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Biomedical subjects

H Ma

Publications and source records attributed to H Ma.

At least 109 records · Page 6Linked to original sources
PubMed2000

Beam propagation properties of radial laser arrays.

A detailed study of phase-locked and non-phase-locked radial laser arrays is presented. The closed-form propagation expressions for the beamlets and the resulting beam are given, which enable us to study beam propagation properties of radial laser arrays for both phase-locked and non-phase-locked cases. Numerical calculation examples are given to illustrate the application of our analytical results and the differences between phase-locked and non-phase-locked radial arrays.

Journal Article↗
PubMed2000

A method of "unilateral operation" for early repair of unilateral complete cleft palate. Preliminary report.

OBJECTIVE: This article describes a method of "unilateral operation" and the preliminary results of a group of patients with unilateral complete cleft palate undergoing the operation at early age. DESIGN: The "unilateral operation" consists of four relaxation maneuvers. After all of the four maneuvers have been performed on the deformed side of an unilateral complete cleft palate, the deformed side can be moved posteriorly and medially to contact with the normal side. Then the cleft can be closed without tension. RESULTS: From 1995 to 1998, 19 cases of unilateral complete cleft palate were repaired with this method at 5-12 months of age. Postoperatively, there were no deaths nor dehiscences. Under the care and guidance of an experienced speech pathologist, 15 of 17 of these children have normal vocal quality at 1-2 years of age. CONCLUSIONS: The "unilateral operation" is a rational, adequate, and safe method for early repair of unilateral complete cleft palate. It's design addresses four principles. First, operating only on the deformed side of a unilateral complete cleft palate leaves the normal side unperturbed. Second, complete relaxation of the deformed side is achieved before closing the cleft. Third, in comparison with conventional procedures, which operate on both sides of the palate, this method has the advantage of less surgical trauma, less blood loss, and shorter time of operation. Fourth, all of these advantages are beneficial to early cleft palate repair, which is an important factor in achieving good speech.

Anesthesia, General↗
PubMed2000

Dose-dependent changes in the spectrum of mutations induced by ionizing radiation.

We examined the influence of dose on the spectrum of mutations induced at the hypoxanthine guanine phosphoribosyltransferase (Hprt) locus in Chinese hamster ovary (CHO) cells. Independent CHO-K1 cell mutants at the Hprt locus were isolated from cells exposed to 0, 0.5, 1.5, 3.0 and 6.0 Gy (137)Cs gamma rays, and the genetic changes responsible for the mutations were determined by multiplex polymerase chain reaction (PCR)-based exon deletion analysis. We observed dose-dependent changes in mutation spectra. At low doses, the principal radiation-induced mutations were point mutations. With increasing dose, multibase deletion mutations became the predominant mutation type such that by 6.0 Gy, there were almost three times more deletion mutations than point mutations. The dose response for induction of point mutations was linear while that for multibase deletions fit a linear-quadratic response. There was a biphasic distribution of deletion sizes, and different dose responses for small compared to large deletions. The frequency of large (>36 kb) total gene deletions increased exponentially, implying that they develop from the interaction between two independent events. In contrast, the dose response for deletion mutations of less than 10 kb was nearly linear, suggesting that these types of mutations develop mostly from single events and not the interactions between two independently produced lesions. The observation of dose-dependent changes in radiation-induced mutation spectra suggests that the types of alterations and therefore the risks from low-dose radiation exposure cannot be easily extrapolated from high-dose effects.

Animals↗
PubMed2000

Multiplex polymerase chain reaction-based analysis of T-cell receptor gamma gene rearrangements for the determination of T-lymphocyte clonality.

Determination of the frequency of mutations at hprt or other loci in human lymphocytes provides a useful biomarker for human exposure to mutagens. One problem, however, is distinguishing between unique mutants and sibling mutants arising as progeny of an earlier mutant cell. We have developed a multiplex polymerase chain reaction (PCR)-based method to analyze T-cell receptor (TCR) gamma gene rearrangements for determination of T-cell clonality in mutational spectrum analysis. PCR primers for different subgroups of the V gene segment of the TCR gamma gene were selected at different sites in the TCR gamma gene so that the size of PCR products could define which V subgroup was involved in rearranged TCR gamma genes; gamma genes involving different V and J subgroups could be determined directly by PCR. Mutant T-lymphocytes with rearranged TCR gamma genes containing the same V and J subgroups were analyzed using PCR-based denaturing polyacrylamide gel electrophoresis. All of the 161 hprt mutant clones analyzed contained rearranged TCR gamma genes. Rearrangements among all subgroups of the V and J gene segments of the TCR gamma gene could be detected. VgammaI and Jgamma1/2 subgroups were involved in 69 and 71% of rearranged TCR gamma genes, respectively. This PCR-based analysis of TCR gamma gene rearrangements provides a simple and comprehensive method for identifying the clonality of mutant T-lymphocytes in human hprt mutant lymphocyte assay and mutational spectrum analysis.

Electrophoresis, Polyacrylamide Gel↗
PubMed2000

Lp85 calpain is an enzymatically active rodent-specific isozyme of lens Lp82.

PURPOSES: To clone and sequence the cDNA for Lp85 calpain from young rat lens, and to test for Lp85 protein expression and proteolytic activity. METHODS: RT-PCR and molecular cloning were performed on total RNA from 12 day-old rats. Lp85 protein expression was visualized by immunoblotting using a specific antibody developed to the unique peptide sequence in Lp85. Proteolytic activity was assessed by casein zymography. Transient expression of Lp85 and previously characterized lens-specific calpain Lp82 were separately performed in mammalian COS-7 cells. RESULTS: The 2410-bp cDNA for rat lens Lp85 encoded a protein of 737 amino acid residues with a calculated molecular weight of 85.0 kDa and a predicted pI of 5.67. The amino acid sequence of Lp85 was identical to Lp82 except for an insert region of 28 amino acids in domain IV of the calcium-binding region. mRNA and protein for Lp85 were present only in rat and mouse lenses and not in other tissues or species. Lp85 protein concentrations were highest in the nuclear region, most concentrated in the insoluble fraction, disappeared with lens maturation, and Lp85 exhibited migration similar to Lp82 on native PAGE gels. Lp85 was enzymatically active when expressed in COS-7 cells. CONCLUSIONS: Lp85 is a newly classified, lens- and rodent-specific, enzymatically active, member of the AX1 (alternative exon 1) subclass of calpains. In conjunction with Lp82 and m-calpain in lens, Lp85 may be responsible for proteolysis during normal lens development and maturation or during cataract formation in young rodents.

Amino Acid Sequence↗
PubMed2000

Contribution of calpain Lp82-induced proteolysis to experimental cataractogenesis in mice.

PURPOSE: The purpose of the present experiments was to provide a biochemical mechanism for the involvement of lens-specific calpain Lp82 in experimental cataractogenesis in mice. METHODS: Nuclear cataracts were produced by culturing lenses from 4-week-old mice and rats in calcium ionophore A23187 or by injection of buthionine sulfoximine (BSO) into 7-day-old mice. Casein zymography, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, immunoblot analysis, calcium determinations, in vitro precipitation, and cleavage site analysis by mass spectrometry were performed on lens samples. RESULTS: Amino acid sequences for Lp82 were found to be highly conserved in lenses from mouse to cow, and expressed Lp82 proteolytic activity was high in the mouse and rat. Lenses from mice were more susceptible to A23187-induced cataract and BSO cataracts than rats. Both types of cataracts showed rapid elevation of calcium, activation of Lp82 and m-calpain, and proteolysis of crystallins. Lp82 caused in vitro precipitation of crystallins; and in contrast to m-calpain, Lp82 truncated only the first five amino acids from the C-terminus of alphaA-crystallin. CONCLUSIONS: Under pathologic conditions of massive elevation of lens calcium found in young rodent lenses, overactivation of Lp82 and m-calpain leads to rapid truncation of crystallins at both common and unique cleavage sites, precipitation of truncated crystallins, and cataract.

Amino Acid Sequence↗
PubMed2000

Molecular analysis of hprt mutant lymphocytes from 1, 3-butadiene-exposed workers.

1,3-Butadiene (BD) has been shown to be a potent animal carcinogen and a probable human carcinogen, yet the molecular mechanisms of BD genotoxicity and carcinogenicity still are not fully understood. Our hypothesis is that metabolites of BD induce specific structural changes in the human hprt gene like those observed in vitro in TK6 cells and in vivo in the mouse. Characteristic mutations in BD-exposed subjects can be identified and used as biomarkers for monitoring genotoxic effects associated with BD exposure. Molecular analysis of hprt mutant lymphocytes from BD-exposed workers and unexposed control subjects was carried out to identify changes in the structure of the hprt gene. A multiplex polymerase chain reaction (PCR) assay was used to detect exon deletions in 360 hprt mutant clones. We determined that exon deletions were significantly more frequent (P < 0.05) in BD-exposed workers (17.5%) than in control subjects (9.7%). Sequence analysis of hprt cDNA from 175 independent mutants indicated that the distribution of the types of mutations was different between the workers and the unexposed control subjects. There was a significant increase in -1 frameshift mutations in BD-exposed workers, predominantly in repeated DNA sequences, and single-base substitutions were decreased to 66% in the workers compared to 83% in the control subjects (P < 0.05). In addition to the spectral changes, hprt clonal assays revealed an elevation in mutant frequency in the lymphocytes of workers (N = 10) when compared with that in unexposed control subjects (N = 11; P < 0. 05). There also was a twofold increase of A:T --> T:A transversions in BD-exposed workers (16% in BD-exposed workers compared to 8% in controls, P = 0.25). Some of the BD-associated changes in mutational spectra observed in our study have the potential for application in monitoring genotoxic effects related to butadiene exposure.

Adult↗
PubMed2000

Co-operation between protein-acetylating and protein-methylating co-activators in transcriptional activation.

Nuclear hormone receptors (NRs) activate transcription by binding to specific enhancer elements associated with target genes. Transcriptional activation is accomplished with the help of complexes of co-activator proteins that bind to NRs. p160 co-activators, a family of three related 160 kDa proteins, serve as primary co-activators by binding directly to NRs and recruiting additional secondary co-activators. Some of these (CBP/p300 and p/CAF) can acetylate histones and other proteins in the transcription complex, thus helping to modify chromatin structure and form an active transcription initiation complex. We recently discovered co-activator-associated arginine methyltransferase 1 (CARM1), which binds to p160 co-activators and thereby enhances transcriptional activation by NRs on transiently transfected reporter genes. CARM1 also methylates specific arginine residues in the N-terminal tail of histone H3 in vitro. A related arginine-specific protein methyltransferase, PRMT1, also binds p160 co-activators and enhances NR function. PRMT1 methylates histone H4 in vitro. The enhancement of NR function by CARM1, PRMT1 and p300 depends on their interactions with p160 co-activators. In the presence of p160 co-activators, some pairs of these three secondary co-activators provide a highly synergistic enhancement of NR function on transiently transfected reporter genes. We have also observed an enhancement of NR function on stably integrated reporter genes by these co-activators. We propose that the synergy of co-activator function between p300, CARM1 and PRMT1 is due to their different but complementary protein modification activities.

Acetylation↗
PubMed2000

Influence of specific regions in Lp82 calpain on protein stability, activity, and localization within lens.

PURPOSE: To determine the influence of specific regions within Lp82 calpain on protein stability, enzymatic activity, and localization within lens and to test the influence of an Lp82 knockout mouse on normal maturational proteolysis in lens. METHODS: DNA constructs for Lp82 and Lp82-related proteins were subcloned into the pcDNA 3.1 vector. The constructs contained a substitution of the novel sequence (NS) region from p94 for the AX1 N-terminal region of Lp82 and insertions of the p94 IS1 and IS2 regions into Lp82. Transient expression of these Lp82-related proteins was performed in COS-7 mammalian cells. Immunoblotting and casein zymography were used to measure protein stability and enzymatic activity of the expressed proteins. Homologous recombination was used to knock out p94 gene expression and p94 splice variants such as Lp82 and Lp85 in the lenses of 10-day-old mice. Confocal microscopy revealed the immunohistochemical localization Lp82 and Lp85 within lens. RESULTS: Insertion of IS1 into Lp82 resulted in a lack of stable protein and loss of enzymatic activity. In contrast, substitution of the NS region for AX1 and insertion of IS2 into Lp82 had no effect on the stability of the Lp82-related proteins. p94 knockout mice at 10 days of age exhibited a total absence of Lp82 activity in the lens but normal activity for the separate mu- and m-calpain gene products. Calcium-induced in vitro proteolysis was retarded in these Lp82/p94 knockout lenses. Lp82 and Lp85 immunostaining was intense throughout the cytoplasm of the cortical and nuclear fibers of newborn mouse lenses with little staining in the epithelium. In contrast, immunostaining for the ubiquitous m-calpain was highest in the epithelium and bow region, with much lower levels in the nucleus. The naturally occurring IS3 insert in Lp85 also promoted the association of Lp85 with the perinuclear region of the nucleated lens fibers. CONCLUSIONS: The lack of the IS1 region in Lp82 accounts for the stability and abundance of enzymatically active Lp82 protein in rodent lenses. Conversely, the presence of the IS1 region is responsible for the lability of p94 and Rt88 calpains in muscle and retina, respectively. The insert in Lp85 may promote membrane association. A consequence of the specific loss of Lp82 in the lens may be to retard normal maturational proteolysis.

Animals↗
PubMed2000

Identification and characterization of a retina-specific calpain (Rt88) from rat.

PURPOSE: To identify and characterize a newly discovered calpain termed Rt88 from rat retina. METHODS: Rt88 in retina under normal physiological conditions was characterized in Sprague-Dawley rats of various ages by competitive RT-PCR, Northern blot analysis, cDNA cloning and sequencing. Recombinant Rt88 was expressed in the baculovirus system and characterized by casein zymography and immunoblotting. RESULTS: Rt88 was sequenced and found to be similar to muscle calpain p94 except for three differences. A different exon 1 (as in lens Lp82 calpain) was present, and exons 15 and 16 in the unique IS2 region of muscle p94 were deleted. Of eleven tissues studied, mRNA for Rt88 was found only in retina where Rt88 increased with maturation and then remained constant. Casein zymography showed that rRt88 was proteolytically active after activation by calcium, but intact rRt88 was rapidly broken due to the presence of the IS1 region in domain II. CONCLUSIONS: Rt88 is a retina-specific, calcium activated protease from the calpain superfamily (EC 3.4.22.17) of cysteine proteases. Rt88 is a recently identified member of the AX1 subfamily of calpains showing alternative exon 1 usage. So far, all AX1 subfamily members are from eye. Rt88 may perform specific proteolytic functions during development, normal turnover, or pathological degeneration of retinal proteins.

Amino Acid Sequence↗
PubMed2000

[Application of monocyte strains (THP-1 cells) in study on silicosis in vitro].

OBJECTIVE: To explore the application of human blood monocyte strain (THP-1 cells) with properties of pulmonary alveolar macrophage in study on pathogenesis of silicosis in vitro. METHODS: Effects of cell culture supernatant of THP-1 stimulated by silica or induced and differentiated by phorbol ester (PMA) on proliferation of fibroblast (CHL), formation of Ag-NORs granule, migration of pulmonary alveolar epithelium (CCL-64) and occurrence of silicosis-like pathological changes were observed in rats. Chemo-illuminescence stimulated by silica in PMA-primed THP-1 cells was studied, as compared with that by PMA. RESULTS: Supernatant of silica-stimulated THP-1 cell culture could effectively enhance proliferation of CHL cells and increase the mean number of Ag-NORs granule and their dispersion, with a good dose-response relationship, which correlated highly with cytotoxicity index, pulmonary alveolar macrophage (PAM), caused by silica. And, they could also inhibit the migration of CCL-64 and the repair of epithelial damage. The supernatants from silica-stimulated PAM and THP-1 cell culture could cause early silicotic nodule-like lesions in rats. Chemo-illuminescence response in PMA-primed THP-1 cells and PAM was enhanced by stimulation with silica in a dose-dependent pattern. CONCLUSION: PMA-primed THP-1 cells may have a prospect of wide application in study on pathogenesis of silicosis and production of silicosis-related cytokine and oxygen free radicals in vitro.

Animals↗
PubMed2000

[Study of human tissue engineering cartilage].

OBJECTIVE: To investigate the technique of human tissue-engineered cartilage and to study the medical collagen membrane of guided tissue regeneration (GTR) as the carrier of in vitro chondrocytes culture. METHODS: Tissue engineering technique was used to make human Tissue-engineered cartilage, which was examined histologically and functionally. RESULTS: It was found that the chondrocytes seeded on the medical collagen membrane of GTR grew well. A layer of milk white and cartilage-like tissue grew on the surface of medical collagen membrane of GTR after 1 week. It was demonstrated that the cartilage-like tissue was strong enough to be transferred after being implanted for 8 weeks. The cartilage-like tissue was proved to be human tissue engineered cartilage by HE stain and Alcian blue-poncean S stain. The chondrocytes could secrete chondroitin sulfate as proved by Lev-Spicer stain. CONCLUSIONS: The medical collagen membrane of GTR has characteristics of three-dimensional structure and cell reticular function, and it has the possibility to be developed as a natural scaffold for tissue engineering. The results indicate that it is possible to make human tissue-engineered cartilage with tissue-engineering technique.

Animals↗
PubMed2000

[Occurrence and control of frost in Tilia amurensis and Fraxinus mandshurica young plantations].

The changes of minimum temperature periodical biological phenomena and frost in yound Tilia amurensis and Fraxinus mandshurica plantation stands were systematically analyzed based on the vertical gradient observation and plot investigation. Meanwhile, the resistance of Tilia amurensis to late frost was also studied. The results showed that the phenophase of T. amurensis was later than that of F. mandshurica. Influenced by significant temperature inversions in this area, the phenophase of T. amurensis and F. mandshurica changed regularly in different aspects and slope positions. The sprouts on west slope started earlier than that on east slope. The higher they grew on the slope, the earlier they sprouted, with the earliest sprout at the top of slope. Late frost in this area only took place when the trees were sprouting, but air temperature decreased significantly at the same time. The degree of injury from the late frost could be controlled effectively by selecting suitable site. Sites down the slope, especially the east slope, were not suitable for T. amurensis and F. mandshurica plantation in this research area. Chemical treatment and biological shading could prevent late frost injury through putting off sprout. Mixed plantations could prevent F. mandshurica and T. anurensis from late frost injury significantly, and the frost injury index and the proportion of the tree number of different injury grades were lower than those in pure stands.

Climate↗
PubMed2000

Association of coagulation factor VII with the risk of myocardial infarction in the Chinese.

OBJECTIVE: To elucidate the association of plasma factor VII coagulant activity (FVIIc) with the risk of myocardial infarction (MI) and to assess the influence of factor VII gene MspI polymorphism and lipid metabolism on FVIIc in the Chinese. METHODS: A total of 137 patients with angiographically confirmed MI and 125 healthy individuals were evaluated retrospectively. Plasma FVIIc was measured by one-stage prothrombin time, and FVII genotype was determined after MspI digestion of polymerase chain reaction-amplified genomic DNA. Serum lipid levels were assessed by routine methods. RESULTS: MI patients had significantly higher levels of FVIIc (119.5% +/- 22.7% vs 99.9% +/- 21.8%, P < 0.01) and total serum cholesterol (5.80 +/- 1.06 mmol/L vs 5.53 +/- 1.08 mmol/L, P < 0.05) than controls, but only FVIIc independently correlated with the risk of MI (OR = 1.04, P < 0.01). There were no significant differences in FVII genotype or allele frequency between patients and controls (P > 0.05). Subjects with the Gln353 allele were associated with significantly lower FVIIc levels than Arg353 homozygotes (99.7% +/- 19.3% vs 111.4% +/- 24.6%, P < 0.05). Serum triglyceride was positively correlated with plasma FVIIc in both control (r = 0.25, P < 0.01) and case (r = 0.87, P < 0.01) groups, but this correlation was restricted to Arg/Arg genotype (r = 0.68, P < 0.01). A significant correlation of total serum cholesterol with FVIIc only appeared in Arg/Arg homozygotes (r = 0.17, P < 0.01). CONCLUSIONS: Our findings support the role of plasma FVIIc as a risk factor for MI in Chinese. Plasma triglyceride and FVII gene MspI polymorphism are two independent determinants of FVIIc. Assay of this polymorphism will be helpful in determining who will benefit most from lipid-lowing therapy.

Adolescent↗
PubMed2000

[Surgical treatment of single level unstable degeneration with foraminal stenosis].

OBJECTIVES: Lumbar spine single level unstable degeneration with foraminal stenosis was treated with unilateral decompression, disc excision, posterolateral interbody fusion utilizing single BAK cage and count-lateral facet joint screw fixation. The short-term and mid-term clinical results were evaluated. METHODS: There were thirty patients (13 male, 17 female) with an average age of 46.5 years. From posterior approach, all patients underwent unilateral decompression, disc excision, interbody fusion with posterolateral inserted single BAK cage, and count-lateral facet joint screw fixation. RESULTS: All patients underwent surgery safely without severe complications occurred such as infection and neurological damages. The average follow-up time was 12 months (6 - 18 months) with complete relief of symptoms. Solid fusion was achieved in all but 2 patients at final follow-up. 90% of the patients obtained successful clinical outcome. CONCLUSIONS: Complete decompression of the neural foramen can relief the symptoms, and interbody fusion utilizing threaded cage can restore the height of disc space and withstand axial loading of the spine. Addition of the facet joint fixation increased the postoperative segment stability and enhances solid fusion. With less invasive and preservation of part of the posterior elements of the lumbar spine and the solid fusion achieved, we consider it a sound procedure for the treatment of single level unstable degeneration with foraminal stenosis of lumbar spine. Long-term follow-up results needs to be observed.

Adult↗
PubMed2000

[Isolation and phenotypic analysis of lamina propria mononuclear cells from colonoscopic biopsy specimens].

This study was directed to the method of isolation of lamina propria mononuclear cells (LPMC) from mucosal biopsy specimens and the phenotypic analysis of the cells. Ten biopsy specimens, taken individually from 8 patients with ulcerative colitis (UC), 5 normal controls and 22 patients with colorectal cancer, were collected to compare the factors that influence isolation and cell yield and to analyze the lymphocyte subsets by means of two-color flow cytometry. LPMC yield averaged 10(6) with a viability of more than 95% in UC, twice the yields in other two groups. The percentages of total T, B cells in three groups were similar (P > 0.05). When the UC group was compared with the other two groups, a significantly higher proportion of CD3(+)-CD4(+)-T cell (49.98% vs 37.54% and 37.25%, P < 0.01) was noted, whereas a lower proportion of CD3(+)-CD8(+)-T cell (23.64% vs 31.52% and 31.07%, P < 0.01) was observed. These data showed that the yield and viability of LPMC isolated from biopsy specimens were good enough for a phenotypic or functional analysis, which might be helpful to mucosal immune research on gut disorders, such as UC.

Biopsy↗
PubMed2000

[HPLC quantitative analysis of berberine absorpted with macroporous resin in Rhizoma Coptidis and its preparation zuo jin wan].

Absorptive ability and elution program of macroporous resin to the berberine in the Rhizoma Coptidis and its preparation Zuo Jin Wan (containing Rhizoma Coptidis and Fructus Evodiae) were explored. The extract of 70% MeOH of samples were disolved in water, then alkalized to pH 12 with ammonia solution. The berberine was absorpted by the macroporous resin, the washed off water soluble impurity with alkalescent water, and eluted with 50% MeOH containing 0.5% H2SO4. The results of quantitative analysis of the berberine by HPLC were satisfied.

Adsorption↗