Contrasting Effects of ENU Induced Embryonic Lethal Mutations of thequakingGene

Multiple alleles of the quaking (qk) gene have a variety of phenotypes ranging in severity from early embryonic death to viable dysmyelination. A previous study identified a candidate gene, QKI, that contains an RNA-binding domain and encodes at least three protein isoforms (QKI-5, -6 and -7). We have determined the genomic structure of QKI, identifying an additional alternative end in cDNAs. Further we have examined the exons and splice sites for mutations in the lethal allelesqk^l-1, qk^kt1, qk^k2,andqk^kt3.The mutation inqk^l-1creates a splice site in the terminal exon of the QKI-6 isoform. Missense mutations in the KH domain and the QUA1 domains inqk^k2andqk^kt3,respectively, indicate that these domains are of critical functional importance. Although homozygotes for each ENU induced allele die as embryos, their phenotypes as viable compound heterozygotes with qk^vdiffer. Compound heterozygousqk^vanimals carryingqk^kt1, qk^k2,andqk^kt3all exhibit a permanent quaking phenotype similar to that ofqk^v/qk^vanimals, whereasqk^v/qk^l-1animals exhibit only a transient quaking phenotype. Theqk^l-1mutation eliminates the QKI-5 isoform, showing that this isoform plays a crucial role in embryonic survival. The transient quaking phenotype observed inqk^v/qk^l-1mice indicates that the QKI-6 and QKI-7 isoforms function primarily during myelination, but that QKI-5 may have a concentration-dependent role in early myelination. This mutational analysis demonstrates the power of series of alleles to examine the function of complex loci and suggests that additional mutant alleles of quaking could reveal additional functions of this complex gene.     

Frequency separation by an excitatory-inhibitory network

We consider a situation in which individual features of the input are represented in the neural system by different frequencies of periodic firings. Thus, if two of the features are presented concurrently, the input to the system will consist of a superposition of two periodic trains. In this paper we present an algorithm that is capable of extracting the individual features from the composite signal by separating the signal into periodic spike trains with different frequencies. We show that the algorithm can be implemented in a biophysically based excitatory-inhibitory network model. The frequency separation process works over a range of frequencies determined by time constants of the model’s intrinsic variables. It does not rely on a “resonance” phenomenon and is not tuned to a discrete set of frequencies. The frequency separation is still reliable when the timing of incoming spikes is noisy.     

Contrasting effects of ENU induced embryonic lethal mutations of the quaking gene.

Multiple alleles of the quaking (qk) gene have a variety of phenotypes ranging in severity from early embryonic death to viable dysmyelination. A previous study identified a candidate gene, QKI, that contains an RNA-binding domain and encodes at least three protein isoforms (QKI-5, -6 and -7). We have determined the genomic structure of QKI, identifying an additional alternative end in cDNAs. Further we have examined the exons and splice sites for mutations in the lethal alleles qkl-1, qkkt1, qkk2, and qkkt3. The mutation in qkl-1 creates a splice site in the terminal exon of the QKI-6 isoform. Missense mutations in the KH domain and the QUA1 domains in qkk2 and qkkt3, respectively, indicate that these domains are of critical functional importance. Although homozygotes for each ENU induced allele die as embryos, their phenotypes as viable compound heterozygotes with qkv differ. Compound heterozygous qkv animals carrying qkkt1, qkk2, and qkkt3 all exhibit a permanent quaking phenotype similar to that of qkv/qkv animals, whereas qkv/qkl-1 animals exhibit only a transient quaking phenotype. The qkl-1 mutation eliminates the QKI-5 isoform, showing that this isoform plays a crucial role in embryonic survival. The transient quaking phenotype observed in qkv/qkl-1 mice indicates that the QKI-6 and QKI-7 isoforms function primarily during myelination, but that QKI-5 may have a concentration-dependent role in early myelination. This mutational analysis demonstrates the power of series of alleles to examine the function of complex loci and suggests that additional mutant alleles of quaking could reveal additional functions of this complex gene.     

Feral cats on Stewart Island; their foods,and their effects on kakapo

Abstract

The foods of feral house cats (Felis catus) on Stewart Island were determined by examining 229 scats collected during surveys of the distribution and numbers of kakapo (Strigops habroptilus), an endangered ground-parrot species. Rats occurred in 93% of the scats, birds in 44. 1%, wetas (large orthopterans) in 26.2%, and lizards in 24.0%. Twelve (70.6%) of the 17 species of birds were native. Kakapo remains were found in 6 (5.1%) of the 118 scats collected from areas where kakapo have been recorded.     

A cross-cultural study of taste discrimination with Australians and Japanese

As part of a larger cross-cultural study of the chemoreceptiveabilities and preferences of Australians and Japanese, thisstudy investigated the differential taste sensitivity of subjectsfrom both cultures. The results indicate that there are no significantdifferences between the abilities of subjects from the two culturesto discriminate small increments (just noticeable differences)in the intensities of the four common tastants: sucrose, sodiumchloride, citric acid and caffeine. Furthermore, the Weber ratiosfound with each tastant were within the range of those reportedin the literature. These findings represent further evidencefor the view that differences in responses of subjects fromdifferent cultures to chemosensory stimuli are restricted topreference behaviour arising from experience rather than fromgenetically-based influences. ³Present address: Faculty of Science and Technology, Universityof Western Sydney, Bourke Street, Richmond, NSW 2753, Australia ⁴Present address: CSIRO Biometrics Unit, Institute of AnimalProduction and Processing, PO BOx 52 North Ryde NSW 2113, Australia     

Crockett's Test of Fit for the Bivariate Poisson

An improved version of the test of CROCKETT (1979) for testing for the bivariate Poisson distribution is given and evaluated.     

Abnormality in the fissioning control of a strain of asexual Dugesia dorotocephala found near Fort Collins,Colorado

Asexual Dugesia dorotocephala, collected from a new site several miles northwest of Fort Collins, Colorado, appeared similar, at the time of collection, to ones collected from other sites in the same general locale. However, these exhibited marked differences in the more crowded conditions of laboratory culture: abnormally long, 30–50 mm specimens, seemingly unable to fission, developed. Since previous studies of asexual D. dorotocephala had revealed an inhibitory effect of cohorts on fissioning (Best et al., 1969, 1974, 1975; Pigon et al., 1974), experiments were conducted with this new strain to ascertain the effect of population density (group size) on fissioning incidence. Results are described which show that this inhibitory effect of cohorts on fissioning is exaggerated in this new strain.     

Chlorpyrifos: Ecotoxicological Risk Assessment for Birds and Mammals in Corn Agroecosystems

A tiered risk assessment was conducted for the use of granular and liquid formulations of chlorpyrifos in corn agroecosystems in the U.S. The initial screening Tier I assessment suggested that under high-exposure scenarios the granular and some spray formulations present potential hazards to birds. Higher tiered probabilistic risk assessments were conducted separately for the granular and liquid formulations. The probabilistic assessment indicated that risk to birds from exposure to granular formulation is small and that this route of exposure would not be a significant source of mortality. Similarly, the assessment of potential exposure of birds to food items contaminated with chlorpyrifos showed that the risk from exposure via food was small, even if it was assumed that birds feed only on the treated fields. Although they have potentially greater sensitivity to chlorpyrifos, effects in nestling birds consuming food items from fields treated with granular chlorpyrifos were negligible. However, risks to young birds may be greater where the major source of food is from fields treated with liquid formulations of chlorpyrifos. A review of field studies showed that wildlife mortality incidents associated with use of either granular or liquid formulations of chlorpyrifos are not widely apparent in agroecosystems. Based on the multiple lines of evidence, we conclude that the presumption that chlorpyrifos use in corn agroecosystems will result in extensive mortality of terrestrial wildlife, particularly birds and mammals, is not supported by the scientific evidence.