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CNRC - Mouse Metabolic Research Unit

Houston, Texas

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CNRC - Mouse Metabolic Research Unit
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CLAMS

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Capabilities

The MMRU CLAMS unit can house up to 76 mice at a time. This highly versatile system is capable of monitoring/controlling the following parameters, in virtually any permutation:

Feeding Mass Monitor

feeding mass monitor

The CLAMS system monitors the amount of food consumed by the mouse, and the frequency and duration of each meal. The combination of these parameters enables investigators to assess appetite and satiety.

Food, in powdered form, is placed in a feeding assembly that rests on a precision modified Mettler Toledo Balance (0.01-210 g range). The mouse accesses food by eating from a spring loaded dish through an anti-foraging guard; this guard also prevents full body access to the dish.

Spillage is accounted for by a larger dish, beneath the main food cup, that catches anything that spills over the edge. This spillage collection cup also rests on the balance, and though spilled food is not accessible to the mouse, the mass remains on the balance. The mass of food consumed is monitored continuously.

Feeding bout information is gathered by disturbances on the balance, following defined set values (as determined by the investigator) for "minimum valid weight" and "maximum idle time.” "Minimum valid weight" is defined as the minimum amount of food that must be consumed in order to record a feeding event. This value can be as little as 20 mg. "Maximum idle time" defines the time that must elapse between balance disturbances to define separate meals. Because food is eaten by the mouthful, the balance often settles between bites. By setting a time value for between bites, a series of bites can be grouped as a meal. Each meal is therefore associated with a start time, finish time, and mass of food consumed. Special Teflon feeders are available for use with high fat diets.

  • System capacity for this parameter: 76 mice (28 of which can simultaneously provide indirect calorimetry)
  • Maximum housing duration within these cages: 3 months
  • Equilibration period recommendation: 2 to 3 days
  • Weight range: 10 to 60 g

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Automated Food Access Control

The food access control system provides an automated means to control availability of food to the mouse. A computer controlled pneumatic arm opens and closes the food gate, depending upon time of day and/or mass of food consumed. A hinged food guard prevents harm to the mouse if it is feeding at the time at which the food gate closes. As the food gate closes, the food cup lowers out of the reach of the mouse. Food access is accomplished by defining four parameters: Time On (tON), Time Off (tOff), Duration (DUR; length of food access in hours), and Limit (mass of food consumed in grams). Examples of strategies for feeding regimes can be seen in the figure below.

This system enables pair feeding and meal feeding studies to be performed with a high level of reliability, precision, and accuracy. Indeed, the system can be programmed such that all mice within an experiment are provided access to equal amounts of food as that consumed by a specified "master" mouse or group of mice. In addition to being highly time efficient, this pair-feeding approach also avoids the one day delay between groups that occurs with the traditional manual approach to pair-feeding.

  • System capacity for this parameter: 48 mice
  • Maximum housing duration within these cages: 3 months
  • Equilibration period recommendation: 0 to 2 days
  • Weight range: 10 to 60 g

View graphs illustrating control of food access dependent on Weight (A), Time (B,C), or both (D). Examples given for wild-type (control) versus ob/ob mice.

Food access control graphs A-D

Activity/Locomotion Monitoring

The Columbus Instruments Opto M3 is a multi-channel activity monitoring system for the continuous measurement of ambulatory and total movement. Infra-red beams are projected at 0.5" spacing across the cage. During movement, the beams are broken by the mouse, and this sends signals to a central computer. The beams can detect movement along both the X (length of cage) and Z (height) axes. The system is a component of the calorimetry cages.

activity monitoring system Running wheel

Additionally, 12 of these cages can be modified to include free running wheels. The system records the number of revolutions, distance, and speed run, and the time of day when the activity occurs.

  • System capacity for this parameter: 28 mice
  • Maximum housing duration within these cages: 1 month
  • Equilibration period recommendation: 2 to 3 days
  • Weight range: 10 to 60 g

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Body Temperature Telemetry

Emitter

Columbus Instruments has teamed with Mini Mitter® for continuous monitoring of core body temperature within the CLAMS. The revolutionary transmitting device does not require batteries, and thereby eliminates the time and expense involved in refurbishment. Through the use of the ER-4000 Energizer-Receiver system (a component of the calorimetry cages), the transmitter (G2 E-Mitter; 1.5g weight; surgically implanted within the abdominal cavity) is energized via magnetic impulses. The device continually transmits body temperature information that is recorded by the programmed computer.

  • System capacity for this parameter: 16 mice
  • Maximum housing duration within these cages: 1 month
  • Recovery from surgery: 2 weeks
  • Equilibration period recommendation: 2 to 3 days
  • Weight range: 20 to 60 g

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Calorimetry System (with or without free running wheels)

The calorimetry system monitors oxygen and carbon dioxide concentrations at the inlet and outlet ports of a chamber through which a known volume of air flows. This information enables the calculation of oxygen consumption, carbon dioxide production, and respiratory exchange ratio, providing accurate and reproducible data on whole body energy expenditure.

The MMRU has two calorimetry systems permitting either 1 experiment with up to 28 mice, or 2 experiments with up to 16 and 12 mice, respectively, to be run concurrently. The two systems have different configurations: automated food access control and telemetry are available on the 16 cage system, and voluntary wheel running capability with food monitoring available on the 12 cage system.

  • System capacity for this parameter: 28 mice (12 and 16)
  • Maximum housing duration within these cages: 1 month
  • Equilibration period recommendation: 2 to 3 days
  • Weight range: 10 to 60 g

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Treadmill with Calorimetry

treadmill with calorimetryThe modular treadmill is comprised of one master lane and one slave lane. These are enclosed in individual chambers, with each housing an exercise belt, associated pulleys and electrical stimuli. The chambers have a "Metabolic Option" that provides measurement of VO2, VCO2, RER, and, energy expenditure. The treadmill chambers provide each mouse with 1.75" (4.4 cm) of headroom and are 2" (5 cm) wide. The length of the running surface is 12" (25.4 cm), and the volume of the enclosure is approximately 2 liters. The incline of each treadmill lane is individually adjustable in 5° increments from -10° to +25°. Tread speed is adjustable over the range of 2 to 50 meters per minute with a resolution of 0.1 meters per minute. The mouse comes into contact with PVC, Lexan and UHMW (ultra-high molecular weight plastic) materials within the treadmill.

The lanes are equipped with stimulus grids to promote running. A scrambled electrical stimulus is presented as a series of 200 millisecond pulses with an adjustable pulse repetition rate of 1 to 4 per second. The intensity is also adjustable from 0.35mA to 3.4mA. LED lamps indicate stimulus grid excitation and switches are provided to engage or terminate stimulus in each lane.

For Reservations: Please e-mail Dr. Fiorotto or Firoz Vohra with your request and specify: date(s), time(s), and how long you wish to use it for.

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mouse treadmill

Treadmill

Exer-3/6 (Columbus Instruments) is the third generation, general purpose three (rats) or six (mice) lane animal exerciser utilizing single belt construction with opaque PVC dividing walls suspended over the tread surface. An included drive motor controller provides smooth and continuous adjustment of speed in the range 2.5-100 m/m in 0.1 meter/minute increments per second. The treadmill inclination can be altered from -15° to +25° in 5° increments. The exercising belt is made with special material that facilitates the animals' grip and is easy to clean. The treadmill has the electrical stimulus system option composed of six shock grids, each with individual on/off switches. Stimulus intensity is adjustable and LED lamps indicate which stimulus grid is active. Software included, provides remote control over the treadmill and settings for speed and acceleration, records distance traveled and data is saved in CSV format for Excel or similar statistical software.

For Reservations: Please e-mail Dr. Fiorotto or Firoz Vohra with your request and specify: date(s), time(s), and how long you wish to use it for.

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Request procedure

  1. Contact Dr. Fiorotto or other members of the MMRU Steering Committee and discuss experimental needs (types of measurements, animal numbers, mouse size, diet, responsibilities of the investigator).
  2. Submit an amendment to IACUC to include these measurements on your protocol if you don't already have this. The following are descriptions you can use for some of the measurements.
    • Energy expenditure will be measured in the mice using the CLAMS instrument located in the CNRC.
    • The mice will be transferred to CNRC animal facility where they will be singly housed and allowed to equilibrate for up to 1 week in standard caging (for outside PIs).
    • They will be housed for 48-72 hours in specialized CLAMS feeder cages to familiarize themselves with the feeding system and to estimate food intake. They then will be transferred to the calorimetry chambers for 72 hours for simultaneous monitoring of food intake, activity, and energy expenditure. To determine energy expenditure, the system monitors O2 and CO2 gas fractions at both the inlet and outlet ports of each chamber through which a known flow of air is passing. The gas fraction and flow measurements are used to compute VO2, VCO2, RER (respiratory exchange ratio) and heat production (energy expenditure). Food intake and feeding pattern are measured automatically from the weight of feed removed from specialized feed hoppers installed within the chamber. Activity in the x and z axes is estimated by monitoring the number of infra-red beams broken by the mouse movements.* Precise details of the measurements can be found in protocol AN5020.
    • At the end of the study, the mice will be returned from the CNRC to Taub animal facility (for outside PIs).
    • If you wish to measure Resting Metabolic Rate include the following sentence at this point: "On the last day that the mice are in the calorimetry cages, the feeders will be closed at 6 am (at lights on) and energy expenditure measured for an additional 8 hours so that resting metabolic rate can be estimated."
  3. Submit the completed online MMRU application form. This will be reviewed by Dr Marta Fiorotto. The purpose of this review process is twofold, to ensure:
    • that all appropriate institutional approvals for use are in place (e.g., IACUC protocol, IBC protocol, and transfer request); and
    • the efficient scheduling of MMRU capabilities so that all investigators have access to the MMRU in a fair and unbiased manner.
  4. You will be contacted within 72 hours with optional dates; confirm schedule with Dr. Fiorotto within 24 hours so that you don't lose your spot. For investigators outside the CNRC, the time frame requested must take into consideration the transfer of the mice.

If your mice are housed outside the CNRC, proceed to Step 5. Otherwise, proceed to Step 9.

  1. Contact Chris Southern, CNRF Manager (713-798-6735; southern@bcm.edu) immediately to obtain assurance that your mice are coming from a clean room in either TMF or the TMF tower facility and that there is no evidence of disease in the room in which they are currently housed. If these assurances cannot be provided, mice will be refused entry to the CNRC CNRF until they have been quarantined at Taub and verification is obtained that they are "clean".
  2. Our facility has limited available mouse space. Once Chris Southern is assured that it is OK to bring your mice into the CNRF, arrangements need to be made with him to ensure there is sufficient space in our facility to house the mice. Also, Chris Southern will need to know what will happen to the mice after they are studied in the MMRU.
  3. To transfer the mice, fill out an online transfer request found on the CCM home page under "Forms". The mice will be moved to CNRF room 1068. Once approved, you will be asked to identify the cages you want moved. You do not move the mice; CCM moves them, according to federal and TMC policies. The transfer can be done quickly once you have IACUC approval and your MMRU time is booked.
  4. The next step is to obtain access card to the CNRF. Fill out and print the CNRC ACCESS CARD REQUEST form and give it to Michael LeCompte, (CNRC Security Manager, located at the front desk of CNRC). The form verifies that you have an IACUC approved animal protocol and that all personnel that require access to the CNRF are listed on and approved to work on the protocol. In the "Specific job-related functions/ responsibilities that require a CNRC access card" block of the form, please include the Protocol Number, Protocol Title, the Name of Primary Investigator and the Expected Termination Date of the Project. The CNRC Access Request must be submitted and signed off by Dr. Marta Fiorotto, director of the MMRU, as the approving sponsor.
  5. When you are all set, contact Firoz Vohra, MMRU Engineer, fvohra@bcm.edu, 713-798-6756 to finalize details of your experiment.

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