Availability of and access to critical habitats in regulated rivers: effects of low-head barriers on threatened lampreys

1.  Conservation of freshwater animal populations requires their access to, as well as sufficient availability of, critical habitats, such as those for reproduction. Abundant small-scale barriers may cause extensive fragmentation of freshwater habitat but, by comparison to larger structures their effects are rarely considered by catchment managers. The relationship between the distribution of, and access to, spawning habitat in a regulated river, characterized by abundant small barriers, was examined for river lamprey Lampetra fluviatilis , a threatened migratory fish.
2.  Telemetry of adult lamprey in the River Derwent, North East England was used to quantify upriver migration and access to spawning habitat, together with surveys of spawning habitat availability and spawning activity between 2002 and 2007.
3.  Access in to the Derwent appeared severely restricted by a tidal barrage, beyond which lamprey migrated rapidly in unobstructed reaches. Of all lamprey tagged in the lower 4 km of river, or ascending the barrage, 64% and 17% passed the first and second weirs respectively, with high flows crucial for this. Although over 98% of lamprey spawning habitat occurred more than 51 km upstream, on average just 1.8% of river lamprey spawners were recorded there.
4.  In order to protect or rehabilitate species or species assemblages, greater attention needs to be paid to the relative spatial distribution of low-head barriers and the resultant availability of key habitats within individual catchments. This is particularly important given the renewed emphasis internationally on low-head hydropower solutions as a source of renewable energy, and the rapid growth in numbers of low-head barriers in many catchments.     

Chemopreventive and renal protective effects for docosahexaenoic acid (DHA): implications of CRP and lipid peroxides

Background

The fish oil-derived ω-3 fatty acids, like docosahexanoic (DHA), claim a plethora of health benefits. We currently evaluated the antitumor effects of DHA, alone or in combination with cisplatin (CP) in the EAC solid tumor mice model, and monitored concomitant changes in serum levels of C-reactive protein (CRP), lipid peroxidation (measured as malondialdehyde; MDA) and leukocytic count (LC). Further, we verified the capacity of DHA to ameliorate the lethal, CP-induced nephrotoxicity in rats and the molecular mechanisms involved therein.

Results

EAC-bearing mice exhibited markedly elevated LC (2-fold), CRP (11-fold) and MDA levels (2.7-fold). DHA (125, 250 mg/kg) elicited significant, dose-dependent reductions in tumor size (38%, 79%; respectively), as well as in LC, CRP and MDA levels. These effects for CP were appreciably lower than those of DHA (250 mg/kg). Interestingly, DHA (125 mg/kg) markedly enhanced the chemopreventive effects of CP and boosted its ability to reduce serum CRP and MDA levels. Correlation studies revealed a high degree of positive association between tumor growth and each of CRP (r = 0.85) and leukocytosis (r = 0.89), thus attesting to a diagnostic/prognostic role for CRP. On the other hand, a single CP dose (10 mg/kg) induced nephrotoxicity in rats that was evidenced by proteinuria, deterioration of glomerular filtration rate (GFR, -4-fold), a rise in serum creatinine/urea levels (2–5-fold) after 4 days, and globally-induced animal fatalities after 7 days. Kidney-homogenates from CP-treated rats displayed significantly elevated MDA- and TNF-α-, but reduced GSH-, levels. Rats treated with DHA (250 mg/kg, but not 125 mg/kg) survived the lethal effects of CP, and showed a significant recovery of GFR; while their homogenates had markedly-reduced MDA- and TNF-α-, but -increased GSH-levels. Significant association was detected between creatinine level and those of MDA (r = 0.81), TNF-α ) r = 0.92) and GSH (r = -0.82); implying causal relationships.

Conclusion

DHA elicited prominent chemopreventive effects on its own, and appreciably augmented those of CP as well. The extent of tumor progression in various mouse groups was highly reflected by CRP levels (thus implying a diagnostic/prognostic role for CRP). Further, this study is the first to reveal that DHA can obliterate the lethal CP-induced nephrotoxicity and renal tissue injury. At the molecular level, DHA appears to act by reducing leukocytosis, systemic inflammation, and oxidative stress.     

Generation of medaka gene knockout models by target-selected mutagenesis

We have established a reverse genetics approach for the routine generation of medaka (Oryzias latipes) gene knockouts. A cryopreserved library of N-ethyl-N-nitrosourea (ENU) mutagenized fish was screened by high-throughput resequencing for induced point mutations. Nonsense and splice site mutations were retrieved for the Blm, Sirt1, Parkin and p53 genes and functional characterization of p53 mutants indicated a complete knockout of p53 function. The current cryopreserved resource is expected to contain knockouts for most medaka genes.     

An efficient model development strategy for bioprocesses based on neural networks in macroscopic balances: Part II

There is a need for efficient modeling strategies which quickly lead to reliable mathematical models that can be applied for design and optimization of (bio)-chemical processes. The serial gray box modeling strategy is potentially very efficient because no detailed knowledge is needed to construct the white box part of the model and because covenient black box modeling techniques like neural networks can be used for the black box part of the model. This paper shows for a typical biochemical conversion how the serial gray box modeling strategy can be applied efficiently to obtain a model with good frequency extrapolation properties. Models with good frequency extrapolation properties can be applied under dynamic conditions that were not present during the identification experiments. For a given application domain of a model, this property can be used to considerably reduce the number of identification experiments. The serial gray box modeling strategy is demonstrated to be successful for the modeling of the enzymatic conversion of penicillin G In the concentration range of 10-100 mM and temperature range of 298-335 K. Frequency extrapolation is shown by using only constant temperatures in the (batch) identification experiments, while the model can be used reliable with varying temperatures during the (batch) validation experiments. No reliable frequency extrapolation properties could be obtained for a black box model, and for a more knowledge-driven white box model reliable frequency extrapolation properties could only be obtained by incorporating more knowledge in the model. Copyright 1999 John Wiley & Sons, Inc.     

A Xenopus tribbles orthologue is required for the progression of mitosis and for development of the nervous system

The product of the Drosophila gene tribbles inhibits cell division in the ventral furrow of the embryo and thereby allows the normal prosecution of gastrulation. Cell division is also absent in involuting dorsal mesoderm during gastrulation in Xenopus, and to ask whether the two species employ similar mechanisms to coordinate morphogenesis and the cell cycle, we isolated a putative Xenopus homologue of tribbles which we call Xtrb2. Extensive cDNA cloning identified long and short forms of Xtrb2, termed Xtrb2-L and Xtrb2-S, respectively. Xtrb2 is expressed maternally and in mesoderm and ectoderm at blastula and gastrula stages. Later, it is expressed in dorsal neural tube, eyes, and cephalic neural crest. Time-lapse imaging of GFP-tagged Xtrb2-L suggests that during cell division, it is associated with mitotic spindles. Knockdown of Xtrb2 by antisense morpholino oligonucleotides (MOs) disrupted synchronous cell divisions during blastula stages, apparently as a result of delayed progression through mitosis and cytokinesis. At later stages, tissues expressing the highest levels of Xtrb2 were most markedly affected by morpholino knockdown, with perturbation of neural crest and eye development.     

Immuno-corticotropin interactions in a nociceptive environment in the Wistar rat

In pregnant rats, oral administration of ammonium nitrate, stress with ether and antigenic stimulation were found to induce immune variations, hormonal changes and evince the organism's capacities of detoxification. An activation of the immune system and immunosuppression have been recorded respectively during xenobiotics administration and antigenic stimulation, and during stress. Corticotrophe response occurred on the 6th day of gestation and was more pronounced from the 12th day onwards in animals receiving ammonium nitrate. At the end of the gestation period, however, the corticotrophe response became stable in treated animals. Ammonium nitrate administration seemed to drive a major toxicity effect, clearly observed through increased levels of methemoglobine and coincided with a significant decrease in the level of glutathione, confirming a mechanism of detoxification.     

Linkage of one gene for familial glucocorticoid deficiency type 2 (FGD2) to chromosome 8q and further evidence of heterogeneity

In several cases of familial glucocorticoid deficiency (FGD), referred to as FGD type 1, mutations have been described in the coding exon of the adrenocorticotropin receptor (melanonocortin receptor type 2, MC2R) gene. However, for the majority of cases (FGD type 2), no mutations were found in this gene. In the more informative families, the involvement of the MC2R locus could be excluded by linkage or sequencing analysis and, as there was no obvious candidate gene, a genome linkage scan was performed. Fourteen families were studied in this report. Evidence of linkage was found with markers on chromosome 8q in three out of the 14 families (maximum heterogeneity LOD score of 2.81 at D8S1763). These three families were consanguineous and the gene could be located by homozygosity mapping between markers D8S285 and D8S1718 in a 8.8-cM region. No potential candidate genes were apparent in the region. Linkage to this region could be excluded in some families from our sample giving highly negative LOD scores with the markers of the region. This result suggests that at least one other gene, located on a different region, must be responsible for FGD in these families and provides new evidence of genetic heterogeneity of this disorder.     

N-Linked glycosylation of a baculovirus-expressed recombinant glycoprotein in insect larvae and tissue culture cells

The potential of insect cell cultures and larvae infected with recombinant baculoviruses to produce authentic recombinant glycoproteins cloned from mammalian sources was investigated. A comparison was made of the N-linked glycans attached to secreted alkaline phosphatase (SEAP) produced in four species of insect larvae and their derived cell lines plus one additional insect cell line and larvae of one additional species. These data survey N-linked oligosaccharides produced in four families and six genera of the order Lepidoptera. Recombinant SEAP expressed by recombinant isolates of Autographa californica and Bombyx mori nucleopolyhedroviruses was purified from cell culture medium, larval hemolymph or larval homogenates by phosphate affinity chromatography. The N-linked oligosaccharides were released with PNGase-F, labeled with 8- aminonaphthalene-1-3-6-trisulfonic acid, fractionated by polyacrylamide gel electrophoresis, and analyzed by fluorescence imaging. The oligosaccharide structures were confirmed with exoglycosidase digestions. Recombinant SEAP produced in cell lines of Lymantria dispar (IPLB-LdEIta), Heliothis virescens (IPLB-HvT1), and Bombyx mori (BmN) and larvae of Spodoptera frugiperda, Trichoplusia ni , H.virescens , B.mori , and Danaus plexippus contained oligosaccharides that were structurally identical to the 10 oligosaccharides attached to SEAP produced in T.ni cell lines. The oligosaccharide structures were all mannose-terminated. Structures containing two or three mannose residues, with and without core fucosylation, constituted more than 75% of the oligosaccharides from the cell culture and larval samples.