Production of IL-10 by CD4(+) regulatory T cells during the resolution of infection promotes the maturation of memory CD8(+) T cells.

Memory CD8(+) T cells are critical for host defense upon reexposure to intracellular pathogens. We found that interleukin 10 (IL-10) derived from CD4(+) regulatory T cells (Treg cells) was necessary for the maturation of memory CD8(+) T cells following acute infection with lymphocytic choriomeningitis virus (LCMV). Treg cell-derived IL-10 was most important during the resolution phase, calming inflammation and the activation state of dendritic cells. Adoptive transfer of IL-10-sufficient Treg cells during the resolution phase 'restored' the maturation of memory CD8(+) T cells in IL-10-deficient mice. Our data indicate that Treg cell-derived IL-10 is needed to insulate CD8(+) T cells from inflammatory signals, and reveal that the resolution phase of infection is a critical period that influences the quality and function of developing memory CD8(+) T cells.

[Inter-laboratory Study on the Modified Methods for Analyzing Bisphenol A Content for Migration Tests from Polycarbonate Food Apparatuses, Containers, and Packaging].

An inter-laboratory study involving 24 laboratories was conducted to validate the modified analytical method for the migration solution of heptane for the determination of bisphenol A migrating from polycarbonate food processing materials. In this study, two concentrations of samples were blindly coded. Each laboratory determined the analyte (bisphenol A, phenol and p-tert-butylphenol) concentration in each sample according to the established protocol. The obtained values were analyzed statistically using internationally accepted guidelines. Horwitz ratios were calculated based on the reproducibility relative standard deviation (RSDR), which was estimated from the inter-laboratory study, and predicted RSDR, which was calculated using the Horwitz/Thompson equation. Horwitz ratios of the two samples ranged from 0.15 to 0.37 for the three compounds, meeting the performance criteria of less than 2 set by the Codex Alimentarius for analytical method approval. These results showed that this modified analytical method shows good performance as an analytical method for the migration solution of heptane.

The Membrane-Like Structure From Extensor Tendon to the Nail in the Distal End of Digits: An Anatomical Study of Structure, Function, and Utility.

METHODS: The nail structures of 6 cadavers were investigated in each of the 10 digits of the hand. In the histological study, the thickness, length, and location of the SEP were measured in each digit of 3 cadavers. In the other 3 cadavers, the moving distance of the SEP was measured macroscopically with the distal interphalangeal joint in flexion at 0 to 60 degrees for confirmation of the function. This moving distance could be considered as an indicator of the SEP straining the surrounding (retaining) structure and improving the stability of the nail in pinches. RESULT: The SEP was recognized in all the digits. The average length of the SEPs was 2.38 ± 0.11 mm (mean ± SE). The average thickness of the SEPs was 0.35 ± 0.02 mm. The nail matrix and its feeding artery were found beneath the SEP in all digits. The average moving distance of the SEP was 1.38 ± 0.06 mm. This moving distance could be considered sufficiently large to support the role of SEP in the pinches compared with the excursion of the extensor tendon at the DIP joint in a previous report. CONCLUSIONS: The SEP has been shown to play an essential role in fingertip stabilization in pinches. It can serve as an anatomical marker to avoid iatrogenic damage to the nail matrix in surgical approaches.

First dorsal metacarpal artery perforator-based propeller flap: functional anatomy and clinical application in soft-tissue defects of the dorsal hand and digits.

BACKGROUND: Many approaches have been reported to repair soft-tissue defects of the hand using dorsal metacarpal artery flaps. Use of a perforator-based propeller flap from the first intermetacarpal space to the dorsum of the hand has been described. The aim of this study was to confirm the functional anatomy of a first dorsal metacarpal artery (FDMA) perforator flap. METHODS: Twenty-nine fixed cadaveric hands were dissected to determine the origin, course, and branches of the FDMA. Clinically, five cases of soft tissue defects of the hand underwent reconstructive surgery using an FDMA perforator-based propeller flap. RESULTS: The FDMA was found in 27 specimens (93%). The ulnar branch of the FDMA always supplied the cutaneous perforator (mean ± SD, 4.3 ± 1.6), and the most distal cutaneous perforating branch was found along the metacarpal long axis within 25 mm of the tip of the metacarpal head with high frequency (28/29, 97%). In the two hands that had aplasia of the FDMA, well-developed perforators arose directly from the radial artery and advanced to the metacarpal head. Seven hands (24%) had perforators arising from the palmar arterial system, penetrating through or passing close by the second metacarpal bone. In clinical application, all the flaps survived completely without major complications. CONCLUSIONS: The FDMA perforator-based propeller flap is minimally invasive and technically simple. It is expected to be a new option for hand reconstruction.

Interleukin-10 improves stroke outcome by controlling the detrimental Interleukin-17A response.

BACKGROUND: Lymphocytes have dichotomous functions in ischemic stroke. Regulatory T cells are protective, while IL-17A from innate lymphocytes promotes the infarct growth. With recent advances of T cell-subtype specific transgenic mouse models it now has become possible to study the complex interplay of T cell subpopulations in ischemic stroke. METHODS: In a murine model of experimental stroke we analyzed the effects of IL-10 on the functional outcome for up to 14 days post-ischemia and defined the source of IL-10 in ischemic brains based on immunohistochemistry, flow cytometry, and bone-marrow chimeric mice. We used neutralizing IL-17A antibodies, intrathecal IL-10 injections, and transgenic mouse models which harbor a deletion of the IL-10R on distinct T cell subpopulations to further explore the interplay between IL-10 and IL-17A pathways in the ischemic brain. RESULTS: We demonstrate that IL-10 deficient mice exhibit significantly increased infarct sizes on days 3 and 7 and enlarged brain atrophy and impaired neurological outcome on day 14 following tMCAO. In ischemic brains IL-10 producing immune cells included regulatory T cells, macrophages, and microglia. Neutralization of IL-17A following stroke reversed the worse outcome in IL-10 deficient mice and intracerebral treatment with recombinant IL-10 revealed that IL-10 controlled IL-17A positive lymphocytes in ischemic brains. Importantly, IL-10 acted differentially on αß and γδ T cells. IL-17A producing CD4+ αß T cells were directly controlled via their IL-10-receptor (IL-10R), whereas IL-10 by itself had no direct effect on the IL-17A production in γδ T cells. The control of the IL-17A production in γδ T cells depended on an intact IL10R signaling in regulatory T cells (Tregs). CONCLUSIONS: Taken together, our data indicate a key function of IL-10 in restricting the detrimental IL-17A-signaling in stroke and further supports that IL-17A is a therapeutic opportunity for stroke treatment.

Extracellular signal-regulated kinases 2 (Erk2) and Erk5 in the central nervous system differentially contribute to central sensitization in male mice.

Nervous systems are designed to become extra sensitive to afferent nociceptive stimuli under certain circumstances such as inflammation and nerve injury. How pain hypersensitivity comes about is key issue in the field since it ultimately results in chronic pain. Central sensitization represents enhanced pain sensitivity due to increased neural signaling within the central nervous system (CNS). Particularly, much evidence indicates that underlying mechanism of central sensitization is associated with the change of spinal neurons. Extracellular signal-regulated kinases have received attention as key molecules in central sensitization. Previously, we revealed the isoform-specific function of extracellular signal-regulated kinase 2 (Erk2) in spinal neurons for central sensitization using mice with Cre-loxP-mediated deletion of Erk2 in the CNS. Still, how extracellular signal-regulated kinase 5 (Erk5) in spinal neurons contributes to central sensitization has not been directly tested, nor is the functional relevance of Erk5 and Erk2 known. Here, we show that Erk5 and Erk2 in the CNS play redundant and/or distinct roles in central sensitization, depending on the plasticity context (cell types, pain types, time, etc.). We used male mice with Erk5 deletion specifically in the CNS and found that Erk5 plays important roles in central sensitization in a formalin-induced inflammatory pain model. Deletion of both Erk2 and Erk5 leads to greater attenuation of central sensitization in this model, compared to deletion of either isoform alone. Conversely, Erk2 but not Erk5 plays important roles in central sensitization in neuropathic pain, a type of chronic pain caused by nerve damage. Our results suggest the elaborate mechanisms of Erk signaling in central sensitization.

Th17 cells express interleukin-10 receptor and are controlled by Foxp3⁻ and Foxp3+ regulatory CD4+ T cells in an interleukin-10-dependent manner.

T helper 17 (Th17) cells are important for host defense against extracellular microorganisms. However, they are also implicated in autoimmune and chronic inflammatory diseases, and as such need to be tightly regulated. The mechanisms that directly control committed pathogenic Th17 cells in vivo remain unclear. We showed here that IL-17A-producing CD4+ T cells expressed interleukin-10 receptor α (IL-10Rα) in vivo. Importantly, T cell-specific blockade of IL-10 signaling led to a selective increase of IL-17A+IFN-γ⁻ (Th17) and IL-17A+IFN-γ+ (Th17+Th1) CD4+ T cells during intestinal inflammation in the small intestine. CD4+Foxp3⁻ IL-10-producing (Tr1) cells and CD4+Foxp3+ regulatory (Treg) cells were able to control Th17 and Th17+Th1 cells in an IL-10-dependent manner in vivo. Lastly, IL-10 treatment of mice with established colitis decreased Th17 and Th17+Th1 cell frequencies via direct signaling in T cells. Thus, IL-10 signaling directly suppresses Th17 and Th17+Th1 cells.

Ocular drift reflects volitional action preparation.

Human cognitive behavior is predictive rather than reflexive because of volitional action preparation. Recent studies have shown that the covert process of volitional action preparation can be decoded from overt fixational eye movements of fixational/microsaccades and pupil dilation. Ocular drift, the slowest fixational eye movements, is also under the active neural control, but its relationship with cognitive behavior is unknown. Here, we examined whether ocular drift also reflects volitional action preparation. We analyzed ocular drift while adult humans maintained fixation on a central visual stimulus as they prepared to generate a volitional saccade. We adopted the antisaccade paradigm in which subjects generate a targeting saccade toward the opposite direction of a peripheral visual stimulus. Our findings are the following five points. First, ocular drift was slower when subjects prepared for targeting saccade initiation than when such preparation was unnecessary. Second, ocular drift was slowed down with elapsed time from fixation initiation, which was associated with the facilitation of targeting saccade initiation. Third, ocular drift was further slowed on correct antisaccade trials than when subjects failed to suppress targeting saccades toward peripheral stimuli. Fourth, such correlation with antisaccade performance was observed immediately after fixation initiation in ocular drift, but it emerged more slowly in the other fixational eye movements. Fifth, subjects with unstable fixation because of faster ocular drift had poorer antisaccade performance. We suggest that fixation stability measured by ocular drift can be used to decode the covert process of volitional action preparation along with the other fixational eye movements.

IL-10 Receptor Signaling Empowers Regulatory T Cells to Control Th17 Responses and Protect from GN.

Background Th17 cells are central pathogenic mediators of autoimmune disease, including many forms of GN. IL-10 receptor signaling (IL-10R) in regulatory T cells (Tregs) has been implicated in the downregulation of Th17 cells, but the underlying molecular mechanisms and functional relevance of this process remain unclear.Methods We generated mice with Treg-specific IL-10Ra deficiency and subjected these mice to nephrotoxic serum-induced nephritis as a model of crescentic GN. Immune responses and Treg phenotypes were extensively analyzed.Results Compared with controls, mice with IL-10Ra-/- Tregs showed a spontaneously overshooting Th17 immune response. This hyper-Th17 phenotype was further boosted during GN and associated with aggravated renal injury. Notably, abrogation of IL-10Ra signaling in Tregs increased dendritic cell activation and production of Th17-inducing cytokines. In contrast, Treg trafficking and expression of chemokine receptor CCR6 remained unaffected, indicating mechanisms of Th17 control, differing from those of previously identified CCR6+ Treg17 cells. Indeed, the capacity for direct in vitro suppression of Th17 responses by IL-10Ra-/- Tregs was significantly impaired. As underlying pathology, analyses conducted in vitro and in vivo using double-fluorescent reporter mice revealed strikingly decreased IL-10 production by IL-10Ra-/- Tregs. To assess, whether reduced IL-10 could explain the hyper Th17 phenotype, competitive cotransfer experiments were performed. Supporting our concept, IL-10Ra-/- T cells differentiated into Th17 cells at much higher frequencies than wild type T cells did during GN.Conclusions IL-10R engagement optimizes Treg-mediated suppression of Th17 immunity. We hypothesize a feed-forward loop, in which IL-10Ra signaling reinforces IL-10 secretion by Tregs which potently controls Th17 development via direct and indirect mechanisms. IL-10R thus may be a promising therapeutic target for the treatment of GN.

Autopsied case of non-plaque-type dura mater graft-associated Creutzfeldt-Jakob disease presenting with extensive amyloid-ß deposition.

We present an autopsied case of non-plaque-type dura mater graft-associated Creutzfeldt-Jakob disease (dCJD) with extensive amyloid-ß (Aß) deposition in the brain. A 39-year-old Japanese woman presented with memory disturbance and abnormal behavior. The patient had a history of craniotomy with dura matter-graft transplant for a head injury which occurred when she was 19 years old. Magnetic resonance imaging (MRI) showed hyperintensities in the cerebral cortex and striatum on diffusion-weighted images, particularly on the dura mater-grafted right side. Her clinical symptoms, including rapidly progressing cognitive impairment, myoclonus, and periodic sharp wave complexes on electroencephalogram, could not be distinguished from typical sporadic CJD cases. The patient died 11 months after symptom onset, and pathological investigations showed extensive spongiform degeneration with prion protein (PrP) deposition without Kuru plaques; these observations were essentially the same as those of typical sporadic CJD cases. Furthermore, Aß immunohistochemistry showed extensive diffuse staining in the cerebral neocortex, plaque-type deposition, positive staining in the pia mater, and cerebral amyloid angiopathy. Although the MRI findings suggested that the pathological involvement originated from the dura mater-grafted right side, the PrP and Aß depositions showed no apparent regionalization and laterality. Tau-pathology including neurofibrillary tangles was hardly identified. The proteins phosphorylated α-synuclein and phosphorylated transactivation response DNA-binding protein 43 kDa were not detected on immunostaining. Although this report describes only one case, various speculations were made based on detailed clinical and pathological observations in conjunction with previous reports of dCJD. In particular, this report provides significant insight into the characteristics and progression of dCJD pathology and its relationship with Aß pathology.

AMCase is a crucial regulator of type 2 immune responses to inhaled house dust mites.

Chitinases are enzymes that cleave chitin, a component of the exoskeleton of many organisms including the house dust mite (HDM). Here we show that knockin mice expressing an enzymatically inactive acidic mammalian chitinase (AMCase), the dominant true chitinase in mouse lung, showed enhanced type 2 immune responses to inhaled HDM. We found that uncleaved chitin promoted the release of IL-33, whereas cleaved chitin could be phagocytosed and could induce the activation of caspase-1 and subsequent activation of caspase-7; this results in the resolution of type 2 immune responses, probably by promoting the inactivation of IL-33. These data suggest that AMCase is a crucial regulator of type 2 immune responses to inhaled chitin-containing aeroallergens.

A new substitute for formalin: Application to embalming cadavers.

The development of formalin-free fixatives is an urgent issue in gross anatomy because of the health hazard and the tissue-hardening actions of formalin. We recently identified the fixative, antimicrobial, and preservative effects of N-vinyl-2-pyrrolidone (NVP), a precursor of the water-soluble macromolecular polymer polyvinylpyrrolidone, in animal experiments. The aim of the present study is to investigate whether NVP solution can be used as an alternative to formalin in human cadaveric dissection. Twelve donated cadavers were infused with NVP via the femoral and common carotid arteries using a peristaltic pump. Experienced teaching staff members in our department dissected the cadavers and examined their macroanatomical properties. The NVP-embalmed corpses showed no sign of decomposition or fungal growth. The bodies remained soft and flexible. Notably, the shoulder, elbow, wrist, phalangeal, hip, knee, cervical spine, and temporomandibular joints were highly mobile, almost equivalent to those of living individuals. The range of motion of most joints was greater in the NVP-fixed than formalin-fixed cadavers. Under the dermis, the subcutaneous fat was markedly reduced and the connective tissues were transparent, so the ligaments, cutaneous nerves, and veins were easily discernible. The abdominal wall and the visceral organs remained pliable and elastic, resembling those of fresh cadavers. The lungs, liver, and gastrointestinal tract were moveable in the thoracic and abdominal cavities and were readily isolated. NVP can be used successfully as a fixative and preservative solution for human cadavers; furthermore, NVP-embalmed bodies could be valuable for learning clinical skills and for training, and for developing innovative medical devices. Clin. Anat. 31:90-98, 2018. © 2017 Wiley Periodicals, Inc.

Absence of connexin43 and connexin45 does not disturb pre- and peri-implantation development.

Gap junctional intercellular communication is assumed to play an important role during pre- and peri-implantation development. In this study, we eliminated connexin43 (Cx43) and connexin45 (Cx45), major gap junctional proteins in the pre- and peri-implantation embryo. We generated Cx43 -/- Cx45 -/- embryos by Cx43 +/- Cx45 +/- intercrossing, because mice deficient in Cx43 (Cx43 -/-) exhibit perinatal lethality and those deficient in Cx45 (Cx45 -/-) exhibit early embryonic lethality. Wild-type, Cx43 -/-, Cx45 -/-, and Cx43 -/- Cx45 -/- blastocysts all showed similar outgrowths in in vitro culture. Moreover, Cx43 -/- Cx45 -/- embryos were obtained at the expected Mendelian ratio up to embryonic day 9.5, when the Cx45 -/- mutation proved lethal. The Cx43 -/- Cx45 -/- embryos seemed to have no additional developmental abnormalities in comparison with the single knockout strains. Thus, pre- and peri-implantation development does not require Cx43 and Cx45. Other gap junctional proteins are expressed around these stages and these may compensate for the lack of Cx43 and Cx45.

Fixational saccade-related activity of pedunculopontine tegmental nucleus neurons in behaving monkeys.

Fixational saccades are small, involuntary eye movements that occur during attempted visual fixation. Recent studies suggested that several cognitive processes affect the occurrence probability of fixational saccades. Thus, there might be an interaction between fixational saccade-related motor signals and cognitive signals. The pedunculopontine tegmental nucleus (PPTN) in the brainstem has anatomical connections with numerous saccade-related and limbic areas. Previously, we reported that a group of PPTN neurons showed transient phasic bursts or a pause in activity during large visually guided and spontaneous saccades, and also showed sustained tonic changes in activity with task context. We hypothesised that single PPTN neurons would relay both fixational saccade-related and task context-related signals, and might function as an interface between the motor and limbic systems. We recorded the activity of PPTN neurons in behaving monkeys during a reward-biased task, and analysed neuronal activity for small fixational saccades during visual fixation, and compared it with the activity for large visually guided targeting saccades and large spontaneous saccades during intertrial intervals. A population of PPTN neurons exhibited a fixational saccade-related phasic increase in activity, and the majority of them also showed activity modulation with large targeting saccades. In addition, a group of these neurons showed a task-related tonic increase in activity during the fixation period, and half of them relayed the saccade signal only when the neuron exhibited higher tonic activity during the task execution period. Thus, fixational saccade-related signals of PPTN neurons overlap with tonic task-related signals, and might contribute to the cognitive modulation of fixational saccades.

Fixational saccades alter the gap effect.

The reaction times of saccadic eye movements have been studied extensively as a probe for cognitive behavior controlled by large-scale cortical and subcortical neural networks. Recent studies have shown that the reaction times of targeting saccades toward peripheral visual stimuli are prolonged by fixational saccades, the largest miniature eye movements including microsaccades. We have shown previously that the frequency of fixational saccades is decreased by volitional action preparation controlled internally during the antisaccade paradigm (look away from a stimulus). Instead, here we examined whether fixational saccade modulation induced externally by sensory events could also account for targeting saccade facilitation by the same sensory events. When targeting saccades were facilitated by prior fixation stimulus disappearance (gap effect), fixational saccade occurrence was reduced, which could theoretically facilitate targeting saccades. However, such reduction was followed immediately by the rebound of fixational saccade occurrence in some subjects, which could eliminate potential benefits from the previous fixational saccade reduction. These results do not mean that fixational saccades were unrelated to the gap effect because they indeed altered that effect by delaying targeting saccade initiation on trials without the fixation gap more strongly than trials with it. Such changes might be attributed to the disruption of volitional saccade preparation because the frequency of fixational saccades observed in this study was associated with the ability of volitional control over antisaccade behavior. These results suggest that fixational saccades alter the gap effect on targeting saccade reaction times, presumably by disrupting volitional saccade commands.

[Extradural temporopolar approach for surgical management of paraclinoid lesions].

OBJECTIVE: Surgical treatment of paraclinoid tumors adjacent to important anatomical structures, such as the optic nerve, optic chiasm, pituitary stalk, and internal carotid artery, should emphasize maximum resection and preservation of visual function. Thus, early localization and exposure of the optic nerve, and complete mobilization and decompression of the optic nerve and internal carotid artery, are necessary in order to prevent intraoperative neurovascular injuries. However, this technique requires wide exposure of the optic-carotid space through the interpeduncular cistern. We have developed an extradural temporopolar approach for resection of paraclinoid tumors, which can also allow early devascularization of arteries that feed the tumors. We evaluated the surgical outcomes of this approach, paying special attention to clinical and visual outcomes. PATIENTS AND METHODS: Thirteen patients(4 men, 9 women;24-78 years, mean age 54 years), underwent tumor removal using an extradural temporopolar approach between March 2000 and April 2013. We retrospectively reviewed medical charts, radiological findings, intensive care unit flow sheets, and surgical records. RESULTS: Histological diagnoses included craniopharyngioma(4 cases), pituitary adenoma(3 cases), medial sphenoid ridge meningioma(2 cases), tuberculum sellae meningioma(2 cases), trigeminal neurinoma(1 case), and malignant epidermoid(1 case). Tumors were 1.5-6.0cm in length(mean 3.2cm). Tumors were cystic in all 4 craniopharyngiomas and solid in the other 9 cases. Preoperative neurological deficits included visual disturbance in 10 patients, double vision caused by oculomotor nerve palsy in 2 patients, and vertigo in 1 patient. Additional orbitozygomatic craniotomies were performed in 8 patients. Total tumor removal was performed in 7 patients and subtotal removal performed in 6. The pituitary stalk was microscopically preserved in all patients. Postoperative complications included transient diabetes insipidus in 2 patients, chronic subdural hematoma in 1 patient, and abducens palsy in 1 patient. All complications were completely resolved. Surgical outcomes on discharge were recorded as follows:good recovery(11 patients), moderate disability(1 patient), and severe disability(1 patient, who suffered preoperative consciousness disturbance). Visual outcomes were improved in 7 patients, unchanged in 5, and worsened in 1, with recurrence. CONCLUSIONS: The present extradural temporopolar approach, which allows early decompression of the optic nerve, and early devascularization and detachment of the tumor, may lead to greater tumor resection and improved visual outcomes in patients with paraclinoid tumors.

Distribution pattern of the celiac, cranial mesenteric, and caudal mesenteric arteries to the gastrointestinal tract in the common marmoset (Callithrix jacchus).

Gastrointestinal diseases pose problems to captive common marmosets. Therefore, knowledge of the anatomy of the arterial supply to the gastrointestinal tract is an important prerequisite for implementing appropriate veterinary care. The common marmoset's intestinal tract has a well-developed cecum specialized for the fermentative digestion of tree gums. This specialized gastrointestinal tract may have a unique pattern of arterial distribution. This study aimed to elucidate the species-specific gastrointestinal tract arterial anatomy of the common marmoset. We traced the celiac, cranial mesenteric, and caudal mesenteric arteries in six male and nine female common marmosets using the latex injection method. We found that the celiac artery gave rise to the left gastric, common hepatic, splenic, and caudal pancreaticoduodenal arteries. In addition to these arteries, the celiac artery gave origin to the middle colic or jejunal arteries in seven or one cases, respectively. The branches of the cranial mesenteric artery consisted of 3-6 arteries, including the middle colic, caudal pancreaticoduodenal, jejunal, right colic, ileocolic, and ileal arteries, as well as a common trunk of the ventral cecal and ileal branches, and the dorsal cecal and colic branches. In four cases, the cranial mesenteric artery gave rise to the jejunal, ileocolic, and ileal arteries. In one of the 13 cases, the celiac and cranial mesenteric arteries formed a common trunk. The caudal mesenteric artery branched into the left colic, sigmoid, and cranial rectal arteries in all the cases. These findings provide an anatomical basis for gastrointestinal veterinary care of common marmosets.

Connectivity of the Claustrum-Endopiriform Complex with the Presubiculum and Hippocampal Regions in the Common Marmoset (Callithrix jacchus).

We have investigated the hippocampal connectivity of the marmoset presubiculum (PreS) and reported that major connections of PreS in the rat were conserved in the marmoset. Moreover, our results indicated the presence of several additional projections that were almost absent in the rat brain, but abundant in the marmoset, such as direct projections from CA1 to PreS. However, little is known about the connectivity between the frontal brain regions and PreS or hippocampal formation. Therefore, we investigated the distribution of cells of the origins and terminals of the presubicular and hippocampal projections in the marmoset frontal brain regions using the retrograde and anterograde tracer cholera toxin B subunit. In cases of tracer injections into all layers of PreS, many neurons and terminals were labeled in the claustrum-endopiriform (Cl-En) complex almost entirely along the rostrocaudal axis. Even in cases where the injection site involved the superficial (not deep) layers of PreS, labeled neurons and terminals were distributed over a wide rostrocaudal range of the Cl-En complex, but their number and density were significantly lower than the whole-layer injection cases. In cases where the injection site was confined to the hippocampal formation, labeled cells and terminals were localized at a restricted portion of the Cl-En complex. Here, we demonstrate for what we believe to be the first time the strong, reciprocal connections of the Cl-En complex with PreS and projections from the Cl-En complex to the hippocampal regions (CA1 and the subiculum) in the marmoset. Our findings indicate that the Cl-En complex may exert a strong influence on the cortical and subcortical outputs from PreS and, in turn, the entire memory circuitry in the marmoset brain.

Blast-Induced Central Auditory Neurodegeneration Affects Tinnitus Development Regardless of Peripheral Cochlear Damage.

Blast exposure causes serious complications, the most common of which are ear-related symptoms such as hearing loss and tinnitus. The blast shock waves can cause neurodegeneration of the auditory pathway in the brainstem, as well as the cochlea, which is the primary receptor for hearing, leading to blast-induced tinnitus. However, it is still unclear which lesion is more dominant in triggering tinnitus, the peripheral cochlea or the brainstem lesion owing to the complex pathophysiology and the difficulty in objectively measuring tinnitus. Recently, gap detection tests have been developed and are potentially well-suited for determining the presence of tinnitus. In this study, we investigated whether the peripheral cochlea or the central nervous system has a dominant effect on the generation of tinnitus using a blast-exposed mouse model with or without earplugs, which prevent cochlear damage from a blast transmitted via the external auditory canal. The results showed that the earplug (+) group, in which the cochlea was neither physiologically nor histologically damaged, showed a similar extent of tinnitus behavior in a gap prepulse inhibition of acoustic startle reflex test as the earplug (-) group, in which the explosion caused a cochlear synaptic loss in the inner hair cells and demyelination of auditory neurons. In contrast, both excitatory synapses labeled with VGLUT-1 and inhibitory synapses labeled with GAD65 were reduced in the ventral cochlear nucleus, and demyelination in the medial nucleus of the trapezoid body was observed in both groups. These disruptions significantly correlated with the presence of tinnitus behavior regardless of cochlear damage. These results indicate that the lesion in the brainstem could be dominant to the cochlear lesion in the development of tinnitus following blast exposure.

Research Application of Laser-induced Shock Wave for Studying Blast-induced Cochlear Injury.

The ear is the organ most susceptible to explosion overpressure, and cochlear injuries frequently occur after blast exposure. Blast exposure can lead to sensorineural hearing loss (SNHL), which is an irreversible hearing loss that negatively affects the quality of life. Detailed blast-induced cochlear pathologies, such as the loss of hair cells, spiral ganglion neurons, cochlear synapses, and disruption of stereocilia, have been previously documented. However, determining cochlear sensorineural deterioration after a blast injury is challenging because animals exposed to blast overpressure usually experience tympanic membrane perforation (TMP), which causes concurrent conductive hearing loss. To evaluate pure sensorineural cochlear dysfunction, we developed an experimental animal model of blast-induced cochlear injury using a laser-induced shock wave. This method avoids TMP and concomitant systemic injuries and reproduces the functional decline in the SNHL component in an energy-dependent manner after LISW exposure. This animal model could be a platform for elucidating the pathological mechanisms and exploring potential treatments for blast-induced cochlear dysfunction.