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The promotive effect of latrunculin B on maize root gravitropism is concentration dependent

The promotive effect of latrunculin B on maize root gravitropism is concentration dependent. Blancaflor, E. B.; Hou, G.-C. 76343-94-7 are also occured in this study.; Mohamalawari, D. R. (Plant Biology Division, The Samuel Roberts Noble Foundation, Ardmore, OK 73401, USA). Advances in Space Research, 31(10), 2215-2220 (English) 2003 Elsevier Science Ltd. CODEN: ASRSDW. ISSN: 0273-1177. DOCUMENT TYPE: Journal CA Section: 11 (Plant Biochemistry) The cytoskeleton has been proposed to be a key player in the gravitropic response of higher plants. A major approach to det. the role of the cytoskeleton in gravitropism has been to use inhibitors to disrupt the cytoskeleton and then to observe the effect that such disruption has on organ bending. Several investigators have reported that actin or microtubule inhibitors do not prevent root gravitropism, leading to the conclusion that the cytoskeleton is not involved in this process. However, there are recent reports showing that disruption of the actin cytoskeleton with the actin inhibitor, latrunculin B, promotes the gravitropic response of both roots and shoots. In roots, curvature is sustained during prolonged periods of clinorotation despite short periods of gravistimulation. These results indicate that an early gravity-induced signal continues to persist despite withdrawal of the const. gravity stimulus. To investigate further the mechanisms underlying the promotive effect of actin disruption on root gravitropism, we treated maize roots with varying concns. of latrunculin B in order to det. the lowest concn. of latrunculin B that has an effect on root bending. After a 10-min gravistimulus, treated roots were axially rotated on a one rpm clinostat and curvature was measured after 15 h. The results show that 100 nM latrunculin B induced the strongest promotive effect on the curvature of maize roots grown on a clinostat. Moreover, continuously gravistimulated roots treated with 100 nM latrunculin B exhibited stronger curvature responses while decapped roots treated with this concn. of latrunculin B did not bend during continuous gravistimulation. The stronger promotive effect of low concns. of latrunculin B on the curvature of both clinorotated and continuously gravistimulated roots suggests that disruption of the finer, more dynamic component of the actin cytoskeleton could be the cause of the enhanced tropic responses of roots to gravity. .

Effect of low-dose latrunculin B on anterior segment physiologic features in the monkey eye

Effect of low-dose latrunculin B on anterior segment physiologic features in the monkey eye. Okka, Mehmet; Tian, Baohe; Kaufman, Paul L. (Department of Ophthalmology and Visual Sciences, University of Wisconsin-Madison Medical School, Madison, USA). Archives of Ophthalmology (Chicago, IL, United States), 122(10), 1482-1488 (English) 2004 American Medical Association. CODEN: AROPAW. ISSN: 0003-9950. DOCUMENT TYPE: Journal CA Section: 1 (Pharmacology) To det. if low doses of topical latrunculin B (LAT-B) will increase outflow facility and decrease intraocular pressure without damaging the cornea and if they will inhibit miotic and accommodative responses to pilocarpine in monkeys. 92-13-7 and 76343-94-7 are also occured in this study. We measured intraocular pressure (Goldmann tonometry) before and after 1 and 9 doses of 0.005% and 0.01% topical LAT-B and vehicle given twice daily on successive weeks; outflow facility (perfusion) following 15 doses; central corneal thickness (ultrasonic pachymetry) before and after 1 and 9 doses of 0.01% LAT-B and vehicle; pupillary diam. (calipers); and accommodation (refractometry) before and after 1 dose of 0.005% and 0.02% LAT-B. Latrunculin-B dose-dependently decreased intraocular pressure, multiple doses more than a single dose. Maximal mean±SEM hypotension after 1 dose was 2.5±0.3 mm Hg (0.005% LAT-B; n=8; P<.001) or 2.7±0.6 mm Hg (0.01% LAT-B; n=8; P<.005); maximal mean±SEM hypotension after 9 doses was 3.2±0.5 mm Hg (0.005% LAT-B; n=8; P<.001) or 4.4±0.6 mm Hg (0.01% LAT-B; n=8; P<001). Outflow facility was increased by mean±SEM 75% ± 13% (n=7; P<.005). Central corneal thickness was not changed after 1 or 9 doses of 0.01% LAT-B. Miotic and accommodative responses to i.m. pilocarpine were dose-dependently inhibited. With 0.02% LAT-B, inhibition of miosis was substantial, whereas the inhibition of accommodation was only about 25%. With 0.005% LAT-B, the effects were trivial. In ocular normotensive monkeys, 0.005% and 0.01% LAT-B administered topically increases outflow facility and/or decreases intraocular pressure without corneal effects. Multiple doses reduce intraocular pressure more than a single dose. Latrunculin-B dose-dependently relaxes the iris sphincter and ciliary muscle, with some sepn. of miotic and accommodative effects. Multiple treatments with low topical doses of LAT-B may substantially reduce outflow resistance in eyes with glaucoma without adversely affecting the cornea. .