Comparative model of minimal spinal cord injury reveals a rather anti-inflammatory response in the lesion site as well as increased proliferation in the central canal lining in the neonates compared to the adult rats.

Spinal cord injury (SCI) resulting from trauma decreases the quality of human life. Numerous clues indicate that the limited endogenous regenerative potential is a result of the interplay between the inhibitory nature of mature nervous tissue and the inflammatory actions of immune and glial cells. Knowledge gained from comparing regeneration in adult and juvenile animals could draw attention to factors that should be removed or added for effective therapy in adults. Therefore, we generated a minimal SCI (mSCI) model with a comparable impact on the spinal cord of Wistar rats during adulthood, preadolescence, and the neonatal period. The mechanism of injury is based on unilateral incision with a 20 ga needle tip according to stereotaxic coordinates into the dorsal horn of the L4 lumbar spinal segment. The incision should harm a similar amount of gray matter on a coronal section in each group of experimental animals. According to our results, the impact causes mild injury with minimal adverse effects on the neurological functions of animals but still has a remarkable effect on nervous tissue and its cellular and humoral components. Testing the mSCI model in adults, preadolescents, and neonates revealed a rather anti-inflammatory response of immune cells and astrocytes at the lesion site, as well as increased proliferation in the central canal lining in neonates compared with adult animals. Our results indicate that developing nervous tissue could possess superior reparative potential and confirm the importance of comparative studies to advance in the field of neuroregeneration.

Optically Actuated soft Microrobot Family for Single-cell Manipulation.

Precisely controlled manipulation of non-adherent single cells is often a pre-requisite for their detailed investigation. Optical trapping provides a versatile means for positioning cells with sub-micrometer precision or measuring forces with femto-Newton resolution. A variant of the technique, called indirect optical trapping, enables single-cell manipulation with no photodamage and superior spatial control and stability by relying on optically trapped microtools biochemically bound to the cell. High-resolution 3D lithography enables us to prepare such cell manipulators with any pre-defined shape, greatly extending the number of achievable manipulation tasks. Here, we present for the first time a novel family of cell manipulators that are deformable by optical tweezers and rely on their elasticity to hold cells. This provides a more straightforward approach to indirect optical trapping by avoiding biochemical functionalization for cell attachment, and consequently by enabling the manipulated cells to be released at any time. Using the photoresist Ormocomp, we characterize the deformations achievable with optical forces in the tens of pN range and present three modes of single-cell manipulation as examples to showcase the possible applications such soft microrobotic tools can offer. The applications described here include cell collection, 3D cell imaging and spatially and temporally controlled cell-cell interaction. This article is protected by copyright. All rights reserved.

Bouncing dynamics of inertial self-propelled particles reveals directional asymmetry.

This study aims to examine experimental conditions in which active particles are forced by their surroundings to move forward and backward in a continuous oscillatory manner. The experimental design is based on using a vibrating self-propelled toyrobot called hexbug, which is placed inside a narrow channel closed on one end by a rigid moving wall. Using the end-wall velocity as a controlling factor, the main forward mode of the hexbug movement can be turned to mostly rearward mode. We investigate the bouncing hexbug motion on both experimental and theoretical grounds. The Brownian model of active particles with inertia is employed in the theoretical framework. The model itself uses a pulsed Langevin equation in order to simulate abrupt changes in velocity that mimic hexbug propulsion in the moments when its legs make contact with the base plate. Significant directional asymmetry is caused by the legs bending backward. We demonstrate that the simulation successfully reproduces the experimental characteristics of hexbug motion after regressing the spatial and temporal statistical characteristics, especially when directional asymmetry is under consideration.

Precision spinal gene delivery-induced functional switch in nociceptive neurons reverses neuropathic pain.

Second-order spinal cord excitatory neurons play a key role in spinal processing and transmission of pain signals to the brain. Exogenously induced change in developmentally imprinted excitatory neurotransmitter phenotypes of these neurons to inhibitory has not yet been achieved. Here, we use a subpial dorsal horn-targeted delivery of AAV (adeno-associated virus) vector(s) encoding GABA (gamma-aminobutyric acid) synthesizing-releasing inhibitory machinery in mice with neuropathic pain. Treated animals showed a progressive and complete reversal of neuropathic pain (tactile and brush-evoked pain behavior) that persisted for a minimum of 2.5 months post-treatment. The mechanism of this treatment effect results from the switch of excitatory to preferential inhibitory neurotransmitter phenotype in dorsal horn nociceptive neurons and a resulting increase in inhibitory activity in regional spinal circuitry after peripheral nociceptive stimulation. No detectable side effects (e.g., sedation, motor weakness, loss of normal sensation) were seen between 2 and 13 months post-treatment in naive adult mice, pigs, and non-human primates. The use of this treatment approach may represent a potent and safe treatment modality in patients suffering from spinal cord or peripheral nerve injury-induced neuropathic pain.

Assessing the Viscoelasticity of Photopolymer Nanowires Using a Three-Parameter Solid Model for Bending Recovery Motion.

Photopolymer nanowires prepared by two-photon polymerization direct laser writing (TPP-DLW) are the building blocks of many microstructure systems. These nanowires possess viscoelastic characteristics that define their deformations under applied forces when operated in a dynamic regime. A simple mechanical model was previously used to describe the bending recovery motion of deflected nanowire cantilevers in Newtonian liquids. The inverse problem is targeted in this work; the experimental observations are used to determine the nanowire physical characteristics. Most importantly, based on the linear three-parameter solid model, we derive explicit formulas to calculate the viscoelastic material parameters. It is shown that the effective elastic modulus of the studied nanowires is two orders of magnitude lower than measured for the bulk material. Additionally, we report on a notable effect of the surrounding aqueous glucose solution on the elasticity and the intrinsic viscosity of the studied nanowires made of Ormocomp.

A method to prepare large resin sections for counting myelinated axons in rodent CNS and PNS structures.

We present a method that allows preparing histological sections from large blocks of nervous tissue embedded in epoxy resin. Resin-embedding provides excellent resolution especially for the myelin-rich white matter and is often being used for visualizing the myelinated axons in peripheral nerves. However, because of the limited penetration of the reagents, only very small tissue specimens can be processed in this way. Here, we describe a method that enables to embed large specimens and their sectioning on a standard sliding microtome. To process the large specimens, modifications in several steps of the processing technique had to be made. In this paper we demonstrate, that with this technique 1-3 µm thick transversal sections can be prepared from the resin-embedded specimens as large as rat brain hemisphere. Such a large section allows simultaneously: 1.) overviewing and delineating the gross anatomical structures, and 2.) observing the subcellular details at the highest possible optical magnifications. Such a large section with excellent resolution allows application of unbiased stereological methods and reliable quantification of very small objects within the area of interest.

Spinal subpial delivery of AAV9 enables widespread gene silencing and blocks motoneuron degeneration in ALS.

Gene silencing with virally delivered shRNA represents a promising approach for treatment of inherited neurodegenerative disorders. In the present study we develop a subpial technique, which we show in adult animals successfully delivers adeno-associated virus (AAV) throughout the cervical, thoracic and lumbar spinal cord, as well as brain motor centers. One-time injection at cervical and lumbar levels just before disease onset in mice expressing a familial amyotrophic lateral sclerosis (ALS)-causing mutant SOD1 produces long-term suppression of motoneuron disease, including near-complete preservation of spinal α-motoneurons and muscle innervation. Treatment after disease onset potently blocks progression of disease and further α-motoneuron degeneration. A single subpial AAV9 injection in adult pigs or non-human primates using a newly designed device produces homogeneous delivery throughout the cervical spinal cord white and gray matter and brain motor centers. Thus, spinal subpial delivery in adult animals is highly effective for AAV-mediated gene delivery throughout the spinal cord and supraspinal motor centers.

Quantitative analyses of cellularity and proliferative activity reveals the dynamics of the central canal lining during postnatal development of the rat.

According to previous opinion, the derivation of neurons and glia from the central canal (CC) lining of the spinal cord in rodents should occur in the embryonic period. Reports of the mitotic activity observed in the lining during postnatal development have often been contradictory, and proliferation was ascribed to the generation of ependymocytes, which are necessary for the elongation of CC walls. Our study quantifies the intensity of proliferation and determines the cellularity of the CC lining in reference to lumbar spinal segment L4 during the postnatal development of rats. The presence of dividing cells peaks in the CC lining on postnatal day 8 (P8), with division occurring in 19.2% ± 3.2% of cells. In adult rats, 3.6% ± 0.9% of cells still proliferate, whereas, in mice, 10.3% ± 2.3% of cells at P8 and only 0.6% ± 0.2% of cells in the CC lining in adulthood are proliferating. In the rat, the length of the cell cycle increases from 100.3 ± 35.7 hours at P1 to 401.4 ± 80.6 hours at P43, with a sudden extension between P15 and P22. Despite the intensive proliferation, the total cellularity of the CC lining at the L4 spinal segment significantly descended in from P8 to P15. According to our calculations, the estimated cellularity was significantly higher compared with the measured cellularity of the CC lining at P15. Our results indicate that CC lining serves as a source of cells beyond ependymal cells during the first postnatal weeks of the rat. J. Comp. Neurol. 525:693-707, 2017. © 2016 Wiley Periodicals, Inc.

Low-level laser therapy with 810 nm wavelength improves skin wound healing in rats with streptozotocin-induced diabetes.

OBJECTIVE: The aim of present study was to evaluate whether low-level laser therapy (LLLT) can reverse the impaired wound healing process in diabetic rats. BACKGROUND DATA: Impaired wound healing in diabetic patients represents a major health problem. Recent studies have indicated that LLLT may improve wound healing in diabetic rats, but the optimal treatment parameters are still unknown. MATERIALS AND METHODS: Male Sprague-Dawley rats (n=21) were randomly divided into three groups: a healthy control group, a diabetic sham-treated group, and a diabetic LLLT-treated group. Diabetes mellitus was then induced by streptozotocin administration to the two diabetic groups. One 4 cm long full thickness skin incision and one full thickness circular excision (diameter=4 mm) were performed on the back of each rat. An infrared 810 nm laser with an output of 30 mW, a power density of 30 mW/cm(2), and a spot size of 1 cm(2) was used to irradiate each wound for 30 sec (daily dose of 0.9 J/cm(2)/wound/day). RESULTS: In diabetic rats, the histology of LLLT-treated excisions revealed a similar healing response to that in nondiabetic controls, with significantly more mature granulation tissue than in the sham-treated diabetic control group. LLLT reduced the loss of tensile strength, and increased the incision wound stiffness significantly compared with sham-irradiated rats, but this did not achieve the same level as in the nondiabetic controls. CONCLUSIONS: Our study demonstrates that infrared LLLT can improve wound healing in diabetic rats. Nevertheless, further research needs to be performed to evaluate the exact underlying mechanism and to further optimize LLLT parameters for clinical use.

Cough, expiration and aspiration reflexes: possible anesthetic implications - a brief review.

Systematic study in animals indicated, that in addition to cough there are 2 distinct airway reflexes. The aspiration reflex (AspR) characterized by rapid and strong gasp-like inspiration provoked by stimulation of nasopharynx, nasal phyltrum or auricle of ear. The expiration reflex (ExpR) manifests by prompt expiration, induced by laryngeal stimulation. Both reflexes strongly activate the brainstem inspiratory or expiratory generators, respectively, and inhibit the opposite respiratory and various functional disorders. This paper indicates several functional disorders occurring during manipulation with airways in anaesthesiological practice, which can be influenced positively or negatively by application of these special reflexes (asphyxia, breath-holding, laryngospasm, bronchospasm, sleep apnoea episodes, arrhythmia, collapse, etc.). The AspR, ExpR and CR (cough reflex) have important clinical relevance in anaesthesia and emergency medicine applicable also in domestic therapy and in hardly accessible places particularly by application of ICT (Information & Communication Technologies) using a mobile connection of the patient with the remote hospital centre.

Resuscitation and auto resuscitation by airway reflexes in animals.

Various diseases often result in decompensation requiring resuscitation. In infants moderate hypoxia evokes a compensatory augmented breath - sigh and more severe hypoxia results in a solitary gasp. Progressive asphyxia provokes gasping respiration saving the healthy infant - autoresuscitation by gasping. A neonate with sudden infant death syndrome, however, usually will not survive. Our systematic research in animals indicated that airway reflexes have similar resuscitation potential as gasping respiration. Nasopharyngeal stimulation in cats and most mammals evokes the aspiration reflex, characterized by spasmodic inspiration followed by passive expiration. On the contrary, expiration reflex from the larynx, or cough reflex from the pharynx and lower airways manifest by a forced expiration, which in cough is preceded by deep inspiration. These reflexes of distinct character activate the brainstem rhythm generators for inspiration and expiration strongly, but differently. They secondarily modulate the control mechanisms of various vital functions of the organism. During severe asphyxia the progressive respiratory insufficiency may induce a life-threatening cardio-respiratory failure. The sniff- and gasp-like aspiration reflex and similar spasmodic inspirations, accompanied by strong sympatho-adrenergic activation, can interrupt a severe asphyxia and reverse the developing dangerous cardiovascular and vasomotor dysfunctions, threatening with imminent loss of consciousness and death. During progressive asphyxia the reversal of gradually developing bradycardia and excessive hypotension by airway reflexes starts with reflex tachycardia and vasoconstriction, resulting in prompt hypertensive reaction, followed by renewal of cortical activity and gradual normalization of breathing. A combination of the aspiration reflex supporting venous return and the expiration or cough reflex increasing the cerebral perfusion by strong expirations, provides a powerful resuscitation and autoresuscitation potential, proved in animal experiments. They represent a simple but unique model tested in animal experiments.

Latent airway hyperresponsiveness: a phenomenon bordering bronchial asthma definition.

The basic features of bronchial asthma are dyspnea with wheezing and objectively confirmed obstructive respiratory disorder reversible after inhalation of bronchodilators. In stable intermittent bronchial asthma, these features are not present; therefore confirmation of asthma consists of the presence of bronchial hyperresponsiveness (BHR). In the present study, there were 902 bronchoprovocation tests performed for the verification of BHR. A significant criterium for BHR is a decrease of FEV(1) of 20% from the baseline level. Every test either positive or negative was finished with inhalation of four doses of salbutamol through a spacer. We obtained 675 bronchoprovocation tests negative and 227 positive. Among the 675 subjects with a negative test there were 49 subjects who after inhalation of salbutamol had an increase in FEV(1) of ≥20% above baseline. The bronchodilatatory response of these 49 subjects, makes one think about the so-called latent bronchospasm present already at baseline, limiting further constriction during bronchoprovocation tests. The detection of such latent bronchospasm in BHR increases the number of patients with an objectively confirmed bronchial asthma from 25.0% to 30.5%. Our results suggest that bronchodilation test be performed in all patients with suspected bronchial asthma to allow detecting latent bronchospasm as an initial stage of the disease.

Reversal of functional disorders by aspiration, expiration, and cough reflexes and their voluntary counterparts.

Agonal gasping provoked by asphyxia can save ~15% of mammals even from untreated ventricular fibrillation (VF), but it fails to revive infants with sudden infant death syndrome (SIDS). Our systematic study of airway reflexes in cats and other animals indicated that in addition to cough, there are two distinct airway reflexes that may contribute to auto-resuscitation. Gasp- and sniff-like spasmodic inspirations (SIs) can be elicited by nasopharyngeal stimulation, strongly activating the brainstem generator for inspiration, which is also involved in the control of gasping. This "aspiration reflex" (AspR) is characterized by SI without subsequent active expiration and can be elicited during agonal gasping, caused by brainstem trans-sections in cats. Stimulation of the larynx can activate the generator for expiration to evoke the expiration reflex (ExpR), manifesting with prompt expiration without preceding inspiration. Stimulation of the oropharynx and lower airways provokes the cough reflex (CR) which results from activating of both generators. The powerful potential of the AspR resembling auto-resuscitation by gasping can influence the control mechanisms of vital functions, mediating reversal of various functional disorders. The AspR in cats interrupted hypoxic apnea, laryngo- and bronchospasm, apneusis and even transient asphyxic coma, and can normalize various hypo- and hyper-functional disorders. Introduction of a nasogastric catheter evoked similar SIs in premature infants and interrupted hiccough attacks in adults. Coughing on demand can prevent anaphylactic shock and resuscitate the pertinent subject. Sniff representing nasal inspiratory pressure and maximal inspiratory and expiratory pressures (MIP and MEP) are voluntary counterparts of airway reflexes, and are useful for diagnosis and therapy of various cardio-respiratory and neuromuscular disorders.

Chronic spinal compression model in minipigs: a systematic behavioral, qualitative, and quantitative neuropathological study.

The goal of the present study was to develop a porcine spinal cord injury (SCI) model, and to describe the neurological outcome and characterize the corresponding quantitative and qualitative histological changes at 4-9 months after injury. Adult Gottingen-Minnesota minipigs were anesthetized and placed in a spine immobilization frame. The exposed T12 spinal segment was compressed in a dorso-ventral direction using a 5-mm-diameter circular bar with a progressively increasing peak force (1.5, 2.0, or 2.5 kg) at a velocity of 3 cm/sec. During recovery, motor and sensory function were periodically monitored. After survival, the animals were perfusion fixed and the extent of local SCI was analyzed by (1) post-mortem MRI analysis of dissected spinal cords, (2) qualitative and quantitative analysis of axonal survival at the epicenter of injury, and (3) defining the presence of local inflammatory changes, astrocytosis, and schwannosis. Following 2.5-kg spinal cord compression the animals demonstrated a near complete loss of motor and sensory function with no recovery over the next 4-9 months. Those that underwent spinal cord compression with 2 kg force developed an incomplete injury with progressive partial neurological recovery characterized by a restricted ability to stand and walk. Animals injured with a spinal compression force of 1.5 kg showed near normal ambulation 10 days after injury. In fully paralyzed animals (2.5 kg), MRI analysis demonstrated a loss of spinal white matter integrity and extensive septal cavitations. A significant correlation between the magnitude of loss of small and medium-sized myelinated axons in the ventral funiculus and neurological deficits was identified. These data, demonstrating stable neurological deficits in severely injured animals, similarities of spinal pathology to humans, and relatively good post-injury tolerance of this strain of minipigs to spinal trauma, suggest that this model can successfully be used to study therapeutic interventions targeting both acute and chronic stages of SCI.

Magnetosomes on surface: an imaging study approach.

In this study, we deposited isolated magnetosomes from magnetotactic bacteria Magnetospirillum strain AMB-1 onto solid surfaces using spin coating (SC) and drop coating (DC) techniques. Four imaging techniques have been used to visualize the sample structure: scanning and transmission electron microscopy (SEM, TEM), atomic and magnetic force microscopy (AFM, MFM). Additionally, dynamic light scattering was applied to measure the hydrodynamic radius of agglomerated/aggregated magnetosomes in a liquid environment. This manuscript discusses observed differences between structures obtained by two deposition techniques, i.e. possible interactions and factors responsible for magnetosomes' formation, their morphology on surfaces as a result of agglomeration and aggregation phenomena. Moreover, topography and homogeneity of obtained structures as well as thickness of protein-based membrane were also examined and described. Using high-resolution TEM, we analyzed the size of magnetic cores, their crystal structure and quality. We found that the SC technique provides a homogenous layer of magnetosomes and hydrophilization of silicon surfaces improves the deposition of magnetosomes. However, due to strong hydrogen interaction to the hydrophilic silicone surface, the organic membrane of magnetosomes is mostly flattened. As a matter of fact, the size distributions of magnetosomes deposited by SC and DC techniques (logarithmic-normal tendency) differ from the Feret diameter distribution (normal). Furthermore, our study confirms the good crystalline quality of magnetosomes' cores. It also shows that they are magnetic in the all their volume.

Severe nocturnal cardiac arrhythmias caused by sleep apnea-induced hypoxemia in males.

Nocturnal cardiac arrhythmias (NCA) were analyzed in patients with sleep apnea/hypopnea syndrome (SAHS) and controls. Occurrence and severity of NCA were compared in 33 SAHS patients and 16 control subjects, matched for cardiovascular risk factors. Continuous overnight polysomnography provided ECG, respiratory and sleep parameters for a comparative analysis. Various types and severity of NCA were detected already in moderate SAHS (apnea/hypopnea index = 26 ±15.6/h), reflecting the respiratory and atherosclerotic changes. Moderately severe arrhythmias, represented with benign and 2 complex types were caused by hypoxemia characterized by AHI, minimal SaO2, and lower values after desaturation. Three-time higher prevalence of complex arrhythmias in SAHS patients was not significantly different by usual statistical comparison, likely due to a low number of controls and a joint occurrence of various types and complex severity of arrhythmias in some patients. Therefore, a complex assessment of different types and varying severity of arrhythmias would require a scale specifically constructed for their evaluation.

Do differences in sleep architecture exist between persons with type 2 diabetes and nondiabetic controls?

BACKGROUND: It has been shown previously that the suppression of slow-wave sleep (SWS) markedly reduced insulin sensitivity and led to an impairment of glucose tolerance. We hypothesized that a decreased amount of SWS is a feature peculiar to subjects with type 2 diabetes. METHOD: A retrospective case-control study analyzed polysomnographic recordings and covariate data of 22 type 2 diabetic and 22 nondiabetic subjects [n = 44; 8 women, 36 men, aged 57.5 +/- 5.5 years, body mass index (BMI) 33.8 +/- 5.9 kg/m(2), apnea-hypopnea index (AHI) 29.6 +/- 22.2 episodes/hr] matched individually for sex, race, age, BMI, and severity of sleep-related breathing disorders (SRBD). We assessed differences in sleep architecture between the study group and the control group. Primary end points included the percentage of total sleep time spent in each sleep stage. RESULTS: Despite similar age and severity of SRBD, subjects with type 2 diabetes demonstrated a significantly decreased amount of SWS (3.9 +/- 5.95% vs 8.4 +/- 4.57%; p = 0.012), increased percentage time in rapid eye movement sleep (24.1 +/- 12.14% vs 13.8 +/- 6.96%; p = 0.005), and higher arousal index (44.3 +/- 19.53/hr vs 35.7 +/- 12.67/hr; p = 0.037) compared to nondiabetic controls. After adjustment for sex, BMI, AHI, and smoking, age and presence of type 2 diabetes were independent predictors of the decreased SWS percentage (p = 0.001). Variables in this model accounted for 34% of the variance in the SWS percentage in our cohort. CONCLUSIONS: Results demonstrated distinct differences in sleep architecture in our cohort with decreased amounts of SWS in type 2 diabetes. These findings suggest that polysomnographic recognition of altered sleep architecture may be partially implicated in the early detection of persons with type 2 diabetes.

The effect of equal daily dose achieved by different power densities of low-level laser therapy at 635 and 670 nm on wound tensile strength in rats: a short report.

OBJECTIVE: The aim of our study was to compare the effects of different power densities of LLLT at 635 and 670 nm achieving a daily dose of 5 J/cm(2) on wound tensile strength (TS) in rats. BACKGROUND DATA: Optimal parameters of low-level laser therapy (LLLT) are still unknown. MATERIALS AND METHODS: Under general anesthesia, one full-thickness skin incision was performed on the back of each rat (n = 40) and immediately closed using an intradermal running suture. Rats were separated into five groups depending on treatment parameters: (1) sham irradiated control group (SIC); (2) 635 nm laser-treated group at 4 mW/cm(2) (L-635/4); (3) 635 nm laser-treated group at 15 mW/cm(2) (L-635/15); (4) 670 nm laser-treated group at 4 mW/cm(2) (L-670/4); and (5) 670 nm laser-treated group at 15 mW/cm(2) (L-670/15). The total daily dose was 5 J/cm(2). Seven days after surgery each wound was removed for wound TS measurement. RESULTS: The lowest wound TS results were measured in the SIC rats (10.5 +/- 2.8 g/mm(2)). Higher wound TS results were measured in group L-670/15 (11.5 +/- 2.5 g/mm(2)) and group L-635/4 (11.7 +/- 4.3 g/mm(2)) rats, while significantly higher results were found in group L-670/4 (15.8 +/- 4.4 g/mm(2)) and group L-635/15 (15.9 +/- 4.8 g/mm(2)). The differences were significant between certain groups (p < 0.01: SIC vs. L-635/15, SIC vs. L-670/4; p < 0.05: L-635/4 vs. L-635/15, L-635/4 vs. L-670/4, L-635/15 vs. L-670/15, L-670/4 vs. L-670/15). CONCLUSION: Both red lasers significantly increased wound TS at selected parameters. Whereas the 635 nm laser significantly improved wound healing by using the higher power density, the 670 nm laser improved healing using a lower power density.

Decrease in wound tensile strength following post-surgical estrogen replacement therapy in ovariectomized rats during the early phase of healing is mediated via ER-alpha rather than ER-beta: a preliminary report.

BACKGROUND: In cases of acute surgery or trauma, the most effective method of increasing the level of estrogen in postmenopausal women is its administration immediately pre- or postsurgery. However, in our previous study (J Surg Res 2008; 147:117-122) we showed that postsurgical administration of nonspecific estrogen receptor (ER) agonist decreases wound tensile strength. Therefore, the aim of this study was to evaluate whether this effect is mediated via the alpha or beta ER. MATERIALS AND METHODS: Three months prior to the wound healing experiment, 18 rats were anesthetized and underwent ovariectomy (OVX), while another six rats were sham operated. Two parallel full thickness skin incisions were performed on the back of each rat. Doses of 1mg/kg of either PPT (ER-alpha agonist) or DPN (ER-beta agonist) were administered to 12 OVX rats for 6 d postoperatively, whereas all other animals received vehicle. After 6 d, all animals were sacrificed and samples removed for wound tensile strength measurement and histologic evaluation. RESULTS: The mean wound tensile strength of PPT-treated rats (6.8+/-1.9 g/mm2) was significantly lower compared with all other groups (P<0.05). No significant differences were observed between DPN-treated (8.9+/-2.2 g/mm2), non-OVX vehicle-treated (8.7+/-2.0 g/mm2), and OVX vehicle-treated (9.1+/-1.7 g/mm2) rats. Nevertheless, no remarkable differences were found between groups during histologic evaluation. CONCLUSION: Our results indicate that the wound tensile strength decrease is mediated through the alpha rather than beta ER.

Response of ependymal progenitors to spinal cord injury or enhanced physical activity in adult rat.

Ependymal cells (EC) in the spinal cord central canal (CC) are believed to be responsible for the postnatal neurogenesis following pathological or stimulatory conditions. In this study, we have analyzed the proliferation of the CC ependymal progenitors in adult rats processed to compression SCI or enhanced physical activity. To label dividing cells, a single daily injection of Bromo-deoxyuridine (BrdU) was administered over a 14-day-survival period. Systematic quantification of BrdU-positive ependymal progenitors was performed by using stereological principles of systematic, random sampling, and optical Dissector software. The number of proliferating BrdU-labeled EC increased gradually with the time of survival after both paradigms, spinal cord injury, or increased physical activity. In the spinal cord injury group, we have found 4.9-fold (4 days), 7.1-fold (7 days), 4.9-fold (10 days), and 5.6-fold (14 days) increase of proliferating EC in the rostro-caudal regions, 4 mm away from the epicenter. In the second group subjected to enhanced physical activity by running wheel, we have observed 2.1-2.6 fold increase of dividing EC in the thoracic spinal cord segments at 4 and 7 days, but no significant progression at 10-14 days. Nestin was rapidly induced in the ependymal cells of the CC by 2-4 days and expression decreased by 7-14 days post-injury. Double immunohistochemistry showed that dividing cells adjacent to CC expressed astrocytic (GFAP, S100beta) or nestin markers at 14 days. These data demonstrate that SCI or enhanced physical activity in adult rats induces an endogenous ependymal cell response leading to increased proliferation and differentiation primarily into macroglia or cells with nestin phenotype.