Comparison of thymocyte and T lymphocyte gangliosides from C3H/HeN and C3H/HeJ mice

Gangliosides have been prepared from resting murine thymocytes and splenic T cells. Profoundly different two-dimensional thin layer chromatography (2D TLC) patterns were observed between these two cell types. Thymocytes contained 28-30 discrete gangliosides of which eight represented major gangliosides. Splenic T lymphocytes from both strains had much simpler patterns, with six to seven major gangliosides and 12-13 minor gangliosides. Computerized analysis of the thymocyte ganglioside patterns between LPS-responder C3H/HeN mice and lipopolysaccharide (LPS)-hyporesponsive C3H/HeJ mice revealed no significant difference in the major gangliosides. However, with splenic T cell gangliosides, there is a striking difference in the relative proportion of three homologous gangliosides between the two strains. Consistent with previous observations on macrophage gangliosides, the ratio of N-acetylneuraminic acid-containing ganglioside to N-glycolylneuraminic acid-containing ganglioside was higher in both thymocytes and T-cells from the LPS-responder strain. These results show that sialic acid-containing glycolipids from thymocytes and T lymphocytes between endotoxin responder and hyporesponder strains manifest small but significant changes. These differences are present in unstimulated cell populations and may represent a manifestation of the Lps gene.     

Functional and morphologic studies of the adrenal cortex and kidney in ovine toxaemia of pregnancy

Functional and morphologic studies of the adrenal cortex and kidney have been carried out in pregnant sheep with spontaneous or dietary restriction-induced ovine toxaemia. It was found that proteinuria was an inconstant feature and no animal showed glomerular lesions analogous to those found in human preeclampsia; thus ovine toxaemia cannot be regarded as a precise experimental model for human toxaemia of pregnancy. The elevation of blood cortisol levels and the morphologic appearance of the adrenal zona fasciculata found in such animals suggest an adrenal response comparable to that caused by adrenocorticotrophic hormone. In addition, animals with severe disease showed evidence of stimulation of the renin-angiotensin-aldosterone system as reflected by elevated blood renin and aldosterone concentrations and raised renal juxtaglomerular indices. Ultrastructural changes in the adrenal zona glomerulosa and renal juxtaglomerular myoepithelioid cells in toxaemic animals resembled those described in non-pregnant sodium-depleted sheep. The finding of juxtaglomerular peripolar cell mitoses and granule exocytosis, the latter only being previously observed in sodium depleted sheep, together with the ultrastructural changes in the adrenal zona glomerulosa and juxtaglomerular myoepithelioid cells, suggest that sodium depletion may play a role in this disease.     

Preoperative gentling does not attenuate septal-lesion induced hyperreactivity

Rats were either gentled or not gentled for 10 minutes a day for 7 days. At the end of this time a lesion was made in the region ventral to the anterior septum or in the lateral septum, or the rat was given a sham lesion. Reactivity to the experimenter was tested at 2, 7, and 14 days postoperatively. The reactivity scores of animals gentled preoperatively were not different from those of animals which had not been gentled but the animals of both groups were significantly more reactive than animals given a sham lesion. It is concluded that preoperative handling does not attenuate the increase in defensive behavior induced by lesions of the lateral septum or of the region ventral to the anterior septum.     

Substantia nigra stimulation evoked antidromic responses in rat neostriatum

Summary Electrical stimulation of the substantia nigra of rats elicits a burst of small amplitude waves with a latency of 4–6 ms that may last for 10–15 ms throughout much of the neostriatum. Frontal cortex stimulation also elicits a burst response, which can occlude the substantia nigra response. The substantia nigra evoked burst response was still present after chronic neocortical ablation or thalamic transection or both treatments combined. The response corresponds to the first sharp negative wave of the substantia nigra evoked neostriatal field potential. Single substantia nigra evoked action potentials were recorded in neostriatum with a mean latency of 9.8 ms, ranging from 4–22 ms. These action potentials were considered to be antidromic because 1) they were occluded during appropriate collision intervals by orthodromic action potentials elicited by frontal cortex stimulation. Subthreshold frontal cortex conditioning stimulation did not alter the threshold for activation from substantia nigra. The refractory period for the axon was at least as long as that for the soma and ranged between 0.8–2.0 ms. The antidromic responses failed to follow low frequency stimulation (< 40 Hz for 3000 ms). This failure occurred in the axon between substantia nigra and globus pallidus. The burst response and first sharp negative wave of the field potential probably represent the antidromic activation of the ubiquitous and densely packed medium spiny neostriatal projection neurons. These responses 1) occur at the same latency, 2) respond in the same manner to twin pulse and repetitive stimulation and 3) are occluded by frontal cortex stimulation in the same manner as antidromic action potentials.     

Murine peritoneal macrophage gangliosides inhibit lymphocyte proliferation

Gangliosides have been shown to act as immunoregulatory agents by altering proliferative responses of lymphocytes to both antigens and mitogens. Most early studies have utilized brain gangliosides and have required high concentrations. The role of endogenous gangliosides from macrophages has remained unexplored. In this study, thioglycolate-elicited murine peritoneal macrophage gangliosides were purified and added to cultures of murine lymphocytes. Nanogram amounts caused a profound inhibition of LPS-induced DNA synthesis of splenocytes and of purified B lymphocytes, without demonstrable cellular toxicity. No effect was seen using asialo-GM1. This effect was present across a wide range of lipopolysaccharide (LPS) doses. Nanogram amounts of macrophage gangliosides also inhibited concanavalin A (ConA)-mediated lymphocyte proliferation. Inhibition of LPS-induced mitogenesis was present even if gangliosides were removed from the extracellular environment after 15-60 min of incubation prior to the addition of LPS. This inhibition was reversible with incubation of ganglioside pre-treated lymphocytes in medium containing serum. These inhibitory properties of macrophage gangliosides are distinct from those found in studies using brain gangliosides, and support a potential role for macrophage gangliosides as negative modulators of lymphocyte proliferation.     

Pulmonary endothelial cell killing by human neutrophils. Possible involvement of hydroxyl radical

Human blood neutrophils stimulated by a variety of agents were shown to have cytotoxic effects on bovine pulmonary artery endothelial cells. Effective agonists included immune complexes, opsonized zymosan and 12-O-tetradecanoyl phorbol acetate. Unstimulated human neutrophils and neutrophils stimulated with N-formyl-methionyl-leucyl-phenylalanine or with platelet-activating factor failed to induce significant killing even though secretory release of lysosomal enzymes occurred. In comparing the effects of the different agonists, endothelial cell killing showed a better correlation with the production of H2O2 than with the generation of O2-. Endothelial cell killing by stimulated human neutrophils was inhibited by catalase but not by soybean trypsin inhibitor or superoxide dismutase. Killing was also inhibited by two scavengers (N, N-dimethylthiourea and D-mannitol) of hydroxyl radical and by deferoxamine mesylate, an iron-chelator. Iron-saturated deferoxamine mesylate was significantly less effective in protecting the endothelial cells against killing. Agents that were protective against endothelial cell killing did not interfere with the generation of O2- in stimulated neutrophils. These results suggest that leukocyte-induced endothelial cell killing in vitro can be induced by some but not all agonists for neutrophils and that the killing is oxygen-dependent and may be directly due to hydroxyl radical production.