bluuebunny/crossref_metadata_2025 huggingface dataset:
Genetics and Medicine: An Evolving Relationship
Authors: Scriver Charles R. , Laberge Claude , Clow Caroline L. , Fraser F. Clarke
Published: October 2006

The rapid expansion of knowledge in human and medical genetics has revealed at least 6 percent average heterozygosity per structural gene locus, in excess of 2300 Mendelian (single gene) variants and several hundred chromosomal variants in man. This means that with the exception of monozygous twins, no two individuals are alike in their phenotype. Therefore, each person has a relative state of health, and genetic factors contribute significantly to disease. The ubiquity of genetic diversity requires the development of services for genetic screening, diagnosis, and counseling to prevent and treat a major portion of disease in modern society. Specific programs in Quebec and Canada illustrate how individuals and populations can be served by such services. Better education of citizens and health professionals in human genetics is essential for the further improvement of genetics services in society.
Role of Ornithine Decarboxylase in Cardiac Growth and Hypertrophy
Authors: Bartolome Jorge , Huguenard John , Slotkin Theodore A.
Published: October 2006

Inhibition of cardiac ornithine decarboxylase (ODC) by α-difluoromethylornithine (DFMO) did not prevent normal cardiac growth in mature rats but attenuated isoproterenol-induced hypertrophy. Hypertrophy caused by triiodothyronine was not prevented by DFMO. There appear to be both ODC-dependent and ODC-independent processes contributing to the subcellular mechanisms associated with growth, which must be considered in the potential laboratory and clinical use of DFMO.
The Molecules That Initiate Cardiac Hypertrophy Are Not Species-Specific
Authors: Hammond Graeme L. , Lai Yiu-Kay , Markert Clement L.
Published: October 2006

Extracts from hypertrophying dog hearts perfused through isolated rat hearts increase the synthesis of messenger RNA and initiate hypertrophy in the treated hearts. Total RNA extracted from experimental and control hearts was translated in vitro and hybridized with polyuridylate. Synthesis of protein and polyadenylate-containing RNA was greater in rat hearts perfused with extracts of hypertrophying dog hearts than in control hearts. The results demonstrate that molecules from hypertrophying dog hearts are not species-specific since they are effective in stimulating transcription of messenger RNA in rat hearts as well as in dog hearts.
Control of Extracellular Potassium Levels by Retinal Glial Cell K
+
Siphoning
Authors: Newman Eric A. , Frambach Donald A. , Odette Louis L.
Published: October 2006

Efflux of K
+
from dissociated salamander Müller cells was measured with ion-selective microelectrodes. When the distal end of an isolated cell was exposed to high concentrations of extracellular K
+
, efflux occurred primarily from the endfoot, a cell process previously shown to contain most of the K
+
conductance of the cell membrane. Computer simulations of K
+
dynamics in the retina indicate that shunting ions through the Müller cell endfoot process is more effective in clearing local increases in extracellular K
+
from the retina than is diffusion through extracellular space.
Cell Recognition During Neuronal Development
Authors: Goodman Corey S. , Bastiani Michael J. , Doe Chris Q. , du Lac Sascha , Helfand Stephen L. , Kuwada John Y. , Thomas John B.
Published: October 2006

Insect embryos, with their relatively simple nervous systems, provide a model system with which to study the cellular and molecular mechanisms underlying cell recognition during neuronal development. Such an approach can take advantage of the accessible cells of the grasshopper embryo and the accessible genes of
Drosophila
. The growth cones of identified neurons express selective affinities for specific axonal surfaces; such specificities give rise to the stereotyped patterns of selective fasciculation common to both species. These and other results suggest that early in development cell lineage and cell interactions lead to the differential expression of cell recognition molecules on the surfaces of small subsets of embryonic neurons whose axons selectively fasciculate with one another. Monoclonal antibodies reveal surface molecules in the
Drosophila
embryo whose expression correlates with this prediction. It should now be possible to isolate the genes encoding these potential cell recognition molecules and to test their function through the use of molecular genetic approaches in
Drosophila
.
Mitogenic Growth Factors and Nerve Dependence of Limb Regeneration
Authors: Brockes Jeremy P.
Published: October 2006

Regeneration of the amphibian limb after amputation depends on division of blastemal cells, the progenitor cells of the regenerate. This division is controlled, at least in the early stages of regeneration, by the nerve supply to the blastema. A monoclonal antibody to newt blastema cells has provided evidence that Schwann cells and muscle fibers contribute to the blastema, and identifies blastemal cells whose division is persistently dependent on the nerve. Glial growth factor, a molecule identified by its action on rat Schwann cells, is present in the newt blastema and is lost on denervation.
Neuronal Phosphoproteins: Physiological and Clinical Implications
Authors: Nestler Eric J. , Walaas S. Ivar , Greengard Paul
Published: October 2006

The presence of a great variety of neuron-specific phosphoproteins in nervous tissue supports the view that protein phosphorylation plays many roles in neuronal function. The physiological significance of several of these phosphoproteins has already been established. Some neuronal phosphoproteins have been detected throughout the entire nervous system, whereas the distribution of others is limited to one or a few neuronal cell types. These various neuron-specific phosphoproteins are proving of value in the study of the physiology, anatomy, developmental biology, and pathophysiology of the nervous system.
Isolation and Culture of a Tetraploid Subpopulation of Smooth Muscle Cells from the Normal Rat Aorta
Authors: Goldberg Itzhak D. , Rosen Eliot M. , Shapiro Howard M. , Zoller Lawrence C. , Myrick Kyl , Levenson Stephen E. , Christenson Lisa
Published: October 2006

Smooth muscle cells with 4C (double diploid) DNA content have been found in major arteries. The proportion of 4C cells increases with normal aging and with hypertension. These cells may represent a state of arrest at the G
2
phase of the cell cycle or may be examples of true tetraploidy. Flow cytometric cell sorting was used to isolate 4C smooth muscle cells from the rat aorta, and the cells were cultured. Flow cytometry, Feulgen microdensitometry, and karyotyping of the progeny of the 4C cells established the presence of true tetraploid cells. These findings demonstrate the presence of reproductively viable tetraploid cells in a normal mammalian tissue.
Transcription and Promoter Usage of the
myc
Gene tn Normal Somatic and Spermatogenic Cells
Authors: Stewart Timothy A. , Bellvé Anthony R. , Leder Philip
Published: October 2006

In somatic cells the level of
myc
transcription is not restricted to particular cell types but correlates closely with the rate of cell division. Such transcription involves the use of two active
myc
promoters and produces two messenger RNA species that are differentially represented among the transcripts of different tissues. In apparent contrast to somatic cells, mitotically and meiotically dividing germ cells have very few
myc
transcripts and appear to proliferate, at least for a few divisions, in the absence of
myc
transcription. These results raise interesting questions regarding the role of the
myc
gene product in terminally differentiating cells, particularly of the germ line series.
Evidence for Cholinergic Neurites in Senile Plaques
Authors: Kitt Cheryl A. , Price Donald L. , Struble Robert G. , Cork Linda C. , Wainer Bruce H. , Becher Mark W. , Mobley William C.
Published: October 2006

In the neocortices and amygdalae of young and aged macaques, cholinergic axons were identified by means of a monoclonal antibody to bovine choline acetyltransferase. Many fine, linear, immunoreactive profiles were seen in these animals. In the older animals, some cholinergic axons showed multifocal enlargements along their course. In some instances, neurites with choline acetyltransferase immunoreactivity were associated with deposits of amyloid (visualized with thioflavin T fluorescence). The appearance of these amyloid-associated abnormal cholinergic processes was similar to that of neurites in senile plaques, as shown by conventional silver impregnation techniques. Cholinergic systems thus give rise to some of the neurites within senile plaques.
Magnetic Microspheres Prepared by Redox Polymerization Used in a Cell Separation Based on Gangliosides
Authors: Kronick Paul L. , Campbell Graham LeM. , Joseph Kenneth
Published: October 2006

A facile method is described for making magnetic microspheres that bind specifically to cell surfaces, in order to separate cells magnetophoretically. Control over the sizes of the spheres is effected by using their magnetic cores as part of a redox polymerization system. The use of the microspheres is demonstrated with a separation involving C-1300 neuroblastoma cells, 10 percent of which express the ganglioside G
M1
in their membranes. The G
M1
-containing cells were separated with better than 99 percent purity, while the deficient cells were obtained at least 98 percent pure. The separation, which was carried out under sterile conditions, required only 6 minutes.
Reversible Cerebral Atrophy in Recently Abstinent Chronic Alcoholics Measured by Computed Tomography Scans
Authors: Carlen Peter L. , Wortzman G. , Holgate R. C. , Wilkinson D. A. , Rankin J. C.
Published: October 2006

Eight chronic alcoholics received repeated computed tomography scans. Four, who maintained abstinence and functionally improved, showed partially reversible cerebral atrophy. Two nonabstinent patients and two abstinent patients who had completed functional improvement before the first scan showed no change in atrophy.
Stimulation of Prostaglandin Biosynthesis by Urine of the Human Fetus May Serve as a Trigger for Parturition
Authors: Strickland Daniel M. , Saeed Sheikh A. , Casey M. Linette , Mitchell Murray D.
Published: October 2006

Urine of the human fetus stimulated prostaglandin biosynthesis in vitro by increasing the conversion of arachidonic acid into prostaglandins. The stimulatory activity in urine from fetuses delivered at term after labor of spontaneous onset was greater than that in urine from fetuses delivered by cesarean section at term before the onset of labor. Such stimulation of prostaglandin biosynthesis by the fetal membranes, by way of a substance released into the urine and thence into amniotic fluid, could serve as a signal for the initiation of parturition.
Enhanced Dexamethasone Resistance in Cystic Fibrosis Cells: Potential Use for Heterozygote Detection and Prenatal Diagnosis
Authors: Breslow J. L. , Epstein J. , Fontaine J. H. , Forbes G. B.
Published: October 2006

Cultured skin fibroblasts from patients with cystic fibrosis (CF) are more resistant to dexamethasone toxicity than are normal cells. We now report that, when fibroblasts cultured from obligate CF heterozygotes are exposed to dexamethasone, they have an intermediate survival compared to normal and homozygous CF cells. When dexamethasone survival was tested on cells from four patients undergoing amniocentesis, cells from a woman at risk of producing a child with CF showed significant dexamethasone resistance, similar to that of fibroblasts derived from known CF homozygotes; the other amniotic cell specimens showed dexamethasone sensitivity similar to that of normal skin fibroblasts. These data suggest that the dexamethasone resistance previously observed in skin fibroblasts may also be useful in the prenatal diagnosis of CF.
Spectrographic Representation of Globular Protein Breathing Motions
Authors: Pickover Clifford A.
Published: October 2006

Two useful ways of describing the frequency composition of the breathing motions of globular proteins are the spectrogram and three-dimensional power spectrum, representations similar to those frequently used in speech analysis. In this report "low-frequency" vibrations of globular proteins, corresponding to the collective oscillations of atoms from many different residues, are considered. Radii of gyration fluctuations provide a sensitive way to characterize such concerted motions.
Rapid Mechanical Responses of the Dark-Adapted Squid Retina to Light Pulses
Authors: Tasaki Ichiji , Nakaye Toshio
Published: October 2006

Dark-adapted squid retinas respond to brief light pulses with early and late mechanical responses. These responses are mechanical counterparts of the early and late receptor potentials.
Seizure Protection and Increased Nerve-Terminal GABA: Delayed Effects of GABA Transaminase Inhibition
Authors: Gale Karen , Iadarola Michael J.
Published: October 2006

Changes in γ-aminobutyric acid (GABA) occurring in the presence and in the absence of GABA-containing nerve terminals were estimated in rats in which the dense GABA projection to the substantia nigra was surgically destroyed on one side of the brain. The net increase in GABA of the denervated nigra was compared with that of the intact nigra at various times after a single injection of γ-vinyl-GABA, which irreversibly inhibits GABA transaminase. Total GABA reached a maximum within 12 hours, but the GABA pool associated with nerve terminals did not increase until 36 hours and peaked at 60 hours. The onset and peak of anticonvulsant activity against maximal electroshock seizures directly paralleled the time course for the increase in GABA in nerve terminals, but was not positively correlated with that independent of the terminals. This result supports the concept that elevating GABA in nerve terminals facilitates GABA-mediated synaptic transmission and predicts anticonvulsant activity.
Immunoglobulin Gene Rearrangement in Immature B Cells
Authors: Maki Richard , Kearney John , Paige Christopher , Tonegawa Susumu
Published: October 2006

Two types of immature B cells, namely fetal liver hybridomas and the leukemic cell line 70Z/3, both of which have cytoplasmic μ chains but no light chains, were examined for DNA rearrangements of their light chain and heavy chain immunoglobulin genes. In the fetal liver hybridomas, which were constructed from fetal liver cells and a tumor cell, no light chain gene rearrangement was observed, whereas in the 70Z/3 cell line a κ light chain rearrangement probably occurred. The results suggest that, although the lack of light chain synthesis can be due to a lack of gene rearrangement, there may also be transcriptional regulation, which may also be important for the expression of light chain immunoglobulins in immature B cells.
Skin Tumor-Promoting Activity of Benzoyl Peroxide, a Widely Used Free Radical-Generating Compound
Authors: Slaga T. J. , Klein-Szanto A. J. P. , Triplett L. L. , Yotti L. P. , Trosko J. E.
Published: October 2006

Benzoyl peroxide, a widely used free radical-generating compound, promoted both papillomas and carcinomas when it was topically applied to mice after 7,12-dimethylbenz[
a
]anthracene initiation. Benzoyl peroxide was inactive on the skin as a complete carcinogen or as a tumor initiator. A single topical application of benzoyl peroxide produced a marked epidermal hyperplasia and induced a large number of dark basal keratinocytes, effects similar to those produced by the potent tumor promoter 12-
O
-tetradecanoyl phorbol-13-acetate. Benzoyl peroxide, like other known tumor promoters, also inhibited metabolic cooperation (intercellular communication) in Chinese hamster cells. In view of these results caution should be recommended in the use of this and other free radical-generating compounds.
Serotonin and Octopamine in the Nematode
Caenorhabditis elegans
Authors: Horvitz H. Robert , Chalfie Martin , Trent Carol , Sulston John E. , Evans Peter D.
Published: October 2006

The biogenic amines serotonin and octopamine are present in the nematode
Caenorhabditis elegans
. Serotonin, detected histochemically in whole mounts, is localized in two pharyngeal neurons that appear to be neurosecretory. Octopamine, identified radioenzymatically in crude extracts, probably is also localized in a few neurons. Exogenous serotonin and octopamine elicit specific and opposite behavioral responses in
Caenorhabditis elegans
, suggesting that these compounds function physiologically as antagonists.
Selective Modification of Glutathione Metabolism
Authors: Meister Alton
Published: October 2006

Glutathione, a tripeptide thiol found in virtually all cells, functions in metabolism, transport, and cellular protection. It participates in the reduction of disulfides and other molecules, and conjugates with compounds of exogenous and endogenous origin. It protects cells against the destructive effects of reactive oxygen intermediates and free radicals. Modifications of glutathione metabolism may be achieved by administration of selective enzyme inhibitors, and also by giving compounds that increase glutathione synthesis. Such effects are useful in chemotherapy and radiation therapy and in protecting cells against the toxic effects of drugs, other foreign compounds, and oxygen.
Vitamin D: Two Dihydroxylated Metabolites Are Required for Normal Chicken Egg Hatchability
Authors: Henry Helen L. , Norman Anthony W.
Published: October 2006

When hens are raised to sexual maturity from hatching with 1,25-dihydroxyvitamin D
3
[1,25(OH)
2
D
3
] as their sole source of cholecalciferol (vitamin D
3
), fertile eggs appear to develop normally but fail to hatch. When hens receive a combination of 1,25(OH)
2
D
3
and 24R,25-dihydroxyvitamin D
3
[24,25(OH)
2
D
3
], hatchability equivalent to that with hens given vitamin D
3
is obtained. These results suggest a biological role for 24,25(OH)
2
D
3
not previously recognized.
Redox Delivery System for Brain-Specific, Sustained Release of Dopamine
Authors: Bodor Nicholas , Simpkins James W.
Published: October 2006

Dopamine was transformed into a redox chemical system for delivery to the brain. The lipoidal form allowed penetration of the blood-brain barrier. Oxidative and hydrolytic processes then transformed the delivery form into a quaternary ammonium precursor of dopamine. The quaternary ammonium precursor was rapidly eliminated from the general circulation, whereas that formed in the brain was locked in, thereby providing a significant and sustained brain-specific dopaminergic activity.
Chromosomal Mosaicism Confined to the Placenta in Human Conceptions
Authors: Kalousek D .K. , Dill F. J.
Published: October 2006

Placental and fetal tissues from 46 human pregnancies were cultured and cytogenetically analyzed in an attempt to document the existence of chromosomal mosaicism confined strictly to tissues of extraembryonic origin. In two gestations in which chromosomal mosaicism was found, it was expressed exclusively in placental chorionic cells and was not detected in cells derived from the embryo proper. This demonstration of confined chorionic mosaicism may have implications for the understanding of the fetoplacental unit and for prenatal diagnosis.
Evidence for the Recessive Nature of Cellular Immortality
Authors: Pereira-Smith O. M. , Smith J. R.
Published: October 2006

Fusion of immortal cell lines with normal human fibroblasts or certain other immortal cell lines yields hybrids having limited division potential. Cellular immortality was found to be a recessive phenotype in hybrids. It was also found that at least two separate events in the normal cell genome can result in immortality. In fusions involving certain immortal parent cells, these events can be complemented to result in hybrids with finite division capacity.
Pavlovian Conditional Tolerance to Haloperidol Catalepsy: Evidence of Dynamic Adaptation in the Dopaminergic System
Authors: Poulos Constantine X. , Hinson Riley
Published: October 2006

An experiment with rats has demonstrated that Pavlovian conditioning factors determine the occurrence of tolerance to haloperidol catalepsy. Rats exhibited tolerance only in the environment previously associated with the drug. Previous research involving receptor binding techniques implicated an increase in the number of brain dopamine receptors as the mediator of neuroleptic tolerance. The present findings demonstrate that this change, by itself, cannot account for the conditional occurrence of such tolerance.
Induction of Ovalbumin Synthesis in Immature Chicks by Actinomycin D and Thioacetamide
Authors: Sharma Opendra K.
Published: October 2006

Actinomycin D and thioacetamide induced ovalbumin synthesis and increased serum progesterone concentrations in immature chicks. The increase in progesterone induced by the carcinogens actinomycin D and thioacetamide may account for the induction of ovalbumin synthesis.
Surface Structures Involved in Target Recognition by Human Cytotoxic T Lymphocytes
Authors: Meuer S. C. , Hussey R. E. , Hodgdon J. C. , Hercend T. , Schlossman S. F. , Reinherz E. L.
Published: October 2006

Cloned human cytotoxic T lymphocytes and monoclonal antibodies inhibiting their function (anti-T3
A
, anti-T4
A
, and anti-T8
A
) were used to elucidate the role of T cell surface glycoproteins in cell-mediated lympholysis involving individual classes of gene products of the major histocompatibility complex on target cells. The results indicate that several surface molecules are required for specific target recognition: T3 and T4 on T4+ cytotoxic T lymphocytes and T3 and T8 on T8+ cytotoxic T lymphocytes.
Tumor Cell-Platelet Aggregation: Induced by Cathepsin B-Like Proteinase and Inhibited by Prostacyclin
Authors: Honn Kenneth V. , Cavanaugh Philip , Evens Cynthia , Taylor John D. , Sloane Bonnie F.
Published: October 2006

The ability of tumor cells to metastasize may be related to their ability to promote aggregation of host platelets. The use of inhibitors of cysteine proteinases resulted in parallel inhibition of B16 amelanotic melanoma-induced platelet aggregation and of cathepsin B activity. The antimetastatic agent prostacyclin inhibited platelet aggregation induced by the tumor cells and by papain, a cathepsin B-mimicking agent.
Control of Vascular Contractility by the Cardiac Pacemaker
Authors: Mangel Allen , Fahim Mohammad , van Breemen Cornelis
Published: October 2006

Rhythmic contractile activity, synchronized with pulsatile pressure changes, was recorded from rabbit aorta in vivo. The contractions were locked in frequency to the pulsatile activity of the heart even when the heart was electrically paced to rates as high as 600 cycles per minute; termination of cardiac contractility resulted in their elimination. When the atria and ventricles contracted at different rates, the pulse-synchronized contractions were locked to the atrial rate. Excision of the right atrium, but not the left, resulted in the abolition of pulse-synchronized contractions. It is concluded that a common pacemaker controls cardiac and vascular contractility, coordinating events in the two tissues.
Anticonvulsant Action of Excitatory Amino Acid Antagonists
Authors: Croucher M. J. , Collins J. F. , Meldrum B. S.
Published: October 2006

Compounds that antagonize neuronal excitation induced by dicarboxylic amino acids were tested in two animal models of epilepsy, namely sound-induced seizures in DBA/2 mice and threshold pentylenetetrazol seizures in Swiss mice. Sound-induced seizures could be prevented by intracerebroventricular injection of compounds that block excitation due to N-methyl-D-aspartic acid. The most potent such compound, 2-amino-7-phosphonoheptanoic acid, was anticonvulsant in both test systems when given either intraperitoneally or intracerebroventricularly. Specific antagonists of excitation that is caused by amino acids provide a new class of anticonvulsant agents.
Lack of Correlation Between Hepatic Mitochondrial Membrane Structure and Functions in Ethanol-Fed Rats
Authors: Gordon E. R. , Rochman J. , Arai M. , Lieber C. S.
Published: October 2006

A current hypothesis suggests that alterations in the chemical composition and the subsequent changes in the structure of the membrane could account for the functional derangements observed in the hepatic mitochondria of animals fed ethanol for extended periods. An examination of this hypothesis reveals that the liver mitochondria of ethanol-fed rats show a dissociation between the respiratory functions and the lipid composition and microviscosity of the membranes.
Type II Collagen Autoimmunity in Otosclerosis and Meniere's Disease
Authors: Yoo T. J. , Stuart J. M. , Kang A. H. , Townes A. S. , Tomoda K. , Dixit S.
Published: October 2006

Antibodies to collagen types I, II, and IV were measured in patients with otosclerosis and patients with Meniere's disease. Levels of antibodies to type II collagen were significantly higher in these patients than in control subjects, while no differences were found among levels of antibodies to collagen type I or type IV. These observations suggest a possible role for type II collagen autoimmunity in the etiology of otosclerosis and Meniere's disease.
Bilirubin-Induced Modulation of Cerebral Protein Phosphorylation in Neonate Rabbits in Vivo
Authors: Morphis L. , Constantopoulos A. , Matsaniotis N. , Papaphilis A.
Published: October 2006

Protein phosphorylation in cerebral cell-free preparations from neonate rabbits was inhibited by bilirubin and promoted by aminophylline when these substances had been administered intravenously. In animals given both compounds, the bilirubin-induced inhibition of phosphorylation was partly reversed by aminophylline. Adenosine 3′,5′-monophosphate added in vitro during the assays also increased protein phosphorylation. These data introduce new concepts in the pathogenesis of kernicterus.
Hemoglobin Parchman: Double Crossover Within a Single Human Gene
Authors: Adams Junius G. , Morrison W. Tully , Steinberg Martin H.
Published: October 2006

Structural analysis of a new variant hemoglobin revealed tryptic peptides with the amino acid composition of normal δ-globin, except for two internal peptides, which had the compositions of normal β-globin. The most likely explanation for these findings is that a double, nonhomologous crossover between the δ- and β-globin genes had occurred.
Habituation and Sensitization of Startle Reflexes Elicited Electrically from the Brainstem
Authors: Davis Michael , Parisi Thomas , Gendelman David S. , Tischler Mark , Kehne John H.
Published: October 2006

Repetitive elicitation of startle-like responses by electrical stimulation of the cochlear nucleus led to sensitization followed by habituation. In contrast, repetitive elicitation of startle-like responses by electrical stimulation of the reticular formation led only to sensitization. Since these different locations represent different points along the acoustic startle circuit, the data suggest that sensitization may be related to the motor side of reflex arcs, whereas habituation may be related to the sensory side.
Touching Textured Surfaces: Cells in Somatosensory Cortex Respond Both to Finger Movement and to Surface Features
Authors: Darian-Smith Ian , Sugitani Michio , Heywood John , Karita Keishiro , Goodwin Antony
Published: October 2006

Single neurons in Brodmann's areas 3b and 1 of the macaque postcentral gyrus discharge when the monkey rubs the contralateral finger pads across a textured surface. Both the finger movement and the spatial pattern of the surface determine this discharge in each cell. The spatial features of the surface are represented unambiguously only in the responses of populations of these neurons, and not in the responses of the constituent cells.
Gene Amplification and Drug Resistance in Cultured Murine Cells
Authors: Schimke Robert T. , Kaufman Randal J. , Alt Fred W. , Kellems Rodney F.
Published: October 2006

Resistance of mouse cells to the folate analog, methotrexate, results from selection of increasingly resistant cells on progressive increases of methotrexate in the culture medium. High-level resistance is associated with high rates of synthesis of dihydrofolate reductase and correspondingly high numbers of reductase genes. In some variants high resistance and gene copy number are stable in the absence of selection pressure, whereas in others they are unstable. Analogies are made to antibiotic and insecticide resistance wherein selection of organisms with increased capacity to counteract the drug effect results in emergence of resistance. Gene amplification may underlie many such resistance phenomena.
Interchangeability of Stress and Amphetamine in Sensitization
Authors: Antelman Seymour M. , Eichler Alan J. , Black Cynthia A. , Kocan Donna
Published: October 2006

In view of similarities between the behavioral, biochemical, and electrophysiological effects of amphetamine and stress, we tested the hypothesis that presentation of a stressor, mild tail pressure, can sensitize an animal to the later effects of amphetamine, and vice versa. Our findings supported this hypothesis and suggest that amphetamine and at least some stressors may be interchangeable in their ability to induce sensitization. The data raise the possibility that stress might be a common variable contributing to both amphetamine psychosis and some forms of schizophrenia.
Mediation of Diurnal Fluctuations in Pain Sensitivity in the Rat by Food Intake Patterns: Reversal by Naloxone
Authors: McGivern Robert F. , Berntson Gary G.
Published: October 2006

Rats maintained on a 12-hour light-dark cycle were tested for pain sensitivity after being deprived of food during either the dark or the light phase of the cycle. Diurnal fluctuations in pain sensitivity were observed. The fluctuations followed food intake patterns rather than a natural circadian rhythm, with food deprivation producing a decrease in pain sensitivity. The analgesic response produced by this mild food deprivation was strongly attenuated by naloxone or feeding, suggesting that endogenous opioid systems may be related to patterns of food intake.
Diurnal Rhythm of Cytoplasmic Estrogen Receptors in the Rat Brain in the Absence of Circulating Estrogens
Authors: Roy Edward J. , Wilson Marlene A.
Published: October 2006

The concentration of cytoplasmic estrogen receptors in the brain of ovariectomized female rats varies during the light-dark cycle. There is no variation in the affinity of the receptors for estradiol, and the rhythm is not due to estrogens from nonovarian sources. Pentobarbital reverses the reduction of receptors that occurs in the dark, and melatonin injection in the light partially mimics the action of darkness in reducing receptor levels. The factors that cause this rhythm in brain estrogen receptors may be one means by which light affects reproductive function.
Heroin "Overdose" Death: Contribution of Drug-Associated Environmental Cues
Authors: Siegel Shepard , Hinson Riley E. , Krank Marvin D. , McCully Jane
Published: October 2006

A model of "overdose" deaths among heroin addicts is proposed which emphasizes recent findings concerning the contribution of drug-associated environmental cues to drug tolerance. Results of animal experiments performed to evaluate this model suggest that conditioned drug-anticipatory responses, in addition to pharmacological factors, affect heroin-induced mortality.
Prenatal Exposure to Phenobarbital Permanently Decreases Testosterone and Causes Reproductive Dysfunction
Authors: Gupta Chhanda , Yaffe Sumner J. , Shapiro Bernard H.
Published: October 2006

Exposure of rats to phenobarbital during late prenatal development decreased the concentration of testosterone in plasma and the brain during the late fetal, early postnatal, pubertal, and adult periods, By decreasing the production of testosterone in the brain during the period of sexual differentiation, phenobarbital may lead to sexual dysfunction in later life.
Flexor Reflex Control of the External Sphincter of the Urethra in Paraplegia
Authors: Jolesz Ferenc A. , Cheng-Tao Xu , Ruenzel Paul W. , Henneman Elwood
Published: October 2006

In paraplegics and quadriplegics a profound paralysis of skeletal muscles occurs below the level of the spinal lesion. Unexplained in this state is the development of an overactive external urethral sphincter, which interferes with emptying of the bladder and may lead to infection of the urinary tract. Studies of cats show that the discharge of motoneurons causing this contraction has all the characteristics of a flexor reflex.
Influence of Female Hormonal State on Rhesus Sexual Behavior Varies with Space for Social Interaction
Authors: Wallen Kim
Published: October 2006

The sexual behavior of rhesus monkeys in 15 male-female pairings was observed in both a large and a small area during the follicular and luteal phases of the female's cycle. Males ejaculated in all tests at the follicular phase of the female's cycle and in 53 percent of tests at the luteal phase. However, a significant decline in ejaculation during tests at the luteal phase occurred in the large, but not in the small area. Thus the degree to which the pair's sexual behavior was influenced by the female's hormonal state depended on the spatial conditions of the test.
Female Control of Male Reproductive Function in a Mexican Snake
Authors: Garstka William R. , Crews David
Published: October 2006

Male
Thamnophis melanogaster
court immediately when exposed to estrogen-treated, attractive females and continue courting for 6 to 8 days. Males exposed to estrogen-treated females will court both intact and ovariectomized females. These males undergo a period of testicular recrudescence, whereas males exposed only to ovariectomized females do not. Sexual attractivity can be induced in female
T. melanogaster
without estrogen treatment by heavy feeding, which results in significant increases in liver size and activity.
Aerial Spraying of 2,4,5-T and Human Birth Malformations: An Epidemiological Investigation
Authors: Hanify Jennifer A. , Metcalf Peter , Nobbs Christopher L. , Worsley Keith J.
Published: October 2006

An investigation of the rate of birth malformations in the Northland region of New Zealand provides no evidence to associate spraying of 2,4,5-trichlorophenoxyacetic acid with the occurrence of any malformation of the central nervous system, including spina bifida. A statistically significant association between spray and malformation is found in the case of talipes. Whether this association indicates a causal relation remains to be established.
Two Distinct Central Serotonin Receptors with Different Physiological Functions
Authors: Peroutka Stephen J. , Lebovitz Richard M. , Snyder Solomon H.
Published: October 2006

Two distinct serotonin (5-hydroxytryptamine) receptors designated serotonin 1 and serotonin 2 bind tritium-labeled serotonin and tritium-labeled spiroperidol, respectively. Drug potencies at serotonin 2 sites, but not at serotonin 1 sites, predict their effects on the "serotonin behavioral syndrome," indicating that serotonin 2 sites mediate these behaviors. The limited correlation of drug effects with regulation by guanine nucleotides suggests that serotonin 1 sites might be linked to adenylate cyclase. Drug specificities of serotonin-elicited synaptic inhibition and excitation may reflect serotonin 1 and serotonin 2 receptor interactions, respectively.
Electroencephalographic Tolerance and Abstinence Phenomena During Repeated Alcohol Ingestion by Nonalcoholics
Authors: Zilm Duane H. , Kaplan Howard L. , Capell Howard
Published: October 2006

Certain measures of the auditory average evoked response are sensitive to alcohol and provide evidence for abstinence and tolerance during and after 10 days of alcohol consumption by nonalcoholics. Electroencephalographic techniques provide a single sensitive measure for the study of the etiology of tolerance and abstinence with particular reference to a new area of investigation with nonaddicted humans.
Phosphatidate as a Molecular Link Between Depolarization and Neurotransmitter Release in the Brain
Authors: Harris R. Adron , Schmidt Jim , Hitzemann Barbara A. , Hitzemann Robert J.
Published: October 2006

Phosphatidate, a neuronal phospholipid, stimulated the uptake of calcium by nerve terminals isolated from the striatum of rat brain. This effect was not produced by other phospholipids or glycolipids. Phosphatidate, but not other phospholipids, evoked the release of [
3
H]dopamine from striatal synaptosomes. The magnitude of both effects was similar to that observed after chemical depolarization of the nerve terminals. These results show that phosphatidate is the only membrane lipid component that acts as a functionally competent ionophore and support the suggestion that phosphatidate may serve as a link between depolarization and neurotransmitter release in the brain.
Serum Lipoproteins Modulate Oxygenated Sterol Insertion into Human Red Cell Membranes
Authors: Streuli R. A. , Chung J. , Scanu A. M. , Yachnin S.
Published: October 2006

The insertion of oxygenated sterol compounds into human red blood cell membranes as well as the consequent transformation of the red cells to an echinocyte shape and the expansion of the membranes are impeded by the presence of serum lipoproteins in the incubation medium. All density classes of human serum lipoproteins bind oxygenated sterol compounds, and lipoproteins can act as acceptors of oxygenated sterols previously inserted into red cells. Since oxygenated sterols have been reported to be atherogenic, the modulating and possibly protective effects of serum lipoproteins on oxygenated sterol-induced derangement of cell membrane structure and function may provide a useful model for further study.
Remodeling of Multiterminal Innervation by Nerve Terminal Sprouting in an Identifiable Lobster Motoneuron
Authors: Govind C. K. , Pearce Joanne
Published: October 2006

A single motoneuron provides multiterminal innervation to the limb accessory flexor muscle in lobster. Its nerve terminals and synapses relocate to more distal sites during primary development and growth beyond sexual maturity. This remodeling of multiterminal innervation occurs by sprouting of nerve terminals and synapses from preexisting ones.
Ureaplasma urealyticum
Incriminated in Perinatal Morbidity and Mortality
Authors: Kundsin Ruth B. , Driscoll Shirley G. , Pelletier Paula A.
Published: October 2006

Perinatal morbidity and mortality are associated with colonization of the chorionic surface of the placenta by
Ureaplasma urealyticum
or
Mycoplasma hominis
or both. These organisms are more strongly associated with unfavorable gestational outcome than group B streptococci.
Chlamydia trachomatis
does not appear to be important in the etiology of reproductive casualties. The mechanisms linking the mycoplasmas to perinatal disorders and death are not clear but merit investigation.
Intraventricular Alloxan Eliminates Feeding Elicited by 2-Deoxyglucose
Authors: Woods Stephen C. , McKay L. David
Published: October 2006

Evidence suggests that alloxan reacts with membrane-bound glucoreceptors and that it competes with glucose molecules for these sites. We therefore administered small quantities of alloxan into the cerebrospinal fluid of rats to determine what effect this might have on their ability to react to changes of glucose concentration. Rats treated in this manner did not eat as much as controls in response to the intraperitoneal administration of 2-deoxyglucose or to a 24-hour fast, and they became hypoglycemic significantly sooner than controls when fasted. The data suggest that the function of brain glucoreceptors is to protect the body from sudden decreases of glucose and that these glucoreceptors play little if any role in the normal regulation or maintenance of feeding, body weight, or blood glucose concentrations.
Short-Term Memory: the "Storage" Component of Human Brain Responses Predicts Recall
Authors: Chapman Robert M. , McCrary John W. , Chapman John A.
Published: October 2006

An evoked potential component with a poststimulus peak at about 250 milliseconds is related to the storage of information in short-term memory. This storage component was found in an investigation of brain potentials in relation to a number and letter comparison task. In replications of this experiment at three different light intensities spaced 1.0 log unit apart, the component had essentially the same waveform and pattern of scores. The memory storage interpretation was confirmed in a behavioral experiment that probed short-term memory. Recall was predicted by the magnitude of the storage component.
Intracellular Recordings from Thermosensitive Preoptic Neurons
Authors: Nelson D. O. , Prosser C. Ladd
Published: October 2006

Intracellular recordings were made from locally thermosensitive preoptic neurons in the green sunfish,
Lepomis cyanellus
. Stable resting potentials, action potentials, and spontaneous synaptic activity were observed over approximately 4° to 5°C changes in local brain temperature. A small percentage of the warm-sensitive neurons showed exponential firing-rate responses to temperature. These cells discharged rhythmically, lacked visible synaptic input, and showed slowly depolarizing potentials leading to action potentials. Other linear and nonlinear warm-sensitive and cold-sensitive neurons showed spontaneous excitatory and inhibitory synaptic potentials giving rise to action potentials. Cells that appear to be endogenously active may be true thermodetectors, and other thermosensitive neuronal activity may be synaptically mediated.
Structural Correlates of Seizure Behavior in the Mongolian Gerbil
Authors: Paul Linda A. , Fried Itzhak , Watanabe Kathy , Forsythe Alan B. , Scheibel Arnold B.
Published: October 2006

Hippocampi of seizure-sensitive and seizure-resistant Mongolian gerbils were examined in search of structural correlates of seizure behavior. In animals with well-established seizure histories, differences were found in both presynaptic and postsynaptic structures. Seizing animals had less dense dendritic spines, a greater proportion of mossy tuft area devoted to presynaptic vesicles, and a smaller proportion devoted to spines. The possible relationship of these findings to epilepsy is discussed.
Different Command Neurons Select Different Outputs from a Shared Premotor Interneuron of Crayfish Tail-Flip Circuitry
Authors: Kramer Andrew P. , Krasne Franklin B. , Bellman Kirstie L.
Published: October 2006

In the crayfish a bilateral pair of interneurons (the I3's) are involved in the generation of two types of tail-flip escape responses, one mediated by giant neurons and the other by nongiant circuitry. The I3's make a variety of output connections with the motoneurons and with other interneurons involved in tail flipping. The motoneuronal outputs include strong synapses on telson flexor motoneurons, whose activity during tail flips mediated by lateral giant fibers would be maladaptive. The lateral giants always drive the I3's, but also drive inhibitory neurons that prevent the undesirable outputs of the I3's while permitting their adaptive outputs to be expressed. It is often adaptive for tail flips initiated by nongiant circuitry to utilize the telson flexor muscles that I3 strongly excites. During such tail flips I3 is often fired, and this firing is important in driving the telson flexors.
Investigations in Panama During the Summer of 1930
Authors: Faust Ernest Carroll
Published: October 2006

The material obtained from these investigations has indicated to the writer that the area studied offers extremely valuable opportunities for helminthological and protozoological work. The data obtained will serve as the basis for several important papers which will be published in the near future.
Stimulation of Intestinal Calcium Transport and Bone Calcium Mobilization by Prolactin in Vitamin D-Deficient Rats
Authors: Pahuja D. N. , DeLuca H. F.
Published: October 2006

In vitamin D-deficient rats intestinal calcium transport increased significantly 4 hours after an injection of prolactin, reached a maximum after 8 hours, and declined to preinjection levels after 24 hours. Similarly, in vitamin D-deficient rats fed a diet low in calcium or phosphorus prolactin stimulated an increase in serum calcium in both groups and an increase in serum phosphorus in the rats fed the diet low in phosphorus. Thus it appears that prolactin affects organs involved in calcium regulation in a manner that is independent of the vitamin D endocrine system.
Reduction in Oocyte Number Following Prenatal Exposure to a Diet High in Galactose
Authors: Chen Yuan-Tsong , Mattison Donald R. , Feigenbaum Lionel , Fukui Henry , Schulman Joseph D.
Published: October 2006

When pregnant rats were fed a 50 percent galactose diet there was a striking reduction in oocyte number in the offspring. The most prominent effects were noted after exposure to galactose during the premeiotic stages of oogenesis. Prenatal exposure to galactose or its metabolites may contribute to the premature ovarian failure characteristic of human galactosemia.
Entry of Opioid Peptides into the Central Nervous System
Authors: Rapoport S. I. , Klee W. A. , Pettigrew K. D. , Ohno K.
Published: October 2006

Cerebrovascular permeability of four modified opioid peptides—[D-Ala
2
]methionine enkephalin amide, β-[D-Ala
62
,
14
C- Homoarg
69
]lipotropin 61-69, α-[D-Ala
2
,
14
C-Homoarg
9
]endorphin, and β-[D-Ala
2
,
14
C-Homoarg]endorphin—ranged from 1.4 to 3.9 × 10
-6
centimeters per second in brain regions of the conscious rat. These significant permeabilities should allow the peptides to fill the extracellular brain space with a half time of 3 to 11 minutes, as a result of a step increase in plasma concentration of unbound peptide.
Amino Terminal Sequence of the Major Component of Human Lymphoblastoid Interferon
Authors: Zoon Kathryn C. , Smith Mark E. , Bridgen Pamela J. , Anfinsen Christian B. , Hunkapiller Michael W. , Hood Leroy E.
Published: October 2006

Homogeneous human lymphoblastoid interferon with an apparent molecular size of 18,500 daltons was characterized by its amino acid composition. Analysis of the amino terminal sequence by Edman degradation indicates that the sequence is unique.
Abnormality of the X Chromosome in Human 46,XY Female Siblings with Dysgenetic Ovaries
Authors: Bernstein Renée , Koo Gloria C. , Wachtel Stephen S.
Published: October 2006

An abnormal extra band was found on the short arm of the X chromosome in a 46,XY female and in her 46,XY female fetal sibling. Despite presence of the intact Y chromosome, there was no evidence of testicular differentiation in either subject. Production of H-Y antigen was suppressed in both subjects. The data suggest that development of the mammalian testis requires a normal function of the X chromosome.
Magnesium Deficiency Produces Spasms of Coronary Arteries: Relationship to Etiology of Sudden Death Ischemic Heart Disease
Authors: Turlapaty Prasad D. M. V. , Altura Burton M.
Published: October 2006

Isolated coronary arteries from dogs were incubated in Krebs-Ringer bicarbonate solution and exposed to normal, high, and low concentrations of magnesium in the medium. Sudden withdrawal of magnesium from the medium increased whereas high concentrations of magnesium decreased the basal tension of the arteries. The absence of magnesium in the medium significantly potentiated the contractile responses of both small and large coronary arteries to norepinephrine, acetylcholine, serotonin, angiotensin, and potassium. These data support the hypothesis that magnesium deficiency, associated with sudden death ischemic heart disease, produces coronary arterial spasm.
Suprathreshold Processing of Complex Visual Stimuli: Evidence for Linearity in Contrast Perception
Authors: Ginsburg Arthur P. , Cannon Mark W. , Nelson Michael A.
Published: October 2006

Magnitude estimation experiments show that perceived contrast for both sine and square waves is a linear function of stimulus contrast. The suprathreshold sine:square ratio required for equal perceived contrast derived from these data was verified by contrast matching experiments. These findings imply a high degree of linearity in suprathreshold visual processing of contrast.