Genome-wide mapping with biallelic markers in Arabidopsis thaliana.

Single-nucleotide polymorphisms, as well as small insertions and deletions (here referred to collectively as simple nucleotide polymorphisms, or SNPs), comprise the largest set of sequence variants in most organisms. Positional cloning based on SNPs may accelerate the identification of human disease traits and a range of biologically informative mutations. The recent application of high-density oligonucleotide arrays to allele identification has made it feasible to genotype thousands of biallelic SNPs in a single experiment. It has yet to be established, however, whether SNP detection using oligonucleotide arrays can be used to accelerate the mapping of traits in diploid genomes. The cruciferous weed Arabidopsis thaliana is an attractive model system for the construction and use of biallelic SNP maps. Although important biological processes ranging from fertilization and cell fate determination to disease resistance have been modelled in A. thaliana, identifying mutations in this organism has been impeded by the lack of a high-density genetic map consisting of easily genotyped DNA markers. We report here the construction of a biallelic genetic map in A. thaliana with a resolution of 3.5 cM and its use in mapping Eds16, a gene involved in the defence response to the fungal pathogen Erysiphe orontii. Mapping of this trait involved the high-throughput generation of meiotic maps of F2 individuals using high-density oligonucleotide probe array-based genotyping. We developed a software package called InterMap and used it to automatically delimit Eds16 to a 7-cM interval on chromosome 1. These results are the first demonstration of biallelic mapping in diploid genomes and establish means for generalizing SNP-based maps to virtually any genetic organism.

Polymer nanocomposites exhibiting magnetically tunable microwave properties.

Polymer nanocomposites (PNCs) have been synthesized using Rogers polymer and CoFe2O4 nanoparticles (CFO NPs). X-ray diffraction (XRD) confirms the inverse spinel crystal structure of CFO NPs and transmission electron microscopy (TEM) images show the uniform dispersion of nanoparticles (10 nm ± 1) into the polymer matrix. Magnetic measurements indicate superparamagnetic response near room temperature for all PNCs. A blocking temperature T(B)~298 K was observed and does not vary for different loading fractions of CFO NPs for the PNCs. The saturation magnetization (M(s)) was found to be 11 emu g⁻¹ for 30 wt% CFO, increasing to 32 emu g⁻¹ for the 80 wt% CFO loaded PNC. A large value of coercivity (H(c) = 19 kOe) is also observed at 10 K and is not affected by varying CFO loading. Microwave measurements show significant absorption in the 80 wt% CFO loading PNC and the quality factor shows a strong enhancement with applied magnetic field.

Chemical derivatization of therapeutic proteins.

Despite major advances in redesigning and producing proteins through recombinant DNA technology, many therapeutic proteins are still produced by extraction from biological tissues or fluids, or from nonrecombinant microorganisms. Modification of such proteins, to improve potency and bioavailability and reduce immunogenicity, can only be carried out post-translationally by chemical-derivatization methods. Genetic- and chemical-modification methods are not mutually exclusive, however, and may be combined to optimize protein-engineering strategies, because chemical modification can introduce structural changes that are not encoded by DNA into both recombinant, and nonrecombinant proteins.

The influence of hapten density on the assay of penicilloylated proteins in fluids.

The use of inhibition radioimmunoassays for the measurement of penicilloylated proteins in biological fluids is compromised by the dominant influence of hapten density. Precise quantitation, and therefore assessment of antigenicity and immunogenicity, cannot be achieved in the absence of knowledge of the number and distribution of haptenic groups on the protein carrier. These assays may not, therefore, be appropriate for the measurement of potential allergenic residues in food products.

Interference in the radioallergosorbent test by antibody light chains in rabbit urine.

Immunological techniques have been used to identify and quantitate rabbit antibody light chains in the urine of rabbits. The influence of these light chains on the radioallergosorbent test (RAST) used for the diagnosis of laboratory animal allergy to rabbit urinary protein allergens is described. The presence of IgG antibody specific for rabbit derived antigens in human serum has been confirmed.

Risk assessment of antibiotic residues of beta-lactams and macrolides in food products with regard to their immuno-allergic potential.

In human medicine drug allergy is a well-established side-effect of the therapeutic use of antibiotics, especially the beta-lactams. Side-effects caused by macrolides are uncommon and only a very few of these seem to be caused by allergic mechanisms. Clinically, drug allergy is characterized by a spectrum of reactions ranging from mild skin rashes to angio-oedema or life-threatening anaphylaxis. Concern has been expressed that antibiotic residues in meat and other foods might be responsible for similar hypersensitivity reactions in a small number of individuals. This review assesses the potential risk of such reactions in general, but focuses on allergy to penicillin and macrolide residues in particular. In relation to the risk of primary sensitization, it is unlikely that residues could contribute to the overall immune response in view of the very low levels that are likely to be encountered in comparison with the high levels received during therapeutic use. No evidence has been found that any individual has become sensitized by residues of either penicillins or macrolides. Furthermore, the oral route is much less sensitizing than parenteral administration and immunochemical studies with penicillin indicate that hapten-protein complexes formed in vivo are unlikely to be immunogenic because of their low dose, low epitope density and binding to autologous carrier proteins. For performed allergens, the epitope density was also too low to be immunogenic. Because of the ubiquitous nature of penicillin-producing moulds in nature and the extensive use of beta-lactam antibiotics in human medicine, it is unlikely that epidemiological studies could be undertaken that could allow quantification of the minimal risk. The risk of allergic reactions in pre-sensitized individuals can be assessed similarly and again it is concluded that factors such as dose, oral administration and low epitope density make it unlikely that a significantly antigenic derivative could be formed. However, a review of the literature on penicillin hypersensitivity revealed a very small number of previously sensitized individuals from whom there is reasonable clinical and documentary evidence that penicillin residues in milk triggered an allergic reaction, usually a rash. Although these cases are very rare (less than 10 cases reported in the last 25 years), they illustrate the continuing need to control antibiotic residues vigilantly. Animal models have not proved useful for predicting the risk of hypersensitivity reactions to drugs, since allergy in man is determined by genetic and other factors and no validated methods exist to determine a no-effect level.(ABSTRACT TRUNCATED AT 400 WORDS)

Laboratory animal allergy: the measurement of airborne urinary allergens and the effects of different environmental conditions.

Casella Simquad air samplers, with 0.5 microM cut-off filters, were employed to sample the air in a laboratory animal house environment. The extracts obtained were assayed for laboratory animal urinary protein allergens using the inhibition radioallergosorbent test (RAST inhibition). The results showed that the collection and assay methods were of value and studies were extended to the influence of air change rates and humidity on airborne allergen levels. Reducing the air changes increased allergen levels, whilst increasing the humidity from 54% to 77% caused a significant reduction in allergen levels.

Will physicians replace MHAs?: reflections from Australia.

Tom Weil, in the preceding article, sees the physician executive playing an increasingly significant role in negotiations between payers and service providers, in offering the public acceptable explanations for the inevitable changes in the provision of care, and in developing more cost-effective methods of delivering high-quality health care at affordable prices. Effective involvement of physician executives will be facilitated by their having received professional training somewhat different from that of the traditional MHA. How do these prognostications relate to the health care scene in Australia? Factors that must be taken into account in considering their applicability to Australia include differences in the structure and management of the Australian health care system, the current state of that system, the background of the leadership that makes the key managerial decisions in the Australian system, and emerging trends within the system.

Effects of beta-lactam antibiotics on eukaryotic cells.

A symposium on effects of beta-lactam antibiotics on eukaryotic cells was held as part of the 9th International Congress of Infectious and Parasitic Diseases (Munich, Germany, July 1986). This symposium provided an opportunity to review recent work on the effect of beta-lactam structures on mammalian cells in culture and to speculate on possible clinical implications. This paper is a comment on the subject matter covered by the symposium papers which follow.

Measurement of IgG subclasses in the sera of laboratory workers exposed to rats.

Human IgG antibody subclasses have been measured in the sera of workers exposed to rats, using a crude extract of rat urinary protein antigens, in an ELISA system. The antibody titres in individuals either with or without specific IgE were similar, with the exception of IgG4 where the mean level of this subclass was lower in those individuals with measurable titres of IgE (p less than 0.01). Symptomatic individuals, with specific IgE, also had lower titres of IgG4 than the corresponding asymptomatic, IgE-positive subjects (p less than 0.05). The frequency of positives in each subclass assay was similar in both groups. These findings suggest that higher levels of IgG4 may have a protective rôle.

Reduction in incidence of ampicillin rash by purification of ampicillin.

Purification of ampicillin (Penbritin) with respect to protein impurities has been found significantly to reduce the incidence of rashes in treated patients. This may be related to findings in animals that injections of the isolated protein impurity can induce the formation of circulating IgG antibodies and skin-sensitizing antibodies.

Development and use of three new radioallergosorbent tests in the diagnosis of penicillin allergy.

The synthesis and characterisation of three novel reagents for use in the radioallergosorbent test (RAST) for the diagnosis of penicillin allergy are described. The antigenic determinants involved are the benzyl penicillanyl, thiol-linked benzyl penicillenate and thiol-linked penicillamine. These reagents, and also one specific for the benzyl penicilloyl group, have been used to evaluate the sea of subjects suspected of suffering from penicillin allergy and to explore the aetiology of the respiratory dyspnoea experienced by some workers exposed to penicillin-containing dusts. The use of these reagents, while confirming the importance of the penicilloyl or major determinant of penicillin allergy, has shown that there is heterogeneity in the IgE response of penicillin-allergic patients and some patients have IgE antibody specific for one or more of the new determinants only. These reagents will, therefore, increase diagnostic capabilities. Their use has also confirmed that the disorder induced by occupational exposure to penicillins is not primarily mediated by IgE antibody specific for allergenic determinants represented by any of the available reagents.