Search PubMed⌕ Search

Biomedical subjects

J Silver

Publications and source records attributed to J Silver.

At least 307 records · Page 17Linked to original sources
PubMed1986

Statistical considerations for linkage analysis using recombinant inbred strains and backcrosses.

Recombinant inbred (RI) mouse strains are extremely useful for gene mapping, especially for establishing preliminary map positions for new loci. However, the usual statistical analysis applied to such experiments may lead to erroneous conclusions about linkage unless unusually stringent criteria are adopted for rejecting the null hypothesis. We describe a Bayesian statistical approach for determining the probability of linkage when no prior information is available about the location of the gene to be mapped (the test locus). We present a table that gives the probability of linkage, the most likely position of the test locus with respect to a marker locus, and the interval around the marker locus that has a 95% chance of containing the test locus, for all possible experimental results suggesting linkage in sets of up to 40 RI strains. These results show that for the probability of linkage to be greater than 95%, the number of RI strains inheriting chromosomes recombinant for the test and marker loci must be smaller than previously assumed. The formulas derived for RI strains can be applied, with only minor modifications, to the analysis of Mendelian backcrosses. Differences between the Bayesian approach advocated here and the more traditional analysis of linkage are discussed in detail.

Animals↗
PubMed1986

Genetic study of lymphoma induction by Friend murine leukemia virus in crosses involving AKR mice.

The AKR mouse strain is uniquely susceptible to thymic lymphoma. Friend murine leukemia virus (F-MuLV) induced thymic lymphoma in this strain after a median latency of 3-4 months, whereas in several other mouse strains F-MuLV caused erythroblastosis. In the investigation of genetic determinants of the AKR predisposition to thymic lymphoma, series of congenic mouse strains and progeny of crosses involving AKR mice were inoculated with F-MuLV; these mice were followed for the development of lymphoma. The results suggested that AKR genes on chromosomes 7 and 15, other than inherited ecotropic virus, are involved in the predisposition to rapid onset of thymic lymphoma after inoculation with F-MuLV.

Animals↗
PubMed1986

Common proviral integration region on mouse chromosome 7 in lymphomas and myelogenous leukemias induced by Friend murine leukemia virus.

Friend murine leukemia virus (F-MuLV) induces a variety of hematopoietic neoplasms 2 to 12 months after inoculation into newborn mice. These neoplasms are clonal or oligoclonal and contain a small number of F-MuLV insertions in high-molecular-weight DNA. To investigate whether different tumors have proviral insertions in the same region, a provirus-cellular DNA junction fragment from an F-MuLV-induced myelogenous leukemia was cloned in lambda gtWES, and a portion of the flanking cellular DNA sequence was used in blot-hybridization studies of 34 additional F-MuLV-induced neoplasms. Three of these additional neoplasms (one myelogenous leukemia and two lymphomas) were found to have altered copies of the flanking cellular sequence. Restriction enzyme analysis of genomic DNA from these tumors revealed that in each case a proviral copy of F-MuLV had inserted into the same 1.5-kilobase region; all proviruses had the same orientation. Using mouse-Chinese hamster somatic cell hybrids, we mapped this common integration region, designated Fis-1, to mouse chromosome 7. Fis-1 is distinct from three oncogenes on mouse chromosome 7, Ha-ras, fes, and Int-2, based on restriction enzyme analysis and blot hybridization. Therefore, Fis-1 appears to be a novel sequence implicated in both lymphoid and myeloid leukemias induced by F-MuLV.

Animals↗
PubMed1986

Regulation by vitamin D metabolites of parathyroid hormone gene transcription in vivo in the rat.

In vitro 1,25-dihydroxycholecalciferol (1,25(OH)2D3) decreased levels of preproparathyroid(preproPTH) hormone mRNA. We have now pursued these studies in vivo in the rat. Rats were administered vitamin D metabolites i.p. and the levels of preproPTH mRNA were determined in excised parathyroid-thyroid glands by blot hybridization. PreproPTH mRNA levels were less than 4% of basal at 48 h after 100 pmol 1,25(OH)2D3, with no increase in serum calcium. Gel blots showed that 1,25(OH)2D3 decreased preproPTH mRNA levels without any change in its size (833 basepair). Microdissected parathyroids after 1,25(OH)2D3 (100 pmol) showed mRNA levels for preproPTH were 40 +/- 8% of controls, but for beta-actin were 100% of controls. The relative potencies of vitamin D metabolites were: 1,25(OH)2D3 greater than 24,25(OH)2D3 greater than 25(OH)D3 greater than vitamin D3. In vitro nuclear transcription showed that 1,25(OH)2D3-treated (100 pmol) rats' PTH transcription was 10% of control, while beta-actin was 100%. These results show that 1,25(OH)2D3 regulates PTH gene transcription. PTH stimulates 1,25(OH)2D3 synthesis, which then inhibits PTH synthesis, thus completing an endocrinological feedback loop.

Animals↗
PubMed1986

Iron and haem complexation studies of 2,3-dihydro-1H-imidazo(1,2-b)pyrazole (IMPY, NSC 51143), a tumour cell ribonucleotide reductase inhibitor.

Spectrophotometric studies have been undertaken of the interaction of various iron-based systems with the anti-tumour agent, 2,3-dihydro-1H-imidazo(1,2-b)pyrazole (IMPY, NSC (51143), a ribonucleotide reductase inhibitor. No evidence was obtained of direct complexation in aqueous media at 25 degrees C between IMPY and Fe2+ (aq) (pH 1.5-6.8) or Fe3+ (aq) (pH 1.0-3.5), nor with a mu-oxo-bridged iron dimer (Fe--O--Fe) system. There was definitive spectral evidence of complexation of IMPY with protoporphyrin IX iron (II) at pH 7.4 and 12.9 both in the absence and presence of carbon monoxide bound at the haem-iron site. Binding of IMPY to protoporphyrin IX iron (III), in contrast, was not detected. Binding between IMPY and various iron sites important in biochemistry is discussed briefly, especially in relation to the structural properties of IMPY (from X-ray data) and the Fe--O--Fe bridge system in ribonucleotide reductase and model systems. The difficulties of the use of free heterocyclic nitrogenous bases in medicinal chemistry are discussed.

Antineoplastic Agents↗
PubMed1986

Pseudotumor of the pterygomaxillary space presenting as anesthesia of the mandibular nerve.

Pseudotumor is a term used to describe a space occupying inflammatory lesion which mimics a true neoplastic process in its clinical presentation. In this paper, we report a pseudotumor of the pterygomaxillary space that presented with anesthesia and paralysis of the mandibular nerve. The importance of this case is to call attention to pseudotumors as a clinical entity and to document a case of an extraordinarily aggressive variant that required a surgical approach usually reserved for malignant tumors.

Cranial Nerve Diseases↗
PubMed1985

A hydrophobic transmembrane segment at the carboxyl terminus of thy-1.

The mode of integration of the glycoprotein thy-1 within the cell membrane has been controversial due to an apparent lack of a transmembrane hydrophobic segment. Rat and mouse complementary DNA and genomic clones encoding the thy-1 molecule have been isolated and sequenced. These studies have enabled us to determine the intron-exon organization of the thy-1 gene. Furthermore, they have revealed the existence of a sequence which would encode an extra segment (31 amino acids) at the carboxyl terminus of the thy-1 molecule. These extra amino acids include a 20-amino acid hydrophobic segment which may be responsible for integration of thy-1 within the plasma membrane.

Amino Acid Sequence↗
PubMed1985

Nucleotide sequence of an HLA-DQ alpha chain derived from a DRw9 cell line: genetic and evolutionary implications.

Three families of human Ia molecules, DP, DQ, and DR, have previously been defined. A cDNA clone, pDSH-9.1, encoding the alpha chain of a DQ molecule derived from an HLA-DRw9 homozygous cell line has been isolated and sequenced. Comparison of the nucleotide and predicted protein sequence to those of other DQ alpha subunits reveals that DQ alpha subunits derived from DR4, -7, and -9 cells are very similar to each other but quite different from a DQ alpha subunit derived from a DRw6 cell line. These studies suggest that certain Ia haplotypes have a common evolutionary history. Furthermore, in the context of current serologic and biochemical knowledge, they suggest that the gene encoding the DQ alpha subunit is in strong linkage disequilibrium with the DR locus.

Amino Acid Sequence↗
PubMed1985

Isolation and characterization of mouse Thy-1 genomic clones.

The mouse Thy-1.2 gene was isolated from a C57Bl/6 cosmid library and its nucleotide sequence was determined from an 8-kilobase-long EcoRI fragment. The predicted amino acid sequence indicates that the mouse Thy-1 molecule contains a 19 amino acid leader peptide and the 112 amino acids reported previously from protein sequence analysis, plus 31 extra amino acids at the carboxyl terminus. These 31 amino acids contain a stretch of 20 amino acids, at positions 124-143, which is highly hydrophobic. RNA transfer blot analysis of RNA from mouse tissues indicates that the sequence coding for these 31 amino acids is present on poly(A)-containing RNA of brain and thymus tissues. This hydrophobic segment very likely provides the basis for integration of Thy-1 within the plasma membrane. The entire coding sequence of Thy-1 is distributed among three exons, encoding amino acid residues -19 to 8, -7 to 106, and 107 to 143, respectively. Comparison of the mouse and rat Thy-1 genes shows that both have a similar gene organization and encode a highly conserved transmembrane segment.

Amino Acid Sequence↗
PubMed1985

Regulation by vitamin D metabolites of messenger ribonucleic acid for preproparathyroid hormone in isolated bovine parathyroid cells.

We have recently determined that high calcium concentrations, in parallel with their suppressive effects on parathyroid hormone (PTH) secretion, reversibly and specifically decrease preproPTH mRNA in cultured bovine parathyroid cells. In order to determine whether vitamin D metabolites also regulate the content of preproPTH mRNA, we tested their effects on bovine parathyroid cells in the same culture system. Levels of preproPTH mRNA were determined by dot-blot hybridization or blot hybridization with a labeled cloned cDNA probe. Incubation with 1,25-dihydroxycholecalciferol at doses varying from 10 pM to 0.1 microM caused a direct decrease in mRNA down to 50% of control values at 48 hr. There was no evidence that 1,25-dihydroxycholecalciferol, even at the highest concentrations, had any toxic effects on cell number or viability or on total RNA or RNA synthesis. Levels of alpha-actin mRNA did not change in the same experiments, and the suppression of preproPTH mRNA was reversible. When the relative potency of various vitamin D metabolites in suppressing preproPTH mRNA was evaluated, 1,25-dihydroxycholecalciferol greater than 24,25-dihydroxycholecalciferol greater than 25-hydroxycholecalciferol greater than vitamin D3 (cholecalciferol). These effects were highly specific and suggest that vitamin D metabolites play an important role in regulating the production of PTH.

Animals↗
PubMed1985

The human Thy-1 gene: structure and chromosomal location.

The human Thy-1 gene has been isolated and sequenced and compared to the rat and mouse Thy-1 genes. All three genes are organized in the same way: one exon encoding the majority of the signal peptide, another encoding the transmembrane segment, and a third encoding the remainder of the protein. One major structural difference between the human and rodent Thy-1 glycoproteins is that the former contains two instead of three glycosylation sites. RNA blot analysis of a human T-cell line expressing the T3 complex showed an absence of Thy-1 mRNA, excluding the possibility that Thy-1 represents one of the component chains of T3. The structural gene for human Thy-1 was localized to the long arm of chromosome 11 by nucleic acid hybridization to genomic DNA isolated from somatic cell hybrids.

Amino Acid Sequence↗
PubMed1985

Specific alteration of NCAM-mediated cell adhesion by an endoneuraminidase.

A phage endoneuraminidase that specifically cleaves alpha-2, 8-linked polysialic acid has been found to be a useful probe for examining the biological role of this sugar moiety on the neural cell adhesion molecule (NCAM). The enzyme caused a 3.3-fold increase in the rate of NCAM-dependent aggregation of membrane vesicles from chicken embryonic brain, without the nonspecific effects previously encountered with the use of exoneuraminidases. The enhancement of aggregation was closely correlated with removal of sialic acid as assessed by electrophoretic mobility. Extension of this analysis to cultures of spinal ganglia indicated that removal of sialic acid by the endoneuraminidase results in an increase in the thickness of neurite bundles. This enhancement of fasciculation was reversed by addition of anti-NCAM Fab, suggesting that the enzyme treatment was not toxic and did not produce nonspecific effects on adhesion. Injection of the enzyme into the eyes of 3.5-d chicken embryos consistently produced a striking array of abnormalities in those parts of the neural retina that contained the highest concentrations of NCAM at the time of injection. These perturbations included a dramatic thickening of the neural epithelium in the posterior eye, a failure of cells in this region to elongate radially, formation of an ectopic optic fiber layer, and an incomplete association of the presumptive pigmented epithelium with the neural retina. These results provide the first direct evidence that the polysialic acid on NCAM has a regulatory effect on adhesion between living cells, and that the amount of this carbohydrate is critical for the normal morphogenesis of nerve tissue.

Animals↗
PubMed1985

Vitamin D3 uptake by the isolated perfused rat liver from lipoprotein fractions is separate from cholesterol and triglyceride uptake.

Using the isolated perfused rat liver we examined the uptake of [14C] or [3H] vitamin D3 and [14C] triglycerides or [3H] cholesterol by the liver of normal rats, from different lipoprotein fractions, as measured by disappearance from the perfusate. When incorporated into chylomicrons only 43% of the vitamin D3 remained in the perfusate at 60 min (i.e. 57% uptake) as compared to 68% of the triglycerides (i.e. 32% uptake). When added on very low density lipoproteins (VLDL) at 60 min 37 +/- 3% (n = 6) of the vitamin D3, 38 +/- 2% of the cholesterol (n = 3) (P NS), and 83 +/- 4% of the triglycerides (n = 3) remained in the perfusate (P less than 0.0005 for cholesterol:triglycerides and vitamin D3:triglycerides). For high density lipoprotein fraction (HDL) isolated perfused livers were studied with and without albumin present in the perfusate. Without albumin 19 +/- 8% (n = 3) of the vitamin D3 and 43 +/- 8% (n = 3) of the cholesterol remained in the perfusate at 60 min. The results with albumin present were 40 +/- 1% (n = 5) of the vitamin D3 and 63 +/- 4% (n = 5) of the cholesterol at 60 min (P less than 0.0005). The cholesterol:cholesterol ester ratio of the VLDL fraction was 8.8:1 and of the HDL fraction 1:1.4. There was no metabolism of vitamin D3 during the 1 h perfusion. These results suggest that vitamin D3 is in equilibrium with the lipoprotein surface, and the hepatic uptake of vitamin D is a surface phenomenon independent of lipoprotein metabolism.

Animals↗
PubMed1985

A defective ecotropic provirus closely linked to the albino locus.

A congenic mouse strain (NFS.C) carrying the albino region of chromosome 7 from strain C58/Lw on an ecotropic virus-negative NFS background inherited a noninducible but apparently full-size provirus reactive with an ecotropic virus-specific probe. This unexpressed ecotropic provirus maps close to the albino locus but is distinct from the Fgv-1 provirus located in the same region. The presence of this unique provirus in the albino region of chromosome 7 is potentially important, since it may provide a means of obtaining molecular clones of a chromosomal region, deletions of which are involved in profound metabolic, reproductive, and embryological abnormalities.

Albinism↗
PubMed1985

Erbb is linked to the alpha-globin locus on mouse chromosome 11.

A fragment of the human gene for c-erb-B was used to map homologous sequences in mice. Analysis of somatic cell hybrids and recombinant inbred and congenic mouse strains indicated that this gene, designated Erbb, is closely linked to the gene for alpha-globin on mouse chromosome 11. Several genes controlling hematopoietic differentiation map to mouse chromosome 11.

Animals↗