Alterations of excitatory amino acid receptors in the brain of manganese-treated mice

An excessive activation of excitatory amino acid (EAA) receptors has been associated with oxidative stress, which is considered the primary cause of manganese (Mn) poisoning neurotoxicity. Therefore, the EAA receptor distribution was analyzed by autoradiographic methods in several brain regions during Mn intoxication. We found that chronic treatment of mice with MnCl2 during 8 wk significantly alters the L-[3H]glutamate (L-[3H]Glu) binding to total glutamate (Glu) receptors, as well as to N-methyl-D-aspartate (NMDA) and quisqualate (QA) receptor subtypes. A generalized decrease of 16-24% of the L-[3H]Glu binding to total Glu receptors was found in all cortex, hippocampus, basal ganglia (except globus pallidus), and cerebellum. Saturation studies showed a significant reduction of the maximal number of receptors (Bmax) in Mn-treated mice, whereas the affinity (Kd) was not altered. L-[3H]Glu binding to NMDA sites was mainly decreased (10-21%) in a few cortical regions, basal ganglia (except globus pallidus), and hippocampus, whereas binding to QA receptor subtype was diminished (16-30%) in cortex, hippocampus, and cerebellum. The decrease of Glu receptor binding sites during Mn poisoning could reflect a receptor downregulation more than neuronal loss, since these reductions are moderate and diffuse. Thus, this down-regulation might mean a protection mechanism against an excitotoxic process associated with Mn toxicity.

Motor activity and quantitative autoradiographic analysis of muscarinic receptors in the brain of rats subjected to the forced swimming test

A cholinergic dysfunction has been involved in the neurobiological mechanisms of stress and depression. In the present study, we determined the autoradiographic distribution of muscarinic cholinergic receptors in the brain of rats subjected to the forced swimming test for 15 days. Motor activity was automatically analyzed daily before swimming. In the forced swimming test group, both total horizontal activity and ambulatory movements exhibited a significant decrease, when the data from 1st and 15th day were compared. Neither the affinity of [3H]-quinuclidinyl benzilate nor the maximal number of receptors were affected by the forced swimming test in the caudate-putamen, cortex, and hippocampus. The distribution of [3H]-quinuclidinyl benzilate binding sites did not show significant differences in the 30 analyzed areas. Further analysis of muscarinic receptor subtypes after forced swimming test would be necessary to discard any cholinergic involvement.

Manganese poisoning reduces strychnine-insensitive glycine binding sites in the globus pallidus of the mouse brain

Manganese (Mn) poisoning is characterized by central nervous system manifestations, including psychiatric disturbances and extrapyramidal disorders. This metal is thought to produce neuronal degeneration due to cytotoxic products originated by oxidative stress and through an indirect excitotoxic process. In previous studies, we have found a reduction in the density of N-methyl-D-aspartate (NMDA) recognition sites in some brain areas of Mn-treated mice. Due to the close relationship between NMDA sites and strychnine-insensitive glycine (Gly) modulatory sites in the NMDA receptor complex, the [3H]-glycine ([3H]-Gly) binding was analyzed by autoradiographic methods in the brain of mice treated with manganese chloride for 8 weeks. Among all analyzed areas, only the globus pallidus showed a significant reduction in [3H]-Gly binding (27-28%). The Gly binding decrease, focalized in the globus pallidus, could reflect a degeneration of structures containing strychnine-insensitive Gly receptors, since this area is the most frequently reported damaged brain region in Mn intoxication. However, it might also be due to a Gly receptor down-regulation to control NMDA complex activation during Mn poisoning.

Evidence that specific mtDNA point mutations may not accumulate in skeletal muscle during normal human aging

It is unclear at present whether specific mtDNA point mutations accumulate during normal human aging. In order to address this question, we used quantitative PCR of total DNA isolated from skeletal muscle from normal individuals of various ages to search for the presence and amount of spontaneous mtDNA point mutations in two small regions of the human mitochondrial genome. We observed low levels of somatic mutations above background in both regions, but there was no correlation between the amount of mutation detected and the age of the subject. These results contrasted with our finding of an age-related increase in the amount of the mtDNA "common deletion" in these very samples. Thus, it appears that both somatic mtDNA point mutations and mtDNA deletions can arise at low frequency in normal individuals but that, unlike deletions, there is no preferential amplification or accumulation of specific point mutations in skeletal muscle over the course of the normal human life span.

Mitochondrial myopathy simulating spinal muscular atrophy

A patient with a severe progressive neuromuscular disorder resembling spinal muscular atrophy is reported. The initial muscle biopsy was consistent with a denervating process. DNA analysis did not reveal deletions in exons 7 and 8 of the survival motor neuron gene. Histology, histochemistry, and biochemistry of a second muscle biopsy suggested mitochondrial myopathy accompanying the denervating features. Immunohistochemistry using anti-DNA antibodies revealed only nuclear staining in skeletal muscle, suggesting mitochondrial DNA depletion. In patients with clinical features of spinal muscular atrophy and no deletions in the survival motor neuron gene, mitochondrial DNA depletion should be considered.

Multiple mitochondrial DNA deletions in sporadic inclusion body myositis: a study of 56 patients

Inclusion body myositis, a chronic inflammatory disorder, is the most common cause of myopathy in adults over the age of 50. Diagnosis is based on clinical features and distinctive morphological findings by both light and electron microscopy. The causes of inclusion body myositis are still unknown. Ultrastructural mitochondrial changes and ragged-red fibers are common in patients with sporadic inclusion body myositis, and multiple [correction of mutiple] mitochondrial DNA (mtDNA) deletions have been reported in 3 such patients, suggesting that mtDNA mutations may have a pathogenetic role. We studied 56 patients with sporadic inclusion body myositis, using a combination of clinical, morphological, biochemical, and molecular genetic analyses to determine the frequency and the distribution of mtDNA deletions. Using the polymerase chain reaction, we found multiple mtDNA deletions in 73% of patients, compared to 40% of normal age-matched control subjects and 47% of disease control subjects. The presence of deletions correlated with morphological evidence of ragged-red, cytochrome c oxidase-negative fibers, and with defects of complexes I and IV of the electron transport chain. Although aging may account for a proportion of mtDNA deletions in patients with sporadic inclusion body myositis and control subjects, mtDNA alterations may be accelerated in sporadic inclusion body myositis.

Fatigue of resin-bonded amalgam restorations

Standardized MOD cavities were prepared in 80 human premolars, which were treated with either adhesive resin or copal varnish and then restored with amalgam. Fracture resistance of these groups was compared after 24 hours of storage, 4 weeks of storage with thermocycling, and after 500 days of storage. The buccal cusps were loaded at an angle of 30 degrees to the tooth long axis until fracture occurred. Additionally, survival curves were compared for adhesive resin and copal varnish groups that had been repeatedly load cycled until fracture occurred. The 24-hour adhesive resin group was significantly stronger than the corresponding copal varnish group (P < 0.05). However, no significant differences between adhesive resin and copal varnish were found for the other thermocycling, extended 500-day storage, or load cycling tests. In conclusion, the strengthening effect of an adhesive resin on teeth restored with MOD amalgam restorations was transient.

Chromosome 12-linked autosomal dominant scapuloperoneal muscular dystrophy

Scapuloperoneal syndromes are characterized by their distribution of muscle weakness and wasting. The reported pattern of inheritance has been variable. Both neurogenic and myopathic forms of autosomally dominantly inherited scapuloperoneal syndrome have been described. It has been suggested that these are variants of other neuromuscular diseases. We examined 44 members from a family with 14 members affected with a scapuloperoneal syndrome. Physiological and histological analysis implied that this condition is predominantly myopathic. Linkage analysis was done to confirm the genetic etiology of the disease in this family and to evaluate the possibility that it is a allelic variant of other neuromuscular diseases. Genetic analysis demonstrated linkage of the disease to chromosome 12, which makes it genetically distinct from other loci known to cause neuromuscular disease. Muscle fibers with hyaline desmin-containing cytoplasmic inclusions in combination with focal myopathic changes may be a disease-specific morphological marker of the disease.

Ascaris lumbricoides infestation as a cause of intestinal obstruction in children: experience with 87 cases

PURPOSE

The purpose of this study is to describe the occurrence and management of bowel obstruction caused by Ascaris lumbricoides, a common parasite in warm climates that affects children with limited socioeconomic means.

METHODS

Eighty-seven patients with intestinal infestation owing to Ascaris lumbricoides were treated in the past 10 years (1984-1994). There were 48 (55.2%) girls and 39 (44.8%) boys. The mean age was 4.6 years, with peak occurrence at 2 years of age. Half the patients had a history of passing worms by mouth or anus. The majority of patients, 64 (73.5%), presented with a subacute clinical course; 23 (26.5%) had acute presentation, with severe abdominal pain, fever, dehydratation, vomiting, and abdominal distension and required vigorous fluid resuscitation and emergency surgical intervention. Diagnosis was achieved with plain abdominal roentgenograms, which showed a "whirlpool" pattern of intraluminal worms in most cases.

RESULTS

Six patients had been incorrectly diagnosed as having appendicitis; two cases had appendicitis owing to Ascaris in the cecum and distal ileum. The majority of cases with a subacute presentation respond to medical (anthelmintic) management using oral administration of racine oil and piperazine. Of the 23 patients taken to the operating room, 11 required external "milking" of the obstructing bolus of worms from the ileum into the colon, six required intestinal resection and end-to-end anastomosis, six had an appendectomy, and three needed an enterotomy to manually extract the worms. In one case, initial management consisted of an ileostomy because of intraoperative instability owing to sepsis. Subsequently, after stabilization and treatment with anthelmintic agents, closure of the stoma with an end-to-end ileocolostomy was performed. There was no significant postoperative morbidity or mortality.

CONCLUSION

These observations suggest that physicians should have a high index of suspicion for parasitic infestation in warm climates where economically deprived children present with symptoms of intestinal obstruction. Ascaris lumbricoides may be the cause of these events in endemic areas. Oral piperazine and racine oil can successfully resolve most subacute cases; however, aggressive resuscitation and prompt surgical intervention in patients with intestinal obstruction result in a satisfactory outcome.

A new mutation associated with MELAS is located in a mitochondrial DNA polypeptide-coding gene

We report a patient with mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes (MELAS) who harbored a novel missense mutation at mtDNA position 9957 in the gene specifying subunit III of cytochrome c oxidase (COX III). This T-->C transition converted Phe-251, a highly conserved amino acid in the C-terminus of the polypeptide, to Leu. The mutation, which was not present in 107 normal controls or in 57 patients with various mitochondrial diseases, was heteroplasmic in both muscle and blood of the proband and in blood from his asymptomatic mother. These results provide evidence that the MELAS clinical phenotype can be due not only to mutations in mtDNA-encoded tRNA genes, but in polypeptide-coding genes as well.

Immunohistochemical alterations of dystrophin in congenital muscular dystrophy

The dystrophin distribution in the plasma muscle membrane using immunohystochemistry was studied in 22 children with congenital muscular dystrophy. The dystrophin was detected by immunofluorescence in muscle biopsy through a polyclonal antibody. All the cases had patchy interruptions of the fluorescence in the plasma membrane. A large patchy interruption of the sarcolemma was found in 17 cases, small interruption in 12, and a combination of large and small patchy discontinuity in 7. Small gaps around the fiber like a rosary were found in 15 cases. The frequency of these abnormalities ranged cases from: all fibers in 5 cases, frequent in 8, occasional in 5, and rare in 4. Five cases had total absence of immunofluorescence. These results suggest that the dystrophin expression is abnormal in this group of children and that this type of abnormalities can not be differentiated from early Becker muscular dystrophy nor childhood autosomal recessive muscular dystrophy through immunohystochemistry alone.

Paucity of deleted mitochondrial DNAs in brain regions of Huntington's disease patients

Mitochondrial DNA deletions (delta-mtDNAs), originally found at high levels in patients with sporadic mitochondrial encephalomyopathies, have also been found to accumulate at extremely low levels during normal human aging, especially in long-lived postmitotic tissues such as muscle and brain. We have now quantitated the amount of one such delta-mtDNA species, the so-called 'common deletion', in brain regions from patients with Huntington's disease (HD). Surprisingly, we found a marked decrease in the amount of this delta-mtDNA in the occipital cortex and putamen as compared to age-matched controls; however, no change was found in caudate. Using immunohistochemistry of brain sections, we found no differences in the staining pattern for selected respiratory chain polypeptides between the HD and control tissues. The reduction in the amount of delta-mtDNAs in HD may be related in part to the astrocytic gliosis in the affected areas, in which the deletion-rich neurons are replaced by relatively deletion-poor astrocytes.

Segregation patterns of a novel mutation in the mitochondrial tRNA glutamic acid gene associated with myopathy and diabetes mellitus

We have identified a novel mtDNA mutation in a 29-year-old man with myopathy and diabetes mellitus. This T-->C transition at mtDNA position 14709 alters an evolutionarily conserved nucleotide in the region specifying for the anticodon loop of the mitochondrial tRNA(Glu). The nt-14709 mutation was heteroplasmic but present at very high levels in the patient's muscle, white blood cells (WBCs), and hair follicles; lower proportions of mutated mtDNA were observed in WBCs and hair follicles of all examined maternal relatives. In the patient's muscle, abnormal fibers showed mitochondrial proliferation, severe focal defects in cytochrome c oxidase activity, and absence of cross-reacting material for mitochondrially synthesized polypeptides. These fibers had higher levels of mutated mtDNA than did surrounding "normal" fibers. Although the percentage of mutated mtDNA in WBCs from family members were distributed around the percentage observed in the mothers, the pattern was different in hair follicles, where the mutated population tended to increase in subsequent generations. PCR/RFLP analysis of single hairs showed that the intercellular variations in the percentage of mutated mtDNA differed among family members, with younger generations having a more homogeneous distribution of mutated mtDNA in different hair follicles. These results suggest that the intercellular distribution of the mutated and wild-type mtDNA populations may drift toward homogeneity in subsequent generations.

Autoreceptor presynaptic control of dopamine release from striatum is lost at early stages of manganese poisoning

Manganese (Mn) poisoning in man produces an early psychotic disorder that is later followed by a Parkinson-like syndrome. Since alterations in the brain DA system are thought to be involved, we assessed the presynaptic autoreceptor regulation of K(+)-evoked 3H-DA release from superfused striatal slices of mice treated i.p. with 5 mg Mn/kg weight/day for 2 and 8 weeks. Mn poisoning did not change basal and evoked DA release. In controls, 1 microM apomorphine (APO), a D2-like DA receptor agonist, produced an inhibition of K(+)-evoked 3H-DA release that was blocked by the D2-like DA receptor antagonist, S(-)-sulpiride (1 microM). Yet, APO lost its capacity to inhibit the K(+)-evoked 3H-DA release after 2 weeks of Mn poisoning. After 8 weeks of Mn poisoning, APO was again able to reduce K(+)-evoked 3H-DA release. MK-801 (0.3 microM), a NMDA-glutamate receptor antagonist, could restore APO inhibitory control on DA release lost at week 2 of Mn poisoning. These findings suggest a NMDA-glutamate-receptor-mediated loss of autoreceptor presynaptic control of striatal DA release at early Mn poisoning.

Myoclonic epilepsy with ragged-red fibers (MERRF): an immunohistochemical study of the brain

Myoclonic epilepsy with ragged-red fibers (MERRF) is a maternally inherited disorder of oxidative phosphorylation due to specific point mutations within the mitochondrial tRNA(Lys) gene. Mitochondrial dysfunction in the central nervous system (CNS) of patients with MERRF accounts for the neurological manifestations of the disease. Antibodies against subunits of complex I, III, IV and V of the respiratory chain were used to study the expression of these proteins in the frontal cortex, cerebellum and medulla from an autoptic case of MERRF. We found a selective decreased expression of subunit II of cytochrome c oxidase (COX-II) in these regions. Immunohistochemical abnormalities were more widespread than the lesions described by traditional histopathological techniques and made possible an attempt of explanation for the neurological symptoms of the patient.

High levels of mitochondrial DNA with an unstable 260-bp duplication in a patient with a mitochondrial myopathy

Other investigators reported the presence of low levels of a 260-bp heteroplasmic duplication of mitochondrial DNA in patients with mitochondrial DNA deletions and their asymptomatic mothers. In this study, we were not able to detect this polymorphism in 30 patients with mitochondrial DNA deletions, but the 260-bp duplication was detected in relatively high levels (32% in muscle) in a patient with a slowly progressive mitochondrial myopathy. The duplication was also present in cultured fibroblasts (10%) and in WBC (< 1%). Mitochondrial dysfunction in this patient was evidenced in muscle by the presence of ragged-red fibers and a partial decrease in cytochrome c oxidase activity. We also detected low levels of mitochondrial DNA harboring a triplication of the 260-bp region, indicating that this polymorphism is unstable. Taken together, our results suggest that an unstable 260-bp duplication, which includes important mitochondrial DNA cis-acting regulatory sequences, may be pathogenic per se, if present at high levels.

Gap junctions between fibroblasts in rat myotendon

We applied conventional and freeze-fracture electron microscopy to study intercellular contacts between the processes of fibroblasts in the myotendon of the rat exterior digitorium longus. The results showed well defined gap junctions between the cell processes, while other cell junctional structures such as tight junctions and desmosomes were not recognizable. The present study suggests that the gap junctions represent a structure to coordinate the activities of fibroblasts distributed in the myotendon of the muscle.

Huntington's disease gene: regional and cellular expression in brain of normal and affected individuals

Huntington's disease (HD) is an autosomal dominant disorder characterized by involuntary movements, dementia, and progressive, global, but regionally accentuated, brain atrophy. The disease affects the striatum most severely. An expansion of a trinucleotide repeat on chromosome 4p16.3 within the coding region of a gene termed IT15 has been identified as the mutation causing HD. The normal function of IT15 and the mechanisms by which the presence of the mutation causes HD are unknown. Although IT15 expression has been detected in the brain, as well as in other organ tissues, by Northern blot and in situ hybridization, it is not known whether a preferential regional or cellular expression of IT15 exists within the central nervous system of normal, affected, and presymptomatic individuals. Using quantitative in situ hybridization methods, we examined extensively the regional and cellular expression of IT15. In controls, IT15 expression was observed in all brain regions examined with the highest levels seen in cerebellum, hippocampus, cerebral cortex, substantia nigra pars compacta, and pontine nuclei. Expression in the striatum was intermediate and expression in the globus pallidus was low. IT15 was expressed predominantly in neurons; a low but significant level of expression was seen in glial cells. Analysis of grain counts per square micrometer in neurons showed that the regional differences in the level of mRNA expression were related to density and size of neurons in a given region and not primarily to differences in levels of mRNA expression in individual cells after correction for cell size. Neurons susceptible to degeneration in HD did not selectively express high levels of IT15 mRNA. In HD brains (grades 2-4), the distribution and levels of IT15 mRNA were comparable with controls in all areas except in neostriatum where the intensity of labeling was significantly reduced. Presymptomatic HD brains had a striatal expression similar to controls and surviving striatal neurons in more advanced HD had an expression of IT15 within normal limits. It is apparent from these results that the presence of expanded trinucleotide repeats in HD does not result in the absence of IT15 mRNA expression or in altered patterns or levels of expression. The lack of correlation between the levels of IT15 mRNA expression and susceptibility to degeneration in HD strongly suggests that the mutant gene acts in concert with other factors to cause the distinctive pattern of neurodegeneration in HD.

Phenotype-genotype correlations in skeletal muscle of patients with mtDNA deletions

Large-scale deletions of mitochondrial DNA (mtDNA) have been associated with a subgroup of mitochondrial encephalomyopathies, usually characterized by progressive external ophthalmoplegia (PEO) and mitochondrial proliferation in muscle fibers. We and others have shown that muscle from patients with mtDNA deletions have variable cytochrome c oxidase (COX) deficiency and reduction of mitochondrially-synthesized polypeptides in affected muscle fibers. The present work summarizes the phenotype-genotype correlations observed in patients' muscle. In situ hybridization revealed that, while most COX-deficient fibers had increased levels of mutant mtDNA, they almost invariably had reduced levels of normal mtDNA. PCR quantitation of both deleted and wild-type mtDNAs in normal and respiration-deficient muscle fibers from patients with the "common deletion" showed that deleted mtDNAs were present in normal fibers (31 +/- 26%), but their percentages were much higher in affected fibers (95% +/- 2%). Absolute levels of deleted mtDNA were also increased in affected fibers, whereas absolute levels of wild-type mtDNA were significantly reduced. Taken together, our results suggest that although a specific ratio between mutant and wild-type mitochondrial genomes is probably the major determinant of the respiratory chain deficiency associated with mtDNA deletions, the reduction in the absolute amounts of wild-type mtDNA may also play a significant pathogenetic role.

Manganese toxicity: free amino acids in the striatum and olfactory bulb of the mouse

We studied the levels of twenty two free amino acids in the striatum and olfactory bulb of mice treated during nine weeks with daily intraperitoneal injections of manganese chloride at a concentration of 5.0 mg Mn+2/kg body weight. In the olfactory bulb the contents of alanine, alpha-amino-n-butyrate, arginine, asparagine, aspartate, citrulline, GABA, glutamate, glycine, isoleucine, leucine, methionine, phenylalanine, serine, threonine, tyrosine, and valine were diminished. No alterations were observed in the concentrations of free amino acids in the striatum of Mn-treated mice. The changes detected in the olfactory bulb merit a thorough evaluation in order to determine its importance on the pathophysiology of manganese poisoning.

Inhibition of pig oocyte in vitro fertilization by the action of components of the zona pellucida

The aim of the present study was to determine whether the previous addition of porcine zona pellucida (ZP) components to spermatozoa of the same species has an inhibitory effect on in vitro fertilization (IVF). Boar spermatozoa were exposed to whole porcine solubilized zona pellucida (SZP), ZP glycoproteins (55 kDa and 90 kDa) and peptides (37 kDa, 40 kDa and 68kDa). Doses tested were 40, 70 and 100 mug/ml. In vitro fertilization was clearly inhibited by each component when the oocytes were compared with those fertilized with untreated spermatozoa. All the components had an effect in a dose dependent manner.