Clutch size relative to tree cavity size in Northern Flickers

We analysed clutch size versus nest size in 153 broods of the Northern Flicker Colaptes auratus , a woodpecker using natural cavities in British Columbia, Canada. Larger volume cavities were less susceptible to predation and cavity size was positively associated with the age and body size of males and with the body condition of female parents. Although clutches varied between 4 and 11 eggs, and the floor area of cavities varied about 5-fold, we found no relationship between clutch size and floor area or cavity volume. To see if there were fitness consequences to clutch size relative to nest size, we examined hatching success and nestling mortality in flicker broods. Hatching success was not related to cavity size, but crowding slightly reduced nestling survival even when clutch size was controlled statistically. However, there was no effect of cavity size on the total number of nestlings fledged. Newly excavated flicker cavities were smaller than reused cavities suggesting a cost to excavation. This cost, coupled with the minimal fitness consequences of overcrowding, may explain why flickers do not adjust clutch size to cavity size.     

Stream ecosystem response to, and recovery from, experimental exposure to selenium

The effects of selenium on streamecosystems were studied in outdoor,experimental stream mesocosms during a dosingperiod in which sodium selenite was added atnominal concentrations of 30 µg/L,10 µg/L, and 2.5 µg/L. The durationof the high, medium, and low treatments were573 d, 972 d, and 311 d, respectively. Apost-dosing period of three years (hightreatment) and two years (medium, lowtreatments) also was studied. Seleniumconcentrations in water, sediment, plants, andmacroinvertebrates were measured throughoutthe dosing and recovery periods. Fatheadminnows and bluegill sunfish were periodicallyheld in the streams to measure seleniumaccumulation and its effects on fish survivaland reproduction. Quantitative samples ofmacroinvertebrates were collected to assessselenium effects on macroinvertebratecommunities.Mean selenium concentration inwater was quite close to the nominalconcentration. Selenium accumulated in thesediment in all three treated streams, but notin the control streams. Sediment seleniumdecreased slowly after dosing ceased, but wasstill significantly higher than in controlstreams three years (high treatment) and twoyears (medium treatment) later.Macrophytetissue selenium concentrations weresignificantly greater in all three treatmentsthan those in the control streams duringdosing. Macrophyte selenium bioaccumulationfactors (BAFs) ranged from about 300 to 1900. Tissue selenium decreased rapidly in all threetreatments after dosing ended.During dosing,selenium concentrations in animals from allthree treatments were significantly higherthan in those from control streams. The BAFsfor macroinvertebrates ranged from 1100 to2000. Isopods accumulated more, and amphipodsless, selenium than other invertebrates. Therewere no significant effects of selenium onmacroinvertebrate abundance, richness ordiversity. Several macroinvertebrates werenot affected by exposure to selenium, butisopod and Tubifex populations weredramatically reduced in the high and mediumtreatments. After dosing, mean seleniumconcentration in macroinvertebrates decreasedslowly.Bluegill sunfish accumulated seleniumduring dosing and after selenium additionsceased. Tissue selenium was highest in theliver, followed by the gonads, skeletalmuscle, and whole body. Tissue seleniumconcentrations one (high, medium) and two(high) years after dosing were lower thanduring dosing, but whole body, skeletal muscleand liver concentrations were high enough tobe considered potentially toxic.Recovery ofselenium contaminated streams includes bothreduction of tissue selenium concentration tonon-toxic levels in fish and their foodorganisms and recovery of populations of taxadeleteriously affected by selenium exposure. Our results suggest that when selenium iseliminated from the water in streams, seleniumconcentrations in sediment, plants,macroinvertebrates, and fishes will decreaseto levels that approach concentrationsconsidered to be non-toxic to fish andwildlife and that affected populations willrecover within several years. Based onselenium accumulation in the food chain andthe presence of real, but not statisticallysignificant, effects on fish mortality andreproduction in the low treatment streams, wesupport a selenium water quality criterion forthe protection of fishes and sensitiveinvertebrates of 2 µg/L or less.     

Measuring antibody affinity and performing immunoassay at the single molecule level

Fluorescence correlation spectroscopy (FCS) enables direct observation of the translational diffusion of single fluorescent molecules in solution. When fluorescent hapten binds to antibody, analysis of FCS data yields the fractional amounts of free and bound hapten, allowing determination of the equilibrium binding constant. Equilibrium dissociation constants of anti-digoxin antibodies and corresponding fluorescein-labeled digoxigenin obtained by FCS and fluorescence polarization measurements are identical. It is also possible to follow a competitive displacement of the tracer from the antibody by unlabeled hapten using FCS in an immunoassay format. The fluorescence polarization immunoassay for vancomycin detection was used to test the FCS approach. Fitting of the FCS data for the molar fractions of free and bound fluorescein-labeled vancomycin yielded a calibration curve which could serve for determination of the vancomycin concentration in biological samples.     

Microbial Uptake,Toxicity, and Fate of Biofabricated ZnS:Mn Nanocrystals

Despite their importance in nano-environmental health and safety, interactions between engineered nanomaterials and microbial life remain poorly characterized. Here, we used the model organism E. coli to study the penetration requirements, subcellular localization, induction of stress responses, and long-term fate of luminescent Mn-doped ZnS nanocrystals fabricated under “green” processing conditions with a minimized ZnS-binding protein. We find that such protein-coated quantum dots (QDs) are unable to penetrate the envelope of unmodified E. coli but readily translocate to the cytoplasm of cells that have been made competent by chemical treatment. The process is dose-dependent and reminiscent of bacterial transformation. Cells that have internalized up to 0.5 μg/mL of nanocrystals do not experience a significant activation of the unfolded protein or SOS responses but undergo oxidative stress when exposed to high QD doses (2.5 μg/mL). Finally, although they are stable in quiescent cells over temperatures ranging from 4 to 42°C, internalized QDs are rapidly diluted by cell division in a process that does not involve TolC-dependent efflux. Taken together, our results suggest that biomimetic QDs based on low toxicity inorganic cores capped by a protein shell are unlikely to cause significant damage to the microbial ecosystem.     

The effect of pH on glucoamylase production, glycosylation and chemostat evolution of Aspergillus niger

The effect of ambient pH on production and glycosylation of glucoamylase (GAM) and on the generation of a morphological mutant produced by Aspergillus niger strain B1 (a transformant containing an additional 20 copies of the homologous GAM glaA gene) was studied. We have shown that a change in the pH from 4 to 5.4 during continuous cultivation of the A. niger B1 strain instigates or accelerates the spontaneous generation of a morphological mutant (LB). This mutant strain produced approx. 50% less extracellular protein and GAM during both chemostat and batch cultivation compared to another strain with parental-type morphology (PS). The intracellular levels of GAM were also lower in the LB strain. In addition, cultivation of the original parent B1 strain in a batch-pulse bioreactor at pH 5.5 resulted in a 9-fold drop in GAM production and a 5-fold drop in extracellular protein compared to that obtained at pH 4. Glycosylation analysis of the glucoamylases purified from shake-flask cultivation showed that both principal forms of GAM secreted by the LB strain possessed enhanced galactosylation (2-fold), compared to those of the PS. Four diagnostic methods (immunostaining, mild methanolysis, mild acid hydrolysis and beta-galactofuranosidase digestion) provided evidence that the majority of this galactose was of the furanoic conformation. The GAMs produced during batch-pulse cultivation at pH 5.5 similarly showed an approx. 2-fold increase in galactofuranosylation compared to pH 4. Interestingly, in both cases the increased galactofuranosylation appears primarily restricted to the O-linked glycan component. Ambient pH therefore regulates both GAM production and influences its glycosylation.     

Mercury poisoning in a wild mink

Mercury poisoning was diagnosed in a clinically-ill wild mink (Mustela vison) on the basis of clinical signs, histopathologic lesions and tissue mercury concentrations. The probable source of mercury was through ingestion of fish from the nearby South Saskatchewan River which is known to be contaminated with mercury. This is believed to be the first documented case of mercury intoxication of a wild animal in North America.     

Intestinal lipoprotein synthesis. Comparison of nascent Golgi lipoproteins from chow-fed and hypercholesterolemic rats

Hypercholesterolemia, induced by a cholesterol-enriched diet, is associated with distinctive modifications in the serum lipoproteins of a variety of species. Present in the serum of these animals are several classes of lipoproteins enriched in cholesteryl esters and apolipoprotein E. To investigate the role of intestinal lipoprotein synthesis in diet-induced hypercholesterolemia, we characterized nascent lipoproteins retrieved from Golgi apparatus-rich fractions of intestinal epithelial cells from chow-fed control and hypercholesterolemic rats. To eliminate chylomicrons from the preparations, rats were fasted overnight prior to the experiments. Golgi very low density lipoproteins (d less than 1.006 g/ml) from control rats were triglyceride-rich lipoproteins that migrated slightly slower than pre-beta migrating serum very low density lipoproteins. These particles contained apoproteins B-240, A-IV, and A-I. Golgi very low density lipoproteins from hypercholesterolemic rats were likewise triglyceride-rich lipoproteins migrating electrophoretically like control Golgi very low density lipoproteins and they contained apoproteins B-240, A-IV, and A-I. However, these latter particles contained less triglyceride and more cholesterol compared to control Golgi very low density lipoproteins. In addition, by radioisotope incorporation studies, Golgi very low density lipoproteins from hypercholesterolemic rats contained relatively more apoprotein A-IV (21.6 vs. 11.0%) and less apoprotein B-240 (17.0 vs. 27.0%) than found in control Golgi very low density lipoproteins. Approximately 60% of the total apoprotein radioactivity was found in apoprotein A-I in both preparations. We conclude that intestinal lipoprotein synthesis is modified by diet-induced hypercholesterolemia. The significance of these modifications with respect to the marked hypercholesterolemia observed in these animals remains to be determined.     

Uptake of glucose and orthophosphate by the american oyster.

The uptake, by oysters, of glucose is approximately 10–15 ng/hr/g wet weight, when glucose concentration in the saline was at 50 μg/ml. The removal of inorganic orthophosphate was approximately at a rate of 0.36 ng/hr/g wet weight. Radioactive studies indicate that these substrates are metabolized by oysters. The technique developed can be used to study oyster metabolism in the laboratory.