The population-attributable fraction for time-dependent exposures using dynamic prediction and landmarking

The public health impact of a harmful exposure can be quantified by the population-attributable fraction (PAF). The PAF describes the attributable risk due to an exposure and is often interpreted as the proportion of preventable cases if the exposure was extinct. Difficulties in the definition and interpretation of the PAF arise when the exposure of interest depends on time. Then, the definition of exposed and unexposed individuals is not straightforward. We propose dynamic prediction and landmarking to define and estimate a PAF in this data situation. Two estimands are discussed which are based on two hypothetical interventions that could prevent the exposure in different ways. Considering the first estimand, at each landmark the estimation problem is reduced to a time-independent setting. Then, estimation is simply performed by using a generalized-linear model accounting for the current exposure state and further (time-varying) covariates. The second estimand is based on counterfactual outcomes, estimation can be performed using pseudo-values or inverse-probability weights. The approach is explored in a simulation study and applied on two data examples. First, we study a large French database of intensive care unit patients to estimate the population-benefit of a pathogen-specific intervention that could prevent ventilator-associated pneumonia caused by the pathogen Pseudomonas aeruginosa. Moreover, we quantify the population-attributable burden of locoregional and distant recurrence in breast cancer patients.     

Genetic polymorphism and cancer susceptibility: evidence concerning acetyltransferases and cancer of the urinary bladder

Acetyltransferase enzymes expressed in hepatic and extrahepatic tissues are products of an acetyltransferase gene locus. Acetylation capacity is regulated by simple autosomal Mendelian inheritance of two codominant alleles at this locus. Human slow acetylators are predisposed to bladder cancer from arylamine chemicals. The role of the bladder in arylamine metabolism and of bladder acetyltransferases in the etiology of bladder cancer is not fully understood, but the acetylator genotype-dependent expression of arylamine N-acetyltransferase and N-hydroxyarylamine O-acetyltransferase in bladder cytosol may contribute towards the genetic predisposition of human slow acetylators to arylamine-induced bladder cancer.     

Reduplication and repetition of person markers in Guaporé isolates

The person marking system of the language isolate Kwazá, spoken in the Brazilian Amazon, has several unusual properties. Its bound inflectional person suffixes can be reduplicated in order to express temporal and aspectual notions in a rather un-iconic way. The reduplicated segments are not defined by phonotactic boundaries, such as the syllable, but they are based on morphological units, disregarding their phonotactic structure. The origin and nature of this rare type of reduplication are not very clear. Morphologically based reduplication is not attested in the neighbouring languages with which Kwazá forms a linguistic area. However, Kwazá person markers are also involved in an unusual type of recursive construction that is encountered in the neighbouring languages, too. Recursive application of person markers occurs in Kwazá to express quoted speech in a transparent manner and has also given rise to less transparent expressions such as the desiderative. Similar constructions in the Aikanã and Wari’ languages suggest that this quotative construction is an areal feature of at least the Brazilian part of the Guaporé region. The quotative construction may help to understand the poorly understood phenomenon of seemingly redundant person marking in Kanoê, another language isolate of the region. It remains a question whether it also plays a role in the origin of the unique morphologically determined reduplication constructions of Kwazá.     

Notes on the induced reproduction and development of the tigerfish,Hydrocynus vittatus (Characidae), embryos and larvae

Synopsis In South Africa, the distributional range of tigerfish,Hydrocynus vittatus, has diminished over the past fifty years mainly as a result of migration barriers and reduced river flow. A project to restock traditional tigerfish waters has been envisaged for many years but did not materialise due to an inability to spawn this species artificially. Several hormones were therefore tested for their potency to induce ovulation in this species. Gonadotropin releasing hormones (GnRh) were used in combination with dopamine receptor antagonists. Human chorionic gonadotropin (HCG) was administered in conjunction with catfish pituitary gonadotropin. Both sexes were successfully stripped and the eggs were inseminated artificially. Tigerfish eggs are small (0.65 mm diameter), demersal and slightly adhesive. Hatching occurs 22 h 30 min after insemination and free embryos are pelagic and display continuous vertical movement for a period of three days. Embryonic development was photographed until first feeding, 5 days after hatching. From these results as well as field observations, it is concluded that tigerfish spawns on a sandy substrate in the vicinity of aquatic vegetation.     

Marine Bacteroidetes enzymatically digest xylans from terrestrial plants

Marine Bacteroidetes that degrade polysaccharides contribute to carbon cycling in the ocean. Organic matter, including glycans from terrestrial plants, might enter the oceans through rivers. Whether marine bacteria degrade structurally related glycans from diverse sources including terrestrial plants and marine algae was previously unknown. We show that the marine bacterium Flavimarina sp. Hel_I_48 encodes two polysaccharide utilization loci (PULs) which degrade xylans from terrestrial plants and marine algae. Biochemical experiments revealed activity and specificity of the encoded xylanases and associated enzymes of these PULs. Proteomics indicated that these genomic regions respond to glucuronoxylans and arabinoxylans. Substrate specificities of key enzymes suggest dedicated metabolic pathways for xylan utilization. Some of the xylanases were active on different xylans with the conserved β-1,4-linked xylose main chain. Enzyme activity was consistent with growth curves showing Flavimarina sp. Hel_I_48 uses structurally different xylans. The observed abundance of related xylan-degrading enzyme repertoires in genomes of other marine Bacteroidetes indicates similar activities are common in the ocean. The here presented data show that certain marine bacteria are genetically and biochemically variable enough to access parts of structurally diverse xylans from terrestrial plants as well as from marine algal sources.