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Biomedical subjects

L Ma

Publications and source records attributed to L Ma.

At least 397 records · Page 22Linked to original sources
PubMed1997

[Biotherapeutic efficacy of adoptive transfer of CD3AK cells in combination with cyclophosphamide and kappa-selenocarrageenan in P 388 leukemic mice].

OBJECTIVE: To study the antileukemia efficacy of a combination of adoptive transfer of CD3AK cells, cyclophosphamide (CTX), and kappa-selenocarrageenan (KSC) in P 388 leukemic mice. METHODS: CD3AK cells in normal DBA/2 murine splenocytes were induced with anti-CD3 antibody and low dose recombinant interleukin-2 (rIL-2). The P 388 murine leukemia model was induced by i.p. injection of P 388 cells into normal DBA/2 mice. The tumor-bearing mice were administrated with adoptively transferred CD3AK Cells and/or CTX and/or KSC. RESULTS: After tumor inoculation, the cellular immune function of P 388-bearing mice was supressed markedly. Adoptive transfer of CD3AK cells with low dose rIL-2 into the P 388 mice significantly enhanced the splenocyte proliferation (SP) induced by Con A, the NK cell activity and the splenocytic IL-2 production and prolonged their survival (45.19%); CTX (200 mg/kg) alone prolonged the survival of P 388-bearing mice (29.90%), but further decreased the immunodeficiency; combination of CTX and CD3AK passive transfer could prevent the reduction of SP, NK activity and IL-2 production in the leukemic mice and prolonged the survival (59.45%), combination of KSC and adoptively transfected CD2AK cells and/or CTX had a much better therapeutic efficacy for P 388 murine leukemia, 12.50%-75.00% of the leukemic mice were cured. CONCLUSION: KSC is a hopeful biological response modifier in cancer biotherapy, and tumor killing effector cells and chemotherapy plus BRM might be a promising candidate for human leukemia biotherapy.

Adoptive Transfer↗
PubMed1997

[Capillary isoelectric focusing of protein].

A capillary isoelectric focusing (CIEF) method was developed for the separation of proteins with different pI. Uncoated capillary (57 cm x 50 microm i.d.) was used instead of commercial coated column because of its ease in use and a longer lifetime. Polymeric additive, methylcellulose (MC-1500), acts as dynamic coating of the silica wall to suppress electroendosmosis. TEMED was used to extend the pH range of ampholine. Taurine was added to the ampholyte mixture to eliminate the aggregation of proteins. The uniform design, a new experimental design method suited for experiments of a large number of factors and levels, was used for the optimization of experimental conditions, such as concentrations of ampholine, MC-1500, TEMED and Taurine. U6* (6(4)) table was chosen to arrange experiments. Regression equations of maximum current, mean migration time and criterion of resolution power were obtained after the treatment of experimental results by SAS software. Optimized experimental conditions were obtained according to multivariate regression equations. Carrier ampholyte which consists of 3.2%-4.8% ampholine 3-10, 0.06%-0.18% MC-1500, 0.8% TEMED and 1%-2% taurine will produce good resolution. Cathode and anode solutions were 20 mmol/L NaOH and 20 mmol/L HsPO4, respectively. Low pressure (34.5kPa) was applied at the inlet of the capillary simultaneously after 31 minutes of isoelectric focusing at 25 kV to mobilize the focused acidic protein zone to pass through the detector. Human serum albumin (HSA) and human epidermal growth factor (hEGF) were separated by this method using an ampholyte mixture of 4% ampholine 3-10, 0.8% TEMED, 1% taurine and 0.12% MC-1500. Data analysis indicated that the coefficients of variation of pressure and the method are all 1.2%. The results demonstrated that the method established is applicable to basic, neutral and acidic proteins, and can be used for the determination of pI by internal calibration.

Ampholyte Mixtures↗
PubMed1997

[Capillary isoelectric focusing method and its applications].

Capillary isoelectric focusing (CIEF) is reviewed in this article with 64 references. Separation mechanism, manipulation of electroosmosis, mobilization methods, detectors and some problems associated with the determination of samples are discussed. Different methods for performing CIEF are evaluated. Non-cross-linked polyacrylamide coated capillary is recommended. As for untreated column, dynamical coating with cellulose polymers allows a residual electroosmotic flow to carry the focused zone to pass through the detector. Some applications, such as separation of transferrin isoform, human Hb variants, t-PA glycoform, are presented.

Electrophoresis, Capillary↗
PubMed1997

[Fluorescence spectra study on 2, 3, 7, 8-tetrachloro-n-ethyl-phenothiazine].

In this paper we gave been discussed the variation law of fluorescence intensity of 2, 3, 7, 8-tetracloro-N-ethyl-phenothazine under different conditions. The experimental results show the best emit light system of fluorescence. It has theoretical significance and practical value on raising seneitivity of organic photoconductor.

English Abstract↗
PubMed1997

[Study on fluorescence method of pefloxacin].

Pefloxacin is a new kind of antibiotic. In this paper, a sensitive fluorescence method has been developed for the analysis of Pefloxacin. It has stronger fluorescence excitation. The fluorescence of Pefloxacin was measured at excitation wavelength 282nm and emission wavelength 440nm. The method is highly sensitive with lower limit of detection, calibration curves were linear between 1 x 10(-9) - 1 x 10(-6)mol/L, with a regression coefficient of 0.9999. At the same time, recoveries of pefloxacin in Human serum Albumin and Urine are 95% and 105% respectively.

Anti-Infective Agents↗
PubMed1997

Unique crystalline inclusions in neonatal pig small intestine epithelial cells.

In this study we describe the presence of novel crystalline inclusions in the jejunal and ileal epithelium of newborn pigs. Hampshire/Yorkshire piglets (0-3 days) were anesthetized with pentobarbital and tissues were recovered following laparotomy. Sections of jejunum and ileum were prepared with a variety of fixatives for paraffin and methacrylate embedment for the light and electron microscopy. The characteristics of these crystalline structures have been demonstrated by cytochemical staining, immunohistochemical staining, and ultrastructural studies. Using light microscopy, it was determined that 10.8% of villus epithelial cells in the jejunum contained inclusions, whereas inclusions were present in 26.6% of the villus epithelial cells in the ileum. Inclusions were absent in crypt epithelial cells of both areas of the intestine, and the percentage of cells with inclusions increased towards the villus tip. Preliminary histochemical analysis has been unrevealing. The inclusions are periodic acid/Schiff's (PAS) reagent-negative, and do not stain for the presence of concentrated proteins. Using electron microscopy, the inclusions are found to be clustered in the supra-nuclear region of the cells and are generally oriented with the long axis of the cell. The crystals vary in size and have a dense core region surrounded by a regular less dense periphery.

Animals↗
PubMed1997

Cloning and sequencing of draTG genes and their downstream region of Azospirillum brasilense Yu62.

An 8-kb fragment was cloned by probing the gene library of Azospirillum brasilense Yu62 with the 4.0-kb draTG fragment of A. brasilense Sp7. DNA hybridization of this fragment demonstrated that draTG genes were located in a 3.0-kb EcoR I-Kpn I fragment, and were contiguous to the nifH gene. This 3.0-kb fragment was completely sequenced on both strands. Sequence analysis of the fragment revealed that it included the full-length draTG genes and two ORFs downstream of draG (ORF3 and incomplete ORF4). The draTG and downstream ORF3 are presumed to be cotranscribed as a single operon. Promoter element analysis of the sequenced region showed that there were some elements of the sigma 54-dependent promoter (DPEs and UASs) in the upstream region of draG and ORF3. This suggests that the draG and ORF3 might be transcribed independently in addition to being cotranscribed with draT. Both the DNA and amino acid sequences of the draTG genes from A. brasilense Yu62 were compared with those of other nitrogen-fixing bacteria. The results showed the draTG genes were highly conservative. There were only a few changes among strains and/or species. Homology analysis of ORF revealed that the ORF3 immediately downstream of draG was homologous not only with the ORF at the same position in Rhodospirillum rubrum and A. lipoferum, but also with the ORF14 of Azotobacter vinelandii and the ORF4 showed extensive similarity to yafJ of Escherichia coli.

Amino Acid Sequence↗
PubMed1997

Pathology of esophageal cancers: local experience and current insights.

Esophageal cancer is very popular in Hong Kong. The tumor is often prevalent in males and has a modal peak of occurrence in the 7th decade. The pathogenesis of the esophageal neoplasm is still uncertain but likely to be multi-factorial. The commonest histological subtype is squamous cell carcinoma. Besides, mucoepidermoid carcinoma/adenosquamous carcinoma, adenocarcinoma, small cell carcinoma, sarcomatoid carcinoma, adenoid cystic carcinoma, undifferentiated carcinoma, melanoma and gastrointestinal autonomic nerve tumor are also found in a minority of patients. The proportion of various histologic subtypes is different from the Western populations. Concerning the genetic alternation, P53 mutation is common in esophageal squamous cell carcinoma. Esophageal cancer has its unique pattern of P53 mutations in Hong Kong. In addition, intramural metastasis and multiple lesions are characteristic features in esophageal squamous cell carcinoma. Important pathologic factors in determining the prognosis of patients with esophageal cancer includes completeness of surgical resection, stages, tumor dimension as well as MIB-1 scores and the presence of P53 mutations.

Carcinoma, Adenosquamous↗
PubMed1997

Sequencing and analysis of function of the promoter region of draTG genes from Azospirillum brasilense Yu62.

From Azospirillum brasilense Yu62, we cloned and sequenced the upstream region of draTG. No identified genes were found in this region except for portion of nifH, which is transcribed divergently from draTG. However, some potential regulatory elements were found, which include downstream promoter elements (DPE), upstream activator sequences (UAS), and A + T-rich regions. This suggests that the region between draT and nifH might be a regulatory region rather than an encoding region, and the promoter of dra operon would probably be a RpoN-dependent promoter. A draT::cam transcriptional fusion plasmid pAT1 was constructed in pAF300. The expression of draT was studied in Escherichia coli and A. brasilense by Cmr assay. The result showed that draT could be transcribed in A. brasilense but not in E. coli while grown aerobically on an LD plate. This suggests that the transcription of draT needs some factors which are absent in E. coli, and the draT upstream region has the promoter function. Using the promoter-probe vector pCB182, a draT::lacZ transcriptional fusion plasmid pCT1 was constructed. beta-galactosidase activity was determined in vivo in E. coli, in the presence or absence of NifA of Klebsiella pneumoniae, respectively. The results demonstrated that NifA was not involved in the transcriptional regulation of draTG.

ADP Ribose Transferases↗
PubMed1997

[Determination of the content for micronomicin sulfate by ultraviolet spectrophotometric derivatization].

An ultraviolet spectrophotometric method for determination of micromonicin (MCR) was developed by the reaction of MCR with o-pathaldehyde (OPA) and obtained a derivative absorbing ultraviolet in special wave length. The comparison was made between this method and high performance liquid chromatography (HPLC). The results indicate that the method is simple, rapid, precise and reproducible.

Aminoglycosides↗
PubMed1996

Human cholesteryl ester transfer protein gene proximal promoter contains dietary cholesterol positive responsive elements and mediates expression in small intestine and periphery while predominant liver and spleen expression is controlled by 5'-distal sequences. Cis-acting sequences mapped in transgenic mice.

The plasma cholesteryl ester transfer protein (CETP) facilitates the transfer of high density lipoprotein cholesteryl esters to other lipoproteins and appears to be a key regulated component of reverse cholesterol transport. Earlier studies showed that a CETP transgene containing natural flanking sequences (-3.4 kilobase pairs (kbp) upstream, +2.2 kbp downstream) was expressed in an authentic tissue distribution and induced in liver and other tissues in response to dietary or endogenous hypercholesterolemia. In order to localize the DNA elements responsible for these effects, we prepared transgenic mice expressing six new DNA constructs containing different amounts of natural flanking sequence of the CETP gene. Tissue-specific expression and dietary cholesterol response of CETP mRNA were determined. The native pattern of predominant expression in liver and spleen with cholesterol induction was shown by a -3.4 (5'), +0.2 (3') kbp transgene, indicating no major contribution of distal 3'-sequences. Serial 5'-deletions showed that a -570 base pairs (bp) transgene gave predominant expression in small intestine with cholesterol induction of CETP mRNA in that organ, and a -370 bp transgene gave highest expression in adrenal gland with partial dietary cholesterol induction of CETP mRNA and plasma activity. Further deletion to -138 bp 5'-flanking sequence resulted in a transgene that was not expressed in vivo. Both the -3.4 kbp and -138 bp transgenes were expressed when transfected into a cultured murine hepatocyte cell line, but only the former was induced by treating the cells with LDL. When linked to a human apoA-I transgene, the -570 to -138 segment of the CETP gene promoter gave rise to a relative positive response of hepatic apoA-I mRNA to the high cholesterol diet in two out of three transgenic lines. Thus, 5'-elements between -3,400 and -570 bp in the CETP promoter endow predominant expression in liver and spleen. Elements between -570 and -370 are required for expression in small intestine and some other tissues, and elements between -370 and -138 contribute to adrenal expression. The minimal CETP promoter element associated with a positive sterol response in vivo was found in the proximal CETP gene promoter between -370 and -138 bp. This region contains a tandem repeat of a sequence known to mediate sterol down-regulation of the HMG-CoA reductase gene, suggesting either the presence of separate positive and negative sterol response elements in this region or the use of a common DNA element for both positive and negative sterol responses.

Animals↗
PubMed1996

Elevated blood pressure and enhanced myocardial contractility in mice with severe IGF-1 deficiency.

To circumvent the embryonic lethality of a complete deficiency in insulin-like growth factor 1 (IGF-1), we generated mice homozygous for a site-specific insertional event that created a mutant IGF-1 allele (igf1m). These mice have IGF-1 levels 30% of wild type yet survive to adulthood, thereby allowing physiological analysis of the phenotype. Miniaturized catheterization technology revealed elevated conscious blood pressure in IGF-1(m/m) mice, and measurements of left ventricular contractility were increased. Adenylyl cyclase activity was enhanced in IGF-1(m/m) hearts, without an increase in beta-adrenergic receptor density, suggesting that crosstalk between IGF-1 and beta-adrenergic signaling pathways may mediate the increased contractility. The hypertrophic response of the left ventricular myocardium in response to aortic constriction, however, was preserved in IGF-1(m/m) mice. We conclude that chronic alterations in IGF-1 levels can selectively modulate blood pressure and left ventricular function, while not affecting adaptive myocardial hypertrophy in vivo.

Adenylyl Cyclases↗
PubMed1996

Affinity chromatography of trypsin using chitosan as ligand support.

Chitosan beads were prepared for use as affinity adsorbent carrier. The affinity ligand, chicken ovomucoid, was immobilized on the chitosan via a cross-linker, glutaraldehyde. The results showed that 60 mg chicken ovomucoid could be immobilized on l g chitosan, and the maximum binding capacity for trypsin was about 8.10(4) U/g dry adsorbent. The procedure for preparing the chitosan-based affinity adsorbents was much safer and simpler than when a Sepharose-based matrix was the support. Columns packed with the affinity adsorbents were employed for trypsin chromatography. The experimental results revealed that the affinity adsorbents possessed good mechanical strength and storage stability and could be also operated repeatedly. Chitosan was suitable for use as an affinity adsorbent support for laboratory-scale and large-scale purification.

Adsorption↗
PubMed1996

Myotonic protein kinase expression in human and bovine lenses.

Myotonic dystrophy (DM) is an autosomal dominant trait closely associated with CGT repeat expansions in the same locus on human chromosome 19q13.3. The expansions occur in the 3'untranslated region of a transcription unit encoding a serine-threonine kinase (DM kinase) of a new class based upon structure and function. Lens cataracts are a prominent finding in myotonic dystrophy. DM kinase was shown to be expressed in human and bovine lenses at the RNA level and in human lenses at the protein level. Sequencing of PCR products of RNA extracted from normal human lenses demonstrated an exact match to published genomic and cDNA 3' UTR sequences. Northern blots of bovine lens RNA showed that the transcript is similar in size to the transcript detected in other tissues that are affected in myotonic dystrophy. A polyclonal antibody (DM-2) was produced against recombinant DM protein kinase in rabbits. Development of Western blots with DM-2 showed a single reactive band of 67 kDa. Immunofluorescent studies of formalin-fixed human lens sections detected the DM kinase in the perinuclear cytoplasm of normal human lens epithelial cells and more diffusely in superficial subcapsular cortical fibers. In contrast, the same antibody labeled the nucleus most prominently in a single DM lens.

Animals↗