The effects of exogenous melatonin on the morphology of thyrocytes in pinealectomized and irradiated rats.

We investigated the effects of exogenous melatonin on the thyrocytes morphology in gamma-irradiated rats under condition where the pineal gland, as a main physiological source of endogenous melatonin, was removed. Three months after pinealectomy animals were divided into two groups: one group of animals was treated with 0.5 ml of vehicle (ethanol diluted in water) and other group was injected intraperitoneally 2 mg/kg of melatonin dissolved in 0.5 ml of vehicle daily during the period of fourteen days. After this treatment all the animals were irradiated with a single dose of 8 Gy gamma rays. Ionising radiation induced apoptosis, hydropic swelling or/and necrosis in both groups of animals, however these changes were less discerned in the thyrocytes of melatonin-treated animals. Our findings demonstrate that administration of exogenous melatonin prior to irradiation reduces radiation-induced thyrocytes damage.

Antioxidant capacity of the neurohormone melatonin.

The aim of this study was to elucidate the antioxidant behaviour of melatonin (M) and determine its activity-structure relationship. M or 5-metoxy-N acetyltriptamine is a neurohormone secreted by the pineal gland, which plays a proven role in maintaining sleep-wake rhythms. The antioxidant capacity of M was analysed using the oxygen radical absorbance capacity (ORAC) assay. Furthermore, spectral measurements for aerobic photolytic reaction of neutral red (NR) and degree of inhibition of photolysis with M, glutathione (GSH), ascorbic acid (AA) and vitamin E analogue Trolox were studied at room temperature 25 degrees C, using visible (VIS) and ultra-violet (UV) radiations. In the ORAC assay 2,2-azobis (2-amidino-propane)dihydrochloride (AAPH) a peroxyl radical generator, ROO degrees ; H2O2-Cu2+, mainly a hydroxyl radical generator, degrees OH; and Cu2+ a transition metal were used. Although some studies indicated that M is a powerful antioxidant, no one has compared its antioxidant capacities with GSH, E-vitamin and AA, using three free radical (FR) generators in an assay which utilizes an area-under curve technique and thus combines both inhibition time and inhibition degree of FR action by an antioxidant into a single quantity. In the current study, we used ORAC assay with three FR generators. The assay is based on propensity of the fluorescence emitted by the protein beta-phycoerythrin (beta-PE) from porphyridium cruentum to be quenched when exposed to FR action. M in our experiments acted as a universal antioxidant against ROO degrees and degrees OH radicals. Also, M served as an antioxidant in the presence of Cu2+. M, which is a lipid-soluble compound, was a twice more powerful antioxidant than vitamin E, and four times than AA or GSH. Furthermore, M inhibited aerobic photolysis of NR photoinduced with VIS and UV rays faster and more effectively, than AA, GSH or vitamin E. AA with NR, under aerobic conditions during irradiation with VIS and UV acted as a pro-oxidant. M may be the premier molecule to protect the cells from oxidative stress.

[Characteristics of the ependyma in various parts of the subcommissural organs in rats]. / Neke odlike ependima pojedinih dijelova subkomisuralnog organa u pacova.

In this work the authors have researched ependyma of some parts of subcommissural organ of rats by optic microscopy. 4% formaldehyde was injected in vivo in carotid arteries. After immolation their brains were extracted together with brain meninges and embedded in celiodine. Celoidine blocks have been sliced and then coloured by Nissle's method. Horizontal and frontal brain dissections were performed with a purpose to acquire a good sight into the subcommissural organ. On the basis of optic microscopy of the examined material, numerous morphological variations in the size and appearance of subcommissural organ were determined as well as the presence of many layers of ependymal cells close to the posterior commissura.

[Morphometric aspects of ultrastructural details of rat thyrocytes which have been irradiated and pretreated with melatonin]. / Morfometrijski prikaz ultrastrukturnih detalja tireocita ozracenih i melatoninom pretretiranih pacova.

In this work the authors investigated by qualitative and quantitative analysis of ultrastructural details of thyreocytes in irradiated rats with and without of melatonin treatment. On the basis histological qualitative and stereological analysis of materials and by the comparison of results in the animals who received and who didn't receive melatonin before irradiation it can conclude that melatonin modifies behaviour the thyroid glands in irradiation stress.

[Histological structure of the distal segment of the respiratory tract]. / Histoloska grada distalnih segmenata respiratornog trakta.

The respiratory system consists of morphologically and functionally distinct sub-divisions-the air-conditioning part and respiratory portion is were O2 and CO2 exchange actually occurs across the delicate, very thin walls of the pulmonary alveoli. The final bifurcation of bronchiole yields terminal bronchiole. The epithelium is gradually reduced from ciliated columnar in the larger bronchioles to ciliated or non-ciliated low cuboidal in the terminal segment. Here non-ciliated Clara cells are plentiful. Only under EM one can clearly identify the lining cells of the alveoli: type I are squamous pneumocytes, type II are large granular alveolar cells and macrophages (dust cells). The hallmarks of pneumocytes type II are the numerous osmiophilic, lamellated inclusion bodies. In TEM there is evidence connecting these bodies with the production of stabilizing surface active material, which prevents the collapse of the alveoli; colled surfactant, different from that of the Clara cells.

[Morphometric characteristics of thyroid cells in irradiation-stressed rats treated with pinealectomy and melatonin]. / Morfometrijske odlike tireocita pinealektomisanih i melatoninom tretiranih pacova u iradijacionom stresu.

The authors were investigating the qualitative and quantitative characteristics of the cells of the thyroid gland of pinealectomized and melatonin treated rats whose body irradiated with 8 Gy gamma rays. It was established that melatonin decreased height of the thyreocytes in peripherical and central part of gland, and nuclear volume of thyreocytes only in the central part of gland. The results suggest the role of melatonin in determination of the behaviour of thyreocytes upon Pinealeotomy and Radiation.

Histochemical aspects and fine structural characteristics of thyreocytes in pinealectomized and melatonin treated rats prior to irradiation.

The authors were investigating the histochemical and electron microscopic characteristics of thyreocytes in pinealectomized rats treated with melatonin, prior to irradiation. They observed that the animals that did not receive melatonin show a higher degree of the destruction appearing at the level of all ultrastructural organelles and a very low expression of the DNA and RNA histochemical reaction. These results suggest the role of melatonin in the determination of the thyreocyte behaviour under given irradiation conditions.

[Morphometric aspects of seminiferous tubules in rats treated with melatonin and whole body irradiation (stereologic analysis)]. / Morfometrijski aspekt sjemenih kanalica totalno ozracenih pacova tretiranih melatoninom (stereoloska analiza).

The volume density of the seminiferous epithelium, lumen of tubules and the testis interstitium in the shampinealectomized adult Wistar rats was determined after melatonin treatment and whole-body irradiation with 8 Gy of gamma rays produced by 60 Co. The solvent was injected to the control group of animals. By the comparison of stereological results, it was shown that melatonin modifies the quantitative characteristics of seminiferous tubules reducing the effects of irradiation originally produced.

[Early histological changes in the thyroid gland in irradiated rats without a pineal body]. / Rane histoloske promjene stitnjace ozracenih pacova u uslovima anepifizije.

The authors investigated histological characteristics of the thyroid gland in irradiated rats under the conditions of anepiphysia. Pseudo-epiphysectomized rats and epiphysectomized rats were irradiated in toto with a single dose of 8 Gy gamma irradiation. The animals were decapitated on the 121st day of the postoperative period, in other words, on the 6th day following irradiation. The animals with an intact epiphysis showed significant changes in the histological structure of the thyroid, but they were of a considerably lesser intensity when compared to the changes observed in epiphysectomized rats. On the basis of the differences observed in behavioural characteristics as well as the degree of mortality, we propose that pineal gland absence has determined the behaviour of the glandular parenchyma, as well as of the whole organism in the given conditions.

Histoenzymological reactions of the thyroid gland in irradiated and previously melatonin-treated irradiated rats.

The authors were investigating the histoenzymological reactions of the thyroid gland of melatonin-treated and untreated rats, in toto irradiated by 8 Gy gamma rays. Although both groups reacted positively, the reaction intensity of the melatonin-treated group was more intense. It is suggested that melatonin has radiothyreoprotective effects under given conditions.