Biomedical subjects

W F Reynolds

Publications and source records attributed to W F Reynolds.

At least 37 records · Page 2Linked to original sources

PubMed1999

Pharmacology of Casimiroa edulis IV. Hypotensive effects of compounds isolated from methanolic extracts in rats and guinea pigs.

Bioassay-directed fractionation of the methanolic extract of seeds of Casimiroa edulis led to the isolation of seven constituents with cardiovascular activity, namely the new compound synephrine acetonide and the known compounds N-monomethylhistamine, N,N-dimethylhistamine, proline, N-methylproline, gamma-aminobutyric acid and casimiroedine. In anesthetized rats, both histamine derivatives produced transient hypotension mediated via H1-histaminergic receptors and in the case of N,N-dimethylhistamine, via nitric oxide release. Synephrine acetonide produced transient hypertension and tachycardia, mediated via alpha- and alpha- and beta-adrenergic receptores, respectively. The chromatographic zone containing N-methyproline, proline and gamma-aminobutyric acid elicited marked and prolonged hypotension. Finally, casimiroedine did not modify the blood pressure of anesthetized rats, but lowered it persistently in anesthetized guinea pigs. It was concluded that hypotension produced by C. edulis is due to several active components. The immediate effect can be attributed to the histamine derivatives acting on H1-receptors. More prolonged hypotension would be produced by the mixture of amino acids through an unknown mechanism, as well as by casimiroedine, possibly by activation of H3-receptors. Hypotension is partially offset by synephrine acetonide through adrenergic mechanisms.

Animals↗

PubMed1999

Limonoids from Swietenia macrophylla and S. aubrevilleana.

An investigation of the seeds of Swietenia macrophylla and S. aubrevilleana (Meliaceae) is reported. Three new compounds, augustineolide (1) and 3beta,6-dihydroxydihydrocarapin (2) from S. macrophylla and 6-acetoxyhumilinolide C (3) from S. aubrevilleana were isolated and characterized along with fifteen known compounds. Four of the compounds were subjected to an antifeedant bioassay on the final instar larvae of Spodoptera frugiperda. The antifeedant activity was comparable to that of bicyclononanolides previously tested.

Animals↗

PubMed1997

An allelic association implicates myeloperoxidase in the etiology of acute promyelocytic leukemia.

Myeloperoxidase (MPO) catalyzes a reaction between chloride and hydrogen peroxide to generate hypochlorous acid and other reactive compounds that have been linked to DNA damage. The MPO gene is expressed at high levels in normal myeloid precursors and in acute myeloid leukemias (AMLs) which are clonal derivatives of myeloid precursors that have lost the ability to differentiate into mature blood cells. Two MPO alleles differ at -463 G/A within a cluster of nuclear receptor binding sites in an Alu element. The -463 G creates a stronger SP1 binding site and retinoic acid (RA) response element (RARE) in the allele termed Sp. In this study, we investigate potential links between MPO genotype, MPO expression level, and myeloid leukemia. The SpSp MPO genotype is shown to correlate with increased MPO mRNA levels in primary myeloid leukemia cells. This higher-expressing SpSp genotype is further shown to be overrepresented in acute promyelocytic leukemia-M3 (APL-M3) and AML-M4, suggesting that higher levels of MPO are associated with an increased risk for this subset of leukemias.

Alleles↗

PubMed1997

Immunohistochemical and genetic evidence of myeloperoxidase involvement in multiple sclerosis.

The myeloperoxidase enzyme (MPO) is expressed specifically in myeloid cells and catalyzes the formation of hypochlorous acid and other cytotoxic oxidants. We previously reported that two alleles of MPO exist which differ in promoter strength due to a base difference in an Alu-encoded hormone response element. The present study shows that the higher expressing MPO genotype is overrepresented in early onset multiple sclerosis in females, implicating MPO in this demyelinating disease. Contrary to the general conception that macrophages lack MPO, immunohistochemical analysis shows that MPO is present in microglia/macrophages in and around MS lesions as shown by colocalization with major histocompatibility antigens HLA-DR and phagocytized myelin. Also, MPO mRNA sequences are detected in cDNA derived from isolated human adult microglia. This is the first evidence that MPO is present in microglia/macrophages at MS lesions, that MPO gene expression occurs in microglia and that MPO plays a role in MS pathogenesis as shown by the allelic disequilibrium in early onset disease.

Adult↗

PubMed1996

An Alu element in the myeloperoxidase promoter contains a composite SP1-thyroid hormone-retinoic acid response element.

An Alu element preceding the myeloperoxidase gene (MPO) contains four hexamer motifs related to the consensus recognition sequence for nuclear hormone receptors (AGGTCA), arranged as direct repeats with spacing of 2, 4, and 2 nucleotides (DR-2-4-2). Gel shift experiments and transient transfection assays demonstrate that these sequences include binding sites for retinoic acid and thyroid hormone receptors and function in vivo to activate transcription of a chloramphenicol acetyltransferase reporter gene. The first DR-2 elements of the series do not bind known receptors but do bind the SP1 transcription factor. Two alleles of the MPO gene exist that differ at one position within this element, resulting in one allele with and one without a strong SP1 binding site. The element with the SP1 site activates transcription by 25-fold in transient transfection assays, while the alternative allele confers severalfold less transcriptional activity. Most cases of acute myelocytic leukemia are homozygous for the allele with the SP1 binding site, suggesting this element plays an important role in regulating the MPO gene in myeloid leukemias. This MPO-Alu is a representative of an Alu subclass numbering approximately 400,000 copies, suggesting many genes may be regulated by such elements.

Alleles↗

PubMed1995

The consensus sequence of a major Alu subfamily contains a functional retinoic acid response element.

Alu repeats are interspersed repetitive DNA elements specific to primates that are present in 500,000 to 1 million copies. We show here that an Alu sequence encodes functional binding sites for retinoic acid receptors, which are members of the nuclear receptor family of transcription factors. The consensus sequences for the evolutionarily recent Alu subclasses contain three hexamer half sites, related to the consensus AGGTCA, arranged as direct repeats with a spacing of 2 bp, which is consistent with the binding specificities of retinoic acid receptors. An analysis was made of the DNA binding and transactivation potential of these sites from an Alu sequence that has been previously implicated in the regulation of the keratin K18 gene. These Alu double half sites are shown to bind bacterially synthesized retinoic acid receptors as assayed by electrophoretic mobility shift assays. These sites are further shown to function as a retinoic acid response element in transiently transfected CV-1 cells, increasing transcription of a reporter gene by a factor of approximately 35-fold. This transactivation requires cotransfection with vectors expressing retinoic acid receptors, as well as the presence of all-trans-retinoic acid, which is consistent with the known function of retinoic acid receptors as ligand-inducible transcription factors. The random insertion of potentially thousands of Alu repeats containing retinoic acid response elements throughout the primate genome is likely to have altered the expression of numerous genes, thereby contributing to evolutionary potential.

Animals↗

PubMed1995

Developmental stage-specific regulation of Xenopus tRNA genes by an upstream promoter element.

Typically the internal promoter elements of tRNA genes are necessary and sufficient to support transcription. Here a sequence element preceding a Xenopus tRNA gene is shown to be required for transcription in late stage, but not early stage oocyte extracts. The constitutive tyrD gene is expressed in both early and late oocyte extracts, whereas the early oocyte-specific tyrCooc gene is only expressed in early extracts. An upstream promoter element (URR), between positions -42 and -14 of the tyrD gene, mediates this differential expression. The URR is required for tyrD transcription in late oocyte extracts. Placing the URR upstream of the tyrCooc gene allows this gene to be transcribed in late extracts. The URR is irrelevant to transcription in early extracts; transcription of tyrD or tyrCooc requires only the internal promoter sequences. This indicates the polymerase III transcriptional machinery changes during oogenesis, resulting in a stringent upstream sequence requirement. Mutations within the URR are shown to alter the preferred site of initiation by RNA polymerase III. Shifting the position of the URR upstream by one-half helical turn also repositioned the site of initiation, suggesting the URR directs the placement of the initiation factor complex or polymerase itself.

Animals↗

PubMed1995

3 beta-aminospirosolane steroidal alkaloids from Solanum triste.

The alkaloid fraction of the MeOH extract of the aerial parts of Solanum triste afforded the new steroidal alkaloid, (22R,25R)-3 beta-amino-5-spirosolene [2], and its previously synthesized dihydro derivative, (22R,24R)-3 beta-amino-5 alpha-spirosolane [3], which is reported here for the first time as a natural product. The structures were elucidated by spectral techniques including 1H-nmr, 13C-nmr, and 1H-1H COSY, HMQC, HMBC, and NOESY nmr experiments.

Chromatography, Thin Layer↗

PubMed1995

Isolation and characterization of cytotoxic and antibacterial tetrasaccharide glycosides from Ipomoea stans.

Three new tetrasaccharide glycosides, differing from one reported previously in the type of short-chain fatty acids ester-linked to the tetrasaccharide core, have been isolated and identified from an oligosaccharide fraction of Ipomea stans. Preliminary screening tests showed that the fraction containing these compounds had pronounced cytotoxicity towards three human tumor cell lines as well as specific antibiotic activity against two bacterial strains.

Anti-Bacterial Agents↗

PubMed1993

The tyrosine phosphatase cdc25 selectively inhibits transcription of the Xenopus oocyte-type tRNAtyrC gene.

The Xenopus tyrosine tRNAtyrC (TyrC) genes are developmentally regulated. These multicopy genes are expressed in early oocytes and inactivated as oocytes reach maturity. As shown here, this developmental regulation can be reproduced in vitro in extracts of early and late stage oocytes: the TyrC gene is transcribed in early oocyte extracts but is virtually inactive in mature oocyte extracts. The inability to transcribe the TyrC gene is not due to the lack of functional pol III transcriptional components, since the somatic-type TyrD gene is fully active in mature oocyte extracts. Instead, the loss of TyrC transcription appears to be due to a change in the template specificity of transcription factor TFIIIC: addition of TFIIIC from immature extracts restores TyrC transcription in mature extracts. In mixtures of immature and mature extracts, the transcriptional activity of the TyrC gene is reduced. The presence of sodium vanadate, an inhibitor of tyrosine phosphatases, increases the level of TyrC transcription in the extract mixtures. Also, cdc25 phosphatase treatment of immature extracts causes a decrease in TyrC transcription which is reversed by addition of exogenous TFIIIC. These findings indicate that changes in phosphorylation state alters the template specificity of TFIIIC leading to the selective inactivation of oocyte type TyrC genes.

Animals↗

PubMed1992

Cell culture of Taxus as a source of the antineoplastic drug taxol and related taxanes.

Callus cultures of Taxus cuspidata and Taxus canadensis were induced using different tissue explants including green and red arils, seed contents, young stems and needles. Callus derived from stem segments displayed the best growth in defined media. The culture medium was supplemented with reducing agents and phenolic-binding compounds to inhibit callus darkening and subsequent growth reduction. T. cuspidata explant growth was affected by different concentrations and ratios of 2,4-D and kinetin. Callus tissues of T. cuspidata were extracted for taxol after 2 months in culture and analysed by HPLC. The presence of taxol (0.020 +/- 0.005% of the extracted dry weight) was indicated based on retention time, U.V. spectra, peak purity as assessed by photo-diode array spectroscopy and compared with an authentic taxol standard, as well as by 1H-NMR analysis. Suspension cultures of T. cuspidata were established from the callus cultures, subsequently immobilized onto glass fiber mats, and maintained as immobilized cultures for 6 months. The immobilized cell cultures also produced taxol at levels up to 0.012 +/- 0.007% of the extracted dry weight.

2,4-Dichlorophenoxyacetic Acid↗

PubMed1992

Differential expression of oocyte-type class III genes with fraction TFIIIC from immature or mature oocytes.

The Xenopus OAX genes can be expressed in oocytes but are virtually inactive in somatic tissues. The tRNA(Met1) (tMET) genes also appear to be developmentally regulated. We have examined the reason for the differential expression of these class III genes. Analysis of the transcriptional activities of extracts derived from immature and mature oocytes revealed that the developmental regulation of these genes can be reproduced in vitro. We have partially purified the required transcription factors B and C from these extracts to ascertain the components responsible for this differential activity. The immature oocyte C fraction activates the tMET and OAX genes when reconstituted with either the immature or mature oocyte-derived B fraction. In contrast, the mature oocyte C fraction fails to activate these genes regardless of which B fraction is used. Both C fractions activated the somatic 5S gene. Purification of the oocyte C fractions by phosphocellulose or B box DNA affinity chromatography failed to separate additional activities responsible for the differential expression of OAX or tMET. By using template exclusion assays, the inability of the mature oocyte C fraction to activate transcription was correlated with an inability to form stable transcription complexes with the tMET or OAX gene.

Animals↗

PubMed1991

The Xenopus YB3 protein binds the B box element of the class III promoter.

We have isolated a Xenopus cDNA encoding the YB3 protein which binds specifically to the B box promoter element of class III genes. Northern analysis shows YB3 is expressed in a variety of adult tissues. Fractionation of oocyte S150 extracts demonstrates YB3 is present in phosphocellulose fraction IIIC, as well as in the fraction isolated by B box DNA affinity chromatography. Silver staining indicates that YB3, or a protein of the same mobility in SDS gels, is the most abundant component in either fraction.

Adenoviridae↗

PubMed1989

Sequences preceding the minimal promoter of the Xenopus somatic 5S RNA gene increase binding efficiency for transcription factors.

Sequences preceding the minimal promoter play a role in the differential expression of the Xenopus somatic and oocyte-type 5S RNA genes. In this report, the somatic sequences between -32 and +37 are shown to increase transcriptional activity in microinjected embryos, yet have little to no effect in microinjected oocyte nuclei. In vitro, these sequences increase activity in whole oocyte S150 extracts, but not in oocyte nuclear extracts. In S150 extracts, these somatic sequences facilitate binding by a commonly required factor(s), other than TFIIIA, which forms a stable complex with the 5S gene. This transcriptional enhancement is also apparent in a reconstituted system using purified TFIIIA and partially purified TFIIIB and TFIIIC.

Animals↗

PubMed1988

Sequence differences upstream of the promoters are involved in the differential expression of the Xenopus somatic and oocyte 5S RNA genes.

The Xenopus somatic and oocyte 5S RNA genes are differentially expressed in extracts of whole oocytes. In such extracts, sequence differences preceding the internal promoters significantly alter the relative activities of these genes. Following exchange of the sequences preceding the promoter, the activity of the somatic 5S gene decreased and that of the oocyte 5S gene increased. As a result, a 100 fold somatic transcriptional advantage was reduced to 5 fold. Analysis of deletion mutants showed that the relevant sequence differences are located between -34 and +37 relative to the initiation site. The observed transcriptional modulation is due both to sequence differences 5' to the initiation site and at positions 30 and 37 within the coding region.

Animals↗

PubMed1988

Effect of sequence differences between somatic and oocyte 5S RNA genes on transcriptional efficiency in an oocyte S150 extract.

The differential expression of the Xenopus laevis somatic and oocyte 5S RNA genes is partially, but not solely, due to several base differences near the 5' boundary of the internal control region. A hybrid oocyte 5S gene with somatic-type base changes at +47, +53, +55, and +56 had intermediate transcriptional activity in oocyte S150 extracts. These base substitutions also resulted in increased affinity for a factor(s), other than TFIIIA, which forms a stable complex with the 5S gene.

Animals↗

PubMed1985

Torsional stress induces an S1 nuclease-hypersensitive site within the promoter of the Xenopus laevis oocyte-type 5S RNA gene.

The internal promoter of the Xenopus laevis oocyte-type 5S RNA gene is preferentially cleaved by S1 and Bal-31 nucleases in plasmid DNA. S1 nuclease sensitivity is largely dependent on supercoiling; however, Bal-31 cleaves within the 5S RNA gene in linear as well as in supercoiled DNA. The S1 nuclease-hypersensitive site is centered at position +48-52 of the gene at the 5' boundary of the promoter. A DNAase I-hypersensitive site is induced at this position upon binding of the transcription factor, TFIIIA, specific for the 5S RNA gene. The somatic-type 5S RNA gene promoter is not preferentially cleaved by S1 nuclease or Bal-31 nuclease in supercoiled DNA, nor does TFIIIA induce a DNase I site at position +50. This differential promoter response may be related to a 4-fold difference in TFIIIA affinity between the oocyte and somatic 5S RNA genes.

Animals↗

PubMed1984

Eukaryotic transcription complexes.

Accurate transcription of eukaryotic genes in vitro is preceeded by the assembly of the template DNA into stable DNA-protein complexes. Such complexes have been reported for genes transcribed by each of the three eukaryotic RNA polymerases. DNAase I protection or footprint assays have yielded information as to the sites of protein factor binding. These sites correlate with many of the sequences which have been implicated as promoter elements through analysis of deletion mutants. Stable transcription complexes are also formed in microinjected Xenopus oocytes and such complexes can be shown to exist in vivo in nuclei and chromatin. The propagation of active transcription complexes may prove to be a crucial element in cellular differentiation.

Animals↗