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Biomedical subjects

M Schwarz

Publications and source records attributed to M Schwarz.

At least 325 records · Page 18Linked to original sources
PubMed1991

Color-coded Doppler sonography of vertebral arteries.

Color-coded Doppler sonography of the vertebral arteries was performed in 86 patients who had a history of vertebrobasilar disease. The origin of the artery was visualized in 87.2% on the right and 70.9% on the left side. The inter-transverse portion of the vertebral artery was visualized in 95% on the right and 97% on the left side. The atlas loop could be visualized in 88.4% on the right and 84.9% on the left side. Pathologic findings were hypoplasia (n = 4), stenosis (n = 19), dissection (n = 2), occlusion (n = 7), kinking (n = 12), cervical tumors (n = 3), and subclavian steal syndrome (n = 3). Nine postoperative patients had subclavian and vertebral artery reimplantation to the common carotid artery. The characteristic color-coded Doppler sonographic features of these findings are presented and discussed.

Angiography↗
PubMed1991

[Pseudarthrosis of the capitate bone with special reference to ligamentous stabilization].

Non-union of the capitate is rare. So far, six cases of non-union have been reported. The authors add a new case report, involving a 29-year old tobacco worker with a typical history. The length of the capitate was restored by corticocancellous bone grafting. The mechanism by which non-union occurs is discussed, showing that the uninjured palmar V ligament in the wrist is responsible.

Bone Screws↗
PubMed1991

[Hypersupination dislocation of the distal radio-ulnar joint after distal radius fracture].

Following an intraarticular distal radius fracture of the scaphoid, scapholunate dissociation and fracture of the ulnar styloid process without dislocation, the distal radius fracture healed with rotational deformity. In the course of conservative treatment, a dislocation of the distal radioulnar joint in locked hypersupination developed. Due to the locked rotational deformity, standard X-rays were difficult to assess. Only with the help of a CAT-scan, were the authors able to visualize the distal radioulnar joint dislocation and later control the postoperative result.

Adult↗
PubMed1990

Phenobarbital enhances the formation of reactive oxygen in neoplastic rat liver nodules.

The effect of treatment of rats with the liver monooxygenase inducer phenobarbital on the formation of reactive oxygen in neoplastic liver nodules and the surrounding normal tissue was investigated. Liver nodules were induced by treatment of rats with diethylnitrosamine (single i.p. injection of 0.15 mumol/kg body weight on day 1 after birth) followed by chronic administration of phenobarbital-sodium (PB; 0.05% in diet) after weaning. Groups of rats were kept on PB until sacrifice or were withdrawn from the promoter 3-6 weeks prior to killing. Emission of chemiluminescence was used as a sensitive means to detect the formation of reactive oxygen in microsomal preparations from the various tissues incubated with NADPH and the chemiluminigenic detector lucigenin. In addition, a 2-dimensional photon counting system has been developed that permits the analysis of the spatial distribution of lucigenin-chemiluminigenic signals over liver tissue sections incubated with reduced phosphopyridine dinucleotides. In general, we observed increased levels of reactive oxygen formation in liver nodules when compared with the normal liver tissue. Highest levels were seen in nodules that stemmed from PB-induced rats. Studies on the expression and activity of cytochrome P-450 in liver nodules as well as experiments with specific inhibitors point towards a participation of the liver monooxygenase system in reactive oxygen formation, although additional metabolic pathways seem to be involved as well. The observed increases in reactive oxygen in liver nodules of PB-treated rats might be related to the promoting activity of this drug.

Acridines↗
PubMed1990

Blockade of excitatory neurotransmission in the globus pallidus induces rigidity and akinesia in the rat: implications for excitatory neurotransmission in pathogenesis of Parkinson's diseases.

Bilateral microinjections of the selective N-methyl-D-aspartate (NMDA) antagonist, (-)-2-amino-7-phosphonoheptanoate (AP7), 0.02-0.5 nmol, into the globus pallidus and ventral-posterior portions of the caudate-putamen result in an increase in the muscle tone (rigidity) and catalepsy (akinesia) in rats. NMDA blocked the actions of AP7 on motility in sensitive regions of the globus pallidus and caudate-putamen. Topographical differences in the action of AP7 in the striatum were detected in the dorsal-ventral and rostral-caudal direction. Microinjections of AP7 into the nucleus accumbens induced neither an increase in the muscle tone nor catalepsy in rats, while ventral regions of the caudate-putamen were sensitive to both actions of AP7. Microinjections of AP7 into the dorsal caudate-putamen resulted in a moderate or no increase in the muscle tone. AP7 failed to induce catalepsy from dorsal regions of the caudate-putamen. These data identify the globus pallidus and a defined subregion of the caudate-putamen as crucial sites where excitatory neurotransmission acts to regulate the final set-point of the respective output neurons providing modulation of the passage of motor information through the basal ganglia.

2-Amino-5-phosphonovalerate↗
PubMed1990

Substantia nigra: a site of action of muscle relaxant drugs.

Sites of action of centrally active muscle relaxant drugs are not well defined. Clinical experience with such drugs suggests that the spinal cord may be one of the important regions from which pathologically increased muscle tone may be relieved. Supraspinal centers that may also be involved in the expression of muscle relaxant action have not yet been defined. We report here that microinjections of therapeutically relevant muscle relaxants into the midbrain tegmentum of genetically spastic rats decrease muscle tone. The substantia nigra is the region from which midazolam, baclofen, and tizanidine (drugs used clinically in the treatment of spasticity), or gamma-vinyl-GABA, (-)-2-amino-7-phosphonoheptanoate, and [D-pro2-D-phe7-D-trp9]-substance P (experimental drugs active in animal models of spasticity), reduce muscle tone in genetically spastic rats and Hoffmann reflexes in normal rats. The effects of muscle relaxant drugs are topographically restricted to the substantia nigra pars reticulata and are receptor specific. These observations disclose a previously unknown function of the substantia nigra in mediating muscle relaxation.

Animals↗
PubMed1990

Detection of genomic alterations in carcinogen-induced mouse liver tumors by DNA fingerprint analysis.

DNA fingerprint analysis was used to study structural abnormalities in the genome of mouse liver tumor cells. Liver tumors were induced in three strains of mice, namely C57BL/6J, C3H/He and B6C3F1, by a single injection of 20 micrograms/g body wt. diethylnitrosamine on day 15 after birth. DNA from liver tumors was digested with Hinfl restriction enzyme and hybridized on Southern blots with wild-type bacteriophage M13 DNA as probe. The resulting fingerprints of tumor DNA were compared with those of DNA from normal liver tissue. Genomic aberrations were detected in two out of 68 tumors analyzed, one stemming from a C57BL/6J and the other from a C3H/He mouse.

Animals↗
PubMed1990

Cerebral and spinal MR-findings in patients with postrepair myelomeningocele.

In 114 patients with postrepair myelomeningocele MRI of the spine was performed. Tethered cord (89%) and associated malformations (syrinx, lipoma etc.) (33%) were the most important findings. Additional MRI scans of the head (44 patients) revealed numerous further anomalies. Arnold Chiari malformation was found in 76% of the patients (ACM I:32%, ACM II:44%). In the ACM II group compression of lower cranial nerves, brain stem, and cerebellum can lead to considerable neurologic symptoms. Therefore in patients with progressive neurologic dysfunction a complete investigation of the whole spine and brain is necessary. MRI proves to be the diagnostic procedure of choice in patients with dysraphic myelodysplasia.

Adolescent↗
PubMed1990

Mutations in the Ha-ras proto-oncogene in spontaneous and chemically induced liver tumours of the CF1 mouse.

Mutations in codon 61 of the Ha-ras proto-oncogene have been shown to occur with a high frequency in both spontaneous and carcinogen-induced liver tumours of the B6C3F1 mouse. In the present study we analysed the frequency and pattern of Ha-ras mutations in liver tumours in a different strain of mice, namely the CF1 mouse. These liver tumours occurred spontaneously or after administration of either aflatoxin B1, phenobarbital or dieldrin. Mutation analysis was performed by in vitro amplification of DNA using the polymerase chain reaction combined with selective oligonucleotide hybridization. Our results demonstrate the presence of mutations in the Ha-ras gene in liver tumours of the CF1 strain. In total, 6 out of 35 liver tumours of male CF1 mice, two of them occurring after treatment with the tumour promoter phenobarbital solely, contained mutations at either the first or second base of codon 61 of the Ha-ras gene. The types of mutations found in liver tumours of the CF1 mouse were very similar to those described in the B6C3F1 mouse, indicating that mutations in the Ha-ras proto-oncogene may represent a critical event in mouse hepatocarcinogenesis.

Aflatoxin B1↗
PubMed1990

Quantitative analysis of enzyme-altered foci in rat hepatocarcinogenesis experiments--I. Single agent regimen.

Considerable recent attention has focused on the quantitative analysis of enzyme-altered foci in rodent hepatocarcinogenesis experiments. These foci are believed to represent clones of premalignant cells. A method is presented for the quantitative analysis of these foci that takes into account both the total number of focal transections observed in each liver cross-section and the size distribution of these transections. The method, which has a natural interpretation within the framework of a two-mutation model for carcinogenesis, yields estimates of rates of initiation and of growth rates of enzyme-altered foci as functions of dose of the agent under consideration. Definitions of initiation and promotion potencies are proposed. The method is illustrated by application to an experiment in which rats were administered N-nitrosomorpholine at various concentrations in their drinking water.

Adenosine Triphosphatases↗
PubMed1990

Physical recklessness in adolescence. Trait or byproduct of depressive/suicidal states?

The authors assessed adolescents (264 psychiatric inpatients and 742 high school students) with a new instrument (the Sommerfeldt-Clark Adolescent Recklessness Scale) to test whether adolescents show individual differences on a dimension ranging from physical caution to physical recklessness. The three dimensions that emerged reflect an interest in weapons and military dangers, which we have tentatively labeled "foolhardiness"; the combination of dangerous driving and substance abuse; and involvement with smoking, drug use, and "bad company." The personality traits of "venturesomeness" and "impulsiveness" were significantly correlated with all three recklessness factors. The first two factors showed no significant relationship with patient status, diagnosis of mood disorder, or history of suicidal behavior; the third factor was associated with inpatient status and a history of suicide attempts.

Adolescent↗
PubMed1990

Transcription of a mutant collagen I gene is a cell type and stage-specific marker for odontoblast and osteoblast differentiation.

The Mov13 allele of the mouse alpha 1(I) collagen gene carries a retroviral insert in its first intron and had been reported to be transcriptionally silent. We have recently shown, however, that this mutant gene is expressed in odontoblasts of transplanted teeth derived from homozygous and heterozygous carrier embryos. The expression of the Mov13 allele has now been followed throughout in vivo development of mandibular teeth and bone in heterozygous animals, by in situ hybridization with a probe that specifically recognizes transcripts of the mutant gene. We show that the onset of its transcription precisely coincides with the final differentiation of odontoblasts and the onset of dentinogenesis, i.e. on day E16 for the incisor and at birth for the first molar. The mutant allele is also transcribed in osteoblasts of mandibular bone, again starting precisely with the onset of osteogenesis (day E13/14). No other cells were seen to transcribe the mutant gene. By these criteria, transcription of the Mov13 allele constitutes a true differentiation marker for odontoblasts and osteoblasts. Expression of the mutant allele in these two specialized cell types, in contrast to its transcriptional block in all other mesodermal cells ('fibroblasts'), suggests tissue-specific differences in the regulation of the alpha 1(I) collagen gene.

Alleles↗
PubMed1990

[Wide-gauge bile duct endoprostheses with a port irrigation system. A new method of prolonging the drainage function].

The maintenance of adequate drainage by the bile ducts is crucial in all the endoscopic or percutaneous transhepatic procedures used today for the treatment of obstructive jaundice. We use wide-gauge polyurethane bile duct endoprostheses (F16; 5.3 mm - F20; 6.7 mm). Occlusion need not be expected to occur earlier than 4-6 months after placement. The implantation of a subcutaneous port system connected to the prosthesis by means of an F5 (1.6 mm) catheter allows not only X-ray examination of the function, but also lavage of the prosthesis and the biliary ducts. It is possible to add bile-dissolving substances, thus preventing crystallization of bile. In this way the patency of the prosthesis can be maintained for substantially longer. This also means a definite improvement in the quality of life.

Cholestasis↗
PubMed1990

[Oral health status of apprentices].

3011 students of vocational schools in Rostock were examined for obtaining informations about their caries prevalence (DMF/T and DMF/S) and the periodontal treatment needs (CPITN). Those students, who need a special proof to be good for their occupation and therefore had a regular dental care, have a much more better oral health status than other students in vocational schools (successful treated 40%:20%, degree of treatment (FM/T) 80%:71%, DMF/T 8.5:10.3). Concerning the periodontal status of the 6 sextants 55.6% of the students hat code 0 of CPITN, 33.5% the 1, 10.3% code 2 and 0.6% the code 3. Summarizing recommendations are given for the improvement of passing from the regular dental care for young adults to dental care of the adult population.

Adolescent↗