Urbanization and human health

Urbanization involves a physical change in which increasing proportions of populations live in urban settings, however defined. It also implies considerable changes in the ways in which these people live, how they earn their livelihoods, the food which they eat, and the wide range of environmental factors to which they are exposed. There is another underlying assumption that, increasingly, urban populations will be more healthy than their rural counterparts and that higher levels of urbanization will equate with better health status. This paper discusses some of the assumptions underlying this contention. It takes issue with certain of them, particularly the assumption that urbanization affects the health of all residents equally. It is manifestly evident that in many cities, particularly in the developing world, the poor are exposed to greater risks and have much lower health status than their richer neighbours. In addition, whilst urban residents may theoretically have a better access to health care and services than do residents in many rural areas, and whilst many indicators of health do appear better in more highly urbanized societies than ones less so, there are caveats. The paper introduces the concept of epidemiological transition, which suggests that, whilst life expectancy might be higher in many urbanized countries and in certain cities, the inhabitants are often merely suffering from different forms of ill-health, often chronic or degenerative, rather than infective. In certain cities in middle-income countries, residents, particularly the poor, are exposed to a double risk of both infection and chronic degenerative ailments. The paper concludes with a consideration of more general recent statements from the World Health Organization among others, on the impact of urbanization on health. The 'Healthy Cities' project is also discussed. WHO identifies a range of general determinants of urban health: physical, social, cultural and environmental. Many represent the by-products of modernization and especially industrialization. It is emphasized that urbanization, and the concentration of human beings into new areas in particular, can bring exposure to new risk factors for large numbers of people. The growth of infectious and parasitic disease in some urban settings must therefore be recognized, as must the emergence of chronic diseases, with the concomitant need for investment in new types of health and social care. However, a number of constraints militate against the achievement of improved urban health, especially in developing countries.(ABSTRACT TRUNCATED AT 400 WORDS)

In vitro transcription analysis of DNA adducts induced by cyanomorpholinoadriamycin

The reaction of cyanomorpholinoadriamycin (CMA) with DNA results in the formation of sequence-specific complexes with DNA. These complexes were revealed as blocked transcripts in an in vitro transcription assay--of 14 high-intensity blockages detected in the 120 bp probed in this assay, 12 were prior to GpG or CpC sequences. Slow read-through past the first few sites exhibited first-order kinetics, with half-lives of 25-200 min. Bidirectional transcription footprinting revealed nine high-intensity sites, eight of which were defined by a GpG element (nontemplate strand). Reaction of CMA with single-strand DNA, followed by a primer-extension assay, revealed four major blockages all of which were at GpG sites on the initial single-strand DNA. From a combination of these three experimental approaches, it appears that CMA yields dominantly intrastrand cross-links between adjacent guanine residues. Since CMA is also known to form interstrand cross-links, these appear to occur at GpC sequences but are minor in comparison to the extent of formation of intrastrand cross-links.

Bis-daunomycin hydrazones: interactions with DNA

A series of bis-daunomycin hydrazones were synthesised from diester diamide linking groups derived from alpha,omega-dicarboxylic acids. All members of the series bis-intercalated into DNA, as evidenced by doubling of the lengthening of rod-like DNA compared to daunomycin, and by a 1000-5000 fold slower dissociation from DNA than daunomycin under detergent sequestration conditions. The bis-hydrazones exhibited neighbour exclusion, and occupied 6 bp under saturating conditions of drug. A unique DNA sequence specificity was apparent from transcriptional footprinting of 100 bp of DNA, with the greatest preference for 5'-CACA sites.

Evaluation of porphyrin characteristics required for photodynamic therapy

The cytotoxicity (in the dark), phototoxicity (red light) and subcellular localization (using confocal laser scanning microscopy) were determined for 15 porphyrins (1-15) in C6 glioma cells. The partition coefficient in 2-octanol was also determined for each porphyrin at pH 7.4. The cytotoxicity increased with pi (log of partition coefficient) up to pi values of +2. The 7 porphyrins with cationic side chains exhibited a classical parabolic correlation between phototoxicity and pi, with maximal activity at a pi value of approximately 1.0. There was also a significant correlation between subcellular localization and degree of phototoxicity, with the three most photosensitive porphyrins all possessing cationic side chains, and all three localizing in mitochondria.

Evaluation of tumour and tissue distribution of porphyrins for use in photodynamic therapy

A range of pure, monomeric porphyrins were synthesised and their localising capacities compared to HpD and Hp at 6 h and 24 h post injection in the mouse C6 intracerebral glioma model as well as in normal brain, skin, muscle, kidney, spleen, liver, lung and whole blood. The partition coefficients were examined between PBS and 2-octanol over the pH range 7.4-6.6 and pH profiles were established. A parabolic relationship was observed between log (porphyrin tumour concentration) at pH 7.4, with maximal tumour localisation at log (partition coefficient), pi, of approximately zero. Porphyrins with side chains with nett cationic character also exhibited up upward (parabolic) dependence on pi for most tissues studied, with maximal porphyrin localisation at pi of 0-0.5. In contrast, those porphyrins with nett anionic character exhibited a downward (negative) parabolic trend for all eight tissues studied, with minimal porphyrin localisation at pi of approximately zero. Four porphyrins (4, 11, 12, 13) exhibited similar or better tumour localisation than HpD, and two (11 and 12) offer promise as lead compounds for the design of improved porphyrins for use in PDT.

Synthesis of Porphyrins Derived From the Amidation of Protoporphyrin IX for Use as Potential Chemotherapeutic Agents

A series of pure porphyrins (3)-(11) derived from amidation of the carboxylic acid groups of protoporphyrin IX was synthesized in high yield by using 1,11-carbonyldiimidazole as the coupling reagent. Preliminary biological evaluation of these porphyrins revealed that (3) and (10) localize in tumour tissue in concentrations 20 times greater than the surrounding normal tissue. Porphyrins (3)-(5) were found to localize in mitochondria, and this is proposed to account for their greater photosensitivity effectiveness when compared with hematoporphyrin derivative. The extent of binding of the basic porphyrins (3) and (4) to DNA was ascertained by absorbance titrations with DNA, and binding constants were found to be (1.0-1.5) × 106 dm3 mol-1 with six base pairs occluded for both compounds.

The DNA sequence specificity of cyanomorpholinoadriamycin

Cyanomorpholinoadriamycin (1 microM) was reacted in a transcription buffer with DNA of an initiated transcription complex. Subsequent elongation of the initiated complex revealed permanent transcriptional blockages at 16 sites after only 5 min of drug-DNA reaction time. The most dominant sites were immediately prior to 5'-CC (six) and 5'-GG (six) sequences of the non-template strand, consistent with the presence of intrastrand crosslinking between adjacent guanine residues. Minor levels of blockage were at 5'-GC and 5'-CG sequences and may reflect low levels of interstrand crosslinking.

Subcellular localization of porphyrins using confocal laser scanning microscopy

The in vitro subcellular distribution patterns of 10 porphyrins, varying in hydrophobicity and charge, were studied using confocal laser scanning microscopy on two cell lines (V79 and C6 glioma cells) for incubation times up to 24 h. All of the porphyrins were taken up rapidly by both cell lines and distinct classes of subcellular distribution patterns were observed: general cytoplasmic staining; localization in lysosomes (usually associated with general cytoplasmic staining); localization in mitochondria (and general cytoplasmic staining); localization in mitochondria with subsequent uptake into lysosomes. Structure-localization relationships which have emerged are that porphyrins with dominantly cationic side chains localize in mitochondria, whereas those with a more anionic character tend to localize in lysosomes.

Ca(2+)-dependent structural transitions of the platelet glycoprotein IIb-IIIa complex. Preparation of stable glycoprotein IIb and IIIa monomers

The platelet membrane glycoprotein (GP) IIb-IIIa complex is the receptor for adhesive proteins on activated platelets that mediates platelet aggregation. In the present study, factors affecting the structural stability of the purified GP IIb-IIIa complex and the dissociated subunits were investigated. Purified GP IIb-IIIa was incubated in various Ca2+ concentrations, and the percentage of dissociated subunits was quantitated by sucrose gradient sedimentation. Two Ca(2+)-dependent transitions were observed, one at about 60 microM Ca2+, where half of the complexes became dissociated, and the other at 0.1 microM Ca2+, where half of the dissociated subunits became incapable of reforming heterodimer complexes when higher Ca2+ concentrations were readded. This loss in ability to reform heterodimer complexes was caused primarily by a Ca(2+)-dependent transition in GP IIIa, leading to an apparent unfolding of this subunit, followed by the formation of high molecular weight aggregates. The formation of these aggregates was time- and temperature-dependent and could not be reversed by added Ca2+. Although Mg2+ prevented dissociation of GP IIb-IIIa, it failed to promote reassociation of the dissociated subunits. Based on these findings, conditions were developed for the preparation of dissociated GP IIb and GP IIIa such that 70% of the subunits remained functional in that they retained the ability to reform heterodimer complexes.

In vitro transcription analysis of DNA alkylation by nitrogen mustard

A synchronized in vitro transcription assay has been used to probe the sequence specificity of alkylation of DNA by nitrogen mustard. Transcriptional blockages were detected with use of a 497-base-pair PvuII/SalI restriction fragment of a modified pBR322 vector when initiation of transcription was commenced after the DNA had been alkylated but not if the initiated transcription complex was subjected to alkylation before the elongation phase. The intensity of transcriptional blockages increased with alkylation time and was maximal after 1.5 h at a mustard concentration of 200 microM. There was also evidence of alkylation of the promoter region with increasing mustard concentration. The transcriptional blockage pattern changed at some sites as elongation time was increased and three types of blockages were observed-partial transcription (one or two nucleotides) past an initial blockage site, delayed but normal transcription past some sites, and complete termination at most sites. Eight of the nine blockage sites detected were at G or GG sequences on the template strand, with an apparent specificity for 5'-CTGT sequences of the template strand. Seven of the nine sites were capable of inter- or intrastrand cross-links, including three possible G-G interstrand cross-links spanning an intervening base-pair. In the 103-bp segment probed by this procedure, transcriptional blockages were detected (with one exception) only at sites corresponding to G on the template strand where inter- or intrastrand cross-linking was possible but not for similar sequences on the non-template strand.

cDNA cloning and expression of platelet p24/CD9. Evidence for a new family of multiple membrane-spanning proteins

This study was designed to clone, sequence, and express the full-length cDNA for the human platelet p24/CD9 antigen. A 1.3-kilobase cDNA clone was identified that has an open reading frame encoding a mature protein of 228 amino acids (approximately 25,400 Da) containing 10 cysteine residues and four putative transmembrane domains. The identity of the clone was confirmed by: (i) its predicted size, (ii) identity to four peptide sequences from the isolated protein including the NH2 terminus, and (iii) expression of the isolated clone in Xenopus oocytes and Chinese hamster ovary cells. p24/CD9 has sequence identity (24-34%) to four other cell-surface proteins: ME491, a melanoma antigen; CO-029, a carcinoma antigen; CD37, a leukocyte antigen; and SM23, an antigen of the parasitic helminth Schistosoma mansoni. The five proteins have a similar number of amino acids and are characterized by the presence of four putative transmembrane domains. These data indicate the presence of a new family of surface antigens that may function in cellular activation and differentiation.

Barbourin. A GPIIb-IIIa-specific integrin antagonist from the venom of Sistrurus m. barbouri

Sixty-two snake venoms were screened to identify those which specifically inhibit the adhesive protein binding function of the glycoprotein (GP) IIb-IIIa complex, the receptor-mediating platelet aggregation. Although 52 of these venoms inhibited GPIIb-IIIa, only one of these, from the southeastern pigmy rattlesnake, Sistrurus m. barbouri, was specific for GPIIb-IIIa versus other integrins. The peptide responsible for this activity, termed barbourin, was sequenced and found to be highly homologous to other peptides of the viper venom GPIIb-IIIa antagonist family but was the first member which did not contain the Arg-Gly-Asp (RGD) amino acid sequence, believed to be required for inhibition of receptor function. Instead, barbourin contains the sequence, Lys-Gly-Asp (KGD). The conservative Lys for Arg substitution appears to be the sole structural feature which imparts integrin specificity to barbourin, since venom peptide analogs with Lys substitutions were also specific for GPIIb-IIIa. Thus, barbourin represents a new structural model useful for designing potent and GPIIb-IIIa-specific compounds that may have therapeutic value as platelet aggregation inhibitors.

Adhesive properties of the beta 3 integrins: comparison of GP IIb-IIIa and the vitronectin receptor individually expressed in human melanoma cells

Glycoprotein IIb-IIIa (alpha IIb beta 3) and the vitronectin receptor (alpha v beta 3), two integrins that share the common beta 3 subunit, have been reported to function as promiscuous receptors for the RGD-containing adhesive proteins fibrinogen, vitronectin, fibronectin, von Willebrand factor, and thrombospondin. The present study was designed to establish a cell system for the expression of either GP IIb-IIIa or the vitronectin receptor in an otherwise identical cellular environment and to compare the adhesive properties of these two integrins with those of native GP IIb-IIIa and the vitronectin receptor constitutively expressed in HEL cells or platelets. M21 human melanoma cells lack GP IIb-IIIa and use the vitronectin receptor to attach to vitronectin, fibrinogen, fibronectin, and von Willebrand factor. To study the functional properties of GP IIb-IIIa in these cells, we transfected GP IIb into M21-L cells, a variant of M21 cells (Cheresh, D.A., and R.C. Spiro. 1987. J. Biol. Chem. 262:17703-17711), which lack the expression of functional alpha v and are therefore unable to attach to vitronectin, fibrinogen, and von Willebrand factor. Transfectants expressing GP IIb were isolated by immunomagnetic beads and surface expression of the GP IIb-IIIa complex was documented by FACS analysis and immunoprecipitation experiments performed with 125I-labeled M21-L/GP IIb cells. Comparative functional studies demonstrated that GP IIb-IIIa expressed in M21-L/GPIIb cells as well as native GP IIb-IIIa constitutively expressed in HEL-5J20 cells (an HEL variant lacking alpha v beta 3) mediated cell attachment to immobilized fibrinogen, but not to vitronectin or von Willebrand factor, whereas the vitronectin receptor expressed in M21 cells and HEL-AD1 cells (an HEL variant expressing alpha v beta 3) mediated cell attachment to fibrinogen, vitronectin, and von Willebrand factor. Similarly, PGl2-treated resting platelets attached to immobilized fibrinogen but not to vitronectin or von Willebrand factor, and this attachment could be inhibited by mAb A2A9 (directed against a functional site on the GP IIb-IIIa complex). However, in contrast to platelets, which adhered to vitronectin and von Willebrand factor after stimulation by thrombin or PMA, activation of the protein kinase C pathway in M21-L/GP IIb or HEL cells did not induce cell adhesion to vitronectin or von Willebrand factor.(ABSTRACT TRUNCATED AT 400 WORDS)

Isolation and characterization of phosmidosine. A new antifungal nucleotide antibiotic

A new nucleotide antibiotic, phosmidosine was isolated from a culture filtrate of a newly isolated streptomycete identified as Streptomyces sp. RK-16. HRFAB-MS and elemental analysis established the molecular formula of C16H24N7O8P. 1H, 13C and 31P NMR indicated the presence of a methyl phosphate group and UV spectra were similar to those of 8-hydroxyadenosine. The antibiotic inhibited spore formation of Botrytis cinerea at the concentration of 0.25 micrograms/ml.

Inhibition of fibrinogen binding to GP IIb-IIIa by a GP IIIa peptide

The glycoprotein IIb-IIIa complex (GP IIb-IIIa) mediates platelet aggregation and is a member of the cytoadhesin family of receptors that bind adhesive proteins such as fibrinogen, fibronectin, and von Willebrand factor. Despite the wide range of cell-substrate interactions mediated by these receptors, ligand binding domains have not yet been identified on any of the integrins. The present study was designed to determine potential fibrinogen binding domain(s) on the GP IIb-IIIa complex. Synthetic peptides derived from residues 1-288 of the amino-terminal portion of GP IIIa were tested for their abilities to block the binding of fibrinogen to purified GP IIb-IIIa in a solid-phase microtiter assay. Two overlapping peptides encompassing residues 204-229 of GP IIIa were identified which blocked fibrinogen binding in this assay. Polyclonal antibodies to these peptides blocked fibrinogen binding to purified GP IIb-IIIa as well as platelet aggregation. The overlapping residues of these two peptides GP IIIa (211-222), SVSRNRDAPEGG-NH2, blocked the binding of fibronectin, von Willebrand factor, and vitronectin to purified GP IIb-IIIa. Finally, direct binding of GP IIIa (204-229) to fibrinogen and fibronectin was demonstrated by enzyme-linked immunosorbent assay. We conclude from these studies that the amino acid sequence 211-222 of GP IIIa is critically involved in adhesive protein binding, and may represent an important portion of the GP IIb-IIIa ligand binding domain.

Problems and potential of researching epidemiological transition: examples from Southeast Asia

The concept of epidemiological transition is now quite widely recognized, if not so widely accepted. The transition appears to progress at varying speeds and to different extents spatially; it seems that there can be considerable international, regional and local variations in its progress. The paper examines this contention in the case of a number of countries in Southeast Asia, principally Hong Kong, Malaysia and Thailand. Drawing on evidence from this region, the paper highlights the importance when researching epidemiological transition of the time period under consideration; socio-cultural variations; the nature and quality of data, and spatial scale. It makes some suggestions as to the potential of the concept of epidemiological transition in health care planning and development studies.

Fluorinated anthracyclines: interactions with DNA

Four fluorine containing derivatives of anthracyclines (daunomycin and adriamycin) were synthesised, and comprised C-13, 1,1,1-trifluoroethyl-hydrazones of each anthracycline, and C-14 4-F and 4-CF3-benzoate esters of adriamycin. All four derivatives intercalated into DNA in a manner similar to their parent anthracycline. The ester derivatives exhibited 3-4-fold higher binding affinity to DNA, and slower DNA dissociation kinetics than adriamycin. This stabilisation derives from additional contacts of the C-14 side chain to the DNA minor groove. The hydrazone derivatives showed lower binding affinity to DNA, and dissociated from DNA 3-4 times faster than the parent compound. The 19F resonance of the bound drug was broadened to 120 Hz and shifted 60 Hz downfield (0.32 ppm) relative to the sharp (7.5 Hz) peak of the free drug. These values imply a rapid exchange between the free and DNA bound forms (DNA lifetime greater than 5 ms), with the fluorine group residing in a hydrophobic region in close contact with the DNA minor groove. The 4-8 fold lesser specific potency of the ester derivatives supports the concept that DNA binding is an important factor, but not sole determinant of biological activity of these analogues.

Platelet membrane glycoproteins: functions in cellular interactions

The understanding of the structure and function of platelet membrane glycoproteins has been facilitated by studies showing that they belong to larger gene families of cell surface receptors involved in cellular interactions. In some instances (e.g. GP IIb-IIIa and GP Ib-IX) the study of the platelet proteins has served as a prototype for relatively newly described gene families (e.g. integrins and LRG proteins, respectively). In other instances, e.g. PECAM-1, the background of information on immunoglobulin domain-containing proteins has served to indicate functions. Receptor-ligand interactions have been characterized at the molecular level, and studies of genetic defects affecting platelet receptors have contributed significantly to understanding structure-function relationships. Gene transfection studies provide encouraging results that might lead to gene therapy. The knowledge about platelet ligand-receptor processes contributes not only to our understanding of normal platelet function, but also to a more generalized understanding of adhesive mechanisms used by many cells to interact with their environment.