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PubMed2002

PIXE micro-beam mapping of metals in human peri-implant tissues.

Previous investigations did not agree about the possible presence of titanium and other metals in the tissues around endosteal dental implants and joint prostheses. Indeed, while some authors reported diffusion of metals into the tissues, some others did not find evidence of this phenomenon. In the present study, four dental titanium implants, removed with the surrounding tissues from patients at various time intervals after the insertion, were studied by means of the micro-beam proton-induced X-ray emission (PIXE micro-beam) technique, which draws maps showing the tissue distribution of elements with a detection limit of about 1 ppm. One implant was built in commercially pure titanium, two others in titanium coated with titanium plasma spray, and the fourth in Ti-Al-V alloy. Their composition was confirmed by the PIXE micro-beam analyses. The removed samples were embedded in epoxy and processed with a cutting-grinding appliance, mounted on plastic holders, and ground up to a thickness of about 35 microm. Optical microscope examinations were also carried out, to compare the optical findings with the elemental maps obtained with the PIXE micro-beam. One implant, removed after 70 days because the patient had developed peri-implantitis, had some inflammatory soft tissue attached, with no evidence of metal leakage. The other three implants had been removed after 6, 7 and 9 years of valid clinical service, because of the fracture of the prosthetic abutment or the implant stem. At the optical microscope, all these fixtures were embedded in mature bone. The elemental maps indicated small titanium deposits in about 5% of the bone bordering the implants, while aluminum, when present in the fixture, leaked diffusely into the surrounding bone and vanadium was not found in the tissues. These results suggest that titanium may be found occasionally in peri-implantar tissues, but has very little tendency to spread, while the presence of aluminum in the implant alloy may cause an important leakage of this metal.

Journal Article↗
PubMed1997

Genetic refinement of dominant optic atrophy (OPA1) locus to within a 2 cM interval of chromosome 3q.

Autosomal dominant optic atrophy (OPA, MIM 165500) is an eye disease characterised by variable optic atrophy and reduction in visual acuity. It has an insidious onset in the first decade of life and is clinically highly heterogeneous. It is associated with a centrocecal scotoma of varying size and density and an acquired blue-yellow dyschromatopsia. Recent studies of three large Danish pedigrees have mapped a gene for dominant optic atrophy (OPA1) to a 10 cM region on chromosome 3q, between markers D3S1314 and D3S1265 (3q28-qter). Genetic linkage analysis in five British pedigrees confirms mapping to chromosome 3q28-qter. Haplotype analysis of a seven generation pedigree positions the disease causing gene between loci D3S3590 and D3S1305, corresponding to a genetic distance of 2 cM. This represents a significant linkage refinement and should facilitate positional cloning of the disease gene.

Adolescent↗
PubMed2001

Noncontact quantitative spatial mapping of stress and flexural rigidity in thin membranes using a picosecond transient grating photoacoustic technique.

This paper describes a purely optical technique for measuring and spatially mapping out stress and rigidity in thin membranes. Its application to a membrane of aluminum nitride that has significant spatial nonuniformities in its elastic properties demonstrates the method. The attractive features of this technique--fast, noncontacting measurement, good spatial resolution, ability to quantify in-plane anisotropy--make it potentially useful for characterizing elements of microelectromechanical structures, masks for advanced lithography systems, acoustic filters, and other devices in which the mechanical properties of membranes are important.

Journal Article↗
PubMed2002

No ON-OFF maps in supragranular layers of ferret visual cortex.

Primary visual cortex contains functional maps of a number of stimulus properties including ocular dominance, orientation, direction, color, and spatial frequency. These maps must be organized with respect to each other and to a single continuous retinotopic map of visual space such that each stimulus parameter is represented at each point in space. In the ferret, geniculo-cortical inputs to cortical layer IV are segregated into ON- and OFF-center patches, suggesting the possibility that there might be an additional cortical map in this species. We have used optical imaging of intrinsic signals to search for ON-OFF maps in ferret visual cortical cells and have found none. This suggests that the high degree of ON-OFF segregation seen subcortically in the ferret may play a role in the development of visual cortical receptive fields rather than in adult cortical function.

Aminobutyrates↗
PubMed2002

Reduction of intraocular pressure and glaucoma progression: results from the Early Manifest Glaucoma Trial.

OBJECTIVE: To provide the results of the Early Manifest Glaucoma Trial, which compared the effect of immediately lowering the intraocular pressure (IOP), vs no treatment or later treatment, on the progression of newly detected open-angle glaucoma. DESIGN: Randomized clinical trial. PARTICIPANTS: Two hundred fifty-five patients aged 50 to 80 years (median, 68 years) with early glaucoma, visual field defects (median mean deviation, -4 dB), and a median IOP of 20 mm Hg, mainly identified through a population screening. Patients with an IOP greater than 30 mm Hg or advanced visual field loss were ineligible. INTERVENTIONS: Patients were randomized to either laser trabeculoplasty plus topical betaxolol hydrochloride (n = 129) or no initial treatment (n = 126). Study visits included Humphrey Full Threshold 30-2 visual field tests and tonometry every 3 months, and optic disc photography every 6 months. Decisions regarding treatment were made jointly with the patient when progression occurred and thereafter. MAIN OUTCOME MEASURES: Glaucoma progression was defined by specific visual field and optic disc outcomes. Criteria for perimetric progression were computer based and defined as the same 3 or more test point locations showing significant deterioration from baseline in glaucoma change probability maps from 3 consecutive tests. Optic disc progression was determined by masked graders using flicker chronoscopy plus side-by-side photogradings. RESULTS: After a median follow-up period of 6 years (range, 51-102 months), retention was excellent, with only 6 patients lost to follow-up for reasons other than death. On average, treatment reduced the IOP by 5.1 mm Hg or 25%, a reduction maintained throughout follow-up. Progression was less frequent in the treatment group (58/129; 45%) than in controls (78/126; 62%) (P =.007) and occurred significantly later in treated patients. Treatment effects were also evident when stratifying patients by median IOP, mean deviation, and age as well as exfoliation status. Although patients reported few systemic or ocular conditions, increases in clinical nuclear lens opacity gradings were associated with treatment (P =.002). CONCLUSIONS: The Early Manifest Glaucoma Trial is the first adequately powered randomized trial with an untreated control arm to evaluate the effects of IOP reduction in patients with open-angle glaucoma who have elevated and normal IOP. Its intent-to-treat analysis showed considerable beneficial effects of treatment that significantly delayed progression. Whereas progression varied across patient categories, treatment effects were present in both older and younger patients, high- and normal-tension glaucoma, and eyes with less and greater visual field loss.

Adrenergic beta-Antagonists↗
PubMed2002

Optical imaging of intrinsic signals in somatosensory cortex.

The methods of optical intrinsic signal (OIS) imaging and microelectrode mapping of single neuron receptive fields (RFs) were used in combination (in the same squirrel monkey or cat) to characterize the spatial and temporal attributes of the response of contralateral SI cortex to cutaneous flutter stimulation. A change in the location of the stimulated skin site was accompanied by a shift in the locus of the SI optical response. The spatial ordering of the optical responses to independent stimulation of each site in an array of skin sites was consistent with the features of SI topographical organization described in published RF mapping studies. While the single neuron RF mapping observations and the optical response obtained at a given time after onset of flutter stimulation always were positively correlated, the degree of correlation improved progressively with time after stimulus onset (the longest stimulus duration used was 10 s). Analysis of the temporal development of the optical response to cutaneous flutter stimulation revealed that not only does absorbance increase to attain a maximum in the SI region which receives its main input from the stimulated skin site, but at the same time absorbance declines to below-background values in an extensive region of surrounding cortex. The results are interpreted to indicate that the pattern of SI activity evoked by a cutaneous flutter stimulus exhibits increasing spatial contrast (becomes progressively more distinguishable from the activity of surrounding cortex) over periods of continuous stimulation at least as long as 10 s. This time-dependent 'funneling' of the SI spatial activity pattern is proposed to underlie the prominent enhancement of human spatial discriminative capacity which occurs (e.g. Physiol. Behav. 5 (1970) 1431) when oscillatory tactile stimuli are used.

Animals↗
PubMed1990

Intraocular pressure effects on optic nerve-head oxidative metabolism measured in vivo.

The effects of acute intraocular pressure (IOP) on the reduction/oxidation ratio of cytochrome a, a3 were measured from intact cat optic nerve by microfiber reflection spectrophotometry. This enabled the real-time analysis of optic nerve-head oxidative metabolism following IOP or mean arterial pressure (MAP) changes. Findings included: (1) cytochrome a, a3 became more reduced and relative blood volume decreased at lower perfusion pressures, even at IOP of less than 20 mm Hg; (2) metabolic inhibition began at variable perfusion pressures but invariably progressed as perfusion pressure declined; and (3) increased IOP or decreased MAP caused metabolic inhibition. These findings demonstrate that: (1) optic nerve metabolic dysfunction is possible at low IOPs; (2) lowering IOP can reverse metabolic dysfunction; (3) the metabolic response is dependent on IOP and/or MAP changes; and (4) the metabolic inhibition is related to optic nerve ischemia.

Animals↗
PubMed2003

Optical aberrations of intraocular lenses measured in vivo and in vitro.

Corneal and ocular aberrations were measured in a group of eyes before and after cataract surgery with spherical intraocular lens (IOL) implantation by use of well-tested techniques developed in our laboratory. By subtraction of corneal from total aberration maps, we also estimated the optical quality of the intraocular lens in vivo. We found that aberrations in pseudophakic eyes are not significantly different from aberrations in eyes before cataract surgery or from previously reported aberrations in healthy eyes of the same age. However, aberrations in pseudophakic eyes are significantly higher than in young eyes. We found a slight increase of corneal aberrations after surgery. The aberrations of the IOL and the lack of balance of the corneal spherical aberrations by the spherical aberrations of the intraocular lens also degraded the optical quality in pseudophakic eyes. We also measured the aberrations of the IOL in vitro, using an eye cell model, and simulated the aberrations of the IOL on the basis of the IOL's physical parameters. We found a good agreement among in vivo, in vitro, and simulated measures of spherical aberration: Unlike the spherical aberration of the young crystalline lens, which tends to be negative, the spherical aberration of the IOL is positive and increases with lens power. Computer simulations and in vitro measurements show that tilts and decentrations might be contributors to the increased third-order aberrations in vivo in comparison with in vitro measurements.

Aged↗
PubMed2006

An optically driven pump for microfluidics.

We demonstrate a method for generating flow within a microfluidic channel using an optically driven pump. The pump consists of two counter rotating birefringent vaterite particles trapped within a microfluidic channel and driven using optical tweezers. The transfer of spin angular momentum from a circularly polarised laser beam rotates the particles at up to 10 Hz. We show that the pump is able to displace fluid in microchannels, with flow rates of up to 200 microm(3) s(-1) (200 fL s(-1)). The direction of fluid pumping can be reversed by altering the sense of the rotation of the vaterite beads. We also incorporate a novel optical sensing method, based upon an additional probe particle, trapped within separate optical tweezers, enabling us to map the magnitude and direction of fluid flow within the channel. The techniques described in the paper have potential to be extended to drive an integrated lab-on-chip device, where pumping, flow measurement and optical sensing could all be achieved by structuring a single laser beam.

Microfluidic Analytical Techniques↗
PubMed2004

Functional segregation of plural regions representing cardinal contours in cat primary visual cortex.

Our previous data based on an imaging study suggested that, in cat area 17, the representations of cardinal orientations overlap less than the representation of their nearby angles. The purpose of this study was to further investigate the underlying single-cell properties. Optical imaging was performed first to map the cortical regions corresponding to the four principal contours, the two cardinals and the two obliques. The cortical region activated by a principal orientation but not by the +10 degrees or -10 degrees neighbouring angles, namely the area with optically relative independent orientation selectivity (RIOS), was mapped together with the regions that overlapped with the +10 degrees and/or -10 degrees neighbouring angles (non-RIOS). Electrode penetrations were targeted to the RIOS and non-RIOS regions in each of the four orientations. A comparison between the RIOS and the non-RIOS regions documented a significantly higher percentage of cells with the orientation preference of the cardinal orientations in the cardinal RIOS region than that seen in the other regions. Additionally, the difference in the tuning width of cells between the RIOS and non-RIOS in the cardinal region was significantly larger than the difference between the RIOS and non-RIOS in the oblique region. The cells in the cardinal RIOS region were tuned more sharply and the cells in cardinal non-RIOS region more broadly than the oblique RIOS and/or the non-RIOS region, which showed no significant difference. These data strongly suggest the existence of functional segregation in the region corresponding to the cardinal contours.

Animals↗
PubMed2004

Serial magnetization transfer imaging in acute optic neuritis.

In serial studies of multiple sclerosis lesions, reductions in magnetization transfer ratio (MTR) are thought to be due to demyelination and axonal loss, with later rises due to remyelination. This study followed serial changes in MTR in acute optic neuritis in combination with clinical and electrophysiological measurements to determine if the MTR changes over time mirror the picture in multiple sclerosis lesions, further validating MTR as a marker of tissue integrity. Twenty-nine patients were recruited who had acute optic neuritis for a median of 13 days (range 7-24 days) since the onset of visual symptoms. A clinical examination and measurement of visual evoked potentials (VEP) was performed on each patient. Their optic nerves were imaged with a fat-saturated fast spin echo (FSE) sequence and a magnetization transfer sequence. Twenty-one had multiple subsequent examinations over the course of 1 year. In addition, 27 control subjects had their optic nerves imaged up to three times over 1 year. A blinded observer segmented the optic nerves from the MTR maps. Lesions were defined on the acute FSE images and, from the coordinates, the ratio of mean lesion MTR : healthy nerve MTR (lesion ratio) was calculated for each dataset. The time-averaged mean MTR in control optic nerves was 47.7 per cent units (pu). In diseased optic nerves, baseline mean MTR was 47.3 pu, with a mean lesion ratio of 0.98. The diseased optic nerve MTR and lesion ratio declined over time with a nadir at about 240 days at a mean MTR value of 44.2 pu and mean lesion ratio of 0.91. Subsequently, diseased optic nerve MTR appeared to rise; after 1 year the diseased optic nerve mean MTR was 45.1 pu (mean lesion ratio 0.93), although the difference was not significant compared with the nadir value. For each 0.01 increase in time-averaged lesion ratio logMAR visual acuity recovery improved by 0.03 (95% CI, 0.002, 0.08, P = 0.02). Time-averaged VEP central field latency was shorter by 6.1 ms (95% CI 1.5, 10.7, P = 0.012) per 1 pu rise in time-averaged diseased optic nerve MTR. The early fall in diseased optic nerve MTR is consistent with demyelination and Wallerian degeneration of transected axons. The late nadir compared with studies of multiple sclerosis lesions may have been due to slow clearance of myelin debris. Remyelination may have influenced subsequent MTR changes. The observations support using MTR to monitor symptomatic demyelinating lesions.

Acute Disease↗
PubMed2003

Processing deficits in primary visual cortex of amblyopic cats.

Early esotropic squint frequently results in permanent visual deficits in one eye, referred to as strabismic amblyopia. The neurophysiological substrate corresponding to these deficits is still a matter of investigation. Electrophysiological evidence is available for disturbed neuronal interactions in both V1 and higher cortical areas. In this study, we investigated the modulation of responses in cat V1 to gratings at different orientations and spatial frequencies (SFs; 0.1-2.0 cycles/degrees) with optical imaging of intrinsic signals. Maps evoked by both eyes were well modulated at most spatial frequencies. The layout of the maps resembled that of normal cats, and iso-orientation domains tended to cross adjacent ocular dominance borders preferentially at right angles. Visually evoked potentials (VEPs) were recorded at SFs ranging from 0.1 to 3.5 cycles/degrees and revealed a consistently weaker eye for the majority of squinting cats. At each SF, interocular differences in VEP amplitudes corresponded well with differences in orientation response and selectivity in the maps. At 0.7-1.3 cycles/ degrees, population orientation selectivity was significantly lower for the weaker eye in cats with VEP differences compared with those with no VEP amplitude differences. In addition, the cutoff SF, above which gratings no longer induced orientation maps, was lower for the weaker eye (> or =1.0 cycles/degrees). These data reveal a close correlation between the loss of visual acuity in amblyopia as assessed by VEPs and the modulation of neuronal activation as seen by optical imaging of intrinsic signals. Furthermore, the results indicate that amblyopia is associated with altered intracortical processing already in V1.

Amblyopia↗
PubMed2005

Component spatial pattern analysis of chemicals by use of two-dimensional electro-optic terahertz imaging.

We demonstrate a method of chemical mapping by using the transillumination terahertz (THz) images obtained by two-dimensional electro-optic THz imaging. The images and spectral data were measured between 0.1 and 1.0 THz. An experimental sample consisting of three chemicals was prepared, with one in two concentrations. By introducing the component spatial pattern analysis based on the least-squares method, the chemical composition, spatial distribution, and difference in concentration were clearly determined.

Journal Article↗
PubMed1993

Partial cloning of a squid microtubule-associated protein (MAP H1) and the identification of the microtubule binding domain.

An approximately 420-kDa ATP binding protein, referred to as MAP H1, has previously been shown to be involved in microtubule-dependent vesicle motility in the squid giant axon. To gain further insight into the structure and function of this protein, partially overlapping cDNA clones encoding approximately a quarter of the MAP H1 molecule were identified from two squid optic lobe libraries using affinity-purified antibodies to squid MAP H1. One clone in particular (KS18), which hybridizes to an approximately 13-kb message, encodes a series of almost identical repeats of a 16-amino-acid sequence that is tandemly repeated. The sequence of clone KS18 is unique and does not correspond to any nucleotide or amino acid sequence in the data base. The presence of repeated elements within the microtubule binding domain of several other MAPs prompted us to investigate whether the MAP H1 repeats are involved in microtubule binding. In-vitro-synthesized polypeptides containing these repeats sediment with taxol-stabilized microtubules in a microtubule binding assay. The predicted secondary structure of the 16-amino-acid repeat region of MAP H1 contains alternating beta-sheets and turns and could form the globular domain seen in negative-stain electron micrographs of MAP H1.

Amino Acid Sequence↗
PubMed1986

Retinotopic and chronotopic organization of goldfish retinal ganglion cell axons throughout the optic nerve.

The organization of the retinal ganglion cell (RGC) axons within the goldfish optic nerve head and optic nerve was established by labeling select groups of axons either autoradiographically or with cobaltous lysine. In the optic nerve head, the axons are organized eccentrically with respect to their time of development. Axons of older RGCs are located dorsally and those of younger RGCs are located ventrally. The retinal sectors map across the rostrocaudal axis of the optic nerve head, resulting in four dorsoventrally oriented columns that contain, from rostral to caudal, the axons of ventronasal, dorsonasal, dorsotemporal, and ventrotemporal RGCs. Thus, the optic nerve head is organized into orthogonally oriented laminae. One dimension maps the age of the axons and the other maps the retinal sector of the axons' origin. The optic nerve is organized virtually in the same fashion as the optic nerve head. However, glial septa that invade the optic nerve severely distort, but do not eliminate, the columnar organization of the retinal sectors. These septa deflect many RGC axons and disrupt nearest-neighbor relationships. The distortions produced by the glial septa include folding of the columns and distortion of the chronological lamination. However, the glial septa do not extend into the optic foramen. Therefore, a virtually undistorted columnar organization reappears in the optic foramen. Several roles for the glial septa are discussed.

Animals↗
PubMed1997

Decreased retinal ganglion cell number and misdirected axon growth associated with fissure defects in Bst/+ mutant mice.

PURPOSE: The autosomal semidominant mutation Bst (belly spot and tail) is often associated with small and atrophic optic nerves in adult mice and shares several important attributes with heritable optic nerve atrophy in humans. In this article, the authors present adult and developmental studies on the retinal phenotype in Bst/+ mice. METHODS: Retinal ganglion cells in adult Bst/+ mice were labeled retrogradely with horseradish peroxidase injected into the right optic tract. Labeled ganglion cells were mapped in whole-mounted retinas ipsilateral and contralateral to the injection site. The number of axons in optic nerves of these and other cases were quantified using an electron microscopic method. Eyes of neonatal, embryonic day 15 (E15), and embryonic day 12 (E12) Bst/+ mutants were examined histologically to understand the etiology of the retinal phenotype. RESULTS: Approximately 60% of adult Bst/+ mice have deficient direct pupillary light responses. This neurologic phenotype is associated with a reduction in the number of retinal ganglion cells from the wild-type average of 67,000 to less than 20,000 in Bst/+ mutants. Ganglion cells with crossed projections are more severely affected than those with uncrossed projections. Histologic analysis of eyes from E12 mice reveals a delayed closure of the optic fissure. Despite this abnormality, other ocular structures appear relatively normal. However, some E15 mutants exhibit marked disorganization of the retinal neuroepithelium, and ganglion cell axons are found between pigmented and neural retina. At birth, optic nerves of affected mice are smaller than those of wild-type mice, ectopic axons are found within the eyes, and the ganglion cell layer contains many dying cells. CONCLUSIONS: The expression of the retinal phenotype in Bst/+ mutants is highly variable-ranging from a complete absence of ganglion cells to numbers comparable to that in wild-type mice. The reduction in ganglion cell number in affected adult Bst/+ mice is attributable to the failure of ganglion cell axons to reach the optic nerve head early in development. Delayed fusion of the fissure is consistently associated with the Bst/+ genotype and probably contributes to the failure of ganglion cell axons to grow out of the eye.

Animals↗
PubMed2003

Apertureless scanning near-field optical microscopy for ion exchange channel waveguide characterization.

We report the characterization of an integrated Ag+/Na+ ion exchange waveguide realized in a silicate glass substrate using apertureless scanning near-field optical microscopy. Our experimental set-up is based on the combination of a commercial atomic force microscope with an optical confocal detection system. Thanks to this system, the topography and evanescent optical field at the waveguide top surface are mapped simultaneously. Also, the process of apertureless scanning near-field optical microscopy image formation is analysed. In particular, fringe patterns appearing in the image reveal the intrinsic interferometric nature of the collected signal, due to interference between the field scattered by the tip end and background fields related to guide losses. We give a quantitative interpretation of these fringes. Evanescent intensity mapping on the sample surface allowed us to extract physical waveguide parameters. In particular, it shows an unambiguous multimode beat along the waveguide propagation axis. Furthermore, we show that analysis of this intensity profile reveals back-reflection effects from the waveguide exit facet. The resulting standing waves pattern allows us to evaluate the eigenmode propagation constants.

Equipment Design↗