[Studies on crowded dental arch. IV. Relationship between the degree of crowding and the model analysis].
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Malocclusion↗
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Some causes of crowding and re-crowding of lower anterior teeth following orthodontic treatment.
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Malocclusion↗
An independent evaluation of four quantitative emergency department crowding scales.
BACKGROUND: Emergency department (ED) overcrowding has become a frequent topic of investigation. Despite a significant body of research, there is no standard definition or measurement of ED crowding. Four quantitative scales for ED crowding have been proposed in the literature: the Real-time Emergency Analysis of Demand Indicators (READI), the Emergency Department Work Index (EDWIN), the National Emergency Department Overcrowding Study (NEDOCS) scale, and the Emergency Department Crowding Scale (EDCS). These four scales have yet to be independently evaluated and compared. OBJECTIVES: The goals of this study were to formally compare four existing quantitative ED crowding scales by measuring their ability to detect instances of perceived ED crowding and to determine whether any of these scales provide a generalizable solution for measuring ED crowding. METHODS: Data were collected at two-hour intervals over 135 consecutive sampling instances. Physician and nurse agreement was assessed using weighted kappa statistics. The crowding scales were compared via correlation statistics and their ability to predict perceived instances of ED crowding. Sensitivity, specificity, and positive predictive values were calculated at site-specific cut points and at the recommended thresholds. RESULTS: All four of the crowding scales were significantly correlated, but their predictive abilities varied widely. NEDOCS had the highest area under the receiver operating characteristic curve (AROC) (0.92), while EDCS had the lowest (0.64). The recommended thresholds for the crowding scales were rarely exceeded; therefore, the scales were adjusted to site-specific cut points. At a site-specific cut point of 37.19, NEDOCS had the highest sensitivity (0.81), specificity (0.87), and positive predictive value (0.62). CONCLUSIONS: At the study site, the suggested thresholds of the published crowding scales did not agree with providers' perceptions of ED crowding. Even after adjusting the scales to site-specific thresholds, a relatively low prevalence of ED crowding resulted in unacceptably low positive predictive values for each scale. These results indicate that these crowding scales lack scalability and do not perform as designed in EDs where crowding is not the norm. However, two of the crowding scales, EDWIN and NEDOCS, and one of the READI subscales, bed ratio, yielded good predictive power (AROC >0.80) of perceived ED crowding, suggesting that they could be used effectively after a period of site-specific calibration at EDs where crowding is a frequent occurrence.
Crowding↗
Suppressive and facilitatory spatial interactions in foveal vision: foveal crowding is simple contrast masking.
Spatial interactions are a critical and ubiquitous feature of spatial vision. These interactions may be inhibitory (reducing sensitivity as occurs in crowding) or facilitatory (enhancing sensitivity). In this work, we had four goals. 1. To test the hypothesis that foveal crowding depends on target size by measuring the extent of crowding for novel targets that were limited in their spatial frequency content. We used a large range of target sizes and spatial frequencies. 2. To assess whether the critical spatial frequency model (Hess, Dakin, & Kapoor, 2000) provides a general model for foveal crowding. To test this model, we measured crowding for a direction-identification task that did not require judging the orientation of the gap. 3. To test the hypothesis that foveal crowding is simply contrast masking by remote flanks we measured and compared crowding in a direction-identification experiment with masking by remote flanks in a detection experiment. In each of the experiments, our targets and flanks were composed of Gabor features, thus allowing us to control the feature contrast, spatial frequency, and orientation. 4. To assess the relationship between suppressive and facilitatory spatial interactions in foveal vision. Our results show that (1) foveal crowding is proportional to feature size over the more than 50-fold range of target sizes that we examined. Over this large range, foveal crowding is scale invariant. Our results also show it is the size of the envelope (SD) rather than the carrier (SF) that determines the extent of crowding in the fovea. 2. Crowding that occurs in the direction-identification task is quite similar to crowding where orientation information is available. Thus we conclude that the critical spatial frequency model does not provide a general explanation for foveal crowding. 3. Threshold elevation for crowding is similar to threshold elevation for masking as predicted by our test-pedestal model. Thus we conclude that foveal crowding is simple contrast masking. 4. Based on our comparison of threshold changes in crowding and masking, we conclude that in foveal vision, the suppressive spatial interactions due to nearby flanks are similar in the two tasks. However, the facilitatory interactions are quite different. In the crowding task, we find very little evidence for facilitation by flankers, whereas in the detection task, we find strong facilitation. We suggest that facilitation of detection by remote flanks may be, at least in part, a consequence of uncertainty reduction.
Contrast Sensitivity↗
"Crowding" in normal and amblyopic vision assessed with Gaussian and Gabor C's.
The purpose of this study was to investigate the extent and specificity of crowding in the normal fovea and periphery, and the central field of amblyopes, using "C"-like patterns. In the first experiment we measured the extent of crowding for C-patterns comprised of Gaussian patches, over a range of target sizes using a four-alternative forced-choice (up, down, left, right) method. We found that the extent of foveal crowding is proportional to target size. In contrast, in normal periphery and in the central field of amblyopes, crowding extends over large spatial distances and is not size dependent. Crowding for our stimuli occurred with both same-polarity and opposite polarity patches. To test whether the extended crowding in amblyopia resulted from a shift in the spatial scale of analysis, we measured crowding with band-limited C-patterns (comprised of Gabor patches) in a gap localization task (2-AFC). With band-limited stimuli, and a task that does not involve judging the orientation of the gap, the amblyopic eyes showed crowding over a longer distance than that of normal observers. We also tested the orientation specificity of crowding by varying the orientation of the flanks. In normal fovea, crowding is orientation specific: in amblyopia it is not. While crowding in normal fovea can be explained by simple pattern masking, crowding seen in normal periphery and amblyopes cannot. Instead we suggest that crowding in amblyopic and peripheral vision is a result of extended pooling at a stage following the stage of feature detection.
Amblyopia↗
Mixed macromolecular crowding accelerates the oxidative refolding of reduced, denatured lysozyme: implications for protein folding in intracellular environments.
The oxidative refolding of reduced, denatured hen egg white lysozyme in the presence of a mixed macromolecular crowding agent containing both bovine serum albumin (BSA) and polysaccharide has been studied from a physiological point of view. When the total concentration of the mixed crowding agent is 100 g/liter, in which the weight ratio of BSA to dextran 70 is 1:9, the refolding yield of lysozyme after refolding for 4 h under this condition increases 24% compared with that in the presence of BSA and 16% compared with dextran 70. A remarkable increase in the refolding yield of lysozyme by a mixed crowding agent containing BSA and Ficoll 70 is also observed. Further folding kinetics analyses show that these two mixed crowding agents accelerate the oxidative refolding of lysozyme remarkably, compared with single crowding agents. These results suggest that the stabilization effects of mixed macromolecular crowding agents are stronger than those of single polysaccharide crowding agents such as dextran 70 and Ficoll 70, whereas the excluded volume effects of mixed macromolecular crowding agents are weaker than those of single protein crowding agents such as BSA. Both the refolding yield and the rate of the oxidative refolding of lysozyme in these two mixed crowded solutions with suitable weight ratios are higher than those in single crowded solutions, indicating that mixed macromolecular crowding agents are more favorable to lysozyme folding and can be used to simulate the intracellular environments more accurately than single crowding agents do.
Animals↗
[Effects of crowding on immune functions in mice].
The effects of several types of crowding on immune functions were studied in mice. This study consisted of two experiments. Experiment one: Male BALB/c mice were initially housed in groups of four mice per cage. After fourteen days of acclimation, the mice were randomly divided into three groups, Control (four mice per cage, control group), Crowd-I (four mice per small space) and Crowd-II (sixteen mice per cage). These conditions were maintained for seven days. The results of experiment one were as follows: (1) The percentage of lymphocytes in the blood of Crowd-II was significantly lower than that of Control (p < 0.05). (2) The percentage of neutrophils and the absolute number of neutrophils in blood of Crowd-II were significantly higher than in Control (p < 0.05). (3) Superoxide production activity (NBT reduction activity) of blood neutrophils in Crowd-II tended to be depressed, and phagocytic activity of neutrophils was significantly depressed in Crowd-II as compared with Control (p < 0.01). These results suggest that the complexity of interrelationships among mice caused by an increase in the number of animals per cage is a very important stress factor. Experiment two: Male BALB/c mice were initially housed in groups of five mice per cage. After fourteen days of acclimation, the mice were divided into three groups, Control (five mice per cage, control group), Crowd-(1) (five mice per cmall space) and Crowd-(2) (twenty mice per cage). In Control and Crowd-(1), the same mice were used as in the acclimation period. These conditions were maintained for seven days. In this period, on the second day, all the mice were injected intraperitoneally with sheep red blood cells (SRBC). The results of experiment two were as follows: (1) The specific humoral immune response to SRBC was investigated in terms of the number of PFC in the spleens and hemagglutination in sera, but significant differences were not found among the groups. (2) Plasma IgG levels in the Crowd-(1) were significantly higher than those in Control (p < 0.05). (3) Both superoxide production activity and phagocytic activity of neutrophils were significantly depressed in Crowd-(2) as compared with Control (p < 0.01, respectively), whereas each neutrophil function of Crowd-(1) tended to be enhanced as compared with Control.
Animals↗
Mixed macromolecular crowding accelerates the refolding of rabbit muscle creatine kinase: implications for protein folding in physiological environments.
The effects of four single macromolecular crowding agents, Ficoll 70, dextran 70, polyethylene glycol (PEG) 2000, and calf thymus DNA (CT DNA), and three mixed crowding agents containing both CT DNA and polysaccharide (or PEG 2000) on the refolding of guanidine hydrochloride-denatured rabbit muscle creatine kinase (MM-CK) have been examined by activity assay. When the total concentration of the mixed crowding agent is 100 g/l, in which the weight ratio of CT DNA to Ficoll 70 is 1:9, the refolding yield of MM-CK after refolding for 3 h under these conditions increases 23% compared with that in the presence of 10 g/l CT DNA, 18% compared with 100 g/l Ficoll 70, and 19% compared with that in the absence of crowding agents. A remarkable increase in the refolding yield of MM-CK by a mixed crowding agent containing CT DNA and dextran 70 (or PEG 2000) is also observed. Further folding kinetics analyses show that these three mixed crowding agents remarkably accelerate the refolding of MM-CK, compared with single crowding agents. Aggregation of MM-CK in the presence of any of the three mixed crowding agents is less serious than that in the presence of a single crowding agent at the same concentration but more serious than that in the absence of crowding agents. Both the refolding yield and the refolding rate of MM-CK in mixtures of these agents are increased relative to the individual agents by themselves, indicating that mixed macromolecular crowding agents are more favorable to MM-CK folding and can be used to reflect the physiological environment more accurately than single crowding agents.
Animals↗
Crowding is unlike ordinary masking: distinguishing feature integration from detection.
A letter in the peripheral visual field is much harder to identify in the presence of nearby letters. This is "crowding." Both crowding and ordinary masking are special cases of "masking," which, in general, refers to any effect of a "mask" pattern on the discriminability of a signal. Here we characterize crowding, and propose a diagnostic test to distinguish it from ordinary masking. In ordinary masking, the signal disappears. In crowding, it remains visible, but is ambiguous, jumbled with its neighbors. Masks are usually effective only if they overlap the signal, but the crowding effect extends over a large region. The width of that region is proportional to signal eccentricity from the fovea and independent of signal size, mask size, mask contrast, signal and mask font, and number of masks. At 4 deg eccentricity, the threshold contrast for identification of a 0.32 deg signal letter is elevated (up to six-fold) by mask letters anywhere in a 2.3 deg region, 7 times wider than the signal. In ordinary masking, threshold contrast rises as a power function of mask contrast, with a shallow log-log slope of 0.5 to 1, whereas, in crowding, threshold is a sigmoidal function of mask contrast, with a steep log-log slope of 2 at close spacing. Most remarkably, although the threshold elevation decreases exponentially with spacing, the threshold and saturation contrasts of crowding are independent of spacing. Finally, ordinary masking is similar for detection and identification, but crowding occurs only for identification, not detection. More precisely, crowding occurs only in tasks that cannot be done based on a single detection by coarsely coded feature detectors. These results (and observers' introspections) suggest that ordinary masking blocks feature detection, so the signal disappears, while crowding (like "illusory conjunction") is excessive feature integration - detected features are integrated over an inappropriately large area because there are no smaller integration fields - so the integrated signal is ambiguous, jumbled with the mask. In illusory conjunction, observers see an object that is not there made up of features that are. A survey of the illusory conjunction literature finds that most of the illusory conjunction results are consistent with the spatial crowding described here, which depends on spatial proximity, independent of time pressure. The rest seem to arise through a distinct phenomenon that one might call "temporal crowding," which depends on time pressure ("overloading attention"), independent of spatial proximity.
Contrast Sensitivity↗
Conflict management by hamadryas baboons (Papio hamadryas hamadryas) during crowding: a tension-reduction strategy.
Primates change a variety of behavioral responses during short-term exposure to crowding. Under crowded conditions, rates of aggression, submissive behavior, and affiliative behavior may increase or decrease. Different patterns of change among these three categories of response have been interpreted as various coping "strategies" for managing the increased risk of conflict under crowded conditions. Grooming is of particular interest because this behavior is known to have a calming influence on the recipient and could be used to manage conflict under tense situations. A captive group of nine hamadryas baboons (Papio hamadryas hamadryas) composed of two harems was observed under short-term crowding to determine whether this species adopts conflict-management strategies similar to those described in other primates. The aggression, submission, affiliation, and displacement activities of the six adults in the group (two males and four females) were recorded, and behaviors in their small indoor quarters was compared with baseline behaviors in the outdoor section of their enclosure, which had over 10 times more space. Repeated-measures analysis of variance (ANOVA) was used to compare behavioral rates during crowding with baseline rates recorded immediately after crowding and during matched controls collected at the same time of day as the crowding sessions. Aggression and submission rates did not change significantly across conditions. Huddling together and proximity increased during crowding, and females increased grooming of their harem male during crowding. Displacement activities (e.g., pacing and self-grooming) increased during crowding, but scratching, an indicator of anxiety in primates, did not. The pattern of behavior exhibited by this group conforms to an active "tension-reduction" strategy in which animals successfully reduce the higher risk of aggression during crowding.
Aggression↗
Crowding and mental health.
An epidemiologic investigation of the mental needs and services of 1645 respondents, aged 17 to 92 years and living in a representative southeastern county in Florida, revealed that 7.8% of the sample lived in crowded conditions. The crowded respondents scored significantly higher than did the uncrowded on both a depression scale and on the Health Opinion Survey. Associations between crowding and high scores on both scales were strongest among: respondents in the childrearing and middle years of life, blacks at all income levels, whites in the intermediate annual family income range of $6000 to $9999, and especially, females rather than males. Consistently, the crowded black population, and particularly, crowded white women, had much higher scores than did the uncrowded women. A multiple regression analysis showed that three variables--being a female, having a lower income, and crowding--accounted for 16.5% of the variance. The discussion emphasizes that the relationship between crowding and higher scores on indices of emotional distress is quite complicated. In crowded situations, depression may be a costly, semi-adaptive reaction to excessive interpersonal stimulation. Women living in crowded situations appear to be at high risk for depressive illness; their plight brings to mind the classic animal experiments which showed that the maternal behavior of females deteriorated in crowded situations.
Adolescent↗
Chronic stress and psychological well-being: evidence from Thailand on household crowding.
This paper examines the effect of one form of chronic stress--household crowding--on psychological well-being, as measured by multiple inverse indicators of psychological well-being. We rely on data from a large (n = 2017) random sample of households in Bangkok, Thailand, a context that has a higher level and broader range of crowding than typically found in the United States. Objective household crowding is found to be detrimental to psychological well-being, controlling for a number of background characteristics. The effect of objective crowding is mediated by subjective crowding, which has strong, consistent and direct detrimental effects on well-being. There is no evidence of a gender effect. Extended family households are not uncommon in Bangkok, but the effects of objective and subjective crowding are similar in both two- and three-generation households, as well as in one- and multiple-couple households. The argument that subjective crowding is an effect, rather than a cause, of psychological well-being is examined and rejected. The findings suggest that crowding, as a chronic source of stress, constitutes a major threat to psychological well-being. Although the empirical analyses are based on data from one city, we frame the issue of household crowding in a historical and theoretical context in order to suggest in which cultural settings household crowding is most likely to have detrimental effects on psychological well-being.
Adaptation, Psychological↗
Prediction of mandibular incisor and canine crowding changes in the mixed dentition.
To test the hypothesis that preeruptive tooth positions and dental arch parameters might forecast crowding changes, a sample of 47 aboriginal children (26 males, 21 females) was selected stringently on the basis of Class 1 characteristics and an untreated dentition unaffected by caries or attrition. Crowding scores, radiographic relationships of 765E, and dental arch dimensions were evaluated for the mixed dentition (Stage 1, 8.91 +/- 1.05 years) and earliest emergence of the permanent dentition (Stage 2, 12.48 +/- 0.97 years). Changes between the stages were calculated and the sample was divided into two groups, according to an increase (Group 1) or decrease (Group 2) in incisor and canine crowding. Multivariate and multiple regression analyses were used to identify predictors (Stage 1 radiographic and dental arch parameters) of incisor and canine crowding behavior. Dental arch form and tooth size were important factors in measuring the amount of incisor or canine crowding at Stage 1 and Stage 2. Neither the radiographic nor the dental arch predictors proved useful in forecasting crowding changes. Group 2 dental arches tended to be initially narrower, shallower, and more crowded; however, they showed greater molar and canine width expansion and lessened arch depth reduction than Group 1 cases. Many cases showed a reduction in canine crowding from mixed to permanent dentition. This appeared to be largely independent of the observed incisor crowding. Sexual, racial, and individual variations in dentofacial pattern reinforce the need to carefully consider interceptive extraction or space-regaining therapy for each patient because of the unpredictability of crowding behavior during the transition from mixed to permanent dentition.
Australia↗
Metabolic buffering exerted by macromolecular crowding on DNA-DNA interactions: origin and physiological significance.
Crowding, which characterizes the interior of all living cells, has been shown to dramatically affect biochemical processes, leading to stabilization of compact morphologies, enhanced macromolecular associations, and altered reaction rates. Due to the crowding-mediated shift in binding equilibria toward association, crowding agents were proposed to act as a metabolic buffer, significantly extending the range of intracellular conditions under which interactions occur. Crowding may, however, impose a liability because, by greatly and generally enhancing macromolecular association, it can lead to irreversible interactions. To better understand the physical determinants and physiological consequences of crowding-mediated buffering, we studied the effects of crowding, or excluded volume, on DNA structures. Results obtained from isothermal titration calorimetry (ITC) and UV melting experiments indicate that crowding-induced effects are marginal under conditions that a priori favor association of DNA strands but become progressively larger when conditions deteriorate. As such, crowding exerts "genuine" buffering activity. Unexpectedly, crowding-mediated effects are found to include enthalpy terms that favorably contribute to association processes. We propose that these enthalpy terms and preferential stabilization derive from a reconfiguration of DNA hydration that occurs in dense DNA-rich phases obtained in crowded environments.
Base Pair Mismatch↗
Suppressive and facilitatory spatial interactions in peripheral vision: peripheral crowding is neither size invariant nor simple contrast masking.
Peripheral vision is characterized by reduced spatial resolution and inhibitory spatial interactions that extend over long distances. This work had three goals. (1) We considered whether the extensive crowding in peripheral vision is a consequence of a shift in the spatial scale of analysis. To test this, using a large range of target sizes and spatial frequencies, we measured the extent of crowding for targets that were limited in their spatial frequency content. (2) We considered whether crowding in peripheral vision can be explained on the basis of contrast masking by remote flanks. To test this hypothesis, we measured and compared crowding in a direction-identification experiment with masking by remote flanks in a detection experiment. In each of the experiments, our targets and flanks were composed of Gabor features, thus allowing us to control the feature contrast, spatial frequency, and orientation. (3) We examined the relationship between the suppressive and facilitatory interactions in peripheral contrast detection and crowding. Our results show that unlike the normal fovea (Levi, Klein, & Hariharan, 2002), peripheral crowding is not scale invariant nor is it attributable to simple contrast masking. Rather, our results suggest that inhibitory spatial interactions in peripheral crowding extend over larger distances than in the fovea for targets of the same size. In peripheral vision, the critical distance for crowding is approximately 0.1 times the target eccentricity. Observers can easily detect the features that compose our targets (Gabor patches) under conditions where crowding is strong. Thus, we speculate that peripheral crowding occurs because the target and flanks are combined or pooled at a second stage, following the stage of feature extraction. In peripheral vision, this pooling takes place over a large distance.
Contrast Sensitivity↗
[Gnathometric changes in examinees with and without early findings of crowding--a longitudinal study].
The longitudinal sample of children of both sexes (31 without crowding and 39 with crowding) has been investigated to examine the influence of clinically estimated findings in the deciduous dentition in the volume of jaw growth as well as in the occurrence of some malocclusions in the mixed dentition. The children were examined for the first time at the age of 4.5 and again 3 years later. The results have pointed out the following: there was no essential difference in the volume of transversal and sagittal jaw growth in reference to early findings; in both groups the significant enlargement of transversal and sagittal dimensions was recorded; mean of the width of the upper dental arch are significantly higher in the group without crowding in primary dentition; mean of the length of the upper dental arch are somewhat higher in the examinees with early findings of crowding at the first examination, namely in the examinees without early finding of crowding at the second examination; mean of the overjet are somewhat higher in the group with early finding of crowding; distribution of the examinees in the mixed dentition according the orthodontic diagnosis does not show essential differences in regard to early finding; the largest number of the examinees in the mixed dentition shows the symptoms of the primary crowding regardless of the earlier findings; only 29.1% examinees without early finding of crowding, maintain the same characteristic in the mixed dentition; in the 26.4% examinees with early finding of crowding, there comes to the spontaneous loss of the primary symptoms during the change of teeth namely to the transfer to the group with no crowding.
Child↗
Accelerated recovery of Atlantic salmon (Salmo salar) from effects of crowding by swimming.
The effects of post-crowding swimming velocity (0, 0.35, and 0.70 m/s) and recovery time (1.5, 6, and 12 h) on physiological recovery and processing quality parameters of adult Atlantic salmon (Salmo salar) were determined. Atlantic salmon crowded to a density similar to that of a commercial slaughter process (>200 kg/m(3), 40 min) were transferred to a swimming chamber for recovery treatment. Osmolality and concentrations of cortisol, glucose and lactate in blood plasma were used as physiological stress indicators, whereas image analyses of extent and duration of rigor contraction, and fillet gaping were used as measures of processing quality. Crowded salmon had a 5.8-fold higher plasma cortisol concentration than control salmon (P<0.05). The elevated plasma cortisol concentration was reduced by increasing the swimming velocity, and had returned to control levels after 6 h recovery at high water velocity. Similar effects of swimming velocity were observed for plasma osmolality and lactate concentration. A lower plasma glucose concentration was present in crowded than in control fish (P<0.05), although a typical post-stress elevation in plasma glucose was observed after the recovery treatments. Lower muscle pH was found in crowded compared with control salmon (P<0.05), but muscle pH returned to control levels after 6 h recovery at intermediate and high swimming velocities and after 12 h in the low velocity group. Crowding caused an early onset of rigor mortis contraction. However, subjecting crowded salmon to active swimming for 6 h before slaughter delayed the onset of rigor mortis contraction from 2.5 to 7.5 h post mortem. The extent of rigor mortis contraction was also affected by crowding and post-stress swimming activity (P<0.05), and the largest degree of contraction was found in crowded salmon. In conclusion, active swimming accelerated the return of plasma cortisol, hydromineral balance, and the energy metabolism of adult Atlantic salmon to pre-stress levels. Moreover, an active swimming period delayed the onset of rigor mortis contraction, which has a positive technological implication for the salmon processing industry.
Animals↗
Crowding-induced changes in basal and stress levels of thyrotropin and somatotropin in male rats.
The effects of crowding on thyrotropin (TSH) and somatotropin (GH) secretion were studied in two-month-old male rats. Crowded rats (9-10 per cage) showed lower serum GH levels than controls (3 per cage). Likewise, serum GH was lower in crowded rats after acute exposure to stress. However, percentage inhibition of GH secretion induced by acute stress was similar in crowded and control rats. Crowding reduced the TSH response to acute stress. The results found with the administration of hypothalamic regulatory factors suggest that the impaired GH and TSH secretion observed in crowded rats was not likely to be at the pituitary level. Therefore, altered neuroendocrine control of GH and TSH secretion appears to exist in crowded rats. Preliminary results obtained in rats crowded from weaning to adulthood suggest that food restriction only partially accounts for the changes observed in crowded rats.
Animals↗