title: Study of cellular response induced by low intensity ultrasound frequency sweep pattern on myelomonocytic lymphoma U937 cells.
abstract: OBJECTIVE
  This study will analyze the mechanical effects (immediate lysis) and biological effects (cell survival, apoptosis, cell cycle) on U937 cells subjected to different sonication conditions with increasing and decreasing frequencies and burst rate (number of burst of a repeating signal in a specific time unit), in order to determine the best conditions of sonication to produce high mortality, apoptosis and inhibition of hyperproliferation.
  
  
  METHODS
  Cells are been stressed by pulse wave ultrasounds with increasing and decreasing frequencies between 400 and 620 kHz, at burst rates of 0.5, 10, 50 Hz and 50 % duty cycle (percentage of one period in which a signal is active), ultrasound intensities (spatial average-temporal peak) 0.045 and 0.09 W/cm(2). The sonication durations were 90 and 180 s.
  
  
  RESULTS
  The decreasing mode was found to be better than the increasing mode for 10 and 50 Hz burst rates, while at 0.5 Hz the increasing mode gave better results for the time of 180 s. For 10 Hz burst rate, decreasing frequency, 180 s, 0.09 W/cm(2), 20 % survival rate was found; after 6-h incubation, cells showed 13 % of early apoptosis and 11 % of late apoptosis. For these conditions of sonication, the hyperproliferation of cells was inhibited.
  
  
  CONCLUSIONS
  Survival rate decreases for increasing intensity and duration with each burst rate. The best performance is decreasing mode in a range between 620 and 400 kHz, duty cycle 50 %, burst rate 10 Hz. In these conditions after 180 s duration, the average survival rate is 20 %, the survived cells manifest apoptosis after 6-h incubation and hyperproliferation is prevented. The results seem to lead toward a non-invasive and effective purging of leukemic cells.
authors.affiliation: Dipartimento di Meccanica, Matematica e Management, Politecnico di Bari, Viale Japigia 182, 70126 Bari, Italy.
authors.forename: Mariantonietta
authors.initials: M
authors.lastname: Ivone
authors.affiliation: Dipartimento di Meccanica, Matematica e Management, Politecnico di Bari, Viale Japigia 182, 70126 Bari, Italy.
authors.forename: Carmine
authors.initials: C
authors.lastname: Pappalettere
authors.affiliation: Department of Anatomy, Fukuoka University, School of Medicine, 7-45-1 Nanakuma, Fukuoka, 814-0180 Japan.
authors.forename: Akiko
authors.initials: A
authors.lastname: Watanabe
authors.affiliation: Department of Anatomy, Fukuoka University, School of Medicine, 7-45-1 Nanakuma, Fukuoka, 814-0180 Japan.
authors.forename: Katsuro
authors.initials: K
authors.lastname: Tachibana
mesh_terms: D017209:Apoptosis; D002470:Cell Survival; D006801:Humans; D008223:Lymphoma / Q000473:pathology / Q000503:physiopathology / Q000628:therapy*; D020298:U937 Cells; D014464:Ultrasonic Therapy / Q000379:methods*
keywords: Cell cycle; Cell lysis; Hyperproliferation apoptosis; Low intensity ultrasound