns in apo A-IV gene and protein expression in freely feeding (FF) and food-restricted (FR; food provided 4 h daily for 4 wk) rats that were killed at 3-h intervals throughout the 24-h diurnal cycle. In FF rats, the intestinal apo A-IV mRNA and protein levels showed a circadian rhythm concomitant with the feeding pattern. The daily pattern of fluctuation of apo A-IV, however, was altered in FR rats, which had a marked increase in intestinal apo A-IV levels during the 4-h feeding period of light phase. In both FF and FR rats, increased plasma corticosterone (Cort) levels temporally coincided with the increasing phase of intestinal apo A-IV mRNA and protein expression. Depletion of Cort by adrenalectomy abolished the diurnal rhythm by decreasing the apo A-IV expression during the dark period but did not change the feeding rhythm. Exposure of adrenalectomized rats to consistent Cort level (50-mg continuous release Cort pellet) resulted in fixed apo A-IV levels throughout the day. These results indicate that intestinal apo A-IV exhibits a diurnal rhythm, which can be regulated by endogenous Cort independently of the light-dark cue. The fact that intestinal apo A-IV levels were consistent with the food intake during the normal diurnal cycle as well as during the cycle of 4-h feeding each day suggests that intestinal apo A-IV is involved in the regulation of daily food intake.

Animals↗

PubMed2004

Separation of polyethylene glycols and their amino-substituted derivatives by high-performance gel filtration chromatography at low ionic strength with refractive index detection.

The chromatographic analysis of polyethylene glycols (PEG) and their amino-substituted derivatives, with an average molecular mass of 2000 and 3350 is described. The PEG derivatives were perfectly separated by TSK-GEL G4000PW(XL) column, which was widely used in high-performance size-exclusion chromatography (SEC), at low ionic strength with refractive index detection. It was shown that ion-exchange interactions were mainly involved in the retention mechanism of these compounds on TSK-GEL G4000PW(XL) column, since retention volume decreased when salt concentration were added to the mobile phase and varied with the pH of the eluent. Additionally, size exclusion for PEG chains plays a role. Organic modifiers also had effect on chromatographic behaviors of PEG compounds.

Amines↗

PubMed2004

Specific inhibition effects of N-pentafluorobenzyl-1-deoxynojirimycin on human CD4+ T cells.

We first synthesized N-pentafluorobenzyl-1-deoxynojirimycin (5F-DNM), one new derivative of 1-deoxynojirimycin (DNM). Effects on human peripheral blood mononuclear cells (PMBC) and secretion of cytokines from human PBMC by 5F-DNM were investigated. It was first found that 5F-DNM remarkably inhibited the secretion of interleukin-4 (IL-4) and had a specific inhibition on the expression of CD4 molecules. 5F-DNM, much less toxic than cyclosporin A, might be used as a new candidate of immunosuppressant for specifically treating Th2-mediated immune diseases.

1-Deoxynojirimycin↗

PubMed2004

Preparation and characterization of a p-tert-butyl-calix[6]-1,4-benzocrown-4-bonded silica gel stationary phase for liquid chromatography.

A p-tert-butyl-calix[6]-1,4-benzocrown-4-bonded silica gel stationary phase (CR6BS) was first prepared via 3-glycidoxypropyltrimethoxysilane as coupling reagent for high performance liquid chromatography. The structure of the new stationary phase was characterized by diffuse reflectance infrared fourier transform spectroscopy (DRIFT), elemental analysis and thermal analysis. The chromatographic performance of the bonded-stationary phase was evaluated by using neutral, acidic and basic solutes as probes. Meanwhile, comparative study of the new stationary phase with a p-tert-butyl-calix[6]arene-bonded silica gel stationary phase (C6BS, the parent) and ODS was done under the same chromatographic conditions. The results show that the new stationary phase has an excellent reversed-phase property, which is similar to C6BS and ODS. However, the selectivities for some aromatic compounds are different from the parent phase (C6BS) and ODS, especially the latter. In one hand, as hybrid of calixarene and crown ether, CR6BS with the oxygen atoms of ether-bridge can provide the complexation sites for the solutes, lacking of C6BS. On the other hand, the rigid conformation of CR6BS may be responsible to the different performance partially. CR6BS exhibits high selectivity in the separation of alkylated aromatics from their parents as compared with C6BS.

Aniline Compounds↗

PubMed2004

Transactivating effect of hepatitis C virus core protein: a suppression subtractive hybridization study.

AIM: To investigate the transactivating effect of hepatitis C virus (HCV) core protein and to screen genes transactivated by HCV core protein. METHODS: pcDNA3.1(-)-core containing full-length HCV core gene was constructed by insertion of HCV core gene into EcoRI/BamHI site. HepG2 cells were cotransfected with pcDNA3.1(-)-core and pSV-lacZ. After 48 h, cells were collected and detected for the expression of beta-gal by an enzyme-linked immunosorbent assay (ELISA) kit. HepG2 cells were transiently transfected with pcDNA3.1(-)-core using Lipofectamine reagent. Cells were collected and total mRNA was isolated. A subtracted cDNA library was generated and constructed into a pGEM-Teasy vector. The library was amplified with E. coli strain JM109. The cDNAs were sequenced and analyzed in GenBank with BLAST search after polymerase chain reaction (PCR). RESULTS: The core mRNA and protein could be detected in HepG2 cell lysate which was transfected by the pcDNA3.1(-)-core. The activity of beta-galactosidase in HepG2 cells transfected by the pcDNA3.1(-)-core was 5.4 times higher than that of HepG2 cells transfected by control plasmid. The subtractive library of genes transactivated by HCV core protein was constructed successfully. The amplified library contained 233 positive clones. Colony PCR showed that 213 clones contained 100-1 000 bp inserts. Sequence analysis was performed in 63 clones. Six of the sequences were unknown genes. The full length sequences were obtained with bioinformatics method, accepted by GenBank. It was suggested that six novel cDNA sequences might be target genes transactivated by HCV core protein. CONCLUSION: The core protein of HCV has transactivating effects on SV40 early promoter/enhancer. A total of 63 clones from cDNA library were randomly chosen and sequenced. Using the BLAST program at the National Center for Biotechnology Information, six of the sequences were unknown genes. The other 57 sequences were highly similar to known genes.

Gene Expression Regulation, Viral↗

PubMed2004

Thrombin and lysophosphatidic acid receptors utilize distinct rhoGEFs in prostate cancer cells.

Thrombin and lysophosphatidic acid (LPA) receptors play important roles in vascular biology, development, and cancer. These receptors activate rho via G(12/13) family heterotrimeric G proteins, which are known to directly activate three distinct rho guanine nucleotide exchange factors (rhoGEFs) that contain a regulator of G protein signaling (RGS) domain (RGS-rhoGEFs). However, it is not known which, if any, of these RGS-rhoGEFs (LARG (leukemia-associated rhoGEF), p115rhoGEF, or PDZrhoGEF) plays a role in G protein-coupled receptor-stimulated rho signaling. Using oligonucleotide small interfering RNAs that suppress specific RGS-rhoGEF expression, we show that thrombin receptor stimulation of rho is primarily mediated by LARG in HEK293T and PC-3 prostate cancer cell lines. In contrast, the LPA-stimulated rho response in PC-3 cells is dependent on PDZrhoGEF expression. Suppression of p115rhoGEF had no effect. Thus different rhoGEFs (LARG and PDZrhoGEF) mediate downstream rho signaling by the thrombin and LPA receptors.

Cell Line, Tumor↗

PubMed2004

Obesity induced by a high-fat diet downregulates apolipoprotein A-IV gene expression in rat hypothalamus.

Apolipoprotein A-IV (apo A-IV) is an anorectic protein produced in the intestine and brain that has been proposed as a satiety signal. To determine whether diet-induced obesity alters apo A-IV gene expression in the intestine and hypothalamus, rats were fed a high-fat (HF), low-fat (LF), or standard chow (CHOW) diet for 2, 4, 6, 8, or 10 wk. Rats fed the HF diet had significantly greater body weights than rats given the LF and CHOW diets. Intestinal and plasma apo A-IV levels were comparable across dietary groups and time. LF and CHOW rats had comparable hypothalamic apo A-IV mRNA across the course of the experiment. However, HF rats had a slow and progressive diminution in hypothalamic apo A-IV mRNA over time that became significantly lower than that of LF or CHOW rats by 10 wk. Intragastric infusion of lipid emulsion to animals that were fasted overnight significantly stimulated hypothalamic apo A-IV mRNA in LF and CHOW rats but had no effect in HF rats. These results demonstrate that chronic consumption of a HF diet significantly reduces apo A-IV mRNA levels and the response of apo A-IV gene expression to dietary lipids in the hypothalamus. This raises the possibility that dysregulation of hypothalamic apo A-IV could contribute to diet-induced obesity.

Adaptation, Physiological↗

PubMed2004

Transcriptional regulation by the estrogen receptor of antioxidative stress enzymes and its functional implications.

We previously reported that antiestrogen-liganded estrogen receptor beta (ERbeta) transcriptionally activates the major detoxifying enzyme quinone reductase (QR) (NAD(P)H:quinone oxidoreductase). Our studies also indicate that upregulation of QR, either by overexpression or induction by tamoxifen, can protect breast cells against oxidative DNA damage caused by estrogen metabolites. We now report on the upregulation of glutathione S-transferases Pi (GST-Pi) and gamma-glutamylcysteine synthetase heavy subunit (GCSh) expression by antiestrogens. Studies indicate the regulation of GST-Pi and GCSh transcriptional activity by ER. While ER regulation is mediated by an electrophile response element (EpRE), we identified mechanistic differences in the involvement of other transcription factors. Regardless of these differences, ER beta-mediated regulation of GST-Pi and GCSh point towards an important role for ER beta in cellular protection against oxidative stress. A protective role is supported by our observation of inhibition of estrogen-induced DNA damage upon upregulation of GST-Pi and GCSh expression.

Antioxidants↗

PubMed2004

Diurnal rhythm of apolipoprotein A-IV in rat hypothalamus and its relation to food intake and corticosterone.

Apolipoprotein A-IV (apo A-IV) is a satiety protein synthesized in the small intestine and hypothalamus. To further understand the roles of central apo A-IV in the management of daily food intake, we have examined the diurnal patterns of hypothalamic apo A-IV gene and protein expression in freely feeding and food-restricted (food provided 4 h daily between 1000 h and 1400 h) rats. In freely feeding rats, the hypothalamic apo A-IV mRNA and protein levels fluctuated, with high levels during the light phase, peaking at 0900 h (3 h after lights on), and low levels during the dark phase, with a nadir at 2100 h (3 h after lights off). The daily patterns of the fluctuation, however, were altered in food-restricted rats, which had a marked decrease in hypothalamic apo A-IV mRNA and protein levels during the 4 h-feeding period of the light phase. Although corticosterone (CORT) secretion temporally coincided with the decreasing phase of apo A-IV in the hypothalamus, depletion of CORT by adrenalectomy significantly decreased, rather than increased, hypothalamic apo A-IV mRNA and protein levels. These results indicate that the diurnal expression of hypothalamic apo A-IV is regulated by factors other than the circulating CORT, for example, the reduced food intake and body weight in adrenalectomized animals. The fact that hypothalamic apo A-IV level and food intake were inversely related during the normal diurnal cycle as well as in the period of restricted feeding suggests that hypothalamic apo A-IV is involved in the regulation of daily food intake.

Adrenalectomy↗

PubMed2004

Growth arrest and apoptosis of human hepatocellular carcinoma cells induced by hexamethylene bisacetamide.

AIM: To investigate the cellular effects of hybrid polar compound hexamethylene bisacetamide (HMBA) on the growth and apoptosis of human hepatocellular carcinoma cells and to provide the molecular mechanism for potential application of HMBA in the treatment of liver cancer. METHODS: Effects of HMBA on the growth of human hepatocellular carcinoma SMMC-7721 cells were assayed by MTT chronometry. Apoptosis induced by HMBA was detected by phase-contrast microscopy, flow cytometry, propidium iodide staining and immunocytochemical analysis. RESULTS: The growth of SMMC-7721 cells was significantly inhibited by HMBA, and the growth inhibitory rate was 51.1%, 62.6%, 68.7% and 73.9% respectively after treatment with 5.0, 7.5, 10.0 and 12.5 mmol/L of HMBA. In the cells treated with 10 mmol/L of HMBA for 72 h, the population of cells at sub-G(1) phase significantly increased, and the apoptotic bodies and condensed nuclei were detected. Moreover, treatment of SMMC-7721 cells with 10 mmol/L of HMBA down-regulated the expression of Bcl-2 anti-apoptotic protein, while slightly up-regulated the level of pro-apoptotic protein Bax. CONCLUSION: Treatment with 10.0 mmol/L of HMBA can significantly inhibit the growth and induce apoptosis of human hepatocellular carcinoma SMMC-7721 cells by decreasing the ratio of Bcl-2 to Bax.

Acetamides↗

PubMed2004

Ingested fat and satiety.

Apolipoprotein A-IV (apo A-IV) is secreted by the intestine associated with chylomicron. Intestinal apo A-IV synthesis is stimulated by fat absorption, probably mediated by chylomicron formation. The stimulation of apo A-IV synthesis in the jejunum and ileum is attenuated by intravenous leptin infusion. Intestinal apo A-IV synthesis is also stimulated by a factor from the ileum, probably peptide tyrosine-tyrosine (PYY), which has been demonstrated to affect satiety. Apo A-IV has been proposed to physiologically control food intake, and this inhibitory effect is centrally mediated. Recently, apo A-IV was demonstrated in the hypothalamus. The hypothalamic apo A-IV level was reduced by food deprivation and restored by lipid feeding. Intracerebroventricular administration of apo A-IV antiserum stimulated feeding and decreased the hypothalamic apo A-IV mRNA level, implying that feeding is normally limited by endogenous apo A-IV. Central administration of neuropeptide Y (NPY) significantly increased hypothalamic apo A-IV mRNA levels in a dose-dependent manner. The stimulation of intestinal synthesis and secretion of apo A-IV by lipid absorption are rapid; thus, apo A-IV is capable of short-term regulation of food intake. Evidence also suggests apo A-IV's involvement in long-term regulation of food intake and bodyweight. The chronic ingestion of high fat blunts the intestinal apo A-IV response to lipid feeding and may therefore explain why chronic intake of high fat predisposes animals and humans to obesity.

Animals↗

PubMed2004

Ribozyme- and siRNA-mediated suppression of RGS-containing RhoGEF proteins.

Given recent efforts to determine the sequence information on thousands of genes in the human genome, the current challenge is to identify the functions of these genes, including those encoding the regulator of G-protein signaling protein gene superfamily, and to establish their roles in particular signaling pathways in a native system. Increasingly, reverse genetic approaches are being used to address these questions. This article compares two powerful approaches [ribozyme and "short interfering" RNA (siRNA) techniques] under identical conditions for the first report on the suppression of endogenous RGS domain-containing RhoGEFs. The siRNA technique was found to be much more potent than ribozyme targeting at the same mRNA site of RGS-RhoGEFs. Also, the three siRNAs targeting LARG, PDZ-RhoGEF, and p115-RhoGEF are able to discriminate the closely related sequences within this RGS-RhoGEF gene family.

Amino Acid Sequence↗

PubMed2004

Development of a fluorescent high throughput assay for tau aggregation.

A high throughput assay for measuring tau aggregation using fluorescent resonance energy transfer (FRET) is described. Full-length recombinant tau labeled with Cy3 or Cy5 dye is used as ligand, and the induction of aggregation is accomplished by the addition of arachidonic acid. In the presence of this fatty acid, tau aggregation is measured by FRET in a 384-well format. The nature of tau aggregation is further characterized by competition with unlabeled tau and cross-linking experiments. It is concluded that the FRET observed under the experimental condition is due to the accumulation of tau dimers and tetramers. A model for tau aggregation is presented. The performance of this assay in a high throughput format is demonstrated and can be used to identify inhibitors of tau aggregation.

Arachidonic Acid↗

PubMed2004

The fate of glomerular mesangial IgA deposition in the donated kidney after allograft transplantation.

OBJECTIVE: To investigate the fate of the mesangial IgA deposits in the donor kidney after allograft transplantation. METHODOLOGY: Routine pre-transplant cadaveric donor kidney biopsy and repeated renal biopsies were performed at months 1, 3, and 6 after renal transplantation. The patients, 342 in number, were divided into IgA positive deposition kidney group (group A, n = 83) and non-IgA deposition kidney group (group B, n = 259). There were no significant differences between the two groups' sex, age, time of hemodialysis, warm ischemia time, cold ischemia time, complement-dependent cytotoxicity, level of panel-reactive assay, and the distribution of original disease. RESULTS: Recipients in group A received donor kidney with glomerular mesangial proliferation and marked diffuse granular IgA deposition. All of them showed edema, nephrotic range protienuria, microhematuria, hypoalbuminemia, hypertension, and delayed graft function. Borderline change was higher in group A than in group B, 37.3 and 16.2% (p < 0.001), respectively. Acute allograft rejection was higher in group A than in group B, 31.3 and 19.3% (p < 0.001), respectively. The glomerular mesangial IgA deposits gradually disappeared from the mesangial regions in grafts of acute rejection. Graft survival in both groups was not significant, being 93.8 and 95.6% in 1 yr, and 86.7 and 88.3% in 3 yr. CONCLUSION: Clinical features of the recipients which received from donor kidney with glomerular mesangial proliferation and marked diffuse granular IgA deposition: edema, proteinuria, microhematuria, hypoalbuminemia, hypertension, and delayed graft function. The presence of IgA deposits on donated kidney, by a possible increase of the immunogenicity of these kidneys, might be a cause of increased rejection. There were no significant differences between the two groups on long-term allograft survival.

Adult↗

PubMed2004

Gastrointestinal satiety signals IV. Apolipoprotein A-IV.

The focus of this article is to review evidence that apolipoprotein A-IV (apo A-IV) acts as a satiety factor. Additionally, information regarding the general involvement of apo A-IV in the regulation of food intake and body weight is stated. Apo A-IV is a glycoprotein synthesized by the human intestine. In rodents, both the small intestine and liver secrete apo A-IV, but the small intestine is the major organ responsible for circulating apo A-IV. There is now solid evidence that the hypothalamus, especially the arcuate nucleus, is another active site of apo A-IV expression. Intestinal apo A-IV synthesis is markedly stimulated by fat absorption and does not appear to be mediated by the uptake or reesterification of fatty acids to form triglycerides. Rather, the local formation of chylomicrons acts as a signal for the induction of intestinal apo A-IV synthesis. Intestinal apo A-IV synthesis is also enhanced by a factor from the ileum, probably peptide tyrosine-tyrosine (PYY). The inhibition of food intake by apo A-IV is mediated centrally. The stimulation of intestinal synthesis and secretion of apo A-IV by lipid absorption are rapid; thus apo A-IV likely plays a role in the short-term regulation of food intake. Other evidence suggests that apo A-IV may also be involved in the long-term regulation of food intake and body weight, as it is regulated by both leptin and insulin. Chronic ingestion of a high-fat diet blunts the intestinal as well as the hypothalamic apo A-IV response to lipid feeding. It also suppresses apo A-IV gene expression in the hypothalamus. Whereas it is tempting to speculate that apo A-IV may play a role in diet-induced obesity, we believe the confirmation of such a proposal awaits further experimental evidence.

Animals↗

PubMed2004

Preparation and characterization of a new p-tert-butyl-calix[8]arene-bonded stationary phase for high-performance liquid chromatography.

A new p-tert-butyl-calix[8]arene-bonded silica gel stationary phase (CABS) was prepared via 3-glycidoxypropyltrimethoxysilane as a coupling reagent for HPLC. Its structure was characterized by diffuse reflectance infrared Fourier transform spectroscopy (DRIFT), elemental analysis and thermal analysis. The chromatographic performance of new packing was evaluated by using basic, acidic and neutral aromatic compounds as probes compared with conventional ODS. The results show that the new stationary phase has an excellent reversed-phase property and high selectivities for substituted aromatics compared with ODS, because CABS can provide various sites for the analytes, such as hydrogen-bonding interactions, pi-pi interactions, and inclusion complex, besides hydrophobic interactions.

Journal Article↗

PubMed2004

[Survey of type 1 diabetes incidence in children from 1997 to 2000 in Beijing area].

OBJECTIVE: The incidence of type 1 diabetes varied in different countries, different nations and different regions. This survey was conducted to clarify the incidence of type 1 diabetes of children in Beijing area between 1997 and 2000, to compare and analyze the difference in incidence of type 1 diabetes between the 2 periods of 1988 - 1996 and 1997 - 2000. METHOD: According to the criteria of WHO Diabetes Mondial (DIAMOND), data were collected from all the children younger than 15 years of age in Beijing area who had the onset of type 1 diabetes during Jan. 1st, 1997 to Dec. 31st, 2000. Using the capture-recapture methods, 95% confidence intervals of incidence were calculated with Poisson's distribution formula. The significance of differences was tested with Chi-square method. RESULTS: The incidences of type 1 diabetes during 1997 - 2000 were around 0.76/100 000 to 1.21/100 000. The average yearly incidence was 1.014/100 000 (95% confidence interval was 0.98/100 000 - 1.16/100 000). There was no significant difference in the incidence between 1988 - 1996 and 1997 - 2000, and it showed the same result when the incidences were adjusted by age according to the Chinese population census in 2000 (The incidence was 0.83/100 000 in 1988 - 1996 and 0.86/100 000 in 1997 - 2000, respectively). The incidence was higher in 10 - 14 year-old group than the younger groups (P = 0.002). There was no significant difference between male and female groups, either. CONCLUSIONS: No significant difference was found between the periods 1988 - 1996 and 1997 - 2000 when the average yearly incidence of type 1 diabetes of children in Beijing was compared. These results were different from the other countries' reports that the incidence of type 1 diabetes was increasing by 3% - 5% per annum. There was no significant difference between male and female groups either and there was a higher incidence of type 1 diabetes in 10 - 14 yr group than the other groups in 1997 - 2000. Although the life-style of Beijing people changed a lot, it didn't affect the incidence of type 1 diabetes in children in this area. But since many people migrated to Beijing from other parts of the country, the changes in constitutive proportions of population might have some impacts on the results of the survey.

Age Factors↗

PubMed2004

[An early comprehensive prevention and treatment of sepsis in severely burned patients with delayed fluid resuscitation].

OBJECTIVE: To study an early comprehensive prevention and treatment of sepsis in severely burned patients with delayed fluid resuscitation. METHODS: From January 1990 to December 2001, 72 cases of patients with delayed fluid resuscitation were admitted to our burn department. Two different periods were divided and analyzed retrospectively. The first period was from January 1990 to December 2001 and the span of the second period was from January 1995 to December 2001. RESULTS: (1)The mortality rate and incidence of sepsis in the second period (6.5 percent and 17.4 percent) were significantly lower than those of the first period (23.0 percent and 57.7 percent, P<0.05 and P<0.01). (2)The time of wound healing in the second period was (1.9+/-0.9) hours, it was lower than that of the first period (6.6+/-2.5) hours. (3)The serum contents of tumor necrosis factor (TNF) and blood lactic acid (BLA) were increased at all times in two periods and were markedly increased in the first period (all P<0.01). CONCLUSION: Our data demonstrated that measures adopted in the second period for patients with delayed fluid resuscitation, including early excision, early rapid adequate resuscitation, early enteral feeding, increased immunity function, early applying antibactials, xenotransfusion of ultraviolet-irradiated blood, application of recombinant human-growth factor (rh-GH), epidermal growth factor (EGF), basic fibroblast growth factor (bFGF), are beneficial to the prevention and treatment of sepsis in severely burned patients with delayed fluid resuscitation.

Adult↗