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Biomedical subjects

J H Edwards

Publications and source records attributed to J H Edwards.

At least 19 recordsLinked to original sources
PubMed2005

Amendment effects on soil test phosphorus.

Applications of animal manures have increased soil test P values in many parts of the USA and thus increased the risk that soil P will be transferred to surface water and decrease water quality. To continue farming these areas, landowners need tools to reduce the risk of P losses. A field experiment was conducted near Kurten, TX, on a Zulch fine sandy loam (thermic Udertic Paleustalfs) with Bray-1 P values exceeding 3000 mg P kg(-1) soil (dry wt.) in the A(p) horizon to evaluate the effectiveness of soil amendments for reducing soil test P values. Soils were amended annually from 1999 to 2001 with 1.5 and 5.0 Mg gypsum ha(-1), 1.4 Mg alum ha(-1), or 24.4 Mg ha(-1) of waste paper product high in Al alone or in combination with 1.5 Mg gypsum ha(-1) and/or 1.4 Mg alum ha(-1). These treatments supplied a maximum of 225 and 1163 kg ha(-1) yr(-1) of Al and Ca, respectively. Soil Bray-1 P and dissolved reactive P levels were monitored from 1999 to 2004. None of the soil amendment treatments affected Bray-1 P values. Only annual additions of 5.0 Mg gypsum ha(-1) from 1999 to 2001 significantly reduced soil dissolved reactive P. Dissolved reactive P levels reached minimal levels after two applications of 5.0 Mg gypsum ha(-1) but increased in 2003 and 2004. These results indicate that soil dissolved reactive P levels can be reduced if sufficient amounts of gypsum were added to supply Ca in amounts similar to the soil test P values.

Agriculture↗
PubMed2003

Sib-pairs in multifactorial disorders: the sib-similarity problem.

Common disorders are, by definition, the major cause of ill health and death. Most can be modified by avoiding or shielding an environment, as in sunburn and coeliac disease, by replacing some deficient substance, as in diabetes or myxoedema, or by empirical methods of evident effect as in schizophrenia and depressive illness. As expected, all show an increased incidence in relatives and the identification of the more influential loci involved may define unexpected links in the metabolic map: these may be amenable to therapy, or, in autoimmune disorders and asthma, define precipitating factors by sequencing the receptor involved. The major investment in trawling the genotype for influential loci has been by affected sib-pairs with parents (ASPs). Over a hundred major studies have been published with very limited success. No substantial study of normal sib-pairs has been undertaken, making this family of surveys one of the largest undertaken in the absence of controls. Possible reasons for this limited success and the many suggestive false positives are considered.

False Positive Reactions↗
PubMed1999

Report and abstracts of the Sixth International Workshop on chromosome 9.

A meeting on chromosome 9 was held on Tuesday, 27 October 1998 in Denver, with 38 participants (see appendix). Since the last meeting several of the positional cloning efforts on chromosome 9q have come to fruition, and the most detailed discussion was on 9p. Dr Ian Dunham from the Sanger Centre explained the strategy to be used for sequencing chromosome 9, and encouraged collaboration in the preparatory mapping. He indicated that some priority could be given to those regions where people in the field had a strong interest and could identify relevant PAC clones. At this short meeting it was clearly not possible to construct a comprehensive map of chromosome 9, and it was decided that efforts should be made to maintain links to sources of information on the chromosome 9 web page (http:@www.gene.ucl.ac.uk/chr9/). The discussions at the meeting are summarized in four sections: 9p, 9cen-q31, 9q32-9q34 and comparative mapping. Many of the posters presented at the meeting were also presented at the ASHG meeting (28-31 October 1998). They are listed here and are published in The American Journal of Human Genetics, vol. 63 (supplement). Abstracts for posters presented only at this meeting are appended to this report.

Animals↗
PubMed1998

Penrose and sib-pairs.

Penrose's sib-pair papers (1935-1953) are discussed in relation to recent applications. His essential contribution that parental typing was an inefficient addition to sib-pair data for linkage detection remains. Parents now have even less to offer with contemporary markers in the detection of linkage, although not the enumeration of haplotypes. Attention is drawn to two little known papers by Penrose on multifactorial disease, and it is suggested that this term should replace polygenic in relation to family analyses. The convention established by Penrose, both as author and editor, of raw data being published alongside its analysis, which later fell into disuse on grounds of sheer bulk, can now be remedied by the Internet, and has been for the largest set of sib-pair data on diabetes (Davies et al. Nature 371 (1994), 130-136). This is essential if the contributions to the identity and location of alleles possibly relevant to common disorders, none of which are likely to be more than suggestive in any single study, can be combined to assess consistency and joint evidence. Attention is drawn to a third little known paper by Penrose of high relevance to the strategy of familial investigations in multifactorial disorders. All five of the Penrose papers discussed here can be viewed at http:/(/)www.gene.ucl.ac.uk/anhumgen/.

England↗
PubMed1997

The sib-pair problem. I. Affected pairs with parents. Constant penetrance models.

Affected sib pairs with typed but unaffected parents, conveniently termed foursomes, have become a major source of information on genetic susceptibility to common disease. So far most methods of analysis have been based on extensions of the single locus analyses developed, and successfully applied, to the mendelian disorders. However, unifactorial methods are not suited to multifactorial disorders. The power of methods of detecting linkage in the presence of more than one locus with one or more susceptibility alleles is considered. The relevance of familial clustering to predicting the presence of loci with susceptibility or resistance alleles sufficiently frequent and effective to have an appreciable influence on population incidence is discussed. The mathematical problem of clustering due to numerous alleles of small effect was resolved by Pearson in 1901 in relation to claims that the mendelian model of an allele at a single locus determining a distinct phenotype was necessary to explain the familial concentrations that had been observed in several species. The apparent inconsistency between the mendelian and polygenic models was resolved by Fisher's demonstration in 1918 that there was no essential difference between these two extreme forms of phenotypic determination. Although constant penetrance models are unrealistic, and no longer necessary since Pearson's analysis, the assumption is implicit in most recent analyses and has the advantage of simplicity in providing a lower limit on the sample sizes necessary.

Disease Susceptibility↗
PubMed1995

CEPH consortium map of chromosome 14.

Families from the linkage panel of Centre d'Etude du Polymorphisme Humain have been used to generate a linkage map containing 68 loci; 13 genes, 33 di- and 4 tetranucleotide repeats, one oligonucleotide ligation assay (OLA), and 17 RFLPs. This map integrates markers from several previous maps, and has undergone further error checking. 43 loci have been placed with odds of 1000:1 or greater, five with odds of 100:1, with an average interval of 3.5 cM. An additional 20 loci have been placed within defined intervals.

Chromosome Mapping↗
PubMed1994

Comparative genome mapping in mammals.

The mammals all have similar amounts of DNA, usually distributed over 40-60 chromosomes. Most of the differences in karyotype are related to fixation of less than 100 reciprocal translocations which have occurred over less than 100 million years. This allows the genome mapping of the main laboratory and farmyard species to help, and to be helped by, mapping of the human genome.

Animals↗
PubMed1994

The two locus problem.

The problem of detecting linkage between two loci expressed as similar phenotypes and two or more marker loci from a set of families is discussed and a solution advanced. The term amphigenic is suggested for such conditions.

Genetic Linkage↗
PubMed1994

Mouse homologues of human hereditary disease.

Details are given of 214 loci known to be associated with human hereditary disease, which have been mapped on both human and mouse chromosomes. Forty two of these have pathological variants in both species; in general the mouse variants are similar in their effects to the corresponding human ones, but exceptions include the Dmd/DMD and Hprt/HPRT mutations which cause little, if any, harm in mice. Possible reasons for phenotypic differences are discussed. In most pathological variants the gene product seems to be absent or greatly reduced in both species. The extensive data on conserved segments between human and mouse chromosomes are used to predict locations in the mouse of over 50 loci of medical interest which are mapped so far only on human chromosomes. In about 80% of these a fairly confident prediction can be made. Some likely homologies between mapped mouse loci and unmapped human ones are also given. Sixty six human and mouse proto-oncogene and growth factor gene homologies are also listed; those of confirmed location are all in known conserved segments. A survey of 18 mapped human disease loci and chromosome regions in which the manifestation or severity of pathological effects is thought to be the result of genomic imprinting shows that most of the homologous regions in the mouse are also associated with imprinting, especially those with homologues on human chromosomes 11p and 15q. Useful methods of accelerating the production of mouse models of human hereditary disease include (1) use of a supermutagen, such as ethylnitrosourea (ENU), (2) targeted mutagenesis involving ES cells, and (3) use of gene transfer techniques, with production of 'knockout mutations'.

Animals↗
PubMed1993

Evolution and environmental change.

The effects of agriculture have been to improve the stock by selective breeding at a necessary loss of some capacities to withstand epidemics, while movements of products and stock have increased the speed with which epidemics spread. Some implications are considered. In relation to human genetics there is also evidence of a lack of selection, rather than any directed selection, and this will necessarily have some long-term effects. However, they are not well understood and are certainly slight, but cumulative. All that can be done at present is to maintain the lowest practical exposure to mutagens: the best understood, radioactivity, does not appear to be a serious hazard in the absence of catastrophic events or inappropriate medical usage.

Animals↗
PubMed1993

Skeletal muscle bioenergetics in myotonic dystrophy.

Skeletal muscle function of 15 patients with myotonic dystrophy (dystrophia myotonica, DM) was investigated using 31P magnetic resonance spectroscopy to evaluate bioenergetics and intracellular pH at rest and during exercise and recovery. Results from DM patients, normal controls and mitochondrial myopathy patients were compared in order to assess the possible contribution of abnormal mitochondrial metabolism to muscle dysfunction in DM. In resting DM muscle, intracellular pH (pHi) was normal, but there were significant elevations in the concentration ratios of Pi/ATP, phosphomonoesters/ATP and phosphodiesters/ATP. In patients with the most severe exercise intolerance the phosphocreatine/ATP ratio was also reduced. Resting muscle of 11 mitochondrial myopathy patients showed similar changes to those of the most exercise-intolerant DM patients. In exercising DM muscle, energy stores were rapidly depleted as in mitochondrial myopathy. Muscle acidified in all subjects, but in DM the decrease in pHi was less than in normal muscle. Recovery half-times for phosphocreatine, Pi and ADP were normal in DM but slow in mitochondrial myopathy. The initial rate of phosphocreatine repletion after exercise was rapid in DM, consistent with high [ADP], but slow in mitochondrial myopathy in spite of elevated [ADP]. Because recovery is an oxidative process, we conclude that there was no decrease in the oxidative capacity of the muscles in this group of DM patients. In the subjects in whom it could be measured, the rate of recovery of intracellular pH was greater in the 3 DM patients (0.14, 0.15 and 0.16 U/min) than in the 7 normal controls (0.08-0.12 U/min, mean 0.10). The results do not rule out a minor abnormality in glycogenolysis, but they suggest that the failure to acidify normally during exercise is probably due to rapid proton efflux.

Adenosine Diphosphate↗
PubMed1993

Inhalation challenge in pigeon breeder's disease: BAL fluid changes after 6 hours.

The purpose of this study was to determine the cellular events occurring 6 h after bronchial inhalation challenge, in a group of pigeon breeders. Twelve subjects agreed to undergo challenge, either with nebulized pigeon serum (Ps) (n = 10), or with saline (n = 2). The development of characteristic symptoms was used to detect a positive response in combination with monitoring tests (white blood cell count (WBC), body temperature, and spirometry). An initial bronchoalveolar lavage (BAL) was performed before inhalation challenge, and a further BAL on the previously spared right middle lobe subsegment or lingula 6 h after challenge. Paired bronchoalveolar lavage fluid (BALF) samples were analysed for urea, albumin, total and differential WBC, interleukin-1 and interleukin-2. There was a significant increase in total cells, lymphocytes, T-lymphocytes, and neutrophils; numbers.ml-1 of BALF in responders. A monitoring score reflecting severity of patient response correlated with an increase in all cell types (p < 0.05). In conclusion, responders developed both a BALF lymphocytic and neutrophilic "alveolitis" following inhalation challenge, the degree of BALF "alveolitis" correlating with the severity of patient response.

Adult↗