New species and new records of bryozoan species from fouling communities in the Madeira Archipelago (NE Atlantic)

Hull fouling is considered to be the most significant vector of introduction of marine non-indigenous species (NIS) in the Madeira Archipelago (NE Atlantic) because these islands provide a vital passage route for many ships. The transfer of species between boat hulls and artificial substrates in marinas is known to be high. Bryozoans are among the most common groups of marine invertebrates growing on this type of substrate. In recent years, significant advances have been made in our knowledge about the biodiversity of bryozoans in the Madeira Archipelago. Nonetheless, the currently recognized numbers remain far from reflecting the actual bryozoan species richness. In this context, we examine bryozoan samples stemming from NIS monitoring surveys on artificial substrates along the southern coast of the Madeira Archipelago, in four recreational marinas and in two offshore aquaculture farms. This has yielded new information about ten bryozoan species. Two of them, Crisia noronhai sp. nov. and Amathia maderensis sp. nov., are described for the first time, although at least the first one was previously recorded from Madeira but misidentified. Bugula ingens, Cradoscrupocellaria insularis, Scruparia ambigua, and Celleporaria brunnea are recorded for the first time in Madeira. Moreover, the material of C. brunnea was compared with the type, and a biometric analysis was performed with material from the Atlantic and Mediterranean. All samples identified as C. brunnea in both regions are the same species, and the variations described in the literature apparently reflect high intracolonial variability. Finally, we provide new information for the descriptions of 4 additional bryozoans, namely, Crisia sp. aff. elongata, Cradoscrupocellaria bertholletii, Scrupocaberea maderensis, and Tricellaria inopinata.

Regional communication and media analysis of aquaculture in Atlantic islands

The way the media portrays aquaculture-related events can influence how this industry is perceived by the public and affect its success. Since media are an important source of public information, media content analysis has been carried out in several regions of the world. This study aimed to determine which aspects of aquaculture were more exposed and how they were discussed by regional media in the Madeira archipelago, an oceanic group of Portuguese islands. Analysis of aquaculture's media coverage in the two most-read regional newspapers of Madeira was carried out over a 5-year period (2017 to 2021). For each news article, the assessment focused on the geographic scope, the main topics covered, the stakeholders with access to the debate, and the general tone of the article (risk/benefit framework). A total of 297 articles were analyzed. Results indicate the occurrence of trigger events that contributed to a shift in the amount of news published and in the way media framed aquaculture. In general, political and economic issues dominated the coverage, whereas social, environmental, scientific, and landscape matters received less media attention. The voice of the government was predominant throughout the 5 years in analysis and aquaculture was generally framed with a balanced tone, slightly more negative. Open and transparent communication between the stakeholders and the media is fundamental for the sustainable development of the aquaculture industry.

Polystyrene microplastics exposure modulated the content and the profile of fatty acids in the Cladoceran Daphnia magna

A growing number of studies has shown that the exposure to microplastics (MPs) of different polymeric compositions can induce diverse adverse effects towards several aquatic species. The vast majority of such studies has been focused on the effects induced by the administration of MPs made by polystyrene (PS; hereafter PS-MPs). However, despite the increase in the knowledge on the potential toxicity of PS-MPs, there is a dearth of information concerning their role in affecting energy resources and/or their allocation. The present study aimed at exploring the impact of 21-days exposure to three concentrations (0.125, 1.25 and 12.5 μg mL^-1) of PS-MPs of different sizes (1 and 10 μm) on fatty acids (FAs) profile of the freshwater Cladoceran Daphnia magna. The exposure to the highest tested concentration of PS-MPs induced an overall decrease in D. magna total FAs content, independently of the particle size. Moreover, a change in the accumulation of essential FAs by the diet was noted, with an enhanced synthesis of monounsaturated FAs-rich storage lipids. However, a sort of adaptation to counteract the adverse effects and to re-establish the FAs homeostasis was observed in individuals treated with high PS-MPs concentration, independently of their size. These results indicate that the exposure to PS-MPs could alter the allocation or induce changes in FAs composition in D. magna, with potential long-term consequences on life-history traits of this zooplanktonic species.

The effect of microplastics pollution in microalgal biomass production: A biochemical study

Microplastics (MPs) are widely spread throughout aquatic systems and water bodies. Given that water quality is one of the most important parameters in the microalgal-based industry, it is critical to assess the biochemical impact of short- and long-term exposure to MPs pollution. Here, the microalga Phaeodactylum tricornutum was exposed to water contaminated with 0.5 and 50 mg L^-1 of polystyrene (PS) and/or polymethyl methacrylate (PMMA). Results show that the microalgal cultures exposed to lower concentrations of PS displayed a growth enhancement of up to 73% in the first stage (days 3-9) of the exponential growth phase. Surprisingly, and despite the fact that long-term exposure to MPs contamination did not impair microalgal growth, a steep decrease in biomass production (of up to 82%) was observed. The production of photosynthetic pigments was shown to be pH-correlated during the full growth cycle, but cell density-independent in later stages of culturing. The extracellular carbohydrates production exhibited a major decrease during long-term exposure. Still, the production of extracellular proteins was not affected by the presence of MPs. This pilot laboratory-scale study shows that the microalgal exposure to water contaminated with MPs disturbs its biochemical equilibrium in a time-dependent manner, decreasing biomass production. Thus, microalgal industry-related consequences derived from the use of MPs-contaminated water are a plausible possibility.

Microalgal-based biopolymer for nano- and microplastic removal: a possible biosolution for wastewater treatment

The increasing water pollution caused by the presence of nano- and microplastics has shown a need to pursue solutions to remediate this problem. In this work, an extracellular polymeric substance (EPS) producing freshwater Cyanothece sp. strain was exposed to nano- and microplastics. The bioflocculant capacity of the biopolymer produced was evaluated. The influence of different concentrations (1 and 10 mg L^-1) of polystyrene nano- and microplastics in the extracellular carbohydrates and in the EPS production was studied. The presence of nano- and microplastics induced a negative effect on the microalgal growth (of up to 47%). The results show that the EPS produced by Cyanothece sp. exhibits high bioflocculant activity in low concentrations. Also, the EPS displayed very favourable characteristics for aggregation, as the aggregates were confirmed to consist of microalga, EPS and both the nano- and microplastics. These results highlight the potential of the microalgal-based biopolymers to replace hazardous synthetic flocculants used in wastewater treatment, while aggregating and flocculating nano- and microplastics, demonstrating to be a multi-purposed, compelling, biocompatible solution to nano- and microplastic pollution.

Marine vs freshwater microalgae exopolymers as biosolutions to microplastics pollution

Microalgae can excrete exopolymer substances (EPS) with a potential to form hetero-aggregates with microplastic particles. In this work, two freshwater (Microcystis panniformis and Scenedesmus sp.) and two marine (Tetraselmis sp. and Gloeocapsa sp.) EPS producing microalgae were exposed to different microplastics. In this study, the influence of the microplastic particles type, size and density in the production of EPS and hetero-aggregates potential was studied. Most microalgae contaminated with microplastics displayed a cell abundance decrease (of up to 42%) in the cultures. The results showed that the formed aggregates were composed of microalgae and EPS (homo-aggregates) or a combination of microalgae, EPS and microplastics (hetero-aggregates). The hetero-aggregation was dependent on the size and yield production of EPS, which was species specific. Microcystis panniformis and Scenedesmus sp. exhibited small EPS, with a higher propension to disaggregate, and consequently lower capabilities to aggregate microplastics. Tetraselmis sp. displayed a higher ability to aggregate both low and high-density microplastics, being partially limited by the size of the microplastics. Gloeocapsa sp. had an outstanding EPS production and presented excellent microplastic aggregation capabilities (adhered onto the surface and also incorporated into the EPS). The results highlight the potential of microalgae to produce EPS and flocculate microplastics, contributing to their vertical transport and consequent deposition. Thus, this work shows the potential of microalgae as biocompatible solutions to water microplastics treatment.

Characterization of poly(2-hydroxyethyl methacrylate) (PHEMA) contact lens using the Langmuir monolayer technique

The behavior of poly(2-hydroxyethyl methacrylate) (PHEMA) polymer monolayer spread on water was studied under various experimental conditions. The influence of subphase pH and temperature, compression speed, elapsed time from the deposit of the monolayer and the recording of the surface pressure-area (π-A) isotherms, as well as the number of polymer molecules deposited at the air/water surface (surface concentration) was studied. The obtained results show that PHEMA exhibits a very stable monolayer given that it is unaffected by modifications in the majority of these variables. Only the elapsed time between the spreading of the monolayer and the beginning of compression causes a small change in the π-A isotherms that consists in an increase in the area occupied by the film. This is attributed to the greater unfolding with time of the polymer's monomers at the air/water interface. The plateau that appears on π-A curves of the PHEMA monolayer is attributed to the reorientation of their hydroxyethyl polar groups through their C-O-C bonds, as well as to the reorientation of the ethylene (CH(2)) groups that link the monomers, which provokes a folding of the polymer's chains causing an accordion configuration. The existence of this structure is confirmed by the presence of numerous noise peaks in the relative thickness versus time curve corresponding to this region. In the same fashion, the images observed from Brewster angle microscopy (BAM) reveal the existence of light-dark "bands" relative to the different regions of this particular structure.

Host and parasite factors affecting the invasion of mononuclear phagocytes by Trypanosoma cruzi

Epimastigotes and trypomastigotes of Trypanosoma cruzi enter mouse and human macrophages by phagocytosis. Organisms are initially found in a parasitophorous vacuole, and fusion with lysosomes promptly ensues. Epimastigotes are rapidly killed and digested in phagolysosomes. Trypomastigotes, however, soon escape the confines of the vacuolar system and reach the cytoplasm, where they replicate. Metacyclic trypomastigotes are quickly taken up by mouse and human macrophages. In contrast, blood-form trypomastigotes are resistant to interiorization by mononuclear phagocytes. This effect can be overcome, without affecting parasite survival, by opsonization of the parasites with immunoglobulin G (IgG)-class antibodies or by removal of trypomastigote surface peptides with trypsin. The major surface glycoprotein (relative molecular mass 90 000) of the mammalian stages of T. cruzi has been implicated in this antiphagocytic effect. This surface glycoprotein seems to have glycosidase activity, and the antiphagocytic effect may be mediated via the removal of sugar residues necessary for parasite internalization by macrophages. This enzyme activity may explain other evasion mechanisms displayed by T. cruzi bloodstream forms. These include antibody-mediated complement lysis and Fc-receptor-mediated phagocytosis. Trypomastigotes are, however, promptly killed in mouse and human macrophages activated by either in vivo infection or in vitro treatment with sensitized, antigen-stimulated, T-cell products. Increased production of reactive oxygen intermediates by activated cells has been implicated as the mechanism of intracellular killing in mononuclear phagocytes. Opsonization by IgG-class antibodies enhances uptake of the parasites but does not affect their fate in normal mononuclear phagocytes. In contrast, it enhances their killing by activated macrophages, suggesting that antibodies may have a major protective role only in the presence of concomitant cell-mediated immunity.

Estudio morfométrico mediante técnicas de imagen de la vena de Trolard en su anastomosis al seno longitudinal superior

OBJECTIVE

The main objective of this work is to allow the anatomical localization of the vein of Trolard (VT) or great anastomotic vein, before neurosurgical approaches to the parietal region.

MATERIAL AND METHODS

Thirty four patients were subjected to cerebral angiography. Measurements of different points related to the anatomy of the vein were taken in 41 studies on the lateral projection. A statistical analysis was performed.

CONCLUSIONS

The measures obtained are of practical utility to locate the final portion of the vein of Trolard in its anastomotis to the sagittal superior sinus (SLS) for planning neurosurgical approaches to the parietal region.

[Prevalence of electrocardiographic abnormalities in 2,000 aged and non-aged chagasic patients]

PURPOSE

To assess the prevalence of main electrocardiographic alterations in chagasic patients at University of Triângulo Mineiro Medical School, and compare such alterations between aged and non-aged patients.

METHODS

Electrocardiograms (ECG) of 2,000 chagasic patients were interpreted. Age, color, sex and concomitant systemic hypertension, congestive heart failure (CHF) and megaesophagus and/or megacolon were registered. Chi-square test was employed to compare aged (60 years or more; n = 378) and non-aged (age less than 60 years; n = 1622) chagasics.

RESULTS

ECG were normal in 9.6% of the patients. The main alterations were: ventricular premature complexes (VPC) 42.2%, left ventricular enlargement (LVE) 38.8%, right bundle branch block (RBBB) 32.4%, left anterior hemiblock 29.2% and ventricular repolarization changes 28.2%. The aged group exhibited greater (p < 0.05) proportion of male patients (1.7:1 vs 1.1:1), white than non-white (3.6:1 vs 2.2:1) and larger percentages (p < 0.01) of systemic hypertension (18.2 vs 7.5) and CHF (26.4 vs 12.0). The following alterations were significantly more common on aged chagasic: VPC (62.7 vs 37.5), LVE (43.4 vs 37.1), atrial fibrillation (19.6 vs 5.5), supraventricular premature complexes (11.9 vs 5.2), electrically inactive zone (9.5 vs 6.6), wandering atrial pacemaker (4.5 vs 2.2) and 2nd-degree atrioventricular (AV) block (2.9 vs 1.5). The non-aged chagasic had greater percentage (p < 0.05) than aged group of normal ECG (10.7 vs 5.0), RBBB (34.1 vs 24.9) and 1st degree AV block (9.7 vs 6.3).

CONCLUSION

There was a high prevalence of ECG alterations in chagasic patients seeking medical attention. The different frequencies of those alterations between aged and non-aged chagasic may result of conditions more frequently seen in aged, like ischemic heart disease, CHF and systemic hypertension or to a probable more severe cardiac denervation in non-aged chagasic.

Characterization of a candidate gene for GP72, an insect stage-specific antigen of Trypanosoma cruzi

The Trypanosoma cruzi insect stage-specific antigen GP72 was purified from epimastigotes and the amino acid sequences of peptide fragments determined. Oligonucleotides derived from these data were used to amplify and clone a cDNA sequence, which was used to isolate a full-length gene. All the sequenced peptides were encoded within the gene. The characteristics of the encoded 62,600-Da protein, including a potential amino-terminal signal sequence, a hydrophobic carboxy-terminus, and a large number of potential O-glycosylation sites, are consistent with the properties of GP72. No sequence homologies were found in searches of DNA and protein data banks. GP72 is encoded by a single pair of non-telomeric allelic genes.

Variations induced by different methodologies in Trypanosoma cruzi surface antigen profiles

An attempt was made to reconcile published data on the cell surface profile of Trypanosoma cruzi epimastigotes. Cloned parasites were used to compare the effects of centrifugal forces, radioiodination catalyst and protein solubilization methods on the autoradiographic profile of putative surface antigens. Harvesting and washing procedures, and antigen extraction methods, greatly influenced the results obtained, whilst the iodination catalyst was not of critical importance. Mobility in different gel electrophoresis systems, Western blots and partial proteolysis maps indicated that two previously described epimastigote-specific surface antigens (GP72 and Mr 75,000) possibly are distinct molecules.

A common major surface antigen on amastigotes and promastigotes of Leishmania species

Enzymatic surface iodination and biosynthetic labeling with [35S]methionine, combined with immunoprecipitation by sera from patients with different forms of Leishmaniasis revealed a 65,000 Mr glycoprotein as the immunodominant moiety in promastigotes and amastigotes of the nine Leishmania species and isolates examined. Sera from patients with one form of Leishmaniasis recognized this component strongly, not only in the homologous, but also in the heterologous species. In addition to the crossreactivity displayed by immune sera, the 65,000 Mr glycoprotein (gp) common to all Leishmania species presented a characteristic shift to Mr 50,000 when samples were run in sodium dodecyl sulfate-polyacrylamide gel electrophoresis under nonreducing conditions. These results are in agreement with our previous studies (7), where a simple and similar profile was obtained for several geographic isolates of L. donovani, with a major surface glycoprotein of 65,000 Mr displaying the same characteristics described here. The structural similarity of the major 65,000 Mr gp of the six Leishmania species was demonstrated by Cleveland mapping. It is suggested that immunological specificities may be contributed by minor differences in glycosylation of this molecule. In keeping with recent data (13-15), where strong cross protection among different Leishmania species has been obtained by prophylactic immunization with irradiated whole promastigotes, this glycoprotein may be a good candidate for an antigen to be used for immunoprophylaxis of all forms of Leishmaniasis.

Apparent generation of a segmented mRNA from two separate tandem gene families in Trypanosoma cruzi

Using a cDNA for an abundant Trypanosoma cruzi mRNA as probe, we have cloned and sequenced a gene which is organized in at least 20 nearly perfect tandem repeats of 940 base pairs. The 5' end of the mRNA has been sequenced by primer extension and found to contain a 35 nucleotide mini-exon (or spliced-leader) sequence that is ubiquitous in trypanosome mRNAs. This sequence, however, is not present in the tandem genomic repeats which encode the exon containing the major portion of the mRNA. Previous studies have shown that the 35-nucleotide sequence is encoded by a separate tandem gene family. One model to explain the formation of a segmented mRNA invokes priming of transcription by a small RNA which contains the leader sequence at its 5' end. However, northern blot analysis of total trypanosome RNA reveals a ladder of molecules larger than the mature mRNA, which appear to be faithful multimeric copies of the tandem gene. The discrete sizes of these RNAs correspond to those expected for partially processed precursors. These observations lend credence to the possibility of an alternative model where segmented mRNAs are generated by inter-molecular splicing.

Effect of treatment on the cellular composition of cutaneous lesions in leprosy patients

We report on the cellular composition of the cutaneous lesions of 38 leprosy patients prior to and after 12-18 months of chemotherapy. All of the patients with tuberculoid (TT) disease had OKT4/OKT8 ratios that exceeded 1.0. In the indeterminate patients, the ratio varied depending upon the immune status of the individual. A low ratio of OKT4/OKT8 cells (0.25) was found in the LL patients as previously reported. The low ratio of OKT4/OKT8 in the lesions of lepromatous patients did not undergo significant changes after treatment in spite of a marked reduction in the number of intracellular bacilli.

Minichromosomal repetitive DNA in Trypanosoma cruzi: its use in a high-sensitivity parasite detection assay

We have isolated genomic clones containing members of a tandemly repeated DNA family from Trypanosoma cruzi. This family, which contains a 195-base pair (bp) repeating unit, is the most abundant repetitive DNA in this organism. DNA sequencing analysis of three adjacent tandem repeats as well as two independent nonadjacent repeats showed relatively little sequence heterogeneity. Surprisingly, the three tandem elements contained a 585-bp open reading frame. However, blot hybridization of RNA from epimastigotes as well as blood-form trypomastigotes failed to show evidence for transcription of these sequences. Fractionation of whole T. cruzi DNA in sucrose gradients or in agarose gels followed by hybridization with appropriate radioactive probes showed that the size distribution of DNA bearing the 195-bp repetitive element is distinct from that of kinetoplast DNA as well as from that of DNA bearing tubulin genes. Hybridization of the 195-bp element probe with DNA from six different T. cruzi strains was positive; hybridization with DNA of other protozoa was negative with the single exception of Leptomonas collosoma , which displayed a weak cross-hybridization signal. Clones bearing this repetitive element are shown to be useful as probes for identification and counting of T. cruzi cells by dot-blot hybridization. The sensitivity of this assay permits detection of the DNA of 30 parasites in blood samples.

Defective gamma interferon production in leprosy. Reversal with antigen and interleukin 2

Antigen and mitogen-induced gamma interferon (gamma-IFN) production was studied in peripheral blood mononuclear cells from 34 leprosy patients. 17 of 18 lepromatous leprosy and borderline lepromatous patients (LL and BL) failed to release gamma-IFN in response to specific antigen (Mycobacterium leprae) and displayed reduced responses to mitogen (concanavalin A) stimulation. In contrast, cells from six tuberculoid and borderline tuberculoid patients (TT and BT) produced considerable levels of gamma-IFN under the same experimental conditions. Normal controls failed to respond to M. leprae and most displayed good responses to concanavalin A. Mid-borderline patients (BB) showed intermediate levels of gamma-IFN release. gamma-IFN release by lepromatous patients could be partially restored with purified interleukin 2 and M. leprae antigen but not with interleukin 2 alone.

The cutaneous infiltrates of leprosy. A transmission electron microscopy study

The dermal lesions of 18 patients with leprosy have been examined by transmission electron microscopy. The patients exhibited a spectrum of disease from polar lepromatous to polar tuberculoid with intermediate stages in various states of therapy and relapse. The nature and quantities of inflammatory cells and bacteria have been determined by electron microscopy to supplement previous light and fluorescence microscopy studies. Lepromatous leprosy was characterized by many parasitized foam cells containing large, multibacillary vacuoles with intact, osmiophilic Mycobacterium leprae: Bacteria were embedded in an electron-lucent matrix. No extracellular bacteria were evident. Only small numbers of scattered lymphocytes were found. As one approached the borderline state, smaller numbers of bacilli were present as singlets and doublets in small vacuoles of macrophages. The more reactive forms showed increasing bacillary fragmentation, larger numbers of lymphoid cells, and an occasional epithelioid cell. At the tuberculoid end of the spectrum, clear evidence of an exuberant lymphocyte response was evident. Large numbers of T cells with extremely long and complex filipodia were closely associated with epithelioid and multinucleated giant cells. Many of the mononuclear phagocytes appeared nonviable, and areas of necrosis were evident. Bacillary remnants were scarce and the cytoplasm of the epithelioid cells contained occasional dense bodies and many stacks of endoplasmic reticulum and mitochondria. These results suggest that Leu 3a/OKT4 helper cells may be capable of driving the effector function of mononuclear phagocytes. This would lead to a significant microbicidal effect on M. leprae, perhaps through the production of toxic oxygen intermediates.

Surface antigens of Leishmania donovani promastigotes

Surface antigen profiles of Leishmania donovani promastigote isolates have been studied. Surface patterns of Brazilian and African isolates display remarkable similarities and are extremely simple, consisting of three major peptides of 65,000, 25,000, and 23,000 mol wt. Surface iodination and biosynthetic labeling coupled to immunoprecipitation techniques revealed that a single major determinant of 65,000 mol wt is recognized in all strains by sera from kala-azar patients from both Brazil and Africa. This major determinant is not brought down by sera from normal individuals and shows no significant cross-reactivity with sera from Chagas' disease, leprosy, or syphilis patients. Binding to concanavalin A suggests a glycoprotein nature for this antigen. Sera from patients with cutaneous leishmaniasis (L. braziliensis) also recognized the same 65,000-mol wt determinant, although to a lesser extent. The possibility that this major surface antigen is shared, with minor differences, not only by L. donovani strains but between Leishmania species in general is suggested.

The cutaneous infiltrates of leprosy: cellular characteristics and the predominant T-cell phenotypes

We report on the characteristics of cells in the cutaneous lesions and blood of 21 patients with lepromatous, tuberculoid, and intermediate forms of leprosy. A large proportion of the infiltrates in lepromatous lesions consist of macrophages heavily parasitized with Mycobacterium leprae. The T cells in the lesions are devoid of OKT4/Leu 3a-positive ("helper") cells and consist almost exclusively of OKT8/Leu 2a-positive ("suppressor") populations. In contrast, the tuberculoid infiltrates contain well-organized epithelioid and giant-cell granulomas and only remnants of bacilli, and the predominant T cell is from the OKT4/Leu 3a-positive subset. In both tuberculoid and lepromatous infiltrates, T cells and macrophages expressed HLA-DR antigen. No marked alteration in the distribution of blood T-cell phenotypes was noted. We conclude that there is a marked difference between T-cell subsets in lepromatous and tuberculoid infiltrates, which may influence the microbicidal activity of macrophages in the lesions.

Lymphokines enhance the capacity of human monocytes to secret reactive oxygen intermediates

Supernatants from mitogen- or antigen-stimulated human blood mononuclear cells enhanced the capacity of human monocytes or monocyte-derived macrophages (MDM) to release H(2)O(2) or O(2) in response to phorbol myristate acetate or zymosan. The stimulatory effect of lymphokines (LK) lasted approximately 5 d, regardless of the time of their addition. However, the magnitude of stimulation depended on whether LK were added to freshly explanted monocytes or to MDM. When LK were added on day 0 of culture, they enhanced MDM H(2)O(2)-releasing capacity approximately 40% measured on day 3, when H(2)O(2)-releasing capacity in the controls was maximal. Addition of LK on day 2 retarded the decline in H(2)O(2)-releasing capacity normally seen by day 5, so that LK-treated cells released about twice as much H(2)O(2) as the controls. Addition of LK to MDM that had already lost most of their H(2)O(2)-releasing capacity (e.g., on day 4-6) restored it to an average of 60% of the values seen with freshly explanted monocytes. In this case, LK-treated cells were about 12 times more active than cells incubated in medium alone. The effects of LK were dose- and time-dependent, with maximal effects requiring 3 d of exposure. The specific activities of superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, and myeloperoxidase, and the specific content of glutathione were not diminished in LK-treated MDM, suggesting that increased synthesis of H(2)O(2) rather than decreased catabolism probably explained the greater release of H(2)O(2) from LK-treated cells. In contrast, release of H(2)O(2) was suppressed 93+/-4% by exposing monocytes for 4 d to hydrocortisone (50%-inhibitory concentration, 1.9+/-0.3 x 10(-7) M). Thus, the oxidative metabolism of human mononuclear phagocytes can be markedly modulated in vitro: augmented by mediators released from lymphocytes during an immune response, and suppressed by antiinflammatory corticosteroids.

Trypanosoma cruzi: induction of microbicidal activity in human mononuclear phagocytes

Antigen-stimulated peripheral blood mononuclear cells from 14 patients with chronic Chagas' disease were examined for their ability to generate soluble factor(s) capable of activating human macrophages to a microbicidal state. Mononuclear cell factors (MCF) from all but one patient were capable of inducing macrophages to a state where they were able to kill trypomastigotes of Trypanosoma cruzi. Macrophage microbicidal activity against this organism was nonspecific, because it could be induced by lymphokine from PPD-positive subjects exposed to heat-killed BCG or by concanavalin A stimulation of normal donors cells. A factor(s) generated by the stimulation of mononuclear cells from normal donors by T. cruzi antigen did not induce macrophage microbicidal activity. Opsonization of the organisms with specific IgG did not alter their fate in normal macrophages, but enhanced their killing in MCF-activated cells. Induction of macrophage activation in the human system differed from the results previously described in mice in a few features: 1) Optimal microbicidal activity did not require daily addition of the soluble factors. 2) The MCF dose-response curve was shifted to lower concentrations. 3) MCF activity generated by antigen-stimulated peripheral blood lymphocytes correlates with their proliferative responses to antigen. Half of the patients showed low proliferative responses and correspondingly lower MCF activity. Mitogen responses were normal in all patients. No correlation was found between low or high responses and clinical manifestations of disease.

Trypanosoma cruzi: induction of microbicidal activity in human mononuclear phagocytes

Antigen-stimulated peripheral blood mononuclear cells from 14 patients with chronic Chagas' disease were examined for their ability to generate soluble factor(s) capable of activating human macrophages to a microbicidal state. Mononuclear cell factors (MCF) from all but one patient were capable of inducing macrophages to a state where they were able to kill trypomastigotes of Trypanosoma cruzi. Macrophage microbicidal activity against this organism was nonspecific, because it could be induced by lymphokine from PPD-positive subjects exposed to heat-killed BCG or by concanavalin A stimulation of normal donors cells. A factor(s) generated by the stimulation of mononuclear cells from normal donors by T. cruzi antigen did not induce macrophage microbicidal activity. Opsonization of the organisms with specific IgG did not alter their fate in normal macrophages, but enhanced their killing in MCF-activated cells. Induction of macrophage activation in the human system differed from the results previously described in mice in a few features: 1) Optimal microbicidal activity did not require daily addition of the soluble factors. 2) The MCF dose-response curve was shifted to lower concentrations. 3) MCF activity generated by antigen-stimulated peripheral blood lymphocytes correlates with their proliferative responses to antigen. Half of the patients showed low proliferative responses and correspondingly lower MCF activity. Mitogen responses were normal in all patients. No correlation was found between low or high responses and clinical manifestations of disease.

Specific glycoprotein antigens on the surface of insect and mammalian stages of Trypanosoma cruzi

Two major surface antigens on Trypanosoma cruzi, the causative agent of Chagas disease, have been described [Nogueira, N., Chaplan, S., Tydings, J., Unkeless, J. & Cohn, Z. (1981) J. Exp. Med. 153, 629-639]. One, a Mr 75,000 glycoprotein (GP), is specific for the culture forms (insect-host stages) of the organisms--epimastigotes and metacyclic trypomastigotes. The other, a Mr 90,000 GP, was found in vertebrate-host stages of the organisms--bloodstream-form trypomastigotes. We now report that these two major surface antigens of T. cruzi seem to be unrelated proteins, as judged by tryptic and chymotryptic peptide analysis. Antibodies were raised in rabbits against epimastigote or trypomastigote proteins which had been immunoprecipitated with human antisera. These trypomastigote and epimastigote protein antisera reacted only with the homologous immunogen, as determined by immunoprecipitation of surface-labeled organisms and by immunofluorescence. The Mr 75,000 GP is detected only in cultured (insect stage) epimastigotes and metacyclic trypomastigotes. The Mr 90,000 GP is only present in bloodstream-form trypomastigotes, amastigotes, and trypomastigotes obtained from infected muscle cells in vitro. Therefore, the insect and vertebrate stages of this species display distinctive surface GPs that can be identified by surface labeling and immunoprecipitation techniques in six strains of T. cruzi (Y, CL, Peru, Colombiana, SF-12, and SF-21) isolated from widely different areas of South America.

Trypanosoma cruzi. Surface antigens of blood and culture forms

The surface polypeptides of both cultured and blood forms of Trypanosoma cruzi were iodinated by the glucose oxidase-lactoperoxidase technique. Blood-form trypomastigotes (BFT) isolated form infected mice displayed a major 90,000-Mr component. In contrast, both epimastigotes and trypomastigotes obtained form acellular cultures expressed a smaller 75,000-Mr peptide. Both major surface components were presumably glycoproteins in terms of their binding to concanavalin A-Sepharose 4B. Within a 3-h period, both blood and culture forms synthesized their respective surface glycoproteins (90,000 Mr and 75,000 Mr, respectively in vitro. [35S]methionine-labeled surface peptides were immunoprecipitated with immune sera of both human and murine origin. A panel of sera form patients with chronic Chagas' disease and hyperimmunized mice recognized similar surface peptides. These immunogens were the same components as the major iodinated species. The major BFT surface peptide was readily removed by trypsin treatment of the parasites, although the procedure did not affect the 75,000-Mr peptide from the culture forms. Two-dimensional polyacrylamide gel electrophoresis revealed that the 90,000-Mr peptide found on BFT was an acidic protein of isoelectric point (pI) 5.0, whereas, the 75,000-Mr peptide form culture-form trypomastigotes has a pI of 7.2. The 90,000-Mr component is thought to be responsible for the anti-phagocytic properties of the BFT (1).

Lymphokine enhances the expression and synthesis of Ia antigens on cultured mouse peritoneal macrophages

Soluble products from antigen stimulated Trypanosoma cruzi-immune spleen cells enhanced the expression of Ia antigens on proteose-peptone-elicited mouse peritoneal macrophages (M phi). Acquisition of Ia paralleled M phi activation, previously shown to be mediated by this same source of lymphokine (LK). Expression of Ia and four other plasma membrane antigens was monitored by quantitative binding and radioautographic studies with 125I-monoclonal antibodies. Immune LK selectively enhanced expression of Ia and, to a lesser extent, H-2D relative to control LK from antigen-stimulated noninfected spleen. The levels of three other non-major histocompatibility complex (MHC) antigens, including the trypsin-resistant Fc receptor, were similar in cells exposed to both sources of LK. As little as 1% immune LK induced one-half maximal expression of Ia. Kinetic studies revealed that much of the Ia on freshly explanted peritoneal M phi was lost during the 1st d of culture. In the continued presence of immune LK, Ia was re-expressed on virtually all M phi by the 2nd and 3rd d. Alternatively, > 95% Ia negative populations were obtained by culturing the cells 3 d; then, addition of LK induced Ia on most cells within 1 d. Once induced, Ia persisted on the M phi surface for at least 2 d. [35S]methionine radiolabeling indicated that immune LK selectively increased radiolabeling of M phi Ia, again with other non-MHC-linked plasma membrane polypeptides as controls. LK-induced Ia-bearing M phi were tested as primary mixed leukocyte reaction stimulators. 1 x 10(5)-2 x 10(5) M phi did not stimulate 4.5 x 10(6) responding T cells, whereas 10(4) dendritic cells induced strong responses, as previously described. Because Ia-positive M phi do not actively sensitize T cells in a model immune response, we propose that M phi MHC products serve primarily as recognition sites for previously sensitized T cells, thereby enhancing T cell-mediated M phi activation.

Trypanosoma cruzi. Factors modifying ingestion and fate of blood form trypomastigotes

Blood form trypomastigotes of the Y and CL strains of Trypanosoma cruzi were tested for their ability to enter and infect mouse peritoneal macrophages. Both strains failed to enter macrophages in appreciable numbers, whereas metacyclic trypomastigotes purified from acellular cultures were ingested with ease. Macrophage parasitization was enhanced manyfold after the removal of an antiphagocytic substance by trypsinization. This occurred without modification of parasite viability. Opsonization with hyperimmune mouse serum also enhanced the uptake of blood form trypomastigotes by macrophages. This effect was mediated by the macrophage Fc receptor. The effects of serum and trypsinization were additive at high parasite:cell ratios. Neither trypsin-mediated nor antibody-dependent opsonization of the organisms modified the fate of either strain within resident macrophages. However, lymphokine-activated macrophages were capable of destroying both strains, and antibody opsonization further enhanced this process.

Activation of macrophages in vivo and in vitro. Correlation between hydrogen peroxide release and killing of Trypanosoma cruzi

As reported previously, mouse peritoneal macrophages could be activated to kill intracellular trypomastigotes of Trypanosoma cruzi, the agent of Chagas' disease, in either of two ways: by immunizing and boosting the mice (3), or by culturing resident or inflammatory macrophages in spleen cell factor(s) (SCF) in vitro (2). Macrophages activated in vivo became less trypanocidal with time in culture, and cells activated in vitro lost trypanocidal capacity when CSF was removed (2). In the present study, the ability of macrophages to release H2O2 in response to phorbol myristate acetate (PMA) could be induced in vivo and in vitro, and reversed in vitro, in a manner correlating closely with changes in trypanocidal activity. Macrophages could be activated in vitro with SCF in a time-dependent and dose-dependent fashion, so that they released as much H2O2 as macrophages activated in vivo. The sensitivity of epimastigotes and trypomastigotes to enzymatically generated H2O2 suggested that the generation of H2O2 by activated macrophages could be plausible explanation for their trypanocidal activity. Of the biochemical correlates of macrophage activation reported to date, increased ability to release H2O2 seems most closely allied to enhanced capacity to kill an intracellular pathogen.

Trypanosoma cruzi: in vitro induction of macrophage microbicidal activity

Normal, resident and inflammatory mouse peritoneal macrophages can be induced to display microbicidal activity against trypomastigotes of Trypanosoma cruzi by exposure to products from antigen-pulsed, sensitized spleen cell populations. Optimal macrophage microbicidal activity was achieved by constant exposure and daily renewal of the spleen cell factors. Macrophages obtained after an intraperitoneal injection of mild inflammatory agents were rapidly induced, displaying trypanocidal activity 24 h after exposure to the active spleen cell factor(s), and by 48 h, parasites were no longer observed. Resident peritoneal macrophages required 24 h longer for activation. Removal of the factor(s) before achieving complete disappearance of intracellular parasites led to resumed growth of the surviving organisms. The spleen cell factor(s) is effective when added either before or after exposure of the macrophages to trypomastigotes, and does not itself alter parasite viability. Dilution of the factor(s) up to 1:16 still results in significant trypanocidal activity. In vivo activated cells, obtained after a specific secondary challenge of animals infected with T. cruzi or Bacille Calmette-Guérin, lose their trypanocidal activity under in vitro conditions. This loss of activity can be prevented or restored by the addition of the active spleen cell factor(s). Induction of trypanocidal activity is also obtained with products from Concanavalin A- or lipopolysaccharide-stimulated normal spleen cells.

Trypanosoma cruzi: the immunological induction of macrophage plasminogen activator requires thymus-derived lymphocytes

In this article we describe methods in which unstimulated mouse peritoneal macrophages were induced to secrete high livels of plasminogen activator under in vitro conditions. The exposure of sensitized peritoneal or spleen cell populations from Trypanosoma cruzi-infected animals to either viable or heat-killed trypanosomes lead to the release of an inducing factor(s). Maximal levels of plasminogen activator secretion are achieved by the incubation of such factors (s) with unstimulated macrophages for 48 h. A significant increase in enzyme secretion was already observed after a 24 h incubation. The production of the inducing factor(s) by sensitized cells was immunologically specific and unrelated antigens did not stimulate the production of the factor(s) by sensitized peritoneal or spleen cell populations. The inducing factor(s) was produced by nylon-wool-fractionated spleen and peritoneal cells which had been depleted of marcrophages. Pretreatment of sensitized spleen cells with anti-theta serum and C abolished the production of the activating factor(s). The active supernatant fluids were able to induce secretion of macrophage plasminogen activator across H-2 barriers. Attempts to induce trypanocidal activity in unstimulated macrophages have not been successful.

Trypanosoma cruzi: modification of macrophage function during infection

Infection of mice with Trypanosoma cruzi and subsequent intraperitoneal challenge with heat-killed trypanosomes elicits peritoneal macrophages which display in vitro microbicidal activity against trypomastigotes of T. cruzi. These cells also display other activated properties including rapid spreading, intense membrane activity, secretion of high levels of plasminogen activator, and ingestion mediated by the C3 receptor. An intravenous infection with BCG, followed by an intraperitoneal challenge with mycobacterial antigens brings about macrophages with similar properties. These criteria of macrophage activation were compared in normal and BCG- or T. cruzi-immune mice, with or without an intraperitoneal challenge with specific or unrelated antigens. Trypanocidal activity is displayed by both BCG- and T. cruzi-immune macrophages after intraperitoneal challenge with either antigen. Resident-immune macrophages from both T. cruzi- and BCG-infected mice show a trypanostatic, rather than trypanocidal activity. Macrophages from noninfected mice, challenged with the same antigens, show neither trypanostatic nor trypanocidal activity. Increased secretion of plasminogen activator shows a definite immunological specificity. Challenge with the specific antigen induces the appearance of macrophages secreting high levels of plasminogen activator, while unrelated antigens induce much smaller levels. Noninfected mice challenged with the same antigens do not display any enchancement in secretion. In contrast, increased spreading and phagocytosis mediated by the complement receptor are also displayed by cells from noninfected mice challenged with any of the agents tested.

Trypanosoma cruzi: mechanism of entry and intracellular fate in mammalian cells

The mode of entry and intracellular fate of epimastigotes and trypomastigotes of Trypanosoma cruzi in cultured cells was studied. Electron microscopic observations indicated the uptake by phagocytosis of both forms into mouse peritoneal macrophages and of trypomastigotes and transition forms into other cultured cell types. In each instance the organisms were initially surrounded by a plasma membrane-derived phagosome. Trypsin and chymotrypsin treatment of the macrophages completely abolished attachment and ingestion of both forms, indicating that protease-sensitive structures on the macrophage plasma membrane mediate ingestion. The macrophage Fc or C3b receptors were not essential for uptake of T. cruzi in the conditions used. Cytochalasin B inhibited ingestion but not the attachment of both forms by macrophages. Epimastigotes were not taken up by HeLa, L cells, and calf embryo fibroblasts. In macrophages, epimastigotes were killed and digested within phagolysosomes. In contrast, trypomastigotes and transition forms escaped from the phagocytic vacuole and then multiplied in the cytoplasmic matrix. Amastigotes released from infected cells exhibited properties similar to those of trypomastigotes and were able to enter all cell types studied and multiply intracellularly.

Studies on the selective lysis and purification of Trypanosoma cruzi

The mechanism by which culture forms of Trypanosoma cruzi are lysed by normal mammalian sera was examined. Lysis is restricted to the epimastigote form of the organism and is not dependent on the presence of agglutinins. Lysis is a complement-dependent process, the activity being generated by the alternate pathway. The selective lysis by serum was exploited to purify viable trypomastigotes by means of centrifugation in an albumin column. Essentially pure trypomastigote populations are now being employed in cell culture experiments.