Mutation in the abcb7 gene causes abnormal iron and fatty acid metabolism in developing medaka fish

The medaka fish (Oryzias latipes) is an emerging model organism for which a variety of unique developmental mutants have now been generated. Our recent mutagenesis screening of the medaka isolated a unique mutant that develops a fatty liver at larval stages. Positional cloning identified the responsible gene as medaka abcb7. Abcb7, a mitochondrial ABC (ATP binding cassette) half-transporter, has been implicated in iron metabolism. Recently, human Abcb7 was found to be mutated in X-linked sideroblastic anemia with cerebellar ataxia (XLSA/A). The homozygous medaka mutant exhibits abnormal iron metabolism in erythrocytes and accumulation of lipid in the liver. Microarray and in situ hybridization analyses demonstrated that the expression of genes involved in iron and lipid metabolisms are both affected in the mutant liver, suggesting novel roles of Abcb7 in the development of physiologically functional liver. The medaka abcb7 mutant thus could provide insights into the pathogenesis of XLSA/A as well as the normal function of the gene.     

Molecular understanding of chronic pancreatitis: a perspective on the future.

Despite the recent development of medical imaging technology, chronic pancreatitis can only be diagnosed when the disease is fully established. This is due to the lack of specific and sensitive markers for this disease. The discovery of mutations in the cationic trypsinogen gene in patients with hereditary pancreatitis and a high incidence of mutations in the cystic fibrosis transmembrane conductance regulator gene in patients with chronic pancreatitis might be important clues to understanding the molecular mechanisms of this disease. The interaction between ethanol and ion channels might be the missing link between alcohol ingestion and chronic pancreatitis.     

Coronary hemodynamics and cardiac beating modulate atrial natriuretic factor release from isolated Langendorff-perfused rat hearts

The role of coronary hemodynamics and cardiac beating on atrial natriuretic factor (ANF) release was studied in the isolated Langendorff-perfused rat heart. ANF release was measured by radioimmunoassay. When the coronary flow rate was changed, ANF release decreased or increased in a flow-dependent manner. When the perfusion pressure was changed, ANF release also increased or decreased, respectively, with concomitant changes in coronary flow rate. Furthermore, perfusion with 50 mM potassium chloride showed immediate cardiac arrest and a decrease of ANF release to an undetectable level with a significant decrease in coronary flow. However, low but readily detectable amounts of ANF were released when coronary flow rate was maintained. These results may suggest that coronary hemodynamics and cardiac beating could be factors modulating ANF secretion from the atrium.     

Ultrastructure and Atrial Natriuretic Peptide(ANP)-like Immunoreactivity of Cardiocytes in the Larval, Metamorphosing and Adult Specimens of the Japanese Toad, Bufo japonicus formosus

The distribution of an atrial natriuretic peptide (ANP)-like material in the cardiocytes of larval, metamorphosing, and adult specimens (both breeding and non-breeding) of the toad, Bufo japonicus formosus , was studied immunohistochemically, ultrastructurally and immunocytochemically. Histochemically, ANP-immunoreaction was positive in the atrium and ventricle in stage 33 larvae, while negative in the ventricle in stage 40 larvae. In adult toads, the reaction was stronger in the right than in the left atrium but quite weak in the ventricles, particularly those of non-breeding specimens. Electron microscopy indicated a very small number of secretory granules in the atrial and ventricular cardiocytes of embryos as early as the limb-bud stage (stage 28), and as development proceeded, the number of these granules increased rapidly in atrial but not in ventricular cardiocytes. In metamorphosing animals, a small population of larger granules (200–250 nm) was noted next to those of ordinary size (the median, 110 nm) in the same cell. In adult toads, granules of about 120 nm and 200 nm in median size were found in the same cell. Postembedding immunogold staining consistently indicated ANP-immunoreactivity in these granules in atrial and ventricular cardiocytes. The plasma content of immunoreactive ANP was considerably higher in breeding (20.5 ± 5.9 pg/ml) than in non-breeding toads (5.4 ± 1.7 pg/ml). These results are discussed in relation to presently available data on the physiological role of ANP.     

Dominant induction of vaccine antigen-specific cytotoxic T lymphocyte responses after simian immunodeficiency virus challenge

Cytotoxic T lymphocyte (CTL) responses are crucial for the control of human and simian immunodeficiency virus (HIV and SIV) replication. A promising AIDS vaccine strategy is to induce CTL memory resulting in more effective CTL responses post-viral exposure compared to those in natural HIV infections. We previously developed a CTL-inducing vaccine and showed SIV control in some vaccinated rhesus macaques. These vaccine-based SIV controllers elicited vaccine antigen-specific CTL responses dominantly in the acute phase post-challenge. Here, we examined CTL responses post-challenge in those vaccinated animals that failed to control SIV replication. Unvaccinated rhesus macaques possessing the major histocompatibility complex class I haplotype 90-088-Ij dominantly elicited SIV non-Gag antigen-specific CTL responses after SIV challenge, while those induced with Gag-specific CTL memory by prophylactic vaccination failed to control SIV replication with dominant Gag-specific CTL responses in the acute phase, indicating dominant induction of vaccine antigen-specific CTL responses post-challenge even in non-controllers. Further analysis suggested that prophylactic vaccination results in dominant induction of vaccine antigen-specific CTL responses post-viral exposure but delays SIV non-vaccine antigen-specific CTL responses. These results imply a significant influence of prophylactic vaccination on CTL immunodominance post-viral exposure, providing insights into antigen design in development of a CTL-inducing AIDS vaccine.     

Habitat variables associated with encounters of Hottentot Buttonquail Turnix hottentottus during flush surveys across the Fynbos biome

The Hottentot Buttonquail Turnix hottentotus is an endangered terrestrial turnicid and is endemic to the Fynbos biome, South Africa. Due to its secretive nature and apparent rarity almost nothing is known about the species, but its range has been subject to anthropogenic modification, invasion by alien plant species and is vulnerable to climate change. To model covariates associated with the presence of Hottentot Buttonquail we undertook flush surveys across the Fynbos biome, covering 275 km. Habitat variables at encounter sites were recorded in vegetation plots, as well as locations without encounters. There was a critical number of observers needed during a flush survey in order to account for buttonquail presence, with no encounters with less than five participants. After accounting for this, we found probability of encounters decreased with increasing time-since-fire. Probability of encounters were also negatively associated with increasing percentage grass and other vegetation cover. We also found no association between percentage cover of Restionaceae plants and encounter probability, considered previously to be the best indicator of Hottentot Buttonquail presence. This information will be of use to those interested in managing habitat for this species and should inform future conservation efforts.     

Major histocompatibility complex class I-restricted cytotoxic T lymphocyte responses during primary simian immunodeficiency virus infection in Burmese rhesus macaques

Major histocompatibility complex class I (MHC-I)-restricted CD8(+) cytotoxic T lymphocyte (CTL) responses are crucial for the control of human immunodeficiency virus (HIV) and simian immunodeficiency virus (SIV) replication. In particular, Gag-specific CTL responses have been shown to exert strong suppressive pressure on HIV/SIV replication. Additionally, association of Vif-specific CTL frequencies with in vitro anti-SIV efficacy has been suggested recently. Host MHC-I genotypes could affect the immunodominance patterns of these potent CTL responses. Here, Gag- and Vif-specific CTL responses during primary SIVmac239 infection were examined in three groups of Burmese rhesus macaques, each group having a different MHC-I haplotype. The first group of four macaques, which possessed the MHC-I haplotype 90-010-Ie, did not show Gag- or Vif-specific CTL responses. However, Nef-specific CTL responses were elicited, suggesting that primary SIV infection does not induce predominant CTL responses specific for Gag/Vif epitopes restricted by 90-010-Ie-derived MHC-I molecules. In contrast, Gag- and Vif-specific CTL responses were induced in the second group of two 89-075-Iw-positive animals and the third group of two 91-010-Is-positive animals. Considering the potential of prophylactic vaccination to affect CTL immunodominance post-viral exposure, these groups of macaques would be useful for evaluation of vaccine antigen-specific CTL efficacy against SIV infection.     

Role of cholecystokinin in the intestinal phase of pancreatic circulation in dogs

The regulatory mechanisms of postprandial pancreatic hyperemia are not well characterized. The aim of this study is to clarify the role of cholecystokinin (CCK) in the intestinal phase of pancreatic circulation. Pancreatic, gastric, and intestinal blood flows were measured by ultrasound transit-time blood flowmeters in five conscious dogs. Pancreatic and gastric secretion and blood pressure were also monitored. Synthetic CCK octapeptide (CCK-8) or gastrin heptadecapeptide (gastrin-17) was infused intravenously, and milk was infused into the duodenum with or without loxiglumide, a specific CCK-A receptor antagonist. CCK-8 induced dose-related increases of pancreatic, but not gastric or intestinal, blood flow and protein secretion without affecting systemic blood pressure. Gastrin-17 did not affect pancreatic blood flow. An intraduodenal infusion of milk increased pancreatic and intestinal blood flows and pancreatic protein secretion. Loxiglumide completely inhibited pancreatic blood flow and protein responses to CCK-8 and milk but not the intestinal blood flow response. CCK is a potent and specific pancreatic vasodilator, with its effect mediated by CCK-A receptors. CCK plays an important role in the regulation of the intestinal phase of the pancreatic circulation in dogs.     

Sox9b/sox9a2-EGFP transgenic medaka reveals the morphological reorganization of the gonads and a common precursor of both the female and male supporting cells

We have established an enhanced green fluorescent protein (EGFP) transgenic medaka line that mimics the expression of sox9b/sox9a2 to analyze the morphological reorganization of the gonads and characterize the sox9b-expressing cells during gonadal formation in this fish. After the germ cells have migrated into the gonadal areas, a cluster of EGFP-expressing cells in the single gonadal primordium was found to be separated by the somatic cells along the rostrocaudal axis and form the bilateral lobes. We observed in these transgenic fish that EGFP expression persists only in the somatic cells directly surrounding the germ cells. As sex differentiation proceeds, dmrt1 and foxl2 begin to be expressed in the EGFP-expressing cells in the XY and the XX gonads, respectively. This indicates that the sox9b-expressing cells reorganize into two lobes of the gonad and then differentiate into Sertoli or granulosa cells, as common precursors of the supporting cells. Hence, our sox9b-EGFP medaka system will be useful in future studies of gonadal development.