We report on 2 patients (3 1/2 year-old-male and 6-year-old female) with the ring 15 chromosome syndrome and speech delays and review 25 cases from the literature. The main characteristics of this syndrome include growth retardation (100%), variable mental retardation (95%), microcephaly (88%), hypertelorism (46%), and triangular facies (42%). Other frequent findings include delayed bone age (75%), brachydactyly (44%), speech delay (39%), frontal bossing (36%), anomalous ears (30%), café-au-lait spots (30%), cryptorchidism (30%), and cardiac abnormalities (30%). The average age at diagnosis was 8.1 years. The average maternal and paternal age at the time of birth was 28 and 31 years, respectively.
Slow pulsatile movements of Schwann cells in vitro were studied quantitatively by using time-lapse cinemicrography. Schwann cells from peripheral nerves of 3-day-old rats were cultured in serum-free medium. Most Schwann cells showed intermittent episodes of pulsatile movement; each episode consisted of one or several contractile pulses. About half of the episodes consisted of a single pulse, and episodes with more than four pulses were rare. The average episode of activity lasted 2.6 min, while the average duration of a single pulse was 1.5 min. The mean quiescent interval between episodes of activity was 3.7 min. Some cells showed no pulsatile activity. Active cells averaged 6.6 episodes/h. The fraction of time which a Schwann cell spent in pulsatile activity varied widely, with an average of 28%. Behavior of Schwann cells in HEPES-buffered Hanks saline was generally similar to that in the complete medium. Raising K+ to 40 mM or Ca++ to 10 mM did not markedly affect the time course of the pulsatile motility, although the contractions were more vigorous in the high Ca++. Pulsatile movement was reversibly inhibited by cytochalasin B and appeared to be potentiated by drugs that disrupt microtubules.
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