Course and Outcome of Bacteremia Due to Staphylococcus Aureus: Evaluation of Different Clinical Case Definitions

In a retrospective survey of patients hospitalized in the University Hospital of Basel, Switzerland, the course and outcome of 281 cases of true bacteremia due to Staphylococcus aureus over a 7-year period were analyzed. The main purpose was to evaluate different case definitions. In 78% of cases the source of bacteremia was obvious; vascular access sites (27%) and wounds (10%) were the most common sources. Metastasizing foci were more common in cases of primary vs. secondary bacteremia (P <.001). The incidence of endocarditis was higher in cases in which no portal of entry was defined (P <.03). The overall mortality rate was high at 34% partly because of inappropriate initial antibiotic therapy. With the introduction of an infectious disease service at the hospital, the fraction of misjudged results of blood culture diminished 2.5-fold. Among the differently defined cases, the mortality rate was significantly higher for cases of complicated vs. uncomplicated bacteremia (P <.01), for cases of primary vs. secondary bacteremia (P = .05), and for patients with endocarditis or other secondary foci (P <.001). Since only one methicillin-resistant strain was isolated, multiresistant staphylococci were not a problem in the hospital. Different case definitions allowed the detection of patients at increased risk for complications and death. In the treatment of sepsis with no evident focus, initial antimicrobial therapy should include the use of agents with antistaphylococcal activity

The three-dimensionally articulated oral apparatus of a Devonian heterostracan sheds light on feeding in Palaeozoic jawless fishes

Attempts to explain the origin and diversification of vertebrates have commonly invoked the evolution of feeding ecology, contrasting the passive suspension feeding of invertebrate chordates and larval lampreys with active predation in living jawed vertebrates. Of the extinct jawless vertebrates that phylogenetically intercalate these living groups, the feeding apparatus is well-preserved only in the early diverging stem-gnathostome heterostracans. However, its anatomy remains poorly understood. Here, we use X-ray microtomography to characterize the feeding apparatus of the pteraspid heterostracan Rhinopteraspis dunensis (Roemer, 1855). The apparatus is composed of 13 plates arranged approximately bilaterally, most of which articulate from the postoral plate. Our reconstruction shows that the oral plates were capable of rotating around the transverse axis, but likely with limited movement. It also suggests the nasohypophyseal organs opened internally, into the pharynx. The functional morphology of the apparatus in Rhinopteraspis precludes all proposed interpretations of feeding except for suspension/deposit feeding and we interpret the apparatus as having served primarily to moderate the oral gape. This is consistent with evidence that at least some early jawless gnathostomes were suspension feeders and runs contrary to macroecological scenarios that envisage early vertebrate evolution as characterized by a directional trend towards increasingly active food acquisition

The role of miniaturization in the evolution of the mammalian jaw and middle ear

The evolution of the mammalian jaw is one of the most important innovations in vertebrate history, and underpins the exceptional radiation and diversification of mammals over the last 220 million years. In particular, the transformation of the mandible into a single tooth-bearing bone and the emergence of a novel jaw joint—while incorporating some of the ancestral jaw bones into the mammalian middle ear—is often cited as a classic example of the repurposing of morphological structures. Although it is remarkably well-documented in the fossil record, the evolution of the mammalian jaw still poses the paradox of how the bones of the ancestral jaw joint could function both as a joint hinge for powerful load-bearing mastication and as a mandibular middle ear that was delicate enough for hearing. Here we use digital reconstructions, computational modelling and biomechanical analyses to demonstrate that the miniaturization of the early mammalian jaw was the primary driver for the transformation of the jaw joint. We show that there is no evidence for a concurrent reduction in jaw-joint stress and increase in bite force in key non-mammaliaform taxa in the cynodont–mammaliaform transition, as previously thought. Although a shift in the recruitment of the jaw musculature occurred during the evolution of modern mammals, the optimization of mandibular function to increase bite force while reducing joint loads did not occur until after the emergence of the neomorphic mammalian jaw joint. This suggests that miniaturization provided a selective regime for the evolution of the mammalian jaw joint, followed by the integration of the postdentary bones into the mammalian middle ear

Sensory Evolution and Ecology of Early Turtles Revealed by Digital Endocranial Reconstructions

In the past few years, new fossil finds and novel methodological approaches have prompted intensive discussions about the phylogenetic affinities of turtles and rekindled the debate on their ecological origin, with very distinct scenarios, such as fossoriality and aquatic habitat occupation, proposed for the earliest stem-turtles. While research has focused largely on the origin of the anapsid skull and unique postcranial anatomy, little is known about the endocranial anatomy of turtles. Here, we provide 3D digital reconstructions and comparative descriptions of the brain, nasal cavity, neurovascular structures and endosseous labyrinth of Proganochelys quenstedti, one of the earliest stem-turtles, as well as other turtle taxa. Our results demonstrate that P. quenstedti retained a simple tube-like brain morphology with poorly differentiated regions and mediocre hearing and vision, but a well-developed olfactory sense. Endocast shape analysis indicates that an increase in size and regionalization of the brain took place in the course of turtle evolution, achieving an endocast diversity comparable to other amniote groups. Based on the new evidence presented herein, we further conclude that P. quenstedti was a highly terrestrial, but most likely not fossorial, taxon

Sensory Evolution and Ecology of Early Turtles Revealed by Digital Endocranial Reconstructions

In the past few years, new fossil finds and novel methodological approaches have prompted intensive discussions about the phylogenetic affinities of turtles and rekindled the debate on their ecological origin, with very distinct scenarios, such as fossoriality and aquatic habitat occupation, proposed for the earliest stem-turtles. While research has focused largely on the origin of the anapsid skull and unique postcranial anatomy, little is known about the endocranial anatomy of turtles. Here, we provide 3D digital reconstructions and comparative descriptions of the brain, nasal cavity, neurovascular structures and endosseous labyrinth of Proganochelys quenstedti, one of the earliest stem-turtles, as well as other turtle taxa. Our results demonstrate that P. quenstedti retained a simple tube-like brain morphology with poorly differentiated regions and mediocre hearing and vision, but a well-developed olfactory sense. Endocast shape analysis indicates that an increase in size and regionalization of the brain took place in the course of turtle evolution, achieving an endocast diversity comparable to other amniote groups. Based on the new evidence presented herein, we further conclude that P. quenstedti was a highly terrestrial, but most likely not fossorial, taxon

Feeding biomechanics suggests progressive correlation of skull architecture and neck evolution in turtles

The origin of turtles is one of the most long-lasting debates in evolutionary research. During their evolution, a series of modifications changed their relatively kinetic and anapsid skull into an elongated akinetic structure with a unique pulley system redirecting jaw adductor musculature. These modifications were thought to be strongly correlated to functional adaptations, especially to bite performance. We conducted a series of Finite Element Analyses (FEAs) of several species, including that of the oldest fully shelled, Triassic stem-turtle Proganochelys, to evaluate the role of force distribution and to test existing hypotheses on the evolution of turtle skull architecture. We found no support for a relation between the akinetic nature of the skull or the trochlear mechanisms with increased bite forces. Yet, the FEAs show that those modifications changed the skull architecture into an optimized structure, more resistant to higher loads while allowing material reduction on specific regions. We propose that the skull of modern turtles is the result of a complex process of progressive correlation between their heads and highly flexible necks, initiated by the origin of the shell

Extended Data Fig. 1 in The oldest three-dimensionally preserved vertebrate neurocranium

Extended Data Fig. 1 | Eriptychius PF 1795 shown in the context of the surrounding matrix. a,b, Tomograms showing sections through the part of the specimen preserved in the matrix. c–e, 3D render of the articulated Eriptychius specimen part preserved in epoxy relative to the matrix part,(c) in anatomical ventral view,(d) lateroventral view and (e) laterally with the matrix rendered transparent.Published as part of Dearden, Richard P., Lanzetti, Agnese, Giles, Sam, Johanson, Zerina, Jones, Andy S., Lautenschlager, Stephan, Randle, Emma & Sansom, Ivan J., 2023, The oldest three-dimensionally preserved vertebrate neurocranium, pp. 1-19 in Nature 2023 on page 8, DOI: 10.1038/s41586-023-06538-y, http://zenodo.org/record/836840

Extended Data Fig. 9 in The oldest three-dimensionally preserved vertebrate neurocranium

Extended Data Fig. 9 | Consensus result of the Bayesian analysis. Majority rule consensus tree resulting from the Bayesian phylogenetic analysis described in the methods.Node values correspond to posterior probabilities.Published as part of Dearden, Richard P., Lanzetti, Agnese, Giles, Sam, Johanson, Zerina, Jones, Andy S., Lautenschlager, Stephan, Randle, Emma & Sansom, Ivan J., 2023, The oldest three-dimensionally preserved vertebrate neurocranium, pp. 1-19 in Nature 2023 on page 16, DOI: 10.1038/s41586-023-06538-y, http://zenodo.org/record/836840

Fig. 2 in The oldest three-dimensionally preserved vertebrate neurocranium

Fig. 2 | The neurocranial cartilages of E. americanus PF 1795 based on computed tomography data. a–c, Cranial cartilages in estimated life position, with cartilages coloured in pairs in dorsal (a), ventral (b) and anterior (c) view. d,e, Mediolateral cartilages A in dorsal view (d) and median dorsal cartilage in ventral view (e) rendered with a vertical height map texture to emphasize the surface topology.f, Reconstruction of the forebrain relative to the cranial cartilages using a lamprey as a model9,52, shown in dorsal view.g, Cartilages in dorsal view,rendered transparent to show internal vasculature (red). h,i, Cartilages in preserved position in anterior view with dermal skeleton shown (h) and removed (i). Colours in a,b,c,f,h,i as in Fig.1 with the following additions.Green,dermal skeleton.Red dashed line represents inferred position of mouth in c,h,i. In d and e lighter colours denote areas closer to the camera. Abbreviations as in Fig. 1 with the following additions:antorb. proc,antorbital process;ext.vasc.op., external vascular openings;forebr.,forebrain;lat., lateral;medlat. cart,mediolateral cartilage;med. dors.cart,median dorsal cartilage;med., medial; med.vent.cart.,median ventral cartilage;med.vent. ridge,median ventral ridge;olf.bulb,olfactory bulb;pin., pineal organ;pin.op., pineal opening;vent.,ventral.Scale bar in a is shared by b,c; scale bar in d is shared by e.Published as part of Dearden, Richard P., Lanzetti, Agnese, Giles, Sam, Johanson, Zerina, Jones, Andy S., Lautenschlager, Stephan, Randle, Emma & Sansom, Ivan J., 2023, The oldest three-dimensionally preserved vertebrate neurocranium, pp. 1-19 in Nature 2023 on page 3, DOI: 10.1038/s41586-023-06538-y, http://zenodo.org/record/836840