[Longitudinal surveillance of schistosomiasis in hilly regions of Sichuan Province from 2015 to 2019]

OBJECTIVE

To investigate the changes in the endemic situation of schistosomiasis in national surveillance sites of Sichuan Province, so as to provide the scientific evidence for formulating the schistosomiasis elimination strategy.

METHODS

From 2015 to 2019, 63 national schistosomiasis surveillance sites were assigned in Sichuan Province, in which Schistosoma japonicum infections were monitored in humans, livestock, wild feces and snails. The monitoring data were descriptively analyzed.

RESULTS

A total of 94 119 person-time local residents were serologically screened for S. japonicum infections in 63 national surveillance sites of Sichuan Province from 2015 to 2019, with sero-prevalence rates ranging from 1.28% to 3.11%, and the sero-positives were predominantly detected in local residents at ages of over 50 years and in farmers. A total of 94 119 person-time mobile populations were serologically screened for S. japonicum infections in the national surveillance sites during the 5-year period, with sero-prevalence of 1.10% to 1.59%. There were no egg-positives identified in either local residents or mobile populations. Among the 6 126 herd-time livestock detected, no egg-positives were identified, and no S. japonicum infection was detected in the 205 wild feces. Snail survey was performed covering an area of 8 484.08 hm², and 724.80 hm² snail habitats were identified, including 2.43 hm² emerging snail habitats and 63.00 hm² re-emerging snail habitats. The mean occurrence of frames with snails was 6.87% to 19.63%, and the mean density of living snails was 0.18 to 0.62 snails/0.1 m² in the national surveillance sites of Sichuan Province from 2015 to 2019; however, no S. japonicum infection was detected in snails.

CONCLUSIONS

The endemic situation of schistosomiasis has reduced to the lowest level in Sichuan Province; however, there is a rise in snail habitats, and there is still a risk of schistosomiasis resurgence. Further improvements of the surveillance system for schistosomiasis are required to achieve the goal of schistosomiasis elimination in Sichuan Province as soon as possible.

Effects of mutant Vpr/Vpx on HIV-2 assembly demonstrated by immunoelectron microscopy

The virion-associated accessory proteins Vpr and Vpx of human immunodeficiency virus type 2 (HIV-2) are required for efficient viral replication. Vpr could be important for Vpx assembly. To investigate the interaction of Vpr and Vpx with respect to the effects of reverse transcriptase (RT) activity, viral particle information and Vpx expression site directed mutagenesis was carried out to construct Vpr, Vpx and double Vpr/Vpx HIV-2 mutants. These mutants were used for infection of peripheral blood mononuclear cells (PBM), human acute lymphoblastomic leukaemia cells (CEM-CM3) and HeLa CD4+ cells. Visualization of Vpx expression was carried out using FITC and gold labelling by means of laser scanning confocal microscopy and semi quantitative immunoelectron microscopy. Intracellular and extracellular localizations of Vpx were determined by means of fine structural analysis. Up to 80-90% reduction in the RT activity, total number of viral particles, and average Vpx expression was observed after infection of target cells with the Vpr mutant strains. In addition, intracellular Vpx expression was reduced to 51.2% with the Vpr mutant. Only 0.02% Vpx expression was detected after mutation at amino acid 62. These results provide evidence that Vpr or Vpr/Vpx mutants reduce RT activity and interfere with the expression of Vpx in HIV-2 particles during viral assembly. Vpr is efficient for Vpx corporation during viral assembly.

Determination of tramadol by capillary gas chromatography with flame ionization detection. Application to human and rabbit pharmacokinetic studies

A rapid, sensitive, precise and accurate capillary gas chromatographic assay with flame ionization detection was developed for the determination of tramadol in human, rabbit, pig and dog plasma. It is comprised of only a one-step extraction procedure with dichloromethane at pH 11.15 and gas chromatography on a capillary column. The recoveries of tramadol and meperidine (internal standard) were greater than 88%. Calibration graphs were linear over the concentration range 12.5-10,000 ng/ml with a coefficient of variation, both within-day and between-day, of less than 10% at any level. The limit of detection was 8 ng/ml of plasma based on signal-to-noise ratio of 3. Six other clinically used analgesics were investigated to check for potential interferences and their analytical conditions. The specificity of this assay was checked with two major metabolites of tramadol (M1: O-demethyltramadol; M2: N-demethyltramadol). Tramadol in plasma did not decompose significantly at -20 degrees C for 56 days. Pharmacokinetic application with intravenous tramadol in humans and rabbits revealed that tramadol followed a two-compartment open model with one distribution phase and one elimination phase. The distribution and elimination half-lives in humans were 1.02 and 141.9 min. The distribution and elimination half-lives in rabbits were 7.31 and 63.2 min, respectively.

Essential role of filopodia in chemotropic turning of nerve growth cone induced by a glutamate gradient

Pathfinding of growing neurites depends on turning of the growth cone in response to extracellular cues. Motile filopodia of the growth cone are known to be critical for mediating contact-dependent guidance of the growth cone. However, whether filopodia also play an essential role in growth cone turning response induced by a diffusible chemotropic substance is unclear. Growth cones of cultured Xenopus spinal neurons exhibited chemotropic turning responses in a gradient of glutamate within a limited range of concentrations. This turning response depends on the activation of the NMDA subtype of glutamate receptors and requires the presence of extracellular Ca2+. Time-lapse differential interference contrast microscopy with quantitative analysis of filopodia dynamics showed a close correlation between an increased number of filopodia on the side of the growth cone facing the glutamate source and the turning. Such filopodia asymmetry was observed within minutes after the onset of the glutamate gradient, before any detectable turning of the growth cone. In Ca(2+)-free medium, no filopodia asymmetry was induced by the glutamate gradient, and no growth cone turning was observed. Furthermore, elimination of filopodia with a low concentration of cytochalasin B completely abolished the turning response without substantially affecting neurite extension. Thus, filopodia may be required for chemotropic guidance of the growth cone, and an asymmetry in filopodia distribution may be an early cellular event responsible for determining the direction the growth cone advances.