The multi-CDK inhibitor dinaciclib reverses bromo- and extra-terminal domain (BET) inhibitor resistance in acute myeloid leukemia via inhibition of Wnt/ß-catenin signaling.

Acute myeloid leukemia (AML) is a highly aggressive hematologic cancer with poor survival across a broad range of molecular subtypes. Development of efficacious and well-tolerable therapies encompassing the range of mutations that can arise in AML remains an unmet need. The bromo- and extra-terminal domain (BET) family of proteins represents an attractive therapeutic target in AML due to their crucial roles in many cellular functions, regardless of any specific mutation. Many BET inhibitors (BETi) are currently in pre-clinical and early clinical development, but acquisition of resistance continues to remain an obstacle for the drug class. Novel methods to circumvent this development of resistance could be instrumental for the future use of BET inhibitors in AML, both as monotherapy and in combination. To date, many investigations into possible drug combinations of BETi with CDK inhibitors have focused on CDK9, which has a known physical and functional interaction with the BET protein BRD4. Therefore, we wished to investigate possible synergy and additive effects between inhibitors of these targets in AML. Here, we describe combination therapy with the multi-CDK inhibitor dinaciclib and the BETi PLX51107 in pre-clinical models of AML. Dinaciclib and PLX51107 demonstrate additive effects in AML cell lines, primary AML samples, and in vivo. Further, we demonstrate novel activity of dinaciclib through inhibition of the canonical/ß-catenin dependent Wnt signaling pathway, a known resistance mechanism to BETi in AML. We show dinaciclib inhibits Wnt signaling at multiple levels, including downregulation of ß-catenin, the Wnt co-receptor LRP6, as well as many Wnt pathway components and targets. Moreover, dinaciclib sensitivity remains unaffected in a setting of BET resistance, demonstrating similar inhibitory effects on Wnt signaling when compared to BET-sensitive cells. Ultimately, our results demonstrate rationale for combination CDKi and BETi in AML. In addition, our novel finding of Wnt signaling inhibition could have potential implications in other cancers where Wnt signaling is dysregulated and demonstrates one possible approach to circumvent development of BET resistance in AML.

Interleukin 4 is localized to and released by human mast cells.

Recent attention has focused on the T helper type 2 (Th2) lymphocyte as a source of interleukin 4 (IL-4) in allergic disease. However, Th2 cells themselves require a pulse of IL-4 to initiate this synthesis. Here we provide immunohistochemical evidence of IL-4 localization to human mast cells of the skin and respiratory tract, and demonstrate that immunoglobulin E-dependent stimulation of purified human lung mast cells leads to the rapid release of IL-4 into the extracellular environment. We propose that mast cell activation in an allergic response provides a rapid and local pulse of IL-4 into the local environment essential for the triggering of T lymphocytes into sustained IL-4 production and to initiate inflammatory cell accumulation and activation.

Neuronal plasticity that underlies improvement in perceptual performance.

The electrophysiological properties of sensory neurons in the adult cortex are not immutable but can change in response to alterations of sensory input caused by manipulation of afferent pathways in the nervous system or by manipulation of the sensory environment. Such plasticity creates great potential for flexible processing of sensory information, but the actual effects of neuronal plasticity on perceptual performance are poorly understood. The link between neuronal plasticity and performance was explored here by recording the responses of directionally selective neurons in the visual cortex while rhesus monkeys practiced a familiar task involving discrimination of motion direction. Each animal experienced a short-term improvement in perceptual sensitivity during daily experiments; sensitivity increased by an average of 19 percent over a few hundred trials. The increase in perceptual sensitivity was accompanied by a short-term improvement in neuronal sensitivity that mirrored the perceptual effect both in magnitude and in time course, which suggests that improved psychophysical performance can result directly from increased neuronal sensitivity within a sensory pathway.

Electrical microstimulation of cortical area MST biases heading perception in monkeys.

As we move through the environment, the pattern of visual motion on the retina provides rich information about our movement through the scene. Human subjects can use this information, often termed "optic flow", to accurately estimate their direction of self movement (heading) from relatively sparse displays. Physiological observations on the motion-sensitive areas of monkey visual cortex suggest that the medial superior temporal area (MST) is well suited for the analysis of optic flow information. To test whether MST is involved in extracting heading from optic flow, we perturbed its activity in monkeys trained on a heading discrimination task. Electrical microstimulation of MST frequently biased the monkeys' decisions about their heading, and these induced biases were often quite large. This result suggests that MST has a direct role in the perception of heading from optic flow.

How are moving images segmented?

Visual images are segmented perceptually by a variety of cues, including color and motion. Recent experiments, using perceptual and neurophysiological approaches, have explored the complex interaction between these attributes. A full account will certainly include the effects of directed attention.

Extrastriate cortex: A signature of perception grows.

Neuronal activity in area MT of the extrastriate visual cortex is correlated with the choices monkeys make on perceptual tasks. New evidence suggests that this correlation is stronger on some tasks than others.

Spatial summation in the receptive fields of MT neurons.

Receptive fields (RFs) of cells in the middle temporal area (MT or V5) of monkeys will often encompass multiple objects under normal image viewing. We therefore have studied how multiple moving stimuli interact when presented within and near the RF of single MT cells. We used moving Gabor function stimuli, <1 degrees in spatial extent and approximately 100 msec in duration, presented on a grid of possible locations over the RF of the cell. Responses to these stimuli were typically robust, and their small spatial and temporal extent allowed detailed mapping of RFs and of interactions between stimuli. The responses to pairs of such stimuli were compared against the responses to the same stimuli presented singly. The responses were substantially less than the sum of the responses to the component stimuli and were well described by a power-law summation model with divisive inhibition. Such divisive inhibition is a key component of recently proposed "normalization" models of cortical physiology and is presumed to arise from lateral interconnections within a region. One open question is whether the normalization occurs only once in primary visual cortex or multiple times in different cortical areas. We addressed this question by exploring the spatial extent over which one stimulus would divide the response to another and found effective normalization from stimuli quite far removed from the RF center. This supports models under which normalization occurs both in MT and in earlier stages.

Inflammatory infiltrates in human coronary atherosclerosis.

The nature and density of coronary arterial inflammatory infiltrates were studied in autopsy material from 53 patients with no clinical or pathological evidence of ischaemic heart disease and from 22 acute cardiac deaths. Adventitial aggregates of inflammatory cells were present in 46% of cases and were slightly more frequent in arteries from patients with ischaemic heart disease. The majority of these cells were lymphocytes and immunohistochemical studies with monoclonal antibodies indicated that both B and T cells were present. Staining with polyclonal antibodies to macrophage antigens confirmed that some adventitial cells were macrophages. The reactions of foam cells within the atheromatous plaques were extremely variable but some foam cells gave unequivocably positive reactions with macrophage antibodies. There was a good overall correlation between the numbers of intimal and medial foam cells and the density of the adventitial lymphocytic infiltrates. It is suggested that these infiltrates develop as a secondary feature of atheromatous lesions and are unlikely to play a major role in their initiation or in the development of complications.

Multiple uses of visual motion. The case for stability in sensory cortex.

The problem of 'readout' from sensory maps has received considerable attention recently. Specifically, many experiments in different systems have suggested that the routing of sensory signals from cortical maps can be impressively flexible. In this review, we discuss many of the experiments addressing readout of motion signals from the middle temporal area (also known as V5) in the macaque monkey. We focus on two different types of output: perceptual reports (categorical decisions, usually) and motion-guided eye movements. We specifically consider situations in which multiple-motion vectors present in the stimulus are combined, as well as those in which one or more of the vectors in the stimulus is selected for output. The results of these studies suggest that in some situations multiple motions are vector averaged, while in others multiple vectors can be maintained. Interestingly, in most of the experiments producing a single (often average) vector, the output is a movement. However, many perceptual experiments involve the simultaneous processing of multiple-stimulus motions. One prosaic explanation for this pattern of apparently discrepant results is that different downstream structures impose different rules, in parallel, on the output from sensory maps such as the one in the middle temporal area. We also specifically discuss the case of motion opponency, a specific readout rule that has been posited to explain perceptual phenomena such as the waterfall illusion (motion aftereffect). We present evidence from a recent experiment showing that an opponent step must occur downstream from the middle temporal area itself. This observation is consistent with our proposal that significant processing need occur downstream from sensory structures. If a single output is to be used for multiple purposes, often at once, this necessitates a degree of task invariance on the sensory information present even at a relatively high level of cortical processing.

The effects of schedule of reinforcement on stimulus overselectivity in autistic children.

Recent research demonstrated that when autistic children are presented a discrimination task with multiple cues, they typically respond to an abnormally limited number, usually one, of the available cues. This phenomenon, termed "stimulus overselectivity," has been implicated as a possible basis for many of the behavioral deficits characteristic of autism. The present investigation was conducted to systemically analyze the effects of changing the schedules of reinforcement during discrimination training on subsequent stimulus overselectivity. Twelve autistic children were taught a discrimination involving multiple visual cues, with a CRF schedule of reinforcement. The children were then overtrained on either the same (CRF) schedule or on a partial (VR:3) reinforcement schedule. Subsequent overselectivity on single-cue test trials was then assessed. Results suggested that significantly less overselectivity occurred when the children were presented with the VR:3 reinforcement schedule during overtraining. These results are discussed in terms of variables influencing overselectivity and in terms of implications for designing treatment procedures for autistic children.

Immunohistochemistry on resin sections: a comparison of resin embedding techniques for small mucosal biopsies.

We have modified resin embedding methods to provide optimal information from endoscopic biopsies. Mucosal biopsies were fixed either in buffered formalin and processed for embedding in Araldite or in acetone containing protease inhibitors and embedded in glycol methacrylate (GMA). GMA embedding generated an immunophenotypic profile similar to that obtained in frozen sections while yielding far superior morphology and greater numbers of sections from small biopsies. The phenotypic markers included those for T cells, macrophages, mast cells, eosinophils and neutrophils. We have also demonstrated collagens, cell adhesion molecules and integrin molecules. Sections of similar quality were obtained with Araldite but the repertoire of antibodies was restricted to those which can be applied to formalin fixed, paraffin embedded tissues. We suggest that for optimal results, small biopsies to be subjected to immunochemistry are fixed in acetone at -20 C with the inclusion of protease inhibitors and embedded in GUIA with careful temperature control.

Clustering of response selectivity in the medial superior temporal area of extrastriate cortex in the macaque monkey.

Ever since being described by Mountcastle (Mountcastle, 1957), columnar organization of sensory cortical areas has provided key leverage into understanding the functional organization of neocortex. Columnar or clustered organization of neurons sharing like properties is now known to be widespread, and probably universal in primary sensory areas. Visual cortex in primates consists of a primary area and a large number of secondary areas, which are organized in a manner both hierarchical and parallel (Felleman & Van Essen, 1991; Young, 1993; Young et al., 1995). One major component in the organization of extrastriate visual cortex appears to be the division into dorsal and ventral "streams" of processing (Ungerleider & Mishkin, 1982), each of which is organized hierarchically. Within each, columnar organization exists at early stages, but becomes less clear at higher levels. Columnar organization has been described at the highest level of the ventral stream, inferotemporal cortex (IT, Saleem et al., 1993; Fujita & Fujita, 1996; Tanaka, 1996), but has not been well characterized at the higher levels of the dorsal stream. Hints of such organization are found in the literature (Saito et al., 1986; Lagae et al., 1994), but systematic measurements are needed. In this paper, I report the existence of clustered organization in the medial superior temporal area (MST) of the dorsal stream, which is arguably the highest dominantly visual area on this pathway. I have measured the selectivity of both single- and multiple-unit activity along oblique electrode penetrations through this area to three different kinds of optic flow stimuli, and find that nearby neurons are more similar in their tuning than are more distant ones. This observation documents the existence of some form of clustered organization and supports the importance of this area in the processing of optic flow information.

Tissue preparation for the demonstration of surface antigen by immunoperoxidase techniques.

The fixation and drying regimes for frozen sections and cytocentrifuge preparations for the demonstration of surface antigens, such as immunoglobulins and iron binding proteins, vary enormously between different groups of workers. A method using freeze-dried sections and acetone fixation was compared with 16 other methods of fixation and found to be the best for tissue preservation and antigen demonstration. Freeze drying was found to improve the cytological preservation of air-dried sections considerably.

Tuning bandwidths for near-threshold stimuli in area MT.

It is not known whether psychophysical performance depends primarily on small numbers of neurons optimally tuned to specific visual stimuli, or on larger populations of neurons that vary widely in their properties. Tuning bandwidths of single cells can provide important insight into this issue, yet most bandwidth measurements have been made using suprathreshold visual stimuli, whereas psychophysical measurements are frequently obtained near threshold. We therefore examined the directional tuning of cells in the middle temporal area (MT, or V5) using perithreshold, stochastic motion stimuli that we have employed extensively in combined psychophysical and physiological studies. The strength of the motion signal (coherence) in these displays can be varied independently of its direction. For each MT neuron, we characterized the directional bandwidth by fitting Gaussian functions to directional tuning data obtained at each of several motion coherences. Directional bandwidth increased modestly as the coherence of the stimulus was reduced. We then assessed the ability of MT neurons to discriminate opposed directions of motion along six equally spaced axes of motion spanning 180 degrees. A signal detection analysis yielded neurometric functions for each axis of motion, from which neural thresholds could be extracted. Neural thresholds remained surprisingly low as the axis of motion diverged from the neuron's preferred-null axis, forming a plateau of high to medium sensitivity that extended approximately 45 degrees on either side of the preferred-null axis. We conclude that directional tuning remains broad in MT when motion signals are reduced to near-threshold values. Thus directional information is widely distributed in MT, even near the limits of psychophysical performance. These observations support models in which relatively large numbers of signals are pooled to inform psychophysical decisions.

Power spectrum analysis of bursting cells in area MT in the behaving monkey.

It is widely held that visual cortical neurons encode information primarily in their mean firing rates. Some proposals, however, emphasize the information potentially available in the temporal structure of spike trains (Optican and Richmond, 1987; Bialek et al., 1991), in particular with respect to stimulus-related synchronized oscillations in the 30-70 Hz range (Eckhorn et al., 1988; Gray et al., 1989; Kreiter and Singer, 1992) as well as via bursting cells (Cattaneo et al., 1981a; Bonds, 1992). We investigate the temporal fine structure of spike trains recorded in extrastriate area MT of the trained macaque monkey, a region that plays a major role in processing motion information. The data were recorded while the monkey performed a near-threshold direction discrimination task so that both physiological and psychophysical data could be obtained on the same set of trials (Britten et al., 1992). We identify bursting cells and quantify their properties, in particular in relation to the behavior of the animal. We compute the power spectrum and the distribution of interspike intervals (ISIs) associated with individual spike trains from 212 cells, averaging these quantities across similar trials. (1) About 33% of the cells have a relatively flat power spectrum with a dip at low temporal frequencies. We analytically derive the power spectrum of a Poisson process with refractory period and show that it matches the observed spectrum of these cells. (2) About 62% of the cells have a peak in the 20-60 Hz frequency band. In about 10% of all cells, this peak is at least twice the height of its base. The presence of such a peak strongly correlates with a tendency of the cell to respond in bursts, that is, two to four spikes within 2-8 msec. For 93% of cells, the shape of the power spectrum did not change dramatically with stimulus conditions. (3) Both the ISI distribution and the power spectrum of the vast majority of bursting cells are compatible with the notion that these cells fire Poisson-distributed bursts, with a burst-related refractory period. Thus, for our stimulus conditions, no explicitly oscillating neuronal process is required to yield a peak in the power spectrum. (4) We found no statistically significant relationship between the peak in the power spectrum and psychophysical measures of the monkeys' performance on the direction discrimination task.(ABSTRACT TRUNCATED AT 400 WORDS)

Effects of inferotemporal cortex lesions on form-from-motion discrimination in monkeys.

The inferotemporal cortex of primates plays a prominent role in the learning and retention of visual form discriminations. In this experiment we investigated the role of inferotemporal (IT) cortex in the discrimination of two-dimensional forms defined by motion cues. Six monkeys were trained to a criterion level of performance on two form-from-motion problems. Three of these animals received complete bilateral lesions of IT cortex, while the other three served as unoperated controls. All animals were then retrained to criterion to evaluate the effects of IT lesions on the retention of form-from-motion learning. Compared with the control group, the lesion group was significantly impaired on both problems. Following retention testing, we trained both groups of monkeys on two new form-from-motion problems to investigate the effects of IT lesions on acquisition rates for new learning. The lesion group performed well on the new problems; the learning rates of the operated and control groups were not significantly different. When forms were defined by luminance cues, monkeys with IT lesions, like those in previous studies, were impaired both for retention and for acquisition. These findings indicate that the anterograde effects of IT lesions on learning new form discriminations are less severe for forms defined by motion cues than for forms defined by luminance cues. However, the retrograde effects of IT lesions on retention are severe for forms defined by either cue.

Chronic Salmonella eimsbuettel septicaemia presenting with intermittent sweats and haematuria.

An unusual presentation is reported of salmonellosis, frank haematuria and chronic septicaemia arising during an outbreak of food poisoning caused by Salmonella eimsbuettel. The patient whose gut was colonized gave a history of chronic pyrexia and weight loss and suffered an intermittent urinary infection but had no gastroenteritis.

Cortical microstimulation influences perceptual judgements of motion direction.

Neurons in the visual cortex respond selectively to perceptually salient features of the visual scene, such as the direction and speed of moving objects, the orientation of local contours, or the colour or relative depth of a visual pattern. It is commonly assumed that the brain constructs its percept of the visual scene from information encoded in the selective responses of such neurons. We have now tested this hypothesis directly by measuring the effect on psychophysical performance of modifying the firing rates of physiologically characterized neurons. We required rhesus monkeys to report the direction of motion in a visual display while we electrically stimulated clusters of directionally selective neurons in the middle temporal visual area (MT, or V5), an extrastriate area that plays a prominent role in the analysis of visual motion information. Microstimulation biased the animals' judgements towards the direction of motion encoded by the stimulated neurons. This result indicates that physiological properties measured at the neuronal level can be causally related to a specific aspect of perceptual performance.

Neuronal correlates of a perceptual decision.

The relationship between neuronal activity and psychophysical judgement has long been of interest to students of sensory processing. Previous analyses of this problem have compared the performance of human or animal observers in detection or discrimination tasks with the signals carried by individual neurons, but have been hampered because neuronal and perceptual data were not obtained at the same time and under the same conditions. We have now measured the performance of monkeys and of visual cortical neurons while the animals performed a psychophysical task well matched to the properties of the neurons under study. Here we report that the reliability and sensitivity of most neurons on this task equalled or exceeded that of the monkeys. We therefore suggest that under our conditions, psychophysical judgements could be based on the activity of a relatively small number of neurons.