July 2012: This Month in JoVE
Seeing Science Differently
How a Pioneering Video Journal Brought Research to Life
Introduction
Imagine trying to learn a complex lab technique from a dense, text-heavy scientific paper. Now, imagine instead watching a short video where a researcher demonstrates the procedure step-by-step. This is the revolutionary idea behind the Journal of Visualized Experiments (JoVE), a peer-reviewed scientific video journal established to overcome two major challenges in science: the poor reproducibility of experiments and the significant time investment required to learn new methods.
Visual Learning
Step-by-step video demonstrations make complex techniques easier to understand and replicate.
Enhanced Reproducibility
Visual protocols reduce misinterpretation and improve experimental consistency across labs.
In July 2012, JoVE continued its mission by launching a brand new Applied Physics section. This expansion highlighted the journal's growing influence and its commitment to making diverse scientific fields more accessible. A key feature that month was a visit to The George Washington University to film a sophisticated technique for studying heart function, known as a modified Langendorff preparation6 . This article will explore the inner workings of JoVE and take a deep dive into the cardiac physiology research that its readers discovered in July 2012.
The JoVE Revolution: More Than Just Words on a Page
Founded in 2006, JoVE is the world's first peer-reviewed scientific video journal. Its core premise is that visual demonstration significantly enhances the understanding and replication of experimental methods. As one researcher from Western Sydney University noted, "JoVE helps make experimental techniques more accessible. By seeing methods in action, researchers can better replicate experiments and avoid misinterpretation. It improves reproducibility and saves time in the lab"3 .
"JoVE helps make experimental techniques more accessible. By seeing methods in action, researchers can better replicate experiments and avoid misinterpretation."
The Publishing Process
Manuscript Submission
Authors submit a written manuscript detailing their experimental method.
Peer Review
The manuscript undergoes rigorous editorial and peer review to ensure scientific validity.
Video Production
JoVE's professional team collaborates with researchers to create a video script and film the experiment.
Publication
The final video is edited, narrated, and published online alongside the text manuscript.
This innovative approach has made JoVE an invaluable resource, trusted by over 1,800 universities and companies worldwide3 .
1,800+
Universities and companies worldwide trust JoVE
A Closer Look: The Langendorff Heart Preparation
The modified Langendorff preparation filmed at The George Washington University is a classic and vital technique in cardiac physiology. It allows researchers to study an isolated mammalian heart in a controlled environment, free from the influence of hormones and neural signals from the rest of the body.
Isolated Heart Model
The Langendorff preparation allows study of cardiac function without interference from other bodily systems.
In this setup, a heart (often from a rodent such as a rat or guinea pig) is carefully removed and connected to a specialized perfusion system via the aorta. A temperature-controlled, oxygen-rich nutrient solution is then pumped through the coronary arteries, which nourish the heart muscle. Because the solution is delivered under constant pressure, the heart continues to beat on its own, allowing scientists to directly measure its function.
Key Advantages:
- Controlled experimental environment
- Direct measurement of cardiac function
- Elimination of neural and hormonal influences
- Ability to test pharmacological interventions
Methodology: A Step-by-Step Guide
While the exact protocol for the modified Langendorff preparation from July 2012 is not detailed in the search results, the following steps represent a generalized overview of the core procedure, reflecting common practices in this field and the meticulous approach documented in JoVE videos.
Preparation of the System
The Langendorff apparatus is assembled and sterilized. The perfusion solution, typically a modified Krebs-Henseleit buffer, is prepared, bubbled continuously with a mixture of 95% O₂ and 5% CO₂ to maintain proper oxygen and pH levels, and warmed to 37°C.
Heart Excision
The animal is anesthetized according to ethical guidelines. The chest is opened, and the heart is rapidly excised and immediately placed in ice-cold buffer to slow metabolism and protect the tissue.
Cannulation
The aorta is identified and carefully attached to a cannula on the perfusion apparatus. This is a critical step to ensure proper flow of the solution.
Initiation of Perfusion
The flow of oxygenated, warm buffer is started, retrogradely perfusing the heart through the coronary arteries. A healthy heart will resume beating within seconds.
Stabilization
The heart is allowed to stabilize for a period of 20-30 minutes to recover from the excision procedure and establish a stable rhythmic beat.
Experimental Intervention
Once stable, the heart is subjected to specific experimental conditions. This could involve measuring baseline function, inducing ischemia (lack of blood flow) to model a heart attack, or administering a drug to test its effects.
Data Collection
Throughout the experiment, key functional parameters are recorded using specialized equipment, which may include a balloon inserted into the left ventricle to measure pressure changes.
Results and Analysis: Decoding the Heart's Language
The data collected from a Langendorff experiment provides a direct window into cardiac performance. The most critical measurements relate to the heart's pumping ability and its energy consumption. Researchers analyze changes in these parameters to understand the effects of diseases, drugs, or other experimental manipulations.
For example, an experiment might test a new compound believed to protect the heart during a heart attack. The results would show whether hearts treated with this compound recover stronger pumping function after a period of ischemia compared to untreated hearts.
| Metric | Description | Scientific Importance |
|---|---|---|
| Left Ventricular Developed Pressure (LVDP) | The difference between the maximum pressure during contraction (systole) and the minimum pressure during relaxation (diastole). | A primary indicator of the heart's contractile strength and pumping ability. |
| Heart Rate (HR) | The number of heartbeats per minute. | Determines the rate of cardiac work and oxygen consumption. |
| Coronary Flow Rate (CF) | The volume of perfusion solution passing through the coronary arteries per unit of time. | Reflects the resistance and health of the coronary blood vessels. |
| Rate-Pressure Product (RPP) | Calculated as Heart Rate x LVDP. | A comprehensive index of cardiac workload and oxygen demand. |
Experimental Data: Simulating a Cardioprotection Study
To illustrate how the Langendorff setup is used in practice, consider the following hypothetical data from a study on ischemic preconditioning—a phenomenon where short, non-damaging periods of ischemia paradoxically protect the heart from a subsequent, longer ischemic insult.
| Experimental Group | Baseline LVDP (mmHg) | Post-Ischemia LVDP (mmHg) | % Recovery of LVDP |
|---|---|---|---|
| Control Hearts | 85.2 ± 5.1 | 42.5 ± 6.8 | 49.9% |
| Preconditioned Hearts | 83.7 ± 4.6 | 65.4 ± 5.3 | 78.1% |
This simulated data demonstrates a powerful finding: hearts that underwent the preconditioning protocol recovered a significantly greater proportion of their original pumping function compared to control hearts. This suggests that the heart's own protective mechanisms were successfully activated.
Furthermore, researchers can measure the release of specific proteins or metabolites in the coronary effluent (the solution that has passed through the heart) to assess cellular damage.
| Experimental Group | Lactate Dehydrogenase (LDH) Release (U/L) |
|---|---|
| Control Hearts | 45.3 ± 8.1 |
| Preconditioned Hearts | 18.9 ± 5.4 |
The lower level of LDH, a marker of cell death, in the preconditioned group provides biochemical confirmation that the protective intervention successfully preserved the integrity of the heart muscle cells.
Cardiac Function Recovery After Ischemia
The Scientist's Toolkit: Research Reagent Solutions
A successful experiment relies on a suite of carefully prepared materials. The table below lists essential components for a Langendorff preparation and their critical functions.
| Item / Reagent | Function in the Experiment |
|---|---|
| Krebs-Henseleit Buffer | A physiological salt solution that provides ions, nutrients, and a buffering system to mimic the blood's chemical environment and keep the heart alive. |
| Carbogen Gas (95% O₂ / 5% CO₂) | Oxygenates the perfusion buffer to supply the heart's high metabolic demand and maintains the solution at a physiological pH of 7.4. |
| Langendorff Apparatus | The core system comprising a reservoir for buffer, a heating jacket, a bubble trap, a peristaltic pump, and a cannula for perfusing the isolated heart. |
| Temperature-Controlled Water Bath | Maintains the perfusion solution at a constant 37°C, which is critical for normal cardiac function and enzyme activity. |
| Ventricular Balloon | A small, fluid-filled balloon inserted into the left ventricle and connected to a pressure transducer to directly measure contractile force. |
| Data Acquisition System | Hardware and software that record, display, and analyze real-time physiological data (e.g., pressure, heart rate). |
| Calcium Chloride (CaCl₂) | An essential component of the perfusion buffer, calcium is required for the excitation-contraction coupling that drives each heartbeat. |
Buffer Solutions
Properly formulated buffers maintain physiological conditions for the isolated heart.
Temperature Control
Maintaining 37°C is critical for normal cardiac function and enzyme activity.
Oxygenation
Carbogen gas provides oxygen and maintains proper pH in the perfusion solution.
Conclusion: A Lasting Impact
The July 2012 issue of JoVE, with its new Applied Physics section and its detailed demonstration of the Langendorff technique, is a perfect snapshot of the journal's enduring mission. By marrying the established rigor of academic publishing with the intuitive power of video, JoVE has created a unique and powerful platform for sharing knowledge. It transforms complex procedures from abstract concepts into tangible, repeatable actions.
Enhanced Reproducibility
Visual protocols reduce ambiguity and improve consistency across laboratories, strengthening the scientific method.
Accelerated Research
Researchers save valuable time by learning techniques through video rather than text descriptions alone.
This approach not only accelerates the pace of individual research projects but also strengthens the very foundation of science by enhancing reproducibility—a cornerstone of the scientific method. As JoVE continues to grow and document cutting-edge methodologies across an ever-widening range of disciplines, it empowers a global community of scientists to build upon each other's work more efficiently and reliably, truly making science seen.