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1999 (1)
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1Author    RainerH. LangeRequires cookie*
 Title    Are Yolk Phosvitins Carriers for Specific Cations? Comparative Microanalysis in Vertebrate Yolk Platelets  
 Abstract    Qualitative X-ray microanalysis of frozen-dried cyclo-stome, teleost and amphibian yolk platelets has demon­ strated the general and undoubtable presence of P, S, Cl (!) and K, the probable presence of Na and the irregular presence of Ca and Mg. Iron occurred only in trace amounts if at all. Details of the process of yolk utilization by the embryo are still enigmatic. Indirect evidence ob­ tained from particular features of the glycolipophos-phoprotein molecules building up the yolk platelets as main constituents has, therefore, become a matter of recent interest. Thus, the highly phosphorylated phosvitins ("cation exchange-resin") may play a role as carrier of cations essential for embryonic growth (Taborsky [1]); studies on cation-binding as well as on the entailing conformational changes of the phos­ vitin molecule are numerous (Taborsky [1, 2]). Re­ cent observations on yolk platelets in this laboratory, however, do not fit into the frame of a very specific role of yolk-phosphoproteins in the transport of selected cations. Although the investigation has been performed only on the usual qualitative basis, the broad collection of material and the regularity of findings render the observations significant. Cryosections of whole eggs (Lampetra planeri [Bloch], Cyclostomata; Pelvicachromis pulcher, Cich-lidae, Teleostei; Triturus sp., Salamandridae, Am­ phibia) or isolated yolk platelets (M yxine glutinosa L., Cyclostomata) were dried at subzero temperatu­ res onto pure carbon specimen supports for scanning electron microscopy. Lamprey and teleost material fixed in Na-phosphate buffered glutaraldehyde was used for comparison. Elemental analysis was carried out at 25 kV in a Philips PSEM 500 scanning elec­ Reprint requests to Prof. Dr. R. H. Lange. 0341-0382/81/0700-0686 $01.00/0 tron microscope equipped with energy-dispersive Edax system (3 -4 spectra -100000 to 400000 total counts each — per species, point probe diameter 1 |im). Ooplasmic inclusions corresponding both in size and frequency to yolk platelets of the various species were identified in the scanning mode and a point probe was then positioned on their interior. Ele­ ments markedly and undoubtedly present in all un­ fixed samples and absent in the carbon support be­ tween single platelets were: P, S, Cl, and K. Ca was also present in Lampetra, Pelvicachromis and Triturus (as judged from its clear K ß peak at 4.01 keV, while Ca-K or at 3.69 keV fuses with K-K ß at 3.59 keV). Due to the peculiar background spectrum (Lange and Blödom [3]) we shall not enter into detailed dis­ cussion of the probable presence of some Na and Mg. Fe was never unequivocally demonstrated, but traces might have occurred in the cyclostomes. Whereas P and S probably represent covalently bound protein constituents, the presence of chloride (only irregularly present following fixation, abso­ lutely absent from neutral underground) in this highly anionic protein ambiance is remarkable. Re­ sults with respect to iron were disappointing, espe­ cially considering recent biochemical work (Tabors­ ky [2]). It is concluded that K+ is regularly and undoubt­ edly present in considerable amounts in yolk pla­ telets; this holds true for Ca2+, but to a lesser degree (not found in M yxine). The occurrence of Na+ (and in Lampetra some Mg2+) is probable but evidence is at present unsatisfactory for technical reasons. The presence of traces of Fe cannot be excluded. Due to the presence of chloride, the above cations can only in part be bound by the phosphate groups of the highly anionic yolk-platelet proteins. By combining the recent results in yolk-platelet crystal research (Lange [4]; Ohlendorf et al. [5]) with morphometry of the ooplasm and attempts at micro-analytic quantitation, important quantitative data on both a relative and absolute scale will eventually become available. 
  Reference    Z. Naturforsch. 36c, 686—687 (1981); received January 21 1981 
  Published    1981 
  Keywords    Cyclostomes, Teleosts, Amphibia, Phosvitin, Cations 
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 TEI-XML for    default:Reihe_C/36/ZNC-1981-36c-0686_n.pdf 
 Identifier    ZNC-1981-36c-0686_n 
 Volume    36 
2Author    Rüdiger RiehlRequires cookie*
 Title    Pomatoschistus minutus III. Determination of Amino Acid Component  
 Abstract    The oocytes of the marine goby Pomatoschistus minutus were analyzed for their amino acid content. Most of the amino acids exist as protein, only a little part is free or peptide-bound. Among the protein-bound amino acids, high levels of glutamic acid, proline, alanine, aspartic acid, valine and leucine were detected. These represent more than 60% of the protein amino acids. Among the free acids, glutamic acid, serine and alanine, are dominant. There are no certain proofs o f the occurrence o f peptide pools in the oocytes o f Pomatoschistus minutus. 
  Reference    Z. Naturforsch. 35c, 1094—1095 (1980); received June 9/July 16 1980 
  Published    1980 
  Keywords    Oocytes, Yolk, Amino Acid Component, Pomatoschistus minutus, Teleost 
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 TEI-XML for    default:Reihe_C/35/ZNC-1980-35c-1094_n.pdf 
 Identifier    ZNC-1980-35c-1094_n 
 Volume    35 
3Author    Ghanashyam TripathiRequires cookie*
 Title    Scaling of Some Metabolic Enzymes in Liver of a Freshwater Teleost: An Adaptive Mechanism  
 Abstract    The activities of mitochondrial malate dehydrogenase (m M DH) and the total mito­ chondrial proteins increase as a function of body mass in the freshwater catfish, Clarias batrachus. It clearly indicates an increase in energy production in larger-sized individuals for various purposes including prey-predator interactions. The higher activity of lactate dehydro­ genase (LDH) in larger fish may indicate more production of lactate for gluconeogenesis in the liver to meet emergency requirements of increased energy demand. However, the activity of cytoplasmic malate dehydrogenase (cMDH) decreases with the increasing body mass of the fish which reflects reduction in N ADPH production and, in turn, reduced lipogenesis in liver of larger individuals. Thus, the present observations suggest an adaptive mechanism dealing with the higher energy budget, and reduced synthetic activities (lipogenesis) in the liver of larger-sized freshwater catfish. This type of biochemical scaling might be also support­ ing other metabolic pathways in order to adjust some physiological functions for survival in the aquatic environment. 
  Reference    Z. Naturforsch. 54c, 1103—1106 (1999); received July 12/September 1 1999 
  Published    1999 
  Keywords    Teleost, Liver, Scaling, Lactate Dehydrogenase, Malate Dehydrogenase 
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 TEI-XML for    default:Reihe_C/54/ZNC-1999-54c-1103.pdf 
 Identifier    ZNC-1999-54c-1103 
 Volume    54