Schistosomatium douthitti: effects of Lymnaea catascopium age on susceptibility to infection

Laboratory-reared Lymnaea catascopium snails (1–269 days old) were exposed individually to different numbers of Schistosomatium douthitti miracidia. Increasing the exposure dosage from 3 to 10 miracidia generally increased infection rates, in some age classes up to 100%. Successful re-exposure of snails not infected after a primary exposure was possible. Neonatal snails were least likely to become infected, primarily because miracidia were not attracted to them. Snails 12–55 days old were most susceptible to infection. Miracidia were readily attracted to these snails, and many were ingested and subsequently penetrated the host esophageal wall. Miracidial penetration of external snail surfaces was rare. Susceptibility of older snails (65–269 days) progressively declined with age. Many miracidia were entangled and immobilized in mucus produced by these snails, and fewer were ingested. No conspicuous host cellular responses to mother sporocysts were observed in any of the snails sectioned. A comparison of susceptibility of deliberately stunted snails and comparably aged controls of normal size indicated that the former were more susceptible.     

Growth and characterization of human skin epithelial cell cultures

Summary In 129 of 140 attempts, human skin cells were successfully cultured on the dermal collagen bed of sterile, dead pigskin. Diploid epithelial cells grew selectively on the collagen bed; fibroblasts grew on the glass surfaces of the culture dishes. The cultures could be subdivided physically up to six times at a 1:2 split ratio, but at least 24 to 48 cell generations were produced over the months the cells could be carried. Much of the cell multiplication resulted in maturation into distinct basal, squamous, granular, and keratinized cell layers. The cultured cells were considered epithelial because of their shape, possession of intercellular bridges, desmosomes and tonofibrils, and because they formed maturating epithelium in vitro and upon transplantation back to the original human donor. As the cells grew they digested the pigskin collagen, thus producing clear zones that could be used to monitor and quantitate cell growth. Multiplication of epithelial cells, rather than migration, was indicated by mitotic figures in colchicine-treated cultures and by DNA synthesis. Expert technical assistance was provided by Nancy Allen (cell culture); William Towler (electron microscopy); James Malone, Nona Scaife, and Joy M. Nicolet (cytogenetics); R. Thomas Campbell and Dorothy Sarver (photography); and V. L. Angerstein, Susan Ekker, and Arnater Yarbrough (histology). This work was supported by The United Fund Cancer Society of Summit County, the Greater Cleveland Associated Foundation (grant no. 3G3490X1), the National Institute of General Medical Services (grant no. 1 R01 GM 21929-01), and the Charles E. Merrill Trust.     

Ultrastructure of the Invasion of Eimeria magna Sporozoites into Cultured Cells*†‡

SYNOPSIS. Monolayers of bovine kidney cells were overlaid with Eimeria magna sporozoites and observed with phase-contrast optics until penetration of the cells by the parasites had begun. Cells and penetrating parasites were fixed with glutaraldehyde and OsO₄-containing ruthenium red, dehydrated, and embedded in situ. Cells being penetrated were selected for study in the electron microscope. The lack of intracellular staining with ruthenium red and intact plasmalemmas of cells being penetrated, was accepted as evidence that the sporozoites did not disrupt the plasma membranes. The sporozoite caused invagination of the host cell plasmalemma until the parasite was entirely within the cell, after which the invagination was sealed off by short pseudopodia enclosing the sporozoite within a membrane-lined vacuole inside the cell. Often myelin-forms, apparently of host cell origin, were seen in the space between the sporozoite and the cell.     

Ex vivo thickness measurement of cartilage covering the temporomandibular joint

Articular cartilage covers the temporomandibular joint (TMJ) and provides smooth and nearly frictionless articulation while distributing mechanical loads to the subchondral bone. The thickness of the cartilage is considered to be an indicator of the stage of development, maturation, aging, loading history, and disease. The aim of our study was to develop a method for ex vivo assessment of the thickness of the cartilage that covers the TMJ and to compare that with two other existing methods. Eight porcine TMJ condyles were used to measure cartilage thickness. Three different methods were employed: needle penetration, micro-computed tomography (micro-CT), and histology; the latter was considered the gold standard. Histology and micro-CT scanning results showed no significant differences between thicknesses throughout the condyle. Needle penetration produced significantly higher values than histology, in the lateral and anterior regions. All three methods showed the anterior region to be thinner than the other regions. We concluded that overestimated thickness by the needle penetration is caused by the penetration of the needle through the first layer of subchondral bone, in which mineralization is less than in deeper layers. Micro-CT scanning method was found to be a valid method to quantify the thickness of the cartilage, and has the advantage of being non-destructive.     

Contact sensitization: A new approach to risk assessment

The murine local lymph node assay is a novel predictive test for the identification of skin sensitizing chemicals. The method measures sensitization potential of a chemical in mice as a function of proliferative activity induced in lymph nodes draining the site of topical exposure to that test chemical. Here we describe the use of the local lymph node assay for evaluation of the relative potency of skin sensitizing chemicals via derivation of the concentration required to produce a threshold positive reaction. Subsequently, the development of risk assessments based on comparisons with index contact allergens is outlined.     

Penetration of soil aggregates of finite size

Summary Maximum penetrometer pressure was measured on artificial soil aggregates of finite size (2–29 mm) using blunt probes (total cone angle 60°) driven at 3 mm min⁻¹. Maximum penetrometer pressure increased asymptotically with increase in dimensionless aggregate radius,b/a, wherea andb are the probe and aggregate radii, respectively. A theory was developed for penetration of blunt probes into soil aggregates of finite size. The theory assumed that plastic failure occurs out to a radius,R, and that beyond this only elastic straining occurs. This theory can be applied to estimate the radial and tangential stresses adjacent to a blunt probe. The estimated radial and tangential stresses increased with increase in dimensionless aggregate radius,b/a. The radius of the plastic front,R, around the probe is predicted to increase with increased aggregate size. The results also demonstrate the effect of soil shear cohesion and internal friction angle onR. The results are discussed with reference to root penetration.     

Assessment of alcohol percentage test for fungal surface hydrophobicity measurement

Aim: To determine whether assessing the penetration of solutions with different concentrations of ethanol (alcohol percentage test: APT) on fungal surfaces is effective in characterization of hydrophobicity on fungal surfaces. Methods and Results: APT and contact angle (CA) measurements were conducted on nine hydrophobic and two hydrophilic fungal strains from the phyla of Ascomycota, Basidiomycota and Zygomycota. There was a strong positive correlation (R² = 0·95) between the APT and CA measurements from eight of the nine hydrophobic stains (four pathogenic and mycotoxigenic Fusarium taxa, one melanosporaceous biotrophic taxon, Alternaria sp, Penicillium aurantiogriseum and Cladosporium cladosporioides). Hydrophilic control strains, Mortierella hyalina and Laccaria laccata, had CAs <90° and no measurable degree of hydrophobicity using the APT method. Conclusions: The APT method was effective in measuring the degree of hydrophobicity and can be conducted on different zones of fungal growth. Significance and Impact of the Study: Characterization of fungal surface hydrophobicity is important for understanding of its particular role and function in fungal morphogenesis and pathogenesis. APT is a simple method that can be utilized for fungal hydrophobicity measurements when CA cannot be measured because of obscured view from aerial mycelia growth.     

Mesenchymal stromal cell‐derived factors promote the colonization of collagen 3D scaffolds with human skin cells

The development of stem cell technology in combination with advances in biomaterials has opened new ways of producing engineered tissue substitutes. In this study, we investigated whether the therapeutic potential of an acellular porous scaffold made of type I collagen can be improved by the addition of a powerful trophic agent in the form of mesenchymal stromal cells conditioned medium (MSC‐CM) in order to be used as an acellular scaffold for skin wound healing treatment. Our experiments showed that MSC‐CM sustained the adherence of keratinocytes and fibroblasts as well as the proliferation of keratinocytes. Moreover, MSC‐CM had chemoattractant properties for keratinocytes and endothelial cells, attributable to the content of trophic and pro‐angiogenic factors. Also, for the dermal fibroblasts cultured on collagen scaffold in the presence of MSC‐CM versus serum control, the ratio between collagen III and I mRNAs increased by 2‐fold. Furthermore, the gene expression for α‐smooth muscle actin, tissue inhibitor of metalloproteinase‐1 and 2 and matrix metalloproteinase‐14 was significantly increased by approximately 2‐fold. In conclusion, factors existing in MSC‐CM improve the colonization of collagen 3D scaffolds, by sustaining the adherence and proliferation of keratinocytes and by inducing a pro‐healing phenotype in fibroblasts.     

Mouse genetics identifies unique and overlapping functions of fibroblast growth factor receptors in keratinocytes

Fibroblast growth factors (FGFs) are key regulators of tissue development, homeostasis and repair, and abnormal FGF signalling is associated with various human diseases. In human and murine epidermis, FGF receptor 3 (FGFR3) activation causes benign skin tumours, but the consequences of FGFR3 deficiency in this tissue have not been determined. Here, we show that FGFR3 in keratinocytes is dispensable for mouse skin development, homeostasis and wound repair. However, the defect in the epidermal barrier and the resulting inflammatory skin disease that develops in mice lacking FGFR1 and FGFR2 in keratinocytes were further aggravated upon additional loss of FGFR3. This caused fibroblast activation and fibrosis in the FGFR1/FGFR2 double‐knockout mice and even more in mice lacking all three FGFRs, revealing functional redundancy of FGFR3 with FGFR1 and FGFR2 for maintaining the epidermal barrier. Taken together, our study demonstrates that FGFR1, FGFR2 and FGFR3 act together to maintain epidermal integrity and cutaneous homeostasis, with FGFR2 being the dominant receptor.