Microplastics in the Volta Lake: Occurrence, distribution, and human health implications

Pollution of plastic waste in aquatic ecosystems in Ghana is of significant concern with potential adverse effects on food safety and ecosystem function. This study examined the abundance and distribution of microplastics (MPs) in freshwater biota samples namely: the African river prawn (Macrobrachium vollenhovenii), the Volta clam (Galatea paradoxa), Nile tilapia (Oreochromis niloticus), and sediment from the Volta Lake. Both biota and sediment samples were subjected to microscopic identification and FTIR analysis. In biota samples, the highest mean microplastic abundance of 4.7 ± 2.1 items per individual was found in the prawn, while the Nile tilapia recorded the least (2.8 ± 0.6 items per individual). A total of 398 microplastic particles were observed in sediment samples from the Volta Lake. Microfibers were the major plastic shapes identified in biota and sediment samples. We examined the relationship between microplastic abundance, biota size, and sediment properties. Despite the lack of statistical significance, microplastic shape, size, and polymer composition in assessed organisms mirrored those in the benthic sediment. Polyethylene, polypropylene, polyester, and polystyrene were the four dominant polymer types identified in the organisms and sediments. Although the estimated human exposure was relatively low compared with studies from other regions of the world, the presence of microplastics raises concern for the safety of fisheries products consumed by the general populace in the country. This research is essential for developing effective mitigation measures and tackling the wider effects of microplastic contamination on Ghana's freshwater ecosystems, particularly the Volta Lake.

Potential human health risks associated with ingestion of heavy metals through fish consumption in the Gulf of Guinea

Heavy metal pollution of the marine environment has toxic implications for both the aquatic biota and human health. We examined the levels of Zinc (Zn), Lead (Pb), Copper (Cu), Cadmium (Cd), Arsenic (As) and Mercury (Hg) in muscles of Sardinella maderensis, Dentex angolensis, Sphyraena sphyraena and Penaeus notialis caught from the coastal waters of Ghana using inductively coupled plasma mass spectrometry method. Penaeus notialis recorded the highest concentrations of all the metals (Cu:12.08 ± 1.46 µg/g, Zn: 19.20 ± 2.27 µg/g, As: 8.46 ± 2.42 µg/g, and Cd: 0.03 ± 0.01 µg/g) except Hg. Mercury was relatively high in D. angolensis (0.14 ± 0.03 µg/g). Apart from As, all metals were within globally permissible daily limits for consumption by human per meal. The estimated Target Hazard Quotient due to the intake of Hg through D. angolensis consumption exceeded the threshold value across all age categories. Carcinogenic risks due to As intake through P. notialis consumption far exceeded the 10^-6 threshold for all age groups in Ghana. It is recommended that the consumption of these fish species particularly, the shrimp P. notialis be done cautiously to avoid possible future health challenges.

Occurrence of microplastics in wild oysters (Crassostrea tulipa) from the Gulf of Guinea and their potential human exposure

The high dependence on plastics in Ghana has resulted in the generation of large quantities of plastic waste which are poorly managed and improperly disposed into the aquatic environments. This study assessed the spatial distribution and abundance of microplastics in mangrove oysters (Crassostrea tulipa): a major fishery resource of commercial importance in Ghana. The results showed that 84.0% of all individuals examined had ingested microplastics. A total of 276 microplastic items were recovered from the 120 individual oysters. Densu (100%) and Volta (93%), two estuaries situated in urban areas, had a greater incidence of microplastics than Whin (77%) and Nakwa (66%), estuaries situated in peri-urban and rural settlements, respectively. The mean microplastic abundance ranged from 1.4 to 3.4 items/individual and 0.34 to 1.7 items/g tissue wet weight. Fiber accounted for 69% of microplastic shapes, followed by fragments (27%) and films (4%). Polymer analysis showed polyethylene (PE), polypropylene (PP) and polystyrene (PS) as the most common types in oysters. The estimated microplastic intake per capita per year was one magnitude higher than the mean for other countries. This high rate of human exposure to microplastics requires an eminent policy formulation to guide the use, management and disposal of plastic waste in Ghana.

Correction to: Geochemical contamination in the Densu Estuary, Gulf of Guinea, Ghana

The correct equations are presented below.

Geochemical contamination in the Densu Estuary, Gulf of Guinea, Ghana

Chemical contaminants are released from mining, domestic and industrial effluents into an aquatic environment. Sediments (n = 10) were collected with an Eckman grab at ten stations in the Densu Estuary for ecological risk assessment. The spatial distribution of organic characteristics and ecological risk of metals-zinc, lead, copper, mercury, iron, and manganese in sediment-were analyzed using standard methods. The organic parameters occurred in the ranges, as follows: % C, 0.76 to 2.05, % TN, 0.06 to 0.015; % TP, 0.44 to 1.38; and C/N, 12.31 to 34.81. The ranges of metal concentrations (mg/kg) were as follows: Fe, 201.10 to 720.90; Mn, 40.10 to 152.70; Zn, 7.3 to 158.3; Pb, 1.9 to 84.7; Cu 3.4 to 23.0; and Hg, 0.01 to 0.05. The mean concentration of metals in the sediment were Fe > Mn > Pb > Zn > Cu > Hg. The highest mean concentration of Fe suggested redox conditions in the Densu Estuary. There is a low contamination factor (CF) for five metals (Zn, Hg, Fe, Cu, and Mn) (CF < 1) to high contamination of Pb (3 < CF ≤ 6). The average Pb concentration was above local and geological backgrounds, suggesting an anthropogenic source of pollution from industrial and domestic effluents and agrochemicals. The sediment was extremely enriched by Pb (EF > 50) with a positive index of geoaccumulation (0 < Igeo ≤ 2) than other metals. There is considerable to a very high degree of contamination (DC) (3 ≤ DC ≥ 6) of metals in the sediment of Densu Estuary. The potential ecological risk index (≤ 40 PERI < 80) suggested a very low to moderate ecological risk of metal pollution. The study provides baseline knowledge on geochemical contamination in tropical estuarine systems for the development of effective chemical control strategies towards sustainable management of coastal waters.

Environmental radioactivity and trace metals in surficial sediments from estuarine systems in Ghana (Equatorial Africa), impacted by artisanal gold-mining

This paper reports concentrations of γ-emitter radionuclides (⁴⁰K, ¹³⁷Cs, ²¹⁰Pb, ²²⁶Ra, ²²⁸Ra, ²²⁸Th and ²³⁴Th) and some metals (Al, Cr, Fe, Co, Ni, Cu, Zn, As, Sr, Cd, Sb, Cs, Pb, Th and U) in surficial sediments from the Ankobra, Pra and Volta estuaries, in Ghana. Artisanal gold-mining in the Ankobra and Pra basins promoted moderate enrichments of As, Sb, Cu, Cs and Cr in their estuarine sediments, with respect to the reference background of the Volta Estuary. Radionuclide concentrations were in the range found in the Earth's crust. Present data do not support any conclusion on their potential enrichments due to gold-mining activities. Radionuclide isotopic ratios revealed a transfer of ²²⁸Ra from sediments to the water column. Pearson correlation coefficient matrices showed different patterns, which were reasonably understood after novel approaches: i) inter-estuaries comparison of slopes in the linear regressions of element-concentrations vs Al, Fe and Cs; ii) study of Al-normalized concentrations of elements; iii) excess ²¹⁰Pb informing on local sedimentary conditions. The metal enrichments observed in the Ankobra and Pra estuaries are associated with the Fe-rich compounds in sulphide ores (such as FeAsS) transported along the river course and deposited in the estuary.

Experimental study on the use of granulometric speciation for the radiometric dating of recent sediments

Theoretical and experimental studies have shown that activity concentrations of fallout radionuclides (such as ¹³⁷Cs and excess ²¹⁰Pb) decrease with particles size in aqueous suspensions. This paper is aimed at reviewing the theoretical fundamentals for granulometric speciation of radionuclides, and at exploring its practical use in the analytical context of gamma spectrometry for the radiometric dating of recent sediments, with view to: i) improving the detection of ¹³⁷Cs (since its use as independent chronostratigraphic mark is challenging in the southern hemisphere because its low fallout rate), ii) supporting refined CIC models and normalization techniques in ²¹⁰Pb-based radiogeochronologies. The work uses surface sediments sampled from the Tinto Estuary (SW Spain), affected by mining and phosphate-fertilizer industries, and from the Ankobra Estuary (Ghana), affected by intensive artisanal gold-mining. Granulometric classes have been separated by a sieving column with decreasing mesh sizes and the obtained cumulative percentage of mass mathematically described by a Rosin-Rammler particle-size distribution. The target radionuclides for gamma spectrometry were ²¹⁰Pb, ²²⁶Ra and¹³⁷Cs, complemented with ⁴⁰K, ²³⁴Th and ²²⁸Ra. Results revealed that, far from ideal experiments, under actual environmental conditions the increase in activity concentrations with decreasing particle sizes is too moderate, and in general they are affected by larger counting uncertainties due to the small available amount of mass. Indeed, there was no correlation between grain-size and ¹³⁷Cs concentrations (p = 0.25), and similarly for excess ²¹⁰Pb (p = 0.53). No effect of the organic matter content was observed in ¹³⁷Cs (p = 0.58) and excess ²¹⁰Pb (p = 0.85) concentrations. Present results pose some concerns to the general use of granulometric speciation in the context of gamma spectrometry for supporting the radiometric dating of recent sediments. A detailed discussion on the use of normalization methods is also presented.

Correction to: Probabilistic risk assessment and risk mapping of metals in tropical estuarine sediments using the Aquarisk model

The original version of this article unfortunately contained a mistake in the article title.

Probabilistic risk assessment and risk mapping of metals in tropical estuarine sediments using the Aquarisk model

Total sediment concentrations of Cd, Cu, Pb, Zn, As, and Hg obtained from the Ankobra, Sakumo II, and Volta estuaries in Ghana were used to generate contaminant probability density distributions and species sensitivity distributions in AQUARISK. Results of the tier 1 assessment showed Cu, Cd, Zn, and Pb were not of concern in the Ankobra as their measured values and the 99th percentile of the fitted distributions were lower than the SQG low-trigger values. Mercury (Hg) and As were however, identified to be of concern in this estuary. In the Sakumo II estuary, Cu, Cd, Pb, and Hg have been identified to be of concern because their concentrations are higher than the SQG low-trigger values. Hg has been identified as the only metal of concern in the Volta estuary. The total proportion of species likely to be affected by the combined concentration of Cd, Cu, and Zn measured from Ankobra, Sakumo II, and Volta were 14%, 16%, and 12%, respectively, according to the Bur III distributional analysis of the ecotoxicology data. The measured median sediment concentrations of As and Hg in the Ankobra estuary greatly exceeded the median sediment concentration targets to achieve a 5% or less exceedence of the SQG low value. Similarly, in the Sakumo II estuary, the measured median sediment concentrations of Cu, Pb, and Hg greatly exceeded the median sediment concentration targets to achieve a 5% or less exceedence of the SQG low. For the Volta estuary however, other metals except Hg fall below the target values.

Settling fluxes and ecotoxicological risk assessment of fine sedimentary metals in Tema Harbour (Ghana)

Sediment traps were deployed in the Tema Harbour to estimate the settling fluxes of silt-clay particles and associated metals (Fe, Mn, Pb, Cr, Cu, Zn, Ni, Hg, Sn and As) and characterise their potential ecotoxicological risks. The mean daily settling fluxes of the silt-clay particles and associated metals ranged from 42.7 to 85.0gm^-2d^-1 and 1.3×10^-2 to 49.4mgm^-2d^-1, respectively, and were characterised by large fluctuations at each station. The silt-clay and metal fluxes strongly correlated, indicating the important role of the silt-clay particles in metal transport and distribution in the harbour. Geochemical indices indicated anthropogenic influences on the harbour as the Pb, Cr, Zn, Hg, Sn and As content in the settling silt-clay particles exceeded their average crustal concentrations. Sediment quality guidelines indicated these metals pose appreciable ecotoxicological risks, particularly As. Increasing temporal trends in As necessitates increased pollution control efforts at the harbour.

Settling fluxes and sediment accumulation rates by the combined use of sediment traps and sediment cores in Tema Harbour (Ghana)

Settling fluxes and sediment accumulation rates in coastal Tema Harbour (Ghana) were investigated by the combined analyses of results in sediment traps and sediment cores. Sediment traps were deployed at 5 stations within the Tema Harbour at two sampling depths and were retrieved every two weeks till the end of 12weeks to estimate the Settling Fluxes (SFs). Four sediment cores from the harbour were analysed for their radioactivity (⁷Be, ²³⁴Th, ²¹⁰Pb, ²¹²Pb, ²²⁶Ra, ⁴⁰K and ¹³⁷Cs) profiles to quantify Sediment Accumulation Rates (SARs). The sediment cores exhibited variable bulk density profiles, indicating highly dynamic and non-steady sedimentation conditions. ⁷Be-derived gross-estimates of very recent SARs using the constant flux-constant sedimentation (CF-CS) model were in the range of 2.5-9.0g·cm^-2·y^-1. These values were much lower than the estimated average SFs (15.2-53.8g·cm^-2·y^-1), indicating sediment resuspension plays an important role. On a decadal time scale, conventional ²¹⁰Pb sediment dating models did not allow any estimation of SARs in the Tema Harbour. Thus, the ²¹⁰Pb-based TERESA model was applied to depict a reliable scenario for sedimentation with time-averaged SARs in the range of 1.4-3.0g·cm^-2·y^-1 and fluxes of matter contributed by the marine inflow and local sources. Sediment accretion rates of 1.7-3cm·y^-1 were also inferred, which may pose a moderate problem of sustainability for the Tema Harbour. This study reveals how the geochemical behaviour of different radionuclides with Gamma spectrometry in the marine environment can be used to obtain reliable information on the complex dynamics of Suspended Particulate Matter (SPM), even in a very disturbed and anthropic environment as a coastal harbour area where (1) conventional ²¹⁰Pb-based dating methods fail and (2) the use of sediment traps and ²³⁴Th and ⁷Be profiles in sediment cores show serious constraints.

Radioecological assessment and radiometric dating of sediment cores from dynamic sedimentary systems of Pra and Volta estuaries (Ghana) along the Equatorial Atlantic

The Volta and Pra estuaries (Ghana, West Africa) are dynamical sedimentary systems whose natural equilibrium is being affected by anthropogenic activities. This paper reports depth-distributions of ²¹⁰Pb, ²²⁶Ra, ²³⁴Th, ⁴⁰K, ²²⁸Ra and ¹³⁷Cs for two sediment cores from these estuaries. Bulk densities were not steady-state and well correlated with ⁴⁰K (p < 0.00005). Unsupported ²¹⁰Pb profiles were incomplete, non-monotonic and showed large fluctuations. The assumptions involved in the common ²¹⁰Pb-based dating models were not meet in these dynamical scenarios, and the use of ¹³⁷Cs as a time-marker is difficult in Equatorial and South-Hemisphere countries due to its low fallout rates. Chronologies have been solved with the new ²¹⁰Pb-based TERESA model, which operates with varying but statistically correlated fluxes and sediment accumulation rates (SAR). The core from the Volta reflects the conditions prevailing after the construction of the Akosombo Dam, with a mean SAR of 1.05 ± 0.03 g cm^-2·y^-1, while a higher value of 2.73 ± 0.06 g cm^-2·y^-1 was found in the Pra, affected by intense gold mining activities along its course. Radiological and radioecological assessments have been conducted by applying the UNSCEAR protocols and the ERICA model, respectively. The measured radionuclide concentrations do not pose any significant risk for the environment and human health.

Integrated hazard, risk and impact assessment of tropical marine sediments from Tema Harbour (Ghana)

The potential ecological hazard, risk and impact of tropical marine sediments from the Tema Harbour (Greater Accra, Ghana) was investigated by integrating Corophium volutator and Hediste diversicolor whole-sediment toxicity bioassays with data on the metals (Cd, Pb, Cr, Ni, Cu, Zn and As) concentrations of the sediments. The whole-sediment toxicity bioassay results showed that sediments of the Tema Harbour are potentially hazardous to marine benthic invertebrates. C. volutator exhibited a higher vulnerability to the sediment toxicity than H. diversicolor, although the latter showed higher biota-sediment accumulation factors for the investigated metals. Statistically significant correlations were observed between C. volutator mortality and sediment Cd concentration (r = 0.84, p < 0.05; n = 6) and between H. diversicolor mortality and sediment Cu concentration (r = 0.94, p < 0.05; n = 5). Comparison of metal concentrations with international action levels for contaminated sediment disposal indicates that the Tema Harbour sediments contain potentially hazardous concentrations of Cu and Zn. This study shows that sediments from the Tema Harbour are not suitable for disposal at sea without remediation. There is, therefore, a need to improve environmental management and regulate the disposal of dredged material originating from the Tema Harbour.

Assessment of DDT, HCH and PAH contamination and associated ecotoxicological risks in surface sediments of coastal Tema Harbour (Ghana)

This study assessed DDTs, HCHs and PAHs contamination in sediments from the Tema Harbour (Ghana) and the associated ecotoxicological risks. The results showed widespread DDTs, HCHs and PAHs contamination in the harbour sediments with mean concentrations ranging from 6.0-12.8, 2.8-12.7 and 2750-5130μg·kg^-1d·w, respectively. The silt-clay and total organic carbon contents of the sediments poorly correlated with the pollutant concentrations. DDTs and HCHs contamination relate to past use of DDT and lindane, which under the anoxic harbour conditions resulted in disproportionately higher concentrations of p,p'-DDD and γ-HCH in the sediments. No conclusion could be drawn on the sources of PAHs as either petrogenic or pyrogenic. The pollutant concentrations in the harbour sediments, particularly γ-HCH, may pose high ecotoxicological risks. In comparison to a previous study, this study indicates there has been a considerable reduction in PAH contamination in the Tema Harbour since the last major oil spill in 2007.

Distribution and enrichment of trace metals in marine sediments from the Eastern Equatorial Atlantic, off the Coast of Ghana in the Gulf of Guinea

We present results of a preliminary geochemical assessment of Cd, Pb, V, As, Ni, Cu, Zn, Mg, Al, K, Ca, and Fe in marine sediments from the Eastern Equatorial Atlantic, off the Coast of Ghana. Samples were taken along 4 regions G1, G2, G3 and G4 at approximately 25m, 100m, and 250m, 500m and 1000m depths. Elemental compositions were assessed through the estimation of Al-normalized enrichment factors and geochemical accumulation indices, and the concentrations determined to produce any potential toxic effects to biota. Significant enrichment of the bottom sediments with Cd, Ni and As were observed at some locations with sediments showing signs of heavy pollution with As at region G4. Apart from Ni, V and As which were beyond threshold effects levels at most regions, all other metals were below probable effect levels. Both natural and anthropogenic processes controlled trace metal accumulation and distribution in the Ghanaian coastal environment.

Polycyclic aromatic compounds (PAHs and oxygenated PAHs) and trace metals in fish species from Ghana (West Africa): bioaccumulation and health risk assessment

We report the concentrations of 28 PAHs, 15 oxygenated PAHs (OPAHs) and 11 trace metals/metalloids (As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Se, and Zn) in muscle and gut+gill tissues of demersal fishes (Drapane africana, Cynoglossus senegalensis and Pomadasys peroteti) from three locations along the coast of the Gulf of Guinea (Ghana). The concentrations of ∑28PAHs in muscle tissues averaged 192ngg(-1) dw (range: 71-481ngg(-1) dw) and were not statistically different between locations. The concentrations of ∑28 PAHs were higher in guts+gills than in muscles. The PAH composition pattern was dominated by low molecular weight compounds (naphthalene, alkyl-naphthalenes and phenanthrene). All fish tissues had benzo[a]pyrene concentrations lower than the EU limit for food safety. Excess cancer risk from consumption of some fish was higher than the guideline value of 1×10(-6). The concentrations of ∑15 OPAHs in fish muscles averaged 422ngg(-1) dw (range: 28-1715ngg(-1)dw). The ∑15 OPAHs/∑16 US-EPA PAHs concentration ratio was >1 in 68% of the fish muscles and 100% of guts+gills. The log-transformed concentrations of PAHs and OPAHs in muscles, guts+gills were significantly (p<0.05) correlated with their octanol-water partitioning coefficients, strongly suggesting that equilibrium partitioning from water/sediment into fish tissue was the main mechanism of bioaccumulation. The trace metal concentrations in the fish tissues were in the medium range when compared to fish from other parts of the world. The concentrations of some trace metals (Cd, Cu, Fe, Mn, Zn) were higher in guts+gills than in muscle tissues. The target hazard quotients for metals were<1 and did not indicate a danger to the local population. We conclude that the health risk arising from the consumption of the studied fish (due to their PAHs and trace metals content) is minimal.

Studies on organochlorine pesticide residue in fishes from the Densu river basin, Ghana

The study was carried out to determine the levels of organochlorine pesticide residue in five fish species Chrysichthys nigrodigitatus, Hepsetus odoe, Tilapia zilli, Heterotis niloticus and Oreochromis niloticus from the Densu river basin (Weija) in Ghana. The fishes sampled from the Weija fish landing site were selected on the basis of their importance to local human fish consumption. The detectable organochlorine pesticides were γ-Hexachlorocyclohexane (HCH), δ-Hexachlorocyclohexane, aldrin and dieldrin. Others investigated were alpha endosulfan, endosulfan sulfate, p,p'-DDT and its metabolite p,p'-DDE, endrin and its metabolite endrin aldehyde and endrin ketone. The total contamination levels of the individual fishes varied in the decreasing order of 9.19 ng g(-1) (O. niloticus), 4.16 ng g(-1) (T. zilli), 3.69 ng g(-1) (C. nigrodigitatus), 3.68 ng g(-1) (H. odoe) and 3.09 ng g(-1) (H. niloticus). The highest organochlorine pesticide residue recorded in the study was alpha-endosulfan while dieldrin was the least pesticide observed. Analysis of variance indicated significant statistical differences for most organochlorine pesticide residues in the samples. The levels of organochlorine pesticides found in fish samples in the study were below maximum residue limit for food safety stipulated by EU, US FDA, FAO, Italy and Australia and thus safe for human consumption.

Occupational exposure to pesticides: blood cholinesterase activity in a farming community in Ghana

A survey was undertaken to establish the extent of pesticide exposure in a farming community. Cholinesterase (ChE) activity in whole blood was used as a marker for assessing exposure to pesticides. Complete data were gathered for 63 farmers at Akumadan (exposed) and 58 control subjects at Tono, both prominent vegetable-farming communities in Ghana, by means of a questionnaire and blood cholinesterase analyses (acetylcholine assay). Although whole-blood ChE was significantly lower in the exposed than the control participants, it was not significantly correlated with either confounders of age, sex, body weight, and height or high-risks practices. The high-risks practices revealed during the survey included lack of use of personal protective clothing, short reentry intervals, and wrong direction of spraying of pesticides by hand or knapsack sprayer. About 97% of exposed participants had experienced symptoms attributable to pesticide exposure. The frequent symptoms were reported as weakness and headache. There is the need to review safety precautions in the use and application of pesticides in Ghana.

Accumulation of persistent organochlorine contaminants in milk and serum of farmers from Ghana

In the present study, the concentrations of persistent organochlorine (OC) pesticides such as dichlorodiphenyltrichloroethane and its metabolites (DDTs), hexachlorocyclohexane isomers (HCHs), hexachlorobenzene (HCB) and dieldrin in pooled samples of human breast milk (n=109), and serum (n=115) from vegetable farmers in Ghana, during 2005, were determined. Gas chromatography with mass spectrometry was used to quantify residue levels on a lipid basis of the OCs. The pattern of OCs in human fluid showed that DDTs was consistently the prevalent OC in milk and blood. The levels of DDTs, HCHs, and dieldrin in the breast milk samples were found to correlate positively with age of the milk sample donors (r(s)=0.606, 0.770, and 0.540, respectively). When blood serum levels of the OCs were compared between male and female farmers, no pronounced relationship for HCHs and HCB (p>0.05) was observed. However, DDTs and dieldrin residues were significantly higher (p<0.05) in males than in females. There was association between breast milk and serum residues. When daily intakes of DDTs and HCHs to infants through human breast milk were estimated, some individual farmers (in the case of DDTs) and all farmers (in the case of HCHs) accumulated OCs in breast milk above the threshold (tolerable daily intake, TDI, guidelines proposed by Health Canada) for adverse effects, which may raise concern on children health.

Anaplasma phagocytophilum-Borrelia burgdorferi coinfection enhances chemokine, cytokine, and matrix metalloprotease expression by human brain microvascular endothelial cells

Borrelia burgdorferi and Anaplasma phagocytophilum coinfect and are transmitted by Ixodes species ticks. Clinical indicators suggest that A. phagocytophilum coinfection contributes to the severity, dissemination, and, possibly, sequelae of Lyme disease. Previous in vitro studies showed that spirochete penetration through human brain microvascular endothelial cells of the blood-brain barrier is facilitated by endothelial cell-derived matrix metalloproteases (MMPs). A. phagocytophilum-infected neutrophils continuously release MMPs and other vasoactive biomediators. We examined B. burgdorferi infection of brain microvascular barriers during A. phagocytophilum coinfection and showed that coinfection enhanced reductions in transendothelial electrical resistance and enhanced or synergistically increased production of MMPs (MMP-1, -3, -7, -8, and -9), cytokines (interleukin 6 [IL-6], IL-10, and tumor necrosis factor alpha), and chemokines (IL-8 and macrophage inflammatory protein 1alpha) known to affect vascular permeability and inflammatory responses.

Anaplasma phagocytophilum-infected neutrophils enhance transmigration of Borrelia burgdorferi across the human blood brain barrier in vitro

The manifestations of Lyme disease, caused by Ixodes spp. tick-transmitted Borrelia burgdorferi, range from skin infection to bloodstream invasion into the heart, joints and nervous system. The febrile infection human granulocytic anaplasmosis is caused by a neutrophilic rickettsia called Anaplasma phagocytophilum, also transmitted by Ixodes ticks. Previous studies suggest that co-infection with A. phagocytophilum contributes to increased spirochetal loads and severity of Lyme disease. However, a common link between these tick-transmitted pathogens is dissemination into blood or tissues through blood vessels. Preliminary studies show that B. burgdorferi binds and passes through endothelial barriers in part mediated by host matrix metalloproteases. Since neutrophils infected by A. phagocytophilum are activated to release bioactive metalloproteases and chemokines, we examined the enhanced B. burgdorferi transmigration through vascular barriers with co-infection in vitro. To test whether endothelial transmigration is enhanced with co-infection, B. burgdorferi and A. phagocytophilum-infected neutrophils were co-incubated with EA.hy926 cells (HUVEC-derived) and human brain microvascular endothelial cells in Transwell cultures. Transmigration of B. burgdorferi through endothelial cell barriers was determined and endothelial barrier integrity was measured by transendothelial electrical resistivity. More B. burgdorferi crossed both human BMEC and EA.hy926 cells in the presence of A. phagocytophilum-infected neutrophils than with uninfected neutrophils without affecting endothelial cell integrity. Such a mechanism may contribute to increased blood and tissue spirochete loads.

African trypanosome interactions with an in vitro model of the human blood-brain barrier

The neurological manifestations of sleeping sickness in man are attributed to the penetration of the blood-brain barrier (BBB) and invasion of the central nervous system by Trypanosoma brucei gambiense and Trypanosoma brucei rhodesiense. However, how African trypanosomes cross the BBB remains an unresolved issue. We have examined the traversal of African trypanosomes across the human BBB using an in vitro BBB model system constructed of human brain microvascular endothelial cells (BMECs) grown on Costar Transwell inserts. Human-infective T. b. gambiense strain IL 1852 was found to cross human BMECs far more readily than the animal-infective Trypanosoma brucei brucei strains 427 and TREU 927. Tsetse fly-infective procyclic trypomastigotes did not cross the human BMECs either alone or when coincubated with bloodstreamform T. b. gambiense. After overnight incubation, the integrity of the human BMEC monolayer measured by transendothelial electrical resistance was maintained on the inserts relative to the controls when the endothelial cells were incubated with T. b. brucei. However, decreases in electrical resistance were observed when the BMEC-coated inserts were incubated with T. b. gambiense. Light and electron microscopy studies revealed that T. b. gambiense initially bind at or near intercellular junctions before crossing the BBB paracellularly. This is the first demonstration of paracellular traversal of African trypanosomes across the BBB. Further studies are required to determine the mechanism of BBB traversal by these parasites at the cellular and molecular level.

In vitro toxicity of palladium(II) and gold(III) porphyrins and their aqueous metal ion counterparts on Trypanosoma brucei brucei growth

The trypanocidal effects of aqueous gold(III) and palladium(II) and their metalloporphyrin derivatives on Trypanosoma brucei brucei growth in culture have been studied using an Alamar Blue indicator assay. All the experiments were conducted in the dark. As previously described for mercury(II), cadmium(II) and lead(II) porphyrins [Chem.-Biol. Interact. 139 (2002) 177], the toxicity of the metalloporphyrin complex of palladium(II) to T. b. brucei parasites was much higher compared to the aqueous free palladium(II) and free base porphyrin. Palladium(II) porphyrin, free palladium(II), and the free base porphyrin were trypanocidal to T. b. brucei at concentrations >1.5 x 10(-6), >6.1 x 10(-6) and >1.9 x 10(-5) M, respectively. While gold(III) porphyrin was effective against the parasites at concentrations >4.8 x 10(-6) M, its aqueous gold(III) was toxic at concentrations as low as 2.0 x 10(-7) M due to the generation of free radicals in the presence of this metal ion which enhanced its toxicity to the T. b. brucei parasites. Although some cell division was observed in some of the cells treated with palladium(II) porphyrin, some dividing cells had no nucleus due to unequal division and delivery of the nuclei into the daughter cells. As a result, the rate of cell division decreased with time and cell death occurred within 24 h. Interestingly, trypanosomes treated with metalloporphyrin complexes displayed different morphological features from those cells treated with free base porphyrin or metal ions. Of all the porphyrins and free metal ions tested, only mercury(II) porphyrin and aqueous gold(III) ion were toxic to the trypanosomes in the 10(-7) M range. The chemotherapeutic potential of these observations is discussed.

Enhanced conformational changes in DNA in the presence of mercury(II), cadmium(II) and lead(II) porphyrins

The interactions of the metalloporphyrins of tetrakis (1-methylpyridinium-4yl)porphyrin ([M(TMPyP)](4+)) where M=Hg(II), Cd(II) and Pb(II)) with pBluescript II plasmid DNA have been studied by the measurement of circular dichroism (CD), UV-visible and fluorescence spectra at 0.1 M NaNO(3), pH 7.5 and 25 degrees C. The CD spectra of the DNA changed quite significantly, with the conformational changes in the presence of the metalloporphyrins being much more enhanced compared to that of their free metal ion counterparts. The conformational changes in DNA upon binding to the Hg(II) porphyrin and Hg(II) were, however, different from those of the Cd(II) porphyrin, Pb(II) porphyrin, Pb(II), Cd(II) and H(2)(TMPyP)(4+). In the concentration range of 0-2.30 x 10(-5) M of DNA, the absorption spectra of H(2)(TMPyP)(4+) showed substantial hypochromicity at 423 nm and a red shift of Deltalambda=16 nm in the presence of DNA whereas the Hg(II)-, Pb(II)- and Cd(II) porphyrins showed blue shifts of absorption maximum wavelengths of Deltalambda=-17 nm, Deltalambda=-35 nm and Deltalambda=-4.5 nm, respectively. Furthermore, the shifted absorption maximum wavelengths/nm of the porphyrins in excess amount of DNA were comparable; 438, 439, 440 and 440 for H(2)(TMPyP)(4+), Hg(II)-, Pb(II)- and Cd(II) porphyrins, respectively. The changes in absorption spectra for Hg(II)-, Pb(II)- and Cd(II) porphyrins revealed that these metalloporphyrins dissociated upon binding to DNA which was confirmed by CD as well as fluorescence spectra. The CD results, UV-Vis and fluorescence data indicate that the metalloporphyrins interact differently with DNA based on their binding modes. And the enhanced changes in conformation of DNA in the presence of the metalloporphyrins are due to the synergistic effects of the simultaneous binding of the metal ions and the free base porphyrin to DNA compared to their free metal ion counterparts: [M(TMPyP)](4+)+DNA+2H(+) right harpoon over left harpoon [M(II)(DNA)H(2)(TMPyP)(4+)]. The detailed equilibrium reactions have been described along with suggestions of possible applications in the medical and biological fields.

Toxic effects of mercury(II), cadmium(II) and lead(II) porphyrins on Trypanosoma brucei brucei growth

The effects of free mercury(II), cadmium(II) and lead(II) ions and their metalloporphyrin-derivatives on Trypanosoma brucei brucei growth in culture were studied. All experiments were conducted in the dark. IC(50) values on growth obtained in 24-h time-course experiments were 1.5 x 10(-7), 2.4 x 10(-6), 4.4 x 10(-6) and 2.6 x 10(-5) M for mercury(II) porphyrin, cadmium(II) porphyrin, lead(II) porphyrin and free base porphyrin, respectively. While the IC50 values for Hg2+, Cd2+ and Pb2+ were 3.6 x 10(-6), 1.5 x 10(-5) and 1.6 x 10(-5) M, respectively. These results clearly indicate that the toxicity of the metalloporphyrin complexes of mercury(II), cadmium(II) and lead(II) to T. b. brucei parasites was much higher compared to their free metal ions and free base porphyrin at low concentrations. It was also observed after 8 h incubation that the metalloporphyrins were effective in inhibiting the division of the parasites at concentrations >1.25 x 10(-7) M for mercury(II) porphyrin, concentrations >1.2 x 10(-6) M for cadmium(II) and lead(II) porphyrins and at concentrations >3.6 x 10(-6) M for Hg2+ ion. These observations were not detected in samples treated with the free metal ions and the free base porphyrin at the same concentrations. Interestingly, trypanosomes treated with metalloporphyrin complexes displayed different morphological features from those cells treated with free base porphyrin or metal ions. The chemotherapeutic potential of the metalloporphyrins of H2TMPyP for treatment of African trypanosomiasis is discussed.

Metalloporphyrin mediated DNA cleavage by a low concentration of HaeIII restriction enzyme

The plasmid DNA scission by the restriction enzyme HaeIII was investigated in the presence of tetrakis(1-methylpyridinium-4-yl)porphyrin (H2TMPyP) and its manganese(III), iron(III), nickel(II), cobalt(III) and zinc(II) derivatives. The effect of metalloporphyrins on plasmid DNA cleavage was ascertained by gel electrophoresis. UV-Vis absorption spectroscopy and circular dichroism (CD) spectroscopy. In the absence of the metalloporphyrins, plasmid DNA scission did not occur in the presence of a low concentration of HaeIII (0.2 units microL(-1)) at 37 degrees C after 1 h incubation. However, DNA cleavage occurred in the presence of the metalloporphyrins and HaeIII (0.2 units microL(-1)) at 37 degrees C after 1 h incubation. Gel electrophoresis results indicate the catalytic effect of metalloporphyrins (Mn(III)-, Fe(III)-, Co(III)- and Zn(II)TMPyP) by binding to both DNA and the enzyme through electrostatic interaction, which was confirmed by the change in UV-Vis and CD spectra. A mechanism for the enhanced DNA cleavage is proposed.

Evaluation of a commercial immunodiagnostic kit incorporating lipoarabinomannan in the serodiagnosis of pulmonary tuberculosis in Ghana

We evaluated 'Mycodot', a commercially marketed immunodiagnostic test for tuberculosis which detects antibodies to lipoarabinomannan antigen. Serum was tested from 52 patients with newly diagnosed smear-positive pulmonary tuberculosis, of whom 20 were HIV-positive and 32 HIV-negative. Control sera were taken from 40 patients of whom 20 had acute non-tuberculous lobar pneumonia and 20 patients had no respiratory disease. The test was found to have a very high specificity of 97.5% (95% CI:92.5-100%). However, the sensitivity in HIV-negative patients was 56% (95% CI:39-73%), and was substantially lower at 25% (95% CI:6-44%) in HIV-positive patients.

IN CONCLUSION

'Mycodot' was found to be a highly specific and easily performed assay. However, the poor sensitivity, especially in HIV-infected patients, renders it unlikely to be useful either as a primary or adjunctive diagnostic test for tuberculosis, particularly in countries with a high prevalence of HIV. A larger trial of this assay in Ghana was not deemed necessary.

Current trends in the incidence of cerebrovascular accidents in Accra

The incidence of cerebrovascular accidents (CVA) in Accra during three periods--1960-1968, 1976-1983, and 1990-1993, was compared. There was dramatic increase in the incidence between 1990-1993. Uncontrolled hypertension due to non-compliance with drug therapy seems to be the main cause. The economic plight of the people may explain the non compliance. The case fatality was between 41.9% to 50.3% for the years 1990-1993. Cardiovascular diseases, notably hypertension and CVA, have become the major causes of morbidity and mortality in Accra.