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Altruism

Altruism

Altruistic behaviors are “unselfish” behaviors—those that help another individual at the expense of the individual carrying out the behavior. Despite the negative consequences for the altruistic animal, these behaviors are thought to have evolved for several reasons.

Inclusive Fitness

Inclusive Fitness

Most altruistic behavior—in which one animal helps another at a cost to themselves—occurs between relatives. Scientists think these altruistic behaviors evolved because they increase the inclusive fitness of the animal providing help.

Egoism and Altruism

Egoism and Altruism

Voluntary behavior with the intent to help other people is called prosocial behavior. Why do people help other people? Is personal benefit such as feeling good about oneself the only reason people help one another?

Radical Chain-Growth Polymerization: Chain Branching

Radical Chain-Growth Polymerization: Chain Branching

The skeletal structure of polymers synthesized via radical polymerization is always branched. For example, the polymerization of ethylene by radical polymerization results in a low-density grade of polyethylene with a heavily branched skeletal structure. Here, the radical site abstracts hydrogen from the growing chain, and the radical site shifts from the end (a primary carbon center) to anywhere within the growing chain (a secondary carbon center). Consequently, the part of the chain from the...

Radical Chain-Growth Polymerization: Overview

Radical Chain-Growth Polymerization: Overview

Chain-growth or addition polymerization is successive addition reactions of monomers with a polymer chain. In radical chain-growth polymerization, the reaction proceeds via a free-radical intermediate. The free radical is formed from radical initiators, which spontaneously generate free radicals by homolytic fission. Organic peroxides (such as dibenzoyl peroxide, as shown in Figure 1) or azo compounds are popular radical initiators. A low concentration ratio of radical initiator to monomer is...

Radical Chain-Growth Polymerization: Mechanism

Radical Chain-Growth Polymerization: Mechanism

The radical chain-growth polymerization mechanism consists of three steps: initiation, propagation, and termination of polymerization. The polymerization initiates when a free radical generated from the radical initiator adds to the unsaturated bond in the monomer. The unpaired electron of the free radical and one π electron in the unsaturated bond creates a σ bond between the free radical and the monomer. As a result, the other π electron in the unsaturated bond converts this species into the...

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Related Experiment Video

Updated: Jun 24, 2026

Lung Rapid Recovery Procurement Combined with Abdominal Normothermic Regional Perfusion in Controlled Donation after Circulatory Death

Lung Rapid Recovery Procurement Combined with Abdominal Normothermic Regional Perfusion in Controlled Donation after Circulatory Death

Published on: August 15, 2022

A nonsimultaneous, extended, altruistic-donor chain.

Michael A Rees¹, Jonathan E Kopke, Ronald P Pelletier

¹Department of Urology, University of Toledo Medical Center, Toledo, OH 43614, USA. michael.rees2@utoledo.edu

The New England Journal of Medicine

|March 13, 2009

Summary

A chain of 10 kidney transplants, initiated by one altruistic donor, demonstrates the potential of paired donation registries. This innovative approach extended over 8 months, involving multiple centers and non-simultaneous surgeries.

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Last Updated: Jun 24, 2026

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Published on: August 15, 2022

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Area of Science:

Nephrology
Transplantation immunology
Surgical innovation

Background:

Kidney transplantation is a vital treatment for end-stage renal disease.
Paired donation registries facilitate living donor kidney transplants when direct donation is not possible.
Altruistic donors can initiate chains of compatible recipients.

Observation:

A single altruistic donor initiated a 10-kidney-transplant chain coordinated by two paired-donation registries.
The chain involved six transplant centers across five states over an 8-month period.
Five transplants occurred simultaneously, while five utilized "bridge donors" extending the chain up to 5 months post-initial transplant.

Findings:

This case study details the successful execution of a non-simultaneous kidney paired donation chain.
The extended timeline highlights the flexibility and adaptability of paired donation protocols.
The successful transplantation of 10 recipients underscores the efficacy of coordinated registry efforts.

Implications:

Non-simultaneous paired donation chains can significantly expand the donor pool.
This strategy offers a viable solution for patients with incompatible donors.
Further exploration of registry coordination and flexible protocols can optimize kidney exchange programs.