From Words to Action: Comparing the Disparities Between National Drug Policy and Local Implementation in Tijuana, Mexico and Vancouver, Canada

In 2009, Mexico passed a national drug policy reform decriminalizing the possession of small amounts of certain drugs for personal use with the aim of diverting drug-dependent individuals from prison and towards addiction treatment. However, the public health approach codified by the reform has not yet led to a meaningful change in local police practices nor contributed to the meaningful scale-up of harm reduction and addiction treatment services in many Mexican cities. Specifically, in Tijuana, Baja California, there continues to be a variety of local level barriers – including arbitrary police behaviours – that hinder the ability of people who inject drugs (PWID) from accessing vital harm reduction services. This has implications for the growing HIV epidemic in Mexico’s northern border region, given that access to harm reduction interventions has been shown to effectively reduce the risk of HIV infection among PWID. In contrast to the largely enforcement-based local response seen in Tijuana, the municipal Four Pillars approach implemented in Vancouver, Canada in 2001 was passed as a public-health oriented response to the rising prevalence of HIV/AIDS among PWID in the Downtown Eastside of Vancouver. Centered on the balancing of four approaches – harm reduction, treatment, prevention and enforcement – the Four Pillars approach in Vancouver has led to a well-resourced local harm reduction and addiction treatment system. This local emphasis on harm reduction contrasts with the Canadian Conservative federal government’s opposition to harm reduction approaches. However, police-public health partnerships along with strong political support have led to the substantial scale up of harm reduction services as well as the reduction of HIV/AIDS among PWID in Vancouver, unlike what has been observed in Tijuana. This commentary therefore aims to assess the discrepancies between federal policy and local responses to drug-related harms in order to fully understand the impact and implications of national drug policies in shaping local response to drug related harms among populations of PWID. Through a comparison of the drug policy landscape in two cities linked by a large North American drug trafficking route - Tijuana, Mexico and Vancouver, Canada, - this commentary suggests that drug policy reform in and of itself will have little impact at the local level unless it is appropriately resourced and meaningfully supported by key stakeholders

Expression and function of FGF-4 in peri-implantation development in mouse embryos

One of the earliest events in mammalian embryogenesis is the formation of the inner cell mass (ICM) and the subse- quent delamination of primitive endoderm. We have found that mRNA for fibroblast growth factor (FGF)-4, but not FGF-3, is expressed in preimplantation mouse blastocysts and that the FGF-4 polypeptide is present in ICM cells. ICM-like embryonal carcinoma cells and embryonic stem cells also express FGF-4. Conversely, differentiated embryonal carcinoma cells in the endoderm lineage express FGF-3, but not FGF-4 mRNA. Although mouse embryos expressed FGF-4 mRNA from the 1-cell stage, embryos cultured from the 2-cell through the blastocyst stage in the presence of recombinant FGF-4 did not respond mitogenically. However, when ICMs that were isolated by immunosurgery were cultured with FGF- 4, the number of morphologically distinct, differentiated parietal endoderm cells growing out onto the coverslip increased, without an increase in the number of undiffer- entiated ICM cells. ICM outgrowths cultured with FGF-4 increased their secretion of 92×103 Mrgelatinase and tissue plasminogen activator, a hallmark of migrating cells. Receptors for FGF-4 (FGFR-3 and FGFR-4) are expressed in all cells of the mouse blastocyst. These findings indicate that FGF-4 produced by undifferentiated ICM cells acts in the peri-implantation period of embryogenesis to influence the production and behavior of endoderm cells derived from them. Key words: fibroblast growth factor, mouse embryogenesis, metall

Genes for extracellular matrix-degrading metalloproteinases and their inhibitor, TIMP, are expressed during early mammalian development

Extracellular matrix (ECM) remodeling accompanies cell migration, cell-cell interactions, embryo expansion, uterine implantation, and tissue invasion during mammalian embryogenesis. We have found that mouse embryos secrete functional ECM-degrading metalloproteinases, including collagenase and stromelysin, that are inhibitable by the tissue inhibitor of metalloproteinases (TIMP) and that are regulated during peri-implantation development and endoderm differentiation. mRNA transcripts for collagenase, stromelysin, and TIMP were detected as maternal transcripts in the unfertilized egg, were present at the zygote and cleavage stages, and increased at the blastocyst stage and with endoderm differentiation. These data suggest that metalloproteinases function in cell-ECM interactions during growth, development, and implantation of mammalian embryos

Insulin-like growth factor II acts through an endogenous growth pathway regulated by imprinting in early mouse embryos

We present evidence that insulin-like growth factor II (IGF-II) mediates growth in early mouse embryos and forms a pathway in which imprinted genes influence development during preimplantation stages, mRNA and protein for IGF-II were expressed in preimplantation mouse embryos, but the related factors IGF-I and insulin were not. IGF-I and insulin receptors and the IGF-II/mannose-6-phosphate receptor were expressed. Exogenous IGF-II or IGF-I increased the cell number in cultured blastocysts, but a mutant form of IGF-II that strongly binds only the IGF-II receptor did not. Reduction of IGF-II expression by antisense IGF-II oligonucleotides decreased the rate of progression to the blastocyst stage and decreased the cell number in blastocysts. Preimplantation parthenogenetic mouse embryos expressed mRNA for the IGF-II receptor but not for either IGF-II ligand or the IGF-I receptor, indicating that the latter genes are not expressed when inherited maternally. These data imply that some growth factors and receptors, regulated by genomic imprinting, may control cell proliferation from the earliest stages of embryonic development

Matrix Metalloproteinase 13 Is Induced in Fibroblasts in Polyomavirus Middle T Antigen-Driven Mammary Carcinoma without Influencing Tumor Progression

Matrix metalloproteinase (MMP) 13 (collagenase 3) is an extracellular matrix remodeling enzyme that is induced in myofibroblasts during the earliest invasive stages of human breast carcinoma, suggesting that it is involved in tumor progression. During progression of mammary carcinomas in the polyoma virus middle T oncogene mouse model (MMTV-PyMT), Mmp13 mRNA was strongly upregulated concurrently with the transition to invasive and metastatic carcinomas. As in human tumors, Mmp13 mRNA was found in myofibroblasts of invasive grade II and III carcinomas, but not in benign grade I and II mammary intraepithelial neoplasias. To determine if MMP13 plays a role in tumor progression, we crossed MMTV-PyMT mice with Mmp13 deficient mice. The absence of MMP13 did not influence tumor growth, vascularization, progression to more advanced tumor stages, or metastasis to the lungs, and the absence of MMP13 was not compensated for by expression of other MMPs or tissue inhibitor of metalloproteinases. However, an increased fraction of thin collagen fibrils was identified in MMTV-PyMT;Mmp13−/− compared to MMTV-PyMT;Mmp13+/+ tumors, showing that collagen metabolism was altered in the absence of MMP13. We conclude that the expression pattern of Mmp13 mRNA in myofibroblasts of invasive carcinomas in the MMTV-PyMT breast cancer model recapitulates the expression pattern observed in human breast cancer. Our results suggest that MMP13 is a marker of carcinoma-associated myofibroblasts of invasive carcinoma, even though it does not make a major contribution to tumor progression in the MMTV-PyMT breast cancer model

CHOLESTEROL METABOLISM IN THE MACROPHAGE

Phagocytosis of cholesterol-containing particles resulted in the formation of an intralysosomal cholesterol compartment. Cholesterol was excreted out of the macrophage with a single exponential rate which depended on the concentration of acceptor lipoproteins in the medium. Exchange kinetics performed on cells which had ingested particulate cholesterol suggested that excretion occurred by the same mechanism as exchange. Cholesterol esters as particulate albumin coacervates were taken up by macrophages and hydrolyzed by a lysosomal cholesterol esterase with optimal activity at pH 4.0. Cholesteryl linoleate was hydrolyzed much more readily than cholesteryl palmitate. The amount of cholesterol esterase and its specific activity increased during the in vitro cultivation of macrophages. Intralysosomally, cholesteryl linoleate and palmitate were hydrolyzed to free cholesterol which was excreted from the macrophage and recovered in the medium. Since cholesteryl linoleate was hydrolyzed more rapidly than free cholesterol was excreted into the medium, free cholesterol accumulated intralysosomally. Cholesteryl palmitate was hydrolyzed more slowly, and the rate of hydrolysis was limiting for excretion of the free cholesterol from within the lysosome