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Equivalent Size (equivalent + size)
Selected AbstractsPrenatal growth and development of the modern human labyrinthJOURNAL OF ANATOMY, Issue 2 2004Nathan Jeffery Abstract The modern human bony labyrinth is morphologically distinct from that of all other primates, showing derived features linked with vestibular function and the overall shape of the cranial base. However, little is known of how this unique morphology emerges prenatally. This study examines in detail the developing fetal human labyrinth, both to document this basic aspect of cranial biology, and more specifically, to gain insight into the ontogenetic basis of its phylogenetically derived morphology. Forty-one post-mortem human fetuses, ranging from 9 to 29 weeks gestation, were investigated with high-resolution magnetic resonance imaging. Quantitative analyses of the labyrinthine morphology revealed a number of interesting age-related trends. In addition, our findings show that: (1) the prenatal labyrinth attains an adult equivalent size between 17 and 19 weeks gestation; (2) within the period investigated, shape changes to all or most of the labyrinth cease after the 17,19-week size maturation point or after the otic capsule ossifies; (3) fetal cochlea development correlates with the surrounding petrosal morphology, but not with the midline basicranium; (4) gestational age-related rotations of the ampullae and cochlea relative to the lateral canal, and posterior canal torsion are similar to documented phylogenetic trends whereas other trends remain distinct. Findings are discussed in terms of the ontogenetic processes and mechanisms that most likely led, in part, to the emergence of the phylogenetically derived adult modern human labyrinth. [source] Invasive alien plants infiltrate bird-mediated shrub nucleation processes in arid savannaJOURNAL OF ECOLOGY, Issue 4 2007S. J. MILTON Summary 1,The cultivation and dissemination of alien ornamental plants increases their potential to invade. More specifically, species with bird-dispersed seeds can potentially infiltrate natural nucleation processes in savannas. 2To test (i) whether invasion depends on facilitation by host trees, (ii) whether propagule pressure determines invasion probability, and (iii) whether alien host plants are better facilitators of alien fleshy-fruited species than indigenous species, we mapped the distribution of alien fleshy-fruited species planted inside a military base, and compared this with the distribution of alien and native fleshy-fruited species established in the surrounding natural vegetation. 3Abundance and diversity of fleshy-fruited plant species was much greater beneath tree canopies than in open grassland and, although some native fleshy-fruited plants were found both beneath host trees and in the open, alien fleshy-fruited plants were found only beneath trees. 4Abundance of fleshy-fruited alien species in the natural savanna was positively correlated with the number of individuals of those species planted in the grounds of the military base, while the species richness of alien fleshy-fruited taxa decreased with distance from the military base, supporting the notion that propagule pressure is a fundamental driver of invasions. 5There were more fleshy-fruited species beneath native Acacia tortilis than beneath alien Prosopis sp. trees of the equivalent size. Although there were significant differences in native plant assemblages beneath these hosts, the proportion of alien to native fleshy-fruited species did not differ with host. 6Synthesis. Birds facilitate invasion of a semi-arid African savanna by alien fleshy-fruited plants, and this process does not require disturbance. Instead, propagule pressure and a few simple biological observations define the probability that a plant will invade, with alien species planted in gardens being a major source of propagules. Some invading species have the potential to transform this savanna by overtopping native trees, leading to ecosystem-level impacts. Likewise, the invasion of the open savanna by alien host trees (such as Prosopis sp.) may change the diversity, abundance and species composition of the fleshy-fruited understorey. These results illustrate the complex interplay between propagule pressure, facilitation, and a range of other factors in biological invasions. [source] Mortality after uveal and conjunctival melanoma: which tumour is more deadly?ACTA OPHTHALMOLOGICA, Issue 2 2009Emma Kujala Abstract. Purpose:, We aimed to model and compare mortality rates for uveal melanoma (UM) and conjunctival melanoma (CM) by adjusting for differences in tumour size and local recurrence. Methods:, Population-based mortality data for 240 and 85 patients with primary UM and CM and 91 and 23 patients with disseminated UM and CM, respectively, were compared with cumulative incidence analysis. Cox proportional hazards multivariate regression with time-dependent variables was used to adjust for differences in tumour diameter, thickness and recurrence rates. Results:, The 10-year cumulative incidences of metastatic death from UM and CM were 39% (95% confidence interval [CI] 33,45) and 32% (95% CI 21,44), respectively. After adjusting for tumour size, risk of death from CM was higher than from UM (hazard ratio [HR] 1.9; p = 0.039). Additional adjustment for more frequent local recurrence of CM diminished the difference (HR 1.5; p = 0.25). Survival periods after systemic metastasis of UM and CM were comparable (median 8 months). Conclusions:, Clinical observations show longer survival after primary CM than after primary UM. This reflects the smaller average size of CM. However, a primary CM of a given size is more deadly than a UM of equivalent size because primary CM tends to recur after treatment and, possibly, because additional lymphatic dissemination occurs with CM. [source] Conservative versus primary surgical treatment of acoustic neuromas: a comparison of rates of facial nerve and hearing preservationCLINICAL OTOLARYNGOLOGY, Issue 3 2008T.P.C. Martin Objectives:, To determine whether patients with small to medium sized acoustic neuromas managed conservatively suffer reduced rates of facial nerve and hearing preservation when compared with patients undergoing primary surgery. Design:, An intention-to-treat comparison between patients managed conservatively at first presentation and those managed with primary surgery. Setting:, Tertiary referral neurotological centre in Birmingham, UK. Participants:, Data were drawn from our database of 487 sporadic acoustic neuromas managed from 1997 to present day. Main outcome measures:, Facial nerve status (assessed using the House-Brackmann system) was collated for all conservatively managed patients (n = 167) and compared with that expected when calculated from primarily surgically managed tumours of equivalent size (n = 121). A chi-square test was employed to test the statistical significance of any difference. Hearing preservation (maintenance of AAO-HNS Class) in patients presenting with Class A or B hearing was compared between conservatively managed patients and those with primary surgical management. Results:, Observed facial nerve preservation in conservatively managed patients was significantly better (P < 0.001) than expected when calculated from rates of facial nerve preservation in surgically managed patients. Hearing preservation was also significantly more successful in conservatively managed patients (Pearson chi-square: P < 0.000). Conclusions:, An initial period of conservative management is a safe and reasonable management policy in all acoustic neuromas up to 2 cm in size at the cerebello-pontine angle. Given that there are no failsafe ways of deciding potential for growth in acoustic neuromas, initial conservative management of these tumours offers superior hearing and facial nerve preservation when compared with primary surgical treatment. [source] | |||||||||||||