Induced rebuilding of aspartase conformation.
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Aspartate Ammonia-Lyase↗
Biomedical subjects
L Ma
Publications and source records attributed to L Ma.
Immunological characterization of the complex forms of chloroplast translational initiation factor 2 from Euglena gracilis.
Euglena gracilis chloroplast translational initiation factor 2 (IF-2chl) occurs in several complex forms ranging in molecular mass from 200 to 800 kDa. Subunits of 97 to greater than 200 kDa have been observed in these preparations. Two monoclonal antibodies were prepared against the 97-kDa subunits of IF-2chl. Both of these antibodies recognize all of the higher molecular mass forms of this factor, suggesting that these subunits are closely related. Gel filtration chromatography indicates that the higher molecular mass subunits of IF-2chl are present in the higher molecular mass complexes, whereas the smaller subunits are present in the 200-400 kDa forms of IF-2chl. Probing extracts of light-induced and dark-grown cells with the antibodies indicates that the light induction of this chloroplast factor results from the synthesis of new polypeptide rather than from the activation of an inactive precursor form of the protein. Both the higher and lower molecular mass subunits of IF-2chl are present in 30 S initiation complexes as indicated by Western analysis. The binding of IF-2chl to chloroplast 30 S ribosomal subunits requires the presence of GTP, but does not require fMet-tRNA, messenger RNA, or other initiation factors. Neither polyclonal nor monoclonal antibodies against E. gracilis IF-2chl cross-react with Escherichia coli IF-2 or with animal mitochondrial IF-2.
Animals↗
Case-control study of factors associated with failure to detect breast cancer by mammography.
BACKGROUND: Although mammography is widely used to detect breast cancer, it is recognized that not all cancers can be seen on mammographic images. PURPOSE: Our purpose was to examine factors associated with failure to detect breast cancer by mammography. METHODS: A case-control study was carried out in which subjects in whom histologically verified breast cancer was not detected by mammography (false negatives) were contrasted with subjects in whom breast cancer had been detected by mammography (true positives). Mammograms from individuals with histologically confirmed breast cancer were classified independently by two radiologists who were unaware of the clinical or other characteristics of the subjects. Histologic slides of all tumors were reviewed by one pathologist. RESULTS: Three variables were found to be independently and significantly associated with failure to detect breast cancer by mammography. Breast cancer was less likely to be detected by mammography in the presence of extensive parenchymal densities (odds ratio [OR] = 9; 95% confidence interval [CI] = 1.8-44.3), a tumor of lobular histology (OR = 7; 95% CI = 2.2-22.1), and tumors of small size (OR = 0.10; 95% CI = 0.0-0.9). CONCLUSION: Our results indicate that biologic factors are associated with failure to detect some breast cancers by mammography and indicate directions for future research in breast imaging.
Adult↗
Spectroscopic characterization of the alternate form of S-methylcoenzyme M reductase from Methanobacterium thermoautotrophicum (strain delta H).
Two forms (MR1 and MR2) of S-methylcoenzyme M reductase were purified from Methanobacterium thermoautotrophicum (strain delta H) as recently described (Rospert, S., Linder, D., Ellerman, J. and Thauer, R.K. (1990) Eur. J. Biochem. 194, 871-877). MR2 was at least 50-fold more active than MR1, independent of assay conditions. The two forms are spectroscopically similar, but not identical, by UV-visible, magnetic circular dichroism and resonance Raman spectroscopies. MR2 exhibited an EPR signal corresponding to 20% of the enzyme-bound nickel. Strong EPR signals similar to those previously assigned to Ni(I)F430 bound to methylreductase in Methanobacterium thermoautotrophicum (strain Marburg) (Albracht, S.P.J., Ankel-Fuchs, D., Bocher, R., Ellerman, J., Moll, J., Van der Zwann, J.W. and Thauer, R.K. (1988) Biochim. Biophys. Acta 955, 86-102) were observed in MR2-rich, log-phase, as well as in MR1-rich, slow-growing bacteria. Log-phase cells had dramatically different EPR spectra depending on whether they were removed from the fermenter (under gas flow) before or after cooling to 10 degrees C. EPR spectra of slow-growing cells were insensitive to harvesting conditions. The possible biological significance of the alternate form of methylreductase is discussed.
Circular Dichroism↗
The gene encoding vacuolar H(+)-ATPase subunit C is overexpressed in multidrug-resistant HL60 cells.
Previous studies have suggested that vacuolar H(+)-ATPase activity may play a role in modulating drug transport mechanism in multidrug resistant HL60 cells. In the present study we have used a cDNA of human vacuolar H(+)-ATPase subunit C (SC-H(+)-ATPase) to analyze expression of this gene in HL60 cells isolated for resistance to adriamycin or vincristine. The results demonstrate that development of resistance to either agent results in a major increase in the levels of SC-H(+)-ATPase mRNA. Furthermore in resistant cells which have partially reverted to drug sensitivity there is a parallel reduction in SC-H(+)-ATPase mRNA levels. Southern blot analysis shows that the SC-H(+)-ATPase gene is not amplified in the resistant cells. These results therefore demonstrate a correlation between the development of multidrug resistance and enhanced expression of the SC-H(+)-ATPase gene.
Base Sequence↗
Molecular and functional analysis of the XPBC/ERCC-3 promoter: transcription activity is dependent on the integrity of an Sp1-binding site.
The human XPBC/ERCC-3 gene, which corrects the excision-repair defect in xeroderma pigmentosum group B cells and the UV-sensitive CHO mutant 27-1 cells, appears to be expressed constitutively in various cell types and tissues. We have analysed the structure and functionality of the XPBC/ERCC-3 promoter. Transcription of the XPBC/ERCC-3 gene is initiated from heterogeneous sites, with a major startpoint mapped at position -54 (relative to the translation start codon ATG). The promoter region does not possess classical TATA and CAAT elements, but it is GC-rich and contains three putative Sp1-binding sites. In addition, there are two elements related to the cyclic AMP (cAMP)-response element (CRE) and the 12-O-tetradecanoyl phorbol-13-acetate-response element (TRE) in the 5'-flanking region. Transient expression analysis of XPBC/ERCC-3 promoter-CAT chimeric plasmids revealed that a 127-bp fragment, spanning position -129 to -3, is minimally required for the promoter activity. Transcription of the XPBC/ERCC-3 promoter depends on the integrity of a putative Sp1-binding site in close proximity to the major cap site. Band shift assays showed that this putative Sp1-binding site can interact specifically with a nuclear factor, most likely transcription factor Sp1 (or an Sp1-like factor) in vitro.
Animals↗
Bulk organic solvent-water systems as a possible model to predict alkyl p-aminobenzoate partitioning in liposomes.
This study compares the bilayer-water distribution coefficients of a homologous series of n-alkyl p-aminobenzoates in liposomes with their respective distribution coefficients in octanol-water, oleyl alcohol-water, and hexane-water systems. The data indicate that the bilayer-water distribution coefficient is quite sensitive to changes in solute structure and to the structural organization of the bilayer and that octanol, oleyl alcohol, and hexane are able to reflect the partitioning changes that occur in the liposomal bilayer with respect to increasing the alkyl chain length of n-alkyl p-aminobenzoates. For this particular homologous series, the hexane-water system tended to underestimate the bilayer-water distribution coefficients, whereas octanol-water and oleyl alcohol-water systems overestimated solute partitioning into the bilayer. The similarity of the lipid environment, with respect to solute partitioning, in the organic solvent system and that in liposomes can be ascertained by using the Collander relationship.
4-Aminobenzoic Acid↗
Atypical hyperplasia and breast cancer risk: a critique.
The purpose of this paper is to examine critically the evidence that atypical hyperplasia (AH) is a risk factor for breast cancer. First, we appraised studies that have examined the association between AH and breast cancer risk for their adherence to widely accepted standards for the conduct of research. Second, we examined the available evidence to determine the plausibility of an association between AH and breast cancer risk using the guidelines proposed by Bradford Hill. A total of 18 studies (11 cohort studies, two case-control studies, and five cross-sectional studies) were found that were published in the English language from January 1960 to March 1992 that examined the association of AH as a distinct entity and breast cancer risk. A systematic approach was adopted to examine the collected studies for their adherence to methodologic standards, which showed wide variation among studies. A meta-analysis was carried out, based on a total sample size of 182,980 women. Of 16 studies that gave point estimates of risk, 14 exceeded unity and 12 were significantly different from unity. The pooled estimate from all studies of the association between AH and breast cancer, gave an overall odds ratio (OR) of 3.67 (95 percent confidence interval = 3.16-4.26). The test of the hypothesis of homogeneous association was rejected (chi 2 = 151.6, df = 14, P < 0.0001), indicating significant variability among the ORs of individual studies. The conclusions from the application of the Bradford Hill criteria indicated strongly that AH is a risk factor for breast cancer.
Bias↗
The role of interferon-gamma in lymphocytic thyroiditis: its functional and pathological effect on human thyrocytes in culture.
Interferon-gamma (IFN-gamma) has been recognized to possess diverse non-immunological effects on epithelial cells such as cellular growth and differentiation. We have previously demonstrated that IFN-gamma suppressed thyroid-stimulating hormone (TSH)-stimulated thyroglobulin (TG) synthesis in human thyrocytes through inhibition of TG gene transcription. To define the pathological mechanism involved in the action of IFN-gamma, we studied the ultrastructural changes of human thyrocytes cultured in monolayer. Stimulation of the thyrocytes with TSH 10 mU/ml for 2 days resulted in marked increase in TG release into the medium. This was accompanied by elongation of microvilli, increase in follicles and acinar formation, increase in secretory granules and prominence of Golgi apparatus and rough-surfaced endoplasmic reticulum. Addition of IFN-gamma (500 U/ml) resulted in marked degeneration with shrinkage of the cell membrane, vacuolation of cytoplasm, swollen mitochondria and presence of lysosomal granules. Co-culturing the thyrocytes with the IFN-gamma and TSH resulted in suppression of the morphological responsiveness to TSH. There was also suppression of TSH-induced TG secretion. However, at 500 U/ml IFN-gamma did not cause lysis of the thyrocytes as estimated by the cellular DNA content. Furthermore, binucleated cells were frequently encountered in those wells that were treated with IFN-gamma for either 2 or 5 days. The findings suggest that IFN-gamma resulted in de-differentiation and degeneration of the thyrocytes, which subsequently regained the growth potential and showed attempts at regeneration. This may explain why most patients with lymphocytic thyroiditis recover from the acute injury and do not suffer from permanent hypothyroidism.
Cells, Cultured↗
Mesocolonic lymphangioma: a case report with immunoperoxidase and electron microscopic studies.
A 14 yr old girl presented with a large cystic mass in the transverse mesocolon which was completely excised. Cystic lymphangioma was diagnosed, based on the specific histologic, immunoperoxidase and ultrastructural findings.
Adolescent↗
Adenocarcinoma arising in a diverticulum of the urinary bladder.
A case of adenocarcinoma arising from a diverticulum of the bladder is reported. A review of literatures together with the local statistics is presented.
Adenocarcinoma↗
[Magnesium sulfate in prevention of preterm labor].
To observe the efficacy of magnesium sulfate in the treatment of preterm labor, 65 uncomplicated cases of preterm labor between 28 and 36 weeks of gestation were studied prospectively during Sep. 1988-May 1991. They were divided into two groups randomly. 30 cases were treated with magnesium sulfate and 35 cases with barbiturates or bed rest. The prevention of delivery for at least 48 hours after the initiation of therapy was achieved in 23 of the 30 cases (76.67%) of the magnesium sulfate group and in 3 of the 35 cases (8.57%) in the control group. Delay of more than 7 days was achieved in 17 of the 30 cases (56.67%) and in 2 of the 35 cases (5.71%). The postponement of delivery between the two groups. There was highly significantly difference (P less than 0.01). There was a significant correlation of cervical dilation at the onset of treatment to success of controlling preterm labor. In the magnesium sulfate group, the mean magnesium level to achieve tocolysis was 2.8 +/- 0.35 mmol/L (mean +/- s). The side effects to the mothers, fetus, and the neonates were mild and not prominent.(ABSTRACT TRUNCATED AT 250 WORDS)
Female↗
Clonal Epstein-Barr virus in lymphoepithelioma-like carcinoma of the stomach: demonstration of viral genome by in situ hybridization and Southern blot analysis.
Lymphoepithelioma (LE), originally described in the nasopharynx, is an undifferentiated carcinoma with heavy lymphocytic infiltrate. The tumor is common in Southeast Asia, particularly in southern China, where the Epstein-Barr virus (EBV) association has been documented more consistently than in Western countries. Tumors histologically similar to LE have been described also in other anatomical sites, mostly of fore-gut origin, such as salivary gland, tonsil, lung, thymus, and more recently stomach. We are reporting a case of poorly differentiated gastric adenocarcinoma with marked lymphocytic infiltrate resembling LE (LE-like carcinoma) in a Chinese without evidence of nasopharyngeal carcinoma. In situ hybridization for EBV revealed that the tumor cells but not the lymphoid cells harbored the virus. Tumor cells both in syncytial and glandular areas were positive for EBV. By Southern blot analysis EBV was demonstrated in the DNA extracted from the tumor, while the adjacent normal gastric tissue was negative. Moreover, analysis of the EBV termini revealed a clonal episomal form of the virus. Our case further supports the hypothesis that EBV is associated with LE-like gastric carcinoma. It also strongly suggests that EBV infection has preceded, and thus most likely contributed to, the clonal expansion in this tumor.
Aged↗
[Chemical studies on immunologically active polysaccharides of Ganoderma lucidum(Leyss. ex Fr.) Karst].
BN3B, the polysaccharide component of the fruit of Ganoderma lucidum, has been shown to have immune activity. From BN3B four homogeneous polysaccharides were separated and purified. Chemical studies on the main components BN3B1 and BN3B3 indicated that BM3B1 contained only glucose and should be a glucan containing beta-(1----6) and (1----3)glycoside bonds and that BN3B3 was an arabinogalactan containing beta-(1----6) and (1----3)glycoside bonds.
Adjuvants, Immunologic↗
HL-60 cells isolated for resistance to vincristine are defective in 12-O-tetradecanoylphorbol-13-acetate induced differentiation and the formation of a functional AP-1 complex.
HL-60 cells isolated for resistance to vincristine are multidrug resistant and defective in the cellular accumulation of drug. Further studies demonstrate that these cells are also highly defective in 12-O-tetradecanoylphorbol-13-acetate (TPA) induced differentiation to macrophages. Analysis of this system demonstrates that certain protooncogenes which may contribute to differentiation are expressed at similar levels in sensitive and resistant cells. Thus, treatment of cells with TPA results in a reduction in the levels of c-myb and c-myc mRNA, while the expression of c-fos, c-jun, and junB is greatly enhanced. Immunoprecipitation experiments also demonstrate a TPA induced increase in the c-jun protein in both sensitive and resistant cells. Gel mobility shift assays show that TPA induces AP-1 formation in sensitive cells, whereas in parallel experiments with the HL-60/Vinc isolate, AP-1 is essentially absent. It has been found, however, that in resistant cells which have reverted to drug sensitivity, the levels of TPA inducible AP-1 is essentially identical to that of sensitive cells. Revertant and sensitive cells differentiate at similar levels in the presence of TPA. These studies therefore demonstrate that HL-60/Vinc cells are defective in the TPA induction of a functional AP-1 complex and that this may account for the inability of these cells to differentiate to macrophages. The molecular basis of the finding that AP-1 is not formed in resistant cells remains to be determined.
Cell Adhesion↗
[Role of neutrophil and hydroxyl radical in shock-induced gut origin infection].
The relative roles of hydroxyl radical and neutrophils in the pathogenesis of shock-induced mucosal injury and gut origin infection (GOI) were determined. The incidence of GOI was higher in the shocked rats (30 mmHg for 30 min) than the sham-shock controls (87% vs 12.5%; P less than 0.01). Administration of the hydroxyl radical scavenger, dimethyl sulfoxide (DMSO) or iron chelator and deferoxamine reduced the incidence of GOI from 87% to 20% and 40% respectively (P less than 0.05). DMSO and deferoxamine appeared to prevent shock-induced GOI by blunting the magnitude of shock-induced mucosal injury. In contrast, neutrophil depletion did not prevent GOI or protect the intestinal mucosal in the shocked rats. Instead, the incidence of systemic spread of bacteria past the mesenteric lymph nodes to the livers and spleens of the shocked rats was higher in the neutrophil depleted rats (56%) than any other group (7%) (P less than 0.01). Thus, shock-induced GOI and intestinal injury appears to be mediated by xanthine oxidase generated oxidants such as hydroxyl radical rather than neutrophil-generated factors. In addition, neutrophil depletion may be clinically deleterious, since it promotes systemic sepsis rather than preventing shock-induced GOI.
Animals↗
[Effect of Tremella polysaccharide on IL-2 production by mouse splenocytes].
Tremella polysaccharide (TP) is an important component isolated from Tremella fuciformis Berk. In this study, the in vitro effect of TP on IL-2 production was examined in activated mouse splenocytes. TP (1, 5, 10 and 50 micrograms/ml) significantly increased mouse splenocyte IIL-2 production. In aged mice, the level of IL-2 production is much lower than that in young controls. TP (0.05, 0.5 and 5 micrograms/ml) restored the IL-2 production to normal level as the young control. Furthermore, TP (0.05, 0.5 and 5 micrograms/ml) was found to partly antagonize the suppressive effect of hydrocortisone on IL-2 production. The antagonistic effect of TP (5 micrograms/ml) on the inhibitory activity of cyclosporin A was also observed.
Animals↗
Ni(II) and Ni(I) forms of pentaalkylamide derivatives of cofactor F430 of Methanobacterium thermoautotrophicum.
A series of pentaalkylamide forms of F430 and of its 12,13-diepimer have been generated and characterized. Carbodiimide-assisted N-hydroxysulfosuccinimide activation of all five peripheral carboxylates of the F430 macrocycle allows nucleophilic attack by a number of primary amines (RNH2, R- = CH3-, CH3CH2-, CF3CH2-, CH3(CH2)3-) generating the pentaalkylamide derivatives. The identity of each derivative has been verified by fast-atom bombardment mass spectrometry (FAB-MS). The solubility of these derivatives in aprotic organic solvents varies as the amine alkyl substituent (R-) is changed. Electrochemical measurements have shown that the Ni(II/I) reduction potentials in N,N-dimethylformamide (DMF) are approximately -1 V (Ag/AgCl). Reduction by sodium amalgam in THF generates the Ni(I) form of the F430 diepimer pentabutylamide. The visible and EPR spectra of this Ni(I) species are very similar to the corresponding spectra of Ni(I) F430M (Jaun, B. and Pfaltz, A. (1986) J. Chem. Soc. Chem. Commun. 1327-1329.).
Amides↗