Hepatic glucokinase is induced by dietary carbohydrates in rainbow trout, gilthead seabream, and common carp

Glucokinase (GK) plays a central role in glucose homeostasis in mammals. The absence of an inducible GK has been suggested to explain the poor utilization of dietary carbohydrates in rainbow trout. In this context, we analyzed GK expression in three fish species (rainbow trout, gilthead seabream, and common carp) known to differ in regard to their dietary carbohydrate tolerance. Fish were fed for 10 wk with either a diet containing a high level of digestible starch (>20%) or a diet totally deprived of starch. Our data demonstrate an induction of GK gene expression and GK activity by dietary carbohydrates in all three species. These studies strongly suggest that low dietary carbohydrate utilization in rainbow trout is not due to the absence of inducible hepatic GK as previously suggested. Interestingly, we also observed a significantly lower GK expression in common carp (a glucose-tolerant fish) than in rainbow trout and gilthead seabream, which are generally considered as glucose intolerant. These data suggest that other biochemical mechanisms are implicated in the inability of rainbow trout and gilthead seabream to control blood glucose closely.     

The carp M1 muscle‐specific creatine kinase subisoform is adaptive to the synchronized changes in body temperature and intracellular pH that occur in the common carp Cyprinus carpio

The three previously cloned Cyprinus carpio muscle‐specific subisoforms of creatine kinase (CK, EC 2.7.3.2) designated M1‐, M2‐ and M3‐CK were examined. At temperatures <15° C and at pH >7·7, specific activities of M1‐CK were three to eight‐fold higher than specific activities of M3‐ and rabbit (R) M‐CK. At pH 8·0, M1‐CK exhibited its highest specific activity at 15° C. Michaelis constants of PCr () and ADP () of M1‐CK were relatively stable at pH between 7·1–8·0 and 25–5° C. Its calculated activation energy of catalysis (E_a) at pH 8·0 was lower than at pH 7·1. Circular dichroism spectroscopy results showed that changes in secondary structures in M1‐CK at the pH and temperatures studied were much less than in the cases of RM‐ and M3‐CK. The M1‐CK enzyme seemed to have evolved to adapt to the synchronized changes in body temperature and intracellular pH of C. carpio.     

The effects of disturbance and enemy exclusion on performance of an invasive species, common ragweed, in its native range

Common ragweed (Ambrosia artemisiifolia) is an abundant weed in its native North America, despite supporting a wide range of natural enemies. Here, we tested whether these enemies have significant impacts on the performance of this plant in its native range. We excluded enemies from the three principal life-history stages (seed, seedling, and adult) of this annual in a series of field experiments; at the adult stage, we also manipulated soil disturbance and conspecific density. We then measured the consequences of these treatments for growth, survival, and reproduction. Excluding fungi and vertebrate granivores from seeds on the soil surface did not increase germination relative to control plots. Seedling survivorship was only slightly increased by the exclusion of molluscs and other herbivores. Insecticide reduced damage to leaves of adult plants, but did not improve growth or reproduction. Growth and survivorship of adults were strongly increased by disturbance, while higher conspecific density reduced performance in disturbed plots. These results indicate ragweed is insensitive to attack by many of its natural enemies, helping to explain its native-range success. In addition, they suggest that even though ragweed lost most of its insect folivores while invading Europe, escape from these enemies is unlikely to have provided a significant demographic advantage; instead, disturbance is likely to have been a much more important factor in its invasion. Escape from enemies should not be assumed to explain the success of exotic species unless improved performance also can be demonstrated; native-range studies can help achieve this goal.     

A study on an herbivorous fish, Oreochromis niloticus L., diet and its quality in two Ethiopian Rift Valley lakes, Awasa and Zwai

The natural food of Oreochromis niloticus from two Ethiopian Rift Valley lakes, Awasa and Zwai, was studied from the stomach contents. The food was analyzed to determine its chemical composition. The major consumed nutrient by the Awasa population was carbohydrate whereas in the Zwai population it was lipid. Microscopic identification revealed that Microcystis sp. and Botryococcus braunii are the dominant algae present in the food of the fishes from Lakes Zwai and Awasa, respectively. Assimilation efficiency of total organic matter is somewhat low, 28.3% for Awasa and 14.7% for Zwai populations. Both populations assimilated protein to a greater extent than other nutrients. In both lakes the quality of the food, expressed as a ratio of digestible protein to digestible energy, is adequate (>4 mg kJ ⁻¹) for growth, but the Awasa population appears to have higher growth and better condition.     

Growth,condition, and maturity schedules of an estuarine fish species change in estuaries following increased hypoxia due to climate change

Understanding challenges posed by climate change to estuaries and their faunas remains a high priority for managing these systems and their communities. Freshwater discharge into a range of estuary types in south‐western Australia between 1990 and 2015 is shown to be related to rainfall. This largely accounts for decreases in discharge in this microtidal region being more pronounced on the west coast than south coast, where rainfall decline was less. Results of an oxygen‐balance model imply that, as demonstrated by empirical data for the Swan River Estuary, declines in discharge into a range of estuary types would be accompanied by increases in the extent of hypoxia. In 2013–15, growth and body condition of the teleost Acanthopagrus butcheri varied markedly among three permanently open, one intermittently‐open, one seasonally‐closed and one normally‐closed estuary, with average time taken by females to reach the minimum legal length (MLL) of 250 mm ranging from 3.6 to 17.7 years. It is proposed that, in a given restricted period, these inter‐estuary variations in biological characteristics are related more to differences in factors, such as food resources and density, than to temperature and salinity. The biological characteristics of A. butcheri in the four estuaries, for which there are historical data, changed markedly between 1993–96 and 2013–15. Growth of both sexes, and also body condition in all but the normally‐closed estuary, declined, with females taking between 1.7 and 2.9 times longer to attain the MLL. Irrespective of period, body condition, and growth are positively related. Age at maturity typically increased between periods, but length at maturity declined only in the estuary in which growth was greatest. The plasticity of the biological characteristics of A. butcheri, allied with confinement to its natal estuary and ability to tolerate a wide range of environmental conditions, makes this sparid and comparable species excellent subjects for assessing estuarine “health.”     

The shift from C-19 to C-21 steroid synthesis in spawning male common carp, Cyprinus carpio, is regulated by the inhibition of androgen production by progestogens produced by spermatozoa

There is a rapid shift in the steroidogenic pathway from androgen to progestogen production in spawning male common carp, Cyprinus carpio. Experiments were conducted to determine the mechanism regulating this shift using in vitro cultures of testicular fragments and isolated sperm of spermiating male carp. The levels of 11-ketotestosterone (11-KT) continually increased for 48 h with or without gonadotropin (GtH) stimulation, suggesting that 11-KT is the principal androgen produced by carp testes. Ovine prolactin (oPRL) enhanced GtH-stimulated 11-KT production, but by itself had no effect. Gonadotropin, carp pituitary extract, and pregnenolone all enhanced the production of 11-KT, testosterone (T), and 17 alpha-hydroxyprogesterone (17-P) in a dose-dependent manner. No 17 alpha,20 beta-dihydroxy-4-pregnen-3-one (17,20 beta-P) was detected in response to any of these agents; 17 alpha,20 alpha-dihydroxy-4-pregnen-3-one (17,20 alpha-P) was not measured. Both 17,20 beta-P and 17,20 alpha-P inhibited 11-KT production in a dose-dependent manner in the presence of either GtH, 17-P, or T. Isolated sperm and testicular fragment preparations both produced 17,20 beta-P and approximately tenfold more 17,20 alpha-P when incubated with 17-P. Only testicular fragments, however, produced 11-KT. We conclude that androgen synthesis occurs only within somatic cells of common carp testes. GtH, and perhaps PRL, stimulates the production of steroid precursors that, under normal physiological conditions, are metabolized to androgens.(ABSTRACT TRUNCATED AT 250 WORDS)     

Variability in natural behaviour, and observed reactions to an ROV, by mid-slope fish species

The behaviour of eight large benthopelagic fish taxa was analysed using video records collected with an ROV on the mid-slope of the Bay of Biscay. The studied species were roundnose grenadier (Coryphaenoides rupestris), orange roughy (Hoplostethus atlanticus), deep-sea scorpionfish (Trachyscorpia cristulata echinata), and black scabbardfish (Aphanopus carbo), as well as individuals belonging to the families Alepocephalidae, Chimaeridae, and Scyliorhinidae, and to the order Squaliformes. Some of the observed fish were grouped at the family taxonomical level due to visual identification to species being unreliable. Assumed natural (undisturbed) behaviour was categorised in terms of (i) body position with respect to the bottom sea floor, (ii) locomotion and (iii) activity type. Reaction (disturbed) behaviour to the approaching ROV was categorised in terms of reaction type and distance. Environmental conditions (depth, temperature, current speed and direction) and observation conditions (ROV speed and altitude) were recorded simultaneously with fish observations in order to explain the variability in the observed reaction behaviour. A multivariate analysis identified three groups corresponding to a behaviour pattern of a sit and wait strategist (one species), an active bottom hunter (three taxa), and a group of species displaying little activity in their bottom habitat (three taxa). At species level the environmental and observation conditions had some explanatory power for individual behaviour variability. It is hypothesised that the varied behaviour of mid-slope benthopelagic fish contributes to maintain a high species diversity of large predators in an energy poor environment.     

Attracting Common Carp to a bait site with food reveals strong positive relationships between fish density,feeding activity,environmental DNA,and sex pheromone release that could be used in invasive fish management

Measurement of environmental DNA (eDNA) is becoming a common technique to survey for rare and invasive fish due to its sensitivity and specificity. However, its utility is limited by an incomplete understanding of factors governing its sources and fates. Failure to detect eDNA is especially difficult to interpret so surveillance techniques often collect large numbers of samples across broad regions. If, however, fish could be reliably attracted to a single location where their eDNA could be easily measured that would be useful. We conducted a proof‐of‐concept study of this idea using invasive Common Carp. We monitored the distribution of radio‐tagged Carp and their eDNA across a 67 ha lake focusing at the bait site while a pheromone (Prostaglandin F_2α; PGF_2α) was also measured to determine their reproductive condition. Prior to baiting, Carp were patchily distributed and while eDNA was occasionally detectable, it was patchy and only loosely associated with moderately dense groups of fish. Further, neither Carp, nor their eDNA were consistently measurable at the bait site and surrounding region, and the pheromone was not measurable at all. However, once baiting commenced, Carp started visiting the bait site and feeding, especially at night, where eDNA levels increased 500‐fold as fish densities doubled and PGF_2α became detectable. Fish presence, eDNA and pheromone concentrations peaked at night after 6 days, strongly suggesting feeding activity was the main driver. While the presence of eDNA precisely coincided with this aggregation, levels had dropped dramatically within 5 m. PGF_2α levels dropped less rapidly and demonstrated the presence of live mature fish. We suggest that food could be used to train fish to come to locations where they otherwise are too scarce to be reliably measured, increasing their eDNA release, making them measurable, and their reproductive condition also discernable by measuring pheromones.     

Hydrogen peroxide production by alveolar macrophages is increased and its concentration is elevated in the breath of rats exposed to hypoxia: relationship to lung lipid peroxidation

Hypoxic exposure triggers a generation of reactive oxygen species that initiate free radical damage to the lung. Hydrogen peroxide is the product of alveolar macrophages detectable in the expired breath. We evaluated the significance of breath H(2)O(2) concentration for the assessment of lung damage after hypoxic exposure and during posthypoxic period. Adult male rats were exposed to normobaric hypoxia (10 % O(2)) for 3 hours or 5 days. Immediately after the hypoxic exposure and then after 7 days or 14 days of air breathing, H(2)O(2) was determined in the breath condensate and in isolated lung macrophages. Lipid peroxidation was measured in lung homogenates. Three-hour hypoxia did not cause immediate increase in the breath H(2)O(2); 5-day hypoxia increased breath H(2)O(2) level to 458 %. After 7 days of subsequent air breathing H2O2 was elevated in both groups exposed to hypoxia. Increased production of H(2)O(2) by macrophages was observed after 5 days of hypoxia and during the 7 days of subsequent air breathing. Lipid peroxidation increased in the periods of enhanced H(2)O(2) generation by macrophages. As the major increase (1040 %) in the breath H(2)O(2) concentration found 7 days after 3 hours of hypoxia was not accompanied by lipid peroxidation, it can be concluded that the breath H(2)O(2) is not a reliable indicator of lung oxidative damage.     

Discovery and characterization of an antibody, anti-egressin, that is able to inhibit Trypanosoma cruzi egress in vitro

Trypanosoma cruzi, a protozoan parasite, is the etiologic agent of Chagas disease. The disease is characterized by acute and chronic phases, with high and low parasitemia, respectively. A strong immune activation is necessary for the host to enter the chronic phase; however, immune mechanisms participating in the reduction of parasites between the acute and chronic phases of the disease have been very difficult to elucidate. We report here the discovery of anti-egressin, an antibody present in serum from chronically infected BALB/c mice that is able to inhibit parasite egress from infected BALB/c fibroblast cultures in vitro. The antibody is very concentrated in serum from these mice; chronic serum may be diluted 1:20 while still maintaining functional activity. Isotype analysis of anti-egressin has suggested it to be IgG2a. Further analysis revealed that anti-egressin was specific for a component expressed on the surface of infected host cells. The specificity of anti-egressin toward the extracellular portion of infected host cells was demonstrated both by using a quantitative assay measuring released trypomastigotes and through immunocytochemical staining. The novel role of anti-egressin in the inhibition of parasite egress from infected host cells has not been described in the literature to date. We believe that anti-egressin plays an important role in achieving the low parasitemia characteristic of chronic Chagas disease.     

Interrelationships between ornithine,glutamate and GABA-III. an ornithine aminotransferase activity that is resistant to inactivation by 5-fluoromethylornithine

5-Fluoromethylornithine (5-FMOrn) is a specific inactivator of l-ornithine:2-oxoacid aminotransferase (OAT). However, a certain proportion of the OAT activity in mouse brain, liver and kidney is not inactivated by this compound. In the present work, the occurrence, distribution and subcellular localization of this 5-FMOrn-resistant OAT is reported. It was shown that the 5-FMOrn-resistant brain enzyme is kinetically different from the corresponding liver enzyme, and it also differs from the 5-FMOrn-sensitive OAT. The most conspicuous difference between the 5-FMOrn-resistant OAT of liver and brain is the sensitivity of the latter against excessive concentrations of its substrate 2-oxoglutarate.5-FMOrn and GABA are reversible inhibitors of the 5-FMOrn-resistant enzyme. Both compounds compete with Orn for the enzymes active site. A number of known inactivators of GABA-T which are at the same time inactivators of OAT, and canaline, a natural inhibitor of OAT, inactivate both the 5-FMOrn-sensitive and the 5-FMOrn-resistant enzyme. Gabaculine is the most potent inhibitor of the 5-FMOrn-resistant enzyme that is presently known. Our results are compatible with the suggestion that the 5-FMOrn-resistant OAT is an isoenzyme. From the fact that this form of OAT prevails in the brain, and its occurrence in the nerve ending fraction of brain homogenates supports the view that 5-FMOrn-resistant OAT may be involved in the intraneuronal generation of neurotransmitter glutamate and/or GABA from Orn as precursor. Further support in favour of this notion are previous findings which suggest feedback inhibition of OAT by GABA in GABAergic nerve endings.     

Endopolyploidy is a common response to UV-B stress in natural plant populations,but its magnitude may be affected by chromosome type

Background and AimsUltraviolet-B radiation (UV-B) radiation damages the DNA, cells and photosynthetic apparatus of plants. Plants commonly prevent this damage by synthetizing UV-B-protective compounds. Recent laboratory experiments in Arabidopsis and cucumber have indicated that plants can also respond to UV-B stress with endopolyploidy. Here we test the generality of this response in natural plant populations, considering their monocentric or holocentric chromosomal structure.MethodsWe measured the endopolyploidy index (flow cytometry) and the concentration of UV-B-protective compounds in leaves of 12 herbaceous species (1007 individuals) from forest interiors and neighbouring clearings where they were exposed to increased UV-B radiation (103 forest + clearing populations). We then analysed the data using phylogenetic mixed models.Key ResultsThe concentration of UV-B protectives increased with UV-B doses estimated from hemispheric photographs of the sky above sample collection sites, but the increase was more rapid in species with monocentric chromosomes. Endopolyploidy index increased with UV-B doses and with concentrations of UV-B-absorbing compounds only in species with monocentric chromosomes, while holocentric species responded negligibly.ConclusionsEndopolyploidy seems to be a common response to increased UV-B in monocentric plants. Low sensitivity to UV-B in holocentric species might relate to their success in high-UV-stressed habitats and corroborates the hypothesized role of holocentric chromosomes in plant terrestrialization.     

Nerve growth factor exhibits an antioxidant and an autocrine activity in mouse liver that is modulated by buthionine sulfoximine,arsenic, and acetaminophen

Abstract

Nerve growth factor (NGF) is one of the several structurally related proteins, named neurotrophins (NTs), that regulate neuronal survival, development, function, and plasticity. Moreover, NGF is an important activator of antioxidant mechanisms. These NGF functions are mediated by tropomyosin-related kinase receptor A (TrkA). Although NTs and their receptors have been shown to be expressed in visceral tissues, the extent to which NTs are involved in the physiology of visceral tissues is less clear. NGF is the most expressed NT in adult mouse livers. Although NGF is an important modulator of antioxidant mechanisms in neural tissues, few studies describe the relationship between oxidative stress and NGF expression in the liver. In this study, we demonstrate that ngfb mRNA is positively modulated in mouse livers after oxidative injury via intraperitoneal injection of 14 mg/kg sodium arsenite, 6 mmol/kg L-buthionine-S-R-sulfoximine (BSO), or 300 mg/kg acetaminophen (APAP). In addition to the upregulation of ngfb, we observed the phosphorylation of the NGF high-af?nity receptor TrkA in the liver as well as the downstream phosphorylation of Akt, NF-kB nuclear migration and iκbα and tx-1 mRNA upregulation. These effects were abolished when a neutralizing anti-NGF antibody was used. Furthermore, this anti-NGF antibody alone induced oxidative stress in the liver by decreasing the reduced glutathione, increasing the oxidized glutathione, and downregulating tx-1 mRNA. Thus, NGF plays a critical role in liver protection against oxidative stress and xenobiotic injury as well as maintains a reduced thiol state.     

Bound simian virus 40 translocates to caveolin-enriched membrane domains, and its entry is inhibited by drugs that selectively disrupt caveolae.

Simian virus 40 (SV40) entry leading to infection occurred only after the virus was at the cell surface for 1.5 to 2 h. SV40 infectious entry was not sensitive to cytosol acidification, a treatment that blocks endocytosis via clathrin-coated vesicles. Instead, SV40 infectious entry was blocked by treating cells with the phorbol ester PMA or nystatin, which selectively disrupts caveolae. In control experiments, transferrin internalization was sensitive to cytosol acidification but was not sensitive to PMA or nystatin. Also, absorbed transferrin entered cells within minutes. Finally, bound SV40 translocated to caveolin-enriched membrane complexes isolated by a Triton X-100 insolubility protocol. Treatment with nystatin did not impair SV40 binding but did block the partitioning of virus into the caveolin-enriched complexes.     

Strong population genetic structure and its management implications in the mud carp Cirrhinus molitorella, an indigenous freshwater species subject to an aquaculture and culture-based fishery

This study investigated population genetic structure and diversity of mud carp Cirrhinus molitorella, a species widely used in aquaculture and culture-based fisheries in China and Mekong River riparian countries. Seven newly developed and one published microsatellite DNA markers were used to analyse samples from six wild locations, four hatchery broodstocks and one farmed site from the Mekong, Red and Pearl Rivers. Significant genetic structure was detected in C. molitorella, with isolation-by-distance being a strong force in the Mekong. Pair-wise F(ST) , Fisher's exact tests for population differentiation, permutation tests and individual-based structure analysis all support the recognition of a sample originating from Toul Krasaing Lake (Cambodia) and one between Kratie and Stung Treng (Cambodia) as distinct from the remainder of the sampled range. Samples from the main upper Mekong and the Nam Khan River were significantly differentiated, but on a time scale inferred to be short (i.e. by genetic drift, not sufficient for evolution of new microsatellite alleles). The Mekong stock of C. molitorella was strongly differentiated from those from the Red and Pearl Rivers, inferred to be on an evolutionary time scale. Finer-scale sampling is warranted to further improve the understanding of genetic interactions among fish from the Mekong and its tributaries. Detailed studies on the ecology of C. molitorella (e.g. migration pathways and preferred spawning habitats) would provide useful information to explain the patterns of genetic structure detected here, and deepen insights about evolutionary distinctiveness of the population units.