Mutants of Saccharomyces cerevisiae cell division cycle defective in cytokinesis. Biosynthesis of the cell wall and morphology

The four temperature-sensitive mutants of Saccharomyces cerevisiae in the cell division cycle defective in cytokinesis (cdc, 3, 10, 11 and 12), have been analyzed with respect to the biosynthesis of the cell wall polymers. After 3 hours of incubation at the non-permissive temperature (37°C) these strains stop growing. The synthesis of glucan, mannan and chitin (wall polymers) level off in a similar time, but glucan, mannan and chitin synthases remained active for at least 4 hours.If the mutants are analyzed by transmission and scanning electron microscopy different pictures emerge. Two of the mutants cdc 10 and cdc 12, after 3 hours of incubation at 37°C present apparently normal cytoplasms and cell wall surfaces with multiple elongated buds. The other two mutants, cdc 3 and cdc 11, present a completely disarranged cytoplasmic content and damage at the level of the plasma membrane is evident.These and other observations, suggest that between the execution points of cdc 3 (0.27) and cdc 10 (0.58), essential processes in the assembly of cell membrane occur.This work was supported in part by a grant from la Comisión de Investigación Científica y Técnica of the Spanish Ministerio de Educación y Ciencia (Project no. 4593-1980).     

The influence of ionic composition on the distribution of nematode species in springs of the province of Granada (Spain)

The ionic composition of 38 mineral springs in the province of Granada (Spain), and the distribution of 45 species of nematodes belonging to orders Monhysterida, Araeolaimida, Chromadorida and Enoplida were examined. Water chemistry is used to make two diagrams representing anionic and cationic composition. Diagrams for anionic composition (given the greater variance seen in the springs considered) are used to illustrate the distribution of individual species. The results obtained from species distribution and the correlation between species made it possible to group species which could be associated with springs where each of the anions considered predominated. A greater number of species groups was found to inhabit springs in which chloride concentrations was less than 50% of the total concentration of anions.     

Granulosa cells as a source and target organ for tumor necrosis factor-alpha

Tumor necrosis factor (TNF-alpha), a 17 kDa cytokine, is a product of activated macrophages which was recently shown to be produced by rat and bovine granulosa cells. In the present work, human granulosa cells derived from preovulatory follicles were used. It was demonstrated that human granulosa cells produce TNF-alpha (5-10 units/300,000 cells per 15 h). This production was increased by addition of follicle-stimulating hormone or by a combination of human chorionic gonadotrophin and CSF to the culture media. TNF was also found in bovine follicular fluid and the concentration was higher in the periovulatory than mid-cycle follicles. TNF-alpha was found to increase prostaglandin F-2 alpha production by human granulosa cells (P less than 0.001). We conclude that granulosa cells are both a source and target organ for TNF-alpha.     

The bull shark (Carcharhinus leucas) and largetooth sash (Pristis perotteti) in Lake Bayano,a tropical man-made impoundment in Panama

Synopsis The Río Bayano in eastern Panama is one of many tropical rivers in which bull sharks (Carcharhinus leucas) and largetooth sawfish (Pristis perotteti) have been known to occur. Since both species can osmoregulate in fresh water throughout life, theoretically, both could survive in landlocked situations for many years.P. perotteti reproduces in fresh water, butC. leucas ordinarily does not, so only the former would appear to have the potential for establishing a breeding stock in such a landlocked freshwater body.The damming of the Rio Bayano and the creation of a large impoundment in 1976 provides a test of the ability of members of both species trapped there to survive and to establish breeding stocks. In 1980 and 1981 three mature femaleC. leucas were found dead in Lake Bayano and three sub-adult femaleP. perotteti were taken by trammel net. These events confirm the ability of both to survive in fresh water for long periods, but the establishment of breeding stocks appears doubtful and the question may not be answered for many years.     

Photoperiod and ambient temperature as environmental cues for seasonal thermogenic adaptation in the Djungarian hamster,Phodopus sungorus

For their seasonal control of thermogenesis Djungarian hamsters rely on environmental cueing by both photoperiod and ambient temperature. Their total potential for adaptive improvements of nonshivering thermogenesis is constant in summer and winter. The shortening of photoperiod in fall is used to anticipate about half of the total improvement in thermogenesis, in advance of any experience of cold, as can be concluded from the photoperiodic control of thermogenesis, cold resistance, and the protein content, cyctochrome oxidase activity and content of mitochondria in brown adipose tissue. The remainder of the seasonal thermogenic adaptation is due to stimulatory responses to chronic exposure to cold.This research was supported by the Deutsche Forschungsgemeinschaft, Schwerpunktprogramm Mechanismen der Temperaturregulation und -Adaptation.     

Determination of 3-methoxy-4-hydroxyphenylglycol in urine by high-performance liquid chromatography with amperometric detection

A reversed-phase high-performance liquid chromatographic method has been used for the quantitative determination of 3-methoxy-4-hydroxyphenylglycol (MHPG) in urine. After incubation with glusulase, free MHPG is extracted into ethyl acetate and further isolated by a combination of thin-layer chromatography (TLC) and high-performance liquid chromatography (HPLC). The addition of amperometric detection provides increased sensitivity to a highly specific assay.     

The photoreaction center of Rhodospirillum rubrum mutant strain F24.1

Rhodospirillum rubrum strain F24.1 is a spontaneous revertant of nonphototrophic mutant F24 derived from wild-type strain S1. Strain F24 shows no detectable photochemical activity and contains, at most, traces of the photoreaction center polypeptides. Strain F24.1 has a phototrophic growth rate close to that of the wild-type strain (Picorel, R., del Valle-Tascón, S. and Ramírez, J.M. (1977) Arch. Biophys. Biochem. 181, 665–670) but shows little photochemical activity. Light-induced absorbance changes in the near-infrared, photoinduced EPR signals and ferricyanide-elicited absorbance changes indicate that strain F24.1 has a photoreaction center content of 7–8% as compared to strain S1. Polyacrylamide gel electrophoresis of isolated F24.1 chromatophores shows the photoreaction center polypeptides to be present in amounts compatible with this value. Photoreaction center was prepared from strain F24.1 and showed no detectable difference with that of strain S1. It is concluded that strain F24.1 photosynthesis is due entirely to its residual 7–8% of typical photoreaction center.     

Coordination on Networks: Does Topology Matter?

Effective coordination is key to many situations that affect the well-being of two or more humans. Social coordination can be studied in coordination games between individuals located on networks of contacts. We study the behavior of humans in the laboratory when they play the Stag Hunt game – a game that has a risky but socially efficient equilibrium and an inefficient but safe equilibrium. We contrast behavior on a cliquish network to behavior on a random network. The cliquish network is highly clustered and resembles more closely to actual social networks than the random network. In contrast to simulations, we find that human players dynamics do not converge to the efficient outcome more often in the cliquish network than in the random network. Subjects do not use pure myopic best-reply as an individual update rule. Numerical simulations agree with laboratory results once we implement the actual individual updating rule that human subjects use in our laboratory experiments.     

Experimental Adaptation of Rotaviruses to Tumor Cell Lines

A number of viruses show a naturally extended tropism for tumor cells whereas other viruses have been genetically modified or adapted to infect tumor cells. Oncolytic viruses have become a promising tool for treating some cancers by inducing cell lysis or immune response to tumor cells. In the present work, rotavirus strains TRF-41 (G5) (porcine), RRV (G3) (simian), UK (G6-P5) (bovine), Ym (G11-P9) (porcine), ECwt (murine), Wa (G1-P8), Wi61 (G9) and M69 (G8) (human), and five wild-type human rotavirus isolates were passaged multiple times in different human tumor cell lines and then combined in five different ways before additional multiple passages in tumor cell lines. Cell death caused by the tumor cell-adapted isolates was characterized using Hoechst, propidium iodide, 7-AAD, Annexin V, TUNEL, and anti-poly-(ADP ribose) polymerase (PARP) and -phospho-histone H2A.X antibodies. Multiple passages of the combined rotaviruses in tumor cell lines led to a successful infection of these cells, suggesting a gain-of-function by the acquisition of greater infectious capacity as compared with that of the parental rotaviruses. The electropherotype profiles suggest that unique tumor cell-adapted isolates were derived from reassortment of parental rotaviruses. Infection produced by such rotavirus isolates induced chromatin modifications compatible with apoptotic cell death.