Entrapped Sediments as a Source of Phosphorus in Epilithic Cyanobacterial Proliferations in Low Nutrient Rivers

Proliferations of the benthic mat-forming cyanobacteria Phormidium have been reported in rivers worldwide. Phormidium commonly produces natural toxins which pose a health risk to animal and humans. Recent field studies in New Zealand identified that sites with Phormidium proliferations consistently have low concentrations of water column dissolved reactive phosphorus (DRP). Unlike other river periphyton, Phormidium mats are thick and cohesive, with water and fine sediment trapped in a mucilaginous matrix. We hypothesized that daytime photosynthetic activity would elevate pH inside the mats, and/or night time respiration would reduce dissolved oxygen. Either condition could be sufficient to facilitate desorption of phosphates from sediment incorporated within mats, thus allowing Phormidium to utilize it for growth. Using microelectrodes, optodes and pulse amplitude modulation fluorometry we demonstrated that photosynthetic activity results in elevated pH (>9) during daytime, and that night-time respiration causes oxygen depletion (<4 mg L^-1) within mats. Water trapped within the mucilaginous Phormidium mat matrix had on average 320-fold higher DRP concentrations than bulk river water and this, together with elevated concentrations of elements, including iron, suggest phosphorus release from entrapped sediment. Sequential extraction of phosphorus from trapped sediment was used to investigate the role of sediment at sites on the Mangatainoka River (New Zealand) with and without Phormidium proliferations. Deposition of fine sediment (<63 μm) was significantly higher at the site with the most extensive proliferations and concentrations of biological available phosphorus were two- to four- fold higher. Collectively these results provide evidence that fine sediment can provide a source of phosphorus to support Phormidium growth and proliferation.     

Seasonal human coronavirus antibodies are boosted upon SARS-CoV-2 infection but not associated with protection

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Genetic analysis of a Drosophila neural cell adhesion molecule: interaction of fasciclin I and Abelson tyrosine kinase mutations

Drosophila fasciclin I is a homophilic cell adhesion molecule expressed in the developing embryo on the surface of a subset of fasciculating CNS axons, all PNS axons, and some nonneuronal cells. We have identified protein-null mutations in the fasciclin I (fas I) gene, and show that these mutants are viable and do not display gross defects in nervous system morphogenesis. The Drosophila Abelson (abl) proto-oncogene homolog encodes a cytoplasmic tyrosine kinase that is expressed during embryogenesis primarily in developing CNS axons; abl mutants show no gross defects in CNS morphogenesis. However, embryos doubly mutant for fas I and abl display major defects in CNS axon pathways, particularly in the commissural tracts where expression of these two proteins normally overlaps. The double mutant shows a clear defect in growth cone guidance; for example, the RP1 growth cone (normally fas I positive) does not follow its normal path across the commissure.     

Bacteroides fragilis Toxin Coordinates a Pro-carcinogenic Inflammatory Cascade via Targeting of Colonic Epithelial Cells

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Role of macrophages during Theiler's virus infection.

Theiler's virus, a murine picornavirus, causes a persistent infection of the central nervous system with chronic inflammation and primary demyelination. We examined the nature of infected cells at different times postinoculation (p.i.) with a combined immunocytochemistry-in situ hybridization assay. The virus was found in the gray matter of the brain, mostly in neurons, during the first week p.i. During the following weeks, the virus was present in the spinal cord, first in the gray and white matter, then exclusively in the white matter. Approximately 10% of infected cells were astrocytes at any time during the study. Infected oligodendrocytes were first noticed on day 14 p.i. and amounted to approximately 6% of infected cells. The number of infected macrophages increased with time and reached a plateau by day 21 p.i., when at least 45% of infected cells were macrophages. The role of blood-borne macrophages during infection was studied by depleting them with mannosylated liposomes containing dichloromethylene diphosphonate. The virus did not persist in the majority of the mice treated with liposomes. These mice showed only minimal mononuclear cell infiltration and no demyelination.     

Adverse effects of tempol on hidrosaline balance in rats with acute sodium overload

We studied the effects of tempol, an oxygen radical scavenger, on hydrosaline balance in rats with acute sodium overload. Male rats with free access to water were injected with isotonic (control group) or hypertonic saline solution (0.80 mol/l NaCl) either alone (Na group) or with tempol (Na-T group). Hydrosaline balance was determined during a 90 min experimental period. Protein expressions of aquaporin 1 (AQP1), aquaporin 2 (AQP2), angiotensin II (Ang II) and endothelial nitric oxide synthase (eNOS) were measured in renal tissue. Water intake, creatinine clearance, diuresis and natriuresis increased in the Na group. Under conditions of sodium overload, tempol increased plasma sodium and protein levels and increased diuresis, natriuresis and sodium excretion. Tempol also decreased water intake without affecting creatinine clearance. AQP1 and eNOS were increased and Ang II decreased in the renal cortex of the Na group, whereas AQP2 was increased in the renal medulla. Nonglycosylated AQP1 and eNOS were increased further in the renal cortex of the Na-T group, whereas AQP2 was decreased in the renal medulla and was localized mainly in the cell membrane. Moreover, p47-phox immunostaining was increased in the hypothalamus of Na group, and this increase was prevented by tempol. Our findings suggest that tempol causes hypernatremia after acute sodium overload by inhibiting the thirst mechanism and facilitating diuresis, despite increasing renal eNOS expression and natriuresis.     

A comparison of snRNP-associated Sm-autoantigens: human N, rat N and human B/B''.

N is a tissue-specific, Sm-epitope bearing, snRNP-associated protein found predominantly in brain. The cDNA sequence encoding human N is compared to those for rat N and human B/B'. The amino acid sequences of human and rat N are 100% conserved. Although the amino acid sequences of N and B/B' are very similar to each other, B/B' contains 50 amino acids which are not present in N. On Northern blots the cDNAs encoding N and B/B' recognize two different RNA species. A comparison of the codon usage, as specified by the open reading frames of N and B/B' as well as results from Southern blots, show that N and B/B' are derived from different genes.