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T Douglas

Publications and source records attributed to T Douglas.

At least 37 records · Page 2Linked to original sources
PubMed1996

Immunomagnetic isolation of magnetoferritin-labeled cells in a modified ferrograph.

Pan T, helper, and cytotoxic lymphocytes were isolated from the human peripheral blood mononuclear cell fraction by antibody staining, ferritin labeling, and deposition on glass slides. Two distinct forms of ferritin were used: one was native horse spleen ferritin, and the other was magnetoferritin. Magnetoferritin was obtained by reconstituting the horse spleen ferritin iron core with superparamagnetic magnetite instead of the usual paramagnetic ferrihydrite crystal. The cell deposition on microscopic glass slides in the magnetic field was obtained by an instrument that was adapted from an industrial magnetic deposition analyzer, the ferrograph. The identity of cells in the magnetic deposits was confirmed by comparing the cell fractions in the feed and in the eluate with the use of flow cytometry. The immunostaining protocol amplified the number of ferritin molecules per cell surface antigen 20-70 times. Magnetoferritin, but not native ferritin, imparted a sufficient magnetic moment to cells to deplete the labeled cell population between 67 and 88% of its initial concentration in a magnetic field of 1.67 Tesla (T), a field gradient of 2.57 T/mm, and a flow rate of 0.01 ml/min. This study showed that the magnetic moment of magnetoferritin was sufficient for immunomagnetic isolation of lymphocytes from mononuclear cell preparations in the modified ferrograph.

Animals↗
PubMed1995

Prostate-specific antigen values at the time of prostate cancer diagnosis in African-American men.

OBJECTIVE: To determine if African-American men with newly diagnosed prostate cancer (PC) have higher pretreatment serum prostate-specific antigen (PSA) values after adjustment for clinical stage, age, and tumor grade, and to determine if any difference detected is related to tumor volume difference. DESIGN: Consecutive case series of newly diagnosed PC patients between January 1990 and September 1994 and cohort analytic study of PC patients treated by radical prostatectomy (RP) and who had whole-mount pathologic tumor volume assessment between May 1993 December 1994. SETTING: Tertiary care military medical center. PATIENTS: A total of 541 evaluable newly diagnosed PC patients (408 white and 133 black) having pretreatment PSA assessment at one laboratory; 91 patients undergoing RP had whole-mount tumor volume analysis. INTERVENTIONS: Medical record review for pretreatment PSA value, race, tumor grade, clinical stage, and age, as well as whole-mount pathologic assessment of RP specimen and measurement of tumor volume. MAIN OUTCOME MEASURES: The PSA differences between black and white PC patients with adjustments for age, biopsy tumor grade (Gleason score), and clinical stage (TNM stage); PSA differences between black and white PC patients undergoing RP with adjustment for age, RP grade, clinical stage, and tumor volume. RESULTS: The mean (geometric) PSA value for 133 black men was 14.00 ng/mL compared with 8.29 ng/mL for 408 white men (P < .001). The black patients had higher PSA values across all stage, grade, and age categories. The racial difference in PSA levels remained statistically significant when stage, grade, and age were simultaneously controlled for (P < .001). Multivariable odds ratio testing revealed that even after adjustment for stage, grade, and age, black patients were 2.2 times as likely as white patients to have a PSA value greater than 10.0 ng/mL (95% confidence interval, 1.3 to 3.6). Tumor volume (geometric mean) was 5.42 cm3 and 2.10 cm3 for black and white RP patients, respectively (P = .002). Across all clinical stages (T1a to T3), black men had tumor volumes 1.3 to 2.5 times greater than those of white men. Multivariable analysis of covariance revealed that tumor volume and stage of disease were important predictors of PSA level, but race, grade, and age were not. (The percentage of white and black patients whose cancer was detected by screening [75.4% vs 70.4%] or who had symptoms [37.7% vs 29.6%] was not significantly different.) CONCLUSIONS: As a group, African-American men with newly diagnosed PC have higher PSA values at initial diagnosis than white men. This PSA difference appears to be due to larger tumor volumes within clinical (TNM) stage categories among black patients. Elevated PSA value was a surrogate for larger tumor volume in this cohort of black men. This stage-for-stage tumor volume disparity even in an equal-access health care environment should prompt further study of screening behavior and/or biological differences of PC in the black population.

Age Distribution↗
PubMed1995

Classical and quantum magnetic phenomena in natural and artificial ferritin proteins.

Artificial ferritin has been synthesized with control of both the magnetic state (antiferromagnetic or ferrimagnetic) and the particle size over an ofer of magnitude in the number of iron atoms. The magnetic properties of the artificial ferritin were compared with those of natural horse spleen ferritin in a range of temperatures (20 millikelvin to 300 kelvin) and fields (1 nanotesla to 27 tesla). In the classical regime, the blocking temperature was found to correlate with the average particle size. A correlation was also observed in the quantum regime between the resonance frequency of macroscopic quantum tunneling of the Néel vector and the particle size. At high magnetic fields (to 27 tesla), a spin flop transition with a strong dependence on orientation was seen in the natural ferritin, providing evidence of antiferromagnetism in this system.

Animals↗
PubMed1995

Reconstitution of manganese oxide cores in horse spleen and recombinant ferritins.

The formation of Mn(III) oxyhydroxide (MnOOH) cores within the nanoscale cavity of the iron storage protein ferritin has been investigated by electron microscopy and visible absorption spectroscopy. At pH 8.9, discrete amorphous MnOOH cores were formed within horse spleen apoferritin at a range of metal:protein ratios, as well as in ferritin molecules seeded with a small ferrihydrite nucleus. Analysis of the resultant core size distributions showed that the reconstitution of horse spleen apoferritin with Mn(II) was similar to that observed previously for Fe(II) reconstitution in recombinant human L-chain ferritin, suggesting that horse spleen apoferritin does not exhibit Mn(II) oxidase activity at pH 8.9. Reconstitution with MnOOH shows essentially "all-or-nothing" behavior in which many protein molecules remain unmineralized whilst others are loaded to maximum capacity. Kinetic studies showed no significant differences between horse spleen ferritin, recombinant H- and L-chain homopolymers, and H-chain variants containing site-directed modifications at the ferroxidase and putative Fe nucleation centers. Our results indicate that the reconstitution of ferritin with MnOOH cores proceeds by a nonspecific pathway. We propose that the outer surface of the protein inhibits the development of MnOOH nuclei in bulk solution whereas the inner surface is inactive, enabling nucleation and growth to proceed unperturbed within the cavity. One possibility is that differences in the general polyelectrolyte properties of these two surfaces, rather than site-specific charges, account for the "Janus" behavior of the molecule. A similar mechanism might also increase the specificity of iron oxide mineralization in ferritins that lack ferroxidase centers.

Animals↗
PubMed1995

Initial assessment of magnetoferritin biokinetics and proton relaxation enhancement in rats.

RATIONALE AND OBJECTIVES: We evaluated the biokinetics and proton relaxation enhancement of magnetoferritin, a recently developed class of superparamagnetic iron oxides, in rats. METHODS: "Equine" magnetoferritin was administered intravenously at 5 mg protein and 1.4 mg Fe/kg in nude rats carrying subcutaneous xenografted human small-cell lung carcinoma with and without preinjection of 100 mg/kg equine apoferritin. Blood clearance, in vivo biodistribution, and proton relaxation enhancement were assessed by variable field relaxometry, immunohistochemistry, and magnetic resonance (MR) imaging at 1.5 T. RESULTS: Magnetoferritin clearance from blood followed biexponential kinetics, with a short initial half-life of 1.4-1.7 min. A second, longer component lasted for several hours. Histochemical staining, MR imaging, and ex vivo relaxometry revealed rapid uptake of magnetoferritin in the liver, spleen, and lymph nodes. There was no difference in biodistribution after apoferritin preinjection. CONCLUSION: In the rat, equine magnetoferritin is rapidly sequestered by cells of the reticuloendothelial system, with no direct involvement of ferritin receptors. These properties may allow the use of magnetoferritin as an MR contrast agent for the liver and spleen.

Animals↗
PubMed1994

Further characterisation of forms of haemosiderin in iron-overloaded tissues.

The biochemical and biophysical properties of isolated haemosiderins have been compared to that of another iron-containing protein, termed prehaemosiderin, which sediments through chaotropic potassium iodide only after 20 h of ultracentrifugation, in contrast to that of haemosiderin which is recovered after 2 h of ultracentrifugation. The iron/protein ratio and iron/phosphate ratio were less that that of the corresponding haemosiderin, while the elemental composition was also reduced in many of the prehaemosiderin samples. Mossbauer spectroscopy and electron diffraction identified the predominant presence of ferrihydrite in prehaemosiderin species even though the secondary haemochromatosis haemosiderin iron cores were essentially goethite-like. The majority of the prehaemosiderins isolated showed the presence of an additional peptide band at 17 kDa in addition to that at 21 kDa. Further Mossbauer studies of haemosiderin isolated from untreated secondary haemochromatosis patients showed that goethite was the predominant form of iron present, thereby indicating that the presence of this form of ferrihydrite was not wholly attributable to chelation therapy.

Animals↗
PubMed1994

Persistent oral contrast agent lining the intestine in severe mucosal disease: elucidation of radiographic appearance.

Plain radiographs and computed tomographic scans obtained in a severely neutropenic patient with acute lymphoblastic leukemia and cytomegalovirus-associated enterocolitis revealed a pattern of prolonged mucosal adherence of oral contrast agent to the small bowel. This pattern was seen as long as 16 weeks after administration of contrast agent and has been seen previously only in patients who have received bone marrow transplants. Two sets of intestinal biopsy specimens contained crystals that coated denuded mucosa at the site of ulceration and later were trapped within the lamina propria. Electron diffraction and energy-dispersive radiographic analysis showed that these crystals were composed of barium sulfate.

Administration, Oral↗
PubMed1992

Epidermal growth factor protects portal hypertensive gastric mucosa in ischemia/reperfusion: the role of capillary endothelia and prostaglandins.

BACKGROUND: Epidermal growth factor (EGF) protects gastric mucosa against a variety of injurious agents, but the mechanism is unclear. Because the abnormal microvasculature of portal hypertensive (PHT) gastric mucosa is a major target of ischemia/reperfusion (I/R) injury, we used this model to assess EGF's protective role at the microvascular level. METHODS: Rats with PHT (staged portal vein ligation) received either EGF, 20 micrograms/kg, or saline solution intravenously, with or without indomethacin pretreatment (20 mg/kg subcutaneously). I/R was produced by withdrawing blood to systemic pressures of 30 mm Hg for 20 minutes and reinfusing it. Stomachs were excised 20 minutes later and evaluated for gross and histologic necrosis, microvascular permeability, mucosal ultrastructure and vimentin, and cyclooxygenase immunofluorescence. RESULTS: In saline-treated rats, gross and histologic damage involved 46% +/- 3% of glandular mucosa and 23% +/- 3% of mucosal sections, respectively. Microvascular permeability was increased 43-fold over that of normal control rats. Vimentin immunofluorescence intensity was reduced to 36% +/- 4% that of normal control rats. EGF pretreatment reduced histologic necrosis to 2% +/- 1% (p less than 0.01). Microvascular permeability and vimentin intensity were almost normalized. Indomethacin partially reversed the mucosal protection induced by EGF. CONCLUSIONS: EGF significantly reduces I/R injury to PHT gastric mucosa. Microvascular endothelia of PHT gastric mucosa are the major target of I/R injury and the site of EGF's protective action. Prostaglandins in part mediate EGF's protective action.

Animals↗
PubMed1977

Glyoxalase I polymorphism in the mouse: a new genetic marker linked to H-2.

Two electrophoretically distinct variants of glyoxalase I (Glo-I) are present in mouse (Mus musculus). The two forms are controlled by two codominant alleles Glo-1a (common) and Glo-1b (rare) at an autosomal locus. A linkage study showed that Glo-1 maps at approximately 3 centimorgans from the Ss locus of the H-2 histocompatibility region. A similar linkage relationship exists in man between GLO and HLA, the human homolog of the H-2 gene complex. Thus, the chromosomal segment evolutionarily preserved in the two species is longer than previously suspected, and it includes genes with no obvious functional relation to the other components of the major histocompatibility complex. Several features of the Glo-1 polymorphism in the mouse recommend it as a marker of choice for the H-2 region.

Animals↗
PubMedDate not supplied

Magnetoferritin: characterization of a novel superparamagnetic MR contrast agent.

A protein-encaged superparamagnetic iron oxide has been developed and characterized by using horse spleen apoferritin as a novel bioreactive environment. The roughly spherical magnetoferritin molecules, 120 A in diameter, are composed of a monocrystalline maghemite or magnetite core 73 A +/- 14 in diameter. Except for the additional presence of iron-rich molecules of higher molecular weight, the appearance and molecular weight (450 kd) of magnetoferritin are identical to that of natural ferritin; the molecules are externally indistinguishable from their precursor, with a pI (isoelectric point) in the range 4.3-4.6. The measured magnetic moment of the superparamagnetic cores is 13,200 Bohr magnetons per molecule, with T1 and T2 relaxivities (r1 and r2) of 8 and 175 L.mmol-1 (Fe).sec-1, respectively, at body temperature and clinical field strengths. The unusually high r2/r1 ratio of 22 is thought to arise from ideal core composition, with no evidence of crystalline paramagnetic inclusions. T2 relaxation enhancement can be well correlated to the field-dependent molecular magnetization, as given by the Langevin magnetization function, raised to a power in the range 1.4-1.6. With its nanodimensional biomimetic protein cage as a rigid, convenient matrix for complexing a plethora of bioactive substances, magnetoferritin may provide a novel template for specific targeting of selected cellular sites.

Animals↗
PubMedDate not supplied

Three-dimensional modeling of biopsy protocols for localized prostate cancer.

Prostate cancer is the most common malignant tumor in American men, yet only a small percentage of men will develop clinically significant disease. Needle core biopsies are used to confirm the presence of cancer prior to surgery. While needle core biopsies have shown some ability to predict tumor volume and grade in prostatectomy specimens, for the individual patient they are neither sensitive nor specific enough to guide therapy. In this paper, we describe a system for simulating needle biopsies on three-dimensional models of cancerous prostates reconstructed from serial sections. First we segment the serial sections, delineating tumors and landmarks. Next, we register the sections using a color-merging scheme, and reconstruct the three-dimensional model using modified-shape-based interpolation. The resulting volume can be rendered, and simulated needle core biopsies can be taken from the reconstructed model. We use our system to simulate two different biopsy protocols on a reconstructed prostate specimen.

Biopsy, Needle↗