18F-Fluorothymidine (FLT) as tumor response predictor for anti-epidermal growth factor receptor (EGFR) antibody in human lung cancer xenograft

e22088

Background: Specific EGFR inhibition therapies are currently promising and advanced in the clinical setting. It is revealed patients with a colorectal cancer bearing mutated K-ras do not benefit from cetuximab, a chimeric mouse-human antibody to EGFR. However, appropriate evaluation of the therapeutic effects has not been clarified yet, because of the lack of reliable tumor response predictors. Measurement of tumor proliferative activity by PET using FLT may serve to assess early response of the therapy. The purpose of this study is to determine whether 18F- FLT is useful to evaluate very early response to cetuximab treatment in human lung cancer cell line xenograft. Methods: Human tumor xenograft model was established in male BALB/c athymic mice by human lung cancer cell line NCI-H1975, which expresses L858R/T790M-EGFR. These mice were assigned to two groups (n=5, each group): control and cetuximab-treated groups. Cetuximab was intra-peritoneally given 1.0mg/body once on the first day. Biodistribution of 3H-FLT (%Inject Dose/g/kg) were studied two days after the treatment. Immunohistochemical staining of EGFR, phosphorylated EGFR (pEGFR), and nuclear antigen Ki-67 as a tumor cell proliferation marker in tumor tissues were also studied to assess early effects of cetuximab. Results: FLT uptake was high in tumors compared with any other organs. Two days after the cetuximab therapy, the mean value of FLT uptake in tumor was significantly decreased to 55% of control value (0.38 ± 0.03 in control group vs. 0.21 ± 0.07 in cetuximab-treated group; p < 0.05). There were no statistical differences in the tumor volume and body weight of mice between each group. High expression of EGFR and Ki-67 were observed in this xenograft. As compared with control, Ki-67 expression was remarkably decreased in cetuximab-treated group, while there were no definite changes in expression of EGFR and pEGFR. Conclusions: In this animal model, FLT uptake and Ki-67 expression were decreased in cetuximab- treated group just two days after the treatment start. These results indicate FLT-PET can be a useful predictor to evaluate very early response to molecular targeted medicine such as cetuximab before significant change of tumor size.

No significant financial relationships to disclose.

Telomeric associations correlate with telomere length reduction and clonal chromosome aberrations in giant cell tumor of bone

Giant cell tumor of bone (GCTB) is characterized cytogenetically by frequent telomeric associations (tas). To explore the mechanisms behind the formation of tas in GCTB and to investigate their karyotypic consequences, the frequencies of tas and clonal aberrations other than tas in 20 GCTBs were compared to telomere length and status, as assessed by quantitative PCR, fluorescence in situ hybridization (FISH), and expression levels of four genes involved in telomere maintenance. Based on the G-banding results, the tumors were divided into two groups, one with a high frequency of tas and one with a low frequency. Clonal aberrations were found to be restricted to the group with a high level of tas, and the same group showed a significantly larger reduction in telomere length in tumor cells compared to peripheral blood cells. Furthermore, 65 out of 66 tas analyzed by FISH were negative for telomeric sequences. The expression levels of TERT, TERF1, TERF2, and POT1 did not correlate with telomere length or the frequency of tas. Thus, the present findings provide strong support for the notion that decreased telomere length is a prerequisite for tas in GCTBs and that the clonal changes occurring in GCTBs are derived from tas.

PGE2 signal via EP2 receptors evoked by a selective agonist enhances regeneration of injured articular cartilage

OBJECTIVE

The effect of the prostaglandin E2 (PGE2) signal through prostaglandin E receptor 2 (EP2) receptors on the repair of injured articular cartilage was investigated using a selective agonist for EP2.

METHODS

Chondral and osteochondral defects were prepared on the rabbit femoral concave in both knee joints, and gelatin containing polylactic-co-glycolic acid microspheres conjugated with or without the EP2 agonist was placed nearby. Animals were sacrificed at 4 or 12 weeks post-operation, and regenerated cartilage tissues and subchondral structure remodeling were evaluated by histological scoring. The quality of regenerated tissues was also evaluated by the immunohistochemical staining of EP2, type II collagen, and proliferating cell nuclear antigen (PCNA). As an evaluation of side effects, the inflammatory reaction of the synovial membrane was analyzed based on histology and the mRNA expression of matrix metalloproteinase3 (MMP3), tissue inhibitor of metalloproteinase 3 (TIMP3), and interleukin-1 beta (IL-1 beta). Also, the activity of MMP3 and the amount of tumor necrosis factor-alpha (TNF-alpha) and C-reactive protein in joint fluid were measured.

RESULTS

In both models, the EP2 agonist enhanced the regeneration of the type II collagen-positive tissues containing EP2- and PCNA-positive chondrocytes, and the histological scale of regenerated tissue and subchondral bone was better than that of on the control side, particularly at 12 weeks post-operation. No inflammatory reaction in the synovial membrane was observed, and no induction of pro-inflammatory cytokines was found in joint fluid.

CONCLUSION

Selective stimulation of the PGE2 signal through EP2 receptors by a specific agonist promoted regeneration of cartilage tissues with a physiological osteochondral boundary, suggesting the potential usefulness of this small molecule for the treatment of injured articular cartilages.

Detection of Virulence to Resistance Gene Sr36 Within the TTKS Race Lineage of Puccinia graminis f. sp. tritici

The stem rust resistance gene Sr36 confers a near-immune resistance reaction to many races of Puccinia graminis f. sp. tritici and is highly effective against race TTKSK (syn. Ug99), which possesses unusually broad virulence combinations. Because this gene is widely used in United States soft winter wheat germplasm and cultivars, it has been considered to be an important source of resistance to TTKSK. In 2007, moderately susceptible infection responses were observed on wheat lines and cultivars carrying Sr36 in a field screening nursery for stem rust at Njoro, Kenya. We derived 18 single-pustule isolates from stem rust samples collected from the 2007 Njoro nursery. The isolates were evaluated for virulence on 20 North American stem rust differential lines and on wheat lines and cultivars carrying Sr36, Sr31+Sr36, and Sr24+Sr31. Of the 18 isolates, 10 produced infection types 3+ to 4 on line W2691SrTt-1 (monogenic for Sr36) and other lines that carry Sr36 and belonged to a new virulence phenotype that was not detected in previous years. These isolates were identified as race TTTSK. The remaining eight isolates were identified as races TTKSK (five isolates) and TTKST (three isolates), with avirulence and virulence, respectively, to Sr24. Thirteen simple sequence repeat (SSR) markers were used to examine the genetic relationships among the three races in the TTKS lineage. All isolates in the lineage shared an identical SSR genotype and were clearly different from North American races. In all, 16 wheat cultivars and 60 elite breeding lines, postulated to possess Sr36, were susceptible to race TTTSK. The occurrence of race TTTSK with combined virulence on Sr31 and Sr36 has further broadened the virulence spectrum of the TTKS lineage and rendered an important source of resistance ineffective.

Diagnostic value of vascular endothelial growth factor and endostatin in malignant pleural effusions

OBJECTIVE

To assess the value of vascular endothelial growth factor (VEGF) and endostatin in the differential diagnosis of malignant and tuberculous pleural effusions (PE).

METHODS

Effusion samples were collected from 62 patients with malignant PE caused by lung cancer and from 64 patients with tuberculous pleurisy. Concentrations of pleural fluid VEGF and endostatin were measured simultaneously using enzyme-linked immunosorbent assay (ELISA) and enzyme immunoassay, respectively. The sensitivity, specificity and accuracy were calculated.

RESULTS

PE levels of VEGF and endostatin were found to be significantly elevated in effusions with malignancy rather than in those of tuberculous origin (both P < 0.01). For VEGF, the sensitivity, specificity and accuracy in diagnosing malignant pleural effusions were respectively 71%, 61% and 66%, while for endostatin the values were respectively 69%, 83% and 76%. A combination of VEGF and endostatin can increase these to respectively 81%, 97% and 89%.

CONCLUSIONS

Elevated levels of VEGF and endostatin in pleural effusions may be helpful in diagnosing malignant pleural effusions, while a combination of VEGF and endostatin can increase the sensitivity, specificity and accuracy of differentiating malignant from tuberculous pleural effusions.

'Chimeric' grafts assembled from multiple allodisparate donors enjoy enhanced transplant survival

Certain components of a graft that provoke alloimmunity may not be vital for graft function or critical as targets of rejection. Corneal transplantation is an example of this, because graft epithelium plays a role in allosensitization, whereas corneal graft endothelium-which shares the same alloantigens-is the critical target in allorejection. In this study, we found that exploiting this biology by replacing donor epithelium of an allograft with an allodisparate third-party epithelium yields a marked enhancement in transplant survival. Such 'chimeric' allografts consisted of a C3H/He (H-2(k)) corneal epithelium over a C57BL/6 (H-2(b)) epithelial-denuded cornea (or v.v.) and orthotopically placed on BALB/c (H-2(d)) hosts. Conventional corneal allografts (C3H/He or C57BL/6) or isografts (BALB/c) were also transplanted on BALB/c hosts. Alloreactive T-cell frequencies (CD4(+) interferon [IFN]-gamma(+)) primed to the graft endothelium were strongly diminished in chimeric hosts relative to conventionally allografted hosts. This was corroborated by a decreased T-cell infiltration (p = 0.03) and a marked enhancement of allograft survival (p = 0.001). Our results represent the first successful demonstration of chimeric tissue, epithelial-denuded allograft plus third-party allodisparate epithelium, in the promotion of allograft survival. Moreover, chimeric grafting can be readily performed clinically, whereby corneal allograft rejection remains a significant problem particularly in inflamed graft beds.

Differential placental hormone gene expression during pregnancy in a transgenic mouse containing the human growth hormone/chorionic somatomammotropin locus

The human (h) growth hormone/chorionic somatomammotropin (GH/CS) gene locus presents a unique model to gain insight into the molecular mechanisms that have allowed a closely related family of genes to be expressed in two distinct cell lineages/tissues: pituitary somatotrophs and placental syncytiotrophoblasts. However, studies of external factors that regulate gene expression have been somewhat limited by (i) a lack of human cell lines expressing endogenous GH or CS appropriately; and (ii) the fact that the GH/CS locus is unique to primates and thus does not exist in rodents. In the current study, a transgenic (171 h GH/CS-TG) mouse was generated containing the intact hGH/CS gene cluster and hGH locus control region (LCR) in a 171-kilobase DNA fragment. Pituitary and placental-specific expression of hGH/CS RNA was detected at embryonic day (E) 18.5. Immunostaining of hGH was seen in somatotrophs of the anterior pituitary beginning in late gestation. The presence of hCS protein was detected in the placental labyrinth in trophoblasts functionally analogous to the syncytiotrophoblast of the chorionic villi. This pattern of gene expression is consistent with the presence of essential components of the hGH/CS LCR. Transcript levels for hCS-A, hCS-B and placental hGH-variant increased in 171 hGH/CS-TG placenta during gestation (E11.5-E18.5), as previously observed in human placental development. Throughout gestation, hCS-A RNA levels were proportionately higher, accounting for 91% of total CS RNA by E18.5, comparable to term human placenta. Finally, the previous correlation between the transcription factor AP-2alpha and hCS RNA expression observed in developing primary human cytotrophoblast cultures, was extended to pregnancy in the 171 hGH/CS-TG mouse. The 171 hGH/CS-TG mouse thus provides a model to investigate hGH/CS gene expression, including in pregnancy.

Arterial properties in relation to genetic variations in the adducin subunits in a white population

BACKGROUND

Adducin is a membrane skeleton protein, which consists of either alpha- and beta- or alpha- and gamma-subunits. We investigated whether arterial characteristics might be related to the genes encoding ADD1 (Gly460Trp-rs4961), ADD2 (C1797T-rs4984), and ADD3 (IVS11+386A>G-rs3731566).

METHODS

We randomly recruited 1,126 Flemish subjects (mean age, 43.8 years; 50.3% women). Using a wall-tracking ultrasound system, we measured the properties of the carotid, femoral, and brachial arteries. We studied multivariate-adjusted phenotype-genotype associations, using a population- and family-based approach.

RESULTS

In single-gene analyses, brachial diameter was 0.15 mm (P = 0.0022) larger, and brachial distensibility and cross-sectional compliance were 1.55 x 10(-3)/kPa (P = 0.013) and 0.017 mm(2)/kPa (P = 0.0029) lower in ADD3 AA than ADD3 GG homozygotes with an additive effect of the G allele. In multiple-gene analyses, the association of brachial diameter and distensibility with the ADD3 G allele occurred only in ADD1 GlyGly homozygotes. Otherwise, the associations between the arterial phenotypes in the three vascular beds and the ADD1 or ADD2 polymorphisms were not significant. In family-based analyses, the multivariate-adjusted heritability was 0.52, 0.38, and 0.30 for brachial diameter, distensibility, and cross-sectional compliance, respectively (P < 0.001). There was no evidence for population stratification (0.07 < or = P < or = 0.96). Transmission of the mutated ADD3 G allele was associated with smaller brachial diameter in 342 informative offspring (-0.12 +/- 0.04 mm; P = 0.0085) and in 209 offspring, who were ADD1 GlyGly homozygotes (-0.14 +/- 0.06 mm; P = 0.018).

CONCLUSIONS

In ADD1 GlyGly homozygotes, the properties of the brachial artery are related to the ADD3 (A386G) polymorphism, but the underlying mechanism needs further clarification.

2-[18F]-2-deoxy-D-glucose (FDG) uptake in human tumor cells is related to the expression of GLUT-1 and hexokinase II

BACKGROUND

The uptake of 2-[18F]-2-deoxy-D-glucose ((18)F-FDG) is widely used as a marker of increased glucose metabolism to monitor progression of cancers with positron emission tomography (PET). Many tumors have been shown to overexpress facilitated glucose transporters, especially GLUT-1 and a glycolytic enzyme, hexokinase II.

PURPOSE

To define whether a quantitative relationship exists between the expression levels of GLUT-1 and hexokinase II, and (18)F-FDG uptake in human cancer xenografts.

MATERIAL AND METHODS

We determined the expression levels of both GLUT-1 and hexokinase II in normal cells and in five different human cancer cell lines (AGS, A431, A549, Colo 320 HSR, and HepG2) using Western blot analysis. In vitro assays of 18F-FDG uptake in cultures were performed, and subsequently representative cell lines were inoculated onto the flanks of severe combined immunodeficient (SCID) mice. To establish an orthotopic model of human hepatocellular carcinoma (HCC), cells were injected into the intraportal vein of SCID mice. (18)F-FDG uptake in vivo was assessed by subjecting mice to PET imaging.

RESULTS

All cell lines were shown to express higher amounts of GLUT-1 and hexokinase II compared with fibroblast controls. Our results from in vitro (18)F-FDG uptake assays also correlated with the Western blot results. All xenografts gave highly positive results at microPET imaging, and a strong correlation (R(2)=0.88, P<0.001) was found between the maximum standardized uptake values (SUV(max)) and the expression of GLUT-1 proteins.

CONCLUSION

Our data indicate that the expression levels of GLUT-1 and hexokinase II as well as in vitro assays of FDG uptake serve as good screening tests to evaluate the feasibility of cell lines to be further developed into xenograft cancer models for small-animal PET imaging.

[Experience of chest wall reconstruction with newly developed material]

After the chest wall resection, its reconstruction is often needed. A 45-year-old male lung adenocarcinoma patient with chest wall invasion underwent upper lobectomy of the right lung with partial resection of 4-6th ribs. The size of the removed chest wall was 11 x 6.5 cm. We reconstructed the chest wall with Bard Composix E/X Mesh. This prosthesis is consisted of a polypropylene mesh and an expanded polytetrafluoroethylene sheet This material is seems to be useful in the reconstruction of chest wall in both preventing pulmonary adhesion and enabling good wound healing.

Evaluation of urinary 1-hydroxypyrene,S-phenylmercapturic acid,trans,trans-muconic acid, 3-methyladenine, 3-ethyladenine, 8-hydroxy-2′-deoxyguanosine and thioethers as biomarkers of exposure to cigarette smoke

The objective was to evaluate the utility of urinary 1-hydroxypyrene (1-OHP), S-phenylmercapturic acid (S-PMA), trans,trans-muconic acid (t,t-MA), 3-methyladenine (3-MeAd), 3-ethyladenine (3-EtAd), 8-hydroxy-2'-deoxyguanosine (8-OHdG) and thioethers as biomarkers for assessing the exposure in adult smokers who switched from smoking conventional cigarettes to candidate potential reduced exposure products (PREP) or who stopped smoking. Two electrically heated smoking systems (EHCSS) were used as prototype cigarettes that have significant reductions in a number of mainstream smoke constituents as measured by smoking machines relative to those from conventional cigarettes. Urine samples were collected from a randomized, controlled, forced-switching study in which 110 adult smokers of a conventional cigarette brand (CC1) were randomly assigned to five study groups. The groups included the CC1 smoking group, a lower-tar conventional cigarette (CC2) smoking group, EHCSS1 group, EHCSS2 group and a no smoking group that were monitored for 8 days. Biomarkers were measured at baseline and day 8. The daily excretion levels of these biomarkers were compared among the groups before and after switching, and the relationships between the daily excretion levels of these biomarkers and cigarette smoking-related exposure were investigated using Pearson product-moment correlation and multiple regression analyses. It was concluded that under controlled study conditions: (1) 1-OHP, S-PMA and t,t-MA are useful biomarkers that could differentiate exposure between smoking conventional and EHCSS cigarettes or between smoking conventional cigarettes and no smoking; between S-PMA and t,t-MA, the former appeared to be more sensitive; (2) 3-MeAd could only differentiate between smoking conventional cigarettes and no smoking; the results for 3-EtAd were not conclusive because contradictory results were observed; (3) 8-OHdG had a questionable association with smoking and therefore the utility of this biomarker for smoking-related exposure could not be established; and (4) urinary excretion of thioethers as a biomarker lacked sensitivity to demonstrate a clear dose-response relationship in conventional cigarette smokers, although it could differentiate the excretion levels between those subjects who smoked a conventional cigarette and those who stopped smoking.

Molecular genetic analysis of interleukin-1 promoter and receptor antagonist tandem repeat polymorphisms among HLA-identical renal transplant recipient and donor pairs

The cytokine gene polymorphisms as well as the minor histocompatibility antigen (mHAg) disparities have been thought to result in transplant graft rejection and graft-versus-host reaction between HLA-identical donor/recipient pairs. We detected interleukin (IL)-1 promoter and receptor antagonist tandem repeat polymorphisms among 21 HLA identical renal transplant recipient and donor pairs; of 21 pairs, 15 (71%) showed at least one locus difference between donor and recipient, and 73% of the pairs with the disparities at these loci showed either recipient to donor (R-->D) or donor to recipient (D-->R) positive CD4+ cell response measured by a modified Cylex assay developed in our laboratory. Allele 2 of IL-1 receptor antagonist genotype (IL-1ra VNTR), a gene associated with an increasing IL-1beta production, was detected in the three recipients who developed rejections. One HLA-identical pair that had variations on all four loci of IL-1 gene cluster consistently showed positive CD4+ cell immune responses between the donor and the recipient. This study may provide information of the role of non-HLA genes participating in allograft rejection; this demonstrates that in addition to the disparities of the mHAgs, the non-HLA antigens have to be considered as risk factors in HLA-identical solid organ transplantation.

In vitro triplex formation and functional analysis of TFOs designed against human c-sis/PDGF-B proto-oncogene

PDGF (platelet derived growth factor) has been shown to play an important role in tumorigenesis, tumor growth, atherosclerosis and inflammation and other various pathologic settings. PDGF-B chain gene is 92% homologous to v-sis oncogene of the simian sarcoma virus. Thus PDGF-B gene is also called c-sis proto-oncogene. This report provides 3 TFOs (triplex-forming oligonucleotides) to inhibit the expression of c-sis/PDGF-B gene. The results from gel mobility shift analysis,in vitro transcription, DNase I footprinting and protein binding assays demonstrate that the TFOs we designed can form sequence-specific stable triplex with the target, and can effectively suppress the downstream gene transcription and inhibit transcription factors binding. They can be used for preparation of drugs to inhibit tumor growth and for the therapy of atherosclerosis, inflammation, etc.

Compositional Belief Update

In this paper we explore a class of belief update operators, in which the definition of the operator is compositional with respect to the sentence to be added. The goal is to provide an update operator that is intuitive, in that its definition is based on a recursive decomposition of the update sentence's structure, and that may be reasonably implemented. In addressing update, we first provide a definition phrased in terms of the models of a knowledge base. While this operator satisfies a core group of the benchmark Katsuno-Mendelzon update postulates, not all of the postulates are satisfied. Other Katsuno-Mendelzon postulates can be obtained by suitably restricting the syntactic form of the sentence for update, as we show. In restricting the syntactic form of the sentence for update, we also obtain a hierarchy of update operators with Winslett's standard semantics as the most basic interesting approach captured. We subsequently give an algorithm which captures this approach; in the general case the algorithm is exponential, but with some not-unreasonable assumptions we obtain an algorithm that is linear in the size of the knowledge base. Hence the resulting approach has much better complexity characteristics than other operators in some situations. We also explore other compositional belief change operators: erasure is developed as a dual operator to update; we show that a forget operator is definable in terms of update; and we give a definition of the compositional revision operator. We obtain that compositional revision, under the most natural definition, yields the Satoh revision operator.

Combined effects of HLA-Cw6 and cigarette smoking in psoriasis vulgaris: a hospital-based case-control study in China

BACKGROUND

Psoriasis is not only related to genetic factors but also to environmental factors. However, the combined effect of genetic and environmental factors in the development of psoriasis has still been unclear.

OBJECTIVE

The study was to analyze the combined effect of HLA-Cw6 and smoking on psoriasis vulgaris.

METHODS

A hospital-based case-control was conducted study. One hundred seventy-eight cases and 178 controls received this epidemiological investigation and HLA typing by polymerase chain reaction utilizing sequence-specific primers.

RESULTS

The risk of psoriasis was related to smoking, the adjusted odds ratio (OR) being 2.07 (P < 0.01), and there is a graded positive association between the risk of psoriasis and intensity or duration of smoking. Stressful life events increased the risk of psoriasis (OR = 7.87, P < 0.01). We found the waist-hip ratio (WHR) increased the risk of psoriasis vulgaris, and OR was 2.67 (P < 0.01) in China. Individuals harboring the HLA-Cw6 gene obviously increased the risk of psoriasis, OR being 9.93 (P < 0.01) after adjusted for potential confounder factors, while the OR of psoriasis for HLA-B57 was 2.41 (P < 0.05). Significant combined effect between HLA-Cw6 and HLA-B57 for psoriasis was found (OR = 10.51, P < 0.01). A striking finding is that the risk of psoriasis for smokers with HLA-Cw6 increased about 11-fold than non-smokers without HLA-Cw6, and the risk increased some 20-fold in individuals with HLA-Cw6 having stressful life events compared with one without HLA-Cw6 and stressful life events.

CONCLUSION

Our study suggested that the combined effect between HLA-Cw6 and cigarette smoking or stressful life events may play an important role in the development of psoriasis vulgaris in Han Chinese population.

Optical properties of a bio-inspired gradient refractive index polymer lens

The design, fabrication, and properties of one of a new class of gradient-index lenses are reported. The lens is an f/2.25 GRIN singlet based on a nanolayered polymer composite material, designed to correct for spherical aberration. The light gathering and focusing properties of the polymer lens are compared to a homogeneous BK7 glass singlet with a similar f-number. The modulation transfer function of the polymer GRIN lens exceeded that of the homogeneous glass lens at all spatial frequencies and was as much as 3 times better at 5 cyc/mm. The weight of the polymer lens was approximately an order of magnitude less than the homogeneous glass lens.

Genetics of Leaf Rust Resistance in Brambling Wheat

The CIMMYT-developed spring wheat 'Brambling' has a high level of adult-plant resistance (APR) to leaf rust caused by Puccinia triticina. Our objectives were to determine the genetic basis of resistance in seedlings and adult plants and the magnitude of genotype × environment effects on the expression of APR. Brambling was crossed with spring wheat 'Jupateco 73S' that is highly susceptible to current predominant P. triticina races in Mexico and the United States. The F₁, F_2:3, F_4:5, F_4:6, and F_5:7 recombinant inbred lines (RILs) were evaluated under artificial field epidemics in Mexico and St. Paul, MN. The RILs also were tested with five races of P. triticina in greenhouse seedling experiments. A DNA marker was used to postulate the presence of slow-rusting gene Lr34 in the RILs. F₁ data suggested strong dominant effect of the APR genes in Brambling. The proportion of homozygous susceptible lines in each generation indicated the presence of three effective resistance genes in adult plants of Brambling in tests in Mexico and three or four genes in tests in St. Paul. The RILs segregated for seedling genes Lr14a and Lr23 and adult-plant slow-rusting gene Lr34 derived from Brambling and Lr17a from Jupateco 73S. Gene Lr23 conditioned APR to P. triticina races present in the St. Paul nursery and accounted for the additional effective gene at this location. Expression of APR was influenced by the environment in the RILs, even though Brambling displayed a consistent response, indicating that stability of APR can be achieved by combinations of slow-rusting resistance genes.

Apical tooth germ cell-conditioned medium enhances the differentiation of periodontal ligament stem cells into cementum/periodontal ligament-like tissues

BACKGROUND AND OBJECTIVE

Limitations of current periodontal regeneration modalities in both predictability and extent of healing response, especially on new cementum and attachment formation, underscore the importance of restoring or providing a microenvironment that is capable of promoting the differentiation of periodontal ligament stem cells (PDLSCs) towards cementoblast-like cells and the formation of cementum/periodontal ligament-like tissues. The aim of this study was to investigate the biological effect of conditioned medium from developing apical tooth germ cells (APTG-CM) on the differentiation and cementogenesis of PDLSCs both in vitro and in vivo.

MATERIAL AND METHODS

Using the limiting dilution technique, single-colony-derived human PDLSCs were isolated and expanded to obtain homogeneous populations of PDLSCs. Morphological appearance, cell cycle analysis, bromodeoxyuridine incorporation, alkaline phosphatase (ALP) activity, mineralization behavior, gene expression of cementoblast phenotype and in vivo differentiation capacities of PDLSCs co-cultured with APTG-CM were evaluated.

RESULTS

The induced PDLSCs exhibited several characteristics of cementoblast lineages, as indicated by the morphological changes, increased proliferation, high ALP activity, and the expression of cementum-related genes and calcified nodule formation in vitro. When transplanted into immunocompromised mice, the induced PDLSCs showed tissue-regenerative capacity to produce cementum/periodontal ligament-like structures, characterized by a layer of cementum-like mineralized tissues and associated periodontal ligament-like collagen fibers connecting with the newly formed cementum-like deposits, whereas control, untreated PDLSCs transplants mainly formed connective tissues.

CONCLUSION

Our findings suggest that APTG-CM is able to provide a cementogenic microenvironment and induce differentiation of PDLSCs along the cementoblastic lineage. This has important implications for periodontal engineering.

Detection of Virulence to Resistance Gene Sr24 Within Race TTKS of Puccinia graminis f. sp. tritici

The stem rust resistance gene Sr24 is effective against most races of Puccinia graminis f. sp. tritici, including race TTKS (syn. Ug99), and is used widely in commercial wheat cultivars worldwide. In 2006, susceptible infection responses were observed on wheat lines and cultivars carrying Sr24 in a field stem rust screening nursery at Njoro, Kenya. We derived 28 single-pustule isolates from stem rust samples collected from the 2006 Njoro nursery. The isolates were evaluated for virulence on 16 North American stem rust differential lines; on wheat lines carrying Sr24, Sr31, Sr38, and SrMcN; and on a wheat cultivar with a combination of Sr24 and Sr31. All isolates were identified as race TTKS with additional virulence on Sr31 and Sr38. These isolates were divided into two groups: group A (seven isolates and the two control isolates), producing a low infection type, and group B (21 isolates), producing a high infection type on Sr24, respectively. Isolates of group B represented a new variant of race TTKS with virulence to Sr24. Eighteen simple sequence repeat (SSR) markers were used to examine the genetic relationship between these two groups of isolates in race TTKS and five North American races (MCCF, QCCQ, RCRS, RTHS, and TPMK) that are representative of distinct lineage groups. All isolates of race TTKS shared an identical SSR genotype and were clearly different from North American races. The virulence and SSR data indicated that the new variant of race TTKS with Sr24 virulence likely has arisen via mutation within the TTKS genetic lineage. We propose to revise the North American stem rust nomenclature system by the addition of four genes (Sr24, Sr31, Sr38, and SrMcN) as the fifth set. This revision recognizes the virulence on Sr31 and differentiates isolates within race TTKS into two separate races: TTKSK and TTKST, with avirulence and virulence on Sr24, respectively. The occurrence of race TTKST with combined virulence on Sr24 and Sr31 has substantially increased the vulnerability of wheat to stem rust worldwide.