The Wnt family of cell signalling molecules in postimplantation development of the mouse

The mammalian Wnt gene family consists of at least ten members, all of which share a common structure. The N-terminus encodes a putative signal peptide sequence, suggesting that Wnt proteins are secreted. A number of absolutely conserved cysteine residues imply that inter- or intramolecular disulphide bonding is important to Wnt protein function. Wnt RNAs are localized to discrete regions of the postimplantation embryo and fetus, particularly within the developing central nervous system. Studies on Wnt gene expression strongly suggest that Wnt-mediated signalling is likely to be an important aspect of mouse development. One member of the family, Wnt-1, has been studied in some detail. By generating mutant alleles, we have demonstrated that Wnt-1 regulates regional development of the central nervous system at early somite stages. There is circumstantial evidence that some aspects of the pathway through which Wnt-1 action is mediated may be evolutionarily conserved. We propose that the Wnt family plays a major role in cell-cell interactions in the mouse.

Genetic manipulation of the mouse via gene targeting in embryonic stem cells

Gene targeting applied to totipotent embryonic stem (ES) cells is a very powerful means of creating highly specific mutations of genes in the mouse. The successful application of this technology is however constrained by both the types of mutations that can be generated at a target locus and the ability to reconstruct a germline chimera from the manipulated cells. We have developed two cell lines that can be routinely transmitted through the germline of chimeras after cloning and prolonged selection in tissue culture. We have also established a variety of methods for generating non-selected mutations at the X-linked hprt locus in ES cells. Our observations at this locus have enabled us to generate successfully a subtle mutation at the non-selectable Hox-2.6 locus.

Does the platinum-free interval predict the incidence or severity of hypersensitivity reactions to carboplatin? The experience from Women & Infants’ Hospital

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Background: Carboplatin (C) is a standard treatment for gynecologic cancers, but its use in recurrence is associated with an increased risk of hypersensitivity reactions (HSR) in those previously treated with C. However there is no way to predict those at risk for a C-HSR. We sought to evaluate whether the time between C was predictive of incidence and severity of HSRs. Methods: Patients treated with C between 1/1997 and 12/2005 were identified through our chemotherapy database. Records were reviewed for: dates and number of C regimens and cycles, age, drug allergies, cancer type, and date and symptoms of HSR. Severity was defined as mild if symptoms were rash, pruritis or severe for hypo/hypertension, vomiting, dyspnea, wheezing, chest pain, edema, rigors or generalized hives. Fisher’s exact test or Chi Square was used to compare categorized variables. Results: 126 patients were identified who had multiple C regimens. The median age was 60 (range, 40–90) and 89% were treated for ovarian cancer. 63 (50%) experienced C HSRs of which 36 (29%) were severe. The mean time between C regimens was 21 months for those with no HSRs and 24 months for those with HSRs (p = 0.1). The time between C regimens significantly predicted the incidence of HSRs (see table ). Of those receiving a 3rd regimen of C, 8/8 had a HSR and these were severe in seven (88%). Neither age nor presence of other drug allergies was associated with a risk of C HSR. Of interest, 60 patients received >8 (range 9–19) cycles with the first C regimen, and none of the patients reacted after cycle 8. Conclusions: A duration of greater than 12 months between C regimens is associated with an increased risk of both any- and severe- HSR. Our data also suggests that upfront treatment with C beyond eight cycles is not associated with an increased risk of HSR. Strategies for decreasing the risk of C HSR may be best focused on women receiving a repeat regimen after a platinum-free duration over 12 months or those receiving a 3rd regimen of C.

[Table: see text]

No significant financial relationships to disclose.

The RASSF1A isoform of RASSF1 promotes microtubule stability and suppresses tumorigenesis

The RASSF1A isoform of RASSF1 is frequently inactivated by epigenetic alterations in human cancers, but it remains unclear if and how it acts as a tumor suppressor. RASSF1A overexpression reduces in vitro colony formation and the tumorigenicity of cancer cell lines in vivo. Conversely, RASSF1A knockdown causes multiple mitotic defects that may promote genomic instability. Here, we have used a genetic approach to address the function of RASSF1A as a tumor suppressor in vivo by targeted deletion of Rassf1A in the mouse. Rassf1A null mice were viable and fertile and displayed no pathological abnormalities. Rassf1A null embryonic fibroblasts displayed an increased sensitivity to microtubule depolymerizing agents. No overtly altered cell cycle parameters or aberrations in centrosome number were detected in Rassf1A null fibroblasts. Rassf1A null fibroblasts did not show increased sensitivity to microtubule poisons or DNA-damaging agents and showed no evidence of gross genomic instability, suggesting that cellular responses to genotoxins were unaffected. Rassf1A null mice showed an increased incidence of spontaneous tumorigenesis and decreased survival rate compared with wild-type mice. Irradiated Rassf1A null mice also showed increased tumor susceptibility, particularly to tumors associated with the gastrointestinal tract, compared with wild-type mice. Thus, our results demonstrate that Rassf1A acts as a tumor suppressor gene.

Identification of quantitative trait loci for wood and fibre properties in two full-sib properties of Eucalyptus globulus

Regions of the genome influencing wood and fibre traits in Eucalyptus globulus Labill. have been identified in two full-sib pedigrees that share a common male parent. The first pedigree, cross A, contains 148 progeny, and the second pedigree, cross B, contains 135 progeny. Subsets of progeny of these two controlled crosses were planted at seven sites throughout Australia in 1990. Wood cores were taken at 0.9 m above ground in 1997, and wood and fibre traits were analysed for each individual. Three quantitative trait loci (QTL) affecting wood density, one QTL affecting pulp yield and one QTL affecting microfibril angle have been located in both pedigrees, using single-factor analysis of variance. Other QTLs affecting these traits, as well as fibre length and cellulose content, were located in cross A only.

Bovine mastitis: an evolving disease

Mastitis remains a major challenge to the worldwide dairy industry despite the widespread implementation of mastitis control strategies. The last forty years have seen a dramatic decrease in clinical mastitis incidence but this has been accompanied by a change in the relative and absolute importance of different pathogens. Escherichia coli and Streptococcus uberis are now the two most common causes of bovine mastitis and are an increasing problem in low somatic cell count herds. This paper reviews the changes in incidence and pattern of mastitis in the UK over the last four decades and discusses some of the possible explanations for these changes. It focuses in particular on apparent changes in the behaviour of E. coli and its ability to cause persistent intramammary infection; which may be as a result of bacterial adaptation or the unmasking of previously unrecognized patterns of pathogenesis. The prospects for novel approaches to mastitis control are discussed, as are the current and future challenges facing the industry.

Hippocampal alpha 7 and alpha 4 beta 2 nicotinic receptors and working memory

Nicotine and other nicotinic receptor agonists have been found in a variety of studies to improve memory, while nicotinic receptor blockade can impair memory. The critical neural mechanisms for nicotinic involvement with memory are still under investigation. Initial evidence supports the involvement of the ventral hippocampus. Lesions in this area block nicotine-induced memory improvement and mecamylamine-induced impairment. Local ventral hippocampal application of the nicotinic channel blocker mecamylamine impairs memory in the 8-arm radial maze. Both alpha 4 beta 2 and alpha 7 nicotinic receptors seem to be involved. Ventral hippocampal infusions of high doses of the alpha 4 beta 2 nicotinic antagonist dihydro-beta-erythrodine (DH beta E) and the alpha 7 nicotinic antagonist methyllycaconitine (MLA) impair memory performance on the 8-arm radial maze. However, high doses of these drugs may limit specificity and they cause preconvulsant effects, which in themselves may affect memory. The current study used the more challenging 16-arm radial maze to determine the effects of lower doses of these drugs on memory and to differentiate effects on working and reference memory. Adult female Sprague-Dawley rats were trained on a working and reference memory task in the 16-arm radial maze and then were implanted with bilateral chronic guide cannulae directed to the ventral hippocampus. After recovery from surgery, the rats received acute intrahippocampal infusions of dose combinations of DH beta E and MLA. In the first study, DH beta E (0 and 6.75 microg/side) and MLA (0, 6.75, 13.5 and 27 microg/side) were administered in a counter-balanced order. In the second study, lower doses of DH beta E (0, 1.6375, 3.275 and 6.75 microg/side) were administered alone or with MLA (0 and 6.75 microg/side) in a counter-balanced order. In the first study, DH beta E caused a significant increase in both working and reference memory errors. MLA at a dose of 27 microg/side caused a significant increase in working memory errors, but this dose had no significant effect on reference memory errors. Interestingly, no additive effects were seen with combined administration of DH beta E and MLA in this study, and at the doses used, no effects were seen on response latency. In the second study, lower doses of DH beta E did not cause a significant deficit in working memory performance. Co-administration of MLA with these subthreshold doses did precipitate a memory impairment. The current results confirm the specificity of the memory deficits caused by these drugs. These results support the involvement of alpha 4 beta 2 and alpha 7 nicotinic receptors in the ventral hippocampus as being critical for memory function.

Accommodation, occlusion, and disparity matching are used to guide reaching: a comparison of actual versus virtual environments

The authors used a virtual environment to investigate visual control of reaching and monocular and binocular perception of egocentric distance, size, and shape. With binocular vision, the results suggested use of disparity matching. This was tested and confirmed in the virtual environment by eliminating other information about contact of hand and target. Elimination of occlusion of hand by target destabilized monocular but not binocular performance. Because the virtual environment entails accommodation of an image beyond reach, the authors predicted overestimation of egocentric distances in the virtual relative to actual environment. This was confirmed. The authors used -2 diopter glasses to reduce the focal distance in the virtual environment. Overestimates were reduced by half. The authors conclude that calibration of perception is required for accurate feedforward reaching and that disparity matching is optimal visual information for calibration.

Accommodation, occlusion, and disparity matching are used to guide reaching: a comparison of actual versus virtual environments

The authors used a virtual environment to investigate visual control of reaching and monocular and binocular perception of egocentric distance, size, and shape. With binocular vision, the results suggested use of disparity matching. This was tested and confirmed in the virtual environment by eliminating other information about contact of hand and target. Elimination of occlusion of hand by target destabilized monocular but not binocular performance. Because the virtual environment entails accommodation of an image beyond reach, the authors predicted overestimation of egocentric distances in the virtual relative to actual environment. This was confirmed. The authors used -2 diopter glasses to reduce the focal distance in the virtual environment. Overestimates were reduced by half. The authors conclude that calibration of perception is required for accurate feedforward reaching and that disparity matching is optimal visual information for calibration.

The influence of Inter-Electrode Distance on the RMS of the SEMG signal

The aim of this research was to study the dependency of RMS of SEMG on inter-electrode distance. A group of ten healthy subjects (five males and five females) performed isometric elbow flexions of the right arm at 20, 50 and 80% of their maximal voluntary contraction (MVC). The SEMG signal was recorded using surface electrodes placed at a distance of 18 and 36 mm over the biceps brachii muscle. RMS-SEMG signals were analysed for average amplitude. At 20% MVC, no significant change was observed on the RMS value due to the spacing of the electrodes. The effect, however, was significant at 50 and 80% of MVC. Moreover, the study shows that SEMG amplitude is closely related to the level of force.

Engineering chromosomal rearrangements in mice

The combination of gene-targeting techniques in mouse embryonic stem cells and the Cre/loxP site-specific recombination system has resulted in the emergence of chromosomal-engineering technology in mice. This advance has opened up new opportunities for modelling human diseases that are associated with chromosomal rearrangements. It has also led to the generation of visibly marked deletions and balancer chromosomes in mice, which provide essential reagents for maximizing the efficiency of large-scale mutagenesis efforts and which will accelerate the functional annotation of mammalian genomes, including the human genome.