Atrial natriuretic peptide detected by immunocytochemistry in peripheral organs of Tupaia belangeri

ANP (atrial natriuretic peptide), a peptide found in granules of mammalian atrial cardiac myocytes, has been shown to be active in regulation of blood pressure and body water homeostasis. The existence of ANP in atrium, pituitary, adrenal gland, and kidney of the rat had been immunocytochemically demonstrated with an antibody against rat ANP (102-126). We used the same antibody in immunocytochemical studies for the detection of ANP in peripheral organs of the tree shrew (Tupaia belangeri). The antibody stained granules in myocytes of cardiac atria which indicated that it reacted with tree shrew ANP. In contrast to the rat, no immunoreactive cells were found in pituitaries and adrenal glands. However, in the kidneys distal tubules in outer medulla and cortex were labeled. Ascending limbs of distal tubules were intensely stained when either the peroxidase-antiperoxidase (PAP) or the indirect immunofluorescence method were used. Collecting ducts and convoluted distal tubules in the outer cortex showed a granular type of staining when the immunofluorescence method was used. These data indicate that ANP is present in epithelial cells of distal tubules and collecting ducts, where it may be involved in the regulation of renal salt excretion.     

Cytologischer Nachweis von postreduktion bei einer phanerogame

Ohne ZusammenfassungMit 1 Textabbildung (3 Einzelbildern).     

Atrial natriuretic peptide detected by immunocytochemistry in peripheral organs of Tupaia belangeri

Summary ANP (atrial natriuretic peptide), a peptide found in granules of mammalian atrial cardiac myocytes, has been shown to be active in regulation of blood pressure and body water homeostasis. The existence of ANP in atrium, pituitary, adrenal gland, and kidney of the rat had been immunocytochemically demonstrated with an antibody against rat ANP (102–126). We used the same antibody in immunocytochemical studies for the detection of ANP in peripheral organs of the tree shrew (Tupaia belangeri). The antibody stained granules in myocytes of cardiac atria which indicated that it reacted with tree shrew ANP. In contrast to the rat, no immunoreactive cells were found in pituitaries and adrenal glands. However, in the kidneys distal tubules in outer medulla and cortex were labeled Ascending limbs of distal tubules were intensely stained when either the peroxidase-antiperoxidase (PAP) or the indirect immunofluorescence method were used. Collecting ducts and convoluted distal tubules in the outer cortex showed a granular type of staining when the immunofluorescence method was used. These data indicate that ANP is present in epithelial cells of distal tubules and collecting ducts, where it may be involved in the regulation of renal salt excretion.     

Cephalodiate Arten der GattungLecidea sensu lato (Ascomycetes lichenisati)

(1) The ability to produce cephalodia is usually a genus-specific character in lichens. (2)Lecidea shushanii Thoms., is a member of the genusTephromela, closely related toT. aglaea. It is not clear, whether or not the cephalodia of this taxon are true cephalodia or colonies of epiphytic cyanobacteria and whether or notLecidea shushanii is an independent species. (3)Lecidea dovrensis Nyl., is, in contrast to the traditional concept, not conspecific withLecidea alpestris Sommerf., but an earlier name forLecidea pallida Th. Fr. (4)Lecidea dovrensis is described in some detail. Chemically the species is characterized by the presence of isousnic acid (previously unknown in lecideoid lichens). It is restricted to areas north of the 60th parallel with an oceanic climate. (5) In connection with the attempt to clarify the taxonomic relationships ofLecidea dovrensis, figures of ascus apical structures of the following species are given (marked by an asterisk are genera where we found discrepancies with published data):Austrolecia antarctica, Catillaria chalybeia, Lecidea alpestris, L. caesioatra, L. limosa, Lecidoma demissum, Koerberiella wimmeriana, Micarea assimilata, M. crassipes, M. melaenida, M. prasina, Pilophorus robustus, Placodiella olivacea, Placolecis opaca, Porpidia trullisata, Protoblastenia rupestris, Psilolechia lucida, Psorula rufonigra, Squamarina gypsacea, Xanthopsorella texana. (6) Among crustaceous lichens we find no groups related toLecidea dovrensis. We supportTimal's concept of including this species in the genusPilophorus. Pilophorus, as well asLecidea dovrensis is characterized by the same ascus type, by a similar structure of thallus, cephalodia, paraphyses, and ascocarp (although there is no pseudopodetium developed inLecidea dovrensis), and the presence of isousnic acid. In addition, both taxa are restricted to cool oceanic climates and non-calciferous substrates. The following combination is proposed:Pilophorus dovrensis (Nyl.)Timdal, Hertel & Rambold, comb. nova. (7) The species of theLecidea alpestris-group form an independent genus, probably near toAustrolecia Hertel.

Frau Prof. Dr.Elisabeth Tschermak-Woess zu ihrem 70. Geburtstag gewidmet.     

Characteristics of 2-oxoglutarate and glutamate transport in spinach chloroplasts

The transport of glutamate, 2-oxoglutarate and malate in intact spinach chloroplasts was determined using a double-silicone-layer centrifugation technique in which the silicone layers stayed separated at the end of centrifugation. Glutamate was found to be transported via the dicarboxylate but not the 2-oxoglutarate translocator. Hence the kinetic parameters (i.e.K _m,K _i andV _max) determined in glutamate-preloaded chloroplasts represent the kinetic constants of the dicarboxylate translocator. Measurements from malate- or succinate-preloaded chloroplasts represent the aggregate values of both the dicarboxylate and the 2-oxoglutarate translocators. Calculations showed that the 2-oxoglutarate and glutamate transport required to support the high fluxes of photorespiratory NH₃ recycling could be achieved if the transport of these two dicarboxylates occurred on separate translocators. It is proposed that during photorespiration the transport of 2-oxoglutarate into and glutamate out of the chloroplast occurred via the 2-oxoglutarate and the dicarboxylate translocators, respectively. These transports are coupled to malate counter-exchange in a cascade-like manner resulting in a net 2-oxoglutarate/glutamate exchange with no net malate uptake.Abbreviation 2-OG 2-oxoglutarate     

Gill surface area of water-breathing freshwater fish

Summary To provide a hitherto lacking review which focuses on gill surface area of freshwater fish, we collected and analysed morphometric data from the literature. The scaling exponent of gill area ranges from 0.36 to 1.13, with a mean value of 0.76. The absolute values for the largest gill areas are about 5 times as high as those of the smallest. This range resembles that of marine fish, if specially adapted steady swimmers, such as tunnies and some sharks, are excluded. Generally it appears that the gill areas of freshwater fish are smaller than those of comparable marine species. To establish whether a relationship exists between gill area and swimming activity or oxygen content of water, the activity of each species and the oxygen content of its habitat were estimated and checked against the gill area. ANOVA revealed that activity explains the presence of the smallest gill areas only, while oxygen content does not correlate with gill area at all. The morphometric variables determining gill area (total length of filaments, average lamellar density, average lamellar area) are highly correlated; total gill area correlates mainly with lamellar density and to a lesser degree with filament length; lamellar area varies independently. Different populations of the same species exhibit striking differences with respect to gill areas, total length of filaments, average lamellar density and average lamellar area. These differences point to a substantial morphological plasticity of the gill system.     

Phosphorylation of a 51-kDa envelope membrane polypeptide involved in protein translocation into chloroplasts

In this report we demonstrate that a 51-kDa outer-envelope membrane protein (P51) is involved in protein translocation into chloroplasts. Furthermore it is shown that phosphorylation of P51 is functionally related to the process of binding and/or importing precursor proteins into chloroplasts. Several lines of evidence have been obtained supporting this suggestion. First, protein import into chloroplasts was inhibited by the membrane-impermeable agent pyridoxal 5'-phosphate, which has been shown to react with a component of the protein-import apparatus. Phosphorylation of envelope membrane polypeptides using [gamma-32P]ATP in the presence of pyridoxal 5'-phosphate resulted in an increased incorporation of 32P radiolabel into a 51-kDa membrane polypeptide (P51). A close correlation between the inhibition of protein import and the increase in the phosphorylation state of P51, both as a function of PLP concentration, was observed. Second, binding of purified precursor proteins to chloroplasts resulted in a specific increase in the phosphorylation state of P51. This effect was not exerted by the mature form of the precursor protein lacking the presequence. Third, internally generated ATP was able to compete specifically with externally added [gamma-32P]ATP for the phosphorylation of P51. Fourth, digestion of the outer-envelope membrane with low amounts of thermolysin resulted in a loss of protein import activity, which was associated with the removal of the phosphorylation site of P51. Phosphorylation of P51 proceeds with an apparent Km (ATP) of about 5 microM, which is much lower than the ATP concentration required for the protein translocation itself. We suggest that two different ATP-dependent processes are involved in protein translocation into chloroplasts. P51 represent presumably a regulatory component of the protein-import apparatus or the protein receptor itself.     

The tertiary structure of Aspergillus saitoi minor ribonuclease (Ms) predicted from the structure of RNase T1

Ribonuclease Ms from Aspergillus saitoi is a small acidic protein (11 714 Da) containing 106 amino acids of known sequence. Unlike other enzymes belonging to the RNase T₁ family this ribonuclease is base-unspecific. Using interactive computer graphics and energy minimisation we predicted the structure of RNase Ms on the basis of sequence homology to RNase T₁ of known structure. In this report the predicted structure of this protein is presented and characterised.