Structural organization of collagen in Metridium senile

The structure and distribution of collagen fibres in Metridium senile mesoglea has been investigated using high and small angle X-ray diffraction techniques on conventional and synchrotron sources. The mesoglea collagen axial spacing appears very close to that of rat tail tendon, which is at variance with the values previously obtained from electron microscopic observations. The different intensity distribution of the small angle X-ray diffraction maxima recorded for mesoglea and rat tail tendon indicates a different distribution of electron density inside the repeating period. Furthermore the absence of the first order, the weak second order and the strong third and sixth orders in the patterns of wet and dry mesogleal collagen could explain that only a periodicity of 20–22 nm corresponding to one-third of the true axial period observed in the electron micrographs. The analysis of the reflections at 0.29 and 1.1–1.4 nm characteristics of the collagen molecular structure have been used to determine the distribution and orientation of the collagen fibres in unstretched and stretched samples     

Chiral separation of unmodified α-hydroxy acids by ligand exchange HPLC using chiral copper(II) complexes of (S)-phenylalaninamide as additives to the eluent

Copper(II) complexes of (S)-phenylalaninamide have been successfully used for the direct enantiomeric separation of unmodified (R,S)-α-hydroxy acids in reversed phase high-performance liquid chromatography (RP-HPLC). The effect of various parameters (pH, eluent polarity, selector concentration) on enantioselectivity is discussed. Evidence is provided that a mechanism of ligand exchange is actually occurring during the chromatographic separation. The method is very convenient and easy to use, and the chiral selector is commercially available and can be recovered at the end of the analysis. A conventional achiral RP-ODS-2 column is used and no pretreatment of the samples is required. This method allows the accurate determination of the enantiomeric excess of α-hydroxy acids in synthetic and biological samples. © 1995 Wiley-Liss, Inc.     

Monitoring urinary excretion of 5-hydroxymethyluracil for assessment of oxidative DNA damage and repair

Urinary excretion of oxidized nucleobases and nucleosides has been used as a biomarker of oxidative DNA damage and repair. Most studies have focused on the measurements of 8-oxo-7,8-dihydro-2'-deoxyguanosine; however, the urinary levels of other DNA modifications may represent useful indicators of oxidative stress. We developed a method for the determination of 5-hydroxymethyluraciI (5-HMUra), consisting of the separation of the modified base in urine by HPLC and quantification by GC/MS in the selective ion monitoring mode. This experimental approach was subsequently validated in human samples, with the effect of storage and the inter- and intra-individual variations in 5-HMUra excretion being evaluated. Results showed that 5-HMUra is stable in samples frozen at-80 °C for at least 4 months. Inter-individual variations in 5-HMUra excretion were observed when the results were expressed either as nmoles excreted per kg per day (1.2-2.4) or corrected by creatinine values (7.2-12.2 nmoles 5-HMUra per mmoles creatinine). Intra-individual variability was low, varying slightly at different time collections for several individuals. Differences in the excretion of 5-HMUra in urine collected at three different 8-h intervals during the day were not significant and, in particular, the levels of 5-HMUra calculated from the overnight or the 24-h samples were highly correlated. These results indicate that monitoring urinary levels of 5-HMUra could be a suitable indicator of oxidative damage in human studies.     

An analysis of Xq deletions

We characterized by fluorescence in situ hybridization and Southern blotting 14 partial Xq monosomies, 11 due to terminal deletions and 3 secondary to X/autosome translocations. Three cases were mosaics with a XO cell line. In view of the possible role played by telomeres in chromosome segregation, we hypothesize a relationship between the loss of telomeric sequences in terminal deletions and the presence of 45,X cells. A correlation between phenotype and extent of deletion revealed that there is no correspondence between the size of the deletion and impairment of gonadal function. Turner stigmata are absent in patients without an XO cell line, when the breakpoint is distal to Xg24. A low birthweight is present whenever the breakpoint is at q22 or more proximal.     

The unstable region of Streptomyces ambofaciens includes 210 kb terminal inverted repeats flanking the extremities of the linear chromosomal DNA

Physical maps of the chromosomes of three strains of Streptomyces ambofaciens were constructed by ordering Ase I fragments generated from the genomic DNA as a single linear chromosome of about 8 Mb. The physical maps of the three strains were very similar. For strain DSM40697, a Dra I map was obtained by positioning the Dra I sites relative to the Ase I map. Eighteen genetic markers as well as the deletable and amplifiable region were assigned to the Ase I and Dra I fragments in this strain. The resulting genetic map resembled that of Streptomyces coelicolor A3(2). The twoterminal Ase I fragments exhibited retarded pulsed-field gel electrophoresis mobility, demonstrating that proteins are covalently bound at this position. A restriction map of this region was made using four additional endonucleases. Repeated sequences present at both ends of the chromosome were mapped as long terminal inverted repeats stretching over 210 kb. This corresponds to the longest terminal inverted repeats so far characterized. The deletable region of S. ambofaciens was localized at the chromosomal extremities.     

Proactive Control Strategies for Overt and Covert Go/NoGo Tasks: An Electrical Neuroimaging Study

Proactive and reactive inhibition are generally intended as mechanisms allowing the withholding or suppression of overt movements. Nonetheless, inhibition could also play a pivotal role during covert actions (i.e., potential motor acts not overtly performed, despite the activation of the motor system), such as Motor Imagery (MI). In a previous EEG study, we analyzed cerebral activities reactively triggered during two cued Go/NoGo tasks, requiring execution or withholding of overt or covert imagined actions, respectively. This study revealed activation of pre-supplementary motor area (pre-SMA) and right inferior frontal gyrus (rIFG), key nodes of the network underpinning reactive inhibition of overt responses in NoGo trials, also during MI enactment, enabling the covert nature of the imagined motor response. Taking into account possible proactive engagement of inhibitory mechanisms by cue signals, for an exhaustive interpretation of these previous findings in the present study we analyzed EEG activities elicited during the preparatory phase of our cued overt and covert Go/NoGo tasks. Our results demonstrate a substantial overlap of cerebral areas activated during proactive recruitment and subsequent reactive implementation of motor inhibition in both overt and covert actions; also, different involvement of pre-SMA and rIFG emerged, in accord with the intended type (covert or overt) of incoming motor responses. During preparation of the overt Go/NoGo task, the cue is encoded in a pragmatic mode, as it primes the possible overt motor response programs in motor and premotor cortex and, through preactivation of a pre-SMA-related decisional mechanism, it triggers a parallel preparation for successful response selection and/or inhibition during the response phase. Conversely, the preparatory strategy for the covert Go/NoGo task is centered on priming of an inhibitory mechanism in rIFG, tuned to the instructed covert modality of motor performance and instantiated during subsequent MI, which allows the imagined response to remain a potential motor act.     

The neolignans of Licaria canella

The trunk wood of Licaria canella contains, besides dillapiol and elemicin, the neolignans canellin-A, -B and -C, for which the respective structures of 1-allyl-4,8-dihydroxy-3,5-dimethoxy-7-methyl-6-piperonylbicyclo-[3,2,1]octane; 3a-allyl-4,5-dimethoxy-3-methyl-2-piperonyl-2,3,3a,6,7,7a-hexahydro-6-oxobenzofuran and 1-allyl-4,8-dihydroxy-5-methoxy-7-methyl-6-piperonyl-3-oxobicyclo-[3,2,1] octane are proposed.