R.C. Srimal

Enhancement of wound healing by curcumin in animals

Tissue repair and wound healing are complex processes that involve inflammation, granulation, and remodeling of the tissue. In this study, we evaluated the in vivo effects of curcumin (difeurloylmethane), a natural product obtained from the rhizomes of Curcuma longa on wound healing in rats and guinea pigs. We observed faster wound closure of punch wounds in curcumin‐treated animals in comparison with untreated controls. Biopsies of the wound showed reepithelialization of the epidermis and increased migration of various cells including myofibroblasts, fibroblasts, and macrophages in the wound bed. Multiple areas within the dermis showed extensive neovascularization, and Massons Trichrome staining showed greater collagen deposition in curcumin‐treated wounds. Immunohistochemical localization of transforming growth factor‐β1 showed an increase in curcumin‐treated wounds as compared with untreated wounds. In situ hybridization and polymerase chain reaction analysis also showed an increase in the mRNA transcripts of transforming growth factor‐β1 and fibronectin in curcumin‐treated wounds. Because transforming growth factor‐β1 is known to enhance wound healing, it may be possible that transforming growth factor‐β1 plays an important role in the enhancement of wound healing by curcumin.

Effect of alcohols on the permeability of blood-brain barrier.

Effect of alcohols on the permeability of blood-brain barrier was studied in anaesthetised dogs using sodium fluorescein as circulant. Entry of sodium fluorescein in the cerebrospinal fluid (CSF) was measured spectrophotofluorometrically. Methyl, ethyl, propyl and butyl alcohols were used in the study. Methyl alcohol did not increase the entry of sodium fluorescein in CSF compared to control. However, ethyl, propyl and butyl alcohols significantly increased the entry of sodium fluorescein. The increase was dependent upon the length of alkyl chain of alcohols. Longer was the aliphatic chain more marked was the effect. The increase in permeability was also dependent upon the concentration of the alcohol. Thus 90% ethyl alcohol was more effective than 30% and this effect was concentration-dependent. The increase in permeability of blood-brain barrier could be correlated to the lipid solubility of alcohols.

Role of free radicals in pulmonary thromboembolism in mice

Involvement of free radicals and their scavenging enzymes in mice pulmonary thromboembolism, induced by intravenous infusion of collagen and adrenaline, has been studied. Malonaldehyde (MDA) and activities of xanthine oxidase (XO), catalase (CAT) and superoxide dismutase (SOD) were estimated in platelets, heart and lung homogenates. MDA increased in all the tissues sharply, while animals showed 70-80% thrombocytopenia. Xanthine oxidase activity in these animals increase significantly in heart. However, increased SOD activity and decreased catalase activity was observed in platelets. Intravenous administration of superoxide dismutase (5 mg/kg), catalase (5 mg/kg) and mannitol (200 mg/kg) protected the mice against pulmonary thromboembolism. The importance of free radicals in mice pulmonary thromboembolism has been demonstrated.

Alterations in free radical scavenging mechanisms following blood-brain barrier disruption

It has been reported earlier that rat microvessels which constitute the blood-brain barrier (BBB) are rich in free radical scavenging enzymes. In the present investigation, BBB of rat was disrupted by intravenous infusion of the hypertonic saline and changes in enzymes--namely, superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and glutathione reductase (GR)--were evaluated in the brain microvessels at 30 min after the intravenous administration of hypertonic saline, being the time of peak effect. There was a significant increase in the activities of CAT (40%), GPx (26%), and SOD (16%) over the control values. In addition, within 90 min BBB was found to be reestablished and the levels of enzymes reverted to normal. Malondialdehyde (MDA) levels and activity of lactate dehydrogenase (LDH) remained unaltered during and following disruption, suggesting that there was no change in the membrane lipid environment. Similarly, there was no cell lysis. The results suggest that the disruption of BBB following hypertonic saline administration might be due to an increase in the generation of free radicals in the brain microvessels.

Immunomodulation by morphine in Plasmodium berghei-infected mice.

The effect of morphine on immunomodulation and host defense have been investigated during Plasmodium berghei infection in BALB/c mice. A single low (5.0 mg/kg) subcutaneous dose of morphine strongly suppressed (sometimes completely eliminated) the parasitaemia, whereas a high dose (80.0 mg/kg) exerted mild potentiating effect. Mice treated with the low dose showed a significant (p < 0.05) increase in the total number of circulating leukocytes, the number (pool-size) of peritoneal macrophages, and the phagocytic activity of peritoneal macrophages, in vitro. Conversely, in mice treated with the high dose, all these parameters were diminished. Silica (3.0 mg/mouse), administered intravenously, abrogated the morphine-induced protective effects but did not affect its potentiation of the infection. Naloxone pretreatment (4.0 mg/kg) completely blocked the protective effects of morphine, suggesting the mediation via naloxone-sensitive opiate-receptors; paradoxically, it did not affect the potentiating effects. These observations indicate that morphine exerted a dose-dependent, biphasic effect on the course of P. berghei infection in mice, apparently by modulating the macrophage-mediated protective mechanisms.

Analysis of histamine receptors in the central thermoregulatory mechanism of Mastomys natalensis.

1 The effect of intracerebroventricular (i.c.v.) injection of histamine on the rectal temperature of Mastomys natalensis at ambient temperatures of 10, 24 and 33°C has been studied. 2 Low doses (0.1–1.0 μg) of histamine produced hypothermia while larger doses (5–20 μg) produced dose‐dependent hyperthermia. The hypothermic effect was significantly antagonized by mepyramine while the hyperthermia was blocked by cimetidine. 3 Histamine H1‐receptor agonists, 2‐methyl‐histamine and 2‐pyridyl‐ethylamine, also produced hypothermia which could be blocked by mepyramine. 4 Histamine H2‐receptor agonists, impromidine and dimaprit, produced hyperthermia which was antagonized by cimetidine. 5 Pretreatment of the animals with a β‐adrenoceptor antagonist, MJ1999, did not affect the response to histamine. 6 The hyperthermic effect of histamine (10 μg) was most marked at 10°C and was attenuated at 33°C. 7 It is concluded that both H1‐ and H2‐histamine receptors are present in the brain of Mastomys. The H1‐receptors mediate hypothermia and H2‐receptors hyperthermia.

EFFECT OF CLONIDINE ON THE EXCITABILITY OF VASOMOTOR LOCI IN THE CAT

1 The effect of clonidine on the direct excitability of hypothalamic, medullary and spinal vasomotor loci has been investigated in cats anaesthetized with chloralose. 2 Clonidine inhibited the excitability of these loci when it was localized to the central sites by intracerebroventricular, intravertebral arterial or intrathecal injection in very low doses (1‐2 μg). 3 Topical application of clonidine (0.01% and 1.0%) to the floor of the fourth ventricle inhibited pressor responses evoked either by stimulation of medullary or hypothalamic vasomotor areas. Inhibition of the pressor responses was accompanied by hypotension and bradycardia in many experiments. 4 It appears that effects of clonidine on the vasomotor loci of the medulla oblongata and the spinal cord contribute to its hypotensive action.

On the mechanism of potentiation of apomorphine-induced stereotypy due to electroconvulsive shock

Electroconvulsive shock-induced changes in the intensity of stereotype induced by apomorphine, the binding of [3H]spiroperidol in the corpus striatum, the accumulation of [3H]dopamine in brain and the permeability of the blood-brain barrier, were monitored in rats 30 min after single, or 24 hr after chronic (once daily for 7 days) electroconvulsive shock. There was significant potentiation in stereotypy induced by apomorphine after chronic electroconvulsive shock. The binding of [3H]spiroperidol did not show any change in the affinity (Kd) or density (Bmax) of receptors in the striatum after acute or chronic electroconvulsive shock. The accumulation of dopamine increased significantly in the hypothalamus after acute electroconvulsive shock and in the corpus striatum and hypothalamus after chronic electroconvulsive shock. A significant increase in the entry of sodium fluorescein into the hypothalamus occurred after acute electroconvulsive shock; it increased in all the regions of the brain after chronic electroconvulsive shock. Alteration in the blood-brain barrier (BBB) by electroconvulsive shock leading to increased accumulation of dopamine in the corpus striatum may be responsible for the potentiation of stereotypy.

Status of antioxidants in brain microvessels of monkey and rat

Levels of certain antioxidants namely reduced glutathione (GSH), ascorbic acid (Vit C), alpha-tocopherol (Vit E) and antioxidant enzymes, superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and glutathione reductase (GR) were compared in monkey and rat brain microvessels which constitute the blood-brain barrier (BBB). The BBB of both the species contains appreciable amounts of the antioxidants to protect against oxidative damage. The level of protection in rat seems to be more efficient than monkey since rat microvessels contain higher concentrations of some of the bio-antioxidants. The comparative status of enzymatic and non-enzymatic protective system against oxidation in the brain microvessels has been discussed.

Effect of varying concentration of ethanol on systemic hemodynamics and regional circulation

The effect of ethanol (0.5 g/kg, IV) at different concentrations (30%, 60%, and 90%) was studied in male cats using radioactive microspheres on systemic hemodynamics and regional circulation. Ethanol produced a significant fall in systolic, diastolic and mean blood pressure. A significant reduction in heart rate, left ventricular work, cardiac output and total peripheral resistance was also observed. No change occurred in stroke volume. A significant decrease in blood flow to left ventricle, right ventricle and interventricular septum was observed, but the vascular resistance of these regions was unaltered. Brain blood flow was not affected by various concentrations of ethanol. The vascular resistance significantly decreased in spinal cord, medulla, pons, midbrain, hypothalamus, thalamus, caudate nucleus, cerebellum and cortex. The average brain blood flow (ml/min/100 g) was 35.63 in control, 37.17 in 30%, 35.56 in 60% and 35.05 in 90% ethanol-treated cats. Spleen, liver, pancreas, gastrointestinal tract, skin, muscle and bone did not show any significant change in the blood flow, while vascular resistance following ethanol treatment. The blood passing through the arteriovenous shunts was significantly decreased by ethanol. It is concluded that ethanol produces marked cardiovascular changes which are not affected by varying the concentration of ethanol.