Biomedical subjects

Y Shani

Publications and source records attributed to Y Shani.

23 records · Page 2Linked to original sources

PubMed1986

Structure and expression of the vasoactive intestinal peptide (VIP) gene in a human tumor.

To identify the VIP biosynthetic pathways, we have isolated the human VIP gene, using synthetic oligodeoxynucleotides. These specific hybridization probes were constructed according to the neuroblastoma VIP-cDNA sequence and contained up to 39 bases. The gene structure was deduced by direct chemical nucleotide sequencing. Six exons were thus far discovered; among them two short exons, one encoding VIP and the second encoding PHM-27 (a peptide having a N-terminal histidine and C-terminal methionine amide, closely related in sequence and activity to VIP). As a model system for VIP gene expression, we used a human buccal tumor producing elevated amounts of VIP. In these cells, a major transcript of the VIP-gene was identified as a long RNA containing intron sequences. The occurrence of elevated quantities of a high molecular weight, intron containing, gene transcript which is not processed directly into mature RNA suggests that VIP gene expression may be regulated at the RNA processing level.

Base Sequence↗

PubMed1986

Hypothalamic vasoactive intestinal peptide messenger ribonucleic acid is increased in lactating rats.

Vasoactive intestinal peptide (VIP) has been proposed as an inducer of PRL release. Moreover, immunocytochemical studies suggested an increase in the VIP content in the hypothalamus of lactating rats. We investigated whether this increase is regulated at the level of gene transcription. A sensitive RNA detection assay that uses in vitro transcribed RNA probes corresponding to specific exons of the VIP gene was devised to study VIP gene expression. Using this method, an approximately 2000-base long RNA containing the coding sequences for VIP was detected in rat hypothalamus. This RNA also contains the coding sequences for the VIP-related peptide PHM/I (peptide histidine methionine amide or isoleucine amide). An identical VIP-encoding RNA was previously identified in the rat cerebral cortex. A 2-fold increase was observed in hypothalamic VIP mRNA during lactation. In addition, the levels of this mRNA increased in the hypothalamus at the time of sexual maturation. Taken together, our results suggest a physiological regulation of VIP gene expression associated with its potential role as a neuroendocrine hormone.

Animals↗

PubMed1984

Detection of mRNAs containing regulatory peptide coding sequences using synthetic oligodeoxynucleotides.

To understand the regulation of the production of peptide hormones, it is vital to elucidate their biosynthetic pathways. We chose to study a major regulatory peptide, vasoactive intestinal peptide (VIP), a peptide possessing both neurotransmitter and neurohormone actions. To identify the specific peptide mRNA we are using, as hybridization probes, radiolabeled synthetic oligodeoxynucleotides with sequence complementary to the predicted peptide mRNA sequence. Employing this approach, we identified and partially purified a approximately 1600-base long mRNA containing VIP related sequences which can be translated in vitro into VIP-immunoreactive polypeptides. Such mRNA was detected in normal VIP producing tissue (rat brain), as well as in a tumor producing VIP (human buccal tumor). This mRNA differs in size from a known VIP-mRNA identified in human neuro-blastoma cells, suggesting the possibility of different VIP-mRNAs in different cell types.

Animals↗

PubMedDate not supplied

Studies toward the biosynthesis of vasoactive intestinal peptide (VIP).

In view of the potential biological importance of VIP, we have begun to examine the regulation of its biosynthesis. For this purpose we have, as a first step, searched for an enriched source of VIP biosynthesis. By a combination of chromatographic procedures and radioimmunoassays we discovered an as yet unknown source for VIP production, namely a human buccal tumor, containing 0.67 +/- 0.05 ng VIP/micrograms protein which is greater than the richest source in brain (the cerebral cortex). Thus, we decided to use the tumor tissue for VIP-mRNA purification and characterization. To identify VIP-mRNA we are using as hybridization probes, synthetic oligodeoxynucleotides with relatively unambiguous nucleotide sequence complementary to the predicted VIP-mRNA sequence. These probes are synthesized, using the deoxynucleoside phosphoramidite approach, to a length of 17 bases each, and contain all the possible DNA sequences according to the genetic code. These specific probes are then radioactively labelled using the reaction catalyzed by the enzyme polynucleotide kinase and afterwards hybridized to mRNA, which had been resolved on denaturing agarose gels. Employing this approach, we identified a single putative VIP-mRNA band which was then partially purified by sucrose gradient centrifugation. Upon in vitro translation in a rabbit reticulocyte lysate cell free system, this mRNA was found to code for VIP immunoreactive proteins. In conclusion, our studies suggest the existence of high molecular weight precursors to VIP cross-reactive with anti-VIP antibodies, that are coded for by a partially purified mRNA containing VIP sequences.

Base Sequence↗

PubMedDate not supplied

Near-field optical photomask repair with a femtosecond laser.

We present a high-resolution near-field optical tool designed for repair of opaque defects in binary photomasks. Both instrument design and near-field imaging and patterning results will be presented. Designed for ablative processing of thin metal films, the MR-100 incorporates an industrial amplified femtosecond laser, third harmonic generator and built-in autocorrelator. The ultrashort duration of the femtosecond pulses enables the tool to remove chrome layers with negligible damage to the surrounding metal or the underlying quartz substrate. The micropipette based near-field writing head can deliver power densities of hundreds of GW/cm2 to spots of several hundred nanometres and below. Repairs on sample masks will be presented and the repair quality will be discussed.

Journal Article↗