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PubMed2006

Dental morphology and crowding. A multivariate approach.

The objective of this study was to compare, combined and individually, the mesiodistal (MD) and buccolingual (BL) tooth sizes as well as their respective crown proportions in the permanent dentition in dental arches with moderate, mild, and no crowding. Dental casts from two-hundred 12 to 16-year-old school children from a typical high school from Lima, Peru, were used. The MD and BL tooth sizes of all permanent teeth except second and third molars were measured, and their crown proportion (MD/BL ratio) was estimated. Each dental arch was classified as presenting moderate (-5.1 mm or more of discrepancy), mild (-0.1 and -5 mm of discrepancy), and no crowding (zero or a positive discrepancy). Combined and tooth-specific comparisons among the crowding groups for the tooth sizes as well as crown proportions were performed with a multivariate analysis of variance (MANOVA, using Wilks lambda). Combined MD tooth sizes and crown proportions differed among crowding groups. Subsequent individual comparisons indicated differences for MD tooth size of all upper teeth and for lower premolars and central incisors. Differences were also detected for crown proportions of the upper second premolar, canine, and both incisors; as well as for the lower first premolar, canine, and central incisor. No differences were found for the BL tooth sizes among crowding groups. MD tooth sizes and crown proportions from specific teeth are significantly different between dental arches with moderate, mild, and noncrowded arches. This study helps to understand the odontometric component of the dental crowding multifactorial origin.

Adolescent↗
PubMed2003

Crowding-dependent production of colony-stimulating factors by cultured syngeneic or allogeneic hematopoietic cells.

Mitogenic stimulation in vitro of mouse T lymphocytes induces the production of the hematopoietic cytokines granulocyte-macrophage colony-stimulating factor and IL-3. The present experiments showed that simple crowding of murine spleen or lymph node cells was a sufficient inducing stimulus. Crowding did not have this consequence for thymus or marrow cells or spleen cells from nu/nu or Rag-1-/- mice lacking T lymphocytes. Crowding for as short a period as 24 h was sufficient to allow subsequent cytokine production in sparse cultures. Purified T lymphocytes also exhibited low levels of crowding induction of cytokine production and cytokine production was enhanced by IL-2 and IFN-gamma. However, IFN-gamma-/- spleen cells exhibited similar crowding-induced colony-stimulating factor production to that of control spleen cells. Excess cell crowding inhibited cytokine production. This inhibition was not caused by receptor internalization of cytokines but may contribute to the failure to observe IL-3 production in lymphoid organs in vivo. Coculture of allogeneic spleen or peritoneal cells was a strong inducing signal for colony-stimulating factor production but this parameter was unable to detect autoreactivity of T lymphocytes in mice that lack suppressor of cytokine signaling 1 and exhibit T lymphocyte activation.

Animals↗
PubMed2002

Effects of macromolecular crowding on protein folding and aggregation studied by density functional theory: statics.

Proteins are neither purified nor diluted inside the living cell. Thus it is indispensable to take into account various interactions between the protein of interest and other macromolecules for understanding the properties of proteins in physiological conditions. Here we focus on excluded volume interactions which are omnipresent in dense or crowded solutions of proteins and macromolecules or "crowding agents." A protein solution with macromolecular crowding agents is modeled by means of a density functional theory. Effects of macromolecular crowding on protein aggregation and stability are investigated in particular. Phase diagrams are obtained in various parameter spaces by solving the equation of state. Two generic features are found: the addition of the crowding agent (1) enhances the aggregation of the denatured proteins, and (2) stabilizes the native protein unless the aggregation occurs. The present theory is qualitatively in good agreement with experimental observations and unifies previous theories regarding the crowding effects on protein stability and aggregation.

Journal Article↗
PubMed1993

The relationship of crowding to the eruptive position of the lower permanent incisors.

The aim of this study was to examine the positions of newly erupted lower permanent incisors and their relationship to crowding. Forty-one crowded and 37 uncrowded dental casts of children in the early mixed dentition were examined by means of digitization using a reflex microscope. Two aspects of alignment were considered: rotation and labio-lingual displacement. Rotations of the incisors were defined as deviations from 'ideal' predicted angles. Displacement of the incisors was measured as the distance between the most labial and most lingually placed incisors. The study showed an increase in rotations amongst the crowded sample. The result of the investigation of the relationship between crowding and displacement was inconclusive. There would appear to be significant differences between the positions of newly erupted crowded and uncrowded incisors. Crowding, however, was not the only factor causing irregularity.

Child↗
PubMed1997

Effects of mating dynamics and crowding on sex ratio variance in mice.

Mating units of six virgin females and one adult stud male were established to test for the effects of timing of mating and crowding of pregnant females on litter sex ratios in mice. Females either copulated during periods when no other female of the mating unit copulated simultaneously (single mating condition) or when more than one female copulated (multiple matings condition). Two crowding conditions were imposed on the animals: the females of 14 mating units were placed into individual cages after mating (isolated condition), while females of the other 13 mating units remained in the original group until shortly before littering (crowded condition). Sex ratio variance did not deviate from random expectation in litters arising from the multiple matings periods. However, in litters arising from single mating periods, extreme sex ratios were found significantly less frequently than expected by chance. Higher sex ratio variance in litters arising from multiple matings periods is attributed to the timing of mating being at higher variance under this condition, which is known to affect sex ratios in other rodents. Crowding significantly reduced sex ratio variance further. Reduced sex ratio variance under single mating and crowded conditions is speculated to follow from competition for resources between preimplantation embryos, which may be further increased by stressful effects of crowding. Loss of embryos after implantation appeared not to be responsible for the above effects.

Animals↗
PubMedDate not supplied

Dental crowding in primary dentition and its relationship to arch and crown dimensions.

PURPOSE: The purpose of this study was to compare dental arch size, mesiodistal and buccolingual crown widths, and crown shapes between 2 groups of children, 1 with anterior crowding in both dental arches and another with anterior spacing in both dental arches. METHODS: Sixty-one sets (27 crowded and 34 spaced arches) of dental casts of normal occlusions were examined. RESULTS: For both lower and upper arches, crowded arches had statistically significantly smaller arch widths than did the spaced arches. The buccolingual width of the upper second primary molar of the crowded arches was statistically significantly larger than that of the spaced arches. However, there were little significant differences between crowded and spaced arches in arch length, mesiodistal crown width, and crown shape. CONCLUSIONS: It can be concluded that the factor that determines whether a primary dental arch is crowded is the absolute width of the arch.

Cephalometry↗
PubMed2004

[Clinical research on unilateral extraction for moderate crowding].

OBJECTIVE: To clinically investigate the results of unilateral extraction in the treatment of special moderate crowding cases. METHODS: 22 patients with harmonic profile and moderate crowding were selected and treated by unilateral extraction with Edgewise technique. The patients crowding was 6 - 9 mm and focused on one side of the arch. 22 patients with moderate crowding were treated by bilateral extraction as control. RESULTS: 22 patients have been treated successfully within 18 months. Crowding was completely resolved. Midline coincidence was basically maintained.Good intercuspation was achieved. There is no significant difference in dental arch symmetry between unilateral extraction and bilateral extraction (P > 0.05). CONCLUSION: Unilateral extraction can be successful in the treatment of special moderate crowding cases.

Adolescent↗
PubMedDate not supplied

[Can the crowd pressure on primary health services be managed?].

The crowd pressure which is placed on Primary Care Services frequently overwhelms the capacity of response of said services. In certain cases the crowd pressure coincides with low demand per inhabitant and year (as compared with the expected average in our environment), while on other occasions there coexist high crowd pressures with high frequencies. The automatic assumption that excess crowding--larger need for human resources obviates the analysis of the organizational factors and of individuals who contribute to the crowding increase. Sometimes, assigning more resources to cope with excess crowding of unidentified origins contributes towards keeping those causes alive, rather than solving them. We propose a method of analysis of excess care demand based on the answer to a short series of questions, while at the same time proposing certain management measures which could be useful to cope with excess demand, depending on the cause or causes which have been found to apply.

Health Services Needs and Demand↗
PubMed1982

A comparison of 15 year old children with excellent occlusion and with crowding of the teeth, Angle Class I malocclusion, in respect of face size and shape and tooth size.

The biological conflict that manifests itself in crowding of the teeth in man has fascinated orthodontists for generations. Correlations between tooth size and tooth arrangement can be shown, but such correlations tend to leave much unexplained in practical terms. The present report presents data from a preliminary examination of face size and shape and tooth size in boys and girls of 15-16 years, of which 47 had excellently arranged teeth and 91 showed crowding. Measurements were taken from lateral and posteroanterior cephalometric X-ray films and from dental casts. The statistical test used was the standard student t-test. Girls' faces were found to be on average significantly smaller than boys' whether the teeth were well arranged or were crowded. The comparisons of face size and shape of boys and girls with well arranged teeth with the faces of those with crowded teeth was less definite in its outcome. Girls' total tooth substance was on average significantly smaller than boys' whether the teeth were well arranged or crowded. Boys and girls with crowded teeth had a larger mean total tooth size than boys and girls with well arranged teeth.

Adolescent↗
PubMed1981

Short-term juvenile crowding arrests the developmental formation of dendritic spines on tectal interneurons in jewel fish.

Development of jewel fish tectal interneurons was measured as a function of crowded development. The number of dendritic spines on the apical dendrites of pyriform interneurons was counted in the stratum album centrale plexiform layer because previous research indicated that this was the region in which both social deprivation and acute juvenile crowding produced neuronal deficits. Results showed that 100- and 130-day-old uncrowded juveniles had spine densities equivalent to 160-day-old juveniles crowded at 15 fish/3.6 liter for 60 days. Thus, no spine formation occurred after the onset of crowding. Sibling 160-day-old juveniles reared in the uncrowded condition (1 fish/4.6 liter) had already acquired the normal complement of spines exhibited by 4-year-old adults reared at low density (1 fish/25 liter). These results show that acute crowding can arrest the normal course of neuronal development in juvenile jewel fish.

Animals↗
PubMed1981

Jewel fish retain juvenile schooling pattern after crowded development.

Juvenile jewel fish were crowded between 100 and 160 days of age (15 fish/3.6 liters) in a double-walled aquarium sharing water flow with uncrowded siblings (15 fish/69.4 liters). Photographs of schooling in a 73-liter aquarium were made after 30 and 60 days of crowding. Distances maintained between each fish and its 1st-5th nearest neighbors and orientation angles between 1st nearest neighbors were measured. After 30 days, crowded juveniles maintained significant nonrandomly aggregated distances to their 1st-5th neighbors, spacing significantly closer than uncrowded siblings. After 60 days, crowded juveniles maintained both closer, nonrandom distances to 1st-5th neighbors and significantly more parallel orientation to 1st nearest neighbors. Thus, whereas uncrowded juveniles followed the normal developmental pattern of dispersion, crowded siblings retained juvenile spacing behavior.

Aggression↗
PubMed1982

Effects of chronic crowding stress on midbrain development: changes in dendritic spine density and morphology in jewel fish optic tectum.

This study investigates the effects of a biologically relevant stressor, crowding, on the development of neurons in the major teleostean brain area, the optic tectum. Adult jewel fish were reared for approximately 4 years under conditions of moderate density (3.3 liter/fish), or under uncrowded control conditions (25 liter/fish). Quantitative morphometric measures of Golgi-stained tissue were used to test whether long-term crowding at moderate density produced developmental deficits lasting beyond the juvenile period. Chronic crowding did not affect body size or gross tectal growth. However, crowding significantly decreased the density of dendritic spine formation on apical dendrites of pyriform interneurons in the basal region of the tectum (stratum album centrale). Additionally, the shapes of spines on this segment of the apical dendrite were altered by crowding: relative frequencies of overall spine length and spine stem length changed significantly. These results are interpreted in the context of cytoarchitectural changes produced by more extreme developmental stressors in previous studies.

Animals↗
PubMed1994

Effect of crowding on corticosterone responses to central adrenergic stimulation.

The social stress of crowding for 3, 7 and 14 days considerably reduced the increase in serum corticosterone elicited by intracerebroventricular administration of isoprenaline, a beta-adrenergic agonist, on the 3rd and 7th days of crowding. The corticosterone response to clonidine, an alpha 2-adrenergic agonist, was significantly diminished only after 3 days of crowding and this reduction was paralleled by a significant decrease in hypothalamic histamine content. The stimulatory effect of phenylephrine, an alpha 1-adrenergic agonist, was not significantly changed by crowding stress. Social crowding stress caused almost total and persistent reduction in the hypothalamic-pituitary-adrenocortical (HPA) responsiveness to noradrenaline which stimulates the HPA axis via both alpha- and beta-adrenergic receptors.

Animals↗
PubMedDate not supplied

Environmental crowding modifies responding to noxious stimuli and the effects of mu- and kappa-agonists.

The effects of social crowding in rats on nociception and analgesic actions of mu- and kappa-opioid agonists agonist qualitatively different stimuli were examined. Crowding produced higher control thresholds for electroshock and paw pinch pressure but not for noxious heat. Naloxone did not effect shock thresholds in crowded or noncrowded rats but it produced hyperalgesia in both groups when pressure and heat were the stimuli. Crowding reduced the antinociceptive potency against pressure of kappa- and mu-agonists but the opposite effect was seen with heat. A comparison of the ratios of potencies against pressure and heat indicates that crowding differentially modified kappa- and mu-receptor systems.

Analgesics, Opioid↗
PubMed1985

Post-weaning crowding induces corticoadrenal hyperreactivity in male mice.

The effect of various population densities on corticoadrenal function was studied in prepuberal male mice. High population densities decreased body weight gain. Neither adrenal weight nor basal serum corticosterone were modified by crowding. However, corticoadrenal response to some acute stresses such as noise and forced swimming was higher in crowded mice. As corticoadrenal response to adrenocorticotropin remained unaffected, it appears that crowding induced pituitary-adrenal hyperreactivity. Neither the defecation rate nor exploratory activity were altered by crowding, suggesting a dissociation between pituitary-adrenal responsiveness and behavioral measures presumably related to emotional arousal. These discrepancies may possibly be due to the higher sensitivity of corticoadrenal function to environmental changes. Our results suggest that crowding would be suitable as a model for chronic continuous stress.

Acute Disease↗
PubMed1986

Body weight gain and food intake alterations in crowd-reared rats.

The effect of being reared in a crowd for 6 continuous weeks postweaning on body weight gain, food intake and gland weight (thymus, adrenals and testes) was studied in Sprague-Dawley adult male rats. Crowd-reared rats (10 per cage) showed a significantly lower body weight at the end of the crowding period as compared to control rats (5 per cage). After 200 days of being reared under the same conditions (5 per cage), the body weights of crowd-reared rats were still significantly lower than those of control rats. However, the body weight gain during this period was the same for both groups. Crowd-reared rats also had significantly lower thymus weight and higher adrenal gland and testes weights as compared to those weights of control rats. In addition, food intake was similar for both groups.

Animals↗
PubMed1984

The influence of persistent crowding on the age changes of behavioral parameters and survival characteristics of rats.

One hundred fifty-six male Sprague-Dawley rats were submitted to crowding (12 rats/Makrolon-IV cage) from an age of 5 months onwards. An equal number from the same age cohort served as a control (6 rats/Makrolon-IV cage). As part of an age-test program, behavioral parameters (spontaneous motor activity, reactive motor activity and maze-learning ability) were measured at various ages between 8 and 30 months. The rats were sacrificed for additional measurements after the behavioral tests. Survival curves and age-specific mortality rates were calculated for those rats which died spontaneously in the course of the study. Control rats showed a significant decrease in spontaneous motor activity after an age of 18 months. Reactive motor activity of the controls revealed a fall in the number of large movements between 9 and 15 months, whereas the number of small movements increased up to an age of 30 months. Crowding conditions increased significantly both spontaneous and reactive activity. Maze-learning ability declined significantly with age in the controls whereas crowded rats revealed a tendency to better performance which seemed to be submitted to a seasonal rhythm. Crowded rats showed an improved survival characteristic, beginning at an age of 700 days. Mortality curves turned out to be distinct and parallel by straight line regression. It has been concluded that the positive effects of crowding on behavioral parameters and survival could be attributed to a decrease in vulnerability rather than to a lowered rate of aging.

Aging↗
PubMed2006

Emergency department crowding: old problem, new solutions.

Emergency department (ED) crowding is becoming an increasing problem in EDs throughout the United States for a multitude of reasons, including an increase in patient volume and a decrease in available EDs. Crowding has an adverse impact on the ability to deliver quality and timely care and may contribute to adverse patient outcomes. Conceptually, factors that contribute to ED crowding can be divided into three domains, which correspond to their "sites of action": input, throughput, and output. A number of measures have been developed to better quantify crowding and its effects. More research needs to be done to better understand the factors that contribute to crowding, the impact of this problem on patients and ED throughput, and how to alleviate this nationwide crisis.

Crowding↗