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Biomedical subjects

J H Simon

Publications and source records attributed to J H Simon.

At least 127 records · Page 7Linked to original sources
PubMed1976

A polyethylene glycol/dextran procedure for the isolation of chromatin proteins (histones and nonhistones) from wheat germ.

A new procedure is described for the isolation of both histone and non-histone chromatin proteins, based on a polyethylene glycol (PEG)/dextran two-phase partition system. Chromatin is solubilized in high salt (5 M NaC1) and mixed with PEG and dextran to separate proteins (partitioned into the upper, PEG-rich phase) from nucleic acid (DNA recovered almost exclusively in the lower, dextran-rich phase). The proteins are then absorbed onto Bio-Rex 70 by dialysis to low salt (0.05 M NaC1), followed by salt elution to recover first non-histone proteins (less than 0.55 M NaC1), then histones (2 M NaC1). Cross-contamination is not detectable in either group of proteins. The procedure is rapid, gentle, and lends itself well to scale-up. The proteins are kept in pH range 7.0--8.1, and are not exposed to the denaturing reagents characteristic of most preparative procedures for chromatin proteins. Though developed specifically for the isolation of proteins from chromatin of wheat germ, the procedure should be readily applicable to other sources as well. Wheat germ (isolated wheat embryos) appears to be an excellent source of chromatin proteins; 100 g yields 225--300 mg histones and 30--45 mg nonhistone proteins, depending on technique.

Amino Acids↗
PubMedDate not supplied

Contrast-enhanced MR imaging in the evaluation of treatment response and prediction of outcome in multiple sclerosis.

MR imaging is becoming increasingly important in the evaluation of multiple sclerosis based on its sensitivity to acute, often subclinical events in the brain and because it provides a basis for measuring the accumulation of disease over time. Contrast-enhanced MR imaging in particular evaluates disease at the fundamental level of events affecting the blood-brain barrier. This review emphasizes (a) recent developments in the use of contrast-enhanced MR imaging as a measure of disease in patient groups and individuals and (b) its emerging role in evaluating new therapies.

Adrenal Cortex Hormones↗
PubMedDate not supplied

MR imaging of spinal lymphoma.

Magnetic resonance findings are described in a patient with spinal lymphoma using a high field strength magnet and surface coil technique. Using this noninvasive technique, it was possible to visualize both tumor growth and extent in the spinal canal. The infiltration into the canal through a neural foramen and into bone was also visualized as well as the extent of the paraspinal tumor component. None of the currently used imaging modalities--myelography, plain radiography, CT, or radioisotope studies--could provide the same information alone.

Adult↗
PubMedDate not supplied

A comparison of default and reduced bandwidth MR imaging of the spine at 1.5 T.

The value of a reduced bandwidth MR imaging technique was tested prospectively in 51 spinal MR examinations by using default (16 kHz) bandwidth, 2000/30, 90 (TR/TEs) and 600/30, and reduced (8 kHz) bandwidth, 2000/48, 92 and 600/30, techniques at 1.5 T. Bandwidth reduction was used to maintain the signal-to-noise ratio for a reduced scan time. Concerns have been raised as to the effect of bandwidth reduction at high field, since a savings in time or an increased signal-to-noise ratio occur at the expense of increased chemical shift misregistration artifact. However, when appreciable, the chemical shift-related artifact in the spine was typically located in the frequency-encoding direction at the vertebral body/disk space interface or the dural sac/epidural fat interface in the lower lumbosacral region and was easily distinguished from pathologic lesions. There were no missed diagnoses with the reduced bandwidth technique. This study suggests that chemical shift-related artifact will rarely be confused with pathology by an experienced reader and suggests a clinical role for the bandwidth technique to decrease scanning time in uncooperative patients or to allow acquisition of additional imaging planes in a reasonable time.

Adolescent↗
PubMedDate not supplied

Dual cervical thoracic coil for spine magnetic resonance imaging.

The need for repositioning of surface coils and patients in MR examinations of the cervical and thoracic spine prolongs examination time. A new receiver design is proposed which overcomes this problem. The device is composed of two actively decoupled receiver coils mounted on the frame of a Philadelphia collar. These coils may be used separately to image either the thoracic or cervical spine or together to produce larger field-of-view images of the combined region. Signal-to-noise ratios of the separate cervical and thoracic spine images are not degraded as a result of mounting the receivers together. The full cervical and thoracic region is shown to be imaged at a signal-to-noise ratio significantly higher than that afforded by the body coil. A retrospective review of our case load suggests that a time saving could be achieved in approximately 1/3 of spine examinations by using this coil.

Humans↗
PubMedDate not supplied

Technical aspects on magnetic resonance imaging of the spine at 1.5 tesla.

Technical aspects on surface coil magnetic resonance imaging of the spine using a superconducting system with a field strength of 1.5 tesla are described. By using a flat surface coil instead of the body coil the image quality was markedly improved and the signal-to-noise ratio (S/N) was increased approximately 2.6 times. Small voxels resulted in low S/N. The best image quality was achieved with a slice thickness of 5 mm, a field of view of 20 to 24 cm and a matrix of 256 X 256. Interleaved slices provided superior image quality compared with contiguous slices at the expense of acquisition time. For sagittal images the phase encoding gradient should be in the cranio-caudal direction to minimize motion artifacts. To obtain T1 and T2 images of high quality, spin echo pulse sequences with TR 600/TE 20 ms and TR 2000/TE 40 to 80 ms are useful.

Epidural Space↗
PubMedDate not supplied

Magnetic resonance imaging and the acquired immunodeficiency syndrome dementia complex.

It is now recognized that patients infected by the virus linked to the acquired immunodeficiency syndrome (AIDS) can develop dementia symptoms as the initial and sometimes only symptomatology for AIDS. This appears to be a syndrome whose origin is independent of secondary non-viral infection or malignancy. Magnetic resonance imaging (MRI) in three patients with well documented AIDS dementia revealed high signal periventricular white matter lesions. In one case, large lesions were not apparent on computed tomography and gross inspection of the fixed brain prior to autopsy. In two cases in which serial in vivo MR studies were obtained, there was a progressive increase in lesion volume over a short (several months) period of observation. Periventricular white matter lesions may be an early sign accompanying AIDS dementia, and the degree of changes correlated well with the clinical picture in our patients.

Acquired Immunodeficiency Syndrome↗
PubMedDate not supplied

Quantitative determination of MS-induced corpus callosum atrophy in vivo using MR imaging.

To quantitate the extent of corpus callosum atrophy in multiple sclerosis, midsagittal corpus callosum areas were determined in 48 controls with normal MR scans and 41 patients with definite multiple sclerosis. The mean midsagittal corpus callosum area was 601 mm2 (range 405-791), 641 mm2, and 561 mm2 for all adult controls, for adult males, and for adult females, respectively. Control values were significantly greater than the means determined for all multiple sclerosis (MS) patients (508 mm2, range 281-758), for MS men (528 mm2), or for MS women (498 mm2). The degree of corpus callosum atrophy paralleled the estimated volume of periventricular and corpus callosum high-signal lesions, suggesting a possible cause-effect relationship. The results indicate that corpus callosum atrophy occurs commonly in patients with typical clinical forms of multiple sclerosis.

Adult↗
PubMedDate not supplied

Metastatic lesions involving the cerebellopontine angle.

PURPOSE: To evaluate the clinical and MR findings of metastatic lesions involving the cerebellopontine angle (CPA), which may be useful in differentiating them from the more commonly occurring benign CPA lesions. METHODS: Clinical and MR findings of 14 patients with clinical/radiologic (seven) or pathologic (seven) diagnoses of CPA metastasis were retrospectively reviewed. RESULTS: Useful clinical findings included acute onset and rapid progression of cranial nerve symptoms, especially 7th and/or 8th cranial nerve deficits (92.9%). Cranial nerve symptoms could be unilateral (50%) and frequently involved multiple cranial nerves (64.3%). MR findings showed significantly more extensive disease than suggested by clinical presentation, with 100% of patients having multiple cranial nerve involvement and 85.7% bilateral. Useful MR findings included small and/or bilateral CPA-enhancing lesions with relative isointensity to brain parenchyma on precontrast MR, with associated findings of multiple and/or bilateral cranial nerve and/or leptomeningeal lesions. CONCLUSIONS: These associated findings suggest that cerebrospinal fluid dissemination and/or leptomeningeal extension may be an important pathway for metastatic spread to the CPA. Because the CPA metastasis may be the initial or only site of metastasis, and may occur many years after the initial diagnosis of malignancy, MR findings with clinical correlation are not only useful for the detection of CPA metastases, but also for their differentiation from the more common benign CPA tumors.

Adult↗