Kinetics of gametogenesis

Cell and Tissue Research - In the rat (Wistar-WU) sexual differentiation of the gonads occurs between days 14 and 15 post conception (p.c.). At this time the oogonia and their parallel population...     

Detection and identification ofPodophyllotoxin produced by cell cultures derived from podophyllum hexandrum royle

The phenylpropanoid derived lignan podophyllotoxin, occurring inPodophyllum species, is used as a starting compound for the chemical synthesis of the antitumour agents etoposide (VP-16-213) and teniposide (VM-26). At present, the availability of this lignan becomes increasingly limited. As an alternative source, cell cultures originating fromPodophyllum hexandrum Royle were initiated. Analysis of the cell extracts using different HPLC systems as well as TLC, indicated the presence of podophyllotoxin. After prepurification of the extracts by means of ITLC, the identity was confirmed by mass spectrometric analysis. Dark-grown cultures accumulated considerable higher amounts of podophyllotoxin in comparison with the light-grown cultures.     

Production of 5-methoxypodophyllotoxin in cell suspension cultures of Linum flavum L.

Cell suspension cultures of Linum flavum L., routinely grown on a NAA-containing medium, accumulated low levels of the phenylpropanoid-derived lignan 5-methoxypodophyllotoxin (5-MPT), up to 0.004% on a dry weight basis. Feeding experiments with the precursor L-phenylalanine resulted in a 3–5-fold increase in 5-MPT levels, but caused the levels of PAL activity to fall. Treatment of the cultures with the elicitor Nigeran, either alone or in combination with phenylalanine, caused the 5-MPT production to cease, even though PAL activity was rapidly enhanced by these treatments. Transfer of the cultures to NAA-free medium resulted in a 40–50 fold higher level of 5-MPT accumulation, the PAL activity levels being lowered compared to the routinely grown cells. With these more differentiated cultures, phenylalanine feeding and elicitor treatment, both on its own and in combination with the precursor, had no effect on 5-MPT production, even though the PAL activity levels were higher than in the untreated cells. It can be concluded that in lignan-accumulating cultures of L. flavum, PAL activity is nearly always detectable and seems to show a reciprocal relationship with 5-MPT accumulation.Abbreviations 5-MPT 5-methoxypodophyllotoxin - PAL phenylalanine ammonia lyase (EC 4:3:1.5) - NAA naphthaleneacetic acid     

FECAL METHANOGENS AND VERTEBRATE EVOLUTION

It has been assumed that the feeding habits of vertebrates predispose the variety of intestinal differentiations and the composition of the microbial biota living in their intestinal tracts. Consequently, the presence of methanogenic bacteria in the various differentiations of the large intestine and the foregut of herbivorous vertebrates had been attributed primarily to the existence of anaerobic habitats and the availability of carbon dioxide and hydrogen originating from the fermentative microbial digestion of plant-based diets. However, Australian ratites, many murids, and several New World primates lack methanogens, despite their intestinal differentiations and their vegetarian feeding habits. Crocodiles, giant snakes, aardvarks, and ant-eaters on the other hand release significant amounts of methane. A determination of methane emissions by 253 vertebrate species confirmed that competence for intestinal methanogenic bacteria is shared by related species and higher taxa, irrespective of different feeding habits. In “methanogenic” branches of the evolutionary tree, a variety of differentiations of the large intestine evolved and, in some cases, differentiations of the foregut. In contrast, the lack of competence for methanogens in chiropterans/insectivores and carnivores apparently has precluded the evolution of specialized fermenting differentiations of the digestive tract. Our observations reveal that the presence of intestinal methanogenic bacteria is under phylogenetic rather than dietary control: competence for intestinal methanogenic bacteria is a plesiomorphic (primitive-shared) character among reptiles, birds, and mammals. This competence for methanogenic bacteria has been crucial for the evolution of the amniotes.     

Ein Beitrag zur Nomenklatur sphinctozoider Schwämme (Porifera)

The sphinctozoid sponge generaFania Senowbari-Daryan 1990 andSpica Termier &Termier 1977 are preoccupied.Fania is replaced byFanthalamia nom. nov. andSpica by the younger synonymFistulispongia Termier &Termier 1977. The invalid subfamily name FaniinaeSenowbari-Daryan 1990 is replaced by Fanthalamiinae n. subfam. The invalid family and subfamily names SpicidaeTermier &Termier 1977 and SpicinaeSenowbari-Daryan 1990 respectively are replaced by FistulispongiidaeTermier atTermier 1977 and FistulispongiinaeSenowbari-Daryan 1990. The generaWaagenium de Laubenfels 1957 andCatubria Merla 1931 were previously overlooked.Waagenium DeLaubenfels 1957 is a younger synonym ofColospongia Laube 1865. The position ofCatubria Merla 1931 is uncertain. Most probablyCatubria is an alga.     

Transient reduction in secreted 32 kD chitinase prevents somatic embryogenesis in the carrot (Daucus carota L.) variant ts11

At the nonpermissive temperature, somatic embryos of the temperature-sensitive (ts) carrot (Daucus carota L.) cell variant ts11 only proceed beyond the globular embryo stage in the presence of medium conditioned by wild-type cells. The causative component in the conditioned medium has been identified as an acidic 32 kD endochitinase. An antiserum raised against the 32 kD chitinase detected this protein in culture medium from ts11 embryo cultures grown at the permissive temperature as well as at the nonpermissive temperature. No difference in biochemical characteristics or in effect on ts11 embryo development could be detected between the 32 kD chitinase purified from wild-type cultures and the chitinase from ts11 cultures grown at the permissive or at the nonpermissive temperature. Compared to the amount present in a ts11 embryo culture at the permissive temperature, a reduction in the amount of 32 kD chitinase was observed during the temperature-sensitive period at the nonpermissive temperature. These results imply that the arrested embryo phenotype of ts11 is not the result of a structural difference in its 32 kD chitinase, but is the result of a transient decrease in the amount of 32 kD chitinase present. Morphological observations indicate that the ts11 phenotype is pleiotropic and also affects the cell wall of nonembryogenic cells. © 1995 Wiley-Liss, Inc.     

Localization of Reactive Cysteine Residues by Maleidoyl Undecagold in the Mitochondrial Creatine Kinase Octamer

Octamers of mitochondrial creatine kinase (Mi-CK) wore modified with the thiol-specific reagents N-ethylmaleimide or the gold-coupled derivative, maleidoyl undecagold. The kinetics of inhibition of the Mi-CK catalysis was shown to be comparable for both reagents, suggesting that the large gold cluster complex is accessible to the reactive cysteines. SDS-PAGE analysis revealed that two of eight cysteines per Mi-CK monomer were labeled with maleidoyl undecagold with a similar affinity for the functional maleimide group. Gel exclusion chromatography of labeled molecules showed that the octameric structure of Mi-CK was preserved after thiol modification. Freeze-dried gold-labeled octamers visualized by electron microscopy under cryoconditions were enhanced in contrast and showed a well-preserved fourfold symmetry of the end-on view, Image analysis of gold-labeled Mi-CK exhibited an averaged end-on view with four strong contrast signals located at the periphery of the notamer, whereas the center of the molecule remained electron translucent. We conclude that the two cysteine residues per monomer labeled with maleidoyl undecagold are located at the octamer's perimeter and we discuss the possible role of these reactive cysteines in enzyme catalysis.     

Creatine metabolism and the consequences of creatine depletion in muscle

Currently, considerable research activities are focussing on biochemical, physiological and pathological aspects of the creatine kinase (CK) — phosphorylcreatine (PCr) — creatine (Cr) system (for reviews see [1, 2]), but only little effort is directed towards a thorough investigation of Cr metabolism as a whole. However, a detailed knowledge of Cr metabolism is essential for a deeper understanding of bioenergetics in general and, for example, of the effects of muscular dystrophies, atrophies, CK deficiencies (e.g. in transgenic animals) or Cr analogues on the energy metabolism of the tissues involved. Therefore, the present article provides a short overview on the reactions and enzymes involved in Cr biosynthesis and degradation, on the organization and regulation of Cr metabolism within the body, as well as on the metabolic consequences of 3-guanidinopropionate (GPA) feeding which is known to induce a Cr deficiency in muscle. In addition, the phenotype of muscles depleted of Cr and PCr by GPA feeding is put into context with recent investigations on the muscle phenotype of gene knockout mice deficient in the cytosolic muscle-type M-CK.Abbreviations Cr creatine - Crn creatinine - PCr phosphorylcreatine - CK creatine kinase - M-CK cytosolic muscle type CK isoenzyme - Mi-CK mitochondrial CK isoenzyme - AGAT L-arginine: glycine amidinotransferase - GAMT S-adenosylmethionine: guanidinoacetate methyltransferase - Arg arginine - Met methionine - GPA guanidinopropionate=-guanidinopropionate - PGPA phosphorylated GPA - GBA 3-guanidinobutyrate=-guanidinobutyrate - CPEO chronic progressive external ophthalmoplegia