Search PubMed⌕ Search

Biomedical subjects

H Scherer

Publications and source records attributed to H Scherer.

At least 91 records · Page 5Linked to original sources
PubMed1991

[Microendoscopy of the Eustachian tube and the middle ear. Indications and clinical application].

Progressive miniaturization of flexible fibreoptic systems has made it possible for the first time to perform atraumatic endoscopy of the Eustachian tube and tympanic cavity with the ear drum intact. With the aid of special actively steerable microcatheters, flexible fibrescopes having outer diameters of 350 to 650 microns are inserted into the opening of the naso-pharyngeal tube and advanced into the tympanic cavity under direct visual control. This new technique is indicated for any disturbance of sound conduction and in those sensorineural hearing disorders in which direct inspection of the middle ear cavity can provide information on the pathogenesis of the disturbance. In the future it may thus replace purely diagnostic tympanoscopy. In combination with fibre-delivery laser systems, this new method forms the basis of "microendoscopically controlled laser surgery" of pathological changes within this anatomical region.

Ear, Middle↗
PubMed1991

Measuring three dimensions of eye movement in dynamic situations by means of videooculography.

A primary function of the vestibular system is the stabilisation of the eye during head movement. Consequently, evaluation of reflex eye movements represents an essential means to both clinical diagnosis and researching of the vestibular function. Movements in the eye can be resolved into three orthogonal components, i.e. horizontal, vertical and torsional. As an improvement on most current techniques, which provide only measurement of the horizontal and vertical components, videooculography (VOG) facilitates non-invasive measurement of all three of the defined components. To date, only the scleral coil technique, which involves the semi-invasive placement of coil rings onto the bulbi, yields a continuous measure of eye torsion. Employment of suitable solid-state devices permit the integration of a compact, high resolution video recording system. In the basic configuration, eye movements can be observed and simultaneously recorded for later analysis or documentation. The video images of the eye are obtained by means of a miniaturised CCD video sensor mounted on a light-occluding mask. Image processing of the acquired video images determines horizontal and vertical coordinates of eye position online. Ocular torsion, as reflected by the rotation of the natural iris, is measured for each video frame. The VOG algorithm has been implemented on a PC based workstation, which permits online observation, recording and evaluation of eye movements. In addition, the technique has found clinical application as a portable eye-movement observation and recording system, allowing bedside examination and recording of transient symptoms. Preliminary results from various studies, including the objective evaluation of positional nystagmus (BPPN), are presented.

Eye Movements↗
PubMed1990

Synaptoporin, a novel putative channel protein of synaptic vesicles.

By homology screening of a rat brain library, we have isolated cDNAs that encode a novel member of the synaptophysin/connexin channel protein superfamily. The deduced protein, named synaptoporin, displays 58% amino acid identity to synaptophysin, with highly conserved transmembrane segments, but a divergent cytoplasmic tail. Northern blot analysis and PCR amplification of RNA from different rat tissues indicate expression of synaptoporin transcripts in the CNS. Antibodies against a synthetic peptide or a fusion construct encompassing the cytoplasmic tail region of synaptoporin detect a polypeptide of 37 kd that copurifies with small synaptic vesicles. Our data suggest the existence of a family of vesicular channel proteins whose members may be differently distributed among synaptic vesicle subpopulations.

Amino Acid Sequence↗
PubMed1990

[Endoscopic-controlled laser lithotripsy of salivary calculi. In vitro studies and initial clinical use].

An in vitro study was performed to examine the application of a laser beam for the fragmentation of salivary stones. In accordance with the absorption and reflection spectra of sections of salivary stones, optimal fragmentation was achieved using a pulsed excimer laser with a pulse width of 60 ns and a wave-length of 308 or 351 nm. Further studies on particle size were conducted and a new "sialoendoscope" technique was developed. Twelve patients suffering from a sialolithiasis of the submandibular gland were treated. Under continuous endoscopic monitoring a laser-induced shock wave lithotripsy was performed. In 11 cases complete fragmentation and removal of the salivary stones was achieved. This approach to laser lithotripsy of salivary stones with endoscopic monitoring represents a novel method that permits treatment on an outpatient basis under local anaesthesia, with little inconvenience to the patient.

Calcium Phosphates↗
PubMed1989

[Effect of static magnetic fields on the acoustic action potential of the cochlea in guinea pigs].

Several experiments carried out during the past years indicate that strong magnetic fields induce disturbed blood circulation in capillaries and arterioles. When exposed to a magnetic field, disturbed blood circulation was found in the capillaries in frog webs as well as changes in skin temperature in several kinds of species. In our experiments we assessed the influence of a 8.5 T static magnetic field on the function of the inner ear of guinea pigs by monitoring the cochlea action potential. When blood circulation is disturbed in this organ it shows a rapid decline in function. Even when exposed to the magnetic field for 3 h, we could find no change in the function of the inner ear of the guinea pigs.

Action Potentials↗
PubMed1989

Cervical receptors and the direction of body sway.

A study was performed to determine whether the predominant direction of body sway is influenced by changes of head-to-trunk position. A group of ten patients suffering from acute unilateral vestibular loss was compared with a group of ten healthy subjects. Body sway was assessed by measurement on a posture platform. Center-of-force stabilograms were recorded with the subjects' eyes closed. After a baseline interval in the normal head-to trunk orientation, the head was torsioflexed with respect to the trunk and the locus of the center-of-force further assessed over a defined interval. It was observed that the patient group manifested a systematic translation of the direction of body sway that was associated in a consistent manner with the unilateral deficit. This translation occurred synchronously with head torsioflexion and could also be reproduced when turning the trunk with the head fixed, so that a semicircular canal influence could be excluded. It appears that cervical proprioceptive input to the central vestibular system is responsible for the effect observed.

Head↗
PubMed1989

Cervico-ocular eye movements in relation to different neck torsion velocities.

Rotation of the trunk with a fixed head causes isolated stimulation of cervical afferent input. Eleven patients with marked cervico-ocular reactions (COR) were selected. A neck torsion test (NTT) was performed with the help of a special apparatus. The resulting cervically induced eye movements consisted of two components. In addition to a cervical nystagmus, with its slow, compensatory phase, a deviation of the mean eye position (shift) in an anticompensatory direction, opposite to trunk rotation was observed. The COR in relation to different neck torsion velocities distinctly showed a tuning curve with maximum reactions between 4 degrees/s and 9 degrees/s. Above these values, a strong decrease in COR resulted. The optimal working range vastly differs from that of the vestibulo-ocular reflex (VOR).

Adult↗
PubMed1988

Neural adhesion molecule L1 as a member of the immunoglobulin superfamily with binding domains similar to fibronectin.

Diverse glycoproteins of cell surfaces and extracellular matrices operationally termed 'adhesion molecules' are important in the specification of cell interactions during development, maintenance and regeneration of the nervous system. These adhesion molecules have distinct functions involving different cells at different developmental stages, but may cooperate when expressed together. Families of adhesion molecules which share common carbohydrate domains do exist, despite the structural and functional diversity of these glycoproteins. These include the Ca2+-independent neural adhesion molecules: N-CAM, myelin associated glycoprotein (MAG) and L1. L1 is involved in neuron-neuron adhesion, neurite fasciculation, outgrowth of neurites, cerebellar granule cell migration, neurite outgrowth on Schwann cells and interactions among epithelial cells of intestinal crypts. We show here that in addition to sharing carbohydrate epitopes with N-CAM and MAG, L1 is also a member of the immunoglobulin superfamily. It contains six C2 domains and also shares three type III domains with the extracellular matrix adhesion molecule fibronectin.

Amino Acid Sequence↗
PubMed1988

Caloric stimulation during short episodes of microgravity.

Caloric testing was performed during parabolic flight at the NASA Reduced Gravity Facility in Houston, Texas. Six test subjects were stimulated with continuous unilateral air insufflation (25 degrees R), in a manner similar to the experiments performed in the extended weightlessness of orbital flight during the SL1 and D1 Spacelab missions. Nystagmus response was recorded by electro-oculography and eye video image. It was the purpose of the experiments to re-examine the apparent discrepancy between the disappearance of caloric nystagmus during short episodes of weightlessness and the finding that caloric responses can be elicited during periods of extended weightlessness. The present results agree with those of earlier experiments in that a prompt reduction of caloric nystagmus occurs on transition from hypergravity (1.8 G) to weightlessness. The time constant of nystagmus decay was estimated to be approximately 2-3s, a value which cannot be explained by cupular mechanics. A central gating mechanism involving the labyrinthine canal and otolithic afferents is proposed for the observed modulation of caloric nystagmus.

Caloric Tests↗
PubMed1987

Identification of cDNA clones of the mouse neural cell adhesion molecule L1.

Two cDNA clones of the neural cell adhesion molecule L1 (Mr 200,000) were isolated using lambda gt10 and lambda gt11 libraries constructed from postnatal day 8 mouse brain poly(A)+ RNA. Clone K21 was selected and identified using immunoaffinity purified polyclonal antibodies. It was then used to isolate a secondary clone (K21-1), which hybridized with an oligonucleotide probe synthesized by reverse translation of the aminoterminal sequence of the 80 kDa carboxyterminal proteolytic fragment of L1. Blot hybridization analysis indicated that L1 is encoded by a single gene and transcribed by a single 6 kb mRNA which is present only in cells or tissues known to express L1.

Animals↗
PubMed1987

Thermal stimulation of the vestibular labyrinth during orbital flight.

During the European Spacelab mission (SL1) in 1983, caloric testing was performed for the first time in long-term weightlessness. After 2 days into orbital flight an unequivocal caloric nystagmus was observed in both subjects tested which corresponded in both quality and intensity with that measured in one-g conditions on Earth. The subsequent D1 mission enabled the experiment to be repeated on further subjects and with improved measurement procedures. As with the SL1 findings, the observed caloric nystagmus response proved to be equivalent to that measured during baseline testing on Earth. Renewed consideration of peripheral and central mechanisms, which might be involved in the elicitation of the caloric response--both in one-g and zero-g environments--has led to the reopening of a number of associated issues. One important observation which has been addressed by various research groups concerns the influence of the labyrinth's orientation to the gravity vector on the caloric response. The present authors have examined a group of healthy subjects in various body positions in the sagittal plane. The interindividual variability in the response behavior was found to be high; indeed single cases were observed in which the nystagmus response did not invert from the supine to the prone positions. These findings are discussed together with earlier reports in the literature.

Caloric Tests↗
PubMed1987

Control of cattle mange in southern Africa using ivermectin.

Seven trials including 768 cattle were conducted in South Africa and Namibia to evaluate the efficacy of the systemic parasiticide ivermectin when administered subcutaneously at a dose rate of 200 micrograms/kg against sarcoptic (Sarcoptes scabiei var. bovis), chorioptic (Chorioptes bovis) and psoroptic (Psoroptes ovis var. bovis) mange mites. The efficacy of a single treatment against Psoroptes and Sarcoptes was greater than against Chorioptes. There was marked clinical cure in all treated cases with loss of crusts and hair regrowth. The number of cases of psoroptic mange in two large herds, of which 42.4% of 724 animals were clinically affected prior to mass treatment, was reduced by 99.3% following a single subcutaneous treatment with ivermectin; a single animal from which mites were recovered may not have been treated. The apparent prevalence and prospects for control and eradication of cattle mange in South Africa and Namibia are discussed.

Administration, Oral↗
PubMed1987

[Causes and treatment of seasickness].

Seasickness is usually induced by conflicting sensory cues. However, very little is known about the neural pathways and processes which play a role in the development of nausea. Since the symptoms, for example, pallor, sweating and vomiting are all of parasympathetic origin, the common antiemetic drugs are anticholinergically efficient. More recently, additional drugs and modified forms of application have been introduced to reduce the soporific side effects. It is pointed out that onboard behaviour and even choice of vessel can be of more importance than use of antivertiginous drugs. Besides attention to the individual adaptation to the atypical seagoing environment, simple behaviour patterns such as fixation on the horizon, avoiding of head movements and reduction of conflicting sensory cues can be very effective in reducing symptoms.

Antiemetics↗