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H van den Ende

Publications and source records attributed to H van den Ende.

33 records · Page 2Linked to original sources
PubMed1988

Light Affects Flagellar Agglutinability in Chlamydomonas eugametos by Modification of the Agglutinin Molecules.

The effect of light on the sexual competence of a light-sensitive mating type minus strain (mt(-)) of Chlamydomonas eugametos obtained by crossing a light-sensitive mating type plus strain (mt(+)) with a light-insensitive mt(-) strain is described. As previously demonstrated for the mt(+) parent, this study of one of the mt(-) offspring shows that (a) a light-sensitive mechanism affects flagellar agglutinability in a rapid process that does not require protein synthesis; (b) only the activity of the flagellar agglutinins (glycoproteins responsible for agglutination) is susceptible to light while agglutinins on the cell body surface are not affected by light. We further demonstrate that (a) membrane vesicles naturally released from nonagglutinable dark gametes remain inactive. Extracts of these vesicles also remain inactive even though they contain agglutinin-like components; (b) inactive mt(-) agglutinin is present in extracts of flagella from nonagglutinable dark gametes by comparison of its chromatographic, electrophoretic, and immunogenic properties with those of active agglutinin. When purified of all other flagellar proteins, it remains inactive; (c) a monoclonal antibody directed against the sexual agglutination site of the mt(-) agglutintin discriminates between active and inactive agglutinins when present in a native state on the flagellar surface, but is unable to discriminate between them when they are denatured in sodium dodecyl sulfate-electrophoresis gels and blotted onto nitrocellulose. Taken collectively these observations suggest that light activation involves the chemical modification of the agglutinins in situ on the flagellar surface.

Journal Article↗
PubMed1986

Cellular Interactions during the Mating Process in Chlamydomonas eugametos.

A method to determine the mating competence of Chlamydomonas eugametos was developed. The contribution of each mating type in the pair formation was investigated using asymmetric gamete mixtures. It was established that pair formation is not mediated by a pheromonal attraction mechanism between partner gametes, but depends on collision chances. On the other hand, it was demonstrated that during transient contacts between partner gametes the flagellar agglutinability of both partners is stimulated, evidently to prepare a successful mating. The plus mating type was generally less agglutinable than the minus mating type and was a rate-limiting factor in the mating process.

Journal Article↗
PubMed1985

Sexual Agglutination in the Unicellular Green Alga Chlamydomonas eugametos: Identification and Properties of the Mating Type plus Agglutination Factor.

Gametes of the unicellular green alga Chlamydomonas eugametos agglutinate via their flagella. The mating type plus agglutination factor was solubilized by relatively mild treatments such as a short pH shock or an osmotic shock indicating that it is an extrinsic membrane component. It was also extracted in the nonionic detergent Triton X-100. A simple two-step procedure consisting of gel filtration over Sepharose 4B-cross-linked followed by anion exchange chromatography of the void volume yielded an electrophoretically pure preparation of a single high molecular weight glycoprotein. The agglutination factor sedimented as a 9.3 S particle (assuming a density of 1.50) in sucrose gradients. This low value, compared with the high apparent molecular weight seen during gel filtration and electrophoresis, suggests that the agglutination factor is a rod-like molecule. This was confirmed by viewing rotary-shadowed preparations in the electron microscope. A population of long slender molecules was revealed (328 +/- 20 nanometers), many of which had a knob at one end and a flexible region about one fourth of the length from the other end.

Journal Article↗
PubMed1983

Variable amounts of translatable ferritin mRNA in bean leaves with various iron contents.

RNA was isolated from bean leaves with various iron and ferritin contents. The amount of translatable ferritin mRNA in these RNAs was determined by wheat-germ cell-free translation and immunoprecipitation with anti-bean seed ferritin serum. The levels of ferritin mRNA present in total RNA of the leaves are reflected by the in vivo levels of ferritin in the corresponding leaf tissues. This implies that the iron-dependent regulation of phytoferritin synthesis, in contrast with the regulation of animal ferritin synthesis, occurs at the level of transcription.

Ferritins↗
PubMed1982

An antiserum against a glycoprotein functional in flagellar adhesion between Chlamydomonas eugametos gametes.

Chlamydomonas eugametos gametes agglutinate sexually by their flagellar surfaces. The agglutination factor on mating type minus (mt-) gametes is thought to be a glycoprotein named PAS-1.2. To test this idea, an antiserum was raised against purified PAS-1.2, which reacted with isolated PAS-1.2 (immunoprecipitation tests) and blocked the ability of isolated PAS-1.2 to induce sexual twitching in mt+ gametes. When tested with living cells, the antiserum specifically agglutinated mt- gametes and induced a reaction resembling twitching. Mt+ flagella were shown to bind the antiserum (indirect immunofluorescence) but much less than mt- gametes. Mt- gametes pretreated with Fab fragments of the antiserum were unable to reproduce sexually, while treated mt+ gametes were unaffected. This effect presumably results from the ability of the serum to block mt- sexual agglutination, for mt- isoagglutinin was completely inactivated by the serum, while mt+ isoagglutinin was unaffected. It is therefore argued that PAS-1.2 is the in vivo mt- agglutination factor. However it is shown that the antiserum was able to react in vitro not only with PAS-1.2 but with several other proteins in both mt- and mt+ flagella.

Agglutination↗
PubMed1982

A note on the deep abdominal reflex.

Deep abdominal reflexes were recorded electromyographically in six patients with lesions of the upper motor neuron. The responses were bilateral, usually with identical latencies which ranged from 16.5 to 25 ms. Individual variation was never greater than 2 ms. It is postulated that these bilateral responses of abdominal muscles were independent stretch reflexes and were not mediated across the midline through an intraspinal pathway.

Abdominal Muscles↗
PubMed1977

The hyphal wall of Mucor mucedo. 1. Polyanionic polymers.

Treatment of isolated hyphal walls of Mucor mucedo with nitrous acid resulted in the release of two water-soluble polyanions: (a) a glycuronan, containing all the neutral sugars and uronic acid present in the hyphal wall and (b) an inorganic polyphosphate. The glycuronan could also be extracted quantitatively with salt solutions of high ionic strength and partially with a solution of potassium hydroxide. This is presented as evidence that the glycuronan is a genuine constituent of the cell wall, non-covalently bound to glucosamine-containing polymers which are susceptible to depolymerization by nitrous acid. By treatment with acid the glycuronan was partly converted to crystalline poly(glucuronic acid) with the properties of mucoric acid. This strongly suggests that mucoric acid, which can be extracted from the walls of M. mucedo by alkali after acid treatment, is not a genuine wall component but arises by partial acid hydrolysis of the heteropolymeric glycuronan.

Amino Acids↗
PubMed1977

The hyphal wall of Mucor mucedo. 2. Hexosamine-containing polymers.

Nitrous acid, which specifically depolymerises polymers containing hexosamines with a primary amino group, was used to analyse the hexosamine-containing polymers in the hyphal wall of Mucor mucedo. N-Acetylglucosamine was found to occur in three polymeric fractions. One fraction which was solubilised by HNO2 treatment contained-N-acetylglucosamine interspersed with glucosamine; no homopolymer of glucosamine (chitosan) was detected. Another fraction became HNO2-soluble after treatment with pronase or alkali; this points to the occurrence of a heteropolymer containing N-acetylglucosamine and glucosamine in which some of the glucosamine residues are linked to peptides via their amino groups. The residue remaaining after pronase and HNO* treatment appeared to consist of a homopolymer of N-acetylglucosamine (chitin).

Acetylglucosamine↗
PubMed1968

Relationship between sexuality and carotene synthesis in Blakeslea trispora.

When stimulated by equivalent amounts of progametangia-inducing hormones, cultures of the minus mating type of Blakeslea trispora produce about the same quantities of carotenoids as mated cultures of the fungus, which suggests that the stimulation of carotene synthesis during the sexual activity of mated cultures is the result of hormonal action. These hormones were isolated and purified. From spectroscopic analysis of purified samples, it appears that the hormones are identical with trisporic acids B and C. When both mating types of B. trispora were cultivated in one vessel but were kept apart by membrane filters, the formation of sex hormones was not inhibited. Physical contact between the mating types is obviously not required for the induction of sexual activity. The sex hormones also formed in combined cultures of B. trispora-plus and Zygorhynchus moelleri (a homothallic species), but not in combined cultures of B. trispora-minus and Z. moelleri. This is evidence for the hypothesis that the hormones are produced by B. trispora-plus only.

Carotenoids↗
PubMedDate not supplied

An assay of relative cell wall porosity in Saccharomyces cerevisiae, Kluyveromyces lactis and Schizosaccharomyces pombe.

We have developed a new assay to determine relative cell wall porosity in yeasts, which is based on polycation-induced leakage of UV-absorbing compounds. Polycations with a small hydrodynamic radius as measured by gel filtration (poly-L-lysine) caused cell leakage independent of cell wall porosity whereas polycations with a large hydrodynamic radius (DEAE-dextrans) caused only limited cell leakage due to limited passage through the cell wall. This allowed the ratio between DEAE-dextran- and poly-L-lysine-induced cell leakage to be used as a measure of cell wall porosity in Saccharomyces cerevisiae, Kluyveromyces lactis and Schizosaccharomyces pombe. Using this assay, we found that the composition of the growth medium affected cell wall porosity in S. cerevisiae. In addition, we could show that cell wall porosity is limited by the number of disulphide bridges in the wall and is dependent on cell turgor. It is argued that earlier methods to estimate cell wall porosity in S. cerevisiae resulted in large underestimations.

Cell Wall↗
PubMedDate not supplied

The glucanase-soluble mannoproteins limit cell wall porosity in Saccharomyces cerevisiae.

The cell wall porosity of batch-grown Saccharomyces cerevisiae was maximal in the early exponential phase and fell off rapidly to lower levels in later growth phases. Treatment of stationary-phase cells with alpha-mannosidase restored wall porosity to the level of cells in early exponential phase. When cells in the early exponential phase were treated with alpha-mannosidase, or tunicamycin, an inhibitor of N-glycosylation, even higher porosities were obtained. Mutants with truncated mannan side-chains in their wall proteins also had very porous walls. The importance of the mannan side-chains for wall porosity was also seen during sexual induction. Treatment with alpha pheromone, which leads to the formation of wall proteins with shorter mannan side-chains, enhanced wall porosity. Disulphide bridges also affect cell wall porosity. They were predominantly found in the glucanase-soluble wall proteins. Because the main part of the mannan side-chains is also found in this family of wall proteins, our results demonstrate that the glucanase-soluble mannoproteins limit cell wall porosity in yeast.

Benzenesulfonates↗