Motilin in human milk: identification and stability during digestion

The presence of motilin in human milk and the influence of human milk on the degradation of [125I][Nle13] porcine motilin by gastric and duodenal fluids were investigated. Milk and plasma samples were collected from 14 mothers, and motilin was measured by radioimmunoassay. Plasma levels were 416 +/- 37 pg/mL. In 8 defatted samples the motilin level was 105 +/- 14 pg/mL, in the six others levels were above 1000 pg/mL but dilution curves were non-linear. After solid-phase extraction milk levels were 108 +/- 21 pg/mL in 13 samples, in 1 sample the dilution curve was still non-linear. The stability of motilin after ingestion was studied in vitro by incubating [121I][Nle13] porcine motilin with gastric and intestinal juices obtained from newborns (10 times diluted). Incubations were performed at 37 degrees C at pH 1.8, 3.2 and 5.8 for the gastric fluid and at pH 7.4 for the duodenal fluid. After different times of intervals (5, 10, 20 and 30 minutes) intact motilin was precipitated with trichloroacetic acid and the radioactivity of the supernatant was determined. Motilin was rapidly degraded by gastric juice. The breakdown was greatest at pH 3.2 (74% after 30 minutes) and lowest at pH 5.8 (29%), the pH after milk feeding in neonates. Degradation by intestinal juice at pH 7.4 was also very rapid (77% after 30 minutes). Human milk and BSA inhibited partially the gastric digestion at pH 3.2 (17 and 29%, respectively). Digestion by intestinal juice was not affected by human milk and BSA. These results suggest that digestion of motilin in the stomach may be sufficiently retarded by human milk in the newborn to exert a biological role.     

The Arabidopsis LATERAL ORGAN BOUNDARIES-domain gene ASYMMETRIC LEAVES2 functions in the repression of KNOX gene expression and in adaxial-abaxial patterning

The normal development of lateral organs of the shoot requires the simultaneous repression of meristem-specific genes and the activation of organ-specific genes. ASYMMETRIC LEAVES2 (AS2) is required for the development of normal leaf shape and for the repression of KNOX genes in the leaf. AS2 is a member of the recently identified, plant-specific LATERAL ORGAN BOUNDARIES (LOB)-domain gene family. Expression of AS2 at high levels resulted in repression of the KNOX homeobox genes BREVIPEDICELLUS, KNAT2, and KNAT6 but not of the related SHOOT MERISTEMLESS gene. Overexpression of AS2 also led to a perturbation of normal adaxial-abaxial asymmetry in lateral organs, resulting in the replacement of abaxial cell types with adaxial cell types. These results indicate that AS2 is sufficient to induce adaxial cell fate and repress KNOX gene expression.     

Taking the fungal highway: mobilization of pollutant-degrading bacteria by fungi

The capacity of fungi to serve as vectors for the dispersion of pollutant-degrading bacteria was analyzed in laboratory model systems mimicking water-saturated (agar surfaces) and unsaturated soil environments (glass-bead-filled columns). Two common soil fungi (Fusarium oxysporum and Rhexocercosporidium sp.) forming hydrophilic and hydrophobic mycelia, respectively, and three polycyclic aromatic hydrocarbon degrading bacteria (Achromobacter sp. SK1, Mycobacterium frederiksbergense LB501TG, and Sphingomonas sp. L138) were selected based on the absence of mutual antagonistic effects. It was shown that fungal hyphae act as vectors for bacterial transport with mobilization strongly depending on the specific microorganisms chosen: The motile strain Achromobacter sp. SK1 was most efficiently spread along hyphae of hydrophilic F. oxysporum in both model systems with transport velocities of up to 1 cm d(-1), whereas no dispersion of the two nonmotile strains was observed in the presence of F. oxysporum. By contrast, none of the bacteria was mobilized along the hydrophobic mycelia of Rhexocercosporidium sp. growing on agar surfaces. In column experiments however, strain SK1 was mobilized by Rhexocercosporidium sp. It is hypothesized that bacteria may move by their intrinsic motilitythrough continuous (physiological) liquid films forming around fungal hyphae. The results of this study suggest that the specific stimulation of indigenous fungi may be a strategy to mobilize pollutant-degrading bacteria leading to their homogenization in polluted soil thereby improving bioremediation.     

Development of a set of simple bacterial biosensors for quantitative and rapid measurements of arsenite and arsenate in potable water

Testing for arsenic pollution is commonly performed with chemical test kits of unsatisfying accuracy. Bacterial biosensors are an interesting alternative as they are easily produced, simple, and highly accurate devices. Here, we describe the development of a set of bacterial biosensors based on a nonpathogenic laboratory strain of Escherichia coli, the natural resistance mechanism of E. coli against arsenite and arsenate, and three reporter proteins: bacterial luciferase, beta-galactosidase and Green Fluorescent Protein (GFP). The biosensors were genetically optimized to reduce background expression in the absence of arsenic. In calibration experiments with the biosensors and arsenite-amended potable water, arsenite concentrations at 4 microg of As/L (0.05 microM) were routinely and accurately measured. The currently most quantitative system expressed the bacterial luciferase as reporter protein, responding proportional with a concentration range between 8 and 80 microg of As/L. Sensor cells could be stored as frozen batches, resuspended in plain media, and exposed to the aqueous test sample, and light emission was measured after 30-min incubation. Field testing for arsenite was achieved with a system that contained beta-galactosidase, producing a visible blue color at arsenite concentrations above 8 microg/L. For this sensor, a protocol was developed in which the sensor cells were dried on a paper strip and placed in the aqueous test solution for 30 min after which time color development was allowed to take place. The GFP sensor showed good potential for continuous rather than end point measurements. In all cases, growth of the biosensors and production of the strip test was achieved by very simple means with common growth media, and quality control of the sensors was performed by isolating the respective plasmids with the genetic constructs according to simple standard genetic technologies. Therefore, the biosensor cells and protocols may offer a realistic alternative for measuring arsenic contamination in potable water.     

4He Impurities in 3He: Energetics and Dynamics

We have developed the optimized Fermi Hypernetted Chain Theory of a single impurity atom in a Fermi liquid, and have applied the theory to a ⁴He atom in bulk ³He. Previous applications of the theory for one component have produced excellent agreement with the experimental equation of state of ⁴He; the resulting equation of state of bulk ³He is about 0.4 K above the experimental one. Within the same theory, we obtain the pressure dependence of the chemical potential of ⁴He in bulk ⁴He, ³He in ³He, as well as the chemical potential of a ⁴He impurity in ³He. The pressure dependence of the impurity chemical potential agrees well with the experimental data, but we have a constant energy offset of about 1.2 K that disallows conclusive statements. This offset is partly explained by the relative inaccuracy of the ³He equation of state. We then calculate the self-energy of a single ⁴He impurity in ³He. Our results for the effective mass m^* ₄ fall within the experimental error of the best available data; they increase from about m^* ₄/m₄1.4 at zero pressure, to m^* ₄/m₄1.6 at p=20 atm. We show that this effective mass enhancement is, to about equal parts, due to hydrodynamic backflow and to the coupling to particle-hole excitations. When the latter are turned off in the collective approximation of the impurity-background correlations one obtains a significantly lower effective mass, m^* ₄/m₄1.2–1.35.     

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Permeabilität galvanisch beschichteter Polymerfolien. I. Methode zur Messung der Gaspermeabilität

The construction and function of an apparatus for the determination of gas permeability through metallized polymer films is described. The test gases N₂, O₂, and CO₂ penetrate under pressure differences from 100 torr to 20 bar through galvanized ABS films (acrylonitrile–butadiene–styrene copolymer). The metallic layers consists of chemically deposited Ni and a galvanic deposited Cu having a thickness of 2–30 μm. The quantity of permeated gases is determined by gas chromatography. The lowest permeability coefficient obtained is 10^?17 (cm³ cm/cm² sec torr). Leak effects can be measured quantitatively. The permeability of gas mixtures (i.e., air) can also be investigated. The apparatus allows the determination of extremely low permeability rates as well as those for conventional polymer systems.     

Bilateral accidental rupture of the fibrous capsules surrounding mammary prosthesis. Case report

A complication of augmentation mammaplasty is presented. Bilateral traumatic rupture of the surrounding fibrous capsule occurred without disruption of the prosthetic envelope. Questions are also raised about the effects of pregnancy on the maturing fibrous capsule.