Rare Idiopathic Adult Intussusception: A Case Report.

Intussusception is highly uncommon in adults, with most cases caused by a pathological lead point that requires surgical resection. This case presentation highlights a rare example of idiopathic intussusception in a young male adult. Our patient is a 23-year-old African American male who presented at the Piedmont Macon Medical Center emergency department in February 2023 with acute-onset severe periumbilical pain, nausea, vomiting, and diarrhea. Computed tomography (CT) imaging was inconclusive, and his diagnosis of an ileo-ileal intussusception in the distal ileum was made during an exploratory (diagnostic) laparoscopy. Based on a visual inspection of the bowel demonstrating no evidence of inflammation, adhesions, lesions, ischemia, or a pathological lead point, manual reduction without resection was indicated. While intussusception is rare in adults, it is an important clinical prognosis that should be carefully considered in the differential diagnosis.

Synaptotagmin-7 Counteracts Short-Term Depression during Phasic Dopamine Release.

Dopamine neurons switch from tonic pacemaker activity to high-frequency bursts in response to salient stimuli. These bursts lead to superlinear increases in dopamine release, and the degree of this increase is highly dependent on firing frequency. The superlinearity and frequency dependence of dopamine release implicate short-term plasticity processes. The presynaptic Ca2+-sensor synaptotagmin-7 (SYT7) has suitable properties to mediate such short-term plasticity and has been implicated in regulating dopamine release from somatodendritic compartments. Here, we use a genetically encoded dopamine sensor and whole-cell electrophysiology in Syt7 KO mice to determine how SYT7 contributes to both axonal and somatodendritic dopamine release. We find that SYT7 mediates a hidden component of facilitation of release from dopamine terminals that can be unmasked by lowering initial release probability or by predepressing synapses with low-frequency stimulation. Depletion of SYT7 increased short-term depression and reduced release during stimulations that mimic in vivo firing. Recordings of D2-mediated inhibitory postsynaptic currents in the substantia nigra pars compacta (SNc) confirmed a similar role for SYT7 in somatodendritic release. Our results indicate that SYT7 drives short-term facilitation of dopamine release, which may explain the frequency dependence of dopamine signaling seen in vivo.

The Mycobacterium tuberculosis MmpL3 inhibitor MSU-43085 is active in a mouse model of infection.

IMPORTANCE: MmpL3 is a protein that is required for the survival of bacteria that cause tuberculosis (TB) and nontuberculous mycobacterial (NTM) infections. This report describes the discovery and characterization of a new small molecule, MSU-43085, that targets MmpL3 and is a potent inhibitor of Mycobacterium tuberculosis (Mtb) and M. abscessus survival. MSU-43085 is shown to be orally bioavailable and efficacious in an acute model of Mtb infection. However, the analog is inactive against Mtb in chronically infected mice. Pharmacokinetic and metabolite identification studies identified in vivo metabolism of MSU-43085, leading to a short half-life in treated mice. These proof-of-concept studies will guide further development of the MSU-43085 series for the treatment of TB or NTM infections.

Improved green and red GRAB sensors for monitoring dopaminergic activity in vivo.

Dopamine (DA) plays multiple roles in a wide range of physiological and pathological processes via a large network of dopaminergic projections. To dissect the spatiotemporal dynamics of DA release in both dense and sparsely innervated brain regions, we developed a series of green and red fluorescent G-protein-coupled receptor activation-based DA (GRABDA) sensors using a variety of DA receptor subtypes. These sensors have high sensitivity, selectivity and signal-to-noise ratio with subsecond response kinetics and the ability to detect a wide range of DA concentrations. We then used these sensors in mice to measure both optogenetically evoked and behaviorally relevant DA release while measuring neurochemical signaling in the nucleus accumbens, amygdala and cortex. Using these sensors, we also detected spatially resolved heterogeneous cortical DA release in mice performing various behaviors. These next-generation GRABDA sensors provide a robust set of tools for imaging dopaminergic activity under a variety of physiological and pathological conditions.

Improved dual-color GRAB sensors for monitoring dopaminergic activity in vivo.

Dopamine (DA) plays multiple roles in a wide range of physiological and pathological processes via a vast network of dopaminergic projections. To fully dissect the spatiotemporal dynamics of DA release in both dense and sparsely innervated brain regions, we developed a series of green and red fluorescent GPCR activation-based DA (GRABDA) sensors using a variety of DA receptor subtypes. These sensors have high sensitivity, selectivity, and signal-to-noise properties with subsecond response kinetics and the ability to detect a wide range of DA concentrations. We then used these sensors in freely moving mice to measure both optogenetically evoked and behaviorally relevant DA release while measuring neurochemical signaling in the nucleus accumbens, amygdala, and cortex. Using these sensors, we also detected spatially resolved heterogeneous cortical DA release in mice performing various behaviors. These next-generation GRABDA sensors provide a robust set of tools for imaging dopaminergic activity under a variety of physiological and pathological conditions.

A genetic selection for Mycobacterium smegmatis mutants tolerant to killing by sodium citrate defines a combined role for cation homeostasis and osmotic stress in cell death.

Mycobacteria can colonize environments where the availability of metal ions is limited. Biological or inorganic chelators play an important role in limiting metal availability, and we developed a model to examine Mycobacterium smegmatis survival in the presence of the chelator sodium citrate. We observed that instead of restricting M. smegmatis growth, concentrated sodium citrate killed M. smegmatis. RNAseq analysis during sodium citrate treatment revealed transcriptional signatures of metal starvation and hyperosmotic stress. Notably, metal starvation and hyperosmotic stress, individually, do not kill M. smegmatis under these conditions. A forward genetic transposon selection was conducted to examine why sodium citrate was lethal, and several sodium-citrate-tolerant mutants were isolated. Based on the identity of three tolerant mutants, mgtE, treZ, and fadD6, we propose a dual stress model of killing by sodium citrate, where sodium citrate chelate metals from the cell envelope and then osmotic stress in combination with a weakened cell envelope causes cell lysis. This sodium citrate tolerance screen identified mutants in several other genes with no known function, with most conserved in the pathogen M. tuberculosis. Therefore, this model will serve as a basis to define their functions, potentially in maintaining cell wall integrity, cation homeostasis, or osmotolerance. IMPORTANCE Bacteria require mechanisms to adapt to environments with differing metal availability. When Mycobacterium smegmatis is treated with high concentrations of the metal chelator sodium citrate, the bacteria are killed. To define the mechanisms underlying killing by sodium citrate, we conducted a genetic selection and observed tolerance to killing in mutants of the mgtE magnesium transporter. Further characterization studies support a model where killing by sodium citrate is driven by a weakened cell wall and osmotic stress, that in combination cause cell lysis.

Discovery and characterization of antimycobacterial nitro-containing compounds with distinct mechanisms of action and in vivo efficacy.

Nitro-containing compounds have emerged as important agents in the control of tuberculosis (TB). From a whole-cell high-throughput screen for Mycobacterium tuberculosis (Mtb) growth inhibitors, 10 nitro-containing compounds were prioritized for characterization and mechanism of action studies. HC2209, HC2210, and HC2211 are nitrofuran-based prodrugs that need the cofactor F420 machinery for activation. Unlike pretomanid which depends only on deazaflavin-dependent nitroreductase (Ddn), these nitrofurans depend on Ddn and possibly another F420-dependent reductase for activation. These nitrofurans also differ from pretomanid in their potent activity against Mycobacterium abscessus. Four dinitrobenzamides (HC2217, HC2226, HC2238, and HC2239) and a nitrofuran (HC2250) are proposed to be inhibitors of decaprenyl-phosphoryl-ribose 2'-epimerase 1 (DprE1), based on isolation of resistant mutations in dprE1. Unlike other DprE1 inhibitors, HC2250 was found to be potent against non-replicating persistent bacteria, suggesting additional targets. Two of the compounds, HC2233 and HC2234, were found to have potent, sterilizing activity against replicating and non-replicating Mtb in vitro, but a proposed mechanism of action could not be defined. In a pilot in vivo efficacy study, HC2210 was orally bioavailable and efficacious in reducing bacterial load by ~1 log in a chronic murine TB infection model.

Malignant Extrapleural Solitary Fibrous Tumor.

Solitary fibrous tumors (SFTs) are rare spindle cell neoplasms of mesenchymal origin that are most commonly found in the pleura, although they have also been documented in extrapleural locations. SFTs affect males and females in equal distribution, and they typically occur between the fourth and seventh decades of life. Since SFTs are usually benign and asymptomatic, the majority of them are discovered incidentally on computed tomography (CT) or magnetic resonance imaging (MRI) imaging, unless they grow to a size that causes mass effect symptoms on other organs. Nonetheless, imaging is not sufficient to diagnose an SFT, and therefore, biopsy is recommended for further analysis. Advances in immunohistochemistry and molecular diagnostics have identified CD34 and NAB2-STAT6, respectively, as the most consistent markers for SFTs. The risk of SFT metastasis can be determined through the use of a four-variable risk-stratification model developed by Demicco et al., which is based upon the risk factors of patient age, tumor size, mitotic count per 10 high-power fields, and the degree of tumor necrosis. The management of SFTs involves a wide surgical resection of the tumor while preserving surrounding organs and structures. Post-operative surveillance involves imaging the primary tumor site for up to five years due to the risk of local recurrence. At this time, neither radiation therapy nor chemotherapy after resection have yet to show benefit, and therefore, they are not currently recommended. This case report discusses the management of a 68-year-old woman who was diagnosed with a malignant extrapleural SFT in her right medial upper thigh.

The Rip1 intramembrane protease contributes to iron and zinc homeostasis in Mycobacterium tuberculosis.

Mycobacterium tuberculosis is exposed to a variety of stresses during a chronic infection, as the immune system simultaneously produces bactericidal compounds and starves the pathogen of essential nutrients. The intramembrane protease, Rip1, plays an important role in the adaptation to these stresses, at least partially by the cleavage of membrane-bound transcriptional regulators. Although Rip1 is known to be critical for surviving copper intoxication and nitric oxide exposure, these stresses do not fully account for the regulatory protein's essentiality during infection. In this work, we demonstrate that Rip1 is also necessary for growth in low-iron and low-zinc conditions, similar to those imposed by the immune system. Using a newly generated library of sigma factor mutants, we show that the known regulatory target of Rip1, SigL, shares this defect. Transcriptional profiling under iron-limiting conditions supported the coordinated activity of Rip1 and SigL and demonstrated that the loss of these proteins produces an exaggerated iron starvation response. These observations demonstrate that Rip1 coordinates several aspects of metal homeostasis and suggest that a Rip1- and SigL-dependent pathway is necessary to thrive in the iron-deficient environments encountered during infection. IMPORTANCE Metal homeostasis represents a critical point of interaction between the mammalian immune system and potential pathogens. While the host attempts to intoxicate microbes with high concentrations of copper or starve the invader of iron and zinc, successful pathogens have acquired mechanisms to overcome these defenses. Our work identifies a regulatory pathway consisting of the Rip1 intramembrane protease and the sigma factor, SigL, that is essential for the important human pathogen, Mycobacterium tuberculosis, to grow in low-iron or low-zinc conditions such as those encountered during infection. In conjunction with Rip1's known role in resisting copper toxicity, our work implicates this protein as a critical integration point that coordinates the multiple metal homeostatic systems required for this pathogen to survive in host tissue.

Robotic Ventral Transabdominal Preperitoneal Repair of Uncomplicated Spigelian Hernia.

Spigelian hernias are rare herniations through the Spigelian fascia, with an incidence rate of 0.12-2.0% of all hernias. Diagnosis may be difficult due to a potential lack of symptoms until complications arise. Therefore, imaging with either ultrasound or CT with oral contrast is recommended to confirm the diagnosis if a Spigelian hernia is suspected. Once the diagnosis has been established, it is essential that operative repair be performed as soon as possible because 24% of Spigelian hernias become incarcerated, and 27% of Spigelian hernias lead to strangulation. Management options include open surgery, laparoscopic surgery, and robotic surgery. This case report discusses the management of a 47-year-old man with an uncomplicated Spigelian hernia that was repaired with the robotic ventral transabdominal preperitoneal repair technique.

Molecular Mechanisms of MmpL3 Function and Inhibition.

Mycobacteria species include a large number of pathogenic organisms such as Mycobacterium tuberculosis, Mycobacterium leprae, and various non-tuberculous mycobacteria. Mycobacterial membrane protein large 3 (MmpL3) is an essential mycolic acid and lipid transporter required for growth and cell viability. In the last decade, numerous studies have characterized MmpL3 with respect to protein function, localization, regulation, and substrate/inhibitor interactions. This review summarizes new findings in the field and seeks to assess future areas of research in our rapidly expanding understanding of MmpL3 as a drug target. An atlas of known MmpL3 mutations that provide resistance to inhibitors is presented, which maps amino acid substitutions to specific structural domains of MmpL3. In addition, chemical features of distinct classes of Mmpl3 inhibitors are compared to provide insights into shared and unique features of varied MmpL3 inhibitors.

Synaptotagmin-1 is a Ca2+ sensor for somatodendritic dopamine release.

Modes of somatodendritic transmission range from rapid synaptic signaling to protracted regulation over distance. Somatodendritic dopamine secretion in the midbrain leads to D2 receptor-induced modulation of dopamine neurons on the timescale of seconds. Temporally imprecise release mechanisms are often presumed to be at play, and previous work indeed suggested roles for slow Ca2+ sensors. We here use mouse genetics and whole-cell electrophysiology to establish that the fast Ca2+ sensor synaptotagmin-1 (Syt-1) is important for somatodendritic dopamine release. Syt-1 ablation from dopamine neurons strongly reduces stimulus-evoked D2 receptor-mediated inhibitory postsynaptic currents (D2-IPSCs) in the midbrain. D2-IPSCs evoked by paired stimuli exhibit less depression, and high-frequency trains restore dopamine release. Spontaneous somatodendritic dopamine secretion is independent of Syt-1, supporting that its exocytotic mechanisms differ from evoked release. We conclude that somatodendritic dopamine transmission relies on the fast Ca2+ sensor Syt-1, leading to synchronous release in response to the initial stimulus.

Gait Abnormalities and Aberrant D2 Receptor Expression and Signaling in Mice Carrying the Human Pathogenic Mutation DRD2I212F.

A dopamine D2 receptor mutation was recently identified in a family with a novel hyperkinetic movement disorder. That allelic variant D2-I212F is a constitutively active and G protein-biased receptor. We now describe mice engineered using CRISPR-Cas9-mediated gene editing technology to carry the D2-I212F variant. Drd2I212F mice exhibited gait abnormalities resembling those in other mouse models of chorea and/or dystonia and had striatal D2 receptor expression that was decreased approximately 30% per Drd2I212F allele. Electrically evoked inhibitory postsynaptic conductances in midbrain dopamine neurons and striatum from Drd2I212F mice, caused by G protein activation of potassium channels, exhibited slow kinetics (e.g., approximately four- to sixfold slower decay) compared with Drd2 +/+ mice. Current decay initiated by photolytic release of the D2 antagonist sulpiride from CyHQ-sulpiride was also ∼fourfold slower in midbrain slices from Drd2I212F mice than Drd2 +/+ mice. Furthermore, in contrast to Drd2 +/+ mice, in which dopamine is several-fold more potent at neurons in the nucleus accumbens than in the dorsal striatum, reflecting activation of Gα o versus Gα i, dopamine had similar potencies in those two brain regions of Drd2I212F mice. Repeated cocaine treatment, which decreases dopamine potency in the nucleus accumbens of Drd2 +/+ mice, had no effect on dopamine potency in Drd2 I212F mice. The results demonstrate the pathogenicity of the D2-I212F mutation and the utility of this mouse model for investigating the role of pathogenic DRD2 variants in early-onset hyperkinetic movement disorders. SIGNIFICANCE STATEMENT: The first dopamine receptor mutation to cause a movement disorder, D2-I212F, was recently identified. The mutation makes receptor activation of G protein-mediated signaling more efficient. To confirm the pathogenesis of D2-I212F, this study reports that mice carrying this mutation have gait abnormalities consistent with the clinical phenotype. The mutation also profoundly alters D2 receptor expression and function in vivo. This mouse model will be useful for further characterization of the mutant receptor and for evaluation of potential therapeutic drugs.

Co-activation of GPCRs facilitate GIRK-dependent current.

The activity of dopamine neurons is dependent on both intrinsic properties and afferent projections. One potent form of inhibition is mediated by the activation of two inhibitory G protein-coupled receptors, D2 and GABAB receptors. Each of these receptors activates G protein-coupled inwardly rectifying potassium (GIRK) channels. Recordings in brain slices have shown that co-activation using saturating concentrations of agonists results in occlusion of the GIRK current. The present study examined the interaction between D2 and GABAB receptors using transient applications of sub-saturating concentrations of agonists where the co-application of one agonist resulted in both facilitation and inhibition (desensitization) of the other. The heterologous facilitation was modelled based on the known cooperative interaction between the G protein ßγ subunits and GIRK channels. The results indicate that a low tonic level of G ßγ results in facilitation of GIRK current and a high level of G ßγ results in occlusion. The kinetics of the current induced by transient receptor activation is prolonged in each case. The results suggest that the cooperative interaction between G ßγ subunits and GIRK channels determines both the amplitude and kinetics of GPCR-dependent current. KEY POINTS: Inhibitory D2 and GABAB receptors modulate dopamine neuron activity through shared G protein-coupled inwardly rectifying potassium (GIRK) channels. This study reports robust bidirectional interactions between these two converging receptor pathways. Coincident activation of D2 and GABAB receptors leads to facilitation of GIRK channel currents, augmenting both amplitude and prolonging the duration of phasic responses. Activation of either D2 or GABAB receptors also acutely desensitized the GIRK channel current induced by D2 receptor activation that rapidly recovers following termination of desensitizing stimulus. Results demonstrate that the activity of either G protein-coupled receptor system must be considered in the context of other G protein-coupled receptors.

Cellular Tolerance Induced by Chronic Opioids in the Central Nervous System.

Opioids are powerful analgesics that elicit acute antinociceptive effects through their action the mu opioid receptor (MOR). However opioids are ineffective for chronic pain management, in part because continuous activation of MORs induces adaptive changes at the receptor level and downstream signaling molecules. These adaptations include a decrease in receptor-effector coupling and changes to second messenger systems that can counteract the persistent activation of MORs by opioid agonists. Homeostatic regulation of MORs and downstream signaling cascades are viewed as precursors to developing tolerance. However, despite numerous studies identifying crucial mechanisms that contribute to opioid tolerance, no single regulatory mechanism that governs tolerance in at the cellular and systems level has been identified. Opioid tolerance is a multifaceted process that involves both individual neurons that contain MORs and neuronal circuits that undergo adaptations following continuous MOR activation. The most proximal event is the agonist/receptor interaction leading to acute cellular actions. This review discusses our understanding of mechanisms that mediate cellular tolerance after chronic opioid treatment that, in part, is mediated by agonist/receptor interaction acutely.

Extramedullary Tibial Guide Alignment Is Not Affected by Excess Lower Limb Fat Distribution in Total Knee Arthroplasty.

Background The goal of this study is to investigate whether excess lower limb fat distribution affects tibial guide alignment in conventional total knee arthroplasty (TKA) with extramedullary guides. A thicker soft tissue envelope may affect the accuracy of extramedullary cutting guide placement and subsequent instrumentation. Previous studies have used body mass index (BMI) to stratify patients, a poor proxy of lower limb fat distribution, which may explain conflicting results reported on this topic to date. This study overcomes this issue by using a novel, radiographic anthropometric index to assess lower limb fat distribution. Methodology This is a single-surgeon, single-implant, single-centre retrospective series of 102 consecutive primary TKAs. The suprapatellar fat index (SPFI) and BMI were recorded for all patients, and postoperative tibial component alignment measurements were calculated. Secondary outcome measures included femoral component alignment, femorotibial alignment, length of hospital stay, tourniquet time, blood loss, and complications/reoperations. Results In this study, 102 patients (average age of 69) had an average BMI of 30.8 kg/m2 (19.2-45.5 kg/m2) and an average SPFI of 0.26 (0.09-0.57). Multiple regression analysis demonstrated that increasing leg fat distribution did not affect tibial component alignment in the coronal or sagittal plane. Conclusions Excess lower limb fat distribution, simply measured using the SPFI, does nothave a significant effect on tibial component positioning when extramedullary guides are used in conventional TKA.

Miracles, Martyrdom and Violence: Historical Origins of the Patron Saints of Trauma and Orthopaedic Surgery.

Patron saints have been adopted to protect against disease and disability in the Christian world since the Middle Ages. A patron saint most often has a morbid connection to their affiliated ailment, although patronage may stem from physical attributes or a miracle performed. The purpose of this study is to identify and describe patron saints associated with injury, musculoskeletal disease and orthopaedic pathology. Saints were identified by a systematic review of multiple reference texts. Additional searches were performed in online academic databases, alongside biographic research of primary and secondary archives. Seven patron saints associated with trauma and orthopaedic conditions were identified. These include St. Ignatius, who pioneered deformity-correction surgery on himself and St. Kostka, patron saint of broken bones who was the victim of his infamously cruel brother Paul. St. Alphonsus Liguori, patron saint of spinal conditions, suffered such a severe cervical kyphosis that his chin eroded his chest. Further saints identified include St. Cosmas and St. Damian as patrons of musculoskeletal oncology, and St. Amalberga and St. Roch as patrons of upper and lower limb injuries, respectively. Over the centuries, patron saints have provided hope for patients in the absence of effective treatments, and as role models for physicians with few resources. Their lives and legends provide valuable insight into an important historical aspect of medical culture.

Therapeutic efficacy of antimalarial drugs targeting DosRS signaling in Mycobacterium abscessus.

A search for alternative Mycobacterium abscessus treatments led to our interest in the two-component regulator DosRS, which, in Mycobacterium tuberculosis, is required for the bacterium to establish a state of nonreplicating, drug-tolerant persistence in response to a variety of host stresses. We show here that the genetic disruption of dosRS impairs the adaptation of M. abscessus to hypoxia, resulting in decreased bacterial survival after oxygen depletion, reduced tolerance to a number of antibiotics in vitro and in vivo, and the inhibition of biofilm formation. We determined that three antimalarial drugs or drug candidates, artemisinin, OZ277, and OZ439, can target DosS-mediated hypoxic signaling in M. abscessus and recapitulate the phenotypic effects of genetically disrupting dosS. OZ439 displayed bactericidal activity comparable to standard-of-care antibiotics in chronically infected mice, in addition to potentiating the activity of antibiotics used in combination. The identification of antimalarial drugs as potent inhibitors and adjunct inhibitors of M. abscessus in vivo offers repurposing opportunities that could have an immediate impact in the clinic.

Agonist-Specific Regulation of G Protein-Coupled Receptors after Chronic Opioid Treatment.

Chronic treatment of animals with morphine results in a long lasting cellular tolerance in the locus coeruleus and alters the kinase dependent desensitization of opioid and nonopioid G protein-coupled receptors (GPCRs). This study examined the development of tolerance and altered regulation of kinase activity after chronic treatment of animals with clinically relevant opioids that differ in efficacy at the µ-opioid receptors (MOR). In slices from oxycodone treated animals, no tolerance to opioids was observed when measuring the MOR induced increase in potassium conductance, but the G protein receptor kinase 2/3 blocker, compound 101, no longer inhibited desensitization of somatostatin (SST) receptors. Chronic fentanyl treatment induced a rightward shift in the concentration response to [Met5]enkephalin, but there was no change in the kinase regulation of desensitization of the SST receptor. When total phosphorylation deficient MORs that block desensitization, internalization, and tolerance were virally expressed, chronic treatment with fentanyl resulted in the altered kinase regulation of SST receptors. The results suggest that sustained opioid receptor signaling initiates the process that results in altered kinase regulation of not only opioid receptors, but also other GPCRs. This study highlights two very distinct downstream adaptive processes that are specifically regulated by an agonist dependent mechanism. SIGNIFICANCE STATEMENT: Persistent signaling of MORs results in altered kinase regulation of nonopioid GPCRs after chronic treatment with morphine and oxycodone. Profound tolerance develops after chronic treatment with fentanyl without affecting kinase regulation. The homeostatic change in the kinase regulation of nonopioid GPCRs could account for the systems level in vivo development of tolerance that is seen with opioid agonists, such as morphine and oxycodone, that develop more rapidly than the tolerance induced by efficacious agonists, such as fentanyl and etorphine.