Methods of exposure assessment: lead-contaminated dust in Philadelphia schools.

This study was conducted to develop a method that would accurately assess children's exposure to lead in schools in Philadelphia, Pennsylvania. We examined three wipe sample protocols: one included accessible surfaces such as desktops and windowsills, the second included inaccessible surfaces such as the top of filing cabinets and light fixtures, and the third included hand wipes of the study participants. Surface wipes were collected at 10 locations from accessible and inaccessible classroom surfaces (n = 11 at each location) and from the palms of student subjects in the same locations (n = 168). We found a significant difference in lead dust concentrations determined by the three protocols (F = 4.619; 2,27 degrees of freedom; p = 0.019). Lead dust concentrations were significantly elevated at the inaccessible surfaces yet they were uniformly low on the accessible surfaces and the children's palms. These findings were consistent with observed changes in blood lead levels of study participants: after 6 months of exposure to the study locations, 156 of 168 children experienced no change in blood lead level, whereas 12 experienced only a minimal change of 1-2 microg/dL. The mere presence of lead in inaccessible dust in the school environment does not automatically constitute a health hazard because there may not be a completed exposure pathway

The human pathogen, Schistosoma mansoni, lacks the cognate sequence for human telomerase reverse transcriptase (hTERT) and relies on the snail host, Biomphalaria glabrata homologous enzyme for its intra-molluscan development.

Data Availability: Data will be made available on requestSupplementary Files are available online at: https://assets-eu.researchsquare.com/files/rs-3069723/v1/0b4848eb1c2387c026138564.pdf .The human telomerase reverse transcriptase (hTERT) is the catalytic sub-unit of the ribonuclear protein, telomerase. Together with telomerase RNA, the enzyme complex participates in the maintenance of telomeres at the proximal ends of chromosomes, adding species-specific repeats to the 3’end of the telomere. The regulation of hTERT is tightly linked to the cell cycle and cell differentiation states governing either malignancy or senescence, making it a prospective therapeutic target of cell proliferation in cancer. Malignancy behaves like a parasitic disease in that it only progresses by depending on biochemical and molecular pathways of the host. The snail host/schistosome relationship provides a facile model to examine the regulation of the cancer transcriptome, such as the gastropod homolog of hTERT. To test this hypothesis in relation to the development of larval Schistosoma mansoni in the Biomphalaria glabrata, we utilized an in-silico approach to identify the hTERT homolog of B. glabrata. The human hTERT amino acid sequence (ID 014746) shows a strong homology (E-value of 2e86) to the B. glabrata ortholog (733 amino acids, accession XP_013074763.1). BLASTp analyses using S. mansoni as the query suggested that the parasite lacks a cognate TERT. To study the regulation of the snail-like hTERT in relation to schistosome development, transcriptome analysis was performed which revealed a temporal regulation of the telomerase before and during S. mansoni infection, with an upregulation of B. glabrata hTERT transcription evident by 30 minutes after exposure to the parasite. The anti-telomerase drugs, BPPA and BIBR at 100 ng/mL before infection blocked shedding of parasite cercariae. These findings indicate that the schistosome may rely on the telomerase of its host for asexual reproduction, development and proliferation.Clement B.T. Knight Foundation

Immunobiology of schistosomiasis

Although malaria and hookworm disease appear to be on the decline, another dreaded parasitic disease-schistosomiasis-is on the increase. Presently, the number of infected individuals with schistosomes is estimated to be 250 million, and even though only a small proportion of them become sick and die, schistosomiasis remains a medical problem of great significance. The high incidence of infection of man with Schistosoma mansoni, Schistosoma japonicum or Schistosoma haematobium, as well as the chronic debilitating diseases produced, places these organisms among the world\u27s most important infectious agents. This paper discusses the nature of immunity to schistosomiasis