Increased mitral valve insufficiency during precordial "whoop"

A patient with rheumatic mitral valve stenosis and regurgitation presented with shortness of breath and a "noise" in her chest. Cardiac auscultation revealed an intermittent late systolic "whoop." An increase in severity of mitral valve insufficiency during the periods of "whoop" was observed by pulsed Doppler, hemodynamic tracings and left ventriculography.     

Mutations in the retinal guanylate cyclase (RETGC-1) gene in dominant cone-rod dystrophy

The dominant cone-rod dystrophy gene CORD6 has previously been mapped to within an 8 cM interval on chromosome 17p12-p13. The retinal- specific guanylate cyclase gene (RETGC-1), which maps to within this genetic interval and previously was implicated in Leber's congenital amaurosis, was screened for mutations within this family and in a panel of small families and individuals with various cone and cone- rod dystrophy phenotypes. A missense mutation (E837D) was identified in affected members of the CORD6 family, as well as a second missense mutation (R838C) in three other families with dominant cone-rod dystrophy. RETGC-1 is only the fourth gene to be implicated in cone-rod dystrophy and this is the first report of dominant mutations in this gene.      

Comparison of antibiogram, virulence genes, ribotypes and DNA fingerprints of Vibrio cholerae of matching serogroups isolated from hospitalised diarrhoea cases and from the environment during 1997-1998 in Calcutta, India

This study identified 17 matching serogroups of Vibrio cholerae belonging to serogroups other than O1 and O139 isolated from human cases and from the environment during a concurrent clinical and environmental study conducted in Calcutta, a cholera endemic area. Isolates within these matching serogroups were compared by various phenotypic and genotypic traits to determine if the environment was the source of the organisms associated with the disease. Clinical strains of V. cholerae were resistant to a greater number of drugs and exhibited multi-drug resistance compared with their environmental counterparts. Except for the presence of the genes for the El Tor haemolysin and the regulatory element ToxR in most of the strains of V. cholerae examined, non-O1, non-O139 V. cholerae strains lacked most of the other known virulence traits associated with toxigenic V. cholerae O1 or O139. Restriction fragment-length polymorphism of virulence-associated genes, ribotypes and DNA fingerprints of strains of matched serogroups showed considerable diversity, although some gene polymorphisms and ribotypes of a few strains of different serogroups were similar. It is concluded that despite sharing the same serogroup, environmental and clinical isolates were genetically heterogeneous and were of different lineages.     

Studies on pathogenesis of fowl pox: virological study

One-month-old WLH chickens were inoculated with a field isolate of fowl pox virus (FPV) by intradermal (i.d.) and intratracheal (i.t.) routes. In intradermally infected chickens, the virus in titrable amounts was first detected in the skin at the inoculation site on day 2 and in lungs on day 4 followed by viraemia on the day 5 post-infection (p.i.). Subsequently the virus was recovered from liver, spleen, kidney and brain, but not from the heart. The chickens infected by i.t. route showed an almost similar outcome with minor differences as the virus was first demonstrated in the lungs on day 2 p.i., viraemia occurred on day 4 p.i. Initiation of pocks at the inoculation site in i.d. infected birds was observed on days 3 to 4 p.i., generalized cutaneous pock lesions appeared from 7 to 8 days p.i.     

Spurious automated red cell parameters due to cold agglutinins--a report of two cases

Although automation in hematology has resulted in improved accuracy of results, there are certain clinical conditions in which even the technologically advanced cell counters give out spurious results. It is therefore important that operators of these instruments are aware of these factitious results and the clues in the automated data that can be of help in identifying them. Two cases with spurious automated red cell parameters due to cold agglutinins are reported here.     

Use of the gel-based DiaMed-ID microtyping system for crossmatching enhances sensitivity

A host of newer techniques have been introduced over the past decade in blood bank serological testing. One such technology which has been in vogue in the west since early 1990s is the gel test. The procedures used are standardized and they provide clear and stable reactions that improve result interpretation. The principle involves the differential passage of red cell agglutinates and free red blood cells through a dextran acrylamide gel. The results are stable and may be read even after many hours. The test is easy to perform, sensitive and reproducible. We report our experience in compatibility testing with use of the DiaMed micro typing system which is based on the gel technology. Over a one year period since this technology was introduced in our blood bank, we noticed a startling 65 fold rise (p<0.0001) in the reported number of incompatible units in one year which rose from a paltry 4 (0.02%) to 260 (1.6%). We found the DiaMed system easy to use and as our findings suggest it proved to be more sensitive than the conventional tube agglutination technique.     

Glycolipids of Mycobacterium tuberculosis Strain H37Rv Are Potential Serological Markers for Diagnosis of Active Tuberculosis

A simple and cost-effective diagnostic tool (TB Screen Test) for the screening of patients with pulmonary and extrapulmonary tuberculosis and for differentiation of those individuals from individuals without tuberculosis, other common infections, and healthy controls has been developed. The serological responses of purified mycobacterial glycolipid antigens were examined by a liposome agglutination assay. The assay was able to detect very low antiglycolipid antibody concentrations in the infected individuals. The sera from the tuberculosis patient group had significantly higher concentrations of antiglycolipid antibody than the sera from uninfected control subjects, with 94% sensitivity and 98.3% specificity. Glycolipids of Mycobacterium tuberculosis H37Rv antigens were isolated, purified, and characterized. After interchelation with liposome particles, these purified antigens specifically bound to the antiglycolipid antibodies present in the sera of patients with tuberculosis, resulting in the formation of a blue agglutination. This protocol clearly differentiates healthy controls and M. bovis BCG-vaccinated subjects from those with active tuberculosis. The resultant diagnostic tool, the TB Screen Test, is more economical and rapid (4 min) than other currently available products and can be used for the mass screening of a heavily afflicted population.     

Glycosylphosphatidylinositols are required for the development of Trypanosoma cruzi amastigotes.

Induction of a glycosylphosphatidylinositol (GPI) deficiency in Trypanosoma cruzi by the heterologous expression of Trypanosoma brucei GPI-phospholipase C (GPI-PLC) results in decreased expression of major surface proteins (N. Garg, R. L. Tarleton, and K. Mensa-Wilmot, J. Biol. Chem. 272:12482-12491, 1997). To further explore the consequences of a GPI deficiency on replication and differentiation of T. cruzi, the in vitro and in vivo behaviors of GPI-PLC-expressing T. cruzi were studied. In comparison to wild-type controls, GPI-deficient T. cruzi epimastigotes exhibited a slight decrease in overall growth potential in culture. In the stationary phase of in vitro growth, GPI-deficient epimastigotes readily converted to metacyclic trypomastigotes and efficiently infected mammalian cells. However, upon conversion to amastigote forms within these host cells, the GPI-deficient parasites exhibited a limited capacity to replicate and subsequently failed to differentiate into trypomastigotes. Mice infected with GPI-deficient parasites showed a substantially lower rate of mortality, decreased tissue parasite burden, and a moderate tissue inflammatory response in comparison to those of mice infected with wild-type parasites. The decreased virulence exhibited by GPI-deficient parasites suggests that inhibition of GPI biosynthesis is a feasible strategy for chemotherapy of infections by T. cruzi and possibly other intracellular protozoan parasites.     

Modelling HA protein-mediated interaction between an influenza virus and a healthy cell: pre-fusion membrane deformation.

We present a mathematical model for pre-fusion interaction between an influenza virus and a healthy cell. Our model describes the role played by hemagglutinin (HA) protein clusters in bringing the viral membrane into close contact with the host cell membrane as a first step of the fusion process between the two membranes. The viral membrane is modelled as a lipid bilayer with bending rigidity. Using the calculus of variations, we compute the deformation of the viral membrane under the influence of HA protein clusters. Our numerical results support the hypothesis of dimple formation in the fusion site proposed in the literature. The asymmetric nature of the protein molecules due to various reasons such as tilting is the primary cause for the dimple formation. We discuss the effects of spontaneous curvature, the protein cluster radius, fusion-site size and the bending moment exerted by the protein cluster. We also examine the effects of membrane tension and the presence of a host cell on the dimple shape. Our results support previous experimental observations.