[Colonoscopy for early detection of colorectal cancer in average-risk population].
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Colonic Neoplasms↗
Biomedical subjects
Z Levy
Publications and source records attributed to Z Levy.
Mechanisms for evolving hypervariability: the case of conopeptides.
Hypervariability is a prominent feature of large gene families that mediate interactions between organisms, such as venom-derived toxins or immunoglobulins. In order to study mechanisms for evolution of hypervariability, we examined an EST-generated assemblage of 170 distinct conopeptide sequences from the venoms of five species of marine Conus snails. These sequences were assigned to eight gene families, defined by conserved elements in the signal domain and untranslated regions. Order-of-magnitude differences were observed in the expression levels of individual conopeptides, with five to seven transcripts typically comprising over 50% of the sequenced clones in a given species. The conopeptide precursor alignments revealed four striking features peculiar to the mature peptide domain: (1) an accelerated rate of nucleotide substitution, (2) a bias for transversions over transitions in nucleotide substitutions, (3) a position-specific conservation of cysteine codons within the hypervariable region, and (4) a preponderance of nonsynonymous substitutions over synonymous substitutions. We propose that the first three observations argue for a mutator mechanism targeted to mature domains in conopeptide genes, combining a protective activity specific for cysteine codons and a mutagenic polymerase that exhibits transversion bias, such as DNA polymerase V. The high D:(n)/D:(s) ratio is consistent with positive or diversifying selection, and further analyses by intraspecific/interspecific gene tree contingency tests weakly support recent diversifying selection in the evolution of conopeptides. Since only the most highly expressed transcripts segregate in gene trees according to the feeding specificity of the species, diversifying selection might be acting primarily on these sequences. The combination of a targeted mutator mechanism to generate high variability with the subsequent action of diversifying selection on highly expressed variants might explain both the hypervariability of conopeptides and the large number of unique sequences per species.
Animals↗
A lyso-platelet activating factor phospholipase C, originally suggested to be a neutral-sphingomyelinase, is located in the endoplasmic reticulum.
Recently a putative mammalian neutral-sphingomyelinase was cloned [Tomiuk et al. (1998) Proc. Natl. Acad. Sci. USA 95, 3638-3643; GenBank accession number AJ222801]. We have overexpressed this enzyme in cultured cells and demonstrate, using four different tagged constructs, that it is localized at the endoplasmic reticulum and not at the plasma membrane. This localization precludes a role for enzyme AJ222801 in the sphingomyelin cycle. Furthermore, a recent publication demonstrated that this enzyme has lyso-platelet activating factor (PAF) phospholipase C activity [Sawai et al. (1999) J. Biol. Chem. 274, 38131-38139]. Together, these data suggest a role for enzyme AJ222801 in the regulation of PAF metabolism.
Animals↗
Main risk factors for nephropathy in type 2 diabetes mellitus are plasma cholesterol levels, mean blood pressure, and hyperglycemia.
BACKGROUND: The control of hyperglycemia is of major importance in the treatment of patients with type 1 diabetes mellitus. However, there is no consensus about the required degree of metabolic control in patients with type 2 diabetes mellitus and about the role of hyperglycemia in diabetic nephropathy and in the development of atherosclerosis in relation to other risk factors. PATIENTS AND METHODS: A prospective, long-term follow-up study was conducted on 574 patients, aged 40 to 60 years, with recent onset of type 2 diabetes mellitus. Patients were initially normotensive and had normal renal function and a normal urinary albumin excretion rate (<30 mg/24 h). The patients were followed up for 2 to 9 years (mean +/- SD, 7.8 +/- 0.9 years). Levels of hemoglobin A1c and plasma lipids, mean blood pressure, and body mass index (calculated as the weight in kilograms divided by the square of the height in meters) were determined periodically. Cigarette smoking and socioeconomic status were recorded. Renal status was evaluated by the logarithm of the final urinary albumin excretion rate and by the decline in reciprocal creatinine values. Definite clinical events including death, nonfatal myocardial infarction, angina pectoris, congestive heart failure, and peripheral vascular disease were recorded. RESULTS: At the end of the study the urinary albumin excretion rate remained normal (<30 mg/24 h) in 373 patients (65%), 111 (19%) had microalbuminuria (30-300 mg/24 h), and 90 (16%) had overt albuminuria (>300 mg/24 h). Logistic regression models demonstrated that the correlation between hemoglobin A1c levels and the risk of albuminuria is exponential. Multiple logistic regression analysis indicated that levels of total cholesterol, mean blood pressure, and hemoglobin A1c were the main factors associated with the decrease in renal function and with the increase in albuminuria. The combination of values higher than the 50th percentile of all 3 factors defined a high-risk patient population. These high-risk patients had an odds ratio of 43 (95% confidence interval, 25-106) for microalbuminuria and 15 (95% confidence interval, 9-25) for clinical events related to arteriosclerosis compared with the rest of the group. Low levels of high-density lipoprotein, body mass index, cigarette smoking, low socioeconomic status, and male sex were all significantly associated with diabetic nephropathy, as well as with the manifestations of arteriosclerosis. CONCLUSIONS: The combination of blood pressure values in the high-normal range with moderately elevated levels of total cholesterol and hemoglobin A1c defines a high-risk group for the progression to diabetic nephropathy and for clinical events related to arteriosclerotic cardiovascular disease.
Adult↗
A Leuconostoc lactis protein with homology to ribosomal protein S1 shares common epitopes and common DNA binding properties with a mammalian DNA binding nuclear factor.
A mouse testis cDNA expression library (Clontech) was screened with a synthetic oligonucleotide ligand containing CT-rich motifs derived from the rat skeletal muscle actin gene promoter. These motifs bind nuclear proteins, and seem to be involved in the regulation of the gene. Analysis of isolated clones, which expressed proteins that specifically bind the oligonucleotide, indicated that they were derived from a single gene. This gene was identified as a contaminant of bacterial origin (Leuconostoc lactis). The cloned gene from L. lactis encodes a protein with significant homology to bacterial ribosomal protein S1, which we designated LrpS1-L. Band shift analysis and competition experiments indicated that both the bacterial protein and a mouse nuclear protein specifically bind to the same CT-rich motif of the skeletal muscle actin promoter. Furthermore, antibodies against the recombinant bacterial protein interfered with the formation of complex between the CT-rich element and the mouse nuclear protein. These results indicate that the bacterial LrpS1-L protein and the mammalian protein bind the same CT-rich motif and share common antigenic epitopes.
Actins↗
Reduced levels of dystrophin associated proteins in the brains of mice deficient for Dp71.
Duchenne muscular dystrophy (DMD) is a progressive degenerative lethal muscle disease. A significant proportion of DMD affected children suffer also from mental retardation. The rod shaped protein, dystrophin, which is absent from or defective in the muscle of DMD patients, binds to a number of membrane associated proteins (known collectively as dystrophin associated proteins [DAPs]). The levels of DAPs is greatly reduced in the muscle of DMD patients and mdx mice, which lack dystrophin. In addition to dystrophin isoforms, the DMD gene codes also for several smaller proteins. One of the small proteins, Dp71, is expressed in most or all non-muscle tissues and is the major DMD gene product in the brain. The function of the small DMD gene products is unknown. Here we show that mutant mice which do not express the smaller non-muscle products of the DMD gene have a reduced level of DAPs in their brain. This suggests that Dp71 is important for the formation and/or stabilization of a DAPs complex in brain.
Animals↗
Ethical issues of animal welfare in Jewish thought.
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Animal Experimentation↗
A 71-kilodalton protein is a major product of the Duchenne muscular dystrophy gene in brain and other nonmuscle tissues.
The known Duchenne muscular dystrophy (DMD) gene products, the muscle- and brain-type dystrophin isoforms, are 427-kDa proteins translated from 14-kilobase (kb) mRNAs. Recently we described a 6.5-kb mRNA that also is transcribed from the DMD gene. Cloning and in vitro transcription and translation of the entire coding region show that the 6.5-kb mRNA encodes a 70.8-kDa protein that is a major product of the DMD gene. It contains the C-terminal and the cysteine-rich domains of dystrophin, seven additional amino acids at the N terminus, and some modifications formed by alternative splicing in the C-terminal domain. It lacks the entire large domain of spectrin-like repeats and the actin-binding N-terminal domain of dystrophin. This protein is the major DMD gene product in brain and other nonmuscle tissues but is undetectable in skeletal muscle extracts.
Amino Acid Sequence↗
A novel product of the Duchenne muscular dystrophy gene which greatly differs from the known isoforms in its structure and tissue distribution.
A novel transcript of the Duchenne muscular dystrophy gene has been identified. This 6.5 kb mRNA contains sequences from the 3' untranslated region of dystrophin mRNA and from the regions coding for the C-terminal and the cysteine-rich domains. However, probes for the regions encoding the spectrin-like repeats and the actin-binding domain, as well as probes for the first exons of the muscle- and brain-type dystrophin mRNA, did not hybridize with this new mRNA. Significant amounts of the 6.5 kb mRNA were found in a variety of non-muscle tissues, such as liver, testis, lung and kidney, but not in skeletal muscle. The abundance of this mRNA in the brain is at least as high as that of the previously described 14 kb brain-type dystrophin mRNA.
Animals↗
Duchenne muscular dystrophy gene product is not identical in muscle and brain.
Duchenne muscular dystrophy (DMD) is an X-linked recessive disorder resulting in progressive degeneration of the muscle. It affects about 1 in 3,500 male children. Becker's muscular dystrophy is a less severe disease allelic to DMD. Some 30% of DMD patients suffer from various degrees of mental retardation. The giant DMD gene spans about 2,000 kilobases and codes for a 14-kilobase messenger RNA and a protein of molecular weight 427,000. DMD mRNA is most abundant in skeletal and cardiac muscle and less so in smooth muscle. We reported that the expression of the gene is developmentally regulated during the differentiation of primary muscle cultures and in myogenic cell lines in a way similar to the expression of muscle-specific genes such as myosin light chain 2 and skeletal muscle actin. Similar results have been obtained with human primary myogenic cells. Significant levels of DMD mRNA are found in brain tissue. Here we show that the transcript of the DMD gene and the amino terminal of the encoded protein differ in brain and muscle. The 5' ends of these mRNA species are derived from different exons. The results suggest that the two mRNA types are transcribed from different promoters.
Animals↗
The nucleotide sequence of a rat myosin light chain 2 gene.
A rat myosin light chain 2 gene was characterized by nucleotide sequence and S1 mapping analyses. It contains seven exons separated by six introns. The corresponding mRNA is predicted to be 654 nucleotides long (excluding polyA sequences), with 5'-nontranslated, coding, and 3'-nontranslated lengths of 56, 510, and 88 nucleotides, respectively. The predicted amino acid sequence is identical to that from rabbit except that the rat sequence lacks one of two Gly residues located at positions 12 and 13 in the rabbit sequence. From the nucleotide sequence, nascent rat myosin light chain 2 is predicted to have Met Ala preceding Pro at the N-terminal end.
Amino Acid Sequence↗
The nucleotide sequence of the rat cytoplasmic beta-actin gene.
The nucleotide sequence of the rat beta-actin gene was determined. The gene codes for a protein identical to the bovine beta-actin. It has a large intron in the 5' untranslated region 6 nucleotides upstream from the initiator ATG, and 4 introns in the coding region at codons specifying amino acids 41/42, 121/122, 267, and 327/328. Unlike the skeletal muscle actin gene and many other actin genes, the beta-actin gene lacks the codon for Cys between the initiator ATG and the codon for the N-terminal amino acid of the mature protein. The usage of synonymous codons in the beta-actin gene is nonrandom, and is similar to that in the rat skeletal muscle and other vertebrate actin genes, but differs from the codon usage in yeast and soybean actin genes.
Actins↗
Multiple molecular forms of snake venom phosphodiesterase from Vipera palastinae.
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Chemical Phenomena↗