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Biomedical subjects

C Ma

Publications and source records attributed to C Ma.

At least 91 records · Page 5Linked to original sources
PubMed1999

Preparation of primary cell cultures from lamprey.

The lamprey is an important model for studies of evolution and comparative biology. The ability to culture cells from lamprey tissues makes it possible to employ an in vitro approach to address basic questions in these areas. Methods are described for the initiation of cell cultures derived from tissues of adult and larval sea lamprey (Petromyzon marinus). Primary cultures initiated from gill, muscle, gut, brain, ovary, heart and kidney were viable for up to eight months and several of the cultures were propagated for multiple passages. Most cultures were initiated from tissue explants in basal nutrient medium supplemented with fetal bovine and trout sera on a culture surface treated with fibronectin and collagen. Variations of these culture conditions to meet the specific growth requirements of certain cell types are discussed.

Animals↗
PubMed1999

Genetic screens in yeast to identify mammalian nonreceptor modulators of G-protein signaling.

We describe genetic screens in Saccharomyces cerevisiae designed to identify mammalian nonreceptor modulators of G-protein signaling pathways. Strains lacking a pheromone-responsive G-protein coupled receptor and expressing a mammalian-yeast Galpha hybrid protein were made conditional for growth upon either pheromone pathway activation (activator screen) or pheromone pathway inactivation (inhibitor screen). Mammalian cDNAs that conferred plasmid-dependent growth under restrictive conditions were identified. One of the cDNAs identified from the activator screen, a human Ras-related G protein that we term AGS1 (for activator of G-protein signaling), appears to function by facilitating guanosine triphosphate (GTP) exchange on the heterotrimeric Galpha. A cDNA product identified from the inhibitor screen encodes a previously identified regulator of G-protein signaling, human RGS5.

Cloning, Molecular↗
PubMed1999

Neonatal tetanus associated with topical umbilical ghee: covert role of cow dung.

BACKGROUND: Previous studies in Pakistan have shown that ghee (clarified butter) is commonly applied to umbilical wounds of neonates, and have documented that such applications are a risk factor for neonatal tetanus (NNT). In-use contamination of ghee with Clostridium tetani has been demonstrated, but mechanisms underlying the risk of ghee have been incompletely evaluated epidemiologically. METHODS: Detailed information on ghee usage, including fuels used to heat it, was obtained from cases of NNT (n = 229) and their matched controls (n = 687) from a population-based study of NNT in Punjab Province, Pakistan. Design variables were created to evaluate the impact of different fuel sources on risk of ghee applications. RESULTS: Nearly one-third of all infants had ghee applied, and it was nearly always heated before application to umbilical wounds of newborns. After controlling for all factors found to be significantly associated with NNT in conditional logistic regression, only ghee that had always been heated with dried cow dung fuel was significantly associated with NNT. Topical antimicrobials and ghee were never applied together. CONCLUSIONS: Ghee applications to umbilical wounds, when heated with 'clean' fuels, appear to pose no increased risk of NNT, although handling practices undoubtedly result in hazardous microbial contamination. In contrast, ghee heated with dung fuel was significantly associated with NNT. The effective promotion of topical antimicrobials might help reduce ghee use, since the intended purpose of each is to enhance healing.

Administration, Topical↗
PubMed1999

Regulation of matrix metalloproteinases (MMPs) and their tissue inhibitors in human myometrial smooth muscle cells by TGF-beta1.

The objective of the present study was to determine whether transforming growth factor beta (TGF-beta) regulates the expression of matrix metalloproteinases (MMP) and the tissue inhibitor of MMP (TIMP) in myometrial smooth muscle cells. Using primary cultures of human myometrial smooth muscle cells we found that these cells express MMP-1, MMP-3, TIMP-1 and TIMP-2 mRNA and protein, with significantly higher values of TIMP than MMP. We also found that TGF-beta1 (1 ng/ml) increased the expression of TIMP-1 mRNA, while it reduced the expression of MMP-1 and MMP-3 mRNA, compared with untreated controls. In addition, TGF-beta1 slightly increased the production of TIMP-1, but not TIMP-2. Production of MMP-1 and MMP-3 was reduced by treatment with TGF-beta1, compared with the untreated control. A major portion of MMP-1 released into the culture-conditioned media was in complex with TIMP-1, and the levels of this complex were reduced by treatment with TGF-beta1. In conclusion, the data indicate that myometrial smooth muscle cells express MMP and TIMP mRNA and protein, and their expression is differentially regulated by TGF-beta1. Such a differential regulation of MMP and TIMP by TGF-beta may influence the rate of extracellular matrix (ECM) turnover following tissue injury, induced during myomectomy and Caesarean section, or in leiomyomas during growth.

Cells, Cultured↗
PubMed1999

Physical characteristics of a miniature multileaf collimator.

A preliminary study of the physical characteristics of a miniature multileaf collimator (mMLC) used with 4 MV x rays is reported. The mMLC attached to the accessory mount of a class C or D Varian linear accelerator (Varian Oncology Systems, Palo Alto, CA) with a source to aperture distance of 65 cm. The field penumbra using the small leaves was found to be consistent with the anticipated field penumbra using photon jaws at the same source to aperture distance as the mMLC. The percentage depth dose values of square fields were found to be consistent with the fields collimated with the upper and lower jaws. Output factors for the very small fields were found to vary rapidly. Circular fields could be produced with depth dose characteristics similar to those produced using conical tertiary collimators, commonly used for radiosurgery, but with a broader penumbra.

Dose-Response Relationship, Radiation↗
PubMed1999

Regulation of transforming growth factor-beta1 expression by granulocyte macrophage-colony-stimulating factor in leiomyoma and myometrial smooth muscle cells.

Human myometrium and leiomyomas express granulocyte macrophage-colony-stimulating factor (GM-CSF), transforming growth factor-beta (TGFbeta), and their receptors. Overexpression of TGFbeta and, to a limited extent, GM-CSF has been associated with tissue fibrosis throughout the body, including leiomyomas. The objective of the present study was to determine the action of GM-CSF on leiomyoma and myometrial smooth muscle cells (LSMC and MSMC) and examine whether the action of GM-CSF is mediated through the induction of TGFbeta1 expression. Using competitive quantitative RT-PCR and enzyme-linked immunosorbent assay, we found that LSMC express significantly higher GM-CSF messenger ribonucleic acid (mRNA; 0.6 +/- 0.1 x 10(3) copies of mRNA/microg total RNA) and protein (0.75 +/- 0.2 ng/mL) than MSMC (0.5 +/- 0.1 x 10(2) copies of mRNA and 0.45 +/- 0.07 ng/mL protein; P < 0.05). In addition, LSMC expressed significantly higher TGFbeta1 mRNA (1.6 +/- 0.3 x 10(4) copies of mRNA/microg total RNA) than MSMC (2.4 +/- 0.4 x 10(3) copies) and synthesized and secreted more TGFbeta1 protein (1.7 +/- 0.2 vs. 0.5 +/- 0.02 ng/mL); whereas MSMC contained more cell-associated TGFbeta1 (56.2 +/- 1.2 ng/mL) than LSMC (35.2 +/- 1.2 ng/mL; P < 0.05). We found that GM-CSF (0.01-100 ng/mL) has limited mitogenic activity for LSMC but not for MSMC determined by the rate of [3H]thymidine incorporation and cell proliferation assay. However, GM-CSF at 1 ng/mL increased its own production, the expression of TGFbeta1 mRNA, the cell-associated TGFbeta1 protein content in both cell types, and TGFbeta1 released into the culture-conditioned medium of LSMC (P < 0.05). TGFbeta1 also increased its own mRNA and protein expression, but had no effect on cell-associated TGFbeta1 in both cell types (P < 0.05). Cotreatment of LSMC and MSMC with GM-CSF and TGFbeta1 induced changes similar to those produced by GM-CSF in both cells. In conclusion, our data suggest that GM-CSF is not a mitogen for MSMC and LSMC, but it regulates its own expression and the expression of TGFbeta1 by these cells, a regulatory interaction that may account for the GM-CSF-induced tissue fibrosis that occurs in leiomyomas.

Culture Media, Conditioned↗
PubMed1999

Anti-herpes simplex virus activity of alkaloids isolated from Stephania cepharantha.

By screening water and MeOH extracts of 30 Chinese medicinal plants for their anti-herpes simplex virus (HSV)-1 activity, a MeOH extract of the root tubers of Stephania cepharantha HAYATA showed the most potent activity on the plaque reduction assay with an IC50 value of 18.0 microg/ml. Of 49 alkaloids isolated from the MeOH extract, 17 alkaloids were found to be active against HSV-1, including 13 bisbenzylisoquinoline, 1 protoberberine, 2 morphinane and 1 proaporphine alkaloids, while benzylisoquinoline and hasubanane alkaloids were inactive. Although N-methylcrotsparine was active against HSV-1, as well as HSV-1 thymidine kinase deficient (acyclovir resistant type, HSV-1 TK-) and HSV-2 (IC50 values of 8.3, 7.7 and 6.7 microg/ml, respectively), it was cytotoxic. FK-3000 was found to be the most active against HSV-1, HSV-1 TK- and HSV-2 (IC50 values of 7.8, 9.9 and 8.7 microg/ml) with in vitro therapeutic indices of 90, 71 and 81, respectively. FK-3000 was found to be a promising candidate as an anti-HSV agent against HSV-1, acyclovir (ACV) resistant-type HSV-1 and HSV-2.

Alkaloids↗
PubMed1999

Inhibitory effects of constituents from Cynomorium songaricum and related triterpene derivatives on HIV-1 protease.

From CH2Cl2 and MeOH extracts of the stems of Cynomorium songaricum RUPR. (Cynomoriaceae), ursolic acid and its hydrogen malonate were isolated as inhibitors of human immunodeficiency virus type 1 (HIV-1) protease, with 50% inhibitory concentrations (IC50) of 8 and 6 microM, respectively. Amongst various synthesized dicarboxylic acid hemiesters of related triterpenes, inhibitory activity tended to increase in the order of oxalyl, malonyl, succinyl and glutaryl hemiesters, for triterpenes such as ursolic acid, oleanolic acid and betulinic acid. The most potent inhibition was observed for the glutaryl hemiesters, with an IC50 of 4 microM. From the water extract of the stems of C. songaricum, flavan-3-ol polymers, consisting of epicatechin as their extender flavan units, were also found to be potent inhibitory principles against HIV-1 protease.

Acetylation↗
PubMed1999

Cellular expression of a leech netrin suggests roles in the formation of longitudinal nerve tracts and in regional innervation of peripheral targets.

Netrins are secreted, diffusible proteins that direct axonal growth. To study the functions of netrins in the relatively simple and easily accessible nervous system of the leech Hirudo medicinalis, we have cloned a leech netrin and have characterized its expression during embryogenesis. By probing a leech cDNA library at low stringency with chick netrin probes, we have identified a complete cDNA clone that bears significant sequence similarity to netrins of other species. In situ hybridization and dye filling of individual neurons show that this leech netrin is expressed by several identifiable central neurons in every segmental ganglionic primordium during early stages of embryogenesis. Some of these neurons, including the bipolar cells which are thought to be involved in setting up longitudinal tracts, express this gene only transiently during embryogenesis, while others continue to express it in the adult. In addition, leech netrin is expressed by ventral but not dorsal longitudinal muscle cells in each segment before central neurons project their axons to the periphery. These highly specific expression patterns are consistent with the hypothesis that leech netrin plays a role in forming the major interganglionic neuronal tracts and in defining ventral versus dorsal domains of peripheral innervation.

Amino Acid Sequence↗
PubMed1999

Studies of molecular pharmacophore/receptor models for GABAA/benzodiazepine receptor subtypes: binding affinities of substituted beta-carbolines at recombinant alpha x beta 3 gamma 2 subtypes and quantitative structure-activity relationship studies via a comparative molecular field analysis.

Binding affinities of a series of 44 beta-carbolines with various substituents at the 3-, 4-, 6- and 7-positions are reported at 5 distinct recombinant GABAA/benzodiazepine receptor (BzR) subtypes [alpha x beta 3 gamma 2 (x = 1-3, 5, 6)]. Many of these ligands displayed better selectivity for the alpha 1 containing GABAA isoform. The most selective BCCT 2 and SPH 195 (17) displayed potent affinity (Ki = 0.72 and 7.2 nM for the alpha 1 beta 3 gamma 2 receptor subtype, respectively) and an overall selectivity of 20 and 23 fold, respectively, for the alpha 1 beta 3 gamma 2 receptor subtype. These are the most selective ligands in vitro for the alpha 1 containing GABAA/Bz receptor isoform reported to date to our knowledge. QSAR studies of these ligands for each receptor subtype have been carried out via a Comparative Molecular Field Analysis (CoMFA) and an included volume analysis. Geometries and charge distributions of these ligands have been optimized using ab initio methods (J. Med. Chem., 1992, 35, 4001-4010). Active conformations of flexible 3-alkoxylated beta-carbolines have been examined via a CoMFA approach. QSAR studies via CoMFA support the previous hypothesis that beta-carbolines with different intrinsic activities may follow an alternative alignment rule when they bind into the pharmacophore/receptor site of the BzR. Examination of binding affinities of beta-carbolines by this modeling strategy has established some of the differences, in particular, topologic differences between the lipophilic pockets in the alpha 1 beta 3 gamma 2, alpha 2 beta 3 gamma 2, alpha 3 beta 3 gamma 2, alpha 5 beta 3 gamma 2 and alpha 6 beta 3 gamma 2 subtypes as well as some of the similarities among the pharmacophore/receptor models of these five distinct GABAA/Bz receptor subtypes.

Binding Sites↗
PubMed1999

Studies of molecular pharmacophore/receptor models for GABAA/BzR subtypes: binding affinities of symmetrically substituted pyrazolo[4,3-c]quinolin-3-ones at recombinant alpha x beta 3 gamma 2 subtypes and quantitative structure-activity relationship studies via a comparative molecular field analysis.

A series of symmetrically substituted pyrazoloquinolinones was synthesized to probe the BzR binding site of different GABAA/Bz receptor subtypes. The affinities of the ligands for different BzR subtypes have been determined by radioligand binding assays on 5 distinct recombinant GABAA receptor isoforms [alpha x beta 3 gamma 2 (x = 1,2,3,5, or 6)]. Most of the ligands synthesized exhibited potent biological activity in vitro. Among them, 3 ligands exhibited enhanced affinity for the alpha 2 beta 3 gamma 2 subtype in comparison to the other subtypes, six ligands demonstrated higher affinity for the alpha 3 beta 3 gamma 2 subtype, while 2 ligands showed some enhanced affinity for the alpha 5 beta 3 gamma 2 subtype. The remainder of the ligands exhibited relatively higher affinities at the alpha 1 containing subtype. To map out the steric and electronic differences between the benzodiazepine binding subtypes, a QSAR analysis by the method of Comparative Molecular Field Analysis (CoMFA) of each receptor subtypes was carried out.

Binding Sites↗
PubMed1999

[The effect of inhibition of nitric oxide synthesis on vasoregulatory factors in pregnant rats].

OBJECTIVE: To study the effect of the inhibition of nitric oxide(NO) synthesis on plasma endothelin (ET), prostaglandlin I2(PGI2), thromboxane (TXA2) and angiotensin (ANGII) in pregnant rats, and to investigate the role of these factors in the pathogenesis of pregnancy-induced hypertension(PIH). METHODS: Pregnant rats were divided into two groups randomly. Saline solution or L-nitro arginine methyl ester (L-NAME) 125 mg/day was given subcutaneously from day 14 of gestation till delivery. Systolic blood pressure, urine protein, platelet count, and weight of pups and placentae were determined. Plasma NO, ET, PGI2, TXA2 and ANGII were measured by RIA. RESULTS: Pregnant rats which were given L-NAME produced physical signs similar to those of PIH, such as increase in systolic blood pressure (140.6 +/- 3.8) mmHg and urine protein (801.38 +/- 57.12) mg/L, and decrease in platelet count (533 +/- 42) x 10(9)/L and weight of pups and placentae. Compared with controls, plasma NO, PGI2 and ANG II were decreased significantly while plasma ET and TXA2 were increased significantly in rats given L-NAME. CONCLUSION: Inhibition of NO synthesis can cause imbalance of several vaso-regulatory factors, which may be responsible for the pathogenesis of PIH.

6-Ketoprostaglandin F1 alpha↗
PubMed1999

[Clinical study on 24 cases of eclampsia with cerebral malaria].

OBJECTIVE: To explore the clinical characteristics of eclampsia with cerebral malaria. METHODS: A retrospective analysis was done in 24 in-patient cases of eclampsia with cerebral malaria in Mnazimmoja Hospital of Zanzibar from Jul. 1995-Oct. 1998. All had varying degrees of coma, high fever and convulsion with anemia and splenomeguly. In all cases, malarial parasitein in blood smear was positive and underwent anti-malaria treatment, anti-eclamptic convulsion treatment and complex treatment for the prevention of complications, so that 20 of them could terminate pregnancy rapidly. RESULTS: 17 patients were conscious 2-3 days after complex treatment. Their vital signs were gradually stable and pregnancy termination was smooth. 7 patients died, 4 of them due to complicated with blackwater fever and renal failure, one with cardiopneumatic failure, postpartum hemorrhage and puerperal infection respectively. The number of fetal deaths, stillbirth and live births was 8, 7 and 9 respectively. CONCLUSION: Eclampsia with cerebral malaria is an acute and dangerous obstetrical disease. Complex therapy, we think, should be given mainly to the patients. Termination of pregnancy is the key to effective cure of the disease.

Abortion, Induced↗
PubMed1999

[Molecular cloning of hTRT catalytic domain and its expression in tumors].

OBJECTIVE: To study the expression of hTRT gene in tumors and its significance in cancer diagnosis. METHODS: The expression of hTRT in HeLa cells and PG cells was estimated by RT-PCR and the hTRT cDNA encoding the catalytic domain from HeLa cells were cloned and sequenced. Using in situ hybridization (ISH) techniques, the expression of hTRT mRNA in 54 human tumors were observed and compared with the expression of hTR. RESULTS: hTRT was detected in both HeLa and PG cells. Sequencing showed that the cloned hTRT catalytic domain cDNA was identical with that reported in the literature. hTRT and hTR expressions were detected in 38/46 and 40/46 malignant tumors respectively, while both hTRT and hTR were not detected in 8 benign tumors. CONCLUSION: hTRT was detected in both HeLa and PG cancer cells. hTRT catalytic domains were highly conservative. The expression of hTRT and hTR were both high in malignant tumors and they were strongly correlated. Our results suggest that detection of hTRT was valuable to clinical oncology diagnosis.

Catalytic Domain↗
PubMed1999

[Studies on the lactate oxidase producing conditions by Edwardsiella tarda].

A bacterium producing lactate oxidase was re-screened from five strains based on previous researches. The lactate oxidase activity was the highest in strain L1 and this stain was chosen as the enzyme source. Morphological and physiological studies revealed that the bacterial strain L1 belongs to the Edwardsiella tarda Biogroup I. This stain is different from the reported strains Mycobacterium and Pediococcus, which produce lactate oxidase. The enzyme producing conditions were studied in shaking cultures, and the effects of initial pH, riboflavin, lactate and ammonia sulphate concentrations on the production were carried out respectively. The bacteria resource of enzyme is significant to pyruvate production by enzymatic method, and to the enzyme assay of lactate for medical diagnosis, and the application of enzyme electronic probe.

Culture Media↗
PubMed1999

[Longitudinal observation on a schistosome-infected snail spot as a source of infection in a mountainous village of Dali city].

AIM: To observe longitudinally the changes in survival and infection rate of Oncomelania snails in a positive snail spot in Yunnan. METHODS: A positive snail spot in a ditch in Shalimuzhuang Village, Dali City, was continually observed on the changes in the density of snail population and natural infection rate of the snails by random environmental sampling for 8 times in 4 successive years. RESULTS: During the 8 times of snail survey, living snails were found relatively stable in the ditch, in which positive snails were obtained in 6 occasions, the average infection rate being 3.99%. CONCLUSION: The density and the positive rate of snails in the mountain region remains relatively stable as a source of human infection. Elimination of the positive snail spots is necessary for controlling schistosomiasis.

Animals↗