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Biomedical subjects

H Ma

Publications and source records attributed to H Ma.

At least 181 records · Page 10Linked to original sources
PubMed1998

[Changes of erythrocyte and platelet membrane lipid pattern in different subtypes of dementia].

OBJECTIVE: To investigate the changes of platelet and erythrocyte membrane lipids and phospholipid composition in different types of dementia. METHODS: There were 19 patients with Alzheimer's disease, 25 patients with Binswanger's disease, 23 patients with multi-infarct dementia, 11 patients with single cortical infarct dementia, 7 patients with vascular dementia of haemodynamic type, 18 patients with dementia following Parkinson's disease, and 25 senile controls. Platelet and erythrocyte membrane cholesterol, total phospholipids and individual phospholipids were quantified. RESULTS: When compared with senile controls, the decrease of total phospholipids, phosphatidylcholine and phosphatidylethanolamine and the increase of cholesterol and cholesterol/total phospholipids ratio on the erythrocyte and platelet membrane were found in patients with Binswanger's disease and in those with multi-infarct dementia. The increase of erythrocyte and platelet membrane cholesterol, cholesterol/phospholipids ratio was found, but there was no significant change in membrane total phospholipids and phospholipid composition in patients with single cortical infarct dementia. CONCLUSION: Metabolic disorders of platelet and erythrocyte membrane phospholipids were noted in patients with Binswanger's disease. These disorders were related to white matter low attenuation.

Aged↗
PubMed1998

[A clinical and pathological study of cerebellar medulloblastoma in adult patients].

OBJECTIVE: In order to study the clinicopathological characteristics, histogenesis and prognosis of medulloblastoma in the adult patients. METHODS: Altogether 27 patients of medulloblastoma admitted form 1974-1995 were reviewed. RESULTS: In all of the cases, age ranged from 16 to 55, (average 25.8 years) with 21 tumors localized in the cerebellar vermis, and 6 tumors in the cerebellum. Among them, 12 cases were completely while 14 cases were subtotally removed and biopsy was done in only one case. In the 21 patients to be followed up, 7 survived for 2.5-17 years after the operation, and 14 died. The average survival period was 41.6 months. One year survival rate was 71.4%, five years and ten years survival rates were 14.3% respectively. Regarding to the histological types, 14 cases were considered to be classic and 13 cases were desmoplastic by histological classification. CONCLUSION: Medulloblastoma keeps still the ability of differentiation to neurons and astrocytes confirmed by electronmicroscopy and immunohistochemical staining for Syn, NSE and GFAP. Factors considered responsible to the prognosis included age, tumor location, various therapeutic measurements and the histological classification.

Adolescent↗
PubMed1998

[Single-tube nested polymerase chain reaction technique in detecting Mycobacterium tuberculosis DNA].

OBJECTIVE: To study the sensitivity and specificity of single-tube nested polymerase chain reaction (SN-PCR) technique in detecting Mycobacterium tuberculosis DNA in paraffin-embedded tissues. METHOD: BCG DNA and the paraffin-embedded tissues of 30 cases with typical tuberculous lymphadenitis were examined to detect the IS6110 specific insertion sequences DNA of Mycobacterium tuberculosis complex by general PCR(G-PCR), double-tube nested PCR (DN-PCR) and SN-PCR techniques. RESULT: Fifteen fg or more BCG DNA could show positive results by DN-PCR and SN-PCR techniques, while 480 fg by G-PCR method. The positive rates of G-PCR, DN-PCR, and SN-PCR in detecting Mycobacterium tuberculosis DNA in 30 cases with tuberculous lymphadenitis were 43%, 100%, and 100% respectively, all of which were significantly different (P < 0.01) from that of the acid-fast staining method (10%). Significant differences in the positive rates also existed between G-PCR and DN-PCR, G-PCR and SN-PCR (both P < 0.01), while the positive rates of DN-PCR and SN-PCR were found same. CONCLUSION: The sensitivities of nested PCR techniques in detecting Mycobacterium tuberculosis are significantly higher than that of G-PCR, whereas the sensitivities as well as the specificities of SN-PCR and DN-PCR are the same. Thus SN-PCR seems more practicable.

DNA, Bacterial↗
PubMed1998

[A multiexponential model in cavity ring-down absorption spectroscopy].

A multiexponential model of cavity ring-down absorption spectroscopy is established for taking into account the laser linewidth effects. It is demonstrated that by fitting the logarithmic ring-down function to a truncated polynomial, absorption coefficent can be extracted from coefficients of the first as well as higher order terms of the fitted polynomial. The new fit model results in higher accuracy and broader dynamic range than the previous single exponential model.

English Abstract↗
PubMed1998

Cloning and expression of mRNA for calpain Lp82 from rat lens: splice variant of p94.

PURPOSE: To describe mRNA for Lp82, a lens-specific form of calcium-activated protease (EC 34.22.17, calpain) in rat. METHODS: Total RNA was extracted from lenses of 12-day-old rats, reverse transcribed, and amplified using polymerase chain reaction (PCR) with degenerate primers for the active site of calpains. Tissue specificity and relative amounts of mRNA for Lp82 in rat lens and other tissues were demonstrated by reverse transcription-PCR using gene-specific primers. PCR products were subcloned and sequenced using standard techniques. RESULTS: Abundant amounts of mRNA for Lp82, a variant of muscle-type calpain p94, were discovered only in lens and not in seven other tissues assayed. When translated, the Lp82 mRNA would code for protein containing the usual cysteine active site residues and calcium-binding domains. Remarkably, the Lp82 cDNA product was identical to that of muscle-type calpain p94, except for deletions of most of the nucleotides coding for three unique insert regions termed NS, IS1, and IS2 found in p94. Compared with p94, a different exon 1 was present, and the nucleotides for all exons 6, 15, and 16 were deleted in Lp82. CONCLUSIONS: Lp82 is a lens-specific calpain. It is a splice variant of muscle-type calpain p94, resulting from deletions of IS1 and IS2 regions and a different exon 1, possibly from an alternative, lens-specific promoter in the p94 gene. Lp82 is important because it may have lens-specific functions suited to the unique properties of the lens. Lp82 may also give insight into the functions of NS, IS1, and IS2 regions in p94, which is important in normal muscle physiology and in the study of limb-girdle muscular dystrophy type 2A in humans.

Amino Acid Sequence↗
PubMed1997

Apoptosis induced by tea polyphenols in HL-60 cells.

In order to search for tumor cells apoptosis inducer, the apoptosis effects and mechanism of tea polyphenols were studied. Tea polyphenols are active compounds purified from tea. The apoptosis effects of tea polyphenols were observed on the human promyelocytic leukemic cells (HL-60) by an MTT reduction test, DNA agarose gel electrophoresis and a transmission electronic microscopy technique. After HL-60 cells were treated by tea polyphenols in 250 microg/ml for 5 h, DNA extracted from HL-60 cells showed a typical internucleosomal DNA degradation, i.e. DNA ladder and apoptotic vehicles were observed. The effects of tea polyphenols were shown to be similar to their cytotoxic activity in HL-60 cells. These results suggest that the mechanism of antitumor action of tea polyphenols is related to its apoptosis-inducing activity.

Apoptosis↗
PubMed1997

A genome-based resource for molecular cardiovascular medicine: toward a compendium of cardiovascular genes.

BACKGROUND: Large-scale partial sequencing of cDNA libraries to generate expressed sequence tags (ESTs) is an effective means of discovering novel genes and characterizing transcription patterns in different tissues. To catalogue the identities and expression levels of genes in the cardiovascular system, we initiated large-scale sequencing and analysis of human cardiac cDNA libraries. METHODS AND RESULTS: Using automated DNA sequencing, we generated 43,285 ESTs from human heart cDNA libraries. An additional 41,619 ESTs were retrieved from public databases, for a total of 84,904 ESTs representing more than 26 million nucleotides of raw cDNA sequence data from 13 independent cardiovascular system-based cDNA libraries. Of these, 55% matched to known genes in the Genbank/EMBL/DDBJ databases, 33% matched only to other ESTs, and 12% did not match to any known sequences (designated cardiovascular system-based ESTs, or CVbESTs). ESTs that matched to known genes were classified according to function, allowing for detection of differences in general transcription patterns between various tissues and developmental stages of the cardiovascular system. In silico Northern analysis of known gene matches identified widely expressed cardiovascular genes as well as genes putatively exhibiting greater tissue specificity or developmental stage specificity. More detailed analysis identified 48 genes potentially overexpressed in cardiac hypertrophy, at least 10 of which were previously documented as differentially expressed. Computer-based chromosomal localizations of 1048 cardiac ESTs were performed to further assist in the search for disease-related genes. CONCLUSIONS: These data represent the most extensive compilation of cardiovascular gene expression information to date. They further demonstrate the untapped potential of genome research for investigating questions related to cardiovascular biology and represent a first-generation genome-based resource for molecular cardiovascular medicine.

Blotting, Northern↗
PubMed1997

A bacterial group II intron encoding reverse transcriptase, maturase, and DNA endonuclease activities: biochemical demonstration of maturase activity and insertion of new genetic information within the intron.

The Lactococcus lactis group II intron Ll.ltrB is similar to mobile yeast mtDNA group II introns, which encode reverse transcriptase, RNA maturase, and DNA endonuclease activities for site-specific DNA insertion. Here, we show that the Lactococcal intron can be expressed and spliced efficiently in Escherichia coli. The intron-encoded protein LtrA has reverse transcriptase and RNA maturase activities, with the latter activity shown both in vivo and in vitro, a first for any group II intron-encoded protein. As for the yeast mtDNA introns, the DNA endonuclease activity of the Lactococcal intron is associated with RNP particles containing both the intron-encoded protein and the excised intron RNA. Also, the intron RNA cleaves the sense-strand of the recipient DNA by a reverse splicing reaction, whereas the intron-encoded protein cleaves the antisense strand. The Lactococcal intron endonuclease can be obtained in large quantities by coexpression of the LtrA protein with the intron RNA in E. coli or reconstituted in vitro by incubating the expressed LtrA protein with in vitro-synthesized intron RNA. Furthermore, the specificity of the endonuclease and reverse splicing reactions can be changed predictably by modifying the RNA component. Expression in E. coli facilitates the use of group II introns for the targeting of specific foreign sequences to a desired site in DNA.

Bacterial Proteins↗
PubMed1997

Oncogenic raf-1 induces the expression of non-histone chromosomal architectural protein HMGI-C via a p44/p42 mitogen-activated protein kinase-dependent pathway in salivary epithelial cells.

The enzyme activity of mitogen-activated protein kinase (MAP kinase) increases in response to agents acting on a variety of cell surface receptors, including receptors linked to heterotrimeric G proteins. In this report, we demonstrated that Raf-1 protein kinase activity in the mouse parotid glands was induced by chronic isoproterenol administration in whole animals. To investigate the molecular nature underlying cellular responses to Raf-1 activation, we have stably transfected rat salivary epithelial Pa-4 cells with human Raf-1-estrogen receptor fusion gene (DeltaRaf-1:ER) and used mRNA differential display in search of messages induced by DeltaRaf-1:ER activation. Through this approach, the gene encoding non-histone chromosomal protein HMGI-C was identified as one of the target genes activated by oncogenic Raf-1 kinase. Activation of Raf-1 kinase resulted in a delayed and sustained increase of HMGI-C expression in the Pa-4 cells. The induction of HMGI-C mRNA level is sensitive to both the protein synthesis inhibitor cycloheximide and transcription inhibitor actinomycin D. The role of the extracellular signal-related kinase (ERK) signaling pathway in the HMGI-C induction was highlighted by the result that the MAP kinase kinase (MEK) inhibitor, PD 98059, blocked DeltaRaf-1:ER- and 12-O-tetradecanoylphorbol-13-acetate-stimulated HMGI-C induction. Altogether, these findings support the notion that the Raf/MEK/ERK signaling module, at least in part, regulates transcriptional activation of the chromosomal architectural protein HMGI-C.

Amino Acid Sequence↗
PubMed1997

Selenite nuclear cataract: review of the model.

Selenite overdose cataract, an experimental model of nuclear cataract produced in young rats is reviewed. Topics include procedures for cataract production and assessment, metabolic and molecular changes in the epithelium of the lens, calcium accumulation, activation of calcium-activated protease system, mechanisms for crystallin precipitation, anti-cataract drug testing and relevance to human cataract.

Animals↗
PubMed1997

The Dictyostelium MAP kinase kinase DdMEK1 regulates chemotaxis and is essential for chemoattractant-mediated activation of guanylyl cyclase.

We have identified a MAP kinase kinase (DdMEK1) that is required for proper aggregation in Dictyostelium. Null mutations produce extremely small aggregate sizes, resulting in the formation of slugs and terminal fruiting bodies that are significantly smaller than those of wild-type cells. Time-lapse video microscopy and in vitro assays indicate that the cells are able to produce cAMP waves that move through the aggregation domains. However, these cells are unable to undergo chemotaxis properly during aggregation in response to the chemoattractant cAMP or activate guanylyl cyclase, a known regulator of chemotaxis in Dictyostelium. The activation of guanylyl cyclase in response to osmotic stress is, however, normal. Expression of putative constitutively active forms of DdMEK1 in a ddmek1 null background is capable, at least partially, of complementing the small aggregate size defect and the ability to activate guanylyl cyclase. However, this does not result in constitutive activation of guanylyl cyclase, suggesting that DdMEK1 activity is necessary, but not sufficient, for cAMP activation of guanylyl cyclase. Analysis of a temperature-sensitive DdMEK1 mutant suggests that DdMEK1 activity is required throughout aggregation at the time of guanylyl cyclase activation, but is not essential for proper morphogenesis during the later multicellular stages. The activation of the MAP kinase ERK2, which is essential for chemoattractant activation of adenylyl cyclase, is not affected in ddmek1 null strains, indicating that DdMEK1 does not regulate ERK2 and suggesting that at least two independent MAP kinase cascades control aggregation in Dictyostelium.

Amino Acid Sequence↗
PubMed1997

Steroid recognition and regulation of hormone action: crystal structure of testosterone and NADP+ bound to 3 alpha-hydroxysteroid/dihydrodiol dehydrogenase.

BACKGROUND: Mammalian 3 alpha-hydroxysteroid dehydrogenases (3 alpha-HSDs) modulate the activities of steroid hormones by reversibly reducing their C3 ketone groups. In steroid target tissues, 3 alpha-HSDs act on 5 alpha-dihydrotestosterone, a potent male sex hormone (androgen) implicated in benign prostate hyperplasia and prostate cancer. Rat liver 3 alpha-HSD belongs to the aldo-keto reductase (AKR) superfamily and provides a model for mammalian 3 alpha-, 17 beta- and 20 alpha-HSDs, which share > 65% sequence identity. The determination of the structure of 3 alpha-HSD in complex with NADP+ and testosterone (a competitive inhibitor) will help to further our understanding of steroid recognition and hormone regulation by mammalian HSDs. RESULTS: We have determined the 2.5 A resolution crystal structure of recombinant rat liver 3 alpha-HSD complexed with NADP+ and testosterone. The structure provides the first picture of an HSD ternary complex in the AKR superfamily, and is the only structure to date of testosterone bound to a protein. It reveals that the C3 ketone in testosterone, corresponding to the reactive group in a substrate, is poised above the nicotinamide ring which is involved in hydride transfer. In addition, the C3 ketone forms hydrogen bonds with two active-site residues implicated in catalysis (Tyr55 and His117). CONCLUSIONS: The active-site arrangement observed in the 3 alpha-HSD ternary complex structure suggests that each positional-specific and stereospecific reaction catalyzed by an HSD requires a particular substrate orientation, the general features of which can be predicted. 3 alpha-HSDs are likely to bind substrates in a similar manner to the way in which testosterone is bound in the ternary complex, that is with the A ring of the steroid substrate in the active site and the beta face towards the nicotinamide ring to facilitate hydride transfer. In contrast, we predict that 17 beta-HSDs will bind substrates with the D ring of the steroid in the active site and with the alpha face towards the nicotinamide ring. The ability to bind substrates in only one or a few orientations could determine the positional-specificity and stereospecificity of each HSD. Residues lining the steroid-binding cavities are highly variable and may select these different orientations.

Aldehyde Oxidoreductases↗
PubMed1997

The G protein alpha subunit (GP alpha1) is associated with the ER and the plasma membrane in meristematic cells of Arabidopsis and cauliflower.

Towards the elucidation of the cellular function(s) of GP alpha1, we have characterized its subcellular localization using immunofluorescence and cell fractionation. GP alpha1 is not present in nuclei or chloroplasts. It is a membrane-bound protein, and analysis of isolated endoplasmic and plasma membranes indicates a good correlation between GP alpha1 in both the plasma membrane and the ER compartment. Interestingly, these results may suggest more different functions for GP alpha1: it might be involved in transmission of extracellular signals across the plasma membrane and in the cytoplasm, and/or it may also be involved in regulating some aspects of the ER functions or membrane trafficking between both membranes.

Arabidopsis↗
PubMed1997

Minimally invasive cryosurgery--technological advances.

The technological advances which have caused renewed interest in cryosurgery are the development of intraoperative ultrasound to monitor the therapeutic process and the development of new cryosurgical equipment designed to use supercooled liquid nitrogen. The thin, highly efficient probes, available in several sizes, can be placed in diseased sites via endoscopy or percutaneously in minimally invasive procedures. The manner of use is to place the probe in the desired location in the diseased tissue with ultrasound guidance. If required by the size or location of the tumor, as many as five probes can be inserted and cooled to -195 degrees C simultaneously. The process of freezing is monitored by ultrasound which displays a hypoechoic (dark) image when the tissue if frozen. Rapid freezing, slow thawing, and repetition of the freeze/thaw cycle are standard features of technique. Clinical applications which have become common in the past 4 years include the treatment of prostatic cancer and liver tumors. The cases selected for cryosurgery are generally those for which no conventional treatment is possible. However, especially in prostatic cancer, the operative morbidity is so low and the results of therapy are sufficiently good in the short term to merit consideration of use in earlier stages of the disease. Diverse tumors in other sites, such as the brain, bronchus, bone, pancreas, kidney, and uterus, have also been treated in small numbers by cryosurgery. Judging from this experience, further expansion in the use of cryosurgical techniques seems certain.

Cryosurgery↗
PubMed1997

Changes in calpain II mRNA in young rat lens during maturation and cataract formation.

The purpose of these experiments was to describe the expression of mRNA for calpain II proteolytic enzyme (EC 3.4.22.17) during normal maturation of rat lens and in cataract formation. Quantitative RT-PCR indicated that the concentration of mRNA for calpain II in whole lens was 3-24 times higher than in age-matched rat liver, kidney, lung and brain, and it was at least five times higher than in young human lens. mRNA levels for calpain II were highest in the outer regions of young rat lens at 5 x 10(6) copies microgram-1 total RNA. Early-stage experimental cataract caused increased calpain II mRNA, while mature nuclear cataract showed a 64% loss. In contrast, mRNA levels for GAPDH, beta-actin, and lens-specific structural protein beta A4 remained constant during experimental cataract formation. Unlike the lower and constant levels in rat liver, kidney and lung; calpain II mRNA levels in whole rat lens decreased with age. These data help explain the high enzymatic activity of calpain II in young rat lens, susceptibility of young rat lens to a variety of cataracts showing increased calcium and calpain-induced proteolysis, and low calpain enzyme activity in human lens. Since the up-regulation of calpain II mRNA was more dynamic than either the amounts of calpain II enzyme or proteolysis of crystallins in cortex, resulting proteolytic activity against the bulk of lens proteins seems to be regulated by post-translational factors, such as increased calcium. The precise role of the up-regulation of calpain II mRNA is unknown, but we hypothesize that it may be associated with the initial cataractogenic response in the epithelial cells or peripheral cortical fibers.

Animals↗