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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 179 (1996), S. 837-842 
    ISSN: 1432-1351
    Keywords: Eye growth ; Emmetropization ; Monochromatic light ; Fish ; Chromatic aberration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract By rearing fish in various monochromatic illuminations we investigated (1) the potential for compensation of refractive error due to chromatic aberration, (2) the contributions of the chromatic channels to emmetropization, and (3) the role of color cues in the control of eye growth. Cichlid fish (Aequidens pulcher) were reared for 6 months (12 h light/12 h dark) in monochromatic lights (623.5, 534.1, 485.0 nm; spectral purity 5–10 nm). Light levels were isoirradiant at 1.1·1012 quanta/s/cm2. Two control groups were reared in white light with down-welling illuminances of 0.2 and 33 lx. Nasotemporal diameters (NTDs) of the eyes were measured in relation to lens size. Due to the oblique axis of highest acuity vision in cichlids, NTD is considered to be a more important dimension than axial length. Variances in NTD were equally small in all rearing groups. NTDs were enlarged with increasing wavelengths of the rearing lights with highly significant values over controls in the red-light group. The wavelength-dependent size of the eyes matched the changes in focal length due to longitudinal chromatic aberration. Complete recovery from eye enlargement was observed after fish reared in red light were exposed to a white light regime for 5 weeks. Small variances in NTD in all groups indicated stringent control of eye growth in the absence of color cues. The reversibility of the increase in NTD in fish reared in red light suggests that the eyes were emmetropized by visually guided mechanisms. Eye size in fish reared in white light was intermediate between the values expected if only blue-sensitive single or the red- and green-sensitive double cones contributed to the control of eye growth. This suggests that all chromatic channels participate in emmetropizing the fish eye.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 184 (1999), S. 403-412 
    ISSN: 1432-1351
    Keywords: Key words Emmetropization ; Myopia ; Dopamine ; 6-Hydroxy-dopamine ; Crystalline lens
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract We investigated the suitability of fishes as animal models to study the involvement of the retinal dopaminergic system in the visually guided control of eye growth (emmetropization). Advantages of such a model system are (i) that all dopaminergic cells in the retina can be destroyed without apparent damage to other neurons, (ii) simple optical design and short depth of field of the eye, and (iii) continuous growth throughout life. Depleting the retina of dopamine in Aequidens pulcher (Cichlidae) had no apparent effect on refractive state, since size and focal length of the eye were reduced by the same amount. Furthermore, imposed defocus was compensated at a normal rate in spite of the absence of retinal dopamine. In A. pulcher, the dopaminergic system of the retina thus appears not to have an essential role in emmetropization. Our results furthermore suggest that in eyes of more complicated optical design, manipulation of the retinal dopaminergic system may lead to unrelated effects indistinguishable from direct interference with emmetropization. A major disadvantage of the fish model was that refractive state of the eye could not be measured accurately in vivo with standard methods.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    HNO 47 (1999), S. 941-946 
    ISSN: 1433-0458
    Keywords: Schlüsselwörter Kraftfahreignung ; Verkehrsmedizin ; Fahrerlaubnis ; Hörvermögen ; Gleichgewichtsstörungen ; Key words Traffic medicine ; Driving license ; Driving suitability ; Hearing impairment ; Balance disorders
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary An absolute requirement for acquiring a driving license according to German law consists in the suitability for driving a motor vehicle. The ”driving license decree” defines these requirements; in case of doubt the administrative authority may demand a medical certificate. According to law (enactment: 1.1.99) these medical certificates must be refunded by either appropriate medical specialists, company doctors or public health officers. The criterions for appraisal are set down in the guidelines for driving ability which are edited by the advisory board for traffic medicine; a new edition will be published soon. Concerning otorhinolaryngology hearing impairment and dizziness are the most relevant diseases. Bilateral deafness is no general exception for confering a driving license for the classes A and B; for classes C and DE hearing loss, established from the pure tone audiogram must not exceed 60%; an exceptional case is a three year demonstration of reliability in class B. Permanent dizziness or vertigo attacks are in most cases incompatible with confering driving licenses. The most important issue for medical appraisal is to determine the amount of compensation of the impaired sense organ. Therefore in cases of multiple disabilities more stringent criterions must be established.
    Notes: Zusammenfassung Die Erteilung einer Fahrerlaubnis ist unter anderem an das Vorliegen einer entsprechenden Kraftfahreignung gebunden; in Zweifelsfällen kann die zuständige Verwaltungsbehörde die „Beibringung eines ärztlichen Gutachtens anordnen”, das nach §11 der am 1.1.99 in Kraft getretenen sog. Fahrerlaubnisverordnung in Zukunft nur durch verkehrsmedizinisch qualifizierte Fachärzte, Amtsärzte oder Arbeits-bzw. Betriebsmediziner erstattet werden soll. Auf HNO-ärztlichem Gebiet sind vor allem Hör- und Gleichgewichtsstörungen verkehrsmedizinisch relevant; die Begutachtungsleitlinien zur Kraftfahreignung des Gemeinsamen Beirats für Verkehrsmedizin (5.Aufl. 1996), die demnächst in Neuauflage erscheinen, beinhalten die entsprechenden Begutachtungskriterien. Eine beidseitige Ertaubung gilt nicht grundsätzlich als Hindernis für die Erteilung einer Fahrerlaubnis der Klassen A und B; bei den Klassen C und DE kann bei einem Hörverlust von 60% und mehr (ermittelt anhand des Tonschwellenaudiogramms bei regelmäßigem Verlauf der Tongehörskurve) die Voraussetzung für die Kraftfahreignung nicht mehr gegeben sein (Ausnahme: eine mindestens 3jährige Bewährung in Klasse B). Bei Kraftfahrzeugen, die der Fahrgastbeförderung gemäߧ15d StVZO dienen, ist der so Behinderte nicht in der Lage, den Anforderungen gerecht zu werden. Ständige oder anfallsweise Gleichgewichtsstörungen sind nicht mit der Kraftfahreignung vereinbar. Auffällige Befunde in der Gleichgewichtsprüfung ohne subjektive Symptomatik schließen die Kraftfahreignung in der Regel nur für einspurige Kraftfahrzeuge aus. Von zentraler Bedeutung für die gutachterliche Beurteilung ist das Ausmaß der Kompensation einer gestörten Sinnesfunktion. Bei multisensorischen Defiziten haben daher strengere Beurteilungskriterien Anwendung zu finden.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Monatsschrift Kinderheilkunde 146 (1998), S. 467-470 
    ISSN: 1433-0474
    Keywords: Schlüsselwörter Rezidivierende Parotitis ; Mumps ; Parotisschwellung ; Sialographie ; Key words Recurrent parotitis ; Mumps ; Parotid swelling ; Sialogram
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Background: Apart from mumps, recurrent parotitis is the most common inflammatory salivary gland disease in childhood. The cause is still unknown. Case report: We present a ten-year-old boy with a recurrent swelling of the left parotid gland, who had difficulties in chewing and a sensation of tension on the left face. Since one year the child wore orthodontic appliances. There were no serological signs of viral infection or an autoimmune process. Ultrasound demonstrated an enlarged left parotid gland with multiple hypoechoic areas. The sialogramm revealed the typical image of multiple cystic ectasies and stenoses of the duct. Treatment of choice were saliva liberating measures. Four months later parotitis relapsed and orthodontic applicances were removed. Since then the patient was free of relapses. Discussion: Recurrent parotitis shoud be treated symptomatically, because of its favourable prognosis. An inflammation of the parotid gland secondary to trauma to Stensen’s duct caused by orthodontic applicances is suggested.
    Notes: Zusammenfassung Hintergrund: Die rezidivierende Parotitis stellt nach der Parotitis epidemica die häufigste entzündliche Speicheldrüsenerkrankung im Kindesalter dar, deren Pathogenese ungeklärt ist. Fallbericht: Wir stellen einen 10 Jahre alten, seit 1 Jahr orthodontisch versorgten Jungen mit einer rezidivierenden einseitigen Schwellung der Glandula parotis vor, dessen Hauptbeschwerden durch Kauschmerzen sowie ein uncharakteristisches Spannungsgefühl der betroffenen Gesichtsseite gekennzeichnet waren. Serologisch fanden sich keine Hinweise auf eine Virusinfektion oder Autoimmunerkrankung. In der Sonographie zeigte sich eine vergrößerte Parotis mit multiplen echoarmen Arealen. Die durchgeführte Sialographie erbrachte das typische Bild von multiplen zystischen Gangektasien und -stenosen. Therapeutisch verordneten wir speicheltreibende Maßnahmen. Nachdem es 4 Monate später zu einem Rezidiv gekommen war, wurde die orthodontische Versorgung entfernt. Seitdem ist der Patient rezidivfrei. Diskussion: Aufgrund ihrer guten Prognose sollte die rezidivierende Parotitis mit möglichst konservativen Maßnahmen behandelt werden. Ursächlich könnte die Parotitis durch Mikrotraumen am Ausführungsgangsystem infolge Manipulation durch die orthodontische Versorgung ausgelöst worden sein.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    European journal of pediatrics 157 (1998), S. 814-815 
    ISSN: 1432-1076
    Keywords: Key words Varicella infection ; Neurology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Varicella-related neurological complications usually appear after the rash. Pre-eruptive neurological complications of primary varicella zoster virus infections have been rarely described. We report on a 5.5-year-old boy who developed encephalitis 4 days before the onset of a mild vesicular skin rash and 5 days after known exposure. Primary varicella zoster virus infection was confirmed serologically. Cranial magnetic resonance imaging revealed temporary inflammatory oedema in the right cerebellar peduncle. Conclusion Neurological complications of varicella may appear up to 2.5 weeks before the onset of the exanthema. Physicians treating patients with ataxia or encephalitis should inquire about exposure to varicella zoster virus.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Microsystem technologies 1 (1995), S. 191-195 
    ISSN: 1432-1858
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Technology
    Notes: Abstract Monolithically clamped bridge-on-diaphragm (BOD) structures for pressure sensor applications were fabricated by means of Nd: YAG-laser micromachining and anisotropic KOH-etching techniques. The pressure/frequency-dependence of the BOD structures was measured by acoustical resonance excitation and optical detection of the microbridge and applying an external pressure between-0.8 bar and+1 bar to the diaphragm. In this vacuum/atmospheric pressure range the pressure/frequency-characteristic is quite linear with a sensitivity of about 4.5 kHz/bar and a fundamental bridge resonance frequency of 82 kHz. Extensive finite-element modelling has been carried out to optimize the geometrical dimensions of the BOD structures with respect to maximum sensitivity and pressure range. Using the same BOD structure layout it is possible to realize pressure sensors with applications ranging from 0.5 to 12 bar by only varying the thickness of the diaphragm. Varying the BOD structure layout to smaller dimensions the pressure sensors can be operated up to 100 bar with sensitivities of about 141 Hz/bar.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 184 (1999), S. 361-369 
    ISSN: 1432-1351
    Keywords: Key words Color vision ; Chromatic aberration ; Spherical aberration ; Depth of field ; Pupil shape
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The focal length of the vertebrate eye is a function of wavelength, i.e. the eye suffers from longitudinal chromatic aberration. Chromatic defocus is a particularly severe problem in eyes with high light-gathering ability, since depth of field is small due to a pupillary opening that is large in relation to the focal length of the eye. Calculations show that in such eyes only a narrow spectral band of light can be in focus on the retina. For the major part of the visual spectrum, spatial resolution should be limited by the optics of the eye and far lower than the resolving power achievable by the retinal cone photoreceptor mosaic. To solve this problem, fishes with irises unresponsive to light have developed lenses with multiple focal lengths. Well-focused images are created at the wavelengths of maximum absorbance of all spectral cone types. Multifocal lenses also appear to be present in some terrestrial species. In eyes with mobile irises, multifocal lenses are correlated with pupil shapes that allow all zones of the lens, with different refractive powers, to participate in the imaging process, irrespective of the state of pupil constriction.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 287 (1997), S. 435-446 
    ISSN: 1432-0878
    Keywords: Key words: Presynaptic bodies ; Morphology ; Plasticity ; Molecular features ; Photoreceptors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. The morphological diversity and dynamic aspects of presynaptic bodies are summarised. Molecular characteristics of the presynaptic machinery are discussed and the signals that control the plasticity of the presynaptic bodies are examined. A review is presented of recent findings regarding the physiology of tonically active synapses. The significance of the synaptic bodies and their dynamic changes in retinal and pineal photoreceptors are considered.
    Type of Medium: Electronic Resource
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