bluuebunny/crossref_metadata_2025 huggingface dataset:
On potassium functional feedback in neuromuscular junction
Authors: Matyushkin D. P. , Shabunova I. A. , Sharovarova G. M. , Vinogradova I. M.
Published: January 2005

The dependance of the reversal potential (Erev) of intracellular end‐plate potentials (epp) on activity patterns was studied in frog neuromuscular preparations. A shift of Erev to the positive side was found with change in frequency of stimulation from 1/sec to 50/sec. This shift corresponds to the increase of potassium concentration in the synaptic cleft to 7.0 mM. The effect of potassium concentration [K+]0 in the bath solution on quantal content (m) of epp was studied. The quantity m increased when [K+]0 was varied within the range 4.7–8.7 mM; m decreased when [K+]0 was > 8.7 mM. Such a relationship between m and [K+]0 is accounted for by the combined effect of potassium on transmitter secretion and electrongenic processes in motor nerve terminals.

The correlation between the change of m with [K+]0 and initial epp amplitudes was found and was attributed to potassium efflux from post‐synaptic region in varying quantity depending on the initial epp amplitudes. A scheme of synaptic self‐regulation by means of potassium feedback is suggested.
Induction of pinocytosis in cerebral vessels by acute hypertension and by hyperosmolar solutions
Authors: Hansson Hans‐Arne , Johansson Barbro B.
Published: January 2005

A new approach is described to study the mechanism of protein leakage through the endothelial cells in acute hypertension and after intracarotid infusion of hyperosmolar solutions. The luminal surface of the cerebrovascular endothelial cells was labeled with choleragenoid‐peroxidase before the blood‐brain barrier (BBB) dysfunction was induced. Numerous pinocytotic vesicles and some trans‐endothelial channels were formed and showed labeling of parts of their membranes.

Our results indicate that the mechanism behind the protein leakage induced by hypertension and by hyperosmolar solutions is the same – ie, transendothelial pinocytosis.
Specificity of brain cathepsin D: Cleavage of model peptides containing the susceptible phe‐phe regions of myelin basic protein
Authors: Marks N. , Benuck M. , Hashim G.
Published: January 2005

Brain cathepsin D, purified by affinity chromatography on Sepharose pepstatin columns, was incubated with synthetic peptides corresponding to the susceptible regions of the myelin basic protein encompassing the two Phe‐Phe bonds. One peptide, Leu‐Gly‐Arg‐Phe‐Phe‐Gly‐Gly, was cleaved by cathepsin D at the Phe‐Phe bond while another, Val‐His‐Phe‐Phe‐Lys‐Asn‐Gly, was resistant to cleavage. To determine if this was a result of His flanking the Phe‐Phe bond, or chain length on the N‐terminal side, two decapeptides were synthesized differing only in the presence or absence of His adjacent to Phe. The results show that both of the decapeptides were cleaved by cathepsin D at the Phe‐Phe linkages. In addition, prolonged incubation led to release of N‐terminal Lys, indicating an additional cleavage at the Phe‐Lys bond. In contrast to the limited cleavage by cathepsin D, pepsin split all four peptides. These results support earlier work on the limited proteolysis of basic protein at the Phe‐Phe bond and suggest additional sites upon prolonged exposure. Such peptides may have utility as alternative substrates for basic protein or as models for subsequent synthesis of possible inhibitors of the enzyme.
A sensitive radioenzymatic assay for catechol drugs
Authors: Durrett Lenard R. , Ziegler Michael G.
Published: January 2005

This assay measures picogram quantities of catechol drugs and endogenous catecholamines in body tissues and fluids. The catechols are converted to their 3H‐O‐methyl metabolites during incubation with 3H‐S‐adenosylmethionine and the enzyme catechol‐O‐methyltransferase. The radiolabeled compounds are then separated by solvent extraction and thin‐layer chromatography. Most drugs containing the catechol structure can be radiolabeled and separated from norepinephrine and epinephrine by this technique to provide simultaneous measurement of endogenous and exogenously administered catechols. The disposition of isoproterenol in tissues and fluids of man and experimental animals is measured to illustrate the utility of this assay. The reactivity of several commonly administered catechol drugs with COMT is described and the possible implications discussed.
Histochemical localization of carbonic anhydrase in vertebrate nervous tissue
Authors: Parthe V.
Published: January 2005

The histochemical method of Häusler was employed to demonstrate carbonic anhydrase (CA, carbonate hydrolase, 4.2.1.1.) in tissue sections. The CA reaction was inhibited in the presence of 5 mM acetazolamide. In the frog and fish retinas the CA activity was positive in the Müller fiber, the laminated segment of the cones and the myelin of the axons, and was negative in the laminated segment of the rods, the photoreceptor ellipsoid and myoid, the horizontal, bipolar, amacrine and ganglion cells, and the pigment epithelium. In the spinal cord of cat and fish the CA activity was positive in the myelin of the axons, the perineuronal oligodendroglia and the protoplasmic astrocytes, and was negative in the cell body, dendrite, and axon of the neurons and in the fibrous astrocytes. In the dorsal root ganglion of the cat CA reaction was positive in the satellite cells and the myelin, and was negative in the neuronal cell body and its processes. The capillaries in central nervous tissue show no CA reaction. The erythrocyte is CA positive while the mitochondria are CA negative.
Na+, K+‐ATPase and ouabain binding activities of chick embryo dorsal root ganglia supported by and deprived of nerve growth factor
Authors: Skaper Stephen D. , Varon Silvio
Published: January 2005

Recently we have shown that nerve growth factor (NGF) influences the coupled movements of Na+ and K+ across the membrane of chick embryo dorsal root ganglion (DRG) and other target cells. These ionic effects of NGF are consistent with a model in which NGF acts through the classical Na+,K+‐ATPase pump. Direct evidence for NGF‐induced alteration of this pump has been sought in the present study through two approaches. In one approach, DRG cell dissociates were incubated for 6 hours without NGF (to allow development of the ionic defect), and [3H]ouabain binding to the cells was measured before and during a delayed administration of NGF. No differences were detected in either total binding or binding time. In the second approach, intact DRG or DRG dissociates were incubated for 6 hours with or without NGF, or received NGF after 6 hours of deprivation, and Na+,K+‐ATPase (ouabain‐sensitive) activity was measured in the corresponding microsomal preparations. Activity levels were found to be the same in all cases, and were unchanged by addition of NGF directly to the enzyme preparations. Different concentrations of Na+, K+, or ATP affected in identical manners the enzyme preparations from NGF‐treated and NGF‐deprived ganglia, speaking against NGF‐imposed changes in the affinities of the corresponding enzyme sites. Also unsuccessful were attempts to reveal NGF‐related differences by testing ouabain‐sensitive ATPase activity (1) in the presence of varying concentrations of cyclic AMP or of Ca2+, (2) after treatment with Triton X‐‐100 or in the presence of vanadate, or (3) on addition of a 100,000g DRG extract. These negative findings are discussed in terms of the Na+,K+‐ATPase hypothesis for NGF action.
Effect of nerve growth factor producing cells on anaplastic glioma and pheochromocytoma clones: Involvement of other factors
Authors: Vinores Stanley A. , Koestner Adalbert
Published: January 2005

When the NGF‐secreting C‐6 rat glioma cells were intracerebrally injected with F98 rat anaplastic glioma cells into rats syngeneic for the F98 cells, an increased mean survival time was observed for rats developing tumors compared with those injected with only anaplastic glioma cells. Thirty percent of the rats injected with both cell types showed no signs of tumor at 90 days. Pretreatment of the anaplastic glioma cells with conditioned medium of C‐6 cells did not duplicate these results unless the C‐6 cells were pretreated with 17β‐estradiol, which appears to induce secretion of an adhesion factor as well as NGF. These rats survived even longer and 33% were free of tumors as 90 days. Histological examination of tumors of the nonsurviving rats revealed that they were basically well differentiated with only small anaplastic areas remaining. Both NGF and conditioned medium from C‐6 and another NGF‐secreting line, S‐180 mouse sarcoma, induce process formation in F98 cells and in PC12 pheochromocytoma cells, but the processes that appear following NGF exposure are morphologically different from those induced by conditioned medium. Conditioned‐medium‐treated cells also have a flatter appearance. In F98 cells, NGF takes longer to induce processes than does conditioned medium. The NGF‐induced effects observed in both cells are neurtralized by anti‐NGF IgG, but those induced by conditioned media are not. Nerve growth factor (NGF) induced increased adhesiveness in F98 rat anaplastic glioma and PC12 rat pheochromocytoma cells. Conditioned media are not. Nerve growth factor induced increased adhesive‐ and PC12 cells. Anti‐NGF IgG did not influence this effect on F98 cells and only partially neutralized the effect on PC12 cells, indicating that other factors may be operative in this system. Conditioned medium collected from C‐6 cells pretreated with 17β‐estradiol induced the highest degree of adhesiveness observed in both F98 and PC12 cells, and this action was unaffected by anti‐NGF IgG in either case. Conditioned media from other cell lines, a variety of selected proteins, and dBcAMP did not induce increased adhesiveness. The factor responsible for this effect is nondialyzable, heat‐sensitive, and ammoniumsulfate‐precipitable, and its secretion appears to be stimulated by 17β‐estradiol.
Effect of CDP‐choline on the biosynthesis of phospholipids in brain regions during hypoxic treatment
Authors: Alberghina M. , Viola M. , Serra I. , Mistretta A. , Giuffrida A. M.
Published: January 2005

Acute administration of CDP‐choline (i.p. 100 mg/Kg b.w.), 10 min before the intraventricular injection of labeled precursors, [2‐3H]glycerol and [1‐14C]‐palmitate, was able to correct the impairment caused by hypoxic treatment of lipid metabolism in some brain regions, ie, cerebral hemispheres, cerebellum, and brainstem.

After CDP‐choline treatment, an increase of the specific radioactivity of total lipids and of phospholipids was observed in mitochondria purified from the three above‐mentioned brain regions of the hypoxic animals, while no effect on the other subcellular fractions was found. CDP‐choline had a stimulating effect particularly on the incorporation of both precursors into mitochondrial PC, PE, and polyglycerophosphatides isolated from the three brain regions examined.

The results obtained show that the action of CDP‐choline in restoring lipid metabolism was more pronounced in brain mitochondria, which, among subcellular fractions, were the most affected by the hypoxic treatment.
Isolation and partial amino acid sequence analysis of nerve growth factor from the guinea pig prostate
Authors: Rubin Jeffrey S. , Bradshaw Ralph A.
Published: January 2005

Nerve growth factor (NGF) has been purified from the guinea pig prostate using a modification of the Bocchini‐Angeletti method for isolating 2.5S NGF from mouse submaxillary glands. As with the mouse preparation, guinea pig prostate NGF appears to migrate as a high molecular weight entity at physiological pH. Following dissociation, NGF, active in neurite proliferation assays and similar in size to mouse 2.5S NGF, can be isolated by chromatography on a column of carboxymethyl‐cellulose at pH 4.8. Based on gel filtration, SDS‐polyacrylamide gel analysis, and amino‐terminal sequence studies, this material consists of two, noncovalently linked, identical polypeptide chains each with a molecular weight of about 13,000. The amino‐terminal third of the polypeptide chain is at least 90% identical to the corresponding region of the murine molecule, confirming the homology of the guinea pig prostate protein to NGFs obtained from different tissues in other species. However, in contrast to the mouse preparation, the putative high molecular weight form of guinea pig NGF does not contain a subunit with arginine esteropeptidase activity. Although there is an abundance of this enzymatic activity in the homogenate, it does not appear to be associated with the fractions containing NGF. This apparent difference in the mouse and guinea pig material is of interest because the mouse γ subunit, possessing the arginine esteropeptidase activity, has been alleged to participate in the processing of a precursor of the β NGF polypeptide chain.
Sequestration requirements for the degradation of 125I‐labeled β nerve growth factor bound to embryonic sensory neurons
Authors: Stach Robert W. , Wagner Barbara J.
Published: January 2005

Nerve growth factor interacts with responsive cells by binding to cell surface membrane receptors. There are two different receptors on both embryonic sensory and sympathetic neurons, a high‐affinity (type I) receptor and a lower‐affinity (type II) receptor. Sequestration, which we have defined as bound nerve growth factor that becomes inaccessible to the external milieu with time, occurs through the type I receptor on both sensory and sympathetic neurons. We describe here a process subsequent to sequestration involving internalization and degradation of bound nerve growth factor and showing that bound nerve growth factor is not degraded under the following conditions: (1) low temperature, ie 4°C; (2) when a large excess of unlabeled nerve growth factor is added concomitantly with the labeled nerve growth factor and the temperature is raised from 4°C to 37°C; (3) when metabolic inhibitors sodium fluoride and dinitrophenol are added concomitantly with the labeled nerve growth factor and the temperature is raised from 4° to 37°C. On the other hand, conditions that allow bound nerve growth factor to be degraded are the following: (1) incubation of the sensory nerve cells at low temperature (ie, 4°C) only in the presence of labeled nerve growth factor, then raising the temperature to 37°C; (2) when sodium fluoride and dinitrophenol are added when the temperature is raised to 37°C; (3) when excess unlabeled nerve growth factor is added when the temperature is raised to 37°C.

These studies are consistent with the idea that nerve growth factor has to bind to the cells in order to be degraded; however, binding is not sufficient for degradation to occur. Second, the bound nerve growth factor must be sequestered in order to be degraded. Third, the process of internalization of the bound nerve growth factor, unlike sequestration, is not an energy‐dependent process. Thus, it seems reasonable to suggest the following steps for the interaction of nerve growth factor with responsive cells: binding to a cell surface membrane receptor, followed by sequestration of the bound nerve growth factor, and finally, internalization of the sequestered nerve growth factor.
Nerve growth factors in chick tissues
Authors: Ebendal Ted , Hedlund Kjell‐Olof , Norrgren Gunilla
Published: January 2005

Bioassays of factors promoting nerve growth in embryonic ganglia are described. Chick embryo extract evokes fiber outgrowth in both sympathetic and ciliary ganglia explanted into a collagen gel. The response is not suppressed by antibodies directed against mouse nerve growth factor (NGF). Chick embryo extract also supported survival of neurons in both intact and dissociated ganglia. In addition to these non‐NGF activities, preliminary evidence is presented for the release of a NGF‐like factor from cultured iris of the adult chick.
Stimulation of chick neuroblast proliferation in culture by brain extracts
Authors: Barakat I. , Sensenbrenner M. , Labourdette G.
Published: January 2005

Chick neuroblasts from 6‐day‐old embryos were grown on a collagen substrate in minimum Eagle's medium supplemented with 5% horse serum. We found that [3H]thymidine incorporation in these cultures decreased drastically from day 2 to day 3 after seeding. Addition of brain extract from 8‐day‐old chick embryos (CBe8) to the nutrient medium after 24 hours of culture elicited a very important stimulation of [3H]thymidine incorporation. Extracts of brains from adult animals were much less effective. It was shown that the increase of tritiated‐thymidine incorporation reflected proliferation of neuroblasts in the culture, at least between day 2 and 4. The activity of the brain extracts was destroyed by trypsin treatment, which suggests that the factor responsible for the stimulation of the proliferation is a polypeptide. The CBe8 and the brain extract of adult chicken (CBa) were fractionated by gel filtration. An active fraction was eluted at a volume indicating an apparent molecular weight of roughly 70,000. At that stage of the study results suggest that a polypeptide (tentatively called neuroblast proliferation factor, NPF) present in the embryonic chick brain extract, is a proliferation factor for chick neuroblasts in primary culture.
Growth from regenerating goldfish retinal cultures in the absence of serum or hormonal supplements: Tissue extract effects
Authors: Johnson James E. , Turner James E.
Published: January 2005

The minimal requirements for the regeneration of optic nerve fibers in vitro were established in a serum‐free retinal explant preparation. This serum‐free preparation was developed as a prerequisite for testing the growth‐promoting activity of tissue extracts prepared from the primary target of regenerating fibers. Explants taken from goldfish retinas 14 days after a prior optic nerve crush were capable of long‐term survival and regenerated neurite outgrowth without serum or hormonal supplements. Serum‐free conditions for explant outgrowth required only a basic Leibovitz (L‐15) media containing 0.6% methyl cellulose (MC). Explants were also capable of neurite outgrowth in L‐15 media alone when culture dishes were preplated with MC. MC treatment permitted both the regeneration of neurites in serum‐free L‐15 and a significant increase in the rate and extent of neurite outgrowth when combined with 10% fetal calf serum (FCS). Explants grown in L‐15 with both MC and FCS produced a 2.5‐fold increase in the length of neurite outgrowth over MC alone and a 1.5‐fold increase in the length of neurite outgrowth over FCS alone. MC activity which permitted minimal serum‐free regeneration and optimal serum supplemented regeneration was determined to be substrate related. Retinas were dissociated to determine if ganglion cells, like the intact explant, were capable of survival and neurite regeneration in serum‐free conditions. These cells survived and extended long neurites when grown in L‐15 with FCS or with FCS and MC, but they did not survive in serum‐free L‐15 with MC.

The minimal serum‐free conditions for explant for explant survival and neurite regeneration were used as a model system to test the growth‐promoting activity of crude tissue extracts prepared from the goldfish brain. Extracts prepared from the primary target region, the optic tectum, stimulated a significant 2.5‐fold increase in the length of regenerating neurites. The optic tectal extract (OTex) stimulated outgrowth with significantly high specific activity when compared with extracts of identical protein concentrations prepared from the cerebellum (Cex). At a minimal protein concentration of 150 μg/ml, the OTex stimulated a 1.5‐fold increase in neurite outgrowth above Cex.

These results indicated that a serum‐free culture preparation had been established for optic nerve regeneration. This culture system has proven to be an extremely sensitive bioassay model without the masking effect of a serum supplement. Serum‐free cultures may be used in further studies to determine the role neurotrophic factors may play in a widely used model of successful central nervous system (CNS) regeneration.
Separate factors produced by the CNS of the snail Helisoma stimulate neurite outgrowth and choline metabolism in cultured neurons
Authors: Barker David L. , Wong Richard G. , Kater Stanley B.
Published: January 2005

Neurons from the snail Helisoma require a brain‐derived factor(s) for neurite outgrowth in both organ and isolated cell culture. This factor is released from the CNS of Helisoma when brains are incubated in defined medium, producing a conditioned medium (CM). In addition to its growth‐promoting activity, CM also enhances total uptake of 3H‐choline and the incorporation of 3H‐choline into specific metabolites: acetylcholine, phosphorycholine and lipid.

This choline metabolism‐enhancing factor(s) is distinct and separable from neurite growth‐promoting factor: 1. Over 95% of neurite growth‐promoting activity can be removed from CM by adsorption to a polylysine surface while there is no loss of choline metabolism‐enhancing activity. 2. When central ganglia were treated with anisomycin, a potent inhibitor of molluscan protein synthesis, the choline metabolism‐enhancing activity was completely absent from the resulting CM, while the growth promoting activity was reduced by only 35%. These results suggest that the Helisoma CNS produces a variety of trophic factors that are involved in regulating the interaction between neuronal growth and metabolism.
Astrocytes and lymphocytes: Intercellular communication by growth factors
Authors: Fontana A.
Published: January 2005

A proliferation and hypertrophy of astrocytes and their processes are characteristic in inflammatory diseases of the brain. The mechanisms leading to this astrocytic reaction and the functional meaning of this response are unknown. This article reviews the evidence that by their ability to respond to lymphocyte‐derived growth factors and to secrete immunoregulatory molecules, astrocytes may participate in immune responses in the central nervous system.
Epidermal growth factor binding and mitogenic activity on purified populations of cells from the central nervous system
Authors: Simpson D. L. , Morrison R. , de Vellis J. , Herschman H. R.
Published: January 2005

Binding of 125I‐epidermal growth factor (EGF) to purified populations of rat astrocytes, oligodendrocytes, and neurons was measured. Astrocytes bound 40,000–100,000 EGF molecules per cell, while oligodendrocytes bound only 6,000–10,000 EGF molecules per cell. In contrast, neurons had little or no capacity to bind 125I‐EGF. EGF alone was able to stimulate incorporation of tritiated thymidine fivefold in purified astrocyte cultures incubated in serum‐free medium. When EGF was added to the previously described chemically defined medium for astrocytes, incorporation of tritiated thymidine in purified astrocytes was equivalent to that observed in medium containing 10% fetal calf serum. Addition of EGF to this chemically defined medium also doubled the proliferative capability of the medium for cultured astrocytes. EGF was maximally effective in stimulating 3H‐thymidine incorporation at concentrations between 1–10 ng/ml.
Stimulation of proliferation and maturation of rat astroblasts in serum‐free culture by an astroglial growth factor
Authors: Pettmann B. , Weibel M. , Daune G. , Sensenbrenner M. , Labourdette G.
Published: January 2005

Astroblasts from brain hemispheres of newborn rats were cultivated for 5 days in a complete medium containing 10% fetal calf serum. Cultures were then grown in basal medium in absence of serum. In these conditions, after 15 days only a few cells remained. When the basal culture medium was supplemented with insulin and transferrin (IT medium) the number of the remaining cells was twice higher. However, it was still lower than that found in the 5‐day cultures before serum was removed. Thus the IT medium does not allow a good survival of the cells. Addition to the medium of an astroglial growth factor (AGF) from bovine brain soluble extract led to a tenfold increase of the cell number compared to cultures maintained in the basal medium alone. Effects of the factor on cell survival and on proliferation were examined independently. It was found that the factor did not greatly increase the survival of the cells but that it stimulated the proliferation. Addition of the growth factor to the IT medium elicited an increase of the levels of S‐100 protein and of the activity of glutamine synthetase, two proteins which are specific to astroglial cells in the central nervous system.

These results indicate that the astroglial brain factor allows growth and maturation of the rat astroblasts maintained in serum‐free medium.
Purification, characterization, and biological properties of the eye‐derived growth factor from retina: Analogies with brain‐derived growth factor
Authors: Barritault Denis , Plouët Jean , Courty José , Courtois Yves
Published: January 2005

Several ocular tissues contain a polypeptide growth factor(s) (eye‐derived growth factor(s) or EDGF) that stimulates the proliferation of a large variety of cells from different tissues or species. Partial purification of EDGF from adult bovine retina was accomplished by acid precipitation, blue Ultrogel chromatography, and high‐pressure liquid chromatography. EDGF has an isoelectrical point at pH 4.5 ± 0.5 and an apparent molecular weight of 17,500 ± 3,500 measured by high‐pressure liquid chromatography. On the basis of these data as well as its biological properties EDGF is different from other known growth factors. The specific activity of highly purified EDGF is 1,000‐fold greater than that of a 20,000g supernatant of a crude retinal extract. At this stage of purification, EDGF stimulates replicative DNA synthesis and cell proliferation of bovine epithelium lens cells at a concentration of 14 ng/ml of culture medium and for these cells is as efficient as purified brain fibroblast growth factor.

The same purification steps were applied to crude bovine brain extracts. Growth factor activity was recovered exactly as for EDGF with slightly smaller apparent molecular weight 14,000 ± 3,500, suggesting a great similarity between the two tissues as a source of growth factors. A purification of about 2,500‐fold was obtained and cell proliferation stimulated at a concentration of 100 ng/ml. Interestingly an inhibitory activity not retained on blue Ultrogel was recovered from both preparations.
DNA‐polymerases in neuron and glial cells of developing and aging mouse brain
Authors: Shrivastaw Keshaw Prasad , Philippe Michel , Chevaillier Philippe
Published: January 2005

DNA‐polymerases α and β were studied in neuron and glial cells of mouse during developing and aging brain. Maximum activity of α‐enzyme was found to be prenatal, though a very low but significant level could be detected in aging brain. Furthermore, this pattern was found to be dependent upon cell types that shift in peak activity just before birth in glial cells in contrast to neurons. DNA‐polymerase‐β remained high throughout the period studied though a second peak of activity was also observzd at day 30 in both cell types, suggesting a possible role in DNA‐replication in addition to DNA‐repair. It was found that β‐enzyme from glial cells behaves differently than the same enzyme from neurons.
Ornithine as a precursor of glutamate and GABA: Uptake and metabolism by neuronal and glial enriched cellular material
Authors: Shank Richard P. , LeM. Campbell Graham
Published: January 2005

The uptake and metabolism of (U‐14C) L‐omithine by several cellular preparations was examined and compared to corresponding data for glutamine and α‐ketoglutarate. Five fractions were obtained from the cerebellum of 10‐to 14‐day‐old mice; two fractions were enriched in astrocyte cell bodies, whereas one was comprised primarily of granule cell bodies, and another was enriched in nerve terminals. Metabolic studies were also conducted on two synaptosomal preparations prepared from rat cerebral tissue.

The uptake of ornithine by the cerebellar fractions was mediated by one or two saturable transport systems with apparent Km values between 50 and 200 μM. Uptake inhibition experiments indicated that ornithine is transported primarily, if not exclusively, by the basic amino acid carrier(s), and that glutamine is transported in part by this carrier. Ornithine was metabolized to proline, glutamate, and to a lesser extent aspartate, glutamine and GABA. Under the conditions of our experiments, the cell bodies metabolized ornithine somewhat more readily than did the nerve terminal enriched fraction obtained from the mouse cerebellum. Our data indicate that the conversion of ornithine to GABA occurs predominantly, if not exclusively, via the pathway involving glutamate rather than putrescine. In comparison to data for glutamine and α‐ketoglutarate, the metabolism of omithine to glutamate was slow.

Although the results of our study are consistent with the hypothesis that ornithine serves as a metabolic precursor of the neurotransmitter pools of glutamate and GABA, our data do not support a major role for omithine in this capacity. Based on a comparison of the availability of omithine, glutamine and α‐ketoglutarate, and the rates at which they are each transported into synaptosomes and metabolized therein to glutamate and GABA, our data suggest that glutamine and α‐ketoglutarate are used more extensively to replenish these transmitter pools.
The effect of centrally administered neuropeptides on the development of stress‐induced gastric ulcers in rats
Authors: Hernandez Daniel E. , Nemeroff Charles B. , Orlando Roy C. , Prange Arthur J.
Published: January 2005

Neurotensin (NT) and bombesin, which are heterogeneously distributed in both brain and gastrointestinal tissue of several mammalian species, inhibit the formation of stress‐induced gastric ulcers in rats. Many other endogeneous neuropeptides have also been reported to be present in brain and gastrointestinal tissue. present study was conducted to evaluate the effect of some of these peptides the development of cold‐restraint stress (CRS)‐induced gastric ulcers in rats. addition, the effect of thyrotropin‐releasing hormone (TRH), which antagonizes many of the CNS effects of NT, was investigated to determine whether tripeptide antagonizes the cytoprotective effect of NT in this CRS model.

All peptides were initially administered intracisternally (ic) in doses equimolar to 30 μg NT. As previously reported, NT (30 μg, ic) completely prevented development of gastric ulcers in rats exposed to three hours of CRS. Bombesin, β‐endorphin, substance P, and somatostatin also exhibited cytoprotective activity, Several other peptides studied in the CRS model exerted no significant effects the development of gastric ulcers; these included cholecystokinin octapeptide, gastrin, leu‐enkephalin, met‐enkephalin, and bradykinin. Two peptides, vasculative intestinal polypeptide and TRH, significantly increased the severity of ulcerations.

The cytoprotective effect of NT was dose dependent. In contrast, lower doses of β‐endorphin, substance P, and somatostatin were cytoprotective whereas higher doses were not. Finally, concomitant ic injections of TRH antagonized the cytoprotective effects of NT and bombesin, but not that of,β‐endorphin. The present results suggest that certain brain peptides may participate in modulating the gastric mucosal barrier, thereby increasing or decreasing its vulnerability to stress‐induced lesions.
Autoradiographic analysis of 3H‐glutamate, 3H‐dopamine, and 3H‐GABA accumulation in rabbit retina after kainic acid treatment
Authors: Hampton C. K. , Redburn D. A.
Published: January 2005

We have previously reported that exposure of isolated rabbit retina to 10−3M kainic acid produces profound morphological changes in specific retinal neurons (Hampton et al, 1981). We noted specific swelling of horizontal cell bodies and neurites, necrosis of cell bodies in the amacrine and ganglion cell layers, and swelling of elements in the inner plexiform layer. We now report a differential sensitivity to kainic acid of specific subclasses of amacrine cells autoradiographically labeled with 3H‐glutamate, 3H‐GABA, or 3H‐dopamine. Three different effects were observed: (1) Labeling of neurons after incubation in 3H‐glutamate was uniformly reduced while labeling of glia was much less affected. ( 2 ) The accumulation of 3H‐dopamine was also decreased by kainic acid in two of the three labeled bands of the inner plexiform layer. The outermost labeled band was insensitive to kainic acid at the highest concentration tested (10.−2M). These findings provide a basis for the subclassification of dopaminergic amacrine cells into at least two subclasses based on their sensitivity to kainic acid. (3) Kainic acid caused a dramatic increase in the labeling of GABAergic amacrine cell bodies and their terminals. This increased intensity may reflect a compensatory increase in uptake activity in response to kainic acid‐induced depletion of endogenous GABA stores. These results confirm the highly toxic nature of kainic acid and demonstrate a high degree of specificity and complexity in its action in the retina.
Growth, differentiation, and viability of fetal rat cortical and spinal cord implants into adult rat spinal cord
Authors: Patel U. , Bernstein J. J.
Published: January 2005

Successful transplantation of the fetal brain into adult host brain has been accomplished. These studies explore the growth, differentiation, and viability of E11, E12, and El5 rat fetal cortex and fetal spinal cord implantation into the spinal cord of adult rats (donor and host, Sprague‐Dawley). Under deep Chloropent anesthesia, 70 rats had 1‐mm cubes of fetal cortex inserted with pressure or by stylus injection subpially between the dorsal horn and dorsal column (left side), or implantation of whole segments of fetal spinal cord. Animals were prepared for light microscopy 14 and 21 days and 1, 2, and 3 months later. Implants by both fetal tissues had a 69% survival rate. The younger the fetal implant the higher the success of the implant (E11 > E15). The diameter of fetal spinal cord implants reached the diameter of control postnatal animals after 30 days. The implants not only increased in mass (up to 7‐fold in some cases) but differentiated and matured (apolar, unipolar, bipolar, and multipolar) neurons were observed one to three months postimplantation. By 30 days postimplantation, fetal neurons had large, often crenated nuclei, with a large single prominent nucleolus. The most successful implants were the young E11 fetal spinal cord into the adult host spinal cord. These implants represent an initial successful transplantation of fetal spinal cord into adult spinal cord.
Synaptogenesis and myelination in dissociated cerebral microcarrier cell cultures
Authors: Shahar A. , Reuveny S. , Amir A. , Kotler M. , Mizrahi A.
Published: January 2005

A new approach for cultivating dissociated cerebral neurons is described. It is based on a rapid attachment of neurons to the DEAE‐cellulose cylindrical MC and their subsequent interconnection to form cell‐MC conglomerates. Intensive fiber growth followed by synaptogenesis and progressive myelin formation are indicative of optimal conditions of nutrition and oxygenation.
Ganglioside–basic protein interaction: Protection of gangliosides against neuraminidase action
Authors: Yohe H. C. , Jacobson Ronald I. , Yu Robert K.
Published: January 2005

The ability of acidic phospho‐ and sphingolipids to interact with basic proteins was studied by double diffusion analysis. The phospholipids, tri‐ and diphosphoinositide, and the sphingolipid, sulfatide, interacted with myelin basic protein as evidenced by precipitin line formation. Of the sialoglycosphingolipids (gangliosides) tested, only the myelin‐specific monosialoganglioside, GM4

The ganglioside nomenclature used here is according to the system of Svennerholm [1963]. The gangliosides are designated as follows: GM4 = I3NeuAcGalCer; GM3 = II3NeuAcLacCer; GM1 = II3NeuAcGgOse4Cer; GD1a = IV3 NeuAc, II3NeuAcGgOse4Cer; GD1b = II3(NeuAc)2GgOse4Cer; and GT1b = IV3NeuAc, II3(NeuAc)2GgOse4Cer.

, formed a precipitin line with myelin basic protein. In addition, myelin basic protein retarded the activity of Clostridium perfringens neuraminidase against GM4 and the disialoganglioside, GD1b. Examination of purified rat brain myelin suggested the presence of a neuraminidase activity intrinsic to myelin. This finding, in concert with ganglioside‐myelin basic protein complexes which selectively protect against neuraminidase, may provide a physiological explanation for the simplified ganglioside pattern found in myelin.
Presynaptic modulation of activity and molecular forms of acetylcholinesterase in the rat superior cervical ganglion during early postnatal development
Authors: Klinar B. , Sketelj J. , Sket D. , Brzin M.
Published: January 2005

Preganglionic nerve trunk of the rat superior cervical ganglion was transected shortly after birth in order to evaluate the influence of preganglionic nerves on the development of acetylcholinesterase and choline acetyltransferase in ganglionic neurons. In spite of an early decentralization, specific activity of acetylcholinesterase in the ganglion is increasing during the first 3 wk of life until it is about equal to the activity which remains in the superior cervical ganglion decentralized in an adult animal. Thus, the preganglionic nerves, which per se contribute the presynaptic fraction of total ganglionic AChE activity in normal innervated ganglia, apparently exert no significant regulatory effect on the specific activity of the fraction of acetylcholinesterase affiliated with the developing ganglionic cells. However, the absence of innervation during development is strongly reflected in the pattern of acetylcholinesterase molecular forms. The activity of the 16 S molecular form of AChE remains high in the developing superior cervical ganglion, decentralized at birth, in contrast to the substantial absolute and relative decrease of specific activity of this form during development of a normally innervated ganglion. A high proportion of 16 S AChE probably reflects a shift of decentralized immature ganglion nerve cells toward a cholinergic character. In accordance with this assumption, choline acetyltransferase activity in early decentralized ganglia is significantly higher than that in the ganglia decentralized in adult animals.
Effects of blinding and pinealectomy on regional brain monoamine concentrations
Authors: Niles Lennard P. , Brown G. M. , Mishra R. K.
Published: January 2005

The effects of blinding with or without pineal ablation on brain monoamine levels were studied in male rats. Brain dopamine (DA), norepinephrine (NE), epinephrine (E), and serotonin (5‐HT) were measured by radioenzymatic assays. Four weeks following pinealectomy, E levels were significantly enhanced in the frontal cortex. Chronic blinding decreased striatal DA levels and increased striatal 5‐HT levels in both sham‐operated and pinealectomized (Px) animals.

In a second experiment Px animals were sacrificed 1 or 7 d after pinealectomy in order to examine the short‐term effects of pinealectomy. There were no differences between controls and Px animals in their cortical levels of DA, NE, and E and their hippocampal and hypothalamic 5‐HT levels. However, the E concentrations measured 1 d after surgery were significantly greater than after 7 d. The implications of these findings with regard to the reported role of the pineal and melatonin in brain homeostasis and endocrine regulation are discussed.
Some factors affecting the concentrations of para‐hydroxyphenylacetic acid and meta‐hydroxyphenylacetic acid in the mouse caudate nucleus
Authors: McQuade P. S. , Juorio A. V.
Published: January 2005

Acid hydrolysis of mouse caudate homogenates results in a significantly increased concentration of para‐hydroxyphenylacetic acid (p‐HPAA). Thus p‐HPAA appears to be significantly present as an acid‐labile conjugate in the mouse caudate nucleus. Saline injection also increased the concentration of the acid metabolite of the tyramines.

The subcutaneous injection of either meta‐hydroxyphenylacetic acid (m‐HPAA) or p‐HPAA or both produced at 0.5 hr and 2.0 hr large increases in the mouse caudate nucleus concentrations of m‐ and/or p‐HPAA. Similarly at 2.0 hr the injection of a combination of para‐ and meta‐tyramine caused large increases in the acid metabolite concentrations.

Probenecid, at a dose of 500 mg/kg, increased striatal p‐HPAA and m‐HPAA concentrations. Probenecid, injected prior to the administration of p‐HPAA and m‐HPAA, did not reduce the increased concentrations of these two acid metabolites previously observed after the administration of the acid metabolites alone. It thus appears that p‐HPAA and m‐HPAA are transported from the brain by a probenecid‐sensitive mechanism, but in the presence of high blood concentrations, p‐HPAA and m‐HPAA may enter the brain by a mechanism that is not affected by probenecid.
Cell proliferation in growing cultures of dissociated embryonic mouse brain: macromolecule and ornithine decarboxylase synthesis and regulation by hormones and drugs
Authors: Bhat N. R. , Shanker G. , Pieringer R. A.
Published: January 2005

Primary cultures of cells dissociated from embryonic mouse brain were demonstrated to be a useful system for studying cell proliferation and its regulation. Ornithine decarboxylase activity was closely correlated with the rate of DNA and RNA synthesis during cell growth, suggesting that the enzyme is as good an indicator of cell proliferation in these cultures as it is in vivo. Both DNA synthesis and ornithine decarboxylase activity were stimulated by insulin. The enzyme was stimulated five‐ to sixfold by insulin and approximately twofold by butyrate, cis‐retinoic acid, and 12‐O‐tetradecanoylphorbol‐13‐acetate. No effect on the enzyme activity was observed with triiodothyroinine, hydrocortisone, growth hormone, cyclic AMP, or cyclic GMP.
Development of synaptic transmission by cholinergic neurons in culture
Authors: Puro D. G. , Yeh H. H.
Published: January 2005

We examined the development of cholinergic transmission at synapses formed in culture by retinal neurons derived from the embryonic chick. In our experimental system, striated muscle cells served as postsynaptic targets for cholinergic retinal neurons. Functional retina‐muscle synapses could be formed in cultures containing either retinal explants or dissociated retinal cells. Plating a low density of dissociated cells permitted the study of relatively isolated, visually identifiable, cholinergic neurons. We found that, early in the functional maturation of retina‐muscle synapses, the release of acetylcholine occurs spontaneously, but cannot be evoked by the putative excitatory transmitter, glutamate. This stage is followed by the emergence of transmitter release that is evocable by glutamate in a receptormediated and calcium‐dependent manner. This ability to transmit excitatory information across a synapse is expressed in culture by neurons derived from retinas that are at an early stage of morphogenesis.
Evidence from phospholipid metabolism changes for muscarinic cholinergic receptors on rat anterior pituitary cells
Authors: Hauser G. , Parks J. M.
Published: January 2005

In incubations of dissociated adult rat anterior pituitary cells with [32P]orthophosphate, carbamylcholine causes an increase in phosphatidic acid labeling accompanied by a small reduction in phosphatidylinositol labeling. Carbamylcholine and oxotremorine produce about the same maximum change while that caused by pilocarpine is smaller. Low concentrations of atropine, quinuclidinyl benzilate, and scopolamine completely inhibit the effect caused by carbamylcholine, whereas d‐tubocurarine does not decrease the stimulation, even at higher concentrations. The muscarinic antagonists alone produce a rise in phosphatidylinositol labeling and a drop in phosphatidic acid labeling, an effect opposite from that produced by the agonists, but d‐tubocurarine alone has no effect. Thus changes in phospholipid metabolism are mediated through muscarinic cholinergic receptors in dissociated rat anterior pituitary cells, confirming the presence of functional binding sites. The present studies also demonstrate the utility of experiments on precursor incorporation into phospholipids in identifying the existence on cells or tissues of certain receptor classes.
Serum vulnerability and time‐dependent stabilization of neurites induced by nerve growth factor in PC12 pheochromocytoma cells
Authors: Skaper S. D. , Selak I. , Varon S.
Published: January 2005

Cultures of PC12 pheochromocytoma cells were established on a polyornithine substratum in medium supplemented with the chemically defined N1 mixture in the presence or absence of Nerve Growth Factor (NGF). Normal cell proliferation in the absence of NGF was equally competent when fetal calf serum (FCS) was replaced with N1‐supplemented medium. The differentiation of PC12 cells, which occurs upon NGF treatment, ultimately results in cell death without the addition of 0.1% FCS to the N1‐supplemented medium. The combination of N1, 0.1% FCS, and NGF permits the PC12 cells to develop a neuritic outgrowth much earlier than when higher (1—10%) FCS levels are used. Neurite retraction is caused in a dose‐dependent manner by a delayed presentation of FCS. Within 2 days of serum presentation, however, neurites regrow to achieve that percentage of neurite‐bearing cells which is seen without a serum challenge. Moreover, the retraction response becomes less pronounced with time over the 8‐day culture period for any given serum concentration. Among the N1 ingredients, only insulin and transferrin are needed by PC12 cells for survival whether in the dividing state or not. Neurite growth was not dependent on any of the N1 components.
Taurine uptake by chick embryo retinal neurons and glial cells in purified culture
Authors: Adler R.
Published: January 2005

The properties and cellular distribution of a high‐affinity uptake mechanism for taurine have been investigated using separate populations of purified chick embryo neural retina neurons and glia. Purified neuronal monolayers, cultured in serumfree medium, were incubated in radioactive taurine under different conditions and studied autoradiographically and biochemically. Labeling with radioactive taurine was detected in the perikaryon of most of the neurons present in the cultures. Neuronal uptake occurred by means of a high‐affinity mechanism which was completely inhibited at low temperatures or in the absence of sodium ions. The uptake was linear for at least 1 hr and, as is the case in vivo, could be inhibited by γ‐aminobutyric acid (GABA) or β‐alanine. Incubation in ouabain, glutamate, or high K+ concentrations failed to cause any increase in the amount of taurine released by neurons preloaded with the radioactive amino acid. The rather widespread distribution of high‐affinity taurine uptake was confirmed using separate retinal cultures rich in glial cells. Practically 100% of the glial cells appeared labeled after incubation in 10−7 M [3H] taurine, and this uptake was also inhibited by low‐temperature, Na+‐free medium, GABA, or β‐alanine. Several pieces of evidence indicate that high‐affinity taurine uptake coexists with uptake mechanisms for other amino acids, such as GABA, glutamate, and aspartate, in retinal neurons as well as glial cells. These in vitro populations offer a promising experimental system for the investigation of the effects of taurine on retinal cells.