Aquatic toxicity of one dimensional carbon nanomaterials

The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file.Title from PDF of title page (University of Missouri--Columbia, viewed on October 28, 2010).Thesis advisor: Dr. Baolin Deng.Vita.Ph. D. University of Missouri--Columbia 2010.This study determined the toxicity of one dimensional carbon nanomaterials (CNMs) to amphipods, midge, oligochaetes and juvenile mussels in water and sediment. As-produced or modified carbon nanotubes (CNTs) and silicon carbide nanowires (SiCNW) were selected to represent CNMs. Sediment tests were conducted for 10-d with SiCNW and for 14- and 28-d with CNTs using amphipods. Sonicated SiCNW in water were toxic to the amphipods but not to the midge, oligochaetes or mussels and non-sonicated SiCNW in water were not toxic to amphipods. Sonicated or non-sonicated CNT in water were toxic to all four benthic invertebrates. CNTs spiked into sediments were mildly toxic to amphipods reduced in toxicity. During exposures, the test organisms were coated with the CNMs and the organisms also ingested and accumulated these CNMs in their guts. Overall, the toxicity of the CNMs (CNTs or SiCNW) appears to be the effect of the coating of respiratory surfaces or the blocking of the digestive tract of the exposed benthic invertebrates. The metals dissolution from the as-produced CNTs could also have contributed to the toxicity.Includes bibliographical reference

Community perceptions affecting uptake & retention on antiretroviral therapy by PLHIV: a qualitative study among residents of an urban informal settlement in Kenya

Introduction: Lack of HIV treatment and loss of follow up measures is associated with high mortality among persons living with HIV (PLHIV) in sub-Saharan Africa. Especially in resource-limited populations. Respondents diagnosed with HIV through a home-based testing and counseling program in an informal settlement in Kenya, were referred to health facilities of their choice for antiretroviral therapy (ART). This qualitative study explored the community’s experiences and perceptions on factors associated with ART uptake and retention.Methodology: Using convenient purposive sampling, we recruited 46 adults (21 women and 25 men) among them HIV infected and non-infected residents of the Kibera informal settlement in Nairobi, Kenya. Using a standardized discussion guide, six focus group discussions of 6-9 individuals were conducted. Discussions were recorded verbatim and complimented by tape recording to ensure accuracy. Transcription was done and coding done using a Priori codes. Thematic content analysis was done using Atlas 3.0.Results: Availability of many health facilities offering HIV services in Kibera informal settlement facilitated access to and uptake of ART. Respondents preparation procedures that prevented same-day ART enrolment were often perceived as denial of treatment.“They talk too much of treatment and when you go you are turned away” Said one respondent. Reported perceived poor staff attitude, Rudeness, Judgmental behaviours and Delays, were often perceived as lack of respect for Participants were reported to hinder retention in ART services.“He will look at your physical appearance, put your card aside and ask his colleague whether tea is ready” Participants disliked adherence counseling with written commitments after missed appointments and often felt that these measures too reflected lack of respect by health care providers. They wanted to cancel treatment because they said we had to commit ourselves by signing….”Conclusion: Individuals diagnosed with HIV generally accessed HIV treatment facilities following referral after HBTC. Participants perceived some standard treatment procedures. Reckoning Staff behavior and Communication as barriers hindering retention on ART. Supportive interpersonal relationship strategies between Respondents, providers and innovative patientcentered treatment plans and adherence counseling models should be adopted in treatment programs. This will promote uptake and retention of ART in communities.Keywords: HIV infection, retention in ART, adherence counseling, psychosocial and communication barriers, Responded satisfactio

Glucose-6-phosphate dehydrogenase deficiency allelic variants and their prevalence in malaria patients in Eritrea

Introduction: glucose 6-phosphate dehydrogenase (G6PD) deficiency is the most common enzymopathy with a relatively high frequency in malaria-endemic regions. In Eritrea, there is scanty knowledge of G6PD deficiency. The aim of the study was to characterize and determine the prevalence of four common G6PD allelic variants. Methods: three hundred and fourteen dried blood spot samples from unrelated microscopically diagnosed malaria patient Eritrean ethnic groups living in five zobas (regions) of Eritrea were analysed by PCR-RFLP method to identify the G6PD B, G6PD A (A376G), G6PD A-(G202A), and G6PD Mediterranean (C563T) variants. To confirm the RFLP results, samples positive for A376G but negative for G202A variants were subjected to Sanger sequencing and a subset of PCR products (exon 5) directly sequenced to identify A376G and other mutations. Results: for G6PD genotyping, G6PD B was detected in 87.5% and A376G detected in 12.5% of malaria patients, whereas G202A and C563T were absent. Bivariate statistical analysis showed a statistically significant association between G6PD genotypes and zoba (P < 0.004 < 0.05). Sequencing revealed the expected A376G variant. In exon 5, four common (A376G) mutations, three uncommon mutations rs782669677 (535G→A) and one potentially new mutation (451G→C), relative to the reference, mRNA NM_001042351 were detected. Bioinformatic analysis of these mutations' potential functional impact suggests minimal effect on protein function. Conclusion: this is the first report indicating that G6PD B and G6PD A genotypes are prevalent in Eritrea. Similar findings were reported in neighboring countries. Further studies including phenotype analysis are needed to corroborate the observed results

Synergistic Antiplasmodial Activity of Artemisia annua fractions against in vitro cultures of Plasmodium falciparum

Background: Artemisia annua has a very rich phytochemistry comprising several classes of compounds, mainly monoterpenes, sesquiterpenes, and flavonoids.  It has been used in China for about 2000 years in the treatment of fever. Objective: The aim was to determine if there is any synergistic effect on the Artemisia annua phytochemicals. Materials and methods: Artemisia annua used in this study was obtained from a hybrid of the plant grown in the Tanzania highlands (2000-2200 m altitude) in Arusha by Natural Uwemba System for Health (N.U.S.Ag). The dried leaves were ground, and sequentially extracted with hexane, dichloromethane (DCM), methanol and water and the extracts were then combined. The extract was then fractionated using high performance liquid chromatography (HPLC). The effect of the combined crude extract was tested at different doses on in-vitro cultures (a CQ sensitive isolate D6 and CQ resistant isolate W2) of Plasmodium falciparum. The fractions and different blends of these were tested at different doses to determine their role, if any, on the activity of the full blend of the plant. Results: Of nine fractions thus tested against D6 and W2, four had activities of less than 3.9µg /ml, three fractions had activities of between 4.77-14.76 µg/ml and the remaining two had activities above 250g/µml. The seven more active fractions were re-evaluated in a subtractive bioassay procedure, in which one of each fraction was excluded at a time from the full 7-component blend. The activity of the combined seven active compounds was 10.40+0.50 µg/ml against W2.  Of these, one showed IC50 of less than 3.9 µg/ml and all blends showed IC50 at below 27µg/ml. Conclusion: The results show that different components of A. annua contribute to the synergistic anti-Plasmodium activity. The results constitute a useful basis for identifying the components of the plant other than artemisinin that contribute to the activity of herb. Key words- Artemisia annua, malaria, Plasmodium falciparum, artemisinin, synergy

Comparison of PCR with the Routine Procedure for Diagnosis of Tuberculosis in a Population with High Prevalences of Tuberculosis and Human Immunodeficiency Virus

Direct smear examination with Ziehl-Neelsen (ZN) staining for the diagnosis of tuberculosis (TB) as employed in most low-income countries is cheap and easy to use, but its low sensitivity is a major drawback. The low specificity of chest X-rays, used for the diagnosis of smear-negative TB, risks high levels of overdiagnosis. Major advances in molecular techniques, which rapidly identify mycobacterial DNA in sputa, may overcome these obstacles. In this study, the AMPLICOR PCR system was used to diagnose pulmonary TB in a developing country with high prevalences of both TB and human immunodeficiency virus (HIV). The sensitivity and specificity of this technique were compared to those of the usual diagnostic techniques. Sputum specimens were collected from 1,396 TB suspects attending the Rhodes Chest Clinic, Nairobi, Kenya. The specimens were analyzed for the presence of Mycobacterium tuberculosis by PCR; culture on Löwenstein-Jensen medium was used as the “gold standard.” All culture-positive samples were genotyped to identify the mycobacterial species. The sensitivity and specificity of PCR were 93 and 84%, respectively. HIV status did not affect the sensitivity of PCR. A total of 99.7% of the true smear-positive and 82.1% of the true smear-negative TB patients were correctly identified by PCR. PCR detected M. tuberculosis in 11.7% of the culture-negative suspects, 60% of which had one or two PCR-positive sputum specimens. Of the 490 positive cultures, 486 were identified as M. tuberculosis. The high sensitivity of Amplicor PCR merits usage in a clinical setting with high TB and HIV burdens. Thus, PCR can be considered as an alternative to ZN staining in combination with chest X-ray for diagnosis of TB; however, cost-effectiveness studies and operational studies are required to support an evidence-based decision of introducing PCR for TB control in high-burden environments

Antimycoplasmal Activities of Compounds from Solanum aculeastrum and Piliostigma thonningii against Strains from the Mycoplasma mycoides Cluster

Infections caused by Mycoplasma species belonging to the ‘mycoides cluster’ negatively affect the agricultural sector through losses in livestock productivity. These Mycoplasma strains are resistant to many conventional antibiotics due to the total lack of cell wall. Therefore, there is an urgent need to develop new antimicrobial agents from alternative sources such as medicinal plants to curb the resistance threat. Recent studies on extracts from Solanum aculeastrum and Piliostigma thonningii revealed interesting antimycoplasmal activities hence the motivation to investigate the antimycoplasmal activities of constituent compounds. The CH2Cl2/MeOH extracts from the berries of S. aculeastrum yielded a new β-sitosterol derivative (1) along with six known ones including; lupeol (2), two long-chain fatty alcohols namely undecyl alcohol (3) and lauryl alcohol (4); two long-chain fatty acids namely; myristic acid (5) and nervonic acid (6) as well as a glycosidic steroidal alkaloid; (25R)-3β-O-α-L-rhamnopyranosyl-(1→2)-O-[α-L-rhamnopyranosyl-(1→4)]-β-D-glucopyranosyloxy-22α-N-spirosol-5-ene (7) from the MeOH extracts. A new furan diglycoside, (2,5-D-diglucopyranosyloxy-furan) (8) was also characterized from the CH2Cl2/MeOH extract of stem bark of P. thonningii. The structures of the compounds were determined on the basis of spectroscopic evidence and comparison with literature data. Compounds 1, 3, 4, 7, and 8 isolated in sufficient yields were tested against the growth of two Mycoplasma mycoides subsp. mycoides (Mmm), two M. mycoides. capri (Mmc), and one M. capricolum capricolum (Mcc) using broth dilution methods, while the minimum inhibitory concentration (MIC) was determined by serial dilution. The inhibition of Mycoplasma in vitro growth was determined by the use of both flow cytometry (FCM) and color change units (CCU) methods. Compounds 4 and 7 showed moderate activity against the growth of Mmm and Mmc but were inactive against the growth of Mcc. The lowest MIC value was 50 μg/ml for compound 7 against Mmm. The rest of the compounds showed minimal or no activity against the strains of Mycoplasma mycoides tested. This is the first report on the use of combined FCM and CCU to determine inhibition of in vitro growth of Mycoplasma mycoides. The activity of these compounds against other bacterial strains should be tested and their safety profiles determined

Electrochemical Reduction of CO2 Catalyzed by Re(pyridine-oxazoline)(CO)3Cl Complexes

A series of rhenium tricarbonyl complexes coordinated by asymmetric diimine ligands containing a pyridine moiety bound to an oxazoline ring were synthesized, structurally and electrochemically characterized, and screened for CO2 reduction ability. The reported complexes are of the type Re(N-N)(CO)3Cl, with N-N = 2-(pyridin-2-yl)-4,5-dihydrooxazole (1), 5-methyl-2-(pyridin-2-yl)-4,5-dihydrooxazole (2), and 5-phenyl-2-(pyridin-2-yl)-4,5-dihydrooxazole (3). The electrocatalytic reduction of CO2 by these complexes was observed in a variety of solvents and proceeds more quickly in acetonitrile than in dimethylformamide (DMF) and dimethyl sulfoxide (DMSO). The analysis of the catalytic cycle for electrochemical CO2 reduction by 1 in acetonitrile using density functional theory (DFT) supports the C–O bond cleavage step being the rate-determining step (RDS) (ΔG⧧ = 27.2 kcal mol–1). The dependency of the turnover frequencies (TOFs) on the donor number (DN) of the solvent also supports that C–O bond cleavage is the rate-determining step. Moreover, the calculations using explicit solvent molecules indicate that the solvent dependence likely arises from a protonation-first mechanism. Unlike other complexes derived from fac-Re(bpy)(CO)3Cl (I; bpy = 2,2′-bipyridine), in which one of the pyridyl moieties in the bpy ligand is replaced by another imine, no catalytic enhancement occurs during the first reduction potential. Remarkably, catalysts 1 and 2 display relative turnover frequencies, (icat/ip)2, up to 7 times larger than that of I