Freeze-etched preparations of the ventricular surfaces of ependymal cells clearly reveal the presence of pinocytotic vesicles opening into the third ventricle and large vacuoles formed by broad cell projections. The density of the vesicular openings is approximately 20 per micron2. The ependymal cells in the median eminence of the frog are adjoined by tight junctions comprised of five to eight interconnected junctional strands, whereas near the median eminence in the mouse only one to two such strands form the tight junction of the ependymal cells. Gap junctions between the adjacent ependymal cells are detected near the median eminence in the mouse but not in the frog.

Animals↗

PubMed1977

Purification of histamine receptor, (III) Characterization of receptor rich membrane fraction of small intestinal smooth muscle of the cat.

Intracellular localization of histamine receptors in small intestinal smooth muscle of the cat was studied by investigating distribution of marker enzymes in the receptor rich fraction. Distribution of membrane markers coincided with that of the radiochemically labeled receptor fraction. Membrane fraction was further purified and it was concluded that the histamine receptor rich fraction is mainly composed of cell membrane. The chemical composition of the fraction lent support to this conclusion.

Adenosine Triphosphatases↗

PubMed1977

Purification of histamine receptor (V).--Assesment of the double labeling method--.

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Animals↗

PubMed1977

Purification of histamine receptor (VI). An improved double labeling method with "double protection".

Studies were done on the specific labeling of the histaminergic H1-receptor of the longitudinal smooth muscle of cat small intestine. A procedure involving 'double protection' combined with the double labeling technique was developed. The first protection was the usual with a protective antihistamine, promethazine, and the second was cross protection of non-specific sites with non-hitaminergic drugs, thioriazine and atropine. Muscle tissue protected with promethazine against non-radioactive dibenamine was treated with 3H-dibenamine in the presence of these second protectors. The second protectors covered non-receptor sites which had been protected from non-radioactive dibenamine with promethazine. The dose-response curves were carefully checked in each experiment to confirm that the second protectors did not interfere with the specific coverage provided by the first protector. Finally 14C-dibenamine was applied to measure non-specific binding after which the labeled muscles were fractionated and the radioactivity was counted. The specificity of labeling achieved in the receptor-rich fraction by this method is discussed.

Animals↗

PubMed1977

Purification of histamine receptor. (IV) Specificity of binding of various drugs to the histamine receptor-rich fraction and to solubilized binding sites.

Studies were made on tritiated histamine binding to the receptor-rich membrane fraction and solubilized sites and its displacement by various drugs. H1-Agonists and antagonists displaced histamine most effectively. A H2-agonist and atropine were less effective and propranolol, phentolamine and imidazole acetic acid had little effect. The solubilized binding sites showed the same specificity of binding as the membrane fraction. Membrane fragments had two binding constants, whereas solubilized sites had only one. Solubilized sites bound similar amounts of histamine and dibenamine: the latter was applied to intact tissue under conditions which would presumably cause specific binding to histamine receptors. These binding characteristics show that the method used was adequate for purification of histamine receptors from smooth muscle of cat small intestine.

Animals↗

PubMed1977