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Biomedical subjects

C Ainsworth

Publications and source records attributed to C Ainsworth.

At least 19 recordsLinked to original sources
PubMed2002

Molecular characterisation of Victorian Newcastle disease virus isolates from 1976 to 1999.

OBJECTIVE: To characterise Newcastle disease virus isolates obtained in Victoria from 1976 to 1999 and identify the diversity of FO cleavage signal. DESIGN: RT-PCR using viral RNA extracted from positive NDV allantoic fluid was performed to amplify a segment of the NDV F and HN genes. Molecular characterisation of the nucleotide and amino acid sequences within the FO cleavage site was undertaken. RESULTS: All isolates contained 'avirulent FO cleavage signal sequence of varied amino acid composition. CONCLUSIONS: Molecular characterisation of past and present NDV FO cleavage signal sequences will provide valuable epidemiological information and assist in understanding the genetic origins and relationships of outbreaks.

Amino Acid Sequence↗
PubMed2001

Birth of a miracle.

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Cloning, Organism↗
PubMed2001

Stop the clock.

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Age Factors↗
PubMed2001

Brain gain.

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Cloning, Organism↗
PubMed2001

Prevalence of imaginary companions in a normal child population.

Approximately 1800 children between the ages of 5 and 12 years were randomly selected and asked whether they had present or past experiences of imaginary companions. It was found that 829 (46.2%) children reported experiences of imaginary companions. These findings were unexpected as previous studies had suggested that imaginary companions are generally experienced by fewer, much younger children. There were no significant differences in creativity scores between children who reported imaginary companions compared with those who did not. Imaginary companions were reported by more girls than boys, and were not restricted to very young children.

Child↗
PubMed2000

Coordinating cell fate and morphogenesis in Drosophila renal tubules.

Using the renal tubules of Drosophila as an example, we explore how cell specification leads to the morphogenetic movements that underlie the generation of tissue architecture. Taking two stages of development, we show first that the tubule cells are allocated by signalling between the endodermal and ectodermal compartments of the posterior gut. Activation of the Wnt pathway patterns the ectodermal anlage, resulting in the expression of tubule genes in a subset of cells and their eversion from the hindgut to form the tubule primordia. We argue that early gene expression directs these morphogenetic movements but not the complete programme of tubule differentiation. In the second example we show that the allocation of the mitogenic tip cell lineage in each tubule is required not only for the normal pattern of cell division but also for the stereotyped three-dimensional arrangement of the mature tubules. Analysis of mutants in which the tip cell lineage is misspecified reveals that both daughters of the tip cell progenitor are required for the tubules to navigate through the body cavity, so that the distal tips locate in their characteristic positions. We show that the regulator of Rac, Myoblast city is essential for this second morphogenetic process.

Animals↗
PubMed1999

Disclosing special needs to parents. Have we got it right yet?

Parents' perceptions of how they were told that their child has special needs were examined. Thirty-nine families on the Isle of Wight completed a structured interview. Participants formed two groups. The first group comprised of 23 families who had a child aged from birth to 5 years with special needs. In the second group there were 16 families who had a child aged between 15 and 20 years with special needs. Parents were asked about their perceptions of how their child's special needs were disclosed, their satisfaction with how they were told and what improvements they would have liked. Differences between the two cohorts were examined, and changes in how services were perceived were investigated. Overall, parents in the group with younger children were more satisfied about the way in which they were told that their child had special needs than those with older children. Implications for service delivery and future research are considered.

Adolescent↗
PubMed1998

Sex determination in plants.

The majority of flowering plants produce flowers that are "perfect." These flowers are both staminate (with stamens) and pistillate (with one or more carpels). In a small number of species, there is spatial separation of the sexual organs either as monoecy, where the male and female organs are carried on separate flowers on the same plant, or dioecy, where male and female flowers are carried on separate male (staminate) or female (pistillate) individuals. Sex determination systems in plants, leading to unisexuality as monoecy or dioecy, have evolved independently many times. In dioecious plant species, the point of divergence from the hermaphrodite pattern shows wide variation between species, implying that the genetic bases are very different. This review considers monoecious and dioecious flowering plants and focuses on the underlying genetic and molecular mechanisms. We propose that dioecy arises either from monoecy as an environmentally unstable system controlled by plant growth substances or from hermaphroditism where the underlying mechanisms are highly stable and control does not involve plant growth substances.

Animals↗
PubMed1997

Variable domain structure of kappaIV human light chain Len: high homology to the murine light chain McPC603.

Antibody light chains of the kappa subgroup are the predominant light chain component in human immune responses and are used almost exclusively in the antibody repertoire of mice. Human kappa light chains comprise four subgroups. To date, all crystallographic studies of human kappa light chains were carried out on proteins of the kappaI subgroup. The light chain produced by multiple myeloma patient Len. was of the kappaIV subgroup, it differed by only one residue from the germ-line gene encoded protein. The variable domain fragment of the light chain was crystallized from ammonium sulfate in space group C222(1). The crystal structure was determined by molecular replacement and refined at 1.95 A resolution to an R-factor of 0.15. Protein Len has six additional residues in its CDR1 segment compared to the kappaI proteins previously characterized. The kappaIV variable domain, Len, differs in only 23 of 113 residues from murine kappa light chain McPC603. The RMS deviation upon superimposing their alpha-carbons was 0.69 A. The CDR1 segment of the human and murine variable domains have the same length and conformation although their amino acid sequences differ in 5 out of 17 residues. Structural features were identified that could account for the significantly higher stability of the human kappaIV protein relative to its murine counterpart. This human kappaIV light chain structure is the closest human homolog to a murine light chain and can be expected to facilitate detailed structural comparisons necessary for effective humanization of murine antibodies.

Amino Acid Sequence↗
PubMed1997

Leaf senescence in Brassica napus: cloning of senescence related genes by subtractive hybridisation.

A subtractive hybridisation technique was developed to clone cDNAs representing genes that showed enhanced expression during leaf senescence in Brassica napus. A number of different genes were identified that, when analysed by northern hybridisation, showed different patterns of expression during leaf development but were all expressed at increased levels during senescence. Sequence analysis of these cDNAs showed that several types of genes were found including two different proteases, glutamine synthetase, ATP sulphurylase, catalase, metallothionein, ferritin and an antifungal protein. The possible roles of these gene products in the senescence process are discussed.

Amino Acid Sequence↗
PubMed1995

Isolation and characterisation of cDNA clones representing the genes encoding the major tuber storage protein (dioscorin) of yam (Dioscorea cayenensis Lam.).

cDNA clones encoding dioscorins, the major tuber storage proteins (M(r) 32,000) of yam (Dioscorea cayenesis) have been isolated. Two classes of clone (A and B, based on hybrid release translation product sizes and nucleotide sequence differences) which are 84.1% similar in their protein coding regions, were identified. The protein encoded by the open reading frame of the class A cDNA insert is of M(r) 30,015. The difference in observed and calculated molecular mass might be attributed to glycosylation. Nucleotide sequencing and in vitro transcription/translation suggest that the class A dioscorin proteins are synthesised with signal peptides of 18 amino acid residues which are cleaved from the mature peptide. The class A and class B proteins are 69.6% similar with respect to each other, but show no sequence identity with other plant proteins or with the major tuber storage proteins of potato (patatin) or sweet potato (sporamin). Storage protein gene expression was restricted to developing tubers and was not induced by growth conditions known to induce expression of tuber storage protein genes in other plant species. The codon usage of the dioscorin genes suggests that the Dioscoreaceae are more closely related to dicotyledonous than to monocotyledonous plants.

Amino Acid Sequence↗
PubMed1995

Adenosine diphosphate glucose pyrophosphorylase genes in wheat: differential expression and gene mapping.

A full-length cDNA clone representing the large (shrunken-2) subunit of ADP-glucose pyrophosphorylase (AGP; EC 2.7.7.27) has been isolated from a cDNA library prepared from developing grain of hexaploid wheat (Triticum aestivum L., cv. Chinese Spring). The 2084-bp cDNA insert contains an open reading frame of 1566 nucleotides and primer-extension analysis indicated that the 5' end is 10 nucleotides shorter than the mRNA. The deduced protein contains 522 amino acids (57.8 kDa) and includes a putative transit peptide of 62 amino acids (6.5 kDa). The similarity of the deduced protein to the small subunit of AGP and to other AGP genes from plants and microorganisms is discussed. Northern hybridisation shows that the Agp1 genes (encoding the small subunit in the wheat endosperm) and the Agp2 genes (encoding the large subunit in the wheat endosperm) are differentially expressed in the wheat grain. Transcripts from both gene sets accumulate to high levels in the endosperm during grain development with the majority of the expression in the endopsperm rather than the embryo and pericarp layers. Although enzyme activity is detected in developing grains prior to 10 d post anthesis, only the Agp1 genes are active at this time (the Agp2 genes are not expressed until 10 d post anthesis). The possibility that the enzyme expressed during early grain development is a homotetramer of small subunits is discussed. The Agp1 and Agp2 genes are arranged as triplicate sets of single-copy homoeoloci in wheat. The Agp2 genes are located on the long arms of chromosomes 1A, 1B and 1D, about 80 cM from the centromere. The Agp1 genes have been mapped to a position just distal to the centromere on the long arms of chromosomes 7A, 7B and 7D.

Amino Acid Sequence↗
PubMed1995

Male and female flowers of the dioecious plant sorrel show different patterns of MADS box gene expression.

Male and female flowers of the dioecious plant sorrel (Rumex acetosa) each produce three whorls of developed floral organs: two similar whorls of three perianth segments and either six stamens (in the male) or a gynoecium consisting of a fertile carpel and two sterile carpels (in the female). In the developing male flower, there is no significant proliferation of cells in the center of the flower, in the position normally occupied by the carpels of a hermaphrodite plant. In the female flower, small stamen primordia are formed. To determine whether the organ differences are associated with differences in the expression of organ identity genes, cDNA clones representing the putative homologs of B and C function MADS box genes were isolated and used in an in situ hybridization analysis. The expression of RAD1 and RAD2 (two different DEFICIENS homologs) in males and females was confined to the stamen whorl; the lack of expression in the second, inner perianth whorl correlated with the sepaloid nature of the inner whorl of perianth segments. Expression of RAP1 (a PLENA homolog) occurred in the carpel and stamen whorls in very young flower primordia from both males and females. However, as soon as the inappropriate set of organs ceased to develop, RAP1 expression became undetectable in those organs. The absence of expression of RAP1 may be the cause of the arrest in organ development or may be a consequence.

Amino Acid Sequence↗
PubMed1994

Comparison of crystal structures of two homologous proteins: structural origin of altered domain interactions in immunoglobulin light-chain dimers.

The sequence and structure of a second human kappa 1 immunoglobulin light-chain variable domain, Wat, has been determined. The R-factor is 15.7% for 1.9-A data. One hundred and ninety-five water molecules were identified; 30 water molecules were located in identical positions in each of the monomers. Some of the water molecules are integral parts of the domains. This light chain is encoded by the same variable domain gene that encoded the previously characterized kappa I variable domain, Rei. Due to limited somatic mutation, the two highly homologous proteins differ in only 20 of the 108 residues. Wat crystallized in space group P6(4) while Rei crystallized in space group P6(1); in both crystals, the asymmetric unit was the noncovalent dimer. Although the basic domain structure is the same for both proteins, the relative positions of the domains within the two dimers differ. This difference is most likely accounted for by the replacement of Tyr36 in Rei by Phe in the Wat protein. Residue Tyr36 is part of the hydrogen-bonding network in the interface between the domains in Rei. Losing the hydrogen-bonding capability of residue 36 by replacement of Tyr by Phe alters the network of hydrogen bonds between the domains, resulting in a different domain-domain contact. The details of lattice contacts in the two crystals were compared. One type of contact that extends the beta-sheet of the individual domains was conserved, but because it involved different symmetry elements within the crystal, different crystal packing resulted. In the Wat crystal, one of the contacts shows an example of how a symmetrical binding site can "bind" an asymmetrical object. Further, the examination of the Wat crystal also illustrates how the different crystalline environments of the domains of the dimer results in different distributions of temperature factors for the residues within the domains.

Amino Acid Sequence↗
PubMed1993

Isolation and analysis of a cDNA clone encoding the small subunit of ADP-glucose pyrophosphorylase from wheat.

A full-length cDNA clone from hexaploid bread wheat, encoding the small subunit of ADP-glucose pyrophosphorylase, has been isolated from an endosperm cDNA library. The cDNA insert has an open reading frame which encodes a protein of 473 amino acids (52.1 kDa). The presence of a chloroplast/amyloplast transit peptide of 22 amino acids is proposed. The deduced amino acid sequence exhibits a high degree of homology with the small subunit ADP-glucose pyrophosphorylase proteins from rice (with 90% of identical amino acids) and potato (with 86% of identical amino acids) and contains conserved sequence elements which are thought to represent the substrate binding and allosteric activator sites. The genes are organised as single-copy loci on chromosomes 7A, 7B and 7D in the wheat genome and are highly expressed during grain development. Homologous transcripts are expressed in leaves and roots.

Amino Acid Sequence↗
PubMed1993

Expression, organisation and structure of the genes encoding the waxy protein (granule-bound starch synthase) in wheat.

A full-length cDNA clone representing the waxy protein (GBSSI) isolated from a hexaploid wheat developing grain cDNA library has been used to characterise the organisation and expression of the waxy genes in wheat. The genes are organised as a triplicate set of single copy homeoloci on chromosome arms 4AL, 7AS and 7DS. The genes are active throughout grain filling where the main 2.3 kb transcript accumulates to high levels. The 2.3 kb transcript is not expressed in leaves where the presence of a related, but less homologous, transcript of 1.6 kb suggests that a different set of genes operates. Gel analysis and purification of the waxy protein isolated from starch granules, followed by N-terminal amino acid sequencing in conjunction with data from hybrid select translation experiments and sequence analysis of the cDNA, shows that the mature protein has a molecular weight of 60kDa (615 amino acids) and that the preprotein includes a chloroplast/amyloplast transit peptide of 7kDa (75 amino acids). Analysis of the derived amino acid sequence and alignment with five other plant waxy proteins shows that they exhibit substantial homology. The wheat protein differs from all others in that it contains an 11 amino acid insertion towards the N-terminus. The protein contains the conserved motif KTGGL found in other waxy proteins and which has been implicated as the active site in glycogen synthase.

Amino Acid Sequence↗
PubMed1989

Structure of a second crystal form of Bence-Jones protein Loc: strikingly different domain associations in two crystal forms of a single protein.

We have determined the structure of the immunoglobulin light-chain dimer Loc in a second crystal form that was grown from distilled water. The crystal structure was determined to 2.8-A resolution; the R factor is 0.22. The two variable domains are related by local 2-fold axes and form an antigen binding "pocket". The variable domain-variable domain interaction observed in this crystal form differs from the one exhibited by the protein when crystallized from ammonium sulfate in which the two variable domains formed a protrusion (Chang et al., 1985). The structure attained in the distilled water crystals is similar to, but not identical with, the one observed for the Mcg light-chain dimer in crystals grown from ammonium sulfate. Thus, two strikingly different structures were attained by this multisubunit protein in crystals grown under two different, commonly used, crystallization techniques. The quaternary interactions exhibited by the protein in the two crystal forms are sufficiently different to suggest fundamentally different interpretations of the structural basis for the function of this protein. This observation may have general implications regarding the use of single crystallographic determinations for detailed identification of structural and functional relationships. On the other hand, proteins whose structures can be altered by manipulation of crystallization conditions may provide useful systems for study of fundamental structural chemistry.

Bence Jones Protein↗