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Biomedical subjects

D F Adams

Publications and source records attributed to D F Adams.

At least 55 records · Page 3Linked to original sources
PubMed1992

Relative production of IL-1 beta and TNF alpha by mononuclear cells after exposure to dental implants.

Interleukin-1 (also known as osteoclast activating factor, OAF) is a cytokine produced primarily by monocytes and macrophages and is thought to mediate many of the immunologic, metabolic, and endocrine alterations seen with microbial infection, tissue injury, inflammatory disease, and bone loss. Stimuli for IL-1 production include microorganisms, endotoxins (LPS), antigen-antibody complexes, clotting components, and other cytokines. The purpose of this study was to determine whether dental implants stimulated peripheral blood mononuclear cells (PBMCs) to produce IL-1 beta (OAF) as well as tumor necrosis factor (TNF alpha). This production may lead to bone loss or failure of an implant. Three duplicates of five different implants were incubated with 2 x 10(6) PBMCs/ml in 20% autologous serum; the esterase positive PBMCs amounted to 14.5%. Measured by radioimmunoassay techniques and compared to controls, all of the implants except one caused significant in vitro generation of IL-1 beta and TNF alpha. The stimulation of IL-1 beta/TNF alpha production by these materials suggests that they are not physiologically inert and that the IL-1 beta (OAF) production may contribute to a less favorable osseoadaptation. OAF has a physiologic (homeostatic) role in maintenance and alteration of osseous structures, but the level at which physiologic becomes pathologic is unknown. Although there were statistical differences between the cellular response to these implants, the clinical significance of the differences remains to be determined.

Cells, Cultured↗
PubMed1992

Needle-tip localization during CT-guided abdominal biopsy: comparison of conventional and spiral CT.

OBJECTIVE: This study was performed to determine whether the time required for needle-tip localization during biopsy of the abdomen would be reduced if continuous-volume data acquisition, also known as spiral CT, were used for guidance instead of conventional CT. SUBJECTS AND METHODS: Forty patients had biopsies of an abdominal mass; half underwent needle-tip localizations with conventional CT and half with spiral CT. The times required to localize the needle for 104 needle passes were calculated; scanning and reconstruction times were included, and the radiologist's technique and procedural difficulties were deliberately excluded. The mean needle localization times with conventional and spiral CT were compared for the upper abdominal and pelvic regions by using the two-tailed unpaired Student's t-test. RESULTS: The mean time (+/- SE) for spiral CT was 35 +/- 2 sec compared with 105 +/- 18 sec for conventional CT (p < .001). When analyzed by region, times with spiral CT were shorter in both the upper abdomen (means, 37 sec for spiral CT vs 150 sec for conventional CT, p < .001) and pelvis (means, 25 sec for spiral CT vs 74 sec for conventional CT, p = .038); the magnitude of the improvement was greater in the upper abdomen. CONCLUSION: The time required to find the needle tip during guided biopsy of an abdominal mass is reduced with spiral CT compared with conventional CT. This improvement is partly a result of the ability to eliminate respiratory misregistration with spiral CT, which is not possible with conventional multisectional CT; hence the greater advantage in upper abdominal biopsy.

Abdominal Neoplasms↗
PubMed1992

Diagnosis and treatment of refractory periodontitis.

Clinicians are occasionally frustrated in arresting the progress of periodontal destruction. The refractory lesion is a problem with a complex and incompletely articulated cause that results in ill-defined and often misdirected treatment. This paper discusses whether refractory periodontitis is a specific entity or whether other periodontal conditions can become refractory.

Chronic Disease↗
PubMed1991

Identification of spirochetes related to Treponema pallidum in necrotizing ulcerative gingivitis and chronic periodontitis.

BACKGROUND: Spirochetes are commonly associated with periodontal disease, but it is not known whether these treponemes are pathogenic or merely opportunistic. We sought to determine whether spirochetes present in periodontal disease share antigens thought to be unique to spirochetes that are known pathogens. METHODS: We examined dental plaque from 24 healthy subjects, from ulcerative sites in 17 patients with ulcerative gingivitis, and from areas of involvement in 19 patients with chronic periodontitis, using an immunocyto-chemical technique with monoclonal antibodies against pathogen-specific determinants on 47-kd and 37-kd molecules from Treponema pallidum subspecies pallidum. Serum was tested against T. pallidum by immunoblotting and by serologic assays for syphilis. RESULTS: Spirochetes with a pathogen-specific epitope on a 47-kd molecule were not found in plaque samples from any of the 24 healthy subjects, but they were identified in plaque samples from 11 of 17 patients with ulcerative gingivitis (P less than 0.001) and from 10 of 19 patients with periodontitis (P less than 0.01). Monoclonal antibodies directed against a 37-kd molecule reacted with spirochetes in plaque samples from 1 of 14 controls, from all 11 patients with gingivitis from whom samples could be obtained (P less than 0.001), and from 14 of 19 patients with periodontitis (P less than 0.001). Five of 18 normal subjects had IgG against 47-kd and 37-kd molecules, but none had IgG against 14-kd or 12-kd molecules from T. pallidum subspecies pallidum. Among 19 patients with ulcerative gingivitis, IgG was identified against 47-kd molecules in 15, against 37-kd molecules in 12, against 14-kd molecules in 4, and against 12-kd molecules in 15. CONCLUSIONS: The spirochetes found in dental plaque from patients with ulcerative gingivitis or chronic periodontitis have antigens that are thought to be unique to pathogenic treponemes. This close antigenic relation suggests that T. pallidum or a closely related organism may be involved in the pathogenesis of periodontal disease.

Adult↗
PubMed1991

Pathogen-related oral spirochetes from dental plaque are invasive.

Spirochetes that share pathogen-restricted antigens with Treponema pallidum subsp. pallidum have been identified in dental plaque and diseased gingival tissues, but it is not known whether these spirochetes possess virulence characteristics. In this study, plaque spirochetes were able to transmigrate a tissue barrier in vitro and were identified on the other side by using monoclonal antibodies specific for pathogen-restricted determinants from T. pallidum subsp. pallidum. This invasive capability is shared with T. pallidum subsp. pallidum, but cultured oral and intestinal treponemes did not perforate the tissue barrier. Cocultures indicated that invasive treponemes do not create opportunities for cultivable oral treponemes to cross the barrier. These findings indicate that gingival tissues may be a port of entry for previously unrecognized invasive spirochetes in humans.

Adult↗
PubMed1990

Biodistribution and clearance of contrast-carrying MREV liposomes.

Contrast-carrying liposomes (CCLs) have been shown to increase the attenuation coefficient of the liver and spleen during computed tomographic (CT) imaging. A modification of the reverse-phase evaporation preparative technique ("MREV") led to production of CCLs that entrap contrast media efficiently. After intravenous injection, MREVs are phagocytized by the Kupffer cells of the liver and the macrophages of the spleen. The biodistribution and clearance of MREVs were studied to evaluate their potential for clinical use, MREVs carrying iodine-125-iotrolan were administered intravenously to 12 rats at doses of 400 mg lipid (containing 400 mg iodine) per kilogram body weight. Pairs of rats were anesthetized and scanned at 3 hours, and 1, 7, 14, 27 and 48 days; CT attenuation values of liver, spleen, blood, kidneys and bladder were measured. Immediately following CT, the rats were killed and tissue specimens were radioassayed. Maximum iodine content in liver and spleen was reached at one day and sustained at high levels for seven days. Biologic removal half-time of the agent in both the liver and spleen was six days. Maximum CT enhancements over baseline were observed at 24 hours and reached 210 delta HU in the liver and 880 delta HU in the spleen per gram iodine injected per kilogram body weight. It is concluded that MREVs have appropriate imaging characteristics, biodistribution, and clearance to be effective CT contrast agents.

Animals↗
PubMed1990

Production and characterization of improved liposomes containing radiographic contrast media.

The authors have investigated liposomes prepared by the reverse-phase evaporation method (REVs) and a modification of this technique that employs a microemulsifier (MREVs), for the delivery of radiographic contrast media (RCM) to the liver and spleen. The modification entailed substituting a Microfluidizer (Microfluidics Inc., Newton, MA) for the sonication step of the REV technique. The MREV procedure is amenable to large-scale production and continuous-flow operation and yields products with high RCM encapsulation. Efficiently entrapped are ionic, high-osmolar diatrizoate (24.38 +/- 2.62% versus 8.35 +/- 0.55%; MREV versus REV), and nonionic, low osmolar Iotrolan (Schering AG, Berlin, FRG) (24.84 +/- 2.13% versus 7.25 +/- 1.19%) RCM with iodine-to-lipid ratio of 1.5:1. The MREV procedure, therefore, has practical advantages over the REV method. High liver and spleen uptakes of Iotrolan-containing vesicles were noted in normal rats. The diatrizoate MREVs lost their contents on contact with serum, resulting in urinary excretion of this agent. Computed tomography values of splenic and hepatic sections, 1 hour after intravenous injection of Iotrolan MREV (500 mgI/kg), are 0.78, and 0.08 Hounsfield Units (HU)/mgI/kg, respectively (versus 0.01, and 0.006 HU/mgI/kg for free Iotrolan).

Animals↗
PubMed1988

Application of the maximum likelihood principle to separate exponential terms in T2 relaxation of nuclear magnetic resonance.

The method of maximum likelihood has been implemented for the estimation of multiple exponential components of T2 decay curves in spin echo NMR measurements on biologic tissues. Each Each component contributes an exponential term described by two parameters (initial amplitude and T2) to the T2 decay curve. The maximum likelihood method estimates the parameters and their standard errors for all terms simultaneously, avoiding the subjectivity inherent in methods such as graphical peeling. In the model used, it was assumed that water protons are compartmentalized and that the measured spin echo signals from the protons undergoing relaxation obey the Poisson distribution. A system of non-linear equations was derived and solved iteratively for the values of the exponential parameters which maximize the likelihood of obtaining the observed data under these assumptions. The approach was implemented for bi- and tri-exponential models on a MicroVAX II computer (Digital Equipment Corporation, Maynard, MA). Simulations of bi- and tri-exponential data, with and without system noise, were analyzed to assess the accuracy and reproducibility of the method. A subset of the simulations was repeated with non-linear least squares techniques and was compared to the results obtained with maximum likelihood. Rabbit muscle and gerbil brain samples were measured and analyzed with the maximum likelihood method. The simulations showed that within specific limits on relative sizes and relaxation rates of components, these parameters can be estimated with errors less than 5%. The comparison to non-linear least squares analysis showed that the maximum likelihood method is generally superior in estimating the parameters in difficult cases. The results from tissue measurements demonstrate that the method is effective even in cases where graphical peeling would clearly not yield reliable results.

Algorithms↗
PubMed1988

NMR of skeletal muscle. Differences in relaxation parameters related to extracellular/intracellular fluid spaces.

The relationships between the T1 and T2 relaxation times, tissue water content and extracellular fluid space of two types of skeletal muscle groups were studied in rabbits and rats by means of NMR proton spectroscopy (10 MHz). Although there was no significant difference in the total water content between muscles rich in type I (74.5 +/- .8%; soleus) or type II (75.0 +/- .7%; gastrocnemius) fibers, the respective T1 (521 +/- 25 vs. 486 +/- 16 millisecond; p less than .01) and T2 (39.5 +/- 1.8 vs. 36.5 +/- 1.0 millisecond; p less than .01) relaxation times were consistently prolonged. The longer relaxation times of the soleus as compared with the gastrocnemius muscle were related to a larger extracellular fluid space as measured by (35S) sulfate +34.5%; p less than .01). For this reason, it seems likely selective changes in these spaces will be detectable by NMR proton imaging.

Animals↗
PubMed1988

Developmental changes in proton magnetic resonance relaxation times of cardiac and skeletal muscle.

Proton magnetic resonance relaxation time measurements were used to study developmental changes in rabbit cardiac and skeletal muscles during the last days of gestation and at several postnatal times. Tissue water content decreased steadily during late fetal and early postnatal stages of development. During this period T1 and T2 for cardiac and skeletal muscles also decreased. The relaxation times stabilized after the 20th postnatal day, and at this juncture the T1 and T2 values for myocardium remained consistently higher than for skeletal muscle. The developmental changes in proton relaxation time probably represent changes in water distribution and mobility as well as macromolecular structure during muscle maturation.

Animals↗
PubMed1988

Magnetic resonance imaging of skeletal muscle. Prolongation of T1 and T2 subsequent to denervation.

The changes seen in the T1 and T2 relaxation times, water content and size of the extracellular fluid spaces of rat muscle samples following 15 days of denervation were studied by in vitro proton NMR spectrometry (10 MHz). Two different skeletal muscle groups (gastrocnemius and soleus) were studied. Denervation led to longer T1 values: 548 +/- 61 msec vs. 486 +/- 16 msec (P less than .05) for the gastrocnemius and 581 +/- 27 msec vs. 521 +/- 25 msec (P less than .05) for the soleus. Similar increases in T2 were measured. The sizes of the extracellular fluid spaces of denervated muscle were significantly larger despite a minor increase in total water content. Overall, the relaxation times of skeletal muscle correlated better with the size of the extracellular fluid space than with the total water content.

Animals↗
PubMed1987

The production and evaluation of contrast-carrying liposomes made with an automatic high-pressure system.

An automatic, high-pressure system (Microfluidizer) has been found useful for producing contrast-carrying liposomes on an industrial scale. The goal of this investigation was to determine the feasibility of using this new microemulsification process to manufacture contrast-carrying microemulsified liposomes (MELs). Seven contrast media (three ionic, four nonionic) were encapsulated into the MELs. Light and electron microscopy, light scattering, radioisotope, and CT scan techniques were used to characterize these MELs, and the contrast entrapments among the studied media were compared. The contrast-carrying MELs had good properties for imaging normal reticuloendothelial tissues, selectively. They had a narrow size range (0.1-3.0 micron), a single bilayer wall, high liver and spleen upake, and low leakage rates. The nonionic media were significantly more effectively entrapped in the MELs than the ionic media (P less than .05). The iodine-to-lipid weight ratio was about 1:16 for ionic media and 1:4 for nonionic media. Physical properties of the contrast media such as osmotic pressure and charge appeared to affect contrast entrapment. It was concluded that the microemulsification process is a useful system for producing contrast-carrying liposomes continuously, on a large scale and in a reproducible manner.

Animals↗
PubMed1987

Nuclear magnetic resonance spectroscopy of acute and evolving pulmonary hemorrhage. An in vitro study.

The proton NMR relaxation times of lung tissue were determined in a rabbit model of acute and evolving pulmonary hemorrhage (PH). Pure PH was simulated by injecting blood into a single lobe using endobronchial catheterization. In vitro spectroscopic measurements of T1 and T2 were made and total water content was determined on lung samples that were excised at regular intervals. T1 and T2 were markedly longer in lungs with acute PH than in normal lungs (T1: 818 +/- 44 vs. 643 +/- 4 msec; T2 164.0 +/- 16.3 vs. 88.1 +/- 3.4 msec). Within the first 24 hours, evolving PH was characterized by a rapid and progressive decrease in T1 (-50%) and T2 (-57%). Up to seven days after the instillation of blood, the T1 (450 +/- 43 msec) and T2 (69.7 +/- 1.9 msec) of lung with modeled PH remained below values of normal lung. The observed shortening of the relaxation times of lung disease with PH was closely paralleled by a decrease in tissue water content.

Animals↗
PubMed1987

Myelinated and nonmyelinated nerves: comparison of proton MR properties.

The magnetic resonance (MR) relaxation rates of protons were compared in the myelinated and nonmyelinated nerves of the garfish. The long, large olfactory nerve of the garfish, as an easily accessible source of nonmyelinated axons, is uniquely suited for such a comparison. The T1 and T2 measurements revealed distinct and consistent differences between nonmyelinated olfactory nerves and myelinated optic and oculomotor nerves. Comparisons between water content, lipid content, and relaxation rates indicated that the differences in MR properties represent complex differences in the distribution and physical environment of the constituent lipid and water protons.

Animals↗
PubMed1987

The concentration of lipopolysaccharide on individual root surfaces at varying times following in vivo root planing.

Material with endotoxin activity has been detected in extracts prepared from pooled, periodontally involved teeth, and it has been shown that root planing in vivo reduces the level of such material. However, questions concerning the concentration of endotoxin on the diseased surfaces of individual teeth and questions concerning how rapidly individual root planed tooth surfaces retoxify in vivo have not been addressed previously. Citric acid extracts were prepared from individual, periodontally diseased teeth that had been extracted either from the oral cavity without prior root planing or at varying times up to 12 weeks following root planing. Using a chromogenic Limulus Amebocyte Lysate (LAL) assay, we were able to quantitate the amount of endotoxin associated with diseased root surfaces of individual teeth. We concluded that the extracted material contained endotoxin since it activated LAL and since the LAL-activation was heat-stable, acid-stable and neutralizeable by polymyxin B. The levels of endotoxin found on the root surfaces of these individual, periodontally involved teeth at varying times following in vivo root planing support the following conclusions: the concentration of endotoxin present on diseased root surfaces is markedly reduced, but not eliminated, by in vivo root planing, significant retoxification of root planed surfaces occurs within a relatively short time period after root planing and biological responses to such toxification conceivably may lead to subsequent phases having reduced levels of endotoxin.

Adult↗
PubMed1986

Biologic effects and potential hazards of nuclear magnetic imaging.

The biologic effects and potential hazards of nuclear magnetic resonance imaging are difficult to quantitate because of the low energy levels currently in use. It is clear, however, that both static and rapidly moving magnetic fields can be a hazard when magnetic field strength is sufficiently high and/or the rapidity of change is fast enough. Additionally, radiofrequency is clearly a hazard when the energy level is high enough. Chronic exposure is less well understood. This new imaging technique presents risks in many ways reminiscent of the previous investigations conducted during the introduction of ultrasound two decades ago.

Electromagnetic Phenomena↗