An improved model for the induction of experimental adhesions.

BACKGROUND: The creation of ischemic buttons from parietal peritoneal tissue using a ligature is among the most established models for adhesion induction. However this model is plagued by slipping of ligatures and subsequent obliteration of the buttons when the animals mobilize postoperatively. Here we describe an improved model that involves creating the buttons with a backstitch ligature, and compare it to the traditional model. METHODS: A total of 160 ischemic buttons were created in 20 adult Wistar rats. Ischemic buttons in the control group (n = 80) were created using the traditional technique whereas ischemic buttons in the investigative group (n = 80) were created using the novel technique with a backstitch ligature. The resulting adhesions and the frequency of slipped ligatures were analyzed on postoperative day 10. RESULTS: Slipping of the ligature with obliteration of the button occurred in 18.8% (n = 15/80) of buttons in the control group and in 3.8% (n = 3/80) of buttons in the investigative group (p < .01). Adhesions formed to 69.2% (n = 45/65) of the remaining buttons in the control group and to 62.3% (n = 48/77) of the remaining buttons in the investigative group (p = .38). CONCLUSION: There was no statistically significant difference in adhesion quantity between the models. However, the novel technique significantly reduced postoperative slipping of the ligatures with obliteration of buttons. As a result, a greater number of intact buttons are available for data collection. Furthermore slipped sutures, which act as foreign bodies in uncontrollable locations, no longer confound adhesion formation to the remaining buttons.

Circadian periodicity of cerebral blood flow revealed by laser-Doppler flowmetry in awake rats: relation to blood pressure and activity.

Cardiovascular parameters such as arterial blood pressure (ABP) and heart rate display pronounced circadian variation. The present study was performed to detect whether there is a circadian periodicity in the regulation of cerebral perfusion. Normotensive Sprague-Dawley rats (SDR, approximately 15 wk old) and hypertensive (mREN2)27 transgenic rats (TGR, approximately 12 wk old) were instrumented in the abdominal aorta with a blood pressure sensor coupled to a telemetry system for continuous recording of ABP, heart rate, and locomotor activity. After 5-12 days, a laser-Doppler flow (LDF) probe was attached to the skull by means of a guiding device to measure changes in brain cortical blood flow (CBF). After the animals recovered from anesthesia, measurements were taken for 3-4 days. The time series were analyzed with respect to the midline estimating statistic of rhythm (i.e., mean value of a periodic event after fit to a cosine function), amplitude, and acrophase (i.e., phase angle that corresponds to the peak of a given period) of the 24-h period. The LDF signal displayed a significant circadian rhythm, with the peak occurring at around midnight in SDR and TGR, despite inverse periodicity of ABP in TGR. This finding suggests independence of LDF periodicity from ABP regulation. Furthermore, the acrophase of the LDF was consistently found before the acrophase of the activity. From the present data, it is concluded that there is a circadian periodicity in the regulation of cerebral perfusion that is independent of circadian changes in ABP and probably is also independent of locomotor activity. The presence of a circadian periodicity in CBF may have implications for the occurrence of diurnal alterations in cerebrovascular events in humans.