Biomedical Engineering Reference
In-Depth Information
by antioxidant mechanisms, ROS may cause
oxidative stress (Nordberg and Arner
2001
) that,
in turn, can result in udder oedema, milk fever,
retained placenta and mastitis in cows (Miller
and Brezezinska-Slebodzinska
1993
) . Therefore,
the circadian organisation is important for
avoiding excessive oxidative stress (Hardeland
et al.
2000
) , the periodical formation of free
radicals and other potentially harmful oxidants.
Thus, rhythmicities in free radical formation is
related to the oxygen consumption in mammals
active during the day and with the circadian
rhythms of locomotor activity (Hardeland et al.
2000
). The stress response varies daily and is
governed by rhythmic gene expression under
the control of the circadian clock (Simonetta
et al.
2008
). The circadian clock gene period is
essential for maintaining a robust antioxidative
defence. Both the ROS production and ROS
defence processes are controlled (partly or fully)
by the circadian clock. Since ROS production
occurs in a circadian manner, circadian varia-
tions have been found in many ROS defence
systems (Langmesser and Albrecht
2006
) .
with activation of the adrenergic system and
adrenal cortex (Cornelissen and Fagard
2005
) .
These diurnal changes result from both external
stimuli and endogenous homeostatic control
mechanisms.
14
Conclusions
The melatonin is synthesised in a rhythmic
manner with high levels during the dark phase
of a natural or any imposed light-dark cycle.
The rhythmic levels of the circulating mela-
tonin hormone provide information concerning
the temporal position and duration of darkness
(i.e. the clock or the oscillator information).
Thus, melatonin acts as a coordinator of inter-
nal physiological rhythm under the SCN. The
widely accepted role of melatonin as one of the
most important endogenous mediators of pho-
toperiodic messages governs central or periph-
eral circadian clock. There is an increasing
interest in beneficial effects of melatonin in the
therapy of circadian rhythm disorders. An
increasing body of evidence indicates that treat-
ment with melatonin is an effective and safe
way of manipulating breeding of some photo-
period-sensitive animals such as sheep, goat
and deer. The role of melatonin also exists in
buffalo, domestic pig, wild pig and horse and
may be exploited to increase production of
milk, meat and their productivity. The synchro-
nisation of feeding and eating behaviours in
ruminants with nutrient utilisation efficiency
will help the optimisation of production. Such
chronobiological insights into modern ruminant
production will offer prospects to improve ani-
mal production and health. Ruminant feed
intake is an evolutionary bioscience interfacing
viable ruminant longevity, adequately safe and
secure food supply and quality environment.
Knowledge on feeding and eating rhythm and
times affect diurnal and postprandial intake pat-
terns will enable predicting diurnal patterns in
rumen, post-rumen and peripheral nutrient
assimilation. These will suggest optimal, sub-
optimal and unfavourable times of nutrient sup-
ply to mammary cells and milk synthesis.
13
Circadian Rhythm of
Cardiovascular Parameters
Rhythmic patterns in the activities of cardiovas-
cular system have been well documented in
humans (Ruesga and Estrada
1999
) and in domes-
tic animals (Piccione et al.
2005
) . Rhythmic
variations in arterial blood pressure and electro-
cardiographic patterns in the athletic horse
indicate that exercise acts as an exogenous syn-
chroniser to modulate the periodicity of the car-
diovascular system (Piccione et al.
2001,
2002
) .
The diurnal variability in cardiovascular func-
tions occurs to match the requirements of differ-
ent level of activities at different times of the day.
Heart rate, stroke volume and blood pressure vary
with changes in activity, posture and other exter-
nal stimuli to adjust oxygen or blood perfusion of
specific tissue or organ performing activity.
Cardiovascular parameters, such as heart rate and
blood pressure, are higher during the day and
lower at night (Veerman et al.
1995
) , parallel
