PubMed Health⌕ Search

Biomedical subjects

A Severini

Publications and source records attributed to A Severini.

At least 19 recordsLinked to original sources
PubMed2006

Genomic cartography of varicella-zoster virus: a complete genome-based analysis of strain variability with implications for attenuation and phenotypic differences.

In order to gain a better perspective on the true variability of varicella-zoster virus (VZV) and to catalogue the location and number of differences, 11 new complete genome sequences were compared with those previously in the public domain (18 complete genomes in total). Three of the newly sequenced genomes were derived from a single strain in order to assess variations that can occur during serial passage in cell culture. The analysis revealed that while VZV is relatively stable genetically it does posses a certain degree of variability. The reiteration regions, origins of replication and intergenic homopolymer regions were all found to be variable between strains as well as within a given strain. In addition, the terminal viral sequences were found to vary within and between strains specifically at the 3' end of the genome. Analysis of single nucleotide polymorphisms (SNPs) identified a total of 557 variable sites, 451 of which were found in coding regions and resulted in 187 different in amino acid substitutions. A comparison of the SNPs present in the two gE mutant strains, VZV-MSP and VZV-BC, suggested that the missense mutation in gE was primarily responsible for the accelerated cell spread phenotype. Some of the variations noted with high passage in cell culture are consistent with variations seen in the IE62 gene of the vaccine strains (S628G, R958G and I1260V) that may help in pinpointing variations essential for attenuation. Although VZV has been considered to be one of the most genetically stable human herpesviruses, this initial assessment of genomic VZV cartography provides insight into ORFs with previously unreported variations.

Base Sequence↗
PubMed2003

Long-term results of balloon dilation of benign bile duct strictures.

PURPOSE: To evaluate the results of percutaneous balloon dilation of benign bile duct strictures in a series of patients with a long follow-up period. MATERIAL AND METHODS: 56 patients with benign bile duct strictures underwent balloon catheter dilation. These patients had strictures of various origins: postsurgical, postlocal not surgical treatments, associated with gallstones, due to primary sclerosing cholangitis and to Mirizzi's syndrome. In 41 cases the diagnosis was made on the basis of radiological findings and history and in 15 cases on the basis of transluminal biopsy. RESULTS: In 87.5% of cases the treatment was immediately successful. There were no early recurrences, but 7 (21%) recurrences were seen over 1 year after treatment; of these, 57% underwent another balloon dilation procedure with a positive long-term outcome. CONCLUSION: The long-term success rate obtained in 72% of this series confirms that percutaneous bile duct dilation is a valid alternative to surgery without being burdened by complications; the procedure is also a valid alternative to the approach using endoscopic stents.

Adult↗
PubMed2002

Prevalence of human papillomavirus in Mazandaran Province, Islamic Republic of Iran.

We report the prevalence of human papillomavirus (HPV) types in 100 cervical biopsy specimens in Mazandaran province. HPV DNA was detected in 78.6% of cervical carcinoma cases, 64.3% of dys/ metaplasia and 9% of normal cases. Significant correlation was found between the presence of HPV DNA and development of cervical carcinoma. HPV types 16 and 18 were detected in 60.6% of HPV-positive cervical carcinoma cases, whereas HPV31 and 33 were found in 21.2%, and HPV6 and 11 in 18.2%. Among HPV-positive dys/metaplasia cases, 55.6% were positive for HPV16 and 18, 22.3% for HPV6 and 11, and 11.1% for HPV31 and 33. Only HPV6 and 11 were detected in 4 (100%) normal biopsy specimens.

Biopsy↗
PubMed2000

Diagnostic and interventional radiology in the post-operative period and follow-up of patients after rectal resection with coloanal anastomosis.

Surgical treatment of carcinoma of the distal third of the rectum with anal sphincter preservation is increasingly used in accredited cancer centers. This study aimed to evaluate the diagnostic usefulness of radiological investigations in the management of patients who had undergone resection with coloanal anastomosis for carcinoma of the rectum, in the immediate post-operative period, during closure of the protective colostomy and in the follow-up of symptomatic recanalized patients. A total of 175 patients who had undergone total rectal resection with end-to-side anastomosis for carcinoma of the distal third of the rectal ampulla, most of whom had received postoperative radiotherapy, were evaluated radiologically. In the postoperative period radiological investigation was ordered only for symptomatic patients to detect pathology of the anastomosis and the pouch sutures and was used direct film abdominal radiography and contrast-enhanced radiography of the rectal stump with a water-soluble radio-opaque agent. Before closure of the colostomy, 2 months after rectal excision or approximately 4 months after if postoperative radiotherapy was given, the anastomosis and pouch of all patients, even asymptomatic ones, were studied with water-soluble contrast enema to check for normal canalization. In the follow-up after recanalization radiological examinations were done to complete the study of the large intestine if the endoscopist was not able to examine it up to the cecum. Of the 175 patients examined radiologically during the postoperative period and/or subsequent follow-up, 95 showed no pathological findings. Seventy-nine patients had fistulas of the coloanal anastomosis or the pouch, 23 of which supplied a presacral collection. In the absence of severe sepsis, the only therapeutic measures were systemic antibiotics and washing of the surgical catheters to maintain efficient operation. In 2 patients in whom transanal drainage was performed radiologically the fistula was cured in 1 week. In 36 cases of cicatricial stenosis, 17 at the coloanal anastomosis and 19 at the pouch, radiological examination always detected the lesion, correctly defining its anatomical characterisitics, nature and extension. Of the 19 cases of stenosis treated radiologically, 15 recovered an adequate intestinal calibre for tients operated on, 21 cases of reccurrence were detected. Radiological examination was requested as the first investigation in only one of these cases, for a patient with subocclusion. Radiological investigations in patients who have undergone colonanal anastomosis are of read diagnostic value in the immediate post-operative period, during closure of the protective colostomy and in the follow-up of symptomatic recanalized patients.

Anal Canal↗
PubMed2000

TP53 mutations and mdm2 protein overexpression in cholangiocarcinomas.

Tumor suppressor protein p53 is a positive regulator of MDM2 gene expression and the mdm2 protein can bind to p53, preventing the transactivation of p53 responsive genes, thus mimicking TP53 mutation. The authors looked for alterations that could affect, directly and indirectly, p53 function in 13 patients with extrahepatic cholangiocarcinoma. Molecular analysis by single strand conformation polymorphism and DNA sequencing revealed that TP53 gene mutations occurred in only 2 of 13 cholangiocarcinomas. High levels of mdm2 protein were found, by immunohistochemical staining, in 61% of the cholangiocarcinomas and in almost all specimens (70%) displaying stabilized p53 protein in the absence and in the presence of TP53 mutations. The finding of co-overexpressed mdm2 and p53 proteins in cholangiocarcinomas indicates that they can upregulate the expression of mdm2 protein to a level sufficient for binding and accumulating p53 in a presumably inactive complexed form. The presence of TP53 mutations or upregulation of MDM2 gene expression in 9 of the 13 cholangiocarcinomas strongly supports that the impairment of the p53 pathway is an important and specific step in cholangiocarcinoma pathogenesis. At variance with other authors, no alteration of p16ink4/CDKN2 gene was observed in all 13 cholangiocarcinomas.

Aged↗
PubMed1999

Evaluation of temperature distribution during hyperthermic treatment in biliary tumors: a computational approach.

A computational approach is adopted to predict the temperature distribution in the biliary tissue during hyperthermic treatments in biliary tumors. Two different models are developed: an axisymmetric model and a three-dimensional model. In the first model the Pennes bioheat transfer equation is applied. It is aimed at simulating the thermoregulatory effect of the capillary bed and it can also give a pressure criterion to determine whether the blood perfusion term should be included in the mathematical model. The second model is aimed at simulating the convective effect of the large hepatic vessels: A constant Nusselt number is assumed on the sides of the vessels. The simulations of the three-dimensional model have been carried out with and without capillary perfusion in the tissue, i.e., respectively in the worst case and in the best case that may occur during heating. The results show that it is possible to obtain therapeutic temperature values in the tissue for time intervals considered acceptable by physicians. Moreover, the model is able to give more precise information about the volumes of tumoral tissue heated above therapeutic temperatures with the hyperthermic technique considered.

Bile Duct Neoplasms↗
PubMed1996

Branched structures in the intracellular DNA of herpes simplex virus type 1.

Herpes simplex virus type 1 (HSV-1) replication produces large intracellular DNA molecules that appear to be in a head-to-tail concatemeric arrangement. We have previously suggested (A. Severini, A.R. Morgan, D.R. Tovell, and D.L.J. Tyrrell, Virology 200:428-435, 1994) that these DNA species may have a complex branched structure. We now provide direct evidence for the presence of branches in the high-molecular-weight DNA produced during HSV-1 replication. On neutral agarose two-dimensional gel electrophoresis, a technique that allows separation of branched restriction fragments from linear fragments, intracellular HSV-1 DNA produces arches characteristic of Y junctions (such as replication forks) and X junctions (such as merging replication forks or recombination intermediates). Branched structures were resolved by T7 phage endonuclease I (gene 3 endonuclease), an enzyme that specifically linearizes Y and X structures. Resolution was detected by the disappearance of the arches on two-dimensional gel electrophoresis. Branched structures were also visualized by electron microscopy. Molecules with a single Y junction were observed, as well as large tangles containing two or more consecutive Y junctions. We had previously shown that a restriction enzyme which cuts the HSV-1 genome once does not resolve the large structure of HSV-1 intracellular DNA on pulsed-field gel electrophoresis. We have confirmed that result by using sucrose gradient sedimentation, in which both undigested and digested replicative intermediates sediment to the bottom of the gradient. Taken together, our experiments show that the intracellular HSV-1 DNA is held together in a large complex by frequent branches that create a network of replicating molecules. The fact that most of these branches are Y structures suggests that the network is held together by frequent replication forks and that it resembles the replicative intermediates of bacteriophage T4. Our findings add complexity to the simple model of rolling-circle DNA replication, and they pose interesting questions as to how the network is formed and how it is resolved for packaging into progeny virions.

Animals↗
PubMed1995

Polyurethane-coated, self-expandable biliary stent: an experimental study.

RATIONALE AND OBJECTIVES: We describe a self-expanding metallic biliary Gianturco-Rösch stent coated with polymeric material. The coating was designed to prevent the growth of neoplastic and reactive tissue within the biliary ducts. METHODS: The stents were coated with a solvent-casting technique, which consists of dissolving polyurethane (polyether urethane or polycarbonate urethane) pellets in a solvent (dimethylacetamide), dipping the stent in the solution, and completely evaporating the solvent. In vitro mechanical characterization of the stent was performed to determine the adhesion of the coating to the metallic cage, the best introducer caliber for implantation of the device, and the relationship between the stent's diameter and radial stress. RESULTS: Reports in the literature on the biostability of polycarbonate urethane compared with polyether urethane prompted us to use the former material to coat the stents. The solvent technique gives a smooth internal surface of the stent wall, leaving in relief the coated structure of the stent on the external surface. The functional tests demonstrated that the coating did not compromise the original characteristics of the stent in terms of self-expandability, axial flexibility, and increased radial rigidity of the device. CONCLUSION: Functional tests verified coating stability and device handling, which are the first steps toward in vivo experimentation.

Bile Ducts↗
PubMed1995

Mechanism of inhibition of duck hepatitis B virus polymerase by (-)-beta-L-2',3'-dideoxy-3'-thiacytidine.

We have used the endogenous reverse transcriptase reaction of viral core particles from duck liver to elucidate the mechanism of inhibition of duck hepatitis B virus (DHBV) replication by the nucleoside analog (-)-beta-L-2',3'-dideoxy-3'-thiacytidine (3TC). As is the case in human immunodeficiency virus replication, 3TC-5'-triphosphate (3TC-TP) acts as a chain terminator for the DNA polymerase activities. The results of several different experiments support this conclusion, which explains the potent activity of 3TC against the hepadnaviruses. In isolated DHBV core particles, 3TC-TP inhibited the reverse transcriptase in a manner that resembled competitive inhibition with respect to dCTP. However, the kinetics of inhibition was not linear on a double-reciprocal plot for the highest concentrations of 3TC-TP and the lowest concentration of dCTP. This anomaly would be expected if binding to the nucleotide site was followed by DNA chain termination. Calculations that used only the linear part of the curve yielded a Ki of 0.78 +/- 0.10 microM 3TC-TP. The inhibition of core particles incubated in vitro with 3TC-TP was not reversed by removal of the free inhibitor. 3TC-TP inactivated the reverse transcriptase activity in a concentration-dependent manner. The Km of the chain termination reaction was calculated at 0.71 +/- 0.05 microM. Similar competitive kinetics and irreversible inhibition were also obtained on the endogenous DNA polymerase from viral particles from serum, suggesting that 3TC-TP also acts as a chain terminator of the DNA-directed DNA polymerase of DHBV replication.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Suprapubic cystotomy as treatment for severe hemorrhagic cystitis after bone marrow transplantation.

We analyzed the success of suprapubic cystotomy in patients with severe hemorrhagic cystitis after bone marrow transplantation. Seventy-three out of 963 patients developed severe hemorrhagic cystitis which resulted in urinary tract obstruction after high-dose cytoreductive therapy. Eleven patients (15%) failed medical treatment and required emergency suprapubic cystotomy. Three of these patients died of other complications prior to resolution of HC. Of the remaining 8 patients who underwent surgery, 4 are alive. The mortality rate was significantly higher in patients who required surgery than in those who responded to medical therapy. Patients whose HC required surgery also had a greater transfusion requirement than those who responded to medical therapy. We conclude that surgical treatment of severe HC should be undertaken only after failure of medical therapy.

Adolescent↗
PubMed1994

Study of the structure of replicative intermediates of HSV-1 DNA by pulsed-field gel electrophoresis.

DNA from HSV-1-infected cells was separated by pulsed-field gel electrophoresis into two virus-specific bands: one that migrated as the linear monomer genome (152 kb) and another that remained at the origin of the gel. The latter band contained the replicating HSV-1 DNA, as determined by pulse-labeling with [3H]thymidine. To investigate the structure of this "gel origin" DNA, we constructed a HSV-1 KOS mutant bearing a unique PacI restriction site (HSV-1 PAC1DTK). Partial digestion of gel origin PAC1DTK DNA at late times postinfection (24-48 hr) demonstrated the presence of linear concatemers on pulsed-field gel electrophoresis. Within each concatemer, the long (L) regions of adjacent monomer genomes were found in the two possible orientations. In addition, shorter-than-unit-size fragments that corresponded in size to the left end fragments of the viral genome were detected with the UL region in the two possible orientations. At early times postinfection (8-12 hr), digestion with PacI released only a trace of linear fragments, and most of the gel origin DNA did not migrate on pulsed-field gel electrophoresis. Multiple cuts with EcoRI (a restriction enzyme that cuts the HSV-1 KOS genome 12 times) were necessary to release linear fragments that migrated from the origin of the gel. These results indicate that replicative intermediates of HSV-1 DNA are linked in a large network that needs to be unraveled before packaging takes place. This network may be composed of linear molecules linked together by frequent recombination events or of products of a mode of replication other than simple rolling circle (e.g., theta replication).

Animals↗
PubMed1994

[Self-expanding metal stents in the treatment of neoplastic esophageal stenosis. The technic and preliminary results].

Self-expanding metal stents have been recently used for the treatment of neoplastic esophageal stenoses. In our series, nitinol Strecker stents were implanted in ten patients with malignant esophageal intrinsic or extrinsic strictures, as a definitive palliation. Thirteen stents in all were used: two stents were positioned in three patients to recanalize the esophagus. The prostheses could always be inserted in the treated patients and in all of them swallowing was markedly improved. No major early complications were observed after stent insertion. All the stents but one were patent until the patient's death. Two patients are alive and bearing well-functioning stents. Self-expanding metal stents are to be preferred to plastic endoscopic tubes because their caliber is smaller at the time of insertion and they do not require general anesthesia, as endoscopic tubes sometimes require. Moreover, their complication rate is lower for both early and late complications. Tumor ingrowth through the stent mesh with stent occlusion is the major pitfall of these prostheses, together with the impossibility to use them when esophageal fistulas are present: these limitations will be soon overcome when silicone-coated expandable stents are on the market.

Aged↗
PubMed1994

[Digital fluorography in gastroenterological radiology].

The clinical value of two digital fluoroscopy systems not connected to a PACS was investigated and compared with that of conventional radiology. Some critical variables were considered: image intensifier diameter, image definition, examination time, acquisition speed, patient exposure and finally film consumption. The main problems in the use of the digital techniques consisted in the limited size of the examination fields, which was not big enough to demonstrate the whole colon during double contrast enema, and in the difficult representation of the actual size on the image printed on the laser films. Definition was considered as sufficient for GI examinations. The main advantages consisted in acquisition speed, allowing detailed examinations of cervical esophagus, cardias and fistulous tracts, reduced patient dose and finally the real time visualization of the acquired image on the TV monitor.

Digestive System↗
PubMed1993

The outcome of cholangitis after percutaneous biliary drainage in neoplastic jaundice.

The purpose of this paper is to evaluate factors affecting the outcome of cholangitis after PTBD in jaundiced cancer patients. Twenty nine patients with neoplastic jaundice (male/female ratio 13/16, median age 55 years) with full clinical data, were treated by PTBD and developed cholangitis at a median of 9 days later. Four patients (14%) died of biliary sepsis a median of one month after PTBD while the other 25 survived a median of 6 months, with one week median duration of cholangitis. The probability of the cholangitis resolving was analyzed by time to resolution and it was found that 50% and 100% of the recoveries occurred 5 and 9 months respectively from the onset of the complication. The series was analyzed to determine the role of several variables (disease/patient/treatment related) in the resolution of cholangitis. Only a low stricture site, a large initial drainage catheter (10F) and a temperature increase exceeding 39 degrees C were correlated with a positive outcome. We conclude that PTBD-related cholangitis has, in our experience, a good chance of cure, low mortality rate and satisfactory 6 months median survival.

Acute Disease↗
PubMed1992

[Percutaneous gastrostomy].

Percutaneous gastrostomy was developed over the last years as an alternative method to surgical and endoscopic procedures, either for enteral feeding or for drainage of secretions or fluid collections communicating with the upper gastrointestinal (GI) tract. January 1990 through January 1992, 15 percutaneous gastrostomies and 2 percutaneous jejunostomies were performed at the Gastroenterologic Radiology Division of INT, Milan, Italy. The catheters were always inserted under local anesthesia, generally using special gastrostomy sets. Catheter insertion was possible in all the patients who underwent the procedure: in 12 cases gastrostomy allowed enteral feeding till the patients died and in 1 case the catheter is still working. In 2 cases the procedure was performed for drainage of gastroenteric secretions and the catheter was left in situ as a definitive palliation. In 1 patient the catheter was removed after draining a collection due to an anastomotic fistula. No major complications were observed in 17 procedures. In our experience, the indication according to which percutaneous gastrostomies and jejunostomies were performed for enteral feeding was always affected by the presence of a stenosis, in the upper GI tract. Other indications to the procedure, for enteral feeding, are functional swallowing disorders. Finally, it must be emphasized that when tight stenoses of the upper GI tract are present, percutaneous gastrostomy is the sole alternative to surgery.

Aged↗
PubMed1991

An assay for proteinases and their inhibitors based on DNA/ethidium bromide fluorescence.

Proteinases and their inhibitors have become the subject of intense research interest recently, since they control a multitude of very important biological processes, from the development of lambda phage to hypertension in humans. We have developed a simple and sensitive assay for detecting the activity of proteinases and of their proteinase inhibitors. The assay is based on ethidium bromide fluorescence, according to the following principles: (i) Ethidium bromide increases its fluorescence by 25-fold when it intercalates between base pairs of double-stranded DNA. (ii) Histones prevent this large increase in fluorescence by binding with high affinity to DNA thus blocking ethidium bromide intercalation. (iii) A proteinase that digests histones will make more DNA available for ethidium bromide intercalation, thereby producing an increase of fluorescence. Proteinase activity can easily be determined, in the presence of a DNA/histone complex, from the rate of ethidium fluorescence increase. In contrast, activity of a proteinase inhibitor is quantitated by the inhibition of fluorescence gain in the presence of a known amount of proteinase. This assay is rapid, simple, inexpensive, and, at the same time, accurate and sensitive enough to allow quantitation of nanogram amounts of various broad-specificity proteinases and their inhibitors. We show some possible applications of the assay (i) in testing column fractions during protein purifications, (ii) quantitation of alpha 1-antitrypsin in human serum, and (iii) detection of proteinase activity in cell extracts.

DNA↗
PubMed1991

Diagnostic accuracy of the double-contrast enema for colonic polyps in patients with or without diverticular disease.

The accuracy of the double-contrast enema for the diagnosis of polypoid lesions in the presence or absence of diverticula was evaluated by retrospectively reviewing the medical records of 202 patients subjected to examination and endoscopy. Analysis of the data on 215 polypoid lesions showed that (a) the diagnostic accuracy of the examination is not affected significantly by the presence of diverticula; (b) the sensitivity of the examination is highly dependent on the size of the polyps (smaller or larger than 0.5 cm) but not on the form (sessile or pedunculated); and (c) the positive predictive value is higher in patients without diverticula. The double-contrast enema was confirmed to be a valid method for the diagnosis of polypoid lesions.

Barium Sulfate↗