The effect of an interleukin receptor antagonist (IL-1ra) on colonocyte eicosanoid release

We investigated whether an interleukin 1 receptor antagonist (IL-1ra) altered cellular release of prostanoids and leukotrienes in a transformed colonic cell line (CACO-2) in the presence of proinflammatory stimuli. Cellular inflammation was induced by treatment with lipopolysaccharide (LPS) or the cytokine, interleukin 1 beta (IL-1(beta)). In a separate set of experiments, cells were pretreated with IL-1ra prior to exposure to LPS or IL-1(beta). Prostaglandin E(2) and leukotriene B(4) (LTB(4)) levels were quantified by ELISA assays. Both LPS and IL-1(beta) exposure were noted to stimulate cellular PGE(2) release, a response which was significantly inhibited by IL-1ra treatment. Either stimulant when administered alone failed to stimulate release of LTB(4). When administered after IL-1ra pretreatment however, both stimuli caused a significant increase in LTB(4) release. These results suggest that a cytokine receptor antagonist can selectively influence eicosanoid production in this cell line. Furthermore, this study suggests that a IL-1ra may have a future clinical role in the treatment of inflammatory disorders of the colon which are intimately linked to enhanced eicosanoid synthesis.     

On the analytic solution of electrotonic spread in branched passive dendritic trees

From the classical work of Rall it is known that the spread of electric potential in a passive dendritic tree may be obtained by expressing the initial conditions as a linear combination of a set of trigonometric eigenfunctions, each decaying with the associated time constant. It is shown here that in order to evaluate the permissible parameters in these eigenfunctions one may formulate the boundary conditions at all the junctions and endings of the dendritic tree as a set of homogeneous linear equations in which the parameters in the eigenfunctions are the unknowns. These equations have a nontrivial solution if the relevant determinant vanishes, a condition that permits the evaluation of the various parameters, thus providing an analytic approach to the expression of the eigenfunctions as well as the decay time constants. The above approach is illustrated by application to a dendritic tree that has a parent segments and two generations of offspring segments, without any restrictions as to the relative diameters or lengths of the various segments in the tree. General properties of the tree may be readily derived, like the variation of the eigenvalues on scaling of the lengths or diameters of all the segments. A few special cases with specified dimensions of the various segments are derived from the general case. In the case of a dendritic tree that fulfills the equivalent cylinder conditions, all of the eigenvalues and eigefunctions of the tree may be determined by the proposed method, including those that do not apply to the equivalent cylinder. The orthogonality properties of the eigenfunctions are discussed.     

Overlaps and parallels in the regulation of intrinsic multiple-antibiotic resistance in Escherichia coli

Chromosomally encoded systems present in a variety of bacteria appear to play a central role in determining the intrinsic level of resistance to many commonly used antibiotics. Work with the Gram-negative bacterium Escherichia coli has shown that there is significant similarity at the amino acid sequence level among the structural components of these resistance systems as well as among their genetic regulators. This review describes two of the better-studied regulatory systems, marRAB and soxRS, as well as two regulated multidrug-efflux systems, encoded by emrAB and acrAB, and focuses on conserved themes in their primary structures and environmental stimuli. The observed resistance to clinically important antibiotics appears to reflect an overlap with broad-ranged adaptive responses by free-living bacteria to noxious plant materials in their natural environment.     

Influence of endurance exercise performance on hemodynamic and hormonal responses to lower body negative pressure (LBNP) and +Gz tolerance in the aspect of individual sensitivity to motion sickness

A possible relationship between endurance exercise training, susceptibility to motion sickness, and orthostatic tolerance was investigated. Male subjects underwent acceleration tolerance tests, lower body negative pressure, and Coriolis tests. During the experimental protocol, hemodynamic parameters were measured including heart rate, stroke volume, blood pressure, and cardiac output, and blood was drawn and analyzed for various hormones. Specific results are presented and discussed.     

The Role of Pea Chloroplast [alpha]-Glucosidase in Transitory Starch Degradation

Pea chloroplastic [alpha]-glucosidase (EC 3.2.1.20) involved in transitory starch degradation was purified to apparent homogeneity by ion exchange, reactive dye, hydroxylapatite, hydrophobic interaction, and gel filtration column chromatography. The native molecular mass and the subunit molecular mass were about 49.1 and 24.4 kD, respectively, suggesting that the enzyme is a homodimer. The enzyme had a Km of 7.18 mM for maltose. The enzyme's maximal activity at pH 7.0 and stability at pH 6.5 are compatible with the diurnal oscillations of the chloroplastic stromal pH and transitory starch accumulation. This pH modulation of the [alpha]-glucosidase's activity and stability is the only mechanism known to regulate starch degradative enzymes in leaves. Although the enzyme was specific for the [alpha]-D-glucose in the nonreducing end as the glycon, the aglycon moieties could be composed of a variety of groups. However, the hydrolysis rate was greatly influenced by the aglycon residues. Also, the enzyme could hydrolyze glucans in which carbon 1 of the glycon was linked to different carbon positions of the penultimate glucose residue. The ability of the [alpha]-glucosidase to hydrolyze [alpha]-1,2- and [alpha]-1,3-glucosidic bonds may be vital if these bonds exist in starch granules because they would be barriers to other starch degradative enzymes. This purified pea chloroplastic [alpha]-glucosidase was demonstrated to initiate attacks on native transitory chloroplastic starch granules.     

Magnesium Adenosine 5[prime]-Triphosphate-Energized Transport of Glutathione-S-Conjugates by Plant Vacuolar Membrane Vesicles

By characterization of the uptake of glutathione-S-conjugates, principally dinitrophenyl-S-glutathione (DNP-GS), by vacuolar membrane vesicles, we demonstrate that a subset of energy-dependent transport processes in plants are not H+-coupled but instead are directly energized by MgATP. The most salient features of this transport pathway are: (a) its specific, obligate requirement for MgATP as energy source; (b) the necessity for hydrolysis of the [gamma]-phosphate of MgATP for uptake; (c) the insensitivity of uptake to uncouplers of the transtonoplast H+ gradient (carbonylcyanide 4-trifluoromethoxyphenylhydrazone, gramicidin-D, and NH4Cl); (d) its pronounced sensitivity to vanadate and partial inhibition by vinblastine and verapamil; (e) the lack of chemical modification of DNP-GS either during or after transport; (f) the capacity of S-conjugates of chloroacetanilide herbicides, such as metolachlor-GS, but not free herbicide, to inhibit uptake; and (g) the ability of vacuolar membrane vesicles purified from a broad range of plant species, including Arabidopsis, Beta, Vigna, and Zea, to mediate MgATP-dependent, H+-electrochemical potential difference-independent DNP-GS uptake. On the basis of these findings it is proposed that the transport of DNP-GS across the vacuolar membrane of plant cells is catalyzed by a glutathione-conjugate transporter that directly employs MgATP rather than the energy contained in the transtonoplast H+-electrochemical potential difference to drive uptake. The broad distribution of the vacuolar DNP-GS transporter and its inhibition by metolachlor-GS are consistent with the notion that it plays a general role in the vacuolar sequestration of glutathione-conjugable cytotoxic agents.     

Tagging and mapping the thermo-sensitive genic male-sterile gene in rice (Oryza sativa L.) with molecular markers

The thermo-sensititve genic male-sterile (TGMS) gene in rice can alter fertility in response to temperature and is useful in the two-line system of hybrid rice production. However, little is known about the TGMS gene at the molecular level. The objective of this study was to identify molecular markers tightly linked with the TGMS gene and to map the gene onto a specific rice chromosome. Bulked segregant analysis of an F₂ population from 5460s (a TGMS mutant line) x Hong Wan 52 was used to identify RAPD markers linked to the rice TGMS gene. Four hundred RAPD primers were screened for polymorphisms between the parents and between two bulks representing fertile and sterile plants; of these, 4 primers produced polymorphic products. Most of the polymorphic fragments contained repetitive sequences. Only one singlecopy sequence fragment was found, a 1.2-kb fragment amplified by primer OPB-19 and subsequently named TGMS1.2. TGMS1.2 was mapped on chromosome 8 with a RIL population and confirmed by remapping with a DHL population. Segregation analysis using TGMS1.2 as a probe indicated that TGMS1.2 both consegregated and was lined with the TGMS gene in this population. It is located about 6.7 cM from the TGMS gene. As TGMS1.2 is linked to the TGMS gene, the TGMS gene must be located on chromosome 8.This research was supported by the Rockefeller Foundation and China National High-Tech Research and Development Program. The first author is a Rockefeller Career Fellow at Texas Tech University     

Pollen fertility restoration by nuclear gene Fr in CMS common bean: an Fr linkage map and the mode of Fr action

The Fr gene in common bean, Phaseolus vulgaris L., is a unique gene for the study of plant nuclear-mitochondrial interactions because it appears to directly influence plant mitochondrial genome structure, resulting in the restoration of pollen fertility in cytoplasmic male sterile plants. This gene action is distinct from other pollen fertility restoration systems characterized to date. As a first step towards the map-based cloning of this unusual nuclear gene, we identified RAPD markers linked to Fr using bulked segregant analysis of near-isogenic lines. Using DNA gel blot hybridization, we localized the identified RAPD markers to a linkage group on the common bean RFLP map and constructed a linkage map of the Fr region using both RAPD markers and RFLP markers. Analysis of the mode of Fr action with the aid of identified Fr-linked DNA markers indicated that Fr functions in a semidominant fashion, showing dosage effect in controlling the dynamics of a heteroplasmic mitochondrial population. We also present our observations on the developmental distinctions, crucial in the accurate mapping of the Fr gene, between spontaneous cytoplasmic reversion and Fr-driven fertility restoration, two phenomena that are phenotypically indistinguishable.     

Sex chromosome complement and developmental diversity in pre-and post-hatching porcine embryos

To examine sex and development relationships in porcine embryos in early gestation, 10 gilts were killed on Day 4, 5, or 6 post mating (first day of standing estrus = Day 0). Embryos recovered immediately after slaughter were cultured in Medium 199 with colcemid (0.05mug/ml), fixed on slides, and stained with 4% Giemsa. The number of cells in each specimen was counted from the slides, and, whenever cell dispersion allowed, sex was determined by presence or absence of the Y-chromosome in at least 2 spreads from each embryo. Three gilts slaughtered on Day 4 yielded 2- and 4-cell stage embryos (n = 38), but no data on sex could be obtained due to lack of mitosis or readable metaphase spreads. Three Day 5 litters had individual specimens ranging from 8 to 14 cells (n = 8), 32 to 64 cells (n = 10), and 13 to 31 cells (n = 11), with the sex determined in 15 of these. Cell numbers ranged from 18 to 165 (n = 14), 16 to 32 (n = 9), 36 to 82 (n = 12), and 16 to 30 (n = 9) in the 4 gilts slaughtered on Day 6, with the sex determined in 26 of these. Embryos within each litter were divided into low, medium and high cell numbers by 3 equal divisions of the range of cell numbers. Three Day-5 embryos and 1 Day-6 embryo were lost during preparation; neither the cell numbers nor the sex could be determined in 4 Day-5 and in 3 Day-6 embryos. The overall sex ratio approximated 1:1, but on Day 5, the ratios for males to females were 0:5, 1:3 and 6:0 for the low, medium and high cell number groups, respectively. Embryos of undetermined sex in these same groups numbered 3, 1 and 3, respectively. On Day 6 the distribution was 1:11, 4:2 and 8:0 in favor of the males, while embryos of undetermined sex in the low, medium and high cell number groups numbered 5, 7 and 2, respectively. Chi-square analysis of the combined Day-5 and Day-6 results indicated the presence of significantly more females among embryos with low cell numbers and more males in the high cell number group (P < 0.01).