PubMed Health⌕ Search

Biomedical subjects

M Nemer

Publications and source records attributed to M Nemer.

108 records · Page 6Linked to original sources
PubMed1976

Developmental shifts in the synthesis of heterogeneous nuclear RNA classes in the sea urchin embryo.

Three molecular classes with different properties can be distinguished in the heterogeneous nuclear RNA (HnRNA) of sea urchin embryos. The relative proportions of these classes, which we have previously designated alpha, beta and gamma HnRNA, undergo marked changes during development from morula to early gastrula. Such changes suggest the existence of more than a single HnRNA function, as well as specific roles for different HnRNA classes in embryonic development.

Age Factors↗
PubMed1976

Methylated blocked 5' terminal sequences of sea urchin embryo messenger RNA classes containing and lacking poly(A).

Sea urchin embryo mRNAs of three distinct classes--histone mRNA, nonhistone mRNA containing poly(A), "[+A] mRNA," and nonhistone mRNA lacking poly(A), "[-A]mRNA"--all contain blocked 5' terminal sequences in which 7-methylguanosine is linked 5'-5' via a triphosphate bridge to a 2'-0-methylated nucleotide. Only one general type of 5' terminal structure, 7mGpppXmpYp, is present. Additional 2'-0-methylation in the Y residue has not been found either in early or late stage embryos. A substantial proportion of the polyribosomal mRNAs in all three classes contain this blocked structure. Whereas both classes of nonhistone mRNAs have internal base methylations, histone mRNAs lack such modifications.

Adenosine↗
PubMed1975

Properties of sea urchin embryo messenger RNA containing and lacking poly(A).

Various properties of nonhistone messenger RNA species containing poly(A), [+A]mRNA, and lacking poly(A), [-A]mRNA, are described: the rates of turnover of these mRNA classes are not significantly different, as indicated by their similar rates of entry into and decay from the cytoplasm; each mRNA class is essentially entirely transcribed from unique DNA sequences; the ratio of [+A] to [-A] nonhistone mRNA increases with increase in size of free polyribosome, although the average molecular weights of these mRNAs are similar in each polysomal size class. These results indicate that the [+A]mRNA species tend to be more fully loaded with ribosomes than the nonhistone [-A]mRNA species.

Animals↗
PubMed1970

Cytoplasmic extraction: polyribosomes and heterogenous ribonucleoproteins without associated DNA.

Two methods are described for preparing cytoplasmic extracts from sea urchin embryos. One method, involving homogenization, yields DNA structures that cosediment with polyribosomes and subribosomal ribonucleoproteins. In addition this method also yields extraneous structures containing RNA that cosediment with polyribosomes. The DNA is not associated with polyribosomes, as shown by buoyant density analysis. Furthermore, this DNA appears to be spurious, because its release into a cytoplasmic extract does not occur when a different method of cell disruption, involving passage of embryos through a hypodermic needle, is used. With this second method, polyribosomes are obtained without extraneous cosedimenting RNA structures and subribosomal ribonucleo-proteins are obtained in the virtual absence of DNA.

Animals↗
PubMed1965

Messenger RNA in early sea-urchin embryos: cytoplasmic particles.

Three structures containing messenger RNA can be demonstrated in the cytoplasm of early sea-urchin embryos: (i) particles that sediment more slowly than ribosomes and contain newly synthesized DNA-like RNA, (ii) light polyribosomes, which also contain this newly synthesized RNA, and (iii) heavy polyribosomes, which seemingly contain only already existing or "maternal" messenger RNA and account for the bulk of the synthesis of protein.

Animals↗
PubMed1965

Messenger RNA in early sea-urchin embryos: size classes.

Rapidly labeled RNA from four-cell embryos and blastulae of sea urchins was analyzed by sedimentation and for ability to form DNA-RNA hybrids. The RNA was derived from polyribosomes and from the "gel interphase," an extraction compartment resulting from treatment of whole embryos with phenol and known to be enriched with nuclei. The RNA from both sources displayed a high degree of structural complementarity to DNA. This DNA-like RNA of the polyribosomes sedimented in discrete classes, rather than in the sedimentation continuum demonstrable for the labeled RNA of the gel interphase. Thus messenger RNA appears to emerge in the cytoplasm in discrete size classes.

Animals↗
PubMedDate not supplied

Expression of atrial natriuretic factor gene in heart ventricular tissue.

A novel peptide hormone, atrial natriuretic factor (ANF), was recently isolated and characterized in mammalian atria. This hormone has potent natriuretic diuretic and vasorelaxant activities. Since ANF bioactivity was initially found in atria but not in ventricles, it was assumed that the ANF gene is specifically expressed in atria. We now report that ANF mRNA is present in ventricular tissue as well as in atria. This is clearly demonstrated by in situ hybridization and by Northern blot analysis. Rat ventricular ANF mRNA concentration is a hundred-fold lower than in atria. As in atria, the 126 amino acids precursor form of ANF is predominant in ventricles and it is present at a thousand-fold lower concentration. The ten-fold discrepancy in the ratio of ANF mRNA to immunoreactivity between atria and ventricles could reflect a higher rate of peptide release in the latter. Thus, ventricular ANF production may be physiologically significant in view of the much larger ventricular mass.

Animals↗
PubMedDate not supplied

Atrial natriuretic factor (ANF) gene expression in the Brattleboro rat.

Atrial natriuretic factor (ANF) is a 28-amino acid peptide hormone of cardiac origin. It has natriuretic, diuretic and vasorelaxant properties and inhibits several cardiovascular modulators. Because of the possible effects of arginine vasopressin (AVP) on ANF secretion, we have investigated ANF gene expression in Brattleboro rats which are genetically deficient in AVP. Our results indicate that cardiac ANF mRNA and ANF content are higher in Brattleboro rats compared to Long-Evans controls, whereas the plasma levels are similar in both groups. Typical secretory granules containing immunoreactive ANF are present in ventricular cardiocytes of Brattleboro but not of Long-Evans rats. These data suggest that ANF release may be uncoupled from its synthesis in the absence of AVP.

Animals↗
PubMedDate not supplied

Gene structure of human cardiac hormone precursor, pronatriodilatin.

Atrial cardiocytes contain granules typical of protein-secreting cells, and atrial extracts are known to contain a powerful natriuretic and diuretic activity and to possess smooth muscle relaxant activity. A variety of active atrial peptides have been isolated, including a family of related peptides showing natriuretic, diuretic and smooth muscle relaxant activities in rat and human atria; these peptides were named atrial natriuretic factor (ANF). Another unrelated peptide from pig atria, cardiodilatin, is thought to possess only smooth muscle relaxant activity. Its partial amino acid sequence shows no homology with ANF sequences. The sequence analysis of a large form (106 amino acids) of ANF and of ANF complementary DNA clones indicates that cardiodilatin and ANF peptides are synthesized from a common precursor. This precursor also contains a signal peptide sequence expected of a secretory protein. We now describe the complete structure and sequence of the human gene for this novel hormone precursor that we call pronatriodilatin.

Alleles↗