ABCS 433 -2023 GF3.bin

ABCS 403: ENVIRONMENTAL PHYSIOLOGY Lecture Slides GF3 Photoperiodism & Photodynamic action By Dr. Godfred Futagbi 31/01/2023 ABCS 433 by Dr. Godfred Futagbi...

ABCS 403: ENVIRONMENTAL PHYSIOLOGY Lecture Slides GF3 Photoperiodism & Photodynamic action By Dr. Godfred Futagbi 31/01/2023 ABCS 433 by Dr. Godfred Futagbi 1  Photoperiodism Photoperiodism is the ability of organisms to measure daylength, (typically by monitoring night length), respond by adjusting their behaviour and physiology to seasonal fluctuations in the environment regarding the length of day (photoperiod) Photoperiod is inversely correlated to the nightly duration of melatonin secretion in animals. Melatonin is secreted from the pineal gland exclusively during the dark of night, thus serving as an endogenous signal of night length (=> the length of day) 31/01/2023 ABCS 433 by Dr. Godfred Futagbi 2  Photoperiodism Because photoperiod is the most reliable information to detect the time of year, many mammals use photoperiod to time breeding so that mothers can raise their offspring when environmental conditions are favourable and food resources are available In all, it permits organisms to determine the time of year and develop seasonally suitable physiological and behavioural responses to it. 31/01/2023 ABCS 433 by Dr. Godfred Futagbi 3  Photodynamic action Many photobiological processes are normal and essential to the physiology of organisms (eg. photosynthesis, synthesis of vitamin D, circadian rhythms, bioluminescence) But some non-physiological photochemical reactions can be damaging These destructive reactions are the result of the interference of certain dyes called photosensitizers, usually in the presence of oxygen or an inherited biochemical defect This is photodynamism- conversion of certain substances in the skin of animals into other substances by the action of light 31/01/2023 ABCS 433 by Dr. Godfred Futagbi 4  Photodynamic action: photooxidation reaction that is associated with injury to biological structures and disruption of their function upon absorption of light by pigment or dye in the presence of oxygen Frontiersin.org 31/01/2023 ABCS 433 by Dr. Godfred Futagbi 5 31/01/2023 ABCS 433 by Dr. Godfred Futagbi 6  Photodynamic action Photodynamic substances: porphyrin (hydroa-blisters), eosin (haemolysis of rbcs), rose bengal, hematoporphyrin, and phylloerythrin-are fluorescent dyes Many secondary plant products are known photosensitizers Some plants having photodynamic pigments, eg Hypericum (St. Johnswort’s disease) buckwheat (Fagopyrism) 31/01/2023 ABCS 433 by Dr. Godfred Futagbi 7  Photodynamic action: Beneficial uses Photodynamic therapy (PDT) is a two-stage treatment that combines light energy with a drug (photosensitizer) designed to destroy cancerous and precancerous cells after light activation. – The drug converts innocuous oxygen to cytotoxic reactive oxygen species under an appropriate light Application in pest control Broad spectrum killing of microbes 31/01/2023 ABCS 433 by Dr. Godfred Futagbi 8