scholarly journals Epithelial dynamics shed light on the mechanisms underlying ear canal defects

Development ◽  
2020 ◽  
Vol 147 (23) ◽  
pp. dev194654 ◽  
Author(s):  
Juan M. Fons ◽  
Mona Mozaffari ◽  
Dean Malik ◽  
Abigail R. Marshall ◽  
Steve Connor ◽  
...  
Keyword(s):  
Explant Culture ◽  
Mutant Mice ◽  
Sound Waves ◽  
Ear Canal ◽  
Primary Canal ◽  
Complex Processes ◽  
Underlying Causes ◽  
Canal Atresia ◽  
First Time ◽  
Periderm Formation

ABSTRACTDefects in ear canal development can cause severe hearing loss as sound waves fail to reach the middle ear. Here, we reveal new mechanisms that control human canal development and highlight for the first time the complex system of canal closure and reopening. These processes can be perturbed in mutant mice and in explant culture, mimicking the defects associated with canal atresia. The more superficial part of the canal forms from an open primary canal that closes and then reopens. In contrast, the deeper part of the canal forms from an extending solid meatal plate that opens later. Closure and fusion of the primary canal was linked to loss of periderm, with failure in periderm formation in Grhl3 mutant mice associated with premature closure of the canal. Conversely, inhibition of cell death in the periderm resulted in an arrest of closure. Once closed, re-opening of the canal occurred in a wave, triggered by terminal differentiation of the epithelium. Understanding these complex processes involved in canal development sheds light on the underlying causes of canal atresia.

scholarly journals Anatomy and Development of the Mammalian External Auditory Canal: Implications for Understanding Canal Disease and Deformity

2021 ◽  
Vol 8 ◽  
Author(s):  
Mona Mozaffari ◽  
Robert Nash ◽  
Abigail S. Tucker
Keyword(s):  
Tympanic Membrane ◽  
External Auditory Meatus ◽  
Integrated System ◽  
Sound Waves ◽  
Ear Canal ◽  
Multi Stage ◽  
Anatomical Adaptations ◽  
Clinical Questions ◽  
Canal Atresia ◽  
Conductive Hearing

The mammalian ear is made up of three parts (the outer, middle, and inner ear), which work together to transmit sound waves into neuronal signals perceived by our auditory cortex as sound. This review focuses on the often-neglected outer ear, specifically the external auditory meatus (EAM), or ear canal. Within our complex hearing pathway, the ear canal is responsible for funneling sound waves toward the tympanic membrane (ear drum) and into the middle ear, and as such is a physical link between the tympanic membrane and the outside world. Unique anatomical adaptations, such as its migrating epithelium and cerumen glands, equip the ear canal for its function as both a conduit and a cul-de-sac. Defects in development, or later blockages in the canal, lead to congenital or acquired conductive hearing loss. Recent studies have built on decades-old knowledge of ear canal development and suggest a novel multi-stage, complex and integrated system of development, helping to explain the mechanisms underlying congenital canal atresia and stenosis. Here we review our current understanding of ear canal development; how this biological lumen is made; what determines its location; and how its structure is maintained throughout life. Together this knowledge allows clinical questions to be approached from a developmental biology perspective.

Are seasonal lakes as productive as permanent lakes? A case study from Ireland

2010 ◽  
Vol 67 (8) ◽  
pp. 1291-1302 ◽  
Author(s):  
Helder Cunha Pereira ◽  
Norman Allott ◽  
Catherine Coxon
Keyword(s):  
Seasonal Variation ◽  
Linear Regression ◽  
Chlorophyll A ◽  
Algal Biomass ◽  
P Limitation ◽  
Underlying Causes ◽  
Western Ireland ◽  
Log Linear ◽  
First Time

This paper compares, for the first time, nutrient levels and chlorophyll a measured in a set of seasonal lakes with those reported for permanent lakes in the literature. Twenty-two turloughs (karstic seasonal lakes) in western Ireland were sampled monthly from the onset of flooding (October) until they dried out (6 to 9 months). The turloughs showed similar levels of nutrients and chlorophyll a to those reported for Irish and international lakes. Chlorophyll a peaked between November and February in the majority of turloughs, sometimes with values higher than those measured in mesotrophic lakes in summer. A significant log-linear regression was found between total phosphorus and chlorophyll a, which suggests P limitation of algal biomass in the majority of the turloughs. The regression characteristics were not significantly different than those described in similar studies of permanent lakes. Patterns in seasonal variation of nutrients are also presented, their underlying causes being discussed in relation to their transport within catchments. Our results show that despite being predominantly winter phenomena, turloughs can be as productive as permanent lakes.

IMAGING DIAGNOSIS—EAR CANAL DISTENSION FOLLOWING EXTERNAL AUDITORY CANAL ATRESIA

2008 ◽  
Vol 49 (3) ◽  
pp. 267-269 ◽  
Author(s):  
ABBY R. CAINE ◽  
MIKE E. HERRTAGE ◽  
JANE F. LADLOW
Keyword(s):  
External Auditory Canal ◽  
Imaging Diagnosis ◽  
Ear Canal ◽  
Canal Atresia

scholarly journals Language and Language Policy of Komi-Permyaks in the 1920-1930s

2021 ◽  
Vol 6 (4) ◽  
pp. 76-90
Author(s):  
Mikhail S. Kamenskikh
Keyword(s):  
Language Policy ◽  
Education System ◽  
National Policy ◽  
Sufficient Conditions ◽  
Written Language ◽  
Complex Processes ◽  
First Time

The article is devoted to the particularities of latinization policy of the written Komi Permyaks’ language in the 1930s. As some national and foreign researchers think, the processes of Latinization were most challenging for finno-ugric peoples of the USSR; for this reason, the reforms of the written Komi Permyaks’ language reflect complex processes of policy both within the language sphere and wider – in the national policy of the USSR. Based on available sources, many of which have been introduced into scientific use for the first time, the article analyzes the development of native written language of Komi Permyaks in the 1920-30s, the policy of the Komi district committee on implementation of Latin graphs, and estimates the factors that influenced the failure to adopt the Latin alphabet of the Komi-permyak language in paperwork and education system. The author concludes that, for wider popularity of the Latin alphabet for the Komi-permyak language, there were not sufficient conditions (financial, administrative ones, etc.), so the majority of officials and intelligentsia used Russian to communicate. However, further policy of its implementation could have inspired the usage of this alphabet since later a new Komi alphabet based on Cyrillic symbols was actually adopted.

scholarly journals Low hatching success in the critically endangered kākāpō (Strigops habroptilus) is driven by early embryo mortality not infertility

2020 ◽  
Author(s):  
James L. Savage ◽  
Jodie M. S. Crane ◽  
Nicola Hemmings ◽  
Keyword(s):  
Hatching Success ◽  
Wild Population ◽  
Bird Species ◽  
Early Embryo ◽  
Critically Endangered ◽  
Major Barrier ◽  
In The Wild ◽  
Underlying Causes ◽  
First Time ◽  
Effective Conservation

AbstractIn many endangered species, reproductive failure is a major barrier to recovery. The critically endangered kākāpō (Strigops habroptilus) exemplifies this challenge: 61% of their eggs fail to hatch, and of these 73% show no sign of development. Undeveloped eggs have previously been attributed to male infertility, but recent studies of non-threatened bird species suggest fertilisation failure is rare in the wild. The underlying causes of fertilisation failure and embryo death differ, so distinguishing between them is essential for effective conservation management. Here we show that the majority (72%, n=124) of undeveloped kākāpō eggs are fertilised, and combine this with conservation programme data on natural copulations, artificial inseminations, and paternity of developed eggs, to generate the most precise estimate to date of fertility in a wild population. We also demonstrate, for the first time in a wild bird, that artificial insemination results in greater numbers of sperm reaching the egg.

scholarly journals Why do imagery and perception look and feel so different?

2020 ◽  
Vol 376 (1817) ◽  
pp. 20190703 ◽  
Author(s):  
Roger Koenig-Robert ◽  
Joel Pearson
Keyword(s):  
Convincing Evidence ◽  
Neural Mechanisms ◽  
Cortical Layers ◽  
Theme Issue ◽  
External Stimulation ◽  
The Past ◽  
Underlying Causes ◽  
First Time ◽  
Flow Of Information ◽  
Shed Light

Despite the past few decades of research providing convincing evidence of the similarities in function and neural mechanisms between imagery and perception, for most of us, the experience of the two are undeniably different, why? Here, we review and discuss the differences between imagery and perception and the possible underlying causes of these differences, from function to neural mechanisms. Specifically, we discuss the directional flow of information (top-down versus bottom-up), the differences in targeted cortical layers in primary visual cortex and possible different neural mechanisms of modulation versus excitation. For the first time in history, neuroscience is beginning to shed light on this long-held mystery of why imagery and perception look and feel so different. This article is part of the theme issue ‘Offline perception: voluntary and spontaneous perceptual experiences without matching external stimulation'.

Cell rearrangement and segmentation in Xenopus: direct observation of cultured explants

Development ◽  
1989 ◽  
Vol 105 (1) ◽  
pp. 155-166 ◽  
Author(s):  
P.A. Wilson ◽  
G. Oster ◽  
R. Keller
Keyword(s):  
Explant Culture ◽  
Dorsal Side ◽  
Convergent Extension ◽  
Cell Behaviour ◽  
Cell Rearrangement ◽  
Radial Cell ◽  
Cell Intercalation ◽  
First Time ◽  
The Relationship ◽  
Somitic Mesoderm

We make use of a novel system of explant culture and high resolution video-film recording to analyse for the first time the cell behaviour underlying convergent extension and segmentation in the somitic mesoderm of Xenopus. We find that a sequence of activities sweeps through the somitic mesoderm from anterior to posterior during gastrulation and neurulation, beginning with radial cell intercalation or thinning, continuing with mediolateral intercalation and cell elongation, and culminating in segmentation and somite rotation. Radial intercalation at the posterior tip lengthens the tissue, while mediolateral intercalation farther anterior converges it toward the midline. This extension of the somitic mesoderm helps to elongate the dorsal side of intact neurulae. By separating tissues, we demonstrate that cell rearrangement is independent of the notochord, but radial intercalation - and thus the bulk of extension - requires the presence of an epithelium, either endodermal or ectodermal. Segmentation, on the other hand, can proceed in somitic mesoderm isolated at the end of gastrulation. Finally, we discuss the relationship between cell rearrangement and segmentation.

Targeted disruption of Hoxd-10 affects mouse hindlimb development

Development ◽  
1997 ◽  
Vol 124 (22) ◽  
pp. 4505-4514 ◽  
Author(s):  
E.M. Carpenter ◽  
J.M. Goddard ◽  
A.P. Davis ◽  
T.P. Nguyen ◽  
M.R. Capecchi
Keyword(s):  
Spinal Cord ◽  
Regional Identity ◽  
Nerve Fibers ◽  
Mutant Mice ◽  
Sesamoid Bone ◽  
Sacral Plexus ◽  
Targeted Disruption ◽  
Lateral Motor Column ◽  
Spinal Segments ◽  
Underlying Causes

Targeted disruption of the Hoxd-10 gene, a 5′ member of the mouse HoxD linkage group, produces mice with hindlimb-specific defects in gait and adduction. To determine the underlying causes of this locomotor defect, mutant mice were examined for skeletal, muscular and neural abnormalities. Mutant mice exhibit alterations in the vertebral column and in the bones of the hindlimb. Sacral vertebrae beginning at the level of S2 exhibit homeotic transformations to adopt the morphology of the next most anterior vertebra. In the hindlimb, there is an anterior shift in the position of the patella, an occasional production of an anterior sesamoid bone, and an outward rotation of the lower part of the leg, all of which contribute to the defects in locomotion. No major alterations in hindlimb musculature were observed, but defects in the nervous system were evident. There was a decrease in the number of spinal segments projecting nerve fibers through the sacral plexus to innervate the musculature of the hindlimb. Deletion of a hindlimb nerve was seen in some animals, and a shift was evident in the position of the lumbar lateral motor column. These observations suggest a role for the Hoxd-10 gene in establishing regional identity within the spinal cord and imply that patterning of the spinal cord may have intrinsic components and is not completely imposed by the surrounding mesoderm.

Tenebrionidae (Coleoptera) of the Maritime Provinces of Canada

2008 ◽  
Vol 140 (6) ◽  
pp. 690-713 ◽  
Author(s):  
Christopher G. Majka ◽  
Patrice Bouchard ◽  
Yves Bousquet
Keyword(s):  
Nova Scotia ◽  
North America ◽  
New Brunswick ◽  
Prince Edward Island ◽  
Forest Ecosystems ◽  
Trophic Group ◽  
Undescribed Species ◽  
Maritime Provinces ◽  
Underlying Causes ◽  
First Time

AbstractThe Tenebrionidae of the Maritime Provinces of Canada are surveyed. Forty-eight species have been reported from the region. Eleven of these species (ten Palearctic and one Nearctic) have been introduced to the region, five of which are apparently now extirpated. Dates of first detection of these species are provided for each province and North America. Thirteen species are newly recorded in New Brunswick, 25 in Nova Scotia, and 15 on Prince Edward Island, for a total of 53 new provincial records. Of these, 18 species including Bolitophagus corticola Say, Neatus tenebrioides (Palisot de Beauvois), Helops gracilis Bland, Blapstinus substriatus Champion, Hymenorus obesus Casey, Hymenorus picipennis Casey, Hymenorus pilosus (Melsheimer), Mycetochara bicolor (Couper), Mycetochara binotata (Say), Mycetochara fraterna (Say), Platydema excavatum (Say), Platydema teleops Triplehorn, Corticeus praetermissus (Fall), Alobates pennsylvanicus (DeGeer), Haplandrus fulvipes (Herbst), Xylopinus saperdioides (Olivier), an undescribed species of Paratenetus Spinola, and an undescribed species of Neatus LeConte are newly recorded for the Maritime Provinces as a whole. One of these, Helops gracilis, is recorded for the first time in Canada. The fauna is discussed from the perspective of the patterns of distribution of species in the region and their possible underlying causes. Island faunas are discussed, as is the saproxylic component of the fauna, with a brief consideration of the importance of this trophic group in the dynamics of forest ecosystems in the region.

Management of congenital ear canal atresia

1953 ◽  
Vol 63 (10) ◽  
pp. 916-946 ◽  
Author(s):  
Howard P. House
Keyword(s):  
Ear Canal ◽  
Canal Atresia
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