Collagen-polysaccharide gel as a model of the ground substance of connective tissue

Samples of gel formed at 37°C in solutions containing tropocollagen and various polysaccharides were studied with the electron microscope. Contracting gel clots were formed in solutions containing chondroitin sulfate, proteoglycan from tracheal cartilage, and gum arabic as the polysaccharide component. Examination under the electron microscope showed that these clots were permeated by transversely striated collagen fibrils with a period of 64 nm. The connection between the density of the gel thus formed and the nature of the polysaccharide component is discussed. Gel forming in solutions containing tropocollagen and various polysaccharides can be regarded as a suitable model of the ground substance of connective tissue.Laboratory of Histophysiology, Institute of Clinical and Experimental Medicine, Academy of Medical Sciences of the USSR, Siberian Branch, Novosibirsk. (Presented by Academician of the Academy of Medical Sciences of the USSR V. P. Kaznacheev.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 82, No. 10, pp. 1216–1218, October, 1976.     

Hyperplastic lymphoid tissue in HIV/AIDS: an electron microscopic study

The purpose of this study was to characterize the ultrastructure of lymphoid tissue from HIV/AIDS patients and to evaluate it as a reservoir and source of HIV. HIV has been demonstrated in lymph nodes and tonsils and adenoids, by immunohistochemistry (IHC), in situ hybridization (ISH), and transmission electron microscopy (TEM), to be associated with germinal center (GC) follicular dendritic cells (FDC). The presence of HIV in the larger gastrointestinal tract-associated lymphoid tissue (GALT) has been much less studied. Whether FDC themselves are productively infected by HIV in any of the lymphoid sites is controversial. Lymph nodes, tonsils, and gastrointestinal biopsies were fixed in neutral buffered glutaraldehyde and prepared for TEM. Mature HIV particles were abundant in GC of hyperplastic lymph nodes, tonsils, and the GALT. They were enmeshed within an electron-dense matrix associated with an all-encompassing branching FDC network of processes. HIV particles were seen budding from both FDC and lymphocytes. The greatest numbers of particles were seen in hyperplastic lymphoid tissue from untreated individuals and in lymph nodes co-infected with opportunistic organisms, such as Mycobacterium avium complex. In addition to HIV, unidentifiable "particles" of varying sizes, possibly including other viruses, were regularly seen in association with FDC. Ultrastructural study graphically demonstrated the abundance of HIV particles associated with the complex FDC network of hyperplastic lymph nodes, tonsils, and GALT. HIV was shown to productively infect FDC, as well as lymphocytes.     

Ripening of the uterine cervix of the guinea-pig after treatment with the progesterone antagonist onapristone (ZK 98.299): an electron microscopic study

The effects of the progesterone antagonist (AG) onapristoneZK 98.299 on the uterine cervix were investigated by electronmicroscopic examination in guinea-pigs during late pregnancy.Treatment with the AG led to dissolution, splitting up and dissociationof collagen fibres as well as expansion of the inter-fibrillarspaces due to oedema. This was associated with an increasednumber of polymorphonuclear granulocytes, macrophages and mastcells as well as with the appearance of highly active fibroblasts.The possible roles of these cells in the dissociation of collagenousfibres are discussed. Comparing the AG-induced prominent transformationof the uterine cervix with the morphological signs characteristicof cervical ripening in untreated guinea-pigs at term pregnancy,no significant differences could be observed. This suggeststhat AG brings about ripening and dilatation of the cervix ina physiological manner and may be, after thoughtful toxicologicalscreening, an extremely useful agent for obstetrical indications     

Prostatic-type tissue in the uterine cervix

The female genital tract can give rise to a variety of metaplastic and ectopic tissue types. We report a case of incidental prostatic-type tissue in a loop excision specimen for cervical intra-epithelial neoplasia (CIN). We also review the histogenesis, potential pitfalls and immunohistochemistry of this diagnosis.     

Nevus cell aggregates in the placenta. A histochemical and electron microscopic study

This is a report of the histochemical and ultrastructural analysis of nevus cell aggregates in the placenta from a neonate with a giant pigmented nevus. Although the distinction between aberrant migration of neural crest elements and blood-borne metastasis from the giant pigmented nevus is not readily resolved, the authors favor the former as an explanation of this unusual placental lesion.     

An electron microscopic study of uterine arteries during pregnancy

The mesometrial arteries of pregnant guinea pigs are not mere blood conducting channels. Instead they are dynamic in nature. The cells forming the intima and media exhibited significant structural modifications during pregnancy. The endothelial cells became hypertrophied and attenuated. Their cytoplasm showed an increase in the amount of ribosomes, rough endoplasmic reticulum and lysosome-like bodies during pregnancy. Dense bodies that were often closely associated with the Golgi apparatus were seen in pregnant animals. These bodies exhibited a graduation in size within each cell and were thought to be the precursors of the lysosome-like bodies. Similar structures were also seen in smooth muscle cells of the mesometrial arteries of pregnant animals. The endothelium of these arteries was often discontinuous in full term pregnant animals. In that case, the underlying smooth muscl4 cells provided the lining surface. Irrespective of which type of cells formed the lumen of these arteries, they became coated with a “fuzzy” layer which specifically stained intensely with phosphotungstic acid, suggesting that this layer might be a mucoprotein. The smooth muscle cell of the arterial media also became hypertrophied during pregnancy. The cytoplasm exhibited a gradual increase in free ribosomes and rough endoplasmic reticulum, mitochondria and microtubules throughout pregnancy. During the latter half of pregnancy many smooth muscle cells developed extensive amounts of smooth endoplasmic reticulum whose vesicles often were filled with an electron opaque secretory material. It is suggested that the development of unusually large quantities of smooth endoplasmic reticulum might be associated with steroid metabolism. Unusually thick basement membranes were formed around the modified smooth muscle cells of full term pregnant animals and the surfaces of these cells often exhibited large numbers of microvilli. The microvilli seemed to disrupt the continuous patterns of the basement membrane.     

The septohippocampal projection in the rat: an electron microscopic horseradish peroxidase study

In order to identify the specific targets of the septohippocampal projection in the rat, horseradish peroxidase localization at the electron microscopic level was used. Following injections of free horseradish peroxidase into the medial septum, sections of the dorsal hippocampal formation were reacted with diaminobenzidine and processed for electron microscopy by routine methods. Sections were viewed unstained. Horseradish peroxidase labeling in the dentate gyrus was predominantly in the supra- and infragranular layers. All postsynaptic elements were neuronal. They included granule cell somata and somata and dendrites of hilar cells; these may include pyramidal basket cells. No synaptic contacts with vascular or glial elements were found. These results provide a basis for comparing the specific targets of the septohippocampal projection with those of the sympathohippocampal pathway, which innervates the dentate following lesions of the septohippocampal projection.     

Pulmonary plasma cell granuloma—an electron microscopic and tissue culture study

A case of pulmonary plasma cell granuloma studied by electron microscopy and tissue culture is reported. Ultrastructurally, it showed a polymorphic composition in which a variety of inflammatory cells, collagen fibres and capillary vessels were identified. In vitro there was an initial emigration of inflammatory cells, followed by a predominance of fibroblasts and histiocytes. This pattern of growth is similar to that obtained from explants of granulation tissue and gives support to the previously suggested view that these lesions are inflammatory pseudotumours.     

Organization of the fibrous connective tissue of the fallopian tubes in fertile and climacteric periods: a scanning electron microscopic and stereologic study

The extracellular matrix (ECM) of the fallopian tubes is subject to several changes due to hormonal influences and aging. However, there is a lack of studies regarding its arrangement in older women. We aimed to analyze the organization of ECMcomponents, including collagen and elastic fibers, in the fallopian tube’s ampulla from young and old women by means of scanning electron microscopical and stereological methods. Twenty-one samples were analyzed: 12 from female cadavers in a fertile age (G1) and 9 from the climacteric period (G2). Masson’s trichrome stain was used to observe collagen and smooth muscle, while Weigert’s Fuchsin-Resorcin was employed to observe elastic fibers. Statistical analysis was performed by the Wilcoxon-Mann-Whitney test with the aid ofthe R^© software. The tissue was also fixed for scanning electron microscopic analysis in a modified Karnovsky solution and the three-dimensional organization of fibrous connective tissue was observed and compared. Statistically significant differences (P < 0.01) were found in all stereologic comparisons of the extracellular matrix between the groups, which revealed a higher volumetric density of the fibrous tissue in the climacteric group. Scanning electron microscopy showed degenerative alterations of extracellular matrix. According to our results, aging caused significant changes to the elements of the extracellular matrix and the smooth muscle of the fallopian tubes.