User:Cyim3

Clara Yim

UWO Biology 4931G - Seminar in Physiology

The first Wikipedia page I would like to review is Opossum. This article merely mentions the opossum’s immunity to various species of snakes but it fails to discuss the physiological basis behind this remarkable ability. Since the opossum has been relatively well-documented as a snake venom-resistant species, I believe the mechanisms by which this species is able to protect against the lethal effects of snake venom should be discussed to improve upon the content and its potential therapeutic implications for treating venomous snake bites.

The next page I would like to review is Envenomation. Minimal content (one sentence) is provided for the subheading “Antivenom Treatments”. I would like to discuss the recent developments in therapeutics for venomous snake bites, particularly the use of supposed “antivenom” plant extracts and snake venom toxin inhibitors in conjunction with current antibody-based antivenoms.

The last page I would like to review is Leptin. Though there is abundant content, it does not address its effects in birds, particularly in migratory species since leptin has recently been identified to play an important role in the success of migration. I believe a more detailed discussion of its physiological and behavioural effects in migratory birds would provide a better understanding of leptin's role in mediating adiposity.

Article for review: Leptin
Leptin has been well-documented to play a role in regulating energy homeostasis in various mammalian systems; this article discusses its effects in mice and rabbits, for example, as they are more commonly used in medical research. The medical and clinical significance of the results seen in these mammals is undoubtedly evident, such as its role in certain inflammatory-related diseases and sleep disorders. However I believe that discussing the effects of leptin system in birds will improve this article since the effects of a functional, active leptin system has been demonstrated to be key in the success of migratory strategies in migrant bird species. The role of a leptin-like system in birds should be discussed to better understand its role in mediating adiposity and the success of completing energetically demanding flights. With the recent decline in migratory bird species, it is important to understand the physiological mechanisms employed by birds to potentially develop new conservation strategies of at-risk species.

3 Key References:

Lohmus et al (2002) looked at the effects of leptin on food intake behaviour in great tits (Parus major), a wild non-migratory passerine. Key Points:
 * Leptin signalling depresses feeding rate and cumulative food intake in the great tit, compared to birds without leptin administration.
 * The effects of the leptin signalling, particularly increases in physical activity, is related to fitness behaviour exhibited by wild birds that increases its fitness, such as mat searching, territorial defense, and construction of nests.
 * It has been implicated that wild birds have evolved a greater dependence on leptin signals compared to domesticated birds, in order to better control its energy stores in preparation for migration or unpredictable changes in their habitat.

Zajac et al (2011) tested the effects of leptin on FA transport and metabolism in white-throated sparrows (Zonotrichia albicollis) and its potential role and importance in bird migration. Key Points:
 * In birds, fat is the most suitable fuel type used in flight, and the largest portion of energy is deposited as fat rather than protein or carbohydrates.
 * Since leptin has been identified as an indicator of energy homeostasis in many vertebrates, it has also been implicated in regulating the transport and oxidation of FAs in migratory birds.
 * In non-avian vertebrates, leptin increases the activity of fatty acid oxidative enzymes and reduces the expression of fatty acid transporters.
 * In birds, however, leptin does not affect fatty acid oxidative enzymes or transporters; rather photoperiod is sufficient to induce changes in fatty acid metabolism.

Cerasale et al (2011) examined the behavioural and physiological effects of an activated leptin-like system in white-throated sparrows (Zonotrichia albicollis), a migratory passerine. They looked at behavioural and physiological differences associated with leptin administration, between sparrows in migratory and non-migratory states. Key Points:
 * Leptin homologues have been documented in non-mammalian vertebrate systems, exerting similar effects in reducing food intake, increasing energy expenditure and reducing fat mass.
 * The avian leptin gene has not currently been found and the existence of an avian leptin has been highly debated in the scientific community; however, the existence of a functional avian leptin receptor strongly suggests a leptin-like system is involved in regulating avian energy balance.
 * Migratory state sparrows are able to alter the physiological and behavioural anorectic responses normally associated with the induction of the leptin-like system.
 * While non-migratory sparrows injected with leptin exhibit reduced foraging rates, migratory sparrows with activated leptin systems do not display changes in foraging behaviour.
 * Sparrows in migratory states with active leptin signalling also maintain their body mass and fat mass.
 * The ability of migratory birds to control the actions of leptin allow them to accumulate energy stores in preparation for long-distance migratory flights.

References

Cerasale DJ, Zajac DM, and Guglielmo CG (2011) Behavioural and Physiological effects of photoperiod-induced migratory state and leptin on a migratory bird, Zonotrichia albicollis: Anorectic effects of leptin administration. Gen Comp Endocrinol 174: 276–286.

Lohmus M, Sundstrom LF, Halawani ME, and Silverin B (2002) Leptin depresses food intake in great tits (Parus major). Gen Comp Endocrinol 131: 57–61.

Zajac DM, Cerasale DJ, Landman S, Guglielmo CG (2011) Behavioral and physiological effects of photoperiod-induced migratory state and leptin on Zonotrichia albicollis: II. Effects on fatty acid metabolism. Gen Comp Endocrinol 174: 269—275.