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Effects of the administration of angiotensin II on cardiac glycogen metabolism in the rat.
Full text linkChanges in glycogen metabolism after an intravenous injection of angiotensin II
were investigated in the left and right ventricles of the rat heart, as a
function of location within the ventricular wall. Hearts were cut into
100-microns thin section, all of which were analysed for glycogen content,
glucose incorporation into glycogen and 2-deoxyglucose uptake and phosphorylation
after the intravenous injection of 14C-labelled sugar. In control hearts,
glycogen levels were uniform across the wall in both ventricles, while the rate
of sugar uptake and phosphorylation, and that of glucose incorporation into
glycogen, were significantly higher in the subendocardial myocardium of the left
ventricular wall. After angiotensin II administration, heart glycogen levels
decreased slightly in the left, but not in the right ventricle, while
2-deoxyglucose uptake and phosphorylation, and glucose incorporation into
glycogen, increased 2,5- and 5-fold, respectively. With regard to the
distribution across the wall of the left ventricle after angiotensin
administration, glycogen levels and glucose incorporation into glycogen were
uniformly distributed, whereas sugar phosphorylation was still higher in the
subendocardium
Transmural differences of lipofuscin pigment accumulation in the left ventricule of rat heart during growth and aging.
No full textIn view of the higher metabolic rate in subendocardial heart tissue, the rate of
age-related lipofuscin pigment accumulation was explored in different regions of
the left ventricle heart wall of Sprague-Dawley rats. Hearts were removed from
2-, 6-, 12- and 24-month-old rats, and lipofuscin pigment accumulation was
assessed in the subepicardial and subendocardial layers, either by measuring
extractable fluorescent material, or by direct visualization with fluorescence
microscopy. Findings showed that the amount of extractable fluorescent material
and the number, size and brightness of the fluorescent lipofuscin granules
increased with age in all the myocardial tissue layers. The rate of accumulation
of extractable fluorescent material was higher in subendocardial compared to
subepicardial tissue. At the microscope, fluorescent granules exhibited a
different morphological appearance in the subendocardial and subepicardial tissue
of the two older age-groups. These data support the hypothesis that liposoluble
age-pigment deposition is linked to the rate of local oxidative metabolism
A NEW METHOD FOR THE INVESTIGATION OF ENDOCRINE-REGULATED AUTOPHAGY AND PROTEIN-DEGRADATION IN RAT-LIVER
No full textEffect of dietary restriction on the age-related changes in hormone-regulated protein breakdown
No full textChanges in the transmural distribution of antioxidant enzyme activities across the left ventricle heart wall from rats fed ad libitum or food-restricted during growth and aging.
No full textData on vulnerability to injury and on the larger age-related accumulation of
lipofuscin in the subendocardial myocardium prompted us to investigate the
changes in the levels and in the transmural distribution of catalase (C),
glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD) activities across
the left ventricle heart wall of rats fed ad libitum a standard diet or submitted
to intermittent feeding during growth and aging. Enzyme activities were assayed
by standard techniques on subepicardial, midmyocardial or subendo- cardial tissue
obtained by cutting the heart wall into 100-microm-thick sections at the
cryostat. The levels of GSH-Px and of C (but not of SOD) activity increased with
age and reached their highest values in the subendocardial region by adulthood or
senescence, respectively. No effect was observed of intermittent feeding on
age-related changes in enzyme levels and transmural distribution
The brown adipose tissue of hyperthyroid rats. A biochemical and ultrastructural study.
No full textMale Sprague-Dawley rats were treated with triiodothyronine (100 micrograms/100
g/day) for 2, 4, 7, 14 and 21 days and the biochemical and ultrastructural
changes of the brown adipose tissue were investigated. Results showed that the
tissue weight, DNA and phospholipid content increased very early (by day 2 or 4)
and that triglycerides increased later. These hormonal effects are not inhibited
by the beta 1-antagonist propranolol. From the morphological point of view,
triiodothyronine administration induced the early proliferation and maturation of
adipocyte precursors (interstitial cells and preadipocytes). It is concluded that
triiodothyronine administration causes a very early hyperplasia in the brown
adipose tissue similar to that observed during exposure to cold by mechanisms
that may not be secondary to the involvement of norepinephrine
Ageing-related changes in the in vivo function of rat liver macroautophagy and proteolysis
No full textAutophagy is a universal, highly regulated mechanism responsible for the
degradation of long-lived proteins, cytomembranes and organelles during fasting
and may be the cell repair mechanism that mediates the anti-ageing effects of
calorie restriction (Bergamini and Gori, 1995). The function of autophagy was
studied in vivo on male Sprague Dawley rats fed ad libitum or 40% food
restricted. Autophagy was induced in overnight fasted rats by the injection of an
anti-lipolytic agent and was investigated by electron microscopy. Changes in
regulatory plasma nutrients and hormones were assessed and rate of proteolysis
was calculated from the release of 14C(6)-valine from pre-labelled resident
proteins. Results in rats fed ad libitum showed that autophagic-proteolytic
response to antilypolitic agents was paramount in one month-old rats; was high
but delayed in 2 month-old rats, decreased remarkably in 6 month-old rats and
almost negligible at older age. Parallel ageing-related changes were observed in
the effects of treatment lowering glucose and insulin plasma levels. Calorie
restriction prevented all changes. In view of the known suppressive effects of
insulin, it may be concluded that the age-changes of autophagy are secondary to
the ageing-related alteration in glucose metabolism and hormone levels, whose
appearance is delayed by calorie restriction. Data may support the hypothesis
that ad libitum feeding accelerates the rate of ageing by raising insulin plasma
levels and suppressing autophagy and membrane maintenance, and that calorie
restriction may break this vicious circle
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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