Partial migration: niche shift versus sexual maturation in fishes

Summary Many fish populations have both resident and migratory individuals. Migrants usually grow larger and have higher reproductive potential but lower survival than resident conspecifics. The decision about migration versus residence probably depends on the individual growth rate, or a physiological process like metabolic rate which is correlated with growth rate. Fish usually mature as their somatic growth levels off, where energetic costs of maintenance approach energetic intake. After maturation, growth also stagnates because of resource allocation to reproduction. Instead of maturation, however, fish may move to an alternative feeding habitat and their fitness may thereby be increased. When doing so, maturity is usually delayed, either to the new asymptotic length, or sooner, if that gives higher expected fitness. Females often dominate among migrants and males among residents. The reason is probably that females maximize their fitness by growing larger, because their reproductive success generally increases exponentially with body size. Males, on the other hand, may maximize fitness by alternative life histories, e.g. fighting versus sneaking, as in many salmonid species where small residents are the sneakers and large migrants the fighters. Partial migration appears to be partly developmental, depending on environmental conditions, and partly genetic, inherited as a quantitative trait influenced by a number of genes.     

Estimating tree-based dynamic treatment regimes using observational data with restricted treatment sequences

A dynamic treatment regime (DTR) is a sequence of decision rules that provide guidance on how to treat individuals based on their static and time-varying status. Existing observational data are often used to generate hypotheses about effective DTRs. A common challenge with observational data, however, is the need for analysts to consider “restrictions” on the treatment sequences. Such restrictions may be necessary for settings where (1) one or more treatment sequences that were offered to individuals when the data were collected are no longer considered viable in practice, (2) specific treatment sequences are no longer available, or (3) the scientific focus of the analysis concerns a specific type of treatment sequences (eg, “stepped-up” treatments). To address this challenge, we propose a restricted tree–based reinforcement learning (RT-RL) method that searches for an interpretable DTR with the maximum expected outcome, given a (set of) user-specified restriction(s), which specifies treatment options (at each stage) that ought not to be considered as part of the estimated tree-based DTR. In simulations, we evaluate the performance of RT-RL versus the standard approach of ignoring the partial data for individuals not following the (set of) restriction(s). The method is illustrated using an observational data set to estimate a two-stage stepped-up DTR for guiding the level of care placement for adolescents with substance use disorder.     

Vertically stratified frugivore community composition and interaction frequency in a liana fruiting across forest strata

Vertical stratification is a key feature of tropical forests and structures plant–frugivore interactions. However, it is unclear whether vertical differences in plant-frugivore interactions are due to differences among strata in plant community composition or inherent preferences of frugivores for specific strata. To test this, we observed fruit removal of a diverse frugivore community on the liana Marcgravia longifolia in a Peruvian rain forest. Unlike most other plants, Marcgravia longifolia produces fruits across forest strata. This enabled us to study effects of vertical stratification on fruit removal without confounding effects of plant species and stratum. We found a high number of visits of a few frugivore species in the understorey and a low number of visits of many different frugivores in the canopy and midstorey. Whereas partial and opportunistic frugivores foraged across strata with differing frequencies, obligate frugivores were only found eating fruits in the higher strata. Avian frugivores foraging in the canopy were mainly large species with pointed wings, whereas under- and midstorey avian foragers were smaller with rounded wings. Our findings suggest a continuous shift in the frugivore community composition along the vertical gradient, from a few generalized frugivores in the understorey to a diverse set of specialized frugivores in the canopy. This shift in the frugivore community leads to correlated, reciprocal changes from specialized to generalized plant-frugivore interactions. Thus, we conclude that vertical niche differentiation between species in tropical forests persists even when food resources are available across strata. This highlights its role for promoting biodiversity and ecosystem functioning.     

3D 13C/1H NMR-based assignments for side-chain resonances of Lactobacillus casei dihydrofolate reductase. Evidence for similarities between the solution and crystal structures of the enzyme

Summary ¹³C-based three-dimensional ¹H–¹H correlation experiments have been used to determine essentially complete ¹³C and ¹H resonance assignments for the amino acid side chains of uniformly ¹³C/¹⁵N labelled L. casei dihydrofolate reductase in a complex with the drug methotrexate. Excellent agreement is observed between these assignments and an earlier set of partial assignments made on the basis of correlating nuclear Overhauser effect and crystal structure data, indicating that the tertiary structure of the enzyme is similar in solution and in the crystal state.To whom correspondence should be addressed.     

催产时鳝卵磷酸酶活性的变化及其与排卵的关系

本实验采用Gomori组织化学法和磷酸苯二钠法,分别检测黄鳝卵ALP、ACP的细胞定位和活性变化。结果表明,催产后72h,ALP活性显著高于临近注射时(Oh),催产后48h和96h(p<0.05);临产前(催产后96h),ACP活性极显著高于试验组其它各时程(p<0.01)。提示ALP和ACP活性增强与卵母细胞成熟、排放有直接关系。本研究为探索排卵机制提供资料。     

Evaluation of Probiotic Properties of Novel Brazilian Lactiplantibacillus plantarum Strains

Probiotics and Antimicrobial Proteins - Beneficial effects of Lactiplantibacillus plantarum strains have been widely reported. Knowing that the effects of probiotic bacteria are strain-dependent,...     

PATTERNS OF PLANT ONTOGENY THAT MAY INFLUENCE GENOMIC STASIS

It is an axiom in biology that genes control the ontogeny and ultimately the final form of an organism. In plants a given morphological form can often arise through more than one ontogenetic pattern of cell divisions. Different ontogenetic patterns have different properties with regard to the final age in cell divisions of the initials in the meristems for a given morphological form. If mutation per genome per cell division is an important biological metric, then since the age of a cell in cell divisions is a function of ontogeny, the cellular ontogeny will influence the degree of mutation-loading in meristematic initials. Thus, ontogeny and form may affect the genes (by promoting or lessening genomic stasis) as well as, of course, being determined by the genes. This paper explores mathematically the relationship between different patterns of cell division and mutation-loading.     

A transposon insertion in the Arabidopsis SSR16 gene causes an embryo-defective lethal mutation

The SSR16 gene of Arabidopsis has been identified as a gene encoding a ribosomal protein S16 homolog through analysis of a transposon insertion mutation. The insertion mutation is lethal, arresting embryonic development at approximately the transition from the globular to the heart stage of embryonic development. Co-segregation of the mutant phenotype with the transposon-borne drug-resistance marker and loss of the inserted transposon concomitant with phenotypic reversion provided evidence that the transposon had caused the mutation. Sequences flanking the insertion site were amplified from DNA of viable heterozygotes by thermal asymmetric interlaced (TAIL) PCR. The amplified fragment flanking the 3' end of the inserted element was sequenced and found to be identical to an Arabidopsis expressed sequence tag (EST). The EST, in turn, contained a coding sequence homologous to the ribosomal protein S16 (RPS16) of bacteria such as Escherichia coli, Bacillus subtilis and Salmonella typhimurium , as well as Neurospora crassa mitochondria and higher plant plastids. Thus the gene identified by the embryo-defective lethal insertion mutation encodes an RPS16 homolog and has been designated the SSR16 gene.