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Biomedical subjects

M Bansal

Publications and source records attributed to M Bansal.

At least 91 records · Page 5Linked to original sources
PubMed1992

Magnetic resonance imaging in diagnosis of transient osteoporosis of the hip.

The results of magnetic resonance (MR) imaging in six patients with transient osteoporosis of the hip were reviewed. Short TR/TE (repetition time/echo time) images demonstrated diffusely decreased signal intensity in the femoral head and intracapsular region of the femoral neck. Increased signal intensity was noted with progressive T2 weighting. Bone biopsies were performed in four patients. Histologic findings were nonspecific and included fat necrosis, marrow edema, increased bone resorption, and reactive bone formation. Repeat MR scans in two patients, performed six and eight months after the initial scans, showed an almost complete return to normal marrow signal. All patients became asymptomatic without bony deformity. In the appropriate clinical setting, MR scanning can aid in the diagnosis of transient osteoporosis as the cause of a painful hip.

Acute Disease↗
PubMed1991

Antibacterial effects of fibrin glue-antibiotic mixtures.

In the present in vitro study, we investigated the duration of action and antibacterial effects of nonautologous fibrin glue (FG) combined with antibiotics (Abs) including Ciprofloxacin, Teicoplanin, Cefoxitin, and Gentamicin; the effect of FG alone on bacterial growth was also evaluated. The rate of Ab diffusion from combined FG-Ab clots was evaluated by separate elution with pooled human serum (HS) and normal saline (NS); supernatants were removed daily and assayed for active concentrations of each Ab. The effects of FG and combined FG-Ab clots on bacterial growth were evaluated by inoculating brain-heart infusion (BHI) with Staphylococcus aureus, followed by the addition of FG or FG-Ab clots; a separate set of studies was also performed with the addition of mouse lung homogenate (MLH) as well. The addition of Ab to FG clots resulted in continuous diffusion of the Ab into the surrounding HS or NS for up to 5 to 7 days; however, more than two-thirds of the Ab diffused out within 2 to 3 days regardless of the Ab used. The antibacterial effects of FG-Ciprofloxacin and FG-Teicoplanin clots were significant compared to those of FG clots not containing Ab. In addition, the presence of FG clots (in BHI) resulted in a reduction in bacterial growth compared to that of BHI alone. The addition of MLH to BHI resulted in increased bacterial growth, but this effect was inhibited by the presence of combined FG-Ab clots.(ABSTRACT TRUNCATED AT 250 WORDS)

Anti-Bacterial Agents↗
PubMed1991

DNA polymorphism and local variation in base-pair orientation: a theoretical rationale.

Basepair stacking calculations have been carried out to understand the conformational polymorphism of DNA and its sequence dependence. The recently developed self-consistent parameter set, which is specially suitable for describing irregular DNA structures, has been used to describe the geometry of a basepair doublet. While for basepairs without any propeller, the favourable stacking patterns do not appear to have very strong features, much more noticeable sequence dependent stacking patterns emerge once a propeller is applied to the basepairs. The absolute minima for most sequences occurs for a doublet geometry close to the B-DNA fibre models. Hence in the B-DNA region, no strong sequence dependent features are found, but the range of doublet geometries observed in the crystal structures generally lie within the low energy contours, obtained from stacking energy calculations. The doublet geometry corresponding to the A-DNA fibre model is not energetically favourable for the purine-pyrimidine sequences, which prefer small roll angle values when the slide has a large negative value as in A-DNA. However positive roll with large negative slide is allowed for GG, GA, AG and the pyrimidine-purine steps. This is consistent with the observed geometries of various steps in A-DNA crystals. Thus the general features of the basepair doublets predicted from these theoretical studies agree very well with the results from crystal structure analysis. However, since most sequences show an overall preference for B-type doublet geometry, the B----A transition for random sequence DNA cannot be explained on the basis of basepair stacking interactions.

Base Composition↗
PubMed1990

Local variability and base sequence effects in DNA crystal structures.

The importance and usefulness of local doublet parameters in understanding sequence dependent effects has been described for A- and B-DNA oligonucleotide crystal structures. Each of the two sets of local parameters described by us in the NUPARM algorithm, namely the local doublet parameters, calculated with reference to the mean z-axis, and the local helical parameters, calculated with reference to the local helix axis, is sufficient to describe the oligonucleotide structures, with the local helical parameters giving a slightly magnified picture of the variations in the structures. The values of local doublet parameters calculated by NUPARM algorithm are similar to those calculated by NEWHELIX90 program, only if the oligonucleotide fragment is not too distorted. The mean values obtained using all the available data for B-DNA crystals are not significantly different from those obtained when a limited data set is used, consisting only of structures with a data resolution of better than 2.4 A and without any bound drug molecule. Thus the variation observed in the oligonucleotide crystals appears to be independent of the quality of their crystallinity. No strong correlation is seen between any pair of local doublet parameters but the local helical parameters are interrelated by geometric relationships. An interesting feature that emerges from this analysis is that the local rise along the z-axis is highly correlated with the difference in the buckle values of the two basepairs in the doublet, as suggested earlier for the dodecamer structures (Bansal and Bhattacharyya, in Structure & Methods: DNA & RNA, Vol. 3 (Eds., R.H. Sarma and M.H. Sarma), pp. 139-153 (1990)). In fact the local rise values become almost constant for both A- and B-forms, if a correction is applied for the buckling of the basepairs. In B-DNA the AA, AT, TA and GA basepair sequences generally have a smaller local rise (3.25 A) compared to the other sequences (3.4 A) and this seems to be an intrinsic feature of basepair stacking interaction and not related to any other local doublet parameter. The roll angles in B-DNA oligonucleotides have small values (less than +/- 8 degrees), while mean local twist varies from 24 degrees to 45 degrees. The CA/TG doublet sequences show two types of preferred geometries, one with positive roll, small positive slide and reduced twist and another with negative roll, large positive slide and increased twist.(ABSTRACT TRUNCATED AT 400 WORDS)

Algorithms↗
PubMed1990

The tissue diagnosis of metabolic bone disease. Role of histomorphometry.

Those aspects of bone histology and histomorphometry that need to be understood by clinicians to put histomorphometry into proper perspective are presented. An increasingly important component of the histologic diagnosis of the metabolic diseases of bone is the quantification of the various histologic features as seen in undecalcified bone biopsies. This article is intended to review some of the histologic features of the metabolic diseases of bone and their corresponding histomorphometric parameters as they are used in diagnosis. The methods of obtaining both direct and derived values as well as the reporting of the results are presented in detail.

Biopsy↗
PubMed1989

Molecular mechanics studies on poly(purine).poly(pyrimidine) sequences in DNA: polymorphism and local variability.

Energy minimization has been carried out on three poly(purine).poly(pyrimidine) sequences--d(G)10.d(C)10, d(A)10.d(T)10, and d(AG)5.d(CT)5--using the molecular mechanics program AMBER (Assisted Model Building and Energy Refinement). In order to extensively scan the conformational space available, five different helical models were studied, three of them being right-handed helices while the other two were left helical. For all three sequences the right-handed A- and B-type helices are energetically slightly preferred over the left helices, but the energy difference between the various right-handed helices is only marginal. A detailed analysis has been carried out to characterize the local structural variability in the refined structures, both in terms of torsion angles as well as other parameters such as base-pair tilt, wedge roll, and wedge tilt, etc. All three sequences exhibit similar structural features for a particular form, but both the forms A and B show significant deviations from fiber models. In particular, the A-form structures have higher unit rise (2.7 A), and lower unit twist (31 degrees) and base-pair tilt (12 degrees), compared to the fiber model, which has corresponding values of 2.56 A, 32.7 degrees, and 20 degrees, respectively. All these changes indicate that the refined models are closer to the A-form structure observed in crystals of oligonucleotides. In the refined B-for models, the helical parameters are close to the fiber B-form, although the torsion angles show considerable variations. None of the three sequences examined, including the d(A)n.d(T)n sequence, show any pronounced curvature for the B-form structure.

Base Sequence↗
PubMed1989

A self-consistent formulation for analysis and generation of non-uniform DNA structures.

A fully self-consistent formulation is described here for the analysis and generation of base-pairs in non-uniform DNA structures, in terms of various local parameters. It is shown that the internal "wedge parameters" are mathematically related to the parameters describing the base-pair orientation with respect to an external helix axis. Hence any one set of three translation and three rotation parameters are necessary and sufficient to completely describe the relative orientation of the base-pairs comprising a step (or doublet). A general procedure is outlined for obtaining an average or global helix axis from the local helix axes for each step. A graphical representation of the local helix axes in the form of a polar plot is also shown and its application for estimating the curvature of oligonucleotide structures is illustrated, with examples of both A and B type structures.

Algorithms↗
PubMed1989

Changes seen in lymph nodes draining the sites of large joint prostheses.

We report the histological findings seen in the lymph nodes draining the sites of large joint prostheses. Two patients underwent multiple prosthetic joint replacements. In one patient, the regional lymph nodes were enlarged during the revision of a total hip prosthesis, and a representative lymph node was resected. The other patient had undergone a pelvic lymph node dissection as part of a staging procedure for prostatic carcinoma. By light microscopy, the lymph nodes from both patients showed markedly dilated nodal sinuses filled with macrophages containing abundant eosinophilic, PAS-positive, granular material. Polarization microscopy revealed needle-like particles within the cytoplasm of the macrophages. We believe that the histological appearance of the lymph nodes represents a florid foreign body reaction to fragments of polyester or polyethylene derived from the articulating surfaces of the joint prostheses and transported to the regional lymph nodes via the lymphatic circulation. Sinus histiocytosis seen in the lymph nodes draining the sites of joint prostheses may resemble, and must be distinguished from, other conditions invoking a sinus pattern of lymphadenopathy, as well from benign and malignant diseases that involve the lymph nodes in a pattern mimicking sinus histiocytosis.

Adult↗
PubMed1989

Osteoporosis and familial idiopathic scoliosis: association with an abnormal alpha 2(I) collagen.

A positive family history is considered a risk factor for osteoporosis (OP) although the genetic or biochemical basis for this relationship remains undefined. Various mutations affecting normal synthesis of type I collagen have been reported in osteogenesis imperfecta (OI), a heritable disorder of connective tissue. Family A, in which the proband and a daughter are afflicted with OP and idiopathic scoliosis was examined for defects in collagen metabolism. Dermal fibroblast cultures were established to investigate de novo collagen synthesis. SDS-PAGE revealed an abnormally migrating alpha 2(I) chain and procollagen in two generations. Examination of the kinetics of type I collagen pC & N-propeptide processing demonstrated a rate 2x control in the proband. The phenotype family A is not OI. It shares features with families B & C, having familial clustering of OP. However, collagen synthesis was not abnormal in family B & C. These data suggest that in family A the alpha 2(I) structural defect may be related to defective skeletal matrix formation.

Adolescent↗
PubMed1989

Computed tomographic evaluation of fatty neoplasms of the extremities. A clinical, radiographic, and histologic review of cases.

Eleven lipomatous tumors of the extremities (7 liposarcomas, 4 lipomas) were evaluated radiographically by several modalities, including computed tomography (CT) in all lesions. Lipomas were seen on CT scan as well delineated, homogeneous masses with negative attenuation coefficients ranging from -95 to -160. Liposarcomas were inhomogeneous, multilobulated, poorly delineated lesions located exclusively in the subfascial or intramuscular planes, with an intermediate range of attenuation coefficients between those of fat and those of muscle. In six of seven liposarcomas, definite low density areas were identified by attenuation coefficient as fatty tissue. Magnetic resonance imaging (MRI) was obtained in two patients and was helpful in defining the extent of the tumors and their relationship to vital structures, but MRI could not differentiate benign from malignant tissue. Computed tomography is recommended as the cornerstone in the initial radiographic evaluation of growing or painful lipomatous soft tissue masses of the extremities.

Adult↗
PubMed1988

Concentric joint space narrowing of the hip associated with hemosiderotic synovitis (HS) including pigmented villonodular synovitis (PVNS).

Concentric joint space narrowing of the hip is an expected radiographic finding in cases of inflammatory arthritis such as rheumatoid arthritis or sepsis. However, similar joint space narrowing is associated with chronic hemorrhagic conditions that produce hemosiderotic synovitis. Hemosiderotic synovitis results from chronic intra-articular bleeding such as occurs in pigmented villonodular synovitis, generalized bleeding diathesis, synovial hemangioma, and chronic trauma. Five hips in five patients with concentric joint space narrowing not associated with inflammatory arthritis or with hemophilia were reviewed clinically, radiographically, and pathologically. All patients had a hemosiderotic synovitis. The definitive diagnosis of pigmented villonodular synovitis was made pathologically in two cases that demonstrated nodular areas of giant cell proliferation, collagen production, and lipid-laden histiocytes on histologic samples.

Adult↗
PubMed1988

Histochemical demonstration of iron but not aluminum in a case of dialysis-associated osteomalacia.

A patient undergoing hemodialysis is described in whom osteomalacia developed despite protracted treatment with calcitriol. Appropriately stained biopsy sections exhibited iron at all marrow-osteoid interfaces and a small fraction of trabecular mineralization fronts. Aluminum, the metal usually associated with osteomalacia in patients undergoing hemodialysis, was not histochemically demonstrable, even though spectrophotometrically measured bone aluminum content was substantial. These observations suggest two interpretations: iron may have caused osteomalacia through effects on bone cells and at mineralization fronts; alternatively, aluminum may have caused osteomalacia while remaining histochemically undetectable. It is possible that both metals exerted toxic effects simultaneously.

Aluminum↗
PubMed1988

Theoretical studies on alpha-helix--DNA interactions.

The interaction energies between (Ala)10 and alpha-helix fragment and different nucleotide sequences in right-handed B-form have been optimized using semi-empirical potential energy functions. The energies are calculated for two different orientations of the alpha-helix, viz., when the alpha-helix axis taken in the N----C direction is (i) parallel and (ii) antiparallel to the 5'-3' ascending strand of DNA, proximal to it. When both the DNA molecule as well as the alpha-helix are treated as rigid molecules it is found that a polyalanine alpha-helix has slightly more favourable contacts when it is in the proximity of a four nucleotide sequence of 5'-(N-A-T-N)-3' type, where N is either a purine or a pyrimidine. However, when the two interacting molecules are allowed to undergo local structural variations then the interaction energy appears to be independent of the base sequence confirming the non-specific nature of these interactions.

Base Composition↗
PubMed1988

A general procedure for generation of curved DNA molecules.

A general method for generation of base-pairs in a curved DNA structure, for any prescribed values of helical parameters--unit rise (h), unit twist (theta), wedge roll (theta R) and wedge tilt (theta T), propeller twist (theta p) and displacement (D) is described. Its application for generation of uniform as well curved structures is also illustrated with some representative examples. An interesting relationship is observed between helical twist (theta), base-pair parameters theta x, theta y and the wedge parameters theta R, theta T, which has important consequences for the description and estimation of DNA curvature.

Algorithms↗