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A Simeone

Publications and source records attributed to A Simeone.

117 records · Page 7Linked to original sources
PubMed1982

Sequence organization of the ribosomal spacer of D.melanogaster.

We subcloned several fragments of the rDNA nontranscribed spacer (NTS) of D.melanogaster and analysed their nucleotide sequence. The central portion contains a variable number of 240 base pair repeated sequences ending with two contiguous Alu I sites. Within every repeat there is a 42 base pair sequence perfectly homologous to the transcription initiation site from -18 to +24. Sequences homologous to the basic 240 bp repeat are present both at the end of the unique 1900 bp region downstream to the transcription termination site and within the unique region preceding the transcription initiation site up to nucleotide -140. These results are discussed in relation to the general problem of ribosomal gene units and their evolution.

Animals↗
PubMedDate not supplied

Activation of major histocompatibility complex class I mRNA containing an Alu-like repeat in polyoma virus-transformed rat cells.

Class I genes of the major histocompatibility complex (MHC) appear to be activated in mouse cells transformed by the DNA tumour virus simian virus 40 (SV40). Conversely, suppression of MHC class I genes has been reported in adenovirus-12-transformed baby kidney rat cells. We have now investigated the expression of genes encoded by the rat MHC locus in rat fibroblast cells transformed by polyoma virus (Py). Using a mouse genomic H-2 clone as a probe in Northern transfer hybridization analysis, we have observed a high level of expression of rat MHC class I messenger RNA in all the transformed rat cell lines analysed. The class I 1.6-kilobase (kb) mRNA activated in Py-transformed rat cells appears to contain an Alu-like type II repeat element, as the same 1.6-kb mRNA is detected using either the H-2 class I sequence or a repetitive Alu-like type II element as a probe. High levels of heterogeneous poly(A)+ transcripts of 0.5-0.8 kb are also observed in Py-transformed rat cells using probes containing an Alu-like type II repetitive element.

Animals↗
PubMedDate not supplied

A human homoeo box gene specifically expressed in spinal cord during embryonic development.

Several genes involved in the determination of Drosophila body segments share a conserved DNA sequence of 183 nucleotides termed the homoeo box. Homologous homoeo box sequences have been detected in the genome of species ranging from insects and anellids to vertebrates, and a number of homoeo box-containing genomic DNA clones have been isolated from Xenopus, mouse and human. We have recently isolated human complementary DNA clones containing homoeo box sequences, representing transcripts from four different genes. We report here the nucleotide sequence of one of these clones (HHO.c10) and show that the corresponding gene is transcribed in human embryos and fetuses at 5-10 weeks post-conception. A major polyadenylated transcript of approximately 2.1 kilobases (kb), as well as RNA species of higher relative molecular mass (Mr), are specifically expressed at a constant level in spinal cord throughout this developmental period.

Base Sequence↗
PubMedDate not supplied

Differential and stage-related expression in embryonic tissues of a new human homoeobox gene.

The homoeobox is a 183 base-pair (bp) DNA sequence conserved in several Drosophila genes controlling segmentation and segment identity. Homoeobox sequences have been detected in the genome of species ranging from insects and anellids to vertebrates and homoeobox containing genes have been cloned from Xenopus, mouse and man. We recently isolated human homoeobox containing complementary DNA clones, that represent transcripts from four different human genes. One clone (HHO.c10) is selectively expressed in a 2.1 kilobase (kb) polyadenylated transcript in the spinal cord of human embryos and fetuses 5-10 weeks after fertilization. We report the characterization of a second cDNA clone, termed HHO.c13, that represents a new homoeobox gene. This clone encodes a protein of 255 amino-acid residues, which includes a pentapeptide, upstream of the homoeo domain, conserved in other Drosophila, Xenopus, murine and human homoeobox genes. By Northern analysis HHO.c13 detects multiple embryonic transcripts, which are differentially expressed in spinal cord, brain, backbone rudiments, limb buds and heart in 5-9-week-old human embryos and fetuses, in a striking organ- and stage-specific pattern. These observations suggest that in early mammalian development homoeobox genes may exert a wide spectrum of control functions in a variety of organs and body parts, in addition to the spinal cord.

Amino Acid Sequence↗
PubMedDate not supplied

Otx genes in evolution: are they involved in instructing the vertebrate brain morphology?

Previous mouse models have indicated that Otx1 and Otx2 play an important role in brain and sense organ development and, together with the Drosophila orthodenticle (otd) gene, they share a high degree of reciprocal functional equivalence. Interestingly, mouse models replacing the same region of the Otx2 locus with Otx1, otd or lacZ genes have revealed the existence of a differential post-transcriptional control between the visceral endoderm (VE) and epiblast cells. Indeed Otx1, otd or lacZ mRNA were transcribed in both tissues but translated only in the VE. Embryos lacking OTX1 or OTD proteins in the epiblast and derived tissues, such as the neuroectoderm and axial mesendoderm (AME), fail to maintain the anterior identity and result in a headless phenotype. This finding leads us to hypothesise that, during evolution, the specification of the vertebrate-type brain may have required epiblast cells to translate Otx2 mRNA in order to establish maintenance properties. The establishment of this regulatory control might have been reflected into a remarkable reorganisation of the rostral CNS architecture and might have represented an important event in the evolution of the vertebrate head. Current data suggest that the Otx2 replaced region and in particular the 3' untranslated region (UTR), may contain regulatory element(s) necessary to translate and/or stabilise Otx2 mRNA in epiblast and its derivatives.

3' Untranslated Regions↗
PubMedDate not supplied

[Apropos of a case of myopathy with histologic and electrophysiologic findings of both a myogenic and neurogenic nature].

The authors describe the case of a 36 years old woman suffering from muscular weakness with proximo-distal distribution to legs, and proximal to arms. The disease, appeared during the third decade of life, is slowly becoming more serious. Hematochemical analyses are all within a normal standard; EMG and histopathologic findings prove the existence of both a protopathic and neurogenic trouble in studied muscles. A therapy based on prednisone (50 mg/die) and ACTH (1 mg each 5 days) for a fourty days period doesn't cause essential changes in symptomatology. A cousin (on her mother's side) of our patient suffers from probable "sporadic distal myopathy". The authors discuss if the disease, shown by this patient, may be considered as an atypical form of SDM or if, what appears more probable, it must be nosographically framed as "scapuloperoneal atrophy".

Adult↗
PubMedDate not supplied

[Mondini's dysplasia: a rare cause of recurrent meningitis in childhood].

Recurrent meningitis in children may be due to immune deficiency or abnormal communication of CSF spaces with mucosal spaces (basal skull fractures, encephalocele, etc.). We report a 6-year-old boy, suffering from recurrent meningitis and sensorineural hearing loss. CT scans of the temporal bones demonstrated a bilateral Mondini dysplasia. In patients with this congenital inner ear anomaly, recurrent meningitis may be due to a CSF-middle ear fistula. We think that it is necessary to investigate all patients with recurrent meningitis and sensorineural hearing loss with CT scans of the temporal bones.

Cerebrospinal Fluid Otorrhea↗