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関連する概念動画

Positive and Negative Feedback Loops01:18

Positive and Negative Feedback Loops

Animal organs and organ systems constantly adjust to internal and external changes through a process called homeostasis ("steady state"). Examples of these changes include regulation of the level of glucose or calcium in the blood or internal responses to external temperatures. Homeostasis requires  maintaining an internal dynamic equilibrium:
Mechanism of Lamellipodia Formation01:31

Mechanism of Lamellipodia Formation

Cells migrating in response to external stimuli form lamellipodia, which are thin membrane protrusions supported by a mesh of linked, branched, or unbranched actin filaments. These actin filaments interact with myosin motor proteins, creating the dynamic actomyosin complex within the cytoskeleton. Contractility, or the ability to generate contractile stress, is inherent to the actomyosin complex. It helps cells detect the stiffness of the surrounding ECM and exert contractile force for...
Cell Signaling Feedback Loops01:07

Cell Signaling Feedback Loops

Positive and negative feedback loops are crucial for regulating biological signaling systems. These feedback loops are processes that connect output signals to their inputs.
Negative feedback loops
Most signaling systems have negative feedback loops that can perform different functions such as output limiter, and adaptation.
Output limiter
Upon receiving an input signal, the cellular response rapidly increases until a threshold is reached. Beyond this threshold, a negative feedback loop...
Changes in the Appendicular Skeleton with Age01:09

Changes 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...
Development of the Limb Synovial Joints01:07

Development of the Limb Synovial Joints

Joints form during embryonic development in conjunction with the formation and growth of the associated bones. The embryonic tissue that gives rise to all bones, cartilage, and connective tissues of the body is called mesenchyme.
The mesenchymal stem cells differentiate into chondrocytes that form the hyaline cartilage, and later the cartilaginous model of the bone. This model further transforms into a bone. This process is known as endochondral ossification.
During development, the limbs...
Root Loci for Positive-Feedback Systems01:23

Root Loci for Positive-Feedback Systems

The Hartley oscillator is a positive feedback system that sustains oscillations by feeding the output back to the input in phase, thereby reinforcing the signal. Positive feedback systems can be viewed as negative feedback systems with inverted feedback signals. In these systems, the root locus encompasses all points on the s-plane where the angle of the system transfer function equals 360 degrees.
The construction rules for the root locus in positive feedback systems are similar to those in...

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関連する実験動画

Updated: Jul 25, 2026

Three and Four-Dimensional Visualization and Analysis Approaches to Study Vertebrate Axial Elongation and Segmentation
12:59

Three and Four-Dimensional Visualization and Analysis Approaches to Study Vertebrate Axial Elongation and Segmentation

Published on: February 28, 2021

ポジティブなフィードバックループは,脊椎動物の肢体の成長とパターンを調整します.

L Niswander1, S Jeffrey, G R Martin

  • 1Department of Anatomy, School of Medicine, University of California at San Francisco 94143-0452.

Nature
|October 13, 1994
PubMed
まとめ

線維細胞成長因子 (FGF) とソニック・ヘッジホッグ (SHH) のシグナル伝達経路は,四肢の発達を調節する. FGF4とSHHはポジティブなフィードバックループを確立し,肢の成長とパターンの形成に不可欠です.

科学分野:

  • 発達生物学 発達生物学について
  • 分子生物学は分子生物学である.
  • 遺伝学 遺伝学とは

背景:

  • 肢体の発達は,アピカル外皮脊 (AER) と底辺のメゼンキームからの信号によって調整されます.
  • 線維細胞成長因子 (FGF) は,Fgf4RNAが後部AERに局所化し,FGF4を内生的なリッジ信号として示唆することで,AERの機能を置換することができます.
  • 後肢の縁にある極化活動ゾーン (ZPA) はパターニングに不可欠であり,Sonic hedgehog (SHH) は主要な極化信号として特定されました.

研究 の 目的:

  • 肢体の発達中のFgf4およびShh遺伝子発現の分子調節を調査する.
  • 手足のパターニングにおけるAERとZPAの信号相互作用を解明する.
  • FGF4とSHHが,四肢の成長とパターンのためのフィードバックループを確立する役割を決定する.

主な方法:

  • 遺伝子発現パターンの分析 (Fgf4とShh RNAの局所化).
  • AERにおけるFgf4発現に対するShh発現細胞の影響を調査する.
  • FGF4とレチノ酸によるShh発現の誘導と維持をメゼンキームで調べる.

主要な成果:

  • Shhを発現する細胞は,アピカル外皮のFgf4発現を調節することが判明した.

さらに関連する動画

Chicken Recombinant Limbs Assay to Understand Morphogenesis, Patterning, and Early Steps in Cell Differentiation
08:08

Chicken Recombinant Limbs Assay to Understand Morphogenesis, Patterning, and Early Steps in Cell Differentiation

Published on: January 12, 2022

Analysis of Cell Differentiation, Morphogenesis, and Patterning During Chicken Embryogenesis Using the Soaked-Bead Assay
06:49

Analysis of Cell Differentiation, Morphogenesis, and Patterning During Chicken Embryogenesis Using the Soaked-Bead Assay

Published on: January 12, 2022

関連する実験動画

Last Updated: Jul 25, 2026

Three and Four-Dimensional Visualization and Analysis Approaches to Study Vertebrate Axial Elongation and Segmentation
12:59

Three and Four-Dimensional Visualization and Analysis Approaches to Study Vertebrate Axial Elongation and Segmentation

Published on: February 28, 2021

Chicken Recombinant Limbs Assay to Understand Morphogenesis, Patterning, and Early Steps in Cell Differentiation
08:08

Chicken Recombinant Limbs Assay to Understand Morphogenesis, Patterning, and Early Steps in Cell Differentiation

Published on: January 12, 2022

Analysis of Cell Differentiation, Morphogenesis, and Patterning During Chicken Embryogenesis Using the Soaked-Bead Assay
06:49

Analysis of Cell Differentiation, Morphogenesis, and Patterning During Chicken Embryogenesis Using the Soaked-Bead Assay

Published on: January 12, 2022

  • FGF4は,レチノ酸と組み合わせて,メゼンキーム内のShh発現を活性化することができます.
  • FGF4だけでShh発現を維持することができ,ZPAとAERの間のポジティブなフィードバックループを示します.

    • 結論:

    • 肢体の発達中にAER (FGF4) とZPA (SHH) の間に相互のシグナルループが存在する.
    • このFGF4-SHHフィードバックメカニズムは,四肢の成長と前後部のパターンの調整に不可欠です.
    • これらの分子相互作用を理解することは,脊椎動物の四肢形成の遺伝的コントロールの洞察を提供します.