bluuebunny/crossref_metadata_2025_split huggingface dataset:
H3‐Receptors Control Histamine Release in Human Brain
Authors: Arrang Jean‐Michel , Devaux Bertrand , Chodkiewicz Jean‐Paul , Schwartz Jean‐Charles 
Published: October 2006

AbstractThe regulation of histamine release was studied on slices prepared from pieces of human cerebral cortex removed during neurosurgery and labeled with l‐[3H]‐histidine. Depolarization by increased extracellular K+ concentration induced [3H]histamine release, although to a lesser extent than from rat brain slices. Exogenous histamine reduced by up to 60% the K+‐evoked release, with an EC50 of 3.5 ± 0.5 × 10−‐8M. The H3‐receptor antagonists impromidine and thioperamide reversed the histamine effect in an apparently competitive manner and enhanced the K+‐evoked release, indicating a participation of endogenous histamine in the release control process. The potencies of histamine and the H3‐receptor antagonists were similar to those of these agents at presynaptic H3‐autoreceptors controlling [3H]histamine release from rat brain slices. It is concluded that H3‐receptors control histamine release in the human brain.
Brain Levels of NADH and NAD+ Under Hypoxic and Hypoglycaemic Conditions In Vitro
Authors: Garofalo O. , Cox D. W. G. , Bachelard H. S. 
Published: October 2006

AbstractThe effects of hypoxia and hypoglycaemia on the redox state in vitro have been studied. NADH and NAD+ were extracted simultaneously from superfused cerebral cortex slices and assayed by bioluminescence. The results show a nonsignificant increase in NADH and the redox ratio in „mild hypoxia,” whereas „severe hypoxia” produced an increase of over 200% in NADH and in the NADH/NAD+ ratio. When the glucose in the incubation medium was reduced from its control value of 10 mM to 0.5 mM, significant decreases in NADH and the redox ratio to 60% of control value were observed. Further decreasing the glucose to 0.2 mM gave lower levels of NADH and the redox ratio (40% of control). The effects on the redox state of alternative substrates to glucose were also tested. Re placement of glucose by 10 mM pyruvate decreased the NADH by 77% and the NADH/NAD+ ratio by 79%. Replacement of glucose with 10 mM lactate gave decreases of 70% and 71%, respectively, whereas in the presence of 15 mM 2‐deoxyglucose and 5 mM glucose, the NADH was decreased by 56% and the ratio by 50%. The results are discussed in relation to levels of creatine phosphate and ATP, as well as evoked action potentials, observed from parallel studies.
Low [3H]Cytochalasin B Binding in the Cerebral Cortex of Newborn Rat
Authors: Morin Anne M. , Dwyer Barney E. , Fujikawa Denson G. , Wasterlain Claude G. 
Published: October 2006

AbstractThe concentrations of glucose transporter in the cerebral cortex and brainstem of neonatal (4–7 days old) and adult rats were measured using [3H]cytochalasin B binding. There was significantly lower binding in neonatal cortex (1.9 ± 0.7 pmol/mg protein) compared to adult (8.9 ± 2.5 pmol/mg protein). Scatchard analysis indicates this difference is due to a lower Bmax (neonate, 9.7 pmol/mg protein; adult, 18.6 ± 1.3 pmol/mg protein). Measurement of [3H]cytochalasin B binding in microvessels prepared from cortex of adult (28.1 ± 3.5 pmol/mg protein) and neonate (12.8 ± 1.9 pmol/mg protein) indicates a lower binding in the microvasculature of neonates, whereas no such difference was seen in the binding in microvessels prepared from adult and neonatal brainstem (adult, 11.8 ± 2.3 pmol/mg protein; neonate, 9.4 ± 2.7 pmol/mg protein). In both adult and neonate brain, there is an enrichment of glucose transporters in the microvasculature.
Membrane Interactions Are Altered in Myelin Isolated from Central and Peripheral Nervous System Tissues
Authors: Karthigasan Jeevajothie , Kirschner Daniel A. 
Published: October 2006

AbstractIsolated myelin has been used for determinations of membrane surface charge density and topographical mapping of components in the membrane. To determine how similar such myelin is to myelin of intact tissue, we have used x‐ray diffraction to compare their intermembrane interactions. The interactions were monitored by measuring the myelin period in samples treated with distilled water, buffered saline at pH 4–9 and ionic strength 0.06–0.18, and saline containing HgCl2 or triethyl tin sulfate. Myelin was isolated from whole brains and sciatic nerves of mice by conventional methods involving sucrose gradient centrifugation and osmotic shock. Consistent with previous findings, electron microscopy showed that the multilamellar morphology, staining, and repeat periods of isolated myelin were essentially like those of intact myelin; however, the membrane stacks were less extensive than those in whole tissue. X‐ray diffraction revealed that isolated CNS myelin was like intact myelin in showing reversible compaction in acidic media and in distilled water. However, unlike the myelin in whole tissue, isolated CNS myelin did not swell in hypotonic or alkaline media, or in the presence of HgCl2‐saline or triethyl tin. The altered membrane interactions could result from an increase in adhesiveness of the apposed membrane surfaces. Reorganization of proteolipid protein and/or a reduction of surface charge could account for the change in surface properties of isolated CNS myelin. Isolated PNS myelin, like the membranes in whole tissue, showed both compaction and swelling; however, the membrane pairs were disordered in the swollen structure. This irregular membrane swelling could result from charge variation in the extracellular surfaces.
Light‐Induced Dopamine Release from Teleost Retinas Acts as a Light‐Adaptive Signal to the Retinal Pigment Epithelium
Authors: Dearry Allen , Burnside Beth 
Published: October 2006

AbstractIn the retinal pigment epithelium (RPE) of lower vertebrates, melanin pigment granules migrate in and out of the cells' long apical projections in response to changes in light condition. When the RPE is in its normal association with the retina, light onset induces pigment granules to disperse into the apical projections; dark onset induces pigment granules to aggregate into the cell bodies. However, when the RPE is separated from the retina, pigment granule movement in the isolated RPE is insensitive to light onset. It thus seems likely that a signal from the retina communicates light onset to the RPE to initiate pigment dispersion. We have examined the nature of this retina‐to‐RPE signal in green sunfish, Le‐pomis cyanellus. In isolated retinas with adherent RPE, light‐induced pigment dispersion in the RPE is blocked by treatments known to block Ca2+‐dependent transmitter release in the retina. In addition, the medium obtained from incubating previously dark‐adapted retinas in the light induces light‐adaptive pigment dispersion when added to isolated RPE. In contrast, the medium obtained from incubating dark‐adapted retinas in constant darkness does not affect pigment distribution when added to isolated RPE. These results are consistent with the idea that RPE pigment dispersion is triggered by a substance that diffuses from the retina at light onset. The capacity of the conditioned medium from light‐incubated retinas to induce pigment dispersion in isolated RPE is in hibited by a D2 dopamine antagonist, but not by D! or α‐adrenergic antagonists. Light‐induced pigment dispersion in whole RPE‐retinas is also blocked by a D2 dopamine antagonist. These results suggest that the diffusible substance is dopamine and that retinal dopamine stimulates pigment dispersion by interacting with D2 dopaminergic receptors on the RPE cell surface. Direct measurement of the endogenous catecholamine content of isolated dark‐adapted retinas and of the medium surrounding isolated retinas incubated in the dark or in the light demonstrates that dopamine is the predominant catecholamine of green sunfish retinas, and that light onset stimulates the overflow of endogenous dopamine—but not that of norepinephrine or epinephrine—from isolated retinas. These results suggest that illumination increases dopamine release in teleost retinas. Together, our findings are consistent with the idea that dopamine acts as a paracrinic messenger of light‐adaptive stimuli by diffusing from its site of release in the retina to distant nonsynaptic receptors on RPE cells.
Two Affinity States for [3H]Imipramine Binding to the Human Platelet 5‐Hydroxytryptamine Carrier: An Explanation for the Allosteric Interaction Between 5‐Hydroxytryptamine and Imipramine
Authors: O'Riordan Catherine , Phillips Orla M. , Williams D. Clive 
Published: October 2006

Abstract:5‐Hydroxytryptamine (5‐HT) showed a biphasic effect on the dissociation rate of [3H]imipramine from human platelet membranes: At low concentrations (EC50, ∼ 2.5 μM), 5‐HT stimulated the rate, as expected for mutually exclusive binding of 5‐HT and imipramine; at higher concentrations (EC50, ∼ 40 μM), 5‐HT reduced this stimulated rate, a result consistent with 5‐HT binding at a site that is physically distinct from both the imipramine binding site and the 5‐HT transport recognition site of the 5‐HT carrier. This modulatory effect could be mimicked by tryptamine, was saturable and independent of Na+ concentration, and could also be demonstrated for detergent‐solubilized carriers. Monophasic association kinetics for [3H]imipramine binding were found. Heat stability experiments showed biphasic thermal inactivation curves. These results are consistent with [3H]imipramine binding to two classes of binding sites at the 5‐HT carrier on human platelet membranes, with affinities three‐ to fivefold different. 5‐HT can convert the lower‐affinity state into the higher‐affinity state.
Antigens and Antibodies as Cell Phenotypes
Authors: Schultz Jack 
Published: October 2006

The paradoxical features of transplantation specificity—its strict genetic control in transfers of tissue from strain to strain as compared with its malleability on tissue passage in foreign immunological environments where the host does not reject the implant (F
1
hybrid passage, tolerance actively acquired by immature hosts, and so on)—present a challenge to genetic interpretation. The attempt is made in this article to show parallels between this behavior and such changes as the transformation of serotypes in
Paramecium
, in which the activity of genetic units becomes fixed as a cytoplasmic state—a cellular heredity persistent under specified environmental conditions but capable of change to an alternative state—while the genetic structure of the cell remains constant. The reactions appear to differ from those in the
Paramecium
case in that the diverse loci control a mosaic of different specificities, which change relatively independently of each other, in contrast to mutual exclusion of cytoplasmic states influenced by the different loci in
Paramecium
.

The process of antibody formation is considered as a change in cellular phenotype from the same point of view. The primary response in the stem cells of the lymphoid tissues is interpretable as the establishment of a new cytoplasmic state in response to a nuclear stimulus by the foreign antigen. For the secondary response, the suggestion is made that a reaction of antigen with cellular antibody at the surface of stem cells exhibiting the primary response serves as the stimulus for specific proliferation of antibody-forming clones of cells. A parallel is drawn with the fertilization reaction, specifically with regard to the initiation of cleavage in eggs by antisera to them.
Finally, a general chromosomal mechanism is sought for these phenomena, on the basis of activities of specific chromosome regions in response to special developmental stimuli, such as the disproportionate local synthesis of deoxyribonucleic acid demonstrated in the giant chromosomes of the Diptera. By a correlation of such activities with the nucleocytoplasmic system of ribonucleic acid granules on membranes, a possible mechanism appears for the formation, in response to environmental stimuli, of cytoplasmic states which might supply the persistent pattern required for this type of cell heredity. The analogies made, it is believed, provide a framework for the design of test experiments.
Drugs in the Brain
Authors: Roth Lloyd J. , Barlow Charles F. 
Published: October 2006

In our studies on the entry of drugs into the central nervous system we have found the technique of autoradiography combined with radioassay to be a valuable research tool. It has disclosed such unsuspected phenomena as the dual routes of entry into the brain of acetazolamide. Although many factors controlling drug entry remain to be studied, we propose certain general conclusions.1) The anatomical boundaries of brain are clearly reflected by the penetration and accumulation of all compounds we have studied—a finding that confirms the original proposition that whole-brain homogenates are inadequate for the study of drug and brain relationships.2) Circulation, expressed as regional blood flow or volume of capillary blood, was seldom decisive in influencing entry or accumulation of exogenous substances in the brain. To date, the only compounds demonstrated to be circulation-dependent are trifluoroiodomethane and thiopental. Both are extremely fat-soluble. Tissue binding appears to be an additional factor in the case of thiopental.3) Penetration is retarded by myelin. All substances we have studied have shown a relatively slower rate of entry into this tissue. In immature brain, before myelinization has taken place, the primordial white matter is readily penetrated. We have suggested that entry into mature white matter is retarded by the lamellated membranes of the myelin sheath, which should be regarded, therefore, as a component of the blood-brain barrier. The small interstitial space indicated by the limited entry of sulfate ion is an additional hindrance to dispersal of exogenous substances into brain parenchyma. The blood-brain barrier is a complex anatomical, physiological, and biochemical phenomenon, and no unitary hypothesis is adequate to embrace all the observed events.4) Accumulation of a drug in the brain implies some form of binding or interaction between drug and tissue. Findings on injection of phenobarbital, thiopental, or diphenylhydantoin illustrate such an accumulation. These binding interactions may be nonspecific, as is probable in the case of drugs bound to plasma protein. However, a more fundamental significance is suggested when a drug is found to bind, react with, or accumulate in, a specific anatomical structure of the brain. We have made reference to this possibility in connection with the localization of isonicotinic acid hydrazide or its metabolites in the hippocampus, and we have also reported the striking accumulation of acetazolamide in hippocampus, caudate nucleus, and hypothalamus. Although the binding process is poorly understood, further investigation of these phenomena should lead to a clearer understanding of regional variations in brain chemistry. While one should not assume that the demonstration of a focal concentration of a drug implies site of action, correlation between pharmacological action, electrophysiological events, biochemical changes, and temporal and regional drug concentrations may indeed exist.
Continuously Cultured Tissue Cells and Viral Vaccines
Authors:   Committee on Tissue Culture Viruses and Vaccines
Published: October 2006

1) Continuously cultured tissue cells afford numerous potential advantages for the propagation of viruses to be used in vaccines.
2) Because continuously cultured tissue cells sooner or later become capable of growing into neoplasms when transplanted into a suitable host, every possible precaution should be taken to ensure that viral vaccines grown in cell cultures are free from living cells and cell particles larger than 0.5 to 1.0 micron.
3) The radical abnormalities that occur in cell lines derived from neoplasms and those that develop sooner or later in cell lines derived from normal tissue cannot be ignored. However, no evidence has been recorded (i) that untoward consequences follow administration of cell-free preparations from such cultures to humans or (ii) that oncogenic or other viral activity is associated with the ability of cells of these lines to grow into neoplasms when transplanted into a suitable host. It seems very unlikely, nevertheless, that acceptance could be won at present for the general use of a live-virus vaccine prepared from a virus grown in cells showing evidences of malignancy. This conclusion is based more on psychological and public relations considerations than on the available scientific information, which, however, needs considerable augmentation. In this connection, careful consideration should be given to the question whether the absence of the cited kinds of abnormalities from a continuously cultured cell system is a sufficient indicator of freedom from oncogenic potential. In the absence of unfavorable data, we judge that present knowledge does not preclude judicious extension of clinical trials, in volunteers, of appropriately filtered and otherwise controlled experimental live-virus vaccines grown in carefully selected continuously cultured cell systems. Only in this way can sufficient data be collected, and adequate criteria be developed, to define eventually the conditions for acceptability of such preparations for general administration to humans.
4) Every possible effort should be devoted to the development of non-oncogenic and otherwise acceptable cell lines from normal tissues for use in viral vaccine production. It is suggested that exploratory studies begin with continuously cultured mixed-cell populations in the diploid state and stabilized cloned cultures. Criteria for the selection and monitoring of cell lines, and progressive steps leading to large-scale application are outlined.
5) If the need for immunization against a particular viral disease should be deemed sufficiently urgent, and if no practicable alternative were available, serious consideration might be given to a vaccine prepared by inactivating the virus, grown in such a selected stabilized cell line as HeLa or human skin epithelium. The conditions of preparation would have to be such as would inactivate the most resistant known viruses and infective nucleic acids with a generous margin of safety.
6) Principal areas needing intensified research emphasis are indicated.
Paleomagnetic Study of Antarctic Deep-Sea Cores
Authors: Opdyke N. D. , Glass B. , Hays J. D. , Foster J. 
Published: October 2006

The magnetic inclinations and intensities of about 650 samples from seven deep-sea cores taken in the Antarctic were measured on a spinner magnetometer. This series of measurements provided a magnetic stratigraphy, based on zones of normally or reversally polarized specimens for each core, which was then correlated with the magnetic stratigraphy of Cox
et al.
One core (V16-134) gave a continuous record of the paleomagnetic field back to about 3.5 million years.

When selected samples were subjected to alternating-field demagnetization, most were found to have an unstable component that was removed by fields of 150 oersteds; all samples from two cores were partially demagnetized in a field of 150 oersteds. The average inclination in these two cores was then in good agreement with the average inclination of the ambient field for the latitude of the core site. It was also found that the intensities of the samples decreased at the points of reversal; this finding is to be expected if, as has been postulated by the dynamo theory, the intensity of the dipole field decreases to zero and builds again with opposite polarity. We believe that the magnetization of the cores results from the presence of detrital magnetite, although other magnetic minerals also may be present.
Four faunal zones (φ, χ, ψ, and ω) have been recognized in these Antarctic cores on the basis of upward sequential disappearance of Radiolaria. The faunal boundaries and reversals consistently have the same relations to one another, indicating that they are both time-dependent phenomena.
Using previously determined times of reversal, one may date the following events in the cores:
1) Radiolarian faunal boundaries: φ-χ, 2 million years; χ-ψ, 0.7 million years; ψ-ω, 0.4 to 0.5 million years. These dates are in good agreement with ages previously extrapolated from radiometric dates.
2) Initiation of Antarctic diatom-ooze deposition, approximately 2.0 million years ago.
3) First occurrence of ice-rafted detritus, approximately 2.5 million years ago.
One can also calculate rates of sedimentation, which vary in the cores studied from 1.1 to about 8.0 millimeters per 1000 years. Sedimentation rates for the Indian Ocean cores are higher than for the Bellingshausen Sea cores. The near coincidence of faunal changes and reversals in the cores suggests but does not prove a causal relation.
We conclude from this study that paleomagnetic stratigraphy is a unique method for correlating and dating deep-sea cores, and that future work with such cores may provide a complete or nearly complete record of the history of the earth's magnetic field beyond 4 million years.
EDUCOM: Interuniversity Communications Council
Authors: Miller James G. 
Published: October 2006

The Interuniversity Communications Council has been formed to provide collaboration among institutions of higher learning in their efforts to utilize the emerging communication sciences. Given a W. K. Kellogg Foundation grant for administration, eight charter members announced the nonprofit organization in June 1965. There now are 50 institutional members, representing 167 separate campuses. Interuniversity task forces have been assigned to the study of computerized regional and national educational information processing networks, educational systems and technology, computer-based systems for clinical activities, the copyright problems inherent in the new media, the use of the new information technologies in continuing education, and the use of computers in academic management. Other task forces will also be established.
All information-processing activities in higher education are of concern to EDUCOM, including computational use of computers, computerized programmed instruction, library automation, educational radio and television, computerized cognitive aids, and the use of computers in clinical operations and university administration. Its primary purposes are to organize interuniversity cooperation in these fields, to disseminate reports on the state of educational information technologies, to investigate areas of critical development, and to facilitate useful applications.
Test of Continental Drift by Comparison of Radiometric Ages
Authors: Hurley P. M. , Rand J. R. , Pinson W. H. , Fairbairn H. W. , de Almeida F. F. M. , Melcher G. C. , Cordani U. G. , Kawashita K. , Vandoros P. 
Published: October 2006

1) The distribution of age values obtained by potassium-argon determinations and whole-rock rubidium-strontium determinations appears to be almost identical for West African rocks of the pervasive Eburnean Orogenic Cycle and basement rocks at opposite locations in South America.
2) There is also a close correlation, with respect to potassium-argon age determinations on micas, rubidium-strontium determinations on total-rock samples, and the extent to which these two sets of values differ, between rocks of the Pan-African Orogenic Cycle and rocks of the Caririan Orogenic Cycle in Brazil, where these two groups of rocks lie opposite each other in the two continents.
3) When Africa and South America are "fitted together," the sharply defined boundary between the Eburnean and the Pan-African age provinces in West Africa strikes directly toward the corresponding age boundary in northeast Brazil.
4) The transition from the 550-million-year Pan-African age province to the 2000-million-year age province in the Congo Craton in Cameroun-Gabon is matched in the rocks near the corresponding part of the east coast of Brazil. However the geological and age data are insufficient to do more than suggest the possibility of another age-boundary correlation here.
5) The evidence reported here supports the hypothesis of continental drift.