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Biomedical subjects

M Melli

Publications and source records attributed to M Melli.

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

DNA sequences complementary to human 7 SK RNA show structural similarities to the short mobile elements of the mammalian genome.

A complementary DNA clone of 7 SK RNA from HeLa cells was used to study the genomic organization of 7 SK sequences in the human genome. Genomic hybridizations and genomic clones show that 7 SK is homologous to a family of disperse repeated sequences most of which lack the 3' end of the 7 SK RNA sequence. Only few of the genomic K sequences are homologous to both 3' and 5' 7 SK probes and presumably include the gene(s) for 7 SK RNA. The sequence of four genomic 7 SK clones confirms that they are in most cases pseudogenes. Although Alu sequences are frequently found near the 3' and 5' end of K DNA, the sequences immediately flanking the pseudogenes are different in all clones studied. However, direct repeats were found flanking directly the K DNA or the K-Alu unit, suggesting that the K sequences alone or in conjunction with Alu DNA might constitute a mobile element.

Base Sequence↗
PubMed1984

Structure and evolution of the 7SL RNA component of the signal recognition particle.

We have cloned and characterized cDNA copies of larval and adult Drosophila 7SL RNA. The Drosophila 7SL sequence shares 66.3% homology with that of human 7SL RNA. The homology is not evenly distributed along the sequence, but is concentrated in blocks in the central part of the molecule. We have analysed the secondary structure of Drosophila and human 7SL RNA free in solution by digestion with single and double strand specific nucleases. Similar experiments with the 7SL RNA bound to proteins within the signal recognition particle show essentially the same digestion pattern. A model of the secondary structure common to Drosophila and human 7SL RNA is presented.

Animals↗
PubMed1984

Comparative evaluation of blood viscosity in diabetic retinopathy.

The viscosity of the whole blood, plasma and serum, haematocrit and plasma fibrinogen were studied in diabetic patients with (DR) and without (D) retinopathy and in non-diabetic control subjects (C). Blood viscosity was significantly higher in diabetics than in controls. No significant differences in viscosity of the whole blood were found when various types of retinopathy were compared according to the severity of retinal damage. Plasma viscosity was significantly higher (P less than 0.01) than controls (C) only in diabetic patients with retinopathy (DR). Serum viscosity was significantly increased compared with controls (C) only in diabetic patients affected by proliferative retinopathy. Plasma fibrinogen was significantly higher than controls (C) both in diabetics with retinopathy (DR) and without retinopathy (D). Haematocrit did not show a significant difference in the three groups considered (C, D, DR).

Adult↗
PubMed1983

The organization of the 7SL RNA in the signal recognition particle.

Digestion of the signal recognition particle (SRP) of dog pancreas with micrococcal nuclease results in the stepwise cleavage of the 300 nucleotide 7SL RNA moiety producing five major fragments approximately 220 (1), 150 (2), 72 (3), 62 (4) and 45 (5) nucleotides long. The RNA molecule is initially cut once yielding fragments 1 and 3. Further degradation releases fragments 2, 4 and 5. The introduction of the first nick into the 7SL RNA does not alter the structure nor the function of the SRP. Further degradation of the RNA results in disruption and loss of activity of the particle. The sequence of the RNA fragments shows that the nuclease causes discrete cuts in the RNA with minimal nibbling indicating that only few sites are accessible to the action of the enzyme. The five major products of nuclease digestion together span almost the entire length of the 7SL RNA. Nicking occurs mainly around the boundary region between the central S sequence and the flanking Alu sequences constituting the 7SL RNA (1). The S fragment is bound to the four largest polypeptides while the 5' and 3' Alu fragments are associated with the two smallest protein constituents of the SRP.

Animals↗
PubMed1983

A new method for the rapid measurement of analgesic activity in rabbits.

A simple and rapid method is described for the screening of narcotic and non-narcotic analgesics in conscious rabbits. This method is based upon the increase in threshold by electrical stimulation of the ears of rabbit, by analgesics. A reliable dose-response and time-response relations were observed for both groups of analgesics. Naloxone did not produce a hyperalgesia when given alone. It antagonized, however, the analgesic activity of morphine without altering that of aspirin. From these results it is concluded that nociception induced by electrical stimulation of rabbit ears is a simple and rapid method for the screening of analgesics as well as their interactions with specific antagonists.

Analgesics, Opioid↗
PubMed1983

[Blood viscosity and erythrocyte deformability in diabetic retinopathy].

The whole blood and plasma viscosity, hematocrit and plasma fibrinogen were studied in 26 diabetic patients (11 with and 15 without retinopathy) and in 25 non-diabetic control subjects. Blood viscosity, plasma viscosity and plasma fibrinogen were significantly higher in diabetics than in controls, but no significant differences were found when diabetics with retinopathy were compared to diabetics without retinopathy. The red cell deformability was significantly reduced in diabetics if compared with that of controls; the statistical significance of this reduction was confirmed only in the group of diabetics with retinopathy, but failed when the group of diabetics without retinopathy was considered.

Adult↗
PubMed1982

Cloning and characterization of cDNA copies of the 7S RNAs of HeLa cells.

We have cloned cDNA copies of in vitro adenylated 7S RNA of HeLa cells. The most representative clones in the library contain DNA fragments copied from the 7SL and 7SK small RNAs. The two classes of recombinants share no homology. The 7SL RNA contains at the 5' end of the molecule sequences homologous to the Alu sequence family. Hybridization to human genomic DNA shows that the 7SL and 7SK clones are homologous to two different families of repetitive sequences.

Cloning, Molecular↗
PubMed1982

Human 7SL RNA consists of a 140 nucleotide middle-repetitive sequence inserted in an alu sequence.

We have cloned and sequenced a cDNA copy of in vitro-polyadenylated 7SL RNA of HeLa cells. The cloned fragment is 303 bp long and has a composite structure. A central block of 140 bp is homologous to a new set of human middle-repetitive sequences. This block appears to be inserted in an Alu consensus sequence, 100 bp from the 5' end and 40 bp from the 3' end of the Alu monomer. Two 6 bp direct repeats are found at the junction between the Alu flanking sequences and the central element. The analysis of several clones shows the existence of sequence microheterogeneity in the 5' portion of the molecule. The 7L DNA probably represents a subset of the Alu family of DNA, highly conserved in evolution.

Base Sequence↗
PubMed1982

Reversal by acetylsalicylic acid of the captopril-induced inhibition of angiotensin converting enzyme in the hindquarters of guinea-pig.

The conversion of angiotensin I to angiotensin II was studied in the isolated perfused hindquarters of guinea-pig. The relative enzyme activity was determined by vasoconstrictor response to the peptides and by the contraction of rat ascending colon superfused with the venous effluent. 45% of conversion of angiotensin I to angiotensin II was determined in this preparation as measured by vasoconstrictor responses. However, only 22% of conversion was detected in the venous return as measured in the rat colon. Captopril significantly inhibited angiotensin converting enzyme activity in this preparation. Acetylsalicylic acid, however, partially prevented the inhibitory effect of Captopril on converting enzyme activity in this vascular bed. The possible interactions of angiotensin converting enzyme activity and endogenous prostaglandins are discussed.

Angiotensin I↗
PubMed1981

Microdissection and cloning of DNA from a specific region of Drosophila melanogaster polytene chromosomes.

Fragments from section 3 of the salivary gland X chromosome of D. melanogaster were dissected with a micromanipulator. The DNA was extracted, cut and ligated to a lambda vector in a volume of a few nanoliters in an oil chamber monitored through a microscope. From about 10 pg of DNA we obtained 80 recombinant clones, a sample of which were analysed and shown to contain Drosophila DNA which hybridises in situ to the region of section 3 of the X chromosome. With this technique we can isolate clones from any desired region as small as 200 kb from the euchromatic arms of polytene chromosomes.

Bacteriophage lambda↗
PubMed1977

Presence of histone mRNA sequences in high molecular weight RNA of HeLa cells.

Pulse-labeled HeLa cell RNA centrifuged under denaturing conditions was hybridized with DNA of recombinant phages containing sea urchin histone genes. This cross-hybridization showed the presence of histone mRNA sequences in high molecular weight RNA molecules. Treatment of the cells with actinomycin to stop RNA synthesis resulted in the rapid decay of this high molecular weight RNA followed by an increase of 9S histone mRNA in the cytoplasm. The results are consistent with the presence in HeLa cells of a high molecular weight precursor to histone messengers.

Coliphages↗
PubMed1977

Synthesis of histone messenger RNA of HeLa cells during the cell cycle.

Hybridization of HeLa cell RNA to the DNA of a recombinant phage containing sea urchin histone genes shows that histone mRNA of HeLa cells is synthesized throughout the entire cell cycle. Furthermore, histone messenger is synthesized in cells treated with cytosine arabinoside, an inhibitor of DNA duplication. Although histone RNA is found in the nucleus, the amount of cytoplasmic histone messenger is drastically reduced, in agreement with previous work. The absence of coupling between histone mRNA synthesis and DNA duplication shows that the regulatory process which determines the presence or absence of histone mRNA in the cytoplasm of HeLa cells is not at the transcriptional level.

Cell Cycle↗