The ventilatory response to hypoxia and hypercapnia is absent in the neonatal fat-tailed dunnart

Simpson, Shannon J.; Fong, Angelina Y.; Cummings, Kevin J.; Frappell, Peter B.

doi:10.1242/jeb.072413

Cited by 4 publications

(1 citation statement)

References 39 publications

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“…In newborn marsupials, the upper airway musculature (required for effective suckling behaviors [183,184,337]) and rib structures are well developed, with intercostal muscles innervated by motor neurons [304,305]. However, the DIAm is a thin sheet and plays little, if any, role in the generation of negative P th for respiration [304,305], there is an impaired/ lack of descending respiratory drive [197,627], reduced chemosensitivity [628] and the lungs are similarly immature when compared to other mammals, with the extent of compartmentalization and vascularization ranging from canalicular to rudimentary [197,408,627]. Consequently, these muscular and alveolar deficiencies necessitate alternative modes of gaseous exchange, particularly via transcutaneous mechanisms [197,198,408,462,627].…”

Section: Development Of Diaphragm Motor Behaviorsmentioning

confidence: 99%

Evolution and Functional Differentiation of the Diaphragm Muscle of Mammals

Fogarty¹,

Sieck²

2019

Comprehensive Physiology

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Symmorphosis is a concept of economy of biological design, whereby structural properties are matched to functional demands. According to symmorphosis, biological structures are never over designed to exceed functional demands. Based on this concept, the evolution of the diaphragm muscle (DIAm) in mammals is a tale of two structures, a membrane that separates and partitions the primitive coelomic cavity into separate abdominal and thoracic cavities and a muscle that serves as a pump to generate intra-abdominal (P ab ) and intra-thoracic (P th ) pressures. The DIAm partition evolved in reptiles from folds of the pleural and peritoneal membranes that was driven by the biological advantage of separating organs in the larger coelomic cavity into separate thoracic and abdominal cavities, especially with the evolution of aspiration breathing. The DIAm pump evolved from the advantage afforded by more effectively generation of both a negative P th for ventilation of the lungs and a positive P ab for venous return of blood to the heart and expulsive behaviors such as airway clearance, defecation, micturition, and child birth. Didactic SynopsisThe DIAm separates abdominal and thoracic cavities; thus, it is a partition, and its evolution reflects that important role in isolating organs into separate thoracic and abdominal cavities. However, the DIAm is also a muscle, and is most often described as the principal pump muscle of inspiration. However, the DIAm also serves as a pump for generating both negative P th and positive P ab in other motor behaviors. Accordingly, the evolution of the DIAm is more complex and should be considered in the context of its dual physiological roles as a partition and muscular pump. In considering DIAm evolution, we adopt the guiding concept of symmorphosis or economy of design, where biological structures are not over designed for their functional roles. Thus, this is a tale of the evolution of two diaphragms, a partition and a muscular pump that separates thoracic and abdominal cavities but also affects generation of P th and P ab .

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Section: Development Of Diaphragm Motor Behaviorsmentioning

confidence: 99%

Evolution and Functional Differentiation of the Diaphragm Muscle of Mammals

Fogarty¹,

Sieck²

2019

Comprehensive Physiology

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Editorial: Untangling the oxygen transport cascade: a tribute to Peter Frappell (Frapps)

Polymeropoulos

Milsom

2021

J Comp Physiol B

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Breeding in the fat-tailed dunnart following ovarian suppression with the gonadotrophin-releasing hormone agonist Lucrin® Depot

Witt

Rodger

2018

Reprod. Fertil. Dev.

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Lucrin Depot (AbbVie), a 1-month microsphere gonadotrophin-releasing hormone (GnRH) agonist preparation, was investigated as a potential agent to synchronise cycling in the fat-tailed dunnart (Sminthopsis crassicaudata). Forty-eight randomly selected females were treated with 5 or 10mgkg-1 Lucrin Depot (n=24 per dose). Eighteen females per treatment had their reproductive activity scored at 4, 8, 12 and 16 weeks using two ovarian (Graafian follicle and corpus luteum status) and two reproductive tract (uterine and vaginal muscularity and vascularity) parameters that formed a reproductive activity score. Six females per treatment were paired with a male at 4 weeks. Fertility was assessed between 8 and 16 weeks by pouch check, and thereafter by dissection. The effects of the 5 and 10mgkg-1 doses were statistically equivalent. Females showed suppression at 4-8 weeks, an increase in reproductive activity at 8-12 weeks and all were cycling normally at 16 weeks. Six pouch young were born at 12 weeks to two females treated with the 5mgkg-1 dose. Nine embryos were recovered at 16 weeks from two females treated with the 10mgkg-1 dose. In conclusion, Lucrin Depot can suppress breeding, and fertile mating can occur in subsequent cycles in the dunnart. There is potential for Lucrin Depot to be used as an assisted breeding tool, but it may need to be combined with ovarian stimulation treatment to achieve practical levels of synchronisation in the fat-tailed dunnart.

show abstract

The ventilatory response to hypoxia and hypercapnia is absent in the neonatal fat-tailed dunnart

Cited by 4 publications

References 39 publications

Evolution and Functional Differentiation of the Diaphragm Muscle of Mammals

Evolution and Functional Differentiation of the Diaphragm Muscle of Mammals

Editorial: Untangling the oxygen transport cascade: a tribute to Peter Frappell (Frapps)

Breeding in the fat-tailed dunnart following ovarian suppression with the gonadotrophin-releasing hormone agonist Lucrin® Depot

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