Biomedical subjects

P Monti

Publications and source records attributed to P Monti.

At least 37 records · Page 2Linked to original sources

PubMed1999

Glucocorticoids increase the endocytic activity of human dendritic cells.

We have investigated the effect of glucocorticoids (GC) on antigen uptake molecule expression and on endocytic activity of human dendritic cells (DC). Human monocyte-derived DC were differentiated in vitro for 7 days with granulocyte macrophage colony stimulating factor and IL-4 in the presence or absence of dexamethasone 10(-8) M (Dex). Dex-treated DC showed an enhancement of mannose receptor (MR)-mediated endocytosis (measured as uptake of FITC-dextran) and of fluid-phase endocytosis [measured as uptake of Lucifer yellow (LY)] The effect was dose dependent and correlated with the length of exposure to Dex. The expression of receptors involved in antigen capture was investigated by FACS analysis. Dex up-regulates MR, CD16 and CD32 expression on DC. After maturation with tumor necrosis factor-alpha or CD40 ligand in Dex-treated DC, despite a reduction induced by maturation the endocytic activity of FITC-dextran and LY, the expression of MR, CD16 and CD32 remained higher than in control DC. In view of the fact that antigen capture was increased in cells cultured with Dex, we evaluated the ability to present soluble antigen that needs to be taken up and processed. Cells differentiated in the presence of Dex showed much lower efficiency in presenting tetanus toxin to specific autologous T cell lines. In conclusion our data suggest a new mechanism by which GC may influence immune responses. In fact with the increase in endocytic activity, Dex favors the scavenging of antigen from the external milieu, decreasing antigen concentration and availability, and simultaneously inhibiting the capacity to stimulate T cells.

Antigen Presentation↗

PubMed1998

Applications of Raman spectroscopy to ophthalmology: spectroscopic characterization of disposable soft contact lenses.

Disposable soft contact lenses based on HEMA-MAA hydrogels are examined using Raman and ATR/FTIR vibrational spectroscopies and thermal analysis. The main factors dealing with physical, chemical, and biological biocompatibility are evaluated in relation to those of long-wear soft contact lenses with the aim of individuating the most biocompatible lens. The Raman spectra of HEMA-MAA lenses show that some biocompatibility factors are affected by environmental conditions and, in particular, by changes in pH and ionic strength values.

Biocompatible Materials↗

PubMed1998

Molecular epidemiology in a cluster of cases of postoperative Pseudomonas aeruginosa endophthalmitis.

Between September and October 1994 we observed three cases of Pseudomonas aeruginosa endophthalmitis in a single ophthalmology center. Endophthalmitis progressed rapidly following surgical intervention, and the three patients completely lost vision in the affected eye. Microbiological surveillance culture specimens were obtained from environmental sites, the operating team, intraocular lenses, irrigation fluids, and surgical equipment. P. aeruginosa was isolated from the internal tubing system of automated cataract surgical equipment. The strains of P. aeruginosa cultured from vitreous and anterior chamber specimens of case patients and from the surgical equipment were analyzed with pulsed-field gel electrophoresis. Genomic DNA typing of these isolates showed an identical banding pattern on ethidium bromide-stained gels. We believe that this is the first reported outbreak of P. aeruginosa endophthalmitis traced to automated surgical equipment. Genomic DNA typing emerged as a practical and reliable option for the epidemiological investigation of the outbreak.

Aged↗

PubMed1998

Ultraviolet-light induced p53 mutational spectrum in yeast is indistinguishable from p53 mutations in human skin cancer.

Ultraviolet (UV) light has been associated with the development of human non-melanoma skin cancers (NMSC). Such cancers often exhibit mutations in the p53 tumour suppressor gene. In order to determine the UV-induced p53 mutation spectrum, a yeast expression vector that harbours a human wild-type p53 cDNA was UV-irradiated in vitro and transfected into a yeast strain that contained the ADE2 gene regulated by a p53-responsive promoter. Forty-five mutant clones contained 51 mutations. Seven mutations were tandem base pair substitutions, four of which being CC-->TT, hallmark mutations of UV mutagenesis. Eighty percent (41/51) of the mutations were single or non-tandem base pair substitutions, the majority of which (27/41) were C-->T transitions. Ninety-five percent of such mutations occurred at dipyrimidine sites. Through a rigorous statistical test, the UV-induced p53 mutation spectrum appears to differ significantly (P < 0.008) from the one induced by the antineoplastic drug chloroethyl-cyclohexyl-nitrosourea, and to be indistinguishable from the one observed in NMSC (P = 0.4). These results demonstrate that the assay allows the determination of carcinogen-specific p53 mutation fingerprints and represents a new tool for molecular epidemiology.

DNA, Complementary↗

PubMed1997

Heterogeneous p53 mutations in a Burkitt lymphoma from an AIDS patient with monoclonal c-myc and VDJ rearrangements.

This study investigates the timing of p53 mutations detected in the malignant cells of a Burkitt's lymphoma cell line (BRG-P) with respect to other maturation or transforming events. The BRG-P cell line, derived from an AIDS patient, was of special value since it displayed subclones that had undergone an isotype switch from IgM to IgA1 (BRG-M and BRG-A cells). BRG-M and BRG-A cells were characterized by the same monoclonal c-myc and VDJ rearrangements and by the expression of Ig receptors with specificity for a 45 kDa protein of human breast cells. Analysis of p53 mutations in the different BRG subclones showed that 1) BRG-M cells displayed 2 different p53 mutations in trans; since the original BL cells also showed the same mutations, this finding indicated that both occurred in vivo; 2) one of the p53 alleles of BRG-A cells was lost, while the other showed a mutation different from those seen in BRG-M cells; and 3) all 3 mutations observed in BRG-M or BRG-A cells resulted in the functional inactivation of the transcriptional activation function of p53. Together, our data demonstrate that p53 mutations were relatively late events during lymphomagenesis. Moreover, in view of the role of p53 in cell apoptosis, it is conceivable that BRG cells were subjected to a strong selective pressure that favored p53 inactivation. Such inactivation was possibly required to counterbalance other potentially apoptotic events, including the presence of a deregulated c-myc oncogene and signals delivered by the host environment in situ.

B-Lymphocytes↗

PubMed1997

Determining mutational fingerprints at the human p53 locus with a yeast functional assay: a new tool for molecular epidemiology.

In order to isolate experimentally induced p53 mutations, a yeast expression vector harbouring a human wild-type p53 cDNA was treated in vitro with the antineoplastic drug chloroethyl-cyclohexyl-nitroso-urea (CCNU) and transfected into a yeast strain containing the ADE2 gene regulated by a p53-responsive promoter. p53 mutations were identified in 32 out of 39 plasmids rescued from independent ade- transformants. Ninety-two percent of CCNU induced mutations were GC-targeted single base pair substitutions, and GC > AT transitions represented 73% of all single base pair substitutions. In 70% of the cases the mutated G was preceded 5' by a purine. The distribution of the mutations along the p53 cDNA was not random: positions 734 and 785 appeared as CCNU mutational hotspots (n=3, P<0.0003) and CCNU induced only GC > AT transitions at those positions. The features of these CCNU-induced mutations are consistent with the hypothesis that O6-alkylguanine is the major causative lesion. One third of the CCNU-induced mutants were absent from a huge collection of 4496 p53 mutations in human tumours and cell lines, thus demonstrating that CCNU has a mutational spectrum which is uniquely different from that of naturally selected mutations. This strategy allows direct comparison of observed natural mutation spectra with experimentally induced mutation spectra and opens the way to a more rigorous approach in the field of molecular epidemiology.

Antineoplastic Agents, Alkylating↗

PubMed1997

Simple identification of dominant p53 mutants by a yeast functional assay.

Analysis of families with germline p53 mutations shows that the mutant p53 allele behaves as a dominant oncogene at the genetic level, although it behaves as a recessive oncogene at the cellular level, since tumours invariably show mutation or loss of both wild-type alleles. At the biochemical level it is possible that some clinically important mutant p53 proteins may be carcinogenic through a dominant mechanism. We show that p53 mutants can be readily classified according to their dominant potential using a simple yeast functional assay. Wild-type p53 is constitutively expressed from a TRP1 vector, p53 mutants are expressed from an otherwise identical LEU2 vector and net transcriptional activity is scored using an ADE2-based reporter. Twenty seven p53 mutants were tested: 19 were recessive, i.e. gave white colonies, and eight showed dominant activity, i.e. gave pink/red colonies. This simple assay should facilitate studies on p53 dominance.

DNA, Complementary↗

PubMed1997

Whole-body gamma irradiation modifies bile composition in the pig.

The effects of 6 Gy whole-body 60Co gamma irradiation on bile composition in pigs were studied to determine possible alterations in the quality of the bile, which may be a determining factor in diarrhea as well as nutrient malabsorption, which classically occurs after irradiation. The bile duct of pigs was catheterized to allow a total and continuous deviation of bile over several weeks, before and after irradiation. After measurement of the volume and sampling, bile was returned to the animal via a duodenal catheter. Bile samples were then analyzed for cholesterol, phospholipid and total bile acid content. Individual bile acids were quantified by HPLC analysis. Bile flow was significantly decreased during the first 24 h and after the fifth day postirradiation. Whereas cholesterol, phospholipid and total bile acid concentrations were not altered, profiles of individual bile acids were modified significantly as early as the first day postirradiation. Moreover, the change of these profiles with time was specific for each bile acid. Such modifications in bile acid profiles resulted in a change in the properties of the bile acid pool in an increased proportion of dihydroxylated bile acids known to interfere with gut functions, and it is reasonable to suggest that radiation-induced changes in bile acid profiles may be involved in radiation-induced gastrointestinal disorders.

Animals↗

PubMed1997

Prepulse inhibition of the startle reflex: preliminary study of the effects of a low dose of alcohol in humans.

The present study was designed to examine the effects of a low dose of alcohol on prepulse inhibition (PPI) of the startle response and self-report measures of affect. Eighteen subjects participated in a counterbalanced repeated-measures design in which they received a beverage with alcohol during one session and a nonalcohol beverage during a different experimental session. The startle response was probed in two separate 10-min blocks immediately after consumption of the alcohol. Although alcohol significantly suppressed the startle response in general, it did not do so to an extent that compromised detection of PPI. The effects of alcohol on PPI were primarily evident in the first block and were dependent on baseline levels of PPI, such that alcohol resulted in a reduction of PPI in subjects who demonstrated low PPI at baseline and an increase in PPI for subjects with high PPI at baseline. Alcohol also significantly increased self-reported stimulation during the first block and increased negative affect during the second block. These findings suggest that baseline PPI may reflect an important individual difference that is predictive of the direction and magnitude of alcohol-induced changes in sensorimotor gating.

Adult↗

PubMed1996

Utilization of the Draw a Person Test in the elderly.

The purpose of this study was to assess quantitative and qualitative changes that occurred in the drawing of the human figure during depression and dementia in the elderly. A modified scale version of the Draw a Person Test (DAP) is presented. The first study (80 subjects) enabled the reduction of the number of items from 73 to 20 according to interrater reliability and diagnostic sensitivity to differentiate patients with dementia from control subjects. The second study (160 subjects: 51 with dementia, 70 with major depression, 39 elderly controls) used this 20-item DAP for cognitive assessment. The second study also featured an additional qualitative assessment (DAP 50) considering five components based upon a projective examination of the drawings. Combination of the 20-item DAP and the DAP 50 provides a complete approach to patients in accordance with the affective dimension. Results showed the ability of the 20-item DAP to discriminate dementia from depression with a better cutoff score of 7 and the usefulness of the DAP 50 in the investigation of impaired components during depression and dementia in the elderly, with the goal of specifying key aspects of psychopathology in dementia.

Aged↗

PubMed1996

p53 is frequently mutated in Barrett's metaplasia of the intestinal type.

Barrett's Esophagus (BE) is a complication of gastroesophageal reflux in which the normal squamous epithelium of the lower esophagus is replaced by metaplastic tissue. The clinical significance of this condition is the associated predisposition to adenocarcinomas (ADCs). Three types of BE have been characterized: the gastric fundic (F) type, the gastric cardial (C) type, and the intestinal (I) type. The latter is the most closely associated with the development of ADCs; the causes of this bias remain unknown. To determine whether p53 and/or K-ras gene alterations (a) are present in preneoplastic lesions and (b) are associated with a specific histotype, we performed PCR-based denaturing gradient gel electrophoresis (DGGE) analysis of exon 1 (codons 12-13) of K-ras gene and of exons 5-8 of the p53 gene in biopsies obtained from 30 patients with BE of the I type (9 patients), combined I type (I + C +/- F; 10 patients) and non-I type (C, F, or C + F; 11 patients). None of the cases under study revealed K-ras mutations, whereas biopsies from 12 patients showed at least one p53 DGGE variant. Four patients showed the exact same variants in leukocytes also (polymorphisms), whereas eight cases revealed specific DGGE variants only in biopsies. The molecular characterization of these variants revealed that four of them showed a single base pair substitution, and four showed multiple mutations. Of 17 somatic mutations, all but 1 were base pair substitutions located mainly in exons 7 and 8. The majority of these mutations were GC targeted (13 of 16; 81%), 54% (7 of 13) of which were transitions occurring at CpG sites. All somatic mutations were found in BE with at least one I component. The association with the histotype was statistically significant (P < 0.03; pure I type versus non-I type; P < 0.04, combined I type versus non-I type; Fisher's exact test). Loss of heterozygosity in the vicinity of the p53 locus was evaluated by PCR using a highly polymorphic variable number of tandem repeats marker on 25 out of 30 cases. Ninety-two % of the cases analyzed were informative, and none of them showed LOH. In conclusion, we showed that p53 mutations are frequently observed in specimens from BE patients of the I-type, whereas no involvement of K-ras (exon 1) mutational activation was observed. In light of the key roles that the p53 protein plays in controlling cell cycle and cell diploidy, this result may suggest why this type of metaplasia is the most closely associated to the development of ADCs.

Adult↗

PubMed1994

Repression of growth-regulated G1 cyclin expression by cyclic AMP in budding yeast.

A yeast cell becomes committed to the cell division cycle only if it grows to a critical size and reaches a critical rate of protein synthesis. The coordination between growth and division takes place at a control step during the G1 phase of the cell cycle called Start. It relies on the G1-specific cyclins encoded by CLN1, 2 and 3, which trigger Start through the activation of the Cdc28 protein kinase. In fact, the Cln cyclins are rate-limiting for Start execution and depend on growth. Here we report that the cyclic AMP signal pathway modulates the dependency of Cln cyclins on growth. In particular, more growth is required to trigger Start because CLN1 and CLN2 are repressed by the cAMP signal, thus explaining the previously observed cAMP-dependent increase of the critical size and critical rate of protein synthesis. Cln3 is not inhibited by the cAMP pathway and counteracts this mechanism by partially mediating the growth-dependent expression of other G1 cyclins.

Cell Division↗

PubMed1992

In vitro interaction between Saccharomyces cerevisiae CDC25 and RAS2 proteins.

In Saccharomyces cerevisiae the CDC25 protein is a positive regulator of RAS/cAMP pathway [1-4], enhancing the GDP-releasing rate of RAS2 protein [5]. In this work we have tried to detect a direct interaction between CDC25 and RAS2 gene products. The results indicate that both the whole RAS2 protein and a truncated version that lacks approximately 25 C-terminal residues interact specifically with the CDC25 protein. On the contrary, a derivative of RAS2 that lacks the 112 C-terminal residues as well as the p21TI-ras is not able to bind the CDC25 protein in our assay conditions. The 310 C-terminal aminoacids of CDC25 bind RAS2 while a C-terminus deletion within this aminoacid stretch abolishes the binding. The possible physiological significance of these findings is discussed.

Blotting, Western↗

PubMed1992

cAMP-mediated increase in the critical cell size required for the G1 to S transition in Saccharomyces cerevisiae.

In Saccharomyces cerevisiae, cyclic AMP is required for cellular growth. In this study we show that cAMP also specifically inhibits the G1-S transition of the S. cerevisiae cell cycle by increasing the critical cell size required at start, the major yeast cell cycle control step. In fact: (a) addition of cAMP delays the time of entering into the S budded phase of small G1 cells, while it is ineffective on large fast-growing cells. (b) If cell growth is strongly depressed, cAMP permanently inhibits cell cycle commitment of cells arrested at the alpha-factor-sensitive step. The cell fraction inhibited by cAMP is inversely correlated with the average cell size of treated populations. (c) The critical protein content (Ps) and the critical cell volume (VB) required for budding in unperturbed exponentially growing yeast populations are largely increased by cAMP. On these bases, we propose a new cAMP role at start.

Cell Cycle↗

PubMed1992

Raman spectroscopy in the study of biocompatibility.

This review deals with the application of Raman spectroscopy to the study of the biocompatibility of orthopaedic and ophthalmological materials and includes an introduction, a brief theory on the fundamental concepts of the technique, a description of the method and of the traditional and non-traditional instrumentation and a brief treatment of the surface properties of the different classes of materials. In the orthopaedic field, Raman studies on the structures of glasses, ceramic materials, carbon fibres and polymers before and after implantation are reviewed, particularly as far as structural modifications at the biomaterial-tissues interface are concerned. In the ophthalmological field, the chemical biocompatibility of hydrophobic and hydrophilic polymers for intraocular and intrastromal implants and for soft contact lenses is considered with respect to the presence of monomeric reactive centres in hydrophobic materials and the water amount in hydrophilic ones. The progress of the multichannel Raman technique for 'in-vivo' measurements is also described.

Biocompatible Materials↗

PubMed1991

Structural properties and biocompatibility of polymers used in ophthalmology.

The chemico-physical and structural properties and biocompatibility of new polymers used for intraocular lens manufacture are studied. In particular, the vibrational infrared and Raman spectra of fluorinated polymethacrylates are presented and discussed in relation to those of polymethylmethacrylate (PMMA), in order to correlate their structure with their properties and biocompatibility. The thermal analysis points out that the polymers are more stable than polymethylmethacrylate and the biocompatibility tests show that they are as biocompatible as polymethylmethacrylate.

Animals↗

PubMed1989

Responses to smoking-related stimuli and early relapse to smoking.

Prior to engaging in treatment for smoking cessation, subjects were tested for their responsiveness to cigarette smoking cues. Subjects performed a role-play with a confederate who lit their preferred brand of cigarette. Heart rate (HR) and galvanic skin conductance were assessed continuously, while urge to smoke and anxiety were rated subjectively after the role-play. Three months after treatment ended, subjects were divided into groups of continuous quitters, verified by expired carbon monoxide measurement, and relapsers. The results showed a significant difference between the groups in the pattern of pretreatment HR response to the lighting of the cigarette; relapsers displayed a sharp HR deceleration in response to the stimulus, while quitters' HR did not decelerate. The theoretical and clinical significance of these results is discussed.

Adult↗

PubMed1989

Cell size modulation by CDC25 and RAS2 genes in Saccharomyces cerevisiae.

A detailed kinetic analysis of the cell cycle of cdc25-1, RAS2Val-19, or cdc25-1/RAS2Val-19 mutants during exponential growth is presented. At the permissive temperature (24 degrees C), cdc25-1 cells show a longer G1/unbudded phase of the cell cycle and have a smaller critical cell size required for budding without changing the growth rate in comparison to an isogenic wild type. The RAS2Val-19 mutation efficiently suppresses the ts growth defect of the cdc25-1 mutant at 36 degrees C and the increase of G1 phase at 24 degrees C. Moreover, it causes a marked increase of the critical cell mass required to enter into a new cell division cycle compared with that of the wild type. Since the critical cell mass is physiologically modulated by nutritional conditions, we have also studied the behavior of these mutants in different media. The increase in cell size caused by the RAS2Val-19 mutation is evident in all tested growth conditions, while the effect of cdc25-1 is apparently more pronounced in rich culture media. CDC25 and RAS2 gene products have been showed to control cell growth by regulating the cyclic AMP metabolic pathway. Experimental evidence reported herein suggests that the modulation of the critical cell size by CDC25 and RAS2 may involve adenylate cyclase.

Adenylyl Cyclases↗