Samples of articular cartilage from four different human joints were obtained at surgery. Serial scanning electron micrographs taken at a magnification of 1000× were used to reconstruct an 0.25 mm2 area of articular surface. Within these given areas both normal and degenerated portions were seen. This study supports the concept that the surface morphology of articular cartilage varies from joint to joint and from area to area within a joint. This information should be useful for the interpretation of light and electron micrographs, as well as histochemical and biochemical data.
Palisade-shaped nerve endings of the small normal hairs of the rat snout were examined with the electron microscope (fixation by perfusion). The terminals are located inside the ‘glassy membrane’ in the area of the neck of the hair root. The 10–20 radially arranged terminal axons are in direct contact with the basement membrane of the epithelium of the external root sheath. The axons are surrounded on all sides by leaf-shaped processes of the Schwann cells. The surfaces of these cell processes are marked by numerous vesicle-like invaginations (approx. 1000 Å dia.). Transverse sections from several areas of the palisadeshaped nerve endings are compared with longitudinal sections. In the upper area ‘empty’ vesicles (approx. 500–600 Å in diameter) occur, along with electron-dense vesicles (approx. 800–1100 Å in diameter); in the middle area, the axons are distended and contain accumulations of mitochondria.
The permeability of the capillaries as well as the endocytotic capacity of the secretory cells have been studied in the anterior pituitary gland of the rat. Using tracers of a wide range of dimensions (40 to 225 Å) and of different chemical composition: peroxidase, hemoglobin, catalase, ferritin, dextrans and glycogen, it has been shown that capillaries were permeable to all the tracers studied. Horseradish peroxidase (HRP) and hemoglobin diffuse between parenchymal cells, whereas the other tracers remain concentrated at the level of the basement membrane that surrounds the capillaries. HRP is the only tracer that is usually taken up by the secretory cells. The uptake of HRP was found to be more extensive in somatotrophs and mammotrophs than in corticotrophs and thyrotrophs. In the cytoplasm, HRP was localized in smooth vesicles and lysosomes. No HRP was detected in the gonadotrophs of either control or castrated animals. After thyroidectomy, the uptake of HRP as well as exocytosis, were decreased in thyrotrophs. In the adrenalectomized rats, the stimulated corticotrophs showed a marked increase in the number of peroxidase-positive structures. Administration of dexamethanose to the adrenalectomized animals produced in the corticotrophs an accumulation of secretory granules and a marked decrease in HRP uptake.
A surface film with a thickness of 280–570 Å covers the mesothelium of serous membranes in the rat. This film can be stained with ruthenium red. Its considerable water-binding capacity produces the reflecting surface of the serous membranes. The friction of the organs is thereby greatly reduced. Only a small amount of serous fluid must be produced to keep the surface moist. The glucosamino glycans of the surface film are probably synthesized by the mesothelial cells.
The parietal layer of Bowman's capsule was examined in the rat in control animals and in animals made hypertensive by treatment with desoxycorticosterone acetatesaline and by clipping of the renal artery. At an early stage of elevation of blood pressure and, occasionally, prior to elevation of blood pressure, the epithelial cells of this layer showed basal cytoplasmic protrusion and reduplication accompanied by an increase in the thickness of the basement membrane. These changes preceded evidence of glomerular or renal arteriolar pathology. They presumably reflect either a response of this layer to increased blood pressure and modified glomerular function, or a direct effect of the factors that also induces blood pressure elevation. In either case, they imply a greater functional significance for the parietal layer than has usually been attributed to it.
Immune aspermatogenesis was induced in young rats by the method of Freundet al. (1954) and testes were studied by electron microscopic and histochemical methods. At time of sacrifice the testes of several animals were markedly atrophic as demonstrated by reduction in weight. Sections of seminiferous tubules exhibited primarily profiles of Sertoli cells but germinal elements were sparse or absent. The ultrastructure of Sertoli cells appeared to be normal except for the presence of areas of dilated smooth endoplasmic reticulum and fragments of phagocytized germ cells in the cytoplasm.
Smooth muscle cells of the guinea-pig sphincter pupillae were fixed in the presence of 3% lanthanum nitrate. Although only small amounts of lanthanum were found in plasmalemmal vesicles, large deposits were present within a membrane system resembling sarcoplasmic reticulum. The significance of these findings is discussed in relation to the use of lanthanum nitrate as an extracellular tracer.
The ultrastructural development of the rabbit Leydig and Sertoli cells was studied from the 16th to the 29th fetal day. The interest is focused on the differentiation of endoplasmic reticulum. In Leydig cells the full proliferation and maturation of agranular endoplasmic reticulum antedates the critical period in the development of the Wolffian ducts and male external genitalia. In Sertoli cells there is a less pronounced proliferation of agranular endoplasmic reticulum during the period when the Müllerian-inhibiting hormone is expected to act. Together with recent histochemical and biochemical evidence these findings support the hypothesis that fetal Sertoli cells secrete a Müllerian-inhibiting steroid hormone and that fetal Leydig cells secrete an androgen which stimulates the development of the Wolffian ducts and male external genitalia.
Electron microscopical evidence for the existence of an important serotonergic input to the rat median eminence is presented. This evidence is based on the demonstration of degenerating nerve terminals in the external layer of the rat median eminence following the application of 5,6-dihydroxytryptamine or 5,7-dihydroxytryptamine, drugs known to exert more or less selective toxic effects on central serotonin neurons.
A simplified insect haemocyte classification has been formulated by a light microscopic examination of the haemolymph of insects from fifteen Orders. Six cell types or developmental stages can be distinguished: (1) Prohaemocytes, (2) Plasmatocytes, (3) Granular Cells, (4) Spherule Cells, (5) Cystocytes, and (6) Oenocytoids.
Examination of the sensory surface of the tentacles of sea anemones and corals prepared by the Freon critical-point method has revealed three primary structures: ciliary cones consisting of a cilium surrounded by a cluster of shorter stereocilia, single long cilia, and microvilli. The ciliary cones occur on, and the single cilia and microvilli occur both on and between, the nematocyst- and spirocyst-bearing regions of the tentacles. The similarity of the anthozoan ciliary cones to the ciliary sensory structures in the lateral line, and the auditory and vestibular organs of vertebrates is noted and the possible functional significance of the coelenterate structures is discussed.
Mouse lingual epithelium incorporates significant amounts of L-proline-2, 3-H3 one hour after intraperitoneal injection of the tritiated amino acid. All viable cell strata incorporated approximately equal amounts of proline as assessed by autoradiographic techniques. Grain counts at 30 minutes, 1 hour, 4 hours and 24 hours, the four time periods studied, indicated a progressive incorporation of proline up to 4 hours following injection. Preferential incorporation of proline into any one cell structure or group of structures was not observed. Keratohyalin granules (KHG's) demonstrated incorporated proline; however, usually only one silver grain appeared over each granule, and, based on grain counts, the amount of proline incorporated by KHG's appeared slightly less than the general labeling observed in KHG-containing cells. This finding supports recent biochemical studies which have indicated a considerably lower proline content of keratohyalin than had previously been reported. Significant proline incorporation into the epithelial basal lamina was not observed during the 24 hours of this study. Thus, while recent recombination experiments have conclusively demonstrated that epithelial basal cells synthesize considerable quantities of basal lamina in a 24 hour period; it would appear that epithelial basal cells contribute little to a formed, intact basal lamina. This finding lends credence to the concept of a long basal lamina turnover time.
Histological, histochemical, and ultrastructural investigations have been carried out on ageing costal and tracheal cartilage of rats. The following age groups of animals have been studied: 1, 7, 14, 20, 30, 45, 75 days, 6 months, and 2 years.
Biopsy specimens of human intestines in various disease states and from laboratory animal intestines have been stained with ruthenium red and inspected by electron microscopy. Ruthenium red reaction product is found as a homogeneous deposit and also in the form of coarse and fine granules. Microvilli and the glycocalyx are stained relatively constant by ruthenium red. The intercellular space of the epithelium shows a strikingly variable ruthenium red staining. This variation is apparently not related to the method but indicates differences or variations in the functional state of the membranes. It remains an open question whether the ruthenium red reaction is a histochemical reaction, marking certain substances present in in the intercellular area or whether it should be considered as a tracer for the transport of materials. Goblet cells and necrobiotic cells usually show a constant ruthenium red staining. In the lamina propria the reaction product is very inconstant, possibly on account of the long penetration path from the lumen. The phagolysosomes of macrophages are marked by ruthenium red rather regularly. No fundamental, but only quantitative differences have been found between the various kinds of tissue studied.
The innervation of the epithelium of the avian trachea was investigated in the domestic fowl (Gallus domesticus) with cholinesterase and fluorescence techniques and electron microscopy. In the subepithelial tissues there were many nerves associated with acetylcholinesterase but only a very few containing catecholamines. The nerves were arranged in two interconnected plexuses, one plexus of myelinated and unmyelinated axons lying external to the tracheal cartilages, and another plexus of unmyelinated axons and ganglion cells lying between the cartilages and the epithelium. The presence of intraepithelial axons was established with the electron microscope. The majority of the intraepithelial axons lay near to the basal cells and the ciliated cells and some approached close to the surface of the epithelium. Two types of vesicle, agranular and granular occurred in the axon profiles. Convincing evidence for synapses between intraepithelial axons and epithelial cells was not seen. A sensory function is suggested for these axons.
Mouse fibroblasts were grown in a ‘deficient’ medium consisting solely of Hank's salt solution. Treatment of cells after 48 hours in deficient medium with the cationic dye, mepacrine, resulted in an altered formation of lysosomes. Cells grown in full medium form dense, multi-vesiculated lysosomes in response to mepacrine. Cells grown in deficient medium form large electron lucent vacuoles containing peripherally located dense globules. The significance of the observations in relation to the deficiency of the medium is discussed.
The stratified squamous epithelia of the esophagus and stomach were investigated with the electron microscope in mice. Langerhans cells (LC) were observed within the epithelia of both organs. In specimens which had been fixed with glutaraldehyde and osmium tetroxide, the morphology of these cells corresponds completely to the morphology of epidermal LC.
The uptake of 3H-GABA in the visual system of half-head preparations of Musca and Drosophila was studied by means of light and electron microscope autoradiography. Of all three ganglia, only the first synaptic region, the lamina ganglionaris, showed accumulation of radioactive grains, and there a preferential glial uptake could be found. Under normal light conditions at incubation (constant light flux of 100 Lux) the maximum of radio-activity was found in the marginal glia cells. Increasing the time of incubation produced also an increase in the number of grains per surface unit in the marginal glia cells. After changing the light intensity during incubation, quantitative modifications of the distribution of radio-activity were observed: incubating with stroboscopic illumination, the number of grains diminished in the marginal glia cells and remained constant in the epithelial cells; incubated in darkness, the epithelial cells became more intensely labelled whilst the number of grains decreased in the marginal cells.
The microanatomy of the adult auditory system of the cricket, Teleogryllus commodus, is described with special attention to the number and arrangement of the groups of scolopidia forming the tympanal organ.
The course of c-mitosis in early embryos ofBotryllus schlosseri is arrested in a bizarre c-metaphase configuration in which the chromosome arms are tightly paired and sister kinetochores are well separated. This new type of c-metaphase chromosomes occurs because kinetochores are normally separated during prometaphase and sister c-chromatids tend to adhere to each other.
