Showing papers by "Radboud University Nijmegen published in 1974"

The cell masses in the brain stem of the turtle Testudo hermanni; a topographical and topological analysis.

Abstract: The ventricular sulcal pattern and the cytoarchitectonic organization of the brain stem of the turtle Testudo hermanni have been studied in transversely cut, Nissl stained serial sections. Four longitudinal sulci, the sulcus medianus inferior, the sulcus intermedius ventralis, the sulcus limitans and the sulcus medianus superior could be distinguished. With the aid of the usual cytoarchitectonic criteria 54 cell groups have been delimited; 12 of these are primary efferent or motor nuclei, 13 are primary afferent or sensory centers; 10 of the nuclei distinguished are considered as belonging to the reticular formation. The remaining 19 cell masses can be indicated as “relay” nuclei. In order to provide a basis for experimental hodological work the topographical position of the nuclei is illustrated in photomicrographs of representative levels and in graphical reconstructions. In order to elucidate the morphological pattern of the cell masses and their relationship to the ventricular sulci the brain stem was subjected to a topological analysis. Essentially this method requires that (1) the cell masses are projected upon the ventricular surface and that (2) this surface, with its sulci marked on it and with the outlines of the subjacent cell masses projected upon it, is flattened out. This analysis yielded the following results: The sulcus limitans extends throughout the rhombencephalon, dividing this brain part into a basal plate and an alar plate. In the basal plate the sulcus intermedius ventralis marks the boundary between an area ventralis and an area intermedioventralis containing, respectively, the somatic motor nuclei of primary and higher order, and the visceral motor centers. Yet the terms somatic motor zone and visceral motor zone are not applicable to these two areas as a whole since both contain a number of non-motor centers. Thus the intermedioventral zone harbours two general somatic sensory centers, i.e., the spinal- and princeps nuclei of V. The medial parts of the tegmentum isthmi and of the tegmentum mesencephali contain somatic motor centers of primary and higher order, and thus may be considered rostral continuations of the rhombencephalic ventral zone. The rhombencephalic alar plate contains visceral sensory, general somatic sensory and special somatic sensory centers, but these do not show a simple ventrodorsal arrangement. A prominent feature is that the special somatic sensory nuclei of termination of VIII, the cerebellar nuclei, and a number of special somatic sensory centers of higher order together constitute a continuous zone which extends from the rhombencephalic alar plate, via the isthmus into the lateral part of the tegmentum mesencephali. In the isthmus region the sulcus limitans does not mark the ventral boundary of this zone, but rather passes over its middle.

Binocular brightness combinations: Additive and nonadditive aspects

Abstract: A conjoint measurement procedure is used for the measurement of binocular brightness as a function of left and right luminance inputs. For nonzero stimulation, the data confirm earlier findings: the system can be described as additive with a scale exponent of 1. If zero stimulation is included, however, no additive solution can be found (due to Fechner’s paradox). This fact, combined with various critical remarks in the literature with respect to the existence of a real luminance-averaging system, has led us to propose a model which takes account of Fechner’s paradox, and incorporates “realistic” exponents without requiring a multistage processing mechanism where different levels are characterized by different sensory scales. The proposed model makes the weighting coefficients for the two eyes dependent in a continuous way on the strength of stimulation in the two eyes, especially on the amount of contrast of the monocular stimuli. For zero background stimulation, contrast can be expressed in terms of luminance of the stimulus. In this way, the model is reduced to a simple testable form. While it much simpler than Engel’s (1969) model, the experimental results indicate that it might also work for the more general case.

Role of the thyroid in the development of the obese-hyperglycemic syndrome in mice (ob ob).

Abstract: Some aspects of thyroid activity in obese mice were investigated. Protein-bound iodine (PBI), hormonal iodine (HI), total thyroxin (TT4) in plasma, 131I uptake and release from the thyroid and apical cell width, and nuclear volume of the thyroid epithelial cells were determined in various age groups in obese and nonobese mice. On the basis of the results of the comparison between the obese and nonobese mice, it was concluded that the genetically obese mouse is hypothyroid. This conclusion is supported by the finding that body temperature that is low in obese mice, can be raised by thyroxin injections to normal values. An increased sensitivity for exogenous thyroxin can be shown also in the induction of liver mitochondrial α-glycerophosphate dehydrogenase. The possibility that hypothyroidism is one of the causes of the obese-hyperglycemic syndrome is discussed.

Dimensions of polar pathways through rabbit gallbladder epithelium. The effect of phloretin on nonelectrolyte permeability.

Abstract: The permeability of rabbit gallbladder to hydrophilic nonelectrolytes, with molecular weights from 20 to 60,000, has been studied. Restriction in the diffusion of the small electrolytes is very significant up to glycerol, which suggests permeation through aqueous pores with equivalent radii of 4 A. An extracellular pathway is responsible for the permeation of the larger solutes. This extracellular pathway shows no restriction in diffusion of molecules up to the size of inulin. Dextran (15,000 to 17,000 mol wt) is significantly restricted. Albumin permeability is <10−8 cm sec−1. These observations can be equated with equivalent, pore radii of ≈40 A for the shunt pathway.

The transsynaptic relationship between dopamine and serotonin in the caudate nucleus of cats.

Abstract: In order to study the relationship between dopamine (DA) and serotonin (5-HT) mechanisms in the caudate nucleus of cats, a behavioural analysis has been made of effects brought about by simultaneously or successively administered injections of DA, 5-HT, carbachol and some related compounds into the DA-sensitive caput nuclei caudati rostromedialis (CRM-area) and the 5-HT-sensitive caput nuclei caudati anteroventralis (CAV-area) in cats. The data reported here show that inhibition of the 5-HT activity in the CAV-area abolishes the effects elicited by activation of the DA mechanism in the CRM-area, and that inhibition of the DA mechanism in the CRM-area does not influence the effects elicited by inhibition of the 5-HT activity in the CAV-area. Furthermore, this study shows that inhibition of the cholinergic mechanism in the CAV-area abolishes the effects elicited by the activation of the DA mechanism in the CRM-area.

Topological analysis of the brain stem: a general introduction.

Abstract: This paper introduces a research project within the framework of which the brain stems of twelve representative vertebrates will be analysed according to a new procedure termed topological analysis. The first part reviews the development of the concept that the brain stem essentially consists of a number of longitudinal zones or columns. From this review it appears that, although during the past 80 years a considerable amount of evidence favoring this concept has been accumulated, a number of important questions pertaining to number, delimitation and content of the zones in the brain stem are still awaiting a definitive answer. The second part of this paper is devoted to a detailed description and a critical evaluation of the topological procedure. This procedure, which has been especially designed to facilitate the study of the zonal pattern of the brain stem, essentially involves two steps. First the cell masses are projected back to their site of origin at the ventricular surface, and next the ventricular surface, with its sulci and the projections of the cell masses marked upon it, is flattened out, i.e., is subjected to a one-to-one topological transformation. In the third part of this paper the choice of the species which will be studied within the framework of our program is discussed. The species selected are: the lamprey Lampetra fluviatilis, the shark Squalus acanthias, the actinopterygians Acipenser fulvescens, Lepisosteus osseus and Salmo irideus, the brachiopterygian Polypterus ornatipinnis, the lungfish Lepidosiren paradoxa, the crossopterygian Latimeria chalumnae, the amphibians Ambystoma mexicanum and Rana esculenta, the turtle Testudo hermanni, and the opossum Didelphis virginiana. In the final part the objectives of the project are discussed. Most important among these are: (1) furnishing clear and succinct analyses of the brain stems of representatives of all groups of vertebrates, (2) specification of the fundamental plan of the brain stem, (3) facilitation of the establishment of homologies and simplification of the nomenclature and (4) presentation of a sound basis for experimental hodological work.

Bio-degradation and utilization of silica and quartz.

Abstract: A mesophilic bacterium,Proteus mirabilis, which was known to be able to accumulate monomer silicate ions, a thermophilic bacterium,Bacillus caldolyticus, originating from a habitat with high silica concentrations, and a silicautilizing plant,Equisetum arvense, were all found to produce monomer silica from its polymer. The monomer silica, resulting from the mineralysis of either experimentally polymerized silica, or from quartz, is taken up byP. mirabilis cells, and also byEquisetum, which then deposits the silica again as a polymer in its stem and leaves. WithB. caldolyticus, which does not utilize the depolymerized product under the given conditions, we found that the intensity of the mineralysis depends on the growth rate of the organism.

Na-K-ATPase activity in the cochlea of the rat during development.

Abstract: The development of the Na-K-activated ATPase enzyme system was studied in the stria vascularis of rats from 6-46 days post partum. In 68-day-old animals a rather high Na-K-ATPase activity was observed. Thereafter the activity increased gradually until the 12th day. A surprisingly sharp increase of the Na-K-ATPase activity was found from 12–18 days. The adult level was reached between 19 and 25 days after birth, which coincides with the functional maturity of the cochlea. These data, together with comparable data on the development of the ERP and the ionic composition of the endolymph, confirm the assumption that the Na-K-ATPase system in the stria vascularis is responsible for the maintenance of the cation gradients and for the generation of the ERP.

Enlargement of epididymal adipocytes in relation to hyperinsulinemia in obese hyperglycemic mice (ob-ob).

Abstract: The diameters of epididymal fat cells of 12–17-day-old obese and normal littermates were compared following operative removal of the epididymal fat body. The animals were kept alive and checked for obesity at an age of 6 wk. Fat cells of the genetically obese mice began their fast growth between day 12 and day 14. At this age, it is possible to identify on the basis of fat-cell diameters three classes, representing +/+, ob/+, and ob ob , respectively, which shows that the ob allel is incompletely dominant. Measurements of the plasma-insulin concentration revealed that hyperinsulinemia, which is characteristic for the obese hyperglycemic syndrome, is not manifested before the beginning of the fourth week. Since hyperinsulinemia becomes evident at a later stage in development than the rapid increase in growth rate of the fat cells, it seems that the insulin resistance and the hyperinsulinemia cannot be the primary cause of the enlargement of the epididymal adipocytes.

Effects of apomorphine on self-stimulation behavior

Abstract: Self-stimulation behavior was studied in untreated rats and rats injected with apomorphine with electrodes implanted in the nucleus accumbens, the lateral hypothalamus, the catecholaminergic cell-groups A9–A10 and the locus coeruleus. Apomorphine (0.2 mg/kg s. c.) consistently facilitated self-stimulation in a number of rats but inhibited this behavior in others. This individual variation could be observed in all four groups of rats but was further analysed in the rats with an electrode in the A9–A10 area. The effect of the drug was highly reproducible for individual animals. Extinction after reduction of the rewarding current to zero could not be demonstrated as long as the drug was active. These results substantiate the hypothesis that apomorphine is able to replace the reinforcing action of intracranial rewarding stimulation.

SUCCESSFUL TREATMENT OF GALACTORRHOEA AND AMENORRHOEA AND SUBSEQUENT RESTORATION OF OVARIAN FUNCTION BY A NEW ERGOT ALKALOID 2-BROM-α-ERGOCRYPTINE

Abstract: SUMMARY Three patients with galactorrhoea and menstrual disturbances, due to hyperprolactinaemia and of more than 2 years duration, are described. Administration of 2-Brom-α-ergocryptine effectively lowered the plasma prolactin concentrations in all three patients and restored the normal cyclic ovarian activity. One pregnancy was noticed during therapy. The role of prolactin on ovarian function is discussed. 2-Brom-α-ergocryptine seems to be an effective drug in the long-term treatment of galactorrhoea associated with menstrual disturbances.

The neuronal organization of cerebellar lobe C1 in the mormyrid fish Gnathonemus Petersii (teleostei).

Abstract: The corpus cerebelli of mormyrid fishes is strongly developed and differentiated into four lobes: C1−C4. Although all of these lobes contain the characteristic cerebellar layers: granular, ganglionic and molecular, they show distinct architectonic differences. A previous study revealed that the ganglionic layer of C1, in addition to Purkinje elements contains conspicuous giant cells. In the present paper the results of a further analysis of C1 are reported. This analysis is based on serially sectioned brains of Gnathonemus petersii, stained according to Nissl, Bodian and Haggquist. Semi-thin sections were stained with p-phenylenediamine. Routine EM techniques were used to visualize synaptic relations. Mossy fibres and granule, Golgi, Purkinje and stellate cells are located characteristically throughout C1. It appeared that the giant cells of a previous study represent the largest elements of a population which has been termed now the eurydendroid cells. The average size of the latter is somewhat larger than that of the Purkinje cells, but both groups of cells show a considerable overlap in the size of their somata. Purkinje cells and eurydendroid cells are present throughout the ganglionic layer and both have a flattened, sagittally oriented, dendritic tree that extends into the molecular layer. Yet, the eurydendroid cells (EC) display the following characteristics which distinguish them from Purkinje cells (PC): (1) In EC the Nissl substance is dispersed diffusely throughout the soma, whereas in PC it tends to be concentrated around the nucleus, (2) The soma/nucleus ratio for EC is distinctly larger than for PC, (3) The dendritic trees of EC extend over a larger stretch of the molecular layer than those of PC, hence the term EC, (4) The dendrites of EC are more widely spaced and oriented less strictly parallel to each other than those of PC, (5) The dendrites of EC are somewhat irregular in outline and not covered with spines, in contrast to those of PC, (6) The axons of EC are oriented radially and join bundles of coarse fibres which leave the cerebellum whereas the axons of PC extend and ramify within the ganglionic layer, (7) The somata of EC, contrary to those of PC, are enveloped by a dense axonal plexus which forms numerous synaptic terminals on them. The numerical ratio of EC: PC was 1:5.5. The circuitry in C1 and the possible functional roles of its constituent neurons are discussed. It is pointed out that in this lobe the axons of PC impinge on EC and that the latter constitute its output system.