The Langendorff heart or isolated perfused heart assay is an ex vivo technique used in pharmacological and physiological research using animals and also humans. [1] Named after the German physiologist Oskar Langendorff, this technique allows the examination of cardiac contractile strength and heart rate without the complications of an intact animal or human. [2] After more than 100 years, this method is still being used. [3]
In the Langendorff preparation, the heart is removed from the animal's or human's body, severing the blood vessels; it is then perfused in a reverse fashion (retrograde perfusion) via the aorta, usually with a nutrient rich, oxygenated solution (e.g. Krebs–Henseleit solution or Tyrode's solution). The backwards pressure causes the aortic valve to shut, forcing the solution into the coronary vessels, which normally supply the heart tissue with blood. This feeds nutrients and oxygen to the cardiac muscle, allowing it to continue beating for several hours after its removal from the animal or human. This is a useful preparation because it allows the addition of drugs (via the perfusate) and observation of their effect on the heart without the complications involved with in vivo experimentation, such as neuronal and hormonal effects from living animal or human. [4] This preparation also allows the organ to be digested into individual cells by adding collagenase to the perfusate. This can be done before the experiment as a technique for cell harvesting, or after the experiment to measure its effects at the cellular level.
The first isolated perfused heart was created using frog tissue in 1866. [5]
Cardiopulmonary bypass (CPB) is a technique in which a machine temporarily takes over the function of the heart and lungs during surgery, maintaining the circulation of blood and oxygen to the body. The CPB pump itself is often referred to as a heart-lung machine or "the pump". Cardiopulmonary bypass pumps are operated by perfusionists. CPB is a form of extracorporeal circulation. Extracorporeal membrane oxygenation (ECMO) is generally used for longer-term treatment.
Dead space is the volume of air that is inhaled that does not take part in the gas exchange, because it either remains in the conducting airways or reaches alveoli that are not perfused or poorly perfused. It means that not all the air in each breath is available for the exchange of oxygen and carbon dioxide. Mammals breathe in and out of their lungs, wasting that part of the inhalation which remains in the conducting airways where no gas exchange can occur.
The adenosine receptors (or P1 receptors) are a class of purinergic G protein-coupled receptors with adenosine as the endogenous ligand. There are four known types of adenosine receptors in humans: A1, A2A, A2B and A3; each is encoded by a different gene.
Microdialysis is a minimally-invasive sampling technique that is used for continuous measurement of free, unbound analyte concentrations in the extracellular fluid of virtually any tissue. Analytes may include endogenous molecules to assess their biochemical functions in the body, or exogenous compounds to determine their distribution within the body. The microdialysis technique requires the insertion of a small microdialysis catheter into the tissue of interest. The microdialysis probe is designed to mimic a blood capillary and consists of a shaft with a semipermeable hollow fiber membrane at its tip, which is connected to inlet and outlet tubing. The probe is continuously perfused with an aqueous solution (perfusate) that closely resembles the (ionic) composition of the surrounding tissue fluid at a low flow rate of approximately 0.1-5μL/min. Once inserted into the tissue or (body)fluid of interest, small solutes can cross the semipermeable membrane by passive diffusion. The direction of the analyte flow is determined by the respective concentration gradient and allows the usage of microdialysis probes as sampling as well as delivery tools. The solution leaving the probe (dialysate) is collected at certain time intervals for analysis.
Machine perfusion (MP) is a technique used in organ transplantation as a means of preserving the organs which are to be transplanted.
Cardioplegia is a solution given to the heart during cardiac surgery, to minimize the damage caused by myocardial ischemia while the heart is paused.
Ischemic preconditioning (IPC) is an experimental technique for producing resistance to the loss of blood supply, and thus oxygen, to tissues of many types. In the heart, IPC is an intrinsic process whereby repeated short episodes of ischaemia protect the myocardium against a subsequent ischaemic insult. It was first identified in 1986 by Murry et al. This group exposed anesthetised open-chest dogs to four periods of 5 minute coronary artery occlusions followed by a 5-minute period of reperfusion before the onset of a 40-minute sustained occlusion of the coronary artery. The control animals had no such period of “ischaemic preconditioning” and had much larger infarct sizes compared with the dogs that did. The exact molecular pathways behind this phenomenon have yet to be fully understood.
Vascular permeability, often in the form of capillary permeability or microvascular permeability, characterizes the capacity of a blood vessel wall to allow for the flow of small molecules or even whole cells in and out of the vessel. Blood vessel walls are lined by a single layer of endothelial cells. The gaps between endothelial cells are strictly regulated depending on the type and physiological state of the tissue.
The Organ Care System (OCS) is a medical device designed by Transmedics to allow donor organs to be maintained for longer periods of time prior to transplant. The system mimics the elements of human physiology and keeps organs in an environment and temperature similar to the human body. The system allows for organ preservation that last longer than the standard organ preservation method of putting organs on ice, static cold storage, which can cause cold ischemia. When put on ice, organs begin to deteriorate about three to four hours after retrieval. On the other hand, the Paragonix SherpaPak Cardiac Transport System can offer uniform cooling by suspending the donor heart in a preservation solution and provides continuous temperature monitoring.
Myocardial perfusion imaging or scanning is a nuclear medicine procedure that illustrates the function of the heart muscle (myocardium).
Earl Howard Wood was an American cardiopulmonary physiologist who helped invent the G-suit, brought heart catheterization into a clinical reality and introduced dynamic volumetric computed tomography for the study of the heart and lungs.
Coronary perfusion pressure (CPP) refers to the pressure gradient that drives coronary blood pressure. The heart's function is to perfuse blood to the body; however, the heart's own myocardium must, itself, be supplied for its own muscle function. The heart is supplied by coronary vessels, and therefore CPP is the blood pressure within those vessels. If pressures are too low in the coronary vasculature, then the myocardium risks ischemia with subsequent myocardial infarction or cardiogenic shock.
Krebs–Henseleit solution, developed by Hans Krebs and Kurt Henseleit, is a solution containing sodium (Na), potassium (K), chloride (Cl), calcium (Ca), magnesium sulfate (MgSO4), bicarbonate (HCO3), phosphate (PO4), glucose, and sometimes supplemented with albumin, and tromethamine (THAM).
Retrograde perfusion (retroperfusion) is an artificial method of providing blood supply to an organ by delivering oxygenated blood through the veins. It may be performed during surgery that interrupts the normal arterial supply of blood to that organ.
Oskar Langendorff was a German physician and physiologist known primarily for his experiments on the isolated perfused heart, the so-called Langendorff Heart apparatus. In addition, he is credited with discoveries in respiration and in the conduction of impulses in the sympathetic and peripheral nervous system. His work has served as the basis for the use of retrograde perfusion in science and medicine.
The slice preparation or brain slice is a laboratory technique in electrophysiology that allows the study of neurons from various brain regions in isolation from the rest of the brain, in an ex-vivo condition. Brain tissue is initially sliced via a tissue slicer then immersed in artificial cerebrospinal fluid (aCSF) for stimulation and/or recording. The technique allows for greater experimental control, through elimination of the effects of the rest of the brain on the circuit of interest, careful control of the physiological conditions through perfusion of substrates through the incubation fluid, to precise manipulation of neurotransmitter activity through perfusion of agonists and antagonists. However, the increase in control comes with a decrease in the ease with which the results can be applied to the whole neural system.
An organ-on-a-chip (OOC) is a multi-channel 3-D microfluidic cell culture, integrated circuit (chip) that simulates the activities, mechanics and physiological response of an entire organ or an organ system. It constitutes the subject matter of significant biomedical engineering research, more precisely in bio-MEMS. The convergence of labs-on-chips (LOCs) and cell biology has permitted the study of human physiology in an organ-specific context. By acting as a more sophisticated in vitro approximation of complex tissues than standard cell culture, they provide the potential as an alternative to animal models for drug development and toxin testing.
Rottlerin (mallotoxin) is a polyphenol natural product isolated from the Asian tree Mallotus philippensis. Rottlerin displays a complex spectrum of pharmacology.
George Edward Billman is an American physiologist and professor at Ohio State University. After receiving a Ph.D from the University of Kentucky in 1980, Billman began his professional career at the University of Oklahoma. In 1984, he joined the Ohio State staff, where he became an associate professor in 1990 and a full professor in 1996.
Cell isolation is the process of separating individual living cells from a solid block of tissue or cell suspension. While some types of cell naturally exist in a separated form, other cell types that are found in solid tissue require specific techniques to separate them into individual cells. This may be performed by using enzymes to digest the proteins that binds these cells together within the extracellular matrix. After the matrix proteins have been digested, cells remain loosely bound together but can be gently separated mechanically. Following isolation, experiments can be performed on these single isolated cells including patch clamp electrophysiology, calcium fluorescence imaging, and immunocytochemistry.