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M Filion

Publications and source records attributed to M Filion.

At least 19 recordsLinked to original sources
PubMed1992

Cell-specific transcription of the peripherin gene in neuronal cell lines involves a cis-acting element surrounding the TATA box.

Peripherin is a neurone-specific intermediate filament protein expressed mostly in the peripheral nervous system. To localize sequences that are important for the regulation of peripherin gene transcription, we have functionally dissected its promoter. Transfection into different cell lines and deletion mapping of peripherin-lacZ hybrid constructs indicated that the first 98 bp preceding the transcription start site of the gene were sufficient to confer cell-type specific expression. DNase I footprinting experiments revealed three protected sequences in this region, that were named PER1, PER2 and PER3. The PER2 and PER3 elements, localized between -98 to -46, interact with proteins that seem widely distributed. Deletion of these elements severely decreased the level of reporter gene activity. The PER1 element, which overlaps the TATA box, interacts with a DNA-binding protein prevailing in peripherin expressing cell lines. However, the core promoter, which contains the PER1 element, was inefficient in driving gene expression. Experiments designed to test the contribution of each element showed that PER2 and PER3 were important in determining the level of expression, while PER1 was important for cell-type specificity. In fact the polyoma virus enhancer linked to the peripherin gene core promoter was found to limit reporter gene activity to peripherin expressing cell lines. Together, these experiments indicate that co-operative interactions between different regions of the promoter are necessary for efficient and cell-type specific transcription of the peripherin gene in a subset of neuronal cells.

Animals↗
PubMed1992

Alloimmunization to platelet antigen HPA-1a (PIA1) is strongly associated with both HLA-DRB3*0101 and HLA-DQB1*0201.

Antibodies to the platelet HPA-1a antigen can elicit in the newborn a condition known as neonatal alloimmune thrombocytopenic purpura (NAITP). Previous studies based on RFLP analysis showed that 100% of HPA-1a-negative women who produced anti-HPA-1a antibodies (responders) were HLA-DRw52a (DRB3*0101). However, this specificity could also be found in some HPA-1a-negative women not producing anti-HPA-1a antibodies (nonresponders). We have analyzed in detail by PCR-SSOP the HLA-DR, -DQ, and -DP loci of 36 responders and 10 nonresponders. We found that while the allele DRB3*0101 was present in the vast majority of responders (91%), there were exceptions. Furthermore, the DQB1*0201 allele was found to be present in almost all responders (94%), but again was also found in nonresponders. The risk of alloimmunization to HPA-1a in an HPA-1b homozygous mother significantly increases with the presence of either allele, the odds ratio being 39.7 for DQB1*0201 and 24.9 for DRB3*0101. Sequencing of exon 2 of these two alleles from responders indicated no sequence difference when compared with the consensus sequences. This indicates that they do not represent variants when compared with the same alleles found in some nonresponders.

Alleles↗
PubMed1991

Abnormal spontaneous activity of globus pallidus neurons in monkeys with MPTP-induced parkinsonism.

The goal of the study was to determine abnormalities in the spontaneous activity of globus pallidus neurons at the output of the basal ganglia, in cynomolgus monkeys rendered parkinsonian by the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). In parkinsonian compared to intact monkeys, the mean spontaneous firing rate of the neurons of the internal segment of the globus pallidus (GPi) increased but that of the prevailing neuronal population in the external segment (GPe) inversely decreased. Correspondingly, the mean modal interval between spikes shortened, suggesting increased excitation, in both the GPi and GPe. However, the mean proportion of intervals longer than 100 ms increased in the GPe but remained unchanged in the GPi, suggesting increased inhibition only in the GPe. In the two populations, bursting activities and the mean variability of firing rate increased. Concurrently, a small and distinct neuronal population located in the GPe and another located at the periphery of both the GPi and GPe displayed minor changes, which were however different from those observed in the GPi and in the prevailing neuronal population of the GPe. The intensity of changes varied with time and severity of nigral lesion. In severe parkinsonism, the neuronal activity at the output of the basal ganglia (GPi) is excessive.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1991

Effects of dopamine agonists on the spontaneous activity of globus pallidus neurons in monkeys with MPTP-induced parkinsonism.

The mixed (D1 and D2) dopamine agonist apomorphine was injected (10-200 micrograms/kg, s.c.) to cynomolgus monkeys before and after they were rendered parkinsonian by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Motor behavior was examined together with corresponding neuronal activity in the external (GPe) and internal (GPi) segments of the globus pallidus, including a small population of neurons localized within the GPe and displaying a characteristic discharge at low frequency with bursts (LFB), and border (Bor) neurons localized at the periphery of the pallidal segments. In the intact animal strong but not weak doses of the drug induced generalized agitation without apparent neuronal effects. In 1 parkinsonian animal that showed some recuperation of normal behavioral and pallidal activity, weak doses induced agitation and partly reduced the signs of parkinsonism, again without apparent neuronal effects. The same results were obtained before day 21 after MPTP in a parkinsonian monkey that did not recuperate. After day 21, however, the drug acted at a shorter latency, completely abolished the signs of parkinsonism, induced dyskinesia, increasing with repetition of injections, and clear neuronal effects. The same results were obtained from the start in another monkey in which recordings were begun 398 days after MPTP. Nearly all GPi neurons decreased their firing rate following apomorphine. The reverse was true of the predominant neuronal population in the GPe. In both cases, the intensity of the changes in firing rate varied much between neurons following the same dose of apomorphine. When the changes in firing rate were moderate or null, abnormal bursting firing patterns were normalized. Both LFB and Bor neurons decreased their firing rate following apomorphine; LFB neurons being extremely sensitive. The selective D2 agonist RU-24213 induced behavioral and neuronal effects identical to those of apomorphine.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1991

Restricted expression of the Lytechinus pictus Spec1 gene homologue in reciprocal hybrid embryos with Strongylocentrotus purpuratus.

Hybrid embryos were derived from reciprocal crosses of Strongylocentrotus purpuratus and Lytechinus pictus sea urchins. The expression of proteins specific for L. pictus was restricted in these hybrid embryos, while this was not so for most proteins specific for S. purpuratus. In particular, the aboral ectoderm-specific calcium-binding protein Spec1 was expressed at normal levels in hybrid embryos, but its L. pictus homologue, LpS1, was considerably reduced. LpS1 mRNA accumulated in hybrid plutei to only 4-5% of its normal level. Transcription of the LpS1 gene was substantially reduced in hybrid embryos, as determined by a nuclear RNA run-on assay. Southern blot analysis of genomic DNA indicated that there was no detectable loss or rearrangement of LpS1 DNA in hybrid embryos. Thus, the Spec1 gene is expressed normally in hybrid embryos, but the transcription of its homologue, the LpS1 gene, is considerably restricted.

Animals↗
PubMed1990

The mouse keratin 19-encoding gene: sequence, structure and chromosomal assignment.

Keratin 19 (K19) is synthesized mainly in embryonic and adult simple epithelia, but has also been found in stratified epithelia as well. K19 is the smallest known keratin and is remarkable in that, contrary to all other keratins, it does not have a designated partner for the formation of filaments, implying that regulation of its expression is different from other keratin-encoding genes. As a first step in elucidating the mechanisms by which the K19 gene is regulated in relatively undifferentiated embryonic and in terminally differentiated adult tissues, a series of overlapping clones containing the complete mouse K19 gene was isolated from a mouse genomic library and characterized. The nucleotide (nt) sequence extends over 5119 nt and includes six exons. A region of 303 nt upstream from the transcription start point (tsp) was also sequenced. Comparison with the human and bovine K19 genes revealed the existence of homologies in both the coding and noncoding regions. The putative promoter region of the mouse K19 gene is highly homologous to the corresponding sequences of the human and bovine K19 genes. It contains an ATA box, a CAAT box and two potential Sp1-binding sites. Significant homologies were also found between the sequences of the introns of the mouse, human and bovine genes: this was particularly evident in introns 2, 3, 4 and 5. Intron 1, which showed the greatest degree of divergence, was found to contain many repetitive elements. Finally, it is shown that the mouse K19 gene cosegregates with the type-I keratin-encoding gene locus (Krt-1) on chromosome 11.

Amino Acid Sequence↗
PubMed1990

Angle dependency in strength measurements of the ankle plantar flexors.

Muscle strength (or muscular moment) generated during dynamic contractions varies with joint angle. This raises the question about the choice of a representative angle in the evaluation of strength capacity. To assess this angle dependency in strength measurements, dynamic moment-angle curves for plantar flexor muscles were obtained in 43 healthy subjects (28 men and 15 women) with a controlled acceleration dynamometer at 0.52 rad s-1 (30 degrees s-1) and using maximal static preloading before the beginning of movement to attenuate the force development phase. Differences between gender and correlations between strength and anthropometric measures were calculated at each 0.087 rad (5 degrees). The plantar flexion moment was larger in men, in general, but this difference was largest when the ankle was most dorsiflexed. The correlations between moment and anthropometric measures were also higher in the first half of the plantar flexion movement. These results stress the importance of reporting joint angles at which moment of force measures were made. Furthermore, they show that the maximal strength capacity of the plantar flexors is best represented by the moment measured in dorsiflexion angles when the muscles are lengthened.

Ankle Joint↗
PubMed1990

[Anatomo-physiologic substratum of akinesia in primates].

Severe akinesia can be observed in macaques following MPTP injections destroying dopaminergic nigrostriatal neurons. Akinesia also results from inhalation of toxic substances inducing bilateral lesions of the two pallidal nuclei and of the pars reticulata of the substantia nigra, and not of the pars compacta. Most of the recent studies of the anatomo-physiological substratum of akinesia used MPTP injections. Deoxyglucose studies have shown a clear increase in the neuronal activity of the medial nucleus of the pallidum and of its thalamic projection territory. Electrophysiological studies have shown a major modification of the spontaneous activity of medial pallidal neurons which is influenced in an excessive and non selective manner by sensorimotor inputs. Analysis of the relative three dimensional geometry of nervous arborizations have shown that the striato-pallido-nigral system is extremely convergent. Akinesia consecutive to nigrostriate lesions could be linked to an excessive and anarchic activation of this system. The contradiction which exists between akinesia with an abnormal activity of the medial pallidum and akinesia with bilateral pallidal lesions could only be apparent if akinesia was linked to the ineffective emission or to the interruption of messages to the thalamus.

Animals↗
PubMed1989

Responses of pallidal neurons to striatal stimulation in intact waking monkeys.

Extracellular single-unit activity was recorded from neurons of the internal and external pallidal segments, and from 'border cells' at the periphery of the segments, in 3 waking cynomolgus monkeys during electrical stimulation of 3 sites bilaterally in the striatum: one in the caudate nucleus and two in the putamen. Nearly 90% of each of the 3 types of neurons responded to at least one ipsilateral stimulation site. Contralateral stimulation was much less effective, except for border neurons. Neurons responding exclusively to caudate stimulation were located in a dorsomedial zone of the pallidum, those responding exclusively to putamen were in a larger ventrolateral zone, and those responding to both nuclei were in an intermediate zone, larger at rostral than at caudal levels. The great majority of responses consisted of an initial inhibition, at a mean latency of 14 ms, followed by excitation, at a mean latency of 35 ms. Later components of weaker magnitude, often comprising inhibition, occurred in only 30% of the cases. Only border neurons displayed an initial excitation preceding the early inhibition. The responses were not different in the internal and external pallidal segments, except for the slightly more frequent occurrence of excitation in the latter segment. The early inhibition was always displayed by neurons located in the center of the pallidal zone of influence of each striatal stimulation site, and was ended and often curtailed by excitation. At the periphery of the zone, excitation occurred alone or as the initial component of responses. This topological arrangement suggests that excitation is used, temporally, to control the magnitude of the central striatopallidal inhibitory signal and, spatially, to focus and contrast it onto a restricted number of pallidal neurons.

Action Potentials↗
PubMed1989

Responses of pallidal neurons to striatal stimulation in monkeys with MPTP-induced parkinsonism.

Extracellular single unit activity was recorded from neurons of the internal (GPi) and external (GPe) pallidal segments, and from 'border cells' (Bor) which are part of the nucleus basalis, in 2 cynomolgus monkeys rendered parkinsonian by MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine). Cell counts showed that at least 90% of the nigral neurons of the compacta-type were degenerated. Electrical stimulation was applied to 3 sites bilaterally in the striatum: one in the caudate nucleus and 2 in the putamen. The results were compared to those obtained in intact monkeys. In the parkinsonians, more neurons of the 3 types responded to ipsilateral stimulation. The difference was even greater for contralateral responses, except in the case of Bor neurons. Greater proportions of the 3 types of neurons also responded to 2 and 3 sites and showed convergent responses to both the caudate nucleus and the putamen. The magnitude of the responses was larger. These results are in accordance with the excessive and unselective responses of the same neurons to passive limb movement, obtained in the same animals and described previously. The electrical stimulation allowed more detailed analyses of the responses. The major change in the responses of GPi and Bor neurons was the more frequent and larger late inhibitions, whereas the excitations were larger in GPe neurons. Long lasting oscillatory responses occurred frequently in the parkinsonians, mainly in GPi, and at frequencies close to the tremor displayed by the animals. Responses beginning with early inhibition were displayed by neurons located in the center of the pallidal zone of influence of each striatal stimulation site, as in intact animals, but in the GPi of the parkinsonians they were less frequently curtailed by excitation. Moreover, in the parkinsonians, the zones of influence were larger in both GPi and GPe, mainly because of the expansion of their periphery, where responses began with excitation and had lower thresholds than in intact animals. The dopamine agonist apomorphine normalized the responses in the parkinsonians. Thus, both the temporal and spatial magnitudes of inhibitions and excitations are abnormal at the output of the basal ganglia in parkinsonism.

Action Potentials↗
PubMed1989

Distinct afferents to internal and external pallidal segments in the squirrel monkey.

The use of retrograde fluorescence double-labeling method has revealed that the internal (GPi) and external (GPe) segments of globus pallidus in squirrel monkey receive projections from different cell populations in striatum and subthalamic nucleus. Striatal neurons projecting either to GPi or GPe formed wide and nonoverlapping cell bands oriented obliquely and covering large portions of putamen and caudate nucleus. Subthalamic neurons projecting to GPe were more abundant and more laterally located than those projecting to GPi. A few cells branching to GPi and GPe were found in subthalamic nucleus but not in striatum. Thus, different striatal and subthalamic neuronal populations influence GPi and GPe in primates.

Animals↗
PubMed1988

cDNA sequence and homologies of the "57-kDa" nucleotide-binding subunit of the vacuolar ATPase from Arabidopsis.

Functional and structural similarities among a wide variety of endomembrane H+-ATPases suggest that they form a distinct class with a common origin. Immunological studies (Manolson, M. F., Percy, J. M., Apps, D. K., Xie, X. S., Stone, D. K., and Poole, R. J. (1987) in Proceedings of the Membrane Protein Symposium (Goheen, S. C., ed) pp. 427-434, Bio-Rad, Richmond, CA, and M. F. Manolson, J. M. Percy, D. K. Apps, X. S. Xie, D. K. Stone, M. Harrison, D. J. Clarke, R. J. Poole, unpublished data) support this idea and suggest an evolutionary relationship between the endomembrane and F0F1 ATPases. Further examination of relationships necessitates comparison of protein/nucleic acid sequence data. To this end, we have cloned and sequenced the cDNA encoding the 57-kDa polypeptide of the Arabidopsis vacuolar membrane H+-ATPase. To our knowledge, this is the first report of the sequence of a "57-kDa" subunit for plant or animal endomembrane H+-ATPase. This cDNA encodes a hydrophilic polypeptide containing a putative ATP binding site. Lack of a secretion signal sequence suggests it is not processed through the endoplasmic reticulum but translated on cytosolic ribosomes. Comparison of protein sequences shows the 57-kDa subunit from Arabidopsis to be nearly identical with the corresponding subunit in Neurospora vacuolar membrane H+-ATPase, very similar to the beta subunit of the archaebacterium Sulfolobus, and slightly, but nevertheless significantly, homologous to the alpha and beta subunits of the F0F1-ATPases. These results suggest that these different classes of ATPases have evolved from a common ancestor.

Adenosine Triphosphate↗
PubMed1988

Tandem duplication and divergence of a sea urchin protein belonging to the troponin C superfamily.

The Spec1 and Spec2 proteins of the sea urchin Strongylocentrotus purpuratus are related to calmodulin, troponin C, and myosin light chains by sequence similarity in their four calcium binding domains. These domains, the EF-hands, are distinct helix-loop-helix structures of about 40 amino acids. The Spec1 and Spec2 genes are expressed specifically in aboral ectoderm cells of the developing embryo; however, the function of the Spec proteins in these cells is unknown. To find conserved regions of the proteins that might be important for structure and function, Spec homologues from Lytechinus pictus, a distantly related sea urchin, were sought. L. pictus embryos do not synthesize detectable amounts of the 14,000-17,000-Da Spec proteins as determined by two-dimensional gel electro-phoresis, but do synthesize three 34,000-Da proteins that cross-react with Spec1 antibodies and display a similar ontogenetic pattern of expression. cDNA clones were isolated by hybridization to a synthetic oligonucleotide corresponding to the EF-hand. One clone, LpS1, encodes an mRNA with developmental properties like those of the S. purpuratus Spec mRNAs. However, LpS1 contains an open reading frame for a protein of 34,000 Da rather than 17,000 Da, and antibodies raised against part of the LpS1 reading frame demonstrate that LpS1 encodes a 34,000-Da protein in L. pictus embryos. The sequence of LpS1 reveals the presence of eight EF-hand domains, which share structural homology with the Spec1 or Spec2 EF-hands; however, little else in the protein sequence is conserved. The results support the hypothesis that the LpS1 gene arose from a duplication of an ancestral Spec gene and that the overall structural features of the Spec family of proteins are more conserved than the amino acid sequences.

Amino Acid Sequence↗
PubMed1988

Identification of a proliferation-related transcript with an elevated expression in the mid-gestation mouse embryo.

Polyadenylated RNA enriched in transformation specific sequences from hamster embryo fibroblast cells transformed by HSV-2 was used to construct a cDNA library. A cDNA clone (pKG4) contained a sequence which was upregulated in HSV-2 transformed cells and also in fibroblastic cell lines transformed by SV40 and 3-methylcholanthrene. The expression of the KG4 sequences in HSV-2-transformed cells was found to be modulated by the growth state of the cells. In confluent cells its level was reduced 5-times compared to the homologous RNAs from exponentially growing cells. Expression of the KG4 sequence was also examined in mouse embryos from day 8 onwards and in adult tissues. During development, KG4 is expressed at all times examined. However, there is a dramatic increase in expression on day 11. In adult tissues, a low and variable level of expression was observed. These findings suggest that the KG4 sequence is related to cellular proliferation.

Animals↗
PubMed1988

Abnormal influences of passive limb movement on the activity of globus pallidus neurons in parkinsonian monkeys.

Extracellular single unit activity was recorded in the globus pallidus of waking Macaca fascicularis during passive limb movement. The main upper and lower limb joints were investigated bilaterally. The animals were either intact or rendered parkinsonian by the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Cell counts showed that at least 90% of nigral neurons of the compacta-type were degenerated in the parkinsonian animals. In the intact animals, only 17% of the pallidal neurons responded to the natural stimulus. As already reported by others, the responses were typically related to movement about a single contralateral joint and in only one direction. In the parkinsonian animals, however, more neurons responded, often more vigorously, to the same stimulation. In many of these neurons the responses were elicited by movement about more than one joint of both upper and lower limbs or ipsi-and contralateral sides and in more than one direction. The increase in number and magnitude and loss of specificity of responses were much greater in the internal pallidal segment, where the number of responding neurons quadrupled. These results suggest that dopaminergic mechanisms regulate gain and selectivity in the basal ganglia. In animals with decreased dopaminergic functions, the excessive and unselective motor responses may explain all 3 major signs of parkinsonism: rigidity, tremor and akinesia.

Animals↗
PubMed1988

Influence of contractile tension development on dynamic strength measurements of the plantarflexors in man.

The influence of the contractile tension rise time on isokinetic force-angle records has been inferred from static force-time curves but has not been experimentally determined. The purpose of this study is thus to describe the influence of the contractile rise time on the force-angle curves produced during maximal voluntary, acceleration controlled, isokinetic plantarflexions at 30 degrees/s. Since we could not measure directly the period of force development unbiased by changes in muscle length during the movements, we devised an experimental strategy which allowed the computation of the dynamic force-time curve. Thus in five normal men, we first recorded force-angle curves produced during maximal voluntary plantarflexion movements preceded by maximal static pre-loading (D:-10 degrees Max) in order to eliminate the period of tension development from the force-angle record. Next, we recorded force-angle curves produced during maximal voluntary contractions initiated from two different starting angles without pre-loading (D:-10 degrees Min and D:0 degrees Min) to include the period of tension rise. The dynamic force-time curve was computed by correcting these force-angle curves (D:-10 degrees Min and D:0 degrees Min) for the hypothetical loss in force due to muscle shortening. We compared the relative (to remove the effects of force magnitude) computed dynamic force-time curves with relative static force-time curves measured at three different angles. We found the shape and several other parameters of all three static and both computed dynamic force-time curves to be similar (p greater than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Specific induction of cellular gene transcription in herpes simplex virus type 2-transformed cells.

In spite of much work, the mechanism of oncogenic transformation by herpes simplex virus (HSV) is as yet unknown. It has been proposed that HSV type 2 (HSV-2) can transform cells by a 'hit and run' mechanism. In the past we have demonstrated that several polypeptides can be immunoprecipitated from HSV-2-transformed cells, but not from control cells or adenovirus-transformed cells, by rabbit hyperimmune sera to HSV-2. It is possible that the expression of these proteins might be the result of activation of cellular genes during transformation. We have now isolated cDNAs representing transcripts of genes that are expressed at higher levels in HSV-2-transformed hamster embryo fibroblasts than in the parental cells. Cytoplasmic transcripts and genomic sequences homologous to three clones (pAA8, pHD1 and pLC7) were analysed. Northern blot analyses showed that 0.75 kb transcripts which hybridize to the three cDNAs were present in HSV-2-transformed cells and were completely absent or present at low levels in control hamster fibroblasts. These transcripts were not present in mouse cells transformed by other DNA viruses or by a chemical carcinogen. The expression of these transcripts seemed to be confined to certain HSV-2-transformed cell lines. Southern blot analysis suggested that the 0.75 kb transcripts corresponding to these cDNAs may have arisen from a single gene. Nuclear run-off experiments indicated that activation occurred at the level of transcription. The activation of the gene or genes corresponding to these cDNAs may be an integral part of the mechanism of transformation by HSV-2.

Animals↗