Search for the Pair Production of Dark Particles X with K_{L}

We present the first search for the pair production of dark particles X via K_{L}^{0}→XX with X decaying into two photons using the data collected by the KOTO experiment. No signal was observed in the mass range of 40-110 MeV/c^{2} and 210-240 MeV/c^{2}. This sets upper limits on the branching fractions as B(K_{L}^{0}→XX)<(1-4)×10^{-7} and B(K_{L}^{0}→XX)<(1-2)×10^{-6} at the 90% confidence level for the two mass regions, respectively.

Application of inorganic phosphate limitation to efficient isoprene production in Pantoea ananatis.

AIMS: Establishment of an efficient isoprene fermentation process by adopting inorganic phosphate limitation as the trigger to direct metabolic flux to the isoprene synthetic pathway. METHODS AND RESULTS: We constructed isoprene-producing strains of Pantoea ananatis (a member of the Enterobacteriaceae family) by integrating a heterologous mevalonate pathway and a metabolic switch that senses external inorganic phosphate (Pi) levels. This metabolic switch enabled dual-phase isoprene production, where the initial cell growth phase under Pi-saturating conditions was uncoupled from the subsequent isoprene production phase under Pi-limiting conditions. In fed-batch fermentation using our best strain (SWITCH-PphoC/pIspSM) in a 1-l bioreactor, isoprene concentration in the off-gas was maintained between 300 and 460 ppm during the production phase and at 20 ppm during the cell growth phase, respectively. The strain SWITCH-PphoC/pIspSM produced totally 2·5 g l-1 of isoprene from glucose with a 1·8% volumetric yield in 48 h. CONCLUSIONS: This proof-of-concept study demonstrated that our Pi-dependent dual-phase production system using a P. ananatis strain as a producer has potential for industrial-scale isoprene fermentation. SIGNIFICANCE AND IMPACT OF THE STUDY: This Pi-dependent dual-phase fermentation process could be an attractive and economically viable option for the production of various commercially valuable isoprenoids.

Safety and Feasibility of a Pancreaticoduodenectomy with Total Meso-Pancreatoduodenum Excision: Analysis in Various Periampullary Disorders.

BACKGROUND/AIMS: This study aimed to evaluate the safety and feasibility of a pancreaticoduodenectomy with total meso-pancreatoduodenum excision (tMPDe) as an new anatomical concept. METHODOLOGY: A total of 90 patients underwent PD for various periampullary diseases. Of these, 52 patients received a conventional PD (cPD), while 38 patients underwent a tMPDe. Surgical outcomes were compared between the two study groups. RESULTS: Operative time was equivalent in the two groups; however, the estimated blood loss (cPD, 1360 ml; tMPDe, 995 ml; median, P = 0.026) and blood transfusion rate (cPD, 63%; tMPDe, 31% ; P = 0.001) were significantly decreased in tMPDe. Morbidity had no significant difference between cPD and tMPDe, and tMPDe showed no characteristic complications. With regard to oncological aspects, tMPDe was superior to cPD. Risk factors analysis revealed the operative time (P = 0.003), estimated blood loss (P < 0.001), and blood transfusion (P < 0.001) to be significant predictive risk factors for postoperative morbidity but not tMPDe procedure (P = 0.794). CONCLUSIONS: tMPDe is safe and superior to cPD because it is a bloodless operation with a good oncological outcome: We concluded that tMPDe should be adaptable to various periampullary diseases, including benign and low-grade malignant disorders.

Distal pancreatectomy utilizing a flexible stapler closure eliminates the risk of pancreas-related factors for postoperative pancreatic fistula.

OBJECTIVES: To identify the risk factors for clinically relevant pancreatic fistula after distal pancreatectomy with a flexible cartridge stapler, TL60. METHODS: Forty consecutive patients who underwent a distal pancreatectomy by the TL60 stapler were retrospectively reviewed in association with postoperative complications. RESULTS: The overall morbidity rate was 43% (17 patients), and mortality was null. Pancreatic fistula was the most frequent postoperative complication, seen in 11 patients (27.5%): grade A in 4 (10%) and grade B in 7 (17.5%). No grade C pancreatic fistula was observed. Univariate analyses of risk factors demonstrated that pancreas-related factors, including diabetes mellitus, thickness and texture of the pancreatic parenchyma, transection line for the pancreas, pancreatic duct ligation, and use of artificial patches had no impact on the occurrence of pancreatic fistula. A multivariable logistic regression analysis identified operative time (≥ 300 min) as the only notable predictor of clinically relevant pancreatic fistula (odds ratio = 3.253, 95% confidence interval 1.739-5.752; p = 0.031). CONCLUSION: Distal pancreatectomy with the use of the TL60 stapler eliminated the risk of pancreas-related factors for the occurrence of clinically relevant pancreatic fistula.

Detection of thymocytes apoptosis in mice induced by organochlorine pesticides methoxychlor.

The thymus has long been known to be vulnerable to atrophy when exposed to variety of stimuli, including hormones, immunosuppressive pharmaceuticals, and environmental chemicals. The organochlorine pesticide methoxychlor (MXC) is an immunosuppressive agent thought to affect thymic atrophy by inducing apoptosis of thymocyte T cells. We sought to develop an experimental protocol to detect in vivo thymocyte apoptosis induced by MXC in Balb/c mice. We treated the mice with 150-400 mg/kg MXC. We then measured thymus weight, cell counts, caspase activity (3/7, 8, and 9), annexin V labeling of phosphatidylserine (PS) and DNA fragmentation. In MXC-treated mice we observed decreases in thymus weight and cell counts and increases in caspase activity (3/7, 8, and 9), annexin V PS labeling and DNA fragmentation. These results suggest that MXC induces thymic atrophy caused by thymocyte apoptosis, and that our protocol may be useful for detecting in vivo thymocyte apoptosis induced by environmental chemicals in short-time.

Role of dimerization of the membrane-associated growth factor kit ligand in juxtacrine signaling: the Sl17H mutation affects dimerization and stability-phenotypes in hematopoiesis.

The Kit ligand (KL)/Kit receptor pair functions in hematopoiesis, gametogenesis, and melanogenesis. KL is encoded at the murine steel (Sl) locus and encodes a membrane growth factor which may be proteolytically processed to produce soluble KL. The membrane-associated form of KL is critical in mediating Kit function in vivo. Evidence for a role of cytoplasmic domain sequences of KL comes from the Sl17H mutation, a splice site mutation that replaces the cytoplasmic domain with extraneous amino acids. Using deletion mutants and the Sl17H allele, we have investigated the role of the cytoplasmic domain sequences of KL in biosynthetic processing and cell surface presentation. The normal KL protein products are processed for cell surface expression, where they form dimers. Both Sl17H and the cytoplasmic deletion mutants of KL were processed to the cell surface; however, the rate of transport and protein stability were affected by the mutations. Deletion of cytoplasmic domain sequences of KL did not affect dimerization of KL. In contrast, dimerization of the Sl17H protein was reduced substantially. In addition, we have characterized the hematopoietic cell compartment in Sl17H mutant mice. The Sl17H mutation has only minor effects on hematopoiesis. Tissue and peritoneal mast cell numbers were reduced in mutant mice as well as in myeloid progenitors. Interestingly, long-term bone marrow cultures from Sl17H mice did not sustain the long-term production of hematopoietic cells. In addition, homing of normal hematopoietic progenitors to the spleen of irradiated Sl17H/Sl17H recipient mice was diminished in transplantation experiments, providing evidence for a role of Kit in homing or lodging. These results demonstrate that the membrane forms of KL exist as homodimers on the cell surface and that dimerization may play an important role in KL/Kit-mediated juxtacrine signaling.

Helicobacter bilis colonization of the biliary system in patients with pancreaticobiliary maljunction.

BACKGROUND: Helicobacter bilis is considered to be a causative factor in the pathogenesis of biliary cancer. This study investigated the prevalence of H. bilis colonization of the biliary system of patients with pancreaticobiliary maljunction (PBM). METHODS: Bile juice and biliary tissue samples were collected from 17 patients with PBM and 27 controls who had benign biliary disease without PBM. DNA extracted from each biliary sample was subjected to polymerase chain reaction (PCR) analysis for H. bilis and Helicobacter pylori. RESULTS: PCR assays revealed that 12 of the 17 patients with PBM were positive for H. bilis DNA, compared with eight of 27 patients without PBM (P = 0.009). Among patients with PBM, H. bilis DNA was identified in six of eight children, including a 2-month-old infant, and in six of nine adults. The high prevalence of H. bilis DNA in the biliary system of patients with PBM was independent of age, sex, common bile duct dilatation, configuration of the pancreatic and bile ducts, and amylase activity in bile. CONCLUSION: H. bilis colonization of the biliary system is extremely common in patients with PBM. This may point to a role in the pathogenesis of biliary cancer.

Unusual cutaneous features of syphilis in patients positive for human immunodeficiency virus.

Dermatologists commonly find it difficult to diagnose syphilis, because of its protean clinical features. In cases of co-infection with human immunodeficiency virus (HIV) syphilis may present particularly unusual clinical features, further confounding the diagnosis. We report two cases of syphilis/HIV co-infection in Japanese patients showing uncommon skin features that made the diagnosis of syphilis difficult. These cases underline the need for dermatologists to be more aware of atypical cutaneous features of syphilis in patients positive for HIV.

Pathology of lethal peripartum broad ligament haematoma in 31 Thoroughbred mares.

REASONS FOR PERFORMING STUDY: Broad ligament haemorrhage in peripartum mares is a life-threatening disease and there are few reports on the aetiology and pathogenesis of broad ligament haematoma. OBJECTIVES: To obtain information regarding the sites for the early diagnosis and pathogenesis of broad ligament haematoma of mares. METHODS: Thirty-one mares that died of broad ligament haematoma peripartum were examined pathologically for bleeding sites. The arterial distribution of 5 young mares with several parities served as negative controls. RESULTS: Age and/or multiparity were the predisposing factors for the disease. Arterial injuries were most commonly observed in the uterine artery (24 of 31 mares). Among these, the proximal uterine artery that lies within 15 cm of the bifurcation of the iliac artery was the most frequent site for rupture (18 mares). The lesions occurred preferentially at the bifurcations, lateral part of curvatures and abrupt flexures of the artery. The morphology of the injuries was classified into 3 types: ruptures with and without longitudinal fissures, and transections. Histologically, the arterial wall adjacent to the rupture showed atrophy of smooth muscle cells with fibrosis of the tunica media and disruption and/or calcification of the internal elastic lamina. CONCLUSIONS: Arterial injuries that led to broad ligament haematoma in peripartum mares occurred most frequently in the proximal uterine artery, and atrophy of smooth muscle cells with fibrosis of the arterial wall was as one of the predisposing factors in aged and multiparous mares. POTENTIAL RELEVANCE: Monitoring small aneurysms, mural tearing, medial fibrosis at the proximal uterine artery by transrectal echography could provide useful information for the early diagnosis and possible prevention of broad ligament haematoma of peripartum mares.

Large-Scale Channel Migration in the Sittang River Estuary.

An estuary is a dynamic environment where marine and fluvial processes meet to form complex and transient morphology. The estuary morphology is largely determined by net sediment transport by two-way tidal flows, but the hydrodynamics also depends on the morphology of the tidal channels. The estuary inherently accommodates cyclic processes that are internally generated through hydro-morphodynamic interactions. In addition, the estuary evolves in response to changes in external forces by natural and anthropogenic factors. Morphological changes under the different controls often hinder the comprehension of the evolutionary processes of estuaries. Here we explored morphological changes in the Sittang River estuary, Myanmar, which has great morphological dynamism from extreme tidal energy and large sediment inputs, through field surveys and satellite imagery analysis. We identify an autocyclic process in a sedimentary system driving large-scale channel migration in decadal to multidecadal cycles. We show that drastic changes of the estuary morphology occasionally occur with rapid bank erosion through modulation of the cyclic channel migration under conflicting tidal and fluvial forces. This extreme case with minimal human intervention highlights channel migration as a key process in morphological evolution of tide-dominated estuaries undergoing active infilling.

Histological, immunohistochemical and pathological features of the pituitary gland of odontocete cetaceans from the Western gulf of Mexico.

Pituitary glands were recovered from dolphins and small whales found stranded along the Texas coast of the Gulf of Mexico over a 15-year period (1991-2006). One hundred animals of 14 species were found to be suitable for inclusion in this study. Of these, 72 were Atlantic bottlenose dolphins (Tursiops truncatus). Other species included were the melon-headed whale (Peponocephala electra), spinner dolphin (Stenella longirostris), striped dolphin (Stenella coeruleoalba), pantropical spotted dolphin (Stenella attenuata), pygmy sperm whale (Kogia breviceps), dwarf sperm whale (Kogia sima), Risso's dolphin (Grampus griseus), the short finned pilot whale (Globicephala macrorhyncha), false killer whale (Pseudorca crassidens), Fraser's dolphin (Lagenorhynchus hosei), rough-tooth dolphin (Steno bredanensis), Gervais's beaked whale (Mesoplodon europaeus) and an infant sperm whale (Physeter catodon). The pituitary weights in T. truncatus ranged from 0.69 g in a 109-cm long neonate to 3.44 g in a large (277 cm) male. More typical weights were in the range of 0.95-2.35 g (mean=1.65+/-0.70 g) The cetacean pituitary consisted of two distinct parts, the adenohypophysis and the neurohypophysis, which were separated by a thin fibrous membrane in all species examined, in contrast to terrestrial mammals in which the parts are apposed and joined through a pars intermedia. Cell types were identified with conventional stains and immunohistochemistry. Cells positive for adrenocorticotropic hormone, follicle stimulating hormone, growth hormone, melanocyte stimulating hormone, luteinizing hormone and prolactin were identified with appropriate antibodies. Lesions, which were few, included one pituicytoma of the pars nervosa and a squamous cyst in T. truncatus, and colloid cysts in several species. Nodular aggregates of single cell types were common, probably representing a physiological variant.

Prognostic significance of preoperative inflammatory response biomarkers in patients undergoing curative thoracoscopic esophagectomy for esophageal squamous cell carcinoma.

BACKGROUND: Recent studies have revealed significant relationships between the lymphocyte-to-monocyte ratio (LMR), neutrophil-to-lymphocyte ratio (NLR), and platelet-to-lymphocyte ratio (PLR) and survival in various cancers. The purpose of this study was to confirm whether the LMR, NLR, and PLR have prognostic values, independent of clinicopathological criteria, in patients undergoing curative resection for esophageal cancer. METHODS: The LMR, NLR and PLR were calculated in 147 consecutive patients who underwent curative esophagectomy between January 2006 and December 2014. Receiver operating characteristics (ROC) curve analysis was conducted to identify the optimal cutoff values of each biomarkers. RESULTS: In multivariate analysis for cancer-specific survival (CSS), pTNM stage (p < 0.0001) and low LMR (p = 0.0081) were selected as independent prognostic factor. Similarly, pTNM stage(p < 0.0001) and low LMR (p = 0.0225) were found to be independent prognostic factor for overall survival (OS). There was no significant relationship between LMR, NLR and PLR and survival in patients with stage I or II, however, significant relationships between LMR and CSS or OS were observed in patients with stage III esophageal cancer. CONCLUSIONS: LMR can be used as a novel predictor of postoperative CSS and OS in patients with esophageal cancer and that it may be useful in identifying patients with a poor prognosis even after radical esophagectomy.

The thyroid gland in bottlenose dolphins (Tursiops truncatus) from the Texas coast of the Gulf of Mexico: normal structure and pathological changes.

Fresh thyroid glands (n=60) from Atlantic bottlenose dolphins that died after stranding along the Texas coast between 1991 and 2005 were examined. Organ weight ranged from 11 g in a neonate (length 109 cm) to 58 g in a large (249 cm) male. More typical weights were 25-45 g (mean=30.6 g). Glands tended to be larger in pregnant and lactating females (mean 37.4 g; n=5) than in non-pregnant animals of comparable size. In infancy, the gland tended to be compact, relatively homogeneous, and sometimes partly lobular, but with advancing age it became more lobular, the lobules being defined by fibrous bands. In one 8-year-old female (233 cm), and in a large male (295 cm) aged>25 years the gland was represented by a cluster of lobules. Lobulation was not necessarily accompanied by increased weight, distinguishing it from hyperplasia. With age, variation in follicle size and colloid density tended to increase. Two animals (3%) had adenomas and five (8%) had discrete hyperplastic nodules, not to be confused with lobulation. Five (8%) had macroscopically identifiable colloid-filled cysts (1-4 mm in diameter). Nine animals (15%) had squamous cysts (4-15 mm) containing creamy white fluid. Other abnormalities included patchy or diffuse interstitial fibrosis (six cases, 10%) amyloidosis (two cases), thyroiditis (one case) and vasculitis (one case). No malignant neoplasms were found. Cells presumed to be C cells (light cells, parafollicular cells) were identified immunohistochemically with synaptophysin antibody.

Connexin43 suppresses MFG-E8 while inducing contact growth inhibition of glioma cells.

Gap junction expression has been reported to control the growth of a variety of transformed cells. We undertook parallel analysis of connexins Cx32 and Cx43 in glioma cells, which revealed potential mechanisms underlying this phenomenon and led to several novel findings. Cx43, but not Cx32, suppressed C6 glioma cell growth. Paradoxically, Cx32 transfection resulted in severalfold more dye transfer than Cx43. However, Cx43 transfectants shared endogenous metabolites more efficiently than Cx32 transfectants. Interestingly, a significant portion of Cx43 permeants were incorporated into macromolecules more readily than those that transferred via Cx32. Cx43 induced contact inhibition of cell growth but in contrast to other reports, did not affect log phase growth rates. Cell death, senescence, or suppression of growth factor signaling was not involved because no significant alterations were seen in cell viability, telomerase, or mitogen-activated protein kinase activity. However, suppression of cell growth by Cx43 entailed the secretion of growth-regulatory factors. Most notably, a major component of conditioned medium that was affected by Cx43 was found to be MFG-E8 (milk fat globule epidermal growth factor 8), which is involved in cell anchorage and integrin signaling. These results indicate that Cx43 regulates cell growth by the modulation of extracellular growth factors including MFG-E8. Furthermore, the ability of a Cx to regulate cell growth may rely on its ability to mediate the intercellular transfer of endogenous metabolites but not artificial dyes.

Modified total meso-pancreatoduodenum excision with pancreaticoduodenectomy as a mesopancreatic plane surgery in borderline resectable pancreatic cancer.

BACKGROUND: A superior mesenteric artery (SMA)-first approach has been considered to be an efficient technique in pancreaticoduodenectomy when the SMA is a factor of borderline resectable pancreatic head cancer (BRPHC). However, this excellent procedure has limitations in terms of tumor resection with an intact coverage including the pancreatic tumor and the tumor-draining lymphovascular systems and the ability to achieve a complete regional lymphadenectomy. METHODS: A modified mesenteric plane procedure has been developed that provides improved regional lymphadenectomy and permits adjustment of the surgical approach, which is based on the direction of the tumor infiltration. RESULTS: Of 55 patients taken to surgery, 19 had peritoneal dissemination and/or liver metastasis at staging laparoscopy, and the procedure revealed tumor infiltration to the SMA and/or hepatic artery (HA) in 4 patients. Finally, 32 patients with BRPHC have undergone the procedure between April 2009 and June 2015. Twenty-four of 32 patients (75.0%) had negative resection margins, and the median number of lymph nodes harvested was 34. Lymph nodes around the SMA tested positive for metastasis in 13 patients (40.6%), and those around the HA tested positive for metastasis in 7 patients (21.9%). Complications occurred in 14 patients (43.7%), with no perioperative mortality. Overall survival rates were 65.3% at 1 year and 35.2% at 3 years. CONCLUSIONS: Short-term results with the procedure may encourage surgical management for BRPHC.

Feasibility of intensity-modulated radiotherapy combined with gemcitabine and S-1 for patients with pancreatic cancer.

The aim of the present study was to establish whether intensity-modulated radiotherapy (IMRT) with concurrent gemcitabine and S-1 is a feasible treatment option for patients with locally advanced pancreatic ductal adenocarcinoma. Patients with pancreatic ductal adenocarcinoma were prospectively enrolled. An IMRT dose of 50.4 Gy in 28 fractions with concurrent gemcitabine at a dose of 600 mg/m2 and S-1 at a dose of 60 mg were administrated. Adverse events and associated dosimetric factors were assessed. Between February 2012 and January 2014, 17 patients with borderline resectable and 4 with unresectable pancreatic cancer were enrolled. None of the patients experienced grade 3 or worse nausea and vomiting. The planning target volume (≥200 vs. <200 ml) was a statistically significant predictive factor for neutrocytopenia (≥500 vs. 500/µl, P=0.02). Concurrent IMRT with gemcitabine and S-1 for patients with locally advanced pancreatic cancer is feasible, with tolerable hematological toxicities and low gastrointestinal toxicities.

The enhancing effects of anion channel blockers on sperm activation by bicarbonate.

We found that anion channel blockers such as phosphotungstate and 4,4'-diisothiocyanatostilbene-2,2'-disulfonate (DIDS) enhanced HCO3(-)-induced activation on porcine epididymal sperm. In the presence of these compounds, HCO3- increased the motility, respiration rate and especially the cAMP content of the sperm to a greater extent than did HCO3- alone. The enhancing effects were not observed in the absence of HCO3-, but were evident when the concentration of HCO3- was low. These compounds did not significantly alter the intracellular pH and did inhibit the adenylate cyclase activity of the sperm plasma membrane. When these compounds were added to sperm homogenate with ATP, the cAMP formed was reduced compared to the control. In addition, these compounds inhibited both the SO4(2-) influx and efflux of the sperm. From these results, we conclude that the anion channel blockers tested principally inhibit the efflux of endogenous HCO3- derived from metabolic CO2, so that HCO3- accumulates intracellularly and stimulates the adenylate cyclase of the sperm.

The activating effects of bicarbonate on sperm motility and respiration at ejaculation.

Mature porcine sperm preserved in the cauda epididymis are quiescent. At ejaculation, they are mixed with the seminal vesicle fluid containing HCO3- and are rapidly activated. The role of HCO3- on the sperm activation process at ejaculation was studied in vitro. HCO3- quickly increased the motility, respiration rate and cAMP content of the porcine epididymal sperm. The extent of activation was proportional to the pCO2 in the medium. The activating effect of HCO3- on the motility was observed even in the absence of fructose as well as in the presence of KCN. 8-Bromoadenosine 3',5'-cyclic monophosphate and theophylline showed similar activating effects to that of HCO3-. However, HCO3(-)-free seminal plasma, Ca2+, amino acids, intermediates of the Krebs cycle, substrates of respiration and increases in the intracellular pH, extracellular pH or ionic strength of the medium had no effect. Fructose sustained the active state of the sperm and gradually increased both the motility and respiration rate when the dose of HCO3- was low. The anion channel blocker enhanced the activating effect of HCO3-. These results suggest that, upon ejaculation, HCO3- is a unique activator in vivo which makes the quiescent sperm motile via the HCO3(-)-adenylate cyclase-cAMP system, to which an endogenous HCO3- derived from metabolic CO2 may be related.

Effects of a membrane-bound trypsin-like proteinase and seminal proteinase inhibitors on the bicarbonate-sensitive adenylate cyclase in porcine sperm plasma membranes.

Plasma membranes were purified from flagella of porcine cauda epididymal sperm and proteolytic regulation of bicarbonate-sensitive adenylate cyclase was studied. It was found that the epididymal sperm plasma membrane contained a trypsin-like proteinase which inactivated adenylate cyclase. Bicarbonate activates adenylate cyclase as reported previously, but, at the same time, the anions enhance the inactivation of the enzyme by the membrane-bound trypsin-like proteinase. This phenomenon is not due to the direct activation of the proteinase, but closely related to the activation of adenylate cyclase by bicarbonate. It was also found that seminal proteinase inhibitors blocked the inactivation of adenylate cyclase and maintained the bicarbonate activation of the enzyme at high level. Actually, bicarbonate keeps adenylate cyclase fully active in ejaculated sperm, because membrane-bound proteinase is completely inhibited by the seminal proteinase inhibitors. These results suggest that the interactions between membrane-bound proteinase and seminal proteinase inhibitor are involved in the regulation of the bicarbonate-sensitive adenylate cyclase system.

Identification of a stromal cell type characterized by the secretion of a soluble integrin-binding protein, MFG-E8, in mouse early gonadogenesis.

Mfge8 (milk fat globule-EGF-factor 8) encodes a soluble integrin-binding protein containing two Notch-like EGF domains and two discoidin domains. It mediates cell-to-cell interaction by binding to integrin alphavbeta3 via the RGD motif of its second EGF domain. Mfge8 was first expressed at 10.0 dpc in cells of the coelomic epithelium covering the mesonephros, and at 10.5 dpc Mfge8-expressing cells were found in the mesenchyme underneath the coelomic epithelium of the genital ridges. At 11.5-12.5 dpc, Mfge8 expressing cells were found in the stromal tissues subjacent to the coelomic epithelium that envelop the fetal gonad of both sexes. MFG-E8 protein was accumulated extracellularly in the interstitial tissues at the boundary of the mesonephros and the genital ridges. A comparison of the expression domains of Mfge8 and several gene markers showed that Mfge8 expression did not significantly overlap with the expression domain of Wt1 or Emx2, but partially with that of Lhx9 in 11.5-day XY gonads. Comparison of the expression pattern of Mfge8 with that of Hsd3beta1 in the 12.5-day testes revealed that the Mfge8-positive cells constitute a previously uncharacterized somatic cell type which is distinct from Sertoli cells, Leydig cells, peritubular myoid cells and the endothelial cells.