On the complexity of fundamental computational problems in pedigree analysis.

Pedigree analysis is a central component of many current efforts to locate genes that contribute to diseases or to valuable traits. The analysis usually involves solving one of two very computation-intense problems. We analyze the complexity of these two problems. Surprisingly, we show that both problems are NP-hard even for pedigrees that contain no inbreeding loops.     

Characterization of a light-dependent glutamate synthase activity in Chlamydomonas reinhardtii

Photosynthetically active vesicles prepared from Chlamydomonas reinhardtii retained a light-dependent glutamate synthase activity which was highly specific for 2-oxoglutarate (K_m=2.1 mM) and L-glutamine (K_m=0.9 mM) as amido group acceptor and donor respectively. This activity was inhibited by azaserine, p-hydroxymercuribenzoate and 3-(p-chlorophenyl)-1,1-dimethyl urea.Light-dependent synthesis of glutamate was also obtained by coupling Chlamydomonas photosynthetic particles to purified ferredoxin-glutamate synthase, using ascorbate and 2,6-dichlorophenol-indophenol as electron donor. This system was also specific for 2-oxoglutarate (K_m=1 mM) and L-glutamine (K_m=0.8 mM) as substrates, and was stimulated by dithioerythritol. Azaserine and p-hydroxymercuribenzoate, but not 3-(p-chlorophenyl)-1,1-dimethyl urea, inhibited the reconstituted activity; high concentrations of 2-oxoglutarate were inhibitory.Abbreviations A Absorbance - CCP p-Trichlorometoxi-carbonylcyanide-phenylhydrazone - Chl Chlorophyll - CMU 3-(p-Chlorophenyl)-1,1-dimethyl urea - DPIP 2,6-Dichlorophenol-indophenol - DTE Dithioerythritol - MSX L-Methionine, D-L, sulfoximine - MV Methyl viologen     

Nerve Growth Factor Effect on Adenosine Transport in Cultured Chromaffin Cells

Chromaffin cells both recently isolated or in culture present a high-affinity adenosine transporter with a Km value of 1 microM. When cells were exposed to nerve growth factor (NGF; 10 ng/ml), the adenosine transporter affinity decreased to 3 microM. This value was maintained from 3 days after plating to the end of the culture period. A change in the transport capacity was observed, with a significant increase (approximately 200-260%) in NGF-cultured cells throughout the period studied.     

Glutathione status and sensitivity to GSH-reacting compounds of Escherichia coli strains deficient in glutathione metabolism and/or catalase activity

The intracellular concentrations of total glutathione, GSSG and protein · S-SG, the total excreted glutathione concentration, and the susceptibility towards GSH-reacting compounds were assayed in strains of Escherichia coli deficient in biosynthesis and/or reduction of glutathione. A deficiency in glutathione reductase displaced the glutathione status towards the oxidized forms. This displacement was more clearly appreciated in strains additionally deficient in glutathione biosynthesis. A deficiency in catalase activity also produced an increase in the oxidation of glutathione. The most severe changes were observed in the concentrations of protein-glutathione mixed disulfides and in the amount of glutathione excreted to the medium. Increased sensitivities towards compounds known to interact with cellular GSH were observed in glutathione reductase deficient strains, although these effects were enhanced in strains additionally deficient in GSH biosynthesis     

Scaling-up of a batch whey fermentation by Kluyveromyces fragilis

Summary A whey fermentation by Kluyveromyces fragilis was scaled-up to a 1000-dm³ stirred fermentor, by varying the stirrer speed, the air-flow rate and the initial concentration of lactose. Its evolution was simulated by applying the same unstructured model (consisting of a microbial specific growth rate of pseudo-first order with respect to the COD concentration and constant biomass yield per unit COD removed) set up in previous experiments using 8- to 80-dm³ fermentors. Despite the great scale-up ratios, very different operating conditions, and geometric dissimilarity, a series of empirical regressions previously developed allowed approximate, but acceptable prediction of the stoichiometric and kinetic coefficients of the above mathematical model, thus confirming the capability of this model to provide a reliable basis for further scale-up of this fermentation process to a production scale.     

The three-dimensional structure of the zona pellucida in growing and atretic ovarian follicles of the mouse

Summary The present study provides further details on the fine-structural three-dimensional architecture of the zona pellucida (ZP) in growing and atretic follicles of mice by use of ruthenium red in combination with the detergents Triton X100 and saponin. These detergents were used for extraction of the soluble fraction of the zonal proteins in an attempt to expose the structural zonal glycoproteins, which in turn can be viewed as minute three-dimensional networks upon transmission- and scanning electron-microscopic examination. By use of these methods, the ZP of growing follicles appeared to be formed by interconnected filaments which also bind to globular structures building up a three-dimensional lattice. In contrast, the ZP of stage I as well as other (II and III) stages of atretic follicles showed a structure characterized by the presence of closely packed granules connected with short filaments to form a close-mesh reticulum. This structural change of the ZP, which in the present study is also associated with the disappearance of gap junctions within the granulosa and cumulus cell population, might represent one of the early events involved in the onset of atresia. These changes, most probably depending on an altered secretory activity of both oocytes and follicle cells, might lead to a degradation of the ZP network structure and to its subsequent increased density (condensation). All these morphodynamic events eventually contribute to a sequestration of the oocyte in the early stage of atresia.     

Changes of Escherichia coli cell cycle parameters during fast growth and throughout growth with limiting amounts of thymine

It is generally accepted that during fast growth of Escherichia coli, the time (D) between the end of a round of DNA replication and cell division is constant. This concept is not consistent with the fact that average cell mass of a culture is an exponential function of the growth rate, if it is also accepted that average cell mass per origin of DNA replication (M_i) changes with growth rate and negative exponential cell age distribution is taken into account. Data obtained from cell composition analysis of E. coli OV-2 have shown that not only (M_i) but also D varied with growth rate at generation times () between 54 and 30 min. E. coli OV-2 is a thymine auxotroph in which the replication time (C) can be lengthened, without inducing changes in , by growth with limiting amounts of thymine. This property has been used to study the relationship between cell size and division from cell composition measurements during growth with different amounts of thymine. When C increased, average cell mass at the end of a round of DNA replication also increased while D decreased, but only the time lapse (d) between the end of a replication round and cell constriction initiation appeared to be affected because the constriction period remained fairly constant. We propose that the rate at which cells proceed to constriction initiation from the end of replication is regulated by cell mass at this event, big cells having shorter d times than small cells.Abbreviations OD₄₅₀ and OD₆₃₀ Optical density at a given wavelength in nm Dedicated to Dr. John Ingraham to honor him for his many contributions to Science     

The 18p- syndrome. Report of five cases

Five children, three males and two females were found to have a short arm deletion of chromosome 18. Four of them display some of the typical features of this syndrome: microcephaly, round face, hypertelorism, broad-based nose, "carp-mouth", microrethrognathia, pterygium colli, dysplastic and low set ears, clinodactily, failure to grow, muscular hypotony and mental retardation. Different hypotheses are discussed in order to explain the variable phenotypical expression of the 18 p-syndrome.