Ultrastructural cytochemistry of anchoring filaments of human lymphatic capillaries and their relation to elastic fibers.

In previous studies "anchoring filaments" of human lymphatic capillaries have been shown to consist of microfibrils having histochemical and ultrastructural characteristics similar to elastin-associated microfibrils. When not associated with an elastin component, these microfibrils are referred to as "oxytalan microfibrils." In this study, alpha-glycol-containing carbohydrates and glycoconjugated sulfate groups, originating from sulphydryls and/or disulfide bridges, have been detected in anchoring filament microfibrils of human lymphatic capillaries by Thiery reaction (PA-TCH-SP) and "Hight Iron Diamine" cytochemical method (HID), respectively. Both of these chemical groups belong to the putative glycoprotein of which the microfibrils are constituted. Similar molecular characteristics have been demonstrated in elastic fiber microfibrils and oxytalan microfibrils of connective tissue. These findings suggest a close molecular similarity among these different types of microfibrils. Thus, whatever their individual location or denomination (anchoring filaments, oxytalan fibers, or elastin-associated microfibrils), these microfibrils form an uniform population of fibrous elements. These findings further support a structural (and functional) continuity between the lymphatic capillary wall and the elastic network of adjacent connective tissues previously described and termed "Fibrillar Elastic Apparatus" (FEA). Of interest, endothelial cells also selectively react positively to the PA-TCH-SP and HID methods.

A fibrillar elastic apparatus around human lymph capillaries.

A fibrillar elastic apparatus around the wall of human lymph capillaries is demonstrated by means of histochemical and ultrastructural techniques. This apparatus consists of three interlinked components listed here in order of increasing distance from the capillary wall: 1) oxytalan fibres connected to the abluminal surface of the endothelial cells, known also as "anchoring filaments" and consisting of bundles of microfibrils; 2) elaunin fibres consisting of microfibrils and a small amount of elastin; and 3) typical elastic fibres consisting of microfibrils and abundant elastin. The microfibrillar constituent has similar ultrastructural features in the three components of the elastic apparatus. Microfibrils have a diameter of 12-14 nm, an electron-transparent core and a wall with 3-5 electron-dense subunits and oblique cross striations with a period of 15-17 nm. Microfibrils are the common element of the three components of the elastic apparatus and they link them to one another and to the elastic network of the perivascular connective tissue. An elastic apparatus was not found around blood capillaries and it can thus provide a histological marker to identify lymph capillaries. The possible role of the lymphatic elastic apparatus in the physiological activity of the lymphatic absorbing network is discussed and it is proposed that its disconnection from the elastic network of the tissue may promote pathological conditions such as lymphoedema or diseases related to impaired immune responses.

Morphometric analysis of elastic fibers in human skin lymphatic capillaries.

In contrast to their absence near dermal blood capillaries, elastic fibers are commonly seen adjacent to dermal lymphatic capillaries under light microscopy. Based on morphometric analysis, the elastic fiber network that surrounds these skin lymphatic capillaries is predominantly oriented longitudinally to the lymphatic vessel wall. Quantitative analysis reveals that the density of these pericapillary elastic fibers are almost twice that of the intercapillary elastic fibers but only about one-half as thick. These data suggest that dermal lymph capillaries are surrounded by a specific elastic network of functional significance, morphologically distinct from that seen in the intercapillary dermis. Because lymphatic capillaries are often difficult to identify especially when collapsed, this elastic network may facilitate the positive identification of dermal lymphatic capillaries by light microscopy and thereby help differentiate them from blood capillaries. The possible role of this lymphatic elastic network in the absorptive activity of the dermal lymphatic system is also discussed.

Massive haemorrhagic pericardial effusion in beta-thalassaemia major.

The case of a child with beta-thalassaemia major who developed a massive haemorrhagic pericardial effusion is reported and in whom the clinical picture completely resolved after pericardiocentesis. Possible causes are discussed and the role of echocardiography in the follow-up of thalassaemic patients is emphasized.

Morphology of the peritoneal membrane during continuous ambulatory peritoneal dialysis.

In the last 3 years we performed 52 peritoneal biopsies (PB) in 31 patients on continuous ambulatory peritoneal dialysis (CAPD). Samples of the parietal peritoneum were obtained either during insertion of the catheter or while it was being repositioned or removed. PB was performed in 13 patients before initiating CAPD and in 27 after 7-49 months of CAPD while 7 had PB during peritonitis, and, again, in 5 of these cases, PB was repeated after 1-4 months for light, electron transmission, and scanning electron microscopy. BP after CAPD showed that mesothelial cells were irregularly spaced, and at times we observed alterations in the cellular structure. Rarely were these cells degenerating, while rarefaction and in many cases complete absence of microvilli were observed. In some cases the submesothelial layers showed rarefaction of the connective tissue and sclerosis. During peritonitis, PB showed more alterations with marked degeneration and in some cases necrosis of the mesothelium and alterations of connective tissue. PB performed some months after peritonitis showed only a partial regression of these alterations and sclerotic patches, and no microvilli were noted in the mesothelium.

[Morphological study by scanning electron microscopy of the lymphatic vessels of the guinea pig]. / Studio morfologico al microscopio elettronico a scansione (SEM) dei vasi linfatici di cavia.

The purpose of this study was to describe the morphology of the whole lymphatic way: from capillaries to thoracic duct including cisterna chili using scanning electron microscopy and Evan's technique. We observed the lymph vascular wall that is: the endothelial surface, the muscular layer and the adventitial one. All these vessels were covered by an endothelial surface, with raised nuclei and long cell axes oriented parallel to the direction of flow. The borders between adjacent endothelial cell were often seen and open junctions were noted in lymphatic capillaries. The technique we used, permitted the removal of connective tissue by HC1 hydrolysis, so that smooth muscle cells could be examined. The latter showed a great variety of aspects and a very irregular course. The adventitial layer was thin in capillaries and became complex in thoracic duct where collagen fibers and connective elements were seen.

[Mesentery collector valves in the guinea pig: morpho-functional aspects]. / Le valvole dei collecttori mesenteriali di cavia: aspetti morfo-funzionali.

In guinea pig mesenterial lymph vessels there are many bicuspid valves, which determine the flow centralwards of lymph. Our observations, based on the study of 52 guinea pig lymph collectors, demonstrated a different number of valves on different parts of each vessel. In fact we found more valves in the part near the intestinal wall and the mesenterial lymph node than in the middle part of the vessel. Besides we measured the time of flow in these different portions by Indian ink injection and we found a correlation between valve number and flow. In fact the time of flow decreases with the increase of the number of valves the shortest being near the intestinal wall and the mesenterial lymph node and the longest being in the middle part of the collectors. The experimental data indicate that the valves have an important role in the lymph circulation because they favour the flow lymph velocity.