Prediction of post-operative necrosis after mastectomy: A pilot study utilizing optical diffusion imaging spectroscopy

<p>Abstract</p> <p>Introduction</p> <p>Flap necrosis and epidermolysis occurs in 18-30% of all mastectomies. Complications may be prevented by intra-operative detection of ischemia. Currently, no technique enables quantitative valuation of mastectomy skin perfusion. Optical Diffusion Imaging Spectroscopy (ViOptix T.Ox Tissue Oximeter) measures the ratio of oxyhemoglobin to deoxyhemoglobin over a 1 × 1 cm area to obtain a non-invasive measurement of perfusion (StO₂).</p> <p>Methods</p> <p>This study evaluates the ability of ViOptix T.Ox Tissue Oximeter to predict mastectomy flap necrosis. StO₂measurements were taken at five points before and at completion of dissection in 10 patients. Data collected included: demographics, tumor size, flap length/thickness, co-morbidities, procedure length, and wound complications.</p> <p>Results</p> <p>One patient experienced mastectomy skin flap necrosis. Five patients underwent immediate reconstruction, including the patient with necrosis. Statistically significant factors contributing to necrosis included reduction in medial flap StO₂(p = 0.0189), reduction in inferior flap StO₂(p = 0.003), and flap length (p = 0.009).</p> <p>Conclusion</p> <p>StO₂reductions may be utilized to identify impaired perfusion in mastectomy skin flaps.</p

Sawfishes stealth revealed using computational fluid dynamics

Detailed computational fluid dynamics simulations for the rostrum of three species of sawfish (Pristidae) revealed that negligible turbulent flow is generated from all rostra during lateral swipe prey manipulation and swimming. These results suggest that sawfishes are effective stealth hunters that may not be detected by their teleost prey's lateral line sensory system during pursuits. Moreover, during lateral swipes, the rostra were found to induce little velocity into the surrounding fluid. Consistent with previous data of sawfish feeding behaviour, these data indicate that the rostrum is therefore unlikely to be used to stir up the bottom to uncover benthic prey. Whilst swimming with the rostrum inclined at a small angle to the horizontal, the coefficient of drag of the rostrum is relatively low and the coefficient of lift is zero

The sensory biology and feeding behaviour of sawfish

The family of pristid sawfish face a global crisis, with all species listed as critically endangered on the IUCN Redlist. One characteristic that all species have in common may also be a major factor contributing to their decline; the elongated rostrum that bears lateral teeth (the ‘saw’). As the saw becomes easily entangled in fishing gear and is also a valuable trophy, sawfish are regularly taken as by-catch. However, the use of the saw has never been studied. My objective is to identify the importance of the saw during prey manipulation, and to assess the relative importance of three sensory modalities (vision, electroreception and mechanoreception) in the same context. The morphology of the rostrum of pristid sawfish was analysed and compared to rhinobatid shovelnose rays and the extinct sclerorhynchid sawfish, as these three families are monophyletic. Comparison of the internal structure of the rostrum in the three taxa indicates that in pristids the anterior portion of the rostrum lengthened, which results in a slimmer construction than that of the sclerorhynchid rostrum. Moreover, pristid rostral teeth grow continuously from the base, whereas sclerorhynchids possess functional rostral teeth and dormant replacement teeth. Characteristics of the pristid rostrum are interpreted as adaptations to reduce weight and therefore potentially allow fast lateral swipes of the rostrum during food manipulation. Contrary to other batoids, the atlanto-occipital joint of pristids allows free movement of the cranium in all directions. Feeding observations of juvenile freshwater sawfish Pristis microdon lead to the establishment of an ethogram in the context of prey manipulation. Results indicate that an average feeding event that leads to the successful ingestion of a fish is comprised of five behaviours, of which at least one includes the use of the saw. However, freshwater sawfish use their saw during prey manipulation in three distinctive behaviours. Comparison of the two dimensional sensory array of the electroreceptive ampullae of Lorenzini in rhinobatids and pristids reveals how the elongation of the rostrum may have expanded the food spectrum of pristids: the total number of ampullary pores distributed ventrally on the head and rostrum of the pristid Anoxypristis cuspidata (490.3 ± 68.7) equals that of the rhinobatids Glaucostegus typus (452.0 ± 162.8) and Aptychotrema rostrata (461.5 ± 17.7). However, A. cuspidata possesses more than seven times the number of pores on the dorsal surface of the rostrum (297.1 ± 56.6 pores) than the rhinobatids (A. rostrata 40.7 ± 2.3 pores, G. typus 24.9 ± 5.1 pores), indicating that pristids can potentially sense the electric field of prey in the water column. One retina of a juvenile freshwater sawfish P. microdon was analysed in a retinal wholemount. The density distribution of photoreceptors shows several peaks mediating acute vision, which is comparable to the retina of a white tip reef shark Triaenodon obseus. These peaks may help sawfish to maneouvre structurally complex habitats, such as mangrove roots in rivers in order to hide from predators. Peaks in the rod and cone density of the temporal region may be useful during prey manipulation with the rostrum. Detailed knowledge of sawfish biology is crucial for maintaining optimal health of these endangered species in captivity and alleviating future fishing pressure

The function of the sawfish's saw

Jawed fishes that possess an elongated rostrum use it to either sense prey or to manipulate it, but not for both. The billfish rostrum, for instance, lacks any sensory function and is used to stun prey, while paddlefishes use their rostrum to detect and orient towards electric fields of plankton. Sturgeons search through the substrate with their electroreceptive rostrum, and engulf prey by oral suction. Here, we show that juvenile freshwater sawfish Pristis microdon are active predators that use their toothed rostrum — the saw — to both sense prey-simulating electric fields and capture prey. Prey encountered in the water column is attacked with lateral swipes of the saw that can stun and/or impale it. We compare sawfish to shovelnose rays, which share a common shovelnose ray-like ancestor and lack a saw.2 page(s

First insights into the function of the sawshark rostrum through examination of rostral tooth microwear

Potential roles of the rostrum of sawsharks (Pristiophoridae), including predation and self-defence, were assessed through a variety of inferential methods. Comparison of microwear on the surface of the rostral teeth of sawsharks and sawfishes (Pristidae) show that microwear patterns are alike and suggest that the elongate rostra in these two elasmobranch families are used for a similar purpose (predation). Raman spectroscopy indicates that the rostral teeth of both sawsharks and sawfishes are composed of hydroxyapatite, but differ in their collagen content. Sawfishes possess collagen throughout their rostral teeth whereas collagen is present only in the centre of the rostral teeth of sawsharks, which may relate to differences in ecological use. The ratio of rostrum length to total length in the common sawshark Pristiophorus cirratus was found to be similar to the largetooth sawfish Pristis pristis but not the knifetooth sawfish Anoxypristis cuspidata. Analysis of the stomach contents of P. cirratus indicates that the diet consists of demersal fishes and crustaceans, with shrimp from the family Pandalidae being the most important dietary component. No prey item showed evidence of wounds inflicted by the rostral teeth. In light of the similarities in microwear patterns, rostral tooth chemistry and diet with sawfishes, it is hypothesised that sawsharks use their rostrum in a similar manner for predation (sensing and capturing prey) and possibly for self-defence