Cephalopod myocardial receptors: Pharmacological studies on the isolated heart ofSepia officinalis (L.)

Summary This paper presents a synopsis of the information available about the pharmacological action of various substances on the cephalopod heart, with special emphasis on the central heart ofSepia officinalis. Threshold concentrations, EC₅₀ values and maximum effective concentrations have been experimentally determined. Studies with various transmitter substances, analogous compounds and antagonists have led to the following picture: Acetylcholine is the natural inhibitory transmitter substance; it acts via receptors with nicotinic properties which can be blocked by d-tubocurarine and -bungarotoxin. The probable excitatory transmitter system is represented by a noradrenergic innervation. Noradrenaline has a positive inotropic and a positive chronotropic action on in vitro heart preparations. A positive inotropic response can also be evoked by serotonin (5-HT); this effect is not due to stimulation of the catecholamine receptor, as is shown by cross-over experiments with specific blocking agents. Furthermore, a peptidergic receptor system has been described which reacts with the molluscan cardioactive peptide FMRF amide most effectively. It is assumed that cardioactive peptides may reach the central heart in the circulating blood; the sites of synthesis and release are still unknown. Possibly the NSV-layer of the vena cava is involved in hormonal cardiovascular regulation processes.     

Attosecond real-time observation of electron tunnelling in atoms

Atoms exposed to intense light lose one or more electrons and become ions. In strong fields, the process is predicted to occur via tunnelling through the binding potential that is suppressed by the light field near the peaks of its oscillations. Here we report the real-time observation of this most elementary step in strong-field interactions: light-induced electron tunnelling. The process is found to deplete atomic bound states in sharp steps lasting several hundred attoseconds. This suggests a new technique, attosecond tunnelling, for probing short-lived, transient states of atoms or molecules with high temporal resolution. The utility of attosecond tunnelling is demonstrated by capturing multi-electron excitation (shake-up) and relaxation (cascaded Auger decay) processes with subfemtosecond resolution.     

Chemical studies on the silver staining of nucleoli

The uptake of Ag-ions by isolated nucleoli of rat liver cells was studied. Nucleolar proteins separated by electrophoresis were examined for selective silver-staining. A mechanism for preferential Ag-staining of the nucleoli is discussed.     

Total atresia of the ovaries ofTilapia leucosticta (Cichlidae) after intoxication with the insecticide Lebaycid

Summary Intoxication with sublethal Lebaycid concentrations led to total atresia of the ovaries in 90% of the treated specimens ofTilapia leucosticta. The gonads were filled with atretic follicles and mature eggs were never found. In regeneration trials, intoxicated fish proved to be unable to spawn for at least 9 weeks.This work was undertaken with the aid of Prof. Dr E. Kulzer.     

Comparative ultrastructural and cytochemical analysis of the cephalopod systemic heart and its innervation

Summary The present knowledge of the morphology of cephalopod central hearts is presented. The cytological characteristics of the epicardial, myocardial and endothelial tissue layers are reviewed. Myocardial cells are characterized as obliquely striated myocytes with a high level of oxidative metabolism. The voluminous myocardium is intensively penetrated by nerve fibers controlling the myogenic heart rhythm by different chemical transmitter systems. Catecholaminergic fluorophores and acetylcholinesterase activity could be localized by means of histochemical and cytochemical investigations. A glio-interstitial cell system is shown to be present in connection with nerve fibers and also uncombined between heart muscle cells. Its content of large different-sized inclusions is described and their function discussed.     

The peripheral innervation of the heart ofEledone moschata demonstrated by histofluorescence microscopy

Summary A fluorescence histochemical investigation of the cardiac nerves ofEledone moschata has demonstrated that they contain catecholamines. This suggests that the cephalopod heart is supplied by a double innervation, where cholinergic and aminergic mechanisms work antagonistically. This is similar to the vertebrate cardiac innervation and therefore represents a convergent evolution.     

In vivo inhibition of citrate cleavage enzyme by polychlorinated biphenyls

Summary Polychlorinated biphenyls (Aroclor 1254, PCB) administered in the diet (0.01%, w/v) to rats inhibited citrate cleavage enzyme. The results suggest that the decreased activity might in part account for decreased fatty acid synthesis in the livers of PCB-treated rats.This research was supported by a grant from the National Institutes of Health (ES-00040). Aroclor 1254 was a gift of Monsanto Company, St. Louis, Missouri, USA.