Colcemid effects on homologue pairing and crossing over during fetal mouse oogenesis

Summary Colcemid was administered to gestational day 13 female mice to test effects on homologue pairing, synapsis and recombination of fetal oogenesis. Pairing abnormalities were detected in pachytene oocytes by light and electron microscopy examination of bivalents and synaptonemal complexes. Reduction of total chiasmata per treated diplotene oocyte (22.74) compared to controls (31.07) was found.     

Influence of Various Parameters on Collapse Behaviour of Thin Cylinders

Axial compression experiments on as received aluminum tubes and tubes with wall thickness eccentricity incorporated by off centre machining showed that the eccentricity caused transition of their collapse mode from axisymmetric to diamond. The numerical simulation of the collapse phenomenon was undertaken using a static non-linear Finite Element Analysis in ANSYS, and results are found to compare well with the experimental load compression and energy absorption responses for axisymmetric concertina and non-axisymmetric diamond modes. Having validated the numerical model with experiments, it has been used to undertake a systematic study of the load - compression characteristics and collapse mode transitions of the tubes with varying eccentricities in wall thickness and boundary conditions, as well as the material properties.     

Altered brain cholinergic enzymes activity in the genetically obese rat

Genetically obese male Zucker rats (fa/fa) and their lean littermates (Fa/-) were used in this experiment. Fourteen-week-old obese and lean littermates were sacrificed and choline acetyltransferase (ChAT) and acetylcholinesterase (AChE) enzymes were assayed in specific brain regions. The assays of these enzymes indicate that obese animals had a significantly lower ChAT activity in the cerebellum, pons, and cerebral cortex and a significant increase in ChAT activity in the thalamus and hypothalamus. Meanwhile, the cerebral cortex, cerebellum, midbrain, thalamus and hypothalamus of the obese animals showed significantly higher AChE activity than their lean littermates. It was concluded from this study that obesity may be associated with changes in the enzymes of the brain cholinergic system.     

A threshold stochastic volatility model

This article introduces a new model to capture simultaneously the mean and variance asymmetries in time series. Threshold non‐linearity is incorporated into the mean and variance specifications of a stochastic volatility model. Bayesian methods are adopted for parameter estimation. Forecasts of volatility and Value‐at‐Risk can also be obtained by sampling from suitable predictive distributions. Simulations demonstrate that the apparent variance asymmetry documented in the literature can be due to the neglect of mean asymmetry. Strong evidence of the mean and variance asymmetries was detected in US and Hong Kong data. Asymmetry in the variance persistence was also discovered in the Hong Kong stock market. Copyright © 2002 John Wiley & Sons, Ltd.     

Endogenous nitric oxide release required for long-term synaptic depression in the cerebellum.

Conjunctive stimulation of climbing and parallel fibres in the cerebellum evokes a long-term depression of parallel-fibre Purkinje-cell transmission, a phenomenon implicated as the cellular mechanism for cerebellar motor learning. It is suspected that the increase in cyclic GMP concentration that occurs after activation of climbing fibres is required to evoke long-term depression. Excitatory amino acids are known to cause the release of nitric oxide (NO), resulting in elevation of the cGMP level in the cerebellum. Here we report that endogenous NO is released after stimulation of climbing fibres, that long-term depression evoked by conjunctive stimulation of parallel and climbing fibres is blocked by haemoglobin (which strongly binds NO) or L-NG-monomethyl-arginine (an inhibitor of NO synthase), and that exogenous NO or cGMP can substitute for the stimulation of climbing fibres to cause long-term depression in rat cerebellar slices. These results demonstrate that the release of endogenous NO is essential for the induction of synaptic plasticity in the cerebellum.     

Involvement of p34cdc2 in establishing the dependency of S phase on mitosis

Mutants of cdc2+ can disrupt the dependency of S phase on completion of the previous mitosis. By changing the state of p34cdc2 it is possible to reprogramme a cell from entering mitosis to undergoing S phase. This leads to the proposal that the cell cycle can be considered a p34cdc2 cycle, and has implications for the evolution of life cycles.     

Stormwater Management in Hong Kong

IntroductionStormwater management(SWM) in Hong Kong isthe responsibility of the drainage servicesdepartment (DSD) of the Governmentof the HongKong Special Administrative Region.Thedepartment is charged with the formulation ofpolicy and the design,construction,operation andmaintenance of all public stormwater drainagesystems,as well as approving private drainsthrough an administrative framework.　 The principal concern of SWM is the reductionof the risk and extent of flooding.Thus,thesuc…     

DNA in wheat seeds from European archaeological sites

We have used hybridization analysis to detect ancient DNA in wheat seeds collected from three archaeological sites in Europe and the Middle East. One of these samples, carbonizedT. spelta dated to the first millennium BC, has yielded PCR products after amplification with primers directed at the leader regions of the HMW (high molecular weight) glutenin alleles. Sequences obtained from these products suggest that the DNA present in the Danebury seeds is chemically damaged, as expected for ancient DNA, and also indicate that it should be possible to study the genetic variability of archaeological wheat by ancient DNA analysis. Finally, we describe a PCR-based system that enables tetraploid and hexaploid wheats to be distinguished.