Density-dependent inhibitory effect of transforming growth factor-β on human fibroblasts involves the down-regulation of platelet-derived growth factor α-receptors

We have previously found that transforming growth factor-β1 (TGF-β1) inhibits the mitogenic activity of platelet-derived growth factor (PDGF) in cultures of human neonatal fibroblasts in a density-dependent fashion. In the present investigation we determined the effect of TGF-β1 on the PDGF α-receptor, which binds all PDGF isoforms, as well as on the β-receptor, which binds only PDGF-BB with high affinity. We found that the inhibitory effect of TGF-β1 on PDGF-AA-induced mitogenesis was density-dependent; when dense cell cultures were preincubated with TGF-β1, there was an complete inhibition of ³H-thymidine incorporation, whereas the effect was less in sparse cultures. A similar density-dependent effect of TGF-β1 was seen in PDGF-BB treated cells, although less pronounced. The binding of ¹²⁵I-labeled PDGF-AA and PDGF-BB to the α-receptor was significantly reduced after treatment with TGF-β1 in dense cultures, whereas the sparse cultures were less affected. A decrease of α-receptor mRNA was also seen. The levels of β-receptor protein and mRNA were unaffected. We conclude that the growth inhibitory effect of TGF-β1 is cell density-dependent and involves down-regulation of PDGF α-receptors. © 1993 Wiley-Liss, Inc.     

PROTEINS OF AXONAL TRANSPORT: INTERACTION OF RAPIDLY TRANSPORTED PROTEINS WITH LECTINS

Rapidly transported fucose-labelled glycoproteins from the optic system of the rabbit were solubilised with the non-ionic detergent Berol 172. The major labelled components were bound to wheat germ agglutinin or Concanavalin A coupled to Sepharose but not to other lectins or glycoproteins. It was concluded that rapidly transported proteins contain exposed N-acetyl-D-glucosamine     

Rapid Migration of Inositol Phospholipids with Axonally Transported Substances in the Rabbit Optic Pathway

Following an intraocular injection of myo-[2-3H]inositol, the axonal transport of labelled water-soluble substances and inositol phospholipids was investigated. Evidence was obtained for a rapid axonal transport of a relatively small amount of labelled inositol phospholipids. In contrast to other axonally transported phospholipids, there was no significant accumulation of labelled, rapidly transported inositol phospholipids in the nerve terminal region at later time intervals following the isotope administration.     

Thyroxine,methimazole, and thyroid microsomal autoantibody titres in hypothyroid Hashimoto's thyroiditis.

Ten hypothyroid patients with Hashimoto''s thyroiditis were treated with methimazole 30 mg in addition to thyroxine 0.15 mg daily. Another 10 hypothyroid patients with Hashimoto''s thyroiditis were given thyroxine 0.15 mg alone. After 22 weeks of treatment significant decreases in thyroid microsomal autoantibody titres were observed in both groups (p less than 0.01). There was no difference in the mean change in titre between the two groups. When the patients treated with methimazole were subsequently given thyroxine 0.15 mg alone for a further 22 weeks no additional change in titre was observed. The data suggest that thyroxine, by normalising serum thyroid stimulating hormone concentrations, may reduce the autoantigenic properties of the thyrocytes with a subsequent decrease in autoantibody titres.     

Separation of enantiomeric amines and acids using chiral ion-pair chromatography on porous graphitic carbon

The application of porous graphitic carbon as adsorbing phase for direct separation of enantiomeric acids and amines using chiral ion-pair chromatography is described. The enantiomeric amines were separated as diastereomeric ion pairs with N-benzyloxycarbonylglycyl-L -proline, N-benzyloxycarbonylglycylglycyl-L -proline, or captopril as the chiral counterion. High enantioselectivities were obtained for amines having a hydrogen bonding function in the vicinity of the asymmetrical carbon atom. Quinine was the chiral counterion used to separate the enantiomeric acids. The strongly UV-absorbing quinine improved detection of solutes having low UV-absorbing properties, e.g., (R,S)-2-chloropropionic acid, by “indirect detection.” Retention and stereoselectivity of enanticmeric acids were regulated by the quinine concentration and by the addition of carboxylic acids as well as polar modifiers, e.g., methanol and 2-propanol, to the mobile phase. © 1992 Wiley-Liss, Inc.     

Comparison of the effect of excessive light on chlorophyll fluorescence (77K) and photon yield of O2 evolution in leaves of higher plants

High-light treatments (1750–2000 mol photons m^–2 · s^–1) of leaves from a number of higher-plant species invariably resulted in quenching of the maximum 77K chlorophyll fluorescence at both 692 and 734 nm (F _M, 692 and F _M, 734). The response of instantaneous fluorescence at 692 nm (F _O, 692) was complex. In leaves of some species F _O, 692 increased dramatically in others it was quenched, and in others yet it showed no marked, consistent change. Regardless of the response of F _O, 692 an apparently linear relationship was obtained between the ratio of variable to maximum fluorescence (F _V/F _M, 692) and the photon yield of O₂ evolution, indicating that photoinhibition affects these two variables to approximately the same extent. Treatment of leaves in a CO₂–free gas stream containing 2% O₂ and 98% N₂ under weak light (100 mol · m^–2 · s^–1) resulted in a general and fully reversible quenching of 77K fluorescence at 692 and 734 nm. In this case both F _O, 692 and F _M, 692 were invariably quenched, indicating that the quenching was caused by an increased non-radiative energy dissipation in the pigment bed. We propose that high-light treatments can have at least two different, concurrent effects on 77K fluorescence in leaves. One results from damage to the photosystem II (PSII) reaction-center complex and leads to a rise in F _O, 692; the other results from an increased non-radiative energy dissipation and leads to quenching of both F _O, 692 and F _M, 692 This general quenching had a much longer relaxation time than reported for pH-dependent quenching in algae and chloroplasts. Sun leaves, whose F _V/F _M, 692 ratios were little affected by high-light exposure in normal air, suffered pronounced photoinhibition when the exposure was made under conditions that prevent photosynthetic gas exchange (2% O₂, 0% CO₂). However, they were still less susceptible than shade leaves, indicating that the higher capacity for energy dissipation via photosynthesis is not the only cause of their lower susceptibility. The rate constant for recovery from photoinhibition was much higher in mature sun leaves than in mature shade leaves, indicating that differences in the capacity for continuous repair may in part account for the difference in their susceptibility to photoinhibition.Abbreviations and symbols kDa kilodalton - LHC-II light-harvesting chlorophyll-protein complex - PFD photon flux density (photon fluence rate) - PSI, PSII photosystem I, II - F _O, F _M, F _V instantaneous, maximum, variable fluorescence emission - absorptance - _a photon yield of O₂ evolution (absorbed light) C.I.W.-D.P.B. Publication No. 925     

Micro-site performance of evergreen and deciduous dwarf shrubs in a subarctic heath in relation to nitrogen status

The relationship between micro-site nitrogen status (total soil N conc., total vegetation N, and leaf N conc.) and performance (biomass) for two evergreen and two deciduous dwarf shrubs was studied in a subarctic heath. One deciduous species, Vaccinium uliginosum , dominated on sites having the highest vegetation nitrogen content and highest leaf nitrogen concentrations. The evergreen Empetrum hermaphroditum dominated on sites with a low total vegetation nitrogen content and low leaf nitrogen concentrations. Two other species, V. myrtillus (deciduous) and V. vitis-idaea (evergreen), showed intermediate patterns that were not clearly separated from either V. uliginosum or Empetrum . Soil nitrogen content showed no significant differences between micro-sites. Possible physiological reasons for the observed patterns are discussed.     

Transgenic HLA-DR alpha faithfully reconstitutes IE-controlled immune functions and induces cross-tolerance to E alpha in E alpha 0 mutant mice

We have constructed transgenic mice that express the human class II MHC molecule HLA-DR alpha on a genetic background in which the equivalent endogenous gene, H-2 IE alpha, is not expressed. In these mice, DR alpha complemented the E beta chain such that tissue-specific expression of an interspecies hybrid DR alpha-E beta heterodimer was obtained. Despite 25% amino acid differences between DR alpha and E alpha, immune responsiveness to IE-controlled antigens, clonal deletion of IE-reactive T cells, and alloantigenicity were quantitatively and qualitatively indistinguishable in IE-positive mice and in mice that had integrated at least four copies of the transgene. These results demonstrate a remarkable degree of structural, regulatory, and functional conservation. They also suggest that tolerance induction involves only discrete portions of MHC molecules.     

Proteolysis of tubulin and microtubule-associated proteins 1 and 2 by calpain I and II. Difference in sensitivity of assembled and disassembled microtubules

Calpain I and II (EC 3.4.22.17) are Ca2+-activated neutral thiol-proteases. Isolated brain tubulin and microtubule-associated proteins were found to be good substrates for proteolytic degradation by brain calpain I and II. The assembly of microtubules was totally inhibited when the calpains were allowed to act on microtubule proteins initially, and a complete disassembly was found after addition of calpain I to assembled microtubules. The high-molecular weight microtubule-associated proteins were degraded within a few minutes following incubation with calpain as shown by SDS-polyacrylamide gel electrophoresis and electron microscopy. When calpain was added to pre-formed microtubules, either in the presence or in the absence of microtubule-associated proteins, the proteolysis was significantly reduced. When tubulin was pre-assembled by taxol, the formation of proteolytic fragments was decreased indicating that assembly alters the availability of tubulin sites for proteolytic cleavage by calpain. Digested tubulin spontaneously formed aberrant polymers. No considerable change of apparent net charge was seen, thus indicating that calpain cleaves off fragments containing neutral amino acid residues and/or that the fragments of tubulin remain associated as an entity with the same charge as native tubulin. The results suggest that the calpains act as irreversible microtubule regulators.     

Identification and characterization of alkali-tolerant clostridia isolated from biodeteriorated casein-containing building materials

Summary Reports on malodour in buildings constructed in the late 1970s gave rise to thorough investigations on the possible role of vapours of chemical compounds emitted by building materials. The odour could be related to the use of casein as an additive to improve the fluidity of concrete materials used as a self-levelling floor topping compound. Casein was suggested to be degraded by microorganisms, resulting in an accumulation of malodorous substances in the topping compounds.Bacteria isolated from biodeteriorated concrete materials containing caseins exhibited unusual tolerance towards high pH. Two dominant species were found among a total of 80 sporeforming, anaerobic isolates from concrete and raw products of caseins, namely Clostridium bifermentans and Clostridium sporogenes. C. bifermentans had a maximal pH tolerance of 12.2 while C. sporogenes could reproduce up to pH 11.7. The study includes the identification of the clostridia with API multitest as well as an investigation of the volatile organic acid and monoamine patterns. About 100 cfu clostridia/g material could be obtained during the isolation procedures.