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Urine:

Introduction to Titration

JoVE 5699

Source: Laboratory of Dr. Yee Nee Tan — Agency for Science, Technology, and Research


Titration is a common technique used to quantitatively determine the unknown concentration of an identified analyte.1-4 It is also called volumetric analysis, as the measurement of volumes is critical in titration. There are many types of titrations…

 General Chemistry

Osmoregulation in Fishes

JoVE 10989

When cells are placed in a hypotonic (low-salt) fluid, they can swell and burst. Meanwhile, cells in a hypertonic solution—with a higher salt concentration—can shrivel and die. How do fish cells avoid these gruesome fates in hypotonic freshwater or hypertonic seawater environments?

Fish employ osmoregulatory strategies to balance bodily levels of water and dissolved ions (i.e., solutes), such as sodium and chloride. Imagine two solutions separated by a membrane that is permeable to water. Although water crosses the membrane in both directions, more water flows (i.e., there is net water movement) into the solution with a higher solute concentration; this is the essential part of osmosis. Osmoconformers maintain an internal solute concentration—or osmolarity—equal to that of their surroundings, and so they thrive in environments without frequent fluctuations. All osmoconformers are marine animals, although many marine animals are not osmoconformers. Most fish are osmoregulators. Osmoregulators maintain internal osmolarity independent of the environment, making them adaptable to changing environments and equipped for migration. Osmosis tends to equalize ion concentrations. Since fish require ion levels different from environmental concentrations, they need energy to maintain a solute gradient that optimizes

 Core: Biology

Fundamentals of Breeding and Weaning

JoVE 10293

Source: Kay Stewart, RVT, RLATG, CMAR; Valerie A. Schroeder, RVT, RLATG. University of Notre Dame, IN


Millions of mice and rats are bred for use in biomedical research each year. Worldwide, there are several large commercial breeding facilities that supply mice to research laboratories, but many facilities choose to also breed mice and…

 Lab Animal Research

Pelvic Exam I: Assessment of the External Genitalia

JoVE 10144

Source:
Alexandra Duncan, GTA, Praxis Clinical, New Haven, CT
Tiffany Cook, GTA, Praxis Clinical, New Haven, CT
Jaideep S. Talwalkar, MD, Internal Medicine and Pediatrics, Yale School of Medicine, New Haven, CT


The pelvic exam can feel invasive to patients, so it is important to do everything possible to…

 Physical Examinations II

The ELISA Method

JoVE 5061

An enzyme-linked immunosorbent assay (ELISA) is typically performed to detect the presence and/or amount of a target protein of interest within an experimental sample. Detection of the target protein is made possible by antibodies, which make the ELISA an immunoassay. Through a series of incubation and washing steps, these antibodies, which are frequently linked, or conjugated, to an enzyme,…

 Basic Methods in Cellular and Molecular Biology

Endocrine Signaling

JoVE 10719

Endocrine cells produce hormones to communicate with remote target cells found in other organs. The hormone reaches these distant areas using the circulatory system. This exposes the whole organism to the hormone but only those cells expressing hormone receptors or target cells are affected. Thus, endocrine signaling induces slow responses from its target cells but these effects also last longer. There are two types of endocrine receptors: cell surface receptors and intracellular receptors. Cell surface receptors work similarly to other membrane bound receptors. Hormones, the ligand, bind to a hormone specific G-protein coupled receptor. This initiates conformational changes in the receptor, releasing a subunit of the G-protein. The protein activates second messengers which internalize the message by triggering signaling cascades and transcription factors. Many hormones work through cell surface receptors, including epinephrine, norepinephrine, insulin, prostaglandins, prolactin, and growth hormones. Steroid hormones, like testosterone, estrogen, and progesterone, transmit signals using intracellular receptors. These hormones are small hydrophobic molecules so they move directly past the outer cell membrane. Once inside, and if that cell is a target cell, the hormone binds to its receptor. Binding creates a conformational change in the receptor

 Core: Biology

Antibody Generation: Producing Monoclonal Antibodies Using Hybridomas

JoVE 10499

Source: Frances V. Sjaastad1,2, Whitney Swanson2,3, and Thomas S. Griffith1,2,3,4
1 Microbiology, Immunology, and Cancer Biology Graduate Program, University of Minnesota, Minneapolis, MN 55455
2 Center for Immunology, University of Minnesota, Minneapolis, MN 55455
3 Department of Urology, University of Minnesota, Minneapolis, MN 55455
4 Masonic…

 Immunology

Considerations for Rodent Surgery

JoVE 10285

Source: Kay Stewart, RVT, RLATG, CMAR; Valerie A. Schroeder, RVT, RLATG. University of Notre Dame, IN


The Guide for the Care and Use of Laboratory Animals1 dictates that rodent survival surgery be performed aseptically. Aseptic technique utilizes specific practices that minimize the contamination of the surgical site, including…

 Lab Animal Research

Method of Standard Addition

JoVE 10201

Source: Laboratory of Dr. Paul Bower - Purdue University


The method of standard additions is a quantitative analysis method, which is often used when the sample of interest has multiple components that result in matrix effects, where the additional components may either reduce or enhance the analyte absorbance signal. That results in…

 Analytical Chemistry

Calibration Curves

JoVE 10188

Source: Laboratory of Dr. B. Jill Venton - University of Virginia


Calibration curves are used to understand the instrumental response to an analyte and predict the concentration in an unknown sample. Generally, a set of standard samples are made at various concentrations with a range than includes the unknown of interest and the…

 Analytical Chemistry
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