Effects of neurokinin-1 receptor agonism and antagonism in the rostral ventromedial medulla of rats with acute or persistent inflammatory nociception

The rostral ventromedial medulla (RVM), a central relay in the bulbospinal pathways that modulate nociception, contains high concentrations of substance P (Sub P) and neurokinin-1 (NK1) receptors. However, the function of Sub P in the RVM is poorly understood. This study characterized the actions of Sub P in the RVM in the absence of injury and then used two NK1 receptor antagonists, L-733,060 and L-703, 606, to probe the role of endogenously released Sub P in the development and maintenance of persistent inflammatory nociception of immune or neurogenic origin. In uninjured rats, microinjection of Sub P in the RVM produced a transient thermal antinociception that was attenuated by pretreatment with L-733,060 or L-703,606. It did not alter threshold to withdrawal from tactile stimulation with von Frey filaments. Microinjection of the antagonists alone did not alter paw withdrawal latency (PWL) or threshold suggesting that Sub P is not tonically released in the RVM in the absence of injury. However, microinjection of either antagonist in the RVM was sufficient to reverse heat hyperalgesia 4 h, 4 days or 2 weeks after intraplantar (ipl) injection of complete Freund's adjuvant (CFA). Antagonism of NK1 receptors in the RVM did not prevent or reverse tactile hypersensitivity induced by CFA, but did attenuate that produced by capsaicin. NK1 receptor antagonism did not prevent the development of thermal hyperalgesia, tactile hypersensitivity or spontaneous pain behaviors induced by mustard oil (MO). The results suggest that Sub P has bimodal actions in the RVM and that following inflammatory injury, it can play a critical role as a pronociceptive agent in the development and maintenance of hyperalgesia and tactile hypersensitivity. However, its actions are highly dependent on the stimulus modality and the type of injury, and this may be an additional basis for the poor efficacy of NK1 receptor antagonists in clinical trials.     

Examining the auditory nerve fiber response to high rate cochlear implant stimulation: chronic sensorineural hearing loss and facilitation

Neural prostheses, such as cochlear and retinal implants, induce perceptual responses by electrically stimulating sensory nerves. These devices restore sensory system function by using patterned electrical stimuli to evoke neural responses. An understanding of their function requires knowledge of the nerves responses to relevant electrical stimuli as well as the likely effects of pathology on nerve function. We describe how sensorineural hearing loss (SNHL) affects the response properties of single auditory nerve fibers (ANFs) to electrical stimuli relevant to cochlear implants. The response of 188 individual ANFs were recorded in response to trains of stimuli presented at 200, 1,000, 2,000, and 5,000 pulse/s in acutely and chronically deafened guinea pigs. The effects of stimulation rate and SNHL on ANF responses during the 0-2 ms period following stimulus onset were examined to minimize the influence of ANF adaptation. As stimulation rate increased to 5,000 pulse/s, threshold decreased, dynamic range increased and first spike latency decreased. Similar effects of stimulation rate were observed following chronic SNHL, although onset threshold and first spike latency were reduced and onset dynamic range increased compared with acutely deafened animals. Facilitation, defined as an increased nerve excitability caused by subthreshold stimulation, was observed in both acute and chronic SNHL groups, although the magnitude of its effect was diminished in the latter. These results indicate that facilitation, demonstrated here using stimuli similar to those used in cochlear implants, influences the ANF response to pulsatile electrical stimulation and may have important implications for cochlear implant signal processing strategies.     

A genome-wide search for linkage to asthma phenotypes in the genetics of asthma international network families: evidence for a major susceptibility locus on chromosome 2p

Asthma is a complex disease and the intricate interplay between genetic and environmental factors underlies the overall phenotype of the disease. Families with at least two siblings with asthma were collected from Europe, Australia and the US. A genome scan using a set of 364 families with a panel of 396 microsatellite markers was conducted. Nonparametric linkage analyses were conducted for asthma and three asthma-related phenotypes: bronchial hyper-reactivity (BHR), strict definition of asthma and atopic asthma. Nine chromosomal regions with LOD scores greater than 1.5 were identified (chromosomes 1q, 2p, 3q, 4p, 4q, 6q, 12q, 20p and 21). Linkage refinement analysis was performed for three BHR loci by genotyping single nucleotide polymorphisms at an average marker density of 1 cM. The LOD scores increased to 3.07 at chromosome 4p and 4.58 at chromosome 2p, while the chromosome 6p locus did not refine. The LOD score at the chromosome 2p locus is highly significant on a genome-wide basis. The refined locus covers a region with a physical size of 12.2 Mb. Taken together, these results provide evidence for a major asthma susceptibility locus on chromosome 2p.     

Immune phenomena involved in the in vivo regression of fibrosarcoma cells expressing cell-associated IL-1alpha

Constitutive expression of cell-associated, but not secreted, interleukin-1alpha (IL-1alpha) by oncogene-transformed fibrosarcoma cells induced regressing tumors in mice, a phenomenon that was abrogated by the IL-1 inhibitor, the IL-1 receptor antagonist (IL-1Ra). On the contrary, non-IL-1alpha-expressing tumor cells induce progressive tumors in mice. In vivo and ex vivo experiments have shown that regression of IL-1alpha-positive fibrosarcoma cells depends on CD8(+) T cells, which can also be activated in CD4(+) T cell-depleted mice, with some contribution of natural killer cells. In spleens of mice bearing the non-IL-1alpha-expressing fibrosarcoma cells, some early and transient manifestations of antitumor-specific immunity, such as activation of specific proliferating T cells, are evident; however, no development of cytolytic T lymphocytes or other antitumor protective cells could be detected. In spleens of mice bearing the non-IL-1alpha-expressing fibrosarcoma cells, the development of early tumor-mediated suppression was observed, and in spleens of mice injected with IL-1alpha-positive fibrosarcoma cells, protective immunity developed in parallel to tumor regression. Treatment of mice bearing violent fibrosarcoma tumors with syngeneic-inactivated, IL-1alpha-positive fibrosarcoma cells, at a critical interval after injection of the malignant cells (Days 5-12), induced tumor regression, possibly by potentiating and amplifying transient antitumor cell immune responses or by ablation of tumor-mediated suppression. Membrane-associated IL-1alpha may thus serve as an adhesion molecule, which allows efficient cell-to-cell interactions between the malignant and immune effector cells that bear IL-1Rs and function as a focused cytokine with adjuvant activities at nontoxic, low levels of expression. Our results also point to the potential of using antitumor immunotherapeutic approaches using cell-associated IL-1alpha.     

Bim mediates apoptosis of CD127(lo) effector T cells and limits T cell memory

Following an acute T cell response, most activated effector cells die, while some survive and become memory cells. The pro-apoptotic Bcl-2 family member, Bcl-2 interacting mediator of death (Bim) is critical for eliminating most effector T cells, while expression of CD127 (IL-7Ralpha) has been proposed to mark effector cells destined to become memory cells. Here, we examined the effects of Bim on the death of effector T cells in relationship to CD127 expression and on development of T cell memory following lymphocytic choriomeningitis virus (LCMV) infection. We found that large numbers of CD127(lo) LCMV-specific CD4(+) and CD8(+) T cells were lost in wild-type mice, but were spared in Bim(-/-) mice. Further, while the numbers of CD127(hi) T cells declined only slightly during contraction of the response in wild-type mice, they increased significantly in Bim(-/-) mice due to re-expression of CD127 on CD127(lo) T cells that had avoided apoptosis. Functional memory T cells were significantly increased in Bim(-/-) mice; however, they underwent a slow attrition due to decreased proliferative renewal. Taken together, these data suggest that the absence of Bim-mediated death of LCMV-specific CD4(+) and CD8(+) T cells in vivo can increase T cell memory, but other homeostatic mechanisms control the long-term maintenance of memory cells.     

Local frequency dependence in transcranial ultrasound transmission

The development of large-aperture multiple-source transducer arrays for ultrasound transmission through the human skull has demonstrated the possibility of controlled and substantial acoustic energy delivery into the brain parenchyma without the necessitation of a craniotomy. The individual control of acoustic parameters from each ultrasound source allows for the correction of distortions arising from transmission through the skull bone and also opens up the possibility for electronic steering of the acoustic focus within the brain. In addition, the capability to adjust the frequency of insonation at different locations on the skull can have an effect on ultrasound transmission. To determine the efficacy and applicability of a multiple-frequency approach with such a device, this study examined the frequency dependence of ultrasound transmission in the range of 0.6-1.4 MHz through a series of 17 points on four ex vivo human skulls. Effects beyond those that are characteristic of frequency-dependent attenuation were examined. Using broadband pulses, it was shown that the reflected spectra from the skull revealed information regarding ultrasound transmission at specific frequencies. A multiple-frequency insonation with optimized frequencies over the entirety of five skull specimens was found to yield on average a temporally brief 230% increase in the transmitted intensity with an 88% decrease in time-averaged intensity transmission within the focal volume. This finding demonstrates a potential applicability of a multiple-frequency approach in transcranial ultrasound transmission.     

Collagen density promotes mammary tumor initiation and progression

Background

Mammographically dense breast tissue is one of the greatest risk factors for developing breast carcinoma. Despite the strong clinical correlation, breast density has not been causally linked to tumorigenesis, largely because no animal model has existed for studying breast tissue density. Importantly, regions of high breast density are associated with increased stromal collagen. Thus, the influence of the extracellular matrix on breast carcinoma development and the underlying molecular mechanisms are not understood.

Methods

To study the effects of collagen density on mammary tumor formation and progression, we utilized a bi-transgenic tumor model with increased stromal collagen in mouse mammary tissue. Imaging of the tumors and tumor-stromal interface in live tumor tissue was performed with multiphoton laser-scanning microscopy to generate multiphoton excitation and spectrally resolved fluorescent lifetimes of endogenous fluorophores. Second harmonic generation was utilized to image stromal collagen.

Results

Herein we demonstrate that increased stromal collagen in mouse mammary tissue significantly increases tumor formation approximately three-fold (p < 0.00001) and results in a significantly more invasive phenotype with approximately three times more lung metastasis (p < 0.05). Furthermore, the increased invasive phenotype of tumor cells that arose within collagen-dense mammary tissues remains after tumor explants are cultured within reconstituted three-dimensional collagen gels. To better understand this behavior we imaged live tumors using nonlinear optical imaging approaches to demonstrate that local invasion is facilitated by stromal collagen re-organization and that this behavior is significantly increased in collagen-dense tissues. In addition, using multiphoton fluorescence and spectral lifetime imaging we identify a metabolic signature for flavin adenine dinucleotide, with increased fluorescent intensity and lifetime, in invading metastatic cells.

Conclusion

This study provides the first data causally linking increased stromal collagen to mammary tumor formation and metastasis, and demonstrates that fundamental differences arise and persist in epithelial tumor cells that progressed within collagen-dense microenvironments. Furthermore, the imaging techniques and signature identified in this work may provide useful diagnostic tools to rapidly assess fresh tissue biopsies.     

Within-Breath Control of Genioglossal Muscle Activation in Humans: Effect of Sleep-Wake State

Pharyngeal dilator muscles are clearly important in the pathogenesis of obstructive sleep apnoea syndrome. Substantial data support the role of a local negative pressure reflex in modifying genioglossal activation across inspiration during wakefulness. Using a model of passive negative pressure ventilation, we have previously reported a tight relationship between varying intrapharyngeal negative pressures and genioglossal muscle activation (GGEMG) during wakefulness. In this study, we used this model to examine the slope of the relationship between epiglottic pressure ( P _epi) and GGEMG, during stable NREM sleep and the transition from wakefulness to sleep. We found that there was a constant relationship between negative epiglottic pressure and GGEMG during both basal breathing (BB) and negative pressure ventilation (NPV) during wakefulness (slope GGEMG/ P _epi 1.86 ± 0.3 vs. 1.79 ± 0.3 arbitrary units (a.u.) cmH₂O⁻¹). However, while this relationship remained stable during NREM sleep during BB, it was markedly reduced during NPV during sleep (2.27 ± 0.4 vs. 0.58 ± 0.1 a.u. cmH₂O⁻¹). This was associated with a markedly higher pharyngeal airflow resistance during sleep during NPV. At the transition from wakefulness to sleep there was also a greater reduction in peak GGEMG seen during NPV than during BB. These data suggest that while the negative pressure reflex is able to maintain GGEMG during passive NPV during wakefulness, this reflex is unable to do so during sleep. The loss of this protective mechanism during sleep suggests that an airway dependent upon such mechanisms (as in the patient with sleep apnoea) will be prone to collapse during sleep.     

DNA damage response and MCL-1 destruction initiate apoptosis in adenovirus-infected cells

Expression of adenovirus E1A deregulates cell proliferation to facilitate viral DNA replication, prompting the initiation of apoptosis signaled primarily through proapoptotic BAK in productively infected cells. We demonstrate here that in uninfected cells, BAK is complexed with the anti-apoptotic BCL-2 family member Myeloid Cell Leukemia 1 (MCL-1). E1A expression during infection resulted in the specific down-regulation of MCL-1 through destabilization of the protein and loss of the mRNA. Upon loss of the MCL-1-BAK complex, BAK complexed with either BAX in proapoptotic E1B mutant adenovirus-infected cells, or with the adenovirus BCL-2 homolog E1B 19K in cells infected with the wild-type virus in which apoptosis is inhibited. Loss of MCL-1 was required to initiate the apoptotic pathway in infected cells as restoration of MCL-1 expression rescued infected cells from E1A-induced apoptosis. Analogous to E1A expression, DNA damage down-regulates MCL-1, and adenovirus infection resulted in the accumulation of phosphorylated H2AX and ataxia-telangiectasia mutant protein (ATM), hallmarks of DNA double-strand breaks. Thus, MCL-1 may function by maintaining BAK in an inactive state, and the loss of MCL-1 upon activation of the DNA damage response, perhaps through replication stress induced in virus infected cells, may be required to initiate the apoptotic response.     

Morbidity of DSM-IV Axis I disorders in patients with noncardiac chest pain: Psychiatric morbidity linked with increased pain and health care utilization

The present study examined current and lifetime psychiatric morbidity, chest pain, and health care utilization in 229 patients with noncardiac chest pain (NCCP), angina-like pain in the absence of cardiac etiology. Diagnostic interview findings based on the Diagnostic and Statistical Manual of Mental Disorders (4th ed.; DSM-IV; American Psychiatric Association, 1994) revealed a psychiatrically heterogeneous sample of whom 44% had a current Axis I psychiatric disorder. A total of 41% were diagnosed with a current anxiety disorder, and 13% were diagnosed with a mood disorder. Overall, 75% of patients had an Axis I clinical or subclinical disorder. Lifetime diagnoses of anxiety (55%) and mood disorders (44%) were also prevalent, including major depressive disorder (41%), social phobia (25%), and panic disorder (22%). Patients with an Axis I disorder reported more frequent and more painful chest pain compared with those without an Axis I disorder. Presence of an Axis I disorder was associated with increased life interference and health care utilization. Findings reveal that varied DSM-IV Axis I psychiatric disorders are prevalent among patients with NCCP, and this psychiatric morbidity is associated with a less favorable NCCP presentation. Implications for early identification of psychiatric disorders are discussed.