The chondrocyte and its pericellular microenvironment together represent the chondron, historically considered the primary structural, functional and metabolic unit of articular and other hyaline cartilages. This review summarises research over the last 10 years to establish the molecular anatomy, functional properties and metabolic contribution of the chondron in articular cartilage homeostasis, and its failure during the initiation and progression of degenerative osteoarthritis.

Intralobular lymphatics in the guinea pig pancreas were demonstrated enzyme-histochemically showing the extent, distribution and fine structure by combined light and transmission electron microscopy. 5′-nucleotidase(5′-Nase)-positive lymphatic vessels were present throughout the pancreas. Intralobular lymphatics among the acini were comparatively rare and generally independent of the blood capillaries, pancreatic ducts and acini. These lymphatics revealed the usual structural features, such as typical intercellular junctions and very tenuous vascular walls without continuous basal laminae. Fine precipitates of the cerium-based reaction product for 5′-Nase activity were found to be associated with cell membranes of the lymphatic endothelium and pinocytotic vesicles. Lymphatics were not closely related to the endocrine islets, although alkaline phosphatase(ALPase)-positive blood capillaries were well developed. Collecting lymphatic vessels with valves with weaker 5′-Nase activity were also detected in the interlobular connective tissue. ALPase activity, absent in the lymphatics, was positive in the blood capillaries, suggesting that it is also a useful way of demonstrating, histochemically, the blood capillaries in the guinea pig pancreas.

Investiture of new microvessels within an injured peripheral nerve trunk may determine the success that the local environment has in promoting axonal sprouting and regeneration. We therefore examined microvessel investment of 24 h–14 d proximal nerve stump preparations in rat sciatic nerves. The stumps, later destined to form neuromas, were created by sciatic nerve transection with resection of distal branches to prevent distal reinnervation. Microvessels were studied in the proximal stump in semithin whole mount sections of nerve and by analysis of India ink perfused microvessel profiles. Quantitative image analysis was made of the luminal profiles of vessels perfused with India ink from unfixed sections of the stumps, contralateral uninjured nerves and sham-exposed but uninjured nerves. Evidence of angiogenesis was observed in stumps 7 d after transection, indicated by a rise in the total numbers of perfused microvessels and in the numbers of 2–6 μm diameter perfused microvessels. There was a shift in the histogram of the percentage of perfused microvessels towards the 2–4 μm range and a reduction in the mean microvessel luminal area in the stumps. By 14 d, new microvessels were larger, indicated by an increase in total luminal area. New microvessels were prominent in the epineurial connective tissue or between layers of perineurial cells of former fascicles. Microvessels probably share a battery of trophic signals with other proliferating cellular elements in the milieu of the injured peripheral nerve trunk.

A 14 d ovarian primordium was transplanted with a fetal testis (13–18 d and 21 d of gestation) or a neonatal testis (15, 20, 30 and 45 d after birth) into the renal subcapsular position of an adult male rat. Two weeks after transplantation, transplants were examined as to the degree of ovarian and testicular differentiation. In the combination of a 14 d ovary and a 13 d testis, there were 3 types of result: either the ovary or the testis alone developed or both gonads developed well. Ovaries transplanted in union with 15–18 d testes did not develop, although the testes developed normally. Some ovaries in union with 21 d testes developed normally. In combination with infantile testes, the incidence of developed ovaries increased as the age of testes advanced. These results suggest that the 13 d fetal testes begin to suppress the development of cotransplanted 14 d ovaries, that 14–18 d fetal testes maintain such suppressive effects and that this effect gradually diminishes in infantile testes as they progress toward 45 d after birth.

Connective tissues synthesise and secrete a family of matrix metalloproteinases (MMPs) which are capable of degrading most components of the extracellular matrix. Animal studies suggest that the MMPs play a role in bone turnover. Using specific polyclonal antisera, immunohistochemistry was used to determine the patterns of synthesis and distribution of collagenase (MMP-1), stromelysin (MMP-3), gelatinase A (MMP-2) and gelatinase B (MMP-9) and of the tissue inhibitor of metalloproteinases-1 (TIMP-1) within developing human osteophytic bone. The different MMPs and TIMP showed distinct patterns of localisation. Collagenase expression was seen at sites of vascular invasion, in osteoblasts synthesising new matrix and in some osteoclasts at sites of resorption. Chondrocytes demonstrated variable levels of collagenase and stromelysin expression throughout the proliferative and hypertrophic regions, stromelysin showing both cell-associated and strong matrix staining. Intense gelatinase B expression was observed at sites of bone resorption in osteoclasts and mononuclear cells. Gelatinase A was only weakly expressed in the fibrocartilage adjacent to areas of endochondral ossification. There was widespread but variable expression of TIMP-1 throughout the fibrous tissue, cartilage and bone. These results indicate that MMPs play a role in the development of human bone from cartilage and fibrous tissue and are likely to have multiple functions.

Pregnant female mice were divided on day 12 post coitum into a control and an experimental group. The experimental group was given a single intraperitoneal dose of 0.015 ml/g body weight of 25% solution of alcohol in distilled water while the control group was exposed to a similar weight related dose of normal saline. The optic nerves were isolated from the offspring of both control and experimental groups at wk 2, 3 and 5 (i.e. during the juvenile period of postnatal development) and analysed by light and electron microscopy. Although in both groups the optic nerve grew in size rapidly during the period studied, the rate of growth in the experimental groups lagged behind that of the controls. The difference was initially significant but tailed off, so that by wk 5 it was no longer significant. The time of initial onset and progression of myelinogenesis in the optic nerve of alcohol exposed mice also lagged behind that of controls. In both groups the size distribution of the myelinated nerve fibres in the optic nerve was unimodal with a positive skewing for all ages. The spectrum of size distribution of the nerve fibres was, however, broader in controls than in the corresponding experimental groups. With increasing age the proportion of small and medium size fibres was greater in the experimental group than in the controls, while for the large diameter fibres the reverse was observed. It is suggested that this study may shed light on the teratogenic effect of ‘binge’ drinking during pregnancy and that it is the critical period when exposure occurs that is more important than the duration of administration.

Out of a total of 21 exencephalic p53-deficient embryonic and newborn mice, 6 (28.6%) possessed fused maxillary incisor teeth. On histological analysis of the 5 examples seen on day 19.5 of gestation and newborn mice, 3 varieties were observed: an example of ‘simple’ fusion, 3 examples of simple fusion each of which contained a ‘dens in dente’ (‘tooth within a tooth’), and a single example in which the fused teeth were associated with a median supernumerary incisor tooth which, while deeply indenting the labial surface of the fused teeth, was in all locations a completely separate unit. 3-D reconstructions of the fused teeth demonstrated that they were all of the fusio subtotalis variety. No gross abnormalities were observed in the other dentition in these mice. It is noted that in mice fused maxillary incisor teeth are relatively commonly associated with both hypervitaminosis A-induced and trypan blue-induced exencephaly. It is believed that the presence of dens in dente within fused maxillary incisor teeth has only once been reported in mice, and the association between fused maxillary incisor teeth and a median supernumerary incisor tooth has not previously been reported in this species.

An ultrastructural study was undertaken on cartilage resorption at the site of initial endochondral bone formation in the mouse mandibular condyle on d 16 of pregnancy. After resorbing the bone collar, the osteoclasts extended their cell processes into the cartilage matrix and made contact with hypertrophic chondrocytes. By means of cell processes or vacuolar structures, these osteoclasts entrapped the calcified cartilage matrices, cell debris, and the degraded uncalcified cartilage matrices. In particular, since the calcified cartilage matrices were sometimes seen to be disrupted within the osteoclastic vacuolar structures, they were probably disposed of by the osteoclasts. Invading endothelial cells giving rise to capillaries also directly surrounded the degraded uncalcified cartilage matrices and small deposits of cell debris. In addition, hypertrophic chondrocytes that had attached to or were in the process of attaching to the invading osteoclasts often enclosed the small calcified cartilage matrices. Other cell types that have often been reported in other regions of cartilage resorption were not seen at the site of initial endochondral bone formation in this study. Our findings in relation to cartilage resorption may therefore represent unique features of the site of initial endochondral bone formation site. We consider that the manner of cartilage resorption is likely to vary by site, age, and species.

The morphological involution and histochemical changes of the Syrian hamster (Mesocricetus auratus) epididymis induced by a short light period were investigated. Under short-day conditions, the epididymis showed marked morphological changes including a decrease in luminal diameter, disappearance of spermatozoa, increase of interductal tissue, increase of intraepithelial lipofuscin deposits, the presence of phagolysosomes in the principal cells and macrophage-like cells, and a considerable modification of most clear cells. With lectin histochemistry changes were found in the glycoconjugates of principal cells of the regressed epididymis, either a decrease (PNA, WGA, HPA and DBA) or an increase (MAA) in the affinity of lectins to the Golgi area, or a decrease (HPA) or an increase (PNA) in lectin binding to stereocilia. Both morphological and histochemical results showed that, under this light condition, the cauda epididymidis presented the most prominent alterations, and that the epididymis showed increased absorptive activity and a decreased synthesis of glycoproteins. All these changes are probably due to the decrease in testosterone levels.

Previous pathological reports have indicated that swollen and vacuolated motoneuron cell bodies are the most predominant feature characterising Wobbler mouse motoneuron disease, but there has been little supportive evidence using area measurements. The present study focuses on the possible role of changes in neuronal nuclear and perikaryal volumes in the cervical spinal cord ventral horn, using new and traditional stereological probes which provide unbiased estimates of volume. Semithin sections from the ventral horn of Wobbler mice and age and sex-matched phenotypically normal littermates were examined at 2 ages (young and old). The young Wobbler group had significantly larger volume weighted mean perikaryal volumes compared with age-matched controls, reflecting the presence of large swollen cells characteristic of this group; this situation was reversed in the control group. Number-weighted perikaryal volume estimates in the old Wobbler group were smaller than in age-matched controls. The variation in perikaryal volume was greatest in the young Wobbler group in which the coefficient of variation was 127%. The mean number weighted and volume weighted mean nuclear volumes were significantly smaller in the old Wobbler group compared with age-matched controls and young Wobbler groups. The application of new stereological probes has enabled us to document more precisely these changes in neuronal structure in the Wobbler mutant mouse.

The histological changes in hair follicles in hairless rats derived from the Wistar strain (hW, hairless Wistar) were examined from birth to maturity and compared with those of age-matched normal Wistar rats. In the 1st hair cycle, the hair follicles of hW rats were shorter and less well developed than those of Wistar rats. In early anagen, eosinophilic bodies were observed in some hair follicles which showed immature histological features. By using Tdt-mediated dUTP nick end labelling (TUNEL) method and electron microscopic examination, these bodies were confirmed to be apoptotic bodies. These follicles seemed to disappear by abnormal regression. In late anagen phase, the follicles in which the apoptosis did not occur showed enlarged hair roots with hypertrophy of the inner root sheath. Subsequently, when the follicles in normal Wistar rats synchronously regressed in the catagen phase, most of the follicles in hW rats similarly entered the catagen phase, but a few follicles did not regress completely and showed aberrant hair root enlargement. Finally, both types of follicle in hW rats formed follicular cysts. These abnormalities in follicle development (abnormal follicular regression and follicular cyst formation) appear to be associated with the hairlessness in this rat strain.

Design-based stereology is employed to estimate total numbers of myocyte nuclei and mean myocyte volume per nucleus in ventricles of fetal and early postnatal human hearts. Organs were collected postmortem from subjects varying in age from 16 gestational wk to 40 postnatal wk. Numbers of myocyte nuclei per unit volume of ventricle were estimated using physical disectors (parallel pairs of sections). Absolute numbers were calculated by multiplying nuclear packing densities by ventricular volumes estimated from ventricular mass and tissue density. Volumes per nucleus were obtained via estimates of the combined volumes of all myocytes (or of the myocardium as a whole) and the numbers of myocyte nuclei. The findings showed that numbers of myocyte nuclei increase linearly from 16 wk towards term. They were also consistent with the notion that hyperplasia ceases abruptly at birth or soon afterwards. The net rate of production of myocyte nuclei was about 38×107/wk (2.3 million nuclei/h). The total volume of myocytes continued to expand in the same way from 16 wk to at least 35 wk of gestation. Published studies on the incidence of binucleate myocytes during early postnatal growth of the ventricles of rats suggest that the volume of a myocyte doubles prior to nuclear division. Prenatal growth in the human heart is consistent with this mechanism. Myocardial hypertrophy after birth must occur by cellular hypertrophy without karyokinesis.

Tracings of serial histological sections from 4 human embryos at different Carnegie stages were used to create 3-dimensional (3D) computer models of the developing heart. The models were constructed using commercially available software developed for graphic design and the production of computer generated virtual reality environments. They are available as interactive objects which can be downloaded via the World Wide Web. This simple method of 3D reconstruction offers significant advantages for understanding important events in morphological sciences.

The Annual General Meeting of the Anatomical Society of Great Britain and Ireland was held at the St George's Hospital Medical School, University of London, from 17th to 19th December 1996. A symposium on ‘Neural Crest Development’ was held on 18th December. The following are abstracts of communications and posters presented at the meeting.

Olfactory neuroepithelium of adult vertebrates retains a population of basal stem cells capable, throughout life, of dividing and differentiating into mature olfactory receptor neurons (see Farbman, 1994). The rate of turnover of olfactory receptor neurons is influenced, in part, by environmental conditions (Hinds et al. 1984). The olfactory system is known, however, to undergo a general decline in function with age. Age-related changes have been described in the rat olfactory bulb, with a decline in size in later life (Hinds & McNelly, 1981). However, this was thought to be secondary to changes within the olfactory epithelium as changes in the number of olfactory receptor neurons directly influence the size of the olfactory bulb. Thus the primary deficit in declining olfactory function may reside in the olfactory epithelium. Studies in humans demonstrated that olfactory function diminishes with increasing age (Ship et al. 1996), suggesting a possible decrease in the number of olfactory sensory neurons. Although the structure of both developing and mature olfactory epithelium (Farbman, 1994) have been well characterised, less information exists on changes relating specifically to ageing. A reduction in thickness of the olfactory epithelium was evident in ageing humans, with a concomitant loss of the normal zonal distribution of supporting and sensory cell nuclei, a less well defined boundary between respiratory and sensory epithelia, and an increase in pigment granules within the supporting cells (Naessen, 1971). Similar lysosome-like inclusion bodies were also noted in olfactory epithelium of adult rabbits (Mulvaney, 1971) and dogs over the age of 17 y (Hirai et al. 1996). Decreases both in the total area of olfactory epithelium and in dendritic knob density have been described in rats aged 29 mo and above (Hinds & McNelly, 1981). This is unlikely to be due to a loss of regenerative capacity since, in hamsters, regeneration of olfactory receptor neurons is observed in aged animals (Morrison & Costanzo, 1995). A scanning electron microscopic comparison of young and old rat olfactory epithelium revealed changes in membrane-limited dense bodies in olfactory receptor neuronal cell bodies (Naguro & Iwashita, 1992). In old rats (21 and 36 mo), large irregular bodies were found in the supranuclear area of olfactory receptor neurons and were also abundant throughout the sustentacular cells, resulting in cell enlargement and the loss of about 2 layers of olfactory receptor neuron perikarya. They contained lipid droplets and numerous irregular osmiophilic lamellae resembling lipofuscin granules (Naguro & Iwashita, 1992). No attempt was made to quantify these age related changes. The present study aimed to detail fully the morphological changes in the aged mouse olfactory epithelium and is a continuation of a previous pilot study (Appleton et al. 1996).

The superficial artery of the arm with a course anterior to the median nerve is found at an incidence of ≈13%, and it continues as the radial artery twice as frequently than as the ulnar artery; less frequently it continues as both arteries (Bergman et al. 1988). We report a rare case in which the superficial brachial artery continued as the common interosseous artery only and the deep brachial artery continued as the radial and superficial ulnar arteries in the cubital fossa.

European Tissue Culture Society

The 42nd International Congress of the European Tissue Culture Society will be held at the Johannes Gutenberg University, Mainz, Germany, on 12–15 October 1997. The theme will be ‘Multicellular organisation in vitro — from cells to tissue models’. It will include sessions on developmental and tumour biology, organotypic cultures and artificial organs, and genetically engineered cells in biotechnology and the clinic. Further information may be obtained from Prof. W. Mueller-Klieser, Institute of Physiology and Pathophysiology, Johannes Gutenberg University – Mainz, Duesbergweg 6, D-55099 Mainz, Germany (tel.: 49 6131 395761; fax 49 6131 395560).