Search for rhythmicity during hibernation in the European hamster

Temporal patterns of hibernation were studied by continuous monitoring of body temperature by radiotelemetry over 6 months in European hamsters, Cricetus cricetus, at constant temperature and photoperiod. Entrances into hibernation occurred mostly at the end of the night (0000–0800 hours), while arousals were randomly distributed between day and night. This is at variance with a control of bout duration by a clock with a period of 24 h. Consequently, the timing of entrances implies a phase-resetting of the circadian clock on each arousal. Persistence of circadian rhythmicity with a period different from 24 h during deep hibernation was investigated examining whether the durations of torpor bouts were integer multiples of a constant period. A non-parametric version of the classical contingency test of periodicity was developed for this purpose. Periods ranging from 21 to 29 h were tested. Nine animals out of ten showed at least one significant period in this range (P<0.01), either below 24 h (21.8±0.5 h, n=4) or above (27.3±0.5 h, n=7). However, we have found a theoretical model of bout durations for which the contingency test of periodicity sometimes gives false significant results. This indicates that the power of the test is weak. With this reservation our results suggest that a circadian oscillator controls the duration of a bout of hibernation, which would occur after an integer, but variable and possibly temperature-dependent number of cycles.Abbreviations _b a contingency test (see Appendix) - SCN suprachiasmatic nuclei - period - T _b body temperature     

First record of Emetha audouini, a cymothoid isopod parasite, from cultured sea bass Dicentrarchus labrax in Greece

For the first time, Emetha audouini (Milne Edwards, 1840), a cymothoid isopod, is reported parasitising cage cultured sea bass Dicentrarchus labrax L., 1758 in Greece. The specimens observed are larvae (Pulli II). They were found in great numbers in the buccal and branchial cavity of young (3.5 m.o. old) sea bass, in an intensive cage farm facility. This parasite is certainly transferred to sea bass from wild populations of Sparidae or Centracanthidae. Serious lesions were visible and typical of a crustacean infection, with extensive and deep skin damage in the head area. The cumulative mortality, over a 2 wk period, was 10.75%. The parasitic problem was successfully dealt with by optimization of management practices rather than use of costly and dangerous chemotherapeutants.     

Metazoan parasite species in cultured mussel Mytilus galloprovincialis in the Thermaikos Gulf (North Aegean Sea, Greece)

This is the first study on parasites of cultured Mytilus galloprovincialis L. in Greek waters, and is based on samples collected every 2 to 3 mo between September 2000 and November 2001 at 3 stations in the Thermaikos Gulf. Each sample comprised 40 mussels. We found 4 metazoan parasite species: hydroid Eugymnanthea inquilina, gill turbellarian Urastoma cyprinae, trematode Proctoces maculatus and gut copepod Mytilicola intestinalis. Of 840 mussels examined, 406 (48.3%) mussels were harbouring hydroids of E. inquilina, 278 (33.1%) were infested with U. cyprinae, 94 (11.2%) were infested with M. intestinalis, and only 7 (0.8%) were infested with P. maculatus. The prevalence and intensity of these parasites were related to temperature and pollution. Mussels infested with these parasites had significantly lower condition indices than non-infested mussels; larger mussels were more often infested than smaller ones.     

13C Nuclear magnetic relaxation study of segmental dynamics of hyaluronan in aqueous solutions

(13)C spin-lattice relaxation times (T(1)) and nuclear Overhauser enhancements (NOE) were measured as a function of temperature and magnetic field strength for the hetero-polysaccharide hyaluronan in water solutions. The relaxation data of the endocyclic ring carbons were successfully interpreted in terms of chain segmental motions by using the bimodal time-correlation function of Dejean de la Batie, Laupretre and Monnerie. On the basis of the calculated correlation times for segmental motion and amplitudes of librational motions of the C-H vectors at the various carbon sites of the HA repeating unit, we concluded that intramolecular hydrogen bonding of the secondary structure of HA plays a major role in the conformational flexibility of this carbohydrate molecule. The internal rotation of the free hydroxymethyl groups about the exocyclic C-5-C-6 bonds superimposed on segmental motion has been described as a diffusion process of restricted amplitude. The rate and amplitude of the internal rotation indicate that the hydroxymethyl groups are not involved in intramolecular hydrogen bonding. Finally, the motional parameters describing the local dynamics of the HA chain were correlated with the secondary structure of HA in aqueous solutions.     

Electron microscopic study of yeast RNA polymerase A: Analysis of single molecular images

The structural features of the yeast DNA-dependent RNA polymerase A (I) were examined by Scanning Transmission Electron Microscopy. The enzyme was adsorbed in its monomeric form and negatively stained prior to digital image acquisition at low dose. The signal to noise ratio of single particle images was improved through averaging of a large number of previously aligned and partitioned images. Six classes of images were obtained reproducibly which corresponded to different projections of the enzyme. The enzyme structure was characterized by its elongated shape of 15.5 by 10.5 nm and by the presence of two curved arms which defined a longitudinal cleft. By analogy with theEscherichia coli enzyme, these arms could correspond to the two large subunits A135 and A190.     

Proton spin-lattice relaxation-rates and nuclear Overhauser enhancement,in relation to the stereochemistry of β-d-mannopyranose 1,2-orthoacetates

Data are reported on spin-lattice relaxation-rates and nuclear Overhauser enhancement of protons of exo and endo diastereoisomers of 1,2-O-(1-methoxyethylidene) and 1,2-O-(1-benzyloxyethylidene) derivatives of 3,4,6-tri-O-acetyl-β-d-mannopyranose, and of some specifically deuterated analogs of these derivatives. The results verified assignments of the orientation at the quaternary carbon atom of the acetal ring, and yielded information about the orientations favored by the exocyclic C-methyl and benzyloxy substituents.     

High-field, C-N.M.R. spectroscopy of β-d-glucans, amylopectin, and glycogen

¹³C-N.m.r. spectra of several d-glucans, recorded at 100 MHz, have afforded information about structural detail not previously accessible at lower frequencies. Spectra of (1→4)- and (1→3)-linked β-d-glucans of oats, barley, and lichenan of Iceland moss demonstrate the presence, in each, of three, non-equivalent, 4-O-substituted residues, that the ratio of these to 3-O-substituted residues averages 2.4–2.5, and hence that the patterns of repeating sequences in the three polymers are essentially the same. A comparison of wheat amylopectin with a minor, amylopectin-like fraction of wheat starch indicates that they are strictly analogous in basic structure, and differ only in that the average length of branches in the minor fraction is 20–25% shorter. By combining the advantages of high-field operation with the use of dimethyl sulfoxide as solvent, a large number of distinctive resonances have been observed, representing end-units, branch-points, and residues adjacent to branch-points. Accordingly, these signals are even more prominent in the spectrum of glycogen, reflecting the higher incidence of branching in this polymer. At 100 MHz, the excellent resolution and sensitivity afforded constitute a potent basis for assessing the purity of polysaccharide preparations, as illustrated with wheat amylose and barley β-d-glucans.     

An examination of 13C- and 1H-chemical shifts in relation to the conformational stabilities of D-glucopyranose disaccharides and polysaccharides

Regioselective preparation of methyl 3,6-di-O-benzyl-β-d-galactopyranoside, methyl 2,4-di-O-benzyl-β-d-galactopyranoside, and methyl 3,4-di-O-benzyl-β-d-galactopyranoside by the stannyl method is described.     

Quantitative study and modelling of the litter decomposition in a European alluvial forest. Is there an influence of overstorey tree species on the decomposition of ivy litter (Hedera helix L.)?

The influence on the decomposition rate of ivy litter (Hedera helix L.) of three ligneous overstorey species (oak, Quercus robur L., white poplar, Populus alba and ash, Fraxinus excelsior L.) that support ivy was studied in an alluvial hardwood forest. The ivy provides an abundant litter at the end of spring. The decomposition of ivy litter and the nutrient release rate were analyzed over four months during the growing season of the canopy trees, the hypothesis being that throughfall could slow down the mass loss rate of ivy depending on the support species. Mathematical models for mass loss and nutrient (P, N, K and Mg) release rates were developed. Mass loss rate and the release rate of magnesium, nitrogen and phosphorus show significant differences depending on species whereas no influence of species was observed on the release rate of potassium. The results illustrate the significant effect of oak compared to ash and poplar in slowing down mass loss rate and nitrogen, phosphorus and magnesium release rates. The mass loss rate over time under the three species followed the proposed exponential model, whereas the release rates of phosphorus and magnesium did not follow this model. This model is fitted to the data in two cases out of three for potassium. Magnesium and potassium are released more rapidly when nitrogen accumulates and the phosphorus content does not change significantly. No species × date interaction was observed, except in the case of magnesium. The species effect is interpreted as an effect of composition of throughfalls and presence or absence of inhibitory substances such as phenolic compounds.