The enteric neural receptor for 5-hydroxytryptamine

An enteric neural receptor for serotonin (5-HT) has been characterized. This receptor was assayed, using 3H-5-HT as a radioligand, by rapid filtration of isolated enteric membranes and by radioautography. In addition, intracellular recordings were made from ganglion cells of the myenteric plexus. High affinity, saturable, reversible, and specific binding of 3H-5-HT was demonstrated both to membranes of the dissected longitudinal muscle with adherent myenteric plexus and the mucosa-submucosa. Radioautographs showed these 3H-5-HT binding sites to be in myenteric ganglia and in a broad unresolved band at the mucosal-submucosal interface. Antagonists active at receptors for other neurotransmitters than 5-HT, at either of the two known types of CNS 5-HT receptor, and at 5-HT uptake sites on serotonergic neurons failed to inhibit binding of 3H-5-HT. The structural requirements of analogues for binding to the enteric 5-HT receptor matched the known pharmacology of M or neural 5-HT receptors. A novel 5-HT antagonist was found. This compound, N-acetyl-5-hydroxytryptophyl-5-hydroxytryptophan amide (5-HTP-DP), antagonized the action of 5-HT on type II/AH cells of the myenteric plexus but did not affect the release or actions of acetylcholine (nicotinic or muscarinic) or substance P. 5-HTP-DP was also an equally potent displacer of 3H-5-HT from its binding sites on enteric membranes. It is concluded that the sites responsible for specific binding of 3H-5-HT are enteric M or neural 5-HT receptors. These receptors differ from those now known to be present in the CNS.     

IgG purification to measure the level of an iodinated thyroglobulin peptide, the 3,5,3',5' tetraiodo-l-tyrosyl-l-tyrosine in human serum

Antibodies reacting with 3,5,3',5' tetraiodo-l-tyrosyl-l-tyrosine (I2Tyr-I2Tyr) were elicited in rabbits by immunization with an oxidized yeast conjugate coupled with I2Tyr-I2Tyr. Ion-exchange chromatography was used to purify immunoglobulins, in order to improve the specificity in measurement of I2Tyr-I2Tyr level in patient serum. IgG binding capacity versus I2Tyr-I2Tyr was considerably increased after immunoglobulin purification.     

Communicating junctions between pillar cells in the gills of the atlantic hagfish,Myxine glutinosa

Summary In the respiratory lamellae of the gills of the atlantic hagfish,Myxine glutinosa, pillar cells are coupled by communicating junctions. It is suggested that these cells behave like a functional syncytium.Supported by the DFG, SFB 146. The authors are indebted to Drs F. Walvig and H. Stolte for kindly providing the hagfish. The expert technical assistance of G. Voss-Wermbter, Dipl.-Ing., and H. Heidrich is gratefully acknowledged.     

Gradient distribution pattern of muscarinic receptors in N1E 115 mouse neuroblastoma cells

The distribution pattern of muscarinic receptors in N1E 115 mouse neuroblastoma cells after linear and non-linear gradient centrifugation was investigated. In untreated cells, at least two forms of the receptors, with different densities, were found.     

The AA and ANA rat lines, selected for differences in voluntary alcohol consumption

The offspring of rats that voluntarily select larger quantities of alcohol are heavier consumers of alcohol than the offspring of rats that tend to avoid it. Such selective breeding, repeated over many generations, was used to develop the AA (Alko, Alcohol) line of rats which prefer 10% alcohol to water, and the ANA (Alko, Non-Alcohol) line of rats which choose water to the virtual exclusion of alcohol. In addition to demonstrating the likely role of genetic factors in alcohol consumption, these lines have been used to find behavioral, metabolic, and neurochemical correlates of differential alcohol intake. Some of the line differences that have been found involve the reinforcing effects of ethanol, the changes in consumption produced by alcohol deprivation and nutritional factors, the behavioral and adrenal monoamine reactions to mild stress, the development of tolerance, the accumulation of acetaldehyde during ethanol metabolism, and the brain levels of serotonin. It is hoped that these studies will lead to a better understanding of the genetically-determined mechanisms that influence the selection of alcohol.     

Deficiency of kallikrein-like enzyme activities in cerebral tissue of patients with alzheimer's disease

Summary We examined the changes in the intracerebral activities, at the time of postmortem autopsy, in patients with Alzheimer's disease. When compared with the control group, the activity of kallikrein-like enzyme was significantly decreased, while prolyl endopeptidase activity increased, in the patients group. Aprotinin inhibited 50% of the activity of the former enzyme at 2×10^–7M. Taken together with the results of a multivariate study, the above findings may indicate that intracerebral kallikrein deficiency plays an important role in the pathogenesis of Alzheimer's disease.     

Immunohistochemical localization of glutamine synthetase in human liver

Glutamine synthetase (GS) of human liver was recognized with a polyclonal antibody to pig brain GS, but failed to stain with an antibody against rat liver GS. Using the latter antibody GS of human liver was shown to be localized within small rings of 1 to 3 hepatocytes surrounding the terminal hepatic venules. This pattern was analogous to that seen in rat and mouse liver.     

Absence of immunosuppression in DBA/2 mice vaccinated with Trypanosoma cruzi treated with actinomycin-D

The subcutaneous (s.c.) vaccination of DBA/2 mice with 4 weekly doses of 3 x 10(7) living metacyclic forms of T. cruzi, Y strain, obtained from culture in axenic medium and treated for 24 h with actinomycin-D (50 micrograms/10(7) parasites), a drug that promotes an irreversible blockade of the parasite replication, do not induce any detectable degree of humoral and cellular immunosuppression as assessed by a) the production of anti-SRBC antibodies, b) the permanence of delayed cutaneous reaction to T. cruzi antigen, to PPD and DNCB and c) the degree of blastogenic transformation of spleen lymphocytes in the presence of the specific antigen.