Martin E. Matthiessen

HISTOCHEMISTRY AND DEVELOPMENT OF THE HUMAN EYELIDS

The development of the eyelids involves numerous complicated biological and embryological problems, which have received little attention in the past in particular problems concerning the development of human eyelids. In this connection the processes associated with the growth of the eyelids and their subsequent junction should be emphasized, as also the importance of this junction for the differentiation of the structures situated behind the eyelids. Furthermore, the disjunction of the eyelids at later stage of embryonic development should be mentioned, together with the formation of the cilia and associated glands and the role which they play in the disjunction process as well as their possible influence on the keratinization of the margins of the eyelids. Also the development of the lipid-producing Meibomian glands should be mentioned. The purpose of the present study was to clarify, if possible, these problems and a t the same time to draw up a biological time-table for the development of the different structures of the eyelids.

The histiocyte in human foetal tissues: its morphology, cytochemistry, origin, function, and fate.

SummaryBased upon a material comprising human foetuses cytochemical studies of a widespread type of cell were carried out. Apart from amoeboid mobility the cell is characterized by pinocytotic and phagocytotic activity.In early development stages these cells are seen intravascularly and penetrating the vessels. Later they are seen in connection with the formation of the vascular epiphyseal cartilaginous canals and in the vitreous body, the synovial joints and dental anlage. Furthermore these cells are seen at the removal of the epithelial cells of the dental lamina and the junctional epithelium in the two palatine processes. The cells concerned are seen also in the deep periosteal layer at the centre of the diaphysis synchronously with the vaseularization of the periosteum and prior to the periosteal invasion. Based upon morphology and cytochemistry the theory is advanced that these cells form the chondroclasts and the multinucleated osteoclasts. By contrast, the diaphysial osteoblasts are derived from invading pre-osteoblasts from the cambium-layer of the periosteum.These cells are also seen along the basal surface of the neural apparatus and invading the brain vesicles.On the basis of morphology and cytochemistry the cell type is designated a histiocyte and its origin is traced back to primitive leucocytes.

Cell junctions of the human enamel organ.

SummaryThe nature and distribution of cell contacts have been examined in the human enamel organ in bell stage. The lateral cell surfaces of secretory ameloblasts are linked at their distal (apical) and proximal (basal) parts by junctional complexes consisting of tight junctions, large intermediate junctions (zonulae adherentes), occasional gap junctions and one or more series of desmosomes. Scattered desmosomes and large gap junctions link epithelial cells of the external enamel epithelium, stellate reticulum, stratum intermedium and internal enamel epithelium including secretory ameloblasts. Furthermore the above-mentioned layers are also linked together by desmosomes and gap junctions.With increasing maturation of the enamel organ an increase in size and number of gap junctions is observed. Some possible implications of the role of the different junctions are considered. The gap junctions probably participate in cell differentiation in the normal morphogenesis of the teeth as well as in metabolic and ionic coupling of the cells of the enamel organ. By means of tight junctions, adjacent secretory ameloblasts cooperate to form a physical barrier which might prevent the diffusion of some types of molecules or substances (e.g. secretory material distally and acid mucopolysaccharides proximally) through the interspaces between the cells. Adhering junctions might assist in regulation of the mechanical properties of the enamel organ as a whole.

Histochemistry and development of the human eyelids. II. A cytochemical and electron microscopical study.

In a previous study, the development of the human eyelids was investigated in a material comprising human foetuses of crown-rump lengths varying from 8 to 220 mm (Andersen, Ehlers and Matthiessen, 1965). The development passes through three stages: ( 1 ) The stage of growth: The period from the initial ectoderm proliferation till the junction of the eyelids (crown-rump length from about 12 mm to about 40 mm), (2) The stage of differentiation: From junction to the beginning of disjunction (crown-rump length from about 40 mm to about 150 mm), and (3) The stage of maturation: The remaining part of the development of the eyelids, characterized by continued growth and maturation of the various structures of the eyelids. The study dealt mainly with the first two stages, and time-tables were drawn up for the appearance and development of the different structures, and the development was discussed from a functional point of view. However, certain problems remained and will be dealt with in the present paper: ( 1 ) Does the junction of the eyelids give rise to an epithelial adhesion only between the two eyelids, or are desmosomes, or another epithelial contact, formed at the site of the junction? (2) The more intimate relationship between the epithelium of the junction

Immunohistochemistry of the intercellular matrix components and the epithelio-mesenchymal junction of the human tooth germ.

SummaryThe immunohistochemical localization of heparan sulphate, collagen type I, III and IV, laminin, tenascin, plasma- and cellular fibronectin was studied in tooth germs from human fetuses. The lamina basalis ameloblastica or membrana preformativa, which separates the pre-ameloblasts from the pre-dentin and dentin, contained heparan sulphate, collagen type IV, laminin and fibronectin. Enamel reacted with antifibronectin, but the reaction varied depending on the type of fibronectin and the source of antibody. In early pre-dentin, collagen type I, laminin, tenascin and fibronectin were present. In late pre-dentin and dentin collagen type I was found in intertubular dentin and in the zone between enamel and dentin. The close relationship between collagen type I in dentin and fibronectin in immature enamel is interesting, as it may contribute to the stabilization of the amelodentinal interface. In dental pulp, collagen type IV and laminin were found in the endothelial basement membranes. Collagen type I and III, tenascin and fibronectin were localized to the mesenchymal intercellular matrix.The results of this study have supported the assumption that the lamina basalis ameloblastica is a basement membrane, and have lead to the suggestion that ameloblasts are producers of fibronectin or a fibronectin-like substance.

Disintegration of the junctional epithelium of human fetal hard palate.

SummaryAn ultrastructural and a histochemical study of the disintegration of the human fetal palatinal junctional epithelium was carried out.Special attention was focused both on the epithelium proper as well as on participation of the surrounding mesenchyma.Epithelial autophagia was noticed in the form of inclusion bodies with cellular remnants as well as general cellular disintegration. The disintegration was correlated to the cellular activity of acid phosphatase and AS-esterase. The differences between human and non-human material were recorded and discussed.In the surrounding mesenchyma, histiocytes (macrophages) were noticed participating in the epithelial disintegration, while ordinary mesenchymal cells seemed without importance.The study of activity of alkaline phosphatase reveals that the rapidly growing ossification center of the vomer was touching the superior aspect of the epithelial junctional seams, where the epithelial disintegration starts.Based upon the findings the following sequential steps of disintegration were discussed: 1) pressure from the outside (the vomer anlage), 2) epithelial autophagia and 3) heterophagia of epithelial remnants (invading histiocytes).The ultrastructure and histochemistry of the so-called epithelial pearls were described.The intercellular substance of the palatinal processes was found to consist of hyaluronic acid and of chondroitin-4- and/or-6-sulfate. The mutual ratio of the glycosaminoglucuronoglycans was discussed.

HEREDITARY CRYSTALLINE CORNEAL DYSTROPHY OF SCHNYDER

A family with three members affected by hereditary crystalline corneal dystrophy of Schnyder is reported. Penetrating keratoplasty was performed in two of the affected members. Clear grafts were obtained. The buttons were examined by light‐ and electronmicroscopy. The epithelium was normal. In the superficial stroma, deposits, often of a crystalline nature, were seen. Electron microscopically the deposits appeared as empty spaces, either of regular geometrical form suggestive of crystals, or smaller, rounded and more irregular. The collagen fibrils were normal. Staining for acid mucopolysaccharides revealed no abnormalities. Adjacent to the lipid deposits were found cells which contained membrane bound granules which appeared empty or contained crystal‐like material. The cells were shown to contain non‐specific As‐acetate esterase and β‐hydroxybutyrate dehydrogenase.

Swelling of Mitochondria in Immersion-Fixed Liver Tissue

In order to study the occurrence of swollen and disrupted mitochondria in tissue preserved for electron microscopy by ordinary fixation methods, liver tissue from miniature pig fetuses was immersion-fixed in fixatives with various types and concentrations of fixing agents and vehicles. Also commercial and purified products have been tested, different fixation times and temperatures as well as the consequences of a short rinsing in buffer solutions prior to fixation. Furthermore, the significance of delayed fixation (autolysis) was studied. It was found that swollen and disrupted mitochondria occur predominantly in liver cells exposed to low concentrations of glutaraldehyde. It is shown that this phenomenon is a result of a specific effect of glutaraldehyde on the mitochondrial membranes. It is not accompanied by parallel changes of other organelles or nuclei, and it not provoked by other fixing agents, vehicles or by delayed fixation (autolysis).

Fixation of foetal pig liver for electron microscopy

SummaryLight and electron microscopic investigations of the ability of various fixatives to preserve foetal pig liver tissue (immersion fixed 5 min, 20 min, and 40 min after the death of the mother) gave the following results:1)Fixation with 4% formaldehyde gives, in all circumstances, an unacceptable tissue preservation.2)Fixation with 2.5% glutaraldehyde gives fair tissue preservation in a ca. 130 μ thick zone below the surface.3)Fixation with a fixative mixture containing 2% formaldehyde and 1.25% glutaraldehyde or 2% formaldehyde, 1% glutaraldehyde and 1% acrolein gives good tissue preservation in a ca. 500 μ thick zone under the surface.4)The addition of DMSO does not improve tissue preservation.5)Delayed fixation of liver tissue removed from the foetus after the uterus has been placed in an incubator for 40 min has only a slight effect on tissue preservation.

The ultrastructure of human fetal odontoblasts

SummaryThe ultrastructure of odontoblasts of deciduous teeth from two human fetuses (CRL 159 and 195 mm) was investigated. The human odontoblast is a polarized cell with a characteristic localization of its organelles and demonstrates similarities with odontoblasts from non-human materials. Vesicular and granular elements were found to be formed in the Golgi complex, and these elements were also observed in the odontoblastic process, thereby indicating a secretory process. No special organization of the predentinal collagen fibrils was observed. In the newly formed dentin a thin sheath of non-mineralized material was seen to surround the odontoblastic process. The ultrastructural findings are correlated to the findings of recent histochemical investigations.