Habitat-specific predation susceptibilities of a littoral rotifer to two invertebrate predators

The rotifer Euchlanis dilatata lives associated with submerged vegetation in the littoral zone of freshwater lakes and ponds. I assessed habitat-specific predation susceptibilities for this rotifer in the presence of three aquatic macrophytes (Myriophyllum exalbescens, Elodea canadensis, and Ceratophyllum demersum) and two predators (damselfly nymphs — Enallagma carunculata; and cnidarians — Hydra). Rotifer survival was greatest on Myriophyllum in the presence of both predators. Conversely, the presence of the other macrophyte species actually increase rotifer suspectibility to predation by damselfly nymphs. I also manipulated plant structural complexity. As predicted, decreasing the relative complexity of each plant resulted in lower rotifer survival.     

4-Thiaproline reduces heart lipid peroxidation and collagen accumulation in the diabetic db/db mouse

Summary Collagen accumulation is a main pathological feature of diabetic cardiomyopathy. The underlying mechanisms seem to be increased cross linking by reactive carbonyles. The purpose of the study was to decrease the collagen content of total ventricular tissue by the oral administration of thiaproline, which could reduce collagen due to its functions as a proline analogue, blocking collagen production and as a free oxygen radical scavenger, blocking reactive carbonyles and oxygen species and subsequently collagen cross linking.Thiaproline was administered to genetically diabetic db/db mice and compared to untreated animals. Total ventricular collagen as expressed by hydroxyproline was significantly lower in the treated group (means 0.23 micromoles/10 tissue in the treated vs 0.35 micromoles/100 mg tissue in the untreated group, p < 0.001). Significantly more collagen could be eluted in the treated group (p < 0.001) and carboxymethyllysine was significantly reduced in the treated group (p < 0.001). Di-tyrosine and glycemic control did not differ between the groups. Glutathione was significantly increased in the TP treated experimental group (p < 0.001) and lipid peroxidation products were significantly decreased (means 0.221 absorbance in the treated group versus 0.321 absorbance in the untreated diabetic group) correlating with total ventricular collagen content (r = 0.87, p < 0.01).We conclude that thiaproline reduced total ventricular collagen content by inhibiting collagen cross linking as reflected by increased solubility of collagen and expressed by higher elution quantity of collagen. Thiaproline, and/or its metabolites induced increase of heart glutathione which may well have been scavenging reactive carbonyles derived from lipid peroxidation and advanced stage nonenzymatic glycosylation as shown by decreased total ventricular carboxy-methyllysine and lipid peroxidation products paralleling reduced heart collagen content.It remains to be shown that the successful reduction of heart collagen by thiaproline is paralleled by improved functional properties.     

Cloned DNA probes distinguish endemic and exotic Entomophaga grylli fungal pathotype infections in grasshopper life stages

Entomophaga grylli is a fungal pathogen of grasshoppers and at least three pathotypes are recognized world-wide. Pathotypes 1 and 2 are endemic to North America while the Australian pathotype 3 had been released into two field sites in North Dakota between 1989 and 1991. Grasshoppers were collected over the summer at the field sites in 1992 and assessed for pathotype infection by cloned DNA probe analysis. The three most predominant grasshopper species that were infected ( Melanoplus sanguinipes, M. bivittatus and Camnula pellucida ) were assessed for pathotype infection with respect to their life stages (nymphal instars and adult males and females). Pathotype 1 predominantly infected grasshoppers in the subfamilies Oedipodinae and Gomphocerinae and pathotype 2 predominantly infected grasshoppers in the subfamily Melanoplinae. Early-instar M. sanguinipes and M. bivittatus had higher pathotype 2 infection frequencies, while late-instar and adult C. pellucida had higher pathotype 1 infection frequencies. Cross-infection by the pathotypes did occur in up to 3% of the individuals, on a per species basis, and primarily in later instar and adult grasshoppers. Pathotype 3 infections occurred in later instar and adults of the three grasshopper species. Infection of grasshoppers by E. grylli pathotypes is discussed with reference to the fungal life cycles.     

Direct sequence analysis of proteins by in-source fragmentation during delayed ion extraction.

Continuous segments of amino acid sequence information as long as 41 residues have been deduced by interpretation of matrix-assisted laser desorption/ionization-generated ion signals dominated by Cn fragmentation within the ion source of a linear time-of-flight mass spectrometer utilizing delayed ion extraction. The technique has been applied successively to five proteins of mass 12.2 kDa to 18.3 kDa, yielding segments of continuous sequence as long as 41 residues without the need for prior proteolytic fragmentation. Intact crosslinks such as disulfides or heme linkages interrupt the generation of these data.     

Monitoring calcium-induced conformational changes in recoverin by electrospray mass spectrometry.

Recoverin is a calcium-binding protein that regulates the vertebrate photoresponse by inhibiting rhodopsin kinase in response to high calcium concentrations. It is heterogeneously N-acylated by myristoyl and related fatty acyl residues that are thought to act as "calcium-myristoyl switches," whereby, in the presence of Ca2+, the N-terminal acyl group is extended away from recoverin and, in the absence of calcium, it is more closely associated with the protein. Here we use electrospray ionization mass spectrometry (ESI/MS) to examine hydrogen isotopic exchange rates for specific regions of both acylated and nonacylated recoverin in the presence and absence of calcium. The deuterium exchange rates of three regions in the hydrophobic myristoyl binding pocket of acylated recoverin decreased in the absence of calcium. This effect is most likely due to the closer association of the acyl group with the protein under these conditions. In contrast, rates of deuterium incorporation increased in the absence of calcium for other regions, including the two functional calcium-binding sites. In addition to supporting the calcium-myristoyl switch hypothesis, a comparison of the behavior of acylated and unacylated recoverin revealed that the N-acyl group (N-lauroyl or N-myristoyl) exerts a significant stabilizing influence on the dynamics of recoverin. We demonstrate that the new technique of monitoring hydrogen isotopic exchange by ESI/MS can be used to obtain useful information concerning protein structures in solution using smaller amounts of protein and under more physiologically relevant conditions than is typically possible with NMR or X-ray crystallography.     

GABA concentrations in the striatum following repetitive cerebral ischemia

GABAergic neurons in the striatum are very sensitive to the effects of ischemia. The progressive decline in striatal GABA following transient forebrain ischemia in gerbils may be secondary to either a decreased production or an increase in reuptake mechanisms or both. The current experiment was designed to evaluate release of GABA by stimulation with K+ or inhibition of its uptake with nipecotic acid or their combination (K+ nipecotic) after repetitive forebrain ischemia in gerbils by in-vivo microdialysis on Days 1, 3, 5, and 14 following the insult. Infusion of nipecotic acid or potassium chloride, resulted in a significant increase in extracellular GABA. This response was significantly decreased in the post-ischemic animals. The synergistic effect of increased GABA concentrations by the infusion of nipecotic acid+potassium chloride seen in the controls was not evident in the post-ischemic animals. In conclusion, though there is a reduction in the extracellular GABA concentrations in the first week following an ischemic insult, restorative mechanisms are operative in the second week as seen by the increasing GABA concentrations.     

Molecular heterogeneity of canine cholecystokinin in portal and peripheral plasma

The release of molecular forms of cholecystokinin (CCK) into the portal and peripheral blood in response to an intraduodenal perfusion of sodium oleate (9 mmol X h-1) was studied in six conscious dogs with chronic portal vein catheters. Immunoreactive CCK as concentrated from 20 ml plasma by C18 SEP PAK cartridges and the pattern of molecular forms of CCK were studied by G50 gel filtration. CCK-like immunoreactivity (CCK-LI) was measured in the column eluates with antibody 5135, which measures gastrin and CCK equally and requires the intact carboxyl-terminus for full recognition. Gastrin was measured specifically with antibody 1611. Intraduodenal perfusion with oleate did not alter basal gastrin release. Release of CCK-LI by intraduodenal oleate was calculated by the increments of the integrated CCK-LI peaks over basal. Total CCK-like immunoreactivity (CCK-LI), calculated by integration of all CCK-LI peaks in gel filtration eluates, increased over basal by 12 fmol/ml in the portal and by 6 fmol/ml in the peripheral plasma after intraduodenal perfusion with sodium oleate. The main molecular forms eluted on gel filtration in positions of CCK33,39 and of CCK8. The pattern of CCK in the peripheral plasma was similar to that in the portal plasma except that in the peripheral plasma large molecular forms were more abundant than small forms. This finding was confirmed when CCK39 and CCK8 were infused either into the portal vein or into the peripheral vein and peripheral plasma CCK levels were measured. Elimination of CCK8 after portal vein infusion compared to peripheral vein infusion was about 3 times higher than that of CCK39. The abundance of large molecular forms of CCK in the circulating blood which are similar in potency to small forms, underlines their role in the physiology of CCK.     

Non-ependymal cilia in the habenulae and the interpeduncular nucleus of the frog tadpole

Summary Cilia of the 9+2 pattern are found electron microscopically in nonependymal cells of the habenulae and the interpeduncular nucleus of the tadpole of Rana esculenta at an early stage of development (8 mm length, head to tip of tail). A comparison is made between these and the ependymal and sensory cilia in the same specimens. The cilia project into the neuropil emerging from a perikaryon rich in free ribosomes and displaying a prominent Golgi apparatus. These perikarya contain dense core vesicles. Synapses with vesicles of the clear spherical type have been observed along the ciliary shaft. On a purely morphologic basis the authors hypothesize that these cilia, at least in this early ontogenetic stage, may extend considerably the conducting surface of the cell and represent a sensory structure which could be stimulated by terminal processes belonging to distantly located cells. In addition, they could also be involved in the trophic exchange of material with the adjacent structures.     

Slide staining device for use during space flight.

A slide staining device is described that performs Gram and Wright stains during space flight. Reagents and liquid wastes are contained within a closed system.     

Platelet activating factor. Stimulation of the lipoxygenase pathway in polymorphonuclear leukocytes by 1-O-alkyl-2-O-acetyl-sn-glycero-3-phosphocholine

1-O-Alkyl-2-O-acetyl-sn-glycero-3-phosphocholine (AAGPC) triggered the release of [3H]arachidonate but not [14C]stearate from cellular phospholipids in cytochalasin B-treated rabbit polymorphonuclear leukocytes. Concentrations of AAGPC up to 20 nM caused a dose-dependent release and subsequent metabolism of the released [3H]arachidonic acid. Most of the release of the [3H]arachidonate had taken place within the first 2 min of stimulation. Phosphatidylinositol and phosphatidylcholine served as the sources of [3H]arachidonate with about 50% of the label coming from each pool. Challenge of cytochalasin B-treated polymorphonuclear leukocytes with AAPGC led to the production of [3H]hydroxyeicosatetraenoic acids and [3H]dihydroxyeicosatetraenoic acids. No significant production of [3H]prostaglandins or [3H]thromboxanes was detected. AAGPC also caused a dose-dependent degranulation of cytochalasin B-treated rabbit polymorphonuclear leukocytes as shown by the release of beta-glucuronidase and lysozyme. Both the AAGPC-stimulated production of arachidonate metabolites and the degranulation response were blocked by eicosatetraynoic acid and non-dihydroguaiaretic acid at similar inhibitor concentrations. These findings suggest the bioactions of AAGPC on polymorphonuclear leukocytes may be mediated by the release of arachidonic acid and the production of mono- and dihydroxyeicosatetraenoic acids.