Staining glycol methacrylate embedded cartilage with triethyl-carbocyanin DBTC ("ethyl-stains all") with special reference to the interlacunar network

Kraftionema allantoideum, a new genus and family of Ulotrichales (Chlorophyta) adapted for survival in high intertidal pools

The marine, sand-dwelling green alga Kraftionema allantoideum gen. et sp. nov. is described from clonal cultures established from samples collected in coastal, high intertidal pools from south eastern Australia. The species forms microscopic, uniseriate, unbranched, 6-8 μm wide filaments surrounded by a gelatinous capsule of varying thickness. Filaments are twisted, knotted, and variable in length from 4 to 50 cells in field samples but straighter and much longer in culture, up to 1.5 mm in length. Cell division occurs in several planes, resulting in daughter cells of varying shape, from square to rectangular to triangular, giving rise to gnarled filaments. Mature cells become allantoid, elongate with rounded ends, before dividing one time to form bicells comprised of two domed cells. Adjacent bicells separate from one another and mature filaments appeared as a string of loosely arranged sausages. A massive, single, banded chloroplast covered 3/4 of the wall circumference, and contained a single large pyrenoid encased in a starch envelope that measures 1.5-2.5 μm. Filaments were not adhesive nor did they produce specialized adhesive cells or structures. Reproduction was by fragmentation with all cells capable of producing a new filament. No motile or reproductive cells were observed. Filaments in culture grew equally well in freshwater or marine media, as well as at high salinity, and cells quickly recovered from desiccation. Phylogenetic analysis based on the nuclear-encoded small subunit ribosomal RNA (18S) shows the early branching nature of the Kraftionema lineage among Ulotrichales, warranting its recognition as a family (Kraftionemaceae).

The biological reality of the interlacunar network in the embryonic, cartilaginous, skeleton: a thiazine dye/absolute ethanol/LR White resin protocol for visualizing the network with minimal tissue shrinkage

Third toe phalanges of chicks aged 8-13 days in ovo and 7-day post-natal rat femoral growth plate were examined to determine whether the interlacunar network (IN), a structure with no lipoprotein membrane component or cytoplasmic organelles, is a genuine component of young growth cartilage. In chick phalanges dehydrated by 70% (v/v) ethanol and LR White resin, variable metachromatic staining of the interlacunar network by toluidine blue and red staining by picro-Sirius red indicate the presence of glycosaminoglycans and collagen. The network in phalanges dehydrated by 80% (v/v) ethanol appears little different; however, the network is much less widely detectable in phalanges dehydrated by 90% (v/v) ethanol and, after dehydration by absolute ethanol, is almost completely undetectable. In contrast, when the young cartilage is permeated by a thiazine dye such as toluidine blue, using a solution of dye in the aldehyde fixative, the network is widely detectable, following dehydration by absolute ethanol, both in chick phalanges and in rat growth plate. Comparison of projected areas shows that the extent to which whole chick feet are found to have shrunk, by the time that they are photographed under LR White resin, is determined principally by the extent of dehydration, by 70% (v/v) or absolute ethanol; post-shrinkage areas are 33% or 35% of areas measured in buffer for 70% (v/v) ethanol/LR White resin and 71% or 75% for absolute ethanol/LR White resin (the higher value in each is for the toluidine blue treatment). The network is thus present in radically shrunk tissue, but, significantly, is also fully represented in tissue shrunk by only a conventional margin and is therefore not produced as an artefact by exceptional tissue shrinkage as has been suggested.

Thionin staining of paraffin and plastic embedded sections of cartilage

The usefulness of thionin for staining cartilage sections embedded in glycol methacrylate (GMA) and the effect of decalcification on cartilage sections embedded in paraffin and GMA were assessed. Short decalcification periods using 5% formic acid or 10% EDTA did not influence the staining properties or the morphology of cartilage matrix and chondrocytes. The standard stain safranin O-fast green for differential staining of cartilage was used as control in these experiments. Prolonged exposure of safranin O stained sections to fast green resulted in disappearance of the safranin O stained matrix, thereby hampering the quantitative measurement of negatively charged glycosaminoglycans (GAG). Thionin stained evenly throughout all cartilage layers, independent of the staining times. In contrast to safranin O, thionin did not show metachromasia in nondehydrated cartilage sections, which made it more suitable for assessing cartilage quality in GMA embedded cartilage. To evaluate the selectivity of thionin staining in cartilage, chondroitinase ABC and trypsin digestions were carried out. Thionin staining was prevented by these enzymes in the territorial matrix, representing the interlacunar network and the chondrocyte capsule. Staining with thionin of the interterritorial matrix was only slightly reduced, possibly representing keratan sulfate and hyaluronic acid in cartilage of elderly patients. Comparison of thionin stained GMA embedded cartilage with safranin O stained paraffin embedded sections showed significant similarity in optical densitometry, indicative of the specificity of thionin bound to negatively charged GAG in cartilage. In GMA embedded cartilage morphology was relatively intact compared to paraffin embedded sections due to less shrinkage of chondrocytes and the interlacunar network.

A system of interlacunar network and thick fibrils in human hyaline cartilage

A system consisting of an interlacunar network and thick fibrils was demonstrated in the matrix of human fetal and neonatal hyaline cartilage, using an osmium-ferrocyanide mixture as a second fixative. The network appeared as irregular strands consisting of hyaluronidase-sensitive, amorphous and fine fibrillar material. The thick fibrils measured 75-125 microns in diameter, each appearing to consist of several collagen fibrils twisted into a cable and cemented by dense amorphous material. Strands of the network were seen to cross and focally distort the thick fibrils, suggesting that the strands exert some tensile forces on the thick fibrils. During the first year of life the network rapidly became undemonstrable, but the thick fibrils persisted into adulthood. This system of interlacunar network and thick fibrils appears to form an integral functional unit which may play an organizational role in the formation of cartilagenous matrix during development. Furthermore, it may contribute to the mechanical strength of the collagen framework in hyaline cartilage.