Beta cell compensation for insulin resistance in Zucker fatty rats: increased lipolysis and fatty acid signalling

AIMS/HYPOTHESIS

The aim of this study was to determine the role of fatty acid signalling in islet beta cell compensation for insulin resistance in the Zucker fatty fa/fa (ZF) rat, a genetic model of severe obesity, hyperlipidaemia and insulin resistance that does not develop diabetes.

MATERIALS AND METHODS

NEFA augmentation of insulin secretion and fatty acid metabolism were studied in isolated islets from ZF and Zucker lean (ZL) control rats.

RESULTS

Exogenous palmitate markedly potentiated glucose-stimulated insulin secretion (GSIS) in ZF islets, allowing robust secretion at physiological glucose levels (5-8 mmol/l). Exogenous palmitate also synergised with glucagon-like peptide-1 and the cyclic AMP-raising agent forskolin to enhance GSIS in ZF islets only. In assessing islet fatty acid metabolism, we found increased glucose-responsive palmitate esterification and lipolysis processes in ZF islets, suggestive of enhanced triglyceride-fatty acid cycling. Interruption of glucose-stimulated lipolysis by the lipase inhibitor Orlistat (tetrahydrolipstatin) blunted palmitate-augmented GSIS in ZF islets. Fatty acid oxidation was also higher at intermediate glucose levels in ZF islets and steatotic triglyceride accumulation was absent.

CONCLUSIONS/INTERPRETATION

The results highlight the potential importance of NEFA and glucoincretin enhancement of insulin secretion in beta cell compensation for insulin resistance. We propose that coordinated glucose-responsive fatty acid esterification and lipolysis processes, suggestive of triglyceride-fatty acid cycling, play a role in the coupling mechanisms of glucose-induced insulin secretion as well as in beta cell compensation and the hypersecretion of insulin in obesity.

Dominantly inherited ataxias in Portugal

We analysed the clinical features of 82 patients with dominantly inherited ataxia in a cohort survey. All patients fulfilled the diagnostic criteria for Machado-Joseph disease. The mean age of onset of symptoms was 39.8 (+/- 12.5) years and the duration of the disease was 9.2 (+/- 6.7) years. Ataxia, peripheral neuropathy, and fasciculation scores correlated with age of onset and duration of disease. Upper motor neuron scores failed to correlate with age of onset. In a follow-up study we analysed the clinical data of 46 patients two years after the first examination. A paired t-test was used to compare differences between observations. The results are in agreement with those of the cross-section in time, suggesting a deterioration of the symptoms with the evolution of the disease. We conclude that dynamic definition of the disease according to age of onset and duration of symptoms is preferable to subdivision into classical types.

Linkage studies of Friedreich ataxia by means of blood-group and protein markers

Friedreich ataxia (FA) is an autosomal recessive, neuro-degenerative disorder in which the pathogenetic mechanism remains unidentified despite extensive biochemical studies. Genetic-linkage studies provide an alternative approach to determining the basic defect. Linkage analysis between FA and 36 polymorphic-blood-group and protein markers has been carried out on three separate patient populations--16 families from the inbred Acadian population of Louisiana, 21 French-Canadian families from Quebec, and nine apparently unrelated British families--in an attempt to determine the chromosomal location of the disease mutation. Neither evidence of linkage to any of the markers investigated nor heterogeneity among the populations was found for any of the comparisons. The negative lod scores exclude the locus for FA from greater than 20% of the genome.

MPTP potentiates iron-induced lipid peroxidation without the involvement of free radicals derived from oxygen

We demonstrate here that MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) potentiates iron-catalyzed lipid peroxidation in intact erythrocytes, whereas it does not mediate hydrogen peroxide catalysed lipid peroxidation. The malonaldehyde formation which results from this lipid peroxidation is generated in the absence of superoxides, hydroxyl radicals, hydrogen peroxide or singlet oxygen. The MPTP reaction is blocked by addition of iron +2 chelator but not by iron +3 chelator. These results suggest that an iron-MPTP complex promotes the formation of lipid peroxidation by interacting directly with membrane polyunsaturated lipids.

Erythrocyte antioxidant activity in human patients with Parkinson's disease

Three groups have reported defective antioxidant mechanisms in substantia nigra of patients with Parkinson's disease, namely a decreased catalase and peroxidase activity, a reduction of glutathione and, more recently, a diminished nigral glutathione peroxidase activity. We decided to investigate these mechanisms in erythrocytes to determine whether these brain defects represent generalized or genetic aberrations, in which case they should also be present in blood cells. The glutathione cycle has been investigated (reduced and oxidized glutathione, glutathione reductase and peroxidase) plus the activities of catalase and superoxide dismutase. The basal malonaldehyde content of erythrocytes was used as an index of endogenous lipid peroxidation. None of the above-mentioned parameters were found altered in erythrocytes of parkinsonians, suggesting that no genetic or generalized biochemical abnormalities underly the deficiencies detected in substantia nigra.

Ecogenetics of Parkinson's disease: prevalence and environmental aspects in rural areas

We make use of the unique combination of a homogeneous genetic and racial origin in the rural population of Quebec and the facilities of free and universal access to medical care, to study the distribution of the prevalence of Parkinson's disease in the 9 rural hydrographic regions of the Province. Through 3 different methods of ascertainment, confirmed by two control probes, we demonstrate that the prevalence of Parkinson's disease is of uneven distribution within rural areas. We further investigated the characteristics of the regions of high prevalence. These regions which are predominantly agricultural and areas of intensive market gardening were also the areas with the highest use of pesticides.

Ecogenetics of Parkinson's disease: 4-hydroxylation of debrisoquine

It is postulated that Parkinson's disease is the result of environmental factors acting on genetically susceptible individuals against a background of normal ageing. Many potentially neurotoxic xenobiotics are detoxified by hepatic cytochrome P450. The function of one such system was studied in forty patients with Parkinson's disease and forty normal control subjects. Significantly more parkinsonian than control subjects had partially or totally defective 4-hydroxylation of debrisoquine. Poor metabolisers of debrisoquine tended to have had earlier onset of disease.

1-Methyl-4-phenyl-pyridinium-induced inhibition of nicotinamide adenosine dinucleotide cytochrome c reductase

The effect of 1-methyl-4-phenyl-pyridinium (MPP+), the main toxic metabolite of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), a parkinsonism-causing neurotoxin, upon the activity of nicotinamide adenine dinucleotide (NADH) cytochrome c reductase (EC 1.6.99.3) and upon that of glutathione reductase (EC 1.6.4.2) was monitored spectrophotometrically. For the cytochrome c reductase, the increase in absorbance of reduced cytochrome c was measured at 550 nm; for evaluating glutathione reductase, the absorbance of nicotinamide adenine dinucleotide phosphate (NADPH) was followed at 340 nm. MPP+ but not MPTP reversibly inhibited NADH cytochrome c reductase, but not glutathione reductase. This may be a direct mechanism of cell toxicity by this neurotoxin.

A method to quantitate Coomassie blue-stained proteins in cylindrical polyacrylamide gels

A method for the quantitation of Coomassie blue-stained proteins in cylindrical polyacrylamide gels is described. It involves an elution of the dye with an 80% methanol solution in a sealed Pyrex tube at 100 degrees C for 3 h and a measurement of its concentration at 585 nm. Using a 6.5% polyacrylamide gel and bovine serum albumin as a protein standard, the curve of absorbance of the dye solution as a function of the amount of protein was observed to be linear up to 30-40 micrograms of protein and as little as 0.8-1.0 micrograms of protein could be measured. The validity of the method was indicated by the values obtained for the relative proportions of the human erythrocyte membrane proteins. Using this method, the color yields of several proteins varying widely with respect to their size, amino acid composition, and carbohydrate content were determined in a 6.5% polyacrylamide gel. The results showed that they were generally the same except for proteins having a high carbohydrate content which were significantly lower.

Comparative behavioral, biochemical and pigmentary effects of MPTP, MPP+ and paraquat in Rana pipiens

We demonstrate that injections of 1-methyl-4-phenyl-1,2,3,6-tetra-hydropyridine (MPTP), 1-methyl-4-phenyl-pyridinium ion (MPP+) and Paraquat (PQ+) produce in Rana Pipiens different behavioral, biochemical and skin pigmentation changes. MPTP causes in frogs the main symptoms of Parkinsonism (rigidity, akinesia and tremor) and it darkens the skin of animals. It also decreases brain and, less so, adrenal medulla dopamine. These effects are blocked by Pargyline. MPP+ causes the same symptoms but more rapidly. In contrast, skin pigmentation is clearly lightened. Brain and particularly adrenal dopamine reserves are nearly abolished. Pargyline increases these effects. Paraquat, in a cumulative fashion, eventually causes the same behavioral changes and a slight increase in pigmentation. It initially produces an increase in brain and adrenal dopamine concentrations, but later a significant dopamine concentration decrease. Pargyline potentiates these long term effects, blocks the dopamine increase, but reverses the PQ+ effect upon melanin, producing the same depigmentation as MPP+ alone.

A catalyst function for MPTP in superoxide formation

We demonstrate that 1-methyl-4-phenyl-1,2-dihydropyridine (MPDP) can be generated, in an alternate pathway, from the catalyst action of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) upon the iron redox equilibrium reaction. Superoxide and ferric iron are instantaneously produced after addition of MPTP to a solution of ferrous iron. This reaction is oxygen and pH dependent. Superoxide, through a iron dependent Haber-Weiss reaction with peroxide, can generate the cytotoxic hydroxyl radical. A small portion of the superoxide reacts with MPTP to produce the reactive species X. which, in the presence of Fe+3 can also generate MPDP.

The specific vulnerability of the substantia nigra to MPTP is related to the presence of transition metals

We demonstrate that the high concentration of transition metals in the substantia nigra could be a major factor responsible for the specificity of cell damage by the Parkinsonism-causing neurotoxin MPTP. It will be shown that these metals in vitro, and MPTP, each potentiate the autoxidation of dopamine and the production of aminochrome through the generation of superoxide, hydroxyl radicals, hydrogen peroxide and reactive semiquinones. Moreover, the same metals contribute to the oxidation of MPTP itself, further enhancing dopamine autoxidation.

Gel chromatography on a Sepharose 4B column: earlier elution of protein-sodium dodecyl sulfate complexes of low Stokes radii

A procedure is described for the determination of the Stokes radius of a detergent micelle by gel chromatography. It was observed that different lots of Sepharose 4B can exhibit a wide variation in the permeation of their gel pores. It is shown that this variation is due to differences in their pore size distribution. It has been observed that protein-sodium dodecyl sulfate (SDS) complexes of high Stokes radii eluted on a Sepharose 4B column with Stokes radii lower than the theoretical, as it has been previously reported but that protein-SDS complexes of low Stokes radii (less than 70 A), contrary to what might have been expected, eluted with Stokes radii higher than the theoretical. Evidence was obtained that their anomalous elution is due to an interaction of the detergent SDS with the gel pores of small diameter.

New amphibian models for the study of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)

We report the development of two animal models in amphibians (frogs and salamanders) in whom 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) produces the behavioral (neurological) and biochemical equivalents of the human disease and, in addition, a measurable modification in at least one form of pigment-bearing cell from the neural crest, the skin melanocyte. We propose that this new approach can become an inexpensive, easily quantifiable model for the study of the effect of MPTP on the central and peripheral nervous systems. We also demonstrate that the toxic effect of MPTP can be completely abolished in vivo by treatment with a monoamine oxidase inhibitor and potentiated by an inhibitor of catechol-O-methyltransferase. MPTP is catabolised by oxidation into toxic metabolites, but 1-methyl-4-phenylpyridinium ion (MPP+), the proposed end-metabolite, is even more toxic than MPTP in this model, possibly through a different mechanism.

Plasma cholesteryl sulfate in Friedreich's ataxia

Alteration of membrane fluidity and anomalies of membrane structural proteins have been suspected in Friedreich's ataxia. Plasma lecithin:cholesterol acyltransferase (LCAT) activity is also lowered in this disease, presumably because of a substrate effect. The membrane-stabilizing effect of cholesteryl sulfate (CS) and its inhibitory effect on LCAT activity prompted us to measure this substance in the plasma of Friedreich's ataxia patients as well as in normal subjects and in patients with Charlevoix-Saguenay disease. Plasma cholesteryl sulfate concentrations were significantly higher in Friedreich's ataxia, with levels above the upper limit of normal in nearly half of the cases. This increase was unrelated to age, sex or plasma cholesterol levels, but closely associated with the severity of the disease and thus considered to be secondary. A similar phenomenon (except the association with severity) was observed in Charlevoix-Saguenay ataxia. Levels also tended to be higher in first-degree relatives of Friedreich cases. The significance of these findings is discussed in the light of recent knowledge and experimental data obtained in this laboratory on rats made deficient in essential fatty acids. The highest concentrations of CS observed in Friedreich's ataxia (1097 micrograms/dL, 6 times the normal mean) was only 25% as high as the concentrations reported to inhibit LCAT activity.

Cardiac malic enzyme in Friedreich's disease

We measured the activity of cytosolic and of mitochondrial malic enzyme in the hearts from 4 patients with Friedreich's disease and from two non-ataxic control subjects. There was a wide variability in the results and the slight overall decreases in both enzyme activities were not considered to be statistically significant. From these and other results, we conclude that deficient mitochondrial malic enzyme activity is not a constant or primary feature of Friedreich's disease.

Recessive ataxia in Acadians and "Cajuns"

The physician exposed to a large number of patients with a recessive form of ataxia, will occasionally observe slower progression forms which lack many of the severe features or cardinal symptoms of Friedreich's disease. We have studied 31 such cases in Acadians of the Maritime Provinces of Canada, and in their separated "cousins" from Louisiana, now called "Cajuns". These patients are compared to a consecutive series of 22 Friedreich's disease cases in French Canada. It is shown that the age of onset is slightly later, but the progression much slower and the age at death older in the Acadian patients. These cases develop signs of pyramidal and posterior column involvement gradually and later than the classical Friedreich. As a result, pes cavus and scoliosis are less marked, as well as muscle weakness and cardiomyopathy. On the other hand, the rate of progression of areflexic ataxia, the "core disease", is identical in both groups. The main difference in progression rates of the disorders occurs after 10-12 years of evolution, thus after the period of hormono-ponderal growth. These differences, coupled to the diverging genetic and genealogical backgrounds, are sufficiently large for the presumption of distinct disorders. Whether they are due to allelic mutations, linked but different genes, genes affecting the same metabolic pathway, but elsewhere or to completely distinct entities, will have to be left to further studies, but their existence in completely different populations and milieux is worthy of report.

Familial periodic ataxia responsive to acetazolamide

Two cases, a father and son, of recurrent cerebellar ataxia in the same family are reported, suggesting a familial trait for the dysfunction. In the older male the onset of each episode (30-90 min.) was signalled by dysarthria which then progressed towards gait ataxia; the son presented closely similar clinical symptoms. Physical examination and blood chemistry revealed no obvious neurological deficit or biochemical abnormalities, with the exception of I-III and III-IV evoked auditory wave interpeak latencies, which were found markedly abnormal on the left side in the father but not in the son; the EEG of both individuals showed some diffuse, slow wave abnormalities. A low dose of acetazolamide, 250 mg daily, has successfully repressed recurrence of the attacks over the past six months. Temporary withdrawal for 14 days of the carbonic anhydrase inhibitor in the father coincided with two observed ataxic episodes.

A clinical classification of hereditary ataxias

We present a working and flexible classification of inherited ataxic syndromes based on the use of simple tools available to every clinician: a good history (particularly pinpointing the age of onset, the rate of progression and the mode of inheritance) and a neurological examination (identifying the presence of ataxia, deep tendon reflexes in the knee, optic nerve, retinal and/or 8th nerve signs). This classification is easily coded for computer translation on any personal computer. The place occupied by a given disorder may, by contiguity, give a clue to its pathophysiology.

Origin of Friedreich's disease in Quebec

We have been able to trace 40 cases of classical Friedreich's disease from 14 previously unrelated French Canadian kindreds to one common ancestral couple arriving in New France in 1634: Jean Guyon and Mathurine Robin. One member of this couple presumably introduced one gene for Friedreich's disease into the French Canadian population. This gene has now been traced over 12 generations to both parents of the present cases. We plan to use this knowledge to study the spectrum of clinical manifestations of this gene and to carry out gene chromosomal localization studies, using the techniques of linkage and of molecular biology. Such studies in rare autosomal recessive disorders have previously been judged to be almost impossible.

Distribution of apolipoprotein E phenotypes in Friedreich's ataxia

Allelic polymorphism at the apolipoprotein E (apo E) gene locus (alleles epsilon 2, epsilon 3, and epsilon 4) is responsible for the existence of 6 discrete electrophoretic phenotypes of plasma apo E. Since the presence of the epsilon 2 allele in the genotype tends to be associated with higher triglyceride levels, a study was undertaken to determine if a higher frequency of this allele could account for the presence of higher plasma triglycerides in subsets of patients with Friedreich's Ataxia. The frequency of the apo E phenotypes was determined in 37 subjects with Friedreich's Ataxia and compared with that of 102 normolipidemic and 102 hyperlipidemic individuals. There was no increased prevalence of the E3/2 phenotype and the epsilon 2 allele in the Friedreich's sample as is found in a hyperlipidemic sample. Furthermore, the epsilon 2 subset did not have significantly higher plasma triglycerides than the non-epsilon 2 subset and the hypothesis was rejected. On the other hand, there was a trend for a decreased frequency of the E4/3 phenotype in the Friedreich's sample relative to the hyperlipidemic group but the difference did not reach statistical significance. The apo E phenotype distribution was also measured in a smaller sample of Charlevoix-Saguenay disease; this led to the discovery of two siblings with the relatively rare E2/2 phenotype and unexpectedly low levels of plasma lipid and lipoprotein concentrations. Plasma apolipoprotein E concentrations in both diseases were within the normal range except for subjects bearing the E2/2 phenotype.

Friedreich's ataxia: malic enzyme activity in cellular fractions of cultured skin fibroblasts

We have measured the activity of malic enzyme NADP+ dependent in the nuclear, mitochondrial, lysosomal and cytosolic fractions of cultured skin fibroblasts from twelve patients with Friedreich's ataxia and nine control subjects. Hexosaminidase, cytochrome-C-oxidase, lactate dehydrogenase and malic enzyme NAD+ dependent were used as marker enzymes. The activity of malic enzyme NADP+ dependent was not significantly reduced in the mitochondrial fraction of patients with Friedreich's ataxia as compared with controls. When corrected for possible contamination between mitochondrial and cytosolic fractions, malic enzyme NADP+ dependent activity was still not significantly reduced in patients with Friedreich's ataxia. Unless critical methodological differences were overlooked in this or previously published studies, we conclude that mitochondrial malic enzyme deficiency is not the primary genetic defect underlying Friedreich's ataxia.

Lysosomal enzymes in ataxia: discovery of two new cases of late onset hexosaminidase A and B deficiency (adult Sandhoff disease) in French Canadians

We have measured in leukocytes the following lysosomal enzymes in 11 Friedreich disease cases, 11 "atypical" recessive ataxias, 13 neurological controls and 16 normal controls: hexosaminidase A and B; beta-galactosidase and neuraminidase (labile and cold stable, or A and B). The lysosomal enzyme deficiencies known to produce certain forms of spinocerebellar degeneration were not present in Friedreich's disease or the Charlevoix-Saguenay syndrome. The very small scale survey of "atypical" recessive ataxias revealed 3 cases of severe deficiencies in hexosaminidase activity. Two adult brothers presenting with the clinical phenotype of Kugelberg-Welander disease (one also with ataxia), were shown to have a severe deficiency of both HEX A and HEX B activity (Sandhoff biochemical pattern). This is the first such report. A further adult female patient, unrelated to the others, had a severe isolated deficiency of HEX B and presented with a very slowly progressive and mild ataxia with severe internal strabismus. These patients and their families are being studied clinically and biochemically in greater detail and will be reported elsewhere. However these preliminary findings justify screening for such lysosomal defects in all cases of "atypical" recessive ataxia.

Visual evoked potentials and brain stem auditory potentials in Friedreich's ataxia--a longitudinal study

Six patients with Friedreich's ataxia, 4 males and 2 females, their ages ranging from 13 to 33 years, were studied. The early manifestations started between age 7 and 13 with an evolution time between 6 and 20 years. Serial visual and brain stem auditory evoked potential recordings were made. A progressive increase in latency, reduction in amplitude and in latency inter-ocular difference of P100 were observed. The pattern of the reversal checker-board visual evoked potential was preserved. A disorganized BAEP pattern, a well defined potential I, a very small potential V and a delay in the interpeak latency were constant findings. The assumption is made of a progressive involvement of both visual and central auditory pathways. Pathophysiological mechanisms are discussed.

Hair trace elements in Friedreich's disease

Concentrations of zinc, copper, manganese, chromium, cobalt and selenium were measured in the hair obtained from subjects with Friedreich's disease, other inherited ataxias and neurological control patients. Although zinc and copper concentrations were significantly higher in Friedreich than in the two control groups, the mean values for all groups were well within the normal range. No major deficiency in zinc or selenium was demonstrated in Friedreich's disease using the approach. This does not, however, indicate that there is no defect in zinc and selenium metabolism, availability or transport in this disorder.

The Quebec Cooperative Study of Friedreich's Ataxia: 1974-1984--10 years of research

In this paper the author reviews the progress accomplished in the understanding of Friedreich's disease since the start of the "Quebec Cooperative Study of Friedreich's Ataxia" in 1974. The last ten years have indeed seen important strides taken in the definition and nosography of the hereditary ataxias and the characterization of a number of new entities. Biochemically, the principal leads uncovered during the initial prospective survey, have been pursued to great detail. Unfortunately no clear-cut constant and severe enzyme block in the principal metabolic pathways has yet been identified, despite intensive studies. It is postulated that the defect may instead be a regulatory one and involve a decreased availability or utilization of one of the vitamin cofactors that are known experimentally, or clinically, to produce central nervous system damage with ataxia: Vitamin E, Biotin or Pantothenic Acid. Studies in that direction and in molecular genetics to localize the Friedreich's disease gene are being undertaken for the next phase of the Cooperative Study.

Platelet taurine content in Friedreich's disease

We have studied the concentrations of taurine and of 6 other amino acids in platelets from 12 patients with Friedreich's disease and 12 age sex-matched normal control subjects. No significant differences could be demonstrated between the two groups. The glycine/serine ratio was lower in all the patients but this change did not reach statistical significance. From these and other data, we conclude that the taurine retention deficit observed previously in Friedreich's disease cannot be the primary causal defect.

The natural history of Machado-Joseph disease. An analysis of 138 personally examined cases

We have examined 138 cases of a disorder previously described in people of Portuguese origin and which has received many names. By computer analysis of 46 different items of a standardized neurological examination carried out in each patient, we have been able to delineate the main components of the clinical presentation, to conclude that the marked variability in clinical expressions does not negate the homogeneity of the disorder, and to describe the natural history of this entity which should be called, for historical reasons, "Machado-Joseph Disease". This hereditary disease has an autosomal dominant pattern of inheritance, presenting as a progressive ataxia with external ophthalmoplegia, and should be classified within the group of "Ataxic multisystem degenerations". When the disease starts before the age of 20, it may present with marked spasticity, of a non progressive nature but often so severe that it can be accompanied by "Gegenhalten" countermovements and dystonic postures but little frank dystonia. There are few true extrapyramidal symptoms except akinesia. When the disease starts after the age of 50, the clinical spectrum is mostly that of an amyotrophic polyneuropathy with fasciculations accompanying the ataxia. For all the other cases the clinical picture is a continuum between these two extremes, the main determinant of the clinical phenotype being the age of onset and a secondary factor, the place of origin of the given kindred. The ataxic and amyotrophic components are clearly progressive with time in contrast to the spasticity component. Although the majority of known cases are of Portuguese origin, this is not obligatory. The next research endeavour should be a search for the chromosomal site of the gene, using molecular biology technology such as those for recombinant DNA.

Etiology of Parkinson's disease: A research strategy

In this essay I present a new "global approach hypothesis" to explain the pathophysiology of Parkinson's disease: "Susceptibility to Parkinsonism is genetically determined and is reflected in all cells. I propose that idiopathic Parkinson's disease is the combined result of a generalized cell aging process accelerated, in susceptible individuals, by a variety of often repetitive trigger factors. These factors have in common the fact that they cause a transient increase in turnover within catecholamine producing neurons, centrally as well as peripherally. This results in accumulation within these neurons of free radicals. When the level of the toxic substances, in quantity or in time of exposure, exceeds the scavenging capacity of the cell, damage to organelles and to membranes results, leading to the formation of Lewy bodies through an autoimmune reaction to damaged filaments and to cell death, particularly in the pigmented neurons of the brainstem. The progressive cell depletion leads to a compensatory increase in catecholamine turnover in the remaining pigmented cells, and an ever-accelerating degenerative process. The resulting neurotransmitter imbalance in the basal ganglia explains the symptoms of Parkinson's disease". In the light of this hypothesis, our research objectives should be (1) to delineate the limits of true Parkinson's disease from all phenocopies; (2) to identify individuals susceptible to parkinsonism and the most common trigger factors; (3) to reduce the metabolic effects of unavoidable trigger factors and (4) to protect susceptible individuals by increasing the functional availability of free radical trapping agents.

Familial subsets in idiopathic Parkinson's disease

In the present paper we explore in some detail the hypothesis that the presence of familial aggregations in 10-15% of Parkinson's disease cases is due in great part to the existence of well-defined familial subsets, rather than to chance occurrences. We describe the clinical and genetic characteristics of the two main subsets: "Essential tremor-related Parkinsonism" and the "Familial akineto-rigid Syndrome" previously identified. The former type of Parkinsonism is associated at random, but with increased frequency, to an autosomal dominant disorder, usually essential tremor but occasionally OPCA. Two possible susceptibility factors were uncovered in this entity: an increased incidence of familial hyperthyroidism (augmentor factor) and a decreased incidence of the generally frequent HLA Haplotypes A1B8 or A2B5 (Protective factors). The other presentation, the "familial akineto-rigid syndrome", appears to be a definite disease entity with an autosomal recessive mode of inheritance (normal parents, increased incidence of identical parkinsonism in sibs, increased consanguinity rate in parents). This newly defined disorder deserves much further genetic and biochemical analysis.

Diagnostic problems in Parkinson's disease

The diagnosis of Parkinson's disease is not as easy as previously claimed, and presents a number of pitfalls. We present three rules, or aphorisms, to help the general practitioner in overcoming these diagnostic difficulties: Know well the basic disease and its symptoms. Use tricks to elicit apparently absent 'primary' symptoms. Beware of unusual symptoms or case histories. Examples of difficulties encountered at each level are given. Such analysis should permit the physician to classify his extrapyramidal patient within one of the many types of 'parkinsonism' as shown in Table 1.

Neurotensin affects hyperactivity but not stereotypy induced by pre and post synaptic dopaminergic stimulation

The effects of intraventricular administration of neurotensin (0.9, 3.75 and 15.0 micrograms) on hyperactivity and stereotypy induced by either amphetamine (1 mg/kg), nomifensine (20 mg/kg), apomorphine (0.5 mg/kg) or N-n-propylnorapomorphine (0.5 mg/kg) were examined. Results indicate that for each drug treatment, the effects of neurotensin were identical: hyperactivity was significantly reduced while stereotypy remained unaffected. Results also revealed that neurotensin significantly increased the hypothermia induced by apomorphine and N-n-propylnorapomorphine. Possible mechanisms which could underly neurotensin's selective inhibitory action on hyperactivity produced by both pre and post synaptic dopaminergic stimulation are discussed.

Oropharyngeal dysphagia and oculopharyngeal muscular dystrophy

Oculopharyngeal muscular dystrophy is an autosomal dominant transmitted condition seen mainly in French Canada. The largest number of publications on these patients concerns a Quebec family whose descendants have spread throughout the United States. Families of different ethnic origins have also been reported from around the world, although there is no evidence that the neuromuscular disease reported is the same, despite the similarity of the syndrome. When severe oropharyngeal dysphagia results, these patients can significantly benefit from a cricopharyngeal myotomy.

A prospective study of 50 cases of familial Parkinson's disease

In a recent paper (Barbeau and Pourcher, 1982) we demonstrated that so-called "idiopathic" Parkinson's disease is not a homogeneous entity, and defined the existence of a sub-group of patients with genetic parkinsonism. To investigate this last possibility, and to uncover possible metabolic clues as to the etiology of such cases, we carried out a prospective study of 50 kindreds with "familial" parkinsonism. Two control groups were similarly studied: 50 kindreds with essential tremor (neurological control group) and 50 kindreds originating from spouses of the previous patients (non neurological control group). We uncovered two main patterns of genetic transmission within the parkinsonian patients: a parkinsonism related to dominant essential tremor (34 kindreds; 10% of all Parkinsonians) and a recessive "akineto-rigid syndrome" (10 kindreds; 3-4% of all Parkinsonians). A further 4 kindreds assumed a pseudo-dominant pattern but were probably recessive. Finally 2 kindreds were obviously other entities presenting as "phenocopies" of Parkinson's disease. Metabolically, hyperthyroidism appeared to be more frequent in essential tremor and "essential-tremor related parkinsonism" kindreds, while hypothyroidism and possibly hypoparathyroidism (post surgery) seemed more frequent in the recessive akineto-rigid syndrome kindreds.

Taurine and tolerance to opioid peptides

The finding that taurine may possess an ability to inhibit development of tolerance to opioid peptides was demonstrated in the present study. Tolerance was produced in rats by five IVT administrations of DAME during 3 consecutive days. Pretreatment with taurine that had been injected IVT 10 min prior to every administration of DAME suppressed the development of tolerance to both the akinetic and analgetic effects of the peptide. In addition, taurine pretreatment inhibited the induction of hyperlocomotor activity which was observed in tolerant animals as the number of the DAME injections was increased. Tolerance to WDS effects also resulted from the repeated administration of the peptide. However, it could not be concluded from the present experimental condition that taurine affects development of tolerance to WDS, since the amino acid suppressed the induction of WDS from the first injection of DAME.

Effects of taurine on tolerance to [D-Ala2, Met5]enkephalinamide in rats

Effects of taurine on tolerance to [D-Ala2, Met5]enkephalinamide (DAME) were investigated in rats. Tolerance was produced by five intraventricular administrations of DAME (50 microgram) during 3 consecutive days. The magnitude of developed tolerance to DAME was not uniform for each behavioral parameter; tolerance to analgesia effects developed more intensively and rapidly from the repeated injections of the peptide than that to akinesia effects. Pretreatment with taurine (9.5 X 10(-2) M) which was injected in a volume of 10 microliter intraventricularly 10 min prior to every administration of DAME suppressed the development of tolerance to both analgesia and akinesia effects of this peptide, whereas pretreatment with L-leucine at the same concentration did not. Spontaneous locomotor activity was measured for 1 h after the 90-min behavioral observation period was completed. That activity increased with the number of the peptide injections. Taurine pretreatment inhibited the induction of 'hyper'-locomotor activity. These results support the view that taurine may possess an ability to inhibit development of tolerance to morphine-like peptides in rats.

Tissue lipids in acute acrylamide intoxicated rats

A preliminary survey of tissue lipid composition in acrylamide intoxicated rats is reported. The animals were injected intraperitoneally with acrylamide 50 mg/kg body weight per day for 10 days. Liver cholesterol, mainly in the ester fraction, was decreased in treated rats. When fatty acid composition of liver cholesterol esters was examined, the proportions of linoleate and stearate were found to be decreased and were compensated by the increase of palmitate. Atrophy of epididymal fat pad resulted in severe triglyceride depletion and a relative increase in the proportion of phospholipids and cholesterol. There was also a reduction of linoleate, palmitate and palmitoleate in triglycerides and phospholipids of this tissue. There were, however, only minor changes in the fatty acid profile of the sciatic nerve.

Quantitative metabolic profiling of alpha-keto acids in Friedreich's ataxia

The plasma distribution of alpha-keto acids was measured in 26 subjects including 8 patients with Friedreich's ataxia, 8 with the recessive spastic ataxia of Charlevoix-Sageunay and 10 healthy volunteers. The groups were matched with regards to age, sex, weight and the study was conducted under standardized dietary intake. The result indicate significant differences in the alpha-keto acids distribution between the groups.

Effect of a valine load test on plasma alpha-keto acids in Friedreich ataxia

To test the physiological significance in vivo of our previous in vitro finding of reduced valine dehydrogenase (VDH) activity in patients with Friedreich's Ataxia, we subjected ataxic patients and controls to an oral valine load test (1.0g) and measured the levels of branched chain alpha-keto acids in the plasma for 24 hours. We demonstrated a significantly higher peak for a alpha-keto isovaleric acid in Friedreich's Ataxia and a general trend towards higher than control values in all other alpha-keto acids measured, and at all times in the experiment. These changes are compatible with the postulated defect in regulation of the activity of VDH in this illness, but because of their small amplitude, they also indicate that a VDH deficiency is not the genetic defect in Friedreich's Ataxia.

Glutamate and aspartate do not modify the ataxic gait of acrylamide treated animals

The purpose of this experiment was to examine the effects of intraventricular injections of glutamate and aspartate on the gait of animals rendered ataxic by the administration of acrylamide. Contrary to their previously reported corrective influence on ataxia induced by 3-acetyl pyridine, these amino acids did not modify the ataxic gait of acrylamide treated animals. This suggests that glutamate and aspartate can act in cerebellar but not in peripheral types of ataxia in animals.

Pilot study of threonine supplementation in human spasticity

Threonine supplementation (500 mg/day) was given to 6 patients with genetic spasticity syndromes for a period of 12 months, followed by a 4-month observation period without medication. All 6 patients showed partial improvement of spasticity, intensity of knee jerks and muscle spasms without changes in true pyramidal tract signs. The improvement in motor performance, objectively measured, averaged 29% (19% in upper limbs and 42% in lower limbs). The range of overall improvement was 19--35% (7--30% for upper limbs; 25--67% for lower limbs). No toxic clinical or biochemical side effects were encountered. Thus threonine, a precursor of glycine, produced the same effect on spasticity than that previously observed with glycine. It is concluded that threonine supplementation is feasible and safe and that it deserves a controlled trial in well defined (preferably genetic) cases of spasticity.

A possible genetic pattern of taurine urinary excretion in Friedreich's Ataxia

The taurine urinary excretion pattern, before and after an oral load of 250 mg taurine, was studied in normal control subjects and in patients with typical Friedreich's ataxia. It was demonstrated that in both situations the ataxic patients fell within the sub-types of "intermediate" and "high taurine excretors" while non were "low taurine excretors". It was also demonstrated that the excretion of taurine after a load in the obligate heterozygotes parents of the ataxic patients was intermediate between normal controls and patients. It is postulated that patients with Friedreich's Ataxia lack normal regulation of the high affinity-low capacity uptake system for taurine (the TH system) in the brush border of kidney tubules. The low affinity-high capacity uptake system in the same membranes (the TL system) appears to be normal in Friedreich's patients. The normal allele could be called THN and the variant THF and this trait would be inherited in an autosomal recessive fashion if it is linked to the Friedreich phenotype. Whether this finding is or is not the basic genetic defect in Friedreich's Ataxia will require more studies to clarify, but it is of interest to note that a similar pattern appears to be present in the fibroblasts of these patients.

Pituitary responses to a neuroactive tripeptide (TRH) in Friedreich's ataxia families

Oral glucose tolerance, thyroid function tests, as well as thyrotropin, prolactin and growth hormone release after administration of thyrotropin releasing hormone, were evaluated in patients with Friedreich's ataxia and unaffected family members. Impaired glucose tolerance was found in the majority of family members, affected or not. Thyroid hormone levels and PRL and TSH responses to TRH, were similar in all and normal. However, GH responses to TRH were abnormal in half of the patients, but in none of the unaffected family members. Paradoxical responses to neuropeptides may characterize some Friedreich's ataxia patients, and may predict the possibility of therapeutic maneuvers with such peptides in these patients.

Leukocyte valine dehydrogenase activity in Friedreich's ataxia

We studied the activity of valine dehydrogenase (VDH) in leukocytes of 14 Friedreich's ataxia patients and of 14 normal control subjects. There was a significant 26% mean decrease in enzyme activity in the patients, a finding which could be responsible for the chronic accumulation of some alpha-keto acids with toxic metabolic consequences in that disease. However the deficiency was not present in all patients with the typical symptoms, nor was its magnitude sufficient to be considered the primary genetic defect in Friedreich's Ataxia.

Friedreich's disease 1982: etiologic hypotheses a personal analysis

The author reviews the arguments for and against the four etiologic hypotheses in Friedreich's disease that have been proposed since 1974: the "pyruvate hypothesis", the "lipid-membrane hypothesis", the "energy-defect hypothesis" and finally the "taurine hypothesis". While none of these hypotheses are mutually exclusive, the author shows that all of these mechanisms play some role in the pathophysiology of the symptoms, but that only the "taurine hypothesis" appears to be compatible with all the known facts and the biochemical abnormalities reported. The author proposed that the taurine retention defect (possibly due to a block in the high affinity-low capacity transport of taurine - The TH System) is a primary event in Friedreich's disease. Whether it is the primary genetic event still has to be determined.