A very small viral double-stranded RNA

UmV is a double-stranded RNA (dsRNA) virus of the corn fungal pathogen Ustilago maydis. UmV has no infectious cycle. Some UmV subtypes have viral dsRNAs encoding secreted toxins that kill sensitive cells of the same species and related species. There are three viral subtypes, P1, P4 and P6, which differ in the specificity of their secreted killer toxins. Each has three size classes of dsRNA: H (heavy), M (medium) and L (light). The L segments of UmV are unique in being derived from one end of the larger M segments. We have sequenced P1 L and placed it at the 3 end of the P1 M1 plus strand. In their overlapping regions, these dsRNAs are identical in sequence. In vitro translation of P1 M1 results in a peptide whose size is consistent with its being encoded by the non-L region of M1. P1 L is a very small dsRNA of 355 bp. It has no long open reading frames and produces no detectable in vitro translation product. The sequence of P1 L suggests that it is derived by a process unique among dsRNA viruses: replication and packaging of the 3 end fragment of a processed mRNA.     

Studies on phenol and chinosol used as preservatives in tuberculin PPD solutions

Phenol and chinosol (8-hydroxyquinoline sulfate), used extensively in commercial preparations of tuberculin PPD, were compared for their antimicrobial activity and their stability during storage.     

A longitudinal study of medical specialty choice and certainty level.

Two successive classes of entering medical students at the University of Colorado participated in a longitudinal study on the development of medical specialty choice. Students indicated specialty choices and their degree of certainty about them in the freshman, sophomore, and senior years. Results indicated that students were highly uncertain of their choices at the beginning of medical school but became very certain by graduation. Nearly three-fourths switched specialties between freshman and senior years. In general, there was no relationship between degree of certainty and switching. The exception occurred in family practice. The least specialty switching occurred with internal medicine and the most with psychiatry. Increasing numbers of students chose internal medicine over the four years.     

Radiology Image Management in a Teaching Hospital Network Scenario: Initial Experience

INHS Asvini has the distinction of emerging as the first Armed Forces Hospital with networked radiology images, sourced principally from a recently installed Digital Substraction Angiography (DSA) machine (Siemens Polystar Top 1000 MA). In recent times, newer imaging machines offer digital images that are in DICOM format. DICOM denotes ‘Digital Imaging and Communications in Medicine”. Image management at INHS Asvini, involves transfer of DSA images in DICOM format, their conversion into Joint Photographic Experts Group (JPG) format and subsequent transmission of JPG images through a robust networking system that connects all departments/OPD/Wards, facilitating direct access of images to a variety of specialists and specialities. Clearly, this encouraging outcome is a small but useful step heralding the concept of ‘anytime anywhere’ images, and has the scalable expansibility of including CT and MRI images in future.Key Words: DICOM, Hospital network, Image management     

The function of natural killer cells: education, reminders and some good memories

The effector response of natural killer (NK) cells is determined by opposing signals received through activating and inhibitory receptors. A process termed NK cell education, which is guided by the recognition of Major Histocompatibility Complex class I (MHC-I) molecules, determines how efficiently activating receptors respond to stimulation. This ensures NK cell tolerance to healthy tissues while allowing robust responses to diseased host cells. It was thought that NK cells are educated during their development in the bone marrow and that education fixes the NK cells' functional properties. However, recent findings suggest that the function of mature peripheral NK cells can adapt to changes in their environment and that the persistent exposure to normal-self is essential to maintain NK cell reactivity. Notwithstanding, NK cell stimulation in the context of inflammation can stably improve the functional properties of NK cells.     

Thrombopoietin contributes to neuronal damage in experimental bacterial meningitis

Thrombopoietin (Tpo), which primarily regulates megakaryopoiesis, and its receptor (c-Mpl) are expressed in the brain, where Tpo exhibits proapototic effects on neurons. In the present study, we investigated the implication of Tpo in experimental pneumococcal meningitis. Following intrathecal infection with the encapsulated Streptococcus pneumoniae strain D39, we observed upregulation of Tpo mRNA expression at 12 h and 24 h in brain homogenates of wild-type C57BL/6 mice. c-Mpl mRNA expression was upregulated at 12 h and returned to baseline at 24 h. Compared to wild-type mice, mutants with homozygous Tpo receptor ablation (c-Mpl(-/-)) displayed reduced microglial activation and neuronal apoptosis in the dentate gyrus. Concentrations of bacteria in blood or cerebrospinal fluid (CSF), as well as CSF pleocytosis, were not significantly different between wild-type and c-Mpl(-/-) mice. In human postmortem brain, Tpo protein was colocalized to macrophages during encephalitis. In murine primary microglia and RAW264.7 macrophages, upregulation of Tpo mRNA was induced by D39-conditioned medium but not by bacterial lipopeptide or by medium conditioned by pneumococcal mutants defective in hydrogen peroxide formation (ΔspxB) or pneumolysin (Δpln). We conclude that Tpo acts as a mediator of neuronal damage in bacterial meningitis.     

In vitro activity of new artemisinin derivatives against Plasmodium falciparum clinical isolates from Gabon

Nowadays, artemisinins are the mainstay of malaria treatment, but initial indications of resistance against clinically used derivatives are present. In this study, ten new artemisinin derivatives were tested in vitro against Plasmodium falciparum laboratory strains as well as clinical isolates from Gabon. All derivatives were highly active, with 50% inhibitory concentrations (IC(50) values) <13 nM in the clinical isolates. The activity of one fluoro-containing derivative did not correlate with that of the parent compound, suggesting a different activity profile. New artemisinin derivatives with different activity profiles are of special interest as they represent an important class of candidates for pre-clinical testing in clinical parasite isolates adapted to currently used artemisinins, since derivatisation is one possible strategy to prolong the clinical usefulness of this important class of antimalarials.