Amyloid precursor protein in aged nonhuman primates

In individuals with Alzheimer disease and in aged nonhuman primates, deposits of amyloid occur in senile plaques in brain parenchyma and in the walls of some meningeal and cortical vessels. Amyloid is primarily composed of beta/A4, a 4-kDa peptide derived from the transmembrane form of an amyloid precursor protein (APP). We examined the distribution of beta/A4 and APP (outside the beta/A4 domain) in cerebral cortices of monkeys ranging in age from 4 to 41 years. In all animals, APP immunoreactivity was present in cell bodies, proximal dendrites, and axons of cortical neurons. In aged animals, all of which showed senile plaques, large APP-positive axons were conspicuous, and APP immunoreactivity was present in neurites around beta/A4-immunoreactive plaques. In some plaques, APP-immunoreactive elements were located in proximity to deposits of beta/A4. The presence of APP immunoreactivity in neuronal perikarya, dendrites, axons, and in neurites within beta/A4-containing plaques supports the hypothesis that neurons can serve as one source of amyloid deposited in brain parenchyma.

Development of senile plaques. Relationships of neuronal abnormalities and amyloid deposits

The evolution of senile plaques and the relationships among neuritic elements, extracellular deposits of the beta-amyloid protein (beta/A4), and vascular beta/A4 are poorly understood. Immunocytochemical methods were used to examine fixed-frozen prefrontal cortices of 14 rhesus monkeys (Macaca mulatta) (14 to 37 years of age) for the presence of abnormal fibers/neurites, alpha 1-antichymotrypsin (alpha-ACT), and beta/A4. Age-associated alterations included abnormal fibers/neurites, presence of beta/A4, and association of alpha-ACT with beta/A4 in plaques and blood vessels. Vascular amyloid was present only in the oldest monkeys. The topographic distribution of abnormal fibers/neurites was mapped with acetylcholinesterase (AChE) histochemistry, and deposits of amyloid were visualized with immunocytochemistry for beta/A4. beta/A4 often was associated with neurites, but many neurites lacked demonstrable beta/A4. Thus in aged monkeys, abnormal neurites may provide one type of focus for the accumulation of the amyloid precursor, which is subsequently abnormally processed to form beta/A4. Our data in rhesus monkeys suggest that fiber and neuritic abnormalities increase with age and that they may precede the majority of beta/A4 deposits; the initial stages of neurite formation and parenchymal amyloid deposits may be independent of the appearance of vascular amyloid; and these processes may be synergistic with advanced age.

The binding of glycolytic enzymes to the cytoskeleton--influence of pH

In a continuing study of the interactions between glycolytic enzymes and cytoskeletal structure, the influence of a variation of the pH of the eluting medium has been investigated. This treatment resulted in an increased degree of binding of most of the glycolytic enzymes with a decrease in pH, with the most marked increases in binding occurring with phosphofructokinase, glyceraldehydephosphate dehydrogenase, enolase and pyruvate kinase. The significance of this data has been discussed with reference to the relative affinities of interaction of the individual glycolytic components and the physiological correlations of these phenomena.

Large amounts of neocortical beta A4 deposits without neuritic plaques nor tangles in a psychometrically assessed, non-demented person

An 88-year-old mentally normal woman (Blessed test score = 27) had very large amounts (397/mm2) of deposits stained by anti-beta A4 serum in the first temporal gyrus. Senile plaques and neurofibrillary tangles were lacking on sections stained with the Bodian's silver method, with anti-tau and anti-paired helical filament (anti-PHF) antibodies. The following beta A4 deposits were found in decreasing order of frequency: diffuse (64.8%), stellate (24.4%), primitive (10.2%), classic (0.6%) plaques. Compact plaques were not observed. Diffuse deposits predominated in layers I, III and IV. On the contrary, the rare classic plaques were located in layers II and III. No amyloid angiopathy was seen with Congo red stain although beta A 4 deposits were seen in vessel walls with immunocytochemistry. These data indicate that severe diffuse beta A4 deposits in the neocortex do not induce dementia. They suggest that the development of senile plaques composed of beta A4 amyloid and of degenerating neurites is not related solely to the density of the diffuse beta A4 deposits. Nor does it depend on the regional susceptibility of the nervous tissue since beta A4 deposits were seen in highly vulnerable cortical areas. Some other, as yet unknown, factors seem necessary. In addition, determination of beta A4 level in the neocortex is not sufficient for the diagnosis of dementia of Alzheimer type.

Amyloid in the brains of aged squirrel monkeys

In this immunocytochemical study, the brains of nine squirrel monkeys (Saimiri sciureus), ranging from 8 to 27 years of age, were examined for the presence and distribution of beta/A4 amyloid, a 4-kilodalton peptide. In aged squirrel monkeys, amyloid is associated primarily with intracerebral and meningeal capillaries and arterioles and occurs to a lesser degree as small and/or diffuse deposits in the neural parenchyma and in the dense cores of senile plaques. Cerebrovascular amyloid is found primarily in neocortex, amygdala, and septum verum and is rare or nonexistent in other subcortical gray structures, white matter, cerebellum, and spinal cord; this pattern of localization is comparable to that in humans with cerebral amyloid angiopathy. There is a significant correlation between cerebrovascular and parenchymal deposits of amyloid. However, cerebrovascular amyloid is always the most abundant form in squirrel monkeys, even in cases of severe cerebral amyloidosis. In contrast to squirrel monkeys, aged rhesus monkeys (Macaca mulatta) develop mostly parenchymal deposits of amyloid and have relatively less vascular amyloid. This species difference in the histological distribution of amyloid suggests that separate mechanisms may influence the accumulation of amyloid in cerebral blood vessels and in the neural parenchyma. These data also indicate that the squirrel monkey can serve as a model for investigations of cerebrovascular amyloidosis.

The influence of molecular crowding on the binding of glycolytic enzymes to cytoskeletal structure

In a study of the interactions between glycolytic enzymes and cytoskeletal structure, the effect of increasing the degree of molecular crowding by the addition of protein was studied. This treatment resulted in an increased degree of binding of all the glycolytic enzymes, but with the most marked increases occurring with phosphofructokinase, enolase and pyruvate kinase. The significance of this data has been discussed in relation to the relative affinities of interaction of the individual components, the influence of molecular crowding and the physiological significance of this phenomenon.

On the interactions of catalase with subcellular structure

The interaction of mouse liver catalase with subcellular membranes was studied, and an ionic interaction with a variety of membranes, including those derived from the microsomes, was observed. The interaction with microsomal membranes was found to be abolished by pre-treatment of catalase with neuraminidase, indicating a functional significance for catalase-bound sialic acid. Catalase activity was found to be enhanced when bound to membranes, and evidence for a weak association of catalase with peroxisomal structure in mouse liver was also obtained. It is concluded that mouse liver catalase has a capacity to bind to a variety of subcellular membranes in vivo and that this interaction may be consistent with a general protective role for the enzyme, as well as being compatible with a model of peroxisomal biogenesis which involves the interaction of catalase with microsomal membranes.

On the compartmentalization of catalase, fatty acyl-CoA oxidase and urate oxidase in mammalian livers, and the influence of clofibrate treatment on this microlocalization

The compartmentalization of catalase, fatty acyl-CoA oxidase and urate oxidase was examined in the livers of mice, rats and guinea pigs, using the technique of digitonin extraction in order to avoid the trauma associated with centrifugation procedures. The results are interpreted as indicating that an appreciable proportion of catalase activity occurs in the cytoplasmic compartment of these cells. Following treatment of the animals with clofibrate, the specific activity in both peroxisomal and cytoplasmic compartments was increased, with a higher proportion of cytoplasmic catalase being evident in mice. The results for catalase were compared with those for fatty acyl-CoA oxidase and urate oxidase both of which were indicated as showing a closer association with the peroxisomal compartment than was the case for catalase. These data have been discussed in relation to their significance on present understanding of peroxisomal structure and function.

Chemical modification of the actin binding site of rabbit muscle aldolase by diethylpyrocarbonate

To extend the available information on the significance of the interactions between glycolytic enzymes and the actin component of the cellular ultrastructure, investigations into the compositional characteristics of the actin binding site on one of the major glycolytic enzymes, aldolase, have been undertaken. As the electrostatic nature of the association has been previously reported indicative of a cationic region on the enzyme involved in the binding, these studies have investigated the possibility of the involvement of histidine residues in this binding region. By the use of the histidine specific reagent, diethylpyrocarbonate, we have been able to establish a difference in nature of an actin binding domain and the active site domain which does contain an essential histidine. The results have been discussed in relation to the significance of this finding with respect to the binding of aldolase to subcellular structure.

Changes to the integral membrane protein composition of mouse liver peroxisomes in response to the peroxisome proliferators clofibrate, Wy-14,643 and di(2-ethyl-hexyl)phthalate

Peroxisomes were purified from livers of control mice and from mice treated with three agents which induce proliferation of hepatic peroxisomes - namely two structurally unrelated hypolipidemic drugs, clofibrate (ethyl-alpha-p-chlorophenoxyisobutyrate) and Wy-14,643 (4-chloro-6[2,3-xylidino)-2-pyrimidinylthio]acetic acid), and a plasticizer, DEHP (di-(2-ethylhexyl)phthalate). Membranes were isolated from these purified peroxisomes and analysed by SDS-polyacrylamide gel electrophoresis. All membranes which were tested, displayed two predominant integral membrane proteins of apparent molecular weights of 68 kDa and 70 kDa respectively, as well as a number of minor components. Treatment of animals with clofibrate, Wy-14,643 and DEHP was observed to result in each case in an increased proportion of the 70 kDa protein in the peroxisomal membranes. These treatments also resulted in increased peroxisomal fatty acid oxidation in livers and an increase in the proportion of catalase activity in the cytosolic fraction of liver cells. These results have been discussed in relation to alterations in the molecular composition of the membranes, the mechanisms of peroxisome proliferation and the inducibility of peroxisomal membrane proteins.

The influence of calcium ions on the adsorption of glycolytic enzymes to cellular structure

In order to provide information on the influence of Ca2+ ions on the adsorption of glycolytic enzymes to cellular structure, the release of these enzymes from digitonized cells has been studied. Increases in the calcium ion concentration were found to cause corresponding decreases in the extent of release of all the glycolytic enzymes, as well as a parallel increase in the extent of polymerization of actin. These observations have been discussed in relation to the effect of physiological concentrations of these ions on the association between glycolytic enzymes and the cytoskeleton.

The influence of deoxyribonuclease I and cytochalasin D on the release of glycolytic enzymes from digitonized cells

In permeabilized cells, deoxyribonuclease I has been demonstrated to cause a decrease in the extent of binding to cellular structure of all of the glycolytic enzymes other than phosphofructokinase, with this decrease being most marked for aldolase and glyceraldehydephosphate dehydrogenase. Cytochalasin D, in contrast, did not produce this type of effect. These results have been discussed in relation to the evidence for the existence of a complex of glycolytic enzymes which binds to elements of the cytoplasmic matrix, and the possible organization of this complex.

The influence of fructose-1:6-bisphosphate on the release of glycolytic enzymes from cellular structure

In order to provide information on the relative binding characteristics of glycolytic enzymes, the effect of fructose-1,6-bisphosphate (FBP) on the release of glycolytic enzymes from cultured pig kidney cells treated with digitonin has been studied. In the absence of FBP, a differential release of these enzymes was observed, with the order of retention being aldolase greater than glyceraldehyde-3-phosphate dehydrogenase greater than glucosephosphate isomerase, triosephosphate isomerase, phosphoglycerokinase, phosphoglucomutase, lactate dehydrogenase, enolase, pyruvate kinase and phosphofructokinase. In the presence of fructose-1,6-bisphosphate, the release of aldolase was considerably enhanced, whereas the release of phosphofructokinase and pyruvate kinase was decreased by this metabolite. No significant alterations in the rate of release of the other enzymes was caused by FBP. These data have been discussed in relation to their contribution to the knowledge of the degree of association and order of binding between glycolytic enzymes and the cytoplasmic matrix.

On the ontogeny and interactions of glyceraldehyde-3-phosphate dehydrogenase

The interaction of GAPDH with cellular structure has been studied in the major tissues of the mouse during development. Overall the data provides a clear indication that interactions between GAPDH and cellular structure are appreciable in all major tissues, at least during early stages of development, and an analysis of the isozyme status of the enzyme in both soluble and bound compartments for all tissues at all developmental stages indicates the presence of only a single GAPDH isozyme in the mouse. Possible reasons for the lack of an extensive multiplicity of this enzyme in mammalian tissues (the only tetrameric glycolytic enzyme to display this restriction) and for the large amounts of GAPDH in many cell types are discussed in relation to the large number of proteins that GAPDH interacts with in the cell.

On the differential release of glycolytic enzymes from cellular structure

In an endeavour to extend the available information on the biological significance of the interactions between glycolytic enzymes and cellular ultrastructure, the role of release of enzymes from digitonized fibroblasts has been studied. Lactate dehydrogenase and phosphofructokinase were rapidly and quantitatively eluted under the experimental conditions, while glyceraldehyde-3-phosphate dehydrogenase and aldolase were retained to an appreciably greater extent by the cells. This differential release of glycolytic enzymes has been related to the known binding propensities between those enzymes and subcellular structures, and are interpreted as providing additional confirmatory evidence of the importance of aldolase and glyceraldehyde-3-phosphate dehydrogenase, in particular, to these associations. The data also shed light on the order of binding of these glycolytic components - phosphofructokinase being indicated as binding subsequently (and probably separately) to aldolase and glyceraldehyde-3-phosphate dehydrogenase. These results have been discussed in relation to the available data on the associations between glycolytic enzymes and cellular structure, the possible physiological significance of this phenomenon, and the access to these problems provided by the present technique.

Confirmation that catalase is a glycoprotein

Catalases which had been purified from the livers of mouse, rat and guinea pig were subjected to mild periodate oxidation followed by reduction with sodium boro[3H]hydride in order to test for the presence of sialic acid. A radioactively labelled moiety resulted, which behaved as a derivative of N-acetyl neuraminic acid during mild acid hydrolysis, neuraminidase treatment, ion exchange chromatography and paper chromatography. It is concluded that mammalian catalases are glycoproteins, and possess variable amounts of N-acetyl neuraminic acid in their carbohydrate moiety.

On the multiplicity of the enzyme catalase in mammalian liver

The literature on the complex multiplicity of mammalian catalase and the nature of the epigenetic modifications undergone by this enzyme has been reviewed, along with relevant comment on the subcellular localization and biological role of the enzyme. The epigenetic causations of multiplicity are established as being multifactorial and include oxidoreductive conversions of sulphydryl groups, the covalent attachment of carbohydrate, and partial proteolysis of the enzyme. Each of these epigenetic transformations may give rise to sets of multiple forms, and overlaps between these separate sets may give rise to extremely complex multiplicity patterns. It is concluded that any interpretation of catalase multiplicity which places emphasis on a single epigenetic causation is not compatible with the scope and variety of the available data on this enzyme. Instead, a holistic approach is urged - one giving due emphasis to the multiple causation of catalase multiplicity, and the interrelationships of these causations in the cellular situation. Rather than viewing the multiplicity of this enzyme as merely a series of interesting chemical modifications, emphasis is directed towards the fact that catalase heterogeneity provides a sensitive indication of the functional variations which occur within separate compartments of the subcellular structure, and hence becomes an essential element in any satisfactory understanding of the role of this enzyme in cellular processes.

On the developmental multiplicity and subcellular interactions of pyruvate kinase

The interactions of the isozymes of pyruvate kinase with cellular structure have been studied in the major tissues of the mouse during development. Overall, these data provide a firm indication that the interactions between this enzyme and cellular structure are appreciable in most tissues during all stages of development, and an analysis of the isozyme status of the enzyme in both soluble and bound compartments has been effected. Evidence has been provided that the A4 form of pyruvate kinase interacts to a greater extent with subcellular structure than does the C4 form, and the C4 form in turn interacts to a greater extent to subcellular structure than does the B4 form.

Studies on the topographical localization of the binding sites for substrate and for actin on the enzymes, glyceraldehydephosphate dehydrogenase and phosphofructokinase

The effect of proteolysis on the catalytic activity and the binding capacity for actin has been studied in the case of both glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and phosphofructokinase (PFK). With both of these enzymes, the differential response of these two parameters is interpreted as an indication of the distinct topographical separation of the active sites and binding sites. These results have been discussed in relation to the positioning of the catalytic and binding sites on these enzymes, the nature of their interaction with actin, their relative stability in cellular situations and the phenomenon of enzyme ambiguity.

On the ontogeny and interactions of phosphofructokinase in mouse tissues

The distribution and interactions of phosphofructokinase isozymes with cellular structure have been studied in the major tissues of the mouse during development. The ontogenic patterns of isozymes which were obtained were consistent with those observed for other species and are interpreted in terms of the presence of three genes and three homotetrameric forms of the enzyme (A4, B4 and C4) in the tissues of the mouse. In addition, the data provides a clear indication that interactions between the enzyme and cellular structure are appreciable in all major tissues and at all stages of development, with all isozyme types exhibiting such interactions. The significance of the study of subcellular interactions of these isozymes in contributing to a comprehensive physiological rationale for this mammalian enzyme and its multiple forms is discussed.

Evidence for the spatial separation of the binding sites for substrate and for cytoskeletal proteins on the enzyme aldolase

The effect of the proteolysis of aldolase on both the substrate specificity of the enzyme and binding capacity for actin have been studied. Carboxypeptidase A, trypsin, chymotrypsin and pepsin, all acted to cleave peptides from the C-terminal portion of the enzyme, resulting initially in a marked loss of activity towards fructose-1:6-bisphosphate (FBP), without impairment of activity towards fructose-1-phosphate (F1P). In some cases, however, further proteolysis caused reductions in activity with F1P as well. By correlating the size of the peptide fragments released by these enzymes with the known sequence of aldolase, evidence has been provided that cleavage of His-359 and/or Tyr-361 lead to the loss of FBP activity, while further cleavage of up to six amino acids begin to affect activity against F1P, as well. In regard to the ability of the proteolysed aldolase to bind to F-actin, it was evident from these studies that binding ability was not impaired in the initial stages of proteolysis referred to above, but was retained until the enzyme was extensively degraded. This differential behaviour of the active and binding sites on aldolase clearly establish their separate topographical localization. These results have been discussed in relation to the positioning of these separate sites on the enzyme, the nature of the interaction between aldolase and actin and the phenomenon of enzyme ambiquity in cells and tissues.

On the developmental properties and tissue interactions of hexokinase

The interactions of the isozymes of hexokinase with cellular structure have been studied in the major tissues of the mouse during development. Overall, these data provide a clear indication that interactions between hexokinase and cellular structure are appreciable in all major tissues and at all stages of development, and an analysis of the isozyme status of the enzyme in both soluble and bound compartments has been effected. Further evidence in support of the already well documented interaction of hexokinase I to subcellular material in adult brain and kidney tissues is provided and extended to show that such interactions are extensive in both these tissues throughout development. In addition, evidence is provided that considerable hexokinase II activity is present in mouse foetal tissues in both the soluble and bound fractions and this isozyme is also shown to be the predominant "bound" form of the enzyme in adult skeletal muscle. By contrast, hexokinase III and IV are shown to be largely located in the cytosolic fraction of liver. The metabolic implications of these enzyme-structural interactions during development are discussed, as is the possibility of a functional linkage between hexokinase, which is bound to the mitochondria, and other enzymic components of the glycolytic sequence.

Ontogenic variations in the interactions of lactate dehydrogenase isozymes with cellular structure

The interactions of the LDH isozymes with cellular structure have been studied in the major tissues of the mouse during development. Overall, there is a clear indication that interactions between LDH and cellular structure are appreciable in all major tissues and at all stages of development, and an analysis of the isozyme status of the enzyme in both soluble and bound compartments has been effected. Information has been provided supporting the preferential binding of the A type activity to actin filaments. The data provided also support the concept of pelletable B type LDH in kidney and brain during the postnatal period. Binding was particularly extensive in the early embryonic stages, and the significance of this phenomenon, and the subcellular interactions observed to varying degrees in all the tissues throughout development, have been discussed in relation to the known metabolic characteristics of these separate tissue situations.

On the ontogeny of aldolase isozymes and their interactions with cellular structure

In an endeavour to extend the available information on the biological significance of the interactions between aldolase and cellular ultrastructure, the extent of association has been studied in the tissues of the mouse during the major stages of development from embryo to adult. Analysis of the isozyme status in these compartments and the latency of the enzyme during tissue differentiation was also effected. In all tissues investigated, a considerable variation in the degree of association of aldolase with structure was evident during development. Binding was particularly extensive in the early embryonic stages, but regardless of the tissue or the stage of differentiation, binding preference was directed towards A-type activity over the B- and C-type of enzyme. Substantial latent activity of aldolase was evident only in brain in the postnatal stages of development, and not in the other tissues or early stages of ontogeny. The significance of these ontogenic phenomena have been discussed, along with the physiological variations in individual tissues during maturation.

The influence of insulin on the flux of lipid metabolism in vivo

The effects of insulin on the balance of lipid metabolism have been investigated by measuring the relative in vivo incorporation of 3H- and 14C-labelled glycerol into the major tissues and lipid classes of diabetic mice over a three day period. Several significant alterations in the relative uptake of label were caused by the insulin treatment. Generally, there were indications of decreased synthesis and degradation of lipids in most tissues, but with an increased synthesis of hepatic triacylglycerol being a notable exception to these trends. These data indicate that insulin treatment produces widespread changes in the relative emphasis of lipid metabolism, and allow a detailed description of these responses in relation to the individual tissues and lipid classes of the living animal. The implications of these metabolic changes have been discussed in relation to hormonal effects, and tissue specific and whole body aspects of the regulation of lipid metabolism.

On the flux of lipid metabolism in diabetic animals

The influence of diabetes on the balance of lipid metabolism has been studied by measuring the simultaneous incorporation in vivo of 3H- and 14C-labelled glycerol into all the major tissues and lipid classes of diabetic mice. The induction of the diabetic condition caused significant alterations in the relative utilization of these labels, with double isotope ratios (3H/14C) being increased in the total lipid fractions of all tissues, but most extensively in muscle and adipose tissue. A degree of individuality was evident in relation to the response of tissue phospholipids, particularly in regard to the incorporation of tritium label into phosphatidyl choline fractions. These data establish that diabetes causes widespread and major perturbations of lipid metabolism in these animals, and indicate the detailed nature of the responses in relation to individual tissues and lipid classes. The implications of these alterations have been discussed with respect to tissue-specific and whole body aspects of the regulation of lipid metabolism.

Sequential alterations in the micro-localization of catalase in mouse liver after treatment with hypolipidemic drugs

A comparative study has been carried out on the micro-localization of catalase in mouse tissues subsequent to treatment with a representative range of hypolipidemic drugs. A commonality of effect was shown by clofibrate (ethyl-alpha-p-chlorophenoxyisobutyrate), Wy-14,643 (4-chloro-6-[2,3 xylidino)-2-pyrimidinylthio] acetic acid), RMI-15,414 (5-tetradecyloxy-2-furancarboxylic acid) and aspirin (acetyl salicylic acid), in that treatments with each of these drugs was associated with the release of peroxisomal catalase into the cytoplasmic compartment of liver and kidney. It was also noticeable that this increased cytosolic activity was characterized by the presence of an 'aged' form of the enzyme with different mobility and activity characteristics to that of the peroxisomal enzyme. Possible molecular bases for these effects and their relationship to peroxisomal biogenesis are discussed.

On the role of peroxisomes in the metabolism of lipids--evidence from studies on mammalian tissues in vivo

Recent investigations into the role of peroxisomes in mammalian lipid metabolism have employed double isotope methodologies to examine the influence of peroxisomal agents on lipid turnover in the liver and extra hepatic tissues of the living animal. The action of these agents, all of which caused extensive changes in the flux of lipid metabolism in the treated animals, may best be viewed in relation to their effects on the common pathway of fatty acid oxidation in peroxisomes. Clofibrate, for example, acts through induction of peroxisomal oxidases and catalase; glycolate and ethanol through activation of this pathway; and aminotriazole and allylisopropylacetamide through inhibition of the catalase step in the sequence. The data from these studies provide support for the concept of an important contributory and regulatory role of peroxisomes in relation to the overall balance of lipid metabolism, and emphasize that these organelles play a significant role in the oxidation of common fatty acids, as well as a potential for the elimination of fatty acids that are poorly oxidized by mitochondria. Additionally, the data raise intriguing questions on the extension of peroxisomal influence to include phospholipid metabolism and the substantial degree of inter-tissue communication which is involved in the balance of lipid metabolism in the whole animal.

Interactions between glycolytic enzymes and components of the cytomatrix

Evidence is provided that enzymes absorb to cellular structures in a wide range of tissues. In particular, the interactions between glycolytic enzymes and the microfilaments of the cytoplasm are described. The relevance of these interactions to the compartmentation of carbohydrate metabolism is discussed. Examples are given of the variations in degree of binding during alteration of tissue metabolism and, for individual glycolytic enzymes, during fetal development and differentiation. Overall, these data support the concept that metabolic activities in the cytoplasm have an organized structure. Just as the structural elements of the cytosolic compartment have evolved with the capacity to assemble and disassemble in response to the changing requirements of the organism, so the metabolic elements appear to have evolved a parallel system that provides for the appropriate positioning of an energy-producing sequence in relation to the specific, dynamic requirements of the cytoskeleton.

Relationships between the flux of lipid metabolism in vivo and the uncoupling of respiratory control

The influence of dinitrophenol treatment on the balance of lipid metabolism in mouse tissues has been studied by measuring the incorporation in vivo of 3H- and 14C-labelled glycerol. Several significant alterations in the relative utilization of these labels were observed in treated animals, with the greatest influence being evident in liver lipids, and diverse responses occurring in kidney, heart, muscle and adipose tissue. These data establish that dinitrophenol perturbs lipid metabolism in all the major tissues of the animal, and point to the detailed nature of this response in the individual classes of neutral and phospholipids. The implications of individual changes have been discussed in relation to the relative roles of mitochondria and peroxisomes in the regulation of mammalian lipid metabolism.

On the role of catalase in the oxidation of tissue fatty acids

The role of catalase in lipid metabolism has been studied by means of a comparison of the turnover characteristics of the major lipid classes in the normal mouse with those of animals in which the catalase activity had been inhibited and blocked by aminotriazole and allylisopropylacetamide. Double isotope ratios were determined in the lipid fractions of several tissues following the injection of labeled glycerol, and a number of significant differences were identified between these treatments. Since catalase is recognized as an integral component of the peroxisomal pathway of fatty acid oxidation, these results may be taken as indicating that interruption of the process of peroxisomal beta-oxidation in this manner cause extensive perturbations of lipid metabolism in the living animal, and these perturbations extend well beyond those tissues where the predominant localization of these organelles occurs. The concept which derives from these data--that of a significant regulatory role of peroxisomes in relation to the overall balance of lipid metabolism in the animal body--is described and discussed.

On the synthesis and incorporation of catalase and urate oxidase into the peroxisomes of mouse liver

The processes associated with the biogenesis of peroxisomes in mouse liver have been studied by following the incorporation of radiolabelled leucine into major enzymic components of this organelle. Maximal incorporation of label into peroxisomal catalase and urate oxidase occurred within 2 hr, with the urate oxidase being labelled before catalase, but subsequent to the incorporation of phospholipid into this organelle. Subsequently, immunoprecipitation of catalase from the large granular fraction of mouse liver was shown to result in the isolation of a catalase molecule which had lost a peptide of approx. 2000 dalton from each subunit by comparison with the newly-synthesized enzyme. It was observed that the modification of catalase was obviated by the presence of leupeptin and iodoacetamide and this information has enabled the purification of both modified and unmodified forms of the enzyme. The possible significance of these data has been discussed and the major features incorporated into a working model of peroxisomal biogenesis.

Brain monoamine abnormalities in the two types of Creutzfeldt-Jakob disease

Analysis of monoamine concentrations in brain tissue was carried out on the two types of Creutzfeldt-Jakob disease (CJD). The results showed decreased levels of catecholamines compared to control cases in a number of areas, and the reductions were most pronounced for dopamine. In general, the case classified as the amyotrophic form of CJD showed a greater degree of a monoamine loss than the case with spongiform encephalopathy, which is the typical transmissible form of CJD. These findings support the scarce available data indicating disturbances in the catecholaminergic systems in these types of brain diseases, and may have therapeutic implications.

Changes in expression of glial antigens M1 and C1 after cerebellar injury

In response to mechanical injury in the adult mouse cerebellum, Bergmann glia and astrocytes of the granular layer exhibit abnormally increased expression of M1 antigen, while expression of C1 antigen in Bergmann glia is reduced. these reciprocal changes in two different astrocytic antigenic determinants (each recognized by monoclonal antibodies) are easily detected in the immediate area of the wound 4 days after the lesion. Although loss of C1 antigen from Bergmann glia remains localized to the area of the wound, abnormal M1 expression becomes widespread in cerebellar astrocytes, also affecting the contralateral side of the injured cerebellum at its peak 8 to 12 days after injury. These findings suggest that previous observations of abnormal expression of the two antigens in the cerebellum of mutant mice (Sommer, I., and M. Schachner (1981) J. Supramol. Struct. 16: 53-74) might be interpreted with the view that a glial reaction to pathological state might be induced by genetically programmed neuronal cell death and/or abnormal development. We therefore postulate that expression of M1 in astrocytes that normally do not express this antigen and repression of C1 in normally positive astrocytes are indicative of a distinct functional state of astroglia, reactive gliosis.

Descriptive epidemiology of Creutzfeldt-Jakob disease in Chile

Descriptive epidemiological data are presented from a survey of 35 cases of Creutzfeldt-Jakob disease (CJD) that occurred in Chile in the period 1955 to 1977. The average mortality in Chile (0.31 deaths per 1 million) and in urban Santiago (0.73 deaths per 1 million) is compared with data reported from other countries. An increasing incidence in recent years is probably related to a greater awareness of the disease. The familial occurrence of CJD in nine patients from five affected families is described, and its analysis suggests a genetically determined susceptibility with incubation periods of more than 30 years. Horizontal transmission of the disease may have occurred in one patient in whom the disease developed 13 years after the patient married into a family with seven other affected members.