A simple and efficient method for poly-3-hydroxybutyrate quantification in diazotrophic bacteria within 5 minutes using flow cytometry

The conventional method for quantification of polyhydroxyalkanoates based on whole-cell methanolysis and gas chromatography (GC) is laborious and time-consuming. In this work, a method based on flow cytometry of Nile red stained bacterial cells was established to quantify poly-3-hydroxybutyrate (PHB) production by the diazotrophic and plant-associated bacteria, Herbaspirillum seropedicae and Azospirillum brasilense. The method consists of three steps: i) cell permeabilization, ii) Nile red staining, and iii) analysis by flow cytometry. The method was optimized step-by-step and can be carried out in less than 5 min. The final results indicated a high correlation coefficient (R²=0.99) compared to a standard method based on methanolysis and GC. This method was successfully applied to the quantification of PHB in epiphytic bacteria isolated from rice roots.

A broad pH range and processive chitinase from a metagenome library

Chitinases are hydrolases that degrade chitin, a polymer of N-acetylglucosamine linked β(1-4) present in the exoskeleton of crustaceans, insects, nematodes and fungal cell walls. A metagenome fosmid library from a wastewater-contaminated soil was functionally screened for chitinase activity leading to the isolation and identification of a chitinase gene named metachi18A. The metachi18A gene was subcloned and overexpressed in Escherichia coli BL21 and the MetaChi18A chitinase was purified by affinity chromatography as a 6xHis-tagged fusion protein. The MetaChi18A enzyme is a 92-kDa protein with a conserved active site domain of glycosyl hydrolases family 18. It hydrolyses colloidal chitin with an optimum pH of 5 and temperature of 50°C. Moreover, the enzyme retained at least 80% of its activity in the pH range from 4 to 9 and 98% at 600 mM NaCl. Thin layer chromatography analyses identified chitobiose as the main product of MetaChi18A on chitin polymers as substrate. Kinetic analysis showed inhibition of MetaChi18A activity at high concentrations of colloidal chitin and 4-methylumbelliferyl N,N′-diacetylchitobiose and sigmoid kinetics at low concentrations of colloidal chitin, indicating a possible conformational change to lead the chitin chain from the chitin-binding to the catalytic domain. The observed stability and activity of MetaChi18A over a wide range of conditions suggest that this chitinase, now characterized, may be suitable for application in the industrial processing of chitin.

Chemoprotective activity of mixed valence polyoxovanadates against diethylsulphate in E. coli cultures: insights from solution speciation studies

Cell survival after treatment with dimethylsulphate in the presence of polyoxovanadates.

Superoxide radical-generating compounds activate a predicted promoter site for paraquat-inducible genes of the Chromobacterium violaceum bacterium in a dose-dependent manner

The purpose of the present study was to functionally evaluate the influence of superoxide radical-generating compounds on the heterologous induction of a predicted promoter region of open reading frames for paraquat-inducible genes (pqi genes) revealed during genome annotation analyses of the Chromobacterium violaceum bacterium. A 388-bp fragment corresponding to a pqi gene promoter of C. violaceum was amplified using specific primers and cloned into a conjugative vector containing the Escherichia coli lacZ gene without a promoter. Assessments of the expression of the β-galactosidase enzyme were performed in the presence of menadione (MEN) and phenazine methosulfate (PMS) compounds at different final concentrations to evaluate the heterologous activation of the predicted promoter region of interest in C. violaceum induced by these substrates. Under these experimental conditions, the MEN reagent promoted highly significant increases in the expression of the β-galactosidase enzyme modulated by activating the promoter region of the pqi genes at all concentrations tested. On the other hand, significantly higher levels in the expression of the β-galactosidase enzyme were detected exclusively in the presence of the PMS reagent at a final concentration of 50 μg/mL. The findings described in the present study demonstrate that superoxide radical-generating compounds can activate a predicted promoter DNA motif for pqi genes of the C. violaceum bacterium in a dose-dependent manner.

Influence of βS allele in the lipid peroxidation and antioxidant capacity parameters

INTRODUCTION

The oxidative process plays a fundamental role in the pathophysiology of sickle cell anemia (SCA), and population and environmental characteristics may influence redox balance. The aim of this study was to evaluate lipid peroxidation and antioxidant capacity in Brazilian Hb S carriers undergoing different therapies.

METHODS

Blood samples from 270 individuals were analyzed (Hb SS, n = 68; Hb AS, n = 53, and Hb AA, n = 149). Hemoglobin genotypes were assessed through cytological, electrophoretic, chromatographic, and molecular methods. Plasma lipid peroxidation and antioxidant capacity were measured by spectrophotometric methods.

RESULTS

Patients with SCA who used iron-chelating drugs combined with hydroxyurea, associated with regular transfusions, showed lower levels of TBARS (P ≤ 0.05), higher levels of TEAC (P ≤ 0.01), and lower TBARS/TEAC ratio (R = 255.8). The redox profile of Hb AS subjects was not statistically different (P > 0.05) from that of Hb AA subjects.

CONCLUSION

The data suggest that oxidative stress is lower in the patients with SCA who received regular blood transfusions associated with the combined use of HU and iron chelators than the group received only HU. The redox system of the Hb AS carriers is compatible with the control group.

Polymorphisms of the promoter and exon 3 of the receptor for advanced glycation end products (RAGE) in Euro- and Afro-Brazilians

The receptor for advanced glycation end products (RAGE or AGER), a member of the immunoglobulin superfamily, is involved in pathologies such as atherosclerosis and diabetes. Over 50 SNPs were reported for RAGE, among which were the promoter region polymorphisms -429T>C (rs1800625), -374T>A (rs1800624) and a 63-bp deletion (-407 to -345 bp), all related to increased RAGE expression. Additionally, in the exon 3, a putative site of binding ligands, the missense variation G82S (rs2070600) was associated with skin disorders in patients with diabetes. We have determined allele, genotype and haplotype frequencies of RAGE polymorphisms -429T>C, -374T>A, 63-bp deletion and G82S in Euro-Brazilians (n = 108) and Afro-Brazilians (n = 91), characterized according to the predominant ancestry of the individuals. The allele frequencies for Euro- and Afro-Brazilians were as follows: -429C, 12.5% vs. 12.1% (P = 0.90); -374A, 31.5% vs. 26.2% (P = 0.25); 63del, 0.0% vs. 3.8% (P = 0.004); and 82S, 1.9% vs. 0.6% (P = 0.24). Absolute linkage disequilibrium was found between the promoter polymorphisms -429T>C and -374T>A plus the 63-bp deletion (D'=1.000; P < 0.0001). The haplotype frequencies differed (P = 0.003) between Euro- and Afro-Brazilians. Our results showed that the frequencies of the 63-bp deletion were higher in Afro-Brazilians, while the other analysed polymorphisms were similarly distributed in the studied populations. The -374T>A plus 63-bp deletion polymorphism captures more than 80% of the haplotypic variation in the studied population.

Induction of a gloverin-like antimicrobial polypeptide in the sugarcane borer Diatraea saccharalis challenged by septic injury

Diatraea saccharalis (Fabricius, 1794) (Lepidoptera: Crambidae) is an important pest for Brazilian sugarcane. In the present study, we detected two distinct spots in hemolymph from septic injured larvae (HDs1 and HDs2), which are separated by 2DE gel electrophoresis. Both spots were subjected to in-gel tryptic digestion and MALDI-TOF/TOF analysis, which revealed the sequence VFGTLGSDDSGLFGK present in both HDs1 and HDs2. This sequence had homology and 80% identity with specific Lepidoptera antimicrobial peptides called gloverins. Analyses using the ImageMaster 2D software showed pI 8.94 of the HDs1 spot, which is similar to that described to Hyalophora gloveri gloverin (pI 8.5). Moreover, the 14-kDa molecular mass of the spot HDs1 is compatible to that of gloverins isolated from the hemolymph of Trichoplusia ni, Helicoverpa armigera and H. gloveri. Antimicrobial assays with partially purified fractions containing the HDs1 and HDs2 polypeptides demonstrated activity against Escherichia coli. This is the first report of antimicrobial polypeptides in D. saccharalis, and the identification of these peptides may help in the generation of new strategies to control this pest.

Diamidine activity against trypanosomes: the state of the art

Aromatic diamidines and related compounds are DNA minor groove binders that have been screened against a variety of pathogenic microorganisms such as bacteria, fungi and protozoa and show promising results. Parasitic infections are widespread in developing countries and are major contributors to human mortality and morbidity, causing considerable economic hardship. Trypanosomes are unicellular protozoan organisms that cause serious public health problems in developing countries: African trypanosomiasis (sleeping sickness) in Africa, and Chagas' disease, in Latin America. Sleeping sickness, caused by sub-species of Trypanosome brucei (T. brucei gambiense and T. brucei rhodesiense), is a fatal disease if left untreated, with about 60 million people currently at risk. Trypanosoma cruzi is the etiological agent of Chagas' disease, an important parasitic illness that affects nearly 17 million individuals in endemic areas. The fact that the available clinical drugs are expensive, toxic, require long treatment periods, frequently exhibit reduced activity towards certain parasite strains and evolutive stages, and are beginning to show development of resistance, demonstrates the urgent need for the development of new drugs for both pathologies. For some time much attention has been focused on the effect of diamidines (and related compounds) on African trypanosomes. However more recent studies have pointed to their potential activity against T.cruzi. In this review the current therapeutic state of the art of aromatic diamidines and related compounds used against T.brucei and T.cruzi is reviewed with a focus on their potential use as antiparasitic drugs for the treatment of both these important neglected diseases.

A prospective study on Shiga toxin-producing Escherichia coli in children with diarrhea in Paraná State, Brazil

AIMS

To examine stool specimens from children with diarrhea from Paraná State, southern Brazil, for presence of STEC.

METHODS AND RESULTS

A PCR screening assay for stx genes was used to examine a loopful of confluent colonies of 306 stool samples cultures. In six (1.96%) of them, DNA fragments of the expected size were observed, and the presence of stx was confirmed by DNA sequencing. Then up to 100 single colonies from each of the six stool cultures were analyzed using the same PCR protocol. However, stx-positive colonies were found only in two of the cultures. The E. coli strains belonged to serotypes O69:H11 and O178:H19, and presented genotypes stx(1)eae ehxA and stx(1) respectively. Shiga toxin production was confirmed using the VTEC Screen Seiken. Except ampicillin, they were susceptible to all the antimicrobials tested.

CONCLUSIONS

These results show that STEC may be an important cause of diarrhea in children of Paraná State, and that they are present in low numbers in stools. The strains belonged to serotypes not commonly found associated with STEC and probably present low virulence.

SIGNIFICANCE AND IMPACT OF STUDY

These results indicate that molecular methods are required to diagnosis of STEC infections.

Diagnostic value of combining immunostaining for CD3 and nuclear morphometry in mycosis fungoides

BACKGROUND

Mycosis fungoides (MF) is the most common skin lymphoid neoplasm. In initial stages, differential diagnosis of MF from other benign dermal lymphoid infiltrates (BDLI) may be impossible on morphological basis alone. In previous studies, only deletion of CD7 in MF proved to be of diagnostic help, but not the ratio between immunoexpression of CD4 and CD8.

METHODS

30 cases of MF and 11 cases of BDLI were analysed, in order to compare morphometric parameters, which could be of diagnostic aid. As CD7 is frequently deleted in MF, immunohistochemical detection of T-cells was made using an antibody to CD3. Images of 100 CD3-positive cells per case in both groups were captured and analysed using a simple computer program for nuclear perimeter, area, diameter and nuclear contour index.

RESULTS

All parameters showed statistically significant higher values for MF. Area was the variable with the strongest discriminating power between the two groups of patients. Thus even if morphological evaluation is not accurate to distinguish benign versus malignant dermal lymphoid infiltrates, due to the variability of size and shape of these cells, a more sensitive method promptly shows this difference.

CONCLUSION

Results suggest that morphometry of CD3-positive lymphoid cells may add valuable information in the differential diagnosis of MF and benign dermatoses.

Phenotypic and genotypic traits of Shiga toxin-producingEscherichia colistrains isolated from beef cattle from Paraná State, southern Brazil

AIMS

To investigate the prevalence and characteristics of Shiga toxin-producing Escherichia coli (STEC) in cattle from Paraná State, southern Brazil.

METHODS AND RESULTS

One hundred and seven faeces cattle samples were cultured on Sorbitol-MacConkey agar. Escherichia coli colonies were tested for production of Shiga toxin using Vero-cell assay. A high prevalence (57%) of STEC was found. Sixty-four STEC were serotyped and examined for the presence of stx(1), stx(2), eae, ehxA and saa genes and stx(2) variants. The isolates belonged to 31 different serotypes, of which three (O152:H8, O175:H21 and O176:H18) had not previously been associated with STEC. A high prevalence of stx(2)-type genes was found (62 strains, 97%). Variant forms found were stx(2), stx(2c), stx(2vhb), stx(2vO111v/OX393) and a form nonclassifiable by PCR-RFLP. The commonest genotypes were stx(2)ehxA saa and stx(1)stx(2)ehxA saa.

CONCLUSIONS

A high frequency of STEC was observed. Several strains belong to serotypes previously associated with human disease and carry stx(2) and other virulence factors, thus potentially representing a risk to human health.

SIGNIFICANCE AND IMPACT OF THE STUDY

This is the first study of STEC in Paraná State, and its findings emphasize the need for proper cattle handling to prevent human contamination.

Cutaneous adverse reaction to 2-chlorodeoxyadenosine with histological flame figures in patients with chronic lymphocytic leukaemia

INTRODUCTION

2-Chlorodeoxyadenosine (cladribine or 2-CdA) is a purine analogue that has been used successfully in hairy cell leukaemia (HCL). Moreover, it has been increasingly used to treat chronic lymphoproliferative syndromes and paediatric acute myeloid leukaemia. Cutaneous side-effects associated with this drug have seldom been described in cases of HCL.

PATIENTS AND METHODS

We describe three patients with chronic lymphocytic leukaemia that presented generalized skin eruptions after treatment with 2-CdA.

RESULTS

All patients had advanced disease, receiving 2-CdA as a second or third line chemotherapy. Skin lesions were severe and chemotherapy had to be discontinued. Histological examination of skin biopsies showed an eosinophil-rich infiltrate with flame figures, similar to what is observed in Wells' syndrome (eosinophilic cellulitis). Corticosteroids were effective to control the eruptions.

CONCLUSIONS

Cutaneous adverse reactions associated with 2-CdA have seldom been observed in the treatment of HCL. However, as this purine analogue has been used in more advanced cases these may be more frequent and severe. The pathophysiology of these lesions is unclear, but it is probably related to drug-induced change in T-cell imbalance in severely immunosuppressed patients.

Humoral immune response of water buffalo monitored with three different antigens of Toxocara vitulorum

Humoral immune response of water buffalo naturally infected with Toxocara vitulorum was monitored using three different antigens of this parasite in serum and colostrum of buffalo cows and calves. Soluble extract (Ex) and excretory/secretory (ES) larval antigens and perienteric fluid antigen (Pe) of adult T. vitulorum were used to measure the antibody levels by an indirect ELISA. Serum of 7-12 buffalo cows for the first 365 days and colostrum of the same number of buffalo cows for the first 60 days of parturition, and serum of 8-10 buffalo calves for the first 365 days after birth were assayed. The ELISA detected antibodies against all three T. vitulorum antigens in the colostrum and serum of 100% of buffalo cows and calves examined. The highest antibody levels against Ex, ES and Pe antigens were detected in the buffalo cow sera during the perinatal period and were maintained at high levels through 300 days after parturition. On the other hand, colostrum antibody concentrations of all three antigens were highest on the first day post-parturition, but decreased sharply during the first 15 days. Concomitantly to the monitoring of immune response, the parasitic status of the calves was also evaluated. In calves, antibodies passively acquired were at the highest concentrations 24 h after birth and remained at high levels until 45 days coincidentally with the peak of T. vitulorum infection. The rejection of the worms by the calves occurred simultaneously with the decline of antibody levels, which reached their lowest levels between 76 and 150 days. Thereafter, probably because of the presence of adults/larvae stimulation, the calves acquired active immunity and the antibodies started to increase slightly in the serum and plateaued between the days 211 and 365. All three antigens were detected by the serum antibodies of buffalo calves; however, the concentration of anti-Pe antibody was higher than anti-EX and anti-ES, particularly after 90 days of age. By conclusion, the buffalo cows develop immunity and keep high levels of antibodies against T. vitulorum-Ex, ES and Pe antigens and these antibodies are transferred to their calves through the colostrum. This passively acquired immunity does not protect the calves against the acquisition of the infection, but these antibodies, passively or actively acquired, may have an important role during worm rejection by the calves and prevention of intestinal reinfection.

Host and parasite apoptosis following Trypanosoma cruzi infection in in vitro and in vivo models

The mechanism of cell death which occurs during Chagas' cardiopathy is disputed. To address this issue we analyzed the molecular pathways implicated in the death of cardiomyocytes during T. cruzi invasion and found that they undergo apoptosis during both in vitro and in vivo infections. However, the death rates and onset were related to the parasite stocks belonging to different biodemes, which can be correlated to the different histological inflammation findings that have already been reported. Our in vitro data provide additional support for this hypothesis since higher levels and earlier apoptosis induction were noted during the interaction with the Dm28c (type I) as compared to the Y and CL stocks (type II). Modifications of the surface carbohydrates of the infected cardiomyocytes were observed and these molecular events may be acting as "eat me" tags for their final engulfment by macrophages and/or other non-professional phagocytes. The analysis of other host cell types showed that the in vitro infection of fibroblasts did not result in host apoptosis even when a highly infective stock was used. Conversely, infected macrophages undergo apoptosis but at a higher degree than cardiomyocytes. Apoptotic intracellular parasites were observed to varied extents depending on the T. cruzi stock, which was related to the parasite invasion and proliferation. In summary, our results show that during T. cruzi infection, the extent of apoptosis varies according to the host cell type and the parasite stocks. The apoptosis of both host and T. cruzi can contribute to the silent spreading and persistence of the parasite without triggering an exacerbated inflammatory response.

Inter-domain cross-talk controls the NifA protein activity of Herbaspirillum seropedicae

Herbaspirillum seropedicae is an endophytic diazotroph, which colonizes sugar cane, wheat, rice and maize. The activity of NifA, a transcriptional activator of nif genes in H. seropedicae, is controlled by ammonium ions through a mechanism involving its N-terminal domain. Here we show that this domain interacts specifically in vitro with the N-truncated NifA protein, as revealed by protection against proteolysis, and this interaction caused an inhibitory effect on both the ATPase and DNA-binding activities of the N-truncated NifA protein. We suggest that the N-terminal domain inhibits NifA-dependent transcriptional activation by an inter-domain cross-talk between the catalytic domain of the NifA protein and its regulatory N-terminal domain in response to fixed nitrogen.

Control of nitrogenase reactivation by the GlnZ protein in Azospirillum brasilense

The glnZ mutant of Azospirillum brasilense (strain 7611) showed only partial recovery (20 to 40%) after 80 min of ammonia-induced nitrogenase switch-off, whereas the wild type recovered totally within 10 min. In contrast, the two strains showed identical anoxic-induced switch-on/switch-off, indicating no cross talk between the two reactivation mechanisms.

Uridylylation of the PII protein from Herbaspirillum seropedicae

The PII protein is apparently involved in the control of NifA activity in Herbaspirillum seropedicae. To evaluate the probable role of PII in signal transduction, uridylylation assays were conducted with purified H. seropedicae PII and Escherichia coli GlnD, or a cell-free extract of H. seropedicae as sources of uridylylating activity. The results showed that alpha-ketoglutarate and ATP stimulate uridylylation whereas glutamine inhibits uridylylation. Deuridylylation of PII-UMP was dependent on glutamine and inhibited by ATP and alpha-ketoglutarate. PII uridylylation and (or) deuridylylation in response to these effectors suggests that PII is a nitrogen level signal transducer in H. seropedicae.

Phytate from an alternative dietary supplement has no effect on the calcium, iron and zinc status in undernourished rats

A mixture of cereal bran, eggshells and cassava leaf powder, known as multimixture (MM), has been widely used in developing countries as a dietary supplement to combat malnutrition in children. The introduction of phytate from cereal bran in infant diets has generated serious controversy about MM due to the mineral chelating effect of phytate. This paper reports on a study to investigate the bioavailability of calcium, iron and zinc in rats fed with a deficient diet supplemented with MM. Undernourished rats were treated with a deficient diet (DD) to which MM containing different phytate and mineral concentrations was added. Body weight gains, Ca, Fe, Zn and phytate balances, blood hemoglobin concentration and the mineral content of tissue were determined. DD supplemented with 5% and 25% of MM increased the rats' hemoglobin blood concentration, fur regrowth, Ca concentration in the femur and promoted body weight gain 40 times higher than did the DD. Extra calcium, iron and zinc added to the diet with 25% of MM did not increase the rats' growth rates. Both the addition of NaCl, KF and KI in MM and the use of dephytinized bran in the MM composition led to a significant increase in the rats' growth (P < 0.0001); however, these changes failed to increase Ca, Fe and Zn bioavailability. Our findings suggest that the Ca, Fe and Zn bioavailability was not affected by the MM phytate content or by the concentrations of NaCl, KF and KI in the diet.

Modulation induced by estradiol in the acute phase of Trypanosoma cruzi infection in mice

We investigated the effect of 17beta-estradiol on mice resistant to infection by Trypanosoma cruzi. Infected Balb/C, C3H and C57BL/6 female mice had a longer survival time than males, C57BL/6 showing the highest difference (50% cumulative mortality in females versus 100% in males). This lineage was treated with estradiol (from 0.05 microg to 500 microg/mouse) 1 day before infection. Treatment with 50 microg or 500 microg estradiol/ mouse increased mortality and parasitaemia. Low doses had no effect or tended to reduce both parameters. Given that estradiol presented no in vitro effect on trypomastigotes or epimastigotes, the involvement of a direct hormonal effect on the parasite is improbable. Alterations in the humoral T. cruzi-specific response were also discarded, since the kinetics and concentration of anti-T. cruzi IgG were not affected by the treatment. Females infected during an estradiol-descending phase (meta-oestrus) survived longer than those infected during other phases of the oestrous cycle. We confirmed that estradiol interferes with T. cruzi infection.

16S ribosomal DNA characterization of nitrogen-fixing bacteria isolated from banana (Musa spp.) and pineapple (Ananas comosus (L.) Merril)

Nitrogen-fixing bacteria isolated from banana (Musa spp.) and pineapple (Ananas comosus (L.) Merril) were characterized by amplified 16S ribosomal DNA restriction analysis and 16S rRNA sequence analysis. Herbaspirillum seropedicae, Herbaspirillum rubrisubalbicans, Burkholderia brasilensis, and Burkholderia tropicalis were identified. Eight other types were placed in close proximity to these genera and other alpha and beta Proteobacteria.

Effects of denaturing and stabilizing agents on the inhibitory activity and conformational stability of Schizolobium parahyba chymotrypsin inhibitor

The conformational stability of the Schizolobium parahyba chymotrypsin inhibitor (SPCI) was investigated based on conformational changes and inhibitory activity in the presence of chaotropic and stabilizing agents. At 90 degrees C, the half-lifetime of SPCI was 154 min, while in the presence of 1 M KCl and 20% PEG 20,000, it was drastically reduced to 6 and 3 min, respectively. In contrast, at 90 degrees C, the SPCI structure remained unaltered with the addition of 1 mM DTT and 56% glycerol. The reduction of the two disulfide bonds caused conformational changes in the SPCI without altering the inhibitory activity, suggesting that disulfide bonds are irrelevant to the maintenance of SPCI conformation. Unfolded structures were formed in the presence of 6 M GdnHCl, while in the presence of 8 M urea, destabilization was due to peptide bond rupture. These results suggest that the thermal inactivation of SPCI involves conformational changes and that hydrophobic and electrostatic interactions play a significant role, while the disulfide bonds are of secondary importance in maintaining the high thermal stability of SPCI.

In vitro trypanocidal activities of a novel series of N, N-dimethyl-2-propen-1-amine derivative

The trypanocidal activity of several 3-(4'-bromo-[1,1-biphenyl]-4-yl) -3-(4-X-phenyl)-N,N-dimethyl-2-propen-1-amine derivatives of the three evolutionary stages of Trypanosoma cruzi, namely the bloodstream trypomastigote form and both the proliferative epimastigote and amastigote forms, were studied. For both proliferative forms of T. cruzi, total lysis occurred at 10-60 microM for trypomastigotes at 40-200 muM. The following order of susceptibility was established: amastigotes > epimastigotes > trypomastigotes. The most were the bromo (X = g) and unsubstituted (X = b) compounds, which had 13- and 8-fold higher activity against trypomastigotes, respectively, than nifurtimox. Cytotoxicity in the Chinese hamster V-79 cell line, measured as inhibition of cell proliferation showed that all the compounds had the same range of IC50 (7.0-12.4 muM). The halogen (X = a,g,h) and the unsubstituted derivatives (X = b) were the least toxic in the series together with the compound (X = f).

Complete regression of melanocytic nevi: clues for proper diagnosis

A histopathological study of a distinct papule isolated from a patient's neck is reported and compared to 80 melanocytic nevi. The histogenesis of this unique tumor indicates that it probably represents the residual of a melanocytic nevus in which nevi cells have disappeared but fat infiltration and fibrosis of the dermis and the typical aspects of other cutaneous elements persisted. The finding of focal acantholytic dyskeratosis in multiple foci of the lesion may indicate melanocytic cells regression. Lesions with the histopathological appearance of melanocytic nevi, even in the absence of nevi cells, may be discovered scrutinizing the associated alterations.

Focal acantholytic dyskeratosis: a snare for the pathologist. Report of two cases associated to psoriasis and fibrous papule of the nose

Two specimens containing clinically inapparent histologic features of acantholytic dyskeratosis (on the base of a fibrous papule of the nose and overlying a psoriatic lesion) are presented. The authors discuss the conduct to be followed by the pathologist in similar cases. The general pathologist should be well trained in dermatopathology since cutaneous biopsies account for 10 to 25% of the specimens submitted for histologic diagnosis or, even, form the major part of the workload (Berry). There is a wall between the physician who submits the skin biopsies (who may be or not a dermatologist) and the pathologist. The clinical information provided by dermatologists is scant and incomplete and physicians who are not dermatologists seldom submit any information. The histological pictures found in skin biopsies are, often, common to several nosological entities and an adequate understanding of their meaning is desirable for a thorough evaluation. We ought to assess it with the maximum scientific severity, searching to solve the puzzle without depreciating the information received. In this report the authors analyse the histopathological approach to the cutaneous lesions of two patients. They displayed the association between acantholytic dyskeratosis (AD) and another cutaneous pathology. Findings like these may obstruct the final diagnosis to be issued by the pathologist.(ABSTRACT TRUNCATED AT 250 WORDS)