Are brood sex ratios adaptive?—The effect of experimentally altered brood sex ratio on nestling growth,mortality and recruitment

Brood sex ratios (BSRs) have often been found to be nonrandom in respect of parental and environmental quality, and many hypotheses suggest that nonrandom sex ratios can be adaptive. To specifically test the adaptive value of biased BSRs, it is crucial to disentangle the consequences of BSR and maternal effects. In multiparous species, this requires cross-fostering experiments where foster parents rear offspring originating from multiple broods, and where the interactive effect of original and manipulated BSR on fitness components is tested. To our knowledge, our study on collared flycatchers (Ficedula albicollis) is the first that meets these requirements. In this species, where BSRs had previously been shown to be related to parental characteristics, we altered the original BSR of the parents shortly after hatching by cross-fostering nestlings among trios of broods and examined the effects on growth, mortality and recruitment of the nestlings. We found that original and experimental BSR, as well as the interaction of the two, were unrelated to the fitness components considered. Nestling growth was related only to background variables, namely brood size and hatching rank. Nestling mortality was related only to hatching asynchrony. Our results therefore do not support that the observed BSRs are adaptive in our study population. However, we cannot exclude the possibility of direct effects of experimentally altered BSRs on parental fitness, which should be evaluated in the future. In addition, studies similar to ours are required on various species to get a clearer picture of the adaptive value of nonrandom BSRs.     

Hearing in honeybees: localization of the auditory sense organ

Airborne sound signals emitted by dancing honeybees (Apis mellifera) contain information about the locations of food sources. Honeybees can perceive these near field sounds and rely on them to decode the messages of the dance language. The dance sound is characterized by rhythmical air particle movement of high velocity amplitudes. The aim of the present study was to identify the sensory structures used to detect near field sound signals. In an operant conditioning experiment, bees were trained to respond to sound. Ablation experiments with these trained bees revealed that neither mechanosensory hairs on the antennae or head nor bristle fields at the joints of the antenna, but Johnston's organ, a chordotonal organ in the pedicel of the antenna, is used to detect near field sound in honeybees.     

Metabolic engineering of Synechococcus elongatus for photoautotrophic production of mannitol

With multiple applications in food, pharmaceutical, and chemical industries as antioxidant or nonmetabolizable sweetener; the bioproduction of d -mannitol is gaining global attention, especially with photosynthetic organisms as hosts. Considering the sustainability prospects, the current work encompasses metabolic engineering of a widely used cyanobacterial strain, Synechococcus elongatus PCC 7942, and two newly isolated fast-growing cyanobacterial strains; S. elongatus PCC 11801 and S. elongatus PCC 11802, for mannitol production. We engineered these strains with a two-step pathway by cloning genes for mannitol-1-phosphate dehydrogenase (mtlD) and mannitol-1-phosphatase (mlp), where the mtlD expression was under the control of different promoters from PCC 7942, namely, P_rbc225, P_cpcB300, P_cpcBm1, P_rbcLm17, and P_rbcLm15. The strains were tested under the “switch conditions,” where the growth conditions were switched after the first 3 days, thereby resulting in differential promoter activity. Among the engineered strains of PCC 11801 and PCC 11802, the strains possessing P_rbc225-mtlD module produced relatively high mannitol titers of 401 ± 18 mg/L and 537 ± 18 mg/L, respectively. The highest mannitol titer of 701 ± 15 mg/L (productivity 60 mg/L.d, yield 895 µM/OD₇₃₀) was exhibited by the engineered strain of PCC 7942 expressing P_cpcB300-mtlD module. It is by far the highest obtained mannitol yield from the engineered cyanobacteria.     

On the analytic solution of electrotonic spread in branched passive dendritic trees

From the classical work of Rall it is known that the spread of electric potential in a passive dendritic tree may be obtained by expressing the initial conditions as a linear combination of a set of trigonometric eigenfunctions, each decaying with the associated time constant. It is shown here that in order to evaluate the permissible parameters in these eigenfunctions one may formulate the boundary conditions at all the junctions and endings of the dendritic tree as a set of homogeneous linear equations in which the parameters in the eigenfunctions are the unknowns. These equations have a nontrivial solution if the relevant determinant vanishes, a condition that permits the evaluation of the various parameters, thus providing an analytic approach to the expression of the eigenfunctions as well as the decay time constants. The above approach is illustrated by application to a dendritic tree that has a parent segments and two generations of offspring segments, without any restrictions as to the relative diameters or lengths of the various segments in the tree. General properties of the tree may be readily derived, like the variation of the eigenvalues on scaling of the lengths or diameters of all the segments. A few special cases with specified dimensions of the various segments are derived from the general case. In the case of a dendritic tree that fulfills the equivalent cylinder conditions, all of the eigenvalues and eigefunctions of the tree may be determined by the proposed method, including those that do not apply to the equivalent cylinder. The orthogonality properties of the eigenfunctions are discussed.     

Operational patterns affecting lactic acid production in ultrafiltration cell recycle bioreactor

Lactic acid production with cell recycling on an ultrafiltration tubular membrane reactor was studied; higher lactic acid concentrations as well as productivities were obtained under long-term fermentations compared with other high cell density systems. Different operational conditions, namely dilution rates and start-up modes, were assessed. Performances were very different at the three different dilution rates tested (D = 0.20 h(-1), D = 0.40 h(-1), or D = 0.58 h(-1)). The different behaviours are discussed and factors responsible for them are presented. The best way to operate for lactic acid production is chosen, the dilution rate of D = 0.40 h(-1) being the one providing the best overall performance. On the other hand, results show that of the two start-up modes tested, continuous start (membrane open) permits higher permeabilities throughout the operational runs than batch start (membrane closed). Operational stability was found to be directly associated with membranes that work at "steady state," the membrane permeability being kept around 15 L/m(2) h. Optimized cell bleed can improve time of operation if such membrane permeability can be maintained for a longer time. A comparison of results with those obtained in other lactic acid production systems is presented; such comparison shows that this tubular ultrafiltration membrane cell recycle reactor presents three important advantages: (1) concomitant lactic acid concentrations and productivities; (2) long periods of operation at reasonable permeabilities; and (3) good mechanical stability permitting the use of steam sterilization. (c) 1995 John Wiley & Sons, Inc.     

小麦提型不育系和杂交种种子生活力遗传改良初探

本试验共选用了4个提型不育系(A系)及其保持系(B系)、4个恢复系(R系)及其川7B/R4份F~1|代材料,用不同遗传背景的B、R系及川7B/R材料与A系杂交,种子成熟时收获干燥考种,度过休眠期后进行发芽试验。结果表明,父本对F~0|种子千粒重存在胚乳直感现象;川3A、川4A与其它B系杂交,其F~0|种子的千粒重、饱满度、发芽率和发芽势均有不同程度的提高;川4A×R和川6A×R的杂种种子千粒重多分别比川4A×川7B/R和川6A×川7B/R的高,但前种组合(A×R)的种子发芽和发芽率远不如后一种组合(A×川7B /R)的种子,且前种组合的穗发芽率也较高。作者认为,利用A系与农艺性状相近、但遗传背景各异的B系杂交,或在R系中输入抗提型细胞质负影响的高种子生活力基因, 是提高A系和杂交种种子生活力的值得注意的途径。 Abstract:The objective of this paper is trying to grope for ways of improving sced viability of A-line and hybrid in wheat with T.timopheevi cytoplasm.Four A lines and their B lines,4 restorers (R line) and 4 crosses of Chuan 7B/R were used.The combinations of A×B,A×R and A×Chuan 7B/R were madc,and 1 000-grain weight (GW),rate of pre-harvest sprouting(RPHS),germinating energy(GE) and germination percentage (GP) of their F0 seeds were investigated.The results showed that the GW,full weight,GE and GP of the seeds of Chuan 3A and 4A×other B lines were higher than those of Chuan 3A×3B and chuan 4A×4B;although the GW of Chuan 4A and 6A×R were heavier than those of Chuan 4A and 6A×Chuan 7B/R,the GE and GP of the latter crosses increased largely and their RPHScs were less.Therefore,it was considered as effective ways for improvement on seed viability,that A lines cross with other B lines having different genetic background but similar agronomic characters and that the gene(s) concerning high seed viability were transferred into restorers.     

Changes in eicosapentaenoic acid content of Navicula saprophila, Rhodomonas salina and Nitzschia sp. under mixotrophic conditions

Three species of microalgae able to produce eicosapentaenoic acid(EPA) were collected from brackish and sea water around Japan. The species were identified as Navicula saprophila, Rhodomonassalina and Nitzschia sp. EPA as a proportion of total fatty acids increased in the presence of acetic acid for Rhodomonas salina and Nitzschia sp. However, Navicula saprophila displayed the greatest productivity of EPA and the EPA content of its biomass was enhanced under mixotrophic conditions in the presence of acetic acid. This revised version was published online in August 2006 with corrections to the Cover Date.     

Effects of litter accumulation and water table on morphology and productivity of Phragmites australis

Phragmites australis (Common reed) occurs in the interface between water and land. The water depth gradient from deep water to dry land is inversely related to litter accumulation. Eutrophication can result in an excessive production of litter, which may have a large impact on the occurrence of P. australis in this gradient. In an outdoor pot experiment, it was investigated how water tables in combination with substrates containing variable amounts of litter affect morphology and productivity of P. australis. Vegetatively propagated P. australis was grown in pots filled with river sand, litter, and different mixtures of sand and litter (25, 50 and 75% by volume). Four water table treatments were applied; drained (–12 cm), waterlogged (0 cm), flooded (+12 cm), and weekly fluctuating drained and flooded conditions (–12/+12 cm of water relative to substrate level). When drained, no differences between substrate treatments were present. Waterlogging, flooding fluctuating water table treatments caused growth reduction in substrate containing litter. The plants formed short shoots and thin rhizomes. With increasing water table, allocation of dry matter to stems increased at the expense of leaves and rhizomes. At intermediate levels of litter in the substrate, allocation to leaves was lowest. In both instances a lower leaf weight ratio (LWR) was (partly) compensated for by a higher specific leaf area (SLA), resulting in less pronounced differences in leaf area ratio (LAR). Aquatic roots developed when plants were waterlogged or flooded, and increased when litter was present in the substrate. Aquatic roots were formed in the top soil layer when waterlogged. The percentage of aquatic roots increased with increasing amount of litter in the substrate when plants were flooded. It was concluded that the morphological responses of P. australis to litter strongly constrain its ability to maintain itself in deep water when the substrate contains litter. This might one of the explanations for the disappearance of P. australis along the waterward side of littoral zones.     

Human Platelet Sulfotransferase Shows Seasonal Rhythms

Our study aimed to investigate the possible presence of seasonal changes in platelet phenolsulfotransferase (ST) in a group of 20 healthy, drug-free subjects of both sexes and between 24 and 37 years of age. Blood samples were taken four times a year in the period immediately following the equinoxes and the solstices. The results showed that both STs underwent seasonal changes: the lowest values were found in autumn and in winter, and the highest in the summer. A positive correlation between the two STs and the length of the photoperiod was observed in winter, whereas in the spring we detected a negative correlation between the TL ST and the photoperiod length. Future studies should clarify whether platelet ST of patients with mood disorders shows a similar seasonality.     

Stabile production of a thrombin resistant pro-urokinase derivative (PRO-UKS1) by Namalwa KJM-1 cells adapted to serum-free medium

Pro-UKS1 was designed as a thrombin-resistant derivative of pro-urokinase (pro-UK) by introducing a glycosylation site using site-directed mutagenesis. An expression plasmid for pro-UKS1, pMo1UKS1SEd1-5, was constructed and introduced into Namalwa KJM-1 cells (Hosoiet al., 1988), and cells resistant to G418 and Methotrexate (MTX) were obtained. Amongst them, the highest pro-UKS1 producer (resistant to 500 nM of MTX), clone 41-8, was selected and further characterized. Clone 41-8 was cultured in serum-free ITPSGF medium (Hosoiet al., 1988). Under the conventional conditions, the concentration of pro-UKS1 reached 26 g ml^–1. Addition of glucose and tri-iodothyronine (T₃) improved productivity, and the maximal productivity of pro-UKS1 was 67 g ml^–1 day^–1. In this conditioned medium, content of pro-UKS1 was above 80% of total proteins.Abbreviations BSA bovine serum albumin - dhfr dihydrofolate reductase - HEPES 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid - kb kilobase pairs - kDa kilodaltons - MTX Methotrexate - PBS phosphate buffered saline - pro-UK pro-urokinase - SDS-PAGE sodium dodecyl sulfate-polyacrylamide gel electrophoresis - T₃ tri-iodothyronine - Tween-PBS phosphate buffered saline containing 0.05% Tween 80