PubMed Health⌕ Search

Biomedical subjects

D Spector

Publications and source records attributed to D Spector.

At least 19 recordsLinked to original sources

Mitral annulus calcification--a window to diffuse atherosclerosis of the vascular system.

Mitral annulus calcification (MAC) is a chronic, non-inflammatory, degenerative process of the fibrous support structure of the mitral valve. It occurs more often in women and the elderly. MAC is associated with known atherosclerotic risk factors such as diabetes mellitus, hypertension and hypercholesterolemia. It is also known that patient with MAC have higher prevalence of left atrial and left ventricular enlargement, hypertrophic cardiomyopathy, atrial fibrillation, aortic valve calcification and stenosis, various cardiac conduction defects, bacterial endocarditis, cardiovascular events and stroke, though the etiological basis is unknown. Pathological studies from the 80s present a theory that MAC is a form of atherosclerosis. In order to test this theory we conducted during the last years a few clinical studies to examine the association of MAC and known atherosclerotic phenomena. We found higher prevalence of aortic atheroma in patients with MAC and atheroma thickness. We also found in MAC patients higher prevalence of carotid artery stenosis, coronary artery stenosis, peripheral artery stenosis and higher levels of beta2-Glycoprotein I antibodies in patients with MAC thickness equal or greater than 5 mm. These studies support the theory that MAC is a form of atherosclerosis and define a group of patients with higher prevalence of atherosclerotic disease in multiple blood vessels. The purpose of this review is to summarize the data concerning MAC and atherosclerotic processes, emphasizing that MAC in itself may be an atherosclerotic process.

Arteriosclerosis↗

A genetic investigation of the essential role of glutathione: mutations in the proline biosynthesis pathway are the only suppressors of glutathione auxotrophy in yeast.

In an attempt to elucidate the essential function of glutathione in Saccharomyces cerevisiae, we searched for suppressors of the GSH auxotrophy of Deltagsh1, a strain lacking the rate-limiting enzyme of glutathione biosynthesis. We found that specific mutations of PRO2, the second enzyme in proline biosynthesis, permitted the growth of Deltagsh1 in the absence of exogenous GSH. The suppression mechanism by alleles of PRO2 involved the biosynthesis of a trace amount of glutathione. Deletion of PRO1, the first enzyme of the proline biosynthesis pathway, or PRO2 eliminated the suppression, suggesting that gamma-glutamyl phosphate, the product of Pro1 and the physiological substrate of Pro2, is required as an obligate substrate of suppressor alleles of PRO2 for glutathione synthesis. A mutagenesis of a Deltagsh1 strain also lacking the proline pathway failed to generate any suppressor mutants under either aerobic or anaerobic conditions, confirming that glutathione is essential in yeast. This essential function is not related to DNA synthesis based on the terminal phenotype of glutathione-depleted cells or to toxic accumulation of non-native protein disulfides. Analysis of the suppressor strain demonstrates that normal glutathione levels are required for the tolerance to oxidants under acute, but not chronic stress conditions.

Alleles↗

A proteome analysis of the cadmium response in Saccharomyces cerevisiae.

Cadmium is very toxic at low concentrations, but the basis for its toxicity is not clearly understood. We analyzed the proteomic response of yeast cells to acute cadmium stress and identified 54 induced and 43 repressed proteins. A striking result is the strong induction of 9 enzymes of the sulfur amino acid biosynthetic pathway. Accordingly, we observed that glutathione synthesis is strongly increased in response to cadmium treatment. Several proteins with antioxidant properties were also induced. The induction of nine proteins is dependent upon the transactivator Yap1p, consistent with the cadmium hypersensitive phenotype of the YAP1-disrupted strain. Most of these proteins are also overexpressed in a strain overexpressing Yap1p, a result that correlates with the cadmium hyper-resistant phenotype of this strain. Two of these Yap1p-dependent proteins, thioredoxin and thioredoxin reductase, play an important role in cadmium tolerance because strains lacking the corresponding genes are hypersensitive to this metal. Altogether, our data indicate that the two cellular thiol redox systems, glutathione and thioredoxin, are essential for cellular defense against cadmium.

Cadmium↗

Yap1 and Skn7 control two specialized oxidative stress response regulons in yeast.

Yap1 and Skn7 are two yeast transcriptional regulators that co-operate to activate thioredoxin (TRX2) and thioredoxin reductase (TRR1) in response to redox stress signals. Although they are both important for resistance to H2O2, only Yap1 is important for cadmium resistance, whereas Skn7 has a negative effect upon this response. The respective roles of Yap1 and Skn7 in the induction of defense genes by H2O2 were analyzed by two-dimensional gel electrophoresis. Yap1 controls a large oxidative stress response regulon of at least 32 proteins. Fifteen of these proteins also require the presence of Skn7 for their induction by H2O2. Although about half of the Yap1 target genes do not contain a consensus Yap1 recognition motif, the control of one such gene, TSA1, involves the binding of Yap1 and Skn7 to its promoter in vitro. The co-operative control of the oxidative stress response by Yap1 and Skn7 delineates two gene subsets. Remarkably, these two gene subsets separate antioxidant scavenging enzymes from the metabolic pathways regenerating the main cellular reducing power, glutathione and NADPH. Such a specialization may explain, at least in part, the dissociated function of Yap1 and Skn7 in H2O2 and cadmium resistance.

DNA, Fungal↗

A new antioxidant with alkyl hydroperoxide defense properties in yeast.

To isolate new antioxidant genes, we have searched for activities that would rescue the tert-butyl hydroperoxide (t-BOOH)-hypersensitive phenotype of a Saccharomyces cerevisiae strain deleted for the gene encoding the oxidative stress response regulator Skn7. We report the characterization of AHP1, which encodes a 19-kDa protein similar to the AhpC/TSA protein family within a small region encompassing Cys-62 of Ahp1p and the highly conserved N-terminal catalytic AhpC/TSA cysteine. Ahp1p contains a peroxisomal sorting signal, suggesting a peroxisomal localization. AHP1 exerts strong antioxidant protective functions, as demonstrated both by gene overexpression and deletion analyses, and is inducible by peroxides in an Yap1- and Skn7-dependent manner. Similar to yeast Tsa1p, Ahp1p forms a disulfide-linked homodimer upon oxidation and in vivo requires the presence of the thioredoxin system but not of glutathione to perform its antioxidant protective function. Furthermore, in contrast to Tsa1p, which is specific for H2O2, Ahp1p is specific for organic peroxides. Therefore, with respect to substrate specificity, Ahp1p differs from Tsa1p and is similar to prokaryotic alkyl hydroperoxide reductase AhpC. These data suggest that Ahp1p is a yeast orthologue of prokaryotic AhpC and justifies its name of yeast alkyl hydroperoxide reductase.

Amino Acid Sequence↗

Cytomegalovirus activates interferon immediate-early response gene expression and an interferon regulatory factor 3-containing interferon-stimulated response element-binding complex.

Interferon establishes an antiviral state in numerous cell types through the induction of a set of immediate-early response genes. Activation of these genes is mediated by phosphorylation of latent transcription factors of the STAT family. We found that infection of primary foreskin fibroblasts with human cytomegalovirus (HCMV) causes selective transcriptional activation of the alpha/beta-interferon-responsive ISG54 gene. However, no activation or nuclear translocation of STAT proteins was detected. Activation of ISG54 occurs independent of protein synthesis but is prevented by protein tyrosine kinase inhibitors. Further analysis revealed that HCMV infection induced the DNA binding of a novel complex, tentatively called cytomegalovirus-induced interferon-stimulated response element binding factor (CIF). CIF is composed, at least in part, of the recently identified interferon regulatory factor 3 (IRF3), but it does not contain the STAT1 and STAT2 proteins that participate in the formation of interferon-stimulated gene factor 3. IRF3, which has previously been shown to possess no intrinsic transcriptional activation potential, interacts with the transcriptional coactivator CREB binding protein, but not with p300, to form CIF. Activating interferon-stimulated genes without the need for prior synthesis of interferons might provide the host cell with a potential shortcut in the activation of its antiviral defense.

2-Aminopurine↗

Adenovirus-mediated gene transfer of macrophage colony stimulating factor to the arterial wall in vivo.

Macrophage colony stimulating factor (MCSF) is believed to play a key role in one of the earliest events in atherosclerosis, ie, monocyte to macrophage differentiation in the arterial intima. The aim of this study was to examine the biological effects of vascular wall expression of MCSF. A recombinant adenovirus vector encoding human MCSF (AdMCSF) was generated by standard techniques of homologous recombination in 293 cells. The rabbit carotid artery was transduced with AdMCSF. As negative controls, carotid arteries were transduced with either an adenoviral vector encoding beta-galactosidase, an adenoviral vector encoding apolipoprotein E, or diluent alone. Intima-media thickness ratio was calculated 5 and 21 days after transduction. The cell type present in intimal infiltrates was analyzed by immunohistochemistry. MCSF expression was demonstrated in the vessel wall of AdMCSF-transduced vessels by reverse transcription-polymerase chain reaction and immunofluorescence. In contrast to control vessels, adenovirus-mediated MCSF expression was associated with an intimal cellular infiltrate consisting of smooth muscle cells and small numbers of macrophages. Whereas the intima-media thickness ratio was greater in AdMCSF-transduced vessels at 5 days, this difference was no longer statistically significant at 21 days. These results suggest that MCSF may play a role in recruitment of monocytes and macrophages to the vessel wall and may contribute to smooth muscle cell proliferation and migration.

Adenoviridae↗

In situ analysis of changes in telomere size during replicative aging and cell transformation.

Telomeres have been shown to gradually shorten during replicative aging in human somatic cells by Southern analysis. This study examines telomere shortening at the single cell level by fluorescence in situ hybridization (FISH). FISH and confocal microscopy of interphase human diploid fibroblasts (HDFs) demonstrate that telomeres are distributed throughout the nucleus with an interchromosomal heterogeneity in size. Analysis of HDFs at increasing population doubling levels shows a gradual decrease in spot size, intensity, and detectability of telomeric signal. FISH of metaphase chromosomes prepared from young and old HDFs shows a heterogeneity in detection frequency for telomeres on chromosomes 1, 9, 15, and Y. The interchromosomal distribution of detection frequencies was similar for cells at early and late passage. The telomeric detection frequency for metaphase chromosomes also decreased with age. These observations suggest that telomeres shorten at similar rates in normal human somatic cels. T-antigen transformed HDFs near crisis contained telomere signals that were low compared to nontransformed HDFs. A large intracellular heterogeneity in telomere lengths was detected in two telomerase-negative cell lines compared to normal somatic cells and the telomerase-positive 293 cell line. Many telomerase-negative immortal cells had telomeric signals stronger than those in young HDFs, suggesting a different mechanism for telomere length regulation in telomerase-negative immortal cells. These studies provide an in situ demonstration of interchromosomal heterogeneity in telomere lengths. Furthermore, FISH is a reliable and sensitive method for detecting changes in telomere size at the single cell level.

Cell Division↗

Neurocognitive effects of aluminum.

The neurocognitive effects of aluminum (Al) were studied in 35 hemodialysis patients. Higher Al levels were associated with a decline in visual memory. As Al levels increased, patients with lower vocabulary scores (a measure of premorbid intelligence) showed a decline in attention/concentration, frontal lobe functions, and on several neurocognitive measures, while those with higher vocabulary scores revealed no Al-related decline. These results suggest that individuals with lower verbal intelligence may possess less well-developed compensatory strategies to overcome the neurocognitive effects associated with Al. These data also indicate that Al is neurotoxic and, therefore, potential sources of environmental Al should be identified and eliminated.

Adult↗

UL34, the target of the herpes simplex virus U(S)3 protein kinase, is a membrane protein which in its unphosphorylated state associates with novel phosphoproteins.

Previous studies (F. C. Purves, D. Spector, and B. Roizman, J. Virol. 65:5757-5764, 1991) have shown that the protein kinase encoded by the U(S)3 gene mediates posttranslational modification of a viral phosphoprotein with an apparent M(r) of 30,000 encoded by the UL34 gene. Here we report the following. (i) UL34 protein is not phosphorylated in cells infected with recombinant viruses deleted in the U(S)3 gene. (ii) Several new phosphoproteins (apparent M(r)s, 25,000 to 35,000) are present in cells infected with recombinant viruses deleted in the U(S)3 gene or with viruses carrying a mutation in the UL34 gene that precluded phosphorylation of the UL34 gene product by the U(S)3 protein kinase, but not in cells infected under conditions which permit phosphorylation of the UL34 protein. These proteins are genetically unrelated to the product of the UL34 gene. (iii) Polyclonal rabbit anti-UL34 protein serum precipitated not only the UL34 protein but also the other (25,000- to 35,000-M(r)) phosphoproteins from lysates of cells infected with U(S)3- virus. (iv) The UL34 gene product is a membrane protein inasmuch as the polyclonal anti-UL34 serum reacted with surfaces of intact, unfixed, infected cells and the antigen-antibody complex formed in this reaction contained the UL34 protein. (v) Small amounts of the UL34 protein were present in virions of infected cells. We conclude that the UL34 gene product is a membrane protein exclusively phosphorylated by the U(S)3 protein kinase which can either directly or indirectly form complexes with several other phosphoproteins. Experiments done thus far suggest that these phosphoproteins are present only under conditions in which the UL34 protein is not phosphorylated.

Amino Acid Sequence↗

Mutational analysis of the ICP4 binding sites in the 5' transcribed noncoding domains of the herpes simplex virus 1 UL 49.5 gamma 2 gene.

A previous report (P. Mavromara-Nazos and B. Roizman, Proc. Natl. Acad. Sci. USA 86:4071-4075, 1989) demonstrated that substitution of sequences of the thymidine kinase (tk) gene, a beta gene, extending from -16 to +51 with sequences extending from -12 to +104 of the gamma 2 UL 49.5 gene in viral recombinant R3820 conferred upon the chimeric gene gamma 2 attributes in the context of the viral genome in a productive infection. The UL49.5 gene sequences extending from -179 to +104 contain four DNA binding sites for the major regulatory protein ICP4. Of these sites, two map between nucleotides +20 and +80 within the sequence which confers gamma 2 regulation upon the chimeric gene. To determine the role of these ICP4 binding sites in conferring the gamma 2 gene attributes, sequences comprising the two ICP4 binding sites were mutagenized and used to reconstruct the R3820 recombinant virus. In addition, a new recombinant virus (R8023) was constructed in which tk sequences extending from -240 to +51 were replaced with wild-type or mutated sequences contained between nucleotides -179 to +104 of the UL 49.5 gene. Vero cells infected with the recombinant viruses in the presence or absence of phosphonoacetate, a specific inhibitor of viral DNA synthesis, were then tested for accumulation of tk RNA by using an RNase protection assay. The results indicate that in the recombinant R3820, a mutation which destroyed one of the two UL49.5 ICP4 DNA binding sites significantly reduced the accumulation of tk RNA at both early and late times after infection. The effect of this mutation was less pronounced in cells infected with the R8023 virus, whose chimeric tk gene contains the two upstream UL49.5 ICP4 binding sites. None of the mutations affected the sensitivity of the chimeric genes to phosphonoacetate. The mutated site appears to be involved in the accumulation of RNA.

Animals↗

The herpes simplex virus 1 protein kinase encoded by the US3 gene mediates posttranslational modification of the phosphoprotein encoded by the UL34 gene.

Earlier studies have shown that a herpes simplex virus 1 (HSV-1) open reading frame, US3, encodes a novel protein kinase and have characterized the cognate amino acid sequence which is phosphorylated by this enzyme. This report identifies an apparently essential viral phosphoprotein whose posttranslational processing involves the viral protein kinase. Analyses of viral proteins phosphorylated in the course of productive infection revealed a phosphoprotein whose mobility was viral protein kinase and serotype dependent. Thus, the corresponding HSV-1 and HSV-2 phosphoproteins differ in their electrophoretic mobilities, and the phosphoprotein specified by the HSV-1 mutant deleted in US3 (R7041) differs from that of the corresponding HSV-1 and HSV-2 proteins. Analyses of HSV-1 x HSV-2 recombinants mapped the phosphoprotein between 0.42 and 0.47 map units on the prototype HSV-1 DNA map. Within this region, the UL34 open reading frame was predicted to encode a protein of appropriate molecular weight which would also contain the consensus target site for phosphorylation by the viral protein kinase as previously defined with synthetic peptides. Replacement of the native UL34 gene with a UL34 gene tagged with a 17-amino-acid epitope from the alpha 4 protein identified this gene as encoding the phosphoprotein. Finally, mutagenesis of the predicted phosphorylation site on UL34 in the viral genome, and specifically the substitution of threonine or serine with alanine in the product of the UL34 gene, yielded phosphoproteins whose electrophoretic mobilities could not be differentiated from that of the US3- mutant. We conclude that the posttranslational processing of the UL34 gene product to its wild-type phenotype requires the participation of the viral protein kinase. While the viral protein kinase is not essential for viral replication in cells in culture, the UL34 gene product itself may not be dispensable.

Amino Acid Sequence↗

Role of alpha-transinducing factor (VP16) in the induction of alpha genes within the context of viral genomes.

In herpes simplex virus 1, the five alpha genes are induced by alpha-transinducing factor (alpha TIF; VP16), a virion protein, acting in concert with Oct-1 and other cellular proteins on a cis-acting site in the promoter domain of alpha genes. Because alpha TIF is an essential virion protein, its function as an inducer can best be evaluated only by mutating the cis-acting site. Earlier we reported on a series of 17 mutations in and around the cis-acting site of a 275-bp alpha 27 promoter fused to a reporter gene and recombined into the viral genome. These recombinant viruses were tested in Vero cells in the presence of cycloheximide, and we demonstrated that mutations in the sequence required for Oct-1 binding abolished transactivation whereas mutations in the alpha TIF-dependent GARAT sequence decreased but did not abolish transactivation. We now report that (i) in limited-passage human embryonic lung cells, alpha gene expression from promoters mutated in the GARAT sequences is often higher and more variable than in Vero cells, (ii) in the absence of cycloheximide, the mutant viruses show less significant impairment of reporter gene expression, (iii) Oct-1 can bind either to the overlapping octamer element or to various TAATGARAT sequences with differing degrees of binding strength and these relative binding levels correlate well with levels of gene expression observed in infected cells, (iv) in the cis-acting site upstream of the alpha 4 gene, no degenerate overlapping Oct-1 sequence exists, and therefore in this instance Oct-1 must be binding directly to the TAATGARAT sequence, (v) extension of the alpha 27 promoter by an additional 1,334 bp results in much higher expression of the reporter gene as a result of additional upstream cis-acting sites, and (vi) obliteration of the most proximal Oct-1 binding element within the 275-bp promoter dramatically reduces gene expression even in the presence of the additional upstream cis-acting sites.

Animals↗

Myogenesis and histogenesis of skeletal muscle on flexible membranes in vitro.

Primary muscle cell cultures consisting of single myocytes and fibroblasts are grown on flexible, optically clear biomembranes. Muscle cell growth, fusion and terminal differentiation are normal. A most effective membrane for these cultures is commercially available Saran Wrap. Muscle cultures on Saran will, once differentiated, contract vigorously and will deform the Saran which is pinned to a Sylgard base. At first, the muscle forms a two-dimensional network which ultimately detaches from the Saran membrane allowing an undergrowth of fibroblasts so that these connective tissue cells completely surround groups of muscle fibers. A three-dimensional network is thus formed, held in place through durable adhesions to stainless steel pins. This three-dimensional, highly contractile network is seen to consist of all three connective tissue compartments seen in vivo, the endomysium, perimysium and epimysium. Finally, this muscle shows advanced levels of maturation in that neonatal and adult isoforms of myosin heavy chain are detected together with high levels of myosin fast light chain 3.

Animals↗

Mutational analysis of the promoter region of the alpha 27 gene of herpes simplex virus 1 within the context of the viral genome.

In herpes simplex virus 1-infected cells, the first set of genes to be expressed (alpha genes) is induced by the alpha gene trans-inducing factor (alpha TIF), a virion structural protein. The cis-acting site in the 5' untranscribed domain of alpha genes was previously reported to be the sequence 5'-GYATGNTAATGARATTCYTTGNGGG noncoding (where Y is a pyrimidine, R is a purine, N is any base), which binds a host protein designated alpha H1 (also termed the octamer binding protein, OTF-1, Oct-1, etc.) and which, together with this and possibly other proteins, forms complexes with alpha TIF. To determine the role of the various components of this cis-acting site and of other sequences shared by the alpha genes, we constructed 17 mutants spanning 110 nucleotides of the promoter domain of the alpha 27 gene and made a series of chimeric genes. Each chimeric gene embodying one set of these mutations was inserted into the viral genome and measurements were made of (i) accumulated mRNA under conditions in which only alpha genes were expressed and (ii) the capacity of the mutated sequence to form complexes containing alpha TIF and alpha H1 proteins. We report that (i) transversions in the "TAAT" sequence abolished both complex formation and induction of the chimeric alpha gene, (ii) mutations in the octamer binding site sequence upstream from TAAT or of the downstream GARAT abolished alpha TIF complex formation and also reduced alpha mRNA accumulation, (iii) mutations in a "CAAT" box also reduced expression of mRNA without affecting the formation of DNA-protein complexes containing alpha TIF, and (iv) mutations in sequences immediately downstream from TAATGARAT and in a pair of GA-rich elements reduced alpha mRNA expression whereas mutations between these elements had no effect on the accumulation of the mRNA. The results are consistent with the conclusion that both the alpha H1 octamer binding site ATGNTAAT and the GARAT sequence play a significant role in the induction of alpha genes. For optimal gene expression, however, additional elements downstream from the GARAT sequence and in other regions of the alpha promoter must be present.

Animals↗

Proglucagon processing similar to normal islets in pancreatic alpha-like cell line derived from transgenic mouse tumor.

A pancreatic alpha-like cell line has been established from a glucagonoma arising in transgenic mice expressing a hybrid gene consisting of the rat glucagon-promoter sequence fused to the sequence encoding the SV40 T-antigen oncoprotein. The alpha-tumor cell 1 (alpha TC1) line maintained many characteristics of differentiated alpha-cells for greater than 40 passages in culture and expressed levels of glucagon mRNA 5- to 10-fold higher than those reported previously in rat and hamster islet cell lines. By radioimmunoassay, the cells synthesized considerable amounts of glucagon, glucagonlike peptide I (GLP-I), the major proglucagon fragment, and small amounts of unprocessed proglucagon but no free GLP-II. This distribution of peptides is similar to that found in extracts of rodent pancreases and is distinct from that seen with other islet cell lines, which process proglucagon in patterns more characteristic of intestinal cells. The GLP-I peptide in the alpha TC1 cell line was in the form of GLP-I-(1-37), which is inactive as a stimulator of insulin secretion, and not GLP-I-7-37) or -(7-36)-amide peptides, both of which are potent insulin secretagogues. The alpha TC1 cell line produced glucagon-related peptides in a relatively uniform pattern by immunocytochemistry, and electron microscopy revealed typical alpha-type (glucagon) secretory granules. Although the cell line was derived from an islet tumor producing only glucagon, the alpha TC1 cell line also produced insulin in addition to the glucagon peptides.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenoma, Islet Cell↗

Early effects of subtotal nephrectomy and food restriction on urinary calcium in the rat.

Urinary calcium excretion (UCa) is normal several weeks following subtotal nephrectomy (Nx) in the rat, despite factors such as magnified solute load per nephron which should promote hypercalciuria. To define the levels of UCa during the first few weeks after Nx and to determine if the development of compensatory mechanisms governing renal conservation of calcium are detectable, we measured UCa in Nx and sham Nx rats with matched food intake (10 g/day) from 10 days before through 20 days following Nx. In the sham Nx animals, UCa rose during the first 5 days following surgery from 27 +/- 8 to 66 +/- 5 microM/day and then plateaued for the remaining time. In Nx rats, UCa also rose during the first 5 postoperative days from 23 +/- 5 to 110 +/- 10 microM/day (Nx vs. sham Nx, p less than 0.05), but then fell over the next 3 days to levels observed simultaneously in sham Nx animals. The rise in UCa after Nx, but not after sham Nx, was associated with a doubling of urine flow rate and increased urinary titratable acid excretion. In parathyroidectomized rats, UCa also rose following Nx; however, maximum UCa was then sustained for at least 4 days. In an additional sham Nx group fed 20 g/day, no increase in UCa occurred following surgery. Thus, hypercalciuria is present following Nx in the rat, in part possibly attributable to increased acid excretion. The transient nature of calciuria reflects an adaptive phenomenon, most likely hyperparathyroidism. Diminished food intake following surgery independently contributes to hypercalciuria, regardless of the status of renal mass.

Animals↗