The Sister-Chromatid Exchange Assay in Human Cells.

The semiconservative nature of DNA replication allows the differential labeling of sister chromatids that is the fundamental requirement to perform the sister-chromatid exchange (SCE) assay. SCE assay is a powerful technique to visually detect the physical exchange of DNA between sister chromatids. SCEs could result as a consequence of DNA damage repair by homologous recombination (HR) during DNA replication. Here, we provide the detailed protocol to perform the SCE assay in cultured human cells. Cells are exposed to the thymidine analog 5-bromo-2'-deoxyuridine (BrdU) during two cell cycles, resulting in the two sister chromatids having differential incorporation of the analog. After metaphase spreads preparation and further processing, SCEs are nicely visualized under the microscope.

Metabolically-active bacteria in reclaimed water and ponds revealed using bromodeoxyuridine DNA labeling coupled with 16S rRNA and shotgun sequencing.

Understanding the complex microbiota of agricultural irrigation water is vital to multiple sectors of sustainable agriculture and public health. To date, microbiome characterization methods have provided comprehensive profiles of aquatic microbiotas, but have not described which taxa are likely metabolically-active. Here, we combined 5­bromo­2'-deoxyuridine (BrdU) labeling with 16S rRNA and shotgun sequencing to identify metabolically-active bacteria in reclaimed and agricultural pond water samples (n = 28) recovered from the Mid-Atlantic United States between March 2017 and January 2018. BrdU-treated samples were significantly less diverse (alpha diversity) compared to non-BrdU-treated samples. The most abundant taxa in the metabolically-active fraction of water samples (BrdU-treated samples) were unclassified Actinobacteria, Flavobacterium spp., Pseudomonas spp. and Aeromonas spp. Interestingly, we also observed that antimicrobial resistance and virulence gene profiles seemed to be more diverse and more abundant in non-BrdU-treated water samples compared to BrdU-treated samples. These findings raise the possibility that these genes may be associated more with relic (inactive) DNA present in the tested water types rather than viable, metabolically-active microorganisms. Our study demonstrates that the coupled use of BrdU labeling and sequencing can enhance understanding of the metabolically-active fraction of bacterial communities in alternative irrigation water sources. Agricultural pond and reclaimed waters are vital to the future of sustainable agriculture, and thus, the full understanding of the pathogenic potential of these waters is important to guide mitigation strategies that ensure appropriate water quality for intended purposes.

Use of the LLNA:BrdU-ELISA for Skin Sensitization Hazard Assessment.

Allergic contact dermatitis (ACD) continues to be an occupational and environmental health issue. Consequently, there is a need to employ predictive tests to reduce the incidence of skin sensitization leading to clinical manifestations of ACD. For more than a decade, the murine local lymph node assay (LLNA) has been the method of choice for the identification of skin sensitizers. While the original LLNA protocol has been extensively evaluated and subjected to exhaustive validation, the use of radioisotope (i.e., tritiated thymidine; 3HTdR) has discouraged utilization of this powerful assay in some countries. To promote further utilization of this method, the original LLNA protocol was refined to use 5-bromo-2'-deoxyuridine, a nonradioactive analog of 3HTdR. The LLNA:BrdU-ELISA has been reviewed, validated, and approved for use internationally, and its performance is regarded as equivalent to the traditional LLNA. Here, we provide guidance on how to perform and interpret data from this assay.

Chronic atypical antipsychotics, but not haloperidol, increase neurogenesis in the hippocampus of adult mouse.

It is suggested that altered neuroplasticity contributes to the pathophysiology of schizophrenia and antipsychotics may exhibit some of their therapeutic efficacies by improving neurogenesis and/or proliferation of neural progenitors. The aim of this study is to investigate whether chronic antipsychotics treatment affect neurogenesis in adult mouse hippocampus. Animals were administered olanzapine, quetiapine, clozapine, risperidone, aripiprazole, or haloperidol via the osmotic minipump for 21days and then injected with 5-bromo-2'-deoxyuridine (BrdU) to label mitotic cells. BrdU-positive cells in the hippocampus were quantified by stereology. Aripiprazole, quetiapine, clozapine, and olanzapine significantly increased density of BrdU-positive cells in the hippocampus. Interestingly, other antipsychotic drugs had tendency to increasing BrdU-positive cells, whereas haloperidol had propensity to decrease with a marginal significance. These results suggest that differences of neurogenesis among these drugs may, at least in part, account for their pharmacological profiles.

5-Acetyl goniothalamin suppresses proliferation of breast cancer cells via Wnt/ß-catenin signaling.

Styryl lactones are plant-derived compounds from genus Goniothalamus with promising anti-proliferation and anticancer properties. However, the exact mechanism and the target for their activities remained unclear. In the present study, we investigated the effect of 5-acetyl goniothalamin (5GTN) from Goniothalamus marcanii on Wnt/ß-catenin signaling pathway which is a key regulator in controlling cell proliferation in breast cancer cells (MCF-7 and MDA-MB-231). 5GTN, a naturally occurring derivative of goniothalamin (GTN) mediated the toxicity to MCF-7 and MDA-MB-231 cells in a dose- and time- related manner, and was more potent than that of GTN. 5GTN strongly inhibited cell proliferation and markedly suppressed transcriptional activity induced by ß-catenin in luciferase reporter gene assay. In consistent with this view, the expression of Wnt/ß-catenin signaling target genes including c-Myc, cyclin D1 and Axin2 in MCF-7 and MDA-MB-231 cells were suppressed after treatment with 5GTN. It was concomitant with cell cycle arrest at G1 phase and cell apoptosis in MCF-7 cells. In addition, 5GTN enhanced glycogen synthase kinase (GSK-3ß) activity and therefore reduced the expression of active form of ß-catenin protein in MCF-7 and MDA-MB-231 cells. Taken together, 5GTN exhibited a promising anticancer effect against breast cancer cells through an inhibition of Wnt/ß-catenin signaling. This pathway may be served as a potential chemotherapeutic target for breast cancer by 5GTN.

Birthdate of parvalbumin-neurons in the Parvafox-nucleus of the lateral hypothalamus.

The Parvafox-nucleus in the lateral hypothalamus is characterized by the presence of two distinct neural populations, the Parvalbumin (Parv) and the Foxb1-expressing ones. Foxb1-neurons are born at day 10 in the subventricular zone of the mouse mammillary region. It would be interesting to know if the subpopulation of Parv- neurons develop independently at different times and then meet the Foxb1- expressing neurons in the lateral hypothalamus, their final settling place. The aim of this study was to define the period of birth of the Parv-positive neurons using an in-vivo Bromodeoxyuridine-based method in rats. Parv-neurons are generated from embryonic day 10 to day 13, with a peak at day 12. Thus, it appears that the birthdates of the two subpopulations in these two species is similar, perhaps suggesting that they are born from the same neuroepithelial region.

Development and utilization of an ex vivo bromodeoxyuridine local lymph node assay protocol for assessing potential chemical sensitizers.

The murine local lymph node assay (LLNA) is widely used to identify chemicals that may cause allergic contact dermatitis. Exposure to a dermal sensitizer results in proliferation of local lymph node T cells, which has traditionally been measured by in vivo incorporation of [(3) H]methyl thymidine. A more recent non-isotopic variation of the assay utilizes bromodeoxyuridine (BrdU) incorporation in vivo. To further improve the utility of this assay, we developed an ex vivo BrdU labeling procedure eliminating the need for in vivo injections. The results of this assay correctly identified a strong sensitizer (i.e., trimellitic anhydride) as well as weak/moderate sensitizers (i.e., eugenol, cinnamaldehyde and hexylcinnaminic aldehyde). As anticipated, neither non-sensitizers isopropanol and lactic acid nor the false negative chemical nickel II sulfate hexahydrate induced a positive threshold response in the assay. The results of this assay are in close agreement with those of the in vivo LLNA:BrdU-enzyme-linked immunosorbent assay labeling procedure. We also used the ex vivo BrdU LLNA procedure to evaluate ammonium hexachloroplatinate, ammonium tetrachloroplatinate and cis-diamminedichloroplatinum(II) and the assay correctly identified them as sensitizers based on the calculation of EC2 values. We conclude that this ex vivo BrdU labeling method offers predictive capacity comparable to previously established LLNA protocols while eliminating animal injections and the use of radioisotope. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.

Hippocampal CA field neurogenesis after pilocarpine insult: The hippocampal fissure as a neurogenic niche.

Pilocarpine model for temporal lobe epilepsy has shown aberrant neurogenesis, but mainly restricted to the dentate gyrus (DG). Herein, by using a modified protocol, combining pilocarpine with ipratropium bromide, we unexpectedly observed a heretofore-unrecognized distinct cellular population expressing the neuroprogenitor marker doublecortin (DCX) on post insult days (PID) 10, 14 and 18, mainly located in the temporal segment of the hippocampal fissure (hf). Some of these DCX+ cells possessed high morphological complexity and seemed to disperse toward the CA fields. Next, we injected bromodeoxyuridine (BrdU) in early (PID 2-4) and delayed (PID 5-7) fashions and killed the rats 7-35 days later for immunohistochemical and anatomical analysis. Massive increase of BrdU labeling was found in the delayed group and the neural stem cell-specific marker nestin was highly expressed in the same narrow band on PID7, so was glial fibrillary acidic protein (GFAP). Using double labeling with BrdU and a mature neuron marker NeuN, we found discrete but clear BrdU+/NeuN+ double labeled cells in the Cornu Ammonis (CA) pyramidal cell layer on PID35. Based on immunohistochemical and anatomical observations, as well as time-course analysis of BrdU, nestin, GFAP, DCX and NeuN expressions in this population of cells located in/near hf, we wish to suggest that this structure harbors neurogenic niches, in addition of the possible dispersion of neuroprogenitors from subgranular niches to CA fields also revealed by this study. Our results support the few previous reports demonstrating hippocampal CA field neurogenesis in adult rats. Mechanistic basis of the phenomenon is discussed.

Decreased Diethylnitrosamine-induced Liver Preneoplastic Lesions by Estradiol-3-benzoate Treatment.

To clarify whether inhibitory effect of estrogen on liver tumor is associated with cell proliferation, we investigated its role in diethylnitrosamine (DEN)-induced rat preneoplastic lesions, with time sequenced manners. F344 male rats (n = 90) were divided into three groups at 5 weeks of age. The mini-osmotic pumps providing a continuous infusion of DEN was implanted into the abdominal cavity of each animal in group 1, 2 and 3 at 6 weeks of age. To see the effect of estrogen, pellet containing 1 or 10 µg of estradiol- 3-benzoate (EB) was implanted subcutaneously in the animals of groups 2 or 3, respectively, one week prior to DEN treatment. Ten animals of each group were euthanized at 10, 14 and 18 weeks after DEN treatment. Liver tissues at each time point were fixed in 10% phosphate-buffered formalin and were processed and embedded in paraffin and 5 µm sections mounted on a silanized slide. Glutathione S-transferase placental form (GST-P) positive foci and 5-bromo-2-deoxyuridine (BrdU) labeling cells were detected at each time point. Area of GST-P positive foci in DEN+EB 1 or 10 µg group was significantly decreased compared to DEN alone at 14 weeks (p < 0.01 or p < 0.05, respectively) an at 18 weeks (p < 0.05 or p < 0.01, respectively). BrdU index in DEN+EB 1 or 10 µg groups was significantly decreased compared to DEN alone at 14 weeks and at 18 weeks (p < 0.01). Taken together, we conclude that EB treatment decrease the DEN-induced liver preneoplastic lesions and this may be associated with decrease of cellular proliferation.

Influence of Preoperative Portal Vein Branch Ligation in Regeneration of Remaining Rat Liver with or without Jaundice

Purpose: The goal of this study is to define whether or not preoperative portal vein embolization has any additional role in the total amounts of liver regeneration and functional improvement after major hepatectomy in rat model. In addition, this study is to define obstructive jaundice has any positive or negative effect on it. METHODS: There were a total of 650 rats, divided into three experimental groups. Experiment A was done under the normal liver status, experiment B was done under the obstructive jaundice status, experiment C was done under the external biliary drainaged status. Each experimental group was divided into three groups that had been made by different surgery. One was 70% partial hepatectomy, another was 70% portal vein branch ligation, and the other was 70% portal vein ligation followed by 70% hepatectomy. Each operational group required over 60 rats for serial data collection which was taken at the operation and 6, 12, 24, 48, 72 hours after operation. RESULTS: We finally observed that there was no additional regeneration of remaining liver by doing preoperative portal vein embolization. It was same in obstructive jaundice group and external biliary drainaged group. And also, there was no significant fucntional improvement or deterioration by existence of obstructive jaundice. Conclusion: We conclude it is no worth doing preoperative portal vein embolization for getting additional liver regeneration and obstructive jaundice does not has significant positive or negative effect on liver regeneration and hepatic function in itself.