Filament-directed intercellular contacts during differentiation of cultured chick myoblasts

Detergent-extracted, critical point dried chicken myoblasts at early stages of development in tissue culture were observed by electron microscopy. It was found that the organization of filaments within these cells changes significantly during development. A particular specialization of the cellular filament framework is the formation of microprocesses; long extensions of the cellular filament system. These microprocesses appear to be involved in cell-to-cell contact. The filaments of these processes appear to integrate with the filament system of a contacted cell, and possibly transmit tension from one cell to another. The role of these structures in effecting muscle differentiation by forming cytoplasmic connections and the implications for muscle gene expression are discussed.     

A combined small‐angle X‐ray and neutron scattering study of the structure of purified soluble gastrointestinal mucins

The structures of purified soluble porcine gastric (Muc5ac) and duodenal (Muc2) mucin solutions at neutral and acidic pH were examined using small‐angle X‐ray scattering and small‐angle neutron scattering experiments. We provide evidence for the morphology of the network above the semidilute overlap concentration and above the entanglement concentration. Furthermore, we investigated the gelation of both types of mucin solutions in response to a reduction in pH, where we observed the formation of large‐scale heterogeneities within the polymer solutions, typical of microphase‐separated gels. The concentration dependence of the inhomogeneity length scale (Ξ) and the amplitude of the excess scattering intensity [I_ex(0)] are consistent with previously studied gelled synthetic polymeric systems. The persistence lengths of the chains were found to be similar for both Muc5ac and Muc2 from Kratky plots of the neutron data (8 ± 2 nm). © 2014 Wiley Periodicals, Inc. Biopolymers 101: 1154–1164, 2014.     

Polyploidization of the BTC-32 cell line from Triatoma infestans (Hemiptera,Reduviidae)

The cytophotometric evaluation of the Feulgen-DNA content of the BTC-32 cells at passage 160 after 6 days of growth demonstrated that polyploidy is relatively frequent in this cell line. 4C values were assumed to pertain to diploid nuclei at the S or G2 phases but also to polyploid nuclei at the G1 phase. Polyploidy in 4C nuclei is assumed to be attained by endomitosis. However, there are morphological indications that polyploidization in cells with an 8C–128C Feulgen-DNA content could result from cellular and nuclear fusions, possibly mediated by viral particles present in the cell culture. Micronucleation was also frequent; it was assumed to be promoted by viral action or deficiency in some culture medium nutrient. These nuclear characteristics should be considered when using the BTC-32 cell line for monitoring the action of infective agents or their products.     

Location of enzymes of androgen and estrogen biosynthesis in the testis of the ground squirrel (Citellus lateralis)

The intratesticular localization of enzymes of androgen and estrogen biosynthesis was studied in the ground squirrel (Citellus lateralis). In mature animals, interstitium and tubules were isolated by manual dissection. Microsomes were prepared and enzymes assayed by analysis of product formation after incubation with appropriate 3H-labeled substrates. In the immature testis, tubules and interstitium are not readily separable; thus, distribution was inferred after analysis of whole testicular microsomes from control, follicle-stimulating hormone (FSH)-treated, and luteinizing hormone (LH)-treated animals. To verify the cellular composition of tissues and the status of steroidogenic organelles in Leydig and Sertoli cells, samples were also analyzed by light and electron microscopy. In mature squirrels, enzymes of androgen biosynthesis were concentrated in the interstitium; however, levels present in the tubules were sufficient to account for a substantial fraction of whole testicular activity (1/3 to 1/5). By contrast, virtually all of the testicular aromatase was accounted for by that in the seminiferous tubules. The purity of these fractions was checked by light microscopy; they showed little cross-contamination. In whole testicular microsomes of immature squirrels, androgen biosynthetic enzymes had a much lower specific activity than in mature animals; however, the opposite was true for aromatase, its activity being approximately 5-fold higher in prepubertal animals. Luteinizing hormone treatment markedly stimulated hydroxylase and lyase but not aromatase. Luteinizing hormone also induced an increase in Leydig cell size and a dramatic proliferation of smooth endoplasmic reticulum. These changes were correlated with increased serum testosterone. As shown previously in rats, 3 beta-hydroxysteroid dehydrogenase was independent of LH control. Follicle-stimulating hormone had no effect on any of the enzymes studied, but induced some increase of agranular reticulum in Sertoli cells. Results from immature squirrels thus corroborate data from mature animals, showing a predominant interstitial location of androgen biosynthetic enzymes. While we cannot explain the absence of FSH stimulation of aromatase activity, the data do not refute the findings in mature animals showing a predominant tubular location of this enzyme. We conclude that the distribution of steroidogenic enzymes in the testis of squirrels differs in several important respects from rats, although both are members of the order Rodentia.     

Brillouin microscopy for the evaluation of hair micromechanics and effect of bleaching

Brillouin microscopy is a new form of optical elastography and an emerging technique in mechanobiology and biomedical physics. It was applied here to map the viscoelastic properties of human hair and to determine the effect of bleaching on hair properties. For hair samples, longitudinal measurements (i.e. along the fibre axis) revealed peaks at 18.7 and 20.7 GHz at the location of the cuticle and cortex, respectively. For hair treated with a bleaching agent, the frequency shifts for the cuticle and cortex were 19.7 and 21.0 GHz, respectively, suggesting that bleaching increases the cuticle modulus and—to a minor extent—the cortex modulus. These results demonstrate the capability of Brillouin spectroscopy to address questions on micromechanical properties of hair and to validate the effect of applied treatments.