A nursing approach to elevated cholesterol and triglycerides: case studies.
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Adult↗
Biomedical subjects
T Thomas
Publications and source records attributed to T Thomas.
Selectivity of polyamines in triplex DNA stabilization.
Triplex DNA has been recently studied as an anti-gene strategy to suppress the transcription of specific genes. A major challenge in this area is to stabilize triplex DNA at physiological conditions. We studied the effects of putrescine, spermidine, spermine, their synthetic homologs, and their acetyl derivatives on triple- and double-stranded structures formed from poly(dA) and poly(dT) by measuring their respective melting temperatures. In the presence of polyamines, the absorbance (A) versus temperature (T) profile showed two transitions: Tm1, corresponding to triplex-->duplex+single-stranded DNA, and Tm2, corresponding to duplex melting. In the presence of 0.5 mM putrescine, Tm1 and Tm2 were 44.8 and 71 degrees C, respectively, in 10 mM sodium cacodylate buffer (pH 7.2). In contrast, triplex DNA was not detectable when the A versus T profile of the polynucleotides was monitored in the absence of putrescine. Tm2 was also lower (55 degrees C) in the absence of putrescine. With 2.5 microM spermidine or 0.1 microM spermine, Tm1 values were 42.8 and 54.4 degrees C and Tm2 values were 65 and 82 degrees C, respectively. As the concentration of polyamine was increased, the difference between Tm1 and Tm2 decreased, and both melting transitions merged into one Tm, corresponding to the melting of triplex DNA to single strands. In a series of putrescine homologs, H2N (CH2)nNH2 where n = 2-6 (n = 4 for putrescine), H2N(CH2)3NH2 was the most effective diamine to stabilize the poly(dA).2poly(dT) triplex. At 10 mM concentration, diaminopropane stabilized the triplex DNA such that the Tm1 was 10 degrees C higher than that in the presence of an equimolar concentration of putrescine.(ABSTRACT TRUNCATED AT 250 WORDS)
Acetylation↗
Inhibition of calcium signalling in murine splenocytes by polyamines: differential effects on CD4 and CD8 T-cells.
Transmembrane Ca2+ influx is recognized as a universal second messenger that transduces T-cell activation signals to cytoplasm and nucleus, thereby stimulating transcription and cell division. To examine the role of endogenous factors that regulate mitogenic Ca2+ signalling of T-cells, we measured the concanavalin (Con) A-induced increase in cytoplasmic free calcium ([Ca2+]i) in spleen cells of BALB/c mice, using flow cytometry with an indicator dye, Indo-1 acetoxymethyl ester (Indo-1/AM). Con A is a polyclonal activator of T-cells. Unstimulated splenocytes had a [Ca2+]i of 100 nM. [Ca2+]i increased with Con A in a dose-dependent manner up to a concentration of 50 micrograms/ml. In the presence of 50 micrograms/ml Con A, [Ca2+]i was 350 nM. Natural polyamines (putrescine, spermidine and spermine) inhibited Con-A-induced Ca2+ influx in a dose-dependent manner. Putrescine was the most effective polyamine in desensitizing the Ca2+ signal, and decreased [Ca2+]i from 350 nM in the absence of putrescine to 250 nM in the presence of 100 microM putrescine. This effect was not mimicked by structurally related homologues or inorganic cations, suggesting a specific structural effect of the polyamine. H.p.l.c. analysis showed that polyamines were internalized during incubation of cells in vitro. In experiments using monoclonal anti-CD4 and anti-CD8 antibodies, we found a differential effect of putrescine on Ca2+ influx in CD4 and CD8 subpopulations of T cells. For CD4+ cells, [Ca2+]i decreased from 625 nM to 420 nM in the presence of 500 microM putrescine, whereas [Ca2+]i was not affected by putrescine in CD8+ cells. These data suggest that natural polyamines have cell-specific effects on mitogen-stimulated Ca(2+)-influx in T-cell subsets.
Animals↗
Aldose reductase inhibitors: an approach to the treatment of diabetic nerve damage.
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Aldehyde Reductase↗
Genes coding for basement membrane glycoproteins laminin, nidogen, and collagen IV are differentially expressed in the nervous system and by epithelial, endothelial, and mesenchymal cells of the mouse embryo.
The pattern of laminin A, B1, B2, nidogen, and collagen alpha 1 (IV) gene expression in the 12.5-day mouse embryo was determined by in situ hybridization. Laminin B1, B2, and collagen alpha 1 (IV) mRNAs were present in many epithelial and mesenchymal compartments. Laminin A mRNA had a more restricted distribution, being present in cells closely associated with basement membranes and also in the ependymal layer of the neural tube. Nidogen was not produced by any epithelium, but was abundant in mesenchymal and endothelial cells. These results demonstrate that mesenchymal cells contribute significantly to basement membrane production, and that many cells not associated with typical basement membranes produced high levels of mRNAs coding for basement membrane components. Very few cell types produced all five gene products, and some tissues preferentially expressed only one or two of the five genes. This study shows that basement membranes at the epithelial-mesenchymal interface in the majority of mouse embryonic tissues are assembled from components derived from both cell types, and that heterogeneous matrix structures containing different laminin subunits and/or nidogen are likely to be present in the central nervous system and other tissues of the midgestation mouse embryo.
Animals↗
Studies on the effects of an ornithine decarboxylase inhibitor on lupus nephritis reveal a post-transcriptional modification of the enzyme.
Upregulation of ornithine decarboxylase (ODC) activity and polyamine levels is found in the kidney of MRL-lpr/lpr (lpr) mouse, an animal model of lupus. To understand the molecular genetics of ODC regulation in lpr mouse, we analyzed ODC mRNA and activity in the kidney of lpr and normal BALB/c and MRL(-)+/+ mice. Although ODC activity was significantly higher in lpr kidney, its mRNA level was lower compared to normal strains, as measured by Northern blot hybridization. Treatment of lpr mouse with difluoromethylornithine (DFMO) reduced ODC activity in lpr kidney to the level of normal strains. In contrast, ODC mRNA level increased 12-fold by DFMO treatment. These results suggest that post-transcriptional modification of ODC in lpr genetic background might be responsible for increased ODC activity and polyamines. The beneficial effect of DFMO on murine lupus suggests a pathogenic role for altered ODC regulation in lpr mouse.
Animals↗
The danger of convulsions precludes the use of regional block for caesarean section in fulminating preeclampsia. Proposer.
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Journal Article↗
Expression of laminin and nidogen genes during the postimplantation development of the mouse placenta.
The expression patterns of laminin A, B1, B2, and nidogen genes were identified by in situ hybridization in postimplantation mouse extraembryonic tissues and maternal decidua during the period when the chorioallantoic placenta is established. Laminin and nidogen genes were not coordinately expressed either in the decidua or in trophoblast cells, indicating that these genes are regulated independently in these cell types during the establishment of the placenta. Laminin A mRNA was absent from the decidua except in the outer layer of cells adjacent to the myometrium and in the central decidual zone adjacent to the remnant of the uterine epithelium on Day 9. At this stage laminin B1, B2, and nidogen genes were strongly expressed in these cells and also in other regions of the decidua. Laminin B1 mRNA was present at higher levels in the decidua capsularis than in the decidua basalis, while nidogen mRNA showed highest expression in the decidua basalis. Laminin B2 mRNA was produced uniformly throughout the decidua at very high levels, suggesting that laminin B2 chains may be an important component of the decidual matrix. By Day 11, the nidogen gene was expressed only in endothelial cells lining the maternal blood spaces within the decidua. Laminin B1 and nidogen mRNAs were found at high levels within trophoblast giant cells at all stages, while laminin A mRNA was detected in trophoblast giant cells at later stages and laminin B2 mRNA was not produced in high levels by these cells. The patterns of gene expression show a very high degree of regional specialization, suggesting that the extracellular matrices in different regions of the decidua and extraembryonic membranes are likely to be composed of quite different ratios of laminin and nidogen polypeptides.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
The role of adenosine in hypoxic pulmonary vasoconstriction in the anaesthetized rat.
In nine artificially ventilated rats anaesthetized with Saffan, systemic hypoxia induced a tachycardia followed by a bradycardia, a fall in systemic arterial pressure and an increase in pulmonary artery pressure (PPA) indicating pulmonary vasoconstriction. This increase in PPA was abolished by the adenosine receptor antagonist 8-phenyltheophylline (8-PT, 10 mg kg-1 I.V.). Further, in seven rats the Pa,O2 achieved during hypoxia was greater after 8-PT than before (38 vs. 40 mmHg). We suggest that adenosine makes a major contribution to hypoxia-induced pulmonary vasoconstriction in the rat. The better maintenance of Pa,O2 during hypoxia may reflect improved perfusion of well-ventilated alveoli.
Adenosine↗
A link between adenosine, ATP-sensitive K+ channels, potassium and muscle vasodilatation in the rat in systemic hypoxia.
1. In anaesthetized rats, systemic hypoxia evoked hyperventilation, tachycardia, a fall in arterial pressure, vasodilatation in skeletal muscle and increases in K+ concentration measured in arterial plasma ([K+]a), venous efflux from muscle ([K+]v) and in right atrial plasma ([K+]at). The ATP-sensitive potassium (K+ATP) channel inhibitor glibenclamide (10 or 20 mg kg-1 i.v.) reduced the muscle vasodilatation and increase in [K+]v, but had no significant effect on the other changes. 2. The adenosine receptor antagonist, 8-phenyltheophylline (8-PT, 10 mg kg-1 i.v.) had similar effects to glibenclamide. 3. Glibenclamide reduced the muscle vasodilatation evoked by the adenosine analogue, 2-chloroadenosine given i.v. (30 micrograms kg-1). 4. Infusion of adenosine (0.3 mg kg-1 min-1 for 5 min) into the hindlimb evoked muscle vasodilatation and an increase in [K+]v, both of which were abolished by 8-PT. 5. We propose that during systemic hypoxia, part of the muscle vasodilatation that can be attributed to adenosine is due to the action of K+, which is released from skeletal muscle fibres through glibenclamide-sensitive K+ channels (possibly K+ATP channels) that are activated by adenosine. This may be a general mechanism for the vasodilator influence of adenosine.
2-Chloroadenosine↗
Capacity to form choroid plexus-like cells in vitro is restricted to specific regions of the mouse neural ectoderm.
Neural ectoderm was dissected from 9.5-day and 8.5-day gestation mouse embryos and divided into forebrain, midbrain, hindbrain and spinal cord regions. Forebrain and hindbrain material from 9.5-day neural ectoderm was further divided into presumptive choroid plexus regions and regions that would normally form nervous tissue in vivo. All tissues were plated onto a basement membrane substratum for culture in vitro. It was found that explants of neural ectoderm that would normally form choroid plexus in vivo, readily differentiated to form choroid plexus-like cells in culture. Cells from hindbrain segments and forebrain regions, which would normally form nervous tissue, also had the potential to differentiate into cells resembling the choroid plexus epithelium in culture, provided that the normal cell-cell interactions were disrupted. Cells from the midbrain neuromeres of 9.5-day embryos, which do not form a choroid plexus in vivo, did not form this lineage in vitro. However, cells cultured from the earlier head-fold stage midbrain neural ectoderm could develop into choroid plexus epithelium. There was no evidence that neural ectoderm from the spinal cord had the developmental potential to form choroid plexus epithelial cells at either of these two developmental stages. These studies show that the restrictions in the potential of neural ectoderm stem cells to form different lineages proceeds according to morphological divisions that appear along the anterior-posterior axis during the early stages of brain development. These results suggest that the division of neural ectoderm into segments which contain discrete stem cell populations may be a general feature of the early phase of development of the central nervous system.
Animals↗
Structural specificity of polyamines in modulating the binding of estrogen receptor to potential Z-DNA forming sequences.
Estrogen receptor (ER) is a gene-regulatory protein that mediates the action of estradiol. In order to examine the role of conformational dynamics of DNA in estrogenic regulation of gene expression, we studied the binding of ER to poly(dA-dC).poly(dG-dT) which undergoes transition to a left-handed Z-DNA form. This type of dinucleotide repeats are widely distributed in mammalian genome and are present in estrogen response elements. Binding affinity of ER for the polynucleotide was assessed by its ability to release ER bound to DNA-cellulose. ER binding by poly(dA-dC).poly(dG-dT) was enhanced in the presence of an endogenous polyamine, spermidine, H2N(CH2)4NH(CH2)3NH2. The concentration of spermidine required for facilitating 50% elution of ER (EC50) was 75 microM. This EC50 increased to 500 microM for a spermidine homolog, H2N(CH2)8NH(CH2)3NH2, demonstrating polyamine structural specificity. Spectroscopic measurements showed that the presence of 100-200 microM spermidine initiated changes in the conformation of the polynucleotide indicative of Z-DNA form, but a major alteration to Z-DNA spectrum occurred only at 300 microM concentration. These data suggest that ER favors DNA sequences poised for Z-DNA transition. The efficacy of spermidine homologs in facilitating ER-DNA interaction may be important in predicting their efficiency to replace cellular functions of spermidine.
Animals↗
[Hemangiopericytoma: a case report].
We describe one case of hemangiopericytoma touching a 44-year-old man. It is a rare vascular tumor originating from pericytes surrounding capillaries. The main typical features of it are the difficulty in doing an histologic diagnosis and the impossibility to make out a reliable prognosis. The therapy of choice is a surgical procedure sometimes in combination with radio- and/or chemotherapy.
Adult↗
An epidemic of caterpillar sting dermatitis in a rural West Virginia community.
During a five-week interval which began May 1991, 19 patients presented to a community health center in a rural West Virginia community with a painful dermatitis. The dermatitis was caused by exposure to a single species of caterpillar, Hemileuca maia, larva of the buck moth. The caterpillars were apparently especially abundant during the period. Epidemics of caterpillar stings rarely have been reported. No previous epidemics of stings by the buck moth caterpillar have appeared in the literature.
Adolescent↗
Protein synthesis at the blood-brain barrier. The major protein secreted by amphibian choroid plexus is a lipocalin.
Among the proteins secreted by choroid plexus of vertebrates, one protein is much more abundant than all others. In mammals, birds, and reptiles this protein is transthyretin, a tetramer of identical 15-kDa subunits. In this study choroid plexus from frogs, tadpoles, and toads incubated in vitro were found to synthesize and secrete one predominant protein. However, this consisted of one single 20-kDa polypeptide chain. It was expressed throughout amphibian metamorphosis. Part of its amino acid sequence was determined and used for construction of oligonucleotides for polymerase chain reaction. The amplified DNA was used to screen a toad choroid plexus cDNA library. Full-length cDNA clones were isolated and sequenced. The derived amino acid sequence for the encoded protein was 183 amino acids long, including a 20-amino acid presegment. The calculated molecular weight of the mature protein was 18,500. Sequence comparison with other proteins showed that the protein belonged to the lipocalin superfamily. Its expression was highest in choroid plexus, much lower in other brain areas, and absent from liver. Since no transthyretin was detected in proteins secreted from amphibian choroid plexus, abundant synthesis and secretion of transthyretin in choroid plexus must have evolved only after the stage of the amphibians.
Amino Acid Sequence↗
Differential effects of polyamine homologues on the prevention of DL-alpha-difluoromethylornithine-mediated inhibition of malignant cell growth and normal immune response.
Natural polyamines (putrescine, spermidine, and spermine) are ubiquitous cellular cations that play an important role in cell proliferation and differentiation. Ornithine decarboxylase is the first and a rate-limiting enzyme in the biosynthesis of polyamines. Polyamine depletion using DL-alpha-difluoromethylornithine (DFMO), an inhibitor of ornithine decarboxylase, has been shown to suppress cell growth in a variety of settings, including those of tumor and lymphocyte proliferation. The objective of the present investigation was to examine the inhibitory effects of DFMO on a variety of murine in vitro immune responses, including lymphocyte proliferation in response to T-cell mitogen (concanavalin A), B-cell mitogen (lipopolysaccharide), and alloantigen as well as cytotoxicity. DFMO-mediated inhibition of cell proliferation in these cases correlated with depletion of intracellular polyamines. The inhibitory effects of DFMO were reversed by polyamine repletion with putrescine. Putrescine also reversed the growth-inhibitory effects of DFMO on 4 tumor cell lines that we tested: 28-13-3S, YAC-1, P-815, and K562. However, putrescine homologues exhibited a differential effect in preventing DFMO-mediated inhibition of cell growth in normal lymphocytes and cancer cell lines. Only putrescine homologues containing a shorter methylene chain were effective in preventing the growth-inhibitory action of DFMO on normal immune response. In contrast, only the longer chain homologue 1,5-diaminopentane overcame the effect of DFMO on tumor cell growth. These findings suggest that supplementation with selected polyamine homologues may sustain normal immune response in DFMO-treated individuals while effectively suppressing malignant cell growth. The potential clinical relevance of these observations is discussed.
Animals↗
Effects of the extracellular matrix on fetal choroid plexus epithelial cells: changes in morphology and multicellular organization do not affect gene expression.
We have developed a primary culture system for fetal mouse choroid plexus epithelial cells which maintains their differentiated phenotype. When grown on a reconstituted basement membrane substrate (Matrigel) epithelial cells formed aggregates which became embedded in the matrix and developed into characteristic and highly reproducible multicellular vesicular structures. These vesicles consisted of a squamous layer of epithelial cells with extensive attachment to the matrix substrate, surrounding a fluid-filled lumen. Electron microscopy showed that cells comprising these vesicles had a high degree of membrane specialization and polarized morphology which in many respects mimicked the in vivo morphology. Biochemical analyses demonstrated that under these culture conditions the tissue-specific pattern of gene expression of fetal choroid plexus epithelium was maintained. After 6 days in culture these cells contained approximately the same amount of transthyretin mRNA as the 12.5-day choroid plexus in vivo, and the level of total RNA per cell, which is proportional to the protein synthetic capability of the cells, was also maintained. The pattern of protein secretion was also very similar to that generated by fetal mouse choroid plexus cells in vivo. In contrast choroid plexus epithelial cells attached poorly to collagen I gels. Heterogeneous aggregates were formed in which cell-cell interactions were more extensive than cell-substrate interactions, and in no cases was a central lumen observed. Cells on the surface of large aggregates showed some evidence of membrane polarization, while the majority of cells in the cultures exhibited little evidence of polarized morphology. Despite the striking difference in morphology and multicellular organization these cells still expressed high levels of transthyretin mRNA and maintained the same pattern of protein synthesis as cells cultured on Matrigel. These results indicate that the basement membrane is important for the organization of choroid plexus epithelial cells into a functional epithelium in vitro and thus presumably the maintenance of the integrity of the blood-brain barrier in vivo. In contrast to several other epithelial systems which have been studied, the type of extracellular matrix does not appear to directly influence tissue-specific gene expression by choroid plexus epithelial cells. Thus the level of gene expression is not dependent on the cytoarchitecture and multicellular organization of this cell type.
Animals↗