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Biomedical subjects

G Roth

Publications and source records attributed to G Roth.

At least 19 recordsLinked to original sources
PubMed1992

Motor axon reflex and indirect double discharge: ephaptic transmission? A reappraisal.

Causal mechanisms of the motor axon reflex (MAR) and indirect double discharge (IDD) are re-examined. The hypothesis that these indirect intermediate latency responses result from an axono-axonal ephaptic transmission mechanism has recently been suggested. The various conceivable responses of models of axonal cross-talk are compared with actual observations made from the limbs. We conclude that the ephaptic hypothesis does not explain MAR and IDD, and that the earlier understanding that MAR results from axonal branching and IDD from proximal re-excitation on the axon holds true.

Aged↗
PubMed1992

Is the nucleus corticalis of teleosts a new cholinergic central nervous system for vertebrates?

Acetylcholinesterase histochemistry suggests that the pretectal nucleus corticalis of teleost fish may be cholinergic. Because immunohistochemical analysis with antibodies against choline acetyltransferase provides a more reliable means of recognizing cholinergic central nervous structures, we investigated transverse brain sections of the African cichlid fish, Hemichromis lifalili and Hemichromis guttatus, with standard immunohistochemical techniques and found the nucleus corticalis to contain choline acetyltransferase. This supports the hypothesis that teleosts (unlike all other known vertebrates) have a cholinergic second-order sensory (i.e. visual) circuit.

Animals↗
PubMed1991

Motor neurons and motor columns of the anterior spinal cord of salamanders: posthatching development and phylogenetic distribution.

The posthatching development of rostral (1st-4th) spinal motor neurons was studied in ten species of salamanders, using horseradish peroxidase and cobaltic lysine tracing techniques. Development of spinal motor neurons differs among species in association with differences in life history and general developmental patterns (i.e., between species with aquatic larvae versus those with direct development, with or without ontogenetic repatterning). In the plesiomorphic state, represented by species with aquatic larvae, five types of motor neurons are present: (1) large, multipolar neurons, believed to be primary motor neurons; (2) medial, pear-shaped neurons; (3) larger, spindle-shaped neurons, which increase in number during posthatching development; (4) cone-shaped neurons, and (5) bilaterally arborizing neurons (found only at the rostral pole of the first spinal nucleus). Direct-developing desmognathine salamanders have the plesiomorphic set of motor neurons, but appear to lack Mauthner neurons. Direct-developing plethodontine salamanders have cone-shaped, pear-shaped, and spindle-shaped neurons, but lack primary motor neurons and Mauthner neurons. Direct-developing bolitoglossine salamanders, which exhibit both pedomorphosis and ontogenetic repatterning, have only medial, pear-shaped neurons, and lack primary motor neurons, spindle-shaped neurons, cone-shaped and bilaterally arborizing neurons. At all developmental stages in all species studied, pear-shaped neurons are always found in medial positions and spindle-shaped neurons are always found in lateral positions. Spindle-shaped neurons are found more laterally as development proceeds. The medial and lateral motor columns of salamanders and amniotes differ in their connections with peripheral targets (i.e., axial muscles vs. limbs). This implies a lack of homology of neuron types in salamanders and amniotes, which has been obscured by the current terminology.

Animals↗
PubMed1991

[Standardized controlled antitubercular therapy and results in 755 patients].

755 patients were treated because of tuberculosis from 1984-1989. The treatment was standardized according to the recommendations. INH and RMP were used in over 95% as in the hospital as in the ambulatory phase. During the period of 6 yrs. the use of SM was markedly reduced (21.8%) while the use of PZA increased from 14.6% to 55.0%. At least four drugs were used in 22.5%. In 36.2% mycobacteria were found only before starting treatment. After four weeks treatment further 45.1% were negative. Adverse reactions were registered in 9.3%. Concomitant diseases rendering the treatment were observed in 24.7%. Ten patients died because of tuberculosis. Until now only 3 patients had relapses. Controlled treatment is valuable and therefore recommended.

Adult↗
PubMed1991

[History of medicine and pastoral medicine].

History of medicine and pastoral medicine aim at the healing of ill persons according to their special way of interpretation: either orientated towards the history of medical thinking or laying emphasis on medical ethics of the physician. Both ways lead to medical anthropology and medical ethics, so that medicine constitutes a "secondary philosophy".

Ethics, Medical↗
PubMed1990

Cytoarchitecture of the tectum mesencephali in salamanders: a Golgi and HRP study.

The tectum mesencephali of salamanders shows a morphology that has long been considered primitive when compared with that of frogs. The alternative hypothesis is that the salamander brain is secondarily simplified. In order to test these two hypotheses, the cytoarchitecture of the tectum and the projections of tectal neurons were studied in 11 species of salamanders. Application of the Golgi method reveals three major morphological types. Type 1 has a very wide dendritic arborization mostly confined to the deep fiber layers, and somata are always located within the most superficial part of the periventricular gray matter. Type 2 possesses a wide to medium-size dendritic arborization. In subtype 2a the somata are located in the uppermost part of the gray, and dendrites always reach the uppermost layer of retinal afferents; in subtype 2b the somata are found in deeper parts of the gray, and dendrites arborize in the deeper layers of retinal afferents; and in subtype 2c the somata are also located in deeper parts, but the wide dendritic arborization is confined to deep fiber layers. Type 3 shows the narrowest dendritic arbors that always reach the upper two tectal fiber layers. The somata are found at any depth of the gray matter. HRP experiments reveal a correlation between morphological differences and the projections of tectal neurons. Type 1- and type 2c-like cells constitute the uncrossed tecto-bulbo-spinal tract, whereas type 1- and type 2a-like cells and migrated large spindle-shaped cells (Salamandra) constitute the crossed tecto-bulbo-spinal tract. Type 3-like neurons project to thalamic, pretectal, and isthmic termination sites. The HRP experiments also demonstrate the existence of two classes of mesencephalic trigeminal cells. A comparison shows that salamanders and frogs possess very similar functional and morphological types of tectal cells. However, tectal cells of salamanders show a "juvenile" morphology, and the number of migrated cells is about 10 times higher in frogs compared to salamanders. Both phenomena are seen as the result of secondary simplification of brain structures in the context of paedomorphosis.

Animals↗
PubMed1990

Optic nerves in plethodontid salamanders (amphibia, urodela): neuroglia, fiber spectrum and myelination.

In five species of lungless salamanders, family Plethodontidae, which all show highly developed visual abilities, the ultrastructure of the optic nerve was investigated and the total number of retinal ganglion cell axons, the percentage of myelinated axons, and the volume densities of glia and axons were determined. More than 80% of all axons were smaller than 0.4 micron and only 2-3% were larger than 0.8 micron. In individual nerves the degree of myelination varied between 1 and 9% which is in the range reported for other amphibian species. The miniaturized and highly paedomorphic species Batrachoseps attenuatus was an exception because only very few or even no myelinated axons were present in the nerve, which is unique among gnathostome vertebrates. The five investigated species had total numbers of axons ranging from 26,000 in Batrachoseps attenuatus to about 50,000 in Plethodon jordani. These numbers are the lowest found among vertebrates with an elaborated visual system. The amount of glial material in the optic nerve varied between 25 and 50%, with larger nerves possessing more glia than smaller ones. Ultrastructural analysis revealed that the optic nerve of each species contained both astrocytes and oligodendrocytes, although often in immature form. In Batrachoseps attenuatus the glia showed features of both astrocytes and oligodendrocytes which reflect an undifferentiated state.

Animals↗
PubMed1990

Positive giant potentials: an electromyographic investigation.

Positive giant potentials (PGPs) consist of a peculiar EMG activity which is observed mostly in the large lower limb muscles, and mainly in men, either during the insertion of the needle electrode or during muscle contraction. PGPs have a shape similar to that of positive sharp waves, but with a larger amplitude (up to 25 mV). Their firing rate may reach 200 c/s. PGPs probably have no diagnostic significance since they are frequently observed in healthy individuals. They correspond to an insertional activity and should be recognized as such because they may be mistaken for giant motor unit potentials and thus be the source of diagnostic errors. The mechanism involved in the genesis of PGPs remains a matter of speculation.

Action Potentials↗
PubMed1990

Central olfactory and vomeronasal pathways in salamanders.

Central olfactory and vomeronasal pathways were studied in salamanders of the families Salamandridae and Plethodontidae by means of the HRP method. HRP was injected into the olfactory and accessory olfactory bulb as well as into the lateral/dorsal pallium, the main termination areas of secondary olfactory projections. Fibers leaving the olfactory bulb constitute two main tracts, the lateral olfactory tract (LOT), which is mostly restricted to the ipsilateral telencephalon, and the anterior olfactory habenular tract (AOHT), which represents the main contralateral connection. Fibers of the LOT project to the lateral pallium, dorsal striatum and the habenula. Efferent connections of the accessory olfactory bulb (AOT) terminate within the amygdala pars lateralis. No interspecific differences concerning the targets of central olfactory and vomeronasal projections were observed, but the number of olfactory tracts and their separation from each other varies.

Animals↗
PubMed1990

Cryptogenic hemifacial spasm. A neurophysiological study.

Whether hemifacial spasm (HFS) is due to axono-axonal ephaptic transmission or to facial nucleus abnormal hyperexcitability remains controversial. The neurophysiological hallmark of HFS is the delayed response (DR). This response has an indirect pathway and thus a long latency. It is evoked A) as a distant response in muscles innervated by a facial branch other than the one stimulated, and B) in muscles innervated by the branch stimulated. In this work, 99 single all-or-none DRs of 24 cases of cryptogenic HFS were studied by threshold stimulation of a branch, or of the trunk, of the facial nerve. A) Eighty-eight distant DRs were studied. Fifty-four of them were frequently evoked as double discharges (DDs), or sometimes as multiple discharges, with a 3 to 7 ms interval. A collision technique, using paired stimuli, showed that the second discharge of 12 out of 20 DDs was accompanied by a back-wave due to a proximal ectopic re-excitation on the axon, or to the back-firing of an alpha cell (F-response), or to both. F-waves in HFS were more frequent than in normals or in other facial pathologies. B) Eleven DRs were recorded in muscles innervated by the facial branch stimulated. Some of them persisted when, using a stronger stimulus, the same all-or-none potential was also evoked as a direct response. In other cases both the direct response and the DR were evoked with identical stimulation threshold. The direct-indirect response interval of these 11 DRs was shorter than the normal M-F interval. These findings suggest that, in the case of HFS, axons are interconnected by uni- and bidirectional ephapses. Self-sustained repetitive firing in such a group of axons apparently results from re-excitations occurring both at the ephapse site and at the cellular level (F-responses). Spasm develops when several groups fire together. The changing excitability of the alpha cells modulates the importance of the phenomenon.

Adult↗
PubMed1990

[The causes of severe forms of tuberculosis].

Twenty-six patients (7.5% of all treated infective TB) were investigated with a view to establishing the causes of severe tuberculosis. Most of the patients (17) were alcohol-dependent, several had a protracted course (3), while others had concomitant diseases that had a negative influence on the course of the TB.

Adolescent↗
PubMed1989

Topographic relationships of ipsi- and contralateral visual inputs to the rostral tectum opticum in the salamander Plethodon jordani indicate the presence of a horopter.

Topographies of ipsilateral and contralateral retinal inputs to the optic tectum were studied by means of electrophysiological multi-unit recordings from the superficial layers. It was found that the nasotemporal coordinate of the visual field is represented along a rostrocaudal axis on the contralateral tectal map and along a caudorostral axis on the ipsilateral map. Electrical stimulation of one tectal hemisphere and recording of the response in the other hemisphere revealed that the ipsilateral map is most probably established by an intertectal pathway. In one tectal hemisphere, inputs from the ipsilateral eye match those from the contralateral eye if stimuli are located at a certain distance at arbitrary horizontal angles within the binocular field. This distance varied from 11.8 to 29.5 mm between the 5 individuals examined.

Animals↗
PubMed1989

Morphology of retinal ganglion cells in lungless salamanders (fam. Plethodontidae): an HRP and Golgi study.

The family Plethodontidae consists of nearly two-thirds of all living urodeles; most of them possess highly developed visual abilities. We investigated the morphology of retinal ganglion cells (RGCs) in four representative species by means of the horseradish peroxidase method in flatmounts and in transverse sections and with the Golgi method in transverse sections. In flatmount preparations, four classes of RGCs were found, differing in dendritic arborization, dendritic field size, and stratification pattern of dendrites in the inner plexiform layer (IPL). Class-1 cells had small dendritic fields (29-44 microns 2) and arborized throughout the entire depth of the IPL. Class-2 cells had medium to large dendritic fields (75-206 microns 2) and mostly arborized in two or three laminae or in a diffuse fashion in the IPL. Class-3 cells had medium to large dendritic fields (72-200 microns 2) but sparse dendritic arborization. They only arborized in the proximal lamina of the IPL. Class-4 cells had large dendritic fields (273-626 microns 2) and branched in the most sclerad stratum of the IPL. No large differences in intraspecific soma size of the different RGC classes were detected (although interspecific soma size varied to a considerable degree) and no "giant" cells typically found in other vertebrate retinas were present. The results suggest that, with respect to the pattern of arborization and stratification of dendrites, lungless salamanders possess morphological classes of RGC similar to those found in frogs, but the morphology of RGCs in lungless salamanders seems to be simplified in comparison to frog RGCs. This simplification might be a consequence of paedomorphosis.

Animals↗
PubMed1989

Distribution of substance P-like, leucine-enkephalin-like, and bombesine-like immunoreactivity and acetylcholinesterase activity in the visual system of salamanders.

In the urodele species Salamandra salamandra and Batrachoseps attenuatus, the distribution of the neuropeptides substance P (SP), leucine-enkephalin (LENK), and bombesine (BOMB) was investigated by means of immunohistochemistry in brain areas containing retinofugal projection sites (tectum mesencephali, praetectum, thalamus) as well as in brain regions postsynaptic to the tectum. The activity of acetylcholinesterase (AChE) was studied histochemically. Despite its simplified, two-layered morphology, the salamander tectum shows a high degree of neurochemical differentiation, characterized by a laminar organization of neuropeptide-like immunoreactivity and AChE-activity comparable to that found in the anuran tectum, which has a multi-layered morphology. SP-like immunoreactivity constituted four tectal laminae, two of them occurring in the stratum opticum. LENK-like immunoreactivity formed three laminae, one in the stratum opticum. BOMB-like immunoreactivity formed one lamina within the stratum opticum and one in the tectal efferent layers. Layers 1 and 2 of the stratum opticum revealed high AChE-activity, whereas low activity was found in deep fiber layers containing tectal efferents. The outer cellular layer also revealed AChE-activity. After enucleation of one eye, the contralateral tectum lacked neuropeptide-like immunoreactivity and AChE-activity in the layers containing retinofugal projection sites. No reduction of immunoreactivity was found in nuclei postsynaptic to the tectum. Our experiments suggest that the secondary simplification that has taken place in salamanders with respect to tectal morphology did not affect the neurochemical differentiation of the tectum.

Acetylcholinesterase↗
PubMed1989

[Superior gluteal nerve entrapment neuropathy].

We observed two female patients suffering from chronic gluteal pain of mechanical origin, without paresthesia. In the first case, the muscular pain was associated with weakness of hip abduction and with tenderness of the middle gluteal muscle. An electromyography, a principal examination, confirmed a diagnosis of entrapment of the superior gluteal nerve in one case and of the distal branch in the other. The proposed treatment, as in the case of neuropathic entrapment of the median nerve at the wrist, consists of a local infiltration of corticosteroids. If the symptoms persist, surgical intervention to free the nerve is indicated. For our first patient the clinical and electromyography cure has been completed. The neuropathy by chronic compression of a nerve in the gluteal area seems to be rare, but one has to consider further investigations in the case of chronic gluteal pain.

Adrenal Cortex Hormones↗