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Archive - Jul 21, 2017

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Unexpected Source of Tuna's Precise Control of Movement: Hydraulic Control of Fins by Lymph System

The precise control that tuna have of their fins for tight turns and movement while swimming is aided by hydraulic activity of the lymphatic system, a new study reveals. Furthermore, the authors found that this specialization of the lymphatic system is associated with other fishes in the family Scombridae, suggesting that it may have evolved in response to the demand for the sophisticated maneuvering control in these high-performance species. The new report was published in the July 21, 2017 issue of Science and is titled “Hydraulic Control of Tuna Fins: A role for the lymphatic system in vertebrate locomotion.” While dissecting tuna fins, Vadim Pavlov, PhD, of the Stanford University Hopkins Marine Station in Pacific Grove, California, and colleagues found a chamber-like compartment, or large vascular sinus (VS), located at the base of both the second dorsal and anal fins. When the scientists pumped fluid into the chamber, this provided finely controlled adjustment of the fin. Close video monitoring of tuna as they swam revealed that the degree of fin erection increases when tuna are engaging in behaviors that require frequent changes in movement direction, such as searching and feeding, compared to when the fish are simply cruising. Next, the researchers injected special fluid into the VS of tuna to trace fluid dynamics throughout the system. The injection was present only in a sub-section of vessels with vein-like morphology, a characteristic of the lymphatic system, which helps distribute immune cells. Analyzing fluid naturally found in the VS of tuna revealed a high portion of lymphatic cells relative to that found in blood, further suggesting that the VS is a part of the lymphatic system.

Methicillin-Resistant Staph aureus (MRSA) Emerged Years Before Methicillin Was Introduced into Clinical Practice

Science Advances article]Methicillin-resistant Staphylococcus aureus (MRSA) emerged long before the introduction of the antibiotic methicillin into clinical practice, according to a study published online on July 20,2017 in the open-access journal Genome Biology. It was the widespread use of earlier antibiotics such as penicillin rather than of methicillin itself that caused MRSA to emerge, researchers at the University of St. Andrews, and the Wellcome Trust Sanger Institute, UK, suggest. The article is titled “Methicillin-Resistant Staphylococcus aureus Emerged Long Before the Introduction of Methicillin into Clinical Practice.” The researchers found that S. aureus acquired the gene that confers methicillin resistance - mecA - as early as the mid-1940s - fourteen years before the first use of methicillin. Professor Matthew Holden, molecular microbiologist at the University of St. Andrews, the corresponding author said: "Our study provides important lessons for future efforts to combat antibiotic resistance. It shows that new drugs which are introduced to circumvent known resistance mechanisms, as methicillin was in 1959, can be rendered ineffective by unrecognized, pre-existing adaptations in the bacterial population. These adaptations happen because - in response to exposure to earlier antibiotics - resistant bacterial strains are selected instead of non-resistant ones as bacteria evolve." The mecA gene confers resistance by producing a protein called PBP2a, which decreases the binding efficiency of antibiotics used against S. aureus to the bacterial cell wall. The introduction of penicillin in the 1940s led to the selection of S. aureus strains that carried the methicillin resistance gene. Dr.