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Biomedical subjects

Q Mei

Publications and source records attributed to Q Mei.

At least 37 records · Page 2Linked to original sources
PubMed1999

Local downregulation of enterochromaffin-like cell histamine formation in ulcer healing: a study in rats.

BACKGROUND AND AIMS: Although enterochromaffin-like (ECL) cells are the major source of histamine for the regulation of gastric acid secretion, their role in ulcer healing has not been fully investigated. The present study aimed to investigate changes in ECL cell components as well as markers for somatostatin cells, parietal cells and macrophages during the healing of experimental ulcers in rats. METHODS: Standardised ulcer was induced directly in the rat gastric mucosa by brief application of acetic acid. At different time intervals following ulcer induction (1-15 days), histamine, histidine decarboxylase (HDC), chromogranin A, pancreastatin, vesicular monoamine transporter 2 (VMAT-2), H-K-ATPase, somatostatin as well as ED1 and ED2 (macrophage markers) were localised by immunocytochemistry. ED1- and histamine-immunoreactive cells were counted at different time points. HDC- and VMAT-2-immunoreactive cells were demonstrated by double staining and counted. The mRNA of HDC, chromogranin A and somatostatin was demonstrated by in situ hybridisation and quantitated by computerised image analysis. RESULTS: HDC immunoreactivity and mRNA were markedly reduced in the ECL cells at the ulcer margin from day 1 following ulcer induction and onwards; after day 5 HDC immunoreactivity and mRNA rose gradually and had almost normalised by day 15. This local and transient downregulation of HDC was accompanied by a similar decrease in ECL cell histamine. In contrast to HDC and histamine, other ECL cell components (chromogranin A, pancreastatin, VMAT-2) as well as somatostatin and H-K ATPase were still demonstrable at the ulcer margin and displayed no major changes at any time point studied. Of the macrophage markers, ED1, but not ED2, could be identified at the ulcer margin, and the number of ED1-immunoreactive cells was high in the ulcer margin from day 1 to day 5 after ulcer induction. The increase in ED1-positive cells and the decrease in HDC-expressing cells were coincident in time and localisation. CONCLUSION: The present results revealed a local and transient downregulation of HDC in the ECL cells at the ulcer margin. This may account for the decrease in ECL cell histamine observed. The local infiltration of macrophages into the ulcer margin suggests that inflammatory mediators are involved in the local suppression of ECL cell activity during ulcer healing.

Acetic Acid↗
PubMed1999

Role of a potent inhibitory monoclonal antibody to cytochrome P-450 3A4 in assessment of human drug metabolism.

Cytochrome P-450 (CYP) 3A4 is an inordinately important CYP enzyme that catalyzes the metabolism of a vast array of clinically used drugs. Microsomal proteins of Spodoptera frugiperda (Sf21) insect cells infected with recombinant baculoviruses encoding CYP3A4 cDNA were used to immunize mice and to develop a monoclonal antibody (mAb(3A4a)) specific to CYP3A4 through the use of hybridoma technology. The mAb is both a potent inhibitor and a strong binder of CYP3A4. One and 5 microl (0.5 and 2.5 microM IgG(2a)) of the mAb mouse ascites in 1-ml incubation containing 20 pmol of CYP3A4 strongly inhibited the testosterone 6beta-hydroxylation by 95 and 99%, respectively, and, to a lesser extent, cross-inhibited CYP3A5 and CYP3A7 activity. mAb(3A4a) exhibited no cross-reactivity with any of the other recombinant human CYP isoforms (CYP1A1, CYP1A2, CYP2A6, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, and CYP2E1) in the course of CYP reaction phenotyping and Western immunoblot analyses. The potency of mAb-induced inhibition is insensitive to substrate concentration in human liver microsomes. Therefore, mAb(3A4a) was used to assess the quantitative role of CYP3A4/5 to the metabolism of testosterone and diazepam in five human liver microsomes. The results showed that CYP3A4 and CYP3A5 contribute >95% to both testosterone 6beta-hydroxylation and diazepam 3-hydroxylation and 52 to 73% to diazepam N-demethylation, respectively. In addition, mAb(3A4a) significantly inhibited testosterone 6beta-hydroxylase activity in rhesus monkey liver microsomes to a degree equal to that observed with CYP3A4 in human liver microsomes. By comparison, no inhibition of testosterone 6beta-hydroxylase activity was observed in the presence of dog, rat, and mouse liver microsomes. The selectivity of ketoconazole, a chemical inhibitor of CYP3A4, was probed with mAb(3A4a) and was shown to be highly concentration dependent in the diazepam N-demethylation by human liver microsomes. The results demonstrate that inhibitory and immunoblotting mAb(3A4a) can offer a precise and useful tool for quantitative identification of CYP3A4/5 in the metabolism of drugs in clinical use and drugs in development.

Adult↗
PubMed1999

[Determination of 5-hydroxytryptamine(5-HT) secretion from activated platelets by high performance liquid chromatography/electrochemical detector].

A method of determination of 5-HT secretion from activated platelets by HPLC/ECD was established. Spherisorb C18 column of 4.6 mm i.d. x 100 mm was used in this experiment. The CV was 4.65%, The linear range was 0.002 5-1 mg/L. This method has the advantages of high speed, high sensitivity; specificity, of requiring a minimum of preparation of samples and of relatively low cost for instrumentation and reagents. It could reflect the activated situation of platelet induced by weak activator and be used in other biological sample.

Blood Platelets↗
PubMed1998

Erythroid Krüppel-like factor is essential for beta-globin gene expression even in absence of gene competition, but is not sufficient to induce the switch from gamma-globin to beta-globin gene expression.

Different genes in the beta-like globin locus are expressed at specific times during development. This is controlled, in part, by competition between the genes for activation by the locus control region. In mice, gene inactivation of the erythroid Krüppel-like factor (EKLF) transcription factor results in a lethal anemia due to a specific and substantial decrease in expression of the fetal/adult-stage-specific beta-globin gene. In transgenic mice carrying the complete human beta-globin locus, EKLF ablation not only impairs human beta-globin-gene expression but also results in increased expression of the human gamma-globin genes during the fetal/adult stages. Hence, it may appear that EKLF is a determining factor for the developmental switch from gamma-globin to beta-globin transcription. However, we show here that the function of EKLF for beta-globin-gene expression is necessary even in absence of gene competition. Moreover, EKLF is not developmental specific and is present and functional before the switch from gamma-globin to beta-globin-gene expression occurs. Thus, EKLF is not the primary factor that controls the switch. We suggest that autonomous repression of gamma-globin transcription that occurs during late fetal development is likely to be the initiating event that induces the switch.

Animals↗
PubMed1998

Changes in pituitary adenylate cyclase activating peptide and vasoactive intestinal peptide innervation of rat oxyntic mucosa during ulcer healing.

Pituitary adenylate cyclase activating peptide and vasoactive intestinal peptide belong to the same neuropeptide family. Both peptides are present in nerve fibers in the gastric wall and are thought to be involved in the regulation of inflammatory processes. Experimental ulcers were induced in the rat gastric mucosa by local application of acetic acid. During the healing process we examined the PACAP and VIP innervation by means of immunohistochemistry and in situ hybridization. The ulcer area was examined from day 1 to day 15 after ulcer induction. There was a marked depletion of PACAP in nerve fibers at the ulcer margin from day 1 and onwards. On day 10 and day 15, PACAP-immunoreactive nerve fibers could again be visualized at the ulcer margin. In contrast, VIP immunoreactive nerve fibers were present at the ulcer margin at all time points studied. From day 10 following ulcer induction PACAP- and VIP- immunoreactive nerve fibers were increased in frequency in the smooth muscle beneath the ulcer. An upregulation of VIP and PACAP mRNA was also demonstrated in the myenteric ganglia adjacent to ulcer. The present results indicate that neuronal PACAP and VIP react differently to the inflammation at the ulcer margin but similarly in the smooth muscle during the ulcer healing.

Animals↗
PubMed1998

Characterization of major surface glycoprotein genes of human Pneumocystis carinii and high-level expression of a conserved region.

To facilitate studies of Pneumocystis carinii infection in humans, we undertook to better characterize and to express the major surface glycoprotein (MSG) of human P. carinii, an important protein in host-pathogen interactions. Seven MSG genes were cloned from a single isolate by PCR or genomic library screening and were sequenced. The predicted proteins, like rat MSGs, were closely related but unique variants, with a high level of conservation among cysteine residues. A conserved immunodominant region (of approximately 100 amino acids) near the carboxy terminus was expressed at high levels in Escherichia coli and used in Western blot studies. All 49 of the serum samples, which were taken from healthy controls as well as from patients with and without P. carinii pneumonia, were reactive with this peptide by Western blotting, supporting the hypothesis that most adult humans have been infected with P. carinii at some point. This recombinant MSG fragment, which is the first human P. carinii antigen available in large quantities, may be a useful reagent for investigating the epidemiology of P. carinii infection in humans.

AIDS-Related Opportunistic Infections↗
PubMed1998

[Synthesis of 1,4-dihydropyridines with blood pressure and blood-fat lowering effects].

To develop new drugs with the effects of lowering blood-fat and blood pressure, compounds 1-7 and 10 were synthesized by the reactions of 2-methyl-2-[4-(4-chlorobenzoyl)phenoxy]propionyl chloride with a hydroxyl group in 1,4-dihydropyridines. Compounds 8 and 9 were obtained by the reactions of 2-methyl-2-[4-(4-chlorobenzoyl)phenoxy]propionyl chloride with salicylic aldehyde first, and then with beta-aminocrotonates. All 1-10 are new compounds, and their structures were elucidated by means of 1HNMR and MS. The effects of compounds 1-10 on lowering cholesterol, triglyceride and blood pressure were investigated, and some of which were found to have the effects of lowering triglyceride and blood pressure.

Animals↗
PubMed1997

Effects of chronic nicotine ingestion on pressor response to Nomega-Nitro-L-arginine methyl ester and ex vivo concentration and relaxation response of aorta to L-arginine.

Effects of nitric oxide synthase inhibition on blood vessels were studied in nicotine-treated rats. Male Sprague-Dawley rats drank a nicotine solution with a concentration of 25 or 50 microg/ml for 15 days. The blood pressure and heart rate of chloralose-anaesthetized rats and isolated aortic strip contractions were measured. NomegaNitro-L-arginine methyl ester (L-NAME)-induced hypertension was significantly reduced after chronic nicotine treatment. The Emax of contractions of isolated aortic strips to noradrenaline were dose-dependently enhanced by nicotine and the potentiation was abolished by L-arginine. The relaxation of aortic strips to acetylcholine was significantly decreased in nicotine-treated rats, whereas L-arginine, but not D-arginine, reversed this action. Neither nicotine nor L-NAME affected the heart rate. The results show that chronic nicotine treatment reduced the pressor response of L-NAME.

Acetylcholine↗
PubMed1997

The Probot--an active robot for prostate resection.

As men age, their prostates can enlarge, causing urinary difficulty. Surgery to correct this [transurethral resection of the prostate (TURP)] is a skilled and time-consuming operation requiring many repetitive motions of a cutter. A robot has been developed to perform these motions, relieving the surgeon of much of the burden of surgery. This robot has been tried both in the laboratory and later on human subjects and has proved itself capable of performing prostate resection. The Probot system consists of on-line imaging and three-dimensional prostate model construction, an appropriate surgeon-computer interface, a counterbalanced mounting frame and a computer controlled robot.

Computer Graphics↗
PubMed1997

[Primary culture of fetal rat gastric mucosal epithelium].

A method for primary cell culture of fetal rat gastric fundic epithelial cells was developed. The tissue was incubated with 0.125% trypsin at 4 degrees C for 8-10 hours. The epithelial cells isolated were then cultured in DMEM/F12 medium supplemented with 20% fetal calf serum. Within 24 hours the cells attached to the culture plate and became confluent in 3 days. On phase contrast microscopy, over 90% of cell possessed epithelial characteristics. Immunocytochemical studies showed: (a) 90% of cells were positive in anti-cytokeratin antibody staining; (b) 90% of the epithelial cells contained PAS positive granules; (c) 20% of epithelial cells gave a strong reaction for succinic dehydrogenase activity. Electron microscopy (EM) showed microvilli on the surface of cells, junctional complexes (tight juntion and desmosome), glycogen and mitochondria. Autoradiographic studies showed that these cells possessed the capability to synthesize DNA and this ability was maximum on day 2. This in vitro system may provide a valuable model for studies of cellular functions of gastric mucosa.

Animals↗
PubMed1997

[Effect of butachlor on CH4 emission and anaerobes in paddy soil].

Effects of butachlor on CH4 emission and the count of anaerobes in paddy soil or in the media were studied. The results obtained showed that CH4 emission and growth of methanogens would be greatly affected at field rates of butachlor within 2 weeks, but this adverse effects would disappear as time went on. CH4 emission and methanogenic activities would be retarded by butachlor in media for longer time. The amount of butachlor available to act upon anaerobes depended on application rate and method of application.

English Abstract↗
PubMed1996

Comparison of prostatic volume and dimensions by transrectal and transurethral ultrasonography.

OBJECTIVE: To compare the volumes and dimensions of the prostate gland as measured by transrectal and transurethral ultrasonography (TRUS and TUUS) and to study the prostatic changes that occur in the presence of an urethral instrument. PATIENTS AND METHODS: Twenty men (mean age 71 years, range 43-85) with symptoms of prostatic enlargement underwent TRUS and the dimensions and volumes of their prostates were obtained by the dimensional method and by step planimetry. Within 24 h, all the men were examined cystoscopically under sedoanalgesia and underwent TUUS. Their prostatic volumes and dimensions were again measured by the dimensional method and by step planimetry. Step planimetry was carried out using a specially designed indexer firmly attached to the examination couch or operating table. All the static images and planimetry slices were video recorded for later computer enhancement and to study the three-dimensional changes occurring in the prostate. The volumes and dimensions obtained by TRUS and TUUS were compared. RESULTS: Volumes obtained by transurethral step planimetry were 22% greater than those from transrectal planimetry. Although there was a good correlation (r = 0.984) between transurethral planimetry and the volumes derived using the transurethral dimensions with the prolate ellipsoid formula, the latter produced values 17% and 25% lower by the transurethral and transrectal routes, respectively. These volume estimates varied widely, indicating that the simple addition of a constant to the prolate ellipsoid formula would not correct the volume. Three-dimensional changes of the prostate occurred with TRUS and TUUS: with TUUS, the craniocaudal and anteroposterior diameters were significantly larger (by 7% and 18%, respectively) while the transverse diameter was smaller by 20%. CONCLUSION: The estimated volumes and dimensions of the prostate differed when measured by TRUS and TUUS and three-dimensional changes in the prostate occurred in the presence of an urethral instrument.

Adult↗
PubMed1996

Transrectal ultrasonography: why are estimates of prostate volume and dimension so inaccurate?

OBJECTIVES: To determine why there are variations in the volumes of the prostate obtained by step planimetry and those calculated from the prolate ellipsoid formula using the measured maximum gland dimensions, to assess the reproducibility of estimates of prostate volume from transrectal ultrasonography (TRUS) and to determine the effect of the angle of the transrectal probe, the human error in the clinical setting and the benefit of computer enhancement of the ultrasonograms. PATIENTS AND METHODS: Forty-five men (mean age 72 years, range 43-89) with symptoms of prostatic enlargement were divided randomly into three groups; those in group 1 had their prostate volume estimated three times by measuring the maximal gland dimensions and calculating the volume using the prolate ellipsoid formula (dimensional method) and by step planimetry, to assess the reproducibility of TRUS; men in group 2 had their prostate volume estimated using the dimensional method and by step planimetry with the probe in the optimal axis, and then from scans repeated after deflecting the transrectal probe 5 degrees anteriorly and posteriorly; men in group 3 had their prostate volume estimated once by the dimensional method and by step planimetry. Step planimetry was carried out using a specially designed indexer firmly attached to the examination couch. All 'frozen' images and planimetry slices were videotaped for later computer enhancement. The volumes and dimensions obtained by each method were compared. RESULTS: The volumes obtained by step planimetry were 17% greater than those obtained by the dimensional method because the craniocaudal, anteroposterior and transverse diameters were underestimated significantly by the latter (by 13%, 2% and 7%, respectively). The largest anteroposterior and transverse diameters were included in the same axial scan in only 44%, while the largest craniocaudal diameter was in the midline in only 38%, of the patients. The human error in the clinic was negligible (2%) with a good correlation between the dimensions and volumes obtained in the clinic and those from computer-enhanced images (r = 0.94). There were no advantages in computer enhancing the TRUS images. Volumes calculated from the dimensional method using the maximum dimensions obtained from planimetric contours correlated well with planimetric volumes (r = 0.93). The reproducibility of TRUS showed a mean error of 8% by the dimensional method and 1% by step planimetry. Anterior deflection of the transrectal probe reduced the estimated volume by 2% and posterior deflection increased the volume by 4%, using the dimensional method, while there were no significant volume changes when estimated by step planimetry. CONCLUSION: This study confirms that to estimate accurately the volume of the prostate using the prolate ellipsoid formula, the current methodology needs to be changed. The largest anteroposterior and transverse diameters may need to be measured in different transverse scan slices and the largest craniocaudal diameter in a sagittal scan away from the midline. If volume estimation is to be repeated then step planimetry is reliable and TRUS using the prolate ellipsoid formula is not.

Adult↗
PubMed1996

A single expression site with a conserved leader sequence regulates variation of expression of the Pneumocystis carinii family of major surface glycoprotein genes.

The major surface glycoprotein (MSG) of Pneumocystis carinii is encoded by a family of related but distinct genes distributed throughout the P. carinii genome. Previous reports of the genomic and mRNA MSG structure suggested that there was a highly conserved 5'-untranslated region and a highly variable translated region. In the current study, we demonstrate that there is a single expression site for MSG expression and that different MSG genes are located downstream of this expression site. Isolation of a genomic clone containing the putative 5'-untranslated region has demonstrated that there was a single base sequencing error in what was considered to be the untranslated region. The corrected sequence reveals an extended open reading frame encoding a constant amino-terminal leader domain, with a typical signal peptide, for the MSG protein family. Since this constant amino-terminal domain is encoded by a single copy genomic sequence, a recombination/gene conversion-mediated antigenic switching event is required to effect the known variability in expressed MSG sequences. Therefore, like some bacterial and protozoan pathogens, the opportunistic fungal pathogen P. carinii contains a constant genomic site dedicated to MSG expression and a switchable downstream region for the variable part of the MSG gene family.

Amino Acid Sequence↗
PubMed1996

[Involvement of the nerve fiber elements in the anterior pituitary in the regulation of ACTH secretion].

While peptidergic nerve fibers have been immunoreactively identified in the adenohypophysis of mammals, the function of these fibers in the regulation of hormone secretion remain unknown. The present work was undertaken to investigate possible modulating effects of these fibers on the secretion of ACTH in the anterior pituitary. Electrical field stimulation (EFS) was applied to excite the nerve terminals in anterior pituitary quarters of male rats under static incubation, and the ACTH level was determined by radioimmunoassay. It was found that the ACTH release from the anterior pituitary was significantly enhanced by EFS (30 mA, 0.5 ms and 10 Hz), which could be significantly decreased by adding TTX or veratridine into the incubation medium. However, TTX failed to inhibit AVP-induced ACTH secretion. Since the dispersed cultured anterior pituitary cells did not respond to the same EFS, it was suggested that there might exist dual modulatory mechanisms on the anterior pituitary hormone secretion.

Adrenocorticotropic Hormone↗
PubMed1995

[Experimental and clinical study on pneumocystosis. IV. Use of a 4D7 monoclonal antibody to detect Pneumocystis carinii by immunoperoxidase staining].

This paper reports on the diagnostic utility of the 4D7 monoclonal antibody (McAb) and immunohistochemical (IHC) staining to detect P. carinii. Specimens of 30 pathological sections of lung tissues and 1 smear of aspirated bronchial material from confirmed cases, and 12 sputum smears from high risk patients with pneumonia were examined by immunohistochemical method using the 4D7 McAb. The results showed that both the sensitivity and specificity of the 4D7 McAb-IHC staining were 100% (31/31). A comparison between immunohistochemical staining with GMS and TBO staining was made, no difference in sensitivity was found. However, the IHC method gave a clear back ground that is useful for definite diagnosis.

Antibodies, Fungal↗