Enkephalin analogs with various C-terminal modifications have been synthesized to evaluate the corresponding structural elements in the opioid receptors. The carboxyl group of the C-terminal leucine5 or glycine5 was converted into the mercaptomethyl (-CH2SH) and hydroxymethyl (-CH2OH) groups, starting from leucinthiol or leucinol for Leu5-derivatives and from cysteamine or ethanolamine for Gly5-derivatives. Interactions of synthetic peptides with the opioid receptors were examined by the radioligand receptor binding assays using rat brain and tritiated enkephalin analogs. The data suggest that the C-terminal carboxyl group in enkephalins is important, but not electrostatically, for interaction with delta-opioid receptors. With leucinthiol-enkephalin in biological assays which examine its inhibitory activity for electrically stimulated contractions of isolated smooth muscle, it was found that the reactive thiol group exists in the mu receptors present in the guinea pig ileum. Leucinthiol-enkephalin became bound covalently to this receptor-thiol group via disulfide formation after prolonged incubation.

Affinity Labels↗

PubMedDate not supplied

Cell surface C-reactive protein of rainbow trout lymphocytes.

C-reactive protein (CRP) expressed on rainbow trout (Oncorhynchus mykiss) lymphocytes was investigated to determine what role CRP might have on lymphocyte function. C-reactive protein was detected on the surface (S-CRP) of 25% of peripheral blood lymphocytes (PBL) and 4% of head kidney lymphocytes (HKL) by flow cytometry of cells labelled with biotinylated rabbit anti-rainbow trout CRP IgG and fluorescent-coupled avidin. Purified CRP, when added to cells in culture, bound to both PBL and HKL. Stimulation of PBL and HKL by concanavalin A, phytohemagglutinin, or lipopolysaccharide increased the percentage of S-CRP-positive cells, which suggests the production of CRP by lymphocytes. Treatment of lymphocytes with anti-rainbow trout CRP IgG and complement decreased the number of S-CRP-positive cells.

Acute-Phase Reaction↗

PubMedDate not supplied

Activation of rainbow trout (Oncorhynchus mykiss) phagocytes by muramyl dipeptide.

Immunoenhancing activity of synthetic muramyl dipeptide (MDP) was investigated in relation to the activation of rainbow trout (Oncorhynchus mykiss) phagocytes and to nonspecific protection against challenge with the fish pathogen Aeromonas salmonicida. Head kidney phagocytes collected from MDP-injected fish showed significant chemotactic activity against zymosan-activated normal rainbow trout serum, and phagocytic activities against both A. salmonicida and plastic beads. The MDP-activated phagocytes also showed enhanced superoxide generation. When normal phagocytes were exposed to supernatants of phagocyte or peripheral blood lymphocyte cultures of MDP-injected fish, the cells showed significant chemotactic activity, indicating that the MDP-activated cells produced phagocyte-activating factor. Injection of MDP to fish provided protection against challenge with virulent A. salmonicida.

Acetylmuramyl-Alanyl-Isoglutamine↗

PubMedDate not supplied

Inhibition of phagocytosis by rainbow trout (Oncorhynchus mykiss) macrophages by botulinum C2 toxin and its trypsinized component II.

Botulinum C2 toxin (C2T) is composed of two nonlinked protein components, components I and II. The toxin reconstituted with component I and trypsinized component II inhibited phagocytosis of rainbow trout (Oncorhynchus mykiss) and mouse macrophages. Inhibition in both cell types was observed over a range of toxin concentrations that were not toxic to the cells. Because cytoplasmic action of rainbow trout macrophages is ADP-ribosylated by component I, the inhibition of phagocytosis in trout cells by C2T is probably due to inactivation of cytoplasmic actin. Moreover, phagocytosis by trout cells was also inhibited in a dose-dependent manner by trypsinized component II alone, and did not cause cell death. The present results show that the macrophages of aquatic vertebrates are susceptible to C2T, and that trypsinized component II elicits a novel biological activity by binding to the cell membrane of the macrophages.

Actins↗

PubMedDate not supplied

Suppression of T lymphocyte proliferation by peritoneal macrophages in chickens.

The mechanism of the suppression of lymphocyte proliferation by peritoneal macrophages (MPs) in chickens and the presence of a suppressive substance in the culture supernatant of MPs were studied. The results showed that gelatin- and peptone-induced peritoneal MPs had an inhibitory accessory function against blastogenesis of mitogen-stimulated splenic lymphocytes and that resident peritoneal MPs had an enhanced accessory function. The suppressive factor produced by gelatin-induced peritoneal MPs is a protein having a pI of 3.6 and a molecular weight of 64,000 and it is physically and chemically a relatively stable substance. Moreover, it has no cytotoxic effect against lymphocytes and it was verified that the suppressor in the culture supernatant of MPs was not prostaglandin E2 or alpha-acid glycoprotein.

Animals↗