Sex hormone supplementation improves breathing and restores respiratory neuroplasticity following C2 hemisection in rats.

In addition to loss of sensory and motor function below the level of the lesion, traumatic spinal cord injury (SCI) may reduce circulating steroid hormones that are necessary for maintaining normal physiological function for extended time periods. For men, who comprise nearly 80% of new SCI cases each year, testosterone is the most abundant circulating sex steroid. SCI often results in significantly reduced testosterone production and may result in chronic low testosterone levels. Testosterone plays a role in respiratory function and the expression of respiratory neuroplasticity. When testosterone levels are low, young adult male rats are unable to express phrenic long-term facilitation (pLTF), an inducible form of respiratory neuroplasticity invoked by acute, intermittent hypoxia (AIH). However, testosterone replacement can restore this respiratory neuroplasticity. Complicating the interpretation of this finding is that testosterone may exert its influence in three possible ways: 1) directly through androgen receptor (AR) activation, 2) through conversion to dihydrotestosterone (DHT) by way of the enzyme 5α-reductase, or 3) through conversion to 17ß-estradiol (E2) by way of the enzyme aromatase. DHT signals via AR activation similar to testosterone, but with higher affinity, while E2 activates local estrogen receptors. Evidence to date supports the idea that exogenous testosterone supplementation exerts its influence through estrogen receptor signaling under conditions of low circulating testosterone. Here we explored both recovery of breathing function (measured with whole body barometric plethysmography) and the expression of AIH-induced pLTF in male rats following C2-hemisection SCI. One week post injury, rats were supplemented with either E2 or DHT for 7 days. We hypothesized that E2 would enhance ventilation and reveal pLTF following AIH in SCI rats. To our surprise, though E2 did beneficially impact overall breathing recovery following C2-hemisection, both E2 supplementation and DHT restored the expression of AIH-induced pLTF 2 weeks post-SCI.

Low level CO2 supplementation maintains isocapnia and reveals ventilatory long-term facilitation in rats.

Acute, intermittent hypoxia (AIH) induces ventilatory long-term facilitation (vLTF) in awake, freely behaving rats under poikilocapnic and isocapnic experimental conditions. Establishing pre-clinical methods for vLTF induction that more closely align with successful protocols in humans and anesthetized rats would minimize dissonance in experimental findings and improve translational aspects of vLTF. Here, we tested several levels of low-dose CO2 supplementation during and after AIH to determine 1) the lowest amount of inspired CO2 that would maintain isocapnia in rats during a vLTF protocol, and 2) the net impact of supplemental CO2 on vLTF expression. Rats received one of four levels of inspired CO2 (0%, 0.5%, 1% or 2%) administered during AIH and for the 60 min following AIH to quantify vLTF. Our findings indicated that 2% inspired CO2 was sufficient to maintain isocapnia across the AIH protocol and reveal significant vLTF. These findings provide evidence-based support for using 2% supplemental CO2 during and after AIH when assessing vLTF in rats.

A transcriptome dataset for gonadectomy-induced changes in rat spinal cord.

Circulating sex steroid hormones are critical for neural function and development of neuroplasticity in many regions of the central nervous system. In the spinal cord, our knowledge of steroid hormone influence mostly derives from mechanistic studies of pain processing in dorsal spinal cord circuits; less is known regarding hormonal influence of ventral spinal motor function. Gonadectomy (surgical removal of the testes in males and ovaries in females) rapidly and persistently reduces circulating sex steroids in both females and males, providing a means to interrogate the role of hormones on neural function. Here we provide a next-generation RNA sequencing (RNA-seq) data set to evaluate the impact of gonadectomy on the transcriptome of ventral spinal cord tissue of adult female and male rats.

Nanomole-Scale Assignment and One-Use Kits for Determining the Absolute Configuration of Secondary Alcohols.

Two different protocols were developed and optimized to address the need for (1) high sensitivity or (2) convenient utilization in the determination of the absolute configuration of secondary alcohols. The first protocol uses the competing enantioselective conversion (CEC) method to determine configuration on nanomole scale. Reactions were conducted with 145 nmol of the substrate using a 50 µL microsyringe as the reaction vessel, and the absolute configuration was assigned via qualitative determination of the fast reaction by thin-layer chromatography. This protocol resulted in a 50-fold reduction in material required from previous CEC method studies. The approach was evaluated with benzylic and ß-aryl systems. The second protocol was optimized to address the needs of practicing medicinal chemists. A one-use CEC kit was developed, where the fast reaction was identified by (1)H NMR spectroscopy and thin-layer chromatography. The CEC reaction conditions developed for the microsyringe protocol and the one-use kit both displayed data consistent with pseudo-first-order kinetics in substrate. Therefore, the lower limit of sensitivity for the substrate is limited only by the ability to effectively detect the reaction conversions between alcohol substrate and ester product.

"Alas poor Yorick": What retrospective analysis of canine skulls can tell us about the impact of environmental factors on health.

Necropsies and extensive histological evaluation for clinical and sub-clinical disease of approximately three hundred Portuguese Water dogs are available as part of an ongoing study to assess their state of health at end of life. Throughout life these dogs enjoyed a variety of lifestyles and environments. Here we carry out retrospective quantitative assessments of life-time dietary input and physical activity for each dog. To do this, collagens from skull vault bone and from dentine have been analyzed for ratios of stable isotopes to determine differences in diet that individual dogs experienced during late or early life respectively. Robustness of skull bone (weight/unit of skull size) was used as a relative indicator of the amount of physical activity experienced during a dog's lifetime. These environmental parameters were correlated with the frequency and severity of specific disease processes determined at necropsy. Both measures were shown to exert significant low-level (r < 25%) differential effects on specific diseases. The value of retrospective analysis of environmental influences is discussed.

Nanomole-scale assignment of configuration for primary amines using a kinetic resolution strategy.

The absolute configurations of primary amines were assigned using a kinetic resolution strategy with Mioskowski's enantioselective 1-(R,R) and 2-(S,S) acylating agents. A simple mnemonic was developed to determine the configuration. A pseudoenantiomeric pair of reagents, 1-(R,R) and 2-(S,S)-d(3), was prepared and used to assay primary amines on a micromolar scale. The ESI-MS readout of the resulting acetamide products reproduced the selectivity factors from kinetic experiments. The method can be used on mixtures of amines and was validated with amine samples as small as 50 nmol.

C2 hydroxyl group governs the difference in hydrolysis rates of methyl-α-D-glycero-D-guloseptanoside and methyl-ß-D-glycero-D-guloseptanoside.

A computational investigation into the hydrolysis of two methyl septanosides, methyl-α-D-glycero-D-guloseptanoside and methyl-ß-D-glycero-D-guloseptanoside was undertaken. These septanosides were chosen as model compounds for comparison to methyl pyranosides and allowed direct comparison of α versus ß hydrolysis rates for a specific septanoside isomer. Results suggest that hydrolysis takes place without proceeding through a transition state, an observation that was suggested in previous computational studies on exocyclic bond cleavage of carbohydrates. A conformational analysis of α- and ß-anomers 1 and 2 and their corresponding oxocarbenium 3, coupled with relaxed potential energy surface (PES) scans (M06-2X/6-311+G**, implicit methanol), indicated that hydrolysis of the α-anomer is favored by 1-2 kcal/mol over the ß-anomer, consistent with experiment. Model systems revealed that the lowest energy conformations of the septanoside ring system destabilize the ß-anomer by 2-3 kcal/mol relative to the α-anomer, and the addition of a single hydroxyl group at the C2-position on a minimal oxepane acetal can reproduce the PES for the septanoside 1. These results suggest that the C2 hydroxyl plays a unique role in the hydrolysis mechanism, destabilizing the septanoside via its proximity to the anomeric carbon and also through its interaction with the departing methanol from the α-anomer via hydrogen-bonding interactions.

Age relationships of postmortem observations in Portuguese Water Dogs.

A dog model has been used to evaluate histological changes arising from senescence. Autopsies of 145 Portuguese Water Dogs have been used to evaluate the individual and group "state of health" at time of death. For each dog, weights or dimensions of organs or tissues were obtained, together with histological evaluation of tissues. Twenty-three morphological metrics correlated significantly to age at death. Many of these involved muscles; others were associated with derivatives of embryonic foregut. The latter included lengths of the small intestine and trachea as well as weights of the stomach and some lung lobes. Nearly all of the dogs examined had histological changes in multiple tissues, ranging from two to 12 per dog. Associations among pathologies included inflammatory bowel disease with osteoporosis and dental calculus/periodontitis with atherosclerosis and amyloidosis. In addition, two clusters of histological changes were correlated to aging: hyperplasia, frequency of adenomas, and hemosiderosis constituted one group; inflammation, plasmacytic and lymphocytic infiltration, fibrosis, and atrophy, another. Heritability analysis indicated that many of the changes in tissue/organ morphology or histology could be heritable and possibly associated with IGF1, but more autopsies will be required to substantiate these genetic relationships.

Electrogustometric thresholds: relationship to anterior tongue locus, area of stimulation, and number of fungiform papillae.

is well established that, on the anterior tongue, thresholds for chemical tastants are inversely related to the number of fungiform papillae. However, it is not known whether this is the case for thresholds to electrical currents presented to the lingual surface. In this study, electrical thresholds for 16 subjects were determined at four left-side anterior lingual locations: tongue tip (TT), a region 1.7 cm posterior to the tip, a region 3.4 cm posterior to the TT, and a region 1.7 cm from the tip along the lateral margin. Two electrode sizes were employed (12.5 and 50 mm2), and stimulus duration was held constant at 0.5 s. The number of fungiform papillae was determined using videomicroscopy. Analogous to what is seen with chemical stimulation, an inverse relationship was present between the mean electrical thresholds, expressed in terms of current density, and the number of papillae within the stimulated regions. The TT --which has the highest density of fungiform papillae -- was found to be more sensitive than the other tongue regions evaluated. Also paralleling chemical thresholds, the mean electrical threshold values were lower (i.e., sensitivity was higher) at a given tongue locus for the 50-mm2 than for the 12.5-mm2 stimulus area. Overall, this study demonstrates that thresholds for electrical stimulation vary across discrete regions of the anterior tongue and are specifically related to the number of fungiform papillae within the stimulated regions. These observations provide additional support for the hypothesis that lingual sensations induced by low levels of electrical current are mediated by the taste system.

Electrogustometric thresholds: relationship to anterior tongue locus, area of stimulation, and number of fungiform papillae.

It is well established that, on the anterior tongue, thresholds for chemical tastants are inversely related to the number of fungiform papillae. However, it is not known whether this is the case for thresholds for electrical currents presented to the lingual surface. In this study, electrical thresholds for 16 subjects were determined at four left-side anterior lingual locations: tongue tip (TT), a region 1.7 cm posterior to the TT, a region 3.4 cm posterior to the TT, and a region 1.7 cm from the TT along the lateral margin. Two electrode sizes (12.5 mm2 and 50 mm2) were employed for the anodal current, and stimulus duration was held constant at 0.5 s. The number of fungiform papillae was determined using videomicroscopy. Analogous to what is seen with chemical stimulation, an inverse relationship was present between the mean electrical thresholds, expressed in terms of current density, and the number of papillae within the stimulated regions. The TT-which has the highest density of fungiform papillae--was found to be more sensitive than the other tongue regions evaluated. Also paralleling chemical thresholds, the mean electrical threshold values were lower (i.e., sensitivity was higher) at a given tongue locus for the 50-mm2 than for the 12.5-mm2 stimulus area. Overall, this study demonstrates that thresholds for electrical stimulation vary across discrete regions of the anterior tongue and are specifically related to the number of fungiform papillae within the stimulated regions. These observations provide additional support for the hypothesis that lingual sensations induced by low levels of electrical current are mediated by the taste system.