Lipid-rich Areas Research Articles

Decrease in pH Strongly Enhances Binding of Native, Proteolyzed, Lipolyzed, and Oxidized Low Density Lipoprotein Particles to Human Aortic Proteoglycans

Binding of low density lipoprotein (LDL) to proteoglycans and modification of LDL are key processes in atherogenesis. Recently, it has been demonstrated that during atherogenesis the extracellular pH of atherosclerotic lesions decreases. We have examined the effect of the decreased pH on the binding of LDL to human aortic proteoglycans. The binding of native, oxidized, proteolyzed (alpha-chymotrypsin-treated), or lipolyzed (sphingomyelinase- or phospholipase A(2)-treated) LDL particles to proteoglycans were measured in microtiter well assays at pH 5.5-7.5. We found that the lower the pH, the higher the amount of binding of LDL to proteoglycans. At the lowest pH tested (pH 5.5), the amounts of proteoglycan-bound native, proteolyzed, sphingomyelinase-, and phospholipase A(2)-treated LDL were 20-, 23-, 30-, and 37-fold higher, respectively, than at pH 7.5. Interestingly, although oxidized LDL failed to bind to proteoglycans at neutral pH, there was significant binding at acidic pH. Binding of native and modified LDL to proteoglycans at pH 5.5 was blocked by 1 m NaCl, indicating that at neutral pH LDL binds to proteoglycans via ionic interactions. Inhibition of this binding by acetylation and cyclohexanedione treatment of LDL showed that the positively charged amino acids of apolipoprotein B-100, lysine, and arginine, respectively, mediated the ionic interaction. Taken together, our results suggest that in areas of atherosclerotic arterial intima where the extracellular pH decreases, retention of LDL by proteoglycans is enhanced, leading to extracellular accumulation of LDL and progression of the disease.

Diagnosis of Thin-Cap Fibroatheromas by a Self-Contained Intravascular Magnetic Resonance Imaging Probe in Ex Vivo Human Aortas and In Situ Coronary Arteries

We sought to correlate findings obtained from a self-contained magnetic resonance imaging (MRI) probe with plaque morphology of ex vivo human aortas and coronary arteries. Early detection of thin-cap fibroatheromas (TCFAs) may allow for early preventive treatment of acute coronary syndromes. We developed an intravascular MRI catheter capable of imaging the arterial wall without external magnets or coils by differentiating lipid-rich and fibrotic-rich areas of the atherosclerotic plaque on the basis of differential water diffusion. Aortic samples (n = 16) and coronary arteries were obtained within 12 h of death. Coronary specimens were intermediate in angiographic severity (30% to 60% luminal narrowing, n = 18). Blinded histologic and immunohistochemical analyses of the tissues were performed and correlated to MRI findings. The 16 aortic lesions included four ulcerated plaques, two TCFAs, two thick-cap fibrous atheromas, two intimal xanthomas, and six adaptive intimal thickenings. The MRI scan correctly correlated with the histologic diagnosis in 15 (94%) of 16 lesions. The 18 coronary lesions included one plaque rupture, three TFCAs, seven thick-cap fibrous atheromas, four fibrocalcific plaques, two intimal xanthomas, and one adaptive intimal thickening. The MRI scan correlated with the histologic diagnosis in 16 of 18 lesions (sensitivity 100%, specificity 89%). The self-contained intravascular MRI catheter successfully identified TCFA and may prove to be an important diagnostic approach to determining the presence of lesions with increased risk of causing death or myocardial infarction.

Optimal management of fungal infections of the skin, hair, and nails.

Superficial fungal infections are chronic and recurring conditions. Tinea capitis is a scalp infection, primarily affecting prepubescent children. Ringworm infections, such as tinea corporis and tinea cruris, involve the glabrous skin. Tinea nigra is a rare mycotic infection that may be related to travel abroad. Piedra, black or white, is limited to the hair shaft without involvement of the adjacent skin. Pityriasis (tinea) versicolor and seborrheic dermatitis are dermatoses associated with yeasts of the genus Malassezia that affect the lipid-rich areas of the body. The taxonomy of the Malassezia yeasts has been revised to include nine species, eight of which have been recovered from humans. Tinea pedis, an infection of the feet and toes, is one of the most common forms of dermatophytosis. Onychomycosis is a fungal infection affecting the nail bed and nail plate; it may be chronic and can be difficult to treat. In instances where the superficial fungal infection is severe or chronic, an oral antifungal agent should be considered. Terbinafine, itraconazole, and fluconazole are oral antifungals that are effective in the treatment of superficial mycoses.

Adrenal adenomas: relationship between histologic lipid-rich cells and CT attenuation number

Objective: To evaluate the relationship between lipid-rich cells of the adrenal adenoma and precontrast computed tomographic (CT) attenuation numbers in three clinical groups. Materials and Methods: Thirty-five surgically resected adrenal adenomas were used. The clinical diagnoses of the patients included 13 cases of primary aldosteronism, 15 cases of Cushing's syndrome, and 7 non-functioning tumors. The number of lipid-rich clear cells was counted using a microscopic eyepiece grid that contained 100 squares. The results were expressed as the percentages of lipid-rich areas. Results: There was a strong inverse linear relationship between the percentage of lipid-rich cells and the precontrast CT attenuation number ( R 2=0.724, P<0.0001). There were significantly more lipid-rich cells in the primary aldosteronism and non-functioning tumor cases compared to cases of Cushing's syndrome ( P=0.007 and 0.015, respectively). The CT attenuation numbers of the primary aldosteronism cases were significantly lower than those of Cushing's syndrome ( P=0.0052). Furthermore, the CT attenuation numbers of the non-functioning tumor cases were lower than those of Cushing's syndrome cases. Conclusion: We showed that adrenal adenomas in primary aldosteronism and non-functioning tumors contain significantly more lipid-rich cells than those in Cushing's syndrome. They also showed significantly lower attenuation than that in Cushing's syndrome on CT scans. Our results suggest that precontrast CT attenuation numbers may be helpful in the differentiation of adenomas from non-adenomatous lesions, which include malignancies.

Impact of anatomical location on barrier recovery, surface pH and stratum corneum hydration after acute barrier disruption.

It is not known whether distinct anatomical locations will respond with different recovery rates following acute barrier challenges. To investigate whether barrier parameters differ at five body sites during recovery from acute disruption. Acute barrier disruption was achieved by tape stripping and by acetone extraction of stratum corneum lipids. Transepidermal water loss (to assess barrier function), capacitance (for stratum corneum hydration) and skin surface pH were measured at each of five different body sites in 14 human volunteers. Individual measurements were obtained every 24 h for 96 h. Lipid-rich skin areas (e.g. the forehead) were the most vulnerable to barrier disruption by either method. While acetone treatment affected barrier function and decreased stratum corneum hydration, tape stripping similarly altered barrier function but increased capacitance values. Although the effect of barrier disruption on surface pH appeared to vary with location, no significant pattern of variation emerged. Independent of the method used for barrier disruption, the pH normalized within 96 h. Skin at different body sites shows distinct patterns of barrier recovery that are likely to be related to structural and physiological differences. Therefore, 'anatomically specific' regimens appear possible and relevant for the treatment of cutaneous disorders. In addition, adequate statistical analyses are essential to detect real differences in barrier recovery parameters.

PH Heterogeneity of human and rabbit atherosclerotic plaques; a new insight into detection of vulnerable plaque

Background: Atherosclerotic plaques are heterogeneous with respect to inflammation, calcification, vascularity, oxygen, and temperature. We hypothesized that they also vary in pH and measured pH in living human carotid endarterectomized atherosclerotic plaques (CEA), Watanabe heritable hyperlipidemic (WHHL) rabbit aortas and human umbilical arteries (HUA). Methods and results: We measured pH of CEA of 48 patients, nine WHHL rabbit aortas and 11 HUA specimens (as controls) using a glass type microelectrode mounted on a micromanipulator in a 37 °C incubator. We also used single emission and also dual emission fluorescence ratio imaging microscopy employing pH-sensitive probes to confirm pH heterogeneity. Mean pH measured at 415 points of CEA was 7.55±0.32; at 275 points of WHHL rabbit aortas it was 7.40±0.43; and in 233 points of HUA it was 7.24±0.1. In CEA, pH of yellow (lipid-rich) areas was significantly lower than pH in calcified areas (7.15±0.01 vs. 7.73±0.01, P<0.0001). The coefficients of variation (heterogeneity) of pH in CEA, WHHL rabbit aortas, and HUA were 0.038±0.010, 0.039±0.007, and 0.009±0.003, respectively ( P=0.0001). Fluorescence microscopic imaging confirmed pH heterogeneity in both humans and rabbits but not in HUA. In a variance components analysis 82% of the heterogeneity was due to the within-plaque variation and 2% was attributable to between-plaque variation. Conclusions: Our findings support the hypothesis of pH heterogeneity in plaques, and suggest a possible role for detecting low pH in the detection of plaque vulnerability. The source of pH heterogeneity particularly acidic pH, its impact on the stability of plaques and its potential clinical utility in locating vulnerable plaques remain to be evaluated.

In vivo laser-induced fluorescence detection of pyrene in nematodes and determination of pyrene binding constants for humic substances by fluorescence quenching and bioconcentration experiments.

The bioconcentration of pyrene by bacterivorous thread worms (nematodes) of the species Caenorhabditis elegans was studied with laser-induced fluorescence (LIF) spectroscopy, fluorescence imaging and a radiotracer method. The vibronic band intensities of the LIF spectra indicated that the microenvironment of pyrene in the nematodes was similar to a low-polarity solvent, and thus provided direct evidence that pyrene was accumulated in lipid-rich areas inside the nematodes. The concentration of pyrene in the nematodes was estimated from the monomer/excimer fluorescence intensity ratio. Results from this method were in fair agreement with results using 14C labeled pyrene for measuring pyrene bioconcentration. Preliminary results indicated that LIF measurements of pyrene may be possible even in single nematodes. Fluorescence microscopic observations revealed that pyrene was not adsorbed on the outside of the organisms, but was strongly concentrated in restricted areas inside the worms. In the second part of the study, the effects of six different humic substances (HS) on the bioconcentration of pyrene were investigated and sorption coefficients (KDOC) calculated from reductions in bioconcentration (KDOC(biol)) were compared with sorption coefficients measured with a fluorescence quenching technique (KDOC(flu)). The results of these two different experimental methods agreed well (with KDOC(biol) being slightly lower than KDOC(flu), indicating that the fraction of pyrene that was determined as freely dissolved by the fluorescence quenching method was comparable to the bioavailable fraction.

Radiolabeled MDA2, an oxidation-specific, monoclonal antibody, identifies native atherosclerotic lesions in vivo

Background. Oxidatively modified low-density lipoprotein (LDL) is present in atherosclerotic but not normal arteries and plays a crucial role in the pathogenesis and adverse consequences of atherosclerotic lesions. We previously generated a series of monoclonal antibodies (MoAb) against oxidation-specific neo-epitopes formed during the oxidative modification of LDL. MDA2, a prototype MoAb, recognizes malondialdehyde-lysine epitopes (eg, in malondialdehyde-modified LDL) within atherosclerotic lesions. We describe the in vivo characteristics of MDA2 and initial noninvasive imaging studies of atherosclerosis in rabbits. Methods. To assess the in vivo specificity of MDA2 for atherosclerotic lesions, iodine 125-MDA2 was intravenously injected into 7 LDL-receptor deficient Watanabe heritable hyperlipidemic (WHHL) and 2 normal New Zealand white (NZW) rabbits, and the aortic plaque uptake was evaluated 24 hours later. 125I-Halb, an isotype-matched irrelevant MoAb that binds to human albumin, was injected into 5 WHHL and 2 NZW rabbits as a control. Aortic autoradiography was performed, and the mean uptake of MoAbs was measured as the percent injected dose per gram aortic tissue. Gamma camera imaging was then carried out in 7 WHHL rabbits and 2 NZW rabbits with 99mTc-MDA2. Imaging was carried out at 10 minutes and at 12 or 24 hours. Malondialdehyde-LDL was then injected to clear the blood pool signal, and final images were obtained 2 hours later. Results. Mean uptake of 125I-MDA2 in the entire aorta was 17.4-fold higher in WHHL than in NZW aortas ( P < .001), and 2.8-fold higher than 125I-Halb in WHHL aortas. 125I-MDA2 also had higher specificity for lesioned areas than 125I-Halb (plaque/normal ratio 6.3 vs 2.9, P < .001). Autoradiograph of aortas of 125I-MDA2-injected WHHL rabbits revealed uptake in lipid-stained lesions with absence of signal in adjacent normal arterial tissue. Immunostaining of WHHL lesions, which accumulated MDA2 as noted on autoradiography, revealed that uptake was highest in areas with abundant foam cells and in lipid-rich necrotic core areas. Autoradiograph of aortas from NZW rabbits injected with 125I-MDA2 did not yield any visible signal. Planar gamma camera in vivo scintigraphy revealed a visible signal in 4 7 WHHL rabbits, which was confirmed by aortic Sudan staining. Conclusion. Radiolabeled MDA2 shows excellent in vivo uptake and specificity for atherosclerotic lesions containing abundant oxidation-specific epitopes. The in vivo imaging studies suggest that noninvasive imaging of oxidation-rich atherosclerotic lesions with radiolabeled MDA2 may be feasible in human beings with optimization of the imaging methods.

Immunohistochemical localization of different epitopes of advanced glycation end products in human atherosclerotic lesions

To better understand the role of advanced glycation end products (AGEs) in atherogenesis, we developed specific antibodies against different immunological epitopes of AGE structures, including N ε -(carboxymethyl)lysine-protein adduct (CML) and a structure(s) other than CML (nonCML), and demonstrated the immunohistochemical localization of CML- and nonCML-epitopes in atherosclerotic lesions of human aorta, which were obtained at autopsy from 20 nondiabetic patients (12 males and eight females; mean age, 60.8±16.7 years). Monoclonal anti-CML antibody (6D12) recognized not only AGE-modified proteins, but also CML-modified proteins. On the other hand, polyclonal anti-nonCML antibody reacted to AGE-modified proteins, but not to CML-modified proteins. Both antibodies were unreactive to the early-stage products of glycation, including fructose-modified butyloxycarbonyl-lysine and fructose- ε-aminocaproic acid. Atherosclerotic lesions included diffuse intimal thickening (DIT), fatty streaks (FS), atherosclerotic plaques (AP) and complicated lesions. An immunohistochemical analysis showed both CML- and nonCML-epitopes to be found along the collagen fibers in DIT in subjects more than 40 years old, but not in subjects less than 40 years old. CML-epitopes accumulated mainly in the cytoplasm of macrophage/foam cells, while nonCML-epitopes accumulated exclusively in the extracellular spaces in FS. APs showed the CML-epitope stored macrophage/foam cells, and the accumulation of both CML- and nonCML-epitopes in the lipid-rich fibrous area. An immunohistochemical analysis with a monoclonal antibody against oxidized low density lipoprotein (FOH1a/DLH3) showed the presence of this antigen within the cytoplasm of the macrophage/foam cells in atherosclerotic lesions, which were also positive for the CML-epitopes. These findings thus suggest that the heterogeneous localization of AGEs in atherosclerotic lesions depends on their different epitopes, and that a close link, therefore, exists between the peroxidation of LDL and the formation of AGEs in atherosclerotic lesions.

Subendothelial smooth muscle cells of human aorta express macrophage antigen in situ and in vitro

Cells bearing a smooth muscle cell marker— α-actin and a macrophage marker—CD68 antigen were immunocytochemically identified on `en face' preparations of human aortic intima. Cells, expressing smooth muscle α-actin, macrophage CD68 antigen and both markers, i.e. smooth muscle cells possessing the macrophage antigen, were identified both in grossly normal aortic areas and in atherosclerotic lesions (fatty streaks and atherosclerotic plaques). CD68-positive smooth muscle cells were most common in the lipid-rich areas: fatty streaks and atherosclerotic plaque shoulders. Cells expressing smooth muscle α-actin and CD68 were also revealed in primary cultures prepared from grossly normal and atherosclerotic intima. Cells expressing both antigens were found in all examined cultures. The proportion of these cells in cultures from grossly normal areas and atherosclerotic plaques was similar: 14.5±4.1 and 14.6±4.8%, respectively. Cultures from fatty streaks had a higher content of cells expressing both antigens: 25.1±7.0%. Modified low density lipoprotein-induced intracellular lipid accumulation in cells cultured from grossly normal intima led to a three-fold increase in the number of cells sharing α-actin and CD68 antigen. Accumulation of latex beads by phagocytosis had a similar effect. It was suggested that in atherosclerotic lesions intracellular lipid accumulation and other stimulators of phagocytosis may provoke the expression of macrophage-associated antigen CD68 in settled cells of the subendothelial intima of human aorta.

High expression of genes for calcification-regulating proteins in human atherosclerotic plaques.

Calcification is common in atheromatous plaques and may contribute to plaque rupture and subsequent thrombosis. However, little is known about the mechanisms which regulate the calcification process. Using in situ hybridization and immunohistochemistry we show that two bone-associated proteins, osteopontin (OP) and matrix Gla protein (MGP), are highly expressed in human atheromatous plaques. High levels of OP mRNA and protein were found in association with necrotic lipid cores and areas of calcification. The predominant cell type in these areas was the macrophage-derived foam cell, although some smooth muscle cells could also be identified. MGP was expressed uniformly by smooth muscle cells in the normal media and at high levels in parts of the atheromatous intima. Highest levels of this matrix-associated protein were found in lipid-rich areas of the plaque. The pattern of expression of these two genes contrasted markedly with that of calponin and SM22 alpha, genes expressed predominantly by differentiated smooth muscle cells and whose expression was generally confined to the media of the vessel. The postulated function of OP and MGP as regulators of calcification in bone and the high levels and colocalization of both in atheromatous plaques suggest they have an important role in plaque pathogenesis and stability.

Central nervous system distribution of inhaled toluene

The regional central nervous system distribution of inhaled [ 14C]toluene was studied in the rat. Toluene was detected in all brain regions, with the highest concentrations in the brainstem. The initial uptake of toluene was significantly correlated with the total lipid content of each brain region. Clinical and experimental neurotoxicity of toluene may be due, in part, to an increased concentration of this solvent in lipid-rich brain areas.

Central Nervous System Distribution of Inhaled Toluene

Central Nervous System Distribution of Inhaled Toluene. GOSPE, S. M., JR., AND CALABAN, M. J. Fundam. Appl. Toxicol 11, 540–545. The regional central nervous system distribution of inhaled [ 14 C]toluene was studied in the rat. Toluene was detected in all brain regions, with the highest concentrations in the brainstem. The initial uptake of toluene was significantly correlated with the total lipid content of each brain region. Clinical and experimental neurotoxicity of toluene may be due, in part, to an increased concentration of this solvent in lipidrich brain areas.

The distribution of lipid in the tissues of Antarctic krill, Euphausia superba

1.1. The distribution of lipid in the tissues of Euphausia superba has been examined by histological and chemical methods.2.2. The total lipid content of krill from different catches may vary considerably, and the variations are probably due both to differences in nutritional status and maturity of the roe of female krill.3.3. Female krill contained about twice as much lipid as male krill from the same haul.4.4. The roe is the dominating lipid depot in female krill; in both male and female krill lipid-rich areas are found along the digestive tract, between muscle bundles and beneath the exoskeleton.5.5. Both the phosphoglyceride- and triacylglycerol content of body fractions of E. superba varied in proportion to the total lipid content, thus supporting the contention that both phosphoglycerides and triacylglycerols serve as depot lipids in this species of krill.

Role of isovaleroyl lipids in channeling of sound in the porpoise melon

Physical properties (e.g. specific gravity, adiabatic compressibility and sound velocity) of lipids isolated from tissues from contiguous areas of the fatty melon of an echo-locating porpoise ( Delphinus delphis) were determined to elucidate relations between lipid composition and structure, and sound transmission in the head. Lipid content varied greatly within the melon (13.6–77.6% of the tissue weight) and triacylglycerols (80–100%) were the major lipid components. This lipid class was composed of diisovaleroylglycerides (triacylglycerols containing two isovaleroyl moieties and a long-chain acyl moiety), monoisovaleroyldiacylglycerols and triacylglycerols consisting of long-chain acids. The lipid-rich (>45%) areas in the melon contained a high proportion (>45% of total triacylglycerols) of diisovaleroylglycerides. There were gradations of sound velocities within the melon; the lowest sound velocities were associated with high concentrations of diisovaleroylglycerides (<1400 m/s) and the highest with high concentrations of long-chain triacylglycerols. Assuming an average sound frequency of 75 kHz, and considering dimensions of melon (path length and width of 12–14 cm and 5 cm, respectively), a forward radiating lobe of 15–25 degrees is produced. Thus, the deposition of lipids of different acoustic properties in a three-dimensional matrix within the porpoise melon results in a lens for the projection of sound into the marine environment.

Experimental Infections with Group A Streptococci in Humans

Experimental inoculation of 7 strains of Group A streptococci failed to result in either colonization or infection of normal intact skin of human volunteers. All strains rapidly died on normal skin; suppression of the resident microflora did not affect survival and no difference in survival was seen between inoculation on lipid-rich and lipid-poor body areas. Inoculation on skin damaged by superficial scarification resulted in localized infections when 1 x 10(4) or more organisms were inoculated into the wound by rubbing and covered with an impermeable plastic film. Intradermal inoculation resulted in localized cellulitis, regional lymphadenopathy, and fever. All strains were equally effective in producing localized infections in scarified skin.