The human locus coeruleus 3-D stereotactic anatomy.

PURPOSE: The main goal of this work was to study the stereotactic anatomy of the human locus coeruleus (LC), important relay of adrenergic and dopaminergic human brainstem (HB) circuitry, to allow its easy localization on MRI and in microsurgical procedures. METHODS: Forty LC were studied from 20 adult HB of both sexes. The melanin pigmentation of its cells was used to identify and localize them and so to define the 2-D and 3-D LC contours. These HB were cut on a cryomicrotome with 3-D referenciation. The slices were coloured with haematoxyline-eosin. On the slices, digitized images of the cells were referenced to the midline, the fourth ventricle floor plane and the pontomedullary junction plane with an appropriate computer program. RESULTS: The LC revealed to be a symmetric, thin and elongated nucleus, divergent caudally except in its superior part, with a sub-ependymal location on the superior dorsal lateral pons. The main LC dimensions are: length 12.0-17.0 mm (m 14.5); width 2.5 mm; height 2.0 mm. The 3-D references of the LC center are: 3.2 ± 0.3 mm to the midline; 1.1 ± 0.2 mm to the IV ventricle floor and 18.5 ± 1.5 mm to the ponto-medullary junction. CONCLUSIONS: The human LC is a nucleus thinner and longer than previously described (in average 14.5 mm long and 2-2.5 mm thick), localized 1 mm under the IV ventricle, 3 mm apart from the midline and centered 14-21 mm above de ponto-medullary junction. No correlation was found between LC and pons dimensions, the gender or the age.

Clam dredging effects and subsequent recovery of benthic communities at different depth ranges.

This study aimed to assess the potential effects of clam dredging and the subsequent recovery of the benthic environment. Two experimental areas located at 6 and 18m depth were established in order to analyse whether impacts and recovery of benthic environment are depth-related. Study areas were located within an area closed to dredging and two different plots were established at both depths. One of the plots was subjected to intense clam dredge-fishing, while the other was undisturbed and therefore used as control. Sampling followed a BACI design, with samples for macrobenthic, meiobenthic and sediment particle size analysis being taken by SCUBA divers from both areas before and after fishing stress. For both depths, impacts on the benthic environment were very low resulting in high recovery rates. Nevertheless, at shallower depths communities demonstrated a faster recovery. It was shown that depending on the faunal component used as a bioindicator, different results can be observed. Generally deposit-feeding organisms with scales or chitinous plates and vermiform shape (mainly crustaceans, polychaetes and ophiuroids), without external protection, were the most affected by dredging, while some polychaetes without external protection and with a carnivorous feeding mode seemed to be enhanced by fishing. The low level of perturbations induced by the dredging activities was comparable to the impact of surface waves on the bottom, as experiments were undertaken in wave-dominated environments. The coexistence of storm events during the study period proved to have similar or even more deleterious effects on the benthic environment. It appears that communities from hydrodynamic fishing grounds that are well adapted to natural physical stress are not highly affected by dredging.

Diel variation of the RNA/DNA ratios in Crassostrea angulata (Lamarck) and Ruditapes decussatus (Linnaeus 1758) (Mollusca: Bivalvia).

The aim of this study was to investigate the effect of time of day on RNA/DNA ratios among fed and starved Crassostrea angulata and Ruditapes decussatus juveniles. Sampling to investigate the day and night condition of juveniles was carried out for 48 h. A highly sensitive method for nucleic acid quantification was applied to bivalves. The results suggest that there is some variation in nucleic acid quantities with the time of the day. For the two species analysed, the RNA/DNA ratio was particularly high during the night and was higher in the fed animals. The results seem to indicate that there is some endogenous rhythm in the production of RNA. If there are diel changes in RNA/DNA ratios, it follows that average RNA/DNA ratios can be unrepresentative if there is any day or night bias in sampling.