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Biomedical subjects

P R Morrison

Publications and source records attributed to P R Morrison.

35 records · Page 2Linked to original sources
PubMed1982

Distance cues and depth avoidance on the visual cliff.

The study tested the hypothesis that depth avoidance in chicks is a specific case of general aversion to far patterns. Using a modified visual cliff, 192 male chicks less than 24 hr. old were on one side presented vertical patterns at varying distances from the centerboard and on the other side either a shallow or deep pattern. Control data indicated that, when two vertical patterns are presented on an opaque surface, chicks will descend to the nearer pattern and that this is motivated by aversion to the far pattern rather than attraction to the near one. Further data showed, however, that when a vertical pattern appeared at varying distances on one side of the centerboard and either a shallow or deep pattern appeared on the other, chicks avoided the side with depth at all distances of the vertical pattern. Depth avoidance in chicks then is not mediated by distance cues. While these may influence descent from a centerboard to an opaque surface, avoidance of depth overrides them on the visual cliff.

Animals↗
PubMed1978

Amino acid differences between major and minor hemoglobins from lemmings (Lemmus and Dicrostonyx).

1. Dual hemoglobins were isolated from both Lemmus and Discrostonyx, two genera of microtine rodents of the tribe Lemmini. 2. The dual hemoglobins result from dual alpha-chains and the charge difference Asp----Ala at position alpha 5. 3. The beta-chains of Dicrostonyx and Lemmus hemoglobins differ in charge by Ala----Asp at beta 125. 4. Cladograms are presented for the hemoglobin chains of microtine rodents.

Amino Acid Sequence↗
PubMed1975

Gluconeogenesis in arctic ground squirrels between periods of hibernation.

The hibernation season in the arctic ground squirrel (Citellus undulatus) is broken into 8- to 18- day cycles by short homeothermal periods during which the carboydrate reserves depleted during hibernation are replenished. This study follows a number of metabolities in tissues and body fluids to assess the sources for reconstitution of the glucose reserves: lactate, urea, ammonia, free fatty acid, glycerol, triglyceride, and glucose in plasma; glycogen in liver and muscle; and urea and ammonia nitrogen in urine. Fat is the major energy source during both homeothermal and heterothermal periods, the contribution from glucose being limited to glycolysis. Reconstitution of glycogen is accomplished prior to reentry through maximal use of substrates from all sources including glycolysis, fat, and protein metabolism. Of the new gluconeogenic substrate, one-fourth is supplied from protein and three-fourths from fat.

Ammonia↗
PubMed1975

Impairment of metabolic capability in feral house mice by Klossiella muris invection.

Kidney infection by Klossiella muris in highland house mice from Peru was associated with lowered metabolic capability (57%) and endurance time (25%) at maximum metabolic rate. Administration of coccidiostatic preparations improved the metabolic capability from 7.8 to 10.5 cc 0-2 g hr and the endurance from 2.8 to longer than 10 min. Their colony-reared offspring, which were free from parasites, sustained maximum metabolic rates of 13.8 cc 0-2/g hr also for longer than 10 min. This rate was slightly higher than the values found in both healthy lowland controls: feral house mice from Arkansas and laboratory white mice [lab: HA(ICR)]. Although clinically inapparent under oridinary conditions, the effects of K muris infection were easily demonstrated at high metabolic loads stimulated by cold. Thus emphasizing the importance of such performance tests in assessing the status of experimental subjects.

Animals↗
PubMedDate not supplied

Compatible instrumentation for intraoperative MRI: expanding resources.

Steadfast progress has been made from biopsy to surgery with interventional MRI (iMRI). Such image-guided interventions require specialized instrumentation due to the unusual elements of the MR environment. Suppliers/manufacturers of MR-compatible instrumentation were few in 1994, but now there are more than 50. We present fundamental issues of MR compatibility and a list of known suppliers/manufacturers.

Humans↗
PubMedDate not supplied

MRI of laser-induced interstitial thermal injury in an in vivo animal liver model with histologic correlation.

Laser-induced interstitial thermal therapy (LITT) is a preferred method of minimally invasive therapy. MRI is a noninvasive method by which to monitor the thermal effects of LITT. To properly control such effects, changes in MRI parameters during and after LITT should be correlated with changes in the tissue. T1-weighted fast spin echo (FSE) MRI (1 image/10 seconds) at 1.5 T monitored LITT in vivo in rabbit liver (n = 6) using an interstitial bare delivery fiber (600-microm diameter; 3.0 W; 1,064 nm; 150 seconds). During laser irradiation, MRI signal intensity decreased around the fiber tip; after irradiation, this hypointensity proved reversible and permanent lesions were evident. The lesions had hyperintense margins that were brighter than surrounding normal tissue (P < .001); the tissue in these bright regions was mapped to tissue necrosis characterized by the presence of thermally damaged ghost red blood cells amid generally normal hepatocytes. T1-FSE identified the spatial extent of the LITT lesions.

Animals↗
PubMedDate not supplied

Monitoring and visualization techniques for MR-guided laser ablations in an open MR system.

Our purpose was to develop temperature-sensitive MR sequences and image-processing techniques to assess their potential of monitoring interstitial laser therapy (ILT) in brain tumors (n = 3) and liver tumors (n = 7). ILT lasted 2 to 26 minutes, whereas images from T1-weighted fast-spin-echo (FSE) or spoiled gradient-recalled (SPGR) sequences were acquired within 5 to 13 seconds. Pixel subtraction and visualization of T1-weighted images or optical flow computation was done within less than 110 msec. Alternating phase-mapping of real and imaginary components of SPGR sequences was performed within 220 msec. Pixel subtraction of T1-weighted images identified thermal changes in liver and brain tumors but could not evaluate the temperature values as chemical shift-based imaging, which was, however, more affected by susceptibility effects and motion. Optical flow computation displayed the predicted course of thermal changes and revealed that the rate of heat deposition can be anisotropic, which may be related to heterogeneous tumor structure and/or vascularization.

Brain Neoplasms↗
PubMedDate not supplied

MRI monitoring of laser ablation using optical flow.

The optical flow method is used for visualizing and quantifying the dynamics of tissue changes observed by MRI during thermal ablations. An approach was implemented for parallel two-dimensional optical flow calculations including the replacement of spurious velocities. Velocity magnitude results were found to be accurate in low-noise cases in tests using series of synthetic images. Optical flow results are presented from thermal ablation experiments utilizing a homogeneous polyacrylamide gel phantom and heterogeneous rabbit liver tissue in vivo, exhibiting heating and cooling with the accompanying quantitative characterization of the dilation and contraction of the thermally affected region. Results demonstrate that optical flow is capable of noninvasive real-time monitoring and control of interstitial laser therapy (ILT).

Acrylic Resins↗