Histochemical observations on the localisation and origin of sphingomyelin, cerebroside and cholesterol in the normal and atherosclerotic human artery

Are intramural suction-squeezing effects generated by the variations in radial wall stress during each heart beat the motor of atherosclerosis? A new concept

In the early sixties, the existence of predilection sites for atherosclerotic lesions inside the arterial circulation led to the concept that low wall shear stress (WSS) was responsible, together with systemic factors like high blood pressure, hypercholesterolemia, or diabetes, for the genesis and progression of atherosclerosis. It was found later that oscillating WSS and high WSS gradients could also be incriminated. Yet, this concept, which is broadly accepted today, fails to explains several facts, for instance that some arteries (e.g. epicardial coronary arteries) are more prone to become atherosclerotic than other ones exposed to the same systemic factors (e.g. hepatic and brain arteries). In this paper, we present a quite different concept. It is based on the fact that the increase in intravascular pressure and flow that occur in the arteries during systole generates, at the predilection sites of atherosclerotic lesions (bends, bifurcations, and branchings), an increase of radial wall stress in the outer layers of the arterial wall so that this stress becomes momentarily tensile. These cyclic stress increases have a suction effect that is likely to facilitate the diffusion of atherogenic cells and substances inside the wall. Furthermore, since arteries are not primarily structured to resist inversions of radial stress, they may also create damages (e.g. disruptions of cell membranes and elastic lamellae) followed by inflammations and micro-haemorrhages in the wall. This new concept may provide a complementary (or possibly alternative) explanation of atherosclerosis.

Histochemistry of lipid storage diseases

Diagnosis of lipid storage disturbances by routine histopathological means is fraught with difficulty. This problem was obviated by use of a simplified histochemical protocol, that is herein presented, to differentiate the more common lipidoses, as well as other clinical entities that are frequently confused with some of the lipidoses.

Oral leukoplakias. A microradiographic and lipid-histochemical study

Biopsies from 13 oral leukoplakias and from normal tissue specimens in the contralateral region of each patient were examined microradiographically and lipid-histochemically using freeze-sectioned and freeze-dried sections. The investigation showed that an epithelial zone of cell layers with different degrees of keratinization and varying dry mass concentrations occurred in oral leukoplakias. A concentrated localization of phospholipids, free fatty acids and cholesterols was found in the zones with a high dry mass content and, consequently, high keratin content, while a negative lipid reaction was obtained in the zones where the dry mass concentration was low.

The relation of lipids to the mineral components in salivary calculi

Using lipid histochemical and microradiographic methods, the distribution of lipids and the inorganic component in different areas of salivary calculi was investigated. Two main groups of lipids were found, i.e. hydrophilic phospholipids and hydrophobic lipids. The hydrophilic phospholipids were shown to be composed mainly of phosphosphingosides and of the hydrophobic lipids cholesterol was demonstrated. Phosphosphingosides were localized in more or less lamellar zones as also in large homogeneous areas. In some cases the calculi were surrounded by a structureless non-mineralized zone exhibiting a strongly positive reaction for phosphosphingosides. Cholesterol was found in isolated band-formed areas. Phosphosphingosides and cholesterol were especially prevalent in areas showing a low or slight degree of mineralization. In areas showing a high degree of mineralization the corresponding lipids gave a weak or absent histochemical reaction. After EDTA-decalcification, however, an increase in the concentration of lipid was noticed in high mineralized areas, indicating a masking process. The influence of various factors on the presence and distribution of different lipids was discussed.

Temporal bone pathology in an active case of glue ear

A child aged 3 1/2 died from a cardiac condition after many and prolonged antibiotic courses: bilateral glue ear had been treated for the previous 18 months. Histopathology showed cholesterol granulomata in the mastoid air cells, with evidence of old hemorrhage, and of former inflammation of bone. The exudate was histiocytic with some giant cells. An 'orange spot' on the tympanic membrane was hyperaemic middle-ear mucosa, heavily infiltrated by plasma cells, lymphocytes and histiocytes. There was no evidence of hypersecretion. Some of the most abnormal areas were around the stapedial niche and the round window.

Phospholipases in arterial tissue. IV. The role of phosphatide acyl hydrolase, lysophosphatide acyl hydrolase, and sphingomyelin choline phosphohydrolase in the regulation of phospholipid composition in the normal human aorta with age

The role of phospholipases in the regulation of the changing phospholipid composition of normal human aortae with age was studied. Portions of grossly and histologically lesion-free ascending aortae from 16 females and 29 males obtained at autopsy, were analyzed for deoxyribonucleic acid (DNA), phospholipid, and cholesterol content and phospholipid composition. Enzymic activity toward four substrates, lecithin (LE), phosphatidyl ethanolamine, lysolecithin, and sphingomyelin (SP), was determined on portions of the same homogenate. By regression analysis for correlation between all determinations and age the following results were obtained: (a) total phospholipids and choleserol increased linearly with age; (b) the increase in sphingomyelin accounted for about 70% of the phospholipid increment; (c) hydrolysis of lecithin and phosphatidyl ethanolamine increased markedly with age, that of lysolecithin only moderately; (d) hydrolysis of sphingomyelin decreased with age; and (e) an inverse relation between the SP/LE ratio and age and sphingomyelinase/lecithinase activity and age was obtained. These results were interpreted to indicate that a causal relation exists between the fall in sphingomyelinase activity, both absolute and relative to lecithinase activity, and the accumulation of sphingomyelin with age.