[Production of hyaluronidase by cultured human tumor cells]

The presence of hyaluronidase was detected at pH 3.8 in eight out of twelve human cancer cell line culture media. Eight cell lines derived from primary tumours and four from metastases. In three culture media the enzymatic activity was lower than 0.035 pU/cell/h. In five others (in a hepatoma cell line and in four metastasis-derived cell lines) the activity was higher than 0.057 pU/cell/h. A tumour-derived fibroblast culture was negative. The optimal activity was observed at a pH comprised between 3.6 and 4. Salt inhibition of hyaluronidase was reversible. The enzyme was denaturated by a 10-min heating at 70 degrees C. The enzyme was not strictly specific for hyaluronan hydrolysis but also digested chondroitin sulfates. PH20, a spermatozoid protein that has homologies with the bee venom hyaluronidase, was not expressed by cell lines tested.

The origin of hyaluronectin in human tumors

The origin of tumor stroma hyaluronectin (HN), a glycoprotein that binds to hyaluronan (HA), has long remained unknown. Histological observations of human tumors suggest that tumor HN could originate from stroma fibroblasts, and in some cases from inflammatory cells. The fibroblast origin was confirmed by the discovery of HN-like antigen along with hyaluronan in culture medium of tumor-derived fibroblasts. An HA-binding protein was characterized in the culture medium of peripheral blood mononuclear cells (PBMC) in both normal subjects and tumor-bearing patients and was found to be human HN. Cultivated monocytes did not produce HA. HN was not related to the HA-binding site CD44. Sequencing of brain HN-derived peptides demonstrated that each determined peptide sequence was similar to a sequence of the proteoglycan PG-M/versican, suggesting that HN is the HA-binding moiety of the proteoglycan. One probe was synthesized from human PBMC by polymerase chain reaction with primers derived from HN sequences also found in versican. Northern blots were positive only with HN-producing cells. The main RNAs were in the 6-8 kb range, and there was a limited proportion of smaller RNA, which was compatible with the size expected from the HN molecular mass. Southern blotting of monocytes and tumor cells demonstrated that the gene was limited to a unique band. We conclude that HN, an extracellular component of brain, connective embryonic, inflammatory and tumoral tissues, is a PG-M/versican-derived molecule. Our results suggest that tumor HN, which originates from fibroblasts and monocytes of tumor stroma, is a molecular component of the host-tumor relationship and could play a role in the regulation of HA activity in oncogenesis.

Identification and characterization of Saccharomyces cerevisiae EXO1, a gene encoding an exonuclease that interacts with MSH2

A two-hybrid screen was used to identify Saccharomyces cerevisiae genes encoding proteins that interact with MSH2. One gene was found to encode a homologue of Schizosaccharomyces pombe EXO1, a double-stranded DNA-specific 5'-3' exonuclease. S. cerevisiae EXO1 interacted with both S. cerevisiae and human MSH2 in two-hybrid and coimmunoprecipitation experiments. exo1 mutants showed a mutator phenotype, and epistasis analysis was consistent with EXO1 functioning in the MSH2-dependent mismatch repair pathway. exo1 mutations were lethal in combination with rad27 mutations, and overexpression of EXO1 suppressed both the temperature sensitive and mutator phenotypes of rad27 mutants.

Hyaluronan: fundamental principles and applications in cancer

Hyaluronan (HYA) plays a particular role in cancer cell microenvironment. A component of the desmoplasia. HYA is associated to other macromolecules and contributes to the net structure of the matrix. Cancer cells exhibit binding sites (CD44, RHAMM) for HYA. The cell adhesion to HYA can influence the cell motility and different factors could interplay to facilitate cell detachment from HYA. HYA protects cancer cells against immune cell attack. Serum HYA is often increased in metastatic patients.

Nature and electronic structure of the Ni-X dinuclear center of Desulfovibrio gigas hydrogenase. Implications for the enzymatic mechanism

The recent determination of the X-ray crystal structure of Desulfovibrio gigas hydrogenase has revealed that the active site is a Ni-X dinuclear center [Volbeda, A., Charon, M. H., Piras, C., Hatchikian, E. C., Frey, M., & Fontecilla-Camps, J. C. (1995) Nature 373, 580-587]. This unexpected result calls for a re-examination of the magnetic and redox properties that have been attributed previously to a mononuclear Ni center. We have used a combination of dosimetric and electron paramagnetic resonance (EPR) techniques to investigate the nature and the electronic structure of the Ni-X center in the redox forms of D. gigas hydrogenase giving EPR signals. The metal atom X was first shown to be Fe by accurate metal content analyses. Next, by determining the EPR characteristics of a polycrystal powder, it was shown that the redox form of the enzyme studied in the X-ray crystal experiments was essentially Ni-A. The temperature dependence of the Ni-A, Ni-B, Ni-C, and Ni-L EPR signals was studied over a large temperature range. No deviation from Curie's law could be detected, which places strong constraints upon the magnitude of the possible magnetic interactions between the Ni and Fe centers. When these results and the other available magnetic data are analyzed in the light of the crystal structure, it is concluded that the Fe center is diamagnetic in all the redox states of the enzyme. On the basis of these results, a mechanistic scheme consistent with a large body of experimental data can be proposed for Ni-containing hydrogenases.

Increase of spontaneous intrachromosomal homologous recombination in mammalian cells expressing a mutant p53 protein

Homologous recombination plays an essential role in processes involved in genome stability/instability, such as molecular evolution, gene diversification, meiotic chromosome segregation, DNA repair and chromosomal rearrangements. p53 devoid cells exhibit predisposition to neoplasia, defects in G1 checkpoint and high genetic instability but a normal rate of point mutations. We investigated the effect of a p53 mutation, on spontaneous homologous recombination between intrachromosomal direct repeat sequences, in mouse L cells. In these cells, wild type for the p53 gene, we have overexpressed the mutant p53(175(Arg>His)) protein leading to a p53 mutant phenotype, as verified by the absence of a G1 arrest after gamma-irradiation. We show that the rate of spontaneous recombination is increased from five- to 20-fold in the mutant p53 lines. Moreover, this increase is observed in gene conversion as well as in deletion events. Our results provide new insights into the molecular mechanisms of genetic instability due to a defect of p53.

[Good practices of publication of clinical cases of pharmacovigilance: comments, Groupe de Travail sur les Bonnes Pratiques de Publication de Cliniques en Pharmacovigilance: commentary]

This paper introduces some comments on the complete text of Good Pharmacovigilance Publishing Practices, which forms appendix number 2 of the Good Pharmacovigilance Practices now published by the French Drug Agency, as was Good Clinical Practices. Each good practice is printed in italic and presented in a frame; the following comments are designed to facilitate its application. The technical terms that are used in this text are presented according to the glossary in Good Pharmacovigilance Practices.

Free-floating thrombus and embolic risk in patients with angiographically confirmed proximal deep venous thrombosis. A prospective study

BACKGROUND

A free-floating thrombus (FFT) is often considered to be a risk factor for pulmonary embolism (PE), despite adequate anticoagulation therapy, in patients with proximal deep venous thrombosis.

METHODS

Ninety-five patients underwent prospective assessment according to the presence (FFT group [n = 62]) or absence (occlusive thrombus group [n = 28]) of an FFT. On day 1, color venous duplex scanning, venography (reference method), perfusion lung scanning, and, if results of the lung scan were abnormal, pulmonary angiography were performed. On day 10 (range, days 9-11), the lung scan was repeated, as well as pulmonary angiography if the lung scan demonstrated impairment. A 3-month clinical follow-up visit was scheduled. Five patients were retrospectively excluded from analysis for uncertain diagnosis of FFT. Patients were treated with intravenous unfractionated heparin sodium adjusted for activated partial thromboplastin time (n = 1) or subcutaneous low-molecular-weight heparin (n = 89) (nadroparin calcium, 225 Institut Choay factor Xa inhibitory units per kilogram for 12 hours). Warfarin sodium therapy was initiated on day 3 (range, days 2-4).

RESULTS

Both groups were well-matched according to age, sex, risk factors, and delay from onset of symptoms to treatment. Positive and negative predictive values of color venous duplex scanning for the diagnosis of an FFT were 91% and 55%, respectively. On admission, PE prevalence was 64% in the FFT group (40 of 62 patients) and 50% in the occlusive thrombus group (14 of 28 patients) (P = .19). Two patients were excluded on follow-up analysis (range, days 9-11) for preventive vena cava filtering (due to major bleeding in 1 and cholecystectomy in the other); the recurrent rate of PE was 3.3% in the FFT group (2 of 61 patients) and 3.7% in the occlusive thrombus group (1 of 27 patients). No symptomatic recurrent PE occurred between day 10 (range, days 9-11) and 3 months. Four patients died of evolutive neoplasm after hospital discharge.

CONCLUSIONS

No higher risk for PE was observed in patients with free-floating proximal deep venous thrombosis; anticoagulant therapy should prevent recurrent PE in such patients.

[Spermatocytic seminoma. Apropos of 4 cases]

The records of 4 patients treated for a spermatocytic seminoma between 1974 and 1993 were reviewed. We described pathological and clinical features of this entity of seminoma which differs from those of classic seminoma. Spermatocytic seminoma is an essentially non metastasizing neoplasm unless complicated by the rare development of a sarcomatous component or metastatic spread.

Bilateral secondary renal neoplasm mimicking renal abscesses

An exceptional case is presented of a 32-year-old woman with a bilateral renal mass interpreted as abscesses. Biopsies under ultrasound guidance revealed metastatic cervical carcinoma which is a relatively rare entity.

Predictors of distant recurrence in clinical stage I or II endometrial carcinoma treated by combination surgical and radiation therapy

A retrospective analysis of 201 patients with clinical Stage I or II endometrial carcinoma treated by combined surgery and radiation therapy from January 1976 to December 1992 is reported. The aim of the study was to determine predictors, if any, for distant recurrence. Twenty-eight patients (13.9%) in our series developed a recurrence. The most common sites were peritoneal carcinosis (28.6%), bones (28.6%), and lungs (21.4%). Seventy-eight percent appeared within 3 years, and actuarial survival rates at 12, 36, and 60 months after recurrence were 39.2, 14.2, and 7.1%, respectively. An analysis of predictive factors significant for the development of distant recurrence was performed. Significant factors by univariate analysis were age (P = 0.019), stage (P = 0.02), grade (P = 0.014), depth of myometrial invasion (P = 0.007), lymph node involvement (P < 0.001), and peritoneal cytology (P = 0.006). A multivariate analysis of these variables showed that lymph node involvement was the strongest predictor for distant recurrence.

Productivity-induced sulphur enrichment of hydrocarbon-rich sediments from the Kimmeridge Clay Formation

This work aims to highlight the relationship between primary productivity, sulphate reduction and organic carbon preservation in cyclic marine sediments from the Kimmeridge Clay Formation. A concomitant increase of the total sulphur content with the preserved organic content (TOC), shows the progressive supply of both metabolisable organic matter and resistant organic matter is linked to primary productivity. However, variations in sulphate reduction efficiency, based on elemental abundance and isotopic composition of sulphur, reveal that the proportion of metabolisable vs. resistant organic matter has varied along the cycles. This is interpreted in terms of the variation in organic delivery. Organic sulphur content is found to be proportional to the organic matter content, whereas concentrations of pyritic sulphur are constant at very high (> 10% TOC) values. This result is explained by a limitation of available iron for pyritisation at times of very high organic flux. Under such conditions, HS- in excess could be responsible for the early formation of organo-sulphur compounds and thus for the preservation of highly aliphatic (i.e. lipid-rich) organic matter.

Spin-spin interactions between the Ni site and the [4Fe-4S] centers as a probe of light-induced structural changes in active Desulfovibrio gigas hydrogenase

In typical NiFe hydrogenases like that from Desulfovibrio gigas, the active state of the enzyme which is obtained by incubation under hydrogen gas gives a characteristic Ni-C electron paramagnetic resonance (EPR) signal at g = 2.19, 2.14, and 2.01. The Ni-C species is light-sensitive, being converted upon illumination at temperatures below 100 K in a mixture of different Ni-L species, the most important giving an EPR signal at g = 2.30, 2.12, and 2.05. This photoprocess is considered to correspond to the dissociation of a hydrogen species initially coordinated to the Ni ion in the Ni-C state. When the [4Fe-4S] centers of the enzyme are reduced, the proximal [4Fe-4S]1+ cluster interacts magnetically with the Ni center, which leads to complex split Ni-C or split Ni-L EPR spectra only detectable below 10 K. In order to probe the structural changes induced in the Ni center environment by the photoprocess, these spin-spin interactions were analyzed in D. gigas hydrogenase by simulating the split Ni-L spectra recorded at different microwave frequencies. We shown that, upon illumination, the relative arrangement of the Ni and [4Fe-4S] centers is not modified but that the exchange interaction between them is completely canceled. Moreover, the rotations undergone by the Ni center magnetic axes in the photoconversion were determined. Taken together, our results support a Ni-C structure in which the hydrogen species is not in the first coordination sphere of the Ni ion but is more likely bound to a sulfur atom of a terminal cysteine ligand of the Ni center.

Hyaluronan and hyaluronectin production in injured rat thoracic aorta

The aim of our study was to investigate the production of hyaluronan (HA) by the intima-media during the sclerotic response to aortic injury with a catheter balloon in the rat. In addition we analyzed, for the first time in this model, the production of a glycoprotein (hyaluronectin, HN) which binds specifically to HA. HA and HN were analyzed in control (D0), 14 (D14) and 28 (D28) days after injury using biochemical and immunohistochemical techniques. Intima-media DNA content and wet weight increased significantly on D14 and declined on D28 (but remained significantly increased in comparison to controls). HA content (median in D0 = 448 ng) increased significantly on D14 (2P < 0.04) and on D28 (2P < 0.02). HN content (median in D0 = 920 ng) increased significantly on D14 (2P < 0.05) but decreased on D28 to return to the control level. On D0 the amount of HN was about 3 times higher than that of HA (median ratio HA/HN = 0.34). The ratio remained unchanged on D14 but significantly increased on D28 (2P < 0.02). HPLC and Western blotting showed no difference between HN extracted from normal aorta and HN extracted from injured aorta at D14. Different isoforms of HN were present in both cases, ranging from 400 to 45 kDa. The HA increase on D14 and D28 was not related to a change in hyaluronidase activity of aortic tissue. Immunohistochemical analysis showed at D0 a small amount of HA around arterial smooth muscle cells (ASMC) in media, at D14 more HA was localized around and between ASMC in media and neointima but at D28 it was localized mainly near the vessel lumen. HN formed all the time (D0, D14 and D28) a continuous layer localized near the vessel lumen. In vitro studies showed that production of HA and HN was stimulated when ASMC proliferate and HA at high concentrations (1-100 micrograms/ml) reduced, in a dose dependent manner, ASMC growth. In conclusion our results show that both neointima formation in vivo and ASMC proliferation in vitro correlated with increased HA and HN production. This suggests that HA and HN are probably involved in the formation of neointima. On the other hand, the finding that HA continued to increase in the aorta when neointima decreased and that high concentrations of HA reduce ASMC proliferation in culture suggest that HA might be involved in the regression of neointima.

Apolipoprotein E and low-density lipoprotein binding and internalization in primary cultures of rat astrocytes: isoform-specific alterations

Apolipoprotein (apo) E is likely involved in redistributing cholesterol and phospholipids during compensatory synaptogenesis in the injured CNS. Three common isoforms of apoE exist in human (E2, E3, and E4). The apoE4 allele frequency is markedly increased in both late-onset sporadic and familial Alzheimer's disease (AD). ApoE concentration in the brain of AD subjects follows a gradient: ApoE levels decrease as a function of E2 > E3 >> E4. It has been proposed that the poor reinnervation capacity reported in AD may be caused by impairment of the apoE/low-density lipoprotein (LDL) receptor activity. To understand further the role of this particular axis in lipid homeostasis in the CNS, we have characterized binding, internalization, and degradation of human 125I-LDL to primary cultures of rat astrocytes. Specific binding was saturable, with a KD of 1.8 nM and a Bmax of 0.14 pmol/mg of proteins. Excess unlabeled human LDL or very LDL (VLDL) displaced 70% of total binding. Studies at 37 degrees C confirmed that astrocytes bind, internalize, and degrade 125I-LDL by a specific, saturable mechanism. Reconstituted apoE (E2, E3, and E4)-liposomes were labeled with 125I and incubated with primary cultures of rat astrocytes and hippocampal neurons to examine specific binding. Human LDL and VLDL displaced binding and internalization of all apoE isoforms similarly in both astrocytes and neurons. 125I-ApoE2 binding was significantly lower than that of the other 125I-apoE isoforms in both cell types. 125I-ApoE4 binding was similar to that of 125I-apoE3 in both astrocytes and neurons. On the other hand, 125I-apoE3 binding was significantly higher in neurons than in astrocytes. These isoform-specific alterations in apoE-lipoprotein pathway could explain some of the differences reported in the pathophysiology of AD subjects carrying different apoE alleles.

Evidence of involvement of CD44 in endothelial cell proliferation, migration and angiogenesis in vitro

Angiogenesis is essential for tumor growth and metastasis. In the process of angiogenesis, the interaction between adhesive proteins of endothelial cells and extracellular matrix components plays an important role by mediating cell attachment, which is indispensable for their motility, and by transmitting the regulatory signals for cell locomotion and proliferation. In this study, we examined the hypothesis that CD44 expressed on the endothelial cell surface is involved in the angiogenesis process. The experiments using calf pulmonary artery endothelial cells (CPAE) and a human microvascular endothelial cell line (HMEC-1) show that a monoclonal antibody against CD44 (clone J 173) inhibits endothelial cell proliferation by about 30% and migration by 25-50%, and abolishes the stimulating effect of hyaluronan polysaccharides on endothelial cell migration and proliferation. This antibody also suppresses the capillary formation of CPAE in an in vitro model of angiogenesis using fibrin matrix. These results provide evidence of the involvement of endothelial-cell-associated CD44 in angiogenesis.

[Methodology of a scientific study: from the formulation of the problem to the interpretation of the results--applications to radiology]

A scientific article should convey valid information to the reader. To reach this goal, the article must meet several criteria. First, the problem must be clearly stated. For example with medical imaging, the two types of studies are: -a descriptive study depicting a particular situation; -a comparative analytical study, either evaluating a diagnostic method or searching for prognostic factors. The process of defining the sample population can be distinguished: -Experimental studies can compare two groups of people who, after drawing lots, received differential treatment. -Alternatively, observational studies can investigate either representative samples, exposed versus nonexposed cases, or control cases. Characteristics of the variables are very important. Statistical methods facilitate the analysis of three types of variables: qualitative, quantitative and survival variables. Statistical analysis is used to extrapolate the results of the sample population of the study to the target population. Then, presentation, interpretation and extrapolation of the results must be done using three methods: First, the descriptive study should accurately depict the disease. It must be representative of the pathology relative to the clinical manifestations and avoid any bias. Then, the comparative analytical study for revealing the prognostic factors. These types of studies can be divided into three steps: -by performing the suitable statistical tests, a significant correlation between the prognostic factors and the outcome of the disease can or cannot be demonstrated; -any bias must be eliminated; -this correlation can be quantified by measuring it as a risk; Finally, the evaluation of the diagnostic methods are mostly used in medical imaging to determine which factors need to be measured. Five criteria can be followed for these types of studies: -to obtain good technical quality; -to interpret the results consistently; -to give valid information (requiring proper classification of the clinical signs of the patients according to the definition of disease); -to be helpful in determining the treatment; -to be efficient for the patient and the population. The results of a study on the diagnostic value of a medical test must be expressed as an index of sensitivity, or the rate of true positives versus negatives. This facilitates the calculation of the positive predictive value, i.e. the probability for a patient to become ill if the medical test is positive, versus the negative predictive value, i.e. the probability for a patient to remain healthy if the test is negative. The rigorous methodology of scientific work requires: -clear formulation of the problem; -good definition of the situation and the variables to be measured; -the proper method to collect the data; -the description of the study protocol.

Complete coordination of the four Fe-S centers of the beta subunit from Escherichia coli nitrate reductase. Physiological, biochemical, and EPR characterization of site-directed mutants lacking the highest or lowest potential [4Fe-4S] clusters

The beta subunit of the nitrate reductase A from Escherichia coli contains four groups of cysteine residues (I-IV) which are thought to bind the four iron-sulfur centers (1-4) of the enzyme. The fourth Cys residue of each group was replaced by Ala by site-directed mutagenesis, which led to the C26A, C196A, C227A, and C263A mutants. Physiological and biochemical effects of the mutations were investigated on both the membrane-bound and the soluble forms of the enzyme. In addition, detailed redox titrations of the mutants were monitored by EPR spectroscopy. The C196A and C227A mutations resulted in the full loss of the four Fe-S clusters and of the Mo-cofactor, leading to inactive enzymes. In contrast, the C26A and C263A mutants retained significant nitrate reductase activities. The EPR analysis showed that the highest redox potential [4Fe-4S] cluster (center 1) was selectively removed by the C263A mutation and that the C26A replacement likely eliminated the lowest potential [4Fe-4S] cluster (center 4). In both mutants, the three remaining Fe-S clusters kept the same spectral and redox properties as in the wild type enzyme. These results enabled the determination of the Cys ligands of center 1 to be completed and led to a proposed model for the coordination of the four Fe-S centers by the four Cys groups of the beta subunit. In this model, the four clusters are organized in two pairs, (center 1, center 4) and (center 2, center 3), which is in good agreement with the magnitude of intercenter magnetic interactions observed by EPR and with the stability of the different mutants. The possible implications on the intramolecular electron transfer pathway are discussed.