[Lysozyme--an enzyme of both historical and current interest as a therapeutical agent]. / Lysozym--ett enzym av historiskt och åter aktuellt intresse som läkemedel.

Lysozyme, a bacteriolytic protein discovered by Fleming in 1922 and found to be phylogenetically ancient and almost ubiquitous among living organisms, is probably the most studied enzyme in biology and medicine. Evidence of its involvement in resistance to bacterial infection is compelling but remains indirect. Muramyl peptides (fragments of bacterial cell wall peptidoglycan) exert many effects on the immune system and the CNS, and appear to contribute to non-specific resistance to infection, fever, fatigue, and the pathogenesis of bacterial infection. Synthetic muramyl peptide analogues are currently used as adjuvants in vaccine trials in humans. Several pathological conditions are associated with changes in lysozyme concentrations, and egg-white lysozyme treatment has been tried on a small scale. With the cloning of the human lysozyme gene in yeast cells the enzyme can now be produced on a large scale, which will enable its therapeutic applications to be evaluated.

Lymphoid organs in sturgeons (Acipenseridae).

Lymphoid (lymphomyeloid) tissues in sturgeons (hybrid sturgeon, Huso huso X Acipenser ruthenus, and white Pacific sturgeon, A. transmontanus) were investigated by dissection, histology and transmission electron microscopy. The main lymphomyeloid tissues are the thymus, the spleen, the anterior part of the kidney, the meningeal myeloid tissue, the pericardial tissue and lymphoid masses of the intestine, especially in the spiral valve. The kidney is the main hemopoietic tissue. The meningeal tissue is bone marrow-like (myeloid), mainly granulopoietic, but it also contains lymphoid elements. The pericardial tissue is predominantly lymphoid. The pericardial tissue has a lymph node-like appearance. It seems to be the site of interaction between lymphocytes and vascular endothelium. The thymus contains cortex and medulla. The spleen, as in higher vertebrates, is differentiated into white and red pulp. The highly diversiform and well developed lymphoid tissues of sturgeons may serve as basis of efficient immune mechanisms.

Plasma cells in adult Atlantic hagfish, Myxine glutinosa.

Hagfishes, the most primitive vertebrates, are of special interest for the evolution of immune responses. Eptatretus stoutii, the Pacific hagfish, is able to mount cellular and humoral immune responses but all attempts to demonstrate in them the presence of plasma cells have failed. In the present study we demonstrate for the first time plasma cells identifiable by ultrastructural criteria in the pronephros, a primitive lymphohaemopoietic organ, of Myxine glutinosa, the Atlantic hagfish.

Structural studies on lymphomyeloid tissues of the dogfish, Scyliorhinus canicula L.

The structure and ultrastructure of the lymphomyeloid epigonal and Leydig organs of the dogfish Scyliorhinus canicula L. were investigated. The tissues produce leucocytes, mainly granulocytic cells, but also some lymphocytes and plasma cells. Lymphocytes sometimes form nodule-like aggregations, especially in the epigonal organ. Granulocytes are probably stored within the lymphomyeloid tissues and enter the circulation on maturation. They may also release biologically active substances into the blood.

On the adrenergic system of ganoid fish: the beluga, Huso huso (chondrostei).

The adrenergic system of the beluga, Huso huso, was studied by glyoxylic acid fluorescence histochemistry, analyses of catecholamine content in various organs and studies of the effects of acetylcholine and adrenaline on isolated strip preparations from blood vessels, spleen, atrium and ventricle. Chromaffin cells were found mainly in the walls of the posterior cardinal veins, and to some extent also in the wall of the celiaco-mesenteric artery. The plasma concentration of adrenaline was high enough to affect the contraction force of the isolated atrial and ventricular strips, thus adding an adrenergic component to a possible cholinergic inhibitory vagal control of the heart. Fluorescence histochemistry revealed no direct adrenergic innervation of the heart, but blood vessels in the heart and elsewhere received a rich supply of adrenergic nerve terminals. Adrenaline contracted the celiaco-mesenteric artery and the spleen, and produced positive inotropic effects on the paced atrial and ventricular strip preparations. Acetylcholine contracted the ventral aorta and the celiaco-mesenteric artery, and reduced the contraction force of paced ventricular and, especially, atrial preparations. It is concluded that the beluga has a well developed adrenergic system consisting of both chromaffin cells and adrenergic neurons with varicose nerve terminals of the type found in the higher vertebrates.

Autonomic nerve control of the swimbladder of the goldsinny wrasse, Ctenolabrus rupestris.

The autonomic nerve control of the swimbladder of the goldsinny wrasse has been studied by experiments with isolated strips from the muscularis mucosae, drug effects on gas secretion in vivo, fluorescent histochemistry and quantitative analysis of catecholamine content. Vagotomy, atropine and mecamylamine significantly inhibited induced gas secretion, suggesting a cholinergic vagal secretory innervation of the gas gland. The anterior part of the mucosa (secretory part) is contracted by acetylcholine and alpha-adrenoceptor agonists. These responses are competitively antagonized by atropine and phentolamine or yohimbine respectively. The posterior (resorbent) part of the mucosa is contracted by acetylcholine, but beta-adrenoceptor agonists relax the acetylcholine-precontracted preparations. These responses are competitively blocked by atropine and propranolol respectively. The pA2-values from all experiments with antagonists are well comparable with values obtained for the same drugs in other teleost or mammalian tissues. Tyramine, 5-hydroxytryptamine or phenylephrine had mixed effects on the posterior part. This effect is at least in part due to release of nervously stored catecholamines. Fluorescent histochemistry revealed a strong innervation by both smooth and varicose adrenergic fibres in all parts of the swimbladder, noradrenaline being the dominant catecholamine. Yellow fluorescent cells, which may contain 5-hydroxytryptamine, were also seen in the swimbladder mucosa. No conclusive evidence for a cholinergic innervation of the muscularis mucosae was obtained.