Search PubMed⌕ Search

Biomedical subjects

R Schmid

Publications and source records attributed to R Schmid.

At least 253 records · Page 14Linked to original sources
PubMed1985

The influence of interstimulus interval on the development of vestibular habituation to repeated velocity steps.

In order to clarify the problem of which stimulus parameters affect vestibular habituation, a group of cats was submitted to repeated velocity steps involving changes in either the step amplitude or the interval between two consecutive steps. In the first two experiments, the protocol was the same as in a previous study which used steps of 160 degrees/s separated by 60 s, except that the steps were of 80 degrees/s and 16 degrees/s. In the remaining experiments the step amplitude was kept constant (160 degrees/s) and the interstimulus interval was changed: each step was delivered either immediately after the reversal of the nystagmus elicited by the preceding step (only a few beats in the reversed direction were allowed to occur) or immediately before (no beats in the reversed direction). Vestibular habituation was found to occur in both experiments of the first series. Nevertheless, the marked initial suppression of the response, that was reported as one aspect of vestibular habituation to steps of 160 degrees/s, was clearly present when steps of 80 degrees/s were used, but was not as clear when the step amplitude was reduced to 16 degrees/s. The experiments of the second series showed that a typical vestibular habituation still occurs when steps are delivered just after the reversal of nystagmus. On the contrary, no habituation was observed when steps preceded the reversal of nystagmus. It was concluded that the presence of an anticompensatory phase is interpreted by the central nervous system as a sign that the response evoked in a reflex way is functionally meaningless or even detrimental. An habituation process is then started to suppress the response.

Animals↗
PubMed1985

New experimental data on cat's optokinetic responses. Is there need to revise previous models of the optokinetic reflex?

New data on cat's optokinetic reflex (OKR) provided by Godaux and Vanderkelen (1984) have been interpreted by using a nonlinear model of OKR previously proposed by the authors. A general agreement between experimental data and theoretical predictions was obtained. In particular, the steep decrease of OKR gain observed experimentally at high frequencies appeared as a straightforward consequence of the intrinsic nonlinearity of OKR. In contrast with a recent statement by Gillis et al. (1984), it was concluded that the new data seem to confirm, rather than disprove, previous models of cat's OKR.

Animals↗
PubMed1985

Biotechnology in Japan 1984--a mini-review. Part 2: Government agencies, universities and research institutes.

Major developments in Japanese biotechnology in 1984 are reviewed. Besides industry and academia, research associations (companies and governmental research institutions guided by ministries) carry out joint fundamental research in biotechnology. Another important long-range aspect is the Technopolis Concept, which aims at decentralizing research and technological activities.

Agriculture↗
PubMed1984

Determination of glucitollysine for the quantitation of non-enzymatic glucosylation by ion exchange chromatography and reverse phase liquid chromatography.

A specific and sensitive method for the quantitative determination of the stable, reduced glucose-lysine adduct, glucitollysine (GL), in plasma protein samples is described. The method uses standard amino acid ion exchange chromatography followed by reverse phase high performance liquid chromatography after derivatisation of GL to a fluorescent product. Moreover, GL was characterised and identified in plasma samples by means of mass spectroscopy. GL measured in plasma samples of eleven type I diabetics and two healthy controls showed a significant linear correlation to concomitantly determined haemoglobin AI and glucosylated plasma proteins, but did not correlate with plasma glucose levels. This method allows the estimation of non-enzymatic glucosylation in biological samples with a high degree of specificity and sensitivity down to the low nanogram range.

Adolescent↗
PubMed1984

Chemical modification of the F0 part of the ATP synthase (F1F0) from Escherichia coli. Effects on proton conduction and F1 binding.

The purified F0 part of the ATP synthase complex from Escherichia coli was incorporated into liposomes and chemically modified by various reagents. The modified F0-liposomes were assayed for H+ uptake and, after reconstitution with F1, for total and dicyclohexylcarbodiimide-sensitive ATPase activity. The water-soluble carbodiimide, 1-ethyl-3-(-3-dimethylaminopropyl)carbodiimide methiodide, (1.2 mM), inhibited H+ uptake to a great extent. Binding of F1 was almost unaffected, but the hydrolysis of ATP was uncoupled from H+ transport. This is reflected by the inhibition of dicyclohexylcarbodiimide-sensitive ATPase activity. Woodward's reagent K, N-ethyl-5-phenylisoxazolium-3'-sulfonate, inhibited both H+ uptake and total ATPase activity. Modification of arginine residues by phenylglyoxal (20 mM) was followed by inhibition of the F1 binding activity by 80% of the control. H+ translocation was reduced to 70%. Diethylpyrocarbonate (3 mM) exhibited a strong inhibiting effect on H+ uptake but not on F1 binding. Modification of tyrosine (by tetranitromethane) as well as lysine residues (by succinic anhydride) did not affect F0 functions. From the data presented we conclude that carboxyl-groups, different from the dicyclohexylcarbodiimide-binding site, are involved in H+ translocation through F0 and, in part, in the functional binding of F1. Furthermore, for the latter function, also arginine residues seem to be important. The role of histidine residues remains unclear at present.

ATP Synthetase Complexes↗
PubMed1984

The effects of caffeine on near point plus acceptance.

Forty-two university students participated in a study of reading with +0.50 sphere or yokes prism base down for overconvergence and base up for underconvergence. Sixty-four percent of the group improved with a mean of +10.79 wpm. The level of coffee consumption of each student was recorded. A negative correlation existed between the intake of caffeine and reading improvement, r = -.81, p less than .001. Two students reduced their coffee consumption and transformed their loss in words per minute to a significant gain. A double-blind protocol was used in this study. A placebo lens (plano) controlled for subject and investigator bias. The relationship between caffeine and accommodation was investigated by means of a monocular test through a +4.D sphere. The location of the blur point was indicative of the state of tonicity of the ciliary system. Pre- and post-tests of the blur point for 14 subjects who were tested before and after consuming 150 mg of caffeine showed a significant change. The experimental group showed an increase of -0.52D while the control group showed a change of +0.36D. r = .781, p less than .01.

Accommodation, Ocular↗
PubMed1983

Current concepts in diagnosis. Approach to the patient with cholestatic jaundice.

On the basis of clinical evaluation, the physician should decide whether extrahepatic biliary obstruction is highly unlikely, possible, or very likely. If it is highly unlikely, no further workup for obstruction is indicated unless the clinical picture is altered on follow-up examination. Further evaluation of the biliary tree is warranted in other patients. Ultrasonography is currently the noninvasive imaging technique of first choice. Computed tomography is indicated if ultrasonography has yielded technically inadequate results or in special circumstances when it is anticipated that decisions regarding further diagnostic evaluation or treatment will be importantly influenced by the results. Negative findings obtained in a technically adequate examination may represent a logical stopping point in the workup of patients in whom obstruction is considered merely a possibility to be excluded, but they should not dissuade the clinician from further diagnostic evaluation if obstruction is considered very likely. Indeed, in selected circumstances, such as cases in which choledocholithiasis is suspected after cholecystectomy, direct cholangiography is appropriate as an initial test. If evidence of obstruction is obtained by noninvasive imaging, direct cholangiography will be required in many patients before treatment, and the choice between percutaneous or retrograde cholangiography should be made on an individual basis. The challenge to the clinician is to minimize the risk, expense, and time involved in obtaining sufficient information for a definitive diagnosis and treatment.

Cholangiography↗
PubMed1983

Model interpretation of visual-vestibular interaction in patients with labyrinthine and cerebellar pathologies.

Oculomotor responses to combined optokinetic and vestibular stimulations in labyrinthine and cerebellar defective patients are discussed in terms of parametric changes in a model describing the interaction between the vestibulo-ocular reflex (VOR) and the optokinetic reflex (OKR). By making a few reasonable hypotheses about model parameter variations in relation to the type of pathology, the experimental results obtained by several authors can correctly be predicted and explained by the model. The model can therefore be used to define a set of parameters giving an estimate of the state of the system subserving VOR-OKR interaction in the examined patients. The model is also shown to be a powerful tool to assess the validity and the diagnostic significance of the procedures used to test VOR-OKR interaction.

Cerebellum↗
PubMed1983

Effects of unilateral flocculus lesions on vestibulo-ocular responses in the cat.

Unilateral lesions of the cerebellar flocculus were performed in three chronically-implanted adult cats. Following the lesion a spontaneous nystagmus was observed in the dark, with the fast phase directed to the lesioned side. Vestibulo-ocular responses in the dark became asymmetrical. Responses to velocity steps exciting the labyrinth ipsilateral to the lesion were strongly increased. A decrease, although less marked, was observed in the opposite direction. Responses to sinusoidal oscillations in the dark were also asymmetric with respect to both the cumulative eye displacement during rotation in the two directions and the interval between two consecutive reversals of eye movement. These differences were greater at the lower tested frequencies (0.01 HZ) than at the higher (0.1 HZ). Spontaneous nystagmus disappeared in about 10 days and a complete symmetry of the vestibulo-ocular responses was restored in about 3 weeks. It is concluded that a unilateral lesion of the flocculus leads to two separate, but interacting, effects upon vestibulo-ocular responses.

Animals↗