Molecular prenatal diagnosis of Smith–Lemli–Opitz syndrome is reliable and efficient

Smith–Lemli–Opitz (RSH) syndrome (SLOS, OMIM 270400) is a relatively common, autosomal recessive disorder of cholesterol biosynthesis with a broad spectrum of phenotypic abnormalities caused by mutations of the 7-dehydrocholesterol reductase gene (DHCR7) on chromosome 11. Prenatal diagnosis can be established by detection of elevated 7-dehydrocholesterol or of SLOS-causing mutations in the DHCR7 gene. We report here our experience with molecular prenatal diagnosis of SLOS. Mutation analysis of the DHCR7 gene was performed in chorionic villus samples of 13 pregnancies of couples with a family history of SLOS and known SLOS genotypes. This approach is accurate and reliable. If facilities for biochemical analysis are not available, or in cases with ambiguous biochemical patterns, molecular prenatal diagnosis is an attractive, alternative option. Copyright © 2002 John Wiley & Sons, Ltd.     

The biology of a subtropical population of Halictus ligatus Say (Hymenoptera: Halictidae)

Summary A large population of Halictus ligatus was studied in the subtropical climate of Knights Key, Monroe County, Florida. The dissection of 858 female bees caught on flowers and 420 bees from completely excavated nests gives the following picture of phenology, colony development and social organisation. In the Florida keys, H. ligatus is continuously brooded and multivoltine. However, towards the coldest time of year young gynes may rest in their natal nests rather than found a new colony. This may result in a partial synchronisation of nest initiation when warm weather returns after a particularly cold spell. Most nests are started by a single foundress that usually survives until near the end of the production of reproductives. The first brood is very variable in size and males average 11% of the bees produced at this stage. This figure increases to 56% when the first brood workers begin provisioning. Queens are produced some time after the rise in male production and colony longevity is extended by the presence of some worker brood during this phase. Queens average 16% larger than their workers but appear to exert little inhibition of worker reproductivity: 57% of worker bees mate and 68% show ovarian development. This population is unique amongst social halictines in being continuously brooded, multivoltine and in having such weak physiological caste differentiation. It seems to represent an intermediate stage between the primitively eusocial colonies of H. ligatus found in temperate regions and the communal-like ones of the tropics.     

Social evolution and its correlates in bees of the subgenus Evylaeus (Hymenoptera; Halictidae)

Summary Eleven behavioural characteristics of eight species of the subgenus Evylaeus were analysed using principal components analysis. The first component axis represents social level and explains over forty percent of the total variation in the data. The following characteristics are highly correlated with social level — (i) a reduction in the proportion of males in the first brood, (ii) a reduction in the proportion of workers that mate, (iii) a reduction in the proportion of workers that have developed ovaries, (iv) an increase in the mean number of workers, (v) increased contact between adults and developing brood and (vi) an increase in the size difference between queens and workers. Because these factors appear, in general, to be under the control of the queen it is argued that parental manipulation has been an important component of social evolution in these bees. The number of worker broods and the mechanism of male production are also related to social level but are less important. Nest architecture, nest defense and polygyny seem to be unrelated to social level. Variation in nest architecture may be in response to edaphic features of the substrate. The lack of any relationship between polygyny and social level implies that the semisocial route to eusociality was not the one taken. It is likely that polygyny can only occur where the substrate is suitable for the winter hibernation of sisters in their natal nest. Multivariate methods are useful in determining the relative social level of closely related halictine species.     

Identification of material flow systems

Material Flow Analysis (MFA) has become an important instrument in environmental science and pollution research. In this paper, we look at the MFA problem as a particularly structured system identification problem. Special emphasis is given to the linear, static case, where we describe a procedure for reconciliating the flow measurements and for estimating the unmeasured flows and the transfer coefficients by taking into account a priori restrictions such as balance equations.     

Neurobiology of the homing pigeon—a review

Homing pigeons are well known as good homers, and the knowledge of principal parameters determining their homing behaviour and the neurological basis for this have been elucidated in the last decades. Several orientation mechanisms and parameters—sun compass, earth’s magnetic field, olfactory cues, visual cues—are known to be involved in homing behaviour, whereas there are still controversial discussions about their detailed function and their importance. This paper attempts to review and summarise the present knowledge about pigeon homing by describing the known orientation mechanisms and factors, including their pros and cons. Additionally, behavioural features like motivation, experience, and track preferences are discussed. All behaviour has its origin in the brain and the neuronal basis of homing and the neuroanatomical particularities of homing pigeons are a main topic of this review. Homing pigeons have larger brains in comparison to other non-homing pigeon breeds and particularly show increased size of the hippocampus. This underlines our hypothesis that there is a relationship between hippocampus size and spatial ability. The role of the hippocampus in homing and its plasticity in response to navigational experience are discussed in support of this hypothesis.     

工业粉体下落过程粉尘排放特性的实验研究

根据与维也纳工业大学化学工程研究所共同确定的实验方案,在实验室开发并设计了一套自由下落装置,研究粉体下落过程中粉尘的排放特性。通过实验主要测定下落高度、空气湿度和质量流量对粉尘排放的影响。实验结果表明,下落高度和空气湿度对粉尘排放均有影响,且空气湿度对粗粒子的排放影响较大,对细粒子影响较小;随着质量流量的增加,粉尘产生率逐渐减小,但质量流量的增加也会增加粉尘浓度,加重了对工人的危害。建立了影响因素与粉尘产生率之间的数学模型,经检验,二者之间存在显著相关,实测值与理论计算值基本一致,可以应用已建立的数学模型定量评价粉尘产生量。