Beta-adrenergic receptors in rat myocardium: direct detection by a new fluorescent beta-blocker.

A new fluorescent beta-blocker, 9-amino-acridin propranolol (9-AAP), was administered i.v. to rats. Multiple fluorescent 9-AAP binding sites were observed on cardiac muscle cells in frozen sections. Intensity and density of cardiac 9-AAP fluorescence were markedly reduced following pretreatment with (+/-)- and (-)-propranolol but not with (+)-propranolol. Our findings suggest that 9-AAP may label beta-adrenergic receptor sites in rat myocardium.     

Alpha- and beta-adrenergic receptors in rat myocardium membranes after prolonged ethanol inhalation

Summary After 3 weeks of continuous ethanol intoxication by inhalation, the maximal number and affinity of the -and -receptors of rat heart were unchanged. These data indicate that adrenergic receptor disturbances are not involved in the mechanism of chronic ethanol-induced triglyceride deposition in the heart.Acknowledgments. This work was supported by grants from the Institut National de la Santé et de la Recherche Médicale. We wish to thank Mr M. Clément for skilled technical assistance in performing chronic ethanol inhalation treatments.     

Direct evidence for pH-dependent Fc receptors on proximal enterocytes of suckling rat gut

Summary By means of an erythrocyte-antibody rosette technique, Fc receptors, functional at pH 6.0 but not at 7.2, were shown to be present on enterocytes isolated from duodenum and jejunum (but absent from ileum) of 12–20-day-old suckling rats.     

Direct evidence for pH-dependent Fc receptors on proximal enterocytes of suckling rat gut.

By means of an erythrocyte-antibody rosette technique, Fc receptors, functional at pH 6.0 but not at 7.2, were shown to be present on enterocytes isolated from duodenum and jejunum (but absent from ileum) of 12-20-day-old suckling rats.     

Beta-adrenergic blocking agents as potent antagonists of mescaline-induced contractions in the rat uterus

Summary In the isolated rat uterus, mescaline induces contractions that are notably antagonized by catecholamines, by -adrenergic stimulants and certain -adrenergic blocking agents as well as by chlorpromazine, amitriptyline and methysergide.     

Isometric relaxation in rat myocardium: load dependence and influence of caffeine

When caffeine plus calcium is added to the perfusing medium, isometric relaxation of rat myocardium is no longer affected by length changes occurring during the twitch. The dependence of isometric relaxation on the initial muscle length is still present and more pronounced after caffeine addition.     

Isometric relaxation in rat myocardium: Load dependence and influence of caffeine

Summary When caffeine plus calcium is added to the perfusing medium, isometric relaxation of rat myocardium is no longer affected by length changes occurring during the twitch. The dependence of isometric relaxation on the initial muscle length is still present and more pronounced after caffeine addition.     

Beta-adrenergic blocking agents as potent antagonists of mescaline-induced contractions in the rat uterus.

In the isolated rat uterus, mescaline induces contractions that are notably antagonized by catecholamines, by beta-adrenergic stimulants and certain beta-adrenergic blocking agents as well as by chlorpromazine, amitriptyline and methysergide.     

Tissue sodium and potassium: Direct detection in the electron microscope

Résumé Une nouvelle technique pour découvrir sodium et potassium en sections glacés de tissus biologiques est décrivée.     

Thiamine disulfide anhydride: A new fluorescent derivative of thiamine

Zusammenfassung Es wird die Isolierung eines neuen fluoreszierenden Thiaminderivates beschrieben.     

Inhibition of succinic oxidase activity of beef heart mitochondria by a new fluorescent metabolite,zoanthoxantin

Résumé La zoanthoxantine est un nouveau composé aromatique, très fluorescent, caractérisé par le chromophore 1,3,5,7-tétrazacyclopent[f]azulen. On démontre l'action inhibitrice de ce métabolite sur une préparation submitochondriale de cur de buf et le type d'inhibition en a été déterminé. On envisage, aussi la possiblité d'utiliser la zoanthoxantine comme indicateur moléculaire dans la zone d'inhibition.

---

---

We are indebted to Professor A. Azzi for helpful criticism and discussion.     

Inhibition of rat adjuvant arthritis by a new immunosuppressive agent rubidomycin

Résumé Un nouveau composé anthracyclique à propriétés antibiotiques et cytotoxiques, la Rubidomycine (Daunomycine), a été administré à des rats peu après injection intra-dermique d'adjuvant complet de Freund. Par comparaison avec un groupe témoin qui a été traité avec un autre antibiotique, la tétracycline, non réputé cytotoxique, on a constaté une réduction marquée des lésions systémiques et de l'arthrite de la maladie provoquée par l'adjuvant.

---

---

Work conducted during the tenure of a Nuffield Research Fellowship.

---

Junior Fellow, Medical Research Council.     

A new type of antiserum to thyrotropin-releasing hormone; detection of new TRH-immunoreactive cell groups in rat hypothalamus

Summary We produced a new type of antiserum to thyrotropin-releasing hormone (TRH) in rabbits. The immunogen is TRH-BSA, the production of which is based on the formation of an amide bond using carbodiimide (EDC). The specificity of the antiserum was assessed by enzyme immunoassay (EIA) and immunohistochemistry. When using the anti-TRH serum for immunohistochemistry in rat hypothalamus, new magnocellular groups were detected in the ventrolateral parts of the posterior hypothalamus and the dorsal parts of the third ventricle. Colchicine treatment was found not to be necessary to visualize perikarya containing TRH.     

Study by a rapid mixing method of the interaction between a fluorescent cholinergic agonist and membrane fragments rich in cholinergic receptors from Torpedo marmorata]

The analysis by stopped-flow of the interaction of fluorescent agonist (C5DACho1) with the acetylcholine receptor in its membrane-bound form reveals several kinetic steps: a fast one, in the millisecond range, associated with the binding of C5DACho1 to a high affinity state and a "medium" and "slow" one, the last one representing possibly an isomerisation of the receptor molecule towards the high affinity state.     

Intramitochondrial inclusions in maturing and senescent muscle cells of rat myocardium

Summary Intramitochondrial myelin-like structures were found in ventricular myocardial cells of the rat heart. These inclusions were found in both the first 2 postnatal weeks and in senescent stages. The origin of such myelin-like structures could be related to an age-dependent metabolic change, specifically to an inability to oxidize long-chain fatty acids described in both periods.Acknowledgment. This work was supported by grant No. 801/82 of CAICYT.     

Beta-adrenergic stimulation of androgen production by fetal mouse Leydig cells in primary culture

The responsiveness of fetal mouse Leydig cells to catecholamines (epinephrine, norepinephrine), a beta-agonist agent (L-isoproterenol) and hCG was investigated in vitro. Fetal Leydig cells when freshly isolated were unable to respond to L-isoproterenol (10(-5) M). However, L-isoproterenol, epinephrine and norepinephrine significantly stimulated androgen production by fetal Leydig cells after 24 h of primary culture. Androgen production was increased in both conditions and to a greater extent by hCG. Propranolol blocked the stimulatory effect of L-isoproterenol and epinephrine. It is concluded that catecholamines can regulate fetal testosterone biosynthesis.     

Calcium binding in chemically skinned fibers of rat myocardium during force development

Summary The amout of bound calcium and force were measured in chemically skinned rat myocardial fibers during isometric contraction at different concentrations of free Ca²⁺. The data obtained suggest that calcium binding by cardiac myofibrils is cooperative and probably depends on mechanical tension.The author expresses his gratitude to Dr V. I. Kapelko for valuable discussion of the experimental results.