Show Advanced Search


Containing Text
- - -
Filter by author or institution
Filter by publication date
October, 2006
Filter by journal section

Filter by science education


Tensile Strength of Resorbable Biomaterials

JoVE 10471

Source: Peiman Shahbeigi-Roodposhti and Sina Shahbazmohamadi, Biomedical Engineering Department, University of Connecticut, Storrs, Connecticut

For over 4000 years, sutures have been used as a medical intervention. The earliest records indicate linen was the biomaterial of choice. Catgut, which is still in use today, was reportedly used to …

 Biomedical Engineering

Abdominal Exam IV: Acute Abdominal Pain Assessment

JoVE 10120

Source: Joseph Donroe, MD, Internal Medicine and Pediatrics, Yale School of Medicine, New Haven, CT

Abdominal pain is a frequent presenting concern in both the emergency department and the office setting. Acute abdominal pain is defined as pain lasting less than seven days, while an acute abdomen refers to …

 Physical Examinations II

Optical Materialography Part 2: Image Analysis

JoVE 10433

Source: Faisal Alamgir, School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA

The imaging of microscopic structures of solid materials, and the analysis of the structural components imaged, is known as materialography. Often, we would like to quantify the internal three-dimensional microstructure of a…

 Materials Engineering

Abdominal Exam III: Palpation

JoVE 10089

Source: Alexander Goldfarb, MD, Assistant Professor of Medicine, Beth Israel Deaconess Medical Center, MA

Abdominal palpation, if performed correctly, allows for examination of the large and relatively superficial organs; for a skilled examiner, it allows for assessment of the smaller and deeper structures as well. The amount of…

 Physical Examinations II

Regulation of Transpiration by Stomata

JoVE 11099

During photosynthesis, plants acquire the necessary carbon dioxide and release the produced oxygen back into the atmosphere. Openings in the epidermis of plant leaves is the site of this exchange of gasses. A single opening is called a stoma—derived from the Greek word for “mouth.” Stomata open and close in response to a variety of environmental cues.

Each stoma is flanked by two specialized guard cells that create an opening when these cells take up water. The transport of ions regulates the amount of water in guard cells. When trigger, pumps translocate hydrogen ions out of the guard cell. This hyperpolarization of the membrane causes voltage-gated potassium channels to open and allow solutes, such as potassium ions and sucrose, to enter the guard cells. The increased concentration of solutes drives water into the guard cells, which accumulates in the vacuole. As a result, the guard cells bow and deform into a kidney shape, creating the stoma opening. When solutes leave guard cells, water follows, resulting in guard cell shrinkage, and closure of the opening. A variety of environmental and internal signals triggers stomata opening. For example, blue light activates light-sensitive receptors on the cell surface that initiate a molecular cascade leading to stomata opening. In addition, when the concentration

 Core: Biology


JoVE 10743

Oxidative phosphorylation is a highly efficient process that generates large amounts of adenosine triphosphate (ATP), the basic unit of energy that drives many processes in living cells. Oxidative phosphorylation involves two processes—electron transport and chemiosmosis. During electron transport, electrons are shuttled between large complexes on the inner mitochondrial membrane and protons (H+) are pumped across the membrane into the intermembrane space, creating an electrochemical gradient. In the next step, protons flow back down their gradient into the mitochondrial matrix via ATP synthase, a protein complex embedded within the inner membrane. This process, called chemiosmosis, uses the energy of the proton gradient to drive the synthesis of ATP from adenosine diphosphate (ADP). The electron transport chain is a series of complexes that transfer electrons from electron donors to electron acceptors via simultaneous reduction and oxidation reactions, otherwise known as redox reactions. At the end of the chain, electrons reduce molecular oxygen to produce water. The shuttling of electrons between complexes is coupled with proton transfer, whereby protons (H+ ions) travel from the mitochondrial matrix to the intermembrane space against their concentration gradient. Eventually, the high concentration of protons in the interm

 Core: Biology

Bacterial Signaling

JoVE 10713

At times, a group of bacteria behaves like a community. To achieve this, they engage in quorum sensing, the perception of higher cell density that results in a shift in gene expression. Quorum sensing involves both extracellular and intracellular signaling. The signaling cascade starts with a molecule called an autoinducer (AI). Individual bacteria produce AIs that move out of the bacterial cell membrane into the extracellular space. AIs can move passively along a concentration gradient out of the cell, or be actively transported across the bacterial membrane. When cell density in the bacterial populations is low, the AIs diffuse away from the bacteria, keeping the environmental concentration of AIs low. As bacteria reproduce and continue to excrete AIs, the concentration of AIs increases, eventually reaching a threshold concentration. This threshold permits AIs to bind membrane receptors on the bacteria, triggering changes in gene expression across the whole bacterial community. Many bacteria are broadly classified as gram positive or gram negative. These terms refer to the color that the bacteria take on when treated with a series of staining solutions which were developed by Hans Christian Joachim Gram over a century ago. If bacteria pick up a purple color, they are gram-positive; if they look red, they are gram-negative. These stain colors are pic

 Core: Biology

X-ray Diffraction

JoVE 10446

Source: Faisal Alamgir, School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA

X-ray diffraction (XRD) is a technique used in materials science for determining the atomic and molecular structure of a material. This is done by irradiating a sample of the material with incident X-rays and then measuring the …

 Materials Engineering


JoVE 10153

Source: Jaideep S. Talwalkar, MD, Internal Medicine and Pediatrics, Yale School of Medicine, New Haven, CT

Through auscultation, the clinician is able "to eavesdrop on the workings of the body" to gain important diagnostic information.1 Historically, the term "auscultation" was synonymous with…

 Physical Examinations I

Proper Adjustment of Patient Attire during the Physical Exam

JoVE 10147

Source: Jaideep S. Talwalkar, MD, and Joseph Donroe, MD, Internal Medicine and Pediatrics, Yale School of Medicine, New Haven, CT

In order to optimize the predictive value of the physical examination, the provider must perform maneuvers correctly. The proper use of drapes is an important component of correctly performing…

 Physical Examinations I
More Results...