Subchronic toxicity of Sideritis scardica, Lamiaceae on male Wistar rats.

INTRODUCTION: Sideritisscardica, Lamiaceae, is a plant with anti-inflammatory, antirheumatic, digestive, and antimicrobial properties that is widely used in folk medicine throughout the Balkan Peninsula. The name derives from the Greek word 'sideros', meaning iron, and it is believed that the plant was also used by soldiers to heal wounds caused by cutting weapons.

A Study of the Chemical Composition, Acute and Subacute Toxicity of Bulgarian Tanacetum parthenium Essential Oil.

BACKGROUND: Tanacetum parthenium (L.) Sch.Bip. (T. parthenium) is an aromatic perennial plant belonging to the Asteraceae family, also known as feverfew. It is widely distributed in various regions of Europe and other parts of the world. The plant has a rich background in the traditional medicine of many nations and has been used as a remedy for fever, pain, inflammation, asthma, rheumatism, menstrual disorders, etc. Methods: GC-MS analysis was conducted to determine the chemical composition of the isolated essential oil (EO). Using the method proposed by Litchfield and Wilcoxon, the average lethal dose (LD50) of the EO on Wistar rats was determined for two routes of administration: oral (p.o.) and intraperitoneal (i.p.). The subacute toxicity of the EO was also tested by oral administration of a daily dose of 1.0 g/kg body weight (BW) for 28 days. The toxicity of the EO was evaluated by observing and evaluating changes in behavior, body weight, basic hematological and serum biochemical parameters, and histopathological changes of the internal organs. RESULTS: Thirty-seven volatile organic compounds representing 94.58% of the total oil composition were tentatively detected in the obtained T. parthenium EO. The dominant compounds were camphor (45.47%), trans-chrisantenyl acetate (21.65%), camphene (9.48%), and cis-isogeraniol (5.42%). The results showed that the EO was not toxic when administered in acute oral doses. The acute mean lethal dose for intraperitoneal administration was LD50 i.p. = 2.13 g/kg BW. In the subacute study involving administration of an oral dose of EO for 28 days, there were a number of changes in the hematological and serum biochemical parameters of the blood compared with the control group of animals. However, no symptoms of toxicity, changes in the body weight of the rats, death, or pathological changes in the histological indicators of the examined organs-brain, heart, stomach, liver, spleen and kidney-were found. Extrapolating the results obtained from the rat experiments, we can state that the EO is safe for use in doses below 1 g/kgBW for a period not exceeding one month.

Composition and chronic toxicity of dry methanol-aqueous extract of wild-growing Satureja montana.

INTRODUCTION: Saturejamontana is a wild growing medicinal plant, part of the Lamiaceae family. This herb is well known as a source of phenolic compounds, which can vary in a broad range depending on different factors and exert many pharmacological activities.

Expression of leptin, NGF and adiponectin in metabolic syndrome.

Adipose tissue secretes a variety of adipokines involved in the regulation of energy metabolism and insulin resistance. Metabolic syndrome corresponds to a clinical condition in which white adipose tissue is characterized by an increased production and secretion of inflammatory molecules which may have local effects on adipose tissue physiology but also systemic effects on other organs. The aim of this study was to assess the expression of leptin, NGF and adiponectin in women with metabolic syndrome compared to healthy controls. Plasma leptin, NGF and adiponectin levels were measured by the ELISA method. Leptin and NGF immunohistochemical expression was analyzed in subcutaneous adipose tissue. The results indicated that in women with metabolic syndrome waist circumference, body mass index, HOMA index, glucose, total cholesterol and triglyceride levels were significantly increased in parallel with overxpressed plasma levels of leptin and NGF and decreased adiponectin. The immunohistochemical expression of leptin and NGF was very strong. In conclusion, this is the first study demonstrating a complex of immunochemical and immunohistochemical expression of the key adipokines including leptin, NGF and adiponectin in women with metabolic syndrome. Locally-produced pro-inflammatory adipokines probably contribute to the ethiopathogenic mechanisms ofmetabolic syndrome.

Adipose tissue hormones and appetite and body weight regulators in insulin resistance.

Impaired sensitivity to insulin (the so called insulin resistance, IR) occurs in a number of genetic and acquired conditions, including obesity, non-insulin dependent diabetes mellitus, polycystic ovary syndrome (PCOS) and metabolic syndrome (MS). In this review we discuss the correlation between IR, the adipose tissue hormones and appetite and body weight regulators. Leptin acts as a major adipostat: it suppresses food intake and activates catabolic pathways associated with increased energy production. It improves the peripheral insulin sensitivity and affects beta-cell function. Adiponectin is the only adipocytokine discovered so far that has anti-atherogenic properties. There is a reverse correlation between the serum adiponectin levels and the degree of obesity, IR, impaired glucose tolerance, dyslipidemia and atherosclerosis. Ghrelin stimulates food intake; of all circulating orexigenic hormones ghrelin is the most thoroughly studied. Ghrelin levels are decreased in MS and PCOS patients as this hormone is negatively correlated with body mass. Resistin is a hormone secreted by adipose tissues; a growing body of evidence suggests that it might be implicated in the link between obesity and diabetes. It has been found that the hormone's levels are significantly higher in obese people than those in normal body mass people. The recently discovered adipose tissue hormones, vaspin, visfatin, omentin-1 and their effect on IR development, have been increasingly researched.

Adipocytokines, neuropeptide Y and insulin resistance in overweight women with gynoid and android type of adipose tissue distribution.

UNLABELLED: The AIM of the study was to compare the levels of certain adipose tissue hormones in women with the two main morphological types of obesity - android and gynoid obesity. MATERIALS AND METHODS: The study included 2 groups of age- and weight-matched women with android (n = 32) and gynoid (n = 27) type of obesity, and a group of age-matched healthy women (n = 24) with normal weight and body constitution. Leptin, resistin, tumour necrosis factor alpha (TNFalpha), neuropeptide Y (NPY), glucose and insulin were measured. HOMA index was calculated. RESULTS: Leptin levels in the women with gynoid obesity did not differ significantly from those in the controls and the women with android obesity. The controls had significantly lower leptin levels compared with the android obesity women. NPY was significantly higher in the control women compared to the women with android obesity and did not differ significantly between the two groups of obese women. TNFalpha levels in all groups were very similar. Resistin did not show significant differences between all groups but tended to have the lowest levels in the controls. In the women with android obesity, insulin was significantly higher than that in the women with gynoid obesity and the controls. Insulin resistance was found in the women with android obesity only. Basal insulin and HOMA index in the women with gynoid obesity did not differ significantly from the values in the control group. CONCLUSION: The results from this study contribute to understanding the association of adipose tissue hormones and insulin resistance in obesity. When adipose tissue is predominantly distributed in the abdominal area at similar amount and percentage of body fats, leptin production is higher and insulin resistance develops. In the gynoid type of adipose tissue predisposition, overt insulin resistance is not found, leptin levels does not differ significantly from those in the control group.

Morphological characteristics of neonatal adipose tissue.

The aim of the present work was to study the morphological characteristics of neonatal adipose tissue using rats as an animal model. The results revealed that the subcutaneous adipose tissue of newborns consists of packets of unilocular adipose cells (one large lipid drop occupying the whole cell and pushing the cytoplasm and the nucleus to the cell periphery) and some multilocular fat cells (several lipid droplets of different size and an almost centrally located nucleus). All the adipocytes demonstrated positive immunohistochemical expression for leptin, whereas the multilocular adipose cells were positive for cyclin D1. These findings suggest that the multilocular adipose cells are preadipocytes that have not yet finished proliferation and differentiation and could under some external and/or internal stimuli conclude their development and become mature unilocular adipocytes, thus increasing fat mass.

Opposite effects of pravastatin and atorvastatin on insulin sensitivity in the rat: role of vitamin D metabolites.

OBJECTIVE: Recent studies indicate that pravastatin improves whereas other statins impair glucose homeostasis in humans, but the underlying mechanisms are not clear. We examined the effect of pravastatin and atorvastatin on insulin sensitivity in a rat model. METHODS: Pravastatin (40 mg/kg/day) or atorvastatin (20mg/kg/day) were administered for 3 weeks and insulin sensitivity was assessed by measuring fasting plasma insulin, HOMA-IR, non-esterified fatty acids (NEFA) and glycerol levels, as well as by the hyperinsulinemic euglycemic clamp. RESULTS: Pravastatin had no effect on fasting insulin and HOMA-IR but significantly reduced plasma NEFA and glycerol levels and increased glucose infusion rate (GIR) during the hyperinsulinemic clamp. Increase in GIR induced by pravastatin was not abolished by NO synthase inhibitor, l-NAME, indicating that this effect did not result from the improvement of endothelial function. Atorvastatin increased fasting insulin, HOM-IR, NEFA and glycerol levels as well as reduced GIR. Statins had no effect on leptin, HMW adiponectin, resistin, visfatin, interleukin-6 and TNF-α. Pravastatin increased plasma concentrations of 25-hydroxy- and 1,25-dyhydroxyvitamin D(3) (25-OH-D(3) and 1,25-(OH)(2)-D(3)), and its effect on insulin sensitivity was mimicked by exogenous 1,25-(OH)(2)-D(3). Atorvastatin reduced plasma 25-OH-D(3) but had no effect on 1,25-(OH)(2)-D(3). Decrease in insulin sensitivity induced by atorvastatin was not corrected by supplementation of vitamin D(3) despite normalization of plasma 25-OH-D(3) level. CONCLUSIONS: Pravastatin and atorvastatin have opposite effects on insulin sensitivity and vitamin D(3) status. Pravastatin-induced increase in insulin sensitivity is mediated by elevation of 1,25-(OH)(2)-D(3). In contrast, atorvastatin-induced decrease in insulin sensitivity is independent of lowering 25-OH-D(3).

Serotonin-producing cells in human gastric mucosa--immunohistochemical and electron microscopic study.

UNLABELLED: The great many hormones released by the endocrine cells of the glands and lining epithelium of gastric mucosa determine its significance for the processes in the gastrointestinal tract. One of these hormones, serotonin, plays an important role in the regulation of the motility, secretion and sensation in the gastrointestinal tract. The aim of the present study was to conduct immunohistochemical and electron microscopic studies of serotonin-producing EC cell of gastric mucosa. MATERIAL AND METHODS: Gastric mucosa biopsies were obtained and studied immunihistochemically for serotonin expression in the mucosa endocrine cells. Electron microscopic study was performed to specify the processes of synthesis, accumulation and release of secretory product by those cells. RESULTS: The immunohistochemical study revealed a considerable number of serotonin-containing EC cells scattered in the lining epithelium and between the glands in the corpus and pyloric region of the stomach. The electron microscopic study followed the stages of formation of the secretory granules from the initial accumulation of granular substance, its membrane packing and formation of mature granules to their disintegration in the secretory process. CONCLUSIONS: Serotonin as a neurotransmitter and gastrointestinal hormone appears to be a key to understanding a number of symptoms of gastrointestinal disorders like nausea, vomiting, pain, diarrhea and constipation. A detailed study of serotonin functions in the gastrointestinal tract realised through different types of receptors, and of the development of specific antagonists and agonists to these receptors would open up new opportunities for a more efficient treatment of gastrointestinal disorders.

Prenatal and postnatal differentiation of the small intestine in rat.

UNLABELLED: The gastrointestinal tract in the early prenatal development is an endoblastic mesenchyme-lined tube. The endoblast differentiates and gives origin to all epithelial structures (covering epithelium, glands). The mesenchyme develops into connective tissue, blood vessels, the smooth muscle cells of lamina muscularis mucosae and muscular tunic. Neuroectoblast cells participate in these processes--individual cells with future endocrine function, nerve cells and fibers that form nerve plexuses and vegetative ganglia. AIM OF THE PRESENT STUDY: To trace the changes in the small intestine development during the prenatal period in rat embryos and fetuses, and during the postnatal period in newborn rats. We specifically studied the beta-actin expression in the cytoskeletal structures of the covering epithelium and in the contractile elements of the differentiating smooth muscle cells. The presence and localization of the enteroendocrine EC cell was studied using the immunohistochemical expression of serotonin in them. MATERIAL AND METHODS: Material from rat embryos and fetuses aged 8-11, 12-15, 16-20 days of gestation and small intestine fragments from newborn rats was studied using routine hematoxylin-eosin staining, enzymohistochemically for succinate dehydrogenase and immunohistochemically for beta-actin and serotonin. RESULTS: In the early embryogenesis (8-11 day of gestation), the primitive gut of rat embryos is an endoblastic tube of 2-3 layers of cuboidal cells covered with a thin layer of mesenchyme. In the subsequent stages of embryonic and fetal development the processes of differentiation run at different rates in the different tissues. The maturation process in the small intestine wall of one-day-old newborn rats is incomplete. The mucosa presents with shallow crypts and loosely set villi. Differentiated resorptive and enteroendocrine EC cells are found in the lining epithelium. CONCLUSION: The changes we found in the beta-actin expression in the contractile elements of the differentiating smooth muscle cells and the cytoskeletal structures of the lining epithelium probably reflect the induction interference between the derivatives of the mesenchyme and endoblast.

Clinical and experimental study of autologous fat grafting after processing by centrifugation and serum lavage.

BACKGROUND: This clinical and experimental study compared adipose tissue transplant behavior after two different techniques of purifying: centrifugation at 3400 rpm for 3 min and serum lavage without centrifugation. METHODS: Clinical evaluation was performed under standardized conditions for lipofilling on a series of 51 female patients, intentionally selected to have similar characteristics and assigned to two groups based on the method of processing. Experimentally, a culture system in diffusion chambers with vitaline membranes was designed to mimic the behavior and to study the morphology of the adipose tissue used for autografting. Survival, structure, and proliferation of the adipose cells in vitro were examined by classical histologic H&E staining and immunohistochemistry for leptin and cyclin D1. RESULTS: The main differences encountered experimentally were the presence of a greater amount of preadipocytes in the noncentrifuged adipose tissue cultures and more distinctly expressed cell proliferation. The postoperative clinical results favored of the serum lavage purifying technique. CONCLUSION: Our data suggest that with transplantation of noncentrifuged adipose tissue more active preadipocytes are applied which could possibly lead to better potential chances of survival and even de novo development of fat.

Autologous fat transplantation in the facial region--clinical and morphological studies of 30 cases.

OBJECTIVE: This study presents the results of a clinicomorphological study of autologous fat transplantation in the face region. The aim was to investigate and compare adipose tissue morphology after it was purified by two methods--centrifugation and serum lavage, and to find a correlation between the histological outcomes and the postoperative results. PATIENTS AND METHODS: The evaluation was performed on a series of 30 patients assigned into two groups of 15 patients. Centrifuged adipose tissue was transplanted in one of the groups, and noncentrifuged (saline solution washed) in the other group. In all cases fat was obtained by syringe liposuction of subgluteal zones, processed by one of the two methods and then transplanted. Part of the material was fixed between vitaline membranes and embedded in paraffin. Histological analysis was performed after hematoxylin eosin staining of the slides. Post-operative effect was assessed by comparison of the pre- and postoperative photos on a 4-grade scale. RESULTS: The morphological analysis revealed that adipose tissue was damaged by neither of the purification methods but the serum lavage preserved greater number of non-differentiated fat cells and connective tissue fragments. Furthermore, our clinical results suggested clearly that the noncentrifuged adipose tissue transplantation was more advantageous than the other type of transplantation. CONCLUSION: The present study is an attempt to make a contribution towards a better understanding of the mechanisms involved in fat graft preservation.

Bcl-2/Bax ratio, mitochondrial membranes and aerobic enzyme activity in cardiomyocytes of rats after submaximal training.

INTRODUCTION: Mitochondria are an active and continuous source of reactive oxygen species (ROS) during respiration. The ROS increased production during endurance training is a result of an augmented electron transport through the respiratory chains, making in this way the mitochondria a potential target for oxidative damage. The Bcl-2 protein family plays a central role in the transition of apoptotic signals towards the mitochondria in stress-induced apoptosis. AIM: The present work studied the effect of endurance training on the expression of the apoptotic proteins Bcl-2 and Bax in rat cardiomyocytes, as well as the concomitant changes in the ultrastructure of the mitochondria and activity of some enzymes residing there. MATERIAL AND METHODS: Two groups of male Wistar rats were used. One was the control and the other was trained on treadmill with submaximal loading for eight weeks. At the end of the trial, samples of the myocardium of all the experimental animals were obtained. Immunohistochemical reactions for Bcl-2 and Bax and enzymehistochemical reactions for succinate dehydrogenase and NADH2-cytochrome C-reductase were done. The results were analyzed using specialized software. Transmission electron microscopical study was carried out too. RESULTS: In the myocardium of the trained animals the expression of Bcl-2 and Bcl-2/Bax ratio were significantly higher compared to the controls. The mitochondria had intact outer and inner membranes, with no signs of swelling. Mitochondria with denser packed cristae were found predominantly. No significant differences were found in the activity of the investigated enzymes in the cardiomyocytes of the animals from both groups. CONCLUSIONS: In the myocardium of the experimental animals endurance training for eight weeks does not lead to activation of apoptotic processes via the mitochondrial pathway. This type of exercise training could be used for cardioprotection in order to elevate apoptotic threshold of cardiomyocytes.

ATP and LPL histochemical activity of rat cardiomyocytes and adipocytes treated with androgenic anabolic steroids.

AIM: To study the effect of short-term and long-term treatment with retabolil, an androgenic anabolic steroid, on the activity of the enzymes ATP and LPL in rat cardiomyocytes and adipocytes. MATERIAL AND METHODS: Six male Wistar rats (mean weight 195-200 g.) were given retabolil 50 mg/kg once subcutaneously, another six were treated with retabolil at the same dose subcutaneously once a week for 6 weeks and another six were used as controls treating them with physiological saline in the same way. After six weeks the animals were sacrificed. Fragments of the left ventricle of the heart and of the subcutaneous tissue from the gluteal region were resected and enzyme-histochemical reactions for ATP and LPL were performed on fresh cryostat sections. RESULTS: The cardiomyocytes of the rats treated only once with retabolil showed no changes in the ATP and LPL activity in comparison with the controls. In the rats given a long-term treatment with retabolil, the enzyme-histochemical reaction for ATP was better expressed while that for LPL was weak. The subcutaneous adipose tissue of the long-term retabolil-treated animals contained some adipocytes that expressed positive LPL and ATP activity. CONCLUSIONS: Our data suggest that androgenic anabolic steroids exert an effect on the activity of the enzymes ATP and LPL in rat cardiomyocytes and adipocytes which depends on the duration of treatment.

Effects of submaximal training and anabolic androgenic steroids administration on steroidogenic enzyme activity in rat Leydig cells.

The purpose of the present study was to investigate the single and combined effects of submaximal training and anabolic androgenic steroids (AAS) treatment on the activity of 3beta hydroxysteroid dehydrogenase (3betaHSD) in rat Leydig cells (LC). Forty male Wistar rats were distributed into 4 groups. Half of them exercised on treadmill. After 2 weeks half of the trained and sedentary rats received weekly either 10 mg x kg(-1) Nandrolone Decanoate (ND) or Placebo (Pl) i.m. for 6 weeks. The day after the last exercises all the groups: 1) sedentary + Pl (SP); 2) sedentary + ND (SND); 3) trained + Pl (TP) and 4) trained + ND (TND) were decapitated. On fresh cryostat sections of the testes of each animal enzymehistochemical reaction for the activity of 3betaHSD was carried out. Our results demonstrate that in sedentary rats ND treatment decreased the activity of 3betaHSD in the LC in comparison to SP. Endurance training also decreased the activity of 3betaHSD in TP group compared to SP. On sections of the testes of group TND a pronounced reduction in the enzyme activities of 3betaHSD in the LC was found in comparison with the other groups. In conclusion we suggest that submaximal endurance training and/or administration of AAS downregulate the steroidogenic enzyme activity of rat Leydig cells.

Cytochemical and immunohistochemical evidence of direct origin of white adipocytes from mesenchymal cells.

AIM: By using histochemical, enzymohistochemical and immunohistochemical methods the present study aims to find out specific morphological markers in the precursors of the white subcutaneous adipocytes of human and rat embryos, which could be used for identification and help in clarification of the origin of that cell type. MATERIAL AND METHODS: On cryostat sections of subcutaneous tissue from the thigh region of human embryos and hind limb of rat embryos histological hematoxylineosin staining, Sudan III-hematoxylin staining and enzyme-histochemical reactions for lipoprotein lipase are performed. On paraffin section of the same material immunohistochemical reaction for leptin is performed. RESULTS: The analysis reveals that the earliest preadipocytes possess specific histochemical, enzymohistochemical and immunohistochemical features, which characterize exclusively these cells but not the fibroblasts and endothelial cells scattered around in the subcutaneous tissue. These features include lipid drops, positive enzymohistochemical reaction for lipoprotein lipase and immunohistochemical expression for leptin. CONCLUSION: The results could be used as evidence of direct origin of the white adipocytes from the embryonal mesenchyme through their own progenitor cells rather than through fibroblasts or endothelial cells.

Formation of the basal lamina in human embryonal adipose cells--immunohistochemical and ultrastructural evidence.

AIM: The aim of the present study was to investigate the formation of the basal lamina in adipose cells during human embryonal development using transmission electronmicroscopy and immunohistochemistry (reactions for collagen type IV and laminin). MATERIAL AND METHODS: Material (subcutaneous tissue from the gluteal region) was taken from human embryos aged 6 to 12 weeks of gestation. Part of the material was prepared for immunohistochemical investigation for collagen type IV and laminin by the peroxidase-antiperoxidase (PAP) method with universal PAP mouse kit (Dako Corporation, Santa Barbara, CA, USA) and primary antibodies--monoclonal mouse anti-human collagen type IV in dilution 1:100 and monoclonal mouse anti-human laminin in dilution 1:100 (Dako Corporation, Santa Barbara, CA, USA). Part of the same material was frozen at -18 degreesC and on fresh 5 microm thick cryostat sections Sudan III-hematoxylin staining was performed for lipids' demonstration after Daddi (1986). Another part of the same material was prepared for electron microscopic examination with TEM Philips CM 12. RESULTS: The results showed that from the 6th week of gestation onward human preadipose cells accumulated lipid droplets in their cytoplasm and expressed positive immunoreactivity for collagen type IV and laminin. First signs of basal lamina could be seen at places outside the plasmalema. Well-developed rough endoplasmatic reticulum was observed which could be associated with the production of collagen and laminin. A time and place related expression was seen in the immunohistochemical and the electronmicroscopical results. CONCLUSION: Formation of the basal lamina of the human adipocytes begins with the onset of adipogenesis and differentiation during the early human embryogenesis (6th week of gestation). The role of collagen type IV and laminin molecules is suggested in this process.

Cytochemical study of in situ differentiation of white adipose cells in rat.

AIM: The aim of the present study was to follow up the histochemical and enzyme-histochemical characteristics of differentiating white adipose cells of rat in situ. METHOD: Nine rat fetuses aged 15-21 day of gestation were used. Fragments from the subcutaneous tissue of lower limb were frozen at -18 degrees C. On consecutive cryostat sections Sudan III-hematoxylin staining and enzyme-histochemical reactions for NADH2-cytochrome C-reductase, glucose-6-phosphate dehydrogenase, lactate dehydrogenase and lipoprotein lipase were performed. RESULTS: The onset of the rat adipocyte differentiation was detected at days 15-16 of gestation. It was seen as appearance and accumulation of lipid droplets, rounding of the cells and displacement of the nuclei to the cell periphery. Gradually, with the advance of gestational age the number of differentiating adipose cells increased and lipid packages, composed of mature-like unilocular adipocytes and multilocular adipocytes that had not yet completed their differentiation, were formed. The differentiating embryonal adipose cells expressed positive enzyme-histochemical reactions for NADH2-cytochrome C-reductase, glucose-6-phosphate dehydrogenase, lactate dehydrogenase and lipoprotein lipase. CONCLUSION: The described histochemical and enzyme-histochemical characteristics could be used as markers for distinguishing the earliest embryonal adipose cells in rat, which is impossible with the classic histological techniques. At the same time they might be accepted as the primary morphological criteria of adipocyte differentiation in situ.

Electron microscopic study of the differentiation of rat white subcutaneous adipocytes in situ.

UNLABELLED: In the present study we investigated the process of differentiation of rat subcutaneous white adipocytes in situ using electron microscopy. MATERIAL AND METHODS: Rat fetuses (Wistar rat) at 15 - 21 days of pregnancy were used. Sections of the subcutaneous tissue of a hind leg were prepared for examination with transmission electron microscopy by routine techniques. RESULTS: The electron microscopic study showed that the embryonal differentiation of rat subcutaneous white adipose cells in situ started on the 15 - 16th day of gestation and was expressed by lipid accumulation and concomitant changes in the cell organelles. We observed the following in the differentiating adipocytes: 1. abundant glycogen granules; 2. appearance and accumulation of lipid droplets with gradual formation of several lipid droplets or one large lipid drop which pushed the nucleus to the periphery and rounded the cell; 3. large elongated mitochondria with densely packed transverse cristae; disintegration of cristae, swelling and vacuolization occurring in some of the mitochondria; 4. well developed endoplasmic reticulum with elongated and dilated cisternae; the initial predominance of rough endoplasmatic reticulum being superseded by prevalence of smooth endoplasmatic reticulum. The ultrastructural analysis we did revealed the consecutive stages in the adipocyte differentiation and the formation of adipocyte phenotype during the embryonal development of the rat.