Ramifications of Vorticity on Aggregation and Activation of Platelets in Bi-Leaflet Mechanical Heart Valve: Fluid-Structure-Interaction Study.

Bileaflet mechanical heart valves (BMHV) are widely implanted to replace diseased heart valves. Despite many improvements in design, these valves still suffer from various complications, such as valve dysfunction, tissue overgrowth, hemolysis, and thromboembolism. Thrombosis and thromboembolism are believed to be initiated by platelet activation due to contact with foreign surfaces and nonphysiological flow patterns. The implantation of the valve causes nonphysiological patterns of vortex shedding behind the leaflets. This study signifies the importance of vorticity in platelet activation and aggregation in BMHV implants. A two-phase model with the first Eulerian phase for blood and the second discrete phase for platelets is used here. The generalized cross model of viscosity has been used to simulate the non-Newtonian viscosity of blood. A fluid-structure-interaction model has been used to simulate the motion of leaflets. This study has also estimated the platelet activation state (PAS), which is the mathematical estimation of the degree of activation of platelets due to flow-induced shear stresses that cause thrombus formation. The regions in the fluid domain with a higher vorticity field have been found to contain platelets with relatively higher PAS than regions with relatively lower vorticity fields. Also, this study has quantitatively reported the effect of vorticity on platelet aggregation. Platelet densities in fluid areas with higher vorticity are higher than densities in fluid areas with lower vorticity, indicating that highly activated platelets aggregate in areas with stronger vorticity.

Hepatic flexure in right sub diaphragmatic space and its embryological basis and clinical importance.

The knowledge of variations in the large intestine and liver is of clinical importance from the anatomical and embryological points of view. Different positions of the hepatic flexure of large intestine, although generally asymptomatic, may have different impact on manifestations of disease. During routine cadaveric study of the abdominal region we observed a case where the hepatic flexure was interposed between the right dome of the diaphragm and the anterior surface of the liver. The liver appeared bilobulated and on the anterior surface the right and left hepatic lobes were separated by a deep furrow. The left wall of the furrow was attached to the falciform ligament. We have tried to explain such high position of hepatic flexure from an embryological point of view and to evaluate its possible clinical relevance. This abnormal site of hepatic flexure could cause chronic respiratory infections, twisting of the gut, volvulus and intestinal obstruction. Moreover it may alter the normal liver dullness on percussion. So clinicians and surgeons should be aware of this variant position of the hepatic flexure.

Assessment of folic Acid and DNA damage in cleft lip and cleft palate.

Studies have identified the risk factors like folic acid deficiency during gestational period, family history for orofacial clefts, drugs like antiepileptic, vitamin A. But, the data regarding the folic acid status in children with cleft lip/palate is hardly evaluated in depth. Here, an assessment of folic acid and DNA damage were carried out in children with orofacial anomalies. Folic acid level and DNA damage were evaluated by folic acid assay (direct chemiluminescent technology) and single cell gel electrophoresis or comet assay method respectively. The mean value of plasma folic acid by direct chemiluminescent technology was 6.5±3.6 nmol/L and the normal value in children ranges from 11.3 to 47.6 nmol/L. The amount of damaged DNA, measured as the tail length of the comet in cases, was 19.4±8.9 µm and the mean percentage of DNA in tail was 16.5±3.7. Folic acid deficiency could be the reason for DNA damage.

Variant insertion of the fibularis tertius muscle is an evidence of the progressive evolutionary adaptation for the bipedal gait.

Fibularis tertius (FT) is often considered as part of extensor digitorum longus (EDL) muscle. The muscle is absent in hominoid apes and with the acquisition of the bipedal gait; the muscle emerged as a recent addition in the human foot. From its various modes of insertions, it is evident that the muscles of the sole are in search of its distal attachment, which can best support the relatively weak human midfoot. We describe an unusual insertion of the muscle in support of this hypothesis.