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T Meier

Publications and source records attributed to T Meier.

106 records · Page 6Linked to original sources
PubMed1991

Serially homologous development of the peripheral nervous system in the mouthparts of the grasshopper.

Segmentally homologous neurogenesis and neuronal differentiation processes characterize the formation of the peripheral nervous system in the developing mouthparts of the grasshopper embryo. The peripherally located neurons derive from the ectoderm in each of the embryonic mouthparts. The major nerve branches serving the mandibles, maxillae, and labium are established by peripheral pioneer neurons, which project their axons into the central nervous system via a set of guidepost cells. The two secondary nerve branches in each appendage are established by fasciculation of peripheral afferent pioneers and central efferent pioneers or by efferent pioneers alone. Sensory cells differentiate and connect with the peripheral nerve branches after a basic peripheral nerve scaffold has been established. The serial homology of these developmental processes in the mouthparts and in the thoracic legs is striking and can be documented at the level of individual identified cells. Thus despite the enormous differences in gross structure and function among cephalic mouthparts and true thoracic legs, many aspects of neurogenesis and early neuronal differentiation are remarkably conserved in all of these appendages.

Aging↗
PubMed1991

Comparison of 15 monoclonal antibodies against tumor-associated antigens of transitional cell carcinoma of the human bladder.

Quantitative urinary immunocytology with our monoclonal antibody (mab) 486p 3/12 proved to be valuable for diagnostic use in bladder-cancer patients' urine, especially in the followup of patients with superficial bladder carcinoma. To evaluate the use of other monoclonal antibodies in bladder cancer, we compared 15 mabs directed against bladder-tumor-associated antigens from seven research groups in a broad panel of cellular and tissue specimens (bladder tumor, prostatic adenoma, and kidney stone). Quantitative evaluation was done in cytocentrifuged preparations and tissue specimens. None of the 15 mabs was bladder-tumor-specific. All 15 stained normal urothelium to some extent and six stained granulocytes. Each of the 15 seemed to identify a different cellular antigen, as can be clearly demonstrated by the staining pattern of different regions in the normal kidney. The sensitivity of quantitative urinary immunocytology in bladder-tumor patients can be improved by using a panel, rather than one mab in bladder-tumor patients, but specificity decreases simultaneously. A main reason for the poor specificity of quantitative urinary immunocytology with all 15 mabs is that false-positive results are obtained with all mabs in kidney-stone patients. Our quantitative urinary immunocytology method is a general tool for the diagnostic use of all mabs in bladder-tumor patients. Mabs that have a high sensitivity might be useful in the followup of patients with superficial bladder carcinoma. None of the 15 mabs (because of their poor specificity) seems to be helpful in quantitative urinary immunocytology for screening a population for bladder carcinoma.

Antibodies, Monoclonal↗
PubMed1991

Homologous patterns in the embryonic development of the peripheral nervous system in the grasshopper Schistocerca gregaria and the fly Drosophila melanogaster.

To determine the generality of developmental mechanisms involved in the construction of the insect nervous system, the embryonic development of the peripheral nervous system in the grasshopper Schistocerca gregaria was characterized at the level of identified neurons and nerve branches and then compared to that previously described from the fly Drosophila melanogaster. For this, immunocytochemistry using a neuron-specific antibody was carried out on staged grasshopper embryos. Our results show that initially a simple peripheral nerve scaffolding is established in each segment of the animal. This scaffolding consists of a pair of intersegmental nerves that are formed by identified afferent and efferent pioneer neurons and a pair of segmental nerves that are formed by afferent pioneers situated in limb buds. Subsequently, identified sets of sensory neurons differentiate in a stereotyped spatiotemporal pattern in dorsal, lateral and ventral clusters in each segment and project their axons onto these nerves. Although segment-specific differences exist, serial homologs of the developing nerves and sensory neurons can be identified. A comparison of these results with those obtained from Drosophila shows that virtually the same pattern of peripheral nerves and sensory structures is formed in both species. This indicates that the construction of the peripheral nervous system in extremely divergent modern insects relies on conserved developmental mechanisms that evolved in ancestral insects over 300 million years ago.

Animals↗
PubMed1991

Bioactivation of asymmetric N-dialkylnitrosamines in rat tissues derived from the ventral entoderm.

Aliphatic methylalkylnitrosamines with a chain length of three to six carbon atoms are powerful oesophageal carcinogens in rats and have been shown to methylate target organ DNA preferentially. This class of carcinogens is efficiently metabolized not only in the oesophageal mucosa but also in the mucosa of the nasal and oral cavity, trachea and bronchioli, i.e., tissues derived from the rat ventral entoderm. In order to determine whether more than one cytochrome P450 isozyme is involved in the bioactivation of asymmetrical aliphatic dialkylnitrosamines in these tissues, we have studied the effects of various modulators of nitrosamine metabolism, including dietary zinc deficiency, ethanol and disulfiram, on DNA alkylation by N-nitrosomethyl-n-butylamine (NMBA) and its ethyl analogue N-nitrosoethyl-n-butylamine (NEBA). Formation of O6-methyl- and O6-ethyldeoxyguanosine by a single dose of NMBA and NEBA, respectively, was quantified after a survival time of 6 h by immuno-slot-blot assay. In control rats, methylation of DNA by NMBA was highest in oesophagus, followed by nasal mucosa, liver and lung. Formation of O6-ethyldeoxyguanosine from NEBA, however, was twice as high in liver as in nasal mucosa and lung and four times as high in liver as in oesophagus. In oesophagus, trachea and bronchioli, both nitrosamines were selectively metabolized in mucosal cells. Bioactivation of NMBA and NEBA was almost completely inhibited in nasal mucosa by ethanol. In contrast, a striking interorgan shift in DNA methylation by NMBA from liver (-50%) to lung (+100%), oesophagus (+300%) and nasal mucosa (+400%) was obtained with dietary disulfiram, whereas only 20-50% increases in extrahepatic DNA ethylation were determined for NEBA.(ABSTRACT TRUNCATED AT 250 WORDS)

Alkylation↗
PubMed1990

[Focal size and shock wave pressure: a comparison of three different physical shock wave generators].

Shock-wave delivery and focal size of three different generators-electrohydraulic, electromagnetic and piezoelectric--were compared. Pressure measurements were uniformly made by needle hydrophone (piezoelectric transducer). The smallest focus, 17 x 3 x 3 mm, was achieved with the piezoelectric system (50% isobars), while the focus with the electromagnetic generator was much larger (50 x 7 x 4 mm). With the electrohydraulic generator the focal size of the 60% isobars was 20 mm in the longitudinal axis. The highest pressure, 1512 bar, was achieved with the piezoelectric lithotriptor (mean shock-wave pressure in focus: electrohydraulic 1000 + 100, electromagnetic 1000 + 25, piezoelectric 1400 + 27 bar). The rapid positive pressure rise was followed by a slower pressure fall and a small negative wave. In the focal region the negative pressure wave was between 112 and 200 bar with the electrohydraulic system, 100-146 bar with the electromagnetic one, and 134 bar with the piezoelectric one. The significance of the negative wave is not clear; perhaps it contributes to the development of the cavitation effect and facilitates stone fragmentation.

Electromagnetic Phenomena↗
PubMed1990

[Peripheral neuropathy with monoclonal gammopathy].

The case is reported of a patient with IgM-kappa paraproteinemia and polyneuropathy (PN) with very slow nerve conduction velocities. The association of demyelinating PN with severely decreased nerve conduction velocities and an IgM-kappa paraprotein usually suggests the diagnosis of monoclonal gammopathy of undetermined significance (MGUS), but less often of clinically manifest macroglobulinemia. Demyelinating PN with IgG-lambda- or IgA-lambda paraproteinemia occurs often in the uncommon but readily treatable osteosclerotic myeloma. A monoclonal protein combined with peripheral neuropathy involving predominant pain, temperature and autonomic loss (small fibre neuropathy) is by and large pathognomonic for primary systemic amyloidosis or amyloidosis associated with multiple myeloma or Waldenström's macroglobulinemia. Mild sensorimotor axonal polyneuropathy is an unspecific syndrome found in all gammopathies. It is important to differentiate between paraproteinemia with clinically pure chronic sensory PN and paraneoplastic sensory polyneuropathy. Unlike amyotrophic lateral sclerosis (ALS), paraproteinemias associated with a motor neuron disease-like syndrome sometimes evolve unusually slowly and exhibit neurophysiologically subclinical lesions of sensory nerve fibers. Mononeuropathy or multifocal neuropathy with a monoclonal protein is typical of cryoglobulinemia. Demyelinating PN of osteosclerotic myelomas presenting with one or a small number of bone lesions usually regress after excision or irradiation of the plasma cell proliferations. Immunosuppressants and plasmapheresis in the treatment of the demyelinating IgM-kappa neuropathies, of paraproteinemia with the motor neuron disease-like syndrome, and of mononeuropathy or multifocal neuropathy with cryoglobulinemia, are of doubtful value.(ABSTRACT TRUNCATED AT 250 WORDS)

Demyelinating Diseases↗
PubMed1990

Embryonic development and evolutionary origin of the Orthopteran auditory organs.

Two different types of ears characterize the order of Orthopteran insects. The auditory organs of grasshoppers and locusts (Caelifera) are located in the first abdominal segment, those of bushcrickets and crickets (Ensifera) are found in the tibiae of the prothoracic legs. Using neuron-specific antibody labelling, we describe the ontogenetic origin of these two types of auditory organs, use comparative developmental studies to identify their segmental homologs, and on the basis of homology postulate their evolutionary origin. In grasshoppers the auditory receptors develop by epithelial invagination of the body wall ectoderm in the first abdominal segment. Subsequently, at least a part of the receptor cells undergo active migration and project their out-growing axons onto the next anterior intersegmental nerve. During this time the receptor cells and their axons express the cell-cell adhesion molecule, Fasciclin I. Similar cellular and molecular differentiation processes in neighboring segments give rise to serially homologous sensory organs, the pleural chordotonal organs in the pregenital abdominal segments, and the wing-hinge chordotonal organs in the thoracic segments. In more primitive earless grasshoppers pleural chordotonal organs are found in place of auditory organs in the first abdominal segment. In bushcrickets the auditory receptors develop in association with the prothoracic subgenual organ from a common developmental precursor. The auditory receptor neurons in these insects are homologous to identified mechanoreceptors in the meso- and metathoracic legs. The established intra- and interspecies homologies provide insight into the evolution of the auditory organs of Orthopterans.

Animals↗
PubMed1990

Description of a simple method to study some aspects of the pathogenesis of arteriosclerosis by perfusion of arterial segments.

A perfusion apparatus is described which permits the perfusion of arterial segments of about 5 cm in length. It works under physiological conditions. During the perfusion, temperature and pressure constancy or pressure variation, respectively, pulsation, sufficient oxygen supply, and high sterility are guaranteed. Hitherto, the duration of the perfusion has been extended to 10 h. After this time the endothelium was well preserved. The method shall be used for the study of some problems in arteriosclerosis research.

Animals↗
PubMed1984

[Metabolic triglyceride storage disorders. A report of 2 cases of systemic carnitine deficiency].

Two cases of triglyceride storage in liver, kidney, heart, and skeletal muscle are described in infants who died at the age of 1 1/2 years and 4 d, respectively. In the first patient, a previously normal girl, the clinical symptoms began two months before death with encephalopathy (vomiting, unconsciousness), liver enlargement, hypoglycemia, increase in serum transaminases. These signs disappeared within the following days. Some weeks later she died during the second attack. The 4-d-old boy, the second child of healthy consanguineous parents, showed at the third day of life an impaired sucking, muscular hypotonia, respiratory arrest and bradycardia. An intensive therapy was inefficient. At autopsy gross examination showed only a moderately enlarged yellow liver and an edematous brain in the first case and pale organs in the second one but no cause of death. The microscopial examination of all tissues of both cases showed fat storage within the four organs mentioned above. The common histochemical methods for neutral lipids were positive, the Schultz-reaction for cholesterol and cholesterol esters was negative. The lipid loaden cells did not show birefringence in polarized light. A predominance and strong fat storage of the type I fibres was found in the skeletal muscle. The storage of triglyceride could be confirmed by histochromatography, a thin-layer chromatography of tissue sections. The triglyceride accumulation in liver, heart, kidney, and skeletal muscle is a characteristic feature of systemic carnitine deficiency. The clinical symptoms of the first patient are in agreement with reports of this disease also. A carnitine deficiency in a newborn was not yet described. Family studies revealed a low carnitine concentration in the mother's serum in both cases, while the serum of father and brother resp. sister showed normal carnitine levels.

Carnitine↗
PubMed1983

[Tremor reaction to mental and emotional stress].

Reactions of tremor before and after stress were registered with a new method. Reactions with informatory-mental stress (adding tests with increasing time pressure) can only be interpreted by considering performance. Reactions with informatory-emotional stress (University examination; tasks in a central TV control room) are task specific when tremor is inter-individually normalized.

Fingers↗
PubMed1981

How is the exact length of an internode determined.

(1) The length of the human ventral spinal roots in the newborn and in the adult were compared with the length of the internodes in these roots. Internodes of fibers of a given caliber were more than twice as long in the adult sacral roots than in the cervical roots. The factors of root elongation corresponded closely to the factors of internode elongation. (2) Internode length was in a statistically significant linear relation with fiber caliber in individual roots. The slope of the regression lines differed among roots, and were steeper caudally. If data from roots having different elongation factors were pooled there was no longer a linear relationship between fiber caliber and internode length. Internode length, therefore, correlated directly and quantitatively with root elongation; it was not directly linked to fiber caliber. (3) The total Schwann cell population per fiber was nearly stable from the newborn to the adult, but the sacral roots had 5 times as many Schwann cells as the cervical roots. Calculations based on the number of internodes and on the length of fetal roots at the onset of myelination showed that the mean "initial length" of the Schwann cell at the onset of myelination was 187 micrometer, the same for all roots. (4) The Schwann cell population per fiber is determined by 2 reciprocal growth phases: elongation of the fetal fiber up to the onset of myelination corresponds to a multiplication of Schwann cells each having a given initial length. Schwann cell populations stabilize after the onset of myelination; from then on the geometry of each internode is determined by its passive elongation. The timing of myelination is critical for determining the ultimate length of the Schwann cell. If myelination does not begin before a fiber system has attained approximately one eighth of its definitive size, the longest internodes of that system will average 1.5 mm and most will remain below 2 mm, regardless of body size.

Adult↗
PubMedDate not supplied

Early action of nerve determines motor endplate differentiation in rat muscle.

The formation of a motor endplate is characterized by a complex series of changes in the properties of the subsynaptic acetylcholine receptors (AChRs). Among the last changes to occur are the shortening of the apparent mean open time of their ion channels from about 4 to 1 ms and an increase in the single-channel conductance. This conversion of channel gating at the endplate seems to be induced by the motor neurone. We report here that fast channel gating also develops at nerve-free endplate sites of fibres that had been denervated while gating was still slow. At such sites, junctional folds will develop in the absence of the nerve terminal. Although the conversion of channel gating and the formation of junctional folds are late events in endplate development, the neural signals inducing these changes must therefore act at the earliest stages of junctional development.

Animals↗
PubMedDate not supplied

Immunohistochemical profiles of 30 monoclonal antibodies against cytokeratins 8, 18 and 19. Second report of the TD5 workshop.

In the first report of the TD5 workshop (TD5-1), the epitope specificities of 30 different monoclonal antibodies against cytokeratins 8, 18 and 19 were determined. This second report presents the immunohistochemical profiles of these antibodies using human appendix and normal skin for evaluation. Each antibody was tested by one or two different laboratories recruited from the Dutch Working Group on Immunohistochemistry and Cytochemistry. Eight different laboratories participated. The histological specimens were pretreated by the participants in three different ways for immunohistochemistry: microwave antigen retrieval in citrate buffer, enzymatic digestion to restore epitope exposure, no specific treatment (untreated paraffin-embedded samples), and tested blindly without knowledge of cytokeratin or epitope specificity of the antibodies at three different concentrations of 50, 10 and 1 microg/ml. Most of the tested antibodies (29/30) were useful in at least one pretreatment method, with microwave antigen retrieval being the most sensitive approach. For some antibodies, very high backgrounds were observed. Furthermore, it can be concluded that 11 MAbs performed well using all three staining protocols, including untreated paraffin-embedded sections. Interestingly, all the antibodies with documented selected specificity towards cytokeratin 8 (i.e. 178, 191, 199, 202 and 206) are reactive with an immunodominant region corresponding to amino acids 340-365 on cytokeratin 8, which evidently is well-suited as target for immunohistochemical interactions. Similarly, three antibodies with the same capacity to react with untreated samples had specificity against cytokeratin 19 (i.e. 179, 197 and 204) in the corresponding region in this filament, i.e. amino acids 311-335, or the KS 19.1 epitope. None of the six antibodies against the other major cytokeratin 19 epitope (BM 19.21) were found useful for immunohistochemistry on untreated samples. The overall conclusions from the present investigation are that all cytokeratin-8-specific antibodies with defined epitope specificities were very useful. Only one of the major two epitopes on cytokeratin 19 seems to be available for efficient immunohistochemistry. Cytokeratin 18 exposes some epitopes outside the immunodominant region reactive with the antibodies 190, 203 and 205 which can be used for untreated samples. The implications of these findings are of significance both for diagnostic histopathology and for the biology of tumor marker epitope expression in tissues.

Animals↗
PubMedDate not supplied

Noninvasive prediction of SAR distributions with an electro-optical E field sensor.

An integrated electro-optical (eo) E field sensor is developed on the basis of a Ti:LiNbO3 Mach-Zehnder interferometer. A measuring device based on the lock-in principle is introduced to register the E field in phase and amplitude using this E field probe. Segmented electrodes are used to minimize influences from the dielectric surroundings on the base point capacitance of the receiving dipole. The operating point is stabilized against drift phenomena resulting from optical damage and pyroelectric effect. Sensitivity, dynamic range, harmonic distortions and mechanical properties of a prototype of this electro-optical E field sensor are evaluated. A phantom setup in the SIGMA-60 applicator was developed to test this electro-optical sensor for hyperthermia applications. Power deposition patterns of various standard adjustments of the SIGMA ring are visualized in an elliptical lamp phantom. Simultaneously, E field in phase and amplitude is determined on a closed curve in 10 degrees steps around the phantom in a substitute bolus. The numbers are stored and utilized as boundary conditions in a two-dimensional finite elements code which calculates the SAR distribution on an appropriate triangular grid inside the closed curve. An excellent qualitative agreement is obtained between visualized and calculated SAR patterns. This novel measurement method is therefore suitable for noninvasive monitoring of SAR patterns during clinical application of regional radiofrequency hyperthermia.

Electrodes↗