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PubMed1999

Contact air abrasion.

The advantages of contact air abrasion techniques are readily apparent. The first, of course, is the greatly increased ease of use. Working with contact also tends to speed the learning curve by giving the process a more natural dental feel. In addition, as one becomes familiar with working with a dust stream, the potential for misdirecting the air flow is decreased. The future use of air abrasion for deep decay removal will make this the treatment of choice for the next millennium.

Air Abrasion, Dental↗

PubMed2002

Post-project appraisals in adaptive management of river channel restoration.

Post-project appraisals (PPAs) can evaluate river restoration schemes in relation to their compliance with design, their short-term performance attainment, and their longer-term geomorphological compatibility with the catchment hydrology and sediment transport processes. PPAs provide the basis for communicating the results of one restoration scheme to another, thereby improving future restoration designs. They also supply essential performance feedback needed for adaptive management, in which management actions are treated as experiments. PPAs allow river restoration success to be defined both in terms of the scheme attaining its performance objectives and in providing a significant learning experience. Different levels of investment in PPA, in terms of pre-project data and follow-up information, bring with them different degrees of understanding and tbus different abilities to gauge both types of success. We present four case studies to illustrate how the commitment to PPA has determined the understanding achieved in each case. In Moore's Gulch (California, USA), understanding was severely constrained by the lack of pre-project data and post-implementation monitoring. Pre-project data existed for the Kitswell Brook (Hertfordshire, UK), but the monitoring consisted only of one site visit and thus the understanding achieved is related primarily to design compliance issues. The monitoring undertaken for Deep Run (Maryland, USA) and the River Idle (Nottinghamshire, UK) enabled some understanding of the short-term performance of each scheme. The transferable understanding gained from each case study is used to develop an illustrative five-fold classification of geomorphological PPAs (full, medium-term, short-term, one-shot, and remains) according to their potential as learning experiences. The learning experience is central to adaptive management but rarely articulated in the literature. Here, we gauge the potential via superimposition onto a previous schematic representation of the adaptive management process by Haney and Power (1996). Using PPAs wisely can lead to cutting-edge, complex solutions to river restoration challenges.

Communication↗

PubMed1998

Large-scale functional connectivity in associative learning: interrelations of the rat auditory, visual, and limbic systems.

Large-scale functional connectivity in associative learning: interrelations of the rat auditory, visual, and limbic systems. J. Neurophysiol. 80: 3148-3162, 1998. Functional relations between specialized parts of the brain may be important determinants of learned behaviors. To study this, we examined the interrelations of the auditory system with several extraauditory structures in two groups of rats having different behavioral histories. Both groups were trained to associate a tone conditional stimulus (CS) with an aversive unconditional stimulus (US). For one group, a light presented with the tone predicted the absence of the US (group TL-). In the other group, the light was a neutral stimulus (group TL0). Fluorodeoxyglucose (FDG) incorporation was measured in the presence of the tone-light compound. Because the tone-light compound was physically identical for both groups, neural differences between groups reflected differences in the learned associative properties of the stimuli. Covariances of FDG uptake in the auditory system and extraauditory structures were examined using partial least squares. Three strong covariance or functional connectivity patterns were identified. The first pattern mainly reflected similarities between groups, with strong interrelations between the subcortical auditory system and the thalamocortical visual system, cerebellum, deep cerebellar nuclei, and midline thalamus. This pattern of interactions may represent part of a common circuit for relaying the associative value of the tone CS to the cerebellum and the midline thalamus. The external nucleus of the inferior colliculus and medial division of the medial geniculate nucleus were associated more strongly with this pattern for group TL-, which was interpreted as representing the change of the associative value of the tone by the light, mediated through extraauditory influences on these two regions. A second pattern involved midbrain auditory regions, superior colliculus, zona incerta, and subiculum and was stronger for group TL0. The relations between midbrain structures may represent the excitatory conditioned response (CR) evoked by the tone in this group. The final pattern was strongest in group TL- and involved interrelations of the thalamocortical auditory system with hippocampus, basolateral amygdala, and hypothalamus. This pattern may represent the learned inhibition of the CR to the tone in the presence of the light. These findings are consistent with behavioral studies suggesting that at least two types of associations are formed during associative learning. One is the sensory relation of the stimuli and another is the relation between the CS and the affective components of the US. These behavioral associations are mapped to the patterns of functional connectivity between auditory and extraauditory regions.

Acoustic Stimulation↗

PubMed2025

Deep clinical and genetic analysis of 17p13.3 region: 38 pediatric patients diagnosed using next-generation sequencing and literature review.

BACKGROUND: Chromosome 17p13.3 is a region of genomic instability associated with different neurodevelopmental diseases. The malformation spectrum of 17p13.3 microdeletions ranges from an isolated lissencephaly sequence to Miller-Dieker syndrome, while 17p13.3 microduplications result in autism, learning disabilities, microcephaly and other brain malformations. This study aims to provide a more comprehensive delineation of the clinical and genetic characteristics associated with 17p13.3 alterations. METHODS: We retrospectively analyzed the next-generation sequencing (NGS) data of more than 40 thousand patients from January 2016 to December 2021 and identified 38 pediatric patients with copy-number variations (CNVs) or single-nucleotide variations (SNVs) in 17p13.3 region. Published patients with CNVs in the 17p13.3 region were also collected and we performed a Chi-square test to compare the phenotype spectrum of microdeletions and microduplications. RESULTS: Among the 27 CNV patients, 20 patients with microdeletions and 7 patients with microduplications were found. PAFAH1B1 was the most frequently deleted gene and CRK was the most frequently duplicated gene. Affected genes in 11 SNV patients included PAFAH1B1 and PRPF8. Developmental delay was the most common abnormality detected in the 38 patients (29/38, 76.3%). Of note, Case 10 presented omphalocele and Case 23 presented scoliosis, webbed neck and bone cyst, all of which were unusual variant phenotypes in this region. The Chi-square test revealed that epilepsy, lissencephaly and short stature were statistically significant with microdeletions, while behavioral abnormalities and hand and foot abnormalities were significant with microduplications (p < 0.01). CONCLUSIONS: While PAFAH1B1, YWHAE and CRK are associated with major phenotypes of 17p13.3, RTN4RL1 may be involved in white matter changes and HIC1 might contribute to the occurrence of omphalocele. This study provided a comprehensive understanding of genetic information and phenotype spectrum of the 17p13.3 region.

Humans↗

PubMed2000

Toward a psychology of positive youth development.

This article analyzes the development of initiative as an exemplar of one of many learning experiences that should be studied as part of positive youth development. The capacity for initiative is essential for adults in our society and will become more important in the 21st century, yet adolescents have few opportunities to learn it. Their typical experiences during schoolwork and unstructured leisure do not reflect conditions for learning initiative. The context best suited to the development of initiative appears to be that of structured voluntary activities, such as sports, arts, and participation in organizations, in which youths experience the rare combination of intrinsic motivation in combination with deep attention. An incomplete body of outcome research suggests that such activities are associated with positive development, but the developmental processes involved are only beginning to be understood. One promising approach has recorded language use and has found that adolescents participating in effective organizations acquire a new operating language that appears to correspond to the development of initiative.

Adolescent↗

PubMed2003

Distinct contributions of small and large conductance Ca2+-activated K+ channels to rat Purkinje neuron function.

The cerebellum is important for many aspects of behaviour, from posture maintenance and goal-oriented reaching movements to timing tasks and certain forms of learning. In every case, information flowing through the cerebellum passes through Purkinje neurons, which receive input from the two primary cerebellar afferents and generate continuous streams of action potentials that constitute the sole output from the cerebellar cortex to the deep nuclei. The tonic firing behaviour observed in Purkinje neurons in vivo is maintained in brain slices even when synaptic inputs are blocked, suggesting that Purkinje neuron activity relies to a significant extent on intrinsic conductances. Previous research has suggested that the interplay between Ca2+ currents and Ca2+-activated K+ channels (KCa channels) is important for Purkinje cell activity, but how many different KCa channel types are present and what each channel type contributes to cell behaviour remains unclear. In order to better understand the ionic mechanisms that control the behaviour of these neurons, we investigated the effects of different Ca2+ channel and KCa channel antagonists on Purkinje neurons in acute slices of rat cerebellum. Our data show that Ca2+ entering through P-type voltage-gated Ca2+ channels activates both small-conductance (SK) and large-conductance (BK) KCa channels. SK channels play a role in setting the intrinsic firing frequency, while BK channels regulate action potential shape and may contribute to the unique climbing fibre response.

Anesthetics, Local↗

PubMed2006

Morphological and electrophysiological properties of GABAergic and non-GABAergic cells in the deep cerebellar nuclei.

The deep cerebellar nuclei (DCN) integrate inputs from the brain stem, the inferior olive, and the spinal cord with Purkinje cell output from cerebellar cortex and provide the major output of the cerebellum. Despite their crucial function in motor control and learning, the various populations of neurons in the DCN are poorly defined and characterized. Importantly, differences in electrophysiological properties between glutamatergic and GABAergic cells of the DCN have been largely elusive. Here, we used glutamate decarboxylase (GAD) 67-green fluorescent protein (GFP) knock-in mice to unambiguously identify GABAergic (GAD-positive) and non-GABAergic (GAD-negative, most likely glutamatergic) neurons of the DCN. Morphological analysis of DCN neurons patch-clamped with biocytin-containing electrodes revealed a significant overlap in the distributions of the soma sizes of GAD-positive and GAD-negative cells. Compared with GAD-negative DCN neurons, GAD-positive DCN neurons fire broader action potentials, display stronger frequency accommodation, and do not reach as high firing frequencies during depolarizing current injections. Furthermore, GAD-positive cells display slower spontaneous firing rates and have a more shallow frequency-to-current relationship than the GAD-negative cells but exhibit a longer-lasting rebound depolarization and associated spiking after a transient hyperpolarization. In contrast to the rather homogeneous population of GAD-positive cells, the GAD-negative cells were found to consist of two distinct populations as defined by cell size and electrophysiological features. We conclude that GABAergic DCN neurons are specialized to convey phasic spike rate information, whereas tonic spike rate is more faithfully relayed by the large non-GABAergic cells.

Action Potentials↗

PubMed1994

[Stress in school-age children].

In April 1988, following preliminary research, Notre Dame Elementary School in Edmunston, N.B. initiated a pilot project entitled Management of Children's Stress. Using a three-dimensional process, parents, teachers and students collaborated to empower all students enrolled at the school to effectively manage their day-to-day stress. To prepare, the children, parents and teachers participated in nine- and 15-hour education sessions, respectively. Various techniques, including deep breathing exercises, stretching, relaxation techniques and listening to music, were considered. Visualization, maximizing the mind's potential to envision relaxing images, became the preferred technique. In addition to complementing other relaxation techniques used by the children, visualization facilitated their learning; developed and improved their concentration, motivation and self-confidence; gave them a positive self-image; and reduced health problems. The project has surpassed all expectations. In March 1993, it became part of a Quality of Life Education Project at the school.

Child↗

PubMed1996

Effects of cerebellar lesions on saccade simulations.

Experimental studies involving cerebellar lesions have been important tools for learning about the operation of the saccadic eye movement system. These studies have been used to further develop a neural network model for horizontal saccadic eye movement control. The neural control mechanism is first order time optimal, initiated by the deep layers of the superior colliculus and terminated by the cerebellar fastigial nucleus. The neural circuit consists of neurons in the paramedian pontine reticular formation (burst, tonic and pause cells), the vestibular nucleus, abducens nucleus, oculomotor nucleus, cerebellum, substantia nigra, nucleus reticularis tegmenti pontis, the thalamus, the deep layers of the superior colliculus and the oculomotor plant for each eye. Agonist burst cell activity is initiated with maximal firing due to an error between the target and eye position, and continues until the internal eye position in the cerebellar vermis reaches the desired position, then decays to zero. The cerebellar vermis is responsible for adapting the duration of maximal firing based on the initial position of the eye. There are two sets of neural integrators in the neural network. One operates within the cerebellar vermis to predict the width of the pulse, and the other within the paramedian pontine reticular formation to maintain the eyes at their destination. Antagonist neural activity is inhibited during the agonist burst activity. After the agonist burst, antagonist neural activity rises with a stochastic rebound burst and from input from the fastigial nucleus, then falls to a tonic firing level necessary to keep the eye at its destination. The onset of the antagonist tonic firing is stochastic, weakly coordinated with the end of the agonist burst, and under cerebellar control. A common mechanism of action is described, based on cerebellar gating, through the fastigial nucleus, that explains a number of different saccadic eye movement types, including dynamic overshoot, glissadic overshoot and undershoot, and undershoot. A linear homeomorphic oculomotor muscle model is used in the simulations of the operation of the neural network. Each of the neural sites in the model fire similar to experimental data, and simulate fast eye movements.

Cerebellum↗

PubMedDate not supplied

Ethological models in research into the neural mechanisms of short-term memory.

Rats are protected against intake of toxic diets by specific evolutionary prepared behavioral adaptations. Intake of potentially dangerous novel food is reduced by neophobia. The taste signal is stored for several hours in a short-term memory file from which it gradually emerges in form of a permanent gustatory engram labeled as safe, when there are no adverse effects of feeding, or as aversive, when visceral symptoms of poisoning appear in the critical post-ingestion interval. The experimental evidence reviewed indicates that positive labeling (manifested by attenuation of neophobia) requires intact higher brain functions whereas the aversive experience (manifested by conditioned taste aversion) is recorded even under deep coma. The biological significance of the different neural mechanisms underlying the above forms of gustatory-visceral associations is discussed.

Animals↗

PubMed2002

Neuronal premotor networks involved in eyelid responses: retrograde transneuronal tracing with rabies virus from the orbicularis oculi muscle in the rat.

Retrograde transneuronal tracing with rabies virus from the right orbicularis oculi muscle was used to identify neural networks underlying spontaneous, reflex, and learned blinks. The kinetics of viral transfer was studied at sequential 12 hr intervals between 3 and 5 d after inoculation. Rabies virus immunolabeling was combined with the immunohistochemical detection of choline acetyltransferase expression in brainstem motoneurons or Fluoro-Ruby injections in the rubrospinal tract. Virus uptake involved exclusively orbicularis oculi motoneurons in the dorsolateral division of the facial nucleus. At 3-3.5 d, transneuronal transfer involved premotor interneurons of trigeminal, auditory, and vestibular reflex pathways (in medullary and pontine reticular formation, trigeminal nuclei, periolivary and ventral cochlear nuclei, and medial vestibular nuclei), motor pathways (dorsolateral quadrant of contralateral red nucleus and pararubral area), deep cerebellar nuclei (lateral portion of interpositus nucleus and dorsolateral hump ipsilaterally), limbic relays (parabrachial and Kölliker-Fuse nuclei), and oculomotor structures involved in eye-eyelid coordination (oculomotor nucleus, supraoculomotor area, and interstitial nucleus of Cajal). At 4 d, higher order neurons were revealed in trigeminal, auditory, vestibular, and deep cerebellar nuclei (medial, interpositus, and lateral), oculomotor and visual-related structures (Darkschewitsch, nucleus of the posterior commissure, deep layers of superior colliculus, and pretectal area), lateral hypothalamus, and cerebral cortex (particularly in parietal areas). At 4.5 and 5 d the labeling of higher order neurons occurred in hypothalamus, cerebral cortex, and blink-related areas of cerebellar cortex. These results provide a comprehensive picture of the premotor networks mediating reflex, voluntary, and limbic-related eyelid responses and highlight potential sites of motor learning in eyelid classical conditioning.

Animals↗

PubMed2001

Rabbit classical eyeblink conditioning is altered by brief cerebellar cortical stimulation.

A pair of studies examined how cortical intracerebellar stimulation (ICS) affects eyeblink conditioning in the rabbit. Rabbits were implanted with chronic bipolar stimulating electrodes in the cell body layers of cerebellar lobule H-VI. Brief (40 ms) trains of intracranial stimulation (100 Hz, 250 microA) were delivered during training trials [forward pairings of a tone-conditioned stimulus (CS) with an air puff unconditioned stimulus (US)]. In Experiment 1, the onset of ICS varied randomly within sessions. US-onset-coincident ICS proved detrimental to the maintenance of conditioning [measured as the percentage of trials on which conditioned responses (CRs) were made] compared to ICS that ended 60 ms before US onset. Based on these findings, a second experiment compared a group trained with ICS consistently delivered at US onset to groups trained with ICS consistently delivered either at CS onset or between the two stimuli, as well as to unstimulated control subjects. Animals receiving CS- or US-coincident ICS learned slowest, whereas animals receiving middle stimulation learned more quickly than all other groups. In both Experiments 1 and 2, highly trained animals produced blinks in direct response to the stimulation. These data are discussed in terms of a new hypothesis concerning interactions between cerebellar cortex and the deep cerebellar nuclei during eyeblink conditioning--a rebound from inhibition hypothesis.

Animals↗

PubMed2005

Aphasia owing to subcortical brain infarcts in childhood.

The aim of this study was to further define the clinical features of subcortical aphasia in children with deep brain infarcts and to define the sequelae associated with childhood strokes. We retrospectively studied nine children with left subcortical brain infarcts who presented with acquired language disorder and underwent language investigations based on standardized tests. Stroke in these patients involved the left internal capsule, lenticular or thalamic nuclei, or a combination of these. Early aphasic manifestations following the deep cerebral infarcts affected language expression. These included mutism, nonfluent speech, word finding difficulties, and phonemic and semantic paraphasia. Speech comprehension was generally more preserved. All patients subsequently improved, although variably; sequelae such as dysfluency, word finding difficulties, and written language learning impairment could be detected through standardized tests in six of them (all younger than 6 years at the time of the infarct). Two of the three remaining patients (both older than 6 years at the time of the infarct) had a full recovery. Our study confirms the concept of childhood subcortical aphasia, depicts the linguistic profile in these patients, and sustains the indication of systematic formal language assessment during the follow-up of all children with subcortical infarct involving the dominant hemisphere.

Adolescent↗

PubMed1995

Making the biopolitical subject: Cambodian immigrants, refugee medicine and cultural citizenship in California.

Linking the health profession to the normalization of citizenship, scholars influenced by Michel Foucault claim that while biomedicine attends to the health of bodies, it is also constitutive of the social and bureaucratic practices that socialize subjects of the modern welfare state. Yet, we seldom learn about how patients themselves draw the medical gaze, nor how their resistances to biomedical intervention both invite and deflect control. I try to show this by means of clinicians' and Khmer refugees' interpretations of their encounters. This study illustrates that refugee medicine is a mix of good intentions, desire to control diseased and deviant populations, and the exigencies of limited resources which often favor medicalization. Californian clinicians, many of them Asian-Americans, display a deep faith in the efficacy of modern medicine for third world patients so that they can function in the new country. Khmer refugees, in contrast, seek rather specific resources while wishing to elude control over the body and mind that goes with medical care. I argue that the biomedical gaze is not such a diffused hegemonic power but is itself generated by the complex contestation of refugee subjects pursuing their own goals. Clinicians and refugees are equally caught up in webs of power involving control and subterfuge, appropriation and resistance, negotiation and learning that constitute biopolitical lessons of what becoming American may entail for an underprivileged Asian group.

Acculturation↗

PubMed2004

Extensile triradiate approach in the management of combined acetabular fractures.

INTRODUCTION: We investigated the results of combined acetabular fractures that were treated through the extensile triradiate approach in this study. MATERIALS AND METHODS: Between January 1996 and January 2001, a total of 48 acetabular fractures were treated surgically (mainly combined fractures). Twenty-five of the combined acetabular fractures that were surgically treated through the triradiate approach with a minimum of 2 years' follow-up were included in the study. The mean patient age was 42 years. There were 8 both-column, 6 T-shaped, 2 anterior column/posterior hemitransverse, 4 transverse with comminuted roof area, 4 posterior wall with comminuted roof area, and 1 posterior column/posterior wall fracture. Associated injuries included two full-thickness chondral injuries of the head, one Pipkin type II fracture, five posterior and one central dislocation of the ipsilateral femoral head, and acetabular marginal impaction in four hips. The average follow-up was 44 months. RESULTS: The postoperative reduction was graded as excellent in 68% and imperfect in 8% of the patients. The hips were evaluated functionally according to the modified Postel-D'Aubigne score and rated as excellent in 7 patients (28%), good in 13 patients (52%), fair in 3 patients (12%) and poor in 2 patients (8%). There were 2 deep infections (8%), 2 avascular necroses of the head (8%), and 4 (16%) non-disabling heterotopic ossifications. CONCLUSION: Our results support the idea that open reduction with the triradiate approach provides good visualization and direct reduction of combined acetabular fractures. Its learning curve for combined fractures is shorter than that for single approaches and provides at least the same rate of anatomical reduction. It should be in the armamentarium of a surgeon dealing with such fractures.

Acetabulum↗

PubMed1998

Differential effects of task complexity on contextual interference in a drawing task.

A large number of studies demonstrated the beneficial effects of contextual interference (CI) created by a random practice of different task variations during training on the retention and transfer of motor skills. Current interpretations of this phenomenon assume that random practice engages the subjects in deep and elaborate processing of movement related information, whereas blocked practice results in more superficial processing leading to poorer performance on later retention and transfer tests. According to this line of interpretation, we hypothesised that the complexity of the task to be learned could modulate the effects of CI. If the task is sufficiently complex, it could force the subjects to rely on such elaborate processing, and the beneficial effects of the intertask interference created by random practice could be obscured in that case. We tested this hypothesis by analysing the effects of practice schedule (random vs. blocked), on the acquisition, retention and transfer of learning in a drawing task where subjects had to reproduce accurately, without visual control, geometrical patterns presented on a video screen, as a function of task complexity defined by the number of segments (two, three or four) of each pattern. The results indicated a clear beneficial effect of random over blocked practice on delayed retention and transfer. However, this CI effect was only observed in subjects who learned the simplest movements, and was not observed in subjects who practised the more complex task. These results are discussed in terms of intratask interference created by the planning of multiple movements and the processing of knowledge of results (KR) when the number of drawing movements is increased. These findings support the assumption that the level of cognitive effort in which the subjects are engaged during training is a main factor influencing long-term retention and transfer of motor skills.

Adolescent↗

PubMed2003

Animal self-medication and ethno-medicine: exploration and exploitation of the medicinal properties of plants.

Early in the co-evolution of plant-animal relationships, some arthropod species began to utilize the chemical defences of plants to protect themselves from their own predators and parasites. It is likely, therefore, that the origins of herbal medicine have their roots deep within the animal kingdom. From prehistoric times man has looked to wild and domestic animals for sources of herbal remedies. Both folklore and living examples provide accounts of how medicinal plants were obtained by observing the behaviour of animals. Animals too learn about the details of self-medication by watching each other. To date, perhaps the most striking scientific studies of animal self-medication have been made on the African great apes. The great ape diet is often rich in plants containing secondary compounds of non-nutritional, sometimes toxic, value that suggest medicinal benefit from their ingestion. Chimpanzees (Pan troglodytes), bonobos (Pan paniscus) and gorillas (Gorilla gorilla) are known to swallow whole and defecate intact leaves. The habit has been shown to be a physical means of purging intestinal parasites. Chimpanzees and man co-existing in sub-Saharan Africa are also known to ingest the bitter pith of Vernonia amygdalina for the control of intestinal nematode infections. Phytochemical studies have demonstrated a wide array of biologically-active properties in this medicinal plant species. In light of the growing resistance of parasites and pathogens to synthetic drugs, the study of animal self-medication and ethno-medicine offers a novel line of investigation to provide ecologically-sound methods for the treatment of parasites using plant-based medicines in populations and their livestock living in the tropics.

Animals↗

PubMed1985

Cytoskeletal architecture and immunocytochemical localization of microtubule-associated proteins in regions of axons associated with rapid axonal transport: the beta,beta'-iminodipropionitrile-intoxicated axon as a model system.

Axons from rats treated with the neurotoxic agent beta,beta'-iminodipropionitrile (IDPN) were examined by quick-freeze, deep-etch electron microscopy. Microtubules formed bundles in the central region of the axons, whereas neurofilaments were segregated to the periphery. Most membrane-bounded organelles, presumably including those involved in rapid axonal transport, were associated with the microtubule domain. The high resolution provided by quick-freeze, deep-etch electron microscopy revealed that the microtubules were coated with an extensive network of fine strands that served both to cross-link the microtubules and to interconnect them with the membrane-bounded organelles. The strands were decorated with granular materials and were irregular in dimension. They appeared either singly or as an extensive anastomosing network in fresh axons. The microtubule-associated strands were observed in fresh, saponin-extracted, or aldehyde-fixed tissue. To explore further the identity of the microtubule-associated strands, microtubules purified from brain tissue and containing the high molecular weight microtubule-associated proteins MAP 1 and MAP 2 were examined by quick-freeze, deep-etch electron microscopy. The purified microtubules were connected by a network of strands quite similar in appearance to those observed in the IDPN axons. Control microtubule preparations consisting only of tubulin and lacking the MAPs were devoid of associated strands. To learn which of the MAPs were present in the microtubule bundles in the axon, sections of axons from IDPN-treated rats were examined by immunofluorescence microscopy using antibodies to MAP 1A, MAP 1B, MAP 2, and tubulin. Anti-MAP 2 staining was only marginally detectable in the IDPN-treated axons, consistent with earlier observations. Anti-MAP 1A and anti-MAP 1B brightly stained the IDPN-treated axons, with the staining exclusively limited to the microtubule domains. Furthermore, thin section-immunoelectron microscopy using colloidal gold-labeled second antibodies revealed that both anti-MAP 1A and anti-MAP 1B stained fuzzy filamentous structures between microtubules. In view of earlier work indicating that rapid transport is associated with the microtubule domain in the IDPN-treated axon, it now appears that MAP 1A and MAP 1B may play a role in this process. We believe that MAP 1A and MAP 1B are major components of the microtubule-associated fibrillar matrix in the axon.

Animals↗