MHC class Ib-restricted CTL provide protection against primary and secondary Listeria monocytogenes infection

Infection of B6 mice with the intracellular pathogen Listeria monocytogenes (LM) results in the activation of CD8(+) T cells that respond to Ag presented by both MHC class Ia and class Ib molecules. Enzyme-linked immunospot analysis reveals that these CTL populations expand and contract at different times following a primary sublethal LM infection. Between days 4 and 6 postinfection, class Ib-restricted CTL exhibit a rapid proliferative response that is primarily H2-M3 restricted. The peak response of class Ia-restricted CD8(+) T cells occurs a few days later, after the majority of bacteria have been cleared. Although class Ia-restricted CTL exhibit a vigorous recall response to secondary LM infection, we observe limited expansion of class Ib-restricted memory CTL, even in MHC class Ia-deficient mice (B6.K(b-/-)D(b-/-)). Despite this lack of enhanced expansion in vivo, class Ib-restricted memory CTL retain the ability to proliferate and expand when provided with Ag in vitro. Furthermore, we demonstrate that in vivo depletion of CD8(+) T cells in LM-immune B6.K(b-/-)D(b-/-) mice severely impairs memory protection. Together, these data demonstrate that class Ib-restricted CTL play an important role in clearing a primary LM infection and generate a memory population capable of providing significant protection against subsequent infection.     

Ascorbate inhibits edema in brain slices

Ascorbate is an essential antioxidant in the CNS, localized predominantly in neuronal cytosol. Slices of mammalian brain rapidly lose ascorbate, however, when incubated in ascorbate-free media; brain slices also take up water and swell. Here we investigated water gain in coronal slices of rat forebrain incubated with and without ascorbate for 1-3 h at 34 degrees C. Slices progressively gained water in ascorbate-free media, with a significant 12% water increase after 3 h at 34 degrees C, compared with the water content of slices after a 1-h recovery period at 24 degrees C, immediately following slice preparation. Inclusion of 400 micro M ascorbate in the medium led to an increase in tissue ascorbate content and prevented water gain at 34 degrees C. By contrast, water gain was not inhibited by isoascorbate or thiourea, which are antioxidants that are not accumulated in brain cells. The oxidant H2O2 enhanced water gain, whereas a cocktail of NMDA and non-NMDA receptor blockers inhibited edema formation to the same extent as ascorbate. These data demonstrate that brain edema, linked to glutamate-receptor activation, can result from intracellular oxidative stress and that this can be prevented by ascorbate.     

NMR evidence for differential phosphorylation‐dependent interactions in WT and ΔF508 CFTR

The most common cystic fibrosis (CF)‐causing mutation in the cystic fibrosis transmembrane conductance regulator (CFTR) is deletion of Phe508 (ΔF508) in the first of two nucleotide‐binding domains (NBDs). Nucleotide binding and hydrolysis at the NBDs and phosphorylation of the regulatory (R) region are required for gating of CFTR chloride channel activity. We report NMR studies of wild‐type and ΔF508 murine CFTR NBD1 with the C‐terminal regulatory extension (RE), which contains residues of the R region. Interactions of the wild‐type NBD1 core with the phosphoregulatory regions, the regulatory insertion (RI) and RE, are disrupted upon phosphorylation, exposing a potential binding site for the first coupling helix of the N‐terminal intracellular domain (ICD). Phosphorylation of ΔF508 NBD1 does not as effectively disrupt interactions with the phosphoregulatory regions, which, along with other structural differences, leads to decreased binding of the first coupling helix. These results provide a structural basis by which phosphorylation of CFTR may affect the channel gating of full‐length CFTR and expand our understanding of the molecular basis of the ΔF508 defect.     

Leg position learning by an insect. I. A heat avoidance learning paradigm

A new learning paradigm which employs a natural aversive stimulus, tightly constrains learned behavior and demonstrates learning in individual animals is described. Locusts were restrained so that only the femoro-tibial joint of a single metathoracic leg was free to move. Animals were required to maintain a particular range of femoro-tibial joint angle to avoid heating of the head. The position of the tibia was sampled by an on-line computer which set the limits of joint angle and controlled the aversive stimulus while storing data for further analysis. Control animals received patterns of aversive stimuli identical to those received by experimental animals but independent of their own joint position. Quantitative evaluation of the learned behavior of individual animals allowed the identification of three different behavioral strategies by which learning was achieved.     

Discrimination of a colony stimulating factor subclass by a specific receptor on a macrophage cell line

Utilizing the high affinity interactions between pure ¹²⁵I-L cell colony stimulating factor and its receptor(s) on the murine macrophage cell line J774, a murine radioreceptor assay (RRA) has been developed. The murine RRA selectively detects a colony stimulating factor (CSF) subclass (CSF-1) previously defined by murine radioimmunoassay (RIA) (E.R. Stanley, Proc. Nat. Acad. Sci., USA, 76:2969–2973 ('79)). CSF-1 stimulates macrophage production exclusively, and the occurrence of the CSF-1 receptor(s) appears to be restricted to cells of the mononuclear phagocytic system (L.J. Guilbert and E.R. Stanley, J. Cell Biol. 85:153–160 ('80)). The murine CSF-1 RRA failed to detect a variety of other CSF subclasses, growth factors, and hormones. In contrast to data obtained with the murine CSF-1 RIA, human CSF-1 (e.g., human urinary CSF) is detected by the mouse CSF-1 RRA almost as sensitively as murine CSF-1. In addition, there was an absolute correlation between CSF-1 levels determined by murine CSF-1 RRA and those determined by a human CSF-1 RIA for a variety of human CSF-1 sources. The murine CSF-1 RRA is a sensitive (sensitivity 5 units or 1.0 femtomole of CSF-1 protein), rapid, and highly specific assay for CSF-1 in both murine and human sources.