Estimated copepod production rate and structure of mesozooplankton communities in the coastal Barents Sea during summer–autumn 2007

The southern Barents Sea is considered to be the most productive area in the Arctic Ocean; however, there are no assessments of daily production rates in the coastal waters. During the summer and autumn of 2007, we investigated the variation of mesozooplankton community structure relative to environmental conditions at 12 coastal stations. Copepods dominated the total zooplankton biomass and abundance during both periods. Diversity indices and the total biomass of zooplankton communities differed significantly between the two seasons. Cluster analyses revealed two distinct groups of stations which were associated with Ura Bay and the adjacent open sea, respectively. Daily production rates of the copepod species examined were calculated using three methods based on: (1) a temperature-dependent equation and (2) two multiple regressions that consider temperature, body weight, and chlorophyll a concentration. Significant seasonal differences for daily production rates were found using all three model equations (p?<?0.05): 358?±?188–1,775?±?791 versus 198?±?85–1,584?±?559?μg?dry?mass?m^?3?day^?1. Results of principal components analyses demonstrated that the abundance and biomass of herbivorous species were related to variation in chlorophyll a concentration while the abundance and biomass of other species (omnivorous copepods and Ctenophora) were related mainly with water temperature and salinity. Mesozooplankton biomass was higher during this study relative to previous studies. Computed copepod production rates were higher compared with other Arctic seas confirming a high productive potential of the coastal southern Barents Sea.     

Interaction of ACTH synthetic fragments with rat adrenal cortex membranes.

Synthetic peptide, corresponding to the amino acid sequence 11-24 of human adrenocorticotropic hormone (ACTH), was labeled with tritium (specific activity of 22 Ci/mmol). [(3)H]ACTH (11-24) was found to bind to rat adrenal cortex membranes with high affinity and specificity (K(d) = 1.8 +/- 0.1 nM). Twenty nine fragments of ACTH (11-24) have been synthesized and their ability to inhibit the specific binding of [(3)H]ACTH (11-24) to adrenocortical membranes has been investigated. Unlabeled fragment ACTH 15-18 (KKRR) was found to replace in a concentration-dependent manner [(3)H]ACTH (11-24) in the receptor-ligand complex (K(i) = 2.3 +/- 0.2 nM). ACTH (15-18) was labeled with tritium (specific activity of 20 Ci/mmol). [(3)H]ACTH (15-18) was found to bind to rat adrenal cortex membranes with high affinity (K(d) = 2.1 +/- 0.1 nM). The specific binding of [(3)H]ACTH (15-18) was inhibited by unlabeled ACTH (11-24) (K(i) = 2.2 +/- 0.1 nM). ACTH (15-18) at the concentration range of 1-1000 nM did not affect the adenylate cyclase activity in adrenocortical membranes.     

Flow Cytometry Analysis of Neural Differentiation Markers Expression in Human Glioblastomas May Predict Their Response to Chemotherapy

Glioblastoma multiforme (GBM) represents an extremely chemoresistant tumour type. Here, authors analysed the immunophenotype of GBM tumours by flow cytometry and correlated the immunophenotypic characteristics with sensitivity to chemotherapy. The expression of selected neural and non-neural differentiation markers including A2B5, CD34, CD45, CD56, CD117, CD133, EGFR, GFAP, Her-2/neu, LIFR, nestin, NGFR, Pgp and vimentin was analysed by flow cytometry in eleven GBM (WHO gr.IV) patients. The sensitivity of tumour cells to a panel of chemotherapeutic agents was tested by the MTT assay. All tumours were positive for A2B5, CD56, nestin and vimentin. CD133, EGFR, LIFR, NGFR and Pgp were expressed only by minor tumour cell subpopulations. CD34, CD45, CD117, GFAP and Her-2/neu were constantly negative. Direct correlations were found between the immunophenotypic markers and chemosensitivity: A2B5 vs lomustine (r² = 0.642, P = 0.033), CD56 vs cisplatin (r² = 0.745, P = 0.013), %Pgp⁺ vs vincristine (r² = 0.846, P = 0.008), and %NGFR⁺ vs daunorubicine (r² = 0.672, P = 0.047) and topotecan (r² = 0.792, P = 0.011). In contrast, inverse correlations were observed between: EGFR vs paclitaxel (r² = ?0.676, P = 0.046), CD133 vs dacarbazine (r² = ?0.636, P = 0.048) and LIFR vs daunorubicine (r² = ?0.878, P = 0.004). Finally, significant associations were also found among sensitivities to different chemotherapeutic agents and among different immunophenotypic markers. In conclusion, histopathologically identical GBM tumours displayed a marked immunophenotypic heterogeneity. The expression of A2B5, CD56, NGFR and Pgp appeared to be associated with chemoresistance whereas CD133, EGFR and LIFR expression was characteristic of chemosensitive tumours. We suggest that flow cytometric imunophenotypic analysis of GBM may predict chemoresponsiveness and help to identify patients who could potentially benefit from chemotherapy.     

DDESC: Dragon database for exploration of sodium channels in human

Background

Hepcidin/LEAP-1 is an iron regulatory hormone originally identified as an antimicrobial peptide. As part of a systematic analysis of the evolution of host defense peptides in primates, we have sequenced the orthologous gene from 14 species of non-human primates.

Results

The sequence of the mature peptide is highly conserved amongst all the analyzed species, being identical to the human one in great apes and gibbons, with a single residue conservative variation in Old-World monkeys and with few substitutions in New-World monkeys.

Conclusion

Our analysis indicates that hepcidin's role as a regulatory hormone, which involves interaction with a conserved receptor (ferroportin), may result in conservation over most of its sequence, with the exception of the stretch between residues 15 and 18, which in New-World monkeys (as well as in other mammals) shows a significant variation, possibly indicating that this structural region is involved in other functions.     

Spontaneous curvature of phosphatidic acid and lysophosphatidic acid

The formation of phosphatidic acid (PA) from lysophosphatidic acid (LPA), diacylglycerol, or phosphatidylcholine plays a key role in the regulation of intracellular membrane fission events, but the underlying molecular mechanism has not been resolved. A likely possibility is that PA affects local membrane curvature facilitating membrane bending and fission. To examine this possibility, we determined the spontaneous radius of curvature (R(0p)) of PA and LPA, carrying oleoyl fatty acids, using well-established X-ray diffraction methods. We found that, under physiological conditions of pH and salt concentration (pH 7.0, 150 mM NaCl), the R(0p) values of PA and LPA were -46 A and +20 A, respectively. Thus PA has considerable negative spontaneous curvature while LPA has the most positive spontaneous curvature of any membrane lipid measured to date. The further addition of Ca(2+) did not significantly affect lipid spontaneous curvature; however, omitting NaCl from the hydration buffer greatly reduced the spontaneous curvature of PA, turning it into a cylindrically shaped lipid molecule (R(0p) of -1.3 x 10(2) A). Our quantitative data on the spontaneous radius of curvature of PA and LPA at a physiological pH and salt concentration will be instrumental in developing future models of biomembrane fission.     

HIM1, a new yeast Saccharomyces cerevisiae gene playing a role in control of spontaneous and induced mutagenesis

We have identified a new Saccharomyces cerevisiae gene, HIM1, mapped on the right arm of the chromosome IV (ORF YDR317w), mutations in which led to an increase in spontaneous mutation rate and elevated the frequencies of mutations, induced by UV-light, nitrous acid, ethylmethane sulfonate and methylmethane sulfonate. At the same time, him1 mutation did not result in the increase of the sensitivity to the lethal action of these DNA-damaging agents. We tested the induced mutagenesis in double mutants carrying him1 mutation and mutations in other repair genes: apn1, blocking base excision repair; rad2, rev3, and rad54, blocking three principal DNA repair pathways; pms1, blocking mismatch repair; hsm2 and hsm3 mutations, which lead to a mutator effect. Epistatic analysis showed a synergistic interaction of him1 with pms1, apn1, and rad2 mutations, and epistasis with the rev3, the rad54, the hsm2, and the hsm3. To elucidate the role of the HIM1 in control of spontaneous mutagenesis, we checked the repair of DNA mispaired bases in the him1 mutant and discovered that it was not altered in comparison to the wild-type strain. In our opinion, our results suggest that HIM1 gene participates in the control of processing of mutational intermediates appearing during error-prone bypass of DNA damage.     

Discrimination against deoxyribonucleotide substrates by bacterial RNA polymerase

Nucleic acid polymerases have evolved elaborate mechanisms that prevent incorporation of the non-cognate substrates, which are distinguished by both the base and the sugar moieties. While the mechanisms of substrate selection have been studied in single-subunit DNA and RNA polymerases (DNAPs and RNAPs, respectively), the determinants of substrate binding in the multisubunit RNAPs are not yet known. Molecular modeling of Thermus thermophilus RNAP-substrate NTP complex identified a conserved beta' subunit Asn(737) residue in the active site that could play an essential role in selection of the substrate ribose. We utilized the Escherichia coli RNAP model system to assess this prediction. Functional in vitro analysis demonstrates that the substitutions of the corresponding beta' Asn(458) residue lead to the loss of discrimination between ribo- and deoxyribonucleotide substrates as well as to defects in RNA chain extension. Thus, in contrast to the mechanism utilized by the single-subunit T7 RNAP where substrate selection commences in the inactive pre-insertion site prior to its delivery to the catalytic center, the bacterial RNAPs likely recognize the sugar moiety in the active (insertion) site.     

Childhood thyroid cancer, radiation dose from Chernobyl, and dose uncertainties in Bryansk Oblast, Russia: a population-based case-control study

A population-based case-control study was conducted to estimate the radiation-related risk of thyroid cancer in persons who were exposed in childhood to (131)I from the Chernobyl accident of April 26, 1986 and to investigate the impact of uncertainties in individual dose estimates. Included were all 66 confirmed cases of primary thyroid cancer diagnosed from April 26, 1986 through September 1998 in residents of Bryansk Oblast, Russia, who were 0-19 years old at the time of the accident, along with two individually matched controls for each case. Thyroid radiation doses, estimated using a semi-empirical model based on environmental contamination data and individual characteristics, ranged from 0.00014 Gy to 2.73 Gy and had large uncertainties (median geometric standard deviation 2.2). The estimated excess relative risk (ERR) associated with radiation exposure, 48.7/Gy, was significantly greater than 0 (P = 0.00013) but had an extremely wide 95% confidence interval (4.8 to 1151/Gy). Adjusting for dose uncertainty nearly tripled the ERR to 138/Gy, although this was likely an overestimate due to limitations in the modeling of dose uncertainties. The radiation-related excess risk observed in this study is quite large, especially if the uncertainty of dose estimation is taken into account, but is not inconsistent with estimates previously reported for risk after (131)I exposure or acute irradiation from external sources.     

Interaction with Grb14 results in site-specific regulation of tyrosine phosphorylation of the insulin receptor

The dynamics of interaction of the insulin receptor (IR) with Grb14 was monitored, in real time, in living human embryonic kidney cells, using bioluminescence resonance energy transfer (BRET). We observed that insulin rapidly and dose-dependently stimulated this interaction. We also observed that insulin-induced BRET between the IR and protein tyrosine phosphatase 1B (PTP1B) was markedly reduced by Grb14, suggesting that Grb14 regulated this interaction in living cells. Using site-specific antibodies against phosphorylated tyrosines of the IR, we showed that Grb14 protected the three tyrosines of the kinase loop from dephosphorylation by PTP1B, while favouring dephosphorylation of tyrosine 972. This resulted in decreased IRS-1 binding to the IR and decreased activation of the extracellular signal-regulated kinase pathway. Increased Grb14 expression in human liver-derived HuH7 cells also seemed to specifically decrease the phosphorylation of Y972. Our work therefore suggests that Grb14 may regulate signalling through the IR by controlling its tyrosine dephosphorylation in a site-specific manner.