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Biomedical subjects

W Lang

Publications and source records attributed to W Lang.

At least 19 recordsLinked to original sources
PubMed1992

[Hickman catheter for long-term parenteral therapy. A prospective interdisciplinary study].

160 patients with a median age of 38 years (range two months to 84 years) having silicone rubber central venous access catheters for long-term parenteral nutrition or chemotherapy were studied prospectively. Two different types of catheters were used, the Broviac-type "life-cath" and the Groshong -catheter. Intraoperative complications were not noticed. Parenteral therapy was performed in 124 patients (81%) without any complications. After a mean postoperative interval of 36 weeks there were 34 catheters removed because of end of therapy. 78 patients died with the catheter in place. 40 catheters had to be removed before end of therapy due to catheter-related complications. Occlusion of the lumen occurred in nine patients after an interval from three to 20 weeks. Explantation of catheters due to a suspected catheter-related sepsis was performed in 17 patients. Both types of catheter showed a high cumulative patency rate of 90% after a twelve months period. However, there were catheters that had to be removed before planned end of therapy. Thus, the cumulative rate of functioning catheters is lower (44% of all catheters).

Adolescent↗
PubMed1992

Changes of cortical activity when executing learned motor sequences.

Fifteen right-handed subjects performed a learned sequence of four movements (flex index finger, extend hand, extend index finger, flex hand) either with their left or their right hand. The sequence of movements had to be continuously repeated for 20 s (period of execution). In the beginning of each period of execution large negative DC potentials were recorded in positions located above the mesial fronto-central cortex (Cz) and the sensorimotor hand areas of either hemisphere (C3 and C4). In contrast, DC potentials were absent in Cz at the end of the period of execution. In recordings from a position above the sensorimotor hand area contralateral to the performing side, negative DC potentials declined to some extent during task execution but were still present at the end of the period. Variations of both the amplitude and topography of negative cortical DC potentials during task-execution indicate changes of both the size and pattern of cortical activity. These findings were consistently found at both the beginning and end of the experiment. Motor performance as quantified by movement times and inter-onset latencies of movements showed no change, either during the periods of execution or when comparing the beginning of the experiment with the end. Conclusions are: (1) the execution of a learned motor sequence task cannot be associated with a particular size and pattern of cortical activity. (2) A pronounced decline of neural activity in the mesial, fronto-central area constitutes the predominant feature of the changes of cortical activity during the period of execution.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

The changing pattern of human immunodeficiency virus-associated cerebral toxoplasmosis: a study of 46 postmortem cases.

Frequency, pathogenesis and morphological features of toxoplasmosis were assessed in a consecutive autopsy study. Among 204 patients who died from AIDS in Zurich during 1981-1990, 46 (23%) showed morphological evidence of cerebral toxoplasmosis. In 38 out of 46 cases (83%), toxoplasmosis was restricted to the central nervous system (CNS) and, therefore, pathogenetically classified as reactivation of a latent infection. Acute, systemic toxoplasmosis most frequently involved heart and lungs in addition to the CNS and was observed in 7 cases (15%). These patients probably acquired the infection during HIV-induced immunosuppression. Latent infection with intracerebral tissue cysts but no inflammatory response was present in only one case. Diffuse, necrotizing toxoplasma encephalitis with widespread, confluent areas of necrosis was mainly observed during the early period of the AIDS epidemic and restricted to 6 patients (13%) who did not receive chemotherapy. The majority of patients (83%) had multiple, macroscopically well-circumscribed abscesses with preferential location in the cerebral hemispheres. Of all CNS regions, the rostral basal ganglia were most frequently affected (78% of cases). Since 1989, chronic, burnt-out lesions were observed. These were mainly composed of lipid-laden macrophages and immunocytochemistry for Toxoplasma gondii usually failed to detect the parasite. This changing pattern of CNS lesions probably reflects improved clinical management of patients with AIDS.

Acquired Immunodeficiency Syndrome↗
PubMed1992

Frontal DC potentials in auditory selective attention.

Selective dichotic listening during periods of 35 sec was associated with negative shifts of the cortical DC potential. Amplitudes of negative DC potentials had maxima in frontal, in particular, in anterior frontal records. The temporal pattern of negative DC potentials was different between the fronto-lateral records of the two hemispheres: in records from the right side, DC potentials declined during the 35 sec observation period, whereas they remained sustained in those of the left side. Different instructions ("attend left ear," "attend right," "attend both") and different levels of pitch separation between deviants and standards had no effects on frontal negative DC potential shifts, which are discussed in terms of higher order control of selective dichotic listening.

Adult↗
PubMed1992

Frontocentral DC-potential shifts predicting behavior with or without a motor task.

This study was designed to investigate the predictive value of the event-related potentials (ERPs) preceding the initiation of a difficult perceptual-memory task and to investigate whether these ERPs require a motor movement on the part of the subject for their occurrence. Across 4 conditions the DC-potential shifts were recorded from 23 right-handed subjects using DC amplifiers. Although the start of each trial began with a ready signal, the conditions differed in that the subjects initiated the task by a button press in 2 conditions and the computer initiated it in 2 others without a press. The results showed that, especially in the frontocentral electrode sites, the DC-potential shifts which began those trials ending in correct performance were more negative relative to those trials ending in an incorrect response. Those conditions which required the subjects to self-initiate the trial and those which were initiated by the computer showed similar results indicating that the negative DC-potential shifts preceding correct performance are neither produced by nor depend on a task initiating motor movement. The onset of the DC-potential shifts preceded task initiation by up to 4.1 sec indicating that they were more than the Bereitschaftspotential.

Adult↗
PubMed1992

Cortical DC potential shifts accompanying auditory and visual short-term memory.

Negative DC potential shifts appeared over the scalp during the performance of verbal and non-verbal short-term memory tasks. Three items were successively presented (presentation of memory items) and then had to be retained in memory for 3 sec (memory retention) before being compared to a probe which was either a member (in set) or not a member (out of set) of the memory set. Verbal items (the digits "1" through "9") were tested in the auditory and visual modality and non-verbal items (musical notes) were tested in the auditory modality. Stimulus modality had a significant effect on DC potential shifts during both presentation of memory items and memory retention. There was a sustained negative shift during these periods which was larger over frontal regions with auditory than with visual material whereas the negative shift was larger over posterior temporal regions with visual than with auditory material. Out of 21 subjects who participated in the study, 9 reported the use of visual images in the auditory task, 5 used subvocal auditory rehearsal in the visual task and 7 used imagery concordant with the stimulus modality being memorized. These different strategies had a significant effect on the amplitudes and distribution of the DC potential shifts. The speed of response affected the amplitude of the DC potential shifts in the frontal regions, being larger with fast RTs than with slow RTs but only when verbal items were being processed. These results indicate that stimulus modality, modality of mental imagery, and speed of scanning of the memory store affect DC potential shifts during a 3 sec period of memory retention.

Acoustic Stimulation↗
PubMed1992

Significance of left-sided heart disease for the detection of patent foramen ovale by transesophageal contrast echocardiography.

Detection of patent foramen ovale by contrast echocardiography is based on transient inversion (right atrial pressure higher than left atrial pressure) of the interatrial pressure gradient. Therefore, the presence of left-sided heart disease with potential elevation of left atrial pressure might obscure the diagnosis of patent foramen ovale. Accordingly, 150 patients (88 men, 62 women; mean age 51.7 +/- 15.2 years) were evaluated for a patent foramen ovale by transesophageal contrast echocardiography. Additionally, atrial septal motion during normal respiration and during the Valsalva maneuver was analyzed. Patency of the foramen ovale was observed in 20 (27%) of 74 patients without left-sided heart disease and with previous arterial embolism, in none (0%) of 25 patients with left-sided heart disease and embolism, in 7 (39%) of 18 patients without left-sided heart disease and without embolism and in 3 (9%) of 33 patients with left-sided heart disease and without embolism. The detection rate of patent foramen ovale was lower in patients with than without left-sided heart disease (5% vs. 29%, p = 0.0007) but was similar in patients with and without embolism (20% vs. 19.5%, p = NS). Abnormal atrial septal motion was more frequently observed in patients with left-sided heart disease (p = 0.0003) and was inversely correlated to detection of patent foramen ovale (p = 0.0003). Multivariate analysis revealed an independent association between the absence of left-sided heart disease and the detection of patent foramen ovale (p = 0.0003). These data suggest that in patients with left-sided heart disease, patency of the foramen ovale may be missed even by transesophageal contrast echocardiography.

Adult↗
PubMed1992

Different risk factor profiles in young and elderly stroke patients with special reference to cardiac disorders.

The risk factors of ischemic cerebrovascular disorders in 77 young patients (< or = 40 years) were compared to those in 138 older patients (> 40 years). The risk factor profile of patients with juvenile stroke was considerably different from that of older patients. Migrainous headache and mitral valve prolapse occurred more frequently in the younger age group, whereas hypertension, diabetes mellitus, high levels of cholesterol and triglycerides were found more often in older patients with stroke. 65% of the women under the age of 40 took oral contraceptives which compares to the baseline community value of 28% of women in childbearing age in this country. Cardiac disorders such as atrial fibrillation, left ventricular hypertrophy, coronary heart disease including a history of myocardial infarction, as well as mitral valve disease were demonstrated more often in the group of elderly patients. 7 out of 77 younger patients (9.1%), and 59 out of 138 older patients (42.8%) were considered to belong to a group with "high cardiac risk for stroke". The results of this study indicate that electrocardiographic screening is of prime importance for detecting cardiac risk factors. However, echocardiographic examination often yields additional diagnostic information, particularly in younger patients. The conflicting opinions concerning the relevance of certain risk factors for ischemic stroke could partly be explained by the fact that these risk factors are distributed unevenly depending on age.

Adolescent↗
PubMed1992

Preparation, purification and characterization of chlorohaemin.

Preparation of chlorohaemin (CAS 16009-13-5) is performed on the basis of the method of Labbe and Nishida (acetone-acetic acid-SrCl2 method) with some significant modifications. Instead of blood as starting material, a fresh preparation of purified human erythrocytes is used. This avoids any contamination with serum and erythrocyte proteins and lipids of the end product. Special care is taken to remove contaminating globin by introducing some specific purification steps during isolation and recrystallisation. The yield is in the range 65-75% of theory, and the purity of the product is better than 99.9% as shown by elemental analysis and specific tests on various compounds as possible contaminants which originate from the starting material such as lipids and proteins and/or from the different steps of preparation and purification during the procedure. The pure chlorohaemin which is the compound of choice as reference substance for the AHD method in haemoglobinometry is characterized by LSI mass spectrometry (m/z = 616, haemin ion), field desorption-mass spectrometry (m/z = 652), by IR-spectroscopy, and by UV/VIS absorption spectroscopy (pyridine haemochrome spectrum, AHD spectrum).

Blood Proteins↗
PubMed1992

[Clinical significance of peripheral vascular resistance for early bypass occlusion rate. Errors and dangers in measuring vascular resistance].

An estimation of the peripheral resistance was performed during 264 peripheral bypasses. After completion of the distal anastomosis, saline was infused via the proximal graft end in constant flow rates. The mean distal pressure was used for calculation of peripheral resistance. There was a close correlation between the peripheral resistance (based on flow rates of 100 ml/min) and the 30 day graft failure rates. Below the level of 450 mPRU the failure rate was 4%, above 750 mPRU, however, this rate was more than 20%. It is concluded, that the estimation of the peripheral vascular resistance during the operation is a valuable tool to estimate the prognosis of graft patency.

Aged↗
PubMed1992

[Diabetic gangrene in peripheral vascular occlusion. Saving the extremity by popliteo-pedal venous bypass].

23 patients with diabetic gangrene and complete occlusion of all 3 tibial arteries were treated by 26 popliteopedal vein bypass grafts. All 6 early graft failures resulted in major amputations. The cumulative graft patency rate was 76% after 6 years. One patient needed lower-leg amputation despite a functioning graft. All other limbs were saved (mean follow-up period: 24.8 months). It is concluded that despite a palpable popliteal pulse an angiographic examination should be performed, when the infectious lesion cannot be controlled by local treatment and pedal pulses are absent.

Aged↗
PubMed1991

Distribution of ischemic cerebrovascular events in cardiac embolism.

Distribution and number of ischemic cerebrovascular events were studied in 57 patients who suffered from heart disorders with proven or highly probable source of cardiac embolism and compared to 39 patients with ulcerations of the craniocervical vessels. Patients with coexisting lesions were excluded from the present study. Out of the 57 patients with cardiac disorders, a single episode of cerebral embolism occurred in 33 patients. Of the 24 patients with recurrent ischemic episodes, different vascular territories were involved in only six cases. There was no evidence of a distinct distribution of vascular territories involved in cerebral embolism. The left middle cerebral artery was affected in 42.9%, the right middle cerebral artery in 23.8%, the vertebrobasilar territory in 19%, and the ophthalmic arteries in 14.2%. Statistical analysis revealed no significant differences in lesion localization between the group with a cardiac source of embolism and the group with ulcerations of the craniocervical vessels. There was a high frequency of patients with recurrent cardiogenic emboli in the ophthalmic (6 of 9 patients) as well as in the vertebrobasilar (6 of 12 patients) circulation who experienced a delayed initiation of cardiac assessment. The possibility of cardiac embolism should be considered in any patient with cerebral ischemia, independently of the vascular territory affected.

Adult↗
PubMed1991

On the functionality of the visually deprived occipital cortex in early blind persons.

In early blind mammals, the deprived visual cortex undergoes anatomical and functional alterations. Its functional role was investigated in the early human blind by using patterns of cortical activation as measured by scalp-recorded event-related slow negative DC potential shifts. The blind showed higher occipital negativity than did sighted persons both during a tactile reading task and a non-reading tactile control task. Results point to a possible role for the blind's visual cortex in tactile processes.

Adult↗
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↗