Radioautographic study of the cellular proliferation of retinal pigment epithelium in axolotls

The proliferative activity of the pigment epithelium cells in the axolotl eyes was studied using 3H-thymidine in two types experiments: after the removal of lens, iris and retina and upon the cultivation of the pigment epithelium pieces in the cavity of lens-less eye. Irrespective of the operation type, the level of proliferation of the pigment epithelium cells changed regularly with respect to the time of observation. In the intact eye, the level of proliferation of the pigment epithelium cells was not high: the index of labelled nuclei equaled 0.5%, no mitoses were found. The highest values of the index of labelled nuclei (12.6-32.1%) and of the mitotic index (0.54-1.07%) were registered on the 10-20th days after the operation. After 40 days, the indices of proliferative activity of the pigment epithelium cells approached gradually those for the intact eye. The cultivation of the pigment epithelium cells in the cavity of a lens-less eye for 50 days did not result in their transdifferentiation into retina cells. The layered retina found in 7.7% of cases after the removal of lens, iris and retina could regenerate either from the cells of the retina growth zone localized in the region of embryonic split, or due to transdifferentiation of the pigment epithelium cells.     

Melanin granule metabolism in the iris and retinal pigment epithelium in adult tritions after completion of eye regeneration

It was concluded that the newly synthesized melanin granules were replaced in the pigmented tissues of the newt eye on the basis of redistribution of the cells of pigment epithelium of retina and iris labelled by 3H-DOPA 2.5 and 6.5 months after the isotope injection. The replacement of melanin granules and, correspondingly, melanin synthesis proceed more actively in the peripheral zones of the pigment epithelium of retina. The depigmentation of cells preceding the melanin synthesis appears to be realized with the participation of macrophages.     

Genetic mechanisms of cell transdifferentiation

Studies have been considered, which concern identification of regulatory genes in adult newts and their expression during retinal and lens regeneration. B.L. Astaurov repeatedly urged to join efforts of geneticists and embryologists in studies of the mechanisms underlying biological phenomena. This was also true for studies of regeneration. Such studies became possible only after introduction of molecular biology methods. Studies of the mechanisms underlying regeneration have been recently carried out jointly by geneticists and developmental biologists. This review presented at the conference dedicated to the 100th anniversary of B.L. Astaurov deals with these aspects in studies of regeneration.     

Risk Factors for Death in 632 Patients with Sickle Cell Disease in the United States and United Kingdom

Background

The role of pulmonary hypertension as a cause of mortality in sickle cell disease (SCD) is controversial.

Methods and Results

We evaluated the relationship between an elevated estimated pulmonary artery systolic pressure and mortality in patients with SCD. We followed patients from the walk-PHaSST screening cohort for a median of 29 months. A tricuspid regurgitation velocity (TRV)≥3.0 m/s cuttof, which has a 67–75% positive predictive value for mean pulmonary artery pressure ≥25 mm Hg was used. Among 572 subjects, 11.2% had TRV≥3.0 m/sec. Among 582 with a measured NT-proBNP, 24.1% had values ≥160 pg/mL. Of 22 deaths during follow-up, 50% had a TRV≥3.0 m/sec. At 24 months the cumulative survival was 83% with TRV≥3.0 m/sec and 98% with TRV<3.0 m/sec (p<0.0001). The hazard ratios for death were 11.1 (95% CI 4.1–30.1; p<0.0001) for TRV≥3.0 m/sec, 4.6 (1.8–11.3; p = 0.001) for NT-proBNP≥160 pg/mL, and 14.9 (5.5–39.9; p<0.0001) for both TRV≥3.0 m/sec and NT-proBNP≥160 pg/mL. Age >47 years, male gender, chronic transfusions, WHO class III–IV, increased hemolytic markers, ferritin and creatinine were also associated with increased risk of death.

Conclusions

A TRV≥3.0 m/sec occurs in approximately 10% of individuals and has the highest risk for death of any measured variable.

The study is registered in ClinicalTrials.gov with identifier

{"type":"clinical-trial","attrs":{"text":"NCT00492531","term_id":"NCT00492531"}}NCT00492531     

Lactate dehydrogenase isoenzymes during regeneration of the lens and retina in adult tritons

The range of lactate dehydrogenase (LDG) isozymes has been studied at the consecutive stages of retina regeneration from pigmented epithelium cells and lens regeneration from iris margin in adult crested newts. It was shown that the spectra of LDG isozymes peculiar to pigment epithelium cells and iris and characterized by the predominance of slowly migrating forms are replaced in the lens and retina regenerates by spectra characterized by the predominance of rapidly migrating isozymes which are peculiar to definitive lens and retina.     

A web server to locate periodicities in a sequence

Summary : FT is a tool written in C++, which implements the Fourier analysis method to locate periodicities in aminoacid or DNA sequences. It is provided for free public use on a WWW server with a Java interface. Availability : The server address is http://o2.db. uoa.gr/FT Contact : shamodr@atlas.uoa.gr