Sex Differences in Plasma Steroid Concentrations and Singing Behaviour during Ontogeny in Canaries (Serinus canaria)

The relationship between the ontogenetic pattern of sex steroids and the differentiation of sexually dimorphic song in canaries of both sexes was studied. Songs were recorded to assess the temporal course of different developmental stages. Song parameters such as length and frequency of tours were measured. Parallel to behavioural observations, all birds were bled regularly every 20–30 days from the age of 15 days to day 235. The plasma samples were analyzed by RIA to measure testosterone (T), dihydrotestosterone (DHT) and estradiol-17β (E₂). The following results were obtained: 1) In young male canaries we distinguish three different stages of song development: subsong, starting at the age of 30 days, plastic song, and juvenile autumnal song finally giving way to the rigid and stable utterances of the reproductive period in next spring. During ontogeny the length and frequency of tours increase gradually. Female canaries were not observed singing regularly during their first year of life, whereas males sing very frequently. 2) Both sexes show tendencies to elevated titres of testosterone before the onset of juvenile moult. These titres correspond to those of paired males during the reproductive cycle. Song development is not correlated with the ontogenetic pattern of testosterone: the process of crystallization from the amorphic songs uttered by juveniles progresses gradually to the autumnal song in late autumn, when the titres of T in males are low (< 200 pg/ml). Female T and DHT levels during ontogeny correspond to those of the males. 3) There are sex differences in the estradiol pattern. Males show higher titres in several stages of development than females.     

The mixed xylem sap proteome of Fusarium oxysporum-infected tomato plants

Secreted proteins are known to play decisive roles in plant–fungus interactions. To study the molecular details of the interaction between the xylem-colonizing, plant-pathogenic fungus Fusarium oxysporum and tomato, the composition of the xylem sap proteome of infected tomato plants was investigated and compared with that of healthy plants. Two-dimensional gel separation and mass spectrometry yielded peptide masses and peptide sequences of 33 different proteins. Despite the absence of complete genome sequences of either tomato or F. oxysporum , 21 proteins were identified as tomato proteins and seven as fungal proteins. Thirteen of the tomato proteins were specific for infected plants. Sixteen tomato proteins were found in xylem sap for the first time, four of which were identified based on matches to expressed sequences only. Coding sequences for new proteins from F. oxysporum were identified through either direct matching to a database sequence, matching of peptide sequences to genome or expressed sequence tag databases of other Fusarium species, or PCR with degenerate primers on cDNA derived from infected plants followed by screening of a F. oxysporum BAC library. Together, these findings provide an excellent basis for further exploration of the interaction between xylem-colonizing pathogens and their hosts.     

Role of the Host Cell in Bacteriophage Morphogenesis: Effects of a Bacterial Mutation on T4 Head Assembly

In certain bacterial mutants, called groE, T4 phage head assembly is blocked specifically, implying that the host plays a direct role in head assembly. The block occurs early in the assembly process at the level of action of T4 gene 31.     

Differential Stimulation of PEP-carboxylation in Guard Cells and Mesophyll Cells by Ammonium or Fusicoccin

Dark CO₂-fixation in guard cells of Vicia faba was much moresensitive to ammonium than in mesophyll cells. Addition of ammonium(5.0 mol m^–3; pH₀ 7.6) caused up to a 7-fold increasein dark CO₂-fixation rates in guard cell protoplasts (GCP),whereas in leaf slices, mesophyll cells, and mesophyll protoplaststhe increase was only about 1.4-fold. In both cell or tissuetypes, total CO₂-fixation rates were higher in the light (2–12-foldhigher in GCP and 28-fold in mesophyll); these rates were onlyslightly changed by ammonium treatment. However, separationof ¹⁴C-labelled products after fixation of CO₂ in the lightby GCP revealed a large ammonium-induced shift in carbon flowfrom starch and sugars to typical products of C₄-metabolism(mainly malate and aspartate). In contrast, in mesophyll cellsamino acid and malate labelling was only moderately increasedby ammonium at the expense of sucrose. The data suggest thatin vivo ammonium might facilitate stomatal opening and/or delaystomatal closing through an increased production of organicacids. Key words: PEP-carboxylation, guard cell protoplasts, ammonium, fusicoccin     

Distribution and behaviour of Common Scoter Melanitta nigra relative to prey resources and environmental parameters

Offshore wind farms are proposed around the coast of the UK and elsewhere in Europe. These sites tend to be located in shallow coastal waters that often coincide with areas used by over-wintering Common Scoter Melanitta nigra . A large-scale study was undertaken to ascertain the relationship of the spatial distribution of Common Scoter in Liverpool Bay with prey abundance and environmental and anthropogenic variables that may affect foraging efficiency. The highest numbers of Common Scoter coincided with sites that had a high abundance and biomass of bivalve prey species. There was strong evidence that the maximum observed biomass of bivalves occurred at a mean depth of c. 14 m off the Lancashire coast and at c. 8 m off the north Wales coast. This coincided well with the distribution of Common Scoter at Shell Flat, but less well with the distribution of birds off North Wales. Common Scoters were observed in lowest numbers or were absent from areas in which anthropogenic disturbance (shipping activity) was relatively intense, even when these areas held a high prey biomass. Commercial fishing activities did not appear to contribute to this disturbance.     

Microbiological Synthesis of Fat: THE EFFECTS OF NITROGEN LEVEL ON THE METABOLISM OF PENICILLIUM LILACINUM THOM IN A SUCROSE MEDIUM

1. A study has been made of the relationships between the synthesesof carbohydrate, protein, and fat by Penicillium lilacinum Thomin presence of different amounts of sodium nitrate us a definedsucrose salts medium.
2. Under the defined experimental conditionsincreases in the concentrationof NO^–₂ in the medium werefollowed by increases in therates at which nitrogen and sugarwere taken up by the fungus,in the quantities assimilated,and in total and protein nitrogenin the felt. These conditionsprevailed so long as unassimilatedsugar was available.
3. Mediaof lower NO^–₃ concentration (for example, 0·32or 0·64 per cent. (w/v) NaNO^–₂;) yielded feltsricher in carbohydrate than were those grown in media of higherNO^–₂; content (0·96 or 1·28 per cent. (w/v)NaNO₃ The carbohydrate content of the felts increased graduallyuntil the sugar in the medium was exhausted; carbohydrate contentthen decreased.
4. Media of lower NO^–₃; concentration weremore conduciveto fat synthesis than those of higher NO^–₃;content.

     

Ammonium and phosphate regenerationby the zooplankton of an Amazon floodplain lake

SUMMARY. 1. Regeneration of ammonium and phosphate by macro-zooplankton (Cladocera. adult copepods. and copepodites) was measured in Lake Calado. an Amazon floodplain lake, Macrozooplanktonabundances ranged between 1×10⁴ and 3×10⁵ individuals m⁻².
2. Phosphate regeneration ranged from 0.2 to 1.3 μ mol PO₄ m⁻² b⁻¹at station 1. located 2 km from the Solimoes River, and from 1.6 to8.3 μ mol PO₄ m⁻² h ⁻¹ at station 3, located 7 km from the SolimoesRiver. Ammonium regeneration at stations 1 and 3 ranged from 1.7 to11.9 and from 13.4 to 77.2 μ mol NH₄ m⁻² h⁻¹. respectively.
3. Zooplankton regenerated ammonium and phosphate at similarrates during rising and falling waier. Regeneration by macrozooplankton was low compared to other tropical lakes and compared to microbesand microzooplankton in Lake Calado.     

Behavioural study of plasticity in host preferences of Trichogramma maidis (Hym.: Trichogrammatidae)

Abstract. To test the relative importance of genetic and environmental factors in host preferences of Trichogramma maidis Pint. & Voeg., a polyphagous parasitoid, the oviposition behaviour was analysed on two host species: Anagasta kuehniella used for mass rearing) and Ostrinia nubilalis a target pest). Females were compared according to the species on which they had been reared, and to that on which they had an oviposition experience. To quantify an oviposition sequence, the most frequent behavioural succession was established for each experimental situation, individual sequences were then compared with this standard one to count the number of additional behaviours. An affinity coefficient positively related to host acceptance was then calculated from these additional behaviours. A preference for O.nubilalis versus A kuehniella appeared, but rearing on A. kuehniella enhanced the level of spontaneous affinity for this unnatural host. These initial preferences were modified by an oviposition experience: the affinity for a given host was higher after an oviposition on the same species, which suggests a female's ability to learn. This learning ability was higher on the non-preferred host, which led to an equivalent final parasitic performance on both hosts. Moreover, the learning ability was specific to a given host, since the oviposition on a given species did not provide any improvement in the level of affinity for the other species.     

The Contribution of TRPV4-Mediated Calcium Signaling to Calcium Homeostasis in Endothelial Cells

A large variety of cation transport systems are involved in the regulation of calcium homeostasis in endothelial cells. The focus of the present study is to determine the contribution of nonselective cation channels from the TRP (transient receptor potential) family to cellular calcium homeostasis of porcine aortic endothelial cells (PAEC). One member of the TRPV (vanniloid) subfamily, TRPV4, has previously been shown to be involved in cation transport induced by a large variety of stimulations including osmolarity, temperature, mechanical stress, and phosphorylation. Here, we demonstrate the existence of several TRP proteins, including TRPV4, in PAEC using RT-PCR. To test whether this channel is functional, we performed FURA-2 calcium measurements and whole-cell patch-clamp experiments. We observed the induction of large calcium signals following mechanical stress, altered extracellular temperature, and the selective TRPV4 activator 4-α -PDD. These effects were diminished in the presence of the TRPV4 inhibitor miconazole, suggesting the involvement of this channel in mediating endothelial calcium signals. The large amounts of transported calcium and the short signaling ways suggest a potentially important role of this channel in many physiological processes.