Ultrathin cross-section of the Malpighian tubule (MT) in <i>T</i>. <i>cavicola</i> at the beginning of overwintering.

<p><b>(a)</b> The apical part of the epithelial cell with numerous mitochondria (M) and spherites (S). The apical plasma membrane is differentiated into microvilli of up to 5 μm long (MV). LU, lumen of the MT. <b>(b)</b> The perinuclear cytoplasm containing many mitochondria (M) and spherites (S). <b>(c)</b> The basal part of the epithelial cell with spherites (S) and mitochondria (M). The basal plasma membrane with typical multiple infoldings and a few mitochondria. Muscle cell (MC) beneath the epithelium of the MT. BL, basal lamina. <b>(d)</b> Golgi apparatus (GA) and mitochondria (M) in the perinuclear region of the epithelial cell. Scale bar: 2 μm (a, b, c) and 500 nm (d).</p

Rates (in %) of the Malpighian tubule epithelial cell samples containing autophagic structures in <i>Troglophilus cavicola</i> and <i>T</i>. <i>neglectus</i> during overwintering, observed by TEM.

<p>Rates (in %) of the Malpighian tubule epithelial cell samples containing autophagic structures in <i>Troglophilus cavicola</i> and <i>T</i>. <i>neglectus</i> during overwintering, observed by TEM.</p

Abundances of autophagosomes per 100 μm² in the epithelial cells of the Malpighian tubules in <i>Troglophilus cavicola</i> and <i>T</i>. <i>neglectus</i> during three time frames of overwintering, as determined using IFM.

<p>Abundances of autophagosomes per 100 μm² in the epithelial cells of the Malpighian tubules in <i>Troglophilus cavicola</i> and <i>T</i>. <i>neglectus</i> during three time frames of overwintering, as determined using IFM.</p

Ultrathin cross-section of the Malpighian tubule (MT) in <i>T</i>. <i>cavicola</i> in the middle of overwintering.

<p><b>(a)</b> Apical part of the cell with numerous mitochondria (M). Spherites (S) containing electron-lucent concentric layers. MV, microvilli. Scale bar: 2 μm. <b>(b)</b> Perinuclear region of the epithelial cell with mitochondria (M) and spherites (S). Scale bar: 1 μm. <b>(c)</b> The basal part of the epithelial cell with the nucleus (N), spherites (S) and mitochondria (M). MC, muscle cell. Scale bar: 2 μm. <b>(d)</b> A spherite (S) composed of electron-lucent and electron-dense concentric layers. Scale bar: 500 nm.</p

A part of the Malpighian tubule (MT) of <i>T</i>. <i>cavicola</i> at the beginning of overwintering.

<p>Light microsccopy allows to see the general appearance of a MT composed of the epithelium (EP), and the lumen (LU).</p

Ultrathin cross-section of the Malpighian tubule (MT) in <i>T</i>. <i>cavicola</i> at the end of overwintering.

<p><b>(a)</b> Epithelial cells (EC) and a muscle cell (MC). Fully-formed spherite in which the dense core is in a contact with the membrane (1). Cases of gradually exploited spherites (2–5). In 2 and 3 the dense spherital cores lost the contact with the membrane. In 4, only one concentric ring of the spherite material and the membrane could be recognized. In 5, the dense core of the spherite is completely exploited; only the membrane is present. LU, lumen of the MT; S, spherite. Scale bar: 2 μm. <b>(b)</b> The perinuclear region of the EC with spherites (S). Scale bar: 1 μm. <b>(c)</b> Apical part of the EC. LU, lumen of the MT; M, mitochondrium; S, spherite. Scale bar: 2 μm. <b>(d)</b> Basal part of the EC and the basal lamina (BL). S, spherite. Scale bar: 2 μm.</p

Descriptive statistics (mean ± StD; min − max) of autophagosome abundances per 100 μm² in the epithelial cells of the Malpighian tubules in <i>Troglophilus cavicola</i> and <i>T</i>. <i>neglectus</i>, and Mann-Whitney U test between the sexes.

<p>Significant differences in bold.</p

Peptides at the Interface: Self-Assembly of Amphiphilic Designer Peptides and Their Membrane Interaction Propensity

Self-assembling amphiphilic designer peptides have been successfully applied as nanomaterials in biomedical applications. Understanding molecular interactions at the peptide–membrane interface is crucial, since interactions at this site often determine (in)­compatibility. The present study aims to elucidate how model membrane systems of different complexity (in particular single-component phospholipid bilayers and lipoproteins) respond to the presence of amphiphilic designer peptides. We focused on two short anionic peptides, V₄WD₂ and A₆YD, which are structurally similar but showed a different self-assembly behavior. A₆YD self-assembled into high aspect ratio nanofibers at low peptide concentrations, as evidenced by synchrotron small-angle X-ray scattering and electron microscopy. These supramolecular assemblies coexisted with membranes without remarkable interference. In contrast, V₄WD₂ formed only loosely associated assemblies over a large concentration regime, and the peptide promoted concentration-dependent disorder on the membrane arrangement. Perturbation effects were observed on both membrane systems although most likely induced by different modes of action. These results suggest that membrane activity critically depends on the peptide’s inherent ability to form highly cohesive supramolecular structures

Image1_Western diet-induced ultrastructural changes in mouse pancreatic acinar cells.tif

Mouse models of diet-induced type 2 diabetes mellitus provide powerful tools for studying the structural and physiological changes that are related to the disease progression. In this study, diabetic-like glucose dysregulation was induced in mice by feeding them a western diet, and light and transmission electron microscopy were used to study the ultrastructural changes in the pancreatic acinar cells. Acinar necrosis and vacuolization of the cytoplasm were the most prominent features. Furthermore, we observed intracellular and extracellular accumulation of lipid compounds in the form of lipid droplets, structural enlargement of the cisternae of the rough endoplasmic reticulum (RER), and altered mitochondrial morphology, with mitochondria lacking the typical organization of the inner membrane. Last, autophagic structures, i.e., autophagosomes, autolysosomes, and residual bodies, were abundant within the acinar cells of western diet-fed mice, and the autolysosomes contained lipids and material of varying electron density. While diets inducing obesity and type 2 diabetes are clearly associated with structural changes and dysfunction of the endocrine pancreas, we here demonstrate the strong effect of dietary intervention on the structure of acinar cells in the exocrine part of the organ before detectable changes in plasma amylase activity, which may help us better understand the development of non-alcoholic fatty pancreas disease and its association with endo- and exocrine dysfunction.</p

Development of an Advanced Intestinal in Vitro Triple Culture Permeability Model To Study Transport of Nanoparticles

Intestinal epithelial cell culture models, such as Caco-2 cells, are commonly used to assess absorption of drug molecules and transcytosis of nanoparticles across the intestinal mucosa. However, it is known that mucus strongly impacts nanoparticle mobility and that specialized M cells are involved in particulate uptake. Thus, to get a clear understanding of how nanoparticles interact with the intestinal mucosa, in vitro models are necessary that integrate the main cell types. This work aimed at developing an alternative in vitro permeability model based on a triple culture: Caco-2 cells, mucus-secreting goblet cells and M cells. Therefore, Caco-2 cells and mucus-secreting goblet cells were cocultured on Transwells and Raji B cells were added to stimulate differentiation of M cells. The in vitro triple culture model was characterized regarding confluence, integrity, differentiation/expression of M cells and cell surface architecture. Permeability of model drugs and of 50 and 200 nm polystyrene nanoparticles was studied. Data from the in vitro model were compared with ex vivo permeability results (Ussing chambers and porcine intestine) and correlated well. Nanoparticle uptake was size-dependent and strongly impacted by the mucus layer. Moreover, nanoparticle permeability studies clearly demonstrated that particles were capable of penetrating the intestinal barrier mainly via specialized M cells. It can be concluded that goblet cells and M cells strongly impact nanoparticle uptake in the intestine and should thus be integrated in an in vitro permeability model. The presented model will be an efficient tool to study intestinal transcellular uptake of particulate systems