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Biomedical subjects

B C Bowen

Publications and source records attributed to B C Bowen.

36 records · Page 2Linked to original sources
PubMed1994

MR angiography of occlusive disease of the arteries in the head and neck: current concepts.

MR angiography has many applications in the evaluation of cerebrovascular disease (aneurysm, vascular malformation, neoplasm, arterial and venous occlusive disease) [1]. Of these, the most common application may be in the assessment of arterial occlusive disease in patients at risk for stroke [2]. Consequently, the accuracy of MR angiography vs conventional angiography in this assessment will most likely determine the extent to which MR angiography is routinely used in clinical practice. In this paper, we review the results of clinical trials in which MR angiography has been used to evaluate arterial occlusive disease in the head and neck and describe those recent developments that promise improved visualization of the vasculature.

Arterial Occlusive Diseases↗
PubMed1993

Akinetic-rigid syndrome in a 13-year-old girl with HIV-related progressive multifocal leukoencephalopathy.

A 13-year-old HIV-infected girl presented with a rapidly progressive akinetic-rigid syndrome. Cranial magnetic resonance imaging revealed bilateral centrum semiovale lesions extending into the basal ganglia. Detailed histopathological study of a biopsy specimen from the involved regions resulted in a diagnosis of progressive multifocal leukoencephalopathy (PML). This case illustrates that an akinetic-rigid syndrome may be a rare presentation of PML. HIV-related PML may have unusual radiological features. Brain biopsy may be necessary to confirm PML in cases associated with atypical clinical and radiological presentations.

AIDS-Related Opportunistic Infections↗
PubMed1993

Ocular pulsation in neurofibromatosis. A clinical/neuroradiologic correlation.

A 61-year-old woman presented with early cataract formation in an eye which had been pulsating synchronously with her heart beat all of her life. This report presents the first, to our knowledge, three dimensional reconstruction CT images of this form of neurofibromatosis 1. It also documents by MRI and MRA the association of an asymptomatic carotid-ophthalmic junction aneurysm ipsilateral to the sphenoid dysplasia.

Blood Flow Velocity↗
PubMed1992

Pseudotumor cerebri from cranial venous obstruction.

Dural sinus hypertension from cerebral venous outflow impairment is a cause of pseudotumor cerebri. The authors documented six such patients: two with unilateral neck dissection, one with surgical ligation of the dominant sigmoid sinus, two with thrombosed central intravenous catheterization, and one with dural sinus thrombosis. The site of cerebral venous outflow obstruction was variable and identified in three patients with computed tomography, conventional magnetic resonance imaging, magnetic resonance angiography, and/or angiography. Magnetic resonance angiography used in two patients characterized the venous flow pattern and identified the site of obstruction, confirming magnetic resonance angiography as an effective noninvasive blood flow technique in diagnosing and following these patients. Three patients were treated successfully with medical therapy and one patient with optic nerve fenestration. The two patients with thrombosed central venous catheters had serious systemic illnesses and suffered permanent visual loss.

Adult↗
PubMed1992

Magnetic resonance applications in cerebral injury.

CT and MR imaging are complementary in the evaluation of cerebral head trauma. CT is still more useful for the initial evaluation of the acutely unstable patient who has a head injury. However, many lesions are identified by MR imaging such as cortical contusions, small subdural hematomas, and diffuse axonal injuries that may not be seen on CT examinations. In addition, MR angiography can play an important role in the diagnostic evaluation of the trauma patient. MR angiography can be clinically useful in delineating vascular abnormalities such as arterial occlusions, arteriovenous fistulae, dissecting aneurysms, and venous sinus occlusion. In pediatric trauma, MR imaging appears to be superior to CT in assessing head injuries, particularly those due to child abuse.

Adult↗
PubMed1991

Magnetic resonance imaging of spinal infection.

The findings on magnetic resonance imaging in various types of spinal infection are described, including disc space infection and osteomyelitis, epidural abscess, paraspinal abscesses, and meningitis. The characteristic appearance of spinal infection on both plain and gadolinium-enhanced magnetic resonance is contrasted with that of the normal spine.

Abscess↗
PubMed1990

MR signal abnormalities in memory disorder and dementia.

MR imaging of the brain, performed in 86 normal subjects and 113 patients with objective memory disorder or dementia, demonstrated white- and gray-matter areas of high signal intensity on long TR images (short and long TE). Hyperintensities were analyzed with respect to size (on a scale of 0-3) and location: lesions were periventricular, subcortical, or cortical. The patients with memory disorder and dementia were categorized as having probable/possible Alzheimer disease, a combination of Alzheimer disease and multiinfarct cognitive disorder, or multiinfarct cognitive disorder alone on the basis of clinically determined Hachinski ischemic scores. Significant correlations were found between age and scores for periventricular lesions (r = .40, p less than .0005) and subcortical lesions (r = .39, p less than .0005) in normal subjects. Correlations were also found between the Hachinski ischemic score and scores for periventricular lesions (r = .21, p less than .01), subcortical lesions (r = .27, p less than .0002), and cortical lesions (r = .32, p less than .0005) in subjects with memory disorder/dementia. Comparing multiinfarct cognitive disorder, Alzheimer disease, and normal groups, the mean scores for periventricular lesions were 12.0 +/- 4.6, 7.6 +/- 4.8, and 3.4 +/- 2.6, while mean scores for subcortical lesions were 10.8 +/- 12.2, 4.1 +/- 6.4, and 0.8 +/- 1.2, respectively. Periventricular lesions were present in 99-100% of patients with Alzheimer disease and multiinfarct cognitive disorder. On the other hand, subcortical lesions, which were identified in 100% of patients with multiinfarct cognitive disorder, were present in only about half of the patients with Alzheimer disease. Thus, scores for both periventricular and subcortical lesions are positively correlated with age and risk factors for cerebrovascular disease and also are significantly increased in the presence of objective memory disorder or dementia. These results imply that in the subject groups considered here, elderly patients with vascular dementia are most likely to have severe white-matter abnormalities on MR scans. The score for subcortical lesions appears to be more helpful than the score for periventricular lesions in distinguishing vascular dementia from Alzheimer disease and normal aging, so that a patient with prominent subcortical white-matter abnormalities is more likely to have a diagnosis of vascular than degenerative dementia.

Adult↗
PubMed1981

DNA fragments associated with chromosome scaffolds.

Following extensive digestion of HeLa metaphase chromosomes with either Hae III endonuclease or micrococcal nuclease, nonhistone protein scaffolds may be isolated. Scaffolds isolated after Hae III digestion have about 1.5% of the chromosomal DNA attached to them. This DNA is heterogeneous in size, ranging from about 0.2 to 20 kbp. It can be cleaved with either Eco RI or Hae III - Eco RI, producing a series of repeated fragments, of which the most abundant is 1.7 kbp in length. The 1.7-kdp fragment is tandemly repeated and is enriched (about 50-fold) in the scaffold-associated DNA. It is located primarily on human chromosome 1 and is probably a component of human satellites II and III. Scaffolds isolated after micrococcal nuclease digestion have about 0.1% of chromosomal DNA attached. This DNA is present in two size classes - fragments larger than 10 kbp and fragments approximately 0.2 kbp long. Restriction enzyme digestion of this DNA gives no prominent repeated fragments. Its reassociation kinetics are similar to those of total DNA, indicating that it is not enriched in either highly repetitive or middle repetitive sequences.

Chromosomes↗
PubMed1978

Molecular weight of T2 NaDNA from viscoelasticity.

The viscoelastic properties of T2 DNA solutions are used to determine the NaDNA molecular weight in four independent ways from the theory of the beads-springs model. The four molecular weights are 131.9, 132.7, 130.5, and 127.6 X 10(6). The average of these values, adjusted for the probable errors in viscoelasticity and concentration measurements, is (126 +/- 5) X 10(6). The four molecular weights are termed Mtaugamma11, Mtaueta, Mtaugamma, and MtauA; each is different in its sensitivity to molecular weight distribution. Their agreement suggests (1) that the theoretical equations relating each M to the corresponding measured properties are valid, (2) that T2 DNA behaves as a partially free-draining polymer chain, and (3) that our solutions were nearly homogeneous in DNA size. We show that serious errors can result if the viscoelastic properties are not extrapolated to their limits at zero shear rate, as well as at zero DNA concentration, before calculating molecular weight.

Coliphages↗
PubMed1976

Electron microscopy of membrane-free folded chromosomes from Escherichia coli.

Membrane-free folded chromosomes were purified from log-phase cultures of Escherichia coli and prepared for electron microscopy by aqueous (Kleinschmidt and Zahn) spreading. The appearance of the chromosomes depended on the salt concentrations in spreading. At certain salt concentration, the chromosomes resembled rosettes, with supercoiled loops of DNA radiating from a central core containing RNA. The rosettes support previous models deduced from physical studies of folded chromosomes. Apparently, cores contain must of the visible RNA, and the organization of the core is linked to the organization of the DNA loops.

Chromosomes, Bacterial↗
PubMedDate not supplied

MR signal abnormalities in memory disorder and dementia.

MR imaging of the brain, performed in 86 normal subjects and 113 patients with objective memory disorder or dementia, demonstrated white- and gray-matter areas of high signal intensity on long TR images (short and long TE). Hyperintensities were analyzed with respect to size (on a scale of 0-3) and location: lesions were periventricular, subcortical, or cortical. The patients with memory disorder and dementia were categorized as having probable/possible Alzheimer disease, a combination of Alzheimer disease and multiinfarct cognitive disorder, or multiinfarct cognitive disorder alone on the basis of clinically determined Hachinski ischemic scores. Significant correlations were found between age and scores for periventricular lesions (r = .40, p less than .0005) and subcortical lesions (r = .39, p less than .0005) in normal subjects. Correlations were also found between the Hachinski ischemic score and scores for periventricular lesions (r = .21, p less than .01), subcortical lesions (r = .27, p less than .0002), and cortical lesions (r = .32, p less than .0005) in subjects with memory disorder/dementia. Comparing multiinfarct cognitive disorder, Alzheimer disease, and normal groups, the mean scores for periventricular lesions were 12.0 +/- 4.6, 7.6 +/- 4.8, and 3.4 +/- 2.6, while mean scores for subcortical lesions were 10.8 +/- 12.2, 4.1 +/- 6.4, and 0.8 +/- 1.2, respectively. Periventricular lesions were present in 99-100% of patients with Alzheimer disease and multiinfarct cognitive disorder. On the other hand, subcortical lesions, which were identified in 100% of patients with multiinfarct cognitive disorder, were present in only about half of the patients with Alzheimer disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMedDate not supplied

Spinal dural arteriovenous fistulas: evaluation with MR angiography.

PURPOSE: To show that postgadolinium three-dimensional time-of-flight MR angiography shows abnormal intradural vessels associated with spinal dural arteriovenous fistula better than routine MR imaging and provides screening information useful for subsequent diagnostic conventional angiography and/or posttreatment evaluation. METHODS: Precontrast and postcontrast MR imaging and MR angiograms, as well as subsequent digital subtraction angiograms, were obtained for eight patients with dural arteriovenous fistulas, diagnosed with digital subtraction angiography and verified with surgery. In four patients, MR studies also were obtained after surgery. RESULTS: All patients had cord hyperintensity of T2-weighted images and postgadolinium enhancement on T1-weighted images. Five had vessellike signal abnormalities in the subarachnoid space on MR. Abnormal intradural vessels were detected in all eight patients with MR angiography. Comparison with digital subtraction angiography revealed these vessels to be primarily enlarged veins of the coronal venous plexus on the cord surface. In six patients, the medullary vein draining the fistula was demonstrated, indicating the level of the fistula, later identified by digital subtraction angiography. After surgical obliteration of the fistula, the draining medullary vein and most or all of the abnormal coronal veins were no longer demonstrated, with decrease or resolution of cord hyperintensity on T2-weighted images. CONCLUSION: Postgadolinium, spinal MR angiography in cases of suspected dural arteriovenous fistula provides information about intradural veins that supplements the diagnostic value of the MR imaging results, facilitates the subsequent digital subtraction angiography study, and, in treated cases, reflects the success of surgery and/or embolization.

Aged↗
PubMedDate not supplied

Radiation-induced brachial plexopathy: MR and clinical findings.

A 54-year-old man had a slowly progressive bilateral brachial plexopathy 17 months after surgery and radiation therapy for a stage IV supraglottic carcinoma. MR imaging at presentation showed a symmetric pattern of parascalene and interscalene hyperintense signal on T2-weighted images and after contrast enhancement. Although hyperintense signal has been more often associated with recurrent tumor than with delayed radiation injury or fibrosis, the location and pattern of the signal abnormalities suggested a diagnosis of radiation-induced plexopathy. This diagnosis was confirmed by the relative stability of the neurologic and MR findings 30 months after treatment.

Brachial Plexus↗