A primer for data assimilation with ecological models using Markov Chain Monte Carlo (MCMC).

Data assimilation, or the fusion of a mathematical model with ecological data, is rapidly expanding knowledge of ecological systems across multiple spatial and temporal scales. As the amount of ecological data available to a broader audience increases, quantitative proficiency with data assimilation tools and techniques will be an essential skill for ecological analysis in this data-rich era. We provide a data assimilation primer for the novice user by (1) reviewing data assimilation terminology and methodology, (2) showcasing a variety of data assimilation studies across the ecological, environmental, and atmospheric sciences with the aim of gaining an understanding of potential applications of data assimilation, and (3) applying data assimilation in specific ecological examples to determine the components of net ecosystem carbon uptake in a forest and also the population dynamics of the mayfly (Hexagenia limbata, Serville). The review and examples are then used to provide guiding principles to newly proficient data assimilation practitioners.

A prospective study of causes of haemolysis during venepuncture: tourniquet time should be kept to a minimum.

BACKGROUND: Haemolysis is defined as the release of cellular components of erythrocytes and other blood cells into the extracellular space of blood. These cellular components can cause interference in laboratory measurements, potassium being a commonly measured analyte to be affected. A number of factors have been implicated in the aetiology of haemolysis. We undertook this study to enable us to identify and hence rectify causes of haemolysis in samples from patients on acute medical and surgical wards. METHODS: We performed a prospective study of 353 blood sampling events during February and March 2007. A proforma was used to obtain detailed information of each blood-taking episode. Information from the proforma was linked to the incidence of haemolysis obtained from the hospital computer system. RESULTS: The incidence of haemolysis among the samples studied was 6.5%. While staff group, method of sampling, tourniquet time and number of attempts at venepuncture were each univariately associated with haemolysis, stepwise logistic regression resulted in a final model which only included tourniquet time (odds ratio for haemolysis if tourniquet time >1 min was 19.5 [95% confidence interval [CI] 5.6-67.4%]). CONCLUSION: Tourniquet time of more than a minute is associated with a significant increase in risk of haemolysis. Advice on tourniquet time is included in phlebotomy training within the hospital; hence a campaign of appropriately channelled continuing education on this issue may be successful in reducing the haemolysis rate.

Sgd 101/75: a sympathomimetic that can be used to identify a new subtype of alpha-adrenoceptor, the alpha 1s-adrenoceptor.

When Sgd 101/75 was compared with clonidine in a number of tests for CNS activity, Sgd 101/75 exhibited little activity in any test. Sgd 101/75 raised BP without affecting HR in several species of anaesthetised animals. The rise in BP was subject to tachyphylaxis, could be antagonised by alpha 1-adrenoceptor antagonists, and was obtainable in reserpinised animals. The vasopressor effect of NA was antagonised by Sgd 101/75. Thus Sgd 101/75 is a directly acting partial agonist for vascular alpha 1-adrenoceptors. On the coaxially stimulated guinea-pig ileum and field stimulated rat vas deferens, the twitch response to single pulse stimulation was reduced by NA or clonidine stimulating prejunctional alpha 2-adrenoceptors. Sgd 101/75 antagonised these inhibitory effects competitively (pA2 for antagonism of clonidine on the vas = 6.12). Sgd 101/75 acted as a specific partial agonist on the alpha 1-adrenoceptors of the guinea-pig taenia caecum that subserve relaxation of this tissue. Sgd 101/75 was a full agonist on the alpha 1-adrenoceptors of the rat anococcygeus in vitro. Phenoxybenzamine (300 pM for 30 min, followed by 20 washes over the next 30 min) reduced contractions of the anococcygeus to Sgd 101/75, but produced little inhibition of NA-induced contractions. In phenoxybenzamine-pretreated preparations, Sgd 101/75 (400 microM) did not antagonise NA (maximal effect and EC50 values not changed significantly), so it was concluded that Sgd 101/75 and NA interact with different alpha 1-adrenoceptor subtypes in this tissue. The subtype specifically activated by Sgd 101/75 was designated the alpha 1s-adrenoceptor. The mouse anococcygeus contained alpha 1s-adrenoceptors, whereas this receptor was absent from the rabbit anococcygeus.

A rare case of dysphagia: hypopharyngeal amyloidosis masquerading as a post-cricoid tumour.

Amyloidoses are a group of disorders in which deposition of abnormal amounts of protein complexes (amyloid) occurs in a variety of tissues. The upper aerodigestive tract may be affected, particularly the larynx, but hypopharyngeal involvement is rarely reported. We present a unique case of amyloidosis of the post-cricoid region causing dysphagia. This case report highlights the need for otolaryngologists to consider the possibility of submucosal amyloid deposition, in the absence of mucosal lesions, in patients who present with dysphagia secondary to an obstructive lesion of the post cricoid region.

Salt intake and reproductive function in sheep.

Producers have the possibility to combat human-induced dryland salinity by planting salt-tolerant plants such as saltbush. Saltbush has the potential to be used as a source of food for livestock at a time and place where pasture is not viable. However, saltbush contains high concentrations of sodium chloride salt and some other anti-nutritional factors that have the potential to affect feed and water intake and, directly or indirectly, the reproductive capacity of sheep. High-salt diet during gestation induces a small modification of the activity of the renin-angiotensin system (RAS) that has an important role in the maintenance of the salt-water balance in non-pregnant and pregnant sheep. In contrast, the main effect of salt ingestion during pregnancy is observed on the biology of the offspring, with changes in the response of the RAS to salt ingestion and altered thirst threshold in response to an oral salt ingestion. These changes, observed later in life, are the result of fetal programming following the ingestion of salt by the mother. It seems that the exposure to salt during pregnancy could provide an advantage to the offspring because of this adaptive response. The response may be particularly useful, for example, when grazing herbivores are fed halophytic forages adapted to saline soils.

Feeding pregnant ewes a high-salt diet or saltbush suppresses their offspring's postnatal renin activity.

If ewes consumed a high-salt diet or saltbush during the last 3 months of pregnancy and for 3 weeks after birth, we expected the renin activity of their lamb to be suppressed at birth and at 3 weeks of age. We also expected an increase in the concentration of cations other than sodium in the ewe's milk and an increase in the plasma Na concentration of the lamb at birth. To test these hypotheses, Merino ewes were fed a high-salt diet (14% NaCl) in an animal house and compared to control ewes eating a control diet (2% NaCl). In addition, we compared ewes grazing saltbush (about 13% salt in diet) to ewes grazing pasture from day 60 of pregnancy to 3 weeks after birth. Lambs born to ewes consuming saltbush had 85% lower (P < 0.001) renin activity than offspring from ewes consuming pasture at 3 weeks of age. Similarly, lambs born to ewes consuming a high-salt diet had 20% lower renin activity at birth and 3 weeks (P = 0.07). Feeding ewes a high-salt diet or saltbush altered the mineral composition of the milk; the largest change was a 10% increase in K levels (P 0.05). Consuming a high-salt diet or saltbush lowered the plasma Na of ewes at 130 days of gestation (by 3-5 mmol/l; P < 0.001), but only lambs from ewes fed the high-salt diet had a lower plasma Na at birth (P < 0.05). Suppression of the renin activity of lambs could lead to permanent physiological changes in salt balance in later life.

Dietary exposure of pregnant ewes to salt dictates how their offspring respond to salt.

We investigated changes in salt preference, food and water intake, renin activity and salt excretion in adult offspring from ewes that were fed a high-salt diet (14% NaCl, high-salt offsrping) or grazed saltbush (saltbush offspring) from day 60 of pregnancy until day 21 of lactation. High-salt offspring were compared to offspring born to ewes consuming a control diet (2% NaCl) and saltbush offspring were compared to offspring from ewes which grazed a control diet of dry pasture. All offspring were weaned at 3 months of age and grazed the same clover-based pasture until testing started at 8 months of age. The preference for a low-salt diet (0.5% NaCl) when offered with an alternative (7% NaCl) did not differ between the offspring groups. High-salt offspring and saltbush offspring had a lower food intake (14% and 27% respectively) and lower water intake (35% and 20% respectively) than their control offspring. Both high-salt offspring and saltbush offspring had lower basal renin activity than their respective controls. After consuming salt, the renin activity of the saltbush offspring continued to be lower than controls whereas the renin activity of the high-salt offspring became similar to controls. In general, the saltbush offspring excreted an oral salt load more rapidly, though this depended on the extent of the salt load. This important adaptation of offspring born to ewes that consumed saltbush during pregnancy may improve their ability to cope with high-salt diets such as saltbush when they consume it themselves. However, the high-salt offspring did not possess such beneficial adaptations.

Short course preoperative radiotherapy is the single most important risk factor for perineal wound complications after abdominoperineal excision of the rectum.

AIM: To determine factors associated with perineal wound complications following abdominoperineal excision of the rectum (APER) for rectal adenocarcinoma and their effects on time to healing. PATIENTS AND METHODS: We studied all cases of APER performed in our unit by four consultants over 7 years. Seven out of nine factors considered important in wound healing were analysed using logistic regression and a multivariate model was built to examine interactions. Wound persistence was calculated using the Kaplan-Meier method. RESULTS: Data were available for 94 of 96 patients [male:female, 3:2, median age 72.5 (IQR: 64-78)]. Thirty-nine (41%) patients had 25 Gray, 3-portal, fractionated 5-day short course preoperative radiotherapy (SCPRT). Dukes stages were A (34%), B (26%), C (40%). Perineal wound complications occurred in 44 (47%), 16% of these requiring return to theatre. Local recurrences occurred in 13 (15%). There was no evidence to suggest that either patient gender, age, smoking status, preoperative albumin or haemoglobin level, or T stage were associated with the development of wound complications. The odds of wound complications for a patient who had SCPRT was over 10 times that for a patient who did not have preoperative radiotherapy (odds ratio 10.15, 95% CI: 3.80-27.05, n = 94). Seventy-four per cent of SCPRT and 96% of non-SCPRT wounds had healed by 1 year. Estimated failed wound healing rates at 30 and 90 days were 64% (95% CI: 46-78) and 48% (95% CI: 30-64) in SCPRT patients compared with 23% (95% CI: 12-35) and 9% (95% CI: 3-20) in non-SCPRT patients (log rank test P < 0.0001). CONCLUSION: Patients who have an APER are over 10 times more likely to have a perineal wound complication if they have SCPRT than not. Two-thirds of these will not have healed by 1 month, half by 3 months and over a quarter will still remain unhealed at 1 year. This has important implications for patient management decisions. Large prospective studies are needed to evaluate the effects of a selective policy for radiotherapy administered to patients requiring APER.