The modalities of the sexual cycle of Octopus vulgaris in the southern Moroccan Atlantic (Tantan, Boujdour)

The reproduction of Octopus vulgaris between Tan Tan and Boujdour is studied. The samples used are sorted monthly from commercial catches of coastal trawlers operating in this area from December 2001 to May 2003. The study shows that sexual maturity is in advance for males than for females. Two spawning periods are made out by the follow-up of the RGS: a spring period from March to July, and an autumnal period, which is less intense, between September and October. The division of spermatogonia and spermatocytes reaches its maximal intensity in July and December, whereas the spermiogenesis is active until the time of mating. The vitellogenesis starts in mid-December and extends until the following spawning period. This reveals a later gonadic development for females than for males; approximately seven months for females and three months for males.     

Unusual complexation of Cu(I) by pyrimidine/pyridine-pyrazole derived ligands exploiting the molecular function of 2-mercapto-4,6-dimethylpyrimidine - Syntheses, crystal structures and electrochemistry

Reaction of 2 equiv. amount of copper(II) chloride dihydrate with 2 equiv. of methyl-5-methyl-1-(4,6-dimethyl-2-pyrimidyl)pyrazole-3-carboxylate (DpymPzC) in presence of 1 equiv. of 2-mercapto-4,6-dimethylpyrimidine (DpymtH) at pH ∼ 6 afforded the tricoordinated copper(I) complex [Cu(DpymPzC)Cl] (1). The same reaction with copper(II) perchlorate hexahydrate, as the metal salt under the same equivalent ratio at pH ∼ 6 formed the tetracoordinated copper(I) complex [Cu(DpymPzC)₂]ClO₄ (2). In both the cases, the role of DpymtH is nothing but only to reduce the copper(II) salt in situ finally forming the copper(I) complex. On the other hand, the direct reaction between the copper(I) thiocyanate and DpymPzC in 2:2 equiv. ratio produced a tricoordinated copper(I) complex [Cu(DpymPzC)SCN] (3). In a similar reaction of 2 equiv. amount of copper(II) chloride dihydrate with 2 equiv. amount of ethyl-5-methyl-1-(2-pyridyl)pyrazole-3-carboxylate (PyPzC) in presence of 1 equiv. of DpymtH at pH ∼ 6, an intense red coloured microcrystalline compound (4) was obtained. In contrast, 1 equiv. of PyPzC and 2 equiv. of DpymtH on reaction with 1 equiv. of copper(II) chloride dihydrate at pH ∼ 6 produced a novel tetranuclear mixed coordinated [Cu₄(DpymtH)₄Cl₄] complex (5). Here DpymtH plays dual role - a reducing agent for the copper(II) salt followed by a chelating ligand towards copper(I) so formed in situ. Among the above species, 1, 2 and 5 are crystallographically characterized. In 1, the central copper atom is in distorted triangular planar geometry with N₂Cl chromophore whereas in 2, the same is in distorted tetrahedral geometry with N₄ chromophore. Notably, the extent of distortion from the ideal geometry is more in 2. In 5, which is in chair conformation, out of four copper atoms, two being in S₂Cl chromophore are tricoordinated and the remaining two are tetracoordinated with NS₂Cl chromophore. The metal centers are bridged through DpymtH in its ‘thione’ form. Interestingly, the chelation (in part) results in formation of the highly stable four-membered two chelate rings around the two tetracoordinated copper atoms in 5. The two copper centers along the long arm of the chair are separated through a distance of 5.190 Å while those in the short arm are at a length of 3.629 Å. The electronic, IR spectra and electrochemistry of the complexes 1, 2 and 5 have also been investigated.     

Prostaglandin E2 is crucial in the response of podocytes to fluid flow shear stress

Podocytes play a key role in maintaining and modulating the filtration barrier of the glomerulus. Because of their location, podocytes are exposed to mechanical strain in the form of fluid flow shear stress (FFSS). Several human diseases are characterized by glomerular hyperfiltration, such as diabetes mellitus and hypertension. The response of podocytes to FFSS at physiological or pathological levels is not known. We exposed cultured podocytes to FFSS, and studied changes in actin cytoskeleton, prostaglandin E₂ (PGE₂) production and expression of cyclooxygenase-1 and–2 (COX-1, COX-2). FFSS caused a reduction in transversal F-actin stress filaments and the appearance of cortical actin network in the early recovery period. Cells exhibited a pattern similar to control state by 24 h following FFSS without significant loss of podocytes or apoptosis. FFSS caused increased levels of PGE₂ as early as 30 min after onset of shear stress, levels that increased over time. PGE₂ production by podocytes at post-2 h and post-24 h was also significantly increased compared to control cells (p < 0.039 and 0.012, respectively). Intracellular PGE₂ synthesis and expression of COX-2 was increased at post-2 h following FFSS. The expression of COX-1 mRNA was unchanged. We conclude that podocytes are sensitive and responsive to FFSS, exhibiting morphological and physiological changes. We believe that PGE₂ plays an important role in mechanoperception in podocytes.     

Distribution et écologie des associations d’ostracodes récents de l’estuaire de Tahadart (Maroc Nord-Occidental)

Forty-five ostracod species were identified for the first time in the Tahadart estuary (NW Morocco). They can be grouped into five different ecological assemblages, which characterise four estuarine ecozones. A first ecozone occurs in temporary waters located between the tidal channels of the inner estuary and it is characterised by ostracod species typical of fresh to brackish waters. In the main estuary area, the ostracod fauna is dominated by clearly euryhaline species that account for nearly 70% of the entire fauna. The relative abundance of the different assemblages allows us to subdivide the estuarine environment along a longitudinal profile into mouth, outer and inner estuary. The estuary's mouth displays the highest values of marine euhaline, phytal and periphytal as well as ubiquitous species and the lowest values of very euryhaline species; the latter are the only species present in the inner estuary. The outer estuary exhibits intermediate percentages of the different ecological assemblages. This distribution, characterized by the absence of limnic species, points to the influence of marine waters in an open estuary with a low fresh water input. In the estuary's mouth, as well as in the outer estuary, where the slikke and schorre are well developed, the distance to the emersion line is underlined by the lower occurrence of marine and ubiquitous species and the higher occurrence of the very euryhaline ones. The Tahadart estuary displays a moderate to high ostracod diversity with distinct differences among the ecological zones. The stress of this environment is highlighted by the low diversity characteristics of extreme environments, alike in the inner estuary and in some areas located far from the emersion level. The relative position with respect to the emersion line, as well as the presence of gross detritic sediments and vegetation, appear to be of importance for the good development of the ostracods.     

Temporal population variability in local forest communities has mixed effects on tree species richness across a latitudinal gradient

Among the local processes that determine species diversity in ecological communities, fluctuation‐dependent mechanisms that are mediated by temporal variability in the abundances of species populations have received significant attention. Higher temporal variability in the abundances of species populations can increase the strength of temporal niche partitioning but can also increase the risk of species extinctions, such that the net effect on species coexistence is not clear. We quantified this temporal population variability for tree species in 21 large forest plots and found much greater variability for higher latitude plots with fewer tree species. A fitted mechanistic model showed that among the forest plots, the net effect of temporal population variability on tree species coexistence was usually negative, but sometimes positive or negligible. Therefore, our results suggest that temporal variability in the abundances of species populations has no clear negative or positive contribution to the latitudinal gradient in tree species richness.     

Evaluation des dégâts par les vers blancs (Coleoptera : Scarabaeoidea) dans les parcelles de régéneration du chêne-liège (Quercus suber L.) en forêt de la Mamora (Maroc) et recherche de médiateurs chimiques pour une lutte biologique

Résumé

Au cours des dernières décennies, les essais de régénération du chêne-liège en forêt de la Mamora se sont heurtés à des attaques massives de vers blancs sur les racines des jeunes plants, avec un taux de réussite des plantations ne dépassant guère 12% dans la majorité des parcelles de régénération. La biologie de Sphodroxia maroccana Ley (Coleoptera : Melolonthidae), le ravageur principal, a été en partie élucidée, avec encore des lacunes concernant la période exacte ?émergence des mâles par rapport aux femelles, la longévité des imagos et la sex-ratio. La sècheresse esti vale est parmi les autres causes de dépérissement des jeunes plants. Lors de la première année suivant la plantation dans des parcelles expérimentales, la mortalité cumulée due aux attaques larvaires et à la sècheresse a varié entre 41% et 68% selon les blocs considérés dans les parcelles. La mortalité liée aux attaques des larves de S. maroccana était comprise entre 24 et 43%, avec une distribution en taches des dégâts, plus ou moins importantes selon la densité initiale des plants. L’isolement par micro-extraction en phase solide des effluves femelles de S. maroccana a permis ?identifier le résorcinol (1,3-benzènediol) comme composé phéromonal présumé. La fonction de cette molécule comme phéromone reste toutefois à démontrer.     

Detection of BrdU-label retaining cells in the lacrimal gland: implications for tissue repair

The purpose of the present study was to determine if the lacrimal gland contains 5-bromo-2′-deoxyuridine (BrdU)-label retaining cells and if they are involved in tissue repair. Animals were pulsed daily with BrdU injections for 7 consecutive days. After a chase period of 2, 4, or 12 weeks, the animals were sacrificed and the lacrimal glands were removed and processed for BrdU immunostaining. In another series of experiments, the lacrimal glands of 12-week chased animals were either left untreated or were injected with interleukin 1 (IL-1) to induce injury. Two and half days post-injection, the lacrimal glands were removed and processed for BrdU immunostaining. After 2 and 4 weeks of chase period, a substantial number of lacrimal gland cells were BrdU⁺ (11.98 ± 1.84 and 7.95 ± 1.83 BrdU⁺ cells/mm², respectively). After 12 weeks of chase, there was a 97% decline in the number of BrdU⁺ cells (0.38 ± 0.06 BrdU⁺ cells/mm²), suggesting that these BrdU-label retaining cells may represent slow-cycling adult stem/progenitor cells. In support of this hypothesis, the number of BrdU labeled cells increased over 7-fold during repair of the lacrimal gland (control: 0.41 ± 0.09 BrdU⁺ cells/mm²; injured: 2.91 ± 0.62 BrdU⁺ cells/mm²). Furthermore, during repair, among BrdU⁺ cells 58.2 ± 3.6 % were acinar cells, 26.4 ± 4.1% were myoepithelial cells, 0.4 ± 0.4% were ductal cells and 15.0 ± 3.0% were stromal cells. We conclude that the murine lacrimal gland contains BrdU-label retaining cells that are mobilized following injury to generate acinar, myoepithelial and ductal cells.     

Relationship between plasmid loss and gene expression in Bacillus thuringiensis

The large genome of Bacillus thuringiensis was shortened by provoking plasmid loss, and the effect of such loss on the expression of both chromosomal and plasmid-harboured genes was studied. It was evidenced that the genomic material shortening of B. thuringiensis allows for the improvement of the expression of some of the constructive genes. Indeed, it was shown that curing was an efficient tool to obtain mutant strains with better expression of chromosomal genes. In fact, totally cured strains, HD1Cry-B and BNS3Cry, showed higher chitinolytic and/or proteolytic activities than the corresponding wild and/or partially cured ones. Although total curing is drastic for plasmid-harboured gene expression, the authors obtained partially cured strains, Cur255 and CurHD1, with a doubled level of delta-endotoxin production, and a 1.5-fold improvement of the bacteriocin-specific activity, respectively. In addition, the latter strains showed better relative proteolytic activities.