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Biomedical subjects

M Bansal

Publications and source records attributed to M Bansal.

At least 73 records · Page 4Linked to original sources
PubMed1994

Polyethylene and metal debris generated by non-articulating surfaces of modular acetabular components.

We report a prospective study of the liner-metal interfaces of modular uncemented acetabular components as sources of debris. We collected the pseudomembrane from the screw-cup junction and the empty screw holes of the metal backing of 19 acetabula after an average implantation of 22 months. Associated osteolytic lesions were separately collected in two cases. The back surfaces of the liners and the screws were examined for damage, and some liners were scanned by electron microscopy. The tissues were studied histologically and by atomic absorption spectrophotometry to measure titanium content. The pseudomembrane from the screw-cup junction contained polyethylene debris in seven specimens and metal debris in ten. The material from empty screw holes was necrotic tissue or dense fibroconnective tissue with a proliferative histiocytic infiltrate and foreign-body giant-cell reaction. It contained polyethylene debris in 14 cases and metal in five. The two acetabular osteolytic lesions also showed a foreign-body giant-cell reaction to particulate debris. The average titanium levels in pseudomembranes from the screw-cup junction and the empty screw holes were 959 micrograms/g (48 to 11,900) and 74 micrograms/g (0.72 to 331) respectively. The tissue from the two lytic lesions showed average titanium levels of 139 and 147 micrograms/g respectively. The back surfaces of the PE liners showed surface deformation, burnishing, and embedded metal debris. All 30 retrieved screws demonstrated fretting at the base of the head and on the proximal shaft. Non-articular modular junctions create new interfaces for the generation of particulate debris, which may cause granulomatous reaction.

Acetabulum↗
PubMed1994

Magnetic resonance imaging of the hip after displaced femoral neck fractures.

This study was designed to determine the sensitivity of magnetic resonance imaging (MRI) in the detection of ischemia or avascular necrosis after displaced intracapsular hip fractures. Magnetic resonance imaging was performed on 20 patients who had hemiarthroplasties performed for Garden IV intracapsular fractures. Sixteen patients had in vivo coronal T1-weighted spin-echo imaging from the day of injury to 60 days after fracture. After hemiarthroplasty, all 20 resected femoral heads had in vitro T1 imaging. A coronal slab was then cut from the center of the femoral head and studied histologically. The in vivo, in vitro, and histologic slides correlated well. None of the MRI images depicted areas of ischemia or avascular necrosis in patterns observed in nontraumatic necrosis. Avascular bone can be indistinguishable from normal bone in both MRI and histologic sections for a considerable amount of time after vascular insult. Magnetic resonance imaging is not a prognosticator for posttraumatic osteonecrosis in the first two weeks after fracture.

Adult↗
PubMed1994

Intramedullary deposits of hydroxyapatite crystals in a patient with rheumatoid arthritis.

A 63-year-old women with a 12-year history of rheumatoid arthritis (RA) had calcific deposits in the periarticular soft tissues with subsequent involvement of the medullary canals of adjacent bones. Except for the RA, there was no evidence of other abnormalities of the bones or mineral homeostasis. Chemical analyses of the deposits identified the crystalline material as apatite. Although the deposition of apatite in the soft tissues of RA is known to occur rarely, this is the first known case of intraosseous apatite deposition.

Arthritis, Rheumatoid↗
PubMed1994

Jaw enlargement complicating secondary hyperparathyroidism in three hemodialysis patients.

Over a period of two years we saw three patients with longstanding chronic renal failure in whom the size and shape of the jaws had gradually changed. Clinical, metabolic, and radiologic observations suggested that secondary hyperparathyroidism had caused the disfigurement, and bone histology supported this conclusion in each case. The appearance of our subjects resembled that of patients morbidly afflicted with osteitis fibrosa before its association with hyperparathyroidism was widely known. Jaw enlargement is a potential consequence of secondary hyperparathyroidism in dialysis patients.

Adult↗
PubMed1993

Inhibition of rat mammary carcinogenesis by inositol hexaphosphate (phytic acid). A pilot study.

Since phytic acid (inositol hexaphosphate, InsP6) and inositol (Ins) have been demonstrated to have anti-tumor and anti-cell proliferative action in several experimental models of carcinogenesis, in a pilot study we have examined their effect on 7,12-dimethylbenz(a)anthracene (DMBA)-induced rat mammary tumor model. Starting a week prior to induction with DMBA, the drinking water of female Sprague-Dawley rats was supplemented with either: 15 mM InsP6, 15 mM Ins, or 15 mM InsP6 + 15 mM Ins; a control group received no inositol compounds. Animals (55-day-old) were given a single dose of DMBA (20 mg) in 1 ml of sesame oil by oral intubation. Four additional groups not receiving DMBA, but drinking tap water, InsP6, Ins, or InsP6 + Ins of the same molarity as experimental groups were observed for the duration of the study to monitor for any putative toxicity following this long-term treatment. As opposed to the DMBA-only group, rats treated with InsP6 +/- Ins showed a 48% reduction in the number of tumors/tumor bearing animal (tumor multiplicity) and a 40% reduction in the number of tumors/rat. In contrast to 20% rats in DMBA-only group, only 0-8% animals in the treatment group had 5 or more tumors. Likewise, the tumor incidence was reduced by 19% in InsP6 +/- Ins as compared to control untreated animals. The tumors in the treated groups were also 16% smaller in size. Data from this pilot study suggest that in addition to being effective against colon cancer, InsP6 +/- Ins may be protective against mammary carcinoma as well; additional studies are however warranted.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1993

Conformational polymorphism in G-tetraplex structures: strand reversal by base flipover or sugar flipover.

Guanine rich sequences adopt a variety of four stranded structures, which differ in strand orientation and conformation about the glycosidic bond even though they are all stabilised by Hoogsteen hydrogen bonded guanine tetrads. Detailed model building and molecular mechanics calculations have been carried out to investigate various possible conformations of guanines along a strand and different possible orientations of guanine strands in a G-tetraplex structure. It is found that for an oligo G stretch per se, a parallel four stranded structure with all guanines in anti conformation is favoured over other possible tetraplex structures. Hence an alternating syn-anti arrangement of guanines along a strand is likely to occur only in folded back tetraplex structures with antiparallel G strands. Our study provides a theoretical rationale for the observed alternation of glycosidic conformation and the inverted stacking arrangement arising from base flipover, in antiparallel G-tetraplex structures and also highlights the various structural features arising due to different types of strand orientations. The molecular mechanics calculations help in elucidating the various interactions which stabilize different G-tetraplex structures and indicate that screening of phosphate charge by counterions could have a dramatic effect on groove width in these four stranded structures.

Base Composition↗
PubMed1993

Case report 772. Stress fracture of the hip secondary to renal osteodystrophy and erosion of ischium due to amyloid deposition.

We have reported the case history of a 72-year-old woman who was on hemodialysis for 15 years. Her course was marked by many of the musculoskeletal complications of ESRD including CTS, stromal amyloid deposition of synovium, amyloid cystic degeneration of bone, and inflammation of the synovium due to the deposition of calcium oxalate and calcium pyrophosphate microcrystals. She also had evidence of metabolic bone disease: moderate osteoporosis related to secondary hyperparathyroidism and osteomalacia related to aluminum deposition at the mineralization front. The pathological and radiological findings associated with her bone disease are described.

Aged↗
PubMed1993

Soft tissue chondromas: diagnosis and differential diagnosis.

The authors evaluated three cases of soft tissue chondromas in patients aged 55, 57, and 78 years. Two of the lesions occurred in the foot and one in the hand. All three patients had long histories (over 1 year) of a palpable mass and all three had roentgenograms showing well-demarcated lobulated soft tissue lesions with both central and peripheral calcifications. Recognition of this rare benign chondroid lesion on imaging studies is significant since it may be misinterpreted as an aggressive lesion or a primary synovial abnormality.

Aged↗
PubMed1992

Hairpin and parallel quartet structures for telomeric sequences.

The role of thymine residues in the formation of G-quartet structures for telomeric sequences has been investigated using model oligonucleotides of the type d(G4TnG4), with n = 1-4. Sequences d(G4T3G4) and d(G4T4G4) adopt a G-quartet structure formed by hairpin dimerization in 70 mM NaCl as judged by a characteristic circular dichroism signature with a 295 nm positive and 265 nm negative bands while d(G4TG4) adopts a parallel G-quartet structure like d(G12) which exhibits a strong positive band at 260 nm and a negative band at 240 nm. The sequence d(G4T2G4) exhibits a mixture of both conformations. The stability of hairpin G-quartet structures decreases with decrease in the number of intervening thymine residues. Potassium permanganate, a single strand specific probe has been used to establish the presence of loops composed of T residues in the hairpin G quartet structures formed by the oligonucleotides d(G4TnG4) with n = 2-4 in 70 mM NaCl. The formation of hairpin G quartet structure for the above sequences is further supported by the enhanced electrophoretic mobility observed on non-denaturing polyacrylamide gels. Human telomeric sequence d(TTAGGG)4 which showed enhanced electrophoretic mobility like Tetrahymena telomeric sequence d(T2G4)4 also exhibited a characteristic CD spectrum for a folded-back G-quartet structure. A detailed model for G-quartet structure involving hairpin dimer with alternating syn-anti-syn-anti conformation for the guanine residues both along the chain as well as around the G tetrad with at least two thymine residues in the loop is proposed. Intermolecular association of short telomeric sequences reported here provides a possible model for chromosomal pairing.

Animals↗
PubMed1992

Double helix conformation, groove dimensions and ligand binding potential of a G/C stretch in B-DNA.

The self-complementary DNA fragment CCGGCGCCGG crystallizes in the rhombohedral space group R3 with unit cell parameters a = 54.07 A and c = 44.59 A. The structure has been determined by X-ray diffraction methods at 2.2 A resolution and refined to an R value of 16.7%. In the crystal, the decamer forms B-DNA double helices with characteristic groove dimensions: compared with B-DNA of random sequence, the minor groove is wide and deep and the major groove is rather shallow. Local base pair geometries and stacking patterns are within the range commonly observed in B-DNA crystal structures. The duplex bears no resemblance to A-form DNA as might have been expected for a sequence with only GC base pairs. The shallow major groove permits an unusual crystal packing pattern with several direct intermolecular hydrogen bonds between phosphate oxygens and cytosine amino groups. In addition, decameric duplexes form quasi-infinite double helices in the crystal by end-to-end stacking. The groove geometries and accessibilities of this molecule as observed in the crystal may be important for the mode of binding of both proteins and drug molecules to G/C stretches in DNA.

Base Sequence↗
PubMed1992

Effect of short-term hypomagnesemia on the chemical and mechanical properties of rat bone.

Magnesium is known to have an essential role in determining the properties of bone, but the way in which Mg exerts its actions remains unclear. Although long-term Mg deficiency is known to produce osteopenia, the effects of short-term Mg deficiency have not been established. To test the hypothesis that Mg deficiency results in an altered pattern of initial mineralization and concomitant altered bone properties, the radiographic, histologic, chemical, and mechanical properties of the bones of rats given a Mg-deficient diet were compared to those of rats pair-fed the same diet supplemented with Mg. Short-term Mg-deficiency in the diet of growing rats produced a significant decrease in both the trabecular bone volume and the mineral content of the newly formed metaphysis, a significant increase in the Ca:P ratio, and a slight, but significant increase in hydroxyapatite crystallite size and/or perfection in the metaphysis. Comparable, but not significant, trends were found in the diaphyses. Metaphyseal bone osteocalcin levels were reduced in the Mg-deficient rats and lipid was more easily extracted from their bones. No detectable alterations in radiographic microstructure were noted. Mechanically, a significant decrease in the maximum three-point bend strength of the femurs of Mg-deficient rats was observed. These data support the hypothesis that short-term Mg deficiency affects the pattern of bone mineral formation.

Animals↗
PubMed1992

Case report 706: Silicone-induced reactive synovitis.

In a patient with a disrupted silicone prosthesis, the presence of a swollen articulation should suggest the presence of silicone-induced reactive synovitis. Diagnosis of the entity rests on the identification of particulate matter by polarized microscopy and/or scanning electron microscopy--studies that will not be performed routinely unless the diagnosis is suggested preoperatively. The case presented is that of a 68-year-old woman in whom a silicone elastomer trapeziometacarpal prosthesis had been implanted 5 years previously. Painful swelling had ensued, and biopsy confirmed the diagnosis.

Aged↗
PubMed1992

Titanium wear debris in failed cemented total hip arthroplasty. An analysis of 71 cases.

Seventy-one cemented total hip arthroplasties (THAs) were reviewed following removal of the all-titanium alloy femoral stem. Fifty-one hips were primary arthroplasties that failed due to aseptic loosening, 8 were previous revisions with aseptic loosening, and 12 were removed for infection. The average duration of service for the three groups was 4.5 years, 5.0 years, and 3.7 years, respectively. Femoral bone loss in aseptically loose, primary THA was graded as severe in 51%, moderate in 24%, and mild in 20%. Femoral endosteolysis was present in 94%, while acetabular osteolysis was seen in 6%. Histological evaluation of tissues from failed primary arthroplasties revealed polymethyl methacrylate debris in 75% of cases, polyethylene debris in 80%, metal debris in 75%, and chronic inflammatory cells in all cases. Metallic debris was not seen in the failed revision cases and in only 17% of the infected cases. Examination of retrieved femoral components revealed burnishing of the head in all cases, while 71% of stems with aseptic loosening were abraded from the cement. Metal levels from 12 cases averaged 2,111 mg/g of dry tissue (range, 60-11,823); synovial fluid levels from 8 other cases averaged 106 mg/l (range, 22-340). While it is not certain whether metallic particles are a primary cause of loosening or are generated secondarily, their presence seems to accelerate bone loss and loosening.

Adult↗
PubMed1992

Groove width and depth of B-DNA structures depend on local variation in slide.

The groove widths of DNA helix, especially minor groove width, are generally believed to be important for recognition of DNA by various types of ligands. It has been postulated earlier that large negative propeller twist, in the AT rich regions compresses the minor groove of duplex DNA. A systematic study has now been carried out by generating models with different values of local doublet and intra-basepair parameters and calculating their minor groove widths. It is found that several local doublet parameters affect the minor groove width but it depends most strongly on the local step parameters roll and slide when each parameter is considered individually. However, a detailed analysis of the various local parameters within the B-DNA family of crystal structures indicates that propeller twist and slide are most strongly correlated with the observed values of minor groove width. The groove depth is also strongly correlated with slide. Thus the local base sequence dependent variations in slide can modify both the groove width and depth and consequently determine the ligand binding properties of DNA.

Base Sequence↗
PubMed1992

Assessment of renal osteodystrophy in hemodialysis patients.

We performed a prospective study of 30 patients undergoing chronic hemodialysis to determine which of 6 generally available diagnostic procedures provided the most useful information for the assessment of bone disease in hemodialysis patients. The 6 procedures were: routine biochemical measurements, N-terminal parathyroid hormone (N-PTH), radiographic analysis of hands and clavicles, bone density determination by dual photon absorptiometry (DPA), deferoxamine stimulation test, and iliac crest bone biopsy. Serum N-PTH was elevated in 83% of patients but was not significantly associated with abnormalities of other biochemical parameters. No significant relationship was demonstrated between biochemical data and radiographic findings or between biochemical data and bone density by DPA. All patients with abnormal DPA had an elevation of N-PTH; therefore, DPA did not reveal any unsuspected disease. Bone biopsies were done in 20 patients and findings in each were consistent with uremic osteodystrophy, including osteitis fibrosa cystica in 11 patients and aluminum-associated bone disease in 2 patients. Six patients had mixed disease, and 1 patient had osteoporosis. Despite 11 positive deferoxamine tests, bone biopsy revealed aluminum deposition in only 7 of these patients, suggesting extraosseous aluminum accumulation in the remaining 4. Evaluation of the positive and negative predictive accuracies of DPA, x-ray analysis, N-PTH levels, and aluminum bone deposition revealed that normal DPA or x-ray findings do not exclude bone disease, that N-PTH level is a good marker for secondary hyperparathyroidism, and that a negative deferoxamine test excludes aluminum-associated bone disease. Discriminant analysis also reinforced these conclusions.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorptiometry, Photon↗
PubMed1992

Metallic debris in femoral endosteolysis in failed cemented total hip arthroplasties.

A prospective study was undertaken to quantitate metallic and cement debris in 12 consecutive patients with femoral endosteolysis (FE) and aseptic loosening of a cemented total hip arthroplasty. The mean interval between primary and revision surgery was 9.6 years. The average time to onset of FE was 8.9 years. There were four stems each of cobalt-chromium (Co-Cr), stainless steel (SS), and titanium alloy. At revision, tissue was retrieved from FE, the femoral bone-cement pseudomembrane, and the joint pseudocapsule. Histology of these tissues was studied using light and polarized microscopy. Metal and barium levels were measured by atomic absorption spectrophotometry. A histiocytic reaction and particulate cement debris were seen in every case. Polyethylene wear debris was noted in 11 of 12 cases (92%), and metallic debris in four cases (33%). Detectable metal levels were found in the FE in all cases. Metal levels were on average 2.5 times higher in FE than in femoral pseudomembrane, and 4.2 times higher than in joint pseudocapsule. This difference was statistically significant for the Co-Cr and SS groups. Barium levels in areas of FE were on average 1.7 times and 42.4 times higher than in femoral pseudomembrane and joint pseudocapsule, respectively. The difference seen between the FE and the joint pseudocapsule tissue was significant for all three alloy groups. The authors' data demonstrated higher metal and barium levels in FE than in the other tissue sites. Polyethylene and cement debris were noted in nearly every case. Cement, polyethylene, and metallic particulate wear debris may contribute to the pathogenesis and progression of FE.

Adult↗
PubMed1992

Cobalt-alloy metal debris in periarticular tissues from total hip revision arthroplasties. Metal contents and associated histologic findings.

To investigate the hypothesis that an association exists between the presence of metallic particulate or ionic debris released from the components of a total hip replacement and the histologic reaction in the surrounding tissues, cobalt, chromium, nickel, and molybdenum levels were measured in periarticular tissue from 22 individuals who had revision surgery. Total tissue content of the four elements (averaged per case) ranged from 2.7 to 250 micrograms of metal per gr of dried tissue (mean, 39 micrograms/gr); however, within each case, the tissue-metal content varied more widely. The highest total tissue-metal contents occurred in cases revised for infection. Fibrosis, histiocytic reaction, hemorrhage, and necrosis were the most frequent histologic findings. Polyethylene and cement particles each appeared in approximately half of all sections, while microscopic metal particles were seen only in tissues from the infected hips. Tissue-metal content did not correlate with the histologic findings, with any of the demographic variables, nor with duration of implantation. Ratios of the individual constituent elements generally reflected the cobalt-chromium alloy composition, suggesting that metal debris was present predominantly as wear particles. Only for tissues with very low metal contents did departures of these ratios indicate the presence of ionic corrosion products. The extremely low metal contents measured in many cement-bone interfacial tissues and the few metal particles found histologically suggest that metal particles may have been less important in inflammatory reaction and loosening than cement or polyethylene particles.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗