Biomedical subjects

D P Mukherjee

Publications and source records attributed to D P Mukherjee.

At least 19 recordsLinked to original sources

PubMed2003

An animal evaluation of a paste of chitosan glutamate and hydroxyapatite as a synthetic bone graft material.

The objective of this study was to develop a synthetic bone graft in a paste form. Reported here are the results of the evaluation of a paste of chitosan glutamate (Protosan) and hydroxyapatite (referred to as a paste) used in a critical size defect model in rats. Eight-millimeter--diameter cranial defects were made in rat calvaria following a protocol approved by the animal review committee. Five groups were studied: (1) empty control, (2) defect filled with paste only, (3) defect filled with the paste containing bone-marrow aspirate, (4) defect filled with paste containing BMP-2, and (5) defect filled with paste containing osteoblasts cultured from bone-marrow aspirate. The sacrifice intervals were 9 and 18 weeks. Calvaria containing the defect were harvested, and the bone mineral density (BMD) was determined by dual energy X-ray absorptiometry. Push-out strength measurements were also performed. The BMD values of empty control were significantly lower than those of other groups at both 9 and 18 weeks. The mechanical properties, that is, push-out strengths and area under the push-out load and displacement were not significantly different between the samples. Histological examination of Goldner-trichromestained undecalcified sections showed the presence of mineralized bone spicules in the defect areas that were more prominent in those filled with paste and osteoblasts cultured from bone-marrow aspirate. Hence, this study demonstrated that the paste of chitosan glutamate and hydroxyapatite-containing osteoblasts cultured from bone-marrow aspirate would be an effective material to repair bone defects.

Animals↗

PubMed2003

A biomechanical evaluation of the role of labrum on anterior/posterior translation of shoulders at different degrees of abduction.

The objective of the study was to investigate the effects of anterior and posterior labrums on the anterior/posterior translations of shoulders. Thirteen cadaver shoulders were arthroscopically evaluated and nine were selected based on the absence of any pathological findings. These shoulders were tested intact, vented and after sequential arthroscpoic incision of the anterior and posterior labrums. The anterior/posterior translations were measured in a specially designed apparatus. The loads vs. displacement curves were obtained. The loads vs. displacement curves of the shoulders before and after labrum incision did not show any appreciable differences. Moreover the measured loads at 6 mm displacement did not show any statistically significant differences due to labrum incision. It was concluded that both anterior and posterior labrum incisions of the shoulders did not show any appreciable differences in anterior/posterior laxity. An arthroscopic technique was successfully developed to isolate the effect of labrum on the shoulder laxity.

Aged↗

PubMed2001

The growth of chondrocytes into a fibronectin-coated biodegradable scaffold.

Porous scaffolds made from a biodegradable copolymer of trimethylene carbonate and glycolide were evaluated for tissue-engineered medical products. We examined the scaffold coated with cell adhesion protein and fibronectin and cultured under a dynamic mixing condition to enhance the growth of chondrocytes. Our hypothesis was that the combination of coating and dynamic mixing would be beneficial to the viability of the chondrocytic cells. Fibronectin was selected as the model protein because of its availability and routine assaying methods. Sterile samples of scaffolds of about 1 mm in thickness were coated with fibronectin at 37 degrees C for 1.5 h. Four groups of scaffolds were used: uncoated static or dynamic, and coated static or dynamic. Scaffold samples were placed in either a Petri dish or a spinner flask (static vs. dynamic groups) after inoculation with rat chondrocytes of an initial cell density of 1.29 x 10(5) cell/mL. After 7, 14, 21, and 28 days, each sample was fixed, embedded, and sectioned at 5 micro thickness. The sections were double-label immunostained using antibodies against cellular fibronectin synthesized by adherent cells as a measure of cell viability. A Hoechst 33258 nuclear stain was used to measure the number of cells attached to the scaffold at each time interval. The slides were examined using a fluorescence microscope to determine the cell ingrowth. At least 25 fields/treatment group (except the 7 day group) were measured. The data showed that cell in-growths into the porous scaffolds were higher at all time periods for the coated dynamic group than those for the other three groups.

Animals↗

PubMed2000

Fatigue properties of hydroxyapatite-coated dental implants after exposure to a periodontal pathogen.

We studied the fatigue properties of rods (4 mm diameter) of hydroxyapatite-coated, titanium alloy implant material after it was exposed to a periodontal pathogen, Actinobacillus actinomycetemcomitans (Aa). We varied the crystallinity of the hydroxyapatite (HA) coating in these rods to the levels of, 60.5%, 52.8%, and 47.8%. Each rod was first inoculated with Aa in the log phase of its growth cycle. After 48 h, we counted the adhered cells. We measured the dissolution of HA coating due to bacterial exposure alone by determining the calcium and phosphate concentrations in the bacterial growth media. Once the adherent bacteria were removed from these rods, we subjected them to 5 million cycles of fatigue testing after immersion in Lactated Ringer's solution. We then determined the calcium and phosphate concentrations in the fatigue media. We found additional coating loss after fatiguing of the samples. This coating loss was a cumulative effect of bacterial exposure and fatigue loading of the hydroxyapatite-coated dental implant alloy. The lower crystallinity sample showed a higher loss of coating within the range of crystallinity studied here. The HA coating in implants during clinical use may undergo such changes, because they are exposed to the same bacteria.

Aggregatibacter actinomycetemcomitans↗

PubMed2000

An in vitro study of the effect of bony buttressing on fixation strength of a fractured atrophic edentulous mandible model.

PURPOSE: The purpose of this study was to measure the resistance to displacement in an adult bovine rib mandible model as the vertical dimension of the bone decreases, and to compare the fixation strength of titanium miniplates and reconstruction plates. MATERIALS AND METHODS: Five groups of 6 ribs each were tested based on the vertical dimension of the rib and method of fixation (group 1, 40 mm, miniplate), (group 2, 30 mm, miniplate), (group 3, 20 mm, miniplate), (group 4, 10 mm, miniplate), (group 5, 10 mm, reconstruction plate). In the 4 groups stabilized with a miniplate, a 3-hole-per-segment, 2.0-mm titanium miniplate and 6.0-mm monocortical titanium screws were used. In group 5, a 3-screw-per-segment, 2.4-mm titanium reconstruction plate and 2.4-mm bicortical titanium screws were used for fixation. A 2-dimensional beam model (Class III lever) was established, and an Instron machine was used initially to develop a load-displacement curve to 100 N for each specimen. An osteotomy was then created, and the segments were reduced without preload. The ribs were then loaded to failure in the Instron machine. The load-displacement curve and failure load were recorded. RESULTS: There was no significant difference (P < or = .05) between any of the groups before the osteotomy. At 75 N, groups 1 and 2 were superior to group 5 in resistance to displacement. Group 4 showed significantly less (P < or = .05) resistance to displacement than the other experimental miniplated subgroups. As loads increased, groups 1 and 2 continued to show increased resistance to displacement when compared with groups 3, 4, and 5. Loads to failure for groups 1 and 2 were comparable to group 5. CONCLUSIONS: Decreased resistance to displacement occurs with decreasing vertical dimension of the bovine rib. In fractures of the edentulous mandible, a miniplate is more likely to provide adequate fixation if the mandible is 30 to 40 mm in height (nonatrophic). At higher loads, groups with greater vertical height (30 mm and 40 mm) provided resistance to displacement equivalent to the 10-mm group repaired with a reconstruction plate. Therefore, fractures of the atrophic mandible may be better treated with more rigid techniques.

Alveolar Bone Loss↗

PubMed2000

Effect of carbon coating on the properties of gamma irradiated ultra-high-molecular-weight polyethylene specimens.

We reported the effect of carbon coating on the changes in properties of the ultra-high-molecular-weight polyethylene standard material (Hospital for Special Surgery) alter gamma irradiation in air and storage for 2 years. The coating showed a slight improvement in crystallinity (X-ray) and tensile properties (under cyclic loading) over the uncoated and irradiated control group. The oxidation level as measured by Fourier- transform infrared spectroscopy was unaffected by coating.

Air↗

PubMed1998

Impact of safe water for drinking and cooking on five arsenic-affected families for 2 years in West Bengal, India.

The groundwater in seven districts of West Bengal, India, covering an area of 37,000 km2 with a population of 34 million, has been contaminated with arsenic. In 830 villages/wards more than 1.5 million people, out of the total population, drink the arsenic-contaminated water. Safe water from a source having < 0.002 mg 1(-1) arsenic has been supplied for 2 years to five affected families comprising 17 members (eight of them with arsenical skin-lesions) of different age groups for impact assessment study in terms of loss of arsenic through urine, hair and nail. The study indicates random observable fluctuations of arsenic concentration in urine among members on different scheduled sampling days with a declining trend, particularly during the first 6 months. Furthermore, the investigation showed that despite having safe water for drinking and cooking, the study group could not avoid an intake of arsenic, time and again, through edible herbs grown in contaminated water, food materials contaminated through washing, and the occasional drinking of contaminated water. After minimizing the level of contamination, a noteworthy declining trend after 8 months was observed in urine, hair and nails in all the cases, but not to that level observed in a normal population, due to prevailing elevated background level of arsenic in the area. The eight members, who had already developed skin lesions, are far from recovering completely, indicating a long-lasting damage. Statistical interpretation of the data are considered.

Adolescent↗

PubMed1998

Comparison of fixation strengths of locking head and conventional screws, in fracture and reconstruction models.

PURPOSE: Claimed clinical advantages of the locking-head mandibular reconstruction plating system include the ability to achieve stability with fewer numbers of screws per bony segment as compared with conventional screws. The purpose of this study was to test the hypothesis that increased resistance to displacement will be obtained when using locking-head as compared with the same number of conventional screws per segment in both fracture and reconstruction models. MATERIALS AND METHODS: Eight groups were tested based on the screw number (two or four), screw type (locking-head or conventional), and fracture (bony apposition) or reconstruction model (1-cm defect). Two-dimensional beam mechanics using adult bovine ribs and the Instron machine were used to develop a load-displacement curve up to 150 N for each specimen. An osteotomy was then created and the segments were reduced, with preload (fracture model) or with a 1-cm defect (reconstruction model), and plated using the Synthes locking-head plate with either two or four bicortical locking-head (4.0-mm) or conventional (2.7-mm) screws per segment. The fixed ribs were loaded to 150 N, and the displacement was recorded. RESULTS: Locking-head screws provided superior resistance when using two screws per segment in the reconstruction model as compared with conventional screws. Minimal difference was seen between other screw types within a model. The fracture model offered significantly greater (3.1 to 3.7X) resistance to displacement than did the reconstruction model. CONCLUSIONS: Locking-head screws provided significantly increased resistance to displacement when only two screws per segment were used in the reconstruction model. When four screws per segment were used, there was no significant difference between locking-head and conventional screw types in either model. The effect of bony buttressing is significant and may explain why miniplates often fail in the atrophic mandible but are successful in the fully dentate patient.

Animals↗

PubMed1998

The duration of pretreatment with ticlopidine prior to stenting is associated with the risk of procedure-related non-Q-wave myocardial infarctions.

OBJECTIVES: This study sought to determine whether the duration of pretreatment with the adenosine diphosphate receptor antagonist ticlopidine prior to intracoronary stenting is associated with the incidence of procedure-related non-Q-wave myocardial infarctions (MIs). BACKGROUND: Dual antiplatelet therapy with ticlopidine and aspirin is routinely used with stenting, although ticlopidine is commonly not begun until the day of the procedure. Periprocedural MIs are at least partially platelet-dependent events. As the maximal platelet inhibitory effects of this drug take 2 to 3 days to be realized, we hypothesized that longer treatment prior to stenting would be associated with lower rates of procedure-related MIs. METHODS: We reviewed outcomes in 175 consecutive patients treated with ticlopidine prior to stenting at the Cleveland Clinic Foundation. Those patients with an elevation in creatine kinase above our laboratory normal (>210 IU/L) with > or =4% MB fraction on routine evaluation were defined as having a non-Q-wave MI. RESULTS. There were 28 patients (16%) who had a non-Q-wave MI. Longer duration of ticlopidine pretreatment was strongly associated with a lower incidence of procedure-related non-Q-wave MIs (duration of pretreatment <1 day, 29% had MI; 1 to 2 days, 14%; > or =3 days, 5%; chi-square for trend=9.6; p=0.002). Ticlopidine pretreatment of > or =3 days was associated with a significant reduction in the risk of non-Q-wave MI (unadjusted odds ratio 0.18, 95% confidence interval=0.04 to 0.78, p=0.01) compared with pretreatment of <3 days. CONCLUSIONS: Among patients undergoing intracoronary stenting, beginning ticlopidine therapy several days prior to the procedure is associated with a reduced risk of procedural non-Q-wave MIs.

Blood Vessel Prosthesis Implantation↗

PubMed1997

Mechanical stability of thoracolumbar pedicle screw fixation. The effect of crosslinks.

STUDY DESIGN: Pedicle screw fixation for unstable thoracolumbar spine injuries is relatively new. The effect of one or two crosslinks on rotational and lateral bending stiffness was studied. OBJECTIVE: To determine the rotational and bending stiffness values of thoracolumbar fractures fixed by the AO's internal fixation system with zero, one, or two crosslinks. METHODS: Eight embalmed thoracolumbar spine segments. (T12-L2) were instrumented at T12 and L2 with a pedicle screw-rod system. Rotational stiffness was determined for 10 cycles to 2.5 degrees, 3.5 degrees, and 5 degrees of rotation, with and without one or two crosslinks, and lateral bending stiffness for 10 cycles to 0.25, 0.40, and 0.50 inch. The results showed a clear trend toward increased stiffness with crosslinks. RESULTS: The stiffness values of the two-crosslink construct at 2.5 degrees and 3.5 degrees of rotation were significantly higher than those of the zero-crosslink system. Also, the bending stiffness of the two-crosslink construct was significantly higher than that of no-crosslink system at all of the displacements. CONCLUSIONS: Rotational stiffness values of the two-crosslink construct were significantly higher than those of the zero-crosslink system, at 2.5 degrees and 3.5 degrees of rotation. Lateral bending stiffness of the two-crosslink system was higher than that of the zero-crosslink system at all levels of displacement.

Biomechanical Phenomena↗

PubMed1997

Biomechanical evaluation of new fixation devices for mandibular angle fractures.

This biomechanical study investigated the effectiveness of fixation devices of simulated angle fractures in sheep mandibles. The fractures were stabilized by a Leibinger 8-hole three-dimensional (3-D) plate, a Synthes eight-hole mesh plate, and a Synthes six-hole reconstruction plate with 2.0-mm and 2.4-mm mono- and bicortical screws. Each mandible was tested in bending (class III cantilever model). The bone mineral density of the mandibles was measured by computed tomography scan. The Leibinger 3-D plate showed plate deformation in bending of > 230 N. None of the plates showed failure in the bone/screw interface. The gap and displacement values for the mesh and 3-D plate were comparable to those of the reconstruction plate. These results indicate that a 3-D or mesh plate can be used for fixation of mandibular angle fractures.

Animals↗

PubMed1996

Cyclic fatigue of hydroxyapatite-coated titanium alloy implant material--effect of crystallinity.

Titanium alloy (ASTM F-136) rods were coated with hydroxyapatite (HA) of 3 levels of crystallinity, which were determined by X-ray diffraction (XRD) analysis to be 60.5%, 52.8%, and 47.8%. Fourier Transform Infrared (FTIR) spectroscopy analysis showed the removal of the hydroxyl and carbonate groups as compared to the original HA powder. It appears that these changes are caused by the high temperature plasma spray coating process. Cyclic fatigue testing in a lactated Ringer's solution to 5 million cycles showed no statistical difference in calcium dissolution among the 3 crystalline levels, whereas phosphorus dissolution was lowest from the highest crystalline coating sample. The mechanical properties, however, did not change in response to fatigue loading.

Alloys↗

PubMed1995

Anterior screw fixation of type II odontoid fractures. A biomechanical study.

STUDY DESIGN: This study examined the torsional and shear stiffness of Type II odontoid fractures that were stabilized with two 3.5-mm cannulated AO screws or a single 4.5-mm cannulated Herbert screw. OBJECTIVE: To determine the stability of a commonly used two-screw method versus a single-screw fixation method. Insertion of a single screw could make the procedure technically easier. SUMMARY OF BACKGROUND DATA: Biomechanical studies have shown the 4.5-mm Herbert screw to generate greater compressive forces than 3.5-mm cannulated screws, which are commonly used to anteriorly stabilize Type II odontoid fractures. No previous biomechanical studies have compared the shear or torsional stiffness of Type II odontoid fractures stabilized with these screws. METHODS: Twelve cadaver C2 vertebrae were harvested and an osteotomy was performed to simulate a Type II fracture pattern. Six were stabilized with two 3.5-mm cannulated screws, and the remaining were stabilized with a single 4.5-mm cannulated Herbert screw. Each specimen then was tested in torsion through +/- 0.75 degrees, +/- 1.25 degrees, and +/- 1.75 degrees for 10 cycles each. Shear forces then were applied from an anterior to posterior direction to a maximum load of 44.48 N. RESULTS: The mean torsional stiffness for the Herbert screw was 1196 N.m/deg, which was significantly greater than the mean stiffness of the 3.5-mm screw fixation, which measured 434 N.m/deg. The mean shear stiffness for the Herbert screw fixation was 106.9 kN/m, compared to 86.1 kN/m for the 3.5-mm cannulated screw. This was not statistically significant. CONCLUSIONS: The biomechanical properties of the 4.5-mm cannulated Herbert screw suggest it may lend itself for use in fixation of Type II odontoid fractures. With only a single screw to insert, this technically demanding procedure may be less daunting.

Aged↗

PubMed1995

Bacterial colony counting using distance transform.

A distance-transform based technique is presented for the segmentation of monochrome images of colonies grown on membrane filters. This is used to count the number of Escherichia coli in a given water sample, which is used as a parameter for determining water quality. The result is compared with fuzzy c-means clustering approach.

Algorithms↗

PubMed1993

Myotrophin induces early response genes and enhances cardiac gene expression.

We have identified and partially sequenced a soluble factor, myotrophin, from spontaneously hypertensive rat hearts and hypertrophic human hearts that enhances myocyte protein synthesis and stimulates myocardial cell growth. Our studies suggest that myotrophin may be a biochemical link between hemodynamic stress and myocardial cellular hypertrophy. When rat neonatal cardiac myocytes maintained in culture were incubated with myotrophin for 30 minutes, they showed a marked increase in c-myc, c-fos, and c-jun messenger RNA levels. Cardiac myocytes treated for 24 hours with myotrophin showed a fourfold increase in connexin 43 (gap junction protein), a sixfold increase in atrial natriuretic factor, a threefold increase in skeletal alpha-actin, and a threefold increase in total myosin transcript levels. Studies on myosin isoforms showed a selective increase in the beta-myosin heavy chain transcript levels but no reciprocal decrease in alpha-myosin heavy chain transcript levels. Our data suggested that myotrophin appears to be a primary modulator for myocardial cell growth and differentiation and may play an important role in the pathogenesis of cardiac hypertrophy. Myotrophin may be involved in the upregulation of myofibrillar protein and the activation of cardiac gene transcription during growth and hypertrophy of the myocardium, and the induction of early response gene expression may be linked to this response.

Actins↗

PubMed1993

The application of new composite materials for total joint arthroplasty.

The material and design issues for the composite hip stem development are examined. The development of the "isoelastic" hip is based on the hypothesis that the matching of the material modulus to that of cortical bone will result in an optimal stress transfer to the bone, resulting in a minimal bone loss. The biomechanical data showed no statistical difference in strain transfer in the bone before or after implantation of low modulus stems. The clinical reports of a number of earlier "isoelastic" devices showed evidence of loosening and lack of stability. The current interest has been in the development of femoral components made from carbon fiber reinforced polyaryletherketone, polysulfone, and carbon/carbon composites. As these materials are optimized, it is important to look into matching the rigidity of bone. Moreover, the unsupported neck area needs to be as strong as metal, like Ti6-Al4-V, to prevent failure, whereas the femoral component inside the bone needs to have lower rigidity. Therefore, monolithic composite material from neck area to the distal stem will not withstand the loading needs and a material optimization scheme is required to come up with a long-lasting composite device. Lastly, the price vs. patient benefits for these composite material stems need to be established.

Cost-Benefit Analysis↗

PubMed1987

Biological affinities between the migrant groups of fishermen of Puri Coast, Orissa, India.

Biological affinities between the three endogamous groups of marine fishermen of Puri are examined with the help of nine anthropometric measurements and 22 dermatoglyphic traits of fingers and palms. The results are interpreted in the light of their ethnic, geographical, and migrational backgrounds. Multiple discriminant analysis and Mahalanobis's generalized distances suggest higher discrimination of populations with reference to anthropometric traits as compared to that in dermatoglyphic variables. While the nature of interpopulation distances conforms to the geographic pattern in anthropometrics, no clear picture emerges in the dermatoglyphic distances supporting either ethnic or geographic evidence.

Adult↗

PubMed1985

A new synthetic monofilament absorbable suture made from polytrimethylene carbonate.

The physical and biologic characteristics of a new synthetic absorbable monofilament suture, glycolide trimethylene carbonate (GTMC) are presented. The suture was formulated to combine predictable in vivo performance of synthetic absorbable sutures with the handling characteristics of a monofilament suture. Three in vivo studies were described: strength, gross and microscopic absorption and reaction, and radiolabelled decay. The studies carried out in rats showed cumulative strength retention of sizes 0, 00, 4-0 and 5-0 of 81 per cent at 14 days, 59 per cent at 28 days and 30 per cent at 42 days. Strength retention was consistent throughout the size spectrum. Absorption of sizes 00 and 4-0 were studied in subcutaneous implantations in rabbits. Histologic assessment of absorption obtained from serial sections at intervals of three to nine months showed that, in both sizes, complete absorption occurred between six and seven months. At six months, 83 per cent of size 00 was absorbed and size 4-0 was 93 per cent absorbed. At seven months, no implanted material was discernible histologically. Untoward tissue reactions, such as acute inflammatory cells, abscesses or tissue necrosis, were not observed. There were no signs of cellular mobilization of any kind observed remote from the implant. Absorption of GTMC sutures was achieved through the action of mononuclear and multinuclear macrophages which were confined to the implant and sequestered by a fibrous connective tissue capsule. When implant absorption was complete, resorbtion of the macrophage component was observed which was replaced by a narrow cord of fibrous tissue and collagen. The results of studies of radiolabelled sutures carried out in the subcutaneous tissues of rats revealed urine and expired CO2 to be the major excretary routes of the metabolites. By 22 to 24 weeks, 0.1 to 0.7 per cent of the total implanted radioactivity remained at the suture sites. Tissue deposition and excretion of radioactivity suggests similar metabolism of the sutures in both species. We conclude that GTMC sutures maintain good strength with little or no absorption during the critical wound healing period, absorbs completely from tissues in six to seven months with minimal tissue reaction and, therefore, provides an absorbable, flexible, monofilament material with extended support that is strong and effective.

Absorption↗