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PubMed1987

Cholesterol ester crystals in polarized light show pathways in the human brain.

It is well known that crystals of cholesterol esters exhibit birefringence. In the central nervous system such crystals are formed in the course of myelin degeneration following axonal interruption. Thus, anterogradely degenerated tracts assume birefringence. In the human brain, where modern tracing techniques commonly used in animals cannot be applied, anterogradely degenerated fiber systems can be visualized in formalin-fixed frozen tissue by simple polarizing microscopy. Using this phenomenon, tracing cerebral connections may permit one to interpret neuropsychological symptoms unique to man (aphasia, amnesia, neglect). Also, it should be a useful addition to routine neuropathology for it shows the long-distance effects of a brain lesion; it would facilitate the study of peripheral nerve pathology; and it would yield information about the age of a lesion.

Brain↗

PubMed1995

Phase behaviour of novel phospholipid analogues.

The phase behaviour of phospholipid analogues containing a phosphoramide moiety was investigated using polarized light microscopy. A complex liquid-crystalline polymorphism consisting of lamellar, and normal topology hexagonal and intermediate phases was observed and found to depend on the structure of the phosphoramide headgroup and its methylation. In addition, a lower consolute phase boundary in the micellar solution part of the phase diagram was observed in some systems. The aggregation behaviour of these novel amphiphiles was compared with that of quaternary ammonium and oligo-ethylene oxide amphiphiles.

Amides↗

PubMed1990

Spontaneous formation of pigmentary precipitates in bile salt-depleted rat bile and its prevention by micelle-forming bile salts.

During studies on the effect of bile salt-pool depletion in the bile-fistula rat (adult male Sprague-Dawley), the spontaneous formation of an orange-brown precipitate was noted. The nature of this phenomenon and its relationship to BS and calcium concentration was investigated in depth. Bile from 18 animals was collected in the dark into transparent tubes containing sodium azide, ascorbic acid, and glucaro-1,4-lactone. The tubes were flushed with nitrogen, sealed, and incubated at 37 degrees C. The pigmentary precipitate formed in all the bile salt-depleted (less than 3-5 mM) bile samples (i.e., those collected after 5-7 h of external biliary drainage), but not in bile salt-rich biles. It appeared within 30-240 min after collection, both in bile samples collected at room temperature and at 37 degrees C, initially as a pale flocculation and then slowly sedimenting to form, after centrifugation, a solid, dark-orange pellet. There were no pH changes during incubation, and bile cultures were negative. Under polarizing microscopy, the precipitate appeared amorphous, and there was no evidence of birefringence. High-performance liquid chromatography showed that unconjugated bilirubin was the prevalent pigmentary component, but significant amounts of monoconjugated bilirubin also coprecipitated. Lipid chemistry showed the presence of lecithin (80.1% of total lipids), which was rich in palmitoyl and linoleoyl fatty acids, and of fatty acids (predominantly palmitic and oleic). Infrared spectroscopy and x-ray diffraction showed the presence of calcium bilirubinate and palmitate. In-vivo replenishment of the bile salt pool by intravenous infusion of either taurocholate or taurochenodeoxycholate (1 mumol/min) completely prevented the pigmentary precipitation. In vitro experiments showed inhibition of the precipitate formation by the addition of individual bile salt in concentrations approximating their critical micellar concentration. Precipitate formation was hastened by the addition of calcium chloride (4-12 mM), but only in bile salt-depleted biles. As the composition of the precipitate closely resembles that of human brown-pigment stones and sludge, these findings may provide new insights into an understanding of the pathogenesis of pigment gallstone disease.

Animals↗

PubMed1987

Development of intracellular lipid deposits in the lipid-laden cells of atherosclerotic lesions. A cytochemical and ultrastructural study.

In atherosclerotic lesions of rabbits fed a cholesterol-rich diet, the lipid deposits of foam cells derived from monocytes, smooth muscle and endothelial cells were studied by physical, cytochemical and ultrastructural methods. Beginning with the third week of diet, the lipid material that could be visualized at the light microscope level by Oil red O and Nile red staining was progressively accumulated in the intimal cells of the atherosclerotic lesions. In the early stages of foam cell formation, the deposits occurred especially as intracytoplasmic non-membrane bound lipid inclusions (lipid droplets). In polarizing microscopy these appeared as a mixture of iso-, and anisotropic material. The latter were birefringent and showed an axial symmetry with a black cross image, suggesting that the lipids were in a liquid crystalline state. In chemically-fixed specimens, the content of lipid inclusions was preserved in various degrees. In freeze-fractured preparations they displayed a layered onion-like arrangement with smooth cleavage faces surrounding an amorphous core. Upon incubation with filipin, that specifically binds to 3 beta-hydroxysterols, the peripheral layers of the inclusions were labeled, revealing the existence of unesterified cholesterol. In the advanced stages of foam cell formation, lipids were additionally accumulated in the lysosomal compartment as polymorphic multilamellar structures concentrically arranged, with cleavage faces devoid of intralamellar particles. The presence of acid phosphatase showed that these features were modified lysosomes and were tentatively named lysosomal lipid bodies. In the latest stages examined cholesterol crystals developed within lysosomal lipid bodies usually enclosed in multilamellar structures. This lipid coat may represent the place of crystal formation and presumably acts as barrier for the turnover of the crystalline cholesterol, thus impeding plaque regression.

Acid Phosphatase↗

PubMed1991

On the anisotropy of the canine diaphragmatic central tendon.

We studied the mechanical and anatomical anisotropy of the canine diaphragmatic central tendon (CT). Dumb-bell-shaped strips with effective dimensions of 10 x 2 mm (length x width) were cut from different regions of the canine diaphragmatic CT in two different orientations relative to the direction of neighboring muscle fibers. Specimens sampled with their long axial dimension oriented parallel to the neighboring muscle fibers were named Group-1 and those sampled with an orientation perpendicular to the neighboring muscle fibers were named Group-2. Results from one-dimensional stress-strain and tensile failure strength tests revealed that the CT is a nonlinear, inelastic, and anisotropic material. Group-1 specimens were found to have a higher stiffness, higher failure strength and higher strain energy density at failure than Group-2 specimens. Polarized microscopy showed that multiple sheets of collagen fiber bundles formed an orthogonal network in the tendon. Collagen fiber bundles along Group-1 direction formed parallel trajectory lines connecting the neighboring costal and crural muscles; bundles along Group-2 direction were observed to orient 90 degrees away. At the central apex region of the CT, collagen bundles of Group-1 formed a fan-like trajectory pattern. This collagen network architecture was compared favorably to the trajectories of an approximated principal stress field in the CT due to simulated contractile forces from its adjacent costal and crural muscles. These combined results suggest a structure-function relationship for the anatomical and mechanical anisotropy in the canine diaphragmatic CT.

Animals↗

PubMed1991

Mineral-associated hepatic injury: a report of seven cases with X-ray microanalysis.

The patterns of hepatic injury associated with various minerals were studied in seven patients. The subjects included one patient who was a sandblaster (silica by inhalation), one patient who was a dental laboratory technician (silica and chromium-cobalt alloy by inhalation), one patient with inhalational talcum powder abuse, and four chronic intravenous (IV) drug abusers (talc by IV injection). In all cases, the liver was examined by light and polarizing microscopy, and by scanning electron microscopy with energy-dispersive x-ray microanalysis. In the two patients with silica exposure, silica-containing sclerohyaline nodules were diffusely present in portal tracts and lobules. Both chromium-cobalt alloy and silica were present in the dental technician. In contrast, in all cases of talc exposure, aggregates of talc-laden macrophages were present in portal and centrilobular areas. Three IV drug abusers and the talcum powder abuser had histologic evidence of chronic hepatitis, most probably of viral etiology. We conclude that mineral type plays an important role in the pathogenesis and fibrogenesis of hepatic lesions. Compared with silica, talc primarily elicits a macrophage response without granuloma formation or fibrosis. Hepatic silicosis is a rare complication in dental laboratory technicians, and chromium-cobalt alloy may contribute to hepatic injury and fibrosis in this setting.

Adult↗

PubMed1992

Stromal amyloid in pheochromocytomas.

Amyloid has been documented in the stroma of a number of neuroendocrine tumors. It is usually associated with elaboration of a polypeptide hormone product. Twenty-three adrenal pheochromocytomas occurring in 18 patients were graded for the extent of amyloid deposits on the hematoxylin-eosin-stained slides, confirmed to be amyloid by Congo red stain and polarization microscopy. Fourteen of 20 cases (70%) showed evidence of stromal amyloid; in two thirds of these cases, it was considered abundant. The awareness of amyloid deposits in approximately 70% of pheochromocytomas is important for surgical pathologists, as this occurrence has not been thought to be common in these tumors and might be a source of diagnostic difficulty.

Adrenal Gland Neoplasms↗

PubMed1992

Renal insufficiency secondary to 2,8-dihydroxyadenine urolithiasis.

A 48-year-old man with a history of recurrent urolithiasis and chronic renal failure underwent a nephrectomy for a renal mass. At surgery the mass proved to be a calculus impacted in a dilated calyx. Gross examination of the kidney revealed chalky white deposits in the deep medulla and papillary tips. Histologic examination revealed chronic interstitial nephritis with brown spicules within some tubular epithelial cells and larger deposits of brown crystals within tubular lumina, the interstitium of the medulla, and papillary tips. Polarization microscopy revealed individual crystals scattered throughout the renal parenchyma. Although the arrangement of the crystals was reminiscent of uric acid, and, in fact, a clinical diagnosis of gouty nephropathy was made, x-ray diffraction analysis demonstrated crystals of 2,8-dihydroxyadenine. Enzymatic studies confirmed the complete absence of adenine phosphoribosyltransferase activity in erythrocyte lysates.

Adenine↗

PubMed1993

Tracheobronchial AL amyloidosis: histologic, immunohistochemical, ultrastructural, and immunoelectron microscopic observations.

We have studied three cases of localized amyloidosis in the lower respiratory tract. Amyloid was nodularly or diffusely deposited in the lamina propria of the tracheobronchial mucosa. Its nature was confirmed by Congo red staining with green birefringence on polarized microscopy. "Tracheobronchopathia osteoplastica" also was demonstrated. Plasma cells and lymphocytes were scant in the amyloid mass. Few fibroblasts and even fewer macrophages were seen. The number of plasma cells was not increased in the bone marrow in any of our cases. Amyloid fibrils were demonstrated by electron microscopic examination. The amyloid P component was detected by immunohistochemical methods. The precursor protein of amyloidosis was shown to be amyloid L protein by the postembedding protein-A gold technique with anti-light chain antisera. The role of the plasma cells in amyloid formation, however, could not be ascertained. Based on these observations, amyloid fibril formation in tracheobronchial amyloidosis appears to be related to light chains secreted by local plasma cells, combined with amyloid P, calcium, and other factors.

Adult↗

PubMed1987

Synovial fluid lipid abnormalities in various disease states: review and classification.

Although lipids are not usually present in large quantities in normal synovial fluids or in the usual synovial fluid seen in most rheumatologic conditions, their presence in synovial fluid may have diagnostic importance. As summarized in Table 2, analysis of synovial fluids for lipid constituents is relatively simple. On standing or after centrifugation, significant amounts of lipids may layer out and be visible as a supernatant. On microscopic examination, lipid droplets are usually easily seen and should be stainable with appropriate dyes (oil red O or Sudan III or IV), or may occasionally be visualized as intracellular or extracellular inclusions by polarized microscopy. Small (0.5 to 2.0 microns) intracellular inclusions containing triglycerides may be seen in neutrophils from most synovial fluids, and are of no diagnostic importance. Cholesterol crystals may be readily recognized microscopically by their characteristic flat, plate-like appearance and notched corners Synovial fluid may also be analyzed for cholesterol and triglycerides in routine clinical laboratories, and free fatty acids and lipolytic enzymes in special lipid laboratories. The presence of massive increases in cholesterol associated with microscopically visible cholesterol crystals is usually associated with chronic RA, occasionally in the setting of super-imposed bacterial infection. The presence of gross or microscopic lipid droplets is usually associated with trauma and hemorrhagic effusions. When present in this setting, the clinician should entertain a high suspicion for a significant intraarticular injury, such as fracture, meniscal tear, or severe ligamentous injury. In addition, however, several instances of non-traumatic inflammatory effusions associated with intracellular and extracellular lipid droplets have been reported.(ABSTRACT TRUNCATED AT 250 WORDS)

Cholesterol↗

PubMed1983

Scrapie prions aggregate to form amyloid-like birefringent rods.

A large scale purification protocol employing zonal rotor centrifugation has been developed for scrapie prions. The extensively purified fractions derived using this protocol contained only one major protein, designated PrP, and rod-shaped particles. The rods measured 10 to 20 nm in diameter and 100 to 200 nm in length by negative staining; no other particles were consistently observed. SDS denaturation caused the rods to disappear, prion infectivity to diminish, and PrP to become sensitive to protease digestion. Arrays of prion rods ultrastructurally resembled purified amyloid and showed green birefringence by polarization microscopy after staining with Congo red dye. The rods appear to represent a polymeric form of the scrapie prion; each rod may contain as many as 1,000 PrP molecules. Our findings raise the possibility that the amyloid plaques observed in transmissible, degenerative neurological diseases might consist of prions.

Amyloid↗

PubMed1994

Collagen organization in an oriented fibrous capsule.

X-ray diffraction and polarized light microscopy studies were carried out on a fibrous capsule to examine the collagen organization produced in a granuloma response. The capsule had been formed around a silicone tube covered with polyester mesh following implantation in a sheep. The fibrous capsule has previously been shown to include a substantial amount of type III collagen, in addition to type I collagen. Whereas granulomas generally show little order, the sample in the present study has a high degree of orientation of the collagen fibrils along the tube direction. X-ray diffraction patterns of the capsule showed an axial D period near 65 nm, a value similar to that of other type III collagen-containing tissues. This axial period is less than the 67 nm period seen in tendon and bone, which contain only type I collagen. The decreased D period is consistent with an increase in the tilting of the collagen molecules with respect to the fibril axis.

Animals↗

PubMed1990

Trichothiodystrophy: review of sulfur-deficient brittle hair syndromes and association with the ectodermal dysplasias.

Trichothiodystrophy appears to represent a central pathologic feature of a specific hair dysplasia associated with several disorders in organs derived from ectoderm and neuroectoderm. The key finding is brittle hair with low sulfur content, but alternating dark and light bands under polarizing microscopy, trichoschisis, and absent or defective cuticle are additional important clues for the diagnosis of trichothiodystrophy. Our review of the literature revealed extensive associated findings in trichothiodystrophy. Classification of patients with trichothiodystrophy and other dysplasias is difficult because diminution of sulfur-rich protein in hair is not a sufficient marker to allow precise differentiation, although several similar ectodermal dysplasias can be excluded by demonstration of abnormal sulfur content in hair of patients with trichothiodystrophy. Patients with trichothiodystrophy should have a thorough evaluation for other associated manifestations, including investigation of photosensitivity and DNA repair defects. Detection of low-sulfur brittle hair syndrome is also important for genetic counseling because the disease appears to be inherited in an autosomal recessive pattern.

DNA Repair↗

PubMed1990

Effect of platinum(II) chemotherapeutic agents on properties of DNA liquid crystals.

We have investigated the X-ray and optical properties (CD spectra and polarization microscopy) of liquid-crystalline phases and dispersions formed on pretreatment of low molecular weight DNA with the platinum(II) coordination complexes, cis-diammine-dichloroplatinum(II) (DDP), 2,2'-bipyridinedichloroplatinum(II) (1) and 2,2'-bipyridineethylenediammineplatinum(II) (2). It is demonstrated that the platination of DNA leads to the ordering of neighbouring molecules of DNA in liquid-crystalline phases being diminished. The intense bands observed in the CD spectra of liquid-crystalline dispersions prepared from DNA pretreated with 1 or 2 can be used to determine the orientation of the latter compounds with respect to the helical axis of the DNA and to detect distortions in the secondary structure of DNA. The possible causes of the appearance of the intense bands in the CD spectra of liquid-crystalline phases and alterations in the manner of packing of the molecules of DNA within them are discussed.

Animals↗

PubMed1987

Liver histopathology in autopsied drug-addicts.

Liver specimens of 150 randomly selected autopsied drug addicts from the province of Milan (Italy) were studied using light microscopy, polarized light and immunohistochemical methods. Simple histological changes and the main diagnoses are described. The main histological diagnoses in order of frequency were: non-specific reactive hepatitis (NSRH) (52%), chronic aggressive hepatitis (CAH) (24%), acute hepatitis (AH) (12%), normal liver (6%), steatosis only (3.3%) and cirrhosis (2%). In 24 cases (16%) one or more viral antigens (HBsAg, HBcAg and Delta Ag) were detected in hepatocytes by immunohistochemical methods. Three liver specimens revealed epithelioid cell granulomas, but in no case was birefringent material identified in the liver. AH and CAH were more frequent in the group of livers with viral antigens. Our histological and immunohistochemical data confirm the current opinion that, in most cases, liver pathology in drug addicts has a viral aetiology, while no significant pathogenic role has been identified for drugs, alcohol or contaminants. Recurrent infections by one or several viruses possibly explain the relatively peculiar histological features of hepatitis in drug addicts.

Adult↗

PubMed1992

The validity of the cholesterol nucleation assay.

The validity of the cholesterol nucleation assay rests on the assumption that all cholesterol crystals are removed at the start of the assay so that de novo formation of crystals can be studied. In this paper we have tested the validity of this assumption. Cholesterol crystals were added to supersaturated model bile. Subsequently the mixtures were either filtered over a 0.22 micron filter or centrifuged at 37 degrees C for 2 h at 100,000 x g. After ultracentrifugation the isotropic interphase was collected. Using polarized light microscopy no crystals could be visualized in this fraction. However, the nucleation time of the isotropic interphase decreased from 6.8 +/- 1.1 days to 1.8 +/- 0.2 days (mean +/- S.E., P less than 0.01, n = 5) when 10-100 micrograms/ml crystals were added prior to centrifugation. Similar results were observed when instead of centrifugation the mixtures containing crystals were filtered. After filtration over a 0.22 micron filter no crystals could be detected in the filtrate. Yet the nucleation time of the filtrate decreased from 6.4 +/- 0.7 days to 3.1 +/- 0.5 days (mean +/- S.E.) when 10 micrograms/ml cholesterol crystals were added before filtration (n = 10, P less than 0.01). Since no cholesterol crystals could be detected at the start of the assay the reduction in nucleation time must have been brought about by cholesterol microcrystals that passed through the filter. Supplementation of cholesterol crystals to model bile did not accelerate the nucleation time when the samples were passed over a 0.02 micron filter, indicating that the size of the microcrystals was larger than 20 nm. The effect of addition of cholesterol crystals prior to filtration over a 0.22 micron filter was also tested in the crystal growth assay recently developed by Busch et al. ((1990) J. Lipid Res. 31, 1903-1909). Addition of crystals had only a minor effect on the assay. In conclusion, the reduced nucleation time of biles from gallstone patients is probably not only due to the presence of promoting or the absence of inhibiting proteins, but can be caused by the presence of small cholesterol crystals in these biles.

Bile↗

PubMed1994

Analysis of malaria pigment from Plasmodium falciparum.

The biochemical pathway for the production of malaria pigment (haemozoin) forms a fundamental difference between host and parasite and is likely to be an important drug target. A simple method for the isolation of malaria pigment is described. The resultant product retained the in vivo crystalline appearance of pigment as judged by polarizing microscopy. Conditions were found for the disaggregation and separation of pigment. As malaria pigment can adsorb drugs, haem, and iron, such separation techniques are useful tools for studies on the impairment of haemoglobin digestion and pigment formation by antimalarials.

Animals↗

PubMed2006

Hydroxyapatite grafting promotes new bone formation and osseointegration of smooth titanium implants.

Titanium is the ideal metal for intra-osseous dental implants. It permits the natural formation of an oxide layer on its surface and thereby it prevents the release of potentially toxic molecules. New formation of bone around implants, partially placed into the bone marrow cavity, is a gradual process that runs from the endosteum to the surface of the implant. Deposition of hydroxyapatite crystals on collagen type I fibrils is initiated by acidic proteins and leads to bone mineralization. This study analyzed the effects of hydroxyapatite upon peri-implant bone formation after insertion of smooth titanium implants. Screw-shaped smooth titanium implants of 3.75 mm thickness and 8.5 mm length were inserted into the metaphysis of rabbit tibia, either together with bovine hydroxyapatite into the right tibia or in controls without hydroxyapatite into the left tibia. Polyfluorochrome tracers (alizarin complex, calcein, tetracycline) were injected subcutaneously at different time intervals after implantation to evaluate the time frame of bone new formation over a period of 8 weeks. All samples were processed for histology and analyzed by fluorescence and polarizing microscopy. Our results showed a higher quantity of mature type I collagen fibers around implants and an acceleration of bone formation in the presence of hydroxyapatite. Mainly immature organic matrix was formed at the surface of implants in controls. The presence of hydroxyapatite seems to promote the maturation of collagen fibers surrounding the titanium implants and to support osteoconduction. Moreover, new formation of bone was faster in all samples where implants were inserted together with hydroxyapatite.

Animals↗