Differences in heat-induced cell killing as determined in three mammalian cell lines do not correspond with the extent of heat radiosensitization

Three different cell lines, Ehrlich ascites tumour (EAT) cells, HeLa S3 cells and LM mouse fibroblasts, were used to investigate whether or not the extent of heat killing (44 degrees C) and heat radio-sensitization (44 degrees C before 0-6 Gy X-irradiation) are related. Although HeLa cells were the most heat-resistant cell line and showed the least heat radiosensitization, we found that the most heat-sensitive EAT cells (D0, EAT = 8.0 min; D0, LM = 10.0 min; D0, HeLa = 12.5 min) showed less radiosensitization than the more heat-resistant LM fibroblasts (TERHeLa less than TEREAT less than TERLM). Therefore, it is concluded that the routes leading to heat-induced cell death are not identical to those determining heat radiosensitization. Furthermore the inactivation of DNA polymerase alpha and beta activities by heat seemed not to correlate with heat survival alone but showed a positive relationship to heat radiosensitization. The possibility of these enzymes being a determinant in heat radiosensitization is discussed.     

Histopathological and parasitological study of the gastrointestinal tract of dogs naturally infected with Leishmania infantum

Background

A nationwide survey on the microbial etiology of cases of subclinical mastitis in dairy cows was carried out on dairy farms in Sweden. The aim was to investigate the microbial panorama and the occurrence of antimicrobial resistance. Moreover, differences between newly infected cows and chronically infected cows were investigated.

Methods

In total, 583 quarter milk samples were collected from 583 dairy cows at 226 dairy farms from February 2008 to February 2009. The quarter milk samples were bacteriological investigated and scored using the California Mastitis Test. Staphylococci were tested for betalactamase production and presence of resistance was evaluated in all specific udder pathogens. Differences between newly infected cows and chronically infected cows were statistically investigated using logistic regression analysis.

Results

The most common isolates of 590 bacteriological diagnoses were Staphylococcus (S) aureus (19%) and coagulase-negative staphylococci (CNS; 16%) followed by Streptococcus (Str) dysgalactiae (9%), Str. uberis (8%), Escherichia (E.) coli (2.9%), and Streptococcus spp. (1.9%). Samples with no growth or contamination constituted 22% and 18% of the diagnoses, respectively. The distribution of the most commonly isolated bacteria considering only bacteriological positive samples were: S. aureus - 31%, CNS - 27%, Str. dysgalactiae - 15%, Str. uberis - 14%, E. coli - 4.8%, and Streptococcus spp. - 3.1%. There was an increased risk of finding S. aureus, Str. uberis or Str. dysgalactiae in milk samples from chronically infected cows compared to findings in milk samples from newly infected cows. Four percent of the S. aureus isolates and 35% of the CNS isolates were resistant to penicillin G. Overall, resistance to other antimicrobials than penicillin G was uncommon.

Conclusions

Staphylococcus aureus and CNS were the most frequently isolated pathogens and resistance to antimicrobials was rare.     

Positions of multiple insertions in SSU rDNA of lichen-forming fungi

Lichen-forming fungi, in symbiotic associations with algae, frequently have nuclear small subunit ribosomal DNA (SSU rDNA) longer than the 1,800 nucleotides typical for eukaryotes. The lichen-forming ascomycetous fungus Lecanora dispersa contains insertions at eight distinct positions of its SSU rDNA; the lichen-forming fungi Calicium tricolor and Porpidia crustulata each contain one insertion. Insertions are not limited to fungi that form lichens; the lichen ally Mycocalicium albonigrum also contains two insertions. Of the 11 insertion positions now reported for lichen-forming fungi and this ally, 6 positions are known only from lichen-forming fungi. Including the 4 newly reported in this study, insertions are now known from at least 17 positions among all reported SSU rDNA sequences. Insertions, most of which are Group I introns, are reported in fungal and protistan lineages and occur at corresponding positions in genomes as phylogenetically distant as the nuclei of fungi, green algae, and red algae. Many of these positions are exposed in the mature rRNA tertiary structure and may be subject to independent insertion of introns. Insertion of introns, accompanied by their sporadic loss, accounts for the scattered distribution of insertions observed within the SSU rDNA of these diverse organisms.      

A rapid and potent DNA vaccination strategy defined by in vivo monitoring of antigen expression

Induction of immunity after DNA vaccination is generally considered a slow process. Here we show that DNA delivery to the skin results in a highly transient pulse of antigen expression. Based on this information, we developed a new rapid and potent intradermal DNA vaccination method. By short-interval intradermal DNA delivery, robust T-cell responses, of a magnitude sufficient to reject established subcutaneous tumors, are generated within 12 d. Moreover, this vaccination strategy confers protecting humoral immunity against influenza A infection within 2 weeks after the start of vaccination. The strength and speed of this newly developed strategy will be beneficial in situations in which immunity is required in the shortest possible time.