Haematological response to parvovirus B19 infection in homozygous sickle-cell disease.

Infection with human parvovirus B19 is known to cause aplastic crises in patients with homozygous sickle-cell disease. We studied the haematological consequences of parvovirus B19 infection in 280 such patients who had been followed up from birth in Jamaica. Evidence of seroconversion was routinely sought with a baculovirus-based, enzyme immunoassay in serum samples taken during aplastic crises and in all stored annual serum samples. 70% of patients had seroconverted by age 20 years; of 177 infections, haematological change was typical of aplastic crises in 118 (67%), minor in 16 (9%), and not discernible in 43 (24%). This assay increased the detection of unsuspected seroconversion-an observation important in planning a strategy for parvovirus B19 immunisation.

Force-deflection properties of superelastic nickel-titanium archwires.

This in vitro study compared the force-deflection behavior of 8 superelastic nickel-titanium orthodontic wires (0.017 x 0.025 in) under controlled moment and temperature. To simulate leveling a lateral incisor, brackets and first molar tubes without tip and angulation were used. The wires (n = 5) were ligated into stainless steel brackets attached to a plastic jig to simulate a mandibular arch. A testing machine (Instron) applied deflections of 0.2 to 2.0 mm at 35 degrees C in the lateral incisor area. Force-deflection diagrams were determined from the passive position to an activation of 2 mm and then during deactivation. Forces on deactivation at a deflection of 1 mm were compared by analysis of variance. Significant differences (P < .05) in forces were observed among wires. All wires exhibited superelastic behavior, but in stratified loading levels.

Torsional properties of commercial nickel-titanium wires during activation and deactivation.

This study evaluated torsional moments on activation and deactivation in commercial, nickel-titanium wires that are intended for use in the initial phases of orthodontic treatment. Nine commercial, rectangular nickel-titanium wires (0.017 x 0.025 in) were tested in torsion. One wire was conventional nickel-titanium, and the others were superelastic nickel-titanium wires. The specimens were tested in a torsiometer for rotations between 10 and 40 degrees in activation and deactivation. Wires E27, RF and R had the highest moments during activation and deactivation, without evidence of the plateau typical of the superelastic effect. Plateaus of constant moment were observed for wires C27, C35, E35, MO, NS, and NI. Torsional moments varied among superelastic nickel-titanium wires, even with wires that had the same transition temperature range. Some superelastic wires had torsional moments that were comparable with conventional nickel-titanium wires.

Further support for a Palaearctic origin of Leishmania.

The fossil record and systematics of murid rodents, reservoirs of zoonotic cutaneous leishmaniasis in the Palaearctic, Oriental, African, Nearctic and Neotropical, strongly support a Palaearctic origin of Leishmania. The fossil record and systematics of phlebotomine sand flies reinforce this idea. Interpretations of molecular data that place the origin of Leishmania in the Neotropical are inconsistent with the natural histories of reservoirs and vectors. The evolutionary pattern of New World rats (Sigmodontinae) indicates that they may be the most important reservoirs of zoonotic cutaneous leishmaniasis throughout their range.

Palaearctic origin of Leishmania.

The hypothesis of a Palaearctic origin of Leishmania in the early Cenozoic, dispersal to the Nearctic in the late Eocene and to the Neotropical in the Pliocene is presented. It is further hypothesized that murid rodents and their immediate ancestors have been important mammalian reservoirs since the origination of Leishmania. Biochemical, molecular, biogeographical, entomological, mammalalogical and ecological support for these hypotheses are reviewed.

Short report: a focus of Leishmania mexicana near Tucson, Arizona.

Twenty-eight white-throated woodrats (Neotoma albigula) collected in Pima County, Arizona were screened for Leishmania using culture and the polymerase chain reaction (PCR). Two rodents were culture positive. Isoenzyme analysis determined the isolates to be Leishmania mexicana. The two culture-positive and four additional rodents were determined to be Leishmania-positive by the PCR. These isolates extend the geographic and ecologic range of enzootic leishmaniasis in the United States and represent a new host record.

Leishmaniasis in Texas: prevalence and seasonal transmission of Leishmania mexicana in Neotoma micropus.

The annual prevalence of Leishmania mexicana in Neotoma micropus from 16 southern Texas localities was determined by screening 192 N. micropus using in vitro culture. Eight woodrats also were screened using the polymerase chain reaction (PCR). Forty-six Sigmodon hispidus from four localities were also tested. Seasonal transmission was investigated through trap-recapture studies at three localities and analysis of infections in juveniles. Fourteen N. micropus from four localities were culture-positive for L. mexicana, indicating an annual non-zero prevalence at these localities of 5.6-27%. Four additional infections at two foci were detected only by the PCR. Transmission occurred in the fall in each case in which season of transmission could be determined. No S. hispidus were positive. These data support the hypothesis that N. micropus is a reservoir of L. mexicana in Texas.

Isolation of Leishmania mexicana from Neotoma micropus collected in Texas.

A female Neotoma micropus infected with Leishmania was collected in Zavala County, Texas, on 15 January 1990. The infection was limited to lesions at the bases of the ears, and the parasite grew readily in Schneider's Drosophila medium supplemented with 20% fetal bovine serum. Isozyme analysis determined the parasite to be Leishmania mexicana.

Antiemetic therapy for chemotherapy-induced vomiting: metoclopramide, benztropine, dexamethasone, and lorazepam regimen compared with chlorpromazine alone.

Twenty-six children aged 4 to 15 years who were to receive cancer chemotherapy were enrolled in a double-blind, randomized, crossover trial that compared the antiemetic efficacy of a four-drug regimen (the MBDL regimen: metoclopramide, 8 mg/kg; benztropine, 0.04 mg/kg; dexamethasone, 0.7 mg/kg; lorazepam, 0.1 mg/kg), given over 24 hours, with the efficacy of chlorpromazine, 3.3 mg/kg, given in four doses over 24 hours. The MBDL regimen was more effective than chlorpromazine in both objective and subjective measures of antiemetic control. Of 26 children, 23 (89%) had less vomiting on the MBDL regimen, and 20 (77%) of 26 patients or parents preferred this regimen (p less than 0.01). The MBDL regimen reduced the number of vomiting episodes by a mean of 4.0 (p less than 0.01) and reduced the duration of vomiting by a mean of 3.7 hours (p less than 0.01). A moderate level of sedation was documented at some stage in the 24-hour period of observation in 27% on the MBDL regimen and in 35% receiving chlorpromazine. Dystonia was seen in 1 (4%) of 26 children. We conclude that the MBDL regimen is safe in children and more effective than chlorpromazine.