Relationship Between Male Size and Newborn Size in the Seaweed Pipefish, Syngnathus Schlegeli

Relationships between male size, number, and weight of newborn were determined in the seaweed pipefish, Syngnathus schlegeli, with paternal care of embryos in the brood pouch. While the number of newborn increased linearly with the increase in male size, the pouch volume increased exponentially with the male size. This resulted in embryo density in the pouch negatively correlating with the male size. Newborn dry weight was negatively correlated with the embryo density in the pouch. Thus, larger males were considered to brood embryos at lower densities and give birth to heavier newborn. Neither paternal size nor embryo density seemed to have an effect upon developmental stage and total length of the newborn. Substantial weight loss of embryos during incubation indicated that paternal nutritional contribution to embryos is insignificant; therefore, the tendency of larger males to produce heavier newborn may not relate to allocation of paternal nourishment. Because egg weight increased with the female size, larger males are considered to receive the eggs of larger females and give birth to heavier newborn that developed from heavier eggs. Lower embryo density in larger males is attributable to the larger size of the heavier eggs. Assuming the pouch to be a cylindrical tube and the egg to be a sphere, geometrical calculations revealed that the relationship between the volumetric fraction of the pouch used by eggs (i.e. functional volume) and the male size was negatively quadric and had a peak. Increase in egg diameter increased the male size at which the functional volume of the pouch is maximized. Thus it appears that the size relationship of mates in pipefish is related to effective use of the pouch space.     

Pathology of the adult central nervous system induced by genetic inhibition of programmed cell death in Drosophila pupae

In the spinster (spin) mutant of Drosophila melanogaster, the extent of programmed cell death (PCD) in the abdominal ganglion 6 h after puparium formation (APF) is significantly reduced. The shortening of the abdominal ganglion, which is normally completed 48 h APF, does not occur. After eclosion, neurodegeneration accompanied by accumulation of autofluorescent materials is manifested in the central nervous system (CNS) of the spin mutant. The materials accumulated in the spin-mutant CNS contain a substance that is immunopositive to an antibody against GM2 ganglioside. Halving the dosage of three cell death genes, rpr, grim, and hid, blocks shortening of the abdominal ganglion and induces neurodegeneration accompanied by accumulation of autofluorescent materials in the adult CNS. These observations suggest that the primary action of the spin mutation is to reduce the extent of PCD 6 h APF, which concomitantly leads to a failure in shortening of the abdominal ganglion and to neurodegeneration of the adult CNS. Arch.     

A comparative study on the hydroperoxide and thiol specificity of the glutathione peroxidase family and selenoprotein P

Glutathione peroxidase catalyzes the reduction of hydrogen peroxide and organic hydroperoxide by glutathione and functions in the protection of cells against oxidative damage. Glutathione peroxidase exists in several forms that differ in their primary structure and localization. We have also shown that selenoprotein P exhibits a glutathione peroxidase-like activity (Saito, Y., Hayashi, T., Tanaka, A., Watanabe, Y., Suzuki, M., Saito, E., and Takahashi, K. (1999) J. Biol. Chem. 274, 2866-2871). To understand the physiological significance of the diversity among these enzymes, a comparative study on the peroxide substrate specificity of three types of ubiquitous glutathione peroxidase (cellular glutathione peroxidase, phospholipid hydroperoxide glutathione peroxidase, and extracellular glutathione peroxidase) and of selenoprotein P purified from human origins was done. The specific activities and kinetic parameters against two hydroperoxides (hydrogen peroxide and phosphatidylcholine hydroperoxide) were determined. We next examined the thiol specificity and found that thioredoxin is the preferred electron donor for selenoprotein P. These four enzymes exhibit different peroxide and thiol specificities and collaborate to protect biological molecules from oxidative stress both inside and outside the cells.     

Proteases involved in long-term potentiation

Much attention has been paid to proteases involved in long-term potentiation (LTP). Calpains, Ca-dependent cysteine proteases, have first been demonstrated to be the mediator of LTP by the proteolytic cleavage of fodrin, which allows glutamate receptors located deep in the postsynaptic membrane to move to the surface. It is now generally considered that calpain activation is necessary for LTP formation in the cleavage of substrates such as protein kinase Czeta, NMDA receptors, and the glutamate receptor-interacting protein. Recent studies have shown that serine proteases such as tissue-type plasminogen activator (tPA), thrombin, and neuropsin are involved in LTP. tPA contributes to LTP by both receptor-mediated activation of cAMP-dependent protein kinase and the cleavage of NMDA receptors. Thrombin induces a proteolytic activation of PAR-1, resulting in activation of protein kinase C, which reduces the voltage-dependent Mg2+ blockade of NMDA receptor-channels. On the other hand, neuropsin may act as a regulatory molecule in LTP via its proteolytic degradation of extracellular matrix protein such as fibronectin. In addition to such neuronal proteases, proteases secreted from microglia such as tPA may also contribute to LTP. The enzymatic activity of each protease is strictly regulated by endogenous inhibitors and other factors in the brain. Once activated, proteases can irreversibly cleave peptide bonds. After cleavage, some substrates are inactivated and others are activated to gain new functions. Therefore, the issue to identify substrates for each protease is very important to understand the molecular basis of LTP.     

The phosphatidylinositol 3-kinase (PI3K)-Akt pathway suppresses Bax translocation to mitochondria

Bax, a proapoptotic member of the Bcl-2 family, localizes largely in the cytoplasm but redistributes to mitochondria in response to apoptotic stimuli, where it induces cytochrome c release. In this study, we show that the phosphatidylinositol 3-OH kinase (PI3K)-Akt pathway plays an important role in the regulation of Bax subcellular localization. We found that LY294002, a PI3K inhibitor, blocked the effects of serum to prevent Bax translocation to mitochondria and that expression of an active form of PI3K suppressed staurosporine-induced Bax translocation, suggesting that PI3K activity is essential for retaining Bax in the cytoplasm. In contrast, both U0126, a MEK inhibitor, and active MEK had little effect on Bax localization. In respect to downstream effectors of PI3K, we found that expression of active Akt, but not serum and glucocorticoid-induced protein kinase (SGK), suppressed staurosporine-induced translocation of Bax, whereas dominant negative Akt moderately promoted Bax translocation. Expression of Akt did not alter the levels of Bax, Bcl-2, Bcl-X(L), or phosphorylated JNK under the conditions used, suggesting that there were alternative mechanisms for Akt in the suppression of Bax translocation. Collectively, these results suggest that the PI3K-Akt pathway inhibits Bax translocation from cytoplasm to mitochondria and have revealed a novel mechanism by which the PI3K-Akt pathway promotes survival.     

Changes in N-acetyl-beta-D-glucosaminidase activity in the urine and urinary albumin excretion in magnesium deficient rats

To discover the details of the effects of magnesium (Mg) deficiency on kidney function, the course of changes in N-acetyl-beta-D-glucosaminidase (NAG) activity in the urine and in urinary albumin excretion were examined in rats fed a Mg-deficient diet. NAG activity in the urine and urinary albumin excretion in rats fed the Mg-deficient diet significantly increased from 7 d until the end of the feeding period. We suggest that Mg-deficient diet rapidly induces kidney function insufficiency.     

Surgical stress during operation for gastrointestinal cancer increases plasma thioredoxin levels and decreases mitochondrial membrane potential in peripheral blood lymphocytes

Surgical stress is difficult to evaluate quantitatively. It has been reported that mitochondrial membrane potential (delta psi(m)) in the peripheral blood lymphocytes (PBLs) is decreased by surgical stress. Thioredoxin (TRX), a small protein with redox-active dithiol/disulfide in the active site, is induced by a variety of oxidative stresses and secreted from the cells. Accumulating evidence shows that plasma levels of TRX are elevated in oxidative stress-associated disorders. In the present study, we examined plasma levels of TRX in cases undergoing operations for gastrointestinal cancer. Plasma levels of TRX were significantly elevated on the first postoperative day compared with the pre-operative levels. The changes in the plasma TRX levels tended to show an inverse relationship with the changes in delta psi(m) in PBLs, which shows a significant decrease caused by surgical stress. Plasma TRX levels as well as delta psi(m) in PBLs are valuable markers to evaluate surgical stress.     

Gene expression profile analysis of the mouse liver during bacteria-induced fulminant hepatitis by a cDNA microarray system

Fulminant hepatic failure (FHF) is a disease characterized by sudden and severe impairment of liver function. To elucidate the mechanism involved in FHF, we adopted a murine model of FHF by administrating mice with heat-killed Propionibacterium acnes (P. acnes), followed by a low dose of lipopolysaccharide (LPS), and analyzed the dynamic change of gene expression profile of the murine liver using an in-house cDNA microarray system which contained most of the cDNAs encoding chemokines/cytokines and their receptors (33 chemokines/21 chemokine receptors, 28 cytokines/35 cytokine receptors) as well as 230 liver related proteins mostly selected by serial analysis of gene expression (SAGE). Among them, 335 genes were found to differ by more than 2-fold in at least one time point comparing with normal liver. Hierarchical cluster analysis revealed that except for a few genes, such as heme oxygenase (HO)-1 and nicotinamide N-methyltransferase (NNMT) of which expression increased, the expression of most of the genes encoding drug metabolizing enzymes decreased with the progress of the disease. The expression of the genes encoding chemokines/cytokines was dramatically changed, such as Mig, IP-10, RANTES, TNF-alpha, and IFN-gamma. In addition, the expression of those that were not previously linked to this murine model was also identified to be changed. These include endogenous IL-18 binding protein (IL-18BP), CXCL16 (the ligand of Bonzo, CXCR6) as well as ESTs. Taken together this study has shown the systemic and comprehensive gene expression profile during FHF and may contribute to better understanding of the mechanism of FHF.     

Arg tyrosine kinase is involved in homologous recombinational DNA repair

c-Abl plays important roles in cellular response to DNA damage. However, possible roles for Arg (Abl-related gene) in DNA damage response are unknown. Here, we show that ionizing radiation (IR)-induced Rad51 focus formation is reduced in Arg-deficient cells generated from a chicken B cell line by targeted disruption. This is consistent with the findings that Arg-deficient cells display hypersensitivity to IR, elevated frequencies of IR-induced chromosomal aberrations, and reduced targeted integration frequencies. All of these abnormalities in DNA damage repair are also observed in ATM-deficient cells but not in c-Abl-deficient cells. Finally, we show that Arg interacts with and phosphorylates Rad51 in 293T cells. These results suggest that Arg plays a role in homologous recombinational (HR) DNA repair by phosphorylating Rad51.