Spontaneous contractions and stretch-evoked responses of isolated lymph nodes

Summary In this study the spontaneous activities of prescapular lymph nodes, which were isolated from calves, goats and sheep and mesenteric lymph nodes of guinea-pigs were recorded and analysed in the frequency domain. Stretch-evoked contractions of the mesenteric lymph nodes were also recorded and their frequency characteristics analysed.The preparations were placed in a Krebs solution which was kept at 37° C and bubbled continuously with a mixture of 95% O₂ and 5% CO₂. The tension changes occurring in the lymph nodes were recorded. The patterns obtained were initially transformed into numerical values which were then used to obtain autocorrelation functions and power spectra, according to the time series analysis method. A passive stretch of 100 s duration was applied to the mesenteric lymph nodes and the responses were examined using the transient response-frequency characteristics method.It was observed that prescapular and mesenteric lymph nodes had spontaneous activities due to the contractions of the smooth muscles within the nodes. A frequency analysis of these contractions indicated that at least three contractile components were responsible for the contractions; these components contract within the frequency bands of 0.01–0.04 Hz, 0.05–0.07 Hz and 0.09–0.14 Hz respectively. It was also observed that the spontaneous activities could be regulated and synchronized by stretch. It is suggested that these contractions of the lymph nodes play an essential role in lymph propulsion within the nodes.