Involvement of aquaporin in thromboxane A2 receptor-mediated, G12/13/RhoA/NHE-sensitive cell swelling in 1321N1 human astrocytoma cells

The physiological role of the thromboxane A₂ (TXA₂) receptor expressed on glial cells remains unclear. We previously reported that 1321N1 human astrocytoma cells pretreated with dibutyryl cyclic AMP (dbcAMP) became swollen in response to U46619, a TXA₂ analogue. In the present study, we examined the detailed mechanisms of TXA₂ receptor-mediated cell swelling in 1321N1 cells. The cell swelling caused by U46619 was suppressed by expression of p115-RGS, an inhibitory peptide of Gα_12/13 pathway and C3 toxin, an inhibitory protein for RhoA. The swelling was also inhibited by treatment with Y27632, a Rho kinase inhibitor and 5-(ethyl-N-isopropyl)amiloride (EIPA), a Na⁺/H⁺-exchanger inhibitor. Furthermore, cell swelling was suppressed by the pretreatment with aquaporin inhibitors mercury chloride or phloretin in a concentration-dependent manner, suggesting that aquaporins are involved in U46619-induced 1321N1 cell swelling. In fact, U46619 caused [³H]H₂O influx into the cells, which was inhibited by p115-RGS, C3 toxin, EIPA, mercury chloride and phloretin. This is the first report that the TXA₂ receptor mediates water influx through aquaporins in astrocytoma cells via TXA₂ receptor-mediated activation of Gα_12/13, Rho A, Rho kinase and Na⁺/H⁺-exchanger.     

RNA-Induced Interference with Animal Virus Infection

Some RNAs, including both single- and double-stranded RNAs, when incubated with chick embryo cell culture induce cellular resistance against viruses. Evidence was now obtained indicating that the induction of cellular resistance by RNA depends on the cellular metabolic activity, especially on the synthesis of cellular RNA and protein. Thus, inhibitors of RNA and protein synthesis, actinomycin D and cycloheximide, were found to inhibit the development of an antiviral state when added before, or during the relatively early period of, incubation of the cells with RNA. In the course of induction of cellular resistance, three stages may be distinguished, the priming stage, the developing stage, and the established resistant stage.     

Humans but Not Chimpanzees Vary Face-Scanning Patterns Depending on Contexts during Action Observation

Human and nonhuman primates comprehend the actions of other individuals by detecting social cues, including others’ goal-directed motor actions and faces. However, little is known about how this information is integrated with action understanding. Here, we present the ontogenetic and evolutionary foundations of this capacity by comparing face-scanning patterns of chimpanzees and humans as they viewed goal-directed human actions within contexts that differ in whether or not the predicted goal is achieved. Human adults and children attend to the actor’s face during action sequences, and this tendency is particularly pronounced in adults when observing that the predicted goal is not achieved. Chimpanzees rarely attend to the actor’s face during the goal-directed action, regardless of whether the predicted action goal is achieved or not. These results suggest that in humans, but not chimpanzees, attention to actor’s faces conveying referential information toward the target object indicates the process of observers making inferences about the intentionality of an action. Furthermore, this remarkable predisposition to observe others’ actions by integrating the prediction of action goals and the actor’s intention is developmentally acquired.     

Electrophoretic Studies on Plant Protoplasts I. pH Dependence of Zeta Potentials of Protoplasts from Various Sources

Electrophoretic mobilities of plant protoplasts from varioussources were measured, as a function of the pH of the medium,by a micro-electrophoresis technique to characterize the protoplastsin terms of curves of zeta potential vs. protoplast surfacepH (pH_s). The shape of the curves of zeta potential vs. pH_scurves differed among preparations of protoplasts isolated fromvarious species and strains. The isoelectric points (pI) ofthe protoplasts measured in this study were between 3.0 and4.0. These differences among the protoplasts suggest that itmay be possible to develop an electrophoretic method for theselection of protoplasts. The shape of the curves of zeta potentialvs. pH_s also indicated that carboxyl groups, as well as phosphategroups, may contribute to the negative charges on the surfaceof protoplasts. (Received October 14, 1988; Accepted February 22, 1989)     

Revision of the theory of phototropism in plants: a new interpretation of a classical experiment

Went's classical experiment on the diffusion of auxin activity from unilaterally illuminated oat coleoptile tips (Went 1928), was repeated as precisely as possible. In agreement with Went's data with theAvena curvature assay, the agar blocks from the illuminated side of oat (Avena sativa L. cv. Victory) coleoptile tips had, on an average, 38% of the auxin activity of those from the shaded side. However, determination of the absolute amounts of indole-3-acetic acid (IAA) in the agar blocks, using a physicochemical assay following purification, showed that the IAA was evenly distributed in the blocks from the illuminated and shaded sides. In the blocks from the shaded and dark-control halves the amounts of IAA were 2.5 times higher than the auxin activity measured by theAvena curvature test, and in those from the illuminated half even 7 times higher. Chromatography of the diffusates prior to theAvena curvature test demonstrated that the amounts of two growth inhibitors, especially of the more polar one, were significantly higher in the agar blocks from the illuminated side than in those from the shaded side and the dark control. These results show that the basic experiment from which the Cholodny-Went theory was derived, does not justify this theory. The data rather indicate that phototropism is caused by the light-induced, local accumulation of growth inhibitors against a background of even auxin distribution, the diffusion of auxin being unaffected.Abbreviation IAA indole-3-acetic acid     

Expression of lipoprotein lipase gene in combined lipase deficiency

The expression of the gene for lipoprotein lipase (LPL) was studied in brown adipose tissue and the liver of combined lipase deficient (cld/cld) and unaffected mice. The mRNA specific for LPL was detected in both animals. Although the size of LPL mRNA in cld mice was similar to that of unaffected mice, the mRNA concentration in affected animals was higher than in unaffected animals. We also studied the LPL gene mutation in cld mice by Southern blot analysis. No restriction fragment length polymorphisms were observed after digestion with 16 endonucleases. These data indicate that there is no gene insertion or deletion, but do not exclude the possibility of point mutation in the LPL structural gene. However, the present results agree with the hypothesis that the genetic defect in cld is not due to a mutation in the LPL structural gene, but instead involves the defective post-translational processing of LPL or defective cellular function affecting transport and secretion of this enzyme group.     

A case of sporotrichosis caused by two genetically differentSporothrix schenckii strains

A survey for the natural occurrence of Fusarium mycotoxins, deoxynivalenol (DON), nivalenol (NIV) and zearalenone (ZEN), in Dutch cereals (totaling 29 samples) harvested in 1984/1985, showed that 90%, 79% and 62% of samples were contaminated with DON, NIV and ZEN, respectively. Average contents (ng/g) in the total of positive samples were 221 (DON), 123 (NIV) and 61 (ZEN). Among the cereals examined, the highest concentrations (ng/g) was 3198 (DON), 1875 (NIV) and 677 (ZEN) in a yellow corn sample for animal feed. The results of this survey show that Dutch cereals were relatively significantly contaminated with Fusarium mycotoxins.     

Analysis of restriction profiles of Mitochondrial DNA from Sporothrix schenckii and related fungi

Restriction profiles by HaeIII of mitochondrial DNA were studied for classification and distinction of Sporothrix schenckii (100 strains), S. schenckii var. luriei (1), S. curviconia (1), S. inflata (7), Ceratocystis stenoceras (17) and C. minor (7). These 6 species showed unique restriction profiles which could be discriminated from each other. S. schenckii was further separable into 11 types, S. inflata into 4 types, C. stenoceras into 4 types and C. minor into 7 types based on restriction profile heterogeneity.     

A novel IgA protease from Clostridium sp. capable of cleaving IgA1 and IgA2 A2m(1) but not IgA2 A2m(2) allotype paraproteins

Three bacterial strains of Bifidobacterium and Clostridium sp. from patients with inflammatory bowel disease (I.B.D.) and Streptococcus pneumoniae from a patient with pneumonia were identified to produce extracellular proteases cleaving IgA into Fab and Fc fragments. Although the proteases from the Bifidobacterium and the Streptococcus pneumoniae showed the characteristics of typical IgA1 proteases, cleaving the IgA of only the IgA1 subclass, the protease from Clostridium sp. revealed a dual substrate specificity, in that it cleaved both IgA1 and IgA2 of the A2m(1) allotype. The latter protease, however, did not show any activity with respect to the IgA2 of the A2m(2) allotype. Fc fragments isolated from the IgA1 and the IgA2 A2m(1) by digestion with the Clostridium sp. protease were identified to have an identical amino terminal residue of valine. The site of cleavage in both the alpha 1 and the alpha 2 of A2m(1) by the protease was assumed to be an identical peptide bond at Pro(221)-Val(222), which is a common one present just before the hinge of both the alpha 1 and the alpha 2 of the A2m(1) but not of the alpha 2 of the A2m(2). The protease was sensitive to ethylene-diamino tetraacetic acid, a chelating agent, similar to other already reported IgA1 proteases.     

Clostridium ramosum, an IgA protease-producing species and its ecology in the human intestinal tract

A bacterial strain isolated from feces of a patient with ulcerative colitis, which had been shown to produce a novel immunoglobulin A (IgA) protease (cleaving both the human IgA1 subclass and IgA2 subclass of A2m(1) allotype) extracellularly, was identified as Clostridium ramosum. By using a selective medium (propionate-rifampicin-gentamicin-colimycin-polymyxin medium) devised for C. ramosum, analysis of the population level of this organism was performed to determine its ecology in the human intestinal tract. C. ramosum was isolated in 20 of 25 fecal samples (80%) from patients with inflammatory bowel disease (I.B.D.) and in 112 of 135 samples (83%) from patients without I.B.D. (control group). C. ramosum was also isolated from 6 of 11 biopsy samples (55%) of the inflamed rectal mucosa from patients with ulcerative colitis and from five of 15 samples (33%) from the intact mucosa of the control group. The population levels of C. ramosum in most of the biopsy samples ranged from 2.3 to 5.0 log10 per gram. The IgA protease-positive C. ramosum was found in only four of 135 fecal samples (3%) and one of 15 biopsy samples (6.7%) from the control group. These results indicate that IgA protease-positive C. ramosum is not likely to play a role in the induction of I.B.D., unless the organism is first isolated from the patient with I.B.D.