Effect of chronic stress on gastric emptying and plasma ghrelin levels in rats

Chronic stress is associated with gastrointestinal functional diseases. Although the pathophysiology seems to be associated with gastrointestinal motility, their mechanisms remain unclear. We investigated gastric emptying and chemical mediators under conditions of continuous stress, which were produced using 8-week-old male Wistar rats kept in a cage filled with water to 2 cm height for 5 days. We examined gastric emptying by the phenol red method and chemical mediators at 4, 8, and 24 h and 3 and 5 days after initiation of stress restraint. Plasma ACTH level was significantly higher in the stress throughout the period of measurement. Continuous stress delayed gastric emptying until 24 h: peak delay was observed at 8 h, whereas gastric emptying was accelerated on days 3 and 5. Plasma noradrenalin level was significantly elevated at every time point until 24 h. Guanethidine pretreatment eliminated the delay in gastric emptying at 8 h. Active ghrelin was significantly increased on days 3 and 5 after peak (at 24 h) plasma total and desacyl ghrelin in the stress group. Number of ghrelin-immunoreactive cells and level of preproghrelin mRNA expression in the gastric body increased in parallel with plasma active ghrelin level. Pretreatment with growth hormone secretagogue receptor antagonist at 5 days partially inhibited the stress-induced acceleration of gastric emptying. Delayed gastric emptying at acute phase of continuous stress was mediated via sympathetic pathway, while acceleration at chronic phase was mediated via increased active ghrelin release from the stomach.     

Performance of polyethylene tubes as pheromone lures for the sorghum plant bug, Stenotus rubrovittatus (Hemiptera: Heteroptera: Miridae)

The sorghum plant bug, Stenotus rubrovittatus (Matsumura) (Hemiptera: Heteroptera: Miridae), is a pest that infests rice in many regions of Japan. Three sex attractant pheromone components—hexyl butyrate, (E)-2-hexenyl butyrate, and (E)-4-oxo-2-hexenal—were identified in S. rubrovittatus. Because the longevity of a synthetic rubber septum dispenser is not sufficient for it to be an effective S. rubrovittatus pheromone lure, the performances of an alternative pheromone dispenser—a polyethylene tube—was examined. Hexyl butyrate and (E)-2-hexenyl butyrate are essential components of S. rubrovittatus male attraction, and the application of (E)-4-oxo-2-hexenal strongly enhanced the attractiveness of such “tube-type” lures. A 5:1:10 blend of hexyl butyrate, (E)-2-hexenyl butyrate, and (E)-4-oxo-2-hexenal was found to be the best blend ratio for male attraction in the tube-type lures. Tube-type lures attracted more males than rubber lures. Furthermore, the attractiveness of the tube-type lures was maintained for more than 28 days in the field. These results suggest that tube-type lures made of polyethylene plastic are suitable for monitoring S. rubrovittatus in fields.     

ASC, a novel 22-kDa protein, aggregates during apoptosis of human promyelocytic leukemia HL-60 cells

The cytoskeletal and/or nuclear matrix molecules responsible for morphological changes associated with apoptosis were identified using monoclonal antibodies (mAbs). We developed mAbs against Triton X-100-insoluble components of HL-60 cells pretreated with all-trans retinoic acid. In particular, one mAb recognized a 22-kDa protein that exhibited intriguing behavior by forming an aggregate and appearing as a speck during apoptosis induced by retinoic acid and other anti-tumor drugs. Cloning and sequencing of its cDNA revealed that this protein comprises 195 amino acids and that its C-terminal half has a caspase recruitment domain (CARD) motif, characteristic of numerous proteins involved in apoptotic signaling. We referred to this protein as ASC (apoptosis-associated speck-like protein containing a CARD). The ASC gene was mapped on chromosome 16p11.2-12. The antisense oligonucleotides of ASC were found to reduce the expression of ASC, and consequently, etoposide-mediated apoptosis of HL-60 cells was suppressed. Our results indicate that ASC is a novel member of the CARD-containing adaptor protein family.     

Unique mutations in mitochondrial DNA of senescence-accelerated mouse (SAM) strains

Mitochondrial DNA (mtDNA) is exclusively inherited maternally and hence could offer a good method for tracing the lineage of mouse strains. We examined the mtDNA sequence of senescence-accelerated mouse (SAM) strains as well as other laboratory strains of inbred mice to deduce the ancestral strain of SAM. Four unique mutations were identified at bases 2256, 10,847, 11,181, and 13,053 in SAM strains. The mutations were not found in other mouse strains including AKR/J, one of the parental strains of SAM. Comparison of the mtDNA sequences also led to the consensus mtDNA sequence of laboratory strains of inbred mice. The seven laboratory strains of common inbred mice showed polymorphisms at base 9348, thymine repeat from base 9818, and adenine repeat from base 9821, and could be classified into five types by combination of the differences. Although we could not identify mouse strains with the same type of mtDNA as SAM in this study, the polymorphisms would provide a promising clue to ascertain the ancestral strain(s) of SAM. The polymorphism in mtDNA could be used to ascertain the genealogy of other mouse strains as well.     

Dexamethasone increases both catecholamines and methionine-enkephalin in cultured bovine adrenal chromaffin cells and human extramedullary pheochromocytoma cells

The effect of dexamethasone on dispersed cells in primary monolayer culture from bovine adrenal medulla and human extramedullary pheochromocytoma was examined by estimating the level of catecholamines (CAs) and Methionine-enkephalin (Met-enk) in the medium and cells. In cultured bovine adrenal chromaffin cells, dexamethasone caused significant increase in Met-enk levels 18 hours after administration. There was no release of Met-enk and CAs in the medium 10 min after administration, although nicotine did cause a significant release of Met-enk and CAs. A dose response increase in the level of CAs and Met-enk in bovine adrenal chromaffin cells was obtained with doses varying between 0 and 10(-6)M dexamethasone 18 hours after administration. In cultured human extramedullary pheochromocytoma cells, dexamethasone significantly increased the levels of norepinephrine and Met-enk in a dose dependent manner 24 hours after administration. These results suggest that dexamethasone does not act as a secretagogue but may be related to the synthesis of Met-enk and CAs.     

Molecular nature of methicillin-resistant Staphylococcus aureus derived from explosive nosocomial outbreaks of the 1980s in Japan

Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) with Panton-Valentine leukocidin (PVL) genes is increasing worldwide. Nosocomial outbreak-derived (hospital-acquired) MRSA (HA-MRSA) in Japan in the 1980s was also largely PVL(+). PVL(+) HA-MRSA and CA-MRSA shared the same multi-locus sequence type (ST30) and methicillin resistance cassette (SCCmecIV), but were divergent in oxacillin resistance, spa typing, PFGE analysis or clfA gene analysis. PVL(+) HA-MRSA, which probably originated in PVL(+)S. aureus ST30, was highly adhesive (carrying cna and bbp genes), highly-toxic (carrying luk(PV) and sea genes) and highly drug-resistant. PVL(+) HA-MRSA was once replaced by other PVL(-) HA-MRSA (e.g., ST5), and is re-emerging as CA-MRSA.     

Evolution and genetic structure of the great tit (Parus major) complex

The great tit complex is divided into four groups, each containing several subspecies. Even though the groups are known to differ markedly on morphological, vocal and behavioural characters, some hybridization occurs in the regions where they meet. The great tit has often been referred to as an example of a ring species, although this has later been questioned. Here, we have studied the genetic structure and phylogenetic relationships of the subspecies groups to clarify the evolutionary history of the complex using control region sequences of the mitochondrial DNA. The subspecies groups were found to be monophyletic and clearly distinct in mitochondrial haplotypes, and therefore must have had long-independent evolutionary histories. This conflicts with the ring species assignment and supports the formation of secondary contact zones of previously temporarily isolated groups. According to the phylogenetic species concept, all the subspecies groups could be considered as separate species, but if the definition of the biological species concept is followed, none of the subspecies groups is a true species because hybridization still occurs.     

Neuron-specific expression of a chicken gicerin cDNA in transient transgenic zebrafish

Gicerin, a novel cell adhesion molecule which belongs to the immunoglobulin superfamily, is expressed temporally and spatially in the developing chick brain and retina. The previous in vitro experiments using transfected cells showed that gicerin can function as a cell adhesion molecule which has both homophilic and heterophilic binding activities. For the in vivo analyses of gicerin in neural development, we tried to utilize a zebrafish system, a vertebrate suitable for studying early development. We generated transient transgenic animals by microinjecting DNA constructs into zebrafish embryos. Chicken gicerin, under control of the neurofilament gene promoter, was preferentially expressed in neuronal cells and gicerin-expressing neurons exibited a fasciculation formation with neighboring gicerin-positive axons, which may be partly due to homophilic cell adhesion activity of gicerin. These experimental results suggest that this fast and efficient transgenic animal system is useful for studying the functional roles of neuron-specific genes during the development. Special issue dedicated to Dr. Kinya Kuriyama.