Behavioral control through the direct, focal silencing of neuronal activity.

The ability to optically stimulate and inhibit neurons has revolutionized neuroscience research. Here, we present a direct, potent, user-friendly chemical approach for optically silencing neurons. We have rendered saxitoxin (STX), a naturally occurring paralytic agent, transiently inert through chemical protection with a previously undisclosed nitrobenzyl-derived photocleavable group. Exposing the caged toxin, STX-bpc, to a brief (5 ms) pulse of light effects rapid release of a potent STX derivative and transient, spatially precise blockade of voltage-gated sodium channels (NaVs). We demonstrate the efficacy of STX-bpc for parametrically manipulating action potentials in mammalian neurons and brain slice. Additionally, we show the effectiveness of this reagent for silencing neural activity by dissecting sensory-evoked swimming in larval zebrafish. Photo-uncaging of STX-bpc is a straightforward method for non-invasive, reversible, spatiotemporally precise neural silencing without the need for genetic access, thus removing barriers for comparative research.

A brainstem circuit for gravity-guided vertical navigation.

The sensation of gravity anchors our perception of the environment and is crucial for navigation. However, the neural circuits that transform gravity into commands for navigation are undefined. We first determined that larval zebrafish (Danio rerio) navigate vertically by maintaining a consistent heading across a series of upward climb or downward dive bouts. Gravity-blind mutant fish swim with more variable heading and excessive veering, leading to inefficient vertical navigation. After targeted photoablation of ascending vestibular neurons and spinal projecting midbrain neurons, but not vestibulospinal neurons, vertical navigation was impaired. These data define a sensorimotor circuit that uses evolutionarily-conserved brainstem architecture to transform gravitational signals into persistent heading for vertical navigation. The work lays a foundation to understand how vestibular inputs allow animals to move efficiently through their environment.

Multisensory navigational strategies of hatchling fish for dispersal.

Animals influence how they disperse in the environment by sensing local cues and adapting how they move. However, controlling dispersal can present a particular challenge early in life when animals tend to be more limited in their capacities to sense and move. To what extent and by what mechanisms can newly hatched fish control how they disperse? Here, we reveal hatchling sensorimotor mechanisms for controlling dispersal by combining swim tracking and precise sensory manipulations of a model species, zebrafish. In controlled laboratory experiments, if we physically constrained hatchlings or blocked sensations of motion through vision and the lateral line, hatchlings responded by elevating their buoyancy and passively moving with faster surface currents. Complementarily, in stagnant water, hatchlings covered more ground using hyperstable swimming, strongly orienting based on graviception. Using experimentally calibrated hydrodynamic simulations, we show that these hatchling behaviors nearly tripled diffusivity and made dispersal robust to local conditions, suggesting this multisensory strategy may provide important advantages for early life in a variable environment.

Limiting medical certainties? Funding challenges for German and comparable public healthcare systems due to AI prediction and how to address them.

Current technological and medical advances lend substantial momentum to efforts to attain new medical certainties. Artificial Intelligence can enable unprecedented precision and capabilities in forecasting the health conditions of individuals. But, as we lay out, this novel access to medical information threatens to exacerbate adverse selection in the health insurance market. We conduct an interdisciplinary conceptual analysis to study how this risk might be averted, considering legal, ethical, and economic angles. We ask whether it is viable and effective to ban or limit AI and its medical use as well as to limit medical certainties and find that neither of these limitation-based approaches provides an entirely sufficient resolution. Hence, we argue that this challenge must not be neglected in future discussions regarding medical applications of AI forecasting, that it should be addressed on a structural level and we encourage further research on the topic.

Easing Restrictions During Vaccine Scarcity. How Mitigation Measures Help Tackling Associated Moral and Behavioral Challenges.

Background: When vaccines became first available during the Covid-19 pandemic, their demand significantly exceeded their supply. In consequence, the access to vaccines, initially, was distributed unequally. At the same time, governments started easing pandemic restrictions for vaccinated and recovered persons and restoring their freedoms since their risk of transmitting the virus is significantly reduced. Evidence: We show that restoring freedoms for vaccinated and recovered persons - while upholding restrictions for the rest of the population - is morally unfair during vaccine scarcity. Further, it may yield unintended side-effects, including perverse incentives, growing rifts in society, and the expansion of marginalization. Policy Options & Recommendations: We recommend accompanying easing for vaccinated and recovered individuals by mitigation measures for those who are neither vaccinated nor recovered. We propose, first, to temporarily lift the same restrictions for negative-tested individuals, as for vaccinated or recovered people. Second, the state must ensure broad and easy access to testing for everyone - free of charge. Conclusion: If done right, these mitigation measures create (at least temporarily) equal access to freedom for everybody - solving the moral problem of unfair access to freedoms and counteracting possible negative consequences.

A primal role for the vestibular sense in the development of coordinated locomotion.

Mature locomotion requires that animal nervous systems coordinate distinct groups of muscles. The pressures that guide the development of coordination are not well understood. To understand how and why coordination might emerge, we measured the kinematics of spontaneous vertical locomotion across early development in zebrafish (Danio rerio) . We found that zebrafish used their pectoral fins and bodies synergistically during upwards swims. As larvae developed, they changed the way they coordinated fin and body movements, allowing them to climb with increasingly stable postures. This fin-body synergy was absent in vestibular mutants, suggesting sensed imbalance promotes coordinated movements. Similarly, synergies were systematically altered following cerebellar lesions, identifying a neural substrate regulating fin-body coordination. Together these findings link the vestibular sense to the maturation of coordinated locomotion. Developing zebrafish improve postural stability by changing fin-body coordination. We therefore propose that the development of coordinated locomotion is regulated by vestibular sensation.

Wound Coverage Options for Soft Tissue Defects Following Calcaneal Fracture Management (Operative/Surgical).

Soft tissue defects and wound healing complications related to calcaneus fractures may result in significant morbidity. The management of these soft tissue complications requires following reconstructive principles that provide the requisites for preservation of the injured limb and the maximization of function. Soft tissue complications are addressed with methods that commensurate with the degree of injury, ranging from local wound care to free flap reconstruction. With the orthoplastic approach to both bone and soft tissue plastic reconstruction, outcomes for limb salvage are greatly enhanced. This article discusses in detail the reconstructive ladder for soft tissue injuries associated with calcaneus fractures.

Balance Sense: Response Motifs that Pervade the Brain.

Measuring how the brain encodes and processes an animal's own motion presents major technical challenges. New approaches demonstrate the viability and merit of measuring vestibular responses throughout the entire brain.

Repeated shock stress facilitates basolateral amygdala synaptic plasticity through decreased cAMP-specific phosphodiesterase type IV (PDE4) expression.

Previous studies have shown that exposure to stressful events can enhance fear memory and anxiety-like behavior as well as increase synaptic plasticity in the rat basolateral amygdala (BLA). We have evidence that repeated unpredictable shock stress (USS) elicits a long-lasting increase in anxiety-like behavior in rats, but the cellular mechanisms mediating this response remain unclear. Evidence from recent morphological studies suggests that alterations in the dendritic arbor or spine density of BLA principal neurons may underlie stress-induced anxiety behavior. Recently, we have shown that the induction of long-term potentiation (LTP) in BLA principal neurons is dependent on activation of postsynaptic D1 dopamine receptors and the subsequent activation of the cyclic adenosine 5'-monophosphate (cAMP)-protein kinase A (PKA) signaling cascade. Here, we have used in vitro whole-cell patch-clamp recording from BLA principal neurons to investigate the long-term consequences of USS on their morphological properties and synaptic plasticity. We provided evidence that the enhanced anxiety-like behavior in response to USS was not associated with any significant change in the morphological properties of BLA principal neurons, but was associated with a changed frequency dependence of synaptic plasticity, lowered LTP induction threshold, and reduced expression of phosphodiesterase type 4 enzymes (PDE4s). Furthermore, pharmacological inhibition of PDE4 activity with rolipram mimics the effects of chronic stress on LTP induction threshold and baseline startle. Our results provide the first evidence that stress both enhances anxiety-like behavior and facilitates synaptic plasticity in the amygdala through a common mechanism of PDE4-mediated disinhibition of cAMP-PKA signaling.

Control of Movement Initiation Underlies the Development of Balance.

Balance arises from the interplay of external forces acting on the body and internally generated movements. Many animal bodies are inherently unstable, necessitating corrective locomotion to maintain stability. Understanding how developing animals come to balance remains a challenge. Here we study the interplay among environment, sensation, and action as balance develops in larval zebrafish. We first model the physical forces that challenge underwater balance and experimentally confirm that larvae are subject to constant destabilization. Larvae propel in swim bouts that, we find, tend to stabilize the body. We confirm the relationship between locomotion and balance by changing larval body composition, exacerbating instability and eliciting more frequent swimming. Intriguingly, developing zebrafish come to control the initiation of locomotion, swimming preferentially when unstable, thus restoring preferred postures. To test the sufficiency of locomotor-driven stabilization and the developing control of movement timing, we incorporate both into a generative model of swimming. Simulated larvae recapitulate observed postures and movement timing across early development, but only when locomotor-driven stabilization and control of movement initiation are both utilized. We conclude the ability to move when unstable is the key developmental improvement to balance in larval zebrafish. Our work informs how emerging sensorimotor ability comes to impact how and why animals move when they do.

Maintaining Levels of Lower Extremity Amputations.

Patients who have undergone a lower extremity amputation may develop an unstable soft tissue envelope of the amputation stump. This envelope may result in pain that prohibits prosthetic use or may become chronically infected. Providing stable soft tissue coverage at the amputation site may provide relief from pain and cure of infection. Additionally, a stable amputation soft tissue envelope may assist with the ability of that patient to maintain his or her existing level of ambulation, overall sense of wellness, and ability to maintain social integration. Salvage of a lower extremity amputation level may significantly improve a patient's overall quality of life. Attempts to salvage an amputation level that is plagued by unstable wounds, pain, or infection are warranted in those patients who have the physiologic reserves to undergo salvage of their amputation level. This article presents an approach to the salvage of lower extremity amputations utilizing both local tissue rearrangements and free tissue transfer techniques.

Early Clinical Outcomes of a Novel Antibiotic-Coated, Non-Crosslinked Porcine Acellular Dermal Graft after Complex Abdominal Wall Reconstruction.

BACKGROUND: Non-crosslinked porcine acellular dermal grafts (NCPADG) are currently the mainstay biomaterial for abdominal wall reconstruction (AWR) in complex hernia patients. We report early clinical outcomes using a novel rifampin/minocycline-coated NCPADG for AWR. STUDY DESIGN: A multi-institutional retrospective review was performed of patients who underwent ventral hernia repair using XenMatrix AB Surgical Graft (CR Bard, Inc [Davol]). Patient demographics, hernia and procedure characteristics, and surgical site occurrences/postoperative complications were reviewed up to 6 months after AWR. RESULTS: Seventy-four patients underwent AWR using XenMatrix AB Surgical Graft. Open AWR was performed in 52 patients (70.3%), and 22 patients (29.7%) underwent laparoscopic VHR. Median hernia size/area was 66.0 cm(2) (range 9.4 to 294.5 cm(2)). Sixteen patients (21.6%) had previous wound infections, and 16 patients (21.6%) had violation of the gastrointestinal tract during hernia repair. The most common locations of NCPADG placement were within the intraperitoneal (32.4%) and onlay (21.6%) positions, respectively. Median hospital length of stay was 4 days. Within 30 days after AWR, 6 (8.1%) patients were readmitted, postoperative seroma formation developed in 4 (5.4%) patients, 1 patient required percutaneous drainage, and surgical site infections developed in 5 (6.8%) patients. At 6 months follow-up, hernia recurrence had developed in 4 (5.4%) patients. CONCLUSIONS: Data suggest that use of a novel rifampin/minocycline-coated NCPADG was associated with a low rate of postoperative surgical site occurrences/postoperative complications during the first 30 days of follow-up in complex AWR patients. In addition, data suggest a low rate of hernia recurrence at 6-month follow-up. Additional study is warranted to determine whether early antimicrobial protection of the device translates into longer-term protection of the repair.

Morphology and dendritic maturation of developing principal neurons in the rat basolateral amygdala.

The basolateral nucleus of the amygdala (BLA) assigns emotional valence to sensory stimuli, and many amygdala-dependent behaviors undergo marked development during postnatal life. We recently showed principal neurons in the rat BLA undergo dramatic changes to their electrophysiological properties during the first postnatal month, but no study to date has thoroughly characterized changes to morphology or gene expression that may underlie the functional development of this neuronal population. We addressed this knowledge gap with reconstructions of biocytin-filled principal neurons in the rat BLA at postnatal days 7 (P7), 14, 21, 28, and 60. BLA principal neurons underwent a number of morphological changes, including a twofold increase in soma volume from P7 to P21. Dendritic arbors expanded significantly during the first postnatal month and achieved a mature distribution around P28, in terms of total dendritic length and distance from soma. The number of primary dendrites and branch points were consistent with age, but branch points were found farther from the soma in older animals. Dendrites of BLA principal neurons at P7 had few spines, and spine density increased nearly fivefold by P21. Given the concurrent increase in dendritic material, P60 neurons had approximately 17 times as many total spines as P7 neurons. Together, these developmental transitions in BLA principal neuron morphology help explain a number of concomitant electrophysiological changes during a critical period in amygdala development.

Prenatal stress, regardless of concurrent escitalopram treatment, alters behavior and amygdala gene expression of adolescent female rats.

Depression during pregnancy has been linked to in utero stress and is associated with long-lasting symptoms in offspring, including anxiety, helplessness, attentional deficits, and social withdrawal. Depression is diagnosed in 10-20% of expectant mothers, but the impact of antidepressant treatment on offspring development is not well documented, particularly for females. Here, we used a prenatal stress model of maternal depression to test the hypothesis that in utero antidepressant treatment could mitigate the effects of prenatal stress. We also investigated the effects of prenatal stress and antidepressant treatment on gene expression related to GABAergic and serotonergic neurotransmission in the amygdala, which may underlie behavioral effects of prenatal stress. Nulliparous female rats were implanted with osmotic minipumps delivering clinically-relevant concentrations of escitalopram and mated. Pregnant dams were exposed to 12 days of mixed-modality stressors, and offspring were behaviorally assessed in adolescence (postnatal day 28) and adulthood (beyond day 90) to determine the extent of behavioral change. We found that in utero stress exposure, regardless of escitalopram treatment, increased anxiety-like behavior in adolescent females and profoundly influenced amygdala expression of the chloride transporters KCC2 and NKCC1, which regulate GABAergic function. In contrast, prenatal escitalopram exposure alone elevated amygdala expression of 5-HT1A receptors. In adulthood, anxiety-like behavior returned to baseline and gene expression effects in the amygdala abated, whereas deficits emerged in novel object recognition for rats exposed to stress during gestation. These findings suggest prenatal stress causes age-dependent deficits in anxiety-like behavior and amygdala function in female offspring, regardless of antidepressant exposure.

Reconstruction of the Pediatric Lateral Malleolus and Physis by Free Microvascular Transfer of the Proximal Fibular Physis.

Traumatic injury to the pediatric growth plate can result in growth disturbances, late angular deformity, and limb length inequalities. Complete traumatic loss the entire growth plate complex (physis, epiphysis, and distal metaphysis) of the ankle can lead to severe joint instability and loss of function. In the growing child, physeal preservation is paramount; however, the reconstructive options are limited. We report a case of post-traumatic loss of the distal fibular physis resulting in severe ankle valgus in a pediatric patient after a Gustilo grade 3B open injury. Ankle valgus secondary to post-traumatic necrosis of the lateral ankle physeal complex was successfully managed by microvascular free transfer of the ipsilateral proximal fibula physis. The 24-month follow-up examination demonstrated continued growth of the free vascularized physeal graft and a stable ankle. The donor site had healed without incident. The patient was able to return to age-appropriate play, sports, and social integration.

Prenatal Stress Alters the Development of Socioemotional Behavior and Amygdala Neuron Excitability in Rats.

Prenatal stress (PS) is a risk factor for neurodevelopmental disorders with diverse ages of onset and socioemotional symptoms. Some PS-linked disorders involve characteristic social deficits, such as autism spectrum disorders and schizophrenia, but PS also promotes anxiety disorders. We propose the diversity of symptoms following PS arises from perturbations to early brain development. To this end, we characterized the effects of PS on the developmental trajectory of physiology of the amygdala, a late-developing center for socioemotional control. We found that PS dampened socioemotional behavior and reduced amygdala neuron excitability in offspring during infancy (at postnatal days (P)10, 14, 17 and 21), preadolescence (day 28), and adulthood (day 60). PS offspring in infancy produced fewer isolation-induced vocalizations and in adulthood exhibited less anxiety-like behavior and deficits in social interaction. PS neurons had a more hyperpolarized resting membrane potential from infancy to adulthood and produced fewer action potentials. Moreover, adult amygdala neurons from PS animals expressed larger action potential afterhyperpolarizations and H-current relative to controls, further limiting excitability. Our results suggest that PS can suppress socioemotional behavior throughout development and produce age-specific alterations to amygdala physiology.

Bone morphogenetic proteins: indications and uses.

The BMPs are a group of growth factors that have varied roles in the development and maintenance of many organ systems. Several of the BMPs have osteogenic potential, and exert their effects via complex and highly regulated pathways. At present, only rhBMP-2 and rhBMP-7 are available for clinical use, but only rhBMP-2 is readily available, and from a practical standpoint is considered the only commercially available BMP. Only a few studies exist on BMP use in foot and ankle surgery, but these have shown promising results with low complication rates. BMP is an adjuvant to bone healing,and does not substitute for structural bone needs. In addition, rhBMP-2 outside spinal fusions is considered to be US Food and Drug Administration off-label, and should be used only in patients who are at high risk for bone healing problems.

Low Wound Complication Rates for the Lateral Extensile Approach for Calcaneal ORIF When the Lateral Calcaneal Artery Is Patent.

BACKGROUND: Historically, the lateral extensile approach for calcaneal fracture osteosynthesis has had relatively high rates of wound healing problems. The vascular territory (angiosome) of the lateral foot is now known to be dependent upon the lateral calcaneal branch of the peroneal artery (LCBP artery). We postulated that patency of the LCBP artery may have a profound positive impact on incisional wound healing for calcaneal open reduction and internal fixation (ORIF). METHODS: Ninety consecutive calcaneal fractures that met operative criteria were preoperatively evaluated for the presence of a Doppler signal in the LCBP artery and were followed for the development of wound healing problems. RESULTS: Among these 90 fractures, 85 had a positive preoperative Doppler signal along the course of the LCBP artery (94%) and 5 had no Doppler signal (6%). All patients underwent ORIF via a lateral extensile approach. Overall, incisional wound healing problems occurred in 6 of 90 calcaneal incisions (6.5%). All 5 feet that exhibited an absent Doppler signal in the LCPB artery developed an incisional wound healing complication (5/6, approximately 83%): 2 large apical wounds and 3 major dehiscence/slough. However, among the 84 feet that possessed a positive preoperative Doppler signal in the LCBP artery, there was only 1 (1/84, approximately 1%) incisional wound healing problem (P < .0001, Fischer's exact test). Smokers with a positive Doppler signal in the LCBP artery did not develop a wound healing complication. CONCLUSIONS: This study suggests a strong link to low incisional wound healing complications for the lateral extensile approach to the calcaneus when a preoperative Doppler signal is present in the LCBP artery. We believe this simple examination should be routinely performed prior to calcaneal ORIF. LEVEL OF EVIDENCE: Level III, comparative case series.

Thy1-expressing neurons in the basolateral amygdala may mediate fear inhibition.

Research has identified distinct neuronal circuits within the basolateral amygdala (BLA) that differentially mediate fear expression versus inhibition; however, molecular markers of these populations remain unknown. Here we examine whether optogenetic activation of a cellular subpopulation, which may correlate with the physiologically identified extinction neurons in the BLA, would differentially support fear conditioning versus fear inhibition/extinction. We first molecularly characterized Thy1-channelrhodopsin-2 (Thy1-ChR2-EYFP)-expressing neurons as a subpopulation of glutamatergic pyramidal neurons within the BLA. Optogenetic stimulation of these neurons inhibited a subpopulation of medial central amygdala neurons and shunted excitation from the lateral amygdala. Brief activation of these neurons during fear training disrupted later fear memory in male mice. Optogenetic activation during unreinforced stimulus exposure enhanced extinction retention, but had no effect on fear expression, locomotion, or open-field behavior. Together, these data suggest that the Thy1-expressing subpopulation of BLA pyramidal neurons provide an important molecular and pharmacological target for inhibiting fear and enhancing extinction and for furthering our understanding of the molecular mechanisms of fear processing.

Postnatal maturation of GABAergic transmission in the rat basolateral amygdala.

Many psychiatric disorders, including anxiety and autism spectrum disorders, have early ages of onset and high incidence in juveniles. To better treat and prevent these disorders, it is important to first understand normal development of brain circuits that process emotion. Healthy and maladaptive emotional processing involve the basolateral amygdala (BLA), dysfunction of which has been implicated in numerous psychiatric disorders. Normal function of the adult BLA relies on a fine balance of glutamatergic excitation and GABAergic inhibition. Elsewhere in the brain GABAergic transmission changes throughout development, but little is known about the maturation of GABAergic transmission in the BLA. Here we used whole cell patch-clamp recording and single-cell RT-PCR to study GABAergic transmission in rat BLA principal neurons at postnatal day (P)7, P14, P21, P28, and P35. GABAA currents exhibited a significant twofold reduction in rise time and nearly 25% reduction in decay time constant between P7 and P28. This corresponded with a shift in expression of GABAA receptor subunit mRNA from the α2- to the α1-subunit. The reversal potential for GABAA receptors transitioned from depolarizing to hyperpolarizing with age, from around -55 mV at P7 to -70 mV by P21. There was a corresponding shift in expression of opposing chloride pumps that influence the reversal, from NKCC1 to KCC2. Finally, we observed short-term depression of GABAA postsynaptic currents in immature neurons that was significantly and gradually abolished by P28. These findings reveal that in the developing BLA GABAergic transmission is highly dynamic, reaching maturity at the end of the first postnatal month.