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Biomedical subjects

M Rabinowitz

Publications and source records attributed to M Rabinowitz.

At least 55 records · Page 3Linked to original sources
PubMed1984

The relationship between prenatal exposure to lead and congenital anomalies.

We obtained umbilical cord blood from 5,183 consecutive deliveries of at least 20 weeks' gestation and analyzed them for lead concentration. Those demographic and socioeconomic variables, including lead, which were shown on univariate analysis to be associated with increased risk for congenital anomalies were evaluated and controlled by entering them into a stepwise logistic-regression model with malformation as the outcome. Coffee, alcohol, tobacco, and marijuana use, which were associated with lead level, but not risk of malformation, were also controlled. The model was reduced in steps by eliminating the variables with the highest P value, until the most parsimonious model was created. The relative risk for anomalies associated with lead was then calculated while holding other covariates constant. Lead was found to be associated, in a dose-related fashion, with an increased risk for minor anomalies.

Abnormalities, Drug-Induced↗
PubMed1984

Expression of rabbit ventricular alpha-myosin heavy chain messenger RNA sequences in atrial muscle.

We have constructed and isolated a cardiac myosin heavy chain (HC) cDNA clone, pMHC alpha 81, with mRNA from ventricular heart muscle of hyperthyroid rabbits. The clone encodes approximately 480 amino acids of the COOH terminus of light meromyosin and all of the 3' nontranslated region of the corresponding mRNA. Nuclease S1 analyses indicated that the clone is transcribed in hyperthyroid, but not in hypothyroid ventricles and, therefore, corresponds to ventricular alpha-HC mRNA. With probes from the more divergent 3' non-translated region of pMHC alpha 81 and also from selected portions of two previously characterized rabbit cDNA clones ( pMHC alpha 252 and pMHC beta 174), we analyzed the myosin HC mRNAs of atrial, fast skeletal, and slow skeletal muscles by nuclease S1 mapping. In atrial muscle, only one major transcript was detected. The sequence of this transcript was indistinguishable from ventricular alpha-HC mRNA in the 3' nontranslated region and in two coding segments. In contrast, the sequence divergence between the ventricular alpha-HC mRNA and the mRNAs of ventricular beta, fast skeletal, and slow skeletal myosin HCs was clearly detected. There appeared to be, however, considerable homology between coding sequences of ventricular beta and slow skeletal myosin HC mRNAs. The results strongly suggest that rabbit atrial and ventricular alpha-HCs are encoded by the same gene.

Amino Acid Sequence↗
PubMed1984

Regulation of myosin synthesis by thyroid hormone: relative change in the alpha- and beta-myosin heavy chain mRNA levels in rabbit heart.

The expression of mRNAs for two cardiac myosins has been examined in the ventricles of hypo- and hyperthyroid rabbits by means of cloned cDNA sequences corresponding to the mRNAs of the alpha- and beta-myosin heavy chains (HCs). The temporal change in the relative levels of the alpha- and beta-HC mRNAs after 3,5,3'-triiodothyronine (T3) treatment of hypothyroid rabbits was determined by nuclease S1 mapping. In the hypothyroid state, only HC beta-mRNA was expressed in the ventricles. The HC alpha-mRNA was first detectable 4 h after administration of T3 (200 micrograms/kg) to hypothyroid animals. By 12 h, HC alpha-mRNA represented 20% of total myosin mRNA, increasing to 50% by 24 h and to about 90% by 72 h. The relationship between the relative mRNA levels and relative synthesis rates of the myosin HCs was evaluated in 5-6-week-old normal and thyrotoxic rabbits. Myosin synthesis rates were determined by labeling of protein in vivo with [3H]leucine. The V1 (HC alpha) and V3 (HC beta) isomyosins were separated by affinity chromatography with monoclonal antibodies, and the HCs were isolated electrophoretically. In a normal euthyroid group of animals and in animals 12 and 24 h after administration of 200 micrograms of 3,5,3',5'-tetraiodothyronine/kg, the relative mRNA levels and relative synthesis rates of the alpha- and beta-HCs were not significantly different. Our results show that, first, thyroid hormone causes a rapid accumulation of HC alpha-mRNA and loss of HC beta-mRNA and, second, in normal and thyrotoxic rabbits, the relative synthesis rates of HC alpha and HC beta reflect the relative abundance of the alpha- and beta-HC mRNAs.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Analysis of cloned mRNA sequences encoding subfragment 2 and part of subfragment 1 of alpha- and beta-myosin heavy chains of rabbit heart.

Two cardiac myosin heavy chain cDNA clones, pMHC alpha 252 and pMHC beta 174, were constructed using rabbit ventricular mRNA isolated from adult thyrotoxic and normal hearts, respectively. The complete DNA sequences of the 2.2- and 1.4-kilobase inserts of pMHC beta 174 and pMHC alpha 252, respectively, were obtained. The 736 amino acids specified by pMHC beta 174 begin 439 (1.3 kilobases) residues from the heavy chain NH2 terminus and include a 400-amino acid segment of subfragment 1 and the entire subfragment 2 region. Clone pMHC alpha 252 encodes 465 amino acids encompassing all of subfragment 2 and a portion of light meromyosin. Comparison of these two clones revealed extensive sequence overlap which included 1107 nucleotides specifying a 369-amino acid segment corresponding to subfragment 2. Within this region 78 (7%) base and 32 (8.7%) amino acid mismatches were noted. These differences were clustered within discrete regions, with the subfragment 1/subfragment 2 junctional region being particularly divergent. Structural differences between pMHC alpha 252 and pMHC beta 174 indicate that these two clones represent two similar but distinct myosin heavy chain genes whose expression is responsible for ventricular myosin heavy chain isoforms alpha and beta, respectively. The derived amino acid sequences of both clones exhibit extensive homology (greater than 81%) with sequences obtained by direct analysis of adult rabbit skeletal muscle myosin heavy chain protein. The sequences corresponding to the subfragment 2 region are consistent with an alpha-helical conformation with a characteristic 7-residue periodicity in the linear distribution of nonpolar amino acids. Conversely, subfragment 1 sequences specified by pMHC beta 174 suggest a folded highly irregular structure.

Amino Acid Sequence↗
PubMed1984

Cadmium content of umbilical cord blood.

Cadmium was measured in the umbilical cord blood at birth from 94 healthy babies. Samples were dried and ashed at low temperatures with an oxygen plasma prior to atomic absorption spectrometry. The concentration of cadmium ranged from 0.003 to 0.210 microgram/dl, with a mean of 0.045 +/- 0.063 (SD). Blood lead, maternal smoking, and proximity of residence to automobile traffic were not statistically related to cadmium levels.

Automobiles↗
PubMed1984

Characterization of genomic clones specifying rabbit alpha- and beta-ventricular myosin heavy chains.

We have isolated gene sequences coding for the alpha- and beta-myosin heavy chains (HC) of rabbit ventricular muscle. A rabbit genomic library was screened with previously characterized cDNA clones specifying part of the light meromyosin and the entire subfragment 2 portion of alpha- and beta-myosin HCs, as well as with a clone containing the 3' nontranslated sequences of the alpha-myosin HC mRNA. Seven strongly hybridizing clones were analyzed in detail. One genomic clone encoded all of the 3' nontranslated sequences of an alpha-cDNA clone and, therefore, contained the 3' end of the alpha-myosin HC gene. Electron microscopic heteroduplex analysis and DNA sequence analysis showed that this clone overlapped a second genomic clone providing more than 25 kilobase pairs of the alpha-myosin HC gene. The exons within this region corresponded to approximately equal to 85% of the mRNA and were separated by at least 28 introns. A clone for the beta-myosin HC gene was also identified by Southern blot hybridization, by heteroduplex mapping, and by comparing the DNA sequence of a subfragment 2 exon to sequences of the alpha- and beta-cDNA clones. The introns of the alpha- and beta-myosin HC genes were in the same position but showed marked variation in length. These results conclusively showed that the alpha- and beta-myosin HCs are products of separate genes.

Animals↗
PubMed1983

Initiation of transcription of the yeast mitochondrial gene coding for ATPase subunit 9.

We have determined transcriptional initiation sites for the ATPase subunit 9 gene on the yeast mitochondrial genome. Using S1 nuclease mapping, in vitro capping of primary transcripts with GTP and guanylyl transferase, and in vitro transcription analysis with purified mitochondrial RNA polymerase, we find the major site of transcriptional initiation to be at a point 630 nucleotides upstream of the coding region for the gene. In addition, we find much lower levels of initiation at a second site 78 nucleotides downstream of the first. Both initiation sites occur at the same position within a nonanucleotide sequence which we have previously found associated with initiation of rRNA synthesis. This work further supports the notion that this nonanucleotide sequence is an integral component of mitochondrial promoters and indicates that the same RNA polymerase is used for transcription of both mRNA and rRNA in yeast mitochondria.

Adenosine Triphosphatases↗
PubMed1983

Identification of multiple transcriptional initiation sites on the yeast mitochondrial genome by in vitro capping with guanylyltransferase.

We have studied transcriptional initiation in the mitochondria of the yeast Saccharomyces cerevisiae by analyzing mitochondrial transcripts from grande and petite yeast after labeling in vitro with vaccinia virus guanylyltransferase and [alpha-32P]GTP. This procedure labels triphosphate-terminated RNA which arises from transcriptional initiation. Exploiting the extremely low GC content (18%) of yeast mitochondrial DNA, we digested the in vitro capped transcripts with the G-specific ribonuclease T1; this resulted in 27 oligonucleotides varying in size from 2 to 51 nucleotides. RNA from 14 overlapping petites was analyzed and 20 transcripts were localized by deletion mapping. Nineteen oligonucleotides were sequences and 13 were identified and precisely localized by comparison with known DNA sequences. In all cases, transcription is initiated at a consensus nonanucleotide sequence which can be considered part of the yeast mitochondrial promoter. We identified initiation sites for the 21 S and 14 S rRNAs; the phenylalanine, f-methionine, and glutamic tRNAs; two sites for the OLI-1 gene; and three for the ori (rep) regions. Most promoters appear to give rise to very long multigene primary transcripts. Examples are multigene transcripts for the glutamic tRNA and COB genes and for the OLI-1, serine tRNA, and Var genes. Since the consensus nonanucleotide sequences at the ori regions are similar to those at other transcriptional initiation sites, it is likely that the same RNA polymerase primes DNA replication and gene transcription.

Base Sequence↗
PubMed1983

Cloned mRNA sequences for two types of embryonic myosin heavy chains from chick skeletal muscle. II. Expression during development using S1 nuclease mapping.

We have examined the expression of two embryonic myosin HC mRNAs using two cDNA clones (110 and 251) which we have previously constructed from RNA isolated from 14-day-old embryonic chick skeletal muscle. Sequence divergence in the 3' nontranslated regions enabled us to analyze the differential expression of the mRNAs corresponding to the two clones using the S1 nuclease mapping procedure. Clone 251 mRNA is expressed primarily in embryonic fast muscle, where its transcripts appear to be the predominant species. This mRNA is minimally expressed in the posthatching period, but it is not detected in adult leg and breast muscle. Messenger RNA for clone 110 is also primarily expressed in embryonic fast muscle. However, in the posthatching and adult stages of development, it continues to be expressed at a low level in leg muscle but not in breast muscle. The differential expression of these mRNAs during development strongly indicates that they correspond to two different genes coding for embryonic myosin HCs. Other myosin HC mRNAs which were partially homologous to the clone 110 or 251 mRNAs were also identified by S1 nuclease mapping. Using the probes from these two clones, a minimum of four other developmentally expressed forms were detected. Two of these correspond to "neonatal" myosin HCs, while the other two code for different adult myosin HCs present in leg and in breast muscle, respectively. The results therefore suggest a much greater diversity of myosin HC mRNAs expressed during development than previously reported.

Animals↗
PubMed1983

Cloned mRNA sequences for two types of embryonic myosin heavy chains from chick skeletal muscle. I. DNA and derived amino acid sequence of light meromyosin.

Two myosin heavy chain cDNA clones (251 and 110), constructed from chick embryonic skeletal muscle mRNA, were subjected to extensive DNA sequence analysis. A complete description of the DNA sequence of clone 251 was obtained. This 1.5-kilobase pair cDNA sequence specified the COOH-terminal 439 amino acids of the myosin heavy chain, and included the entire 3' nontranslated region. The translated and 3' nontranslated sequences were purine- (64%) and AT-(71%) rich, respectively. The derived amino acid sequence of clone 251 correlated well with sequences obtained by direct amino acid sequencing of adult rabbit back muscle myosin heavy chain protein (87% homology), as well as with cloned myosin heavy chain sequences from other species. Comparison of clone 251 with a partial DNA sequence of clone 110 revealed significant structural differences both in the translated, and 3' nontranslated regions. This data indicates that these two clones represent two distinct myosin heavy chain genes. The protein sequence specified by clone 251 corresponds to the light meromyosin portion of the myosin heavy chain rod. These sequences, like other myosin heavy chain rod sequences, are alpha-helical and exhibit 7- and 28-residue periodicities in the linear distribution of nonpolar, and basic and acidic amino acids, respectively.

Amino Acid Sequence↗
PubMed1983

Stringent requirement for Ca2+ in the removal of Z-lines and alpha-actinin from isolated myofibrils by Ca2+-activated neutral proteinase.

Treatment of isolated myofibrils with Ca2+-activated neutral proteinase (CANP) results in specific removal of Z-line and of alpha-actinin. To investigate the ionic requirement for these processes, we measured Z-line removal by phase-contrast and interference microscopy and alpha-actinin removal by sodium dodecyl sulphate/polyacrylamide-gel electrophoretic analysis of myofibrillar proteins. The proteolytic digestion of native purified proteins was measured directly on polyacrylamide gels and by the fluorescamine technique. We found that the removal of Z-line and alpha-actinin as well as the release of proteolytic degradation products from isolated myofibrils by CANP occur only in the presence of Ca2+; Sr2+, Ba2+, Mn2+, Mg2+, Co2+ and Zn2+ are all ineffective. In contrast with this stringent requirement for Ca2+, the proteolytic activity of CANP measured with denatured casein, native and denatured haemoglobin, native actin and tropomyosin also occurs in the presence of other bivalent cations, in the following order: Ca2+ greater than Sr2+ greater than Ba2+. These data suggest that only Ca2+ can produce the conformational change in myofibrils that renders them susceptible to the action of CANP, whereas its proteolytic activity is stimulated by several bivalent ions.

Actinin↗
PubMed1983

Identification of a single transcriptional initiation site for the glutamic tRNA and COB genes in yeast mitochondria.

We have identified a single transcriptional initiation site for the glutamic tRNA and COB (cytochrome b) genes by using the complementary techniques of in vitro capping of RNA and in vitro transcription. In the capping reaction, mitochondrial RNA is labeled with [alpha-32P]GTP by vaccinia virus guanylyltransferase. This reaction is specific for the 5' ends of RNA retaining the terminal triphosphate of transcriptional initiation. Exploiting the extremely low G+C content (18%) of yeast mitochondrial DNA, we digested in vitro capped transcripts from various petite deletion mutants with the G-specific RNase T1. By petite deletion mapping, a capped transcript giving rise to a 51-base RNase T1-generated oligonucleotide was localized near the glutamic tRNA gene. When the sequence of this oligonucleotide was determined, it perfectly matched the DNA sequence 391 base upstream of the glutamic tRNA. Purified yeast mitochondrial RNA polymerase initiated transcription in vitro at the same site as shown by the sequence of the 33-base oligonucleotide product of the reaction performed in the absence of CTP. Initiation starts at a nonanucleotide sequence previously implicated in yeast mitochondrial transcriptional initiation. Because there is no evidence of an initiation site in the 1,050 bases between the glutamic tRNA and COB genes, the two genes are likely to be transcribed together. Further evidence of a long common transcript was provided by RNA blot hybridization.

Base Sequence↗
PubMed1982

Transcriptional initiation and processing of the small ribosomal RNA of yeast mitochondria.

We have identified the nucleotide at which transcription initiates on the yeast mitochondrial small (14 S) rRNA gene by sequencing of RNA labeled at the 5' initiating triphosphate with vaccinia virus guanylyltransferase [alpha-32P]GTP (in vitro capping reaction). Initiation occurs within the stem of a 12-base palindromic repeat. The initiation sequence has homology with the large (21 S) ribosomal RNA initiation sequence that has been previously determined. We have also sequenced the 5' and 3' ends of the mature 14 S rRNA after labeling with T4 polynucleotide kinase and RNA ligase, respectively. These sequences demonstrate that about 80 nucleotides are cleaved from the 5' end of a precursor to produce the mature 14 S rRNA. This cleavage is imprecise in that the processing occurs at one of five adjacent nucleotides 77 to 81 nucleotides downstream from the 5' initiation site. The 3' ends of this precursor and the mature 14 S rRNA are unique and identical.

Base Sequence↗