The identification of myogenic precursor cells (mpc) is a key factor in determining the early events in the myogenesis and regeneration of skeletal muscle. Although satellite cells have long been established as the providers of myoblastic cells, very little is really known (apart from their anatomical location in relation to muscle fibres and their ability to migrate) about the precise role of satellite cells in myogenesis. Numerous techniques for labelling mpc have been devised, but none of these has proven to be completely reliable in firmly establishing the origin of myogenic cells. The use of tritiated thymidine to label DNA in proliferating mpc (which are not specifically distinguishable at the time) and the subsequent location of their labelled progeny in myotube nuclei has revealed a great deal of data on the timing of myogenesis, but not about the nature of mpc themselves. DNA synthesis can also be detected by antibodies to the thymidine analogue, bromodeoxyuridine, and also by antibody staining for proliferating nuclear cell antigen. Like tritiated thymidine, these other markers are not specific for muscle but are general markers for DNA synthesis. In situ hybridisation of various muscle-specific genetic markers and their products has been informative, as has immunolabelling of myogenin, MyoD1 and desmin. Desmin labelling has been particularly instructive in identifying mpc because it is one of the first muscle-specific proteins to be produced in mpc. This review covers some of the techniques mentioned above and their usefulness in determining the early events in myogenesis.

The formation of the first epidermal generations and in particular of the shedding complex in the developing scales of the lizards Anolis lineatopus and Podarcis muralis was studied by electron microscopy. The initially linear and bilayered epidermis turned into symmetric papillae, which became asymmetric scales. The outer periderm was more electrondense than the following layer, provisionally named ‘inner periderm’ but probably derived from the basal layer. Coarse thick filaments progressively filled the cytoplasm of the inner periderm or formed reticulate bodies resembling avian peridermal granules. Peridermal cells cornified slightly and could be shed in ovo. From the basal layer various suprabasal epithelial layers were produced. The first layer contained keratohyalin-like granules and was identified as a clear layer. Beneath it a spinulated (Anolis) or serrated (Podarcis) oberhäutchen differentiated. The clear and ‘oberhäutchen’ layers constitute the first shedding complex. The first epidermal layers that were shed consisted of flaking periderm or periderm together with the clear layer. The differentiation of a mesos layer was under way before hatching, when the epidermal morphology resembled a stage 4–5 of the adult shedding cycle. Fibroblasts under the inner side of the scale made few contacts with the basement membrane and their cytoplasmic elongations were mostly oriented parallel to the dense lamina. Instead, fibroblasts under the basal layer of the outer scale surface (BLOS) made numerous contacts with the basement membrane, suggesting that more dermal–epidermal interactions take place on this side of the scale.

Fibre optic confocal imaging (FOCI) enabled subsurface fluorescence microscopy of the skin of hairless mice in vivo. Application of acridine orange enabled imaging of the layers of the epidermis. The corneocytes of the stratum corneum, the keratinocytes in the basal layers and redundant hair follicles were visualised at depths greater than 100 μm. Cellular and nuclear membranes of keratinocytes of the skin were visualised by the use of acridine orange and DIOC5(3). Imaging of the skin after injection of FITC-dextran revealed an extensive network of blood vessels with a size range up to 20 μm. Blood cells could be seen moving through dermal vessels and the blood circulation through the dermal vascular bed was video-taped. The fluorescent dye 4-di-2-ASP showed the presence of nerves fibres around the hair follicles and subsurface blood vessels. Comparison was made between images obtained in vivo using FOCI and in vitro scanning electron microscopy and conventional histology. FOCI offers the potential to study dynamic events in vivo, such as blood flow, skin growth, nerve regeneration and many pathological processes, in ways which have not previously been possible.

The endocrine pancreas of the toad consists of rounded islets of various sizes embedded in the exocrine tissue. Isolated cells are also present. At least 4 types of endocrine cell are distinguishable by shape, size and electrondensity of the secretory granules as well as by their immunoreactivity with different antisera: insulin, somatostatin, pancreatic polypeptide, and glucagon cells. Insulin cells can be divided into 2 types according to their cytoplasmic electrondensity. Colocalisation of different hormones in the same cell is rarely observed. The close contact between endocrine and exocrine cells and the scarcity of nerve supply is indicative of a paracrine control of hormone secretion.

Muscle fibre type composition and distribution in the biceps brachii (long head) and triceps brachii (long head) of the rat and rabbit were investigated using the following histochemical techniques: myosin ATPase, with preincubation at pH 10.4 and 4.35; succinate dehydrogenase (SDH) and glycogen phosphorylase. The muscle fibres were classified into slow-twitch (SO), fast-twitch glycolytic (FG), fast-twitch oxidative glycolytic (FOG and FOg) and fast-twitch oxidative fibres (FO). Significant differences in the regional distribution of muscle fibre types have been observed between the rat and the rabbit. In the rat, SO fibres were restricted to the deep regions of both biceps and triceps brachii, whereas FG fibres were located in the intermediate and superficial regions (the superficial regions contained the highest percentages of FG fibres). In the rabbit, SO and FG fibres were spread over the entire muscle, although SO and FG fibres were most abundant in the deep and superficial regions respectively. These findings indicate that the biceps and triceps brachii are more regionalised in the rat than in the rabbit.

Six muscles of the mallard duck (Anas platyrhynchos), the common coot (Fulica atra) and the yellow-legged gull (Larus cachinnans) were analysed morphometrically, with special emphasis on their functional implications and physiological needs. Oxidative fibres always had significantly smaller size than anaerobic fibres, although no differences in the number of capillaries per fibre were found. This resulted in greater capillary counts per unit of fibre area and perimeter in oxidative than anaerobic fibres, which indicates that the greater demand for oxygen supply may be achieved by decreasing the size of the muscle fibre rather than by increasing the number of associated capillaries. Fast oxidative fibres of the pectoralis and the triceps of the gull had greater sizes than the fast oxidative fibres of the mallard and the coot, which correlates with the difference in energetic demands between flapping and gliding flight. Greater fibre cross-sectional areas and perimeters seem suited to afford the long-lasting activity with low metabolic demands required during gliding. By contrast, mallards and coots attain a high oxidative metabolism, during sustained flapping flight, by reducing fibre size at the expense of a diminished ability for force generation. Between-species comparisons of the hindlimb muscles only yielded differences for the anaerobic fibres of the gastrocnemius, as an important adaptive response to force generation during burst locomotion. The need to manage sustained swimming abilities effectively may result in similar FOG fibre morphometry of the hindlimb muscles studied, indicating that a compromise between the oxygen flux to the muscle cell and the development of power is highly optimised in oxidative fibres of the bird species studied.

We used immunohistochemical techniques to demonstrate the distribution of receptors for the cytokine tumour necrosis factor-α on the popliteal lymph node and the adipose tissue surrounding it for 5 d following a simulated immune challenge to one hind leg in the rat. We found different patterns of expression of receptors on adipocytes surrounding a lymph node to a distance of about 1 mm, and on those more remote from the node. Sites recognised by an antibody to type I tumour necrosis factor receptors appeared on the challenged node and the adipocytes surrounding it within 30 min of an injection of bacterial lipopolysaccharide, but appeared on adipocytes surrounding the unchallenged popliteal node only 24 h later. Adipocytes distant from the node, both within the same depot and in the contralateral depot, showed no response. Sites recognised by an antibody to type II tumour necrosis factor receptors were present at all times on lymph nodes and the adipocytes close to them, but appeared on more distant adipocytes only 24 h after immune challenge, in both challenged and unchallenged legs. These data support the proposal, based on in vitro studies, that the adipose tissue surrounding major lymph nodes is specialised to respond to cytokines derived from lymphoid cells, and participates in the immune responses of the adjacent node.

This study examines the variability in the anatomy of mandibles of differing ages and different stages of tooth loss. Mandibles from individuals between 19 and 96 y were sectioned into 2 mm thick vertical plane-parallel slices and cleaned of marrow and periosteum. The apparent density (mass per unit volume in g/ml) from midline (MID) and mental foramen region (MF) sites was determined by weighing the slices and dividing by a volume calculated as the product of section thickness and the mean area of the 2 sides of the section. The cortical thickness of the inferior border and the basal and alveolar bone heights were measured in radiographs of the slices. Mandibular apparent density was negatively correlated with the cross sectional area (midline r=−0.48, mental foramen r=−0.45), and at the midline was significantly greater in edentulous than in dentate individuals (means (±s.e.m.) edentulous n=13: 1.43 (±0.07) g/ml; dentate n=17: 1.27 (±0.04) g/ml, P<0.05). Where a large enough age range was available, mandibular apparent bone density showed a significant increase with age (midline males: r=0.53, n=18) especially for dentate individuals (r=0.91, n=8). There was a correlation between the apparent densities at the two sites in the same mandible (r=0.64), with the values obtained for the midline being significantly greater than for the mental foramen region (midline 1.34 (±0.04) g/ml; mental foramen 1.19 (±0.04) g/ml, P<0.001, paired t test). The mandible shows great interindividual variability, but there may be a considerable reduction in cross sectional girth of the mandible following tooth loss, and, unlike postcranial sites, an increase in apparent density with age.

This study examined the tissue level mineralisation density distribution in mandibles from 88 adult humans. Mandibles (19–96 y) were sectioned vertically in midline (MID), mental foramen (MF), and third molar (M3) regions. Surgical fragments from M3 were obtained from individuals aged 16–38 y. All specimens were cleaned, embedded in PMMA, micromilled and examined by digital 20 kV backscattered electron (BSE) stereology. Quantitation was based on rescaling image histograms to the signal range between a monobrominated (0) and a monoiodinated (255) dimethacrylate resin standard. Mineralisation density increased with age (r=0.70; P<0.0001): the mean for 39 individuals aged between 16 and 50 y was significantly lower (P<0.0001) than for 35 individuals over 51 y (mean (±S.E.M.): 158.20 (1.63) and 174.71 (1.27) normalised grey level units respectively). There was good correlation in mean mineralisation density between different sites in the same mandible, but MID was significantly less highly mineralised than the other sites: MID 173.90, MF 177.34, M3 177.11 (P<0.002 and 0.01 for MF and M3 respectively; paired t test), as was the alveolar bone density when compared with the bone of the inferior cortex (e.g. MID: 171.13 (1.53) and 174.46 (1.14) P<0.0001). No sex difference was found. Partially dentate mandibles generally had regions of higher mineralisation than fully dentate and edentulous mandibles. The lowest density bone occurred at the alveolar crest anteriorly and superolingually at M3, matching sites of net resorption following tooth loss. Highest densities were found inferolingually at MID, inferiorly at MF and buccally at M3, matching the sites thought to experience the highest functional strains. This stresses the importance that local factors may have in the remodelling of the edentulous mandible. Morphology showed that there is a preponderance of highly mineralised cement lines, and of packets containing dead, mineralised, osteocytes.

The arrangement of the enteric ganglia and nerve fibre plexuses was examined in the submucous and mucous layers and around Peyer's patches of the porcine small intestine to clarify their organisation. Immunohistochemistry of vasoactive intestinal peptide (VIP) and neurofilament proteins in wholemounts, chopped or paraffin sections was used to locate the neural elements. The ganglia of the internal and external submucous plexuses were situated at 2 different topographic locations, being clearly demarcated by the submucosal vascular arcades and differing in neuronal composition. The internal submucous plexus was the only contributor to the plexus surrounding the follicles of Peyer's patches as a continuous mesh of 3 ganglionated nerve subplexuses. VIP-immunoreactive fibres from this mesh innervated the dome. The mucosal plexus, which was subdivided into 4 subunits — the outer proprial, inner proprial, pericryptal and villous plexuses — contained a few solitary neuronal perikarya. Labelling for neurofilament proteins revealed Dogiel types II, IV and VI neurons. The observations reveal several new features in the enteric nervous system of the pig and clarify its nomenclature.

Serial transverse histological sections of the human craniovertebral junction (CVJ) of 4 normal human embryos (aged 45 to 58 d) and of a fetus (77 d) were used to create 3-dimensional computer models of the CVJ. The main components modelled included the chondrified basioccipital, atlas and axis, notochord, the vertebrobasilar complex and the spinal cord. Chondrification of the component parts of CVJ had already begun at 45 d (Stage 18). The odontoid process appeared to develop from a short eminence of the axis forming a third occipital condyle with the caudal end of the basioccipital. The cartilaginous anterior arch of C1 appeared at 50–53 d (Stages 20–21). Neural arches of C1 and C2 showed gradual closure, but there was still a wide posterior spina bifida in the oldest reconstructed specimen (77 d fetus). The position of the notochord was constant throughout. The normal course of the vertebral arteries was already established and the chondrified vertebral foramina showed progressive closure. The findings confirm that the odontoid process is not derived solely from the centrum of C1 and that there is a ‘natural basilar invagination’ of C2 during normal embryonic development. On the basis of the observed shape and developmental pattern of structures of the cartilaginous human CVJ, we suggest that certain pathologies are likely to originate during the chondrification phase of development.

Data on femoral neck-shaft angles were collected for 30 modern, historic and prehistoric human population samples, and analysed with respect to sexual dimorphism, bilateral asymmetry, geographical patterning and general economic level. Although some samples had modest sexual dimorphism in this angle, and some individuals exhibited clear asymmetry, there were no consistent patterns of sexual or side differences across human populations. Similarly, there was no evidence for geographic differences, since broad regional groups lacked significant differences and mean angles were not correlated with latitude. However, there is a significant increase in mean neck-shaft angles across populations with an increasingly sedentary existence and with mechanisation. The last reflects the developmental plasticity of this feature with respect to habitual load levels during ontogeny of the hip region.

Remodelling of bone occurs in response to physical stress. Habitual squatting is associated with modifications of the neck of the talus (squatting facets) and its trochlear/malleolar surfaces (trochlear extensions), and individual populations exhibit different incidences of these modifications that reflect their lifestyle. The occurrence of talar modifications was therefore investigated in a population of late Byzantine (13th century AD) adult male skeletons. Lateral squatting facets occurred most frequently (37.7%), but medial (0.6%), combined (0.6%) and continuous (gutter-like) facets (0.6%) were also observed. Lateral (8.0%), medial (10.9%) and continuous (lateral/central/medial) extensions (4.6%) of the trochlear surface were all present in the late Byzantine population. There was no evidence of side dimorphism. The occurrence of lateral squatting facets in the late Byzantine population was greater than that reported for modern Europeans, but similar to that reported for some populations of modern Indians. The frequency of occurrence of trochlear extensions in the late Byzantine population was substantially less than in modern Indian populations, but similar to modern Europeans. Therefore, it is unlikely that precisely the same factors determine the expression of squatting facets and trochlear extensions.

In order to clarify the fundamental structure of the host defence mechanism in chicken caeca, a detailed analysis of the distribution of lymphoid nodules (LNs) was carried out on longitudinal sections of both the mesenteric (side of the ileocaecal ligament) and the antimesenteric mucosa. An overwhelming majority of solitary or aggregated LNs were located in the mesenteric mucosa, although a few were also found in the antimesenteric mucosa. Of the total LNs, 45.7% were detected at the proximal 7.8% section in the caecal tonsil. LNs (21.4%) were also concentrated in the distal 22.0% section corresponding to the apex. A moderate concentration of LNs (13.1%) was found at the transitional 20.0% region between the base and body. Approximately 80.2% of total LNs were found at the above 3 regions in the mesenteric mucosa. In many cases, the frequency of LNs in the caecal tonsils was opposite to that at the apices. Aggregated LNs were mainly found in the caecal tonsils, transitional region and apex. Almost all aggregated LNs consisted of fundamental nodular units possessing M cells in their follicle associated epithelia. The aggregated LNs in the above 3 regions therefore could provide immunological surveillance against caecal luminal contents. In particular, the cooperative function between LNs of the caecal tonsil and apex might be highly important in maintaining the caecal microenvironment.

The recent exchange on cartilage ultrastructure, the localisation of keratan sulphate (KS) therein and the influence of oxygen tension on both (Stockwell & Scott, 1997; Archer et al. 1997; Caterson, 1997) raised important issues which need clarification and extension. We wish to correct certain statements and to examine more rigorously principles which will establish a foundation for future discussion.

Morphological variations of the brachial plexus and variants in the distribution of the anterior division of the middle trunk are relatively frequent. Two of the rarest anomalies occurred in the left brachial plexus of a 62-y-old Japanese male, 1 of 104 plexuses dissected between 1996 and 1997 at Kanazawa University Faculty of Medicine. The superior trunk of the brachial plexus was formed by the anterior primary division of C5 and C6 and a thin branch (0.5 mm in diameter) from C4, the middle trunk by the C7, and the inferior trunk by C8 and T1 (Fig.). We could not determine whether there was a branch derived from T2 to T1, since the subject had died of lung carcinoma. The entire anterior division of the middle trunk crossed the axillary artery and joined the medial root of the median nerve which was the continuation of the medial cord after the cord branched off the ulnar nerve. The lateral cord pierced coracobrachialis and divided into the musculocutaneous nerve and the lateral root of the median nerve just after emerging from the muscle, finally joining the medial root of the median nerve superficial to the brachial artery ∼115 mm distal to the lower border of latissimus dorsi to form the median nerve. The musculocutaneous nerve gave rise to the nerves to biceps brachii, brachialis, and the long head of biceps brachii and finally continued as the lateral cutaneous nerve of the forearm. The branch to coracobrachialis had already been cut and its course could not be traced.

The amount of time officially available for the teaching of gross anatomy to medical undergraduates was substantially curtailed during the 1960s, both in the USA and in Europe (Kahn, 1966; Todd, 1968). Since then, this trend has been further enhanced by the expanding introduction of problem-based learning (Pallie & Miller, 1982; Albanese & Mitchell, 1993) deplored by many gross anatomists, radiologists and surgeons (Collins et al. 1994; Anderson & Brown, 1996). But a modification of the content of anatomical teaching has become unavoidable, and is a matter for concern — although very little rejoicing — to the professional morphologist involved in teaching. The few studies which have been aimed at defining a suitable core programme were designed to determine the anatomical knowledge required for various clinical specialties (Lippert & Bernsau, 1972; Quast-Höttge, 1972). These studies showed that the identified knowledge exceeds by far any currently available time for teaching anatomy to medical undergraduates (Lippert, 1974). Against this background, the present study was designed from a different concept, our aim having been to investigate the requirement of anatomical knowledge in general medical practice. The actual paper is a synopsis of the results obtained for 12 topics of systematic gross anatomy evaluated under this criterion. It is an attempt to contribute to a pragmatic solution to a pressing problem.

Variations in the hamstring muscles are not common. We describe here a rare anomalous muscle in the popliteal fossa and speculate on its functional significance.

With the exception of the 7th vertebra, both past and recent literature describe the lower cervical vertebrae as possessing similar morphological characteristics (Soemmering, 1794; Cruveilhier, 1862; Luschka, 1862; Henle, 1871; Braus-Elze, 1954; Romanes, 1981; Williams et al. 1989; Benninghof, 1994). Gross anatomical differences from the 3rd to the 7th cervical vertebrae comprise the shapes of the vertebral body and uncinate and spinous processes (Putz, 1976; Penning, 1988; Lang, 1990) and the more developed anterior tubercle and anterior root of the transverse process of the 6th cervical vertebra (C6) (Paturet, 1951). During routine examination of a series of dried skeletons, the articular processes (AP) of C6 were found to be distinct from the rest of the cervical vertebrae. The aim of this study was to confirm this unusual appearance of the C6 process by inspecting a sample of dried skeletons. We report the morphology of the AP of C6 in 76 well preserved complete adult skeletons (58 males, 18 females; age 31–77 y) and 5 young specimens from the Anatomical Institutes of Alicante, Valencia and Murcia (Spain) and Munich (Germany). Another 12 skeletons were excluded from the study due to arthritic changes in their cervical APs.

John Zachary Young, universally known as JZ, was born in Bristol on 18 March 1907 and died on 4 July 1997. The Zachary in his name was said to be of Cornish origin. His ancestor Thomas Young achieved fame through his modulus and through the Young–Helmholtz theory of colour vision. JZ was educated at Marlborough, which school also produced another notable scientist, student of and early collaborator with JZ, Peter Medawar. Having acquired an interest in zoology at school, JZ read zoology at Magdalen College, Oxford, and then obtained a scholarship to work at the Zoological Section in Naples. There he began to investigate the autonomic innervation of the gut of fish. While in Naples he rediscovered the giant axons of the squid but, unlike L. W. Williams in 1909, he immediately recognised their importance. His observations led to the fundamental studies on the generation of the membrane potential and conduction of the action potential of axons by Hodgkin and Huxley. During his time in Naples before the War, JZ began his lifelong interest in the brain and behaviour of cephalopods.