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Links between the lunar cycle and the life cycle (migration patterns, locomotor activity, pulses in recruitment) of the European eel (Anguilla anguilla) are well documented. In this study, we hypothesized that the orientation of glass eels at sea is related to the lunar cycle. The European eel hatches in the Sargasso Sea and migrates across the Atlantic Ocean towards Europe. Upon reaching the continental shelf, the larvae metamorphose into glass eels and migrate up the estuaries, where some individuals colonize freshwater habitats. How glass eels navigate pelagic waters is still an open question. We tested the orientation of 203 glass eels in a transparent circular arena that was drifting in situ during the daytime, in the coastal Norwegian North Sea, during different lunar phases. The glass eels swimming at sea oriented towards the azimuth of the moon at new moon, when the moon rose above the horizon and was invisible but not during the other moon phases. These results suggest that glass eels could use the moon position for orientation at sea and that the detection mechanism involved is not visual. We hypothesize a possible detection mechanism based on global-scale lunar disturbances in electrical fields and discuss the implications of lunar-related orientation for the recruitment of glass eels to estuaries. This behaviour could help glass eels to reach the European coasts during their marine migration.

Calanus finmarchicus were reared from eggs to adults at 12°C and 16°C with non‐limiting food in combination with ambient (600 μatm) and high (1100 μatm) pCO2. These conditions are likely to be encountered by the species at the southern margins of its biogeographical range by the end of the century. Dry weight (DW), carbon (C) and nitrogen (N) mass, oil‐sac volume (OSV), fatty acid composition (FA), and oxygen consumption rates (OCR) were measured on newly molted stage CV copepodites and recently molted adult females. By focusing our measurements on these precise events in the life cycle, we were able to obtain a more accurate comparison of growth and respiration across treatments. Copepods raised at 12°C had a significantly greater DW, OSV, and C and N mass than those raised at 16°C High pCO2, independent of temperature, was associated with a further increase in the DW and C content of the copepods. Interactive effects of temperature and pCO2 resulted in a larger OSV at low temperature and high pCO2. Mass‐specific respiration rates were significantly lower at lower temperatures and elevated pCO2 suggesting that the increase in mass (DW, C, and OSV) resulted from reduced metabolic cost. The composition of fatty acids in the copepods varied mainly with temperature. Two fatty acids varied with pCO2: 16:0 tended to decrease with higher pCO2 and 18:3n−3 tended to increase with higher pCO2. These observations suggest that elevated pCO2/lower pH in future oceans may have a beneficial effect on C. finmarchicus. [ABSTRACT FROM AUTHOR]

The copepod Lepeophtheirus salmonis is an obligate ectoparasite of salmonids. Salmon lice are major pests in salmon aquaculture and due to its economic impact Lepeophtheirus salmonis is one of the most well studied species of marine parasite. However, there is limited understanding of how increased concentration of pCO2 associated with ocean acidification will impact host-parasite relationships. We investigated the effects of increased pCO2 on growth and metabolic rates in the planktonic stages, rearing L. salmonis from eggs to 12 days post hatch copepodids under three treatment levels: Control (416 µatm), Mid (747 µatm), and High (942 µatm). The pCO2 treatment had a significant effect on oxygen consumption rate with the High treatment animals exhibiting the greatest respiration. The treatments did not have a significant effect on the other biological endpoints measured (carbon, nitrogen, lipid volume, and fatty acid content). The results indicate that L. salmonis have mechanisms to compensate for increased concentration of pCO2and that populations will be tolerant of projected future ocean acidification scenarios. The work reported here also describes catabolism during the lecithotrophic development of L. salmonis, information that is not currently available to parameterize models of dispersal and viability of the planktonic free-living stages. [ABSTRACT FROM AUTHOR]

As climate trends accelerate, ecosystems will be pushed rapidly into new states, reducing the potential efficacy of conservation strategies based on historical patterns. In the Gulf of Maine, climate-driven changes have restructured the ecosystem rapidly over the past decade. Changes in the Atlantic meridional overturning circulation have altered deepwater dynamics, driving warming rates twice as high as the fastest surface rates. This has had implications for the copepod Calanus finmarchicus, a critical food supply for the endangered North Atlantic right whale (Eubalaena glacialis). The oceanographic changes have driven a deviation in the seasonal foraging patterns of E. glacialis upon which conservation strategies depend, making the whales more vulnerable to ship strikes and gear entanglements. The effects of rapid climate-driven changes on a species at risk undermine current management approaches. [ABSTRACT FROM AUTHOR]

The Subarctic copepod, Calanus finmarchicus, is an ecologically critical foundation species throughout the North Atlantic Ocean. Any change in the abundance and distribution of C. finmarchicus would have profound effects on North Atlantic pelagic ecosystems and the services that they support, particularly on the coastal shelves located at the southern margins of the species' range. We tested the hypothesis that the physiological rates and processes of C. finmarchicus, determining its vital rates, are unaffected by increases in CO2 concentration predicted to occur in the surface waters of the ocean during the next 100 years. We reared C. finmarchicus from eggs to adults at a control (580 µatm, the ambient concentration at the laboratory's seawater intake) and at predicted mid-range (1200 µatm) and high (1900 µatm) pCO2. There was no significant effect of pCO2 on development times, lipid accumulation, feeding rate, or metabolic rate. Small but significant treatment effects were found in body length and mass (in terms of dry, carbon and nitrogen mass), notably a somewhat larger body size at the mid-pCO2 treatment; that is, a putatively beneficial effect. Based on these results, and a review of other studies of Calanus, we conclude that the present parameterizations of vital rates in models of C. finmarchicus population dynamics, used to generate scenarios of abundance and distribution of this species under future conditions, do not require an "ocean acidification effect" adjustment. A review of research on planktonic copepods indicates that, with only a few exceptions, impacts of increased CO2 are small at the levels predicted to occur during the next century. [ABSTRACT FROM AUTHOR]

Heterologous antibodies to gamma-glutamyl transferase (gamma GT), an ectoenzyme associated with the apical surface of many types of epithelial cells involved in secretion and transport, have been used to identify and partially characterize the spectrum of antigens in a series of epithelial tissues that exhibit a range of enzyme activities. In addition to antigens corresponding to the subunits of the active enzyme (mol wt 55K, 30K), antigens of mol wt approximately 85-greater than or equal to 95K have been detected using an antibody raised against the enzyme purified in nonionic detergent. The latter species are shown to share antigenic determinants with and to be structurally related to the enzyme subunits; however, they do not blind significantly to antibodies raised to protease-solubilized gamma GT. Further, they constitute the major antigens in tissues that exhibit relatively low levels of enzyme activity. These polypeptides are apparently larger than a recently characterized biosynthetic precursor of the gamma GT subunits. Although they do not have gamma GT activity themselves and their function is undefined, the possibility that they may represent highly glycosylated polypeptides related either to gamma GT precursors (that persist without processing) or to the large enzyme subunit merits consideration. [ABSTRACT FROM AUTHOR]

A secretory granule fraction has been isolated from rat parotid by discontinuous gradient centrifugation using hyperosmotic sucrose-Ficoll solutions of low ionic strength. The secretion granule fraction comprises 25% of the total tissue alpha-amylase activity and is judged to be of high purity, both morphologically and by its low level of contamination by enzyme activities associated with other organelles. Secretion granules were lysed by capitalizing on their lability in KCl-containing media, and the low density granule membranes were separated from residual organelle and soluble contaminants by flotation in a sucrose gradient. Residual, poorly extractable secretory contaminants of the granule membrane subfraction were selectively removed by a saponin- (10 micrograms/ml) Na2SO4 (0.3 M) wash, apparently with negligible disruption of granule membrane structure. Based on detailed consideration of the extent of contamination by residual mitochondria and incompletely removed secretory polypeptides, it is possible to estimate that approximately 95% of the protein associated with the purified secretion granule membrane is bona fide granule membrane protein. Further analyses indicate that gamma-glutamyltransferase constitutes a marker enzymatic activity shared by granule membranes and the apical domain of the plasma membrane. Sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoretograms of radio-iodinated granule membrane polypeptides are characterized by 20-25 radioactive bands of which 5-6 are suggested to be glycoproteins by virtue of their binding of concanavalin A. The limited polypeptide composition of the secretion granule membrane (in comparison to membranes of other cellular compartments) and the high phospholipid-protein ratio (4.4 mg/mg) may reflect the functional specialization of this storage container for secretory proteins. [ABSTRACT FROM AUTHOR]

Whole humic acid extracts are usually too polydisperse for reliable molecular-weight measurement to be made in the ultracentrifuge by the sedimentation velocity technique. Consequently, the humic acid used in this study was fractionated with respect to molecular weight into fractions of low polydispersity by extensive use of gel-permeation chromatography and other fractionation techniques. The sedimentation and diffusion coefficients of the fractions were determined and molecular-weight values calculated. These values ranged approximately from 2 × 103 to 1.5 × 106, the higher figure not necessarily representing the upper limit for these substances. On the basis of the frictional parameters calculated from the experimental data, it is proposed that the molecule adopts the solution conformation of a randomly coiled polymer in which branching may be significant, particularly at higher molecular weights. [ABSTRACT FROM AUTHOR]

Three common gel-chromatography materials have been calibrated for humic acid, using fractionated samples the molecular weights of which were calculated by combining sedimentation coefficients determined on the ultracentrifuge with diffusion coefficients. The gel materials were found to have the following fractionation ranges for humic acid when tris buffer was used: Sephadex G-100, 2500 to 100000; Bio Gel P-150, below 1000 to 40000; Sepharose 6B, 1500 to 2500000. Borax buffer appeared to extend the range of Sephadex G-100 to lower molecular weights. A brief comparison is made of the retention behaviours of humic acid, proteins, and dextrans on the gel materials. [ABSTRACT FROM AUTHOR]

An abstract of the article "First Report of Laurel Wilt, Caused by Raffaelea lauricola, on Sassafras (Sassafras albidum) in Alabama" by C.A. Bates, S.W. Fraedrich, and T.C. Harrington is presented.

The copepod Lepeophtheirus salmonis is an obligate ectoparasite of salmonids. Salmon lice are major pests in salmon aquaculture and due to its economic impact Lepeophtheirus salmonis is one of the most well studied species of marine parasite. However, there is limited understanding of how increased concentration of p CO 2 associated with ocean acidification will impact host-parasite relationships. We investigated the effects of increased p CO 2 on growth and metabolic rates in the planktonic stages, rearing L. salmonis from eggs to 12 days post hatch copepodids under three treatment levels: Control (416 µatm), Mid (747 µatm), and High (942 µatm). The p CO 2 treatment had a significant effect on oxygen consumption rate with the High treatment animals exhibiting the greatest respiration. The treatments did not have a significant effect on the other biological endpoints measured (carbon, nitrogen, lipid volume, and fatty acid content). The results indicate that L. salmonis have mechanisms to compensate for increased concentration of p CO 2 and that populations will be tolerant of projected future ocean acidification scenarios. The work reported here also describes catabolism during the lecithotrophic development of L. salmonis, information that is not currently available to parameterize models of dispersal and viability of the planktonic free-living stages., Competing Interests: The authors declare there are no competing interests., (©2019 Thompson et al.)

Directed neuronal, astroglial, and oligodendroglial cell migrations comprise a prominent feature of mammalian brain development. Because molecular motor proteins have been implicated in a wide spectrum of processes associated with cell motility, we initiated studies to define the pool of myosins in migrating cerebellar granule neurons and type-1 neocortical astrocytes. Our analyses identified two isoforms of a novel unconventional myosin, which we have cloned, sequenced, and designated myr 8a and 8b (eighth unconventional myosin from rat). Phylogenetic analysis indicates that myr 8 myosins comprise a new class of myosins, which we have designated class XVI. The head domain contains a large N-terminal extension composed of multiple ankyrin repeats, which are implicated in mediating an association with the protein phosphatase 1 (PP1) catalytic subunits 1alpha and 1gamma. The motor domain is followed by a single putative light-chain binding domain. The tail domain of myr 8a is comparatively short with a net positive charge, whereas the tail domain of myr 8b is extended, bears an overall neutral charge, and reveals several stretches of poly-proline residues. Neither the myr 8a nor the myr 8b sequence reveals alpha-helical coiled-coil motifs, suggesting that these myosins exist as monomers. Both immunoblot and Northern blot analyses indicate that myr 8b is the predominant isoform expressed in brain, principally at developmental time periods. The structural features and restricted expression patterns suggest that members of this novel class of unconventional myosins comprise a mechanism to target selectively the protein phosphatase 1 catalytic subunits 1alpha and/or 1gamma in developing brain.

N-Acetylaspartate is a highly specific marker for neurons and is present at high concentrations in the central nervous system. It is not present at detectable levels anywhere else in the body other than brain. Glial cells express a high-affinity transporter for N-acetylaspartate, but the molecular identity of the transporter has not been established. The transport of N-acetylaspartate into glial cells is obligatory for its intracellular hydrolysis, a process intimately involved in myelination. N-Acetylaspartate is a dicarboxylate structurally related to succinate. We investigated in the present study the ability of NaDC3, a Na(+)-coupled high-affinity dicarboxylate transporter, to transport N-acetylaspartate. The cloned rat and human NaDC3s were found to transport N-acetylaspartate in a Na(+)-coupled manner in two different heterologous expression systems. The Michaelis-Menten constant for N-acetylaspartate was approximately 60 microM for rat NaDC3 and approximately 250 microM for human NaDC3. The transport process was electrogenic and the Na(+):N-acetylaspartate stoichiometry was 3:1. The functional expression of NaDC3 in the brain was demonstrated by in situ hybridization and reverse transcription-polymerase chain reaction as well as by isolation of a full-length functional NaDC3 from a rat brain cDNA library. In addition, the expression of a Na(+)-coupled high-affinity dicarboxylate transporter and the interaction of the transporter with N-acetylaspartate were demonstrable in rat primary astrocyte cultures. These studies establish NaDC3 as the transporter responsible for the Na(+)-coupled transport of N-acetylaspartate in the brain. This transporter is likely to be an essential component in the metabolic role of N-acetylaspartate in the process of myelination.

Lasp-1 is a unique LIM and src homology 3 (SH3) domain-containing protein that was initially identified as a 40 kDa cAMP-dependent phosphoprotein in the HCl-secreting gastric parietal cell. Because cAMP is a potent stimulator of parietal cell acid secretion, we have hypothesized that changes in lasp-1 phosphorylation might be involved in the regulation of ion transport-related activities, perhaps by modulating interactions among cytoskeletal and/or vesicle-associated proteins. In this study, we demonstrate that the cAMP-dependent acid secretory agonist, histamine, induces a rapid, sustained rise in parietal cell lasp-1 phosphorylation and this increase in phosphorylation is closely correlated with the acid secretory response. In addition, elevation of intracellular cAMP concentrations appear to induce a partial redistribution of lasp-1 from the cell cortex, where it predominates along with the gamma-isoform of actin in unstimulated cells, to the beta-actin enriched, apically-directed intracellular canalicular region, which is the site of active proton transport in the parietal cell. Additional studies demonstrate that although lasp-1 mRNA and protein are expressed in a wide range of tissues, the expression is specific for certain actin-rich cell types present within these tissues. For example, gastric chief cells, which contain relatively little F-actin and secrete the enzyme, pepsinogen, by regulated exocytosis, do not appear to express lasp-1. Similarly, lasp-1 was not detected in pancreatic acinar cells, which secrete enzymes by similar mechanisms and also contain relatively low levels of F-actin. Lasp-1 also was not detectable in proximal tubules in the kidney, in gastrointestinal smooth muscle, heart or skeletal muscle. In contrast, expression was prominent in the cortical regions of ion-transporting duct cells in the pancreas and in the salivary parotid gland as well as in certain F-actin-rich cells in the distal tubule/collecting duct. Interestingly, moderate levels of expression were also detected in podocytes present in renal glomeruli and in vascular endothelium. In primary cultures of gastric fibroblasts, lasp-1 was present mainly within the tips of lamellipodia and at the leading edges of membrane ruffles. Taken together these results support the hypothesis that the lasp-1 plays an important role in the regulation of dynamic actin-based, cytoskeletal activities. Agonist-dependent changes in lasp-1 phosphorylation may also serve to regulate actin-associated ion transport activities, not only in the parietal cell but also in certain other F-actin-rich secretory epithelial cell types.

Caveolae are 50-100 nm, nonclathrin-coated, flask-shaped plasma membrane microdomains that have been identified in most mammalian cell types, except lymphocytes and neurons. To date, multiple functions have been ascribed to caveolae, including the compartmentalization of lipid and protein components that function in transmembrane signaling events, biosynthetic transport functions, endocytosis, potocytosis, and transcytosis. Caveolin, a 21-24 kDa integral membrane protein, is the principal structural component of caveolae. We have initiated studies to examine the relationship of detergent-insoluble complexes identified in astrocytes to the caveolin-caveolae compartment detected in cells of peripheral tissues. Immunolocalization studies performed in astrocytes reveal caveolin immunoreactivity in regions that correlate well to the distribution of caveolae and caveolin determined in other cell types, and electron microscopic studies reveal multiple clusters of flask-shaped invaginations aligned along the plasma membrane. Immunoblot analyses demonstrate that detergent-insoluble complexes isolated from astrocytes are composed of caveolin-1alpha, an identification verified by Northern blot analyses and by the cloning of a cDNA using reverse transcriptase-PCR amplification from total astrocyte RNA. Using a full-length caveolin-1 probe, Northern blot analyses suggest that the expression of caveolin-1 may be regulated during brain development. Immunoblot analyses of detergent-insoluble complexes isolated from cerebral cortex and cerebellum identify two immunoreactive polypeptides with apparent molecular weight and isoelectric points appropriate for caveolin. The identification of caveolae microdomains and caveolin-1 in astrocytes and brain, as well as the apparent regulation of caveolin-1 expression during brain development, identifies a cell compartment not detected previously in brain.

We developed a panel of monoclonal antibodies to cerebellar astroglial cells and selected for study those that revealed microdomain structures on the cell surface of neocortical and cerebellar astrocytes. One antibody, 15D7-AD7, recognized the approximately 72 kDa polypeptide doublet that was identified previously by the polyclonal antibody D4 as a component of the microdomain structure formed between migrating neurons and radial glial cell processes (Cameron and Rakic [1994] J. Neurosci. 14:3139-3155). Immunofluorescent localization studies reveal a spatial and temporal pattern of 15D7 immunoreactivity in multiple brain regions that correlates well with time periods when neuronal cell migration is a prominent morphogenetic event. In areas where the process of migration is underway, 15D7 immunoreactivity is detected simultaneously in both radial glial cells and cells that have the positional and morphologic features characteristic of migrating neurons. Subsequent to the completion of migration, immunoreactivity is detected in the transitional forms of radial glial cells and mature astrocytes, but not in neurons. Cell aggregation analyses reveal that 15D7 antibodies perturb the rate of aggregation for astrocyte-astrocyte, neuron-neuron, and mixed cell-cell combinations. Taken together, the present studies suggest that the polypeptides recognized by the 15D7 antibodies likely participate in an adhesive process, principally within the ventricular and subventricular zones, that is essential at the onset of the cell migration process.

To identify glial membrane proteins that contribute to the process of neuronal migration in the developing brain, we developed a polyclonal antiserum (D4) and a monoclonal antibody (NJPA1: neuron-glial junctional polypeptide antibody) that recognize membrane proteins localized to the plasmalemmal junction between migrating neurons and adjacent radial glial fibers (Cameron and Rakic, 1994). Here, we show that in the developing cerebral cortex, immunoreactivity for these junctional polypeptides is present throughout the neuronal migratory pathway but becomes minimal or absent where radial glial cell processes enter the marginal zone region, the barrier at which newly arrived neurons normally stop their migration and detach from their glial fiber substrate. We thus tested, using imprints of embryonic cerebral wall and slice preparations, whether the junctional membrane proteins detected by our antibodies contribute to the regulation of neuronal migration in the cerebral cortex. The rate of neuronal migration on glial cell substrates was reduced significantly in the presence of D4 or NJPA1 antibodies. Antibody exposure typically led to the withdrawal of leading processes, changes in microtubular organization and, in some instances, to detachment of neurons from their glial cell substrates. These results suggest that the polypeptides recognized by the D4 and NJPA1 antibodies are essential for the maintenance of normal neuronal migration. Dismantling of neuron-glial cell junctional domains formed by these membrane proteins may underlie neuronal cell detachment from glial migratory substrates at the interface between cortical plate and marginal zone in the developing cerebral wall.