Synthesis And Applications Of Cyclopalladated Complexes Containing An (sp3)c‒pd Bond

Cyclopalladated complexes (CPCs) possess a number of important properties and have been used in various application studies. However, preparation and uses of optically active CPCs with an (sp3)C–Pd bond have not been thoroughly investigated. In this dissertation, the synthesis and applications of new enantiopure CPCs derived from naturally occurring and optically active D-camphor and L-fenchone are described. The preparation of these CPCs, which contain an (sp3)C–Pd bond, was accomplished by cyclopalladation of D-camphor O-methyloxime, L-fenchone O-methyloxime, L-fenchone oxime and camphor N,N-dimethylhydrazone using Pd(II) salts such as Pd(OAc)2 and Pd(MeCN)2Cl2. Phosphination reactions of CPCs derived from D-camphor O-methyloxime and L-fenchone O-methyloxime, as well as other CN-, CS- and CP-dimeric CPCs having an (sp3)C–Pd bond, were investigated using KPPh2. These alternative CPCs were obtained from 8-methylquinoline, tri-(O-tolyl)phosphine, 2,6-dimethylthioanisole and trimesitylphosphine. In each case, when the CPC reacted with 4.5 equiv. of KPPh2, the corresponding NP-, SP- and PP-ligands were isolated in 13–51% yield. Reactions using only 1 equiv. of KPPh2 gave µ-chloro-µ-diphenylphosphido-CPCs as main products in 26–56% yield. Proposed structures of new compounds obtained in the reactions were confirmed by spectroscopic methods and in some cases by X-ray crystallography. Purity and elemental composition of the synthesized complexes and organic compounds were confirmed by either satisfactory elemental analysis or high resolution mass spectra data

Platinum Complexes with a Phosphino-Oxime/Oximate Ligand

The platinum(II) complex [PtCl2(COD)] (2; COD = 1,5- cyclooctadiene) reacted with 1 and 2 equiv. of 2-(diphenylphosphanyl) benzaldehyde oxime (1) to generate [PtCl2{¿2-(P,N)-2- Ph2PC6H4CH=NOH}] (3) and [Pt{¿2-(P,N)-2-Ph2PC6H4CH=NOH}2]- [Cl]2 (4), respectively. Deprotonation of the oxime hydroxyl group of 3 with Na2CO3 led to the selective formation of the dinuclear species (¿-O)-[PtCl{¿2-(P,N)-2-Ph2PC6H4CH=NO}]2 (5), while the related methylated derivative (¿-O)-[PtMe{¿2-(P,N)-2- Ph2PC6H4CH=NO}]2 (7) could be obtained from the direct reaction of [PtMe2(COD)] (6) with the phosphino-oxime ligand 1. In the case of 4, its treatment with Na2CO3 yielded complex [Pt({¿2-(P,N)-2-Ph2PC6H4CH=NO}2H)][Cl] (8), as a result of the deprotonation of only one of the OH groups of 4. On the other hand, contrary to what was observed with 6, no deprotonation of the oxime occurred in the reaction of [PtMe3I]4 (9) with 1, from which the mononuclear PtIV derivative fac-[PtIMe3{¿2-(P,N)- 2-Ph2PC6H4CH=NOH}] (10) was isolated. The solid-state structures of compounds 3, 4, 7 and 10 were determined by X-ray crystallography. In addition, the potential of all the synthesized complexes as catalysts for the dehydrogenative coupling of hydrosilanes with alcohols is also briefly discussed.Peer Reviewe

Molecular Epidemiology of Foot-and-Mouth Disease Virus in the Context of Transboundary Animal Movement in the Far North Region of Cameroon

Transboundary movement of animals is an important mechanism for foot-and-mouth disease virus (FMDV) spread in endemic regions, such as Cameroon. Several transboundary animal trade routes cross the Far North Region of Cameroon, and cattle moved on foot along these routes often come in contact with native (sedentary and transhumant) herds. The purpose of this study was to investigate the role of transboundary trade cattle in the epidemiology of FMDV in the Far North Region of Cameroon. A total of 582 oropharyngeal fluid (OPF) samples were collected from asymptomatic transboundary trade cattle at official border check points and 57 vesicle epithelial tissues were collected from clinically affected native cattle in the Far North Region of Cameroon during 2010–2014. Viral protein 1 (VP1) coding sequences were obtained from 6 OPF samples from transboundary cattle (4 serotype O, 2 serotype SAT2) and 19 epithelial tissue samples from native cattle (7 serotype O, 3 serotype SAT2, 9 serotype A). FMDV serotype O viruses belonged to two topotypes (East Africa-3 and West Africa), and phylogenetic analyses suggested a pattern of continuous transmission in the region. Serotype SAT2 viruses belonged to a single topotype (VII), and phylogenetic analysis suggested a pattern of repeated introductions of different SAT2 lineages in the region. Serotype A viruses belonged to topotype AFRICA/G-IV, and the pattern of transmission was unclear. Spearman rank correlation analysis of VP1 coding sequences obtained in this study from transboundary and native cattle showed a positive correlation between genetic distance and time for serotype O (ρ = 0.71, p = 0.003) and between genetic distance and geographic distance for serotype SAT2 (ρ = 0.54, p = 0.1). These data suggest that transboundary trade cattle participate in the transmission of FMDV in the Far North Region of Cameroon, however the dynamics and direction of transmission could not be determined in this study. Results of this study contribute to the understanding of transboundary FMDV epidemiology in Central Africa and will help to inform control programs in Cameroon and in the region

Disentangling the role of Africa in the global spread of H5 highly pathogenic avian influenza

The role of Africa in the dynamics of the global spread of a zoonotic and economicallyimportant virus, such as the highly pathogenic avian influenza (HPAI) H5Nx of the Gs/GD lineage, remains unexplored. Here we characterise the spatiotemporal patterns of virus diffusion during three HPAI H5Nx intercontinental epidemic waves and demonstrate that Africa mainly acted as an ecological sink of the HPAI H5Nx viruses. A joint analysis of host dynamics and continuous spatial diffusion indicates that poultry trade as well as wild bird migrations have contributed to the virus spreading into Africa, with West Africa acting as a crucial hotspot for virus introduction and dissemination into the continent. We demonstrate varying paths of avian influenza incursions into Africa as well as virus spread within Africa over time, which reveal that virus expansion is a complex phenomenon, shaped by an intricate interplay between avian host ecology, virus characteristics and environmental variables.USAID under the OSRO/GLO/501/USA and OSRO/GLO/507/USA projects and by European Union’s Horizon 2020 research and innovation programme under grant agreement No 727922 (DELTAFLU). The European Research Council under the European Unionʼs Horizon 2020 research and innovation programme (grant agreement no. 725422-ReservoirDOCS). P.L. acknowledges support by the Research Foundation – Flanders FWO, G066215N, G0D5117N and G0B9317N). B.V. is a postdoctoral research fellow supported by the FWO.http://www.nature.com/naturecommunicationsam2020Microbiology and Plant Patholog

On a certain differential subordination and a condition for starlikeness

No Abstract. Global Journal of Mathematical Sciences Vol. 5(1) 2006: 73-7

A G-protein-coupled chemokine receptor: A putative insertion site for a multi-pathogen recombinant capripoxvirus vaccine strategy

Capripoxviruses (CaPVs) have been shown to be ideal viral vectors for the development of recombinant multivalent vaccines to enable delivery of immunogenic genes from ruminant pathogens. So far, the viral thymidine kinase (TK) gene is the only gene used to generate recombinants. A putative non-essential gene encoding a G-protein-coupled chemokine receptor subfamily homologue (GPCR) was targeted as an additional insertion site. Peste des petits ruminants (PPR) was chosen.as a disease model. A new recombinant CaPV expressing the viral attachment hemagglutinin (H) of the PPR virus (PPRV) in the GPCR insertion site (rKS1-HPPR-GPCR) was generated in the backbone North African isolate KS1 strain of lumpy skin disease virus (LSDV). Comparison with the recombinant CaPV expressing the H of PPRV in the TK gene (rKS1-HPPR-TK) shown to induce protection against both PPR and LSD in both sheep and goats was assessed. The suitability of the GPCR gene to be a putative additional insertion site in the CaPV genome is evaluated and discussed

Risk factors analysis and implications for public health of bovine tuberculosis in the highlands of Cameroon

Bovine tuberculosis (TB) is a neglected zoonosis of cattle that is prevalent but under-investigated in Cameroon. Based on epidemiological data of the disease, this study was designed to assess the risks and public health implications for zoonotic M. bovis infection in cattle and humans in the highlands of Cameroon. Evidence of bovine TB in cattle in the study region was confirmed by the following surveys: abattoir slaughter meat inspection and TB lesion detection rates of 0.20% – 1.69% (over 60.94% of all pathologies that warranted partial or whole carcass condemnation were due to TB lesions); seroprevalence rates of 37.17% and comparative cervical tuberculin test estimations of 4.67% – 7.15%, 12.02% – 15.67% and 20.56% – 24.98% at the ≥ 4mm, ≥ 3mm and ≥ 2mm cut off points, respectively. Genomic deletion analysis of cultured isolates showed evidence of M. tuberculosis from suspected cattle tissue and M. bovis from infected human sputa while spoligotyping identified five cattle M. bovis strains including four unique spoligotype patterns that had not been previously described. The study revealed that the presence of infected animals, age, sex, breed and husbandry practices served as significant (P<0.05) risks to the prevalence and exposure of bovine TB in cattle. The feedbacks from cattle professionals suggested that there was high possibility of cattle to cattle and cattle to human transmission of bovine TB through intimate and repeated cattle / cattle and cattle / human interactions, unawareness of TB control measures, consuming unpasteurised milk and eating raw meat. The findings of this study have important public health implications requiring prompt and decisive actions from the Cameroonian authority towards controlling zoonotic bovine TB in both humans and animals.Keywords: Bovine tuberculosis, epidemiology, risk factors analysis, public health implications, Cameroo

Serotype-Specific Transmission and Waning Immunity of Endemic Foot-and-Mouth Disease Virus in Cameroon

<div><p>Foot-and-mouth disease virus (FMDV) causes morbidity and mortality in a range of animals and threatens local economies by acting as a barrier to international trade. The outbreak in the United Kingdom in 2001 that cost billions to control highlighted the risk that the pathogen poses to agriculture. In response, several mathematical models have been developed to parameterize and predict both transmission dynamics and optimal disease control. However, a lack of understanding of the multi-strain etiology prevents characterization of multi-strain dynamics. Here, we use data from FMDV serology in an endemic setting to probe strain-specific transmission and immunodynamics. Five serotypes of FMDV affect cattle in the Far North Region of Cameroon. We fit both catalytic and reverse catalytic models to serological data to estimate the force of infection and the rate of waning immunity, and to detect periods of sustained transmission. For serotypes SAT2, SAT3, and type A, a model assuming life-long immunity fit better. For serotypes SAT1 and type O, the better-fit model suggests that immunity may wane over time. Our analysis further indicates that type O has the greatest force of infection and the longest duration of immunity. Estimates for the force of infection were time-varying and indicated that serotypes SAT1 and O displayed endemic dynamics, serotype A displayed epidemic dynamics, and SAT2 and SAT3 did not sustain local chains of transmission. Since these results were obtained from the same population at the same time, they highlight important differences in transmission specific to each serotype. They also show that immunity wanes at rates specific to each serotype, which influences patterns of local persistence. Overall, this work shows that viral serotypes can differ significantly in their epidemiological and immunological characteristics. Patterns and processes that drive transmission in endemic settings must consider complex viral dynamics for accurate representation and interpretation.</p></div

Yearly force of infection by serotype.

<p>Estimates derived by model fitting for the time-varying force of infection (FOI) for SAT1, SAT2, SAT2, type O, and type A inferred for the 16-year period preceding data collection represented by a solid line. The dotted line represents the epidemic threshold <i>R</i>₀ = 1; the shaded areas represent estimated FOI that correspond to <i>R</i>₀ > 1 and therefore, sustained chains of transmission within the study population. Note that the scale of the y-axis varies across panels.</p

Age distribution of sampled cattle.

<p>Four hundred sixty nine cattle, ranging in age from one year old to sixteen years old, were sampled for serotype-specific FMDV antibodies.</p