Showing papers by "University of Fribourg published in 1985"

The thalamic connections with medial area 6 (supplementary motor cortex) in the monkey (macaca fascicularis)

Abstract: The interrelationship of medial area 6 (supplementary motor area) with the thalamus was investigated by means of anterograde and retrograde tracing methods. Nine monkeys were prepared for autoradiography or histochemistry with the marker HRP conjugated to the lectin wheat germ agglutinin. Three of the monkeys received injections into the precentral cortex for comparison. Previous observations were confirmed that the thalamic relays to the motor areas are organized as crescent-shaped lamellae which transgress cytoarchitectonic boundaries. The thalamic VA-VL complex receiving fibres from areas 4 and medial area 6 also sends fibres to these same areas. The thalamic relay to medial area 6 comprised the following subdivisions: VLo, VLc, area X of Olszewski, VLm and, to a smaller extent VA. Labeling (mostly anterograde only) was also prominent in some thalamic compartments outside the 'motor' thalamus: R, CL, CM-Pf, MD, LP, PULo. It was noted that rostral and caudal injections into the medial area 6 resulted in different thalamic labeling: The rostral portion was found to be related mainly with VApc, area X and VLc, the central portion with VLo, and the caudal portion with VLc/VLo. This structural inhomogeneity may reflect also a functional rostro-caudal differentiation of the medial area 6. The thalamic territory projecting to the precentral cortex is separate from the above relay and includes principally VPLo. The present anatomical labeling study is in agreement with the conclusion of Schell and Strick (1984) that the SMA, especially its central portion, is an important target of basal ganglia outflow via the thalamic relay VLo. In addition consistent labeling was also found in thalamic subdivisions (area X, VLc) which had been found to receive cerebellar fibres.

Cerebello-cortical linkage in the monkey as revealed by transcellular labeling with the lectin wheat germ agglutinin conjugated to the marker horseradish peroxidase

Abstract: 1. The possibility of a cerebellar linkage, via the thalamus with medial area 6 of the cerebral cortex was further explored in the present experiments (cf. preceding companion paper). 2. It was found that HRP conjugated to the lectin wheat germ agglutinin injected into motor cortical areas was transported beyond the thalamus to the contralateral intracerebellar nuclei when the survival time was 4–7 days. 3. It is suggested that the labeling in the deep cerebellar nuclei occurred via the thalamic relay where cerebellofugal fibre terminals had taken up the marker substance released by corticothalamic fibre terminals or by the retrogradely labeled thalamic perikarya. 4. In general, transcellular labeling of perikarya was weaker than retrograde labeling in the thalamic cells. Some of the nuclear zones in the cerebellum showed relatively dense granulations of the reaction product; in other zones only cells with few granules were seen, and large parts of the nuclei were not labeled at all. 5. The topography of secondary labeling in the cerebellar nuclei depended on the cortical injection sites. In all cases, most labeling was found in the contralateral dentate nucleus. The interposed nucleus received a fair amount of heavy labeling only in the precentral arm and face cases. Very little labeling was seen in the fastigial nucleus and in the cerebellar nuclei ipsilateral to the cortical injections. A somatotopic organization of secondary labeling was noted in the precentral cases with the face being represented caudally, the hindlimb rostrally and the arm between the face and the hindlimb representation. This is in agreement with previous anatomical and electrophysiological investigations. 6. These observations thus lend support to the conclusion that the SMA receives a transthalamic input not only from the basal ganglia but also from the cerebellum, especially from its lateral, neocerebellar portion.

Mechano- and Chemoreceptive Sensilla

Abstract: Arachnids do not have antennae, but bear most of their sensory organs on their extremities. In particular the palps and first two pairs of legs carry a variety of mechano- and chemoreceptors. The basic receptor form is represented by the sensory hair or hair sensillum. According to the mode of innervation we can distinguish two broad categories: (1) hair sensilla with dendrites ending at the hair base (mechanoreceptors), and (2) hair sensilla with dendrites that enter the hair shaft and communicate with the outside through pores in the hair wall (chemoreceptors). Other sensilla, e.g., for thermo- and hygroreception, certainly occur in arachnids but have not yet been studied systematically.

Isolation and biochemical characterization of maleic-acid hydratase, an iron-requiring hydro-lyase

Abstract: A procedure for the isolation of maleic acid hydratase (D-malate hydro-lyase, EC 4.2.1.31) of about 95% purity from rabbit kidneys is described. The enzyme consists of a single polypeptide chain of 582 amino-acid residues with an approximate molecular mass of 68 kDa. The enzyme is very unstable and has an absolute requirement for chloride ions. Addition of sodium sulphide during the purification process was essential to maintain the enzyme in an activatable state. The pure preparation has low activity but responds to activation with Fe2+ ions, Na2S and a thiol. The sequence of adding the activating reagents is critical to achieve optimal activity. Ni2+ and to a lesser extent Co2+ can replace iron in the activation process. The enzyme incorporates 4-5 mol iron/mol and 4.5-6 mol sulphide/mol during activation. In this process an [Fe-S] cluster appears to be built up, as indicated by optical and electron paramagnetic resonance (EPR) spectroscopy. In activated samples exposed to air the [Fe-S] cluster is EPR-detectable through an axial signal with g = 2.01 and g = 2.029 whose temperature and power saturation characteristics were similar to those of other [3Fe-xS] clusters. The activated enzyme, however, is readily inactivated even upon minor manipulation with destruction of the iron-sulfur core.

Influence of external factors on callose and cellulose synthesis during incubation in vitro of intact cotton fibres with [14C]sucrose

Abstract: Seed clusters, with adhering fibres, from individual locules of 36-d-old fruit capsules of Gossypium arboreum L. were fed with [14C]sucrose in vitro. The fibres synthesised, under standard conditions, (1→3)-β-D-glucan (callose) and (1→4)-β-D-glucan (cellulose) in the ratio of approx. 2:1. Under a great variety of different conditions this product ratio remained more or less constant, even when total glucan synthesis was strongly inhibited with 2,4-dinitrophenol or phloretin, or when stimulated with abscisic acid. In attempts to favour cellulose synthesis, no conditions were found where the ratio was substantially reduced. On the other hand, the ratio could be appreciably increased by inhibiting cellulose synthesis, e.g. with 2,6-dichlorobenzonitrile or coumarin, by anionic detergents such as sodium dodecyl sulphate, by low temperatures, or by increasing the osmotic strength of the incubation medium up to conditions causing plasmolysis. Specific degradation of callose, during incubation of the seed clusters, by exogenous exo-(1→3)-β-D-glucanase significantly diminished incorporation of radioactivity into cellulose.

Sensory Nerves and Peripheral Synapses

Abstract: The peripheral nervous system of arachnids is usually represented as fine extensions of the condensed central nervous system (CNS) located in the prosoma (Gerhardt and Kaestner 1938). These fiber bundles emanating from the CNS constitute the major nerves which supply the appendages and the opisthosoma. Only the leg nerves have been studied in some detail. They consist mostly of afferent fibers coming from leg receptors, and of efferent fibers innervating the leg muscles. Some of the efferent fibers belong in another category; they contain small dark granules and are considered to be neurosecretory.

β-glucanases in developing cotton (Gossypium hirsutum L.) fibres

Abstract: Cotton fibres possess several β-glucanase activities which appear to be associated with the cell wall, but which can be partially solubilised in buffers. The main activity detected was that of an exo-(1→3)-β-d-glucanase (EC 3.2.1.58) but which also had the characteristics of a β-glucosidase (EC 3.2.1.21). Endo-(1→3)-β-d-glucanase activity (EC 3.2.1.39) and much lower levels of (1→4)-β-d-glucanase activity were also detected. The exo-(1→3)-β-glucanase showed a maximum late on (40 days post-anthesis) in the development of the fibres, whereas the endo-(1→3)-β-glucanase activity remained constant throughout fibre development. The β-glucanase complex associated with the cotton-fibre cell wall also functions as a transglucosylase introducing, inter alia, (1→6)-β-glucosyl linkages into the disaccharide cellobiose to give the trisaccharide 4-O-β-gentiobiosylglucose.

Laser Flash Photolysis of Chloranil in Solution

Abstract: Chloranil (2,3,5,6-tetrachloro-2,5-cyclohexadiene-1,4-dione; C) in deoxygenated acetonitrile shows transient absorptions which are assigned to the radical anion and to the triplet 3C*. The absorption due to rises ‘instantly’ during the 12 ns laser flash and then more gradually in a time of μs. This observation is explained as electron capture from neat acetonitrile by photoexcited C taking place from both its singlet and triplet states with rate constants estimated as 109 and 104 s−1M−1, respectively.

Encoding and Retrieval Processes in Memory for Prose.

Abstract: The present study was concerned with an exploration of the relative influence of encoding and retrieval effects in memory for discourse. Memory for a passage of prose read under either of two experimenter‐provided perspectives was tested using recognition memory, and both total recall and selective recall, to the reading perspective as well as to the alternative perspective. The results show a small recognition effect for importance at reading and replicated findings of facilitation of alternative perspective information recall by cueing at the point of recall. Interactions between recall variables and perspective were interpreted in terms of a model of an extra encoding effect when the reading perspective material can be effectively integrated with the text's own perspective.

Nuclear charge radii of the even sulphur isotopes 32S, 34S, and 36S and of 31P using muonic atoms.

Abstract: Energies of muonic x rays of the Lyman series of the even sulphur isotopes /sup 32/S, /sup 34/S, and /sup 36/S and of natural phosphorus have been determined with absolute precisions up to 23 parts/10/sup 6/. Equivalent Barrett charge radii R/sub k/,..cap alpha.. have been deduced. Their differences between the sulphur isotopes amount to ..delta..R/sub k/,..cap alpha..( /sup 34/S- /sup 32/ S) = 29.7(1.4) am and ..delta..R/sub k/,..cap alpha..( /sup 36/S- /sup 34/ S) = 18.7(1.5) am. Combining these results with recent elastic electron scattering data, we obtain in a model-independent way ..delta../sup 1/2/( /sup 34/S- /sup 3/ 2S) = 23.1(1.2) am and ..delta../sup 1/2/( /sup 36/S- /sup 3/ 4S) = 13.0(1.2) am.

Nuclear polarization in muonic 90Zr.

Abstract: The energies of muonic x-ray transitions sensitive to the nuclear charge parameters have been measured with a precision up to 9 ppm in muonic /sup 90/Zr. Combining our muonic-atom results for the equivalent nuclear charge radii R/sub k/,..cap alpha.. with recent elastic electron scattering data, the rms radius of /sup 90/Zr could be determined as /sup 1/2/ = 4.2726(9) fm. In addition to the nuclear monopole charge distribution, nuclear polarization correlations between the muonic 1s and 2s and the 1s and the two 2p states could be determined. With additional constraints from elastic electron scattering and theory, the nuclear polarization corrections of the four lowest-lying states could be evaluated with precisions of the order of 15%. Of particular significance is the result for the two 2p states, because the experimentally determined 2p/sub 1/2/ correction is smaller than the nuclear polarization correction in the 2p/sub 3/2/ state, in contrast to current theoretical models.

Splenic architecture reflected in the connective tissue structure of the human spleen.

Abstract: An analysis of the connective-tissue structure of the human spleen can give us information about the basic architecture of the organ. The most important part of the spleen is the lienic center around which the subcapsular zone forms an envelope, like a mantle. This zone has but little depth and develops superficially. The tangential radial beam net (‘Tangentialbalkennetz’) is formed partly by the radial trabeculae of the capsule and partly by the outer branches of thearbor trabecularis. Thisarbor divides into 5–6 branching orders. The branches of orders 1 to 3 surround the parenchyma of the spleen center's inner layer. The lienic lobuli which are found between these branches are relatively large and are connected very extensively with their parenchyma. The branches of orders 4, 5, and 6 enclose the lienic lobuli of the outer layer of the spleen center. The splenic lobuli are defined by the vascular course. Mostly they are provided with one or two arterial influxes and, as a rule, with only one venous drain. Their mutual delimitation is more of a funcitional than of a morphological nature. This led von Herrath12, 13 to coin the term ‘functional spleen lobuli’. The lienic envelope lies between the inside of the capsule and the outermost branchings of thearbor trabecularis. Thisarbor is subdivided by the radial trabeculae, which never have any vessels, into elongated lobuli and serves first and foremost to regulate pressure. The lattice fibers are of high tensile strength and are extensions of the collagenous fibers seen at the microscopic level.