Non-peptide Substance Research Articles

Isolation and partial characterization of platelet aggregation inhibitors in the blood of dialyzed patients.

Platelet aggregation inhibitors were isolated from the blood of dialyzed patients by high-performance liquid chromatography. At least two inhibitors exist in the blood of dialyzed patients. These inhibitors not only inhibit platelet aggregation, but also suppress the chemiluminescence response of platelet. The chromatographic behaviors and the results of enzymatic digestion suggested that these inhibitors are relatively low molecular weight nonpeptidic substances.

Peptides: Pharmacological evidence for three forms of chemical excitability in cultured mouse spinal neurons

Intracellular recordings from mouse spinal neurons growing in monolayer culture were used to study the effects of opioid peptides and substance P on neuronal excitability. Three actions were observed: 1) transmitter-like actions, including a presumptive increase in Cl − conductance and a rapidly desensitizing excitation; 2) modulation of amino acid responses in the absence of, or independent of any other membrane effects; and 3) alteration in spike threshold in the absence of, or independent of any other membrane effects. All three types of effect were observed on the same cell. The same general classes of chemical excitability have been observed with a variety of non-peptide substances, indicating that the multiple effects of peptides are superficially not unique.

An improved method for estimating cholecystokinin in human serum.

Because of difficulties encountered in setting up radioimmunoassays for cholecystokinin (CCK) a sensitive and reliable biological method for estimating this hormone is still needed. The principles of such a biological technique and an improvement to it have already been described, but the serum levels of CCK reported were high and the technique required further refinement and validation. The strips of rabbit gall-bladder used to estimate the concentration of CCK increased in sensitivity to standard solutions of CCK over a 6--8 period before stabilizing, but a single sample of serum increased the sensitivity of the strips of gall-bladder to their maximum immediately. These two problems were eliminated by 'priming' the strips of gall-bladder by exposure to two serum samples before exposure to the standard solutions used for production of a dose--response curve. Thirdly, it was discovered that some non-peptide substances in serum possessed CCK-like activity; by extracting all the small peptides from serum with dextran-coated charcoal the residual activity could be measured and subtracted from the total CCK activity. Finally, the activity of CCK in the serum increased during processing before freezing. This increase was eliminated by taking the blood samples into aprotinin which has been shown to cause dramatic reduction in CCK activity in some experiments. When all these factors were taken into account and the technique suitably modified, the mean level of CCK in the serum of ten normal fasting subjects was found to be 28 milli Ivy Dog units/ml (2.4 pmol/ml), which is only one third of that reported previously.

Identification of a reactive arginyl residue in horse liver alcohol dehydrogenase

Summary One arginyl residue per subunit of horse liver alcohol dehydrogenase modified with [ 14 C] phenylglyoxal has been identified as Arg-84. A single radioactive peptide isolated from a chymotryptic digest of the labeled enzyme consists of the sequence Val-83 to Leu-92. This finding is consistent with those of previous chemical modifications and with the three-dimensional structure of the protein indicating that Arg-84 is in an unusual environment. Another radioactive fraction of the digest contains a non-peptide substance tentatively identified as phenylglycine that presumably derives from a labile derivative of a second arginine residue. The lability of this second arginine derivative may relate to its probable location at the active site of the enzyme.

Conformation of Met5-enkephalin determined by high field PMR spectroscopy

THE discovery by Hughes et al.1 that peptides (the enkephalins) could be the endogenous agonists of opiates in brain represents a challenge to medical chemistry both in its fundamental aspects and for the possible development of new therapeutic approaches. To understand how non-peptidic substances belonging to various chemical classes can mimic the action of the pentapeptide enkephalins it is first necessary to determine the spatial arrangement of the latter. We have thus synthesised large quantities of Met5-enkephalin (H–Tyr–Gly–Gly–Phe–Met–OH) and determined its preferential conformation in solution using high field proton magnetic resonance (PMR) spectroscopy at variable temperatures, coupling constants in relation with Karplus–Bystrov curves2 and conformational energy steric maps3.

“Secretory end-feet”—axon terminals of unusual cytological character and probable neuroglandular significance in Nereis (polychaeta; Annelida)

“Secretory end-feet” (or SEF) in Nereis are large axon terminals which end blindly on the posterior region of the brain floor. They are filled with large mitochondria which usually have a dense matrix and a high concentration of cristae. Prominent dense bodies are frequently found in the mitochondrial matrix and probably consist of lipid. SEF also contain “secretory vesicles,” with dense cores, that cluster adjacent to the basal lamina abutted by the terminals. Their contents are not depleted by reserpine, and give a negative reaction to histochemical tests for the ultrastructural localization of amines. SEF form regions of specialized cell contact (“scalariform junctions”) with neighbouring glial elements. SEF are thought to be highly active centres engaged in the secretion of a nonpeptide substance.