Holocentric chromosome behaviour inCuscuta (Cuscutaceae)

The present study demonstrates thatCuscuta babylonica Choisy has holocentric chromosomes. Evidence for this phenomenon comes from three different observations. (1) Mitosis: During metaphase and anaphase the sister-chromatids are situated parallel to the equatorial plane with no sign of localized kinetochore activity. (2) Inverted meiosis in microsporocytes. (3) X-rayed microsporocytes, in which the numerous chromosome fragments do not show any lagging or formation of micronuclei. We assume that only one out of the three subgenera inCuscuta, namely subg.Cuscuta, has holocentric chromosomes, while the two other subgenera have monocentric chromosomes.     

Acid-base balance of spinal cord fluid in the post-resuscitation period]

Experiments were conducted on dogs which had sustained a 10-minute circulatory arrest caused by electrotrauma; the acid-base balance of the cerebrospinal fluid (CSF) and the blood was studied during the postreanimation period. Although the systemic uncompensated acidosis persisted in the course of the first hour of the postreanimation period, compensation of the CSF acidosis occurred much earlier and the pH was maintained at the initial level for 6 hours. Despite a high lactate concentration for a period of 3 hours of the postreanimation period the bicarbonate concentration remained near the initial one at this period.     

Analysis of repair mechanism choice during homologous recombination

Double-strand breaks (DSBs) occur frequently during cell growth. Due to the presence of repeated sequences in the genome, repair of a single DSB can result in gene conversion, translocation, deletion or tandem duplication depending on the mechanism and the sequence chosen as partner for the recombinational repair. Here, we study how yeast cells repair a single, inducible DSB when there are several potential donors to choose from, in the same chromosome and elsewhere in the genome. We systematically investigate the parameters that affect the choice of mechanism, as well as its genetic regulation. Our results indicate that intrachromosomal homologous sequences are always preferred as donors for repair. We demonstrate the occurrence of a novel tri-partite repair product that combines ectopic gene conversion and deletion. In addition, we show that increasing the distance between two repeated sequences enhances the dependence on Rad51 for colony formation after DSB repair. This is due to a role of Rad51 in the recovery from the checkpoint signal induced by the DSB. We suggest a model for the competition between the different homologous recombination pathways. Our model explains how different repair mechanisms are able to compensate for each other during DSB repair.     

Toxic activity of the blood plasma in the early postresuscitation period

The time course of blood plasma toxicity was studied in dogs in the early postresuscitation period 10 minutes after clinical death because of acute hemorrhage. The duration of dying, the rate of the recovery of the main vitally important body functions were discovered to affect the rate of accumulation in the blood of substances with different molecular weights. There were 3 phases in blood plasma toxicity accumulation. The first phase is marked by the overflow of blood vessels with low-molecular substances, the second one by relative lessening of the content of low-molecular metabolites and an increase in the content of medium-molecular substances. The second phase is in agreement with the maximal rise of blood plasma toxicity. The third phase that develops by the 60th minute of the postresuscitation period is characterized by reduction of the peak activity of all substances under study and by overt toxicity with relative normalization of the main body functions.