Blood pressure depression by the fruit juice of Carica papaya (L.) in renal and DOCA-induced hypertension in the rat

A crude ethanol extract was prepared from the unripened fruit of Carica papaya. Lethality studies showed a dose-mortality relationship with an LD(50) of 325.2 mg/kg in mice administered i.p. Male albino Wistar rats were randomly divided into three batches (15 rats per batch)-renal, DOCA-salt hypertensives and normotensives. Each batch was further divided into three groups-the untreated, hydrallazine and extract treated groups. The mean arterial blood pressure (MAP) and the heart rate were measured in all groups. From the results, the basal (control) MAP were 93.8 +/- 4.5, 175.2 +/- 5. 1 and 181.3 +/- 6.2 mmHg in the normotensive, renal and DOCA-salt hypertensives, respectively. Both hydrallazine (200 microg/100 g i. v) and extract (20 mg/kg.i.v) produced a significant depression of MAP in all groups (p < 0.01 vs controls), but the extract produced about 28% more depression of MAP than hydrallazine in the hypertensive groups. In another group of rats, the extract failed to depress the MAP in rats pretreated with propranolol, but atropine and noradrenaline pretreatment did not prevent the action of the extract on blood pressure. In vitro studies using isolated rabbit arterial (aorta, renal and vertebral) strips showed that the extract (10 microg/mL) produced relaxation of vascular muscle tone which was, however, attenuated by phentolamine (0.5-1.5 microg/mL). It is concluded that the fruit juice of C. papaya probably contains antihypertensive agent(s) which exhibits mainly alpha-adrenoceptor activity.

Pharmacological investigation of oedema induced by venom from the wasp Polistes fuscatus

Subplantar injection of Polistes fuscatus venom induced dose-dependent rat hindpaw oedema. The oedema was significant in the first hour and reached maximum size in the fifth hour after injection of the venom (20-600 micrograms/paw). Low doses of the venom (20-80 micrograms/paw) produced oedema which disappeared within 48 hr after injection, while at doses of 300-600 micrograms/paw, oedema was present in excess of 48 hr. Pharmacological studies suggested that P. fuscatus venom-induced oedema probably has a mechanism which is multimediated. Pretreatment of rats with a combination of cyproheptadine (5 mg/kg)-captopril (2 mg/kg)-dexamethasone (1 mg/kg) inhibited the formation of oedema (maximal swelling) produced by the venom (300 micrograms/paw) by about 79% and improved the time to recovery. Paw swellings caused by 20 and 40 micrograms/paw venom were completely eliminated by the same doses of this drug combination. The kinins, autacoids (histamine and serotonin) and lipogenase derivatives are probably involved in the venom-induced oedema.

Cardiovascular effects of an extract from the roots of a shrub Elaeophorbia drupifera

A crude extract was prepared from the roots of E. drupifera. Lethality studies in mice showed a dose-mortality relationship with an LD(50) of 145 mg/kg mice i.p. The extract (2-260 microg/kg. i.v.) was tested in graded doses on the blood pressure and heart rate of urethane anaesthetized rats. The results showed that the extract decreased both the blood pressure and heart rate in a dose-dependent manner. The maximum decrease in blood pressure (control, 78.3 +/- 6. 5 mmHg) and heart rate (control, 120.2 +/- 5.5 beats/min) produced by the extract was about 46.2% and 41.7% (% control), respectively. Blocking the beta adrenoceptors with propranolol (0.5 microg/kg. i.v. ) did not prevent the action of the extract on both the blood pressure and heart rate, suggesting that the extract was acting at a different site. This view was supported by the observation that the extract significantly depressed the increase in blood pressure and heart rate caused by bilateral occlusion of the common carotid artery. Also, the extract was found to prolong ACh-induced hypotension in the rats. In animals pretreated with atropine sulphate (0.2 mg/kg. i.v), the extract was less effective in depressing the blood pressure. However, this atropine antagonism was surmounted by raising the concentration of the extract. Finally, in vitro studies using isolated arterial strips revealed that the extract also had a relaxant effect on vascular smooth muscle. This relaxant effect was dose-dependent and was attenuated and/or abolished by phentolamine (0.5 microg/mL). Also, the extract relaxed aortic strips precontracted with noradrenaline (1 x 10(-7) mol L(-1)) but failed to relax strips precontracted with KCl (50 mmol/L). We conclude that the crude extract from the roots of E. drupifera probably contains acetylcholine-like agent(s) which interferes with the cholinergic mechanism, as well as catecholamine-like agent(s) exhibiting mainly alpha-adrenoceptor activity.

Biological properties of a venom extract from the sea anemone, Bunodosoma cavernata

Crude extract was prepared from the sea anemone, Bunodosoma cavernata. The protein content of the extract was estimated to be 0.52 mg protein/ml. The extract was standardized based on the percentage inhibition of histamine-induced contraction of the guinea pig ileum, to determine the biological unit of activity (AU) of the extract. As extracts prepared on different occasions lost potency on storage, the stability of the extract was also investigated. Extracts prepared from fresh animals were about 15% more potent than those prepared from freeze-dried animals. However, freeze-dried animal extracts maintained their potency for about 6 months under storage at -20 degrees C. Lethality studies gave an LD50 of 40 microg protein/kg mice i.p. Also, the crude extract dose-dependently hemolyzed human erythrocytes at room temperature. This activity was favoured by higher temperatures, which peaked at about 60degrees C, and by pH in the alkaline range. We conclude that the crude extract from B. cavernata, though highly toxic, may also contain some biologically active agents which include a haemolytic factor and antihistamine(s), as indicated by its histamine-blocking action.

Increased plasma total cholesterol and high density lipoprotein levels produced by the crude extract from the leaves of Viscum album (mistletoe)

The effect of an aqueous extract prepared from the leaves of Viscum album (Mistletoe) on plasma cholesterol and albumin levels in male Wistar rats was studied. Lethality studies revealed that the extract had an LD50 value of 417.0 mg/kg mice, intraperitoneally. The rats were randomly divided into seven (7) groups of 5 rats per group with one animal per metabolic cage. Group one served as the control (C1), groups two to six were treated with extract (200 mg/kg body weight orally and daily) for a maximum of ten (10) weeks, whereas, group seven (C2) received no extract treatment but was fed on normal rat chow. All the rats had free access to rat food and drinking water. The first group (C1) was sacrificed a fortnight after the commencement of the experiment, while group seven (C2) was sacrificed at the end (10th week) of the experiment. The extract-treated groups were sacrificed respectively in the order two, four, six, eight and ten week of extract administration. Whole blood was collected from these groups for analysis. Results showed significant [P < 0.01] increases in the level of total cholesterol (TC) from 1.92 +/- 0.11 mMol/L to 2.59 +/- 0.02 mMol/L (about 35% increase) and high-density lipoproteins (HDL) from 0.95 +/- 0.02 mMol/L to 1.50 +/- 0.08 mMol/L (about 58.50% increase) at week ten. The LDL levels, the total protein and albumin levels did not show any significant change from the control values. From the results, it is suggested that the crude aqueous extract from mistletoe leaf may be relatively safe for therapeutic use as it neither predisposes to cardiovascular risk nor adversely affects protein metabolism following prolonged period of administration.

Gastric acid anti-secretory, anti-ulcerogenic and mucogenic effects of aqueous leaves' extract of Ocimum gratissimum in rats

In this study, albino Wistar rats were placed on normal rats chow + drinking water and/or 500mg/kg, 1000mg/kg body weight of the Ocimum gratissimum extract orally, once daily for 28 days and gastric acid, mucus and ulcers determined. All the rats received normal rat chow + drinking water ad libitum for 28 days. Gastric acid, mucus secretion and ulcer scores were determined with standard procedures. Results showed that the mean basal gastric acid output for control, low dose and high dose groups were 11.28 ± 0.70, 8.04 ± 0.57 and 6.14 ± 0.67 µmol/hr respectively. The high dose extract recipients had a significantly reduced gastric acid output compared with control and low dose. Increase in gastric acid output as induced by histamine was highest in high dose (599.02%), followed by low dose 426.28%, then control (221.28%). Administration of ranitidine was observed to attenuate the effect of histamine in all the groups. The high dose group also had a significantly higher mean gastric mucus and lower ulcer levels compared with other groups. In conclusion, the aqueous leaves extract of Ocimum gratissimum decrease gastric acid secretion and ulceration, it also produced an increase in the gastric mucus secretion. If these results are applied to man, it could be beneficial in the management of peptic ulcers and other related complications.

Changes in blood pressure in the rat induced by the venom extract from a sea anemone-Bunodosoma cavernata

The effect of graded doses of crude sea anemone extract from Bunodosoma cavernata on rat blood pressure was investigated with a view to accessing its effects on the status of the cardiovascular system. From the results, the extract (2-8 ug protein/kg, i.v.) caused only transient hypotension. With higher doses of the extract (10-20 ug protein/kg, i.v.), the transient hypotension was accompanied by a dose-dependent increase in blood pressure. Atropine, mepyramine and propranolol failed to affect the transient hypotension. Of these drugs, only propranolol decreased the extract-induced hypertension. Doses of the extract above 20 ug protein/kg, i.v. produced a decrease in pulse rate and an increase in pulse pressure. We suggest that the extract-induced transient hypotension could be due to the presence of a less potent agent in the extract with acetylcholine-like action, and the hypertensive action of the extract was probably due to the stimulation of the sympathetic division of the autonomic nervous system by agent(s) in the extract.

The epidemiology of Plasmodium falciparum malaria in two Cameroonian villages: Simbok and Etoa

In support of ongoing immunologic studies on immunity to Plasmodium falciparum, demographic, entomologic, parasitologic, and clinical studies were conducted in two Cameroonian villages located 3 km apart. Simbok (population = 907) has pools of water present year round that provide breeding sites for Anopheles gambiae, whereas Etoa (population = 485) has swampy areas that dry up annually in which A. funestus breed. Results showed that individuals in Simbok receive an estimated 1.9 and 1.2 infectious bites per night in the wet and dry season, respectively, whereas individuals in Etoa receive 2.4 and 0.4 infectious bites per night, respectively. Although transmission patterns differ, the rate of acquisition of immunity to malaria appears to be similar in both villages. A prevalence of 50-75% was found in children < 10 years old, variable levels in children 11-15 years old, and 31% in adults. Thus, as reported in other parts of Africa, individuals exposed to continuous transmission of P. falciparum slowly acquired significant, but not complete, immunity.

Stimulation of insulin secretion by Viscum album (mistletoe) leaf extract in streptozotocin-induced diabetic rats

Twenty male white rats (250-300 g) of Wistar strain were randomly divided into two batches, the normoglycaemic batch and the streptozotocin-induced diabetic batch often rats each. Animals in each batch were further divided into two groups of five rats per group. After an overnight fast (12 hrs), animals in each group received D-glucose load (2.0 g/kg.i.v) under pentobarbital anaesthesia, with or without the crude extract (100 mg/kg/iv). Blood samples were collected intravenously at 15 min intervals for 3 hrs. for analysis of glucose, insulin and glucagon levels. From the results, the extract (100 mg/kg) did not appear to have any significant effect on the blood glucose level of normal rats, but produced about 35.3% decrease in the diabetic rats. Despite the apparent lack of action on glucose level of normal rats, the extract stimulated insulin secretion by about 92.9% (% control) in this group, and about 81.5% in the diabetic group (% control). The glucagon level was not altered by the extract in the normal rats. In the diabetic group, there was mild but significant suppression ofglucagon level after the first 1 hr. which lasted for about 50 min. We suggest that this extract from V. album leaves may possess antihyperglycaemic, insulinotropic, and possibly, mild glucagonostatic agent(s) and may therefore be a candidate for the anti-diabetic drugs.