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Biomedical subjects

G Meyer

Publications and source records attributed to G Meyer.

At least 433 records · Page 24Linked to original sources
PubMed1981

Spiny stellates as cells of origin of association fibres from area 17 to area 18 in the cat's neocortex.

Neurons in the cat's area 17 were stained in Golgi-like fashion following injection of horseradish peroxidase into area 18. Such staining allows classification of neurons on the basis of dendritic morphology. The types of neurons found in area 17 are: pyramidal cells in layers 2, 3 and 4ab; spiny stellate cells in the lower part of layer 3, and in layer 4ab; and a few pyramidal and spindle cells in layer 5. The axons of the spiny stellate cells are finer than those of pyramidal cells; they give off collaterals in deeper cortical layers and may bifurcate when entering the white matter. Spiny stellates in area 17 do not project to area 19; after injections are made into area 17, these neurons are found neither in area 18 nor in area 19. The spiny stellate cell with a long axon is thus categorized as a projection neuron which takes part in the pathway from area 17 to ipsilateral and contralateral area 18.

Animals↗
PubMed1981

Polyethylene glycol derivatives of base and sequence specific DNA ligands: DNA interaction and application for base specific separation of DNA fragments by gel electrophoresis.

Various base pair specific DNA ligands comprising a phenyl phenazinium dye, a triphenylmethan dye and Hoechst 33258 were covalently bound to polyethylene glycol (PEG) via ester or ether bonds. The DNA interactions of the PEG derivatives formed were shown to exhibit the same base pair specificity as the parent compounds. Since the PEG chains thus bound to the DNA could be expected to increase drastically the frictional coefficient of the DNA, the PEG derivatives were used for base specific DNA separations in agarose and polyacrylamide gel electrophoresis. The procedures, which do not require any special techniques, are described in detail. The resolution observed in agarose gels allows one to separate equally sized DNA fragments differing as little as 1% in base composition at mean travel distances of about 10 cm. Examples of gels showing the base compositional heterogeneity of restriction fragments obtained from lambda DNA, E. coli DNA and calf thymus DNA are given.

Chemical Phenomena↗
PubMed1981

Electrophysiology of pig distal colon measured during early post-natal development.

1. Brush border membrane (Vm) and transepithelial (Vms) potential differences, transepithelial resistance (Rep) and the brush border membrane/basolateral membrane resistance ratio (Rm/Rs) have been measured in distal colons taken from new-born and 4-day-old pigs. 2. Vm remained independent of the age of the animal. Substituting choline or Tris for Na+ hyperpolarized Vm; substituting SO4(2-) for Cl- or increasing the concentration of K+ depolarized Vm in colons taken from new-born pigs. K+ depolarization was not seen using colons taken from 4-day-old animals. 3. The effect of Na+ or Cl- replacement on Vms and Rm/Rs was in agreement with the hypothesis that the brush border membrane of the distal colon possessed a conductance for both these ions. The brush border membrane of the new-born, but not the 4-day-old pig colon possessed an additional conductance for K+. 4. These electrical measurements were repeated using 4-day-old pig distal colons in the presence of amiloride, to enable values for the electromotive force across the brush border membrane (Em) and the basolateral membrane (Es) to be calculated. The Em of the 4-day-old pig colon was found to be about 23 mV negative with respect to the mucosal solution. Cl- conductance appears to predominate in colons taken from these very young animals. 5. Separate experiments showed net transport of Na+ and measured short-circuit current to be partly dependent upon the presence of Cl. Na+ transport measured in the absence of Cl- was approximately equal to that calculated from the measurement of short-circuit current. 6. It is suggested that the brush border membrane of the neonatal pig colon is conductive to both Na+ and Cl-, that the transport of these ions are partly coupled in some way and that this alone is sufficient to explain the discrepancies noted previously when measuring Na+ flux and short-circuit current in Cl- -containing medium. The possible physiological importance of this transient transport function is discussed.

Animals↗
PubMed1981

Studies of the immune response against a polyoma virus-induced fibrosarcoma in BALB mice using the Winn's tumor neutralization assay.

Rejection of a polyoma-virus induced fibrosarcoma was studied by the adoptive tumor neutralization assay. This assay showed that polyoma immune spleen cells had a specific growth inhibiting effect on admixed polyoma tumor cells; they only delayed the tumor growth of an irrelevant cell line. We provide evidence both for the role of T-cells in this rejection and for a possible participation of macrophages. T-cells action was not strictly H-2 restricted but H-2 preference was observed. Adoptive protection of nude mice showed that T-cells of the recipient did not participate in the reaction.

Animals↗
PubMed1981

Differential sensitivity of T and B cell areas in mouse lymph nodes to exogenous cortisol. A histomorphometrical study.

Intraperitoneal injection of a single high dose of cortisol acetate into young adult BALB/c mice resulted in severe prolonged involution of the axillary lymph nodes, which started to regenerate only three weeks later. Histological and histomorphometrical analysis revealed that cortisol-induced lymphocyte depletion and diminution of lymph nodes was more pronounced in its B cell areas than in the paracortical T cell areas. Lymphocyte-depleted areas in the outer cortex i.e. in the B cell compartment, were characterized by a persisting diffuse reticular framework. Lymphocyte depletion in the paracortex resulted in partial transformation of its normal diffuse structure into "paracortical cords" with intervening patent sinuses. It was concluded that 1) T cell areas in mouse lymph nodes are more resistant to exogenous cortisol than B cell areas, and 2) paracortical cords may be interpreted as basic tissue units of the paracortical area in the mouse lymph node.

Animals↗
PubMed1981

[The dendritic structure of the habenula in the albino mouse].

The habenular complex of adult albino mice is studied with the Golgi method. In the medial habenular nucleus 2 neuronal types were distinguished; one of them is restricted to a small near to the commissura habenularis. The principal neuronal type is characterized by complicated dendritic ramifications and the presence of dendritic glomeruli encapsulated by protoplasmic astroglial membranes. In the lateral habenular nucleus three neuronal types were found, all of them with long, poorly ramified dendrites, but differing with respect to the size of their somata and their dendritic profiles. Thus, concerning their dendritic structure, the two regions of the habenula do not show any similarity.

Axons↗
PubMed1981

[Critical study of immunological assessment in cancer patients (author's transl)].

Immunological assessment of cancer patients has been suggested following the hypothesis of immune surveillance in cancer proposed by Burnet. This short review demonstrates that this hypothesis has not been confirmed by experimental data, this discrepancy with Burnet's hypothesis raising doubts as to the value of immunological assessment in cancer. Critical analysis of the various tests used shows that no specific test is currently available and that the value of non-specific tests is questionable. Finally, the analysis of more than eight thousand tests showed that they are of little aid in diagnosis, prognosis, or prediction of relapse, but that these tests could be useful in the follow-up of immunomodulation. Nevertheless, the availability of analysis of lymphocyte subpopulations by monoclonal antibodies could prove to be a new tool in the follow-up of these patients.

Antibodies, Monoclonal↗
PubMed1980

[A thermosensitive inhibitor of the replication of polyomavirus, an extract from BHK2I cells transformed by the Tsa mutant of this virus].

BHK21 cells transformed by wild type or Ts3 mutant polyoma virus contain an inhibitor of polyoma virus replication when grown at permissive (36 degrees C) as well as non-permissive temperature (39 +/- 0.5 degrees C). Cells transformed by the Tsa mutant contain the inhibitor at the permissive but not at the non-permissive temperature. The inhibitor reappears in the latter cells however, upon shift from the non-permissive to the permissive temperature. If a reversible protein inhibitor (methionyl-adenylate, reversible inhibitor of the aminoacyl-t-RNA synthetase) is applied during the temperature shift experiments, the inhibitor does not reappear indicating that new protein synthesis is required for the recovery of its activity.

Animals↗
PubMed1980

[Comparative induction of viral antigen synthesis in various types of cells infected by polyoma virus].

Induction of synthesis of the viral antigens T and V during polyoma virus infection was studied in primary Mouse and Hamster kidney and brain cultures, as well as in various types of human cells. The results show that: (1) Despite a very low percentage of positive cells by immunofluorescence, Hamster brain cells produced more viral antigen than kidney cells, as opposed to what was found in Mouse brain cells. (2) Most human cells produced neither T nor V antigens. Conversely, a large number of brain cells synthesized the T antigen very early after infection.

Animals↗
PubMed1980

Aggregation of small oligonucleosomal chains into 300-A globular particles.

Chicken erythrocyte oligonucleosomes (trimers to about 20-mers) are able to interact with each other through the very lysine-rich histones (H1 and H5) and form heterogeneous globular particles with a mean diameter of about 300 A. These particles assemble spontaneously during micrococcal nuclease digestion of chromatin in the presence of 30 mM NaCl and contain approximately 25 nucleosomes. They are sensitive to ionic strength and unfold at lower salt concentrations but can be reconstituted by restoring the initial salt concentration. Even at 30 mM NaCl, the particles remain dynamic structures, being in equilibrium with their oligonucleosomal components as revealed by the fact that particle stability depends on the concentration of oligonucleosomes.

Animals↗
PubMed1980

[Significance of arthrography of the knee joint (author's transl)].

A survey on the double-contrast arthrographie of the knee is given. Speical problems of the method and the interpretation of the films are presented. Besides the delineation of the pathological alterations of the menisci, which is possible in about 85 to 95%, the possibility of delineation of other knee joint damage is discussed, their significance being far beyond that of the meniscal lesions. At last the post-operative changes of the knee joint following meniscectomy are summarized including the evaluation of plain films and repeat arthrography. Own investigations on 117 meniscectomized patients are presented. 35 patients had symptoms, on 23 of them a repeat arthrography could be performed. The symptoms could essentially be explained by meniscal remnants and degeneration of the cartilage at the operated site of the knee.

Arthritis↗
PubMed1980

[Immune competence before and after curative radiotherapy in breast cancer (author's transl)].

The level of non-specific immune response was evaluated in 409 operable breast cancer patients by a battery of classical tests performed at least before and after treatment. We propose a synthetic classification of the various tests into 5 categories (from I 1 to I 5) of growing pejorative weight for a rapid and better understanding between the laboratory and the clinicians and also for overall comparison in time. With this type of evaluation the percentage of patients exhibiting depressed immune response was 14 per cent initially and rose to 39 per cent at the end of irradiation. Six months later, however, only 3 per cent of the patients had an immune assessment lower than the initial level. The pronounced immune depression observed by other authors concerned mainly patients having undergone post-operative irradiation after removal of the breast. The curative treatments used here in the hope of avoiding radical breast surgery was performed under much different ballistic, biological and psychological conditions which should be taken into account before condemning the dangers of this method.

Adult↗
PubMed1979

In vivo opiate binding unchanged in tolerant/dependent mice.

The in vivo receptor binding was measured for an opiate agonist and antagonist in the brains of naive mice and of mice made tolerant to and dependent on opiates by morphine pretreatment. There was significant differences between the receptor binding of these substances in the naive and in the tolerant/dependent animals. However, these differences disappeared 8 h after interruption of the morphine supply, although tolerance showed no decline. Therefore, the differences in the binding were obviously not produced by changes in the opiate receptors related to tolerance. Rather, the differences were probably caused by morphine in the brain of the tolerant/dependent mice pretreated with morphine and disappeared because the concentration of the morphine in the brains of these animals dropped during abrupt withdrawal. The fact that tolerance persisted for hours beyond this time indicated that tolerance is a time-dependent phenomenon, not directly dependent on receptor occupation by an agonist.

Animals↗
PubMed1979

Stimulation by HCO3- of Na+ transport in rabbit gallbladder.

Bicarbonate presence in the bathing media doubles Na+ and fluid transepithelial transport and in parallel significantly increases Na+ and Cl- intracellular concentrations and contents, decreases K+ cell concentration without changing its amount, and causes a large cell swelling. Na+ and Cl- lumen-to-cell influxes are significantly enhanced, Na+ more so than Cl-. The stimulation does not raise any immediate change in luminal membrane potential and cannot be due to a HCO3(-)-ATPase in the brush border. The stimulation goes together with a large increase in a Na+-dependent H+ secretion into the lumen. All of these data suggests that HCO3- both activates Na+--Cl- cotransport and H+--Na+ countertransport at the luminal barrier. Thiocyanate inhibits Na+ and fluid transepithelial transport without affecting H+ secretion and HCO3(-)-dependent Na+ influx. It reduces Na+ and Cl- conentrations and contents, increases the same parameters for K+, causes a cell shrinking, and abolishes the lumen-to-cell Cl- influx. It enters the cell and is accumulated in the cytoplasm with a process which is Na+-dependent and HCO3(-)-activated. Thus SCN- is likely to compete for the Cl- site on the cotransport carrier and to be slowly transferred by the cotransport system itself.

Animals↗
PubMed1979

Opiate antagonist--receptor interaction unchanged by acute or chronic opiate treatment.

The apparent pA2 of naloxone, a measure of the apparent receptor affinity for the antagonist, was estimated in naive rats, in rats after acute and various schedules of chronic morphine pretreatment, and in rats during abrupt withdrawal. The results were adjusted to compensate for the amount of pretreatment drug in the rat brains as, otherwise, such a drug could have inflated the apparent pA2 values (see appendix). After this adjustment, a tendency of the apparent pA2 values to be increased after chronic pretreatment disappeared. The apparent pA2 of naloxone in acutely pretreated rats was also unchanged from that in naive rats, while the results in abruptly withdrawn rats were ambiguous. Thus, no change in the affinity of the antagonist for opiate receptors was found and theories suggesting that a conformational change takes place in the opiate receptor during the development of tolerance/dependence could not be supported.

Analgesia↗