Homeostatic behavior of fast Fourier transform power in very low frequency non-rapid eye movement human electroencephalogram.

Basic research shows that the physiological and molecular mechanisms of very low frequency (<1 Hz) electroencephalogram (EEG) waves of non-rapid eye movement (NREM) sleep differ from those of the higher (1-4 Hz) delta frequencies. Human studies show that the across-NREM period dynamics of very low frequency and 1-4 Hz EEG also differ. These differences and the reported failure of very low frequency EEG power to increase after a night of total sleep deprivation raise the question of whether very low frequency EEG shows the other homeostatic properties established for higher delta frequencies. Here we tested the relation of very low frequency EEG power density to prior waking duration across a normal day and whether these low frequencies meet another criterion for homeostatic sleep EEG: conservation of power across a late nap and post-nap sleep. Data from 19 young adults recorded in four separate sessions of baseline, daytime nap and post-nap sleep were analyzed. Power density in very low frequency NREM EEG increased linearly when naps were taken later in the day (i.e. were preceded by longer waking durations). In the night following an 18:00 h nap, very low frequency power was reduced by roughly the amount of power in the nap. Thus, very low frequency EEG meets two major homeostatic criteria. We hypothesize that these low frequencies reflect the executive rather than the functional processes by which NREM sleep reverses the effects of waking brain activity.

Expression of intimin gamma from enterohemorrhagic Escherichia coli in Citrobacter rodentium.

The carboxy-terminal 280 amino acids (Int280) of the bacterial adhesion molecule intimin include the receptor-binding domain. At least five different types of Int280, designated alpha, beta, gamma, delta, and epsilon, have been described based on sequence variation in this region. Importantly, the intimin types are associated with different evolutionary branches and contribute to distinct tissue tropism of intimin-positive bacterial pathogens. In this study we engineered a strain of Citrobacter rodentium, which normally displays intimin beta, to express intimin gamma from enterohemorrhagic Escherichia coli. We show that intimin gamma binds to the translocated intimin receptor (Tir) from C. rodentium and has the ability to produce attaching and effacing lesions on HEp-2 cells. However, C. rodentium expressing intimin gamma could not colonize orally infected mice or induce mouse colonic hyperplasia. These results suggest that intimin may contribute to host specificity, possibly through its interaction with a receptor on the host cell surface.

Role of bacterial intimin in colonic hyperplasia and inflammation.

Enteropathogenic Escherichia coli (EPEC) cells adhere to gut epithelial cells through intimin alpha: the ligand for a bacterially derived epithelial transmembrane protein called the translocated intimin receptor. Citrobacter rodentium colonizes the mouse colon in a similar fashion and uses a different intimin: intimin beta. Intimin alpha was found to costimulate submitogenic signals through the T cell receptor. Dead intimin beta+ C. rodentium, intimin alpha-transfected C. rodentium or E. coli strain K12, and EPEC induced mucosal hyperplasia identical to that caused by C. rodentium live infection, as well as a massive T helper cell-type 1 immune response in the colonic mucosa. Mutation of cysteine-937 of intimin to alanine reduced costimulatory activity in vitro and prevented immunopathology in vivo. The mucosal changes elicited by C. rodentium were interferon-gamma-dependent. Immunopathology induced by intimin enables the bacteria to promote conditions that are favorable for increased microbial colonization.

Citrobacter rodentium infection in mice elicits a mucosal Th1 cytokine response and lesions similar to those in murine inflammatory bowel disease.

Citrobacter rodentium is a classically noninvasive pathogen of mice that is similar to enteropathogenic Escherichia coli (EPEC) in man. Following oral infection of young mice, the organism colonizes the distal colon, and within 1 week the colonic mucosa doubles in thickness and there is massive epithelial cell hyperplasia. Since T-cell responses in mouse models of inflammatory bowel disease (IBD) also cause epithelial hyperplasia, we have investigated the possibility that C. rodentium promotes similar T-cell responses in the mucosa, thereby increasing epithelial shedding, transmission, and replication of the organism. Beginning 6 days after infection, bacteria were observed to be in close association with the epithelial surface and were also visible scattered throughout the lamina propria and in the submucosa. There was a CD3(+)-cell infiltrate into the colonic lamina propria and epithelium as well as mucosal thickening and crypt hyperplasia. The majority of CD3(+) cells were CD4(+) and were not gammadelta+. Reverse transcription-PCR analysis of cytokines also revealed a highly polarized Th1 response (interleukin-12, gamma interferon, and tumor necrosis factor alpha) in the mucosa and a large increase in the epithelial cell mitogen keratinocyte growth factor. None of the changes were seen in mice inoculated with bacteria lacking intimin (which is necessary for colonization), but they were seen in mice inoculated with C. rodentium complemented with intimin from EPEC. This is the first example of a classically noninvasive bacterial pathogen which elicits a strong mucosal Th1 response and which produces pathology similar to that seen in mouse models of IBD, which is also characterized by a strong Th1 response. These results also suggest that the colonic mucosa responds in a stereotypic way to Th1 responses.

Regulation of T cell activation in vitro and in vivo by targeting the OX40-OX40 ligand interaction: amelioration of ongoing inflammatory bowel disease with an OX40-IgG fusion protein, but not with an OX40 ligand-IgG fusion protein.

OX40 is a member of the TNFR superfamily, and is found predominantly on activated CD4-positive T cells. In vitro an OX40-IgG fusion protein inhibits mitogen- and Ag-driven proliferation and cytokine release by splenocytes and lymph node T cells. In contrast, an OX40 ligand-IgG fusion protein enhanced proliferative responses. In normal mice, OX40-positive cells are observed only in lymphoid tissues, including Peyer's patches of the gut. In mice with hapten-induced colitis or IL-2 knockout mice with spontaneous colitis, OX40-positive cells are found infiltrating the lamina propria. Administration of the OX40-IgG fusion protein to mice with ongoing colitis (but not the OX40 ligand-IgG) ameliorated disease in both mouse models of inflammatory bowel disease. This was evidenced by a reduction in tissue myeloperoxidase; reduced transcripts for TNF-alpha, IL-1, IL-12, and IFN-gamma; and a reduction in the T cell infiltrate. Targeting OX40 therefore shows considerable promise as a new strategy to inhibit ongoing T cell reactions in the gut.

IL-4-regulated enteropathy in an intestinal nematode infection.

The relationship between intestinal pathology and immune expulsion of gastrointestinal nematodes remains controversial. Parasite expulsion is associated with intestinal pathology in several model systems and both of these phenomena are T cell dependent. Immune expulsion of gastrointestinal helminth parasites is usually associated with Th2 responses, but the effector mechanisms directly responsible for parasite loss have not been elucidated. In contrast, the intestinal pathology observed in many other disease models closely resembles that seen in helminth infections, but has been attributed to Th1 cytokines. We have used infection with the nematode Trichinella spiralis in mice defective for cytokines or their receptors to investigate cytokine regulation of both immunopathology and parasite rejection. Consistent with previous findings, we found that parasite expulsion is IL-4 dependent. Contrary to expectations, however, the enteropathy is not regulated by IFN-gamma but by IL-4. Moreover, abrogation of severe pathology in TNF receptor-defective animals does not prevent parasite expulsion. TNF is therefore involved in intestinal pathology in nematode infections, apparently under regulation by IL-4- and Th2-mediated responses. This work therefore not only reveals a novel interplay between IL-4 and TNF, but also that the IL-4-dependent protective response against the parasite operates by a mechanism other than merely the gross degradation of the parasite's environment brought about by the immune enteropathy.

Improved manufacture and application of an agarose magnetizable solid-phase support.

A simple, semiautomated, nonhazardous procedure for the production of a magnetizable solid-phase support (MSPS) has been developed based on the extrusion of molten agarose-iron oxide mixtures, which enables manufacture of a range of differently sized spherical agarose-iron oxide beads. This system has enabled scale-up of an original manufacture procedure and reproducible preparation of kg quantities of MSPS suitable for biomolecular purifications. An improved protocol for the isolation of plasmid DNA directly from cell lysates using this MSPS, derivatized with diethylaminoethyl (DEAE) groups, is reported. This involves a modified alkaline lysis, followed by adsorption to and elution from the support, yielding plasmid DNA of a purity comparable with, or better than, other methods of plasmid isolation. Using the same procedure, plasmid DNA can be isolated from bacterial cell culture volumes of 1.5 mL and 100 mL with equal efficiency and purity.