Effect of cholesterol on the hydration properties of ester and ether lipid membrane interphases.

Fluorescence spectroscopy and Molecular Dynamics results show that cholesterol reduces water along the chains in ether lipids by changing the water distribution pattern between tightly and loosely bound water molecules. Water distribution was followed by emission spectra and generalized polarization of 6-dodecanoyl-2-dimethyl aminonaphthalene (Laurdan) inserted in 1,2-dimiristoyl-sn-glycero-3-phosphocholine (DMPC) and 1,2-di-O-tetradecyl-sn-glycero-3-phosphocholine (14: 0 Diether PC) membranes. Molecular Dynamics simulations indicate that the action of cholesterol could be different in ether PC in comparison to ester PC. In addition, Cholesterol seems to act "per se" as an additional hydration center in ether lipids. Regardless of the phase state, cholesterol both in DMPC and 14:0 Diether PC vesicles, changed the distribution of water molecules decreasing the dipole relaxation of the lipid interphase generating an increase in the non-relaxable population. Above 10% Cholesterol/14:0 Diether PC ratio vesicles' interphase present an environment around Laurdan molecules similar to that corresponding to ester PC.

Modulation of Interfacial Hydration by Carbonyl Groups in Lipid Membranes.

The lack of carbonyl groups and the presence of ether bonds give the lipid interphase a different water organization around the phosphate groups that affects the compressibility and electrical properties of lipid membranes. Generalized polarization of 1,2-di-O-tetradecyl-sn-glycero-3-phosphocholine (14:0 diether PC) in correlation with Fourier transform infrared (FTIR) analysis indicates a higher level of polarizability of water molecules in the membrane phase around the phosphate groups both below and above Tm. This reorganization of water promotes a different response in compressibility and dipole moment of the interphase, which is related to different H bonding of water molecules with phosphates (PO) and carbonyl (CO) groups.

Factores de riesgo asociados a hemorragia digestiva alta, en sala común / Risk factors associated to upper gastrointestinal bleeding in non intensive care units

Upper gastrointestinal bleeding--UGB-, as a complication, is well studied at intensive care units (ICU), but is less known in non ICU settings. Objectives: To determine incidence and risk factors of this entity at clinical hospitalization. MATERIALS AND METHODS: A case-control study of patients with gastric ulcer disease diagnosed by endoscopy who presented with melena and hematemesis. Ten controls were taken for each case, matching sex, age and prophylaxis for gastric hemorrhage. Demographic data and other know risks factors were analyzed. RESULT: We found ten bleeding case among 35070 discharges (incidence: 2.8/10000 discharges). Mortality was not increased but the number of transfusion was higher in the bleeding group. We found an assocciation betwen UGB and systemic inflammatory response syndrome--SIRS-(OR: 9.22 IC 95% 2.98-28.17) and diabetes (OR: 7.8 IC 95% 2.3-26.8). The rest of the factors studied did not rich a statistical significance. CONCLUSIONS: UGB during clinical hospitalization is a rare complication that requires an increased staying at hospital and a great number of transfusions. It may be probably associated in a positive way with diabetes and SIRS.

La hemorragia digestiva alta durante la internación es una complicación estudiada en unidades de cuidados críticos, pero se sabe poco de esta complicación en sala común. Objetivos: determinar la incidencia y factores de riesgo de esta patología en sala común. Materiales y Métodos: Estudio casocontrol. Definimos casos, pacientes con endoscopía digestiva realizada por melena o hematemesis, con diagnóstico de enfermedad ulcerosa, se tomaron 10 controles por caso, controlando edad, sexo y uso de profilaxis ulcerosa. Se analizaron datos demográficos y factores de riesgo conocidos para esta patología y se determinó la incidencia en sala común. Resultados: Se produjeron 10 episodios de sangrado sobre 35070 altas (Incidencia 2.8110.000 altas). No hubo mayor mortalidad en los casos pero si requirieron mayor número de transfusiones (1.2 versus (vs) 0.07 paquetes de glóbulos rojos sedimentados en el grupo control. P=O.OOl) y tuvieron una mayor estadía hospitalaria (13.6 vs 6.8 días en el grupo control. P=O.OOl). Existió una asociación significativa entre hemorragia digestiva y presentar SIRS (aR: 9.22 IC95%: 2.9828.17) o Diabetes (aR: 7.8 IC95%: 2.326.8), el resto de los factores no alcanzaron significancia estadística. Conclusión: La hemorragia digestiva durante la internación es una entidad poco frecuente que requiere mayor estadía hospitalaria y necesidad de transfusiones. Asociada posiblemente en forma positiva al ingreso con SIRS, Diabetes, leucocitosis y taquicardia.

Plasmodium vivax and Plasmodium chabaudi: intraerythrocytic traffic of antigenically homologous proteins involves a brefeldin A-sensitive secretory pathway.

We have used a monoclonal antibody (mAb 7C5B71) raised against the erythrocytic stages of Plasmodium vivax to identify a 148-kDa P vivax protein antigen (Pv-148) which crossreacts with an antigenically homologous 190-kDa protein of P. chabaudi (Pc-190). During parasite intraerythrocytic development Pv-148 and Pc-190 are exported into the host cell cytosol and become located in the surface membrane of the infected erythrocyte. Immunofluorescence confocal microscopy and immunoelectron microscopy studies showed that both Pv-148 and Pc-190 are released from the parasite and exported to the host cell cytoplasm in association with tubovesicular membrane (TVM) structures. Fluorescent in vivo labelling of P. chabaudi with Bodipy-ceramide followed by immunofluorescence staining with the mAb supported the association of antigenically homologous Pc-190 with TVM structures. In the presence of brefeldin A (BFA), secretion of antigenically homologous Pc-190 into the host cell cytoplasm was inhibited and the antigen remained in the parasite cytoplasm. BFA also arrested the maturation of the parasite. Taken together these results suggest that Pv-148 and Pc-190 are related parasite proteins that are transported into the host cell through a BFA-sensitive secretory pathway.

[Toxoplasma gondii infection in Amerindians of Venezuelan Amazon]. / Infección por Toxoplasma gondii en Amerindios de la selva amazónica de Venezuela.

We conducted a serological survey for Toxoplasma gondii in 121 Amerindians of the Guajibo ethnic group, 4 to 45 years of age, inhabiting Amazonas State, in the Venezuelan rain forest. The overall prevalence was 88%. Pattern of prevalence and antibody titres were compatible with constant transmission. Sex differences in antibody prevalence were not detected but antibody titres were significantly higher in females. The study is consistent with the presence of risk factors, which favour a frequent exposure of these Amerindians to T. gondii since childhood.

Malaria diagnosis by the polymerase chain reaction: a field study in south-eastern Venezuela.

A polymerase chain reaction (PCR) method that amplifies genus- and species-specific sequences present within the small subunit of ribosomal ribonucleic acid (ssRNA) genes of the human malaria parasites was used for the diagnosis of malaria in south-eastern Venezuela. One hundred blood samples were submitted to deoxyribonucleic acid extraction, PCR amplification and electrophoretic analysis of the PCR products, and the results were compared to those of routine microscopical diagnosis. The sensitivity of PCR for detection of Plasmodium vivax and P. falciparum malaria was 99% and 100%, respectively. However, 6 patients (6%) harboured parasites undetected by microscopy. The PCR assay detected a high proportion of mixed infections: 29% (17/59) of the infections microscopically diagnosed as P. vivax were shown to be mixed infections of P. vivax and P. falciparum. Forty per cent (7/17) of the individuals with a missed P. falciparum infection had received chloroquine in the previous 30 d. These results suggest that, in places where transmission of both P. vivax and P. falciparum occurs, PCR detection of malaria parasites can be a very useful complement to microscopical diagnosis in order to ascertain the true incidence of each species and for the follow-up of patients after specific treatment.

Plasmodium vivax and P. chabaudi: inter-species cross-reacting antigens.

A monoclonal antibody raised by immunization of BALB/c mice with erythrocytic stages of Plasmodium vivax was shown to react with asexual erythrocytic stages of P. chabaudi. The cross-reactivity molecules are antigens of 200 and 148 kDa in P. vivax and of 190 and 70 kDa in P. chabaudi. Immunofluorescence studies of the erythrocytic stages of P. vivax and P. chabaudi indicated that expression of these antigens increased as the parasites' developed from the ring stage to the schizont stage. In the mature trophozoites of P. chabaudi, immunoelectron microscopy revealed clusters of antigen distributed in the cytoplasm of the parasitized erythrocyte. In the schizont, packets of antigen were found associated with the parasitophorous vacuole and the cytoplasm of the infected host cell.

Sensitive detection of Plasmodium vivax in blood by a cell-ELISA using a monoclonal antibody.

An IgM monoclonal antibody (7C5B71) which reacted with the blood stages of Plasmodium vivax, but not with those of Plasmodium falciparum was used in a cell-ELISA to detect parasites in samples of peripheral blood. Blood thin smears were probed with monoclonal antibody 7C5B71 and then reacted with a peroxidase conjugate of the appropriate specificity and the insoluble chromogen amino-ethyl-carbazole. Infected cells which appeared dark red coloured were rapidly identified under a light microscope using a low magnification. The conventional microscopic examination of thin films coloured with Giemsa was used as reference test. Under laboratory conditions the test showed a positive result in samples with a level of parasitaemia of < or = 500 parasites/microliter of blood. In a preliminary field trial the test showed 100 % specificity for the diagnosis of P. vivax malaria.

Diagnosis of malaria by acridine orange fluorescent microscopy in an endemic area of venezuela.

Fluorescent (acridine orange) microscopical examination of capillary centrifuged blood (quantitative buffy coat [QBC] analysis) and Giemsa stained thick blood smears (GTS) were compared for diagnosis of malaria in blood specimens from adults living in malaria transmission areas of the States of Bolivar and Amazonas in southeastern and south Venezuela, respectively. Of a total of 198 GTS examined, 95 subjects (48%) showed parasitaemia. Among the 95 blood films with a positive GTS, 94 were judged positive by the QBC. However, positive QBC tubes were found in 29 out of 103 blood specimens with a negative GTS. Thus, relative to a GTS standard, the sensitivity and specificity of the QBC-test was 99.2% and 72%, respectively. Young trophozoites of Plasmodium vivax and P. falciparum could not be distinguished with certainty. It is confirmed that the QBC offers many advantages compared with the standard diagnosis of malaria parasites, specifically in the speed of staining and ease of interpretation. However, in places where P. falciparum and P. vivax occur, species and stage differentiation should be confirmed with the GTS.

Plasmodium vivax: detection of blood parasites using fluorochrome labelled monoclonal antibodies.

A monoclonal antibody (MoAb) 2C6111 specific for Plasmodium vivax erythrocytic stages was shown to detect parasitized erythrocytes in blood samples collected in the field. This MoAb binds to the mature trophozoite, schizont and gametes of P. vivax and upon examination of 43 wild isolates no evidence of polymorphism was found. To search for P. vivax parasites in human blood a MoAb immunofluorescent test (MoAb-IFT) was developed. The assay is based on the ability of fluorescein isothiocyanate labelled MoAb 2C6111 to combine with parasitized erythrocytes on thin blood smears. A preliminary field trial was carried out in Venezuela to determine the usefulness of MoAb-IFT for the specific diagnosis of P. vivax malaria. Blood samples collected from malarious and non-malarious individuals were examined both by standard microscopy of Giemsa stained thick blood smears (G-TS) and MoAb-IFT. The latter was specific and gave a 100% correlation with G-TS. Sensitivity was close to that usually achieved with Giemsa stained blood films.

In vivo activity of ajoene against rodent malaria.

Ajoene (4,5,9-trithiadodeca-1,6,11-triene 9-oxide), a product initially isolated from extracts of garlic (Allium sativum), was tested for its antimalarial activity in vivo in a well-characterized murine model. A single ajoene dose of 50 mg/kg, on the day of infection, suppressed the development of parasitemia; there were no obvious acute toxic effects from the tested dose. The combination of ajoene (50 mg/kg) and chloroquine (4.5 mg/kg), given as a single dose on the day of the infection, completely prevented the subsequent development of parasitemia in treated mice.

Malaria in the Amazon. Prevalence of Plasmodium falciparum antibodies in Amerindians inhabiting the Venezuelan Amazon.

The acquisition of antibodies to Plasmodium falciparum in various age groups was studied in 511 Amerindians inhabiting the north of the Venezuelan Amazon. The overall prevalence by ELISA was 91.2% and antibodies were acquired early in life. Seropositivity was 69.6% in the group aged two to five years and reached 86% at 10 years of age; 96.9% of the adults aged 31-40 years exhibited high ELISA values to P. falciparum. The high prevalence of malaria antibodies among Amazonians, from early on in life, reflects the high level of malaria transmission in that part of the world.

[The immunoenzymatic assay (ELISA) in the serodiagnosis of Plasmodium vivax]. / El inmunoensayo enzimático (ELISA) en el diagnóstico serológico de Plasmodium vivax.

ELISA was evaluated for the serodiagnosis of Plasmodium vivax using homologous antigen. This was a crude fraction obtained after detergent (NP-40) lysis of human parasitized red blood cells. Antibodies of the classes IgM, IgG, IgA were determined in a pool of eleven sera from patients with P. vivax malaria. The protein A was introduced as secondary probe to screen P. vivax antibodies in 30 sera of patients harbouring a first episode of P. vivax malaria. There was a correlation of 93% with the parasitological diagnosis and the test resulted specific and reproducible.

[Activation of suppressor cells of the delayed hypersensitivity response in BALB/c mice infected or immunized with Leishmania mexicana pifanoi]. / Activación de celulas supresoras de la respuesta de hipersensibilidad tardia en ratones BALB/c infectados o vacunados con Leishmania mexicana pifanoi.

A T suppressor cell population that specifically shut down delayed hypersensitivity responses (DHR) to the parasite was found in both BALB/c mice chronically infected with Leishmania mexicana pifanoi and in naive mice which had received a single IV supraoptimal dose of killed parasites. At the early phase of infection mice exhibited a transitory state of cell-mediated immunity against the parasite that was abrogated when lesions reached their accelerated phase of growth. Results suggest that in both infected and high-dose immunized mice, the activation of T suppressor cells of DHR is related to antigen overload.