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R Negri

Publications and source records attributed to R Negri.

At least 19 recordsLinked to original sources
PubMed1992

Cell-to-cell contact between normal fibroblasts and lymphoblasts deficient in lysosomal enzymes.

Human lymphoblasts deficient in iduronate sulfatase or in alpha-N-acetylglucosaminidase acquire discrete levels of enzyme activity after co-culture with human normal skin fibroblasts. This occurs by direct cell-to-cell contact and not by uptake of secreted fibroblast enzyme. The process is dependent on time and on the number of fibroblasts used. Electron-microscopic examination of the co-culture of the two cell types reveals extensive region of intimate contact. Fibroblastic projections appear frequently in close apposition with lymphoblast invaginations; a diffuse micropinocytotic activity is evident only in fibroblastic cells.

Acetylglucosaminidase↗
PubMed1992

[Immunohistochemical identification of cholesteatoma-associated macrophage populations].

Extensive bone resorption occurring in aural cholesteatoma is responsible for the severe complications of this disease. In the area of active bone destruction, typical multinucleated osteoclasts are rarely seen, but a heavy cellular infiltrate is found. In the present study we tried to characterize the immunophenotype and the functional state of the cells infiltrating the stroma and the epithelial layer of aural cholesteatoma, using a panel of monoclonal antibodies directed against cell type specific antigens. The results were compared with normal retroauricular skin. The vast majority of cells infiltrating the stroma was bone marrow derived and consisted of T-cells and macrophages. By means of the activation markers HLA-DR and Interleukin-2 receptor an immunologically activated state of the majority of infiltrating cells in cholesteatomas was shown. The great number of activated macrophages in cholesteatomas seems to be very important in the cholesteatomatous immunological process. Because of their various immunological functions (antigen presentation to T-lymphocytes, participation in ingestion and killing of different invading microorganisms and synthesizing a great number of substances involved in host defence and inflammation) these cells play a central role in human immunological system. Langerhans cells, however, did not appear to be involved in the immune process of cholesteatoma. The characteristics of the infiltrating cell population with the great number of phagocytic cells suggest an active immune process resulting in autoaggressive bone resorption.

Antibodies, Monoclonal↗
PubMed1991

A single-reaction method for DNA sequence determination.

A chemical method for the determination of DNA sequence is presented. Heating of DNA, labeled at a single 3' extremity, in the presence of formamide results in efficient cleavage of phosphodiester bonds 3' of A, G, and C residues. The relative efficiency is A = G greater than C. The bias between A and G is solved by a simple pretreatment (photoreaction in methylene blue) followed by heating in formamide. The entire procedure does not require any intermediate purification step or handling of hazardous chemicals and allows determination of the sequence on only two electrophoretic lanes. Its simplicity and rapidity favor automatization.

Base Sequence↗
PubMed1990

Attraction, phasing and neighbour effects of histone octamers on curved DNA.

Nucleosome core particles were reconstituted on various DNA fragments containing a Crithidia fasciculata kinetoplast curved tract. The results show that, on curved DNA, nucleosome core particles form six- to sevenfold preferentially, relative to bulk sequences. The preferential deposition occurs at multiple periodic positions, whose distribution reveals a unique rotational setting of DNA with respect to the histone octamer surface and whose average periodicity is 10.26 +/- 0.04. Evidence is provided for a context effect in histone octamer deposition: octamers bound to a segment of curved DNA influence the positions of neighbour octamers. Taken together, the preferential formation of nucleosome core particles and the influence on the localization of neighbouring particles suggest for intrinsically bent sequences the biologically relevant role of organizers of nucleosomal arrays.

Animals↗
PubMed1990

Fragile-X mental retardation in a large five-generation family. A clinical and cytogenetic study.

A number of problems concerning both clinical and genetic or cytogenetic aspects of the fragile-X syndrome remain unsolved. In the present work, a large 5-generation fragile-X family has been clinically and cytogenetically investigated. The results of our study indicated that an unusually high proportion of affected males was present in the family examined; all fragile-X-positive males were profoundly retarded and showed the phenotype typically described for this syndrome; moreover, we observed a variability of penetrance within the pedigree and all fragile-X-positive females in the 4th and 5th generation had some degree of mental impairment. A multistep mutation model has been proposed in order to explain some of these findings.

Adolescent↗
PubMed1990

Morphological changes induced by prolonged TSH stimulation or starvation in the rat thyroid cell line FRTL.

Subconfluent FRTL cells were examined in the electron microscope after the following treatments: i) continuous TSH stimulation; ii) starvation from TSH for 3 or 7 days; iii) seven days of TSH deprivation followed by two days of TSH stimulation. The organelle complement of cells grown in the presence of TSH appeared to be consistent with their secretory properties. Rough endoplasmic reticulum (RER), in the form of round vesicles, and Golgi apparatus, were quite prominent. Cells were not properly polarized. Their dorsal surface was covered with microvilli and occasional pseudopods. After TSH withdrawal the cells flattened on the dish, lost most of their plasma membrane specializations and reorganized actin stress fibers. RER shape was modified from round vesicles to flat cisternae which thereafter almost completely disappeared. The Golgi apparatus did not seem to be modified. Autophagic vacuoles became more prominent. All the modifications were fully reversed after TSH replacement indicating an hormonal regulation in the amount and morphology of some organelle, in particular of the RER.

Animals↗
PubMed1989

Linkage reduction allows reconstitution of nucleosomes on DNA microdomains.

We have established an experimental system for reconstitution of an individual nucleosome on a closed DNA microdomain (operationally defined as a DNA domain of a size so small as to be unable to establish titratable superhelical turns). The microdomain (185 base-pairs (bp), composed of 128 bp encompassing the central part of the Saccharomyces cerevisiae ADH II promoter plus 57 bp of a polylinker) was obtained by ligation under conditions that produced three circularized forms characterized by different linkage numbers. These linkomers were tested for nucleosome reconstitution with S. cerevisiae histones. It was observed that only microcircles with linkage reduction (delta Lk = 1 or 2) could form a nucleosome, as defined by protection of a 145(+/- 2) bp DNA fragment from micrococcal nuclease, relaxed forms (open or closed circles) could not.

Base Composition↗
PubMed1989

Transcription factor IIIB generates extended DNA interactions in RNA polymerase III transcription complexes on tRNA genes.

Transcription complexes that assemble on tRNA genes in a crude Saccharomyces cerevisiae cell extract extend over the entire transcription unit and approximately 40 base pairs of contiguous 5'-flanking DNA. We show here that the interaction with 5'-flanking DNA is due to a protein that copurifies with transcription factor TFIIIB through several steps of purification and shares characteristic properties that are normally ascribed to TFIIIB: dependence on prior binding of TFIIIC and great stability once the TFIIIC-TFIIIB-DNA complex is formed. SUP4 gene (tRNATyr) DNA that was cut within the 5'-flanking sequence (either 31 or 28 base pairs upstream of the transcriptional start site) was no longer able to stably incorporate TFIIIB into a transcription complex. The TFIIIB-dependent 5'-flanking DNA protein interaction was predominantly not sequence specific. The extension of the transcription complex into this DNA segment does suggest two possible explanations for highly diverse effects of flanking-sequence substitutions on tRNA gene transcription: either (i) proteins that are capable of binding to these upstream DNA segments are also potentially capable of stimulating or interfering with the incorporation of TFIIIB into transcription complexes or (ii) 5'-flanking sequence influences the rate of assembly of TFIIIB into stable transcription complexes.

Base Sequence↗
PubMed1988

Antenatal sonographic findings of agenesis of corpus callosum.

Agenesis of the corpus callosum is a central nervous system anomaly that may be associated with other intracranial abnormalities. It is easily diagnosed in the postnatal period by computed tomographic scan and ultrasound. However, its prenatal sonographic diagnosis remains a challenge. This report will evaluate three cases of fetal agenesis of the corpus callosum, review the antenatal sonographic findings and postnatal outcomes, and provide criteria for the antenatal diagnosis.

Adult↗
PubMed1987

Neoplastic invasion of the connective stalks in transitional cell papillary tumors (TCPT) of the bladder.

Neoplastic invasion into the connective stalks of transitional cell papillary tumors of the bladder was assessed in TUR specimens from new cases. There were 21 G1 cases, none of which showed invasion of the connective tissue stalk; this compared with definite invasion in 19 of 77 G2 cases (25%) and in 16 of 17 G3 cases (94%). During a 5 year follow-up period more of the stalk invasive cases had an unfavorable course (fatal outcome or total cystectomy) than of the stalk non-invasive cases; this was statistically significant (p less than 0.01) for the whole group of patients and for the smaller group of patients with G2 tumors (p less than 0.05).

Carcinoma, Papillary↗
PubMed1987

Enhancement of immune response of murine Peyer's patches by a diet supplemented with yogurt.

The first line of defense against pathogens that enter the host by the oral route involves the Peyer's Patches (PP). For centuries many populations of the mediterranean basin have empirically administered soured milk (yogurt) to prevent and treat diarrhoea and entero-colitis. Recent reports have offered evidence in favour of a possible influence of yogurt on the host's immunocompetence. Scope of the present study was to evaluate the influence of a diet supplemented with yogurt on the PP from BALB/c mice. The results reported here suggest that yogurt feeding potentiates the host's cell-mediated immune response by increasing the percentage of B lymphocytes and the PHA and LPS-induced proliferative responses of PP cell suspensions.

Animals↗
PubMed1987

Topological properties of DNA domains and interaction with RNA polymerase II.

We have analyzed the relationship between the alterations of the DNA structure induced by topological constraint and the template properties of promoters in vitro. A cause-effect relationship has been defined in several instances. Experimental protocols have been developed for the study of the topological properties of RNA polymerase II promoters. The goal of these studies is the definition of the intrinsic structural informations of DNA.

DNA↗
PubMed1986

Structure of RNA polymerase II promoters. Coordinate conformational alteration of the upstream activator of the TATA- and RNA-initiation sequences under moderate torsional stress.

Different conformations of the circular DNA domains containing the intergenic region of the Saccharomyces cerevisiae GAL1-GAL10 divergent genes (914 base pairs) were modified by in vitro ligation in various conditions. The effect of increasing torsional stress on the conformation of the composing elements was determined by analysis of the sensitivity to the single strand-specific S1 endonuclease and it was observed that the sites of conformational alterations correspond to the positions relevant for promoter function (upstream activator sequence, TATA sequence, and RNA initiation site).

Base Sequence↗
PubMed1986

Structure of RNA polymerase II promoters. Conformational alterations and template properties of circularized Saccharomyces cerevisiae GAL1-GAL10 divergent promoters.

A DNA fragment encompassing the Saccharomyces cerevisiae GAL1--GAL10 divergent promoters (914 bp) has been circularized in vitro with T4 DNA ligase. We have defined a set of conditions that allows the production of a series of nine topoisomers covering a range from relaxed to highly negatively supercoiled DNA. Topoisomers were recovered in pure form from agarose gels and were analysed singly for the presence of sites sensitive to the single strand-specific endonuclease Pl. In this way, the occurrence of conformational alterations as a function of the linking deficiency of the closed DNA domain has been determined. Interestingly, sites of Pl hypersensitivity localize on the three sequences identified as relevant for the in vitro transcription of the GAL1 moiety of the divergent promoter: the upstream activator sequence (UAS), the TATA sequence, and the RNA initiation site (RIS). In vitro transcription with purified S. cerevisiae RNA polymerase II shows that activation of transcription parallels the appearance of conformational alterations on the UAS, the TATA and the RIS sequences.

Base Composition↗