Influence of the cumulative effect of zoledronic acid on periodontal microcirculation in rats

PURPOSE

To evaluate the effect of repeated administration of zoledronic acid (ZA) on the development and severity of osteonecrosis of the jaws.

METHODS

In the experiment, 36 rats were used, which were divided into 4 groups: group 1 was injected with saline for 6 weeks, group 2 was injected with ZA once, group 3 was injected zoledronic acid for 3 weeks once a week, group 4 was injected with ZA for 6 weeks once a week. While taking medications, the tooth was removed. The volumetric blood flow rate was studied using laser and high-frequency ultrasound Doppler in the area of the periodontium of an extracted tooth in rats with the application of acetylcholine. Bone tissue was examined out using CBCT.

RESULTS

In group 2, there was a violation of blood flow in the mucous membrane, bone microcirculation, but no reliable data was obtained in the bone defect in comparison with group 1. In groups 3 and 4, there was significantly disrupted blood flow. This led to an increase of the osteonecrosis (maximum at the 4th group), which was confirmed by data obtained using CBCT. An inverse relationship was observed between the blood flow of bone tissue and the size of the defect after tooth extraction.

CONCLUSION

The introduction of ZA in a dose-dependent fashion resulted in impaired endothelial vasodilation and impaired blood flow to extraction sockets. These findings might explain the development of osteonecrosis of the mandible following removal of a first molar.

Disorders of microcirculation in the mechanism of bisphosphonate osteonecrosis: preliminary study in rats

We investigated the possibilities of angioprotection and the reduction of osteonecrosis in rats that had been given bisphosphonates. In our experiment, 27 rats were divided into three groups: Group 1 was injected with saline; Group 2 was given zoledronic acid for six weeks; and Group 3 was given zoledronic acid for six weeks, with added doses of sulodexide after three weeks. After that we constructed a model of how the teeth should be extracted. The velocity of linear blood flow in the periodontal area of an extracted tooth in rats was studied using laser and high-frequency Doppler ultrasound (with the application of the vasoactive substance acetylcholine 3% for 1min). We evaluated changes in the structure of the bony tissues of the head using computed tomography, comparing the control group with the saline group. A rapid reduction in microcirculation was detected during the use of zoledronic acid for six weeks. A smaller reduction in microcirculation was detected after three weeks of treatment with sulodexide and zoledronic acid. There was a reduction in blood flow in the mucous membranes and, to a greater extent, in bony tissue. Zoledronic acid causes significant impairment of the periosteal blood flow to the mucous membranes because of a complex of disorders, which includes both the cellular component (impaired endothelium-dependent vasodilation of the mucous membrane vessels) and by reducing the intensity of microcirculation in the mucous membranes and bony tissues. Sulodexide, however, improves the restoration of blood flow and reduces the severity of osteonecrosis.

Endothelial dysfunction: from the particular to the general. Return to the «Old Paradigm»?

The vascular endothelium is a heterogeneous structure with diverse functions, being an active metabolic system. Endothelial cells mediate inflammatory and immune processes, regulate leukocyte adhesion, permeability and vascular tone, participate in the hemostasis system, stimulate the processes of angiogenesis. Endothelial dysfunction can initiate individual disorders, but more often it is a universal link in the pathogenesis of many diseases. Currently, endothelial dysfunction is presented as an imbalance between the production of vasodilating, angioprotective, antiproliferative factors, on the one hand, and vasoconstrictive, prothrombotic, proliferative factors, on the other hand. The manifestations of endothelial dysfunction, the direction and severity of these changes may vary depending on the disease. The review provides examples of combined endothelial disorders in the most studied and common diseases (essential hypertension, type 2 diabetes, systemic diseases of the connective tissue, atherosclerosis, and malignant tumors). Despite the presence of rare cases of isolated endothelial dysfunction, it can be argued that in the absolute majority of diseases, endothelial dysfunction has combined type of violations. The allocation of individual endothelial disorder spectra, typical for a specific disease, is problematic, due to the universality and nonspecificity of the manifestations of endothelial dysfunction. These conclusions allow us to return to the origins of this problem, considering endothelial dysfunction as a holistic concept, not limited to a certain range of its disorders.

Microcirculatory dopplerography as a method to evaluate drugs endothelial protective properties in type 2 diabetic patients

Objective - to identify the most accurate way of drugs endothelial protective properties evaluation. Material and methods. Blood endothelin-1 (E) and acetylcholine-induced endothelial dependent vasodilation (EDV) were measured for 9 months in type 2 diabetic patients receiving either metformin (MET) (group 1) or MET and liraglutide (LIR) (group 2). Results. E was normal in group 1 at baseline and decreased only with glycaemia decline, in group 2 it was primarily increased and declined independently on glycaemia dynamics. In both groups E normalized in 6 months. EDV was impaired primarily in groups 1 and 2 and normalized only in group 2 in 9 months. Conclusions. LIR improves endothelial function, independently on glycaemia. Dopplerography in more accurate in drugs endothelial protective effects evaluation than circulating markers.

[Preclinical studies of drugs on animal stroke models]

Preclinical studies are studies using experimental models of stroke in animals as well as on neurons, cell neuronal cultures and surviving brain slices. They directed both towards testing the efficacy and evaluation of the mechanisms of action of drugs, and the study of the mechanisms of ischemic damage to search for new targets for stroke treatment. This article shows the basic principles of the organization and planning of animal models of ischemic stroke. Modeling of cerebral ischemia on the different models and animal species, the modern principles of assessment of brain damage are considered as well.

[The administration of neurocytoprotectors in a rat model of experimental spinal cord ischemia]

AIM

To study an effect of cortexin on functional recovery and morphology of the spinal cord of rats with spinal cord ischemia.

MATERIAL AND METHODS

Spinal cord ischemia was achieved by ligation of the infrarenal abdominal aorta in 16 rats stratified into two equal groups: the ligation of infrarenal aorta was performed in the control group, aorta ligation was performed also in the experimental group with preliminary intraperitoneally administration of cortexin in a dose of 0.15 mg/kg 30 min before procedure. Evaluation of neurologic deficit was performed by the Tarlov's scale. Morphological evaluation was made by analyzing the histological sections of the lumbar and sacral cord using the Nissl's method of coloring. Statistical analysis was performed as well.

RESULTS AND CONCLUSION

A pronounced and significant effect of cortexin, which was clinically expressed in a decrease in neurological deficit (p=0.0095), morphologically in an increase in the number of normochromic neurons (р=0.01), and a decrease in shrunken neurons (р=0.0001) and shadow cells (р=0.0003), was noted. The results suggest a potential myeloprotective effect of cortexin. The drug can be considered in the context of treatment of vascular myelopathy.

Markers of endothelial dysfunction

Endothelial dysfunction is considered as a universal non-specific link in the pathogenesis of many diseases, primarily the cardiovascular system. This review is devoted to the discussion of the main functions of the endothelium and mechanisms for their implementation. One of the most striking features of endothelial cells is their morphological heterogeneity, which allows us to identify several typical forms of endothelial dysfunction (vasomotor, hemostatic, adhesion and angiogenous). Also, the review presents the most promising predictors of cardiovascular diseases and their complications among endothelial damage markers.

APPLICATION OF GRAFTSKIN TO ACCELERATE HEALING OF ULCERS IN DIABETIC FOOT SYNDROME

Diabetic foot syndrome (DFS) is one of the severe and more frequent complications of diabetes. It is characterized by occurrence of chronic purulent necrotic processes (trophic ulcers) on the foot with damage of skin, soft tissues and osteoarticular system due to pathological changes in the peripheral nervous system (diabetic neuropathy) and vascular system (diabetic angiopathy). This study aimed to evaluate the possibility of accelerating of wound healing in DFS by using the dermal equivalent (graftskin) and determine the safety of the method, factors and indications for its application. The research included 60 patients with DFS who were cured at the period from 2013 to 2016 in departments of purulent surgery of Hospital of war veterans and Municipal hospital № 14 of Saint-Petersburg. The patients were divided into 2 groups by random sampling of two comparable groups in age and sex. The patients of main group were treated by standard method and using application of dermal equivalent (DE) on the area of trophic ulcers. The patients of control group had only standard treatment. The DE showed a high efficacy in the main group of patients. The application of DE in complex treatment of patients with DFS stimulated processes of healing and accelerated the rate of epithelization. The application of DE was the most effective in patients with neuropathic form of DFS.

[Preconditioning by physical factors: role of active forms of oxygen]

In the review mechanisms of protective action of a hyperthermia, light and low-intensity ultrasonic radiation are considered. These physical factors don't cause oxygen starvation, however promote the increase of organ's tolerance to an ischemia/hypoxia. On materials of original articles the analysis of preconditioning mechanisms cause by high temperatures, low-intensive ultrasonic and laser irradiation was carried out at ischemia. By comparison of processes in tissues at influence by physical factors the general triggers--active forms of oxygen (O2*, H2O2, HO*) were revealed.

[Creatine in a metabolism of cell and its protective action at brain ischemia]

The aim of this review was the discussion of creatine involvement in metabolism of nervous tissue cells. The questions of creatine penetration through the blood brain barrier and creatine transporter expression were raised. Also mechanisms of creatine protective effect were considered at experimental models of brain ischemia. It was shown that creatine was involved in energy metabolism (creatine phosphate synthesis), inhibition of excitotoxicity. Besides it had antioxidant and antiproliferative effects. The creatine delivery problem was also discussed. Synthesis of substances capable to get through the blood brain barrier without CRT was the possible solution of the problem. The most perspective substances were creatine amides apparently capable to move through cell membranes without amino acid transporters. Prospects of their application were discussed.

[Appearance of stellate smooth muscle cells in the rat brain after transitory focal ischemia]

One of the poorly studied problems of the pathogenesis of the brain ischemic damage is the early reorganization of blood vessels in the zone of the transitory ischemia. The aim of the present study was to investigate the structural organization and cytochemical characteristics of smooth muscle cells (SMC) in the wall of the intracerebral blood vessels in 16 Wistar rats during the early postischemic period (48 hrs after a 30 minute-long ischemia). Examination of the lesioned hemisphere revealed the stellate cells, demonstrating positive reaction to alpha-smooth muscle actin, which seem to be a special population of structurally modified SMC, uncharacteristic to the intact brain of control animals (n=5). The functional role of these cells remains to be elucidated.

[Effect of intragastric creatine glycine ethylic ether fumarate administration in a rat model of occlusive ischemia]

The aim of the study was to investigate neuroprotective effect of creatine glycine ethylic ether fumarate (creamide). The methods involved intragastric administration of creamide in doses of 30 and 50 mg/kg twice a day for 10 days. Focal 30 minutes cerebral ischemia model by endovascular suture occlusion of the middle cerebral artery in a rat with subsequent reperfusion period for 48 hours was produced. Assessment of creamide stability in gastric juice was performed. Ischemic lesion volume accompanying focal ischemia was visualized and determined. Similar infarction patterns had been found with histological methods. Garcia scale was used for clinical study of neurological deficit in rats. Our data suggest a significant neuroprotective effect of creamide in dosage 50 mg/kg administered twice a day which decreased brain lesion volume produced by ischemic and reperfusion injury.

[Cytoprotective effect of creamide drug in the experimental model of the brain ischemia/reperfusion in rats]

The influence of creatine or its derivates on the cell energy potential may be one of the possibl approaches to induce neuroprotection. Effect of creamide (creatinylglycine ethylic ether fumarate) on the brain injury was studied in the experimental model of the brain ischemia/reperfusion in rats. The experiments were carried out in 14-20 weeks old male Wistar rats weighing 240-300 g, anesthetized by chloral hydrate (430 mg/kg). Creamide was administered intravenously at the doses of 50, 70, 140, and 280 mg/kg. For comparison phosphocreatine was used at the dose of 255 mg/kg. Creamide and phosphocreatine were administered intravenously (in volume of 1 ml within 5 min) 30 min before cerebral middle artery occlusion. Focal cerebral ischemia for 30 min was produced by endovascular suture occlusion with the subsequent 48 h reperfusion period. Creamide administration resulted in dose-dependent decrease of brain ischemic injury. Creamide administered at the doses of 140 and 280 mg/kg was more effective as compared with phosphocreatine (255 mg/kg). The data obtained open new perspectives for further research and development of new creatine-derived drugs with neuroprotective action.

[Mechanisms of cerebral protection from ischemia by tea constituents]

Epidemiological and clinical studies in recent years have shown that regular consumption of green or black tea significantly reduces the risk of cardiovascular diseases, including ischemic stroke. This review presents the clinical and experimental studies of the antiatherogenic, antiplatelet, antioxidant, antiinflammatory and other mechanisms of action of tea and substances in its composition. Effects of tea and its components, are described after long-term, and a short-term consumption. The role of catechins and specific amino acid L-theanine in the possible mechanisms of protection against cerebrovascular disease are discussed.

[Determination of circulation disturbance in the rat lungs in modelling of chronic obstructive disease]

Development of chronic obstructive pulmonary disease (COPD) involves not only the bronchial and respiratory areas of the lungs, but also the system of pulmonary circulation, which begins with the defeat of capillary blood flow. One of radiological methods of studying lung microcirculatory functions is perfusion scintigraphy. We designed the technique of radiological examination and identified its abilities in determination of the role of vascular dysfunctions in experimental model of development of COPD. We assessed the results of pharmacological agents that affect the microcirculatory bed of the lungs and smooth muscles of pulmonary arteries in rats. Studies have shown the promise of the possibility of using the drug sulodexide for studying impaired endothelial function in clinical practice.

[Structural organization of striatal microgliocytes following focal ischemia]

Microgliocytes are currently known as structurally labile cells, that, by changing the length of their processes, control the synaptic organization of the brain. The aim of this study was to investigate structural organization of microglia of the striatum and of the forebrain periventricular area in rat following transitory focal ischemia. In the absence of brain infarction, ischemic lesion was found to activate microglia, which contributed to rearrangement of striatal neuropil. As microgliocytes became activated, they changed their shape from characteristic dendritic one to oval and rounded, which are typical to amoeboid microglia. Microgliocytes were shown to be capable of proliferation.

[Nestin and Musashi1 as the markers of neural stem cells in rat telencephalon following transitory focal ischemia]

Nestin and Musashil (Msi-1) proteins are most often used for labeling of neural stem cells and progenitor cells in vivo, however it remains unclear if these markers really label the same cells. As a result of the study of structural characteristics and localization of nestin- and Msil-expressing cells it was found that these proteins were detected in non-identical cell populations in the brain of intact 15 rats. We failed to find cell groups demonstrating a coexpression of nestin and Msi-1. However, after ischemic lesion of the brain, which was caused in 38 rats by an endovascular occlusion of the left medial cerebral artery for 30 min with the following reperfusion for 48 hours, both markers were detected in cells of subventricular zone and in ependymocytes. These results indicate the changes in cytochemical patterns of the candidate stem cells.

[Amides of creatine: perspectives of neuroprotection]

We evaluated the efficacy of derivatives of creatine and amino acids (CrAA) for decreasing cerebral injury in rats with transient middle cerebral artery occlusion (MCAO). Neuroprotective effects of amides of creatine and glycine (CrGlyOEt), phenylalanine (CrPheNH2), thyrosine (CrTyrNH2), and GABA (CrGABAOEt) were investigated. Brain injury was evaluated on day 2 after transient MCAO using a TTC staining of brain slices. Compared with the MCAO control group, all the CrAms showed decreased cerebral injury (p < 0.05). However CrPheNH2, CrTyrNH2, and CrGABAOEt were toxic after intravenous administration and investigated only after intraperitoneal injection. CrGlyOEt did not show any toxicity at dose of 1 mmol/kg. These data evidenced that creatinyl amides can represent promising candidates for the development of new drugs useful in brain ischemia treatment.

[Early ischemic preconditioning against focal transient and permanent brain ischemia in rats: role of collateral circulation]

We hypothesize that early ischemic preconditioning (IPC) can afford protection against focal brief and prolonged cerebral ischemia with subsequent reperfusion as well as permanent brain ischemia in rats by amelioration of regional cerebral blood flow. Adult male Wistar rats (n=97) were subjected to transient (30 and 60 minutes) and permanent middle cerebral artery (MCA) occlusion. IPC protocol consisted of two episodes of 5-min common carotid artery occlusion + 5-min reperfusion prior to test ischemia either followed by 48 hours of reperfusion or not. Triphenyltetrazolium chloride and Evans blue were used for delineation of infarct size and anatomical area at risk (comprises ischemic penumbra and ischemic core), respectively. Blood flow in the MCA vascular bed was measured with use of Doppler ultrasound. The IPC resulted in significant infarct size limitation in both transient and permanent MCA occlusion. Importantly, IPC caused significant reduction of area at risk after 30 min of focal ischemia as compared to controls [med(min-max) 11.4% (3.59-2 0.35%) vs. 2.47% (0.8-9.31%), p = 0.018] but it failed to influence area at risk after 5 min of ischemia [med(min-max) 7.61% (6.32-10.87%) vs. 8.2% (4.87-9.65%), p > 0.05]. No differences in blood flow were found between IPC and control groups using Doppler ultrasound. This is suggestive of the fact that IPC does not really influence blood flow in the large cerebral arteries such as MCA but it might have some effect on smaller arteries. It seems that, along with well established cytoprotective effects of IPC, IPC-mediated reduction of area at risk by means of improvement in local cerebral blood flow may contribute to infarct size limitation after focal transient and permanent brain ischemia in rats.

[Neuroprotective effects of lipoic acid and superoxide dismutase in the rat model of cerebral ischemia]

BACKGROUND

the present study was aimed at investigation of neuroprotective effects of alpha-lipoic acid (LA) and superoxide dismutase (SOD) in brain ischemia in rats.

METHODS

two models were used to produce brain ischemia: focal ischemia (permanent left middle cerebral artery occlusion) and permanent ligation of both CCA without subsequent reperfusion. Cu/Zn-SOD at a dose 5 mg/kg, i.v. and LA at a dose of 20 mg/kg, i.p. were injected 30 minutes prior or 5 minutes after onset of ischemia. The end-points of the study were histochemically determined: infarction size, ultrastructural changes in the cerebral tissue, and survival rate.

RESULTS

LA administration 30 minutes prior to ischemia dramatically reduced infarction size (p < 0.001). Injection of LA 5 minutes after beginning of ischemia did not affect the infarction size. Besides, infarction ion size was unchanged after injection of SOD 30 minutes prior to ischemia.

CONCLUSION

the LA treatment regimen used in this study resulted in significant cerebral protection against ischemia. In contrast, SOD did not show any protective effects in focal and forebrain ischemia.

[Effect of hepatoprotector remaxol infusion on liver function in obstructive jaundice model in rats]

Remaxol is a new infusion hepatoprotector that contains succinic acid, inosine, methionine and methylglucamine. The hepatoprotective effect of remaxol on the liver function has been studied on the model of obstructive jaundice in rats, on the terms of one and two weeks after ligation of the common bile duct (M. A. Aller, et al., 2004). Sixty rats were randomly divided into six groups: sham-operated rats with cholestasis, 0.9% NaCl treated rats with cholestasis, and remaxol treated rats with cholestasis, all on the one week (per os n=10) and two weeks (n=10) terms. Remaxol was injected into the tail vein in a dose of 1 ml/100 g during the first week after the induction of cholestasis. The rats were removed from the experiment after one and two weeks of postoperative period, respectively. The size and weight of the liver and the degree of ascites were measured, and the blood samples were taken to analyze for bilirubin, alkaline phosphatase, gamma-glutamyl transpeptidase, alanineaminotransferase, aspartataminotransferase. Morphological changes in the liver were also studied. The biochemical parameters of blood and morphological evolution of tissue of liver in both one and two weeks after the induction of cholestasis showed a significant hepatoprotective effect of remaxol.

[Effects of individual and combined administration of ethylmethylhydroxypyridine succinate and ischemic preconditioning on ischemic-reperfusive myocardial injury in rats]

It was shown previously that ethylmethylhydroxypyridine succinate (EMHPS) can produce metabolic cardioprotective action due to its antihypoxant and antioxidant properties. In the present study, the cardioprotective effects of EMHPS administered in doses 50 and 100 mg/kg alone and in combination with ischemic preconditioning have been studied on the model of ischemic-reperfusive myocardial infarction in rats. It is established that both the administration of EMHPS in a dose 50 mg/kg and the ischemic preconditioning produce significant limitation of the infarction size. A combined use of EMHPS in a dose of 50 mg/kg and ischemic preconditioning also provided significant protection, although the effect was not further potentiated. In contrast, EMHPS administered in a dose 100 mg/kg did not ensure reliable protection against infarction, while a combination of this drug dose with the ischemic preconditioning even partially eliminated the infarction-limiting effect of the latter.

[Selective death of the striatum neurons in rats after the transient occlusion of the middle cerebral artery]

The aim of the present investigation was to determine the neuronal population of rat telencephalon that was most sensitive to ischemic damage under the experimental condition of transient focal cerebral ischemia. It was found that 30-minute ischemia of the left hemisphere resulted in a significant decrease of neuronal population in the dorsomedial part of caudatoputamen. Local neural cell death was accompanied by a moderate activation of the astrocytes.

[Ultrasound-induced myocardial preconditioning: analysis of its effectiveness and mechanisms]

It has been shown that exposure of the isolated rat heart perfused according to Langendorff to therapeutic ultrasound (210 kHz and 0.5-1.5 W/cm2 ) induces a cardioprotective response similar to ischemic preconditioning. This reduces the infarct size and improves the postischemic systolic and diastolic function. The ATP-sensitive K+ channel blocker glybenclamide abolished the protection afforded by ultrasound; in contrast, the free radical scavenger N-2-MPG did not influence the ultrasound-induced cardioprotective response.

[The relationship between ischemic preconditioning-induced infarction size limitation and duration of test myocardial ischemia]

Traditionally infarction size reduction by ischemic preconditioning is estimated in duration of test ischemia. This approach limits the understanding of real antiischemic efficacy of ischemic preconditioning. Present study was performed in the in vivo rat model of regional myocardial ischemia-reperfusion and showed that protective effect afforded by ischemic preconditioning progressively decreased with prolongation of test ischemia. There were no statistically significant differences in infarction size between control and preconditioned animals when the duration of test ischemia was increased up to 1 hour. Preconditioning ensured maximal infarction-limiting effect in duration of test ischemia varying from 20 to 40 minutes.

Induction of nestin synthesis in rat brain cells by ischemic damage

Nestin, an intermediate filament protein, is known to be expressed in proliferating and provisional cells in the forming mammalian brain, disappearing on differentiation. The aim of the present work was to identify the morphological types and locations of cells regaining the ability to synthesize nestin after transient total brain ischemia in rats. Transient ischemia was found to be followed by the induction of nestin synthesis in astrocytes in the damaged area; these cells acquired structural features not characteristic of the adult brain, and these persisted in the long term. Nestin synthesis was also induced in proliferation-capable undifferentiated cells in the subventricular zone. The acquisition by astrocytes of some of the phenotypic features of immature glial cells, however, does not provide grounds for the notion that they were transformed into neural stem cells.

[Role of sodium-calcium exchanger in the myocardial protection against ischemia-reperfusion injury]

Present study was aimed at investigation into the role of sodium-calcium exchanger (NCX) in myocardial ischemia-reperfusion injury and ischemic preconditioning (IPC). Experiments were performed in vivo rat model of regional myocardial ischemia-reperfusion. It was shown that inhibition of reverse mode of NCX with selective blocker KB-R7943 at a dose of 10 mg/kg resulted in significant decrease in occurrence and severity of ischemic ventricular tachyarrhythmias. Furthermore, administration of KB-R7943 caused potentiation of the antiarrhythmic effect exerted by single episode of IPC. However, KB-R7943 exerted no effect on myocardial infarction size nor affected infarction size limitation by IPC. In conclusion, inhibition of reverse mode of NCX conferred significant antiarrhythmic effect against ischemic rhythm disorders but it was ineffective in terms of infarction size limitation.

[Ischemic damage-induced nestin synthesis in the rat brain cells]

Nestin, an intermediate filament protein, is known to be expressed in the proliferating and provisional cells of the developing mammalian brain and is lost during differentiation. The aim of the present study was to determine the morphological type and localization areas of the rat brain cells exhibiting the ability to synthesize nestin after a short-term global ischemia of the brain. Induction of nestin synthesis after a short-term ischemia was found within the injured brain areas in astrocytes, which exhibited structural features atypical for these cells in mature brain and maintained them for a long time, and in the morphologically undifferentiated cells of subventricular zone, which were able to proliferate. However, acquisition by astrocytes of some phenotypic properties of immature glial cell does not by itself support the view that they may transform into neural stem cells.

Effects of helium-neon laser irradiation and local anesthetics on potassium channels in pond snail neurons

Intracellular dialysis and membrane voltage clamping were used to show that He-Ne laser irradiation of a pond snail neuron at a dose of 0.7 x 10(-4) J (power density 1.5 x 10(2) W/m2) increases the amplitude of the potential-dependent slow potassium current, while a dose of 0.7 x 10(-3) J decreases this current. Bupivacaine suppresses the potassium current. Combined application of laser irradiation at a dose of 0.7 x 10(-3) J increased the blocking effect of 10 microM bupivacaine on the slow potassium current, while an irradiation dose of 0.7 x 10(-4) J weakened the effect of bupivacaine.

Ischemic preconditioning of the rat brain as a method of endothelial protection from ischemic/repercussion injury

The studies reported here addressed the endothelium-protecting action of local and remote ischemic preconditioning of the brain in rats. Cerebral ischemia lasting 30 min was reproduced by thermocoagulation of the vertebral arteries with simultaneous clamping of the carotid arteries, the procedure being followed by reperfusion via the carotid arteries for 120 min (controls). The early and late phases of ischemic preconditioning and remote preconditioning were reproduced. Brain blood flow was recorded using high-frequency Doppler ultrasonography. The early and late phases of local ischemic preconditioning and the late phase of remote ischemic preconditioning were found to have endothelium-protecting actions apparent as improvements in the recovery of brain blood flow in the post-ischemic period in preconditioned rats, with lower levels of endothelial desquamation and cerebral edema. Blockade of nitric oxide synthesis eliminated the protective effects of both phases of preconditioning.

[The role of oxygen free radicals in the mechanisms of local and distant ischemic myocardial preconditioning]

The phenomenon of ischemic preconditioning consists in increase in myocardial tolerance to ischemia after short periods of ischemia and reperfusion of the myocardium (local preconditioning) or a distant organ (distant preconditioning). This study is dedicated to the role of oxygen free radicals (OFR) in the mechanisms of preconditioning; pharmacological inhibition of OFR with N-2-mercaptopropionylglycin, a synthetic anti-oxidant, was used. Mouse experiments demonstrated a reduction in the infarction-limiting effect of local preconditioning as a result of OFR inhibiting. This confirms the hypothesis according to which OFR play an important role in the mechanisms of launching and mediating the protective effect of local preconditioning. On the contrary, application of the same dose of N2-mercaptopropionylglycin does not lead to a significant weakening of the infarction-limiting effect of distant preconditioning caused by 20 min of ischemia and 15 min of reperfusion of the small intestine. Thus, it is unlikely that OFR participate in the realization of the effect of distant preconditioning caused by small intestinal ischemia. The authors discuss hypothetic molecular mechanisms of distant myocardial preconditioning.

Frequency-dependent effects of low-intensity ultrasound on activity of isolated heart

The experiments with low-intensity ultrasound stimulation of isolated rat heart revealed frequency-dependent effects of ultrasound in a frequency range of 45-298 kHz on cardiac activity.

[Influence of He-Ne laser irradiation and local anesthetics on potassium channels in the snail neurons]

Using clamp method it had been shown that He-Ne laser irradiation of the snail neurons increases the amplitude of voltage-gated slow potassium currents in dose of 0.7 x 10(-4) (fluence 1.5 x 10(2) Wt/m2) and decreases it in dose 0.7 x 10(-3). Bupivacaine and lidocaine suppressed potassium currents. Laser irradiation in dose 0.7 x 10(-3) enhanced the inhibitory effect of bupivacaine (10 mcM) and in dose 0.7 x 10(-4) it decreased the inhibitory effect of bupivacaine. The results of the study suggest mechanisms of the He-Ne laser irradiation effect in combination with pharmacological substances on ion channels of electrically excitable cells.

[Myocardial ischemic postconditioning: a brief ischemia causes conversion of resistent reperfusion-induced ventricular fibrillation into the normal rhythm]

Brief episodes of myocardial ischemia-reperfusion were shown to be protective against reperfusion injury when used during early reperfusion after a prolonged ischemic episode. This phenomenon has been termed myocardial ischemic postconditioning. In this study, an effect of ischemic postconditioning on persistent reperfusion-induced ventricular fibrillation was studied in the rat isolated heart. 2 minutes of global ischemia on the 15th minute of reperfusion after 30 minutes of regional ischemia effectively abolished the persistent ventricular fibrillation. In non-postconditioned hearts, the ventricular fibrillation continued to the end of reperfusion. The ischemic postconditioning seems to exert a strong antiarrhythmic effect protecting the heart against persistent reperfusion-induced ventricular tachyarrhythmias.

[Ischemic adaptation of the rat brain as a method for protection of endothelium from ischemic reperfusion injury]

This study represents results of investigation carried out to determine the endothelium-protective effect of early and late phases of brain ischemic preconditioning as well as local and remote adaptation. The experiments were performed on adult male rats. Prolonged 30-min four vessels brain ischemia followed by 120-min reperfusion on carotid arteries, was performed (control group). Early and late local ischemic preconditioning was due to both 5-min ischemia and 30-min and 48 h reperfusion respectively on carotid arteries. Remote ischemic preconditioning was caused by 30-min ischemia and also by 15-min and 48 h reperfusion, respectively (early and late phases of adaptation) on femoral artery before prolonged brain ischemia described above. To estimate the role of nitric oxide in ischemic adaptation, mechanisms involved both nonselective blocker of NO-synthesis (N omega-nitro-L-arginine) in the time of early adaptation phase and the relatively selective iNOS inhibitor S-methylisothiourea sulfate, given before sustained brain ischemia, on the late preconditioning. Registration of brain blood flow was made by ultrasonic high-frequency Doppler device. Degree of brain edema was studied and evaluation of desquamated endothelial cells in blood was carried out. Early and late phases of local ischemic preconditioning were found to improve the brain blood flow and level of circulatory endothelial cells as well as to reduce degree of edema. The endothelium-protective effect of remote ischemic preconditioning has been proved in this study only on the late phase. Nitric oxygen was found to be important endothelium-protective factor in ischemic preconditioning.

[Effect of the He-Ne laser irradiation on resistance of the isolated heart to the ischemic and reperfusion injury]

The aim of this work was to investigate the myocardial protection against ischemia/reperfusion using low level laser irradiation (LLLI). It has been shown that pulse pressure was higher in the period of post-ischemic reperfusion as compared with the control group. It provided a better restoration of myocardial contractility as well as increasing of coronary flow in the reperfusion period. The amount of ventricular rhythm disorder episodes decreased. These effects of laser application were registered in conditions of coronary flow reduction less than 50%. One of the suggested mechanisms of laser effect is an ATP-sensitive channel activation.

[Photochromotherapy of experimental compression-ischemic neuropathy]

Effects of monochrome light of the green and red spectra (mean wave length 540 and 670 nm, respectively) were studied on experimental rat model of compression-ischemic neuropathy (40 animals). The nerve under compression was exposed to green and red light using light-diode physiotherapeutic unit "Spectr-LC" with different intensity. Electromyographic parameters of the compressed nerve improved significantly after exposure to monochrome green light with intensity 500 mJ/cm2. The effect was dose dependent. Green light produced better effect.

Preconditioning of the small intestine to ischemia in rats

Measures reflecting the state of the small intestine were studied in rats after ischemia lasting 90 min produced by clamping the superior mesenteric artery and reperfusion for 30 min. Preconditioning of the intestine to ischemia was induced by producing intestinal ischemia for 10 min followed by 10 min of reperfusion (ischemic preconditioning), 30-min limb ischemia with 15-min reperfusion (distant ischemic preconditioning), and i.v. L-arginine. The smallest amount of damage to the intestine after 90 min of ischemia and 30 min of reperfusion was seen in the group of rats subjected to ischemic preconditioning. The protective effect of ischemic preconditioning was partially blocked by administration of N-omega-nitro-L-arginine (a blocker of NO synthesis). Doses of L-arginine also had protective effects, though these were smaller than those of ischemic preconditioning. Preliminary ischemia-reperfusion of the limb had no effect on the state of the intestine. Thus: 1) ischemic preconditioning of the intestine is partially associated with activation of nitric oxide synthesis, and 2) distant ischemic preconditioning did not protect the intestine.

[Possibility of angiogenesis stimulation in ischemia by embryonic human brain tissue (initial experimental results)]

The article proves the presence of angiogenic activity of the original specimen of biological genesis obtained from the embryogenic human brain tissue. The investigation was carried out on ischemia models of the rat's myocardium and hind limb.