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Biomedical subjects

A E Clarke

Publications and source records attributed to A E Clarke.

At least 19 recordsLinked to original sources
PubMed1992

Creating the costliest orphan. The Orphan Drug Act in the development of Ceredase.

The FDA recently approved Ceredase, a new treatment for Gaucher's disease, under the provisions of the Orphan Drug Act. Ceredase is unusually expensive, but there are no satisfactory alternative therapies. It appears likely that Ceredase would not have become available without the protection of the Orphan Drug Act, but its expense and the lack of information about its long-term effects on health raise questions about whether the ODA provides appropriate incentives to develop cost-effective technologies.

Adolescent↗
PubMed1992

Structural analysis of the N-linked glycan chains from a stylar glycoprotein associated with expression of self-incompatibility in Nicotiana alata.

Self-incompatibility in flowering plants of the family Solanaceae is mediated by the product of the S-allele. The allelic products of the S-gene in the female sexual tissues of the pistil are glycoproteins in the mol. wt range 28-32 kDa. These S-glycoproteins have been isolated from styles of Nicotiana alata, homozygous for the S1- and S2-alleles. Earlier studies have indicated that the single potential N-glycosylation site on the S1-glycoprotein bears a glycan chain, whereas of the four potential N-glycosylation sites on the S2-glycoprotein, three are glycosylated. This paper describes the purification and characterization of the N-linked glycan chains from these two glycoproteins. Oligosaccharides were cleaved off the glycoproteins using peptide-N4-(N-acetyl-beta-glucosaminyl)asparagine amidase F (N-glycanase F) and separated by anion-exchange HPLC. Four types of hybrid structure were defined by chemical techniques, fast atom bombardment-mass spectrometry (FAB-MS) and 1H-NMR. Although the relative amounts differed, all four structures were found on both the S1- and S2-glycoproteins, and are heterogeneous at some N-glycosylation sites. No O-linked glycans were detected on the S2-glycoprotein. These results are discussed in relation to the potential of the structural diversity residing in this array of glycoforms to play a rôle in allelic specificity.

Alleles↗
PubMed1992

Health status instruments and physical examination techniques in clinical measurement methodologies.

Chronic rheumatic diseases can severely compromise a patient's functional ability. These limitations are often better appreciated through a patient's self-report and a physician examination than through laboratory and radiographic assessments. Researchers are adapting the established health status questionnaires for non-English-speaking patients and for other rheumatic conditions besides rheumatoid arthritis. Rather than tailoring existing instruments for other diseases, some clinician investigators are developing entirely new disease-specific self-assessment questionnaires. Physicians are also addressing the subjectivity of their physical examination techniques. They are devising consistent and sensitive parameters that can be combined with health status questionnaires to monitor disease activity, gauge therapeutics, predict health services utilization, and predict work disability.

Disability Evaluation↗
PubMed1992

Specific expression of an extensin-like gene in the style of Nicotiana alata.

cDNAs and corresponding genomic clones encoding a putative proline-rich protein (NaPRP3) were isolated from libraries prepared from Nicotiana alata style mRNA and genomic DNA. The predicted NaPRP3 protein is structurally similar to extensin in containing six copies of the characteristic extensin sequence Ser-Pro4, but differs in being smaller (151 residues compared with greater than 300 residues) and lacking Tyr residues. In contrast to most extensin genes, the NaPRP3 gene is not induced by mechanical wounding, and its expression is restricted to cells of the transmitting tract of the style.

Amino Acids↗
PubMed1991

Molecular and evolutionary aspects of self-incompatibility in flowering plants.

Self-incompatibility (SI) is widely distributed in flowering plants. In this review, early work on the biology, genetics and distribution of SI is summarized. Approaches to understanding the molecular genetics of SI have been made in two systems-Solanaceous species, for example Nicotiana alata, which have gametophytic systems of SI, and Brassica spp, which have sporophytic systems of SI. The information in both systems is derived from cDNAs that encode pistil glycoproteins (S-glycoproteins) that segregate with S-genotype. Comparison of the sequence data indicates that the gametophytic and sporophytic systems of SI probably arose independently during the evolution of angiosperms. The S-glycoproteins of a solanaceous plant Nicotiana alata, are ribonucleases (RNases). Whether the RNase activity is directly involved in the characteristic arrest of pollen tube growth during self-(incompatible) pollination, is not known. An alternative possibility is that the RNase was 'recruited' during evolution for a function in SI, without involvement of its catalytic function. The nature of the S-gene in pollen is not yet known for either the gametophytic or sporophytic SI systems. This is a key piece of information that will be required to progress our understanding of how the growth of a pollen tube bearing a particular S-allele is arrested within the style bearing an identical S-allele, but is not arrested within the style bearing other S-alleles.

Amino Acid Sequence↗
PubMed1990

Self-incompatibility: a self-recognition system in plants.

Self-incompatibility (SI), a genetically controlled mechanism to prevent inbreeding in plants, offers a relatively simple model system for studying the interactions between plant cells or between a plant cell and the secreted product or products of another cell. Examples of two major types of SI, gametophytic and sporophytic, have been studied by cloning cDNAs corresponding to glycoproteins of the female tissues that segregate with particular variants encoded by the putative S locus. These secreted glycoproteins are envisaged to interact with the currently undescribed pollen component to cause arrest of pollen tube growth.

Amino Acid Sequence↗
PubMed1990

Transformation and regeneration of the self-incompatible species Nicotiana alata Link & Otto.

A transformation and regeneration system has been developed for Nicotiana alata, a plant which is being intensively studied as a model of gametophytic self-incompatibility. Plantlets can be regenerated efficiently from seedling hypocotyls. Kanamycin-resistant, transformed plants have been obtained by cocultivation of regenerating hypocotyls with Agrobacterium tumefaciens strain LBA4404 containing a binary vector. The transformation frequency was low with less than 1% of tissue explants regenerating transformed plants. The transformed plants contained from one to three copies of the introduced DNA. In most cases, the kanamycin resistance phenotype was transmitted to the offspring as a normal Mendelian factor. In one unusual case, none of the offspring inherited the kanamycin resistance of the transformed maternal parent. This plant may have been chimeric or the kanamycin resistance gene may have been inactivated.

DNA, Bacterial↗
PubMed1989

Recent developments in the molecular genetics and biology of self-incompatibility.

A summary of recent work on molecular aspects of self-incompatibility in Nicotiana alata is presented. The amino acid sequences of style proteins corresponding to different S-alleles of N. alata have a high level of homology in some regions and are variable in other regions. The regions of homology include N-terminal sequences as well as most of the glycosylation sites and cysteine residues. The glycosyl substituents may consist of a number of 'glycoforms'. The isolated style S-glycoproteins inhibit in vitro growth of pollen tubes. The S-glycoproteins tested inhibited the growth of pollen of several S-genotypes, and there was some specificity in the interaction. Heat treatment of the isolated S-glycoproteins dramatically increased their activity as inhibitors of pollen tube growth, although the specificity in the interaction was lost. The nature of the S-allele products in pollen is not yet established.

Alleles↗
PubMed1989

Sequence variability of three alleles of the self-incompatibility gene of Nicotiana alata.

Three alleles of the self-incompatibility gene of Nicotiana alata have been cloned and sequenced. A comparison of the sequences shows a surprisingly low level of homology (56%) and the presence of defined regions of homology and variability. The homologous regions include the N-terminal sequence, most of the cysteine residues and glycosylation sites, as well as other blocks throughout the sequence. We interpret these conserved regions as "framework" and nonconserved regions as "hypervariable," following the terminology used to describe analogous regions in the IgG supergene family. The low level of overall homology forms the basis of a general method for isolating S-allele-specific cDNAs. Allele-specific antibodies can be generated using synthetic peptides corresponding to one of the variable regions. When applied to sections of the pistil, these antibodies label the intercellular matrix in the stigma and transmitting tissue of the style and the cell walls in the epidermis of the placenta. HindIII digestion of genomic DNA generates a characteristic pattern of S-gene fragments for each genotype. These restriction fragment length polymorphisms can be used to assign S-genotype to progeny arising from breeding experiments.

Alleles↗
PubMed1989

Identification, isolation, and N-terminal sequencing of style glycoproteins associated with self-incompatibility in Nicotiana alata.

S-Gene-associated glycoproteins (S-glycoproteins) from styles of Nicotiana alata, identified by non-equilibrium two-dimensional electrophoresis, were purified by cation exchange fast protein liquid chromatography with yields of 0.5 to 8 micrograms of protein per style, depending on the S-genotype of the plant. The method relies on the highly basic nature of the S-glycoproteins. The elution profiles of the different S-glycoproteins from the fast protein liquid chromatography column were characteristic of each S-glycoprotein, and could be used to establish the S-genotype of plants in outbreeding populations. In all cases, the S-genotype predicted from the style protein profile corresponded to that predicted from DNA gel blot analysis using S-allele-specific DNA probes and to that established by conventional breeding tests. Amino-terminal sequences of five purified S-glycoproteins showed a high degree of homology with the previously published sequences of N. alata and Lycopersicon esculentum S-glycoproteins.

Amino Acid Sequence↗
PubMed1988

A simple fixation and embedding method for use in hybridization histochemistry on plant tissues.

A simple method for fixing and embedding plant tissue for hybridization histochemistry has been developed. Material is fixed with paraformaldehyde-glutaraldehyde by the phase-partition technique and embedded in LR Gold. The method preserves nucleic acids in situ. Double-stranded 32P-labelled DNA probes hybridized to complementary RNAs in thin and semithin sections. Biotinylated probes detected with immunogold markers have been used to localize transcripts at the electron microscopic level.

DNA Probes↗
PubMed1979

Structural studies on the major component of Gladiolus style mucilage, an arabinogalactan-protein.

The major component of the Gladiolus style mucilage was shown to be an arabinogalactan-protein. The arabinogalactan-protein was isolated from the style extract by affinity chromatography with tridacnin (the galactose-binding lectin from the clam Tridacna maxima) coupled to Sepharose 4B. The isolated arabinogalactan-protein represents 40% of the soluble style extract; it contains 90% (w/w) carbohydrate and 3% protein. The major monosaccharides of the carbohydrate component are galactose and arabinose, in the proportions 6:1. A component with a similar composition was also isolated from the crude extract by precipitation with the beta-glucosyl artifical carbohydrate antigen. The protein moiety of the arabinogalactan-protein remained associated with the carbohydrate after chromatography in urea, and has high contents of serine, glutamic acid, aspartic acid, glycine and alanine. The arabinogalactan-protein is apparently chemically homogeneous; it eluted as a single symmetrical peak from Sepharose 4B, and three fractions collected across the peak were structurally similar. Ultracentrifugal studies showed it to be polydisperse in the mol.wt. range 150 000--400 000. The information obtained from methylation analyses, oxalic acid and enzymic hydrolyses is consistent with a model having a beta 1 leads to 3 galactan backbone, branched through C(O)6 to beta 1 leads to 6 galactan side chains. The arabinose is exclusively present as terminal alpha-L-arabinofuranosyl residues. Enzymic removal of the arabinose residues resulted in a marked decrease in solubility of the molecule. The localization of the arabinogalactan-protein in the mucilage of the style canal was demonstrated cytochemically. The possible roles of the arabinogalactan-protein in relation to recognition of compatible pollen and pollen-tube growth are discussed.

Amino Acids↗
PubMed1979

Allergenicity of concanavalin A in mice.

Concanavalin A (Con A) is a potent allergen in certain strains of mice and in particularly the H-2Kk mice, A/J, CBA/H, and C3H/He. Using a dose of 100 microgram, the subcutaneous route of injection was the most effective means of inducing high, persistent titers of T cell-dependent circulating anti-Con A reagins without the addition of the classical IgE adjuvants, aluminium hydroxide and Bordetella pertussis vaccine. Haptenated Con A induced reagins with antihapten specificity. In the discussion, one possible contributing factor in Con A allergenicity in genetically responder strains of mice is emphasised, namely, persistence in subcutaneous injection sites.

Administration, Intranasal↗
PubMed1978

Young adolescents' beliefs concerning menstruation.

In order to explore the early socialization of attitudes and expectations about menstruation, 54 young adolescent girls (both pre- and postmenarcheal) and boys responded to a questionnaire assessing evaluative attitudes toward menstruation, expected symptomatology, perceived effects on moods and activities, and sources of information for these beliefs. The results showed that even premenarcheal girls and young boys have a reasonably well-defined and mostly negative set of attitudes and expectations. Most believed that menstruation is accompanied by physical discomforts, increased emotionality, and a disruption of activities and social interactions. Although the responses of the 3 groups were remarkably similar, premenarcheal girls had a somewhat less negative evaluation of menstruation than both postmenarcheal girls and boys. Other analysis showed that symptom expectations for "girls in general" were more severe than for selves, though these 2 sets of responses were highly correlated. On the basis of these findings and the data concerning sources of information, the possible role of socialization processes in the menstrual experience is discussed.

Adolescent↗