Core substructure in Mastigocladus laminosus phycobilisomes

A native high molecular complex (M_r 850000) containing about 50% of the allphycocyanin of the phycobilisome but lacking allophycocyanin B was separated from isolated phycobilisomes by gel electrophoresis. It was designated AP_CM since the large linker polypeptide L_CM was exclusively localized in this complex. The complex exhibited a ?196°C fluorescence emission maximum at 673 nm (671 nm at 25°C). In addition, a core complex (designated AP_C, M_r≥1000000) consisting of both AP_CM and AP 680 was isolated by combined gel filtration and linear gradient centrifugation. At 25°C this complex showed dual emission peaks at 670 and 680 nm demonstrating functional independence of the terminal emitters. A complex similar to AP_CM can be isolated from phycobilisomes of Anabaena variabilis. This is evidence that AP_CM is the constitutive center of the tricylindrical core of hemidiscoidal cyanobacterial phycobilisomes. Two models summarizing the structural and functional consequences of the results are presented in the discussion.     

Pattern of cell proliferation in embryogenesis and planula development ofHydractinia echinata predicts the postmetamorphic body pattern

Summary During embryogenesis and planula development of the colonial hydroidHydractinia echinata cell proliferation decreases in a distinct spatio-temporal pattern. Arrest in S-phase activity appears first in cells localized at the posterior and then subsequently at the anterior pole of the elongating embryo. These areas do not resume S-phase activity, even during the metamorphosis of the planula larva into the primary polyp. Tissue containing the quiescent cells gives rise to the terminal structures of the polyp. The posterior area of the larva becomes the hypostome and tentacles, while the anterior part of the larva develops into the basal plate and stolon tips. In mature planulae only a very few cells continue to proliferate. These cells are found in the middle part of the larva. Labelling experiments indicate that the prospective material of the postmetamorphic tentacles and stolon tips originates from cells which have exited from the cell cycle in embryogenesis or early in planula development. Precursor cells of the nematocytes which appear in the tentacles of the polyp following metamorphosis appear to have ceased cycling before the 38th hour of embryonic development. The vast majority of the cells that constitute the stolon tips of the primary polyp leave the cell cycle not later than 58 h after the beginning of development. We also report the identification of a cell type which differentiates in the polyp without passing through a post-metamorphic S-phase. The cell type appears to be neural in origin, based upon the identification of a neuropeptide of the FMRFamide type.     

Influence of interferon-gamma and extracellular tryptophan on indoleamine 2,3-dioxygenase activity in T24 cells as determined by a non-radiometric assay.

The indoleamine 2,3-dioxygenase (EC 1.13.11.17) activity in human T24 cells has been investigated in cell extracts by using a non-radioactive assay. It is enhanced in a dose-dependent manner up to 25-fold by interferon-gamma. The maximum reaction velocity is increased rather than the Km, which remains at 4 mumol/l. Induction of activity starts 3 h after stimulation and reaches a plateau at 21-48 h. Decreased stimulation was observed in the presence of high L-tryptophan concentrations.     

Patterns of expression of trichocytic and epithelial cytokeratins in mammalian tissues II. Concomitant and mutually exclusive synthesis of trichocytic and epithelial cytokeratins in diverse human and bovine tissues (hair follicle, nail bed and matrix, lingual papilla, thymic reticulum)

The hair-forming cells (trichocytes) and the mature hair contain four major trichocytic cytokeratins from each of the subfamilies, basic (Hb1-4) and acidic (Ha1-4); these are related - but not identical - to the epithelial cytokeratins. Here we show, by biochemical methods and immunofluorescence microscopy using antibodies specific for either epithelial or trichocyte cytokeratins, that the same set of hair-type cytokeratins, including two newly identified minor components, designated Hax (type I) and Hbx (type II), are also expressed in cells forming nails, in the filiform papillae of the dorsal surface of human and bovine tongue, and, most surprisingly, in some cells of the epithelial reticulum of bovine and human thymus. By double-label immunofluorescence microscopy, we also show that the expression of the two subsets of cytokeratins, i.e., the epithelial and the trichocytic ones, is not necessarily mutually exclusive, but that certain cells of hair follicles, nail matrix and bed, lingual papillae, and the nonlymphoid cell system of the thymus contain both trichocytic and certain epithelial cytokeratins. This indicates that these cells coexpress representatives of both kinds of cytokeratin. Implications of these findings with respect to problems of regulatory control of cytokeratin synthesis in tissue development and differentiation, and the possible functional meaning of the occurrence of trichocytic cytokeratins in such histologically diverse tissues, are discussed.     

Cytoskeletons of retinal pigment epithelial cells: Interspecies differences of expression patterns indicate independence of cell function from the specific complement of cytoskeletal proteins

Summary In vertebrate tissue development a given cell differentiation pathway is usually associated with a pattern of expression of a specific set of cytoskeletal proteins, including different intermediate filament (IF) and junctional proteins, which is identical in diverse species. The retinal pigment epithelium (RPE) is a layer of polar cells that have very similar morphological features and practically identical functions in different vertebrate species. However, in biochemical and immunolocalization studies of the cytoskeletal proteins of these cells we have noted remarkable interspecies differences. While chicken RPE cells contain only IFs of the vimentin type and do not possess desmosomes and desmosomal proteins RPE cells of diverse amphibian (Rana ridibunda, Xenopus laevis) and mammalian (rat, guinea pig, rabbit, cow, human) species express cytokeratins 8 and 18 either as their sole IF proteins, or together with vimentin IFs as in guinea pig and a certain subpopulation of bovine RPE cells. Plakoglobin, a plaque protein common to desmosomes and the zonula adhaerens exists in RPE cells of all species, whereas desmoplakin and desmoglein have been identified only in RPE desmosomes of frogs and cows, including bovine RPE cell cultures in which cytokeratins have disappeared and vimentin IFs are the only IFs present. These challenging findings show that neither cytokeratin IFs nor desmosomes are necessary for the establishment and function of a polar epithelial cell layer and that the same basic cellular architecture can be achieved by different programs of expression of cytoskeletal proteins. The differences in the composition of the RPE cytoskeleton further indicate that, at least in this tissue, a specific program of expression of IF and desmosomal proteins is not related to the functions of the RPE cell, which are very similar in the various species.     

The stimulating effect of a cold, dark pretreatment on the etioplast/chloroplast transformation of angiosperms. I. The stimulating effect of cold predarkening on different stages of greening under white light

Schönbohm, E., Stute, U., Thienhaus, P. and Werner, U. 1988. The stimulating effect of a cold, dark pretreatment on the etioplast/chloroplast transformation of angiosperms I. The stimulating effect of cold predarkening on different stages of greening under white light. - Physiol. Plant. 72: 541–546.
The etioplast/chloroplast transformation in angiosperms is controlled by light; most of the processes are mediated by phytochrome. We have shown that in the primary leaves of etiolated seedlings of wheat ( Triticum aestivum L. cv. Kolibri), fire-bean ( Phaseolus multiflorus L. cv. Preisgewinner) and in the cotyledons of etiolated sun flower seedlings ( Helianthus annuus L. cv. macrocarpa) the chlorophyll accumulation in the phase after the end of the lag phase can be greatly stimulated by a cold predarkening period. This effect is not necessarily coupled with a red preirradiation. Furthermore the lag phase can be dramatically shortened by the cold, dark pretreatment, whereas the amount of photoconvertible protochlorophyll(ide) in the darkness remains unaffected by the cold, dark pretreatment. The stimulating effect of a cold, predarkening period on greening is fully reversible by a warm, dark phase that is placed between the cold period and the onset of the continuous white light phase. These findings cannot be generalized: We could demonstrate that in the tropical plant Momordica charantia greening under white light was not affected by different temperature pretreatments during predarkening. The stimulating effect of a cold, predarkening period on greening is assumed to have ecological relevance.     

Inhibition of macrophage activation by isoquinolinesulfonamides, phenothiazines, and a napthalenesulfonamide

The influence of isoquinolinesulfonamides (H-7 and H-8), phenothiazines(trifluoperazine and fluphenazine), and a naphthalenesulfonamide (N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (W-7) on stimulated superoxide anion production and phosphatidyl inositol (PI) cycle activity was investigated in the guinea pig alveolar macrophage. All five drugs were able to inhibit superoxide anion production stimulated by n-formyl-nel-leu-phe (FNLP), leukotriene B4 (LTB4), and phorbol-12,13-dibutyrate (PDB). The order of potency was trifluoperazine greater than or equal to fluphenazine greater than H-7 = W-7 greater than H-8. The dose response curves could be shifted to less efficacy by increasing extracellular calcium. By itself, W-7 markedly stimulated 45Ca+2 efflux, fluphenazine and trifluoperazine slightly stimulated 45Ca+2 efflux, while H-7 and H-8 had no effect on 45Ca+2 efflux from macrophages preloaded with 45Ca+2. Consistent with these results, W-7 markedly stimulated PI cycle activity, fluphenazine and trifluoperazine slightly stimulated PI cycle activity, while H-7 and H-8 had no significant effects on PI cycle activity. In addition, W-7 by itself was able to stimulate a weak and short-lived "burst" of superoxide anion production. In order to evaluate whether a site of action of the inhibitors was at protein kinase C and whether protein kinase C was involved in terminating the normally short-lived FNLP- and LTB4-stimulated macrophage activation, fluphenazine and H-7 were used to evaluate the duration of FNLP- and LTB4-stimulated PI cycle activity, at concentrations of the inhibitors that significantly blocked stimulated superoxide anion production. In all cases, FNLP and LTB4 still stimulated PI cycle activity, which still terminated even though protein kinase C was inhibited. These results suggest that all five drugs block protein kinase C, but H-7 was the most specific in its action at protein kinase C, while the phenothiazines and W-7 have multiple sites of action. In addition, these results suggest that protein kinase C may not function to cause the termination of FNLP- and LTB4-stimulated PI cycle activity and subsequent superoxide anion production.     

A study of functionally active amino acids involved in the interaction of HLA-A2 or HLA-A3 molecules with cytolytic T lymphocytes

A large series of HLA-A2/HLA-A3 recombinant genes were generated by using the in vivo recombination technique. These genes have each been modified in the last two-thirds of the third exon such that one or several HLA-A2-specific substitutions have been made in the HLA-A3 gene and vice versa. The recombinant genes were transfected into the murine cell line P815 and the transfectants were used as targets for a series of 20 human CTL lines or clones specific for HLA-A2 or HLA-A3, or restricted by HLA-A2 and specific for influenza A. Several patterns of anti-HLA-A2, anti-HLA-A3, and HLA-A2-restricted anti-influenza CTL activity were observed and when uncloned cell lines were studied, a progressive selection of some clones with a similar pattern of activity was regularly found. From the comparison of these different patterns the following conclusions can be drawn: 1) In most but not all cases both domains of the class I molecule were essential for CTL recognition, but residue 152 was critically important for the majority of CTL tested; 2) amino acids 114/116 were also critical in most cases, and their position close to amino acid 152 in the tertiary structure of the molecule may have some functional significance; and 3) amino acid 161, although highly conserved, plays an unexpected but very important role in CTL function.     

Localization of immunoreactive epidermal growth factor receptors in human nervous system

Epidermal growth factor is a well-defined peptide which stimulates cell growth and elicits cell responses in a variety of tissues by binding to specific receptors, EGF-R. A specific antiserum against the EGF receptor, which has previously been used to characterize EGF-R in human skin, fibroblasts, and smooth muscle, was used to survey the distribution of EGF-R in human nervous system. Portions of formalin-fixed, paraffin-embedded autopsy specimens were examined by use of immunohistochemical staining (PAP technique) with EGF-R antiserum. Many types of nerve cells, e.g., cerebral cortical pyramidal cells, hippocampal pyramidal cells, Purkinje cells, anterior horn cells, and dorsal root ganglion neurons, contained immunoreactive EGF-R. However, immunoreactive EGF-R were not detected in astrocytes, oligodendrogliocytes, and other small neurons such as granule cells. Intense immunostaining for EGF-R was also detected in ependymal cells from choroidal and extrachoroidal locations. Although immunoreactive EGF-R is widely distributed in human nervous system, the functional role of EGF and its receptor in the nervous system remains unknown.     

BCNU-induced protection from hyperbaric hyperoxia: role of glutathione metabolism

To explore the role of the glutathione oxidation-reduction cycle in altering the sensitivity of rats to the effects of hyperbaric hyperoxia, we administered N,N-bis(2-chloroethyl)-N-nitrosourea (BCNU) to decrease tissue glutathione reductase activity. We then exposed these animals and their matched vehicle-treated controls to 100% O2 at 4 ATA. Animals that received BCNU and were immediately exposed to hyperbaric O2 showed enhanced toxicity by seizing earlier in the exposure than controls. Animals that received BCNU 18 h before the hyperbaric O2 exposure were paradoxically protected from the effects of the exposure with a prolongation of their time to initial seizure and a marked increase in their survival time during the exposure. Tissue glutathione concentrations were also measured in the various groups and the hyperbaric O2 exposure produced marked decreases in hepatic glutathione levels in all control animals. In animals treated with BCNU 18 h before exposure, hepatic glutathione concentrations also decreased, but the concentrations had significantly increased during the 18-h waiting period, allowing these animals to maintain hepatic levels in the normal range even during their hyperbaric exposures. We conclude that treatment of rats with BCNU 18 h before exposure to hyperbaric hyperoxia results in enhanced protection of the animals during the exposure.