Retardation of cell cycle progression in yeast cells recovering from DNA damage: A study at the single cell level

Summary Pedigree analyses of individual yeast cells recovering from DNA damage were performed and time intervals between morphological landmark events during the cell cycle (bud emergence and cell separation), were recorded for three generations. The associated nuclear behavior was monitored with the aid of DAPI staining. The following observations were made: (1) All agents tested (X-rays, MMS, EMS, MNNG, nitrous acid) delayed the first bud emergence after treatment, which indicates inhibition of the initiation of DNA replication. (2) Cells that survived X-irradiation progressed further through the cell cycle in a similar way to control cells. (3) Progress of chemically treated cells became extremely asynchronous because surviving cells stayed undivided for periods of varying length. (4) Prolongation of the time between bud emergence and cell separation was most pronounced for cells treated with the alkylating agents MMS and EMS. This is interpreted as retardation of ongoing DNA synthesis by persisting DNA adducts. (5) Cell cycle prolongation in the second and third generation after treatment was observed only with MMS treated cells. (6) In all experiments, individual cells of uniformly treated populations exhibited highly variable responses.Abbreviations DAPI 4,6-diamidino-2-phenyl-indole - EMS ethyl methanesulfonate - MMS methyl methanesulfonate - MNNG N-methyl-N-nitro-N-nitrosoguanidine     

Structural and microanalytical changes in dentition after radiotherapy applied in cases of tumour in the oral cavity region

Morphological observations by means of the scanning electron and optical microscopes as well as microanalytical qualitative and quantitative tests concerning content and distribution of calcium, phosphorus and magnesium in the teeth being in irradiation field were made in patients treated for larynx cancer by methods of radiotherapy. The teeth enamel was in some places thinner and in some others it was lacking. The characteristic defects took place in the form of notches, cracks and of superficial destruction. In X-ray microanalyser the enamel showed some features of demineralization. In dentine, features of demineralization and on the other hand features of remineralization were seen. The root dentin, in which destructive processes but also reparation processes developed by root cement could be seen, was rather characteristic. Clear structural changes and disturbances of mineralization in hard tooth tissues being under therapeutic X-ray irradiation were observed.     

Further characterization of human RNase MRP/RNase P and related autoantibodies

We characterized a panel of human RNase MRP/RNase P autoantibodies by immunoprecipitation, immunodepletion, immunoaffinity purification and immunoblotting. We report on the protein spectrum that is recognized by RNase MRP/RNase P autoantibodies. We also describe another, related patient serum that based on these assays does not immunoprecipitate RNase P/MRP/Th40. This autoantibody KC, however, coimmunoprecipitates the RNase MRP/RNase P associated RNAs from HeLa and La9 cell extracts as shown by nuclease protection experiments.     

After a single treatment with EMS the number of non-colony-forming cells increases for many generations in yeast populations

The course of lethal events occurring in populations of haploid Saccharomyces cerevisiae after DNA-damaging treatments was studied. After X-irradiation and after incubation with methyl methanesulfonate (MMS) populations recovered according to expectation, if one assumes successive dilution of killed cells by the proliferating survivors. However, populations treated with ethyl methanesulfonate (EMS) for many generations of proliferation contained more inviable cells than expected. This behaviour was not due to EMS or toxic reaction products remaining with the cells after treatment but to residual divisions of lethally mutated cells. In addition the data suggest that lethal fixations may occur in cells originating from later than the first generation after EMS treatment.     

Morphology and microanalysis of teeth in scleroderma

The studies were carried out on teeth extracted for stomatological reasons in the persons with generalized scleroderma. The studies included: morphologic examination of the longitudinal and cross-ground sections in the light and scanning microscope, and microanalytic examination of the longitudinal halves of the teeth in the X-ray microprobe. In the course of scleroderma morphological changes of the mesenchymal origin occurred in the teeth hard tissues. The deviation in the calcium and phosphorus contents was relatively significant and an absence of magnesium in the dentine and distinct de?rease in the calcium-phosphorus ratio were observed.     

Quantitative, qualitative and topographic distribution of lead, zinc, iron and copper in hard teeth tissues

The objectives of the paper included a quantitative evaluation qualitative and topographic distribution of four microelements, namely lead, zinc, iron and copper, within enamel prisms, interprismatic region, tubular dentine, and intertubular dentine. The studies were carried out with the use of an X-ray microanalyser and an electron scanning microscope. The values of lead, zinc, iron and copper were higher in the enamel. Topographic curves for all the elements were similar within the enamel and dentin, characterized by unevenly distributed flat zero segments along with several peaks of diversified amplitude, being somewhat denser in the enamel. Qualitative distribution of the elements was also similar, and slightly denser within the enamel, the grains being unevenly scattered.     

RNase MRP and RNase P share a common substrate.

RNase MRP is a site-specific ribonucleoprotein endoribonuclease that processes RNA from the mammalian mitochondrial displacement loop containing region. RNase P is a site-specific ribonucleoprotein endoribonuclease that processes pre-tRNAs to generate their mature 5'-ends. A similar structure for the RNase P and RNase MRP RNAs and a common cleavage mechanism for RNase MRP and RNase P enzymes have been proposed. Experiments with protein synthesis antibiotics have shown that both RNase MRP and RNase P are inhibited by puromycin. We also show that E. coli RNase P cleaves the RNase MRP substrate, mouse mitochondrial primer RNA, exactly at a site that is cleaved by RNase MRP.     

In the path of the Hurricane: impact of Hurricane Irene and Tropical Storm Lee on watershed hydrology and biogeochemistry from North Carolina to Maine,USA

Although many climate predictions suggest that the frequency and intensity of large storm events might increase in the coming decades, few studies document the full impact of such events along their path. Here, we synthesize information on the impact of Hurricane Irene (formed August 21 2011) and Tropical Storm Lee (formed August 30, 2011) on erosion and sediment transport, lake metabolism, riparian hydrology and biogeochemistry, and stream water quality, from North Carolina to Maine. In almost all cases, these storms generated unprecedented changes in water quality (concentrations, loads), from tenfold increases in DOC and 100-fold increases in POC in Maryland, to 100-fold increases in TSS concentrations in Pennsylvania. Overbank flooding and up to 200-year streamflow events were recorded in New York and Vermont. In many cases, particulate loads (e.g. POC, PP, TSS) occurring during Irene and Lee represented more than 30% of the annual load. The dominance of particulate exports over solutes during Irene and Lee is consistent with the mobilization of normally immobile sediment pools, and massive erosion as reported at many locations across the Northeastern US. Several studies reported long lasting (> 1 year) effects of Irene and Lee on cyanobacterial blooms, erosion, or stream suspended sediment concentrations. However, this review also highlighted the lack of a consistent strategy in terms of methods, and measured water quality parameters. This strongly hinders our ability to fully assess the large-scale impact of such events on our environment, and ultimately their impact on our economy and society.