Application of liquid chromatography–mass spectrometry to measure short chain fatty acids in blood

A new liquid chromatography–mass spectrometry method is described to determine concentrations of the short chain fatty acids acetic acid, propionic acid and butyric acid (SCFAs) in human blood plasma. The method is based on reversed phase chromatography followed by post-column neutralization of the mobile phase with ammonia and a consecutive measurement of the SCFAs ammonia adducts using negative electro spray ionization. Sample preparation involved simple organic acid deproteinization, resulting in 100% recovery. SCFAs eluted baseline separated within a 25 min run cycle. A linear response was obtained in the range between 0 and 250 μmol/l (R² ranged from 0.997 to 0.9999). The limit of detection ranged from 0.05 μmol/l for propionic and butyric acid and 0.1 μmol/l for acetic acid. The method was tested by analyzing plasma of arterial blood, from portal vein and hepatic vein blood from patients undergoing a pylorus-preserving pancreaticoduodenectomy. As expected, the highest SCFA concentrations were found in portal plasma, hepatic vein levels were in between, while arterial concentrations were lowest. This newly developed method is suitable to determine SCFA concentrations in human plasma samples.     

Instabilities,bifurcations and fluctuations in chemical systems : L. E. Reichl and W. C. Schieve University of Texas Press, 1982, xi+427 pp, $35.00

The occupancy principle and the mean-transit-time theorem are derived for the passage of a tracer through a system that can be described by a general pool model. It is proved, using matrix theory, that if (and only if) tracer entering the system labels equally all tracee fluxes into the system, then the integral of the tracer concentration is the same in all the pools. It is also proved that if, in addition, all flow out of the system is through the observation point, the first moment of the tracer concentration at the observation point can be used to calculate the total amount of trace in the system. The necessity of this condition is analyzed. Examples are given of models in which the occupancy principle and the mean-transit-time theorem hold or do not hold.     

The Question of a Presupracleithrum in Brachiopterygian Fishes

The presupracleithrum is an exoskeletal pectoral bone that occurs in Paleozoic and Mesozoic actinopterygian fishes. It has been equated more than once with an opercular element in brachiopterygian fishes. In recent cladistic analyses, this alleged homology is used to assign brachiopterygians to actinopterygians. However, a comparison of brachiopterygian and actinopterygian crania shows clearly that the former lack a presupracleithrum.     

Abiotic Stress Tolerance： From Gene Discovery in Model Organisms to Crop Improvement

Productive and sustainable agriculture necessitates growing plants in sub-optimal environments with less input of precious resources such as fresh water. For a better understanding and rapid improvement of abiotic stress tolerance, it is important to link physiological and biochemical work to molecular studies in genetically tractable model organisms. With the use of several technologies for the discovery of stress tolerance genes and their appropriate alleles, transgenic approaches to improving stress tolerance in crops remarkably parallels breeding principles with a greatly expanded germplasm base and will succeed eventually.     

Impact of the Quality of Bowel Cleansing on the Efficacy of Colonic Cancer Screening: A Prospective,Randomized, Blinded Study

Objectives

Efficacy of two low volume bowel cleansing preparations, polyethylene glycol plus ascorbate (PEG+Asc) and sodium picosulfate/magnesium citrate (NaPic/MgCit), were compared for polyp and adenoma detection rate (PDR and ADR) and overall cleansing ability. Primary endpoint was PDR (the number of patients with ≥1 polypoid or flat lesion recorded by the colonoscopist).

Methods

Diagnostic, surveillance or screening colonoscopy patients were enrolled into this investigator-blinded, multi-center Phase IV study and randomized 1:1 to receive PEG+Asc (administered the evening before and the morning of colonoscopy, per label) or NaPic/MgCit (administered in the morning and afternoon the day before colonoscopy, per label). The blinded colonoscopist documented any lesion and assessed cleansing quality (Harefield Cleansing Scale).

Results

Of 394 patients who completed the study, 393 (PEG+Asc, N=200; NaPic/MgCit, N=193) had a colonoscopy. Overall PDR for PEG+Asc versus NaPic/MgCit was 51.5% versus 44.0%, p=0.139. PDR and ADR on the right side of the bowel were significantly higher with PEG+Asc versus NaPic/MgCit (PDR: 56[28.0%] versus 32[16.6%], p=0.007; ADR: 42[21.0%] versus 23[11.9%], p=0.015), as was detection of flat lesions (43[21.5%] versus 25[13.0%], p=0.025). Cleansing quality was better with PEG+Asc than NaPic/MgCit (98.5% versus 57.5% considered successful cleansing). Overall, there were 132 treatment-emergent adverse events (93 versus 39 for PEG+Asc and NaPic/MgCit, respectively). These were mainly mild abdominal symptoms, all of which were reported for higher proportions of patients in the PEG+Asc than NaPic/MgCit group. Twice as many patients in the NaPic/MgCit versus the PEG+Asc group reported tolerance of cleansing solution as ‘very good’.

Conclusions

Compared with NaPic/MgCit, PEG+Asc may be more efficacious for overall cleansing ability, and subsequent detection of right-sided and flat lesions. This is likely attributable to the different administration schedules of the two bowel cleansing preparations, which may positively impact the detection and prevention of colorectal cancer, thereby improving mortality rates.

Trial Registration

ClinicalTrials.gov NCT01689792.     

Whole Cell Formaldehyde Cross-Linking Simplifies Purification of Mitochondrial Nucleoids and Associated Proteins Involved in Mitochondrial Gene Expression

Mitochondrial DNA/protein complexes (nucleoids) appear as discrete entities inside the mitochondrial network when observed by live-cell imaging and immunofluorescence. This somewhat trivial observation in recent years has spurred research towards isolation of these complexes and the identification of nucleoid-associated proteins. Here we show that whole cell formaldehyde crosslinking combined with affinity purification and tandem mass-spectrometry provides a simple and reproducible method to identify potential nucleoid associated proteins. The method avoids spurious mitochondrial isolation and subsequent multifarious nucleoid enrichment protocols and can be implemented to allow for label-free quantification (LFQ) by mass-spectrometry. Using expression of a Flag-tagged Twinkle helicase and appropriate controls we show that this method identifies many previously identified nucleoid associated proteins. Using LFQ to compare HEK293 cells with and without mtDNA, but both expressing Twinkle-FLAG, identifies many proteins that are reduced or absent in the absence of mtDNA. This set not only includes established mtDNA maintenance proteins but also many proteins involved in mitochondrial RNA metabolism and translation and therefore represents what can be considered an mtDNA gene expression proteome. Our data provides a very valuable resource for both basic mitochondrial researchers as well as clinical geneticists working to identify novel disease genes on the basis of exome sequence data.