Timothy R. B. Jones

Detection of Endogenous Retinoids in the Molluscan CNS and Characterization of the Trophic and Tropic Actions of 9-cis Retinoic Acid on Isolated Neurons

Retinoic acid (RA) is an active metabolite of Vitamin A that plays an important role in the growth and differentiation of many cell types. All-trans RA (atRA) is the retinoic acid isomer that has been most widely studied in the nervous system, and can induce and direct neurite outgrowth from both vertebrate and invertebrate preparations. The presence and role of the 9-cis-RA isomer in the nervous system is far less well defined. Here, we used high-pressure liquid chromatography (HPLC) and mass spectrometry (MS) to show for the first time, the presence of both atRA and 9-cis-RA in the CNS of an invertebrate. We then demonstrated that 9-cis-RA was capable of exerting the same neurotrophic and chemotropic effects on cultured neurons as atRA. In this study, significantly more cells showed neurite outgrowth in 9-cis-RA versus the EtOH vehicle control, and 9-cis-RA significantly increased the number and length of neurites from identified neurons after 4 d in culture. 9-cis-RA also extended the duration of time that cells remained electrically excitable in culture. Furthermore, we showed for the first time in any species, that exogenous application of 9-cis-RA induced positive growth cone turning of cultured neurons. This study provides the first evidence for the presence of both atRA and 9-cis-RA in an invertebrate CNS and also provides the first direct evidence for a potential physiological role for 9-cis-RA in neuronal regeneration and axon pathfinding.

Determination of polycyclic aromatic hydrocarbons by high-performance liquid chromatography-particle beam-mass spectrometry

In this article, we report a high-performance liquid chromatography-particle beam-mass spectrometric (HPLC-PB-MS) method for the determination of polycyclic aromatic hydrocarbons (PAHs). The PB interface consists of a concentric ultrasonic nebulizer with temperature-controlled desolvation chamber and a three-stage momentum separator. The HPLCPB-MS method showed greater sensitivity for PAHs with molecular weights above 178 than for those PAHs with molecular weights below 178. The percent relative standard deviations for the determination of 0.5 ng chrysene, 1.0 ng dibenzo[a,h]anthracene, 1.0 ng benzo[g,h,i]perylene, and 2.5 ng coronene were 20%, 2.5%, 13.7%, and 6%, respectively. The detection limits at signal/noise = 3 were 0.2 ng for chrysene, 1.0 ng for dibenzo[a,h]anthracene, 0.5 ng for benzo[g,h,i]perylene, and 1.5 ng for coronene.

Side chain hydroxylation of aromatic compounds by fungi: 3. Direct observation of fungal biotransformation by NMR

The enzymatic hydroxylations by intact fungal cells at the benzylic positions of toluene-d8, meta-fluorotoluene-α,α,α-d3, para-fluorotoluene-α,α,α-d3, ethylbenzene-α,α-d2, meta-fluoroethylbenzene-α,α-d2, and para-fluoroethylbenzene-α,α-d2 can be observed directly in an NMR tube by using 2H NMR as a probe. This technique provides a new method for the rapid screening of microorganisms for biotransformative capability. In all cases, the rate of product accumulation was uniform over a period of at least 4 days. The fluoro-substituted products were formed at a rate independent of the position of substitution, but slower than the corresponding unsubstituted substrates.

Synthesis, characterization and activity studies of vanadia catalysts supported on sol–gel derived Al2O3–ZrO2 mixed oxide

Abstract A series of catalysts with vanadia contents varying between 4 and 18 wt.% were prepared using sol–gel derived alumina–zirconia mixed oxide as a support. The catalysts were characterized employing 51 V , 1 H solid-state MAS NMR, diffuse reflectance FT-IR and BET surface area measurements. The activities of the catalysts were tested for the partial oxidation of ethanol. 51 V NMR studies indicated the presence of tetrahedral vanadate species at all the loadings studied except in the catalyst with a V 2 O 5 loading of 18 wt.%, in which six coordinated vanadia species was observed. Upon outgassing treatment of the calcined catalysts, a new tetrahedral species was observed, indicating the presence of water molecules or hydroxyl groups in the coordination sphere of vanadium. The 1 H MAS NMR studies showed the peaks corresponding to hydroxyl groups of alumina and zirconia. With increase in vanadia loading there was a decrease in the intensity of the basic hydroxyl groups of alumina showing the preferential reaction of vanadia with these groups. The DRIFT studies of the catalysts indicated the vibrations corresponding to agglomerates of V 2 O 5 only in the sample with highest V 2 O 5 content. Ethanol partial oxidation studies of the catalysts showed acetaldehyde as the major product with traces of ether, acetic acid, ethyl acetate, CO x , etc.

Fast atom bombardment mass spectrometry of sodium and potassium oxalates—mass spectrometric evidence for the existence of (sodium–oxalate)– and (potassium–oxalate)– ion pairs in aqueous solutions

Mass spectrometric evidence for the formation of (sodium-oxalate)–(NaC2O4–) and (potassium-oxalate)–(KC2O4–) ion pairs in aqueous solutions of potassium oxalate and sodium oxalate was obtained by analysing different concentrations of sodium and potassium oxalates in water containing 10% glycerol. The results suggest that fast atom bombardment mass spectrometry can be used to reveal the behaviour of ionic species in aqueous solutions. The KC2O4– and NaC2O4– ion pairs form clusters with neutral molecules of potassium oxalate and sodium oxalate and glycerol. No ion pair or cluster formation was observed when dry salts (without glycerol) were analysed. This behaviour differs from what has been observed for alkali halides under similar experimental conditions.

Presence of Ribeiroia ondatrae in the developing anuran limb disrupts retinoic acid levels

The widespread reports of malformed frogs have sparked interest worldwide to try and determine the causes of such malformations. Ribeiroia ondatrae is a digenetic trematode, which has been implicated as one such cause, as this parasite encysts within the developing tadpole hind limb bud and inguinal region causing dramatic limb malformations. Currently, the mechanisms involved in parasite-induced limb deformities remain unclear. We sought to investigate whether the level of retinoic acid (RA), a morphogenetic factor known to play a critical role in limb bud formation, is altered by the presence of R. ondatrae within the infected tadpole. Alteration of RA levels within the limb bud caused by the presence of the parasite may be achieved in three ways. First, metacercariae are actively secreting RA; second, cercariae, upon entering the limb/inguinal region, may release a large amount of RA; finally, the metacercariae may induce either an increase in the synthesis or a decrease in the degradation of the host’s endogenous retinoic acid levels. Here, we show through high performance liquid chromatography and mass spectrometry that limb bud tissue of Lithobates sylvaticus, which has been parasitised, contains 70% more RA compared to the unparasitised control. Furthermore, parasites that have encysted within the limb buds appear to contain substantially less RA (56%) than the free swimming cercariae (defined as the infectious stage of the parasite). Taken together, these data illustrate for the first time that encystment of R. ondatrae leads to an increase in RA levels in the tadpole limb bud and may offer insight into the mechanisms involved in parasite-induced limb deformities.

SUSCEPTIBILITY OF 2-ARYLIDENE-3,5.DIARYL-2,3-DIHYDRO-1,3, 4-THIADIAZOLES TO HYDROLYSIS

Abstract (Z)-2-Benzylidene-2,3-dihydro-3,5-diphenyl-1,3,4-thiadiazole (1 a) undergoes slow hydrolysis during long term storage (ca eleven years) to N′-phenacetyl-N′-phenyl-N-thiobenzhy-drazide (2a); the 2-(4-methoxybenzylidene) derivative behaves similarly.