Trade-offs between succulent and non-succulent epiphytes underlie variation in drought tolerance and avoidance.

Epiphyte communities comprise important components of many forest ecosystems in terms of biomass and diversity, but little is known regarding trade-offs that underlie diversity and structure in these communities or the impact that microclimate has on epiphyte trait allocation. We measured 22 functional traits in vascular epiphyte communities across six sites that span a microclimatic gradient in a tropical montane cloud forest region in Costa Rica. We quantified traits that relate to carbon and nitrogen allocation, gas exchange, water storage, and drought tolerance. Functional diversity was high in all but the lowest elevation site where drought likely limits the success of certain species with particular trait combinations. For most traits, variation was explained by relationships with other traits, rather than differences in microclimate across sites. Although there were significant differences in microclimate, epiphyte abundance, and diversity, we found substantial overlap in multivariate trait space across five of the sites. We found significant correlations between functional traits, many of which related to water storage (leaf water content, leaf thickness, hydrenchymal thickness), drought tolerance (turgor loss point), and carbon allocation (specific leaf area, leaf dry matter content). This suite of trait correlations suggests that the epiphyte community has evolved functional strategies along with a drought avoidance versus drought tolerance continuum where leaf succulence emerged as a pivotal overall trait.

Endogenous altered peptide ligands can affect peripheral T cell responses.

T cells potentially encounter a large number of endogenous self-peptide/MHC ligands in the thymus and the periphery. These endogenous ligands are critical to both positive and negative selection in the thymus; however, their effect on peripheral T cells has not been directly ascertained. Using the murine allelic Hbd (64-76)/I-Ek self-antigen model, we have previously identified altered peptide ligands (APLs) which are able to stimulate some but not all TCR-mediated effector functions. To determine directly the effect of endogenously synthesized APL/MHC complexes on peripheral T cells, we used a TCR transgenic mouse which had reversed our normal antigen system, with Ser69 peptide now being the agonist and Hbd(64-76) being the APL. In this report, we show that the constitutive level of endogenous Hbd(64-76)/I-Ek complexes presented by APCs in vivo is too low to affect the response of Ser69 reactive T cells. However, by increasing the number of Hbd(64-76)/I-Ek complexes expressed by the APCs, TCR antagonism is observed for both primary T cells and T cell hybridomas. In addition, the level of the CD4 coreceptor expressed on T cells and T cell hybridomas. In addition, the level of the CD4 coreceptor expressed on T cells changes the response pattern to endogenously presented Hbd(64-76)/I-Ek ligand. These findings demonstrate that T cells are selected to ignore the constitutive levels of endogenous complexes they encounter in the periphery. T cell responses can be affected by endogenous APLs in the periphery under limited but attainable circumstances which change the efficacy of the TCR/ligand interaction. Thus, endogenous APLs play a role in both the selection of T cells in the thymus and the responses of peripheral T cells.

A kinetic threshold between negative and positive selection based on the longevity of the T cell receptor-ligand complex.

We have developed a unique in vivo system to determine the relationship between endogenous altered peptide ligands and the development of major histocompatibility complex class II- restricted T cells. Our studies use the 3.L2 T cell receptor (TCR) transgenic mouse, in which T cells are specific for Hb(64-76)/I-Ek and positively selected on I-Ek plus self-peptides. To this endogenous peptide repertoire, we have individually added one of six well-characterized 3.L2 ligands. This transgenic approach expands rather than constrains the repertoire of self-peptides. We find that a broad range of ligands produce negative selection of thymocytes in vivo. When compared with the in vitro TCR-ligand binding kinetics, we find that these negatively selecting ligands all have a half-life of 2 s or greater. Additionally, one of two ligands examined with no detectable binding to the 3.L2 TCR and no activity on mature 3.L2 T cells (Q72) enhances the positive selection of transgenic thymocytes in vivo. Together, these data establish a kinetic threshold between negative and positive selection based on the longevity of TCR-ligand complexes.

A family of three mouse potassium channel genes with intronless coding regions.

To understand the molecular mechanisms responsible for generating physiologically diverse potassium channels in mammalian cells, mouse genomic clones have been isolated with a potassium channel complementary DNA, MBK1, that is homologous to the Drosophila potassium channel gene, Shaker. A family of three closely related potassium channel genes (MK1, MK2, and MK3) that are encoded at distinct genomic loci has been isolated. Sequence analysis reveals that the coding region of each of these three genes exists as a single uninterrupted exon in the mouse genome. This organization precludes the generation of multiple forms of the protein by alternative RNA splicing, a mechanism known to characterize the Drosophila potassium channel genes Shaker and Shab. Thus, mammals may use a different strategy for generating diverse K+ channels by encoding related genes at multiple distinct genomic loci, each of which produces only a single protein.

Incidence, outcomes and outcome prediction of unplanned extubation in critically ill children: An 11year experience.

PURPOSE: Unplanned extubation represents loss of control in the ICU, is associated with harm and is used as a measure of quality of care. We evaluated the rates and consequences of unplanned extubation. MATERIALS AND METHODS: Eligible patients were intubated, <18years, and in ICU. Patient, care-related and environmental characteristics were compared in patients who did and did not receive positive pressure ventilation in the 24h after events. Rates are expressed per 100 intubation-days. RESULTS: The 11,310 eligible patient-admissions identified were intubated for 75,519days; 410 (3.39%) patients had 458 unplanned extubation events (0.61 events/100 intubation-days). Annual rates of unplanned extubation reduced from 0.98 in 2004 to 0.37 in 2014. Consequences occurred in 245 (53.5%) events and included cardiac arrest in 9 (2%), bradycardia 52 (11%), and stridor 63 (14%). Positive pressure was provided after 263 (57%) events, and was independently associated with pre-event sedative and muscle relaxant drugs, non-use of restraints, respiratory reason for intubation and recent care by more nurses. CONCLUSION: Unplanned extubation was associated with both significant and no morbidity. Modification of factors including more consistent nurse staffing, restraint use, and increased vigilance in patients with previous events may potentially reduce rates and adverse consequences of unplanned extubation.

Intensive training over 5 days improves colonoscopy skills long-term.

BACKGROUND AND AIMS: Poor standards in colonoscopy services and the introduction of a colorectal cancer screening program in the United Kingdom have highlighted the need to establish high-quality training and competency assessments in colonoscopy. The aims of this study were to evaluate the effectiveness of a 1-week hands-on colonoscopy course utilizing novel assessment tools. METHODS: Twenty-one doctors with varying colonoscopy experience who attended an accelerated colonoscopy training week (ACTW) were prospectively studied. They were trained and assessed in key aspects of colonoscopy. Knowledge was assessed with a multiple choice question (MCQ) paper. Practical hand skills were taught and evaluated using a computer simulator and live case teaching. Actual colonoscopy performance was assessed using Direct Observation of Procedural Skills scores (DOPS) and an objective tri-split video score of insertion technique. Two independent trainers taught and assessed the trainees at the start and end of the ACTW and at a median of 9 months' follow-up. RESULTS: Following training there were significant improvements in the MCQ score (P < 0.001), the simulator test case times (P = 0.02, P = 0.003), and the global DOPS score (P < or = 0.02). All improvements following the accelerated training were sustained at a median follow-up of 9 months. CONCLUSIONS: This study is the first in the literature to describe the positive, sustained impact of an intensive hands-on colonoscopy training course. Measurements of performance in key areas of skill acquisition improved following training.

Review article: Population screening for colorectal cancer.

Colorectal cancer is a common cancer and common cause of death. The mortality rate from colorectal cancer can be reduced by identification and removal of cancer precursors, adenomas, or by detection of cancer at an earlier stage. Pilot screening programmes have demonstrated decreased colorectal cancer mortality; as a result many countries are developing colorectal cancer screening programmes. The most common modalities being evaluated are faecal occult blood testing, flexible sigmoidoscopy and colonoscopy. Implementation of screening tests has been hampered by cost, invasiveness, availability of resources and patient acceptance. New technologies such at computed tomographic colonography and stool screening for molecular markers of neoplasia are in development as potential minimally invasive tools. This review considers who should be screened, which test to use and how often to screen.

Coccidiosis immunization: effects of mushroom and herb polysaccharides on immune responses of chickens infected with Eimeria tenella.

An experiment was conducted to investigate the effects of polysaccharide extracts (E) of two mushrooms, Lentinus edodes (LenE) and Tremella fuciformis (TreE), and an herb, Astragalus membranaceus (AstE), on the immune responses of chickens infected with Eimeria tenella. A total of 180 broiler chickens were assigned to nine groups: three groups were fed with each of the extracts (LenE, TreE, and AstE), three groups were fed with the extracts and immunized with live oocyst vaccine (LenE+V, TreE+V, and AstE+V), a group was immunized with the vaccine only, and there were two controls (E. tenella-infected and noninfected groups). The oocyst vaccine was given at 4 days of age, and the extracts (1 g/kg of the diet) were supplemented from 8 to 14 days of age. At 18 days of age, all birds except those in the noninfected group were infected with 9 x 10(4) sporulated oocysts. The results showed that at 7 days postinfection (p.i.), birds fed the extracts without vaccination had lower body weight (BW) gain than those given the vaccine only. However, the extracts in conjunction with the vaccine significantly enhanced BW gain of the infected chickens compared with the vaccine group. Of the three extracts, LenE and TreE showed a better growth-promoting effect. The extracts largely increased oocyst excretion of droppings during the primary response postvaccination. The cecal peak oocyst output and lesion scores measured at 7 days p.i. were higher in the groups fed the extracts than in the group immunized with the vaccine only, whereas those of the groups fed with the extracts and immunized with the vaccine were not significantly different from the vaccine group. Of the three extracts, both LenE- and AstE-fed groups showed lower cecal oocyst output. Thus, as compared with the extracts, the live, attenuated vaccine showed better results with significantly increased immune response in coccidial infected birds. The polysaccharide extracts may prove useful against avian coccidiosis, and, particularly when they are used in conjunction with vaccine, they have shown preliminary promise against the experimental coccidial infection.

Effect of selective screening for gestational diabetes.

OBJECTIVE: To estimate the percentage of pregnant women who would not be screened and the percentage of women with gestational diabetes mellitus (GDM) who would possibly remain undiagnosed if the American Diabetes Association's (ADA's) new selective screening recommendations are used rather than universal screening for GDM. RESEARCH DESIGN AND METHODS: Since 1987, the University of Michigan Health System has performed universal screening for GDM. In 1997, the ADA recommended that women having all four of the following characteristics need not be screened: age < 25 years, not members of an ethnic/racial group with a high prevalence of diabetes, normal body weight, and no family history of diabetes. We studied a random sample of the 25,118 deliveries at the University of Michigan between 1987 and 1997 to determine the prevalence of these four characteristics in our obstetric population. We also studied the prevalence of these four characteristics in 200 women who were diagnosed with GDM in the Endocrine Testing Unit and delivered at the University of Michigan between 1987 and 1997. RESULTS: Approximately 10-11% of women who delivered possessed all four low-risk characteristics and would not have been screened for GDM according to the new ADA recommendations. Only 4% of women (5 of 141) with GDM who delivered and for whom data on all four characteristics were reported possessed all four low-risk characteristics and would not have been screened. CONCLUSIONS: If the new ADA selective screening recommendations are used, few women with GDM will be missed (4%) but approximately 90% of pregnant women will still need to be screened for GDM.

Survival analysis of adverse effects data in the Beta-Blocker Heart Attack Trial.

Monitoring for adverse effects in an integral part of controlled clinical trials. Traditionally the results of monitoring are reported as either cumulative percentages at the end of the study or cross-sectional percentages at a given time in the study. These results are likely to underestimate the true number of complaints because participants may be withdrawn (e.g., deaths, losses to follow-up, and refusals) before they ever complain of an adverse effect. However, survival analysis methods can be used to compare the distributions of "time to first complaint" in the active and placebo treatment groups, taking into account withdrawals. Participants in the Beta-Blocker Heart Attack Trial were monitored for possible adverse effects. On each follow-up visit they were asked whether they had had any of four conditions (blacking out, fatigue, depression, and bronchospasm) since their previous visit about 3 months earlier. The patients were followed for up to 30 months. For fatigue and bronchospasm, the complaint-free time was significantly longer in the placebo vs. active (propranolol) treatment group (P less than 0.005).

Role of p53 tumor suppressor gene in the toxicity of TCDD, endrin, naphthalene, and chromium (VI) in liver and brain tissues of mice.

It has been postulated that tumor suppressor genes are involved in the cascade of events leading to the toxicity of diverse xenobiotics. Therefore, we have assessed the comparative effects of 0.01, 0.10, and 0.50 median lethal doses (LD(50)) of 2,3,7, 8-tetrachlorodibenzo-p-dioxin (TCDD), endrin, naphthalene, and sodium dichromate (VI) [Cr(VI)] on lipid peroxidation, DNA fragmentation, and enhanced production of superoxide anion (cytochrome c reduction) in liver and brain tissues of p53-deficient and standard C57BL/6NTac mice to determine the role of p53 gene in the toxic manifestations produced by these diverse xenobiotics. In general, p53-deficient mice are more susceptible to all four xenobiotics than C57BL/6NTac mice, with dose-dependent effects being observed. Specifically, at a 0.50 LD(50) dose, naphthalene and Cr(VI) induced the greatest toxicity in the liver tissue of mice, and naphthalene and endrin exhibited the greatest effect in the brain tissue. At this dose, TCDD, endrin, naphthalene, and Cr(VI) induced 2.3- to 3.7-fold higher increases in hepatic lipid peroxidation and 1.8- to 3.0-fold higher increases in brain lipid peroxidation in p53-deficient mice than in C57BL/6NTac mice. At a 0. 10 LD(50) dose, TCDD, endrin, naphthalene, and Cr(VI) induced 1.3- to 1.8-fold higher increases in hepatic lipid peroxidation and 1.4- to 1.9-fold higher increases in brain lipid peroxidation in p53-deficient mice than in C57BL/6NTac mice. Similar results were observed with respect to DNA fragmentation and cytochrome c reduction (superoxide anion production). For example, at the 0.10 LD(50) dose, the four xenobiotics induced increases of 1.6- to 3. 0-fold and 1.5- to 2.1-fold in brain and liver DNA fragmentation, respectively, and increases of 1.5- to 2.3-fold and 1.4- to 2.5-fold in brain and liver cytochrome c reduction (superoxide anion production), respectively, in p53-deficient mice compared with control C57BL/6NTac mice. These results suggest that the p53 tumor suppressor gene may play a role in the toxicity of structurally diverse xenobiotics.

Upper intestinal surveillance in familial adenomatous polyposis.

Our understanding of the natural history of upper gastrointestinal (GI) involvement in familial adenomatous polyposis (FAP) is still evolving, although we know that the main cause of death after colectomy in FAP is upper GI malignancy, affecting 5% of patients. The aim of duodenal surveillance is to target high risk individuals and identify cancers early. We have screened 200 patients prospectively and have observed that duodenal polyposis progresses slowly, but there are some young people who have severe disease who merit close observation. We pay particular attention to endoscopic technique and histological detail, and use a duodenal staging system. Patients are offered randomisation to studies of chemopreventive agents, and those with advanced disease are considered for surgery. Successful management is inhibited by our deficient knowledge of the natural history of upper gastrointestinal polyposis, and by our inability to identify high risk individuals with histological markers rather than because of any technological deficiencies in endoscopic equipment.

A method for isolation and culture of lymphocytes from endoscopic biopsies.

Human small and large intestinal lamina propria lymphocytes have been successfully prepared from endoscopic biopsies by a combined enzymatic and mechanical method which gives higher yields of viable mucosal lymphocytes than previously reported, despite the small size of the biopsy samples. Viability of the cells was demonstrated by dye exclusion and they could be satisfactorily maintained in short-term culture. Phytohaemagglutinin-P (PHA-P) transformation characteristics of intestinal lymphoid cells and those of peripheral blood were studied in 20 patients with Crohn's disease and 10 control subjects. Peripheral blood lymphocytes were separated according to this technique, no decrease in viability being observed when compared to a standard Ficoll-Hypaque gradient technique. Endoscopically abnormal (EA) and endoscopically normal (EN) Crohn's tissue showed significantly different responses to PHA-P (P less than 0.001), EA tissue lymphocytes giving lower blastogenic responses.

The study of self-tolerance using murine haemoglobin as a model self antigen.

T cell tolerance to self proteins involves both thymic and peripheral mechanisms. We have used allotypic differences in murine haemoglobin (Hb) to study the development of tolerance to the abundantly expressed self-protein. In Hb beta s/H-2k mice, the response to Hb beta d is directed against Hb beta d (64-76) presented by I-Ek molecules. Using T cell hybridomas and clones specific for this epitope, we have demonstrated that Hb(64-76)/I-Ek complexes and present on antigen-presenting cells in all lymphoid organs including dendritic cells, B cells and macrophages. In the thymus, the presence of these complexes results in negative selection of transgenic T cells with high levels of Hb(64-76)/I-Ek-specific receptor. However, cells with intermediate levels of specific receptor escape negative selection and can be found in the periphery. Under normal circumstances these cells remain tolerant, but can be activated by mechanisms which increase the number of Hb(64-76)/I-Ek complexes.

The effect of treatment on lymphokine-secreting cells in the intestinal mucosa of children with Crohn's disease.

BACKGROUND: Recent studies have shown both interleukin 2 (IL-2) and interferon gamma (IFN) to be elevated in patients with active Crohn's disease compared to ulcerative colitis or non-inflammatory bowel disease controls. However the effect of treatment on these lymphokines has not been studied. PATIENTS AND METHODS: Using a reverse haemolytic plaque assay the percentage of lymphokine-secreting cells was determined in the intestinal mucosa of children with Crohn's disease before and after 8 weeks of treatment with either enteral nutrition, cyclosporin or steroids. RESULTS: Before treatment, a high percentage of cells isolated from mucosal biopsies secreted IL-2 or interferon-gamma. Eight weeks' treatment with the immunosuppressive agents cyclosporin, or with corticosteroids, produced a significant reduction in the percentage of IL-2 secreting cells, although only for the former was there also a reduction in interferon-gamma secreting cells. Enteral nutrition however, produced a reduction in lymphokine-secreting cells equivalent to cyclosporin and produced the best histological and clinical improvement. CONCLUSION: Enteral nutrition and cyclosporin can down-regulate lymphokine secretion in the gut in Crohn's disease.

Brush cytology of the colon and rectum in ulcerative colitis: an aid to cancer diagnosis.

In a prospective study of 100 patients with ulcerative colitis, 82 of whom had extensive colitis, carcinoma and dysplasia were distinguished cytologically from reactive hyperplasia. Six patients had carcinoma complicating colitis and satisfactory samples were obtained from five; the cytological appearances were interpreted as carcinoma in three and as dysplasia in two. Seventy eight patients had not developed carcinoma or dysplasia; the cytological appearances were interpreted as negative for dysplasia in 75 and indefinite for dysplasia in three. In patients who had developed dysplasia the changes seemed to be more widespread on cytological rather than on histological examination. Brush cytology may complement histological assessment in patients with ulcerative colitis who have developed strictures or in whom there is a high suspicion of neoplastic change.

Upper gastrointestinal pathology in familial adenomatous polyposis: results from a prospective study of 102 patients.

Multiple gastric and duodenal biopsy specimens from 102 asymptomatic patients with familial adenomatous polyposis, taken during a prospective endoscopic screening programme were examined. One hundred patients had microscopic gastroduodenal pathology, often in the absence of macroscopic lesions. Adenomas were found in 94 patients in the duodenum, in the second and third parts. Hyperplasia of villous and crypt epithelium was also seen, sometimes in the absence of adenomas: this may be a precursor of neoplastic change. In the stomach fundic gland polyps were the commonest abnormality, seen microscopically in 44 patients. Chronic antral gastritis was common in patients without fundic polyps. Gastric adenomas were present in six patients, all of whom also had duodenal adenomas. If duodenal adenomas in familial adenomatous polyposis have a similar malignant potential to those in the colorectum sequential endoscopy and biopsy are necessary to detect cancer in these patients.

Comparison of serum and prostatic levels of tobramycin.

Tobramycin sulfate, an aminoglycoside antibiotic, has been shown to be effective in the treatment of complicated urinary tract infections. Because of this, a study was undertaken to determine the penetrance of tobramycin into the prostate gland. It was found that the drug is concentrated at inhibitory levels in the prostate gland after the routinely recommended administration and should be useful in the treatment of bacterial prostatic infection.

Probability summation for multiple patches of luminance modulation.

When components of a compound pattern stimulate different visual mechanisms, psychophysical performance typically improves by a small amount consistent with probability summation amongst independent detectors. Here we extend previous summation experiments by (i) plotting full psychometric functions; and (ii) using compound stimuli with components that varied in up to three stimulus dimensions: spatial frequency (1, 4, 5 or 11 c/deg), orientation (0 degrees, +/-45 degrees ), and position. Stimulus components were isolated circular sine-phase patches of grating centred on up to four corners of an imaginary square surrounding a fixation-point. Combinations of component patches produced compound stimuli made from up to 16 components that differed in various combinations of the three stimulus dimensions. Other than when the spatial frequency was 11 c/deg, results were well described using: (i) probabilistic summation of individual psychometric functions; (ii) the Quick pooling formula; and (iii) the signal detection analysis for 2IFC developed by Tyler and Chen (2000) [Signal detection theory in the 2AFC paradigm: attention, channel uncertainty and probability summation (under review)]. We conclude that in general, nonlinear spatial summation is consistent with probabilistic summation across independent detecting mechanisms that vary in spatial frequency (a range of at least 1-5 c/deg), orientation (a range of 90 degrees ) and position (a range of at least 24 cycles at 4 c/deg). In further experiments, results were found to be consistent with probability summation for pairs of orthogonally oriented step-edge stimuli and a matrix of randomly oriented 11 c/deg sine-wave patches. This casts doubt on the generality of a recent suggestion that local interactions between colinearly oriented detectors within a spatial neighbourhood of around four cycles may contribute to nonlinear spatial summation [Bonneh & Sagi, 1998; Vision Research, 38, 3541-3553].

The interaction of first- and second-order cues to orientation.

The visual system is sensitive to orientation information defined both by first-order (luminance) and by second-order (texture) cues. We consider how these orientation cues are computed and how they affect one another. We measured the perceived orientation of the first and second-order components of Gabor patches (the carrier and envelope, respectively) and report a dependence of the perceived orientation of each on the orientation of the other, and on the spatial frequency of the carrier. Fixing the carrier orientation near that of the envelope interferes with envelope orientation judgements. This interference is reduced by adding a small (subthreshold) rotation to the carrier indicating that the site of interference is early. When the gross relative orientation of carrier and envelope is varied, the carrier appears systematically tilted towards the envelope. However, provided envelope and carrier are separated by more than approximately 10 degrees, the perceived envelope orientation appears tilted away from the carrier. The size of these effects increases with decreasing carrier spatial frequency, and with increasing exposure duration. When the envelope and carrier are both non parallel and non-perpendicular Fourier energy is distributed asymmetrically across orientation. We demonstrate that, for a channel-based orientation code, this asymmetry induces a shift in mean orientation that is sufficient to explain illusory tilting of carriers. The illusory tilting of the envelope, as a function of carrier orientation and spatial frequency, demonstrates that human ability to demodulate contrast information is far from ideal and cannot be explained by existing two-stage filter-rectify-filter models. We propose that illusory tilting of the envelope is due to selective connectivity between first- and second-stage filters whose purpose is to dissociate the type of image structure producing each class of cue.