The influence of a deep-storage reservoir on the physicochemical limnology of a Central Texas River

A study was conducted to determine a physicochemical profile of a new deep-storage reservoir and to determine the influence of impoundment and thermal stratification in the reservoir on the physicochemical limnology of the parent river. The presence of thermal stratification from May through November caused the most significant change in water conditions. Of 23 parameters studied, 12 remained unchanged, 10 improved, and 2 deteriorated (Table VI).The greatest downstream changes in water conditions from those upstream from the reservoir were a decrease in temperature, an increase of ammonia, and the presence of hydrogen sulfide during the period of thermal stratification. Ammonia did not increase to a level considered to be toxic to aquatic species. It could, however, serve as a nutrient for certain species of plants and result in a change in community structure.Water tempeature downstream from the reservoir was always within the annual temperature range of the river upstream from the reservoir; however, the summer maximum in the tailrace was decreased to a temperature that could interfere wih the normal life cycle of many species.     

Spanning the gap: experimental determination of paratenic host specificity of horsehair worms (Nematomorpha: Gordiida)

Abstract. Details of the life cycle of freshwater nematomorphs (gordiids) remain unclear. Free-living aquatic larval gordiids must make a critical transition from an epibenthic aquatic environment to terrestrial hosts. In order to identify potential hosts capable of bridging this ecological gap, the specificity of paratenic hosts of three common species of North American gordiids was investigated. All three species were characterized by an identical infection pattern: low host specificity. Gordiids were able to encyst within annelids, mollusks, crustaceans, insects and a vertebrate. Three species of putative host (a turbellarian, a water mite, and a mosquito larva) were not infected with any of the gordiid species. Internal defense reactions (IDR) and feeding behaviors are implicated as preventing infection in these species. Several of the other host species produced either an IDR or an immune reaction to the cysts, although reactions to the cysts were highly variable between species. In most species, IDR did not cause noticeable harm to the encysted larvae. It is proposed that although many species are easily infected with gordiid cysts, most do not act as natural paratenic hosts. For some of these host groups, especially snails, a role as reservoir host is suggested. Of all hosts included in this study, aquatic insects were identified as the hosts likely responsible for spanning the ecological gap and acting as true hosts for gordiids.     

Zoonoses As Ecological Entities: A Case Review of Plague

As a zoonosis, Plague is also an ecological entity, a complex system of ecological interactions between the pathogen, the hosts, and the spatiotemporal variations of its ecosystems. Five reservoir system models have been proposed: (i) assemblages of small mammals with different levels of susceptibility and roles in the maintenance and amplification of the cycle; (ii) species-specific chronic infection models; (ii) flea vectors as the true reservoirs; (iii) Telluric Plague, and (iv) a metapopulation arrangement for species with a discrete spatial organization, following a source-sink dynamic of extinction and recolonization with naïve potential hosts. The diversity of the community that harbors the reservoir system affects the transmission cycle by predation, competition, and dilution effect. Plague has notable environmental constraints, depending on altitude (500+ meters), warm and dry climates, and conditions for high productivity events for expansion of the transmission cycle. Human impacts are altering Plague dynamics by altering landscape and the faunal composition of the foci and adjacent areas, usually increasing the presence and number of human cases and outbreaks. Climatic change is also affecting the range of its occurrence. In the current transitional state of zoonosis as a whole, Plague is at risk of becoming a public health problem in poor countries where ecosystem erosion, anthropic invasion of new areas, and climate change increase the contact of the population with reservoir systems, giving new urgency for ecologic research that further details its maintenance in the wild, the spillover events, and how it links to human cases.     

A cycle of enzymatic reactions that behaves like a neuronal circuit.

A cycle of four enzymatic reactions with repression or allosteric inhibition of the enzymes has been proposed by analogy to a neural oscillator. The system is analysed in a situation remote from full symmetry. Asymmetry has been introduced by treating one of the reagents as a reservoir substance with constant concentration and having essentially different rate constants for forward and backward reactions. It is demonstrated that, for certain values of parameters, the system can work as a strength of stimulus to frequency transducer. For other values of the parameters, it acquires the features of an excitable system.     

Sampling method adapted for colonial cyanobacteria in a lake environment. Case study of Microcystis aeruginosa in the Grangent reservoir (Loire, France)

New method of sampling adapted to colonial cyanobacteria was developed on the Grangent reservoir (Loire, France). These prokaryotes were sampled using a filtering pump and were counted at laboratory under epifluorescence microscope. This method allowed us to follow the annual cycle of Microcystis aeruginosa, since benthic spring recruitment (cyanobacteria being used as inoculum) until autumnal sedimentation, and even revealed the presence of this cyanobacterian species in winter in the epilimnion. Our study also showed the inadequacy of the standard sampling methods used in limnology, which badly underestimate colonial cyanobacteria.     

Detection of Yersinia enterocolitica in food by PCR amplification

A polymerase chain reaction (PCR) assay was developed for detection of pathogenic, virulent strains of Yersinia enterocolitica . By using both virulence loci virF and ail as markers for pathogenicity, detection of species with a virulence factor present was possible. DNA preparation in the presence of hexadecyl trimethy ammonium bromide (CTAB) was followed by two 44 cycle amplification reactions, one for each of the markers. As few as 10² Y. enterocolitica cells were detected in ground pork in the presence of 10⁵–10⁶ bacteria of other species. The described PCR assay provides a sensitive robust assay for the detection of virulent Y. enterocolitica in food.     

Regulation of redox forms of plasma thiols by albumin in multiple sclerosis after fasting and methionine loading test

Increases in plasma concentrations of total homocysteine (tHcy) have recently been reported in multiple sclerosis (MS) as the alteration of the methionine cycle for the onset of autoimmune diseases. Homocysteine (Hcy) and cysteine (Cys) are generated by the methionine cycle and transsulfuration reactions. Their plasma levels are subjected to complex redox changes by oxidation and thiol/disulfide (SH/SS) exchange reactions regulated by albumin. The methionine loading test (MLT) is a useful in vivo test to assay the functionality of the methionine cycle and transsulfuration reactions. Time courses of redox species of Cys, cysteinylglycine (CGly), Hcy, and glutathione have been investigated in plasma of MS patients versus healthy subjects after an overnight fasting, and 2, 4, and 6 h after an oral MLT (100 mg/kg body weight), to detect possible dysfunctions of the methionine cycle, transsulfuration reactions and alterations in plasma distribution of redox species. After fasting, the MS group showed a significant increase in cysteine-protein mixed disulfides (bCys) and total Cys (tCys). While plasma bCys and tCys in MS group remained elevated after methionine administration when compared to control, cystine (oxCys) increased significantly with respect to control. Although increased plasma concentrations of bCys and tCys at fasting might reflect an enhance of transsulfuration reactions in MS patients, this was not confirmed by the analysis of redox changes of thiols and total thiols after MLT. This study has also demonstrated that albumin-dependent SH/SS exchange reactions are a potent regulation system of thiol redox species in plasma.     

Intermediates in the ferrous oxidase cycle of bleomycin

We have previously shown that the bleomycin-induced autooxidation of ferrous iron follows Michaelis--Menten kinetics which are characteristic of enzymatic reactions [Caspary, W. J., Lanzo, D. A., Niziak, C., Friedman, R., & Bachur, N. R. (1979) Mol. Pharmacol. 16, 256]. In this paper, we identify the iron complexes formed during this reaction. The first is a ferrous iron--bleomycin complex which can be considered the catalyst substrate complex. The product of this reaction is a ferric iron--bleomycin complex which is found in a low-spin and a high-spin form. The relative concentrations of these two forms are a function of pH. Glutathione, a biologically relevant reducing agent, binds to the ferric iron--bleomycin complex, reduces it, and may serve as a model for the reduction of the ferric iron--bleomycin complex to the ferrous state during the catalytic cycle. Oxygen uptake induced by bleomycin and ferrous iron is not inhibited by superoxide dismutase (SOD) or catalase. In the absence of bleomycin, catalase strongly inhibits oxygen uptake. This suggests the presence of a relatively stable intermediate in which the superoxide radical is not readily accessible to superoxide dismutase. At pH 9.3, we are able to observe a transient species by electron spin resonance (ESR). When potassium superoxide is added to the ferric iron--bleomycin complex, the same ESR spectrum is produced. We suggest that a transient species composed of a ferric iron, the superoxide ion, and bleomycin is formed. The precise nature of the binding cannot be determined from the data presented.     

Dynamic Light Regulation of Photosynthesis (A Review)

Regulatory reactions providing the photosynthetic apparatus with the ability to respond to variations of irradiance by changes in activities of the light and the dark stages of photosynthesis within a time range of seconds and minutes are considered in the review. At the light stage, such reactions are related to the changes in both distribution of light energy between two photosystems and probability of nonphotochemical dissipation of absorbed quanta in PSI and PSII. These regulatory reactions operate in a negative feedback mode, thus avoiding overreduction of electron transport chain and minimizing the probability of generation of reactive oxygen species. The crucial role in preventing the generation of reactive oxygen species belongs to dynamic regulation of electron transport activity despite the presence of complex system of their detoxification in chloroplasts. In dark reactions of Calvin cycle, the regulatory responses involve a positive feedback principle being related to redox regulation of activities of several enzymes, which is sensitive to the reduction status of PSI acceptor side. The complex of regulatory reactions based on negative and positive feedback principles provides prolonged functioning of a chloroplast and high stability of photosynthetic activity under various light conditions.     

The Importance of the Manganese-Oxidizing Microorganism Metallogenium personatum for the Retention of Manganese in the Wahnbach Reservoir

The retention of manganese in the water of the Wahnbach reservoir was determined in mass balance calculations. The retention properties for manganese drastically decreased after the phosphorus elimination plant was taken into service. Processes controlling the distribution and mobility of manganese in the reservoir were based on the results of tests conducted to evaluate the role of the microorganism Metallogenium personatum. A substantial retention of manganese in the Wahnbach reservoir was found to be dependent on the presence of this planktonic manganese-oxidizing bacterium. The test results clearly indicate the importance of Metallogenium spec. as catalyst in the removal and oxidation of dissolved Mn(II).     

Novel binuclear chiral zirconium catalysts used in enantioselective strecker reactions

A novel binuclear chiral zirconium catalyst was successfully used in enantioselective Strecker reactions. The catalyst was readily prepared from zirconium t-butoxide (Zr(OtBu)4), (R)-6,6'-dibromo-1, 1'-bi-2-naphthol ((R)-6-Br-BINOL), and (R)-3,3'-dibromo-1, 1'-bi-2-naphthol ((R)-3-Br-BINOL) to form unique binuclear structure. It was revealed that a combination of (R)-6-Br-BINOL and (R)-3-Br-BINOL was essential in these asymmetric reactions and that much lower selectivities were obtained by using other combinations. Two-component (an imine and hydrogen cyanide (HCN)) and three-component (an aldehyde, an amine, and HCN) Strecker reactions proceeded smoothly in the presence of a catalytic amount of the chiral zirconium catalyst to afford the corresponding alpha-amino nitrile derivatives in high yields with high enantioselectivities.     

Predicting the fine-scale spatial distribution of zoonotic reservoirs using computer vision

Zoonotic diseases threaten human health worldwide and are often associated with anthropogenic disturbance. Predicting how disturbance influences spillover risk is critical for effective disease intervention but difficult to achieve at fine spatial scales. Here, we develop a method that learns the spatial distribution of a reservoir species from aerial imagery. Our approach uses neural networks to extract features of known or hypothesized importance from images. The spatial distribution of these features is then summarized and linked to spatially explicit reservoir presence/absence data using boosted regression trees. We demonstrate the utility of our method by applying it to the reservoir of Lassa virus, Mastomys natalensis, within the West African nations of Sierra Leone and Guinea. We show that, when trained using reservoir trapping data and publicly available aerial imagery, our framework learns relationships between environmental features and reservoir occurrence and accurately ranks areas according to the likelihood of reservoir presence.     

Comparative morphology of the venom gland and reservoir in opiine and alysiine braconid wasps (Insecta, Hymenoptera, Braconidae)

Detailed venom reservoir and venom gland intima morphology was investigated in representatives of 178 species and 76 genera of Braconidae belonging to the subfamilies Opiinae (23 genera and 69 species) and Alysiinae (36 genera and 67 species of Alysiini, and 17 genera and 42 species of Dacnusini). The presence of an unsculptured sack–like expansion of the anterior end of the reservoir suggests a relationship between some members of the alysiine tribe Dacnusini, viz. Exotela and Chorebus , and the genera Oenonogaster and Glyphogaster , both of which are currently placed in the Alysiini. The same feature also suggests that Exotela, Chorebus, Oenonogaster and Glyphogaster may be derived from the Opiinae separately from other Alysiinae. Other dacnusines examined are indicated as forming a monophyletic taxon on the basis of their reduced and narrow reservoirs. An anterior insertion of the venom glands on to the reservoir generally supports the Phaenocarpa group of alysiine genera, with some modification, whereas the presence of a discrete, narrow posterior extension of the reservoir represents a synapomorphy for members of the Aspilota group of alysiine genera. The phylogenetic inferences from this venom apparatus study are discussed in the light of the biology of the taxa concerned. Twenty-one new combinations are made in the Opiinae and seven in the Alysiinae.     

Life cycle of the nematode, Abbreviata kazachstanica

Data are given on the life cycle of the nematode Abbreviata kazachstanica. New intermediate hosts of the species have been established as follows: 10 species of Coleoptera, 8 species of Orthoptera and 1 species of Mantoptera. In the intermediate hosts larvae of A. kazachstanica moult twice and in 20 to 23 days (in Orthoptera) and 26 to 29 days (in Coleoptera) reach the invasional stage. Rana ridibunda and Gymnodactilus russovi served as experimental reservoir hosts. The scheme of the developmental cycle of the nematode is given.     

Land/water ecotone effects in reservoirs on the fish fauna

The morphology and function of one tropical and 25 temperate reservoirs are examined in relation to their effect upon the nature of the land/water interface and, further, to what extent the features of these ecotones satisfy the ecological requirements of the reservoir fish species throughout their life cycle during spawning, larval, juvenile and adult stages. The two main conclusions are that (1) reservoir fish species are especially dependent upon land/water ecotones during their early life history and (2) there exists a strong relationship between the extent of the littoral area and the nature of the fish stocks. Several examples are given to show that manipulation of the land/water ecotone is a major tool for the management of reservoirs advantageously for their major functions.     

Redox cycling of 2-(x'-mono, -di, -trichlorophenyl)- 1, 4-benzoquinones, oxidation products of polychlorinated biphenyls

Polychlorinated biphenyl (PCB) preparations are complete liver carcinogens in rodents and efficacious promoters in two-stage hepatocarcinogenesis. Cytochrome P450 isozymes catalyze the oxidation of PCBs to mono- and dihydroxy metabolites. The potential for further enzymatic or nonenzymatic oxidation of ortho- and para-dihydroxy PCB metabolites to (semi)quinones raises the possibility that redox cycling involving reactive oxygen species may be involved in PCB toxicity. Seven synthetic 2-(x'-chlorophenyl)-1, 4-benzoquinones (containing one to three chlorines) were investigated for their participation in oxidation-reduction reactions by following the oxidation of NADPH. These observations were made: (i) NADPH alone directly reduced all quinones but only 2-(2'-chlorophenyl)- and 2-(4'-chlorophenyl)-1,4-benzoquinone supported NADPH consumption beyond that required to quantitatively reduce the quinone. (ii) For all quinones, superoxide dismutase increased NADPH oxidation in excess of the amount of quinone, demonstrating the participation of the superoxide radical. (iii) The presence of microsomal enzymes from rat liver increased the rate of NADPH consumption, but only 2-(2'-chlorophenyl)- and 2-(4'-chlorophenyl)-1,4-benzoquinone autoxidized. (iv) The combination of superoxide dismutase with microsomal enzymes accelerated autoxidation from 1.6- to 6.8-fold higher than that found in the absence of microsomal protein. These data support the concept that in the absence of microsomal protein, there occurs a two-electron reduction of the quinone by NADPH to the corresponding hydroquinone that comproportionates with the large reservoir of quinone to initiate autoxidation. In the presence of microsomes, enzymatic one-electron reduction generates a semiquinone radical whose autoxidation with oxygen propagates the redox cycle. These results show the potential of some 2-(x'-chlorophenyl)-1, 4-benzoquinones to initiate the wasteful loss of NADPH.     

Properties of the radical intermediate obtained on oxidation of 2',7'-dichlorodihydrofluorescein, a probe for oxidative stress

Reduced "leuco" dyes such as dichlorodihydrofluorescein (DCFH(2)) are widely used as profluorescent probes for oxidative stress, although they require a catalyst to be oxidized by hydrogen peroxide and react indiscriminately with oxidizing radicals and the fluorescent product (DCF) is a potential photosensitizer of superoxide generation. In this study, key properties of the radical intermediate in oxidation ("semiquinone," DCFH(.-)/DCF(.)(-)) were measured, to help understand the reactions that can occur in biological systems. The intermediate was generated by oxidizing DCFH(2) or reducing DCF by radiolytically generated radicals and monitoring the reactions using kinetic spectrophotometry. The semiquinone showed pH-sensitive absorption spectral changes, decay kinetics (both in the absence and in the presence of oxygen), and reduction potential, all corresponding to prototropic dissociations with pK(a)'s of approximately 7.1 and 9.0. DCFH(2) has pK(a)'s in a similar region (8-9) and hence pH variations are potentially important in the use of this probe. The rate constant for reaction of the semiquinone with oxygen at pH 7.4 is 5.3 x 10(8) M(-1) s(-1): this reaction, rather than disproportionation of DCFH(.-)/DCF(.)(-), generates DCF in biological systems, concomitantly forming superoxide and hence H(2)O(2) to cycle the catalyst. The midpoint reduction potential of the couple DCF,H(+)/DCFH() is approximately -0.75 V vs. NHE at pH 7.4; DCF is unlikely to be reduced rapidly by common flavoprotein reductases.     

An immunoprecipitin study of the incidence of influenza A antibodies in animal sera in the Ottawa area.

A survey of over 600 'normal' sera from 14 animal species by immunoprecipitin tests in cellulose acetate using viron antigens revealed a high incidence of precipitating activity against a broad range of influenza A virus strains, particularly A2hHong Kong/1/68 and /PR8. However, serum treatments trypsin-heat-periodate, NaIO4, V. cholerae receptor-destroying enzyme (RDE), or kaolin eliminated most precipitating activity, which suggests that it was due to "non-specific" inhibitors of influenze viruses. A resistant minority could not be identified as inhibitor or antibody on this basis. Precipitation of the influenza A major type-specific antigen in virus-soluble antigens by human 7S gamma globulin antibody (IgG), demonstrated to be specific for influenza virus, was established as a reference reaction to identify similar immunoprecipitin reactions occurring between virus-soluble antigens and normal or immune sera. Complement fixation tests provided supplementary evidence for the presence of influenza A antibodies in these sera. Influenza A antibodies were found in only a few sera of six animal species: cat, dog, rabbit, goat, chipmunk, and sheep. Thus the animal species examined in the Ottawa area have not revealed an unequivocal reservoir for human influenza A viruses.     

Chemical oscillations and multiple steady states due to variable boundary permeability

An analysis is made of isothermal chemical reactions occurring in a volume bounded by a membrane and immersed in a reservoir of reactants and products at fixed concentrations. The permeability of the membrane to a given species is taken to be a function of the concentration of that species or of another species. This coupling between reaction and permeation provides feedback and, even for extremely simple (one or two step) reaction mechanisms, shows the following phenomena: (i) multiple steady states, some of which are stable, some unstable; (ii) hysteresis effects; (iii) reversible and irreversible transitions between stable branches of steady states induced by variation of one parameter and dependent on the values of other parameters; (iv) oscillatory temporal approach to a stable steady state; and (v) limit cycles. A method is given for predicting in certain limiting conditions the presence of unstable permeation-reaction feedback loops; the procedure is essentially independent of the details of the reaction mechanism. The theory is proposed as an appropriate construct for certain cellular phenomena, and as one example, is compared with some experiments on glycolysis in yeast cells.     

Hydrolytic reaction catalyzed by poly[N-(substituted)glycine]s having imidazolyl groups in side chains in the presence of liposome

Hydrolytic reactions in the presence of liposomes catalyzed by N epsilon-benzyloxycarbonylhistidine groups introduced into the side chains of poly[N-(3-aminopropyl)glycine] were studied. On increasing the hydrophobicity of the polypeptide catalyst by introducing dodecyl groups into the side chains, and in the presence of dipalmitoylphosphatidylcholine (DPPC) bilayer membranes, p-nitrophenyl palmitate (PNPP) was hydrolyzed more rapidly than p-nitrophenyl acetate (PNPA). The addition of cholesterol or phosphatidylserine to lipid bilayer membranes accelerated the hydrolysis of PNPP catalyzed by the polypeptide catalyst more strongly than that of PNPA. The substrate selectivity and catalytic efficiency of the polypeptide catalyst were found to be controlled by the physical state of the lipid bilayer membranes.