Roy A. Axelsen

A morphological study was undertaken to assess the role of cell deletion by apoptosis in experimental hydronephrosis. Male Sprague-Dawley rats (200 +/- 20 gm) were used. The left ureter was ligated or a sham operation was carried out. Animals were killed from 4 days to 12 weeks after operation. Two parallel studies were undertaken: one to demonstrate and quantitate specific morphological changes in the affected kidney using light and electron microscopy, and the other to measure changes in dry kidney weights. Renal tubular atrophy is an inevitable consequence of chronic occlusion of the ureter. As expected, the present study showed a progressive loss of tissue mass in the hydronephrotic kidney. This occurred from 1 week after permanent ureteric ligation, and was most rapid between 2 and 4 weeks. The tubular epithelium contained cells undergoing a distinct form of cell death termed apoptosis, characterized ultrastructurally in its early stage by the presence of rounded cells with condensed cytoplasm and condensed and marginated nuclear chromatin, and later by the presence of discrete membrane-bounded intact cellular fragments (apoptotic bodies), which were phagocytosed and digested by adjacent viable cells, or were shed into the tubular lumens. Numbers of apoptotic cells or clusters of apoptotic bodies were increased significantly in all animals with ureteric obstruction in comparison with controls. The greatest increases occurred at 2 and 4 weeks, when loss of renal mass was occurring rapidly. Diminished blood flow in hydronephrosis has been well-documented by others, and therefore our results are consistent with studies which have shown mild ischemia to be the cause of tissue atrophy involving apoptosis. We conclude that cell deletion by apoptosis plays an important role in the pathogenesis of renal tubular atrophy associated with hydronephrosis.

A condition closely resembling human melanosis coli was induced in the guinea pig large intestine by daily oral administration of the anthraquinone danthron. Each treatment caused a transient, dose-related wave of apoptosis of the colonic surface epithelial cells. Most of the resulting apoptotic bodies were phagocytosed by intraepithelial macrophages and carried by them through fenestrae in the epithelial basement membrane to the lamina propria. Here, the apoptotic bodies were transformed into typical lipofuscin pigment in macrophage heterolysosomes. Continued danthron administration caused progressive accumulation of pigmented macrophages in the bowel wall, whereas ongoing migration of pigmented macrophages to regional lymph nodes resulted, after danthron was ceased, in sequential loss of the pigmented cells from the superficial and deep lamina propria. Examination of colonic biopsies from patients with melanosis coli shows increased numbers of apoptotic bodies in the surface epithelium and lamina propria, suggesting implication of the same cellular processes in the formation of the pigment in man.

Two related morphological studies were undertaken in rats. In the first, cellular events involved in the development of ischemic renal atrophy induced by renal artery stenosis were recorded. One primary objective was to document the pathogenetic role that a distinct form of cell death, termed apoptosis, played in the development of renal tubular atrophy. A small, partially closed ligating clip was used to produce stenosis of the left renal artery, or a sham operation was performed. Animals were killed 2-28 days after operation. The ensuing ischemic renal atrophy was studied histologically and ultrastructurally, and apoptosis was counted in paraffin sections, using established criteria for its identification. Nuclear [3H]thymidine uptake was used as an indicator of cell proliferation. Morphometric studies recorded changes in area of transected tubular profiles. Correlation was sought between the morphological changes, data gained by the above quantitations, and the progressive reduction in renal mass that occurred during the experiment. Our results showed that during the acute phase (2-8 days), cell death was effected by both apoptosis and necrosis and increased tubular epithelial cell labeling and mitoses provided evidence of epithelial repair. During the chronic phase (10-28 days), when the mass of the ischemic kidney underwent significant reduction, cell death was effected by apoptosis alone, and the level of tubular epithelial cell labeling and mitosis returned to near normal. Intraepithelial macrophages were significant in removing the apoptotic bodies. Area of tubular epithelium was reduced in atrophic tubules, and it is proposed that this reduction may be explained by apoptotic cell deletion, as well as cell shrinkage. In the second study, evidence of regeneration was sought in atrophic kidneys after surgical reversal of renal artery stenosis and, in other animals, after unilateral nephrectomy of the contralateral kidney. Our results showed that regeneration, involving both hypertrophy and hyperplasia, was stimulated only by removal of the hypertrophied contralateral kidney and occurred whether or not stenosis of the renal artery was reversed.

OBJECTIVE: To measure the rate of histopathologically identified ocular surface squamous neoplasia (OSSN) in pterygium specimens. METHODS: All pterygium specimens collected from consecutive patients between April 8, 2003, and February 6, 2008, were submitted for histopathologic examination, and the rate of OSSN was calculated. RESULTS: The rate of OSSN was 9.8% (52 of 533) insequential pterygium specimens. CONCLUSIONS: This rate of unsuspected OSSN suggests that all specimens of pterygium should be submitted for histopathologic examination and that patients in whom OSSN is noted should be examined at more frequent intervals so any clinical OSSN that develops can be identified at an early stage.