Optimizing process-based models to predict current and future soil organic carbon stocks at high-resolution.

From hillslope to small catchment scales (< 50 km2), soil carbon management and mitigation policies rely on estimates and projections of soil organic carbon (SOC) stocks. Here we apply a process-based modeling approach that parameterizes the MIcrobial-MIneral Carbon Stabilization (MIMICS) model with SOC measurements and remotely sensed environmental data from the Reynolds Creek Experimental Watershed in SW Idaho, USA. Calibrating model parameters reduced error between simulated and observed SOC stocks by 25%, relative to the initial parameter estimates and better captured local gradients in climate and productivity. The calibrated parameter ensemble was used to produce spatially continuous, high-resolution (10 m2) estimates of stocks and associated uncertainties of litter, microbial biomass, particulate, and protected SOC pools across the complex landscape. Subsequent projections of SOC response to idealized environmental disturbances illustrate the spatial complexity of potential SOC vulnerabilities across the watershed. Parametric uncertainty generated physicochemically protected soil C stocks that varied by a mean factor of 4.4 × across individual locations in the watershed and a - 14.9 to + 20.4% range in potential SOC stock response to idealized disturbances, illustrating the need for additional measurements of soil carbon fractions and their turnover time to improve confidence in the MIMICS simulations of SOC dynamics.

Physician Wellness in Orthopedic Surgery: Challenges and Solutions.

The growing epidemic of physician burnout suggests that a change is needed. Physician wellness is an ever-growing consideration, especially in orthopedic surgery, where the challenges to wellness are significant. This review provides many common sense wellness principles and solutions in four main components of wellness (physical, mental, emotional, and spiritual) interwoven with current research on the topic. Although directed to orthopedic surgeons, this guide can be applied to all physicians, because they are based on common human principles of wellness. Wellness is not created overnight, so wellness practices that increase the likelihood of experiencing wellness are encouraged.

Intravenous Tranexamic Acid Decreases Blood Transfusions and Blood Loss for Patients with Surgically Treated Hip Fractures.

INTRODUCTION: Tranexamic acid can decrease blood loss related to surgery and trauma. The primary objective of this study is to examine if the use of a single dose of peri-operative TXA significantly decreases the rate of allogenic blood transfusions in the setting of operative care of hip fractures. Secondary objectives included examining if total blood loss was decreased by TXA in operative hip fractures as well as examining the safety of TXA by measuring the rates venous thromboembolism (VTE). METHODS: Retrospective chart review of 505 patients who were operatively treated for hip fractures at a single facility was performed. In a non-randomized fashion, 307 patients received TXA and 198 patients did not. Patients received 1 gram of TXA prior to incision. Blood transfusion was the primary end point. Blood loss was calculated using the hemoglobin balance method. Chart was reviewed for VTE events during hospitalization. RESULTS: 505 patients were analyzed. The use of single perioperative dose of TXA in the surgical management of hip fracture resulted in absolute risk reduction of transfusion of 7.7% and relative risk reduction of transfusion by 29%. This was statistically significant with P =.04. Patients who received TXA on average lost 235 ml less blood compared to those who did not receive TXA (P <.0001). No increase in VTE events were found in either group during hospitalization. CONCLUSION: This study supports the use of TXA is decrease blood loss and transfusion rates in patients with hip fractures. TXA can be used routinely to decrease complications in this usually fragile population.

Copulation induces expression of the immediate early gene Arc in mating-relevant brain regions of the male rat.

The medial amygdala (MeA), bed nucleus of the stria terminalis (BNST), and medial preoptic area (mPOA) are important for the regulation of male sexual behavior. Sexual experience facilitates sexual behaviors and influences activity in these regions. The goal of this study was to determine whether sexual experience or copulation induces plasticity in the MeA, BNST, or mPOA of male rats, as indicated by changes in levels of Arc, which is indicative of activity-dependent synaptic plasticity in the brain. To this end, sexually naïve or experienced males were placed in mating arenas either alone, with an inaccessible estrus female, or with an accessible estrus female. Arc protein levels were then quantified in these three regions using immunohistochemistry. As expected, sexual experience facilitated copulation, as evidenced by a reduction in latencies to mount, intromit, and ejaculate. Copulation also increased the number of Arc-positive cells in the MeA, anterior BNST, posterior BNST, and the posterior mPOA, but not in the central-rostral region of the mPOA. Surprisingly, prior sexual experience did not impact levels of Arc, suggesting that copulation-induced Arc occurs in both sexually naïve and experienced males.

The Lateral Preoptic Area: A Novel Regulator of Reward Seeking and Neuronal Activity in the Ventral Tegmental Area.

The lateral preoptic area (LPO) is a hypothalamic region whose function has been largely unexplored. Its direct and indirect projections to the ventral tegmental area (VTA) suggest that the LPO could modulate the activity of the VTA and the reward-related behaviors that the VTA underlies. We examined the role of the LPO on reward taking and seeking using operant self-administration of cocaine or sucrose. Rats were trained to self-administer cocaine or sucrose and then subjected to extinction, whereby responding was no longer reinforced. We tested if stimulating the LPO pharmacologically with bicuculline or chemogenetically with Designer Receptors Exclusively Activated by Designer Drugs (DREADDs) modifies self-administration and/or seeking. In another set of experiments, we tested if manipulating the LPO influences cocaine self-administration during and after punishment. To examine the functional connectivity between the LPO and VTA, we used in vivo electrophysiology recordings in anesthetized rats. We tested if stimulating the LPO modifies the activity of GABA and dopamine neurons of the VTA. We found that stimulating the LPO reinstated cocaine and sucrose seeking behavior but had no effect on reward intake. Furthermore, both stimulating and inhibiting the LPO prevented the sustained reduction in cocaine intake seen after punishment. Finally, stimulating the LPO inhibited the activity of VTA GABA neurons while enhancing that of VTA dopamine neurons. These findings indicate that the LPO has the capacity to drive reward seeking, modulate sustained reductions in self-administration following punishment, and regulate the activity of VTA neurons. Taken together, these findings implicate the LPO as a previously overlooked member of the reward circuit.

Sex differences in effects of gestational polychlorinated biphenyl exposure on hypothalamic neuroimmune and neuromodulator systems in neonatal rats.

Polychlorinated biphenyls (PCBs) are ubiquitous in the environment and exposure to them is associated with immune, endocrine and neural dysfunction. Effects of PCBs on inflammation and immunity are best described in spleen and blood, with fewer studies on neural tissues. This is an important gap in knowledge, as molecules typically associated with neuroinflammation also serve neuromodulatory roles and interact with hormones in normal brain development. The current study used Sprague-Dawley rats to assess whether gestational PCB exposure altered hypothalamic gene expression and serum cytokine concentration in neonatal animals given an immune challenge. Dams were fed wafers containing a mixture of PCBs at an environmentally relevant dose and composition (20 µg/kg, 1:1:1 Aroclor 1242:1248:1254) or oil vehicle control throughout their pregnancy. One day old male and female offspring were treated with an inflammatory challenge (lipopolysaccharide, LPS, 50 µg/kg, sc) or saline vehicle control approximately 3.5 h prior to tissue collection. Across both basal and activated inflammatory states, PCB exposure caused greater expression of a subset of inflammatory genes in the hypothalamus and lower expression of genes involved in dopamine, serotonin, and opioid systems compared to oil controls. PCB exposure also altered reactions to inflammatory challenge: it reversed the normal decrease in Esr2 hypothalamic expression and induced an abnormal increase in IL-1b and IL-6 serum concentration in response to LPS. Many of these effects were sex specific. Given the potential long-term consequences of neuroimmune disruption, our findings demonstrate the need for further research.

Age-related changes in sexual function and steroid-hormone receptors in the medial preoptic area of male rats.

Testosterone is the main circulating steroid hormone in males, and acts to facilitate sexual behavior via both reduction to dihydrotestosterone (DHT) and aromatization to estradiol. The mPOA is a key site involved in mediating actions of androgens and estrogens in the control of masculine sexual behavior, but the respective roles of these hormones is not fully understood. As males age they show impairments in sexual function, and a decreased facilitation of behavior by steroid hormones compared to younger animals. We hypothesized that an anatomical substrate for these behavioral changes is a decline in expression and/or activation of hormone receptor-sensitive cells in the mPOA. We tested this by quantifying and comparing numbers of AR- and ERα-containing cells, and Fos as a marker of activated neurons, in the mPOA of mature (4-5months) and aged (12-13months) male rats, assessed one hour after copulation to one ejaculation. Numbers of AR- and ERα cells did not change with age or after sex, but the percentage of AR- and ERα-cells that co-expressed Fos were significantly up-regulated by sex, independent of age. Age effects were found for the percentage of Fos cells that co-expressed ERα (up-regulated in the central mPOA) and the percentage of Fos cells co-expressing AR in the posterior mPOA. Interestingly, serum estradiol concentrations positively correlated with intromission latency in aged but not mature animals. These data show that the aging male brain continues to have high expression and activation of both AR and ERα in the mPOA with copulation, raising the possibility that differences in relationships between hormones, behavior, and neural activation may underlie some age-related impairments.

Aging and estradiol effects on gene expression in the medial preoptic area, bed nucleus of the stria terminalis, and posterodorsal medial amygdala of male rats.

Studies on the role of hormones in male reproductive aging have traditionally focused on testosterone, but estradiol (E2) also plays important roles in the control of masculine physiology and behavior. Our goal was to examine the effects of E2 on the expression of genes selected for E2-sensitivity, involvement in behavioral neuroendocrine functions, and impairments with aging. Mature adult (MAT, 5 mo) and aged (AG, 18 mo) Sprague-Dawley male rats were castrated, implanted with either vehicle or E2 subcutaneous capsules, and euthanized one month later. Bilateral punches were taken from the bed nucleus of the stria terminalis (BnST), posterodorsal medial amygdala (MePD) and the preoptic area (POA). RNA was extracted, and expression of 48 genes analyzed by qPCR using Taqman low-density arrays. Results showed that effects of age and E2 were age- and region-specific. In the POA, 5 genes were increased with E2 compared to vehicle, and there were no age effects. By contrast the BnST showed primarily age-related changes, with 6 genes decreasing with age. The MePD had 5 genes that were higher in aged than mature males, and 17 genes with significant interactions between age and E2. Gene families identified in the MePD included nuclear hormone receptors, neurotransmitters and neuropeptides and their receptors. Ten serum hormones were assayed in these same males, with results revealing both age- and E2-effects, in several cases quite profound. These results support the idea that the male brain continues to be highly sensitive to estradiol even with aging, but the nature of the response can be substantially different in mature and aging animals.

Colocalization of Mating-Induced Fos and D2-Like Dopamine Receptors in the Medial Preoptic Area: Influence of Sexual Experience.

Dopamine in the medial preoptic area (mPOA) stimulates sexual activity in males. This is evidenced by microdialysis and microinjection experiments revealing that dopamine receptor antagonists in the mPOA inhibit sexual activity, whereas agonists facilitate behavior. Microdialysis experiments similarly show a facilitative role for dopamine, as levels of dopamine in the mPOA increase with mating. While the majority of evidence suggests an important role for dopamine receptors in the mPOA in the regulation of male sexual behaviors, whether sexual activity or sexual experience influence dopamine receptor function in the mPOA has not been previously shown. Here we used immunohistochemical assays to determine whether varying levels of sexual activity or experience influence the number of cells containing Fos or D2 receptor immunoreactivity. Results show that sexual experience facilitated subsequent behavior, namely experience decreased latencies. Moreover, the number of cells with immunoreactivity for Fos or D2 correlated with levels of sexual experience and sexual activity. Sexual activity increased Fos immunoreactivity. Sexually experienced animals also had significantly more D2-positive cells. Sexually inexperienced animals copulating for the first time had a larger percentage of D2-positive cells containing Fos, when compared to sexually experienced animals. Finally, regardless of experience, animals that had sex prior to sacrifice had significantly more D2-positive cells that contained Fos, vs. animals that did not copulate. These findings are noteworthy because sexually experienced animals display increased sexual efficiency. The differences in activation of D2 and changes in receptor density may play a role in this efficiency and other behavioral changes across sexual experience.

The medial preoptic area modulates cocaine-induced locomotion in male rats.

Cocaine-induced locomotion is mediated by dopamine in the nucleus accumbens (NAc). Recent evidence indicates that the medial preoptic area (mPOA), a region in the rostral hypothalamus, modulates cocaine-induced dopamine in the NAc. Specifically, rats with lesions of the mPOA experienced a greater increase in dopamine following cocaine administration than rats with sham lesions. Whether the mPOA similarly influences cocaine-induced locomotion is not known. Here we examined whether radiofrequency or neurotoxic lesions of the mPOA in male rats influence changes in locomotion that follow cocaine administration. Locomotion was measured following cocaine administration in male rats with neurotoxic, radiofrequency, or sham lesions of the mPOA. Results indicate that bilateral lesions of the mPOA facilitated cocaine-induced locomotion. This facilitation was independent of lesion type, as increased locomotion was observed with either approach. These findings support a role for the mPOA as an integral region in the processing of cocaine-induced behavioral response, in this case locomotor activity.

Estradiol in the Preoptic Area Regulates the Dopaminergic Response to Cocaine in the Nucleus Accumbens.

The sex-steroid hormone estradiol (E2) enhances the psychoactive effects of cocaine, as evidenced by clinical and preclinical studies. The medial preoptic area (mPOA), a region in the hypothalamus, is a primary neural locus for neuroendocrine integration, containing one of the richest concentrations of estrogen receptors in the CNS and also has a key role in the regulation of naturally rewarding behaviors. However, whether estradiol enhances the neurochemical response to cocaine by acting in the mPOA is still unclear. Using neurotoxic lesions and microdialysis, we examined whether the mPOA modulates cocaine-induced neurochemical activity in the nucleus accumbens. Tract tracing and immunohistochemical staining were used to determine whether projections from the mPOA to the ventral tegmental area (VTA) are sensitive to estrogen signaling. Finally, estradiol microinjections followed by microdialysis were used to determine whether estrogenic signaling in the mPOA modulates cocaine-induced changes of dopamine in the nucleus accumbens. Results showed that lesions of the mPOA or microinjections of estradiol directly into the mPOA increased cocaine-induced release of dopamine in the nucleus accumbens. Immunohistochemical analyses revealed that the mPOA modulates cocaine responsiveness via projections to both dopaminergic and GABAergic neurons in the VTA, and that these projections are sensitive to estrogenic stimulation. Taken together, these findings point to a novel estradiol-dependent pathway that modulates cocaine-induced neurochemical activity in the mesolimbic system.

Astrocytes in the medial preoptic area modulate ejaculation latency in an experience-dependent fashion.

While sexually experienced males copulate at a higher frequency than sexually inexperienced males, there is still a great deal of variability in their behavior. Within the medial preoptic area (mPOA) of the hypothalamus, glutamate modulates some of this variability. Glutamate levels, for example, increase during sexual activity, peaking with ejaculation and falling precipitously during the post-ejaculation interval. Whereas lower glutamate levels after ejaculation translates to longer post-ejaculatory intervals, administration of glutamate uptake inhibitors into the mPOA increases the number of ejaculations a male rat achieves over a mating bout, and reduces the latency to ejaculate once mating begins. Because astrocytes modulate the availability of neuronal glutamate, we hypothesized that differences in the number of GFAP-positive astrocytes in the mPOA may account for variability in sexual behavior. To this end, we examined whether the number of astrocytes in the mPOA related to ejaculation latency as well as to the duration of the post-ejaculatory interval (PEI) in sexually experienced and sexually inexperienced males. Results indicate that the number of astrocytes negatively correlated with latency to reach ejaculations in sexually inexperienced but not sexually experienced rats while the number of astrocytes and PEI were not related. Astrocyte numbers did not vary between inexperienced and experienced subjects indicating that astrocyte processes may differentially project to sex-relevant glutamatergic synapses or that glutamatergic innervation of the mPOA changes as a function of sexual experience.

Sexual experience influences mating-induced activity in nitric oxide synthase-containing neurons in the medial preoptic area.

Nitric oxide (NO) acts in the medial preoptic area (mPOA) of the hypothalamus to facilitate the expression of male sexual behavior and has also been widely implicated in mechanisms of experience, learning, and memory. Using immunohistochemistry for Fos, as a marker for neural activity, and nitric oxide synthase (NOS), the enzyme that catalyzes the production of nitric oxide (NO), we examined whether sexual activity and sexual experience influence Fos co-expression in NOS-containing neurons in the mPOA of male rats. Consistent with previous findings, results indicate that mating increased activity in the mPOA, and that sexual experience facilitated the expression of sexual behaviors, together with increased mating-induced Fos and NOS in the mPOA. Results also indicate that mating increased co-expression of Fos in NOS-containing neurons, and that this increase was highest in animals undergoing their first sexual encounter, indicating that initial sexual experience increases NO production in the mPOA of male rats.

Influences of dopamine and glutamate in the medial preoptic area on male sexual behavior.

Several brain nuclei interact to orchestrate the appetitive and consummatory aspects of male sexual behavior. Of these structures, the medial preoptic area (mPOA) of the hypothalamus is of particular interest, as it receives input from all sensory modalities, and damage to this region disrupts copulation in a wide variety of taxa. Furthermore, the mPOA is both responsive to gonadal hormones and involved in endocrine regulation. Neurochemical studies have demonstrated that both dopamine and glutamate levels rise in the mPOA in response to sexual activity, while antagonism of these neurotransmitters impairs male sexual response. Here we review how dopamine and glutamate act in the mPOA to modulate male sexual behavior.

The medial preoptic area modulates cocaine-induced activity in female rats.

Drugs of abuse exert their effects by exploiting natural neurobiological reward mechanisms, especially the mesolimbic dopamine (DA) system. However, the mesolimbic system does not operate in isolation, and input from other reward-relevant structures may play a role in cocaine's rewarding effects. The medial preoptic area (mPOA) of the hypothalamus is involved in the regulation of two essential and naturally rewarding behaviors: sexual and maternal behaviors. It also makes strong neuroanatomical connections with areas of the mesolimbic system, particularly the ventral tegmental area (VTA). As such, the mPOA is a logical candidate for a neuroanatomical locus modulating activity in the mesolimbic system and emergent behavioral expressions of drug reward, yet the role of this structure is largely unexplored. Here, using a female rat model, we show that the mPOA innervates the VTA in a region-specific manner, that lesions of the mPOA augment cocaine-induced Fos expression in the nucleus accumbens (NAc) and cocaine-induced conditioned place preference. We also show that approximately 68% of mPOA-VTA efferents release γ-aminobutyric acid (GABA), over 75% are sensitive to DA as evidenced by colocalization with DA receptors, and nearly 60% of these contain both DA receptors and GABA, which suggests a novel key role for the mPOA in the inhibition of the mesolimbic DA circuit. Combined, these results reveal the mPOA as a critical modulating structure in cocaine-induced mesolimbic activity and behavioral manifestation of reward, at least in part, via GABAergic output that is sensitive to DA input.

Low complication rate associated with raising mature flap for tibial nonunion reconstruction.

BACKGROUND: Tibia fractures may require soft tissue coverage with transposed tissue and can develop nonunions. Tibial defects can be approached with a posterolateral approach or by elevating the previously transposed tissue. No literature has previously reported the efficacy or safety of the latter approach. The purpose of this study was to report the flap survival rate and complications from delayed elevation of transposed soft tissue as part of a protocol for the treatment of tibia nonunions. METHODS: In a retrospective review of patients having local, regional, or free soft tissue transposition for the management of open type III B high-energy tibial fractures and also requiring secondary procedures on the same tibia for treatment of tibial nonunion and/or osteomyelitis that required flap elevation, 23 patients with 24 flaps were identified and studied. The 24 flaps were elevated a total of 72 times as part of a staged protocol for nonunion reconstruction by a single surgeon. Primary end point was flap survival. Mean follow-up after definitive soft tissue coverage was 23.7 months. Mean follow-up after injury was 28.9 months. RESULTS: One flap failed after elevation. On a per elevation surgery basis, the flap survival rate was 98.6% (71 of 72). On a per flap basis, the flap survival rate was 95.8% (23 of 24). CONCLUSIONS: This is the first report of the survival and complication rates for delayed elevation of soft tissue flaps for tibial nonunion reconstruction. A total of 95.8% of flaps survived elevation. Flap elevation seems to be an alternative to posterolateral tibial approaches for treatment of tibial nonunions.

Operative treatment of chest wall injuries: indications, technique, and outcomes.

Most injuries to the chest wall with residual deformity do not result in long-term respiratory dysfunction unless they are associated with pulmonary contusion. Indications for operative fixation include flail chest, reduction of pain and disability, a chest wall deformity or defect, symptomatic nonunion, thoracotomy for other indications, and open fractures. Operative indications for chest wall injuries are rare.

Locking plates have increased torsional stiffness compared to standard plates in a segmental defect model of clavicle fracture.

OBJECTIVE: To evaluate the effect of locked plate technology to resist torsion in a clavicle fracture model of segmental bone loss. METHODS: Forty-four synthetic clavicles were repaired with either 3.5 mm locked compression plate (LCP) or 3.5 mm low-contact dynamic compression plate (LCDCP). They were divided into two groups of 22 specimens. Each group was tested to evaluate torsional stiffness, load at failure, deflection at failure, and unconstrained plate motion. RESULTS: LCP group showed significantly greater stiffness in torsion compared to the LCDCP group (p < 0.001). Average difference was 20.9%. Load at failure was not significantly different (p < 0.07). Deflection at failure was significantly less for the LCP group (p < 0.03). Unconstrained motion or plate 'looseness' was significantly less for the LCP group (p < 0.017). CONCLUSIONS: In a simulated model of segmental clavicle fracture, a LCP provided more stiffness and less deflection than a low-contact dynamic compression plate.

Complications of open trigger finger release.

PURPOSE: Open release of A1 pulleys for trigger finger has been thought of as a relatively benign procedure with a low complication rate. Few studies have examined the rate of complications in trigger finger release. The objective of this study was to retrospectively review the complications documented for a cohort of patients who received open trigger finger releases. METHODS: We conducted a retrospective chart review of 43 patients who had had 78 open trigger finger releases by a single surgeon. Any postoperative complications that were documented were recorded. Complications were then divided into major and minor. Major complications required further surgery or resulted in significant limitations of activities of daily living; minor complications hindered recovery, responded to treatment (if applicable), and either resolved or had little impact on function. RESULTS: Two major complications were noted: a synovial fistula that required excision, and proximal interphalangeal joint arthrofibrosis that required cast application for pain relief. The major complication rate was 3% per trigger release (2/78). Twenty-seven minor complications in 22 digits were documented for these cases, including decreased range of motion, scar tenderness, pain, and wound erythema. The minor complication rate was 28% (22/78). The overall, combined complication rate for these primary interventions was 31% (24/78). CONCLUSIONS: Open trigger finger release is thought to be a low-risk procedure by most practitioners. In this study, we found that major complications do occur infrequently; however, the rate of minor complications was surprisingly high and related mostly to wound complications or loss of finger range of motion. The surgeon performing open trigger finger releases should inform the patient of the likelihood of having these minor complications.

Cobb angle progression in adolescent scoliosis begins at the intervertebral disc.

STUDY DESIGN: Longitudinal radiographic study of patients with progressive idiopathic scoliosis. OBJECTIVE: To determine the relative contributions of vertebral and disc wedging to the increase in Cobb angle during 3 phases of adolescent skeletal growth and maturation. SUMMARY OF BACKGROUND DATA: Both disc wedging and vertebral body wedging are found in progressive scoliosis, but their relative contribution to curve progression over time is unknown. Which occurs first is important for understanding how scoliosis progresses and for developing methods to halt progression. Previous studies have not properly identified maturity, and provide conflicting results. METHODS: Eighteen girls were followed through their adolescent growth spurt with serial spine and hand skeletal age radiographs. Each Cobb angle was divided into disc wedge angles and vertebral wedge angles. The corresponding hand radiographs provided a measure of maturity level, the Digital Skeletal Age (DSA). The disc versus bone contributions to the Cobb angle were then compared during 3 growth phases: before the growth spurt, during the growth spurt and after the growth spurt. Significance of relative changes was assessed with the Wilcoxon 2-sided mean rank test. RESULTS: Before the growth spurt, there was no difference in relative contributions of the disc and the bone (3 degrees vs. 0 degrees, P = 0.38) to curve progression. During the growth spurt, the mean disc component progressed significantly more than that of the vertebrae (15 degrees vs. 0 degrees, P = 0.0002). This reversed following the growth spurt with the vertebral component progressing more than the disc (10 degrees vs. 0 degrees, P = 0.01). CONCLUSION: Adolescent idiopathic scoliosis initially increases through disc wedging during the rapid growth spurt with progressive vertebral wedging occurring later.