The Median Sternotomy: The Unkindest Cut of All? Pearls, Pitfalls, Aphorisms, & Myths.

While some have claimed that a median sternotomy is an 'unkind cut,' when this incision is performed, closed, and managed optimally, it can be one of the 'most kind cuts' used for major operations. The median sternotomy is the most commonly used incision for coronary artery bypass surgery, which is the most common operation performed in the United States at the current time. This approach is, of course, used for many other cardiac and thoracic operations, as well. It is, however, also one of the most misunderstood procedures in Surgery. Because it is an incision that even a novice surgical resident can perform, with proper supervision, the subtleties and nuances of not only opening but also of closing sternotomies are not often conveyed optimally to our trainees. In this treatise we will attempt to comprehensively address these subtleties, nuances, and misunderstandings, both for the benefit of our younger learners, but also, and more importantly, for the benefit of our patients.

The Effect of Comorbidities on Wound Healing.

Wound healing is affected by several factors. Preexisting diagnoses may significantly alter, delay, or inhibit normal wound healing. This is most commonly seen with chronic disorders, such as diabetes and renal failure, but also occurs secondary to aging and substance abuse. Less commonly, genetic or inflammatory disorders are the cause of delayed wound healing. In some cases, it is not the illness, but the treatment that can inhibit wound healing. This is seen in patients getting chemotherapy, radiation, steroids, methotrexate, and a host of other medications. Understanding these processes may help treat or avoid wound healing problems.

What Happens in (the) Vagus, Stays in (the) Vagus.

Many cardiothoracic operations put the nerves of the thorax at risk. In fact, nerve injuries are one of the most common reasons cited in malpractice cases brought against cardiothoracic surgeons. While all physicians learn about the nerves of the thorax during anatomy courses in medical school, little is written about avoiding injury to these important nerves in the cardiothoracic surgical literature. We have, therefore, embarked on an effort to collate information on the anatomy, function, and protection of these nerves, with which every cardiothoracic surgeon should be familiar. We will call this effort "The Nerve Protection Project." Acknowledging that the material to be covered is considerable, we will break the project into a series of editorials. The first installment in this series will address the anatomy and function of the vagus nerve and the protection of this nerve and its branches during cardiothoracic surgical operations, as they are in harm's way during many of these procedures.

In Through the Out Door: Tips and Tricks for Giving Retrograde Cardioplegia.

Antegrade cardioplegia delivery is the most commonly used delivery route. It is given into the aortic root or directly into the coronary ostia. However, there are many reasons to consider using the retrograde delivery of cardioplegia. This treatise will review the background and techniques for delivering retrograde cardioplegia.

String Music: Creating Coronary Artery and other Vascular Anastomoses.

The initial version of this treatise was written as I (Curt Tribble) was learning to do coronary anastomoses over 30 years ago, and I worried that I was not being taught very well how to go about doing them. It seemed to me that my teachers were channeling Dr. Alain Carpentier, who often answered questions about his mitral valve repair techniques by saying, "Oh, you just know." These frustrations were compounded by the fact that the best cardiovascular techniques books, including even those texts dedicated to coronary artery bypass techniques, did not describe these anastomotic techniques in detail, which remains the case to the present day [Kaiser 2007; Copeland 1986].

Complete fusion of a percutaneous aortic valve placed after ventricular assist device.

Severe aortic insufficiency following continuous flow left ventricular assist device (LVAD) placement requires intervention. Conventional corrective approaches are varied and morbid. Increasingly, percutaneous solutions, such as transcatheter aortic valve replacement (TAVR), have been used to rescue these patients. The unique flow characteristics in the aortic root following LVAD implantation may have unintended consequences to the TAVR leaflets. We describe the premature fusion of TAVR leaflets following 159 days of LVAD support. TAVR should be used with some caution in patients with continuous flow LVADs.

Variant Ionotropic Receptors in the Malaria Vector Mosquito Anopheles gambiae Tuned to Amines and Carboxylic Acids.

The principal Afrotropical human malaria vector mosquito, Anopheles gambiae, remains a significant threat to global health. A critical component in the transmission of malaria is the ability of An. gambiae females to detect and respond to human-derived chemical kairomones in their search for blood meal hosts. The basis for host odor responses resides in olfactory receptor neurons (ORNs) that express chemoreceptors encoded by large gene families, including the odorant receptors (ORs) and the variant ionotropic receptors (IRs). While ORs have been the focus of extensive investigation, functional IR complexes and the chemical compounds that activate them have not been identified in An. gambiae. Here we report the transcriptional profiles and functional characterization of three An. gambiae IR (AgIr) complexes that specifically respond to amines or carboxylic acids - two classes of semiochemicals that have been implicated in mediating host-seeking by adult females but are not known to activate An. gambiae ORs (AgOrs). Our results suggest that AgIrs play critical roles in the detection and behavioral responses to important classes of host odors that are underrepresented in the AgOr chemical space.

Antennal-expressed ammonium transporters in the malaria vector mosquito Anopheles gambiae.

The principal Afrotropical malaria vector mosquito, Anopheles gambiae remains a significant threat to human health. In this anthropophagic species, females detect and respond to a range of human-derived volatile kairomones such as ammonia, lactic acid, and other carboxylic acids in their quest for blood meals. While the molecular underpinnings of mosquito olfaction and host seeking are becoming better understood, many questions remain unanswered. In this study, we have identified and characterized two candidate ammonium transporter genes, AgAmt and AgRh50 that are expressed in the mosquito antenna and may contribute to physiological and behavioral responses to ammonia, which is an important host kairomone for vector mosquitoes. AgAmt transcripts are highly enhanced in female antennae while a splice variant of AgRh50 appears to be antennal-specific. Functional expression of AgAmt in Xenopus laevis oocytes facilitates inward currents in response to both ammonium and methylammonium, while AgRh50 is able to partially complement a yeast ammonium transporter mutant strain, validating their conserved roles as ammonium transporters. We present evidence to suggest that both AgAmt and AgRh50 are in vivo ammonium transporters that are important for ammonia sensitivity in An. gambiae antennae, either by clearing ammonia from the sensillar lymph or by facilitating sensory neuron responses to environmental exposure. Accordingly, AgAmt and AgRh50 represent new and potentially important targets for the development of novel vector control strategies.

Mutational analysis of cysteine residues of the insect odorant co-receptor (Orco) from Drosophila melanogaster reveals differential effects on agonist- and odorant-tuning receptor-dependent activation.

Insect odorant receptors are heteromeric odorant-gated cation channels comprising a conventional odorant-sensitive tuning receptor (ORx) and a highly conserved co-receptor known as Orco. Orco is found only in insects, and very little is known about its structure and the mechanism leading to channel activation. In the absence of an ORx, Orco forms homomeric channels that can be activated by a synthetic agonist, VUAA1. Drosophila melanogaster Orco (DmelOrco) contains eight cysteine amino acid residues, six of which are highly conserved. In this study, we replaced individual cysteine residues with serine or alanine and expressed Orco mutants in Flp-In 293 T-Rex cells. Changes in intracellular Ca(2+) levels were used to determine responses to VUAA1. Replacement of two cysteines (Cys-429 and Cys-449) in a predicted intracellular loop (ICL3), individually or together, gave variants that all showed similar increases in the rate of response and sensitivity to VUAA1 compared with wild-type DmelOrco. Kinetic modeling indicated that the response of the Orco mutants to VUAA1 was faster than wild-type Orco. The enhanced sensitivity and faster response of the Cys mutants was confirmed by whole-cell voltage clamp electrophysiology. In contrast to the results from direct agonist activation of Orco, the two cysteine replacement mutants when co-expressed with a tuning receptor (DmelOR22a) showed an ∼10-fold decrease in potency for activation by 2-methyl hexanoate. Our work has shown that intracellular loop 3 is important for Orco channel activation. Importantly, this study also suggests differences in the structural requirements for the activation of homomeric and heteromeric Orco channel complexes.