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Biomedical subjects

L Pozzi

Publications and source records attributed to L Pozzi.

At least 37 records · Page 2Linked to original sources
PubMed1993

Methylation state of the human HLA-DRA gene in T-lymphocytes and B-lymphocytes of transgenic mice. Lack of methylation at one 5'-GCGC site is not required for gene expression.

A consistent lack of DNA methylation at one or both of two GCGC (Hha I) restriction sites in the 5' region of the HLA-DRA gene has been previously documented by the use of methyl-sensitive restriction enzymes in human cells and tissues, irrespectively of their expression of DR alpha products. Evidence presently available, however, does not exclude that a lack of methylation in this region, although not sufficient, might be necessary for gene expression. In this report, we show that only one of the 5'-GCGC sites is protected, although less efficiently than in man, from CG-->mCG modifications in tissues and cells of transgenic mice carrying an expressed single copy of the HLA-DRA gene/diploid genome. We demonstrate that the two 5' GCGC sites of the HLA-DRA transgene are fully methylated in DR alpha- splenocytes (more than 80% T-lymphocytes), while one of them (the most 5' site) is not methylated in a fraction of DR alpha+ splenocytes (more than 95% B-lymphocytes). These results provide evidence that absence of DNA methylation in the 5' region is not necessary for, but might be associated with and possibly secondary to the expression of the DRA gene.

Animals↗
PubMed1993

Systemic expression of HIV-1 tat gene in transgenic mice induces endothelial proliferation and tumors of different histotypes.

The human immunodeficiency virus tat protein, a transactivator of viral and cellular genes, is suspected to be involved in the pathogenesis of acquired immunodeficiency syndrome-associated tumors. We report that transgenic mice carrying a recombinant DNA containing BK virus early region and the human immunodeficiency virus tat gene develop skin leiomyosarcomas, squamous cell papillomas and carcinomas, adenocarcinomas of skin adnexa, glands, and B-cell lymphomas. Although the incidence of hepatocellular carcinoma is low, most animals show a liver cell dysplasia of variable degree. These mice are also affected by skin lesions resembling the early stages of Kaposi's sarcoma. The transgene was detected intact in all the organs of transgenic mice, generally as multiple tandemly integrated copies. BK virus early region and tat were expressed in essentially all tissues and organs of BK virus/tat transgenic mice. This transgenic mouse model is representative of the systemic involvement of tat in human immunodeficiency virus natural infection and may be applied to investigate the role of tat in malignancies associated to acquired immunodeficiency syndrome, to study Kaposi's sarcoma pathogenesis and cell of origin, to characterize preneoplastic conditions established by tat in the skin and liver, and to assess in vivo the efficacy of antiangiogenic and anti-tat-specific drugs.

Adenocarcinoma↗
PubMed1992

Tianeptine increases the extracellular concentrations of dopamine in the nucleus accumbens by a serotonin-independent mechanism.

The effect of various doses of tianeptine on the extracellular concentrations of dopamine was studied in the striatum and nucleus accumbens of the rat. At 5 (but not 2.5) mg/kg intraperitoneally, tianeptine increased the extracellular dopamine only in the nucleus accumbens. At 10 mg/kg, the effect was also seen in the striatum but it was less marked and shorter-lasting. At 10 mg/kg (i.p.), tianeptine significantly raised the extracellular concentrations of dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) in both regions. The effect of 10 mg/kg tianeptine on dopamine and its metabolites was not significantly changed in animals which had received this dose twice daily for 15 days. Intracerebroventricular administration of 150 micrograms/20 microliters 5,7-dihydroxytryptamine, which markedly depleted serotonin in the brain, did not modify the effect of 10 mg/kg tianeptine on the extracellular concentrations of dopamine and HVA in the nucleus accumbens but reduced the effect on DOPAC. Various doses of tianeptine (1, 3 and 10 mg/kg i.p.) did not change the synthesis of serotonin and dopamine in the striatum and nucleus accumbens. The results show that tianeptine increased the extracellular concentrations of dopamine more in the nucleus accumbens than in striatum. The effect on the output of DA in the nucleus accumbens could be involved in the antidepressant activity of tianeptine.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1992

Recognition efficiency of the hepatitis B virus polyadenylation signals is tissue specific in transgenic mice.

The hepatitis B virus genome contains a unique polyadenylation (TATAAA) signal which is differentially utilized in the formation of the various hepatitis B virus transcripts. A head-to-tail multiple-copy insertion of a viral fragment comprising the viral enhancer, the X promoter, the X open reading frame, and the viral poly(A) signal in transgenic mice allowed us to monitor tissue-specific differences in the expression of transcripts initiating from the X promoter. These transcripts are efficiently processed at the first polyadenylation site in the liver, while in the kidney, the brain, and the testis, a portion of the transcripts covers two copies of the transgene, since only the second polyadenylation site is properly recognized. As discussed in this article, this observation suggests a tissue-specific distribution of cellular factors involved in polyadenylation.

Animals↗
PubMed1992

Effect of amineptine on regional extracellular concentrations of dopamine and noradrenaline in the rat brain.

The effect of amineptine (1.25-20 mg/kg i.p.), an antidepressant inhibiting dopamine uptake, on extracellular concentrations of dopamine was studied in the rat striatum and nucleus accumbens by using the microdialysis technique and two Ca++ concentrations (1.26 and 3.4 mM) in the perfusion medium. In one experiment the effect of amineptine was studied on extracellular concentrations of dopamine and noradrenaline in the frontal cortex perfused with a medium containing 1.26 mM Ca++. Basal extracellular concentrations of dopamine in the striatum and nucleus accumbens were significantly higher at 3.4 mM Ca++. At 5 to 20 mg/kg, amineptine dose-dependently increased extracellular dopamine in the striatum and nucleus accumbens. No differences were found in the effect of amineptine in the two brain regions at the two calcium concentrations. When extracellular dopamine was expressed as a percentage of basal values, amineptine (20 mg/kg) caused greater increases in rats perfused with 1.26 mM Ca++ than in rats perfused with 3.4 mM Ca++ in both brain regions. A similar effect was found when 10 microM amineptine was infused through the dialysis fiber. The effect of 10 mg/kg i.p. of amineptine on dopamine output in the two brain regions was prevented by infusing 1 microM tetrodotoxin in the dialysis fiber. In the frontal cortex, 10 and 20 mg/kg of amineptine significantly raised dopamine and noradrenaline concentrations, whereas 5 mg/kg only increased noradrenaline output significantly. At 10 mg/kg i.p., amineptine also increased extracellular noradrenaline in the dorsal hippocampus. Amineptine had no consistent effects on the concentrations of dihydroxyphenylacetic acid and homovanillic acid in the various brain regions.(ABSTRACT TRUNCATED AT 250 WORDS)

3,4-Dihydroxyphenylacetic Acid↗
PubMed1991

Transgenic mice mimic the methylation pattern of the human HLA-DR alpha gene.

The methylation pattern of the human HLA-DR alpha gene has been studied in different tissues of transgenic mice. Offspring from two transgenic lines was selected for this analysis, carrying the integrated HLA-DR alpha gene in either single or multiple (8-10) copies per diploid genome. In transgenic animals two distinct methylation patterns of the HLA-DR alpha gene are generated, due to a complete methylation of all the GCGC and CCGG sites the former, and to unmethylation restricted to one or both the GCGC sites located in the 5' portion of the HLA-DR alpha gene, the latter. Unmethylation restricted to the 5' portion of the HLA-DR alpha gene is a highly conserved feature in human tissues and in vitro cultured cell lines; therefore, it is concluded that the methylation pattern of the human HLA-DR alpha transgene may be faithfully reconstituted in transgenic animals. Northern blotting analysis of the RNA isolated from tissues of the transgenic mouse carrying single-copy HLA-DR alpha transgene demonstrates its tissue specific expression, suggesting that transgenic mice may represent an "in vivo" experimental system to study the relationship between methylation state and transcriptional activation.

Animals↗
PubMed1991

Tissue-specific expression of the HLA-DRA gene in transgenic mice.

Transgenic mice were produced containing a 33 kilobase (kb) DNA fragment encompassing the five exons and all the known regulatory regions of the class II HLA-DRA gene. The transgene displayed regulated expression [constitutive and interferon-gamma (IFN)-gamma induced] of the human products in most mouse tissues. The tissue distribution of the DRA transgene products more closely resembled that of their mouse homologues, the endogenous H-2 Ea products, than the wider distribution of DRA products in humans. This was evident in several tissues (endothelia of small vessels, especially those of glomerular capillaries, Kupffer cells, and epithelial cells lining the gastrointestinal tract), known to differentially express class II molecules in the two species. Thus, the wider human specific pattern of expression requires an exact cis/trans complementation which is incompletely reconstituted in transgenic mice, suggesting that human-specific cis-acting elements may have arisen during evolution to direct the expression of class II genes to those anatomical regions which usually lack them in the mouse. The only example of aberrant expression of the DRA gene in the present series of transgenic mice was in the dendritic and/or epithelial cells of the thymic cortex, which displayed greatly reduced DR alpha levels in spite of a normal expression of the endogenous E alpha molecules.

Animals↗
PubMed1991

Release of dopamine is reduced by diazepam more in the nucleus accumbens than in the caudate nucleus of conscious rats.

The effects of 1-20 mg/kg diazepam were studied on the extracellular concentrations of dopamine (DA), dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) in the nucleus accumbens and striatum of conscious rats, using intracerebral microdialysis. Five, but not 1 mg/kg diazepam significantly reduced extracellular DA, DOPAC and HVA in the nucleus accumbens. Twenty mg/kg diazepam significantly reduced extracellular DA, DOPAC and HVA in the striatum. A significant effect on striatal DOPAC, but not on DA and HVA, was seen with 10 mg/kg diazepam, while no changes were found with 5 mg/kg diazepam. The results suggest that diazepam reduces the release and metabolism of DA in the nucleus accumbens more than in the striatum.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1990

Effects of acute and chronic clozapine on dopamine release and metabolism in the striatum and nucleus accumbens of conscious rats.

1. The effect of single and repeated (once daily for 23 days) oral doses of 20 and 60 mg kg-1 clozapine on dopamine release and metabolism were studied by intracerebral dialysis in the striatum and nucleus accumbens of conscious rats. 2. The basal output of dopamine, dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) in the striatum and nucleus accumbens of rats given clozapine 20 or 60 mg kg-1 chronically, measured one day after the last drug dose, was not significantly different from that of vehicle-treated animals. 3. Challenge doses of 20 or 60 mg kg-1 clozapine produced similar increases in dopamine levels in the striatum and nucleus accumbens of animals which had received vehicle or clozapine 20 or 60 mg kg-1 once daily for 23 days, except that 1 h after administration 60 mg kg-1 clozapine had a greater effect in the nucleus accumbens. 4. In animals treated chronically with clozapine 20 and 60 mg kg-1 or vehicle, DOPAC levels in the striatum and nucleus accumbens were increased to the same extent by challenge doses of clozapine (20 or 60 mg kg-1). In animals treated chronically with clozapine, a challenge dose of 60 mg kg-1 had significantly greater effect on HVA only in the nucleus accumbens. 5. When DOPAC and HVA were measured post mortem in the striatum and nucleus accumbens 2 h after various oral doses of clozapine, it was found that 10 mg kg-1 significantly increased dopamine metabolites only in the nucleus accumbens whereas 100 mg kg-1 had this effect in both regions. Clozapine, 30mgkg-' significantly raised DOPAC levels in both regions but HVA was elevated only in the nucleus accumbens. 6. There appeared to be no appreciable changes in dopamine release and metabolism nor any reduction in the effect of clozapine in the nucleus accumbens after chronic drug treatment. In fact the effect was greater in chronically treated rats, particularly in the nucleus accumbens of animals given 60mgkg' clozapine. 7. It was confirmed that measurement of dopamine metabolites in post mortem tissue provides no valuable information on changes in the availability of synaptic dopamine.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1989

Polyomavirus genome and polyomavirus enhancer-driven gene expression during myogenesis.

The mRNAs for myogenic functions are coordinately transcribed with polyomavirus (Py) early mRNA during in vitro differentiation of mouse C2 myoblast cells. Sequence analysis shows that the A domain of the Py enhancer includes an E1A-like consensus sequence that is also found in the 5' upstream region of two genes expressed during myoblast differentiation: alpha-actin and myosin light chain. Therefore, the coordinate expression of such genes with Py early mRNA may be activated by a common cellular regulatory factor. In the present work, we report that C2 cells surviving Py infection are unable to differentiate and do not express alpha-actin and myosin light-chain mRNAs. Hybrids between such Py-resistant myoblast cells and the parental cells exhibited dominance of the permissibility to Py growth and of the expression of myogenic mRNAs. In C2 cells transiently transfected with a chimeric plasmid (pSVPy12CAT) harboring the bacterial chloramphenicol acetyltransferase (CAT) gene driven by the Py enhancer-promoter region, the CAT gene was expressed irrespective of their stage of differentiation. Moreover, undifferentiated stably transfected cells expressing the CAT gene restricted viral growth. Py-resistant C2 myoblasts transiently transfected with pSVPy12CAT also expressed the CAT gene driven by the Py enhancer. This contradictory finding is similar to results previously obtained by other investigators with cloned genes specific for myogenic functions, and it may be explained by a structural difference between the pSVPy12CAT and the Py genomic organizations in which the viral enhancer operates.

Animals↗
PubMed1978

Radiosensitivity of the helper cell function.

The helper function of T cells primed and irradiated in vivo was tested in vitro by the Mishell-Dutton technique. Spleen cells from mice carrier-primed with HRBC and exposed to 50 to 2000 rads of x-radiation were assayed for their ability to help syngeneic normal spleen cells to mount an in vitro anti-hapten antibody response after stimulation with the conjugate TNP-HRBC. The anti-TNP response was evaluated by the Jerne technique. The helper activity was titrated by adding graded numbers of carrier-primed spleen cells to a constant number of normal spleen cells. The slope of the initial linear portion of the response-cell dose titration curve was taken as an estimated of the helper activity and found to decrease with increasing the x-ray dose. The curve describing the remaining helper activity as a function of the radiation dose shows the presence of two components, one radiosensitive, the other, radioresistant. This suggests the existence either of helper cells at different stages of activation or of two cell subpopulations participating in the helper function.

Animals↗
PubMed1978

[Electrocardiographic records via telephone (author's transl)].

666 electrocardiographic records have been transmitted via telephone from the peripheral Sections of the Cardiology Service of the Arcispedale S. M. Nuova of Florence to the central Unit, during the period november 1976 - June 1978. Transmitters were situated respectively 3, 5 and 15 kilometers from the central set where one or more cardiologists were available along 24 hours. Since the introduction of such tecnique faster electrocardiographic diagnosis in emergency calls was made possible and the immediate presence of a consultant cardiologist in the peripheral Sections required only in exceptional cases. Records of good quality are usually transmitted by this instrumentation (OTE Biomedica, Modello 1181-82) which requires only a minimum of knowledge of electrocardiographic tecnique. Lowering of the conversion voice at either end is avoided by disconnecting the transmitter and the receiving sets at the end of the recording procedure. The low price of such equipment favourably compares with the benefits of its use.

Electrocardiography↗