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Biomedical subjects

W Ma

Publications and source records attributed to W Ma.

At least 217 records · Page 12Linked to original sources
PubMed1998

Effect of dietary curcumin and dibenzoylmethane on formation of 7,12-dimethylbenz[a]anthracene-induced mammary tumors and lymphomas/leukemias in Sencar mice.

Female Sencar mice (6 weeks old) were administered 1 mg of 7,12-dimethylbenz[a]anthracene (DMBA) by oral gavage once a week for 5 weeks. At 20 weeks after the first dose of DMBA, 68% of mice developed mammary tumors (the average 1.08 tumors per mouse) and 45% had lymphomas/leukemias. Feeding 1% dibenzoylmethane (DBM) in AIN 76A diet, starting at 2 weeks before the first dose of DMBA and continuing until the end of the experiment, inhibited both the multiplicity and incidence of DMBA-induced mammary tumor by 97%. The incidence of lymphomas/leukemias was completely inhibited by 1% DBM diet. In contrast, feeding 2% curcumin diet had little or no effect on the incidence of mammary tumors, and the incidence of lymphomas/leukemias was reduced by 53%.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1998

Effects of cannabinoids on preimplantation mouse embryo development and implantation are mediated by brain-type cannabinoid receptors.

We examined the relative importance of G (Gi) protein-coupled brain-type (CB1-R) and spleen-type (CB2-R) cannabinoid receptors in preimplantation embryo development using agonists and antagonists specific to CB1-R and CB2-R. The results establish that endogenous cannabinoid ligands, anandamide and sn-2 arachidonoylglycerol, arrest embryo development in vitro, and this effect is reversed by CB1-R antagonists SR141716A or AM 251, but not by SR144528, a CB2-R antagonist. A CB2-R selective agonist AM 663 failed to affect embryo development. These results suggest that cannabinoid effects on embryo development are mediated by CB1-R. We also observed that delta9-tetrahydrocannabinol ([-]THC) infused in the presence of cytochrome P450 inhibitors interfered with blastocyst implantation. This adverse effect was reversed by coinfusion of SR141716A. The less active stereoisomer (+)THC plus the inhibitors failed to affect implantation. Analysis of tissue levels demonstrated that uterine accumulation of (-)THC occurred when it was infused in the presence of the P450 inhibitors. These results demonstrate that the uterus and perhaps the embryo have the cytochrome P450 enzymes to metabolize (-)THC and neutralize its adverse effects on implantation. Collectively, the present study demonstrates that cannabinoid effects on embryo development and implantation are mediated by embryonic and/or uterine CB1-R, but not CB2-R.

Animals↗
PubMed1998

Role of the adrenal gland and adrenal-mediated chemosignals in suppression of estrus in the house mouse: the lee-boot effect revisited.

Mature female mice, grouped in the absence of a male stimulus, exhibit a suppressed estrous cycle (the so-called Lee-Boot effect). We have designed a series of experiments to elucidate the involvement of the adrenal gland in this phenomenon. Our initial results indicate that adrenalectomized mice exhibit a regular estrous cycle in either isolated or grouped conditions. A single, intact mouse caged with five adrenalectomized females showed repeated normal cycles. When the urine samples from group-caged intact mice or group-caged adrenalectomized mice were applied to the external nares of singly caged females, estrous cycles were inhibited in the animals receiving urine from the intact mice but not from the adrenalectomized mice. In addition, corticosterone therapy restored the function of estrus suppression in grouped, adrenalectomized mice. We had previously shown that the urinary excretion of several volatile compounds (2-heptanone, trans-5-hepten-2-one, trans-4-hepten-2-one, pentyl acetate, cis-2-penten-1-yl acetate, and 2,5-dimethylpyrazine) was adrenal mediated (Science 1986; 231:722-725). A further testing of these compounds in relation to estrus suppression has now revealed that a mixture of these compounds is effective, but removing 2, 5-dimethylpyrazine from the mixture abolished the biological response. The overall results of this study show conclusively an important role of the adrenal gland and adrenal-mediated urinary metabolites in estrus suppression.

Adrenal Glands↗
PubMed1998

RpoS (sigma-S) controls expression of rsmA, a global regulator of secondary metabolites, harpin, and extracellular proteins in Erwinia carotovora.

RpoS (sigma-S or sigma-38) controls a large array of genes that are expressed during stationary phase and under various stress conditions in Escherichia coli and other bacteria. We document here that plant pathogenic and epiphytic Erwinia species, such as E. amylovora; E. carotovora subsp. atroseptica, betavasculorum, and carotovora; E. chrysanthemi; E. herbicola; E. rhapontici; and E. stewartii, possess rpoS genes and produce the alternate sigma factor. We show that rpoS transcription in E. carotovora subsp. carotovora is driven from a major promoter which resides within the nlpD gene located upstream of rpoS as in E. coli. RpoS- E. carotovora subsp. carotovoa strain AC5061, constructed by marker exchange, is more sensitive to hydrogen peroxide, carbon starvation, and acidic pH than its RpoS+ parent strain, AC5006. The basal levels of extracellular pectate lyase, polygalacturonase, and cellulase as well as those of transcripts of E. carotovora subsp. carotovora hrpN (hrpNEcc), the gene for the elicitor of the hypersensitive reaction, are higher in the RpoS- strain than in the RpoS+ parent. Likewise, compared to AC5006, AC5061 causes more extensive maceration of celery petioles. Our findings with the RpoS- mutant and strains carrying multiple copies rpoS+ DNA reveal that rpoS positively controls rsmA expression. We also present evidence that supports the hypothesis that the RpoS effect on extracellular enzyme levels, hrpNEcc expression, and virulence manifests itself by the modulation of rsmA expression.

Bacterial Outer Membrane Proteins↗
PubMed1998

Insulin-like growth factor I modulates induction of apoptotic signaling in H9C2 cardiac muscle cells.

Insulin-like growth factor I (IGF-I) is an important survival growth factor that has been shown to inhibit apoptosis, but the effects of IGF-I on apoptotic signaling remain largely unknown. To investigate IGF-I actions on apoptosis of H9C2 cardiac muscle cells, we have defined the effects of IGF-I on Bcl-2, Bax, caspase 3, DNA fragmentation, and cell survival. The abundance of Bcl-2 and Bax was determined with immunoblotting, and the activities of caspase 3 were assayed with the labeled substrate DEVD-p-nitroanilide. The occurrence of apoptosis was determined by electrophoresis of labeled DNA fragments and by in situ terminal deoxynucleotidyl transferase UTP nick end labeling assay. We found that apoptosis of H9C2 cells, induced by serum withdrawal and doxorubicin, was associated with the induction of Bax and the activation of caspase 3. IGF-I partially inhibited Bax induction, caspase 3 activation, DNA fragmentation, and enhanced cell survival. Interestingly, there is a compensatory rise in the abundance of Bcl-2 upon serum withdrawal and doxorubicin treatment, and IGF-I stimulation resulted in decreased induction of Bcl-2. These results suggest that serum withdrawal- and doxorubicin-induced apoptosis of H9C2 cells probably in part resulted from induction of Bax and caspase 3, and IGF-I inhibited apoptosis by attenuating Bax induction and caspase 3 activation.

Apoptosis↗
PubMed1998

Cleft palate formation in fetal Br mice with midfacial retrusion: tenascin, fibronectin, laminin, and type IV collagen immunolocalization.

OBJECTIVE: This study tested the hypothesis that altered craniofacial morphology does not affect the expression of extracellular matrix (ECM) molecules such as fibronectin (FN), laminin (LN), type IV collagen, and tenascin-C (TN) but is associated with failure of palatal shelf elevation and fusion concomitant with cleft palate formation. DESIGN: To test this hypothesis, a comparative immunohistological analysis of FN, LN, type IV collagen, and TN was undertaken on brachyrrhine (Br/Br) mice and normal (+/+) fetuses during secondary palate formation. Normal and Br/Br fetuses were collected at gestational days E13 and E14 (representing prefusion stages) and E15 and E18 (representing postfusion stages). Cryostat palatal sections (8 microm) were postfixed in methanol, washed, and stained with primary antibody. All sections were washed and coated with secondary antibody (swine-anti-rabbit IgG) and mounted with citifluor. RESULTS: Immunohistological analysis showed that LN and type IV collagen were located near the presumptive medial epithelial seam (MES) or edge (MEE) in +/+ or Br/Br fetuses, respectively. Fibronectin showed a homogeneous distribution at all stages in both groups of mice. In contrast, TN became localized below the presumptive MES or MEE in both groups of mice at E14. In +/+ animals at E15, TN dissipated and became confined to the oral basement membrane by E18. At E15 and E18 in cleft Br/Br mutants, TN stained beneath the MEE. CONCLUSION: Although the distributions of ECM molecules are similar during normal and cleft palatogenesis, differences in TN expression are associated with cleft palate formation.

Animals↗
PubMed1998

The influence of stress on edentulous maxillary bone with different artificial anterior tooth arrangements by three-dimensional photoelasticity.

OBJECTIVE: To investigate the influence of stress on edentulous maxillary bone different artificial anterior tooth arrangements, with the goal to establish theoretical evidence for optimal anterior tooth arrangements in complete denture restoration. MATERIALS AND METHODS: Three-dimensional photoelasticity experimental stress analysis was conducted. Shear stresses were measured and principal stresses were separated into six different models of maxillary central incisor arrangements. RESULTS: The value of maximum stresses and the absolute values of principal stresses and positive stresses were obtained. The distribution curve of shear stresses and principal stresses was also shown. CONCLUSIONS: The horizontal distance between the incisive papilla center and the incisal margin of the maxillary central incisor should be no more than 8 mm, if the anterior mandibular arch is larger than the maxillary arch. The principal stress is a better indicator of stress on edentulous maxillary bone when load is applied at the protrusive occlusal position.

Alveolar Process↗
PubMed1998

[Controlled clinical study on efficacy of fixed-dose compounds rifater/rifinah in antituberculous chemotherapy].

OBJECTIVE: To assess antituberculous efficacy, patients' compliance and application perspective of fixed-dose compounds rifater/rifinah in China. METHOD: Three hundred eight new smear positive pulmonary tuberculosis patients were randomly allocated with a ratio of 2 to 1 into treatment group (227 cases, receiving 2RIFATER/4RIFINAH regimen) and controls (81 cases, 2HRZ/4HR) for observation. RESULT: The sputum negative conversion rates at the 2nd month in the treatment group and the controls were 91.2% and 86.4% respectively, and at the end of the chemotherapy 98.7% and 97.5%. Chest radiography showed remarkable improvement. The resolution of pulmonary lesions in the treatment group and the controls accounted for 95.2% and 93.8% respectively, with cavity closure rates of 68.6% in the treatment group and 67.9% in the controls. The drug adverse reaction rates were 8.9% in both groups, and the default rates were 4.3% and 7.8% respectively. CONCLUSION: Fixed-dose compounds rifater/rifinah show excellent therapeutic efficacy, safety and compliance in antituberculous chemotherapy, which could be recommended for wider use in tuberculosis control in China.

Adolescent↗
PubMed1998

[Investigation on TT virus infection among various populations in Shenzhen].

A polymerase chain reaction assay with nested primers (nested PCR) deduced from the well conserved sequences of TTV ORF1 region was established to detect TTV DNA. PCR products from the 2 patients with non A-G hepatitis were cloned and sequenced to confirm its specificity. By using this assay, we tested the serum samples of 90 normal individuals, 88 paid blood donors, 79 intravenous drug users and 29 patients with non A-G hepatitis in Shenzhen, China. The positive rates of TTV DNA were 7.8%, 9.0%, 41.7% and 44.8%, respectively. TTV DNA was detected in 14 of the 90 normal individuals and 88 paid blood donors without any symptoms of liver disease. The results of this study suggest that TTV infection is common in normal population and the paid blood donors. The intravenous drug users are at high risk for TTV infection. TTV would be responsible for a part of non A-G hepatitis.

Adolescent↗
PubMed1998

[Chitosan pin fixation of rabbit proximal tibia osteotomy].

Degradatable chitosan pin, 4 millimeters in diameter and 30 to 40 millimeters in length, was studied radiographically and histologically (oxytetracycline-labeling) at 3, 6, 12, 24 and 48 weeks after the implantation for fixation of a transverse proximal tibia osteotomy in fourty rabbits. The results showed that new bone formation and oxytetracycline uptake were increased 3-6 weeks after operation and the fracture was completely healed 12 weeks after operation, but in two rabbits the chitosan pin broke, in 3 weeks. Histologically, there was a massive inflammation (non-specific foreign body reaction) 3-12 weeks after implantation, which gradually subsided 24 weeks aften operation. Chitosan pin was slowly degradated in bone and was not replaced by normal tissue 48 weeks after operation. The questions to be addressed in future include how to increase the mechanical strength of chitosan pin and how to improve the characteristics of its surface.

Animals↗
PubMed1998

[Structure and function of saw1--a gene related to differentiation of Streptomyces ansochromogenes].

The DNA sequence of double strands of saw1 gene was determined by the method of chaintermination inhibitors. The result indicated that the 1500 bp of DNA fragment displayed a complete open reading frame (ORF), the encoding regions were located in 419 to 1252 bp positions, saw1 product has 89% identity to amino acids of sigma whiG of Streptomyces coelicolor. When recombinant plasmid containing a 1500 bp saw1 DNA fragment insert in plasmid pIJ702 was introduced into Streptomyces coelicolor C71, the sporulation deficient mutant C71 could form spore and produce grey pigment. The gene function was studied by using the method of gene disruption and the result showed that the saw1 played an important role in developmental changes from aerial hypha to spore formation of Streptomyces ansochromogenes.

Amino Acid Sequence↗
PubMed1998

[Experimental research on laser-induced single-molecule detection].

Single-molecule detection is a kind of ultra-high sensitive detection technique. It is widely used in biology, medicine, environment and so on. Here we report briefly the principle and device of our laser-induced single-molecule detection spectrum instrument. We also report the experimental results on the instrument by using C445 dye, including the affection of sample velocity, energy characteristic, consistence linearity and detection limit. We discuss the effect of photon bleach on experimental results. These results are the base of our future work.

Chemistry Techniques, Analytical↗
PubMed1998

[Ultrasensitive analysis of R6G and R110 in solution].

This paper describes the ultrasensitive detection of R6G and R110 in a flowing aqueous sample, based on laser-induced fluorescence (LIF) combined with mode-locked pulsed excitation and time-correlated single-photon counting. A high repetition rate mode-locked argon ion laser operated at 514.5 nm was used as the excitation source. The laser beam was found tightly into a thin wall capillary flow cell. The probe volume was about 12.6 x 10(-12)L. Fluorescence was collected at 90 degrees using a x 40 microscope objective, and was detected by a fast response PMT detector. A time-gate was used to discriminate Raman scattering light background. Using the criterion of 3 standard deviations above background, the detection limits obtained for R6G and R110 were 3.8 x 10(-14) mol/L and 1 x 10(-13) mol/L respectively, and the average probability was lower than 1 in the presence of a R6G or a R110 molecule in the detection volume.

Lasers↗
PubMed1998

[Analysis of trace Pd in marine deposit samples using laser-excited atomic fluorescence spectrometry].

Laser-excited atomic fluorescence spectrometry and its experimental set-up are introduced in this paper. Using this spectrometer, Pd contents in 36 marine deposit samples of the East-sea continental shelf were analyzed. The results show that the detection limit and the precision of this spectrometer are 50 pg/mL and 6% respectively, and the measurements of Pd in marine deposit samples are reliable.

English Abstract↗
PubMed1998

The aqueous humor is capable of generating and degrading H2O2.

PURPOSE: To determine the ability of the aqueous humor to generate and degrade H2O2, the effect of environmental factors such as oxygen tension and temperature, and the constituents contributing to the observed results. METHODS: Aqueous humor was carefully removed from bovine eyes within 3 hours of death. Standard and new techniques were used to follow H2O2 degradation and formation. Catalase activity was measured by H2O2 decomposition, usually at 100 microM and 10 mM H2O2, and in some cases by O2 generation. RESULTS: Bovine aqueous humor generated and degraded H2O2. The generation of H2O2 was minimal at 0 degrees C but increased as temperature increased, so that at 37 degrees C at 3 hours, approximately 90 microM H2O2 was observed. Degradation was more complex. At 0 degrees C, only a slow rate of degradation was observed. At 25 degrees C, it was more rapid, and a steady state between generation and degradation was observed at approximately 30 microM. However, at 37 degrees C, starting with 100 microM H2O2, degradation was initially rapid, but then generation became predominant and H2O2, concentration increased to more than 100 microM in 3 hours. No H2O2 was generated in the absence of O2, and H2O2 production increased with increasing O2 tension. Both low and high molecular weight components contributed to the degradation, but synthesis was completely dependent on low molecular weight constituents. Ascorbic acid and metal ions such as Cu+ made a major contribution to H2O2 production. Catalase may be the macromolecular component responsible for aqueous H2O2 decay, as evidenced by H2O2 degradation, inhibition by boiling or 3-aminotriazole, and the approximate correspondence between oxygen generation and H2O2 degradation. CONCLUSIONS: The results indicate that the aqueous humor is capable of producing levels of H2O2 that have been shown previously to cause cataract in organ culture. Changes in aqueous humor metal ion content and concentration of oxygen level have profound effects on H2O2 concentration and may effect lens viability. The variation in published H2O2 levels may in part be the result of the conditions under which the aqueous humor was obtained, stored, and used for assay. The observed steady state H2O2 concentration of 1 microM in fresh aqueous from bovine eyes must be maintained by the metabolism of surrounding tissues as well as intrinsic components capable of degrading H2O2.

Animals↗
PubMed1998

GABAergic cells and signals in CNS development.

GABA is formed primarily from decarboxylation of glutamate by a family of cytosolic and membrane-bound GAD enzymes. In the adult, GAD-derived GABA sustains the vitality of the central nervous system (CNS), since blockage of GAD rapidly leads to convulsions and death. In plants, cytosolic GAD synthesizes GABA in response to hormones and environmental stress. Since decarboxylation involves protonation, secretion of GABA serves to buffer cytosolic pH in plant cells. Families of GAD and GABAA receptor/Cl- channel transcripts and encoded proteins emerge early and seemingly everywhere during CNS development, with their abundance closely paralleling neurogenesis and peaking before birth. Micromolar GABA acts at receptor/Cl-channels to depolarize progenitor cells in the cortical neuroepithelium; it also elevates their cytosolic Ca2+ (Cac2+) levels. In some way, these effects decrease proliferation. GABA directs the migration of postmitotic neuroblasts at femtomolar concentrations and stimulates their random motility at micromolar concentrations via Ca2+ signaling mechanisms. Activation of GABAA receptors by micromolar GABA may limit motility via membrane depolarization and elevated Cac2+. These results indicate that in vitro GABA can affect embryogenesis of the CNS through effects on cell proliferation and migration. As neurons differentiate postnatally, Cl(-)-dependent depolarization disappears together with GABAergic Cac2+ signals. Physiologically occurring GABAergic signals at Cl-channels exist in tonic and transient forms. Since the former are found on progenitor cells while both are present in postmitotic neurons, mechanisms to generate transients differentiate in the latter. Surprisingly, tonic and transient forms of GABAergic signaling at Cl-channels are rapidly and smoothly interconvertible and seem to be derived from online GABA synthesis in a surface-accessible compartment of the membrane.

Animals↗
PubMed1997

5-HT1A receptor mRNA expressions differ in the embryonic spinal cord of male and female rats.

During critical periods of development, the effects of testosterone (T) on promoting androgenization of the central nervous system (CNS) are reflected not only by behavior, morphology, and hormone secretion but also by gene expression. The mechanisms involved in sexual differentiation of the CNS, however, remain incompletely defined. The current set of experiments examined with in situ hybridization the dimorphism in 5-HT1A receptor mRNA expression in the embryonic rat spinal cord and the possible role of T in the dimorphism. We found sex-related differences in expression of 5-HT1A mRNA in the spinal cord, which were altered by a single injection of T. The results suggest that this gonadal steroid is responsible for the sexual dimorphism in 5-HT1A mRNA expression occurring during the critical period.

Animals↗