New approaches to second-degree burn healing: Polyvinyl alcohol membrane loaded to arnica combined to laser therapy

Second-degree burns require greater care, as the damage is more extensive and worrisome and the use of a biomaterial can help in the cell repair process, with better planning, low cost, and better accessibility. Arnica has anti-inflammatory and analgesic properties in skin lesions treatments and laser therapy is another therapeutic alternative for burns. Evaluate the effects of arnica incorporated into PVA associated or not with low intensity laser on burns in rats. PVA and PVA with arnica (PVA+A) were obtained and characterized physicochemically. Through in vivo studies, the effects of PVA and PVA+A with or without the application of laser on the lesions allowed histological and immunohistochemical analyzes. PVA+A was biocompatible and with sustained release of the active, being a promising pharmacological tool and confirmed that laser therapy was effective in accelerating the healing process, due to its potential biomodulator, improving inflammatory aspects, promoting rapid healing in skin lesions.

The Influence of Silver Nanoparticles Against Toxic Effects of Philodryas olfersii Venom

Purpose

A silver nanoparticle obtained by reducing salts with solid dispersion of curcumin (130 nm, 0.081 mg mL⁻¹) was used to counteract against the toxic – edematogenic, myotoxic, and neurotoxic – effects of Philodryas olfersii venom.

Methods

The edematogenic effect was evaluated by plasma extravasation in rat dorsal skin after injection of 50 µg per site of venom alone or preincubated with 1, 10, and 100 µL of AgNPs; the myotoxicity was evaluated by measuring the creatine kinase released into the organ-bath before the treatment and at the end of each experiment; and neurotoxicity was evaluated in chick biventer cervicis using the conventional myographic technique, face to the exogenous acetylcholine (ACh) and potassium chloride (KCl) added into the bath before the treatment and after each experiment. Preliminarily, a concentration-response curve of AgNPs was carried out to select the concentration to be used for neutralizing assays, which consists of neutralizing the venom-induced neuromuscular paralysis and edema by preincubating AgNPs with venom for 30 min.

Results

The P. olfersii venom-induced edema (n=6) and a complete neuromuscular blockade (n=4) that includes the total and unrecovered block of ACh and KCl contractures. AgNPs produced a concentration-dependent decrease the venom-induced edema (n=6) from 223.3% to 134.4% and to 100.5% after 10 and 100 µL AgNPs-preincubation, respectively. The preincubation of venom with AgNPs (1 µL; n=6) was able to maintain 46.5 ± 10.9% of neuromuscular response under indirect stimuli, 39.2 ± 9.7% of extrinsic nicotinic receptors functioning in absence of electrical stimulus and 28.3 ± 8.1% of responsiveness to potassium on the sarcolemmal membrane. The CK release was not affected by any experimental protocol which was like control.

Conclusion

AgNPs interact with constituents of P. olfersii venom responsible for the edema-forming activity and neuromuscular blockade, but not on the sarcolemma membrane-acting constituents. The protective effect of the studied AgNPs on avian preparation points out to molecular targets as intrinsic and extrinsic nicotinic receptors.

Bothrops fonsecai snake venom activities and cross-reactivity with commercial bothropic venom

In this work, we examined some biochemical and biological activities of Bothrops fonsecai venom, a pitviper endemic to southeastern Brazil, and assessed their neutralization by commercial bothropic antivenom (CAv). Cross-reactivity of venom with CAv was also assessed by immunoblotting and size-exclusion high performance chromatography (SE-HPLC). Bothrops fonsecai venom had PLA₂, proteolytic and esterase activities that were neutralized to varying extents by venom:antivenom ratios of 5:1 and 5:2 (PLA₂ and esterase activities) or not significantly by either venom:antivenom ratio (proteolytic activity). The minimum hemorrhagic dose (69.2μg) was totally neutralized by both ratios. Clotting time in rat citrated plasma was 33±10.5s (mean±SD; n=5) and was completely neutralized by a 5:2 ratio. Edema formation was dose-dependent (1-30μg/site) and significantly inhibited by both ratios. Venom (10-300μg/mL) caused neuromuscular blockade in extensor digitorum longus preparations; this blockade was inhibited best by a 5:2 ratio. Venom caused myonecrosis and creatine kinase release in vivo (gastrocnemius muscle) and in vitro (extensor digitorum longus) that was effectively neutralized by both venom:antivenom ratios. Immunoblotting showed that venom components of ~25-100kDa interacted with CAv. SE-HPLC profiles for venom incubated with CAv or specific anti-B. fonsecai antivenom raised in rabbits (SAv) indicated that CAv had a higher binding capacity than SAv, whereas SAv had higher affinity than CAv. These findings indicate that B. fonsecai venom contains various activities that are neutralized to different extents by CAv and suggest that CAv could be used to treat envenoming by B. fonsecai.

Toxic effects of the administration of Mikania glomerata Sprengel during the gestational period of hypertensive rats

Herbal medicine is an ancient practice that has been gaining acceptance of the medical class through scientific studies that prove its effectiveness. However, its use should still be cautious. Medicinal plants have potential toxic effects not yet discovered, and may have unproven interactions with other medications. The use of drugs during pregnancy is still very dangerous and vigorously studied; however, there are few studies of herbal medicines in pregnant women. Existing studies prioritize on teratogenic or abortifacient effects. The aim of this study was to analyze the toxic effects of Mikania glomerata Sprengel administration, popularly known as "guaco" during the gestational period of hypertensive rats. For this experimental groups consisting of pregnant Wistar rats received treatments with guaco extract (1 to 2 mL). In order to analyze the possible toxic effects of guaco during pregnancy, weight gain of rats was assessed during pregnancy; reproductive performance of rats, morphological parameters, and fetal placental histology were compared. Although some parameters presented significant differences, we can conclude that changes prioritized by literature, such as toxicity, vasodilation and hypotension, have not been caused by guaco. The only fetal changes observed were due to the maternal hypertension. Some studies have reported vasodilator and hypotensive effects of guaco. However, only a few studies exist, and its actual effects remain unknown. Specific studies should be developed with higher doses of guaco for a definitive conclusion of its toxic and non-toxic effects.

Toxic effects of glibenclamide in fetuses of normoglycemic rats: an alternative therapy for gestational diabetes mellitus

Gestational diabetes mellitus (GDM) is defined as glucose intolerance first diagnosed during the second or third trimester of pregnancy. The treatment aims at glycemic control through changes in the patient's diet with or without exercise, but some patients need insulin therapy. An alternative would be to use oral hypoglycemic agents such as glibenclamide (GLIB). The present study aims to analyze the toxic effects of GLIB in fetuses of pregnant rats which received 5 or 20mg/kg doses of GLIB. Glycemic dosage reveals no significant difference between control (deionized water) and treated groups, showing that these concentrations of GLIB were not effective to cause hypoglycemia in rats. The vitality of the fetuses in all groups was 100%. GLIB administration promoted increase in weight and significant changes in measures of external morphological parameters of treated fetuses. Histological analysis revealed that liver lobes, lobules and central lobular veins were well defined for all treatments. However, GLIB animals presented a light brownish precipitate into the center-lobular veins and in the liver parenchyma among the hepatocytes. These results indicated a possible passage of the drug through the blood-placental membrane, without serious changes that impair the development of neither bone tissue, nor the liver of these animals.

Beneficial effect of crotamine in the treatment of myasthenic rats

INTRODUCTION

Crotamine is a basic, low-molecular-weight peptide that, at low concentrations, improves neurotransmission in isolated neuromuscular preparations by modulating sodium channels. In this study, we compared the effects of crotamine and neostigmine on neuromuscular transmission in myasthenic rats.

METHODS

We used a conventional electromyographic technique in in-situ neuromuscular preparations and a 4-week treadmill program.

RESULTS

During the in-situ electromyographic recording, neostigmine (17 μg/kg) caused short-term facilitation, whereas crotamine induced progressive and sustained twitch-tension enhancement during 140 min of recording (50 ± 5%, P < 0.05). On the treadmill evaluation, rats showed significant improvement in exercise tolerance, characterized by a decrease in the number of fatigue episodes after 2 weeks of a single-dose treatment with crotamine.

CONCLUSIONS

These results indicate that crotamine is more efficient than neostigmine for enhancing muscular performance in myasthenic rats, possibly by improving the safety factor of neuromuscular transmission.

Biological characterization of Bothrops marajoensis snake venom

This study describes the effects of Bothrops marajoensis venom (Marajó lancehead) on isolated neuromuscular preparations of chick biventer cervicis (CBC) and mouse phrenic nerve-diaphragm (PND). At low concentrations (1µg/ml for CBC and 5µg/ml for PND), the venom exhibited a neuromuscular blocking without any damaging effect on the muscle integrity. At higher concentration (20μg/ml for PND), together with the neuromuscular blockade, there was a moderate myonecrosis. The results show differences between mammalian and avian preparations in response to venom concentration; the avian preparation was more sensitive to venom neurotoxic effect than the mammalian preparation. The possible presynaptic mechanism underlying the neuromuscular blocking effect was reinforced by the observed increase in MEPPs at the same time (at 15min) when the facilitation of twitch tension occurred. These results indicate that the B. marajoensis venom produced neuromuscular blockade, which appeared to be presynaptic at low concentrations with a postsynaptic component at high concentrations, leading to muscle oedema. These observations demand the fractionation of the crude venom and characterization of its active components for a better understanding of its biological dynamics.

Cross-neutralization of the neurotoxicity of Crotalus durissus terrificus and Bothrops jararacussu venoms by antisera against crotoxin and phospholipase A2 from Crotalus durissus cascavella venom

We have previously demonstrated that rabbit antisera raised against crotoxin from Crotalus durissus cascavella venom (cdc-crotoxin) and its PLA2 (cdc-PLA2) neutralized the neurotoxicity of this venom and its crotoxin. In this study, we examined the ability of these antisera to neutralize the neurotoxicity of Crotalus durissus terrificus and Bothrops jararacussu venoms and their major toxins, cdt-crotoxin and bothropstoxin-I (BthTX-I), respectively, in mouse isolated phrenic nerve-diaphragm preparations. Immunoblotting showed that antiserum to cdc-crotoxin recognized cdt-crotoxin and BthTX-I, while antiserum to cdc-PLA2 recognized cdt-PLA2 and BthTX-I. ELISA corroborated this cross-reactivity. Antiserum to cdc-crotoxin prevented the neuromuscular blockade caused by C. d. terrificus venom and its crotoxin at a venom/crotoxin:antiserum ratio of 1:3. Antiserum to cdc-PLA2 also neutralized the neuromuscular blockade caused by C. d. terrificus venom or its crotoxin at venom or toxin:antiserum ratios of 1:3 and 1:1, respectively. The neuromuscular blockade caused by B. jararacussu venom and BthTX-I was also neutralized by the antisera to cdc-crotoxin and cdc-PLA2 at a venom/toxin:antiserum ratio of 1:10 for both. Commercial equine antivenom raised against C. d. terrificus venom was effective in preventing the neuromuscular blockade typical of B. jararacussu venom (venom:antivenom ratio of 1:2), whereas for BthTX-I the ratio was 1:10. These results show that antiserum produced against PLA2, the major toxin in C. durissus cascavella venom, efficiently neutralized the neurotoxicity of C. d. terrificus and B. jararacussu venoms and their PLA2 toxins.