Azaterphenyl diamidines as antileishmanial agents

Eighteen diamidino azaterphenyls and analogues were evaluated as anti-leishmanials; nine of the compounds gave IC50 values less than 1 microM, five exhibited values less than 0.40 microM, and two gave values less than 0.10 microM in a Leishmania donovani axenic amastigote assay. The activity of the diamidines strongly depends on the ring N-atom location relative to the amidine groups and correlates with DNA affinity. Transmission electron microscopy studies showed a dramatic dilation of the mitochondrion and evidence of disintegration of the kinetoplast of the amastigotes.     

Exercise restores coronary vascular function independent of myogenic tone or hyperglycemic status in db/db mice

Regulation of coronary function in diabetic hearts is an important component in preventing ischemic cardiac events but remains poorly studied. Exercise is recommended in the management of diabetes, but its effects on diabetic coronary function are relatively unknown. We investigated coronary artery myogenic tone and endothelial function, essential elements in maintaining vascular fluid dynamics in the myocardium. We hypothesized that exercise reduces pressure-induced myogenic constriction of coronary arteries while improving endothelial function in db/db mice, a model of type 2 diabetes. We used pressurized mouse coronary arteries isolated from hearts of control and db/db mice that were sedentary or exercised for 1 h/day on a motorized exercise-wheel system (set at 5.2 m/day, 5 days/wk). Exercise caused a approximately 10% weight loss in db/db mice and decreased whole body oxidative stress, as measured by plasma 8-isoprostane levels, but failed to improve hyperglycemia or plasma insulin levels. Exercise did not alter myogenic regulation of arterial diameter stimulated by increased transmural pressure, nor did it alter smooth muscle responses to U-46619 (a thromboxane agonist) or sodium nitroprusside (an endothelium-independent dilator). Moderate levels of exercise restored ACh-simulated, endothelium-dependent coronary artery vasodilation in db/db mice and increased expression of Mn SOD and decreased nitrotyrosine levels in hearts of db/db mice. We conclude that the vascular benefits of moderate levels of exercise were independent of changes in myogenic tone or hyperglycemic status and primarily involved increased nitric oxide bioavailability in the coronary microcirculation.     

Phenylacetate Metabolism in Thermophiles: Characterization of Phenylacetate-CoA Ligase,the Initial Enzyme of the Hybrid Pathway in <Emphasis Type="Italic">Thermus thermophilus</Emphasis>

Phenylacetate-CoA ligase (E.C. 6.2.1.30), the initial enzyme in the metabolism of phenylacetate, was studied in Thermus thermophilus strain HB27. Enzymatic activity was upregulated during growth on phenylacetate or phenylalanine. The phenylacetate-CoA ligase gene (paaK) was cloned and heterologously expressed in Escherichia coli and the recombinant protein was purified. The enzyme catalyzed phenylacetate + CoA + MgATP --> phenylacetyl-CoA + AMP + MgPP(i) with a V(max) of 24 micromol/min/mg protein at a temperature optimum of 75 degrees C. The apparent K(m) values for ATP, CoA, and phenylacetate were 6, 30, and 50 microM: , respectively. The protein was highly specific toward phenylacetate and showed only low activity with 4-hydroxyphenylacetate. Despite an amino acid sequence identity of >50% with its mesophilic homologues, phenylacetate-CoA ligase was heat stable. The genome contained further homologues of genes, which are postulated to be involved in the CoA ester-dependent metabolic pathway of phenylacetate (hybrid pathway). Enzymes of this thermophile are expected to be robust and might be useful for further studies of this yet unresolved pathway.     

Biohydrogen production in a continuous stirred tank bioreactor from synthesis gas by anaerobic photosynthetic bacterium: Rhodopirillum rubrum

Hydrogen may be considered a potential fuel for the future since it is carbon-free and oxidized to water as a combustion product. Bioconversion of synthesis gas (syngas) to hydrogen was demonstrated in continuous stirred tank bioreactor (CSTBR) utilizing acetate as a carbon source. An anaerobic photosynthetic bacterium, Rhodospirillum rubrum catalyzed water-gas shift reaction which was applied for the bioconversion of syngas to hydrogen. The continuous fermentation of syngas in the bioreactor was continuously operated at various gas flow rates and agitation speeds, for the period of two months. The gas flow rates were varied from 5 to 14 ml/min. The agitation speeds were increasingly altered in the range of 150-500 rpm. The pH and temperature of the bioreactor was set at 6.5 and 30 degrees C. The liquid flow rate was kept constant at 0.65 ml/min for the duration of 60 days. The inlet acetate concentration was fed at 4 g/l into the bioreactor. The hydrogen production rate and yield were 16+/-1.1 mmol g(-1)cell h(-1) and 87+/-2.4% at fixed agitation speed of 500 rpm and syngas flow rate of 14 ml/min, respectively. The mass transfer coefficient (KLa) at this condition was approximately 72.8h(-1). This new approach, using a biocatalyst was considered as an alternative method of conventional Fischer-Tropsch synthetic reactions, which were able to convert syngas into hydrogen.     

Properties of Bacillus anthracis spores prepared under various environmental conditions

Bacillus anthracis makes highly stable, heat-resistant spores which remain viable for decades. Effect of various stress conditions on sporulation in B. anthracis was studied in nutrient-deprived and sporulation medium adjusted to various pH and temperatures. The results revealed that sporulation efficiency was dependent on conditions prevailing during sporulation. Sporulation occurred earlier in culture sporulating at alkaline pH or in PBS than control. Spores formed in PBS were highly sensitive towards spore denaturants whereas, those formed at 45°C were highly resistant. The decimal reduction time (D-10 time) of the spores formed at 45°C by wet heat, 2 M HCl, 2 M NaOH and 2 M H₂O₂ was higher than the respective D-10 time for the spores formed in PBS. The dipicolinic acid (DPA) content and germination efficiency was highest in spores formed at 45°C. Since DPA is related to spore sensitivity towards heat and chemicals, the increased DPA content of spores prepared at 45°C may be responsible for increased resistance to wet heat and other denaturants. The size of spores formed at 45°C was smallest amongst all. The study reveals that temperature, pH and nutrient availability during sporulation affect properties of B. anthracis spores.     

Effect of Antimicrobial Peptides Divergicin M35 and Nisin A on <Emphasis Type="Italic">Listeria monocytogenes</Emphasis> LSD530 Potassium Channels

The aim of this work was to study the effect of antimicrobial peptides: divergicin M35 and nisin A on Listeria monocytogenes LSD 530 potassium (K⁺) channels: ATP-sensitive (K_ATP), calcium-activated (BK_Ca), and depolarization-activated (K_v) types. Increase on K⁺ efflux and inhibition of cellular growth were observed after adding K⁺ channel activators pinacidil, NS1619, and cromakalim to divergicin M35. Increase in K⁺ efflux from log-phase cells was about 18 ± 1.1, 11 ± 0.63, and nmol mg⁻¹ of cell dry weight (CDW) for pinacidil and NS1619, respectively, over the efflux obtained with divergicin M35 alone. Increases in K⁺ efflux obtained by adding the same K⁺ channel activators to nisin A fit a completely different profile. Divergicin M35 activates K⁺ channels, particularly of the K_v and BK_Ca types and to a lesser extent the K_ATP type, causing K⁺ efflux and consequently cell death.     

Rapid and high quality DNA isolation from Origanum onites for RAPD and ISSR analysis

Origanum onites is an economically important medicinal plant with high essential oil content. Lack of an appropriate DNA isolation procedure is a limiting factor for any molecular study of this plant. We have used a protocol for genomic DNA isolation based on a hexadecyltrimethylammonium bromide (CTAB) method described for other plant species. The method involves mortar grinding of leaf tissue, modified CTAB extraction using high salt concentrations and polyvinyl pyrrolidone, and successive isoamyl alcohol/chloroform extractions. The yield was approx. 20 microg DNA per 200 mg of initial fresh plant material. The genomic DNA obtained by this method was suitable to be used in restriction digests, inter simple sequence repeat (ISSR) and randomly amplified polymorphic DNA (RAPD) reactions. This extraction method should facilitate the molecular analysis of Origanum chemotypes.     

Some benzoxazoles and benzimidazoles as DNA topoisomerase I and II inhibitors

Some novel fused heterocyclic compounds of 2, 5-disubstituted-benzoxazole and benzimidazole derivatives, which were previously synthesized by our group, were investigated for their inhibitory activity on both eukaryotic DNA topoisomerase I and II in a cell free system. 2-Phenoxymethylbenzimidazole (17), 5-amino-2-(p-fluorophenyl)benzoxazole (3), 5-amino-2-(p-bromophenyl)benzoxazole (5), 5-nitro-2-phenoxymethyl-benzimidazole (18), 2-(p-chlorobenzyl)benzoxazole (10) and 5-amino-2-phenylbenzoxazole (2) were found to be more potent as eukaryotic DNA topoisomerase I poisons than the reference drug camptothecin having IC(50) values of 14.1, 132.3, 134.1, 248, 443.5, and 495 microM, respectively. 5-Chloro-2-(p-methylphenyl)benzoxazole (4), 2-(p-nitrobenzyl)benzoxazole (6) and 5-nitro-2-(p-nitrobenzyl)benzoxazole (8) exhibited significant activity as eukaryotic DNA topoisomerase II inhibitors, having IC(50) values of 22.3, 17.4, 91.41 microM, respectively, showing higher potency than the reference drug etoposide.     

An autopsy study of maternal mortality in Mozambique: the contribution of infectious diseases

Background

Maternal mortality is a major health problem concentrated in resource-poor regions. Accurate data on its causes using rigorous methods is lacking, but is essential to guide policy-makers and health professionals to reduce this intolerable burden. The aim of this study was to accurately describe the causes of maternal death in order to contribute to its reduction, in one of the regions of the world with the highest maternal mortality ratios.

Methods and Findings

We conducted a prospective study between October 2002 and December 2004 on the causes of maternal death in a tertiary-level referral hospital in Maputo, Mozambique, using complete autopsies with histological examination. HIV detection was done by virologic and serologic tests, and malaria was diagnosed by histological and parasitological examination. During 26 mo there were 179 maternal deaths, of which 139 (77.6%) had a complete autopsy and formed the basis of this analysis. Of those with test results, 65 women (52.8%) were HIV-positive. Obstetric complications accounted for 38.2% of deaths; haemorrhage was the most frequent cause (16.6%). Nonobstetric conditions accounted for 56.1% of deaths; HIV/AIDS, pyogenic bronchopneumonia, severe malaria, and pyogenic meningitis were the most common causes (12.9%, 12.2%, 10.1% and 7.2% respectively). Mycobacterial infection was found in 12 (8.6%) maternal deaths.

Conclusions

In this tertiary hospital in Mozambique, infectious diseases accounted for at least half of all maternal deaths, even though effective treatment is available for the four leading causes, HIV/AIDS, pyogenic bronchopneumonia, severe malaria, and pyogenic meningitis. These observations highlight the need to implement effective and available prevention tools, such as intermittent preventive treatment and insecticide-treated bed-nets for malaria, antiretroviral drugs for HIV/AIDS, or vaccines and effective antibiotics for pneumococcal and meningococcal diseases. Deaths due to obstetric causes represent a failure of health-care systems and require urgent improvement.