Incarcerated Cannulated Cancellous Screw Removal during Total Hip Arthroplasty with a Novel Trick: A Case Report.

Salvage total hip arthroplasty (THA) may be required to manage femoral neck fracture implant failures, avascular necrosis and secondary hip arthritis. Cannulated cancellous screws can become stripped or incarcerated during the initial implantation and pose hardware removal issues. We present a novel technique for safe screw removal in a 62-year-old female patient with a painful right hip. She had undergone cancellous screw fixation for a fracture of the neck of femur ten years ago. There was avascular necrosis with screw cut out leading to secondary hip arthritis necessitating THA. Intra-operatively cannulated cancellous screw along the inferior femoral neck region was incarcerated. After posterior dislocation of the head, the neck was osteotomised, and the screw threads were exposed for possible extraction. However, the thickened femoral neck region with solid cortical bone prevented the screw disengagement in either direction. The screw along the femoral trochanter region was cut with a Harrington cutter and the remaining screw disengaged with careful removal of bony spicules and controlled anticlockwise rotations, to remove the screw in around fifteen minutes. Arthroplasty could be completed uneventfully thereafter. We could remove the screw while avoiding an iatrogenic fracture along the calcar region and excessive bone loss along the screw track. The femoral canal remained uncompromised. The anticipation of a difficult implant removal with a thorough understanding of the devices and techniques, is an invaluable asset to the operating surgeon. With a simple tool and novel technique in a difficult situation, we can save on operating time and minimise complications.

Secondary structure of a calcium binding protein (CaBP) from Entamoeba histolytica.

A calcium binding protein from Entamoeba histolytica, (EhCaBP, M(r) approximately 15 kDa) is the causative agent for amoebiosis and has a very low sequence homology (approximately 30%) with other known CaBPs. Almost complete sequence specific resonance assignments for (1)H, (13)C and (15)N spins in EhCaBP were obtained using double and triple resonance NMR experiments. Qualitative interpretation of the nuclear Overhauser enhancements, chemical shift indices and of hydrogen exchange rates threw valuable light upon the secondary structure of this protein. CaBP is found to have two globular domains each of which consists of two pairs of helix-loop-helix motifs. Though this protein has a very small sequence homology with calmodulins, the topological arrangement of the alpha-helices and beta-strands in EhCaBP resemble them.

Evidence for A+(anti)-G(syn) mismatched base-pairing in d-GGTAAGCGTACC.

Two-dimensional NMR spectroscopy has been used to study the structure and hydrogen bonding scheme of A:G mismatched base pairing in d-GGTAAGCGTACC at pH 5.8. Under the conditions of our study, the molecule forms a B-DNA helix, with the mismatched bases in the A+ anti)-G(syn) conformation. The adenosine exists in the protonated form. The NOESY spectrum in 90% H2O + 10% 2H2O has been used to assign all observable imino and amino protons including those involved in the A+(anti)-G(syn) base pair. Both the proton donors in the A:G mismatched inter-base hydrogen bonding are situated on adenosine.

Solution structure of d-GAATTCGAATTC by 2D NMR. A new approach to determination of sugar geometries in DNA segments.

A new approach based on the correlated spectroscopy (COSY) in 2D NMR has been described for determination of sugar geometries in oligonucleotides. Under the usual low resolution conditions employed in COSY, the intensities of cross peaks depend on the magnitudes of coupling constants. There are five vicinal coupling constants in a deoxyribose ring which are sensitive to the sugar geometry. The presence, absence and rough comparison of relative intensities of COSY cross peaks arising from such coupling constants enable one to fix the sugar conformation to a fair degree of precision. The methodology has been applied to d-GAATTCGAATTC. It is observed that ten out of the twelve nucleotide units in this sequence exhibit a rare O1'-endo geometry. The EcoRI cleavage sites (between G and A) in the dodecanucleotide show an interesting variation in the conformation with the two sugars attached to the Gs acquiring a geometry between C2'-endo and C4'-endo.

Glucose oxidase immobilized electrode for potentiometric estimation of glucose.

Glucose oxidase has been immobilized onto a thin platinum strip, by co-crosslinking with bovine serum albumin and glutaraldehyde. The retention of redox characteristics of glucose oxidase has been verified by cyclic voltammetry. The activity of the immobilized enzyme reduces to a quarter of its value when the enzyme is in solution but improves when coimmobilized with 1 M urea. The potentiometric response builds up and remains stable after 100 s. It is sensitive to the thickness of the immobilizing matrix. pH and temperature. An improvement in the performance of the electrode has been achieved by co-immobilizing 2 M urea and metal ions such as Mg2+ and Mn2+. The presence of Cu has been proved to be detrimental. The electrode has been calibrated in the 0.1-5.0 mM glucose concentration range. It gives a stable response for more than 50 independent assays and can be stored for 60 days without significant loss of function.

Molecular mechanics calculations on a triple stranded DNA involving C+.G-T and T.A+-C mismatched base triples.

We have carried out molecular modeling of a triple stranded pyrimidine(Y). purine(R): pyrimidine(Y) (where ':' refers to Watson-Crick and '.' to Hoogsteen bonding) DNA, formed by a homopurine (d-TGAGGAAAGAAGGT) and homo-pyrimidine (d-CTCCTTTCTTCC). Molecular mechanics calculations using NMR constraints have provided a detailed three dimensional structure of the triplex. The entire stretches of purine and the pyrimidine nucleotides have a conformation close to B-DNA. The three strands are held by the canonical C+.G:C and T.A:T hydrogen bonds. The structure also contains two mismatch C+.G-T and T.A+-C base triples which have been characterized for the first time. In the A+-C base-pair of the T.A+-C triple, both hydrogen donors are situated on the purine (A+(1N) and A+(6N)). We observe a unique hydrogen bonding interaction scheme in case of C+.G-T where one acceptor, G(60), is bonded to three donors (C+(3NH), C+(4NH2) and T(3NH)). Though the C+.G-T base triple is less stable than C+.G:C, it is significantly more stable than T.A:T. On the other hand, T.A+-C is as stable as the T.A:T base triad.

Conformational studies of antiradiation agents by NMR: cysteamine and its derivatives.

The conformations of cysteamine, thiazolidine, and thiazolidine-4-carboxylic acid were determined in aqueous solutions using NMR spectroscopy. At physiological pH, the population ratio of gauche- and trans-conformers was 3:1. The gauche-rotamer is probably responsible for the antiradiation activity and acts through metal chelation involving sulfur and nitrogen atoms. The puckering of the thiazolidine ring was calculated using NMR coupling constants. The observed results were compared with those obtained in the solid state using X-ray diffraction.

Spectroscopic and microscopic studies of buffalo-bull (Bubalus bubalis) spermatozoa.

We have examined the epididymal (caput, corpus and cauda) and ejaculated spermatozoa of bufallo-bull (Bubalus bubalis) employing microscopic and spectroscopic techniques. Fluorescein isothiocyanate conjugated lectins namely concanavalin A (Con A), Dolichos biflorus (DBA), Maclura pomifera (MPA), peanut agglutinin (PNA), soybean agglutinin (SBA) and wheat germ agglutinin (WGA) were used to study the changes in the sperm surface carbohydrate make up as the spermatozoa mature. Quantitative analysis of the lectin binding was made flow cytometrically. 31P-NMR (nuclear magnetic resonance) spectra of the sperms obtained from different regions (head, body and tail) of the epididymis and of the ejaculate were analyzed to assess their metabolic activity. And the kinetics of spin label reduction of these samples was monitored with ESR (electron spin resonance) spectroscopy. These observations are supplemented with the electron microscopic (SEM and TEM) examination of the epididymal and ejaculated spermatozoa.

NMR structural characterisation of a hairpin DNA with two-base loop: solution conformation of d-GGTACIAGTACC.

An inosine-adenosine mismatched base-pair oligonucleotide, d-GGTACIAGTACC has been studied by 1H and 31P NMR spectroscopy. Almost complete 1H and 31P resonance assignments of the oligomer at 0.90 mM concentration and 310 K have been achieved. NMR results demonstrate that the oligomer adopts a hairpin conformation, which has a structure with two purines I6 and A7 forming a two-base loop on a B-DNA stem. Stacking is continued on the 5'-side of the loop, with the I6 stacked upon C5. The base A7, on the 3'-side of the loop stacks partially with I6. All the bases are in anti conformation with respect to their respective sugar moiety.

Protective effect of L-arginine against lipid peroxidation in goat epididymal spermatozoa.

L-arginine plays an important role in physiology of spermatozoa and is shown to enhance the metabolism of these cells. We report here the effect of L-arginine on membrane lipid peroxidation of goat epididymal spermatozoa. Both natural peroxidation as well as that induced by UV radiation, freezing and oxidizing agents have been studied. Irrespective of the nature of induction of peroxidation, L-arginine reduces the extent of lipid peroxidation in a concentration dependent manner. Both L-arginine and alpha-tocopherol act synergistically in protecting against lipid peroxidation induced by the above methods. Thus, in order to provide protection against lipid peroxidation, L-arginine may be added in media used to preserve spermatozoa.

Solvent induced conformational changes in renin inhibitor polypeptide.

Conformation of the renin inhibitor peptide, Pro-His-Pro-Phe-His-Phe-Phe-Val-Tyr-Lys (RIP) has been studied in aqueous solution and in lipid bilayers using 500 MHz 1H NMR spectroscopy. Analysis of the NMR parameters indicates that in aqueous solution, RIP exists as a random coil. On incorporation into lipid bilayers, the peptide adopts a rigid and well defined conformation. The N-terminal end is stabilized by the hydrophobic environment of the lipid bilayer. The C-terminal end is located near the lipid-water interface and attains rigidity due to interaction with the phosphate groups of lipids. The observations emphasize the role of environment in stabilizing significantly different conformations of RIP in three different media--D2O, DMSO and lipid bilayers.

Magnetic resonance studies on the binding of etomidate to lipid bilayers.

Physicochemical studies on the binding of etomidate, a fast acting anaesthetic, with lipid bilayers have been carried out. ESR spin labeling studies indicate that the gel to liquid crystalline phase transition of dipalmitoyl phosphatidyl choline (DPPC) vesicles retains its cooperative nature on incorporation of the anaesthetic. For a 5:1 lipid to drug molar ratio, the phase transition occurs at an unusually lower temperature than those observed with other drug-DPPC systems. Results of 13C NMR and 1H NOE experiments suggest that the drug molecules reside in the close proximity of the terminal of hydrocarbon chains of the lipid molecules. 31P NMR and Electron Microscopic experiments indicate that the presence of etomidate alters the normal lamellar structure of DPPC vesicles into hexagonal (HII) type. Based on these observations, a model for drug-lipid binding has been proposed.

Arginine acts as a protective and reversal agent against glycolytic inhibitors in spermatozoa.

It is known that the amino acid arginine stimulates sperm motility and glycolytic activity. We have earlier studied its efficacy as a stimulator of glycolysis in goat spermatozoa under anaerobic conditions. Here, we have assessed the influence of arginine in reversing the impairment caused by glycolytic inhibitors, iodoacetamide and iodoacetic acid. Glycolysis has been monitored by measuring the consumption of 13C labeled glucose and the amount of 13C labeled lactate produced under different experimental conditions, using 13C NMR. It is observed that both L- and D-arginine are able to prevent and reverse the inhibitory action of glycolytic inhibitors. The reversal effect of arginine gives rise to about eight times higher metabolic activity as compared to the inhibited cells while structurally related amino acids such as nitro-arginine, homo-arginine, lysine and ornithine are ineffective. The energetics of spermatozoa as measured by 31P NMR show a reduction in ATP level in cells incubated with iodoacetamide. Treatment of these cells with both L- and D-arginine restores the ATP level. The results may have significance in the treatment of male infertility.

Maturation of rat spermatozoa: ESR spin labeling studies.

The ability of spermatozoa to reduce nitroxide spin--TEMPO has been used as a parameter to understand maturation, capacitation and calcium uptake of sperm obtained from Holstman strain rats. The rate of spin label reduction by sperm follows the trend--caput greater than cauda greater than corpus. With the increase in age, the electron donating capability shows first a gradual increase, for 60- to 85-day-old rats, peaking at 85 days (corresponding to puberty) and leveling off after 92 days. Calcium uptake takes place in two phases which corresponds to accumulation of and activation by calcium. The presence of polyclonal antibody which is known to cause agglutination, does not adversely affect the sperm activity.

Magnetic resonance studies of intact human spermatozoa.

A correlation has been established between the ability of sperms to reduce the nitroxide spin label--TEMPO and their metabolic activity. The rate of reduction of TEMPO is sensitive to the quantity and quality of sperms and therefore, this property can be developed into a quality rating method. Keeping this in mind, effects of various agents on the spin label reduction rates have been studied. The effect of cold shock on sperms has been found to be harmless and does not lead to loss in metabolic activity. The differential rates of spin label reduction after bubbling N2 and O2 gases through the samples indicate that the process of anaerobic glycolysis imparts higher electron donating capacity to spermatozoa. The method has been used to study influence of inhibitors of electron transport chain (ETC) such as rotenone, antimycin A, KCN and sodium azide which inhibit ETC at different levels.

Synthesis, characterisation and antitumour activity of some quercetin analogues.

Quercetin is one of the most abundant naturally occurring flavonoid and is associated with a wide range of biological activities, such as antioxidant, antiinflammatory and anticancer activities. However, there are multiple problems associated with the bioavailability of quercetin, thereby restricting its use. Taking this into consideration, the structure of quercetin was modified by removal of multiple hydroxyl groups and introduction of substituents such as Cl, OCH3 and N (CH3)2 on the p-position of the B-ring. The effect of structural modification on the anticancer activity was studied using four different cell lines, including MCF-7, HepG2, HCT-15 and PC-3. Compound 1a has shown an activity better than quercetin in HepG2 cell lines, whereas 1c and 1e showed significant growth inhibition of the HCT-15 cell lines.