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Biomedical subjects

G Meyer

Publications and source records attributed to G Meyer.

At least 379 records · Page 21Linked to original sources
PubMed1985

Cortical projections of the nucleus centralis superior and the adjacent reticular tegmentum in the mouse.

After horseradish peroxidase-injections into different cortical areas of the mouse, labeled neurons were observed in the n. centralis superior and in the bilateral adjacent reticular tegmentum, especially in the zone dorsal to the medial lemniscus and the n. reticularis tegmenti pontis. Labeled cells in the n. centralis superior were nearly always concurrent with labeled paramedian cells, the topographical distribution of which was independent of the site of injection.

Animals↗
PubMed1985

Synthesis, transport and localization of a nuclear coded 22-kd heat-shock protein in the chloroplast membranes of peas and Chlamydomonas reinhardi.

The synthesis, transport and localization of a nuclear coded 22-kd heat-shock protein (HSP) in the chloroplast membranes was studied in pea plants and Chlamydomonas reinhardi. HSPs were detected in both systems by in vivo labeling and in vitro translation of poly(A)RNA, using the wheat-germ and reticulocyte lysate systems. Heat-shock treatment of pea plants for 2 h at 42-45 degrees C induces the expression of 10 nuclear coded proteins, among which several (18 kd, 19 kd, 22 kd) are predominant. A 22-kd protein is synthesized as a 26-kd precursor protein and is localized in a chloroplast membrane fraction in vivo. Following post-translational transport into intact chloroplasts in vitro of the 26-kd precursor, the protein is processed but the resulting 22-kd mature protein is localized in the chloroplast stroma. If, however, the in vitro transport is carried out with chloroplasts from heat-shocked plants, the 22-kd protein is preferentially transported to the chloroplast membrane fraction. In C. reinhardi the synthesis of poly(A)RNAs coding for several HSPs is progressively and sequentially induced when raising the temperature for 1.5 h from 36 degrees C to 42 degrees C, while that of several preexisting RNAs is reduced. Various pre-existing poly(A)RNAs endure in the cells at 42 degrees C up to 5 h but are no longer translated in vivo, whereas some poly(A)RNAs persist and are translated. As in pea, a poly(A)RNA coded 22-kd HSP is localized in the chloroplast membranes in vivo, although it is translated as a 22-kd protein in vitro. The in vitro translated protein is not transported in isolated pea chloroplast which, however, processes and transports other nuclear coded chloroplast proteins of Chlamydomonas. The poly(A)RNA coding for the 22-kd HSP appears after 1 h at 36 degrees C. Its synthesis increases with the temperature of incubation up to 42 degrees C, although it decreases after 2 h of heat treatment and the already synthesized RNA is rapidly degraded. The degradation is faster upon return of the cells to 26 degrees C. None of the heat-induced proteins is identical to the light-inducible proteins of the chloroplast membranes.

Journal Article↗
PubMed1985

Construction of K+- and Na+-sensitive theta-microelectrodes with fine tips: an easy method with high yield.

A new method is described to prepare theta-microelectrodes with tips up to 0.15 micron diameter controlled under scanning electron microscope. K+- and Na+-sensitive resins were tested. Method features are the following: i) hard drying of the glass, ii) rehydration of one channel and weak wetting of the other with a three-methylchlorosilane solution before pulling, iii) simultaneous presence of water and silane in the two channels during pulling, iv) gradual silanization from the tip to the shank. Selective and conventional channels did not affect each other and no displacements of resins were observed. The change of potential difference of the selective channel was more than -50 mV/decade. Apical membrane potentials and cell Na+ and K+ activities of the epithelial cells of rabbit gall-bladder (cell diameter: 5-10 micron) were measured with these theta-microelectrodes and with single-barrel microelectrodes of similar tip size: results obtained were not significantly different.

Animals↗
PubMed1985

Production of a monoclonal antibody against an epitope on HeLa cells that is the functional poliovirus binding site.

Cell lines of primate origin carry receptors on their plasma membrane which are responsible for the specific binding of poliovirus. This paper describes the isolation and characterization of a monoclonal antibody reacting with the plasma membrane of HeLa cells. The antibody (D171) was selected for its protection of HeLa cells against the cytopathic effect of poliovirus type 1. This protection was found to extend to all three viral serotypes, while the replication of five other viruses in HeLa cells was not affected. The 125I-labelled purified antibody did not react with cell lines derived from pig, dog or rodents but bound specifically to all lines of human or primate origin. Immunoglobulin or Fab fragments of D171 prevented the binding of 35S-labelled poliovirus to HeLa cells. Conversely, nearly all binding sites of 125I-labelled D171 immunoglobulins or Fab fragments could be blocked after preincubation of HeLa cells with poliovirus. These results indicate that D171 recognizes the poliovirus receptor site on different susceptible cells and that practically all D171 binding sites are involved in the specific attachment of poliovirus to the plasma membrane. To determine whether the epitope recognized by D171 could be separated from the receptor for poliovirus, human-mouse cell hybrids were prepared and analysed. In all 40 clones tested, the susceptibility to poliovirus correlated with the binding of D171.

Animals↗
PubMed1985

[Yield of the thoracoscopic biopsy in experimental pulmonary infections in the immunosuppressed rabbit].

Using thoracoscopy lung biopsy we investigated the bacteriological diagnostic yield in immunodepressed and/or infected NZ rabbits. 84 rabbits were used: 18 controls, 30 immunodepressed rabbits and 36 rabbits immunodepressed and then infected with Aspergillus fumigatus. Candida albicans or B.C.G. The thoracoscopy technique was the one we designed for humans, the instruments were adapted to the size of animals. Thoracoscopy biopsy results were compared to those of surgical biopsies made in the same animals. The results of both techniques were similar: indeed, the sensitivity of thoracoscopy biopsy was 88.9% in immunodepressed rabbits (versus 100% with surgical biopsies), 86% in the group of rabbits infected with B.C.G. (versus 86%), 90.1% in rabbits infected with Aspergillus fumigatus (versus 100%) and 88.9% in rabbits infected with Candida albicans (versus 100%). The indications for thoracoscopic lung biopsy in immunodepressed patients with infectious lung diseases are drawn from these experimental data, from our experience and the known mortality and morbidity of surgical lung biopsy.

Animals↗
PubMed1985

[In vitro opening of human atheromatous coronary arteries using a pulsed laser].

This study was undertaken to assess the respective values of pulsed and continuous laser emission for in vitro recanalisation of very stenosed atheromatous human coronary arteries. The Nd-YAG laser used emitted a 10 Hz 10 ns burst in the infrared band (1 064 microns). Previous spectroscopic studies had shown no specific band of absorption in the spectral field of emission of the usual lasers. The laser beam was focused in the axis of the segment of coronary artery irradiated. The crater or neo lumen obtained usually had irregular walls. No perforation of the arterial wall or macroscopic debris were observed. Histological studies showed minimal burn lesions with sparse coagulation necrosis limited to a few tens of micron thickness. The percentage recanalisation obtained with pulses of 200 mJ attained 50% for a total energy of 450 J delivered in 2 mn. This study confirmed the feasibility of disobliteration of atheromatous coronary arteries by pulsed laser. Our results suggest that ultra short pulsed laser acts more by a mechanical than by a thermal mechanism which may lead to less side effects than observed in vivo with continuous laser emission.

Coronary Disease↗
PubMed1985

Karyometric changes in the development of the medial and lateral preoptic area of the mouse after gonadectomy.

A karyometric study of the medial and the lateral preoptic area of the male albino mouse has been carried out with the aid of a Leitz Image Analysis System (ASM). We have measured nuclear sizes of a control group of sixty mice, aged from the 5th to the 190th day of life. Another group of prepuberally castrated male mice, has been studied at the 25th, 35th, 45th, 55th and 85th postnatal day. The medial and the lateral preoptic area show different development patterns in the control group, and differential effects of castration in these zones were observed. The medial preoptic area, which has frequently been related to changes of sex hormone levels, experiments more important and statistically significant variations than the lateral preoptic area.

Aging↗
PubMed1985

[Therapy of recurrent colorectal cancers].

Colorectal cancers treated for cure by operative means show tumour recurrences and metastases in about 20% of the patients. Of these colon or rectal cancers 75 and 90% respectively can be only operated for palliation. These patients have a better prognosis than those operated primarily for palliation. 25% of the cases especially with suture line recurrences can be operated upon radically enough and exhibit a total five year survival rate of 50%.

Colectomy↗
PubMed1984

Postnatal maturation of nonpyramidal neurons in the visual cortex of the cat.

A Golgi study of nonpyramidal neurons in the visual cortex of kittens aged from 1 to 80 days revealed that different neuronal types undergo a differential sequence of maturation. The earliest nonpyramidal cells to differentiate are large multipolar cells of layers 3-5, which appear around birth and whose axons gradually establish long lateral, intracortical connections. They are followed by spiny stellate cells of layer 4, which appear in the first postnatal, week, and by neuroglioform cells in layers 4 and 5, a cell type which at 10 days displays a highly differentiated axonal plexus. In general, most classes of local axon cells can be identified by the end of the second week, though still possessing a very immature morphology, the axonal-tuft cells of layer 2 maturing later, in the third week. With some exceptions, most neurons exhibit an adultlike axonal arborization by the end of the first month; however, immature chandelier terminals are observed until the 40th day, and in kittens aged from 30 to 80 days, the vertical terminal segments of chandelier cells are larger than in the adult. Some neuronal types seem to present an exuberant growth of axonal fibers in the late postnatal period and a subsequent reduction up to the adult stage.

Animals↗