[Glycoalkaloids in potatoes]. / Les glycoalcaloïdes de la pomme de terre.

With its high concentration in starch and vitamins (C, B1 and B2), the potato, cooked in water, is a very interesting source of energy. Unfortunately, it also contains natural toxins: the glycoalkaloids. Their variable amount can depend, in particular, on different environmental factors. This paper summarizes these factors effects and the glycoalcaloids toxicology.

Determination of alpha-solanine and alpha-chaconine in potatoes by high-performance thin-layer chromatography/densitometry.

A high-performance thin-layer chromatographic (HPTLC) method was used to determine the glycoalkaloids alpha-solanine and alpha-chaconine in potatoes. Alpha-solanine and alpha-chaconine are extracted from dehydrated potatoes with boiling methanol-acetic acid (95 + 5, v/v). The analytes are separated on a Silica Gel 60 F254 HPTLC plate by a saturated mixture of dichloromethane-methanol-water-concentrated ammonium hydroxide (70 + 30 + 4 + 0.4, v/v), which is used for vertical development of the plate up to a distance of 85 mm. For visualization, the plate is dipped 3 times into a modified Carr-Price reagent, 20% (w/v) antimony(III) chloride in acetic acid-dichloromethane (1 + 3, v/v), and subsequently heated on a hot plate at 105 degrees C for 5 min. The glycoalkaloids all appear as red chromatographic zones on a colorless background. Densitometric quantification is performed at 507 nm by reflectance scanning. After determination of the appropriate response function, the proposed method was validated. Good results with respect to linearity, accuracy, and precision were obtained in the concentration range studied.

Synthesis, spectroscopy and catalysis of

Chromium acetyl acetonate [Cr(acac)3] complexes have been grafted onto the surface of two mesoporous crystalline materials; pure silica MCM-41 (SiMCM-41) and Al-containing silica MCM-41 with an Si:Al ratio of 27 (AlMCM-41). The materials were characterized with X-ray diffraction, N2 adsorption, thermogravimetrical analysis, diffuse reflectance spectroscopy in the UV-Vis-NIR region (DRS), electron spin resonance (ESR) and Fourier transform infrared spectroscopy. Hydrogen bonding between surface hydroxyls and the acetylacetonate (acac) ligands is the only type of interaction between [Cr(acac)3] complexes and SiMCM-41, while the deposition of [Cr(acac)3] onto the surface of AlMCM-41 takes place through either a ligand exchange reaction or a hydrogen-bonding mechanism. In the as-synthesized materials, Cr3+ is present as a surface species in pseudo-octahedral coordination. This species is characterized by high zero-field ESR parameters D and E, indicating a strong distortion from O(h), symmetry. After calcination, Cr3+ is almost completely oxidized to Cr6+, which is anchored onto the surface as dichromate, some chromate and traces of small amorphous Cr2O3 clusters and square pyramidal Cr5+ ions. These materials are active in the gas-phase and slurry-phase polymerization of ethylene at 100 degrees C. The polymerization activity is dependent on the Cr loading, precalcination temperature and the support characteristics: a 1 wt % [Cr(acac)3]-AlMCM-41 catalyst pretreated at high temperatures was found to be the most active material with a polymerization rate of 14000 g polyethylene per gram of Cr per hour. Combined DRS-ESR spectroscopies were used to monitor the reduction process of Cr(6+/5+) and the oxidation and coordination environment of Cr(n+) species during catalytic action. It will be shown that the polymer chains initially produced within the mesopores of the Cr-MCM-41 material form nanofibres of polyethylene with a length of several microns and a diameter of 50 to 100 nanometers. These nanofibres (partially) cover the outer surface of the MCM-41 material. The catalyst particles also gradually break up during ethylene polymerization resulting in the formation of crystalline and amorphous polyethylene with a low bulk density and a melt flow index between 0.56 and 1.38g per 10 min; this indicates the very high molecular weight of the polymer.

T1-weighting of Hahn echo-trains in the stray-field for deuterium: prospects for imaging using long echo-train summation.

Hahn-echoes have been observed in stray-field gradients of 37.5 T/m and 74.5 T/m for deuterium in heavy water in a number of forms: liquid, ice, and coordinated in solid copper sulfate and silica gel. In the diamagnetic samples, the application of many pulses (> 1000 or more) in long pulse-trains produced many sustained echoes. This lengthening of T(echo) is caused by T1-weighting of the components of the Hahn echo (even in the absence of spin-locking). In contrast, for the paramagnetic complex, the shortening of T1 greatly reduces T(echo) and only few echoes are obtained. A new protocol for stray field imaging is suggested when T1 is long: long echo-train summation (LETS). The observed magnetisation is much greater for heavy ice than for heavy water because the line-width, and hence the thickness of the excited slice, is greater.

Anti-inflammatory and immunological effects of Centaurea cyanus flower-heads.

Centaurea cyanus flower-heads are used in European phytotherapy for the treatment of minor ocular inflammations. Different pharmacological experiments (inhibition of carrageenan, zymosan and croton oil-induced oedemas, inhibition of plasma haemolytic activity, induction of anaphylatoxin activity) showed that polysaccharides extracted from C. cyanus flower-heads had anti-inflammatory properties and interfered with complement. Moreover, these polysaccharides were found to be mainly composed of galacturonic acid, arabinose, glucose, rhamnose and galactose.

[Activity of street drugs]. / A propos de l'activité des drogues de rue ("street drugs").

In the seized samples, the concentrations of diamorphine (heroin) varied from zero to more than seventy percent and the concentrations of cocaine from zero to more than ninety percent. Such variations in concentrations of active constituents constitute a major risk for those who use and abuse street drugs.

Stray-field imaging of quadrupolar nuclei of half integer spin in solids.

A report is presented on the observation of Hahn echoes from the following quadrupolar nuclei of half integer spin (I) in polycrystalline solids in the large static magnetic field gradient (37.5 T/m) which exists in the fringe field of a superconducting solenoid: 7Li, 23Na, 11B, 65Cu (I = 3/2); 27Al (I = 5/2); 51V, 59Co (I = 7/2); and 115In (I = 9/2). 23Na echo-trains from NaCl (with non-selective excitation) and from Na2SO4 (with selective excitation) are compared quantitatively for two different RF pulse sequences: 90x-(tau-90y-tau-echo-)n and 90x-(tau-90x-tau-echo-)n. The signals obtained from RF pulses corresponding to non-selective 90 degrees pulses were shown to be quantitative, whereas in the selective case smaller signals were obtained since only the central transition contributed. The loss of signal from this cause can be distinguished from small signals resulting from low density of nuclei by use of the second sequence. A 7Li image obtained from LiF in a cylindrical glass-vial is shown.

Determination of 51V quadrupole and chemical shift tensor orientations in V2O5 by analysis of magic-angle spinning nuclear magnetic resonance spectra.

Magic-angle spinning (MAS) 51V nuclear magnetic resonance (NMR) spectra of V2O5 have been recorded at various fields to evidence the relative effects of the quadrupole interaction and electronic shielding at the nucleus. A refinement of the spectra using theoretical simulations has been performed assuming a simultaneous existence of these two anisotropic interactions. The relative orientation of the principal axes for both tensors has been obtained. The results agree with previous single-crystal studies. Reliability of the results is discussed. A fundamental indetermination of the actual relative tensor orientations remains, owing to the powder nature of the sample.

Refinement of solid-state MAS NMR spectra of quadrupolar nuclei: application to the analysis of some 51V compounds.

Magic angle solid-state 51V NMR spectra of several vanadium powder compounds have been recorded. A refinement of these spectra using theoretical simulations of the powder spectra have been performed assuming the simultaneous anisotropic effects of electric field gradients (EFG) and of electronic shielding. It is shown that the relative orientation of the principal axes of the two tensors have to be considered.

Defecography: I. Description of a new procedure and results in normal patients.

To solve frequently encountered clinical problems in the anorectal area, we have developed a simplified dynamic method of defecography. A radiopaque substance, the consistency of normal stools, is introduced into the rectum and the patient is then seated on a specially designed seat composed of superposed air chambers which, for technical reasons, are filled with water. The movements induced by evacuation of the rectum are recorded using 100-mm ampliphotography. After recording findings in 56 normal patients, we are able to define 5 criteria for "normal": increase in anorectal angulation, obliteration of the impression of the puborectal muscle, wide opening of the anal canal, total evacuation of the rectal contents, and normal resistance of the pelvic floor. The mean value of the anorectal angle (ARA) was 91.96 degrees (+/- 1.52 SEM) at rest and 136.76 degrees (+/- 1.51 SEM) during straining. The increase of ARA during straining is 44.8 degrees.

Defecography: II. Contribution to the diagnosis of defecation disorders.

Our simple method of defecography has proved to be more sensitive than clinical evaluation in the detection and description of defecation disorders. Among the different types of disorders, described on the basis of 144 abnormal defecograms, the most common are rectal intussusception (RI), intraanal rectal intussusception (IRI), external manually (EMRP) or spontaneously (ESRP) reducible prolapses, rectocele, and accentuation of the impression of the puborectalis sling (AIPR). Study of the mean values of the anorectal angle (ARA) (normal mean value = 92 degrees at rest) reveals an increase (p less than 0.05) in the ARA in IRI and ESRP and a decrease (p less than 0.05 at rest, p less than 0.001 at strain) in AIPR. The most striking observation is a highly significant increase (p less than 0.001) in the ARA associated with incontinence.

[Plain film findings and contrast enema in colon ischemia (author's transl)]. / Abdomen sans préparation et lavement opaque dans l'ischémie du côlon.

We describe our observations on abdominal roentgenograms without preparation in two cases of segmental colon infarct and eighteen cases of ischemic colitis. In both infarct cases a colic ileus was noted. In one patient the infarcted loop appeared as gas contrasted. In the ischemic cases there were, in addition to the bowel ileus: a colectasis in two patients, a collapsed segment in thirteen and a gas-filled segment in three. When associated to a significant clinical situation the two latter images have some diagnostic value. In the majority of patients, the contrast enema made possible a diagnosis of ischemic colitis; in three it shaved the sigmoid narrowing responsible for the ischemia.