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Showing papers by "Utrecht University published in 1969"


Journal ArticleDOI
TL;DR: In this article, a simple method was described to compute exactly the binding energy (B.E.) of the ground state of three nucleons in the framework of the Faddeev equations.

447 citations


Journal ArticleDOI
TL;DR: In the presence of 3-ketosteroids, the rates of penetration of glycerol were significantly higher than those containing 3β-hydroxy steroids, and Cholesterol-depleted erythrocytes also exhibited considerably increased Glycerol permeability.

310 citations


Journal ArticleDOI
22 Mar 1969-Nature
TL;DR: Polychlorinated biphenyls are widely used in industry, and they are now making an appearance in the world's wildlife.
Abstract: Polychlorinated biphenyls are widely used in industry, and they are now making an appearance in the world's wildlife. Besides being a hazard in their own right, they interfere with the detection of organochlorine insecticides such as DDT.

279 citations


Journal ArticleDOI
TL;DR: It was observed that lecithins with a chain length from 8 to 12 carbon atoms (per acyl chain) are capable of lysing red cells and lipid bilayers, which might indicate that the interaction of the lytic agents with the lipid-constituents of the membrane plays an important role in the process.

148 citations


Journal ArticleDOI
TL;DR: In this article, a critical discussion is presented of some important theories for the electrode impedance in the case that the electroactive species are specifically adsorbed at the electrode-solution interface.

143 citations


Journal ArticleDOI
TL;DR: The shape and the osmotic susceptibility of the protoplasts of this organism appeared to depend on the growth conditions, and the presence of a more rigid membranous structure in cells which have been exposed to a low environmental pH during growth.
Abstract: Bacillus subtilis contained at least five phospholipids, four of which have been isolated and identified as a polyglycerol phospholipid, probably cardiolipin, phosphatidylglycerol, phosphatidylethanolamine, and lysylphosphatidylglycerol. Further purification of the latter phosphoglyceride was obtained by high-voltage electrophoresis, and it was shown that this treatment removed amino acid-containing, nonlipidic material from the phosphoglyceride. This associated material, which is not covalently linked to the lipid, gave rise to minor amounts of a number of amino acids, other than lysine, in acid hydrolysates of the lysylphosphatidylglycerol. The phospholipid composition of B. subtilis appeared to depend on the growth conditions. Addition of glucose to the medium lowered the pH during growth; this was accompanied by an increase in the amount of lysylphosphatidylglycerol and a decrease in the phosphatidylglycerol content, when compared with growth at neutral pH. The amount of the other phospholipids and the total amount of phospholipid remained constant under the different conditions. The shape and the osmotic susceptibility of the protoplasts of this organism appeared to depend on the growth conditions. Cells harvested from a neutral growth medium gave spherical protoplasts which lysed rapidly, whereas cells grown in an acidic medium maintained their rod-shaped form to a great extent after the cell wall had been removed, even after being suspended in a hypotonic medium. The latter observation suggests the presence of a more rigid membranous structure in cells which have been exposed to a low environmental pH during growth.

139 citations


Journal ArticleDOI
TL;DR: The difference in specific radioactivity of (14)C-ethanolamine-labeled endogenous mitochondrial phospholipid before and after incubation indicates that a fraction of mitochondrial phosphatidyl ethanolamine is hydrolyzed more rapidly than the mitochondrialospholipids as a whole.

120 citations


Journal ArticleDOI
F. de Waard1
TL;DR: In the epidemiology of a disease, which is multifactorial to such an extent as the authors believe breast cancer to be, attention should be paid even to “weak” factors and an attempt should be made to assign a place to them in an aetiologic system which is biologically sound.
Abstract: In the epidemiology of a disease, which is multifactorial to such an extent as we believe breast cancer to be, attention should be paid even to “weak” factors and an attempt should be made to assign a place to them in an aetiologic system which is biologically sound. Medical knowledge will help us in doing this, and the exercises in “metabolic epidemiology” will be as useful as statistical manipulations and computer programming. Two developments seem to be taking place, one of them being the teamwork between analytic epidemiology and biochemistry; the other is that we are begining to realize that most so-called chronic diseases of relatively high prevalence are like icebergs in the sea with a vast amount of subclinical abnormalities in the “healthy” population (and therefore in our control groups). Epidemilogie du Cancer du sein: Analyse et Perspectives Dans l'epidemiologie d'une maladie a multiples facteurs, comme l'est a notre avis le cancer du sein, il faudrait s'interesser aussi aux facteurs secondaires et essayer de les integrer a un systeme etiologique qui soit biologiquement valable. Nos connaissances medicales nous aideront a le faire et les exercices d' “epidemiologie metabolique” seront aussi utiles que les manipulations statistiques et l'utilisation d'ordinateurs. Une evolution semble en cours, dont l'un des elements est l'esprit d'equipe qui caracterise les travaux de biochimie et d'epidemiologie analytique; en outre, nous commencons a prendre conscience du fait que la plupart des maladies que l'on dit chroniques et dont l'incidence est relativement elevee ressemblent a des icebergs flottant sur la mer et s'accompagnent d'une grande quantite d'anomalies sub-cliniques dans la population “saine” (et par consequent dans nos groupes-temoins).

78 citations


Journal ArticleDOI
H. Verbiest1
TL;DR: It was concluded that anterolateral operations may be harmful for patients with acute complete transverse lesions of the Cord but that traumatic abnormalities causing compression of the anterior part of the cord or traction and consequent anterior pressure on the cord can be eliminated or corrected under direct vision in a way not possible by laminectomy.
Abstract: A follow-up study of forty-seven patients treated for traumatic lesions of the cervical spine with and without associated neural deficits is presented. Operation was performed six hours to eight months after injury. The objectives of these procedures were to remove any causes of compression of the cord or nerve roots, especially anterior compression, to reduce the dislocation and kyphosis, and to stabilize the cervical spine by interbody fusion. Preoperative and postoperative care is described as well as the exposure used for different levels of the spine and the three types of bone-grafting procedures that were developed to correct and stabilize the deformities associated with the various fractures and fracture-dislocations encountered. Normal or satisfactory alignment was regained in all but three of the forty-one surviving patients, and solid fusion occurred in the forty-one surviving patients who were followed long enough to determine the results of fusion. There was no evidence that the operation had aggravated any neural deficits, although in two of the six patients who died after acute complete transverse cord lesions it was thought that early operation within twelve hours of injury may have contributed to the fatal outcome. The functional results of operation in terms of relief of neck pain and recovery of cord and nerve-root function were encouraging. The prompt recovery of function of a few patients who had not improved after as long as 3.5 months of non-operative treatment suggested that reduction of the dislocation and correction of the kyphosis, combined with removal of the posteriorly extruded disc material in nine patients, had corrected a vascular insufficiency. It was concluded that anterolateral operations may be harmful for patients with acute complete transverse lesions of the cord but that traumatic abnormalities causing compression of the anterior part of the cord or traction and consequent anterior pressure on the cord (the result of angulation of the cervical spine) can be eliminated or corrected under direct vision in a way not possible by laminectomy. It was further concluded that fusion is easily effected through the anterolateral approach, whereas after laminectomy posterior fusion may be difficult or impossible.

77 citations


Journal ArticleDOI
TL;DR: It is suggested that cyclic adenosine monophosphate secreted by the bacteria is used by the amoebae as a means of sensing and orienting towards food.
Abstract: Adenosine-3',5'-cyclic monophosphate was shown to be the compound found in Escherichia coli responsible for the attraction of the amoebae of the cellular slime mold Dictyostelium discoideum. A number of other nucleotides were tested and the following were active: tubercidin-3',5'-cyclic monophosphate, N(6)-2'-O-dibutyryl-adenosine-3',5'-cyclic monophosphate, 5'-methylene adenosine-3',5'-cyclic monophosphonate, guanosine-3',5'-cyclic monophosphate, uridine-3',5'-cyclic monophosphate, cytidine-3',5'-cyclic monophosphate, inosine-3',5'-cyclic monophosphate, and thymidine-3',5'-cyclic monophosphate. They were less active than adenosine-3',5'-cyclic monophosphate. It is suggested that cyclic adenosine monophosphate secreted by the bacteria is used by the amoebae as a means of sensing and orienting towards food.

75 citations


Journal ArticleDOI
TL;DR: In the rat pretreated with sodium pentobarbital and chlorpromazine, none of the amino acids, amino acid mixtures, various di- and tripeptides, or biogenic amines exhibited a significant effect on pituitary-addrenal activity, however, prostaglandin E1 and E2, in contrast to F1α and F2α, stimulated pituitsary ACTH release in rats blocked with Sodium pentobarBital andchlorpromazine.
Abstract: The ACTH-releasing activity of some substances of low molecular weight was tested in several assay systems in the rat, in which attempts were made to block the nonspecific release of ACTH. The rate of corticosteroid production in vitro and corticosterone content of plasma were used as parameters of pituitary ACTH release. In the rat pretreated with sodium pentobarbital and chlorpromazine, none of the amino acids, amino acid mixtures, various di- and tripeptides, or biogenic amines exhibited a significant effect on pituitary-addrenal activity. However, prostaglandin E1 and E2, in contrast to F1α and F2α, stimulated pituitary ACTH release in rats blocked with sodium pentobarbital and chlorpromazine. Angiotensin II, arginine vasopressin, carbachol and a crude CRF from calf brain also activated the pituitary-adrenal system of similarly blocked rats. The corticotrophic effect of these “active agents” was further studied in rats pretreated with sodium pentobarbital, atropine and chlorpromazine; sodium pentobarb...

Journal ArticleDOI
J.F. Verwey1
TL;DR: In this article, the rate of photochemical decomposition of lead halides by u.v. light was investigated by measuring the change of the optical density Δ D after irradiation, and it was found that the time dependence of photolysis in PbCl 2, PbBr 2 and PbI 2 is not essentially different.

Journal ArticleDOI
TL;DR: Annual testicular cycles in the lizards Lacerta sicula and L. muralis appear to be regulated by the interaction between seasonal changes in body temperature and an endogenous rhythmicity in thermal responsiveness, independent of photo-period.
Abstract: Annual testicular cycles in the lizards Lacerta sicula and L. muralis appear to be regulated by the interaction between seasonal changes in body temperature and an endogenous rhythmicity in thermal responsiveness. Photoperiodism does not appear to be an important factor; i.e. testicular activity does not appear to be regulated by daylength. Following testicular regression in July, the lizards are refractory to sexual stimulation by high temperatures (i.e. normal preferred levels) for about five months. High temperatures accelerate gonadal regression and prevent recrudescence during late summer. Reduced temperatures stimulate testicular enlargement and spermatid formation during the autumn; this recrudescence can be blocked by treatment with testosterone. Very low temperatures suppress gonadal activity during mid-winter. Maintenance of lizards at constant high temperatures (33°C) starting in July suppresses testicular recrudescence until December. Also, testicular collapse occurs in lizards transferred to high temperatures after recrudescence has started. The gonads are stimulated by exogenous gonadotropins at 33°C during the fall indicating that high temperatures reduce circulating levels of gonadotropins. The refractoriness to high temperatures is “spontaneously” terminated during midwinter (December) under a wide range of photo-thermal conditions. Low temperatures may accelerate the termination of refractoriness. Thereafter, high temperatures stimulate, and are required for the final development of the testes and accessory sexual structures. Thus, the increase in body temperature following hibernation times the onset of breeding in the spring. Temperature also has a marked influence on appetite and growth, independent of photo-period. Weight gains are greater at 33° than at 20°C. At 33° there is a tendency for abdominal fat bodies to enlarge but with little hepatic growth; whereas, the reverse occurs at 20°C.

Journal ArticleDOI
TL;DR: The galactolipid synthesis is quite resistant to elevated temperature; maximal incorporation of galactose from UDP-galactose was observed at 45 degrees C and the proportion of monogalactosyl diglyceride was greater at the higher temperatures.

Journal ArticleDOI
TL;DR: The temperature dependence of spontaneous, fatty acid-induced, or CaCl(2)-induced swelling suggested that enzymatic activities are responsible for swelling, although swelling due to contaminating lysosomes cannot be excluded entirely.

Journal ArticleDOI
J. van Aken1
TL;DR: In the present article the image formation will be studied as influenced by (a) the length of the cone, (b) the film placement, and (e) the angulation of the x-ray beam.

Journal ArticleDOI
TL;DR: With the glucagon test, all patients with deficiency of the phosphorylase system showed a rise in blood glucose no different from that of normal children, so the statement of Sokal, Lowe, and Sarcione (1962) that a rapid rise of 50 mg./100 ml.
Abstract: The majority of patients with glycogenosis of the liver have one of three types of enzyme deficiency: deficiencyofglucose-6-phosphatase, ofthe debranching enzyme system, or of the phosphorylase system (Illingworth, 1961; Hers and Van Hoof, 1968). The severity of the disease and of its manifestations, such as hypoglycaemia and acidosis, is related to the underlying enzyme defect (van Creveld and Huijing, 1965). Treatment of patients with liver glycogenosis is dietary. The diet aims at reducing the effects of the metabolic disturbance and must vary with the type of enzyme defect (Fernandes and van de Kamer, 1965, 1968). It is important to start dietary management as early as possible, and therefore to diagnose the disease and the enzyme deficiency involved, at an early age. The definitive diagnostic procedure is assay of the enzymes, either in liver tissue orfor debranching enzyme and phosphorylase-in the leucocytes. But it would be useful to have available simpler tests to screen children in whom liver glycogen disease is suspected. Various screening procedures have been recommended, such as the epinephrine tolerance test (Howell, Ashton, and Wyngaarden, 1962), glucagon tolerance test (Hug, 1962; Lowe et al., 1962), and intravenous tolerance test with fructose (Hers, 1959) or galactose (Schwartz, Ashmore, and Renold, 1957). Ockerman (1967) has reviewed the application of these tests. In our experience, they often have drawbacks. With the glucagon test, all our patients with deficiency of the phosphorylase system showed a rise in blood glucose no different from that of normal children. Thus, the statement of Sokal, Lowe, and Sarcione (1962) that a rapid rise of 50 mg./100 ml. or more in blood glucose after intramuscular glucagon virtually rules out liver glycogen disease, does not hold for this group of patients. Moreover, the glucagon test is usually performed after prolonged fasting

Journal ArticleDOI
TL;DR: Morphological evidence is put forward indicating that transport of low molecular material might be the main function of coronet cells, and observations on the synaptic pattern in the epithelium suggest a possible nerve control of the functional activity of the saccus vasculosus via the glial elements.
Abstract: The saccus vasculosus of the rainbow trout, a sac-like outgrowing of the basis of the diencephalon consists of a strongly undulated epithelial wall, separating the cerebrospinal fluid from the endomeningeal matrix fluid. This epithelium is built up by highly specialized coronet cells, glial cells and peculiar so-called pseudo-coronet cells. The coronet cells extend from the ventricular- to the meningeal border. Morphological evidence is put forward indicating that transport of low molecular material might be the main function of these cells. Several cytochemical data support this hypothesis. A possible repulsion and renewal of globules of the coronet cells may represent steps in the functional cycle of these cells. Concerning the transport function, the observation of open connections between the lumina of the blood sinuses and the endomeningeal spaces might be important.

Journal ArticleDOI
TL;DR: In this article, the mean lives of the lowest six excited states in 38Ar were measured with the Doppler shift attenuation method, and the relatively fast decay of the second excited state indicates that positive parity states in the 38Ar are only well described if (ds)−4(fp)2 shell-model configurations are taken into account.

Journal ArticleDOI
B. Kiauta1
01 Jan 1969-Genetica
TL;DR: The morphological and kinetical features of the odonate sex chromosomes are reviewed and trends of the evolution of different modes of sex determination in the order are considered and it was demonstrated, that the present type number of Gomphidae is of secondary rather than of primary origin.
Abstract: The morphological and kinetical features of the odonate sex chromosomes are reviewed and trends of the evolution of different modes of sex determination in the order are considered. The cytological conditions in the familyGomphidae are of particular importance for the understanding of the evolution of sex determination in dragonflies and are discussed in detail.

Journal ArticleDOI
S. Maripuu1
TL;DR: In this article, the Schmidt values and effective values of gyromagnetic ratios have been used to calculate M1 transition probabilities within isobaric-spin doublets for cases without configuration mixing.

Journal ArticleDOI
TL;DR: In the pituitary gland of the Stenohaline teleost Anoptichthys jordani the pro-adenohypophysial acidophilic cells undergo a marked hypertrophy and hyperplasia in deionized water, whereas their activity is suppressed in 20% sea-water, and it is concluded that these cells are involved in osmoregulation.
Abstract: In the pituitary gland of the Stenohaline teleost Anoptichthys jordani the pro-adenohypophysial acidophilic cells undergo a marked hypertrophy and hyperplasia in deionized water, whereas their activity is suppressed in 20% sea-water. Consequently, it is concluded that these cells are involved in osmoregulation. Correlated changes occur in the mucous cells of the epithelium in the oral cavity; these cells are stimulated in deionized water and are degenerating in salt water. The mucous cells in the epithelium of the gills show an inhibition in salt water, whereas the mucous cells in the epidermis are unaffected by either treatment. Since ovine prolactin may also induce a stimulation of the mucous cells in the buccal cavity, it is supposed that the osmoregulatory factor, produced in the adenohypophysis, is a prolactin-like hormone.

Journal ArticleDOI
TL;DR: It was concluded that the initial aggregation of the melanophores may be the result of a reduced extrusion of MSH from the pars intermedia, caused by an increased output of a MIF by the bio-amine producing nuclei.
Abstract: In Xenopus laevis tadpoles the relation between a paired nucleus of bio-amine producing neurons in the caudal hypothalamus and the pars intermedia of the hypophysis was studied.

Journal ArticleDOI
TL;DR: It is concluded that continuous protein synthesis (at a constant rate) is a general feature of the mammalian pancreas under normal conditions.

Journal ArticleDOI
TL;DR: In this paper, the shell model was used to investigate properties of levels in the A = 38 nuclei and an inert 28Si core with a residual two-particle interaction between the outer nucleons was assumed.

Journal ArticleDOI
TL;DR: In this article, it was shown that the initial act for visual perception is the absorption of light in the photo-pigment of the receptor end-organs, and that any theory of visual information processing should in principle be a digital processing theory.
Abstract: The initial act for visual perception is the absorption of light in the photo-pigment of the receptor end-organs. Since both light and the nervous message have a quantal structure, any theory of visual information processing should in principle be a digital processing theory. And not only in principle, since we know for certain that in many situations the number of quanta is rather restricted, so that an over-all thermodynamic theory cannot but fail to adequately describe visual facts.

Journal ArticleDOI
TL;DR: In this article, the first maximum at the long wavelength side of the fundamental absorption of PbBr2 and PbCl2 is an exciton peak and the wavelength dependence indicated that the holes are the dominant mobile charge carriers in these crystals.

Journal ArticleDOI
TL;DR: In this article, the relation between Lagrangian and Feynman rules was studied for diagrams of the Yang-Mills theory with no or one close loop. And the authors showed that with the same set of rules the imaginary part of the two-loop self-energy diagrams receives a non-zero contribution of the unphysical three-ghost intermediate state.

Journal ArticleDOI
TL;DR: Intracerebral implantation of dexamethasone phosphate facilitated the rate of extinction of a pole jumping avoidance response when implanted into various areas in the median and posterior thalamus and in the ventriculus lateralis.

Journal ArticleDOI
TL;DR: Dinitrophenol and liverfluke anthelmintics such as niclofolan, nitroxynil, bromophenophos and hexachlorophene increased ATP-ase activity of rat-liver mitochondria and caused a contracture of striated muscle in vitro.