The Role of Free Radicals in Autophagy Regulation: Implications for Ageing.

Reactive oxygen and nitrogen species (ROS and RNS, resp.) have been traditionally perceived solely as detrimental, leading to oxidative damage of biological macromolecules and organelles, cellular demise, and ageing. However, recent data suggest that ROS/RNS also plays an integral role in intracellular signalling and redox homeostasis (redoxtasis), which are necessary for the maintenance of cellular functions. There is a complex relationship between cellular ROS/RNS content and autophagy, which represents one of the major quality control systems in the cell. In this review, we focus on redox signalling and autophagy regulation with a special interest on ageing-associated changes. In the last section, we describe the role of autophagy and redox signalling in the context of Alzheimer's disease as an example of a prevalent age-related disorder.

Functional specialization of the epithelium in the mesonephric tubules.

An electron microscopy study was aimed to correlate structural differentiation of the epithelium in mesonephric proximal tubules (PT) with the expression of membrane activities of alkaline phosphatase (AP) and 5'-nucleotidase (AMP). Tissue samples of mesonephros were taken from 5 to 16 days old chick embryos. Both enzymes were detected with cerium technique, Mayahara modification of lead capture method was used also for localization of AP. Control incubation was performed with levamisole. The formation of absorptive apparatus was characterized by the differentiation of PT epithelium. Activities of AP and AMP appeared to increase rapidly with the differentiation of epithelium. Reaction products of AP and AMP were detected on brush border as well as on membranes of tubular invaginations, transport tubules and endocytotic vacuoles. The basolateral cell surfaces of epithelium were projected in short interdigitating microvilli and the expression of AP and AMP activities on their membranes suggested the transport role of this structural specialization.

Genetic analysis of the rat hypodactylous mutation.

Autosomal recessive rat hypodactylous mutation Hd leads in homozygous condition to reductive changes of the digital arch of all feet. There is a variable preaxial reduction of the number of fingers in both sexes. Moreover, homozygous males are sterile. Testes of homozygous Hd/Hd and +/Hd adult rats were examined in the light and electron microscopes. Spatial organization of stages of the spermatogenetic cycle was not confirmed in Hd/Hd testes comparing with +/Hd males. Significant decrease in the number of germ cells in seminiferous tubules of Hd/Hd testes was accompanied with loosening and vacuolization of the seminiferous epithelium. The assignment of the Hd locus to RNO10 excluded the suspected homology between rat and mouse Hd mutations. More precise mapping using microsatellite markers revealed close linkage of the Hd locus with the D1OMit8 marker defining Syb2 gene coding for synaptobrevin 2. A chromosomal segment of RNO10 carrying Hd and Syb genes is being incrossed onto BN and SHR inbred strains in order to examine the modifying influences of different genetic backgrounds.

Ultrastructure of the tubal chorion.

The chorion of five cases of ampullar pregnancies aged 9-11 weeks was examined in electron microscope. The appearance of chorion is affected by massive haemorrhage into the tubal lumen which occurs in this type of tubal pregnancy and causes its segregation from the tubal wall. The chorionic villi scattered in haematoma show different structure. The electron microscope investigation reveals that many chorionic villi possess the intact microvillous surface and are similar to normal villi of the intrauterine chorion. The development of syncytiotrophoblastic organelles especially as far rough endoplasmic reticulum, Golgi apparatus and mitochondria suggests that the syncytiotrophoblast may for some period be functional under these unfavourable conditions. The chorionic villi imprisoned in blood clot are often covered by fibrin deposits, their syncytium shows considerable folded nuclei with coarse chromatin aggregations, extremely dilated and degranulated endoplasmic reticulum. When syncytium degenerates the fibrinoid sheets invest the isolated portions of the villi. The necrotic villi as well as the cells of cytotrophoblastic islands are embedded in the fibrinoid masses. The cytotrophoblastic cells resembling the cells of basal plate in placenta are found in the tubal wall adjacent to the haematoma.

The differentiation and involution of the müllerian duct in the rat.

The structural differentiation of the Müllerian ducts of both sexes was studied in rat fetuses from 15 to 21 days of gestation. Differences between the male and female Müllerian ducts were observed from the 17th day onward. The epithelium of male Müllerian duct lost its regular arrangement, the increased lysosomal activity and disintegration of some cells was found. The involution of the male duct was accompanied by the condensation of the surrounding mesenchyme with the participation of macrophages. The female Müllerian duct was lined with simple columnar epithelium; its pattern remained indifferent until birth. The apical migration of centrioles and solitary cilia formation belonged to the typical findings from the 18th day. Neither ciliated cells nor multiple centriole replication were observed in oviductal segment of Müllerian duct.

Involution of the Wolffian duct in the rat.

The involution of Wolffian duct in female rat fetuses from 15 to 21 days of gestation was studied in electron microscope. The female Wolffian duct stopped its differentiation on day 17 and the onset of duct regression was found in 18 days old fetuses. The involution was accompanied by degeneration and disintegration of epithelial cells, removal of basal lamina and elimination of altered cells into periductal mesenchyme. Although the mechanism of programmed cell death contributed to the WD regression the findings of non-altered epithelial cells supported the opinion of possible migration of some WD cells into the mesenchymal cell compartment.

Prenatal development of the rat uterine horns.

The horns of bicornic uterus in the rat develop from the middle parts of Müllerian ducts. Female rat fetuses for this study were taken on 16-21 days of gestation. On the 16th prenatal day the uterine part of Müllerian duct was short, lined with a columnar epithelium and basal lamina around the duct was incomplete. During further development the duct enlarged, epithelial cells became taller and basement membrane was formed. Until birth the epithelium remained relatively indifferent as far as the periductal mesenchyme. Contrary to the animals with a long gestational period and human, the differentiation of uterine wall including uterine mucosa in the rat takes place after birth.

Postnatal development of the rat oviductal epithelium.

Submicroscopic examination of rat oviducts in the early postnatal period showed that the character of the epithelium remained relatively indifferent up to the 6th day. Typical findings in this phase include an apical migration of the centrioles, with subsequent formation of solitary cilia; ciliated cells were an isolated occurrence. Ciliogenesis in the rat oviductal epithelium starts between the 8th and the 10th day. A continuous kinociliary apparatus is formed on the basis of centriole replication. The first secretory and peg cells appear towards the end of the second week.

Differentiation of the müllerian (paramesonephric) duct epithelium in the rat.

Differentiation of the Müllerian duct epithelium was studied in 15- to 21-day female rat foetuses. The proximal segment of the Müllerian duct is formed by the 15th day; it runs parallel to the Wolffian duct and the two are wrapped in a common basement membrane. On the 16th day the genital ducts are clearly separate; the Müllerian duct has a slit-like lumen and is lined with simple columnar epithelium. Throughout the whole of the given period the epithelium retains a relatively indifferent appearance. Characteristic findings from the 18th day include the apical migration of centrioles and the formation of solitary cilia.