Cytoskeletal reorganization in skeletal muscle differentiation: from cell morphology to gene expression.

Actin cytoskeleton profoundly influence a variety of signaling events, including those related to cell growth, survival and differentiation. Recent evidence have provided insights into the mechanisms underlying the ability of cytoskeleton to regulate signal transduction cascades involved in muscle development. This review will deal with the most recent aspects of this field paying particular attention to the role played by actin dynamics in the induction of skeletal muscle-specific genes.

Histochemical detection of sugar residues in chick embryo developing lingual glands with horseradish-peroxidase conjugated lectins.

Tongue anlage were taken in chick embryos from the 7th to the 21st d of incubation and in 3 d old chicken. A battery of 7 different horseradish peroxidase-conjugated lectins (PNA, ConA, DBA, SBA, LTA, WGA, UEA I) was used to study the carbohydrate residues of glycoconjugates at the epithelial cells of the anterior and posterior lingual glands. Some sugar residues, detected at the surface of the epithelial cells in early developmental stages of glandular primordia, seemed to play a role in inducing and regulating the first differentiative steps of the glands. Differences in type, amount, time of appearance and cellular localization between the 2 groups of glands were detected. The group of the anterior lingual glands, adjacent to the entoglossal cartilage (paraentoglossal glands), showed some peculiar histochemical characteristics.

An anatomical study of the healthy human heart by echocardiography with special reference to physiological valvular regurgitation.

110 healthy subjects (45 men and 65 women ranging in age between 24 and 60 years) were studied by 2-dimensional echocardiography. In each subject the diameters of the cardiac chambers, the thickness of the intraventricular septum and posterior wall of the left ventricle in diastole, as well as the diameters and circumferences of the aortic and mitral rings were measured. Moreover, in each subject color doppler echocardiography was performed. Pulmonary valve regurgitation was observed in 47 subjects (42.7%). This finding was not correlated in a statistically significant manner to either age, sex, body weight, or height. The incidence of pulmonary regurgitation, however, tended to decrease with age. In 37 subjects (33.6%), tricuspid regurgitation was detected without any correlation to the above parameters. In 11 cases (10%), mitral regurgitation was observed; its correlation to age was statistically significant (p < 0.05). Aortic regurgitation was noted in 9 (8.2%) cases; its incidence was directly correlated to age (p < 0.01). The observed regurgitations were defined as "physiological" and precise characteristics were chosen so as to distinguish such "physiological" from "pathological" regurgitations.

Scanning electron microscopic evaluation of the alterations induced by polluted air in the rabbit bronchial epithelium.

With the aim of evaluating the influence of polluted air on the respiratory epithelium, ten New Zealand white rabbits, from a group of fifteen kept in the country, were transported to a site located in a metropolitan area. After 40 days, all the rabbits were killed, and the bronchial mucosa studied by scanning electron microscopy (SEM). In the animals exposed to polluted air, the ciliated cells, less numerous than in normal cases, show an evident decrease in the number and size of the cilia, exposing apical microvilli. It is therefore possible to hypothesize that a part of the non-ciliated cells is made up of cells that have lost their cilia. The number of non-ciliated elements and the amount of mucous secretion appear to have noticeably increased. The considerable response of the respiratory epithelium to inhaled agents appears to be confirmed, as is the irritant effect of polluted city air.

Magnetic resonance (MR) evaluation of bone marrow in vertebral bodies.

Magnetic Resonance (MR) imaging was used to examine the hematopoietic bone marrow in the vertebral bodies of eight healthy subjects, and of 35 cancer patients who had been previously treated with radiation therapy. MR was instrumental in distinguishing viable hematopoietic tissue (red marrow) from adipose tissue (yellow marrow), whose presence reflected the extent of radiation-induced bone marrow injury. Different water content in proliferating hematopoietic tissue and adipose tissue enabled clear distinction of the two components even inside the same vertebral body. Three patterns of bone marrow viability were observed in irradiated patients: 1. Patients undergoing therapy at the time of MR study, and patients who had received low-intermediate dose several years before MR examination showed no alteration as compared with healthy controls (i.e. homogeneous presence of red marrow). 2. Patients who had received low-intermediate dose few years before MR, showed either partial re-colonization of yellow marrow or almost complete ablation of active red marrow with rare areas of re-colonization. 3. Patients who had received high dose, showed complete depletion of red marrow (fatty substitution) independently of the length of time elapsed since radiation therapy. Therefore, bone marrow recovery after radiation therapy was associate with two variables: received dose and length of time allowed for re-colonization by surviving hematopoietic tissue. In conclusion, our results provide evidence that MR can be purposively used to study composition and distribution of normal bone marrow, and to asses the extent of radiation-induced bone marrow injury; to monitor bone marrow recovery (or the lack of it); and in the general follow-up of treated cancer patients.