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Biomedical subjects

A Kharlamov

Publications and source records attributed to A Kharlamov.

16 recordsLinked to original sources
PubMed2002

A simple method for the synthesis of silicon carbide nanorods.

SiC nanorods were synthesized by a reaction at a temperature of 1200 degrees C, under an argon gas atmosphere, from silicon and amorphous carbon powders mixed by ball milling. The reaction product, which contain SiC nanorods and nanoparticles, has been characterized by high-resolution transmission electron microscopy, X-ray diffraction, and micro-Raman spectroscopy. The synthesized nanorods are more than 1 micron long with a mean diameter of about 10-30 nm. The nanorods possess a well-defined crystalline structure with a thin layer of amorphous SiO2 on the surface. Raman shifts of SiC nanorods and the role of structural defects are discussed.

Carbon Compounds, Inorganic↗
PubMed2001

Early visual changes in reflected light on non-stained brain sections after focal ischemia mirror the area of ischemic damage.

There is no reliable, simple method for delineation of ischemic regions at early time points after ischemia. We propose that at early times after stroke, ischemic regions can be visualized as a subtle change in reflected light directly in thaw-mounted, dried 20 microm brain sections. In 15 male Sprague-Dawley rats, anesthetized with isoflurane, middle cerebral artery transection and permanent bilateral common carotid artery occlusion was performed and brains were processed in five different ways. Areas of reflective change (RC) on non-stained sections were compared with areas on the adjacent sections delineated by microtubule associated protein 2 (MAP2) antibody, a reliable marker for early post-stroke, in five rats each at 1, 3, and 6 h after focal cerebral ischemia. A statistically significant correlation between ischemic areas (IA) measured on non-stained brain sections (IA(RC)) and adjacent sections immunostained (IM) with MAP2 Ab (IA(IM)) (IA(RC)=0.05+0.88.IA(IM); R2=0.8; n=15; P<0.01) and a small mean difference +/-2 S.D. (-0.9+/-6.0%) indicated that the area measured on non-stained sections reflects the IA measured on MAP2 -IM sections. At 1 and 3 h after ischemia, the ratio between ischemic regions measured on the non-stained sections and on the adjacent sections immunostained with MAP2 Ab were not different from 100% (97.6+/-1.7%, 100.9+/-6.0%). At 6 h post-stroke, the IA measured on the non-stained sections was larger than on the IM sections (109.8+/-2.7%, P<0.01, compared to 100% ratio). Our study demonstrated that this quick and simple method for detection of damaged brain permitted the use of brain tissue for other assays and could be very useful for neuroprotective evaluation and for directed micro-sampling of brain tissue at early times after ischemia.

Animals↗
PubMed2001

Photothrombotic brain infarction results in seizure activity in aging Fischer 344 and Sprague Dawley rats.

This study was designed to determine whether photothrombotic brain infarction could result in epileptic seizures in adult animals. Male Fischer 344 (F344) rats at 2, 6, 12, 24, and 30 months of age and male Sprague Dawley (SD) rats at 2 and 6 months of age underwent photothrombotic brain infarction with the photosensitive dye rose bengal by focusing a wide (6 mm) or narrow (3 mm) diameter white light beam on the skull overlying left hemisphere anterior frontal, midfrontal, frontoparietal, or parietal areas. Animals were monitored with video and EEG recordings. Morphological analysis of infarct size was performed with a computer-assisted image analysis system. The primary finding of this study was that epileptic seizures were recorded in post-mature rats 2 months after lesioning the frontoparietal cortex with large photothrombotic infarcts that extended to the cortical-subcortical interface. These seizures were characterized behaviorally by motor arrest, appeared to originate in the periinfarct area, and could be distinguished from inherited spontaneous bilateral cortical discharges by the morphology, frequency, duration, and laterality of the ictal discharges. Small cortical lesions were ineffective in producing seizures except for one animal that demonstrated recurrent prolonged focal discharges unaccompanied by behavioral change. Stage 3 seizures were observed in a small number of mid-aged and aged animals lesioned with large infarcts in anterior frontal and frontoparietal areas. These results suggest that the technique of photothrombosis can be used to produce neocortical infarction as a means to study mechanisms of secondary epileptogenesis.

Aging↗
PubMed2000

Directed sampling for electrolyte analysis and water content of micro-punch samples shows large differences between normal and ischemic rat brain cortex.

Changes in sodium, potassium, and water content in brain tissue are important in the progression of pathology that follows ischemic stroke. Determining these parameters regionally in rodent models of experimental ischemia has been limited because typical tissue weights of more than 35 mg are too large. Identifying ischemic tissue to direct tissue sampling towards ischemic cortex is also represents a difficult generally unresolved area. We suggest that larger differences between normal and ischemic cortex of sodium, potassium, and water content than previously observed can be obtained from directed sampling of 2-mg brain tissue in a model of focal cerebral ischemia. In five rats, the middle cerebral artery and both common carotid arteries were occluded for 4.9+/-0.13 h (mean+/-SEM). Punch-sampling of 1-mm diameter tissue cores for water content (H(2)O%) by the wet-dry method, and [Na(+)] and [K(+)] by flame photometry, was guided by the observation of a subtle change in the surface reflectivity of ischemic cortex of quickly dried, 20-microm frozen brain sections, that was confirmed by MAP2 immunohistochemistry. The ratio of the lesion areas as determined by the reflective change and MAP2 immunoreactivity was 0.96+/-0.03 (n=5). In ischemic cortex H(2)O% was 79.9%+/-0.8%, [Na(+)] was 550+/-25 mEq/kg dry-weight, and [K(+)] 94.2+/-19.2 mEq/kg dry-weight (n=5), all significantly different from the values in border zone cortex, and in cortex contralateral to ischemic cortex and border zone (for all samples n=60, mean wet weight 2.037+/-0.046 mg). Differences between ischemic and normal cortex were 5.4+/-1.1%, 317+/-21 mEq/kg dry-weight, -304+/-27 mEq/kg dry-weight (n=5) for H(2)O%, [Na(+)], and [K(+)]. These differences between ischemic and normal cortex are 1.4-2.5, 1-3.11, and 1.4-3.5 times greater, respectively, than previous results obtained using samples weighing 35 mg or more. These results extend the association of sodium and potassium with ischemic brain edema in the rodent model, and show that these classical measurements can keep pace with the regionality of histochemical and morphological methods.

Animals↗
PubMed2000

Age-dependent increase in infarct volume following photochemically induced cerebral infarction: putative role of astroglia.

This study demonstrates that the photochemically induced model of stroke is an extremely viable method of inducing cerebral infarction in old animals. The lesions are reproducible both in terms of location and size and compatible with long-term survival of the animal. With this model we demonstrated, one week following surgery, a significantly larger infarct in rats 20 and 24 months of age compared to 4-month-old rats. The older rats also sustained greater neurologic deficits as assessed on a rotarod task. Older rats also were characterized by a glial response that was far less intense than in young animals. While the precise relationship between glia activation and cerebral damage remains to be determined, it would appear that a better understanding of those factors that contribute to the astrocytic response in the aged rat may be of particular benefit in designing therapeutic strategies aimed at reducing the pathologic consequences of cerebral infarction in elderly humans.

Aging↗
PubMed1997

Cycloheximide reduces the size of lesion caused in rats by a photothrombotic model of brain injury.

A reproducible brain lesion can be triggered in rats by treating them systematically with rose bengal and irradiating their skulls with light. This procedure is often referred to as the photothrombotic model of stroke/ injury. Recently we reported that in this model some cells show signs of apoptosis, programmed cell death. Apoptosis can be attenuated by inhibitors of macromolecular synthesis. In the work described here, we tested the hypothesis that the protein synthesis inhibitor cycloheximide will reduce the actual size of a photothrombotic brain lesion. Ten male rats were treated subcutaneously with 2.5 mg kg-1 cycloheximide; 10 rats received saline. One hour later, a photothrombotic injury was induced in the left cortex in all animals; they were sacrificed 24 h after photothrombosis. Nissl staining and computer-assisted analyses were used to assess the volume of the lesion, and to count the Nissl-positive cells. Both assays revealed significant protective action of cycloheximide treatment. In line with previous reports in which we described the occurrence of apoptosis in the model of photothrombotic brain injury our results with cycloheximide suggest that this model of focal brain ischemia can be used to test the neuroprotective efficacy of putative antiapoptotic compounds.

Animals↗
PubMed1996

Pharmacological characterization of apoptotic cell death in a model of photothrombotic brain injury in rats.

We have shown recently in rats that photothrombotic local brain injury that is induced by the intravenous injection of the photosensitive dye rose bengal and skull irradiation with a beam of focused light can trigger the expression of the protein p53 and initiate DNA damage in the area surrounding the thrombotic/necrotic core. We hypothesize that these changes are the signs of injury-induced apoptosis. We used pharmacological tools to characterize the injury-triggered DNA damage that we assayed by TUNEL-labeling, followed by a computer-assisted quantitative analysis. In addition, the morphology of apoptotic cells was visualized by fluorescent staining with propidium iodide. The pharmacological approach included: (a) the inhibition of endonucleases by intracerebroventricular injection of aurintricarboxylic acid (ATA, 20 micrograms/5 microliters); (b) the inhibition of protein synthesis by injecting cycloheximide subcutaneously (2.5 mg/kg); and (c) the blockade of glutamate receptors by injecting 2.5 mg/kg dizolcipine (MK-801) intravenously. These treatments significantly reduced the number of apoptotic cells that we counted in the area surrounding the necrotic core. The results show that injury-induced DNA damage involved de novo synthesis of proteins and an activation of endonucleases, suggesting the occurrence of apoptosis. In this model, apoptosis was associated with an activation of glutamate receptors. Treatments targeted at halting the apoptotic process might provide protection after stroke or after trauma to the brain.

Animals↗
PubMed1996

Neuroprotective effects of melatonin.

The full range of physiological actions of melatonin is not completely known. In mammals, it modulates gonadal function and regulates biological rhythms. Furthermore, it has also been reported to have anxyolitic, sedative, and anticonvulsant properties, both in human and animals. Recently it has been shown that melantonin is a potent, endogenous hydroxyl radical scavenger suggesting that it might interfere with neurodegenerative processing involving free-radical formation and excitatory amino acid release. Using primary cultures of rat cerebellar neurons and in vivo models of brain injury in rats, we demonstrate that melatonin might be considered an endogenous neuroprotective factor useful for the pharmacological treatment of neurological disorders and neural degeneration produced by glutamate excitotoxicity and oxidative stress.

Animals↗
PubMed1996

Protective effect of melatonin against hippocampal DNA damage induced by intraperitoneal administration of kainate to rats.

The pineal hormone melatonin protects neurons in vitro from excitotoxicity mediated by kainate-sensitive glutamate receptors and from oxidative stress-induced DNA damage and apoptosis. Intraperitoneal injection on kainate into experimental animals triggers DNA damage in several brain areas, including the hippocampus. It is not clear whether melatonin is neuroprotective in vivo. In this study, we tested the in vivo efficacy of melatonin in preventing kainate-induced DNA damage in the hippocampus of adult male Wistar rats. Melatonin and kainate were injected i.p. Rats were killed six to 72 h later and their hippocampi were examined for evidence of DNA damage (in situ dUTP-end-labeling, i.e. TUNEL staining) and for cell viability (Nissl staining). Quantitative assay was performed using computerized image analysis. At 48 and 72 h after kainate we found TUNEL-positive cells in the CA1 region of the hippocampus; in the adjacent sections that were Nissl-stained, we found evidence of cell loss. Both the number of TUNEL-positive cells and the loss of Nissl staining were reduced by i.p. administration of melatonin (4 x 2.5 mg/kg; i.e. 20 min before kainate, immediately after, and 1 and 2 h after the kainate). Our results suggest that melatonin might reduce the extent of cell damage associated with pathologies such as epilepsy that involve the activation of kainate-sensitive glutamate receptors.

Animals↗
PubMed1996

Increased brain damage after stroke or excitotoxic seizures in melatonin-deficient rats.

The pineal hormone melatonin is neuroprotective in vitro, and in vivo it is neuroprotective when given in pharmacological doses. Consequently, it has been hypothesized that with aging, as circulating levels of melatonin in mammals normally decrease, the brain might be at increased risk of neurodegeneration. However, direct evidence that melatonin deficiency leads to increased brain vulnerability is still lacking. We created melatonin deficiency in rats by pinealectomy and induced neurodegeneration by two models of focal brain ischemia/stroke and by glutamate receptor-mediated, epilepsy-like seizures. We observed greater neurodegeneration in melatonin-deficient animals than in controls. Our results suggest that endogenous melatonin may play a neuroprotective role, and that melatonin deficiency might be a pathophysiological mechanism in neurodegenerative diseases.

Animals↗
PubMed1994

Photochemical brain injury in rats triggers DNA fragmentation, p53 and HSP72.

The aim of the study was to examine whether apoptosis, apoptosis-related protein p53 and heat-shock protein (HSP) 72 participate in the response of the brain to focal injury. Male Sprague-Dawley rats received intravenously a photosensitive dye rose bengal. Unilateral cortical thrombosis was induced by illuminating the skull of rose bengal-treated rats for 10 min with a focused beam of light. Animals were killed and brains were processed for immunohistochemical detection of DNA fragmentation, p53, and HSP72 kD. DNA fragmentation and p53 were increased only in the perifocal area in the cortex ipsilateral to the thrombotic focus, while HSP72 increased throughout the ipsilateral cortex, except in the immediate perifocal area. The results suggest that in response to focal brain injury, some cells die through an apoptotic process that might involve an accumulation of p53.

Animals↗
PubMed1994

LIGA20, a lyso derivative of ganglioside GM1, given orally after cortical thrombosis reduces infarct size and associated cognition deficit.

A bilateral photochemically induced thrombotic lesion of rat sensorimotor cortex (approximately 3 mm in diameter and 25 mm3 in volume) is associated with a persistent cognition (learning and memory) deficit, which was evaluated with water maze tasks. The N-dichloroacetylsphingosine derivative of lysoGM1 (LIGA20) administered after the lesion either i.v. or per or reduces the infarct size by 30-40% and attenuates the associated cognition deficits, presumably by limiting the extent of damage of neurons at risk located in the surroundings of the infarcted core (i.e., area penumbra). The LIGA20 protection is dose and time dependent. Maximal protection is afforded by a single dose of LIGA20 of 34 mumol/kg i.v. 1 hr after lesion or by a dose of 270 mumol/kg per os when administered 1 hr and 24 hr after the lesion. The protective effect of LIGA20 can be observed when the drug is administered i.v. up to 6 hr after the lesion. The protective efficacy of the oral administration of LIGA20 is related to its physiochemical properties, which, unlike those of GM1, allow absorption from the gastrointestinal tract. LIGA20 given orally reaches the brain promptly and rapidly inserts into the neuronal membranes. Here, by an unknown molecular mechanism, LIGA20 selectively reduces the pathological amplification of Ca2+ signaling elicited by persistent stimulation of ionotropic glutamate receptors in the area penumbra.

Administration, Oral↗
PubMed1993

Semisynthetic sphingolipids prevent protein kinase C translocation and neuronal damage in the perifocal area following a photochemically induced thrombotic brain cortical lesion.

A vascular thrombotic lesion localized to the rat sensorimotor cortex was produced following intravenous injection of the photosensitive dye rose bengal, and its activation with a small beam of high-intensity white light focused to the skull overlaying the sensorimotor cortex. In the sensorimotor cortex at various times after the triggering event, two contiguous brain regions with different degree(s) of neuronal damage can be distinguished: (1) a primary thrombotic ischemic core where the majority of cells are dead and (2) a penumbra region surrounding the core lesion in which a slower progressive neuronal degeneration is occurring. Importantly, in both brain regions the neuronal degeneration is associated with the activation and persistent translocation of protein kinase C (PKC) as indicated by an increase in 4-beta-3H-phorbol-12,13-dibutyrate (3H-PDBu) binding. Moreover, the demonstration that in the area penumbra the neuronal degeneration and the persistent translocation of PKC can be inhibited by a pretreatment with dizocilpine (i.e., MK-801) indicates that the dynamics of the progression of the neuronal degeneration are maintained by glutamate accumulating in the extraneuronal fluids. MK-801 additionally prevents the transcriptional activation of several immediate-early genes (IEGs) (e.g., c-fos) and their cognate third nuclear messenger (i.e., c-Fos) expression present in the hemisphere ipsilateral to the lesion. On the other hand, LIGA4 and LIGA20 derivatives of GM1 lysoganglioside reduce the membrane translocation of PKC and the neuronal damage in the penumbra area, but fail to change the increase of IEG expression in the cortex ipsilateral to the lesion.

Animals↗
PubMedDate not supplied

Sequelae of biochemical events following photochemical injury of rat sensory-motor cortex: mechanism of ganglioside protection.

In culture the protracted and abusive stimulation of glutamate (GLU) receptors results in neuronal death through a mechanism involving the persistent translocation of PKC and the destabilization of (Ca2+)i homeostasis [(Ca2+)i HD]. In contrast, intermittent GLU receptor use elicits a coordinated expression of immediate early genes (IEG) acting as nuclear third messenger. Brain ischemia also is known to result in the paroxysmal abusive stimulation of glutamate receptors. The glutamate receptive elements in turn degenerate largely as a function of their inability to control homeostatic Ca2+ due to the irreversible translocation of PKC. In the present study we employed an in vivo model of focal brain ischemia using the photosensitive dye, Rose bengal. With this model we sought to determine the neuroprotective actions of MK-801, a noncompetitive blocker of GLU at the NMDA-sensitive receptor and of the semisynthetic gangliosides LIGA 4 and LIGA 20 which in vitro have been demonstrated to block PKC translocation. Moreover, we sought to establish whether the persistent stimulation of ionotropic glutamate receptors would led to a change in ionotropic glutamate expression in the focal and perifocal area. Importantly, the perifocal area (i. e., the region surrounding the area of primary insult) is a region in which profound cellular reorganization occurs including neuronal death and glial proliferation and is a key region to target various neuroprotective drugs aimed at ameliorating the neurodegeneration following stroke. Receptor abuse dependent antagonists (RADA) drugs such as gangliosides selectively curtail the amplification steps that specifically differentiate signal transduction following physiological receptor use from that following pathological receptor abuse.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗