Showing papers by "Radboud University Nijmegen published in 1970"
TL;DR: A differential glyoxylate analysis is given that enables differentiation between allantoin, allantoate, ureidoglycolate, and glyxylate, which is more accurate, sensitive, and selective than former methods.
296 citations
TL;DR: A model is proposed which is based upon stabilization experiments, neuronal recordings of other authors and reports from patients with defective visual systems, and a model of antagonistic barriers and mutual neutralization are discussed and indicated in a diagram.
Abstract: In psychophysical experiments described previously we found that a stimulus surrounding a retinal scotoma fills in the scotoma instantaneously with its brightness and color. However, it takes a few seconds to fill in a black stabilized disk which is equally immobile with respect to the retina. An experiment carried out to investigate the cause of this discrepancy suggested that a presumed contrast firing of neurons along the inside border of the black stabilized disk may explain the phenomena. The postulated border contrast discharge may form a barrier for the spreading of brightness information from the surround. If no barrier is generated (as in retinal scotomata) or if it has disappeared (by stabilization) the spreading of the activity itself occurs very rapidly (probably in higher centers). The co-operation of these effects, the activity along the border of a field (the simultaneous contrast) and the filling-in, investigated in the experiments, may explain many perceptual phenomena. A model is proposed which is based upon stabilization experiments, neuronal recordings of other authors and reports from patients with defective visual systems. The well-known first stages (retina-lateral geniculate body-area 17) and a following, yet unlocalized, stage (called “higher center”) are distinguished. Stabilization experiments suggest a spreading capacity and a long adaptation time of this higher center. The spreading of activity is inferred clinically and from observation of the filling-in phenomenon. Long adaptation time is suggested by the slow disappearance of the stabilized image. In normal vision small eye movements, continually activating on-center cells and off-center cells along the contrast border preserve continuous perception of the whole homogeneously illuminated area from transient border activities. Neuronal mechanisms and a model of antagonistic barriers and mutual neutralization are discussed and indicated in a diagram.
258 citations
TL;DR: In this paper, a compilation of coupling constants and low-energy parameters are given for pi N, KN, NN, YN, and meson-meson scattering, and a comparison of SU(3) comparison and predictions are discussed.
218 citations
01 Jan 1970
182 citations
TL;DR: It is unlikely that the 11-cis retinol dehydrogenase from pigment epithelium is directly involved in providing 11- cis retinaldehyde from rhodopsin regeneration, but it may serve to make available 11-Cis retinehyde from Rhodopdsin, digested in phagocytized rod sacs, for the synthesis of visual pigment by the visual cells.
153 citations
TL;DR: Maintenance of the ionic concentrations of the endolymph appears to require in addition active transport of Na+ and Cl− out of the Endocochlear resting potential.
Abstract: The effect, on the endocochlear resting potential (ERP) of anoxemia, cyanide, pH changes and changes of the electrolyte composition of the perilymph was studied.
152 citations
TL;DR: More circumstantial and direct experimental evidence is needed in order to arrive at a definite evaluation of the importance of facilitated O2 diffusion in physiological conditions, including nonsteady-state conditions as present under most physiological circumstances.
116 citations
TL;DR: Quantitative analysis of the phospholipids by two-dimensional thin-layer chromatography showed that the three major phospholipsids are: phosphatidyl ethanolamine, phosph atidyl choline and phosphAtidyl serine.
101 citations
TL;DR: It was found that drift imitating movements regenerate (fill in) a disappeared object as in normal vision, and that the tremor and saccades do not function for this purpose.
76 citations
TL;DR: A role of an adenyl cyclase system in the mechanism of steroid hormone action in insects is suggested, based on the fact that Mg 2+ is required for an optimal response of region 78B upon induction of its activity by ecdysterone.
69 citations
TL;DR: It is concluded that the facilitation of oxygen diffusion in the presence of hemoglobin can be described quantitatively when the chemical reactions are taken into account.
TL;DR: It is concluded that the two activities of inorganic pyrophosphatase and alkaline phosphatase in the molars of 3-day-old hamsters are due to the same enzyme.
Abstract: 1.
Some properties of inorganic pyrophosphatase (PPi-ase) and alkaline phosphatase (p-NPP-ase) in the molars of 3-day-old hamsters are described.
2.
The pH optimum for inorganic pyrophosphatase is 8.7, for alkaline phosphatase 10.3.
3.
The ratio of Mg2+: PPi for optimal inorganic pyrophosphatase activity is 1∶1. There is no clear optimal ratio in the case of p-NPP-ase.
4.
The ratio of the enzymic activity of the membrane bound fraction to the soluble fraction is 3.4∶1 (S.E. 0.37) for PPi-ase and 3.2∶1 (S.E. 0.42) for p-NPP-ase activity.
5.
A mutual substrate competition for the pyrophosphatase and alkaline phosphatase activities is demonstrated.
6.
Both enzymatic activities have similar temperature-activity curves with the same maximum at 38°.
7.
Microdissection of ameloblasts and stratum intermedium cells from lyophilized sections showed the same activity ratio for both enzyme activities: Stratum intermedium: ameloblasts for PPi-ase 4.7 (S. E. 0.93) and for p-NPP-ase 4.2 (S.E. 0.79).
8.
High-voltage, free-flowing electrophoresis of the homogenate gave equal distribution patterns for p-NPP-ase and PPi-ase greatly different from the protein distribution pattern.
9.
It is concluded that the two activities are due to the same enzyme.
TL;DR: Enzymatic activities for the p-hydroxylation of aniline, the N-demethylation of aminopyrine, and the UDPglucuronyl conjugation of p-nitrophenol of regenerating rat liver have been measured in vitro at different intervals following partial hepatectomy.
TL;DR: Electron microscopic observations on sections of squashed glutar-aldehyde-fixed salivary gland X-chromosomes of Drosophila melanogaster provided an ultrastructural map of the band sequence of region 1A1 to 4E3, which revealed a significantly lower number of bands.
Abstract: Electron microscopic observations on sections of squashed glutar-aldehyde-fixed salivary gland X-chromosomes ofDrosophila melanogaster provided an ultrastructural map of the band sequence of region 1A1 to 4E3. Comparison of this map with the map of Bridges (1938) revealed a significantly lower number of bands. Only 67% of the bands depicted in Bridges' map could be identified. This discrepancy seems to be a consequence mainly of the absence of doublet characters of bands on Bridges' map. — A possible relationship between bands and genes is discussed for some regions, including the white-Notch region. It appears that a one to one relationship between bands and genes does exist for two regions, whereas in region 3C1–3C7 more genes than bands are present. In this respect the structural organization of bands at the submicroscopic level is discussed. — The average DNA content of a band at the haploid level is calculated on the basis of the reduction in band number to be 4.5 × 10−5 picogram.
TL;DR: The sweat gland response to acetylcholine was measured in atopic and non‐atopic subjects throughout 1969 and support the assumption of a defect in the autonomic vegetative system in atopics.
Abstract: Summary
The sweat gland response to acetylcholine was measured in atopic and non-atopic subjects throughout 1969. Atopic patients showed both an increased sensitivity and a higher production of sweat throughout the year. These findings support the assumption of a defect in the autonomic vegetative system in atopics.
TL;DR: Experiments with C14-labelled glucose have shown that the inability to utilize glucose at 80° C is not due to an inactivation of the initial steps of the glycolytic pathway, thus blocking the utilization of glucose at this temperature.
Abstract: Conditions for cultivating two extremely thermophilic bacteria, isolated from the hot springs of Yellowstone National Park, are described. One of these strains, Thermus aquaticus, can be grown on either succinate or pyruvate as the best substrates at 78° C. Acetate, glucose, and sucrose can also be utilized at this temperature. The temperature optimum was found to be 70° C, but the bacterium can be adapted to grow on succinate or pyruvate at 80° C. The other strain, YT-G has its growth optimum at 80° C and the maximum temperature was found to be 84° C. At this temperature pyruvate is the only substrate which gives good results, while glucose cannot be used as a carbon source. At 70° C, however, the yields obtained with glucose as a substrate are better than those with pyruvate at 80° C. Experiments with C14-labelled glucose have shown that the inability to utilize glucose at 80° C is not due to an inactivation of the initial steps of the glycolytic pathway. Phosphorylated sugars and a compound corresponding to α-glycerophosphate were found to be formed, the latter being accumulated as a side product of normal glycolysis. The enzymes leading to this product, and those which are involved in the conversion of pyruvate were found to be functioning at 80° C, while intermediate enzymes of the glycolytic pathway are assumed to be less heat resistant, thus blocking the utilization of glucose at this temperature. The ability of strain YT-G to grow on glucose is, however, promptly resumed if the temperature is lowered. Lysozyme treatment was found to lead to a complete conversion of T. aquaticus cells to spheroplast while cells of strain YT-G are only slightly altered by this procedure.
TL;DR: The enzyme-inhibitor complex is formed instantaneously and is strongly dependent on pH and Mg 2+ concentration, and the pH optimum of the inhibitor coincides with the optimal pH value of pancreatic ribonuclease.
TL;DR: The effect of injection of different ecdysterone concentrations into third instar larvae of Drosophila hydei at various stages was studied with regard to changes in genome activity, secretion of mucopolysacharides by the salivary gland cells, and pigmentation.
TL;DR: When placed singly into a novel environment, male mice of the C57BL/6 strain have consistently higher frequencies for rearing behavior than those of the DBA/2 strain, indicating dominance of alleles contributing to high rearing frequencies.
Abstract: When placed singly into a novel environment, male mice of the C57BL/6 strain have consistently higher frequencies for rearing behavior than those of the DBA/2 strain. Hybrids also have high scores for this exploratory act, indicating dominance of alleles contributing to high rearing frequencies. Judging from the variances of the nonsegregating populations, a significant genotype-environment interaction was present. From raw data, the degree of genetic determination was estimated to be about 77±12%.
TL;DR: It is suggested that the retinoldehydrogenase in the rod outer segments may play an important role in the regeneration of the rod sac after stimulation by light.
TL;DR: In this article, subjects with severe fears of harmless snakes were divided into three matched groups of nine, one was a control group, and the other two groups received respectively five sessions of systematic desensitization and five session of flooding.
TL;DR: From the differential titration curves of the α-chains and of Hb and HbO 2 it can be concluded that all carboxyl groups and all Lys and Arg residues are titratable in these molecules.
TL;DR: The sweat response to injected acetylcholine was measured with and without beta‐blockade by propranolol, and atopic subjects showed little or no effect of beta‐ blockade.
Abstract: Summary
The sweat response to injected acetylcholine was measured with and without beta-blockade by propranolol. Three observations were made: (1) In all cases, propranolol tended to increase the response of the sweat gland to acetylcholine. (2) The effect of propranolol was more marked when using stimulation with minimal quantities of acetylcholine. (3) Atopic subjects showed little or no effect of beta-blockade.
These results are compatible with the model presented by Szentivanyi (1968).
TL;DR: The influence of orally administered adenine on the clinical features and on the purine metabolism of two patients with the Lesch-Nyhan syndrome and the relationship between the greatly increased purine synthesis de novo and this enzyme deficiency is studied.
Abstract: The Lesch-Nyhan syndrome is characterized by mental retardation, choreoathetosis, aggressive behaviour with automutilation and hyperuricaemia (9, 17, 18). A number of authors have mentioned the Occurrence of a megaloblastic anaemia in this syndrome ,(7, 11 , 12, 18, 24). The syndrome is an X linked recessive disorder (13, 16, 23). The purine synthesis de novo is greatly increased in these patients (9, 15). Seegmiller found a deficiency of the enzyme hypoxanthine-guanine-phosphoribosyltransferase in patients with this syndrome (22). The relationship between the greatly increased purine synthesis de novo and this enzyme deficiency is at present an important feature of investigation (20). We studied the influence of orally administered adenine on the clinical features (25) and on the purine metabolism of two patients with the Lesch-Nyhan syndrome.
TL;DR: A highly purified RNase inhibitor from rat liver can be obtained by chromatography on columns loaded with carboxymethyl cellulose-RNase and is now available for the preparation of undegraded polyribosomes and ribosomal subunits.
TL;DR: Both in mammals and in fish the enzymatic activities of the N -demethylation of aminopyrine and the p -hydroxylation of aniline are higher after cold-ac Climation than after warm-acclimation of the animals.
TL;DR: The enzyme activities of hepatic N-demethylation of aminopyrine and p-hydroxylation of aniline assayed in vitro in the feral roach appear to be unexpectedly high, with the highest enzyme activities occuring during the summer months.
TL;DR: Kinetic studies at varying acceptor and UDPglucuronate concentrations demonstrate that ultrasonic treatment of the liver homogenate results in a significant increase of the apparent Km-values for UDPglUCuronyltransferase.