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Biomedical subjects

G Meyer

Publications and source records attributed to G Meyer.

At least 451 records · Page 25Linked to original sources
PubMed1979

Tumorigenic clones of hamster brain cells transformed in vitro by polyoma virus. Ultrastructural and immunohistochemical study.

The morphological characteristics of three clones of hamster brain cells transformed in vitro by polyoma virus and of the tumors obtained after subcutaneous grafting of these cells in syngenic animals are reported. These clones appeared to be glial in nature by light and electron microscopy. The initial tumors induced by the three clones presented astrocytic features both by electron microscopy and immunohistochemistry. Analysis of the subsequent in vivo passages showed a decrease in cell differentiation, which was accompanied by a decrease in the latency period; after 2 years of serial transplantation, the tumors seemed poorly differentiated gliomas. A control cell line of hamster cerebellar cells evolved similarly.

Animals↗
PubMed1979

Post-natal development of amiloride sensitive sodium transport in pig distal colon.

1. Both electrophysiological properties and unidirectional Na and Cl fluxes have been determined across distal colons taken from pigs during early post-natal development. 2. The transmural potential difference (Vms) was 5 mV in the new-born and 10 mV in the 4 day old colon. The short circuit current (Scc) showed a three to sixfold increase during the first 10 days of post-natal life. The microvillar membrane potential (Vm) fell from about -45 mV in the new-born to -40 mV in the 4 day old colon. 3. Amiloride had no effect on Vms, Scc or Vm, measured in the new-born animal. It reduced Vms and Scc, caused a hyperpolarization of Vm and increased the microvillar membrane/basolateral membrane resistance ratio (Rm/Rs) in colons taken from older animals. 4. The Scc of distal colons taken from new-born and 1 day old pigs was only half that predicted from unidirectional measurements of Na flux. This discrepancy, which could not be completely accounted for by net CL absorption, disappeared in the older animals. 5. Net transport of Na doubled during the first 24 h of post-natal life. Part of this transport took place through an amiloride sensitive, non-electrogenic, pathway. 6. It is suggested that Na uses mainly a non-electrogenic pathway to cross the mucosa of the new-born pig. This pathway is replaced by an electrogenic amiloride sensitive mechanism in older animals. Aldosterone is thought to initiate these changes in Na tranport.

Amiloride↗
PubMed1979

Bone bonding through bioadhesives: present status.

Until recently use of adhesives was confined to cases in which glued areas could be pre-treated or at least cleaned. Thus, grease or oil contaminated surfaces could not be joined together by glueing. More recently, some adhesives have been developed which allow previous treatment of greasy surfaces to be avoided. Among these we find epoxy resins, acrylics and polyurethances. These adhesives have been used until now in various industries. We have begun a research program with these products and in aiming to design an adhesive which would enable immediate and strong bone bonding and avoid problems of metallic fixation, this study is a continuation of our previous research. Thus we tested - currently available surgical and dental adhesives - original mixtures developed in our laboratory. Mechanical assays were performed on bone samples from human femurs in different conditions : dried, cleaned, fresh, or after immersion in physiological solution. They consist essentially of tensile tests on Lhomargy and Zwick's machine wherein the stress is directed perpendicular to the interface. Variations of tensile strength (in h bar) are related to hardening time and to mixture composition. The specimens are joined together either in monolayers or in multilayers. The use of adequate catalysts ensures setting at room temperature. Torsion tests and fatigue tests are carried out concomitantly. Standardized bevel fermoral osteotomies were performed on mice with a dental saw after I.P. Nembutal anesthesia in order to test biological tolerance : - for the control group we study the evolution of bone repair after circumferential wiring - for the animals under test, bones are glued together with one of the proposed adhesives. Radiological and histological studies (using classical Azantrichrome staining after demineralization) are carried out at regular time intervals. In the control animals particular attention is paid to the time course of the formation, constitution and evolution of callus. In the test animals, we can observe callus formation, bone growth into the adhesive material and glue resorption, and look for specific antigenic phenomena. Despite expected improvements, bone glueing remains a challenge and only restricted clinical applications can be proposed.

Adhesives↗
PubMed1979

[Pharmacokinetics of antineoplastic agents (author's transl)].

The general basis of pharmacokinetics are summarized with the clinical aims of a better utilisation of drugs by the application pharmacokinetic data. The subject is illustrated by some antineoplastic agents especially on high dose methotrexate regimens and clinical use of 5 FU. A pharmacokinetic model may be described with the first agent but for 5 FU no specific model has yet been demonstrated. Some examples of studies on adriamycin and cytosine arabinoside are then given.

Antineoplastic Agents↗
PubMed1979

[Cellular differentiation and malignant transformation (author's transl)].

The mechanisms and determination of differentiation of normal and cancer cells were compared by distinguishing them from the phenomena of regulation, retrodifferentiation and maturation. Reference is made to the laws of order in time and space which are superimposed on the common genetic code during the various types of differentiation. In conclusion, the particular mechanisms of malignant differentiation are discussed by taking melanoma and tumor formation by papova-viruses as examples.

Animals↗
PubMed1978

Neoplastic transformation of hamster brain cells in vitro by polyoma virus.

The transformation of cultivated hamster brain cells by polyoma virus is reported. The transformed cell line contained polyoma virus-specific nuclear, surface and transplantation antigens. Subcutaneous and intracranial inoculations revealed high tumorigenicity of the cells. Brain-specific S 100 protein was found in these tumors with immuno-peroxidase staining, suggesting that they were of a nervous nature. Both in vivo and in vitro, the cells had glial features as studied by phase contrast, light and electron microscopy. Type-H virus-like particles were found in the tumor cells and might have played a role in the viral transformation.

Animals↗
PubMed1978

[Microangiopathic anaemia with thrombocytopaenia. Cure following excision of an angioma of the small intestine (author's transl)].

The association of a mixed anaemia (by occult haemorrhage and microangiopathic haemolysis) with a thrombocytopaenia led to a search for a digestive angioma. Arteriography, followed by exploratory laparotomy with preoperative enteroscopy and frozen section histological examination, led to the discovery of a small bowel angioma (multiple phlebectasias) which was partially resected. A review of the literature emphasised the rarity of intestinal angiomas with thrombocytopaenia (Kasabach and Merrit syndrome) and forms a basis for the discussion of haematological abnormalities (intravascular coagulation, microangiopathic anaemia) which may be induced by such vascular malformations.

Adult↗
PubMed1978

Biological activities of solubilized surface antigens of embryonic and polyoma-virus-transformed cells.

Various antigenic activities of polyoma virus-transformed and embryonic mouse cells were retained after 3M KCl solubilization of surface components. Particularly, transplantation antigen (TSTA) demonstrated by homograft rejection, and surface (S) antigen, detected by inhibition of immunofluorescence on polyoma-virus-transformed mouse cells, could be demonstrated. The crude soluble extracts were partially purified by salting out with (NH4)2SO4. In the case of polyoma-virus-transformed cells, TSTA and a part of S antigen activity were found in the same fraction (60% (NH4)2SO4 saturation) while another part of S antigen was salted out at 80% saturation. By chromatography, S antigen activity was found in 2 zones for transformed cells and in one zone for embryonic cells. One of these zones was common to both cell extracts.

Animals↗
PubMed1978

Polyoma virus, as a model for viral skin carcinogenesis.

Polyoma virus is presented as the simplest model of transformation by a DNA virus. The three possible ways of virus/cell interaction are recalled: lytic infection, abortive infection and malignant transformation. Nuclear and surface antigenic modifications are also recalled as well as their possible correlation with the transformation mechanism. Lastly, in "in vivo" systems, we have tried to schematize the interactions of host and virus-induced tumour.

Animals↗
PubMed1978

[Quantitative age-dependent variations in dendritic spines in the hippocampus (CA1, CA3 and fascia dentata) of the albino mouse].

The dendritic spines of the apical and basal dendrites of pyramidal neurons in CA1 and CA3 and of granule cells in Fascia Dentata were investigated in 19 stages of age, from the 10th to the 190th postnatal day. The results were statistically evaluated. In CA1 and CA3 a first increase in the number of spines (with a maximum at 35 days) is followed by a subsequent decrease up to the 65th day and a further increase up to the 190th day. This developmental pattern is found in the apical dendrites of CA1 and CA3 in all its investigated segments. On the contrary the basal dendrites differ from this pattern. The spines in the Fascia Dentata show a rapid increase up to the 15th postnatal day followed by a slow but constant increase up the end of our study.

Aging↗
PubMed1978

[Psychological factors in the etiology of cancers: methodological problems (author's transl)].

There is a multiplicity of etiological factors in human cancer; psychic factors are probably neither the most important nor the most constant. Nonetheless, owing to the potential infinity of psychological variables, it is necessary to formulate hypotheses in an operational manner. The casuistic method allows a thorough clinical study of objective events, of the manner in which the patient lives them and, especially, of what they mean to him. Such an approach, however, has shortcomings which must be accepted: it cannot administer proof of the hypotheses it advances. The superiority of prospective methods over retrospective methods seems indisputable for there is no evidence that personality traits are not modified by the fatal threat of a serious illness. This criticism also holds for the modified retrospective methods, the so-called predictive methods. Research focussed on particular cancers with a study of limited psychological variables seems desirable.

Humans↗