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PubMed1995

The effect of solid ankle-foot orthoses on movement patterns used in a supine-to-stand rising task.

BACKGROUND AND PURPOSE: Within dynamical pattern theory, ankle motion can be proposed to be a control variable, and solid ankle-foot orthoses (SAFOs) can be considered a constraint to ankle movement. The purpose of this study was to examine the effect of SAFOs on movement patterns used to rise from the supine position to erect stance. SUBJECTS: Thirty-nine nondisabled young adults, ranging in age from 20 to 28 years (X = 22.7, SD = 1.87), participated. METHODS: Subjects were videotaped while rising from a supine position on a floor mat. Each subject performed 10 trials under each of four conditions: without SAFOs, right SAFO, left SAFO, and bilateral SAFOs. Movement patterns were described within three body components (ie, upper extremities, axial region, and lower extremities) by determining the mode and the incidence of each movement pattern under each condition. The subjects' mode movement patterns in the no SAFO condition were compared with mode movement patterns in the SAFO conditions using McNemar tests. RESULTS: Without SAFOs, subjects rose most commonly using a push and reach pattern of the upper extremities, a forward with rotation pattern in the trunk, and an asymmetrical squat in the lower extremities. Changes in the incidence of movement patterns occurred in all of the SAFO conditions when compared with the no SAFO condition. These changes resulted in more asymmetry when SAFOs were worn, and asymmetry was most notable in the axial region. CONCLUSIONS AND DISCUSSION: From a dynamic pattern theory perspective, ankle motion is a control variable for the supine-to-stand rising task.

Adult↗
PubMed2003

Characterization of variant patterns of nodular lymphocyte predominant hodgkin lymphoma with immunohistologic and clinical correlation.

Nodular lymphocyte predominant Hodgkin lymphoma (NLPHL) has traditionally been recognized as having two morphologic patterns, nodular and diffuse, and the current WHO definition of NLPHL requires at least a partial nodular pattern. Variant patterns have not been well documented. We analyzed retrospectively the morphologic and immunophenotypic patterns of NLPHL from 118 patients (total of 137 biopsy samples). Histology plus antibodies directed against CD20, CD3, and CD21 were used to evaluate the immunoarchitecture. We identified six distinct immunoarchitectural patterns in our cases of NLPHL: "classic" (B-cell-rich) nodular, serpiginous/interconnected nodular, nodular with prominent extranodular L&H cells, T-cell-rich nodular, diffuse with a T-cell-rich background (T-cell-rich B-cell lymphoma [TCRBCL]-like), and a (diffuse) B-cell-rich pattern. Small germinal centers within neoplastic nodules were found in approximately 15% of cases, a finding not previously emphasized in NLPHL. Prominent sclerosis was identified in approximately 20% of cases and was frequently seen in recurrent disease. Clinical follow-up was obtained on 56 patients, including 26 patients who had not had recurrence of disease and 30 patients who had recurrence. The follow-up period was 5 months to 16 years (median 2.5 years). The presence of a diffuse (TCRBCL-like) pattern was significantly more common in patients with recurrent disease than those without recurrence. Furthermore, the presence of a diffuse pattern (TCRBCL-like) was shown to be an independent predictor of recurrent disease (P = 0.00324). In addition, there is a tendency for progression to an increasingly more diffuse pattern over time. Analysis of sequential biopsies from patients with recurrent disease suggests that the presence of prominent extranodular L&H cells might represent early evolution to a diffuse (TCRBCL-like) pattern. We also report three patients who presented initially with diffuse large B-cell lymphoma and later developed NLPHL.

Adolescent↗
PubMed2001

A comparison of two methods of evaluating cornea-to-contact lens base curve fluorescein patterns in keratoconus.

PURPOSE: The purposes of the study were as follows: (1) to compare the apical fitting relationship of habitual contact lens fluorescein patterns in keratoconus as determined by clinician assessment of on-eye patterns to those determined by photograph readers looking at slides of fluorescein patterns and (2) to determine the validity of the techniques used in assessing the apical fitting relationships of rigid corneal contact lenses on keratoconic corneas. METHODS: Central fluorescein patterns of rigid contact lens-wearing keratoconus patients enrolled in the Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study were graded as "definite touch," "touch," "clearance," or "definite clearance" by certified clinicians. Photographs of these patterns were evaluated independently by certified, masked photograph readers using the same grading scale. RESULTS: Agreement between "re-reads" of the same fluorescein pattern slides by the photograph readers was substantial (weighted kappa = 0.751). Agreement between assessments of habitual fit fluorescein patterns at the baseline vs. the repeat visits was poor for the photograph readers (weighted kappa = 0.254) and moderate for the clinicians (kappa = 0.480). Agreement between clinicians' and photograph readers' assessment of the habitual contact lens fluorescein pattern at the baseline visit was fair (weighted kappa = 0.382). CONCLUSIONS: Repeatability and validity of this technique were fair to excellent. Many factors influence fluorescein pattern interpretation, and improvement of the objective method of fluorescein pattern assessment by photograph readers will require improved methodology that takes these factors into consideration.

Contact Lenses↗
PubMed2002

Evaluation of tear film interference patterns and measures of tear break-up time.

PURPOSE: The purpose of this study was to compare the agreement within and between examiners when evaluating real-time and digital photographs of TearScope Plus tear film interference patterns. We also evaluated between-examiner agreement of noninvasive digital tear break-up time (NITBUT) using the TearScope, the relation between NITBUT and tear film interference patterns, and the relation between NITBUT and tear break-up time (TBUT). METHODS: Forty nondry eye patients were seen for digital imaging of the tear film using the TearScope Plus mounted on a slit-lamp with the EyeCap Ophthalmic Image Capture System. Two independent examiners first assessed the tear interference pattern in real-time and then captured the patterns and NITBUT digitally for a period of approximately 60 s. Each image series was later graded for interference pattern and NITBUT by the two independent, masked examiners. RESULTS: Within-examiner comparisons of real-time and digital tear pattern photograph grading showed moderate to substantial agreement for experienced examiners (kappa for examiner 1 = 0.76 and kappa for examiner 2 = 0.55). Between-examiner agreement when grading tear patterns was also substantial in real-time (kappa = 0.72) and moderate when using digital photography (kappa = 0.59). The between-examiner mean NITBUT was 11.2+/-6.8 s and the 95% limits of agreement between examiners were -19.2 to +9.2 s. The mean TBUT was 7.6+/-10.4 s, and it was on average 3.7+/-12.0 s shorter than NITBUT (p = 0.06). Thicker tear film interference patterns graded photographically were associated with longer NITBUTs for both examiners (p = 0.001). CONCLUSIONS: There is moderate to substantial within- and between-examiner agreement when comparing real-time and digital tear interference patterns photographs when using the TearScope. Although there is considerable between-examiner variability with the NITBUT test, the thicker lipid layer tear patterns tend to be associated with longer NITBUTs.

Adult↗
PubMed2004

Pattern recognition receptors and their involvement in the pathogenesis of arthritis.

PURPOSE OF REVIEW: Pattern recognition receptors are germ-line encoded receptors that recognize specific pathogen-associated molecules, thereby allowing the innate immune system to distinguish self from nonself structures. Pattern recognition receptors mediate activation of different signaling pathways, resulting in the production of proinflammatory cytokines and the expression of antimicrobial genes. Additionally, pattern recognition receptors play a central role in the activation and direction of the adaptive immune response. This review summarizes recent advances in research trying to elucidate the link between different pattern recognition receptors and inflammatory autoimmune disorders. RECENT FINDINGS: The best known pattern recognition receptors, the toll-like receptors, are involved in the regulation of inflammation during infectious diseases. They affect apoptotic pathways and dendritic cell maturation, and interact with B-cell receptors in priming T-cell responses to host-derived DNA. This brought toll-like receptors and other pattern recognition receptors into focus as potential players in the induction of autoimmune diseases. Indeed, several inflammatory autoimmune diseases have been linked during the past few years to defects or polymorphisms of genes encoding pattern recognition receptors. SUMMARY: The discovery of toll-like receptors and other groups of pattern recognition receptors, such as the caspase recruitment domains or the triggering receptors expressed by myeloid cells, allowed one to draw an increasingly complex picture of immune responses to pathogens. The growing evidence for an involvement of pattern recognition receptors in the pathogenesis of autoimmune disorders warrants further investigation of the expression and function of pattern recognition receptors to develop novel therapeutics for diseases such as rheumatoid arthritis.

Adaptor Proteins, Signal Transducing↗
PubMed1994

Phylogenetic pattern and the quantification of organismal biodiversity.

Biodiversity can be explored at a number of different levels and in principle may be separately quantified at each. Phylogenetic pattern has the potential to quantify and estimate biodiversity at the finest scale, that is, variation among species in features or attributes. This scale is an important one for conservation, as it should form the basis for prioritizing conservation efforts at the species level. Further, recent published objections to differentially weighting species are answered by defining option value at this feature-level. Unfortunately, there has been no consensus on exactly how phylogeny can be used to value species, possibly because proper consideration of the link between pattern and underlying features generally has been unresolved. 'Phylogenetic diversity' (PD) represents just one of several approaches that do consider diversity at the feature-level explicitly. These alternative approaches are discussed in the context of a general framework for using pattern to quantify diversity at a level below that of the original objects. The pattern framework highlights that estimation of biodiversity at a lower level using pattern will require decisions about the nature of the units of diversity, the kind of pattern to be used, the model relating unit items to pattern, and finally how this implies a pattern-based measure reflecting biodiversity. An alternative published model for relating features to a particular form of phylogenetic pattern is considered, and shown to make unwarranted assumptions. A possible alternative definition of the underlying units of diversity is examined, which may represent a different form of option value, also quantifiable using phylogeny. A possible alternative pattern to a phylogenetic tree for the prediction of feature diversity is also discussed. The appeal of these alternative approaches depends on the goals of conservation; in addition, justification for prioritizing or weighting requires that any practical approach avoid arbitrary, unwarranted, assumptions.

Animals↗
PubMed1989

Characterization of Staphylococcus species by ribosomal RNA gene restriction patterns.

The rRNA gene restriction pattern sof 110 strains belonging to 12 staphylococcal species have been determined. The strains, isolated from various sources, were epidemiologically unrelated. Total DNA was cleaved with restriction enzymes HindIII and EcoRI, electrophoretically separated and probed with radiolabelled 16S rDNA from Bacillus subtilis inserted in a plasmid vector, pBR322. Fourty-four distinct HindIII patterns and 44 distinct EcoRI patterns were observed. Strains belonging to different species had different patterns. Although distinct patterns were also observed with some species, a core of common bands could be discerned within each species or subspecies. Analysis of the patterns revealed two taxa in Staphylococcus xylosus which were not evident using phenotypic characteristics. Of 18 strains which were difficult to identify using phenotypic schemes, 15 showed patterns typical of known species. The three remaining atypical strains showed unusual patterns and may belong either to a known species, not included in the study, or to a new species. Since various patterns were observed within some species (e.g.S.aureus and S. epidermidis), rRNA gene restriction patterns may have epidemiological, as well as taxonomic interest.

Animals↗
PubMed2001

Detection of glass patterns by pigeons and humans: implications for differences in higher-level processing.

Glass patterns have been used to examine mechanisms underlying form perception. The current investigation compared detection of Glass patterns by pigeons and humans and provides evidence for substantial species differences in global form perception. Subjects were required to discriminate, on a simultaneous display, a random dot pattern from a Glass pattern. Four different randomly presented Glass patterns were used (concentric, radial, parallel-vertical, and parallel-horizontal). Detection thresholds were measured by degrading the Glass patterns through the addition of random noise. For both humans and pigeons, discrimination decreased systematically with the addition of noise. Humans showed detection differences among the four patterns, with lowest thresholds to radial and concentric patterns and highest thresholds to the parallel-horiZontal pattern. Pigeons did not show a detection difference across the four patterns. Implications for differences in neural processing of complex forms are discussed.

Adult↗
PubMed2005

Evolution of clinical pattern of parthenium dermatitis: a study of 74 cases.

Our aim was to study the evolution of clinical pattern of parthenium dermatitis. Patients with clinical picture consistent with parthenium dermatitis for 3 years or more along with positive patch test to parthenium were studied. Patients were questioned regarding the site(s) of dermatitis at the onset and change in localization in the following years. Patients were classified into airborne contact dermatitis, chronic actinic dermatitis (CAD) pattern or mixed pattern dermatitis. There were 74 patients (49 men and 25 women) with an age range of 22-70 years and the mean duration of 7.7 years. 60 (39 men and 21 women) patients had airborne contact dermatitis, 5 mixed pattern and 9 CAD pattern at the onset. Of the 60 patients with airborne contact dermatitis, 27 (19 men and 8 women) changed to CAD pattern and 11 (6 men and 5 women) to mixed pattern after an average period of 4.2 years. Of the 19 patients photopatch-tested with parthenium, 3 showed photoallergic reaction and the other 3 showed photoaggravation. Our results suggest that the clinical pattern of parthenium dermatitis undergoes a significant change after the onset, i.e. progresses from airborne contact dermatitis to mixed pattern or CAD pattern.

Adult↗
PubMed1994

Some patients with anti-myeloperoxidase autoantibodies have a C-ANCA pattern.

Rapidly progressive glomerulonephritis with or without other signs of systemic vasculitis is often accompanied by antibodies to myeloperoxidase. Such antibodies normally produce a perinuclear pattern on ethanol-fixed neutrophils (perinuclear anti-neutrophil cytoplasm antibodies (P-ANCA)) at indirect immunofluorescence. We report here sera from three patients that are anti-myeloperoxidase-positive in ELISA that instead produce a cytoplasmic pattern (classical anti-neutrophil cytoplasmic antibodies (C-ANCA)), a pattern normally seen in conjunction with antibodies to proteinase 3. These sera did not react with proteinase 3. For two of the sera the specificity of the anti-myeloperoxidase reaction was confirmed with inhibition-ELISA experiments and with immunoblotting. A mouse anti-myeloperoxidase MoAb that produces a cytoplasmic pattern is also described. Competition ELISA experiments show that this antibody and anti-myeloperoxidase sera with cytoplasmic pattern recognize epitopes that are separate from epitopes recognized by another perinuclear pattern producing anti-myeloperoxidase MoAb. 'Cytoplasmic pattern' epitopes as well as 'perinuclear pattern' epitopes can be found on all three major myeloperoxidase isoforms, after separation by ion exchange chromatography. Affinity chromatography, using the cytoplasmic pattern producing anti-myeloperoxidase monoclonal antibody, shows that the epitope recognized by this MoAb is present on all myeloperoxidase molecules. This epitope is not confined to any special subpopulation. These findings indicate that all myeloperoxidase do not relocate after ethanol fixation, and that C-ANCA and P-ANCA epitopes exist simultaneously on the same myeloperoxidase molecule. We propose that the two immunofluorescence patterns arise due to different availabilities of the epitopes in the microenvironment where myeloperoxidase is present.

Aged↗
PubMed2004

Variations in histological patterns of interstitial pneumonia between connective tissue disorders and their relationship to prognosis.

AIMS AND METHODS: Pulmonary parenchymal disease is common in patients with connective tissue disorders (CTDs). However, most reports precede recognition of non-specific interstitial pneumonia (NSIP). We have therefore reviewed 54 lung biopsies from 37 patients with polymyositis/dermatomyositis (PM/DM) (n = 13), Sjögren's syndrome (n = 5), rheumatoid arthritis (n = 17) and systemic lupus erythematosus (SLE) (n = 2) to assess the overall and relative frequencies of patterns of interstitial pneumonia and their impact on prognosis. RESULTS AND CONCLUSIONS: NSIP was the most common pattern with an overall biopsy prevalence of 39% and patient prevalence of 41%. There was variation in prevalence between individual CTDs, with PM/DM commonly showing organizing pneumonia (n = 5), rheumatoid arthritis showing follicular bronchiolitis (n = 6) and Sjögren's syndrome showing chronic bronchiolitis (n = 4). These patterns presented either separately or in association with NSIP, occasionally with different patterns in biopsies from separate lobes. Only four patients showed a pattern of usual interstitial pneumonia (UIP): two with rheumatoid arthritis and one each with PM/DM and SLE. Overall mortality was 24%, the most frequently associated pattern being fibrotic NSIP (n = 5). In nine cases, pulmonary presentation preceded the systemic manifestation of the CTDs. When patients with CTDs present with chronic interstitial lung disease, the most common pattern is NSIP, although there is variation in pattern prevalence between individual disorders and patterns of interstitial pneumonia frequently overlap. These data suggest a different biology for intestitial pneumonias in CTDs when compared with the idiopathic interstitial pneumonias where UIP is the most common pattern. Mortality is similar to that seen in idiopathic NSIP and, coupled with pulmonary presentation occurring prior to the systemic manifestation of disease, this may have a bearing on the origin of some cases of putative idiopathic NSIP.

Adult↗
PubMed1979

The prestalk-prespore pattern in cellular slime molds.

In cellular slime molds the slugs become divided into two regions with different properties, and anterior prestalk-zone and a posterior prespore zone. Although the cells in these zones are normally destined to form the stalk cells and spores of the fruiting body, respectively, they are not irreversibly committed to one sort of differentiation or the other during the slug stage. The volume ratio of the two zones remains almost constant over a wide range of slug sizes. If the prestalk-prespore pattern is distrubed by removing tissue from the slug, conversion of tissue from prestalk to prespore or vice versa occurs as necessary to restore a normal pattern with normal proportions. Conversions also occur in both directions during normal development. The initial formation of the prestalk-prespore pattern may well involve sorting-out, but other mechanisms must be invoked to account for regulation. We describe three different models of the generation of the prestalk-prespore pattern, the'cell-contact model' of McMahon, in which pattern is created by interactions of cells with their immediate neighbors, the 'positional-information model' of various authors, in which pattern formation involves an overall gradient and a gradient-reading mechanism, and the 'activator-inhibitor model' of Gierer and Meinhardt, in which the prestalk-prespore pattern is formed by a system of diffusible substances that affect one another's production. The activator-inhibitor model is the most successful of the models at describing the known features of the prestalk-prespore pattern. The various models lead to a number of distinctive predictions. According to the cell-contact model, small transplants may cause gross changes in the prestalk-prespore pattern, and mutants may exist which severely disrupt pattern formation even if diluted with a large excess of wild-type cells. Positional-information models predict the existence of 'gradient-reading mutants'; slugs that are a mixture of such mutants and wild-type cells would show two prestalk-prespore boundaries, one at the mutant and one at the normal position. Both the activator-inhibitor model and some versions of the positional-information model predict that small transplants will sometimes induce accessory prestalk or prespore zones; the quantitative characteristics of these effects may allow one to make a case in favor of one or other of the two models. Finally, the activator-inhibitor model leads one to expect that mutants may be isolated which normally show accessory prestalk or prespore zones. A search for these phenomena may help determine whether the activator-inhibitor model will continue to enjoy its present preeminent position.

Cell Adhesion↗
PubMed1984

Patterns of histone acetylation in Physarum polycephalum. H2A and H2B acetylation is functionally distinct from H3 and H4 acetylation.

Histone acetylation has previously been correlated with both chromosome replication and transcription. We present evidence that (a) confirms both correlations in the true slime mold, Physarum polycephalum and (b) shows that quite a different pattern of acetate turnover is associated with replication compared with transcription. The pattern associated with replication involves turnover of acetate on all four core histones on species containing one or two acetates per molecule. This pattern was resolved from the transcription-associated pattern by three different procedures: (a) detailed analysis of gels of histones pulse-labelled with acetate; (b) the pattern of acetylation of histones pulse-labelled with [3H]lysine; and (c) the pattern of acetylation of soluble histones. The pattern associated with transcription is restricted to histones H3 and H4 and occurs mostly on highly acetylated species. This pattern was resolved by (a) analysis of gels of histones pulse-labelled with acetate; (b) the pattern of histone acetylation in G2 phase of the cell cycle; and (c) the pattern of histone acetylation in the presence of cycloheximide.

Acetates↗
PubMed2004

Posthospital care transitions: patterns, complications, and risk identification.

OBJECTIVES: To (1) describe patterns of posthospital care transitions; (2) characterize these patterns as uncomplicated or complicated; (3) identify those at greatest risk for complicated transitions. DATA SOURCES/STUDY SETTING: The Medicare Current Beneficiary Survey was used to identify beneficiaries aged 65 and older who were discharged from an acute care hospital in 1997-1998. STUDY DESIGN: Patterns of posthospital transfers were described over a 30-day time period following initial hospital discharge. Uncomplicated posthospital care patterns were defined as a sequence of transfers from higher-to lower-intensity care environments without recidivism, while complicated posthospital care patterns were defined as the opposite sequence of events. Indices were developed to identify patients at risk for complicated transitions. PRINCIPAL FINDINGS: Forty-six distinct types of care patterns were observed during the 30 days following hospital discharge. Among these patterns, 444 episodes (61.2 percent) were limited to a single transfer, 130 episodes (17.9 percent) included two transfers, 62 episodes (8.5 percent) involved three transfers, and 31 episodes (4.3 percent) involved four or more transfers. Fifty-nine episodes (8.1 percent) resulted in death. Between 13.4 percent and 25.0 percent of posthospital care patterns in the 1998 sample were classified as complicated. The area under the receiver operating curve was 0.771 for a predictive index that utilized administrative data and 0.833 for an index that used a combination of administrative and self-reported data. CONCLUSIONS: Posthospital care transitions are common among Medicare beneficiaries and patterns of care vary greatly. A significant number of beneficiaries experienced complicated care transitions-a finding that has important implications for both patient safety and cost-containment efforts. Patients at risk for complicated care patterns can be identified using data available at the time of hospital discharge.

Aftercare↗
PubMed1997

Changing patterns of distress during the adjustment of recent immigrants: a 1-year follow-up study.

A sample of 419 recent immigrants from the former Soviet Union to Israel was assessed, with a 1-year follow-up of 199 of these subjects. The Immigration Related Stressors Scale, Talbieh Brief Distress Inventory and Multidimensional Scale of Perceived Social Support were employed to measure the level and sources of distress, as well as the sources of social support. Three major patterns of change in distress level were distinguished, and their 1-year prevalence rates were established. In total, 44% of the respondents demonstrated the 'normal' pattern, with a permanent low distress level, 33% displayed the 'positive' pattern, with either persistent moderate or decreasing distress, and 23% displayed the 'negative' pattern, with either persistent high or increasing distress. Among the immigrants who demonstrated the positive pattern of change in distress, rates of stressors such as 'anxiety about the future', 'uncertainty in the present', 'depressive state', 'insufficient knowledge of Hebrew' and 'malevolence of Israelis' decreased during the study period. In those who showed the negative pattern, rates of stressors such as 'personality characteristics' and 'lack of acceptance of the host culture/mentality' have increased. Immigrants who showed the normal and positive patterns had greater total social support than those who showed the negative pattern. The level of family support tended be higher among immigrants with the normal pattern, while support by friends tended to be greater among those with the positive pattern of change in distress.

Adaptation, Psychological↗
PubMed2006

What is the biological basis of pattern formation of skin lesions?

Pattern recognition is at the heart of clinical dermatology and dermatopathology. Yet, while every practitioner of the art of dermatological diagnosis recognizes the supreme value of diagnostic cues provided by defined patterns of 'efflorescences', few contemplate on the biological basis of pattern formation in and of skin lesions. Vice versa, developmental and theoretical biologists, who would be best prepared to study skin lesion patterns, are lamentably slow to discover this field as a uniquely instructive testing ground for probing theoretical concepts on pattern generation in the human system. As a result, we have at best scraped the surface of understanding the biological basis of pattern formation of skin lesions, and widely open questions dominate over definitive answer. As a symmetry-breaking force, pattern formation represents one of the most fundamental principles that nature enlists for system organization. Thus, the peculiar and often characteristic arrangements that skin lesions display provide a unique opportunity to reflect upon--and to experimentally dissect--the powerful organizing principles at the crossroads of developmental, skin and theoretical biology, genetics, and clinical dermatology that underlie these--increasingly less enigmatic--phenomena. The current 'Controversies' feature offers a range of different perspectives on how pattern formation of skin lesions can be approached. With this, we hope to encourage more systematic interdisciplinary research efforts geared at unraveling the many unsolved, yet utterly fascinating mysteries of dermatological pattern formation. In short: never a dull pattern!

Algorithms↗
PubMed1987

Activation patterns of embryonic chick lumbosacral motoneurones following large spinal cord reversals.

1. Embryonic chick motoneurones were caused to innervate inappropriate hindlimb muscles by rotating the presumptive lumbosacral region of the neural tube in stage 15-16 embryos which is prior to the outgrowth of motoneurone axons. 2. The activation patterns of motoneurones in control and spinal cord reversal embryos were analysed from electromyographic (e.m.g.) recordings of stage 36 limb muscles during evoked movement sequences in an isolated spinal cord-limb preparation. Histograms representing the frequency of activation were constructed for each muscle. The muscle's pattern of activation was classified as flexor-like or extensor-like and compared to the activation patterns of control muscles. 3. A series of control operations was performed in which the prospective lumbosacral region of the neural tube was removed and replaced in its original orientation. Muscles in these embryos were innervated by their normal motoneurone pools and they were activated normally, indicating that the neural tube operation per se does not alter the activation pattern of motoneurones. Furthermore, some muscles (twelve out of sixty-one) in spinal cord reversal embryos had normal activation patterns and appeared to be innervated by their original motoneurones. Based on these results and the result of a previous study (Landmesser & O'Donovan, 1984 b), it is concluded that motoneurones in reversed spinal cords are activated in a manner appropriate for their original identity. 4. The majority of muscles (thirty-three out of sixty-one) in large spinal cord reversal embryos were activated during an appropriate phase of the kicking cycle. Of the remaining muscles, 16% were activated inappropriately (i.e. extensor muscles were activated as flexors, and vice versa), and 30% had a novel 'mixed' flexor- and extensor-like activation pattern. However, the activation pattern of most muscles differed markedly from that of any other control muscles regardless of whether the muscle was activated appropriately or inappropriately as a flexor or extensor. The abnormal activation patterns are a likely consequence of the diffuse distribution of inappropriate motoneurones projecting to foreign muscles in embryos with large spinal cord reversals. Since it is likely that motoneurones are still activated according to their original identity, the activation patterns of individual foreign motor units projecting to a muscle sum in e.m.g. recordings to produce a novel abnormal activation pattern.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗
PubMed1992

The effect of the stimulation pattern on the fatigue of single motor units in adult cats.

1. The main purpose of this study was to examine the effects of two subtly different stimulus patterns on the force developed by fast-twitch, fatiguable motor units in a cat hindlimb muscle during control (pre-fatigue) and fatiguing contractions. 2. The peak force and the force-time integral responses of nineteen high fatigue (FF) and three intermediate fatigue (FI) motor units of the tibialis posterior muscle in five deeply anaesthetized adult cats were measured at selected times during the course of a 360-s fatigue test. 3. The fatigue test involved a pseudo-random alternation of two patterns of stimulation. One pattern (regular) was composed of a train of stimuli with constant interpulse intervals, set at 1.8 x the twitch contraction time of each unit (interval range, 27-51 ms), and delivered for 500 (or 400) ms. For the total (FF + FI) motor-unit sample, the mean (+/- S.D.) stimulation frequency was 26 +/- 4 Hz (range, 19-37 Hz). The other stimulus pattern (optimized) consisted of three initial stimuli with short (10 ms) interpulse intervals, followed by a constant interpulse-interval train that was adjusted (interval range, 29-62 ms; frequency, 23 +/- 5 Hz; frequency range, 16-36 Hz) such that the total train had the same number of pulses, and the same average frequency and duration as the regular train. 4. The stimulus trains were delivered at 1 s-1 for 360 s, using three-train sequences of each pattern, randomly alternating with one another. The response of the third train in each sequence was selected for the force measurements. The force profile obtained from the fatigue test was subsequently decomposed into two profiles: one attributable to regular and one to optimized stimulation. 5. During the initial responses to the fatigue test, the optimized stimulus pattern produced significantly more force than the regular stimulus pattern. For FF units, the mean increase in peak force (141%) was significantly greater than the increase in the force-time integral (59%). 6. All motor units exhibited an initial potentiation of peak force with the regular stimulation pattern, whereas peak force declined monotonically with the optimized pattern. In contrast, the force-time integral potentiated in the first 30 s for both regular and optimized stimulus patterns. 7. Each motor unit maintained an increased force response to optimized stimulation during the fatigue test, with the greatest relative increase occurring about 120 s into the test, well after the potentiation effect had subsided.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗