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.     

Monoamine Neurotransmitter Metabolism and Locomotor Activity During Chemical Hypoxia

The effects of hypoxia on metabolism of 5-hydroxytryptamine (5-HT or serotonin) and 3,4-dihydroxyphenylethylamine (DA or dopamine) were compared with those on open-field activity in male CD-1 mice. Chemical hypoxia was induced with NaNO2. Hypoxia did not alter striatal concentrations of DA, 5HT, Trp, Tyr, 5-hydroxyindoleacetic acid, or homovanillic acid. However, NaNO2 (75 mg/kg) reduced the rates of conversion of [3H]Tyr to [3H]DA (-41%) and [3H]Trp to [3H]5-HT (-39%). Hypoxia also reduced dihydroxyphenylacetic acid (DOPAC) levels (-27%) and DOPAC/DA ratios (-20%). Open-field behavior, as measured in an automated activity monitor, decreased in a dose-dependent fashion with 75-150 mg/kg of NaNO2 (-35 to -90%). Comparison with previous studies suggests that the syntheses of dopamine, serotonin, and the amino acids are equally vulnerable to hypoxic insults but may be less sensitive than the synthesis of acetylcholine.     

Identification and localization of pre-s-encoded polypeptides from woodchuck and ground squirrel hepatitis viruses.

A segment from the pre-s region of the woodchuck hepatitis virus (WHV) was inserted into an open reading frame vector allowing for the expression in Escherichia coli of viral determinants as part of a fusion protein. The bacterially synthesized fusion molecule contained eight amino acids from beta-galactosidase (beta-gal) at the N terminus, followed by 89 pre-s-encoded amino acids and 219 amino acids of chloramphenicol acetyltransferase (CAT) at the C terminus (beta-gal:pre-s:CAT). This tribrid protein was used to generate antiserum which had a significant titer to the viral portion of the fusion polypeptide. Anti-beta-gal:pre-s:CAT was used in Western blot analysis to identify viral proteins containing pre-s-encoded determinants. Antiserum to the tribrid molecule recognized four WHV polypeptides with molecular masses of 33, 36, 45, and 47 kilodaltons, each of which was also recognized by a monoclonal antibody to WHV surface antigen. Using the same anti-tribrid serum, we also identified analogous polypeptides from ground squirrel hepatitis virus. The antiserum was also used to immunoprecipitate virus particles containing endogenous DNA polymerase activity, indicating that pre-s determinants are found on the surface of mature virions. Based on previous computer studies and the location of pre-s-encoded molecules on the surface of virus particles, a role in hepadnavirus host cell entry is suggested for these polypeptides.     

Membrane and cytoplasmic resistivity properties of normal and sickle red blood cells

The cytoplasmic resistivities and membrane breakdown potentials of normal (AA), sickle-cell-trait (AS), and sickle (SS) red blood cells have been measured by the biophysical methodology of resistive pulse spectroscopy over a range of osmolalities. At isotonicity, the average membrane breakdown potentials are virtually identical for the three types of cells occurring at about 1150 V/cm. Average isotonic cytoplasmic resistivities are somewhat higher for the SS cells (166.7±7.49 ohm-cm) compared to the AA (147.6±1.98 ohm-cm) or AS cells (148.7±1.79 ohm-cm). As medium osmolality is varied, the differences in resistive properties become enlarged, especially at very low and very high osmolalities. At high osmolalities, both types of sickle cells show a large increase in internal resistivity compared to the normals; at low osmolality, the SS samples exhibit a distinctly different membrane breakdown characteristic, decreasing in this parameter, whereas the other two groups increase. Of the 15 SS samples tested, three displayed much higher cytoplasmic resistivities at isotonicity: 218.2±5.25 ohm-cm, compared to an average of 153.5±3.46 ohm-cm for the other 12. The relationship between these high resistivities and the subfraction of irreversibly sickled cells in the sample is discussed.     

Coupling of a loop diuretic-sensitive Na+ influx with the net loop diuretic-sensitive K+ efflux in mouse NIH 3T3 cells

Mouse 3T3 fibroblasts have a loop diuretic sensitive Na+ transport system, responsible for more than 50% of the total Na+ influx. This transport system is dependent on the simultaneous presence of all three ions; Na+, K+, (Rb+) and Cl- in the extracellular medium. The same requirement for these three ions was also found for the loop diuretic-sensitive K+ efflux. In addition, the sensitivities of Na+ influx and Rb+ efflux for the two loop diuretics, furosemide and bumetanide were found to be similar. The similar ionic requirement and sensitivity towards loop diuretics of the two fluxes, support the hypothesis, that this loop diuretic-sensitive Na+ influx in mouse 3T3 cells, is accompanied by the net loop diuretic-sensitive K+ efflux.     

Complex subcellular distributions of enzymatic markers in intestinal epithelial cells

Summary Current procedures for isolating intestinal epithelial cell surface and intracellular membranes are based on the assumption that each organelle is marked by some unique constitutent. This assumption seemed inconsistent with the dynamic picture of subcellular organization emerging from studies of membrane turnover and recycling. Therefore, we have designed an alternative fractionation which is independent ofa priori marker assignments. We subjected mucosal homogenates to a sequence of separations based on sedimentation coefficient, equilibrium density, and partitioning in aqueous polymer twophase systems. The resulting distributions of protein and enzymatic markers define a total of 17 physically and biochemically distinct membrane populations. Among these are: basal-lateral membranes, with Na,K-ATPase enriched 21-fold; brush-border membranes, with alkaline phosphatase enriched as much as 38-fold; two populations apparently derived from the endoplasmic reticulum; a series of five populations believed to have been derived from the Golgi complex; and a series of five acid phosphatase-rich populations which we cannot identify unequivocally. Each of the five enzymatic markers we have followed is associated with a multiplicity of membrane populations. Basallateral, endoplasmic reticulum, and Golgi membranes contain alkaline phosphatase at the same specific activity as the initial homogenate. Similarly, Na,K-ATPase appears to be associated branes at specific activities two-to seven-fold that of the initial homogenate.     

Coordinate release of myosin and a high molecular weight microtubule-associated protein from PC12 cytoskeletons by ATP

The association of two high molecular weight (HMW) structural proteins with the cytoskeletons of rat pheochromocytoma cells, PC12, is regulated by ATP and other nucleotides. Exposure of PC12 cytoskeletons to ATP resulted in the selective solubilization of two HMW proteins, identified as myosin and a 280 kD microtubule-associated protein. These two proteins were rapidly released from the cytoskeleton following incubation with ATP, GTP, CTP, and ADP; non-hydrolysable ATP analog caused protein release to a less marked extent. The effect of the latter two nucleotides indicated that the release of the myosin and the HMW microtubule-associated protein was likely to be the result of nucleotide-induced conformational changes in one or both proteins. Myosin and the HMW microtubule-associated proteins interact with actin in vitro in a nucleotide-sensitive manner. The present data demonstrate that similar interactions are likely to exist within the intact cytoskeleton and suggest that the associations of these structural proteins with the cytoskeleton are regulated by common mechanisms. The results also suggest that the cells may differentially regulate the stability of a subset of these structural proteins in their interactions with other cytoskeletal elements.     

Immunochemical Characterization of Pyruvate Dehydrogenase Complex in Rat Brain

Pyruvate dehydrogenase complex (PDHC) in rat brain was studied immunochemically, using antibodies against the bovine kidney PDHC, by immunoblotting, immunoprecipitation, inhibition of enzyme activity, and enzyme-linked immunoabsorbent assay (ELISA). The immunoblots showed that the antibodies bound strongly to the alpha peptide of the pyruvate dehydrogenase (E1) component, and to the dihydrolipoyl transacetylase (E2) and the dihydrolipoyl dehydrogenase (E3) components of PDHC. A similar immunoblotting pattern was observed in all eight brain regions examined. On immunoblotting of the subcellular fractions, these PDHC peptides were observed in mitochondria and synaptosomes but not in the postmitochondrial supernatants. This agrees with other evidence that brain PDHC is localized in the mitochondria. These results, together with those from sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the immunoprecipitin, also showed that the alpha E1, beta E1, and E3 peptides of rat brain PDHC are very similar in sizes to those of the bovine kidney PDHC, being 42, 36, and 58 kD, respectively. The size of the E2 peptide, 66 kD, is different from that of bovine kidney E2, 73 kD. The relative abundance of PDHC protein in nonsynaptic mitochondria was compared by enzyme activity titration and ELISA. Both methods demonstrated that the amount of PDHC antigen in the mitochondria from cerebral cortex is greater than that in the olfactory bulb mitochondria. This is consistent with the results of the activity measurement. The ELISA also showed that the PDHCs in both mitochondrial populations are antigenically similar.(ABSTRACT TRUNCATED AT 250 WORDS)     

Radiation effects on diamine oxidase activities in intestine and plasma of the rat

Diamine oxidase (DAO; EC 1.4.3.6) activity was measured in plasma and in ileal tissue homogenates prepared from male Sprague-Dawley rats euthanized at 1-15 days after acute whole-body irradiation with 14.5-MeV electrons. Animals irradiated with 1 Gy showed no diminution in plasma and ileal DAO activities through Day 13 relative to nonirradiated controls. Animals irradiated with 5, 10, and 12 Gy displayed marked declines in ileal DAO activity, with levels reaching a nadir on Day 3. This was paralleled by a decrease in plasma DAO activity in all three dose groups. Recovery of ileal and plasma DAO levels was later seen as early as Day 4 in animals irradiated with 5- and 10-Gy doses, but animals receiving 12 Gy did not survive beyond Day 3. The relationship between radiation dose and levels of plasma and ileal DAO on Day 3, the time of maximum decrease at all doses, was also investigated. Ileal DAO activity decreased almost linearly between 2 and 8 Gy. Plasma DAO activity closely paralleled the dose dependency of the ileal levels. These data suggest that plasma DAO activity might be useful as a biologic marker of intestinal epithelial injury and recovery after acute radiation exposure.     

Purine nucleoside phosphorylase synthesis and turnover in human lymphoid cells

We have studied the turnover and synthesis of purine nucleoside phosphorylase by using a polyclonal rabbit antiserum to this protein. The turnover of purine nucleoside phosphorylase was studied in the B lymphoblast cell, WI-L2, by specific immunoprecipitation of [3H]leucine-labeled proteins. The half-lives for total protein and purine nucleoside phosphorylase were 14.5 and 14.1 hr, respectively. For cells cultured in the presence of inosine the half-life of purine nucleoside phosphorylase was reduced to 11.2 hr. The synthesis of purine nucleoside phosphorylase was analyzed during phytohemagglutinin-stimulated T cell transformation by pulse labeling cells with [35S]methionine. Purine nucleoside phosphorylase synthesis increased greater than 10-fold during the first 12 hr of transformation and continued to a maximum of 30-fold. The relative rate of purine nucleoside phosphorylase labeled to total proteins was 0.04% in unstimulated T cells and increased to 0.18% 12 hr after stimulation. These studies identify some preferential synthesis of purine nucleoside phosphorylase during the early stages of T cell transformation.