Field evaluation of latex agglutination test for detecting urinary antigens in visceral leishmaniasis in Sudan

A latex agglutination test to detect urinary antigens for visceral leishmaniasis [VL] was studied. In 204 patients with suspected VL, KAtex had a sensitivity of 95.2% with good agreement with microscopy smears but poor agreement with 4 different serology tests. It was also positive in 2 confirmed VL cases co-infected with HIV. In all KAtex-positive confirmed cases actively followed up after treatment, the test became negative 1 month after completion of treatment. While KAtex had a specificity of 100% in healthy endemic and non-endemic controls, the direct agglutination test [DAT] was positive in 14% of the KAtex-negative healthy endemic controls. KAtex is a simple addition to the diagnostics of VL particularly at field level and as a complementary test for the diagnosis of VL in smear-negative cases with positive DAT results

Field evaluation of latex agglutination test for detecting urinary antigens in visceral leishmaniasis in Sudan

A latex agglutination test to detect urinary antigens for visceral leishmaniasis (VL) was studied. In 204 patients with suspected VL, KAtex had a sensitivity of 95.2% with good agreement with microscopy smears but poor agreement with 4 different serology tests. It was also positive in 2 confirmed VL cases co-infected with HIV. In all K4tex-positive confirmed cases actively followed up after treatment, the test became negative 1 month after completion of treatment. While IC4tex had a specificity of 100% in healthy endemic and non-endemic controls, the direct agglutination test (DAT) was positive in 14% of the KAtex-negative healthy endemic controls. KAtex is a simple addition to the diagnostics of VL particularly at field level and as a complementary test for the diagnosis of VL in smear-negative cases with positive DAT results.

A previously unclassified trypanosomatid responsible for human cutaneous lesions in Martinique (French West Indies) is the most divergent member of the genus Leishmania ss

Two cases of skin lesions similar to those caused by Leishmania parasites have been reported from Martinique. Parasites isolated from these lesions were unlike Leishmania reference strains by isoenzyme analysis and electron microscopy and were assumed to be monoxenous trypanosomatids which normally only infect invertebrates. Both strains have now been retyped by isoenzyme analysis and found to be identical to each other and distantly related to all other Leishmania species. The sequence of the 18S ribosomal RNA gene and partial sequences of the DNA polymerase alpha and RNA polymerase II largest subunit genes were obtained. These sequences indicated that the Martinique parasites clustered with L. enriettii and were basal to all other euleishmania. However, support for both the position basal to all euleishmania and the clustering with L. enriettii was low. The Martinique parasites may cluster with L. (Leishmania) or L. (Viannia) or form a novel clade within the euleishmania either with or without L. enriettii.

Synchrotron protein footprinting: a technique to investigate protein-protein interactions

Traditional approaches for macromolecular structure elucidation, including NMR, crystallography and cryo-EM have made significant progress in defining the structures of protein-protein complexes. A substantial number of macromolecular structures, however, have not been examined with atomic detail due to sample size and heterogeneity, or resolution limitations of the technique; therefore, the general applicability of each method is greatly reduced. Synchrotron footprinting attempts to bridge the gap in these methods by monitoring changes in accessible surface areas of discrete macromolecular moieties. As evidenced by our previous studies on RNA folding and DNA-protein interactions, the three-dimensional structure is probed by examining the reactions of these moieties with hydroxyl radicals generated by synchrotron X-rays. Here we report the application of synchrotron footprinting to the investigation of protein- protein interactions, as the novel technique has been utilized to successfully map the contact sites of gelsolin segment-1 in the gelsolin segment 1/actin complex. Footprinting results demonstrate that phenylalanine 104, located on the actin binding helix of gelsolin segment 1, is protected from hydroxyl radical modification in the presence of actin. This change in reactivity results from the specific protection of gelsolin segment-1, consistent with the substantial decrease in solvent accessibility of F104 upon actin binding, as calculated from the crystal structural of the gelsolin segment 1/actin complex. The results presented here establish synchrotron footprinting as a broadly applicable method to probe structural features of macromolecular complexes that are not amenable to conventional approaches.

Orphans of the AIDS epidemic in the United States: transition-related characteristics and psychosocial adjustment at 6 months after mother's death

This study has two purposes: (1) to describe the characteristics related to the transition to orphanhood for children whose mothers die from AIDS and (2) to examine the psychosocial adjustment of these children at six months following maternal death. Twenty orphans and a control sample of 40 children from the same neighbourhoods, as well as their mothers or care-givers, served as participants. Two assessments occurred: (1) prior to the death of the mother in the orphan group and (2) six months after her death. The results indicated that relatives, particularly maternal grandparents, became the new care-giver of the orphans, no more than one residential move had occurred following the mother's death, and the new care-givers were providing a stable home environment. Child psychosocial adjustment did not change following maternal death.

Following the folding of RNA with time-resolved synchrotron X-ray footprinting

The rapid mixing synchrotron X-ray footprinting technique described in this article allows nucleic acid folding and ligand binding reactions to be followed on a millisecond time resolution with single nucleotide resolution. In principle, the change in .OH protection of every nucleotide in a nucleic acid hundreds of nucleotides long can be monitored separately. In addition, a wide range of solution conditions are compatible with the radiolytic generation of .OH. These characteristics of synchrotron X-ray footprinting create opportunities for conducting thermodynamic and kinetic studies of nucleic acids that are both comprehensive and detailed. Kinetic footprinting studies of a number of systems have been initiated by the Center for Synchrotron Biosciences using this technique.

Leishmania chagasi: genotypically similar parasites from Honduras cause both visceral and cutaneous leishmaniasis in humans

In the Mediterranean region Leishmania infantum causes both visceral and cutaneous leishmaniasis. These two pathologies tend to be caused by distinct parasite zymodemes. We have studied 33 isolates of Leishmania, 2 from sandflies, 5 from visceral cases, and 26 from cutaneous cases in Honduras, to determine if there is a correlation between pathology and parasite type in the New World similar to that in the Mediterranean region. Nine of the 26 cutaneous cases were caused by L. mexicana parasites, which have not been previously reported from Honduras; the remaining 17 cutaneous cases were due to L. chagasi. Only minor differences were found between the Honduran L. chagasi parasites by random amplified polymorphic DNA, differential display, pulsed-field gel electrophoresis, and schizodemes. This suggests that in Honduras the parasite type may not be the only factor determining the clinical outcome of L. chagasi infections.

A phase I/II trial of intravenous L-2-oxothiazolidine-4-carboxylic acid (procysteine) in asymptomatic HIV-infected subjects

Twenty-four asymptomatic, HIV-1-seropositive subjects with CD4 cell counts of > or = 400/microliters participated in a Phase I/II, dose escalation trial of intravenous L-2-oxothiazolidine-4-carboxylic acid (OTC: Procysteine). Four groups of six subjects each were consecutively assigned to receive OTC at an initial dose of 3, 10, 30, or 100 mg/kg, followed by the same dose given twice weekly for 6 weeks. Increases in whole-blood glutathione were observed in the highest dosage group after 6 weeks of therapy. No effects on changes in CD4 cell counts, viral load, or proviral DNA frequency were observed among the four dosage groups, although a decline in beta 2-microglobulin levels was apparent in the highest dosage group. One subject withdrew due to headaches; other probable adverse events including rash, flushing, pruritus, lightheadedness, and diminished concentration were self-limited.

Cutaneous leishmaniasis in Tachira State, Venezuela

Cutaneous and mucocutaneous leishmaniases are widely spread in the mountainous Andean regions of South America. In Venezuela, these regions consist of the coffee-growing states of Trujillo, Merida and Tachira. Entomological and parasitological investigations in three geographically different climatic zones (Lomas Bajas, Delicias and La Grita) in Tachira state have shown a predominance of the sandfly species Lutzomyia spinicrassa (verrucarum group) and two Leishmania species, Leishmania mexicana and Leishmania braziliensis. Two transmission cycles appear to occur: a peridomestic cycle in Lomas Bajas and a sylvatic one in Delicias and La Grita.

Molecular approaches applied to the epidemiology of leishmaniasis in Venezuela

Leishmaniasis is on the increase in Venezuela (ca 30,000 new cases per year) due to deterioration in health management, increased risk groups among inmunosuppressed individuals and increased human penetration into the ecological habitats of sandfly vectors. An STD2-funded project (1989-1992) focused on the Andean state of Táchira, which showed the highest annual index of new cases (ca 200-250). The project aimed at contributing to vector/parasite identification through a combination of molecular and well established field techniques: Newly developed molecular methods distinguished among Lu. spinicrassa, Lu. youngi and Lu. townsendi. These three species of the Verrucarum group are sympatric in the Northeast of the state and could be successfully identified by CHA, DNA probes and RAPD. A Le. braziliensis specific KDNA probe used with squash blots indicated that Lu. spinicrassa is the main vector and that Le. braziliensis is the main parasite species in Táchira state, Venezuela. PCR and the Le. brasiliensis specific DNA probe, schizodemes, isoenzymes and polyclonal antibodies agreed as taxonomic criteria for classification of Leishmania isolated from parasitologically confirmed cases in Tachira. Considerable degree of antigen heterogeneity in Venezuelan Le. braziliensis complex and Le. mexicana complex isolates from Tachira suggests multiple candidate antigens for improving the specificity of immunological diagnosis. The methods developed and tested in Táchira state should be valuable in order to help solving other outstanding epidemiological problems such as following of the epidemiological impact of intervention and vector control measures in highly endemic areas. Future work (STD3 funded, 1993-1996) aims to apply these molecular techniques to a vector control pilot study in Lara state, an area showing the highest incidence of new cases in the country.

Evaluation of quinapril on regional blood flow and cardiac function in patients with congestive heart failure

Quinapril, a nonsulfhydryl ACE inhibitor, was evaluated in ten New York Heart Association (NYHA) functional class (FC) II-III CHF patients to determine its effects on regional blood flow [effective renal plasma flow (ERPF), renal blood flow (RBF), renal vascular resistance (RVR), hepatic blood flow (HBF), hepatic vascular resistance (HVR), segmental limb pressure (SLP), creatinine clearance (CRCL)] and cardiac function [left ventricular ejection fraction (LVEF)]. Previous vasodilator therapy was withdrawn 2 weeks before baseline measurements. Stable regimens of digoxin and diuretics were continued throughout the study. ERPF was assessed using p-aminohippurate (PAH), HBF by indocyanine green (ICG) clearance, and LVEF by radionuclide scintography. Segmental limb pressures were measured by Doppler flow detection. Measurements were performed at baseline (B) and after 4 weeks of quinapril therapy (10 mg BID). Quinapril increased renal (P less than 0.05) and hepatic blood flow (P = 0.06) and significantly reduced renal and hepatic vascular resistance. Glomerular filtration rate and left ventricular ejection fraction were unchanged. Mean arterial pressure and brachial segmental pressures decreased without change in heart rate. Noninvasive cardiovascular assessments indicate that quinapril improves regional blood flow while exhibiting no change in left ventricular ejection fraction, in patients with NYHA FC II-III CHF.

Extended X-ray absorption fine structure studies on the iron-containing subunit of ribonucleotide reductase from Escherichia coli

Iron K-edge X-ray absorption spectra were obtained on the protein B2, the small subunit of ribonucleotide reductase from Escherichia coli. Protein B2 contains a binuclear iron center with many properties in common with the iron center of oxidized hemerythrins. The extended X-ray absorption fine structure (EXAFS) measurements on protein B2 were analyzed and compared with published data for oxyhemerythrin. In protein B2 there are, in the first coordination shell around each Fe atom, five or six oxygen or nitrogen atoms that are directly coordinated ligands. In oxyhemerythrin there are six ligands to each iron. As in oxyhemerythrin, one of the ligands in the first shell of protein B2 is at a short distance, about 1.78 A, confirming the existence of a mu-oxo bridge. The other atoms of the first shell are at an average distance of 2.04 A, which is about 0.1 A shorter than in oxyhemerythrin. In protein B2 the Fe-Fe distance is in the range 3.26-3.48 A, and the bridging angle falls between 130 and 150 degrees. On the basis of these data, there is no direct evidence for any histidine ligands in protein B2, but the noise level leaves way for the possibility of a maximum of about three histidines for each Fe pair. The X-ray absorption spectrum of a hydroxyurea-treated sample was not significantly different from that of the native protein B2, which implies that no significant alteration in the structure of the iron site occurs upon destruction of the tyrosine radical.

Kinetic, structural, and spectroscopic identification of geminate states of myoglobin: a ligand binding site on the reaction pathway

Elementary steps or geminate states in the reaction of gaseous ligands with transport proteins delineate the trajectory of the ligand and its rebinding to the heme. By use of kinetic studies of the 765-nm optical "conformation" band, three geminate states were identified for temperatures less than approximately 100 K. MbCO, which is accumulated by photolysis between 1.2 and approximately 10 K, was characterized by our previous optical and X-ray absorption studies [Chance, B., Fischetti, R., & Powers, L. (1983) Biochemistry 22, 3820-3829]. Between 10 and approximately 100 K, geminate states that are also identified that have recombination rates of approximately 10(3) s-1 and approximately 10(-5) s-1 (40 K). Thus, it is possible to maintain a steady-state nearly homogeneous population of the slowest recombining geminate state, Mb, by regulated continuous illumination (optical pumping). Both X-ray absorption and resonance Raman studies under similar conditions of optical pumping show that the heme structure around the iron in Mb is similar to that of MbCO. In both geminate states, the iron-proximal histidine distance remains unchanged (+/- 0.02 A) from that of MbCO while the iron to pyrrole nitrogen average distance has not fully relaxed to that of the deoxy state. In MbCO the CO remains close to iron but not bound, and the Fe...CO angle, which is bent in MbCO (127 +/- 4 degrees C), is decreased by approximately 15 degrees [Powers, L., Sessler, J. L., Woolery, G. L., & Chance, B. (1984) Biochemistry 23, 5519-5523]. The CO molecule in Mb, however, has moved approximately 0.7 A further from iron. Computer graphics modeling of the crystal structure of MbCO places the CO in a crevice in the heme pocket that is just large enough for the CO molecule end-on. Above approximately 100 K resonance Raman studies show that this structure relaxes to the deoxy state.

Cytochrome c peroxidase compound ES is identical with horseradish peroxide compound I in iron-ligand distances

X-ray absorption studies of compound ES of cytochrome c peroxidase show a short iron-oxygen distance of 1.67 +/- 0.04 A, an iron-histamine distance of 1.91 +/- 0.03 A, and an iron-pyrrole nitrogen average distance of 2.02 +/- 0.02 A. This is identical within the error with the reported structure of horseradish peroxidase compound I [Chance, B., Powers, L., Ching, Y., Poulos, T., Yamazaki, I., & Paul, K. G. (1984) Arch. Biochem. Biophys. 235, 596-611]. Comparisons of the structures of myoglobin peroxide [Chance, M., Powers, L., Kumar, C., & Chance, B. (1986) Biochemistry (preceding paper in this issue)], compound ES, and the intermediates of horseradish peroxidase reveal the possible mechanisms for the stabilization of the free radical species generated during catalysis. The proximal histidine regulates the structure and function of the pyrrole nitrogens and the heme, allowing for the formation and maintenance of the characteristic intermediates.

X-ray absorption studies of myoglobin peroxide reveal functional differences between globins and heme enzymes

X-ray absorption studies of myoglobin peroxide show that although it is not identical with compound I or II of horseradish peroxidase [Chance, B., Powers, L., Ching, Y., Poulos, T., Yamazaki, I., & Paul, K. G. (1984) Arch. Biochem. Biophys. 235, 596-611], it has some structural features in common with both. As seen in compound I, the Fe-O distance is short, but the iron-pyrrole nitrogen distance is contracted with a longer iron-histidine distance like compound II. The iron has a higher oxidation state than Fe3+, suggesting an oxyferryl ion type species. Comparison of the structures of various peroxidase and myoglobin compounds points out systematic differences that may explain the catalytic activity of the pi cation radical as well as some of the differences between globins and heme enzymes.