bluuebunny/crossref_metadata_2025 huggingface dataset:
Doublefoot: a new mouse mutant affecting development of limbs and head
Authors: Lyon Mary F. , Quinney R. , Glenister P. H. , Kerscher S. , Guillot P. , Boyd Y.
Published: September 2009

The mutant doublefoot, Dbf, of the mouse arose spontaneously, and was shown to be inherited as an autosomal dominant, mapping 9–13 cM proximal to leaden, ln, on chromosome 1 and showing no recombination with the microsatellite markers D1Mit24 and D1Mit77. In heterozygotes the phenotype includes many extra toes on all four feet, and the tibia and fibula may be reduced and bowed. The head is shortened and broad and the eyes are held half-closed, and some animals develop hydrocephalus. The tail is kinked and abnormally thick, and the soles of the feet are swollen. Growth is retarded, viability is reduced, and reproduction is impaired in both sexes. Only about 30 % of males are normally fertile, and testis weights and sperm counts may be reduced, although this appears not to be the main cause of poor fertility. In females vaginal opening is delayed and oestrous cycles are irregular, although the animals appear to respond to gonadotrophic hormones. Crosses of Dbf/ + × Dbf/ + are very poorly fertile. Prenatally, Dbf/ + heterozygotes can first be recognized at 11½ days gestation by abnormally broad fore limb buds. Putative Dbf/Dbf homozygotes at 12½ days have similar limbs defects and also split face, due to failure of the maxillae to fuse in the midline. Some homozygotes and a few putative heterozygotes have cranioschisis. At 13½ days, the heads of homozygotes tend to bulge in the frontal region and a bleb of clear fluid is visible medially. At 14½ days Dbf/Dbf fetuses may have oedema and some are dead. From 15½ days onwards no live Dbf/Dbf fetuses have been found. The gene maps close to the locus of Pax3, but crossovers between Dbf and Pax3 have been found, ruling out the possibility that a gain-of-function mutation in Pax3 might be involved.
Deviation from Hardy–Weinberg proportions in finite populations
Authors: Wang Jinliang
Published: September 2009

For a finite diploid population with no mutation, migration and selection, equations for the deviation of observed genotype frequencies from Hardy–Weinberg proportions are derived in this paper for monoecious species and for autosomal and sex-linked loci in dioecious species. It is shown that the genotype frequency deviation in finite random-mating populations results from the difference between the gene frequencies of male and female gametes, which is determined by two independent causes: the gene frequency difference between male and female parents and the sampling error due to the finite number of offspring. Previous studies have considered only one of the causes and the equations derived by previous authors are applicable only in the special case of random selection. The general equations derived here for both causes incorporate the variances and covariances of family size and thus they reduce to previous equations for random selection. Stochastic simulations are run to check the predictions from different formulae. Non-random mating and variation in census size are considered and the applications of the derived formulae are exemplified.
Modifiers of mutation-selection balance: general approach and the evolution of mutation rates
Authors: Kondrashov Alexey S.
Published: September 2009

A general approach is developed to estimate secondary selection at a modifier locus that influences some feature of a population under mutation-selection balance. The approach is based on the assumption that the properties of all available genotypes at this locus are similar. Then mutation-selection balance and weak associations between genotype distributions at selectable loci and the modifier locus are established rapidly. In contrast, changes of frequencies of the modifier genotypes are slow, and lead to only slow and small changes of the other features of the population. Thus, while these changes occur, the population remains in a state of quasi-equilibrium, where the mutation-selection balance and the associations between the selectable loci and the modifier locus are almost invariant. Selection at the modifier locus can be estimated by calculating quasiequilibrium values of these associations. This approach is developed for the situation where distributions of the number of mutations per genome within the individuals with a given modifier genotype are close to Gaussian. The results are used to study the evolution of the mutation rate. Because beneficial mutations are ignored, secondary selection at the modifier locus always diminishes the mutation rate. The coefficient of selection against an allele which increases the mutation rate by υ is approximately υδ2/[U(2−ρ)] = υŝ, where υ is the genomic deleterious mutation rate, δ is the selection differential of the number of mutations per individual in units of the standard deviation of the distribution of this number in the population, ρ is the ratio of variances of the number of mutations after and before selection, and ŝ is the selection coefficient against a mutant allele in the quasiequilibrium population. However, the decline of the mutation rate can be counterbalanced by the cost of fidelity, which can lead to an evolutionary equilibrium mutation rate.
Effective population size/adult population size ratios in wildlife: a review
Authors: Frankham Richard
Published: September 2009

The effective population size is required to predict the rate of inbreeding and loss of genetic variation in wildlife. Since only census population size is normally available, it is critical to know the ratio of effective to actual population size (Ne/N). Published estimates ofNe/N(192 from 102 species) were analysed to identify major variables affecting the ratio, and to obtain a comprehensive estimate of the ratio with all relevant variables included. The five most important variables explaining variation among estimates, in order of importance, were fluctuation in population size, variance in family size, form ofNused (adults υ. breeders υ. total size), taxonomic group and unequal sex-ratio. There were no significant effects on the ratio of high υ. low fecundity, demographic υ. genetic methods of estimation, or of overlapping υ. non-overlapping generations when the same variables were included in estimates. Comprehensive estimates ofNe/N(that included the effects of fluctuation in population size, variance in family size and unequal sex-ratio) averaged only 0·10–0·11. Wildlife populations have much smaller effective population sizes than previously recognized.
A genetic linkage map for the domesticated silkworm,Bombyx mori, based on restriction fragment length polymorphisms
Authors: Shi Jinrui , Heckel David G. , Goldsmith Marian R.
Published: September 2009

We present data for the initial construction of a molecular linkage map for the domesticated silkworm,Bombyx mori, based on 52 progeny from an F2 cross from a pair mating of inbred strains p50 and C108, using restriction fragment length polymorphisms (RFLPs). The map contains 15 characterized single copy sequences, 36 anonymous sequences derived from a follicular cDNA library, and 10 loci corresponding to a low copy number retrotransposon, mag. The 15 linkage groups and 8 ungrouped loci account for 23 of the 28 chromosomes and span a total recombination length of 413 cM; 10 linkage groups were correlated with established classic genetic maps. Scoring data from Southern blots were analysed using two Pascal programs written specifically to analyse linkage data in Lepidoptera, where females are the heterogametic sex and have achiasmatic meiosis (no crossing-over). These first examine evidence for linkage by calculating the maximum lod score under the hypothesis that the two loci are linked over the likelihood under the hypothesis that the two loci assort independently, and then determine multilocus linkage maps for groups of putatively syntenic loci by calculating the maximum likelihood estimate of the recombination fractions and the log likelihood using the EM algorithm for a specified order of loci along the chromosome. In addition, the possibility of spurious linkage was exhaustively tested by searching for genotypes forbidden by the absence of crossing-over in one sex.
Allelic variation at the Gli-A1m, Gli-A2m and Glu-A1m loci and breadmaking quality in diploid wheat Triticum monococcum
Authors: Saponaro C. , Pogna N. E. , Castagna R. , Pasquini M. , Cacciatori P. , Redaelli R.
Published: September 2009

Fifty-six accessions of Triticum monococcum and one accession each of T. beoticum and T. sinskajae were analysed for their storage protein compositions and breadmaking quality as determined by the SDS-sedimentation test. In total 30 different alleles at the Glu-A1m locus coding for high-molecular-weight glutenin subunits (HMW-GS), 25 alleles at the Gli-A1m locus coding for ω- and γ-gliadins and 45 alleles at the Gli-A2m locus controlling the synthesis of α/β-gliadins were detected. Most accessions contained one x-type and one y-type HMW-GS and two genotypes were null for both types of subunits. Two polypeptides within the mobility range of HMW-GS in SDS-PAGE were shown to be ω-type gliadins encoded by genes on the short arm of chromosome 1 A. T. sinskajae and several ‘monococcum’ accessions were shown to share the same alleles at Gli-A1m, Gli-A2m and Glu-A1m, confirming sinskajae as a subspecies of T. monococcum. The SDS-sedimentation volumes of most accessions were very low (11–35 ml), a few accessions showing mean sedimentation volumes as high as 90–93 ml. Through the comparison between biotypes occurring in some accessions of ‘monococcum’, good bread-making quality was found to be associated with the presence of alleles y, c and i at the Gli-A1m locus. All accessions were resistant to leaf rust and rich in protein (≥ 16·5%), and most of them showed resistance to powdery mildew.
Chloride channel 2 gene (Clc2) maps to chromosome 16 of the mouse, extending a region of conserved synteny with human chromosome 3q
Authors: Lengeling Andreas , Gronemeier Monika , Ronsiek Melanie , Thiemann Astrid , Jentsch Thomas J. , Jockusch Harald
Published: September 2009

TheClc2gene of the mouse codes for the ubiquitously expressed chloride channel ClC-2, a member of a family of at least seven voltage gated chloride channels, some of which are implicated in hereditary diseases. Using a mouse interspecies back-cross panel, we have mappedClc2to Chr 16, proximal to the somatostatin geneSmst, extending a region of documented conserved synteny to human Chr 3q.
Does monozygotic twinning occur in mice?
Authors: McLaren Anne , Molland Paul , Signer Esther
Published: September 2009

Published reports suggest that the incidence of monozygotic twinning in women is increased after hormonally induced ovulation. Since some statistical evidence exists to indicate that monozygotic twinning may also occur in mice, we attempted to devise a mouse system in which the incidence of such twinning could be compared after spontaneous versus hormonally induced ovulation, in order to analyse the developmental basis of such an effect. We used phenotypic identity in litters segregating for ten genetic loci (not all independent) to indicate possible twin pairs. DNA fingerprinting using three human minisatellite probes was then performed blind on these pairs and on sibling controls. From a total of over 2000 mice born, 40 apparently identical pairs were identified, on which DNA finger-printing was successfully carried out on 35 pairs. All proved to be derived from different zygotes. We conclude that monozygotic twin pairs are either extremely rare in the stock of mice that we studied, or have such reduced viability that their chance of surviving to weaning is low.
Response to selection from new mutation and effective size of partially inbred populations. II. Experiments withDrosophila melanogaster
Authors: Merchante Montserrat , Caballero Armando , López-Fanjul Carlos
Published: September 2009

Divergent artificial selection for abdominal bristle number inDrosophila melanogasterhas been carried out starting from a genetically homogeneous base population. Lines with two different systems of mating, random (Plines) or between full sibs whenever possible (about 50%), random otherwise (Ilines) were compared. Responses after 40 generations of selection were mostly due to one or two mutations of large effect (0·2 to 2 phenotypic standard deviations) per line. Ten mutations affecting the selected trait were individually studied (five lethal and five non-lethal, these being predominantly additive). These mutations satisfactorily explain the response attained, although some minor mutations may also be involved. No evidence of epistasis for bristle number was found. The average final divergence was 57% larger in thePlines, but it was mostly due to lethals or highly deleterious mutations. Thus, after relaxation of selection, the ranking reversed and the mean divergence became significantly larger in theIlines (14%). Analysis of inbreeding showed that the very small amount of variation created by spontaneous mutations (a heritability for the selected trait of about 3%) was responsible for a reduction in the effective size of about 50% in theIlines (relative to the case with random selection), but only about 10% in thePlines. Mutational heritabilities estimated from the response to selection (0·05–0·18%) were within the range usually found for this trait in previous experiments. REML estimates account for correlations between relatives, and were much larger in those lines where the response was due to lethal mutations, as these do not contribute to response after reaching maximum frequency.
Using marker-maps in marker-assisted selection
Authors: Whittaker J. C. , Curnow R. N. , Haley C. S. , Thompson R.
Published: September 2009

A method of using information on the location of markers to improve the efficiency of markerassisted selection (MAS) in a population produced by a cross between two inbred lines is developed. The method is closer to mapping QTL than the selection index approaches to MAS described by previous authors. We use computer simulations to compare our method with phenotypic selection and two selection index approaches, simulations being performed on three genetic maps. The simulations show that whilst MAS can be considerably more efficient than phenotypic selection differences between the three MAS methods are slight. Which of the MAS methods is best depends on a number of factors: in particular the genetic map, the time scale under consideration and the population size are of importance.
Recombination frequency and wild-type ancestry in linkage group I ofNeurospora crassa
Authors: Lavigne Stella , Frost L. C.
Published: September 2009

A selection of single and double mutant strains was backcrossed repetitively at least four times to each of the wild-types Abbott 4A, Abbott 12aand Lindegren 1A, and then re-isolated. Twelve crisp progeny isolated from the fifth backcross to Abbott 4Awere heterogeneous for recombination frequency in the interval betweencrandme-6while thirteen crisp progeny from the fifth backcross to Lindegren 1Awere homogeneous for recombination frequency in this interval. Thirteen crisp strains from the fifth backcross to Abbott 12awere homogeneous for recombination frequency betweencrandnic-1loci. However, mutant strains which had been backcrossed independently to Lindegren 1Awere heterogeneous for recombination frequency in the intervalscr-aurandaur-nic-1.

In general, recombination frequencies in crosses between strains of the same wild-type ancestry including Abbott 4 and Abbott 12 were significantly higher than those in crosses of Lindegren × Abbott 4 or Lindegren × Abbott 12 ancestry but exceptions were found. Recombination frequencies between the same markers usually, but not always, increased on inbreeding and the changes in frequency were non-uniform in the marked region in some crosses.

The limitations of backcrossing as a means of transferring a mutant marker into a wild-type genome were discussed. It was concluded that inducing marker mutations anew in a given wild strain, preferably Lindegren 1A, might be more successful in obtaining constancy of map distance.
Elements of theS-gene complex
Authors: Pandey Kamla Kant
Published: September 2009

Cultivated plants ofNicotiana alataare self-incompatible and are of two kinds: normal (N); and exceptional (M). N plants are reciprocally compatible withN.langsdorffii; M plants are compatible only as males. M plants contain an unusual allele,SFI, which has a dual action in the style: it rejects both self-pollen, andSfpollen fromN. langsdorffii. The overall results agree with the assumption that theSFIgene produces two kinds of specificity in the style:primaryspecificity, which is responsible for the rejection ofSfpollen; andsecondaryspecificity, which is responsible for the rejection of self-pollen as inSIalleles generally. The genetic sub-units concerned must be closely linked; there was no evidence for their dissociation in the 599 plants studied.

In both compatible and incompatible pollinations,SFIpollen grows more slowly thanSIand, in addition, appears to depress the normal rate of growth ofSIpollen. In consequence, crossesSfSf×SISFI♂ yielded significantly fewer S.I. plants than the 50% expected. The two kinds of pollen grew at comparable rates, however, when F1(M × M) plants involving parents from different original sources were backcrossed toSfSf♀. Progenies then showed the expected 1:1 ratio of S.I. to S.C. plants. These results are assumed to be due to differential behaviour of theSFIallele according to its genetic background. The change in background would be from a degree of homozygosity, in plants from the same source, to a degree of heterozygosity, in crosses between plants from different sources.

The high incidence of theSFIgene inN. alatais considered to be due to the advantage it confers on a self-incompatible population when it is overlapping with a related self-compatible population (having theSfgene). Plants carrying anSFIallele, by rejecting the Sfpollen, will restrict the spread of inbreeding and so be favoured by selection.

The origin of theSFIandSfalleles are discussed in relation to the author's hypothesis ofS-gene structure.
The effects of X-rays on quantitative characters
Authors: Clayton G. A. , Robertson Alan
Published: September 2009

1. The rate of production by X-rays of new genetic variation in two quantitative characters inDrosophila melanogaster(sternital and sternopleural bristles) has been investigated, using ‘plateaued’ populations which had reached the limit under artificial selection and, for sternital bristles only, populations which had been made genetically invariant by inbreeding. The genetic variation was always measured by the response of the population to selection. The X-rays dose given in any generation was always 1800 r. to adults.

2. Seven plateaued lines had eight cycles of alternate irradiation and selection, each with its non-irradiated control. All the responses were small but in three lines they were significantly greater after irradiation.

3. Selection was applied to three different inbred lines, genetically marked to detect contamination, after varying periods of irradiation. At the same time, the inbred lines and lines derived from them which had been mass mated in bottles were selected. The irradiated populations showed a greater response. The new genetic variance produced by the irradiation was approximately 10−5units/r. The estimate of the dose required to introduce new variation equal to that in a standard outbred population was 500,000 r.

4. The effective population size was an important factor in the interpretation of some of these results on the long-term effects of radiation. By observing the variation between replicate lines in the frequency of a gene with a visible effect under these culture conditions (i.e. in a single culture bottle) the effective population size was estimated at sixty. Outbred populations kept under these conditions for many generations showed a reduction of genetic variability in agreement with this value.

5. To investigate the possibility that the deleterious genes produced by irradiation would interfere with the response to artificial selection, a standard outbred population was irradiated and selected. In spite of the observed high frequency of recessive lethals produced, the response to selection was very similar to that of the standard population.
Nutritional studies with Scaleless chickens: I. The Sulphur-Containing Amino Acids
Authors: Abbott U. K. , Asmundson V. S. , Shortridge K. R.
Published: September 2009

Young birds homozygous for the recessive gene,sc, had a significantly lower requirement than their normally feathered siblings for the sulphur-containing amino-acids, methionine and cystine. When fed a synthetic diet lacking in methionine, feathered birds showed the expected abrupt decrease in weight gain while Scaleless birds grew at a rate equivalent to feathered birds receiving the full diet. Scaleless birds receiving the full diet exceeded feathered birds in weight gain during the first part of the feeding trial but they required more food per gram of gain. Between Scaleless groups those fed the deficient diet dropped behind those on full diet in gain after 3 weeks but even after 6 weeks these did not differ in other respects. On the other hand among normal birds those receiving the deficient diet were higher in heat output and had relatively larger thyroid and adrenal glands than those receiving the full diet.

Differences between the two phenotypes are accounted for by (1) the difference in nutritive requirements determined by feather growth, and (2) the resultant differences in heat loss which accounted for the increase in heat output, packed cell volume and heart, thyroid and adrenal gland size of Scaleless birds.

The use of mutants such as Scaleless in studies concerned with requirements for specific physiological or growth purposes is suggested.
Preferential segregation inSaccharomyces
Authors: Shult Ernest E. , Desborough Sharon , Lindegren Carl C.
Published: September 2009

In tetrad data obtained from the Carbondale yeast stock, instances of greater than 50% recombination occur far more frequently than would be expected by chance. In the main, genes exhibiting this effect are located in the vicinity of the centromeres. Difficulties in assigning linear order also persist throughout the total data for certain gene combinations. The affinity hypothesis suffices to account for these two effects; the former resulting from ‘divergent’ combinations of affinity sites in the zygote, the latter, representing nonlinear quasi-linkages resulting from ‘convergent’ combinations.

Chromosome V (ur3-centromere-ch–hi1–is1–an) exhibits quasi-linkage with the genethand reverse-linkage with the genecu2, in Family 108. In each case ‘linkage’ is strongest withchand becomes progressively weaker with the geneshi1,is1andan, respectively, indicating that the preferentially segregating sites involved lie close toch. It was impossible to determine whether the two sites were identical, as would be expected on an hypothesis of ‘polar’ rather than ‘mutual’ affinity.

Intra-ascal matings within tetrads NPD forcu2–ch, yielded quasi-linkage for these genes in F2, showing that the attraction is retained by the sites being segregated.

A second case of reverse linkage forcu1andar4in Family 217, gave a similar effect—i.e. reverse linkage in F1, becoming quasi-linkage in the NPD—intra-ascal F2.

An intra-ascal mating between members of the single PD tetrad forcu1andar4in Family 217 indicated that this tetrad did not result from ‘chance’ failure of otherwise active sites to preferentially segregate.
Modification of selection limits for egg number
Authors: Abplanalp Hans
Published: September 2009

An attempt was made to modify a near-limit of selection response in the egg production of a closed poultry flock which had been under selection for 31 years; to this end the laying hens were subjected to weekly periods of 24-hour feed deprivation, and selected for egg number under these conditions.

In two replicate populations genetic gains of about 20 eggs were made under shock treatment to 40 weeks of age, over 5 and 6 generations of selection. These gains were also manifest under normal management.

Selection, under 24-hour starvation per week, also improved the ability of the selected populations to lay under weekly starvation periods of 33 and 48 hours respectively. Differences between selected and unselected lines increased with the more severe stress treatments. Also it was found that the difference in average egg production between 33-hour and 48-hour treatments was larger in unselected lines than in the selected ones, indicating the existence of genotype-environment interactions.

Correlated responses of reduced egg-weight and body-weight, and somewhat earlier maturity of selected lines correspond with what might be expected under normally effective selection for egg number. These adaptations however varied considerably between replicate lines.
The rate of genetic divergence of sublines in the C57BL strain of mice
Authors: Grewal Manjit Singh
Published: September 2009

The ancestory of Koller's subline of the C57BL strain is not known. A study of the minor skeletal variants in this subHne showed that it differs from the other ten sublines of C57BL more than they difier from each other. It appears to have separated from. the rest before the genotypes of the sublines had been fixed by inbreeding. There is enough evidence to show that it is indeed a branch of C57BL strain.

The rate of divergence of the sublines of C57BL is surprisingly high. It is reconsidered whether the whole of this divergence can be explained by recent mutations or whether residual heterozygosis has also played a part in it.
The genetics of sex-linked anaemia in the mouse
Authors: Falconer D. S. , Isaacson J. H.
Published: September 2009

The gene ‘sex-linked anaemia’ (sla) appeared first in the progeny of a daughter of a male that had been irradiated with 500 r. of X-rays. The daughter was born one month after the irradiation of her father. Mated to an unrelated wild-type male she produced sixteen sons of which six were anaemic. Her fertility was normal. Experience in subsequent matings showed the anaemia to be rather difficult to classify. In litters examined on the day of birth the anaemic young were usually clearly distinguishable by their pale colour. But in older litters, and even in a few at birth, the classification could not be made with confidence. The haematology of the anaemics is described by Grewal (1962).
The pattern of X-chromosome inactivation in the embryonic and extra-embryonic tissues of post-implantation digynic triploid LT/Sv strain mouse embryos
Authors: Speirs S. , Cross J. M. , Kaufman M. H.
Published: September 2009

Spontaneously cycling LT/Sv strain female mice were mated to hemizygous Rb(X.2)2Ad males in order to facilitate the distinction of the paternal X chromosome, and the pregnant females were autopsied at about midday on the tenth day of gestation. Out of a total of 222 analysable embryos recovered, 165 (74·3%) were diploid and 57 (25·7%) were triploid. Of the triploids, 26 had an XXY and 31 an XXX sex chromosome constitution. Both embryonic and extra-embryonic tissue samples from the triploids were analysed cytogenetically by G-banding and by the Kanda technique to investigate their X-inactivation pattern. The yolk sac samples were separated enzymatically into their endodermally-derived and mesodermally-derived components, and these were similarly analysed, as were similar samples from a selection of control XmXp diploid embryos. In the case of the XmXmY digynic triploid embryos, a single darkly-staining Xm chromosome was observed in 485 (82·9%) out of 585, 304 (73·3%) out of 415, and 165 (44·7%) out of 369 metaphases from the embryonic, yolk sac mesodermally-derived and yolk sac endodermally-derived tissues, respectively. The absence of a darkly staining X-chromosome in the other metaphase spreads could either indicate that both X-chromosomes present were active, or that the Kanda technique had failed to differentially stain the inactive X-chromosome(s) present. In the case of the XmXmXp digynic triploid embryos, virtually all of the tissues analysed comprised two distinct cell lineages, namely those with two darkly-staining X-chromosomes, and those with a single darkly staining X-chromosome. Four X-inactivation patterns were consequently observed in this group, namely, (XmXp)Xm, (XmXm)Xp, (Xm)XmXp and XmXm(Xp) in which the inactive X is enclosed in parentheses. The incidence of these various classes varied among the tissues analysed. There was, however, a clear pattern of non-random selective paternal X-inactivation in yolk sac endodermally-derived samples which possessed two inactive X-chromosomes. This finding contrasts with the situation observed in the yolk sac mesodermally-derived and embryonic samples which possessed two inactive X-chromosomes, where the ratio of (XmXm)Xp:Xm(XmXp) was 1:1·20 and 1:1·03, respectively, being clear evidence that random X-inactivation had occurred in these tissues.
The parental origin of de novo X-autosome translocations in females with Duchenne muscular dystrophy revealed by M27ß methylation analysis
Authors: Robinson David O. , Boyd Yvonne , Cockburn David , Collinson Morag N. , Craig Ian , Jacobs Patricia A.
Published: September 2009

The parental origin of 3 de novo X-autosome translocations in females with Duchenne Muscular Dystrophy (DMD) was studied by means of methylation analysis using the X-linked probe M27ß. In all three the translocation was found to be paternal in origin. The parental origin of X-autosome translocations in females with and without DMD is compared with other structural abnormalities of the X and with autosomal translocations.
Genome cryopreservation: a valuable contribution to mammalian genetic research
Authors: Glenister P. H. , Whittingham D. G. , Wood M. J.
Published: September 2009

Mouse embryo banking has become an important asset to geneticists. Individual laboratories can now maintain a far greater diversity of stocks than by conventional breeding alone. Also, many mutations that in the past would have been discarded due to lack of space, can now be preserved for future use. Recent advances in cryopreservation techniques have simplified procedures and, in certain cases, resulted in increased rates of survival.
SKEWED SEX RATIO AT BIRTH IN INDIA
Authors: SETH SWAPAN
Published: September 2009

Scientists commonly use world average data on sex ratio at birth for India for want of dependable ones. Here an attempt is made to redress the problem to some extent. It is shown that this ratio has been high in India since the 1950s. The ratio has been strikingly high, even prior to the time of inception of prenatal sex identification technologies. The ratio shows a rising trend due to several biological reasons. In addition, it has been rising sharply for a couple of decades due to some socio-medical factors. The natural sex ratio at birth in India is noticeably higher than the world average.
The breaking of interfacial waves at a submerged bathymetric ridge
Authors: HULT ERIN L. , TROY CARY D. , KOSEFF JEFFREY R.
Published: September 2009

The breaking of periodic progressive two-layer interfacial waves at a Gaussian ridge is investigated through laboratory experiments. Length scales of the incident wave and topography are used to parameterize when and how breaking occurs. Qualitative observations suggest both shear and convection play a role in the instability of waves breaking at the ridge. Simultaneous particle image velocimetry (PIV) and planar laser-induced fluorescence (PLIF) measurements are used to calculate high resolution, two-dimensional velocity and density fields from which the local gradient Richardson number Rig is calculated. The transition to breaking occurred when 0.2 ≤ Rig ≤ 0.4. In these wave-ridge breaking events, the destabilizing effects of waves steepening in shallow layers may be responsible for breaking at higher Rig than for similar waves breaking through shear instability in deep water (Troy & Koseff, J. Fluid Mech., vol. 543, 2005b, p. 107). Due to the effects of unsteadiness, nonlinear shoaling and flow separation, the canonical Rig > 0.25 is not sufficient to predict the stability of interfacial waves. A simple model is developed to estimate Rig in waves between finite depth layers using scales of the incident wave scale and topography. The observed breaking transition corresponds with a constant estimated value of Rig from the model, suggesting that interfacial shear plays an important role in initial wave instability. For wave amplitudes above the initial breaking transition, convective breaking events are also observed.
On the asymptotic behaviour of large-scale turbulence in homogeneous shear flow
Authors: ISAZA JUAN C. , COLLINS LANCE R.
Published: September 2009

The asymptotic behaviour of large-scale velocity statistics in an homogeneous turbulent shear flow is investigated using direct numerical simulations (DNS) of the incompressible Navier–Stokes equations on a 5123 grid, and with viscous rapid distortion theory (RDT). We use a novel pseudo-spectral algorithm that allows us to set the initial value of the shear parameter in the range 3–30 without the shortcomings of previous numerical approaches. We find there is an explicit dependence of the early-time behaviour on the initial value of the shear parameter. Moreover, the long-time asymptotes of large-scale quantities such as the ratio of the turbulent kinetic energy production rate over dissipation rate, the Reynolds stress anisotropic tensor and the shear parameter itself depend sensitively on the initial value of the shear parameter over the range of Reynolds number we could achieve (26 ≤ Rλ ≤ 63) with the stringent resolution requirements that were satisfied. To gain further insight into the matter, we analyse the full viscous RDT. While inviscid RDT has received a great deal of attention, viscous RDT has not been fully analysed. Our motivation for considering viscous RDT is so that the energy dissipation rate enters the problem, enabling the shear parameter to be defined. We show asymptotic expansions for the short-time behaviour and numerically evaluate the integrals to determine the long-time prediction of viscous RDT. The results are in quantitative agreement with DNS for short times; however, at long times viscous RDT predicts the turbulent energy decays to zero. Through an analysis of the pressure–strain terms, we show that the nonlinear ‘slow’ terms are essential for rearranging turbulent energy from the streamwise direction to the mean shear direction, and this sustains the indefinite growth of the kinetic energy at long times. In effect, the nonlinear pressure–strain correlation maintains the three-dimensionality of the turbulence, countering the tendency of the mean shear to project the turbulence onto the two-dimensional plane of the mean-flow streamlines. We postulate that the predictions of viscous RDT at long times could be improved by introducing a model for the ‘slow’ pressure–strain term, along the lines of the Rotta model.
Psychiatry of old age and ethnic minority older people in the United Kingdom
Authors: Shah Ajit
Published: September 2009

This review examines the demographic changes, the epidemiology of mental disorders and suicides, the potential risk and protective factors, access to secondary care old age psychiatry services (OAPSs) and the policy context pertaining to older people from ethnic minority groups in the United Kingdom. The number of older people from ethnic minority groups is increasing. The prevalence of mental disorders in older people from ethnic minority groups is either similar to or higher than that in the indigenous population. Therefore, the number of older people from ethnic minority groups with psychiatric morbidity is also increasing. Ethnic minority older people also have inequity of access to secondary care OAPSs. There is an urgent need to develop and implement practical strategies to improve access by older people from ethnic minority groups to OAPSs.
Food consumption and nutritional status of people living with HIV/AIDS (PLWHA): a case of Thika and Bungoma Districts, Kenya
Authors: Kuria Elizabeth Nafula
Published: September 2009

Objective

To establish the food consumption, dietary habits and nutritional status of people living with HIV/AIDS (PLWHA) and adults whose HIV status is not established.

Design

Cross-sectional descriptive survey.

Setting

Thika and Bungoma Districts, Kenya.

Subjects

A random sample of 439 adults; 174 adults living with HIV/AIDS and 265 adults whose HIV/AIDS status was not established in Thika and Bungoma Districts.

Results

Majority of PLWHA consume foods that are low in nutrients to build up the immune system and help maintain adequate weight, and there is little variety in the foods they consume. More adults who are HIV-positive are undernourished than those whose status is not established. Of the HIV-positive adults, those with a BMI of ≤18·5 kg/m2 were 23·6 % (Thika 20·0 % and Bungoma 25·7 %) while of the adults whose status is not established those with BMI ≤ 18·5 kg/m2 were 13·9 % (Thika 9·3 % and Bungoma 16·7 %).

Conclusions

Adults who are HIV-positive are more likely to be undernourished than those whose status is not established, as there is a significant difference (P = 0·000) between the nutritional status (BMI) of PLWHA and those whose HIV/AIDS status is not established. PLWHA consume foods that are low in nutrients to promote their nutritional well-being and health.
Cost-effectiveness of mandatory folate fortification v. other options for the prevention of neural tube defects: results from Australia and New Zealand
Authors: Dalziel Kim , Segal Leonie , Katz Rachelle
Published: September 2009

Objective

To provide input to Australian and New Zealand government decision making regarding an optimal strategy to reduce the rate of neural tube defects (NTD).

Design

Standard comparative health economic evaluation techniques were employed for a set of intervention options for promoting folate/folic acid consumption in women capable of or planning a pregnancy. Evidence of effectiveness was informed by the international literature and costs were derived for Australia and New Zealand.

Results

Population-wide campaigns to promote supplement use and mandatory fortification were the most effective at reducing NTD, at an estimated 36 and 31 fewer cases per annum respectively for Australia and New Zealand, representing an 8 % reduction in the current annual NTD rate. Population-wide and targeted approaches to increase supplement use were cost-effective, at less than $AU 12 500 per disability-adjusted life year (DALY) averted ($US 9893, £5074), as was extending voluntary fortification. Mandatory fortification was not cost-effective for New Zealand at $AU 138 500 per DALY ($US 109 609, £56 216), with results uncertain for Australia, given widely varying cost estimates. Promoting a folate-rich diet was least cost-effective, with benefits restricted to impact on NTD.

Conclusions

Several options for reducing NTD appear to fall well within accepted societal cost-effectiveness norms. All estimates are subject to considerable uncertainty, exacerbated by possible interactions between interventions, including impacts on currently effective strategies. The Australian and New Zealand governments have decided to proceed with mandatory fortification; it is hoped they will support a rigorous evaluation which will contribute to the evidence base.
Does legal capacity matter? A survey of WTO Members
Authors: BUSCH MARC L. , REINHARDT ERIC , SHAFFER GREGORY
Published: September 2009

Previous studies of WTO dispute settlement have sought to evaluate whether a Member's legal capacity influences its odds of bringing litigation before the multilateral trade regime. Because direct measures of legal capacity are elusive, these studies have had to use indirect proxies, such as per capita income or number of delegates in Geneva. Yet, the reliability of these measures is questionable. To gauge legal capacity more directly, we surveyed all WTO Members, posing questions concerning their professional staff, bureaucratic organization at home, bureaucratic organization in Geneva, experience handling general WTO matters, and involvement in WTO litigation. Using responses from this survey, we constructed an index of Members' WTO legal capacity that speaks more fully to the challenges of dispute settlement than do commonly used proxies, none of which are strongly correlated with our measure. We supplemented this survey with over three dozen semi-structured interviews with Members' representatives in Geneva, the results of which bear out the importance of properly measuring legal capacity.
Fluvial flux of nitrogen from Great Britain 1974–2005 in the context of the terrestrial nitrogen budget of Great Britain
Authors: Worrall F. , Burt T. P. , Howden N. J. K. , Whelan M. J.
Published: September 2009

Long‐term records of the concentration of nitrogen species from British rivers were compiled in order to assess temporal change in the total fluvial nitrogen flux compared to the other inputs to, and outputs from, the UK terrestrial biosphere. The following nitrogen species are considered: ammoniacal N, nitrate, nitrite, dissolved organic nitrogen, and particulate organic nitrogen. Concentration and flow records were reconstructed from 1974 to 2005 for ammoniacal N, nitrate, nitrate, and dissolved organic nitrogen (DON) and from 1992 for particulate organic nitrogen (PON). The reconstructed fluvial nitrogen time series was compared to records for inorganic fertilizer, atmospheric emissions, industrial and sewage effluent, and imports. The results show that (1) the total dissolved nitrogen flux over the study period, after flow correction, varied from 470 to 980 kt N a−1, which, on average, comprised 69% nitrate N; 26% dissolved organic N; 4% ammoniacal N; and 1% nitrite N; (2) the total nitrogen flux including PON varied from 504 to 1004 kt N a−1; (3) the flux of ammoniacal N shows a significant decline over the study period, but significant increases in both nitrate N and dissolved organic N mean that the total dissolved nitrogen flux still shows a significant increase at a rate of 6.3 kt N a−1; and (4) the dissolved nitrogen flux record shows both a steady increase over the period 1974 to 2005 and sharp discrete rises in response to severe droughts. Flux increases (up to 69% increase compared to the 4 years prior to the drought) in response to severe droughts are not consistent with a storage effect caused by reduced flows but, instead, appear to represent enhanced production in the year of the drought. The long‐term rise of fluvial nitrogen flux from British rivers is in contrast to declines in inputs and other N outputs.
Moderate rates of late Quaternary slip along the northwestern margin of the Basin and Range Province, Surprise Valley fault, northeastern California
Authors: Personius Stephen F. , Crone Anthony J. , Machette Michael N. , Mahan Shannon A. , Lidke David J.
Published: September 2009

The 86‐km‐long Surprise Valley normal fault forms part of the active northwestern margin of the Basin and Range province in northeastern California. We use trench mapping and radiocarbon, luminescence, and tephra dating to estimate displacements and timing of the past five surface‐rupturing earthquakes on the central part of the fault near Cedarville. A Bayesian OxCal analysis of timing constraints indicates earthquake times of 18.2 ± 2.6, 10.9 ± 3.2, 8.5 ± 0.5, 5.8 ± 1.5, and 1.2 ± 0.1 ka. These data yield recurrence intervals of 7.3 ± 4.1, 2.5 ± 3.2, 2.7 ± 1.6, and 4.5 ± 1.5 ka and an elapsed time of 1.2 ± 0.1 ka since the latest surface‐rupturing earthquake. Our best estimate of latest Quaternary vertical slip rate is 0.6 ± 0.1 mm/a. This late Quaternary rate is remarkably similar to long‐term (8–14 Ma) minimum vertical slip rates (>0.4–0.5 ± 0.3 mm/a) calculated from recently acquired seismic reflection and chronologic and structural data in Surprise Valley and the adjacent Warner Mountains. However, our slip rate yields estimates of extension that are lower than recent campaign GPS determinations by factors of 1.5–4 unless the fault has an unusually shallow (30°–35°) dip as suggested by recently acquired seismic reflection data. Coseismic displacements of 2–4.5 ± 1 m documented in the trench and probable rupture lengths of 53–65 km indicate a history of latest Quaternary earthquakes ofM6.8–7.3 on the central part of the Surprise Valley fault.
Poisson's ratios of crystalline rocks as a function of hydrostatic confining pressure
Authors: Wang Qian , Ji Shaocheng
Published: September 2009

The hydrostatic pressure (P) dependence of dynamic Poisson's ratios (υ) has been investigated for 54 samples of the crystalline rocks from the Sulu‐Dabie orogenic belt (China) using pulse transmission techniques. The Poisson's ratio of each sample was calculated from its mean P and S wave velocities from three orthogonal directions corresponding to the tectonic framework (X‐Y‐Z) defined by foliation and lineation. The experimental results display two typical categories of υ – P relationship in the range of 40–800 MPa: (1) with increasing pressure, υ increases rapidly below ∼200 MPa and then becomes quasi‐constant at higher pressures, and (2) υ shows little variation with P. Types 1 and 2 are observed in 32 and 22 samples, respectively. The origin of type 1 can be reasonably interpreted by a small volume fraction (0.1–0.5%) of randomly distributed and randomly oriented thin disk‐shaped microcracks that are progressively closed during pressurization. Type 2 is originated from the combined effects of microcrack orientation, crystallographic preferred orientations, and compositional layering. The present study confirms that the crystalline rocks at pressures above ∼200 MPa show no significant changes in Poisson's ratio with increasing pressure. Below 200 MPa, however, both modal composition and confining pressure play a critical role in influencing the Poisson's ratio.
Conversion of mesospheric HCl into active chlorine during the solar proton event in July 2000 in the northern polar region
Authors: Winkler H. , Kazeminejad S. , Sinnhuber M. , Kallenrode M.‐B. , Notholt J.
Published: September 2009

For the large solar proton event of July 2000, the Halogen Occultation Experiment instrument observed a short‐term decrease of mesospheric HCl in the northern polar region. Atmospheric chemistry and ion chemistry simulations show that HCl is converted into active chlorine species (ClO, Cl, and HOCl). Two main processes drive the transformation of HCl into active chlorine: reactions of negative chlorine species directly increase the concentrations of uncharged active chlorine compounds at the expense of HCl and the production of reactive O(1D) through N(2D) + O2 → O(3P, 1D) + NO has a considerable impact on the neutral chlorine chemistry.