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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Development genes and evolution 177 (1975), S. 89-100 
    ISSN: 1432-041X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Hensen's node was isolated from chick blastoderms of medium-streak to headfold stages from which the endodermal layer had previously been removed. The isolates were culturedin vivo by means of the intra-coelomic grafting technique. Node pieces with the endodermal layer intact served as controls. Endodermal differentiation tendencies gradually decreased from the medium-streak to the pre-head-process stage and completely disappeared at the head-process stage, whereas the controls gave rise to endodermal structures throughout all stages. “Cranial” structures such as oesophagus and trachea, often together with thyroid, parathyroid and/or thymus, were only found in grafts of younger stages, while gizzard, intestine and/or pancreas were observed in many gut-containing grafts throughout all stages. There was a constant high incidence of notochord, muscle, and cartilage formation. The incidence of mesonephric structures, sometimes accompanied by adrenal gland, rose steadily throughout all stages both in experimentals and controls. Neural differentiation tendencies (rhombencephalon and/or spinal cord) were always present in the nodes isolated (with or without endoderm) from the definitive primitive-streak stage onwards, but in nodes from earlier stages the incidence of neural differentiation was significantly lower. The results are discussed in relation to the possible location and determination of the prospective endoderm and mesoderm.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Development genes and evolution 181 (1977), S. 73-87 
    ISSN: 1432-041X
    Keywords: Cleavage ; Cinematography ; Cell dissociation ; Cell numbers ; Axolotl
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The temporal pattern of cleavage in the egg of the axolotl,Ambystoma mexicanum, was studied 1. by time-lapse microcinematography, and 2. by counting the total number of blastomeres dissociated at successive stages. Eggs were filmed from the one-cell stage till the early gastrula either (A) simultaneously from above and below with a “double-camera” assembly, or (B) from the side with a single camera. The animal blastomeres divide synchronously from the 2nd up to and including the 10th cleavage. The cycle length is roughly constant from the 3rd till the 10th cleavage. The cycle from the 2nd to the 3rd cleavage is slightly longer, while that from the 1st to the 2nd cleavage is about 20% longer. After the 10th cleavage the synchrony of divisions is lost owing to variable lengthening of cell cycles in individual blastomeres. Gastrulation starts around the onset of the 15th cleavage in the animal blastomeres. The analysis of films taken in side view reveals seven recurring “cleavage waves”, from the 5th till the 11th cleavage. Cells in the animal, equatorial and vegetative regions in sequence repeatedly pass through the three successive phases of the cleavage cycle—rounding-up, division, and relaxation—but with a shift in phase. The start of the 10th cleavage division of the slowest vegetative cells more or less coincides with that of the 11th division of the animal cells; from then on the cleavage waves become increasingly obscured. Morulae and blastulae were dissociated by placing them in 1/15 M phosphate buffer (pH 7.8) for the duration of 2–3 cleavage cycles and then removing the vitelline membrane. In this solution cell divisions continued without disturbance of the temporal cleavage pattern. The dissociated cells were fixed either just prior to the onset of the next cleavage (up to the 10th cleavage) or at those times when cleavageswould have been expected, had there been no lenthening of cleavage cycles (beyond the 10th cleavage). The total cell number was counted, dividing cells being scored as two. Prior to the 11th cleavage the total cell number increased exponentially. Beyond the 10th cleavage the rate of increase was considerably lower. At the time when gastrulation would have started if the egg had not been dissociated, the total cell counts were 13,000–15,000, whereas the number anticipated without lengthening of cleavage cycles would be of the order of 130,000 (217). The application of Balfour's rule to amphibian eggs is criticized.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Development genes and evolution 167 (1971), S. 183-186 
    ISSN: 1432-041X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Prior to the appearance of the cleavage furrows circular or semicircular zones suggesting surface contraction originate at the future initiation point of the cleavage furrow. They expand and travel in animal-vegetative direction.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Development genes and evolution 181 (1977), S. 89-93 
    ISSN: 1432-041X
    Keywords: Cleavage ; Normal table ; Axolotl
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Films of cleaving embryos of the axolotl,Ambystoma mexicanum, taken by the “double camera” technique, were used in order to arrive at a more detailed staging based on quantitative criteria. Drawings were made of the animal hemispheres just prior to the start of each cleavage cycle from the 6th to the 15th cleavage. The number of cells intersected either by the (apparent) “egg diameter” (up to the 10th cleavage) or by “half the diameter” (from the 10th cleavage onwards) was determined. The cell numbers for each cleavage cycle did not overlap with those of the previous or succeeding cycles. On the basis of these cell numbers, in place of the four Harrison stages 6–9, 10 successive stages were established each of which corresponds to one cleavage cycle.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Development genes and evolution 181 (1977), S. 189-192 
    ISSN: 1432-041X
    Keywords: Xenopus egg ; Fertilization ; Surface wave ; Time-lapse cinematography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In fertilizedXenopus eggs, shortly after egg rotation but well before the occurrence of the cleavage-associated “surface contraction waves”, two circular dark zones originate consecutively from the pigment spot marking the site of sperm entrance. They expand and travel centrifugally over the egg surface.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Marine biology 14 (1972), S. 41-47 
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The number, size, and carbon and nitrogen contents of eggs in the pouches of a euphausiid crustacean, Nematoscelis difficilis Hansen, were examined. A clear linear relationship exists between the number of eggs in the pouch and the body weight of the maternal euphausiid. The eggs are not spherical in shape, and the size of eggs is greater in larger egg masses. The carbon content of the egg masses (50.2%) is higher than that of the bodies (40.7%). The carbon: nitrogen ratio (C/N) is also higher in the egg masses than in the bodies of euphausiids. The carbon content of the eggs is equivalent to 28.4% of the body carbon, the nitrogen content to 19.2% of the body nitrogen.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1432-1831
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Many experimental studies have shown that orthomyxo- and paramyxo-viruses may be pneumotropic, but not enterotropic in mammals. On the other hand, these viruses are both pneumotropic and enterotropic in avian species. We have devised a new method for detecting virus receptor possessing cells (VRPC) in tissue sections. VRPC could be detected in the cells lining the airways of both mice and birds. The mode of distribution of VRPC in mouse digestive system differed remarkedly from that in avian digestive system. VRPC were not found in the epithelium of mouse digestive systems whereas the epithelium of bird digestive system were abundant in VRPC. When the large intestines from mice or duck undergoing laparotomy and inoculated directly into intestine with influenza virus were examined, viral antigen was detected in the epithelial cells of duck colon, but not in mouse intestines. From the study utilizing the new method, it could be concluded that the distribution mode of VRPC is one of the most important factors determining the virus tissue sepcificity.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Biological cybernetics 54 (1986), S. 91-98 
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract A spatio-temporal model of ganglion cell receptive fields is proposed on the basis of receptive field characteristics of cat retinal ganglion cells reported in our previous paper. The model consists of the linear and nonlinear mechanisms in the ganglion cell receptive field. The linear mechanism is assumed to be composed of antagonistic center and surround mechanisms. Then, by integrating these mechanisms we construct a spatio-temporal impulse response function of ganglion cell receptive field. Here we assume that spatio-temporal impulse response function may be factored into spatial and temporal terms. By Fouriertransforming the spatio-temporal impulse response function, we can obtain the spatio-temporal transfer function. Contrast sensitivity characteristics of X-and Y-cells in the cat retina may be explained by the transfer function.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1432-1076
    Keywords: Infantile spasms ; Etiological factors ; Clinical aspects ; Long term prognosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The etiological factors, clinical aspects and long term prognosis were studied in 200 patients with infantile spasms. Forty-eight (24.0%) died and the rest were aged 6 years or more at the time of final follow-up. In 73 (36.5%) the etiology was prenatal, in 44 (22.0%) perinatal, and in 17 (8.5%) postnatal: 18 cases (9.0%) were cryptogenic. The remaining 48 (24.0%) patients were doubtful cases. The mortality of the pre-and perinatal cases at 35.6% and 34.1% respectively was significantly higher than that in the other etiologic groups (P〈0.001). With regard to the onset of spasms, these were very carly in the pre-and perinatal groups, whereas in the postnatal group the onset was late. The onset in the doubtful and cryptogenic groups was in between. Some 44.4% of the cryptogenic cases showed normal mental and physical development after the age of 6 years, whereas less than 10% of the prenatal and perinatal group did so. Almost all of the doubtful cases became mentally subnormal. The incidence of a family history of epilepsy or other convulsive disorders in the first, second and third degree relatives was highest in the cryptogenic cases (40.0%), and lowest in the perinatal cases (9.3%) (P〈0.01). The incidence of laughing attacks was highest in the postnatal cases (42.9%), against no such attacks in cryptogenic cases (P〈0.01). The attacks seemed to be linked with organic brain lesions. Among various factors related to the etiology of infantile spasms, genetic propensity seemed especially important in cryptogenic cases.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1432-1076
    Keywords: EEG ; Evoked potentials ; Newborn ; Intracranial hemorrhage
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The EEG, visual and auditory evoked potentials (VEP, AEP) were evaluated in 16 full-term newborn infants who had intracranial hemorrhage documented by computerized tomography (CT). Three of them had supratentorial, three, supra- and infratentorial hemorrhage, while the other ten had infra- or peri-tentorial bleeding. Three died during the neonatal period. Eight of the 13 surviving infants were neurologically normal and five were abnormal at the time of the follow-up. Those who had normal or mildly abnormal background EEGs all developed normally, while those whose neonatal EEG was severely abnormal subsequently developed neurological sequelae irrespective of the extent of intracranial hemorrhage. The EEG, VEP or AEP is of little value in the diagnosis of intracranial bleeding but the EEG is valuable in assessing the degree of associated parenchymatous damage and is of great prognostic significance.
    Type of Medium: Electronic Resource
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