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Biomedical subjects

C A Stewart

Publications and source records attributed to C A Stewart.

At least 73 records · Page 4Linked to original sources
PubMed1993

Evaluation of magnetic resonance imaging in the diagnosis of osteomyelitis in diabetic foot infections.

To assess the role of magnetic resonance imaging (MRI) in diagnosing osteomyelitis in diabetic foot infections, 47 diabetic patients with clinical suspicion of osteomyelitis, nonhealing foot ulcer, or soft tissue infection of the foot were examined prospectively by MRI and plain radiographs. Pathological confirmation of diagnosis was obtained in 62 bones from 32 patients. In addition, 14 patients with pathological confirmation of diagnosis underwent technetium-99 MDP triple-phase bone and gallium-67 citrate scans. MRI was significantly more sensitive and accurate (P < .01), with equal specificity in comparison to plain radiographs and technetium and gallium scans. MRI also provided a more detailed and accurate depiction of the anatomy. At early clinical follow-up, complete resection of abnormal bone on an MRI scan correlated with clinical healing. In summary, MRI is indicated when plain radiographs are negative for osteomyelitis or when the extent and accurate depiction of the infective process will facilitate surgical planning.

Adult↗
PubMed1993

Visual versus quantified digital radiographic determination of bone density.

Quantitative digital radiography (QDR) was used to assess the ability of physicians to determine bone mineral density (BMD) loss from a series of plain radiographs. Twenty-four spinal cord injured patients underwent QDR of the left knee. Seven of the 24 were selected, each of whom had bone mineral loss from 10-70% in 10% increments as assessed by comparison to average BMD of age-matched controls, and a standardized AP radiograph of the left knee was performed. Twenty-five independent examiners (orthopaedic surgeons and residents) were then asked to view the randomly arranged radiographs and visually determine the amount of BMD loss for each radiograph as compared to a control radiograph at 100%. Chi square analysis of the data revealed that the distribution of responses was significantly different than expected at the p less than .01 level. Taking into account that responses may have erred by +/-10%, the distribution of responses was again found to be significant at the p less than .01 level. An accurate determination of BMD loss was achieved only at 10% bone loss and 70% bone loss. The results of this study suggest that the visual determination of bone loss based on plain radiographs is accurate only at very low or very high levels of bone loss. Using standardized techniques, only near normal radiographs or radiographs with at least 70% BMD loss can be assessed accurately.

Bone Density↗
PubMed1992

Tumor target-derived soluble factor synergizes with IFN-gamma and IL-2 to activate macrophages for tumor necrosis factor and nitric oxide production to mediate cytotoxicity of the same target.

Inflammatory mouse peritoneal macrophages were activated by IFN-gamma in synergy with IL-2 or Lipid A to mediate TNF production for autocrine generation of cytotoxic nitric oxide (NO) to kill P815 or L1210 tumor targets. It was determined that for IL-2, but not Lipid A, to effectively trigger activation of IFN-gamma-primed macrophages, the tumor targets must be also present for interaction with effector macrophages to mediate the production of TNF and NO. IFN-gamma- and IL-2-activated macrophages from syngeneic DBA/2 and allogeneic C3H mice had identical MHC-unrestricted requirements for interaction with DBA/2 mouse-derived P815 and L1210 targets to mediate production of TNF and NO for tumor cytotoxicity. To further define the mechanistic requirements for macrophage-tumor target interaction, IFN-gamma- and IL-2-activated macrophages were separated from P815 targets in culture by a semipermeable membrane. Under these conditions, both TNF and NO were produced by the macrophage, which indicated that the requirement for tumor target-macrophage interaction may be due to a soluble factor produced by the target rather than to direct physical contact. This was confirmed by experiments in which 24-h cell-free culture fluids, derived from either P815 or L1210 tumor targets, substituted for the intact tumor cells in the stimulation of TNF mRNA synthesis and secretion with NO generation of TNF mRNA synthesis and secretion with NO generation by IFN-gamma- and IL-2-activated C3H or DBA/2 macrophages. The activity in 24-h culture fluids derived from P815 and L1210 tumor targets was tentatively designated as tumor-derived recognition factor(s) (TDRF) since it was produced constitutively by the tumor targets and synergized with IFN-gamma and IL-2 to induce macrophage production of TNF and NO for death of the same targets. A variety of nontransformed human and mouse fibroblasts, mouse spleen lymphocytes, and two adherent mouse fibrosarcomas did not produce detectable TDRF activity, whereas two mouse T lymphomas, EL4 and EL4.IL-2, produced TDRF activity similar to L1210 mouse leukemia and P815 mastocytoma. The C3H/MCA, a TDRF-nonproducing mouse fibrosarcoma, was susceptible to cytotoxicity mediated by macrophages activated by IFN-gamma and Lipid A, but not by IL-2 triggering. Exogenous TDRF derived from L1210 targets reconstituted the cytotoxic activity for C3H/MCA MCA targets mediated by IFN-gamma- and IL-2-activated macrophages accompanied by the production of TNF and cytotoxic NO.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1992

Osteoporosis after spinal cord injury.

Dual-photon absorptiometry characterized bone loss in males aged less than 40 years after complete traumatic paraplegic and quadriplegic spinal cord injury. Total bone mass of various regions and bone mineral density (BMD) of the knee were measured in 55 subjects. Three different populations were partitioned into four groups: 10 controls (healthy, age matched); 25 acutely injured (114 days after injury), with 12 reexamined 16 months after injury; and 20 chronic (greater than 5 years after injury). Significant differences (p less than 0.0001) in bone mass mineral between groups at the arms, pelvis, legs, distal femur, and proximal tibia were found, with no differences for the head or trunk. Post hoc analyses indicated no differences between the acutely injured at 16 months and the chronically injured. Paraplegic and quadriplegic subjects were significantly different only at the arms and trunk, but were highly similar at the pelvis and below. In the acutely injured, a slight but statistically insignificant rebound was noted above the pelvis. Regression techniques demonstrated early, rapid, linear (p less than 0.0001) decline of bone below the pelvis. Bone mineral loss occurs throughout the entire skeleton, except the skull. Most bone loss occurs rapidly and below the pelvis. Homeostasis is reached by 16 months at two thirds of original bone mass, near fracture threshold.

Absorptiometry, Photon↗
PubMed1992

Expression of proliferating cell nuclear antigen during the cell cycle of human diploid fibroblasts.

Proliferating cell nuclear antigen mRNA levels were determined in human diploid fibroblasts as they progressed through the cell cycle. PCNA message levels were low at G0, gradually increased following entrance into G1, peaked at G1/S, and declined during S phase. PCNA mRNA was determined to have a half life of 12 hours when cells were blocked at the G1/S interface. PCNA protein levels increased two- to three-fold as cells moved from G0 to S phase.

Cells, Cultured↗
PubMed1992

Age related decline in the expression of proliferating cell nuclear antigen in human diploid fibroblasts.

Proliferating cell nuclear antigen mRNA and protein levels were determined in human diploid fibroblasts of different in vitro ages as they progressed through the cell cycle. Cells were analyzed at G0; at various stages of G1, including the G1/S interface; and during S. At all in vitro ages, PCNA message levels were low to undetectable at G0, were evident 8 to 12 h following entrance into G1, peaked at G1/S and declined during S phase. Message levels were 2-3-fold lower in older populations at all stages of the cell cycle tested. PCNA protein increased from G0 through S phase in both age groups with 2-3-fold less being found in older cells. The decline in PCNA mRNA in older populations was not the result of changes in mRNA turnover or transcription. The results suggest that the reduction in PCNA expression is due to an age related alteration in a post-transcriptional regulatory function. The decline in the expression of the PCNA gene would contribute to the inability of older cells to initiate replicative DNA synthesis.

Cells, Cultured↗
PubMed1991

Intrastriatal dopaminergic agents, muscarinic stimulation, and GABA antagonism compared for rotation responses in rats.

We tested the common hypothesis that rotation on systemic injection of dopaminergic agents in rats with unilateral 6-hydroxydopamine lesions of the substantia nigra is attributable to unequal stimulation of dopamine receptors between the two striata. No rotation occurred when dopamine, apomorphine or amphetamine were injected into dorsal striatum or nucleus accumbens of intact, unanesthetized rats. Intrastriatal haloperidol elicited ipsiversive postural deviation only in conjunction with hypermotility induced by systemic amphetamine. In unilateral 6-hydroxydopamine-lesioned rats, intrastriatal apomorphine elicited rotation directed away from the side of its injection, whether intact or lesioned. Carbachol elicited short-latency rotation, contraversive to injection in dorsal striatum or nucleus accumbens, in both intact and 6-hydroxydopamine-lesioned rats. The rotation response to carbachol was suppressed by atropine administered systemically or into the site of intrastriatal carbachol. Picrotoxin or bicuculline produced contraversive rotation or contralateral myoclonic jerks on injection into the striatum in intact rats. The results show that asymmetric stimulation of striatal dopamine receptors is not sufficient to cause rotation, unless the receptors have been denervated. On the other hand, asymmetric stimulation muscarinic receptors is in itself enough to produce the imbalance of gamma-aminobutyric acid (GABA)ergic striatal outputs responsible for rotation.

Amphetamine↗
PubMed1990

Circumferential quantitative analysis of planar 201T1 myocardial scintigraphy in the diagnosis of coronary artery disease.

Methodology for the computer analysis of 201T1 myocardial perfusion images has been developed by several laboratories. Substantial evidence of the advantage of this approach over visual inspection alone has been reported. The currently available computer analyses use different algorithms to analyze 201T1 kinetics in the myocardium. The authors evaluated and compared two widely used software programs, Medical Data System (MDS): a mean-count profile, and the Cedars Sinai (CS): a maximal-count profile, of planar 201T1 scintigraphy for their ability to detect coronary artery disease (CAD).

Adult↗
PubMed1990

Heterotopic ossification. Effect on dual-photon absorptiometry of the hip.

Dual-photon absorptiometry (DPA) is now widely used to determine bone mineral density of the lumbar spine and hips. Because the resulting images are often not of sufficient resolution to identify many bone or soft tissue abnormalities that may influence results, clinical and radiographic correlation is necessary. Presented are two cases in which results of DPA of the hips were elevated because of the presence of heterotopic ossification.

Absorptiometry, Photon↗