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Immunologia powierzchownych struktur oka

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Norepinephrine (NE) released from the sympathetic nerve endings is the main neurotransmitter controlling melatonin synthesis in the mammalian pineal gland. Although neuropeptide Y (NPY) co-exists with NE in the pineal sympathetic nerve fibers it also occurs in a population of non-adrenergic nerve fibers located in this gland. The role of NPY in pineal physiology is still enigmatic. The present study characterizes the effect of NPY on the depolarization-evoked 3H-NE release from the pig pineal explants. The explants of the pig pineal gland were loaded with 3H-NE in the presence of pargyline and superfused with Tyrode medium. They were exposed twice to the modified Tyrode medium containing 60 mM of K+ to evoke the 3H-NE release via depolarization. NPY, specific agonists of Y1- and Y2-receptors and pharmacologically active ligands of a2-adrenoceptors were added to the medium before and during the second depolarization. The radioactivity was measured in medium fractions collected every 2 minutes during the superfusion. NPY (0.1 - 10 μM) significantly decreased the depolarization-induced 3H-NE release. Similar effect was observed after the treatment with Y2-agonist: NPY13-36, but not with Y1-agonist: [Leu31,Pro34]-NPY. The tritium overflow was lower in the explants exposed to the 5 μM NPY and 1 μM rauwolscine than to rauwolscine only. The effects of 5 μM NPY and 0.05 μM UK 14,304 on the depolarization-evoked 3H-NE release were additive. The results show that NPY is involved in the regulation of NE release from the sympathetic terminals in the pig pineal gland, inhibiting this process via Y2-receptors.
A significant number of cases of clinical canine epilepsy remain difficult to control in spite of the applied treatment. At the same time, the range of antiepileptic drugs is increasingly wide, which allows efficient treatment. In the present paper we describe the pharmacodynamics and pharmacokinetics of the newer antiepileptic drugs which were licensed after 1990 but are still not widely used in veterinary medicine. The pharmacokinetic profiles of six of these drugs were tested on dogs. The results of experimental studies suggest that second generation antiepileptic drugs may be applied in mono- as well as in poli- treatment of canine epilepsy because of the larger safety margin and more advantageous pharmacokinetic parameters. Knowledge of the drugs’ pharmacokinetics allows its proper clinical appliance, which, in turn, gives the chance to improve the efficiency of pharmacotherapy of canine epilepsy.
Calcium ions are involved in several processes occurring in the avian pineal, including the regulation of melatonin secretion. The aim of study was to investigate distribution of calcium ions in the pineal organ of domestic turkey at the level of electron microscopy. The study was performed on 12 female turkeys housed in a cycle of 12L : 12 D (light intensity 300 lux; 07:00 – 19:00), starting from the third week of life. At the age of 12 weeks, the birds were anesthetized with halothane and sacrificed by decapitation at 14:00 and at 02:00 (in darkness). The pineals were fixed using the potassium pyroantimonate method, which enables visualization of calcium ions in the form of electron dense precipitates. Extremely numerous, large precipitates of calcium pyroantimonate were observed between collagen fibres of the connective tissue surrounding the pineal follicles. The number of precipitates in the follicles was much lower than in the neighbouring stroma. Precipitates were numerous in intercellular spaces between cells forming the follicular wall. In contrast, they were infrequently observed in the follicular lumen. In pinealocytes, large amounts of precipitates were present in the nucleus, mitochondria and short, wide cisterns of the smooth endoplasmic reticulum. Precipitates were sparse in the apical prolongations of rudimentary-receptor pinealocytes. The content of precipitates did not differ prominently between individual pinealocytes. Precipitates in the cytosol of both rudimentary-receptor pinealocytes and secretory pinealocytes were much more numerous in the organs taken ex vivo during nighttime than during daytime. Supporting cells contained much fewer precipitates than pinealocytes.
The aim of study was to determine the mechanisms regulating melatonin secretion in the pineal organs of 1-day-old and 9-month-old domestic ducks. The pineals were cultured in a superfusion system under different light conditions. Additionally, some explants were treated with norepinephrine. The pineal glands of 1-day-old ducks released melatonin in a well-entrained, regular rhythm during incubation under a 12 hrs light : 12 hrs dark cycle and adjusted their secretory activity to a reversed 12 hrs dark : 12 hrs light cycle within 2 days. In contrast, the diurnal changes in melatonin secretion from the pineals of 9-month-old ducks were largely irregular and the adaptation to a reversed cycle lasted 3 days. The pineal organs of nestling and adult ducks incubated in a continuous light or darkness secreted melatonin in a circadian rhythm. The treatment with norepinephrine during photophases of a light-dark cycle resulted in: 1) a precise adjustment of melatonin secretion rhythm to the presence of this catecholamine in the culture medium, 2) a very high amplitude of the rhythm, 3) a rapid adaptation of the pineal secretory activity to a reversed light-dark cycle. The effects of norepinephrine were similar in the pineal organs of nestlings and adults. In conclusion, melatonin secretion in the duck pineal organ is controlled by three main mechanisms: the direct photoreception, the endogenous generator and the noradrenergic transmission. The efficiency of intra-pineal, photosensitivity-based regulatory mechanism is markedly lower in adult than in nestling individuals.
Norepinephrine released from sympathetic innervation plays the main role in the regulation of melatonin secretion in mammalian pinealocytes. The present study was conducted for the following reasons: 1) to establish whether the pinealocyte chondriome is controlled by norepinephrine, 2) to determine the effect of adrenergic stimulation on mitochondria, and 3) to characterize adrenoceptors involved in the regulation of the chondriome. The static organ culture of the pineal gland was used. The explants were incubated for 5 consecutive days in control medium and between 20:00 and 08:00 in medium with the presence of 10 μM norepinephrine – adrenergic agonist; isoproterenol – beta-adrenoceptor agonist; cirazoline, methoxamine, M-6364 – alfa1 – adrenoceptors agonists or PMA – activator of PKC. The explants were then subjected to ultrastructural examination and morphometric analysis. The incubation of explants in the presence of norepinephrine or isoproterenol caused a decrease in the relative volume and the numerical density of mitochondria and induced an increase in the percentage of free mitochondria in pinealocytes. Significant changes in these parameters were not observed after treatment with methoxamine, cirazoline, M-6463 and PMA. The results obtained show that the chondriome of pig pinealocytes is controlled by norepinephrine acting via beta-adrenoceptors. Adrenergic stimulation, repeated for five consecutive days of organ culture, causes a decrease in the number of mitochondria and a shift in the distribution of mitochondria from the form of networks and filaments into the form of single particles. This indicates the intensive remodeling of the mitochondria network, which is closely linked to the metabolic status of the cell.
Retinal dysplasia is an abnormal growth and differentiation of the retina during the embryonic and early postnatal life. It is characterized by linear folds of the sensory retina and the formation of rosettes composed of variable numbers of neuronal cells. The morphologic classification of retinal dysplasia in dogs includes single or multiple folds, geographic retinal dysplasia, and retinal dysplasia accompanied by retinal detachment and by other systemic abnormalities. There are multiple potential etiologies for retinal dysplasia, including genetic mutations, viruses, toxins and irradiation. Heritable forms of retinal dysplasia have been reported in many breeds of dogs. Mutations that induce retinal dysplasia have not yet been identified. The aim of this paper was to present selected aspects of retinal dysplasia in dogs and cats.
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