A revision of coregonine fish distribution and abundance in eastern James-Hudson Bay

Synopsis Recent sampling programs conducted in the estuaries of the Eastmain and La Grande rivers (James Bay) and the Great Whale, Little Whale, Innuksuac and Povungnituk rivers (Hudson Bay) revealed patterns of coregonine fish distribution that differ from previous observations. The relative abundance of cisco, Coregonus artedii, and lake whitefish, C. clupeaformis, varied among rivers but did not reveal a latitudinal cline. Previous sampling programs underestimated the abundance of cisco in the Little Whale River. In addition, cisco was the third most abundant species captured in the Povungnituk River, situated 200 km to the north of the previously proposed northern limit at Innuksuac River. As such, the low abundances of cisco in the Great Whale and Innuksuac rivers cannot be attributed to a physiological inability to cope with a reduced growing season. Immature cisco were almost totally absent from the estuaries of the Hudson Bay rivers following spring breakup whereas immature lake whitefish made up 100% of the catch in the Innuksuac River at the same time of year. Species-specific migration patterns in Hudson Bay that differ from those observed in James Bay and the existence of unique juvenile overwintering rivers are 2 hypotheses proposed to explain the discontinuous age-class distribution of cisco and lake whitefish observed in Hudson Bay.Contribution to the program of GIROQ (Groupe Interuniversitaire de Recherche Océanographique du Québec).     

Fetal nicotine exposure produces postnatal up-regulation of adenylate cyclase activity in peripheral tissues

Gestational exposure to nicotine has been shown to affect development of noradrenergic activity in both the central and peripheral nervous systems. In the current study, pregnant rats received nicotine infusions of 6 mg/kg/day throughout gestation, administered by osmotic minipump implants. After birth, offspring of the nicotine-infused dams exhibited marked increases in basal adenylate cyclase activity in membranes prepared from kidney and heart, as well as supersensitivity to stimulation by either a beta-adrenergic agonist, isoproterenol, or by forskolin. The altered responses were not accompanied by up-regulation of beta-adrenergic receptors: in fact, [125I]pindolol binding was significantly decreased in the nicotine group. These results indicate that fetal nicotine exposure affects enzymes involved in membrane receptor signal transduction, leading to altered responsiveness independently of changes at the receptor level.     

Regulation of beta-adrenergic receptor-mediated processes in fetal rat lung: selective desensitization caused by chronic terbutaline exposure

Fetal lung beta-receptors become effectively coupled to lung fluid reabsorption and enzymes involved in surfactant synthesis on the day before birth, a period when circulating catecholamine levels are high. Accordingly, we examined the effects of repeated maternal terbutaline exposure on beta-receptor binding capabilities and beta-receptor-mediated processes in the fetal rat lung. Administration of terbutaline to pregnant rats on gestational day 17-20 produced significant reductions in beta-receptor binding to membrane preparations. Similarly, beta-receptor-mediated stimulation of adenylate cyclase activity and ornithine decarboxylase activity showed marked desensitization in the terbutaline-exposed fetuses. However, the linkage of beta-receptors to lung fluid reabsorption and phosphatidic acid phosphatase, an enzyme involved in surfactant synthesis, did not desensitize with chronic terbutaline pretreatment; both of these processes displayed the normal onset of responsiveness on gestational day 21 in the treated animals, as well as a normal magnitude of response. Hence, beta-receptor-mediated events in the developing lung may be differentially regulated during exposure to agonists, allowing the selective expression or depression of function when circulating catecholamine levels are high.     

Redescription de Proteocephalus paraguayensis (Rudin, 1917) (Cestoda: Proteocephalidae) parasite de Hydrodynastes gigas (Dum., Bibr. & Dum., 1854) du Paraguay

Redescripción de Proteocephalus paraguayensis (Rudin, 1917) (Cestoda: Proteocephalidae), parásito de Hydrodynastes gigas (Dum., Bibr. & Dum., 1854) de Paraguay. Se describe esta especie notable, considerada por Freze (1965) como species inquirenda. Si comparamos esta especie con otras especies de Proteocephalidea, veremos que ella presenta caracteres anatomo-morfológicos propios. Esta especie se caracteriza por: vitelógenos de posición dorsal, adosados a la musculatura interna longitudinal, desbordando en parte sobre el córtex y la médula; formación particular del útero; posición cortical del tronco uterino y medular de los divertículos uterinos; esfínter vaginal proximal; cirro muy alargado; glándula de Mehlis muy desarrollada. Consideramos P. paraguayensis como una especie válida y presumimos que el huesped-tipo es Hydrodynastes gigas (Dum., Bibr. & Dum., 1854). A pesar de las características que posee P. paraguayensis, pensamos que no es oportuno clasificar esta especie en un nuevo género monotípico. Proteocephalus paraguayensis, considered by Freze (1965) as a species inquirenda, is redescribed and figured. When compared with other members of the Proteocephalidea, the species shows the following morpho-anatomical characters: the vitelline follicles in a dorsal position, attached to the internal longitudinal musculature and extending into both the cortex and medulla; a characteristic formation of the uterus; the uterine stem in a cortical position and uterine branches in a medullary position; a proximal vaginal sphincter; a very elongate cirrus; and very large Mehlis' glands. The specific status of Proteocephalus paraguayensis is confirmed. Our specimens were taken from Hydrodynastes gigas (the host according to Rudin was Coluber sp.). Even though the species differs significantly from other proteocephalideans, its systematic and phylogenetic position is not yet clearly demonstrated, and it is decided to refrain from attributing it to a new genus.     

Modulation of Expression and Assembly of Vinculin duringin VitroFibrillar Collagen-Induced Angiogenesis and Its Reversal

A model of collagen-inducedin vitroangiogenesis was used to investigate the modulation of expression and assembly of focal adhesion plaque-associated proteins during the process of differentiation. Human umbilical vein endothelial cells (HUVEC), first attached on an adhesive substratum (gelatin-, fibronectin-, or laminin-coated dish) or adherent collagen gel and then covered by an overlaying collagen gel, organized within 3–4 days in tube-like structures (TLS). Removing the overlaying collagen gel from fully differentiated HUVEC induced a reversion of the process and HUVEC returned to a monolayer pattern. Modulations of focal adhesion-associated proteins occurring in HUVEC during thein vitrodifferentiation process and its reversal were investigated by Western blot analysis. A significant decrease of expression of vinculin, the integrin α₂subunit, talin, α-actinin, and actin was observed in TLS whereas the amount of FVIII-related antigen did not vary as compared to control monolayer cultures. During reversal, all the reduced proteins were markedly reexpressed. Human skin fibroblasts (HSF), submitted to the same experimental conditions, did not form TLS. Most of the focal adhesion proteins in HSF were similarly modulated by an overlaying collagen gel with the exception of vinculin, which was not modified. This particular protein was therefore more thoroughly investigated. In a nondifferentiated monolayer of HUVEC, a significant proportion of vinculin was organized into a detergent-resistant juxtamembranous structure (focal adhesion plaque) which disassembled early in TLS formation and reassembled during the reversal of the process. The reduction of vinculin during TLS formation was preceded by a downregulation of its mRNA while this mRNA was upregulated during reversal of the morphotype. These results suggest that the modulations of the cytoskeletal and focal adhesion proteins and more specifically of vinculin coupled to its subcellular redistribution are critical and early events in the cascade of mechanochemical signaling duringin vitroangiogenesis induced by fibrillar collagen.     

Plasma and erythrocyte manganese concentrations

This study was carried out to assess manganese (Mn) status after an acute episode of myocardial infarction. Plasma and erythrocyte Mn concentrations were measured from admission to hospital to day 15 postadmission in 21 patients suffering from acute myocardial infarction and in three control groups. The determination of Mn in these biological fluids was performed by electrothermal atomic absorption spectrometry. Plasma Mn was higher (p<0.01) and erythrocyte Mn was similar in the acute myocardial infarction group compared to healthy age-matched control group. Plasma and erythrocyte Mn remained unchanged during the 2 wk after acute myocardial infarction and were not correlated to enzyme activities. A decrease of erythrocyte Mn with age, expressed in nmol/L, was noted (p<0.02). These results suggest that plasma and erythrocyte Mn do not provide an indication of myocardial damage. Nonetheless, Mn status in elderly merits further attention.     

A reassessment of the intervention of calmodulin in the regulation of stomatal movement

Commelina cammunis L., a monocotyledonous plant whose stomata are highly sensitive to calcium ions, was used to study calmodulin (CaM) involvement in stomatal movements. CaM was detected and quantified in guard cell and mesophyll cell protoplasts by western blot and by ⁴⁵Ca²⁺-overlays. CaM was found to be 3- to 7-fold more abundant on a per protein basis in guard cell than in mesophyll cell protoplasts. Numerous guard cell proteins that bind CaM in a Ca²⁺-dependent manner were detected by gold-labelled CaM overlays. Using bioassays with epidermal strips, different CaM-antagonists were found to induce a net stimulation of stomatal opening in darkness or under illumination (trifluoperazine > compound 48/80 ∼ fluphenazine > W7 > W5). As CaM is frequently involved in the regulation of phosphorylation processes, the effects of different inhibitors of protein kinases on stomatal movements were studied. In red plus blue light, a promotion of the stomatal aperture was observed in the nanomolar range with K252a and KT5926 and in the micromolar range with KT5720 ≫ ML7 ∼ ML9 ≫ H7 > KN62. Only the inhibitors with a high specificity for Ca²⁺-CaM dependent protein kinases (K252a, KT5926, ML7, ML9) triggered a stomatal opening in darkness and increased stomatal aperture in red plus blue light. Taken together, these data strongly suggest that a Ca²⁺- or a Ca²⁺-CaM-dependent protein kinase plays a central role in the calcium transduction pathway leading to the maintaining of stomatal closure.