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Biomedical subjects

A L Hall

Publications and source records attributed to A L Hall.

At least 37 records · Page 2Linked to original sources
PubMed1987

Stroke treatment: comparison of integrated behavioral-physical therapy vs traditional physical therapy programs.

This was a controlled study of the efficacy of two forms of therapy on upper limb functions of hemiparetic patients--one heavily behavioral and the other based on Bobath therapeutic exercises. It arose from an earlier pilot study comparing EMG biofeedback with physical therapy from which it was concluded that both the elapsed time since the acute stroke and the severity of residual disability were particularly important factors. Of 29 patients included and randomly assigned to one or the other heavily systematized therapies, 18 were classified as having early-severe and 11 as late-mild conditions. Multiple function tests by a "blinded" special technician in another location revealed that overall both forms of therapy obtained worthwhile clinical and statistical improvement, which was maintained at nine-month recheck testing; but there was no statistically significant superiority of one therapy over the other under the very specific circumstances of the research design. Ease of delivering care and other socioeconomic considerations become important factors in choosing either or both of these methods.

Adult↗
PubMed1984

Cultures of shiverer mutant cerebellum injected with normal oligodendrocytes make both normal and shiverer myelin.

Earlier reports suggested that injecting normal optic nerve into organotypic cerebellar cultures from three of the central nervous system hypomyelinated mutant mice resulted in striking local increases in myelination of mutant axons. It has been questioned whether this myelin was produced by the introduced normal glia because there was no "marker" by which the genotype of an individual myelin sheath could be rigorously determined. The present study shows that the myelin sheaths of the central nervous system hypomyelinated mutant shiverer (shi/shi) can be distinguished in vitro from genetically normal myelin by their immunocytochemical reactions and ultrastructure. When shi/shi cultures are injected with normal optic nerve, they produce two kinds of myelin as distinguished by these techniques: shi/shi myelin throughout and, in addition, ultrastructurally and immunocytochemically normal myelin near the optic nerve. These results suggest that the primary defect of the shi/shi mutation involves the oligodendrocyte and support the earlier conclusion that in all of the glial injection experiments to date the genotype of the oligodendrocyte determines the phenotype of the myelin produced.

Animals↗
PubMed1983

The application of matched filtering to x-ray exposure reduction in digital subtraction angiography: clinical results.

This new digital fluorography processing method of matched filtering generates a set of images that have been acquired at continuous video-frame rates (30 per second) over the temporal extent of the bolus (10 seconds), and it combines them to produce the equivalent of a single digital subtraction angiography (DSA) image. Because of the extensive temporal averaging used, the method can provide substantial x-ray exposure reduction per run as compared with conventional techniques for an equivalent signal-to-noise ratio in the final image. The matched filtering technique was compared with conventional pulsed (one per second) DSA images of both extracranial and intracranial arteries, and the results are presented. Matched filtered images provided image quality that was equivalent to that of conventional DSA images at about one-fourth the patient exposure per run for both carotid artery and cerebral vessel studies. Despite long integration times, patient motion irretrievably corrupted image quality in only two of five carotid artery studies and in none of three intracranial studies. Compensation for patient motion is demonstrated, and additional applications and limitations of the technique are discussed.

Angiography↗
PubMed1983

The application of matched filtering to contrast material dose reduction in digital subtraction angiography.

Temporal filtering methods were applied to a 50% reduction of contrast material dose in intravenous digital subtraction angiography (DSA). The performance of matched filtering was reviewed, indicating a 50% reduction of noise through the integration of an entire (greater than 10 sec) DSA image sequence spanning the contrast material bolus arrival and washout. Used in conjunction with 50% contrast material dose reduction, matched filtering could provide final iodine signal-to-noise ratios (SNR) comparable to those of conventional DSA. Half-contrast-material-dose (20 ml) filtered DSA runs were compared with full-contrast-material-dose (40 ml) unfiltered runs for 5 carotid, 2 cerebral, and 4 peripheral studies. In all but 2 studies, the half-contrast-material-dose runs were judged to be diagnostic. In all 4 peripheral studies and in some of the 7 carotid and cerebral studies the 20-ml results were judged to be equivalent to the 40-ml results. It is concluded that the half-contrast-material-dose temporally filtered approach is appropriate for peripheral runoff studies. Matched filtering was experimentally compared with simple integrated remasking. If the identical image sequence was used for each, the two had virtually identical performance for integration times less than 10 sec, consistent with theoretical predictions. Two other applications of matched filtering, SNR enhancement and x-ray exposure reduction, are discussed schematically.

Angiography↗
PubMed1983

Work in progress: the application of temporal filtering techniques to hybrid subtraction in digital subtraction angiography.

Temporal filtering methods were applied to iodine signal-to-noise ratio (SNR) restoration in intravenous hybrid subtraction digital subtraction angiography (DSA). For equal detected exposure rates hybrid subtraction had approximately 35% of the SNR of temporal subtraction. When matched filtering was applied to a DSA run, the filtered result had approximately two times higher SNR than the peak contrast image in the run. Thus, when matched filtering techniques were applied to the hybrid image sequence, the resultant SNR increased to about 70% of that of temporal subtraction. With an additional factor-of-two increase in exposure rate for the hybrid run, SNR parity with temporal subtraction could be achieved. This compared with a factor-of-nine increase in exposure that would be required if no filtering were performed. Experimental hybrid matched filter results, generated with intravenous canine DSA studies, supported the predictions in SNR performance.

Angiography↗
PubMed1982

Radiographic blood pool contrast agents for vascular and tumor imaging with projection radiography and computed tomography.

An emulsion of Ethiodol and Pluronic was evaluated as a vascular (blood pool) imaging agent with both the GE experimental scanned projection radiography system and conventional computed tomography (CT), 475 mg iodine/kg body weight of emulsion, was injected into 11 rabbits with thigh muscle V2 carcinomas. Both projection radiography scans and CT scans visualized aorta, vena cava, pulmonary, and femoral vessels, and distorted vessels around tumors for 20 min after infusion. This persistent vascular visualization allowed CT scanning at multiple contiguous levels, which could be followed by reformatting in the sagittal and coronal planes. Following diatrizoate in identical iodine/kg doses, vascular visualization persisted for only 1 min after infusion. Blood pool agents are ideal for projection radiography systems and CT reformatting of vascular anatomy.

Angiography↗
PubMed1981

Cancer imaging by scanned projection radiography.

We have evaluated scanned projection radiography (SPR) for the diagnosis of cancer. Four rabbits with V2 thigh carcinomas and nine patients with a variety of malignant neoplasms were studied with a GE CT/T 8800 scanner modified for SPR. Images were made before injection of intravenous contrast medium, and additional scans were taken after injection. Temporal subtraction was then performed on the digitized data. Rabbit thigh V2 carcinomas and human lung, liver, and extremity neoplasms were visualized. Contrast enhancement was phasic with early vessel demonstration and subsequent visualization of low density central areas of tumoral necrosis. Liver metastases appeared as poorly defined areas of low density. Because of the combination of high contrast sensitivity plus capability of imaging large tissue volumes on one scan, SPR may be valuable in cancer screening.

Adenocarcinoma↗
PubMed1978

Nature of the vitamin K-dependent CO2 fixation in microsomal membranes.

Vitamin K is a component of a membrane-bound enzyme complex which catalyzes the posttranslational carboxylation of peptide-bound glutamate to form the gamma-carboxyglutamate (Gla) residues of prothrombin. The reaction requires reduced vitamin K, bicarbonate, oxygen, and a carboxylase, and does not require ATP. In a Triton X-100 solubilized carboxylase system, it was found that the naphthoquinone ring structure is essential for activity, as is the 2-methyl group. Menaquinone homologs from MK-1 to MK-4 all had carboxylase activity, whereas menadione was inactive. However, dithiothreitol and other thiols form thioethers with menadione, which restores considerable carboxylation activity to the provitamin. Hydrogenation of the beta-gamma double bond in phylloquinone reduced its activity only slightly. The active species of "CO2" utilized in this carboxylation is CO2 and not bicarbonate. Ribosomes contain Gla residues and are labeled with CO2 when whole microsomes are incubated with CO2 in the presence of NADH and vitamin K. About 25% of the activity is releasable with puromycin, suggesting that Gla residues are formed on both the nascent chains and the structural proteins of ribosomes. The deoxycholate-solubilized carboxylase system can be dialyzed to yield membranous vesicles with enhanced carboxylase activity. The warfarin-binding protein from normal rats, but not that from warfarin-resistant rats, further enhances the carboxylase activity of these reformed vesicles.

1-Carboxyglutamic Acid↗