Frequently Asked Questions

Culex® Questions

No. Although a dilution option is available if desired, the standard Culex® program will collect whole, undiluted blood for every sample. The exception to this is the mouse sampling protocol. Mice have very small amounts of blood. In order to deliver the sample without wasting any blood, it is necessary to use saline. This results in a diluted sample, but the dilution is, programmable, precise and recorded.

Part of the Culex® system is a missed sample detection feature. The sample detection happens at two points during collection. During the sample draw, the sensor looks for blood coming into the reservoir. If it is not there, it will flush and re-try up to 3 times. If the blood is present, it proceeds to delivery. During delivery, the sensor will read the blood throughout the entire process. If there is a change in the properties of the blood, the Culex® will stop the sample, delivering a “short”, but undiluted sample into the vial. The collected volume is recorded in the report.

The reservoir, which is filled with saline, has blood drawn into it from the bottom. Since blood is heavier than the saline, it will stay at the bottom of the reservoir. The blood is then pushed out the bottom of the reservoir and directed to the collection vial. That is, the last blood into the reservoir is the first blood out of the reservoir. The remaining blood is returned to the rat, along with a little saline to keep up fluid levels.

Yes, you can collect either.  Although the tubing set is filled with heparinized saline, this is solely to keep the blood from clotting in the lines, and does not affect clotting in a vial when serum is desired.  For plasma, simply choose a Culex® compatible vial with the correct anticoagulant, OR add the anticoagulant of your choice to the vial before loading vials into the collector.

2 minutes is the minimum time between blood samples.  For some catheters, or for larger sample volumes, minimum times may increase, depending on the connected volume (when using one of the ABC units).

We created a helpful reference that matches Culex® compatible vials with the appropriate collector and carousel.

The small volume collector holds 47 samples, and was originally designed for microdialysis.  It can be used with 300 µl chromacol vials. This collector can be used for blood sampling in rats or mice, or as a stand alone unit for dialysis.  The large volume collector holds 26 samples, and can be used with commercially available vials. It also has an accessory carousel that can adapt it for small volume vials.  It can be used for blood sampling from rodents or large animals, bile sampling, microdialysis, and dried blood spot sampling. Because of this, the large volume collector is the standard collector offered with a Culex® purchase, although clients who wish to substitute the small volume collector may do so.

A standard Culex® cart can accommodate four animals at a time.  For microdialysis sampling simultaneously with blood, you will need two collectors – one for blood and one for dialysates.  In this case, you will need side shelves for the Culex®, which are offered as an accessory part.

Keeping the urine cold minimizes evaporation out of the open sample vial, slows bacterial growth, and prevents possible evaporation of volatile compounds.When frozen according to the instructions, the I-cup keeps urine cold for approximately 16 hours.

BASi offers either 20 ml scintillation vials or 42 ml capped vials for use in the I-cup.  However, the cup will accommodate a variety of containers up to 50ml maximum volume—just make sure it’s short enough to sit under the glass funnel.

The TEND program flushes small amounts of saline into the catheter at regular intervals to keep it patent.  Catheter tending involves flushing 20 ul of heparinized saline through the catheter every 12 min for rats, and 10uL every 12 minutes for mice.  For Empis®, the TEND program (which is optional, and may be turned off), flushes 10 ul of saline every 12 minutes.

Yes. Our customers have partnered with DSI (Data Sciences International) and Emka Technologies for monitoring in both small and large animal models. This model is typically used for safety pharmacology studies. You can search our bibliography for some of the relevant publications.

This answer depends on your study and your test article, but if you are most interested in the vessel with the best patency rates, then arteries have better patency than veins. Because of this, we recommend collecting blood samples from the carotid or femoral arteries. If that is not possible, the femoral, jugular, and then portal vein are alternate options (in that order). Any vessel can be used for dosing.

Tubing sets are designed for single use, however, two-piece tubing sets and Rinse software programs do allow for some reuse. There is no specific guideline on the number of possible reuses- this is dependent on your lab, your compound, and your treatment of the tubing set.

No need to worry, the Culex® has been in use around the world for more than 20 years. In that time, we have had a single reported instance of compound sticking (Haloperidol). We use inert, high quality, biocompatible materials to build our consumables so that this interaction is minimized. However, if you are concerned, we recommend a simple in vitro test to assess your compound. Contact us for a copy of this protocol.

LV stands for Large Volume. This refers to the type of fraction collector, rather than the volume of sample. Large volume fraction collectors have 26 vial positions, while small volume (SV) have 47 via positions. 

Raturn™ Questions

No.  The Raturn responds to the movement of the animal, turning it in the opposite direction of movement to prevent tangling and twisting of tether lines and catheters.  The Raturn is a movement responsive cage that replaces the need for liquid swivels in automated dosing and blood sampling experiments. This eliminates problems with leakage and excess dead volume, and allows the collection of some activity data during experiments.  As the rat moves, an optical switch is triggered, which causes the cage to rotate in a direction opposite the rat’s movement (“unwinding” the rat and the tethers). This also allows for implantation of electronic monitoring devices and microdialysis probes concurrently with blood sampling catheters (as many as will fit through the central opening of the balance arm).

The data suggest that the Raturn is not stressful.  The rat will move around quite a bit in the Raturn when it is first placed in the cage, as it acclimates to its new environment, and then settle down.  The acclimation time to the Raturn is no different than the acclimation time to any other new environment, including a clean home cage. Comparative data on blood pressure, body temperature, and heart rate between a standard home cage and the Culex® is available in the literature.  (H. Kamendi et al., 2010 J.  Pharmacol. Toxicol. Methods  doi: 10.1016/j.vascn.2010.04.014). This whitepaper dives further into the topic of stress on the Raturn.

No. Through close observation and study, BASi has carefully selected the optimal speed of the Raturn for rodent models.

Animals, Surgery, and Handling

The most common animals to sample are rats and mice, although guinea pigs and hamsters are becoming more popular as well.  Swine, primates and canines have been sampled in the large animal units.

This depends on the surgery.  As a rule of thumb, an animal should recover to its presurgical state, based on signs such as weight, activity, food intake, etc.  Major abdominal surgery requires longer recovery times than catheterization or brain probe implantation. For many of our customers, a simple venous or arterial surgery requires 1-3 days of recovery. For a more invasive surgery, such as bile duct implants, the recovery time is commonly 5-7 days.

That depends on your IACUC and your regulations.  The most that we have ever placed is four lines. We do this for bile and blood studies, where the four catheters are: bile duct, duodenal, femoral vein for sampling, and jugular vein for dosing. In order for the animal to recover well from this surgery and be healthy, we recommend using animals 350g and above in these cases.

At BASi, we have placed three catheters in a single mouse (jugular vein, carotid artery, and gastric).  We did this in a bioavailability experiment. This requires a very good surgeon with a steady hand and eye.  Typically, only one or two catheters are placed in a mouse at a time.

Rat catheters: Jugular vein, femoral vein, femoral artery, carotid artery, gastrointestinal/duodenal, portal vein, and bile duct

Mouse catheters: Jugular vein, carotid artery, and gastrointestinal/duodenal

Swine catheter: Jugular vein optimized for minipig models

You can use any catheter or vendor that you prefer. The only critical detail is that the volume of the catheter is known and accurate so that the proper blood volumes are drawn. When programming a sampling protocol, you can either:

  1. Choose the BASi catheter option that most closely matches the dead volume on your catheter OR
  2. Use the ABC option for your protocol. This allows you to enter the connected volume for your catheter. Add the volume of the catheter + any other tubing that you have added to the fluid path (for example, the volume of a Catheter Access Port or Button).

Our customers regularly use Envigo, Charles River, Jackson Laboratories, and Taconic for precannulated mice and rats. You can ask the vendor to use BASi catheters. Alternatively, if you are working with a “standard” vendor catheter, then let us know and we’ll get you the right part number for a compatible Culex® tubing set.

In theory, an animal can be sampled as long as catheters are patent (and the study design is under the limit of blood that can be taken).  IACUC rules for length of experiment must be taken into account. At BASi, the IACUC limit on Culex® experiments is 28 days, although usually an animal is not used for more than one to two weeks.  In most pharmaceutical companies, studies run for no more than 24-48 hours.

Absolutely, it is especially important for animals that are singly housed to have enrichment. You may use any enrichment that does not interfere with the tether.  Any nesting material, nylabones, marbles, treats are just fine. Items such as huts, paper tubes, or any tunneling items are not compatible with a tethered setup.


You can easily use Empis for infusions without the Culex®.  It can also be used for microdialysis. You can also use it without a Raturn™ (ie, with a liquid swivel setup).  Just program in the connected volume of your swivel and dosing lines, so that your dose volumes will be correctly calculated by the instrument software.

Oral gavage, intravenous, intraperitoneal, intragastric, intraduodenal (or anywhere else in the intestine), intramuscular, and subcutaneous dosing routes are all possible.  In theory, if a catheter can be placed into a location, you can dose into it. Manual gavage dosing and tail vein dosing does require slightly different handling techniques than for non-Culex® studies and this may mean that two people are required. Dosing routes that are not compatible with Culex® include inhalation or aerosolized dosing, as well as intracerebral dosing of microvolumes.

Training and Service

Yes, we do.  Training is offered with each Culex® quote.  You can decide whether you want the training or not, although it is highly recommended for new users.  Training covers the use of the instrument, including setup, use in experiments, use of the Empis dosing system (if purchased with a Culex®), break down, care and maintenance.  Basic surgical training in rats is also offered. For customers who are experienced surgeons, a discounted training without surgical instruction can be offered. For customers who want more in depth training, an expanded package can be designed that may include use of mice on the Culex® (including surgery), microdialysis experiments, bile sampling or first pass metabolism experiments and surgery, etc.

No. Our instrument comes pre-assembled. There are a few steps to make sure it is ready to use, but these can easily be performed by the customer.

No, but we highly recommend an uninterruptible power supply (UPS), such as this one. Many labs have a built in back-up, but if it doesn’t immediately start during a power failure, then that can cause problems for a running protocol.

For IT, we recommend treating the computer as a system interface. If the computer must be networked, then make sure it cannot receive automatic updates. If an automatic update occurs, it can impact an ongoing study. Read more about this in the next question.

Yes, it is possible to purchase a compatible laptop from BASi. Alternatively, you may use another compatible computer. The Culex® works on the Windows operating platform. We strongly recommend using a computer with Windows 10 LTSC version (Long-Term Servicing Channel). This specific operating system must be procured through your corporate Microsoft Enterprise agreement. If you do not have access to Windows 10 LTSC, automatic updates should be disabled prior to for the duration of a study (details here). This will only temporarily prevent automatic updates, and will allow you to complete necessary updates at a convenient time. Networked computers may fall under blanket network rules of your IT organization, so you should check with IT to verify that this linked protocol for disabling will be effective.

We recommend a 14″ laptop with at least 2 USB-A ports (version 2.0, 3.0, or higher), Windows LTSC or Windows 10 Pro operating system, Intel or AMD CPU, minimum 8 GB RAM, 256GB SSD. All equipment connected to a Windows 10 computer should have 3.10 or higher firmware. 

Yes, the standard warranty is one year but an extended warranty is available for purchase.

Yes, we have several options, and can work with you to find the best one for your needs. Maintaining the equipment with a BASi service agreement significantly lengthens the life of the equipment, so we highly recommend it. Read more about the options here.

If a Culex® is malfunctioning, you can call BASi and we will make arrangements to have the unit returned and serviced at our facility.  If the instrument is still in the warranty period, the service will be free of charge under the terms of the warranty. If the warranty has expired, we will give you a quote for the repair and service of the instrument.

Culex® ABC (with swivel)

Yes you can.  The Culex® controller and collector are the same hardware whether you have an ABC or a full in vivo sampling system.  You will need to add a cart or frame and Raturn unit to your existing equipment to upgrade to a full Culex® system later on.

Yes you can.  You will need to buy an ABC stand and balance arm with swivel.  After that, your existing controller and collector can transfer onto the new stand and can be used in the ABC configuration.

Yes you can.  The only limitation is that the total connected volume must be less than 300 ul for a rodent ABC, and less than 10 ml for a large animal ABC.  It is a good idea to check and make sure that your swivel will fit into the mounting collar on the balance arm of the rodent ABC. For large animal sampling, the swivel should be mounted on the side of the cage or pen.

Lomir Biomedical makes animal jackets, and has custom Culex® jackets that were designed in conjunction with Culex® researchers for automated sampling.  However, if you prefer another vendor or another jacket style, feel free to use that.

We offer the same training services for the ABC’s as for a full Culex®.  When buying an instrument, training is always offered as a line item on the quote.