Biomedical subjects

D Gardiol

Publications and source records attributed to D Gardiol.

At least 19 recordsLinked to original sources

PubMed2000

Differential regulation of human papillomavirus E6 by protein kinase A: conditional degradation of human discs large protein by oncogenic E6.

The protein Kinase A (PKA) pathway was found to selectively regulate the function of oncogenic but not non-oncogenic E6 proteins. High risk E6 proteins are phosphorylated at their Dlg/PDZ binding motif at the C-terminus by a PKA like activity. This PKA and PDZ binding module is found only for human PV, is strictly conserved in all the transforming HPVs and is absent in all the low risk HPV types. We present evidence of a conditional regulation of E6 induced degradation of Dlg. HPV18E6 positive but not HPV negative keratinocytes exhibit increased Dlg steady state levels under conditions of high PKA activity, with a concomitant increase in the presence of Dlg at tight junctions. In vitro binding experiments show that E6 phosphorylation by PKA reduces its binding to Dlg and molecular modelling can explain this observation in a structural context. E6 dependent degradation of Dlg in cells with high PKA levels is inhibited and this is dependent on phosphorylation of the PDZ binding site in E6. In contrast, the degradation of p53 induced by E6 is not affected by PKA. We propose a differential regulation of E6 for the ubiquitin mediated degradation of specific E6 target proteins.

3T3 Cells↗

PubMed2000

HPV E6 targeted degradation of the discs large protein: evidence for the involvement of a novel ubiquitin ligase.

The Discs Large (DLG) tumour suppressor protein is targeted for ubiquitin mediated degradation by the high risk human papillomavirus (HPV) E6 proteins. In this study we have used a mutational analysis of E6 in order to investigate the mechanism by which this occurs. We first show that the differences in the affinities of HPV-16 and of HPV-18 E6 proteins for binding DLG is reflected in their respective abilities to target DLG for degradation. A mutational analysis of HPV-18 E6 has enabled us to define regions within the carboxy terminal half of the protein which are essential for the ability of E6 to direct the degradation of DLG. Mutants within the amino terminal portion of E6 which have lost the ability to bind the E6-AP ubiquitin ligase, as measured by their ability to degrade p53, nonetheless retain the ability to degrade DLG. Significant levels of DLG degradation are also obtained using wheat germ extracts which lack E6-AP. Finally, we show that the transfer of the DLG binding domain onto the low risk HPV-6 E6 confers DLG binding activity to that protein and, most significantly, allows HPV-6 E6 to target DLG for degradation. These results indicate that E6 mediated degradation of DLG does not involve the E6-AP ubiquitin ligase and, in addition, shows that the high and low risk HPV E6 proteins most likely share a common cellular intermediary in the ubiquitin pathway.

Adaptor Proteins, Signal Transducing↗

PubMed1999

Oncogenic human papillomavirus E6 proteins target the discs large tumour suppressor for proteasome-mediated degradation.

Previous studies have shown that the oncogenic HPV E6 proteins form a complex with the human homologue of the Drosophila tumour suppressor protein, discs large (Dlg). This is mediated by the carboxy terminus of the E6 proteins and involves recognition of at least one PDZ domain of Dlg. This region of E6 is not conserved amongst E6 proteins from the low risk papillomavirus types and, hence, binding of HPV E6 proteins to Dlg correlates with the oncogenic potential of these viruses. We have performed studies to investigate the consequences of the interaction between E6 and Dlg. Mutational analysis of both the HPV18 E6 and Dlg proteins has further defined the regions of E6 and Dlg necessary for complex formation. Strikingly, co-expression of wild type HPV18 E6 with Dlg in vitro or in vivo results in a dramatic decrease in the amount of Dlg protein, whereas mutants of E6 which fail to complex with Dlg have minimal effect on Dlg protein levels. The oncogenic HPV16 E6 also decreased the Dlg levels, but this was not observed with the low risk HPV11 E6 protein. Moreover, a region within the first 544 amino acids of Dlg containing the three PDZ domains confers susceptibility to E6 mediated degradation. Finally, treatment of cells with a proteasome inhibitor overrides the capacity of E6 to degrade Dlg. These results demonstrate that Dlg is targeted by high risk HPV E6 proteins for proteasome mediated degradation.

Amino Acid Sequence↗

PubMed1998

Role of a p53 polymorphism in the development of human papillomavirus-associated cancer.

The E6 oncoprotein derived from tumour-associated human papillomaviruses (HPVs) binds to and induces the degradation of the cellular tumour-suppressor protein p53. A common polymorphism that occurs in the p53 amino-acid sequence results in the presence of either a proline or an arginine at position 72. The effect of this polymorphism on the susceptibility of p53 to E6-mediated degradation has been investigated and the arginine form of p53 was found to be significantly more susceptible than the proline form. Moreover, allelic analysis of patients with HPV-associated tumours revealed a striking overrepresentation of homozygous arginine-72 p53 compared with the normal population, which indicated that individuals homozygous for arginine 72 are about seven times more susceptible to HPV-associated tumorigenesis than heterozygotes. The arginine-encoding allele therefore represents a significant risk factor in the development of HPV-associated cancers.

Alleles↗

PubMed1998

Comparison of human papillomavirus type 18 (HPV-18) E6-mediated degradation of p53 in vitro and in vivo reveals significant differences based on p53 structure and cell type but little difference with respect to mutants of HPV-18 E6.

An important characteristic of the E6 proteins derived from oncogenic associated human papillomaviruses (HPVs) is their ability to target the cellular tumour suppressor protein, p53, for ubiquitin mediated degradation. Several studies have attempted to address the important characteristics of both E6 and p53 for this activity in vitro, but the equivalent determinants have not been extensively assessed in vivo. Indeed, recent studies indicate differences between the in vitro and the in vivo degradation assays. We have performed an extensive analysis of the ability of a range of HPV-18 E6 mutants to direct p53 degradation in vivo. In addition, we have also compared the ability of HPV-18 E6 to direct the degradation of different oligomeric forms of p53 both in human and in murine cells. The results of these studies show that mutants of E6 exhibit very similar phenotypes both in vitro and in vivo. In contrast, mutants of p53 show markedly different susceptibilities in vitro and in vivo to E6-induced degradation, and this is further affected by the nature of the cell type in which the assays are performed. Finally, using a cell line temperature sensitive for the E1 ubiquitin-activating enzyme we have been able to show directly that this enzyme is involved in the process of E6-mediated degradation of p53 in vivo.

Animals↗

PubMed1997

Transbronchial lung biopsy: an analysis of 530 cases with reference to the number of samples.

To evaluate the diagnostic yield (DY) of transbronchial lung biopsies (TBBs), as the relationship between the DY and the number of tissue specimens taken per TBB, we reviewed the histological and clinical data of 530 consecutive TBBs performed in 516 immunocompetent patients, having either a chronic diffuse lung infiltrate, a localized peripheral lung lesion or hilar adenopathies. The DY (positive TBBs/performed TBBs) varied significantly according to the radiographic pattern and the underlying disease. For chronic diffuse pulmonary infiltrates (n = 244), the overall DY was 50%, but higher figures were obtained for hypersensitivity pneumonitis (92%), sarcoidosis stage II-III (75%), lymphangitic carcinomatosis (68%) and pneumoconiosis (54%). The DY was lower in diffuse tuberculosis (38%) and interstitial pulmonary fibrosis (27%). For localized peripheral lung lesions (n = 205), the overall DY was only 29%, while for sarcoidosis stage I it was 56% (n = 63). Data analysis shows that there is a direct correlation between the number of samples obtained per TBB and the overall DY (i.e. 38% with one to three tissue fragments versus 69% with six to 10, p < 0.01). The increment itself depends on the radiographic pattern and/or the underlying disease which indicates that the probability of diagnostic confirmation per individual tissue sample is not always the same. The clinical implication of these findings is that whereas for some pulmonary diseases the DY is already good with few samples, more samples are to be taken to warrant a satisfactory overall DY. Accordingly, we recommend that at least five to six specimens per TBB should be taken. This number should allow a quite good overall DY in patients with diffuse lung infiltrate. On theoretical grounds, more specimens (seven to 10) should be taken for an optimal DY of localized peripheral lung lesions and of sarcoidosis at stage I. In these indications the clinician should therefore compare the risk-benefit of TBB with a high number of biopsies to the results of other diagnostic procedures.

Adolescent↗

PubMed1995

The genes encoding the biotin carboxyl carrier protein and biotin carboxylase subunits of Bacillus subtilis acetyl coenzyme A carboxylase, the first enzyme of fatty acid synthesis.

The genes encoding two subunits of acetyl coenzyme A carboxylase, biotin carboxyl carrier protein, and biotin carboxylase have been cloned from Bacillus subtilis. DNA sequencing and RNA blot hybridization studies indicated that the B. subtilis accB homolog which encodes biotin carboxyl carrier protein, is part of an operon that includes accC, the gene encoding the biotin carboxylase subunit of acetyl coenzyme A carboxylase.

Acetyl-CoA Carboxylase↗

PubMed1994

DNA supercoiling and thermal regulation of unsaturated fatty acid synthesis in Bacillus subtilis.

Bacillus subtilis growing at 37 degrees C synthesizes, almost exclusively, saturated fatty acids. However, when a culture growing at 37 degrees C is transferred to 20 degrees C, the synthesis of unsaturated fatty acids is induced. The addition of the DNA gyrase inhibitor novobiocin specifically prevented the induction of unsaturated fatty acid synthesis at 20 degrees C. Furthermore, it was determined that plasmid DNA isolated from cells growing at 20 degrees C was significantly more negatively supercoiled than the equivalent DNA isolated from cells growing at 37 degrees C. The overall results agree with the hypothesis that an increase in DNA supercoiling associated with a temperature downshift could regulate the unsaturated fatty acids synthesis in B. subtilis.

Bacillus subtilis↗

PubMed1993

Application of the mini-mu phage for the isolation of lac transcriptional fusions in Bacillus subtilis genes.

A cassette containing a selectable cat gene and the lacZ gene without its own promoter has been incorporated into the mini-Mu bacteriophage genome. This mini-Mu derivative, referred to as mMu-Bs, can be used in Escherichia coli for the generation of lacZ transcriptional fusions to Bacillus subtilis genes cloned into plasmids. The resultant fusions can be analyzed in B. subtilis either as multicopy plasmids or as a single copy integrated via a Campbell-like recombination into the wild-type locus of the cloned fragment.

Bacillus subtilis↗

PubMed1992

[Reliability of bronchial tumor typing base on fibroscopically obtained biopsies].

This study is based on the bronchial tumors biopsied and later examined between 1971 and 1986 at the Institute of Pathology, Lausanne. In each case the diagnosis based on the initial biopsy material is compared with the final surgical or autopsy diagnosis (Reference: Histological typing of lung tumours, second edition, WHO, 1981, 2). The series studied is constituted by 163 cases: 144 men (88.3%) and 19 women (11.7%). In 136 cases (83.4%), the biopsy diagnoses are identical to the diagnoses based upon surgical or autopsy material; in 27 cases (16.6%) these diagnoses differ. The positive predictive value of bronchial biopsy appears to be excellent (100%) for small cell and epidermoid carcinoma (CA). It is satisfactory for adenocarcinoma (85.7%) but insufficient for large cell CA (42.3%) and the tumors grouped under "others" (50%). The diagnosis of large cell CA, in situ CA, papillary tumor, undifferentiated CA, or carcinomatous lymphangitis should be considered with caution and in some cases it is advisable to repeat the biopsy. The discrepancies between the initial and final diagnoses can, in all cases, be attributed either to the biopsy specimen being too small and therefore nonrepresentative or, less frequently, to crushing and necrosis of the tissues.

Autopsy↗

PubMed1991

[Biliary calculi in a cohort of autopsies (Lausanne 1974-1981)].

In a sample of 5892 consecutive autopsies of adults (3676 men and 2216 women) performed at the pathology department of the university of Lausanne 1469 instances of cholelithiasis and/or cholecystectomy were noted (686 men and 783 women). The total frequency was 24.1% (18.6% for men, 35.3% for women, sex ratio 1:1.9). These figures, constant over the observation period, are actually among the highest ones in Europe. In comparison with other studies they demonstrate that a marked increase in the incidence of cholelithiasis occurred in Switzerland since the beginning of this century.

Adult↗

PubMed1991

An extensive morphological and comparative study of clinically early and obvious squamous cell carcinoma of the esophagus.

Squamous cell carcinoma of the esophagus appears mainly as an isolated tumor, frequently diagnosed in its latest stage. However, current advances in endoscopy, systematically used for high risk subjects, allow the detection of very early lesions such as epithelial dysplasia or in situ carcinoma. Twenty-eight squamous cell carcinomas were extensively studied: Group A contained 15 clinically "early cancers"; Group B 12 clinically obvious carcinomas and group C one clinically obvious bifocal carcinoma. All 15 "early cancers" were multicentric and composed of large fields of invasive, microinvasive or in situ carcinoma around which were found epithelial dysplasias of various degrees. Lymph node metastases at surgery were found in 26% of these cases. Obvious squamous cell carcinomas were contiguous with dysplastic areas in 16.6% and with in situ carcinomas in 33% of these cases. Half (50%) had lymph node metastases at surgery. There was no dysplasia or in situ carcinoma around the two main tumors of group C. A comparison between the different morphological features of the three groups leads us to question whether the solitary tumor of the esophagus really represents the final evolution of an early multifocal carcinoma.

Carcinoma in Situ↗

PubMed1991

Immunohistochemistry in the differential diagnosis of liver carcinomas.

Immunohistochemical techniques were used to study 177 hepatic tumors (hepatocarcinoma, cholangiocarcinoma, hepatocholangiocarcinoma, adenocarcinoma of unknown origin, and metastatic carcinoma). Phenotypes suggestive of hepatocarcinoma included keratins 8 and 18, factor XIII a, alpha-fetoprotein. C-reactive protein, carcinoembryonic antigen (CEA) cross-reacting antigen; those in effect that excluded hepatocarcinoma were keratins 1, 5, 10, 11, 19, true CEA. C-reactive protein, used for the first time, proved to be a fairly sensitive and specific marker. Factor XIII a, which was thought to be synthesized only by histiocytes, was also present in hepatocytes. Immunohistochemistry appears to be an important tool in the diagnosis of hepatic tumors. As a result of this study, 32 cases were reclassified; several were found to be intermediate between hepatocarcinoma and cholangiocarcinoma. Sixteen cases apparently were true hepatocholangiocarcinomas. In 12 cases of hepatocarcinoma, some tumor cells expressed keratins of bile duct type. It was impossible to differentiate immunohistochemically cholangiocarcinoma from metastatic carcinoma, except in two cases with breast tissue markers.

Adenocarcinoma↗

PubMed1991

Gastrointestinal stromal tumours: an immunohistochemical study of 165 cases.

The phenotype of 165 gastrointestinal stromal tumours was studied by immunohistochemistry. In each case the phenotype was compared to the histological diagnosis. The phenotype was muscle in 49 tumours (30%), neural in 18 (11%), histiocytic in 20 (12%) and mixed in five (3%); 68 tumours (41%) were positive for vimentin only, four tumours had no markers and one tumour was positive for keratin only. Histologically, the tumours were classified as smooth muscle, probably smooth muscle, probably nerve sheath tumours or tumours of undetermined differentiation. In 30 histologically unequivocal muscle tumours, the phenotype was muscle in 28. Half of them, all benign, arose in the oesophagus or gastric cardia. Apart from this group, there was no correlation between phenotype, site of tumour and histological differentiation. Actin was a more sensitive muscle marker than desmin. With the exception of oesophageal tumours, the histological appearances alone could not establish a diagnosis of malignancy and were inadequate in evaluating differentiation. Immunohistochemical examination determined differentiation in 54% of the tumours, but this finding should be interpreted with caution in terms of histogenesis. It allowed us, however, to specify the differential diagnosis in 57 tumours in which the histological diagnosis was uncertain.

Biomarkers↗

PubMed1990

Cloning of the citrate permease gene of Lactococcus lactis subsp. lactis biovar diacetylactis and expression in Escherichia coli.

The citrate plasmid (Cit+ plasmid) from Lactococcus lactis subsp. lactis biovar diacetylactis was cloned into the EcoRI site of plasmid pUC18. This recombinant plasmid enabled Escherichia coli K-12 to transport and utilize citrate as a source of energy, indicating expression of the citrate permease from L. lactis biovar diacetylactis. The citrate permease was under the control of the lac promoter of pUC18. Genetic expression of the Cit+ plasmid in maxicells revealed that the plasmid encoded two polypeptides of 47 and 32 kilodaltons, determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis.

Bacterial Proteins↗

PubMed1989

[Myocarditis in an autopsy cohort].

In a retrospective study 159 cases (1.8%) of myocarditis--7 pediatric--were found among 8663 consecutive autopsies. In 5 cases the diagnosis had been suspected clinically. In 68 cases (42%) it was possible to determine the etiology: 61 cases of septic myocarditis were found, including 4 mycotic, and 4 cases of toxoplasmosis. In 91 cases (58%) the myocarditis was idiopathic. Idiopathic myocarditis was firmly established as cause of death in 10 cases. In the other cases there appeared to be a relation between the extent of the myocardial infiltrate and probable involvement of the process as cause of death.

Adolescent↗

PubMed1989

Immunohistochemistry of dysplasias and carcinomas of the esophageal epithelium.

Two types of high grade dysplasia were associated with invasive carcinomas. The first, deeply localized, had a pagetoid appearance and a particular phenotype: the dysplastic cells had keratins of low molecular weight rarely present in the esophagus; keratins of stratified epithelia were absent. This dysplasia was probably the origin of undifferentiated invasive carcinoma with which it was often associated. The second type, transepithelial, extended through the entire thickness of the epithelium. The abnormal cells presented some differentiation and stained positive for keratins of stratified epithelia. This dysplasia was often associated with differentiated squamous cell carcinoma. An intermediate-type dysplasia shared some characteristics with both main types. Several types of dysplasia and several areas of differently differentiated carcinoma were often associated in the same case. The evolutional potential of the different dysplasias is not known.

Carcinoma↗

PubMed1988

[Current role of biopsy in the diagnosis of hepatic disease].

The criteria for the use of liver biopsy as a diagnostic tool were retrospectively analyzed over a ten-year period in 390 consecutive patients. The four principal conditions in which this procedure was employed were alcoholism (33%), hepatitis (18%), abnormal hepatic tests (16%) and tumors (10%). The development of new, "non-invasive", investigative methods such as echography and tomodensitometry has led to an decrease in the number of liver biopsies performed annually, but no change in the relative frequency of the various indications. In this paper, evidence is presented which demonstrates that hepatic biopsy confirmed the clinical diagnosis in 62.4% of the cases reviewed and fundamentally modified the diagnosis in 20.2%. Based upon these findings, it can be concluded that liver biopsy remains an indispensable diagnostic procedure in the field of hepatology, since it can result in modification of the clinician's diagnosis in one out of five cases.

Adolescent↗