The anti-inflammatory mechanism of MK-447 in rat carrageenin-induced pleurisy

Intrapleural injection of 2% λ-carrageenin caused the accumulation of exudate up to 19 hr. The rate of plasma exudation, measured by the exuded dye amounts for 20 min in the pleural cavity after intravenous injection of pontamine sky blue, showed a peak at 5 hr. Aspirin (100 mg/kg, i. p.) suppressed the dye exudation up to 5 hr, but did not at 7 hr. This inhibition coincided with the decrease of the PG and TXB₂ levels, which were measured by gas chromatography-mass spectrometry, in the pleural exudate. In _vitro experiments, MK-447, a phenolic compound, stimulates PG endoperoxide biosynthesis at lower doses and inhibits it at higher doses, acting as a tryptophan-like cofactor required by PG endoperoxide synthetase. This drug (0.3, 1.0 and 3.0 mg/kg, i. p.) suppressed the dye exudation dose-dependently up to 5 hr, but did not at 7 hr even at a higher dose, in combination with the dose-dependent decrease of the pleural level of PGE₂, which was reported to be a major PG among PGs and TXB₂ in the exudate in inducing the plasma exudation (Harada ; Prostaglandins, : 881, 1982). Thus, the anti-inflammatory action of MK-447 can be explained by inhibition of PGE₂ generation, giving no consideration to the role of oxygen-derived free radicals as a prime mediator in inflammation.     

Purification of achatin-I from the atria of the African giant snail, Achatina fulica, and its possible function.

Achatin-I previously purified from the ganglia of the African giant snail Achatina fulica was isolated from the atria of this snail. Achatin-I appeared to enhance the cardiac activity in two ways; centrally this peptide increased impulse frequency and produced spike broadening of the identified heart excitatory neuron, PON, and peripherally it enhanced amplitude and frequency of the heart beat. Achatin-I showed excitatory actions not only on the heart but on several other muscles.     

The effect of apo E secretion on lipoprotein uptake in transfected cells.

To investigate the role of apolipoprotein E (apo E) secreted by peripheral tissues in local lipoprotein metabolism, we developed a cell strain that constitutively produced and secreted apo E. A fusion plasmid containing rat apo E genomic DNA under control of mouse metallothionein promotor was constructed and transfected into Chinese hamster ovary cells. A stable transformant designated CHO-MAEII constitutively secreted rat apo E mainly in the form of sialylated free protein. The secretion was further enhanced by metal induction up to 1 micrograms apo E/ml per 12 h. When incubated with 125I-labeled very low density lipoprotein (125I-VLDL) at 37 degrees C, CHO-MAEII took up and degraded 125I-VLDL with higher affinity than control cells. Furthermore, considerable amount of methylated 125I-VLDL was degraded by CHO-MAEII, while no methylated 125I-VLDL was degraded by control cells. No significant differences were found in the uptake of 125I-LDL. The data indicated that apo E molecules secreted by CHO-MAEII were transferred to 125-VLDL particles, which caused a higher affinity of these particles for LDL receptors on the cells. It is suggested that apo E secreted from peripheral tissues enhances the uptake of lipoproteins by themselves or by surrounding cells in the local environment which demand cholesterol and express LDL receptors. CHO-MAEII was a good model for these 'auto- or paracrine-like functions' of apo E.     

Assay of alpha-cysteine proteinase inhibitor in serum or plasma

A new proteinase inhibitor has recently been found in human serum or plasma which specifically inhibits cysteine proteinases such as ficin, papain, bromelain and cathepsin B. However, serum contains alpha 2-macroglobulin which also inhibits these cysteine proteinases and, consequently, interferes with the assay of the new alpha-cysteine proteinase inhibitor. Therefore, assay of the inhibitor in serum has not been established previously. In the present method, the alpha 2-macroglobulin is inactivated by preincubating the serum in methylamine solution at 55 degrees C, while the alpha-cysteine proteinase inhibitor retains its activity. The inhibitory power against cysteine proteinases is found to be due mainly to this protein in human serum. This inhibitor is also found in mammals such as cows, pigs and rats. Vitamin E deficient rats show a very high inhibitor level. Therefore, the present method will enable us to investigate the relation between diseases and the activity of the alpha-cysteine proteinase inhibitor. Also, this method is simple and inexpensive. The necessary amount of serum is only 10 microliter.     

Changes in the levels of prostaglandins and thromboxane and their roles in the accumulation of exudate in rat carrageenin-induced pleurisy — a profile analysis using gas chromatography-mass spectrometry —

Injection of γ-carrageenin into t he pleural cavity of rats caused the accumulation of the pleural exudate. When levels of prostaglandins (PGs) and thromboxane (TX) B₂ were quantified by gas chromatography-mass spectrometry as their methyl ester (ME)-dimethyllisopropylsilyl (DMiPS) ether or ME-methoxine-DMiPS ether derivatives, 6-keto-PGF_1α reached the maximum at 1 hr after carrageenin, then PGE₂ and TXB₂ showed peaks at 3 hr and waned off before 9 hr. he PGF_2α level was kept low, but PGD₂, PGE₁ and PGF_1α were not detected. Aspirin (100 mg/kg, i.p.) significantly decreased the PG and TXB₂ levels and suppressed the rate of plasma exudation until 5 hr, but did not at 7 hr, when it was measured by the amount of exuded pontamine sky blue injected intravenously. OKY-025 (300 mg/kg, i.p.), a selective TXA synthetase inhibitor, and tranylcypromine (20 mg/kg, i.p.), a PGI synthetase inhibitor, could not extensively inhibit the accumulation of the exudate. These results suggest that the cyclooxygenase products of arachidonic acid, particularly PGE₂, definitely play an important role in the exudation during the first 5 hr.     

Effects of IAA, Zeatin, Ammonium Nitrate and Sucrose on the Initiation and Development of Floral Buds in Torenia Stem Segments Cultured In Vitro

In Torenia stem segments cultured on a defined medium from whichammonium nitrate and growth regulators were omitted, adventitiousbuds were readily formed from epidermal tissue, with subsequentdifferentiation of floral buds. Using this plant material, thecorrelation between the time of application of various chemicalsand the time-course of floral bud differentiation was investigated.Histological examination showed that adventitious buds werevegetative during the first two weeks of the culture, and floralprimordia appeared after about three to four weeks of culture.We divided the flowering process in Torenia stem segments intothe following 3 phases: the first phase (first 2 weeks) duringwhich adventitious buds are formed, the second phase (3rd and4th weeks) during which floral buds are initiated and the thirdphase (5th to 12th weeks) during which floral buds develop.Then we added IAA, zeatin, ammonium nitrate or a high concentrationof sucrose to the medium during one, two or three of these phases.Ammonium nitrate added during the third phase suppressed floralbud development, but the high concentration of sucrose givenduring this phase stimulated it. These two chemicals influencedonly the development of floral buds previously initiated. Theapplication of IAA during the first phase promoted both theinitiation and development of floral buds. However, its applicationafter 2 weeks of culture failed to promote floral bud formation.Zeatin inhibited floral bud formation in a manner similar toammonium nitrate, but if it was added to the medium only duringthe first phase, it slightly promoted the initiation and developmentof floral buds. (Received July 7, 1981; Accepted October 12, 1981)     

Electrophoretic and biochemical studies of human aldehyde dehydrogenase isozymes in various tissues

Four major ALDH isozymes have been identified in human tissues using starch gel electrophoresis and isoelectric focusing. The isozyme bands have been termed as ALDH I, II, III and IV according to their decreasing electrophoretic migration and increasing isoelectric point. The isozymes have been partially purified via preparative isoelectric focusing. Kinetic characteristics of ALDH I and II were found to be quite similar to ALDH enzyme 2 and enzyme 1 described earlier by Greenfield and Pietruszko (Biochem Biophys Acta, $\text{483}$ 35–45 1977). ALDH III and IV showed a very high Km for propionaldehyde (1.0–1.5 mM at pH 9.5) and were not inhibited by disulfiram at pH 9.5. A variant phenotype of ALDH which lacked in isozyme I was detected in various tissues from Japanese individuals. Comparative kinetic properties of normal and variant enzyme are given.     

Critical requirement for the membrane-proximal cytosolic tyrosine residue for CD28-mediated costimulation in vivo

The YMNM motif that exists in the CD28 cytoplasmic domain is known as a binding site for phosphatidylinositol 3-kinase and Grb-2 and is considered to be important for CD28-mediated costimulation. To address the role of the YMNM motif in CD28 cosignaling in primary T cells, we generated transgenic mice on a CD28 null background that express a CD28 mutant lacking binding ability to phosphatidylinositol 3-kinase and Grb-2. After anti-CD3 and anti-CD28 Ab stimulation in vitro, the initial proliferative response and IL-2 secretion in CD28 Y189F transgenic T cells were severely compromised, while later responses were intact. In contrast to anti-CD3 and anti-CD28 Ab stimulation, PMA and anti-CD28 Ab stimulation failed to induce IL-2 production from CD28 Y189F transgenic T cells at any time point. Using the graft-vs-host reaction system, we assessed the role of the YMNM motif for CD28-mediated costimulation in vivo and found that CD28 Y189F transgenic spleen cells failed to engraft and could not induce acute graft-vs-host reaction. Together, these results suggest that the membrane-proximal tyrosine of CD28 is required for costimulation in vivo. Furthermore, these results indicate that the results from in vitro assays of CD28-mediated costimulation may not always correlate with T cell activation in vivo.