bluuebunny/crossref_metadata_2025 huggingface dataset:
Age‐Related Bidirectional Changes in Neuropeptide Y Peptides in Rat Adrenal Glands, Brain, and Blood
Authors: Higuchi Hiroshi , Yang Hsiu‐Ying T. , Costa Erminio
Published: October 2006

Abstract: Age‐related changes in neuropeptide Y (NPY) regulation were studied in rat adrenal glands, brains, and blood by radioimmunoassay and biochemical characterization using reversed phase HPLC and gel filtration chromatography. NPY immunoreactivity (pmol/g tissue ± SEM) in rat adrenal glands increased from 7 ± 1 (6 weeks old) to 1,500 ± 580 (69 weeks old). Biochemical characterization by HPLC showed that this increase was due to those of NPY and methionine sulfoxide NPY. In contrast, in rat brain, NPY content decreased in an age‐dependent manner specifically in striatum, hippocampus, medulla oblongata, and spinal cord and the sulfoxide form was not detected. In rat blood, the circulating level of NPY was high (3–5 pmol/ml plasma ± SEM) but did not change significantly with age or by adrenal demedullation. Only a small increase of the sulfoxide form of NPY was observed in aged rat plasma. The age‐dependent changes in regulation and modification of NPY in adrenal glands and in specific brain areas may have physiological relevance in the regulation of catecholamine release from adrenal glands and some brain functions during aging.
Distribution of the Glucose‐1,6‐Bisphosphate System in Brain and Retina
Authors: Yip Vera , Pusateri Mary Ellen , Carter Joyce , Rose Irwin A. , Lowry Oliver H.
Published: October 2006

The distribution of glucose‐1,6‐bisphosphate (G16P2) synthase was measured in more than 70 regions of mouse brain, and nine layers of monkey retina. Activities in gray areas varied as much as 10‐fold, in a hierarchical manner, from highest in telencephalon. especially the limbic system, to lowest in cerebellum, medulla, and spinal cord. The synthase levels were significantly correlated among different regions with G16P2 itself, as well as with previously published levels of a brain specific IMP‐dependent G16P2 phosphatase. In contrast, neither G16P2 nor either its synthase or phosphatase correlated positively with phosphoglucomutase. and in all regions the G16P2 levels greatly exceeded requirements for activation of this mutase. This strengthens the view that G16P: has some function besides serving as coenzyme for phosphoglucomutase. However, attempts to correlate the “G16P2 system,” as defined by the three coordinately related elements, synthase, phosphatase, and G16P2, with other enzymes of carbohydrate metabolism, or with regional data of Sokoloff et al. [J. Neurochem. 28, 897–916 (1977)] for glucose consumption, were unsuccessful. This leaves open the possibility that brain G16P2 might serve as a phosphate donor for specific nonmetabolic effector proteins.
Zinc Uptake into Synaptosomes
Authors: Wensink Jan , Molenaar Adriaan J. , Woroniecka Urszula D. , Van den Hamer Cornells J. A.
Published: October 2006

Zinc uptake‘was studied in synaptosomes, isolated by the Ficoll flotation technique, using the radiotracer 65Zn. True uptake of zinc could be discriminated from binding to the outside of the synaptosomes by the absence of accumulation at 0°C and the dependency of the rate of uptake on the medium osmolarity. The zinc uptake, studied in the presence of various zinc‐complexing agents, showed saturation kinetics when analyzed in terms of [Zn]free, yielding Km= 0.25 μM. The zinc uptake was independent of both ATP and the Na+ gradient. No efflux of zinc could be demonstrated from preloaded synaptosomes due to the formation of insoluble zinc complexes inside the synaptosomes. The results are discussed in terms of the modulation of diverse neurochemical processes by zinc.
Selective Alteration in Blood‐Brain Barrier and Insulin Transport in Iron‐Deficient Rats
Authors: Ben‐Shachar Dorit , Yehuda S. , Finberg J. P. M. , Spanier I. , Youdim M. B. H.
Published: October 2006

Abstract: Nutritional iron deficiency induced in rats causes a significant reduction in level of brain nonheme iron and is accompanied by selective reduction of dopamine D2 receptor Bmax. Our previous studies have clearly demonstrated that these alterations can be restored to normal by supplementation with ferrous sulfate; however, neither brain nonheme iron level nor dopamine D2 receptor Bmax can be increased beyond control values even after long‐term iron therapy. The possibility that iron deficiency can induce the breakdown of the blood‐brain barrier (BBB) was examined. A 70 and 100% increase in brain uptake index (BUI) for l‐glucose and insulin, respectively, were noted in iron‐deficient rats. However, the BUI for valine was decreased by 40%, and those for l‐norepinephine and glycine were unchanged. In addition, it was demonstrated that in normal rats insulin is transported into the brain. The data show that iron deficiency selectively affects the integrity of the BBB for insulin, glucose, and valine transport. Whether the effect of iron deficiency on the BBB is at the level of the capillary endothelial cell tight junction is not yet known. However, this study has shown that an important nutritional disorder (iron‐deficiency anemia) has a profound effect on the BBB and brain function.
Oligosaccharide Portion of GM1 Enhances Process Formation by S20Y Neuroblastoma Cells
Authors: Schengrund Cara‐Lynne , Prouty Catherine
Published: October 2006

The oligosaccharide portion of ganglioside GM1 was found to enhance neuritogenesis by S20Y murine neuroblastoma cells grown in vitro. The average length of the neurites produced by cells grown in the presence of the oligosaccharide portion of GM1 was comparable to that of cells grown in the presence of intact GM1. The processes of these cells were significantly longer (p < 0.005, pooled t test) than those of cells grown in the presence of comparable concentrations of sialic acid, lactose, sialyllactose, GD1a, or the oligosaccharide moiety of GD1a. These results suggest that it is the oligosaccharide portion of GM1 that is responsible for the ability of GM1 to enhance process outgrowth by S20Y neuroblastoma cells.
Evidence that Aspartate Aminotransferase Activity and Ketodicarboxylate Carrier Function Are Essential for Biosynthesis of Transmitter Glutamate
Authors: Palaiologos Georgios , Hertz Left , Schousboe Arne
Published: October 2006

Based on the selective inhibition of glutamate release in cerebellar granule cells in primary cultures by the aspartate aminotransferase inhibitor, aminooxyacetic acid, and by the ketodicarboxylate carrier inhibitor, phenylsuccinate, a novel model for synthesis of transmitter glutamate is suggested: Glutamate is formed from glutamine in the mitochondrial intramembrane space by phosphate‐activated glutaminase, transported across the inner membrane in exchange with aspartate, transaminated in the matrix to a‐ketoglutarate, which via the ketodicarboxylate carrier is transferred to the cytoplasm, and transaminated to form transmitter glutamate. Such a mechanism would explain the functional role of aspartate aminotransferase in glutamatergic neurons.
Dihydropyridine Binding Sites Regulate Calcium Influx Through Specific Voltage‐Sensitive Calcium Channels in Cerebellar Granule Cells
Authors: Carboni Ezio , Wojcik Walter J.
Published: October 2006

Abstract: In primary cultures of cerebellar granule cells, [3H]nitrendipine binds with high affinity to a single site (KD 1 nM and Bmax 20 fmol/mg protein). The 1,4‐dihydropyridine (DHP) class of compounds such as nitrendipine, nifedipine, and BAY K 8644 displace [3H]nitrendipine binding at nanomolar concentrations. Verapamil partially inhibits whereas diltiazem slightly increases the [3H]nitrendipine binding. In these cells, the calcium influx that is induced by depolarization is very rapid and is blocked by micromolar concentrations of inorganic calcium blockers such as cadmium, cobalt, and manganese. The calcium influx resulting from cell depolarization is potentiated by BAY K 8644 and partially inhibited (approximately 40%) by nitrendipine and nifedipine. Other non‐DHP voltage‐sensitive calcium channel (VSCC) antagonists, such as verapamil and diltiazem, completely blocked the depolarization‐induced calcium influx. This suggested that nitrendipine and nifedipine block only a certain population of VSCCs. In contrast, verapamil and diltiazem do not appear to be selective and block all of VSCCs. Perhaps some VSCCs can be allosterically modulated by the binding site for the DHPs, whereas verapamil and diltiazem may block completely the function of all VSCCs by occupying a site that differs from the DHP binding site.
Occurrence of a Large Ca2+‐Independent Release of Glutamate During Anoxia in Isolated Nerve Terminals (Synaptosomes)
Authors: Sanchez‐Prieto Jose , González Pilar
Published: October 2006

Abstract: Isolated rat cerebral cortical synaptosomes made anoxic by addition of cyanide developed an inhibition of the Ca2+‐dependent release of glutamate 2 min after the addition of the metabolic inhibitor when the intrasynaptosomal ATP/ADP ratio decreased below 1.7. In contrast, cyanide induced a continuous efflux of glutamate through a Ca2+‐independent pathway that accounted for the release of 25% of total intrasynaptosomal glutamate in 5 min. The results suggest that a Ca2+‐independent release of glutamate could be implicated in the neurotoxic action of this amino acid during anoxia.
Role of Glial Cells for the Basal and Ca2+‐Dependent K+‐Evoked Release of Transmitter Amino Acids Investigated by Microdialysis
Authors: Paulsen R. E. , Fonnum F.
Published: October 2006

Abstract: The role of glial cells for the inactivation and synthesis of precursors for amino acid transmitters was studied in the brains of anesthetized rats in vivo using the microdialysis technique. The dialysis probes were inserted stereotactically into each neostriatum. One neostriatum was treated with the gliotoxin fluorocitrate, whereas the contralateral side served as a control. The basal efflux of amino acids, reflecting the extracellular level, was measured as well as the efflux during depolarization with 100 mM K+ in the dialysis stream. The potassium‐evoked efflux of transmitter amino acids was calcium dependent and thus considered to reflect release from the transmitter pool. γ‐Aminobutyric acid (GABA) and glutamate release from the treated side was higher than the control value during the first 2–3 h, a result indicating an important role of glial cells in the inactivation of released transmitter. After 6–7 h with fluorocitrate, the release of glutamate was lower than the control value, a result indicating an important role of glial cells in the synthesis of precursors for the releasable pool of glutamate. The role of glutamine for the production of transmitter glutamate and GABA in vivo was further investigated by inhibiting glutamine synthetase with intrastriatally administered methionine sulfoximine. The release of glutamate into the dialysis probe decreased to 54% of the control value, whereas the release of GABA decreased to 22% of the control value, a result indicating that glutamine may be more important for transmitter GABA than for transmitter glutamate.
N‐Methyl‐D‐Aspartate Receptors and Ethanol: Inhibition of Calcium Flux and Cyclic GMP Production
Authors: Hoffman Paula L. , Rabe Carolyn S. , Moses Frances , Tabakoff Boris
Published: October 2006

Abstract: Measurements of calcium uptake and cyclic GMP production by cerebellar granule cells grown in primary culture demonstrated that ethanol preferentially inhibited N‐methyl‐D‐aspartate (NMDA) receptor‐gated cation channel function. Concentrations of ethanol as low as 10 mM inhibited NMDA‐stimulated Ca2+ uptake by >30%, and ethanol also inhibited NMDA‐stimulated (Ca2+‐dependent) cyclic GMP accumulation in a similar, dose‐dependent manner. Responses to kainate were significantly less sensitive to ethanol. Studies using various concentrations of NMDA, as well as phencyclidine (PCP) and glycine, suggested that ethanol affected the “coagonist” binding site of the NMDA receptor‐channel complex, rather than the PCP recognition site.
Noradrenaline Metabolism in Neocortex and Hippocampus Following Transient Forebrain Ischemia in Rats: Relation to Development of Selective Neuronal Necrosis
Authors: Miyauchi Yoshitoyo , Wieloch Tadeusz , Lindvall Olle
Published: October 2006

Abstract: Noradrenaline (NA) metabolism tn the neocortex and hippocampus was examined in rats atl 1, 24, and 48 h following 15 min of reversible forebrain ischemia. As assessed by the ratio of accumulated 3,4‐dihydroxyphenylalanine (DOPA) to the tissue NA level after inhibition of DOPA decarboxylase, the NA turnover rates were markedly increased (120‐148% above the control) at 1 h postischemia in both the neocortex and hippocampal formation (CA1 and CA3 plus dentate gyrus). The DOPA:NA ratio went back to control levels after longer postischemic survival times. The ratio between levels of the deaminated NA metabolite, 3,4‐dihy‐droxyphenylethyleneglycol (DOPEG), and NA, which gives another measure of NA turnover rate, Showed similar changes. In the neocortex and the CA3 plus dentate gyrus, the DOPEG:NA ratio was markedly increased (89‐118%) 1 h after the ischemia, but this change had disappeared at 24 and 48 h. Thus, both the DOPA accumulation experiments and the NA and DOPEG measurements indicate that following transient forebrain ischemia, there is an increased NA turnover in the hippocampus and cortex only in the early recirculation period and not after longer postischemic survival times. The degree of neuronal necrosis in ihe CA1 region was examined light microscopically on celestine blue‐acid fuchsin‐stained sections at 24, 48, and 96 h following the ischemic insult. The neuronal damage in CA1 was sparse after 24 h of recovery, had increased markedly after 48 h. and was very pronounced at 96 h. Our data show that the changes in NA turnover in the neocortex and hippocampus follow a different time course than the development of neuronal damage in the hippocampal CA 1 region. The activation of the NA system occurs during and immediately after the period of high extracellular levels of glutamate. Excitatory amino acids have been proposed to be of major importance for the development of ischemic brain damage, whereas the NA afferents to the hippocampus and cortex (originating in the locus coeruleus) seem to have a protective role. We hypothesize that the increased activity of the locus coeruleus system, observed early postischemically in the present study, mitigates the detrimental effects evoked by excessive glutamate receptor stimulation, thereby reducing the degree of neuronal necrosis.
Brain Uptake of L‐Tryptophan and Diazepam: The Role of Plasma Protein Binding
Authors: Fenerty Catherine A. , Lindup W. Edward
Published: October 2006

Abstract: The brain uptake index (BUI) of L‐jtryptophan and diazepam into the right and left hemispheres and the cerebellum has been measured after a bolus injection into the carotid artery of the anaesthetised rat. The effect of a range of albumin concentrations (38 μM to 1.4 mM; 0.25‐9 g/100 ml) on the viscosity and osmotic pressure ot the bolus was studied as a preliminary to the brain uptake experiments. Dextran (Mr 60,000‐90,000) was included in the injection to ensure constant viscosity and osmotic pressure. An increase in albumin concentration up to 2 g/100 ml substantially reduced the BUI of L‐tryptophan, but a further increase in albumin concentration up to 9 g/100 ml respited in only a slow fall in the BUI of L‐tryptophan which was not proportional to the larger fall in the concentration of unbound L‐tryptophan. Furthermore, the use of norharmane as an inhibitor of L‐tryptophan binding did not reveal a simple relationship between its unbound concentration and BUI. A decrease in the unbound concentration of diazepam also reduced its BUI, but again there was no straightforward relationship between this and unbound diazepam concentration. The differences observed in the BUI of inulin from solutions of either dextran or albumin indicate not only that each mac‐romolecule may exert particular effects on the BUI, perhaps by an influence on cerebral blood flow, but also show how difficult it is to devise solutions for injection which differ in respect of only one variable, that of the unbound ligand concentration.
Differential Binding Properties of the Peripheral‐Type Benzodiazepine Ligands [3H]PK 11195 and [3H]Ro 5‐4864 in Trout and Mouse Brain Membranes
Authors: Eshleman A. J. , Murray T. F.
Published: October 2006

Abstract: High‐affinity binding sites for [3H]PK 11195 have been detected in brain membranes of rainbow trout (Salmo gairdneri) and mouse forebrain, where the densities of receptors were 1,030 and 445 fmol/mg of protein, respectively. Ro 5‐4864 (4′‐chlorodiazepam) was 2,200‐fold less potent as a competitor of [3H]PK 11195 binding in the piscine than the murine membranes. Investigation of the regional distribution of these sites in trout yielded a rank order of density of spinal cord > olfactory bulb = optic tectum = rhombencephalon > cerebellum > telencephalon. This site in trout shared some of the characteristics of the peripheral‐type benzodiazepine receptor (PTBR) (also known as the mitochondrial benzodiazepine receptor) in rodents, i.e., high affinity for PK 11195 and the endogenous ligand protoporphyrin IX, but was unique in the low affinity of Ro 5‐4864 (41 μM) and diazepam and the relatively high affinity of the calcium channel ligand diltiazem and two central benzodiazepine ligands, CGS 8216 and CGS 9896. The differential affinity for the two prototypic PTBR ligands in trout is similar to that previously observed in calf and human brain membranes. Structural differences for the trout sites are indicated by the relative inability of diethyl pyrocarbonate to modify histidine residues of the binding site in trout as compared with mouse membranes. Heterogeneity of binding of the two prototypic PTBR ligands in mouse brain membranes was indicated by additivity studies, equilibrium competition experiments, and saturation isotherms, which together support the hypothesis that Ro 5‐4864 discriminates between two [3H]PK 11195 binding sites having high (nanomolar) and low (micromolar) affinity, respectively.
Reduced Glucose Transporter at the Blood‐Brain Barrier and in Cerebral Cortex in Alzheimer Disease
Authors: Kalaria RajesH N. , Harik Sami I.
Published: October 2006

Abstract: We studied the hexose transporter prtotein of the frontal and temporal neocortex, hippocampui, putamen, cerebellum, and cerebral microvessels (which constitute the blood‐brain barrier) in Alzheimer disease and control subjects by reversible and covalent binding with [3H]cytochalasin B and by immunological reactivity. In Alzheimer disease subjects, we found a marked decrease in the hexose transporter in brain microvessels and in the cerebral neocortex and hippocampus, regions that are most affected in Alzheimer disease, but there were no abnormalities in the putajnen or cerebellum. Hexose transporter reduction in cerebrajl microves‐sels of Alzheimer subjects is relatively specific because other enzyme markers of brain endothelium were not significantly altered. The low density of the hexose transporter at the blood‐brain barrier and in the cerebral cortex in Alzheimer disease may be related to decreased in vivo measurements of cerebral oxidative metabolism.
Cholinergic Synaptic Vesicles Contain a V‐Type and a P‐Type ATPase
Authors: Yamagata Susan K. , Parsons Stanley M.
Published: October 2006

Abstract: Fifty to eighty‐five percent of the ATPase activity in different preparations of cholinergic synaptic vesicles isolated from Torpedo electric organ was half‐inhibited by 7 μM vanadate. This activity is due to a recently purified phos‐phointermediate, or P‐type, ATPase. Acetylcholine (ACh) active transport by the vesicles was stimulated about 35% by vanadate, demonstrating that the P‐type enzyme is not the proton pump responsible for ACh active transport. Nearly all of the vesicle ATPase activity was inhibited by N‐ethyl‐maleimide. The P‐type ATPase could be protected from N‐ethylmaleimide inactivation by vanadate, and subsequently reactivated by complexation of vanadate with deferoxamine. The inactivation‐protection pattern suggests the presence of a vanadate‐insensitive, A‐ethylmaleimide‐sensitive ATPase consistent with a vacuolar, or V‐type, activity expected to drive ACh active transport. ACh active transport was half‐inhibited by 5 μM N‐ethylmaleimide, even in the presence of vanadate. The presence of a V‐type ATPase was confirmed by Western blots using antisera raised against three separate subunits of chromaffin granule vacuolar ATPase I. Both ATPase activities, the P‐type polypeptides, and the 38‐kilo‐dalton polypeptide of the V‐type ATPase precisely copurify with the synaptic vesicles. Solubilization of synaptic vesicles in octaethyleneglycol dodecyl ether detergent results in several‐fold stimulation of the P‐type activity and inactivation of the V‐type activity, thus explaining why the V‐type activity was not detected previously during purification of the P‐type ATPase. It is concluded that cholinergic vesicles contain a P‐type ATPase of unknown function and a V‐type ATPase which is the proton pump
Selective Increase of Tetrameric (G4) Acetylcholinesterase Activity in Rat Hindlimb Skeletal Muscle Term Denervation
Authors: Gregory Eugene J. , Hodges‐Savola Cheryl A. , Fernandez Hugo L.
Published: October 2006

Abstract: Acetylcholinesterase (AChE; EC 3.1.1.7) isoenzymes in gracilis muscles from adult Sprague‐Dawley rats were studied 24–96 h after obturator nerve transection. Results show a selective denervation‐induced increase in the globular G4 isoform, which is predominantly associated with the plasmalemma. This enzymatic increase was (a) transient occurring between 24 and 60 h) and accompanied by declines in all other identifiable AChE isoforms; (b) observed after concurrent denervation and inactivation of the enzyme with diisopropylfluorophosphate, but not following treatment with cycloheximide; and (c) more prominent in the extracellular compartment of muscle endplate regions. Aside from this transient change, G4 activity did not fall below control levels, indicating that at least the short‐term maintenance of G4AChE (i.e., at both normal and temporarily elevated levels) does not critically depend on the presence of the motor nerve. In addition, this isoform's activity increases in response to perturbations of the neuromuscular system that are known to produce elevated levels of acetylcholine (ACh), such as short‐term denervation and exercise‐induced enhancement of motor activity. The present study is consistent with the hypothesis that individual AChE isoforms in gracilis muscle are subject to distinct modes of neural regulation and suggests a role for ACh in modulating the activity of G4 AChE at the motor endplate.
Brain Phospholipase A2 Is Activated After Experimental Closed Head Injury in the Rat
Authors: Shohami E. , Shapira Y. , Yadid G. , Reisfeld N. , Yedgar S.
Published: October 2006

Abstract: Head injury was induced in rats by a weight drop device, falling over the left hemisphere. The rats were killed at 15 min, 4 h, and 24 h after injury. Cortical slices were taken from the injured zone, from the corresponding region of the contralateral hemisphere, and from the frontal lobe of both hemispheres. These cortical slices were incubated in the presence of a fluorescent phospholipid analogue, l‐acyl‐2‐(N‐4‐nitrobenzo‐2‐oxa‐I,3‐diazole)aminocaproylphos‐phatidylcholine (C6‐NBD‐PC) which is a substrate for phospholipase A2 (PLA2) in intact cells. The interaction of this substrate with cells produces only one fluorescent product, the fatty acid C6‐NBD‐FA, released from the 2‐position of C6‐NBD‐PC. Thus, the level of C6‐NBD‐FA produced is a direct measure of PLA2 activity. Fifteen minutes after trauma, a 75% increase of PLA2 activity was found in the injured zone. At 4 h, the frontal lobe of the contused, left hemisphere had elevated PLA2 activity, as well as the injured zone (92 and 81%, respectively). At 24 h, PLA2 activity at the site of injury was 245% of sham. In the right, noninjured zone, no significant changes in PLA2 activity were noticed during the entire time course of the experiment. Prostaglandin E2 (PGE2) was extracted from the same cortical slices as those used for PLA2 activity measurement. A significant correlation (Pearson coefficient test, correlation coefficient = 0.469, p < 0.05, n = 21) was found between the elevation of PLA2 activity and PGE2 levels measured in the injured hemisphere, at 4 and 24 h. The elevation of PGE2 production induced by the trauma was abolished when the rats were pretreated with dextran 70,000, which has been previously shown to inhibit PLA2 activity. The results of this study support the hypothesis that activation of brain PLA2 is involved in the increased cerebral production of eicosanoids induced by trauma.
Immunochemical Properties of Ubiquitin Conjugates in the Paired Helical Filaments of Alzheimer Disease
Authors: Perry George , Mulvihill Paul , Fried Victor A. , Smith Harry T. , Grundke‐Iqbal Inge , Iqbal Khalid
Published: October 2006

Abstract: Immunocytochemical and peptide sequencing studies indicate that the regulatory protein ubiquitin (Ub) is incorporated into the paired helical filaments (PHF) of Alzheimer disease. In this study, we showed that some antibodies raised to PHF recognize epitopes of Ub. Analysis of the Ub sequences recognized by the antibodies raised to PHF, along with the known specificity of several monoclonal antibodies raised to artificial Ub conjugates, indicates the immunochemical representation of Ub residues 34–76 in PHF. The Ub epitopes recognized by antibodies raised to PHF are distinct from those recognized by antibodies raised to artificial Ub conjugates in two respects. First, antibodies that are raised to PHF and that recognize Ub react with PHF equally, whether denatured or not, whereas those raised to artificial Ub conjugates show greater reaction after denaturation. Second, mapping of the epitopes recognized by two monoclonal antibodies to PHF onto Ub indicates a distinction in the Ub residues recognized, compared with monoclonal antibodies raised to artificial Ub conjugates. The proximity of their epitopes to the site of conjugation, as well as their affinity for PHF polypeptides, suggests that the PHF antibodies that recognize Ub may be directed specifically to Ub epitopes defined by the protein conjugated to Ub.
Effects of Steroids on Serotonin‐N‐Acetyltransferase Activity of Pineals in Organ Culture
Authors: Yuwiler A.
Published: October 2006

Abstract: Treatment of neonatal, but not adult, rats with glucocorticoids decreases the rise in pineal serotonin N‐acetyltransferase activity upon stimulation with β agonists. Pineals in organ culture and exposed to steroids also show a dose‐dependent decrement in response to β agonists which increases with steroid exposure time. Pineals from neonatal and adult animals are equally sensitive. The effects of steroids on pineals in organ culture appear to be reversible, and the order of potency of different steroids differs from that observed when steroids are administered in vivo. Both in vitro and in vivo steroids appear to act at a site after cyclic AMP generation. Hydroxyindole‐O‐methyltransferase activity in the adult pineal does not appear affected by steroid exposure.
Reduced Protein Kinase C Activity in Ischemic Spinal Cord
Authors: Kochhar Abha , Saitoh Tsunao , Zivin Justin
Published: October 2006

Protein phosphorylation was evaluated in a rabbit spinal cord ischemia model under conditions where cyclic AMP‐dependent protein kinase (PK‐A) and calcium/phos‐pholipid‐dependent protein kinase (PK‐C) were activated. One hour of ischemia did not affect PK‐A activity significantly; however, PK‐C activity was reduced by more than 60%. In vitro phosphorylation of endogenous proteins by endogenous PK‐C revealed that eight particulate and five cytosolic proteins showed stimulated phosphorylation by PK‐C activators in control tissue, although this stimulation was virtually absent in ischemic samples. When control and ischemic particulate fractions were combined, the endogenous protein phosphorylation pattern under PK‐C‐activating conditions was similar to the ischemic sample, which suggests that inhibitory molecules may be present in the ischemic particulate fraction. In vitro phosphorylation of endogenous proteins under PK‐A‐activating conditions in ischemic tissue was similar to that in control tissue. The results suggest that the PK‐C phosphorylation system is selectively impaired in ischemic spinal cord. In addition to reduced PK‐C‐dependent phosphorylation, an Mr 64,000 protein was phosphorylated in ischemic cytosolic samples, but not in control samples. The phosphorylation of the Mr 64,000 protein was neither PK‐C‐dependent nor PK‐A‐dependent. These altered phosphorylation reactions may play critical roles in neuronal death during the course of ischemia.
[3H]N‐[1‐(2‐Thienyl)cyclohexyl]‐3,4‐Piperidine ([3H]TCP) Binding in Human Frontal Cortex: Decreases in Alzheimer‐Type Dementia
Authors: Ninomiya Haruaki , Fukunaga Reiko , Taniguchi Takashi , Fujiwara Motohatsu , Shimohama Shun , Kameyama Masakuni
Published: October 2006

We studied [3H]N‐[1‐(2‐thienyl)cyclohexyl]‐3,4‐piperidine ([3H]TCP) binding to human frontal cortex obtained at autopsy from 10 histologically normal controls and eight histopathologically verified cases with Alzheimer‐type dementia (ATD). Extensively washed membrane preparations were used to minimize the effects of endogenous substances. In ATD frontal cortex, the total concentration (Bmax) of [3H]TCP binding sites was significantly reduced by 40–50%. The apparent dissociation constant (KD) values showed no significant change. The reduction in binding capacity was also apparent in Triton X‐100–treated membrane preparations, and there was a linear correlation between the number of [3H]TCP binding sites and that of N‐methyl‐D‐aspartate (NMDA)‐sensitive [3H]glutamate binding sites. [3H]TCP binding sites spared in ATD brains retained the affinity for the ligand and the reactivity to NMDA, L‐glutamate, and glycine. These results suggest that the primary change in NMDA receptor‐ion channel complex in ATD brains is the reduction of its number, possibly reflecting the loss of neurons bearing these receptor complexes, and that the functional linkage within the receptor complexes spared in ATD brains remains normal.
Ventricular Cerebrospinal Fluid Monoamine Transmitter and Metabolite Concentrations Reflect Human Brain Neurochemistry in Autopsy Cases
Authors: Wester Per , Bergström Ulrica , Eriksson Anders , Gezelius Christer , Hardy John , Winblad Bengt
Published: October 2006

Concentrations of dopamine (DA), its metabolites 3‐methoxytyramine and homovanillic acid (HVA), noradrenaline (NA), its metabolites normetanephrine (NM) and 3‐methoxy‐4‐hydroxyphenylglycol (MHPG), 5‐hydroxytryptamine (5‐HT, serotonin), and its metabolite 5‐hy‐droxyindoleacetic acid (5‐HIAA) were measured in 14 brain regions and in CSF from the third ventricle of 27 human autopsy cases. In addition, in six cases, lumbar CSF was obtained. Monoamine concentrations were determined by reversed‐phase liquid chromatography with electrochemical detection. Ventricular/lumbar CSF ratios indicated persistence of rostrocaudal gradients for HVA and 5‐HIAA post mortem. Ventricular CSF concentrations of DA and HVA correlated positively with striatal DA and HVA. CSF NA correlated positively with NA in hypothalamus, and CSF MHPG with levels of MHPG in hypothalamus, temporal cortex, and pons, whereas CSF NM concentration showed positive correlations with NM in striatum, pons, cingulate cortex, and olfactory tubercle. CSF 5‐HT concentrations correlated positively with 5‐HT in caudate nucleus, whereas the concentration of CSF 5‐HIAA correlated to 5‐HIAA levels in thalamus, hypothalamus, and the cortical areas. These data suggest a specific topographic origin for monoamine neurotransmitters and their metabolites in human ventricular CSF and support the contention that CSF measurements are useful indices of central monoaminergic activity in man.
(+)‐[3H]MK‐801 Binding Sites in Postmortem Human Brain
Authors: Quarum Merrit L. , Parker Joel D. , Keana John F. W. , Weber Eckard
Published: October 2006

The pharmacological specificity and the regional distribution of the N‐methyl‐D‐aspartate receptor‐associated 5‐methyl‐10,11‐dihydro‐5H‐dibenzo[a,d]cyclohepten‐5, 10‐imine maleate (MK‐801) binding sites in human postmortem brain tissue were determined by binding studies using (+)‐[3H]MK‐801. Scatchard analysis revealed a high‐affinity (KD= 0.9 ± 0.2 nM, Bmax= 499 ± 33 fmol/mg of protein) and a low‐affinity (KD= 3.6 ± 0.9 nM, Bmax= 194 ± 44 fmol/ mg of protein) binding site. The high‐affinity site showed a different regional distribution of receptor density (cortex > hippocampus > striatum) compared to the low‐affinity binding site (cerebellum > brainstem). The rank order pharmacological specificity and stereoselectivity of the high‐(cortex) and low‐(cerebellar) affinity binding sites were identical. However, all compounds tested showed greater potency at the high‐affinity site in cortex. The results indicate that (+)[3H]MK‐801 binding in human postmortem brain tissue shows pharmacological and regional specificity.
Bacterial Bioluminescence: Isolation and Expression of the Luciferase Genes from
Vibrio harveyi
Authors: Belas Robert , Mileham Alan , Cohn Daniel , Hilman Marcia , Simon Melvin , Silverman Michael
Published: October 2006

Genes for the luciferase enzyme of
Vibrio harveyi
were isolated in
Escherichia coli
by a general method in which nonluminous, transposon insertion mutants were used. Conditions necessary for light production in
E. coli
were examined. Stimulation of transcription of the genes for luciferase (
lux A
and
lux B
) was required for efficient synthesis of luciferase. To enhance transcription bacteriophage promoter elements were coupled to the cloned lux gene fragments.
Membrane Effects of Thyrotropin-Releasing Hormone and Estrogen Shown by Intracellular Recording from Pituitary Cells
Authors: Dufy Bernard , Vincent Jean-Didier , Fleury Hervé , Du Pasquier Pierre , Gourdji Danielle , Tixier-Vidal Andrée
Published: October 2006

The effects of thyrotropin-releasing hormone and 17 β-estradiol on the electrical membrane properties of a prolactin-secreting pituitary cell line (GH
3
/B6) were studied with intracellular microelectrode recordings. Of the cells tested, 50 percent were excitable and displayed calcium-dependent action potentials when depolarized. When injected directly on the membrane of an excitable cell, thyrotropin-releasing hormone and 17 β-estradiol induced action potentials within 1 minute. The spiking activity was preceded by a progressive increase of the input resistance without any detectable change in the resting membrane polarization. The results reveal a rapid effect of both substances on the membrane of GH
3
/B6 cells. In the case of thyrotropin-releasing hormone, which has both a short-term effect on release of prolactin and a long-term effect on its synthesis, the induced electrical activity may be associated with the stimulation of prolactin production. The physiological implication of 17 β-estradiol-induced, calcium-dependent spiking activity remains to be elucidated.
A Human Syndrome Caused by Immotile Cilia
Authors: Afzelius Björn A.
Published: October 2006

Four subjects who produced immotile sperm were studied. In three of the subjects, who had frequent bronchitis and sinusitis, there was no mucociliary transport, as measured by tracheobronchial clearance. Electron microscopy indicated that cilia from cells of these patients lack dynein arms.
Potassium Accumulation in Muscle: A Test of the Binding Hypothesis
Authors: Palmer Lawrence G. , Gulati Jagdish
Published: October 2006

Living frog skeletal muscle can accumulate potassium in vitro to concentrations up to 580 millimolar. Both the amount of potassium accumulated and the relationship between intracellular and extracellular potassium concentrations indicate that potassium is "free" under all conditions, rather than bound to cellular macromolecules. The data also indicate that at most 20 percent of the cell water is "bound" in the sense that it excludes electrolytes.
Stress and Coping Factors Influence Tumor Growth
Authors: Sklar Lawrence S. , Anisman Hymie
Published: October 2006

Growth of syngeneic P815 mastocytoma in DBA/2J male mice was evaluated as a result of various stress regimens. A single session of inescapable shock resulted in earlier tumor appearance, exaggeration of tumor size, and decreased survival time in recipient animals. Escapable shock had no such effects. The effects of the inescapable shock were mitigated if mice received long-term shock treatment.
Enhancement of Luminance Flicker by Color-Opponent Mechanisms
Authors: Gouras P. , Zrenner E.
Published: October 2006

Color-opponent ganglion cells in the monkey retina respond to luminance flicker at high temporal frequencies. Color opponency, which makes these cells so selective of wavelength at low temporal frequencies, is progressively lost at high frequencies. This loss is due to a frequency-dependent phase shift between the responses of spectrally different center and surround mechanisms in the receptive field of each of these cells. Center and surround responses, which are antagonistic at low temporal frequencies, become synergistic at high ones, making these cells most responsive at high frequencies to those wavelengths to which they are least responsive at low frequencies. This phenomenon can explain the differences between chromatic and luminance flicker in human vision.
Ionophore-Mediated Calcium Entry Induces Mussel Gill Ciliary Arrest
Authors: Satir Peter
Published: October 2006

Lateral cilia of freshwater mussel gills, which normally beat with metachronal rhythm, are arrested pointing frontally by perfusion with 6.25 to 12.5 millimolar calcium and 10
-5
molar A23187, a calcium ionophore. Arrest does not occur in either calcium or ionophore and monovalent cations alone. Activity returns with continued perfusion in potassium chloride or calcium chloride, and more slowly in sodium chloride, after removal of ionophore. These results support the hypothesis that a local rise in internal calcium causes ciliary arrest.
Microtubule Assembly and the Intracellular Transport of Secretory Granules in Pancreatic Islets
Authors: Pipeleers D. G. , Pipeleers-Marichal M. A. , Kipnis D. M.
Published: October 2006

Polymerized and depolymerized tubulin were measured in pancreatic islets under various physiological and pharmacological conditions. Variations in insulin release from islets of fed or fasted rats were accompanied by concomitant changes in tubulin polymerization. Glucose induced the formation of microtubules in vitro independent of extracellular calcium. Total and polymerized tubulin content were decreased by fasting and restored by glucose feeding.
Melatonin Inhibition of the Neonatal Pituitary Response to Luteinizing Hormone-Releasing Factor
Authors: Martin Jeanne E. , Klein David C.
Published: October 2006

Neonatal rat anterior pituitary glands treated in organ culture with 1 nanomolar luteinizing hormone-releasing factor (LRF) showed a tenfold increase in medium luteinizing hormone (LH) concentrations over control values. Simultaneous treatment of the glands with 1 nanomolar melatonin significantly reduced the stimulatory effect of LRF on release of LH. This finding indicates that melatonin can act directly on the neonatal pituitary to inhibit the LH response to LRF.
Low Frequency Electric Field Induced Changes in the Shape and Motility of Amoebas
Authors: Friend Albert W. , Finch E. D. , Schwan H. P.
Published: October 2006

Perpendicular and parallel elongation of the giant amoeba,
Chaos chaos
(
Chaos carolinensis
), have been observed in alternating electric fields over a wide frequency range (from about 1 hertz to about 10 megahertz). The characteristics change as a function of frequency. Simple dielectric forces may be important in the production of these effects.
Target Velocity Signals of Visual Tracking in Vermal Purkinje Cells of the Monkey
Authors: Kase Manabu , Noda Hiroharu , Suzuki David A. , Miller David C.
Published: October 2006

Discharges of Purkinje cells were recorded from the vermis, lobules VI and VII, of a monkey trained to track a visual target. When the monkey tracked a sinusoidally oscillating target, cellular activity changed in phase with the velocity signal of the eye movement. When the monkey fixated a stationary point, almost identical modulation in activity occurred, reflecting the velocity signal of the motion of the retinal image of the target. The data suggest that the vermis participates in the control of smooth pursuit eye movements by providing the oculomotor system with the actual target velocity information which is the sum of eye velocity and retinal image velocity signals.
Ape Limb Bone from the Oligocene of Egypt
Authors: Fleagle J. G. , Simons E. L. , Conroy G. C.
Published: October 2006

An ulna attributed to
Aegyptopithecus zeuxis
provides the first evidence for interpreting the locomotor behavior of the earliest apes. The fossil indicates that
Aegyptopithecus
was an arboreal quadruped and that the primitive hominoid locomotor pattern was most nearly analogous, among living primates, to that of
Alouatta
, the howler monkey.
Insect Diversity in the Fossil Record
Authors: Labandeira Conrad C. , Sepkoski J. John
Published: October 2006

Insects possess a surprisingly extensive fossil record. Compilation of the geochronologic ranges of insect families demonstrates that their diversity exceeds that of preserved vertebrate tetrapods through 91 percent of their evolutionary history. The great diversity of insects was achieved not by high origination rates but rather by low extinction rates comparable to the low rates of slowly evolving marine invertebrate groups. The great radiation of modern insects began 245 million years ago and was not accelerated by the expansion of angiosperms during the Cretaceous period. The basic trophic machinery of insects was in place nearly 100 million years before angiosperms appeared in the fossil record.
Geography of End-Cretaceous Marine Bivalve Extinctions
Authors: Raup David M. , Jablonski David
Published: October 2006

Analysis of the end-Cretaceous mass extinction, based on 3514 occurrences of 340 genera of marine bivalves (Mollusca), suggests that extinction intensities were uniformly global; no latitudinal gradients or other geographic patterns are detected. Elevated extinction intensities in some tropical areas are entirely a result of the distribution of one extinct group of highly specialized bivalves, the rudists. When rudists are omitted, intensities at those localities are statistically indistinguishable from those of both the rudist-free tropics and extratropical localities.
A Bangiophyte Red Alga from the Proterozoic of Arctic Canada
Authors: Butterfield Nicholas J. , Knoll Andrew H. , Swett Keene
Published: October 2006

Silicified peritidal carbonate rocks of the 1250- to 750-million-year-old Hunting Formation, Somerset Island, arctic Canada, contain fossils of well-preserved bangiophyte red algae. Morphological details, especially the presence of multiseriate filaments composed of radially arranged wedge-shaped cells derived by longitudinal divisions from disc-shaped cells in uniseriate filaments, indicate that the fossils are related to extant species in the genus
Bangia
. Such taxonomic resolution distinguishes these fossils from other pre-Ediacaran eukaryotes and contributes to growing evidence that multicellular algae diversified well before the Ediacaran radiation of large animals.
Calibrating Rates of Early Cambrian Evolution
Authors: Bowring Samuel A. , Grotzinger John P. , Isachsen Clark E. , Knoll Andrew H. , Pelechaty Shane M. , Kolosov Peter
Published: October 2006

An explosive episode of biological diversification occurred near the beginning of the Cambrian period. Evolutionary rates in the Cambrian have been difficult to quantify accurately because of a lack of high-precision ages. Currently, uranium-lead zircon geochronology is the most powerful method for dating rocks of Cambrian age. Uranium-lead zircon data from lower Cambrian rocks located in northeast Siberia indicate that the Cambrian period began at ∼544 million years ago and that its oldest (Manykaian) stage lasted no less than 10 million years. Other data indicate that the Tommotian and Atdabanian stages together lasted only 5 to 10 million years. The resulting compression of Early Cambrian time accentuates the rapidity of both the faunal diversification and subsequent Cambrian turnover.
Climatic Consequences of Very High Carbon Dioxide Levels in the Earth's Early Atmosphere
Authors: Kasting James F. , Ackerman Thomas P.
Published: October 2006

The possible consequences of very high carbon dioxide concentrations in the earth's early atmosphere have been investigated with a radiative-convective climate model. The early atmosphere would apparently have been stable against the onset of a runaway greenhouse (that is, the complete evaporation of the oceans) for carbon dioxide pressures up to at least 100 bars. A 10- to 20-bar carbon dioxide atmosphere, such as may have existed during the first several hundred million years of the earth's history, would have had a surface temperature of approximately 85° to 110°C. The early stratosphere should have been dry, thereby precluding the possibility of an oxygenic prebiotic atmosphere caused by photodissociation of water vapor followed by escape of hydrogen to space. Earth's present atmosphere also appears to be stable against a carbon dioxide-induced runaway greenhouse.
Early Archean (3.3-Billion to 3.5-Billion-Year-Old) Microfossils from Warrawoona Group, Australia
Authors: Schopf J. William , Packer Bonnie M.
Published: October 2006

Cellularly preserved filamentous and colonial fossil microorganisms have been discovered in bedded carbonaceous cherts from the Early Archean Apex Basalt and Towers Formation of northwestern Western Australia. The cell types detected suggest that cyanobacteria, and therefore oxygen-producing photosynthesis, may have been extant as early as 3.3 billion to 3.5 billion years ago. These fossils are among the oldest now known from the geologic record; their discovery substantiates previous reports of Early Archean microfossils in Warrawoona Group strata.
Biological Extinction in Earth History
Authors: Raup David M.
Published: October 2006

Virtually all plant and animal species that have ever lived on the earth are extinct. For this reason alone, extinction must play an important role in the evolution of life. The five largest mass extinctions of the past 600 million years are of greatest interest, but there is also a spectrum of smaller events, many of which indicate biological systems in profound stress. Extinction may be episodic at all scales, with relatively long periods of stability alternating with short-lived extinction events. Most extinction episodes are biologically selective, and further analysis of the victims and survivors offers the greatest chance of deducing the proximal causes of extinction. A drop in sea level and climatic change are most frequently invoked to explain mass extinctions, but new theories of collisions with extraterrestrial bodies are gaining favor. Extinction may be constructive in a Darwinian sense or it may only perturb the system by eliminating those organisms that happen to be susceptible to geologically rare stresses.
Periodic Extinction of Families and Genera
Authors: Raup David M. , Sepkoski J. John
Published: October 2006

Eight major episodes of biological extinction of marine families over the past 250 million years stand significantly above local background (
P
< 0.05). These events are more pronounced when analyzed at the level of genus, and generic data exhibit additional apparent extinction events in the Aptian (Cretaceous) and Pliocene (Tertiary) Stages. Time-series analysis of these records strongly suggests a 26-million-year periodicity. This conclusion is robust even when adjusted for simultaneous testing of many trial periods. When the time series is limited to the four best-dated events (Cenomanian, Maestrichtian, upper Eocene, and middle Miocene), the hypothesis of randomness is also rejected for the 26-million-year period (
P
< 0.0002).