Column preconcentration of gold by adsorbing AuCl4- onto methyltrioctyl ammonium chloride-naphthalene and subsequent atomic absorption spectrometric determination.

A sensitive, selective and simple preconcentration method for ultra-trace gold determination has been developed that uses naphthalene-methyltrioctyl ammonium chloride (Aliquat 336s) as an adsorbent. Gold, in the form of AuCl4-, was retained by the adsorbent in the column at a flow rate of 1 ml min(-1). After filtration, the solid mass consisting of the gold complex and naphthalene was dissolved out of the column with 5 ml of N,N-dimethylformamide (DMF), and the metal was then determined by atomic absorption spectrometry. In the initial solution, the calibration graph of absorbance versus gold concentration was found to be linear in the range 0.5-150 ng ml(-1) Au(III) with r=0.997 (n=9), and the 3 s detection limit was 0.428 ng ml(-1). The relative standard deviation for eight replicate measurements of 20 microg of gold was 2.14%. Preconcentration factors of 390 and 650 were achieved using 5 ml and 3 ml of DMF, respectively. The proposed method was successfully applied to the determination of gold in wastewater, processed pool water, slurry pool water, and raw well-water from the Moteh gold mine, and synthetic samples.

Do patents for antiretroviral drugs constrain access to AIDS treatment in Africa?

Public attention and debate recently have focused on access to treatment of acquired immunodeficiency syndrome (AIDS) in poor, severely affected countries, such as those in Africa. Whether patents on antiretroviral drugs in Africa are impeding access to lifesaving treatment for the 25 million Africans with human immunodeficiency virus infection is unknown. We studied the patent statuses of 15 antiretroviral drugs in 53 African countries. Using a survey method, we found that these antiretroviral drugs are patented in few African countries (median, 3; mode, 0) and that in countries where antiretroviral drug patents exist, generally only a small subset of antiretroviral drugs are patented (median and mode, 4). The observed scarcity of patents cannot be simply explained by a lack of patent laws because most African countries have offered patent protection for pharmaceuticals for many years. Furthermore, in this particular case, geographic patent coverage does not appear to correlate with antiretroviral treatment access in Africa, suggesting that patents and patent law are not a major barrier to treatment access in and of themselves. We conclude that a variety of de facto barriers are more responsible for impeding access to antiretroviral treatment, including but not limited to the poverty of African countries, the high cost of antiretroviral treatment, national regulatory requirements for medicines, tariffs and sales taxes, and, above all, a lack of sufficient international financial aid to fund antiretroviral treatment. We consider these findings in light of policies for enhancing antiretroviral treatment access in poor countries.

Defining and refining international donor support for combating the AIDS pandemic.

The international aid effort against AIDS is greatly incommensurate with the severity of the epidemic. Drawing on the data that international aid donors self-reported to the Organization for Economic Cooperation and Development (OECD), we find that, between 1996 and 1998, finance from all rich countries to sub-Saharan Africa for projects designated as AIDS control averaged US $69 million annually, and, assuming a safe margin for under-reporting and misreporting, we estimate that total donor spending on HIV/AIDS control was perhaps twice that at most. Since the late 1980s, aid levels have dropped relative to the prevalence of HIV infection, and stood recently at about $3 per HIV-infected person. Lack of finance is now the primary constraint on progress against AIDS, notwithstanding the widespread belief that a lack of interest from the goveements of poor countries is limiting. We argue that to produce a meaningful response to the pandemic, international assistance must be based on grants, not loans, for the poorest countries; be increased within the next 3 years to a minimum of $7.5 billion or more; be directed toward funding projects which are proposed and desired by the affected countries themselves, and which are judged as having epidemiological merit against the pandemic by a panel of independent scientific experts; and fund concurrent needs, including prevention, drug treatment (such as highly active antiretroviral therapy), and blocking mother-to-child HIV transmission. An effort of this scope and scale will both radically alter the prospects for intervention against AIDS in poor countries, and together with comparable efforts to control other infectious diseases, is easily afforded by the OECD donor economies, whose aggregate national income recently surpassed $21 trillion annually.

Human rights and biomedical research funding for the developing world: covering state obligations under the right to health.

The International Covenant on Economic, Social and Cultural Rights (ICESCR) obligates states to "take steps individually and through international assistance and co-operation. to the maximum of ¿their available resources" to realize the right to health. This obligation, however, is often dismissed because (1) realizing rights through "international assistance" is thought to intrude on state sovereignty and (2) it is impossible to say what is demanded by the "maximum of. available resources." These problems can be circumvented by "reading down" the mutual assistance clause, so that it demands only that steps be taken on a state's own territory, with its pecuniary resources. Industrialized states could use public funds to research diseases such as malaria, AIDS, and tuberculosis, but they have failed to consider their ICESCR obligations in making science funding decisions. These failures point to ubiquitous and grievous violations of international law.

Cytotoxic T lymphocytes can induce a condemned state and synchronous post-mitotic apoptosis of daughter target cells.

We have used time-lapse video microscopy to study cytotoxic T lymphocyte (CTL)-mediated apoptosis of LDb fibroblast target cells at different phases of the cell cycle. When aphidicolin-synchronized target cells were exposed to the CTL clone F5, apoptosis occurred with similar morphology during G1, S/G2 and M phase, showing that apoptosis and mitosis are not mutually exclusive cellular events. Interestingly, following normal mitosis of target cells that had been previously contacted by CTL, pairs of daughter cells would occasionally undergo apoptosis within minutes of each other. Such synchronous post-mitotic apoptosis was also observed when using mitotically unsynchronized target cells, and also when using d11S T cell hybridomas as alternative Fas- (CD95-) based effector cells, even if these effectors were physically washed away after an initial period of co-incubation with the target cells. Our observations show that cytotoxic cells can induce a condemned state in pre-mitotic target cells, which can be inherited by both daughter cells, leading to their synchronous apoptosis after mitosis.

Variant antigenic peptide promotes cytotoxic T lymphocyte adhesion to target cells without cytotoxicity.

Timelapse video microscopy has been used to record the motility and dynamic interactions between an H-2Db-restricted murine cytotoxic T lymphocyte clone (F5) and Db-transfected L929 mouse fibroblasts (LDb) presenting normal or variant antigenic peptides from human influenza nucleoprotein. F5 cells will kill LDb target cells presenting specific antigen (peptide NP68: ASNENMDAM) after "browsing" their surfaces for between 8 min and many hours. Cell death is characterized by abrupt cellular rounding followed by zeiosis (vigorous "boiling" of the cytoplasm and blebbing of the plasma membrane) for 10-20 min, with subsequent cessation of all activity. Departure of cytotoxic T lymphocytes from unkilled target cells is rare, whereas serial killing is sometimes observed. In the absence of antigenic peptide, cytotoxic T lymphocytes browse target cells for much shorter periods, and readily leave to encounter other targets, while never causing target cell death. Two variant antigenic peptides, differing in nonamer position 7 or 8, also act as antigens, albeit with lower efficiency. A third variant peptide NP34 (ASNENMETM), which differs from NP68 in both positions and yet still binds Db, does not stimulate F5 cytotoxicity. Nevertheless, timelapse video analysis shows that NP34 leads to a significant modification of cell behavior, by up-regulating F5-LDb adhesive interactions. These data extend recent studies showing that partial agonists may elicit a subset of the T cell responses associated with full antigen stimulation, by demonstrating that TCR interaction with variant peptide antigens can trigger target cell adhesion and surface exploration without activating the signaling pathway that results in cytotoxicity.

BM28, a human member of the MCM2-3-5 family, is displaced from chromatin during DNA replication.

We have recently cloned and characterized a human member (BM28) of the MCM2-3-5 family of putative relication factors (Todorov, I.T., R. Pepperkok, R.N. Philipova, S. Kearsey, W. Ansorge, and D. Werner. 1994. J. Cell Sci. 107:253-265). While this protein is located in the nucleus throughout interphase, we report here a dramatic alteration in its nuclear binding during the cell cycle. BM28 is retained in the nucleus after Triton X-100 extraction in G1 and early S phase cells, but is progressively lost as S phase proceeds, and little BM28 is retained in detergent-extracted G2 nuclei. BM28 that is resistant to extraction in G1 nuclei is removed by DNase I digestion, suggesting that the protein is chromatin associated. In addition, we present evidence for variations in the electrophoretic mobility of BM28 that may reflect posttranslational modifications of BM28 during the cell cycle. During mitosis, BM28 is present as a fast-migrating form, but on entry into G1, the protein is converted into a slow-migrating form. With the onset of S phase, the slow-migrating form is progressively converted into the fast form. BM28 is phosphorylated at all stages of the cell cycle, but during interphase the fast form is hyperphosphorylated compared with the slow form. These apparent changes in modification may reflect or effect changes in the nuclear binding of BM28. The behavior of BM28 is not dissimilar to related proteins in Saccharomyces cerevisiae, such as Mcm2p, which are excluded from the nucleus after DNA replication. We speculate that BM28 may be involved in the control that limits eukaryotic DNA replication to one round per cell cycle.