Evidence of Dengue Virus Transmission and Factors Associated with the Presence of Anti-Dengue Virus Antibodies in Humans in Three Major Towns in Cameroon

Background

Dengue is not well documented in Africa. In Cameroon, data are scarce, but dengue infection has been confirmed in humans. We conducted a study to document risk factors associated with anti-dengue virus Immunoglobulin G seropositivity in humans in three major towns in Cameroon.

Methodology/Principal Findings

A cross sectional survey was conducted in Douala, Garoua and Yaounde, using a random cluster sampling design. Participants underwent a standardized interview and were blood sampled. Environmental and housing characteristics were recorded. Randomized houses were prospected to record all water containers, and immature stages of Aedes mosquitoes were collected. Sera were screened for anti-dengue virus IgG and IgM antibodies. Risk factors of seropositivity were tested using logistic regression methods with random effects.Anti-dengue IgG were found from 61.4% of sera in Douala (n = 699), 24.2% in Garoua (n = 728) and 9.8% in Yaounde (n = 603). IgM were found from 0.3% of Douala samples, 0.1% of Garoua samples and 0.0% of Yaounde samples. Seroneutralization on randomly selected IgG positive sera showed that 72% (n = 100) in Douala, 80% (n = 94) in Garoua and 77% (n = 66) in Yaounde had antibodies specific for dengue virus serotype 2 (DENV-2).Age, temporary house walls materials, having water-storage containers, old tires or toilets in the yard, having no TV, having no air conditioning and having travelled at least once outside the city were independently associated with anti-dengue IgG positivity in Douala. Age, having uncovered water containers, having no TV, not being born in Garoua and not breeding pigs were significant risk factors in Garoua. Recent history of malaria, having banana trees and stagnant water in the yard were independent risk factors in Yaounde.

Conclusion/Significance

In this survey, most identified risk factors of dengue were related to housing conditions. Poverty and underdevelopment are central to the dengue epidemiology in Cameroon.     

Pharmacogenetic assessment of antipsychotic-induced movement disorders: contribution of the dopamine D3 receptor and cytochrome P450 1A2 genes

Tardive dyskinesia (TD) is characterized by involuntary movements predominantly in the orofacial region and develops in approximately 20% of patients during long-term treatment with typical antipsychotics. The high prevalence of TD and its disabling and potentially irreversible clinical course is an important shortcoming for treatment with typical antipsychotics. The studies presented in this article evaluate the role of single nucleotide polymorphisms in dopamine D3 receptor (DRD3) and CYP1A2 genes for propensity to develop TD in patients with schizophrenia. In theory, a combined pharmacogenetic analysis of pharmacokinetic and pharmacodynamic targets for antipsychotics should improve our ability to identify subpopulations that differ in drug safety profile. This information may in turn contribute to the design of more efficient clinical trials and thus expedite the development and regulatory approval of newer antipsychotic compounds.     

Trophallactic activities in the honeybee brood nest--heaters get supplied with high performance fuel

Honeybees actively regulate their brood temperature by heating between 33 and 36 degrees C if ambient temperatures are lower. Heat is generated by vibrating the flight muscles. Heating rapidly depletes the worker's internal energy; therefore heating performance is limited by the honey that is ingested before the heating process. Stored honey is the predefined fuel for flying and heating, but it is stored at a distance from the broodcomb, causing a potential logistic problem of efficient energy supply in the brood area. Our study focused on the behaviour and the thoracic temperature of the participants in trophallactic food exchanges on the broodcomb. We found that 85.5% of the recipients in a trophallactic food exchange have a higher thoracic temperature during feeding contacts than donors and after the feeding contact the former engage in brood heating more often. The donor bees have lower thoracic temperature and shuttle constantly between honey stores and the broodcomb where they transfer the stored honey to heating bees. Providing heat-emitting workers with small doses of high performance fuel contributes to an economic distribution of resources consistent with physiological conditions of the bees and the ecological requirements of the hive. The trophallaxis-based system is essential to provide the energy-intensive brood warming activity. The emerging independence from ambient temperatures is not only beneficial for brood rearing during times of sudden cold spells, but also enables the honeybees in temperate regions to raise brood in early spring and might be the decisive factor for the occurrence of honeybees in temperate climates in general.     

Purification and characterization of thermostable xylose(glucose) isomerase from Bacillus thermoantarcticus

Xylose isomerase produced by Bacillus thermoantarcticus was purified 73-fold to homogeneity and its biochemical properties were determined. It was a homotetramer with a native molecular mass of 200 kDa and a subunit molecular mass of 47 kDa, with an isoelectric point at 4.8. The enzyme had a K _m of 33 mM for xylose and also accepted D-glucose as substrate. Arrhenius plots of the enzyme activity of xylose isomerase were linear up to a temperature of 85°C. Its optimum pH was around 7.0, and it had 80% of its maximum activity at pH 6.0. This enzyme required divalent cations for its activity and thermal stability. Mn²⁺, Co²⁺ or Mg²⁺ were of comparable efficiency for xylose isomerase reaction, while Mg²⁺ was necessary for glucose isomerase reaction. Journal of Industrial Microbiology & Biotechnology (2001) 27, 234–240. Received 18 March 2001/ Accepted in revised form 03 July 2001     

Toward the production of artemisinin through tissue culture: Determining nutrient-hormone combinations suitable for cell suspension cultures

Summary Artemisia annua L. is the source of a potent antimalarial, artemisinin. As part of a program to produce artemisinin through tissue culture, a series of 14 multifactorial experiments were conducted to determine suitable conditions for initiating and maintaining friable callus fromA. annua. In the first six experiments, three different nutrient formulations [Gamborg B5 (B5), Murashige and Skoog (MS), and Whetmore and Rier (WR)], each with 32 combinations of auxins and cytokinins [2,4-dichlorophenoxyacetic acid (2,4-D) with benzyladenine (BA), or 1-naphthaleneacetic acid (NAA) with 6-furfurylaminopurine (kinetin)], were tested. Both B5 and WR nutrients supported friable callus formation from leaf explants with some combinations of auxin and cytokinin. Inasmuch as friable callus seemed to be produced over a wider range of auxin and cytokinin concentrations in combination with B5, the remaining experiments were conducted solely with this nutrient formulation. In the remaining eight experiments, it was determined that friable callus formed when combinations of NAA with kinetin or 2,4-D and BA were used with B5 medium. Lighter colored, more friable callus formed in response to 2,4-D and BA than with NAA and kinetin. No single combination of concentrations of auxin and cytokinin seemed to be “ideal” for producing friable callus. Ranges of 2,4-D from 0.5 to 2.0 with BA between 0.025 and 0.1, or NAA between 0.5 and 2.0 with kinetin between 0.5 and 1.0 mg/liter, produced acceptable results.     

Applications of Environmental Scanning Electron Microscopy (ESEM) in botanical research

Abstract

Conventional Scanning Electron Microscopy (SEM) is limited by artefacts from sample preparation, while Environmental Scanning Electron Microscopy (ESEM) permits observations of hydrated, non-conductive samples without any preparation. In this short review, the two systems are described and some examples given. In addition, a study of trace element localization by X-ray ESEM microanalysis in Azolla caroliniana cultured in the presence of trace elements is presented. The highest concentration occurred in roots and stem. Leaves showed lower accumulation, with concentrations decreasing from the base to the apex of the shoot, and sharp differences between ventral and dorsal lobes of single leaves, the former accumulating more than the latter. The epidermal cells in the ventral lobes of basal leaves were largely lost in treated plants. The differential localisation of trace elements in the plant protected the dorsal lobes, which are the main photosynthetic part of the plant, the nitrogen-fixing cyanobacterial colonies and the apical meristems from potentially adverse effects of trace elements.     

Design,synthesis and pharmacological evaluation of novel naphthalenic derivatives as selective MT1 melatoninergic ligands

Novel heterodimer analogues of melatonin were synthesized, when agomelatine (1) and various aryl units are linked via a linear alkyl chain through the methoxy group. The compounds were tested for their actions at melatonin receptors. Several of these ligands are MT₁-selective with nanomolar or subnanomolar affinity. In addition, while most of the derivatives behave as partial agonists on one or both receptor subtypes, N-[2-(7-{4-[6-(1-methoxycarbonylethyl)naphthalen-2-yloxy]butoxy}naphthalen-1-yl)ethyl]acetamide (36), a subnanomolar MT₁ ligand with an 11-fold preference over MT₂ receptors, is a full antagonist on both receptors. Our results also confirm that the selectivity seen for the MT₁ receptor arises predominantly from steric factors and is not a consequence of the bridging of melatonin receptor dimers.     

Direct and indirect enhancement of GABAergic neurotransmission by ammonia: implications for the pathogenesis of hyperammonemic syndromes

Experimental evidence indicates that ammonia causes neuroexcitation and seizures. This contrasts with the lethargy, confusion and other manifestations of global CNS depression commonly considered to be major components of hyperammonemic encephalopathies. Substantial data now indicates that ammonia can modulate GABAergic neurotransmission through direct and indirect mechanisms. This modulation consists of an enhancement of GABAergic neurotransmission at concentrations commonly encountered in hyperammonemic states and precedes the suppression of inhibitory neuronal function observed at higher (>1mM) ammonia concentrations. Not only is this increase in GABAergic neurotransmission consistent with the clinical picture of lethargy, ataxia and cognitive deficits associated with liver failure and congenital hyperammonemia, but it also provides a mechanism for testing new therapeutic modalities for the treatment of hyperammonemic encephalopathy.     

Idiotypy of human anti-Candida albicans antibodies: recurrence, presence of a cross-reactive autoanti-idiotypic-like activity, and role in the induction of specific in vitro antibody response

Rabbit anti-idiotypic antibodies (L12) were raised against human anti-mannan of Candida albicans (CA) antibodies isolated from the serum of a normal donor. The absorbed anti-idiotypic antiserum bound to donor anti-CA mannan antibodies but not to control immunoglobulins. Binding was inhibited by CA mannan but not by other polysaccharide antigens. L12 was shown to cross-react with anti-CA mannan-isolated antibodies or with anti-CA antibody-containing sera from individuals unrelated to the donor. IgG fraction isolated from the donor serum was repeatedly absorbed on CA mannan Sepharose to remove anti-mannan antibodies. This IgG fraction (named autoanti-idiotypic fraction) blocked, in a dose-dependent fashion, the binding of rabbit anti-idiotype to donor anti-CA mannan antibodies. Moreover, this CP-depleted IgG fraction cross-reacted with public idiotypic determinants of unrelated anti-CA mannan antibodies. Finally, L12 induced sensitized lymphocytes to produce anti-CA mannan antibodies in vitro in the absence of antigen.     

The Relationship Between Plasma and Brain Quinolinic Acid Levels and the Severity of Hepatic Encephalopathy in Animal Models of Fulminant Hepatic Failure

Abstract: Quinolinic acid is an excitatory, neurotoxic tryptophan metabolite proposed to play a role in the pathogenesis of hepatic encephalopathy. This involvement was investigated in rat and rabbit models of fulminant hepatic failure at different stages of hepatic encephalopathy. Although plasma and brain tryptophan levels were significantly increased in all stages of hepatic encephalopathy, quinolinic acid levels increased three- to sevenfold only in the plasma, CSF, and brain regions of animals in stage IV hepatic encephalopathy. Plasma-CSF and plasma-brain quinolinic acid levels in rats and rabbits with fulminant hepatic failure were strongly correlated, with CSF and brain concentrations ∼10% those of plasma levels. Moreover, there was no significant regional difference in brain quinolinic acid concentrations in either model. Extrahepatic indoleamine-2,3-dioxygenase activity was not altered in rats in stage IV hepatic encephalopathy, but hepatic l -tryptophan-2,3-dioxygenase activity was increased. These results suggest that quinolinic acid synthesized in the liver enters the plasma and then accumulates in the CNS after crossing a permeabilized blood-brain barrier in the end stages of liver failure. Furthermore, the observation of low brain concentrations of quinolinic acid only in stage IV encephalopathy suggests that the contribution of quinolinic acid to the pathogenesis of hepatic encephalopathy in these animal models is minor.