Recalcitrant intussusception: exploring potential associations with Helicobacter pylori infection - a case report and literature review.

BACKGROUND: Intussusception, a common cause of abdominal pain in children, often lacks clear underlying causes and is mostly idiopathic. Recurrence, though rare, raises clinical concerns, with rates escalating after each episode. Factors like pathological lead points and Henoch-Schönlein purpura (HSP) are associated with recurrent cases. On the other hand, the prevalence of Helicobacter pylori (H. pylori), often asymptomatic, in children has been declining. Although its infection is reported to be linked with HSP, its role in recurrent intussusception remains unexplored. Further research is needed to understand the interplay among H. pylori (culprit pathogen), HSP (trigger), and intractable intussusception so as to develop effective management strategies. CASE PRESENTATION: A two-year-old girl experienced four atypical episodes of intussusception at distinct locations, which later coincided with HSP. Despite treatment with steroids, recurrent intussusception persisted, suggesting that HSP itself was not a major cause for intractable presentations. Subsequent identification of H. pylori infection and treatment with triple therapy resulted in complete resolution of her recalcitrant intussusception. CONCLUSION: This instructive case underscored a sequence wherein H. pylori infection triggered HSP, subsequently resulting in recurrent intussusception. While H. pylori infection is not common in young children, the coexistence of intractable intussusception and steroid-resistant recurrent HSP necessitates consideration of H. pylori infection as a potential underlying pathogen.

A multimodal approach integrating cognitive and motor demands into physical activity for optimal mental health: Methodological issues and future directions.

Physical activity is known for its positive effects on cognition and affect, with existing literature suggesting that these mental health benefits may be optimally experienced by incorporating cognitive and motor demands during physical activity (PA). However, the existing body of literature lacks a comprehensive guideline for designing the qualitative characteristics of a PA program. Accordingly, this narrative review aimed to (1) provide a working two-dimension model that operationally defines the cognitive and motor demands involved in PA and the rationale for systematically studying these qualitative aspects of PA, (2) identify methods to assess the cognitive and motor demands of PA and address associated methodological issues, and (3) offer potential future directions for research on the cognitive and motor aspects of PA in support of the development of PA programs designed to maximize PA-induced cognitive and affective benefits. We anticipate this article to inform the need for future research and development on this topic, aiming to create clear, evidence-based guidelines for designing innovative and effective PA interventions.

Increasing DNA damage sensitivity through corylin-mediated inhibition of homologous recombination.

BACKGROUND: DNA repair allows the survival of cancer cells. Therefore, the development of DNA repair inhibitors is a critical need for sensitizing cancers to chemoradiation. Sae2CtIP has specific functions in initiating DNA end resection, as well as coordinating cell cycle checkpoints, and it also greatly interacts with the DDR at different levels. RESULTS: In this study, we demonstrated that corylin, a potential sensitizer, causes deficiencies in DNA repair and DNA damage checkpoints in yeast cells. More specifically, corylin increases DNA damage sensitivity through the Sae2-dependent pathway and impairs the activation of Mec1-Ddc2, Rad53-p and γ-H2A. In breast cancer cells, corylin increases apoptosis and reduces proliferation following Dox treatment by inhibiting CtIP. Xenograft assays showed that treatment with corylin combined with Dox significantly reduced tumor growth in vivo. CONCLUSIONS: Our findings herein delineate the mechanisms of action of corylin in regulating DNA repair and indicate that corylin has potential long-term clinical utility as a DDR inhibitor.

Associations between transfusion reactions and thromboembolism development in blood-transfused patients: A retrospective cohort study.

BACKGROUND: Blood transfusion (BT) may be associated with an increased risk of thromboembolism. The associations between transfusion reactions (TRs) during BTs and potential risk factors for the development of thromboembolism in patients underwent blood transfusion have not been analyzed. Therefore, this study aimed to compare risk factors associated with the development of venous thromboembolism (VTE) or pulmonary embolism (PE) between patients underwent blood transfusion with and without TRs. STUDY DESIGNS AND METHODS: The retrospective study was conducted between April 1, 2017, and March 31, 2020, at a medical center in Taiwan. Blood-transfused patients were grouped into two cohorts as follows: those who experienced TRs and those who did not experience TRs. Both cohorts were subjected to follow-up until March 31, 2021. The endpoints for both groups were the occurrence of VTE or PE or the date of March 31, 2021. To investigate between-cohort risk differences, a Kaplan-Meier survival analysis and multiple Cox proportional hazard model was used. RESULTS: A total of 10,759 patients underwent 59,385 transfusion procedures, with 703 patients in the TR group, and 10,056 patients in the non-TR group. The risk of VTE or PE was twice as high in the TR group than in the non-TR group (adjusted hazard ratio 2.53, 95% confidence interval 1.49-4.29, p = .001). Meanwhile, age, female sex, transfusion frequency increment, and being nondiabetic was associated with an increased risk of developing thromboembolism. CONCLUSION: TRs are associated with increased long-term thromboembolism risk in patients underwent blood transfusion. It is imperative for clinicians to acknowledge this and maintain rigorous follow-up.

Hematological and plasma profiles and ticks and tick-borne pathogens in wild Formosan black bears (Ursus thibetanus formosanus).

BACKGROUND: The endangered Formosan black bear (Ursus thibetanus formosanus) is the largest native carnivorous mammal in Taiwan. Diseases, poor management, illegal hunting, and habitat destruction are serious threats to the survival of bear populations. However, studies on the impact of diseases on bear populations are limited. Therefore, this study aimed to establish a database of the hematological and plasma profiles of free-ranging Formosan black bears and investigate the occurrence of ectoparasites, blood parasites, and vector-borne pathogens. METHODS: Formosan black bears were captured in Yushan National Park (YNP) and Daxueshan Forest Recreation Area (DSY) in Taiwan. Blood samples were collected from each bear for hematological analysis and plasma biochemistry using a hematology analyzer. Parasites and pathogens were detected using a thin blood smear with Wright-Giemsa staining and polymerase chain reaction (PCR) assay. Additionally, macroscopic ectoparasites were collected from bears to detect blood parasites and other pathogens. Moreover, the relationships between the bear variables (sex, age, and occurrence of parasites or pathogens), ectoparasites, and infectious agents were also analyzed. RESULTS: In all, 21 wild bears (14 in YNP and 7 in DSY) were captured and released during the satellite tracking studies. Hematological analysis and plasma biochemistry indicated significant differences in white blood cells (WBC), segments, creatine kinase (CK), and lactate dehydrogenase (LDH) levels between foot snare and culvert-captured bears. Additionally, there were significant differences in total plasma protein (TPP), creatinine, Ca2+, Mg2+, and K+ levels between male and female bears. Moreover, pathogen-infected bears had significantly higher erythrocyte sedimentation rate (ESR; 30 min and 1 h) and globulin levels than uninfected bears. In total, 240 ticks were collected from 13 bears, among which eight adult tick species were identified, including Haemaphysalis flava, Haemaphysalis hystricis, Amblyomma testudinarium, Ixodes ovatus, Dermacentor taiwanensis, Haemaphysalis longicornis, Ixodes acutitarsus, Amblyomma javanense, and nymphs belonging to Haemaphysalis spp. PCR revealed that 13 (61.90%) and 8 (38.10%) bears harbored Hepatozoon ursi and Babesia DNA, respectively. Among the ticks examined, 157 (65.41%) and 128 (53.33%) samples were positive for H. ursi and Babesia, respectively. CONCLUSIONS: To the best of our knowledge, this is the first study to establish a database of the hematological and plasma profiles of wild Formosan black bears and investigate ectoparasite infestation and Hepatozoon and Babesia spp. INFECTION: In conclusion, these findings may serve as a reference for monitoring the health and population of locally endangered bears.

Visfatin Facilitates VEGF-D-Induced Lymphangiogenesis through Activating HIF-1α and Suppressing miR-2277-3p in Human Chondrosarcoma.

Chondrosarcoma is a malignant bone tumor that arises from abnormalities in cartilaginous tissue and is associated with lung metastases. Lymphangiogenesis plays an essential role in cancer metastasis. Visfatin is an adipokine reported to enhance tumor metastasis, but its relationship with VEGF-D generation and lymphangiogenesis in chondrosarcoma remains undetermined. Our results from clinical samples reveal that VEGF-D levels are markedly higher in chondrosarcoma patients than in normal individuals. Visfatin stimulation promotes VEGF-D-dependent lymphatic endothelial cell lymphangiogenesis. We also found that visfatin induces VEGF-D production by activating HIF-1α and reducing miR-2277-3p generation through the Raf/MEK/ERK signaling cascade. Importantly, visfatin controls chondrosarcoma-related lymphangiogenesis in vivo. Therefore, visfatin is a promising target in the treatment of chondrosarcoma lymphangiogenesis.

Effect of Surgeon Volume on Mechanical Complications after Resection Arthroplasty with Articulating Spacer.

Two-stage revision with an antibiotic-loaded cement articulating spacer is a standard treatment for chronic prosthetic knee infection (PKI); however, mechanical complications can occur during the spacer period. There is limited evidence on the association between surgeon volume and mechanical complications after resection arthroplasty (RA) using an articulating spacer. This study aimed to compare the rates of mechanical complications and reoperation after RA with articulating spacers by surgeons with high volumes (HV) and low volumes (LV) of RA performed and analyzed the risk factors for mechanical failure. The retrospective study investigated 203 patients treated with PKIs who underwent RA with articulating spacers and were divided according to the number of RAs performed by the surgeons: HV (≥14 RAs/year) or LV (<14 RAs/year). Rates of mechanical complications and reoperations were compared. Risk factors for mechanical complications were analyzed. Of the 203 patients, 105 and 98 were treated by two HV and six LV surgeons, respectively. The mechanical complication rate was lower in HV surgeons (3.8%) than in LV surgeons (36.7%) (p < 0.001). The reoperation rate for mechanical complications was lower in HV surgeons (0.9%) than in LV surgeons (24.5%) (p < 0.001). Additionally, 47.2% of patients required hinge knees after mechanical spacer failure. Medial proximal tibial angle < 87°, recurvatum angle > 5°, and the use of a tibial spacer without a cement stem extension were risk factors for mechanical complications. Based on these findings, we made the following three conclusions: (1) HV surgeons had a lower rate of mechanical complications and reoperation than LV surgeons; (2) mechanical complications increased the level of constraint in final revision knee arthroplasty; and (3) all surgeons should avoid tibial spacer varus malalignment and recurvatum deformity and always use a cement stem extension with a tibial spacer.

Electrophysiological differences in inhibitory control processing between collegiate level soccer players and non-athletes in the absence of performance differences.

Inhibitory control, the ability to manage conflicting responses and suppress inappropriate actions, is crucial for team sports athletes, including soccer players. While previous studies have shown that soccer players possess superior inhibitory control, the underlying mechanisms responsible for this advantage remain unclear. Thus, this research aimed to investigate the neural processes involved in conflict resolution and response inhibition, comparing collegiate level soccer players with non-athletes. Participants completed a novel go/no-go task that involved conflict resolution and response inhibition, while their electroencephalograms were recorded. Despite no significant difference in behavioral performance between the two groups, soccer players exhibited notable N2 and frontal midline theta modulations in response to conflict resolution and inhibition, which were comparatively weaker in non-athletes. Our findings suggest that expertise in team sports may enhance neural sensitivity to subtle yet significant information, even without a discernible behavioral advantage.

HDAC inhibitors as a potential therapy for chemotherapy-induced neuropathic pain.

Cancer, a chronic disease characterized by uncontrolled cell development, kills millions of people globally. The WHO reported over 10 million cancer deaths in 2020. Anticancer medications destroy healthy and malignant cells. Cancer treatment induces neuropathy. Anticancer drugs cause harm to spinal cord, brain, and peripheral nerve somatosensory neurons, causing chemotherapy-induced neuropathic pain. The chemotherapy-induced mechanisms underlying neuropathic pain are not fully understood. However, neuroinflammation has been identified as one of the various pathways associated with the onset of chemotherapy-induced neuropathic pain. The neuroinflammatory processes may exhibit varying characteristics based on the specific type of anticancer treatment delivered. Neuroinflammatory characteristics have been observed in the spinal cord, where microglia and astrocytes have a significant impact on the development of chemotherapy-induced peripheral neuropathy. The patient's quality of life might be affected by sensory deprivation, loss of consciousness, paralysis, and severe disability. High cancer rates and ineffective treatments are associated with this disease. Recently, histone deacetylases have become a novel treatment target for chemotherapy-induced neuropathic pain. Chemotherapy-induced neuropathic pain may be treated with histone deacetylase inhibitors. Histone deacetylase inhibitors may be a promising therapeutic treatment for chemotherapy-induced neuropathic pain. Common chemotherapeutic drugs, mechanisms, therapeutic treatments for neuropathic pain, and histone deacetylase and its inhibitors in chemotherapy-induced neuropathic pain are covered in this paper. We propose that histone deacetylase inhibitors may treat several aspects of chemotherapy-induced neuropathic pain, and identifying these inhibitors as potentially unique treatments is crucial to the development of various chemotherapeutic combination treatments.

Long-term hematopoietic transfer of the anti-cancer and lifespan-extending capabilities of a genetically engineered blood system by transplantation of bone marrow mononuclear cells.

A causal relationship exists among the aging process, organ decay and disfunction, and the occurrence of various diseases including cancer. A genetically engineered mouse model, termed Klf1K74R/K74R or Klf1(K74R), carrying mutation on the well-conserved sumoylation site of the hematopoietic transcription factor KLF1/EKLF has been generated that possesses extended lifespan and healthy characteristics, including cancer resistance. We show that the healthy longevity characteristics of the Klf1(K74R) mice, as exemplified by their higher anti-cancer capability, are likely gender-, age-, and genetic background-independent. Significantly, the anti-cancer capability, in particular that against melanoma as well as hepatocellular carcinoma, and lifespan-extending property of Klf1(K74R) mice, could be transferred to wild-type mice via transplantation of their bone marrow mononuclear cells at a young age of the latter. Furthermore, NK(K74R) cells carry higher in vitro cancer cell-killing ability than wild-type NK cells. Targeted/global gene expression profiling analysis has identified changes in the expression of specific proteins, including the immune checkpoint factors PDCD and CD274, and cellular pathways in the leukocytes of the Klf1(K74R) that are in the directions of anti-cancer and/or anti-aging. This study demonstrates the feasibility of developing a transferable hematopoietic/blood system for long-term anti-cancer and, potentially, for anti-aging.

Lead Isolation and Capture in Perovskite Photovoltaics toward Eco-Friendly Commercialization.

Perovskite solar cells (PSCs) are developed rapidly in efficiency and stability in recent years, which can compete with silicon solar cells. However, an important obstacle to the commercialization of PSCs is the toxicity of lead ions (Pb2+) from water-soluble perovskites. The entry of free Pb2+ into organisms can cause severe harm to humans, such as blood lead poisoning, organ failure, etc. Therefore, this work reports a "lead isolation-capture" dual detoxification strategy with calcium disodium edetate (EDTA Na-Ca), which can inhibit lead leakage from PSCs under extreme conditions. More importantly, leaked lead exists in a nontoxic aggregation state chelated by EDTA. For the first time, in vivo experiments are conducted in mice to systematically prove that this material has a significant inhibitory effect on the toxicity of perovskites. In addition, this strategy can further enhance device performance, enabling the optimized devices to achieve an impressive power conversion efficiency (PCE) of 25.19%. This innovative strategy is a major breakthrough in the research on the prevention of lead toxicity in PSCs.

Widespread Adoption of Microincision Vitrectomy Surgery Improves Visual Outcomes in Endogenous Endophthalmitis with Poor Initial Vision: A 21-Year Experience in Taiwan.

PURPOSE: To review the presentation and visual prognostic factors of patients with endogenous endophthalmitis before and after the introduction of microincision vitrectomy surgery (MIVS), at a tertiary referral hospital in Taiwan, over a 21-year period. METHODS: We retrospectively analyzed medical records of patients diagnosed with endogenous endophthalmitis before and after the introduction of MIVS between January 2002 and December 2022. RESULTS: Data were collected from 147 patients. Diabetes mellitus was the most common comorbidity (59.9%). Liver abscess (32.7%) was the leading source of infection, followed by urinary tract infection (15.0%), and infective endocarditis (5.4%). Klebsiella pneumoniae (50.4%) was the most common pathogen, followed by Staphylococcus aureus (13.5%), and Candida albicans (8.3%). Poor initial visual acuity worse than counting fingers (CF) (p < 0.001) and diabetes mellitus (p = 0.008) were significantly associated with poor visual outcomes. In the treatment of 98 patients with poor initial visual acuity worse than CF, the proportion of vitrectomy surgeries performed increased from 13/56 (23.2%) to 24/42 (57.1%) (p = 0.001) after the introduction of MIVS. Final visual acuity of CF or better increased from 7/56 (12.5%) to 12/42 (28.6%) after the introduction of MIVS (p = 0.046). Vitrectomy was a better prognostic factor for final visual outcome in patients with poor initial visual acuity of worse than CF (p = 0.011) than other factors. CONCLUSION: In endogenous endophthalmitis patients presenting with poor initial visual acuity, vitrectomy was a better visual prognostic factor. MIVS has allowed more patients to undergo vitrectomy and improved visual outcomes.

MCP-1 controls IL-17-promoted monocyte migration and M1 polarization in osteoarthritis.

Osteoarthritis (OA) is a low-grade inflammatory joint illness in which monocytes migrate and infiltrate synovial tissue, differentiating into the pro-inflammatory M1 macrophage phenotype. IL-17 is a proinflammatory mediator principally generated by Th17 cells, which is elevated in OA patients; nevertheless, investigators have yet to elucidate the function of IL-17 in M1 polarization during OA development. Our analysis of clinical tissues and results from the open online dataset discovered that the level of M1 macrophage markers is elevated in human OA tissue samples than in normal tissue. High-throughput screening demonstrated that MCP-1 is a potential candidate factor after IL-17 treatment in OA synovial fibroblasts (OASFs). Immunohistochemistry data revealed that the level of MCP-1 is higher in humans and mice with OA than in normal tissues. IL-17 stimulation facilitates MCP-1-dependent macrophage polarization to the M1 phenotype. It also appears that IL-17 enhances MCP-1 synthesis in human OASFs, enhancing monocyte migration via the JAK and STAT3 signaling cascades. Our findings indicate the IL-17/MCP-1 axis as a novel strategy for the remedy of OA.

A Retrospective Analysis: Investigating Factors Linked to High Lung-RADS Scores in a Nonsmoking, Non-Family History Population.

Low-dose computed tomography screening for lung cancer is currently targeted at heavy smokers or those with a family history of lung cancer. This study aimed to identify risk factors for lung cancer in individuals who do not meet the current lung cancer screening criteria as stipulated by the Taiwan Health Promotion Agency's low-dose computed tomography (LDCT) screening policy. A cohort analysis was conducted on 12,542 asymptomatic healthy subjects aged 20-80 years old who voluntarily underwent LDCT scans from January 2016 to December 2021. Logistic regression demonstrated that several factors, including age over 55 years, female gender, a body mass index (BMI) less than 23, a previous history of respiratory diseases such as tuberculosis or obstructive respiratory diseases (chronic obstructive pulmonary disease [COPD], asthma), and previous respiratory symptoms such as cough or dyspnea, were associated with high-risk lung radiology scores according to LDCT scans. These findings indicate that risk-based assessments using primary data and questionnaires to identify risk factors other than heavy smoking and a family history of lung cancer may improve the efficiency of lung cancer screening.

Impact of programmed cell death protein 1 inhibitor therapy on the survival of patients with advanced or recurrent uterine cancers: a meta-analysis.

Introduction: No prior meta-analysis has investigated the impact of programmed cell death protein 1 (PD-1) inhibitor therapy on survival outcomes in patients with advanced or recurrent uterine cancers (including both corpus and cervical cancers). Methods: A comprehensive search of PubMed and Embase databases was conducted, covering the past 10 years (up to August 2023) and encompassing all clinical research related to uterine cancer. Five randomized controlled trials and one cohort study met the inclusion criteria and were included in the meta-analysis. Data on patient demographics, clinical characteristics, treatment regimens, and survival outcomes were extracted. Hazard ratios (HRs) for overall survival (OS) and progression-free survival (PFS), as well as the relative risk of grade 3 or higher adverse events, were pooled using random-effects models. Results: Patients receiving PD-1 inhibitors had better OS (HR, 0.65, 95% CI, 0.59-0.72; P<.001) and PFS (HR, 0.59, 95% CI, 0.49-0.70; P<.001) than those receiving variable non-PD-1 inhibitor therapies among 3452 uterine cancer patients. The leave-one-out meta-analysis of the HR of OS showed no individual study impact on the estimation of the overall effect size. Subgroup analysis revealed better OS in the PD-1 inhibitors use than the controls in cervical cancer (HR, 0.68, 95% CI, 0.59-0.79), endometrial cancer (HR, 0.62, 95% CI, 0.54-0.72), and pembrolizumab use (HR, 0.66, 95% CI, 0.57-0.75) subgroups. Patients with advanced cervical cancer, who had CPS > 1, receiving PD-1 inhibitors have statistically significant benefits in OS compared to controls (HR, 0.65, 95% CI, 0.53-0.80). The pooled HR for overall survival was 0.71 (95% CI, 0.60-0.82; P<.001) in patients who received PD-1 inhibitors as compared to those who did not receive PD-1 inhibitors in proficient mismatch repair (MMR) endometrial cancer patients. However, in deficient MMR patients, the HR was 0.30 (95% CI, 0.13-0.70). The relative risk of grade 3 or higher adverse events was not higher in the PD-1 inhibitor group (relative risk, 1.12, 95% CI, 0.98-1.27). Conclusion: Survival was significantly better using PD-1 inhibitor therapy than variable non-PD-1 inhibitor chemotherapies among patients with advanced or recurrent uterine cancers.

The association of socioeconomic status on kidney transplant access and outcomes: a nationwide cohort study in Taiwan.

BACKGROUND: Conflicting evidence exists regarding the relationship between socioeconomic status and access to or outcomes after kidney transplantation. This study analyzed the effects of individual and neighborhood socioeconomic status on kidney transplant access and outcomes in Taiwan. METHODS: We used a retrospective cohort study design and performed comparisons using the Cox proportional hazards model after adjusting for risk factors. Data were collected from the National Health Insurance Bureau of Taiwan data (2003-2012). RESULTS: Patients with high individual and neighborhood socioeconomic status had higher chances of receiving kidney transplants than those with low individual and neighborhood socioeconomic status [adjusted hazard ratio (aHR) = 2.04; 95% CI: (1.81-2.31), p < 0.001]. However, there were no significant differences in post-transplant graft failure or patient mortality in Taiwan between individuals of varying socioeconomic status after five years. When we stratified kidney transplants by domestic and overseas transplantation, there were no significant differences in post-transplant mortality and graft failure, but individuals who received a kidney graft in Taiwan with high individual and neighborhood socioeconomic status experienced lower risks of graft failure (aHR = 0.55; [95% CI 0.33-0.89], p = 0.017). CONCLUSION: A relevant disparity exists in accessing kidney transplantation in Taiwan, depending on individual and neighborhood socioeconomic status. However, results post transplantation were not different after five years. Improved access to waitlisting, education, and welfare support may reduce disparities.

Icodextrin-induced acute generalized exanthematous pustulosis in a patient with peritoneal dialysis.

Icodextrin has been widely prescribed for peritoneal dialysis (PD) patients with inadequate ultrafiltration, but icodextrin induced acute generalized exanthematous pustulosis (AGEP) has been not well recognized in clinical practice. We described a young-aged female with IgA nephropathy and end stage kidney disease under continuous automated peritoneal dialysis. She developed skin erythema with exfoliation over the groin 7th day after initiation of icodextrin based PD dialysate. Initially, her scaling skin lesion with pinhead-sized pustules affected the bilateral inguinal folds, and then it extended to general trunk accompanied by pruritus. She was admitted because of deterioration of skin lesion on 14th day of icodextrin exposure. She was afebrile and physical examination was notable for widespread erythematous papules with pruritus extending over her groins and trunk. Pertinent laboratory examination showed leukocytosis of 18 970 cells/µL with neutrophile count of 17 642 cells/µL (92.3%), and c-reactive-protein: 3.39 mg/dL. Skin biopsy revealed multifocal sub corneal abscess with papillary dermal edema, and upper-dermal neutrophilia with perivascular accentuation, consistent with the diagnosis of AGEP. After discontinuation of PD, she underwent temporary high-flux haemodialysis with treatment of steroid and antihistamine. Her dermatologic lesion resolved without any skin sequalae completely within 4 days, and she underwent icodextrin-free peritoneal dialysis at 17th day. This case highlighted the fact that icodextrin-induced AGEP should be early recognized to avoid inappropriate management.

An Empirical Bayes Approach to Shrinkage Estimation on the Manifold of Symmetric Positive-Definite Matrices.

The James-Stein estimator is an estimator of the multivariate normal mean and dominates the maximum likelihood estimator (MLE) under squared error loss. The original work inspired great interest in developing shrinkage estimators for a variety of problems. Nonetheless, research on shrinkage estimation for manifold-valued data is scarce. In this article, we propose shrinkage estimators for the parameters of the Log-Normal distribution defined on the manifold of N × N symmetric positive-definite matrices. For this manifold, we choose the Log-Euclidean metric as its Riemannian metric since it is easy to compute and has been widely used in a variety of applications. By using the Log-Euclidean distance in the loss function, we derive a shrinkage estimator in an analytic form and show that it is asymptotically optimal within a large class of estimators that includes the MLE, which is the sample Fréchet mean of the data. We demonstrate the performance of the proposed shrinkage estimator via several simulated data experiments. Additionally, we apply the shrinkage estimator to perform statistical inference in both diffusion and functional magnetic resonance imaging problems.