Thermal acclimation in rainbow smelt, Osmerus mordax, leads to faster myotomal muscle contractile properties and improved swimming performance

Summary Rainbow smelt (Osmerus mordax) display an impressive ability to acclimate to very cold water temperatures. These fish express both anti-freeze proteins and glycerol in their plasma, liver, muscle and other tissues to avoid freezing at sub-zero temperatures. Maintenance of glycerol levels requires active feeding in very cold water. To understand how these fish can maintain activity at cold temperatures, we explored thermal acclimation by the myotomal muscle of smelt exposed to cold water. We hypothesized that cold-acclimated fish would show enhanced swimming ability due to shifts in muscle contractile properties. We also predicted that shifts in swimming performance would be associated with changes in the expression patterns of muscle proteins such as parvalbumin (PV) and myosin heavy chain (MyHC). Swimming studies show significantly faster swimming by smelt acclimated to 5°C compared to fish acclimated to 20°C when tested at a common test temperature of 10°C. The cold-acclimated fish also had faster muscle contractile properties, such as a maximum shortening velocity (Vmax) almost double that of warm-acclimated fish at the same test temperature. Cold-acclimation is associated with a modest increase in PV levels in the swimming muscle. Fluorescence microscopy using anti-MyHC antibodies suggests that MyHC expression in the myotomal muscle may shift in response to exposure to cold water. The complex set of physiological responses that comprise cold-acclimation in smelt includes modifications in muscle function to permit active locomotion in cold water

and invasive central nervous system infection

Streptococcus pyogenes is a Gram-positive beta-hemolytic bacteria, also known as group A streptococci, that causes a range of infections. The most common presentation is acute pharyngitis; however, it is also implicated in skin and soft tissue infections, and less commonly bacteremia, osteomyelitis, pneumonia, otitis media and sinusitis. Group A streptococci infections of the central nervous system are exceedingly rare in the antibiotic era. The mechanism of infection is typically contiguous spread from existing infection or via direct inoculation. We present a case of an 81-year-old female with a past medical history of dementia, transient ischemic attacks, type 2 diabetes mellitus, hypertension, descending thoracic aortic aneurysm status post-stent placement in 2008, hepatitis C and hyperlipidemia who initially presented after being found unresponsive at home. Her initial symptoms were primarily of altered mentation and on evaluation was found to be in septic shock with suspicion of meningoencephalitis. Her initial workup included a computed tomography of head which was remarkable for left and right mastoid effusions. A lumbar puncture was performed with cloudy purulent fluid, an elevated white blood cell count, low glucose and elevated protein. The patient was initially started on broad spectrum coverage and soon had 4/4 blood cultures and cerebrospinal fluid cultures growing Streptococcus pyogenes . Empiric vancomycin, ceftriaxone and ampicillin were administered but switched to penicillin G in the setting of elevated total bilirubin and septic shock with multi-organ failure and narrowed to ampicillin–sulbactam based on sensitivities. Unfortunately, the patient deteriorated further due to septic shock and multi-organ failure and later died in the medical intensive care unit

A Case of Invasive Pneumococcal Infection with Septic Shock and Rare Complications

Invasive pneumococcus is a serious illness with potentially devastating outcomes. A 64-year-old female with a medical history of psoriatic arthritis and diabetes was transferred from an outside hospital for ventilator dependent respiratory failure and altered mental status. She initially presented with worsening back pain and was found to have leukocytosis with bandemia and acute renal failure but she was in septic shock upon arrival to our tertiary care center. Her blood cultures grew Streptococcus pneumoniae and MRI of the brain revealed pus within the posterior lateral ventricles and multiple infarcts. MRI of the spine revealed a psoas abscess. Transesophageal echocardiogram revealed mitral valve vegetation and her right eye developed endogenous endophthalmitis. She was treated with intravenous and intravitreal antibiotics and underwent drainage of the abscess with no improvement in mental status. Repeat imaging revealed multiple new thalamic, basal ganglia, and parietal lobe infarcts likely from septic emboli. After a protracted ICU stay, the patient’s family opted for comfort care. The incidence of invasive pneumococcal infections has declined rapidly since the advent of antibiotics and vaccines. With the growing incidence of antibiotic resistance as well as the emergence of new immunomodulating drugs for various pathologies, there is a concern that invasive infections will reemerge. Ventriculitis and endogenous endophthalmitis are very rare complications of pneumococcal bacteremia