Search PubMed⌕ Search

Biomedical subjects

G Roth

Publications and source records attributed to G Roth.

At least 127 records · Page 7Linked to original sources
PubMed1982

Response characteristics and stratification of tectal neurons in the toad Bufo bufo (L.).

In the optic tectum of Bufo bufo the activity of single neurons was recorded during the presentation of moving visual stimuli. The location of the recorded cells was marked iontophoretically by means of alcian blue dye. A total of 132 cells were studied, most of which showed clear differences within their responses to a square and to rectangles oriented either horizontally or vertically. The cells were found primarily within the tectum layers 8 and 6. The majority of them preferred the square to the horizontal bar, and this stimulus to the vertical one. Another group responded best to the horizontal rectangle. Relatively few cells were found in which the vertical stimulus was preferred to the horizontal one. A considerable number of tectal cells showed a change of stimulus preference if the stimulus velocity was changed. No clear correlation between response types and anatomical distribution within the tectum layers could be found.

Animals↗
PubMed1980

High-performance liquid chromatographic determination of epimers, impurities, and content of the glucocorticoid budesonide and preparation of primary standard.

The new glucocorticoid budesonide, a 1:1 mixture of two epimers, was evaluated analytically with respect to drug content, impurities, and epimer distribution in the drug substance. Reversed-phase high-performance liquid chromatographic (HPLC) systems using octadecylsilane columns with different ethanol-water mixtures as eluents were used. Budesonide and its epimers were determined with recoveries of 100.3% (+/- 0.16 SD) and 99.7% (+/- 0.27 SD), respectively. Individual foreign steroids in the ranges of 0.05--0.2 and 0.2--2% were determined with mean recoveries of 93% (+/- 7.6 SD) and 97% (+/- 2.5 SD), respectively. Analysis of eight small-scale production batches of budesonide gave a recovery of 99.9% (+/- 0.39 SD) for the sum of budesonide and impurities. Analytical data and the procedure for preparation of a budesonide primary standard are given. The proposed HPLC procedure is faster, more accurate, more precise, and more selective than the usual pharmacopeial methods for corticosteroids.

Budesonide↗
PubMed1980

Interaction of hormones with receptors and alterations of these processes with age.

A variety of hormone receptor concentrations appear to decrease during aging. Such reductions seem to be closely, if not causally, related to reduced responsiveness. The receptors appear to be lost from target cells during aging. The simple loss of target cells from target tissues is not a sufficient explanation for decreased hormone concentrations, since we can observe these changes in static cell populations. Currently, we are attempting to elucidate the molecular and neuroendocrine mechanisms that are involved in these changes, and we would like to apply some of the mechanisms of hormone receptor control to these problems of altered responsiveness.

Adipose Tissue↗
PubMed1980

Double discharges of distal origin: influence on the firing rhythm.

Double discharges, or doublets, following the direct M response after peripheral nerve stimulation had a distal origin on the axon and were accompanied bay a back-response. This antidromic wave was demonstrated by collision technique or by its occasional recurrent F wave. Double discharges (DD) with a long interval between the two components had their origin in one subunit and were transmitted to another by motor axon reflex. Increse of the post-doublet interval (PDI) duration during EMG was best explained by invasion of the alpha cell by the back-response and the resetting of a new cycle. This invasion was sometimes followed by a recurrent F wave: a shorter PDI resulted. Normal PDI were probably due to blocking of the back-response at the myelinated-non-myelinated junction, without alpha cell invasion: weak or absent Renshaw inhibitory effect on the alpha cell concerned seemed to play a role.

Adult↗
PubMed1980

The role of early sensory experience in the prey catching responses of Salamandra salamandra to stationary prey.

Two groups of newly metamorphosed Salamandra salamandra (L.) were raised with living and with stationary prey, respectively. One year later, the group which had experience exclusively with stationary prey was significantly better in responding to stationary prey than the group which only had experience with moving prey. This was the case both under light and dark conditions. The experiments show that prey-catching behavior in salamanders can be considerably modified by experience.

Animals↗
PubMed1979

Intranervous regeneration. The study of motor axon reflexes.

More than 1000 motor axon reflexes (ARs) have been studied. The AR often has a long latency and the first excited branch almost always has the fastest conduction velocity. Sometimes the potentials of the two branches are recorded at the same needle placement, giving the appearance in the EMG tracing of a coupling discharge. Stimulation of the axons in the muscle produces more ARs than stimulation of the nerve trunk. ARs are recorded in denervated muscles but never in normal subjects. All kinds of lower motor neuron lesions produce ARs. They are more frequent in the Charcot-Marie-Tooth syndrome and hereditary neuropathy with liability to pressure palsies where the axonal lesions are mainly located at the traditional sites of entrapment. The possibility of neurolysis in some of these cases has to be considered. Obstetrical brachial plexus palsies furnish many ARs linking two muscles, thus explaining the associated contractions in these cases.

Electromyography↗
PubMed1979

The influence of prey experience on movement pattern preference in Salamandra salamandra (L.).

Groups of juvenile Salamandra salamandra were raised selectively with different types of prey. The influence of these conditions on the movement pattern preference was studied during the first six months after metamorphosis. Responses to a black horizontal bar moving continuously or stepwise at step frequencies between 0.25 and 8 steps/s were tested. The differently raised groups showed significant differences in their respective preference for stimulus movement patterns which corresponded with the movement pattern of their food. At the same time, superimposed upon this learning process, a general increase in the relative efficiency of continuous stimulus movement with regard to stepwise stimulus movement could be observed.

Animals↗
PubMed1979

Ephaptic recurrent response in man.

The antidromic impulse associated to the ephaptic response can produce a recurrent wave (Fe). Its latency, which is longer than that of the F wave, will augment if the site of stimulation is remote from the muscle. It is therefore a direct-indirect response. The 'Fe' wave is similar to the 'S' response described by Thorne, but the gamma-loop is not implicated. It can be misinterpreted as a desynchronized F wave.

Aged↗
PubMed1979

Ephaptic response in man.

Following the direct M response, peripheral nerve stimulation frequently evokes a second wave which shows all characteristics of an ephaptic response. The antidromic impulse or back response, which is always associated, is detected by a double stimulation technique. The ephaptic response seems not to be related to any specific nerve or muscle pathology, as it is also observed in normal subjects. It is therefore important to differentiate the ephaptic response from a late potential or a double discharge, the latter two having pathological significance.

Adult↗
PubMed1978

Tubular device for intraoral examination of rodents.

The device consists of a tube with a conical end, a base, and a movable stem. The rodent is anaesthetized lightly with ether and inserted quickly into the tube so that the head extends beyond the opening at the conical end, where cheeks, upper and lower incisors are secured to permit illumination and direct visual or microscopic examination of the palate, molars or gingiva.

Animals↗
PubMed1978

[Measurement of fluorescent polarisation in the amniotic fluid to assess fetal lung maturity (author's transl)].

A new method for determining fetal lung maturity is discussed. Molecular mobility can be determined spectrophotometrically by measuring the fluorescent polarisation (FP) in lipid solutions. This method of determining the microviscosity in lipid solutions can now be applied also in the amniotic fluid. Measurement of FP by means of an electro-optical microviscosimeter is proportional to the lipid concentration in the amniotic fluid and is in good correlation with fetal lung maturity. FP was measured between the 17th and 41st weeks of gestation in 147 amniotic fluid samples. During pregnancy the FP value drops significantly from 0.350 to 0.200. A FP value of 0.290 was fixed as the limit value beyond which RDS may be expected to occur. With a limit value of 0.290, the RDS identification probability was calculated at 94%, whereas the calculated probability of RDS was 81% and the exclusion probability of RDS 97%. At the same time, the probabilities, calculated on the parallel determination of the L/S ratio, yielded a slightly more unfavourable result. The drop in the FP level correlates significantly with the increase of the L/S ratio in the investigated amniotic fluid samples (correlation coefficient 0.77). The method, which requires very special equipment, offers many advantages: it is very accurate, simple, well reproducible and can be performed within half an hour at relatively low laboratory cost.

Amniotic Fluid↗