Biomedical subjects

V Shetty

Publications and source records attributed to V Shetty.

At least 37 records · Page 2Linked to original sources

PubMed1999

Biological characteristics of myelodysplastic syndrome patients who demonstrated high versus no intramedullary apoptosis.

Spontaneous intramedullary apoptosis was measured in bone marrow (BM) biopsies of 175 patients with myelodysplastic syndromes (MDS) using in situ end-labeling (ISEL) of fragmented DNA. Two groups of high (n=71) versus low (n =43) levels of apoptosis were identified while 61 patients were ISEL-negative. Semiquantitative assessment of 3 cytokines, the number of macrophages and in vivo labeling indices (LI) were also determined from consecutive sections of the biopsy. Patients with high apoptosis levels tended to have a high LI (p=0.013), more macrophages in their BM biopsies (p=0.006) and higher tumor necrosis factor alpha (TNF-alpha) levels (not significant) compared to patients with no apoptosis. In addition, low risk MDS patients had significantly lower rates of apoptosis (p = 0.047) and lower levels of TNF-alpha (p = 0.055) compared to high-risk MDS patients. We conclude that the genesis of cytopenias in MDS is of multifactorial origin and that cytokine-associated apoptosis clearly identifies a distinct biological subgroup of patients who may benefit selectively by use of anti-cytokine therapies.

Aged↗

PubMed1999

Biologic characteristics of 164 patients with myelodysplastic syndromes.

Rates of proliferation, apoptosis and cytokine expression were measured in bone marrow (BM) biopsies of 164 myelodysplastic syndrome (MDS) patients. There were 107 males and 57 females. Median age was 69 years and 101 had refractory anemia (RA), 17 RA with ringed sideroblasts (RARS), 38 with RA and excess blasts (RAEB) and 8 with RAEB in transformation (RAEB-t). Apoptosis measured by in-situ end labeling (ISEL) was directly related to the number of macrophages (p = 0.028, n = 83). Mean tumor necrosis factor alpha (TNF-alpha) and ISEL positivity were higher in RAEB + RAEB-t patients (p = 0.0554 and p = 0.06 respectively) while hemoglobin was higher for RA + RARS group (p = 0.0472). Patients with high apoptosis had lower white blood cell counts (p = 0.0009), lower percentage of blasts (p = 0.0009) and higher number of macrophages (p = 0.0086). We conclude that measurements of apoptosis, proliferation and cytokine expression provide important biological information which helps to distinguish RA + RARS patients from RAEB + RAEB-t patients, and may be of additive prognostic significance.

Adolescent↗

PubMed1999

The relative extent and propensity of CD34+ vs. CD34- cells to undergo apoptosis in myelodysplastic marrows.

The paradox of peripheral cytopenias despite cellular bone marrow (BM) observed in myelodysplastic syndromes (MDS) has been associated with excessive intramedullary apoptosis of hematopoietic cells. Since MDS is regarded as a stem cell disorder, the present studies were undertaken to examine the relative susceptibility and propensity of early progenitor CD34+ cells to undergo apoptosis as compared to more maturing/matured CD34- cells. Five serial studies were performed on 4 independent groups of 36 newly diagnosed MDS patients. First, in 2 separate groups of 16 and 8 patients each, measurement of the extent of apoptosis in CD34+ and CD34- fractions of the BM aspirate mononuclear cells was carried out using independent biparametric flow cytometry methods, CD34 labeling/terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) (n = 16), and CD34 labeling/reduced uptake of nucleic acid staining dye LDS751 (n = 8). The difference in the median degrees of apoptosis in CD34+ vs. CD34- cells was not statistically significant by either technique (P = 0.583 and P = 0.674 for TUNEL and LDS751, respectively). In the next group of 4 MDS patients, a double-labeling was performed on plastic embedded marrow biopsy sections, to detect CD34 antigen with specific monoclonal antibody and apoptosis by in situ end labeling (ISEL) of fragmented DNA. Despite high overall apoptosis (56.2% +/- 18.4%), only an occasional CD34+ cell was found to be simultaneously labeled with ISEL. Finally, in the last group of 8 MDS patients, CD34+ cells were separated from CD34- cells on affinity column and cultured in serum containing medium for 4 hours. At 0- and 4-hour time points, ISEL was carried out to label apoptotic cells. In addition, a fluorometric assay was employed to estimate the activity of a proapoptotic enzyme, Caspase 3. Both the net increase in % ISEL labeled cells (apoptotic index or AI) and Caspase-3 activity were significantly lower in CD34+ cells as compared to CD34- cells (AI, 0.87% +/- 0.5% vs. 3.97% +/- 1.4%, n = 6, P = 0.028 and Caspase-3 Units/mg protein, 46.9 +/- 25.0 vs. 71.7 +/- 23.03, n = 5, P = 0.042, respectively). We conclude that when estimated in a total population of mononuclear cells, CD34+ cells and CD34- cells show comparable degrees of apoptosis. However, once separated the CD34+ fraction demonstrates lower propensity to undergo apoptosis, thereby suggesting the CD34- fraction as being a possible source for proapoptotic signaling.

Aged↗

PubMed1999

Spontaneous down-regulation of Fas-associated phosphatase-1 may contribute to excessive apoptosis in myelodysplastic marrows.

In this study, we examined the role of Fas-signaling in the apoptotic pathway in myelodysplastic syndromes (MDS). Ficoll-separated mononuclear cells from 18 bone marrow aspirate specimens obtained from 17 MDS patients, 4 normal healthy donors, and 3 acute myeloid leukemia patients transformed from MDS (t-AML) were studied for mRNA expression of Fas-L, Fas, and the effectors of their signaling, Caspase 1 and Caspase 3, using reverse transcriptase polymerase chain reaction. Fas-L, Fas, and Caspase 1 were detectable in all of the samples in the three groups. Caspase 3 was detectable both in MDS and t-AML specimens but was negligible in normal cells. The apoptotic index (AI%) determined by in situ end labeling of fragmented DNA in 4-hour cultures of mononuclear cells was significantly higher in MDS cells compared to normal or t-AML cells (mean +/- SEM: 2.3% +/- 0.4% in MDS, n = 10 vs. 0.6% +/- 0.2%, n = 4, P = 0.014 in normal cells, and 0.2% +/- 0.2%, n = 3, P = 0.007 in t-AML cells). Treatment of MDS cells with anti-Fas-L antibody suppressed apoptosis (AI%: 2.1% +/- 0.6% in untreated vs. 1.37% +/- 0.5% in treated, n = 6, P = 0.02), indicating functional participation of Fas-signaling in MDS. Further, it was found that Fas-L, Fas, and Caspase 1 mRNA expression remained unchanged in 4 hours. Caspase 3 expression appeared in normal cells after 4 hours and was present at both 0 and 4 hours in MDS and t-AML cells. In contrast to persistent expression in normal and t-AML cells, cells from the 5 MDS patients studied consistently showed significantly lowered or undetectable expression of a negative regulator of Fas, called Fas-associated phosphatase-1 (Fap-1) after 4 hours. Thus, the high AI% in MDS corresponds to a rapid decline in Fap-1. Furthermore, in tumor necrosis factor alpha (TNF-alpha) treated HL60 promyelocytic cells, a definite periodicity in the expression of different mRNAs was observed with upregulation of TNF-alpha itself at 30 minutes, increased expression of Fas and the appearance of Fas-L after 2 hours, and a decrease in Fap-1 expression after 8 hours. These results suggest that TNF-alpha not only induces the effectors of Fas-signaling but also may downregulate the inhibitor. We conclude that a spontaneous and rapid down-regulation of Fap-1, possibly induced by TNF-alpha, a cytokine shown to be present in excess in MDS marrows, may underlie the increased apoptotic death of hematopoietic cells in these patients. Interference with Fap-1 turnover may provide a new therapeutic modality for MDS.

Apoptosis↗

PubMed1998

Apparent expansion of CD34+ cells during the evolution of myelodysplastic syndromes to acute myeloid leukemia.

Myelodysplastic syndromes (MDS) are highly proliferative bone marrow (BM) disorders where the primary lesion presumably affects a CD34+ early progenitor or stem cell. We investigated the proliferative characteristics of CD34+ cells of 33 untreated MDS patients (19 RA, 5 RARS, 7 RAEB, 2 RAEBt) and five patients with acute myeloid leukemia after MDS (sAML). All patients received a 1-h infusion of the thymidine analogue iodoor bromodeoxyuridine intravenously before a BM aspirate and biopsy was taken. A double-labeling immunohistochemistry technique by monoclonal anti-CD34 (QBend/10) and anti-IUdR/BrdU antibodies was developed and performed. By this technique we recognised CD34+ and CD34- cells actively engaged in DNA synthesis or not. As MDS evolves a significant increase occurred in the percentage of CD34+ cells of all myeloid cells (mean value: RA/RARS 1.67%; RAEB(t) 8.68%; sAML 23.83%) as well as in the percentage of proliferating CD34+ cells of all myeloid cells (RA/RARS 0.19%; RAEB(t) 0.43%; and sAML 3.30%). This was associated with a decreasing trend in the overall myeloid labeling index (LI: RA/RARS 25.8%, RAEB(t) 24.6% and sAML 21.5%). This decrease in overall myeloid LI is due to an exponential increase in the proportion of CD34+ cells of the proliferating compartment during MDS evolution (RA/RARS 0.35%, RAEB(t) 1.44% and sAML 11.98% of all S-phase cells). These CD34+ cells appeared to proliferate more slowly than their more mature CD34 negative counterparts, since we found a progressive increment in the mean total cell cycling time (Tc) of all myeloid cells during MDS progression (RA/RARS 39.8, RAEB(t) 45.2 and sAML 65.8 h). This study showed that during MDS evolution to sAML the CD34+ compartment develops a growth advantage leading to apparent expansion.

Acute Disease↗

PubMed1998

Tumor necrosis factor-alpha levels decrease with anticytokine therapy in patients with myelodysplastic syndromes.

Tumor necrosis factor-alpha (TNF-alpha) levels were measured in the serum (sTNF-alpha) or bone marrow (BM) biopsies of 43 patients with myelodysplastic syndromes (MDS) who subsequently received therapy with a combination of pentoxifylline and ciprofloxacin (PC) with or without dexamethasone (PCD). All 43 patients received only PC therapy for 12 weeks, after which 18 of 36 nonresponders received PCD. A total of 18 of 43 patients showed a hematologic or cytogenetic response or both. BM TNF-alpha levels were semiquantitatively assessed using immunohistochemistry on a scale of 0-8+ and in the serum using enzyme linked immunoassay. The median TNF-alpha for the entire group was 3.0 in BM and 6.9 pg/ml in the serum, and 14 patients had no detectable levels. Responders had higher BM levels (median 3.5 vs. 2.0) than nonresponders, although this was not statistically significant. During PC therapy, a decline in BM TNF-alpha level was seen in the entire group, which was significant at 2 weeks (p = 0.02), 8 weeks (p = 0.001), and 12 weeks (p = 0.0001). Both responders (p = 0.01) and nonresponders (p = 0.03) had a decline at 8 weeks, but at 12 weeks, only the responders continued to show a significant decline (p = 0.03). We conclude that MDS patients with high BM TNF-alpa levels have a better chance of responding to PCD therapy and that the therapy is quite successful in reducing the TNF-alpha levels in a sustained fashion. Future studies need to be directed at identifying agents that would be more potent suppressors of the proapoptotic cytokines in these patients.

Aged↗

PubMed1997

Torsion-axial force characteristics of SR-PLLA screws.

The torsion axial-force characteristics of biodegradable screws are central to their ability to generate interfragmentary compression when used as lag screws. The purpose of this investigation was to compare the torsion-axial force characteristics of prototype self-reinforced poly-L-lactide (SR-PLLA) screws with conventional titanium screws. Axial forces developed by incremental increases in the torque applied to the individual screws were measured in a test apparatus incorporating an Instron machine. For the SR-PLLA screws, the relationship between applied torque and axial force development was non-linear with a marked relaxation throughout the test range. The axial forces reached a maximum with increasing torque, after which failure of the screws occurred. The response curve for titanium screws of the same length demonstrated a steeper slope. No failures or force relaxation were observed with the titanium screws. The results of this investigation suggest that, at this time, the use of SR-PLLA screws for lag screw fixation should be restricted to low stress bearing areas.

Biodegradation, Environmental↗

PubMed1997

Knowledge, attitude and practice of dental caries and periodontal disease prevention among primary school teachers in Udupi municipality.

Primary school teachers of Udupi municipal corporation were surveyed to determine their knowledge, attitude and practice toward dental caries and periodontal disease prevention. Fourteen schools were selected by cluster sampling and the teachers working in these schools were included in the sample. The questionnaires were completed by one hundred teachers. The results showed that school dental health services must compulsorily hold demonstrations or lectures on prevention of oral diseases during school feasts and parent teacher meetings, in order to involve the teachers and parents in oral health promotion of the child.

Adult↗

PubMed1996

Novel insights into the biology of myelodysplastic syndromes: excessive apoptosis and the role of cytokines.

The paradox of myelodysplastic syndromes (MDS) which present with pancytopenias despite cellular bone marrows (BM) was investigated by conducting detailed studies of proliferation and apoptosis in 89 MDS patients. Our results demonstrated a rapid rate of both proliferation as well as apoptosis. Levels of three cytokines, tumor necrosis factor-alpha (TNF-alpha), transforming growth factor-beta (TGF-beta) and interleukin-1 beta (IL-1 beta) were measured in the same patients. High levels of TNF-alpha were found to correlate with high levels of apoptosis in 83 MDS patients (P = 0.0045). We propose a dual role for TNF-alpha (or other cytokines) in the pathogenesis of MDS. On the one hand, TNF-alpha induces apoptosis in the maturing cells causing pancytopenia while on the other, it stimulates the proliferation of the primitive progenitors accounting for the hypercellular BM frequently seen in MDS. A new model for MDS is presented. The initial abnormality probably affects a primitive hemopoietic progenitor which acquires a growth advantage leading to monoclonal hemopoiesis, which in turn makes these cells susceptible towards acquiring additional mutations and appearance of cytogenetically marked (or unmarked) clones. Cytokines such as TNF-alpha whose source is presently unknown, then contribute towards the clinical syndrome of pancytopenia and hypercellularity.

Antigens, CD34↗

PubMed1996

Experimental analysis of functional stability of sagittal split ramus osteotomies secured by miniplates and position screws.

PURPOSE: This study determined the relative functional stabilities of various miniplate systems and configurations used to stabilize sagittal split ramus osteotomies (SSROs) and compared them with conventional internal screw fixation. MATERIALS AND METHODS: The biomechanical model was a reproducible prototype of a mandible sagittal osteotomy with consistent material and geometric properties. After advancing the distal segment by 7 mm, each set of mandible analogs (1 set = 3 analogs) was fixed bilaterally by one of three miniplate systems applied in various configurations, and tested with and without a supplemental 2.4-mm bicortical screw applied in the retromolar region. Reduced analogs were placed in a straining frame, and simulated masticatory loads were applied alternatively to the mandibular first molars. Ensuing osteotomy site displacements were measured by transducers attached to a computer-based data acquisition program. A coordinate transformation procedure was used to convert the component displacements captured by the individual transducers into a common "instability factor" to reflect fixation stability for each construct and loading condition. Instability factors for the individual constructs were compared with each other and with those obtained from analogs reduced exclusively with 2.4-mm position screws. RESULTS: Osteotomies stabilized with a combination of miniplates and position screws were more stable than those stabilized exclusively with miniplates (P < .0001). Post-hoc comparisons of mean instability factors (Dunnet's method) showed the miniplate-position screw combinations to be more stable than the 2.4-mm position screw system used as standard (P < .05). Miniplate systems alone were the least stable of the test constructs, with differential rates of failure between the individual miniplate systems. CONCLUSIONS: Exclusive use of miniplate fixation may not provide the consistent stability necessary for early functional restoration after SSROs. The addition of a position screw in the retromolar region substantially enhances the fixation stability of miniplate systems. The use of miniplates with retromolar position screws offers both technical and stability advantages over conventional miniplate or internal screw fixation. The fixation stability of the miniplate-position screw combination is independent of the type of miniplate system used.

Analysis of Variance↗

PubMed1996

Functional stability of sagittal split ramus osteotomies: effects of positional screw size and placement configuration.

PURPOSE: This study examined the effects of positional screw size and placement configuration on osteotomy site stability in a sagittal split ramal osteotomy model. MATERIALS AND METHODS: A reproducible analog of a sagittal split ramus osteotomy was developed to facilitate equitable comparisons of fixation stability. The distal segment of each analog was advanced by 7 mm and fixed bilaterally with 2.0-mm or 2.4-mm cortical screws applied in either a linear or a triangular configuration. Reduced analogs were placed in a straining frame, and simulated masticatory loads wee applied alternatively to the mandibular first molars. Ensuring osteotomy site displacements were acquired and registered by displacement transducers attached to a computer-based data acquisition program. A coordinate transformation procedure was used to convert the component displacements captured by the individual transducers into a common "instability factor" to reflect fixation stability for each construct and loading condition. RESULTS: Between configurations, the magnitude of interfragmentary displacement was less when the screws were applied in a triangular than in a linear configuration (P < or = .0001). Within configurations, 2.4-mm cortical screws provided greater stability than 2.0-mm screws. The stability profiles of the 2.0-mm screws, applied in a linear configuration at the superior border, were very similar regardless of whether two or three screws were used. The loads at which the linear systems became unstable were significantly higher (P < or = .0001) than for the triangular systems. Despite the twofold or higher difference in the mean instability factor of the individual test constructs, the SDs for each construct were only one tenth to one fifth of the corresponding means. CONCLUSIONS: None of the internal screw systems were grossly unstable when used to stabilize ramal osteotomies. Other conditions, including quality and strength of investing bone, being equal, cortical screws placed in a triangular configuration provide greater stability than screws placed in a linear configuration. Osteotomy sites stabilized by 2.4-mm screws are more stable than those stabilized by 2.0-mm screws. It does not matter whether two or three screws are applied at the superior border in a linear configuration, provided that the outer screws are an inch apart. The model system has a very good measurement precision and has important implications in optimizing fixation device design and placement configuration.

Bite Force↗

PubMed1996

A 6-year clinical assessment of electronic facial thermography.

OBJECTIVE: To report the findings a 6-year clinical application of ET on patients with orofacial pain. METHODS: ET was conducted (in a blinded manner) using an Agema 870 unit at 0.1 degree C thermal accuracy. A newly devised thermal classification system was applied: 'normal' when zone delta T was from 0.0 to +/-0.25 degree C, "hot' when zone delta T was > +0.35 degree C, 'cold' when zone delta T was < -0.35 degree C, and 'equivocal' when zone delta T was +/-(0.26-0.35) degree C. Study populations consisted of 164 dental patients mainly with diagnostic problems and 164 matched (control) subjects. RESULTS: Our prospective, matched study determined that subjects with 'hot' thermograms had the clinical diagnoses of sympathetically maintained pain, peripheral nerve mediated pain, TMJ arthropathy, and maxillary sinusitis. Subjects with 'cold' thermograms were found to have the clinical diagnoses of peripheral nerve-mediated pain and sympathetically independent pain. Subjects with 'normal' thermograms were found to have the clinical diagnosis of cracked tooth syndrome, trigeminal neuralgia, pretrigeminal neuralgia, or psychogenic facial pain. The new system of thermal classification resulted in 92% (301 of 328) agreement in classification of pain patients and matched controls. CONCLUSION: These studies suggest that ET has promise in aiding the formation of a differential diagnosis of orofacial pain and may help in understanding mechanisms of pain as well as directing therapies.

Adult↗

PubMed1996

A paradigm shift in myelodysplastic syndromes.

A poorly defined transforming event(s) affects the pluripotential bone marrow (BM) stem cell in myelodysplastic syndromes (MDS), conferring a growth advantage upon it which leads eventually to monoclonal hematopoiesis. The progeny of this transformed ancestor undergo recognizable albeit dysplastic maturation. We propose that this picture is further complicated by a variety of cytokines, tumor necrosis factor alpha (TNF-alpha), transforming growth factor beta (TGF-beta) and interleukin 1beta (IL-1beta) which exert a dual effect on the diseased cells. The immature CD34+ cells are stimulated to proliferate, while their later differentiated daughters are induced to undergo apoptosis accounting for the clinical syndrome of pancytopenia despite hypercellular BMs. Studies directed at measuring the rates of proliferation and apoptosis as well as the levels of TNF-alpha, TGF-beta and IL-1beta confirm this hypothesis and are presented in greater detail. A novel approach towards MDS therapy emerges as a result of this paradigm shift based upon the premise that anti-cytokine therapy would prevent excessive intramedullary apoptosis and result in improved cytopenias as well as cause a slowing down of the diseased precursor cell proliferation resulting in resumption of polyclonal hematopoiesis. Because a number of cytokines function through common lipid second messengers, interruption of this pathway should theoretically cause disruption in the signalling of a cascade of cytokines.

Apoptosis↗

PubMed1995

Apoptosis in bone marrow biopsy samples involving stromal and hematopoietic cells in 50 patients with myelodysplastic syndromes.

Cell-cycle kinetics were measured in situ after infusions of iododeoxyuridine and/or bormodeoxyuridine in 50 patients with myelodysplastic syndromes (MDS) and the median labeling index in bone marrow (BM) biopsy samples was 28.6%. Unfortunately, 26 of 50 patients showed that > or = 75% of hematopoietic cells of all three lineages were undergoing programmed cell death (PCD) in their biopsy samples as shown by the in situ end labeling (ISEL) technique. Ten patients had 1/3 and eight had 2/3 ISEL+ cells. Stromal cells were frequently ISEL+ and often S-phase cells were also found to be simultaneously ISEL+. Nucleosomal DNA fragments as a ladder in agarose gel were present in BM aspirates of four patients who showed high ISEL and were absent in two who had no ISEL staining in biopsy samples, but only when DNA was extracted after a 4-hour in vitro incubation in complete medium. Therefore, laddering data confirmed the ISEL findings that the majority of hematopoietic cells in MDS are in early stages of PCD. We conclude that extensive intramedullary cell death may explain the paradox of pancytopenia despite hypercellular marrows in MDS patients. Investigating approaches that protect against PCD in some MDS subsets would be of interest.

Acute Disease↗

PubMed1995

Simultaneous assessment of cell kinetics and programmed cell death in bone marrow biopsies of myelodysplastics reveals extensive apoptosis as the probable basis for ineffective hematopoiesis.

Despite hypercellular bone marrows (BM), peripheral cytopenias are the rule in patients with myelodysplastic syndromes (MDS). This study examined the roles played by cell birth and cell death rates in generating this paradox. Cell kinetics from BM biopsies of 35 MDS patients were measured using intravenous infusions of either iododeoxyuridine or bromodeoxyuridine, or both. Degree of apoptosis or programmed cell death (PCD) was estimated using in situ end-labeling of DNA directly from BM biopsies, which were simultaneously double-labeled from proliferation/PCD. MDS were found to be highly proliferative disorders with large numbers of myeloid, erythroid, and megakaryocytic cells synthesizing DNA. Median cycling time (Tc) of myeloblasts was more rapid than that of patients with acute myeloid leukemia (44.1 hr vs. 56.0 hr). Interestingly, most marrow cells of all three lineages in 32 of 34 evaluable cases were undergoing PCD. In 19 of 32 patients, greater than 75% cells were apoptotic. Surprisingly, large numbers of S-phase cells were found to be simultaneously undergoing PCD, as were stromal cells of the BM microenvironment. We conclude that the extensive apoptosis in hematopoietic cells effectively cancels the high birth rate resulting in ineffective hematopoiesis and accounting for deficient bone marrow function.

Acute Disease↗

PubMed1995

Fracture line stability as a function of the internal fixation system: an in vitro comparison using a mandibular angle fracture model.

PURPOSE: This study was conducted to determine and compare the initial mechanical stability and functional capability of six contemporary internal fixation systems used to fix mandibular angle fractures. MATERIALS AND METHODS: An iterative analog of a mandibular angle fracture was developed to ensure replicability of material properties and fracture configuration across the test constructs. Each of six sets of mandible analog (1 set = 3 mandibles) was reduced according to prescribed technique by a variety of compressive and adaptive fixation systems. The compressive systems included the 1) eccentric dynamic compression plate, 2) Würzburg plate, 3) Luhr plate, and 4) solitary lag screw technique. The Champy miniplate and the Mennen clamp plate represented the adaptive fixation systems. The reduced analogs were placed in a straining frame, and simulated masticatory loads were applied to predetermined occlusal sites. Fracture line displacements were acquired and registered by displacement transducers attached to a computer-based data acquisition program. A coordinate transformation procedure was used to convert the generalized displacements at the fracture line into the individual rotations of the segments. An "instability factor" computed from the force-displacement data recorded at various loading conditions for each test construct was used to characterize a particular system's ability to restrain relative motion at the fracture surfaces. RESULTS: There were minimal variations in the stability profiles of the individual compressive fixation systems. However, the fixation stability provided by the compressive and adaptive systems differed significantly (P < or = .0001). A large initial setting and a susceptibility to variations in loading patterns characterized the functional stability provided by the adaptive systems. Even at low masticatory loads (2 DaN), the adaptive systems had an instability that was two to three times as much as that of the compressive systems. Post-hoc comparisons between pairs of devices showed that angle fractures fixed by compressive systems provided significantly greater stability (P < or = .05) than those fixed by the Champy and Mennen systems. Between the adaptive systems tested, fracture fixation with Mennen plates was more stable than reduction by Champy miniplates (P < or = .05) when averaged over loads. CONCLUSIONS: Compressive fixation systems are biomechanically superior to adaptive systems and provide good immediate functional stability to reduced mandibular angle fractures. The Champy and Mennen systems permit significantly higher motion at the fracture site, even at the attenuated masticatory forces encountered in the early postoperative period. Because the functional stability afforded by these adaptive systems is influenced by variations in the biting patterns, the risk of infection and complicated healing is correspondingly increased. Also, the low displacement resistance of the adaptive systems may not protect the alignment of the mandibular segments through the healing period and may manifest as occlusal discrepancies in the dentate patient. The biomechanical test system developed for this study allows an equitable comparison of fixation stability and appears to be a promising tool for investigating a variety of fixation systems and optimizing device design on a rational basis.

Analysis of Variance↗

PubMed1995

Electronic thermography for the assessment of inferior alveolar nerve deficit.

Neurosensory deficit is one of the major complications encountered in oral and maxillofacial surgery. OBJECTIVES. To determine the efficacy of electronic thermography in objectively assessing neurosensory deficits of the inferior alveolar nerve. STUDY DESIGN. Three studies were conducted measuring skin temperature over the chin region of the face at 0.1 degree C accuracy. RESULTS. (1) Thermal symmetry of the chin region in normal subjects (delta T = 0.2 degree C, SD = 0.02 degree C); (2) Induction of transient thermal asymmetry by local anesthetic injection (delta T = +0.4 degree C, SD = 0.2 degree C); (3) nine subjects with neurologic alterations of the inferior alveolar nerve (delta T = +0.5 degree C, SD = 0.2 degree C). Statistically significant differences were found between control group and experimental groups at p < 0.001 with the use of the Student's t test. CONCLUSIONS. These studies indicate that electronic thermography is capable of detecting sensory changes caused by inferior alveolar nerve injury or by pharmacologic nerve block.

Adult↗

PubMed1995

A multivariate study of non Hodgkin's lymphoma involving proliferation, apoptosis, bcl-2 and the microenvironment.

The study was carried out on 22 patients with non-Hodgkin's lymphoma (NHL) who had received sequential infusions of two thymidine analogues iododeoxyuridine (IUdR) and bromodeoxyuridine (BrdU). Cell cycle kinetic studies seemed to differentiate distinctly between low grade lymphoma (n = 8, LI = 2.6%) compared to that of intermediate grade (n = 9, LI = 13%, p = 0.0001) and high grade NHL (n = 5, LI = 16.3%, p = 0.0062). While the majority of 14 intermediate and high grade lymphomas had a high labeling index there were 3/14 patients with a LI of 5.5%, 5.5% and 4.1% respectively. A decrease in the rate of programmed cell death (PCD) or apoptosis due to the overexpression of bcl-2 has been implicated as the possible pathogenesis for follicular lymphoma. We determined the presence of bcl-2 protein immunohistochemically and apoptosis by in situ end labeling of DNA which detects cells in early stages of PCD not recognized morphologically. Nine NHL patients demonstrated PCD ranging from 1%-40%, while it was undetectable in 13/22 patients. Of these 13 cases, 6 showed the presence of bcl-2 expression. To understand the relationship of the microenvironment to the lymphoma cells, the presence of transforming growth factor beta (TGF-beta) was determined immunohistochemically. TGF-beta was present in all the cases where bcl-2 was present, except one. This study highlights some of the key biological features of NHL cells and their microenvironment.

Apoptosis↗