Development of a Genetically Engineered Mouse Model Recapitulating LKB1 and PTEN Deficiency in Gastric Cancer Pathogenesis

The LKB1 and PTEN genes are critical in gastric cancer (G.C.) development. LKB1, a robust tumor suppressor gene, encodes a serine/threonine kinase that directly triggers the activation of AMPK-an integral cellular metabolic kinase. The role of the LKB1 pathway extends to maintaining the stability of epithelial junctions by regulating E-cadherin expression. Conversely, PTEN, a frequently mutated tumor suppressor gene in various human cancers, emerges as a pivotal negative regulator of the phosphoinositide 3-kinase (PI3K) signaling pathway. This study is set to leverage the H+/K+ ATPase Cre transgene strain to precisely target Cre recombinase expression at parietal cells within the stomach. This strategic maneuver seeks to selectively nullify the functions of both LKB1 and PTEN in a manner specific to the stomach, thereby instigating the development of G.C. in a fashion akin to human gastric adenocarcinoma. Moreover, this study endeavors to dissect the intricate ways in which these alterations contribute to the histopathologic advancement of gastric tumors, their potential for invasiveness and metastasis, their angiogenesis, and the evolving tumor stromal microenvironment. Our results show that conditional deletion of PTEN and LKB1 provides an ideal cancer microenvironment for G.C. tumorigenesis by promoting cancer cell proliferation, angiogenesis, and metastasis.

Anomalous Ferromagnetism of quasiparticle doped holes in cuprate heterostructures revealed using resonant soft X-ray magnetic scattering

We report strong ferromagnetism of quasiparticle doped holes both within the ab-plane and along the c-axis of Cu-O planes in low-dimensional Au/d-La_1.8Ba_0.2CuO₄/LaAlO₃(001) heterostructures (d = 4, 8 and 12 unit-cells) using resonant soft X-ray and magnetic scattering together with X-ray magnetic circular dichroism. Interestingly, ferromagnetism is stronger at a hole doped peak and at an upper Hubbard band of O with spin-polarization degree as high as 40%, revealing strong ferromagnetism of Mottness. For in-ab-plane spin-polarizations, the spin of doped holes in O2p-Cu3d-O2p is a triplet state yielding strong ferromagnetism. For out-of-ab-plane spin-polarization, while the spins of doped holes in both O2p-O2p and Cu3d-Cu3d are triplet states, the spin of doped holes in Cu3d-O2p is a singlet state yielding ferrimagnetism. A ferromagnetic-(002) Bragg-peak of the doped holes is observed and enhanced as a function of d revealing strong ferromagnetism coupling between Cu-O layers along the c-axis.

The effects of phthalate ester exposure on human health: A review

Phthalate esters (PAEs) are one of the most widely used plasticizers in polymer products and humans are increasingly exposed to them. The constant exposure to PAEs-contained products has raised some concerns against human health. Thus, the impacts of PAEs and their metabolites on human health require a comprehensive study for a better understanding of the associated risks. Here, we attempt to review eight main health effects of PAE exposure according to the most up-to-date studies. We found that epidemiological studies demonstrated a consistent association between PAE exposure (especially DEHP and its metabolites) and a decrease in sperm quality in males and symptom development of ADHD in children. Overall, we found insufficient evidence and lack of consistency of the association between PAE exposure and cardiovascular diseases (hypertension, atherosclerosis, and CHD), thyroid diseases, respiratory diseases, diabetes, obesity, kidney diseases, intelligence performance in children, and other reproductive system-related diseases (anogenital distance, girl precocious puberty, and endometriosis). Future studies (longitudinal and follow-up investigations) need to thoroughly perform in large-scale populations to yield more consistent and powerful results and increase the precision of the association as well as enhance the overall understanding of potential human health risks of PAEs in long-term exposure.

Recognizing spatial and temporal clustering patterns of dengue outbreaks in Taiwan

BACKGROUND

Dengue fever is the most common arboviral infection in humans, with viral transmissions occurring in more than 100 countries in tropical regions. A global strategy for dengue prevention and control was established more than 10 years ago. However, the factors that drive the transmission of the dengue virus and subsequent viral infection continue unabated. The largest dengue outbreaks in Taiwan since World War II occurred in two recent successive years: 2014 and 2015.

METHODS

We performed a systematic analysis to detect and recognize spatial and temporal clustering patterns of dengue incidence in geographical areas of Taiwan, using the map-based pattern recognition procedure and scan test. Our aim was to recognize geographical heterogeneity patterns of varying dengue incidence intensity and detect hierarchical incidence intensity clusters.

RESULTS

Using the map-based pattern recognition procedure, we identified and delineated two separate hierarchical dengue incidence intensity clusters that comprise multiple mutually adjacent geographical units with high dengue incidence rates. We also found that that dengue incidence tends to peak simultaneously and homogeneously among the neighboring geographic units with high rates in the same cluster.

CONCLUSION

Beyond significance testing, this study is particularly desired by and useful for health authorities who require optimal characteristics of disease incidence patterns on maps and over time. Among the integrated components for effective prevention and control of dengue and dengue hemorrhagic fever are active surveillance and community-based integrated mosquito control, for which this study provides valuable inferences. Effective dengue prevention and control programs in Taiwan are critical, and have the added benefit of controlling the potential emergence of Zika.

Adaptively shaped mid-infrared pulses from a synchronously pumped optical parametric oscillator

Adaptively shaped, sub-picosecond pulses at 3.4microm are obtained from a synchronously pumped optical parametric oscillator based on periodically poled lithium niobate. A simulated annealing algorithm is used in a learning loop to gain adaptive control of the mid-infrared idler pulse shape via shaping of a chirped near-infrared pump pulse. Both indirect control, via optimization of the signal average power, and direct control, via optimization of the two-photon absorption of the idler in an InGaAs detector, has been demonstrated. Both these optimization parameters lead to compressed idler pulses, with slightly differing pulse shapes. By optimization of the cross correlation signal in an interferometer with unequal arm lengths we are also able to deliver compressed double pulses with a variable time delay.

Temporal and spatial variabilities of atmospheric polychlorinated biphenyls (PCBs), organochlorine (OC) pesticides and polycyclic aromatic hydrocarbons (PAHs) in the Canadian Arctic: results from a decade of monitoring

The Northern Contaminants Program (NCP) baseline monitoring project was established in 1992 to monitor for persistent organic pollutants (POPs) in Arctic air. Under this project, weekly samples of air were collected at four Canadian and two Russian arctic sites, namely Alert, Nunavut; Tagish, Yukon; Little Fox Lake, Yukon; Kinngait, Nunavut; Dunai Island, Russia and Amderma, Russia. Selected POPs, including polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and organochlorine (OC) pesticides, were analyzed in both the gas and particulate phases. This paper summarizes results obtained from this project in the past 5 years. Temporal trends were developed for atmospheric PCBs and OCs observed at Alert using a digital filtration (DF) technique. It was found that trends developed with 5 years of data (1993-1997) did not differ significantly from those determined with 7 years of data (1993-1999). This implies that with the DF technique, long-term trends can still be developed with less than 10 years of data. An acceleration in decline of OC and PCB air concentrations was noted in 1999 for some compounds, although the reason is unknown. Monitoring efforts must continue to assess the effect of this decline on the long-term trends of POPs in the Canadian Arctic. Occasional high trans-/cis-chlordane ratios and heptachlor air concentrations measured at Alert between 1995 and 1997 suggests sporadic fresh usage of chlordane-based pesticides. However, significant decreasing trends of chlordanes along with their chemical signatures has provided evidence that emission of old soil residues is replacing new usage as an important source to the atmosphere. Measurements of OC air concentrations conducted at Kinngait in 1994-1995 and 2000-2001 indicated faster OC removal at this location than at Alert. This may be attributed to the proximity of Kinngait to temperate regions where both biotic and abiotic degradation rates are faster. The PAH concentrations observed at Alert mimic those at mid-latitudes and are consistent with long-range transport to the Arctic, particularly for the lighter PAHs. A decline in particulate PAH was observed, similar to atmospheric sulphate aerosol and can be attributed to the collapse of industrial activity in the former Soviet Union between 1991 and 1995. Spatial comparisons of OC seasonality at Alert, Tagish, Dunai and Kinngait show elevated air concentrations of some compounds in spring. However, elevated spring concentrations were observed for different compounds at different sites. Potential causes are discussed. Further investigation in the atmospheric flow pattern in spring which is responsible for the transport of POPs into the Arctic is required. OC and PCB air concentrations at Alert were found to be influenced by two climate variation patterns, the North Atlantic Oscillation (NAO) and the Pacific North American (PNA) pattern. Planetary atmospheric patterns must be taken into account in the global prediction and modelling of POPs in the future.

Historical alpha-HCH budget in the Arctic Ocean: the Arctic Mass Balance Box Model (AMBBM)

An Arctic Mass Balance Box Model (AMBBM) has been developed to calculate a sequential historical alpha-hexachlorocyclohexane (alpha-HCH) budget in the Arctic Ocean from its introduction in the 1940s up to the present. The AMBBM is created in the context of the Arctic as a receptor, and has three major components: the air concentration module, the loading from Arctic river module and the transport/transformation module. The results of the model provide a more complete depiction of the behavior of alpha-HCH within the Arctic Ocean. Model output includes annual concentrations in Arctic air and water, annual alpha-HCH loading to, removal from the Arctic Ocean and annual cumulative burden of alpha-HCH in the Arctic waters from 1945 to 2000. Our model results compare well with published data in the 1980s and 1990s and show that the alpha-HCH burden in the Arctic Ocean started to accumulate in the early 1940s and reached the highest value of 6670 t in 1982, 1 year before China banned the use of technical HCH. Since then the burden of alpha-HCH in Arctic waters has decreased quickly by an average annual rate of approximately 270 ty(-1) during the 1990s, decreasing from 4220 t in 1990 to 1550 t in 2000. The complete elimination of alpha-HCH from Arctic waters would require another two decades. The total loading between 1945 and 2000 was 27700 t accounting for approximately 0.6% of total global alpha-HCH emission from agricultural land to the atmosphere. Differences in loadings of alpha-HCH to the North American Arctic Ocean and Eurasian Arctic Ocean are also discussed.

Self-assembling peptide hydrogel fosters chondrocyte extracellular matrix production and cell division: implications for cartilage tissue repair

Emerging medical technologies for effective and lasting repair of articular cartilage include delivery of cells or cell-seeded scaffolds to a defect site to initiate de novo tissue regeneration. Biocompatible scaffolds assist in providing a template for cell distribution and extracellular matrix (ECM) accumulation in a three-dimensional geometry. A major challenge in choosing an appropriate scaffold for cartilage repair is the identification of a material that can simultaneously stimulate high rates of cell division and high rates of cell synthesis of phenotypically specific ECM macromolecules until repair evolves into steady-state tissue maintenance. We have devised a self-assembling peptide hydrogel scaffold for cartilage repair and developed a method to encapsulate chondrocytes within the peptide hydrogel. During 4 weeks of culture in vitro, chondrocytes seeded within the peptide hydrogel retained their morphology and developed a cartilage-like ECM rich in proteoglycans and type II collagen, indicative of a stable chondrocyte phenotype. Time-dependent accumulation of this ECM was paralleled by increases in material stiffness, indicative of deposition of mechanically functional neo-tissue. Taken together, these results demonstrate the potential of a self-assembling peptide hydrogel as a scaffold for the synthesis and accumulation of a true cartilage-like ECM within a three-dimensional cell culture for cartilage tissue repair.

Temporal trends of organochlorine pesticides in the Canadian Arctic atmosphere

Temperature normalization (TN), multiple linear regression (MLR), and digital filtration (DF) were used to analyze the temporal trends of an atmospheric dataset on organochlorine pesticides (OCs) collected at the Canadian high arctic site of Alert, Nunavut. Details of these techniques have been presented before (Environ. Sci. Technol. 2001, 35, 1303-1311). Both the TN and DF methods revealed that the majority of OC pesticides declined over the 5 years of study, except endosulfan I and several of the pesticide metabolites, including dieldrin and p,p'-DDE. In comparison to studies conducted in the Great Lakes, atmospheric levels in the Arctic were less dependent on temperature, although seasonal variations were apparent. Generally, levels in the winter were lower than during the rest of the year. A notable exception was p,p'-DDE. Many compounds also showed a second minimum in concentrations during June/July and possible explanations are presented to account for this. The estimated first order half-lives for the decline in OC concentrations were generally found to be comparable or slightly longer than those obtained at temperate locations, with the exception of alpha-HCH, which displayed a much longer half-life in the Arctic (approximately 17 yrs). Sporadic increases in heptachlor as well as increases in the ratio of trans- to cis-chlordane suggest episodic input of chlordanes between 1995 and 1997, especially during the winter.

Grass-air exchange of polychlorinated biphenyls

Three field experiments were performed to assess the clearance, uptake, and exchange kinetics of polychlorinated biphenyls (PCBs) between grass and the atmosphere using mixed- and single-species grass (Holcus lanatus). In the clearance experiment, the grass was artificially contaminated by equilibration with diluted Aroclor vapor then exposed to field air, and the rates of depletion were monitored by sampling at regular intervals to determine clearance rate constants. In the uptake experiment, the uptake of PCBs from the ambient atmosphere was followed in growing grass at ambient concentrations for 3 and 6 weeks by analysis of segmented samples along the length of the sward. In the third experiment, diurnal temperature-driven changes in grass concentrations were measured. The results indicate that the grass is behaving as a two-compartment system: (1) a fast-exchanging surface adsorption site with a response time of hours and a capacity essentially independent of K(OA), the octanol-air partition coefficient and (2) a slow responding site with a response time of weeks, the capacity of which is related to K(OA). The kinetic and equilibrium phenomena involved in grass-air exchange are thus complex and are not adequately described by simple first-order rate constants and equilibrium partitioning coefficients.

Are PCBs in the Canadian Arctic atmosphere declining? Evidence from 5 years of monitoring

A long-term database of weekly air concentrations was examined to establish temporal trends of PCBs in the Arctic atmosphere. Several methods were employed to reduce the intra-annual variability allowing the elucidation of longterm trends for a selection of congeners at Alert located in the Canadian Arctic. These methods included temperature normalization (TN), multiple linear regression (MLR), and digital filtration (DF). Estimation of the slope (m) resulting from the linear regression between the natural logarithm of the partial pressure in air versus reciprocal temperature (In P = m/T + b), required for TN and MLR, proved difficult due to the poor correlation with temperature experienced forthe majority of congeners. Values of m were considerably lower than those obtained from temperate studies, implying that regional air-surface exchange plays a minor role in supporting the observed air concentrations in the Arctic. The lighter congeners generally showed very low slopes, and some even showed positive correlation with 1/T. This might be a result of their relatively fast reaction rates with OH radicals following the onset of 24-h sunlight in spring. Use of DF (in combination with TN and MLR) revealed declining trends for several of the lower chlorinated congeners in the high Arctic atmosphere, with estimated first-order half-lives, t1/2, ranging from approximately 3 to 20 yr. Declining trends of the lower congeners probably reflect falling levels in source regions, as a result of long-range transport to this Arctic site. There were no apparent trends for the higher chlorinated congeners (penta-substituted and above), exceptfor PCB 180, in marked contrast to temperate studies, indicating a lag time for decline between the Arctic and source regions.

Age-dependent increase in C7-1 gene expression in rat frontal cortex

We have previously reported that a fragment of mRNA, denoted as C7-1, which expression was significantly increased in the frontal cortex of aged rats. In the present study, we have cloned and sequenced the full length cDNA of the C7-1 gene. We have found that the open reading frame of this gene encoded a 463-amino-acid protein, which shared 84% identity in amino acid sequence with a subunit of vacuolar H(+)-ATPase (V-ATPase). Further Northern blot analysis revealed that there was an age-dependent increase in C7-1 gene expression in rat frontal cortex, but not in other brain areas. Moreover, application of C7-1 antisense oligonucleotide to cortical neuronal cultures markedly inhibited cell survival. These results together suggest that C7-1 is a marker for the aging process and that upregulation of C7-1 may be important in maintaining the normal function of V-ATPase during aging.

Arylamine N-acetyltransferase: a possible promoter in Helicobacter pylori-related gastric carcinogenesis

BACKGROUND

The hypothesis of an association between peptic ulcer and infection by Helicobacter pylori in the gastroduodenal tract was suggested by Marshall and Warren in 1984. H pylori infection of the stomach is the most frequent infection in the world and exhibits an age-dependent increase. However, only a very small percentage of those infected develop gastric carcinoma, suggesting that H pylori acts as a cofactor in the pathogenesis of gastric carcinoma. N-Acetyltransferase (NAT) is expressed in uroepithelial cells and colon cytosol, while cytosolic acetyltransferase plays a critical role in susceptibility to arylamine-induced bladder and colon cancer. The presence of NAT activity in H pylori has yet to be determined.

METHODS

NAT activity in H pylori from patients with peptic ulcer was studied using an acetyl coenzyme A (AcCoA) recycling assay and high-pressure liquid chromatography with p-aminobenzoic acid and aminofluorene substrates.

RESULTS

The NAT activities from a number of H pylori samples were found to be 0.68 +/- 0.10 nmol/min/10(10) colony-forming units (CFUs) (intact bacteria); and 0.90 +/- 0.22 nmol/min/mg protein (cytosol) for the acetylation of 2-aminofluorene, and 0.63 +/- 0.06 nmol/min/10(10) CFUs (intact bacteria) and 0.72 +/- 0.24 nmol/min/mg protein (cytosol) for the acetylation of p-aminobenzoic acid.

CONCLUSIONS

These studies show that H pylori has NAT activity, from which we speculate that the bioactivation of food-borne heterocyclic aromatic amines into genotoxic and carcinogenic products in the stomach is a possible promoter in the pathogenesis of gastric cancer.

A novel and simple model of the uptake of organic chemicals by vegetation from air and soil

A novel and simple three-compartment fugacity model has been developed to predict the kinetics and equilibria of the uptake of organic chemicals in herbaceous agricultural plants at various times, including the time of harvest using only readily available input data. The chemical concentration in each of the three plant compartments leaf, stem which includes fruits and seeds, and root) is expressed as a function of both time and chemical concentrations in soil and air. The model was developed using the fugacity concept; however, the final expressions are presented in terms of concentrations in soil and air, equilibrium partition coefficients and a set of transport and transformation half-lives. An illustrative application of the model is presented which describes the uptake of bromacil by a soybean plant under hydroponic conditions. The model, which is believed to give acceptably accurate prediction of the distribution of chemicals among plant tissues, air and soil, may be used for the assessment of exposure to, and risk from contaminants consumed either directly from vegetation or indirectly in natural and agricultural food chains.

Recombinant human thrombopoietin (TPO) stimulates erythropoiesis by inhibiting erythroid progenitor cell apoptosis

Thrombopoietin (TPO) has been reported to stimulate erythropoiesis, but the stimulatory mechanism has not been defined. To address this issue, we performed serum-free cell-culture experiments with recombinant human TPO and purified human progenitor cells. We found that TPO alone was able to stimulate the megakaryocyte colony formation in serum-free cultures, but erythroid colonies were never observed. Only in the presence of EPO (erythropoietin) +IL-3 was TPO able to stimulate a small increase (approximately 25%) in erythroid colony formation. Accordingly, we hypothesized that TPO might have an effect on erythroid progenitor cell viability, rather than a direct stimulatory effect. To test this idea, CD34+ cells were cultured for 7d in serum-free methylcellulose in the presence or absence of TPO, after which time KL+ EPO was added to the cultures. Cells which were pre-cultured for 7 d in the presence of TPO gave rise to approximately 6 times as many burst forming unit-erythroid (BFU-E) colonies as cells which were pre-cultured in the absence of TPO. Further, when primitive CD34+, Kit+ MNC were cultured for 3-7 d under serum-free conditions in the presence or absence of TPO, significantly fewer cells cultured in the presence of TPO displayed apoptotic changes when compared to cells cultured in the absence of TPO. Taken together, these results suggest that TPO has little direct stimulatory effect on erythroid progenitor cells, but might indirectly enhance erythropoiesis by preventing very early erythroid progenitor cells from undergoing apoptotic cell death.

The human mammary-derived growth inhibitor (MDGI) gene: genomic structure and mutation analysis in human breast tumors

The mammary-derived growth inhibitor (MDGI) gene is a candidate tumor suppressor gene for human breast cancer. It has been shown to reduce the tumorigenicity of breast cancer cell lines in nude mice, and loss of expression of this gene has been shown in primary breast tumors. Furthermore, the human MDGI gene has been mapped to human chromosome 1p32-p35, a common region of deletion in sporadic breast tumors. We have determined the genomic structure of the human MDGI gene from a cosmid clone mapping to chromosome 1p32-p35 and have more finely mapped the MDGI gene relative to chromosome 1p microsatellite markers. The gene covers approximately 8 kb of genomic DNA and is divided into four exons. In an attempt to identify possible inactivating mutations in the MDGI gene in human breast cancer, we have sequenced all four exons and their surrounding splice junctions in 30 sporadic breast tumors. Ten of these tumors showed loss of heterozygosity (LOH) in the 1p32-p35 region, with 5 tumors showing LOH in the subregion containing the MDGI gene. No mutations were found in this analysis. A polymorphism was identified in exon 2 in the constitutional DNA of 1/30 cases in this study, which resulted in the conversion of a lysine to an arginine residue at codon 53. This variant was present in the constitutional DNA of a further 3/26 women with sporadic breast cancer and 2/90 control individuals (P = 0.20). Despite experimental evidence that MDGI has tumor suppressor activity, our data suggest that mutations in the coding region are uncommon in human breast tumorigenesis.

Regulation of IGFBP-3 expression in breast cancer cells and uterus by estradiol and antiestrogens: correlations with effects on proliferation: a review

This paper reviews actions of antiestrogens on IGF physiology, and discusses the potential significance of the recent observations that (i) effects of antiestrogens on the uterus are correlated with their effects on uterine IGF-I and IGFBP-3 gene expression, and that (ii) the potent antiestrogen and growth inhibitor ICI 182,780 induces autocrine production of IGFBP-3 by estrogen receptor-positive breast cancer cells, while the growth stimulatory action of estradiol is associated with suppression of IGFBP-3 expression.

GT-2: a transcription factor with twin autonomous DNA-binding domains of closely related but different target sequence specificity

A triplet of adjacent, highly similar GT motifs in the phyA promoter of rice functions to support maximal expression of this gene. We have obtained a recombinant clone that encodes a full-length nuclear protein, designated GT-2, which binds specifically to these target sequences. This novel protein contains acidic, basic and proline- + glutamine-rich regions, as well as two autonomous DNA-binding domains, one NH2-terminal and the other COOH-terminal, that discriminate with high resolution between the three GT motifs. A duplicated sequence of 75 amino acids, present once in each DNA-binding domain, appears likely to mediate DNA target element recognition. Each copy of this duplicated protein sequence is predicted to form three amphipathic alpha-helices separated from each other by two short loops. The absence of sequence similarity to other known proteins suggests that this predicted structural unit, which we term the trihelix motif, might be representative of a new class of DNA-binding proteins.