Showing papers by "Radboud University Nijmegen published in 1982"

The medial forebrain bundle of the rat. I. General introduction.

Abstract: This paper is the first of a projected series of studies on the structure and composition of the medial forebrain bundle (MFB) of the rat and the relations of this fiber system to its bed nucleus, the lateral hypothalamic area. The first part of the paper comprises an extensive review of literature on the MFB from its discovery by Ganser in 1882 to the present. This review serves as the basis for an evaluation of our present-day knowledge of the organization of the MFB, which is presented in the second part of this paper. Despite the wealth of information available on the origins and sites of termination of the axons that constitute the MFB, surprisingly little attention has been given to the bundle itself, to its topographic boundaries, its fiber composition, or to the spatial arrangement of its constituent components. These features of the MFB as it extends through the lateral preoptic and lateral hypothalamic areas have been analyzed in normal Kluver-Barrera- and Bodian-stained material. From this analysis, a detailed atlas of the MFB and some of the surrounding structures has been prepared. This atlas, which forms the third section of this paper, illustrates the appearance and organization of the MFB at ten equidistant levels through the lateral preoptic and lateral hypothalamic continuum.

The medial forebrain bundle of the rat. II. An autoradiographic study of the topography of the major descending and ascending components.

Abstract: The medial forebrain bundle (MFB) is a complex fiber system that courses through and partly arises and partly terminates within the lateral preoptic and lateral hypothalamic areas. It consists mainly of thin fibers and may be comprised of as many as 50 descending and ascending components of varying lengths and of different origins and/or destinations (Nieuwenhuys et al., '82). With the aid of an an atlas of the MFB and the surrounding brain areas in the rat presented in the preceding paper (Nieuwenhuys et al., '82), the position and topographic relationships of some 21 components of the bundle have been analyzed in detail, in brains that had been prepared for autoradiography following injections of tritiated amino acids into a number of structures that are known to contribute fibers to the MFB. From this analysis it is clear that most of the labeled components occupy specific and rather constant positions within the MFB. For example, the ascending components are largely confined to the dorsal half of the bundle; those arising from the medial preoptic area and the various hypothalamic nuclei are distributed rather diffusely over much of the MFB; and the descending components that arise from the olfactory tubercle and the magnocellular preoptic nucleus are confined to restricted parts of the bundle. These findings indicate that the neurons which occupy different parts of the lateral hypothalamic area probably receive distinctive inputs, and to a first approximation these are likely to be determined principally by their position within the MFB.

A probabilistic model for the discrimination of visual number

Abstract: This paper proposes a probabilistic model of how humans identify the number of dots within a briefly presented visual display. The model is an application of Thurstone’s law of comparative judgment, and it is assumed that the internal representation of numerosity consists of log-spaced random variables. The discrimination between any two different numerosities is consequently described as a function of max/rain, where max and rain are the larger and smaller numbers, respectively. The model was tested in two experiments in which the Weber fraction for numerosity, corresponding with the critical ratio of max and min, was found to have the value of 162. It was concluded that the classical span of subitizing numerosity is but a special case of the span of discrimination.

The production of mature gametocytes of Plasmodium falciparum in continuous cultures of different isolates infective to mosquitoes

Abstract: In vitro gametocytogenesis of Plasmodium falciparum was observed in all 22 isolates established in this laboratory. Gametocytes were produced in variable numbers--up to 3% of red cells--for a limited period of time after which this stage was seen only very sporadically. Complete maturation of microgametocytes in vitro was obtained in all 14 of the isolates that were tested for exflagellation. Up to 88.2% of membrane-fed Anopheles stephensi were infected from material produced in culture. It was also possible to infect A. gambiae and A. freeborni. Addition of fresh red cells and serum to culture material promoted infectivity of gametocytes. Gametocyte infectivity declined rapidly with time in the membrane feeders held at 38 degrees C.

Associative facilitation of word recognition as measured from a neutral prime

Abstract: It is shown that lexical decision times to strong associates with an associative strength of approximately 40% are facilitated relative to targets following a neutral prime, “blank,” whereas very weak associates with an associative strength of less then 3% are neither facilitated nor inhibited. It is also shown that relative to the “blank” baseline time, a row of crosses inhibits processing of the following target. The latter finding has implications for earlier studies that have used crosses as a neutral prime. In these studies, facilitation effects have been overestimated and inhibition effects have been underestimated. Neely 1976 has proposed a predict-and-match strategy according to which subjects are assumed to predict one or more targets from the prime and to match the actual target onto the predicted targets. A part of this theory is not supported by the present data. The results are discussed in terms of the two-process theory of expectancy (Posner & Snyder, 1975). They are also considered in the light of a recent theory by Becker (1980). As an alternative interpretation of part of the reported data, a coherence assumption by the subjects about all reading materials is introduced.

Two New Test Statistics for the Rasch Model.

Abstract: It is shown that the presently available statistical tests for the Rasch model are insensitive to violation of the unidimensionality axiom. Two new test statistics are presented. The first one,Q 1, is sensitive to the same effects as the presently available statistics, but has some desirable properties of a nonstatistical nature. The second statistic,Q 2, is sensitive to violation of local stochastic independence and unidimensionality and thus fills an existing gap.

Configurational effects on the enumeration of dots: Counting by groups

Abstract: The processing time for quantifying numerosity of two-dimensional dot patterns was investigated as a function of both number of dots and relative proximity between dots. A cluster algorithm (CODE) was first developed as a formal model of how human subjects organize neighboring dots into groups. CODE-based predictions of grouping effects on number processing latencies were then tested with patterns consisting of n dots (range n = 13–23). The results largely confirmed CODE-based predictions and thereby indicated that large collections of dots are preferably counted by groups. Small (n ≤ 5) groups are subitized and their partial results are summed to a running total. Based on criteria other than dot proximity, large (n > 5), proximity-based groups are subdivided into smaller groups of two or three dots, which are again subitized.

Association of methanogenic bacteria with ovine rumen ciliates

Abstract: 1. The frequency of association between methanogenic bacteria and ovine rumen ciliates was studied in the rumen fluid of a fistulated sheep. 2. A period of fasting and flushing of the rumen content with nitrogen resulted in a relatively high association, whereas the intake of food and flushing with hydrogen caused a detachment of the methanogenic bacteria from the ciliates. 3. The changes in the frequency of association can be correlated with the relative attribution to the H2 production by hydrogenogenic bacteria and rumen ciliates.

Cultivation of fertile Plasmodium falciparum gametocytes in semi-automated systems. 1. Static cultures.

Abstract: A semi-automated cultivation apparatus for the in vitro culture of Plasmodium falciparum gametocytes is described This apparatus has been designed to produce large numbers of fertile sexual stages for use in the development of a gamete vaccine or for the infection of suitable mosquitoes These mosquitoes in turn may be used for the development of a possible sporozoite vaccine Loss of red cells during medium change has been eliminated and the addition of warmed fresh medium simplified compared to similar systems described previously Material harvested from this apparatus has been used for infecting mosquitoes Up to 98% of Anopheles stephensi were infected with a mean oocyst count of 24 per positive gut (range one to 109) The importance of satisfactory presentation of gametocytes for mosquito infection is stressed The possible presence of substances in normal human sera which inhibits exflagellation to a variable degree and reduces mosquito infectivity is also discussed

Oxygen supply to tissues: the Krogh model and its assumptions.

Abstract: 4 Akert, K., Moor, H., Pfenninger, K., and Sandri, C., Contributions of new impregnation methods and freeze etching to the problems of synaptic fine structure, in: Mechanisms of synaptic transmission. Prog. Brain Res. 31, pp.223-240. Eds K. Akert and P. G. Waser. Elsevier, Amsterdam 1969. 5 Akert, K., and Sandri, C., Significance of the Maillet method for cytochemical studies of synapses, in: Perspectives in neurobiology. Golgi centennial symposium, pp.387 399. Ed. M. Santini. Raven Press, New York 1975. 6 Bennett, M.V.L., Sandri, C., and Akert, K., Neuronal gap junctions and morphologically mixed synapses in the spinal cord of the teleost Sternarchus albifrons (Gymnotoidei). Brain Res. 143 (1978) 43-60. 7 Chuang, H.H., and Dai, R.X., Concerning the conductivity of the embryonic epithelium in amphibian (in Chinese). Kexue Tongbao 12 (1961) 54-56. 8 Chuang-Tseng, M.P., Chuang, H.H., Sandri, C., and Akert, K., Gap junctions and impulse propagation in embryonic epithelium of amphibian. Cell Tissue Res. 225 (1982) 249-258. 9 Couteaux, R., The differentiation of synaptic areas. Proc. R. Soc. Ser. B 158 (1963) 457-480. l0 Couteaux, R., and P6cot-Dechavassine, M., V6sicules synaptiques et poches au niveau des 'zones actives' de la jonction neuromusculaire. C.r. Acad. Sci., Paris 271 (1970) 2346-2349. 11 Dai, R.X., and Sun, Y.A. Spontaneous potentials of embryonic epithelium in urodeles (Cynops orientalis). Kexue Tongbao (1982), in press. 12 Dreyer, F., Peper, K., Akert, K., Sandri, C., and Moor, H., Ultrastructure of the 'active zone' in the frog neuromuscular junction. Brain Res. 62 (1973) 373-380. 13 Fan, S.F., and Dai, R.X., Electric activity of embryonic epithelium in urodeles (in Chinese). Kexue Tongbao 10 (1962) 38-39. 14 Hanna, R.B., Spray, D.C., Model, P.G., Harris, A.L., and Bennett, M.V.L., Ultrastructure and physiology of gap junctions of an amphibian embryo, effects of CO2. Biol. Bull 155 (1978) 442. 15 Hess, W.R., Beitr/ige zur Physiologie des Hirnstammes. I. Die Methodik der lokalisierten Reizung und Ausschaltung subkortikaler Hirnschnitte, pp. 1-122. Thieme, Leipzig 1932. 16 Heuser, J.E., Reese, T.S., Dennis, M.J., Jan, Y., Jan, L., and Evans, L., Synaptic vesicle exocytosis captured by quick freezing and correlated with quantal transmitter release. J. Cell Biol. 81 (1979)275-300. 17 Jankowska, E., Lundberg, A., Rudomin, P., and Sykova, E., Effects of 4-aminopyridine on transmission in excitatory and inhibitory synapses in the spinal cord. Brain Res. 136 (1977) 387-392. 18 Jones, D.G., Neurons and synapses, in: Studies in biology, No. 5, pp. 1-60. Edward, Arnold Publ., London 1981. 19 Israel, M., Dunant, Y., and Manaranche, R., The present status of the vesicular hypothesis. Prog. Neurobiol. 13 (1979) 237-275. 20 Katz, B., Nerve, muscle and synapses, pp. 1-193. Mc GrawHill, New York 1966. 21 Makowski, L., Caspar, D.I.D., Phillips, W.C., and Goodenough, D.A., Gap junction structures. II. Analysis of the X-ray diffraction data. J. Cell Biol. 74 (1977) 629-645. 22 Moor, H., and MUhlethaler, K., Fine structures in frozenetched yeast cells. J. Cell Biol. 17(1963) 609-628. 23 Peracchia, C., Structural correlates of gap junction permeation. Int. Rev. Cytol. 66 (1980) 81-146. 24 Peracchia, C., and Dulhunty, A.F., Low resistance junctions in crayfish. Structural changes with functional uncoupling. J. Cell Biol. 70 (1976) 419-439. 25 Pfenninger, K., Akert, K., Moor, H., and Sandri, C., Freezefracturing of presynaptic membranes in the central nervous system. Phil. Trans. R. Soc. B, Lond. 261 (1971) 387. 26 Pfenninger, K., Akert, K., Moor, H., and Sandri, C., The fine structure of freeze-fractured presynaptic membranes. J. Neurocytol. 1 (1972) 129-149. 27 Robertson, J.D., The occurrence of a subunit pattern in the unit membranes of club endings in Mauthner cell synapses in goldfish brains. J. Cell Biol. 19 (1963) 201-221. 28 Sandri, C., Van Buren, J.M., and Akert, K., Membrane morphology of the vertebrate nervous system. A study with freeze-etch technique. Prog. Brain Res. 46 (1982) 1-370. Elsevier, Amsterdam. 29 Streit, P., Akert, K., Sandri, C, Livingston, R.B., and Moor, H., Dynamic ultrastructure of presynaptic membranes at nerve terminals in the spinal cord of rats. Anesthetized and unanesthetized preparations compared. Brain Res. 48 (1972) 11-26. 30 Tokunaga, A., Sandri, C., and Akert, K., Ultrastructural effects of 4-aminopyridine on the presynaptic membrane in the rat spinal cord. Brain Res. 163 (1974) 1-8. 31 Zampighi, G., and Robertson, S.D., Fine structure of the synaptic discs separated from the goldfish medulla oblongata. J. Cell Biol. 56 (1975) 92-105. 32 Zimmermann, H., Commentary: Vesicle recycling and transmitter release. Neuroscience 4 (1979) 1773 1803.

Organization of descending pathways to the spinal cord in amphibians and reptiles.

Abstract: Publisher Summary This chapter discusses the organization of descending pathways to the spinal cord in amphibians and reptiles. Non-mammalian vertebrates—such as amphibians and reptiles—show a considerable variation in form and mode of locomotion, which has remarkable repercussions in the central nervous system. In tailless amphibians, the spinal cord occupies only part of the vertebral canal. In tailed amphibians and reptiles, the cord extends throughout the vertebral column. Prior to the development of the modern tracer techniques, the descending pathways to the spinal cord could be experimentally verified by the following procedures: (1) recording the occurrence of retrograde cell changes following spinal cord hemisections and (2) studying the ensuing fiber and (pre)terminal degeneration after lesions placed in the forebrain, brain stem, or spinal cord. Reticulospinal neurons constitute the most primitive descending system involved in motor control in vertebrates. These neurons are usually large, and their coarse axons conduct rapidly and make direct connections with spinal motoneurons and interneurons in all classes from cyclostomes to mammals.

So‐called interval cancers of the breast: Pathologic and radiologic analysis of sixty‐four cases

Abstract: Within a population-based breast cancer screening programs, 209 cancers were detected by regular mammographic screening. Additionally, 66 cancers were discovered between two consecutive screenings after one, two, or three negative screening examinations (interval cancers). The study group consisted of 25,920 women who have been participating since 1975 in a breast cancer screening program in Nijmegen, the Netherlands. In this program, single view mammography (lateromedial projection) was administered as the sole screening examination every two years. Physical examination was not part of the screening program. All previous histologic and radiologic material from 64 of those "interval" patients was available and was reviewed. In 19 of the 64 patients, direct or indirect signs of tumor were seen on the previous screening mammogram on review (observers error). In four cases the site of the tumor lay outside the imaging field (technical error). In 41 cases, no signs of tumor could be seen on the mammograms even on review. By calculated tumor doubling times, 20 of these 41 cases were probably too small to be detected at the last screening ("real" interval cancers). However, 21 cases were probably large enough but were somehow masked from radiologic detection. The mean reasons for this "masking" proved to be: 1) dense breast, 2) poorly outlined tumor mass of diffuse infiltrative type, mainly invasive lobular carcinomas, and 3) intraductal localization. The authors suggest that women with dense breasts be screened more frequently, using more views and modalities and with broader criteria for advising surgical biopsy. They also note that in general the two-year interval between screenings is probably longer than the optimal interval.

Mutagenicity of urine from nurses handling cytostatic drugs, influence of smoking.

Abstract: Mutagenicity towards Salmonella typhimurium TA 100 of urine from smoking nurses, who were occupationally involved in the treatment of patients with cytostatic drugs, was significantly increased in comparison with that of smoking control subjects Mutagenicity towards Salmonella typhimurium TA 100 was not increased in exposed non-smokers when compared to control non-smokers In smoking subjects urinary mutagenicity appeared increased towards Salmonella typhimurium TA 1538 in the presence of S-9 mix Rats pretreated with Aroclor 1254 showed higher mutagenicity in their urine than untreated rats after cyclophosphamide administration Therefore, the synergistic effect of smoking might be due in part to induction of enzymes involved in the mutagenic activation of cytostatic drugs Further, the animal experiments showed that cyclophosphamide (the most frequently used mutagenic cytostatic drug) can be absorbed after oral or percutaneous administration Therefore, it is not excluded that differences in working hygiene between smokers and non-smokers also play a role

An Overview of the Organization of the Brain of Actinopterygian Fishes

Abstract: SYNOPSIS. The brain of actinopterygian fishes can be subdivided into five principal parts, rhombencephalon, cerebellum, mesencephalon, diencephalon and telencephalon, each of which contains a number of separate morphological entities: nuclei, areas or zones. Analysis of the origin and termination of the cranial nerves and their components reveals that many of the morphological entities distinguished in the actinopterygian brain can be interpreted in terms of elementary sensory and motor functions. Experimental anatomical and physiological studies on the fiber connections of the entities thus defined have led to a functional interpretation of many other parts of the brain. Thus, the central circuitry related to such sensory functions as hydrodynamic pressoreception, electroreception, vision, gustation and olfaction are well-known, and the same holds true for the motor systems related to feeding and locomotion. However, there are still many regions in the actinopterygian brain the functional significance of which is poorly understood, and it should be emphasized that most of our knowledge on the organization of the brain of this group rests merely on observations in teleosts. One of the most interesting aspects of actinopterygian neurobiology is that the telencephalon in this group develops in a way which differs fundamentally from that found in all other craniates, and that the telencephalon shows a marked progressive differentiation in the series: polypterids—chondrosteans—halecomorphs—teleosts.

Complexity of coral interactions: Influence of time, location of interaction and epifauna

Abstract: The potential role of competition for space in a community depends on the arrangement of interaction relationships. A survey (255 m2) of the interactions between corals (Scleractinia) on a Caribbean reef (depth 10–30 m) indicated the outcome of 17–35% of the aggressive and defensive interactions to be unpredictable. Experiments on the reef (depth 7–13 m) with pairs of interacting corals — Madracis mirabilis (Duchassing & Michelotti), Agaricia agaricites (L), Montastrea annularis (Ellis & Solander), Eusmilia fastigiata (Pallas) — showed that, after the initial contest through extracoelenteric digestion, there are at least two additional processes which can result in a reversal of dominance: interference by epifauna and sweeper tentacle development. Moreover, the impact of extracoelenteric digestion and the extent of sweeper tentacle development varied over the surface of the corals. Employing laboratory and field experiments to distinguish between the impact of extracoelenteric digestion, epifauna behaviour and sweeper tentacles, we show the three processes combined to explain the coral interaction process in toto. The outcome of the interaction process on the reef depends on numerous, partly unpredictable, variables, including mode of contact and effects of position. Consequently, patterns of community organization resulting from spatial competition will be slow to emerge and easily erased prematurely by disturbances.

Adrenergic mechanisms and chemoreception in the carotid body of the cat and rabbit

Abstract: 1. The effect of β-adrenergic and dopaminergic agonists and antagonists on the chemoreceptor response to graded hypoxia and hypercapnia was tested in nineteen cats and ten rabbits anaesthetized either with chloralose—urethane or pentobarbitone sodium, paralysed with pancuronium bromide and artificially ventilated. 2. The inhibitory action of dopamine was confirmed. The inhibition following intra-arterial bolus injection was blocked by haloperidol; dopamine then excited and this excitation was blocked with propranolol. Adrenaline or noradrenaline caused a transient inhibition followed by a marked excitation. The inhibition was blocked with haloperidol and the excitation blocked with propranolol or metoprolol. Isoprenaline excited without inhibition and this was blocked with propranolol or metoprolol. 3. A novel finding was that the chemoreceptor response to hypoxia was markedly reduced or even abolished with propranolol or metoprolol. The response was enhanced with a constant infusion of isoprenaline, adrenaline or noradrenaline in proportion to the degree of hypoxia, an effect mimicked by raising CO2. The chemoreceptor response to hypoxia was similarly enhanced by haloperidol and depressed by a constant infusion of dopamine in proportion to the degree of hypoxia. 4. The effect of these drugs on the chemoreceptor response to hypercapnia was less constant. In the majority of tests the aminergic agonists and antagonists caused a parallel shift of the CO2 response curves in the same direction as the O2 response curves and by amounts proportional to the degree of hypoxia. In some tests these drugs caused a change in the slope of the CO2 response curves but only if Pa, O2 was less than 60 mmHg. 5. One interpretation of these results is that hypoxia exerts a presynaptic action, causing the release of noradrenaline and dopamine from Type I cells, and that these substances act upon aminergic receptors on the sensory fibre, causing a change in potential and discharge frequency proportional to the rates of dopamine and noradrenaline release. 6. An additional or alternative interpretation is that O2 and CO2 (the latter most probably acting on intracellular pH) alter the sensitivity of the aminergic receptors to their agonists.