Rice cultivar evaluation for phosphorus use efficiency

Phosphorus deficiency is one of the most growth-limiting factors in acid soils in various parts of the world. The objective of this study was to screen 25 rice cultivars (Oryza sativa L.) at low, medium, and high levels of soil P. Number of tillers, root length, plant height, root dry weight and shoot dry weight were related to tissue P concentrations, P uptake and P-use efficiency. Shoot weight was found to be the plant parameter most sensitive to P deficiency. Significant cultivar differences in P use efficiency were found. Phosphorus use efficiency was higher in roots than shoots and decreased with increasing levels of soil P. Positive correlations were found among growth parameters such as plant height, tillers, root and shoot weight, and P content of roots and shoots. These results indicate selection of rice cultivars for satisfactory performance under low P availability can be carried out using shoot and root dry weight as criteria.     

Genetic mapping of three human homologues of murine t-complex genes localizes TCP10 to 6q27, 15 cM distal to TCP1 and PLG

Human homologues of mouse t-complex genes have been cloned and localized physically to chromosome 6p or 6q. TCP1, TCP10, and PLG are human homologues of genes located in the proximal portion of the t-complex on mouse chromosome 17. We present here results of genetic mapping of these human t-complex homologues previously localized to 6q25-q27, 6q21-q27, and 6q26-q27, respectively, by physical techniques. TCP1 and PLG do not recombine with each other and are separated from TCP10 by about 15 cM, while the corresponding mouse genes are no more than 4 cM apart. Genetic mapping with markers well localized cytogenetically places TCP1 and PLG proximal to TCP10 and localizes the latter to the cytogenetic band 6q27. It is likely that the organization of human t-complex homologues on 6q is similar to that of t haplotypes rather than that of wildtype murine chromosome 17.     

1H NMR studies of human C3a anaphylatoxin in solution: sequential resonance assignments, secondary structure, and global fold

The spin systems that comprise the 1H nuclear magnetic resonance (NMR) spectrum of the complement fragment C3a (Mr 8900) have been completely identified by an approach which integrates data from a wide range of two-dimensional NMR experiments. Both relayed and multiple quantum experiments play an essential role in the analysis. After the first stage of analysis the spin systems of 60 of the 77 residues were assigned to the appropriate residue type, providing an ample basis for subsequent sequence-specific assignments. Elements of secondary structure were identified on the basis of networks of characteristic sequential and medium-range nuclear Overhauser effects (NOEs), values of 3JHN alpha, and locations of slowly exchanging backbone amide protons. Three well-defined helical segments are found. Gradients of increasing mobility in distinct segments of the C3a polypeptide are observed, with very high mobilities for several residues near the C- and N-termini, including the complete C-terminal receptor binding site pentapeptide LGLAR. The NMR data, combined with known disulfide linkages and a small number of critical long-range NOEs, provide the global folding pattern of C3a in solution. Identical solution structures were found for both the intact active protein and the largely inactive physiologic product des-Arg77-C3a.(ABSTRACT TRUNCATED AT 250 WORDS)     

Molecular cloning of the cDNA for androgen-dependent sperm-coating glycoproteins secreted by the rat epididymis

cDNA clones coding for two closely related androgen-dependent sperm-coating glycoproteins secreted by the rat epididymis were selected by screening an epididymal cDNA library constructed in lambda gt 11 with affinity-purified antibody directed against the glycoproteins. The largest clone of 956 nucleotides provided coding information for a protein of 246 amino acids of which the first 19 residues comprise a putative signal peptide sequence which when cleaved would produce a mature protein of 227 residues and a molecular mass of 26 kDa. Confirmation of the identity of the clone was provided by a match between the amino acid sequence predicted from the cDNA sequence and the actual amino acid sequence determined for a tryptic peptide fragment of one of the pure glycoproteins. It is probable that the primary amino acid sequence of the two glycoproteins is identical. Northern blot and slot-blot analysis revealed that the mRNA for the glycoproteins is approximately 1250 nucleotides long and that the concentration of the mRNA in the epididymis is androgen-dependent. The glycoproteins and their mRNAs were unique to the epididymis as determined by Western and Northern blots, respectively, since signals were absent from skin, brain, liver, kidney, heart, skeletal muscle and testis. Cross-reacting proteins of slightly smaller apparent molecular mass were detected in extracts of mouse and guinea-pig epididymis, but not rabbit or bull epididymis. Comparison with existing protein data bases revealed that the epididymal glycoproteins display significant sequence homology with yeast carboxypeptidase Y.     

Radiation inactivation probe of membrane-bound enzymes: gamma-glutamyltranspeptidase, aminopeptidase N, and sucrase

gamma-Glutamyltranspeptidase (GGT), aminopeptidase N (AP-N), and sucrase in purified rabbit intestinal brush border membrane vesicles were irradiated in situ at -135 degrees C using high energy electrons. Surviving activities of the enzymes were measured as a function of radiation dose, and the functional unit target sizes (corresponding to carbohydrate-free polypeptides) were determined using target analysis. The in situ functional unit sizes were GGT 59 kDa, AP-N 59 kDa, and sucrase 63 kDa. Together with biochemical data determined previously, it is concluded that the noncovalently attached large (approximately 40 kDa) and small (approximately 25 kDa) subunits of GGT are both required for catalytic activity. Furthermore, these data suggest that (i) the membrane-bound form of AP-N consists of one or more noncovalently attached subunits of 59 kDa, each of which is enzymatically active; and (ii) in situ sucrase activity is associated with a subunit of 63 kDa which is noncovalently attached within the sucrase-isomaltase complex.     

Some aspects of the biology of the red bass, Lutjanus bohar (Forsskal), from the Tigak Islands, Papua New Guinea

The growth rate, food, reproduction and mortality rates of the red bass, Lutjanus bohar , are described for fish associated with coral reefs in the Tigak Islands of Papua New Guinea. Spawning intensity by month was investigated by examination of gonad maturation stages. The length–at–maturity of female L. bohar was estimated from the relationship between changes in gonad index with increasing size. Female fish matured at about 45–0 cm fork length. The Petersen method was used to obtain age–at–length data from length frequency data of L. bohar captured by hook–and–line fishing. The growth of L. bohar was described by a von Bertalanffy growth curve with the parameters AT=0.27 and L_∞ = 81.7 cm. There was a positive correlation between water depth (D) and the length of L. bohar (L) that was described by L = 318–8+ 3.050 D . The mortality rates ( Z ) of L. bohar from shallow (≤30m) and deep (≤80m) water were estimated from length converted catch curves and were 1–181 and 0–64 respectively. The high Z value for the shallow water population of L. bohar was ascribed to the migration of larger specimens into deeper water. The deep water population of L. bohar remains unfished and the estimate of Z was believed to be equivalent to the natural mortality rate ( M ). An empirical method of calculating M gave an estimate of 0.59. Lutjanus bohar is a carnivorous piscivore that feeds throughout the water column.     

Influence of Meloidogyne incognita on Resistant and Susceptible Sweet Potato Cultivars

Effects of several population densities ofMeloidogyne incognita on the sweet potato cultivars Centennial (susceptible) and Jasper (moderately resistant) were studied. Field plots were infested with initial levels (Pi) of 0, 10, 100, 1,000, 5,000, and 10,000 eggs and juveniles/500 cm³ soil in 1980 and 0, 100, 1,000, 2,000, 3,000, 4,000, and 5,000 in 1981. M. incognita population development trends were similar on both cultivars; however, at high Pi, more eggs and juveniles were recovered from Centennial than from Jasper. The highest Pi did not result in the highest mid-season (Pm) counts. Pi was negatively correlated with the number of marketable roots and root weight but positively correlated with total cracked roots, percentage of cracked roots, and cracking severity. Jasper tolerated higher Pi with greater yields and better root quality than Centennial. Cracking of fleshy roots occurred with both cultivars at low Pi.     

Characterization of non-transferrin-bound iron clearance by rat liver

Recent evidence suggests that the hepatic iron-loading characteristic of hemochromatosis may result in part from efficient hepatic clearance of non-transferrin-bound iron, which is increased in this disorder. However, this hypothesis assumes that hepatic clearance remains highly efficient despite excess iron stores. We therefore studied hepatic uptake of non-transferrin-bound iron in the single-pass perfused rat liver under varying conditions. Animals were iron loaded or depleted by dietary manipulation, but no changes in the efficiency of ferrous iron uptake or the kinetic parameters were seen (single-pass extraction, 59-74%; Km, 16-19 microM; Vmax, 30-32 nmol X min-1 X g liver-1). Added divalent zinc, cobalt, and manganese ions reversibly inhibited ferrous iron uptake and the inhibition by zinc was shown to be competitive. Uptake required calcium, was markedly temperature-sensitive (delta E = 14.3 Kcal/mol), and was relatively insensitive to inhibition of cellular energy metabolism. Particles consistent with ferritin cores were seen in lysosomes of hepatic parenchymal cells within 30 min of perfusion with ferrous iron. These results suggest that ferrous iron is cleared from plasma by a passive, saturable transport process that is not regulated by the iron content of the liver and that may be shared with other transition metal ions. Because clearance is highly efficient, increased levels of non-transferrin-bound iron in plasma may present the liver with an obligatory iron load resulting in progressive accumulation and toxicity.     

Effect of human serum and some of its components on neutrophil adherence and migration across an epithelium

The effect of human serum and some of its components on the process of transepithelial migration of human neutrophils was investigated in an in vitro system. 10% autologous serum caused an increase in neutrophil adherence to and migration across canine kidney epithelial cells. This increase in neutrophil binding also occurred if the epithelium but not the neutrophils had been preincubated with serum. The binding was lost if the serum was either preabsorbed over the kidney epithelium before use or heat inactivated. Indirect immunofluorescence studies indicated that IgG, IgM, and a component of C3 bound to the epithelial surface, whereas IgA, IgE, or C5a were not detectable. The majority of epithelial cells were immunofluorescent, however epithelial cells with varying degrees of reactivity were also apparent and approximately 5% of the epithelial cells did not bind IgG, IgM, and C3. When epithelia were simultaneously tested for the presence of either IgG, IgM, or C3, and bound neutrophils the few epithelial cells which did not bind IgG or IgM also did not bind C3 or neutrophils. Studies with monoclonal antibodies against Fc and C3 receptors indicate that neutrophil adherence to the epithelial surface was mediated predominately by the receptors for C3b and C3bi. In response to a chemotactic gradient, bound neutrophils were able to detach and migrate across the epithelium. A separate heat-stable factor(s) in serum was able to increase neutrophil migration across the epithelial monolayer. This factor acted independently of the factors which caused the increase in neutrophil binding as the increase in neutrophil migration also occurred under conditions (preabsorption over the kidney epithelium or heat inactivation) that prevented the increase in neutrophil binding. The increase in neutrophil migration may be caused by the permeability-increasing properties of this factor as both serum and heat-inactivated serum lowered the transepithelial electrical resistance an average of 38 and 35%, respectively, in 40 min. Upon removal of serum or heat-inactivated serum, the resistance returned 100 and 81%, respectively, in 5 h.     

The effect of starvation on RNA: DNA ratios and growth of larval striped bass, Morone saxatalis

Hatchery reared larval striped bass, Morone saxatilis , 8-days-post-hatching were subjected to various feeding/starvation regimes over a period of 14 days.
Batches of larvae from each treatment were sampled over the 14-day period and subdivided for determination of notochord length and RNA:DNA ratio. The best growth was found in fully fed F1000 larvae (exposed to 1000 Artermia nauplii l⁻¹), which reached 8.2 mm after 11 days and 9.6 mm after 14 days. Starved animals after 11 days had notochord lengths of 4.9 mm. Growth curves from feeding-delayed larvae indicated that animals fed after up to 5 days starvation were capable of complete recovery. F100 larvae (exposed to 100 Anemia nauplii 1^−l) had a slower growth rate than F1000 larvae, reaching a notochord length of 7.3 mm after 14 days. RNA:DNA ratios over time closely followed notochord growth curves, with clear differences between starved, F100 and F1000 larvae being established after only 2 days. Equilibrium RNA:DNA ratios of 3.0 and 2.25 were established in F1000 and F100 larvae, respectively, 6.8 days after the beginning of the experiment. The average lag time between a change from the starved to the fed condition and a change in RNA:DNA ratio as determined by the divergence of the nucleic acid curve from the starved condition was 0.66 days.
In treatments where starvation followed various periods of feeding, larvae regressed in notochord length such that the final length at 14 days reflected the degree of feeding. RNA:DNA ratios in these animals again closely followed growth curves with a lag time of 0.81 days.
It was concluded that RNA:DNA ratios provided very accurate indices of growth in striped bass larvae which were highly sensitive to feeding status.