Perirenal fat thickness as a predictor of postoperative complications after laparoscopic distal gastrectomy for gastric cancer.

BACKGROUND: Laparoscopic distal gastrectomy is used widely in surgery for gastric cancer. Excess visceral fat can limit the ability to dissect the suprapancreatic region, potentially increasing the risk of local complications, particularly pancreatic fistula. This study evaluated perirenal fat thickness as a surrogate for visceral fat to see whether this was related to complications after laparoscopic distal gastrectomy. METHODS: Perirenal fat thickness was measured dorsal to the left kidney as an indicator of visceral fat in patients with gastric cancer who underwent laparoscopic distal gastrectomy. Patients were divided into two groups: those with and those without complications. The relationship between perirenal fat thickness and postoperative complications was evaluated. RESULTS: The optimal cut-off value for predicting morbidity using adipose tissue thickness was 10·7 mm; a distance equal to or greater than this was considered a positive perirenal fat thickness sign (PTS). A positive PTS showed a significant correlation with visceral fat area. Multivariable analysis found that a positive PTS was an independent risk factor for complications (hazard ratio 4·42, 95 per cent c.i. 2·31 to 8·86; P < 0·001). CONCLUSION: Perirenal fat thickness as an indicator of visceral fat was an independent predictor of postoperative complications after laparoscopic distal gastrectomy for gastric cancer.

ANTECEDENTES: La gastrectomía distal laparoscópica se utiliza ampliamente en la cirugía del cáncer gástrico. El exceso de grasa visceral puede limitar la capacidad para disecar la región suprapancreática, aumentando potencialmente riesgo de complicaciones locales, especialmente de fistula pancreática. El propósito de este estudio fue evaluar el grosor de la grasa perirrenal como marcador subrogado de grasa visceral para determinar si se relacionaba con complicaciones tras gastrectomía distal laparoscópica. MÉTODOS: El grosor de la grasa perirrenal se midió a nivel dorsal del riñón izquierdo como indicador de grasa visceral en pacientes con cáncer gástrico sometidos a gastrectomía distal laparoscópica. Los pacientes fueron divididos en dos grupos: aquellos con y sin complicaciones. Se evaluó la relación entre grosor de la grasa perirrenal y las complicaciones postoperatorias. RESULTADOS: El punto de corte óptimo para predecir la morbilidad utilizando el grosor del tejido adiposo fue de 10,7 mm, por lo que una distancia igual o mayor a este nivel fue considerado como signo positivo de engrosamiento de la grasa perirrenal (peri-renal fat thickness sign, PTS). Un PTS positivo mostró una correlación significativa con el área de grasa visceral. Los análisis multivariables demostraban que un PTS positivo era un factor de riesgo independiente para complicaciones (razón de oportunidades, odds ratio 4,418; i.c. del 95% 2,307-8,855; P < 0,001). CONCLUSIÓN: El grosor de grasa perirrenal como indicador de la grasa visceral fue un predictor independiente de complicaciones postoperatorias tras una gastrectomía distal laparoscópica por cáncer gástrico.

Morphological lymphocytic reaction, patient prognosis and PD-1 expression after surgical resection for oesophageal cancer.

BACKGROUND: Immune checkpoint inhibitors, such as antibody against programmed cell death protein (PD-1), have demonstrated antitumour effects in patients with malignancies, including oesophageal cancer. A lymphocytic reaction observed by pathological examination is a manifestation of the host immune response to tumour cells. It was hypothesized that a stronger lymphocytic reaction to tumours might be associated with favourable prognosis in oesophageal cancer. METHODS: Using a database of resected oesophageal cancers, four morphological components of lymphocytic reactions (peritumoral, intranest, lymphoid and stromal) to tumours were evaluated in relation to clinical outcome, PD-1 expression by immunohistochemistry and total lymphocyte count in blood. RESULTS: Resected oesophageal cancer specimens from 436 patients were included in the study. Among the four morphological components, only peritumoral reaction was associated with patient prognosis (multivariable P for trend <0·001); patients with a higher peritumoral reaction had significantly longer overall survival than those with a lower reaction (multivariable hazard ratio 0·48, 95 per cent c.i. 0·34 to 0·67). The prognostic effect of peritumoral reaction was not significantly modified by other clinical variables (all P for interaction >0·050). Peritumoral reaction was associated with total lymphocyte count in the blood (P < 0·001), supporting the relationship between local immune response and systemic immune competence. In addition, higher morphological peritumoral reaction was associated with high PD-1 expression on lymphocytes in tumours (P = 0·034). CONCLUSION: These findings should help to improve risk-adapted therapeutic strategies and help stratify patients in the future clinical setting of immunotherapy for oesophageal cancer.

ANTECEDENTES: Los inhibidores de los puntos de control inmunitario (checkpoints) (p.ej. los anticuerpos anti-PD-1) han demostrado efectos antitumorales en pacientes con tumores malignos, incluido el cáncer de esófago. La reacción linfocítica detectada en estudios anatomopatológicos es una manifestación de la respuesta inmune del huésped a las células tumorales. Se estableció la hipótesis de que una mayor reacción linfocítica a los tumores podría asociarse con un mejor pronóstico en el cáncer de esófago. MÉTODOS: Usando una base de datos de 436 cánceres de esófago resecados, se evaluaron cuatro componentes morfológicos (peritumoral, intra-epitelial, linfoide y estromal) de las reacciones linfocíticas a tumores en relación con los resultados clínicos, la expresión inmunohistoquímica de PD-1 y el recuento total de linfocitos en sangre. RESULTADOS: De los cuatro componentes, solamente la reacción peritumoral se asoció con el pronóstico del paciente (P multivariable para tendencia < 0,001): los pacientes con mayor reacción peritumoral presentaron una supervivencia global significativamente más prolongada que aquellos pacientes con menor reacción peritumoral (cociente de riesgos instantáneos multivariable, hazard ratio, HR: 0,48; i.c. del 95%: 0,34 -0,67; P <0,001). El efecto pronóstico de la reacción peritumoral no se modificó significativamente por otras variables clínicas (todas las P para la interacción > 0,05). La reacción peritumoral se asoció con el recuento total de linfocitos en la sangre (P < 0,001), lo que respalda la relación entre la respuesta inmune local y la competencia inmune sistémica. Además, una elevada reacción morfológica peritumoral se asoció con una alta expresión de PD-1 en linfocitos tumorales (P = 0,034). CONCLUSIÓN: Estos hallazgos deberían ayudar a mejorar las estrategias terapéuticas adaptadas al riesgo y contribuir a estratificar a los pacientes en el entorno clínico futuro de la inmunoterapia para los pacientes con cáncer de esófago.

Manipulating megakaryocytes to manufacture platelets ex vivo.

Historically, platelet transfusion has proven a reliable way to treat patients suffering from thrombocytopenia or similar ailments. An undersupply of donors, however, has demanded alternative platelet sources. Scientists have therefore sought to recapitulate the biological events that convert hematopoietic stem cells into platelets in the laboratory. Such platelets have shown good function and potential for treatment. Yet the number manufactured ex vivo falls well short of clinical application. Part of the reason is the remarkable gaps in our understanding of the molecular mechanisms driving platelet formation. Using several stem cell sources, scientists have progressively clarified the chemical signaling and physical microenvironment that optimize ex vivo platelets and reconstituted them in synthetic environments. Key advances in cell reprogramming and the ability to propagate self-renewal have extended the lifetime of megakaryocytes to increase the pool of platelet progenitors.

Frequency of HER2 expression of circulating tumour cells in patients with metastatic or recurrent gastrointestinal cancer.

BACKGROUND: The clinical significance of circulating tumour cell (CTC) detection in gastrointestinal (GI) cancer remains controversial and the molecular biological characteristics of CTCs are poorly understood. METHODS: A total of 87 patients with metastatic or recurrent GI cancer were prospectively enrolled. Circulating tumour cells and their HER2 status were assessed using the CellSearch System. RESULTS: Among the 62 CTC-positive cases, we found 22 discordant cases (35.5%). Among the HER2-negative primary tumours, 17 of 54 developed HER2-positive CTCs. Five of eight had HER2-negative CTCs among the HER2-positive primary tumours. CONCLUSION: The findings in the current study suggest that it is critical to evaluate the HER2 status of not only the primary tumour but also the CTCs because the metastasising tumour cells are the primary target of systemic therapy.

Human equilibrative nucleoside transporter 1 and Notch3 can predict gemcitabine effects in patients with unresectable pancreatic cancer.

BACKGROUND: Pancreatic ductal carcinoma (PDC) is one of the most lethal human carcinomas. Expression patterns of some genes may predict gemcitabine (GEM) treatment efficacy. We examined predictive indicators of survival in GEM-treated patients by quantifying the expression of several genes in pre-treatment endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA) samples from patients with PDC. METHODS: The expressions of human equilibrative nucleoside transporter 1 (hENT1), deoxycitidine kinase, ribonucleoside reductase 1, ribonucleoside reductase 2 and Notch3 in EUS-FNA tissue samples from 71 patients with unresectable PDC were quantified using real-time reverse transcription-polymerase chain reactions and examined for correlations with GEM sensitivity. RESULTS: The log-rank test detected no significant differences in overall survival between GEM-treated patients with low and high mRNA levels of all genes examined. However, low Notch3 mRNA expression was significantly associated with longer overall survival in a multivariate analysis for survival (P=0.0094). High hENT1 expression level was significantly associated with a longer time to progression (P=0.039). Interaction tests for GEM administration and hENT1 or Notch3 mRNA expression were statistically significant (P=0.0054 and 0.0047, respectively). CONCLUSION: hENT1 and Notch3 mRNA expressions in EUS-FNA specimens were the key predictive biomarkers of GEM effect and GEM sensitivity in patients with unresectable PDC.

Loss of programmed cell death 4 induces apoptosis by promoting the translation of procaspase-3 mRNA.

The programmed cell death 4 (Pdcd4), a translation inhibitor, plays an essential role in tumor suppression, but its role in apoptosis remains unclear. Here we show that Pdcd4 is a critical suppressor of apoptosis by inhibiting the translation of procaspase-3 mRNA. Pdcd4 protein decreased more rapidly through microRNA-mediated translational repression following apoptotic stimuli than did the activation of procaspase-3, cleavage of poly(ADP)ribose polymerase (PARP) by active caspase-3, and nuclear fragmentation. Strikingly, the loss of Pdcd4 by the specific RNA interference increased procaspase-3 expression, leading to its activation and PARP cleavage even without apoptotic stimuli, and sensitized the cells to apoptosis. Thus, our findings provide insight into a novel mechanism for Pdcd4 as a regulator of apoptosis.

Automutanolysin disrupts clinical isolates of cariogenic streptococci in biofilms and planktonic cells.

INTRODUCTION: Dental caries remains one of the most common chronic infectious diseases throughout the world. The formation of dental plaque is one of the caries risk factors. As a consequence, the removal of plaque may reduce the incidence of caries development. We identified an autolysin produced by Streptococcus mutans named auto-mutanolysin (Aml). Aml selectively lyses S. mutans and Streptococcus sobrinus. The specificity towards these cariogenic bacteria suggests that Aml may be used to prevent dental caries. Here, with the aim towards therapeutic application, we investigated the lytic activity of Aml against clinical isolates of S. mutans and S. sobrinus using planktonic cells and biofilms. METHODS: Planktonic cell suspensions and biofilms of clinically isolated streptococci were treated with Aml in the absence or the presence of Triton X-100. The lytic activity of Aml was monitored as the change in turbidity. The disruption of biofilms was evaluated by detecting the released DNA by polymerase chain reaction and observing the alteration of optical density of treated biofilms. RESULTS: Triton X-100 enhances the lytic ability of Aml. Using planktonic cells, Aml had various lysis levels against clinical strains. Repeated Aml treatment showed disruption of the biofilm using the representative clinical strains. CONCLUSION: Our study demonstrates that Aml has an ability to lyse planktonic and biofilm cells of clinically isolated mutans streptococci in the presence of Triton X-100. These results suggest the possibility of using Aml as an alternative or additional approach for caries prevention.

Development of fibrinogen gamma-chain peptide-coated, adenosine diphosphate-encapsulated liposomes as a synthetic platelet substitute.

BACKGROUND: The dodecapeptide HHLGGAKQAGDV (H12), corresponding to the fibrinogen gamma-chain carboxy-terminal sequence (gamma 400-411), is a specific binding site of the ligand for platelet GPIIb/IIIa complex. We have evaluated H12-coated nanoparticles (polymerized albumin or liposome) as platelet function-supporting synthetic products. OBJECTIVES: To strengthen the hemostatic ability of H12-coated particles as a platelet substitute, we exploited installation of a drug delivery function by encapsulating adenosine diphosphate (ADP) into liposomes [H12-(ADP)-liposomes]. METHODS AND RESULTS: Via selective interaction with activated platelets through GPIIb/IIIa, H12-(ADP)-liposomes were capable of augmenting agonist-induced platelet aggregation by releasing ADP in an aggregation-dependent manner. When intravenously injected into rats, liposomes were readily targeted to sites of vascular injury as analyzed on computed tomography. In fact, comparable to fresh platelets, liposomes exhibited considerable hemostatic ability for correcting prolonged bleeding time in a busulphan-induced thrombocytopenic rabbit model. In addition, the liposomes showed no activating or aggregating effects on circulating platelets in normal rabbits. CONCLUSION: H12-(ADP)-liposome may thus offer a promising platelet substitute, being made with only synthetic materials and exerting hemostatic functions in vivo via reinforcement of primary thrombus formation by residual platelets in thrombocytopenia at sites of vascular injury, but not in circulation.

Adiponectin induces insulin secretion in vitro and in vivo at a low glucose concentration.

AIMS/HYPOTHESIS: A decrease in plasma adiponectin levels has been shown to contribute to the development of diabetes. However, it remains uncertain whether adiponectin plays a role in the regulation of insulin secretion. In this study, we investigated whether adiponectin may be involved in the regulation of insulin secretion in vivo and in vitro. METHODS: The effect of adiponectin on insulin secretion was measured in vitro and in vivo, along with the effects of adiponectin on ATP generation, membrane potentials, Ca2+ currents, cytosolic calcium concentration and state of 5'-AMP-activated protein kinase (AMPK). In addition, insulin granule transport was measured by membrane capacitance and total internal reflection fluorescence (TIRF) analysis. RESULTS: Adiponectin significantly stimulated insulin secretion from pancreatic islets to approximately 2.3-fold the baseline value in the presence of a glucose concentration of 5.6 mmol/l. Although adiponectin had no effect on ATP generation, membrane potentials, Ca2+ currents, cytosolic calcium concentrations or activation status of AMPK, it caused a significant increase of membrane capacitance to approximately 2.3-fold the baseline value. TIRF analysis revealed that adiponectin induced a significant increase in the number of fusion events in mouse pancreatic beta cells under 5.6 mmol/l glucose loading, without affecting the status of previously docked granules. Moreover, intravenous injection of adiponectin significantly increased insulin secretion to approximately 1.6-fold of baseline in C57BL/6 mice. CONCLUSIONS/INTERPRETATION: The above results indicate that adiponectin induces insulin secretion in vitro and in vivo.

Establishment of immortalized dental follicle cells for generating periodontal ligament in vivo.

The dental follicle is a mesenchymal tissue that surrounds the developing tooth germ. During tooth root formation, periodontal components, viz., cementum, periodontal ligament (PDL), and alveolar bone, are created by dental follicle progenitors. Here, we report the presence of PDL progenitors in mouse dental follicle (MDF) cells. MDF cells were obtained from mouse incisor tooth germs and immortalized by the expression of a mutant human papilloma virus type 16 E6 gene lacking the PDZ-domain-binding motif. MDF cells expressing the mutant E6 gene (MDF( E6-EGFP ) cells) had an extended life span, beyond 150 population doublings (PD). In contrast, normal MDF cells failed to proliferate beyond 10 PD. MDF( E6-EGFP ) cells expressed tendon/ligament phenotype-related genes such as Scleraxis (Scx), growth and differentiation factor-5, EphA4, Six-1, and type I collagen. In addition, the expression of periostin was observed. To elucidate the differentiation capacity of MDF( E6-EGFP ) cells in vivo, the cells were transplanted into severe combined immunodeficiency mice. At 4 weeks, MDF( E6-EGFP ) cell transplants had the capacity to generate a PDL-like tissue that expressed periostin, Scx, and type XII collagen and the fibrillar assembly of type I collagen. Our findings suggest that MDF( E6-EGFP ) cells can act as PDL progenitors, and that these cells may be a useful research tool for studying PDL formation and for developing regeneration therapies.

Familial clustering in subgroups of gastric cancer stratified by histology, age group and location.

AIM: To assess the risk of gastric cancer in a Japanese patient population with the disease by stratification with histology, age, tumour location and the association with family history of gastric or non-gastric tumours. METHODS: A retrospective analysis of 1400 consecutive patients with gastric cancer and 13,467 age- and gender-matched controls from a pre-recorded database using conditional logistic regression models. RESULTS: Young patients (< or = 43 years of age) with gastric cancer of intestinal type had a strong association with family history of gastric cancer in first degree-relatives (OR=12.5). Moreover, when a history of gastric cancer was observed in both parents, there was an increased risk of gastric cancer intestinal type (OR=7.8), more commonly in the proximal and mid-stomach. In contrast, there was an increased risk of diffuse-type cancer when both parents suffered non-gastric cancers (OR=2.1). CONCLUSION: These data suggest that the degree of familial clustering differ in gastric cancer subgroups stratified by histology, age, and stomach location in this Japanese population.

Sonic hedgehog signaling is important in tooth root development.

Hertwig's epithelial root sheath (HERS) is important for tooth root formation, but the molecular basis for the signaling of root development remains uncertain. We hypothesized that Sonic hedgehog (Shh) signaling is involved in the HERS function, because it mediates epithelial-mesenchymal interactions during embryonic odontogenesis. We examined the gene expression patterns of Shh signaling in murine developing molar roots. Shh and Patched2 transcripts were identified in the HERS, whereas Patched1, Smoothened, and Gli1 were expressed in the proliferative dental mesenchyme in addition to the HERS. To confirm whether Shh signaling physiologically functions in vivo, we analyzed mesenchymal dysplasia (mes) mice carrying an abnormal C-terminus of the PATCHED1 protein. In the mutant, cell proliferation was repressed around the HERS at 1 wk. Moreover, the molar eruption was disturbed, and all roots were shorter than those in control littermates at 4 wks. These results indicate that Shh signaling is important in tooth root development. Abbreviations used: BrdU, 5-bromo-2'-deoxyuridine; HERS, Hertwig's epithelial root sheath; NFI-C/CTF, nuclear factor Ic/CAAT box transcription factor; PCNA, proliferating cell nuclear antigen; Ptc, patched; Shh, sonic hedgehog; Smo, smoothened.

Defect in serine 46 phosphorylation of p53 contributes to acquisition of p53 resistance in oral squamous cell carcinoma cells.

To investigate whether dysregulation of p53 phosphorylation confers tumor resistance to p53, we analysed the effects of wild-type p53 on oral squamous cell carcinoma (SCC) cell lines carrying various mutations of p53. Introduction of exogenous p53 neither induced apoptosis nor suppressed colony formation in HSC-3 cells lacking any detectable p53 and HSC-4 cells expressing mutant p53R248Q protein. Consistently, exogenous p53 did not induce proapoptotic p53-target genes in these p53-resistant cells. We found that phosphorylation of exogenous p53 on serine 46 (Ser46) was severely impaired in HSC-3 but not HSC-4 cells. A mutant mimicking Ser46-phosphorylation (p53S46D) enhanced proapoptotic Noxa promoter activity, and overcame the resistance to p53-mediated apoptosis and growth suppression in HSC-3 cells. Conversely, a mutant defective for Ser46-phosphorylation (p53S46A) failed to suppress the growth of p53-sensitive HSC-2 cells. In contrast to HSC-3 cells, p53S46D had no effect on HSC-4 cells, and inhibition of endogenous p53R248Q by siRNA restored p53-mediated apoptosis in HSC-4 cells, indicating a dominant-negative effect of p53R248Q protein on wild-type p53 function. These results demonstrate that the defect in Ser46 phosphorylation accounts for the p53 resistance of HSC-3 cells, and provide evidence for a mechanism underlying the acquisition of p53 resistance in oral SCC.

Hand-assisted laparoscopic and thoracoscopic surgery (HALTS) in radical esophagectomy with three-field lymphadenectomy for thoracic esophageal cancer.

AIM: To prove the feasibility of hand-assisted laparoscopic and thoracoscopic surgery (HALTS) for radical esophagectomy with three-field lymphadenectomy to thoracic esophageal cancer. METHODS: Esophagectomy with three-field lymphadenectomy was performed using HALTS in 19 patients with thoracic esophageal cancer without distant metastasis. Five patients had chemo-radiotherapy prior to surgery. RESULTS: All operations were completed successfully without the need for open surgery. Mean surgical time was 476+/-58 min, and mean blood loss during surgery was 343+/-184 mL. All patients started tube feeding and were moved from the intensive care unit to the general surgery ward the day after surgery. Discharge occurred a median of 10 days after surgery. Fifteen patients could return to full time jobs from 8 to 62 days after surgery (median 22 days) and from 1 to 35 days after discharge (median 9 days). Other three could return to daily activities at home soon as well. No major complications occurred, except one anastomotic leak. In terms of lung function, %FEV(1) was not changed whereas %VC was reduced significantly 1 month after surgery. All but two recurrences have been healthy without a relapse for a mean of 289 days. CONCLUSIONS: These results suggest that HALTS may be a useful surgical technique to reduce the invasiveness of conventional radical esophagectomy with three-field lymphadenectomy for thoracic esophageal cancer.

Adiponectin stimulates glucose utilization and fatty-acid oxidation by activating AMP-activated protein kinase.

Adiponectin (Ad) is a hormone secreted by adipocytes that regulates energy homeostasis and glucose and lipid metabolism. However, the signaling pathways that mediate the metabolic effects of Ad remain poorly identified. Here we show that phosphorylation and activation of the 5'-AMP-activated protein kinase (AMPK) are stimulated with globular and full-length Ad in skeletal muscle and only with full-length Ad in the liver. In parallel with its activation of AMPK, Ad stimulates phosphorylation of acetyl coenzyme A carboxylase (ACC), fatty-acid oxidation, glucose uptake and lactate production in myocytes, phosphorylation of ACC and reduction of molecules involved in gluconeogenesis in the liver, and reduction of glucose levels in vivo. Blocking AMPK activation by dominant-negative mutant inhibits each of these effects, indicating that stimulation of glucose utilization and fatty-acid oxidation by Ad occurs through activation of AMPK. Our data may provide a novel paradigm that an adipocyte-derived antidiabetic hormone, Ad, activates AMPK, thereby directly regulating glucose metabolism and insulin sensitivity in vitro and in vivo.

Central nervous system lesions in adult T-cell leukaemia: MRI and pathology.

Adult T-cell leukaemia (ATL) is a T-cell lymphoid neoplasm caused by human T-cell leukaemia virus type I (HTLV-I). Radiological findings in central nervous system (CNS) involvement have not been well characterised. We reviewed the MRI of 18 patients with ATL who developed new neurological symptoms or signs, and pathology specimens from a 53-year-old woman who died of ATL. MRI findings were divided into three categories: definite, probable, and other abnormal. Definite and probable findings were defined as ATL-related. The characteristic findings were multiple parenchymal masses with or without contrast enhancement adjacent to cerebrospinal fluid (CSF) spaced and the deep grey matter of both cerebral hemispheres, plus leptomeningeal lesion. One patient had both cerebral and spinal cord lesions. Other abnormal findings in eight patients included one case of leukoencephalopathy caused by methotrexate. The histology findings consisted of clusters of tumour cells along perivascular spaces, and scattered infiltration of the parenchyma, with nests of tumour cells. Leptomeningeal infiltration by tumour spread into the parenchyma and secondary degeneration of the neuronal tracts was observed. MRI was useful for detecting CNS invasion by ATL and differentiating it from other abnormalities. The MRI findings seemed to correlate well with the histological changes.

Involvement of enhanced sensitivity of N-methyl-D-aspartate receptors in vulnerability of developing cortical neurons to methylmercury neurotoxicity.

The developing cortical neurons have been well documented to be extremely vulnerable to the toxic effect of methylmercury (MeHg). In the present study, a possible involvement of N-methyl-D-aspartate (NMDA) receptors in MeHg neurotoxicity was examined because the sensitivity of cortical neurons to NMDA neurotoxicity has a similar developmental profile. Rats on postnatal day 2 (P2), P16, and P60 were orally administered MeHg (10 mg/kg) for 7 consecutive days. The most severe neuronal damage was observed in the occipital cortex of P16 rats. When MK-801 (0.1 mg/kg), a non-competitive antagonist of NMDA, was administered intraperitoneally with MeHg, MeHg-induced neurodegeneration was markedly ameliorated. Furthermore, there was a marked accumulation of nitrotyrosine, a reaction product of peroxynitrite and L-tyrosine, after chronic treatment of MeHg in the occipital cortex of P16 rats. The accumulation of nitrotyrosine was also significantly suppressed by MK-801. In the present electrophysiological study, the amplitude of synaptic responses mediated by NMDA receptors recorded in cortical neurons of P16 rats was significantly larger than those from P2 and P60 rats. These observations strongly suggest that a generation of peroxynitrite through activation of NMDA receptors is a major causal factor for MeHg neurotoxicity in the developing cortical neurons. Furthermore, enhanced sensitivity of NMDA receptors may make the cortical neurons of P16 rats most susceptible to MeHg neurotoxicity.

Developmental origin of the rat adenohypophysis prior to the formation of Rathke's pouch.

In amphibians, it has already been shown that the adenohypophysis originates from the anterior neural ridge. During the migration and morphogenesis of this organ, the anterior neural ridge transiently forms a Rathke's pouch-like structure by attaching itself to the rostral tip of the foregut, and finally gives rise to the adenohypophysis by detaching from the foregut and becoming connected to the infundibulum of the hypothalamus. In order to identify the origin of the adenohypophyseal cells in mammalian embryos prior to the formation of Rathke's pouch (RP), we labeled the rostral end of the neural plate and the adjacent area focally with DiI at the open neurula stage (9.5 dpc). After a 48-hours culture of the whole embryos, strongly labeled cells were detected in the RP only when DiI was applied to a small area situated just anterior to the rostral end of the neural plate. By explanting the labeled RP for a further 7 days, we confirmed immunohistochemically that the labeled cells developed into the secretory cells of the adenohypophysis. The developmental origin of the adenohypophysis is identified for the first time in the early mammalian embryo before the formation of RP.

Hexamminecobalt(III) chloride inhibits glucose-induced insulin secretion at the exocytotic process.

Hexamminecobalt(III) (HAC) chloride was found to have a potent inhibitory effect on glucose-induced insulin secretion from pancreatic islets. HAC at 2 mm inhibited the secretion in response to 22.2 mm glucose by 90% in mouse islets. Perifusion experiments revealed that the first phase of insulin secretion was severely suppressed and that the second phase of secretion was completely abrogated. Removal of HAC from the perifusate immediately restored insulin secretion with a transient overshooting above the normal level. However, HAC failed to affect glucose-induced changes in d-[6-(14)C]glucose oxidation, levels of reduced forms of NAD and NADP, mitochondrial membrane potential, ATP content, cytosolic calcium concentration, or calcium influx into mitochondria. Furthermore, HAC inhibited 50 mm potassium-stimulated insulin secretion by 77% and 10 microm mastoparan-stimulated insulin secretion in the absence of extracellular Ca(2+) by 80%. The results of a co-immunoprecipitation study of lysates from insulin-secreting betaHC9 cells using anti-syntaxin and anti-vesicle-associated membrane protein antibodies for immunoprecipitation or Western blotting suggested that HAC inhibited disruption of the SNARE complex, which is normally observed upon glucose challenge. These results suggest that the inhibitory effect of HAC on glucose-induced insulin secretion is exerted at a site(s) distal to the elevation of cytosolic [Ca(2+)], possibly in the exocytotic machinery per se; and thus, HAC may serve as a useful tool for dissecting the molecular mechanism of insulin exocytotic processes.