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PubMed1995

A preliminary report on lower arch crowding in the mature adult.

Changes in lower arch crowding were measured on models of 16 subjects between the ages of 18 and 50 years. Changes in position of various cephalometric points relative to the skull base were measured on 90-degree left lateral cephalograms. Some increase in lower arch crowding was found in 80 per cent of subjects. With one exception, all subjects showed changes in size and orientation of the jaws relative to the skull base varying in amount and direction. Possible causes of increased lower arch crowding in the mature adult are discussed.

Adolescent↗
PubMed1997

Dental crowding: a comparison of three methods of assessment.

This study was designed to explore a new method for the assessment of dental crowding from study models, which would be both valid and reproducible. This was then tested against two previously reported strategies. A single examiner compared the following methods: visual examination, brass wire/callipers, and a reflex microscope with its customized computer program. Sixty study models (30 maxillary and 30 mandibular) were measured using each technique on two separate occasions. The results showed the reflex microscope method to be the most reproducible, followed by the visual examination and brass wire methods. When testing for validity, as there is no absolutely accurate standard of arch measurement, the individual methods must be compared with one another. From the results, it was seen that the mean values for dental crowding using the reflex microscope, in both the upper and lower arches, were very close to a value which equalled the average obtained from the two means of the visual examination and brass wire methods. The results also indicated that the visual examination and brass wire methods showed a positive bias towards over- and underestimating the degree of crowding, respectively.

Alloys↗
PubMed2000

Macromolecular crowding perturbs protein refolding kinetics: implications for folding inside the cell.

We have studied the effects of macromolecular crowding on protein folding kinetics by studying the oxidative refolding of hen lysozyme in the absence and presence of high concentrations of bovine serum albumin and Ficoll 70. The heterogeneity characteristic of the lysozyme refolding process is preserved under crowded conditions. This, together with the observation that the refolding intermediates that accumulate to significant levels are very similar in the absence and presence of Ficoll, suggests that crowding does not alter substantially the energetics of the protein folding reaction. However, the presence of high concentrations of macromolecules results in the acceleration of the fast track of the refolding process whereas the slow track is substantially retarded. The results can be explained by preferential excluded volume stabilization of compact states relative to more unfolded states, and suggest that, relative to dilute solutions, the rates of many protein folding processes are likely to be altered under conditions that more closely resemble the intracellular environment.

Ficoll↗
PubMed2006

Factors regulating thermodynamic stability of DNA structures under molecular crowding conditions.

The condition in a living cell is molecularly crowded with various biomolecules. The total concentration of the biomolecules inside Escherichia coli is in the range of 300-400 g/L. This is distinct from typical biomolecular concentrations of less than 1g/L, which is generally used for experiments in vitro. Here, we analyzed quantitatively the effects of molecular crowding on the thermodynamics of antiparallel G-quadruplex formation via Hoogsteen base pairs and of antiparallel hairpin-looped duplex (HP duplex) formation via Watson-Crick base pairs. The free energy changes for G-quadruplex and duplex formations decreased and increased when the concentration of poly(ethylene glycol) 200 was increased from 0 to 40 wt%, respectively. These results showed that the antiparallel G-quadruplex is stabilized under molecular crowding conditions but the HP duplex is destabilized.

Aptamers, Nucleotide↗
PubMed1998

The effect of extraction of third molars on late lower incisor crowding: a randomized controlled trial.

The problem of late mandibular incisor crowding is a well established phenomenon, the cause of which has been the substance of considerable debate over the years. A central issue is the possible role of the third molars though no definitive conclusions have been consistently drawn. This prospective study was designed to investigate the effects of randomly assigned early extraction of third molars on late crowding of the mandibular incisors. One-hundred-and-sixty-four patients entered the study from 1984 following completion of retention after orthodontic treatment. Seventy-seven patients (47%) returned for records up to a mean of 66 months later, and their start and finish study casts were digitized on a reflex microscope to determine Little's index of irregularity, intercanine width and arch length. Forty-four of the patients had been randomized to have third molars removed. There was no evidence of responder bias. Where third molars were extracted the mean increase in lower labial segment irregularity was reduced by 1.1 mm from a mean of 2.1 mm for the group where third molars were retained (P = 0.15, not statistically significant). This difference was also not considered to be clinically significant. The principal conclusion drawn from this randomized prospective study is that the removal of third molars to reduce or prevent late incisor crowding cannot be justified.

Adolescent↗
PubMed2004

Protein self-association in crowded protein solutions: a time-resolved fluorescence polarization study.

The self-association equilibrium of a tracer protein, apomyoglobin (apoMb), in highly concentrated crowded solutions of ribonuclease A (RNase A) and human serum albumin (HSA), has been studied as a model system of protein interactions that occur in crowded macromolecular environments. The rotational diffusion of the tracer protein labeled with two different fluorescent dyes, 8-anilinonaphthalene-1-sulfonate and fluorescein isothiocyanate, was successfully recorded as a function of the two crowder concentrations in the 50-200 mg/mL range, using picosecond-resolved fluorescence anisotropy methods. It was found that apoMb molecules self-associate at high RNase A concentration to yield a flexible dimer. The apparent dimerization constant, which increases with RNase A concentration, could also be estimated from the fractional contribution of monomeric and dimeric species to the total fluorescence anisotropy of the samples. In contrast, an equivalent mass concentration of HSA does not result in tracer dimerization. This different effect of RNase A and HSA is much larger than that predicted from simple models based only on the free volume available to apoMb, indicating that additional, nonspecific interactions between tracer and crowder should come into play. The time-resolved fluorescence polarization methods described here are expected to be of general applicability to the detection and quantification of crowding effects in a variety of macromolecules of biological relevance.

Animals↗
PubMed2006

The effect of emergency department crowding on the management of pain in older adults with hip fracture.

OBJECTIVES: To evaluate the effect of emergency department (ED) crowding on assessment and treatment of pain in older adults. DESIGN: Retrospective review of ED records from a prospective cohort study. SETTING: Urban, academically affiliated, tertiary medical center. PARTICIPANTS: One hundred fifty-eight patients, aged 50 and older, evaluated and hospitalized from the ED with hip fracture. MEASUREMENTS: Patient-related risk factors: age, sex, nursing home residence, ED triage status, dementia, Acute Physiology in Age and Chronic Health Evaluation II physiological score, and RAND comorbidity score. ED crowding risk factors: ED census and mean length of stay. OUTCOMES: documentation of pain assessment, time to pain assessment, time to pain treatment, patients reporting pain receiving analgesia, and meperidine use. RESULTS: Mean age was 83 (range 52-101), 81.0% of patients complained of pain, mean time to pain assessment was 40 minutes (range 0-600), time to treatment was 141 minutes (range 10-525), and mean delay to treatment was 122 minutes (range 0-526). Of those with pain, 35.9% received no analgesia, 7.0% received nonopioids, and 57.0% received opioids. Of those receiving opioids, 32.8% received meperidine. ED crowding at census levels greater than 120% bed capacity was significantly associated with a lower likelihood of documentation of pain assessment (P = .05) and longer times to pain assessment (P = .01). CONCLUSION: Older adults with hip fracture are at risk for underassessment of pain, considerable delays in analgesic administration after pain is identified, and treatment with inappropriate analgesics (e.g., meperidine) in the ED. Higher levels of ED census are significantly associated with poorer pain management.

Aged↗
PubMed2006

Crowding and confinement effects on protein diffusion in vivo.

The first in vivo measurements of a protein diffusion coefficient versus cytoplasmic biopolymer volume fraction are presented. Fluorescence recovery after photobleaching yields the effective diffusion coefficient on a 1-mum-length scale of green fluorescent protein within the cytoplasm of Escherichia coli grown in rich medium. Resuspension into hyperosmotic buffer lacking K+ and nutrients extracts cytoplasmic water, systematically increasing mean biopolymer volume fraction, , and thus the severity of possible crowding, binding, and confinement effects. For resuspension in isosmotic buffer (osmotic upshift, or Delta, of 0), the mean diffusion coefficient, , in cytoplasm (6.1 +/- 2.4 microm2 s(-1)) is only 0.07 of the in vitro value (87 microm2 s(-1)); the relative dispersion among cells, sigmaD/ (standard deviation, sigma(D), relative to the mean), is 0.39. Both and sigmaD/ remain remarkably constant over the range of Delta values of 0 to 0.28 osmolal. For a Delta value of > or =0.28 osmolal, formation of visible plasmolysis spaces (VPSs) coincides with the onset of a rapid decrease in by a factor of 380 over the range of Delta values of 0.28 to 0.70 osmolal and a substantial increase in sigmaD/ . Individual values of D vary by a factor of 9 x 10(4) but correlate well with f(VPS), the fractional change in cytoplasmic volume on VPS formation. The analysis reveals two levels of dispersion in D among cells: moderate dispersion at low Delta values for cells lacking a VPS, perhaps related to variation in phi or biopolymer organization during the cell cycle, and stronger dispersion at high Delta values related to variation in f(VPS). Crowding effects alone cannot explain the data, nor do these data alone distinguish crowding from possible binding or confinement effects within a cytoplasmic meshwork.

Biological Transport↗
PubMed2006

A study of the factors that influence how senior officers police crowd events: on SIDE outside the laboratory.

This paper fits into the SIDE perspective (Reicher, Spears, & Postmes, 1995; Postmes, Spears, Lea, & Reicher, 2000), which emphasises the importance of integrating the cognitive and strategic dimensions of group processes. Our study examines the decisions made by senior police officers during a simulation exercise of a crowd event. The analysis shows, firstly, that officers are deeply concerned about their accountability to a variety of audiences, both internal and external to the police force. Second, these different audiences pressure them to act in different, and sometimes contradictory, ways. What counts, then, is the overall balance between accountability concerns. Third, this balance - and, with it, police perceptions and decisions - alters in the course of an event. More specifically, with escalating conflict, the balance of accountability concerns moves increasingly in the direction of undifferentiated intervention against crowd members. In discussion, we consider both the theoretical implications of this analysis for research on group processes (in particular the importance of accountability issues once one moves beyond the laboratory and deals with groups that have a past and future and in which membership is more than simply an act of choice) and the practical implications in terms of crowd policing.

Adult↗
PubMed2004

Anomalous subdiffusion is a measure for cytoplasmic crowding in living cells.

Macromolecular crowding dramatically affects cellular processes such as protein folding and assembly, regulation of metabolic pathways, and condensation of DNA. Despite increased attention, we still lack a definition for how crowded a heterogeneous environment is at the molecular scale and how this manifests in basic physical phenomena like diffusion. Here, we show by means of fluorescence correlation spectroscopy and computer simulations that crowding manifests itself through the emergence of anomalous subdiffusion of cytoplasmic macromolecules. In other words, the mean square displacement of a protein will grow less than linear in time and the degree of this anomality depends on the size and conformation of the traced particle and on the total protein concentration of the solution. We therefore propose that the anomality of the diffusion can be used as a quantifiable measure for the crowdedness of the cytoplasm at the molecular scale.

Computer Simulation↗
PubMed2005

Protein self-association induced by macromolecular crowding: a quantitative analysis by magnetic relaxation dispersion.

In the presence of high concentrations of inert macromolecules, the self-association of proteins is strongly enhanced through an entropic, excluded-volume effect variously called macromolecular crowding or depletion attraction. Despite the predicted large magnitude of this universal effect and its far-reaching biological implications, few experimental studies of macromolecular crowding have been reported. Here, we introduce a powerful new technique, fast field-cycling magnetic relaxation dispersion, for investigating crowding effects on protein self-association equilibria. By recording the solvent proton spin relaxation rate over a wide range of magnetic field strengths, we determine the populations of coexisting monomers and decamers of bovine pancreatic trypsin inhibitor in the presence of dextran up to a macromolecular volume fraction of 27%. Already at a dextran volume fraction of 14%, we find a 30-fold increase of the decamer population and 510(5)-fold increase of the association constant. The analysis of these results, in terms of a statistical-mechanical model that incorporates polymer flexibility as well as the excluded volume of the protein, shows that the dramatic enhancement of bovine pancreatic trypsin inhibitor self-association can be quantitatively rationalized in terms of hard repulsive interactions.

Animals↗
PubMed2002

Effects of concurrent infections on Hymenolepis diminuta (Cestoda) and Moniliformis dubius (Acanthocephala). I. General effects and comparison with crowding. 1961.

Hymenolepis diminuta developing in the presence of Moniliformis dubius are lighter, shorter, have a lower average weight:length ratio, and are limited to the posterior part of the intra-intestinal range they occupy in single infections. M. dubius in the concurrent infections are lighter, possibly shorter, have a lower average weight:length ratio, and tend to attach further anterior than in single infections. No effects were noted on the percent recovery of either helminth. Highly significant regressions of the wet weight, length, and weight:length ratio of H. diminuta and M. dubius on the number of larvae administered in single infections have been demonstrated. The weight and length of the H. diminuta, and the weight and weight:length ratios of the M. dubius, from concurrent infections were significantly lower than values predicted for single-species infections with a comparable number of worms. In crowded single-species infections, the distribution of attachment points of the H. diminuta is extended to include the anterior three-fourths of the intestine; in concurrent infections the tapeworms are limited to the posterior part of this range. Under crowded conditions, the M. dubius extend their linear intestinal distribution only slightly, all of the acanthocephalans attaching in the anterior half of the small intestine; in concurrent infections the acanthocephalans tend to be limited to the anterior part of this range. The distributional limitations in concurrent infections and the similarities between the effects of concurrent infection and crowding suggest that similar mechanisms, i.e., competition, possibly for carbohydrate, may be involved in the production of the effects of concurrent infection.

Acanthocephala↗
PubMed1999

[The influence of steric crowding on the electrochemical reduction of amide groups in a pyridylcarboxamide seriesapplication to rote ction of amines in peptide synthesis].

To gain a better understanding of the effect exerted by the 3-hydroxypicolinoyl residue on the antibiotic activity of Pristinamycin IA, the C-N bond of picolinamide was cleaved electrochemically. A mechanistic study demonstrated that the presence of the peptidic macrolactone M markedly modified the expected cathodic behavior of pyridylcarboxamides. In order to assess the influence of steric crowding exerted by M on this original behavior, we look for models using two different approachs. First, tertiary pyridylcarboxamides were used to increase steric hindrance at the amide nitrogen position; second, M was opened by ammonolysis to decrease steric crowding at the amide nitrogen position. The electrochemical behavior of the selected compounds is presented in the first and the second parts of this study. Determination of pyridine nitrogen basicity in an N-substituted-3-methoxypicolinamide series is treated in the third part as a useful probe to evaluate the intensity of steric crowding at the amide nitrogen position. Finally, in the last part of this work, we propose the use of the picolinoyl residue (C6H4N-CO-ou Pic) as a protecting group for amines in peptide synthesis.

Amides↗
PubMed1998

"Crowd-out": what it means for children's health insurance.

As states finalize proposals for the federal Title XXI Children's Health Insurance Program (CHIP), consumers, advocates, legislators, and policymakers across the country are facing the issue of "crowd-out." How can they prevent CHIP's new public funds from "crowding out"--or supplanting--private funds now used to insure children? This issue of States of Health looks at research on crowd-out and reviews what some states have learned as a result of previous Medicaid expansions. Their experiences shed light on the challenge of making sure that Title XXI health care dollars reach the intended consumers, children who lack adequate insurance.

Centers for Medicare and Medicaid Services, U.S.↗
PubMed2003

[Prognosis of utility of modified supracrestal fiberotomy and contact point reproximation in the treatment of anterior segment crowding].

OBJECTIVE: The aim of this study was to evaluate quantitatively the effectiveness and feasibility of the modified supracrestal fiberotomy (MSF) and the contact point reproximation (CPR) in decreasing the relapse of anterior segments rotating and/or crowding after orthodontic treatment. METHODS: A total of 129 patients with crowding and/or rotated anterior teeth were selected for this study, and the average age was 13.07 years (54 males, 75 females). The modified supracrestal fiberotomy was performed on the anterior segments of patients in the experimental group (48 cases). After the anterior teeth were aligned, 23 of the 48 cases received a further treatment of the contact point reproximation on the anterior segments (the subgroup of MSF + CPR), and the other 25 subjects did not receive this treatment (the subgroup of MSF). The control group consisted of 81 cases. All cases wore Hawley retainers for 1.8 to 2.3 years, and all the patients were revisited 2.4 years postretention. The maxillary and mandibular dental models of all the patients were taken before treatment (T1), at the end of the treatment (T2) and 2.4 years postretention (T3). RESULTS: The relapse rate in the experimental group [(T3-T2)/T1 x 100%] was 21.6%, lower than that in the control group (P < 0.001). The relapse rate of mandible in the subgroup of MSF + CPR was 6.56% lower than that of the subgroup of MSF (P < 0.05). But the relapse rate of maxillary in the subgroups of MSF + CPR was similar as that of the subgroup of MSF (P > 0.05). CONCLUSION: The modified supracrestal fiberotomy can effectively alleviate relapse after orthodontic treatment of the crowding and/or rotation of anterior teeth. The treatment combining MSF and CPR can help maintain the stability of post-retention of mandibular anterior teeth.

Adolescent↗
PubMed1975

Cardiomyopathy in crowded rabbits.

Rabbits were crowded 4 to a cage for 2 weeks, then released for 1 week, crowded again for 2 weeks, and so on. Of 44 rabbits subjected to intermittent crowding, only 9 survived for longer than 10 months, 20 died during the 1st month, and 15 died between the 2nd and 9th month of the experiment. Histological sections of the myocardium showed myocytolysis, intersititial edema, and an increased amount of acid mucopoly saccharides in rabbits surviving for 2 weeks and more. The accumulations of acid mucopolysaccharides were apparently unrelated to necrotic foci. Long-term survivors frequently showed myocardial fibrosis and endocardial fibroelastosis, as well as basophilic degeneration of myocardial fibers. The lesions observed were similar to those described in idiopathic endomyocardiopathy in Southern Africa. Therefore, the rabbit may be of some value for research in cardiomyopathies.

Animals↗
PubMed2006

[First molar extraction in patients with crowding: cases analysis].

OBJECTIVE: To evaluate the outcome of first molar extraction in patients with crowding. METHODS: Totally 22 patients (8 males and 14 females) from Clinic of Orthodontics, SUN Yat-sen University School of Stomatology with crowding were collected. The patients were aged 11 years 3 months to 26 years 8 months (mean age 16 years 6 months). All of them treated with 1 to 4 first molar extractions. RESULTS: The average duration of orthodontic treatment was 18.5 months. Normal overjet and overbite was achieved. Good functional occlusion was established. CONCLUSIONS: Patients with severe crowding could be successfully treated with first molar extraction.

Adolescent↗
PubMed1991

In vivo effects of putative crowding factors on development of Hymenolepis diminuta.

During in vitro incubation, Hymenolepsis diminuta secretes substances into the medium that inhibit DNA synthesis in the germinative region of freshly isolated, uncrowded worms. Of the many substances that are released by H. diminuta into the medium, earlier studies indicate that only succinate, acetate, glucosaminic acid, and cGMP are responsible for the inhibition. In the present report, effects of these putative crowding factors on worm development in vivo were examined. At 7 days postinfection the proximal end of the host's intestine was catheterized and perfused with test solution. The test solution contained 28 nM cGMP, 250 microM glucosaminic acid, 120 mM succinate, and 40 mM acetate. The solution was perfused by a peristaltic pump at a rate of 50 ml/day. At 2 wk postinfection, worms were recovered for subsequent analysis. Worms developing in the presence of crowding factors were 53% less in wet weight than control worms. Carbohydrate concentrations in worms from experimental groups were not different from those in control groups; therefore, the inhibition in growth was probably not due to carbohydrate deprivation. Worms from experimental groups had fewer immature, mature, and gravid proglottids than did worms from control groups. The results are consistent with the hypothesis that the tested substances, which inhibit DNA synthesis in H. diminuta in vitro, are a part of the cause of the crowding effect in vivo.

Acetates↗