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Biomedical subjects

A J Fischer

Publications and source records attributed to A J Fischer.

At least 37 records · Page 2Linked to original sources
PubMed1997

N-methyl-D-aspartate-induced excitotoxicity causes myopia in hatched chicks.

OBJECTIVE: To characterize the effect of the amacrine cell-selective toxin N-methyl-D-aspartate (NMDA) on ocular growth in chicks. DESIGN: Single injections of NMDA in doses ranging from 20 to 2000 nmol in 20 microL of sterile saline were made into the vitreous chamber of one eye of 7-day-old white leghorn chicks (six chicks per group); the contralateral (control) eye was injected with saline. Six NMDA-treated eyes were also deprived of form vision by applying a translucent goggle 7 days after treatment, to determine whether myopia could still be induced or enhanced in NMDA-treated eyes. OUTCOME MEASURES: Axial length, equatorial diameter and refractive error, measured immediately after and 7, 14, 21, 28 and 35 days after treatment. RESULTS: NMDA-treated eyes became myopic within 7 days of treatment and remained so until at least 35 days after treatment. During this time the eyes continued to grow but could not be induced to become more myopic by depriving them of patterned images. The half-maximal effective dose of NMDA was calculated to be 670 nmol, 7 days after treatment. CONCLUSIONS: NMDA-induced excitotoxicity destroys retinal pathways by which patterned visual stimuli restrain ocular growth in the chick.

Animals↗
PubMed1996

Characterization of the RFamide-like neuropeptides in the nervus terminalis of the goldfish (Carassius auratus).

FMRFamide-immunoreactivity has been demonstrated in the CNS of many vertebrate species. We sought to further characterize this immunoreactivity in nervus terminalis retinal efferents of the goldfish using an antiserum raised against a bovine morphine modulating peptide (A18Famide). This antiserum robustly labels nervus terminalis efferents to the retina, as well as a sub-population of retinal amacrine cells. Under immunocytochemical conditions the antiserum cross-reacted with neuropeptide Y-like as well as A18Famide-like peptides, but under conditions of radioimmunoassay it was highly specific for A18Famide-like peptides. High pressure liquid chromatography, gel permeation chromatography and radioimmunoassay showed that at least two different RFamide-like peptides, approximately the same size as the bovine RFamide-like peptides, are present in the goldfish nervus terminalis.

Animals↗
PubMed1995

Vestibular hyperreactivity and hyperventilation after whiplash injury.

Vestibular, oculomotor and respiratory tests were performed on 32 patients after whiplash injury caused by a rear-end car collision. Oculomotor functions were generally normal. The cervico-ocular reflex was usually absent or displayed the low gain typical of normal subjects. There was no nystagmic response to static neck torsion. The vestibulo-ocular reflex showed vestibular hyperreactivity (VH) in a significantly large number of cases (n = 17; 53%). The respiratory test results were also typical of the hyperventilation syndrome (HVS) in a significantly large number of cases (n = 12; 38%). The findings of VH and the HVS were not significantly correlated within the patient group. However, the combination of VH and the HVS occurred significantly more often (n = 7; 22%) than could be accounted for by combined false positivity. Most of the significant findings were due to high relative frequencies in the women: 11 out of the 17 women (65%) showed VH, 8 (47%) had the HVS and 5 (29%) showed a combination of VH and the HVS. The findings were not correlated with the patient's age or the time interval between the accident and the examination. VH might have been the result of plastic adaptation to limited head mobility secondary to neck pain. Behavioural and emotional distress might offer alternative explanations for both VH and the HVS.

Accidents, Traffic↗
PubMed1995

Hyperactive VOR and hyperventilation after whiplash injury.

Otoneurological and respiratory tests were performed on 32 patients after whiplash injury caused by a rear-end car collision. Oculomotor and cervico-ocular test results were generally normal. In a significantly large number of case, the vestibulo-ocular reflex (VOR) was hyperactive (n = 17; 53%) and the respiratory test results were typical of the hyperventilation syndrome (HVS) (n = 12; 38%). Hyperactive VOR and the HVS occurred significantly more often in combination (n = 7; 22%) than could be accounted for by combined false positivity. Most of the significant findings were due to high relative frequencies in the women. The hyperactive VOR might have been the result of plastic adaptation to limited head mobility secondary to neck pain. Behavioural and emotional distress might offer alternative explanations for both the hyperactive VOR and HVS.

Adult↗
PubMed1991

Histamine in the treatment of vertigo.

The vasodilating properties of histamine were the basis for histamine treatment of episodic vertigo and other inner ear dysfunctions. The successes obtained led to the development of betahistine: an orally active histamine analogue; its general pharmacology resembles that of histamine. Animal pharmacology experiments proved that betahistine increases cerebral blood flow and probably also affects vestibular neurons. From clinical studies, it appears that betahistine is an effective agent for the symptomatic treatment of Meniere's syndrome. Efficacy has also been shown in the treatment of patients suffering from paroxysmal vertigo.

Animals↗
PubMed1989

Prevention of the Wernicke-Korsakoff syndrome in Australia: a cost-benefit analysis.

The National Health and Medical Research Council (NHMRC) recently has recommended that thiamin be added to cask and flagon wines, fortified wines, beer and flour. This paper presents a cost-benefit analysis of the fortification of alcoholic beverages with thiamin. A total cost-saving in present-value terms of between $60 million and $600 million in 1985 Australian dollars has been calculated. Considerable methodological problems are associated with this type of analysis, and these are discussed. However, the cost-benefit ratio under a range of plausible assumptions remains extremely high--in the region of six to one to 30 to one, or even higher. The methods that are used are compared with those of a 1978 US study, which is appraised critically. The fortification programme that was recommended by the NHMRC is supported strongly on economic grounds.

Australia↗
PubMed1981

Otological aspects of the earpit-deafness syndrome.

The results of a systematic study of the otological aspects in 13 cases of earpit-deafness syndrome are reported. The audiometric, radiological and vestibular findings as well as the results of exploratory tympanotomies with and without stapedectomies are discussed together with the results reported in the literature. A convincing explanation of the poor results of exploratory tympanotomies in cases with mixed hearing loss is not furnished. If the hearing loss is confined to conduction and ankylosis of the stapes or a disconnection of the ossicular chain is suspected, exploratory tympanotomy can be expected to be successful.

Acoustic Impedance Tests↗
PubMed1980

Nasopharyngeal cancer: a clinical study with special reference to age and occupation.

A survey of 63 patients with malignant tumour of the nasopharynx, treated over a 20-year period (1958-1977) is presented. The major types of tumour were squamous cell and anaplastic carcinoma (including lymphoepithelioma) and non-Hodgkin's lymphoma. In some patients other tumours were found, such as cylindroma, rhabdomyosarcoma and extramedullary plasmocytoma. A particularly high incidence of men younger than 40 years was seen with carcinoma and an occupation in a particular branch of industry, indicated as 'metallurgic or allied' (light engineering factories, garages etc). 60Co irradiation was the primary therapy. Adjuvant chemotherapy was used in lymphoma or sarcoma. The survival was significantly better in the younger age group as far as carcinoma is concerned. The possible role of occupational factors is discussed in relation to findings in the literature.

Adolescent↗
PubMed1979

Electronystagmography in the laboratory rat.

A method is described for obtaining electronystagmograms from the awake laboratory rat. Threshold valves for rotation impulse and oscillatory acceleration were determined, as well as the time constant for the horizontal semicircular canal. The time constant appeared to be small. This might be attributed to the rapid natural head movements in this species. No visual suppression of vestibular nystagmus was found in the rat.

Animals↗
PubMed1979

[Motion sickness (author's transl)].

A short introduction to motion sickness is followed by a historical survey of the various theories, with special reference to those concerning the inner ear. The symptomatology and the consequences of the disease are discussed. Prevention and therapy are considered.

Adaptation, Physiological↗
PubMed1978

A tumour in the cerebellopontine angle region: an unusual case.

This paper describes a nearly 60-year old patient with unilateral hearing loss, developed in one year, and complaints of tinnitus and dizziness. Additional findings were unilateral peripheral facial paresis and a diminished corneal reflex. The cause was found to be a metastasis of an anaplastic carcinoma, localized at the site of the internal acoustic porus.

Carcinoma↗
PubMedDate not supplied

Opiate and N-methyl-D-aspartate receptors in form-deprivation myopia.

Pharmacological studies have implicated retinal opiate pathways in the visual regulation of ocular growth. However, the effects of opiate receptor subtype-specific compounds on form-deprivation myopia (FDM) are inconsistent (Seltner et al., 1997), and may be mediated by non-opiate receptors. The purpose of this study was to test whether opiate receptor-inactive (D-) enantiomers elicit the same FDM-suppressing effect as their opiate receptor-active (L-) counterparts. Since some opiates are thought to act at NMDA receptors, we also tested whether NMDA receptor agonists and antagonists influence ocular growth or FDM. We found that both L- and D- enantiomers of morphine-like compounds (dextrorphanol and levorphanol, and D- and L-naloxone) were equally effective in blocking FDM. The NMDA receptor antagonists dextromethorphan, MK801, and AP5 also suppressed FDM. A single toxic dose of NMDA, that destroys many subtypes of amacrine cells (including those that synthesize the opioid peptide enkephalin), induced myopia and ocular enlargement in ungoggled eyes, and eliminated the ability of form-deprivation to enhance ocular growth. The NR-1 subunit of the NMDA receptor was localized to a narrowly stratified, intense stratum at approximately 50% depth in the inner plexiform layer, diffusely throughout the proximal inner plexiform layer, and to many somata in the amacrine and ganglion cell layers. These observations suggest that most effects of opiate receptor ligands on FDM in the chick are mediated by non-opiate receptors, which are likely to include NMDA receptors. NMDA as an excitotoxin transiently enhances ocular growth, but thereafter disables retinal mechanisms that promote emmetropization and FDM. These observations are consistent with a prominent role for pathways utilizing NMDA receptors in FDM and ocular growth-control.

Animals↗