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Biomedical subjects

W Lang

Publications and source records attributed to W Lang.

At least 199 records · Page 11Linked to original sources
PubMed1991

Three-dimensional localization of SMA activity preceding voluntary movement. A study of electric and magnetic fields in a patient with infarction of the right supplementary motor area.

Previous studies by magnetoencephalography (MEG) failed to consistently localize the activity of the supplementary motor area (SMA) prior to voluntary movements in healthy human subjects. Based on the assumption that the SMA of either hemisphere is active prior to voluntary movements, the negative findings of previous studies could be explained by the hypothesis that magnetic fields of current dipole sources in the two SMAs may cancel each other. The present MEG study was performed in a patient with a complete vascular lesion of the right SMA. In this case it was possible to consistently localize a current dipole source in the intact left SMA starting about 1200 msec prior to the initiation of voluntary movements of the right thumb. Starting at about 600 msec prior to movement onset the assumption of a current dipole source in the left primary motor cortex was needed to account for the observed fields. Measurements of brain potentials were consistent with MEG findings of activity of the left SMA starting about 1200 msec prior to movement onset.

Brain Mapping↗
PubMed1991

Alternative splicing of the beta A4 amyloid gene of Alzheimer's disease in cortex of control and Alzheimer's disease patients.

An S1 nuclease protection assay was designed to study the splicing pattern of the alternatively spliced beta A4 amyloid gene (APP gene) of Alzheimer's disease (AD). We determined the splicing pattern of the APP gene in fetal, adult, aged adult and AD human cortex. The results suggest that alternative splicing of the APP gene in AD is not significantly different from age-matched controls, but distinct from the developing fetal brain.

Adult↗
PubMed1991

Decreased serum dehydroepiandrosterone is associated with an increased progression of human immunodeficiency virus infection in men with CD4 cell counts of 200-499.

Dehydroepiandrosterone (DHEA) and its interconvertible sulfate derivative (DHEA-S) are human androgenic steroids that have been reported to inhibit viral expression and have been associated with a decreased risk of cancer. The relationship between serum DHEA and DHEA-S levels and subsequent progression to AIDS was investigated in a sample of human immunodeficiency virus (HIV)-infected men from the San Francisco Men's Health Study followed prospectively since 1984. Among 108 men seropositive for HIV at study entry and with CD4 lymphocyte counts of 200-499 microliters 24 months later, serum DHEA levels below the lower limit of normal (less than 180 ng/dl) at this later date were predictive of subsequent progression to AIDS (relative hazard = 2.34; 95% confidence interval = 1.18-4.63; P = .01) after controlling for hematocrit, age, and log absolute CD4 cell number in a Cox proportional hazards model. This is the first large prospective cohort in which an endocrinologic variable has been observed to independently predict progression to AIDS. These observations, in addition to recent in vitro data, suggest that DHEA might have a protective effect in HIV infection.

Adult↗
PubMed1991

CD8+ T lymphocytes and progression to AIDS in HIV-infected men: some observations.

The relationship between CD8+ lymphocyte counts and progression to AIDS was studied in 340 HIV-1-seropositive men participating in a population-based prospective study. Overall, the relative hazard for developing AIDS during 60 months of observation was slightly elevated (1.08, P = 0.003), indicating an 8% increase in risk of progression for every 100 CD8+ cell count increment. When the data were analyzed in relation to date of diagnosis, the relative hazard was depressed (0.90, P less than 0.001) for the period 6 months prior to diagnosis, but was close to 1.0 for the period 6-36 months prior to diagnosis. These findings suggest a complex relationship between CD8+ cell counts and progression to AIDS, with the possibility that various subsets of the CD8+ compartment play different roles.

Acquired Immunodeficiency Syndrome↗
PubMed1991

The prevalence of oral lesions in HIV-infected homosexual and bisexual men: three San Francisco epidemiological cohorts.

To establish the prevalence of HIV-related oral lesions, we performed oral examinations of members of three San Francisco epidemiological cohorts of homosexual and bisexual men over a 3-year period. Hairy leukoplakia, pseudomembranous and erythematous candidiasis, angular cheilitis, Kaposi's sarcoma, and oral ulcers were more common in HIV-infected subjects than in HIV-negative subjects. Among HIV-infected individuals, hairy leukoplakia was the most common lesion [20.4%, 95% confidence interval (CI) 17.5-23.3%] and pseudomembranous candidiasis was the next most common (5.8%, 95% CI 4.1-7.5%). Hairy leukoplakia, pseudomembranous candidiasis, angular cheilitis and Kaposi's sarcoma were significantly more common in patients with lower CD4 lymphocyte counts (P less than 0.05). The prevalence of erythematous candidiasis and Kaposi's sarcoma increased during the 3-year period. Careful oral examinations may identify infected patients and provide suggestive information concerning their immune status.

Acquired Immunodeficiency Syndrome↗
PubMed1991

HIV encephalopathy: incidence, definition and pathogenesis. Results of a Swiss collaborative study.

The incidence of HIV encephalopathies was determined in an ongoing consecutive autopsy study. Among 345 patients who died from AIDS in Switzerland during 1981-1990, 68 (19%) showed morphological evidence of HIV encephalopathy. Two major histopathological manifestations were observed. Progressive diffuse leukoencephalopathy (PDL) was present in 33 cases and is characterized by a diffuse loss of myelin staining in the deep white matter of the cerebral and cerebellar hemispheres, with scattered multinucleated giant cells but little or no inflammatory reaction. Multinucleated giant cell encephalitis (MGCE) was diagnosed in 32 cases; it's hallmarks are accumulations of multinucleated giant cells with prominent inflammatory reaction and focal necroses. In 3 patients both types of lesions overlapped. Brain tissue from 27 patients was analyzed for the presence of HIV gag sequences using the polymerase chain reaction (PCR) with primers encoding a 109 base pair segment of the viral gene. Amplification succeeded in all patients with clinical and histopathological evidence for HIV encephalopathy but was absent in AIDS patients with opportunistic bacterial, parasitic and/or viral infections. Potential mechanisms by which HIV exerts it's adverse effects on the human CNS are discussed.

AIDS Dementia Complex↗
PubMed1991

The initial immune response to HIV and immune system activation determine the outcome of HIV disease.

A study was conducted to assess the relative contribution of the HIV-1-specific immune response and -nonspecific immune activation to HIV disease progression. The titer of antibody to the p24 core protein and the concentration of serum neopterin were measured in 238 HIV-1-seropositive subjects in a prospective cohort study of homosexual men. Antibody titers were extremely variable among cohort participants but relatively stable over time, suggesting inherent differences in the initial immune response capacity. Neopterin concentrations were also variable at cohort entry but generally increased over time. These two markers, measured at cohort entry, had powerful and independent predictive value for the development of AIDS up to 54 months before diagnosis. Subjects with low antibody titers and high levels of neopterin, had the highest incidence of AIDS (60% over 54 months). Patients with low antibody or high neopterin alone had an intermediate risk (34% incidence) and less than 10% of those with high antibody and low neopterin developed AIDS. We propose that the initial immune response to HIV and virus-mediated immune system activation are independent and innately variable components of an individual's response to HIV infection that interact to determine the clinical outcome.

Acquired Immunodeficiency Syndrome↗
PubMed1991

Population-based estimates of zidovudine and aerosol pentamidine use in San Francisco: 1987-1989.

From the San Francisco Men's Health Study (SFMHS) and the San Francisco General Hospital Cohort we derived partially population-based estimates of zidovudine (ZDV) use in San Francisco from 1987 to 1989. Data from the SFMHS alone were used to make estimates of aerosol pentamidine (AP) use in 1989. From 1987 to 1989, zidovudine use increased from 36 to 68% in participants with AIDS. In participants with symptomatic HIV infection without AIDS and in those with less than 200 CD4 cells, ZDV use increased initially but then leveled off (from 6 to 25% and 24 to 55%, respectively). Zidovudine use with more than 500 CD4 cells increased from 0.5 to 4%. In 1989 AP use with less than 200 CD4 cells was 42% and with AIDS was 44%. Whereas 50% of participants with AIDS and less than 200 CD4 were using both ZDV and AP, only 14% of those without AIDS but with less than 200 CD4 cells were using both. Surprisingly few members of these cohorts are using therapies proven effective in reducing the morbidity and mortality of HIV infection.

Acquired Immunodeficiency Syndrome↗
PubMed1990

[Nervous system pathology in AIDS: results of a collaborative autopsy study from Switzerland].

Neuropathological lesions were studied in a consecutive autopsy series of 206 cases, comprising 61% of all patients who died of Aids in Switzerland between April 1981 and December 1988. Central nervous system involvement was found in 84% of the patients, and 17% showed multiple concomitant intracerebral lesions. Among the non-viral opportunistic infections, cerebral toxoplasmosis was most frequent (24%), whilst among the viral opportunistic infections, cytomegalovirus (CMV) encephalitis was most frequent (7%). A nodular encephalitis consisting of disseminated microglial nodules without morphological or immunocytochemical evidence of CMV occurred in 13.5% of the patients. The majority of these cases showed evidence of extracerebral CMV infection. Progressive multifocal leukoencephalopathy (PML) was observed in 6% of the patients and was associated with widespread tissue destruction and cyst formation. HIV encephalopathy occurred in 38 patients (18%) and showed two characteristic morphological patterns: progressive diffuse leukoencephalopathy (PDL) and multifocal giant cell encephalitis (MGCE). PDL was observed in 22 patients and was characterized by a diffuse demyelination and gliosis of the white matter with little inflammatory infiltrates and scattered multinucleated giant cells which were immunoreactive to HIV antigens. MGCE was found in 16 patients and was characterized by clusters of macrophages, lymphocytes, and HIV-immunoreactive multi-nucleated giant cells. In our view, PDL and MGCE represent two opposite variants of HIV-induced encephalopathies with numerous intermediate manifestations.

Acquired Immunodeficiency Syndrome↗
PubMed1990

[Acute ischemic myelomalacia and colon necrosis in infrarenal aortic aneurysm].

A 54-year-old man suddenly developed a transverse spinal cord syndrome with paralysis of both legs and diffuse abdominal pain. Spinal compression was excluded by myelography. Subsequent computed tomography, however, revealed an aortic aneurysm of 7 cm diameter. At laparotomy extensive mesenteric ischaemia with necrosis of the entire colon and massive peritonitis were noted. It was not possible, because of the peritonitis, to bypass the aneurysm with a graft and only a colectomy was performed. The patient died 48 hours after admission of prolonged cardiocirculatory failure. Autopsy revealed further multiple organ damage in addition to the ischaemic myelomalacia. The common cause of the findings was probably a sudden drop in blood pressure in the presence of severe generalized arteriosclerosis.

Aorta, Abdominal↗
PubMed1990

Supplementary motor area activation while tapping bimanually different rhythms in musicians.

In 15 musicians, cortical DC-potentials were recorded from the scalp before and during the execution of bimanual motor sequences. Subjects (Ss) either tapped with their two index fingers in synchrony (quavers against quavers; "2 against 2") or they tapped quavers against triplets ("2 against 3"). Either the right or the left finger started tapping the quavers (onset time t1), after about 4 s the other finger joined in (t2) either with quavers as well (easy rhythm) or with triplets (difficult rhythm). Ss were free to start the sequences, i.e. to determine the onset times t1 and t2. Shifts of cortical DC potentials were averaged twice; (1) time-locked to t1 and (2) time-locked to t2. When moving in synchrony (easy rhythm) DC-potential shifts and maps of radial current densities across the scalp indicated activations of the two primary motor cortices (MI). When bimanually tapping different rhythms, there was not only an activation of MI cortices, but in addition a very large activation of the mesial, central cortex was observed. It is suggested that this cortical area which mainly contains the supplementary motor area (SMA) has the function of controlling the initiations of movements in the difficult sequence which have to fit into a very precise timing plan. Interestingly, activation of the mesial, central cortex preceded the actual performance of the difficult rhythm by about 4 s. This finding indicates that the preparatory set differs between the two tasks.

Adult↗
PubMed1990

Movement-related potentials accompanying unilateral and bilateral finger movements with different inertial loads.

The present study was aimed at investigating the effect of inertial loading on movement-related potentials (MRPs) recorded from the scalps of normal subjects while performing finger movements. Two experiments were performed. Experiment 1. MRPs preceding and accompanying the execution of voluntary, unilateral finger movements were investigated in 8 subjects under the 3 experimental conditions of: no inertial load, small inertial load (250 g), and large inertial load (400 g). A significant effect of the inertial load on Bereitschaftspotential (BP) amplitude was observed for the 100 msec period preceding movement onset (BP -100 to 0) at precentral electrode sites and following movement onset (N0 to 100) at both precentral and parietal electrode sites. Pairwise comparisons revealed that significant effects were due to differences between the loading and non-loading conditions and not for different amounts of loading. No significant differences were observed for BP onset or early BP amplitudes, indicating that scalp negativity immediately prior to, and during, movement onset is primarily influenced by conditions of inertial loading. Experiment 2. This experiment examined the effect of inertial loading on MRPs for bilateral, simultaneous voluntary finger movements in 10 subjects under conditions of: no inertial load, inertial load applied separately to the left and right fingers, and with identical inertial loads applied to both fingers. No significant effect of inertial load on MRP amplitude was observed. These results are contrasted with those of experiment 1 which show significant effects of inertial loading for unilateral movements and are interpreted in terms of the hypothesis that bilateral movement organization involves 'higher' aspects of motor control than those reflecting adjustment to conditions of inertial loading.

Adult↗
PubMed1990

Cerebral correlates of imagining colours, faces and a map--II. Negative cortical DC potentials.

Cortical activation patterns as measured by negative shifts of the scalp-recorded cortical steady potential ("DC shifts") were assessed in 28 normal subjects during imagining colours, faces, and a spatial map. Imaging resulted in sustained negative DC shifts at temporal, parietal and particularly at occipital sites. The topographic distributions of such DC shifts was modulated as a function of whether spatial or visual imagery was performed. During imaging the spatial map, a parietal maximum was observed, as opposed to a distribution in favour of temporal and occipital sites during imagining faces and colours. Results suggest a neuroanatomical dissociation between visual and spatial imagery. Since a similar visual-spatial dichotomy exists in perception, the finding is interpreted as further evidence of a shared cerebral substrate for images and percepts. The results are discussed in conjunction with the joint blood flow study.

Adult↗
PubMed1990

Elaborative strategies in word pair learning--DC-potential correlates of differential frontal and temporal lobe involvement.

Cortical DC potentials were recorded while subjects were learning word pairs. The use of an elaborative mnemonic strategy resulted in a left frontal sustained negative shift. Its amplitude was independent of whether imagery mnemonics or semantic mnemonics were used. By contrast, posterior temporal potentials differed according to strategy: with imagery mnemonics, subjects had more symmetrical potentials over posterior temporal areas whereas with a semantic strategy, there was a left hemispheric preponderance of the DC potential. An interpretation within Stuss and Benson's theory on the frontal lobes is given.

Adult↗
PubMed1990

Negative cortical potentials when classifying familiar and unfamiliar faces.

Event-related potential (ERPs) were recorded while subjects were classifying familiar faces of celebrities according to profession in one task, or unfamiliar faces according to gender in another task. Familiar faces given rise to an enhancement of the late negative ERP component confined to parieto-occipital sites. The finding is considered to reflect parietal and occipital lobe involvement in the activation of memories pertinent to familiar faces. Moreover, the late negative component was more prominent over the right than the left occipital lobe.

Adult↗