Cerebral swelling caused by deep venous thrombosis immediately after cranioplasty.

Recently, different groups have reported a rare, unexplained complication of sudden death with massive cerebral oedema immediately after cranioplasty.Case presentation: A 34-year-old woman underwent decompressive hemicraniectomy after traumatic brain injury. She was reportedly on oral contraceptives. She developed massive cerebral swelling immediately after an uneventful cranioplasty. After surgery, her pupils became fixed and dilated, and brain MRI revealed massive brain oedema. Magnetic resonance venography displayed occlusion in the deep venous sinus. The oedema was believed to be caused by venous sinus thrombosis. The patient's family declined to avail any surgical and medical treatment, and the patient died on the second postoperative day.Conclusions: Fatal massive cerebral oedema is an uncommon complication after cranioplasty in patients who had previously undergone decompressive craniectomy. Our patient was using oral contraceptives and was thus susceptible to the development of venous sinus thrombosis. Neurosurgeons must be aware of the complications associated with venous sinus thrombosis and discuss it with the patients and their families.

A subarachnoid pleural fistula with massive crystal-clear pleural fluid caused by a lumbar epidural teratoma.

A subarachnoid pleural fistula - a connection between the pleural cavity and the subarachnoid space - generally presents after trauma or surgery. A 1-year 11-month-old girl without a history of trauma or surgery presented with fatigue, cyanosis and dyspnoea. A chest radiograph and computed tomography (CT) demonstrated a massive pleural effusion in the right hemithorax. About 300 ml of a crystal-clear pleural effusion, which looked like pure water, was removed by insertion of a chest drain, but it continued to collect. Cisternography and CT myelography confirmed leakage of cerebral spinal fluid into the right pleural cavity around the thoracolumbar region. Magnetic resonance imaging demonstrated an 11-mm enhanced nodule in the epidural space around the right lumbar (L) 1/2 intervertebral foramen. The patient underwent surgery and epidural tumours attached to the L1 nerve root foramen were completely resected and a fistula of the dura adjacent to the tumour was sutured. Histopathological examination demonstrated a mature teratoma containing a pancreatic component. On retrospective analysis of stored pleural fluid, a raised level of pancreatic enzymes was detected. It is presumed that digestive enzymes secreted by the pancreatic component of the teratoma lysed the dura, resulting in formation of the fistula. When a crystal-clear pleural effusion is present, even in the absence of trauma or surgery, a subarachnoid pleural fistula should be considered. As far as we know, this is the first report of a subarachnoid pleural fistula caused by a paravertebral teratoma.Abbreviations: CSF: cerebrospinal fluid; CT: computed tomography; 111In-DTPA: indium-111 diethylene triamine penta-acetic acid; MRI: magnetic resonance imaging; NIPPV: non-invasive positive pressure ventilation.

Spinal cord subependymoma mimicking syringomyelia in a child: a case report.

Spinal cord subependymomas (SCSEs) in children are extremely rare, and no reports distinguishing SCSEs from syringomyelia have been published. We report a case of a 10-year-old boy who presented with torticollis, scoliosis, as well as pain that had begun in the posterior portion of the neck and progressed to the right shoulder and upper arm. Magnetic resonance imaging showed an intramedullary cyst-like lesion with the same signal intensity as that of cerebrospinal fluid. Idiopathic syringomyelia with scoliosis was first suspected, and a syrinx-subarachnoid space shunt was performed. After surgery, the lesion was slightly smaller; however, 2 years after surgery, it had re-grown, causing excruciating pain but no other symptoms. A second surgery was performed, and gross total resection was achieved. Pathological evaluation revealed SCSE. SCSE needs to be considered as a differential diagnosis for spinal centric cyst-like lesions in children.

Enhancement of photovoltage by electronic structure evolution in multiferroic Mn-doped BiFeO3 thin films.

The bulk photovoltaic effect (BPVE) is a mechanism of recent focus for novel solar cells that exceed the power conversion efficiency of p-n junction solar cells because of the quantum mechanical effect to generate photocurrent known as shift current. Ferroelectrics are receiving attention again because of their high voltage generation by the BPVE and converse piezoelectric effect to realize high performance optical actuators. We have investigated the BPVE in ferroelectric BiFeO3 (BFO) single crystal thin films, whereby the photovoltage was enhanced by Mn doping, and 852 V generation was demonstrated at 80 K. The enhancement mechanism was also investigated using soft and hard X-ray photoelectron spectroscopy (SXPES, HAXPES), and soft X-ray absorption spectroscopy with synchrotron radiation. This report reveals a way to new voltage source applications employing the BPVE for high impedance devices with ferroelectrics. Important aspects for designing ferroelectric materials by impurity doping are also discussed.

Reversible cerebral vasoconstriction syndrome concomitant with cerebral venous sinus thrombosis following ovarian tumor resection: A report of two cases.

BACKGROUND: Reversible cerebral vasoconstriction syndrome (RCVS) presents with characteristic clinical, brain imaging, and angiographic findings. The most common clinical feature of RCVS is a severe acute headache, which is often referred to as a thunderclap headache due to the nature of its presentation. It may occur spontaneously or may be provoked by various precipitating factors. We present a rare case of RCVS concomitant with cerebral venous sinus thrombosis (CVST) in a woman who underwent resection of an ovarian tumor. CASE DESCRIPTION: Case 1 - A 42-year-old woman was admitted to our hospital with severe headache radiating to the neck, with associated vomiting. She revealed a medical history of ovarian cancer and underwent an operation for the resection of the tumor, a month before presentation. After resection, her estradiol (E2) levels were reduced from 288 pg/ml to 31 pg/ml (normal range, 0-49 pg/ml). Initial imaging on admission to our hospital revealed the left posterior convexity subarachnoid hemorrhage. Magnetic resonance angiography (MRA) showed findings consistent with RCVS affecting the left posterior cerebral artery. Magnetic resonance venography (MRV) showed CVST of the left transverse and sigmoid sinuses. Single-photon emission computed tomography (SPECT) showed a left posterior ischemic lesion. These findings improved following treatment with nimodipine and anticoagulant. Case 2 - A 39-year-old woman presented with holocranial headache associated with vomiting. She was diagnosed with an ovarian tumor. She underwent an operation 3 months before presentation. After tumor resection, her E2 level decrease from 193 pg/ml to 19 pg/ml (normal range, 0-49 pg/ml). Magnetic resonance angiography (MRA) confirmed the presence of a vasospasm involving the right anterior cerebral artery. Magnetic resonance venography (MRV) confirmed the presence of thrombosis involving the superior sagittal sinus. She was discharged on postpartum day 31 without neurological deficits after treatment with anticoagulants. At her 3-month follow-up, both MRA and MRV were within the normal limits. CONCLUSION: This is the first report of two women diagnosed with RCVS with concomitant CVST following ovarian tumor resection. Marked reductions in postoperative E2 levels could have contributed to the development of CVST and RCVS.

The Importance of STAT6 in a Schwannoma-like Grade III Solitary Fibrous Tumor/Hemangiopericytoma Located in the Cerebellopontine Angle and Meckel's Cave.

BACKGROUND: Hemangiopericytoma (HPC) is a rare mesenchymal tumor of the brain that occurs in the central nervous system as a solitary fibrous tumor. Surgical treatment of HPC is known to be beneficial, but results on the role of complete resection and adjuvant radiation are conflicting. However, it is often difficult to detect a central nervous system solitary fibrous tumor/HPC before surgery. We describe a presumed left trigeminal schwannoma that was histopathologically shown to be an HPC. CASE DESCRIPTION: A 65-year-old man presented with paresthesia of the second and third branches of the left trigeminal nerve. Magnetic resonance imaging showed a tumoral lesion in the left cerebellopontine angle and Meckel's cave. We suspected a schwannoma and performed surgery, which resulted in only a partial resection because of tumor bleeding and unexpected intraoperative histologic findings. We could not achieve a definitive diagnosis. However, we observed local recurrence and disseminated lesions 5 and 6.5 years later, respectively. We performed a second surgery and were able to definitively diagnose the lesion as a grade III HPC based on the positive expression of STAT6 during immunostaining. CONCLUSIONS: As solitary fibrous tumor/HPC requires gross total resection for effective resolution, it is imperative to consider it in the differential diagnoses of similar tumors. If an unusual pathologic image is found, we recommend rapid immunostaining for STAT6 to reach a definitive conclusion regarding the tumor type. This case highlights the importance of considering HPC when screening or diagnosing central nervous system lesions, especially in this rare location.

Radiation-Induced Spinal Cord Cavernous Malformations Associated with Medulloblastoma: Case Report and Review of the Literature.

BACKGROUND: Radiation-induced spinal cord cavernous malformations (CMs) are rare pathologies compared with radiation-induced cerebral CMs. We present a case of a radiation-induced spinal cord CM developed 31 years after radiation therapy for medulloblastoma. CASE DESCRIPTION: A 37-year-old man developed a symptomatic spinal hemorrhagic lesion 31 years after radiation therapy for medulloblastoma. Magnetic resonance imaging revealed an intramedullary cystic lesion with a fluid-fluid level in the C7 area. Surgery was performed leading to an unclear diagnosis. Two years later, the patient had a relapse and underwent a second operation, allowing a definitive diagnosis of radiation-induced spinal cord CM. This is believed to be the second case of de novo intramedullary CM formation following spinal radiation therapy for medulloblastoma. CONCLUSIONS: Radiation-induced spinal cord CMs should be recognized as a possible late adverse effect in patients treated with radiation therapy for medulloblastoma.

Independently Interpretable Lasso for Generalized Linear Models.

Sparse regularization such as ℓ1 regularization is a quite powerful and widely used strategy for high-dimensional learning problems. The effectiveness of sparse regularization has been supported practically and theoretically by several studies. However, one of the biggest issues in sparse regularization is that its performance is quite sensitive to correlations between features. Ordinary ℓ1 regularization selects variables correlated with each other under weak regularizations, which results in deterioration of not only its estimation error but also interpretability. In this letter, we propose a new regularization method, independently interpretable lasso (IILasso), for generalized linear models. Our proposed regularizer suppresses selecting correlated variables, so that each active variable affects the response independently in the model. Hence, we can interpret regression coefficients intuitively, and the performance is also improved by avoiding overfitting. We analyze the theoretical property of the IILasso and show that the proposed method is advantageous for its sign recovery and achieves almost minimax optimal convergence rate. Synthetic and real data analyses also indicate the effectiveness of the IILasso.

Water Electrolysis Using Thin Pt and RuO x Catalysts Deposited by a Flame-Annealing Method on Pencil-Lead Graphite-Rod Electrodes.

An inexpensive, simple, and high-activity catalyst preparation method has been introduced in this work. Pt and RuO x catalysts were fabricated by soaking inexpensive graphite electrodes (pencil-lead graphite rod: PGR) in catalyst precursor solutions and using a simple flame-annealing method, which results in lower amount of Pt and RuO x catalyst layers. From X-ray photoelectron spectroscopy and near-edge X-ray absorption fine structure analysis, it has been found that platinum and ruthenium were deposited as zero-valence metal (Pt) and oxide (RuO x ), respectively. Catalytic activities of Pt/PGR and RuO x /PGR for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) were evaluated using neutral 1 M Na2SO4 aqueous electrolyte, respectively. Although HER and OER currents using PGR without catalysts were -16 mA cm-2 (at -1.5 V vs Ag/AgCl) and +20 mA cm-2 (at +2.0 V vs Ag/AgCl), they were improved to -110 and +80 mA cm-2 with catalysts (Pt and RuO x ), respectively. Such an inexpensive and rapid catalyst electrode preparation method on PGR using flame-annealing is a very significant method in the initial catalyst activity evaluation requiring a large amount of trial and error.

Intracranial Low-Grade Fibromyxoid Sarcoma: Findings on Electron Microscopy and Histologic Analysis.

BACKGROUND: Low-grade fibromyxoid sarcoma is a rare tumor that manifests as a deep soft tissue mass characterized by a benign histology, but with potentially aggressive clinical behavior and a high rate of recurrence; primary intracranial sarcomas are even rarer. We present a case of primary intracranial low-grade fibromyxoid sarcoma, emphasizing its clinical, radiologic, and histologic features. CASE DESCRIPTION: A 39-year-old woman presented with a recent history of headache and seizures. A right parietal mass was detected on computed tomography and magnetic resonance imaging, and she was subsequently operated on to remove the intracranial mass. Histologic examination of the resected tumor revealed mildly atypical fibroblastic cells embedded within a myxoid matrix. The diagnosis was confirmed by electron microscopy and cytogenetic analyses. CONCLUSIONS: This report describes electron microscopic evaluation of intracranial low-grade fibromyxoid sarcoma, which has an extremely rare occurrence.

Transient ischemic attack in elderly patient with PHACE syndrome.

BACKGROUND: Posterior fossa brain malformations, hemangiomas, arterial anomalies, coarctation of the aorta and cardiac defects, and eye abnormalities (PHACE) is a rare congenital anomaly with a broad spectrum of clinical manifestations. CASE DESCRIPTION: We describe a 75-year-old male with PHACE anomaly, aortic anomaly, malformation of brain, aplastic right carotid artery, and cervical vasculopathy. He presented with a transient ischemic attack with the left hemiparesis, a rare clinical presentation of the PHACE syndrome. He had an uneventful recovery and recently completed a 2-year follow-up after the superficial temporal artery to middle cerebral artery anastomosis. CONCLUSION: PHACE syndrome should be kept in mind, even in individuals of advanced age, in the instance of a TIA, especially in situations which may involve induced hypoperfusion.

Nocardia paucivorans cerebellar abscess: Surgical and pharmacotherapy.

BACKGROUND: Nocardia species are ubiquitous in nature and mainly cause pulmonary disease in humans; however, they can also infect the central nervous system and skin. The management of cerebellar nocardiosis is troublesome and requires multiple considerations of the severity of the underlying systemic disease, difficulties in identifying the bacterium, and frequent delay in initiating adequate therapy. CASE DESCRIPTION: We report a 52-year-old diabetic female patient with Nocardia paucivorans cerebellar abscesses. Brain magnetic resonance imaging (MRI) revealed innumerable small ring-enhancing lesions of posterior fossa. In this report, we present a case of primary single cerebellar abscesses due to N. paucivorans. Early diagnosis and surgical interventions were significant for the patient. The diagnosis was confirmed by DNA sequencing and the organism was susceptible to trimethoprim-sulfamethoxazole (TMP/SMX). The patient was successfully treated with drugs and surgical excision. CONCLUSION: According to the literature, surgical excision or aspiration of cerebellar abscess seems to provide favorable outcomes. In our experience, a successful outcome was achieved with subtotal resection and prolonged adequate antibiotic therapy.

Deep Venous Thrombosis with Decreased Cerebral Blood Flow to the Thalamus was Completely Restored by Factor Xa Inhibitor.

BACKGROUND: Cerebral venous thrombosis is rare and an uncommon cause of stroke and has diverse etiologies and varied clinical presentations. Here, we report 2 cases of deep cerebral venous thrombosis. CASE DESCRIPTION: A 64-year-old woman presented with cerebral venous thrombosis due to a hypercoagulable state associated with ovarian tumor. On initial fluid-attenuated inversion recovery and diffusion-weighted imaging, there was a diffuse high-intensity lesion in the bilateral thalamus. Computed tomography angiography showed occlusion of the straight sinus, vein of Galen, and internal cerebral vein. Single-photon emission computed tomography showed decreased cerebral blood flow in the bilateral thalamus. After 3 weeks of factor Xa inhibitor therapy, the patient's consciousness gradually improved and eventually became clear enough to leave the hospital. She had no neurological deficit. Another patient was a 47-year-old man who presented with splitting headache and drowsiness. Magnetic resonance venography confirmed deep thrombosis of the vein of Galen. He completely recovered after 4 weeks of factor Xa inhibitor therapy. CONCLUSIONS: This study reports on 2 rare cases of decreased cerebral blood flow in the bilateral thalamus on single-photon emission computed tomography, which improved following the administration of factor Xa inhibitor.

Endoscopic Surgery for Thalamic Hemorrhage with Intraventricular Hemorrhage: Effects of Combining Evacuation of a Thalamic Hematoma to External Ventricular Drainage.

OBJECTIVES: Intraventricular hemorrhage (IVH) caused by thalamic hemorrhage leads to hydrocephalus, increased intracranial pressure, and reduced levels of consciousness. The aim of this study was to investigate the efficacy and compare the results of endoscopic surgery for the evacuation of a thalamic and intraventricular hematoma against those of external ventricular drainage (EVD) surgery. MATERIALS AND METHODS: From January 2010 to December 2018, 68 patients with IVH caused by thalamic hemorrhage were treated in our department. Our study was approved by the Institutional Ethics Committee. The included patients were randomly divided into an EVD group and an endoscopic surgery group. The outcome was measured after 3 months using a 30-day mortality rate, pneumonia onset rate, ventriculoperitoneal (VP) shunt dependency rate, and Glasgow Outcome Scale (GOS) score. RESULTS: Thirty-eight of the 68 patients were randomly assigned to the endoscopic surgery group and 30 were assigned to the EVD group. Patients treated with endoscopic surgery had significantly less drainage dependency on day 30 (P = 0.00014 < 0.00005) in comparison to those treated with EVD. The difference in the functional outcomes between the two groups of patients was mainly dependent on the onset of pneumonia and the consciousness level at the time of admission. The onset rate of aspiration-related pneumonia until day 30 was 11% in the endoscopic surgery group and 45% in the EVD group. The VP shunt rates were 27.8% in the endoscopic surgery group and 60% in the EVD group. The endoscopic surgery group had a significantly lower VP shunt rate compared with the EVD group. Intracerebral hemorrhage evacuation late was found to be associated with shunt-dependent rate and hospitalization. CONCLUSIONS: Endoscopic surgery was found to be associated with a lower GOS score and lower onset rates for shunt-dependent hydrocephalus and aspiration-related pneumonia in comparison to EVD. High evacuation rate was associated with lower shunt-dependent rate and short hospitalization.

A bias-corrected estimator in multiple imputation for missing data.

Multiple imputation (MI) is one of the most popular methods to deal with missing data, and its use has been rapidly increasing in medical studies. Although MI is rather appealing in practice since it is possible to use ordinary statistical methods for a complete data set once the missing values are fully imputed, the method of imputation is still problematic. If the missing values are imputed from some parametric model, the validity of imputation is not necessarily ensured, and the final estimate for a parameter of interest can be biased unless the parametric model is correctly specified. Nonparametric methods have been also proposed for MI, but it is not so straightforward as to produce imputation values from nonparametrically estimated distributions. In this paper, we propose a new method for MI to obtain a consistent (or asymptotically unbiased) final estimate even if the imputation model is misspecified. The key idea is to use an imputation model from which the imputation values are easily produced and to make a proper correction in the likelihood function after the imputation by using the density ratio between the imputation model and the true conditional density function for the missing variable as a weight. Although the conditional density must be nonparametrically estimated, it is not used for the imputation. The performance of our method is evaluated by both theory and simulation studies. A real data analysis is also conducted to illustrate our method by using the Duke Cardiac Catheterization Coronary Artery Disease Diagnostic Dataset.

Light stability tests of CH3NH3PbI3 perovskite solar cells using porous carbon counter electrodes.

The CH3NH3PbI3 perovskite solar cells have been fabricated using three-porous-layered electrodes as, 〈glass/F-doped tin oxide (FTO)/dense TiO2/porous TiO2-perovskite/porous ZrO2-perovskite/porous carbon-perovskite〉 for light stability tests. Without encapsulation in air, the CH3NH3PbI3 perovskite solar cells maintained 80% of photoenergy conversion efficiency from the initial value up to 100 h under light irradiation (AM 1.5, 100 mW cm-2). Considering the color variation of the CH3NH3PbI3 perovskite layer, the significant improvement of light stability is due to the moisture-blocking effect of the porous carbon back electrodes. The strong interaction between carbon and CH3NH3PbI3 perovskite was proposed by the measurements of X-ray photoelectron spectroscopy and X-ray diffraction of the porous carbon-perovskite layers.

Cerebellopontine angle epidermoid cysts: clinical presentations and surgical outcome.

Epidermoid cysts constitute less than 1% of intracranial tumors with the majority of them involving cerebellopontine angle (CPA). Although several mechanisms for cranial nerve dysfunction due to these tumors have been proposed, no direct evaluation for hyper- or hypoactive dysfunction has been done. In this case series, pathophysiology of cranial nerve dysfunction in CPA epidermoid cysts was evaluated with special attention to a new mechanism of capsule strangulation caused by stratified tumor capsule. Twenty-two cases with epidermoid cysts of CPA micro-neurosurgically treated in our departments since 2005 were reviewed. Clinical status of the patients before the surgery and post-operative functional outcome were recorded. Available data from the English literature were summarized for comparison. Mass reduction of cyst contents in most cases was usually associated with prompt and marked improvement of the symptoms suggesting neuroapraxia caused by compression of the tumor content and/or mild ischemia. Among them, two cases showed strangulation of the affected nerves by the tumor capsule whose preoperative dysfunction did not improve after surgery in spite of meticulous microsurgical removal of the lesion. Involved facial and abducent nerves in these two cases showed distortion of nerve axis and nerve atrophy distal to the strangulation site. We report the first direct evidence of etiology of cranial nerve dysfunction caused by cerebellopontine angle epidermoid tumors. Young age and rapidly progressive neurological deficit might be the characteristics for strangulation of the affected nerves by the cyst capsule. Even though the number of cases might be limited, immediate decompression and release of the strangulating band might be urged in such patients to prevent irreversible deficits.

Global expression differences and tissue specific expression differences in rice evolution result in two contrasting types of differentially expressed genes.

BACKGROUND: Since the development of transcriptome analysis systems, many expression evolution studies characterized evolutionary forces acting on gene expression, without explicit discrimination between global expression differences and tissue specific expression differences. However, different types of gene expression alteration should have different effects on an organism, the evolutionary forces that act on them might be different, and different types of genes might show different types of differential expression between species. To confirm this, we studied differentially expressed (DE) genes among closely related groups that have extensive gene expression atlases, and clarified characteristics of different types of DE genes including the identification of regulating loci for differential expression using expression quantitative loci (eQTL) analysis data. RESULTS: We detected differentially expressed (DE) genes between rice subspecies in five homologous tissues that were verified using japonica and indica transcriptome atlases in public databases. Using the transcriptome atlases, we classified DE genes into two types, global DE genes and changed-tissues DE genes. Global type DE genes were not expressed in any tissues in the atlas of one subspecies, however changed-tissues type DE genes were expressed in both subspecies with different tissue specificity. For the five tissues in the two japonica-indica combinations, 4.6 ± 0.8 and 5.9 ± 1.5 % of highly expressed genes were global and changed-tissues DE genes, respectively. Changed-tissues DE genes varied in number between tissues, increasing linearly with the abundance of tissue specifically expressed genes in the tissue. Molecular evolution of global DE genes was rapid, unlike that of changed-tissues DE genes. Based on gene ontology, global and changed-tissues DE genes were different, having no common GO terms. Expression differences of most global DE genes were regulated by cis-eQTLs. Expression evolution of changed-tissues DE genes was rapid in tissue specifically expressed genes and those rapidly evolved changed-tissues DE genes were regulated not by cis-eQTLs, but by complicated trans-eQTLs. CONCLUSIONS: Global DE genes and changed-tissues DE genes had contrasting characteristics. The two contrasting types of DE genes provide possible explanations for the previous controversial conclusions about the relationships between molecular evolution and expression evolution of genes in different species, and the relationship between expression breadth and expression conservation in evolution.

Efficacy of monitoring patient's position during neurosurgical procedures: introduction of real-time display and record.

There are many reports on position-related complications in neurosurgical literature but so far, continuous quantification of the patient's position during the surgery has not been reported. This study aims to explore the utility of a new surgical table system and its software in displaying the patient's body positions during surgery on real-time basis. More than 200 neurosurgical cases were monitored for their positions intra-operatively. The position was digitally recorded and could be seen by all the members in the operating team. It also displayed the three-dimensional relationship between the head and the heart positions. No position-related complications were observed during the study. The system was able to serve as an excellent indicator for monitoring the patient's position. The recordings were analyzed and even used to reproduce or improve the position in the subsequent operations. The novel technique of monitoring the position of the head and the heart of the patients and the operating table planes are considered to be useful during delicate neurosurgical procedures thereby, preventing inadvertent procedural errors. This can be used to quantify various surgical positions in the future and define safety measures accordingly.

Evolutionarily diverged regulation of X-chromosomal genes as a primal event in mouse reproductive isolation.

Improper gene regulation is implicated in reproductive isolation, but its genetic and molecular bases are unknown. We previously reported that a mouse inter-subspecific X chromosome substitution strain shows reproductive isolation characterized by male-specific sterility due to disruption of meiotic entry in spermatogenesis. Here, we conducted comprehensive transcriptional profiling of the testicular cells of this strain by microarray. The results clearly revealed gross misregulation of gene expression in the substituted donor X chromosome. Such misregulation occurred prior to detectable spermatogenetic impairment, suggesting that it is a primal event in reproductive isolation. The misregulation of X-linked genes showed asymmetry; more genes were disproportionally downregulated rather than upregulated. Furthermore, this misregulation subsequently resulted in perturbation of global transcriptional regulation of autosomal genes, probably by cascading deleterious effects. Remarkably, this transcriptional misregulation was substantially restored by introduction of chromosome 1 from the same donor strain as the X chromosome. This finding implies that one of regulatory genes acting in trans for X-linked target genes is located on chromosome 1. This study collectively suggests that regulatory incompatibility is a major cause of reproductive isolation in the X chromosome substitution strain.