Technique for performance and evaluation of parapharyngeal hypophysectomy in mice.

Mice at our institution were hypophysectomized to evaluate the effects of growth hormone on the expression of a transfected human factor IX gene. The hypophysectomy was performed in-house by using a parapharyngeal approach modified from previously published surgical techniques. Modifications included: 1) choice of ketamine-xylazine and isoflurane for anesthesia, with butorphanol for postoperative analgesia; 2) use of a V-trough for positioning mice correctly and consistently; 3) selection of increasing sizes of dental burrs to create a foramen in the cranial base through which the pituitary gland was removed; and 4) disuse of a tracheotomy for airway patency. In addition, verification of successful gland removal was assessed by measuring major urinary protein (MUP) in the urine; presence of MUP indicated incomplete hypophysectomy. This assessment enabled antemortem determination of surgical success by using a single urine collection. Each of these modifications contributed to the success of the surgical procedure. We had a safe and reliable anesthetic regimen, consistent positioning of the surgical patient, and smooth and rapid penetration of the cranium. In our experience, the tracheotomy described in previous techniques was unnecessary, as the mice tolerated brief periods of apnea (approximately 5 sec maximum) while the trachea was retracted. Here we seek to provide details that will assist those interested in learning this technique and that will reduce the number of mice needed for practice. Other applications include a method of evaluating the production of growth hormone without euthanizing the animal.

Comparison of simultaneous measurement of mouse systolic arterial blood pressure by radiotelemetry and tail-cuff methods.

Radiotelemetry of mouse blood pressure accurately monitors systolic pressure, diastolic pressure, heart rate, and locomotor activity but requires surgical implantation. Noninvasive measurements of indirect systolic blood pressure have long been available for larger rodents and now are being reported more frequently for mice. This study compared mouse systolic arterial blood pressure measurements using implanted radiotelemetry pressure transducer with simultaneous tail-cuff measurements in the same unanesthetized mice. The pressure range for comparison was extended by inducing experimental hypertension or by observations of circadian elevations between 3 AM and 6 AM. Both trained and untrained tail-cuff operators used both instruments. Every effort was made to follow recommended manufacturer's instructions. With the initial flow-based tail-cuff instrument, we made 671 comparisons (89 sessions) and found the slope of the linear regression to be 0.118, suggesting poor agreement. In an independent assessment, 277 comparisons (35 sessions) of radiotelemetry measurements with the pulse based tail-cuff instrument were made. The slope of the linear regression of the simultaneous measurements of systolic pressures was 0.98, suggesting agreement. Bland-Altman analysis also supported our interpretation of the linear regression. Thus although reliable systolic pressure measurements are possible with either tail-cuff or radiotelemetry techniques, in our hands some tail-cuff instruments fail to accurately detect elevated blood pressures. These data, however, do not distinguish whether this instrument-specific tail-cuff failure was due to operator or instrument inadequacies. We strongly advise investigators to obtain an independent and simultaneous validation of tail-cuff determinations of mouse blood pressure before making critical genotyping determinations.