A liquid-scintillation-based primary standardization of Pb

A new radioactivity solution standard of ²¹⁰Pb has been developed and will be disseminated by the National Institute of Standards and Technology (NIST) as standard reference material (SRM) 4337. This new ²¹⁰Pb solution standard is contained in a 5 mL flame-sealed borosilicate glass ampoule, consists of (5.133±0.002) g of a nominal 1 mol L⁻¹ nitric acid solution, has a density of (1.028±0.002) g mL⁻¹ at 20 °C, has carrier ion concentrations of about 11 μg Pb²⁺ and 21 μg Bi³⁺ per gram of solution, and is certified to contain a massic activity (9.037±0.22) kBq g⁻¹ as of the reference time 1200 EST, 15 June 2006. All of the uncertainties cited above correspond to standard uncertainties multiplied by a coverage factor k=2. The standardization for the ²¹⁰Pb content of the solution was based on 4πβ liquid scintillation (LS) measurements using CIEMAT/NIST ³H-standard efficiency tracing (CNET). Confirmatory determinations were also performed by high-resolution HPGe γ-ray spectrometry, by 2π spectrometry with a Si surface barrier detector of separated ²¹⁰Po, and by 4πβ(LS)–γ(NaI) anticoincidence counting.     

Measurement of contact impedance of electrodes used for deep brain stimulation

High frequency electrical stimulation by means of electrodes implanted into the brain has become an accepted technique for treatment of Parkinson's disease. The electrical field distribution normally inserted into the sub thalamic nucleus minimise abnormal brain activity. Square wave pulses of 1–3.6 V with duration of 60–90 μs at a frequency range of 130–185 pps are generally used. Every electrode unit consists of four cylindrical electrodes positioned in a row and can be switched on independently. This paper determines the contact impedance of the electrodes for different frequencies and proposes improvement to reduce the contact impedance between the electrodes and the brain. Measurements were performed by placing the electrodes in a tank filled with saline. Different frequencies were applied on two electrodes via a resistor. The current was measured through the resistor and the voltage was registered between one of the electrodes and a third non current carrying electrode. The obtained values were used to calculate the contact impedance. The result shows large contact impedance for the used frequency compared to the impedance of the treated tissue, which means that variation in contact impedance can result in variation in the electrical field applied to the tissue.     

The Dubbelman eye model analysed by ray tracing through aspheric surfaces

Dubbelman and co-workers have determined intraocular spacings and surface shapes in living eyes by means of corrected Scheimpflug images in a large number of subjects of different age at several levels of accommodation. They give relationships for key anterior segment parameters as a function of age and level of accommodation. These are used in this paper to build a schematic eye incorporating aspheric surfaces. This eye model is analysed by means of ray tracing with a technique developed for use with a common spreadsheet computer program. The Dubbelman eye model appears to be well corrected for spherical aberration. Compared with measurements on real eyes it agrees well in general, but spherical aberration is negative, while in real eyes it tends to be positive.     

Neuronal migration and dendritic maturation of the medial cerebellar nucleus in rat embryos: an HRP in vitro study using cerebellar slabs

The morphological maturation of medial nuclear neurons of fetal rat cerebella was studied using an in vitro assay. Neurons of this nucleus were identified in isolated preparations of rhombencephalon between embryonic days 16 and 20 (E16-E20) by the intracerebellar decussation of their outgrowing axons within the uncinate fascicle. A small crystal of horseradish peroxidase (HRP) applied either in the region containing the inferior cerebellar peduncle or, preferably, in the lateral cerebellum retrogradely labeled contralateral medial nuclear neurons. In the youngest embryos (E16-E17), HRP-marked neurons were situated rostrally at the dorsal surface of the cerebellum. By E18, the cell mass containing labeled neurons had shifted in a rostrocaudal and dorsoventral direction and finally reached the adult position in E19-E20 embryos. Dendritic differentiation of these neurons followed a similar positional gradient, closely corresponding to the pattern of temporal development. From the most immature monopolar forms located dorsally to the virtually adult stellate neurons in a ventral position, it was possible to trace a continuum of intermediary forms grouped into six well-defined stages. Immature monopolar cells first became transversely bipolar. Then, they changed orientation, assuming a longitudinal radial direction. During this stage, neurons sank into the cerebellar parenchyma. As they reached their final destination, these neurons gradually developed dendrites which radiated from the cell body in an adult-like pattern. It is concluded that the medial nuclear neurons occupy a superficial dorsal position in early phases of cerebellar ontogeny, thereafter undergoing a second, inward migration. The main stages of neuronal dendritic differentiation occur between E16 and E20, indicating that the ingrowth of afferent in puts to the medial nucleus most probably occurs rather early and is concomitant with dendritic development.     

Efferent connections of the centromedian and parafascicular thalamic nuclei in the squirrel monkey: a light and electron microscopic study of the thalamostriatal projection in relation to striatal heterogeneity.

The organization of the thalamostriatal projections arising from the centromedian (CM) and parafascicular (Pf) thalamic nuclei in the squirrel monkey (Saimiri sciureus) was studied at both light and electron microscopic levels. Following selective injections of the anterograde axonal tracer Phaseolus vulgaris-leucoagglutinin (PHA-L) into the CM or Pf, patterns of terminal arborization within the striatum were compared to the biochemical heterogeneity of the striatum as revealed by immunohistochemical staining for the calcium-binding protein calbindin D-28k (CaBP), and histochemical staining for the enzymes acetylcholinesterase (AChE) and nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-diaphorase). The PHA-L-labeled axon terminals within the striatum were further analyzed at the ultrastructural level to characterize their pattern of synaptic organization. Dense and heterogeneous terminal fields occur in the "sensorimotor" territory of the striatum after CM injections, or in the "associative" striatal territory following Pf injections. In the associative territory labeled axons arborize in a diffuse manner predominantly within areas enriched with CaBP, AChE, or NADPH-diaphorase, representing the matrix compartment, and tend to avoid areas poor in these substances, corresponding to the patch/striosome compartment. In the sensorimotor territory labeled axons form bands that occupy a subregion of the NADPH-diaphorase-rich zone in the putamen. The terminal pattern of the CM-striatal projection suggests the existence of a more complex mosaic organization within the sensorimotor territory. Ultrastructural analysis of PHA-L-labeled elements within the striatum reveals that both CM and Pf projections form asymmetric synapses upon dendrites and spines of striatal cells. A total of 339 PHA-L-labeled boutons were examined after CM injections and compared to 293 boutons following Pf injections. After CM injections, 29% of PHA-L-labeled terminals form synapses on dendritic spines and 66% on dendritic shafts, whereas after Pf injections only 12% of synapses occur on dendritic spines compared to 81% on dendritic shafts. Labeled terminals forming axosomatic or axoaxonic synapses were not seen within the striatum following either CM or Pf injections. It is concluded that in the squirrel monkey: 1) Pf-striatal fibers profusely arborize within the matrix compartment of the associative territory, 2) CM-striatal fibers form bands that occupy a subregion of the NADPH-diaphorase-rich zone within the sensorimotor territory, and 3) that both Pf- and CM-striatal projections establish asymmetric synapses with dendrites and spines of medium-sized spiny cells.(ABSTRACT TRUNCATED AT 400 WORDS)     

Functional organization of mustached bat inferior colliculus: II. Connections of the FM2 region

Echolocating bats estimate target distance by analyzing the time delay between frequency-modulated portions of their emitted ultrasonic vocalizations and the resultant echoes. In the companion paper we investigated, in the central nucleus of the inferior colliculus, the representation of the predominant second-harmonic frequency-modulated component (FM2) of the mustached bat biosonar signal (O'Neill et al.: J. Comp. Neurol. 283:000-000,'89). In the present paper we report the connections of this part of the colliculus, as determined by focal, iontophoretic injections of HRP following single-unit mapping of the FM2 representation. It was found that the major inputs to the FM2 region of the inferior colliculus come from the contralateral cochlear nucleus; ipsilaterally from the medial superior olive, periolivary nuclei, and ventral and intermediate nuclei of the lateral lemniscus; and bilaterally from the lateral superior olive and dorsal nucleus of the lateral lemniscus. This study identifies for the first time those specific regions of brainstem nuclei providing input to the central nucleus of the inferior colliculus that process FM2 information in the mustached bat. The primary outputs of the FM2 region project to the medial and dorsal divisions of the medial geniculate body. In sharp contrast to other mammals, we found little evidence of connections to the ventral division of the medial geniculate. Other regions receiving significant inputs from the FM2 area include the deep superior colliculus ipsilaterally and the ipsilateral lateral pontine nuclei. Some fibers also terminated near the midline in the dorsal midbrain periaqueductal gray. Sparse intrinsic connections were also seen to the ipsilateral dorsoposterior division of the central nucleus and to the contralateral inferior colliculus at a location homologous to the injection site in the anterolateral division. The finding that FM2 projections to the medial geniculate heavily favor the medial and dorsal divisions is consistent with the location of "FM-FM" delay-dependent facilitation neurons found by Olsen (Processing of Biosonar Information by the Medical Geniculate Body of the Mustached Bat, Pteronotus parnellii. Dissertation, Washington Univ., St. Louis, '86) in these divisions, and with thalamocortical projection patterns in this species. These findings demonstrate that for the FM portions of the biosonar signal, a transformation from a tonotopic form of processing to a more specialized, convergent pattern of organization occurs at the level of the inferior colliculus outputs.     

Organization of Host Afferents to Cerebellar Grafts Implanted into Kainate Lesioned Cerebellum in Adult Rats

This paper examines the organization of host afferents within cerebellar grafts implanted into kainic acid lesioned cerebellum. Our selection of a cerebellum, a prime example of a 'point-to-point' system, permits precise determination of the degree and the specificity of host-graft interactions. One month after a cerebellar injection of kainic acid, the lesion produced can be divided into two concentric regions: (i) a central necrotic zone, totally depleted of neurons (zone 1), and (ii) a peripheral zone which lacks all Purkinje cells but preserves its cortical lamination (zone 2). Two months after the implantation of solid pieces of embryonic cerebellum, the graft has evolved into a minicerebellar structure, occupying most of zone 1. The grafted minicerebellum consists of a highly convoluted trilaminated cortex with a core containing deep nuclear neurons. Purkinje cells are positioned between the molecular and granular layer with their short and irregular dendrites branching within the former. Donor foetal Purkinje cells migrate into the contiguous portion of the molecular layer of the host zone 2. These embryonic neurons set up within the upper three-quarters of the host molecular layer, and develop monoplanar dendritic trees that span the whole width of the layer. The organization of host-graft interactions was studied by autoradiography of anterogradely transported tritiated leucine, injected in the host bulbar region containing the caudal half of the inferior olivary complex (origin of all vermal climbing fibres) and the dorsally adjacent paramedian reticular nucleus (origin of a few mossy fibres). Numerous labelled fibres cross the host-graft interface from the white matter of the host cerebellum, and provide innervation to the minicerebellar structure. The vast majority of these labelled axons terminate in the molecular layer, forming axonal arborizations that follow the shape of the Purkinje cell dendrites. The labelled climbing fibres are organized into uneven sagittally aligned strips, which mimic that of olivocerebellar projections in control rats. Only a small proportion of host labelled fibres end in the donor granular layer, forming typical mossy fibre rosettes. The latter are present in the region of the graft close to the host-graft interface. In addition, labelled axons are observed climbing over the dendritic trees of grafted Purkinje cells that have invaded a portion of the host molecular layer of zone 2. In all regions containing grafted Purkinje cells and labelled climbing fibres, the density of the innervation is close to normal with practically all Purkinje cells receiving a climbing fibre. The extensive integration of the grafted cells into the deficient neuronal networks of the host clearly illustrates the positive neurotropic effect exerted by immature cerebellar neurons on adult extracerebellar afferent fibres. The hodological integration, allowing a possible restoration of the impaired cerebellar circuitry, takes place respecting the specificity and topographic distribution which characterize the 'point-to-point' arrangement of normal cerebellar circuitry.     

Carcinoma of the alimentary canal — A statistical study based on autopsy data from 1928 to 1972

Summary An analysis of autopsy data shows that during the period 1928–1972 the relative frequency of carcinoma of the stomach has remained practically unchanged. A similar trend is apparant from the mortality statistics for Vienna from 1955 to 1972. Whereas for the lower and middle age groups there is a real decrease during the period 1928–1952, an opposite trend is visible for the highest age group. The stomach and the lower parts of the large intestine are the most frequent sites of carcinoma of the alimentary canal. The frequency distribution is explained on the basis of the contact hypothesis.     

黄雀延髓层状核的传出纤维联系──HRP法研究

向４２只黄雀的延髓展状核加压注入或微电泳泳入ＨＲＰ后，在同侧的脑桥上橄榄核、对侧的脑桥外侧丘系腹核及中脑外侧核背侧部内见到密集的顺行标记终末或纤维；在双侧的延髓巨细胞核出现了大量的逆行标记细胞；在对侧的层状核内既有密集的标记终末又有一些标记细胞．结果表明：层状核的传出纤维投射到同侧上橄榄核，经外侧丘系走行至对侧的外侧丘系腹核和中脑外侧核背侧部，双侧的层状核之间也有交互投射。此外，层状核接受耳蜗亚核──双侧巨细胞核的传入投射．因此，层状核是听觉上行通路中的第二级中继站．     

Engulfment of mast cell secretory granules on skin inflammation boosts dendritic cell migration and priming efficiency

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