Top read articles in the last 30 days
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Abstract
During an immune response, CD8+ T lymphocytes can undergo asymmetric division, giving rise to daughter cells that exhibit distinct tendencies to adopt terminal effector and memory cell fates. Here we show that “pre-effector” and “pre-memory” cells resulting from the first CD8+ T cell division in vivo exhibited low and high rates of endogenous proteasome activity, respectively. Pharmacologic reduction of proteasome activity in CD8+ T cells early during differentiation resulted in acquisition of terminal effector cell characteristics, whereas enhancement of proteasome activity conferred attributes of memory lymphocytes. Transcriptomic and proteomic analyses revealed that modulating proteasome activity in CD8+ T cells affected cellular metabolism. These metabolic changes were mediated, in part, through differential expression of Myc, a transcription factor that controls glycolysis and metabolic reprogramming. Taken together, these results demonstrate that proteasome activity is an important regulator of CD8+ T cell fate and raise the possibility that increasing proteasome activity may be a useful therapeutic strategy to enhance the generation of memory lymphocytes.
Authors
Christella E. Widjaja, Jocelyn G. Olvera, Patrick J. Metz, Anthony T. Phan, Jeffrey N. Savas, Gerjan de Bruin, Yves Leestemaker, Celia R. Berkers, Annemieke de Jong, Bogdan I. Florea, Kathleen Fisch, Justine Lopez, Stephanie H. Kim, Daniel A. Garcia, Stephen Searles, Jack D. Bui, Aaron N. Chang, John R. Yates III, Ananda W. Goldrath, Hermen S. Overkleeft, Huib Ovaa, John T. Chang
Total views: 2204
Abstract
Claudin-low breast cancer is an aggressive subtype that confers poor prognosis and is found largely within the clinical triple-negative group of breast cancer patients. Here, we have shown that intrinsic and immune cell gene signatures distinguish the claudin-low subtype clinically as well as in mouse models of other breast cancer subtypes. Despite adaptive immune cell infiltration in claudin-low tumors, treatment with immune checkpoint inhibitory antibodies against cytotoxic T lymphocyte–associated protein 4 (CTLA-4) and programmed death receptor 1 (PD-1) were ineffective in controlling tumor growth. CD4+FoxP3+ Tregs represented a large proportion of the tumor-infiltrating lymphocytes (TILs) in claudin-low tumors, and Tregs isolated from tumor-bearing mice were able to suppress effector T cell responses. Tregs in the tumor microenvironment highly expressed PD-1 and were recruited partly through tumor generation of the chemokine CXCL12. Antitumor efficacy required stringent Treg depletion combined with checkpoint inhibition; delays in tumor growth were not observed using therapies that modestly diminished the number of Tregs in the tumor microenvironment. This study provides evidence that the recruitment of Tregs to the tumor microenvironment inhibits an effective antitumor immune response and highlights early Treg recruitment as a possible mechanism for the lack of response to immune checkpoint blockade antibodies in specific subtypes of cancer that are heavily infiltrated with adaptive immune cells.
Authors
Nicholas A. Taylor, Sarah C. Vick, Michael D. Iglesia, W. June Brickey, Bentley R. Midkiff, Karen P. McKinnon, Shannon Reisdorf, Carey K. Anders, Lisa A. Carey, Joel S. Parker, Charles M. Perou, Benjamin G. Vincent, Jonathan S. Serody
Total views: 1945
Abstract
TGF-β1 signaling is a critical driver of collagen accumulation and fibrotic disease but also a vital suppressor of inflammation and epithelial cell proliferation. The nature of this multifunctional cytokine has limited the development of global TGF-β1 signaling inhibitors as therapeutic agents. We conducted phenotypic screens for small molecules that inhibit TGF-β1–induced epithelial-mesenchymal transition without immediate TGF-β1 receptor (TβR) kinase inhibition. We identified trihydroxyphenolic compounds as potent blockers of TGF-β1 responses (IC50 ~50 nM), Snail1 expression, and collagen deposition in vivo in models of pulmonary fibrosis and collagen-dependent lung cancer metastasis. Remarkably, the functional effects of trihydroxyphenolics required the presence of active lysyl oxidase–like 2 (LOXL2), thereby limiting effects to fibroblasts or cancer cells, the major LOXL2 producers. Mechanistic studies revealed that trihydroxyphenolics induce auto-oxidation of a LOXL2/3–specific lysine (K731) in a time-dependent reaction that irreversibly inhibits LOXL2 and converts the trihydrophenolic to a previously undescribed metabolite that directly inhibits TβRI kinase. Combined inhibition of LOXL2 and TβRI activities by trihydrophenolics resulted in potent blockade of pathological collagen accumulation in vivo without the toxicities associated with global inhibitors. These findings elucidate a therapeutic approach to attenuate fibrosis and the disease-promoting effects of tissue stiffness by specifically targeting TβRI kinase in LOXL2-expressing cells.
Authors
Ying Wei, Thomas J. Kim, David H. Peng, Dana Duan, Don L. Gibbons, Mitsuo Yamauchi, Julia R. Jackson, Claude J. Le Saux, Cheresa Calhoun, Jay Peters, Rik Derynck, Bradley J. Backes, Harold A. Chapman
Total views: 1794
Abstract
Macrophages are attracted to developing tumors and can participate in immune surveillance to eliminate neoplastic cells. In response, neoplastic cells utilize NF-κB to suppress this killing activity, but the mechanisms underlying their self-protection remain unclear. Here, we report that this dynamic interaction between tumor cells and macrophages is integrally linked by a soluble factor identified as growth and differentiation factor 15 (GDF-15). In vitro, tumor-derived GDF-15 signals in macrophages to suppress their proapoptotic activity by inhibiting TNF and nitric oxide (NO) production. In vivo, depletion of GDF-15 in Ras-driven tumor xenografts and in an orthotopic model of pancreatic cancer delayed tumor development. This delay correlated with increased infiltrating antitumor macrophages. Further, production of GDF-15 is directly regulated by NF-κB, and the colocalization of activated NF-κB and GDF-15 in epithelial ducts of human pancreatic adenocarcinoma supports the importance of this observation. Mechanistically, we found that GDF-15 suppresses macrophage activity by inhibiting TGF-β–activated kinase (TAK1) signaling to NF-κB, thereby blocking synthesis of TNF and NO. Based on these results, we propose that the NF-κB/GDF-15 regulatory axis is important for tumor cells in evading macrophage immune surveillance during the early stages of tumorigenesis.
Authors
Nivedita M. Ratnam, Jennifer M. Peterson, Erin E. Talbert, Katherine J. Ladner, Priyani V. Rajasekera, Carl R. Schmidt, Mary E. Dillhoff, Benjamin J. Swanson, Ericka Haverick, Raleigh D. Kladney, Terence M. Williams, Gustavo W. Leone, David J. Wang, Denis C. Guttridge
Total views: 1680
Abstract
Neural stem cells (NSCs) differentiate into both neurons and glia, and strategies using human NSCs have the potential to restore function following spinal cord injury (SCI). However, the time period of maturation for human NSCs in adult injured CNS is not well defined, posing fundamental questions about the design and implementation of NSC-based therapies. This work assessed human H9 NSCs that were implanted into sites of SCI in immunodeficient rats over a period of 1.5 years. Notably, grafts showed evidence of continued maturation over the entire assessment period. Markers of neuronal maturity were first expressed 3 months after grafting. However, neurogenesis, neuronal pruning, and neuronal enlargement continued over the next year, while total graft size remained stable over time. Axons emerged early from grafts in very high numbers, and half of these projections persisted by 1.5 years. Mature astrocyte markers first appeared after 6 months, while more mature oligodendrocyte markers were not present until 1 year after grafting. Astrocytes slowly migrated from grafts. Notably, functional recovery began more than 1 year after grafting. Thus, human NSCs retain an intrinsic human rate of maturation, despite implantation into the injured rodent spinal cord, yet they support delayed functional recovery, a finding of great importance in planning human clinical trials.
Authors
Paul Lu, Steven Ceto, Yaozhi Wang, Lori Graham, Di Wu, Hiromi Kumamaru, Eileen Staufenberg, Mark H. Tuszynski
Total views: 1665
Abstract
The mammalian target of rapamycin complex 1 (mTORC1) kinase promotes cell growth by activating biosynthetic pathways and suppressing catabolic pathways, particularly that of macroautophagy. A prerequisite for mTORC1 activation is its translocation to the lysosomal surface. Deregulation of mTORC1 has been associated with the pathogenesis of several diseases, but its role in skeletal disorders is largely unknown. Here, we show that enhanced mTORC1 signaling arrests bone growth in lysosomal storage disorders (LSDs). We found that lysosomal dysfunction induces a constitutive lysosomal association and consequent activation of mTORC1 in chondrocytes, the cells devoted to bone elongation. mTORC1 hyperphosphorylates the protein UV radiation resistance–associated gene (UVRAG), reducing the activity of the associated Beclin 1–Vps34 complex and thereby inhibiting phosphoinositide production. Limiting phosphoinositide production leads to a blockage of the autophagy flux in LSD chondrocytes. As a consequence, LSD chondrocytes fail to properly secrete collagens, the main components of the cartilage extracellular matrix. In mouse models of LSD, normalization of mTORC1 signaling or stimulation of the Beclin 1–Vps34–UVRAG complex rescued the autophagy flux, restored collagen levels in cartilage, and ameliorated the bone phenotype. Taken together, these data unveil a role for mTORC1 and autophagy in the pathogenesis of skeletal disorders and suggest potential therapeutic approaches for the treatment of LSDs.
Authors
Rosa Bartolomeo, Laura Cinque, Chiara De Leonibus, Alison Forrester, Anna Chiara Salzano, Jlenia Monfregola, Emanuela De Gennaro, Edoardo Nusco, Isabella Azario, Carmela Lanzara, Marta Serafini, Beth Levine, Andrea Ballabio, Carmine Settembre
Total views: 1664
Abstract
The master cytokine TGF-β mediates tissue fibrosis associated with inflammation and tissue injury. TGF-β induces fibroblast activation and differentiation into myofibroblasts that secrete extracellular matrix proteins. Canonical TGF-β signaling mobilizes Smad2 and Smad3 transcription factors that control fibrosis by promoting gene expression. However, the importance of TGF-β–Smad2/3 signaling in fibroblast-mediated cardiac fibrosis has not been directly evaluated in vivo. Here, we examined pressure overload–induced cardiac fibrosis in fibroblast- and myofibroblast-specific inducible Cre-expressing mouse lines with selective deletion of the TGF-β receptors Tgfbr1/2, Smad2, or Smad3. Fibroblast-specific deletion of Tgfbr1/2 or Smad3, but not Smad2, markedly reduced the pressure overload–induced fibrotic response as well as fibrosis mediated by a heart-specific, latency-resistant TGF-β mutant transgene. Interestingly, cardiac fibroblast–specific deletion of Tgfbr1/2, but not Smad2/3, attenuated the cardiac hypertrophic response to pressure overload stimulation. Mechanistically, loss of Smad2/3 from tissue-resident fibroblasts attenuated injury-induced cellular expansion within the heart and the expression of fibrosis-mediating genes. Deletion of Smad2/3 or Tgfbr1/2 from cardiac fibroblasts similarly inhibited the gene program for fibrosis and extracellular matrix remodeling, although deletion of Tgfbr1/2 uniquely altered expression of an array of regulatory genes involved in cardiomyocyte homeostasis and disease compensation. These findings implicate TGF-β–Smad2/3 signaling in activated tissue-resident cardiac fibroblasts as principal mediators of the fibrotic response.
Authors
Hadi Khalil, Onur Kanisicak, Vikram Prasad, Robert N. Correll, Xing Fu, Tobias Schips, Ronald J. Vagnozzi, Ruijie Liu, Thanh Huynh, Se-Jin Lee, Jason Karch, Jeffery D. Molkentin
Total views: 1655
Abstract
Demyelination in the central nervous system (CNS) leads to severe neurological deficits that can be partially reversed by spontaneous remyelination. Because the CNS is isolated from the peripheral milieu by the blood-brain barrier, remyelination is thought to be controlled by the CNS microenvironment. However, in this work we found that factors derived from peripheral tissue leak into the CNS after injury and promote remyelination in a murine model of toxin-induced demyelination. Mechanistically, leakage of circulating fibroblast growth factor 21 (FGF21), which is predominantly expressed by the pancreas, drives proliferation of oligodendrocyte precursor cells (OPCs) through interactions with β-klotho, an essential coreceptor of FGF21. We further confirmed that human OPCs expressed β-klotho and proliferated in response to FGF21 in vitro. Vascular barrier disruption is a common feature of many CNS disorders; thus, our findings reveal a potentially important role for the peripheral milieu in promoting CNS regeneration.
Authors
Mariko Kuroda, Rieko Muramatsu, Noriko Maedera, Yoshihisa Koyama, Machika Hamaguchi, Harutoshi Fujimura, Mari Yoshida, Morichika Konishi, Nobuyuki Itoh, Hideki Mochizuki, Toshihide Yamashita
Total views: 1632
Abstract
Angiogenesis is a multistep process that requires coordinated migration, proliferation, and junction formation of vascular endothelial cells (ECs) to form new vessel branches in response to growth stimuli. Major intracellular signaling pathways that regulate angiogenesis have been well elucidated, but key transcriptional regulators that mediate these signaling pathways and control EC behaviors are only beginning to be understood. Here, we show that YAP/TAZ, a transcriptional coactivator that acts as an end effector of Hippo signaling, is critical for sprouting angiogenesis and vascular barrier formation and maturation. In mice, endothelial-specific deletion of Yap/Taz led to blunted-end, aneurysm-like tip ECs with fewer and dysmorphic filopodia at the vascular front, a hyper-pruned vascular network, reduced and disarranged distributions of tight and adherens junction proteins, disrupted barrier integrity, subsequent hemorrhage in growing retina and brain vessels, and reduced pathological choroidal neovascularization. Mechanistically, YAP/TAZ activates actin cytoskeleton remodeling, an important component of filopodia formation and junction assembly. Moreover, YAP/TAZ coordinates EC proliferation and metabolic activity by upregulating MYC signaling. Overall, these results show that YAP/TAZ plays multifaceted roles for EC behaviors, proliferation, junction assembly, and metabolism in sprouting angiogenesis and barrier formation and maturation and could be a potential therapeutic target for treating neovascular diseases.
Authors
Jongshin Kim, Yoo Hyung Kim, Jaeryung Kim, Do Young Park, Hosung Bae, Da-Hye Lee, Kyun Hoo Kim, Seon Pyo Hong, Seung Pil Jang, Yoshiaki Kubota, Young-Guen Kwon, Dae-Sik Lim, Gou Young Koh
Total views: 1612
Abstract
Atypical antipsychotics such as olanzapine often induce excessive weight gain and type 2 diabetes. However, the mechanisms underlying these drug-induced metabolic perturbations remain poorly understood. Here, we used an experimental model that reproduces olanzapine-induced hyperphagia and obesity in female C57BL/6 mice. We found that olanzapine treatment acutely increased food intake, impaired glucose tolerance, and altered physical activity and energy expenditure in mice. Furthermore, olanzapine-induced hyperphagia and weight gain were blunted in mice lacking the serotonin 2C receptor (HTR2C). Finally, we showed that treatment with the HTR2C-specific agonist lorcaserin suppressed olanzapine-induced hyperphagia and weight gain. Lorcaserin treatment also improved glucose tolerance in olanzapine-fed mice. Collectively, our studies suggest that olanzapine exerts some of its untoward metabolic effects via antagonism of HTR2C.
Authors
Caleb C. Lord, Steven C. Wyler, Rong Wan, Carlos M. Castorena, Newaz Ahmed, Dias Mathew, Syann Lee, Chen Liu, Joel K. Elmquist
Total views: 1538
Abstract
Recent discoveries of the glymphatic system and of meningeal lymphatic vessels have generated a lot of excitement, along with some degree of skepticism. Here, we summarize the state of the field and point out the gaps of knowledge that should be filled through further research. We discuss the glymphatic system as a system that allows CNS perfusion by the cerebrospinal fluid (CSF) and interstitial fluid (ISF). We also describe the recently characterized meningeal lymphatic vessels and their role in drainage of the brain ISF, CSF, CNS-derived molecules, and immune cells from the CNS and meninges to the peripheral (CNS-draining) lymph nodes. We speculate on the relationship between the two systems and their malfunction that may underlie some neurological diseases. Although much remains to be investigated, these new discoveries have changed our understanding of mechanisms underlying CNS immune privilege and CNS drainage. Future studies should explore the communications between the glymphatic system and meningeal lymphatics in CNS disorders and develop new therapeutic modalities targeting these systems.
Authors
Antoine Louveau, Benjamin A. Plog, Salli Antila, Kari Alitalo, Maiken Nedergaard, Jonathan Kipnis
Total views: 1698
Abstract
There is an increasing recognition that inflammation plays a critical role in neurodegenerative diseases of the CNS, including Alzheimer’s disease, amyotrophic lateral sclerosis, Parkinson’s disease, and the prototypic neuroinflammatory disease multiple sclerosis (MS). Differential immune responses involving the adaptive versus the innate immune system are observed at various stages of neurodegenerative diseases, and may not only drive disease processes but could serve as therapeutic targets. Ongoing investigations into the specific inflammatory mechanisms that play roles in disease causation and progression have revealed lessons about inflammation-driven neurodegeneration that can be applied to other neurodegenerative diseases. An increasing number of immunotherapeutic strategies that have been successful in MS are now being applied to other neurodegenerative diseases. Some approaches suppress CNS immune mechanisms, while others harness the immune system to clear deleterious products and cells. This Review focuses on the mechanisms by which inflammation, mediated either by the peripheral immune response or by endogenous CNS immune mechanisms, can affect CNS neurodegeneration.
Authors
Tanuja Chitnis, Howard L. Weiner
Total views: 1619
Abstract
Microglia are brain-resident myeloid cells that mediate key functions to support the CNS. Microglia express a wide range of receptors that act as molecular sensors, which recognize exogenous or endogenous CNS insults and initiate an immune response. In addition to their classical immune cell function, microglia act as guardians of the brain by promoting phagocytic clearance and providing trophic support to ensure tissue repair and maintain cerebral homeostasis. Conditions associated with loss of homeostasis or tissue changes induce several dynamic microglial processes, including changes of cellular morphology, surface phenotype, secretory mediators, and proliferative responses (referred to as an “activated state”). Activated microglia represent a common pathological feature of several neurodegenerative diseases, including Alzheimer’s disease (AD). Cumulative evidence suggests that microglial inflammatory activity in AD is increased while microglial-mediated clearance mechanisms are compromised. Microglia are perpetually engaged in a mutual interaction with the surrounding environment in CNS; thus, diverse microglial reactions at different disease stages may open new avenues for therapeutic intervention and modification of inflammatory activities. In this Review, the role of microglia in the pathogenesis of AD and the modulation of microglia activity as a therapeutic modality will be discussed.
Authors
Heela Sarlus, Michael T. Heneka
Total views: 1285
Abstract
Oligodendrocytes are glial cells that populate the entire CNS after they have differentiated from oligodendrocyte progenitor cells. From birth onward, oligodendrocytes initiate wrapping of neuronal axons with a multilamellar lipid structure called myelin. Apart from their well-established function in action potential propagation, more recent data indicate that oligodendrocytes are essential for providing metabolic support to neurons. Oligodendrocytes transfer energy metabolites to neurons through cytoplasmic “myelinic” channels and monocarboxylate transporters, which allow for the fast delivery of short-carbon-chain energy metabolites like pyruvate and lactate to neurons. These substrates are metabolized and contribute to ATP synthesis in neurons. This Review will discuss our current understanding of this metabolic supportive function of oligodendrocytes and its potential impact in human neurodegenerative disease and related animal models.
Authors
Thomas Philips, Jeffrey D. Rothstein
Total views: 815
Abstract
Microglial cells are the resident tissue macrophages of the CNS and are widely recognized for their immune surveillance of the healthy CNS. In addition to this well-accepted function, recent findings point to major roles for microglia in instructing and regulating the proper function of the neuronal networks in the adult CNS, but these cells are also involved in creating neuronal networks by orchestrating construction of the whole network during development. In this Review, we highlight recent findings about the steady-state functions of microglial cells, the factors that are important for physiological microglial function, and how microglia help to maintain tissue homeostasis in the CNS.
Authors
Katrin Kierdorf, Marco Prinz
Total views: 808
Abstract
Microglia are the main resident macrophage population of the CNS and perform numerous functions required for CNS development, homeostasis, immunity, and repair. Many lines of evidence also indicate that dysregulation of microglia contributes to the pathogenesis of neurodegenerative and behavioral diseases. These observations provide a compelling argument to more clearly define the mechanisms that control microglia identity and function in health and disease. In this Review, we present a conceptual framework for how different classes of transcription factors interact to select and activate regulatory elements that control microglia development and their responses to internal and external signals. We then describe functions of specific transcription factors in normal and pathological contexts and conclude with a consideration of open questions to be addressed in the future.
Authors
Inge R. Holtman, Dylan Skola, Christopher K. Glass
Total views: 736
Abstract
Amyotrophic lateral sclerosis (ALS) is a degenerative disorder that is characterized by loss of motor neurons and shows clinical, pathological, and genetic overlap with frontotemporal dementia (FTD). Activated microglia are a universal feature of ALS/FTD pathology; however, their role in disease pathogenesis remains incompletely understood. The recent discovery that ORF 72 on chromosome 9 (C9orf72), the gene most commonly mutated in ALS/FTD, has an important role in myeloid cells opened the possibility that altered microglial function plays an active role in disease. This Review highlights the contribution of microglia to ALS/FTD pathogenesis, discusses the connection between autoimmunity and ALS/FTD, and explores the possibility that C9orf72 and other ALS/FTD genes may have a “dual effect” on both neuronal and myeloid cell function that could explain a shared propensity for altered systemic immunity and neurodegeneration.
Authors
Deepti Lall, Robert H. Baloh
Total views: 562
Abstract
There are currently over 1.9 billion people who are obese or overweight, leading to a rise in related health complications, including insulin resistance, type 2 diabetes, cardiovascular disease, liver disease, cancer, and neurodegeneration. The finding that obesity and metabolic disorder are accompanied by chronic low-grade inflammation has fundamentally changed our view of the underlying causes and progression of obesity and metabolic syndrome. We now know that an inflammatory program is activated early in adipose expansion and during chronic obesity, permanently skewing the immune system to a proinflammatory phenotype, and we are beginning to delineate the reciprocal influence of obesity and inflammation. Reviews in this series examine the activation of the innate and adaptive immune system in obesity; inflammation within diabetic islets, brain, liver, gut, and muscle; the role of inflammation in fibrosis and angiogenesis; the factors that contribute to the initiation of inflammation; and therapeutic approaches to modulate inflammation in the context of obesity and metabolic syndrome.
Authors
Alan R. Saltiel, Jerrold M. Olefsky
Total views: 559
Abstract
Spinal cord injury (SCI) lesions present diverse challenges for repair strategies. Anatomically complete injuries require restoration of neural connectivity across lesions. Anatomically incomplete injuries may benefit from augmentation of spontaneous circuit reorganization. Here, we review SCI cell biology, which varies considerably across three different lesion-related tissue compartments: (a) non-neural lesion core, (b) astrocyte scar border, and (c) surrounding spared but reactive neural tissue. After SCI, axon growth and circuit reorganization are determined by neuron-cell-autonomous mechanisms and by interactions among neurons, glia, and immune and other cells. These interactions are shaped by both the presence and the absence of growth-modulating molecules, which vary markedly in different lesion compartments. The emerging understanding of how SCI cell biology differs across lesion compartments is fundamental to developing rationally targeted repair strategies.
Authors
Timothy M. O’Shea, Joshua E. Burda, Michael V. Sofroniew
Total views: 508
Abstract
Prion diseases are a group of progressive and fatal neurodegenerative disorders characterized by deposition of scrapie prion protein (PrPSc) in the CNS. This deposition is accompanied by neuronal loss, spongiform change, astrogliosis, and conspicuous microglial activation. Here, we argue that microglia play an overall neuroprotective role in prion pathogenesis. Several microglia-related molecules, such as Toll-like receptors (TLRs), the complement system, cytokines, chemokines, inflammatory regulators, and phagocytosis mediators, are involved in prion pathogenesis. However, the molecular mechanisms underlying the microglial response to prion infection are largely unknown. Consequently, we lack a comprehensive understanding of the regulatory network of microglial activation. On the positive side, recent findings suggest that therapeutic strategies modulating microglial activation and function may have merit in prion disease. Moreover, studies on the role of microglia in prion disease could deepen our understanding of neuroinflammation in a broad range of neurodegenerative disorders.
Authors
Adriano Aguzzi, Caihong Zhu
Total views: 487
Copyright © 2017 American Society for Clinical Investigation
ISSN: 0021-9738 (print), 1558-8238 (online)