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Biomedical subjects

L Hansen

Publications and source records attributed to L Hansen.

At least 163 records · Page 9Linked to original sources
PubMed1991

[Diagnosis of carotid artery sclerosis with Doppler ultrasound. Description of the method and a prospective comparison with arteriography].

The ultrasound Doppler method for examination of the carotid artery is described. Out of a total of 370 patients examined with ultrasound Doppler for suspected arteriosclerosis in the carotid artery in 1988, 27 were also submitted to digital subtraction arteriography (DSA). The accuracy of the ultrasound examination was compared with DSA 90% (43/48) when differentiating between normal and affected carotid arteries, and 85% (41/48) when differentiating between stenoses of more than or less than 50%. All of the occlusions were correctly identified. It is concluded that ultrasound Doppler examination is an accurate method for diagnoses of stenosis in the carotid artery.

Adult↗
PubMed1991

Abnormal brain spectrin immunoreactivity in sprouting neurons in Alzheimer disease.

Brain spectrin is a major membrane skeleton protein that participates in cellular transport, cell morphogenesis, neurotransmitter release and growth cone adhesion. The present study showed that in Alzheimer disease (AD) neuropil, brain spectrin immunoreactivity is co-localized with synaptophysin in the presynaptic boutons. At the ultrastructural level, brain spectrin immunoreactivity was observed in the presynaptic terminals and in the axoplasm of some myelinated and unmyelinated fibers. In addition to this normal localization of brain spectrin in the AD brain, we also found brain spectrin immunoreactivity associated with abnormal patchy lesions in the AD neuropil. Confocal laser imaging and immunoelectron microscopy revealed that these lesions corresponded to thick cellular processes derived from neurons. The findings that these structures were anti-neurofilament positive but anti-glial fibrillary acidic protein (GFAP) and Ricinus communis agglutinin I (RCA-I) negative confirm their neuronal origin, and rule out the possibility of glial origin. These structures could represent either atypical axonal or dendritic processes derived from sprouting neurons or the accumulation of brain spectrin degradation products in degenerating neurons.

Aged↗
PubMed1991

Parental leave policies for faculty in U.S. medical schools.

OBJECTIVE: To assess medical school policies for maternity and other parental leaves as well as related opportunities for part-time employment, flexibility in tenure systems, and the availability of child care centers. DESIGN: Cross-sectional survey of all 127 U.S. medical schools based on telephone interviews and review of faculty handbooks. MEASUREMENTS AND MAIN RESULTS: Ninety-three percent of medical schools responded. Twenty-two percent of medical schools have no written guidelines for maternity leave, 45% categorize maternity leave as a form of sick or disability leave, and only 34% have developed specific policies. Most schools (61%) require that maternity leave be taken from allotted sick days or from vacation days (or from both) for women to obtain salary support. The time available from sick and vacation leave averages 6.8 weeks. Although 72% of schools make allowances in the tenure probationary period for extended leaves of absence, few have developed specific provisions for childbearing or childrearing. Finally, 18% of medical schools have child care facilities. CONCLUSIONS: Considerable work is needed to develop adequate support for faculty members who are parents. Recommendations include developing specific parental leave policies and flexible tenure systems and providing adequate child care facilities.

Absenteeism↗
PubMed1991

Neocortical damage during HIV infection.

Clinical and pathological evidence of subcortical central nervous system (CNS) damage is observed commonly in patients with human immunodeficiency virus (HIV) encephalitis. Whether other CNS regions are also affected has not been well studied. We report neocortical damage in patients with HIV encephalitis. Using quantitative techniques, we demonstrate statistically significant thinning of the neocortex, with a loss of large cortical neurons. Qualitative and quantitative assessments of neocortical neuropil reveal a loss of synaptic density and vacuolation of dendritic processes. Failure to demonstrate an association of these changes with the presence of HIV antigens suggests that neocortical damage may be an indirect effect of HIV infection of the CNS.

AIDS Dementia Complex↗
PubMed1991

The barley genes Acl1 and Acl3 encoding acyl carrier proteins I and III are located on different chromosomes.

Acyl carrier protein (ACP) is an essential cofactor for plant fatty acid synthesis. Three isoforms occur in barley seedling leaves. The genes Acl1 and Acl3 coding for the predominant ACP I and the minor ACP III, respectively, have been cloned and characterized as has a full-length cDNA for ACP III. Both genes, extending over more than 2.5 kb, have a conserved mosaic structure of four exons and three introns which result in mRNAs of ca. 900 bases. Alignment of the DNA sequences demonstrates that homology is restricted to the two exons coding for the mature protein whereas the remaining segments of the genes including the transit peptide-coding domains lack homology. Southern blot analyses demonstrate that Acl1 and Acl3 represent single copy genes located on chromosomes 7 and 1, respectively. Primer extension analyses identified multiple transcription start sites in both genes. The promoter regions are remarkably different; that of Acl3 resembles those for mammalian housekeeping genes in having a high G + C content plus three copies of an RNA polymerase II recognition GC element and in lacking correctly positioned TATA boxes. These features are in accordance with the hypothesis that Acl1 is specifically expressed in leaf tissue whereas Acl3 is a constitutively expressed gene.

Acyl Carrier Protein↗
PubMed1991

Immunoelectron microscopic study of synaptic pathology in Alzheimer's disease.

Alzheimer's disease (AD) is characterized by an extensive loss of neurons and synapses in the neocortex which correlates strongly with psychometric tests of dementia. To characterize the ultrastructural changes in presynaptic terminals in AD, we studied biopsy material from the frontal cortex. We also examined, at the ultrastructural level, abnormal neurites scattered in the AD neuropil and in the plaque region using sections from autopsy material immunolabeled with anti-synaptophysin. We found that, regardless of amyloid deposits, some presynaptic terminals were distended and contained swollen vesicles and dense bodies. These altered synaptic organelles were similar to those found in dystrophic neurites. The latter structures displayed synaptophysin immunoreactivity, mostly localized to outer membranes of synaptic vesicles and dense bodies. The present study supports the hypothesis of progressive synaptic pathology in AD neocortex and favors the notion that the dystrophic process originates from presynaptic terminals.

Aged↗
PubMed1991

Immunoreactivity of CD45, a protein phosphotyrosine phosphatase, in Alzheimer's disease.

Both protein kinases and phosphoprotein phosphatases are important components of signal transduction systems in cells. Recent studies in Alzheimer's disease (AD) have shown abnormal protein phosphorylation in the cortex suggesting an alteration in these enzymes. In the present study, an antibody against CD45 was used to analyze the status of this protein phosphotyrosine phosphatase in AD. We studied and quantified the immunohistochemical and immunochemical distribution of this integral membrane protein in control and AD brain. We found that anti-CD45 immunostained the great majority of microglia, both resting and activated. These cells were Ricinus communis agglutinin I positive and glial fibrillary acidic protein and neurofilament negative. The AD frontal cortex showed a 35% (P less than 0.01) increase in the number of anti-CD45 immunoreactive microglia as compared with controls. These results were consistent with the immunoblot quantification of CD45 immunoreactivity following native gel electrophoresis. In AD, 30% of the CD45-immunostained microglia were clustered in the neuritic plaques (about six per plaque) while the remaining 70% were scattered in the neuropil. The AD hippocampus showed an increase in CD45-immunoreactive microglia in the molecular layer of the dentate gyrus. At the ultrastructural level, CD45 immunoreactivity was localized exclusively to the plasma membrane of the microglia. The presence of the anti-CD45 immunoreactivity in microglia suggests the possibility that they may require the presence of CD45 as a cell surface receptor which may regulate cell function through modulation of intracellular signaling.

Aged↗
PubMed1991

Patterns of aberrant sprouting in Alzheimer's disease.

Alzheimer's disease (AD) is characterized by extensive synaptic and neuronal loss and by plaque formation in the cortex, but the mechanisms responsible for synaptic plasticity in the neocortex are still not completely understood. To analyze the sprouting response in AD cortex, we compared the patterns of GAP-43 with synaptophysin immunoreactivity. In AD, GAP-43 immunohistochemistry revealed extensive sprouting in the hippocampal molecular layer, stratum polymorphous, CA1 region, and prosubiculum. These regions presented abundant anti-GAP-43-immunoreactive coiled fibers and dystrophic neurites in association with plaques. Some of these sprouting structures were colocalized with anti-synapto-physin- and anti-neurofilament-positive neurites. The AD neocortex was characterized by an overall decrease in GAP-43 immunoreactivity accompanied by sprouting neurites in the areas of synaptic pathology. We conclude that GAP-43 might be involved in the mechanisms of synaptic plasticity in the AD cortex, as well as in the process of aberrant sprouting in the neuritic plaques.

Aged↗
PubMed1991

Palmar skin is not involved in severe atopic eczema.

Irritant hand eczema is a well-known risk in adults, who have suffered from severe atopic dermatitis during childhood. We therefore studied the involvement of the skin on the hands in 29 consecutive patients admitted for severe atopic dermatitis. Only 5 of the 29 patients had eczema in the palmar skin (p less than 0.01; sign test). There was no correlation with the existence of hyperlinearity, extent of disease, concomitant asthma, total serum IgE or work.

Adolescent↗
PubMed1990

Effect of advanced age on p-aminohippurate-induced inhibition of renal tubular secretion in male Fischer 344 rats.

The effect of aging on glomerular filtration, effective renal plasma flow and on the responsiveness of the renal tubular anion secretory system to inhibition by 4-aminobenzoylglycine (p-aminohippurate, PAH) was examined in young (5-month) and old (22-month) Fischer 344 male rats. Plasma clearance, protein binding and renal extraction of [131I]o-iodohippurate, [125I]iothalamate and HPLC-purified [99mTc]mercaptoacetyltriglycine (MAG3), were used as in vivo probes of renal function. The effect of advanced age, without concomitant PAH, on the disposition of these markers was initially determined in ketamine anesthetized, temperature-maintained male rats, ages 5, 14 and 22 months by means of constant infusion clearance studies. Aging per se decreased (P less than 0.05) the kidney-weight normalized or body weight-normalized GFR and effective renal plasma flow rates. GFR values averaged 1.67, 1.43 and 1.32 ml/min per g kidney for the 5-, 14- and 22-month-old rats, respectively. Kidney- or body weight-normalized clearances of MAG3 and o-iodohippurate showed similar (25-27%) decreases, whereas the absolute values (ml/min) for GFR, o-iodohippurate and MAG3 clearance rates were not altered by aging. The effective filtration fraction, extraction ratio and plasma protein binding were also unchanged by advanced age. Overall, the age-related decreases in renal function were minimal in Fischer-344 rats, compared to other species. Differences in data normalization, species and gender account, in part, for discrepancies observed when comparing results in different studies on the effects of advanced age on renal function. Subsequently, we examined the effect of aging on the renal responsiveness to inhibition of tubular anion secretion using constant rate PAH infusion studies, adjusted for age-related changes in renal function. Aging did not alter PAH-induced inhibition of iodohippurate secretion. Inhibition of MAG3 elimination was more pronounced in the old rats compared to the young controls.

Aging↗