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Biomedical subjects

A Romeo

Publications and source records attributed to A Romeo.

At least 19 recordsLinked to original sources
PubMed1996

Transcriptional remodeling and G1 arrest in dioxygen stress in Saccharomyces cerevisiae.

Saccharomyces cerevisiae, which lack a functional SOD1 gene, encoding the cytosolic Cu,Zn-superoxide dismutase (SOD1), exhibit a variety of metabolic defects in aerobic but not in anaerobic growth. We test here the hypothesis that some of these defects may be due to specific transcriptional changes programmed for cell survival under dioxygen stress. Analysis of the budding pattern and generation time showed that the slower proliferation of an sod1Delta mutant strain under air was due to an increase from 42 to 89 min spent in the G1 phase of the cell cycle. This delay in G1 was not due to an overall decline in biosynthetic activity since total protein and mRNA synthesis was not reduced even under 100% O2. However, rRNA synthesis was strongly decreased, e.g. by 80% in the mutant under 100% O2 (in comparison to N2). Under these conditions, the mutant permanently arrested in G1; this arrest was due to an inhibition of the Start function that prepares yeast for S phase. This Start arrest was due to an inhibition of transcription of the autoregulated G1 cyclins, CLN1 and CLN2; the transcription of the constitutive G1 cyclin, CLN3, was unaffected by the stress. Expression of a hyperstable Cln3 prevented the G1 arrest, indicating that it was due solely to the inhibition of cell cycle-dependent cyclin expression. This remodeling of transcription in oxidative stress was seen also in the inhibition of glucose derepression of SUC2 expression. In contrast, the signaling and activation of mating pheromone (FUS1) and copper-responsive (CUP1) promoter activity were not affected by dioxygen stress, while genes encoding other anti-oxidant enzymes (SOD2, CTT1 and CTA1) were strongly induced. The UBI loci, encoding ubiquitin, were particularly good examples of this pattern of negative and positive transcriptional response to the stress. UBI1-UBI3 expression was repressed in the mutant under 100% O2, while expression of UBI4 was strongly induced. The data demonstrate that extensive remodeling of transcription occurs in yeast under a strong dioxygen stress. This remodeling results in a pattern of expression of gene products needed for defense and repair, and suppression of activities associated with normal proliferative growth.

Cyclins↗
PubMed1996

[Adhesion molecules. Current aspects and clinical and therapeutic perspectives].

The study about the adhesion molecules pointed out their pathogenetic role in a lot of diseases within cardiological, nephrological, oncological precincts and in a lot of infectious diseases. Their role was in fact pointed out in the ischemic heart disease and in the reperfusion damage, in the glomerulonephritis, in the tumoural metastatic processes, in the infectious and inflammatory chronic processes. The Authors considered the recent literature and emphasized the therapeutic possibilities that such an experimental approach seems to suggest.

Cardiovascular Diseases↗
PubMed1995

Requirement of b-myb function for survival and differentiative potential of human neuroblastoma cells.

The B-myb gene belongs to a family of transcription factors that also includes A-myb and c-myb. B-myb is expressed in many cell types including human neuroblastoma cells. Here we demonstrate that B-myb expression is down-regulated during retinoic acid-induced neural and glial differentiation of neuroblastoma cells. This modulation is an early event, is maintained at late times of induction, and is in part regulated at the transcriptional level. Constitutive expression of B-myb prevents retinoic acid-induced neural differentiation as reflected by morphological features and the expression of (or lack of) biochemical markers associated with the undifferentiated phenotype. Furthermore, the expression of antisense B-myb transcripts does not allow the rescue of viable cells, suggesting an important role for B-myb in the survival of neuroblastoma cells. These results indicate that B-myb plays a functional role in the differentiative potential of neuroblastoma cells, raising the possibility that this gene is one of the nuclear regulators in the cascade of events leading to cellular differentiation.

Base Sequence↗
PubMed1995

The combined effect of a GnRH analog in premenopause plus postmenopausal estrogen deficiency for the treatment of uterine leiomyomas in perimenopausal women.

Thirty-four perimenopausal women with uterine leiomyomas were treated with intramuscular injections of leuprolide acetate depot each 28 days for 6 cycles, and 12 of them after 168 days of no medication underwent a second 6-month therapy cycle. At the end of the observation period the expected improvement during treatment was maintained at cessation of therapy in 15 patients, due to the effect of the natural postmenopausal estrogen deficiency. Only 3 women underwent hysterectomy, due to the regrowth to baseline values of uterine size. It is concluded that the therapy with gonadotropin-releasing hormone analogs in perimenopause offers an effective alternative to surgery in the treatment of uterine leiomyomas.

Drug Administration Schedule↗
PubMed1995

Seizure and EEG patterns in Angelman's syndrome.

We studied the seizure and polygraphic patterns of 18 patients with Angelman's syndrome. All patients showed movement problems. Eleven patients were also reported to have long-lasting periods of jerky movements. The polygraphic recording showed a myoclonic status epilepticus in nine of them. Seven patients had partial seizures with eye deviation and vomiting, similar to those of childhood occipital epilepsies. These seizures and electroencephalographic patterns suggest that Angelman's syndrome occurs in most of the patients as a nonprogressive, age-dependent myoclonic encephalopathy with a prominent occipital involvement. These findings indicate that, whereas ataxia is a constant symptom in Angelman's syndrome, the occurrence of a transient myoclonic status epilepticus may account for the recurrence of different abnormal movements, namely the jerky ones.

Adolescent↗
PubMed1994

Lack of correlation between N-myc and MAX expression in neuroblastoma tumors and in cell lines: implication for N-myc-MAX complex formation.

Detectable levels of MAX messenger RNA were found in a set of human neuroblastoma tumors and established cell lines. MAX mRNA levels were independent of tumor stage and N-myc genomic amplification. By contrast, N-myc mRNA transcripts were detectable only in tumors with amplification of N-myc gene and in cell lines. Analysis by reverse transcriptase polymerase chain reaction and hybridization to specific oligodeoxynucleotide probes revealed approximately equal amounts of two MAX transcripts in all cases analyzed. Immunoprecipitations with a specific antibody to MAX detected two proteins of M(r) 21,000 and 22,000 in approximately equal amounts in all neuroblastoma lines regardless of N-myc amplification and/or expression. On the other hand, protein binding to the myc DNA consensus sequence correlated with N-myc expression in neuroblastoma cells. Thus, N-myc expression might be a limiting factor in the formation of the N-myc-MAX heterodimer in neuroblastomas.

Amino Acid Sequence↗
PubMed1994

Infantile spasms combined with partial seizures: electroclinical study of eleven cases.

We studied 11 infants (7 males) with combined infantile spasms (IS) and partial seizures. The age of onset of the spasms ranged from 6 days to 9 months. All of the children had neurological or CT/MRI abnormalities, and five also had a family history of epilepsy. The clinical and polygraphic patterns of the clusters of spasms combined with partial seizures were analysed. Ten infants were followed-up for a mean period of 3 years, 4 months (range 1 year 10 months to 4 years 11 months). At the last check-up, the seizures were controlled in 2 patients; the others continued to have spasms and/or partial seizures. All of the patients developed mild to severe psychomotor retardation. This condition defines a subgroup of infants presenting with IS, which is distinct from West syndrome.

Electroencephalography↗
PubMed1994

Relative efficiency of leucocyte removal procedures for the production of leucocyte-poor red cell concentrates assessed by flow cytometry.

Flow cytometry was used to: (1) determine residual leucocyte numbers in red cell suspensions following the range of leucocyte depletion procedures used in our organisation, and (2) to characterize phenotypically the leucocytes using direct immunofluorescence with monoclonal antibodies to cell surface receptors. Under the conditions used, a lower limit of detection of 2.5 leucocytes per microliter (equivalent to 3.43 log10 or 99.96% removal) could be achieved. Filtration through polyester filters was found to remove up to > 99.96% of the initial leucocytes; however, a significant differential efficacy was observed between filters from different manufacturers even when filters with similar costs were compared. The order of filter brands with respect to leucocyte removal found was Pall BPF4 = Erypur Optima G-O > Sepacell R500 > Pall RC50. Phenotyping revealed that increasing filtration efficacy was associated with a preferential removal of lymphocytes; conversely, a second filtration over one brand of filter allowed proportionately more lymphocytes to pass through compared with the first filtration. A saline wash following filtration removed a further 0.5% of the initial leucocyte content, and was associated with a preferential loss of granulocytes. Freeze-thawing the red cell suspension removed fewer leucocytes (96.3%) than did filtration (98.74% to > 99.6%) or filtration followed by washing (99.22%), and also led to preferential loss of granulocytes. Flow cytometry provides a reliable tool for the quality control of leuco-depleted red cells, and allows a qualitative assessment of the residual leucocytes. This information is of value in choosing procedures aimed at decreasing the risk of alloimmunisation and post-transfusion reactions.

Cell Separation↗
PubMed1993

MAC1, a nuclear regulatory protein related to Cu-dependent transcription factors is involved in Cu/Fe utilization and stress resistance in yeast.

The related transcription factors ACE1 of Saccharomyces cerevisiae and AMT1 of Candida glabrata are involved in copper metabolism by activating the transcription of copper metallothionein genes. ACE1 and AMT1 are 'copper-fist' transcription factors which possess a conserved cysteine-rich copper binding domain required for DNA binding. Here we report the identification of a nuclear protein from S. cerevisiae, MAC1, whose N-terminal region is highly similar to the copper and DNA binding domains of ACE1 and AMT1. Loss-of-function mutants of MAC1 have a defect in the plasma membrane Cu(II) and Fe(III) reductase activity, are slow growing, respiratory deficient, and hypersensitive to heat and exposure to cadmium, zinc, lead and H2O2. Conversely, a dominant gain-of-function mutant of MAC1 shows an elevated reductase activity and is hypersensitive to copper. We have identified two target genes of MAC1 whose altered expression in mutants of MAC1 can account for some of the observed mutant phenotypes. First, MAC1 is involved in basal level transcription of FRE1, encoding a plasma membrane component associated with both Cu(II) and Fe(III) reduction. Second, MAC1 is involved in the H2O2-induced transcription of CTT1, encoding the cytosolic catalase. This suggests that MAC1 may encode a novel metal-fist transcription factor required for both basal and regulated transcription of genes involved in Cu/Fe utilization and the stress response.

Amino Acid Sequence↗
PubMed1993

Cryopreservation of red blood cells: effect of freezing on red cell quality and residual lymphocyte immunogenicity.

AIMS: To investigate treatment with glycerol/washing as a potential substitute for freeze-thawing in the production of leucocyte depleted red cell concentrates for patients with a history of non-haemolytic reactions following transfusion. METHODS: The standard procedure of treatment with glycerol/-80 degrees C freezing/thawing/washing was compared with a similar procedure in which freezing was omitted. The quality of the resulting red cell products was assessed in relation to: (1) standard red cell biochemical parameters; (2) leucocyte and lymphocyte subset composition using flow cytometry with fluorescent labelled monoclonal antibodies; and (3) immunogenicity of the residual lymphocytes in mixed lymphocyte culture. RESULTS: Compared with red cells subjected to the standard freeze-thaw technique, red cells undergoing the non-freezing procedure and suspended in additive solutions had significantly better biochemical preservation after 21 days of storage (p < 0.001). Both procedures removed an average 98% of the initial leucocytes at the expense of 18-20% of the red cells. The non-freezing procedure resulted in higher residual concentrations of HLA class II bearing lymphocytes (p < 0.01), but not higher numbers of dendritic cells. Both procedures were equally effective in annulling the residual lymphocytes' ability to act as stimulator cells in one-way mixed lymphocyte culture. CONCLUSIONS: The non-freezing procedure produces a superior product for the provision of red cells to patients with granulocyte antibodies. These products may also offer a lower risk of HLA alloimmunisation to previously unexposed patients.

Blood Preservation↗
PubMed1993

Thermodynamic transitions in networks for letter distinction.

Stochastic learning for a kind of feature detectors is studied. The technique is applied to multilayer neural networks intended for T-C discrimination. After evaluating the generalization error function, the training and generalization curves are found by Monte Carlo simulations. Different phase transitions take place and the overall behaviour agrees with previous discussions concerning designs of the same type.

Artificial Intelligence↗
PubMed1992

Inhibition of proliferation by c-myb antisense RNA and oligodeoxynucleotides in transformed neuroectodermal cell lines.

Transfection of a neuroblastoma cell line with expression vectors containing two different segments of human c-myb complementary DNA in antisense orientation yielded far fewer transfectant clones than did the transfection with the identical segments in sense orientation. In cell clones expressing c-myb antisense RNA, levels of the c-myb protein were down-regulated and the proliferation rate was slower than that of cells transfected with sense constructs or the untransfected parental cell line. Treatment of neuroblastoma and neuroepithelioma cell lines with a c-myb antisense oligodeoxynucleotide strongly inhibited cell growth. These data indicate a definite involvement of c-myb in the proliferation of neuroectodermal tumor cells extending the role of this protooncogene beyond the hematopoietic system. The availability of cell clones that transcribe c-myb antisense RNA provides a useful tool to study the involvement of other genes in the proliferation and differentiation of neuroblastoma cells.

Animals↗
PubMed1991

Transcription of N-myc and proliferation-related genes is linked in human neuroblastoma.

A definite association between the transcription of N-myc oncogene and proliferation-related genes, histone H3, c-myc and p53, was found in a set of 12 primary untreated neuroblastomas and a metastasis of one of these at relapse. Molecular analysis allowed us to discriminate between actually proliferating and non-proliferating tumors, and suggested a link between N-myc and proliferation. Flow cytometric analysis of DNA distribution was less reliable for assessing tumor proliferative activity. Our data also seem to indicate a down-regulation of c-myc by N-myc in human neuroblastoma.

Blotting, Northern↗