Endocrinological studies for artificial breeding of the Japanese ibis,Nipponia nippon,an endangered avian species in Asia

Once the Japanese ibis, or the Japanese crested ibis, was widely distributed in Asia including Japan, Korea, China and Siberia, and was not a rare species. However, this species started to disappear over its entire range beginning in the late 19th or early 20th century. Currently, only a single population of 15–20 individuals survives in wild in Yang Xian, Shaanxi, China. Several individuals, mostly immature birds, are kept in captivity in Beijing zoo. One of them is an adult male captured in 1981 in Japan and sent to Beijing zoo for breeding two years ago. In Japan, only, a single old female survives in captivity. Scientists of the Japanese Ibis Preservation Center in Sado Island and Ueno zoo, Tokyo, had attempted several times to breed Japanese ibises in captivity, but they have failed in all of their attempts. In Beijing zoo, a similar attempt is now being carried out. As the basis of an artificial breeding programme of this and other species of birds, the authors have attempted to establish a noninvasive method for estimation of gonadal activities of birds and also a method to induce a complete series of the ovarian activity,i.e., ovarian growth, ovulation and oviposition, by means of hormone administration to some species of birds. In this communication, the author briefly reports recent results of these attempts in addition to results of measurements of gonadotropin levels in plasma of captive Japanese ibises and white ibises, a closely related species,Threskiornis aethiopicus.     

In vitro study on effect of bardoxolone methyl on cisplatin-induced cellular senescence in human proximal tubular cells

Molecular and Cellular Biochemistry - Bardoxolone methyl [methyl-2-cyano-3, 12-dioxooleana-1, 9(11)dien-28-oate (CDDO-Me)], an activator of the nuclear factor erythroid-derived 2-related factor2...     

Nature and site of action of endogenous nitric oxide in vasculature of isolated pig lungs

Cremona, George, Tim Higenbottam, Motoshi Takao, Edward A. Bower, and Leslie W. Hall. Nature and site of action of endogenousnitric oxide in vasculature of isolated pig lungs. J. Appl. Physiol. 82(1): 23-31, 1997.The site ofaction of endogenous and exogenous nitric oxide (NO) in isolated piglungs was investigated by using arterial, double, and venous occlusion,which allowed precapillary, postcapillary, and venous segments to bepartitioned into arterial, precapillary, postcapillary, and venoussegments. N^G-nitro-L-arginine(L-NNA;10⁵ M) increased resistancein the arterial (35 ± 6.6%, P = 0.003), precapillary (39.3 ± 5.1%,P = 0.001), and venous (18.3 ± 4.8%, P = 0.01) segments,respectively. Sodium nitroprusside(10⁵ M) and NO (80 parts/million) reversed the effects ofL-NNA. Total pulmonary vascularresistance fell with increasing flow, due to a fall in precapillaryresistance and dynamic resistance, and was significantlylower than mean total resistance.L-NNA increased the resistancesbut did not alter the pattern of the pressure-flow relationships. It isconcluded that, in isolated pig lungs, the effect of endogenous NOseems to be dependent on flow in the arterial segment and independentof flow in the precapillary segment, but variation of its release doesnot appear to be fundamental to accommodation to changes in steadyflow.

     

Persistence of plant hormone levels in rice shoots grown under microgravity conditions in space: its relationship to maintenance of shoot growth

We investigated the effects of microgravity environment on growth and plant hormone levels in dark‐grown rice shoots cultivated in artificial 1 g and microgravity conditions on the International Space Station (ISS). Growth of microgravity‐grown shoots was comparable to that of 1 g‐grown shoots. Endogenous levels of indole‐3‐acetic acid (IAA) in shoots remained constant, while those of abscisic acid (ABA), jasmonic acid (JA), cytokinins (CKs) and gibberellins (GAs) decreased during the cultivation period under both conditions. The levels of auxin, ABA, JA, CKs and GAs in rice shoots grown under microgravity conditions were comparable to those under 1 g conditions. These results suggest microgravity environment in space had minimal impact on levels of these plant hormones in rice shoots, which may be the cause of the persistence of normal growth of shoots under microgravity conditions. Concerning ethylene, the expression level of a gene for 1‐aminocyclopropane‐1‐carboxylic acid (ACC) synthase, the key enzyme in ethylene biosynthesis, was reduced under microgravity conditions, suggesting that microgravity may affect the ethylene production. Therefore, ethylene production may be responsive to alterations of the gravitational force.     

Solution NMR structure of selenium-binding protein from Methanococcus vannielii

Selenium is an important nutrient. The lack of selenium will suppress expression of various enzymes that will lead to cell abnormality and diseases. However, high concentrations of free selenium are toxic to the cell because it adversely affects numerous cell metabolic pathways. In Methanococcus vannielii, selenium transport in the cell is established by the selenium-binding protein, SeBP. SeBP sequesters selenium during transport, thus regulating the level of free selenium in the cell, and delivers it specifically to the selenophosphate synthase enzyme. In solution, SeBP is an oligomer of 8.8-kDa subunits. It is a symmetric pentamer. The solution structure of SeBP was determined by NMR spectroscopy. Each subunit of SeBP is composed of an alpha-helix on top of a 4-stranded twisted beta-sheet. The stability of the five subunits stems mainly from hydrophobic interactions and supplemented by hydrogen bond interactions. The loop containing Cys(59) has been shown to be important for selenium binding, is flexible, and adopts multiple conformations. However, the cysteine accessibility is restricted in the structure, reducing the possibility of the binding of free selenium readily. Therefore, a different selenium precursor or other factors might be needed to facilitate opening of this loop to expose Cys(59) for selenium binding.     

Cleavage of the NS2-3 protein in the cells of cattle persistently infected with non-cytopathogenic bovine viral diarrhea virus

The NS2-3 of BVDV is cleaved in cultured cells infected with cp BVDV but not in those infected with ncp BVDV when tested more than 10 hours post infection. However, it is not known whether cleavage of NS2-3 occurs in vivo. In the present study, cleavage of NS2-3 in cattle persistently infected with BVDV was investigated. All BVDV isolated from PI animals were of the ncp biotype, and NS2-3 proteins were detected in bovine fetal muscular cells infected with these viruses. On the other hand, in the leukocytes of those PI animals, NS3 proteins, products of the cleavage of NS2-3 proteins, were detected. In addition, the NS3 proteins were also detected in leukocytes artificially infected with ncp BVDV. These results reveal that the NS2-3 protein of BVDV is cleaved in leukocytes. Furthermore, NS3 proteins were detected in many tissues of PI cattle, such as lymphoid tissue, brain, thyroid, lung, and kidney. These results suggest that the NS2-3 protein of ncp BVDV cleaves in vivo.     

Distinct function of conserved amino acids in the fingers of Saccharomyces cerevisiae DNA polymerase alpha

Structural differences between class A and B DNA polymerases suggest that the motif B region, a wall of the catalytic pocket, may have evolved differentially in the two polymerase families. This study examines the function of the motif B residues in Saccharomyces cerevisiae DNA polymerase alpha (pol alpha). Effects of the mutations were determined by biochemical analysis and genetic complementation of a yeast strain carrying a temperature-sensitive pol alpha mutant. Many conserved residues were viable with a variety of substitutions. Among them, mutations at Asn-948 or Tyr-951 conferred up to 8-fold higher colony formation frequency in a URA3 forward mutation assay, and 79-fold higher trp1 reversion frequency was observed for Y951P in yeast. Purified Y951P was as accurate as wild type in DNA synthesis but approximately 6-fold less processive and 22-fold less active in vitro. Therefore, Y951P may increase the frequency of mutant colony formation because of its low level of DNA polymerase activity in yeast. Mutations at Lys-944 or Gly-952 were not viable, which is consistent with the observation that mutants with substitutions at Gly-952 have strongly reduced catalytic activity in vitro. Gly-952 may provide a space for the nascent base pair and thus may play an essential function in S. cerevisiae DNA pol alpha. These results suggest that class B DNA polymerases have a unique structure in the catalytic pocket, which is distinct from the corresponding region in class A DNA polymerases.     

Palm mutants in DNA polymerases alpha and eta alter DNA replication fidelity and translesion activity

We isolated active mutants in Saccharomyces cerevisiae DNA polymerase alpha that were associated with a defect in error discrimination. Among them, L868F DNA polymerase alpha has a spontaneous error frequency of 3 in 100 nucleotides and 570-fold lower replication fidelity than wild-type (WT) polymerase alpha. In vivo, mutant DNA polymerases confer a mutator phenotype and are synergistic with msh2 or msh6, suggesting that DNA polymerase alpha-dependent replication errors are recognized and repaired by mismatch repair. In vitro, L868F DNA polymerase alpha catalyzes efficient bypass of a cis-syn cyclobutane pyrimidine dimer, extending the 3' T 26000-fold more efficiently than the WT. Phe34 is equivalent to residue Leu868 in translesion DNA polymerase eta, and the F34L mutant of S. cerevisiae DNA polymerase eta has reduced translesion DNA synthesis activity in vitro. These data suggest that high-fidelity DNA synthesis by DNA polymerase alpha is required for genomic stability in yeast. The data also suggest that the phenylalanine and leucine residues in translesion and replicative DNA polymerases, respectively, might have played a role in the functional evolution of these enzyme classes.     

Hyper-phosphorylated retinoblastoma protein suppresses telomere elongation

Immortalized cell lines maintain telomeres by the expression of telomerase or by a mechanism designated alternative lengthening of telomeres (ALT). Although DNA polymerase alpha (pol-alpha) is reported to be required for telomere maintenance, the critical role of pol-alpha in telomere maintenance has not been firmly determined. We examined the role of retinoblastoma protein (pRb) and pol-alpha in the regulation of telomere length, using telomere-fiber FISH. Telomere length varied dependent on the intracellular abundance of pol-alpha or pRb in HeLa cells. A proportion of hyper-phosphorylated pRb (ppRb) molecules localized to sites of telomeric DNA replication in HeLa cells. Pol-alpha might thus contribute to telomere maintenance, and might be regulated by ppRb.     

Evi-1 is a critical regulator for hematopoietic stem cells and transformed leukemic cells

Evi-1 has been recognized as one of the dominant oncogenes associated with murine and human myeloid leukemia. Here, we show that hematopoietic stem cells (HSCs) in Evi-1-deficient embryos are severely reduced in number with defective proliferative and repopulating capacity. Selective ablation of Evi-1 in Tie2(+) cells mimics Evi-1 deficiency, suggesting that Evi-1 function is required in Tie2(+) hematopoietic stem/progenitors. Conditional deletion of Evi-1 in the adult hematopoietic system revealed that Evi-1-deficient bone marrow HSCs cannot maintain hematopoiesis and lose their repopulating ability. In contrast, Evi-1 is dispensable for blood cell lineage commitment. Evi-1(+/-) mice exhibit the intermediate phenotype for HSC activity, suggesting a gene dosage requirement for Evi-1. We further demonstrate that disruption of Evi-1 in transformed leukemic cells leads to significant loss of their proliferative activity both in vitro and in vivo. Thus, Evi-1 is a common and critical regulator essential for proliferation of embryonic/adult HSCs and transformed leukemic cells.