恒温生物における季節的な骨の成長と生理学は,恐竜の生理学に光を当てています
Meike Köhler1, Nekane Marín-Moratalla, Xavier Jordana
1ICREA at the Institut Català de Paleontologia Miquel Crusafont, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain. meike.kohler@icp.cat
Nature
|July 6, 2012
まとめ
周期的な成長は,冷血動物 (エクトーサーム) のみではなく,すべての温血動物 (ホメオサーム・エンドサーム) に共通しています. これは,恐竜の生理学と内熱の進化に関する以前の仮定に異議を唱えます.
科学分野:
- パレオフィジオロジー (古生理学)
- 脊椎動物生理学 脊椎動物生理学
- 進化生物学の進化生物学について
背景:
- 骨組織は周期的な成長の痕跡を示し,絶滅した脊椎動物の生理学に関する議論に影響を与えました.
- 二分法が存在します: エクトサームは温度/代謝に関連した季節的な成長停止を示しますが,エンドサームは継続的に成長すると考えられています.
- この二分論は,恐竜の熱生理学と内熱の進化に関する議論を助長した.
研究 の 目的:
- 多様な環境における野生の反動物における周期的な成長パターンを調査する.
- 周期的成長がエクトーマーに特有のものなのか,それともエンドーマーにおけるより広範な現象なのかを判断する.
- 絶滅した動物の熱生理学を推論する成長線の使用を再評価する.
主な方法:
- 野生の反動物に関する包括的な世界的な研究.
- 周期的な成長の痕跡のための骨組織の分析.
- 成長パターンと環境の季節性,体温,代謝率,およびインスリン型の成長因子-1レベルとの相関.
主要な成果:
- サイクルの成長は,反動物を含むホメオテルミックなエンドサームの普遍的な特徴です.
- 成長停止は,不利な季節に発生し,体温,代謝率,およびIGF-1の低下と関連しています.
- 激しい組織成長は,有利な季節のピーク代謝率と一致し,効率的な資源利用を示しています.
結論:
- ホメオサーミックエンドサームは季節的な成長停止を示し,エクトサーミーの証拠としてその使用に異議を唱える.
- 哺乳類の高い成長率は,内生的な熱生成能力を示唆しています.
- 歯類の年周期は,恐竜のような絶滅した分類体における熱生理学を推論するためのモデルを提供します.
関連する概念動画
01:17Hormones and Bone Tissue
The endocrine system produces and secretes hormones, which interact with the skeletal system. These hormones control bone growth, maintain bone once it is formed, and remodel it.
Hormones That Influence Osteoblasts and/or Maintain the Matrix
Several hormones are necessary for controlling bone growth and maintaining the bone matrix. The pituitary gland secretes growth hormone (GH), which, as its name implies, controls bone growth. This happens in several ways: first, it triggers chondrocyte...
Hormones That Influence Osteoblasts and/or Maintain the Matrix
Several hormones are necessary for controlling bone growth and maintaining the bone matrix. The pituitary gland secretes growth hormone (GH), which, as its name implies, controls bone growth. This happens in several ways: first, it triggers chondrocyte...
01:09Changes in the Appendicular Skeleton with Age
The upper and lower limb initially develops as a small bulge called a limb bud, which appears on the lateral side of the early embryo. The upper limb bud appears near the end of the fourth week of development, with the lower limb bud appearing shortly after.
Initially, the limb buds consist of a core of mesenchyme covered by a layer of ectoderm. The ectoderm at the end of the limb bud thickens to form a narrow crest called the apical ectodermal ridge. This ridge stimulates the underlying...
Initially, the limb buds consist of a core of mesenchyme covered by a layer of ectoderm. The ectoderm at the end of the limb bud thickens to form a narrow crest called the apical ectodermal ridge. This ridge stimulates the underlying...
01:24Bone Formation by Endochondral Ossification
Bone formation, or ossification, begins around the sixth to seventh week of embryonic development. Most bones develop from a cartilaginous template through the process of endochondral ossification. Cartilage formation begins when clusters of mesenchymal cells differentiate into chondrocytes. These chondrocytes proliferate rapidly and secrete an extracellular matrix that becomes encased in a membrane called the perichondrium. The resulting cartilage model provides a template that resembles the...
02:56The Fossil Record
The fossil record documents only a small fraction of all organisms that have ever inhabited Earth. Fossilization is a rare process, and most organisms never become fossils. Moreover, the fossil record only exhibits fossils that have been discovered. Nevertheless, sedimentary rock fossils of long-lived, abundant, hard-bodied organisms dominate the fossil record. These fossils offer valuable information, such as an organism's physical form, behavior, and age. Studying the fossil record helps...
01:27Growth of Cartilage and Bone Tissue
Chondrocytes form a temporary cartilaginous model by dividing and secreting a thick gel-like extracellular matrix. Once the chondrocytes undergo programmed cell death, osteoblasts enter the site of the cartilaginous model. The process of replacing the temporary cartilaginous model with bone in an ordered manner is called endochondral ossification. In endochondral ossification, not all of the cartilage is replaced by bone tissue. Some cartilage that performs a protective and supportive function...
01:40Bone Remodeling
Bone remodeling is a continuous and balanced process of bone resorption by osteoclasts and bone formation by osteoblasts. In adults, it helps maintain bone mass and calcium homeostasis. While mechanical stress can stimulate turnover as part of the normal maintenance and reparative process, several hormones also regulate bone remodeling.