Different red blood cell characteristics in a primitive agnathan (M. glutinosa) and a more recent teleost (O. mykiss) influence their strategies for blood CO2 transport

This study examines how the different red blood cell (rbc) characteristics in two lower vertebrates, the phylogenetically primitive hagfish and a more recent teleost, the rainbow trout, influence their strategies for blood CO2 transport. Deoxygenation of the blood resulted in a significant increase in rbc CO2 content in hagfish, but there were no significant changes in the CO2 content of plasma or whole blood under these conditions. In contrast, deoxygenation increased the CO2 content of the rbc, plasma and whole blood in the trout. These results demonstrate that the Haldane effect is much less important for CO2 transport in the hagfish as compared to the trout. The relative importance of the rbc and plasma in blood CO2 transport were roughly similar in hagfish and trout and were very different from that previously documented in another primitive vertebrate, the lamprey. In trout, however, the role of the rbc in CO2 carriage was increased upon the addition of the beta-adrenergic agonist isoproterenol (10(-5) M) to the blood. Taken together, these results and those recently collected for lampreys demonstrate that changes in rbc characteristics during vertebrate evolution have probably resulted in several important transitions in the strategy for blood CO2 transport.     

Vertical transport of dissolved organic C and N under long-term N amendments in pine and hardwood forests

At the Harvard Forest, Massachusetts, a long-term effort is under way to study responses in ecosystem biogeochemistry to chronic inputs of N in atmospheric deposition in the region. Since 1988, experimental additions of NH₄NO₃ (0, 5 and 15 g N m^–2 yr^–1) have been made in two forest stands:Pinus resinosa (red pine) and mixed hardwood. In the seventh year of the study, we measured solute concentrations and estimated solute fluxes in throughfall and at two soil depths, beneath the forest floors (Oa) and beneath the B horizons.Beneath the Oa, concentrations and fluxes of dissolved organic C and N (DOC and DON) were higher in the coniferous stand than in the hardwood stand. The mineral soil exerted a strong homogenizing effect on concentrations beneath the B horizons. In reference plots (no N additions), DON composed 56% (pine) and 67% (hardwood) of the total dissolved nitrogen (TDN) transported downward from the forest floor to the mineral soil, and 98% of the TDN exported from the solums. Under N amendments, fluxes of DON from the forest floor correlated positively with rates of N addition, but fluxes of inorganic N from the Oa exceeded those of DON. Export of DON from the solums appeared unaffected by 7 years of N amendments, but as in the Oa, DON composed smaller fractions of TDN exports under N amendments. DOC fluxes were not strongly related to N amendment rates, but ratios of DOC:DON often decreased.The hardwood forest floor exhibited a much stronger sink for inorganic N than did the pine forest floor, making the inputs of dissolved N to mineral soil much greater in the pine stand. Under the high-N treatment, exports of inorganic N from the solum of the pine stand were increased >500-fold over reference (5.2 vs. 0.01 g N m^–2 yr^–1), consistent with other manifestations of nitrogen saturation. Exports of N from the solum in the pine forest decreased in the order NO₃-N> NH₄-N> DON, with exports of inorganic N 14-fold higher than exports of DON. In the hardwood forest, in contrast, increased sinks for inorganic N under N amendments resulted in exports of inorganic N that remained lower than DON exports in N-amended plots as well as the reference plot.     

Bombesin stimulates the rapid activation of phospholipase A2-catalyzed phosphatidylcholine hydrolysis in Swiss 3T3 cells.

In Swiss 3T3 fibroblasts bombesin stimulated the release of arachidonic acid in a time- and dose-dependent manner. Arachidonate levels were significantly elevated after only a 2-s stimulation with the agonist. Furthermore, by measuring the arachidonate content of cellular phospholipids after cell activation, it was shown that there was selective depletion from phosphatidylcholine over the same time course. The corresponding production of lysophosphatidylcholine suggested the involvement of a phosphatidylcholine-specific phospholipase A2. Initial arachidonic acid release was not dependent on the presence of extracellular calcium, not activated by treatment of the cells with thapsigargin, and was unaffected by down-regulation of protein kinase C activity, or by treatment of the cells with the protein kinase C inhibitor staurosporine. These data strongly suggest that occupation of the bombesin receptor is closely coupled to activation of phospholipase A2 which results in the rapid release of arachidonic acid from phosphatidylcholine.     

Marine Ecology of Seabirds in Polar Oceans

Patterns of seabird species' distributions differ between theAntarctic and the Arctic. In the Antarctic, distributions areannular or latitudinal, with strong similarities in speciescomposition of seabird communities in all ocean basins at agiven latitude. In the Arctic, communities are arranged meridionally,and show strong differences between ocean basins and, at a givenlatitude, between sides of ocean basins. These differences betweenthe seabird communi ies in the Northern Hemisphere and the SouthernHemisphere reflect differences in the patterns of flow of majorocean current systems. At smaller spatial scales, in both hemispheresthe species composition of seabird communities is sensitiveto changes in watermass characteristics. The distribution of avian biomass is affected by both physicaland biological features of the ocean. In the Antarctic, muchseabird foraging is over deep water, and withinseason, small-scalepatchiness in prey abundance and availability in ice-free watersis likely to be controlledprimarily by the behavior of the prey,rather than by physical features. Thus, prey availability maybe unpredictable in time and space. In contrast, in the NorthernHemisphere, most seabirdforaging is concentrated over shallowcontinental shelves, where currents interact with bathymetryto produce predictable physical features capable of concentratingprey or making prey more easily harvested by seabirds. Ice cover appears to be the most important physical featurein the Antarctic. An entire community of birds is specializedto use prey taken near the ice edge. These prey consist of avariety of species, some of which are normally found much deeperin the water than the birds takingthem can dive. The open-waterportion of the marginal ice zone is also an important foraginghabitat for Antarctic marine birds. In the Arctic, a food webbased on underice algae is used by marine birds, but few ifany data exist on avian use of the open water segment of themarginal ice zone. Recent simultaneous surveys of birds and their prey indicatethat only rarely does the small-scale abundance of birds matchthat of their prey; correlations between predators and preyaregenerally stronger at larger scales. Evidence is accumulatingin the Antarctic that the largestaggregations of krill may bedisproportionately important to foraging seabirds.     

The development of adult abdominal muscles in Drosophila: myoblasts express twist and are associated with nerves.

During metamorphosis, the adult muscles of the Drosophila abdomen develop from pools of myoblasts that are present in the larva. The adult myoblasts express twist in the third larval instar and the early pupa and are closely associated with nerves. Growing adult nerves and the twist-expressing cells migrate out across the developing abdominal epidermis, and as twist expression declines, the myoblasts begin to synthesize beta 3 tubulin. There follows a process involving cell fusion and segregation into cell groups to form multinucleate muscle precursors. These bipolar precursors migrate at both ends to find their correct attachment points. beta 3 tubulin expression continues at least until 51 h APF by which time the adult muscle pattern has been established.     

Extinctions and migrations of Devonian rugose corals in the Eastern Americas Realm

Oliver, W. A., Jr. 1990 04 15: Extinctions and migrations of Devonian rugose corals in The Eastern Americas Realm. Lethaia , Vol. 23 , pp. 167–178. Oslo. ISSN 0024–1164.
Detailed plotting of the stratigraphic ranges of Devonian rugose coral genera within the Eastern Americas Realm reveals new information about the extinctions and migrations of this largely endemic fauna. There were significant faunal turnovers in the Lochkovian, middle Eifelian and late Givetian. as well as in the often discussed late Frasnian. The late Givetian turnover was nearly as great as the Frasnian one. Inward migration was principally from western North America, and the greatest influxes were during the carly Givetian and Frasnian. It seems likely that there were several separate incursions and that some genera were introduced to the east two, or even three times.     

Protozoan Colonization Rates and Trophic Status of Some Freshwater Wetland Lakes

Primary productivity, chlorophyll a, phosphorus and nitrogen nutrients, and other chemical and physical parameters were measured in 13 wetland lakes in northern lower Michigan. These lakes included several examples located in each of the four major wetland types—bogs, fens, marshes, and swamps. Of the four types, the brown-colored waters of the acid bog lakes generally had the highest levels of primary productivity, chlorophyll a, phosphorus, and nitrogen. Primary productivity correlated positively with water color, total-N, and NH₃-N (α≤ 0.05). By these measures, waters of the bogs were the most eutrophic of the four types of wetland lakes. These findings would seem to contradict the generally-held concept that “dystrophic” bog lakes are extremely oligotrophic. Protozoan colonization of artificial substrate islands was monitored at each wetland site. The correlation between protozoan colonization rates (G values in the MacArthur-Wilson noninteractive model) and primary productivity, measured by 24-h light and dark bottle incubations, was significant at the 95% confidence level (r= 0.850, P= 0.001) and with water color at the 90% confidence level (r= 0.599, P= 0.084). It was concluded that protozoan colonization rate was an excellent indicator of the trophic status of wetland lakes.     

Octadecenoic Fattv Acids and their Association with Hemolysis in Malaria

SYNOPSIS. Octadecenoic fatty acids have been implicated in prehemolytic and hemolytic phenomena associated with malaria. Oleic [18:1 (n-9)] and cis-vaccenic [18:1 (n-7)] acids were found and quantified in the major neutral and phospholipids of the erythrocytes and plasmas of normal and Plasmodium lophurae-infected ducks, and in the parasite itself. The octadecenoic fatty acids were elevated over normal values in the major phospholipid classes of infected erythrocytes, in the erythrocyte-specific alkoxy phosphatidylethanolamine of infected erythrocytes, and in the plasma unesterified fatty acids, triacylglycerols, cholesterol esters and phosphatidylcholine of infected ducklings. Oleic acid was the major fatty acid of P. lophurae (33% total lipid fatty acids). Theoretical considerations of octadecenoic fatty acid modifications of erythrocyte membrane structure and function in malaria are discussed.