Spinal pain revealing brucellar spondylodiscitis: a case report

Background Brucellosis is an anthropozoonosis. It is an endemic disease in the Mediterranean basin. The clinical presentation is polymorphic. The osteoarticular form is the most frequent of the focal forms affecting mainly the spine. In our endemic context, the diagnosis can lead to confusion with tuberculosis. Case presentation We report a case of brucellar spondylodiscitis treated initially as tubercular spondylodiscitis with a good initial evolution. Then, the diagnosis was rectified towards a Brucella origin, after a clinical and biological relapse. Diagnostic confirmation was based on the isolation of Brucella spp in the disco-vertebral CT-guided biopsy and the positive Brucella serology. Then, the patient was put on three antibacterial treatments with doxycycline, rifampicin, plus streptomycin over a period of 6 months with a good evolution. Conclusion Brucellar spondylodiscitis is still common in the Maghreb. It is generally insidious and leads to a delay in diagnosis. The clinician must always mention it when faced with spondylodiscitis in an endemic country and ask for brucella serology.

The stratification maxima of the seasonally varying Surface layer in the Arctic Ocean’s Beaufort Gyre

The Beaufort Gyre region of the Arctic Ocean is strongly stratified at the base of the wintertime mixed layer, which impedes the vertical transport of heat, energy, and other tracers. Ice-Tethered Profiler observations during 2004-2018 were used to characterize and investigate the seasonal and interannual variability of the strength, depth, density, and thickness of this highly stratified layer at the base of the mixed layer. This includes investigating the remnant stratification maximum, which formed when the summer mixed layer shoaled. Seasonally, the stratification maximum was never in a steady state. It was largest in October (4.8 × 10−3 rad2/sec2) and decreased during all winter months (to 2.3 × 10−3rad2/sec2 in June), indicating that surface forcing and interior vertical mixing were never in equilibrium during the year. Interannually, the period from 2011-2018 had a higher stratification maximum than then the period from 2005-2010 regardless of the season. The remnant stratification maximum was consistently weaker than the winter stratification maximum from which it formed. The initial evolution of the remnant stratification maximum is used to estimate an effective vertical diffusivity of order 10−6m2/s. No significant geographic variability was found, in part due to high temporal and small scale variability of the stratification maximum layer. Implications for heat transport through to the sea ice cover are discussed.

Does the evolution of division of labour require accelerating returns from individual specialisation?

Recent theory has overturned the assumption that accelerating returns from individual specialisation are required to favour the evolution of division of labour. Yanni et al. (2020) showed that topologically constrained groups, where cells cooperate with only direct neighbours such as for filaments or branching growths, can evolve a reproductive division of labour even with diminishing returns from individual specialisation. We developed a conceptual framework and specific models to investigate the factors that can favour the initial evolution of reproductive division of labour. We found that selection for division of labour in topologically constrained groups: (1) is not a single mechanism to favour division of labour – depending upon details of the group structure, division of labour can be favoured for different reasons; (2) always involves an efficiency benefit at the level of group fitness; and (3) requires a mechanism of coordination to determine which individuals perform which tasks. Given that such coordination is unlikely to evolve before division of labour, this limits the extent to which topological constraints could have favoured the initial evolution of division of labour. We conclude by suggesting experimental designs that could determine why division of labour is favoured in the natural world.

Loricarioid catfish evolved skin denticles that recapitulate teeth at the structural, developmental, and genetic levels

The first vertebrate mineralized skeleton was an external bony armor coated with dental structures. The subsequent emergence of a mineralized endoskeleton and of teeth are considered key innovations in the diversification of vertebrates. Although time clouds our understanding of the initial evolution of these mineralized structures, recent re-emergences may shed light on the underlying processes. Loricarioid catfishes are a lineage that, much like the ancestral vertebrates, bear denticle-clad bony armor from head to tail. Loricarioid denticles (LDs) and oral teeth are very similar in superstructure. We show here that other extra-oral dental structures are found as ancestral characters only in lineages that are distantly related to loricarioids such as sharks or coelacanth, indicating that LDs have independently re-emerged in loricarioid catfishes. We investigate whether the similarities between LDs and teeth extend to their developmental and genetic context, and how their development compares to that of other vertebrate integument structures. Our detailed study of the development of LDs, and gene expression analyses through in situ hybridization confirm that all 12 genes from the tooth-forming gene regulatory network (oGRN) are expressed in developing LDs in a similar way as they are expressed in developing teeth. We then compare the developmental, structural, and genetic aspects of LD and teeth with that of other integument appendages such as fish scales, shark dermal denticles, feathers and hairs. We find that LDs share all developmental cues with teeth and, to a lesser extent, with the other vertebrate integument structures. Taken together, our results indicate that denticles have re-emerged on the trunk of loricarioid catfishes through the ectopic co-option of the oGRN rather than the resurrection of an ancestral trunk-specific denticle genetic pathway.

Epidemiological Aspects of the Initial Evolution of COVID-19 in Microregion of Uberlândia, Minas Gerais (MG), Brazil

COVID-19 is considered by the World Health Organization to be a global public health emergency, which presents regional divergences that affect the epidemiological profile of the disease and are associated with political, economic, social and behavioral aspects. We aimed to analyze the epidemiological characteristics of the disease in the microregion of Uberlândia, Brazil, in order to determine risk factors that contributed to progression of SARS-CoV-2 virus. A cross-sectional study was conducted about micro- and macro-determinants combined with the significance analysis of suspected and confirmed cases in 18 municipalities during the epidemiological weeks (EW) 9 to 26. There were 34,046 notifications, of which 4935 (14.49%) people were diagnosed with COVID-19. Of these, 282 (5.71%) required hospital care and 40 (0.81%) died. Age and presence of associated comorbidities were decisive in the variations of incidence and lethality rates. In general, young people were the most affected and the elderly people, the most exposed to the serious and lethal form (p < 0.0001). Comorbidities such as diabetes and cardiopathies increased 33.5 times the death risk. The dispersion of the virus was centrifugal, in the inter as well as in the intra-municipal level. The disorderly implementation of municipal decrees applied in a decentralized manner in the municipalities seems to have contributed for the incidence rates increasing in the EW 25 and 26.

A warm jet in a cold ocean

Unprecedented quantities of heat are entering the Pacific sector of the Arctic Ocean through Bering Strait, particularly during summer months. Though some heat is lost to the atmosphere during autumn cooling, a significant fraction of the incoming warm, salty water subducts (dives beneath) below a cooler fresher layer of near-surface water, subsequently extending hundreds of kilometers into the Beaufort Gyre. Upward turbulent mixing of these sub-surface pockets of heat is likely accelerating sea ice melt in the region. This Pacific-origin water brings both heat and unique biogeochemical properties, contributing to a changing Arctic ecosystem. However, our ability to understand or forecast the role of this incoming water mass has been hampered by lack of understanding of the physical processes controlling subduction and evolution of this this warm water. Crucially, the processes seen here occur at small horizontal scales not resolved by regional forecast models or climate simulations; new parameterizations must be developed that accurately represent the physics. Here we present novel high resolution observations showing the detailed process of subduction and initial evolution of warm Pacific-origin water in the southern Beaufort Gyre.

Bone metabolism and evolutionary origin of osteocytes: Novel application of FIB-SEM tomography

Lacunae and canaliculi spaces of osteocytes are remarkably well preserved in fossilized bone and serve as an established proxy for bone cells. The earliest bone in the fossil record is acellular (anosteocytic), followed by cellular (osteocytic) bone in the jawless relatives of jawed vertebrates, the osteostracans, about 400 million years ago. Virtually nothing is known about the physiological pressures that would have initially favored osteocytic over anosteocytic bone. We apply focused ion beam–scanning electron microscopy tomography combined with machine learning for cell detection and segmentation to image fossil cell spaces. Novel three-dimensional high-resolution images reveal areas of low density around osteocyte lacunae and their canaliculi in osteostracan bone. This provides evidence for demineralization that would have occurred in vivo as part of osteocytic osteolysis, a mechanism of mineral homeostasis, supporting the hypothesis that a physiological demand for phosphorus was the principal driver in the initial evolution of osteocytic bone.