Publications by authors named "Ammer J"

Aging markedly increases cancer risk, yet our mechanistic understanding of how aging influences cancer initiation is limited. Here we demonstrate that the loss of ZNRF3, an inhibitor of Wnt signaling that is frequently mutated in adrenocortical carcinoma, leads to the induction of cellular senescence that remodels the tissue microenvironment and ultimately permits metastatic adrenal cancer in old animals. The effects are sexually dimorphic, with males exhibiting earlier senescence activation and a greater innate immune response, driven in part by androgens, resulting in high myeloid cell accumulation and lower incidence of malignancy.

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Background: In vivo patch-clamp recording techniques provide access to the sub- and suprathreshold membrane potential dynamics of individual neurons during behavior. However, maintaining recording stability throughout behavior is a significant challenge, and while methods for head restraint are commonly used to enhance stability, behaviorally related brain movement relative to the skull can severely impact the success rate and duration of whole-cell patch-clamp recordings.

New Method: We developed a low-cost, biocompatible, and 3D-printable cranial implant capable of locally stabilizing brain movement, while permitting equivalent access to the brain when compared to a conventional craniotomy.

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Motor cortex generates descending output necessary for executing a wide range of limb movements. Although movement-related activity has been described throughout motor cortex, the spatiotemporal organization of movement-specific signaling in deep layers remains largely unknown. Here we record layer 5B population dynamics in the caudal forelimb area of motor cortex while mice perform a forelimb push/pull task and find that most neurons show movement-invariant responses, with a minority displaying movement specificity.

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Introduction: Pediatric settings often screen children and/or caregivers for social determinants of health (SDH) needs. Although SDH awareness rose with COVID, questions remain regarding best practices for SDH screening in pediatric settings.

Method: We assessed pediatric providers' perspectives on integrating SDH screening into patient care.

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Executing learned motor behaviors often requires the transformation of sensory cues into patterns of motor commands that generate appropriately timed actions. The cerebellum and thalamus are two key areas involved in shaping cortical output and movement, but the contribution of a cerebellar-thalamocortical pathway to voluntary movement initiation remains poorly understood. Here, we investigated how an auditory "go cue" transforms thalamocortical activity patterns and how these changes relate to movement initiation.

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In natural environments our auditory system is exposed to multiple and diverse signals of fluctuating amplitudes. Therefore, to detect, localize, and single out individual sounds the auditory system has to process and filter spectral and temporal information from both ears. It is known that the overall sound pressure level affects sensory signal transduction and therefore the temporal response pattern of auditory neurons.

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In sensory systems, the neuronal representation of external stimuli is enhanced along the sensory pathway. In the auditory system, strong enhancement of binaural information takes place between the brainstem and the midbrain; however, the underlying cellular mechanisms are unknown. Here we investigated the transformation of binaural information in the dorsal nucleus of the lateral lemniscus (DNLL), a nucleus that connects the binaural nuclei in the brainstem and the inferior colliculus in the midbrain.

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The kinetics of the reactions of the vinyl cations 2 [PhC═C-(4-MeO-CH)] and 3 [MeC═C-(4-MeO-CH)] (generated by laser flash photolysis) with diverse nucleophiles (e.g., pyrroles, halide ions, and solvents containing variable amounts of water or alcohol) have been determined photometrically.

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To capture the context of sensory information, neural networks must process input signals across multiple timescales. In the auditory system, a prominent change in temporal processing takes place at an inhibitory GABAergic synapse in the dorsal nucleus of the lateral lemniscus (DNLL). At this synapse, inhibition outlasts the stimulus by tens of milliseconds, such that it suppresses responses to lagging sounds, and is therefore implicated in echo suppression.

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Equilibria for the reactions of benzhydryl cations (Ar2CH(+)) with phosphines, tert-amines, pyridines, and related Lewis bases were determined photometrically in CH2Cl2 and CH3CN solution at 20 °C. The measured equilibrium constants can be expressed by the sum of two parameters, defined as the Lewis Acidity (LA) of the benzhydrylium ions and the Lewis basicity (LB) of the phosphines, pyridines, etc. Least-squares minimization of log K = LA + LB with the definition LA = 0 for (4-MeOC6H4)2CH(+) gave a Lewis acidity scale for 18 benzhydrylium ions covering 18 orders of magnitude in CH2Cl2 as well as Lewis basicities (with respect to C-centered Lewis acids) for 56 bases.

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Passive and active membrane properties determine the voltage responses of neurons. Within the auditory brain stem, refinements in these intrinsic properties during late postnatal development usually generate short integration times and precise action-potential generation. This developmentally acquired temporal precision is crucial for auditory signal processing.

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Chronic GVHD (cGVHD) remains the most important cause of late non-relapse mortality post allogeneic hematopoietic SCT (HSCT). Although first-line treatment of cGVHD with steroids is well established, evidence for second-line treatment remains limited. Here, we report a dual center retrospective analysis of the off-label salvage treatment of steroid-refractory cGVHD with everolimus.

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In the auditory system, large somatic synapses convey strong excitation that supports temporally precise information transfer. The information transfer of such synapses has predominantly been investigated in the endbulbs of Held in the anterior ventral cochlear nucleus and the calyx of Held in the medial nucleus of the trapezoid body. These large synapses either work as relays or integrate over a small number of inputs to excite the postsynaptic neuron beyond action potential (AP) threshold.

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The (1) H NMR chemical shifts of the C(α)H protons of arylmethyl triphenylphosphonium ions in CD2 Cl2 solution strongly depend on the counteranions X(-) . The values for the benzhydryl derivatives Ph2 CHPPh3 (+)  X(-) , for example, range from δH =8.25 (X(-) =Cl(-) ) over 6.

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Bond cleavage and bond formation are central to organic chemistry. Carbocations play a key role in our understanding of nucleophilic substitution reactions that involve both processes. The precise understanding of the mechanism and dynamics of the photogeneration of carbocations and carbon radicals is therefore an important quest.

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In this retrospective analysis, 30 patients with acute GVHD (aGVHD) and 32 patients with chronic GVHD (cGVHD) treated with extracorporeal photopheresis (ECP) performed by the COBE Spectra System were evaluated. After 3 months of ECP treatment, a CR and PR were observed in 9 (30%) and 6 (20%) patients with aGVHD and in 2 (6%) and 12 (38%) patients with cGVHD. In 16 (53%) patients with aGVHD and 9 (28%) with cGVHD ECP treatment was already stopped after 3 months.

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Laser flash irradiation of substituted N-benzhydryl pyridinium salts yields benzhydryl cations (diarylcarbenium ions) and/or benzhydryl radicals (diarylmethyl radicals). The use of 3,4,5-triamino-substituted pyridines as photoleaving groups allowed us to employ the third harmonic of a Nd/YAG laser (355 nm) for the photogeneration of benzhydryl cations. In this way, benzhydryl cations can also be photogenerated in the presence of aromatic compounds and in solvents which are opaque at the wavelength of the quadrupled Nd/YAG laser (266 nm).

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Second-order rate constants k(2) for the reactions of various donor- and acceptor-substituted benzhydrylium ions Ar(2)CH(+) with π-nucleophiles in CH(2)Cl(2) were determined by laser flash irradiation of benzhydryl triarylphosphonium salts Ar(2)CH-PAr(3)(+)X(-) in the presence of a large excess of the nucleophiles. This method allowed us to investigate fast reactions up to the diffusional limit including reactions of highly reactive benzhydrylium ions with m-fluoro and p-(trifluoromethyl) substituents. The rate constants determined in this work and relevant literature data were jointly subjected to a correlation analysis to derive the electrophilicity parameters E for acceptor-substituted benzhydrylium ions, as defined by the linear free energy relationship log k(2)(20 °C) = s(N)(N + E).

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UV irradiation (266 or 280 nm) of benzhydryl triarylphosphonium salts Ar(2)CH-PAr(3)(+)X(-) yields benzhydryl cations Ar(2)CH(+) and/or benzhydryl radicals Ar(2)CH(•). The efficiency and mechanism of the photo-cleavage were studied by nanosecond laser flash photolysis and by ultrafast spectroscopy with a state-of-the-art femtosecond transient spectrometer. The influences of the photo-electrofuge (Ar(2)CH(+)), the photo-nucleofuge (PPh(3) or P(p-Cl-C(6)H(4))(3)), the counterion (X(-) = BF(4)(-), SbF(6)(-), Cl(-), or Br(-)), and the solvent (CH(2)Cl(2) or CH(3)CN) were investigated.

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The identification of the transition state or a short-lived intermediate of a chemical reaction is essential for the understanding of the mechanism. For a direct identification typically transient optical spectroscopy is used, preferentially with high temporal resolution. We combine broad-band femtosecond transient absorption measurements and on-the-fly molecular dynamics calculations to decipher the microscopic evolution of the geometry and solvation of photogenerated benzhydryl cations (Ar(2)CH(+), Ar = phenyl, p-tolyl, m-fluorophenyl, or m,m'-difluorophenyl) in bulk solution.

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A series of p-substituted benzhydryl fluorides (diarylfluoromethanes) were prepared and subjected to solvolysis reactions, which were followed conductometrically. The observed first-order rate constants k(1)(25 °C) were found to follow the correlation equation log k(1)(25 °C) = s(f)(N(f) + E(f)), which allowed us to determine the nucleofuge-specific parameters N(f) and s(f) for fluoride in different aqueous and alcoholic solvents. The rates of the reverse reactions were measured by generating benzhydrylium ions (diarylcarbenium ions) laser flash photolytically in various alcoholic and aqueous solvents in the presence of fluoride ions and monitoring the rate of consumption of the benzhydrylium ions by UV-vis spectroscopy.

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The dorsal nucleus of the lateral lemniscus (DNLL) is an auditory brain stem structure that generates a long-lasting GABAergic output, which is important for binaural processing. Despite its importance in binaural processing, little is known about the cellular physiology and the synaptic input kinetics of DNLL neurons. To assess the relevant physiological parameters of DNLL neurons, their late postnatal developmental profile was analyzed in acute brain slices of 9- to 26-day-old Mongolian gerbils.

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