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Biomedical subjects

G Mangiarotti

Publications and source records attributed to G Mangiarotti.

At least 37 records · Page 2Linked to original sources
PubMed1985

mRNA stabilization controls the expression of a class of developmentally regulated genes in Dictyostelium discoideum.

During the development of Dictyostelium discoideum, several thousand new mRNA species appear in the cytoplasm after the cells have formed stable aggregates. Here we show that six of these late mRNAs, corresponding to six clones randomly chosen from a genomic library, are synthesized from the very beginning of development at a rate comparable to that observed late in development but that transcripts do not accumulate until after aggregation. The early- and late-synthesized mRNAs are identical in size and compete with each other for hybridization to the genomic clones. The early-synthesized mRNAs do not accumulate in the cytoplasm in the preaggregation stage because they are very unstable. Their stability, estimated from the kinetics of incorporation during continuous labeling with (32)P, increases by perhaps an order of magnitude in the postaggregation stage. We conclude that mRNA stabilization is the major controlling factor of the expression of these genes.

Journal Article↗
PubMed1984

Regulation of gene expression in Dictyostelium discoideum cells exposed to immobilized carbohydrates.

When amoebae of Dictyostelium discoideum develop on gels of polyacrylamide that are derivatized with glucosides, they become capable of aggregation at the same time as cells not exposed to glucosides. However, the aggregation centers and streams of adherent cells formed on immobilized glucosides suddenly disintegrate. The cells repeatedly re-aggregate, but never form tight aggregates as they do on other substrata. Tight aggregates formed in the absence of glucosides disperse after their transfer to glucoside gels, and the cells undergo aggregation-disaggregation cycles. The formation of tight aggregates is correlated with the expression of specific post-aggregative poly(A) RNAs. These RNAs are not expressed in cells developing on glucoside gels, and the dispersal of tight aggregates on such gels is accompanied by the almost complete loss of these RNAs. A developmentally regulated membrane glycoprotein called contact site A, which is a marker of aggregation-competent cells, is normally expressed on glucoside gels. Cyclic AMP is also produced, indicating that the strong increase of adenylate cyclase activity during the preaggregation phase is not affected. In conclusion, cell contact with immobilized glucosides specifically inhibits postaggregative gene expression and arrests development at the aggregation stage.

Journal Article↗
PubMed1984

Urokinase treatment for arteriovenous fistulae declotting in dialyzed patients.

Urokinase treatment, previously employed with success in the declotting of deep venous thrombosis and arteriovenous shunts in patients undergoing regular dialytic treatment (RDT), was used in 23 cases of arteriovenous fistula thrombotic occlusion in 18 RDT patients. The treatment was successful in 65.2% of the cases without any negative side effects, except 1 case which may have developed a pulmonary embolism. Patients with severe hypofibrinolysis may need larger doses or may have a recurrence of the thrombotic episode. All therapeutic failures correlated with the presence of fibrosis or sclerosis.

Adult↗
PubMed1983

Different mRNAs have different nuclear transit times in Dictyostelium discoideum aggregates.

Nuclear processing of mRNA precursors in differentiating multicellular Dictyostelium discoideum aggregates is markedly slower than in growing amoebae. Thus, we have been able to determine the time of nuclear processing of individual mRNA species in postaggregating cells by following the incorporation of 32PO4 into nuclear and cytoplasmic RNA complementary to cloned cDNAs. Precursors of mRNAs synthesized during both growth and differentiation remain in the nucleus for about 25 to 60 min. By contrast, typical mRNAs which are synthesized only by postaggregative cells have nuclear processing times between 50 and 100 min. Depending on the particular mRNA, between 20 and 60% of nuclear transcripts are converted into cytoplasmic mRNA. A third class of mRNAs are transcribed from a set of repetitive DNA segments and are expressed predominantly during differentiation. Nuclear precursors of these mRNAs are extensively degraded within the nucleus or very rapidly after transport to the cytoplasm. Those sequences that are stable in the cytoplasm exit from the nucleus only after a lag of over 2 h. Thus, mRNAs encoded by different genes that are subject to different types of developmental controls display different times of transit to the cytoplasm and different efficiencies of nuclear processing. Differential nuclear processing may contribute to the regulation of the level of individual cytoplasmic mRNAs.

Biological Transport↗
PubMed1982

Impaired fibrinolysis in uremia: partial and variable correction by four different dialysis regimes.

In addition to a hemorrhagic diathesis, uremia is accompanied by a clotting tendency, caused by a marked fall in fibrinolytic capacity. Measurement of lysis time of whole blood diluted with phosphate and acetate buffers and of euglobulin lysis times showed that accumulation of inhibitors is primarily responsible. These probably belong to the class of small molecules abnormally retained in uremia. Hemodialysis (HD) offers the best method of correction, mainly because of better elimination of these inhibitors. In contrast, hemofiltration (HF) and, particularly, intermittent peritoneal dialysis (IPD) are much less effective. In IPD, protein loss via the peritoneum is also responsible for a loss of fibrinolytic activators, so that fibrinolysis becomes even poorer, exposing the patient to an increased risk of vascular complications.

Adult↗
PubMed1981

Selection and analysis of cloned developmentally-regulated Dictyostelium discoideum genes by hybridization-competition.

We describe a new technique for selection of cloned gene segments which are expressed preferentially at one developmental stage but at a relatively low level. A nitrocellulose filter replica of plaques of lambda phage which contain approximately 8 KB inserts of genomic DNA is prepared; it is hybridized with a small amount of [32p] labeled mRNA prepared from one developmental stage, in the presence of a several-hundred fold excess of competitor RNA from a different stage. We show that clones of Dictyostelium nuclear DNA which form hybrids under these conditions indeed encode developmentally regulated mRNAs. Our previous analysis of Dictyostelium discoideum differentiation indicated that transcripts from about 12% of the genome appear in mRNA at one defined stage of differentiation - the formation of cell-cell aggregates. A number of our new clones are novel, in that they encode multiple discrete mRNA species all of which accumulate only at the cell aggregate stages; others encode one or more mRNAs which appear at the tight aggregate stage and also one or more which are present throughout differentiation. These latter clones, in particular, would be difficult to identify using other selection techniques.

Cloning, Molecular↗
PubMed1981

Rates of synthesis and degradation of ribosomal ribonucleic acid during differentiation of Dictyostelium discoideum.

Synthesis of ribosomes and ribosomal ribonucleic acid (RNA) continued during differentiation of Dictyostelium discoideum concurrently with extensive turnover of ribosomes synthesized during both growth and developmental stages. We show here that the rate of synthesis of 26S and 17S ribosomal RNA during differentiation was less than 15% of that in growing cells, and by the time of sorocarp formation only about 25% of the cellular ribosomes had been synthesized during differentiation. Ribosomes synthesized during growth and differentiation were utilized in messenger RNA translation to the same extent; about 50% of each class were on polyribosomes. Ribosome degradation is apparently an all-or-nothing process, since virtually all 80S monosomes present in developing cells could be incorporated into polysomes when growth conditions were restored. By several criteria, ribosomes synthesized during growth and differentiation were functionally indistinguishable. Our data, together with previously published information on changes in the messenger RNA population during differentiation, indicate that synthesis of new ribosomes is not necessary for translation of developmentally regulated messenger RNA. We also establish that the overall rate of messenger RNA synthesis during differentiation is less than 15% of that in growing cells.

Dictyostelium↗
PubMed1981

Heparin is unable to prevent contact activation by three different membranes.

In spite of the anticoagulant activity of heparin platelet deposition and contact activation of coagulation occurs during dialysis. We have studied platelet counts, fibrinogen, platelet factor 4, beta-thromboglobulin, thromboxane B2, FRA, C3d and kallikrein values, whole blood and euglobulin lysis times and membrane areas in haemodialysis using cuprophan and cellulose acetate and in haemofiltration with polyacrilonitrile. Deposits on all the three membranes included leucocytes, platelets and fibrin. The coagulation and fibrinolytic systems are activated more intensively with cellulose acetate and more prolongedly with polyacrilonitrile. Platelet factor 4 and beta-thromboglobulin increases suggest platelet activation, only partially dependent on arachidonic acid-mediated pathway as thromboxane B2 is not increased. The complement system is activated whereas serum kallikrein does not alter, suggesting that platelets rather than factor XII are crucial in contact activation.

Adolescent↗
PubMed1980

[Diabetic nephropathy. Review of the current status and practical considerations concerning etiopathogenetic, clinical and therapeutic aspects].

Reference is made to personal research and clinical experience, coupled with a select bibliography, in a survey of the most significant current knowledge with regard to diabetic nephropathy, designed for the nonspecialist practitioner and intended to enable him to update his knowledge without plunging into details, and to quickly decide what measures he should adopt in his daily practice. Questions of histopathology and aetiopathogenesis are examined, together with the relations between proteinuria, hypertension, renal function, and diabetic nephropathy. The clinical profile and progress of the disease are illustrated. Lastly, an account is given of the conventional modes of treatment, and of the still partly unsatisfactory results offered by more recent forms of replacement therapy (dialysis and transplantation).

Anti-Bacterial Agents↗
PubMed1978

[The quarantined dialysis room for Australia-antigen-positive patients. Theoretical, normative, structural, operational, organizational and management aspects].

The technical features of dialysis facilitate the transmission of hepatitis B virus and the outbreak of possibly serious epidemics among patients and hospital staffs. Statistical, epidemiological and clinical data have been collected on many occasions. They serve to emphasise the problem and the need for quarantined centres. The establishment of such a centre for HBsAg-positive patients is discussed in the light of personal experience in the design and setting up of quarantined rooms. The underlying technical and structural requirements are also examined. Reference is also made to two years' experience in the running of a room of this kind. Stress is laid on the importance of having a room for these patients, not only from the clinical standpoint (lessening of contagion), but also from teh social and exonomic standpoint (reduced costs and length of hospital stay, greater rehabilitation).

Cross Infection↗