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Biomedical subjects

S Ranganathan

Publications and source records attributed to S Ranganathan.

At least 19 recordsLinked to original sources
PubMed2006

A symmetrical indexing scheme for decagonal quasicrystals analogous to Miller-Bravais indexing of hexagonal crystals.

The problems of redundancy and superfluous indices in indexing the planes and axes in a decagonal quasicrystal are considered, using a scheme of five coplanar vectors in the quasiperiodic plane and one perpendicular vector. Of all the indexing schemes in use, this scheme offers the maximum advantage. An analogy is drawn to the hexagonal system using Miller-Bravais indices. Based on this, a symmetry-based indexing system for decagonal phases is devised that follows a simplified approximate zone law analogous to the exact zone law for the hexagonal case. The indices based on this scheme will be designated as ;Frank indices'. High-symmetry electron diffraction zone-axis patterns as well as powder X-ray diffraction patterns are indexed using Frank indices and compared with those of other indexing schemes.

Alloys↗
PubMed2006

Quantitative assessment of breast density from digitized mammograms into Tabar's patterns.

We describe a semi-automated technique for the quantitative assessment of breast density from digitized mammograms in comparison with patterns suggested by Tabar. It was developed using the MATLAB-based graphical user interface applications. It is based on an interactive thresholding method, after a short automated method that shows the fibroglandular tissue area, breast area and breast density each time new thresholds are placed on the image. The breast density is taken as a percentage of the fibroglandular tissue to the breast tissue areas. It was tested in four different ways, namely by examining: (i) correlation of the quantitative assessment results with subjective classification, (ii) classification performance using the quantitative assessment technique, (iii) interobserver agreement and (iv) intraobserver agreement. The results of the quantitative assessment correlated well (r2 = 0.92) with the subjective Tabar patterns classified by the radiologist (correctly classified 83% of digitized mammograms). The average kappa coefficient for the agreement between the readers was 0.63. This indicated moderate agreement between the three observers in classifying breast density using the quantitative assessment technique. The kappa coefficient of 0.75 for intraobserver agreement reflected good agreement between two sets of readings. The technique may be useful as a supplement to the radiologist's assessment in classifying mammograms into Tabar's pattern associated with breast cancer risk.

Absorptiometry, Photon↗
PubMed2006

A robust hybrid peptide crystal formed with weak hydrogen bonds.

In the course of our work relating to the design of a bihelical structure (I) from diphenic anhydride by tethering with cystine di-OMe, stable, hard, and rigid crystals, mp 215-218 degrees C were isolated in low yields ( approximately 2%). The crystal structure established that it was a bis amide (II) arising from diphenic acid and cystine di-OMe [(II), C(22)H(22)N(2)O(6)S(2) (a = 9.897 (1) A, b = 12.210 (1) A, c = 18.192 (1) A, sp. gr. P2(1)2(1)2(1))]. An authentic sample of (II) was subsequently prepared in 47% yields by condensation of diphenic acid dichloride with cystine di-OMe. A most surprising feature of II was, despite its high density, rigidity, and hardness, it did not exhibit any normal hydrogen bonds. The nearest approximation to a "usual" hydrogen bond was the single NH...OC linkage that occurred between molecules along a twofold screw axis. In this linkage, N...O = 3.265 A and H...O = 2.43 A, values that are at least 10% longer than those usually observed in peptides. The rigidity of the crystals appears to depend upon many weak hydrogen bonds of the type CH...O, CH...pi, CH...S, and NH...S working in concert. Even these attractions have separations that are at the high end of the range of previously observed values, although some of the weak hydrogen bonds have been rarely reported and have poorly defined ranges. The attractive effect of each of these weak bonds may be enhanced by the occurrence of a number of them in a parallel fashion like rungs in a ladder.

Crystallization↗
PubMed2006

Estimation of iodine in salt fortified with iodine & iron.

BACKGROUND & OBJECTIVE: The National Institute of Nutrition (NIN), Hyderabad has developed double fortified salt (DFS) containing both iodine and iron to control the twin problems of iodine deficiency disorders (IDD) and iron deficiency anaemia (IDA). When the iodine content of DFS was estimated by the conventional iodometric titration using sulphuric acid (H(2)SO(4)), problems such as wide variation between duplicate analysis and under/overestimations of iodine content were encountered, which led to inconsistent results. This study was undertaken to develop a modified method for the estimation of iodine in DFS so as to get reliable iodine content of DFS. METHODS: A modified method was developed using orthophosphoric acid (H(3)PO(4)) and the sensitivity of the method was confirmed by estimating the iodine content of potassium iodate (KIO(3)) standard at different concentrations of iodine (0 to 100 ppm). The iodine content of DFS and iodized salt (IS) from local market and factory was estimated by the modified method as well as the conventional iodometric titration and the results were compared. RESULTS: The pH of DFS was acidic. The time gap between the additions of acid and potassium iodide (KI) played a crucial role in getting the actual iodine content of DFS. The H(2)SO(4) and ferrous sulphate (FeSO(4)) interfered with the estimation of iodine in DFS resulting in underestimation or overestimation of iodine. Modified method (H(3)PO(4)) produced consistent and reliable iodine content of DFS. Both H(2)SO(4) and H(3)PO(4) gave same results when tested with KIO(3) standard, Reference salt and IS (both experimental and purchased from local market). Actually 0.50 ml of 1 per cent KI was sufficient to estimate the iodine content of DFS or IS. INTERPRETATION & CONCLUSION: The results of the present study showed that the conventional method using H(2)SO(4) was not suitable for the estimation of iodine in DFS. The modified method using H(2)PO(4) was ideally suited for the estimation of iodine in DFS. Also, iron from DFS did not interfere during estimation of iodine by this method. As both the conventional and the modified methods gave the same results for the iodine content of IS, it is practically prudent to use the modified method (H(2)PO(4)) for both DFS and IS instead of following one method (H(3)PO(4)) for DFS and another (H(2)SO(4)) for IS. The quantity of KI is also reduced and the order of additions of reagents is changed in the modified procedure.

Anemia, Iron-Deficiency↗
PubMed2005

Role of Chrysosporium keratinophillum in the parasitic evolution of dermatophytes.

Anti-dermatophytic activity of Chrysosporium keratinophillum against species of the genera Trichophyton, Microsporum and Epidermophyton floccosum was tested in vitro. When C. keratinophillum and different species of dermatophytes were inoculated on Sabouraud's dextrose agar plates 2 cm apart, no antagonistic effect of C. keratinophillum on the mycelial growth of dermatophytes was observed. However, conidia production was not observed on the hyphae of Trichophyton rubrum, Trichophyton tonsurans and E. floccosum grown near C. keratinophillum. The secretory substances released by C. keratinophillum inhibited the growth of T. rubrum, T. tonsurans, Trichophyton mentagrophytes var. interdigitale and E. floccosum at a concentration of 2,000 microg ml(-1) when tested by broth dilution technique. No inhibition of the growth was observed for Microsporum gypseum and Microsporum nanum. The anti-fungal activity of secretory substances released by C. keratinophillum was recorded to be heat stable. Results of the present study suggest that the anti-dermatophytic activity of the secretory substances of C. keratinophillum on T. rubrum, T. mentagrophytes var. interdigitale, T. tonsurans and E. floccosum may be responsible in part, for the absence of these dermatophyte species in soil. Considering the global prevalence of C. keratinophillum in soil one may speculate that the anti-dermatophytic activity of C. keratinophillum is one of the early events for the evolutionary divergence of saprophytic archi-dermatophytes to obligate parasitic dermatophyte species.

Antibiosis↗
PubMed2005

MRI and CT findings of cryptococcal vaginitis.

Cryptococcus neoformans is a yeast like fungus, which is commonly found in bird droppings, especially pigeons. Most cases of cryptococcal infections occur in immunocompromised patients or in those who are on long term immunosuppressant therapies. Cryptococcal infection usually presents as a meningoencephalitis or a pulmonary infection. Skin, bone and genital infections are very rare. We report the second case of vaginal cryptococcossis to be reported in English literature and the first to be imaged with CT and MRI.

Adult↗
PubMed2004

Role of many-body correlations in dynamics of liquids.

A time correlation function is written exactly in terms of infinite series with each term containing contributions separately due to two, three, and higher body static correlations. For a time correlation function of force acting on a tagged particle, it is found that contributions due to two and three body static correlation functions are sufficient to understand dynamics of dense gases whereas at the triple point and in the glassy phase it is necessary to include contributions due to a four body correlation function.

Journal Article↗
PubMed2004

Hodgkin-like posttransplant lymphoproliferative disorder in children: does it differ from posttransplant Hodgkin lymphoma?

Epstein-Barr virus (EBV)-mediated lymphoid proliferations occur in patients who are immunocompromised and are reported following bone marrow or solid organ transplantation. Most post-transplant lymphoproliferative disorders (PTLD) are polymorphic in appearance; some are monomorphic and can resemble conventional malignant lymphomas. PTLD that resembles Hodgkin lymphoma has been reported infrequently. We herein report seven cases of PTLD that have large numbers of Reed-Sternberg-like (RS-like) cells and highlight differences in the phenotype of these cases that may distinguish Hodgkin-like PTLD (HL-PTLD) from true Hodgkin lymphoma/disease (HD). All patients were in the second decade of life and were 8 months to 13 years following transplant. HL-PTLD involves lymph nodes that contain a mixed population of small to intermediate-sized lymphocytes with large mononuclear and occasionally binucleate RS-like cells. The large cells of HL-PTLD are pleomorphic B cells that react strongly for CD20 and/or CD79a, express CD30, but are usually negative for CD15 and have few mitoses. They are positive for EBV early RNA (EBER) using an EBER-1 probe, as are some of the background small lymphocytes. A single case of true Hodgkin lymphoma has highly atypical RS-like cells that contain numerous mitoses, does not have CD20 or CD79a reactivity, has CD15 and CD30 staining, and the EBER-1 probe is confined to the large cells only. All patients were managed by withdrawal of immunosuppression and variably treated with either antiviral or anti-CD20 monoclonal antibody, or with chemotherapy. A unique instance of evolution from a HL-PTLD to true HD is also illustrated. In conclusion, HL-PTLD and HD appear to be two related but immunophenotypically and biologically distinct forms of lymphoproliferation in post-transplant patients and may require different protocols for their management.

Adolescent↗
PubMed2004

Prevalence, serotypes and mating patterns of Cryptococcus neoformans in the pellets of different avifauna in Madras, India.

A total of 887 pellets of different avifauna were screened for the presence of Cryptococcus neoformans. One hundred and six of 887 samples (12%) yielded Cr. neoformans in culture. The report on the isolation of Cr. neoformans from the pellets of the crow appears to be new and of greater significance because of the ubiquitous prevalence of this bird in India. The prevalence of both MAT a and MAT alpha mating types were recorded. The serotype D was predominant over serotype A. The findings of the present study reveal the growing diverse ecological niche of Cr. neoformans in a the pellets of various avifauna in India.

Animals↗
PubMed2003

Binary and multiparticle contributions to the velocity autocorrelation function.

A method for including the contribution of many-body correlation effects to the microscopically obtained results of the two-body contribution to the velocity autocorrelation has been proposed. A significant improvement over the results obtained through only binary contribution has been found, as can be judged by comparing the results for force and velocity autocorrelation functions of Lennard Jones fluids with that of molecular dynamic simulations. The agreement of results of self-diffusion coefficient is also quite good with simulation data over a wide range of densities and temperatures.

Journal Article↗
PubMed2003

Molecular dynamics study of a bilayer electron gas: single particle properties.

The single-particle dynamical properties of a strongly coupled, classical, symmetric electronic bilayer system have been investigated by molecular dynamics simulation. Results for the velocity correlation function, the single-particle scattering function, and their respective Fourier transforms have been calculated, and their behavior, as a function of the interlayer separation d, has been analyzed. The single-particle scattering function in particular, shows dramatic effects when the bilayer attains a staggered square lattice structure. This occurs when the interlayer separation is around 0.8a (a is the Wigner-Seitz radius), where our previous study showed a marked decrease in the diffusion coefficient.

Journal Article↗
PubMed2003

Diverse role of LDL receptor-related protein in the clearance of proteases and in signaling.

The low density lipoprotein receptor-related protein (LRP) is a large endocytic receptor that participates in several biological pathways and plays prominent roles in lipoprotein metabolism and in the catabolism of proteinases involved in coagulation and fibrinolysis. LRP also mediates the cellular entry of certain viruses and toxins and facilitates the activation of various lysosomal enzymes. Deletion of the LRP gene in mice is lethal, confirming an important role for this receptor in development, although its exact function in development is still not known. In addition to its role in the endocytosis of numerous ligands, recent studies are emerging that describe a signaling role for this receptor as well.

Animals↗
PubMed2002

Molecular dynamics study of diffusion in a bilayer electron gas.

Molecular dynamics simulations of strongly coupled, classical electronic bilayers, interacting through the Coulomb potential, have been produced and studied. Values of the plasma coupling parameter Gamma between 10 and 80 and interlayer separations d from 0.1 to 3.0, (in units of Wigner-Seitz radius), were considered. The simulation results were used to calculate the intralayer and interlayer pair correlation functions and self-diffusion of charged particles in this system. The variation of self-diffusion with Gamma and d has been analyzed, and it is found that for the largest value of Gamma, the diffusion coefficient does not increase monotonically with layer separation, but has a distinct minimum for values of d slightly less than 1.

Journal Article↗
PubMed2002

A male-specific (cysteine-rich) protein of Oesophagostomum dentatum (Strongylida) with structural characteristics of a serine protease inhibitor containing two trypsin inhibitor-like domains.

A cDNA was isolated from an adult male Oesophagostomum dentatum gene library by screening with a male-specific, partial expressed sequence tag (EST) probe identified previously using a differential display technique. The full-length cDNA of 642 bp included 5' and 3' untranslated regions of 44 and 121 nucleotides, respectively, and encoded a predicted protein with a putative 18 amino acid signal sequence and a mature polypeptide of 14.7 kDa comprising approximately 15% cysteine residues. The amino acid sequence showed similarity with a number of proteins from Caenorhabditis elegans, parasitic nematodes, insects and amphibia, all of which contain a trypsin inhibitor-like cysteine-rich domain. A 3-dimensional structure model constructed for the O. dentatum protein (designated OdmCRP) inferred that it is composed of 2 domains, each with 5 disulfide bonds, which are indicative of the Ascaris family of serine protease inhibitors. These findings indicate that OdmCRP, with 2 structural domains relating to functionally active sites, is a new member of this inhibitor family.

Amino Acid Sequence↗
PubMed2002

Did earthworms contribute to the parasitic evolution of dermatophytes?

The survival of dermatophyte species in the gut of four species of earthworms was studied by feeding the fungi to the earthworms. Recovery of the dermatophyte species in culture from the guts was only possible for Microsporum gypseum and Chrysosporium keratinophilum. In the light of these findings, we presume that earthworms could have influenced the parasitic evolution of certain dermatophytes.

Animals↗