Antero-posterior axis of tibia in patient undergoing total knee replacement in Indian population.

INTRODUCTION: Aim of this CT- based study was to find out a reliable anatomical axis for proper rotational placement of the tibial component during knee replacement surgery in the Indian population. MATERIAL AND METHODS: CT scanning was performed pre-operatively on all the 45 patients (13 men, 32 women, total 68 knees) due to undergo knee replacement for osteo-arthritic knees. The tibial anteroposterior (AP) axis is defined as a line drawn perpendicular to the surgical epicondylar femoral axis and passing through the center of posterior cruciate ligament (PCL) attachment. Angles between various anatomic landmarks and the defined tibial AP axis were identified. RESULTS: The mean angle between line connecting the medial border of patellar tendon and centre of PCL and the defined tibial AP axis was 0.06 (-5 to 7; SD 2.65) and was closest to defined AP axis of tibia. This axis remained the closest irrespective of the varying femoro-tibial angle and severity of tibial bowing. DISCUSSION: In our patients, the line connecting the medial border of patellar tendon to the centre of the PCL has been found to be an independent, reliable and reproducible rotational axis for placing the tibial trial and definitivite prosthesis. This is particularly helpful for those surgeons, who prepare the femur earlier than the tibial cut and trial. CONCLUSION: This tibial AP axis along with other anatomical landmarks is a reliable and reproducible landmark for implanting the tibial prosthesis in a proper rotational alignment in the Indian population.

Helical versus all-trans conformations of oligo(ethylene glycol)-terminated alkanethiol self-assembled monolayers.

The complex mixture of conformational states exhibited by oligo(ethylene glycol)-terminated alkanethiols on Ag and Au surfaces is explored by polarization-dependent X-ray absorption spectroscopy. Three self-assembled monolayers (SAMs) with known helical or all-trans conformations are used as references to characterize a SAM with unknown conformations. This case study is used as a prototype for developing a systematic framework to extract the conformations of SAMs from the polarization dependence of several orbitals. In the case at hand, these are associated with the C-H/Rydberg bonds of the alkane, the C-H/Rydberg bonds of ethylene glycol, and the C-C bonds of the backbone. The C-H/Rydberg orbitals of the alkane and ethylene glycol are distinguished via the chemical shift of the corresponding C 1s core levels.

Low-grade fibromyxoid sarcoma around the knee involving the proximal end of the tibia and patella: A rare case report.

Low-grade fibromyxoid sarcoma (LGFMS) is a distinctive variant of fibrosarcoma. LGFMS is a rare soft tissue tumor that tends to develop in the deep soft tissue of young adults and has the potential for local recurrence or distant metastasis. The current case report presents a 22-year-old male complaining of a slow growing painless mass in the right knee over a period of 10 years. Following complete evaluation by radiological and histopathological examination, a diagnosis of LGFMS was confirmed and a wide excision was performed. Currently, the patient has been under follow-up for the last five years without any evidence of metastasis. The present case report provides further information concerning the diagnosis, imaging and management of LGFMS.

Comparison of the influence of humidity and D-mannitol on the organization of tetraethylene glycol-terminated self-assembled monolayers and immobilized antimicrobial peptides.

We report the use of polarization-modulation infrared reflection-absorption spectroscopy (PM-IRRAS) to characterize the effects of relative humidity (RH) and d-mannitol on the conformations of tetraethylene glycol (EG4)-terminated self-assembled monolayers (SAMs) and immobilized antimicrobial peptides (Cecropin P1 and a hybrid of Cecropin A (1-8) and Melittin (1-18)). These results are used to assess the extent to which d-mannitol can substitute for water in promoting conformational states of the SAMs and oligopeptides similar to those induced by hydration. Our measurements reveal a red shift of the COC asymmetric stretching vibration of the EG4-terminated SAMs with increasing humidity, consistent with a transition from a mixed all-trans/helical (7/2 helix) conformation at 0% RH to a predominantly helical conformation at 90% RH. Significantly, under dry conditions, a thin (2 nm in thickness) overlayer of d-mannitol generated the COC spectroscopic signature of the EG4-terminated SAM measured at high humidity. Comparisons of the effects of humidity and d-mannitol on the secondary structure of the two oligopeptides also revealed both to cause the amide I peak positions, which were measured in dry air (and without d-mannitol) to correspond to α-helical conformations, to undergo red-shifts. The magnitudes of the red-shifts, however, were more pronounced for dry d-mannitol than for high RH, with Cecropin P1 and the hybrid peptide exhibiting amide I peak positions under d-mannitol consistent with bulk aqueous solution secondary structures (random and ß-sheet, respectively). These results are discussed in the context of prior reports of the tendency of d-mannitol to form glassy states in the absence of water. Overall, the results presented in this paper support the hypothesis that d-mannitol can substitute, in at least some ways, for the influence of water on the conformational states of biologically relevant molecules at interfaces. The results provide guidance for the design of interfaces for water-free biologics.

Preventing disulfide bond formation weakens non-covalent forces among lysozyme aggregates.

Nonnative disulfide bonds have been observed among protein aggregates in several diseases like amyotrophic lateral sclerosis, cataract and so on. The molecular mechanism by which formation of such bonds promotes protein aggregation is poorly understood. Here in this work we employ previously well characterized aggregation of hen eggwhite lysozyme (HEWL) at alkaline pH to dissect the molecular role of nonnative disulfide bonds on growth of HEWL aggregates. We employed time-resolved fluorescence anisotropy, atomic force microscopy and single-molecule force spectroscopy to quantify the size, morphology and non-covalent interaction forces among the aggregates, respectively. These measurements were performed under conditions when disulfide bond formation was allowed (control) and alternatively when it was prevented by alkylation of free thiols using iodoacetamide. Blocking disulfide bond formation affected growth but not growth kinetics of aggregates which were ∼50% reduced in volume, flatter in vertical dimension and non-fibrillar in comparison to control. Interestingly, single-molecule force spectroscopy data revealed that preventing disulfide bond formation weakened the non-covalent interaction forces among monomers in the aggregate by at least ten fold, thereby stalling their growth and yielding smaller aggregates in comparison to control. We conclude that while constrained protein chain dynamics in correctly disulfide bonded amyloidogenic proteins may protect them from venturing into partial folded conformations that can trigger entry into aggregation pathways, aberrant disulfide bonds in non-amyloidogenic proteins (like HEWL) on the other hand, may strengthen non-covalent intermolecular forces among monomers and promote their aggregation.

Weak protein-protein interactions revealed by immiscible filtration assisted by surface tension.

Biological mechanisms are often mediated by transient interactions between multiple proteins. The isolation of intact protein complexes is essential to understanding biochemical processes and an important prerequisite for identifying new drug targets and biomarkers. However, low-affinity interactions are often difficult to detect. Here, we use a newly described method called immiscible filtration assisted by surface tension (IFAST) to isolate proteins under defined binding conditions. This method, which gives a near-instantaneous isolation, enables significantly higher recovery of transient complexes compared to current wash-based protocols, which require reequilibration at each of several wash steps, resulting in protein loss. The method moves proteins, or protein complexes, captured on a solid phase through one or more immiscible-phase barriers that efficiently exclude the passage of nonspecific material in a single operation. We use a previously described polyol-responsive monoclonal antibody to investigate the potential of this new method to study protein binding. In addition, difficult-to-isolate complexes involving the biologically and clinically important Wnt signaling pathway were isolated. We anticipate that this simple, rapid method to isolate intact, transient complexes will enable the discoveries of new signaling pathways, biomarkers, and drug targets.

Klippel Feil Syndrome: A Rare Case Report.

INTRODUCTION: In Klippel Feil syndrome, classically there is a triad of short neck, a low posterior hairline and a limited range of neck movements especially of lateral bending. In fewer than 50% of cases have all the three elements. CASE REPORT: In the present case we have found congenital Scoliosis, Sprengel deformity and there were no evidence of renal disease, congenital heart disease and neurological impairment. The present case has classical triad low posterior hairline, short neck and limited cervical range of motion. CONCLUSION: A rare case of Klippel Feil Syndrome is being presented with the aim that such cases should be identified and treated at an early stage to minimize cosmetic & social stigma to her and to her parents.

Improved recognition of error related potentials through the use of brain connectivity features.

Brain error processing plays a key role in goal-directed behavior and learning in human brain. Directed transfer function (DTF) on EEG signal brings unique features for discrimination between correct and error cases in brain-computer interface (BCI) system. We describe the first application of brain connectivity features for recognizing error-related signals in non-invasive BCI. EEG signal were recorded from 16 human subjects when they monitored stimuli moving in either correct or erroneous direction. Classification performance using waveform features, brain connectivity features and their combination were compared. The result of combined features yielded highest classification accuracy, 0:85. In addition, we also show that brain connectivity at theta band around 200 ms after stimuli carry highly discriminant information between error and correct trials. This paper provides evidence that the use of connectivity features improve the performance of an EEG based BCI.