Mitochondrial porin of Neurospora crassa: cDNA cloning, in vitro expression and import into mitochondria.

cDNA encoding porin of Neurospora crassa, the major protein component of the outer mitochondrial membrane, was isolated and the nucleotide sequence was determined. The deduced protein sequence consists of 283 amino acids (29,979 daltons) and shows sequence homology of around 43% to yeast porin; however, no significant homology to bacterial porins was apparent. According to secondary structure predictions, mitochondrial porin consists mainly of membrane-spanning sided beta-sheets. Porin was efficiently synthesized in vitro from the cDNA; this allowed us to study in detail its import into mitochondria. Thereby, three characteristics of import were defined: (i) import depended on the presence of nucleoside triphosphates; (ii) involvement of a proteinaceous receptor-like component on the surface of the mitochondria was demonstrated; (iii) insertion into the outer membrane was resolved into at least two distinct steps: specific binding to high-affinity sites and subsequent assembly to the mature form.     

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.     

Identification of proteins potentially involved in proximal-distal pattern formation in the regenerating forelimb of the newt.

We have used high resolution two-dimensional gel electrophoresis to identify and characterize proteins that may represent products of genes involved in establishing positional information along the proximal-distal axis of the regenerating forelimb of the newt Notophthalmus viridescens. At least 24 proteins have been found whose synthesis and (or) abundance is increased in proximal (midstylopodial) regenerates relative to midzeugopodial (distal) regenerates at either of two regeneration stages, the early dedifferentiation and moderate bud stages. Four of these same proteins show an axial asymmetry at both stages. Ten distal-specific proteins were also identified, although only one was common to both stages. More significantly, 6 of these 34 proteins (molecular masses of 73, 73, 51.5, 44.0, 19.5, and 16.5 kilodaltons and isoelectric points of 6.70, 6.74, 6.0, 6.05, 5.9, and 6.98, respectively) are regulated to proximal levels by treatment of distal regenerates with retinoic acid (RA) at both stages. An additional five are proximalized by RA at only one regeneration stage. Since the effect of RA is to proximalize positional information in blastema cells, these 11 proteins represent gene products that could be involved in a biochemical cascade leading to the establishment of positional information in the regenerating limb along this axis.     

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.     

Treatment with natural human interferon alpha of a CML-patient with antibodies to recombinant interferon alpha-2b

A patient with Philadelphia-chromosome positive chronic myelogenous leukemia developed interferon antibodies on treatment with recombinant interferon alpha-2b. Clinically this event corresponded with progressive disease. No cross-reactivity of antibodies with human leukocyte interferon was found by Western blot. Treatment was switched to human leukocyte interferon with an obvious clinical effect: WBC was reduced and platelet count stabilized, but the effect was transient and no hematologic remission was achieved. Human leukocyte interferon may be an alternative in CML-patients with neutralizing antibodies to recombinant interferon alpha.     

Therapy for acute myeloid leukemia in 119 adults: a comparison of two treatment protocols

Of 119 patients with acute myeloid leukemia, 69 were treated with Adriamycin, Vincristine and Cytosine Arabinoside (Therapy 1) and 50 with Daunorubicin, Cytosine Arabinoside and 6-Thioguanine (Therapy 2) as well as a consolidation therapy. The maintenance therapy with Cytosine Arabinoside and 6-Thioguanine was the same for both groups. The complete remission rate was 44% for Therapy 1 and 68% for Therapy 2 (p less than 0.05). - The median values for remission duration were 7 and 13 months respectively (p = 0.10); for survival time the median values were 18 and 19 months. These figures show in retrospect that high remission rates can be attained through intensive induction therapy and that longer remission duration is correlated with more aggressive induction therapy. A mild form of maintenance therapy seems to have little effect on the duration of complete remission.     

The influence of water on CO2 exchange in the lichen Parmelia praesignis Nyl.

Net photosynthetic rates for the lichen Parmelia praesignis Nyl. were obtained as a function of 5 light levels, 5 temperature levels, and of water content as thalli dried from saturated conditions. Data are described as second order polynomials in the light, and as saturation curves in the dark. Rates in the light were depressed at high water contents reaching maximal rates between 110% and 180% water content and declining as thalli dried. Physiological parameters were derived from the drying curves to investigate temperature and light interactions. Dark respiration parameters are the maximal rate, the water content where the rate is half-maximal, the water content at which respiration is zero, and the maximal water efficiency. In the light, parameters are the maximal net photosynthetic rate, the water content at the maximal rate, the water compensation point, the maximal water efficiency, and the sensitivity of net photosynthesis to change in water content.Values of half-maximal rate water contents for respiration were found to increase as temperatures increased. The greatest maximal net photosynthetic rate occurred at higher temperatures as the light intensity increased. In the light, maximal water efficiency and the sensitivity to changes in water content were generally maximal at temperatures yielding the greatest maximal net photosynthetic rates.     

Organization and function of cytochromeb and ubiquinone in the cristae membrane of beef heart mitochondria

The arrangement and function of the redox centers of the mammalianbc ₁ complex is described on the basis of structural data derived from amino acid sequence studies and secondary structure predictions and on the basis of functional studies (i.e., EPR data, inhibitor studies, and kinetic experiments). Two ubiquinone reaction centers do exist—a QH₂ oxidation center situated at the outer, cytosolic surface of the cristae membrane (Q₀ center), and a Q reduction center (Q _i center) situated more to the inner surface of the cristae membrane. The Q₀ center is formed by theb-566 domain of cytochromeb, the FeS protein, and maybe an additional small subunit, whereas the Q _i center is formed by theb-562 domain of cytochromeb and presumably the 13.4kDa protein (QP-C). The Q binding proteins are proposed to be protein subunits of the Q reaction centers of various multiprotein complexes. The path of electron flow branches at the Q₀ center, half of the electrons flowing via the high-potential cytochrome chain to oxygen and half of the electrons cycling back into the Q pool via the cytochromeb path connecting the two Q reaction centers. During oxidation of QH₂, 2H⁺ are released to the cytosolic space and during reduction of Q, 2H⁺ are taken up from the matrix side, resulting in a net transport across the membrane of 2H⁺ per e^– flown from QH₂ to cytochromec, the H⁺ being transported across the membrane as H (H⁺ + e^–) by the mobile carrier Q. The authors correct their earlier view of cytochromeb functioning as a H⁺ pump, proposing that the redox-linkedpK changes of the acidic groups of cytochromeb are involved in the protonation/deprotonation processes taking place during the reduction and oxidation of Q. The reviewers stress that cytochromeb is in equilibrium with the Q pool via the Q _i center, but not via the Q₀ center. Their view of the mechanisms taking place at the reductase is a Q cycle linked to a Q-pool where cytochromeb is acting as an electron pump.