19 research outputs found
The effect of fasting on the ultrastructure of the hypothalamic arcuate nucleus in young rats
In the present study, we described ultrastructural changes occurring in the
neurons of the hypothalamic arcuate nucleus after food deprivation. Young
male Wistar rats (5 months old, n = 12) were divided into three groups. The
animals in Group I were used as control (normally fed), and the rats in Groups
II and III were fasted for 48 hours and 96 hours, respectively. In both treated
groups, fasting caused rearrangement of the rough endoplasmic reticulum forming
lamellar bodies and membranous whorls. The lamellar bodies were rather
short in the controls, whereas in the fasting animals they became longer and
were sometimes participating in the formation of membranous whorls composed
of the concentric layers of the smooth endoplasmic reticulum. The whorls
were often placed in the vicinity of a very well developed Golgi complex. Some
Golgi complexes displayed an early stage of whorl formation. Moreover, an
increased serum level of 8-isoprostanes, being a reliable marker of total oxidative
stress in the body, was observed in both fasting groups of rats as compared
to the control
Ultrastructural observations on the hypothalamic arcuate nuclei of aged rats in the fasting/refeeding model
The arcuate nucleus of the hypothalamus (ARH) is involved in the control of
energy homeostasis. This is the first study on the ultrastructural response of ARH
neurons in aged rats after short-term fasting and subsequent refeeding. Male
Wistar rats (24 weeks old) were fasted for 48 or 96 hours and were then refed for
24 hours. The controls were normally fed. The rats received water ad libitum. In
both groups of fasting animals, we observed a rearrangement of the arcuate
rough endoplasmic reticulum (RER) and Golgi complexes to form membranous
whorls. Moreover, refeeding for 24 hours did not reverse this process. The RER
was frequently found to be well organized into lamellar bodies composed of
several cisternae. The membranous whorls were composed of concentric layers
of endoplasmic reticulum and Golgi complexes. In addition, multiform lipofuscin
granules were observed in close relationship with Golgi complexes and membranous
whorls. Lipofuscin granules within the neurons of the arcuate nucleus are
assumed to be a morphological manifestation of oxidative stress phenomena,
which are presumably implicated in the formation of membranous whorls in
both fasting and fasting/refed animals. This observation correlates with a significant
increase in 8-isoprostane serum levels in the fasting and fasting/refed animals
as compared to the fed control rats
Myocardial necrosis due to vitamin D3 overdose - scanning electron microscopic observations
Our studies were carried out on the hearts of virgin female Wistar rats treated
with 100.000 i.u. of vitamin D3 (calciol) per os for 3 consecutive days. Multifocal
cardionecrosis was established macroscopically in 70% of the vitamin D-treated
rats on the 7th day of the experiment when the rats were in the acute phase of
intoxication.
Using a scanning electron microscopy (SEM), we received three-dimensional information
about the structural changes to the rat myocardium damaged by
high doses of vitamin D3. The images of necrotic hearts revealed significant
disruption of the structural integrity of the myocardium linked to fragmentation
of the cardiac muscle bundles and a visible disruption of the extracellular matrix
(ECM) components. In healthy hearts, the structural integrity of the myocardium
and the dense network of the extracellular matrix were well preserved. In parallel,
the effect of an increasing concentration of free Ca2+ on the total proteolytic
activity of the heart muscle homogenate of the healthy and necrotic rats was
investigated at neutral pH. These data showed that following vitamin D3 intoxication,
the proteolytic processes in the rat hearts occurred in Ca2+ overload or
saturation. On the basis of our morphological and biochemical results we can
suggest that calcium-activated neutral proteinases may have contributed to the
structural alteration of the extracellular matrix components and were in this way
involved in vitamin D-induced cardionecrosis
The growth and differentiation of aortal smooth muscle cells after calcitriol treatment are associated with microtubule reorganisation - an in vitro study
The smooth muscle cells (SMCs) of the arterial media play a predominant role
in functional and structural alterations of the arterial wall. The transition from
the “contractile” to the “synthetic” phenotype appears to be an early critical
event in the development of atherosclerotic disease. A number of observations
suggest that 1,25(OH)2D3 (calcitriol) is of importance in maintaining normal
cardiovascular function through its receptors in cardiac myocytes or aortal
SMCs. The present study has focused on the microtubular (MT) network reorganisation
after exposure to calcitriol. SMCs isolated by enzymatic digestion
from the aortal media of neonatal rats were cultured on glass cover slips.
1 μM of 1,25(OH)2D3 was added to the culture medium every second day. The
cytoskeletal features of SMCs after calcitriol were visualised by the immunofluorescence
staining of α-tubulin. The alterations in α-tubulin expression and
the distribution of microtubules related to the activities of the vascular smooth
muscle cells, namely adhesion, migration, multilayer formation and cell division,
were observed. A spindle shape, decreased cell adhesion, low expression
of α-tubulin and a longitudinally arranged microtubular network manifested
the high rate of SMC differentiation in the calcitriol-treated culture. A flat
stellate morphology, high expression of α-tubulin and a radially distributed
three-dimensional microtubular network were observed in the SMCs of the
control culture. Destructive changes in the microtubular architecture which
altered the cellular shape were evident in SMCs undergoing apoptosis. Cells
with apoptotic features were more frequent in calcitriol-exposed culture. In
contrast to the regular SMC divisions observed in the control culture, some of
the mitotic cells exposed to calcitriol contained broader bipolar, multipolar or
disordered spindles.
These alterations in the SMCs’ microtubular cytoskeleton after calcitriol treatment
were concomitant with changes in cell growth, differentiation and apoptosis,
and may suggest a similarity to atherosclerotic plaque formation
A scanning electron microscopic study of phenotypic plasticity and surface structural changes of aortal smooth muscle cells in primary culture
Phenotypic modulation of smooth muscle cells (SMCs) from a contractile to
a synthetic state characterised by active proliferation appears to be an early event
in the pathogenesis of atherosclerosis. A similar transition occurs when SMCs are
established in culture. In this study the phenotypic plasticity and surface structural
changes of aortal smooth muscle cells during the transition from the contractile to
the synthetic state and during maturation have been structurally assessed by scanning
electron microscope (SEM). The experiments were performed on SMCs obtained
from aorta of neonatal rats after enzymatic digestion and then cultured on
glass cover slips. SEM observations revealed a three-dimensional appearance characteristic
for different stages of SMCs. Intensively proliferating cells from monolayer
region were large, polygonal in shape with lamellipodia and well spread. Long,
uniform in diameter, finger-like microvilli were densely arranged on the surface of
these cells. In the thickened region of culture, the cells were rather small, generally
spindle-shaped, not well spread, with low density of short, bubble-like microvilli
on the surface. Numerous plasma membrane structural alterations in apoptotic
cells were observed by SEM: loss of cellular adhesion, smoothing, shrinkage and
outpouching of membrane segments have been recognised as markers associated
with the cell injury and death. It was concluded that scanning microscopy
observations would allow a more complete understanding of SMCs and their changes
in culture and atherosclerotic disease
The effect of angiogenesis inhibitor TNP-470 on the blood vessels of the lungs, kidneys and livers of treated hamsters
The growth of solid tumours and their metastases is dependent on the development
of new blood vessels (angiogenesis). Therefore angiogenesis inhibitors are
potential antitumour drugs.
In our previous studies it was found that the angiogenesis inhibitor TNP-470
given to transplantable melanoma-bearing hamsters can decrease the rate of
the tumour growth, although the survival time of the animals treated was not
significantly affected. It was found finally that TNP-470 given in the vicinity of
the growing tumour can cause complete remission of the melanoma in hamsters
treated in this way. To check what side-effects could be evoked by such
treatment, an examination of the morphology of the blood vessels of the lungs,
kidneys and livers of the treated animals was carried out. It was found that the
angiogenesis inhibitor applied did not cause any changes which could be observed
by light and electron microscopes in the structure of the examined blood
vessels of the treated animals
Ultrastructural response of arcuate nucleus neurons to fasting in aged rats
The arcuate nucleus of the hypothalamus (ARH) is involved in the control of
energy homeostasis. Leptin - an adipocyte derived hormone - is known to
act on the hypothalamic nuclei and thus to control body weight by food intake
reduction. Oxidative stress is believed to be implicated in leptin signalling. However,
its relevance for leptin-induced signal transduction within ARH remains
unclear. The goal of the study was to investigate the effect of fasting on morphological
alterations of the neuronal endoplasmic reticulum/Golgi network as
well as on the expression of leptin receptors in the arcuate nucleus of aged
rats. Male Wistar rats, aged 24 months, were fasted for 96 hours. The control
animals were fed ad libitum. Membranous whorls in the ARH neurons were
visualized using the electron microscopy technique. Leptin receptors in the
membranes of ARH neurons were determined immunohistochemically (IHC),
and soluble leptin receptors in the plasma as well as plasma isoprostanes were
quantified immunochemically (ELISA). An intense formation of membranous
whorls was observed, directly associated with the cisternae of the rough endoplasmic
reticulum, as well as lamellar bodies. Interestingly, the whorls were
often localized near a well-developed Golgi complex. Moreover, some Golgi
complexes displayed an early stage of whorl formation. Groups of residual
lipofuscin granules were found in the immediate proximity of the whorls. An
increased immunoreactivity with neuronal leptin receptors suggests that hypersensitive
neurons may still effectively respond to the fasting serum levels of
leptin, mediating ultrastructural transformation of ARH neurons during short-term fasting. Having observed a significant accumulation of lipofuscin granules
and a marked increase of total 8-isoprostane serum level in the fasting rats, we
hypothesize that signal transduction within the neurons of ARH is dependent
on oxidative stress phenomena
Changes in the morphology of the acinar cells of the rat pancreas in the oedematous and necrotic types of experimental acute pancreatitis
Limited experimental models of the oedematous and necrotic types of acute
pancreatitis provide some understanding of the pathophysiology of this disease.
Wistar rats were treated with cerulein at 10 mg/kg of body weight or with
L-arginine at 1.5 or 3 g/kg of body weight in order to induce the oedematous or
necrotic type of acute pancreatitis. After the induction period we examined
samples of pancreata with light and electron microscopes. Morphological
examination showed profound changes in the histology of the pancreas and its
acinar cells and subcellular structures, especially in the group of rats which
received a higher dose of L-arginine, amounting to 3 g/kg body weight. These
included parenchymal haemorrhage and widespread acinar cell necrotic changes.
4-OH-TEMPO successfully prevented morphological deterioration as well as
amylase release, suggesting that the severity of the two types of disease strongly
depends on the intensity of the oxidative stress. Our results lend support to the
assumption that reactive oxygen species play an axial role in the pathogenesis of
both types of acute pancreatitis
Ultrastructure of the ventromedial hypothalamic nucleus in fasted and refed young and old rats
Many hypothalamic nuclei are involved in the regulation of food intake and
energy homeostasis. An ultrastructural investigation of the hypothalamic ventromedial nucleus (VMN), a hypothetical "satiety centre" was performed to explore the morphological basis of altered feeding behaviour of old rats in an experimental model of fasting/refeeding. Young (5 months old, n = 12) and old (24 months old, n = 12) male Wistar rats were fasted for 48 hours, then refed for 24 hours and sampled thereafter. Brain tissue was fixed by perfusion, histological
and ultrathin sections were obtained by routine methods. Although food
intake was similar in control young and old rats, during refeeding old animals consumed less chow than young ones. The EM analysis of VMN neurones of old control rats revealed, besides typical age-related residual bodies, deep indentations of the nuclear envelope and the presence of long, undulating rough endoplasmic
reticulum cisternae in the cell periphery. In both young and old rats
fasting for 48 hours led to the expansion of Golgi complexes and increased folds of the nuclear envelope, which is suggestive of enhanced cellular activity of the
VMN neurones. These fasting-induced alterations were sustained in the VMN
neurones of refed rats in both age groups. The results showed that the VMN
neurones of old control rats differ at the ultrastructural level from young ones. However, starvation and subsequent refeeding cause similar alterations in the hypothalamic neurones of "satiety centre" of both young and old rats
The effect of fasting and refeeding on the ultrastructure of the hypothalamic paraventricular nucleus in young and old rats
In order to explore the morphological basis of the altered feeding behaviour of
old rats, an ultrastructural investigation of the magnocellular neurons of the
hypothalamic paraventricular nucleus (PVN) was performed. Young and old male
Wistar rats, 5 and 24 months old, respectively, and with each age group comprising
12 animals, were divided into 3 groups. The rats in Group I were used as
controls (normally fed), the rats of Group II were fasted for 48 hours and in
Group III the rats were fasted for 48 hours and then refed for 24 hours. The
brains were fixed by perfusion and histological and ultrathin sections were obtained
by routine methods. Common features of the magnocellular PVN neurons
of young and old rats were abundant Golgi complexes and short fragments
of RER localised at the cell periphery. In contrast to young rats, the PVN neurons
of old animals showed deep indentations of the nuclear envelope and agerelated
residual bodies. In both age groups fasting for 48 hours led to the expansion
of the Golgi complexes and dilatation of RER cisternae. In contrast to
those in fed rats, RER cisternae in the neurons of old fasted animals were situated
between the nuclear envelope and the Golgi zone. Prolonged RER cisternae
were distributed in the peripheral cytoplasm of refed old rats. Our observations
suggest that at the ultrastructural level the process of ageing does not change
the responsiveness of magnocellular PVN neurons to fasting-refeeding