Antagonism of stimulation-produced analgesia by naloxone and N-methyl-D-aspartate: role of opioid and N-methyl-D-aspartate receptors

The present study aims to investigate the influence of electrical stimulation of periaqueductal gray (PAG) following peripheral nerve injury and its modulation by naloxone and N-methyl-D-aspartate (NMDA). Chronic neuropathic pain was induced by chronic constriction injury of the sciatic nerve, and subsequently a cannula was implanted in the PAG area for the purpose of electrical stimulation and intra-PAG drug administration. Intra-PAG administration of morphine, ketamine, and their combination were found to elicit antinociceptive response on hot-plate test. Electrical stimulation of PAG was also observed to demonstrate decreased pain response on hot-plate test, and this effect was reversed by the administration of naloxone, NMDA, and their combination, when injected into the PAG area. These findings suggest that apart from the opioid receptors, probably NMDA receptors also have a role to play in stimulation-produced analgesia.

Effect of flaring of natural gas in oil fields of Assam on rice cultivation

Assam (India) is endowed with natural resources like oil, coal and natural gas. The crude oil, one of the most precious natural resources, is found in the districts of upper Assam. During the process of extraction of crude oil, low-pressure natural gas is burnt in the air. Most of the oil wells in upper Assam are located near rice fields and therefore, rice crop grown near the oil wells is exposed to light uninterruptedly causing grain sterility resulting significant loss in grain yield. To identify promising varieties for these areas, we studied the effect of flare on rice varieties with different photoperiod sensitivity. The high light intensity and increased light hours were the factors responsible for substantial loss in grain yield near the flare resulting from delay in flower initiation, reduction of panicle length, having less number of grains per panicle and more grain sterility. To prevent significant loss in yield, photoperiod-sensitive traditional and improved rice varieties should not be grown up to the distance of 80 and 100 m, respectively from the boundary wall of the flare pit. Modern weakly-photoperiod sensitive varieties like Ranjti and Mahsuri can be grown 40 m away from the wall while modern photoperiod insensitive variety like Jaya, can be cultivated 20 m away from the wall without significant loss in yield.

Persistence and safety risk assessment of propineb in Indian tea

A supervised field trial was conducted on tea with propineb at 1,750 and 3,500 g a.i./ha at two locations (Assam and Darjeeling), applied thrice at an interval of 10 days during the year 2006-2007. Propineb residue was measured spectrophotometrically at 435 nm in terms of CS2. The initial deposit of propineb in green tea leaves were found to be in the range of 16.26-35.96 mg/kg and the residue persisted up to 10 days irrespective of doses and locations with half-life value ranging from 2.24 to 2.43 days and preharvest interval of 17.17-21.37 days. Made tea residues ranged from 9.27 to 20.86 mg kg(-1) on 7 days and no residues could be detected on 14 days. Infusion study indicated that propineb did not infuse into tea liquor from made tea. The limit of determination was found to be 0.1 mg kg(-1) in terms of propineb for green tea leaves, made tea, and tea liquor. The tea applied with the recommended dose of propineb is safe for consumption as liquor.

Potassium channel openers exhibit cross-tolerance with morphine in two experimental models of pain

OBJECTIVE

The study was performed to assess the effect of potassium channel openers on morphine tolerance and vice-versa.

METHODS

Swiss albino mice of either gender weighing between 25-30 g were used for the study The study assesses the effect of potassium channel openers (cromakalim, diazoxide and minoxidil) on morphine tolerance and vice-versa, using formalin and tail-flick tests.

RESULTS

The antinociceptive effect of cromakalim and minoxidil was significantly reduced when administered to morphine-tolerant mice, in both the behavioural tests. However reduced analgesic effect of diazoxide was observed on morphine-tolerance in the formalin test but not in the tail-flick test. Tolerance was observed when morphine was administered to animals chronically treated with any of the potassium channel openers. The same effect was observed when morphine was injected into a group treated with a combination of morphine and any of the potassium channel openers.

CONCLUSIONS

This study, therefore, suggests that both morphine and potassium channel openers are cross-tolerant. However such interaction occurs at the level of potassium channels rather than at the level of receptors.

The mechanism of HIV-1 Tat-directed nucleic acid annealing supports its role in reverse transcription

The main function of the HIV-1 trans-activator of transcription (Tat protein) is to promote the transcription of the proviral DNA by the host RNA polymerase which leads to the synthesis of large quantities of the full length viral RNA. Tat is also thought to be involved in the reverse transcription (RTion) reaction by a still unknown mechanism. The recently reported nucleic acid annealing activity of Tat might explain, at least in part, its role in RTion. To further investigate this possibility, we carried out a fluorescence study on the mechanism by which the full length Tat protein (Tat(1-86)) and the basic peptide (44-61) direct the annealing of complementary viral DNA sequences representing the HIV-1 transactivation response element TAR, named dTAR and cTAR, essential for the early steps of RTion. Though both Tat(1-86) and the Tat(44-61) peptide were unable to melt the lower half of the cTAR stem, they strongly promoted cTAR/dTAR annealing through non-specific attraction between the peptide-bound oligonucleotides. Using cTAR and dTAR mutants, this Tat promoted-annealing was found to be nucleated through the thermally frayed 3'/5' termini, resulting in an intermediate with 12 intermolecular base pairs, which then converts into the final extended duplex. Moreover, we found that Tat(1-86) was as efficient as the nucleocapsid protein NCp7, a major nucleic acid chaperone of HIV-1, in promoting cTAR/dTAR annealing, and could act cooperatively with NCp7 during the annealing reaction. Taken together, our data are consistent with a role of Tat in the stimulation of the obligatory strand transfers during viral DNA synthesis by reverse transcriptase.

Lorazepam versus diazepam-phenytoin combination in the treatment of convulsive status epilepticus in children: a randomized controlled trial

BACKGROUND

Convulsive status epilepticus demands urgent and appropriate management with anticonvulsants. Intravenous diazepam is an established drug in the management of convulsive status epilepticus in adults as well as in children. The efficacy of intravenous lorazepam has not been well established in children.

OBJECTIVE

To determine whether intravenous lorazepam is as efficacious as diazepam-phenytoin combination in the treatment of convulsive status epilepticus in children.

STUDY DESIGN

Randomized controlled trial.

METHODS

A total of 178 children were enrolled in the study; 90 in the lorazepam group and 88 in the diazepam-phenytoin combination group. Enrolled subjects were between 1 and 12 years with a clinical diagnosis of convulsive status epilepticus, presenting in pediatric emergency of a tertiary care hospital. They were randomized to receive either intravenous lorazepam (0.1 mg/kg) or intravenous diazepam (0.2 mg/kg)-phenytoin (18 mg/kg) combination at admission and were followed up for subsequent 18 h.

RESULTS

The overall success rate of therapy was 100% in both the groups. There was no statistically significant difference in the two groups (lorazepam versus diazepam-phenytoin combination) in the median time taken to stop the seizure [20s in both groups], the number of subjects requiring more than one dose of the study drug to stop the presenting seizure [lorazepam 6(6.7%) versus diazepam-phenytoin combination: 14 (15.9%); adjusted RR (95% CI)=0.377 (0.377, 1.046); P=0.061] and the number (%) of patients having respiratory depression [lorazepam 4(4.4%) versus diazepam-phenytoin combination 5 (5.6%)]. None of the patients in the two groups required additional anticonvulsant drug to stop the presenting seizure. No patient required mechanical ventilation and none of the patients in the two groups required cross-over to the alternative regimen.

CONCLUSION

Lorazepam is as efficacious and safe as diazepam-phenytoin combination. We recommend use of lorazepam as a single drug to replace the two drug combination of diazepam-phenytoin combination to control the initial seizure in pediatric convulsive status epilepticus.

Reversal of propoxur-induced impairment of step-down passive avoidance, transfer latency and oxidative stress by piracetam and ascorbic acid in rats

Propoxur, a carbamate pesticide has been shown to adversely affect memory and induce oxidative stress. The present study was designed to correlate the effect of propoxur, piracetam (a nootropic drug) and ascorbic acid (an antioxidant) on oxidative stress and cognitive function. Cognitive function was assessed using step-down latency (SDL) on a passive avoidance apparatus and transfer latency (TL) on elevated plus maze. Oxidative stress was assessed by examining brain malondialdehyde (MDA) and non-protein thiol (NP-SH) levels. A significant reduction in SDL and prolongation of TL was found for the propoxur-treated group at weeks 6 and 7 as compared with control (p<0.001). One week treatment by piracetam (400mg/kg/d, i.p.) or ascorbic acid (120mg/kg/d, i.p.) antagonized the effect of propoxur on SDL as well as TL. Both piracetam and ascorbic acid attenuated the propoxur-induced increase in brain MDA levels and decrease in brain NP-SH levels. Results of the present study show that ascorbic acid and piracetam have the potential to reverse cognitive dysfunction and oxidative stress induced by propoxur in the brain.

Oral salbutamol for symptomatic relief in mild bronchiolitis a double blind randomized placebo controlled trial

OBJECTIVES

To determine the efficacy of oral salbutamol for providing symptomatic relief in mild bronchiolitis.

DESIGN

Randomized double-blind placebo controlled trial.

SETTING

Pediatric Outpatient Department of a tertiary care hospital.

SUBJECTS

140 infants (of 310 approached) with a clinical diagnosis of acute bronchiolitis with respiratory rate <or= 70 breath/min, heart rate <or= 200 beats/min, hemoglobin oxygen saturation (SpO2) >or= 95% in room air, no or mild accessory muscle use, and respiratory distress assessment instrument (RDAI) score <or=10. Children were followed up for 14 days.

INTERVENTION

Oral salbutamol (0.1 mg/kg/dose) (n=70) or placebo (n=70) three times a day for 7 days or till complete resolution of symptoms,whichever was earlier.

OUTCOME VARIABLES

Time for resolution of illness (ROI), duration of fever, cough,coryza, noisy breathing, time to achieve normal feeding and normal sleep, and frequency of hospitalization and adverse effects.

RESULTS

Median (SE, 95% CI) duration of resolution of overall illness was similar in the two groups [6 (0, 5 to 7) d in the salbutamol group vs. 5 (1, 4 to 6) days in placebo group; P=0.21]. There was no significant difference in mean duration of fever, cough, coryza, noisy breathing, time to achieve normal feeding and normal sleep; and frequency of hospitalization or adverse effects, between the two groups.However, tremors were observed in 5 infants in the salbutamol group.

CONCLUSION

Oral salbutamol is not superior to placebo in reducing the duration of symptoms in mild cases of acute bronchiolitis in children.

Persistence and vertical distribution of termiticide fipronil in modified ground board test

Fipronil termiticide belongs to phenyl-pyrazole class of chemical compounds. It has broad-spectrum activity particularly against house hold pests such as cockroaches, mosquitoes, locusts, ticks, and fleas at both larval and adult stages. At high dosage it can be used to control subterranean termites in building foundations. To evaluate long term efficacy against termites the persistence and vertical distribution of fipronil was studied under natural weather conditions of Dehradun, India. Fipronil was applied at four concentrations i.e. 0.05, 0.1, 0.25 and 0.5% a.i ha(-1) by drenching 17 x 17 in.(2) plot prepared as per modified ground board test. Soil samples were collected after 22, 38 and 56 months of treatment up to the depth of 75 cm. The soil core was cut into five distinct sections i.e. 0-15, 15-30, 30-45, 45-60 and 60-75 cm depth. The residues were extracted by shaking 20 g soil sample with acetone. The acetone extract was concentrated and cleaned-up over florisil column. Fipronil residues were estimated on GLC at 220, 260, and 300 degrees C oven, injector and detector temperature respectively. Fipronil was found to persist beyond 56 months after application. Two metabolites viz. desulfinyl and sulfide-fipronil were detected in sampling after 22 months of application that also dissipated with time. Fipronil residues were found up to 60 cm depth. The residues in deeper layers dissipate slowly with time and after 56 months of treatment residues were detected only up to 30 cm depth.

Role of paracetamol in treatment of childhood Fever: a double-blind randomized placebo controlled trial

OBJECTIVE

To investigate whether paracetamol administration (i) increases the overall duration of fever; and (ii) is effective and safe, in symptomatic treatment of febrile children.

DESIGN

Randomized double blind placebo controlled trial.

METHODS

The trial was conducted at a tertiary care setting. 210 febrile children (6 months - 6 years) with uncomplicated respiratory tract infection received oral paracetamol (15 mg/kg) or placebo, if axillary temperature was 37.6C. Outcome measures included fever clearance time, rate of fall of temperature, percent reduction of temperature, proportion of afebrile children, symptomatic improvement (based on categorical improvement in activity, alertness mood, comfort, appetite and fluid intake) and clinical and biochemical adverse effects.

RESULTS

Fever clearance time [median (SE, 95% CI)] was comparable between the two groups [paracetamol: 32 (2, 22-37) h; placebo: 36 (1, 33-39) h; P = 0.23]. Paracetamol resulted in significantly higher rate of fall of temperature (paracetamol: 0.33 +/-; 0.16 degrees C/h; placebo 0.07 +/- 0.13 degrees C/h: P <0.001), and percentage reduction of temperature (paracetamol: 85.4 +/- 22.4; placebo 45.5 +/- 34.1; mean difference 39.9; 95% CI 31.9-47.9; P<0.001) during first four hours after drug administration. Proportion of afebrile children after 4 hours (paracetamol: 46.6%; placebo: 12.1%; P <0.001) and symptomatic improvement at 6 hours were significantly higher (P<0.001) after administration of paracetamol as compared to placebo. No serious clinical or biochemical adverse drug effects were observed.

CONCLUSIONS

Paracetamol achieves effective antipyresis and provides early symptomatic improvement in children with febrile illness without prolongation of fever duration or excessive adverse effects.

Persistence and dissipation kinetics of spiromesifen in chili and cotton

In a field study carried out at three different locations, the dissipation of spiromesifen on cotton and chili was studied and its DT50, and DT99 were estimated at each location. Spiromesifen was sprayed on chili at 96 and 192 g a.i. ha(-1) and cotton at 120 and 240 g a.i. ha(-1). Samples of chili fruits were drawn at 0, 1, 3, 5, 7, 10, 15, 21, 30 days after treatment and that of cotton seed and lint at first picking and harvest. Soil samples were drawn 30 days after treatment from 0 to 15 and 15 to 30 cm layer. Quantification of residues was done on GC-MS in Selected Ion Monitoring (SIM) mode in mass range 271-274 m/z. The LOQ of this method was found 0.033 microg g(-1), LOD being 0.01 microg g(-1). The DT50 of spiromesifen when applied at recommended doses in chili fruits was found to be 2.18-2.40 days. Ninety-nine percent degradation was found to occur within 14.5-16.3 days after application. Residues of spiromesifen were not detected in cotton seed and lint samples at the first picking. In soil, no residues of spiromesifen were detectable 15 days after treatment.

Dissipation kinetics of spiromesifen on tea (Camellia sinensis) under tropical conditions

Spiromesifen (Oberon) is a new insecticide and miticide of chemical class ketoenol active against white flies (Bemisia spp., Trialeuroides spp.) and spider mites (Tetranychus and Panonychus spp.). Due to its potential significance in insect resistance management, it is important to establish its behaviour on crop and environment. In the present study, the degradation/dissipation of spiromesifen on tea crop under tropical environmental conditions was studied and its DT(50) (t(1/2)), and DT(90) (time to reduce to 90% of the initial value) were estimated. Spiromesifen was sprayed on tea crop after first rain flush at four different locations @ 96 and 192ga.i.ha(-1). Samples of tea leaves were drawn at 0, 1, 3, 5, 7, 10, 15, 21 and 30 days after treatment and that of soil at 10 days after treatment and at harvest from 0 to 15 and 15 to 30cm layers. After crude extraction of tea leaves for spiromesifen residues with acetone:water, the contents were partitioned with cyclohexane:ethyl acetate and cleaned up on Florosil column. Soil residues were also extracted similarly. Quantification of residues was done on GC-MS in Selected Ion Monitoring (SIM) mode in mass range 271-274m/z. The LOQ of this method was found to be 0.05microgg(-1) while LOD being 0.015microgg(-1). The DT(50) of spiromesifen when applied at recommended doses in tea leaves was found to be 5.0-8.5 days. Ninety-nine percent degradation was found to occur within 33-57 days after application. In soil, no residues of spiromesifen were detectable 10 days after treatment.

Robotically enhanced coronary artery bypass surgery

Robotically enhanced telemanipulation surgery is a rapidly developing technique which enables totally endoscopic cardiac surgery with utmost precision and perfection on both beating heart and arrested heart. Between December 2002 and September 2006, 268 patients underwent robotically enhanced coronary artery bypass surgery using the da Vinci telemanipulation system. Fourteen patients underwent total endoscopic coronary artery bypass surgery. Of these 12 were performed on a beating heart and 2 on an arrested heart. Two-hundred and fifty-four patients had endoscopic takedown of the internal mammary artery followed by minimally invasive direct coronary artery bypass in 193 patients and left anterolateral thoracotomy in 61 patients. The internal mammary artery mobilization time was 36 min (28–76 min) and the left internal mammary artery to left anterior descending artery anastomosis time ranged from 20 to 36 min for the totally endoscopic coronary artery bypass patients. The right internal mammary artery of one patient was anastomosed to diagonal artery totally endoscopically. The mean internal mammary artery flow by Doppler measurement in patients undergoing minimally invasive direct coronary artery bypass was 58 ml min⁻¹. Seven patients required conversion to median sternotomy and coronary bypass surgery on the beating heart. The mean intensive care unit stay was 1.2 days and the mean hospital stay 4.5 days. There was one in-hospital mortality. All 14 patients who underwent total endoscopic bypass surgery had coronary angiography 3 months later which showed 100% patency in 13 patients. One patient had 50% anastomotic narrowing for which coronary angioplasty was performed in the same sitting. By using telematic technology, a complete endoscopic anastomosis is possible in both single vessels and suitable double vessel disease patients. The use of robotics is now extended to achieve complete myocardial revascularization by harvesting both the internal mammary arteries and making a small thoracotomy for direct anastomosis also.

Role of κ- and δ-opioid receptors in the antinociceptive effect of oxytocin in formalin-induced pain response in mice

Oxytocin has been implicated in the modulation of somatosensory transmission such as nociception and pain. The present study investigates the effect of oxytocin on formalin-induced pain response, a model of tonic continuous pain. The animals were injected with 0.1 ml of 1% formalin in the right hindpaw and the left hindpaw was injected with an equal volume of normal saline. The time spent by the animals licking or biting the injected paw during 0-5 min (early phase) and 20-25 min (late phase) was recorded separately. Oxytocin (25, 50, 100 microg/kg, i.p.) dose dependently decreased the licking/biting response, both in the early as well as the late phases. The antinociceptive effect of oxytocin (100 microg/kg, i.p.) was significantly attenuated in both the phases by a higher dose of the non-selective opioid receptor antagonist naloxone (5 mg/kg, i.p.), MR 2266 (0.1 mg/kg, i.p.), a selective kappa-opioid receptor antagonist and naltrindole (0.5 mg/kg, i.p.), a selective delta-opioid receptor antagonist but not by a lower dose of naloxone (1 mg/kg, i.p.) or beta-funaltrexamine (2.5 microg/mouse, i.c.v.), a selective mu-opioid receptor antagonist. Nimodipine, a calcium channel blocker (1 and 5 mg/kg, i.p.) produced a dose-dependent analgesic effect. The antinociceptive effect of oxytocin was significantly enhanced by the lower dose of nimodipine (1 mg/kg, i.p.) in both the phases. Chronic treatment with oxytocin (100 microg/kg/day, i.p. daily for 7 days) did not produce tolerance in both the phases of formalin-induced pain response. The results thus indicate that oxytocin displays an important analgesic response in formalin test; both kappa- and delta-opioid receptors as well as voltage-gated calcium channels seem to be involved in the oxytocin-induced antinociception.