Neuropathological changes in ten cases of neuronal intermediate filament inclusion disease (NIFID):A study using α-internexin immunohistochemistry and principal components analysis (PCA)

Ten cases of neuronal intermediate filament inclusion disease (NIFID) were studied quantitatively. The α-internexin positive neurofilament inclusions (NI) were most abundant in the motor cortex and CA sectors of the hippocampus. The densities of the NI and the swollen achromatic neurons (SN) were similar in laminae II/III and V/VI but glial cell density was greater in V/VI. The density of the NI was positively correlated with the SN and the glial cells. Principal components analysis (PCA) suggested that PC1 was associated with variation in neuronal loss in the frontal/temporal lobes and PC2 with neuronal loss in the frontal lobe and NI density in the parahippocampal gyrus. The data suggest: 1) frontal and temporal lobe degeneration in NIFID is associated with the widespread formation of NI and SN, 2) NI and SN affect cortical laminae II/III and V/VI, 3) the NI and SN affect closely related neuronal populations, and 4) variations in neuronal loss and in the density of NI were the most important sources of pathological heterogeneity. © Springer-Verlag 2005.

Lobe connections and lobe crowding are associated with growth rate in the lichen Xanthoparmelia conspersa

The association between lobe connections and the degree of lobe crowding and radial growth was studied in thalli of the foliose lichen Xanthoparmelia conspersa. In 35 thalli, 15% of the lobes were not physically connected to either of their neighbours before the lobes merged into the centre of the thallus. Twenty-five percent of the lobes were connected in pairs and 29% in groups of three. Approximately 5% of the lobes were interconnected in larger groups of six or more. The mean number of lobes per group in a thallus was positively correlated with thallus diameter and with the degree of lobe growth variation but was unrelated to annual radial growth rate (RGR). The degree of crowding of the lobes in a thallus was defined as a 'crowding index', viz., the product of lobe density and mean lobe width. Crowding index increased rapidly with size in smaller thalli but changed less with size in larger thalli. Crowding index was positively correlated with RGR but was unrelated to lobe growth variation. Lobes removed from large thalli and glued in various configurations to simulate different degrees of crowding did not demonstrate an association between lobe crowding and RGR over one year. These results suggest that the pattern of lobe connectivity of a thallus is associated with lobe growth variation in X. conspersa. The degree of lobe crowding is associated with the increase in RGR with thallus size in smaller thalli and by restricting lobe width, could also be a factor associated with the more constant growth of larger thalli.

Laminar distribution of the pathological changes in the cerebral cortex in variant Creutzfeldt-Jakob disease (vCJD)

To determine the pattern of cortical degeneration in cases of variant Creutzfeldt-Jakob disease (vCJD), the laminar distribution of the vacuolation ("spongiform change"), surviving neurones, glial cell nuclei, and prion protein (PrP) deposits was studied in the frontal, parietal and temporal lobes. The vacuolation exhibited two common patterns of distribution: either the vacuoles were present throughout the cortex or a bimodal distribution was present with peaks of density in the upper and lower cortical laminae. The distribution of the surviving neurones was highly variable in different regions; the commonest pattern being a uniform distribution with cortical depth. Glial cell nuclei were distributed largely in the lower cortical laminae. The non-florid PrP deposits exhibited either a bimodal distribution or exhibited a peak of density in the upper cortex while the florid deposits were either uniformly distributed down the cortex or were present in the upper cortical laminae. In a significant proportion of areas, the density of the vacuoles was positively correlated with either the surviving neurones or with the glial cell nuclei. These results suggest similarities and differences in the laminar distributions of the pathogenic changes in vCJD compared with cases of sporadic CJD (sCJD). The laminar distribution of vacuoles was more extensive in vCJD than in sCJD whereas the distribution of the glial cell nuclei was similar in the two disorders. In addition, PrP deposits in sCJD were localised mainly in the lower cortical laminae while in vCJD, PrP deposits were either present in all laminae or restricted to the upper cortical laminae. These patterns of laminar distribution suggest that the process of cortical degeneration may be distinctly different in vCJD compared with sCJD.

Spatial patterns of the vacuolation in subcortical white matter in sporadic Creutzfeldt-Jakob disease (sCJD)

OBJECTIVE: To study the spatial patterns of the vacuolation ("spongiform change") in the subcortical white matter in the "classical" form of sporadic Creutzfeldt-Jakob disease (sCJD). MATERIAL: Frontal, parietal, occipital and temporal lobes of 11 cases of sCJD. METHOD: Spatial patterns were studied across the white matter at the base of the gyri using spatial pattern analysis. RESULTS: In the white matter of all gyri studied, vacuoles were aggregated into clusters, 50 to > 800 microm in diameter and in 22/37 (59%) of gyri, the clusters of vacuoles exhibited a regular distribution across the base of the gyri. In the remaining gyri, the vacuoles were aggregated into large clusters, at least 400 microm or 800 microm in diameter, but without evidence of a regular distribution. In a significant proportion of gyri, the spatial patterns of the vacuolation were similar to those reported previously for spongiform change and prion protein (PrP) deposits in the corresponding grey matter. CONCLUSIONS: Degeneration of the white matter and the formation of clusters of vacuoles may occur before the degeneration of the grey matter or could be a consequence of pathology affecting the cortico-cortical pathways.

Experimental studies of lobe growth in the lichen Parmelia conspersa (Ehrh. Ex Ach.) Ach.

The radial growth of individual lobes of the foliose lichen, Parmelia conspersa (Ehrh. Ex Ach.) Ach. was studied to determine whether (1) adjacent lobes exchange carbohydrate and (2) marginal competition between lobes influences radial growth. In a survey of thalli of different size, the number of marginal lobes was linearly related to thallus circumference. However, the relationship between mean lobe width and thallus circumference was fitted by a second order polynomial. Hence, mean lobe width may reach a maximum in thalli approx. 3 cm in diameter. The interactions between marginal lobes were studied by either painting single lobes with acrylic paint or by removing lobes from the thallus. Painting the whole lobe virtually stopped its radial growth while partially painted lobes grew less than control lobes. The radial growth of a lobe was unaffected by either completely painting or removing its neighbour. Removal of both neighbouring lobes did not influence the radial growth of a lobe but severing the lobe from the thallus reduced its radial growth. In addition, lobe width increased significantly when both neighbouring lobes were removed. These results suggest that adjacent lobes have a considerable degree of independence and that there is little exchange of carbohydrate between them. In addition, marginal competition between adjacent lobes may restrict the lateral extension of the lobe and this may maintain a more constant mean lobe width in larger thalli. It is possible that the intensity of marginal competition between adjacent lobes may vary with thallus size and this could be a factor determining the growth curve of a foliose lichen throughout its life.

A general linear model for MEG beamformer imaging

A new general linear model (GLM) beamformer method is described for processing magnetoencephalography (MEG) data. A standard nonlinear beamformer is used to determine the time course of neuronal activation for each point in a predefined source space. A Hilbert transform gives the envelope of oscillatory activity at each location in any chosen frequency band (not necessary in the case of sustained (DC) fields), enabling the general linear model to be applied and a volumetric T statistic image to be determined. The new method is illustrated by a two-source simulation (sustained field and 20 Hz) and is shown to provide accurate localization. The method is also shown to locate accurately the increasing and decreasing gamma activities to the temporal and frontal lobes, respectively, in the case of a scintillating scotoma. The new method brings the advantages of the general linear model to the analysis of MEG data and should prove useful for the localization of changing patterns of activity across all frequency ranges including DC (sustained fields). © 2004 Elsevier Inc. All rights reserved.

Lobe growth in foliose lichen thalli

The margins of foliose lichen thalli comprise individual lobes which grow radially and divide. This results in a complex marginal structure in which lobes differing in morphology, state of division, and growth pattern are crowded together. Various aspects of the biology of these lobes are reviewed including their carbohydrate supply, morphology, pattern of division and branching, the effect of lobe overcrowding and interactions between neighbouring lobes. As the thalus grows, lobes become increasingly crowded together and this restricts further lateral growth. Restriction of lobe width may be reponsible for the changes in radial growth rate (RGR) with size observed in foliose species. Various aspects of lobe biology may be responsible for lobe growth variation including the physical independence of lobes from their neighbours, the genetic origin of the lobes, and the pattern of lobe branching. Overall symmetry of a thallus is maintained by a fluctuating pattern of growth of individual lobes in successive months together with competition for space at the margin

Experimental and theoretical characterisation of tunable fibre gratings

This thesis presents details on both theoretical and experimental aspects of UV written fibre gratings. The main body of the thesis deals with the design, fabrication and testing of telecommunication optical fibre grating devices, but also an accurate theoretical analysis of intra-core fibre gratings is presented. Since more than a decade, fibre gratings have been extensively used in the telecommunication field (as filters, dispersion compensators, and add/drop multiplexers for instance). Gratings for telecommunication should conform to very high fabrication standards as the presence of any imperfection raises the noise level in the transmission system compromising its ability of transmitting intelligible sequence of bits to the receiver. Strong side lobes suppression and high and sharp reflection profile are then necessary characteristics. A fundamental part of the theoretical and experimental work reported in this thesis is about apodisation. The physical principle of apodisation is introduced and a number of apodisation techniques, experimental results and numerical optimisation of the shading functions and all the practical parameters involved in the fabrication are detailed. The measurement of chromatic dispersion in fibres and FBGs is detailed and an estimation of its accuracy is given. An overview on the possible methods that can be implemented for the fabrication of tunable fibre gratings is given before detailing a new dispersion compensator device based on the action of a distributed strain onto a linearly chirped FBG. It is shown that tuning of second and third order dispersion of the grating can be obtained by the use of a specially designed multipoint bending rig. Experiments on the recompression of optical pulses travelling long distances are detailed for 10 Gb/s and 40 Gb/s. The characterisation of a new kind of double section LPG fabricated on a metal-clad coated fibre is reported. The fabrication of the device is made easier by directly writing the grating through the metal coating. This device may be used to overcome the recoating problems associated with standard LPGs written in step-index fibre. Also, it can be used as a sensor for simultaneous measurements of temperature and surrounding medium refractive index.

Seasonal growth and growth rate-colony size relationships in six species of saxicolous lichens

The pattern of seasonal growth and the relation of growth rate to colony size were studied in four foliose and two crustose species of saxicolous lichens. A new method of measuring growth was used whereby the advance of a sample of lobes along millimetres marked on the substrate was measured under a magnification of x10. Three peaks of growth were found(in March, June and November) for the foliose species and a single peak (in May to August) for the crustose species. THe peaks of growth corresponded approximately to peaks of rainfall. Growth rate in relation to increasing colony size fell in a smooth exponential curve when expressed on a cm squared/ cm squared/ unit time basis. The result is consistent with a linear radial rate for most of the thallus sizes for the six species. There is also evidence for an exponential incresae in growth rate initially until about 1.5 cm thallus diameter in two of the sepcies when the linear radial rate is achieved.

Factors associated with lobe division in the lichen Parmelia conspersa (Ehrh. ex. Ach.)Ach.

The factors associated with lobe division were studied in thalli of the lichen Parmelia conspersa (Ehrh. ex Ach.)Ach. Lobe division was studied in sequences of adjacent lobes using spatial pattern analysis. In five large thalli, lobe division within the thallus margin was randomly distributed. Correlations between the degree of lobe division, the radial growth of the lobe and lobe morphology were studied in six thalli. Lobe division was positively correlated with either lobe width or area in four thalli. Correlations were observed with radial growth or morphology of the adjacent lobes in two thalli. Dividing and non-dividing lobes were removed from large thalli and glued to pieces of slate with their tips either at the same level or in front of neighbouring lobes. Dividing lobes divided more rapidly when their tips were glued in front of their neighbours. The levels of ribitol, arabitol and mannitol were measured within a 2 mm region of the tip in dividing and non-dividing lobes on four occasions in 1994. Carbohydrate levels were significantly increased in dividing compared with non-dividing lobes. In addition, the mean size of the algal cells was greater in non-dividing compared with dividing lobes especially at the lobe base. However, the percentage of zoosporangia and aplanosporangia did not vary significantly in dividing and non-dividing lobes. These results suggest that: 1) the pattern of lobe division within the thallus margin may be random, 2) lobe division may be determined by lobe size and the location of the lobe tip relative to the neighbouring lobes and 3) there may be an increase in the productivity of lobes associated with lobe division.

Does radial growth of the lichen Parmelia conspersa depend exclusively on growth processes at the lobe tip?

The objective of this study was to test the hypothesis that the radial growth of lobes of the lichen Parmelia conspersa depends largely on growth processes which occur at the lobe tip. First, individual lobes were removed from thalli and portions of the lobe removed to within various distances from the tip. Radial growth of the lobe was unaffected until less than 2 mm of the lobe tip remained. Second, the surfaces of individual lobes were painted with acrylic paint leaving different portions of the lobe exposed. Painting lobes to within 0.5 mm and 1 mm of the tip substantially reduced radial growth. Third, the levels of ribitol, arabitol and mannitol were measured in different regions behind the lobe tip on four occasions during 1994. The concentration of the three carbohydrates was greatest at the lobe tip and the levels declined linearly with distance from the tip. Fourth, painting one vertical half of the lobe tip did not affect radial growth but artificially bisecting the lobe tip with a scalpel reduced radial growth. Although transport of carbohydrate from other regions of the lobe cannot be ruled out, the results support the hypothesis that radial growth in P. conspersa depends largely on processes within a region approximately 2 mm behind the lobe tip.

Are metal ions accumulated by saxicolous lichens growing in a rural environment?

The levels of Mn, Cu, zn, Mg and Ca were measured in the lichens Xanthoparmelia conspersa (Ach.) Hale and Parmelia glabratula ssp. fuliginosa (Fr. ex Duby): Laund. growing on a steep slate rock surface in south Gwynedd, Wales, UK. The objective was to test the following hypotheses: 1) that foliose lichens growing in a rural environment concentrate metal ions relative to the substratum, 2) that the concentration of metal ions increases significantly with thallus size and 3) that individual ions accumulate preferentially either in the marginal lobes or thallus centre. Mg and Ca were present in rainfall whereas all ions were present in rock surface runoff and in the substratum. Levels of Mn, Mg and Ca were increased in runoff collected from the bottom compared with the top of the rock surface. In P. glabratula ssp. fuliginosa thalli, ions were present as follows, Mg > Ca=Mn=Zn>Cu, and there were no significant differences in thalli collected from the top and bottom of the rock surface. With the exception of Mg and Ca, ion levels in thalli were similar to or less than those in the substratum. The levels of Ca, Cu and Zn were similar in thalli from under 1 to over 4 cm in diameter. However, the level of Mg increased with thallus size in X. conspersa while the level of Mn decreased with thallus size in both species. Ion levels were similar in the marginal lobes and centres of large diameter (over 4 cm) and small diameter (under 2 cm) X. conspersa thalli. With the exception of Mg, there was no evidence for a significant accumulation of ions relative to the substratum or with thallus size. In addition, there was no evidence to suggest preferential accumulation of ions either in the thallus centre or marginal lobes.

Factors associated with degeneration of the thallus centre in foliose lichens

Degeneration of the older parts of foliose lichen thalli often lead to the formation of a space or 'window' in the centre of the colonies. The percentage of thalli of different size which exhibited 'windows' was studied in twenty saxicolous lichen populations in south Gwynedd, Wales. The proportion of thalli with 'windows' increased with thallus size. The size class at which 50% and 100% of thalli exhibited 'windows' varied between populations. Differences between populations were not correlated with distance from the sea, aspect, slope or porosity of the substrate or the total number of lichen species present. However, a higher percentage of smaller thalli had 'windows' on rock surfaces with a greater lichen cover. There were no significant differences in the levels of Ca, Mg, Cu or Zn in large (>4 cm) and small (<2 cm) Parmelia conspersa (Ehrh. ex Ach.) Ach. thalli or in the centres and marginal lobes of these thalli. The concentration of ribitol, arabitol and mannitol was significantly reduced in the centre of large thalli compared with the margin of large thalli and the centre of small thalli. However, carbohydrate levels were similar in the centre of large thalli and the margin of small thalli. The data suggest that loss of the thallus centre is a degenerative process related to thallus size. In the field, the formation of 'windows' may be related to the intensity of competition on a substrate. Central degeneration was not associated with a deficiency or an accumulation of Ca, Mg, Cu and Zn in the thallus centre. However, degeneration may be associated with a reduction in carbohydrates in the centre compared with the marginal lobes.

Factors determining the growth curve of the foliose lichen Parmelia conspersa

Growth curves of the foliose lichen Parmelia conspersa (Ehrh. Ex Ach.)Ach. Were obtained by plotting radial growth (RGR, mm yr-1) of the fastest measured lobe, the slowest measured lobe, a randomly selected lobe, and by averaging a sample of lobes from each thallus against thallus diameter. Growth curves derived from the fastest-growing lobe and by averaging lobes were asymptotic and could be fitted by the growth model of Aplin and Hill. Mean lobe width increased with thallus size, reaching a maximum at approx. 4.5 cm thallus diameter. In four out of six thalli, radial growth of lobes over four months was positively correlated with initial lobe width or area. The RGR of isolated lobes was unaffected until the base of the lobe was removed to within 1-2 mm of the tip. The concentration (micrograms mg-1 biomass) of ribitol, arabitol and mannitol was greater in the marginal lobes of large than in small thalli. The results suggested that the growth curve of P. conspersa is determined by processes that occur within individual marginal lobes and can be explained by the Aplin and Hill model. Changes in lobe width and in the productive capacity of individual lobes with thallus size are likely to be more important factors than the degree of translocation within the lobe in determining the growth curve.

Dispersal of soredia from individual soralia of the lichen Hypogymnia physodes (L.) Nyl. in a simple wind tunnel

Dispersal of soredia from individual soralia of the lichen Hypogymnia physodes (L.) Nyl. was studied using a simple wind tunnel constructed in the field. Individual lobes with terminal soralia were placed in the wind tunnel on the adhesive surface of dust particle collectors. Air currents produced by a fan were directed over the surface of the lobes. The majority of soredia were deposited within 5 cm of the source soralium but some soredia were dispersed to at least 80 cm at a wind speed of 6 m s-1. Variation in wind speed had no statistically significant effect on the total number of soredial clusters deposited averaged over soralia but the mean size of cluster and the distance dispersed were greater at higher wind speeds. The number of soredia deposited was dependent on the orientation of the soralium to the air currents. More soredia were deposited with the soralium facing the fan at a wind speed of 9 m s-1. Moisture in the form of a fine mist reduced substantially the number of soredia deposited at a wind speed of 6 m s-1 but had no effect on the mean number of soredia per cluster or on the mean distance dispersed. The data suggest: (1) that wind dispersal from an individual soralium is influenced by wind speed, the location of the soralium on the thallus and the level of moisture and (2) that air currents directed over the surfaces of thalli located on the upper branches of trees would effectively disperse soredia of H. physodes vertically and horizontally within a tree canopy. © 1994.