Reinvestigation of peroxisomal 3-ketoacyl-CoA thiolase deficiency: identification of the true defect at the level of d-bifunctional protein

In this report, we reinvestigate the only patient ever reported with a deficiency of peroxisomal 3-ketoacyl-CoA thiolase (THIO). At the time when they were described, the abnormalities in this patient, which included accumulation of very-long-chain fatty acids and the bile-acid intermediate trihydroxycholestanoic acid, were believed to be the logical consequence of a deficiency of the peroxisomal beta-oxidation enzyme THIO. In light of the current knowledge of the peroxisomal beta-oxidation system, however, the reported biochemical aberrations can no longer be explained by a deficiency of this thiolase. In this study, we show that the true defect in this patient is at the level of d-bifunctional protein (DBP). Immunoblot analysis revealed the absence of DBP in postmortem brain of the patient, whereas THIO was normally present. In addition, we found that the patient had a homozygous deletion of part of exon 3 and intron 3 of the DBP gene, resulting in skipping of exon 3 at the cDNA level. Our findings imply that the group of single-peroxisomal beta-oxidation-enzyme deficiencies is limited to straight-chain acyl-CoA oxidase, DBP, and alpha-methylacyl-CoA racemase deficiency and that there is no longer evidence for the existence of THIO deficiency as a distinct clinical entity.

The cytopathology of metal overload

Researchers have been able to demonstrate the cytotoxicity of copper overload in animal models. This has allowed them to not only localize the intracellular distribution of copper but also to study directly the subsequent organelle injury at the ultrastructural level. The lesions seen in copper overload appear to vary from species to species. In humans, marked mitochondrial abnormalities are seen in Wilson's disease while diet overloaded rats show nuclear destruction and various membranous abnormalities. Sequestration of copper within lysosomes appears to protect hepatocytes from its toxicity. However, the mechanism by which the metal is incorporated into lysosomes is not known.

Cerebrohepatorenal syndrome of Zellweger: a peroxisomal deficiency disorder. Case report and review

The cerebrohepatorenal syndrome of Zellweger (CHRS) is a rare, fatal disorder in newborn infants. Recent research points to a primary absence of tissue peroxisomes, with resulting biochemical defects, as the basic pathology of the condition. We report on an infant with classic neurological and dysmorphic features of CHRS. Increased serum levels of pipecolic acid, bile acid precursors and very-long-chain fatty acids (VLCFA) together with total histological absence of liver peroxisomes confirmed the diagnosis. To our knowledge, this is the first case in Israel to be fully documented by biochemical and ultrastructural techniques. A high index of suspicion is essential among clinicians if further cases are not to be overlooked.

Human peroxisomal 3-oxoacyl-coenzyme A thiolase deficiency

We investigated the peroxisomal beta-oxidation system in liver from a patient with clinical features similar to those in the cerebrohepatorenal (Zellweger) syndrome and with elevated levels in body fluids of very-long-chain fatty acids and intermediates in the biosynthesis of bile acids. The peroxisomal beta-oxidation of fatty acids, measured as the cyanide-insensitive formation of [14C]acetyl units from [14C]palmitoyl-CoA, was very low in the patient (less than 10% of the values in control subjects). Immunoblotting experiments using antibodies to peroxisomal beta-oxidation enzymes indicated that peroxisomal 3-oxoacyl-CoA thiolase (acyl-CoA:acetyl-CoA C-acyltransferase, EC 2.3.1.16) was deficient. Addition of purified rat-liver peroxisomal 3-oxoacyl-CoA thiolase to a reaction mixture containing liver homogenate from the patient restored peroxisomal beta-oxidation. We conclude that the deficiency of peroxisomal 3-oxoacyl-CoA thiolase is responsible for the very low peroxisomal beta-oxidation activity and for the accumulation of very-long-chain fatty acids and intermediates in the biosynthesis of bile acids. Furthermore, the finding that both very-long-chain fatty acids and abnormal bile acids accumulate in this patient suggests that a single peroxisomal 3-oxoacyl-CoA thiolase is involved in the oxidative chain shortening of both very-long-chain fatty acids and the coprostanoic acids.

Pseudo-Zellweger syndrome: deficiencies in several peroxisomal oxidative activities

We describe an infant girl with a clinical, chemical, and pathologic syndrome remarkably similar to Zellweger cerebrohepatorenal syndrome but whose liver parenchymal cells contained abundant peroxisomes. Peroxisomal L-alpha hydroxy acid oxidase, catalase, and the plasmalogen synthesizing enzyme dihydroxy acetone phosphate-acyl transferase activities were normal; other peroxisomal enzymatic activities, including fatty acyl-CoA oxidase and D-amino acid oxidase, were reduced by 80% to 85%. Oxidation of bile acids and pipecolic acid was also deficient. Autopsy revealed the presence of neuronal heterotopia, renal cortical cysts, adrenal atrophy, and accumulation of very long chain fatty acids. The clinical and pathologic features of this case of "pseudo-Zellweger syndrome" reflect a deficiency in multiple peroxisomal activities rather than a defect in peroxisomal biogenesis. The deficient enzymatic activities require flavin adenine dinucleotide, and the underlying defect may be in the utilization of this cofactor.

Extracellular matrix microfibrils are composed of core proteins coated with fibronectin

Extracellular proteins of cultured calf aortic smooth muscle cells consist predominantly of microfibrils 10-20 nm in diameter typical of "elastin-associated" microfibrils described in many tissues. Chemical and immunochemical evidence is presented that microfibrils consist of at least two proteins: core protein and fibronectin. Insoluble proteins of the microfibrils were obtained in the form of a pellet and antibodies raised in rabbits against these components. The antisera reacted with the insoluble microfibrillar proteins and with soluble fibronectin in enzyme-linked immunosorbent assay, and immunostained the extracellular microfibrils in cultured cells. An immunoglobulin (Ig) fraction was prepared and absorbed with fibronectin. The absorbed IgG retained its reactivity with the microfibrillar proteins but was no longer reactive with soluble fibronectin. Immunofluorescence studies were carried out using the absorbed IgG and IgG to soluble fibronectin. Both antibodies showed immunoreactive microfibrils in the extracellular matrix of cells in log phase. However, with increasing time in culture, as the cells reached confluence, the immunofluorescence of microfibrils reacting with the absorbed IgG became less intense, whereas that of microfibrils reacting with IgG to fibronectin increased; in confluent cells, essentially no staining was detected with the absorbed IgG, and a dense network of intensely stained microfibrils was seen with IgG to fibronectin. Treatment of these cultures with urea led to partial dissociation of the fibronectin and increased visualization of the microfibrils with the absorbed IgG; double-label immunofluorescence showed that both proteins occurred on the same microfibrils. The localization of immunoreactive sites to the extracellular microfibrils was confirmed by immunoelectron microscopy. Nearly quantitative cleavage with CNBr failed to dissociate the antigenically active fragments of fibronectin from the CNBr fragments of the core proteins of the microfibrils. It was concluded that microfibrils contain core proteins and fibronectin that are codistributed in insoluble, possibly covalently cross-linked, aggregates. The core proteins are first deposited by the cell and, as a function of time in culture, fibronectin gradually coats their surface.

Peroxisomal defects in neonatal-onset and X-linked adrenoleukodystrophies

Accumulation of very long chain fatty acids in X-linked and neonatal forms of adrenoleukodystrophy (ALD) appears to be a consequence of deficient peroxisomal oxidation of very long chain fatty acids. Peroxisomes were readily identified in liver biopsies taken from a patient having the X-linked disorder. However, in liver biopsies from a patient having neonatal-onset ALD, hepatocellular peroxisomes were greatly reduced in size and number, and sedimentable catalase was markedly diminished. The presence of increased concentrations of serum pipecolic acid and the bile acid intermediate, trihydroxycoprostanic acid, in the neonatal ALD patient are associated with a generalized diminution of peroxisomal activities that was not observed in the patient with X-linked ALD.

Microfibrils, elastic anchoring components of the extracellular matrix, are associated with fibronectin in the zonule of Zinn and aorta

Microfibrils are striated tubules that play a role in the formation of elastin fibers by providing a scaffold upon which newly synthesized elastin is deposited. Ultrastructural and staining studies also demonstrate microfibrils that terminate where elastin is sparse or absent in basal laminae, plasma membranes, and the collagenous matrix. The most striking accumulation of microfibrils is found in the zonule of Zinn, the transparent and elastic suspensory ligament of the lens, which contains no elastin. Application of immunocytochemical staining with a peroxidase-antiperoxidase (PAP) procedure demonstrates that fibronectin is associated with the microfibrils of the zonule and aorta. Aggregates of microfibrils are identical to oxytalan ('acid enduring') fibers that have been described in peridontal membranes and other sites subject to mechanical stress and they can be found in sites as disparate as the rabbit zonule, rat hepatic stroma and human cardiac papillary muscle, indicating that microfibrils are a widely distributed connective tissue element with a function that extends beyond elastogenesis; their association with fibronectin and localization suggests that they serve as an elastic anchoring component of the extracellular matrix.

Lignoceric acid is oxidized in the peroxisome: implications for the Zellweger cerebro-hepato-renal syndrome and adrenoleukodystrophy

The deficient oxidation and accumulation of very-long-chain fatty acids in the Zellweger cerebro-hepato-renal syndrome (CHRS) and X chromosome-linked adrenoleukodystrophy (ALD), coupled with the observation that peroxisomes are lacking in CHRS, prompted us to investigate the subcellular localization of the catabolism of lignoceric acid (C24:0). Peroxisomal and mitochondrial-rich fractions were separated from rat liver crude mitochondria by sucrose density gradient centrifugation. Enzyme activity for the oxidation of [1-14C]palmitic acid to water-soluble acetate was 2- to 3-fold higher in the mitochondrial than in the peroxisomal-rich fraction whereas [1-14C]lignoceric acid was oxidized at a 2- to 3-fold higher rate in the peroxisomal than in the mitochondrial fraction. Moreover, unlike palmitic acid oxidation, lignoceric acid oxidation was not inhibited by potassium cyanide in either rat liver fractions or human skin cultured fibroblasts, showing that lignoceric acid is mainly and possibly exclusively oxidized in peroxisomes. We also conducted studies to clarify the striking phenotypic differences between CHRS and the childhood form of ALD. In contrast to CHRS, we found normal hepatocellular peroxisomes in the liver biopsy of a childhood ALD patient. In addition, in the presence of potassium cyanide, the oxidation of palmitic acid in cultured skin fibroblasts was inhibited by 62% in control and X chromosome-linked ALD patients compared with 88% in CHRS and neonatal ALD. This differential effect may be related to differences in peroxisomal morphology in those disorders.

Hypophosphatasia: clinicopathologic comparison of the infantile, childhood, and adult forms

Histochemical and direct enzyme analysis of osseous tissue from 23 patients with hypophosphatasia revealed that all clinical forms of this inherited metabolic bone disease are characterized by deficiency of alkaline phosphatase (ALP) activity in bone. The severe infantile form has the most profound deficiency, infantile form has the most profound deficiency, yet the cellular source of this enzyme--osteoblasts and their matrix vesicles--are normal by routine light and electron microscopy. Despite radiographic changes in bone metaphyses consistent with rickets, iliac crest biopsy of one affected child revealed no abnormalities; the other had evidence of a mineralization defect, but not as severe as that in affected infants. In this child and several affected adults with osteomalacia, osteoblasts appeared flat and metabolically inactive. Although these histological changes suggested a different pathogenetic mechanism for adult and childhood hypophosphatasia, these changes are most likely secondary to the underlying osteomalacia. Our findings are most consistent with evidence that childhood and adult hypophosphatasia often represent clinical expression of the heterozygous state for ALP deficiency which, when homozygous, results in the clinically severe, recessive, infantile form. Histochemical and direct analysis of bone tissue from controls and patients with hypophosphatasia demonstrated that the severe infantile form is associated with the most severe ALP deficiency. In the milder clinical forms, ALP deficiency in bone is not as profound. In general, the severity of the clinical expression of hypophosphatasia reflects the magnitude of the deficiency of ALP in bone. This is the expected finding for this inborn error of metabolism, which illustrates the major role bone ALP activity has in the process of normal skeletal mineralization.

Cytochemical detection of inherited copper toxicosis of Bedlington terriers

Sections of paraffin-embedded specimens of liver obtained from Bedlington terriers were stained with rhodanine for copper and examined and graded by two pathologists. Their results correlated well with each other, as well as with the results of quantitative determinations of hepatic copper content. Copper toxicosis was established by cytochemistry in 20 of 21 specimens, indicating a sensitivity of 95%. The method is highly specific--none of the 19 specimens obtained from unaffected dogs displayed copper-containing granules suggestive of copper toxicosis. Copper cytochemistry appears to be a satisfactory substitute for chemical analysis of hepatic copper content.

Fatal pulmonary and cerebral fat embolism in systemic lupus erythematosus

A patient with an eight-year history of systemic lupus erythematosus (SLE) and recent onset of recurrent psychosis died after acute deterioration of cardiopulmonary status and level of consciousness. Autopsy disclosed massive pulmonary hemorrhage and unsuspected fat emboli in the lungs, kidney, and brain. This article discusses the significance of systemic fat embolism in SLE, with reference to corticosteroid therapy, fatal pulmonary hemorrhage, and lupus psychosis.

Ultrastructure and staining properties of aortic microfibrils (oxytalan)

Microfibrils are the insoluble, 10- to 12-nm components of the extracellular matrix that are involved in elastogenesis. Reports of their ultrastructure vary: they have been described as tubular and beaded and as nontubular filaments that are devoid of any periodicity. Ultrastructurally, microfibrils resemble oxytalan fibers that have been observed in peridontal membranes, skin, and other locations. Whether microfibrils have the staining characteristics of oxytalan is difficult to determine in tissues because available light microscopic stains also stain elastin. Calf aortic smooth muscle cells grown in media without added ascorbate provide a unique model for examining the ultrastructure and staining characteristics of chemically defined microfibrils. Microfibrils are the predominant insoluble extracellular protein in such cultures, which do not deposit collagen or elastin. These studies demonstrate that microfibrils are tubular structures with 10- and 12-nm striations and have the same staining characteristics as oxytalan, reacting with aldehyde fuchsin and orcein after oxidation. Microfibrillar protein is enriched in glutamic and aspartic acids and the electron density of microfibrils is enhanced by fixation in the presence of cationic dyes. In such preparation, microfibrils are made visible within the core of amorphous elastin as well as in regions that are free of elastin. The widespread distribution of microfibrils (oxytalan) indicates that their function extends beyond elastogenesis. Their localization within tissues suggests that they serve as an elastic attachment protein in sites that are subject to mechanical stress.

Peroxisomes (microbodies) in human liver: cytochemical and quantitative studies of 85 biopsies

The number, intracellular distribution, and staining characteristics of human hepatocellular peroxisomes that had been made visible by cytochemical staining for catalase were evaluated in biopsies from 75 patients with hepatic, inflammatory, or malignant disease and ten normal individuals. Intensity of staining was found to be proportional to enzymatic activity by microspectrophotometry. Scanning transmission electron microscopy (STEM) image analysis demonstrated an inverse relationship between peroxisomal size and contrast. Peroxisomes were more abundant, and often concentrated in a perinuclear configuration in cholestatic and cirrhotic livers. Decreased peroxisomal staining was common in cholestasis, cirrhosis, hepatitis, and in almost all patients with malignancies, both with and without hepatic metastases.

The infrastructure of aortic elastic fibers

Elastic fibers are composed of a central core of elastin that is amorphous and electron-lucent in conventional transmission electron micrographs and peripheral microfibrils. A complex infrastructure within the amorphous elastin of mature rat aorta is made visible by fixation and staining with a glutaraldehyde-ruthenium red mixture in phosphate buffer or osmium-ruthenium red in cacodylate buffer. The infrastructure is composed of at least two interlacing but distinct elastic structural components; a framework of circumferentially orientated microfibrils and a three-dimensional meshwork of filaments that permeate the fiber. The latter resembles a reticulum that has previously been observed in freeze-fractured and negatively stained elastin and attributed to the supramolecular organization of elastin. Microfibrils also extend from the core of the elastic fiber into the surrounding matrix where they appear to function as anchoring fibers. These observations indicate that the elastic properties of the arterial wall are an integrated function of both elastin and microfibrils.

Striated adrenocortical cells in cerebro-hepato-renal (Zellweger) syndrome

Adrenal glands from eight patients with the cerebro-hepato-renal syndrome, a disease in which there are no morphologically demonstrable peroxisomes, were studied histologically; one of the eight was also examined ultrastructurally. Seven of the eight demonstrated striated adrenocortical cells in the inner portion of the adrenal cortex. Ultrastructural examination confirmed that the striated cells contained the lammellae and lamellar-lipid profiles of very long chain fatty acids-cholesterol esters that are characteristic of adreno-leukodystrophy. This morphologic observation further emphasizes the common pathogenetic features of the cerebro-hepato-renal (Zellweger) syndrome and adreno-leukodystrophy.

The internal reticular apparatus of Camillo Golgi: a complex, heterogeneous organelle, enriched in acid, neutral, and alkaline phosphatases, and involved in glycosylation, secretion, membrane flow, lysosome formation, and intracellular digestion

Its topography is one of the most characteristic features of the Golgi apparatus and the reticular nature of this organelle is evident in Golgi's first drawings, in light microscopic enzyme cytochemical preparations, and in high voltage electron micrographs of thick sections. Although individual components of the Golgi apparatus may differ in staining characteristics, morphology, contents, and enzymatic activities, they are integrated into a dynamic topographical and functional unit that is closely associated with the endoplasmic reticulum. Modulation of enzymatic activities and morphological and enzymatic heterogeneity are not surprising in an organelle that is the site of both synthetic and digestive events, including glycosylation, sulfation, formation of secretory granules and lysosomes, and the degradation of endocytized material.

Changes in the components of extracellular matrix and in growth properties of cultured aortic smooth muscle cells upon ascorbate feeding

Culture conditions can modify the composition of the extracellular matrix of cultured calf aortas smooth muscle cells. In the absence of ascorbate the major components of the matrix are microfibrillar proteins; deposition of collagen occurs upon ascorbate supplementation and, with increased time of exposure of cells to ascorbate, collagen becomes the dominant protein of the extracellular matrix (greater than 80%). Collagen accumulation follows a sigmoidal time-course, suggesting that it is a cooperative phenomenon. Covalent crosslinks are not required for collagen accumulation in the matrix. Microfibrillar proteins and increased amounts of proteoglycans and fibronectin accumulate concurrently with collagen but elastin deposition was not observed either with or without ascorbate feeding. Addition of ascorbate leads to a general stimulation of incorporation of [14C]proline into cellular protein and to changes in cell growth parameters and morphology: cell-doubling time decreases from 62 to 47 h and plating efficiency increases approximately fourfold. We conclude that the composition of the extracellular matrix assembled by cultured cells is subject to experimental manipulation and that changes in endogenously deposited matrix may have significant effects on cellular functions.

The cardiomyopathy of Wilson's disease. Myocardial alterations in nine cases

Though myocardial alterations are well recognized in haemochromatosis, little attention has been paid to the cardiac changes in Wilson's disease. To define the extent of myocardial degeneration in newly diagnosed or chronically treated Wilson's disease, we reviewed the autopsy findings in 9 cases with this condition. We compared our observations with those in 3 control cases, selected for comparable age and with liver disease having no known association with cardiac degeneration. Our results revealed cardiac hypertrophy in 5 out of 9 cases of Wilson's disease. There was evidence of interstitial and replacement fibrosis, intramyocardial small vessel sclerosis and focal inflammatory cell inflammation to a variable degree in all cases. One case had AV nodal degeneration, and a 15 year old boy had severe atherosclerosis of the left main coronary artery. Two patients died suddenly, presumably secondary to an arrhythmia; one of these patients had the most marked myocardial alterations. We could not correlate these changes specifically with the tissue levels of copper, treatment with D-penicillamine, or the presence of cirrhosis. We conclude that there are definite morphological abnormalities in the hearts of patients with Wilson's disease consistent with a cardiomyopathy. Though the myocardial changes were non-specific, the fact that 2 patients died suddenly, suggests the need for a prospective study of cardiac function in these patients in the future.

Glycosaminoglycans in the rat aorta. Ultrastructural localization with toluidine blue O and osmium--ferrocyanide procedure

Glycosaminoglycans (GAGs) have been implicated in the pathogenesis of sclerotic vascular disease. The localization of GAGs in the rat aorta was examined by two different ultrastructural cytochemical approaches. These procedures are believed to demonstrate 1) anionic sites, with fixatives that contain either toluidine blue or ruthenium red, both cationic dyes, and 2) polysaccharides, proteoglycans, and glycoproteins, with an osmium--ferrocyanide mixture that binds to vicinal diols. Both procedures stain a network of insoluble, 2--8-nm filaments that bridge collagen fibers, elastin, basement membranes, and plasma membranes. These structures resist digestion with chondroitinase ABC and appear to be identical to the filaments that have previously been demonstrated with ruthenium red. Focal 6--12-nm densities are present where filaments intersect. However, the large granules that are made visible with ruthenium red are not seen in toluidine blue or osmium--ferrocyanide preparations. A soluble and relatively amorphous component surrounds the tightly packed bundles of collagen in the media and is preserved and stained by toluidine blue and osmium--ferrocyanide mixtures.

Primary fixation in osmium-potassium ferrocyanide: the staining of glycogen, glycoproteins, elastin, an intranuclear reticular structure, and intercisternal trabeculae

Primary fixation in an osmium-potassium ferrocyanide (K4Fe(CN)6) mixture combines selective fixation, staining, and extraction of various cellular components; membranes, glycogen, glycoproteins, and elastin are preserved and stained. An intranuclear reticular structure that is composed of 3-6 nm fibers and permeates the entire nucleus, except for the nuclear pores, is demonstrated by electron microscopic examination of tissues prepared in an osmium-potassium ferrocyanide fixative. Condensations of the reticulum parallel the distribution of heterochromatin in interphase nuclei. This preparative procedure also reveals a network of trabeculae that are associated with the cisternae of rough endoplasmic reticulum and connect the parallel cisternae in hepatocytes, plasmacytes, neurons, and pancreatic ancinar cells. The intercisternal trabeculae are associated with both free and bound ribosomes.

A 42-year-old king with a cavitary pulmonary lesion and intestinal perforation

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Idiopathic neonatal iron storage involving the liver, pancreas, heart, and endocrine and exocrine glands

Autopsy studies of two infants, one a newborn, the other 4 months old, revealed massive amounts of iron in lysosomes of hepatocytes and pancreatic acinar cells. Iron, which had been transported across the placenta, accumulated in the same cell types as in adults with primary and secondary hemochromatosis. Hemosiderin was found in cardiac muscle cells, gastric and intestinal glands, and endocrine and exocrine organs including pituitary, thyroid, adrenals, islets of Langerhans, and sublingual and sweat glands. The liver was the most affected organ and the normal hepatic architecture was replaced by hepatocytes which were arranged in cluster, pseudoacinar structures, and multinucleated giant cells embedded in a collagen matrix. The islets of Langerhans were hyperplastic and hypertrophic. Ten similar cases, in five families, have been described; no patients liver longer than 4 months. Neonatal iron storage disease is clinically and pathologically distinct from Zellweger's cerebrohepatorenal syndrome and hypermethioninemia (tyrosinemia) neonatal diseases in which large stores of iron are present in hepatocytes. No abnormalities in serum iron, ferritin, or transferrin concentrations were detected in five parents of the affected children.

The significance of variations in the distribution of copper in liver disease

Biopsy and autopsy specimens of liver from patients with Wilson's disease in various stages, chronic cholestatic conditions (including primary biliary cirrhosis, extrahepatic biliary obstruction, sclerosing cholangitis, and biliary atresia), chronic active hepatitis, and Indian childhood cirrhosis, as well as normal neonates, were examined by means of histochemical techniques for copper and copper-associated protein. The intracellular localization of copper and the lobular distribution of the metal and its associated protein differed in these conditions. Periportal hepatocytes containing granules (lysosomes) that were reactive for copper and for copper-associated protein were characteristic of cholestasis and neonatal liver. However, in cholestasis extralysosomal copper was often present in the hepatocellular cytoplasm. In contrast, in Wilson's disease, despite very high concentrations of copper in the early stages, the metal was diffuse in the cytoplasm, and the histochemical reactions for granular copper and its associated protein were usually negative. Therefore, a failure to stain for copper does not exclude the diagnosis of Wilson's disease. In the late stages of Wilson's disease staining varied in different nodules. In Indian childhood cirrhosis copper was present throughout the parenchyma, with periportal predominance. Differences in the distribution of copper and the cellular changes associated with its deposition suggest that different pathogenetic mechanisms and possibly different intracellular targets are susceptible to the toxic effects of the metal. For diagnosis, staining for copper and for copper-associated protein may assist in the differentiation of primary biliary cirrhosis from chronic active hepatitis.

Cytochemistry of human catalase. The demonstration of hepatic and renal peroxisomes by a high temperature procedure

The cytochemical demonstration of marker enzymes for subcellular organelles permits light microscopic analysis of their structure and function in normal and diseased tissues. Currently available staining procedures for the peroxidatic activity of catalase in peroxisomes of plant and animal cells yield weak and inconsistent light microscopic staining when applied to human tissues. We have developed a simple and sensitive high temperature procedure that clearly and reproducibly stains these abundant, but poorly understood, organelles in biopsy specimens of human liver and kidney. This method utilizes formaldehyde fixation, a modified diaminobenzidine (DAB) medium, incubation at 45 degrees C and postosmication for both light and electron microscopy.

Hydrolase activities in the rat aorta. III. Effects of regular swimming activity and its cessation

It is possible that one of the consequences of regular physical activity could be a change of vascular metabolism. We studied the effects of regular swimming activity on specific activities of aortic hydrolases of male rats. Enzymes included: neutral alpha-glucosidase and lysosomal beta-galactosidase, N-acetyl-beta-glucosaminidase, cathepsin C, acid alpha-glucosidase, and acid cholesteryl esterase. After 8 or 16 weeks of a 1-hour/day swimming protocol, specific activities of four of the six aortic enzymes studied were increased over control levels, increases ranging from 7 to more than 42%. Acid cholesteryl esterase was one of the enzymes most affected by the exercise, increasing 25-30% above control levels. An 8-week sedentary period, after 8 weeks of a swimming regimen, resulted in return of the activity of acid cholesteryl esterase, but not those of the other hydrolases, to control levels. Decreases in body weight, blood pressure, and serum lipid levels also occurred in the swimming rats. Weight reduction per se was excluded as an explanation for the increases in aortic enzymes or decrease in serum cholesterol found with swimming. These findings show that regular physical activity is yet another factor with discrete and significant effects on the catabolic activity of vascular tissue.

Peroxisomes in disease

Cytochemical, biochemical and morphological changes in peroxisomes have been described in human metabolic disorders, in experimental models of disease and in response to drugs and toxins. These include the cerebrohepatorenal syndromes, in which peroxisomes can not be detected and mitochondrial respiration is inhibited, atherosclerosis, alcoholic cardiomyopathy, and tolerance to oxygen toxicity. Although information on the role of peroxisomes in disease is limited, increased awareness of their widespread distribution and the availability of an improved cytochemical procedure for staining peroxisomes in human specimens should provide new insights into their function.

Cytoplasmic copper and its toxic effects. Studies in Indian childhood cirrhosis

Morphological, histochemical, and chemical study of three necropsy specimens of liver in the terminal stage of Indian Childhood Cirrhosis revealed a strikingly high copper content. it is proposed that excess accumulation of copper in the cytoplasm of hepatocytes disturbs the microtubular system, causing hydropic swelling and the formation of Mallory's hyalin. Copper and copper-binding protein showed topographical association with Mallory's hyalin. Diffuse cytoplasmic staining and the lysosomal copper distribution also suggested that copper had a cytotoxic effect. The pattern of copper distribution in Indian Childhood Cirrhosis differs from that in Wilson's disease and in prolonged cholestasis with excessive hepatic copper deposition, indicating a different mechanism of the copper accumulation.

Immunocytochemical localization of hepatic legandin and Z protein utilizing frozen sections for light and electron microscopy

Ligandin (glutathione-s-transferase) and Z protein are soluble hepatocellular proteins that are involved in the transfer of organic ions, including bilirubin and some hormones and carcinogens from the plasma to the liver. The intracellular distribution of ligandin and Z protein was studied by applying the peroxidase-antiperoxidase procedure of L. A. Sternberger (Immunocytochemistry, Prentice Hall Inc., 1974) to paraffin sections and free-floating 10-micrometers frozen sections that were processed for both light and electron microscopy. Ligandin and Z protein were localized to the cytosol of hepatocytes in association with smooth endoplasmic reticulum (SER), but no reaction product was present between cisternae of rough endoplasmic reticulum. Penetration of reagents was enhanced in 10-micrometers frozen sections and the preservation of subcellular structures was equivalent to thicker, unfrozen sections.

Coronary intimal sclerosis in Morquio's syndrome

Mitral valve, coronary arteries, cartilage, and liver were studied by light and electron microscopy in a 15 year old boy with Morquio's syndrome, a genetic mucopolysaccharidosis, in which a deficiency of lysosomal hexosamine sulfatase is associated with accumulations of keratan sulfate in various organs. Coronary artery intimal sclerosis was a prominent feature of this disorder. Ultrastructural examination revealed numerous intimal smooth muscle cells containing storage vacuoles consistent with lysosomes. This was associated with marked interstitial deposition of collagen, elastin, and basement membrane material. Recent studies of human and experimental atherosclerosis have demonstrated the accumulation of cholesterol within vascular smooth muscle cell lysosomes. Intralysosomal accumulation of substrates other than cholesterol is also associated with vascular intimal sclerosis in genetic lysosomal disorders such as Fabry's disease and Hurler's syndrome. Lysosomal storage of undegraded substrate may be an important pathogenetic mechanism in the development of sclerotic vascular lesions.

Hydrolase activities in the rat aorta. II. Effects of hypertension alone and in combination with diabetes mellitus

Hypertension is an important risk factor for atherosclerosis and often occurs in association with diabetes mellitus. Specific activities of hydrolases in homogenates of aortas from rats with renal-clip hypertension, normotension following a period of hypertension, and hypertension combined with streptozotocin-induced diabetes mellitus were measured. Enzymes included: neutral alpha-glucosidase, and lysosomal N-acetyl-beta-glucosaminidase, beta-galactosidase, cathepsin C, acid alpha-glucosidase, and acid cholesteryl esterase. After 6 or 12 weeks of hypertension, specific activities of all enzymes measured were significantly increased, levels ranging from 24% above normal for cathepsin C to 351% above normal for N-acetyl-beta-glucosaminidase. Six weeks of normotension following 6 weeks of hypertension resulted in restoration to normal of four of the six enzyme activities; the remaining two enzymes were significantly below normal levels. Combined hypertension and diabetes mellitus showed smooth muscle cell levels of four of the five hydrolases measured to be significantly lower than those present with hypertension alone. In every instance, histochemical studies of aortas showed acid phosphatase and N-acetyl-beta-glucosaminidase activities which corresponded to the biochemical findings. These findings indicate profound and discrete effects of two clinical risk factors on vascular smooth muscle cell lysosomes.

Hydrolase activities in the rat aorta. I. Effects of diabetes mellitus and insulin treatment

Vascular disease in diabetics could arise in part from altered vessel wall catebolism. Specific activities of hydrolases in aortic smooth muscle cells from rats with streptozotocin-induced diabetes were measured. Enyzmes included: neutral alpha-glucosidase, alpha-mannosidase, and lysosomal N-acetyl beta-glucosaminidase, beta-galactosidase, cathepsin C, acid alpha-glucosidase, and acid cholesteryl esterase. After 4,8, and 11 weeks of diabetes, activities of all enzymes studied were decreased significantly in diabetic vessels, decreases ranging from 15% for cathepsin C to 62% for alpha-mannosidase. After 3 weeks of diabetes, insulin treatment for 1 week restored enzyme levels to normal. After 7 weeks of diabetes, 1 week of insulin treatment did not restore enzyme levels fully to normal (acid cholesteryl esterase was unchanged); 4 weeks of insulin did. Acid phosphatase and N-acetyl beta-glucosaminidase activities were reduced markedly in histochemical studies of diabetic aortas at all time periods and were restored by insulin treatment. Alloxan-induced diabetes gave results similar to those with streptozotocin. Significant decreases of aortic hydrolase activities, including those of lysosomes, occur in experimental diabetes mellitus and could contribute to accumulation of substrates in vascular smooth muscle cells.

The cherry-red spot--myoclonus syndrome

Three young women, 2 of them sisters, were found to have cherry-red spots at the macula when they were children. In 1 patient the spots faded before she was 20 years old. In all 3, incapacitating myoclonus and insidious visual loss developed in adolescence. Their intellect is normal and they have no gargoyle-like features. A variety of lysosomal inclusions were noted in cortical neurons in a biopsy specimen taken from 1 patient in childhood. Liver biopsy fifteen years later revealed mucopolysaccharide-like inclusions in Kupffer cells and hepatocytes. Lipofuscin bodies were abundant in neurons and hepatocytes. The patients excrete sialic acid-containing oligosaccharides not present in normal urine, suggesting a defect in degradation of glycoproteins. The specific enzymatic defect in these patients appears to be a deficiency of lysosomal neuraminidase.

Intralysosomal lipid in long-term maintenance transplant atherosclerosis

Intralysosomal accumulation of lipid has been implicated as an important mechanism in the pathogenesis of atherosclerosis. Although atherosclerosis develops frequently in organ transplants maintained on a long-term basis, to our knowledge no studies to date have demonstrated the intracellular localization of the lipid in this setting. Light and electron microscopic study of a renal artery branch from a transplanted kidney maintained for 3 1/2 years demonstrates that the lipid is sequestered within intimal smooth muscle cell lysosomes. The features of the atherosclerotic plaque in long-term transplantation appear to be identical to spontaneous lesions or those induced experimentally.

Hypophosphatasia: a cytochemical study of phosphatase activities

Skeletal abnormalities with defective formation of mature calcified bone are the most prominent clinical features of hypophosphatasia. Low concentrations of serum and tissue alkaline phosphatase and elevated plasma and urinary levels of phosphorylethanolamine (PEA) are also present. Although PEA is hydrolyzed by serum alkaline phosphatase, the relationship between PEA and the deficiency is unclear. PEA has not previously been tested as a cytochemical substrate for the in situ demonstration of human alkaline phosphatase activity. We have studied alkaline phosphatase activity in hypophosphatasia in tissue sections, utilizing PEA and adenosinetriphosphate (ATP) as well as the usual beta-glycerophosphate and naphthol phosphate substrates. Neutral and acid phosphatase activities were also examined. Our results demonstrate that PEA is a substrate for the localization of alkaline phosphatase in normal human tissue, but is not hydrolyzed in hypophosphatasia in the liver, brain or costochondral junction under alkaline conditions. In the kidney in hypophosphatasia only the straight segments of proximal tubules that rim the medullary rays are reactive with PEA. Similar results in hypophosphatasia were obtained at an alkaline pH with ATP, beta-glycerophosphate, and naphthol phosphate. However, the defect in hypophosphatasia is not a generalized deficiency of membrane-associated phosphatases because membranes that were deficient in alkaline phosphatase activity demonstrated normal reactivity with ATP at neutral pH. In addition, thiamine pyrophosphate was also split by Golgi membranes within the cytoplasm. Acid hydrolysis of beta-glycerophosphate by lysosomes was normal.

Lipid accumulation in human aortic smooth muscle cell lysosomes

Lipid deposition is a central feature of the human atherosclerotic lesion. Deficient lysosomal lipolytic activity has been implicated as a pathogenetic factor in atheroma formation. Cytochemical and ultrastructural examination of the abdominal aortas of 2 normal young males, ages 11 and 23, demonstrates lipid accumulation with lysosomes of intact mural smooth muscle cells. This appears to be an early stage in the process which eventually results in an overloading of lysosomes and the formation of lipid-laden foam cells.

Endocytosis by vascular smooth muscle cells in vivo and in vitro. Roles or vesicles and lysosomes

Overloading of lysosomes of smooth muscle cells with excess substrate may be a key event in the development of hypertensive and atherosclerotic vascular disease. Cellular uptake of materials and its relation to lysosomal function were studied by ultrastructural cytochemistry in aortic smooth muscle cells grown in vitro and in the intact animal. Injection of horseradish peroxidase (HRP) into hypertensive rats resulted in rapid insudation of the material into the environs of medial smooth muscle cells, entrance into surface pinocytic vesicles, and transport via vesicles into the cell interior where material was seen to accumulate within lysosomes. In vitro exposure of calf aortic cells to HRP in the medium resulted in a similar sequence of events. Pinocytic vesicles, seen both in vitro and in vivo, ranged in diameter from 650-1000 A. These dimensions are adequate to permit incorporation of intact lipoproteins of all classes, except the larger chylomicrons.

Lysosomes and the sclerotic arterial lesion in Hurler's disease

A case of Hurler's disease in a mentally retarded, six year old boy is reported. In Hurler's disease a lysosomal hydrolase, l-iduronidase, is deficient, and consequently undegradable mucopolysaccharide accumulates within lysosomes in many tissues. Severe occlusive coronary artery disease and sclerotic aortic lesions are common in very young patients, although their serum lipid and blood pressure levels are normal. Vascular collagen and elastin is increased, but little or no stainable lipid is present. Electron microscopy shows that aortic smooth muscle cells are distended by vacuoles, appearing empty in formalin fixed tissues, that identify them as the "gargoyle" cells in the proliferative lesion. The presence of a basic lysosomal defect and the absence of other contributing metabolic factors suggest that accumulation of an excess of undegradable substrate within smooth muscle lysosomes may be an initiating event in the development of proliferative sclerotic vascular lesions.

Arterial lysosomes and connective tissue in primate atherosclerosis and hypertension

The cellular events that occur in the vessel wall consequent to changes in endothelial permeability result in the progression of vascular disease, particularly atherosclerosis. Female rhesus monkeys were fed an atherogenic diet or were made hypertensive for 6-8 months; and their vessels were then compared with vessels from control monkeys. Length-defined segments of coronary vessels, the thoracic aorta, and the abdominal aorta showed significant increases in total connective tissue in the atherosclerotic and hypertensive groups; pulmonary vessels did not. The diseased aortic segments had increased levels of two lysosomal enzymes, acid phosphatase and beta-N-acetylglucosaminidase; pulmonary vessels were not diseased and did not show these changes. Coronary vessels from the atherosclerotic and hypertensive groups did not show an increase in enzyme levels on biochemical measurements, but focal accumulations of lysosomes were identified by cytochemical techniques. In atherosclerotic lesions, a doubling of cholesterol and more than a tenfold increase in cholesterol ester were found. These connective tissue and lysosomal changes are early features of primate vascular disease and may result from the accumulation of excessive substrate (cholesterol ester) in the lysosomes of vascular smooth muscle cells.