A morphometric analysis, based on mathematical evaluations and stereological methods, has been used to study five left neonatal ovaries, removed from full-term neonates with a 46,XX karyotype free from malformations of the genital apparatus. Each ovary was completely cut obtaining serial sections and one 1-micron-thick section every 1,000 microns was examined. Ovarian length ranged from 9 to 17 mm (mean 13 mm), width from 3.5 to 7 mm (mean 5.7 mm), thickness from 2.5 to 5 mm (mean 4 mm), and volume from 82.23 to 198.3 mm3 (mean 125.88 mm3). In the ovarian cortex, primitive cortical tissue accounted for 10-20% of the total volume, follicles for 10-25% and interstitium for 35-45%; 10-30% of the organ consisted of inner medulla. The total follicle number ranged from 130,000 to 385,000 per ovary, with an average of 266,000 with 95% being represented by primordial follicles. In all ovaries examined follicular growth was still in process, with follicles at different stages of development.

Aberrant crypt foci (ACF) have been identified on the colonic mucosal surface of rodents treated with colon carcinogens and of humans after methylene-blue staining and observation under a light microscope. Several lines of evidence strongly suggest that ACF with certain morphological, histological, cell kinetics, and genetic features are precursor lesions of colon cancer both in rodents and in humans. Thus, ACF represent the earliest step in colorectal carcinogenesis. This paper has the main purpose of reviewing the evidence supporting this view, with particular emphasis on cell and crypt dynamics in ACF. ACF have been used as intermediate biomarkers of cancer development in animal studies aimed at the identification of colon carcinogens and chemopreventive agents. Recently, evidence has also shown that ACF can be effectively employed in chemopreventive studies also in humans.

During human oogenesis two contrasting processes can be observed: germ cell proliferation and differentiation, and contemporaneous germ cell death. It is well known that apoptosis is a type of physiological cell death that occurs in proliferating and differentiating tissues. The aim of this study is to demonstrate, through ultrastructural and in-situ 3' end labelling observations in intact sections of human fetal ovaries, that germ cell loss during fetal life is due to a phenomenon of apoptosis. We evaluated the presence of programmed cell death in female germ cells in fetal ovaries at 18-20 weeks of postconceptional age. The alterations that occur during apoptosis were detected by the electron microscope and include cytoplasmic condensation, organelle relocalization and compaction, chromatin condensation, and finally, production of membrane-enclosed particles containing intracellular material, known as apoptotic bodies, that are phagocytosed. The fragmentation of DNA, characteristic of apoptotic cells, was detected by the use of the in-situ 3' end labelling procedure on histological sections of ovaries where only some nuclei of germ cells were positively stained. The parallel use of these two methods on human ovaries of 18-20 weeks postconceptional age has allowed us to show that the numerical decrease of human female germ cells during the fetal period is due to an apoptotic phenomenon.

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This study investigated the potential of amniotic fluid stem cells (AFSCs) to synthesize mineralized extracellular matrix (ECM) within different porous scaffolds of collagen, poly-D,L-lactic acid (PDLLA), and silk fibroin. The AFSCs were initially differentiated by using an osteogenic medium in two-dimensional culture, and expression of specific bone proteins and the physiologic mineral production by the AFSCs were analyzed. In particular, during differentiation process, AFSCs expressed proteins like Runt-related transcription factor 2 (Runx2), Osterix, Osteopontin, and Osteocalcin with a sequential expression, analogous to those occurring during osteoblast differentiation, and produced extracellular calcium stores. AFSCs were then cultured on three-dimensional (3D) scaffolds and evaluated for their ability to differentiate into osteoblastic cells in vivo. Stem cells were cultured in vitro for 1 week in collagen, fibroin, and PDLLA scaffolds. The effect of predifferentiation of the stem cells in scaffolds on the subsequent bone formation in vivo was determined in a rat subcutaneous model. With the addition of a third dimension, osteogenic differentiation and mineralized ECM production by AFSCs were significantly higher. This study demonstrated the strong potential of AFSCs to produce 3D mineralized bioengineered constructs in vivo and suggests that fibroin may be an effective scaffold material for functional repair of critical size bone defects.