To date, apoptosis has been characterized biochemically by the production of 180-200 bp internucleosomal DNA fragments resulting from the activation of an endonuclease(s). The principal morphological feature of apoptosis is the condensation of chromatin and it has been assumed that this may reflect the oligonucleosomal fragmentation pattern. We have re-examined this dogma by comparing the biochemical and morphological features of cell death in several epithelial cell types (HT-29-I1 colon adenocarcinoma, CC164 mink lung, DU-145 human prostatic carcinoma and MCF-7 human breast adenocarcinoma) and one mesenchymal cell line (Hllras-R3 ras-transformed rat fibroblasts). Cell death was induced either by serum deprivation, TGF-,B1 or etoposide, or by leaving cells to reach confluence. Cell death was assessed with respect to detachment from monolayers, morphological changes and DNA integrity. The DNA-binding fluorophore Hoechst 33258 revealed chromatin condensation patterns consistent with apoptotic cell death in all cell types except MCF-7 cells. Using field inversion gel electrophoresis in conjunction wih conventional 2% agarose gel electrophoresis, cleavage of DNA to 50 kbp fragments was observed in all cases except MCF-7 cells. This preceded the appearance of oligonucleosomal fragments in HT-29-I1, CC164 and Hllras-R3 cells. Although the DNA of DU-145 cells fragmented into 50 kbp units, and although the cells exhibited classical apoptotic morphology, no subsequent internucleosomal cleavage was observed. These results suggest that changes in the integrity of DNA indicative of the release of chromatin loop domains occur before cleavage at internucleosomal sites is initiated and that the latter is not an essential step in the apoptotic process.

This study contributes to the evidence of DNA damage within sperm. High loads of DNA damage measured by the Comet assay were predictive of failure of embryo development after ICSI. As it is likely that sperm with DNA damage contributed to successful fertilization and in-vitro development, potential adverse effects remain to be clarified.

The joint spectral radius of a finite set of real d × d matrices is defined to be the maximum possible exponential rate of growth of long products of matrices drawn from that set. A set of matrices is said to have the finiteness property if there exists a periodic product which achieves this maximal rate of growth. J. C. Lagarias and Y. Wang conjectured in 1995 that every finite set of real d × d matrices satisfies the finiteness property. However, T. Bousch and J. Mairesse proved in 2002 that counterexamples to the finiteness conjecture exist, showing in particular that there exists a family of pairs of 2 × 2 matrices which contains a counterexample. Similar results were subsequently given by V. D. Blondel, J. Theys and A. A. Vladimirov and by V. S. Kozyakin, but no explicit counterexample to the finiteness conjecture has so far been given. The purpose of this paper is to resolve this issue by giving the first completely explicit description of a counterexample to the Lagarias-Wang finiteness conjecture. Namely, for the set

Ultrastructural changes in the interstitial cells of the adult rat testis were studied up to 45 days after administration of a single dose (100 mg/kg) of the antifertility compound ethylene dimethanesulfonate (EDS). Most Leydig cells showed degenerative changes 12 h after treatment. Twenty-four and 48 h after injection, all Leydig cells observed showed gross degenerative changes. At 4 and 14 days, intact Leydig cells could not be identified in the interstitial spaces. Twenty-one days after treatment with EDS, small Leydig cells were visible, and at 45 days, Leydig cells appeared normal. The seminiferous epithelium appeared morphologically normal until 4 days after injection of EDS, when slight abnormalities were observed. At 14 and 21 days, the seminiferous epithelium was grossly abnormal, but at 48 days, spermatogenesis appeared normal. Twelve, 24, and 48 h after treatment, large quantities of material, presumably from dead Leydig cells, were observed within the macrophage cytoplasm. The predominant cell in the interstitial space 4 and 14 days after EDS was the macrophage. Inclusions from the dead Leydig cells within the cytoplasm of the macrophages had almost disappeared. LH receptors (hCG binding) in testicular homogenates were consistent with the cytological changes in Leydig cells. Receptor concentration was low at 24 h and was almost zero at 4 days. This change was accompanied by a decrease in serum testosterone to castrate levels by 2 days. The responses of the endocrine system to destruction of the Leydig cell by EDS, as monitored by serum FSH, LH, and testosterone, were slower than those after castration, indicating that the response to EDS reflects the time required to kill the Leydig cell rather than direct impairment of the steroidogenic pathway. These experiments demonstrate that Leydig cells can be specifically destroyed by a cytotoxic drug. The availability of a specific cytotoxic agent for Leydig cells offers further opportunities to study the interrelationships between the Leydig cell and the seminiferous tubule.