Apolipoprotein(a) phenotypes in cardio-cerebrovascular diseases

We report apolipoprotein(a) (apo(a)) phenotypes of 69 myocardial infarction survivors and 56 stroke patients, and compare them with those of 190 healthy Chinese. The results indicate that the distribution of apo(a) phenotype frequency in cardio-cerebrovascular disease patients is different from those of controls. The frequency of the phenotypes B, S1 and S2 in patients is remarkably higher than those in controls within the same single-band apo(a) phenotype. Moreover, the Lp(a) serum concentrations in CCVD patients are significantly higher than those in controls within the same single-band apo(a) phenotype. The apo(a) phenotype analyses of two pedigrees are shown as a typical autosomal dominant inheritance.

Powerful dominant negative mutants of the human estrogen receptor

We have identified and characterized three human estrogen receptor (ER) mutants, which, at low concentrations, are capable of blocking the intracellular activity of wild type ER. The mutants, a truncated ER (ER1-530), a point mutant (L540Q), and a frameshift (S554fs), were generated by random chemical mutagenesis of the ER hormone binding domain and screened first for low activity in a yeast selection system. In transient co-transfection assays using ER-deficient Chinese hamster ovary cells, all three mutants exhibited less than 10% of the transcription activation activity of wild type ER, and when co-expressed with wild type ER, each of the mutants effectively suppressed the ability of wild type ER to activate transcription of an estrogen-regulated reporter plasmid. When equal amounts of plasmid encoding the ER mutants and wild type ER were used, S554fs, ER1-530, and L540Q suppressed the activity of wild type ER by 80, 55, and 75%, respectively. At a ratio of 1 part S554fs to 10 parts wild type ER, transcription was still inhibited by 40%. Western blot analysis showed that all three mutants were expressed at approximately the same level as wild type ER. Suppression of transcription was specific for ER, since the mutants did not inhibit progesterone receptor-mediated transcription. Not all mutations leading to inactive ER confer the dominant negative phenotype, as five ER mutants rendered transcriptionally inactive by point mutations between residues 516 and 524 of the ER hormone binding domain were poor inhibitors of wild type ER activity. Binding studies showed that the L540Q and S554fs dominant negative mutants bound 17 beta-estradiol with wild type affinity (Kd = 0.3-0.5 nM), whereas ER1-530 exhibited a 15-fold reduction in affinity for estradiol. The three dominant negative ERs showed significant ability to interact with the estrogen response element (ERE) in promoter interference assays, but ER1-530 and S554fs displayed little or no binding to the ERE in gel mobility shift assays where higher affinity for the DNA may be required for the receptor-ERE complex to remain associated during the electrophoresis. These data support the idea that, in all three mutants, it is loss of function of the COOH-terminal transactivation domain which leads to the dominant negative phenotype. S554fs, a powerful dominant negative mutant, is a good candidate for further studies aimed at suppressing the estrogen-dependent growth of human breast cancer cells.

Stable expression of the cardiac sodium-calcium exchanger in CHO cells

A line of Chinese hamster ovary (CHO) cells called CK1.4 was produced by transfection with the gene for the bovine cardiac Na(+)-Ca2+ exchanger. CK1.4 cells stably expressed substantial exchange activity and exchanger protein as shown by immunoprecipitation. Exchange activity was quantified as 45Ca2+ influx that depended on both increasing intracellular Na+ and lowering the concentration of external Na+. Replacing external Na+ with K+ slightly increased 45Ca2+ uptake by CK1.4 cells with basal Na+ and greatly increased 45Ca2+ uptake by Na(+)-loaded cells. Neither exchange activity nor exchanger protein was detected in the nontransfected parental line. By contrast to CK1.4 cells, replacing external Na+ with K+ decreased 45Ca2+ uptake in the nontransfected cells whether or not they were Na+ loaded. Changes in cytosolic free Ca2+ determined with fura-2 were consistent with the 45Ca2+ uptake data. Analysis of poly(A)(+)-RNA by Northern blot confirmed that CK1.4 cells, but not the parental line, expressed the exchanger. Expression of the exchanger was also observed in aortic myocytes and a renal epithelial cell line (LLC-MK2) but not in other lines of renal epithelial cells (MDCK, LLC-PK1) or human dermal fibroblasts. The cardiac exchanger produced substantial 45Ca2+ efflux from CK1.4 cells in response to hormone-evoked release of stored Ca2+. CK1.4 cells are an attractive model for studies of the regulation of the cardiac exchanger because they stably express sufficient exchanger for biochemical and immunological analysis.

The status of elderly women in families viewed from the rate of their heading the household

The author assesses the socioeconomic status of elderly women in China, with a focus on marital status, educational level, and employment. "In family and population studies, the methodology for research on household head rate is held as superior to household size and generation distribution indexes in understanding the change of family structures. This paper attempts to apply this methodology to the study of elderly women's familial status."

Helix-loop-helix transcription factors E12 and E47 are not essential for skeletal or cardiac myogenesis, erythropoiesis, chondrogenesis, or neurogenesis

E12 and E47 are two non-tissue-specific helix-loop-helix (HLH) transcription factors encoded by the E2A gene. Previous studies suggested that they are involved in regulation of differentiation in many tissue types including muscle, blood, and nerve through direct heterodimer interactions with tissue-specific HLH proteins. To gain further genetic insight into the functions of E12 and E47 during cell differentiation, we mutated both copies of the E2A gene in mouse embryonic stem (ES) cells and then tested the effect on differentiation in vitro. We find that the ES cells lacking functional E12 and E47 are capable of differentiating into both skeletal and cardiac muscle, erythrocytes, neurons, and cartilage that the same extent as wild-type cells. These results indicate that the E2A gene is not essential for differentiation of these cell types and suggest that redundant genes may control these developmental pathways.

[Detection of Mycobacterium tuberculosis in sputum specimens of pulmonary tuberculosis by DNA amplification]

The PCR was used to detect M. tuberculosis DNA sequences in uncultured clinical specimens. Two oligonucleotide primers with 20 bp each amplified target template DNA of M. tuberculosis. Amplified DNA product was 245 bp which was identified by agarose gel electrophoresis. The sensitivity of detection of M. tuberculosis genomic DNA and bacteria suspension by PCR was lpg and 13 viable bacteria cell/ml, respectively. In specificity experiments, only M. tuberculosis, M. bovis and BCG were positive by PCR, but all other 14 Mycobacterium tested, including streptomyces lividans and E. coli plasmid PUC19 were negative. The sensitivity of detection of M. tuberculosis by PCR was determined by comparing the fast-acid staining and culture on total 54 sputum specimens of pulmonary tuberculosis and 12 nontuberculosis lung disease. The positive rate of PCR in pulmonary tuberculosis were 37.0%, culture method showed only 14.8%, fast-acid staining were 16.7%. Nontuberculosis lung disease were negative. The results show that DNA amplification is a superior method with high degree of sensitivity and specificity for rapid diagnosis of pulmonary tuberculosis.

Reversible desensitization of fibroblasts to cadmium receptor stimuli: evidence that growth in high zinc represses a xenobiotic receptor

The xenobiotic Cd2+ triggers the production of inositol trisphosphate and releases stored Ca2+ in certain cell types, apparently by binding to a zinc site in the external domain of an "orphan" receptor (no known endogenous stimulus). Cd2+ and bradykinin evoke similar spikes in cytosolic free Ca2+. Growth in high Zn2+ (100-200 microM) abolished the free Ca2+ spike evoked by Cd2+ without affecting the spike produced by bradykinin. Growth in high Zn2+ almost abolished Cd(2+)-evoked production of [3H]inositol mono-, bis-, and trisphosphate. Bradykinin-evoked [3H]inositol phosphate production was not affected by growth in high Zn2+. Growth in high Zn2+ nearly prevented the stimulation of 45Ca2+ efflux by Cd2+ without affecting the stimulation of 45Ca2+ efflux by bradykinin or histamine. Removing Zn2+ from the culture medium and incubating the cells for several hours fully restored responsiveness to Cd2+. Cycloheximide, actinomycin D, or tunicamycin prevented the restoration of Cd2+ responsiveness, indicating that resensitization requires macromolecular synthesis. Growth in high Zn2+ reversibly abolished Ca2+ mobilization evoked by two additional stimuli: a decrease in extracellular pH or Na+ concentration. These findings support the hypothesis that the three stimuli (Cd2+ or a decrease in external pH or Na+ concentration) activate the same orphan receptor. Growth in high Zn2+ apparently desensitizes the cells to the Cd2+ receptor stimuli by repressing receptor synthesis.

[Determination and clinical significance of lipoprotein(a) in cardio-cerebrovascular diseases]

We determined the level of lipoprotein (a) [Lp(a)] in 1,266 healthy persons and established the reference value of Lp(a) in various groups of age and sex. The analysis of lipids in myocardial infarction survivors and stroke survivors suggest that increased Lp(a) is an independent risk factor in cardio-cerebrovascular diseases. The characteristics of abnormal lipids in cardio-cerebrovascular diseases are discussed.

[Identification of twenty-eight species mycobacteria with their cellular fatty acids by capillary gas chromatography]

Cellular fatty acid (FA) of 28 species of mycobacteria were analysed by capillary gas chromatography (GC). There were more than sixty volatile FA before C12:0 have no any difference between species both in quality and quantity. The identification scheme of Mycobacterium based on cellular FA was presented here. According to this scheme, all the tested species could be divided into 8 groups by the FA peak height order of C18:1, C18:0 and TBSA which were quite stable; after that, 17 species (60%) might be identified to species level with help of some distinctive FA such as C19:0, C21:0. Most pathogenic bacteria could be separated by the scheme (M. tuberculosis, M. bovis and some complexes). This scheme was also demonstrated to be objective rationality by computer cluster analysis with cellular FA components.

The conserved dinucleotide AG of the 3' splice site may be recognized twice during in vitro splicing of mammalian mRNA precursors

We have previously used site-directed mutagenesis to introduce an additional branch site into the first intron of the human beta-globin gene at nt -24 between the natural branch site (nt -37) and the normal 3' splice site (nt -1). We found that either the upstream or downstream branch site could be used during in vitro splicing, depending on which site best matched the mammalian branch site consensus YURAC (R = purine; Y = pyrimidine). Here we show that introduction of an additional AG dinucleotide at nt -20 between the downstream branch site and the normal 3' splice site results in alternative 3' splicing. Splicing to the new AG uses the upstream branch site exclusively, presumably because the downstream branch site is only 4 nt from this 3' splice site. We were surprised, however, to find that the presence of the new AG also prevents the use of the upstream branch site for splicing to the normal 3' splice site. Analysis of additional mutants confirmed earlier work [Krainer et al.: Mechanisms of human beta-globin pre-mRNA splicing. In Berg, P. (Ed.), The Robert A. Welch Foundation Conferences on Chemical Research XXIX. Genetic Chemistry: The Molecular Basis of Heredity. Welch Foundation, Houston, TX, 1985, pp. 353-382] that the new AG cannot function by itself as a complete 3' splice site; rather, it appears that alternative 3' splicing initiates at the normal 3' splice site but then searches, once the reaction is underway, for the first AG downstream from the chosen branch site. Taken together, our data suggest that the conserved AG dinucleotide at the 3' splice site may be recognized twice during mammalian mRNA splicing in vitro.

[Rapid identification of Mycobacterium tuberculosis and other mycobacteria with Mycobacterium tuberculosis whole chromosomal DNA probe]

The dot-blots containing DNA isolated from nonmycobacterial and mycobacterial microorganisms were hybridized with 32P-labeled M. tuberculosis whole chromosomal DNA at the various temperatures. The probe did not cross-hybridize to DNA of nonmycobacterial microorganisms (E. coli, Plasmid pUC19, Nocardia asteriodes), nor with DNA from all mycobacteria tested except M. bovis BCG under the higher temperature conditions. Microorganisms could also be directly spotted and lysed on nitrocellulose filters and used for hybridization thus making this technique suitable for clinical diagnosis.

A compensatory base change in human U2 snRNA can suppress a branch site mutation

We have developed an assay to test whether U2 snRNA can base-pair with the branch site during mammalian mRNA splicing. The beta 110 point mutation (GG----AG) within the first intron of human beta-globin generates a new 3' splice site that is preferentially used. We show here that use of the normal 3' splice site can be restored either by improving the match of a cryptic branch site to the branch site consensus or by introducing mutant U2 snRNAs with greater complementarity to the cryptic branch site. These data indicate that human U2 snRNA can form base pairs with the mRNA precursor; however, base pairing appears to be optional because some mammalian branch sites do not match the consensus.

The natural 5' splice site of simian virus 40 large T antigen can be improved by increasing the base complementarity to U1 RNA

The use of alternative 5' splice sites in the simian virus 40 early-transcription unit controls the ratio of large T to small t antigen during viral infection. To study the regulation of these alternative 5' splice sites, we made two mutants which improve the match of the large-T-antigen 5' splice site to the 5' splice site consensus sequence. Whether these mutants were assayed in vitro or in vivo, we found that the efficiency of large-T splicing is increased by improving the match of the large-T-antigen 5' splice site to the consensus. We conclude that the match of a 5' splice site is an important determinant of 5' splice site utilization and that the simian virus 40 large-T-antigen 5' splice site is almost certainly recognized by the U1 small nuclear RNA component of the U1 small nuclear ribonucleoprotein particle.

A compensatory base change in U1 snRNA suppresses a 5' splice site mutation

Indirect evidence suggests that the 5' end of U1 snRNA recognizes the 5' splice site in mRNA precursors by complementary base pairing. To test this hypothesis, we asked whether point mutations in the alternative 12S and 13S 5' splice sites of the adenovirus E1A gene can be suppressed by compensatory base changes in human U1 snRNA. When the mutant E1A and U1 genes are contransfected into HeLa cells, we observe efficient suppression of one mutation at position +5 in the 12S splice site, but exceedingly weak suppression of another mutation at position +3 in the 13S splice site. These and other results suggest that base pairing between U1 and the 5' splice site is necessary but not sufficient for the splicing of mRNA precursors.

Characterization of potent Na+/H+ exchange inhibitors from the amiloride series in A431 cells

Na+/H+ exchange is stimulated in a variety of cell types by addition of mitogenic polypeptides such as epidermal growth factor or platelet-derived growth factor. In order to assess the importance of Na+/H+ exchange in the mitogenic response, it is desirable to have available inhibitors of this process which exhibit high affinity and good specificity. We characterize in this report a number of 5-alkylamino-substituted derivatives of amiloride [3,5-diamino-6-chloro-N-(diaminomethylene)pyrazinecarboxamide++ +] which show much higher affinity than the parent compound for the Na+/H+ antiporter in A431 cells. High affinity is conferred by substitution with two alkyl groups and is increased by introducing a branched alkyl chain. An analogue bearing a 5-anilino group is also very potent. These analogues effectively inhibit the elevation of intracellular pH upon stimulation of Na+/H+ exchange by growth factors. We have assessed other potential inhibitory effects of these compounds on cellular metabolism. In agreement with previous reports, we find that amiloride inhibits protein synthesis both in cells and in cell-free translation systems. While amiloride and its analogues show similar inhibition of protein synthesis in a cell-free system, most analogues inhibit cellular protein synthesis at much lower concentrations than does amiloride. These analogues are also potent inhibitors of purified Na,K-ATPase and cause a profound decrease in intracellular K+ as well as ATP content. These latter effects, however, require analogue concentrations which are 5-7 times higher than those inhibiting cellular protein synthesis.(ABSTRACT TRUNCATED AT 250 WORDS)