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PubMed2001

Clonality analysis using X-chromosome inactivation patterns by HUMARA-PCR assay in female controls and patients with idiopathic thrombocytosis in Taiwan.

OBJECTIVE: Analysis of X-chromosome inactivation patterns (XCIPs) is a useful tool in the diagnosis of clonal disorders. The human androgen receptor (HUMARA) locus is especially useful for clonality study. The present study was conducted 1) to determine the heterozygosity rate for HUMARA locus in Taiwanese women, 2) to determine the frequency of excessive skewing in different cell types, and 3) to determine the utility of XCIPs in the differential diagnosis of thrombocytosis. PATIENTS AND METHODS: XCIPs by HUMARA-PCR assay were performed on purified granulocytes and T cells from 73 female patients presenting with idiopathic persistent thrombocytosis (IT), 10 patients with reactive thrombocytosis (RT), and 46 bone marrow samples from female controls. XCIPs of buccal mucosa cells were also compared with those of T cells in 57 patients with IT. The percentage of clonal granulocytes was calculated after correcting for the degree of Lyonization in T cells. RESULTS: The heterozygosity rate for the HUMARA gene was 89.1% in Taiwanese females. The median age of informative IT patients and controls was 59 (18-92) and 58 (19-89), respectively. Excessive skewing (allele ratio <0.33) was more frequent in granulocytes than in T cells in both controls (12/43 vs 9/43, p = 0.080) and IT patients (56/64 vs 25/64, p < 0.001). XCIPs were the same for both buccal mucosa and T cells in 43 patients but were different in 14 patients. Of the 43 informative controls, 31 had a polyclonal pattern; an ambiguous pattern was found in nine; and the remaining three, aged 71, 73, and 80, respectively, had a clonal pattern. A clonal pattern was found in 42 IT patients, a polyclonal pattern in 12, and an ambiguous pattern in 10 of the 64 IT patients. The frequency of clonal, polyclonal, and ambiguous patterns in the 40 IT patients with age < or = 65 was 55.0%, 30.0%, and 15.0%, respectively. None of the IT patients aged >65 had a polyclonal disease. IT patients aged >65 had a significantly higher frequency of clonal pattern (p = 0.030) and a significantly lower frequency of polyclonal pattern (p = 0.002) than those with age <65. Of the eight heterozygous patients with RT, one aged 80 exhibited a clonal pattern, and the remaining seven had a polyclonal pattern. CONCLUSIONS: The present study on Taiwanese females showed a heterozygosity rate of 89.1% for the HUMARA gene. Our results confirmed that IT is a heterogeneous disorder in terms of clonality. Twenty-three percent of IT patients exhibited a greater than 20% difference in allele expression for buccal mucosa and T cells. Presence of a clonal XCIP in young patients with IT can serve as a positive marker for the diagnosis of clonal thrombocytosis, and elderly patients with polyclonal XCIPs are unlikely to have essential thrombocythemia.

Adolescent↗
PubMed2005

A reappraisal of rhythmic coma patterns in children.

OBJECTIVE: This study was designed to determine the prevalence of rhythmic coma patterns in comatose children and to ascertain the prognostic significance of reactive rhythmic coma patterns. METHODS: We retrospectively analyzed and classified electroencephalogram (EEGs) in comatose children between two months and 18 years of age during the period 1996 - 2003 according to modified Young's classification. Outcome at one-year was scored according to the Paediatric Cerebral and Overall Performance Category Scale. Outcomes were compared using Fisher's exact test and Mann-Whitney test. RESULTS: Analysis of 63 electroencephalogram (EEG) records in 38 patients showed rhythmic patterns in 19 records (30.2%; 9 alpha, 4 spindle, 4 theta and 2 beta coma patterns, total number of children = 14). Aetiology and outcome of alpha coma patterns and other rhythmic coma patterns were similar. In five children, one type of rhythmic pattern changed to another. Records with reactive rhythmic coma 66.7% (6/9), were associated with favourable outcome. Sixty percent of the records (6/10 records in seven children) with non-reactive pattern were associated with unfavourable outcome. This clinically significant difference did not reach statistical significance (lower Paediatric Cerebral and Overall Performance Category Scale score p= 0.14; favourable outcome p=0. 19). CONCLUSION: Rhythmic coma patterns in comatose children are not uncommon. Aetiology, reactivity and outcome of individual patterns are similar and thus make the rhythmic coma patterns distinct EEG signatures in comatose children. There was a clinically significant better outcome with reactive rhythmic coma patterns.

Adolescent↗
PubMed2000

Capillary network patterning during angiogenesis.

1. Although much is known of signalling events associated with angiogenesis, starting with a sprout, less is known of how an intact microvascular network is correctly formed following the initiation of sprouting. The aim of the present report is to evaluate some of the factors that could be involved in directing the patterning of the resulting microvascular bed. 2. Hypothetical 'patterning rules' are discussed and considered in the context of data obtained from studies of angiogenesis. The guidelines suggest that both tissue- and stimulus-specific regulators are involved in directing patterning. 3. Examples of 'patterned' and 'non-patterned' angiogenesis in rat mesentery are given, with evidence to support stimulus-related differences in angiogenesis patterns. 4. Skeletal muscle angiogenesis follows metabolic patterns within the muscle, as discerned through traditional histochemical evaluation. However, further examination, using confocal microscopy and new patterning assays, indicates that branching patterns differ according to stimulus. Patterning guidelines within the tissue may be important in preventing the growth of sinusoidal vessels. 5. The concept of 'angiotypes' is proposed to direct future studies towards understanding how therapeutic angiogenesis or angiostasis applications can be used to obtain correctly patterned microvascular networks. Angiogenesis via 'branching' compared with 'non-branching' angiotypes will involve different signalling pathways. Both sprouting and dividing of capillaries are found in the 'branching' angiotype, with each pattern having several subtypes that would be expected to be mediated via different signalling mechanisms.

Angiotensins↗
PubMed1999

Highly reproducible spatiotemporal patterns of mammalian embryonic movements at the developmental stage of the earliest spontaneous motility.

The principles underlying the variations in patterns of mammalian embryonic movements have not been established. In an attempt to clarify the mechanism that is responsible for the variations in motor patterns, we carried out a precise quantitative spatiotemporal analysis of movements in mouse embryos, using a transplacental perfusion method for the in vitro maintenance of live mammalian embryos. Episodes of spontaneous movements at the inception of motility, at embryonic day 12.5, occurred once every few minutes, lasted for several seconds and consisted of successive movements of body regions, the spatiotemporal patterns of which varied from episode to episode. By analysing and categorizing the patterns of these movements, we found that embryonic movements follow relatively few restricted patterns with respect to the order of the movements of body regions. A further analysis of episodes at high spatiotemporal resolution revealed that most of the episodes in a major category could be classified into two distinct subtypes. Each of these subtypes had its own highly reproducible spatiotemporal patterns of movement. Overall, these results show that early embryonic movements follow relatively few rather stereotyped patterns, and random local fluctuations have little effect on such movement patterns. The appearance of one pattern out of several rather stereotyped patterns may be the main cause of apparent variations in patterns of early embryonic movements. The stereotyped patterns may represent important orderly characteristics of spontaneous embryonic activities that may be involved in the development of orderly structures and functions in higher animals.

Animals↗
PubMed1991

Evidence for a common motion mechanism of luminance-modulated and contrast-modulated patterns: selective adaptation.

Selective adaptation effects were measured with contrast-modulated patterns and sine-wave gratings in order to determine the extent to which the two patterns are processed by common mechanisms. Direction-specific adaptation effects were measured for a contrast-modulated adapting pattern and a test pattern. The contrast-modulated adapting pattern was composed of a sine-wave grating of 8 cycles deg-1 whose contrast was spatially modulated by a sinusoid of 1 cycle deg-1 at one of four levels: 100%, 60%, 30%, or 0%. The results showed that contrast-modulation thresholds for contrast-modulated gratings were raised by 0.3 to 0.5 log units following adaptation to a contrast-modulated grating moving in the same direction as the test pattern, relative to thresholds obtained following adaptation to a contrast-modulated grafting moving in the opposite direction. Cross-adaptation effects were also measured with a sine-wave adapting pattern and a contrast-modulated test pattern. The sine-wave adapting pattern was a sine-wave grating of 1 cycle deg-1 whose contrast was set to one of three levels: 16.4%, 1.25%, or 0%. The contrast-modulated test pattern was a sine-wave grating of 8 cycles deg-1 whose contrast was modulated by a sinusoid of 1 cycle deg-1. The results revealed that contrast-modulation thresholds for contrast-modulated gratings were raised by approximately 0.25 log units following adaptation to moving sine-wave gratings, relative to thresholds obtained following adaptation to a uniform field. Cross-adaptation effects were also obtained with a contrast-modulated adapting pattern and a sine-wave test pattern. The results support the view that signals generated from luminance-domain stimuli and from contrast-domain stimuli are processed by a common motion mechanism.

Adaptation, Ocular↗
PubMed1993

Masking, information integration, and tactile pattern perception: a comparison of the isolation and integration hypotheses.

Two competing models of the effects of pattern element proximity, masking, and perceptual integration on the discriminability of spatiotemporal vibrotactile patterns are compared. Kirman's 'integration hypothesis' predicts that pattern perception is facilitated by a process of perceptual integration which requires that pattern elements be presented in close spatial and temporal proximity. Conversely, the 'isolation hypothesis' predicts that the strong masking effects which occur when pattern elements are presented in close proximity impede the perception of patterns. Traditional masking studies do not provide a fair test of these two hypothesis because they rely on methods that measure the subject's ability to identify the target when the target is presented in conjunction with the mask, rather than the discriminability of the complex percept resulting from the integration of the target and mask. To account for this, a new procedure was devised where the amount of interelement masking and the discriminability of the pattern as a whole were measured independently as the spatial and temporal separation of the pattern elements were varied. As expected under both hypotheses, masking between pattern elements increased as either the spatial or the temporal separation between them was decreased. The pattern discrimination data also support the isolation hypothesis in that the patterns were discriminated less well with increasing temporal element separation with a similar but nonsignificant trend in the case of spatial separation. It is concluded that this new methodology should be applied to a wider range of tactile pattern processing situations in order to assess the generality of the results obtained.

Adult↗
PubMed1990

Calving patterns in seasonal dairy herds.

Two field studies examined the calving patterns of cows in seasonal dairy herds in the Waikato (Field Study 1) and South Taranaki regions (Field Study 2). The first study examined patterns for cows commencing their second or subsequent lactation in herds which had used an inseminating service during the previous season. The second study included first lactation heifers only in 15 herds where animals had been naturally mated, and in 15 herds in which they had been synchronised and then artificially inseminated at the synchronised oestrus. The parameters describing calving patterns were based on the date for each herd's planned start of calving (PSC), which was 282 days from the date on which breeding commenced in the preceding season. The average interval from PSC to mean calving date for the 35 herds in Field Study 1 was 22 days, with individual herds ranging from 15 to 30 days. In herds with heifers which had been naturally mated (Field Study 2), it was 17.6 days compared to 11.0 days for previously synchronised animals. Calculating the intervals from PSC to median calving date and separately for the last two quartiles more effectively described a herd's calving pattern. The duration for the last quartile of the calving pattern was influenced by the extent and timing of induced calving. In Field Study 1, 88.6% of the 35 herd owners induced premature parturition in at least one cow. In these herds, 11.3% of cows were treated and calved prematurely. Only 61.7% of heifers which had previously been naturally mated calved by 3 weeks after PSC. Their calving dates were not evenly distributed over this 3-week period, with 9.8% in the first week and 25.6% in the third week. The calving pattern for heifers which had been previously synchronised showed several distinct peaks. Calvings to the synchronised mating were completed 15 days after PSC, by which time 64.7% of animals had calved. By 3 weeks after PSC, 72.9% of these heifers had calved. The results showed that there was considerable variation in calving patterns in seasonal dairy herds. This variation would have been due to differences in conception pattern, and the way induced calving had been applied. The calving pattern in heifers which had been naturally mated was less concentrated than had been expected. Synchronisation can significantly concentrate the calving pattern of these first lactation animals. The parameters used to describe calving patterns may be less applicable in herds in which a high proportion of animals is induced to calve prematurely, or where a whole herd is synchronised. Nonetheless, they do serve as an illustrative example of the variation in calving patterns among herds.

Journal Article↗
PubMed1997

Stoichiometry of recombinant N-methyl-D-aspartate receptor channels inferred from single-channel current patterns.

Single-channel currents were recorded from mouse NR1-NR2B (zeta-epsilon2) receptors containing mixtures of wild-type and mutant subunits expressed in Xenopus oocytes. Mutant subunits had an asparagine-to-glutamine (N-to-Q) mutation at the N0 site of the M2 segment (NR1:598, NR2B:589). Receptors with pure N or Q NR1 and NR2 subunits generated single-channel currents with distinctive current patterns. Based on main and sublevel amplitudes, occupancy probabilities, and lifetimes, four patterns of current were identified, corresponding to receptors with the following subunit compositions (NR1/NR2): N/N, N/Q, Q/N, and Q/Q. Only one current pattern was apparent for each composition. When a mixture of N and Q NR2 subunits was coexpressed with pure mutant NR1 subunits, three single-channel current patterns were apparent. One pattern was the same as Q/Q receptors and another was the same as Q/N receptors. The third, novel pattern presumably arose from hybrid receptors having both N and Q NR2 subunits. When a mixture of N and Q NR1 subunits was coexpressed with pure mutant NR2 subunits, six single-channel current patterns were apparent. One pattern was the same as Q/Q receptors and another was the same as N/Q receptors. The four novel patterns presumably arose from hybrid receptors having both N and Q NR1 subunits. The relative frequency of NR1 hybrid receptor current patterns depended on the relative amounts of Q and N subunits that were injected into the oocytes. The number of hybrid receptor patterns suggests that there are two NR2 subunits per receptor and is consistent with either three or five NR1 subunits per receptor, depending on whether or not the order of mutant and wild-type subunits influences the current pattern. When considered in relation to other studies, the most straightforward interpretation of the results is that N-methyl-D-aspartate receptors are pentamers composed of three NR1 and two NR2 subunits.

Amino Acid Sequence↗
PubMed2003

The effect of breathing pattern on nebulizer drug delivery.

The significance of using breathing patterns with simplified functional shapes in vented jet nebulizer research is examined. This study is comprised of three parts: (1) The measurement and analysis of human breathing patterns, (2) the subsequent in vitro testing of the effects of breathing pattern differences using a consistent bench test method, and (3) a computer modeling of these effects on the estimated regional drug deposition in the human lung. Breathing through a Pari LC-Star nebulizer caused statistically significant changes (p < or = 0.05) in measured human breathing patterns when compared to normal breathing. Observed changes included an increase in the tidal volume (34%) and period (39%). Additionally, the average duty cycle shifted 12% towards a more symmetrical breath due to the unequal increase in the inhalation and exhalation times (55% and 28%, respectively). The position of the point of maximum flow in each breath phase shifted towards the beginning and end of the breath for the inhale and exhale by 28% and 48%, respectively. The bench testing revealed that breathing pattern shape variation caused statistically significant differences in nebulizer output only in two cases. Decreasing duty cycles and shifting the point of maximum flow towards the beginning of the breath both result in a decrease in output efficiency. Square flow patterns produced slight but consistently higher output efficiencies (average 2.1% higher) and a constant output particle size over the course of each breath, different from the other non-square patterns. Numerical simulations revealed no significant dosage differences resulting from breathing pattern shape variations. However, square wave patterns consistently produced slight overpredictions in comparison with real nebulizer patterns. In contrast, sine wave patterns were found to produce essentially the same results as nebulizer patterns in both the bench tests and in the deposition simulations. This suggests that sine wave shapes are preferable for simulating breathing when bench testing drug delivery using vented jet nebulizers.

Adult↗
PubMed2002

BEST: a novel computational approach for comparing gene expression patterns from early stages of Drosophila melanogaster development.

Embryonic gene expression patterns are an indispensable part of modern developmental biology. Currently, investigators must visually inspect numerous images containing embryonic expression patterns to identify spatially similar patterns for inferring potential genetic interactions. The lack of a computational approach to identify pattern similarities is an impediment to advancement in developmental biology research because of the rapidly increasing amount of available embryonic gene expression data. Therefore, we have developed computational approaches to automate the comparison of gene expression patterns contained in images of early stage Drosophila melanogaster embryos (prior to the beginning of germ-band elongation); similarities and differences in gene expression patterns in these early stages have extensive developmental effects. Here we describe a basic expression search tool (BEST) to retrieve best matching expression patterns for a given query expression pattern and a computational device for gene interaction inference using gene expression pattern images and information on the associated genotypes and probes. Analysis of a prototype collection of Drosophila gene expression pattern images is presented to demonstrate the utility of these methods in identifying biologically meaningful matches and inferring gene interactions by direct image content analysis. In particular, the use of BEST searches for gene expression patterns is akin to that of BLAST searches for finding similar sequences. These computational developmental biology methodologies are likely to make the great wealth of embryonic gene expression pattern data easily accessible and to accelerate the discovery of developmental networks.

Algorithms↗
PubMed2003

Dietary patterns of Hispanic elders are associated with acculturation and obesity.

The association of dietary patterns and obesity, particularly in Hispanics, is relatively poorly understood. This large U.S. population subgroup has a high prevalence of obesity and associated chronic conditions, and Hispanics are changing their dietary practices as they acculturate. Our objectives were 1) to identify dietary patterns among elderly Hispanics in Massachusetts, compared with those of non-Hispanic whites; 2) to associate dietary patterns with acculturation; and 3) to associate dietary patterns with total and central obesity. We used a representative sample of 449 Puerto Rican and 133 Dominican elders and a neighborhood-based sample of 243 non-Hispanic white elders, aged 60 to 92 y, from the cross-sectional Massachusetts Hispanic Elders Study. Obesity and central obesity were assessed with BMI (kg/m2) and waist circumference measurement, respectively. Acculturation was assessed by evaluating language use. Usual diet was assessed with a food frequency questionnaire specifically designed for use with this population. Dietary patterns were defined by cluster analysis of food group variables. We identified five clusters of individuals by dietary pattern, with proportionately greater energy intake from 1) fruit and breakfast cereal, 2) starchy vegetables, 3) rice, 4) whole milk and 5) sweets, respectively. Hispanics were less likely to follow the fruit and cereal or sweets patterns, and more likely to follow the starchy vegetables or milk patterns, than were non-Hispanic whites. Only Hispanics followed the rice pattern. Among Hispanics, acculturation was positively associated with the fruit and cereal pattern, and negatively with the rice pattern. Total and central obesity were positively associated with the rice pattern. Longitudinal studies are needed to clarify the causal nature of these associations.

Acculturation↗
PubMed2000

Idiopathic nonspecific interstitial pneumonia: prognostic significance of cellular and fibrosing patterns: survival comparison with usual interstitial pneumonia and desquamative interstitial pneumonia.

Nonspecific interstitial pneumonia (NSIP) has been proposed as a histologic subtype of idiopathic interstitial pneumonia with lung biopsy findings that are inconsistent with those of other idiopathic interstitial pneumonias. NSIP has a broad spectrum of histologic findings and a variable prognosis. The aim of this study was to determine whether it would be preferable to subdivide NSIP into cellular and fibrosing patterns. The authors classified lung biopsies from 101 patients with idiopathic interstitial lung disease as having histologic patterns of desquamative interstitial pneumonia (DIP), usual interstitial pneumonia (UIP), or cellular or fibrosing NSIP. Survival analysis was performed using the Kaplan-Meier method. Due to histologic, clinical, and survival similarities, the patients with idiopathic NSIP with lung biopsies that showed fibrosing as well as fibrosing and cellular patterns were combined into a single group of NSIP, fibrosing pattern. Of the 101 patients, 16 patients (9 women, 7 men) had idiopathic DIP; 56 patients (17 women, 39 men) had idiopathic UIP; 22 patients (7 women, 15 men) had idiopathic NSIP, fibrosing pattern; and 7 patients (2 women, 5 men) had idiopathic NSIP, cellular pattern. The patients had a mean age of 42, 51, 50, and 39 years respectively. Patients with idiopathic NSIP, cellular pattern had a better 5- and 10-year survival than those with idiopathic NSIP, fibrosing pattern (100% vs 90% and 100% vs 35% respectively, p = 0.027). Survival of patients with idiopathic UIP was worse than that of patients with idiopathic NSIP, fibrosing pattern (p = 0.014). The difference, however, was more evident at 5 years (43% vs 90%) than at 10 years (15% vs 35%). The 5- and 10-year survival of patients with idiopathic NSIP, cellular pattern and DIP was 100%, which was significantly better than that of patients with idiopathic UIP (p <0.0001). Based on these data, NSIP should be separated into cellular and fibrosing patterns, because these histologic patterns are associated with different clinical characteristics and prognoses.

Adult↗
PubMed2006

Short-term reproducibility of a non-dipping pattern in type 2 diabetic hypertensive patients.

BACKGROUND: Little information is available on the reproducibility of nocturnal variations in blood pressure in type 2 diabetic hypertensive patients. OBJECTIVE: We aimed to compare the intrasubject short-term reproducibility of a nocturnal non-dipping pattern and the prevalence of cardiac and extracardiac signs of target organ damage, in a group of type 2 diabetic hypertensive patients and in an age/gender-matched group of non-diabetic hypertensive subjects. METHODS: Thirty-six treated hypertensive patients with long-lasting type 2 diabetes (> 10 years duration) consecutively attending our hospital out-patient hypertension clinic (group I; mean age, 65 +/- 9 years), and 61 untreated non-diabetic subjects with grade 1 and grade 2 uncomplicated essential hypertension, matched for age and gender, and chosen from patients attending an outpatient clinic (group II; mean age, 65 +/- 5 years), were considered for this analysis. All patients underwent blood sampling for routine blood chemistry, 24-h urine collection for microalbuminuria, two 24-h periods of ambulatory blood pressure monitoring (ABPM) within a 4-week period, echocardiography, and carotid ultrasonography. A dipping pattern was defined as a greater than 10% reduction in the average systolic and diastolic blood pressure at night compared with average daytime values. RESULTS: A reproducible nocturnal dipping and non-dipping profile was found in 11 (30.6%) and 21 (58.3%) diabetic patients, respectively; while only in four (11.1%) patients was a variable dipping profile observed. Of the 23 patients with a non-dipping pattern during the first ABPM period, 21 (91.3%) also had this type of pattern during the second ABPM recording. In group II (non-diabetic hypertensive patients), 30 patients (49.2%, P < 0.05) had a dipping pattern, 13 patients (21.3%, P < 0.01) had a non-dipping profile pattern and 18 patients (29.5%, P < 0.01) had a variable dipping pattern. Of the 20 patients with a non-dipping pattern during the first ABPM period, 13 (65.0%) confirmed this type of pattern during the second ABPM recording. Finally, the prevalence of left ventricular hypertrophy (77.7 versus 41.4%, P < 0.01), carotid plaques (80.5 versus 38.3%, P < 0.01), carotid intima-media thickening (54.3 versus 44.0%, P < 0.05) and microalbuminuria (11.1 versus 2.0%, P < 0.01) was significantly higher in group I than in group II. According to a logistic regression analysis, diabetes, left ventricular hypertrophy and carotid plaques were the main independent predictors of the non-dipping (pattern in the overall population. CONCLUSIONS: These findings indicate that intrasubject variability of non-dipper pattern is lower in diabetic than in non-diabetic hypertensive patients, that classification of diabetic hypertensive patients as dipper or non-dipper on the basis of a single ABP recording is more reliable than in non-diabetic patients, and that the more frequent and reproducible non-dipping (pattern in diabetic patients is associated with a more prominent cardiac and extracardiac target organ damage.

Aged↗
PubMed2002

Theory of domain patterns in systems with long-range interactions of Coulomb type.

We develop a theory of the domain patterns in systems with competing short-range attractive interactions and long-range repulsive Coulomb interactions. We take an energetic approach, in which patterns are considered as critical points of a mean-field free energy functional. Close to the microphase separation transition, this functional takes on a universal form, allowing us to treat a number of diverse physical situations within a unified framework. We use asymptotic analysis to study domain patterns with sharp interfaces. We derive an interfacial representation of the pattern's free energy which remains valid in the fluctuating system, with a suitable renormalization of the Coulomb interaction's coupling constant. We also derive integro-differential equations describing stationary domain patterns of arbitrary shapes and their thermodynamic stability, coming from the first and second variations of the interfacial free energy. We show that the length scale of a stable domain pattern must obey a certain scaling law with the strength of the Coulomb interaction. We analyzed the existence and stability of localized (spots, stripes, annuli) and periodic (lamellar, hexagonal) patterns in two dimensions. We show that these patterns are metastable in certain ranges of the parameters and that they can undergo morphological instabilities leading to the formation of more complex patterns. We discuss nucleation of the domain patterns by thermal fluctuations and pattern formation scenarios for various thermal quenches. We argue that self-induced disorder is an intrinsic property of the domain patterns in the systems under consideration.

Journal Article↗
PubMed2005

Pattern recognition using asymmetric attractor neural networks.

The asymmetric attractor neural networks designed by the Monte Carlo- (MC-) adaptation rule are shown to be promising candidates for pattern recognition. In such a neural network with relatively low symmetry, when the members of a set of template patterns are stored as fixed-point attractors, their attraction basins are shown to be isolated islands embedded in a "chaotic sea." The sizes of these islands can be controlled by a single parameter. We show that these properties can be used for effective pattern recognition and rejection. In our method, the pattern to be identified is attracted to a template pattern or a chaotic attractor. If the difference between the pattern to be identified and the template pattern is smaller than a predescribed threshold, the pattern is attracted to the template pattern automatically and thus is identified as belonging to this template pattern. Otherwise, it wanders in a chaotic attractor for ever and thus is rejected as an unknown pattern. The maximum sizes of these islands allowed by this kind of neural networks are determined by a modified MC-adaptation rule which are shown to be able to dramatically enlarge the sizes of the islands. We illustrate the use of our method for pattern recognition and rejection with an example of recognizing a set of Chinese characters.

Journal Article↗
PubMed2005

On optimal current patterns for electrical impedance tomography.

We develop a statistical criterion for optimal patterns in planar circular electrical impedance tomography. These patterns minimize the total variance of the estimation for the resistance or conductance matrix. It is shown that trigonometric patterns (Isaacson, 1986), originally derived from the concept of distinguishability, are a special case of our optimal statistical patterns. New optimal random patterns are introduced. Recovering the electrical properties of the measured body is greatly simplified when optimal patterns are used. The Neumann-to-Dirichlet map and the optimal patterns are derived for a homogeneous medium with an arbitrary distribution of the electrodes on the periphery. As a special case, optimal patterns are developed for a practical EIT system with a finite number of electrodes. For a general nonhomogeneous medium, with no a priori restriction, the optimal patterns for the resistance and conductance matrix are the same. However, for a homogeneous medium, the best current pattern is the worst voltage pattern and vice versa. We study the effect of the number and the width of the electrodes on the estimate of resistivity and conductivity in a homogeneous medium. We confirm experimentally that the optimal patterns produce minimum conductivity variance in a homogeneous medium. Our statistical model is able to discriminate between a homogenous agar phantom and one with a 2 mm air hole with error probability (p-value) 1/1000.

Algorithms↗
PubMed1981

Investigation of cell patterning in the asexual fruiting body of Dictyostelium discoideum using haploid and isogenic diploid strains.

The cell patterning (proportion of spores, stalk cells, and basal disk cells) of individual asexual fruiting bodies of haploid and isogenic diploid strains of D. discoideum was examined to test the hypothesis that the patterning mechanism is based on the 'sensing' of only a single parameter, e.g., cell volume, in dividing the aggregate into the three cell types. If cell patterning is based on sensing only a single parameter, there is no reason to predict a change in cell patterning with ploidy change, and thus haploid and isogenic diploid strains should not differ in their cell patterning. The cell patterning of each of the three pairs of haploid and isogenic diploid strains examined was different. Therefore we conclude that the cell patterning mechanism must involve at least two components not changing in the same way with change in ploidy. The cell patterning of both the haploid and the diploid strains was qualitatively similar, i.e., relationships between the three cell types were described by equations of the same form in the haploid and diploid strains. However a quantitative change in cell patterning led to an increased percentage of stalk and basal disk cells in each diploid compared to its parent haploid. The ratio of basal disk to stalk cell was also greater in the diploids than in their parent haploids. We conclude that these are general ploidy-related changes because the cell patterning of each of the three parent haploid strains was different; the average percentage of stalk cells was 11.6% for X22 (12.4% for its diploid DU162), 20.5% for NP73 (27.2% for its diploid DP62), and 24.5% for HU127 (29.1% for its diploid DU310). One possible patterning mechanism could involve a diffusible signal (s), which shows gene dosage, interacting with cell-surface molecules which we predict occupy a limited number of sites per unit area of the cell membrane. The observed change in cell patterning leading to an increased percentage of stalk cells in diploid strains is predicted from such a model involving diffusible signal interacting with cell-surface molecules.

Cell Aggregation↗
PubMed1993

Laryngeal and diaphragmatic muscle activities and airflow patterns after birth in premature lambs.

The nature and control of early neonatal respiratory patterns were determined in 10 premature, asphyxiated lambs. Severe retardation of early expiratory airflow (braking) characterized an initial pattern (A), but was absent in a final one (B). During a transition pattern (pattern T), pattern A and B airflow types occurred. Close temporal relationships between the airflow patterns and posterior cricoarytenoid (PCA), thyroarytenoid (TA), and diaphragm (D) integrated muscle activities were demonstrated quantitatively. Specifically, in pattern A, the duration of braked expiratory airflow was related to the durations of TA burst activity and the absence of PCA burst activity (r2 = 0.99). In pattern A, pH, but not arterial PCO2 or arterial PO2, differed from that in patterns T and B [7.01 +/- 0.14 (A), 7.11 +/- 0.12 (T), 7.19 +/- 0.08 (B) (P < 0.03)]. Within-breath airflow and respiratory muscle activity relationships and differences in neural and mechanical respiratory timing intervals between patterns suggested that neural feedback was important in the control of central pattern generation. Thus activities of PCA, TA, and D shape the early neonatal airflow patterns and are influenced mainly by neuromechanical, and not chemical, feedback.

Animals↗