Mitochondrial and liver oxidative stress alterations induced by N‐butyl‐N‐(4‐hydroxybutyl)nitrosamine: relevance for hepatotoxicity

The most significant toxicological effect of nitrosamines like N‐butyl‐N‐(4‐hydroxybutyl)nitrosamine (BBN) is their carcinogenic activity, which may result from exposure to a single large dose or from chronic exposure to relatively small doses. However, its effects on mitochondrial liver bioenergetics were never investigated. Liver is the principal organ responsible for BBN metabolic activation, and mitochondria have a central function in cellular energy production, participating in multiple metabolic pathways. Therefore any negative effect on mitochondrial function may affect cell viability. In the present work, ICR male mice were given 0.05% of BBN in drinking water for a period of 12 weeks and were sacrificed one week later. Mitochondrial physiology was characterized in BBN‐ and control‐treated mice. Transmembrane electric potential developed by mitochondria was significantly affected when pyruvate–malate was used, with an increase in state 4 respiration observed for pyruvate–malate (46%) and succinate (38%). A decrease in the contents of one subunit of mitochondrial complex I and in one subunit of mitochondrial complex IV was also observed. In addition, the activity of both complexes I and II was also decreased by BBN treatment. The treatment with BBN increases the susceptibility of liver mitochondria to the opening of the mitochondrial permeability transition pore. This susceptibility could be related with the increase in the production of H₂O₂ by mitochondria and increased oxidative stress confirmed by augmented susceptibility to lipid peroxidation. These results lead to the conclusion that hepatic mitochondria are one primary target for BBN toxic action during liver metabolism. Copyright © 2011 John Wiley & Sons, Ltd.     

Influence of congenital human cytomegalovirus infection and the NKG2C genotype on NK‐cell subset distribution in children

Human cytomegalovirus (HCMV) has been reported to reshape the NK‐cell receptor (NKR) distribution, promoting an expansion of CD94/NKG2C⁺ NK and T cells. The role of NK cells in congenital HCMV infection is ill‐defined. Here we studied the expression of NKR (i.e., NKG2C, NKG2A, LILRB1, CD161) and the frequency of the NKG2C gene deletion in children with past congenital infection, both symptomatic (n = 15) and asymptomatic (n = 11), including as controls children with postnatal infection (n = 11) and noninfected (n = 20). The expansion of NKG2C⁺ NK cells in HCMV‐infected individuals appeared particularly marked and was associated with an increased number of LILRB1⁺ NK cells in cases with symptomatic congenital infection. Increased numbers of NKG2C⁺, NKG2A⁺, and CD161⁺ T cells were also associated to HCMV infection. The NKG2C deletion frequency was comparable in children with congenital HCMV infection and controls. Remarkably, the homozygous NKG2C^+/+ genotype appeared associated with increased absolute numbers of NKG2C⁺ NK cells. Moreover, HCMV‐infected NKG2C^+/+ children displayed higher absolute numbers of NKG2A⁺ and total NK cells than NKG2C^+/? individuals. Our study provides novel insights on the impact of HCMV infection on the homeostasis of the NK‐cell compartment in children, revealing a modulatory influence of NKG2C copy number.     

Two classes of BRC repeats in BRCA2 promote RAD51 nucleoprotein filament function by distinct mechanisms

The human tumor suppressor protein BRCA2 plays a key role in recombinational DNA repair. BRCA2 recruits RAD51 to sites of DNA damage through interaction with eight conserved motifs of approximately 35 amino acids, the BRC repeats; however, the specific function of each repeat remains unclear. Here, we investigated the function of the individual BRC repeats by systematically analyzing their effects on RAD51 activities. Our results reveal the existence of two categories of BRC repeats that display unique functional characteristics. One group, comprising BRC1, -2, -3, and -4, binds to free RAD51 with high affinity. The second group, comprising BRC5, -6, -7, and -8, binds to free RAD51 with low affinity but binds to the RAD51-ssDNA filament with high affinity. Each member of the first group reduces the ATPase activity of RAD51, whereas none of the BRC repeats of the second group affects this activity. Thus, through different mechanisms, both types of BRC repeats bind to and stabilize the RAD51 nucleoprotein filament on ssDNA. In addition, members of the first group limit binding of RAD51 to duplex DNA, where members of the second group do not. Only the first group enhances DNA strand exchange by RAD51. Our results suggest that the two groups of BRC repeats have differentially evolved to ensure efficient formation of a nascent RAD51 filament on ssDNA by promoting its nucleation and growth, respectively. We propose that the BRC repeats cooperate in a partially redundant but reinforcing manner to ensure a high probability of RAD51 filament formation.     

Psychosocial adjustment in colorectal cancer patients undergoing chemotherapy or chemoradiotherapy

Background: Psychosocial adaptation is a measurement that represents the patient's adjustment to those changes involved in their illness. We undertook this study to search for individual characteristics and clinical aspects associated with successful psychosocial adjustment in patients with colorectal cancer (CRC) undergoing (CT) chemotherapy or chemoradiotherapy (CRT). Methods: Seventy-five patients with CRC treated with CT or CRT in a cancer center were included. Psychosocial Adjustment to Illness Scale Self-Reporting (PAIS-SR) questionnaire was used as a measurement of psychosocial adjustment. Results: Psychosocial adaptation was successful in 18 patients (24%) and unsuccessful in 57 patients (76%). Young patients, married patients and males showed lower psychosocial adaptation to disease. This is associated with the decrease in sexual relations, economic resources and psychological symptoms. Patients complained that they were unsatisfied due to the lack of disease and treatment information offered by the heath care team. Conclusions: In the process of adaptation, clinical features such as tumor location and treatment scheme are considered basic, as well as age, education, marital status. Areas such as sexuality, interpersonal and family relationships, economic status and emotional state of patients affected by the disease and treatments provide a deep complexity in the study of the psychosocial adaptation process in patients with CRC.     

A novel homozygous MYO7A mutation involved in a Venezuelan population with high frequency of USHER1B

Background: Macanao’s population in Venezuela has perhaps the greatest incidence of USH1B known in Latin America (79 cases per 100,000 population); however, until now no mutation in the MYO7A gene had been reported for this population.

Materials and Methods: This study aimed to evaluate the entire coding region of the MYO7A gene by direct sequencing of PCR products obtained from patients clinically diagnosed with USH1B.

Results: A novel mutation named c.6079_6081del was detected on exon 45 of the MYO7A gene, causing the loss of a single histidine amino acid at codon 2027 (p.H2027del) located within the second FERM domain of the human protein myosin VIIA. Three patients with clinical diagnosis of USH1B were detected positive in homozygosis for the c.6079_6081del mutation; whereas six people from the same affected family were heterozygotes and three other family members were negative.

Conclusion: We suggest that this new mutation named c.6079_6081del (p.H2027del) is the main cause of deaf-blindness found in this family clinically diagnosed as USH1B. Additional studies should be performed on this population to determine whether the c.6079_6081del mutation is the main cause of USH1B for the rest of the population.     

Morphological measurements of anatomic landmarks in pulp chambers of human anterior teeth

This in vitro study measured key morphological features of pulp chambers in anterior teeth and tested the hypothesis that the distance from the lingual surface (midpoint from the cusp tip to the lingual CEJ) to the pulp chamber (the midpoint from the buccal to the lingual CEJ) was similar for different tooth types. Extracted human teeth were sorted and 100 samples of each of the following tooth types were chosen: maxillary central incisor (UCI), lateral incisor (ULI), and canine (UC), as well as mandibular central incisor (LCI), lateral incisor (LLI), and canine (LC). All teeth were digitally radiographed on a 1-mm X-ray grid. The mean values of measurement C, the distance from the lingual surface to the pulp chamber, varied significantly between tooth types (p<0.001). The mean values and SNK rankings were as follows: LC (5.9+/-0.5 mm)>UC (5.5+/-0.5)=UCI (5.4+/-0.4)>ULI (5.0+/-0.4)>LLI (4.8+/-0.5)>LCI (4.4+/-0.4).     

The effects of three nonoxynol-9 preparations on vaginal flora and epithelium.

To evaluate the effects of nonoxynol-9 (N-9) on the vaginal flora and epithelium, 48 women (16 in each group) were evaluated by use of quantitative vaginal cultures and colposcopy. at baseline and at 0.5, 4, 24, 48, and 72 h after insertion of one of three N-9 preparations (4% gel [Conceptrol], 3.5% gel [Advantage-24], or a 28% vaginal contraceptive film). The proportion positive for H2O2+ or H2O2- lactobacilli did not change significantly with any of the preparations, but lactobacilli concentrations decreased transiently. Both the proportion of women with Gardnerella vaginalis and the concentration of G. vaginalis decreased transiently. The proportion of women with Escherichia coli increased with the 4% gel, and the concentration increased with all preparations. The number with anaerobic gram-negative rods increased, although the concentrations decreased. Symptoms and colposcopic abnormalities were rare. Changes in levels of vaginal bacteria were transient after single applications of N-9, but adverse effects may be enhanced with frequent, chronic use.