Meiofaunal responses to nutrient additions in a Mediterranean stream

1. The effects of a moderate addition of nutrients (twofold N and threefold P) were examined during a 2‐year period to determine the response to nutrient addition in a meiofaunal community inhabiting sandy patches in a Mediterranean stream. 2. The pattern of meiofaunal assemblages exhibits a high degree of intra‐ and interannual variability. This pattern alternates between periods of hydrological stability and disturbances, such as floods and droughts, which is a characteristic of Mediterranean systems. 3. A before–after–control–impact (BACI) design was used to determine the outcome of the addition by comparing an upstream non‐enriched reach with an enriched downstream reach. Analysis of the study data by means of a nonparametric permutational procedure (permanova ) showed that fertilisation had a significant effect. Density and biomass values increased in the most abundant meiofaunal groups, including microcrustaceans, oligochaetes and chironomids. Microcrustaceans were the dominant group in the permanent meiofauna. 4. We also examined differences in microcrustacean secondary production in both reaches. Ostracods and cyclopoid copepods increased their secondary production in the impacted reach as a result of the nutrient addition. 5. Our study demonstrated that moderate nutrient enrichment can affect the biomass and production of stream meiofauna, but it is still unclear whether this effect was because of autotrophic or heterotrophic pathways.     

The Ordovician-Silurian boundary stratotype: consequences of its approval by the IUGS

Lespérance, Pierre J., Barnes, Christopher R., Berry, William B. N., Boucot, Arthur J. & Mu En-zhi 1987 07 15: The Ordovician-Silurian boundary stratotype: consequences of its approval by the IUGS.
The Ordovician-Silurian stratotype at Dob's Linn, Scotland is the second systemic boundary approved by the International Union of Geological Sciences (IUGS). A review of the internationally accepted criteria required of a stratotype shows that few of these are possessed by the Dob's Linn section. The strongest attribute of the section is the presence of zonal graptolites, although the boundary is recognized primarily on a single biological event (base of acuminatus Zone) for which the evolutionary relationships of the taxa are not established. In approving this boundary proposal in 1985, which received only simple majority support within the Ordovician-Silurian Boundary Working Group (OSBWG) and which fails to meet most of the accepted prerequisites for a stratotype, the International Commission on Stratigraphy (ICS) and the IUGS have established an unfortunate precedent. It follows that future systemic boundaries need not meet the accepted standards. It raises serious questions on the assessment and voting procedures of the International Commission on Stratigraphy and on the credence accorded the recommendations developed by the International Subcommission on Stratigraphic Classification of IUGS.     

cDNA-directed expression of rat testosterone 7 alpha-hydroxylase using the modified vaccinia virus, T7-RNA-polymerase system and evidence for 6 alpha-hydroxylation and delta 6-testosterone formation

The modified vaccinia virus, T7-RNA-polymerase cDNA-expression system was used to express rat cytochrome P-450a. Various parameters such as host-cell type and density, and duration of infection were tested to optimize the level of expression of cytochrome P-450a enzyme activity. Cytochrome P-450a expressed from the cDNA sequence was exclusively incorporated into the membrane-containing portions of the cell lysates, as expected from its normal association in the liver endoplasmic reticulum. The enzyme displayed a carbon-monoxide-reduced-cytochrome-P-450a difference spectrum with a Soret maximum of 450 nm. Activity measurements revealed that cytochrome P-450a produced three metabolites of testosterone; 7 alpha-hydroxytestosterone and 6 alpha-hydroxytestosterone and delta 6-testosterone at a ratio of about 38:1:1. Under the appropriate conditions, the vaccinia-virus, T7-RNA-polymerase system produces high levels of a single form of cytochrome P-450 in cells that are virtually devoid of endogenous cytochrome P-450. Analysis of the cytochrome P-450 in its natural membrane-bound state, as opposed to artificial-lipid reconstitution studies of purified enzymes, allows accurate and confident measurements of substrate specificities.     

Radiation-induced cardiomyopathy in the dog

Sequential necropsies and histologic evaluations of young adult beagle dogs were performed after irradiation of the thorax. Total doses to the heart were 36, 44, or 52 Gy given in 4-Gy fractions in 4 weeks. One month after irradiation there was little histologic evidence of damage visible by light microscopy. However, ventricular and septal weights were increased, probably due to edema. At 3 months damage to endothelial and mesothelial cells was evident. By 12 months the myocardium was thinned and focal degeneration and loss of muscle cells and Purkinje fibers were observed. There was extensive subendocardial and epicardial fibrosis as well as intimal proliferation in coronary arteries. Morphometric analyses were performed on the myocardium, pericardium, atria, and aorta. There was a slight increase in perivascular connective tissue in the myocardium. The pericardium was increased in thickness and the ratio of smooth muscle to elastin was decreased in the aorta. Severe fibrosis occurred only in the right atrium. At 1 year there was no clinical evidence of heart failure; however, evidence of myocardial damage was present histologically and functionally. Additional stress and continued aging are likely to enhance the damage and lead to serious complications. The interactions of irradiated lung and heart require further investigation.     

MSI2通过下调circRNA_001214促进急性髓系白血病细胞HL60生长

Musashi-2（MSI2）是一种RNA结合蛋白质,对维持造血干细胞功能具有重要作用。研究表明,MSI2高表达能促进急性髓系白血病（acute myelocytic leukemia, AML）进展,但其作用机制尚不明确。本研究稳定沉默HL60细胞MSI2后,第1、2、3、4 d对照组的相对细胞生长率分别为1.931 ± 0.027、3.070 ± 0.073、4.017 ± 0.092和4.215 ± 0.246;敲减组分别为1.927 ± 0.035、2.564 ± 0.090、2.825 ± 0.097和3.223 ± 0.182,两组相比具有统计学差异,P<0.001;细胞凋亡明显增加(7.967% ± 0.698% vs 3.400% ± 0.322%., P<0.01);G₀/G₁期细胞比例明显增高（67.430% ± 4.390% vs. 50.360% ± 2.160%, P<0.01）;NUMB蛋白明显上调,LEF1明显下降。环状RNA（circular RNA, circRNA）芯片筛选和荧光定量PCR验证显示,MSI2沉默组circRNA_001214表达水平是对照组3.48倍。这一结果也在NALM6细胞得到证实。进一步用生物信息学分析,显示circRNA_001214最可能与miR-1273a、miR-1273e和miR 5095结合,进而影响参与细胞凋亡相关基因（CYCS、AKT1、BAX、TNFRSF10A、TNFRSF10D）、Wnt信号基因（WNT4、WNT2B、WNT7B、 DKK2、SFRP1、CSNKE1和LEF1）以及参与细胞代谢相关基因（RPE, PGAM4, PGAM1, TAT, CBS、RPE、SUCLG2、PGAM4、PGAM1和 IDNK）。总而言之,MSI2可能通过干扰circRNA_001214生成,减少靶miRNA对凋亡、Wnt信号及细胞代谢相关基因表达的影响,促进细胞生长。     

Changes in certain kinetic properties of hepatic microsomal aniline hydroxylase and ethylmorphine demethylase associated with postnatal development and maturation in male rats

1. Changes in certain kinetic properties (V(max.) and apparent K(m)) of hepatic microsomal mixed-function oxidases have been studied as a function of postnatal development and maturation in male rats. 2. Microsomal cytochrome P-450 content changed only slightly between 1 and 12 weeks of age. 3. Aniline hydroxylase activity (V(max.)) increased abruptly between 1 and 2 weeks of age to greater than adult activities and then returned to a plateau value between 4(1/2) and 12 weeks of age. Ethylmorphine demethylase activity remained low and relatively constant between 1 and 3 weeks of age and then increased markedly ( approximately 100%) between 3 and 4(1/2) weeks. 4. The apparent Michaelis constant (K(m)) for aniline hydroxylation increased almost linearly with time between 1 and 6 weeks of age and tended to reach a plateau value thereafter. The apparent K(m) for ethylmorphine demethylation increased between 1 and 3 weeks of age and then decreased abruptly to a constant value between 6 and 12 weeks. 5. The data indicate that developmental changes in the activity of these microsomal oxidases do not correlate temporally with each other or with changes in microsomal cytochrome P-450 content. 6. The most dramatic changes in enzyme activity were associated with early development (1-3 weeks) and weaning (3-4 weeks). 7. Changes in weight of seminal vesicle, a criterion of sexual maturation in male rats, were most prominent between 6 and 8 weeks of age and thus appeared to be separated in time from the prominent changes in enzyme activity.     

Sequence requirements for cytochrome P-450IIB1 catalytic activity. Alteration of the stereospecificity and regioselectivity of steroid hydroxylation by a simultaneous change of two hydrophobic amino acid residues to phenylalanine

The phenobarbital-inducible P-450 forms IIB1 and IIB2 are identical in sequence except for 14 amino acid differences within the carboxyl-terminal half of the molecule. IIB1 has about a 5-10-fold higher turnover number for most monooxygenase substrates examined although the substrate specificities of both enzymes are virtually identical. Both P-450s oxygenate testosterone to yield the 16 alpha-hydroxy, 16 beta-hydroxy, 17-keto, and 16 beta-hydroxy, 17-keto metabolites as major products. A variant IIB2 cDNA, isolated from an uninduced rat liver lambda gt11 library, and when expressed in Hep G2 cells using a vaccinia virus vector, was found to code for a protein that produced the 16 alpha-hydroxy and 17-keto metabolites of testosterone but no 16 beta-hydroxylated products. Although the published sequences of IIB1 and IIB2 are identical within the N-terminal halves of the proteins, sequence analysis of the variant cDNA revealed two amino acid substitutions in this region; Leu58----Phe and I1e114----Phe. When these two amino acid changes were incorporated into IIB1, via construction of a chimeric cDNA, the resultant expressed enzyme did not catalyze the 16 beta-hydroxylation of testosterone or androstenedione. Formation of the 16 alpha-hydroxy and 17-keto metabolites, however, was only slightly reduced compared with the parent IIB1. A IIB1 protein that possessed only the I1e114----Phe replacement catalyzed the production of all four testosterone metabolites with only slightly different product ratios compared with the parent enzyme. The substrate specificity of a IIB1 variant containing only the Leu58----Phe replacement could not be determined, since that protein did not accumulate in cells infected with the corresponding recombinant vaccinia virus. These data suggest that two distinct amino acid residues located within the amino-terminal fourth of IIB1 and IIB2 can affect substrate orientation at the active site.     

Coordinated mRNA and Protein Expression of Human LAMP-1 in Induction of Melanogenesis After UV-B Exposure and Co-Transfection of Human Tyrosinase and TRP-1 cDNAs

In order to better understand the cascade of melanogenic events in melanocytes, this report has introduced our two recent approaches for the expression of melanogenesis/or melanosome-associated genes and encoded proteins in melanocytes (melanoma cells) after repeated exposure to UV -B and after cotransfection of two human genes, i.e., tyrosinase and tyrosinase-related protein-1 (TRP-1). Repeated exposure of UV B (2.5–5.0 mJ/cm²) caused not only upregulation of tyrosinase and TRP-1 genes but also coordinated increase in the gene and protein synthesis expression of Lamp-1 (lysosome-associated membrane protein-1). When COS-7 kidney cells and amelanotic melanoma (C32 and SKMEL-24) and melanotic melanoma (G361 and SK-MEL-23) cells were exposed to cotransfection of human tyrosinase and TRP-1 cDNAs, there was also an increased expression of Lamp-1 mRNA and protein along with tyrosinase activation and new melanin synthesis. Importantly, single transfectants of human tyrosinase cDNA revealed marked cellular degeneration, whereas this degeneration was not seen in single transfectants of TRP-1 cDNA or cotransfectants of human tyrosinase and TRP-1 cDNAs, indicating that TRP-1 prevented, along with Lamp-1, programmed death of melanocytes after transfection of tyrosinase gene. The coordinated expression of TRP-1 and Lamp-1 was further confirmed by antisense oligodeoxynucleotide hybridization experiment against Lamp-1 gene, showing the decreased expression of TRP-1 as identified by three different types of anti-TRP-1 monoclonal antibodies. We propose therefore that human tyrosinase and TRP-l, when activated or expressed together, will coordinate to upregulate the mRNA expression and protein synthesis of Lamp-1. The Lamp-1 molecules will, in turn, cover the inner surface of melanosomal membrane, together with TRP-1 molecules, thus protecting the melanosomal membrane from toxic melanin intermediates generated during melanogenesis in the presence of active tyrosinase. In contrast, the expression of other lysosome-related proteins, e.g., β-galactosidase and CD63 is not stimulated in new melanogenesis.     

西藏色季拉山暗针叶林苔藓多样性及林窗干扰的影响

为了解西藏色季拉山暗针叶林苔藓多样性及林窗干扰的影响,在过去工作积累的基础上研究了色季拉山西坡5块样地内不同林内环境(林窗、林缘和林下)地面、腐木和树附生苔藓生物量特征。结果表明, 地面生单位面积苔藓植物生物量储量最高,平均910.10 g/m²,其次为腐木生(221.90 g/m²),树附生的最低(53.59 g/m²)。林窗地面生苔藓单位面积生物量最高,均值为360.47 g/m²,其次为林下(305.51 g/m²),最小为林缘(244.11 g/m²);林窗、林缘和林下间的地面生苔藓单位面积生物量差异显著(P＜0.05)。沿海拔梯度,林窗苔藓单位面积生物量表现出先增加后减少的趋势。因此,在西藏色季拉山暗针叶林内,林窗对地面生苔藓单位面积生物量有显著影响。