Survival of Escherichia coli and Campylobacter jejuni in untreated and filtered lake water

The survival of Campylobacter jejuni and Escherichia coli in lake water was studied using viable counts. Escherichia coli survived better than C. jejuni in all the test conditions studied. Both the species survived better in filtered than in untreated water. This suggests that predation and/or competition for nutrients affect the survival of both the species in an aquatic environment. Campylobacter jejuni survived less well in filtered autoclaved water and in 0.9% NaCl than in filtered water without autoclaving. The lack of some essential nutrients, which may be degraded by autoclaving, might explain these results.     

Purification and partial characterization of rat kidney histamine-N-methyltransferase

Histamine-N-methyltransferase (EC 2.1.1.8) was purified 1700-fold with a yield of 9% from rat kidney. Purification included ammonium sulfate precipitation, linear gradient DEAE-cellulose chromotography and S-adenosylhomocysteine affinity chromotography. The purified enzyme preparation showed a single protein band in sodium dodecyl sulfate-polyacrylamide gel electrophoresis with a molecular weight of 35 000. The isoelectric point of the enzyme was at pH 5.2. The purified enzyme preparation did not contain detectable amounts of histamine. The purified enzyme was totally inhibited in 100 μM parahydroxymercuric benzoate and in 10 μM iodoacetamide, and it was found to be stabilized with dithiothreitol (1 mM), suggesting that the enzyme has an SH-group in the active center. The K_m values for histamine and S-adenosylmethionine were 6.0 and 7.1 μM, respectively. 50% inhibition of histamine-N-methyltransferase was obtained at 28 μM S-adenosylhomocysteine and 100 μM methylhistamine. The purified enzyme was slightly inhibited in 1 mM methylthioadenosine. Histamine in concentrations higher than 25 μM caused substrate inhibition.     

Water currents and spreading of river load in Lake Pyhäselkä, Saimaa, Finland

During the summers of 1989–1990, the pattern of water flow and the water quality in Lake Pyhäselkä, Finland, were studied using field observations and a 3-dimensional model. The lake receives its major point-source loading, including pulp mill effluents, via the Pielisjoki River in the northeastern part of the lake, where the water is slightly eutrophic. The flow pattern was measured with three types of recording current meters, two of which were conventional mechanical meters and the third a new acoustic current profiler. The profiler was used in direct reading mode on a research vessel and also in self-contained mode on a float installed in the deep basin of the lake. The water-quality part of the model simulates oxygen, BOD, total phosphorus, AOX, and phytoplankton biomass. The three-dimensional model applied here simulates accurately the flow pattern of the water in Lake Pyhäselkä. The results of this study made it possible to detect different flow patterns in the lake. The main load is clearly affected by the wind-induced pattern of flow.     

Improved pregnancy rate with administration of hCG after intrauterine insemination: a pilot study

Background  

In natural cycles, women conceive when intercourse takes place during a six-day period ending on the day of ovulation. The current practice in intrauterine insemination (IUI) cycles is to perform the IUI 24-36 hours after the hCG administration, when the ovulation is already imminent. In this study hCG was administered after the IUI, which more closely resembles the fertilisation process in natural cycles.     

Timing an ontogenetic niche shift: responses of emerging salmon alevins to chemical cues from predators and competitors

Ontogenetic niche shifts are ubiquitous in nature. However, in most species little is known about phenotypic plasticity in the timing of shifts and in the associated characters. Following a period of endogenous feeding on yolk, salmonid alevins emerge from their gravel nests into the open water and start feeding exogenously. We studied, by using replicated artificial nests, whether the responses of emerging Atlantic salmon ( Salmo salar ) alevins to chemical cues from two piscivorous fish predators and conspecific competitors are plastic. We hypothesised that the alevins should delay emergence in response to predator cues, whereas cues from competitors should induce earlier emergence. We found that chemical cues from predatory burbot ( Lota lota ) delayed emergence, whereas cues from brown trout ( S. trutta ) tended to induce earlier emergence. The earlier emergence in response to trout cues was associated with a smaller body size and more yolk resources remaining at emergence, but burbot cues did not alter these traits. Predator cues also influenced the daily pattern of emergence: more alevins emerged during the morning in the burbot treatment, and fewer alevins emerged during the afternoon in the trout treatment. Chemical cues from conspecific competitors had no effect on emergence patterns. The results indicate that salmon alevins exhibit flexible ontogenetic niche shifts in the timing of emergence in response to predator cues, and that the responses are predator-specific. As timing of emergence is a major determinant of territory acquisition, these responses are likely to have an impact on later fitness of the fry.