Lesions In Rat Brain Research Articles

Parametric multiecho proton spectroscopic imaging: application to the rat brain in vivo.

A parametric multiecho variant of proton spectroscopic imaging (SI) is presented using a multiecho SI sequence with uniform phase-encoding of all echoes within each echo train. The acquisition of SI data sets at different echo times (TE) increases the amount of information obtained within the same total measuring time as in standard SI measurements. The gain in information can be used: (a) to choose the most appropriate TE for each metabolite signal with respect to T2, spin coupling, or problems caused by peak overlap; (b) to measure the relaxation time T2 of metabolite signals with high spatial resolution; or (c) to improve the signal-to-noise ratio for metabolite signals with long T2 values by adding spectra calculated from consecutive echoes. The method was tested in vivo on healthy rat brain and applied to study metabolic changes in rat brain lesions.

Regulation of 1,4,5-IP 3, 1,3,4,5-IP 4 and IP 6 binding sites following entorhinal cortex lesions in rat brain

A lesion of the entorhinal cortex produces a loss of more than 80% of the synapses in the outer molecular layer of the hippocampus in the rat. However, this synaptic loss is transient. Beginning a few days after denervation, new synapses are formed, virtually replacing the lost inputs within two months. Synaptic remodelling induced by entorhinal cortex lesion is associated with specific modifications of various neurotransmitters, hormones and growth factors. Many of these substances act at membrane bound-receptors to induce the hydrolysis of phosphatidylinositols generating various inositol phosphates. Some of the key members of this family include inositol 1,4,5-trisphosphate, inositol 1,3,4,5-tetrakispho-sphate and inositol hexakisphosphate which are all associated with the maintenance Ca 2+ homeostasis. To investigate the potential roles and/or alterations of inositol phosphates in entorhinal cortex lesions-induced neuronal plasticity, we quantified specific receptor sites for inositol 1,4,5-trisphosphate, inositol 1,3,4,5-tetrakisphosphate and inositol hexakisphosphate using their respective tritiated ligands, at different periods post-lesion corresponding to the degenerative and subsequent reinnervation phases. [ 3H]inositol 1,4,5-trisphosphate binding sites are maximally increased (30%) between two and eight days post-lesion in the hippocampal formation on both sides of the lesion. In the cortex, [ 3H]inositol 1,4,5-trisphosphate binding increased also bilaterally following the lesion. Changes in [ 3H]inositol 1,3,4,5-tetrakisphosphate binding are delayed and reduced (20% increase) in magnitude compared to these seen for [ 3H]inositol 1,4,5-trisphosphate binding. The maximal peak in [ 3H]inositol 1,3,4,5-tetrakisphosphate binding is observed between eight and 14 days after the lesion in the hippocampal formation and the cortex. On the other hand, decreases in [ 3H]inositol hexakisphosphate binding (up to 30%) in the parietal cortex and the pyramidal cell layer of the hippocampal formation were observed between 14 and 30 days post-lesion. Taken together, these results suggest that inositol 1,4,5-trisphosphate, inositol 1,3,4,5-tetrakisphosphate and inositol hexakisphosphate receptors can be regulated in vivo following entorhinal cortex lesions. A unique time course is observed for each inositol phosphate receptor site studied. This finding supports the hypothesis suggesting that each inositide is differentially involved in the process of neuronal plasticity observed following deafferentation in the entorhinal cortex of rats. The bilateral changes in unilaterally lesioned animals is consistent with secondary synapse turnover associated with deafferentation.

Preparation, characterization and release of microencapsulated bromodeoxyuridine

Biodegradable and biocompatible microspheres with bromodeoxyuridine (BrUrd) have been prepared, characterized and tested in vitro and in vivo. Scanning electron microscopy and image analysis revealed regular spherical shapes and an average size ± SD of 2.47 ± 0.59 μm. Total content of BrUrd as determined by HPLC was within the range of 0.2 − 1.5%. Kinetic analyses of two different preparations showed similar release half-times (approx. 12 hrs), kinetic constants −0.0556, −0.0564, and −0.0557, −0.0597 [h −1], and correlation coefficients of 0.998, and 0.999 when fitted to the first order or biphasic first order kinetics, respectively. Preliminary data from immunocytochemical studies revealed efficient incorporation of BrUrd delivered from these microcapsules into nuclei of proliferating cells surrounding brain lesions in rats.

S-5-4 - Characteristics of memory impairments associated with brain lesions in rats.

S-5-4 - Characteristics of memory impairments associated with brain lesions in rats.

MRI and MRS studies on the time course of rat brain lesions and the effect of drug treatment: volume quantification and characterization of tissue heterogeneity by parameter selection.

Magnetic resonance imaging has been used to follow the time course of lesions induced in the rat brain as an animal model for characterization of the volume of the lesion. The dispersion in spin-spin relaxation has been used to characterize the nature of the brain lesion. Parameter selective estimation of T2, quantitative determination of the lesion size and volume selective in vivo proton spectroscopy have been employed for the purpose. The work has been carried out on rats which were subject to lesioning by ibotenic acid as a model for excitotoxicity and also on rats which received doses of ibotenic acid and subsequent doses of the NMDA antagonist drug MK 801 (dizocilpine). The time course of the progress of the lesions in untreated animals and the effect of neuroprotection by MK 801 was continuously monitored in all test animals. Further, a relatively new inhalation anesthetic agent, isoflurane, has been employed. A more logical and semiquantitative T2 bandwidth demarkation useful in distinguishing different degrees of lesioning from the onset and up to the 'edema' stage through penumbra (mild lesion), medium degree lesion and severe lesion has been proposed.

7β-Hydroxycholesterol and 7β-hydroxycholesteryl-3-esters reduce the extent of reactive gliosis caused by an electrolytic lesion in rat brain

Electrolytic lesions performed in brain cortex of six-day-old or adult rats resulted in the appearance of many reactive astrocytes around the injury site after a postoperative delay of eight days. They were revealed by immunohistochemistry using antibodies against glial fibrillary acidic protein. Injection of tritiated thymidine 24 h prior to autopsy indicated that, in neonates, 50% of the reactive astrocytes were proliferating. Infusion of 2 μl of liposome suspension made of phosphatidylcholine and a monosialoganglioside, in the injury site, immediately after the electrolytic lesion did not modify the extent of the reactive gliosis. Liposomes containing 3 nmol of either 7β-hydroxycholesterol, 7β-hydroxycholesteryl-3-stearate or 7β-hydroxycholesteryl-3-oleate reduced by about 50% the intensity of the reactive gliosis in the frontal cortex of six-day-old rats and by 40% the number of dividing astrocytes. In the adult rat cortex the intensity of the glial reaction was also decreased by 30% by 15 nmol 7β-hydroxycholesteryl-3-oleate. Further investigations demonstrated that it is the 7β-hydroxy function which is needed for the biological activity of these oxysterols.These findings, which demonstrate anti-proliferative and anti-inflammatory properties of 7β-hydroxycholesterol on astrocytes, facilitate the future investigation of the influence of reactive gliosis on functional recovery following brain injury. This anti-proliferative property could also be used in other kinds of pathologies involving glial cell proliferation, such as glioblastomas.

Neuronal uptake of plasma proteins in cryogenic brain lesions. An immunoelectron microscopic study.

A previous light microscopic study on cryogenic brain lesions in rats demonstrated uptake of plasma proteins into damaged neurons within a few minutes after the lesion. The protein concentration was much higher inside the nerve cell bodies than in the surrounding neuropil. This is puzzling since the neuropil to a large extent consists of damaged neuronal processes. The present investigation describes the intracellular localization of albumin in this model using a post-embedding immunoelectron microscopic technique. The distribution of albumin in the lesions was studied after 1, 6 and 12 h survival periods. The intraneuronal albumin was mainly bound to the particulate elements of the cytoplasm and nuclei, while the watery parts of the cells showed no immunoreactivity. The intracellular organelles contained very little albumin, indicating that their membranes may be more resistant to freezing than those of the cells. Most of the neuronal and glial processes in the neuropil were swollen and contained almost no albumin. This explains the contrast between the strong immunoreactivity of the neurons and the vague reactivity of the neuropil in light microscopy.

T2- and diffusion-weighted magnetic resonance imaging of a focal ischemic lesion in rat brain.

We sought to evaluate the application of T2-weighted and diffusion-weighted magnetic resonance imaging techniques in the study of a focal ischemic lesion in the rat brain. Unilateral cortical infarcts were induced using the photosensitive dye rose bengal and 560 nm light irradiation. Magnetic resonance images were recorded from a total of 11 rats at selected intervals from 1.5 hours to several days after induction of the lesion. Parallel experiments were performed in which Evans blue dye was injected into the lesioned animals either immediately after lesion induction (n = 11) or 1 hour before the animals were killed (n = 11). The second procedure was designed to show regions of blood-brain barrier permeability to plasma proteins at the time of sacrifice, whereas the first procedure showed the accumulation and subsequent dispersion of plasma protein following disruption of the blood-brain barrier. Regions of the cortex highlighted by the T2-weighted images corresponded well to the pattern of dye staining seen from the first procedure while the diffusion-weighted images showed visual correspondence with the staining pattern obtained using the second procedure. These results illustrate the complementary use of T2-weighted and diffusion-weighted magnetic resonance imaging in discerning the pathophysiology of developing lesions.

Depletion of connexin43-immunoreactivity in astrocytes after kainic acid-induced lesions in rat brain.

Recent studies have established that the gap junction protein connexin43 is a major structural component of gap junctions between astrocytes in rat brain. Here, we investigated by immunohistochemical methods the effect of kainic acid-induced neuronal degeneration on connexin43 expression by astrocytes. Stereotaxic injections of kainic acid into the thalamus were found to cause a near total depletion of connexin43-immunoreactivity at the lesion site. Areas depleted of connexin43 corresponded to those exhibiting substantial neuronal loss and intense gliosis. These results implicate a neuronal contribution to the regulation of connexin43 expression by astrocytes and, hence, to local control of the potassium spatial buffering capacity afforded by astrocyte gap junctions.

Cortical Microcirculation in a New Model of Focal Laser-Induced Secondary Brain Damage

To study the causes of spatial and temporal evolution of progressive neuro-injury in focal brain ischemia, models with consistent lesion topography are required. In such models, continuous monitoring of the microcirculation in a penumbral area undergoing progressive damage could be possible. We used a fixed-pulse (1.0 s, 40 W) Nd-YAG laser (NYL) to produced discrete brain lesions in rats and monitored the cerebral blood flow (CBF) with laser-Doppler flowmetry (LDF) in nonirradiated areas directly adjacent to the maturing lesion. We also examined the time evolution of the lesion topography over a 4 day period. The lesion volume determined by histopathological methods increased from 3.1 +/- 0.5 to 4.5 +/- 0.5 mm3 (p less than 0.05) during the first 2 h. Simultaneously, LDF indicated severe hypoperfusion (-60 +/- 21%, p less than 0.01) at a zone (1 mm distance from the laser lesion) where progressive neuronal degeneration and increased tissue water content (80.0 +/- 3.3% versus 76.8 +/- 2.1% in normal tissue, n = 7, p less than 0.05) were also observed. At a 4 mm distance from the lesion, hyperemic CBF responses were observed, but no histopathological signs or edema. Secondary brain damage progressed up to 4 days (lesion volume of 6.0 +/- 0.7 mm3). The NYL-induced brain lesion produced a highly reproducible focal injury and progressive neuronal death in a spatial relationship with microcirculatory failure and edema formation. The model allows prospective study of tissue state at a discrete zone, which is separate from the initial injury, but susceptible to secondary brain damage.

21-Aminosteroids Reduce Brain Edema Produced by Cryogenic Brain Lesion in Rats

21-Aminosteroids Reduce Brain Edema Produced by Cryogenic Brain Lesion in Rats

In vivo and in vitro staining of acidophilic neurons as indicative of cell death following kainic acid-induced lesions in rat brain

An in vivo method for positively staining dead neurons was developed and compared with an in vitro staining method using acid fuchsin. Neurons previously killed by intracerebral injections of kainic acid were selectively stained by trypan blue within 15 min of its injection in vivo into the central nervous system of rats. Such staining persisted for at least 4 days in vivo, and there was no evidence that trypan blue itself was toxic to the remaining cells. Intense staining of neurons with acid fuchsin in vitro was first observed in brain sections of rats killed about 6h after kainic acid injection. This time was approximately 2-3 h before trypan blue, in vivo, was able to stain neurons. Thus, the loss of transport mechanisms (at least for trypan blue) apparently occurs subsequent to the development of basic products stainable with acidic dyes. At the earliest times, acid fuchsin stained neurons which had not yet lost Nissl substance, whereas the majority of trypan blue-stained neurons were not stained with Nissl dyes. After 24 h the majority of neurons stained with either acid fuchsin or trypan blue were Nissl-stain negative. The combination of staining with trypan blue in vivo with subsequent counterstaining of brain sections with acid fuchsin in vitro may have a potential use in the determination of the time of neuronal death in vivo.

Effect of dopamine-depleting brain lesions in rat pups: Role of striatal serotonergic neurons in behavior.

Previous results from our laboratory have demonstrated that 3-day-old rats given dopamine (DA)-depleting brain lesions are spared the severe behavioral dysfunctions seen after comparable brain damage in adults. This behavioral sparing is accompanied by a sprouting of serotonin (5-HT)-containing neurons in the striatum. The present results extend these observations by demonstrating that rats given the brain lesions as 15- or 27-day-olds continue to suckle, wean, and grow into adulthood without exhibiting any obvious behavioral dysfunctions, yet striatal 5-HT levels do not increase. Moreover, combined destruction of DA- and 5-HT-containing neurons in 3-day-old rat pups also produced no obvious behavioral dysfunctions. These and other results indicate that increases in striatal 5-HT are not necessary for the behavioral sparing observed after DA-depleting brain lesions in neonatal rats.

Nature and distribution of brain lesions in rats intoxicated with 3-nitropropionic acid: a type of hypoxic (energy deficient) brain damage.

The clinical signs and morphological brain lesions associated with histotoxic hypoxia induced by subcutaneous injection of 3-nitropropionic acid (NPA) in rats are described, and compared to hypoxic brain damage from other causes including ischemia and hypoglycemia. The brains were perfusion-fixed with paraformaldehyde/glutaraldehyde fixative, and examined by light and electron microscopy. Intoxicated rats developed severe neurological disease characterized by somnolence, uncoordinated gait with stereotypical paddling movements, and ventral or lateral recumbency. Recumbent rats had a selective, bilaterally symmetrical pattern of severe morphological injury in the caudate-putamen, hippocampus, and thalamus. Recumbency was a consistent indicator of the development of morphological brain lesions. In contrast to reports describing rat models of ischemia and hypoglycemia, morphological injury was not seen in the cerebral and cerebellar cortices of NPA-intoxicated rats. Ultrastructurally, neuronal alterations ranged from chromatin clumping with increased cytoplasmic lucency to severe cellular shrinkage or swelling with marked mitochondrial swelling (high amplitude swelling). White matter alterations included axonal swelling and adaxonal splitting of myelin lamellae. Vascular changes included perivascular deposits of proteinaceous material presumably from leakage of serum proteins, variable electron lucency of endothelial cell cytoplasm, an apparent increase in pinocytotic vesicles, rare platelet thrombosis of capillaries, and rare intravascular blebs of luminal plasma membrane. As a model of brain damage following energy deficiency, NPA intoxication has the advantages of producing morphological brain injury in a highly predictable anatomical pattern, and at a time paralleling the onset of clinical recumbency.

Localized survival of ciliary ganglionic neurons identifies neuronotrophic factor bands on nitrocellulose blots

A novel and sensitive method has been developed to identify ciliary neuronotrophic factors (CNTFs) from tissue extracts after blotting to nitrocellulose paper. The CNTF proteins are required for the in vitro survival of embryonic chick ciliary ganglionic neurons. Tissue extracts containing such CNTFs are electrophoresed using sodium dodecyl sulfate-polyacrylamide gel electrophoresis and transferred to nitrocellulose paper. Purified ciliary ganglionic neurons are seeded on the surface of the nitrocellulose blot, and the culture is incubated for 24 hr in medium lacking CNTF. CNTF can be localized on the blot because it retains its ability to support the survival of the neurons cultured on the nitrocellulose. A band of viable neurons, easily visualized by staining with a vital dye, is supported by the blotted CNTF polypeptide. The number of neurons surviving on the blotted CNTF is related to the amount of CNTF originally loaded on the electrophoretic gel. As little as 2 ng (16 trophic units) of CNTF protein contained in crude tissue extracts can be loaded on the sodium dodecyl sulfate gel and still be recognized by the cultured neurons. This method was used to identify CNTF polypeptides from extracts of adult rat nerve (24,000 and 19,000 daltons) and from tissue found near experimentally induced adult rat brain lesions (24,000 daltons). The electrophoretic mobilities of these peptides are distinct from the previously purified chick eye CNTF polypeptide (20,400 daltons).

Quinolinic acid: an endogenous metabolite that produces axon-sparing lesions in rat brain.

A current hypothesis links the neuroexcitatory properties of certain acidic amino acids to their ability to cause selective neuronal lesions. Intracerebral injection of the neuroexcitatory tryptophan metabolite, quinolinic acid, has behavioral, neurochemical, and neuropathological consequences reminiscent of those of exogenous excitotoxins, such as kainic and ibotenic acids. Its qualities as a neurotoxic agent suggest that quinolinic acid should be considered as a possible pathogenic factor in neurodegenerative disorders.

Acetylcholine levels increase in rat hippocampus following acute septal lesions: Evidence for interactions between cholinergic and noncholinergic neurons

Acute septal lesions in rat brain resulted in elevation of the amount of particle-bound acetylcholine in the hippocampus irrespective of the extent of damage to the cholinergic septohippocampal projection. Changes in the high affinity choline uptake in the hippocampus were, however, proportional to the degree of destruction of this projection. The results are discussed in terms of possible interactions between the cholinergic and noncholinergic pathways in the system investigated.

Inhibition of adrenocortical responses following olfactory stimulation in rats with stria terminalis lesions

Previous experiments using hypothalamic deafferentation and brain lesions in rats have demonstrated that while anterior hypothalamic deafferentation blocked the adrenocortical response to olfactory stimulation completely, bilateral lesions in the ventolateral medial forebrain bundle and gemini region had only a partial effect. In order to elucidate the pathways mediating this response, the adreno-cortical responses to olfactory stimulation as well as to ether stress, photic, acoustic and sciatic stimulation were studied in rats with bilateral stria terminalis or small basolateral or corticomedial amygdaloid lesions. The adrenocortical responses to all the above modalities were normal and the only response which was completely inhibited was that to olfactory stimulation in rats with stria terminalis lesions. This would indicate that the stria terminalis serves as the hypothalamic afferent pathway activating the pituitary-adrenal reaction to olfactory stimulation.

Relatively brief environmental enrichment aids recovery of learning capacity and alters brain measures after postweaning brain lesions in rats.

Enriched postlesion experience aided in overcoming effects of simultaneous bilateral cerebral lesions made at 30 days of age in one experiment with inbred Fischer rats and in a second experiment with the Berkeley S1 strain. The lesions were directed to the occipital cortex, but in most cases there was also some impairment of the hippocampus. For 60 days after operations, half of the rats lived in small individual cages and half lived in groups in large enriched-environment cages. They were then pretrained and tested on the standard 12 Hebb-Williams problems. Daily injections of methamphetamine (vs. saline) during the period of differential experience in the first experiment produced no effect on the behavioral scores. The second experiment included groups that received only 2 hr/day of enriched experience, and they benefited as much as groups that remained in the enriched environment 24 hr/day. The results of both experiments demonstrated significant beneficial effects of environment when bilateral lesions were made at a later age and when the periods of enriched experience were shorter than had previously been tested. Two additional experiments revealed significant effects of both lesions and environment on weight and RNA/DNA of brain regions.

Enzymatic regulation of adenosine 3',5'-monophosphate (cyclic AMP) in the freezing epileptogenic lesion of rat brain and in homologous contralateral cortex.

AbstractFreezing epileptogenic lesions were made unilaterally in rat cerebral cortex. Such lesions were associated with an increase in adenyl cyclase activity and a decrease in the membrane‐associated phosphodiesterase activity, with a concomitant increase in the level of cyclic AMP. Similar, though less striking, changes occurred in homologous contralateral cortex (‘mirror focus’). The effects of cyclic AMP on brain membrane systems are discussed, with the suggestion that this substance may play an important role in the genesis of focal seizures.