Eminentia thalami: a potential organizing centre in forebrain development?

The initial induction and subsequent patterning of the central nervous system (CNS) are both mediated by morphogenetic signals emanating from some transient cell populations referred to as signalling or organizing centres. Following induction of the CNS, global signals mediate the establishment of its gross mediolateral and anteroposterior axes at gastrulation and early neural plate stages. Subsequent to this, local signals refine these specifications. Local signalling centres usually lie at boundaries of the tissues they pattern. Also, they are rich sources of morphogens, and are capable of ectopically inducing cell fate changes in adjacent tissues when transplanted. The eminentia thalami (EmT) forms a boundary between the diencephalon and telencephalon during embryonic forebrain development. In amphibians and fishes, the EmT continues to be a prominent structure in the postnatal diencephalon though its role in these is still largely unknown. However, in mammals, it appears transient, being identifiable between embryonic days 11 (E11) and 17 (E17) in the mouse, but not discernible at other ages. Though its function is yet to be determined, available experimental evidence suggests that it might act as a signalling centre in forebrain patterning. Therefore, this study aimed at identifying in the EmT members of the Wnt, Fgf and Bmp families of morphogens implicated in patterning elsewhere, and their spatial and temporal patterns of expression; and also determining whether the EmT is able to induce ectopically cell fate changes in adjacent tissues when transplanted. To address the first aim, Reverse-transcription Polymerase Chain Reaction (RTPCR) and In Situ Hybridization were used to determine the spatial and temporal expression of some members of the Wnt, Fgf and Bmp signalling systems in the EmT in both wild-type mice and Pax6 (Sey/Sey) mutants. The results indicate nested expression of some Wnts, Fgfs and Bmps mRNA in the ventricular zone of the wildtype EmT till E14.5, after which they appear down-regulated. Also, Wnt7b and Wnt8b show the strongest expression at these ages and this may indicate a key role for these genes in the function of the EmT in mammals. In Sey/Sey mutants, the EmT was malformed as shown by the mis-expression of its markers. Additionally, the Wnt, Fgf and Bmp genes normally expressed in the wild-type EmT were either not expressed in the mutant or were mis-expressed. The second aim was addressed by transplanting the EmT into the ventral telencephalon, and using immunohistochemistry and in situ hybridization to analyse for the expression in the ventral telencephalon of Lef1, a transcriptional activator in the Wnt/β-catenin signalling pathway, which is not expressed here, as well as Foxg1, Mash1 and Islet1, three transcription factors normally expressed here. EmT explants induced ectopically Lef1 expression in the ventral telencephalon. Also, while the Lef1-expressing ventral telencephalic cells did express Foxg1, a telencephalic marker, they either did not express or sparsely expressed Mash1 and Islet1, which are specific markers of the ventral telencephalon. These results suggest that the EmT may possess some ability to induce cell fate changes in the ventral telencephalon. The role of Wnt/β-catenin signalling in the function of the EmT was also investigated by analysing Lef1, Foxg1 and Mash1 expression in the ventral telencephalon of cultured E13.5 brains in which Wnt signalling had been activated in the ventral telencephalon through small molecule inhibition of GSK3β, a member of the β- catenin destruction complex. Lef1 expression in the ventral telencephalon increased with an increased inhibition of GSK3β activity. Also, while Foxg1 was expressed normally in the ventral telencephalon irrespective of the level of GSK3β inhibition, there was a significant dose-dependent reduction in Mash1 expression here. These results show that up-regulation of Wnt signalling in the ventral telencephalon may result in cell fate changes here, and also suggest that ventral telencephalic cells are competent to respond to Wnt signalling at this stage of development

The molecular and cellular signatures of the mouse eminentia thalami support its role as a signalling centre in the developing forebrain

The mammalian eminentia thalami (EmT) (or thalamic eminence) is an embryonic forebrain structure of unknown function. Here, we examined the molecular and cellular properties of the mouse EmT. We first studied mRNA expression of signalling molecules and found that the EmT is a structure, rich in expression of secreted factors, with Wnts being the most abundantly detected. We then examined whether EmT tissue could induce cell fate changes when grafted ectopically. For this, we transplanted EmT tissue from a tau-GFP mouse to the ventral telencephalon of a wild type host, a telencephalic region where Wnt signalling is not normally active but which we showed in culture experiments is competent to respond to Wnts. We observed that the EmT was able to induce in adjacent ventral telencephalic cells ectopic expression of Lef1, a transcriptional activator and a target gene of the Wnt/β-catenin pathway. These Lef1-positive;GFP-negative cells expressed the telencephalic marker Foxg1 but not Ascl1, which is normally expressed by ventral telencephalic cells. These results suggest that the EmT has the capacity to activate Wnt/β-catenin signalling in the ventral telencephalon and to suppress ventral telencephalic gene expression. Altogether, our data support a role of the EmT as a signalling centre in the developing mouse forebrain. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s00429-015-1127-3) contains supplementary material, which is available to authorized users

Sepsis-Related Lung Injury and the Complication of Extrapulmonary Pneumococcal Pneumonia

Globally, sepsis and pneumonia account for significant mortality and morbidity. A complex interplay of immune-molecular pathways underlies both sepsis and pneumonia, resulting in similar and overlapping disease characteristics. Sepsis could result from unmanaged pneumonia. Similarly, sepsis patients have pneumonia as a common complication in the intensive care unit. A significant percentage of pneumonia is misdiagnosed as septic shock. Therefore, our knowledge of the clinical relationship between pneumonia and sepsis is imperative to the proper management of these syndromes. Regarding pathogenesis and etiology, pneumococcus is one of the leading pathogens implicated in both pneumonia and sepsis syndromes. Growing evidence suggests that pneumococcal pneumonia can potentially disseminate and consequently induce systemic inflammation and severe sepsis. Streptococcus pneumoniae could potentially exploit the function of dendritic cells (DCs) to facilitate bacterial dissemination. This highlights the importance of pathogen-immune cell crosstalk in the pathophysiology of sepsis and pneumonia. The role of DCs in pneumococcal infections and sepsis is not well understood. Therefore, studying the immunologic crosstalk between pneumococcus and host immune mediators is crucial to elucidating the pathophysiology of pneumonia-induced lung injury and sepsis. This knowledge would help mitigate clinical diagnosis and management challenges

Nasopharyngeal Carriage and Antimicrobial Susceptibility Profile of <i>Staphylococcus aureus</i> among Children under Five Years in Accra

This cross-sectional study investigated the Staphylococcus aureus (S. aureus) and methicillin-resistant S. aureus (MRSA) nasopharyngeal carriage epidemiology in Accra approximately five years post-pneumococcal conjugate vaccines introduction in the country. Archived nasopharyngeal swabs collected from 410 children aged under five years old were bacteriologically cultured. The resultant S. aureus isolates were subjected to antimicrobial susceptibility testing and screening for carriage of the mecA and LukF-PV (pvl) genes, following standard procedures. The data obtained were analyzed with Statistical Products and Services Solutions (SPSS) using descriptive statistics and Chi square tests of associations. The isolated bacteria decreased across coagulase-negative Staphylococci (47.3%, n = 194), S. aureus (23.2%, n = 95), Diphtheroids (5.4%, n = 22), Micrococcus species (3.7%, n = 15), Klebsiella pneumoniae (3.2%, n = 13), Moraxella species and Citrobacter species (1.5% each, n = 6), Escherichia coli, Enterobacter species, and Pseudomonas species (0.9% each, n = 2). The MRSA carriage prevalence was 0.49% (n = 2). Individuals aged 37–48 months recorded the highest proportion of S. aureus carriage (32.6%, 31/95). Resistance of S. aureus to the antibiotics tested were penicillin G (97.9%, n = 93), amoxiclav (20%, n = 19), tetracycline (18.9%, n = 18), erythromycin (5.3%, n = 5), ciprofloxacin (2.1%, n = 2), gentamicin (1.1%, n = 1), cotrimoxazole, clindamycin, linezolid, and teicoplanin (0% each). No inducible clindamycin resistance was observed for the erythromycin-resistant isolates. Three (3.2%) of the isolates were multidrug resistant, of which 66.7% (2/3) were MRSA. The pvl gene was associated with 59.14% (55/93) of the methicillin-sensitive S. aureus (MSSA) isolates, but was not detected among any of the MRSA isolates

Preliminary Investigation into Plasmodium-like Piroplasms (Babesia/Theileria) among Cattle, Dogs and Humans in A Malaria-Endemic, Resource-Limited Sub-Saharan African City

Babesia and Theileria are protozoan parasites belonging to the order piroplasmida, transmitted by hard ticks, and can cause diseases known as piroplasmosis. Human infections are usually asymptomatic, except in immuno-compromised persons who present malaria-like symptoms. Moreover, microscopically, the morphologies of Babesia and Theileria can resemble that of the malaria parasite, Plasmodium. In malaria-endemic areas with limited resources, these similarities can increase the possibility of misdiagnosing a patient as having malaria instead of piroplasmosis, which may further lead to inappropriate choice of disease management. This preliminary investigation aimed at detecting Babesia/Theileria in cattle, dogs and humans in some parts of Accra. Whole blood samples were taken from febrile cattle (n = 30) and dogs (n = 33), as well as humans diagnosed with malaria (n = 150). Blood samples of all study subjects were microscopically screened for possible presence of haemoparasites. Samples whose smears had features suggestive of possible piroplasmic infection were all given the label &ldquo;suspected Babesia/Theileria-infected&rdquo; samples. Nested polymerase chain reaction (PCR) was performed on extracted deoxyribonucelic acid (DNA) from all the &ldquo;suspected&rdquo; samples of cattle, dogs and humans, with primer sets that can detect 18S rRNA genes of Babesia/Theileria spp. In addition to this, amplification was performed on the &ldquo;suspected&rdquo; dog samples using the BcW-A/BcW-B primer set which detects the 18S rRNA genes of B. canis, while the BoF/BoR primer set which targets the rap-1 region of B. bovis and another primer set which detects the 18S rRNA genes of most bovine Babesia spp. (including B. divergens) were used on the suspected cattle samples. For the human samples, however, additional amplification was done on the extracted DNA using primers for the three other Babesia targeted (B. divergens, B. bovis and B. canis). Microscopy showed possible Babesia/Theileria infection suspected in all three groups of subjects in the following proportions: cattle (10/30; 33%), dogs (3/33; 9%) and humans (6/150; 4%). DNA from one-third of the &ldquo;suspected&rdquo; dog samples yielded amplification with Babesia canis primers. Moreover, a broad-detecting set of primers (that can amplify some Babesia and Theileria species) amplified DNA from nine (9/30; 30%) of the &ldquo;suspected&rdquo; cattle samples, but none from those of the humans. Although for this study conducted in the city, the Babesia/Theileria primers used did not amplify DNA from the six &ldquo;suspected&rdquo; human samples; the possibility of Babesia/Theileria infection in humans in other parts of the country cannot be overruled. There is therefore a need for further studies on possible emergence of human babesiosis/theileriosis in other parts of Ghana and sequencing for specific identification of any circulating strain

Unravelling the Perspectives of Day and Night Traders in Selected Markets within a Sub-Saharan African City with a Malaria Knowledge, Attitude and Practice Survey

Background: Malaria is still endemic in sub-Saharan Africa, with a high disease burden. Misconceptions about malaria contribute to poor attitudes and practices, further increasing the burden in endemic countries. Studies have examined the knowledge, attitudes, and practices (KAP) of malaria among different populations. However, there seems to be no available literature reporting on the perspectives of day and night market traders. To the best of our knowledge, this is the first report on malaria KAP with a focus on day and night market traders. Methods: A descriptive cross-sectional study involving day and night market traders in 10 selected markets within the Greater Accra Region of Ghana was carried out. Data were collected from consenting respondents using a structured questionnaire. Results: Of the 760 respondents (33.3% (n = 253) night and 66.7% (n = 507) day traders) interviewed, there was no significant difference between the day and night market traders in terms of malaria KAP. Although the market traders had an overall moderate knowledge (54.0% of the day traders and 56.5% of the night traders), misconceptions about malaria (especially that it could be caused by exposure to the sun) still existed among the traders. Moreover, the majority of the traders who demonstrated high knowledge (43.98%, n = 250) did not always take laboratory tests to confirm their suspicion, indicating poor attitude. Furthermore, the market traders’ choice of drug for malaria treatment (p = 0.001) and preferred malaria treatment type (orthodox or herbal) (p = 0.005) were significantly associated with their knowledge level. Conclusions: Despite the observation that no significant difference in KAP exists between day and night market traders, appropriate health education programs and interventions still need to be directed at misconceptions, poor attitudes, and poor practices revealed by this study. This will ultimately help in the prevention and control of malaria in Ghana, and globally