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J C Dias

Publications and source records attributed to J C Dias.

At least 19 recordsLinked to original sources
PubMed2006

Long-time behavior of spreading solutions of Schrödinger and diffusion equations.

We investigate the asymptotic time behavior of the solutions of a large class of linear differential equations that generalize the free-particle Schrödinger and diffusion equations, containing the standard ones as particular cases. We find general scalings that depend only on characteristic features of both the arbitrary initial condition and the Green function associated with the evolution equation. Basically, the amplitude of a long-time solution can be expressed in terms of low order moments of the initial condition (if finite) and low order spatial derivatives of the Green function. These derivatives can also be of the fractional type, which naturally arise when moments are divergent. We apply our results to a large class of differential equations that includes the fractional Schrödinger and Lévy diffusion equations. In particular, we show that, except for threshold cases, the amplitude of a packet may follow the asymptotic law t-alpha, with arbitrary positive alpha.

Journal Article↗
PubMed2004

[Chagas' disease and its control in Latin America: an analysis of possibilities].

Chagas' disease is still a major public health problem in Latin America, affecting about 15 million individuals and leaving tens of millions of others at risk, most of whom are from rural areas and are socially marginalized. The main strategies and tools for the control of the disease are related to the vectorial and transfusional transmission of the parasite. Regular programs have proven effective, as in Brazil, and they depend basically on political will and basic technical and financial conditions. Epidemiologic and operational aspects of Chagas' disease control are discussed in this study, involving the reformulation and improvement of the health systems in affected countries. The fact that control can be attained is emphasized as a challenge to Latin American governments and public health officials. Control of Chagas' disease may be an additional part of the dream of Latin American unity.

English Abstract↗
PubMed2004

Ecological aspects of the vectorial control of Chagas' disease in Brazil.

The feasibility and most important ecological aspects of vectorial Chagas' disease control are discussed. The spread and maintenance of this disease involve multiple ecological and sociopolitical factors that must be taken into account when control programs are planned, executed and evaluated. In spite of its complexity, Chagas disease can be controlled using methods that target specific mechanisms of transmission, the most important being vectorial and transfusional. Major ecological problems in Chagas' disease control do not exist, even in the case of the chemical control of triatomine vectors. The main challenges for the Brazilian Control Program at this moment are: its maintenance as a political priority; the threat of peridomestic vectors; and the consolidation of permanent horizontal and participative epidemiological surveillance systems against the vector.

Journal Article↗
PubMed2003

[Relationships between Trypanosoma cruzi transmission cycles in the county of Bambuí, Minas Gerais, Brazil].

This study examines recent relationships between domestic and sylvatic transmission cycles of T. cruzi in the county of Bambuí, MG, Brazil. In the late l930s, Panstrongylus megistus was found in 75% of houses. Subsequently, Triatoma infestans became the predominant species, found in 20% of urban households and in more than 60% of periurban homes. With intense insecticide control campaigns between l956 and l969, T. infestans was eradicated from the county, transmission of Chagas' disease to man was interrupted, and P. mesgistus appeared in rural residences. Samples of T. cruzi isolated by xenodiagnosis and hemoculture from 43 opossums (Didelphis albiventris) captured in both peridomiciliary and sylvatic areas were characterized by isoenzyme analysis and--regardless of isolation method--were found to present the Z1 zymodeme profile. Through the "Chagas' Disease Epidemiological Surveillance Program", from August l986 to December l988, 154 specimens of P. megistus were captured by the local population in both peridomiciliary and intradomiciliary environments, of which 9.8% were infected with T. cruzi. In isoenzyme analyses of l3 T. cruzi strains isolated from these triatomines, six were found to be of the Z1 zymodeme (sylvatic transmission cycles) and seven were found to be of the Z2 zymodeme (domestic transmission cycle). The capture of P. megistus specimens in intradomiciliary environments that were naturally infected with parasites of both cycle types indicates an overlap of transmission cycles of Chagas' disease in the county of Bambuí. Further evidence for the interrelationship of the two cycles was provided by the isolation of T. cruzi of the Z2 zymodeme from a cat and the participation of the dog as a reservoir of Z1 T. cruzi. The presence of P. megistus in the peridomiciliary environment represents an important link between the sylvatic and intradomestic environments serving as a carrier of Z1 T. cruzi and maintaining the transmission cycles of Z2 T. cruzi in the peridomestic and intradomestic environments thus providing the potential for a gradual reinfestation of the county if the "Epidemiological Surveillance" is interrupted.

English Abstract↗
PubMed2001

Bioconversion of nitriles by Candida guilliermondii CCT 7207 cells immobilized in barium alginate.

Nitrile degradation by Candida guilliermondii CCT 7207 using free and immobilized cell systems was compared. Different specific growth rates were observed for immobilized (mumax=0.021 h(-1)) and the free cells (mumax=0.029 h(-1)). The maximum specific rate of acetic acid formation was 0.387 h(-1) and 0.266 h(-1) for free and immobilized cells, respectively. Cell adhesion to the support materials was confirmed by scanning electron microscopy. When immobilized, the yeast was able to use high nitrile and amide concentrations (aliphatic and aromatic) as nitrogen sources. The results suggest that C. guilliermondii CCT 7207 presents a physiological pattern potentially useful for the bioremediation of polluted environments or for the bioproduction of amides and organic acid of high commercial value.

Alginates↗
PubMed2001

Morphometry of submucous and myenteric esophagic plexus of dogs experimentally reinfected with Trypanosoma cruzi.

We carried out a morphometric study of the esophagus of cross-bred dogs experimentally infected or consecutively reinfected with Trypanosoma cruzi 147 and SC-1 strains, in order to verify denervation and/or neuronal hypertrophy in the intramural plexus. The animals were sacrificed in the chronic stage, 38 months after the initial infection. Neither nests of amastigotes, nor myositis or ganglionitis, were observed in all third inferior portions of esophageal rings analyzed. No nerve cell was identified in the submucous of this organ. There was no significant difference (p>0.05) between the number, maximum diameter, perimeter, or area and volume of the nerve cells of the myenteric plexus of infected and/or reinfected dogs and of the non-infected ones. In view of these results we may conclude that the 147 and SC-1 strains have little neurotropism and do not determine denervation and/or hypertrophy in the intramural esophageal plexuses in the animals studied, independent of the reinfections.

Animals↗
PubMed2001

[Chagas disease, environment, participation, and the state].

Human Chagas Disease (HCD) affects 16 million Latin Americans and is related to environmental and social questions like education, anthropogenic changes, housing, and migration. HCD requires domiciliation of the vector, which is introduced from sylvatic ecotopes or transported passively by humans. HCD is difficult to treat but possible to prevent. As a disease concentrating among poor individuals and regions, its control requires government intervention, involving education, community participation, and access to medical care. Public policies are required for HCD control, requiring participation by political parties and social control of public agencies to ensure program continuity. A consistent environmental policy is needed to prevent the spread of HCD to new areas such as the Amazon Region. Finally, partnerships among affected countries can help foster HCD control, raising self-esteem and helping promote a new political order in Latin America.

Animals↗
PubMed2000

Metabolism of benzonitrile by Cryptococcus sp. UFMG-Y28.

The yeast Cryptococcus sp. UFMG-Y28 can utilize benzonitrile as a nitrogen and possible additional carbon source. The kinetics of growth on Yeast Carbon Base (YCB) added of benzonitrile as sole nitrogen source showed that benzonitrile was metabolized to benzoic acid and ammonia. Liquid chromatography analysis indicated that Cryptococcus sp. UFMG-Y28 metabolized 12 mM benzonitrile to 10 mM benzoic acid. Resting cells cultivated on YCB-propionitrile medium showed nitrilase activity against benzonitrile. This strain appears to be promising for bioconversion of nitriles to high value acids and for bioremediation of sites contaminated with aliphatic and aromatic nitriles.

Benzoic Acid↗
PubMed2000

Enzymatic degradation of nitriles by a Candida guilliermondii UFMG-Y65.

Candida guilliermondii UFMG-Y65, isolated from a gold mine, was able to utilize different nitriles and the corresponding amides as sole source of nitrogen, at concentrations up to 2 M. Resting cells cultivated on YCB-acetonitrile medium showed nitrile hydrolyzing enzyme activities against acrylonitrile and benzonitrile. These enzymes were inducible and intracellular; the optimum pH was 7.0-8.0, and the optimum temperature 25 degrees C-30 degrees C. Liquid chromatographic analysis indicated that C. guilliermondii UFMG-Y65 metabolized 12 mM benzonitrile to 11 mM benzoic acid and 10 mM acrylonitrile to 7.9 mM acrylic acid. The results suggest that C. guilliermondii UFMG-Y65 may be useful for the bioproduction of amides and acids, and for the bioremediation of environments contaminated with nitriles.

Acetonitriles↗
PubMed2000

[Chagas disease in Brazil].

This article presents the current situation for Chagas disease vectors in Brazil, based on data from the Brazilian National Health Foundation (FNS). Over the course of the last 20 years, continuous chemical control has resulted in a clear reduction of triatomine densities and Trypanosoma cruzi in Brazilian dwellings. Results have been particularly promising in relation to Triatoma infestans and Panstrongylus megistus, considered the most important species in the past. In parallel, data from school serological surveys, hospitalized patients, and mortality records show an important decrease in the disease. Nevertheless, some areas of the Brazilian Northeast and some residual foci of Triatoma infestans and Panstrongylus megistus remain as major challenges for public health authorities, requiring effective epidemiological surveillance. States and municipalities are required to assume this task at present, as the traditional Brazilian National Health Foundation is undergoing decentralization.

Animals↗
PubMed2000

[General situation and perspectives of chagas disease in Northeastern Region, Brazil].

Primary and secondary data show the importance and distribution of human Chagas disease (HCD) in Northeast Brazil. Among the 27 detected vector species, Triatoma infestans, Panstrongylus megistus, Triatoma brasiliensis and Triatoma pseudomaculata are epidemiologically important. Major medical impact is attributed to T. infestans and P. megistus, the most domiciliated and vulnerable species, while the other two are native and more difficult to control. Regional differences in transmission and medical impact of HCD exist in the Northeast, where in general the disease appears to be less harmful than in other Brazilian regions like the Southeast and State of Goiás. There is a downward trend in HCD transmission and morbidity in the Northeast, its control in the region is a cause of concern because of the decommissioning of the National Health Foundation without a corresponding assimilation of its routine activities by regional and municipal institutions.

Adolescent↗
PubMed2000

[Epidemiological surveillance of Chagas disease].

Chagas disease still constitutes an important medical problem in affected countries. In some, the extent of the disease is still unknown and control programs have not been implemented. In others the disease has been reduced due to regular control programs and other economic and social factors. Epidemiological surveillance with community participation to guard against disease transmission is now the basic challenge. Applied research and in-depth reformulation of health systems are required to establish efficient and sustainable Chagas disease surveillance programs, considering low density of peridomiciliary vectors as the most relevant factor. In addition, a large population of already infected, poor individuals require specific medical attention and social security. As a consequence of health care decentralization, Federal institutions such as the Brazilian National Health Foundation (FNS) are being progressively decommissioned, and new participants must be engaged in the process. Communities themselves, together with regional and local institutions, must take charge of surveillance in order to guarantee its efficiency and sustainability.

Animals↗
PubMed2000

[Operational aspects of Triatoma brasiliensis control].

Vector control strategies against indigenous species is not easy, due to their capacity to reinvade treated premises from sylvatic ecotopes. Between August 1996 and December 1997 we conducted a study on reinfestation of houses after spraying in a county in the State of Ceará. Of 277 houses examined, 113 (40.8%) were infested (21.7% intradomiciliary and 35.4% peridomiciliary). Of the 433 Triatominae collected, 207 were Triatoma brasiliensis (49% of which intradomiciliary, with a mean of 1.8 insects/house) and 226 were Triatoma pseudomaculata (97% peridomiciliary). The age structure of the two indicated a univoltine development cycle for T. brasiliensis and two cycles per year for T. pseudomaculata. Four months after spraying with deltamethrin SC 25mg ia/m2, 9.7% of the houses were still positive, mainly with peridomestic infestations. Intradomiciliary wall bioassays showed persistence of the insecticide up to 9 months after spraying. Considering the high potential for recolonization of treated premises from sylvatic foci, we propose an operational strategy combining traditional evaluations and community-based surveillance with increased selective interventions and community education.

Animals↗
PubMed2000

[Health care reform, decentralization, prevention and control of vector-borne diseases].

Economic policies are changing Latin American health programs, particularly promoting decentralization. Numerous difficulties thus arise for the control of endemic diseases, since such activities traditionally depend on vertical, and centralized structures. Theoretical arguments in favor of decentralization notwithstanding, no such tradition exists at the county level. The lack of program expertise at peripheral levels, intensive staff turnover, and even corruption are additional difficulties. Hence, the simple bureaucratic transfer of activities from the Federal to county level is often irresponsible. The loss of priority for control of endemic diseases in Latin America may mean the inexorable extinction of traditional control services. Malaria, dengue fever, and Chagas disease programs are examples of the loss of expertise and effectiveness in Latin America. A better strategy for responsible decentralization is required. In particular, a shared transition involving all governmental levels is desirable to effectively modernize programs. Maintenance of regional reference centers to ensure supervision, surveillance, and training is suggested.

Animals↗
PubMed1999

The Southern Cone Initiative against Chagas disease.

Chagas disease (also known as American trypanosomiasis) is now ranked as the most serious parasitic disease of the Americas, with an economic impact far outranking the combined effects of other parasitic diseases such as malaria, schistosomiasis and leishmaniasis. Although the chronic infection remains virtually incurable, transmission can be halted by eliminating the domestic insect vectors and screening blood donors to avoid transfusional transmission. In line with this strategy, governments of the six Southern Cone countries (Argentina, Bolivia, Brazil, Chile, Paraguay and Uruguay) launched in 1991 an ambitious initiative to control Chagas disease through elimination of the main vector, Triatoma infestans, and large-scale screening of blood donors. Now at its mid-point, the programme has achieved remarkable success, with transmission halted over vast areas of the previously endemic regions. Well over 2 million rural houses have been sprayed to eliminate T. infestans, and the programme has already shown significant economic rates of return in addition to the medical and social benefits.

Animals↗
PubMed1999

The noble enigma: Chagas' nominations for the Nobel prize.

Carlos Chagas, a Brazilian physician, discovered the American trypanosomiasis in 1909. Like other remarkable discoveries of those days, his work helped to articulate the insect-vector theory and other theoretical guidelines in tropical medicine. Unlike all other discoveries, all the stages of this work were accomplished in a few months and by a single man. Chagas' discovery was widely recognized at home and abroad. He was twice nominated for the Nobel Prize - in 1913 and in 1921-, but never received the award. Evidence suggests that the reasons for this failure are related to the violent opposition that Chagas faced in Brazil. The contentions towards Chagas were related to a rejection of the meritocratic procedures that gave him prominence, as well as to local petty politics.

Brazil↗
PubMed1998

IFN-gamma in human Chagas' disease: protection or pathology?

An apparently paradoxical role for IFN-gamma in human Chagas' disease was observed when studying the pattern of cytokine production by peripheral blood mononuclear cells (PBMC) obtained from two groups of chagasic patients after specific stimulation with Trypanosoma cruzi-derived antigens. The groups studied were 1) patients treated with benznidazole during the acute phase of Trypanosoma cruzi infection and 2) chronically infected untreated patients. In the treated group, higher levels of IFN-gamma were produced by PBMC from individuals cured after treatment when compared to non-cured patients. In contrast, in the chronically infected group (not treated) higher levels of IFN-gamma were produced by PBMC from cardiac patients in comparison with asymptomatic (indeterminate) patients. This apparently paradoxical role for IFN-gamma in human Chagas' disease is discussed in terms of the possibility of a temporal difference in IFN-gamma production during the initial stages of the infection (acute phase) in the presence or absence of chemotherapy. The maintenance of an immune response with high levels of IFN-gamma production during the chronic phase of the infection may favor cure or influence the development of the cardiac form of the disease.

Chagas Disease↗