Alkaline Phosphatase and Gamma Glutamyltranspeptidase in Human Lymphomas

Alkaline phosphatase (AP) and gamma glutamyltranspeptidase (GGT) were studied in normal lymphoid cells and in 28 cases of human lymphomas (23 of non-Hodgkin's and 5 of Hodgkin's disease). The expression of AP was enhanced in several samples with a high proportion of mature B cells, particularly in centroblastic-centrocytic lymphoma, whereas tissues mainly composed of T cells always showed low levels of this enzyme. GGT levels were high in thymus, as well as in centroblastic-centrocytic lymphoma and other NHL, thus demonstrating no restriction to a particular cell lineage. Some B-cell neoplasms with cellular origin different from that of centroblastic-centrocytic lymphoma, such as chronic lymphocytic leukemia and centrocytic lymphoma, had low levels of both enzymes. The role of investigation with specific antibodies against these two enzymatic activities in the physiology of lymphoma cell membrane is discussed.

External validation of the DASH prediction rule: a retrospective cohort study

Essentials Predicting recurrences may guide therapy after unprovoked venous thromboembolism (VTE). We evaluated the DASH score in 827 patients with unprovoked VTE to verify prediction accuracy. A DASH score ≤ 1 had a cumulative recurrence risk at 1 year of 3.6%, as predicted by the model. The DASH score performed better in younger (< 65 years old) subjects.

SUMMARY

Background The DASH prediction model has been proposed as a guide to identify patients at low risk of recurrence of venous thromboembolism (VTE), but has never been validated in an independent cohort. Aims To validate the calibration and discrimination of the DASH prediction model, and to evaluate the DASH score in a predefined patient subgroup aged > 65 years. Methods Patients with a proximal unprovoked deep vein thrombosis (DVT) or pulmonary embolism (PE) who received a full course of vitamin K antagonist or direct oral anticoagulant (> 3 months) and had D-dimer measured after treatment withdrawal were eligible. The DASH score was computed on the basis of the D-dimer level after therapy withdrawal and personal characteristics at the time of the event. Recurrent VTE events were symptomatic proximal or distal DVT/PE, and were analyzed with a time-dependent analysis. Observed 12-month and 24-month recurrence rates were compared with recurrence rates predicted by the DASH model. Results We analyzed a total of 827 patients, of whom 100 (12.1%) had an objectively documented recurrence. As compared with the original DASH cohort, there was a greater proportion of subjects with a 'low-risk' (≤ 1) DASH score (66.3% versus 51.6%, P < 0.001). The slope of the observed versus expected cumulative incidence at 2 years was 0.71 (95% confidence interval 0.51-1.45). The c-statistic was lower for subjects aged > 65 years (0.54) than for younger subjects (0.72). Conclusions These results confirm the validity of DASH prediction model, particularly in young subjects. The recurrence risk in elderly patients (> 65 years) was, however, > 5% even in those with the lowest DASH scores.

Mycobacterium tuberculosis isolates belonging to katG gyrA group 2 are associated with clustered cases of tuberculosis in Italian patients

Fifty-one consecutive isolates of Mycobacterium tuberculosis, collected during a 2-year period in the north-east of Italy, were subjected to IS6110-RFLP analysis to detect the presence of clusters and assigned to one of the three genotypic groups delineated by single nucleotide polymorphisms in the genes katG and gyrA. All the isolates collected from the local population belonged to group 2 or 3, while group 1 isolates were found only in specimens collected from African immigrants. Clustered cases of tuberculosis, which are likely to be related to recently transmitted infection, were found to be significantly associated with katG gyrA group 2. In the local situation, strains belonging to this group may therefore present a higher risk of transmission.

Three scenarios of clinical claim reimbursement for nosocomial infection: the good, the bad, and the ugly

We studied the extent to which hospitals can expect to receive reimbursement for costs relating to nosocomial infections (NI) under the diagnosis-related groups (DRG) system of clinical claims and calculated the loss of reimbursement due to missed or incorrect registration of infective complications on hospital discharge records (HDR). We calculated clinical claim reimbursement in three scenarios: the good, in which all NI are recorded on HDR; the bad, in which a proportion of NI recorded on HDR observed at the 41 participating hospitals; the ugly, in which none of the NI are recorded on HDR. We analysed in which patients the recording of infective complications changed the DRG clinical claim and the economic consequences on reimbursements. Compared with the ugly scenario, the bad scenario, which is closest to what actually occurs, with only 55.9% of NI (180/322) properly recorded, produced an increased DRG clinical claim in 30 cases, of on average 403 for every NI. Compared with the ugly scenario, the good scenario, produced an increased DRG clinical claim in 45 cases with an average reimbursement of 618. The difference between the bad and the good scenarios shows an average loss of 215 for every case. Our calculated good scenario could cover only 3.8% of direct costs per case attributable to NI. Real, tangible benefits in health, both social and economic, will only accrue from the monitoring and control of NI in hospitals.

New plant-origin food allergens

Plant-origin foods, especially nuts and seeds, are the most important sources of food allergic reactions. An important characteristic is the quantitative and qualitative variability of their content in allergenic molecules, depending on plant growth, ripening, environmental stresses or industrial processing. In this review we will focus on newly identified allergens. Recent research have characterized and extensively studied their biochemistry, structure and immunological properties.

Antimycobacterial activity of N1-[1-[3-aryl-1-(pyridin-2-, 3- or 4-yl)-3-oxo] propyl]-2-pyridinecarboxamidrazones

Infections caused by non-tuberculous mycobacteria and multidrug-resistant Mycobacterium tuberculosis are difficult to treat, and so new compounds potentially active against these bacteria are being sought. A series of 2-pyridinecarboxamidrazone derivatives, recently synthesized, have been evaluated for their inhibitory activity against 17 Mycobacterium avium isolates; the agar dilution method showed different degrees of susceptibility to the new molecules. Four molecules, three of which are chlorine derivatives, inhibited 94% of the strains tested with an MIC of 32 mg/L. These data indicate that these new pyridine-2-carboxamidrazones merit further study as antimycobacterial agents.

Synthesis and antimycobacterial activity of [5-(pyridin-2-yl)-1,3,4-thiadiazol-2-ylthio]acetic acid arylidene-hydrazide derivatives

[5-(Pyridin-2-yl)-1,3,4-thiadiazol-2-ylthio]acetic acid arylidene-hydrazide derivatives were synthesized and tested for their in vitro antimycobacterial activity. Some compounds showed a feable activity against a strain of Mycobacterium tuberculosis and a strain of Mycobacterium avium.

Synthesis and antimycobacterial activity of 5-aryl-1-isonicotinoyl-3-(pyridin-2-yl)-4, 5-dihydro-1H-pyrazole derivatives

5-Aryl-1-isonicotinoyl-3-(pyridin-2-yl)-4,5-dihydro-1H-pyrazole derivatives were synthesized and tested for their in vitro antimycobacterial activity. The compounds showed an interesting activity against a strain of Mycobacterium tuberculosis and a human strain of M. tuberculosis H4.

Synthesis and antimycobacterial activity of some 4H-1,2,4-triazin-5-one derivatives

6-[(Arylmethylenamino)carbonyl]-3-(pyridin-2-yl)-4H-1,2,4-triazin-5-one derivatives were synthesized and tested for their in vitro antimycobacterial activity. Some compounds showed interesting activity against a strain of Mycobacterium tuberculosis.

Infection of macrophage-like THP-1 cells with Mycobacterium avium results in a decrease in their ability to phosphorylate nucleolin

This study of the phosphorylation ability of macrophage-like cells upon infection with Mycobacterium avium was undertaken to establish potential targets of the interference with host response mechanisms. Cytosolic and membrane fractions from noninfected and infected cells were incubated with [gamma-(32)P]ATP, in the presence of Mg(2+) and the absence of Ca(2+), and the patterns of phosphoproteins synthesized were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Lower levels of a 110-kDa phosphoprotein were observed in association with cytosolic fractions from mycobacterium-infected cells compared to noninfected cells or cells treated with lipopolysaccharide or having ingested Escherichia coli or killed M. avium. The 110-kDa phosphoprotein was present in the soluble fraction (230,000 x g supernatant) after the kinase incubation, from where it was partially purified and identified as phosphonucleolin by amino acid sequencing. The decrease in nucleolin phosphorylation observed was not related to changes in the cytosolic or membrane levels of this protein, and was detected also in the cytosolic fraction of (32)P-labeled intact cells.

Antimycobacterial activity of ionic fullerene derivatives

Positively charged fullerene derivatives, moderately soluble in water:DMSO 9:1, have been tested using three strains of Mycobacterium spp. Some compounds inhibit the growth of Mycobacterium tuberculosis, a human clinical isolate, particularly virulent and resistant, at doses as low as 5 microg/mL.

Synthesis and antimycobacterial activity of some N1-[1-[3-aryl-1-(pyridin-2-, 3-, or 4-yl)-3-oxo]propyl]-2- pyridinecarboxamidrazones

N1-[1-[3-aryl-1-(pyridin-2,3-, and 4-yl)-3-oxo[propyl]-2- pyridinecarboxamidrazone derivatives were synthesized and tested for their in vitro antimycobacterial activity. Some compounds showed interesting activity against a strain of Mycobacterium tuberculosis and a strain of Mycobacterium avium.

Myeloperoxidase exerts microbicidal activity against Mycobacterium tuberculosis

We investigated the antimycobacterial role of myeloperoxidase (MPO), one of the most abundant granule proteins in human neutrophils. Our data indicate that purified MPO, in the presence of hydrogen peroxide, exerts a consistent killing activity against Mycobacterium tuberculosis H37Rv and against a clinical isolate. The activity is time and dose dependent and requires the presence of chloride ions in the assay medium.

Synthesis and antimicrobial activity of some 2,5-disubstituted 1,3,4,-thiadiazole derivatives

A series of 5-substituted 2-arylamino-1,3,4-thiadiazole derivatives was prepared. The antimicrobial activity of these compounds against some strains of bacteria and a strain of Candida albicans was determined, together with that of the corresponding thiosemicarbazone derivatives, which are intermediates in the synthetical procedure.

Synthesis and antimycobacterial activity of some indole derivatives of pyridine-2-carboxamidrazone and quinoline-2-carboxamidrazone

A series of pyridine-2-carboxamidrazone and quinoline-2-carboxamidrazone derivatives containing the indole moiety was prepared. Some of the synthesized compounds showed an interesting in vitro antimycobacterial activity against a strain of Mycobacterium tuberculosis.

A new flow cytometric assay for the evaluation of phagocytosis and the oxidative burst in whole blood

Phagocytes play an important role in host defence against microorganisms and different techniques are needed to evaluate their functional activities. Here we describe a rapid, simple and reliable one step procedure to measure the phagocytosis rate and oxidative burst activation of both polymorphonuclear leukocytes (PMN) and monocytes, by means of flow cytometry using only small quantities of whole blood. The two species of bacteria employed as test microorganisms, Staphylococcus aureus and Candida albicans showed a somewhat different behaviour. We found that the present method could be used as an alternative test in the diagnosis of chronic granulomatous disease (CGD). Moreover we were able to analyse, in a one step procedure, defective phagocyte functions in a group of paediatric patients suffering from recurrent microbial infections.

In-vitro antimycobacterial activity of new synthetic amidrazone derivatives

After preliminary in vitro screening of 15 newly synthesized compounds belonging to the chemical class of N1-(aryliden)-4-pyridinecarboxyamidrazones against Mycobacterium tuberculosis reference strain H37 Rv, we determined the minimum inhibitory concentrations (MICs) of the six most promising chemicals against different species of Mycobacterium and different strains of M. tuberculosis. The agar dilution method was employed against M. gordonae, M. bovis, M. kansasi, M. avium, M. fortuitum and on eighteen different strains of M. tuberculosis, isolated from human bronchial aspirates. The results obtained confirmed that the newly synthesized chemicals possessed a very interesting antitubercular activity, their MICs ranging from 4 micrograms/ml to 16 micrograms/ml.

Synthesis and antimycobacterial activity of some 4-pyridinecarboxyamidrazone derivatives

A series of N1-aryliden-4-pyridinecarboxyamidrazone derivatives was prepared. Some of the synthesized compounds showed interesting in vitro antimycobacterial activity against some strains of Mycobacterium and clinical isolates of Mycobacterium tuberculosis.

Evaluation of an immunoenzymatic test (ELISA) for the diagnosis of leptospirosis in Italy

An enzyme-linked immunosorbent assay (ELISA) was assessed to detect in humans IgM and IgG against the main serogroups/serovars of Leptospira present in Italy. Sonicated antigens from strain Wijnberg, serogroups Icterohaemorrhagiae and Riccio 2, serogroup Australis, were used in ELISA and the results were compared to microagglutination test (MAT). IgM were confirmed to be the predominant class of antibodies; the total sensitivity obtained by Wijnberg/ELISA with the sera of patients infected by different serogroups was 81.5% in relation to MAT, better sensitivity was achieved by the use of Riccio 2/ELISA; no reaction occurred with the control sera. Cross-reactivity was noted with some sera of patients with Lyme disease (IgM) and with few sera of patients with autoimmune disease (IgM and IgG). To improve the sensitivity of the ELISA both antigens Wijnberg and Riccio 2 must be employed in the immunoenzymatic assay, since serogroup Australis must be considered as a new emerging serogroup causing human leptospirosis in our country.

Immunodominant antigens recognized by the human immune response to infection by organisms of the species Leptospira interrogans serogroup Australis

Serum samples from patients infected by organisms of Leptospira interrogans serogroup Australis were tested by Western blot to determine the nature of major antigens that are involved in the immune response. Although there was some patient-to-patient variability, immunodominant genus-specific antigens were found to be proteins of apparent molecular ratio 68, 46 and 35-kDa, and lipopolysaccharide (LPS) sub-units in the 35-14-kDa region. Serogroup epitopes specific for Australis were exclusively saccharides of about 32 and 24 kDa: a serovar-specific antigen for serovar lora was of 38-40 kDa and behaved like a protein. Antibodies to the LPS serogroup-specific antigens and to the 38-40 kDa protein were long-lasting and consequently suggest that these immunodominant epitopes are important in resistance to re-infection.

Evidence for (lipo) oligosaccharides in Borrelia burgdorferi and their serological specificity

SDS-PAGE and Western immunoblot profiles have been determined for different strains of Borrelia burgdorferi. Major proteins of 60 kDa, 41 kDa corresponding to flagellin, 34-36 kDa and 30-31 kDa corresponding to OspB and OspA respectively, and 18-20 kDa corresponding to 'pC' fractions were detected. A "rough" lipopolysaccharide which we called lipooligosaccharide (LOS) of 8-11 kDa appeared to be present, being detected by specific silver staining, as in crude Borrelia lysates as in proteinase K digested Borrelia strains, quite similar in shape among the different strains examined. The LOS reacted in Western blotting with immune anti-B. burgdorferi rabbit serum and also with sera collected from humans affected by Lyme borreliosis. The LOS did not react with sera positive for syphilis or leptospirosis, and their immunological specificity is discussed.

Simultaneous flow cytometric method to measure phagocytosis and oxidative products by neutrophils

We developed a rapid and sensitive two-color flow cytometric method which allows the simultaneous quantification of both the phagocytosis rate and the oxidative burst activation of polymorphonuclear leukocytes (PMNLs). The oxidation of hydroethidine (HE) to ethidium bromide (EB) was performed by the oxidative neutrophil products within the cells during the respiratory burst, which was stimulated by phagocytized fluorescein-labeled Staphylococcus aureus. By means of flow cytometry we measured red EB fluorescence emission together with green fluorescence, which was emitted by the ingested fluoresceinated bacteria. The fluorescence intensity was proportional to the number of bacteria ingested. Adherent bacteria were distinguished from the ingested ones. This two-color cellular staining permits measurement of two different functions of neutrophils in one step. This method could be of interest for the determination of the interactions between neutrophils and bacteria and for the investigations on infectious diseases in chronic granulomatous disease patients.

Preliminary evaluation of in-vitro antimycobacterial properties of N1-(aryliden)-2-pyridinecarboxyamidrazones

After preliminary in vitro screening of 17 newly synthesized compounds belonging to the chemical class of N1-(aryliden)-2-pyridinecarboxyamidrazones, active against Mycobacterium tuberculosis H37Rv, the minimum inhibitory concentrations (MICs) of the ten most promising agents against three clinical isolates were determined by agar dilution. Compounds 12 and 14 were the most active, each inhibiting strain H37Rv at concentrations of 8 microg/ml and having a MIC of 16 microg/ml against the human isolates. The results obtained in this preliminary study confirmed the interesting antitubercular properties of these newly synthesized compounds and allowed us to carry out our investigations over a large number of isolated clinical strains.

First human isolate of Leptospira interrogans as serovar bratislava in Italy

A strain of Leptospira interrogans was isolated from a patient suffering from leptospirosis and was typed by the Cross Agglutination Absorption test using monoclonal antibodies prepared against different serovars of the Australis serogroup. This newly isolated strain belonged to serovar bratislava. It is the first reported isolation from man, in Italy, of Leptospira bratislava, thus supporting the emerging role of this serovar in human leptospirosis.

Serosurvey of Leptospira agglutinins among railway employees in the National Railway Compartments of Bologna and Venice

An epidemiological investigation was performed to evaluate the prevalence of anti-leptospiral agglutinins within a selected population: the railway workers of the Italian Railway Compartments of Bologna and Venice. Leptospira infection prevalence was found to be 10.38%, which represents the highest frequency ever reported in Italy. There was a significantly higher prevalence of agglutinins among the staff of the Railway Compartment of Venice. A clear prevalence of the bratislava serovar was registered, followed by the australis serovar and the icterohaemorrhagiae serovar. The influence of different kinds of railway work and that of supposed risk factors, such as hobbies and housing conditions, together with the influence of the ABO blood groups on the distribution of Leptospira agglutinins, are discussed.

Restriction endonuclease analysis of four Borrelia burgdorferi strains

A restriction endonuclease analysis was performed on four strains of Borrelia burgdorferi: one isolated from man (SF), one from Ixodes dammini (B31) and two from I. ricinus (BITS in Italy and B45 in Germany). Digestion by Taq I and Hae III gave the best resolution of the DNA fragments. Three different restriction patterns were obtained: BITS and B45 showed only one band difference. These results correlate with the reactivity of the four strains with monoclonal antibodies.

Rapid flow cytometric studies of Borrelia burgdorferi phagocytosis by human polymorphonuclear leukocytes

The interactions between a strain of Borrelia burgdorferi and human polymorphonuclear leukocytes were studied by flow cytometry in the presence of specific or non-specific opsonizing factors. The capacity of the borrelias to stimulate leukocyte metabolism was also investigated. The results indicated that a low phagocytosis by isolated purified polymorphonuclear leukocytes did occur in the presence or absence of specific antibodies. Within whole blood the percentages of phagocytosting leukocytes increased in the presence of non-specific opsonizing factors. No stimulation of the oxidative metabolism stimulated by Borrelia was observed and PMA or zymosan stimulation of leukocytes was inhibited by the spirochaetes.

Characterization of the first tick isolate of Borrelia burgdorferi from Italy

We report on the first isolation of a spirochetal organism from Ixodes ricinus ticks of the Trieste area (Northern Italy) which was identified as Borrelia burgdorferi by its reactivity with specific monoclonal antibodies directed against the OSPA and flagella proteins.

Leptospiral lipopolysaccharide presence in the outer envelope: electrophoretic evidence and immunological specificity

Purified preparations of lipopolysaccharides (LPS) extracted from two different strains of Leptospira interrogans have been electrophoretically analyzed in order to determine their location at the level of outer envelope (OE). Evidence has been collected for the presence of some LPS fractions in the OE, suggesting that a part of this molecule is embedded in the membrane structure. The serological specificity of the LPS has been in addition tested by means of monoclonal antiserovar antibodies (Moabs); the results indicated that the LPS structure is endowed of the immunodeterminants of the serovar. The remarkable relevance of this finding for the Leptospira taxonomy is discussed.

Chemical and biological properties of a phenol-water extract from Leptospira interrogans. Evidence for the absence of lipopolysaccharide

Leptospira interrogans, serovar copenhageni was extracted by the phenol-water method and the resulting preparation examined for chemical composition and endotoxic activity. Chemical analysis revealed that a number of sugars were present, however, the amount of lipid content was very low. Further, the preparation was devoid of characteristic endotoxic properties, like lethal toxicity, pyrogenicity and the property to induce the local Shwartzman reaction. The extract, however, was active in the limulus lysate gelation test and in the induction of monocyte activation. It is concluded that the leptospira preparation is devoid of endotoxin properties, both from the chemical and from the biological point of view.

Phagocytosis of Campylobacter jejuni and C. coli by peritoneal macrophages

Guinea-pig resident peritoneal macrophages had no activity against freshly isolated Campylobacter jejuni, whilst C. coli was phagocytosed and killed. The number of bacteria killed by macrophages always exceeded the number of those ingested, suggesting an extracellular mechanism of killing.

Heterogeneity of lipopolysaccharide banding patterns in Leptospira spp

Strains of Leptospira interrogans and Leptospira biflexa, examined by electrophoresis after whole cell lysis and protein digestion, revealed the presence of 2-keto-3-deoxyoctonate and an heterogeneous lipopolysaccharide electrophoretic banding pattern, which was characteristic of the species.

Serosurvey on the presence of leptospiral agglutinins in humans in Northern Italy

The article reports data concerning a serosurvey carried out in the province of Gorizia as a part of a research project sponsored by the National Research Council (CNR) on the epidemiological status of leptospirosis in Northern Italy. Microagglutination tests have been carried out on sera taken from randomly chosen healthy people and from humans exposed to occupational hazards, at a representing sample size for each category. The results have shown 8.29% agglutinin prevalence in healthy people, serovars bratislava, sejroe and canicola being predominant. Prevalence agglutinin rates were higher in meat workers (11.76%), sweepers (16.66%) and breeders (40%); in the latter category antibodies to Leptospira hardjo have been found out; this is the first reported instance of human contamination by L. hardjo in Italy.

New trends in the rapid serodiagnosis of leptospirosis

TR/Patoc slide test, ELISA and TIA (Thin-Layer Immunoassay) were evaluated for their use in a rapid serodiagnosis of human leptospirosis. The results obtained indicated that the TR/Patoc slide test is very sensitive and able to detect within a few minutes early antibodies against whichever serovar of leptospires, like the antigens of the Galton test. The value of the ELISA test in detecting antibodies at a low level is confirmed. The TIA assay, employed here for the first time for the diagnosis of leptospirosis, though sensitive seemed too long to perform and consequently it is not a test of choice for a rapid screening of sera.

Activation of complement by leptospires and its bactericidal activity

Bactericidal activity of complement was found to be effective on saprophytic Leptospira biflexa strains and not on Leptospira interrogans strains, by means of viable counting; the killing effect on saprophytic strains was probably due to a direct activation of the complement system via the alternative pathway. On the contrary the pathogenic strains seemed to activate the complement at a lower extent and were, in any case, resistant to the lytic action of the activated complement.

The role of antibodies and serum complement in the interaction between macrophages and leptospires

Guinea-pig macrophages exerted bactericidal activity against both a virulent and a saprophytic strain of leptospira in the presence of the homologous IgG. Serum complement alone rendered the saprophytic strain susceptible to phagocytosis by the same macrophages.

Studies on the interaction between macrophages and leptospires

Guinea-pig macrophages exerted no bactericidal activity against either a virulent or a saprophytic strain of leptospira during a 120 min period of contact at 37 degrees C. However, the same macrophages exhibited weak phagocytic powers towards these two strains of leptospira over a similar period of time.

Cytotoxic activity of supernatant extracts of virulent and saprophytic leptospires

Extracts from supernatants, obtained from culture of virulent strain PB-3 and saprophytic strain Isola Sacra 1, were assayed for cytotoxicity. A cytotoxic factor produced by the pathogenic strain was found to affect specifically the tested cells, at determined concentrations; on the other side a not clear and scarce cytotoxicity was shown for the extract from the saprophytic strain Isola Sacra 1. Cytotoxic factor produced by strain PB-3 was heat resistant and trypsin sensitive, suggesting to be a thermostable protein. An inhibitory doses it induced a typical, cytopathic effect on the treated cells.

Comparative mutagenicity test of dyes on E. coli WP2 and S. typhimurium as indicator organisms

The mutagenic activity of some industrial dyes has been studied. None of these chemical substances reverted E. coli WP2 and S. typhimurium, regardless of their chemical structure, either in the direct test or in the liver microsomal assay.

Mutagenic activity of platinum and ruthenium complexes

cis-Dichlorodiammineplatinum(II) [cis-PtCl2(NH3)2] and dichlorotetrakis (dis-methylsulfoxide) ruthenium(II) [RuCl2(DMSO)4] have been tested as mutagens for strains of Salmonella typhimurium carrying the hisG46 missense mutation. Their activity, which has been compared with the activity of mitomycin C, depends on the presence in the test bacteria of the pKM101 plasmid and is affected in various ways by the function of the excision repair system. More precisely, mitomycin C is mutagenic only for strains with an intact uvr system. cis-PtCl2(NH3)2 and RuCl2(DMSO)4 are mutagens both for uvrB and uvr+ strains, but cis-PtCl2(NH3)2 is more active on the latter, while the converse is true for RuCl2(DMSO)4. It seems, therefore, that each drug interacts with DNA by a different mechanism.