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H F Hoff

Publications and source records attributed to H F Hoff.

At least 73 records · Page 4Linked to original sources
PubMed1980

A technique for localizing LDL by immunofluorescence in formalin-fixed and paraffin-embedded atherosclerotic lesions.

A protocol has been developed by which apo beta, the protein component of plasma low density lipoproteins (LDL), can be localized in four micron-thick sections of formalin-fixed and paraffin-embedded arteries with atherosclerotic involvement from man or non-human primate. An immunofluorescence procedure was employed that utilized affinity column-purified antibody coupled to fluorescein isothiocyanate (FITC). Although fixation reduced the intensity of fluorescence relative to that in cryostat sections, sufficient sensitivity was usually achieved when microscopy was performed using incident-light fluorescence together with a filter system adjusted for maximum absorption of FITC and by using oil immersion objectives. Furthermore, the use of various counterstains altered the color of the autofluorescence, normally strongly yellow, thus greatly enhancing the contrast and visualization of the apple green specific fluorescence. Non-chelated eriochrome black reduced tissue autofluorescence to barely visible levels, a feature useful in black and white photographs to demonstrate the localization pattern of LDL in arteries. This stain also reduced non-specific fluorescence. Other counterstains that proved useful were emthyl green, flazo orange and chelated eriochrome black. The latter two were particularly valuable for cellular detection. At low magnification LDL localization in atherosclerotic lesions from both human aortas and coronary arteries from monkeys fed an atherogenic diet, gave a pattern similar to those reported in cryostat sections of human lesions. At higher magnification, the improved detail of LDL localization could presumably be discerned as a result of immobilization of the soluble antigen by fixation, and by the ability to cut thinner sections of embedded material. This immunofluorescence procedure to localize LDL in formalin-fixed and paraffin-embedded atherosclerotic lesions should prove useful in both prospective as well as retrospective studies on clinical or chemical-pathological correlative studies on human tissues or in studies on atherogenesis using animal models.

Arteriosclerosis↗
PubMed1979

Characterization of low density lipoprotein-like particle in the human aorta from grossly normal and atherosclerotic regions.

Physical and chemical criteria of lipoproteins containing apolipoprotein B, extracted from human aortic intima, were compared with those of plasma low density lipoproteins (LDL). Homogenates of grossly normal intima and advanced atherosclerotic lesions were subjected to differential ultracentrifugation to isolate a d = 1.006--1.063 g/ml density fraction which was extensively characterized. By electroimmunoassay, over 90% of the recovered apolipoprotein B immunological reactivity was found in isolates from both plaques and normal intima. In isolates of plaque and normal intima, particles of the same size as LDL were found, although a small population of very large structures was also present in plaque fractions. Apolipoprotein composition was similar to that of plasma LDL except for the presence of human serum albumin in aortic isolates. Fractions from aorta demonstrated greater electrophoretic mobilities than LDL. The lipid composition of isolates from normal intima was similar to that of LDL. The lipid composition of plaque fractions showed a significant decrease in the cholesteryl ester to free cholesterol ratio and in the triglyceride content in comparison to LDL and to fractions from normal intima. The fatty acid pattern of the cholesteryl ester fraction from isolates of both normal and plaque aortic homogenates demonstrated a significant decrease in the linoleate to oleate ratio as compared to LDL. Our initial studies suggest that althought aortic fractions are similar to LDL by certain criteria, some differences observed are more pronounced in fractions from lesions than from normal intima.

Adult↗
PubMed1979

Correlation in the human aorta of APO B fractions with tissue cholesterol and collagen content.

The amounts of buffer- and Triton-extracted apo B (LDL-protein), as well as the sum of these two fractions, were correlated with the total tissue cholesterol and hydroxyproline content (as a measure of collagen) in grossly normal intima, fatty streaks, and fibrous plaques of human aortas obtained at autopsy. Quantitative values of buffer- and Triton-extracted apo B were obtained by sequentially extracting homogenates of aortic intima with an aqueous buffer and one containing Triton X-100, and measuring the apo B content in each extract by an electroimmunoassay relative to plasma LDL or Triton-treated LDL. Significant positive correlations were obtained between the following: tissue cholesterol and both buffer-extracted and total-extracted apo B in grossly normal intima; tissue cholesterol and Triton-extracted apo B in microdissected fibrotic caps and cores of fibrous plaques, as well as in whole plaques. A positive correlation was also obtained between tissue cholesterol and total-extracted apo B in the necrotic core. A significant negative correlation was found between Triton-extracted apo B and collagen in whole plaques. The calculated mean percent of total tissue cholesterol in the different aortic regions that could be present as part of an intact LDL particle were: 100% in grossly normal intima, 16% in fatty streaks, and 11% in fibrous plaques. The positive correlation between Triton-extracted apo B and cholesterol in plaques suggests one or both of the following: the extracellular pool of cholesterol or some material increasing concurrently with cholesterol interacts with apo B or another part of the LDL particle; or the apo B containing lipoprotein is trapped in the hydrophobic environment of extracellular lipid. Both possibilities would render the particle less soluble in aqueous buffers. The negative correlation between Triton-extracted apo B and tissue collagen and the lack of a significant correlation between buffer-extracted apo B and collagen content suggests that collagen is probably not responsible for apo B retention in the aortic intima.

Adult↗
PubMed1977

Quantification of apolipoprotein B in grossly normal human aorta.

A quantitiative electroimmunodiffusion (EID) assay was developed for apolipoprotein B (apoB), the major apoprotein of human plasma low density lipoproteins (LDL) and very low density lipoproteins (VLDL). Specificity, sensitivity (30-200 ng) and reproducibility (11%) were established. We used this system to determine the amount of buffer-soluble apoB in supernatant fractions from homogenates of the intima from grossly normal human aortas. Assays of whole tissue minces yielded only one-third of the apoB in supernatant fractions. Intimal homogenates contained 0.34-18.45 mug of apoB/mg of tissue, dry weight (mean 5.42 +/- 3.95 SD). We also found that no apoB was detected in the homogenates of adjacent tunica media. Furthermore, most of the intimal apoB was found in the LDL density (d) fraction (d 1.006-1.063) after differential ultracentrifugation, while the VLDL (d less than 1.006) fraction contained only negligible amounts of apoB. By electron microscopy, it was determined that the LDL density fraction contained particles 200-250 A in diameter which were similar in size to plasma LDL. These results suggest that grossly normal aortas contain significant quantities of intact LDL.

Adolescent↗
PubMed1977

Apolipoprotein B retention in the grossly normal and atherosclerotic human aorta.

Apoliporotein B (apoB) was measured in buffer-extracted homogenates of grossly normal and artherosclerotic human aortic intima by means of an electroimmunoassay procedure. The apoB values which were expressed as microgram per mg tissue dry weight, varied widely, ranging from 0.34 to 18.45 in normal intima and from 0.8 to 12.5 in fatty fibrous plaques. No consistent differences in apoB content were found between normal intimas from thoracic and abdominal aortic regions. There was a statistically significant positive correlation between the quantity of buffer-extractable apoB in normal regions and the plasma cholesterol and triglyceride concentration. Buffer-extractable apoB values were significantly higher in fatty fibrous plaques than in ulcerated lesions from the same vessel. However, fatty fibrous plaque apoB values were significantly lower than those from grossly normal regions from the same aorta, although the topographical distribution of apoB was more widespread in plaques than in normal regions, as shown by immunofluorescence studies. This apparent discrepancy reflected the incomplete extraction of apoB from plaques as contrasted to normal regions. The relatively loosely bound apoB, extractable by standard buffers, may represent intact low density lipoprotein (LDL) and/or very low density lipoprotein (VLDL), while the tightly bound fraction may represent insoluble complexes of intact lipoproteins within the plaque or delipidated apoB.

Aorta↗
PubMed1976

Apo-lipoprotein localization in human atherosclerotic arteries.

A study documenting the localization in human arteries of apoproteins from human plasma high density (HDL, low density (LDL), and very low density (VLDL) lipoproteins was undertaken in light of their possible roles in the pathogenesis and regression of the atherosclerotic process in man. Apo A-I from HDL, apo B from LDL, apo C-III from VLDL were all localized by immunohistochemical techniques to generally the same areas of athersclerotic lesions. These consisted of certain bands of collagen and elastic fibers in fatty streaks and fibrous plaques, and extracellular pools of neutral lipid in fibrous plaques. Apoproteins were also occasionally present in areas of diffuse intimal thickening in coronary arteries. Extensiveness and frequency of appearance of apo B in atherosclerotic lesions was greatest in type II hyperlipoproteinemics, thus correlating with the plasma apo B levels. Employing an immuno-peroxidase procedure, apo B was localized ultrastructurally in atherosclerotic lesions to the outer surface of spheres ranging in diameter between 250 and 700 A. These spheres, localized predominantly in lipid cores and between collagen bands, were also seen in negatively-stained preparations of arterial extracts which also reacted positively against anti-apo B, SUGGESTING THAT THE SPHERES MAY REPRESENT NATIVE LDL and VLDL. The superimposed localization of apo A-I, apo B, and apo C-III in atherosclerotic lesions suggests that a specific interaction exists between certain lesion components and these apoproteins.

Apoproteins↗
PubMed1975

Ultrastructural localization of plasma lipoproteins in human intracranial arteries.

The fine-structural localization of apoB, the major protein constituent of both the low and very low density plasma lipoprotein fractions, was described in human middle cerebral and basilar arteries. Using an immunoperoxidase technique together with electron microscopy, apoB was localized only in arteries with atherosclerotic involvement and to the following regions in these arteries: 1. on the outer aspects of extracellular spherical structures with diameters of 250 to 700 A found predominantly in lipid cores and between bands of collagen fibers of advanced atherosclerotic lesions; 2. on the surface of reduplicated elastica; 3. along collagen fibers and; 4. on aggregates of extracellular spherical lipid globules. These results suggest that the extracellular spheres may represent the fine-structural morphology of deposited low and very low density lipoproteins and that free apoB may be bound to lipid globules, elastica, and collagen fibers.

Apoproteins↗
PubMed1975

APO low density lipoprotein localization. Intracranial and extracranial atherosclerotic lesions from human normolipoproteinemics and hyperlipoproteinemics.

APO low density lipoprotein (apoB), the major protein in plasma low (LDL) and very low (VLDL) density lipoproteins, was localized in extracranial and intracranial arteries from normolipoproteinemics and hyperlipoproteinemics to determine if apoB extensiveness and localization varied with plasma lipoprotein profile. Specimens of carotid bifureation, internal carotid, basilar, and middle cerebral arteries from 23 subjects with normal lipoprotein levels, four with elevated LDL (type II), and 13 with elevated VLDL (type IV) values were studied with the employment of immunofluorescence techniques. Although the apoB localization pattern was identical in each group, extensiveness of positive localization was greatest in lesions from type II cases and the same in lesions from type IV and normolipoproteinemics. This suggests that sites of apoB retention are dependent on the chemical and structural changes in atherosclerotic arteries, whereas extensiveness correlates with the apoB concentration gradient between plasma and tissue.

Adult↗