The steroids of hexactinellid sponges

The Hexactinellida ('glass sponges') are commonly considered to be the most basic metazoans. Steroids of 20 species from different taxa were studied for chemotaxonomy and biosynthetic implications. All Hexactinellida contain cholest-5-en-3#-ol (cholesterol) and/or its saturated derivative 5!(H)-cholestan-3#-ol, along with their C-24-alkylated homologues. Where 5!(H)-stanols are present, they regularly co-occur with their 3-keto analogues. The steroid concentrations generally decrease with increasing carbon numbers, similar to sterol distributions typically found in marine sediments. These features argue against de novo sterol biosynthesis operating in hexactinellid sponges. Rather, we suggest a dietary uptake of (⁵-stenols and their stereoselective transformation via 3-keto intermediates to 5!(H)-stanols.     

Prenatal demonstration of a cervical myelocystocele

Myelocystocele is a rare spinal cord disorder and has not been described prenatally. We report a case in which prenatal ultrasound and magnetic resonance imaging (MRI) demonstrated a posterior cervical mass which was initially thought to be a meningocele or an atypical cystic hygroma. Surgery performed at 1 day of age showed this to be a myelocystocele. Therefore, the differential diagnosis of an extracranial cystic mass in the posterior cervical region should be expanded to include myelocystoceles.     

Interstitial deletions without phenotypic effect: Prenatal diagnosis of a new family and brief review

A 39-year-old woman (G4P1SAB2) was referred for amniocentesis for advanced maternal age. An interstitial deletion of the G-dark band 11 pi 2 was found in the fetus. Blood from the mother and her previous son was cultured and the same deletion was found in both. The absence of phenotypic effect in this family further confirms that G-dark euchromatic deletions are compatible with a normal phenotype, and underlines the importance of checking familial karyotypes even when apparently unbalanced structural rearrangements are found at prenatal diagnosis.     

应对不确定性:呼吁建立新的科学政策论坛

科学界和政策界具有不同的目标,这就自然导致了对构成某种变化或现象的"检验"标准的差异,以及用不同的方法去描述不确定性和风险的持性及传达不确定性和风险.这些差异可能损害科学家、决策者和公众之间的有效沟通,同时也限制了科学家所愿意研究的社会紧迫问题的类型.本文主要回顾了一系列处理不确定性问题的方法,阐述了当科学和政策不能很好协调时所可能引起的一些错误.并在此基础上,特别针对解决不确定性问题提出了一些具体建议,包括重构科学规范,建立由科学、政策两方面领导广泛参加的科学政策论坛.     

Flexible bat echolocation: the influence of individual,habitat and conspecifics on sonar signal design

Acoustic signals which are used in animal communication must carry a variety of information and are therefore highly flexible. Echolocation has probably such functions and could prove as flexible. Measurable variabitlity can indicate flexibility in a behaviour. To quantify variability in bat sonar and relate to behavioural and environmental factors, I recorded echolocation calls of Euderma maculatum, Eptesicus fuscus, Lasiurus borealis and L. cinereus while the bats hunted in their natural habitat. I analysed 3390 search phase calls emitted by 16 known and 16 unknown individuals foraging in different environmental and behvioural situations. All four species used mainly multiharmonic signals that showed considerable intra- and inter-individual variability in the five signal variables I analysed (call duration, call interval, highest and lowest frequency and frequency with maximum energy) and also in the shape of the sonagram. A nested multivariate analysis of variance identified the influences of individual, hunting site, close conspecifics and of each observation on the frequency with maximum energy in the calls, and on other variables measured. Individual bats differed in multiple comparisons, most often in the main call frequency and least often in call interval. In a discriminant function analysis with resubstitution, 56–76% of a species' calls were assigned to the correct individual. Distinct individual call patterns were recorded in special situations in all species and the size of foraging areas in forested areas influenced temporal and spectral call structure. Echolocation behaviour was influenced by the presence of conspecifics. When bats were hunting together, call duration decreased and call interval increased in all species, but spectral effects were less pronounced. The role of morphometric differences as the source of individually distinct vocalizations is discussed. I also examined signal adaptations to long range echolocation and the influence of obstacle distance on echolocation call design. My results allow to discuss the problems of echo recognition and jamming avoidance in vespertilionid bats.