Several studies have reported the morphological changes induced by unilateral enucleation during early neonatal life on the developing visual system. This study has examined cellular changes in the superior colliculi by removal of a single eye in adult rats. Anaesthetised male hooded rats aged 90 d had their right eyes removed. Groups of nonenucleated control and enucleated rats were killed when aged either 150 or 390 d. The brains were removed and both the right and left superior colliculi dissected out. The volume of the stratum griseum superficiale (SGS) within these colliculi was estimated stereologically by light microscopy, as well as the numerical density and total number of neurons within this cell layer. The volume of the cell layer was reduced by about 40% on the side contralateral to the enucleated eye but not on the ipsilateral side at both survival periods examined. The numerical density of neurons within the SGS was unaffected by the enucleation so that the colliculi contralateral to the enucleated eye showed a substantial loss of neurons within this cell layer. This study demonstrates the importance of the retinal ganglion cell input, even in adult animals, for maintaining the viability of neurons in the SGS layer of the superior colliculus.

Epidermal growth factor (EGF) has been implicated in the control of embryonic development, but although the receptor is expressed from an early stage, there is little evidence of embryonic expression of EGF. In order to investigate the role of maternally derived EGF during organogenesis, rat embryos were explanted at d 9.5 and cultured in serum depleted of low molecular weight molecules (retenate) which was then supplemented with EGF. Serum depleted of low molecular weight molecules by prolonged filtration loses its capacity to support normal embryonic development, possibly due to the loss of growth promoting factors. The addition of EGF to retenate significantly improved embryonic development with a maximal effect at 8 ng/ml. The addition of an analogue of EGF, long EGF, to retenate also caused a significant increase in development, although at higher concentrations a decrease in its effect was observed, possibly due to down regulation of the EGF receptor. Therefore, embryos may be able to utilise maternally derived EGF during organogenesis. To test the effects of inhibiting the EGF receptor during organogenesis, d 9.5 embryos were cultured in the presence of tyrphostin 47, a specific EGF receptor inhibitor. Tyrphostin 47 caused a significant dose-dependent decrease in the development of embryos which was also observed when tyrphostin 47 was injected into the vitelline circulation at d 11.5 to bypass the effects of the yolk sac. These findings suggest that the EGF receptor is essential for normal organogenesis and may play a role in the control of proliferation and differentiation. Although EGF is not expressed in the rat embryo at this stage, maternally derived EGF may be the ligand for the embryonic EGF receptor.

This study sought to investigate the normal muscle fibre size and type distribution of the human erector spinae, both in thoracic and lumbar regions, in a group of 31 young healthy male (n=17) and female (n=14) volunteers. Two percutaneous muscle biopsy samples were obtained under local anaesthesia, from the belly of the left erector spinae, at the levels of the 10th thoracic and 3rd lumbar vertebrae. Samples were prepared for routine histochemistry for the identification of fibre types. Fibre size (cross-sectional area (CSA) and narrow diameter (ND)) was quantified using computerised image analysis. The mean CSA/ND for each fibre type was greater in the thoracic than the lumbar region, but there was no difference between the 2 regions either for percentage type I (i.e. percentage distribution by number), percentage type I area (i.e. relative area of the muscle occupied by type I fibres) or the ratio describing the size of the type I fibre relative to that of the type II. Men had larger fibres than women, for each fibre type and at both sampling sites. In the men, each fibre type was of a similar mean size, whereas in the women the type I fibres were considerably larger than both the type II A and type II B fibres, with no difference between the latter two. In both regions of the erector spinae there was no difference between men and women for the proportion (%) of a given fibre type, but the percentage type I fibre area was significantly higher in the women.

The erector spinae display muscle fibre characteristics which are clearly very different from those of other skeletal muscles, and which, with their predominance of relatively large type I (slow twitch) fibres, befit their function as postural muscles. Differences between thoracic and lumbar fascicles of the muscle, and between the muscles of men and women, may reflect adaptive responses to differences in function. In assessing the degree of any pathological change in the muscle of patients with low back pain, it seems clear that (1) sex cannot be disregarded and (2) ‘atrophied’ (using the criteria from other muscles) type II fibres are not necessarily abnormal for the erector spinae, particularly in women.

Retrograde tracing with Fluoro-Gold was used to identify the complete population of knee joint afferents in the lumbar dorsal root ganglia of adult female Wistar rats. There was an average of 581±31 (mean±S.D.) afferents supplying each joint. These were found distributed from L1 to L5 with the great majority localised in the L3 and L4 ganglia. Electron microscopy of the posterior articular nerve of the knee revealed an average of 103±15 (mean±S.D.) myelinated and 513±39 unmyelinated axonal profiles. Since about 50–60% of the unmyelinated profiles would be expected to be sympathetic efferents, these numbers are consistent with the numbers of afferents found by Fluoro-Gold retrograde tracing and suggest that the posterior articular nerve contains about 50% of the total number of knee joint afferents in the rat. Immunohistochemistry revealed that an average of 10% of identified joint afferents expressed substance P-like immunoreactivity and that 33% expressed calcitonin gene-related peptide-like immunoreactivity.

Cell–matrix and matrix–matrix interactions are of critical importance in regulating the development, maintenance and repair of articular cartilage. In this study, we examined the structural colocalisation of type VI collagen and fibronectin in isolated chondrons and long-term agarose cultured chondrocytes extracted from normal adult canine articular cartilage. Using double labelling immunohistochemistry in conjunction with dual channel confocal microscopy and digital image processing we demonstrate that type VI collagen and fibronectin are distributed in a similar staining pattern and are colocalised at the surface of cultured chondrocytes and isolated chondrons. The results suggest that type VI collagen and fibronectin may play a role in both cell–matrix adhesion and matrix–matrix cohesion in the pericellular microenvironment surrounding articular cartilage chondrocytes.

To investigate the claim that the primate paranasal sinuses possess not a functional but a structural role associated with the skull architecture (Blaney, 1990), the relationship between the maxillary sinus and the skull architecture was studied ontogenetically in 30 skulls of male and female Japanese macaques (Macaca fuscata). Coronal CT scan series and computerised 3-dimensional images served to evaluate the maxillary sinus. The definitive hemispherical shape of the sinus was already achieved after the completion of the primary dentition. Sinus volume increased with a trend indicating positive allometry. When compared with an ontogenetic data set of orang-utan (Koppe et al. 1995), however, the growth rate of the maxillary sinus of M. fuscata was significantly less. The maxillary sinus both of male and female macaques enlarged according to a common growth pattern. However, no sexual dimorphism could be established for the maxillary sinus size. Although the volume of the right maxillary sinus was normally bigger than that of the left side, the results suggested that asymmetry in maxillary sinus volume is related neither to skull size nor sex. Whereas a correlation analysis showed close relationships between the maxillary sinus volume and external cranial dimensions, the partial correlation coefficients revealed that these relationships were highly influenced by skull size. Although it cannot be ruled out that the paranasal sinuses are to some extent linked to the skull architecture, this study does not support a solely structural role for these air cavities.

In the course of an extensive comparative, structural and developmental study of the cranial and postcranial dermal skeleton (teeth and scales) in osteichthyan fishes, we have undertaken investigations on scale development in zebrafish (Danio (Brachydanio) rerio) using alizarin red staining, and light and transmission electron microscopy. The main goal was to know whether zebrafish scales can be used as a model for further research on the processes controlling the development of the dermal skeleton in general, especially epithelial–mesenchymal interactions. Growth series of laboratory bred specimens were used to study in detail: (1) the relationship of scale appearance with size and age; (2) the squamation pattern; and (3) the events taking place in the epidermis and in the dermis, before and during scale initiation and formation, with the aim of searching for morphological indications of epithelial-mesenchymal interactions. Scales form late in ontogeny, generally when zebrafish are more than 8.0 mm in standard length. Within a population of zebrafish of the same age scale appearance is related to standard length, but when comparing populations of different age the size of the fish at scale appearance is also related to age. Scales always appear first in the posterior region of the body and the squamation then extends anteriorly. Scales develop in the dermis but closely apposed to the epidermal–dermal boundary. Cellular modifications occurring in the basal layer of the epidermis and in the dermis before scale formation clearly indicate that the basal epidermal cells differentiate first, before any evidence of differentiation of the progenitors of the scale-forming cells in the dermis. This strongly suggests that scale differentiation could be initiated by the epidermal basal layer cells which probably produce a molecular signal towards the dermis below. Subsequently dermal cells accumulate close to the epidermis, and differentiate to form scale papillae. The late formation of the scales during ontogeny is due to a late colonisation of the dermis by the progenitors of the scale-forming cells. Because of their late formation during ontogeny and of their regular pattern of development, scales in zebrafish represent a good model for further investigations on the general mechanisms of epithelial-mesenchymal interactions during dermal skeleton development, and in particular for the study of the gene expression patterns.

Nuclear condensation during spermiogenesis in the ostrich follows the basic pattern established in other vertebrates. The fine granular nuclear substance of early spermatids is gradually replaced by numbers of coarse dense granules which appear to arise by aggregation of smaller dispersed elements of the chromatin. The granules increase in size and eventually coalesce to form the compact homogenous mass of chromatin typical of the mature sperm. In ostrich spermatids, however, the aggregation of the nuclear material produces large numbers of longitudinally oriented rod-shaped structures in addition to some granular material. Although fibrillar chromatin has been observed during spermiogenesis in a number of vertebrate species, the hollow nature of the rod-shaped chromatin granules in ostrich spermatids is a unique phenomenon. The spiralisation of the chromatin material observed in ostrich spermatids and in some other nonpasserine birds is possibly related to the reduction in nuclear length demonstrated during spermiogenesis in these species. In common with other nonpasserine birds, spermiogenesis in the ostrich is characterised by the appearance both of a circular and a longitudinal manchette. The circular manchette consists of a single row of microtubules reinforced by additional peripherally arranged microtubules. Links between adjacent microtubules, and between the nucleolemma and some of the microtubules, are evident. The longitudinal manchette consists of arrays of interconnected microtubules arranged in approximately 4–6 staggered, ill defined rows. This structure seems to originate as a result of the rearrangement of the microtubules of the circular manchette and is only formed once the process of chromatin condensation is well advanced. Based on the sequence of morphological events observed during spermiogenesis in the ostrich, it is concluded that the circular manchette is responsible for the initial transformation in shape of the spermatid nucleus. Thereafter, the chromatin condenses independently within the confines of the nucleolemma with the circular manchette merely acting to maintain the shape of the nucleus while this process is underway, to compress the nuclear membrane, and possibly to orientate the subunits of the condensing chromatin. The longitudinal manchette appears to assist in the translocation of material during spermatid elongation. There are indications that the developing acrosome is instrumental in effecting nuclear shaping of the apical (subacrosomal) head region of the ostrich spermatid.

Exposure of male Albino Swiss rats to the nonsteroidal antiandrogen flutamide during the period from gestational day (d) 10 to birth resulted in feminisation of the external genitalia and the suppression of growth of the male reproductive tract. In adulthood, testes were found to be located in diverse positions. True cryptorchidism occurred in 10% of cases, whereas 50% of testes descended to the scrotum and 40% were located in a suprainguinal ectopic region. Varying degrees of tubule abnormality were seen in the testes of flutamide-treated animals, ranging from completely normal tubules with full spermatogenesis (and the expected frequency of the stages of spermatogenesis) to severely abnormal tubules lined with Sertoli cells only. For each individual testis, the overall severity of tubule damage was strongly correlated with its adult location, with intra-abdominal testes worst affected and scrotally-located testes least; only the latter contained normal tubules. Similarly, intra-abdominal testes were the smallest in weight and contained the least testosterone. By contrast, postnatal treatment of male rats with flutamide from birth to postnatal d 14 did not impair development of the external genitalia, the process of testicular descent or adult spermatogenesis. These findings confirm that androgen blockade during embryonic development interferes with testicular descent but also demonstrate that (1) prenatal flutamide treatment per se has a detrimental effect on adult testis morphology but (2) the degree of abnormality of the testes is strongly influenced by location.

Morphological features of the cap enameloid and dental epithelial cells were investigated by light and transmission electron microscopy during the various stages of enameloid mineralisation and early maturation in the tilapia. The pattern of mineralisation along collagen fibrils in the enameloid differed from that in the dentine. Many matrix vesicles were found in the predentine and in the enameloid, suggesting that they may be involved in the initial mineralisation in both regions. Most of the organic matrix disappeared from the cap enameloid during mineralisation and maturation. The disappearance of the organic matrix could be divided into 2 stages. Initially a fine network-like matrix, which probably consisted of glycosaminoglycans and extended between collagen fibrils, began to disappear. At the same time, fine crystallites and electron-dense, fine granular material covered the collagen fibrils as mineralisation of the enameloid began. In the second stage, the maturation of the enameloid, the collagen fibrils degenerated completely and disappeared from the cap enameloid, being replaced by large numbers of large crystals. At the mineralisation stage, the numbers of lysosomal bodies tended to increase in the inner dental epithelial (IDE) cells, which contained a well developed Golgi apparatus and rough endoplasmic reticulum (rER). At the early stage of maturation, a ruffled border was noted at the distal ends of the IDE cells, which contained many mitochondria and lysosomal bodies, but less rER. These features suggest that the cells actively absorb the organic matrix, which includes collagen fibrils, in the cap enameloid. The outer dental epithelial (ODE) cells were translucent cells that contained well developed labyrinthine canalicular spaces from the onset of the mineralisation stage to the middle stage of maturation. The IDE and ODE cells were clearly involved in the mineralisation of the cap enameloid at the mineralisation and maturation stages.

The structure of porcine skin as examined by light microscopy is reviewed and its similarities to and differences from human skin are highlighted. Special imaging techniques and staining procedures are described and their use in gathering morphological information in porcine skin is discussed. Confocal laser scanning microscopy (CLSM) was employed to examine the structure of porcine skin and the findings are presented as an adjunct to the information already available in the literature. It is concluded that CLSM provides valuable additional morphological information to material examined by conventional microscopy and is useful for wound healing studies in the porcine model.

The relationship between IGF-I and changes in muscle fibre phenotype in response to 6 d of stretch or disuse of the lower limb muscles of the rabbit was studied by combining in situ hybridisation and immunohistochemistry procedures. Passive stretch by plaster cast immobilisation of the muscle in its lengthened position not only induced an increase in IGF-I mRNA expression within the individual muscle fibres but also an increase in the percentage of fibres expressing neonatal and slow myosin. This change in phenotype was also found to be accompanied by a rapid and marked increase of muscle mass, total RNA content as well as IGF-I gene expression. In contrast, IGF-I appears not to be involved in muscle atrophy induced by immobilisation in the shortened position and the inactivity which results from this procedure. The level of increase in expression of IGF-I mRNA varied from fibre to fibre. By using adjacent serial sections, the fibres which expressed IGF-I mRNA at the highest levels were identified as expressing neonatal and the slow type 1 myosin. These data suggest that the expression of IGF-I within individual muscle fibres is correlated not only with hypertrophy but also with the muscle phenotypic adaptation that results from stretch and overload.

In Stockwell and Scott's commentary on our papers, in which we concluded from a significant mass of data (a fraction of which was presented in the paper) that we questioned the notion of ‘global patterns’ of matrix distributions within articular cartilage. In part, this was based on the distribution of keratan sulphate and chondroitin sulphate within the knee (both tibial and femoral compartments although only the latter was illustrated in the paper when referring to adult animals) of our model, the marsupial Monodelphis domestica.

In their paper on opossum cartilage, Archer et al. (1996) contend that their ‘data pose questions [ctdot ] to the idea that global patterns of matrix components exist in mammalian articular cartilages’. We believe that this statement is not supported by their data. The points at issue concern the distributions of chondroitin sulphate (CS) and keratan sulphate (KS) in adult cartilage. Earlier work showed that: (1) the highest concentrations of CS are in the midzone of the noncalcified layer of the cartilage (Stockwell & Scott, 1967; Maroudas et al. 1969; Lemperg et al. 1974), while the authors' opossum data apparently show that the intensity of staining with Safranin O (and various antibodies specific for CS) ‘is greatest in the upper third of the tissue depth’; (2) in the noncalcified cartilage, the concentration of KS increases with distance from the articular surface (Stockwell & Scott, 1967; Maroudas et al. 1969; Venn, 1978). By contrast in the opossum, the authors state that there was ‘intense labelling throughout the upper half of the articular cartilage depth’. They considered that this finding, in particular, questions ‘the notions which link KS substitution with conditions of low oxygen tension’, since articular cartilage generally obtains its nutrient and O2 through the articular surface and thence by diffusion through the tissue depth.

I am writing to the Journal of Anatomy as a component of the response by Archer et al. to a letter to the Editor submitted by Professors Robin Stockwell and John Scott. Professor Archer has asked me to comment on their claims and some matters regarding antibodies used in the studies in question. My responses to these issues are indicated below.

Professor T. R. Trevor-Jones, former Professor and Head of the Department of General Anatomy, Faculty of Dentistry, University of the Witwatersrand, died in Gauteng on 19th September 1996.

Anatomical Society of Great Britain and Ireland

15–17 July 1997. Medical School, University of Edinburgh.

6–8 January 1998. University of Newcastle upon Tyne.

24–2 July 2000. University of Cambridge.