Localization by situ hybridization of amplified ribosomal DNA during Xenopus laevis oocyte maturation (a light and electron microscopy study).

The presence of ribosomal DNA has been demonstrated, by light and electron microscopy study of in situ hybridization with 125I-labeled ribosomal RNA, in the Feulgen-positive bodies which appear during maturation in the cytoplasm of Xenopus laevis oocytes. The ultrastructure of these bodies is described.     

Quantitative and ultrastructural studies of excimer laser ablation of the cornea at 193 and 248 nanometers

Excimer laser radiation at 193 nm and 248 nm was used to create linear etch perforations of enucleated calf corneas. The etch depth per pulse was determined for various exposures, and specimens were examined by light and transmission electron microscopy. Compared to 248 nm, excimer laser ablation at 193 nm was found to have a lower threshold for onset of ablation, less increase in etch depth per pulse at increasing fluences, and less structural alteration in adjacent cornea. For 193 nm, structural alterations were minimal, confined to an area less than 0.3 micron wide, and did not increase with increasing fluence. These studies suggest that clinical strategies for excimer laser refractive surgery will employ the 193-nm wavelength, with fluence chosen depending on surgical strategy. Ablation exposures above 600 mJ/cm2 at 193 nm may give the most repeatable etch depth.     

A novel in situ method for the detection of deficient transglutaminase activity in the skin

Received: 9 December 1997 / Received after revision: 15 June 1998 / Accepted: 28 July 1998     

In vitro reconstitution of intermediate filaments form mammalian neurofilament triplet polypeptides.

Intermediate filaments (IF) were reconstituted in vitro from bovine neurofilament triplet polypeptides. Neural IF, solubilized in either low salt or 8 M urea solution, assembled into IF when returned to near-physiological solution conditions. The 68,000-dalton component of the triplet, purified to homogeneity by preparative NaDodSO4 electrophoresis, was renatured and reassembled into short (approximatley 0.05-micrometer) approximatley 10 nm-diameter filaments. These results demonstrate that the triplet polypeptides are components of neural IF and that the 68,000-dalton polypeptide is an IF structural protein.     

Ineffectiveness of chemotherapy in patients with metastatic ependymoma of the cauda equina

Six cases of intraspinal ependymoma metastasizing outside the central nervous system have been reported. This report documents a seventh case. This patient received multiple courses of combination and single-agent chemotherapy without evidence of tumor regression. All seven patients had four things in common: early onset of disease, numerous operations, massive local recurrence at the time distant metastases were noted, and a long time period from diagnosis to death.