P blood group regulation of glycosphingolipid levels in human erythrocytes.

The neutral glycosphingolipid content of normal human erythrocytes was analyzed by a new method which utilizes high performance liquid chromatography. This rapid and accurate technique permits the quantitation of each of the major neutral glycolipids from individual blood samples. A correlation between the P blood group and the relative quantities of neutral glycosphingolipids is demonstrated. Erythrocytes from P1 individuals are shown to contain more globotriaosylceramide and less lactosylceramide than do erythrocytes from P2 individuals. The results of these experiments suggest the existence of a new phenotype in the P blood group system, and have further implications regarding the biosynthesis of the P blood group glycosphingolipids.     

Estimated Drainage of Carbon from the Tricarboxylic Acid Cycle for Protein Synthesis in Suspension Cultures of Paul's Scarlet Rose Cells

The amount of carbon (μmoles of carbon atoms) drained from the tricarboxylic acid cycle for protein synthesis was compared with μmoles of CO₂ released from the cycle at 2-day intervals during the growth of suspension cultures of Paul's Scarlet rose. We concluded that during the period of most rapid protein synthesis (day 0-4) one-sixth as much carbon was drained from the tricarboxylic acid cycle for protein synthesis as was released as CO₂. By day 8, one-thirtieth of the amount of carbon released as CO₂ was incorporated into protein. Net protein synthesis stopped on day 8, but the evolution of CO₂/culture continued at its maximum rate until day 10.     

Differential phosphorylation by GTP and ATP in isolated rod outer segments of the retina.

Isolated bovine rod outer segment protein is phosphorylated with GTP-gamma-32P and ATP-gamma 32P and to a much lesser extent by CTP-gamma-32P and UTP-gamma-32P. Phosphorylation with both GTP (GTP-kinase activity) and ATP (ATP-kinase activity) is markedly stimulated by light; phosphorylation with GTP is lower in dark-adapted and higher in light-adapted rod outer segments than is phosphorylation with ATP. Km values of 20 and 200 muM and Vmax values of 2.1 and 5.9 nmol/(mg min(-1)) were calculated using ATP and GTP, respectively, in light-adapted outer segments. When outer segments are incubated with GTP-gamma-32P under the usual conditions employed in these experiments, no formation of ATP-gamma-32P was detected by the techniques of high-pressure liquid chromatography and thin-layer chromatography. In intact, light-bleached outer segments, GTP appears to specifically phosphorylate rhodopsin. Histone and phosvitin are not phosphorylated to any appreciable extent by GTP. Histone appears to block rhodopsin phosphorylation by GTP while histone and, to some extent, phosvitin, both act as substrates for ATP-kinase activity. Cyclic AMP and other adenine derivates have a marked inhibitory effect on GTP-kinase activity. Phosphate also inhibits GTP-kinase activity but stimulates ATP-kinase activity. Such differences in phosphorylation with GTP and ATP indicate that these activities are either due to separate enzyme systems or, if only one enzyme is involved, the activities are under separate physiological control in the photoreceptor unit.     

Long chain fatty acid binding to human plasma albumin.

The binding of six physiologically important long chain fatty acids to defatted human plasma albumin was measured at 37 degrees in a calcium-free Krebs-Ringer phosphate buffer, pH 7.4. The data were analyzed in terms of multiple stepwise equilibria. With the saturated acids, the magnitude of the equilibrium (association) constants, Ki, increased as the chain length increased: laurate smaller than myristate smaller than palmitate smaller than stearate. Oleate was bound more tightly than stearate; by contrast, linoleate was bound less tightly than stearate. The equilibrium constants, K1 through K12, ranged from 2.4 times 10-6 - 3.5 times 10-3 m-1 for laurate to 2.6 times 10-8 - 3.5 times 10-5 m-1 for oleate. Successive values of Ki decrease for each of the acids, indicating that major cooperative binding effects do not occur over the physiological range of fatty acid concentrations. In no case could the Ki be segregated into distinct classes, suggesting that any grouping of albumin binding sites is somewhat arbitrary. The results were inconclusive concerning whether premicellar association of unbound fatty acid occurs. Although corrections for premicellar association produced very little change in the Ki values for myristate, they raised the Ki for palmitate and stearate by 300 to 700 per cent. A sigmoidal relationship was obtained when the logarithm of Ki was plotted against chain length for the saturated fatty acids containing 6 to 18 carbon atoms, indicating that the binding energy is not simply a statistical process dependent only on the fatty acid chain length. This selectivity that albumin contributes to the binding process may be due to varying degrees of configurational adaptability of its binding sites as the fatty acid increases in length.     

The evolution of adult pollen feeding did not alter postembryonic growth in Heliconius butterflies

For many animals, the availability and provision of dietary resources can vary markedly between juvenile and adult stages, often leading to a temporal separation of nutrient acquisition and use. Juvenile developmental programs are likely limited by the energetic demands of many adult tissues and processes with early developmental origins. Enhanced dietary quality in the adult stage may, therefore, alter selection on life history and growth patterns in juvenile stages. Heliconius are unique among butterflies in actively collecting and digesting pollen grains, which provide an adult source of essential amino acids. The origin of pollen feeding has therefore previously been hypothesized to lift constraints on larval growth rates, allowing Heliconius to spend less time as larvae when they are most vulnerable to predation. By measuring larval and pupal life‐history traits across three pollen‐feeding and three nonpollen‐feeding Heliconiini, we provide the first test of this hypothesis. Although we detect significant interspecific variation in larval and pupal development, we do not find any consistent shift associated with pollen feeding. We discuss how this result may fit with patterns of nitrogen allocation, the benefits of nitrogenous stores, and developmental limitations on growth. Our results provide a framework for studies aiming to link innovations in adult Heliconius to altered selection regimes and developmental programs in early life stages.     

Reconciling the biogeography of an invader through recent and historic genetic patterns: the case of topmouth gudgeon <Emphasis Type="Italic">Pseudorasbora parva</Emphasis>

The genetic variability and population structure of introduced species in their native range are potentially important determinants of their invasion success, yet data on native populations are often poorly represented in relevant studies. Consequently, to determine the contribution of genetic structuring in the native range of topmouth gudgeon Pseudorasbora parva to their high invasion success in Europe, we used a dataset comprising of 19 native and 11 non-native populations. A total of 666 samples were analysed at 9 polymorphic microsatellite loci and sequenced for 597 bp of mitochondrial DNA. The analysis revealed three distinct lineages in the native range, of which two haplogroups were prevalent in China (100%), with a general split around the Qinling Mountains. Dating of both haplogroups closely matched past geological events. More recently, its distribution has been influenced by fish movements in aquaculture, resulting in gene flow between previously separated populations in Northern and Southern China. Their phylogeography in Europe indicate as few as two introductions events and two dispersal routes. Microsatellite data revealed native populations had higher genetic diversity than those in the invasive range, a contrast to previous studies on P. parva. This study confirms the importance of extensive sampling in both the native and non-native range of invasive species in evaluating the influence of genetic variability on invasion success.     

Cultured gill epithelia as models for the freshwater fish gill

We review recent progress in the development of models for the freshwater teleost gill based on reconstructed flat epithelia grown on permeable filter supports in primary culture. Methods are available for single-seeded insert (SSI) preparations consisting of pavement cells (PVCs) only from trout and tilapia, and double-seeded insert (DSI) preparations from trout, containing both PVCs (85%) and mitochondria-rich cells (MRCs, 15%), as in the intact gill. While there are some quantitative differences, both SSI and DSI epithelia manifest electrical and passive permeability characteristics typical of intact gills and representative of very tight epithelia. Both preparations withstand apical freshwater exposure, exhibiting large increases in transepithelial resistance (TER), negative transepithelial potential (TEP), and low rates of ion loss, but there is only a small active apical-to-basolateral "influx" of Cl(-) (and not of Na(+)). Responses to various hormonal treatments are described (thyroid hormone T3, prolactin, and cortisol). Cortisol has the most marked effects, stimulating Na(+),K(+)-ATPase activity and promoting active Na(+) and Cl(-) influxes in DSI preparations, and raising TER and reducing passive ion effluxes in both epithelia via reductions in paracellular permeability. Experiments using DSI epithelia lacking Na(+) uptake demonstrate that both NH(3) and NH(4)(+) diffusion occur, but are not large enough to account for normal rates of branchial ammonia excretion, suggesting that Na(+)-linked carrier-mediated processes are important for ammonia excretion in vivo. Future research goals are suggested.