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Biomedical subjects

M Bach

Publications and source records attributed to M Bach.

At least 91 records · Page 5Linked to original sources
PubMed1995

Asymmetry of motion VEP in infantile strabismus and in central vestibular nystagmus.

Norcia et al. [1] found a nasal-temporal asymmetry of visually evoked potentials (VEP) elicited by motion stimuli in patients with infantile strabismus. Patients with infantile strabismus typically present with an asymmetry of the monocular optokinetic nystagmus (OKN). We here address the question whether the asymmetry of the motion VEP indicates a sensory defect in the afferent visual pathway that could explain the OKN asymmetry. We recorded the VEP to a horizontally oscillating vertical sinusoidal grating in 20 patients with infantile strabismus (esotropia, asymmetry of the monocular optokinetic nystagmus, latent nystagmus) and in 10 normal controls. No asymmetry occurred in the 10 controls. Eight of the 20 patients with infantile strabismus showed a clear difference between the VEPs evoked by back and forth movements with a mirror-like asymmetry between the two eyes (phase shift 180 +/- 20 degrees). However, there was no significant correlation between the degree of VEP and OKN asymmetries. Therefore, we assume that the VEP asymmetry does not reflect the primary cause of the OKN asymmetry. Rather, the OKN asymmetry may be due to a sensory-motor defect in the efferent subcortical pathway, and the VEP asymmetry could be an epiphenomenon. Some of the VEP asymmetry may be a consequence of the latent nystagmus typically released under monocular stimulation, leading to adaptation of the afferent retino-cortical pathway. This suggestion is supported by a marked VEP asymmetry that we found in two patients with an acquired central vestibular nystagmus, an abnormality most likely not combined with a primary defect of the retino-cortical pathway.

Adolescent↗
PubMed1995

The Timed Test of Money Counting: a simple method of recognizing geriatric patients at risk for increased health care.

The purpose of this prospective study was to measure patients' ability to open a purse, take out money, and count it, in order to identify persons in need of increased health care. The study population consisted of 183 patients (mean age 78.9; range: 66-95) in two settings: 78 consecutively admitted geriatric hospital patients who could return home, and 105 community-dwelling patients aged 70 years or older. None was completely dependent on others, nor severely demented. Time for task performance was measured. Further assessment included the Mini-mental State Examination (MMSE), Barthel index of ADL, instrumental activities of daily living (IADL), socioeconomic status, grip strength, Williams board test, and medication profile. The Timed Test of Money Counting (TTMC) was reliable (interrater and intrarater), and showed construct and concurrent validity with other measures of physical function. There was a strong correlation (p < 0.001) between the time required to count money, and to open and close the panel doors of the Williams board. The other functional measures were also significantly correlated with the TTMC. After 18 months, 26 of the patients had died, and 5 were lost to follow-up. The remainder were divided into those who had stable needs (group I), and those with increasing care needs or nursing home placement (group II). Time required for money counting was significantly different (p < 0.001) between groups (30.9 +/- 17.5 seconds for group I, and 122.6 +/- 94.4 seconds for group II).(ABSTRACT TRUNCATED AT 250 WORDS)

Activities of Daily Living↗
PubMed1995

Isolation and characteristics of a steady-state visually-evoked potential in humans related to the motion of a stimulus.

We have examined the visual potential evoked by two motion stimuli. In the first stimulus (termed coherent motion) a random-dot pattern oscillated between phases of coherent and incoherent ("snowstorm") motion, and in the second a random-dot pattern alternated in direction of motion (termed direction change). We found that the response to the coherent motion stimulus is low-pass with respect to speed, has low contrast sensitivity and increases steadily with the contrast of the stimuli. The direction change visually-evoked potential (VEP) is band-pass with respect to speed, has high contrast sensitivity but then saturates and even reduces as the stimulus contrast is raised above 0.1. The behaviour of the direction change VEP is similar in nature to results from psychophysical experiments of motion perception and to the known properties of directionally selective cells of the cortex. On the other hand the behaviour of the coherent motion VEP suggests this may not be mediated by a mechanism specific to motion.

Contrast Sensitivity↗
PubMed1995

Reactivating occupational therapy: a method to improve cognitive performance in geriatric patients.

In this prospective treatment study, the effects of two different occupational therapy strategies were compared in two samples of long-term geriatric inpatients (n = 22 in each group) with slight to moderate dementia according to DSM-III-R. Psychometric ratings after 12 weeks and 24 weeks of treatment have demonstrated that the application of a reactivating occupational therapy programme in addition to functional rehabilitation is significantly more efficient than the application of functional rehabilitation alone on levels of cognitive performance, psychosocial functioning, and the degree of contentedness with life. These results support the assumption that geriatric patients, if stimulated for a longer time, are able to mobilize latent resources of cognitive and psychosocial performance. Reactivating occupational therapy has a place in the treatment of long-term geriatric patients.

Activities of Daily Living↗
PubMed1995

The Timed Test of Money Counting: a short physical performance test for manual dexterity and cognitive capacity.

The competent handling of money is an essential basis for living independently. Seventy-eight consecutively admitted patients to a geriatric hospital underwent the Timed Test of Money Counting (TTMC) which measures patients' ability to open a purse, take out all the money and count it. Further assessment included Mini-Mental State Examination (MMSE), Barthel Index of ADL, Self-maintaining and Instrumental Activities of Daily Living (IADL), grip strength and Williams' Board Test. The TTMC was reliable (inter-rater and intra-rater) and showed construct and concurrent validity with other measures of physical function. Unlike many other physical performance tests the TTMC is quickly performed and requires no special equipment or training.

Activities of Daily Living↗
PubMed1995

Assessment of nutritional risk in the elderly.

To enhance physicians' awareness of nutritional problems in the elderly, a nutritional risk assessment scale was developed and validated. 126 patients (mean age 82.0 +/- 6.7, range 65-96 years) admitted from home to a geriatric hospital were enrolled in the study. After informed consent was obtained, they underwent a comprehensive geriatric assessment of physical, emotional, and cognitive functions, overall functional capacity, and social situation. The nutritional status was assessed by the nutritional risk assessment scale. This scale consists of items relating to gastrointestinal disorders, chronic diseases with pain, immobility, alterations in body weight, appetite, difficulties in eating, cognitive or emotional problems, medication, smoking and drinking habits, and social situation. The maximum score which indicates a high risk is 12. The scores from the nutritional risk assessment scale were compared with a physician's clinical judgement (patients being graded as "obese', "well-nourished', "undernourished') as the "gold standard' and with body mass index, other anthropometric findings, and serum albumin and prealbumin levels. The nutritional risk assessment scale was reliable (inter- and intrarater) and showed construct and concurrent validity. There was a significant correlation with clinical judgement (p < 0.01) and other parameters of nutritional status (p < 0.05). The scores of undernourished patients (n = 37; 5.35 +/- 1.60, range 3-8) were significantly different (p < 0.05) from those who were classified as well nourished (n = 63; 2.66 +/- 1.59, range 0-7) or obese (n = 26; 2.73 +/- 1.76, range 0-7). When implemented as part of a comprehensive geriatric assessment, this questionnaire can be completed within 5-10 min. The nutritional risk assessment scale is simple and reliable and helps in the identification of elderly patients at risk of poor nutrition.

Aged↗
PubMed1995

Predictive value of alexithymia: a prospective study in somatizing patients.

In the present study, the potential role of alexithymia in predicting the long-term treatment outcome was investigated prospectively in 30 patients with DSM-III-R somatoform disorders and anxiety disorders. Using SCID interviews, diagnoses were assessed before inpatient treatment and 2 years after discharge. Patients who met criteria for DSM-III-R undifferentiated somatoform disorder at follow-up exhibited higher pretreatment alexithymia scores (as measured by the TAS) as compared with patients who showed remission of their somatoform disorder or patients who never had met criteria for a somatoform disorder. As a result stepwise logistic regression analyses, high alexithymia scores emerged as a significant predictor of persistent somatization, independent of other measures of psychopathology, sociodemographic variables, and measures of illness severity.

Adolescent↗
PubMed1995

[The Freiburg Vision Test. Automated determination of visual acuity].

The Freiburg Visual Acuity Test is an automatic computerized procedure for self-administered measurement of visual acuity. Landolt-Cs are presented on a monitor in one of eight orientations. The subject presses one of eight buttons, which are spatially arranged according to the eight possible positions of the Landolt-C's gap. To estimate the acuity threshold, a best-PEST procedure is employed, assuming a psychometric function with a constant slope on a logarithmic acuity scale. The discreetness artifacts in computer monitors limit the presentation of small stimuli. By anti-aliasing (smoothing of contours by gray-shading), the spatial resolution was improved by a factor of four, such that the shape of Landolt-Cs with oblique gaps is adequate and visual acuities from 0.06 up to 3.6 can be tested at a distance of 5 m.

Artifacts↗
PubMed1994

Heterologous expression of the human D2S dopamine receptor in protease-deficient Saccharomyces cerevisiae strains.

The cDNA for the human D2S dopamine receptor has been functionally expressed in the unicellular yeast Saccharomyces cerevisiae. The original D2S gene and an elongated D2S gene with an N-terminal fusion to the first 24 amino acids of the STE2 gene from S. cerevisiae were introduced into the episomal yeast expression vector YEp51 under the control of the GAL10 promoter. Expression studies performed in a wild-type strain and in two protease-deficient strains of S. cerevisiae revealed that the receptor was functionally expressed with respect to its ligand-binding properties. The KD values for the binding of the dopamine antagonist [3H]spiperone were calculated to be 1.6 nM for the D2S receptor alone and 1.9 nM for the STE2-D2S chimaera. Both membrane proteins could be further characterized by ligand-displacement studies using certain dopamine agonists and antagonists. D2S dopamine-receptor-specific polyclonal antibodies were used to monitor the heterologous expression of the receptor. Western-blot analysis of membranes prepared from transformed yeast cells producing either the receptor protein alone or the receptor fusion protein revealed apparent molecular masses of 40 kDa (D2S receptor alone) and 42 kDa (STE2/D2S receptor fusion protein). It could be shown that, in comparison to the expression in a wild-type S. cerevisiae strain, the amount of receptor degradation was drastically reduced in the protease-deficient strains. The localizations of the heterologously produced dopamine receptor and of the chimaera in the recombinant yeast were studied by immunogold electron microscopy and were found to be restricted mainly to the vacuole of the cells.

Base Sequence↗
PubMed1994

Alexithymia and somatization: relationship to DSM-III-R diagnoses.

In previous studies, results from psychometric measures suggested an association between alexithymia and somatization. However, alexithymia has not been examined in relation to somatoform disorders and other standard psychiatric diagnoses. In the present study, the prevalence of DSM-III-R diagnoses was determined by SCID interviews among 45 psychiatric inpatients with functional somatic syndromes. In addition, the Toronto Alexithymia Scale (TAS) and the SCL-90-R were administered. Of the sample, 42.2% scored in the alexithymic range of the TAS. The alexithymic patients presented significantly more psychological turmoil and overall psychopathology on the SCL-90-R, as well as a significantly higher number of current DSM-III-R diagnoses. However, alexithymia was unrelated to DSM-III-R somatoform disorders and other DSM-III-R diagnoses, as well as the course of illness. These results suggest that assessing clinical features in addition to psychometric measures seems to be necessary for further validating the potential role of the alexithymia construct in somatic symptom formation.

Adolescent↗
PubMed1994

Asymmetries in preattentive line detection.

We tested the relative contribution of absolute orientation and collinearity to asymmetries in preattentive line detection. Subjects reported the location of a single line that was tilted by 16 deg against the orientation of the background lines. Perceptual pop-out strength was quantified as the threshold presentation time to correctly locate the salient element. We found that (1) threshold times were significantly shorter in vertical than in oblique background lines and that (2) threshold times were significantly shorter in collinear than in non-collinear background lines. Our data suggest that the sensitivity of preattentive processes for orientation gradients is modulated by both collinearity and absolute orientation.

Humans↗
PubMed1994

Motion adaptation governs the shape of motion-evoked cortical potentials.

We recorded visually evoked potentials (VEPs) to motion onset/offset of square-wave gratings (dominant spatial frequency 0.69 c/deg, velocity 4.9 deg/sec, contrast 10%, luminance 15 cd/m2) with three electrode combinations (Oz vs Fz, Oz vs linked ears and parietal vs linked ears). In one experiment (seven subjects), we examined the effect of the duty-cycle of motion vs non-motion (5-80%) on the size of the various motion-evoked components. In another experiment (six subjects, duty-cycle 10%), we examined the effect of motion adaptation on the motion VEP. We observed both a positive VEP component around 110 msec (P1) and a negative component around 180 msec (N200). The amplitude of these components depended on duty-cycle and electrode position: N200 dominated at < or = 20% motion duty-cycle, P1 at > or = 50%; P1 dominated medially, N200 laterally. Motion adaptation enhanced the P1 and reduced the N200 by a factor of 3. Previous controversies regarding the major components of motion-evoked potential may be due to different duty-cycles. The effect of duty-cycle is probably caused by adaptation to the test stimulus; it can be predicted quantitatively by a simple one-parameter model based on the assumption that the VEP amplitude is proportional to the non-adapted proportion of motion-response generators.

Adaptation, Physiological↗
PubMed1994

Asymmetries in texture perception.

Single elements in textures segregate preattentively from the background if they differ in special features from surrounding elements (pop-out). Oblique targets on a background of vertical line elements are more easily detected than vertical targets on a ground of oblique elements. We wanted to find out whether this perceptional asymmetry depends on the absolute orientation or on the alignment of the background lines. Using the method of constant stimuli, we measured the thresholds of detection times in five subjects using four different arrangements of line patterns. The subjects indicated the position of a salient element in a forced-choice procedure. For all subjects, detection times were shortest if background lines were either vertical or collinear. Otherwise, detection times were significantly longer by a factor of 3. Figure-ground segregation is facilitated if background lines are either vertical or collinear.

Form Perception↗
PubMed1994

[Magnetic resonance mammography--even today a routine procedure].

Magnetic resonance imaging of the breast is at this time superior to all other methods of breast cancer diagnosis. Within a few short years since its introduction, magnetic resonance mammography (MRM) can be labelled the "golden standard" for breast imaging and carcinoma detection. Nevertheless, in a certain percentage of high risk patients, there remains an unacceptable number of unclassifiable findings on MRM examination. We were able to demonstrate in 10% of our examined patients small (< 8 mm), occasionally solitary, but usually multiple lesions that exhibited with the use of contrast material an appearance characteristic of carcinoma. Yet in merely half of these cases, that were subsequently surgically examined, significant pathology was found. We assume that some false-negative findings are a matter of the lack of broad acceptance of this diagnostic method by surgeons and pathologists. In order to further the development of MRM in the diagnosis of breast cancer and to ascertain the relevance of these borderline findings, it is important to perfect the techniques of MRM-guided localization of lesions and MRM-guided fine needle biopsies. We except that this would also deepen our knowledge of the pathogenesis of breast carcinoma. MRM is today, however, the examination method of choice for young, high-risk patients, patients with solitary lesions of unknown dignity and patients with markedly fibrocystic breasts.

Adult↗
PubMed1993

Different organization of the tRNA-gene-associated repetitive element, DRE, in NC4-derived strains and in other wild-type Dictyostelium discoideum strains.

The retrotransposon DRE (Dictyostelium repetitive element) was discovered in the course of an extensive study concerning the genomic organization of tRNA genes in the NC4-derived strains AX2 and AX3 of the cellular slime mold Dictyostelium discoideum. As a striking feature, DRE was found exclusively in a constant orientation and at a constant distance upstream from different tRNA genes. About 150-200 DRE with intact 5'-terminal-repeat structures are present in NC4-derived strains. These strains were termed high-copy DRE strains (HCD strains) as opposed to low-copy DRE strains (LCD strains) such as the wild-type D. discoideum isolates DD61, WS380B, OHIO and V12. LCD strains contain only 3-15 DRE with intact 5'-terminal-repeat-structures. However, in addition to these few intact elements, many 5'-truncated DRE elements are present in LCD strains. In HCD strains, most DRE show typical structural characteristics of retrotransposons containing terminal repeats at both ends, which seems to be one prerequisite for active transposition. In LCD strains, however, most DRE elements are 5'-truncated, which is a common feature of eukaryotic LINE elements. Despite their truncated 5'-ends, DRE in LCD strains retain unique integration specificities, i.e. they are always found position-specifically and orientation-specifically integrated in front of tRNA genes, flanked by a 12-16-bp target-site duplication.

Animals↗
PubMed1993

Nucleotide sequence of a putative succinate dehydrogenase operon in Thermoplasma acidophilum.

28 amino acids from the N-terminal region of a putative terminal oxidase from the archaebacterium Thermoplasma acidophilum were determined by Edman degradation. On basis of this amino acid sequence a degenerated oligonucleotide was synthesized and used as a radioactive probe for Southern blot analysis of EcoRI digested genomic DNA. A 2.3 kb EcoRI fragment strongly hybridized to the probe and size selected genomic library from genomic DNA was constructed. Several clones scored positive by screening the library with the degenerated oligonucleotide, from which only one clone contained a EcoRI DNA fragment encoding the 28 amino acid sequence determined by protein sequencing. Sequence analysis revealed the presence of three genes in the typical arrangement of an operon. The first gene codes for a protein containing 11 cystein residues in an arrangement typical for Fe/S proteins. Protein sequence comparison revealed significant homologies to the fumarate reductase and succinate dehydrogenase of other bacteria. The two other genes encode small hydrophobic proteins probably serving as membrane anchor for the Thermoplasma acidophilum succinate dehydrogenase.

Amino Acid Sequence↗