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Biomedical subjects

J van Marle

Publications and source records attributed to J van Marle.

70 records · Page 4Linked to original sources
PubMed1984

Inhibition of the glutamate uptake in the excitatory neuromuscular synapse of the locust by delta-philanthotoxin; a component of the venom of the solitary wasp Philanthus triangulum F. A high resolution autoradiographic study.

Glutamate uptake in insect neuromuscular junctions is inhibited by delta-philanthotoxin. Two other components of the philanthus venom (beta- and gamma-philanthotoxin) do not affect this glutamate uptake. No synergism between the active delta-philanthotoxin and the two inactive components had to be assumed to explain the inhibition by the Philanthus venom.

Animals↗
PubMed1984

Radioactive choline uptake in the isolated rat phrenic nerve-hemidiaphragm preparation. A biochemical and autoradiographic study.

When hemidiaphragms are stimulated via the phrenic nerve in the presence of 10 microM radioactive choline (Ch), the rate of radioactive Ch uptake in the endplate-rich area (EPA) is greater than that in the endplate-poor muscle (M). Ch uptake in the EPA is temperature-dependent, with a Q10 of 2.9 and an activation energy of 19.5 kcal/mol. It is inhibited in a Na+-depleted medium, in the absence of Ca2+, and by 10-20 microM hemicholinium-3 (HC-3) and it is not inhibited by alpha-bungarotoxin even when the muscle is completely paralyzed. In the absence of stimulation the rate of uptake in the EPA is slightly, but not significantly, greater than in M. Using autoradiography, we find an enhanced amount of isotope in the nerve terminals and their immediate vicinities compared with the muscle fibres, in both stimulated and unstimulated hemidiaphragms. There is no enhanced uptake of isotope into the nerve terminals in stimulated tissues in the presence of 26 microM HC-3. The uptake of isotope into the muscle is not altered by any of these treatments. There is a positive correlation between the initial rate of radioactive Ch uptake in the EPA and the amount of isotope in the nerve terminals (the mean corrected grain density above the nerve terminals). Without correcting for the large amount of diffusion that occurs, the ratio of the grain density above the synapses to that above the muscle fibres is 1.66 in tissue stimulated at 1 Hz, 1.04 in stimulated tissues in the presence of 26 microM HC-3, and 1.31 in unstimulated tissues.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1982

Estrogen receptors in human breast cancer. II. Correlation between the histochemical method and biochemical assay.

The present study defines criteria for determining the presence of estrogen-receptors in human breast carcinomas demonstrated by a histochemical assay using 17 beta-estradiol-carboxy-methyl-oxim-bovine serum albumen-FITC. The criteria were: 1) the percentage of cells showing fluorescence; 2) the intensity of the fluorescence observed, and 3) the percentage of epithelial structures in tissue specimens. Using these predefined criteria in 132 human breast carcinomas as 91.6% agreement was found between the results of the histochemical assay and those of the biochemical Charcoal method. The main causes of disagreement (7 of the 11 cases) were sampling errors between the tissue specimens used for the histochemical and biochemical assay, and an insufficient percentage of epithelial structures (less than 15%) to allow biochemical identification of estrogen receptor activity. In the hands of pathologists with experience of the field of histochemistry this histochemical assay may be the method of choice for the assessment of estrogen receptors.

Adult↗
PubMed1982

Estrogen receptors in human breast cancer. I. Specificity of the histochemical localization of estrogen receptors using an estrogen-albumin FITC complex.

An investigation of the specific localization of estrogen receptors in frozen sections of mammary tumors using an estrogen-BSA-FITC complex is presented. The results are discussed in relation to the existing literature. Although the fluorescence is certainly not due to interaction with type I receptors, the reaction is not as non-specific as is suggested sometimes in the literature. It is likely that type II receptors are involved, which are probably localized at the same site as type I receptors.

Animals↗
PubMed1981

Deglycyrrhizinised liquorice (DGL) and the renewal of rat stomach epithelium.

Deglycyrrhizinised liquorice (DGL) stimulated proliferation in the forestomach of the rat but did not stimulate and possibly even inhibited proliferation in the glandular part. DGL increased the number of fundus glands in which labelled mucus secreting cells occur as well as the total number of labelled mucus cells per gland. The mechanism of action proposed for DGL is that DGL stimulates and/or accelerates the differentiation to glandular cells as well as mucus formation and secretion. The accelerated proliferation observed in the forestomach is ascribed to an improved environment in the stomach as a consequence of the enhanced mucus secretion under the influence of DGL.

Animals↗
PubMed1979

Hormonal effects on rat mammary gland in vitro.

The mammogenic and lactogenic effect of various hormones on rat mammary gland has been studied in vitro using an organ culture technique. The effects have been assessed mainly by light microscopy. The study has been confined mainly to the effects and interactions of the lactogenic protein hormones, corticosteroids and progesterone. It establishes the importance of the presence of insulin and serum and of the type of serum for the hormonal effects in vitro. These effects have been studied mainly on the explants obtained from 13 days pregnant rats. In addition explants from non-pregnant rats and at various stages of pregnancy and lactation were studied.

Adrenal Cortex Hormones↗
PubMed1976

Influence of the foetus, placenta and ovary on the mammotrophic activity of pregnant rat serum.

Serum mammotrophic activity was assayed using an organ culture technique with histological endpoints. Using sera of 13 days pregnant rats with 1 to 18 conceptuses, activity was detectable even in the presence of 1 conceptus, but the activity with 1-4 conceptus(es) tended to be less than with 6-18. Serum of rats with 1-3 conceptus(es) was approximately 2-4 times less active than serum of rats with 14 conceptuses. Removal of the conceptuses on day 15 caused loss of mammotrophic activity of the serum, tested 4 days later. When the foetuses, the ovaries or both the foetuses and ovaries were removed on day 15 of pregnancy, mammotrophic activity was present in the serum collected 4 days later. Differences in activity between the treated groups were small. The mammotrophic activity was comparable to the activity of serum of untreated 15 days pregnant rats or 19 days sham-operated pregnant rats. Explanted single fragments of a 19 days pregnant rat placenta released activity into the medium. The placenta retained this capicity even when the foetus had been removed 4 days previously.

Animals↗
PubMedDate not supplied

Ultrastructural evidence for a triple structure of the lateral element of the synaptonemal complex.

This study describes composition and localization of several substructures of the synaptonemal complex (SC) using different techniques. The techniques which were used were surface spreading, critical point drying of isolated SCs, and sectioning of Lowicryl embedded testis material. The lateral elements (LEs) of the SC appear to be composed of three lateral substructures: two morphologically identical major strands and a third strand which is considerably thinner. The thinner strand is localized on the inner side of the two major strands of the lateral element. In late pachytene/early diplotene stages when the SC starts to disintegrate more than three strands can be observed in the LEs. A model is presented and the function of the different substructures is speculated upon.

Animals↗
PubMedDate not supplied

A placebo-controlled study on the efficacy of aspirin and doxycycline in preventing clogging of biliary endoprostheses.

Sixty patients in whom a biliary endoprosthesis was inserted were randomized to receive: (1) placebo, (2) aspirin, or (3) doxycycline, to study the effect on the process of sludge formation. After 2 months all endoprostheses were changed, and the amount and composition of the sludge in the patent stents was analyzed. Half of the patients dropped out. The major component (56%) of the sludge of all groups was protein. No insoluble residue was present. Major deposits of sludge were found at irregularities in the stent wall (side flaps). Both doxycycline and aspirin reduced the dry weight of the sludge. Doxycycline significantly reduced the amount of protein, but scanning electron microscopy still showed abundant bacterial growth. Aspirin reduced the content of all sludge components including protein, suggesting that it decreases "stickiness" of bile. Surprisingly, doxycycline significantly decreased the death rate in the 2 months of the study. We present further evidence for a primary role of protein deposition in the early stages of stent occlusion. This process can be partly inhibited by doxycycline and probably also by aspirin, which could lead to a significant increase in stent patency.

Aspirin↗
PubMedDate not supplied

Morphometric analysis of the vestibular sensory epithelia of young adult rat.

The appearance of vestibular sensory cells and their progressive development has been the subject of many ontogenetic studies. Because deteriorating hair cells are supposed to play a role in balance disorders of the elderly, the final stage of development (i.e. senescence) has been investigated as well. It is generally assumed that the number of hair cells in crista ampullaris, saccule and utricle slowly but steadily decreases with age. However, actual data covering the period between maturation and senescence are scarce. In the present study, rat vestibular epithelia were labeled for actin and tubulin. Morphology was inspected from immediately after weaning until the age of 12 months. Although, postnatal development was no part of this study some data on one day old epithelia are presented for comparison. At postnatal day 1, hair bundles are still shorter than in mature sensory organs, the width of the zonula adherens is less, and the apical cross-sectional area of the epithelial cells is smaller. After one month, maturation is complete. Total cell density is 400-500 per 0.01 mm2, both in the otolith maculae and in the cristae ampullares. During the first year after maturation, no changes in epithelial morphology were observed and cell density remains constant.

Actins↗