Ernährungsbiologie einer rhipidoglossen Kiemenschnecke

Zusammenfassung Die Arbeitsweise und die Leistungen der Rhipidoglossenradula von Theodoxus fluviatilis werden durch die kräftigen 4. Zwischenzähne und die Randbürstenzähne bestimmt. Die 4. Zwischenzähne lockern im wesentlichen die dem Fre\grund anhaftenden oder aufliegenden ein- bis wenigzelligen Algen (Diatomeen, chlorococcale und konjugate Grünalgen), die Randzähne fegen das gelockerte Nahrungsgut quantitativ zusammen. Fädige Grünalgen (z. B. Cladophorales) und Gewebeteile höherer Pflanzen werden nicht abgebissen bzw. abgeschabt.Die Diatomeen werden nur verdaut, wenn die Kieselschalen bereits bei der Nahrungsaufnahme mechanisch zerkleinert werden. Diese Zerkleinerung erfolgt allein auf einem Substrat mit rauher Oberfläche; sie wird durch die während des Bisses zwischen 4. Zwischenzähnen und Substrat auftretenden Reibungskräfte erzielt. Theodoxus wurde bei refiner Diatomeenernährung über mehrere Generationen gezüchtet. Tierisches Eiwei\ ist als Zusatzkost nicht erforderlich. Mit besonderen Hilfsma\nahmen kann Theodoxus im Laboratorium auch mit Cyanophyceen oder besonders mit Flagellaten (Chlamydomonas), die den Schnecken an den im Freiland besiedelten Standorten nicht zur Verfügung stehen, ernährt werden.Sämtliche Grünalgen mit stärkerer Cellulosewandung (Chlorococcales, Conjugatae) sind unverdaulich. Die Unverdaulichlichkeit beruht vermutlich auf einem Fehlen von Cellulasen im Verdauungstraktus. Die Zellmembranen und extrazellularen Scheiden der Cyanophyceen, die aus Hemicellulosen und Pektinen aufgebaut sind, werden im Magen aufgelöst. Theodoxus ist ein reiner Diatomeenfresser. Die ökologische Einnischung in die litorale Steinregion ist vorwiegend ernährungs-physiologisch begründet und erklärt das Vorkommen in Flie\gewassern und an Brandungsufern stehender Sü\gewässer sowie der Ostsee.     

DEVELOPMENT AND GERMINATION OF THE AZOTOBACTER CYST

The fine structure of Azotobacter vinelandii has been studied by means of electron microscopy of ultrathin sections made of the encysting and germinating cells. The organisms were fixed with KMnO₄ and embedded in epoxy resin. On an encystment medium the rod-shaped bacteria begin to assume an almost spherical form and then bark-like exine appears in 1½ to 2 days. The exine thickens and an electron permeable intine forms between it and the shrinking cell body. In 5 days the intine makes up more than half of the cyst volume and begins to show a definite two-layered structure. Meanwhile the peripheral bodies, which may be extensions of the cell membrane of the vegetative cell, disappear as the encystment progresses. The cell wall and membrane of the vegetative cell remain demonstrable as the confining structure of the shrinking central body of the mature cyst. In this central body lipoidal globules appear together with aggregations of nuclear material. Cyst germination begins with an increase in the size of the central body at the expense of the intine. The nuclear aggregations become more diffuse and the lipoidal globules disappear. The exine may be pushed outward and the bark-like fragments separate as the emerging vegetative cell develops. Invagination of the cell wall and membrane may occur at this stage leading to cell division. Empty exines remain as horseshoe-shaped structures.     

Morphologische und experimentelle untersuchungen über die variabilität per farbmuster auf der schale von theodoxus fluviatilis L.

Ohne ZusammenfassungMit Unterstützung der Deutschen Forschungsgemeineshaft.     

Purification and characterization of wheat and pine small basic protein substrates for plant calcium-dependent protein kinase.

A wheat basic protein (WBP) was purified to homogeneity from wheat germ by a protocol involving extraction, centrifugation, batchwise elution from carboxymethylcellulose (CM-52), acidification with trifluoroacetic acid, neutralization and HPLC on a SP5PW cation exchange column. WBP is a 10 kDa protein and is phosphorylated on serine residues by wheat germ Ca(2+)-dependent protein kinase (CDPK). [32P]phosphoWBP exactly comigrates with WBP on SDS-PAGE. WBP does not inhibit either wheat germ CDPK or calmodulin-dependent myosin light chain kinase. Apart from histone H1, WBP is the best endogenous substrate yet found for wheat embryo CDPK. A 12 kDa pine basic protein (PBP) was purified to homogeneity from seeds of stone pine (Pinus pinea L.) by a simple procedure involving batchwise elution from carboxymethylcellulose and cation exchange HPLC. PBP is also a good substrate for CDPK and is phosphorylated on Ser residues. N-terminal sequencing of WBP and PBP revealed that these proteins are homologous to a family of small basic plant proteins having a phospholipid transfer function.     

Sequential synthesis of some proteins in cultured carrot explant (Daucus carota) cells during callus induction

Freshly isolated explants of the secondary phloem of carrot roots were exposed to ¹⁴C-leucine for various periods from t₀—to 18 h and the ¹⁴C labelling of protein was studied by 2-dimensional PAGE followed by fluorograph. The labelling pattern of proteins indicated a sequential activation of synthesis of about 130 proteins during the 18 h experimental period prior to the onset of cell division activity.Abbreviations IAA indole acetic acid - 2iP 2-isopentenyladenine - PVP polyvinylpyrrolidone - CBB Coomassie brilliant blue - RuBPCase ribulosebisphosphate carboxylase - LSC liquid scintillation counter - spec.act. specific radioactivity - u.l. uniformly labelled     

Abnormal bone growth and selective translational regulation in basic fibroblast growth factor (FGF-2) transgenic mice.

Basic fibroblast growth factor (FGF-2) is a pleiotropic growth factor detected in many different cells and tissues. Normally synthesized at low levels, FGF-2 is elevated in various pathologies, most notably in cancer and injury repair. To investigate the effects of elevated FGF-2, the human full-length cDNA was expressed in transgenic mice under control of a phosphoglycerate kinase promoter. Overexpression of FGF-2 caused a variety of skeletal malformations including shortening and flattening of long bones and moderate macrocephaly. Comparison by Western blot of FGF-2 transgenic mice to nontransgenic littermates showed expression of human FGF-2 protein in all major organs and tissues examined including brain, heart, lung, liver, kidney, spleen, and skeletal muscle; however, different molar ratios of FGF-2 protein isoforms were observed between different organs and tissues. Some tissues preferentially synthesize larger isoforms of FGF-2 while other tissues produce predominantly smaller 18-kDa FGF-2. Translation of the high molecular weight isoforms initiates from unconventional CUG codons and translation of the 18-kDa isoform initiates from an AUG codon in the FGF-2 mRNA. Thus the Western blot data from the FGF-2 transgenic mice suggest that tissue-specific expression of FGF-2 isoforms is regulated translationally.     

The influence of the cytosolic oncotic pressure on the permeability of the mitochondrial outer membrane for ADP: implications for the kinetic properties of mitochondrial creatine kinase and for ADP channelling into the intermembrane space

Summary Cytosolic proteins as components of the physiological mitochondrial environment were substituted by dextrans added to media normally used for incubation of isolated mitochondria. Under these conditions the volume of the intermembrane space decreases and the contact sites between the both mitochondrial membranes increase drastically. These morphological changes are accompanied by a reduced permeability of the mitochondrial outer compartment for adenine nucleotides as it was shown by extensive kinetic studies of mitochondrial enzymes (oxidative phosphorylation, mi-creatine kinase, mi-adenylate kinase). The decreased permeability of the mitochondrial outer membrane causes increased rate dependent concentration gradients in the micromolar range for adenine nucleotides between the intermembrane space and the extramitochondrial space. Although all metabolites crossing the outer membrane exhibit the same concentration gradients, considerable compartmentations are detectable for ADP only due to its low extramitochondrial concentration. The consequences of ADP-compartmentation in the mitochondrial intermembrane space for ADP-channelling into the mitochondria are discussed.