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Biomedical subjects

D Osborne

Publications and source records attributed to D Osborne.

105 records · Page 6Linked to original sources
PubMedDate not supplied

Degradation of pesticides in a continuous-flow two-phase microemulsion reactor.

Biocatalytic processes in reversed micelles are limited by the need for continuous reactors in which reaction and separation are feasible. In this paper, we report the design and testing of a continuous-flow centrifugal bioreactor for the enzyme-catalyzed hydrolysis of the common pesticide paraoxon in reverse micelles of Tween 85. In this system, organophosphorus hydrolase catalyzes hydrolysis of the pesticide in an organic-organic two-phase system. The enzyme is retained in one of the phases by encapsulation in reversed micelles, while the other phase is under a continuous flow. This liquid-liquid plug-flow reactor does not leach enzyme because the enzyme is not soluble in the flowing organic phase that contains the paraoxon.

Aryldialkylphosphatase↗
PubMedDate not supplied

An alternative approach to hospital electrical safety.

In the past, the only acceptable method for protecting hospital patients against the hazards of macroshock and microshock was equipotential grounding: a system whereby potential differences between conductive surfaces are minimized, and ground loops are eliminated, through use of a network of grounding conductors connected in a tree-branch configuration to a common reference point. Experience at a major medical facility involving attempts to create and maintain an equipotential grounding system has proven this method to be costly, impractical, and potentially hazardous. Recent improvements in the input circuitry of medical instrumentation and the rapid disappearance of explosive anesthetics from many hospital inventories now make it possible to suggest an alternative approach to electrical safety: the insulated environment.

Electric Conductivity↗
PubMedDate not supplied

SPECT quantification of technetium-99m microspheres within the canine lung.

Attenuation compensated single photon emission CT (SPECT) count rates of 99mTc microsphere activities from 151 selected small regions of interest (ROIs) in an intact canine thorax were compared with the count rates obtained from scintillation camera images of similar ROIs from frozen slices of the thorax. A first-order method was used to compensate the SPECT and scintillation camera images for the effect of Compton scattering. The SPECT and scintillation camera count rates correlated well: r = 0.95 (RMS error 4.8 counts/s) for 19 X 19 X 13 mm thick ROIs. We conclude that regional quantification of 99mTc microspheres within the dog thorax is possible using camera-based SPECT systems.

Animals↗
PubMedDate not supplied

Low dose arterial contrast enhancement for cranial computed tomography in renal insufficiency.

In patients with severe renal insufficiency, the high iodine doses used for intravenous contrast medium enhanced CT can lead to renal injury. To minimize renal toxicity in one such patient, dynamic contrast enhanced CT was performed during right common carotid arterial infusion of 17 ml of 30% diatrizoate meglumine solution. Intense homogeneous contrast enhancement of an otherwise isodense mass permitted a diagnosis of meningioma, with excellent definition of tumor extent.

Diatrizoate↗
PubMedDate not supplied

Anatomic applications of xenon-enhanced CT scanning: visual image analysis and brain-blood partition coefficient studies in man.

The inhalation of nonradioactive xenon, an inert gas that diffuses freely across the blood-brain barrier, resulted in brain enhancement which was quantitated and visualized by computed tomography (CT). Serial CT scans obtained during the buildup and equilibrium phase of xenon inhalation were used in a numerical and visual analysis of xenon accumulation in multiple selected gray- and white-matter regions in 12 patients. The calculated brain-blood partition coefficient (lambda) in normal gray matter was 0.92 +/- 0.11 and in normal white matter, 1.38 +/- 0.14. Asymmetries and delays in xenon enhancement were often visually apparent. The estimated partition coefficient was diminished more with cerebral infarction, intracerebral hematoma, and vasogenic edema than with hypoxic encephalopathy or glioblastoma multiforme. An increase in the rate of xenon accumulation was apparent by visual inspection of the motor cortex contralateral to complex hand movements. Technical factors and potential difficulties in conducting xenon-enhanced CT studies are discussed.

Adolescent↗
PubMedDate not supplied

Assessment of craniocervical junction and atlantoaxial relation using metrizamide-enhanced CT in flexion and extension.

Metrizamide-enhanced computed tomographic (CT) myelography has made it easier to define the relation of the spinal cord to the vertebral canal. A flexion-extension metrizamide-enhanced CT technique has been developed to study the craniocervical junction that refines evaluation of the relation between the spinal cord and the foramen magnum, atlas, and axis. This technique was used to study 15 adults who had had a structurally normal examination of the upper cervical cord and foramen magnum. The average movement of the upper cervical cord was shown to be 1 mm. The advantages of the flexion-extension metrizamide-enhanced CT examination were evident in 10 other patients who had a variety of craniocervical junction pathologies.

Aged↗
PubMedDate not supplied

Examination of the extracranial carotid bifurcation by thin-section dynamic CT: direct visualization of intimal atheroma in man (Part 2).

Examination of the extracranial carotid bifurcation by thin-section computed tomographic (CT) scans after bolus, high-volume contrast enhancement allowed detection of more disease than did arteriograms in six of eight consecutive patients with transient ischemic attacks. In four patients this was on the clinical side of the lesion; in two the disease was in the asymptomatic carotid artery. One patient appeared to show a carotid ulcer; the ulcer was detected on CT. However, at surgery and subsequent histology, the surface of the lesion was endothelialized. The carotid CT examination is performed in the scanner "dead time" between unenhanced and enhanced head CT scans using the same contrast material for both studies. The examinations covers 3-3.6 cm of the carotid bifurcation region. Thin-section CT of the extracranial carotid arteries is a noninvasive examination that on preliminary evaluations appears to have sensitivity at least equal to that of carotid angiography in the detection of intimal disease.

Adult↗
PubMedDate not supplied

Opacification of epidural venous plexus and dura in evaluation of cervical nerve roots: CT technique.

Thin-section computed tomography (CT) after bolus high-volume, intravenous contrast enhancement of the cervical epidural and intervertebral foraminal venous plexus was undertaken in eight patients. Visualization of exiting cervical nerve root by opacification of the surrounding intervertebral plexus was evaluated in 38 foramina. Visualization was judged as excellent in 77% and good in 21%. Thus the nerves were seen satisfactorily in all but one foramen. As the CT scan parallels the long axis of the cervical roots as they pass through the intervertebral foramen, anatomic delineation of the root out to the level of the vertebral artery is excellent. A local widening of the root, which was thought to represent the dorsal root ganglion, was seen in most foramina examined. Excellent filling of the epidural plexus was seen in seven of eight subjects; good opacification was seen in the other subject. In no instance did the study fail to satisfactorily fill the epidural plexus in the cervical vertebral canal. This technique appears to be an excellent method for evaluating the cervical nerve roots and the epidural space.

Cervical Plexus↗
PubMedDate not supplied

Intramedullary penetrance of metrizamide in the dog spinal cord.

Metrizamide computed tomography (CT) myelography is clinically useful in the detection of syringohydromyelia. The mechanism by which intrathecally injected metrizamide migrates into the intramedullary cavity is unknown, although reflux into the central canal of the cord via the obex has been postulated. Since intrathecally injected metrizamide has been shown to penetrate normal brain, similar penetrance of the spinal cord might be expected. Five anesthetized mongrel dogs were examined with sequential CT scanning of the cervical spine for 24 hr after intrathecal introduction of metrizamide. The attenuation values of the specified subarachnoid space and the spinal cord at the level of the atlantoaxial joint were recorded. A significant and reproducible increase with time in attenuation values within the cervical spinal cord accompanied by a progressive decrease in attenuation values of the subarachnoid space was observed. The proposed mechanism of cord enhancement, the implication for cord imaging, and the analysis of patients with syringohydromyelia are discussed.

Animals↗