Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Crowding”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 541 records · Page 30Linked to original sources
PubMed1998

Lower arch crowding in the third decade.

Lower arch crowding and dimensions were measured on study models of 46 untreated subjects, 20 male and 26 female, at age 18 years (T1), 21 years (T2), and 28 years (T3), and the changes during the observation periods calculated. Only very small changes, few of them detectable clinically, were found. The findings are discussed in relation to the changes reported in untreated subjects in other age groups and in orthodontically-treated subjects after retention.

Adolescent↗
PubMed1988

Effects of macromolecular crowding on the association of E. coli ribosomal particles.

The equilibrium for the binding reaction between the 30 S and 50 S ribosomal subunits of E. coli is shifted towards formation of 70 S ribosomes in the presence of a variety of polymers. The polymers also increase a further interaction between 70 S particles to form the 100 S dimer. The requirement for relatively high concentrations of non-specific polymers indicates that the shifts in equilibria arise from excluded volume effects. Analysis using scaled particle theory is consistent with this mechanism. The effects of high concentrations of polymers on the interactions between ribosomal species may make important changes in the function of ribosomes under the crowded conditions which occur in vivo.

Escherichia coli↗
PubMed2004

Stabilization of a DNA duplex under molecular crowding conditions of PEG.

A living cell generally contains macromolecules occupying 20-40% of the total volume. To mimic the crowded cellular condition, we prepared solutions including poly(ethylene glycol) (PEG) as a cosolute and investigated the influence of the cosolute on the DNA duplex stability. In the presence of PEG 200 or PEG 8000, the Tm (melting temperature) of a self-complementary duplex of 5'-dATGCGCAT-3' decreased by 11.8 degrees C in the presence of 20 wt% PEG200 and by 1.5 degrees C in the presence of 20 wt% PEG 8000. The dln K(obs) vs. dln a(w) plots for PEG 200 and PEG 8000 were linear with a negative slope, suggesting the association of water molecules upon the duplex formation. Interestingly, when the NaCl concentration decreased from 1 M to 400 mM, the Tm increased in the presence of PEGs. Our results imply that the nucleic acid stabilities in a living cell may be different from those in in vitro conditions.

Base Pairing↗
PubMed1989

Long-term spontaneous changes following removal of all first premolars in Class I cases with crowding.

The purpose of the study was to evaluate the result in adults of Class I malocclusion cases who had all their first premolars extracted as the sole treatment of space deficiency in the mixed or early permanent dentition. The mean age at premolar removal was 10 1/2 years. Forty-two out of 44 cases were re-examined at a mean age of 30 years and 4 months. Observations of dental occlusion and oral health were compared to observations of control samples. The average malocclusion in the adults, as judged by a score method, was similar to that reported for an appliance-treated sample. Marked spontaneous arch alignment and residual space closure with age was seen in most cases. Despite earlier tooth removal, on average crowding developed to about the same degree as that of an non-extraction normal occlusion sample. No detrimental effects were seen with regard to overjet or overbite. Neither did the figures for lower incisor position at the follow-up examination differ from that of the normal occlusion sample. Although tipping of adjacent teeth towards the extraction site was frequent, especially in the mandible, no effect on marginal bone height was evident as judged by comparison with a non-extraction control sample. The results reveal a significant capacity for spontaneous improvements with age in dental arch morphology and relationship in extraction cases, provided that specific features have been looked for in case selection.

Adolescent↗
PubMed1995

The effects of malnutrition, parental literacy and household crowding on acute lower respiratory infections in young Kenyan children.

This study investigated risk factors for acute lower respiratory infections (ALRI) in young Kenyan children. Exposures included mild-moderate malnutrition, household crowding, and low parental literacy. The study population consisted of 106 toddler-aged children (18-25 months) who were free of ALRI for at least 4 weeks before beginning a 1-year follow-up period. Subjects were visited weekly for morbidity information and monthly for anthropometric measurement. Being underweight (weight-for-age < 80 per cent of expected) was positively associated with ALRI, as was stunting (height-for-age < 90 per cent of expected). No association was found for acute wasting (weight-for-height < 90 per cent of expected). Having more than five siblings or parents with low reading skills were also risk factors. These data suggest that improving nutrition and parental literacy may contribute to lowering the incidence of acute lower respiratory infections. Interventions include breastfeeding, full immunization, diets adequate in quality and quantity, and early treatment through parental recognition of serious infections.

Acute Disease↗
PubMed1987

The crowded carpal sign in volar perilunar dislocation.

Three cases of volar perilunar dislocation were seen at North Carolina Baptist Hospital over a 6-year period. An important finding on anteroposterior radiographs was the overriding of proximal and distal carpal rows giving rise to the "crowded carpal" appearance. Review of the literature demonstrates this configuration in all illustrations of volar perilunar dislocation. Although some authors have noted its presence, the diagnostic significance of this finding has not, to our knowledge, been emphasized.

Adult↗
PubMed2003

Public insurance expansions and crowd out of private coverage.

BACKGROUND: The extent to which persons enrolling in new public insurance programs substitute the public coverage for private insurance is of concern to policy makers. OBJECTIVE: To look at the extent of the substitution resulting from new state programs that cover a broad base of the low-income population and to look at the responses of both families and employers. METHODS: The March CPS for 1991-1993 and 1997-1998 were used to study the responses of families. Two large national surveys of employers with information about the employment-based system in 1993 and 1997 were used to study employer responses. The analysis looks at changes in coverage and employer offer rates before and after the public insurance expansions in selected states and compares these changes to those in a control group in states without expansions. RESULTS: Coverage by private insurance for low-income persons in states with expansions fell by more than expected based on the control states, indicating some substitution of public coverage for private insurance. Changes in employee coverage in own-employer sponsored insurance accord with this result. The expansion of public insurance has a bigger effect on employer offer decisions when a large share of its workers is eligible for public programs. CONCLUSIONS: The results show a significant substitution of public insurance for private coverage in the expansions studied. However, endogeneity of state expansion policies and possible confounding with other policy changes temper the conclusions. More recent public insurance expansions as part of the State Childrens' Health Insurance Program have adopted a range of methods to limit crowd out. Future research is needed to evaluate whether these procedures and rules have succeeded.

Adult↗
PubMed2004

Traumatic asphyxial deaths due to an uncontrolled crowd.

Nine people died of traumatic asphyxia due to an uncontrolled crowd at a community basketball game in New York City in 1991. We reviewed the circumstances, postmortem findings, and the causes of death. The majority of people had petechiae of the conjunctivae and face consistent with chest compression. There were minimal superficial blunt injuries and no fractures or acute intoxications. These deaths are often incorrectly attributed to blunt force injuries, while the cause typically is asphyxia due to chest compression.

Adolescent↗
PubMed2002

Kinetic arrest of crowded soft spheres in solvents of varying quality.

Crowded solutions of multiarm star polymers, representing model colloidal spheres with ultrasoft repulsive interactions, undergo a reversible gelation transition upon heating in solvents of intermediate quality (between good and Theta). This unusual phenomenon is due to the kinetic arrest of the swollen interpenetrating spheres at high temperatures, forming clusters, in analogy to the colloidal glass transition. In this work we demonstrate that the choice of the solvent has a dramatic effect on the gelation transition, because of the different degree of star swelling (at the same temperature) associated with the solvent quality. We construct a generic kinetic phase diagram for the gelation of different stars in different solvents (gelation temperature against effective volume fraction, phi) and propose a critical "soft sphere close packing" volume fraction phi(c) distinguishing the temperature-induced (for phi phi(c)) glass-like gelation. We conclude that appropriate selection of the solvent allows for manipulation of the sol-gel transition in such ultrasoft colloids.

Journal Article↗
PubMed1997

The use of Baypamun N in crowding-associated infectious respiratory disease: efficacy of Baypamun N (freeze dried product) in 2-week-old veal calves.

The efficacy of an immunomodulator, Baypamun N, was tested in 10-20-day-old veal calves from different farms, which were exposed to stress by transport and commingling (crowding). Verum and placebo animals (n = 50, each group) received three intramuscular injections of the investigational products (days 0, 2, 4) starting the day of arrival on the farm. Data from 49 calves in each group could be used for statistical evaluation. The incidence of acute bovine respiratory disease was anticipated to be high during the first 2 weeks after arrival on farm based on experience from other years. The clinical scores in the Baypamun N group were significantly reduced by 52.7% (P < 0.001) compared to the placebo group. The number of antibiotic treatments was significantly reduced by 53.8% (P < 0.001) in the Baypamun N group. Of the calves treated with Baypamun N, 51.02% remained untreated with antibiotics during the first 2 weeks after arrival on the farm compared with only 16.3% of the placebo treated control calves (P < 0.001).

Adjuvants, Immunologic↗
PubMed1997

The use of Baypamun N in crowding associated infectious respiratory disease: efficacy of Baypamun N (freeze dried product) in 4-10 month old horses.

The efficacy of an immunomodulator, Baypamun N, was tested in 4-10-month-old horses which were exposed to stress by weaning, transport and commingling with yearlings from different breeders (crowding). Verum (n = 26) and placebo animals (n = 27) received three intramuscular injections of the investigational preparations (days 0, 2, 9) starting at the day of commingling in one stable. The incidence of acute respiratory disease was high during the first 4 weeks after commingling. Approximately 50% of all horses showed seroconversion due to field infection by EHV1 and EHV4 during the observation period. The clinical scores in the Baypamun N group were significantly reduced by 40.3% (P < 0.05) compared to the placebo group. The proportion of horses with purulent nasal discharge during the observation period (4 weeks) was also significantly reduced by 58.7% (P < 0.01) in the Baypamun N group. Fifty per cent of the horses injected with Baypamun N showed no purulent nasal discharge and therefore no signs of complicated disease of the upper respiratory airways in contrast to only 14.8% in the non-protected placebo group. The challenge conditions studied in this investigation were rather severe because of the permanent exposure of Baypamun N treated individuals to the non-separated and untreated horses (n = 51). This indicates that treatment with Baypamun N is a successful tool to avoid severe clinical consequences of stress in young horses.

Acute Disease↗
PubMed2001

Treatment planning for porcelain veneer restoration of crowded teeth by modifying stone models.

UNLABELLED: The three-dimensional result attainable through porcelain veneer restoration of crowded teeth can be preoperatively determined by diagnostically altering stone study models of the patient's dentition. Techniques for diagnostically preparing and waxing the stone dental models are described in this article, along with the corresponding postoperative restorative results of representative cases. CLINICAL SIGNIFICANCE: Patients with malaligned teeth who are not willing or able to undergo straightening of their teeth with orthodontics, nonetheless may be able to attain straight teeth concomitant with the restoration of their teeth with modified porcelain veneer restorations. This article describes a straight forward treatment planning technique for altering study casts preoperatively, to accurately predict and guide the postoperative outcome.

Adult↗
PubMed1988

Molecular crowding on the cell surface.

Strong steric interactions among proteins on crowded living cell surfaces were revealed by measurements of the equilibrium spatial distributions of proteins in applied potential gradients. The fraction of accessible surface occupied by mobile surface proteins can be accurately represented by including steric exclusion in the statistical thermodynamic analysis of the data. The analyses revealed enhanced, concentration-dependent activity coefficients, implying unanticipated thermodynamic activity even at typical cell surface receptor concentrations.

Animals↗
PubMed1998

Syncytium-inhibiting monoclonal antibodies produced against human T-cell lymphotropic virus type 1-infected cells recognize class II major histocompatibility complex molecules and block by protein crowding.

Four new monoclonal antibodies (MAbs) that inhibit human T-cell lymphotropic virus type 1 (HTLV-1)-induced syncytium formation were produced by immunizing BALB/c mice with HTLV-1-infected MT2 cells. Immunoprecipitation studies and binding assays of transfected mouse cells showed that these MAbs recognize class II major histocompatibility complex (MHC) molecules. Previously produced anti-class II MHC antibodies also blocked HTLV-1-induced cell fusion. Coimmunoprecipitation and competitive MAb binding studies indicated that class II MHC molecules and HTLV-1 envelope glycoproteins are not associated in infected cells. Anti-MHC antibodies had no effect on human immunodeficiency virus type 1 (HIV-1) syncytium formation by cells coinfected with HIV-1 and HTLV-1, ruling out a generalized disruption of cell membrane function by the antibodies. High expression of MHC molecules suggested that steric effects of bound anti-MHC antibodies might explain their inhibition of HTLV-1 fusion. An anti-class I MHC antibody and a polyclonal antibody consisting of several nonblocking MAbs against other molecules bound to MT2 cells at levels similar to those of class II MHC antibodies, and they also blocked HTLV-1 syncytium formation. Dose-response experiments showed that inhibition of HTLV-1 syncytium formation correlated with levels of antibody bound to the surface of infected cells. The results show that HTLV-1 syncytium formation can be blocked by protein crowding or steric effects caused by large numbers of immunoglobulin molecules bound to the surface of infected cells and have implications for the structure of the cellular HTLV-1 receptor(s).

Animals↗
PubMed2004

Crowding and the tilt illusion: toward a unified account.

Crowding, the difficult identification of peripherally viewed targets amidst similar distractors, has been explained as a compulsory pooling of target and distractor features. The tilt illusion, in which the difference between two adjacent gratings' orientations is exaggerated, has also been explained by pooling (of Mexican-hat-shaped population responses). In an attempt to establish both phenomena with the same stimuli--and account for them with the same model--we asked observers to identify (as clockwise or anticlockwise of vertical) slightly tilted targets surrounded by tilted distractors. Our results are inconsistent with the feature-pooling model: the ratio of assimilation (the tendency to perceive vertical targets as tilted in the same direction as slightly tilted distractors) to repulsion (the tendency to perceive vertical targets as tilted away from more oblique distractors) was too small. Instead, a general model of modulatory lateral interaction can better fit our results.

Female↗