Chromosome analysis of esophageal squamous cell carcinoma cell line KYSE 410-4 by repetitive multicolor fluorescence in situ hybridization

Chromosome aberrations are distinctive features of human malignant tumors. Analysis of chromosomal changes can illuminate the molecular mechanisms underlying the development and progression of cancer. To establish the technique of multicolor fluorescence in situ hybridization （M-FISH） for identifying chromosome aberrations in esophageal carcinoma cell line KYSE 410-4, four pools of 6-color whole-chromosome painting probes have been designed and hybridized on the same metaphase spread by four rounds of repetitive FISH. Repetitive 6-color M-FISH was successfully established and the cytogenetic abnormalities in KYSE 410-4 cells were characterized. Chromosome gains occurred at 2q, 3, 8, 17p, and X. An isochromosome 3q was visualized in the cell line, which might be one intermediate mechanism leading to 3p losses and/or 3q gains. Furthermore, 16 structural arrangements were detected, including four derivative chromosomes. The rearrangement of the centromeric regions accounted for approximately 44% of all rearrangements. The results added a more complete and accurate information of the genetic alterations to the classical cytogenetic description of KYSE 410-4 and provided a detailed cytogenetic background data for appropriate use of the cell line. The established 6-color M-FISH was useful for analyzing chromosomes in the whole genome of human tumors.

Dual fluorescence in situ hybridization in detection of HER-2 oncogene amplification in primary hepatocellular carcinoma

BACKGROUND: Molecular cytogenetics of oncogene HER-2 amplification in primary hepatocellular carcinoma (HCC) is still unknown. The aim of this study was to in vestigate the frequency of HER-2 oncogene amplification in primary HCC and its relations to clinicopathological pa rameters and prognosis. METHODS: Forty-two surgical samples from patients with primary HCC were detected for their HER-2 oncogene am plification. The number of chromosome 17 and their ratio were tested by dual fluorescence in situ hybridization (FISH) technique, and then the correlations between HER-2 amplification, clinicopathological characteristics and prog nosis were analyzed statistically. RESULTS: HER-2 oncogene amplification was detected in 9 (21.4%) of the 42 primary HCCs, including 4 patient with high copy (HC) (9.5%) and 5 patients with low copy (LC) (11.9%). HER-2 amplification was associated signifi cantly with tumor size and postoperative survival time o HCC patients (P<0.05), and the presence of HER-2 gene amplification was correlated with postoperative relapse (P— 0.257), but not related to sex, age, AFP level, HBV infec tion, histopathological grading and clinical staging of HCC patients (P>0.05). The HER-2 oncogene copy was exa mined in 31 (73.8%) of the 42 primary HCCs, consisting of 9 patients with HER-2 amplification (21.4%) and 22 pa tients with aneuploidy (52.4%). No significant relation were observed between the HER-2 oncogene copy, patien sex, tumor size, histopathological grading, clinical stag ing, postoperative relapse and survival time (P >0.05); bu the HER-2 oncogene copy was correlated significantly to age, AFP level and HBV infection (P <0.05). CONCLUSIONS: There are a lower frequency of HER-2 oncogene amplification and a higher frequency of chromo- some 17 aneuploidy in primary HCC. HER-2 oncogene amplification may be involved in the development and pro- gression of large HCC in some patients, and seems to be a valuably independent prognostic factor predicting the re- currence and poor survival in patients with large HCC.

Clinical role and importance of fluorescence in situ hybridization method in diagnosis of H pylori infection and determination of clarithromycin resistance in H pylori eradication therapy

H pylori is etiologically associated with gastritis, gas-tric and duodenal ulcers, gastric adenocarcinoma and mucosa-associated lymphoid tissue (MALT) lymphoma. Eradicating H pylori may convert rapidly the outcome of related diseases with the use of more accurate diagnostic molecular tests. Indeed some of the tests cannot give the evidence of current infection; H pylori can be detected by noninvasive and invasive methods, the latter requiring an endoscopy. Eradication failure is a big problem in H pylori infection. Recently, clarithromycin resistance in H pylori strains is increasing and eradicati-on therapy of this bacterium is becoming more difficult. Molecular methods have frequently been applied besides phenotypic methods for susceptibility testing to detect clarithromycin resistance due to mutations in the 2143 and 2144 positions of 23S rRNA gene. Fluorescence in situ hybridization (FISH) method on paraffin embedded tissue is a rapid, accurate and cost-effective method for the detection of H pylori infection and to determine clarithromycin resistance within three hours according to the gold standards as a non-culture method. This method can also be applied to fresh biopsy samples and the isolated colonies from a culture of H pylori, detecting both the culturable bacillary forms and the coccoid forms of H pylori, besides the paraffin embedded tissue secti-ons. This technique is helpful for determining the bac-terial density and the results of treatment where clarith-romycin has been widely used in populations to increase the efficacy of the treatment and to clarify the treatment failure in vitro.

Comparison of Fluorescence in situ Hybridization and Immunohistochemistry for Assessment of HER-2 Status in Breast Cancer Patients

The accurate assessment ofa proto-oncogene, human epidermal growth factor receptor-2 gene （HER-2）, is extremely important for the therapy and prognosis of breast cancer. Currently, immunohistochemistry （IHC） is the method widely used for the detection of HER-2 protein. Fluorescence in situ hybridization （FISH） has been suggested to be a golden standard assay for HER-2 amplification. This study examined the expression and amplification of HER-2 in paraffin-embedded sections of breast cancer tissues, and compared the two methods on the measurement of HER-2 status. HER-2 gene and protein were determined in breast cancer samples from 52 Chinese women by FISH and IHC respectively. The findings indicated that the HER-2 gene amplification was found in 18 cases （34.6%） by FISH and the HER-2 protein over-expression （score 3＋） in 15 cases （28.8%） by IHC. hnmunohistochemically, 28.6% of the cases scored as 2＋ and 93.3% of the cases scored as 3＋ were HER-2-positive by FISH. There was a significant correlation between the HER-2 gene amplification and HER-2 protein over-expression in breast cancer （P〈0.005）. No correlation was noted between the HER-2 gene amplification and any of the clinicopathological parameters examined, including age, menopausal status, menarche age, tumor size, histological tumor type, histological grade, lymph node status, and the expression of ER and PR. It was concluded that the detection of HER-2 gene amplification in breast cancer by FISH is valuable and can compare with HER-2 protein detection by IHC.

Application of fluorescence in situ hybridization in the detection of bladder transitional-cell carcinoma: A multi-center clinical study based on Chinese population

Objective:To evaluate the diagnostic value of fluorescence in situ hybridization(FISH)in bladder cancer.Methods:We enrolled healthy volunteers and patients who were clinically suspected to have bladder cancer and conducted FISH tests and cytology examinations from August 2007 to December 2008.Receiver operating characteristic(ROC)curve analysis was performed and the area under curve(AUC)values were calculated for both the FISH and urine cytology tests.Results:A cohort of 988 healthy volunteers was enrolled to establish a reference range for the normal population.A total of 4807 patients with hematuria were prospectively,randomly enrolled for the simultaneous analysis of urine cytology,FISH testing,and a final diagnosis as determined by the pathologic findings of a biopsy or a surgically-excised specimen.Overall,the sensitivity of FISH in detecting transitional-cell carcinoma was 82.7%,while that of cytology was 33.4%(p<0.001).The sensitivity values of FISH for non-muscle invasive and muscle invasive bladder transitional-cell carcinoma were 81.7%and 89.6%,respectively(p=0.004).The sensitivity values of FISH for low and high grade bladder cancer were 82.6%and 90.1%,respectively(p=0.002).Conclusion:FISH is significantly more sensitive than voided urine cytology for detecting bladder cancer in patients evaluated for gross hematuria at all cancer grades and stages.Higher sensitivity using FISH was obtained in high grade and muscle invasive tumors.

A populational survey of 45S rDNA polymorphism in the Jefferson salamander Ambystoma jeffersonianum revealed by fluorescence in situ hybridization(FISH)

The chromosomal localization of 45S ribosomal RNA genes in Ambystoma jeffersonianum was determined by fluorescence in situ hybridization with 18S rDNA fragment as a probe (FISH-rDNA). Our results revealed the presence of rDNA polymorphism among A.jeffersonianum populations in terms of number,location and FISH signal intensity on the chromosomes. Nine rDNA cytotypes were found in ten geographically isolated populations and most of them contained derivative rDNA sites. Our preliminary study provides strong indication of karyotypic diversification of A.jeffersonianum that is demonstrated by intraspecific variation of 45S rDNA cytotypes. rDNA cytotype polymorphism has been described in many other caudate amphibians. We predict that habitat isolation,low dispersal ability and decline of effective population size could facilitate the fixation and accumulation of variable rDNA cytotypes during their chromosome evolution.

Development of taxonomic rRNA-targeted probes of two harmful algae: Prorocentrum minimum and Karenia mikimotoi by fluorescence in situ hybridization

Harmful algal blooms recently have been under the spotlight throughout the world, because of their nega- tive impact on the marine environment, aquaculture, fisheries as well as public health. The development of methods for rapid and precise identification and quantification of causative species is essential for the warning and monitoring of blooms, among which the techniques based on taxonomic probes are the most favored. In this study, two harmful algae, i.e., Prorocentrum minimum and Karenia mikimotoi were tak- en into consideration. The partial large subunit rDNA （D1-D2） of both species were firstly PCR-amplified, cloned and sequenced. The obtained sequences were then introduced to carry out alignment analysis for gene specific regions. Three respective candidate probes for each species were designed and used to screen the optimal probe by performing fluorescence in situ hybridization （FISH） tests. The results showed that the probes Pmin0443 and Kmik0602 displayed the best hybridization for P. minimum and K.. mikimotoi, respectively. Both the specific （taxonomic） （Pmin0443 and Kmik0602） and the control probes （UniC0512 and UniR0499） were used for cross-reactivity tests with other microalgae in our laboratory. The probes Pmin0443 and Kmik0602 are specific and could be served as taxonomic probes introduced into the tech- niques targeting rRNA, such as FISH, sandwich hybridization, and DNA-microarray assay of P minimum and K. mikimotoi in the future. Finally, FISH analyses with both probes were performed on the simulated field samples. The probes could hybridize exclusively with the target cells well, and no significant differ- ence （p 〉0.05） was observed in the cell densities of the samples determined by FISH and light microscopy （LM）. All suggest that the probes are specific and could be introduced into FISH for the monitoring of both harmful algae.

DETECTING EXPRESSION OF MRP-1/CD9 mRNA IN LUNG CANCERS USING TISSUE MICROARRAYS AND FLUORESCENCE IN SITU HYBRIDIZATION METHODS

Objective： The aim of this study was to investigate the MRP-1/CD9mRNA expression in lung cancer and normal lung tissues and the relationship between its expression and pathologic grades, clinical stages, metastasis and prognosis. Methods： To observe MRP-1/C9mRNA expression, tissue microarray （TMA） containing 54 lung cancers and 10 normal lung tissues was prepared and Fluorescence in situ hybridization was used. Results： The positive rate of MRP-1/CD9 expression was 48.1% in lung cancer, lower than that of normal lung tissues. The statistical difference was significant （P〈0.05）. Its protein expression had no relationship with the patients＇ ages, sex and the macroscopic type of tumor, but had relationships with the histological type, clinical stage, differentiated degree and metastasis. The expression in non-small cell lung cancer （NSCLC） was higher than that in small cell lung cancer （SCLC）; in well-moderately differentiated group was higher than that in poorly differentiated group; Earlier period group （I＋II） was higher than in later period group （Ⅲ＋Ⅳ）; and in group without lymphoid metastasis was higher than in patients with lymphoid metastasis. Conclusion： The progression of the lung cancer maybe related with the descended MRP-1/Cd9 expression, which may be useful in evaluating the prognosis of cancer patients.

Identification of two Skeletonema costatum-like diatoms by fluorescence in situ hybridization

A harmful algae bloom (HAB) is a dense aggregation of algae in a marine or aquatic environment that can result in significant environmental problems. To forecast the occurrence of HAB, development of a rapid and precise detection method is urgently required. In this study, two Skeletonema costatum-like diatoms (SK-1 and SK-2), were identified morphologically under a light microscope, and detected using fluorescent in situ hybridization (FISH). Strain SK-1 was isolated from a frequently HAB affected area of the East China Sea, and strain SK-2 from an aquatic farm in Qingdao, China. Fluorescent DNA probes were designed that were complementary to the ITS sequence (including 5.8S rDNA) of strain SK-1. After hybridization, strong green fluorescence was observed in cells of strain SK-1 under an epifluorescence microscope; however, no such fluorescence was observed with strain SK-2, which indicates that probes hybridized only the DNA of the target strain, SK-1, in species-specific manner, and that the two strains do not belong to a same species. This finding was confirmed by ITS sequence analysis. The FISH technique used in this study was sensitive, simple, and rapid, and is a promising tool for detecting target HAB species in natural environments.

Literature Analysis on Fluorescence in situ Hybridization in China during 2002-2016

In order to explore researches about the chromosome karyotype analysis and fluorescence in situ hybridization(FISH) technology in China,using the bibliometric method,taking " fluorescence in situ hybridization(FISH) " and " chromosome" as key words,this paper made a statistical analysis on the literature published in China National Knowledge Infrastructure(CNKI) during 2002-2016.The results indicated that the number of papers published in 2002 was the smallest(37),while the number of papers published in 2012 was the largest(125).In terms of the distribution of organizations of authors,in 1201 papers,11 organizations published papers ≥15,accounting for 21.65%.In terms of distribution of papers published by different periodicals,11 periodicals published papers ≥10,accounting for 17.65%.In terms of the papers supported by foundation projects,in all papers searched,377 papers were supported by foundation projects,accounting for 31.39%.In terms of the distribution of doctoral and master's dissertations,259 papers were master's dissertations,accounting for 21.57%;92 papers were doctoral dissertations,accounting for 7.66%.

Niche Differentiation of Phenol-Degrading Microorganisms in UASB Granular Sludge as Revealed by Fluorescence in situ Hybridization

A microbial community structure of granules harvested from an anaerobic sludge blanket reactor treating phenolic wastewater was investigated using fluorescence in situ hybridization(FISH)and clone library construction.Clones of Syntrophorhabdaceae and Cryptanaerobacter were observed to be responsible for phenol degradation.For accurate taxonomic assignment of Cryptanaerobacter clones,phylogenetic analysis using nearly full-length 16S ribosomal RNA(rRNA)gene sequences was necessary.Three oligonucleotide probes were designed to detect the following three taxonomic groups:Syntrophorhabdaceae,Cryptanaerobacter,and Syntrophus.FISH analysis of thin sections of anaerobic granules showed a random distribution of bacteria and archaea.However,a well-defined distribution of Syntrophorhabdaceae,Cryptanaerobacter,and Syntrophus was observed.Cryptanaerobacter and Syntrophus were found on the outer layer of the granules and were closely associated with each other,while Syntrophorhabdaceae was located in the deeper part of the granules.Such specific distribution of the bacteria is most likely due to their metabolic association and affinity for the substrate.Phenol degradation in the granular sludge was observed to be carried out in the following way.First,Cryptanaerobacter converts phenol to benzoate,which is then degraded by Syntrophus into acetate.This syntrophic degradation of phenol occurs near the surface of the granule,where the phenol concen-tration is high.In the deeper part of the granule,where the phenol concentration is lower,Syntrophorhabdaceae degrades phenol into acetate.We observed that Syntrophorhabdaceae is less likely to produce benzoate as an intermediate to feed the neighboring organisms,which contradicts the theo-ries presented by previous studies.

Identification of Prorocentrum minimum and Takayama pulchella by fluorescence in situ hybridization through epifluorescence microscopy and flow cytometry

Partial rDNA sequences of Prorocentrum minimum and Takayama pulchella were amplified, cloned and sequenced, and these sequence data were deposited in the GenBank. Eight oligonucleotide probes （DNA probes） were designed based on the sequence analysis. The probes were employed to detect and identify P. minimum and T. pulchella in unialgal and mixed algal samples with a fluorescence in situ hybridization method using flow cytometry. Epifluorescence micrographs showed that these specific probes labeled with fluorescein isothiocyanate entered the algal cells and bound to target sequences, and the fluorescence signal resulting from whole-cell hybridization varied from probe to probe. These DNA probes and the hybridization protocol we developed were specific and effective for P. minimum and T. pulchella, without any specific binding to other algal species. The hybridization efficiency of different probes specific to P. minimum was in the order： PM18S02 PM28S02 〉 PM28S01 〉PM18S01, and that of the probes specific to T. pulcheUa was TP18S02 TP28S01 〉 TP28S02 〉TP18S01. The different hybridization efficiency of the DNA probes could also be shown in the fluorescent signals between the labeled and unlabeled cells demonstrated using flow cytometry. The DNA probes PM18S02, PM28S02, TP18S02 and TP28S01, and the protocol, were also useful for the detection of Mgae in natural samples.

The Cloning and Fluorescence In situ HybridizationAnalysis of Cotton Telomere Sequence

Telomeres form the ends of eukaryotic chromosomes and serve as protective caps that keep chromosomes structure independency and completeness. The first plant telomere DNA was isolated from Arabidopsis thaliana and was shown to have tandemly repeated sequence 5-TTTAGGG-3： The Arabidopsis-type telomere has been found in many plants, but several reports indicate that this sequence is absent in some plants. Up to now, no research has been conducted on the telomere of cotton. In this paper, the Arabidopsis-type telomere sequence was amplified and cloned using the primers designed based on the fragment containing telomere sequence in an Arabidopsis bacterial artificial chromosome （BAC）. Fluorescence in situ hybridization （FISH） with cotton metaphase chromosomes using the Arabidopsis-type telomere sequence as probes indicated that the signals were located at all chromosome ends of seven diploid and two tetraploid cotton species with different signal intensities among chromosome complements of different cotton species, even between long and short arms of the same chromosome. To identify the signals of FISH, the genome DNA of Xinhai 7, a cultivar of Gossypium barbadense, digested by BAL-31 nuclease was introduced in this study. The result of BAL-31 digestion indicated that the hybridization signals of FISH represent the outermost DNA sequence of each cotton chromosomes. So we first proved that the telomeric repeats of cotton cross-hybridize with that of Arabidopsis. The results of terminal restriction fragment （TRF） showed significant variation in telomere length among cotton species. The telomere length of cultivated cotton was close to 20 kb and was larger than those of wild cotton species whose telomere length rahged from 6 to 20 kb.

Aberration of X chromosome in liver neoplasm detected by fluorescence in situ hybridization

BACKGROUND: A diverse range of cytogenetic alterations of autosomal chromosomes has been reported to date. However, few studies have addressed the abnormalities of X chromosome in hepatocellular carcinoma (HCC) except sporadic reports on the deletion of band F1 in X chromo- some , and the clonal analysis of methylation pattern of the X chromosome-linked human androgen receptor gene. Identification of specific X chromosome alterations during the course of neoplastic development would be essential to defining the genetic basis of HCC. Therefore, we studied the regularity of aberration of X chromosome in liver canc- er. METHODS: Hepatocarcinoma cellular lines and tumor tis- sues were detected respectively through DNA probes of X chromosome after fluorescence in situ hybridization ( FI- SH). RESULTS: Increased copies of X chromosome were ob- served in all samples, and four signals of hybridization were of the major type. CONCLUSIONS: Increased copy number of X chromo- some frequently occur in liver cancer. The relationship be- tween copy number of X chromosome and liver cancer genesis needs further investigation. This study is the first of its kind determining the copy number of X chromosome in liver cancer by using FISH.

Using Fluorescence in situ Hybridization to Identify DMD/BMD Deletion Carriers

Objective To identify the deletions in Duchenne/Becker muscular dystrophy (DMD/ BMD) by using fluorescence in situ hybridization (FISH)Methods The exon-specific cosmid DNA probes (representing 18 exons) were used to perform one-color FISH on metaphase and interphase preparations. The peripheral blood samples from 9 normal people (4 males and 5 females) and 5 females from independent deletion DMD/BMD families, as well as 2 amniotic fluid specimens and 2 chorionic villus samples (CVS) from normal pregnant females were analyzed. Results 72%-100% of peripheral blood lymphocyte metaphases or interphases, 60% -70% of amniocyte interphases, and 95 - 99% of chorionic villus cell interphases showed expected signals. One suspected female was identified as deletion carriers and two were excluded.Conclusion FISH in combination with other available techniques allows efficient screening of DMD/BMD deletion carriers, which also lay the ground work for prenatal diagnosis for potential fetal carriers.

Chromosome 11 aneusomy in esophageal cancers and precancerous lesions-an early event in neoplastic transformation:An interphase fluorescence in situ hybridization study from south India

AIM: To detect aneusomic changes with respect to chromosome 11 copy number in esophageal precancers and cancers wherein the generation of cancer-specific phenotypes is believed to be associated with specific chromosomal aneuploidies. METHODS: We performed fluorescence in situ hybridization (FISH) on esophageal tissue paraffin sections to analyze changes in chromosome 11 copy number using apotome-generated images by optical sectioning microscopy. Sections were prepared from esophageal tumor tissue, tissues showing preneoplastic changes and histologically normal tissues (control) obtained from patients referred to the clinic for endoscopic evaluation. RESULTS: Our results demonstrated that aneusomy was seen in all the cancers and preneoplastic tissues, while none of the controls showed aneusomic cells. There was no increase in aneusomy from precancers to cancers. CONCLUSION: Our results suggest that evaluation of chromosome 11 aneusomy in esophageal tissue using FISH with an appropriate signal capture-analysis system, can be used as an ancillary molecular marker predictive of early neoplastic changes. Future studies can be directed towards the genes on chromosome 11,which may play a role in the neoplastic transformation of esophageal precancerous lesions to cancers.

Optimization of fluorescence in situ hybridization (FISH) for the identification of two polar coccoid green algae species

Standard FISH protocols using fluorochrome-labeled oligonucleotide probes have been successfully applied for in situ detection.However,optimized protocols of FISH for specific eukaryotes in marine environments are often not developed.This study optimized the conditions of fluorescence in situ hybridization （FISH） by using two polar isolated microalgae.The modified conditions were as follows：（1） 10 mg·mL^（-1） lysozyme solution pretreatment at 37℃for 30 min;（2） the hybridization buffer including 20%formamide;（3） the hybridization condition was 47℃for 6 h.The cells enumerated by FISH were compared with those enumerated by flow cytometry（FCM） and DAPI to confirm the cell loss and hybridization efficiency.The optimized protocol was also successfully applied to Arctic Ocean samples,which were found to be dominated by Micromonas sp.The modified protocol showed a high relative efficiency and could be successfully applied for the detection of specific microbial eukaryotes in environmental samples.

Chromosomal mapping of 5S and 18S-5.8S-25S rRNA genes in Saccharina japonica(Phaeophyceae)as visualized by dual-color fluorescence in situ hybridization

It has been reported that there was a linkage of 5S rRNA gene to 18S-5.8S-25S rRNA gene in a few of species in Ochrophyta.In regard to the usual two positions of linked 5S rDNA to the 3′end of 25S rDNA,two pairs of primers were designed for amplification to verify this linkage of two genes in a kelp cultivar of Saccharina japonica,one of species in Ochrophyta.This result supplemented the previous report that 5S rDNA was unlinked to 25S rDNA in this kelp.In order to simultaneously visualize this unlinkage of two genes,dual-color fluorescence in situ hybridization(FISH)technique was applied to the cytogenetics of S.japonica.Dual-color FISH images showed that two and four hybridization signals were present in the kelp gametophyte and sporophyte,respectively,metaphase nuclei hybridized simultaneously with the labeled probes of 18S rDNA and 5S rDNA.Both haploid and diploid karyotypes in decreasing length of chromosomes showed that 18S-5.8S-25S rDNA was localized at the interstitial region of Chromosome 23,whereas 5S rDNA resided at the sub-telomeric region of Chromosome 27.These karyotypes suggested that the kelp nuclear genome had only one locus of each rRNA gene,and their loci on different chromosomes indicated the physical unlinkage of 5S rDNA to 18S-5.8S-25S rDNA in this kelp.Therefore,dual-color FISH seems to be a powerful technique for the discrimination and pairing of chromosomes featured in both small size and nearly identical shape in S.japonica.

The Use of Restriction Fragment Length Polymorphism and Fluorescence in Situ Hybridization to Investigate Microbiota of Piglets after Feeding Oregano

A total of 80 piglets (7.9 ± 1.0 kg) were used in a feeding experiment with dried oregano. The diets differed in their oregano content: 0 g, 2 g, 4 g and 8 g oregano/kg feed, corresponding to 0, 23.5, 46.9 and 93.9 mg carvacrol/kg DM. After the experimental period of 5 weeks, 20 piglets of both extreme feeding groups were slaughtered: 10 animals of the control group and 10 animals of the group that received 8 g oregano/kg. Ingesta samples of jejunum, caecum and colon were collected and analyzed by FISH and PCR RFLP to compare the diversity of microbiota. The results showed no significant changes in microbiota in response to oregano. The patterns of the PCR-RFLP showed a similarity of 61.8% - 91.8% in both feeding groups. In conclusion, an effect of oregano on the in- testinal microbiota could not be shown under the methods used.

A Bifunctional-Blocker-Aided Hybridization Chain Reaction Lighting-Up Self-calibrating Nanocluster Fluorescence for Reliable Nucleic Acid Detection

In this work,we proposed a ratiometric silver nanoclusters(AgNCs)fluorescent assay by designing a bifunctional-blockeraided hybridization chain reaction(HCR).Hairpin probe 1(HP1)containing two special DNA fragments(5′-CAC CGC T-3′and 5′-ATT TGC CTT TTG GGG ACG GATA-3′)at two terminals creates a red-emitting AgNC nucleation sequence(rNS,5′-CAC CGC TAT TTG CCT TTT GGG GAC GGATA-3′).We found that the presence of a toehold fragment(5′-TGCCC-3′)in HP1 could silence the rNS.Upon the addition of a target nucleic acid,HCR of HP1 and hairpin probe 2(HP2)could be initiated,resulting in the formation of long chain of DNA duplexes with multibranched rNS.As the toehold fragment in HP1participated in generating duplexes,a strong emission of rNS-templated AgNCs was observed at 670 nm.More significantly,a bifunctional blocker was introduced not only to reduce the background red-emitting fluorescence but also to play as an internal green-emitting AgNCs nucleation sequence.On the one hand,the blocker could increase the signal-to-noise-ratio of the constructed biosensor,and on the other hand,the blocker also helped to prepare ratiometric HCR-AgNCs assay with self-calibrating ability to strengthen its reproducibility.Compared with the traditional HCR-AgNCs sensors,the developed ratiometric assay based on the bifunctional-blocker-aided HCR has higher reliability,which is important for the fabrication of biosensors in various fields for practical biosensing applications.