Electron microscopic studies on guinea pig rib cartilage

Summary The guinea-pig rib cartilage consists of chondrocytes dispersed in an intercellular substance composed of collagen fibrils, often characteristically cross-striated, and polygonal granules. Electron-dense membrane-bounded matrix vesicles are also observed intercellularly, especially in the central, partly calcified zone of the cartilage. With respect to their location in a cross-section of the rib, the chondrocytes differ in size, shape and intracellular fine structure. Thus, three separate types of cells are recognized. Peripheral chondrocytes have a flattened shape and are largely occupied by the nucleus. In the cytoplasm, the granular endoplasmic reticulum is the most extensive organelle. Intermediate chondrocytes are oval or round in shape. The endoplasmic reticulum and the Golgi complex are both prominent. Mitochondria and membrane-bounded cytoplasmic dense bodies are more numerous than in the peripheral cells. The ground cytoplasm often contains a few lipid droplets. In the central chondrocytes, such droplets sometimes fill the entire cytoplasm. Concomitantly, the nucleus is usually completely heterochromatic and the cells are therefore regarded as being metabolically inert.After preparations including ruthenium red staining en bloc, the general stainability of the chondrocytes is decreased. Intracellularly, positive ruthenium red staining of granular material within the Golgi vacuoles are to be observed. Extracellularly, the matrix granules are stained with this polyvalent, cationic dye. Extraction of the cartilage with 4 M guanidine-HCl removes all matrix granules and about 70% of the proteoglycans, measured as hexosamine, from the tissue. It is concluded that the matrix granules contain proteoglycan complexes.Financial support was received from the Swedish Medical Research Council (proj. no. 12X-3355), the Swedish Cancer Society (proj. no. 100-K71-05XK), the King Gustaf V 80th Birthday Fund, the Harald and Greta Jeansson Foundation, the C. B. Nathhorst Foundation, and from the funds of Karolinska Institutet.The skilled technical assistance of Mrs. Eva Lundberg and the secretarial assistance of Mrs. Inger Åhrén are gratefully acknowledged. The authors are indebted to Dr. S. Lohmander for helpful suggestions during the progress of the work.     

Effect of constant magnetic field on the liver of guinea pig. Electron microscopic studies.

Twenty guinea pigs were exposed 1 hour daily, for 3 to 7 weeks to constant magnetic field (CMF), the induction of which was 0.005 T, and 0.3 T. Hepatocytes were examined in semithin sections with light microscope and TEM. The negative photographic plates of the TEM were analyzed and measured with densitometer. It was shown that CMF of the induction 0.005 T and 0.3 T exhibited structural changes in hepatocytes, primarily in mitochondria.     

Electron microscopic observations on absorption in the epithelium of the guinea pig gall bladder

Summary The fine structure of the epithelium of the gall bladder in the guinea pig has been examined after the resorption of Thorotrast. Vesicles at the apex of the epithelial cells containing Thorotrast give evidence of pinocytosis and particles are also found in the intercellular spaces and in dense cytoplasmic bodies. The epithelium exhibits interdigitating lateral cell membranes which are correlated with its function of resorbing large amounts of water.     

Electron microscopic study of the substantia nigra and the strio-nigral projection in the rat

Summary The normal ultrastructure of rat substantia nigra was investigated. Special attention was paid to the different types of boutons, and the mode of termination of the striatonigral connection was examined. Two different types of nigra neurons with deep nuclear membrane indentations were observed. The synaptic organization of rat substantia nigra is very complex. Six types of boutons, with many characteristics, could be differentiated: pleomorphicvesicle boutons (40%), elongated-vesicle boutons (10%), small-round-vesicle boutons (10%), large-round-vesicle boutons (20%), clear-terminal (15%) and dense-core-vesicle boutons (about 5%). Vesicle-containing dendrites were observed entering dendro-dendritic synapses. One to four days after large unilateral striatal lesions were made, a great number of degenerating boutons were seen in the ipsilateral substantia nigra, while the contra-lateral substantia nigra was entirely free of degeneration. The newly defined pleomorphic-vesicle boutons were found almost exclusively in the process of degeneration. The neuronal origin of the other bouton types is discussed.On leave of absence from Anatomical Institut, Semmelweis University, Budapest.     

Electron microscopic study of alpha-actinin.

Electron microscopic studies of the structure of purified α-actinin alone and in complex with F-actin have determined the molecular shape and size of this protein. α-Actinin molecules represent rods of about 300 Å in length and about 20 Å in diameter.     

An electron microscopic study of the photochemical cross-linking of DNA in guinea pig epidermis by psoralen derivatives.

Albino guinea pigs were treated with psoralen derivatives plus 320--400 nm ultraviolet radiation, and DNA was extracted from their epidermis. The DNA was assayed for the presence of interstrand cross-links by standard denaturation-renaturation assays and by a new technique, electron microscopy of the DNA under totally denaturing conditions. The latter method allows individual cross-links to be directly observed and counted. When either 4,5',8-trimethylpsoralen or 8-methoxypsoralen was applied topically to the skin (8--20 microgram/cm2) or administered orally (10--12 mg/kg body weight), followed by exposure to 320--400 nm ultraviolet radiation, most of the epidermal DNA was found to contain a high frequency of cross-links. For example, oral or topical trimethylpsoralen treatment gave an average of one cross-link per 250 nucleotide pairs or about 3 . 10(5) cross-links per guinea pig chromosome. When the dose of either drug was decreased 20-fold to the level used in the clinical treatment of psoriasis, however, no cross-links coulld be detected in the epidermal DNA. The electron microscopic assay is sensitive enough that we can put an upper limit of 1 cross-link per 10(6) nucleotide pairs (80 cross-links per chromosome) for the low dose studies. The significance of these findings to the understanding of the effectiveness of psoralens in psoriasis therapy is discussed.     

Electron microscope studies of experimentalEntamoeba histolytica infection in the guinea pig

Early cellular and vascular changes in response to invasion of lamina propria byEntamoeba histolytica were studied sequentially, at the ultrastructural level, in germfree guinea pigs inoculated intracecally with amebae and enteric flora derived from patients with acute amebic colitis. Approximately one week post-inoculation the animals developed acute colitis with mucosal invasion by trophic amebae. Although epithelial cells at the sites of amebic invasion showed progressive cytoplasmic changes and desquamation resulting in microerosions, most mesenchymal elements in the lamina propria appeared normal without cytopathic changes even when in direct contact with invading amebae. Only the polymorpho-nuclear leukocytes (PMN) apposed or topographically close to amebae exhibited degenerative changes which were characterized by condensation of nucleoplasm and cytoplasm, extracellular release of cytoplasmic components including granules, and, finally, lysis of cell membranes. Capillaries and venules in the lamina propria showed a variety of changes such as swelling and gap formation at the intercellular endothelial junctions and more rarely at the fenestrae. Blood vessels physically close to amebae showed formation of endothelial cytoplasmic blebs which pinched off into the vascular or extravascular space. Platelet and fibrin thromboses were common in the more severely damaged capillaries and venules. Fragments or clumps of fibrin-like material were found also in the extracellular spaces. Amebic invasion of the lamina propria, then, is accompanied by continued epithelial shedding, PMN degeneration, and changes in both capillaries and venules consisting of endothelial damage and occlusive thrombosis. The vascular changes appeared to be closely related to PMN degeneration resulting from interaction of PMN with invading amebae.     

Intravesical BCG administration in the guinea pig. A histomorphological study

Intravesical BCG administration is used as an adjuvant therapy after transurethral resection for superficial bladder cancer in man. The mechanisms of its antitumor activity are not known. The aim of this study was to characterize the histomorphological changes in various organs of the guinea pig after intravesical BCG administration. The BCG preparation used was BCG-RIVM, a Dutch BCG preparation. Instillations were performed in previously undamaged bladders weekly for 6 consecutive weeks and lasted 30 min or 1 h. Different doses were used ranging from 10(3) culturable particles (c.p.) to 5 x 10(7) c.p. of BCG. After 6 weeks, the animals were killed and postmortem examination was performed. The bladder wall, retroperitoneal lymph nodes, spleen, liver, lungs and distant lymph nodes were examined histologically. The BCG therapy, with a dose of 10(6) culturable particles and higher, induced an inflammatory reaction consisting of mononuclear infiltrates in the subepithelial tissue of the bladder wall. In approximately 50% of the animals investigated, the infiltrates were accompanied by non-caseating granulomatous lesions indicated by the presence of epithelioid cells. In general, the epithelial layer of the bladder showed no visible alterations. Similarly, a granulomatous inflammatory reaction was observed in the first retroperitoneal (iliac) lymph nodes draining the bladder. Granulomatous lesions were occasionally also present in liver and lung. In three of the 29 animals investigated, lesions were present both in liver and lungs, and in two of these three animals a granulomatous reaction was observed in the spleen and distant lymph nodes indicating a generalized inflammatory response induced by BCG.(ABSTRACT TRUNCATED AT 250 WORDS)