An ultrastructural study of dolipore septa in Psilocybe mexicana. Volvariella bombycina, Amanita muscaria, Favolus alveolaris, Lycoperdon perlatum, Hericium coralloides, and Dacrymyces stillatus indicated the presence of solid pore occlusions in vegetative mycelium while the occlusions were perforate or absent in the hymenium. Dolipore septa in basidiocarp initials, stipes, and lamellae of P. mexicana lacked occlusions or had perforate pore occlusions. Septa in vegetative mycelium of D. stillatus had parenthesomes with no pores while the septa in the hymenium had parenthesomes with a single pore. Pore occlusions in septa of vegetative hyphae of P. mexicana were digested with trypsin and chymotrypsin. Periodic acid, thiosemicarbazide, and silver proteinate stain for polysaccharides produced no staining of the pore occlusion. Nucleic acid extraction with perchloric acid also had no effect on the pore occlusion. Microfilaments in the pore canal appeared to be attached at regions of electron-dense material within the canal and at the pore occlusion. Serial sections demonstrated that electron-dense regions within the pore canal were rings which did not completely block the canal.
Standard tissue preparation for light and scanning electron microscopy (SEM) uses ethanol as a dehydrating agent but that can also dissolve cholesterol crystals (CC) leaving behind empty tissue imprints or "clefts". Cholesterol crystals may contribute to plaque rupture by their sharp tips that can tear membranes and trigger inflammation. Therefore, use of ethanol in tissue processing can mask the pathological role of CC. Here we evaluated the amount of cholesterol dissolved from CC with single and complete series of standard graded ethanol concentrations (25-100%) used in tissue preparation. Also, solubility of CC in ethanol at physiological levels was measured. Furthermore, we compared the effect of ethanol on CC in fresh human atherosclerotic plaques to matched segments dehydrated using vacuum (-1 atm, 12h). Tissue crystal density ranging from 0 to +3 was measured semi-quantitatively by SEM. For CC exposed to 25% and 100% ethanol for 10 min each, 0.38% and 95% of CC were dissolved respectively. Also, increase in CC solubility was significant at physiological levels of ethanol (0.16%) compared to water (43.4 ± 18.0 ng/mL vs. 30.9 ± 13.9 ng/mL; p < 0.05). We speculate that this could represent a potential mechanism of cardio-protective effects of alcohol consumption. In atherosclerotic plaques, CC density was lower in ethanol vs. saline treatment (+1.2 vs. +2.8; P < 0.01) with visible dissolving noted by SEM. Ethanol has been used for centuries in tissue preparation for microscopy. Here we demonstrate how current tissue preparation methods greatly alter histological findings with SEM by masking the potential mechanism of plaque rupture.
Thermal, rheological, and microstructural properties of myosin (1 and 2% protein) were compared to mixtures of 1% myosin and 1% heat-denatured beta-lactoglobulin aggregates (myosin/HDLG) and 1% myosin and 1% native beta-lactoglobulin (myosin/beta-LG) in 0.6 M NaCl and 0.05 M sodium phosphate buffer, pH 6.0, 6.5, and 7.0 during heating to 71 degrees C. Thermal denaturation patterns of myosin and myosin/HDLG were similar except for the appearance of an endothermic peak at 54-56 degrees C in the mixed system. At pH 7.0, 2% myosin began to gel at 48 degrees C and had a storage modulus (G') of 500 Pa upon cooling. Myosin/HDLG (2% total protein) had a gel point of 48 degrees C and a G' of 650 Pa, whereas myosin/beta-LG had a gel point of 49 degrees C but the G' was lower (180 Pa). As the pH was decreased, the gel points of myosin and myosin/HDLG decreased and the G' after cooling increased. The HDLG was incorporated within the myosin gel network, whereas beta-LG remained soluble.
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