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Biomedical subjects

M D Jackson

Publications and source records attributed to M D Jackson.

At least 19 recordsLinked to original sources
PubMed1991

Graphical analysis and visualization of three-dimensional properties of molecules and solids.

A simple approach is presented for visualizing three-dimensional properties of molecular and crystalline systems by using PC-based molecular drawing software. This allows a scientist with lower-cost PC-graphics capability to carry out analysis of data, such as wave functions and electron density, which would otherwise require a dedicated graphics workstation and expensive specialized software. In this approach, a data set [x,y,z,f1(x,y,z)] is transformed to a new set of data [x,y,z] for values of f1 meeting specified requirements. The function f1, which varies throughout a chemical system is difficult to visualize. However, a more manageable data set is obtained if the set of Cartesian coordinates corresponding to locations in the system where f1 has a specified value are used. This set of points can then be visualized and plotted with standard graphics software or PC-based molecular modeling programs. In addition, the use of PC-based molecular graphics permits one to superimpose the data describing molecular properties on drawings of the molecular geometry. The entire object can then be rotated to facilitate a clear analysis of the property of the molecule.

Chemical Phenomena↗
PubMed1990

Evaluating sources of indoor air pollution.

Evaluation of indoor air pollution problems requires an understanding of the relationship between sources, air movement, and outdoor air exchange. Research is underway to investigate these relationships. A three-phase program is being implemented: 1) Environmental chambers are used to provide source emission factors for specific indoor pollutants; 2) An IAQ (Indoor Air Quality) model has been developed to calculate indoor pollutant concentrations based on chamber emissions data and the air exchange and air movement within the indoor environment; and 3) An IAQ test house is used to conduct experiments to evaluate the model results. Examples are provided to show how this coordinated approach can be used to evaluate specific sources of indoor air pollution. Two sources are examined: 1) para-dichlorobenzene emissions from solid moth repellant; and 2) particle emissions from unvented kerosene heaters. The evaluation process for both sources followed the three-phase approach discussed above. Para-dichlorobenzene emission factors were determined by small chamber testing at EPA's Air and Energy Engineering Research Laboratory. Particle emission factors for the kerosene heaters were developed in large chambers at the J. B. Pierce Foundation Laboratory. Both sources were subsequently evaluated in EPA's IAQ test house. The IAQ model predictions showed good agreement with the test house measurements when appropriate values were provided for source emissions, outside air exchange, in-house air movement, and deposition on "sink" surfaces.

Air Pollution↗
PubMed1990

Magnetic resonance imaging of avascular necrosis of the lunate.

Avascular necrosis (AVN) of carpal bones, particularly the lunate, is often an elusive cause of wrist pain. Physical examination can be indistinguishable from that of a simple wrist sprain, and standard radiographic evaluations are frequently normal. Early diagnosis is critical, since late treatment is often simple observation of the natural history of the disease, which includes progressive collapse of the lunate and derangement of the carpal architecture. Magnetic resonance imaging (MRI) produces images of high contrast, demarcating necrotic from normal bone. We present a case of lunate AVN ("Kienböck's disease") to illustrate the ability of MRI to identify necrotic bone in the wrist. We suggest that MRI is useful in diagnosing AVN in the wrist and that it may allow an earlier diagnosis of lunate AVN than is possible with standard radiographs.

Adult↗
PubMed1989

Factors affecting the sensitivity and specificity of the three-phase technetium bone scan in the diagnosis of reflex sympathetic dystrophy syndrome in the upper extremity.

The three-phase technetium bone scan has been recommended for use in the diagnosis of the reflex sympathetic dystrophy syndrome with a sensitivity and specificity of greater than 90%. A retrospective chart review was conducted of 63 patients who had three-phase technetium bone scan as part of a work-up for unexplained upper extremity pain, to determine the predictive value of the three-phase technetium bone scan in reflex sympathetic dystrophy syndrome, and what factors might affect it. The prevalence of definite or probable reflex sympathetic dystrophy syndrome, as assessed by Kozin's criteria, was 26% in this sample. The 3-hour delayed image demonstrated a sensitivity = 50%; specificity = 92%; positive predictive value = 67%, and negative predictive value = 84%. This was not improved using the data from the blood flow or pool phase. The sensitivity of 50% is lower than previous reports. The predictive value of the three-phase technetium bone scan was affected by the duration of symptoms and the age of the patient. Duration of symptoms less than 6 months, or ages more than 50 years substantially increased the sensitivity and positive predictive value of the three-phase technetium bone scan.

Adult↗
PubMed1989

Predictive value of the three-phase technetium bone scan in diagnosis of reflex sympathetic dystrophy syndrome.

Reflex sympathetic dystrophy syndrome (RSDS) is a painful and disabling problem, the diagnosis of which can be difficult to confirm by objective measures. The three-phase technetium bone scan (TPBS), with a combined sensitivity and specificity of greater than 90%, has been recommended for use in the diagnosis of RSDS. The purpose of this study was to determine the predictive value and usefulness of the TPBS in the diagnosis of RSDS and to discover how the predictive value might be influenced by demographic and medical factors (eg, duration of symptoms). A retrospective chart review was conducted of 119 patients who underwent a TPBS as part of a workup for unexplained limb pain. Twenty-five patients met the Kozin criteria for definite or probable RSDS. All patients were injected with technetium-99m methylene diphosphonate and scanned using established criteria. The three-hour delayed image demonstrated a sensitivity of 44%, a specificity of 92%, a positive predictive value of 61%, and a negative predictive value of 86%. The blood-flow and pool-imaging phases added no further sensitivity or specificity to that achieved by the uptake scan in patients with upper-extremity involvement. Blood-flow and pool-imaging did improve the predictive value of the TPBS in patients with involvement of the lower extremities. We conclude that a more cost-effective approach to diagnosis of upper-extremity RSDS is to use the uptake scan alone.

Adult↗
PubMed1989

Gastroparesis following traumatic brain injury and response to metoclopramide therapy.

Most studies on nutrition in patients with traumatic brain injury (TBI) have focused on the hypermetabolic state immediately after trauma, or the swallowing disorders that frequently follow acute TBI. A less well-known sequela, however, is gastroparesis, which generally manifests itself when patients have advanced from nasogastric to oral feeding programs. Case histories of four patients are reported, all of whom responded to therapeutic intervention with metoclopramide. Results of a radionuclide gastric emptying study, before and after metoclopramide therapy, are presented. The etiologic and physiologic mechanisms behind this disorder are unclear, but demonstration of this disorder and other clinical trials with metoclopramide appear to deserve further consideration in the nutritionally compromised TBI patient.

Brain Injuries↗
PubMed1986

Rocky mountain spotted fever: hepatic lesions in childhood cases.

We studied 16 fatal childhood cases of Rocky Mountain spotted fever (RMSF). Hepatic histologic lesions with statistically significant differences from age- and sex-matched controls were portal triaditis consisting of polymorphonuclear leukocytes and large mononuclear cells, portal vasculitis, sinusoidal leukocytosis, erythrophagocytosis by Kupffer cells, and gross hepatic weight. Hepatocellular necrosis, cholestasis, and congestion were not more frequent in RMSF than in controls. Using immunofluorescence microscopy, we were able to demonstrate rickettsial organisms in portal blood vessels and sinusoidal lining cells of 7 cases.

Adolescent↗
PubMed1984

Pulmonary blastoma: an ultrastructural and histochemical study.

We present a unique case of pulmonary blastoma and describe its histology and ultrastructure. The stromal component exhibited bizarre multinucleated giant cells containing previously undescribed granules. These membrane-limited granules were eosinophilic, periodic acid-Schiff positive, diastase resistant, acid phosphatase and nonspecific esterase negative, immunohistologically negative for lysozyme, albumin, and gamma globulin, and often homogeneously electron dense. A similar electron-dense material accumulated in the rough endoplasmic reticulum of these stromal giant cells, suggesting that the material in the granules is synthetic. The material appeared to be a glycoprotein but was not alpha1-antitrypsin, alpha-fetoprotein, or human chorionic gonadotropin by immunohistologic techniques. These stromal cell granules differ from granules described in epithelial cells of other pulmonary blastomas but resemble granules found in some sarcomas.

Carcinoma, Squamous Cell↗
PubMed1980

Comparison of Ca2+, Sr2+, and Mn2+ fluxes in mitochondria of the perfused rat heart.

The amount of readily exchangeable Ca2+ in mitochondria of an isolated working rat heart is less than 10 ng-ions/g heart. We therefore conclude that either no Ca2+ enters mitochondria or that the Ca+ which does enter is removed continuously. Using Sr2+ and Mn2+, we obtained evidence that the mitochondrial Na+-Ca2+ exchanger was indeed operational in releasing metal from mitochondria of the heart. When Ca2+ in the perfusate was replaced by Sr2+, we found that a significant amount of Sr2+ (approximately 100 ng-ions/g heart) entered mitochondria. When the heart then was returned to a Ca2+-containing perfusate, over 80% of the Sr2+ was washed out of mitochondria within 30 seconds. When low levels of Mn2+ were added to the perfusate, we found that Mn2+ accumulated in mitochondria irreversibly. This is evidence for the operation of the Na+-Ca2+ exchanger because Na+ was found to release Ca2+ and Sr2+ but not Mn2+ from isolated rat heart mitochondria. Our estimates indicate that when the Na+-Ca2+ exchanger is maximally operative, as in the Sr2+-perfused heart, the flux of Sr2+ through mitochondria is at most 10% of the total flux needed for the activation of contraction. The low level of Ca2+ in the mitochondria of Ca2+-perfused hearts suggests a much smaller flux of Ca2+ through the mitochondria in this case. We therefore conclude that mitochondria play little if any role in the beat-to-beat regulation of normal Ca2+ fluxes in the rat heart.

Animals↗
PubMed1980

Environmental and biological effects following application of diazinon impregnated strips within a laboratory animal room.

Rats were exposed to diazinon impregnated strips in a conventional laboratory animal room. The air in the room was monitored for the pesticide. Erythrocyte acetylcholinesterase and plasma pseudocholinesterase activities were determined periodically. Air concentration of the pesticide never exceeded 1.34 microgram/m3. No significant change in enzyme activities were observed.

Acetylcholinesterase↗