Influence of adrenergic agonists and antagonists on lymphokine secretion in vitro

Spleen cells of mice and lymph node lymphocytes of rats were cultured with epinephrine, norepinephrine and alpha- and beta-adrenergic drugs to determine effects on lymphokine secretion. After an incubation of 4.5 h it was found that the naturally occurring catecholamines and adrenergic drugs (isoprenaline, orciprenaline, terbutaline, norfenephrine, phenylephrine, clonidine, dobutamine) could induce the secretion of charge-changing lymphokines and lymphokines that stimulate the migration of lymphocytes. The beta-blocker propranolol inhibited the lymphokine secretion evoked by epinephrine and by beta-adrenergic agonists, whereas the alpha-blocker phentolamine antagonized the effects elicited by alpha-adrenergic drugs. Phenylethylamine also induced a significant secretion of lymphokines. Two non-phenylethylamines had no effect. The stimulatory capacity of adrenergic agonists, the inhibitory activity of the appropriate antagonists and the comparison with two non-phenylethylamines support the hypothesis on specific influence of catecholamines on the lymphocyte function.

Localization of growth hormone-releasing hormone in the human hypothalamus and pituitary stalk

The localization of the recently identified GH-releasing hormone (GHRH) in the human hypothalamus and pituitary stalk was determined by microdissection techniques and a specific RIA for GHRH. The highest concentrations of GHRH immunoreactivity (IR-GHRH) in the hypothalamus were found in the area of the infundibular nucleus (83 +/- 4 ng/mg protein; average +/- range). Lower quantities were found in other hypothalamic regions. Very high concentrations of IR-GHRH were present in the upper portion of the pituitary stalk (1454 +/- 48 ng/mg protein), and they decreased gradually toward the distal end of the stalk (21 +/- 3 ng/mg). This concentration gradient suggests that the peptide reaches the anterior pituitary mainly by way of the long portal vessels. Somatostatin, the second neuropeptide involved in the regulation of GH secretion from the anterior pituitary, had a pattern of distribution along the pituitary stalk very similar to that of IR-GHRH.

Growth hormone releasing factor-like immunoreactivity in human milk

The presence of immunoreactive growth hormone-releasing factor (GRF) in human milk has been demonstrated. By using sequential high performance liquid chromatography, it has been shown that most of the immunoreactivity co-elutes with the synthetic, hypothalamic-like, GRF (1-40). The concentrations of GRF detected (between 152 and 432 pg GRF/ml milk) exceed several fold its values in plasma.

Immunomodulation by some oligopeptides

The influence of bradykinin, some of its analogues, substance P and different partial sequences on lymphoid cells was studied under in vitro conditions. The oligopeptides bradykinin and substance P were found to be able to induce the secretion of charge-changing and chemokinetic lymphokines in very low concentrations. In each case, bell-shaped dose-response curves were registered in a concentration range from 10(-12) to 10(-6) M. An analysis of the lymphokine patterns suggests that T cells are the producer cells of charge-changing lymphokines. Comparing the structure-activity relationships of the peptides, the amino acid sequence Arg-Pro at the N-terminal region of bradykinin and substance P or Pro-Arg at the C-terminal part of tuftsin and rigin appear to be responsible for the lymphokine secretion.

Effects of muramyl dipeptide and trehalose dimycolate on resistance of mice to Toxoplasma gondii and Acanthamoeba culbertsoni infections

The effects of synthetic muramyl dipeptide (MDP) and natural trehalose dimycolate (TDM) against parasitic infections by intracellular Toxoplasma gondii and free-living Acanthamoeba culbertsoni were studied. Significant resistance against oral T. gondii infection was induced by intraperitoneal pretreatment with TDM but not with MDP. The protective effect of TDM against T. gondii was corroborated by a significant reduction in the number of cysts in brains of pretreated animals and elevated serum antibody levels. Partial protection against lethal intranasal A. culbertsoni infection was conferred by specific immunization with viable trophozoites of nonpathogenic Acanthamoeba lugdunensis. The nonspecific resistance induced by intravenous pretreatment with MDP was similar to, whereas that stimulated by TDM was lesser than the protection conferred by A. lugdunensis. The Fc receptor-mediated phagocytosis of 51Cr-labeled sheep red blood cells by alveolar macrophages was enhanced by MDP. The phagocytic activity of peritoneal macrophages was increased by lower doses of TDM.

Trehalose dimycolate from various mycobacterial species induces differing anti-infectious activities in combination with muramyl dipeptide

Significant resistance against influenza virus and Mycobacterium tuberculosis infections was induced when trehalose dimycolate from M. tuberculosis or M. bovis but not M. avium was combined with muramyl dipeptide. Trehalose dimycolate from M. tuberculosis, in contrast to that from M. avium, could confer resistance against Toxoplasma gondii infections.

High levels of vasoactive intestinal peptide in human milk

The presence of immunoreactive vasoactive intestinal peptide (VIP) in human milk has been demonstrated by high performance liquid chromatography and a specific radioimmunoassay. Immunoreactive VIP-like peptide co-eluted with the synthetic marker on a reversed phase C18 column. The levels of the neuropeptide ranged between 67 and 161 pg VIP/ml milk.

Immunoreactive and bioactive somatostatin-like material is present in tobacco (Nicotiana tabacum)

Immunoreactive and biologically active somatostatin-like material is present in extracts of tobacco plants (Nicotiana tabacum). Comparative chromatographic and immunological characterization of this peptide along with synthetic (hypothalamic-like) somatostatin-14 and -28, indicates that both molecular forms are present in the plant. Tobacco-somatostatin inhibits the prostaglandin E2-induced release of growth hormone from cultured anterior pituitary cells. This finding raises questions concerning the evolutionary mechanisms responsible for the presence of this neuropeptide in plants, and the physiological significance of this phenomena.