The measurement of gastric motor function and transit in man by echo planar magnetic resonance imaging

Echo-planar imaging (EPI) can be used to produce snapshot images of the human stomach and antro-pyloro-duodenal segment in real time as an alternative technique to intubation and exposure to ionizing radiation. The method has been further developed to monitor simultaneous gastric motility and gastric emptying of liquid and solid meals. The model has been utilized to study the effects of pharmacological agents on gastric function.Eight normal subjects were imaged in a 0.5-T superconducting magnet for up to 6 h following ingestion of 800 ml tap water, followed by 500 ml porridge test meal + 500 ml tap water. A rapid multislice technique was adopted to image adjacent transverse slices (10 mm thick) through the gastric region. In addition, three subjects were orally dosed with 20 mg of the prokinetic agent Cisapride. Gastric volumes for each slice were calculated and summed to produce a measure of total gastric volume and gastric emptying. Contractile activity at the level of the antro-pyloric segment was detected using sequential 128 ms images at 3 s intervals. Alternate measurements of gastric volume and motility were made for the duration of the study.Gastric emptyingT _1/2's (times to empty 50% of the gastric contents) of 12.9 min for water and 116 min for porridge were in agreement with results obtained by the traditional techniques of gamma scintigraphy and impedance imaging. The frequency of gastric contractions increased from 2.4 contractions per minute (cpm) to 3.2 cpm following water and from 2.9 to 3.2 cpm following porridge. The prokinetic effect of enhanced coordination of antroduodenal contractions was also observed. These studies have demonstrated that EPI can be used to detect and image gastroduodenal function in man, totally noninvasively, and can be used to study the effects of drugs acting on the gastrointestinal tract.     

Interleukin-1 Receptor Antagonist Reduces Neonatal Lipopolysaccharide-Induced Long-Lasting Neurobehavioral Deficits and Dopaminergic Neuronal Injury in Adult Rats

Our previous study showed that a single lipopolysaccharide (LPS) treatment to neonatal rats could induce a long-lasting neuroinflammatory response and dopaminergic system injury late in life. This is evidenced by a sustained activation of microglia and elevated interleukin-1β (IL-1β) levels, as well as reduced tyrosine hydroxylase (TH) expression in the substantia nigra (SN) of P70 rat brain. The object of the current study was to test whether co-administration of IL-1 receptor antagonist (IL-1ra) protects against LPS-induced neurological dysfunction later in life. LPS (1 mg/kg) with or without IL-1ra (0.1 mg/kg), or sterile saline was injected intracerebrally into postnatal day 5 (P5) Sprague-Dawley male rat pups. Motor behavioral tests were carried out from P7 to P70 with subsequent examination of brain injury. Our results showed that neonatal administration of IL-1ra significantly attenuated LPS-induced motor behavioral deficits, loss of TH immunoreactive neurons, as well as microglia activation in the SN of P70 rats. These data suggest that IL-1β may play a pivotal role in mediating a chronic neuroinflammation status by a single LPS exposure in early postnatal life, and blockading IL-1β might be a novel approach to protect the dopaminergic system against perinatal infection/inflammation exposure.     

Competing Effects of Radio Frequency Fields on Carbon Nanotube/Resin Systems: Alignment versus Heating

This work shows that radio-frequency (RF) fields can simultaneously align carbon nanotubes (CNTs) dispersed in a resin and induce Joule heating to cure the resin. The timescales of alignment and curing using RF heating are numerically computed and compared at different field strengths in order to determine a temperature where alignment happens before the matrix crosslinks. Composites are experimentally fabricated at the desired target temperature and are optically analyzed and quantified; the CNT network is successfully aligned in the direction of the applied electric field. This methodology can be used to create composites where the local alignment can be varied across the sample. Composites fabricated using RF fields have higher electrical conductivity in the direction of the aligned CNTs than an oven-cured, randomly aligned sample. Also, RF-cured nanocomposites exhibit higher tensile strength and modulus in the direction of alignment compared to an oven-cured sample. Finally, it is further demonstrated how this methodology can be coupled with a direct ink writing additive manufacturing process to induce alignment in any desired direction, even orthogonal to the shear forces in the extrusion direction.     

PC and PE synthesis: mixed micellar analysis of the cholinephosphotransferase and ethanolaminephosphotransferase activities of human choline/ethanolamine phosphotransferase 1 (CEPT1)

The human choline/ethanolamine phosphotransferase 1 (CEPT1) gene codes for a dual-specificity enzyme that catalyzes the de novo synthesis of the two major phospholipids through the transfer of a phosphobase from CDP-choline or CDP-ethanolamine to DAG to form PC and PE. We used an expression system devoid of endogenous cholinephosphotransferase and ethanolaminephosphotransferase activities to assess the diradylglycerol specificity of CEPT1. A mixed micellar assay was used to ensure that the diradylglycerols delivered were not affecting the membrane environment in which CEPT1 resides. The CEPT1 enzyme displayed an apparent K _m of 36 μM for CDP-choline and 4.2 mol% for di-18∶1 DAG with a V _max of 14.3 nmol min⁻¹ mg⁻¹. When CDP-ethanolamine was used as substrate, the apparent K _m was 98 μM for CDP-ethanolamine and 4.3 mol% for di-18∶1 DAG with a V _max of 8.2 nmol min⁻¹ mg⁻¹. The preferred diradylglycerol substrates used by CEPT1 with CDP-choline as the phosphobase donor were di-18∶1 DAG, di-16∶1 DAG, and 16∶0/18∶1 DAG. A major difference between previous emulsion-based assay results and the mixed micelle results was a complete inability to use 16∶0(O)/2∶0 as a substrate for the de novo synthesis of platelet-activating factor when the mixed micelle assay was used. When CDP-ethanolamine was used as the phosphobase donor, 16∶0/18∶1 DAG, di-18∶1 DAG, and di-16∶1 DAG were the preferred substrates. The mixed micelle assay also allowed the lipid activation of CEPT to be measured, and both the cholinephosphotransferase and ethanolaminephosphotransferase activities displayed the unusual property of product activation at 5 mol%, implying that specific lipid activation binding sites exist on CEPT1. The protein kinase C inhibitor chelerythrine and the human DAG kinase inhibitor R59949 both inhibited CEPT1 activity with IC₅₀ values of 40 μM.     

Effect of DAG on milk fat TAG crystallization

The effect of milk fat and standard DAG on the crystallization behavior of milk fat TAG (MF-TAG) was investigated. When milk fat DAG were added to MF-TAG at the 0.1 wt% level, crystallization was delayed. Racemic purity was shown to be an important factor in the ability of DAG to influence TAG crystallization. Only sn-1,2 isomers of blends of MF-TAG with 0.1 wt% of the racemic mixtures of dipalmitin and diolein increased the activation free energy barrier to MF-TAG nucleation (ΔG _c ) and delayed the subsequent crystallization process by increasing the crystallization induction time (τ_SFC) determined from solid fat content-time measurements. Although crystallization kinetics were affected, the properties of the resulting network structures remained unchanged upon addition of milk fat minor components at the 0.1 wt% level     

Studies toward the synthesis of the shark repellent pavoninin-5

Sharks are the most dangerous predators of people in the sea, resulting in people being mauled and killed each year. A shark repellent could help to diminish this danger. The aglycone of the shark repellent pavoninin-5, (25R)-cholest-5-en-3β,15α,26-triol (5a), was synthesized from diosgenin (9). Removing mercury from the Clemmensen reduction of 9 gave a higher yield of (25R)-cholest-5-en-3β,16β,26-triol, 10a, and was also more environmentally friendly. Attempted methods for the transposition of the C-16β hydroxyl to the 15α position are described. A successful method for this transposition via the 15α-hydroxy-16-ketone, 8a, using the Barton deoxygenation reaction on the 16-alcohol 14b, is reported.     

正确表面预处理对涂料干膜杀菌剂抗微生物活性的影响

通过使用墙体杀菌清洁与非杀菌清洁后涂料干膜的性能比较，评价了杀菌清洗对提高涂料干膜性能的有效性，揭示了怎样用杀菌清洁提高杀菌系统的特性。同时，比较了传统杀菌剂和新式杀菌剂的性能差别。     

Nonlinear decoupling control in the presence of sensor and actuator deadtimes

This work focuses on synthesizing nonlinear decoupling controllers for multivariable nonlinear systems represented by a state-space model, in the presence of deadtimes. The deadtimes appear in both the inputs and the outputs, but not in the states, and are physically associated with sensors and actuators. Simple sufficient conditions for feasibility of closed-loop deadtimes are derived, which rely only on the structural properties of the system. A control law is then derived so that the closed-loop system is input/output linear and decoupled, with deadtimes equal to the smallest ones that satisfy the feasibility conditions. The proposed method is applied to a chemical process. Its performance is evaluated through simulation in the presence of set-point and disturbance changes.     

Variation of Brominated Indoles and Terpenoids Within Single and Different Colonies of the Marine Bryozoan Flustra foliacea

The variation of the brominated indole and diterpenoid content within single and different colonies of the bryozoan Flustra foliacea was investigated. The secondary metabolite profile and concentrations of individual components of F. foliacea samples were established using GC-MS. Samples from 17 different collecting sites were analyzed. The alkaloid and diterpene composition of F. foliacea varied greatly depending upon the site of collection. Investigation of F. foliacea samples from a single site (Helgoland, North Sea) over a period of time showed that the alkaloid and diterpenoid profile remained constant, however concentrations of individual components varied significantly. The alkaloid and diterpenoid composition of different segments of a single colony was found to be constant. Only small differences could be detected in the essential oil composition of different colonies and segments of single colonies of F. foliacea. Two of the F. foliacea alkaloids were found in the gastropods Hydrobia ulva and Gibbula cinerea, and one alkaloid in the common starfish Asteria rubens, all collected from the surface of the bryozoan.     

Tripalmitin–Sodium Dodecyl Sulfate Emulsion Droplet Liquid vs. Solid State Impacts in vitro Digestive Lipolysis

Questions remain as to the impact of lipid structure, including crystallinity, on digestibility and metabolic response. This study was undertaken to determine the impact of triacylglycerol crystallinity on digestibility using undercooled (liquid emulsion, LE) and crystalline (solid emulsion, SE) particles exposed to an in vitro model simulating upper gastrointestinal tract (GIT) digestive conditions. By hot microfluidization, 10 wt% tripalmitin oil‐in‐water emulsions (D_3,2 ~ 0.115 nm) with 0.9 wt% sodium dodecyl sulfate (SDS) were prepared. SE demonstrated complex melting behavior, was predominantly in the beta polymorph, and consisted of a heterogeneous mixture of anisometric particles. In vitro duodenal lipolysis was more extensive for the spherically shaped LE droplets vs. SE (P < 0.05), despite the fact that exposure to simulated gastric conditions (at pH 2, but not at pH 7) induced partial crystallization. Therefore, lipid droplet physical state impacted and was impacted by exposure to gastrointestinal conditions, with differences observed in fatty acid digestive release and implications for lipid absorption.