Cyclic adenosine monophosphate and the enzyme activity of its metabolism in L cells sensitive and resistant to the cytotoxic action of ethidium bromide

Using L-cells both sensitive and resistant to cytotoxic action of ethidium bromide (EB), a study was made of the intracellular level of cAMP, activities of adenylcyclase, phosphodiesterase and cAMP, liberated from cells into the surrounding medium. In EB resistant L-cells compared to EB sensitive ones, the higher level of cAMP with a decreased activity of adenylcyclase and an increased activity of the phosphodiesterase was shown to be associated with an impeded exit of cAMP from cells. It is suggested that the differences in cAMP levels in the EB sensitive and resistant cells are associated with the properties of cAMP-dependent protein kinases of these cells.     

Discrimination of heterozygous carriage of ataxia-telangiectasia by the method of indirect immunofluorescent analysis

Qualitative differences of the stabilization of protein P53 were studied by methods of indirect immunofluorescence with the use of confocal microscopy in cells obtained from members of the family of a patient with ataxia-telangiectasia (AT)—the proband AT6SP and her blood relatives: the sister AT(S)6SP and the father AT(F)6SP—at different time periods after irradiation with various doses of ionizing radiation.     

Visualization of focal nuclear sites of DNA repair synthesis induced by bleomycin in human cells

In this study, we examined DNA repair synthesis in human cells treated with the radiomimetic drug bleomycin, which efficiently induces double-strand breaks (DSBs). Using tyramide-biotin to amplify fluorescent signals, discrete nuclear foci from the incorporation of 5-iododeoxyuridine (IdU) were detected in proliferating human cells treated with bleomycin. We believe this comes from the repair of DSBs. An increase in the number of foci (>5 per nucleus) was detected in a major fraction (75%) of non-S-phase cells labeled for 30 min with IdU 1 h after the end of bleomycin treatment. The fraction of cells with multiple IdU-containing foci was found to decrease 18 h after treatment. The average number of foci per nucleus detected 1 h after bleomycin treatment was found to decrease twofold between 1 and 3.5 h, indicating that the foci may be associated with the slow component of DSB repair. The presence of DSBs in bleomycin-treated cells was confirmed using antibodies against phosphorylated histone H2AX (gamma-H2AX), which is strictly associated with this type of DNA damage. After treatment with bleomycin, non-S-phase cells also displayed heterogeneous nuclear foci containing tightly bound proliferating cell nuclear antigen (PCNA), suggesting an ongoing process of unscheduled DNA synthesis. PCNA is known to be involved in base excision repair, but a fraction of the PCNA foci may also be associated with DNA synthesis occurring during the repair of DSBs.     

Features of the radiosensitivity of cells from ataxia-telangiectasia patients]

Cell survival, single and double DNA strand breaks formation and removal, spontaneous and induced chromosome aberrations and sister chromatid exchange (SCE) levels in gamma-irradiated cells of patients with ataxia-telangiectasia (AT) were studied. Except SCE all of the above indexes of AT cells sensitivity, were higher, than in normal human cells, but lower, than it is commonly characteristic of AT cells in literature. A conclusion is that the analysed AT cells belong to the AT-variant form. Possible mechanisms of high radiosensitivity of AT cells, accompanied by radioresistance of DNA replication, are discussed. The authors suppose that the DNA repair defect in AT cells is not primary.     

Focal sites of DNA repair synthesis in human chromosomes

Nucleotide excision repair (NER) is the principle pathway by which the human cells eliminate UV-induced lesions from their genomic DNA. The process can be visualized through the labelling of the nucleotides that are incoporated into repair patches, following the excision of the damaged stretch of DNA. In this study we have visualized sites of DNA repair synthesis (DRS) in human interphase and metaphase chromosomes after very short times (2.5-30 min) of postirradiation labelling in vivo with 5-iododeoxyuridine. A limited number (<50 per nucleus) of discrete nuclear DRS sites were seen in cells fixed immediately after labelling and the sites are also detectable in interphase and metaphase chromosomes visualized 48h after irradiation (3 J/m2). These observations strongly support the view that within a given short time window distinct chromosome domains are under extensive repair while in many other domains NER is slow. They argue against the general distributative NER process but are consistent with a processive scanning of damaged domains.     

Systems analysis of primary Sjögren's syndrome pathogenesis in salivary glands identifies shared pathways in human and a mouse model

Bone tissue has an exceptional quality to regenerate to native tissue in response to injury. However, the fracture repair process requires mechanical stability or a viable biological microenvironment or both to ensure successful healing to native tissue. An improved understanding of the molecular and cellular events that occur during bone repair and remodeling has led to the development of biologic agents that can augment the biological microenvironment and enhance bone repair. Orthobiologics, including stem cells, osteoinductive growth factors, osteoconductive matrices, and anabolic agents, are available clinically for accelerating fracture repair and treatment of compromised bone repair situations like delayed unions and nonunions. Preclinical and clinical studies using biologic agents like recombinant bone morphogenetic proteins have demonstrated an efficacy similar or better than that of autologous bone graft in acute fracture healing. A lack of standardized outcome measures for comparison of biologic agents in clinical fracture repair trials, frequent off-label use, and a limited understanding of the biological activity of these agents at the bone repair site have limited their efficacy in clinical applications.     

Discrimination of heterozygote currency of ataxia-telangiectasia by indirect immunofluorescent analysis

The qualitative differences in P53 protein stabilization after ionizing irradiation in different doses were found in cells of members of ataxia-telangiectasia (AT) family--proband AT6SP, her sister AT(S)6SP and father AT(F)6SP. The method of indirect immunofluorescence with confocal microscopy was used.     

The atypical of Werner syndrome: effect of laminopathy

A case of adult progeria has been described. During detailed studies of the cells from this patient the nuclear lamina and cytoskeleton aberrations were detected. It has been suggested that this case is an atypical form of Werner syndrome with laminopathy--not the WRN helicase-nuclease defect.