Estrogen increases proenkephalin messenger ribonucleic acid levels in the ventromedial hypothalamus of the rat

The effects of estrogen on proenkephalin (PE) gene expression were measured in neurons of the ventromedial hypothalamus. Slot blot hybridization analysis indicates that the levels of PE mRNA in the ventromedial hypothalamus of ovariectomized rats increase 3.1-fold after 2 weeks of estrogen replacement. In situ hybridization reveals that the estrogen-inducible enkephalinergic neurons are located in the ventrolateral aspect of the ventromedial nucleus, a subnucleus known to contain many estrogen-concentrating neurons. The increase in PE mRNA levels is due to both a 63% increase in the number of detectable PE mRNA-containing neurons and a 2.0-fold increase in the levels of PE mRNA per enkephalinergic neuron (1.63 x 2.0 = 3.3-fold overall induction). This estrogen-regulated enkephalinergic cell group may represent part of the neural network mediating estrogen's effects on reproductive behavior and/or other neuroendocrine processes.     

Left handed �� helix models for mammalian prion fibrils

We propose models for in vitro grown mammalian prion protein fibrils based upon left handed beta helices formed both from the N-terminal and C-terminal regions of the proteinase resistant infectious prion core. The C-terminal threading onto a β-helical structure is almost uniquely determined by fixing the cysteine disulfide bond on a helix corner. In comparison to known left handed helical peptides, the resulting model structures have similar stability attributes including relatively low root mean square deviations in all atom molecular dynamics, substantial side-chain-to-side-chain hydrogen bonding, good volume packing fraction, and low hydrophilic/hydrophobic frustration. For the N-terminus, we propose a new threading of slightly more than two turns, which improves upon the above characteristics relative to existing three turn β-helical models. The N-terminal and C-terminal beta helices can be assembled into eight candidate models for the fibril repeat units, held together by large hinge (order 30 residues) domain swapping, with three amenable to fibril promoting domain swapping via a small (five residue) hinge on the N-terminal side. Small concentrations of the metastable C-terminal β helix in vivo might play a significant role in templating the infectious conformation and in enhancing conversion kinetics for inherited forms of the disease and explain resistance (for canines) involving hypothesized coupling to the methionine 129 sulfur known to play a role in human disease.Key words: prion, amyloid fibril, domain swap, beta helix, computational biology     

A freeze-fracture study of the digestive tract of the parasitic nematode Trichinella

Freeze-fracture preparations of the esophagus and intestine of larvae and adults of the nematode Trichinella spiralis illustrate the distribution of intramembranous particles in membranes of a number of cell types, and several specializations were found. Esophageal glands are prominently linked by gap junctions, but gap junctions were not found between intestinal cells. Muscle cells of the esophagus have rectilinear arrays of particles, thought to be points of adherence of the muscles to the esophageal epithelium. Clusters of particles are associated with these arrays and particle-free areas (probably Z bodies) also occur. Intestinal cells have small particles in their microvilli, large particles in the cells' apical membranes, and intermediate size particles, similar to membranes of other cells, in the lateral and basal membranes. Apical smooth septate junctions and tricellular junctions occur between intestinal cells.     

Neuregulin 3 promotes excitatory synapse formation on hippocampal interneurons

Hippocampal GABAergic interneurons are crucial for cortical network function and have been implicated in psychiatric disorders. We show here that Neuregulin 3 (Nrg3), a relatively little investigated low‐affinity ligand, is a functionally dominant interaction partner of ErbB4 in parvalbumin‐positive (PV) interneurons. Nrg3 and ErbB4 are located pre‐ and postsynaptically, respectively, in excitatory synapses on PV interneurons in vivo. Additionally, we show that ablation of Nrg3 results in a similar phenotype as the one described for ErbB4 ablation, including reduced excitatory synapse numbers on PV interneurons, altered short‐term plasticity, and disinhibition of the hippocampal network. In culture, presynaptic Nrg3 increases excitatory synapse numbers on ErbB4⁺ interneurons and affects short‐term plasticity. Nrg3 mutant neurons are poor donors of presynaptic terminals in the presence of competing neurons that produce recombinant Nrg3, and this bias requires postsynaptic ErbB4 but not ErbB4 kinase activity. Furthermore, when presented by non‐neuronal cells, Nrg3 induces postsynaptic membrane specialization. Our data indicate that Nrg3 provides adhesive cues that facilitate excitatory neurons to synapse onto ErbB4⁺ interneurons.     

REDD1 Is Essential for Optimal T Cell Proliferation and Survival

REDD1 is a highly conserved stress response protein that is upregulated following many types of cellular stress, including hypoxia, DNA damage, energy stress, ER stress, and nutrient deprivation. Recently, REDD1 was shown to be involved in dexamethasone induced autophagy in murine thymocytes. However, we know little of REDD1’s function in mature T cells. Here we show for the first time that REDD1 is upregulated following T cell stimulation with PHA or CD3/CD28 beads. REDD1 knockout T cells exhibit a defect in proliferation and cell survival, although markers of activation appear normal. These findings demonstrate a previously unappreciated role for REDD1 in T cell function.     

A novel subtype of muscarinic receptor identified by homology screening

A new member of the protein superfamily of G-protein coupled receptors has been isolated by homology screening. By virtue of its homology with other muscarinic acetylcholine receptors and its ability to bind muscarinic specific antagonists, this muscarinic receptor subtype is designated M4. The M4 mRNA is preferentially expressed in certain brain regions. The existence of multiple receptor subtypes encoded by distinct genes in the brain has functional implications for the molecular mechanisms underlying information transmission in neuronal networks.     

Caspase-3/CPP32-like activity is not sufficient to mediate apoptosis in an IL-2 dependent T cell line

CTLL cells undergo apoptosis when cultured in the absence of IL-2. The IL-1-converting-enzyme (ICE)/ caspase family has been implicated as an integral component of some forms of apoptosis. Numerous members of the caspase family have been identified, and it appears as if caspase-3/CPP32 plays a critical role. Previously we demonstrated that ICE/caspase-1 expression increases in CTLL cells during apoptosis; however, inhibition of ICE activity did not abrogate apoptotic death. The purpose of this report is to determine if other members of the caspase family are involved in T cell apoptosis induced by growth factor starvation. We show that cytosolic CPP32-like activity, as measured by the cleavage of DEVD-pNA and poly(ADP-ribose) polymerase (PARP), increases during apoptosis following growth factor deprivation. Cytosolic CPP32-like activity is inhibited in cells treated with the broad spectrum ICE family inhibitor boc-aspartyl(OMe)-fluoromethylketone (D-FMK) and by VAD-FMK and DEVD-FMK which have greater specificity for CPP32-like ICE homologs; however, only the broad spectrum ICE inhibitor D-FMK inhibited apoptosis. Our results suggest that apoptosis induced by growth factor deprivation involves the caspase family, but increased CPP32-like activity is not sufficient to mediate apoptosis induced by IL-2 starvation.     

The blood-brain barrier in a reptile, Anolis carolinensis

An electron microscopic study was made of the ultrastructure and permeability of the capillaries in the cerebral hemispheres of the lizard, Anolis carolinensis. The brain of Anolis is vascularized by a loop-type pattern consisting exclusively of arteriovenous capillary loops. The ultrastructure of the endothelium and the arrangement of the various layers from the capillary lumen to the central nervous tissue is similar to that of mammals. The endothelial cells form a continuous layer around the lumen and are joined by tight interendothelial junctions. The basal lamina of the endothelium is also continuous and encloses pericyte processes. The cells of the nervous tissue rest directly on the basal lamina of the capillary and are separated from each other by a 200 Å space. Intravenously injected horseradish peroxidase (MW 40,000) and ferritin (MW 500,000) were used to study the permeability of the capillaries. The entry of horseradish peroxidase and ferritin into the intercellular spaces of the brain is restricted by the tightness of the interendothelial junctions. No vesicular transport of either tracer occurs; however, ferritin does enter the endothelial cells in vacuoles. No tracer molecules are present in the basal lamina, pericytes, or nervous tissue. The different responses of the endothelial cell to the tracers used in this study suggest that endocytotic activities of endothelial cells involve different processes. Vacuoles formed by marginal folds, vacuoles formed by endothelial surface projections or deep invaginations of the plasma membrane, 600–800 Å vesicles, and coated vesicles all seem to differ in the nature of the substances which they endocytose.     

IL-4 suppresses dendritic cell response to type I interferons

Cytokines play an important role in modulating the development and function of dendritic cells (DCs). Type I IFNs activate DCs and drive anti-viral responses, whereas IL-4 is the prototype of a Th2 cytokine. Evidence suggests that type I IFNs and IL-4 influence each other to modulate DC functions. We found that two type I IFNs, IFN-alpha and IFN-beta, stimulated a similar costimulatory profile in myeloid resting DCs. IL-4 suppressed the response of myeloid DCs to both type I IFNs in vitro and in vivo by impairing the up-regulation of MHC and costimulatory molecules and the production of cytokines, such as IL-6 and IL-15, and anti-viral genes, such as Mx-1, upon type I IFN stimulation. In dissecting the mechanism underlying this inhibition, we characterized the positive feedback loop that is triggered by IFN-alpha in primary DCs and found that IL-4 inhibited the initial phosphorylation of STAT1 and STAT2 (the transducers of signaling downstream of IFN-alpha and -beta receptors (IFNARs)) and reduced the up-regulation of genes involved in the amplification of the IFN response such as IRF-7, STAT1, STAT2, IFN-beta, and the IFNARs in vitro and in vivo. Therefore, IL-4 renders myeloid DCs less responsive to paracrine type I IFNs and less potent in sustaining the autocrine positive loop that normally amplifies the effects of type I IFNs. This inhibition could explain the increased susceptibility to viral infections observed during Th2-inducing parasitoses.