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Biomedical subjects

D J Macey

Publications and source records attributed to D J Macey.

At least 73 records · Page 4Linked to original sources
PubMed1984

The effect of catecholamines on branchial and cardiac electrical recordings in adult lampreys (Geotria australis).

A method is described for injecting CAs into the caudal vein of unanaesthetized lampreys and monitoring any subsequent changes in branchial and cardiac electrical recordings. While a dose of 5-6 micrograms kg-1 body wt of norepinephrine increased the rate and amplitude of branchial and cardiac electrical recordings, the same dose of epinephrine produced a comparable effect only on the heart recordings. A dose of 5-6 micrograms kg-1 body wt of dopamine had a relatively small effect on branchial and cardiac electrical recordings. The response to CAs by lampreys is apparently dose related. The above results have been used to suggest possible ways by which CAs influence cardiac and respiratory functions in lampreys.

Animals↗
PubMed1983

A scintigraphic method for the assessment of intraluminal volume and motility of isolated intestinal segments.

The isolated in vivo intestinal segment is a popular experimental preparation for the investigation of intestinal function, but its value has been limited because no method has been available for measuring changes in intraluminal volume under experimental conditions. We report a scintigraphic technique for measuring intraluminal volume and assessing intestinal motility. Between 30 and 180 ml, the volume of a 75-cm segment of canine jejunum, perfused with Tc-99m-labeled tin colloid, was found to be proportional to the recorded count rate. This method has been used to monitor the effects of the hormone vasopressin on intestinal function.

Animals↗
PubMed1982

Comparison of two optimizing algorithms for cerebral blood flow analysis using the intravenous 133Xe wash-out method.

The analysis of cerebral blood flow data using intravenous injection and inhalation of 133Xe requires a correction for the arterial recirculation. With a multi-exponential transfer function a problem exists in estimating the non-linear parameters. In this paper conventional two-compartmental blood flow indices from the intravenous 133Xe clearance method are calculated using Marquardt and variable metric optimizing algorithms. Close agreement was found between these two methods in that they yield similar values for the cerebral transfer function.

Cerebrovascular Circulation↗
PubMed1982

Iron levels and major iron binding proteins in the plasma of ammocoetes and adults of the southern hemisphere lamprey Geotria australis Gray.

1. The major plasma iron binding proteins (IBP) of both larval and adult Geotria australis differ from those of other vertebrates. 2. Larval IBP has a M.W. of approximately 354,000 and is composed of 20 subunits of equal M.W. 3. Adult IBP is a tetramer (M.W. = c. 296,000) which readily dissociates into subunits of approximately 78,000. 4. Confirmation that plasma iron binding proteins were similar to ferritin in larvae and transferrin in adults was provided by pI values, Fe/protein ratios and electron microscopy. 5. Total plasma iron was 19,760 micrograms/100 ml in larvae and 34 micrograms/100 ml in adults.

Animals↗
PubMed1982

The effect of temperature on the oxygen dissociation curves of whole blood of larval and adult lampreys (Geotria australis).

1. Oxygen dissociation curves of the whole blood of larvae and adults of the Southern Hemisphere lamprey Geotria australis have been determined between pH 6.8 and 8.2 at 5, 15 and 25 degrees C. 2. The P50's at temperatures of 5, 15 and 25 degrees C and a pH of 7.75 were respectively 0.57, 0.92 and 1.19 mmHg in larvae and 6.9, 10.3 and 19.0 mmHg in adults. 3. The relatively very high affinity of larval blood for oxygen may reflect an adaptation to low environmental oxygen tensions. 4. The Bohr shift was not significantly affected by either temperature or life-cycle stage. 5. The slope (n) in Hill plots increased with temperature and oxygen saturation, and was greater in adults than in larvae.

Aging↗
PubMed1982

Absolute quantitation of radiotracer uptake in the lungs using a gamma camera.

A transmission-emission method for the absolute quantitation of Tc-99m in the lungs with a computerized gamma camera is described. The method requires no measurements of the linear attenuation coefficients of the lung and chest wall, or of their thickness. It yields results of acceptable accuracy for everyday clinical use and offers the great advantage of avoiding the use of a phantom. The method could be extended for the absolute quantification of Tc-99m agents in soft tissue and bone with errors of less than 10%.

Humans↗
PubMed1980

Streamlining of air flow in the upper airways and trachea.

Streamlining of air flow in the upper airways and trachea has been investigated by inhaling 81m krypton through each side of the nose separately and counting over the lung fields with a gamma camera. 81m Kr inhaled through one nostril was uniformly mixed in the air stream by the time the carina was reached. Gas mixing occurs probably by a combination of diffusion and turbulent flow.

Biophysical Phenomena↗
PubMed1979

The measurement of the depth of a point source of a radioisotope from gamma ray spectra.

The spectrum of the scattered radiation from a 'point' source of 99Tcm located within a slab of tissue-like material has been studied with a 19-phototube gamma camera, a 7.5 cm x 7.5 cm sodium iodide detector and a Ge(Li) counter. Both backscatter and forward scattered radiation contribute to the spectra observed; 'infinite' backscatter is achieved at a thickness of 8 cm. The scattered radiation can be used to estimate the thickness of the overlying material. The scatter from 133Xe and 51Cr was also measured. The depth of a source could usually be determined to within a few millimetres from the proportion of scatter in the spectrum; it was more accurate with the 51Cr (320 keV) than with the lower-energy photopeaks of the other two isotopes. The variation in the spectrum as the source moved across the field of the gamma camera was recorded.

Chromium Radioisotopes↗
PubMed1977

Thermographic assessment of peripheral arterial occlusion.

Infra-red thermography was used to confirm the observation that the temperature differences between corresponding areas of skin on opposing hands are normally minimal and to demonstrate that the skin temperature of the hand distal to an occluded radial or brachial artery was lower than that of the contra-lateral hand. Temperature differences between the two hands decreased with time and had disappeared by the time that recannulation of the occluded artery, gauged by the modified "Allen" test, had occurred. Thermography is a simple and noninvasive technique and provides a useful indicator of the incidence and progress of peripheral arterial occlusion such as that which may follow arterial cannulation.

Arterial Occlusive Diseases↗
PubMedDate not supplied

Time-dependent quantifiable withdrawal from ethanol in the rat: effect of method of dependence induction.

The importance of temporal factors on the presence and severity of ethanol withdrawal signs in the rat was quantified using rating scale, tremor, and acoustic startle paradigms. Ethanol dependence was induced in naive male Wistar rats by liquid diet administration (n = 21) or vapor inhalation (n = 13). Subjects were analyzed for intensity and duration of physiological ethanol dependence in repeated-measures trials conducted over 72 h post-ethanol withdrawal. Indices of dependence included CNS hyperexcitability manifested as observable withdrawal signs increased acoustic startle reactivity, and tremor activity. Data analysis revealed that withdrawal signs, observed and elicited, generally reached peak intensities between 12 and 24 h postwithdrawal and were more readily observed following vapor inhalation than liquid diet administration, probably because of the higher BALs attained with the inhalation procedure. Results suggest a difference in time course observed with the different behavioral paradigms. In particular, a possible sensitization to startle stimuli was exhibited independent of both startle intensity and dependence induction method. The neural substrates governing these behavioral time course differences remain to be determined.

Administration, Inhalation↗
PubMedDate not supplied

Dosimetry considerations of bone-seeking radionuclides for marrow ablation.

Marrow ablation by radionuclide therapy for patients requiring bone marrow transplantation is possible by injecting bone-seeking radiopharmaceuticals. For each radionuclide under consideration, one should determine the (1) amount of activity required to deliver a given radiation dose to marrow, (2) waiting period before reinfusion to limit the radiation dose to the transplant marrow to an acceptable level, and (3) dose to other critical organs. In an attempt to answer these questions, dose estimates for several radionuclides of interest (32P, 90Y, 153Sm, 166Ho, 186Re, and 188Re) have been calculated. All doses are derived following the MIRD methodology. Biodistribution data of 153Sm-labeled phosphates in the rat are used to estimate uptake of similar radiopharmaceuticals in humans. Typically the skeleton retains 50% of the injected activity and 50% is excreted rapidly through the urine, permitting delivery of ablation doses to the marrow, with tolerable doses to other organs. Skeletal retention data measured from a diagnostic dose can be used to calculate the activity required to deliver a desired marrow ablation dose consistent with toxicity limits set by other critical organs.

Animals↗
PubMedDate not supplied

Dosimetry of solid tumors.

Dosimetry data arising from a decade of radioimmunotherapy are summarized along with techniques utilized to arrive at the reported dose estimates. Generality of the MIRD methodology allows it to serve as a vehicle for the calculation of solid tumor dosimetry although several limitations exist. Nonstandard geometries of solid tumors will ultimately necessitate determination of absorbed fractions for the individual tumors. Several approaches currently under investigation are described. For reasons of practicality, solid tumor dosimetry estimates continue to use the assumption of homogeneous activity distribution in a source organ, accounting for either all radiation or only nonpenetrating radiation. As computation tools become available for incorporating inhomogeneous cellular level data, the currently used "average dose" as an index of tumor sterilization will likely be replaced with a statistical distribution based on the number of viable cells in the tumor volume. Estimates of a tumor control dose would be based upon a linear extension of dose coupled with a threshold dose for cell sterilization.

Humans↗
PubMedDate not supplied

Analysis of the gamma ray spectra recorded in the use of Xenon-133 for cerebral blood flow studies.

A problem in the measurement of cerebral blood flow with 133Xenon is the presence of extra-cerebral counts in the total counts recorded with a collimated gamma ray detector looking at the brain. A method of studying qualitatively the contribution of this extra-cranial component in patients is described. This entails the sequential accumulation of gamma ray spectra recorded during the clearance phase of 133Xenon from the brain. It is shown that different CBF indices are obtained for various regions of the recorded gamma ray spectra. The principal component of the extra-cerebral counts at 15 minutes postinjection appears to be intra-cranial, and not the scalp as assumed previously in the spectrum subtraction method.

Brain↗
PubMedDate not supplied

Treatment of a patient with B cell lymphoma by I-131 LYM-1 monoclonal antibodies.

A patient with Richter's syndrome, a malignant lymphomatous transformation of chronic lymphocytic leukemia, had become moribund with rapidly enlarging masses, granulocytopenia and thrombocytopenia despite the use of conventional chemotherapy and radiotherapy. Greater than ten percent of a test dose of I-131 Lym-1, a murine monoclonal antibody produced against Burkitt's African B cell lymphoma, was accumulated by her tumor. The patient was subsequently treated with a series of injections of I-131 Lym-1 with dramatic clinical response, reduction of tumor volume by x-ray computerized tomography and progression of circulating cellular elements toward normality. Her course over the next ten months was not like that to be expected for Richter's syndrome, which has an average survival of four months. This mode of treatment appears promising.

Aged↗