Gravitropism and phototropism of oat coleoptiles: post-tropic autostraightening and tissue shrinkage during tropism.

We measured changes in length on the two opposite sides of the red-light-grown oat (Avena sativa L.) coleoptiles subjected to either gravitropic or phototropic stimulation and subsequently rotated on a horizontal clinostat. The length measurement was conducted using three 5 mm-long zones delimited by ink markers from the tip. Curvature of each zone was analyzed from the length difference between the two sides. Gravitropism was induced by displacing the seedling from the vertical by 30 degrees or 90 degrees for 25 min. Phototropism was induced by exposing the coleoptile to unilateral blue light for 30 s, which provided a fluence (1.0 micromoles m-2) optimal for the pulse-induced positive phototropism or a lower, suboptimal fluence (0.03 micromoles m-2). After negatively gravitropic bending, the upper two zones straightened rapidly at either displacement angle. After positively phototropic bending, straightening occurred, but only in the top zone and at the lower fluence. The upper two zones straightened rapidly, however, when bilateral blue light (30 s; 15 micromoles m-2 from either direction) was applied 25 min after unilateral stimulation at the higher fluence. Bilateral blue light alone induced no curvature. These results confirm that the straightening of gravitropically bent coleoptiles is autonomic, and suggest that a similar autonomic response participates in the straightening of phototropically bent coleoptiles. Suppression of elongation on the concave side of the coleoptile mainly accounted for gravitropic and phototropic curvatures. The concave side of the top zone shrank during both tropisms. This shrinkage progressed at a high rate from the beginning of curvature response, suggesting that a drop in turgor pressure is the main and direct cause of the shrinkage.

Gravitropism of oat and wheat coleoptiles: dependence on the stimulation angle and involvement of autotropic straightening.

Gravitropism of oat (Avena sativa L.) and wheat (Triticum aestivum L.) coleoptiles was investigated in relation to the displacement angle or to the initially set stimulation angle (SA). We measured curvature rates at the early phase of curvature, before it was affected by the drop in SA resulting from the curvature response itself. The plot of the rates against the sines of initial SAs revealed similar curves for oats and wheat, which approached saturation as the sine increased to unity. The two species and previously analyzed rice [Iino et al. (1996) Plant Cell Environ. 19: 1160] appeared to have similar gravisensitivities. Initial SAs below and over 90 degrees yielded comparable rates when the sine values were the same, indicating that the extent of gravitropism is determined by the gravity component perpendicular to the organ's long axis. Long-term curvature kinetics at different SAs indicated that the net curvature rate dropped sharply before the tip reached the vertical position and then the tip approached the vertical slowly, with clear oscillatory movements in the case of wheat. During this late curvature phase, the coleoptile straightened gradually, although none of its parts had yet reached the vertical. When rotated on horizontal clinostats or displaced upwards to reduce SA in the late curvature phase, coleoptiles bent in the opposite direction. These results demonstrated that autotropism counteracts gravitropism to straighten coleoptiles.

Gravitropism of maize and rice coleoptiles: dependence on the stimulation angle.

Gravitropism of maize and rice coleoptiles was investigated with respect to its dependence on the angle of displacement or the initial stimulation angle (ISA). Close examination of curvature kinetics and the response to a drop in stimulation angle (SA) indicated that the gravtropic response during an early but substantial part of the curvature development is directly related to the ISA, there being no effect of the reduction of SA resulting from the curvature response itself. On the basis of this finding, the relationship between the steady SA and the curvature rate was determined. In maize, the curvature rate increased linearly with the sines of SAs up to an SA of 90 degrees. Rice coleoptiles, however, showed a saturation curve in the same range of SAs. The saturation profile was nearly identical between coleoptiles grown in air and those submerged in water, although the latter elongated much faster. Rice coleoptiles appeared to be far more sensitive to gravity than maize coleoptiles. It is concluded that the sensitivity to gravity, assessed through dependence on ISA, is a property inherent to a given gravitropic organ. Long-term measurements of curvature indicated that the coleoptiles bend back past the vertical. This overshooting was marked in submerged rice coleoptiles.

A prospective analysis of subacute thyroid dysfunction after neck irradiation.

PURPOSE: Exposure of the thyroid to therapeutic doses of external irradiation has been demonstrated to induce thyroid dysfunction. This study was designed to assess the relationship between irradiation and early thyroid dysfunction, prospectively. METHODS AND MATERIALS: Twenty patients in whom the thyroid was incidentally exposed to therapeutic doses of irradiation were studied. The dose given to the thyroid was 40-54 Gy over 4-7 weeks. Thyroid function tests, including serum thyroid stimulating hormone (TSH), free thyroxine (free T4), free triiodothyronine (free T3), antithyroglobulin antibody, and antimicrosomal antibody, were performed prior to irradiation and at 3, 6, and 12 months after radiotherapy. RESULTS: Serum TSH levels did not change significantly at 3 months after irradiation (mean TSH level: 1.33 microU/ml before irradiation, 1.74 microU/ml at 3 months, p = 0.11). However, a significant elevation was noted at 6 months (mean TSH: 3.50 microU/ml at 6 months, p = 0.0001, vs. preirradiation), when TSH levels were higher than preirradiation levels in 19 of 20 patients. After irradiation, 13 patients remained in a euthyroid state (euthyroid group), while in the other 7 patients hypothyroidism occurred (hypothyroid group) and thyroid hormone-replacement therapy was performed. After 6 months, elevation of TSH was less significant in the euthyroid group, whereas elevation of TSH persisted continuously and exponentially in the hypothyroid group. Thyroid autoantibodies did not turn positive in any patient during follow-up. CONCLUSIONS: Damage of the thyroid develops in most patients when the organ is exposed to radiation. This radiation-induced damage is initially manifested within 6 months after irradiation.

[Mesenteric desmoid found after surgery of familial polyposis coli; a case report].

A 51-year-old woman manifested with complaints of an abdominal mass 5 years after colectomy. In comparison with the cases previously reported, this desmoid had lower CT value (20-30 HU), and more vascularity with neovascularization on angiography. These findings seem to reflect the characteristic of much cellularity and malignancy of the desmoid.

Poly(A) polymerase from Vigna unguiculata seedlings. A bifunctional enzyme responsible for both poly(A)-polymerizing and poly(A)-hydrolyzing activities.

Poly(A)-specific ribonuclease was co-purified with poly(A) polymerase from Vigna unguiculata seedlings. Both activities were separated into two forms (enzymes I and II) by a final hydrophobic column chromatography. The enzyme I preparation, which was homogeneous as examined by SDS/PAGE, had both poly(A) polymerase and poly(A)-specific ribonuclease activities. The antibody raised to the enzyme I preparation precipitated both enzyme activities. These indicate that a single polypeptide (Mr 63,000) is responsible for both poly(A)-polymerizing and poly(A)-hydrolyzing activities. The poly(A)-specific ribonuclease was a 3'-exonuclease specific to single-stranded poly(A), forming 5'AMP as the sole reaction product. The hydrolytic activity required either Mn2+ or Mg2+ with different optimum concentrations, whereas the polymerizing activity required Mn2+ but not Mg2+. ATP and PPi had little or no effect on the poly(A)-specific ribonuclease activity.

[Subcutaneous fibrosis induced by external irradiation of carcinoma of the uterine cervix].

Two-hundreds and seventy-six patients who were treated with external irradiation alone or combined with intracavitary irradiation and were alive 2-18 years were examined concerning to late complications in the lower abdominal wall. Moderate or severe subcutaneous fibrosis occurred in 14% of the patients. They were not observed below subcutaneous dose of 44 Gy. However, they were noted in 22% with dose of 45-54 Gy and in 100% with dose over 55 Gy. The dose of 50% probability of fibrosis was expected around 53 Gy and 80% of complications were appeared within 3 years after irradiation.