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PubMed1997

Longitudinal radiographic assessment of dense bone islands of the jaws.

OBJECTIVES: This study assessed dense bone island (DBI) inception and growth in jaws. STUDY DESIGN: A population of 2991 patients (age range 5 to 35 years) was studied with at least two panoramic radiographs taken 1 to 10 years apart for each patient. Lesions were digitized and measured with computer measuring software. The size of the earliest DBI was compared with subsequent DBI measurements after the latter measurement was normalized with reference to the size of the nearest tooth. RESULTS: Sixty-nine patients with DBIs were identified. A total of 3.1% of the patients with DBI were found in the 5- to 10-year age range, with the first patient in the DBI group found at 9.4 years. A significantly higher proportion (p = 0.002) of the unaffected patients (26%) was found in the same 5-to 10-year age range. The proportions of patients in the DBI and unaffected groups in older age ranges were similar. Assessment of DBI size changes showed that 43% of the 53 DBIs detected between 9.4 and 19 years enlarged (mean change, 212%), and 17% diminished (mean change, 49%). In comparison, 29.4% of 17 DBIs detected between 20 and 35 years enlarged (mean change, 153%), and 5.9% diminished (mean change, 60%). CONCLUSION: Our results indicate that DBIs are labile lesions, develop during early adolescence, and retain a potential for enlargement, or to a lesser extent shrinkage, into adulthood.

Adolescent↗
PubMed1989

Temperature-induced fusion of small unilamellar vesicles formed from saturated long-chain lecithins and diheptanoylphosphatidylcholine.

Small unilamellar vesicles which form when gel-state long-chain phosphatidylcholines are mixed with micellar short-chain lecithins undergo an increase in size as the long-chain species melts to its liquid-crystalline form. Analysis of the vesicle population with quasi-elastic light scattering shows that the particle size increases from 90-A radius to greater than 5000-A radius. Resonance energy transfer experiments show total mixing of lipid probes with unlabeled vesicles only when the Tm of the long-chain phosphatidylcholine is exceeded. This implies that the large size change represents a fusion process. Aqueous compartments are also mixed during this transition. 31P NMR analysis of the vesicle mixtures above the phase transition shows a great degree of heterogeneity with large unilamellar particles coexisting with oligo- and multilamellar structures. Upon cooling the vesicles below the Tm, the original size distribution (e.g., small unilamellar vesicles) is obtained, as monitored by both quasi-elastic light scattering and 31P NMR spectroscopy. This temperature-induced fusion of unilamellar vesicles is concentration dependent and can be abolished at lower total phospholipid concentrations. It occurs over a wide range of long-chain to short-chain ratios and occurs with 1-palmitoyl-2-stearoylphosphatidylcholine and dimyristoylphosphatidylcholine as well. Characterization of this fusion event is used to understand the anomalous kinetics of water-soluble phospholipases toward these unusual vesicles.

Kinetics↗
PubMed1997

Character displacement in some Cnemidophorus lizards revisited: a phylogenetic analysis.

Ecological studies have demonstrated the role of competition in structuring communities; however, the importance of competition as a vehicle for evolution by natural selection and speciation remains unresolved. Study systems of insular faunas have provided several well known cases where ecological character displacement, coevolution of competitors leading to increased morphological separation, is thought to have occurred (e.g., anoline lizards and geospizine finches). Whiptail lizards (genus Cnemidophorus) from the islands of the Sea of Cortez and the surrounding mainland demonstrate a biogeographic pattern of morphological variation suggestive of character displacement. Two species of Cnemidophorus occur on the Baja peninsula, one relatively large (Cnemidophorus tigris) and one smaller (Cnemidophorus hyperythrus). Oceanic islands in the Sea of Cortez contain only single species, five of six having sizes intermediate to both species found on the Baja peninsula. On mainland Mexico C. hyperythrus is absent, whereas C. tigris is the smaller species in whiptail guilds. Here we construct a phylogeny using nucleotide sequences of the cytochrome b gene to infer the evolutionary history of body size change and historical patterns of colonization in the Cnemidophorus system. The phylogenetic analysis indicates that (i) oceanic islands have been founded at least five times from mainland sources by relatives of either C. tigris or C. hyperythrus, (ii) there have been two separate instances of character relaxation on oceanic islands for C. tigris, and (iii) there has been colonization of the oceanic island Cerralvo with retention of ancestral size for Cnemidophorus ceralbensis, a relative of C. hyperythrus. Finally, the phylogenetic analysis reveals potential cryptic species within mainland populations of C. tigris.

Animals↗
PubMed1999

Patterns of instability of expanded CAG repeats at the ERDA1 locus in general populations.

A highly polymorphic CAG repeat locus, ERDA1, was recently described on human chromosome 17q21.3, with alleles as large as 50-90 repeats and without any disease association in the general population. We have studied allelic distribution at this locus in five human populations and have characterized the mutational patterns by direct observation of 731 meioses. The data show that large alleles (>/=40 CAG repeats) are generally most common in Asian populations, less common in populations of European ancestry, and least common among Africans. We have observed a high intergenerational instability (46. 3%+/-5.1%) of the large alleles. Although the mutation rate is not dependent on parental sex, paternal transmissions have predominantly resulted in contractions, whereas maternal transmissions have yielded expansions. Within this class of large alleles, the mutation rate increases concomitantly with increasing allele size, but the magnitude of repeat size change does not depend on the size of the progenitor allele. Sequencing of specific alleles reveals that the intermediate-sized alleles (30-40 repeats) have CAT/CAC interruptions within the CAG-repeat array. These results indicate that expansion and instability of trinucleotide repeats are not exclusively disease-associated phenomena. The implications of the existence of massively expanded alleles in the general populations are not yet understood.

Alleles↗
PubMed2000

Appropriateness of endotracheal tube size and insertion depth in children undergoing air medical transport.

OBJECTIVES: Guidelines for pediatric endotracheal tube (ETT) size and insertion depth are important in the helicopter EMS (HEMS) setting, where intubated patients are frequently transported by a non-physician flight crew providing protocol-based care in an environment noted for limitations in clinical airway assessment. The objectives of this study were to characterize, in a HEMS pediatric population, the frequency of compliance with guideline-recommended ETT size and insertion depth, and to test for association between guideline noncompliance and subsequent receiving hospital adjustment of ETT size or insertion depth. DESIGN: This retrospective review analyzed 216 consecutive pediatric (age <14) scene and interfacility HEMS transports, of patients intubated before or during HEMS transport, by an urban two-helicopter HEMS service providing protocol-based care with a nurse/paramedic crew configuration. Patients were transported to one of three receiving academic pediatric referral centers. Pediatric Advanced Life Support (PALS) criteria for ETT size and insertion depth were used to assess guideline-appropriateness of pediatric ETTs. Receiving hospital records were reviewed to determine if post-transport ETT size or lipline adjustment were associated with guideline-appropriateness of size and lipline during HEMS transport. Univariate (chi-square and Fisher's exact) and multivariate (logistic regression) statistics were used to assess and control for the following covariates: intubator group (physician, flight crew, ground EMS), transport year, sex, age, transport type (scene versus interfacility), and receiving hospital. For all analyses, statistical significance was set at the 0.05 level. RESULTS: The initial ETT size was within 0.5 mm of guideline-recommended sizes in 178 (83.6%) of the 213 patients for whom this data were available. Inappropriate sized ETTs were nearly always (32 of 35, 91.4%) too small. Compared to initial ETTs placed by ground EMS personnel, initial ETTs placed by flight crew or physicians were more likely to be appropriate as defined by guidelines (P = .008 and .032, respectively). Receiving hospitals changed the ETT size in 18 (8.3% of 216) cases. Receiving hospital ETT size change was more likely with later transport year (P = .018) and less likely in patients over 2 years of age (P = .03); there was no significant association between receiving hospital ETT size change and intubator group (P > .22) or guideline-appropriateness of ETT size (P = 0.94). The initial ETT insertion depth was within 1 cm of the guideline-recommended lipline in 86 (43.2%) of the 199 patients for whom this data were available. Inappropriate liplines were almost always (109 of 113, 96.5%) too deep. Compared to initial ETT liplines determined by ground EMS personnel, initial liplines determined by flight crew (P = .007), but not physician (P = .47) were more likely to be appropriate as defined by guidelines. Receiving hospitals changed the ETT insertion depth in 72 (33.3% of 216) cases. Receiving hospital lipline change was more likely (P = .03) in patients older than 2 years of age, but was not associated with intubator group (P = .75) or lipline guideline-appropriateness (P = .35). CONCLUSIONS: As judged by frequently used guidelines, pediatric ETTs are often too small and commonly inserted too deep. However, this retrospective study, limited by lack of clinical correlation for ETT size and insertion depth, failed to find an association between lack of ETT size or lipline guideline compliance and subsequent ETT adjustment at receiving pediatric centers. This study's findings, which should be confirmed with prospective investigation, cast doubt upon the utility of pediatric ETT size/lipline guidelines as strict clinical or quality assurance tools for use in pediatric airway management.

Age Factors↗
PubMed2001

Reproductive changes in fluctuating house mouse populations in southeastern Australia.

House mice (Mus domesticus) in the Victorian mallee region of southeastern Australia show irregular outbreaks. Changes in reproductive output that could potentially drive changes in mouse numbers were assessed from 1982 to 2000. Litter size in females is positively correlated with body size. When standardized to an average size female, litter size changes seasonally from highest in spring to lowest in autumn and winter. Litter size is depressed throughout breeding seasons that begin when the abundance of mice is high, but is similar in breeding seasons over which the abundance of mice increases rapidly or remains low. Breeding begins early and is extended on average by about five weeks during seasons when mouse abundance increases rapidly. The size at which females begin to reproduce is larger during breeding seasons that begin when mouse abundance is high. An extended breeding season that begins early in spring is necessary for the generation of a house mouse plague, but it is not in itself sufficient. Reproductive changes in outbreaks of house mice in Australia are similar but not identical to reproductive changes that accompany rodent population increases in the Northern Hemisphere. We conclude that food quality, particularly protein, is a probable mechanism driving these reproductive changes, but experimental evidence for field populations is conflicting.

Animals↗
PubMed2000

Experimental excursions on adaptive landscapes: density-dependent selection on egg size.

Theories of density-dependent natural selection suggest that intraspecific competition will favor juveniles of high competitive ability. Empirical evidence has been provided from laboratory selection experiments, but field studies are lacking due to the logistical difficulties of experimentally manipulating population densities in natural settings. Here, we present data from a decade-long experimental field study of side-blotched lizards, Uta stansburiana that overcomes these difficulties. We tested the hypothesis that density-dependent natural selection causes egg size to increase from early to late clutches in this and many other species. Using a novel combination of environmental manipulations of hatchling density and phenotypic manipulations of egg size, we demonstrate that the nature of selection on egg size changes dramatically in the absence of older competitors. The strength of selection on egg size among later-clutch hatchlings released in areas without competitors from early clutches became almost doubled in magnitude, compared to that among hatchlings released in the presence of older competitors. These experimental findings demonstrate density-dependent natural selection on egg size; however, they contradict the classical idea that egg size increases during the reproductive season because of competition between early and late hatchlings. The results indicate that competitive age or size asymmetries between early and late hatchlings can override within-cohort asymmetries due to egg size. We suggest that competition could be an important mediator of oscillating selection pressures in this and other systems. Finally, we discuss the utility of "double-level," simultaneous experimental manipulation of both phenotypic traits that are targets of selection (e.g., egg size) as well the environmental agents of selection (e.g., population density).

Adaptation, Physiological↗
PubMed1985

Size changes of protamine 1 mRNA provide a molecular marker to monitor spermatogenesis in wild-type and mutant mice.

We utilized a cDNA encoding the cysteine-rich, tyrosine-containing mouse protamine, mouse protamine 1 (MP1), to detect the presence of several classes of differentiating germ cells in testicular extracts from wild-type and male sterile mutant mice. This assay is based on the changes in the poly (A) length of MP1-mRNA during spermatogenesis. Testicular extracts of sexually mature CD-1 mice contain a heterogeneous population of protamine-1 mRNA ranging in length from 450 to 580 nucleotides. When the protamine-1 probe was hybridized to testicular RNA preparations from 16- to 20-day-old animals, no MP1-mRNA was detected. Twenty-four-day-old mice contain only the 580-nucleotide form of MP1-mRNA. This size class of protamine mRNA is also present in purified populations of round spermatids, whereas elongating spermatids and residual bodies contain mRNAs ranging from 450 to 580 nucleotides in length, which are identical in size to those present in the testes of sexually mature animals. When the protamine cDNA probe was used to examine the progression of spermiogenesis in three male sterile mouse mutants, blind sterile (bs), quaking (qk) and testicular feminization (Tfm), the results demonstrated that each mutant is pathologically distinct. Analysis of the bs mutant revealed a diminution in the amount of both size classes of MP1-mRNA, in agreement with the cytological reports of reduced numbers of haploid spermatogenic cells in these animals. The presence of both size classes of protamine mRNA in the qk mutant indicates that germ-cell differentiation has proceeded at least to the step-12 spermatid in these animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Androgen-Insensitivity Syndrome↗
PubMed1987

Genome size variation in North American minnows (Cyprinidae). II. Variation among 20 species.

Genome sizes (nuclear DNA contents) from 200 individuals representing 20 species of North American cyprinid fishes (minnows) were examined spectrophotometrically. The distributions of DNA values of individuals within populations of the 20 species were essentially continuous and normal; the distribution of DNA values among species was continuous and overlapping. These observations suggest that changes in DNA quantity in cyprinids are small in amount, involve both gains and losses of DNA, and are cumulative and independent in effect. Significant heterogeneity in mean genome size occurs both between individuals within populations of species and among species. The former averages maximally around 6% of the cyprinid genome and is nearly the same as the amount of DNA theoretically needed for the entire cyprinid structural gene component. The majority of the DNA content variation among the 20 species is distributed above the level of individuals within populations. Comparisons of average genome size difference or distance between individuals drawn from different levels of taxonomic organization indicate that considerably greater divergence in genome size has occurred in the extremely speciose cyprinid genus Notropis as compared with other North American cyprinid genera. This may suggest that genome size change is concentrated in speciation episodes. Finally, no associations were found between interspecific variation in genome size and five life-history characters. This suggests that much of the variation in genome size within and among the 20 species may be phenotypically inconsequential.

Animals↗
PubMed2002

Geometric morphometric differences between Panstrongylus geniculatus from field and laboratory.

The finding of Panstrongylus geniculatus nymphs inside a house in northeastern Antioquia, Colombia, and the reports related to their increasing presence in homes suggest the need for surveillance methods for monitoring the invasion processes. We analyzed the morphological differences between a wild population and its laboratory descendants, using the techniques of geometric morphometry, with the idea that such differences might parallel those between sylvatic and synanthropic populations. The analyses over five generations showed differences in size but not in shape. Head size and wing size were both reduced from sylvatic to laboratory populations, but the decrease in head size occurred only up to the second generation while the decrease in wing size proceeded up to the fifth generation. In contrast, although a decrease in sexual size dimorphism has been proposed as a marker of colonization in human dwellings, we did not detect any significant loss of dimorphism between sexes of P. geniculatus over the five generations studied. We conclude that size changes may have a physiological origin in response to a change of ecotopes, but more than five generations may be required for the expression of permanent morphological markers of human dwellings colonization.

Animals↗
PubMed1992

Age-related changes in glomerular volume and hydroxyproline content in rat and human.

Total 4-hydroxyproline content and volume were measured in the same sample of microdissected glomeruli obtained fro rat and human outer or inner cortex. Glomerular volume was determined by computer-assisted image analysis, and 4-hydroxyproline was measured by a highly sensitive gas-liquid chromatographic method. Results were expressed as weight of basement membrane material by comparison with the amount of 4-hydroxyproline in purified basement membrane/mesangial matrix preparations. Microanalyses were possible in samples containing as few as eight human glomeruli. Rat glomerular size increased sevenfold between 5 wk and 2 yr of age, with volume being consistently 36 to 45% greater in inner than in outer cortex glomeruli. Basement membrane material content per glomerulus markedly increased with age (12-fold); however, when expressed per unit volume, this change was greatly reduced (2-fold). Expressed per volume, inner and outer cortex glomerular content of basement membrane material was always similar, regardless of age. Therefore, a greater glomerular size, in itself, does not accelerate the rate of basement membrane material deposition. Glomerular size distributions (measured by skewness and kurtosis) did not change, indicating that, although glomerular volume increases with age, aging does not appear to cause the emergence of distinct glomerular populations within an age group. Basement membrane material accumulation is probably a generalized change. Human glomeruli increased sevenfold in size from infancy to adulthood and then declined during senescence. Contrary to that in the rat, glomerular basement membrane material content appeared to closely follow size changes, thus, varying little from infancy to senescence if expressed per unit of glomerular volume.

Adolescent↗
PubMed1986

The influence of castration and methimazole on deoxyribonucleic acid content of the pituitary and thyroid glands of White Leghorn cockerels.

The pituitary gland of birds is known to increase in weight with castration and decreases with chemical thyroidectomy. Whether these changes are due to alterations in mitotic activity or to cell size changes has been examined by measurement of deoxyribonucleic acid (DNA) and protein content of these glands. The DNA content of the enlarge pituitary of castrated cockerels is the same as that in the pituitary of normal cockerels. The pituitary size increase may be due to an increase in gonadotrope size including any part of the gonadotrope population which may be obtained by recruitment of other basophils. The retardation in pituitary size and DNA content with methimazole treatment is probably due, at least in part, to growth retardation but may also be due, in part, to the conversion of larger basophils to smaller thyrotropes.

Animals↗