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PubMed1984

Population dynamics of arterial cells. XIV. Evidence for no significant G2 arrest of intimal and medial cells in young nonatherosclerotic swine.

In an earlier study of swine results from analysis of tritiated thymidine data by an "ancestor table" method suggested a substantial arrest of arterial cells in the G2 phase of the cell cycle. A later study with a cytofluorometric method gave contradictory results with no evidence for significant G2 arrest. On reexamination of the earlier data with the ancestor table method in the light of current knowledge, it was found that the fact that nuclei in the S and G2 phases prior to division are larger than those in G1 after division had not been taken into account. The main purpose of the current study was to find out whether the evidence for G2 arrest would entirely disappear if adjustments were made for differences in nuclear sizes before and after division. A baseline group sacrificed 2 hr after tritiated thymidine injection and two experimental groups (one fed hyperlipidemic diet and the other given cholesterol-free mash) sacrificed 47 hr after injection were studied. Using the ancestor table method it was found that virtually all labeled arterial cells divided in both groups; thus there is no evidence for G2 arrest. The data was also analyzed with a form of the "mean grain count halving" method and this also showed all labeled cells dividing.

Animals↗
PubMed1991

Reductions in serum thromboxane, prostacyclin, and leukotriene B4 levels in swine fed a fish oil supplement to an atherogenic diet.

We have reported previously that fish oil rich in omega-3 fatty acids added to a butter-cholesterol atherogenic diet for swine resulted in marked retardation of the atherosclerotic process which many regard as largely an inflammatory response to injury by excessive lipids in the intima. In this report on the same swine we present serum levels of several eicosanoids derived from arachidonic acid via the cyclooxygenase and lipoxygenase pathways. The study involves six swine fed a high fat, high cholesterol diet (BT group) for 4 months, six swine fed the same diet but with 30 ml/day fish oil added (BT + FO), and five swine fed a low fat, low cholesterol mash diet (MA). The serum eicosanoids were measured by radioimmunoassay. Thromboxane B2 levels (ng/dl: means +/- SEM) were 543 +/- 49 for MA, 231 +/- 12 for BT, and 105 +/- 20 for BT + FO, and all differences were statistically highly significant, 6-Keto PGF1 alpha (a relatively stable prostacyclin metabolite) levels were 249 +/- 31 for MA, 184 +/- 12 for BT, and 101 +/- 10 for BT + FO, and all differences were significant. Leukotriene B4 levels at 4 months were 151 +/- 25 for MA, 112 +/- 11 for BT, and 84 +/- 11 for BT + FO. BT + FO was significantly different from both MA and BT, but BT was not significantly different from MA. Leukotriene C4 levels were not significantly different among the three groups. Of special interest was the effect of the BT diet without the FO additive in reducing several eicosanoid levels compared to MA values. The affected eicosanoid levels were reduced still further by the fish oil additive, indicating its ability to inhibit both the cyclooxygenase and the lipoxygenase pathways. The relation of the fish oil-induced inhibition to the observed retardation of atherogenesis is not as yet clear but there are several theoretical possibilities, including reduction in recruitment of monocytes and in proliferation of smooth muscle cells.

Animals↗
PubMed1985

Rapid determination of DNA synthesis in adherent cells grown in microtiter plates.

A specific, rapid, and economical method for measuring the extent of DNA synthesis in adherent rat hepatoma H4-II-E cells grown in 96-well microtiter plates is described. The adherent cells were pulsed for 1 h with [methyl-3H]thymidine, released from the substratum by trypsinization, and collected on fiberglass filters with a MASH II cell harvester. The amount of radioactivity incorporated was directly proportional to the number of cells per well. Growth curves generated by measuring [methyl-3H]thymidine incorporation and counting the number of cells per well were identical. Experiments with inhibitors of DNA, protein, and RNA synthesis demonstrated that this method selectively measured DNA synthesis. In addition, [3H]thymidine uptake showed excellent correlation with autoradiographic assessment of DNA synthesis. This specific and sensitive method for determining DNA synthesis in microtiter cultures should facilitate studies of effects of various growth-controlling agents on epithelial, fibroblastic, and other cells which grow as adherent cells in culture.

Animals↗
PubMed1984

Quantification of intimal cell masses and atherosclerotic lesions in coronary arteries of control and hyperlipidemic swine.

In the current study of swine coronary arteries, we have attempted to quantify the coronary intimal cell masses (ICM) with regard to two aspects: (1) percentage of total arterial wall cells (intimal plus medial) that are in the intima, and (2) percentage of arterial wall area occupied by intima. We have studied 4 coronary sites: left main stem (LMS), proximal right (RCA), proximal left circumflex (LCX), and proximal left anterial descending (LAD). In mash-fed ('normal') swine we carried out the study at 3 ages: 2, 5 and 12 months. In addition, we have carried out a similar study in swine fed hyperlipidemic (HL) diets for 3 or approximately 10 months starting at 2 months of age. In the control swine we found approximately 6% of the arterial wall occupied by intima at 2 months of age with no significant increases by 12 months. There were no consistent significant differences among the 4 coronary artery sites with regard to percentage of wall occupied by intima. When the HL diet was fed, there were significant increases in the percentage of the arterial wall occupied by intima (now atherosclerotic lesion) by 3 months on diet and much larger increases by 10 months (up to 87% of wall occupied by intimal lesion) with extensive regions of lipid-rich, calcific, necrotic debris. After 3 months on HL diet the RCA lesions occupied significantly greater percentages of areas than the other 3 sites but this difference had disappeared by 10 months on the HL diet.

Animals↗
PubMed1987

Atherosclerotic lesions in the coronary arteries of hyperlipidemic swine. Part 1. Cell increases, divisions, losses and cells of origin in first 90 days on diet.

The intima of the proximal portion of the coronary arteries of young swine is normally thickened by accumulations of cells about 90% of which are smooth muscle cells (SMC) and about 10% are of probable monocyte origin. Extracellular components such as collagen and elastic tissue are also present but we have chosen to emphasize their cellular nature by calling the regions of thickened intima, intimal cell masses (ICM). We have previously shown that atherosclerotic lesions produced in the coronary arteries of swine by 90 days of feeding a hyperlipidemic (HL) diet arise almost exclusively in the normally occurring ICM. We are reporting here a study of the pathogenesis of these lesions following killing at 0, 14, 49 and 90 HL diet days with comparisons between ICM in control mash-fed swine and ICM-lesions in the HL swine. We found that in the ICM: lipid accumulation was present by 14 days and increased thereafter; the lipid was mostly in SMC but percentage wise the monocyte-macrophages were involved as much or more, cell division activity was increased 3-4-fold by 49 days, cell numbers in ICM were similar in HL and control swine at 49 days but were about 6-fold greater in the HL swine at 90 days, (now in ICM-lesions), at 90 days, circa 90% of the cells appeared to be of SMC and circa 10% of monocyte origin both in the ICM-lesions of the HL swine and in the normal ICM of the controls. The data suggest but do not prove that early lipid accumulation precedes increased cell divisions especially among the SMC component and this in turn precedes increased numbers of cells in the ICM. Although SMC constitute the major cell component of the ICM-lesion at 90 days, the monocyte-macrophage-like cells also increase in number as a result of the HL diet and constitute a small but definite minor component. One possible explanation for the increased cell division activity is that one of the lipid constituents is acting as mitogen; another possibility is that the effect of a well known mitogen such as platelet-derived growth factor is enhanced by the lipid; another is that the monocytes are being stimulated to produce monocyte-derived growth factor. In any event in the very early stage of atherogenesis in the coronary arteries in these experiments excessive proliferation of resident SMC in the ICM appears to be the predominant feature.

Animals↗
PubMed1989

Modification of lipoprotein patterns and retardation of atherogenesis by a fish oil supplement to a hyperlipidemic diet for swine.

We have studied the effect of addition of 30 ml cod liver oil (FO) daily to a highly atherogenic butter (BT) diet for swine on lesion development in the coronary arteries and aorta, plasma lipoprotein (LP) patterns, plasma levels of thiobarbituric acid-reactive substances (TBARS) and on tritiated thymidine-labeling indices ([3H]TdR LI) of smooth muscle cells (SMC) and monocyte/macrophages (M/M phi) in the atherosclerotic lesions. Seventeen male Yorkshire swine (11.1 +/- 0.4 kg) were divided into 3 groups: BT (n = 6), BT + FO (n = 6) and mash (n = 5). They were fed the respective diets for 4 months. Terminally, fasting plasma was obtained and cholesterol contents were determined in various fractions of lipoproteins separated by density gradient ultracentrifugation, Pevikon block electrophoresis and immunoelectrophoresis. Apoprotein (B, A-I, E and C) contents of the plasma and lipoprotein fractions were determined by polyacrylamide gel electrophoresis and densitometry of gels stained with Coomassie blue. Swine were injected intramuscularly with 0.5 mCi/kg of [3H]TdR 2 h before death. The aorta and coronary arteries were perfusion fixed in situ under anesthesia. Samples were obtained for microscopic morphometry, autoradiography and immunohistochemistry from distal abdominal aorta, thoracic aorta, and proximal coronary arteries; left main (LM), left anterior descending (LAD), left circumflex (LCX), right main (RM), and right coronary artery (RCA). On the BT diet without FO there was extensive atherosclerotic (AS) lesion development, which was drastically reduced by the addition of FO to the BT diet in all sites by from 71 to 94%. The overall plasma cholesterol (CH) levels were reduced only modestly by the FO (816 +/- 64 to 629 +/- 14 mg/dl) but the distribution of CH in the various lipoprotein classes was remarkably altered. The CH in the large lipoprotein molecules containing both B and E apoproteins was reduced from 488 +/- 84 to 204 +/- 17 mg/dl by the FO with an almost corresponding increase in the conventional LDL molecules containing apo B only (158 +/- 29 to 344 +/- 15 mg/dl). We offer the hypothesis that the large apo B,E containing molecules are much more atherogenic than the smaller apo B containing molecules. This hypothesis is supported by a highly significant correlation between extent of lesion development in all arterial sites and plasma levels of CH in apo B,E containing lipoproteins. Plasma TBARS were elevated by the BT + FO diet but seemed to have no significant effect on the lesions.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1990

Dietary fish oil added to a hyperlipidemic diet for swine results in reduction in the excessive number of monocytes attached to arterial endothelium.

Modest numbers of blood monocytes become attached at least temporarily to the endothelium of large arteries in normal swine fed low fat, low cholesterol diets. These numbers are increased several fold when the swine are fed a high saturated fat, high cholesterol atherogenic diet (BT). The main objective of this portion of a broader study was to see if the addition of fish oil (30 ml) to a BT diet (BT + FO) could prevent the increase in attached monocytes induced over arterial endothelium in BT fed swine. Six BT, 6 BT + FO and 5 control mash (MA) swine fed the respective diets for 4 months before killing were available for the current study. Other aspects of this experiment have been presented previously which in brief are that BT + FO resulted in retardation of atherosclerotic lesion development and a shift in lipoprotein components from predominantly apolipoprotein B,E containing with the BT diet to predominantly apo B only with BT + FO. There was a significant positive correlation between lesion development and apo B,E lipoproteins. In the current study we determined by scanning electron microscopy on the first portion of the left anterior descending coronary artery after perfusion fixation under pressure the number of monocytes per mm2 attached over or not over visible lesions. We also determined monocyte percentages in the circulating blood and analyzed the correlation of the numbers of attached monocytes and blood monocyte percentages with various lipoprotein components reported previously.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Plasma corticosterone and meal expectancy in rats: effects of low probability cues.

The plasma corticosterone levels of rats were examined prior to their morning meal on Days 1, 7 and 20 of a regimen of 1 hr access daily to food mash and water. The relationship between external cues and meal provision was varied by feeding some groups immediately upon room entry each morning, and others with a variable interval 90-min delay. On Day 1, corticosterone levels of the hungry rats were elevated around the time of light onset, and until 90 min following room entry. On Day 7, corticosterone levels increased in response to room entry in the delay-fed rats, but did not increase further in immediately fed rats. These results were interpreted as indicating that low, but nonzero, expectancy of meal availability elevates corticosterone levels. On Day 20, the immediately fed rats showed a dip in corticosterone levels after room entry, responding to cues highly predictive of imminent meal availability. Delay-fed rats no longer showed an elevation to room entry. The relationship between corticosterone level and meal expectancy is essentially curvilinear in the hungry rat. The corticosterone levels are high when there is uncertainty about whether food is coming or not, and low when there is a very high or very low probability that food is coming.

Animals↗
PubMed1984

Influence of vagotomy in domestic fowls on feeding activity, food passage, digestibility and satiety effects of two peptides.

The effects of bilateral vagotomy at the level of the proventriculus, in immature female fowls (VAG), on body weight, feeding activity parameters, rate of food passage, digestibility, and satiety effects of bombesin (BBS) and cholecystokinin octapeptide (CCK8), were compared with those in sham-operated controls (SHAM). SHAM birds gained weight at a greater rate postoperatively than before their operation, whereas VAG birds did not. Daily food intake did not change significantly as a result of the operation with either SHAM or VAG birds, and the only effect on feeding activity parameters was on the length of intermeal intervals, which increased in VAG birds. Rate of passage of the layers' mash diet was slower, and its apparent digestibility lower, in VAG than in SHAM birds. Short-term suppression of food intake, following intravenous injections of BBS (10 micrograms/kg) or CCK8 (10 micrograms/kg), did not differ between SHAM and VAG birds. The different postoperative weight gains may have been a consequence of different weights of food digested, and the difference in interval length was probably due to the different rates of food passage. The results of these experiments indicate that efferent information affecting rate of passage and digestibility travels via the vagus, but that afferent information concerned with initiation and termination of meals, and with satiety effects of BBS and CCK8, does not. Instead, such afferent information may travel via the intestinal nerve, which is unique to birds.

Animals↗
PubMed1986

Noise-induced eating in rats facilitated by prior tail pinch experience.

In order to integrate the results of procedures that induce excessive nonregulatory eating, it is necessary to develop new procedures that elicit eating in satiated animals. To that end, the present study examined the effects of 90-dB white noise on eating in satiated rats. Twenty-four rats, including sixteen with prior tail pinch-induced eating experience, were presented with mash in baseline and noise conditions. Whereas white noise induced eating in tail pinch-experienced rats, noise did not do so in naive subjects. It was concluded that experience with eating in response to arousal increased the likelihood that an animal would respond to a different kind of arousal by eating.

Animals↗
PubMed1987

Absence of sparing of spatial navigation, skilled forelimb and tongue use and limb posture in the rat after neonatal dopamine depletion.

Depletion of caudate-putamen dopamine (DA) was produced by intraventricular injection of 6-hydroxydopamine (6-OHDA) in three day old rats. When adult, the rats were given cognitive and motor tasks sensitive to adult dopamine depletion, including: tests of cue and place spatial navigation in a swimming pool, a test of skilled forelimb use, requiring reaching for small pellets of food, a test of tongue protrusion, requiring tongue extension to lick mash from a spatula, a test of limb posture, sensorimotor tests of orienting to tactile stimulation and catalepsy. Despite apparent normal physical appearance and locomotor behavior, the rats were impaired on all tasks except orienting to tactile stimulation and catalepsy. There was a significant positive correlation between the degree of impairment on the behavioral tasks and the extent of caudate-putamen dopamine depletion. The results show that sparing of function following neonatal dopamine depletion is selective and incomplete. The results are discussed with respect to the questions of sparing of function following neonatal lesions, the heterogeneous nature of the neonatal depletions and the contributions of dopamine to complex spatial and motor behavior in the rat.

Animals↗
PubMed1987

Chlordiazepoxide-induced selection of saccharin-flavoured food in the food-deprived rat.

Following a period of food-deprivation, adult male rats were given a choice between three sources of food in a 15 min test. All three consisted of a mash of powdered food and water; saccharin and quinine were added to two of them, respectively. Chlordiazepoxide (5 and 10 mg/kg, IP) significantly reduced the latency to begin eating, and also increased the overall level of food consumption. Its hyperphagic effect was due to a selective increase in ingestion of the saccharin-flavoured food, and was not due to a general increase in food consumption across all three food sources. Analysis of the micro-structure of feeding indicated that the increase in food intake depended upon an increase in the duration of individual bouts. Other feeding parameters were not significantly affected by chlordiazepoxide. These data suggest the CDP treatments affect feeding behaviour selectively, both in relation to the taste characteristics of the food, and also with regard to alterations in the micro-structure of the feeding responses.

Animals↗
PubMed1988

Profile of the selective dopamine D-2 receptor agonist N-0437: its effects on palatability- and deprivation-induced feeding, and operant responding for food.

N-0437 is a potent and highly selective dopamine D-2 receptor agonist, which has been used in the present series of experiments to investigate its potential anorectic properties. In doses of 0.3-3.0 mg/kg (IP), N-0437 significantly reduced consumption of a sweetened palatable mash in nondeprived mice (minimal effective dose, 0.3 mg/kg) and rats (minimal effective dose, 0.56 mg/kg). Reduction in food intake were also produced in rats by the less potent, but selective, D-2 agonist RU 24213 (effective at 10.0 mg/kg), and by d-amphetamine (1.0 and 3.0 mg/kg). The anorectic effect of N-0437 (1.0 mg/kg) was completely antagonized by the selective D-2 antagonist, YM-09151-2 (0.01 mg/kg). Over a series of 10 injections, N-0437 (1.0 mg/kg) maintained its effect to reduce palatable food intake. In food-deprived rats, N-0437 (0.3-3.0 mg/kg, IP) also reduced consumption of standard laboratory food, and dose-dependently reduced operant responding for food under a FR8 schedule of reinforcement. The results of the experiments are discussed in terms of a possible direct effect to reduce feeding responses resulting from stimulation of postsynaptic dopamine D-2 receptors.

Animals↗
PubMed1990

Enhanced anorectic potency of naloxone in rats sham feeding 30% sucrose: reversal by repeated naloxone administration.

The time-course of naloxone-anorexia was monitored in gastric-fistulated rats sham feeding sucrose (10%, 20%, 30%) solutions. Naloxone reduced sham intake dose dependently without affecting feeding initiation and in a manner which resembled the effects of progressive sucrose dilution. However, when rats sham fed 30% sucrose there was a 2-fold increase in the anorectic potency of naloxone. This exaggerated response was prevented by prior repeated naloxone treatment (5 mg/kg IP, bi-daily), concurrent with the stabilization of sham intake levels (4 days). A further experiment ruled out the possibility that tolerance develops to naloxone effects on this treatment schedule, since intact rats showed a suppression of wet mash consumption following repeated naloxone treatment which was equivalent to an acute naloxone challenge. It is proposed that 1) repeated sucrose sham feeding enhances opioid release and leads to opioid receptor adaptation (down-regulation); 2) repeated (chronic) naloxone treatments have an opposite effect on opioid receptors (up-regulation); 3) the two manipulations, in combination, counteract each other's effects. These behavioural data demonstrate dynamic changes in sham-feeding performance as a function of sucrose concentration and naloxone treatments, reinforce the importance of palatability in naloxone-anorexia, and support opioid involvement in orosensory reward.

Animals↗
PubMed1977

Feeding and drinking interactions after acute butyrophenone administration.

The effects on feeding and drinking of various doses of droperidol, haloperidol and spiroperidol were studied in a number of paradigms. All three buryrophenones produced generally similar effects. After food deprivation, feeding was slightly increased at low doses but was decreased at the higher doses; the concomitant postprandial drinking was attenuated at all doses. Desalivate rats showed a marked attenuation of feeding (and prandial drinking) at low doses, but when wet mash was given instead of pellets and water a normal dose-response relationship was obtained. After water deprivation drinking was attenuated at all doses, and when food was also available during the drinking test the food intake was decreased in proportion to the drinking. Drinking was blocked more when food was present than in its absence. Insulin and 2-deoxyglucose induced feeding in sated rats was attenuated but not abolished by haloperidol. The findings are discussed relative to the role of activation and brain catecholamines in feeding and drinking.

Animals↗
PubMed1987

Differential effects of CGS 8216 and naltrexone on ingestional behaviour.

Effects of the pyrazoloquinoline CGS 8216 (a partial benzodiazepine receptor inverse agonist) and the opiate antagonist, naltrexone, were compared in several tests of ingestion in non-deprived and deprived male rats. Both naltrexone (0.1-10.0 mg/kg, SC) and CGS 8216 (1.25-10.0 mg/kg, IP) significantly reduced the consumption of a highly palatable saccharin-glucose solution by non-deprived rats. Both compounds were also effective in reducing, dose-dependently, the intake of palatable sweet or oily mash by non-deprived animals. Hence, naltrexone and CGS 8216 attenuated palatability-induced ingestional responses, and sweet taste was not necessary for this effect to occur. The two drugs also reduced the intake of the saccharin-glucose solution in food-deprived rats, but their effects diverged in water-deprived animals. CGS 8216 had relatively little effect in the thirsty animals, whereas the effect of naltrexone was enhanced. This difference was underscored in a final test of deprivation-induced consumption of water. Naltrexone reduced the drinking, but CGS 8216 had no effect. Taken together, these data indicate that CGS 8216 was more selective in its effects on ingestion.

Animals↗
PubMed1992

The CCK-A receptor antagonist, devazepide, blocks the anorectic action of CCK but not peripheral serotonin in rats.

A role has been proposed for cholecystokinin (CCK)-A-type receptors in mediating the anorectic action produced by serotonergic stimulation in rats. We examined the effect of pretreatment with the CCK-A antagonist devazepide (DVZ) on anorexia produced by peripheral administration of serotonin [5-hydroxytryptamine (5-HT)] or CCK-8 in 3-h food-deprived rats consuming a 30-min test meal of sweetened mash. The anorectic effect of CCK-8 (4.0 nmol/kg, IP) was antagonized in a dose-dependent manner by DVZ (0.03, 0.10, and 0.30 mumol/kg, IP), with even the lowest dose producing a significant reversal. Under identical testing conditions, a supramaximal dose of DVZ (.75 mumol/kg) did not attenuate the reductions in food intake produced by either a moderate (4.0 mumol/kg) or a high dose (10.0 mumol/kg) of 5-HT. These data confirm established findings that the anorectic action of peripheral CCK depends upon CCK-A receptors. However, peripherally administered 5-HT reduces food intake independently of CCKergic function.

Animals↗
PubMed1993

Different effects of nucleus accumbens and ventrolateral striatal dopamine depletions on instrumental response selection in the rat.

This experiment was undertaken to investigate dopaminergic involvement in food-related instrumental behavior. Rats were tested in an operant chamber in which there was a choice between pressing a lever to receive a preferred food (Bioserve pellets) or feeding upon a less preferred food (lab chow). The lever-pressing schedule was a fixed ratio 5 (FR5). Rats usually pressed the lever at high rates to obtain the preferred food, and typically ate little of the lab chow even though it was freely available in the chamber concurrently with the lever-pressing schedule. The neurotoxic agent 6-hydroxydopamine was injected directly into the nucleus accumbens, medial striatum, or ventrolateral striatum to determine the effects of dopamine depletion on the performance of this task. Depletion of dopamine in the nucleus accumbens led to a dramatic shift in behavior in which there was a significant decrease in lever pressing but a significant increase in consumption of lab chow. The shift away from lever pressing and towards chow consumption in rats with accumbens DA depletions was significantly correlated with a decrease in spontaneous locomotor activity. Dopamine depletions in the medial striatum did not significantly affect lever pressing or chow consumption. Ventrolateral striatal dopamine depletions decreased lever pressing but also tended to reduce consumption of lab chow. Rats with ventrolateral striatal dopamine depletions also showed profound deficits in home-cage feeding, and these rats had to receive wet mash or tube feeding to maintain body weight.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗