Overexpression ofapc10 + in fission yeast can suppress the temperature sensitivity ofnuc2-663 mutant but not its sterility

One of the key cell cycle regulators, the anaphase promoting complex (APC) or cyclosome, plays a dual role during mitotic exit. By destroying anaphase inhibitors it promotes sister chromatid separation, and by destroying B-type cyclins it promotes cytokinesis and removes the replication block. Under unfavorable growth conditions, most eukaryotic cells, including the fission yeastSchizosaccharomyces pombe exit mitosis normally but are arrested in G₁ and do not enter the S phase. InS. pombe, mutations in two APC/cyclosome subunits,nuc2-663 andapc10 ^ts, cause mitotic defects at 36°C, and under nitrogen starvation at 25°C they lead to inability of stopping in G₁ and hence to sterility. To gain more insight into the mechanisms regulating APC/cyclosome activity during normal growth and under nitrogen starvation, we screened a genomic library to identify high-copy suppressors of the temperature sensitivity ofnuc2-663. Here we show that overexpression ofapc10 ⁺ allows this strain to grow at 32°C and rescues it from sensitivity to the protease inhibitor N-tosyl-L-phenylalanine chloromethyl ketone at 25°C. These observations are consistent with the proposed role for Apc10p as a positive regulator of the APC/cyclosome. However,apc10 ⁺ does not suppress the sterility ofnuc2-663 mutant cells, suggesting that it plays a specific role in APC regulation (e.g., in substrate recognition) rather than in general APC activation.     

Single calcium channels in neurons of rat spinal ganglia

Using a refined patch clamp technique, a study was made of single calcium channels of spinal ganglia neurons on a cell-attached membrane site in newborn rats; these convey the basic (high threshold) component of calcium current. Findings show that currents carried by calcium ions at a concentration of 60 mM in the recording pipet changes from 0.58±0.05 to 0.43±0.05 pA with a change in potential of 20 mV. This corresponds to a channel conductance of 7±0.5 pS. The distribution of open time was monoexponential with a time constant of about 0.75 msec, independent of membrane potential. Distribution of closed time approached a biexponential time course. The fast component (0.8 msec) was voltage-dependent, while the slow component decreased from 22 to 4 msec when depolarization increased by 20 mV. Using experimentally obtained time parameters which describe single calcium channel function, and assuming a three-tier model of the channel, the numerical values of the constants of transition rates between individual states were determined.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 17, No. 5, pp. 673–682, September–October, 1985.     

A Decade of Observations of Intertidal Benthic Communities at the Water Area of Vitino Specialized Marine Oil Port (Northern Part of Kandalaksha Bay,White Sea): A Methodological View

Biology Bulletin - Studies of the intertidal benthos of the water area of the Vitino Specialized Marine Oil Port using typical hydrobiological methods were carried out for more than ten years. From...     

Study of poly(C) and poly(I)-poly(C) complexes with model phospholipid membranes by infrared spectroscopy

The temperature dependence of poly(C) is shown by the infrared spectroscopy to be different for the free polynucleotide and for the polynucleotide in complexes with membranes. The intensity of stretching vibrations of C = 0 bond of poly(C) in the complex appears to be sensitive to the temperature. The intensity of this band is sharply decreased by increasing the temperature. This effect depends upon concentration of Mg2+-cations. Adsorption of poly(I)-poly(C) on the surface of vesicles from phosphatidylcholine results in the increase of the double helix.     

Stability of bacterial aerosols in static conditions]

The influence of acid exopolysaccharides of some Pseudomonas species on the viability and fractional disperse composition of Salmonella marcescens-9 aerosol under static conditions has been studied. Acid exopolysaccharides have been shown to form membranes around bacteria. These membranes, due to their adsorptive and water-retaining properties, seemingly enhance the viability of bacteria in aerosol, both in the process of its generation and during its suspension in the air under static conditions with different values of relative humidity.