Rabbit and human non-keratinising stratified squamous oesophageal epithelium displays similar microridge structure by scanning electron microscopy.

Since the oesophageal epithelium of common laboratory animals, rats and mice, is keratinized it is unsuitable for comparison with typical non-keratinized stratified squamous human epithelium. It is thus important to find a suitable animal model for the study of human oesophageal tissue changes. This study investigated the microridge structure of immature and adult rabbit specimens, and adult human biopsies by scanning electron microscopy and morphometry. The investigation revealed a similarity between typical squamous human and adult rabbit oesophageal mucosal epithelium. While human epithelium specimens subdivided into two other groups (non-typical squamous and non-squamous); all typical squamous human biopsies were from patients who had normal endoscopy reports and no reflux symptoms. The surface cells of typical squamous human epithelium displayed complex microridge patterns (64% of cell surface) but patterns in non-typical squamous specimens were more variable (38%) (P < 0.001) and cell boundaries less obvious. Rabbit squames displayed clear microridge patterns with an elevation in the percentage of cell surface covered by microridges, with increasing age, from immature to adult specimens (P < 0.001). There was no statistically significant differences between adult rabbit, and 'typical squamous' human biopsies (range 51-65%), results which suggest potential use of a rabbit model to study changes in human oesophageal tissue.

Mucosal changes in mouse duodenum after gamma-irradiation or reserpine treatment.

Although the bulk of the literature implies that most of the radiation-induced effects on small intestine are related to epithelial damage, previous work has indicated that there are structural changes in the neuromuscular component of the wall. The short timescale of changes in villous shape produced by hyperthermia but similar to those seen after radiation, also supports the claim that there is a neuromuscular contribution involved. A preliminary report showed that the radiation-induced changes in the small intestine could be simulated by the administration of reserpine, a drug chosen for its effects on the neuromuscular component of the mucosal wall. A system of villous scoring indicated that the overall effects of the two regimes were approximately equivalent in terms of the changes produced in the shape of the villi. The current paper describes the results of experiments to compare the two regimes over the time scale 1 h to 3 days. The time points were chosen to include likely maximum damage caused by reserpine (18 h after treatment) and radiation (3 days after treatment). Mice were irradiated with 15 Gy gamma-rays from a 60Co source or treated with reserpine (1 mg/kg and 16 mg/kg). Scanning electron microscopy showed some changes in the duodenal mucosal topography of some control groups which may be related to the stress of treatment and are in keeping with previous findings. However, the changes seen in treated groups were greater than those found in the corresponding control samples. The overall villous changes were plotted using a grid score method, which showed that both radiation and reserpine treatment altered the villous morphology in a similar way. Light microscopy and transmission electron microscopy showed that smooth muscle damage was associated with the villous collapse. The work indicates that the intestinal wall can be damaged by many agents and that greater understanding of radiation-induced damage can be gained by comparing it with that produced in other ways.

Exudate variation in the rabbit gastrointestinal tract: a scanning electron microscope study.

The mucosal exudate from the gastrointestinal tract of six adult female New Zealand rabbits was studied using scanning electron microscopy and without any attempt being made to clean the luminal surface before screening. The exudate consisted of mucus, debris and bacteria. Qualitative assessment showed that the nature and distribution of exudate varied along the length of the gastrointestinal tract from the oesophagus to the anal canal, with little variation from animal to animal. Bacterial counts for rod-shaped bacteria were carried out on areas randomly selected from the upper, middle and lower oesophagus and the oesophageal-cardiac junction. The degree of bacterial colonisation was found to decrease along the length of the oesophagus from upper to lower parts, but it was increased at the oesophageal-cardiac junction. This assessment was not undertaken in the other regions of the gastrointestinal tract as the mucosal surface areas could not be easily measured owing to their undulating nature. The study indicates the variability of the mucosal exudate, which should be recognised as part of the true interface between ingested food and the cell surface along the gastrointestinal tract.

Topographical variation in the mucosal surface of oesophageal biopsies.

There have been comparatively few scanning electron microscopic (SEM) studies of mucosal biopsies of the human upper gastrointestinal tract. This study reviews the use of SEM in human oesophageal research and deals with the results of a SEM study of thirty two biopsies of human oesophagus, taken from eighteen patients during endoscopy for upper gastrointestinal symptoms. For each biopsy, three areas of the mucosal surface chosen at random were examined using standard magnifications. The SEM showed three mucosal patterns, which were designated typical squamous, atypical squamous and nonsquamous, each displaying common features in relation to desquamation, cell boundaries and microridges. The two squamous epithelial groups showed surface microridges. The typical group displayed clear cut cell boundaries and well developed microridges arranged in rows. The atypical squamous group showed desquamation, less well developed cell boundaries and variation in microridge patterns. Many nonsquamous specimens displayed simple columnar epithelium, similar to mucosa of gastric type. Care was taken to correlate the surface structure of the oesophagus with the endoscopic appearance. The two assessments were done independently and the material was coded throughout. The broad subdivision of the biopsies into groups using these qualitative topographical criteria gave good correspondence with the endoscopic appearance.

Short- and long-term academic predictors of medical student performance.

The relationship between entry qualifications and performance throughout the medical course was studied in individual cohorts of students admitted in the years 1977 to 1981. A modest but significant relationship with overall initial qualifications was found throughout the course. Students without biology showed a marked disadvantage in the first year but the effect did not persist. There were quite marked variations in all these effects between cohorts; studying only a single cohort could lead to inappropriate conclusions.

The area of the articular surface of the distal end of the human femur.

A simple method of measuring the articular surface area of the distal end of the femur is described. The mean area value was 43.8 +/- 8.6 cm2. The area value was related to the relative size of the bone as measured by the inter-epicondylar distance.

Chondrocyte distribution in the articular cartilage of human femoral condyles.

The distribution of chondrocytes throughout the total thickness of articular cartilage from the femoral condyles of infants, children and adults has been studied using serial sections cut parallel as well as perpendicular to the articular surface. The thickness of the articular cartilage was estimated in fixed sections. In one of the adult specimens, the thickness of the articular cartilage was estimated firstly by direct measurement of the cut surfaces of a series of blocks cut from both condyles and then from the number of parallel sections of the cartilage prepared from those blocks. Cell density was highest in the superficial zone of all specimens examined, declining to lower values in the deep zone of the cartilage. Within this pattern the infant specimens had the highest values for cell density and the adults the lowest, with values for children in an intermediate range. There was no significant variation in cell density across the condyles of the selected adult specimen. The absolute values for cartilage thickness depended on the method used, but in general total thickness was found to approximately double from late gestation to maturity. In the selected adult specimen, the cartilage was thickest just anterior and posterior to the main weight-bearing area of the condyles.

A histological study of human femoral condylar articular cartilage.

Paraffin sections cut both parallel to and perpendicular to the surface were used to study the histological structure of the articular cartilage of the lateral femoral condyle of infants, children and adults. Two main cell types were present--fusiform chondrocytes lying in swirling patterns were the predominant cell type of the cartilage up to and including two years, while a more rounded cell, randomly arranged, was commoner in the older specimens. Evidence suggests that these cells represent two distinct populations of chondrocyte, the round cells being derived from the earlier fusiform cells. Cartilage canals were a feature of the deeper regions of the presumptive articular cartilage in young specimens in which the epiphysis was still cartilaginous. The basophilic tidemark which marks the junction between the calcified and uncalcified cartilage in perpendicular sections was not seen in parallel sections. The calcified cartilage layer contained numerous processes of vascular bone which extended up from the subchondral bone and were a characteristic feature of the cartilage-bone interface. This layer of the articular cartilage cannot therefore be considered to be truly avascular.

Ultrastructural evidence in rabbit ear arteries that barium enters smooth muscle cells through calcium channels.

The calcium channel blocker methoxyverapamil, at 10(-5) mol/l, abolished contractile responses of isolated perfused rabbit ear arteries to barium. Entry of barium into smooth muscle cells was detected by the presence of mitochondrial granules specific for barium. Methoxyverapamil (10(-5) mol/l) prevented the appearance of barium granules. In a further series of experiments, eight out of twelve arteries incubated with barium, 2.5 mmol/l, showed granules; when the incubate contained 2.5 mmol/l of both barium and calcium, granules were found in only one of twelve specimens; thus calcium appears to compete with barium for entry. These results are consistent with the hypothesis that contractile responses to barium depend on entry of barium into the cells through calcium channels.

Mitochondrial granules: are they reliable markers for heavy metal cations?

Mitochondrial granules have been used as markers for heavy metal cations, but since such granules can also be found in tissues in the absence of such cations, an attempt was made to define conditions under which these different granules might be visualised. The tissue used was the smooth muscle of the central ear artery of the rabbit. In all studies, the presence or absence of mitochondrial granules was determined by several observers, using coded specimens so that the previous treatment of the specimens was not at the time known to the observers. Paired tissues were exposed for 30 or 90 minutes at 20, 30 or 39 degrees C to an incubate containing either 10 mmol/l barium or a control barium-free solution. After fixation in osmium tetroxide, there was no difference between the two groups; in both cases granules appeared more frequently the longer the time and the higher the temperature of incubation. In a further series where glutaraldehyde was the fixative, granules were identified in 23 out of 41 tissues incubated with barium, but in only 1 out of 41 control tissues (P less than 0.001). Electron probe microanalysis showed that granules in osmium-fixed tissues contained osmium as the main element, whereas granules in glutaraldehyde-fixed tissues which had been incubated with barium showed barium as the predominant cation. Thus mitochondrial granules can be reliable markers for heavy metal cations, but only under carefully controlled conditions.