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S J Shepherd

Publications and source records attributed to S J Shepherd.

9 recordsLinked to original sources
PubMed2007

Review article: fructose malabsorption and the bigger picture.

Fructose is found widely in the diet as a free hexose, as the disaccharide, sucrose and in a polymerized form (fructans). Free fructose has limited absorption in the small intestine, with up to one half of the population unable to completely absorb a load of 25 g. Average daily intake of fructose varies from 11 to 54 g around the world. Fructans are not hydrolysed or absorbed in the small intestine. The physiological consequences of their malabsorption include increasing osmotic load, providing substrate for rapid bacterial fermentation, changing gastrointestinal motility, promoting mucosal biofilm and altering the profile of bacteria. These effects are additive with other short-chain poorly absorbed carbohydrates such as sorbitol. The clinical significance of these events depends upon the response of the bowel to such changes; they have a higher chance of inducing symptoms in patients with functional gut disorders than asymptomatic subjects. Restricting dietary intake of free fructose and/or fructans may have durable symptomatic benefits in a high proportion of patients with functional gut disorders, but high quality evidence is lacking. It is proposed that confusion over the clinical relevance of fructose malabsorption may be reduced by regarding it not as an abnormality but as a physiological process offering an opportunity to improve functional gastrointestinal symptoms by dietary change.

Adolescent↗
PubMed2005

Personal view: food for thought--western lifestyle and susceptibility to Crohn's disease. The FODMAP hypothesis.

Susceptibility to the development of Crohn's disease involves a combination of genetic and environmental factors. The association of Crohn's disease with westernization has implicated lifestyle factors in pathogenesis. While diet is a likely candidate, evidence for specific changes in dietary habits and/or intake has been lacking. A new hypothesis is proposed, by which excessive delivery of highly fermentable but poorly absorbed short-chain carbohydrates and polyols (designated FODMAPs--Fermentable Oligo-, Di- and Mono-saccharides And Polyols) to the distal small intestinal and colonic lumen is a dietary factor underlying susceptibility to Crohn's disease. The subsequent rapid fermentation of FODMAPs in the distal small and proximal large intestine induces conditions in the bowel that lead to increased intestinal permeability, a predisposing factor to the development of Crohn's disease. Evidence supporting this hypothesis includes the increasing intake of FODMAPs in western societies, the association of increased intake of sugars in the development of Crohn's disease, and the previously documented effects of the ingestion of excessive FODMAPs on the bowel. This hypothesis provides potential for the design of preventive strategies and raises concern about current enthusiasm for putative health-promoting effects of FODMAPs. One of the greatest challenges in defining the pathogenesis of Crohn's disease is to identify predisposing environmental factors. Such an achievement might lead to the development of preventive strategies for, and the definition of, possible target for changing the natural history of this serious disease. The present paper describes a new hypothesis for one such environmental factor.

Crohn Disease↗
PubMed2002

Oomycete plant pathogens use electric fields to target roots.

Plant roots generate electrical currents and associated electrical fields as a consequence of electrogenic ion transport at the root surface. Here we demonstrate that the attraction of swimming zoospores of oomycete plant pathogens to plant roots is mediated in part by electrotaxis in natural root-generated electric fields. The zones of accumulation of anode- or cathode-seeking zoospores adjacent to intact and wounded root surfaces correlated with their in vitro electrotactic behavior. Manipulation of the root electrical field was reflected in changes in the pattern of zoospore accumulation and imposed focal electrical fields were capable of overriding endogenous signals at the root surface. The overall pattern of zoospore accumulation around roots was not affected by the presence of amino acids at concentrations expected within the rhizosphere, although higher concentrations induced encystment and reduced root targeting. The data suggest that electrical signals can augment or override chemical ones in mediating short-range tactic responses of oomycete zoospores at root surfaces.

Electricity↗
PubMed2001

Natural DNA mixtures generated in fraternal twins in utero.

Analysis of multiple genetic loci using short tandem repeats (STR) is widely used in human identity testing because the extensive polymorphism at these loci allows for a high degree of discrimination among individuals. We recently received a forensic case that included several pieces of evidence and reference blood samples. Upon initial testing, one of the suspects had a DNA profile that included three alleles at four of the nine loci tested (vWA, FGA, TH01, and D5S818). At each locus, two of the alleles appeared to be "major" alleles with a third "minor" allele present. The profile appeared to be a mixture of two people. Contamination of this first reference sample was suspected and a second, unopened blood specimen was requested from this individual. The DNA profile from this second reference specimen was identical to that of the original specimen at each locus. One of the evidence samples also displayed an identical mixed DNA profile matching that of the reference specimens mentioned above. The relative peak heights of the two "major" and one "minor" allele remained constant in all three samples. Additional background information revealed that the suspect had not received a bone marrow transplant or blood transfusion. However, it was disclosed that this individual is a fraternal (dizygotic) twin. We hypothesize that an exchange of blood cells between the fetuses occurred in utero and that the additional alleles present in these reference samples are derived from cells contributed by his twin sibling. No additional specimens from the suspect or his twin could be obtained for confirmation, and our hypothesis remains untested. Forensic scientists should be aware of this possibility when faced with a DNA profile in which extra alleles at multiple loci are detected.

Alleles↗
PubMed2000

Loss of heterozygosity detected in a short tandem repeat (STR) locus commonly used for human DNA identification.

Short tandem repeat (STR) markers are commonly used in basic genetic research and in human identification testing. Clinically, STRs can be used to study genetic alterations in tumors. A genetic deletion common to many types of cancer is referred to as the loss of heterozygosity (LOH). Numerous examples of LOH in cancer have been described and some have been mapped to areas located in close proximity to markers employed in human identity testing. Despite this fact, LOH has rarely been observed for STR loci commonly employed in forensic testing. Recently, for medico-legal purposes, we were asked to determine whether a tissue biopsy originated from a particular individual. For a reference source we assessed two specimens, one from normal tissue and one from cancerous tissue. When both reference specimens were used to generate DNA profiles, we observed LOH at one STR locus, D13S317. As demonstrated in other cancers only the cancerous biopsy demonstrated LOH. The forensic community should be cognizant of these unusual circumstances because, as identification of human DNA continues to be used more extensively, certain instances will arise in which reference material will not be readily available. In these situations, archived specimens may be employed as a reference source. Clinical specimens such as tissue biopsies should be used with caution if they have not been confirmed to contain normal tissue.

DNA Fingerprinting↗
PubMed1997

Obstetric outcomes and infant birthweights for Vietnamese-born and Australian-born women in southwestern Sydney.

The southwestern Sydney area has the highest population of Vietnamese immigrants in New South Wales. The purpose of this study was to identify differences in obstetric outcomes and birthweights of infants of Vietnamese-born women and Australian-born women in southwestern Sydney during 1991. There was a higher incidence of gestational diabetes and a lower incidence of pre-eclampsia in Vietnamese-born women. The rate of induction of labour for Australian-born women (23.7 per cent) was almost double the rate for Vietnamese-born women (12.9 per cent). Birthweights of infants of vietnamese-born women were significantly lower at the 10th, 50th and 90th percentile. The use of racially appropriate growth charts will reduce overdiagnosis of growth-restricted infants and therefore unnecessary treatment. These findings highlight the need to take ethnic differences into account when planning health care.

Adolescent↗
PubMed1990

Safety at work for railway staff in Britain.

The recent series of railway accidents raised questions about the safety of British Railways. We have studied trends in accidents to railway staff over a 33-year period, 1954-86, which time has covered the pre- and post-modernization of the railways, in conjunction with large reductions in both staffing and traffic volume. The Railway Inspectorate, which has the duty of investigating and reporting on accidents occurring on railway premises, defines three kinds of accident: train, movement and non-movement. The numbers of railway staff killed and injured in each kind of accident have been studied in relation to the number of staff employed and train-miles run. Trends in the three accident rates derived thereby show quite different patterns: for most of the period under study, train accident rates have shown a linear increase and movement accident rates a linear decrease, whilst non-movement accidents exhibited no particular trend at all. In the last 5 years, however, both movement and non-movement accident rates have decreased sharply, whilst train accident rates have increased above the generally rising trend. Explanations for some of these trends and changes are suggested, but the reasons for others remain obscure.

Accidents, Occupational↗