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  • 1975-1979  (8)
  • 1960-1964  (3)
  • Cell & Developmental Biology  (9)
  • Etonitazene reinforcement  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Psychopharmacology 64 (1979), S. 1-7 
    ISSN: 1432-2072
    Keywords: Etonitazene ; Etonitazene reinforcement ; Concurrent schedules ; Choice procedures ; Rats ; Taste ; Olfaction ; Auditory stimuli ; Discriminative stimuli ; Conditioned reinforcers ; Fixed-ratio schedules
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Etonitazene and water were concurrently available to four rats during daily 1 h sessions in operant conditioning chambers equipped with two levers and two liquid dippers. A food-induced training procedure was used whereby etonitazene drinking was rapidly established by presenting rats with gradually increased drug concentrations with their daily food ration. When food was subsequently removed from the session and given post-session, etonitazene responding persisted. The rats were subsequently trained on fixed-ratio (FR) schedules with concurrent access to etonitazene and water. The number of dipper presentations compared with etonitazene concentrations (0.078–10.0 μg/ml) resulted in a typical inverted U-shaped function while etonitazene intake (μg/kg) increased directly with concentration. After drinking large quantities of etonitazene the rats showed ataxia, hyper-activity, and stereotypy. Extinction tests demonstrated that rats could discriminate between etonitazene and water on the basis of one dipper full of each liquid; the amount of etonitazene in one dipper was 0.0078 μg. Further tests showed that this discrimination was based on taste or immediate post-ingestional feedback rather than olfactory cues. An auditory stimulus was presented concurrently with responses on the drug lever; however, there was no difference in responding for the drug in the presence or absence of this stimulus except at the lowest concentration. After the extinction tests, when the lowest drug concentration was again available with concurrent water, responding was substantially higher in the presence of stimulus associated with availability of etonitazene. The results extend previous work on oral narcotic intake to a lever-press concurrent choice procedure which is sensitive to reinforcing effects of the drug at low concentrations.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Psychopharmacology 59 (1978), S. 225-229 
    ISSN: 1432-2072
    Keywords: Rhesus monkeys ; Etonitazene HCl ; Etonitazene concentration ; Etonitazene reinforcement ; Fixed-ratio schedules ; Etonitazene drinking ; Oral self-administration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Drinking of etonitazene HCl was studied in three rhesus monkeys during daily 3-h sessions. As the drug concentration was increased, the number of liquid deliveries decreased, and etonitazene intake (μg/kg body weight) increased. As fixed-ratio (FR) requirements were increased, rate of responding increased, and liquid deliveries slightly decreased. When water was substituted for the drug, there was a large increase in responding for several sessions, followed by a slow decline to low rates. When etonitazene was reintroduced, responding abruptly increased to previous drug levels. These data suggest that etonitazene can serve as a positive reinforcer when taken orally by rhesus monkeys.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 99 (1979), S. 417-425 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The biosynthesis of NAD has been examined in 3T3 cells. The net synthesis of pyridine nucleotides does not occur when cells are cultured in the absence of performed pyridine ring compounds; however, growth continues normally for up to four cell doublings resulting in cells with a total pyridine nucleotide content that is reduced by as much as 12-fold. The mechanism that adjust the relative amounts of NADP and NAD are also altered such that the amount of NADP relative to NAD increases 5-fold. Both nicotinate and nicotinamide can be used as a precursor for NAD biosynthesis, however nicotinate is utilized less efficiently than nicotinamide. The presence of functional pathways for the biosynthesis of NAD from nicotinate via nicotinate mononucleotide and nicotinate adenine dinucleotide and from nicotinamide via nicotinamide mononucleotide has been demonstrated by identification of biosynthetic intermediates following short term exposure of cells to radiolabelled precursors. When cells are grown in Dulbecco's modified Eagle's medium which contains 33 μM nicotinamide the biosynthesis of NAD proceeds by a single pathway with nicotinamide mononucleotide as the only intermediate. Nicotinamide ribonucleoside which previously has been postulated to be an intermediate in the conversion of nicotinamide to NAD is not an intermediate in NAD biosynthesis.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Minute virus of mice (MVM), a non-defective parvovirus, has been shown to infect cultures of non-pluripotent differentiated teratocarcinoma-derived cells, but pluripotent (and “nullipotent”) embryonal carcinoma cells derived from the same teratocarcinoma resist MVN infection. Somatic cell hybrids between an embryonal carcinoma line and Friend erythroblastic leukemia cells are also resistant to MVM, even though Friend cells are susceptible. Among three blastocyst-derived lines tested, only one, a parietal yolk sac cell line, resists MVM infection. These results suggest that teratocarcinoma cultures may provide useful systems in which to study the cellular factors which mediate susceptibility to this teratogenic and oncolytic virus.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 189 (1977), S. 499-517 
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A study of the development of hemopoiesis in the Mongolian gerbil (Meriones unguiculatus) was conducted in order to determine the temporal sequence, the organs involved and the cytology of blood cell formation in this species. Hemopoiesis in the intrauterine life of the gerbil can be divided into four phases based on the site of blood cell formation: (1) the vitelline phase, (2) the hepatic phase, including thymic histogenesis, (3) the splenic phase and (4) the medullary phase, with the development of secondary lymphoid tissues. At the onset of each of these phases a blast-like cell was identifiable in each hemopoietic organ which, because of its morphology and its presumed multipo-tentiality was classified as a “lymphoid cell.” In the yolk sac phase (gestational day 12) two generations of erythrocytes, a primitive and a definitive, are formed. The liver is by day 15 erythropoietic and megakaryopoietic, but later, a few gran-ulocytes are also found in its extravascular compartment. The thymus is exclusively lymphopoietic from the appearance of its earliest cells on day 15. Splenic hemopoiesis is initiated with the presence of lymphoid cells (day 20) followed later by the appearance of morphologically identifiable blood cell lines. Early normoblastic and granulocytic activity begins in the marrow cavities on day 23, though the marrow is not considered to be a source of circulating blood cells during fetal life. Lymph node histogenesis occurs during the last four days of gestation, first in the cervical region and then in other parts of the body. The finding of undifferentiated lymphoid cells in all organs at the initiation of hemopoiesis and in the peripheral blood throughout gestation is discussed in light of the migratory theory of hemopoiesis.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The morphology and development of junctional complexes between blastomeres of the preimplantation rabbit embryo were investigated using several approaches. Electron microscopic examination of embryos stained en bloc with uranyl acetate, and the study of junction permeability using horseradish peroxidase and lanthanum nitrate provided information on structure, intermembrane spacing and permeability of the junctional complexes. In addition, the freeze fracture technique was used with day 5 and day 6 blastocysts, since the large size of these embryos facilitated use of this method. These experiments showed that although rudimentary junctions were present between blastomeres of the early cleavage stages, effective tight junctions were not present until the blastocyst stage. Electron microscopic examination of thin sections revealed apical foci of membrane approximation or “fusion” between trophoblast cells by day 4. Freeze fracturing revealed a lattice of interconnecting ridges (on the A face) and grooves (on the B face) in the apical region between trophoblast cells of the day 5 blastocyst. This lattice formed a continuous band along the apical margin of each cell, and therefore constituted a zonula occludens. The zonula occludens of the day 5 blastocyst averaged 2-3 ridges per lattice, while day 6 blastocysts had lattices that averaged 5-6 ridges. Also seen in the freeze fracture replicas from the day 5 and day 6 blastocysts were local accumulations of intramembranous particles on the A face. These particles were often observed in aggregates similar to those of previously described gap junctions. It could not be determined whether these small regions of particles were true gap junctions or a possible primitive form of gap junction because the complementary pitted surfaces (B face pits) were not demonstrated.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 0002-9106
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: In order to extend the cytological information available on the structure of the interhemal membrane in cricetid rodents, in particular, and myomorph rodents, in general, we have examined the fine structure of the placental labyrinth in five genera of cricetid rodents (Lemmus, Dicrostonyx, Clethrionomys, Microtus and Peromyscus) and one genus of murid rodent (Acomys). Small pieces of labyrinth from near-term placentas were fixed in glutaraldehyde and osmium tetroxide and processed for electron microscopy. The interhemal membranes of all the species examined were hemotrichorial. The outermost layer of trophoblast, bordering the maternal blood spaces, was celular and often contained some patent fenestrae, whereas the middle and inner trophoblastic layers were apparently syncytial. The outermost trophoblastic layer of all the species contained abundant granular endoplasmic reticulum. The intercellular space between the outer and middle layers was variable in width, primarily due to the complex folding of the surface of the middle layer. The surfaces of the middle and inner layers were closely apposed. The middle trophoblastic layer in several species contained filamentous “glomerular bodies” and the innermost layer, particularly of Peromyscus, contained smooth membranous whorls. A basal lamina separated the innermost trophoblastic layer from the fetal capillary endothelium. The endothelial cells in most of the species contained fenestrated regions. These observations are compared to those on other hemochorial placentas, and common features of cricetid (and myomorph) rodent placental fine structure are emphasized.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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