Homogentisic acid induces morphological and mechanical aberration of ochronotic cartilage in alkaptonuria

Alkaptonuria (AKU) is a disease caused by a deficient homogentisate 1,2-dioxygenase activity leading to systemic accumulation of homogentisic acid (HGA), that forms a melanin-like polymer that progressively deposits onto connective tissues causing a pigmentation called “ochronosis” and tissue degeneration. The effects of AKU and ochronotic pigment on the biomechanical properties of articular cartilage need further investigation. To this aim, AKU cartilage was studied using thermal (thermogravimetry and differential scanning calorimetry) and rheological analysis. We found that AKU cartilage had a doubled mesopore radius compared to healthy cartilage. Since the mesoporous structure is the main responsible for maintaining a correct hydrostatic pressure and tissue homoeostasis, drastic changes of thermal and rheological parameters were found in AKU. In particular, AKU tissue lost its capability to enhance chondrocytes metabolism (decreased heat capacity) and hence the production of proteoglycans. A drastic increase in stiffness and decrease in dissipative and lubricant role ensued in AKU cartilage. Multiphoton and scanning electron microscopies revealed destruction of cell–matrix microstructure and disruption of the superficial layer. Such observations on AKU specimens were confirmed in HGA-treated healthy cartilage, indicating that HGA is the toxic responsible of morphological and mechanical alterations of cartilage in AKU.     

Proteolytic inactivation of an extracellular (1 → 3)-β-glucanase from the fungus Acremonium persicinum is associated with growth at neutral or alkaline medium pH

Abstract The filamentous fungus Acremonium persicinum released high levels of proteolytic enzyme activity into the culture fluid during growth at pH 7 or above. Almost total inhibition of this crude activity by phenylmethylsulfonyl fluoride suggested that it was mainly due to the presence of a serine protease. This protease inactivated one of three extracellular (1 → 3)- β -glucanases produced by this fungus, although the activities of the remaining two (1 → 3)- β -glucanases did not appear to be affected. Growth of A. persicinum in acidic conditions resulted in the presence of much lower extracellular proteolytic activity and no apparent (1 → 3)- β -glucanase inactivation.     

Expression patterns of loricrin in various species and tissues

Abstract. In this study we analyzed the expression patterns of loricrin in various species and tissues using immunohistochemistry, immunoblotting and Northern blots. Loricrin is a glycine-, serine- and cysteine-rich protein expressed very late in epidermal differentiation in the granular layers of normal mouse and human epidermis. Later on in differentiation, loricrin becomes cross-linked as a major component into the cornified cell envelope by the formation of N^ɛ -(γ-glutamyl)lysine isopeptide bonds. This process either occurs directly or by the intermediate accumulation in L-keratohyaline granules of mouse epidermis and human acrosyringia. Loricrin was identified in all mammalian species analyzed by virtue of its highly conserved carboxy-terminal sequences revealing an electric mobility of ∼60 kDa in rodents, rabbit and cow and of ∼35 kDa in lamb and human on sodium dodecyl sulfate polyacrylamide gel electrophoresis. Loricrin is expressed in the granular layer of all mammalian orthokeratinizing epithelia tested including oral, esophageal and fore-stomach mucosa of rodents, tracheal squamous metaplasia of vitamin A deficient hamster and estrogen induced squamous vaginal epithelium of ovary ectomized rats. Loricrin is also expressed in a few parakeratinizing epithelia such as BBN [N-butyl-N-(4–hydroxybutyl)nitrosamine]-induced murine bladder carcinoma and a restricted subset of oral and single vaginal epithelial cells in higher mammals. Our results provide further evidence that the program of squamous differentiation in internal epithelia of the upper alimentary tract in rodents and higher mammals differ remarkably. In addition, we also have noted the distinct distribution patterns of human loricrin and involucrin, another major precursor protein of the cornified cell envelope.     

Pituitary Secretory Granule Topography: Influence of Different Electron Microscopic Preparation Procedures on the Surface of Epon Sections

Human, rat and mouse pituitary tissues have been examined electron microscopically in transmission (TEM), scanning-transmission (STEM) and scanning (SEM) modes for the surface appearance of the secretory granules in tissue sections. Cryofixed and cryosectioned tissue showed only slightly protruding granule profiles which had a smooth surface. Cryofixed, freeze-dried and Epon embedded pituitaries, on the other hand, demonstrated swollen and furrowed surfaces over the granules after contact with water. This topography could also be seen after glutaraldehyde fixation but less after post-fixation in OsO₄. The surface alterations in the sections of pituitary secretory granules are thought to be due to differences in the homogeneity of the resin infiltration, leaving resin-free openings where water can enter. It also seems probable that the Epon resin is more influenced by water than has been previously assumed, based on the findings of efficient elimination of osmium from the granules after incubation of tissue sections in water for only 10 min.     

Can dominance genetic variance be ignored in evolutionary quantitative genetic analyses of wild populations?

Accurately estimating genetic variance components is important for studying evolution in the wild. Empirical work on domesticated and wild outbred populations suggests that dominance genetic variance represents a substantial part of genetic variance, and theoretical work predicts that ignoring dominance can inflate estimates of additive genetic variance. Whether this issue is pervasive in natural systems is unknown, because we lack estimates of dominance variance in wild populations obtained in situ. Here, we estimate dominance and additive genetic variance, maternal variance, and other sources of nongenetic variance in eight traits measured in over 9000 wild nestlings linked through a genetically resolved pedigree. We find that dominance variance, when estimable, does not statistically differ from zero and represents a modest amount (2-36%) of genetic variance. Simulations show that (1) inferences of all variance components for an average trait are unbiased; (2) the power to detect dominance variance is low; (3) ignoring dominance can mildly inflate additive genetic variance and heritability estimates but such inflation becomes substantial when maternal effects are also ignored. These findings hence suggest that dominance is a small source of phenotypic variance in the wild and highlight the importance of proper model construction for accurately estimating evolutionary potential.     

A complex species complex: The controversial role of ecology and biogeography in the evolutionary history of Syllis gracilis Grube, 1840 (Annelida,Syllidae)

The cryptic diversity in the polychaete Syllis gracilis Grube, 1840, in the Mediterranean Sea was examined with an integrative morpho-molecular approach. Individuals of S. gracilis were collected at eleven Mediterranean localities to provide an insight into the role of brackish environments in inducing cryptic speciation. The examination of morphological features combined with a molecular genetic analysis based on a partial sequence of the 16S rRNA gene highlighted discrepancies between morphological and molecular diversity. Morphological data allowed to identify a morphotype with short appendages occurring in coralline algae communities and another one with long appendages observed in brackish-water environments and Sabellaria reefs. Multivariate analyses showed that sampling localities were the greatest source of morphological divergence, suggesting that phenotypic plasticity may play a role in local adaptations of S. gracilis populations. Molecular data showed the occurrence of four divergent lineages not corresponding to morphological clusters. Different species delimitation tests gave conflicting results, retrieving, however, at least four separated entities. Some lineages occurred in sympatry and were equally distributed in marine and brackish-water environments, excluding a biogeographic or ecological explanation of the observed pattern and suggesting instead ancient separation between lineages and secondary contact. The co-occurrence of different lineages hindered the identification of the lineage corresponding to S. gracilis sensu stricto. The discrepancy between morphological and molecular diversity suggests that different environmental and biogeographic features may interact in a complex and unpredictable way in shaping diversity patterns. An integrative approach is needed to provide a satisfactory insight on evolutionary processes in marine invertebrates.