Regulation of the amylase secretion by the yeast Filobasidium capsuligenum and a 2-deoxy-d-glucose resistant mutant

Summary The regulation of extracellular amylase production by the basidiomycetous yeast Filobasidium capsuligenum CCY 64-5-1 was characterized using growing and resting cells. A basal level of amylolytic activity was produced with various carbon sources including glucose. Amylase secretion was repressed by glucose and, more severely, by 2-deoxy-d-glucose, whereas compounds with -1,4-linked glucose, such as methyl glucoside, maltose, -cyclodextrin and soluble starch, served as inducers. Repression was not relieved by exogenously added cAMP. The effects of several metabolic inhibitors on amylase secretion were studied. Following UV-mutagenesis a mutant strain (FC-5) capable of growing in a 2-deoxy-d-glucose supplemented corn starch medium was selected for further characterization. This strain produced more amylase, had acquired an increased resistance against repression by glucose, and retained a growth rate comparable to the wild type. FC-5 was also characterized by a reduced glucokinase activity and an increased hexokinase activity.     

Chromosomal aberrations induced in human cultured cells by liposome-encapsulated deoxyribonuclease I

Experiments of incorporation of a nucleolytic enzyme into human cells cultured in vitro have been carried out with the aim of inducing structural chromosome variations. Human heteroploid cells, either as asynchronous populations or enriched in mitoses, and PHA-stimulated lymphocytes were used as recipients. We found that all these cells when exposed to pancreatic DNAase I encapsulated in liposomes, either of multilamellar (MLV) or of small unilamellar (SUV) type, show an incidence of chromosome damage higher than that induced by the enzyme free in the incubation buffer. Our results indicate that liposomes are suitable vehicles for the transfer of an exogenous nuclease into human cultured cells. The enzyme remains functionally active and interacts with nuclear DNA, giving rise to chromosome lesions.     

Specific Inhibition of Lignification in Bryonia dioica: Effects on Thigmomorphogenesis

Rubbing-induced lignification in Bryonia dioica internodes is significantly impaired by N(o-hydroxyphenyl) and N(o-aminophenyl) sulfinamoyl tertiobutyl acetate, specific inhibitors of cinnamyl alcohol dehydrogenase, an enzyme which is strictly associated with lignin monomer synthesis. Along with the reduction of lignification, these inhibitors counteract the inhibition of elongation due to rubbing. These results indicate that lignification participates in the thigmomorphogenetic growth response of Bryonia dioica internodes. In a general way, the data point to the causal role of lignification in the limitation of plant growth.     

Biphasic fluence-response curves for phytochrome-mediated kalanchoë seed germination : sensitization by gibberellic Acid

The fluence-response curves for the effect of two red pulses separated by 24 hours on the germination of Kalanchoe blossfeldiana Poelln. cv Vesuv seeds, incubated on gibberellic acid (GA₃) are biphasic for suboptimal concentrations. The response in the low fluence range corresponds with a classical red/far-red reversible phytochrome mediated reaction. GA₃ induces an additional response in the very low fluence range, which is also phytochrome mediated. The sensitivity to phytochrome-far-red absorbing form (Pfr), however, is increased about 20,000-fold, so that even far-red fluences become saturating. Both in the very low and low fluence response range, the maximal responses induced by saturating fluences are modulated by the GA₃ concentration. GA₃ having no direct influence on the phytochrome phototransformations, alters the Pfr requirement and determines the responding seed population fraction in the very low and low fluence range. The effet of GA₃ appears to be on the transduction chain of the phytochrome signal.     

Relative biological effectiveness (RBE) of neutrons produced by 50 MeV deuterons and by 34, 45, 65 and 75 MeV protons

RBE of p(34) + Be, p(45) + Be, p(65), + Be, p(75) + Be and d(50) + Be neutron beams produced at the cyclotron "Cyclone" of Louvain-la-Neuve were measured. The biological criterion was the regeneration of the crypts of the intestinal mucosa (50 regenerated crypts per circumference) after abdominal irradiation in mice. Taking the p(65) + Be neutrons as reference, RBE values were found equal to 1.12, 1.07, 1.00 (Ref.), 0.96 and 1.02 respectively. These results are consistent with those published for cell lethality in vitro. However, the RBE variation is smaller than this previously obtained in the laboratory for growth inhibition in Vicia faba.     

Trichodorus persicus n. sp. (Nematoda: Trichodoridae) from Iran

Trichodorus persicus n. sp. is described from the Caspian region of Iran, where it was found in woodland and orchard soil. Males of the new species usually have two ventral cervical papillae anterior to the excretory pore but posterior to the base of the onchiostyle; there are three ventromedian preanal supplements, the posterior one lying near the heads of the retracted spicules; the spicules are 51–61 m long with faint transverse striations distally. Females have two pairs of lateral body pores, large rounded sclerotized thickenings at the vulva and the vagina tapers inwards in lateral view.     

The nuclear migration signal of Xenopus laevis nucleoplasmin.

Nucleoplasmin is the most abundant protein in the nucleus of Xenopus laevis oocytes. Its ability to target to the nucleus when microinjected into the cytoplasm has been the subject of many studies central to our understanding of how proteins segregate into nuclei. Using a cDNA clone we constructed beta-galactosidase-nucleoplasmin hybrids in modified bacterial expression vectors. The fusion proteins were expressed in Escherichia coli, purified and injected into the cytoplasm of X. laevis oocytes. The distribution of the fusion proteins between the cytoplasmic and nuclear compartments were analysed after incubation of various lengths of time. The results show that the signal sequence for nuclear transport is located close to the carboxy terminus of the protein. The signal sequence has been mapped to a small stretch of amino acids, containing a stretch of four lysines analogous to the SV40 large-T antigen signal.     

Chemical, immunological and biological properties of peptides like vasoactive-intestinal-peptide and peptide-histidine-isoleucinamide extracted from the venom of two lizards (Heloderma horridum and Heloderma suspectum)

Having previously isolated helodermin, the major peptide like vasoactive-intestinal-peptide and peptide-histidine-isoleucinamide, from the venom of the lizard Heloderma suspectum, we decided on a systematic exploration of all (VIP-PHI)-like peptides present in the venom of another lizard of the Helodermatidae family: Heloderma horridum. Six (VIP-PHI)-like peptides (PHH1 to 6) were purified to homogeneity from the venom of the lizard H. horridum with PHH3 and PHH4 representing two minor forms. All peptides cross-reacted in radioimmunoassays for helodermin and PHI but not for VIP. They yielded four fragments (T1 to T4) after trypsin digestion. T1, T2 and T3 showed the same retention time by reverse-phase HPLC and the same amino acid composition; the differences were confined to T4, the C-terminal sequence. PHH5 and PHH6 were found to be identical to synthetic helospectins I and II respectively. PHH1 and PHH3 probably resulted from a secondary modification of PHH5, while PHH2 and PHH4 derived from PHH6. Thus, the VIP-like peptides, previously called helospectins, are in fact typical of H. horridum venom. We confirmed that helodermin is the major (VIP-PHI)-like peptide of the venom of H. suspectum and observed its absence in H. horridum venom. Also, we found that positions 8 and 9 of helodermin are occupied by two Glu residues instead of two Gln as previously published. Helospectin-like material was also present in H. suspectum venom but in very small amount. In both venoms all VIP-like peptides were equally potent and efficient when tested for (a) their ability to occupy VIP as well as secretin receptors in rat pancreatic membranes and VIP receptors in rat liver membranes, and (b) the ensuing activation of adenylate cyclase in both membrane preparations.