The effect of carbohydrate rich diet on rat pancreas morphological and ultrastructural characteristics in experimentally induced hypothyroidism

Pankreas je žlezda sa egzokrinom i endokrinom funkcijom. Proizvodi njegove egzokrine komponente od vitalnog su značaja za proces varenja hrane. Endokrine ćelije pankreasa grupisane u Langerhansova ostrvca proizvode insulin i glukagon, hormone koji regulišu metabolizam pre svega ugljenih hidrata i neophodni su za održavanje optimalne koncentracije glukoze u krvi. Sekretna aktivnost pankreasa, naročito njegove endokrine komponente, pod kontrolom je kompleksnih endokrinih, parakrinih i neuralnih mehanizama. Hormoni tireoidne žlezde ključni su regulatori bazalnog metabolizma, rasta i razvića. Potrebni su za normalno funkcionisanje gotovo svih organa i organskih sistema, a njihov značaj u metabolizmu ugljenih hidrata poznat je već decenijama. Funkcije endokrinog pankreasa i tireoidne žlezde, kao i efekti koje ostvaruju njihovi hormoni, uzajamno su povezani i međusobno zavisni. U kliničkoj praksi relativno je česta koegzistencija disfunkcije tireoidne žlezde i razvoj insulinske rezistencije, koja je predvorje nastanka dijabetesa tipa 2. Ishrana bogata prostim šećerima, uz smanjen nivo fizičke aktivnosti karakteristika je savremenog načina života, naročito u industrijski razvijenijim zemljama sveta. Pri kontinuiranom unosu ugljenih hidrata pankreas radi pod povećanim opterećenjem, intenzivno proizvodeći insulin, što dugoročno gledano može dovesti do patofizioloških procesa na nivou unutarćelijskih organela i eventualno do gubitka β- ćelija, odnosno do dijabetesa tipa 2. Osnovni cilj ove teze bio je da se detaljnom analizom stekne uvid u morfofunkcionalne karakteristike pankreasa pacova pod uticajem ishrane obogaćene saharozom, u uslovima sistemskog hipotireoidizma indukovanog metimazolom. U tronedeljnom eksperimentu korišćeni su mužjaci albino pacova Wistar soja, držani pod standardnim laboratorijskim uslovima. Životinje su u odnosu na ponuđeni rastvor u vodi za piće podeljene u četiri grupe. Kontrolna grupa životinja pila je čistu česmensku vodu, hipotireoidizam je indukovan 0.02% rastvorom metimazola, dok je pankreas funkcionalno opterećen unosom 10% rastvora saharoze. Pacovi poslednje grupe pili su kombinovani rastvor metimazola i saharoze, već pomenutih koncentracija. Pankreas je na uobičajen način pripremljen za morfološku i stereološku analizu na nivou svetlosne i elektronske mikroskopije. Pored rutinskih metoda bojenja hematoksilinom i eozinom, toluidin plavim i AZAN-om, korišćene su metode imunohistohemije za detekciju insulina, glukagona, somatostatina, pankreasnog polipeptida, PDX1, α-SMA i Ki67 proteina, kao i specifično bojenje propidijum jodidom. Dobijeni rezultati pokazali su sledeće: - Tronedeljni tretman metimazolom doveo je do uspostavljanja umerenog sistemskog hipotireoidizma, nezavisno od režima ishrane. Nivoi tireoidnih hormona u cirkulaciji bili su smanjeni, a životinje su zaostajale u rastu...The pancreas is a gland with both exocrine and endocrine function. The products of its exocrine component are vital to the food digestion. Its endocrine function is based on secretory action of several types of endocrine cells that cluster together to form islets of Langerhans. Some of them produce insulin and glucagon, hormones that regulate primarily carbohydrate metabolism and are essential for maintaining optimal blood glucose concentrations. Secretory action of the pancreas, especially its endocrine component, is controlled by a complex endocrine, paracrine and neural mechanisms. Thyroid hormones are key regulators of the basal metabolism, growth and development. They are necessary for normal function of almost all organs and organ systems; their importance in the metabolism of carbohydrates has been known for decades. The functions of the endocrine pancreas and thyroid gland, and effects of their hormones are mutually connected and interdependent. In clinical practice the coexistence of thyroid dysfunction and the development of insulin resistance, which is a good prognostic factor for type 2 diabetes occurrence, is relatively frequent. A diet rich in simple sugars, along with reduced physical activity is a feature of modern lifestyle in developed countries of the world. Continuous intake of carbohydrates represents a form of stress in which pancreas intensively produces insulin, which in the long term can lead to pathophysiological processes at the level of intracellular organelles, and eventually to loss of β-cells, i.e. to type 2 diabetes. The aim of this work was to gain an insight into the detailed morpho-functional characteristics of the rat pancreas under the influence of sucrose rich diet, in terms of systemic hypothyroidism induced by methimazole. The obtained results show that: - Moderate systemic hypothyroidism was established after three-week methimazole treatment, regardless of the diet. Levels of thyroid hormones in the circulation were reduced, and the animals fell behind in growth..

Brown adipocytes of sucrose-overfed rats treated with corticosterone: A stereological and ultrastructural study

The aim of this study was to examine the effects of short-term corticosterone treatment on brown adipo­cytes of rats overfed with sucrose. Ultrastructural and stereological analysis showed that brown adipocyte components responded to the applied treatment in conformity with their own dynamics and affinity. Although brown adipocytes generally corresponded to thermogenically active cells, some signs of supression of that function, such as mitochondrial degradation and a pattern of lipid accumulation, were noticeable. Taken together, the presented results indicate that a high carbohydrate diet delays the expected inhibitory influence of corticosterone on brown adipose tissue thermogenesis. For the full expression of corticosterone effects, longer treatment is needed

Immunohistochemical evidence for the presence of a Vasoactive Intestinal Peptide, Neuropeptide Y, and Substance P, in rat adrenal cortex after acute heat stress

Immunohistochemistry revealed the presence of Vasoactive Intestinal Peptide (VIP), Neuropeptide Y (NPY), and the absence of Substance P (SP) immunoreactivity in the rat adrenal cortex. VIP- and NPY-immunoreactivity were detected in nerve fibers around the small blood vessels projecting into the capsule and cortical zones surrounding blood vessels and cortical cells. After acute heat stress, VIP- and NPY-immunoreactivities in the nerve fibers were reduced, probably as a result of the release of these peptides

Immunohistochemical study of enteric nervous system in dexamethasone-treated rats

The gut is supplied with its own nervous system, referred to as the enteric nervous system (ENS). It regulates the various functions of a digestive system such as motility, secretion and digestion and has close interactions with the enteric immune system. The aim of this study was to investigate the alterations of the ENS in dexamethasone-treated rats using two general neuroendocrine markers: protein gene product 9.5 (PGP 9.5) and synaptophysin (SY). As concluded from the changes in a pattern of immunoexpression of the markers applied, some remodeling of the ENS occured. Further investigations are needed to elucidate in more details its nature and importance with respect to gastrointestinal complications seen in diabetes.Publishe

Immunohistochemical study of enteric nervous system in dexamethasone-treated rats

The gut is supplied with its own nervous system, referred to as the enteric nervous system (ENS). It regulates the various functions of a digestive system such as motility, secretion and digestion and has close interactions with the enteric immune system. The aim of this study was to investigate the alterations of the ENS in dexamethasone-treated rats using two general neuroendocrine markers: protein gene product 9.5 (PGP 9.5) and synaptophysin (SY). As concluded from the changes in a pattern of immunoexpression of the markers applied, some remodeling of the ENS occured. Further investigations are needed to elucidate in more details its nature and importance with respect to gastrointestinal complications seen in diabetes

Calcium-SANDOZ®-induced erythrocyte exovesiculation and internalization of hemichromic material into rat brown adipocytes

An ultramicroscopic study of brown adipose tissue (BAT) of rats treated with Ca-SANDOZ® (480 mg/l) for 3 days, revealed erythrocyte exovesiculation and migratory erythrocytic complexes from the capillaries to adipocyte cytoplasm and mitochondria. Two types of erythrocytic material transfer were observed: (i) numerous exocytic vesicles with electron dense material leaving the erythrocytes; (ii) furcated complexes with microholes, embedded in amorphous material. The content of red blood cell (RBC) complexes passed through the capillaries and transferred to the brown adipocytes where it was detectable in the cytoplasm and mitochondria. Light microscopy confirmed sphenoechinocytic transformation of the RBCs in the blood smears of the Ca-SANDOZ® treated rats

Effects of methimazole-induced hypothyroidism on immunohistochemical, stereomorphometric and some ultrastructural characteristics of pancreatic β-cells

The function of pancreatic β-cells is to produce and secrete insulin, a crucial hormone in carbohydrate metabolism. The transcription factor PDX1 is required for insulin gene transcription and mature β-cell function. Since this factor is regulated by triiodothyronine, a disturbance in insulin biosynthesis and/or secretion is usually related to a deficiency of this hormone. In the present study, we used methods of immunohistochemistry, stereology and electron microscopy to explore the correlation between altered thyroid status and insulin synthesis/secretion in a model of methimazole-induced hypothyroidism in rats. In hypothyroid animals fewer functional PDX1-positive β-cells were detected in the islets of Langerhans, while insulin immunostaining was stronger. Stereological analysis of β-cell granules revealed more numerous immature insulin granules in hypothyroid rats. Taken together, these data suggest that the applied treatment caused impaired insulin synthesis and secretion. Rare cells with granules characteristic for both α- and β-cells observed in hypothyroid animals could provide functional compensation for diminished insulin synthesis

BROWN ADIPOCYTES OF SUCROSE-OVERFED RATS TREATED WITH CORTICOSTERONE: A STEREOLOGICAL AND ULTRASTRUCTURAL STUDY

Abstract — The aim of this study was to examine the effects of short-term corticosterone treatment on brown adipocytes of rats overfed with sucrose. Ultrastructural and stereological analysis showed that brown adipocyte components responded to the applied treatment in conformity with their own dynamics and affinity. Although brown adipocytes generally corresponded to thermogenically active cells, some signs of supression of that function, such as mitochondrial degradation and a pattern of lipid accumulation, were noticeable. Taken together, the presented results indicate that a high carbohydrate diet delays the expected inhibitory influence of corticosterone on brown adipose tissue thermogenesis. For the full expression of corticosterone effects, longer treatment is needed

Ossification and development of vertebrae in the Balkan crested newt Triturus ivanbureschi (Salamandridae, Caudata)

Vertebral morphology, development, and evolution have been investigated for many decades, especially in the recent evo-devo era. Nevertheless, comparative data on development and ossification modes within the major tetrapod groups are scarce and frequently suffer from the use of a simplistic approach, resulting in simplistic generalizations about the formation of tetrapod vertebrae. Here, we describe the development and ossification of trunk vertebrae in Triturus ivanbureschi (Salamandridae, Caudata) and compare the results with published data on other related taxa. In so doing, we focus on the modes of ossification and development of the centrum and neural arches by analysing three developmental stages defined by the degree of limb development: stages 47, 52, and 62 according to Glu¨cksohn (1932). Our examination of histological sections through trunk vertebrae enabled us to identify three modes of ossification within single trunk vertebrae: (i) perichordal (direct ossification of the connective tissue surrounding the notochord); (ii) perichondrial (direct ossification of the perichondrium, consisting of cartilage-covering connective tissue), and (iii) endochondral (ossification within the preformed cartilage template). We also noted the presence of intravertebral or notochordal cartilage. Although our results indicate that this cartilage develops within the notochord surrounded by the continuous notochordal sheath, more detailed further studies could shed light on its origin and development

Histological and ultrastructural alterations of rat thyroid gland after short-term treatment with high doses of thyroid hormones

The aim of the present study was to investigate histological alterations of rat thyroid gland after short-term treatment with supraphysiological doses of thyroid hormones. Rats from experimental groups were treated with triiodothyronine (T3) or thyroxine (T4) during five days. In both treated groups, thyrocyte height was reduced and follicular lumens were distended. Progressive involutive changes of the thyroid parenchyma were apparent, including follicular remodeling (fusion) and death of thyrocytes. Morphological changes confirmed by quantitative analysis were more pronounced in the T4-treated group. Our results demonstrate that thyrotoxicosis, whether induced by T3 or T4, leads to different grades of thyroid tissue injury, including some irreversible damages. These changes might be explained at least in part by lack of trophic and cytoprotective effects of the thyroid stimulating hormone. Since the period required for morphophysiological recovery may be unpredictable, findings presented here should be taken into consideration in cases where the thyroid hormones are used as a treatment for thyroid and non-thyroid related conditions. Keywords: Light microscopy, Electron microscopy, Thyroid gland, Thyroid hormones, Wistar rat