Effect of cultural and nutritional conditions on the control of flocculation expression in Saccharomyces cerevisiae

The effect of cultural (temperature and pH) and nutritional conditions (nitrogen and carbon source) on the flocculation expression of three strains was studied. The strains' flocculation ability was determined by placing the cells in a stationary phase of growth in standard flocculation conditions. The flocculation ability of strain NCYC 1195, recently classified in the literature as the NewFlo phenotype, was more sensitive to growth temperature than Flo1 phenotype strains (NCYC 869 and NRRL Y265). The initial pH of the culture medium did not affect the flocculation ability of Flo1 phenotype strains but in the case of strain NCYC 1195 flocculation was repressed when the initial pH of the culture medium was below 3.5. Flocculation in strain NCYC 1195 was also repressed in defined culture medium; this inhibition was not related to a deficiency in any particular nitrogen source, but rather to the poor buffering capacity of the defined medium. All strains showed strong flocculation when grown in glucose, but were nonflocculent in glycerol. It was clearly demonstrated that the phenotypic expression of flocculation could be induced or repressed by changing cultural and nutritional conditions. Two distinct behaviours were also displayed with regard to the effect of the cultural conditions upon flocculation, namely the effect of pH. These different behaviours can be used to distinguish the two flocculation phenotypes.

Population dynamics of flocculating yeasts

The problem of understanding the recognition and specific interactions in a population of yeast flocculating cells is discussed. The biochemistry, physiology and genetics of flocculation is briefly reviewed. Yeast flocculation requires the expression of a specific protein (lectin) on flocculent cells, and carbohydrate (receptors) on neighbouring cells. Adhesion experiments performed with cells whose flocculation is repressed by growth conditions, indicating that the inhibition of flocculation is due to inhibition or inactivation of 'lectin-like' component. Additionally, using adhesion experiments, it is demonstrated that cells of non-flocculent strain interact by establishing a true bond with flocculent cells rather than by entrapment inside the floc matrix. As phenotypic expression of flocculation, for several strains, is shown to be repressed, modulated or induced by modifying growth conditions, the constitutiveness and inducibility of flocculation are also discussed.

Evaluation of crude hydroxypropyl starch as a bioseparation aqueous-phase-forming polymer

A new aqueous two-phase system based on crude hydroxypropyl starch (HPS) and poly(ethylene glycol) (PEG) is described. Unlike other polymer-polymer aqueous two-phase systems, the HPS used is commercially available. Previous works have characterized almost exclusively purified carbohydrates or their derivatives, having neglected the large amount of gums and carbohydrates already used in the paper, food, or textile industries. Two-phase aqueous polymer systems based on such commercial polymers may have as a drawback their degree of purity, which may affect the separation procedure. However, their lower cost should encourage studies on their use in aqueous two-phase polymer extraction. The influence of temperature, pH, and ionic strength on the partition of several different molecular weight and isoelectric point proteins and whole cells was studied. The results obtained were compared with corresponding dextran-PEG systems, Aquaphase PPT-PEG systems, crude dextran-PEG systems, maltodextrin-PEG systems, and Klucel L-pluronic systems. Protein partition coefficient results exhibited higher values than those in corresponding systems. It is shown that this system, based on a crude hydroxypropyl starch, is highly attractive as an initial purification step.

Transport of malic acid in the yeast Schizosaccharomyces pombe: evidence for a proton-dicarboxylate symport

The transport system for malic acid present in Schizosaccharomyces pombe cells, growing in batch culture on several carbon sources, has been studied. It was found that the dicarboxylic acid carrier of S. pombe is a proton-dicarboxylate symporter that allows uphill transport and accumulation as a function of delta pH with the following kinetic parameters at pH 5.0: Vmax = 0.1 nmol of total malic acid s-1 mg (dry weight) of cells-1 and Km = 1.0 mM total malic acid. Malic acid uptake (pH 5.0) was accompanied by disappearance of extracellular protons, the uptake rates of which followed Michaelis-Menten kinetics as a function of the acid concentration. The Km values calculated as the concentrations either of anions or of undissociated acid, at various extracellular pH values, pointed to the monoanionic form as the transported species. Furthermore, accumulated free acid suffered rapid efflux after the addition of the protonophore carbonyl cyanid m-chlorophenyl hydrazone. These results suggested that the transport system was a dicarboxylate-proton symporter. Growth of cells in a medium with glucose (up to 14%, w/v) and malic acid (1.5%, w/v) also resulted in proton-dicarboxylate activity, suggesting that the system, besides being constitutive, was still active at high glucose concentrations. The following dicarboxylic acids acted as competitive inhibitors of malic acid transport at pH 5.0: D-malic acid, succinic acid, fumaric acid, oxaloacetic acid, alpha-ketoglutaric acid, maleic acid and malonic acid. In addition, all of these dicarboxylic acids induced proton movements that followed Michaelis-Menten kinetics.(ABSTRACT TRUNCATED AT 250 WORDS)

Interaction between flocculent and nonflocculent cells of Saccharomyces cerevisiae

Interaction between nonflocculent and flocculent cells of Saccharomyces cerevisiae was studied. Adhesion experiments were done using three types of nonflocculent cells and a flocculent one. Two types of nonflocculent cells were obtained from the flocculent strain by changing environmental growth conditions. The integration of nonflocculent cells in the flocs was observed by two different methods: measurement of the sedimentation capacity of mixtures and microscopic observation of stained nonflocculent cells blended with flocculent cells. It was possible to verify that cell-cell interaction corresponds to a true stable binding and not to a simple entrapment inside the floc matrix.

Development of the aorta in the chick embryo: structural and ultrastructural study

A structural and ultrastructural study was designed to analyze systematically the cellular events which take place in the aortic wall between days 7 and 21 of chick embryo development. Between days 7 and 18, increase in total diameter, number of cell layers, and aortic wall thickness are highly correlated, whereas between days 18 and 21 the total diameter increase is correlated mainly with an increase in vessel lumen diameter. Cell layers of smooth muscle cells showing an immature or synthetic phenotype arise from progressive association and organization of mesenchymal cells originated from an endothelial activation process in which a hyaluronic acid-rich extracellular matrix seems to be involved. It is suggested that the process of endothelial activation takes place between days 7 and 18 of embryonic development provided that within that period the typical cellular events which are involved in such a process take place (hypertrophy, reorientation, invagination, mitotic activity, acquisition of migratory appendages, endothelial detachment and incorporation into adjacent spaces). This endothelial activation has been recognized as a selective multiphasic process required for the transition of endothelial cells into mesenchyma.

Use of monoclonal antibodies for the histopathological diagnosis of human malignancy

This paper describes the use of a panel of seven monoclonal antibodies (selected so as to include reagents reactive with both epithelial and lymphoid cells) for distinguishing between anaplastic carcinoma and high grade lymphoma. Details are given of the immunohistological reactions of these antibodies against a wide range of both normal and malignant tissues and of a number of practical instances in which use of the antibody panel enabled a diagnosis to be made when routine histological examination had been inconclusive.

Apparent non-penetrance for dystopia in Waardenburg syndrome type I, with some hints on the diagnosis of dystopia canthorum

Two large pedigrees with Waardenburg syndrome type I (W--I), i.e. with dystopia canthorum and blepharophimosis, are described to show both the variable expressivity of dystopia canthorum, which may be confused with non-penetrance of this sign, and the possibility to firmly diagnosis it with the new biometric index W, which differentiates a dystopic from a non-dystopic or a non-apparent dystopic subject, the latter within a defined biometric range. A general discussion of the relative value of blepharophimosis and dystopia canthorum as diagnostic features in W--I is presented, to conclude on the greater value of dystopia canthorum, which can be identified with confidence in more than 96% of carriers. Empirical probabilities are given for dystopia canthorum and blepharophimosis in the general populations, based on data from the world literature, useful for all ethnic groups.

[Irapa type spondylo-epiphyso-metaphyseal osteochondrodysplasia. New type of dwarfism with short spine and metatarsals]

A new dwarfism of a spondyloepiphysometaphyseal dysplasia is described among Venezuelan Indians of the Yukpa (Irapa) tribe. Brachyrrhahia, brachymetatarsia and brachyrhyzomelia in upper limbs and manifestations in proximal epiphyses of femora and distal epiphyses of humera, with moderate to serious impairment of gait, but no significance deviations of the spine, are the main clinical findings. It is a well individualized type among a very heterogeneous and ill-defined group of chondrodystrophies. The inheritance is through an autosomal recessive or less probably an X-linked gene.

Probable loose linkage between the ABO locus and Waardenburg syndrome type I

The possibility of linkage was tested in 3 large kindreds with Waardenburg syndrome type I against the ABO locus. Loose linkage is probably present; the recombination fraction in males, females, and both sexes combined seems to be approximately theta' equals 0.175, theta equals 0.255, and theta', theta equals 0.20, respectively. There are still more informative matings to be studied in those pedigrees, as well as the inminent possibility of determining the phase status in several of them, for the ABO locus and a few other loci.