Rickettsia rickettsii isolation from naturally infected Amblyomma parvum ticks by centrifugation in a 24-well culture plate technique.

Rocky Mountain spotted fever is an acute illness caused by Rickettsia rickettsii (R. rickettsii) and is transmitted by the bite of ticks of the genera Dermacentor, Amblyomma and Rhipicephalus. The illness results in a high mortality rate and may be easily confused with other febrile syndromes. In Yucatan State, Mexico, childhood cases with a high mortality have been reported. In this work we report the isolation of a Mexican R. rickettsii strain from a tick egg mass using an alternative method for Rickettsia isolation with 24-well plates. We also identified a potential vector of R. rickettsii in the southeast of Mexico, which is Amblyomma parvum.

Assessment of the effectiveness of descending aortomyoplasty for nonischemic cardiac failure by means of the subendocardial viability index.

INTRODUCTION: Paraaortic or external aortic counterpulsation is been investigated as a definitive ventricular assistance in cases of terminal congestive heart failure and when heart transplantation is counterindicated. Our aims is to assess the haemodynamic effects of an descending aortomyoplasty in a biological model of congestive heart failure. MATERIALS AND METHODS: As specimens, we used 10 "Large White" pigs. Mean weight was 25,3+/-2,14 Kg. After the administration of conventional anaesthesia, dissection of the latissimus dorsi muscle was performed. Then we performed a thoracotomy at the level of the fourth intercostal space to reach the thoracic aorta. The aorta is dissected 7 centimetres from the output of the subclavia artery and it is wrapped by the dissected muscle. A cardiomyostimulator is provided in order to allow the synchronization between the diastole and the muscle contraction. The model of heart failure was provoked using Verapamil plus Propanolol i.v. RESULTS: A significant increase of the systolic and diastolic aortic pressure (54,2+/-4,05 and 27.5+/-6.77 mmHg versus 76.5+/-6.25 and 56.4+/-5.2 mmHg, p<0,001) and a significant decrease of the left ventricle telediastolic pressures were observed (12.9+/-9 versus 2.6+/-1.57 mmHg, p<0,001). An increase of the cardiac output (0.363+/-0.11 versus 0.846+/-0.08 L/min, p<0,001) and the Subendocardial Viability Index (0.968+/-0.076 versus 1.351+/-0,107, p<0,001)were observed in a model of non-ischemic heart failure. CONCLUSION: Descending Aortomyoplasty as a technique to support circulation in cases of acute heart failure, improves the parameters of ventricular function, aiding the functional recovery of the left ventricle and improving significantly cardiac output as well as diastolic and systolic cardiac pressure. In addition to this, improves the Subendocardial Viability Index in cases of acute heart failure, which indirectly reflects an improvement of the Transmural and Subendocardial Perfusion of the failing heart.

Protective effect of melatonin against oxidative stress induced by ligature of extra-hepatic biliary duct in rats: comparison with the effect of S-adenosyl-L-methionine.

In the present research, we studied the effect of the administration of melatonin or S-adenosyl-L-methionine (S-AMe) on oxidative stress and hepatic cholestasis produced by double ligature of the extra-hepatic biliary duct (LBD) in adult male Wistar rats. Hepatic oxidative stress was evaluated by the changes in the amount of lipid peroxides and by the reduced glutathione content (GSH) in lysates of erythrocytes and homogenates of hepatic tissue. The severity of the cholestasis and hepatic injury were determined by the changes in the plasma enzyme activities of alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (AP), g-glutamyl-transpeptidase (GGT), and levels of albumin, total bilirubin (TB) and direct bilirubin (DB). Either melatonin or S-AMe were administered daily 3 days before LBD, and for 10 days after biliary obstruction. LDB caused highly significant increases in plasma enzyme activities and in bilirubin and lipid peroxides levels in erythrocytes and hepatic tissue. At the same time, this procedure produced a notable decrease in the GSH pools in these biological media. Both melatonin and S-AMe administration were effective as antioxidants and hepatoprotective substances, although the protective effects of melatonin were superior; it prevented the GSH decrease and reduced significantly the increases in enzyme activities and lipid peroxidation products produced by biliary ligature. S-AMe did not modify the increased GGT activity nor did it decrease greatly the TB levels (43% melatonin vs. 14% S-AMe). However, S-AMe was effective in preventing the loss of GSH in erythrocytes and hepatic tissue, as was melatonin. The obtained data permit the following conclusions. First, the LDB models cause marked hepatic oxidative stress. Second, the participation of free radicals of oxygen in the pathogenecity and severity of cholestasis produced by the acute obstruction of the extra-hepatic biliary duct is likely. Third, the results confirm the function of S-AMe as an antioxidant and hepatoprotector. Finally, melatonin is far more potent and provides superior protection as compared to S-AMe. Considering the decrease in oxidative stress and the intensity of cholestasis, these findings have interesting clinical implications for melatonin as a possible therapeutic agent in biliary cholestasis and parenchymatous liver injury.

Respiratory cryptosporidiosis: case series and review of the literature.

Five case of intestinal cryptosporidiosis with pulmonary involvement in patients with AIDS are reported. The diagnosis was based on the recognition of acid-fast oocysts in sputum or aspirated bronchial material and stool specimens. Coughing and excess secretions were present in all cases. Four patients had other associated pulmonary pathogens: two Mycobacterium tuberculosis, one Mycobacterium fortuitum and one Cytomegalovirus + Pneumocystis carinii; all of them had a previous (three cases) or simultaneous (one case) diagnosis of intestinal cryptosporidiosis, presenting with diarrhoea and vomiting. In the fifth patient Cryptosporidium was the only pulmonary pathogen found in a bronchial aspirate, and the onset of diarrhoea was 1 month after respiratory detection. Fifty-seven cases of respiratory cryptosporidiosis have been reported since 1980. In 17 of them, no other pathogen was found. Diarrhoea was present in 77% of the patients, cough in 77%, dyspnea in 58%, expectoration in 54%, fever in 45%, thoracic pain in 33%.

Evaluation of the optimal number of faecal specimens in the diagnosis of cryptosporidiosis in AIDS and immunocompetent patients.

This study determines the optimal number of faecal samples that should be examined in order to minimize the occurrence of false-negative results in the diagnosis of cryptosporidiosis using routine techniques. A total of 23,023 faecal samples from 10,870 patients submitted for parasitological examination were processed by the formalin-ethyl acetate concentration technique and stained using a modified Ziehl-Neelsen method. Cryptosporidiosis was diagnosed in 232 patients (2.13%), 44 of whom were infected by HIV, the prevalence rate in this population group being 15.54%. The increase in the number of diagnoses obtained by the examination of n and (n-1) specimens was evaluated statistically. This study found that three is the optimal number of faecal samples that should be examined when cryptosporidiosis is suspected in immunocompetent patients; whereas, only two samples are required for diagnosing this protozoosis in AIDS patients.

[Investigation in medical technology: support for cooperation among countries]. / La investigación en tecnología médica: apoyo a la cooperación entre países.

This paper discusses the results of the research work on medical technology in several countries by research teams whose goals are to prompt the exchange of information and support practical cooperation. Emphasis is placed on the work developed by the Pan American Health Organization, which has supported 45 research proposals on medical technology and stimulated the association of academic groups, national institutions and international agencies. The authors also describe the research activities of the team devoted to medical technology research at the National Institute of Public Health in Mexico.