Influence of Chironomus plumosus larvae on ammonium flux and denitrification (measured by the acetylene blockage- and the isotope pairing-technique) in eutrophic lake sediment

Bythotrephes invaded Harp Lake, Ontario, Canada, in the early 1990s. Here we describe seasonal changes in the size, abundance and life history of the invader. The weight of Bythotrephes could be accurately estimated (r² =0.90) from the length of its body and the state of development of its brood, but substantial (22%) corrections for shrinkage in sugarformalin were required. The seasonality of the size and abundance of Bythotrephes was apparently regulated by the interaction of fish predation, temperature-mediated growth, the availability of the invader's prey, and switches in its reproductive biology. The vernal increase in the growth of the Bythotrephes population lagged behind increases in water temperature and abundances of preferred prey, most probably because of predation by lake herring (Coregonus artedi). Bythotrephes abundance increased rapidly in early July; however, the population maximum was brief. After the abundance of their preferred prey crashed in mid-July, Bythotrephes body size declined, and adult females switched from parthenogenic to resting egg production. Population size declined in consequence. In the summer, female Bythotrephes committed most of their energy to growth between instar I and II, but to egg production for instars II and III. The biology of the Harp Lake population differed from that observed in other recently invaded lakes in several ways – the lag in population growth in the spring, the small change in body size between instars II and III, the decline in body size in August, and the co-incident switch by mature females to resting egg production. These inter-lake differences in biology indicate we have more to learn about Bythotrephes before we can predict its influence on the inland lakes of North America.     

A calmodulin-stimulated Ca-ATPase from plant vacuolar membranes with a putative regulatory domain at its N-terminus

A cDNA, BCA1, encoding a calmodulin-stimulated Ca²⁺-ATPase in the vacuolar membrane of cauliflower (Brassica oleracea) was isolated based on the sequence of tryptic peptides derived from the purified protein. The BCA1 cDNA shares sequence identity with animal plasma membrane Ca²⁺-ATPases and Arabidopsis thaliana ACA1, that encodes a putative Ca²⁺ pump in the chloroplast envelope. In contrast to the plasma membrane Ca²⁺-ATPases of animal cells, which have a calmodulin-binding domain situated in the carboxy-terminal end of the molecule, the calmodulin-binding domain of BCA1 is situated at the amino terminus of the enzyme.     

NATURAL SELECTION ON AVIAN BREEDING TIME: CAUSALITY,FECUNDITY-DEPENDENT,AND FECUNDITY-INDEPENDENT SELECTION

Natural selection on breeding time through postfledgling survival was investigated in a population of blue tits, Parus caeruleus, between 1993 and 1996. In particular, selection acting through large brood sizes among early breeders (fecundity-dependent selection) was separated from selection acting through fitness benefits unrelated to the numerical benefits of large brood sizes (fecundity-independent selection). There was evidence that natural selection favored early breeding in 1993 and 1995 (significantly so in 1993), whereas in 1994 there was a tendency for selection to be stabilizing. Analyses of selection gradients further showed that there was direct selection for both early breeding and large brood sizes in 1993. Experimentally delayed pairs produced a lower proportion of surviving young among their fledglings compared to early pairs, indicating that the seasonal fitness trend is a causal one and not caused by differences between early and late breeders in territory or individual quality. There was no evidence for significant heritability for four reproductive traits (clutch sizes, laying dates, hatching dates, and brood size at fledging) although repeatability values ranged from 0.26 to 0.53. The importance of year-specific selective regimes in the evolution of avian breedings times are discussed and a role for population density in this context is proposed.     

Violaxanthin accessibility and temperature dependency for de-epoxidation in spinach thylakoid membranes

Using DTT and iodoacetamide as a novel irreversible method to inhibit endogenous violaxanthin de-epoxidase, we found that violaxanthin could be converted into zeaxanthin from both sides of the thylakoid membrane provided that purified violaxanthin de-epoxidase was added. The maximum conversion was the same from both sides of the membrane. Temperature was found to have a strong influence both on the rate and degree of maximal violaxanthin to zeaxanthin conversion. Thus only 50% conversion of violaxanthin was detected at 4 °C, whereas at 25 °C and 37 °C the degree of conversion was 70% and 80%, respectively. These results were obtained with isolated thylakoids from non-cold acclimated leafs. Pigment analysis of sub-thylakoid membrane domains showed that violaxanthin was evenly distributed between stroma lamellae and grana partitions. This was in contrast to chlorophyll a and -carotene which were enriched in stroma lamellae fractions while chlorophyll b, lutein and neoxanthin were enriched in the grana membranes. In combination with added violaxanthin de-epoxidase we found almost the same degree of conversion of violaxanthin to zeaxanthin (73–78%) for different domains of the thylakoid membrane. We conclude that violaxanthin de-epoxidase converts violaxanthin in the lipid matrix and not at the proteins, that violaxanthin does not prefer one particular membrane region or one particular chlorophyll protein complex, and that the xanthophyll cycle pigments are oriented in a vertical manner in order to be accessible from both sides of the membrane when located in the lipid matrix.     

Sponge Carrying by Dolphins (Delphinidae,Tursiops sp.): A Foraging Specialization Involving Tool Use?

During long-term research on bottlenose dolphins (Tursiops sp.) in Shark Bay, Western Australia, several individuals were observed carrying sponges, Echinodictyum mesenterinum, on their rostra. Over multiple years, five regularly sighted individuals were usually carrying sponges when encountered (67–100% of encounters). Four additional regularly sighted individuals were observed with sponges just one time each. All five individuals that routinely carried sponges were female. Two of the anomalous, one-time carriers were female, one was likely female, and one was male. Most observations of sponge carrying occurred within a restricted area, a relatively deep water channel (8–10 m deep). Surface observations of sponge carrying, including focal animal observations, revealed a stereotyped surfacing and diving pattern, and occasional indications of prey consumption. Three hypotheses are considered regarding the function of sponge carrying: 1. dolphins were playing with the sponges; 2. the sponges contain some compound of use to the dolphins (e.g. for medicinal purposes); and 3. the sponges were used as a tool to aid in foraging. The foraging tool hypothesis is best supported, but the exact manner in which sponges are used remains to be discovered. Sponge carrying is a behavioural specialization, probably involving foraging, and regularly engaged in by only a small proportion of female dolphins in Shark Bay.     

Backcrossing of nematode-resistant sugar beet: a second nematode resistance gene at the locus containing Hs1pro-1?

Beet cyst nematode-resistant sugar beet plants, containing the Hs1^pro-1 locus from Beta procumbens, show a female transmission frequency of the resistance of ca. 90%. Such plants often suffer from tumour formation on leaves and root systems, and from the occurrence of a so-called multi-top phenotype. With the aim of obtaining resistant sugar beet material lacking these negative traits, nematode-resistant plants with a reduced size of the chromosome segment of the wild beet that carries the Hs1^pro-1 gene were selected from backcrosses between the resistant stocks B883 or AN1-65-2 and susceptible sugar beet (Beta vulgaris). Analysis of such plants, referred to as Sat-minus plants, showed that the transmission frequency of the resistance to subsequent generations had dropped dramatically to ca. 0.5%. The multi-top phenotype was still present in the newly selected material, indicating that improvement of the resistant sugar beet material by further backcrossing will be hard to achieve. Two of the selected resistant offspring plants were analysed at the molecular level. With the aid of AFLP markers it was found that the size of the alien chromosome segment had decreased to 35% and 17% of the original size, respectively. Surprisingly, both plants had lost the Hs1^pro-1 nematode resistance gene that recently was isolated from the original introgression material. This shows that more than one gene conferring resistance must be present in the locus in B883 and AN1-65-2 carrying the resistance gene Hs1^pro-1.     

Degradation of bis(2-ethylhexyl) phthalate constituents under methanogenic conditions

The degradation of bis(2-ethylhexyl) phthalate (DEHP) and its intermediary hydrolysis products 2-ethylhexanol (2-EH) and mono(2-ethylhexyl) phthalate (MEHP) was investigated in a methanogenic phthalic acid ester-degrading enrichment culture at 37°C. 2-Ethylhexanoic acid (2-EHA), a plausible degradation product of 2-EH, was also studied. The culture readily degraded 2-EH via 2-EHA to methane which was formed in stoichiometric amounts assuming complete degradation of 2-EH to methane and carbon dioxide. MEHP was degraded to stoichiometric amounts of methane with phthalic acid as a transient intermediate. DEHP remained unaffected throughout the experimental period (330 days).Abbreviations 2-EH 2-ethylhexyl alcohol - 2-EHA 2-ethylhexanoic acid - BBP butylbenzyl phthalate - Be-CoA benzoyl Coenzyme A - CoA Coenzyme A - DEHP bis(2-ethylhexyl) phthalate - MEHP mono(2-ethylhexyl) phthalate - MSW municipal solid waste - PA phthalic acid - PAE phthalic acid ester - TMS trimethylsilyl derivative     

Steroid metabolism in the hormone dependent MCF-7 human breast carcinoma cell line and its two hormone resistant subpopulations MCF-7/LCC1 and MCF-7/LCC2

Androgen and estrogen metabolism was investigated in the hormone-dependent human breast cancer cell line MCF-7 and its two hormone-resistant sublines MCF-7/LCC1 and MCF-7/LCC2. Using the product isolation method, the activity of aromatase, 5-reductase, 3/β-hydroxysteroid oxidoreductase and 17β-hydroxysteroid oxidoreductase were investigated isolating the following steroids: estriol (E₃), estradiol (E₂), estrone (E₁), 3/β-androstanediol (A-diol), testosterone (T), dihydrotestosterone (DHT), androsterone (AND), androstenedion (4-AD) and androstanedione (A-dion). For all experiments, cells were preincubated with cortisol and subsequently incubated with [¹⁴C]T or [¹⁴C]4-AD as the substrate in medium without phenol red and with serum charcoal stripped of steroids. The results showed no aromatase activity in any of the cell lines under the experimental conditions used, and preincubation with cortisol had no effect on the enzyme activity. With [¹⁴C]T as the substrate, the metabolized level of DHT was very similar in the three cell lines, though MCF-7/LCC1 and MCF-7/LCC2 utilized the substrate to a much lesser extent. The amount of DHT and 4-AD produced were comparable in the two hormone-resistant cell lines, while the amount of 4-AD was significantly higher in MCF-7 cells. No differences in enzyme activity were found in the three cell lines when [¹⁴C]4-AD was used as the substrate. This study showed an altered androgen metabolism in the MCF-7/LCC1 and MCF-7/LCC2 sublines compared to the parent MCF-7. However, since treatment with DHT and T inhibited cell growth equally well in all three tumor cell lines, it is unlikely that the found differences in steroid metabolism was involved in the acquisition of the endocrine resistance of the two MCF-7 sublines.     

Precision and accuracy of radioimmunoassay in the analysis of endogenous 3-indoleacetic acid from needles of scots pine

The precision and accuracy of a radioimmunoassay (RIA) for 3-indoleacetic acid (IAA) were assessed when applied to the analysis of extracts from Pinus sylvestris seedlings. It was found that extracts contained contaminants that adversely affected both the precision and accuracy of quantitative estimates of IAA. When samples were subjected to purification procedures prior to RIA, accurate and more precise estimates were obtained. Parallel analysis with high performance liquid chromatography using a fluorescence detector (HPLC-FL) indicated that HPLC-FL provided accurate estimates of the IAA content of Pinus extracts at the same stage of purification as RIA. The precision of HPLC-FL estimates was similar to that obtained with RIA.     

Communication during suckling in the domestic pig. Effects of continuous noise

The purpose of this study was to analyse the function of the vocalizations of sows and piglets during suckling and to investigate the possible effects on the nursing-suckling interaction of exposure to continuous noise at a high level. Six sows with litters were studied in pens measuring 2.5 × 2.5 m. Three of the sows were exposed to a relatively silent background noise of 59 dB(A) (L_eq 24 h) and three were exposed to fan noise at a level of 85 dB(A). A total of 64 sucklings during Days 2–4 after farrowing were recorded on video. For each suckling, four different parameters were recorded second by second; the visual and acoustic behaviour of the sow and the visual and acoustic behaviour of the piglets. The vocalizations of the piglets probably constituted functionally discrete classes. “High grunt/deep grunt” seemed to cause the sow to expose her udder. “Scream” and “squeak” were statistically associated with the occurrence of fights for teats among the piglets. The function of “croaking” is unclear. The gruntings of the sow progressed according to a typical pattern of an initially slow rate followed by rapid grunting, which in turn was followed by a decline in rate. This pattern was similar for all sows, regardless of the experimental situation. In the silent environment, the piglets seemed to respond to the alterations in grunt rate, which caused a synchronized pattern of behaviour. In the noise-exposed environment, the piglets failed to respond to the gruntings of the sow, which led to a disrupted pattern. Certain indications were found that suggested that the noise-exposed piglets gained less milk than the ones in the silent environment. It is suggested as a hypothesis, that the function of the final massage is to regulate the milk production of the sow according to the prevalent litter size.