Tulane University

About: Tulane University is a education organization based out in New Orleans, Louisiana, United States. It is known for research contribution in the topics: Population & Blood pressure. The organization has 24478 authors who have published 47205 publications receiving 1944993 citations. The organization is also known as: University of Louisiana.

Physiological Mapping of Local Inhibitory Inputs to the Hypothalamic Paraventricular Nucleus

Abstract: Local inhibitory synaptic inputs to neurons of the rat hypothalamic paraventricular nucleus (PVN) were studied by using glutamate microstimulation and conventional intracellular and whole-cell patch-clamp recording in coronal, horizontal, and parasagittal slices of rat hypothalamus. PVN cells were classified as magnocellular or parvocellular neurons on the basis of electrophysiological and post hoc immunohistochemical analyses; GABA-producing neurons were localized with in situ hybridization. Glutamate microstimulation of different sites around the PVN evoked volleys of postsynaptic potentials in 43% of the PVN neurons tested. Some responses to stimulation at each site were blocked by bicuculline, suggesting that they were mediated by the activation of presynaptic GABA neurons. In the coronal plane, presynaptic inhibitory sites were located lateral to the PVN and ventral to the fornix, corresponding to the lateral hypothalamic area and the posterior bed nucleus of the stria terminalis (BNST). In the horizontal plane, presynaptic inhibitory sites were found rostral, lateral, and caudal to the nucleus, corresponding to parts of the anterior hypothalamic area, the posterior BNST, the medial preoptic area, and the dorsomedial hypothalamus. In the parasagittal plane, presynaptic inhibitory neurons were revealed at sites rostral and caudal to the nucleus, corresponding to the medial preoptic area and the dorsomedial hypothalamus, and in a site dorsal to the optic chiasm that included the suprachiasmatic nucleus. These presynaptic sites each contained GABA-producing neurons based on in situ hybridization with a glutamic acid decarboxylase riboprobe and together formed a three-dimensional ring around the PVN. Unexpectedly, both magnocellular and parvocellular neurons received inhibitory synaptic inputs from common sites.

Cross-Talk in the Innate Immune System: Neutrophils Instruct Recruitment and Activation of Dendritic Cells during Microbial Infection

Abstract: Type I inflammatory cytokines are essential for immunity to many microbial pathogens, including Toxoplasma gondii. Dendritic cells (DC) are key to initiating type 1 immunity, but neutrophils are also a source of chemokines and cytokines involved in Th1 response ignition. We found that T. gondii triggered neutrophil synthesis of CC chemokine ligand (CCL)3, CCL4, CCL5, and CCL20, chemokines that were strongly chemotactic for immature DC. Moreover, supernatants obtained from parasite-stimulated polymorphonuclear leukocytes induced DC IL-12(p40) and TNF-alpha production. Parasite-triggered neutrophils also released factors that induced DC CD40 and CD86 up-regulation, and this response was dependent upon parasite-triggered neutrophil TNF-alpha production. In vivo evidence that polymorphonuclear leukocytes exert an important influence on DC activation was obtained by examining splenic DC cytokine production following infection of neutrophil-depleted mice. These animals displayed severely curtailed splenic DC IL-12 and TNF-alpha production, as revealed by ex vivo flow cytometric analysis and in vitro culture assay. Our results reveal a previously unrecognized regulatory role for neutrophils in DC function during microbial infection, and suggest that cross-talk between these cell populations is an important component of the innate immune response to infection.

Growth Hormone (GH)-Releasing Peptide Stimulates GH Release in Normal Men and Acts Synergistically with GH-Releasing Hormone*

Abstract: The acute GH release stimulated by the synthetic hexapeptide, His-DTrp-Ala-Trp-DPhe-Lys-NH2 [GH releasing peptide (GHRP)], was determined in 18 normal men and compared with the effects of GH-releasing hormone, GHRH-(1-44)-NH2. Specificity of effect was assessed by measurement of serum PRL, LH, TSH, and cortisol. GHRP was administered at doses of 0.1, 0.3, and 1.0 microgram/kg by iv bolus. GHRH at a dose of 1.0 microgram/kg was administered alone and together with various does of GHRP. No adverse clinical effects of laboratory abnormalities were observed in response to GHRP. A side-effect of mild facial flushing of 1- to 3-min duration occurred in 16 of the 18 subjects who received GHRH-(1-44)-NH2. Mean (+/- SEM) peak serum GH levels after injection of placebo and 0.1, 0.3, and 1.0 microgram/kg GHRP were 1.2 +/- 0.3, 7.6 +/- 2.5, 16.5 +/- 4.1, and 68.7 +/- 15.5 micrograms/L, respectively. The submaximal dosages of 0.1 and 0.3 microgram/kg GHRP plus 1 microgram/kg GHRH stimulated GH release synergistically. Serum PRL and cortisol levels rose about 2-fold above basal levels only at the 1 microgram/kg dose of GHRP, and there were no changes in serum LH and TSH over the first hour after administration of the peptide(s). GHRP is a potent secretagogue of GH in normal men. Since GHRP and GHRH together stimulate GH release synergistically, these results suggest that GHRP and GHRH act independently. This supports our hypothesis that the GH-releasing activity of GHRP reflects a new physiological system in need of further characterization in animals and man.

Isolation and primary culture of murine alveolar type II cells.

Abstract: Previous attempts to culture mouse alveolar type II (ATII) cells have been hampered by limited purity and cell recovery. We have now obtained culturable ATII cells from female C57BL/6 mice at a purity of 92% +/- 3 (mean +/- SD; n = 20), with viabilities of 96% +/- 2 and total yields of 5.1 +/- 0.7 X 10(6) cells per mouse. Crude lung cell suspensions were prepared by intratracheal instillation of Dispase and agarose followed by mechanical disaggregation of the lungs. Crude cell suspensions were purified by negative selection using a biotinylated-antibody, streptavidin-coated biomagnetic particle system. Cell purities were determined by Pap staining and confirmed ultrastructurally. Purified ATII cells were cultured on fibronectin-coated chamber slides and maintained for up to 5 days in DMEM with 10% fetal bovine serum. Cultures exhibited minimal contamination by Clara cells, mesenchymal cells, or endothelial cells, and the epithelial nature of the cultures was confirmed by positive cytokeratin staining in at least 97% of the cells through day 5. Day 3 cultures demonstrated osmium tetroxide/tannic acid-stained granules consistent with lamellar bodies in 76% +/- 3.6 of the cells. The cultures displayed features distinct from those previously described for adult rat ATII cells, including irregularly-shaped cells and the formation of numerous cytoplasmic projections in direct contact with other cells. These studies indicate that excellent yields of highly purified, culturable ATII cells can be obtained from genetically defined mice. These techniques may provide powerful new models for the study of parenchymal lung disease in vitro.

Entry of exendin-4 into brain is rapid but may be limited at high doses

Abstract: OBJECTIVE: Peripherally administered exendin-4 is in clinical trials for the treatment of diabetes mellitus and obesity. Since its effects on food intake are mediated centrally, we determined the degree and type of its blood-to-brain penetration of the mouse blood–brain barrier (BBB). MEASUREMENTS AND RESULTS: High-performance liquid chromatography showed that exendin-4 was stable in blood, with most of the injected peptide reaching the brain intact. Capillary depletion studies with washout showed that the injected exendin-4 reached brain parenchyma rather than being trapped in the endothelial cells composing the BBB. Multiple-time regression analysis showed that exendin-4 crossed the BBB directly at a fast rate. The rapid brain entry of exendin-4, helped by its high lipophilicity as demonstrated by the octanol/buffer partition coefficient, was not dependent upon circumventricular organs and was not affected by food deprivation for 24 h. The simultaneous i.v. injection of high doses of unlabeled exendin-4 resulted in self-inhibition (saturation) that only became statistically significant (P<0.05) when the results of four experiments were combined; this suggests a possible limit to the amount of peripherally administered exendin-4 that can reach the brain after injection of high doses. CONCLUSION: The results indicate that exendin-4 is well conformed for exerting central effects involved in the control of obesity.