Small Transit Research Articles

Small bowel transit time in patients undergoing capsule endoscopy: Analyzis of determining factors

Background and aim: The quality of a capsule endoscopy (CE) study is largely dependent upon small bowel capsule transit time (SBTT) through the small intestine. Decreased SBTT during CE impaires visualisation of the entire small bowel mucosa. In contrary, prolonged SBTT during CE may be associated with a higher diagnostic yield. We aimed to identify certain risk factors that may help to predict either rapid or delayed SBTT. Patients and methods: A total of 54 consecutive patients undergoing CE without the use of promotility agents were reviewed for the study. Indications for CE were obscure gastrointestinal bleeding or anaemia of unknown origin. Patients received a standard bowel preparation that consisted of a low-residue diet for 24 hours, fluid intake, and ingestion of 4l polypethylene-glycol solution swallowing the PillCam (SB2 Given Imaging capsule). SBTT was calculated by substracting the time of first duodenal image from the time of first cecal image. Patients who experienced capsule failure in reading the coecum were excluded from the analysis. Covariates of patient demographics were analyzed to detect positive associations with SBTT. Results: The mean SBTT was 256.9 minutes (4.3 hrs), with a range between 31 and 469 minutes. Most patients (n=37, 68.5%) recorded a SBTT of 120–350 minutes. T-probe analysis demonstrated a lack of association between SBTT and patient gender, age, quality of bowel preparation, body mass index, hospital status, comorbidity and concomitant medication. There was a trend towards longer SBTT in patients on β-blocker therapy and with an excellent bowel preparation. Conclusions: Small bowel transit time during capsule endoscopy does not appear to be related to factors such as patient age, gender, hospital status, body mass index and quality of bowel preparation. A trend of longer small bowel transit time was detected in patient on β-blocker co-medication and with excellent bowel preparation.

Behind CYP450 interaction tables ñ the effect of gender and age on pharmacokinetics

BackgroundInteraction tables are restricted to unspecified isoenzymes of the families CYP1, CYP2, and CYP3. Data on gender impact has been required by the FDA only after 1993.PurposeThe aim is to...

PHC006 behind CYP450 interaction tables ñ the effect of gender and age on pharmacokinetics

BackgroundInteraction tables are restricted to unspecified isoenzymes of the families CYP1, CYP2, and CYP3. Data on gender impact has been required by the FDA only after 1993.PurposeThe aim is to...

The Effects of Gasoline Prices on Bus Ridership for Different Types of Transit Systems

This study estimates the effects of gas prices on bus ridership for different types of transit systems. Because the price of gas can have a delayed effect on the demand for transit, a dynamic polynomial distributed lag model is utilized which measures short- and longer-run effects. The model is first applied to aggregate data for cities of different sizes and then to three specific small urban and rural transit systems in the Upper Great Plains. The results show that bus ridership is fairly inelastic with respect to gasoline price. Most of the estimated elasticities are in the range of 0.08 to 0.22, with two estimates being as high as 0.5.

Modeling public-transit connectivity with spatial quality-of-transfer measurements

Improving public-transit connectivity is one of the most vital tasks in transit-operations planning. A poor connection can cause some passengers to stop using the transit service. This work analyzes the performance of public-transit networks in terms of the attributes involved with coordination and connectivity. These attributes are primarily concerned with passenger transfers, and include ride, wait and walk times and type of transfers made, that is, with street-crossing, sidewalk, non-walk and one-leg trip. Based on these attributes, transit-connectivity measures are established as a tool to evaluate the pros and cons of each defined zone of transit lines from a connectivity perspective. The zone of transit lines can be associated with small or large transit networks from which two types of analyses can be made: (i) detecting the inefficiency of connectivity-related issues for the zone, and (ii) comparing the measures between different zones to arrive to the conclusion of which zone is more worthy of improvements. This will allow, for instance, the comparison between cities and between zones in the city. In this work a model is developed to integrate spatial and non-spatial data for the construction of a public-transit network spatial repository, which in turn, is used to classify transfers, and calculate the developed connectivity measures. A case study in Auckland, New Zealand, demonstrates the benefits of the model and connectivity measures.

Marginal Cost Pricing and Subsidy of Small Urban Transit

This study analyzes economies of scale and density as a rationale for subsidizing transit agencies in small urban areas. A long-run cost model is estimated with data from 2006 to 2009 for 168 transit agencies that directly operated fixed-route bus service in small urban areas. With vehicle revenue miles used as transit output, results show that small urban transit agencies experience economies of scale and density. A full-cost model is estimated; the model includes the addition of external costs and benefits. External benefits result from the reduced waiting times that follow an increase in service frequency. Results are used to estimate the optimal fare, which is equal to marginal social cost of service. The needed subsidy is calculated as the difference between the revenue generated by the optimal fare and that needed to maintain efficient levels of production. The rationale for subsidies is an important issue, as many agencies have experienced recent reductions in operational funding.

The effects of methane and hydrogen gases produced by enteric bacteria on ileal motility and colonic transit time

Gases produced by intestinal flora may modulate intestinal motor function in healthy individuals as well as those with functional bowel disease. Methane, produced by enteric bacteria in the human gut, is associated with slowed intestinal transit and constipation. The effects of hydrogen, another main gas produced by bacterial fermentation in the gut, on small bowel and colonic motor function remains unrecognized. Therefore, we set out to investigate whether intestinal gases including methane and hydrogen could influence the small bowel motility and colonic transit. Guinea pig ileum was placed in the peristaltic bath with tension transducers attached to measure velocity and amplitude of peristaltic contraction before and after the infusion of control, hydrogen, and methane gases. Also, changes in the intraluminal pressures were monitored before and after the gas infusions. Methane decreased peristaltic velocity and increased contraction amplitude significantly of guinea pig ileum (P < 0.05). The AUC of intraluminal pressure was significantly increased with methane in guinea pig ileum (P < 0.05). In a second experiment, guinea pig colon was placed in the peristaltic bath to measure transit time before and after control, hydrogen, methane, and methane-hydrogen mixture gas infusions. Hydrogen shortened colonic transit time by 47% in the proximal colon, and by 10% in the distal colon, when compared with baselines (P < 0.05). Methane delayed ileal peristaltic conduction velocity by augmenting contractility. Hydrogen shortened colonic transit, and that effect was more prominent in the proximal colon than distal colon.

Yemen: Descending into Despair

Yemen: Descending into Despair

On blind mice and the elephant

A thorough understanding of the network impact of emerging large-scale distributed systems -- where traffic flows and what it costs -- must encompass users' behavior, the traffic they generate and the topology over which that traffic flows. In the case of BitTorrent, however, previous studies have been limited by narrow perspectives that restrict such analysis. This paper presents a comprehensive view of BitTorrent, using data from a representative set of 500,000 users sampled over a two year period, located in 169 countries and 3,150 networks. This unique perspective captures unseen trends and reveals several unexpected features of the largest peer-to-peer system. For instance, over the past year total BitTorrent traffic has increased by 12% , driven by 25% increases in per-peer hourly download volume despite a 10% decrease in the average number of online peers. We also observe stronger diurnal usage patterns and, surprisingly given the bandwidth-intensive nature of the application, a close alignment between these patterns and overall traffic. Considering the aggregated traffic across access links, this has potential implications on BitTorrent-associated costs for Internet Service Providers (ISPs). Using data from a transit ISP, we find a disproportionately large impact on a commonly used burstable (95th-percentile) billing model. Last, when examining BitTorrent traffic's paths, we find that for over half its users, most network traffic never reaches large transit networks, but is instead carried by small transit ISPs. This raises questions on the effectiveness of most in-network monitoring systems to capture trends on peer-to-peer traffic and further motivates our approach.

Male Sterile2 Encodes a Plastid-Localized Fatty Acyl Carrier Protein Reductase Required for Pollen Exine Development in Arabidopsis

Male Sterile2 (MS2) is predicted to encode a fatty acid reductase required for pollen wall development in Arabidopsis (Arabidopsis thaliana). Transient expression of MS2 in tobacco (Nicotiana benthamiana) leaves resulted in the accumulation of significant levels of C16 and C18 fatty alcohols. Expression of MS2 fused with green fluorescent protein revealed that an amino-terminal transit peptide targets the MS2 to plastids. The plastidial localization of MS2 is biologically important because genetic complementation of MS2 in ms2 homozygous plants was dependent on the presence of its amino-terminal transit peptide or that of the Rubisco small subunit protein amino-terminal transit peptide. In addition, two domains, NAD(P)H-binding domain and sterile domain, conserved in MS2 and its homologs were also shown to be essential for MS2 function in pollen exine development by genetic complementation testing. Direct biochemical analysis revealed that purified recombinant MS2 enzyme is able to convert palmitoyl-Acyl Carrier Protein to the corresponding C16:0 alcohol with NAD(P)H as the preferred electron donor. Using optimized reaction conditions (i.e. at pH 6.0 and 30°C), MS2 exhibits a K(m) for 16:0-Acyl Carrier Protein of 23.3 ± 4.0 μm, a V(max) of 38.3 ± 4.5 nmol mg⁻¹ min⁻¹, and a catalytic efficiency/K(m) of 1,873 M⁻¹ s⁻¹. Based on the high homology of MS2 to other characterized fatty acid reductases, it was surprising that MS2 showed no activity against palmitoyl- or other acyl-coenzyme A; however, this is consistent with its plastidial localization. In summary, genetic and biochemical evidence demonstrate an MS2-mediated conserved plastidial pathway for the production of fatty alcohols that are essential for pollen wall biosynthesis in Arabidopsis.

Generalized Transit Delay on Wireless Motility Capsule Testing in Patients with Clinical Suspicion of Gastroparesis, Small Intestinal Dysmotility, or Slow Transit Constipation

The prevalence of generalized transit delay and relation to symptoms in suspected gastroparesis, intestinal dysmotility, or slow transit constipation are unknown. The aims of this study were (1) to define prevalence of generalized dysmotility using wireless motility capsules (WMC), (2) to relate to symptoms in suspected regional delay, (3) to compare results of WMC testing to conventional transit studies to quantify new diagnoses, and (4) to assess the impact of results of WMC testing on clinical decisions. WMC transits were analyzed in 83 patients with suspected gastroparesis, intestinal dysmotility, or slow transit constipation. Isolated regional delays were observed in 32% (9% stomach, 5% small bowel, 18% colon). Transits were normal in 32% and showed generalized delays in 35%. Symptom profiles were similar with normal transit, isolated delayed gastric, small intestinal, and colonic transit, and generalized delay (P=NS). Compared to conventional tests, WMC showed discordance in 38% and provided new diagnoses in 53%. WMC testing influenced management in 67% (new medications 60%; modified nutritional regimens 14%; surgical referrals 6%) and eliminated needs for testing not already done including gastric scintigraphy (17%), small bowel barium transit (54%), and radioopaque colon marker tests (68%). WMC testing defines localized and generalized transit delays with suspected gastroparesis, intestinal dysmotility, or slow transit constipation. Symptoms do not predict the results of WMC testing. WMC findings provide new diagnoses in >50%, may be discordant with conventional tests, and can influence management by changing treatments and eliminating needs for other tests. These findings suggest potential benefits of this method in suspected dysmotility syndromes and mandate prospective investigation to further define its clinical role.

Deletion of the pH Sensor GPR4 Decreases Renal Acid Excretion

Proton receptors are G protein-coupled receptors that accept protons as ligands and function as pH sensors. One of the proton receptors, GPR4, is relatively abundant in the kidney, but its potential role in acid-base homeostasis is unknown. In this study, we examined the distribution of GPR4 in the kidney, its function in kidney epithelial cells, and the effects of its deletion on acid-base homeostasis. We observed GPR4 expression in the kidney cortex, in the outer and inner medulla, in isolated kidney collecting ducts, and in cultured outer and inner medullary collecting duct cells (mOMCD1 and mIMCD3). Cultured mOMCD1 cells exhibited pH-dependent accumulation of intracellular cAMP, characteristic of GPR4 activation; GPR4 knockdown attenuated this accumulation. In vivo, deletion of GPR4 decreased net acid secretion by the kidney and resulted in a nongap metabolic acidosis, indicating that GPR4 is required to maintain acid-base homeostasis. Collectively, these findings suggest that GPR4 is a pH sensor with an important role in regulating acid secretion in the kidney collecting duct.

Il rifornimento della rete commerciale al dettaglio della Provincia di Napoli

The paper proposes a demand analysis and a re-engineering of the distribution network for supplying retailers in the metropolitan area of Napoli (Italy), carried out under the managing supervision of the local Association of Retailers. Notably, while there is a well-established set of infrastructural and operational solutions for more efficient distribution patterns leading to a reduction of freight vehicles•km in urban areas, the issue of their quantitative appraisal still deserves attention. This is also due, in the authors’ view, to the uncertainty in the transferability of (the few) quantitative methods for freight demand forecasts available in the literature to geographical contexts different from those they were implemented in. Firstly, the design and the outcomes of an extensive survey carried out within the metropolitan area of Napoli, in order to estimate the current freight demand, are presented. In more detail, the survey focused on the specific segment of retailers not belonging to a structured organization (i.e. department stores, newspapers, pharmacies, and so on), because of their intrinsic inefficiency and the consequent need for a substantial reorganization. Within this segment, 2.000 retailers (over about 30.000) have been surveyed, following a stratified sampling scheme by commodity group and geographical position. In more detail, six commodity groups (universe share in brackets: textile/clothing (33%), foodstuff (20%), household appliance and electronics (4%), furniture (5%), stationery (11%), other retailers (27%)) and nine territorial clusters (different for urban density, transport network performances and retailers’ characteristics) have been taken into account. As a result, a remarkable traffic has been observed, with some 27.000 consignments per day corresponding to about 260.000 packages. The main destinations are Napoli and its direct suburbs (about 24.000 consignments/day), the main origins are Napoli (9.000), its metropolitan area (11.000), the remaining of the region (2.000) and outside the region (5.000). Then, a re-engineering of the distribution network has been proposed and analyzed. In more detail, interest is primarily focused on rationalizing consignments coming from Campania and destined to the parts of the metropolitan area of Napoli with the highest population densities and road network congestion, that is the cities of Napoli, Nola, Castellammare di Stabia and Sorrento. The re-engineering is based on the introduction of 6 small transit points, three in the city of Napoli and one for each of the remaining cities, aimed at capturing all the consignments supplied within their area of influence, in order to support the protection of high valued urban areas. Notably, the re-engineering project took into account also the presence of significant intermodal nodes and logistic platforms within the study area, as potential higher-level platform for supplying transit points.

Classifying Rural and Small Urban Transit Agencies

Rural and small urban transit agencies are classified into peer groups by the hierarchical cluster analysis and data from the Rural National Transit Database. The objective is to provide a basis for the comparison of individual agency performance with peer group performance as well as econometric analysis between and within peer groups. Rural and small urban transit agencies are first assigned to three groups by service provided: demand–response, fixed-route, and demand–response and fixed-route service. A fourth group is created to accommodate the many transit agencies providing demand–response service that did not report vehicle hour data. The four groups are then clustered by using vehicle mile, vehicle hour (when available), and fleet size variables. Operating statistics for each cluster by group are presented. The process for comparing individual agency performance with its respective cluster is described. The Rural National Transit Database demonstrates its usefulness as a consistent, uniform national data set. However, additional service area information would accommodate clustering based on exogenous, as opposed to endogenous, variables, as necessary with the current data set.

The relationship between symptoms, body mass index, gastrointestinal transit and stool frequency in patients with irritable bowel syndrome

Motility disturbances are involved in the pathophysiology of the irritable bowel syndrome (IBS). Population-based studies have shown an association between increasing body mass index (BMI) and different gastrointestinal (GI) symptoms. The aim of this prospective study was to characterize the relationships between symptoms in IBS, GI transit, as a measure of GI motility, and BMI. We included 96 IBS patients in which 34 patients had diarrhea predominance (D-IBS), 16 had predominant constipation (C-IBS) and 46 had alternating bowel habits (A-IBS). All patients completed a GI symptom questionnaire and underwent a measurement of gastric emptying, small bowel residence and colonic transit. Transit values in 83 healthy individuals served as reference. BMI was calculated. At least one transit abnormality was found in 49 of 96 patients (51%). Increasing severity of urgency, loose stools and reflux were associated with higher BMI. Moreover, patients overweight had significantly faster colonic and rectosigmoid transit and higher stool frequency compared with normal weight patients. The symptom severities of pain/discomfort and bloating were associated with colonic transit abnormalities. In women, transit in the small bowel and colon was significantly slower in C-IBS compared with D-IBS. GI transit is of relevance for the symptom pattern in patients with IBS. High BMI is associated with fast regional bowel transit and may therefore influence some stool-related symptoms in IBS.

Polyethylene glycol plus simethicone in small-bowel preparation for capsule endoscopy

Background Small-bowel contents can hamper the quality of video-capsule endoscopy (VCE). No standardized protocol has been proposed and overnight fasting remains the proposed preparation for VCE. Aims The aim was to evaluate the effects of 2 regimens of bowel preparation on small intestine cleansing, diagnostic yield and capsule transit times. Methods This is a prospective, randomized, blinded, and controlled study. Sixty patients referred for VCE were randomized into 2 groups. Group A ingested 2 l of a polyethylene glycol and simethicone solution 16 h before VCE. Group B were instructed to consume a fibre-free diet and allowed to consume clear liquids the day before VCE. The small-bowel cleansing was graded as “complete” if the entire wall was assessable, “incomplete” if more than 50% of the wall was visible, and “insufficient” if less than 50% of the wall was visible. Results In group A, a “complete”, “incomplete” and “insufficient” small-bowel cleansing was achieved in 42%, 39% and 19% of cases respectively. In group B, a “complete”, “incomplete” and “insufficient” small-bowel cleansing was achieved in 43%, 33% and 24% of cases respectively. No significant differences were observed between the two groups, regarding small-bowel cleansing level ( p = 0.65). No differences were also observed in the diagnostic yield (48.2%, 13.8% and 38% vs 65.5%, 6.9% and 27.6% of positive, suspicious and no findings respectively, in groups A and B [ p = 0.39]) and small-bowel transit times (mean 288 min and 299 min in groups A and B respectively [ p = 0.70]). Conclusions The results of the present study do not support the use of 2 l of a polyethylene glycol and simethicone solution before VCE.

OBSERVATIONAL WINDOW FUNCTIONS IN PLANET TRANSIT SURVEYS

The probability that an existing planetary transit is detectable in one's data is sensitively dependent upon the window function of the observations. We quantitatively characterize and provide visualizations of the dependence of this probability as a function of orbital period upon several observing strategy and astrophysical parameters, such as length of observing run, observing cadence, length of night, transit duration and depth, and the minimum number of sampled transits. The ability to detect a transit is directly related to the intrinsic noise of the observations. In our simulations of observational window functions, we explicitly address noncorrelated (Gaussian or white) noise and correlated (red) noise and discuss how these two noise components affect transit detectability in fundamentally different manners, especially for long periods and/or small transit depths. We furthermore discuss the consequence of competing effects on transit detectability, elaborate on measures of observing strategies, and examine the projected efficiency of different transit survey scenarios with respect to certain regions of parameter space.

A Governance Reform Proposal: Improving Bus Transit Operations in Los Angeles

This article examines key governing issues related to Los Angeles transit operations. The study uses empirical data from the National Transit Database and personal interviews conducted with transit agency officials. Based on technical analysis and evaluation, the authors call for empowering council of governments and small cities to address interagency/intersector coordination and political equity issues, downsizing the Los Angeles County Metropolitan Transportation Authority Headquarters and strengthening autonomy of the “Service Sectors” to better streamline transit operation issues, abolishing small municipal transit operators to refine bus fleet size distribution, and enhancing transit service privatization to yield a better cost efficiency.

Multiple Sequence Motifs in the Rubisco Small Subunit Transit Peptide Independently Contribute to Toc159-Dependent Import of Proteins into Chloroplasts

A large number of plastid proteins encoded by the nuclear genome are posttranslationally imported into plastids by at least two distinct mechanisms: the Toc159-dependent and Toc132/Toc120-dependent pathways. Light-induced photosynthetic proteins are imported through the Toc159-dependent pathway, whereas constitutive housekeeping plastid proteins are imported into plastids through the Toc132/Toc120 pathway. However, it remains unknown which features of the plastid protein transit peptide (TP) determine the import pathway. We have discovered sequence elements of the Rubisco small subunit TP (RbcS-tp) that play a role in determining import through the Toc159-dependent pathway in vivo. We generated multiple hybrid mutants using the RbcS-tp and the E1alpha-subunit of pyruvate dehydrogenase TP (E1alpha-tp) as representative peptides mediating import through the Toc159-dependent and Toc159-independent pathways, respectively. Import experiments using these hybrid mutants in wild-type and ppi2 mutant protoplasts revealed that multiple sequence motifs in the RbcS-tp independently contribute to Toc159-dependent protein import into chloroplasts. One of these motifs is the group of serine residues located in the N-terminal 12-amino acid segment and the other is the C-terminal T5 region of the RbcS-tp ranging from amino acid positions 41 to 49. Based on these findings, we propose that multiple sequence elements in the RbcS-tp contribute independently to Toc159-dependent import of proteins into chloroplasts.

The Troughton &amp; Simms transit circle of Coimbra Astronomical Observatory from the 1850s: An example of the dissemination of technological developments

AbstractYesterday, as today, technological developments led by large and expensive instrumental projects are later on disseminated to smaller and more affordable devices. In 1847, Airy requested a new transit circle for the Greenwich Observatory. When the first observation was performed, on 4 January 1851, Airy's Greenwich Transit Circle (ATC) was the largest instrument of its class in the world. The construction of the ATC implied solving several technical difficulties, for example, the maintenance of the instrument rigidity and the illumination of the graduated circle and telescope field of view. After the ATC completion Troughton &amp; Simms stand at the 1851 Great London Exhibition included two small transit instruments which were praised for their telescope field of view/eyepiece wires illumination. One of which, was based upon the design implemented beforehand on the ATC. In this paper we will discuss the field and eyepiece wire illumination innovations introduced on the ATC and the Simms transit instruments exhibited in 1851. We will also describe the small Troughton &amp; Simms transit circle currently belonging to Coimbra Astronomical Observatory collection that is, we believe, one of the earliest implementation of this ATC lead development (© 2009 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)