Remote and Selective Control of Astrocytes by Magnetomechanical Stimulation.

Astrocytes play crucial and diverse roles in brain health and disease. The ability to selectively control astrocytes provides a valuable tool for understanding their function and has the therapeutic potential to correct dysfunction. Existing technologies such as optogenetics and chemogenetics require the introduction of foreign proteins, which adds a layer of complication and hinders their clinical translation. A novel technique, magnetomechanical stimulation (MMS), that enables remote and selective control of astrocytes without genetic modification is described here. MMS exploits the mechanosensitivity of astrocytes and triggers mechanogated Ca2+ and adenosine triphosphate (ATP) signaling by applying a magnetic field to antibody-functionalized magnetic particles that are targeted to astrocytes. Using purpose-built magnetic devices, the mechanosensory threshold of astrocytes is determined, a sub-micrometer particle for effective MMS is identified, the in vivo fate of the particles is established, and cardiovascular responses are induced in rats after particles are delivered to specific brainstem astrocytes. By eliminating the need for device implantation and genetic modification, MMS is a method for controlling astroglial activity with an improved prospect for clinical application than existing technologies.

Meniscus Repair Techniques.

The menisci play a vital role in maintaining knee function and protecting the chondral surfaces. Acute and chronic tears are common injuries among both young athletes and older patients with early degenerative changes. The progression of physiological derangement and chondral injury after meniscus injury and meniscectomy have prompted interest in expanding meniscus repair techniques. Recent literature encourages an attempt at repair in tear patterns previously declared irreparable if the tissue quality allows. The orthopedic surgeon should understand the multitude of techniques available to them and be prepared to combine techniques to optimize the quality of their repair construct. While biological augmentation may show some promising early results, the quality of the current data precludes strong recommendations in their favor.

Effects of Permethrin or Deltamethrin Exposure in Adult Sprague Dawley Rats on Acoustic and Light Prepulse Inhibition of Acoustic or Tactile Startle.

The effects of permethrin (PRM) and deltamethrin (DLM) on acoustic or light prepulse inhibition of the acoustic startle response (ASR) and tactile startle response (TSR) were studied in adult male Sprague Dawley rats. Preliminary studies were conducted to optimize the parameters of light and acoustic prepulse inhibition of ASR and TSR. Once these parameters were set, a new group of rats was administered PRM (0 or 90 mg/kg) or DLM (0 or 25 mg/kg) by gavage in 5 mL/kg corn oil. ASR and TSR were assessed using acoustic or light prepulses 6, 8, and 12 h after PRM and 2, 4, and 6 h after DLM exposure. PRM increased ASR 6 h post-treatment with no interaction with acoustic prepulse levels and with no effect on TSR. When light was used as the prepulse, PRM increased ASR and TSR at 6 h with no interaction with prepulse levels. DLM decreased ASR and TSR on trials without prepulses but not on trials with acoustic prepulses. DLM also decreased ASR when light prepulses were present 4 h post-treatment. A final experiment assessed whether the house light in the test cabinet affected ASR and TSR after PRM or DLM exposure. Rats had increased ASR and TSR when house lights were on compared with when they were off, but lighting did not differentially interact with PRM or DLM. Light and acoustic prepulses of ASR and TSR have different effects depending on the test agent and the test parameters.

Effect of Mechanical Strain on Cells Involved in Fracture Healing.

Secondary fracture healing is a complex multi-stage process in which the mechanical environment plays a key role. The use of an appropriate mechanical stimulation such as strain is conducive to tissue formation between fracture ends, thus aiding the healing process. However, if the strain is too large or too small, the biological behavior of the cells involved in bone healing will be affected, resulting in non-union or delayed healing. In this review, we summarize the current state of knowledge regarding the effect of strain on cells that play a role in the fracture-healing process. Overall, the related literature suggests that selection of an adequate strain promotes fracture healing through the stimulation of angiogenesis and osteogenesis, along with inhibition of osteoclast differentiation and bone resorption. However, standardized methods for the application of mechanical stimulation are lacking, and a unified consensus on the mechanism by which strain promotes cell differentiation has not yet been reached. These issues, therefore, deserve further investigation.

Aldosterone is Aberrantly Regulated by Various Stimuli in a High Proportion of Patients with Primary Aldosteronism.

CONTEXT: In primary aldosteronism (PA), aldosterone secretion is relatively independent of the renin-angiotensin system, but can be regulated by several other stimuli. OBJECTIVE: To evaluate aldosterone response to several stimuli in a series of patients with PA secondary either to bilateral adrenal hyperplasia (BAH) or unilateral aldosterone-producing adenoma (APA). DESIGN AND SETTING: Prospective cohort study conducted in a university teaching hospital research center. PATIENTS: Forty-three patients with confirmed PA and subtyped by adrenal vein sampling (n = 39) were studied, including 11 with BAH, 28 with APA, and 4 with undefined etiology. We also studied 4 other patients with aldosterone and cortisol cosecretion. INTERVENTIONS: We systematically explored aberrant regulation of aldosterone using an in vivo protocol that included the following stimulation tests performed over 3 days under dexamethasone suppression: upright posture, mixed meal, adrenocorticotropin (ACTH) 1-24, gonadotropin-releasing hormone (GnRH), vasopressin, and serotonin R4 agonist. MAIN OUTCOME MEASURES: Positive response was defined as >50% renin or ACTH-independent increase in plasma aldosterone/cortisol concentration following the various stimulation tests. RESULTS: Renin-independent aldosterone secretion increased in response to several aberrant stimuli (upright posture, GnRH) in up to 83% of patients with APA or BAH in whom ACTH 1-24 and HT4R agonists also produced aldosterone oversecretion in all patients. The mean significant aberrant responses per patient was similar in BAH (4.6) and in APA (4.0). CONCLUSIONS: Aldosterone secretion in PA is relatively autonomous from the renin-angiotensin system, but is highly regulated by several other stimuli, which contributes to the large variability of aldosterone levels in PA patients.

Necessidades do bebê com deficiência física na creche: a percepção de educadoras / Necesidades del bebé con discapacidad física en la guardería: percepción de educadoras / The needs of children with physical disabilities in day care: the perception of educators

RESUMO. Este estudo teve como objetivo investigar a percepção de educadoras frente às necessidades de duas bebês com deficiência física em contexto de inclusão na creche. Realizou-se um estudo de caso múltiplo, com seis educadoras que atendiam a turma de Mariana (24 meses), e quatro educadoras que atendiam a turma de Vitória (18 meses), as quais responderam uma entrevista semiestruturada. Ambas as bebês tinham deficiência física e frequentavam escolas de educação infantil da rede pública de Porto Alegre. Os dados foram analisados através de diversas leituras do material, produzindo um relato clínico. Em relação à Mariana, as educadoras destacaram a necessidade de estímulo e de suporte físico à bebê, bem como a importância do afeto na relação educadora-bebê, presente em um 'olhar a mais', mais sensível. Quanto à Vitória, as educadoras reforçaram a importância da integração entre as áreas da saúde e da educação, assim como de um olhar mais atento às diferentes necessidades da bebê com deficiência. A partir dos resultados, foi possível compreender nesse 'olhar a mais', destacado pelas educadoras como necessário para atender à demanda das bebês com deficiência física, uma exigência de maior disponibilidade corporal e psíquica.

RESUMEN. Este estudio tuvo como objetivo investigar la percepción de educadoras frente a las necesidades del bebé con discapacidad física en el contexto de inclusión en la guardería. Se realizó un estudio de caso múltiple, cuyas participantes fueron seis educadoras que atendían a la clase de Mariana, y cuatro educadoras que atendían a la clase de Vitória, las cuales respondieron una entrevista semiestructurada. Ambas bebés tenían deficiencia física y frecuentaban escuelas de Educación Infantil de la red pública de la ciudad de Porto Alegre/Brasil. Los datos fueron analizados a través de diversas lecturas del material, produciendo un relato clínico. En cuanto a Mariana, 24 meses, las educadoras destacaron la necesidad de estímulo y de soporte físico a la bebé, así como la importancia del afecto en la relación educadora-bebé, que hace presente en una 'mirada a más', más sensible. En cuanto a Vitória, 18 meses, las educadoras reforzaron la importancia de la integración entre las áreas de la salud y la educación, así como de una mirada más atenta a las diferentes necesidades de la bebé con discapacidad. A partir de los resultados, fue posible comprender en esa 'mirada a más', destacada por las educadoras como necesario para atender a la demanda de los bebés con discapacidad física, una exigencia de mayor disponibilidad corporal y psíquica.

ABSTRACT. This study aimed to investigate the perception of educators regarding the needs of two babies with physical disabilities in the context of inclusion in the day care center. A multiple-case study was carried out. The participants were six educators who oversaw Mariana's class, and four educators who oversaw Vitoria's class, and all 10 educators answered a semi-structured interview. Both babies were physically disabled and attended public schools in Porto Alegre/Brazil. The data were analyzed through several readings of the material, which resulted in a clinical report. In relation to Mariana (age 24 months) the educators emphasized the baby's need for stimuli and physical support, as well as the importance of affection in the educator-baby relationship, which was present as a more sensitive 'extra thought'. As for Vitória (age 18 months), educators reinforced the importance of integration between the health and education fields, as well as closer attention to the different needs of the disabled baby. Based on the results, it was possible to observe within that 'extra thought' - highlighted by the educators as necessary to fulfill the needs of babies with physical disabilities - a demand for greater physical and psychic availability.

Neurogenic bowel treatments and continence outcomes in children and adults with myelomeningocele.

PURPOSE: Neurogenic bowel dysfunction (NBD) is a common comorbidity of myelomeningocele (MMC), the most common and severe form of spina bifida. The National Spina Bifida Patient Registry (NSBPR) is a research collaboration between the CDC and Spina Bifida Clinics. Fecal continence (continence) outcomes for common treatment modalities for NBD have not been described in a large sample of individuals with MMC. NSBPR patients with MMC and NBD were studied to determine variation in continence status and their ability to perform their treatment independently according to treatment modality and individual characteristics. METHODS: Continence was defined as < 1 episode of incontinence per month. Eleven common treatments were evaluated. Inclusion criteria were established diagnoses of both MMC and NBD, as well as age ⩾ 5 years (n= 3670). Chi-square or exact statistical tests were used for bivariate analyses. Logistic regression models were used to estimate the odds of continence outcomes by age, sex, race/ethnicity, level of motor function, and insurance status. RESULTS: At total of 3670 members of the NSBPR met inclusion criteria between November 2013 and December 2017. Overall prevalence of continence was 45%. Prevalence ranged from 40-69% across different treatments. Among continent individuals, 60% achieved continence without surgery. Antegrade enemas were the most commonly used treatment and had the highest associated continence rate. Ability to carry out a treatment independently increased with age. Multivariable logistic regression showed significantly higher odds of continence among individuals aged ⩾ 12 years, female, non-Hispanic white, and with private insurance.

Effect of Massage on the TLR4 Signalling Pathway in Rats with Neuropathic Pain.

This study set out to investigate the effect of massage on the Toll-like receptor 4 (TLR4) signalling pathway in the dorsal root ganglia of rats that had undergone spinal nerve ligation (SNL), with the hypothesis that massage could be used as an analgesic. Forty female SD rats were randomly divided into 5 groups: the control group, sham-operated group, model group, sham massage group, and massage group. There were 8 rats in each group. SNL rat models were established in the model group, sham massage group, and massage group. Rats in the sham-operated group underwent surgery to expose the vertebral nerves, but no further procedures were performed. The control group consisted of intact animals. The rats in the massage group underwent massage using a massage simulation machine once a day for 14 d in succession; the hind limbs of the rats in the sham massage group were gently touched with a cloth bag once a day for 14 continuous days. The rats in the control group, the sham-operated group, and the model group did not receive any intervention and were observed for 14 d. Paw withdrawal thermal latency (PWTL) and paw withdrawal mechanical threshold (PWMT) of rats in each group were detected 1 d before modelling and at 1, 3, 7, and 14 d after modelling. Fourteen days after modelling, the expression levels of TLR4, IRAK1, TRAF6, TNF-α, and IL-6 were detected in all rats. The PWTL and PWMT of SNL rats were decreased, while these parameters were elevated after massage. SNL rats showed higher levels of TLR4, IRAK1, TRAF6, IL-6, and TNF-α, and massage effectively lowered the expression levels of these molecules. Inhibiting activation of the TLR4 signalling pathway, which can reduce the release of inflammatory factors, may be one mechanism by which massage treats neuropathic pain.

Compression Bioreactor-Based Mechanical Loading Induces Mobilization of Human Bone Marrow-Derived Mesenchymal Stromal Cells into Collagen Scaffolds In Vitro.

Articular cartilage (AC) is an avascular tissue composed of scattered chondrocytes embedded in a dense extracellular matrix, in which nourishment takes place via the synovial fluid at the surface. AC has a limited intrinsic healing capacity, and thus mainly surgical techniques have been used to relieve pain and improve function. Approaches to promote regeneration remain challenging. The microfracture (MF) approach targets the bone marrow (BM) as a source of factors and progenitor cells to heal chondral defects in situ by opening small holes in the subchondral bone. However, the original function of AC is not obtained yet. We hypothesize that mechanical stimulation can mobilize mesenchymal stromal cells (MSCs) from BM reservoirs upon MF of the subchondral bone. Thus, the aim of this study was to compare the counts of mobilized human BM-MSCs (hBM-MSCs) in alginate-laminin (alginate-Ln) or collagen-I (col-I) scaffolds upon intermittent mechanical loading. The mechanical set up within an established bioreactor consisted of 10% strain, 0.3 Hz, breaks of 10 s every 180 cycles for 24 h. Contrary to previous findings using porcine MSCs, no significant cell count was found for hBM-MSCs into alginate-Ln scaffolds upon mechanical stimulation (8 ± 5 viable cells/mm3 for loaded and 4 ± 2 viable cells/mm3 for unloaded alginate-Ln scaffolds). However, intermittent mechanical stimulation induced the mobilization of hBM-MSCs into col-I scaffolds 10-fold compared to the unloaded col-I controls (245 ± 42 viable cells/mm3 vs. 22 ± 6 viable cells/mm3, respectively; p-value < 0.0001). Cells that mobilized into the scaffolds by mechanical loading did not show morphological changes. This study confirmed that hBM-MSCs can be mobilized in vitro from a reservoir toward col-I but not alginate-Ln scaffolds upon intermittent mechanical loading, against gravity.

Elicitation of the Swallowing Reflex by Esophageal Stimulation in Healthy Subjects: An Evaluation Using High-Resolution Manometry.

The purposes of this human study using high-resolution manometry were to verify whether the swallowing reflex can be evoked by intra-esophageal fluid injection and whether the reflex latency and manometric variables differ depending on the injected location, amount, or speed. Ten healthy individuals participated in this study. The tip of the intranasal catheter for injection was placed at 5 cm (upper), 10 cm (upper-middle), 15 cm (lower-middle), or 20 cm (lower) from the distal end of the upper esophageal sphincter (UES). An intra-esophageal injection of 3 mL or 10 mL of thickened water was administered and controlled at 3 mL/s or 10 mL/s. Latencies from the start of the injection to the onset of UES relaxation were compared regarding injection locations, amounts, and rates. Manometric variables of intra-esophageal injection and voluntary swallowing were compared. The latency became shorter when the upper region was injected. Latency after the 10-mL injection was shorter than that after the 3-mL injection (p < 0.01) when faster injection (10 mL/s) was used. Faster injection induced shorter latency (p < 0.01) when a larger volume (10 mL) was injected. Pre-maximum and post-maximum UES pressures during voluntary swallowing or during spontaneous swallowing when injecting the upper esophageal region were significantly higher than spontaneous swallowing at other regions (p < 0.01). Intra-esophageal fluid injection induces the swallowing reflex in humans. The most effective condition for inducing the swallowing reflex involved a larger fluid amount with a faster injection rate in the upper esophagus.

Investigating the Feasibility of a Modified Quantitative Sensory Testing Approach to Profile Sensory Function and Predict Pain Outcomes Following Intrathecal Baclofen Implant Surgery in Cerebral Palsy.

OBJECTIVES: Intrathecal baclofen (ITB) pumps used to manage spasticity in children with cerebral palsy (CP) also improve pain outcomes for some but not all patients. The purpose of this clinical feasibility study was to explore whether a quantitative sensory testing approach could a) be modified and used to subgroup individuals into sensory profiles and b) test whether the profiles were related to postimplant pain outcomes (i.e., pain responsive or pain persistent). SUBJECTS: A purposeful clinical sample of nine children with CP (mean age = 12.5 years, male = 56%) and complex communication needs participated. METHODS: A prospective within-subject design was used to measure proxy-reported pain before and after ITB implant. Pain response status was determined by proxy-reported pain intensity change (>50% change in maximum rated intensity). A modified quantitative sensory testing (mQST) procedure was used to assess behavioral responsivity to an array of calibrated sensory (tactile/acute nociceptive) stimuli before surgery. RESULTS: Seven individuals with presurgical pain had mQST differentiated sensory profiles in relation to ITB pain outcomes and relative to the two individuals with no pain. Presurgically, the ITB pain responsive subgroup (N = 3, maximum rated pain intensity decreased >50% after ITB implant) showed increased behavioral reactivity to an acute nociceptive stimulus and cold stimulus, whereas the ITB pain persistent subgroup (N = 4) showed reduced behavioral reactivity to cold and repeated von Frey stimulation relative to the no pain individuals. CONCLUSION: Implications for patient selection criteria and stratification to presurgically identify individuals with CP "at risk" for persistent postprocedure pain are discussed.

Thermosensory mapping of skin wetness sensitivity across the body of young males and females at rest and following maximal incremental running.

KEY POINTS: Humans lack skin receptors for wetness (i.e. hygroreceptors), yet we present a remarkable wetness sensitivity. Afferent inputs from skin cold-sensitive thermoreceptors are key for sensing wetness; yet, it is unknown whether males and females differ in their wetness sensitivity across their body and whether high intensity exercise modulates this sensitivity. We mapped sensitivity to cold, neutral and warm wetness across five body regions and show that females are more sensitive to skin wetness than males, and that this difference is greater for cold than warm wetness sensitivity. We also show that a single bout of maximal exercise reduced the sensitivity to skin wetness (i.e. hygro-hypoesthesia) of both sexes as a result of concurrent decreases in thermal sensitivity. These novel findings clarify the physiological mechanisms underpinning this fundamental human sensory experience. In addition, they indicate sex differences in thermoregulatory responses and will inform the design of more effective sport and protective clothing, as well as thermoregulatory models. ABSTRACT: Humans lack skin hygroreceptors and we rely on integrating cold and tactile inputs from A-type skin nerve fibres to sense wetness. Yet, it is unknown whether sex and exercise independently modulate skin wetness sensitivity across the body. We mapped local sensitivity to cold, neutral and warm wetness of the forehead, neck, underarm, lower back and dorsal foot in 10 males (27.8 ± 2.7 years; 1.92 ± 0.1 m2 body surface area) and 10 females (25.4 ± 3.9 years; 1.68 ± 0.1 m2 body surface area), at rest and post maximal incremental running. Participants underwent our quantitative sensory test where they reported the magnitude of thermal and wetness perceptions (visual analogue scale) resulting from the application of a cold (5°C below skin temperature) wet (0.8 mL of water), neutral wet and warm wet (5°C above skin temperature) thermal probe (1.32 cm2 ) to five skin sites. We found that: (i) females were ∼14% to ∼17% more sensitive to cold-wetness than males, yet both sexes were as sensitive to neutral- and warm-wetness; (ii) regional differences were present for cold-wetness only, and these followed a craniocaudal increase that was more pronounced in males (i.e. the foot was ∼31% more sensitive than the forehead); and (iii) maximal exercise reduced cold-wetness sensitivity over specific regions in males (i.e. ∼40% decrease in foot sensitivity), and also induced a generalized reduction in warm-wetness sensitivity in both sexes (i.e. ∼4% to ∼6%). For the first time, we show that females are more sensitive to cold wetness than males and that maximal exercise induce hygro-hypoesthesia. These novel findings expand our knowledge on sex differences in thermoregulatory physiology.

Optical recording reveals topological distribution of functionally classified colorectal afferent neurons in intact lumbosacral DRG.

Neuromodulation as a non-drug alternative for managing visceral pain in irritable bowel syndrome (IBS) may target sensitized afferents of distal colon and rectum (colorectum), especially their somata in the dorsal root ganglion (DRG). Developing selective DRG stimulation to manage visceral pain requires knowledge of the topological distribution of colorectal afferent somata which are sparsely distributed in the DRG. Here, we implemented GCaMP6f to conduct high-throughput optical recordings of colorectal afferent activities in lumbosacral DRG, that is, optical electrophysiology. Using a mouse ex vivo preparation with distal colorectum and L5-S1 DRG in continuity, we recorded 791 colorectal afferents' responses to graded colorectal distension (15, 30, 40, and 60 mmHg) and/or luminal shear flow (20-30 mL/min), then functionally classified them into four mechanosensitive classes, and determined the topological distribution of their somata in the DRG. Of the 791 colorectal afferents, 90.8% were in the L6 DRG, 8.3% in the S1 DRG, and only 0.9% in the L5 DRG. L6 afferents had all four classes: 29% mucosal, 18.4% muscular-mucosal, 34% low-threshold (LT) muscular, and 18.2% high-threshold (HT) muscular afferents. S1 afferents only had three classes: 19.7% mucosal, 34.8% LT muscular, and 45.5% HT muscular afferents. All seven L5 afferents were HT muscular. In L6 DRG, somata of HT muscular afferents were clustered in the caudal region whereas somata of the other classes did not cluster in specific regions. Outcomes of this study can directly inform the design and improvement of next-generation neuromodulation devices that target the DRG to alleviate visceral pain in IBS patients.

Effects of ovarian hormones on the emission of 50-kHz ultrasonic vocalizations during distributed clitoral stimulation in the rat.

Fifty-kHz ultrasonic vocalizations (USVs) are emitted by adult rats during appetitive phases of behavior in response to stimuli thought to be associated with a positive affective state. In particular, 50-kHz USVs with rapid frequency oscillations, known as trills and flat-trills, in which these oscillations are flanked by a monotonic portion, are together positively correlated with appetitive behaviors such as rough and tumble play, drug and natural reward, and mating. Female rats produce 50-kHz USVs during a variety of sexual contexts, yet data are still vague as female sexual behavior is seldom studied on its own. Distributed clitoral stimulation (CLS) offers a unique approach to investigating female 50-kHz USVs as it mimics stimulation received during mating. Although CLS induces a sexual reward state, it is unknown whether CLS elicits trills and flat-trills. We addressed this question using eight ovariectomized rats, we investigated whether ovarian hormones augmented these call subtypes in response to CLS. The combined and separate effects of estradiol benzoate (EB) and progesterone (P), and oil vehicle were assessed through comparison of these call subtypes between CLS and inter-CLS interval. We found that CLS with EB + P significantly increased call duration and rate, lowered peak frequency, and widened the bandwidth of trills. Flat-trills showed a similar pattern except for call duration. Call distribution during the CLS and inter-CLS interval suggest that trill and flat-trills may be indicative of both anticipatory and sexual reward.

The optimal order of stimulation modalities and reproducibility of the multimodal esophageal stimulation paradigm.

BACKGROUND: Esophageal hypersensitivity can be triggered by different stimuli. We use a multimodal stimulation model to study esophageal sensitivity to four sensory modalities: thermal, mechanical, electrical, and chemical stimulation. The optimal order of these stimulations needs further validation. METHODS: Esophageal sensitivity to thermal (heated saline solution), mechanical (balloon distention), electrical (block pulses with electrodes), and chemical stimulation (acid solution, 0.1 N HCl) was assessed in 10 subjects. In one session, thermal stimulation was performed first, followed by mechanical stimulation ("original protocol"). In a second session, mechanical stimulation was performed first, followed by temperature stimulation ("reversed protocol"). Besides, the impact of balloon distention speed (25 mL/min vs 50 mL/min) during mechanical stimulation was evaluated. Secondly, in order to establish reproducibility, independent control sessions of multimodal stimulations in 15 healthy volunteers were used retrospectively. KEY RESULTS: A significant difference in pain perception threshold for thermal stimulation was found between the original and reversed protocol (P = 0.046), indicating that mechanical stimulation can sensitize the esophagus to thermal stimulation. Balloon distention rate had no impact on sensitivity thresholds for mechanical stimulation. Concerning the reproducibility, there were no differences for thermal, mechanical, electrical, and chemical stimulation in any of the control sessions. CONCLUSIONS: The optimal order of the multimodal stimulation protocol was to start with the thermal stimulation, followed by mechanical, electrical, and chemical stimulation. The optimal balloon distention rate was 25 mL/min. Multimodal esophageal stimulation generates reproducible perception scores in health and therefore provides a reliable method to assess esophageal sensitivity changes after interventions that may alter esophageal sensitivity.

Spontaneous and Stimulus-Evoked Respiratory Rate Elevation Corresponds to Development of Allodynia in Spinal Cord-Injured Rats.

Respiratory complications frequently accompany spinal cord injury (SCI) and slowed breathing has been shown to mitigate pain sensitivity. It is possible that elevated respiratory rates (RRs) signal the emergence of chronic pain after SCI. We previously validated the use of remote electric field sensors to noninvasively track breathing in freely behaving rodents. Here, we examined spontaneous (resting) and stimulus-evoked RRs as potential indices of mechanical hypersensitivity following SCI. Adult male Long-Evans rats received a lower thoracic hemisection or contusion SCI, or sham surgery, and underwent weekly assessments of mechanical and thermal sensitivity using the von Frey and Hargreaves tests, respectively. Resting RRs were recorded with remote sensors prior to nociception assays as well as 1 day post-surgery. Evoked RRs were quantified weekly in response to at-level mechanical stimulation provided by a small brush at various stimulation speeds, including those corresponding to the distinct tuning properties of a sub-population of cutaneous afferents known as C-low threshold mechanoreceptors. SCI rats developed mechanical hypersensitivity, which peaked 2-3 weeks after SCI. Compared with at baseline, hemisection SCI rats showed significantly heightened resting RRs at 1 day and 7 days post-injury, and the latter predicted development of pain hypersensitivity. In contusion SCI rats, resting RR increases were less substantial but occurred at all weekly time-points. Increases in brush-evoked RR coincided with full expression of hypersensitivity at 14 (hemisection) or 21 (contusion) days after SCI, and these effects were restricted to the lowest brush speeds. Our results support the possibility that early changes in RR may convey pain information in rats.

Comparison of spontaneous and mechanically-stimulated adenosine release in mice.

Rapid adenosine signaling, on the time frame of seconds, has been discovered in the brain that can modulate neurotransmission or blood flow. Rapid adenosine release can occur spontaneously or be evoked after a mechanical stimulation, but these two modes of adenosine have not been compared. Here, we compared spontaneous and mechanically-stimulated adenosine release in the prefrontal cortex, striatum, and hippocampus of anesthetized mice. For spontaneous adenosine, the number of adenosine events in the prefrontal cortex (40 ±â€¯4 per hour) was significantly lower than in the striatum (54 ±â€¯3) or hippocampus (56 ±â€¯3). Similarly, the concentration per transient was lower in the prefrontal cortex but highest in the striatum. For mechanically-stimulated adenosine, the peak concentration in the prefrontal cortex (8 ±â€¯2 µM) and striatum (8 ±â€¯1 µM) were significantly lower than in the hippocampus (16 ±â€¯2 µM). Comparing the two modes, the hippocampus had high mechanically-stimulated concentration and high spontaneous frequency, while the prefrontal cortex had lower spontaneous frequency and mechanically-stimulated release. However, there is no pattern with the striatum and thus no direct correlations between spontaneous and mechanically-stimulated adenosine. Thus, there may be different pools of adenosine or mechanisms of formation for these two modes. Because of the high frequency of spontaneous events and high concentration of mechanically-stimulated release in the hippocampus, there may be some areas that have stronger adenosine signaling and thus stronger neuromodulatory control by adenosine.

Peripheral Inflammation Accelerates the Onset of Mechanical Hypersensitivity after Spinal Cord Injury and Engages Tumor Necrosis Factor α Signaling Mechanisms.

Previously, we showed that noxious stimulation of the tail produces numerous detrimental effects after spinal cord injury (SCI), including an earlier onset and increased magnitude of mechanical hypersensitivity. Expanding on these observations, this study sought to determine whether localized peripheral inflammation similarly impacts the expression of mechanical hypersensitivity after SCI. Adult rats received a moderate contusion injury at the thoracic level (Tl0) or sham surgery, and were administered complete Freund's adjuvant (CFA) or vehicle in one hindpaw 24 hours later. Examination of locomotor recovery (Basso, Beattie, and Bresnahan [BBB] score) showed no adverse effect of CFA. Mechanical testing with von Frey hairs was done at time-points ranging from 1 h to 28 days after CFA or vehicle treatment, and rats were sacrificed at 1, 7, or 28 days for cellular assessment. Unlike vehicle-treated SCI rats where mechanical hypersensitivity emerged at 14 days, CFA-treated SCI rats showed mechanical hypersensitivity as early as 1 h after CFA administration, which lasted at least 28 days. CFA-treated sham subjects also showed an early onset of mechanical hypersensitivity, but this was maintained up to 7 days after treatment. Cellular assessments revealed congruent findings. Expression levels of c-fos, tumor necrosis factor α (TNFα), TNF receptors, and members of the TNFα signaling pathway such as caspase 8 and phosphorylated extracellular related kinase (pERK) were preferentially upregulated in the lumbar spinal cord of SCI-CFA rats. Meanwhile, c-jun was significantly increased in both CFA-treated groups. Overall, these results together with our previous reports, suggest that peripheral noxious input after SCI facilitates the development of pain by mechanisms that may require TNFα signaling.

Estrogen therapy associated with mechanical vibration improves bone microarchitecture and density in osteopenic female mice.

We investigated the effects of estrogen therapy (ET) associated with low-intensity and high-frequency mechanical vibration (MV) on bone tissue in osteopenic female mice. Fifty 3-month-old female Swiss mice were ovariectomized (OVX) or sham-operated, and distributed after 4 months into the following groups, with 10 animals per group: Sham; Control, OVX + vehicle solution; MV, OVX + MV; ET, OVX + 17ß-estradiol; and MV + ET, OVX + MV and 17ß-estradiol. Both vehicle solution and 17ß-estradiol (10 µg kg-1  day-1 ) were injected subcutaneously 7 days per week, and vibration (0.6 g, 60 Hz) was delivered 30 min per day, 5 days per week. Bone mineral density (BMD) and body composition were evaluated by densitometry at baseline and after 60 days of treatment when the animals were euthanized, and their femurs underwent histomorphometric and histochemical analyses. The Control group showed increased weight and fat percentage, while the ET and MV + ET groups showed increased lean mass but decreased fat percentage. At the end of the treatment period, the BMD decreased in Control, remained constant in Sham and MV, and increased in ET and MV + ET. The MV + ET group showed the greatest bone volume compared with Sham (129%), Control (350%), MV (304%) and ET (14%). No differences occurred in cortical thickness. The Control group showed the highest content of mature collagen fibers, while the MV + ET group showed the highest content of immature collagen fibers. In conclusion, ET plus MV was effective in improving bone quality in osteopenic female mice, and this improvement is associated with specific changes in trabecular but not cortical bone.