Iron in the Hallervorden-Spatz syndrome

The dark discoloration of globus pallidus and substantia nigra pars reticularis in the Hallervorden-Spatz syndrome is due to the accumulation of iron. Routine iron stains detect the metal mostly in microglia and macrophages, but scattered neurons are also reactive. Axonal spheroids are characteristic of the disease, and many of these expansions give a positive iron reaction. Globus pallidus and substantia nigra are normally rich in iron, and additional "storage" of the metal has often been considered the essential factor in the pathogenesis of Hallervorden-Spatz syndrome. However, other equally iron-rich structures, such as the red nucleus and the dentate nucleus, remain unaffected. In normal globus pallidus and substantia nigra pars reticularis, double-label immunofluorescence microscopy of ferritin, as an indirect marker of cellular iron localization, and phosphorylated neurofilament protein reveal close proximity of ferritin-reactive microglial and oligodendroglial processes to tightly packed axons. It is proposed that a primary axonal disorder allows the seepage of iron into the axoplasm. Iron may contribute to the axonal disease, but accumulation of the metal probably should be viewed as an epiphenomenon. Pallidal and nigral iron excess is not unique to Hallervorden-Spatz syndrome, and some previously reported postmortem examinations may actually represent pallidonigroluysian atrophy.

Synapses in the hereditary ataxias

The goal of this investigation was the systematic assessment of synapses in the hereditary ataxias by the immunocytochemical and immunofluorescent visualization of SNAP-25, a protein of the presynaptic membrane. Sections were prepared from the cerebellar cortex, dentate nucleus, basis pontis, inferior olivary nuclei, and the spinal cord in 57 cases of autosomal dominant and recessive ataxia. The neuropathological phenotype included 18 cases of olivopontocerebellar atrophy (OPCA), 14 cases of familial cortical cerebellar atrophy (FCCA), 4 cases of Machado-Joseph disease (MJD), and 21 cases of Friedreich's ataxia (FA). Among the autosomal dominant ataxias, spinocerebellar ataxia type 1 (SCA-1), SCA-2, MJD/SCA-3, and SCA-6 were represented. Expanded guanine-adenine-adenine trinucleotide repeats were confirmed in 7 patients with FA. The abundance of SNAP-25 was estimated by comparing the fluorescence of the regions of interest to that of the frontal cortex, which was considered unaffected by the disease process. Despite severe Purkinje cell loss, abundant SNAP-25 reaction product remained in the molecular layer of FCCA and OPCA. Among the cases of OPCA, those identified as SCA-2 showed the most severe overall synaptic destruction in cerebellum and brain stem. In SCA-1, which caused either OPCA or FCCA, significant synaptic loss was restricted to the inferior olivary nuclei. Sparing of cerebellar cortex and inferior olivary nuclei was the rule for MJD/SCA-3 and FA, though the dentate nucleus showed reduced SNAP-25 immunoreactivity in both ataxias. In FA, preservation of SNAP-25 in the dentate nucleus was characteristic of long survival. Severe cases with short survival revealed synaptic depletion of the dentate nucleus. At the level of the spinal cord, synaptic loss in the dorsal nuclei of Clarke characterized FA and MJD/SCA-3. The inexorable clinical progression of the hereditary ataxias could not be attributed to synaptic loss in a single anatomic structure of cerebellum, brain stem, or spinal cord. Nevertheless, synaptic loss in dentate and inferior olivary nuclei correlated more precisely with the severity of the ataxia than the changes in the cerebellar cortex.

The cellular reactions to experimental intracerebral hemorrhage

The resolution of an intracerebral hemorrhage can be measured by the occurrence of hemosiderin. Extravasation of blood elicits a cellular reaction in the adjacent surviving tissue where the lesion activates resident microglia and attracts many more phagocytes from the blood stream. The signals for this migration into the perifocal reactive zone are not fully understood but it is likely that proteins in the coagulated blood contribute to cellular activation. In order to study the role of plasma proteins in the pathogenesis of the perifocal reactive zone, intracerebral injections of either autologous whole blood (0.1 ml) or an equal volume of washed autologous red blood cells (RBC) in lactated Ringer's solution were made in adult rabbits. The amount of total iron was the same (30 micrograms). The cellular responses to the injections were studied by iron histochemistry and immunocytochemistry for ferritin, the ferritin repressor protein (FRP), the glial fibrillary acidic protein (GFAP), and the complement receptor CR3. Experimental hematomas resolved much more slowly after the injection of whole blood than after the injection of RBC. Qualitative microglial and astrocytic responses were quite similar. However, at 48 h, iron- and ferritin-reactive microglia were more numerous following the injection of whole blood. After injections of either type, ferritin-immunoreactive cells were more abundant than iron-positive cells. This observation implied that the biosynthesis of holoferritin protein and iron incorporation proceeded independently. Expression of CR3 on the surface of microglia was much more prominent after whole blood, suggesting a role of inactivated complement 3b in the attraction of additional phagocytes. Conversion to hemosiderin began at 5 days after the injection of either blood or RBC. The lesions caused initial destruction of astrocytes in the perifocal zone as judged by GFAP- and FRP-immunoreactivity. However, at 5 days, astrocytic processes reentered the perifocal zone and intermingled with microglia and macrophages. It is proposed that this contact between astrocytes and microglia reversed the uncoupling of ferritin biosynthesis and iron incorporation and initiated the storage of iron and formation of hemosiderin.

The heterogeneous distribution of brain transferrin

Immunocytochemistry with antisera to transferrin has often been used to identify oligodendroglia in tissue sections and cultures, but reaction product also occurs in blood vessel walls and nerve cells. There is considerable species variation. Serum transferrin is largely biosynthesized in the liver, and its established physiological role is the transport of iron to tissue sites and delivery of the metal to the interior of cells that have transferrin receptors on their surfaces. In sections of the central nervous system, the visualization of iron and transferrin generally does not coincide, and transferrin may have importance to normal brain function beyond iron transport. For a comparative analysis of transferrin in rabbit and rat brain, polyclonal antisera were raised against purified serum transferrins of these species. The antisera were used for transferrin immunocytochemistry on vibratome sections and for immunochemical detection on electroblots. Transferrin immunocytochemistry and iron histochemistry were compared. The electrophoretic separation of brain extracts and transfer to nitrocellulose membranes permitted the quantitation of the protein and the study of the carbohydrate chains of tissue-bound transferrins by biotinylated lectins. An unexpected result in the rabbit was the dense immunocytochemical reaction product in Bergmann glia and Golgi epithelial cells. Reaction in the cytoplasm of oligodendrocytes was relatively faint in this species except for some selected white matter tracts, e.g. the inferior cerebellar peduncles. In sections of rat brain, oligodendrocytes and vessel walls reacted vigorously in all locations. Transferrin levels in rat brain were substantially higher than in rabbit brain. In the rabbit, maximum transferrin levels occurred in the cerebellum.(ABSTRACT TRUNCATED AT 250 WORDS)

Case report: anti-Cra in pregnancy

A 39-year-old Grenadian multiparous patient presented in the 12th week of pregnancy. Her red cells were found to have the rare Cr(a-) (ISBT Number 202001) phenotype within the Cromer complex, and her serum contained anti-Cra. To date, anti-Cra has not been implicated in hemolytic disease of the newborn (HDN), but there are very few published reports on this topic. This case provided an excellent opportunity for study. The patient's serum showed no detectable functional activity in in vitro antibody-dependent, cell-mediated cytotoxicity assays, and no increase in the strength of the antibody during the pregnancy. The newborn infant showed no clinical signs of HDN, and was of normal weight. This case study suggests that anti- Cra is not implicated in HDN.

The cellular localization of malonyl-coenzyme A decarboxylase in rat brain

Malonyl-coenzyme A (CoA) decarboxylase (E.C.4.1.1.9) activity in brain is low but steadily increases after birth. The main physiological role of this mitochondrial enzyme is thought to be the stabilization of malonyl-CoA levels which change very little with brain growth. In an effort to visualize malonyl-CoA decarboxylase by immunocytochemistry, and to determine its developmental changes, the enzyme was purified by an efficient small-scale procedure involving isolation of mitochondria, extraction at high ionic strength, isoelectric focusing, column chromatography, and preparative polyacrylamide gel electrophoresis. The enzyme from brain showed the same apparent molecular weight (160 kDa) and was immunoreactive with antisera raised against malonyl-CoA decarboxylase from liver. Immunocytochemistry revealed early and extensive labeling of hepatocytes in rat liver but only delayed visualization in the brain. Most nerve cells of the cerebral cortex and many microglia were stained but the neurons of the cerebellar cortex did not become reactive. Golgi epithelial cells and their processes, the Bergmann glia, also showed reaction product.

The pathogenesis of superficial siderosis of the central nervous system

In advanced cases of superficial siderosis of the human central nervous system, the clinical triad of hearing loss, cerebellar ataxia, and myelopathy permits the diagnosis at the bedside, and magnetic resonance imaging readily confirms the hemosiderin deposits in brainstem, cerebellum, and spinal cord. To study the pathogenesis of this condition and explain the selective vulnerability of the cerebellum, experimental siderosis was induced in rabbits by the repeated intracisternal injection of autologous red blood cells. The earliest cellular response in the cerebellar molecular layer was hyperplasia and hypertrophy of microglia as displayed by immunocytochemistry for ferritin. Microglia also contained iron, but ferritin biosynthesis appeared to proceed without commensurate iron accumulation. This early apoferritin response probably occurred due to the presence of heme, rather than iron, in the cerebrospinal fluid and subpial tissue. Ferritin biosynthesis is accelerated when the ferritin repressor protein is dissociated from ferritin messenger ribonucleic acid. A specific antiserum localized ferritin repressor protein predominantly to astrocytes including Bergmann glia. It is proposed that abundance and proximity of ferritin repressor protein--immunoreactive Bergmann glia and ferritin-containing microglia in the cerebellar molecular layer permit prompt cellular interaction in the conversion of heme to ferritin and ultimately hemosiderin.

Experimental superficial siderosis of the central nervous system: biochemical correlates

The pathogenesis of superficial siderosis of the central nervous system (CNS) may be examined by the repeated intracisternal injection of washed autologous red blood cells (RBC). In rabbits, the injections cause the accumulation of iron in the cytoplasm of microglial cells and astrocytes of cerebellar and cerebral cortices. Immunocytochemistry for ferritin reveals enhanced reaction product mainly in microglia but hemosiderin occurs only after extending the injections to 6 months. In an effort to determine the biochemical correlates of these morphological changes, iron, ferritin, ferritin subunits and the ferritin repressor protein (FRP) were quantitated. There was no increase of total iron or ferritin in the exposed cortical areas. However, the injections of RBC caused dramatic shifts of the relative contributions by heavy (H-) and light (L-) ferritin subunits. The initial response was a prompt increase of the H/L ratio to over 4.0 from the normal ratio near 1.0. Extended injections caused the ratio to drop to below unity, and the predominance of L-ferritin at 6 months coincided with the appearance of granular hemosiderin. This investigation also confirmed the presence of FRP in rabbit brain cytosols but the induction of experimental superficial siderosis did not change its levels or in vitro affinity for the iron-responsive element in ferritin messenger ribonucleic acid. It is proposed that the incrustation by hemosiderin which characterizes superficial siderosis of the CNS in humans occurs when prolonged exposure to hemoglobin produces persistent shifts of the H/L-ratios by accumulation of L-ferritin.

The origin of free brain malonate

Rat brain contains substantial concentrations of free malonate (192 nmol/g wet weight) but origin and biological importance of the dicarboxylic acid are poorly understood. A dietary source has been excluded. A recently described malonyl-CoA decarboxylase deficiency is associated with malonic aciduria and clinical manifestations, including mental retardation. In an effort to study the metabolic origin of free malonate, several labeled acetyl-CoA precursors were administered by intracerebral injection. [2-14C]pyruvate or [1,5-14C]citrate produced radioactive glutamate but failed to label malonate. In contrast, [1-14C]acetate, [2-14C]acetate, and [1-14C]butyrate were converted to labeled glutamate and malonate after the same route of administration. The intracerebral injection of [1-14C]-beta-alanine as a precursor of malonic semialdehyde and possibly free malonate did not give rise to radioactivity in the dicarboxylate. The labeling pattern of malonic acid is compatible with the reaction sequence: acetyl-CoA----malonyl-CoA----malonate. The final step is thought to occur by transfer of the CoA-group from malonyl-CoA to succinate and/or acetoacetate. Labeling of malonate from acetate is most effective at the age of 7 days when the net concentration of the dicarboxylic acid in rat brain is still very low. At this age, butyrate was a better precursor of malonate than acetate. It is proposed that fatty acid oxidation provides the acetyl-CoA which functions as the precursor of free brain malonate. Compartmentation of malonate biosynthesis is likely because the acetyl-CoA precursors citrate and pyruvate are ineffective.

Effects of aspirin upon the flushing reaction induced by niceritrol

The usefulness of niceritrol as a lipid-lowering agent is limited by a prostaglandin-mediated flushing reaction after each dose occurring in the early stages of treatment. We have tested the effect of premedication with aspirin on the reaction to 250 mg niceritrol in 30 healthy male volunteers using both subjective and observed assessments of severity. Both 300 mg and 600 mg of aspirin significantly reduced the severity of flushing when compared with placebo. No significant difference was seen between the two dose levels. Prior dosing with aspirin may increase acceptability of niceritrol and hence improve compliance.

Combination treatment with cholestyramine and bezafibrate for heterozygous familial hypercholesterolaemia

Cholestyramine and bezafibrate were compared individually and in combination in the treatment of 18 patients with heterozygous familial hypercholesterolaemia. The study used a double blind, placebo controlled block design with a placebo run in period of two months followed by three phases of active treatment, each of two months' duration. Patients were randomly allocated to one of the six possible sequences of medication so that three patients would be treated with each sequence. Two patients withdrew from the study before completion. The median concentration of total cholesterol decreased from 9.65 mmol/l (interquartile range 8.62 to 8.72) to 7.24 mmol/l (6.70 to 7.52) with cholestyramine, to 8.09 mmol/l (7.18 to 8.68) with bezafibrate, and to 6.31 mmol/l (5.84 to 7.27) with the combination. This fall was due almost entirely to a decrease in the low density lipoprotein cholesterol concentration, and the combination was significantly more effective than either drug alone. The 98% confidence intervals for the median differences between the combination and cholestyramine and the combination and bezafibrate were 0.04 to 1.49 mmol/l and 0.51 to 2.18 mmol/l respectively. These results suggest that this combination is an effective and useful treatment in heterozygous familial hypercholesterolaemia.

Non-enzymatic glycosylation of plasma lipoproteins in vitro

Human very low density lipoprotein (VLDL), low density lipoprotein (LDL) and high density lipoproteins (HDL2 and HDL3) were glycosylated in vitro by incubation with high concentrations of glucose and glucose-6-phosphate. Glycosylated lipoproteins showed enhanced mobility on agarose electrophoresis when compared to control lipoproteins, samples treated with glucose-6-phosphate being more strongly affected. Extent of glycosylation of LDL was determined using thiobarbituric acid, LDL incubated with glucose exhibiting degrees of glycosylation 15-117% in excess of control. LDL incubated with glucose-6-phosphate however, gave values similar to those obtained with control incubations. Amino acid analysis of protein hydrolysates prepared from VLDL and LDL fractions incubated with glucose revealed reductions of up to 53% in the levels of free lysine when compared to control lipoprotein samples. The appearance of 2 novel peaks, probably corresponding to glucosyllysine, was also observed. The effects seen with glucose-6-phosphate however, were not as marked as expected. None of the other amino acids measured were decreased. These data show that plasma lipoproteins can be glycosylated in vitro and that an indication of the degree of glycosylation (by glucose) may be obtainable using thiobarbituric acid. Amino acid analysis revealed that the probable binding site for glucose on the apoproteins are the lysine residues. Although glucose-6-phosphate also binds to lysine residues the effects produced by this agent on plasma lipoproteins may also involve other mechanisms requiring further investigation.