Instability of long inverted repeats within mouse transgenes.

Various sequences in the mammalian genomes are unstable. One class of sequence arrangement is long inverted repeats, which are known to be unstable in bacteria and yeast. While in mammals some evidence suggests that short inverted repeats (<10 bp long) may show instability, nothing is known about the stability of long inverted repeats. Here we describe two unrelated multicopy transgenes in the mouse (loci 109 and OX1-5), each of which contains a long inverted repeat that shows substantial mitotic instability. This instability also occurs in the germline so that mutant transgenes appear within pedigrees at a high frequency. The mutation processes acting at these two inverted repeats are complex and can involve insertion or deletion, and can result in stabilization of the transgene. At transgene 109 mutational events range from very small rearrangements at the centre of the inverted repeat to complete transgene deletion. In addition we show that the rates of mutation at the inverted repeat of transgene OX1-5 can vary between the male and female germlines and between inbred strains of mice, suggesting the possibility of a genetic analysis to identify loci that modulate inverted repeat instability.     

Formation of the sea urchin male pronucleus in vitro: Membrane-independent chromatin decondensation and nuclear envelope-dependent nuclear swelling

We demonstrate that complete sea urchin male pronuclear development in vitro is a two-step process involving membrane-independent chromatin decondensation and nuclear envelope-dependent pronuclear swelling. In the absence of cytoplasmic membrane vesicles (MVs), permeabilized sperm chromatin decondenses into a spherical nucleus of ≈4 μm in diameter. Pronuclear swelling to ≈7 μm requires an intact nuclear envelope, and the degree of swelling is limited by the amount of MVs assembled on the chromatin. Furthermore, after a nuclear envelope is formed, swelling can occur in the absence of additional cytoplasmic MVs. Nuclear swelling also requires ATP hydrolysis, Ca²⁺ and cytosolic factors, some of which are sensitive to heat and to the sulfhy-dryl alkylating agent, N-ethylmaleimide. The requirement for a nuclear envelope and the rate of pronuclear swelling are consistent with previous in vivo observations. © 1995 wiley-Liss, Inc.     

Thermodynamic study of motor behaviour optimization

Our work is aimed at studying the optimization of a complex motor behaviour from a global perspective. First, free climbing as a sport will be briefly introduced while emphasizing in particular its psychomotor aspect called route finding. The basic question raised here is how does the optimization of a sensorimotoricity-environment system take place. The material under study is the free climber's trajectory, viewed as the signature of climbing behaviour (i.e., the spatial dimension). The concepts of learning, optimization, constraint, and degrees of freedom of a system will be discussed using the synergistic approach to the study of movement (Bernstein, 1967; Kelso, 1977). Measures of a trajectory's length and convex hull can be used to define an index whose equation resembles that of an entropy. This index is a measure of the trajectory's overall complexity. Some important concepts related to the thermodynamics of curves will also be discussed. The optimization process will be studied by examining the changes in entropy over time for a set of trajectories generated during the learning of a route (ten successive repetitions of the same climb). It will be shown that the entropy of the trajectories decreases as learning progresses, that each level of expertise has its own characteristic entropy curve, and that for the subjects tested, the mean entropy of skilled climbers is lower than that of average climbers. Basing our analysis on the concepts of degrees of freedom and constraint equations, an attempt is made to relate trajectory entropy to system entropy. Based on the postulate that trajectory entropy is equal to the difference in entropy between the unconstrained and constrained system, a model of motor optimization is proposed. This model is illustrated by an entropy graph reflecting a dynamic release process. In the light of our results, two opposing views will be examined: movement construction vs. movement emergence.     

Use of Genetic and Physical Mapping to Locate the Spinal Muscular Atrophy Locus between Two New Highly Polymorphic DNA Markers

The gene for autosomal recessive forms of spinal muscular atrophy (SMA) has recently been mapped to chromosome 5ql3, within a 4-cM region between the blocks D5S465/D5S125 and MAP-1B/D5S112. We identified two new highly polymorphic microsatellite DNA markers—namely, AFM265wf5 (D5S629) and AFM281yh9 (D5S637)—which are the closest markers to the SMA locus. Multilocus analysis by the location-score method was used to establish the best estimate of the SMA gene location. Our data suggest that the most likely location for SMA is between locus D5S629 and the block D5S637/D5S351/MAP-1B/D5S112/D5S357. Genetic analysis of inbred SMA families, based on homozygosity by descent and physical mapping using mega-YACs, gave additional information for the loci order as follows: cen–D5S6–D5S125/D5S465–D5S435–D5S629–SMA–D5S637–D5S351–MAP–1B/D5S112–D5S357–D5S39–tel. These data give the direction for bidirectional walking in order to clone this interval and isolate the SMA gene.     

Starvation-Induced Stress Resistance in Lactococcus lactis subsp. lactis IL1403

Carbohydrate-starved cultures of Lactococcus lactis subsp. lactis IL1403 showed enhanced resistance to heat, ethanol, acid, osmotic, and oxidative stresses. This cross-protection seems to be established progressively during the transitional growth phase, with maximum resistance occurring when cells enter the stationary phase. Chloramphenicol or rifamycin treatment does not abolish the development of a tolerant cell state but, on the contrary, seems to provoke this response in L. lactis subsp. lactis.     

SR141716A, a potent and selective antagonist of the brain cannabinoid receptor

SR141716A is the first selective and orally active antagonist of the brain cannabinoid receptor. This compound displays nanomolar affinity for the central cannabinoid receptor but is not active on the peripheral cannabinoid receptor. In vitro, SR141716A antagonises the inhibitory effects of cannabinoid receptor agonists on both mouse vas deferens contractions and adenylyl cyclase activity in rat brain membranes. After intraperitoneal or oral administration SR141716A antagonises classical pharmacological and behavioural effects of cannabinoid receptor agonists. This compound should prove to be a powerful tool for investigating the in vivo functions of the anandamide/cannabinoid system.     

Cytogenetic analysis of chromosome 5 from the Mediterranean fruit fly,Ceratitis capitata

A cytogenetic map of chromosome 5 from the Mediterranean fruit fly, Ceratitis capitata, was constructed. Six mutations were located by translocation, transposition or deletion mapping. This knowledge allowed alignment and orientation of the existing linkage map with the polytene chromosomes. In addition, mapping of mutations used as selectable markers in genetic sex-separation strains is an essential prerequisite for the improvement of genetic stability during mass-rearing.