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Digitale Medien

The influence of head position and head reorientation on the axis of eye rotation and the vestibular time constant during postrotatory nystagmus (1992)

Fetter, M. ; Tweed, D. ; Hermann, W. ; [weitere]

Springer

Experimental brain research 91 (1992), S. 121-128

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ISSN: 1432-1106

Schlagwort(e): Vestibuloocular reflex ; Velocity storage ; Active head tilt ; Semicircular canals ; Otolith ; Human

Quelle: Springer Online Journal Archives 1860-2000

Thema: Medizin

Notizen: Summary Reorienting the head with respect to gravity during the postrotatory period alters the time course of postrotatory nystagmus (PRN), hastening its decline and thereby reducing the calculated vestibular time constant. One explanation for this phenomenon is that the head reorientation results in a corresponding reorientation of the axis of eye rotation with respect to head coordinates. This possibility was investigated in 10 human subjects whose eye movements were monitored with a three-dimensional magnetic field — search — coil technique using a variety of head reorientation paradigms in a randomized order during PRN following the termination of a 90°/s rotation about earth vertical. Average eye velocities were calculated over two time intervals: from 1 s to 2 s and from 7 s to 8 s after cessation of head rotation. The time constant was estimated as one third of the duration of PRN. For most conditions, a reorientation of the head with respect to gravity 2 s after the rotation had stopped did not significantly alter the direction of the eye velocity vector of PRN with respect to head coordinates. This strongly indicates that, in humans, PRN is mainly stabilized in head coordinates and not in space coordinates, even if the otolith input changes. This finding invalidates the notion that the shortening of PRN due to reorientation of the head could be due to a change of the eye velocity vector towards a direction (torsion), which is not detectable with the eye recording methods (electrooculography) used in earlier studies. The results regarding the vestibular time constant basically confirm earlier findings, showing a strong dependence on static head position, with the time constant being lowest if mainly the vertical canals are stimulated (60° nose up and 90° left ear down). In addition, the time constant was drastically shortened for tilts away from upright. The reduction in vestibular time constant with head reorientation cannot be explained solely on the basis of the dependence of the time constant on static head position. A clear example is provided by head reorientations back towards the upright position, which results in a decrease in the time constant, rather than an increase that would be expected on the basis of static head position.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00230020

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Digitale Medien

116. Experimentelle Untersuchungen über eine neuartige gesprühte Kunststoffprothese (1981)

Gruss, J. D. ; Braun, B. ; Lehnhardt, F. J. ; [weitere]

Springer

Langenbeck's archives of surgery 355 (1981), S. 517-517

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ISSN: 1435-2451

Schlagwort(e): Polyurethane graft ; Microporosity ; Control angiography ; Scanning electronic microscopy ; Polyurethanprothesen ; Mikroporosität ; Kontrollangiographie ; Rasterelektronenmikroskopie

Quelle: Springer Online Journal Archives 1860-2000

Thema: Medizin

Beschreibung / Inhaltsverzeichnis: Zusammenfassung Die neuen Kunststoffprothesen bestehen aus Polyúrethan, das nach einem speziellen Sprühverfahren verarbeitet wird. Die Prothesen sind längs- und querelastisch sowie mikroporös. In tierexperimentellen Untersuchungen wurden 20mal die terminale Aorta, 24mal die arteria carotis communis und 12mal die arteria femoralis superficialis ersetzt. Die Tiere wurden in regelmäßigen Abst↭den angiographiert. Nach Tötung erfolgten rasterelektronenmikroskopische und histologische Untersuchungen. Von 20 Aortentransplantaten blieben 18 bis zum Zeitpunkt der Tötung, bzw. bis heute offen. In Carotisposition scheinen sich die Transplantate nicht zu bewähren.

Notizen: Summary The new plastic graft consists of polyurethane manufactured in a special spray process. These grafts are elastic both transversally and longitudinally and are microporous. In experiments on animals, the abdominal aorta was substituted 20 times, the common carotid artery 24 times, and the superficial femoral artery 12 times. The animals were regularly subjected to angiographical examinations. After they were killed, they were examined histologically and by means of a scanning electronic microscope. Of the 20 abdominal grafts, 18 have remained open to date. Carotis grafts, however, seemed to fail.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF01286945

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Digitale Medien

Effects of sexual rest or sexual activity on the structure and function of the ventral prostate of the rat (1985)

Aumüller, G. ; Braun, B. E. ; Seitz, J. ; [weitere]

New York, NY [u.a.] : Wiley-Blackwell

The @Anatomical Record 212 (1985), S. 345-352

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ISSN: 0003-276X

Schlagwort(e): Life and Medical Sciences ; Cell & Developmental Biology

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Medizin

Notizen: Previous studies have shown that sexual activity increases the weight of the accessory sex glands significantly, while the organ weights correlate inversely with the assayable androgen receptor concentrations in the prostate of sexually active versus sexually resting rats. In an effort to determine the structural basis of this phenomenon, the ventral prostates of adult rats kept with female rats for 4-6 months (HE-rats) were compared to those kept in groups of 5 males in one cage (HO-rats) for the same period. As an estimate of the secretory function of the gland the concentration of prostatic binding protein (PBP) was determined in prostatic cytosols using a highly specific ELISA. Catecholamines were measured by means of HPLC and subsequent electrochemical detection. Morphological studies included immunocytochemistry of PBP, visualization of adrenergic nerves, stereological analysis of stromal and glandular compartments of the prostate, and electron microscopy of the epithelium.The main findings were as follows: (1) The prostates of HE-rats were 35% heavier than those of the HO-rats. (2) The content in secretion was in the same range in both HE-rats and HO-rats (1.5 and 1.44 mg PBP per 1 mg DNA). (3) Immunocytochemistry and electron microscopy demonstrated a very homogeneous secretion within the glandular lumen of HO-rats with a diminished amount of secretory material within the glandular cells.In HE-rats the glandular lumina were clearly larger in diameter and intraluminal secretion was less homogeneously stained. The height of the epithelium was increased and the individual secretory cells contained several secretory granules. Within the prostatic stroma the profiles of adrenergic nerves were more numerous in HE-rats, and a greater total amount of noradrenaline was present. At the fine structural level signs of enhanced membrane turnover, such as lysosomal structures, were prominent in prostatic epithelium of HE-rats, while in HO-rats mostly dense bodies were observed. The results indicate that sexual activity results in the functional adaption (activity hypertrophy) of the prostate as a result of nerve-associated control of glandular activity.

Zusätzliches Material: 10 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/ar.1092120404

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