Determination of plasma [18F]-6-fluorodopa during positron emission tomography: elimination and metabolism in carbidopa treated subjects

An investigation of the metabolism of [18F]-6-fluorodopa (FDOPA) given to carbidopa treated subjects for scanning by positron emission tomography (PET) has been carried out by analysis of plasma. Reverse phase ion pair HPLC and alumina extraction were employed to fractionate and identify the [18F]-labelled compounds of plasma over a two hour period. During this time, the plasma levels of both total 18F and FDOPA decreased as a bi-exponential function of time. The rates of 18F, but not FDOPA, elimination were observed to decrease with age. In addition to FDOPA, only one other major peak of radioactivity was resolved by HPLC. Identification of this compound as the O-methylated derivative of FDOPA (MeFDOPA) is based on its shared HPLC elution time with in vitro synthesized O-[methyl-14C]-FDOPA. The ratio of the concentration of MeFDOPA to FDOPA (MeFDOPA/FDOPA) in plasma increased linearly with time, and the slope of this linear relationship decreased with the age of the individual.     

Molecular evolution of mitochondrial 12S RNA and cytochrome b sequences in the pantherine lineage of Felidae

DNA sequence comparisons of two mitochondrial DNA genes were used to infer phylogenetic relationships among 17 Felidae species, notably 15 in the previously described pantherine lineage. The polymerase chain reaction (PCR) was used to generate sequences of 358 base pairs of the mitochondrial 12S RNA gene and 289 base pairs of the cytochrome b protein coding gene. DNA sequences were compared within and between 17 felid and five nonfelid carnivore species. Evolutionary trees were constructed using phenetic, cladistic, and maximum likelihood algorithms. The combined results suggested several phylogenetic relationships including (1) the recognition of a recently evolved monophyletic genus Panthera consisting of Panthera leo, P. pardus, P. onca, P. uncia, P. tigris, and Neofelis nebulosa; (2) the recent common ancestry of Acinonyx jubatus, the African cheetah, and Puma concolor, the American puma; and (3) two golden cat species, Profelis temmincki and Profelis aurata, are not sister species, and the latter is strongly associated with Caracal caracal. These data add to the growing database of vertebrate mtDNA sequences and, given the relatively recent divergence among the felids represented here (1-10 Myr), allow 12S and cytochrome b sequence evolution to be addressed over a time scale different from those addressed in most work on vertebrate mtDNA.      

Sea urchin Hox genes: insights into the ancestral Hox cluster

We describe the Hox cluster in the radially symmetric sea urchin and compare our findings to what is known from clusters in bilaterally symmetric animals. Several Hox genes from the direct-developing sea urchin Heliocidaris erythrogramma are described. CHEF gel analysis shows that the Hox genes are clustered on a < or = 300 kilobase (kb) fragment of DNA, and only a single cluster is present, as in lower chordates and other nonvertebrate metazoans. Phylogenetic analyses of sea urchin, amphioxus, Drosophila, and selected vertebrate Hox genes confirm that the H. erythrogramma genes, and others previously cloned from other sea urchins, belong to anterior, central, and posterior groups. Despite their radial body plan and lack of cephalization, echinoderms retain at least one of the anterior group Hox genes, an orthologue of Hox3. The structure of the echinoderm Hox cluster suggests that the ancestral deuterostome had a Hox cluster more similar to the current chordate cluster than was expected Sea urchins have at least three Abd-B type genes, suggesting that Abd-B expansion began before the radiation of deuterostomes.      

ANALYSIS OF PROTEINS UNDERGOING AXONAL TRANSPORT IN NIGRO-STRIATAL NEURONS IN THE RAT

Abstract— An analysis of proteins undergoing axonal transport in nigro-striatal neurons, after the stereotaxic injection of [³H]leucine into the substantia nigra of rat brain was performed. As early as 6 h after the injection [³H]proteins appeared in the caudate-putamen. The maximum accumulation was at 5 days and there was still residual protein radioactivity present at 30 days. About 70 per cent of the total radioactive protein in the caudate-putamen was solubilized by homogenization in 0–5%, (v/v) Triton X-100 and remained in the supernatant on centrifuging for 1 h at 100,000 g. The supernatant fraction, when chroma-tographed on a DEAE-cellulose column, was resolved into four protein peaks (A, B. C and D) which were found to be labelled differently as a function of time after the injection of [³H]leucine. Peak A was substantially labelled in a first phase (6–24 h) and reached its maximum in a second phase (5 days). The proteins comprising this peak appeared to undergo both fast and slow axonal transport. Although some labelling in peak B was evident at 6 h, maximal activity did not occur until 5 days. No radioactivity could be detected in peaks C and D at 6 h. Maximal labelling of these two peaks also occurred at 5 days. These data suggest that the proteins of peaks B, C and D were transported primarily by slow axoplasmic flow. The radioactive protein peaks A and B from the second phase of the transport were excluded from a Sephadex G-200 column, pointing to their high molecular weights (13,000–200,000). Peak B. which had the highest specific radioactivity (c.p.m./mg protein) at 5 days, contained a significant level of tyrosine hydroxylase, an important component of dopaminergic neurons.