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Biomedical subjects

M Zimmermann

Publications and source records attributed to M Zimmermann.

At least 289 records · Page 16Linked to original sources
PubMed1990

Demonstration of extensive brainstem projections to medial and lateral thalamus and hypothalamus in the rat.

We use the method of retrograde transport of colloidal gold with silver intensification to map locations of brainstem neurons projecting to various nuclei of the medial and lateral thalamus (Menetrey, Histochemistry 83, 391-395, 1985; Seeley and Field, Brain Res. 449, 177-191, 1988). In rats injections of less than 1.0 microliters of a gold-wheatgerm agglutinin-horseradish peroxidase complex were restricted to the centrum medianum, centralis lateralis, medialis dorsalis, zona incerta, ventrobasal thalamic complex, or medial or lateral hypothalamus. Injections in the centralis lateralis, with some involvement of centrum medianum and medial medialis dorsalis, labeled numerous neurons throughout the rostrocaudal extent of the midbrain periaqueductal gray, and adjacent reticular formation, dorsal raphe nucleus and substantia nigra. These labeled neurons were distributed bilaterally, but with a preponderance ipsilaterally. Numerous neurons in the deep layers of the ipsilateral superior colliculus and in the anterior pretectal nucleus were also labeled. Many neurons in the pontomedullary raphe nuclei (including nucleus raphe magnus), locus coeruleus and dorsolateral parabrachial nuclei, and in the pontomedullary reticular formation, were labeled bilaterally. Fewer were seen bilaterally in the lateral reticular nucleus and nucleus of the solitary tract, with relatively few in the dorsal aspect of the trigeminal nucleus caudalis. Injections restricted largely to the centrum medianum labeled fewer cells in the brainstem, but with similar distributions. An injection restricted to the centralis lateralis also resulted in a similar distribution of labeled neurons in midbrain and nucleus raphe magnus but did not label neurons at more caudal medullary levels. An injection restricted to zona incerta labeled numerous neurons in a distribution similar to that following medial thalamic injections, except that many more were observed in the contralateral sensory trigeminal nucleus and in the dorsal column nuclei. Injections of the ventrobasal thalamic nucleus labeled many neurons in the trigeminal and dorsal column nuclei, but many fewer neurons in the midbrain, periaqueductal gray and reticular formation compared with medial thalamic injections. Labeled neurons were also seen in the superior and inferior colliculi, due presumably to involvement by the injection of the lateral posterior and magnocellular medial geniculate nuclei, respectively. Injections in the lateral hypothalamus labeled numerous neurons in a distribution similar to that seen following medial thalamic injections.(ABSTRACT TRUNCATED AT 400 WORDS)

Afferent Pathways↗
PubMed1990

Characteristics of A- and C-fibers ending in a sensory nerve neuroma in the rat.

1. We have studied, in vivo, the degree of spontaneous activity, responsiveness to mechanical and chemical stimuli, and the conduction velocities in C- and A-fibers ending in the neuromas formed 8-66 days after ligation and transection of a cutaneous sensory nerve in the rat. 2. Some of these C- and A-fibers developed ongoing activity. The percentage varied considerably between neuromas in different animals, from 0 to 23% (mean, 4.2%), with no major variation in the incidence as a function of neuroma age. 3. The endings of the fibers in the neuroma could be excited by both mechanical and chemical stimuli. From 0 to 26% (mean, 13%) of these fibers had mechanosensitive endings, some of which were located in the muscle/facia tissue outside the neuroma itself. Some fibers were excited by direct application of chemicals to their endings in the neuroma; 3.0% of A- and C-fibers responded to bradykinin, 2.0% to histamine, and 2.8% to adrenaline. There was no systemic variation in the percentages of mechano- or chemosensitive fibers with neuroma age. 4. The C-fiber action potentials showed a continuing decrease in conduction velocities over the 9 wk after nerve transection. More than 4 wk after transection, the conduction velocity of neuroma fibers was 88% that of C-fibers of normal saphenous nerve. 5. We conclude that fibers in a cutaneous nerve neuroma have some sensory capabilities similar to those in normal nerves terminating in the skin. This could be because they are retained after the nerve is transected or because they are initially lost but then regenerate. However, the numbers are restricted, probably because the fibers remain isolated from factors produced by their target skin tissue that are necessary for development and maintenance of sensory functions.

Action Potentials↗
PubMed1990

[Effect of helium-neon-laser radiation on microbes].

In a well-defined in-vitro experiment the effects of a He-Ne-laser of 6 mW output on some dominating microbes in the oral cavity were studied by using a scanning electron microscope. No changes on the surface in the irradiated colonies could be seen even after an exposition lasting for 60 minutes (continuous or pulsated wave). Therefore an antibacterial effect of softlaser-irradiation sometimes described in literature in questionable.

Bacteroides↗
PubMed1989

The localization and release of substance P and calcitonin gene-related peptide at nerve fibre endings in rat cutaneous nerve neuroma.

This study uses radiological and immunocytochemical techniques to investigate the localization, content, transport and release of substance P- and calcitonin gene-related peptide-like immunoreactivity (SP-LI and CGRP-LI, respectively) in nerve fibre endings in 1-, 3- and 5-week-old cutaneous nerve neuromas. Neuromas were induced by ligating and transecting the saphenous nerve in anaesthetized Sprague-Dawley rats. The content of both neuropeptides in 3-week-old saphenous nerve neuroma was significantly reduced compared to that in normal saphenous nerve. At 5 weeks the levels of the peptides in the neuromas had returned to normal but remained reduced in the nerve just proximal to the neuroma. Following a 24-h ligation of the nerve proximal to 3-week-old neuromas there was a diminished immunocytochemical staining for SP-LI and CGRP-LI both proximal and distal to the ligature when compared to that seen at ligations of normal nerves. This indicates a decreased transport of the neuropeptides both to and from the 3-week-old neuromas. The density of neuropeptide staining at ligatures of nerves with 5 week or older neuromas had increased, but still remained less than that seen at ligations of normal nerve. Both a basal and a bradykinin-induced release of SP-LI and CGRP-LI from nerve fibre endings in the neuroma was demonstrated. The basal release was demonstrated by exposing the neuromas, in situ, to solutions containing 50 microM morphine plus 2 mM CoCl2 for 24 h.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

[Biotransformation of benzamidine and benzamidoxime by microsomal enzymes of the rabbit].

At pH 7.4 neither benzamidine (1) is ring-hydroxylated nor benzamidoxime (2) is N-hydroxylated, reduced or ring-hydroxylated by aerobic incubations with microsomal fractions (12000 g supernatant, microsomes) of rabbit liver homogenates and NADPH. Products of hydrolytic processes are also not detected. A very long incubation period and a pH 6.3 are necessary for the detection of a slight reduction of benzamidoxime (2) to benzamidine (1). Results are obtained by use of synthetic reference material and by newly developed HPLC methods. Thus, kinetic studies of the microsomal N-hydroxylation of benzamidine (1) to benzamidoxime (2) in the presence of N-methylbenzamidine (3) performed at pH 7.4 are not influenced by other transformations and provide evidence for the involvement of the same isoenzyme of cytochrome P-450 for both the N-hydroxylation of 1 and the N-dealkylation of 3.

Amidines↗
PubMed1989

[Analgesia by transcutaneous electrical nerve stimulation (TENS)].

Although safe and effective pain control has been achieved using TENS in many fields of medicine, the application of this technique to dentistry remains almost unexplored. In this study the effectiveness of TENS in alleviating pre-existing orofacial pain, in providing analgesia during primary dental treatment of these patients and as an alternative to conventional local anaesthesia during cavity preparation in regular patients was examined. In approximately 80% of patients TENS successfully alleviated pre-existing orofacial pain. Primary dental treatment of these patients, however, was only possible under conventional local anaesthesia. Pain induced by cavity preparation was adequately suppressed by TENS in approximately 80% of all cases.

Adolescent↗
PubMed1989

[Initial experiences with high-dosage afterloading short-term therapy combined with hyperthermia in non-operated cervix cancer].

A system for thermoradiotherapy of cervical carcinoma is presented, that allows combination of high-dosed afterloading short-time therapy by means of the technique being available in the GDR (DEKATRON) with the equipment CALOTHERM, constructed in Institut M. v. Ardenne. The first clinical experiences (3 patients) show, that the expected target temperature of 42 degrees C at the cervix was reached by all means after 6 minutes at least. Complications involved by hyperthermia did not appear with it, so that the continuation of this therapy is planned in form of a phase-I-study.

Brachytherapy↗
PubMed1989

[Survival rate of desmodontal cells in relation to their extraoral dehydration].

The success of tooth replantation following traumatic avulsion depends to a large degree on the vitality of periodontal ligament cells which remain on the root surface. Loss of vitality promotes root resorption. In this study 124 freshly extracted teeth, only front teeth and premolars, were stored in dry environment for periods of 10 to 150 min. The vitality of the residual periodontal ligament tissue was tested by means of the fluorescein-diacetate reaction. The root area covered by vital tissue decreased to 90% after 30 min and to 70% after 45 min of dry storage. Between 60 and 90 min after extraction the vital tissue area decreased rapidly to about 10%.

Adolescent↗
PubMed1988

Microinjections of glutamate or morphine at coincident midbrain sites have different effects on nociceptive dorsal horn neurons in the rat.

Responses of single lumbar spinal neurons to noxious skin heating (50 degrees C, 10 s) were electrophysiologically recorded in barbiturate-anesthetized rats. Responses of all neurons were suppressed by electrical stimulation in the midbrain periaqueductal gray (PAG) or lateral reticular formation (LRF). Microinjection of glutamate (GLU, 0.1-0.3 microliter, 0.5 M) into the PAG rapidly (within 15 s) suppressed (to 13-55% of control) the responses of 6/16 neurons with recovery within 8 min. The remainder were affected less at even higher doses (0.5-1 microliter). Responses of 4/10 neurons were suppressed following GLU microinjected into the LRF. We also tested effects of microinjection of morphine (MOR, 5 micrograms/0.5 microliter) into GLU-sensitive and insensitive PAG sites. Responses of 4 neurons were unaffected, 4 were enhanced (to 130-155%), and 2 suppressed (to 43 and 57%) following MOR in PAG, with enhancement or suppression beginning within 12-20 min and lasting 40 to over 70 min. The differing effects of GLU and MOR may reflect different mechanisms for the descending modulation of spinal nociceptive transmission.

Animals↗
PubMed1988

B vitamins suppress spinal dorsal horn nociceptive neurons in the cat.

To explore the role of vitamin B in neural mechanisms of analgesia, we investigated the effect of a compound of vitamins B1, B6 and B12 (Neurobion, E. Merck) on the nociceptive responses of single neurons in the spinal cord dorsal horn in anesthetized cats. Intrathecal superfusion of Neurobion, using a small pool placed on the spinal surface, produced a significant dose-dependent depression in the responses evoked by noxious skin heating (50 or 52 degrees C, 10 s) of hindfoot skin, but not of spontaneous activity in dorsal horn neurons. These results indicate that the therapeutic effect of vitamin B compounds in the clinical management of pain may involve a suppression of nociceptive transmission at the spinal level.

Animals↗
PubMed1988

Mechanism of the microsomal N-hydroxylation of para-substituted benzamidines.

With the aid of HPLC analyses and simple Michaelis-Menten kinetics, the maximum rates of the microsomal N-oxygenation of various para-substituted benzamidines 1 to benzamidoximes 2 were determined. The presence of electron-donating substituents increased the rates whereas the presence of electron-accepting substituents decreased them. A significant correlation between the logarithm of the maximum rates with the Hammett sigma p constants was found for a reaction constant of rho = -0.88. These results support the postulated radical mechanism for the N-oxygenation by the cytochrome P-450 enzyme system.

Amidines↗
PubMed1988

Inhibition of spinal nociceptive neurons by excitation of cell bodies or fibers of passage at various brainstem sites in the cat.

The relative contribution of cells of origin and fibers of passage to the inhibition of spinal nociceptive neurons from various brainstem sites is not known. The present study therefore quantitatively compares the descending inhibition produced by focal electrical stimulation which indiscriminatively excites all neuronal elements with the inhibition evoked by glutamate microinjections which selectively excite cell bodies at the same sites within the midbrain periaqueductal gray (PAG) and neighboring lateral reticular formation (LRF) and within the medullary nucleus raphe magnus (NRM). In pentobarbital anesthetized cats extracellular recordings were made from 22 lumbar dorsal horn neurons responding to innocuous mechanical skin stimuli and to noxious radiant heating of the glabrous skin at the ipsilateral hindpaw. Glutamate microinjections (1 microliter, 0.5 M) into 6 of 10 sites within the NRM reduced heat-evoked responses in 6 different cats to 69.2 +/- 3.8% of control. Electrical stimulation (180-600 microA) at the same sites and two additional sites in the NRM reduced responses to 50.0 +/- 8.7% of control. At 4 of 10 sites within the PAG glutamate reduced spinal neuronal responses to heat in 4 different cats to 69.4 +/- 6.1% of control. Electrical stimulation at 3 of the same sites and 6 additional sites within the PAG reduced heat-evoked responses to 52.7 +/- 3.5% of control. Microinjections of glutamate into the LRF failed to affect heat-evoked responses in any of the 8 experiments tested, while electrical stimulation at 6 of the same sites in the LRF reduced neuronal responses to heat to 52.4 +/- 7.1% of control.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

The bradykinin-induced release of substance P from nerve fibre endings in the rat saphenous nerve neuroma is not related to electrophysiological excitation.

It has previously been shown that electrical stimulation of a peripheral nerve induces a release of substance P (SP) from cutaneous nerve terminals. In this study, we investigate whether SP is released from nerve fibre endings in experimentally induced rat saphenous nerve neuromas. The neuromas were induced in pentobarbital anaesthetized rats by ligating and cutting the saphenous nerve 5 weeks prior to the release experiments. The 5-week-old neuromas were desheathed, placed in a perspex chamber, in situ, and superfused with Tyrode solution. The SP-like immunoreactivity (SPLI) content of the superfusate was measured by radioimmunoassay. Addition of 90 microM bradykinin to the superfusate resulted in a calcium-dependent release of SPLI. The other inflammatory mediators, histamine and serotonin, did not induce a release of SPLI. Furthermore, repetitive electrical stimulation of the saphenous nerve (50 V, 5 Hz, 0.5 ms) or superfusion of the neuroma with 50 microM veratridine or 40 mM K+ also failed to induce a release of the peptide. The release of SPLI, induced by bradykinin, from nerve fibre endings in the rat cutaneous nerve neuroma, appears to involve a neurochemical interaction that is independent of electrophysiological excitation.

Animals↗
PubMed1988

OFAGE banding patterns of different yeast genera and of intergeneric hybrids.

Electrophoretic karyotypes of yeasts belonging to the species Saccharomyces cerevisiae, Kluyveromyces marxianus and Candida macedoniensis were established by means of OFAGE. Hybrids between S. cerevisiae and K. marxianus as well as between K. marxianus and C. macedoniensis were analyzed by comparing their OFAGE-banding-pattern with the parental banding-patterns. Thus, evidence for exchanges of intact chromosomes and for chromosomal rearrangements could be gained on a molecular level.

Candida↗