Differences in hormone localisation patterns of K and L type enteroendocrine cells in the mouse and pig small intestine and colon

 This study has investigated the patterns of colocalisation of the conventional K cell marker, glucagon-like insulinotropic peptide (GIP), and the L cell markers, glucagon like peptide-1 (GLP-1) and peptide YY (PYY), in enteroendocrine cells (EEC) of the small intestine and colon of mouse and pig. All combinations of the hormones, 3 in a cell, 2 in a cell and 1 at a time, were encountered. In both species, the three most common EEC types contained (1) both GLP-1 and PYY but not GIP, (2) GLP-1 alone or (3) GIP plus GLP-1 without PYY. Few GIP plus PYY cells and rare cells containing all 3 hormones were encountered. Gradients of cell types occurred along the intestine. For example, in mouse, there were no PYY cells in the duodenum and few in the jejunum, but >50 % of labelled EEC in the distal ileum and colon were PYY immunoreactive. By contrast, over 40 % of EEC in the pig duodenum contained PYY, and most also contained either GLP-1 or GIP. The gradient in pig was less pronounced. It is concluded that the traditional classification of K and L cells requires revision, and that there are major inter-species differences in the patterns of colocalisation of hormones that have been used to characterise K and L cells.

A provisional database for the silicon content of foods in the United Kingdom

Si may play an important role in bone formation and connective tissue metabolism. Although biological interest in this element has recently increased, limited literature exists on the Si content of foods. To further our knowledge and understanding of the relationship between dietary Si and human health, a reliable food composition database, relevant for the UK population, is required. A total of 207 foods and beverages, commonly consumed in the UK, were analysed for Si content. Composite samples were analysed using inductively coupled plasma–optical emission spectrometry following microwave-assisted digestion with nitric acid and H2O2. The highest concentrations of Si were found in cereals and cereal products, especially less refined cereals and oat-based products. Fruit and vegetables were highly variable sources of Si with substantial amounts present in Kenyan beans, French beans, runner beans, spinach, dried fruit, bananas and red lentils, but undetectable amounts in tomatoes, oranges and onions. Of the beverages, beer, a macerated whole-grain cereal product, contained the greatest level of Si, whilst drinking water was a variable source with some mineral waters relatively high in Si. The present study provides a provisional database for the Si content of UK foods, which will allow the estimation of dietary intakes of Si in the UK population and investigation into the role of dietary Si in human health.

Teaching presence in computer conferencing : lessons from the United States and Australia

This paper uses the category of teaching presence as a framework to analyze and compare teaching presence in two computer conference contexts. Teaching presence is defined as the design, facilitation, and direction of cognitive and social processes. This paper is based on an interview designed to capture reflections about teaching practices of two instructors, one from the United States and the other from Australia. We first present individual case studies of the two computer conference contexts, followed by conclusions and implications for research and practice.

Low-intensity pulsed ultrasound for chronic patellar tendinopathy : a randomized, double-blind, placebo-controlled trial

Objective. Patellar tendinopathy (PT) is a common and significant clinical condition for which there are few established interventions. One intervention that is currently being used clinically to manage PT symptoms is the introduction of low-intensity pulsed ultrasound (LIPUS). The aim of this study was to investigate the clinical efficacy of LIPUS in the management of PT symptoms.

Methods. A randomized, double-blind, placebo-controlled study was conducted. Volunteers with clinically and radiologically confirmed PT were randomly allocated to either an active-LIPUS (treatment) or inactive-LIPUS (placebo) group. LIPUS was self-administered by participants for 20 min/day, 7 days/week for 12 weeks. All participants also completed a daily, standardized eccentric exercise programme based on best practice. Primary outcomes were change in pain during the participant's most aggravating activity in the preceding week, measured on 10 cm visual analogue scales for both usual (VAS-U) and worst (VAS-W) tendon pain.

Results. Out of 156 individuals who volunteered, 37 met the eligibility criteria and were randomized to either active-LIPUS (n = 17) or inactive-LIPUS (n = 20). Using an intention-to-treat analysis, VAS-U and VAS-W for the entire cohort decreased by 1.6 ± 1.9 cm (P < 0.01) and 2.5 ± 2.4 cm (P < 0.01), respectively. There were no differences between the active- and inactive-LIPUS groups for change in VAS-U (–0.2 cm; 95% CI, –1.5, 1.1 cm) (P = 0.74) or VAS-W (–0.5 cm; 95% CI, –2.1, 1.1 cm) (P = 0.57). A per-protocol analysis provided similar results.

Conclusions. These findings suggest that LIPUS does not provide any additional benefit over and above placebo in the management of symptoms associated with PT.

Physiological, morphological and behavioural effects of selecting zebra finches for divergent levels of corticosterone

The effects of environmental stress on the physiology and behaviour of higher vertebrates has become an important avenue of research in recent years. Evidence from recent studies has suggested that the avian stress-related hormone corticosterone (CORT) may play a role in immunocompetence and sexual selection. We tested whether CORT is immunosuppressive by studying humoral and cell-mediated immune responses in populations of captive zebra finches selected for divergent peak levels of CORT. We also investigated whether selection for peak CORT has an effect on the quality of several sexually selected regions of the male zebra finch; in addition we compared morphometric parameters and the dominance ranking in males from the different selection lines. We also tested whether different components of the immune system compete for limited resources. We found that selection for divergent levels of peak CORT had little effect on humoral immunity, male sexual signal quality or dominance ranking. However, contrary to expectations, we did find a positive relationship between CORT titre and cell-mediated immunity, as well as a greater cell-mediated response in the birds selected for high CORT titre than those selected for low CORT titre. Consistent with predictions, significant negative relationships were found between both testosterone and CORT titre on humoral immunity. Birds from the low CORT lines were significantly larger in terms of skeletal size than those from the high CORT lines. Overall, our results suggest that the cell-mediated immune response is associated with a reduction in the humoral response, but only in males, and that there is no simple relationship between peak CORT levels and immune function.

Mate choice in zebra finches: does corticosterone play a role?

The importance of stress as a factor in influencing life history strategies has received considerable attention in recent years, because it appears to have a substantial impact on an individual's behaviour and physiology. Birds respond to environmental and social stressors by the production of corticosterone, a glucocorticoid hormone released by the adrenal gland. In this experiment, we tested whether female zebra finches preferred males selected to produce low or high peak levels of circulating plasma corticosterone. Plasma corticosterone and testosterone levels of the males were recorded, as were morphometric measurements and perch activity. Spectrophotometric measurements were also taken from several putatively sexually selected regions of the males. The females preferred the males from the low corticosterone lines to the high corticosterone males. In addition to, and consistent with this effect, females preferred males with the lowest corticosterone titres. Male activity, testosterone level, body size and mass had no effect on female preference. Leg and beak brightness were important, however, as were the brightness and chromaticity of the male cheek patch. These results are discussed in relation to contemporary hypotheses in sexual selection, particularly in the context of stress-mediated signalling.

Testing the immunocompetence handicap hypothesis : a review of the evidence

The immunocompetence handicap hypothesis was formulated 12 years ago in an attempt to offer a proximate mechanism by which female choice of males could be explained by endocrine control of honest signalling. The hypothesis suggested that testosterone has a dual effect in males of controlling the development of sexual signals while causing immunosuppression. Our purpose in this review is to examine the empirical evidence to date that has attempted to test the hypothesis, and to conduct a meta-analysis on two of the assumptions of the hypothesis, that testosterone reduces immunocompetence and increases parasitism, to ascertain any statistical trend in the data. There is some evidence to suggest that testosterone is responsible for the magnitude of trait expression or development of sexual traits, but this is by no means conclusive. The results of many studies attempting to find evidence for the supposed immunosuppressive qualities of testosterone are difficult to interpret since they are observational rather than experimental. Of the experimental studies, the data obtained are ambiguous, and this is reflected in the result of the meta-analysis. Overall, the meta-analysis found a significant suppressive effect of testosterone on immunity, in support of the hypothesis, but this effect disappeared when we controlled for multiple studies on the same species. There was no effect of testosterone on direct measures of immunity, but it did increase ectoparasite abundance in several studies, in particular in reptiles. A funnel analysis indicated that the results were robust to a publication bias. Alternative substances that interact with testosterone, such as glucocorticoids, may be important. Ultimately, a greater understanding is required of the complex relationships that exist both within and between the endocrine and immune systems and their consequences for mate choice decision making.

Polyunsaturated fats in meat from Merino, first- and second-cross sheep slaughtered as yearlings

This study examined the level of long chain omega-3 and omega-6 polyunsaturated fats, the ratio of polyunsaturated fat to saturated fat (PUFA/SFA) and the ratio of omega-6 to omega-3 (n-6/n-3) fat in sheep grown under grazing conditions in Australia. The sheep genotypes used were Poll Dorset_growth × Border Leicester Merino (PDg × BLM), Poll Dorset_growth × Merino (PDg × M), Poll Dorsetmuscling × Merino (PDm × M), Border Leicester × Merino (BL × M) and Merino × Merino (M × M). Loin muscles (Longissimus lumborum) collected from 40 ewe and wether sheep slaughtered at 14 months of age were processed for fatty acid determination. After frozen storage, 20 g samples were minced and a 7 g homogenate was processed for muscle lipid extraction using a chloroform:methanol (2:1) procedure. There was an increase in PUFA/SFA as the proportion of Merino genetics increased in the progeny (second-cross < first-cross < Merino), but this was not shown in the n-6/n-3 ratio. The PUFA/SFA trend appeared to be associated with an increase in the level of total polyunsaturated fats, but not a decrease in the level of total saturated fats. The results demonstrate that there is a need to improve the PUFA/SFA content in first- and second-cross animals which are mainly used for meat production in Australia so as to maintain the healthy lipids in meat. Nutritional manipulation through feeding systems or selection of sires for greater heritability of omega-3 fat deposition may be suitable pathways to elevate the ratio of polyunsaturated fatty acids, and in particular omega-3.

Area variation in recreational cycling in Melbourne : a compositional or contextual effect?

Objective: To examine whether compositional and/or contextual area characteristics are associated with area socioeconomic inequalities and between-area differences in recreational cycling.

Setting: The city of Melbourne, Australia.

Participants: 2349 men and women residing in 50 areas (58.7% response rate).

Main outcome measure: Cycling for recreational purposes (at least once a month vs never).

Design: In a cross-sectional survey participants reported their frequency of recreational cycling. Objective area characteristics were collected for their residential area by environmental audits or calculated with Geographic Information Systems software. Multilevel logistic regression models were performed to examine associations between recreational cycling, area socioeconomic level, compositional characteristics (age, sex, education, occupation) and area characteristics (design, safety, destinations or aesthetics).

Results: After adjustment for compositional characteristics, residents of deprived areas were less likely to cycle for recreation (OR 0.66; 95% CI 0.43 to 1.00), and significant between-area differences in recreational cycling were found (median odds ratio 1.48 (95% credibility interval 1.24 to 1.78). Aesthetic characteristics tended to be worse in deprived areas and were the only group of area characteristics that explained some of the area deprivation differences. Safety characteristics explained the largest proportion of between-area variation in recreational cycling.

Conclusion: Creating supportive environments with respect to safety and aesthetic area characteristics may decrease between-area differences and area deprivation inequalities in recreational cycling, respectively.

Song as an honest signal of past developmental stress in the European starling (Sturnus vulgaris)

Bird song is a sexually selected male trait where females select males on the basis of song quality. It has recently been suggested that the quality of the adult male song may be determined by nutritional stress during early development. Here, we test the 'nutritional–stress hypothesis' using the complex song of the European starling. Fledgling starlings were kept under experimental treatment (unpredictable short–term food deprivations) or control conditions (ad libitum food supply), for three months immediately after independence. We measured their physiological and immune responses during the treatment and recorded song production during the following spring. Birds in the experimental group showed increased mass during the treatment and also a significantly suppressed humoral response compared with birds in the control group. There was no difference between the groups in the cell–mediated response. Next spring, males in the experimental group spent less time singing, sang fewer song bouts, took longer to start singing and also sang significantly shorter song bouts. These data support the hypothesis that both the quality and quantity of song produced by individual birds reflect past developmental stress. The results also suggest the 'nutritional–stress hypothesis' is best considered as a more general 'developmental–stress hypothesis'.