The differential effects of PGE on the immune response in normal and immunosuppressed mice

The effect of 16,16-dimethyl-PGE₂-methyl ester (di-M-PGE₂) on humoral and cellular immunoresponsiveness has been compared in normal mice and in mice immunosuppressed by splenectomy and thymectomy plus antithymocyte serum (ATS). Splenectomy resulted in immunosuppression manifested by augmentation of B-16 melanoma growth; this stimulatory effect was reversed by di-M-PGE₂. In animals immunosuppressed by thymectomy plus ATS, di-M-PGE₂ augmented the humoral and cellular immune responses; this was manifested by slowing of the growth of B-16 melanoma and by stimulating the number of plaque-forming cells, hemagglutinin titers, and delayed-hypersensitivity reactions to sheep erythrocytes. In contrast, in normal (nonthymectomized) mice, di-M-PGE₂ was mildly immunosuppressive. Finally, adriamycin-immunosuppressed normal mice and this suppression were reversed by the addition of di-M-PGE₂ to the treatment regimen.     

Inverse modification of antibody responsiveness to RGG in lines of mice selected for high or low responses to somatic antigen of Salmonella

High (H/s) and low (L/s) antibody responder lines of mice selected according to their response to the somatic (s) antigen of Salmonella (Selection IV) have unexpected inverse capacity for antibody production to rabbit gamma globulin (RGG): H/s mice are low or even nonresponders to this antigen, whereas L/s mice are high responders. It was shown that the phenotypic variability within each line is due to environmental factors. RGG was a selection antigen in Selection V; the high (H/p) and low (L/p) responder mice are therefore considered as homozygous for the RGG genes. Responsiveness to RGG was investigated in F₁ and F₂ hybrids obtained by crossing the phenotypically similar RGG responder or nonresponder mice of Selections IV and V. The results support the hypothesis that the same genes control the response to RGG in L/s and H/p lines as well as in H/s and L/p lines. This means that the genes specific for RGG responsiveness were independent from those regulating responses to the s antigen. Unaffected by the selective breeding in Selection IV, they have been fixed by chance in an inverse way in H/s and L/s lines.     

Ca2+o-Independent Veratridine-Evoked Acetylcholine Release from Striatal Slices Is Not Inhibited by Vesamicol (AH5183): Mobilization of Distinct Transmitter Pools

The effect of 2-(4-phenylpiperidino)cyclohexanol (AH5183 or vesamicol), a compound known to block the uptake of acetylcholine (ACh) into cholinergic synaptic vesicles, on the release of endogenous and [14C]ACh from slices of rat striatum was investigated. ACh release was evoked either by electrical stimulation or by veratridine. The effect of electrical stimulation was entirely dependent on external Ca2+. By contrast, veratridine (40 microM) also enhanced ACh release in the absence of Ca2+. Indeed, with veratridine two components were clearly distinguished: one dependent on external Ca2+ and the other not. Vesamicol inhibited [14C]ACh release evoked by both veratridine and electrical stimulation in the presence of external Ca2+, provided it was added to the tissue prior to loading with [14C]choline. With the same treatment vesamicol only slightly affected the release of endogenous ACh. Under the same conditions the Ca2(+)-independent [14C]ACh release evoked by veratridine was not prevented by vesamicol. The differential responsiveness to vesamicol suggests that ACh pools involved in Ca2+o-dependent ACh release are different from those mobilized during Ca2+o-independent ACh release.     

Endoglin is a component of the transforming growth factor-beta receptor system in human endothelial cells.

Endoglin, a dimeric membrane glycoprotein expressed at high levels on human vascular endothelial cells, shares regions of sequence identity with betaglycan, a major binding protein for transforming growth factor-beta (TGF-beta) that co-exists with TGF-beta receptors I and II in a variety of cell lines but is low or absent in endothelial cells. We have examined whether endoglin also binds TGF-beta and demonstrate here that the major TGF-beta 1-binding protein co-existing with TGF-beta receptors I and II on human umbilical vein endothelial cells is endoglin, as determined by specific immunoprecipitation of endoglin affinity-labeled with 125I-TGF-beta. Furthermore, endoglin ectopically expressed in COS cells binds TGF-beta 1. Competition affinity-labeling experiments showed that endoglin binds TGF-beta 1 (KD approximately 50 pM) and TGF-beta 3 with high affinity but fails to bind TGF-beta 2. This difference in affinity of endoglin for the TGF-beta isoforms is in contrast to beta-glycan which recognizes all three isoforms. TGF-beta however is binding with high affinity to only a small fraction of the available endoglin molecules, suggesting that some rate-limiting event is required to sustain TGF-beta binding to endoglin.     

Assessment of genetic diversity and population structure of Xanthomonas oryzae pv. oryzae with a repetitive DNA element.

A repetitive DNA element cloned from Xanthomonas oryzae pv. oryzae was used to assess the population structure and genetic diversity of 98 strains of X. oryzae pv. oryzae collected between 1972 and 1988 from the Philippine Islands. Genomic DNA from X. oryzae pv. oryzae was digested with EcoRI and analyzed for restriction fragment length polymorphisms (RFLPs) with repetitive DNA element as a probe. Twenty-seven RFLP types were identified; there was no overlap of RFLP types among the six races from the Philippines. Most variability (20 RFLP types) was found in strains of races 1, 2, and 3, which were isolated from tropical lowland areas. Four RFLP types (all race 5) were found among strains isolated from cultivars grown in the temperate highlands. The genetic diversity of the total population of X. oryzae pv. oryzae was 0.93, of which 42% was due to genetic differentiation between races. The genetic diversities of strains collected in 1972 to 1976, 1977 to 1981, and 1982 to 1986, were 0.89, 0.90, and 0.92, respectively, suggesting a consistently high level of variability in the pathogen population over the past 15 years. Cluster analysis based on RFLP banding patterns showed five groupings at 85% similarity. The majority of strains from a given race were contained within one cluster, except for race 3 strains, which were distributed in three of the five clusters.     

Partial intercalation with DNA of peptides containing two aromatic amino acids

The interactions with DNA of tetrapeptide amides containing lysine at the N-terminal position and aromatic amino acids at the second and fourth positions (Ala at position three), 1-6, have been investigated by nmr, CD, and viscometric methods. Tetrapeptides with N-terminal lysine and a single aromatic amino acid, 7-10, were investigated as controls. Significant decreases in DNA viscosity occurred on addition of 7, with the aromatic group at the second position, but not with any of the other single aromatic amino acid peptides. All of the tetrapeptides with two aromatic groups caused DNA viscosity decreases which were two to three times larger than with 7. Peptides with p-nitrophenylalanine (p-NO2Phe) as the aromatic group were synthesized for nmr studies because of its simpler aromatic nmr spectrum relative to Phe. Large upfield shifts of the aromatic proton signals were obtained when the amino acid in the second position was L-p-NO2Phe, and the fourth position contained either p-NO2Phe or Phe. Such peptides also caused the largest DNA viscosity decreases on complex formation. Smaller upfield shifts of the aromatic signals were obtained when the amino acid in the second position was L-Phe or a D isomer of Phe or p-NO2Phe. With all peptides, larger upfield nmr shifts were obtained with heat-denatured, recooled DNA than with native DNA under the same conditions. As with nmr, CD results are quite different for the peptides with L and D amino acids at the second position. All of the results can be interpreted in terms of a model in which lysine interacts stereospecifically with the backbone in a DNA double helix and the aromatic group at the second position stacks strongly with the base pairs when the amino acid is an L isomer. The aromatic group at the fourth position can also interact with the base pairs, but primarily through a sideways stacking of the aromatic group with base pairs for either L or D isomers. Because of covalent constraints on the separation distance for the two aromatic groups in the tetrapeptides, they must stack on opposite sides of the same base pair in violation of the neighbor exclusion principle observed with classical intercalators. This stacking at the same base pair no doubt accounts for the larger viscosity decreases in DNA with the peptides containing two aromatic groups relative to those with a single aromatic group.(ABSTRACT TRUNCATED AT 400 WORDS)     

Destruction and reconstitution of the dictyosome in the chrysophycean flagellate,Poterioochromonas malhamensis,after heat-shock,and other heat-shock effects

Summary The viability of the chrysophycean flagellate,Poterioochromonas malhamensis, was examined after treatment of the cells with high temperatures. The fine structure of the cells was studied after heat-shock (42 °C, 16 minutes). Heat injury effects are visible at the nucleus, the chloroplast (distortion of the thylakoids), the mitochondria (increased occurrence of matrical crystalline inclusions) and, especially, at the dictyosome which is completely destroyed into some single vesicles and remnants of cisternae. Most damages are repaired within one hour; the reconstitution of the dictyosome takes 3–6 hours. It is inhibited severely by actinomycin D.The effect on the dictyosome reflects its labile position in the endomembrane system. The dependence of its reconstitution on protein synthesis indicates that membrane components are destroyed by the heat-shock.     

Associations between membranes and microtubules during mitosis and cytokinesis in caulonema tip cells of the mossFunaria hygrometrica

Summary The interphase nucleus in theFunaria caulonema tip cells is associated with many non-cortical microtubules (Mts). In prophase, the cortical Mts disappear in the nuclear region; in contrast to moss leaflets, a preprophase band of Mts is not formed in the caulonema. The Mts of the early spindle are associated with the fragments of the nuclear envelope. Remnants of the nucleolus remain in the form of granular bodies till interphase. The metaphase chromosomes have distinct kinetochores; the kinetochore Mts are intermingled with non-kinetochore Mts running closely along the chromatin. Each kinetochore is associated with an ER cisterna. ER cisternae also accompany the spindle fibers in metaphase and anaphase. In telophase, Golgi vesicles accumulate in the periphery of the developing cell plate where no Mts are found. The reorientation of the cell plate into an oblique position can be inhibited by colchicine. It is concluded that the ER participates in controlling the Mt system, perhaps via calcium ions (membrane-bound calcium ions have been visualized by staining with chlorotetracycline) but that, on the other hand, the Mt system also influences the distribution of the ER. The occurrence and function of the preprophase band of Mts is discussed.