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Biomedical subjects

H Feldmann

Publications and source records attributed to H Feldmann.

At least 37 records · Page 2Linked to original sources
PubMed1991

[Heat radiation--an essential factor of heat transport in caloric vestibular tests? Current experimental findings].

According to the accepted theory, in vestibular testing the caloric stimulus is transported from the auditory canal to the lateral semicircular canal by heat conduction via the bone. Some findings, however, are not consistent with this concept, e.g. the short latency of the vestibular response, and the fact that removing of the osseous bridge does not stop the transport of heat to the semicircular canal. Physically there are three modes of heat transport: conduction, convection, and radiation. So far, only the first two have been discussed with regard to vestibular calorization, however, they fail to explain the findings mentioned above. We carried out experiments on 10 cadaveric temporal bone specimens in order to evaluate the possible effect of heat radiation. With experimental conditions strictly regulated (specimens kept in climate box, 37 degrees C, saturated humidity, standardized irrigation of the auditory canal with 50 ml of water of 50 degrees C in 15 sec., temperature measured by thermistors at selected points of the specimen), the deviation in repeated experiments was within 0.1 degree C. In normal temporal bones a spreading of heat along the osseous structures was found in accordance with heat conduction via the bone. Then the bony bridge between posterior frame of the tympanic membrane and the lateral canal was removed along with the tegmen tympani, leaving the auditory canal and labyrinth connected only by a small anterior-inferior strut. The rise of temperature in the lateral canal, however, was not delayed and reduced, as expected, but faster and greater than in the original situation. If, now, a reflecting shield was inserted in the cleft between tympanic membrane and labyrinth the heat transfer was dramatically reduced. A similar effect could be achieved in the intact middle ear by a shield or by filling the cavity with gel. Convection as means of heat transport could be excluded. The experiments show that heat transport in the vestibular calorization is a complex process, which besides heat conduction involves radiation as an essential factor. This explains a number of experimental and clinical findings that, so far, had been unclear.

Bone Conduction↗
PubMed1991

Transport of heat in caloric vestibular stimulation. Conduction, convection or radiation?

Experiments in temporal bone specimens were carried out under strictly controlled conditions: temperature (37 degrees C) and humidity kept constant; standardized irrigation of the external ear canal by an automated system (in 15 s, 50 ml of water, 11 degrees C above temperature of specimen), thermistor probes of 0.2 mm diameter placed in different parts of the specimens. In the intact temporal bone such an irrigation causes a rise in temperature with a gradient from the external ear canal across the bony bridge to the lateral semicircular canal as expected with heat conduction. After removal of the bony bridge, which is the main route for heat conduction, the rise in temperature in the lateral semicircular canal is greater and faster than in the intact specimen. This effect again is drastically reduced by placing a reflecting shield between tympanic membrane and labyrinth. In the intact middle ear inserting a reflecting shield or filling the cavity with gel also reduces the heat transfer to the labyrinth, although the bony routes for heat conduction are left untouched. The experiments prove that radiation plays an important part in heat transfer in caloric stimulation.

Caloric Tests↗
PubMed1991

[Unilateral paralysis of the abdominal wall musculature caused by thoracic intervertebral disk displacement].

Herniated thoracic discs are rare. Many cases present with local radicular or cord symptoms. We describe a case which became symptomatic by a unilateral paresis of the muscles of the abdominal wall. This radicular syndrome has only been described for lumbar disc herniations before. The differential diagnosis is discussed as well as the importance of myelography and the value of Myelo-CT.

Abdominal Muscles↗
PubMed1990

Yeast homoserine kinase. Characteristics of the corresponding gene, THR1, and the purified enzyme, and evolutionary relationships with other enzymes of threonine metabolism.

THR1, the gene from Saccharomyces cerevisiae, encoding homoserine kinase, one of the threonine biosynthetic enzymes, has been cloned by complementation. The nucleotide sequence of a 3.1-kb region carrying this gene reveals an open reading frame of 356 codons, corresponding to about 40 kDa for the encoded protein. The presence of three canonical GCN4 regulatory sequences in the upstream flanking region suggests that the expression of THR1 is under the general amino acid control. In parallel, the enzyme was purified by four consecutive column chromatographies, monitoring homoserine kinase activity. In SDS gel electrophoresis, homoserine kinase migrates like a 40-kDa protein; the native enzyme appears to be a homodimer. The sequence of the first 15 NH2-terminal amino acids, as determined by automated Edman degradation, is in accordance with the amino acid sequence deduced from the nucleotide sequence. Computer-assisted comparison of the yeast enzyme with the corresponding activities from bacterial sources showed that several segments among these proteins are highly conserved. Furthermore, the observed homology patterns suggest that the ancestral sequences might have been composed from separate (functional) domains. A block of very similar amino acids is found in the homoserine kinases towards the carboxy terminus that is also present in many other proteins involved in threonine (or serine) metabolism; this motif, therefore, may represent the binding site for the hydroxyamino acids. Limited similarity was detected between a motif conserved among the homoserine kinases and consensus sequences found in other mono- or dinucleotide-binding proteins.

Amino Acid Sequence↗
PubMed1990

An element of symmetry in yeast TATA-box binding protein transcription factor IID. Consequence of an ancestral duplication?

TATA-box binding factor TFIID is one of the key factors in transcriptional activation. Surprisingly, the yeast TFDII protein [(1989) Nature 341, 299-303; (1989) Cell 56, 1173-1181; (1989) Proc. Natl. Acad. Sci USA 86, 7785-7789] reveals only limited homology with other DNA-binding proteins. From computer-assisted searches we infer that yeast TFIID possesses a domain structure in which homologous segments are repeated. The greatest similarity is found between two segments, each 33 amino acids in length, in which the positions of four basic residues are strictly conserved. The high homology is also reflected at the gene level. Implications of this novel type of domain structure for possible interactions in transcriptional activation are discussed.

Amino Acid Sequence↗
PubMed1990

[Forensic evaluation of physical damage in the early Middle Ages--a comparison with current occupational disability guidelines].

The legal systems of the Germanic tribes in the early Middle Ages elaborated detailed catalogs of forfeits in compensation for certain physical injuries. The perpetrator had to pay the forfeit to the injured person, or in case of manslaughter, to the tribe of the dead. By doing so he could avert the feud which otherwise faced him. These catalogs of forfeits exactly reflect the relative value that was appointed to certain parts of the body and to sensory functions. The catalog of the Lex Saxonum (c. 802), in which physical injuries are listed, ranging from loss of single phalanges, differentiated between thumb, forefinger, small finger, and the other fingers, to death, is compared with modern grades of disability. There are surprising parallels and interesting contrasts. Bilateral deafness is put on a level with bilateral blindness, the loss of both hands, both feet, both testicles, and death.

Disability Evaluation↗
PubMed1990

[Aneuralgic root paralyses caused by lumbar intervertebral disk displacement. Follow-up of surgical therapy].

It is a controversial issue whether or not a painless paralysis caused by a lumbar disc herniation should be managed surgically because of the possible fatal destruction of the nerve root. In a retrospective study we examined 46 patients concerning the reversibility of their neurological deficits. Our results show that the so called "aneuralgic state" of the lumbar root compression syndrome and the death of the nerve root are not identical. More than half of the patients with the symptoms of nerve root death gained significant improvement above their preoperatively existing paralysis sometimes even up to several years later. The appearance of the compressed root at the time of surgery is of special importance because it allows conclusions concerning the remission of preexisting paresis. Defects of sensibility or the reflex status never improved without simultaneous improvement of paresis. The damage of the nerve root due to disc herniation is discussed with the help of literature sources with special consideration as to the time of reinnervation. Our results demonstrate that patients with an "aneuralgic state" can benefit from disc surgery and thus surgery could be recommended for these patients. Two cases are described.

Female↗
PubMed1989

Characterization of the prephenate dehydrogenase-encoding gene, TYR1, from Saccharomyces cerevisiae.

TYR1, the gene from Saccharomyces cerevisiae, which encodes prephenate dehydrogenase, one of the tyrosine biosynthetic enzymes, has been cloned by complementing a yeast tyr1 mutant strain. The DNA fragment containing the gene is part of a 45-kb cosmid clone which represents a region of chromosome II covering the genetically mapped tyr1 locus. The nucleotide sequence of a 3.1-kb region carrying the TYR1 gene and adjacent regions has been determined. The open reading frame contains 441 codons, corresponding to about 52.2 kDa for the encoded protein. The canonical NAD-binding domain is located within the first 45 amino acids of the protein. By primer extension, we show that there is one transcription start point. Presumably, the expression of TYR1 is not under the general GCN4 control. Instead, we find a dependence on the presence or absence of phenylalanine. These data were obtained by analysing CAT activity in constructs containing promoter fragments of TYR1 and the cat reporter gene.

Amino Acid Sequence↗
PubMed1989

Ty4, a novel low-copy number element in Saccharomyces cerevisiae: one copy is located in a cluster of Ty elements and tRNA genes.

We have identified a composite element, Ty4, in S. cerevisiae that is ca 6.3 kb in length and contains two tau sequences as long terminal repeats. According to hybridization analyses, Ty4 occurs in low but varying copy number (one to four copies) in different yeast strains. By several criteria, Ty4 is a novel type of retroelement which is similar but not related to the other Ty elements in yeast. Two cosmid clones from strain C836 (c90 and c476) carrying individual copies of Ty4 were isolated. By restriction analysis and nucleotide sequence we show that c476 derives from the 'transposition right arm hot spot' of chromosome III [1]. The analysis of c476 revealed that an initiator tRNA(Met) gene is present at this locus and that an unusual concentration of different Ty elements has occurred: in addition to the Ty4, a Ty1 and a Ty2 element were detected in this region, confirming its highly polymorphic character.

Base Sequence↗
PubMed1989

A hot-spot for transposition of various Ty elements on chromosome V in Saccharomyces cerevisiae.

Ty4 is a novel transposable element in the yeast, Saccharomyces cerevisiae, which is present in only a few copies in the genome (Stucka et al. 1989). In strain C836 one of the three copies (Ty4-90) is contained in cosmid clone c90, where it resides on chromosome V. Analysis of this region reveals a "hot-spot" of transposition: in addition to Ty4-90, the locus contains a complete Ty3 element and seven singular delta, sigma and tau elements. Three tRNA genes (for His, Lys, and Ile) are located in this region, and these are closely associated with one or the other of the elements, a phenomenon commonly observed in yeast. A comparison of c90 with corresponding regions from other strains shows that the locus is highly polymorphic and that this polymorphism is explicitly associated with Ty transposition and recombination events.

Base Sequence↗
PubMed1989

Objective evidence of tinnitus in auditory evoked magnetic fields.

The waveforms of the auditory evoked magnetic field in normal-hearing individuals and patients suffering from tinnitus are distinctly different. In tinnitus patients, the magnetic wave M200 (corresponding to the electric wave P200, or P2) is delayed and only poorly developed or even completely missing, while the amplitude of the magnetic wave M100 (corresponding to the electric wave N100, or N1) is significally augmented. A very characteristic feature turned out to be the amplitude ratio of the two waves M200 and M100. Below the age of 50, the amplitude ratio M200/M100 represents a clear-cut criterion to distinguish between tinnitus patients and individuals without tinnitus. In tinnitus patients, the ratio is less than 0.5, independent of age, whereas, in young and middle-aged normal-hearing individuals, it is greater than 0.5. Since in normal-hearing individuals the average amplitude ratio decreases linearly with age, the clusters of amplitude ratios of the two groups begin to overlap beyond the age of 50. The hypothesis is put forward that the decrease of the average amplitude ratio in normal-hearing individuals reflects a degenerative process, probably initiated by multiple exogenous and endogenous factors, which leads to sustained neural activity in the generators of wave M200 and eventually gives rise to the sensation of tinnitus. The absence or poor development of wave M200 is a concomitant phenomenon, resulting from the involved generators being less responsive to external stimuli.

Acoustic Stimulation↗
PubMed1989

[Aspects of the dynamics of delusions].

Delusion ist the outcome of psychotic experience, but can also be seen as a structure of meaning with patterns of mental and anthropological significance of its own. In schizophrenic delusion, there is some 'effort after meaning' manifest, compensating for psychotic disintegration. In the light of generative linguistics, there seems creating of delusional ideas to be performed in separated steps, but contextually linked to integrate them into a holistic delusional view of reality. Subjective evidence of delusional thinking is analyzed on the basis of semantic logics.

Delusions↗
PubMed1989

[The status of psychogenic hearing disorder today].

The general symptoms of psychogenic hearing disorders are pointed out and exemplified by 16 own cases seen by the author in 1987 to 1988. Psychogenic hearing disorders imitate various constellations of findings and histories of genuine organic hearing disorders. The individual's experience and the contemporary consciousness of hearing disorders seem to enter into the individual manifestation. The 16 cases can clearly be divided into 3 groups of equal size: 1. The unilateral acute hearing loss, imitating either an acute traumatic damage or an idiopathic sudden hearing loss. This was seen almost exclusively in children. 2. The bilateral chronic hearing loss. This, too, was seen mainly in children and youths. 3. The acute bilateral recurring or progressing hearing disorder. This was seen predominantly in adults, mimicking dramatic courses ending up in bilateral profound deafness. In part of the cases the psychological background of the neurotic reaction could be explored quite easily. Knowledge of the various manifestations of psychogenic hearing disorders is important, because otherwise, as the reported cases demonstrate, misleading interpretation of findings entails costly diagnostic procedures (computerized tomography, arteriography) and expensive therapeutic measures (hospitalization, fitting of hearing aids).

Adolescent↗
PubMed1989

[Martin Luther's seizure disorder].

Martin Luther's diseases are well documented, because he used to discuss them freely in his letters. There is also a wealth of evidence through reports by his friends. Most of his diseases were common and well known to the contemporary physicians, who accordingly interpreted them correctly: bladder stones, chronic constipation, hemorrhoids. Luther's death obviously was due to a coronary thrombosis. During the last 19 years of his life, in addition to these "natural diseases", Luther also suffered from recurring attacks of a peculiar symptomatology. Luther himself and his friends considered these seizures to be no "natural disease", but Satan punching his flesh, and he compared them to St. Paul's disease (2. Cor. 12). The first of these attacks occurred on July 6, 1527, when Luther was 43 years of age. It began with a roaring tinnitus in his left ear, which increased dramatically and seemed to occupy the left half of his head. Then a state of sickness and collapse followed, however, consciousness was retained throughout the whole period. After a night's rest all the symptoms had subsided, except the tinnitus, which, from that day on, continued for all the following years in varying intensity. Similar attacks with increase of the tinnitus and vertigo as the leading symptoms, seized Luther at irregular intervals and distressed him extremely. Former investigators of Luther's diseases interpreted these attacks as manifestations of a psychiatric disorder and a chronic inflammatory disease of the middle ear. The present detailed study reveals that it was a typical case of Menière's disease of the left ear manifesting itself more than 330 years before Menière's classical observation.

Christianity↗
PubMed1988

Analysis of yeast chromosomal regions carrying members of the glutamate tRNA gene family: various transposable elements are associated with them.

We carried out an analysis on the genomic organisation of the tRNA(Glu) family in S. cerevisiae; eight clones were characterized by restriction mapping, hybridization and sequencing. These data taken together with our earlier findings show that the individual tRNA(Glu3) copies are identical only in their structural part but embedded in entirely different genomic environments. All of the tRNA genes identified here are flanked by elements such as Ty, delta, sigma, and tau. In some cases, sequences from different elements form complex patterns indicating a sophisticated history of these chromosomal regions. A novel observation is that Ty and delta in the regions analyzed are exclusively associated with the tRNA genes. The observed patterns imply that the tRNA genes mark regions of multiple transposition and subsequent excision events, but that these have occurred after the individual tRNA gene copies had been fixed in their present locations. Transcription experiments by the use of micro-injection into Xenopus oocytes suggest that the elements flanking the tRNA genes exert a modulating effect on their expression.

Animals↗
PubMed1988

A series of shuttle vectors using chloramphenicol acetyltransferase as a reporter enzyme in yeast.

Reports from numerous laboratories have shown that the gene coding for the bacterial enzyme chloramphenicol-3-O-acetyltransferase can be used as a reporter gene (cat) in mammalian and plant systems to analyze gene activity at the transcriptional level when combined with endogenous regulatory signals; the enzyme activity can be quantified by a chromatographic or a photometric assay. To adapt this simple and highly sensitive test for the yeast system, we constructed a series of yeast vectors containing the cat gene together with selectable markers for Escherichia coli and yeast; integrating, autonomously replicating and centromere-carrying plasmids were used. We show that the cat gene lacking the endogenous promoter is expressed at low levels in yeast transformants. To demonstrate functional expression of the cat gene placed under the control of a yeast promoter, we chose the PHO5 regulatory region. We found that cat expression was induced via the PHO5 promoter in a manner as observed for the endogenous PHO5 gene, whereas in the repressed state cat expression remained low. Using these vectors, it should be feasible to analyze other sequences conferring promoter activity or other control functions in yeast.

Chloramphenicol O-Acetyltransferase↗