A critical evaluation of the expression of parasitemia in experimental Chagas' disease

This paper aims to study the best way to express the parasitemia of Trypanosoma cruzi's experimentally infected animals. Individual scores may have a great variability, not emphasized by the majority of the authors. A group of 50 rats infected with 1x10(6) trypomastigotes of T. cruzi Y strain was used and the parasitemia was estimated by BRENER' s method. The results showed that the median can avoid false results due to very high or low parasitemias but it does not have the mathematic properties necessary for analysis of variance. The comparison of the means of the original and transformed data, with their respective coefficients of variability (CV), showed that the logarithmic mean (Mlog) have the minor value of CV. Therefore, the Mlog is the best way to express the parasitemia when the data show great variability. The number of the animal for group did not affect the variability of data when the Mlog and CV were used.

INFLUENCE OF MICROBIOTA IN EXPERIMENTAL CUTANEOUS LEISHMANIASIS IN SWISS MICE

Infection of Swiss/NIH mice with Leishmania major was compared with infection in isogenic resistant C57BL/6 and susceptible BALB/c mice. Swiss/NIH mice showed self-controlled lesions in the injected foot pad. The production of high levels of interferon-g (IFN-g) and low levels of interleukin-4 (IL-4) by cells from these animals suggests that they mount a Th1-type immune response. The importance of the indigenous microbiota on the development of murine leishmaniasis was investigated by infecting germfree Swiss/NIH in the hind footpad with L. major and conventionalizing after 3 weeks of infection. Lesions from conventionalized Swiss/NIH mice were significantly larger than conventional mice. Histopathological analysis of lesions from conventionalized animals showed abscesses of variable shapes and sizes and high numbers of parasitized macrophages. In the lesions from conventional mice, besides the absence of abscess formation, parasites were rarely observed. On the other hand, cells from conventional and conventionalized mice produced similar Th1-type response characterized by high levels of IFN-g and low levels of IL-4. In this study, we demonstrated that Swiss/NIH mice are resistant to L. major infection and that the absence of the normal microbiota at the beginning of infection significantly influenced the lesion size and the inflammatory response at the site of infection.

Oral transmission of Chagas disease: importance of Trypanosoma cruzi biodeme in the intragastric experimental infection

Oral transmission of Trypanosoma cruzi has been suspected when epidemic episodes of acute infection were observed in areas devoid of domiciled insect vectors. Considering that the distribution of T. cruzi biodemes differs in sylvatic and domestic cycles, results of studies on biodemes can be of interest regarding oral transmission. The infectivity of T. cruzi strains of different biodemes was tested in mice subjected to infection by the digestive route (gavage). Swiss mice were infected either with the Peruvian strain (Biodeme Type I, Z2b) or the Colombian strain (Biodeme Type III, Z1, or T. cruzi I); for control, intraperitoneal inoculation was performed in a group of mice. The Colombian strain revealed a similar high infectivity and pathogenicity when either route of infection was used. However, the Peruvian strain showed contrasting levels of infectivity and pathogenicity, being high by intraperitoneal inoculation and low when the gastric route was used. The higher infectivity of the Colombian strain (Biodeme Type III) by gastric inoculation is in keeping with its role in the epidemic episodes of acute Chagas disease registered in the literature, since strains belonging to Biodeme III are most often found in sylvatic hosts.

Low efficacy of azithromycin to treat cutaneous leishmaniasis in Manaus, AM, Brazil

An open trial to evaluate the azithromycin efficacy in cutaneous leishmaniasis patients was carried out in Manaus (AM), where Leishmania (Viannia) guyanensis is the main etiologic agent. Forty-one patients with skin lesions of less than 12 weeks duration, without specific treatment for the last three months and a positive imprint to Leishmania sp. were included. From these, 31 (75.6%) were male with median age of 30.2. All of them received a daily-single oral dose of 500 mg of azithromycin for ten days. At 25th day, 16 (39%) presented therapeutic failure and received intramuscular pentavalent antimonial, four were considered lost, 21, that had improved or were inaltered received another ten-day series of azithromycin and were monthly followed, but nine (21.9%) of them presented a poor clinical response and switched to intramuscular pentavalent antimonial on day 55. Of the 12 remaining cases evaluated on day 55, despite of clinical improvement, three asked for antimony therapy and 9 (21.9%) continued the follow-up but, only three were cured on 55th, 85th and 115th days, and six did not come back for final evaluation. The intention-treatment overall response rate was 22% and whole cure was seen in three (7.3%) of cases. Thus, azithromycin showed a low efficacy to treat cutaneous leishmaniasis in Manaus.

The effects of the experimental infection from a focus of transmission of Schistosoma mansoni in a population of Biomphalaria tenagophila (D'Orbigny, 1835) in the region of "Vale do Ribeira de Iguape", Brazil

To observe the effects of the parasitic infection on the biology of B. tenagophila, field and laboratory populations of this mollusk from Itariri, in Vale do Ribeira, Brazil, were experimentally infected. Each mollusk received 10 miracidia of Schistosoma mansoni (SJ lineage) and was observed throughout the parasite's development. The biological variables were compared according to the criteria "group" and "infectious phase". The main damage caused by the parasitic infection manifested itself in reproduction, longevity and lesions on the shell of the mollusks in the patent phase. An infection rate of 58.8% was observed. Microanatomical study of the mollusk's digestive gland and ovotestis revealed the presence of evolving larval forms and cercariae. It was concluded that the effects of the parasitic infection on both populations were moderate, despite the low survival rate of the infected mollusks, the damage did not prevent either reproduction or the elimination of cercariae, which continued for a long time.

Efecto de la temperatura de la piel en la leishmaniasis cutanea experimental

The literature on the thermosensitive properties of strains or species of Leishmania and of other miercorganisms is revised. Cutaneous or mucocutaneous strains that infect animais in the coldest areas of the skin or mucosa in general can not grow in tissue culture at 37°C or higher temperatures and their respiratory metabolism decreases at these temperatures. These facts suggest a thermosensitive event in some important metabolism phase of the organisme. The strains or species that are able to produce visceral leishmaniasis were probably originated from cutaneous strains after genetioally determined physiological adaptation, to warmer temperatures. These strains can not only visceralize in animais and man but will also grow in tissue culture at 36-37°C and the respiratory metabolism will be higher at such temperatures. There are reasons to believe that intermediate strains, i. e., with properties of both groupsí do exist. A thermosensitive physiological event is a more general phenomenon and examples of it can also be found in the fields of virology, bacteriology and mycology. It has practical applications since some of the diseases produced by these agents can be cured by treatments with heat or artificial fever. Experiments along these line were performed on hamsters with a Costa Rican strain of L. braziliensis as an experimental model. Even after intraperitoneal inoculation lesions appear in the nose, ears, paws and tail with a subcutaneous temperature bellow 33°C at 22-24°C. Healing of the lesión is accomplished by increasing room temperature. A good lesión is produced in the rump of the animal if the area is depilated (comercial cream depilatory) previously and the naked skin cooled artificially. Elevated temperature, or the growing back of the hair will tend to diminish or cure the lesion.

Trypanosoma (herpetosoma) Rangeli tejera, 1920: influence of host weight, size of inoculum, and route of infection upon experimental parasitemia

To study the influence of host age, inoculum size, and route of infection on Trypanosoma (Herpetosoma) rangeli, 12 lots of 6.0 g albino mice (NMRI strain) were infected up. with from 25x10¹ to 25x10(6) trypomastigotes/gram body weight harvested from LIT medium. The lower inocula produced low but persistent parasitemias, while the higher inocula produced high levels of parasitemia that fell quickly, suggesting the mobilization of resistance mechanisms. In other experiments, i.p. inoculation produced higher parasitemias than s.c. inoculation, and 6.0 g mice had higher parasitemias than 16.0 or 26.0 g mice. Thus, a standard methodology would seem to be necessary in the study of the various strains and/or species that may make up the T. rangeli complex.

Human immune responses during schistosomiasis mansoni

Studies of immune responses as they occur in patients with schistosomiasis appear to progress relative to corrent technological advances, and to advance despite the understandable inability to pursue in vivo manipulations in this host/parasite system. Emphasis is most often placed on making immunological comparisons between such patient groups as reinfected/non-reinfected, intestinals/hepatosplenic, high/low intensities of infection, infected/uninfected within endemic areas, and those born of infected/uninfected mothers. Based on these types of comparisons, reasonable conjectures can be made regarding the immunological occurrences during this chronic exposure condition. Some consideration is now being given to the immune mechanisms of some of the observations made, and while some of these must then be carried back to experimental models for further manipulation-based analysis, new technological developments continue to assist in the field/bench ability to ask questions that might assist our understanding to a point where this knowledge can be applied to shaping developmental approaches to vaccine development and the goal of alleviating morbidity.

Adverse reactions associated with a Fuenzalida-Palacios rabies vaccine: a quasi-experimental study

The Fuenzalida-Palacios rabies vaccine has been used in South America for rabies post-exposure prophylaxis. To determine the frequency of adverse reactions associated with this vaccine compared to a control group a quasi-experimental study was carried out in Uberlândia, Brazil, from May 1997 to April 1998. Victims of bites or other injuries by dogs or other mammals and who received or not post-exposure prophylaxis with Fuenzalida-Palacios rabies vaccine were compared as to the occurrence of a list of signs and symptoms. Out of 2,440 victims of bites and other injuries from dogs and other mammals 2,114 participated in the study; 1,004 of them provided follow-up information within 10 to 15 days. Headache and pain at the injection sites were the most commonly found symptoms (125/1,000). No neuroparalytic event was detected. Patients who were given Fuenzalida-Palacios rabies vaccine and those who were not had similar incidences of symptoms (risk ratios close to 1). Regarding the occurrence of adverse reactions, Fuenzalida-Palacios rabies vaccine is a valid alternative for rabies post-exposure prophylaxis.

Immunohistochemical expression of oestrogen and progesterone receptors during experimental acute and chronic murine Schistosomiasis mansoni

INTRODUCTION: The responsibility of Schistosoma mansoni in female infertility is still controversial. This study was conducted to evaluate the effect of acute and chronic schistosomiasis mansoni infection on the endometrium using immunohistochemical analysis of uterine hormone receptor expression. METHODS: Twenty-four nonpregnant swiss albino mice were divided into three groups: control, noninfected; acute; and chronic Schistosoma mansoni infection. Histological sections of uterine specimens were examined by light microscope with an image analyzing system to detect structural histological, estrogen receptor (ER) and progesterone receptor (PR) expression in the endometrium. RESULTS: No secretory phase was detected in the endometrium in acute and chronic Schistosoma infection. Hormone receptor expression (ER and PR) showed statistically significant differences among the groups (p< 0.05), with significant low ER hormone expression in chronic infection, compared to control proliferative, control secretory and acute infection cases, and statistically significant high PR expression in both acute and chronic infection cases compared to the control secretory cases (p< 0.05). CONCLUSIONS: Schistosomiasis mansoni seems to have an important impact on the hormone expression of affected women. Further studies to explore the mechanism of such changes are recommended.

Chest pain in the emergency room. Importance of a systematic approach

OBJECTIVE: To evaluate the efficiency of a systematic diagnostic approach in patients with chest pain in the emergency room in relation to the diagnosis of acute coronary syndrome (ACS) and the rate of hospitalization in high-cost units. METHODS: One thousand and three consecutive patients with chest pain were screened according to a pre-established process of diagnostic investigation based on the pre-test probability of ACS determinate by chest pain type and ECG changes. RESULTS: Of the 1003 patients, 224 were immediately discharged home because of no suspicion of ACS (route 5) and 119 were immediately transferred to the coronary care united because of ST elevation or left bundle-branch block (LBBB) (route 1) (74% of these had a final diagnosis of acute myocardial infarction [AMI]). Of the 660 patients that remained in the emergency room under observation, 77 (12%) had AMI without ST segment elevation and 202 (31%) had unstable angina (UA). In route 2 (high probability of ACS) 17% of patients had AMI and 43% had UA, whereas in route 3 (low probability) 2% had AMI and 7 % had UA. The admission ECG has been confirmed as a poor sensitivity test for the diagnosis of AMI ( 49%), with a positive predictive value considered only satisfactory (79%). CONCLUSION: A systematic diagnostic strategy, as used in this study, is essential in managing patients with chest pain in the emergency room in order to obtain high diagnostic accuracy, lower cost, and optimization of the use of coronary care unit beds.

Efficacy of a diagnostic strategy for patients with chest pain and no ST-segment elevation in the emergency room

PURPOSE: To evaluate the efficacy of a systematic model of care for patients with chest pain and no ST segment elevation in the emergency room. METHODS: From 1003 patients submitted to an algorithm diagnostic investigation by probability of acute ischemic syndrome. We analyzed 600 ones with no elevation of ST segment, then enrolled to diagnostic routes of median (route 2) and low probability (route 3) to ischemic syndrome. RESULTS: In route 2 we found 17% acute myocardial infarction and 43% unstable angina, whereas in route 3 the rates were 2% and 7%, respectively. Patients with normal/non--specific ECG had 6% probability of AMI whereas in those with negative first CKMB it was 7%; the association of the 2 data only reduced it to 4%. In patients in route 2 the diagnosis of AMI could only be ruled out with serial CKMB measurement up to 9 hours, while in route 3 it could be done in up to 3 hours. Thus, sensitivity and negative predictive value of admission CKMB for AMI were 52% and 93%, respectively. About one-half of patients with unstable angina did not disclose objective ischemic changes on admission. CONCLUSION: The use of a systematic model of care in patients with chest pain offers the opportunity of hindering inappropriate release of patients with ACI and reduces unnecessary admissions. However some patients even with normal ECG should not be released based on a negative first CKMB. Serial measurement of CKMB up to 9 hours is necessary in patients with medium probability of AMI.

Cellular cholesterol efflux mediated by HDL isolated from subjects with low HDL levels and coronary artery disease

OBJECTIVE: The aim of this study was to verify whether HDL particles isolated from patients with coronary artery disease (CAD) and low HDL-C had diminished ability to promote cholesterol efflux from cultured cells compared with HDL isolated from subjects without CAD and with normal HDL-C. METHODS: Smooth muscle cells isolated from human aortas cultured and radiolabeled with ³H-cholesterol were loaded with cholesterol and incubated with increasing concentrations of HDL isolated from 13 CAD patients with low HDL-C (CAD group) or from 5 controls without CAD (C group). Efflux of cellular cholesterol was measured by cellular depletion of radiolabeled cholesterol and by the appearance of ³H-cholesterol into experimental medium expressed as a percentage of total labeled cholesterol. RESULTS: Cholesterol efflux increased with the amount of HDL present in the medium, and no difference was found between groups at various HDL protein concentrations: efflux was 28 ± 6.3% (C) and 25.5 ± 8.9% (CAD) with 25 mg/mL; 34 ± 4.3% (C) and 31.9 ± 6.6% (CD) with 50 mg/mL and 39.5 ± 3.5% (C) and 37.1 ± 4.4% (CAD) with 100 mg/mL, HDL. CONCLUSION: Because the HDL fraction of CAD patients with low HDL-C have normal ability to extract cholesterol from cells of the vessel wall, it is suggested that low HDL-C atherogenicity should be ascribed to diminished concentrations of HDL particles rather than to the qualitative properties of the HDL fraction.

Effects of both ecdysone and the acclimation to low temperature, on growth and metabolic rate of juvenile freshwater crayfish Cherax quadricarinatus (Decapoda, Parastacidae)

Growth, metabolic rate, and energy reserves of Cherax quadricarinatus (von Martens, 1868) juveniles were evaluated in crayfish acclimated for 16 weeks to either 25ºC (temperature near optimum) or 20ºC (marginal for the species). Additionally, the modulating effect of ecdsyone on acclimation was studied. After 12 weeks of exposure, weight gain of both experimental groups acclimated to 25ºC (control: C25, and ecdysone treated: E25) was significantly higher than that of those groups acclimated to 20ºC (C20 and E20). A total compensation in metabolic rate was seen after acclimation from 25ºC to 20ºC; for both the control group and the group treated with ecdysone. A Q10value significantly higher was only observed in the group acclimated to 20ºC and treated with ecdysone. A reduction of glycogen reserves in both hepatopancreas and muscle, as well as a lower protein content in muscle, was seen in both groups acclimated to 20ºC. Correspondingly, glycemia was always higher in these groups. Increased lipid levels were seen in the hepatopancreas of animals acclimated to 20ºC, while a higher lipid level was also observed in muscle at 20ºC, but only in ecdysone-treated crayfish.