Effects of consumption of edible oils for a period of 4 months on the ultrastructure of the aorta of spontaneously hypertensive rats.

Edible oils have different effects on lipid profiles and on the propensity for producing lipid peroxidation products. These two properties of edible oils can affect arterial structure, ultimately leading to atherosclerosis. Hypertension is said to be a predisposing factor for atherosclerosis and can accelerate its process. This paper investigates the effects of three edible oils, namely soya bean oil, palm oil and ghee, on the ultrastructure of the aortas of spontaneously hypertensive rats at the end of a 4 month feeding period. It was found that ghee produced significant structural changes to the aortic wall when compared with palm oil or soya bean oil, and that no noticeable structural differences were seen to occur on the aortas of the palm oil-fed and soya bean oil-fed groups of rats. This study suggests that the consumption of ghee, rather than palm or soya bean oil, is more likely to lead to the development of atherosclerosis.

Vitamin E levels in soleus muscles of experimentally induced hyperthyroid rats differ consequent to feeding of edible oils.

It has been shown that lipid peroxidation product levels in the soleus muscles of rats fed palm olein were lower than in the soleus muscles of rats fed soya bean oil. A study was carried out to test our hypothesis that the lower level of lipid peroxidation products in the soleus muscle of palm olein-fed rats is due, at least partly, to the higher amount of vitamin E in their soleus muscles. Experimentally induced hyperthyroid rats were fed either ground rat chow or ground rat chow mixed with palm olein oil or soya bean oil for a period of 8 weeks. Euthyroid rats fed ground rat chow for a similar period served as controls. At the end of the 8-week period, the rats were sacrificed and the α-tocopherol and tocotrienol levels in their soleus muscles were measured using high pressure liquid chromatography. It was found that the levels of α-tocopherol (23.682 ± 0.363), α-tocotrienol (1.974 ± 0.040) and γ-tocotrienol (1.418 ± 0.054) in µg/g tissue wet weight in the soleus muscles of hyperthyroid rats fed palm olein oil were statistically significantly higher than those found in the soleus muscles of hyperthyroid rats fed soya bean oil, which were 14.299 ± 0.378, 0.053 ± 0.053 and 0.184 ± 0.120µg/g tissue wet weight, respectively. The result shows that the increased level of a-tocopherol and tocotrienols found in the soleus muscles of hyperthyroid rats fed palm olein oil is responsible, at least partly, for the lower amount of lipid peroxidation products in these muscles compared with the soleus muscles of hyperthyroid rats fed soya bean oil in our earlier study.

Palm olein oil produces less lipid peroxidation products than soya bean oil.

The soleus muscles of hyperthyroid rats were used to investigate the effect of palm olein oil and soya bean oil on the production of lipid peroxidation products. It was found that palm olein oil but not soya bean oil significantly decreased malonaldehyde and conjugated diene levels of the soleus muscles of hyperthyroid rats. These findings suggest that palm olein per se produces less lipid peroxidation products than soya bean oil. Such an assay method gives a composite net picture of the propensity of an oil to produce lipid peroxidation products.

Serum lipids, lipid peroxidation and glutathione peroxidase activity in rats on long-term feeding with soybean oil or palm oil.

The atherogenic potential of soybean oil (Sb) and palm oil (PO) was compared by measuring lipid profile, lipid peroxidation (LP) and activity of the antioxidant enzyme glutathione peroxidase (GSHPx) in rat sera and liver and heart homogenates. Male Rattus norwegicus rats were fed a basal diet, or basal diet fortified with 20% weight/ weight Sb or PO for 4 or 9 months. There was no difference in high density lipoprotein cholesterol:low density lipoprotein cholesterol ratio between the two groups, but triglyceride concentrations were higher in the PO fed rats compared to the Sb fed rats, although the difference diminished after 9 months. No differences in serum LP and GSHPx activity were seen between the two groups. In the liver and heart, LP was lower in PO after 4 months feeding, but the reverse was seen after 9 months. Liver and heart GSHPx activity was higher in the PO group after both treatment periods. In conclusion, both PO and Sb fed rats appeared comparable in their lipid profile, but the PO food had a temporary beneficial effect on the LP process in liver and heart. GSHPx activity however did not correlate well with LP in liver and heart, suggesting involvement of other antioxidants.

Serum lipids, lipid peroxidation and glutathione peroxidase activity in rats on long-term feeding with coconut oil or butterfat (ghee).

We determined the relative atherogenicity of two saturated fats by studying their effects on lipid peroxidation (LP), by way of malonaldehyde (MDA) and conjugated dienes (CD) and glutathione peroxidase (GSHPx) activity in serum, liver and heart; and on serum lipid profile after 4 months and 9 months of feeding. Male Rattus norwegicus rats were fed a basal diet (control) or basal diet fortified with 20% weight/weight butterfat (ghee) (BF) or coconut oil (CO). Serum high-density-lipoprotein-cholesterol (HDL-chol) and HDL-chol:LDL-chol ratio was lower in the BF group compared to CO after both feeding periods. Conjugated dienes (CDs) were higher in the serum and liver after 4 months, and heart after 9 months, of the rats fed BF compared to CO. Serum low-density-lipoprotein-cholesterol (LDL-chol) was higher, but CD were lower at 9 months than at 4 months feeding for all three groups. Liver and heart MDA and CD were higher in both groups after 9 months compared to 4 months. Liver GSHPx activity was higher after 9 months compared to 4 months in the BF group. Heart GSHPx activity was lower after 9 months compared to 4 months for both BF and CO groups. In conclusion, BF is potentially more atherogenic than CO in terms of serum lipids and LP. The unfavourable responses in serum lipids, with the exception of triglycerides, and LP were exaggerated with the longer duration of feeding with both oils.

Serum lipids of castrated rats given hormonal replacement and fed diets with added soybean oil or palm oil.

The effects of castration with/ without testosterone replacement in male rats, and ovarectomy with oestrogen replacement in female rats, on serum lipids were studied. Simultaneous feeding with diets fortified with 20% weight/ weight (w/ w) soybean oil (Sb) or palm oil (P0) were done to determine the influence of these oils on serum lipids in castrated and sex hormone replaced rats. Two month old male and female Rattus norwegicus rats were given the above treatment for 4 months, and their sera assayed for lipid profile. Castration increased HDL-cholesterol (HDLchol) and total cholesterol (Tchol) concentrations. Testosterone or oestrogen replacement in male and female rats respectively increased HDLchol and decreased LDL-cholesterol (LDLchol) concentrations. Testosterone replacement also decreased Tchol concentration back to noncastrated levels, and reduced serum triglycerides (TG) to lower than non-castrated levels. Addition of Sb or P0 to the diet increased the LDLchol in the testosterone or oestrogen replaced male and female rats, but there was no difference between the two groups. P0 raised serum TG of the testosterone replaced group compared to control and Sb groups. In conclusion, testosterone and oestrogen were found to have favourable effects on serum lipids. Sb and P0 did not differ in their effects on lipoprotein cholesterol and Tchol, but P0 raised serum TG as compared to Sb.

The effects of propranolol on skeletal muscle contraction, lipid peroxidation products and antioxidant activity in experimental hyperthyroidism.

1. The mean levels of lipid peroxidation products, namely conjugated diene and malonaldehyde, were increased in the soleus muscles of hyperthyroid cats, while the mean glutathione peroxidase activity was decreased. No corresponding similar changes were noted in the fast extensor digitorum longus muscles and serum. 2. Propranolol administration prevented the increase in conjugated diene level in the soleus muscles of hyperthyroid cat but not the malonaldehyde level. It also prevented the reduction in glutathione peroxidase activity in the slow oxidative soleus muscles of hyperthyroid cats. 3. Maximal twitch tension, subtetanic tension and maximum tetanic tension of soleus and EDL muscles were reduced in hyperthyroid cats. Propranolol administration for 5 weeks to hyperthyroid cats did not prevent the reduction in tension of contractions of these muscles. 4. It is suggested that lipid peroxidation might not be responsible for the myopathy in hyperthyroidism and propranolol administration does not improve skeletal muscle function in hyperthyroid animals.

The effects of thyroxine treatment on slow- and fast-contracting skeletal muscle contractions of the cat and their cyclic AMP level.

1. The effects of thyroxine treatment on soleus and extensor digitorum longus (EDL) muscle contractions and their cyclic adenosine 3',5'-monophosphate (cyclic AMP) levels were examined in anaesthetized cats. 2. Thyroxine treatment decreased the tension of incomplete tetanic contractions of the soleus as well as the EDL muscles. The effect on tension of these muscles was not associated with an increase in the cyclic AMP level of the muscle as is the case with a beta 2-adrenoceptor agonist effect. 3. The results do not support the involvement of cyclic AMP in the tension depressant effect of thyroxine on contractions of skeletal muscle. 4. It is suggested that the muscle weakness and tremor observed in thyrotoxicosis and during administration of beta 2-adrenoceptor agonists are mediated by different mechanisms.

Effects of steroid hormones pretreatment on isoprenaline-induced cyclic adenosine 3',5'-monophosphate in rat lung.

1. Steroid hormones have been shown to regulate the concentration of adrenergic and muscarinic receptors in many tissues. 2. The cyclic adenosine 3',5'-monophosphate (cAMP) content in rat lung tissues in response to either dexamethasone, corticosterone, deoxycorticosterone or progesterone for 7 days were measured following intraperitoneal injection of isoprenaline just before sacrificed. 3. There was a significant increase in cAMP level (P less than 0.001) in dexamethasone and corticosterone-treated rats compared to controls that received isoprenaline alone. 4. Pretreatment with deoxycorticosterone and progesterone suppressed the increase in cAMP in response to isoprenaline. 5. The effect of glucocorticoids in causing bronchodilatation in asthmatic patients is partly due to the restoration of adenyl cyclase responsiveness to beta-agonist.

The effects of naloxone, dexamethasone, deoxycorticosterone and 17-hydroxyprogesterone on blood pressure responses of normal and adrenalectomized rats during hypovolaemic shock.

The roles of, and interactions between, steroids and naloxone, an opioid antagonist, in the reversal of experimental hypotensive shock were studied in normal and adrenalectomized rats. In normal rats treated with dexamethasone or deoxycorticosterone or 17-hydroxyprogesterone the hypotension and shock caused by 1% bodyweight and 2% bodyweight haemorrhage could be substantially reversed by naloxone in a dose-related manner. In contrast, the reversal of hypotension by naloxone was markedly less in adrenalectomized rats. It is concluded that there is a co-ordinate release of pressor catecholamines and depressor enkephalins from adrenal glands in hypovolaemic shock. Eventually, the use of naloxone would be of much less value in the treatment of hypotension or shock in patients with Addison's disease.

The effects of simultaneous atropine and labetalol administration on cardiovascular parameters during anticholinesterase poisoning in anaesthetized cat.

The effects of atropine administration during anticholinesterase poisoning on heart rate, blood pressure and electrocardiographic changes (ECG) were studied in the cat. Administration of atropine intravenously during anticholinesterase poisoning caused a significant increase in heart rate and blood pressure; ECG changes were also seen. The simultaneous intravenous administration of atropine and labetalol during anticholinesterase poisoning abolished the increase in blood pressure and heart rate; ECG readings remained normal. It is suggested that labetalol may be a useful adjuvant in the treatment of anticholinesterase poisoning especially in patients with compromised heart function.

The effect of corticosteroid pretreatment in vivo on the contraction of guinea-pig ileum and duodenum.

The effects of corticosteroid pretreatment on the contraction caused by acetylcholine or electrical stimulation of guinea-pig ileum and duodenum were studied. The acetylcholine dose-response curves for steroid pretreated ileum but not duodenum were significantly shifted to the right; evidence that pretreated ileum required higher dose of acetylcholine than normal to cause 50% maximal contraction. Naloxone enhanced the contraction of normal ileum caused by acetylcholine given at the dose of ED50, but not that of normal duodenum. The dose of morphine required to abolish electrically induced contraction was higher in steroid pretreated ileum than in normal ileum. Hence, corticosteroid pretreatment may affect intestinal contractility via opioidergic mechanisms which are found in the ileum but not in the duodenum.

The effects of 4-methyl-2-thiouracil on fibre type and cross-sectional area in the soleus muscle of the rat.

The effects of 4-methyl-2-thiouracil (MTU, 0.1% in drinking water) on the composition and cross-sectional area of muscle fibres of the rat soleus muscle were studied. The percentage of fast twitch-oxidative-glycolytic (FOG) fibres fell after 2 weeks of treatment with MTU to zero at 8 weeks. In contrast the percentage of FOG fibres in untreated animals fell to 19.2 +/- 2.1% during this period. The mean cross-sectional area of FOG and slow twitch-oxidative (SO) fibres were respectively 39.9% and 23.8% smaller than those of their respective controls 6 weeks after treatment. At 8 weeks the percentage reduction of SO fibre area was 26.8% of the control value. This study indicates that MTU treatment causes atrophy and redistribution of fibre type in the soleus muscle.

Further evidence of the role of cyclic AMP as a mediator of the depressant effects of beta-adrenoceptor agonists and phosphodiesterase inhibitors on slow-contracting mammalian skeletal muscles.

The depressant effects of beta-adrenoceptor agonists and phosphodiesterase inhibitors on contractions of slow-contracting mammalian skeletal muscles are associated with increased muscular cyclic AMP levels. A strong correlation was found to exist between the percentage depression of contraction and the percentage increase in cyclic AMP level, irrespective of the drug used and regardless of the mechanism of cyclic AMP production. The results strongly support the mediatory role of cyclic AMP in the depressant effects of beta-adrenoceptor agonists and phosphodiesterase inhibitors on slow-contracting mammalian skeletal muscle contractions.

Effects of thyroxine treatment on contractions of soleus muscles of anaesthetized cats.

The effects of chronic thyroxine treatment on cat soleus muscle contractions were studied. Maximum twitch tension, contraction time, half relaxation time and tension-time integral of maximal twitches of the soleus muscles of thyroxine treated cats were significantly decreased. Consequently, there was a decrease in tension and degree of fusion of incomplete tetanic contractions of the soleus muscle. The maximum tetanic tension was not statistically significantly changed, suggesting that the effects may be due to a decrease in the duration of the active state of the muscle. Isoprenaline given intravenously during incomplete tetanic contractions of the soleus muscle caused a statistically significant depression of tension in the control group but not in the thyroxine treated group. This further suggests reduction in the duration of the active state of soleus muscles of thyroxine treated cats. Propranolol injected chronically with thyroxine reversed or prevented the depression of tension caused by thyroxine treatment, suggesting the involvement of beta-adrenoceptors in these effects. The decrease in tension and degree of fusion during incomplete tetanic contractions of the thyroxine treated soleus could be responsible, at least partly, for the muscle weakness and tremor of thyrotoxicosis. Cyclic AMP may possibly be the mediator of these effects.

Effects of increasing the frequency of twitches and of isoprenaline on maximal twitches and cyclic AMP levels in slow- and fast-contracting cat skeletal muscles.

Increasing the frequency of twitches and treatment with isoprenaline have been compared for effects on twitch tension, tension-time integral and cyclic adenosine 3', 5'-monophosphate (cyclic AMP) levels in the slow-contracting soleus muscle of cats, anaesthetized with chloralose and pentobarbitone. The effect of change in frequency of contractions on cyclic AMP in the fast-contracting extensor digitorum longus muscle was also examined. Although both isoprenaline and increasing the frequency of contractions depressed twitch tension in the soleus, only isoprenaline enhanced cyclic AMP levels. The effects of isoprenaline were independent of the existing frequency of contractions of the muscle. Increasing the frequency of contractions enhanced twitches in the extensor digitorum longus muscle but did not change cyclic AMP levels. It is concluded that cyclic AMP may mediate effects of beta-adrenoceptor agonists but not those caused by increasing the frequency of contractions on slow- or fast-contracting skeletal muscles.

Effects of alpha- and beta-adrenoceptor agonists and a phosphodiesterase inhibitor (ICI 63 197) on cyclic AMP and GMP levels in bovine splenic nerve.

1. Cyclic AMP and cyclic GMP levels were determined in bovine splenic nerve segments in the absence and presence of (+/-)-isoprenaline, (-)-phenylephrine, clonidine and ICI 63 197 (a phosphodiesterase inhibitor). The chosen concentrations of adrenoceptor agonists were those which are known to affect stimulation-induced overflow of noradrenaline from nerve terminals. 2. The mean levels of cyclic AMP ranged from 229 to 555 pmol/g of microwave irradiated tissue. Mean cyclic GMP levels ranged from 27.9 to 42.2 pmol/g. 3. Isoprenaline enhanced cyclic AMP levels but did not affect cyclic GMP levels. The effect was blocked with (+/-)-propranolol. ICI 63 197 increased cyclic AMP levels but did not change cyclic GMP. Phenylephrine and clonidine caused no consistent changes in cyclic AMP or cyclic GMP levels or in the concentration ratio between these two nucleotides. 4. The results support the involvement of cyclic AMP in the enhancing effect of beta-adrenoceptor agonists and phosphodiesterase inhibitors on stimulation-induced release of noradrenaline from sympathetic nerves.

A study of the incidence of Vibrio parahaemolyticus in Malaysian shrimp undergoing processing for export.

The incidence of Vibrio parahaemolyticus in products of the Malaysian export shrimp processing industry was investigated through the stages from the catch to that of the cooked, peeled and frozen product. The organism was commonly found in freshly caught and landed shrimp, and could be detected by enrichment culture at all stages of processing. The number of V. parahaemolyticus in shrimp varied from nil to 4x10(4), and 19 of the 50 serotypes in the current antigenic scheme were found, O1-K38 and O1-K32 occurring most often. All the isolates were Kanagawa-negative; one strain was a sucrose-positive variant. The study indicated that specifications of 10(2) g-1 for V. parahaemolyticus in raw tropical shellfish are too stringent but that the Malaysian shrimp industry should be able to meet this requirement for cooked shrimp.

Effects of isoprenaline, levodopa and a phosphodiesterase inhibitor (ICI 63,197) on cyclic AMP levels and contractions of soleus muscles in anesthetized cats.

1. Cyclic AMP levels have been determined in the soleus muscles of anaesthetized cats in the absence of drugs, and during depression of incomplete tetanic contractions produced by (-)-isoprenaline, ICI 63,197 (a phosphodiesterase inhibitor) or levodopa. 2. Cyclic AMP levels were elevated at the peak of tension depression produced by isoprenaline. Effects of isoprenaline on cyclic AMP and on contractions were dose dependent and statistically significantly related one to the other. Both effects were blocked by propranolol. 3. ICI 63,197 and levodopa produced isoprenaline-like effects on contractions but times to peak effect and recovery were longer. Cyclic AMP levels estimated during the depressant action were elevated. 4. The results support the involvement of cyclic AMP in the depressant effect of beta-adrenoreceptor agonists on slow-contracting mammalian skeletal muscle.