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Biomedical subjects

T M Burke

Publications and source records attributed to T M Burke.

At least 19 recordsLinked to original sources
PubMed1995

Preliminary investigation of ultrasound scattering analysis to identify women at risk for later invasive cancer. II: Extraction of dominant scattering angle-dependent trends from excised breast tissue.

Normalized estimates of the scattering angle-dependent differential scattering cross-section (DSC) at 1.0 MHz were measured from 278 samples of excised breast tissue taken from 66 women. A comparison of results for samples that contained tissue structures previously associated with an increased probability of developing breast cancer to those that did not contain high-risk structures showed that the average magnitude of DSC estimates was insufficient to identify samples with high-risk lesions. Principal component factor analysis (PCFA) was applied to extract scattering angle-dependent trends common to the entire data base. The normalized estimates of the measured DSCs (NDSC) from tissue samples are compared to estimates previously obtained from isolated breast tissue lobules as well as with results from the PCFA. Results are presented that indicate that the dominant angle-dependent trends in the NDSC results are independent of the age of the patient and are similar to trends extracted from isolated breast tissue lobules. The breast tissue structure common to all of these specimens is the terminal duct.

Adult↗
PubMed1995

Preliminary investigation of ultrasound scattering analysis to identify women at risk for later invasive cancer. I: Motivation and experimental technique for characterization of isolated breast tissue lobules.

A new experimental technique is described that allows the characterization of the angle-dependent ultrasonic scattering properties of isolated breast tissue lobules. A review of breast tissue micro-architecture is presented as background material. Measured estimates of the scatter angle-dependent differential scatter cross-sections (DSC) from 31 excised lobules (14 cancer in situ, 17 noncancer) were examined, and dominant trends described by statistical factors. Three factors were extracted, using principal component factor analysis, which collectively accounted for over 70% of the scatter angle-dependent variation exhibited by the measured data.

Breast Neoplasms↗
PubMed1994

Customized implant abutments: technical notes.

Custom-fabricated angulated abutments can be of value when implant angulation or position jeopardizes esthetics and/or function and makes retrievability difficult. A wax pattern is prepared over a castable pattern or gold cylinder. After the casting is completed, a secondary screw channel is created in the angulated abutment to retain the superstructure and the definitive prosthesis. The rationale for the use of customized angulated abutments is described. Technical procedures are presented that allow for modifications of individual cases.

Dental Abutments↗
PubMed1990

Preliminary results for shear wave speed of sound and attenuation coefficients from excised specimens of human breast tissue.

A pilot study involving 53 specimens of excised human female breast tissue was performed to provide preliminary estimates of the acoustic shear wave speed of sound and linear attenuation coefficient associated with high risk for development of invasive breast cancer. The measured shear wave properties were studied as a function of: 1. whether the tissue was presented as a 2.0 to 4.0 gram mass biopsy sample or a 2.0 to 4.0 gram mass subsample taken from a larger mastectomy source; 2. the time post-excision prior to shear wave characterization; 3. the risk factor associated with the number and types of lesions found in the specimen; and 4. the percent by volume of fat or collagen present in the sample. The shear speed of sound was found to range between 20 and 900 m/s with a tendency for lower speeds as a function of time post excision. The results for shear attenuation coefficients ranged from 300 to 9000 cm-1 and did not show a marked time dependence. Average results from mastectomy specimens differed from those for biopsies, but the difference may have been due to variations in tissue composition and time post excision before shear wave characterization.

Adipose Tissue↗
PubMed1988

Glucose starvation is required for insulin stimulation of glucose uptake and metabolism in cultured microvascular endothelial cells.

In the present study we determined the uptake and disposition of glucose in serum-deprived rabbit coronary microvessel endothelial (RCME) cells. RCME cells exhibited stereospecific hexose uptake inhibited by cytochalasin B. Pretreatment of the RCME cells with potassium cyanide or 2,4-dinitrophenol inhibited 2-deoxyglucose uptake but not 3-O-methylglucose transport. A major proportion (30-60%) of the 2-deoxyglucose present in the RCME cells was not phosphorylated. These two observations suggested that the rate-limiting step in the uptake of 2-deoxyglucose was not transport but rather the phosphorylation of 2-deoxyglucose to 2-deoxyglucose 6-phosphate. When glucose-deprived cells were incubated 2 hr with [U-14C]glucose the disposition of the label was as follows: glycogen 60%, acid-soluble fraction 30%, and lipid less than 5%. In contrast glucose-fed cells exhibited lower overall glucose incorporation, and a slightly different disposition: glycogen 45%, acid-soluble fraction 50%, and lipid 5%. Glucose-deprived RCME cells also exhibited greater basal levels of 2-deoxyglucose uptake compared to glucose-fed cells. RCME cells incubated in the absence of glucose and serum for 16 hr exhibited dose-dependent insulin stimulation of hexose uptake and subsequent metabolism to macromolecules (i.e., glycogen and the acid-soluble fraction). Significant effects of insulin were observed with concentrations as low as 2 x 10(-10) M, well within the physiological range. In contrast, cells preincubated in serum-free culture medium containing 5.5 mM glucose did not exhibit insulin-enhanced hexose uptake or glucose metabolism (even at doses as high as 10(-7) M). These studies indicate that the effects of insulin on rabbit coronary microvascular endothelial cell glucose uptake and metabolism require both serum and glucose deprivation.

Animals↗
PubMed1987

Hydrogen peroxide elicits activation of bovine pulmonary arterial soluble guanylate cyclase by a mechanism associated with its metabolism by catalase.

Guanylate cyclase activity in the soluble extract of bovine pulmonary arteries is activated by hydrogen peroxide generated by glucose oxidase only in the presence of catalase. This mechanism of guanylate cyclase activation is not blocked by scavengers for superoxide anion or hydroxyl radical, but is selectively inhibited by methylene blue, inactivation of catalase and ethanol. The time dependency of increases in guanylate cyclase activity in the presence of peroxides that are substrates for catalase are associated with the spectral detection of compound I, a species of catalase formed during the metabolism of peroxide. Thus, activation of soluble guanylate cyclase appears to be elicited by compound I of catalase or by a mediator generated by this species.

Animals↗
PubMed1987

Hydrogen peroxide elicits pulmonary arterial relaxation and guanylate cyclase activation.

Hydrogen peroxide produces concentration-dependent relaxation of precontracted isolated bovine intrapulmonary arterial rings by a mechanism which is independent of the endothelium or prostaglandin mediators. Relaxant responses to hydrogen peroxide concentrations of up to 100 microM were markedly attenuated by the inhibitor of soluble guanylate cyclase activation, methylene blue (10 microM). Micromolar concentrations of hydrogen peroxide elicit time- and concentration-dependent increase in arterial levels of guanosine 3',5'-cyclic monophosphate that are associated with decreases in force. Soluble guanylate cyclase activity is markedly activated by enzymatically generated hydrogen peroxide in a manner that is most closely associated with the concentration of catalase present in the assay, by a mechanism that is inhibited by superoxide anion and the inactivation of catalase. Our data are most consistent with the involvement of compound I, a species of catalase formed during the metabolism of peroxide, in the mechanism of guanylate cyclase activation. The nature of this mechanism of arterial relaxation suggests that it could contribute to the regulation of pulmonary vascular tone by oxygen tension.

Acetylcholine↗
PubMed1987

A preliminary study on the angular distribution of scattered ultrasound from bovine liver and myocardium.

Measurements were performed on freshly-excised bovine liver and myocardium to determine the ultrasonic scattering nature of the tissues under a variety of experimental conditions. Results for the angular distribution of the differential scattering cross section per unit volume of tissue are reported for scattering angles spanning 170 to 44 degrees for interrogating frequencies of 1.0, 2.25, 3.5 and 5.0 MHz. Fresh and aged tissues, some with abnormally high connective tissue content were analyzed. The results are compared to previously-published works.

Animals↗
PubMed1985

Insulin binding and effects of insulin on glucose uptake and metabolism in cultured rabbit coronary microvessel endothelium.

Microvascular endothelial cells were isolated from rabbit cardiac tissue, and cultivated by standard tissue culture techniques. The conversion of [U-14C]glucose to CO2 and lipids was significantly enhanced by insulin treatment. Insulin stimulated uptake of 2-[3H]deoxyglucose and enhanced the transport of 3-O[3H]methyl-D-glucose. Specific binding of [125I]insulin to RCME cells, displaceable by cold insulin, was also observed. These data demonstrate that insulin is capable of regulating metabolic activities in coronary microvascular endothelium.

3-O-Methylglucose↗
PubMed1984

Angular distribution of scattered ultrasound from a single steel sphere in agar gelatin: a comparison between theory and experiment.

Experimental results for the angular distribution of scattered ultrasound in water from a 0.635 mm diameter steel sphere embedded in agar were obtained for interrogating frequencies of 1.0, 2.25, 3.5 and 5.0 MHz. The experimental results compared favorably with theoretical predictions based on the work of Faran. The results for both theory and experiment are presented in the form of the Differential Scattering Cross Section (DSC) for scattering angles from 170 degrees to 44 degrees. The implications of this study on calculating the expected scattering behavior of gelatin based ultrasound phantoms are briefly discussed.

Acoustics↗
PubMed1984

Association between cyclic GMP accumulation and acetylcholine-elicited relaxation of bovine intrapulmonary artery.

The objective of this study was to examine the relationship between relaxation and cyclic GMP accumulation in bovine intrapulmonary artery in response to acetylcholine. Acetylcholine relaxed or contracted isolated arterial rings possessing an intact or damaged endothelial layer, respectively. Acetylcholine-elicited relaxation of phenylephrine-precontracted rings was accompanied by a time- and concentration-dependent accumulation of arterial cyclic GMP but not of cyclic AMP. Relaxation and cyclic GMP accumulation were both antagonized by atropine and methylene blue. Quinacrine, on the other hand, antagonized relaxation without altering the accumulation of cyclic GMP. Nitroglycerin and S-nitroso-N-acetylpenicillamine also relaxed intrapulmonary rings possessing an intact endothelium and caused a concomitant rise in cyclic GMP but not cyclic AMP levels. Both effects were antagonized by methylene blue but not by atropine or quinacrine. Arterial rings prepared with damaged endothelium contracted to acetylcholine but relaxed to nitroglycerin and S-nitroso-N-acetylpenicillamine. Acetylcholine-elicited contraction was markedly inhibited by atropine, partially inhibited by quinacrine and potentiated by methylene blue. Cyclic GMP levels were increased in endothelium-damaged rings contracted by acetylcholine and this was inhibited both by atropine and methylene blue but not by quinacrine. The effects of quinacrine on acetylcholine-elicited changes in tone appear to be nonspecific. These observations indicate that relaxation of bovine intrapulmonary artery by both acetylcholine and nitrogen oxide-containing vasodilators is closely associated with the accumulation of cyclic GMP. Moreover, there appears to be a clear dissociation between contraction and cyclic GMP accumulation elicited by acetylcholine.

Acetylcholine↗
PubMed1983

Fenbendazole treatment of pregnant bitches to reduce prenatal and lactogenic infections of Toxocara canis and Ancylostoma caninum in pups.

A granulated formulation of fenbendazole was tested in a total of 23 treated and control, pregnant, parasite-free Beagle bitches experimentally infected with Toxocara canis and Ancylostoma caninum. The drug was administered to each treated bitch once daily in canned dog food at a dosage of 50 mg/kg body weight. Each of 2 treatment regimens tested was initiated on the 40th day of pregnancy. One regimen involved daily treatment continuing through the 14th postpartum day, and it resulted in 89% fewer ascarids and 99% fewer hookworms in pups born to medicated bitches, as compared with pups born to unmedicated controls. The other regimen of treatment, which was stopped on the day of parturition, was less effective in reducing ascarid and hookworm burdens (64% and 88% reductions, respectively). Three to 5 bitches from each of the treatment and control groups were allowed to whelp a 2nd litter without further treatment or further exposure to parasite infections. Hookworm burdens in 2nd-litter pups born of bitches that had initially received fenbendazole through the 14th postpartum day were significantly lower (P < 0.01; 85% reduction), when compared with the 2nd-litter control pups. All other parasite burdens were not significantly different. It was concluded that granulated fenbendazole is effective in reducing burdens of Ancylostoma caninum and Toxocara canis in newborn pups when the bitch is treated during the last third of pregnancy, especially when treatment (50 mg/kg/day) extends from the 40th day of pregnancy through the 14th postpartum day.

Ancylostomiasis↗
PubMed1982

Evaluation of granulated fenbendazole as a treatment for helminth infections in dogs.

A granulated formulation of fenbendazole was tested in 95 dogs harbouring naturally occurring infections of Toxocara canis, Ancylostoma caninum, Trichuris vulpis, Dipylidium caninum, and Taenia spp and in 19 laboratory-reared Beagle pups experimentally infected with Toxascaris leonina. The drug was administered in moistened dry dog food or in canned dog food. In dosage titration and confirmational studies, using worm counts in naturally infected dogs, the drug was 98%-100% effective at a dosage of 50 mg/kg of body weight/day for 3 days against the commonly occurring nematodes of dogs (ascarids, hookworms, and whipworms) and against Taenia tapeworms. A dosage of 20 mg/kg for 5 days was equally effective against nematodes, but only 73% of the dogs were cleared of Taenia tapeworms. There was no activity at either dosage against Dipylidium tapeworms. Dosages of 100 or 150 mg/kg for a single treatment and 5 or 25 mg/kg daily for 3 days were unsatisfactory with respect to nematodes and tapeworms. Induced infections of T leonina were eliminated from all treated dogs at the dosage and dosing period tested (50 mg/kg/day for 3 days). Fourteen untreated controls expelled 13% of T leonina burdens. It was concluded that granulated fenbendazole is effective in dogs against natural infections of T canis, A caninum, T vulpis, Taenia spp, and experimentally induced infections of T leonina at a dosage of 50 mg/kg of body weight/day for 3 days.

Animals↗
PubMed1982

X-ray linear attenuation coefficients in the mammographic range for ultrasonic breast phantom materials.

X-ray linear attenuation coefficients for simulated fat and glandular parenchyma used in ultrasound breast phantoms were measured at 15.2, 20.3, 30.0, 40.0, and 60.0 keV and values compared with published figures calculated from the experimentally determined elemental composition of excised breast parenchyma. Agreement was excellent. These ultrasonic tissue-mimicking (TM) materials can be used in radiographic or ultrasound phantoms for testing imaging instruments as well as for training personnel.

Female↗
PubMed1981

Chronic respiratory disease in a horse infected with Dictyocaulus arnfieldi.

A 6-year-old Thoroughbred gelding was examined because of respiratory disease that developed after it was placed on pasture occupied by a donkey. Clinical signs in the gelding included a harsh, dry paroxysmal cough and increased expiratory effort. Eosinophils were seen in smears of mucus aspirated from the trachea and the bronchi. Immature, 5th-stage Dictyocaulus arnfieldi was identified in the tracheal mucus. The cough and other clinical signs were not diminished by corticosteroid therapy or by the administration of bronchodilators. Treatment with 10-fold therapeutic dosages of thiabendazole (440 mg/kg) on each of 2 successive days resulted in permanent cessation of the clinical signs.

Animals↗
PubMed1981

Normalized organ doses for various diagnostic radiologic procedures.

Organ-absorbed doses for 24 diagnostic examination projections were measured using an Alderson Rando phantom. The organs of interest were testes, ovaries, thyroid, eyes, uterus, and active bone marrow. The reported values were normalized to the unit entrance exposure of each examination. Subsequent comparison of these measured values with the experimental and calculated values of other investigators showed reasonable agreement.

Bone Marrow↗