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M Perry

Publications and source records attributed to M Perry.

At least 127 records · Page 7Linked to original sources
PubMed1985

Genomic organization and nucleotide sequence of two distinct histone gene clusters from Xenopus laevis. Identification of novel conserved upstream sequence elements.

We have performed a detailed analysis of the genomic organization and the nucleotide sequence of two distinct Xenopus laevis histone gene clusters totaling approximately 23.5 X 10(3) base-pairs. Each cluster contains at least one copy of each of the five histone genes. However, these genes are present in different arrangements within each cluster and different H1A, H2A and H2B proteins (variants) are encoded by the respective genes of each cluster. Southern blot analysis of genomic X. laevis DNA indicates that each cluster is a member of a distinct family of tandemly repeated histone gene clusters. A comparative analysis of the nucleotide sequences flanking the histone genes within these two clusters has revealed the presence of multiple conserved sequence elements that are specific for each histone gene class and located at preferred upstream positions. Several of these elements correspond to sequences that are known to be required for maximal transcription of the corresponding genes. Most of these sequence elements have not been identified previously, although we find that many of them are present at corresponding locations upstream of histone genes from other organisms. We suggest that the conserved upstream sequence elements may play an important role in the expression of histone genes in vivo.

Amino Acid Sequence↗
PubMed1985

Metabolism of estradiol by true and pseudoperoxidases.

The activation of 14C-labeled estradiol by "true" and "pseudo" peroxidases to form conjugates and other products was compared in four model systems using H2O2, glutathione, Mn2+ or irradiated riboflavin. Albumin was used as acceptor except in the glutathione system. The binding of estradiol to glutathione in the presence of the true peroxidases, lacto- or uterine peroxidase (no H2O2 added), was also examined and the conditions shown to differ from those required with the pseudoperoxidases, microperoxidase or trypsin-digested cytochrome c. The conjugates were purified by chromatography after elution from Amberlite XAD-2 and the relative amounts of these products assessed by autoradiography. The ratio of steroid to glutathione in the main water-soluble metabolite formed with lactoperoxidase was found to be approx 1:1 in a double label experiment with [14C]estradiol and [3H]glutathione. It was also shown, using estradiol labeled with 3H in different positions of the steroid molecule, that lactoperoxidase acts non-specifically in catalyzing the formation of glutathionyl conjugates as indicated by the release of 3H2O. The possible role of peroxidase and glutathione in the metabolism of estrogens and in the formation of artifactual products is discussed.

Animals↗
PubMed1985

Comparative autoradiographic study of parasite-host-cell cyclical relationship in lymphoblastoid cell lines infected with Theileria annulata and Theileria parva in vitro.

Cyclical interactions between intracellular schizonts of the Ankara and Hissar strains of Theileria annulata and the Muguga strain of T. parva and the parasitised host lymphoblasts have been studied autoradiographically by following the incorporation of (3H) thymidine into parasite and host cell nuclei, and also by quantitating the number of schizont nuclei per lymphoblast, at various stages and phases of host cell cycle. The synthesis of DNA by Theileria schizonts and the parasitised host lymphoblasts was found to be asynchronous and to occur at different phases of the host cell interphase stage. While the lymphoblast nuclear DNA incorporates (3H) thymidine during the S phase, schizont nuclei were labelled during the G2 phase of the host lymphoblast interphase stage. The replication of schizont nuclei took place before the metaphase stage of host cell cycle, viz, prometaphase, so that the mean schizont nuclear number at host prometaphase and at anaphase--telophase was consistently more or less double the mean nuclear number at interphase.

Animals↗
PubMed1985

Anti-IgG combined with rate nephelometry for measuring polyethylene glycol-precipitated circulating immune complexes.

Immune complexes from serum were assayed for IgG by a simple rate-nephelometric method after extraction with polyethylene glycol that removes monomeric IgG. A 30-min preincubation of the extracted material in reaction buffer before the anti-IgG is introduced eliminates falsely increased values owing to precipitation that increased baseline light scatter in the reaction buffer. We found good parallelism in the reaction of anti-IgG with the IgG calibrator, aggregated human globulin, or endogenous immune complex. Thus IgG can be used for calibration in place of aggregated human globulin, greatly simplifying the assay. A good correlation was found between the present assay and the C1q-binding test (r = 0.83). The present assay is both sensitive and reproducible. The extraction and assay are straightforward and can be completed in a single morning after an overnight precipitation. The reagents for extraction are easily prepared and inexpensive, and the materials for assay are available in kit form. We believe this approach to be well suited for many clinical laboratories to measure circulating immune complexes.

Antigen-Antibody Complex↗
PubMed1982

Effects of histone hyperacetylation and hypoacetylation on RNA synthesis in HTC cells.

We have analyzed the RNA synthetic activity in intact HTC cells which have artificially high or low levels of histone acetylation. Rates of total RNA synthesis and the number of nascent transcription complexes have been measured for 20-h butyrate-treated cells and for butyrate-released cells which contain hypoacetylated histones. Exposure of HTC cells to butyrate for 20 h leads to a approximately 40% decrease in the number of nascent RNA molecules and a corresponding approximately 40% decrease in the rate of total RNA synthesis. During the induction of hypoacetylation following the release of cells from butyrate, rates of RNA synthesis and the number of nascent transcripts remain unchanged. Between the fifth and eighth h of release from butyrate, the number of nascent transcripts and the rate of total RNA synthesis increase to control cell levels. This increase in the number of nascent RNA polymerase complexes, while occurring when bulk histone is hypoacetylated, is temporally correlated with an increase in the rate of acetylation for a subset of histones. In contrast, changes in levels and rates of histone acetylation were found to be without effect on the average rate of RNA chain elongation. Additionally, we have found that the complexity of nuclear RNA is unchanged by a 20-h exposure of HTC cells to butyrate, suggesting that the approximately 40% decrease in frequency of nascent polymerase complexes produced by butyrate does not result from the complete loss of transcription of a large number of genes.

Acetylation↗
PubMed1982

Hydrolysis of plasma triacylglycerol-rich lipoproteins from immature and laying hens (Gallus domesticus) by lipoprotein lipase in vitro.

Very-low-density (VLD) lipoproteins and portomicrons were isolated from the plasma of immature and laying hens and their size, lipid composition and susceptibility to hydrolysis by lipoprotein lipase were compared. In agreement with other studies, VLD lipoproteins from laying hens were found to be smaller and have a different lipid composition than VLD lipoproteins from immature hens. Portomicrons from immature and laying hens had mean diameters of about 150 nm and similar lipid compositions. Hydrolysis of VLD lipoproteins from immature hens, and portomicrons from immature and laying hens, proceeded rapidly until at least 40% of the substrate had been used. In contrast only 1--15% of laying-hen VLD-lipoprotein triacylglycerol was readily hydrolysis occurred slowly. The limited susceptibility of laying-hen VLD lipoproteins appeared to be due to their low content of lipoprotein lipase activator apoprotein, which occurred despite an abundance of activator in the high-density lipoproteins of laying-hen plasma. The results provide further evidence that the liver of the laying hen synthesizes specialized lipoproteins. Their limited susceptibility to hydrolysis by lipoprotein lipase is probably a major factor in ensuring transport of lipid to yolk rather than to other tissues. The form of transport of dietary lipid, however, is similar in immature and laying hens.

Age Factors↗
PubMed1982

Histone acetylation increases the solubility of chromatin and occurs sequentially over most of the chromatin. A novel model for the biological role of histone acetylation.

The effect of histone acetylation on chromatin solubility has been studied. Nucleosome cores are fairly soluble over a range of Mg2+ and Na+ concentrations. Increasing the amount of Na+ relative to a fixed concentration of Mg2+ leads to increased solubility. Although the effect is not large, acetylated cores are more soluble than control cores, all other factors being equal. Acetylated oligonucleosomes are vastly more soluble than control oligonucleosomes with the greatest differential seen in the presence of Mg2+ at low ionic strengths. Solubility of acetylated oligonucleosomes is favored when the majority of the histones in the nucleosomes are all highly acetylated. Contiguous highly acetylated nucleosomes are enriched in the rapid kinetic form of histone acetylation after short term exposure to butyrate. These observations have been exploited in a fractionation scheme for chromatin based on the levels of hyperacetylation attained after varied times of exposure to sodium butyrate. Essentially all DNA sequences in an unsynchronized cell population are associated with rapidly acetylated histones. Since it is highly unlikely that each cell has its own discrete set of sequences bound to acetylated histone and since the amount of rapidly acetylated histone in a single cell is relatively small (approximately 10% of total histone), we surmise that rapid acetylation migrates throughout much of the chromatin, perhaps in a sequential and highly organized manner. We postulate that the biological role of histone acetylation is to provide a means for sequentially exposing the entire chromatin for surveillance for DNA damage and possibly for recognition of different regions of the DNA by specific (regulatory?) proteins.

Acetylation↗
PubMed1981

The effect of histone hyperacetylation on the nuclease sensitivity and the solubility of chromatin.

We have examined the effects of histone hyperacetylation upon nuclease digestion of nuclei and subsequent fractionation of chromosomal material in the presence of MgCl2. DNase I shows a maximum sensitivity towards hyperacetylated nuclei at somewhat elevated ionic strengths (150-200 mM NaCl), whereas micrococcal nuclease exhibits no specificity for acetylated nuclei over a broad range of ionic strengths. Fractionation in the presence of MgCl2 of hyperacetylated nuclei digested with micrococcal nuclease results in a substantial increase in the amount of soluble chromatin relative to that obtained with control nuclei. This increased yield of Mg2+-soluble chromatin results from the recruitment into this fraction of oligonucleosomes containing extremely hyperacetylated histones. These results suggest that contiguous nucleosomes containing highly acetylated histones may be altered in their ability to interact with themselves and with other nucleosomes.

Acetylation↗
PubMed1980

Oedeme bleu: a reappraisal.

The case-histories of four patients with self-induced lymphoedema show a distinctive organic syndrome, but the underlying mental mechanisms in these patients show no common thread other than an apparent wish to draw attention to an untreatable condition. A policy of non-intervention may reduce or limit the eventual disability.

Adult↗
PubMed1980

Cardiac physiologic-metabolic changes after chronic low-level heavy metal feeding.

Female Long-Evans hooded rats received 0 or 5 parts per million Cd, Pb, or Cd + Pb in the drinking water from weaning to 20 mo. Growth, measured as body weight, and organ weights were comparable among heavy metal and control animals. Indirect blood pressure responses measured trimonthly are discussed. Analysis of His bundle electrograms (HBE) and electrocardiograms recorded in sodium pentobarbital-anesthetized animals at 20 mo demonstrated that Cd selectively depressed conduction system excitability proximal to the common His bundle (atrioventricular node region), whereas Pb and Pb + Cd impaired conductivity distal to the common His bundle (His-Purkinje system). Perchloric acid extracts of liquid N2-freeze-clamped isolated perfused hearts, derived from a subpopulation of control and Cd-fed rats in which HBE analyses were not performed, were analyzed by phosphorus-31 nuclear magnetic resonance (31P-NMR) spectroscopic techniques to quantitate [31P]phosphate metabolite profiles. Cardiac active tension and atrioventricular node excitability were depressed in the Cd group. High-energy phosphate and glycerol 3-phosphorylcholine concentrations were depressed. Results demonstrate potentially significant pathophysiological changes within cardiovascular tissues that develop in the absence of overt heavy metal toxicity manifestations.

Animals↗