Cytotoxicity and probable mechanism of action of sulphimidazole

Sulphimidazole (1-methyl-2((4-aminophenyl)-sulphonyl)-amino-5-nitroimidazole) is a new compound in which a p-aminobenzenesulphonamide radical has been attached at position 2 of the 5-nitroimidazole ring. It possesses a useful spectrum of activity in vitro against various anaerobic microorganisms and its action against aerobic and facultative bacteria is synergically enhanced in association with trimethoprim. In the present study, we determined the cytotoxicity in vitro of sulphimidazole and trimethoprim, both alone and in combination, and analysed the viability of Vero cells and the protein content of their cell lysate in the presence of increasing concentrations of these drugs. Also, in order to verify the hypothesis that the action of sulphimidazole against aerobic and facultative bacteria is mediated by the sulphonamide component of the molecule, while that against anaerobic bacteria depends on the action of the nitro group of the 5-nitroimidazole ring, we studied the mechanism of action of the new compound both indirectly, by means of microbiological techniques, and directly, by determining its oxidoreduction potential with respect to that of metronidazole. The results show that sulphimidazole is only slightly toxic in vitro for Vero cells, either alone or in association with trimethoprim, and that the combination of the two functional groups in a single molecule not only maintains its structure-activity relationship intact but also broadens its antibacterial spectrum.

Topology of the stable serpin-protease complexes revealed by an autoantibody that fails to react with the monomeric conformers of antithrombin

Solving the structure of the stable complex between a serine protease inhibitor (serpin) and its target has been a long standing goal. We describe herein the characterization of a monoclonal antibody that selectively recognizes antithrombin in complex with either thrombin, factor Xa, or a synthetic peptide corresponding to residues P14 to P9 of the serpin's reactive center loop (RCL, ultimately cleaved between the P1 and P'1 residues). Accordingly, this antibody reacts with none of the monomeric conformers of antithrombin (native, latent, and RCL-cleaved) and does not recognize heparin-activated antithrombin or antithrombin bound to a non-catalytic mutant of thrombin (S195A, in which the serine of the charge stabilizing system has been swapped for alanine). The neoepitope encompasses the motif DAFHK, located in native antithrombin on strand 4 of beta-sheet A, which becomes strand 5 of beta-sheet A in the RCL-cleaved and latent conformers. The inferences on the structure of the antithrombin-protease stable complex are that either a major remodeling of antithrombin accompanies the final elaboration of the complex or that, within the complex, at the most residues P14 to P6 of the RCL are inserted into beta-sheet A. These conclusions limit drastically the possible locations of the defeated protease within the complex.

Medium effects on the antioxidant activity of dipyridamole

Very strong medium effects have been observed when testing the antioxidant activity of dipyridamole (DP) in different media such as benzene, tert-butanol, methanol solutions and egg yolk lecithin unilamellar and multilamellar vesicles. Actually, dipyridamole behaves as a very poor antioxidant in benzene while its ability to inhibit the lipid peroxidation reaction increases with increasing solvent polarity, being the highest in lipid vesicles. This behavior can not be rationalized on the basis of the classical chain breaking mechanism which operates in the case of phenolic and amine antioxidants and involving the transfer of a hydrogen atom to peroxyl radicals. An explanation is instead given in terms of an electron transfer reaction which leads to the oxidation of DP by the chain carrying peroxyl radical to give the dipyridamole cation radical, DP+*, and the peroxyl anion LOO-, and whose rate constant is expected to increase in strongly polar media. EPR and electrochemical data supporting this interpretation have been collected.

In-vitro studies of two 5-nitroimidazole derivatives

This paper reports the findings obtained using two new compounds belonging to the 5-nitroimidazole family: sulphuridazole (V1) and sulphonidazole (V2). We first assessed their antimicrobial activity on Clostridia spp. and then extended the study to Gram-positive and Gram-negative aerobic microorganisms and to Candida albicans. Their MICs were compared with those of metronidazole. The findings show that the antibacterial and antimycotic activity of sulphonidazole is greater than that of sulphuridazole, while metronidazole is not active against any aerobic organism. It also emerges that the NO2 group is indispensable for all the microorganisms assayed and that sulphuridazole and sulphonidazole are the first two 5-nitroimidazoles active against C. albicans. The redox potentials of the 5-nitroimidozoles studied suggest that their action mechanism is mainly based on redox processes.

Highly sensitive immunoradiometric assay for serum thyroglobulin with minimal interference from autoantibodies

Five monoclonal antibodies (MAbs) directed against antigenic domains on thyroglobulin (Tg) not recognized by most anti-Tg human autoantibodies (aAbs) have been used to develop an improved IRMA for serum Tg with a limit of detection of 0.2 micrograms/L. Samples are incubated for 3 h in tubes coated with four anti-Tg MAbs. After washing, the tubes are incubated with the tracer MAb for 20 h at room temperature. Dilution and reproducibility tests demonstrated assay reliability. Tests performed on samples with (n = 361) or without (n = 283) aAbs showed that the TG IRMA Pasteur is largely independent of the marked interference generally caused by aAbs. These results were confirmed with an extended population of 2759 samples. For a cutoff of 1 micrograms/L, sensitivity and specificity were 0.97 and 1, respectively, in a follow-up of differentiated thyroid carcinoma in patients treated by total thyroidectomy.

Highly sensitive immunoradiometric assay for serum thyroglobulin with minimal interference from autoantibodies

Five monoclonal antibodies (MAbs) directed against antigenic domains on thyroglobulin (Tg) not recognized by most anti-Tg human autoantibodies (aAbs) have been used to develop an improved IRMA for serum Tg with a limit of detection of 0.2 micrograms/L. Samples are incubated for 3 h in tubes coated with four anti-Tg MAbs. After washing, the tubes are incubated with the tracer MAb for 20 h at room temperature. Dilution and reproducibility tests demonstrated assay reliability. Tests performed on samples with (n = 361) or without (n = 283) aAbs showed that the TG IRMA Pasteur is largely independent of the marked interference generally caused by aAbs. These results were confirmed with an extended population of 2759 samples. For a cutoff of 1 micrograms/L, sensitivity and specificity were 0.97 and 1, respectively, in a follow-up of differentiated thyroid carcinoma in patients treated by total thyroidectomy.

[Value of human cardiac troponin I determination in the diagnosis of acute myocardial infarction]

Immunoenzymatic assay (IEMA) of human cardiac Troponin I (TnI c) was used in patients admitted to the coronary care unit with acute myocardial infarction (AMI). TnI c was detected in all patients with AMI. The detection of TnI c was earlier after the onset of pain (4.5 +/- 2.3 hours) than that of CKMB activity (6.3 +/- 3.6 hours), p = 0.003. The kinetics of TnI c are usually monophasic and parallel to that of CKMB activity. The peak value occurs 12.2 +/- 4.6 hours and 15.8 +/- 9.0 hours after the onset of pain in patients treated by thrombolysis. The TnI c disappears from the plasma between 5 and 9 days after the onset of pain, later than CKMB activity (p = 0.0001). In 49 patients admitted for AMI treated by thrombolysis, the comparative sensitivities of TnI c (threshold: 0.1 ng/ml) and of CKMB activity (threshold: 15 IU/l; CK > or = 100 Ul/l) were, at the first sampling on admission, 61% and 22% respectively (p = 0.0002) (average interval from onset of pain to first blood sampling: 3.4 +/- 1.3 hours). TnI c was not detected in the plasma of 145 normal subjects nor in any of the 6 patients with severe muscular trauma or rhabdomyolosis (specificity: 100%). This IEMA is a specific and a sensitive method of diagnosing acute and subacute myocardial infarction. It is ideal for the detection of myocardial necrosis in complex clinical situations when the usual enzymatic markers may be ineffective.

Two-site enzyme immunoassay of CD4 and CD8 molecules on the surface of T lymphocytes from healthy subjects and HIV-1-infected patients

A highly sensitive two-site enzyme immunoassay (Capcellia) was developed to determine the concentration of CD4 and CD8 molecules expressed on the surface of human T lymphocytes. This assay, performed in one step (20 min), involves the specific immunocapture of T lymphocytes and reaction of the CD4 or CD8 molecules with an enzyme-labeled monoclonal antibody (mAb). The results were expressed as molar concentrations of the T-cell markers on the basis of results obtained with calibrated CD4 and CD8 standards. The assay was sensitive enough to detect 0.4 pmol/L CD4 or 0.8 pmol/L CD8, which corresponded to approximately 20 x 10(6) CD4+ or CD8+ T cells per liter of blood. Mean concentrations in healthy adults were 17.2 pmol/L for CD4 and 22.1 pmol/L for CD8. The CD4 concentration was < 8 pmol/L in 50% of HIV-1-infected patients and in 95% of AIDS patients. Given the epitopic specificity of the mAb to CD4 we used, these values correspond to the concentration of CD4 molecules free of envelope glycoprotein (gp)120.

Two-site enzyme immunoassay of CD4 and CD8 molecules on the surface of T lymphocytes from healthy subjects and HIV-1-infected patients

A highly sensitive two-site enzyme immunoassay (Capcellia) was developed to determine the concentration of CD4 and CD8 molecules expressed on the surface of human T lymphocytes. This assay, performed in one step (20 min), involves the specific immunocapture of T lymphocytes and reaction of the CD4 or CD8 molecules with an enzyme-labeled monoclonal antibody (mAb). The results were expressed as molar concentrations of the T-cell markers on the basis of results obtained with calibrated CD4 and CD8 standards. The assay was sensitive enough to detect 0.4 pmol/L CD4 or 0.8 pmol/L CD8, which corresponded to approximately 20 x 10(6) CD4+ or CD8+ T cells per liter of blood. Mean concentrations in healthy adults were 17.2 pmol/L for CD4 and 22.1 pmol/L for CD8. The CD4 concentration was &lt; 8 pmol/L in 50% of HIV-1-infected patients and in 95% of AIDS patients. Given the epitopic specificity of the mAb to CD4 we used, these values correspond to the concentration of CD4 molecules free of envelope glycoprotein (gp)120.

Quantitative analysis of proliferating sinusoidal cells in dimethylnitrosamine-induced cirrhosis. An immunohistochemical study

Proliferating lipocytes (fat-storing cells or perisinusoidal stellate cells of the liver) were detected by in vivo incorporation of bromodeoxyuridine (BrdU) in an experimental model of cirrhosis in the rat by dimethylnitrosamine. Lipocytes were identified by sequential double immunohistochemical staining on frozen sections using anti-desmin antibodies as a marker of cytoplasmic intermediate filaments followed by anti-BrdU antibodies to identify S-phase nuclei in animals treated for 7, 14 or 21 days. The number of desmin-positive (lipocytes) and desmin-negative (Kupffer and endothelial cells) sinusoidal cells incorporating BrdU was recorded. The labelling index of lipocytes was calculated as the percentage of BrdU-labelled desmin-positive cells with respect to total number of lipocytes. In control animals, when the total number of lipocytes was 153.9 +/- 11/mm2 (mean +/- 1 S.E.) the number of desmin-positive S-phase sinusoidal cells never exceeded 6.8 +/- 1.2/mm2 with a maximum labelling index of 4.3 +/- 0.5%. At 7 days of treatment, the values were respectively 236 +/- 26.5/mm2, 53.2 +/- 5.9/mm2 and 22.6 +/- 0.5% (p less than 0.001 vs. controls), while, at 21 days they were 272.5 +/- 21.2/mm2, 23.3 +/- 4.0/mm2 and 8.5 +/- 1.1% respectively (p less than 0.01). These results show that hyperplasia of lipocytes represents an early reaction to dimethylnitrosamine-induced liver injury. The local accumulation of lipocytes appears to occur in areas where fibrous septa develop later on.

Steatosis associated with immotile cilia syndrome: an unrecognized relationship?

The present study deals with a case of hepatic parenchymal steatosis in a child with primary ciliary dyskinesia (immotile cilia syndrome) well documented by functional and ultrastructural evaluation of the ciliary epithelia. Hepatic steatosis was associated with ultrastructural evidence of retention of material either in the cisternae of the endoplasmic reticulum or in proximity of the Golgi apparatus of hepatocytes. It is suggested that the absence of dynein in the axoneme is probably part of a diffuse genetic defect which may extend to cytoplasmic, non axonemal, dynein and lead to a disturbance of various microtubule-dependent cell activities.

Enumeration of S-phase cells in normal rat liver by immunohistochemistry using bromodeoxyuridine-antibromodeoxyuridine system

The visualization of incorporation sites of the thymidine analog bromodeoxyuridine (BrdU) into DNA, detected by immunocytochemistry, has been proposed as an index of the percentage of S-phase cells in a variety of tissues and as an easy, less expensive alternative to autoradiography. This technique has not yet been applied to the study of physiological cell renewal in the normal liver. In the present study, results obtained with this method in the liver of normal young adult rats is reported. BrdU was administered in vivo and subsequent incorporation was detected by the PAP technique using monoclonal anti-BrdU antibodies. The nuclei exhibiting a positive reaction within the liver were few and accounted for about 0.45% of all hepatocytes. Positive cells were located preferentially in zone 1, which contained 82.7% of the labeled cells. Zone 2 contained 15.4%, while only 1.9% of the labeled cells were found in zone 3. Positive-staining Kupffer cell nuclei were rare (about 0.5% of all Kupffer cells) and were distributed randomly in the hepatic lobule. These findings provide quantitative data about hepatocyte renewal in the normal liver in the absence of a growth stimulus. The simplicity and the reproducibility of this technique suggests that further application of this method in situations assessing hepatic regeneration are indicated.

Phenotypic analysis of inflammatory infiltrate in rats with dimethylnitrosamine-induced cirrhosis

The present study is concerned with the immunohistochemical characterization in situ of the mononuclear infiltrate accompanying the formation of septa and the development of cirrhosis in the liver of rats treated with dimethylnitrosamine (DMN), i.p. (10 microliters/kg, 3 days a week for 3 weeks). Monoclonal antibodies against macrophages, pan T cells, T cell subsets and B cells have been applied on cryostat sections of animals given DMN for 7, 14 and 21 days. The maximum increase of macrophages and lymphocytes was observed at days 7 and 14 respectively. At all times T lymphocytes appeared as the major component of the inflammatory infiltrate with a largely predominant population of cytotoxic/suppressor T cells. At day 21, with evidence of nodulation of parenchyma, macrophages levelled off while T cells remained numerous without changes in the inducer-helper T cells/cytotoxic-suppressor T cells ratio which remained always less than 1. B cells were always few. These findings illustrate the early influx of lymphocytes in DMN-induced liver injury and help to define the lymphocyte subsets associated with inflammation and fibrosis in a reproducible animal model.

Immunohistochemical identification of proliferating cells following dimethylnitrosamine-induced liver injury

The present study is concerned with changes in the number and localization of S-phase cells in the liver of rats exposed to dimethylnitrosamine (DMN). S-phase cells were detected by immunohistochemistry after injection of bromodeoxyuridine (BrdU) and exposure of paraffin sections of liver tissue to the antibody anti-BrdU. With respect to controls, the number of S-phase cells increased four to fivefold in DMN-treated animals in the first week of treatment and remained significantly higher thereafter, in association with the formation of septa. At all times, the labelling index was higher in littoral cells than in hepatocytes. No labelling was observed in biliary cells. This behaviour is different from that reported in other situations, for instance in regeneration after partial hepatectomy, which suggests that besides hepatocytes and littoral cells replacement, an involvement of the latter cell line in the inflammatory reaction, synthesis of extracellular matrix components and formation of septa may account for this particular pattern.

Antigen-capture ELISA for viral haemorrhagic septicaemia virus serotype I

An antigen-capture ELISA for viral haemorrhagic septicaemia virus serotype I (VHSV I) was developed. The assay employs two monoclonal antibodies (mAb) directed against distinct epitopes of the viral envelope glycoprotein (Gp). The antigen bound by the capture mAb (A17) was detected by addition of a second mAb (L7) conjugated to horseradish peroxidase, followed by addition of the enzyme substrate. The technique is highly sensitive, enabling detection of the virus at a protein concentration as low as 1 ng/ml of total proteins (1.5 fmol of envelope Gp per ml) in purified preparations. VHSV I was also detected in culture supernatants (5 x 10(5) PFU/ml) and in extracts of kidney and spleen of rainbow trout infected experimentally (5 x 10(5) PFU/ml). The assay was highly specific: infectious haematopoietic necrosis virus, infectious pancreatic necrosis virus, spring viraemia of carp virus, pike fry rhabdovirus, eel rhabdovirus and perch rhabdovirus could not be detected by the antigen-capture ELISA for VHSV I.

Modulation of extracellular matrix components during dimethylnitrosamine-induced cirrhosis

Liver fibrosis was induced in rats after administration of dimethylnitrosamine (DMN) intraperitoneally three times a week for 3 weeks. Incomplete septa appeared after 7 days and evidence of nodulation of the parenchyma was observed after 21 days. Both distribution of extracellular matrix components (collagen type I, type III and type IV, laminin, fibronectin, heparan sulphate proteoglycan) and the distribution of desmin as a marker of lipocytes (Ito cells) and of iso-alpha-smooth muscle actin were studied with immunoperoxidase. Changes in the distribution of extracellular matrix components outlined both the formation of septa and the development of nodules with changes in the sinusoidal pattern evoking aspects of capillarization. The number of desmin-positive cells increased in DMN-treated animals, showing a prominent reaction in the fibrous septa. In the normal liver, lipocytes were positive for laminin and negative for actin, but septal and juxta-septal lipocytes were positive for both antigens, suggesting the presence of transitional cells with mixed immunoreactivity. This was confirmed by ultrastructural studies which showed typical intraseptal myofibroblasts and other elements exhibiting the structural features of both myofibroblasts and lipocytes.

Quantitative study of apoptosis in normal rat gastroduodenal mucosa

The occurrence of apoptosis in the normal gastrointestinal mucosa has been given little consideration until now, although the phenomenon may be of interest in the light of recent hypotheses about its role in physiological cell renewal. In the present study, a quantitative evaluation conducted on normal gastric and duodenal mucosa of young rats has shown that apoptosis is a rare but constant phenomenon: 1.4 +/- 1.1 (mean +/- 1 s.d.) apoptotic bodies were observed within the surface epithelium of single gastric pits and 3 +/- 1 in duodenal villi. In both situations, the apoptosis showed a preferential localization in the juxtaluminal segments of the epithelium. This phenomenon appears distinct from passive exfoliation of mucosal cells and, as an expression of 'programmed cell death', it is likely to contribute to the normal intestinal epithelial cell turnover.

Association between high concentrations of Mr 52,000 cathepsin D and poor prognosis in primary human breast cancer

The Mr 52,000 cathepsin D is the precursor of a lysosomal protease secreted in excess by breast cancer cells. This protease can degrade extracellular matrices and proteoglycans and is induced by estrogens in estrogen receptor-positive breast cancer cell lines. In a 4- to 6-yr retrospective cohort study, the concentration of the total cathepsin D (precursor plus intermediate and mature chains) was assayed in cytosols of primary tumors from 242 pre/perimenopausal and 154 postmenopausal breast cancer patients in a solid-phase immunoassay using two specific monoclonal antibodies. Patients were initially divided into groups with low, intermediate, or high concentrations of cathepsin D corresponding to the quartiles of the overall distribution. Using these groupings, the level of Mr 52,000 cathepsin D was not significantly associated with the recognized prognostic factors of age, lymph node involvement, tumor size, and/or grade of anaplasia. A significant association was found between cathepsin D concentrations and estrogen receptor status only among pre/perimenopausal patients. Receptor-positive tumors (greater than or equal to 10 fmol of estrogen receptor/mg of cytosol protein) had a significantly greater proportion of patients with high Mr 52,000 cathepsin D concentrations. Patients with high Mr 52,000 cathepsin D concentrations (greater than 78 pmol/mg for pre/perimenopausal and greater than 24 for postmenopausal patients) have shorter recurrence-free survival (P = 0.06 for pre/peri- and P = 0.039 for postmenopausal patients) and have a trend toward shorter overall survival (P = 0.30 and P = 0.089 for pre/peri- and postmenopausal groups, respectively). In multivariate analysis, Mr 52,000 cathepsin D status was found to be an independent prognostic factor for recurrence-free survival of about the same import as lymph node status for both menopausal groups. This first retrospective study demonstrates that the level of Mr 52,000 cathepsin D in cytosol of primary breast cancer biopsies is an independent prognostic factor in predicting relapses in both pre/peri- and postmenopausal patients.

A two-site immunoenzymometric assay of 52-kDa pro-cathepsin D, and its use in human breast diseases

After isolating monoclonal antibodies specific for the 52-kDa precursor of cathepsin D (cath-D), which is secreted in excess in both hormone-dependent and hormone-independent breast cancer, we developed a two-step double-determinant immunoenzymometric assay that is specific for this pro-enzyme. The assay combines the use of a monoclonal antibody specific for the precursor and bound to microtiter plates, and a second antibody directed against a smaller processed form of the mature enzyme, coupled to alkaline phosphatase. The specificity of the assay relies on separate and sequential additions of the antigen and the conjugated second antibody. It allows rapid measurement of the analyte in plasma and cytosols of normal and neoplastic mammary tissues, with a detection limit of 5 fmol and a maximal interassay coefficient of variation of 9%. This assay is particularly useful for tissue cytosol samples where the pro-enzyme form co-exists with large quantities of the mature processed forms of the enzyme. Comparative assays of 52-kDa pro-cath-D and total cath-D in cytosols of breast cancers and benign mastopathies indicate that the present assay better discriminates between benign and cancerous mammary tumors.

A two-site immunoenzymometric assay of 52-kDa pro-cathepsin D, and its use in human breast diseases

After isolating monoclonal antibodies specific for the 52-kDa precursor of cathepsin D (cath-D), which is secreted in excess in both hormone-dependent and hormone-independent breast cancer, we developed a two-step double-determinant immunoenzymometric assay that is specific for this pro-enzyme. The assay combines the use of a monoclonal antibody specific for the precursor and bound to microtiter plates, and a second antibody directed against a smaller processed form of the mature enzyme, coupled to alkaline phosphatase. The specificity of the assay relies on separate and sequential additions of the antigen and the conjugated second antibody. It allows rapid measurement of the analyte in plasma and cytosols of normal and neoplastic mammary tissues, with a detection limit of 5 fmol and a maximal interassay coefficient of variation of 9%. This assay is particularly useful for tissue cytosol samples where the pro-enzyme form co-exists with large quantities of the mature processed forms of the enzyme. Comparative assays of 52-kDa pro-cath-D and total cath-D in cytosols of breast cancers and benign mastopathies indicate that the present assay better discriminates between benign and cancerous mammary tumors.