Characterization and cytochemical localization of an ATP diphosphohydrolase from Leishmania amazonensis promastigotes.

An ATP diphosphohydrolase was identified in the plasma membranes isolated from promastigote forms of Leishmania amazonensis. Both ATP and ADP were hydrolysed at similar rates by the enzyme. Other nucleotides such as UTP, GTP and CTP were also degraded, revealing a broad substrate specificity. Adding ATP and ADP simultaneously, the amount of hydrolysis achieved was compatible with the presence of a single enzyme. ATPase activity was not affected by addition of vanadate, ouabain, thapsigargin, dicyclohexylcarbodiimide, oligomycin and bafilomycin A, thus excluding involvement of P-, F- and V-type ATPases. The effects of pH in the range 6.5-8.5 were examined using ATP or p-NPP as substrate. At pH 7.4, the phosphatase activity decreased, and did not show a significant contribution to ATP hydrolysis. In addition, the enzyme was not inhibited by levamisole and ammonium molybdate, excluding alkaline phosphatase and nucleotidase activities, respectively. Sodium azide (5-10 mM) caused inhibition of the ATP and ADP hydrolysis in a dose-dependent manner. Calcium was the best activating metal ion for both ATPase and ADPase activities. Ultrastructural cytochemical microscopy showed ATP diphosphohydrolase on the surface and flagellar pocket of the parasite. We have proposed that L. amazonensis ATP diphosphohydrolase may participate in the salvage pathway of nucleosides.

[Acute thyroiditis]. / Tiroidites agudas.

We review the pathophysiology, clinical features and therapy of acute thyroiditis. Four cases are reported stressing the role of fine needle aspiration for the diagnosis of this clinical entity.

Hearing loss from combined exposures among petroleum refinery workers.

Workers from a refinery (n = 438) were interviewed, had their hearing tested and had their exposures to noise and solvents assessed. Measurements suggested that most exposures to noise and solvents were within exposure limits recommended by international agencies; however, the prevalence for hearing loss within the exposed groups ranged from 42 to 50%, significantly exceeding the 15-30% prevalence observed for unexposed groups. The adjusted odds ratio estimates for hearing loss were 2.4 times greater for groups from aromatics and paraffins (95% CI 1.0-5.7), 3 times greater for the maintenance group (95% CI 1.3-6.9) and 1.8 times greater for the group from shipping (95% CI 0.6-4.9), when compared to unexposed workers from the warehouse and health clinic. The results of acoustic reflex decay tests suggest a retrocochlear or central auditory pathway involvement in the losses observed in certain job categories. These findings indicate that factors in addition to noise ought to be considered when investigating and preventing occupational hearing loss.

[Education of the workers and their participation in occupational health programs]. / La educación de los trabajadores y su participación en los programasde salud ocupacional.

In addition to being exposed to the variables and factors that affect the health of the entire population, workers are vulnerable to other risk factors of a biological, chemical, physical, psychosocial and biotechnological nature. These factors cause work-related accidents and occupational and other work-related diseases. Biological factors may be present at workplaces and can spread rapidly in a dense population such as that of an industrial community. Chemical factors can cause acute intoxication and chronic and prepathological conditions, and physical factors include vibrations and ionizing and non-ionizing radiation. The risks related to posture, physical exertion, fatigue and stress can impair the health of healthy individuals and aggravate existing conditions in the handicapped and predisposed individuals. Finally, work practices increase the incidence of some pathological conditions. It is important to study these factors because when they are well understood they can be eliminated or controlled, and their possible harmful effects avoided. This is why prevention needs to be studied in the setting of a functional dynamic. Professionals in the field of prevention, which must include sociologists and psychologists, must train workers with the help of appropriate educational technology. Workers must participate actively in work programs, along with employers and organizations that represent them. The setting for joint participation in the field of prevention and workers' health--the enterprise in which measures are being promoted, and at the regional and national levels for framing standards and regulations, determining general policies, drawing up labor statutes, and setting up institutions for control and surveillance--imposes on the parties (particularly workers and organizations representing them) a series of rights and obligations that require training for proper observance. The author notes in particular that participation in prevention work means that workers must be given instruction in occupational health. Proper and effective training must impart an understanding of the risks, their consequences, the relationship between exposure, disease and health, and the techniques for the elimination and control of unhealthy, toxic, dangerous and uncomfortable situations, as well as an understanding of health promotion and well-being. This training must be provided by the public administration, and especially, by the institutions responsible for education, the drafting of laws and regulations, advisory services, research, and surveillance of conditions in all working situations.(ABSTRACT TRUNCATED AT 400 WORDS)