Behavioral origin of sound-evoked activity in mouse visual cortex.

Sensory cortices can be affected by stimuli of multiple modalities and are thus increasingly thought to be multisensory. For instance, primary visual cortex (V1) is influenced not only by images but also by sounds. Here we show that the activity evoked by sounds in V1, measured with Neuropixels probes, is stereotyped across neurons and even across mice. It is independent of projections from auditory cortex and resembles activity evoked in the hippocampal formation, which receives little direct auditory input. Its low-dimensional nature starkly contrasts the high-dimensional code that V1 uses to represent images. Furthermore, this sound-evoked activity can be precisely predicted by small body movements that are elicited by each sound and are stereotyped across trials and mice. Thus, neural activity that is apparently multisensory may simply arise from low-dimensional signals associated with internal state and behavior.

Neutrophil influx and chemokine production during the early phases of the antitumor response to the vascular disrupting agent DMXAA (ASA404).

5,6-Dimethylxanthenone-4-acetic acid (DMXAA) acts through tumor vascular disruption and cytokine production and is the first of its class to enter phase 3 trials. We characterized leukocytes and cytokines in murine Colon 38 tumors before and after DMXAA treatment. Tumor mass declined 50% 24 hours after DMXAA administration, but the leukocyte count per gram of tumor increased threefold owing to a large influx of Ly6G(+)CD11b(+)F4/80(-) cells with the morphology of neutrophils. However, B and T lymphocytes, natural killer cells, and macrophages in the tumor all decreased in numbers. Seven chemokines were substantially induced in the tumor, spleen, and serum 4 hours after DMXAA administration. Using cultured spleen cell subpopulations, CD11b(+) cells (largely monocytes and macrophages) were shown to be the primary producers of tumor necrosis factor alpha, interleukin 6 (IL-6), and macrophage inflammatory 1alpha (MIP-1alpha). CD49b(+) natural killer cells produced IP-10, whereas CD45R(+) B lymphocytes produced regulated upon activation normal T cell express sequence. T lymphocytes were not major producers of cytokines in the response to DMXAA. Murine peripheral blood leukocytes (PBLs) produced a similar panel of cytokines in culture to that detected in mouse serum after DMXAA treatment. Cytokines in human PBL cultures were subsequently measured with the aim of identifying potential serum markers of the human response to DMXAA. IP-10 (P < .001), monocyte chemoattractant protein 1 (P < .001), and sCD40L (P < .01) were decreased, whereas IL-8 (P < .001) and MIP-1alpha (P = .03) were increased in DMXAA-treated compared with untreated PBL cultures from a group of 12 donors.

A comparison of the ability of DMXAA and xanthenone analogues to activate NF-kappaB in murine and human cell lines.

DMXAA (5,6-dimethylxanthenone-4-acetic acid), the most potent of a series of xanthenone (XAA) analogues developed in this laboratory, is currently undergoing combination clinical trials as an antivascular agent for cancer treatment. XAAs have a complex mode of action, and in vitro assays that are predictive of in vivo antitumor activity have been difficult to develop. In this study, we have utilized a series including XAA, DMXAA, and mono-substituted XAA derivatives to determine firstly whether in vitro NF-kappaB activation of mouse cell lines predicts for the in vivo antitumor potential of this class of agents, and secondly whether the relative activity of these analogues is similar in murine and human cell lines. Electromobility shift assays were used to measure NF-kappaB activation in murine HECPP endothelial and 70Z/3 pre-B cells, and in human HPLNEC.B3 endothelial and Raji B-lymphoma cells. A significant correlation was obtained between NF-kappaB activation in HECPP cells by a series of XAA analogues at 100 microg/ml (r = 0.78, p = 0.008) and at 300 microg/ml (r = 0.75, p = 0.01) and the amount of hemorrhagic necrosis induced in Colon 38 tumors. Different structure-activity relationships were observed in human and murine cell lines. 8-MeXAA, which was inactive in HECPP and 70Z/3 murine cell lines, showed similar NF-kappaB activation to DMXAA in human HPLNEC.B3 cells and Raji B-lymphoma cells. These results suggest that the receptor protein(s) in human cells that mediate the human response may have a lower stringency to that for murine cells. We also noted differences in the dose-response relationships for NF-kappaB activation between lymphoid and endothelial lines that were species independent. With increasing concentrations of DMXAA, NF-kappaB activation in both murine and human lymphoid lines showed a reproducible fluctuation, while in endothelial lines, the intensity of NF-kappaB activation was relatively constant above a threshold concentration. The results demonstrate interspecies differences in the NF-kappaB response to XAA analogues, and may also reflect the complex nature of NF-kappaB regulation.

Induction of tumour necrosis factor and interferon-gamma in cultured murine splenocytes by the antivascular agent DMXAA and its metabolites.

The induction of haemorrhagic necrosis by 5,6-dimethylxanthenone-4-acetic acid (DMXAA) in transplantable murine tumours depends on the in situ synthesis of cytokines, particularly tumour necrosis factor (TNF). Since the in vivo action of DMXAA would be greatly clarified by the development of an in vitro model, we investigated whether DMXAA could induce cytokines in cultured murine splenocytes. DMXAA alone induced low amounts of TNF with an optimal concentration of 10 microg/mL and an optimal time of 4 hr. When combined with low concentrations of lipopolysaccharide, deactivated-lipopolysaccharide (dLPS) or phorbol-12-myristate-13-acetate that did not elicit TNF production alone, synergistic TNF production was obtained. DMXAA also induced interferon-gamma at an optimal dose of 300 microg/mL, but the addition of dLPS had no further effect. Decreasing culture pH, although not changing the optimal concentrations for stimulation, increased both TNF and interferon-gamma production in response to DMXAA. The major DMXAA metabolites, DMXAA-glucuronide and 6-hydroxy-5-methylxanthenone-4-acetic acid, did not induce either cytokine alone, in combination with dLPS or at low pH. The results indicate that DMXAA rather than a metabolite is responsible for cytokine induction and suggest that the microenvironment of the tumour may be responsible for the observed selective induction of cytokines in tumour tissue.