Visualizing the interaction of Acanthamoeba castellanii with human retinal epithelial cells by spontaneous Raman and CARS imaging

Improved understanding of the mechanism of nutrient’s uptake can enable targeted manipulation of nutrient sensing pathways in medically important pathogens to a greater degree than is currently possible. In this context, we present the use of spontaneous Raman micro-spectroscopy (RMS) and coherent anti-Stokes Raman spectroscopy (CARS) to visualise the time-dependent molecular interactions between the protozoan Acanthamoeba castellanii and host human cells. Human retinal pigment epithelial (ARPE-19) cells were prelabelled with deuterated Phe (L-Phe(D8)) and the uptake of the host derived L-Phe(D8) by A. castellanii trophozoites was measured by RMS for up to 48 hours post infection (hpi). This approach revealed a time-dependent uptake pattern of this essential amino acid by A. castellanii trophozoites during the first 24 hpi with complete enrichment with L-Phe(D8) detected in trophozoites at 48 hpi. In contrast, cell free A. castellanii trophozoites showed a modest uptake of only 16-18% L-Phe(D8) from L-Phe(D8)–supplemented culture medium after 3h, 24h and 48h hpi. CARS microscopy was successfully used to monitor the reprogramming of lipids within the trophozoites as they engaged with host cells. The methodology presented here provides new advances in the ability to analyze the kinetic of amino acid acquisition by A. castellanii from host cell and extracellular environment, and to visualize lipid reprogramming within the trophozoite

The agglomeration of polyethylene particles in the cell culture environment

The colloidal stability of polyethylene particles in standard cell culture conditions to gain insight into the possibility of particle agglomeration was analyzed. The change in zeta potential (zp) of the particles when suspended in solutions of varying protein species and concentrations was measured. The two particle species were shown to have very similar size distributions by number with the majority of the particles within the phagocytosable range. The zp results show a moderately negative potential for bovine serum albumin (BSA) at low concentrations, becoming less negative with increasing concentration

Lateral direction of penetration into acetabular sockets using a 32 mm diameter femoral head

A cohort of 35 explanted acetabular sockets was examined to ascertain the direction of penetration. The penetration relative to the open face of the socket was measured using the shadowgraph method and the corresponding anatomical direction was then deduced using anterior-posterior radiographs. A median anatomical penetration direction of 17.5° lateral to the sagittal plane was found (range 27° medial to 44° lateral). These observations confound explanation through analysis of the motion and loading of the hip joint.</p

The influence of femoral head surface roughness on the wear of ultrahigh molecular weight polyethylene sockets in cementless total hip replacement

A theoretical relationship was recently proposed relating the wear behavior of polymetric bearing materials articulating against hard counterfaces. This model attempts to predict the influence of surface roughness on wear. Laboratory-based studies have been used to establish the validity of these relationships, but their application to the clinical situation has not been investigated fully. Forty-two retrieved PCA hip joints have been assessed. The total wear volume was calculated from the penetration measured using the shadowgraph method, and roughness of the articulating surfaces was recorded using noncontacting profilometry. The roughness of the explanted femoral heads was observed to increase (median S(a) - 10.35 nm worn region, 3.05 nm peripheral region), while that of the acetabular liner fell dramatically (median S(a) - 41 nm worn region, 212 nm unworn region). No evidence of a relationship between the topography of the worn regions of the femoral head and that of the acetabular liner could be found. Similarly, the strength of the association between the surface roughness and the clinical wear factor was considerably poorer than that achieved in laboratory experiments. A number of reasons for this observation are proposed. Most deleterious was considered to be the inability of the roughness parameters to describe the damaging features of the surface adequately. Uncertainty as to when the surface of the component degrades during its life serves to introduce further doubt as to the application of the wear models in the clinical environment. In conclusion, this study fails to provide clinical evidence to substantiate the relationship between surface finish and wear rate. The adoption of standardized measurement parameters and techniques would facilitate the direct comparison of joint types and the selection of the most advantageous materials.</p