Polarized tip-enhanced Raman spectroscopy at liquid He temperature in ultrahigh vacuum using an off-axis parabolic mirror.

Tip-enhanced Raman spectroscopy (TERS) combines inelastic light scattering well below the diffraction limit down to the nanometer range and scanning probe microscopy and, possibly, spectroscopy. In this way, topographic and spectroscopic as well as single- and two-particle information may simultaneously be collected. While single molecules can now be studied successfully, bulk solids are still not meaningfully accessible. It is the purpose of the work presented here to outline approaches toward this objective. We describe a home-built, liquid helium cooled, ultrahigh vacuum TERS. The setup is based on a scanning tunneling microscope and, as an innovation, an off-axis parabolic mirror having a high numerical aperture of ∼0.85 and a large working distance. The system is equipped with a fast load-lock chamber, a chamber for the in situ preparation of tips, substrates, and samples, and a TERS chamber. Base pressure and temperature in the TERS chamber were ∼3 × 10-11 mbar and 15 K, respectively. Polarization dependent tip-enhanced Raman spectra of the vibration modes of carbon nanotubes were successfully acquired at cryogenic temperature. The new features described here including very low pressure and temperature and the external access to the light polarizations, thus the selection rules, may pave the way toward the investigation of bulk and surface materials.

Accessory muscle in the hypothenar region: a functional approach.

An accessory muscle was found in the hypothenar region on both hands during routine cadaver dissection. This muscle originated from the tendon of the flexor carpi radialis, crossed the palma manus region superficially and inserted together with the abductor digiti minimi muscle into the ulnar aspect of the basis of the fifth proximal phalanx. The muscle was supplied by one branch arising from the main trunk of the ulnar nerve. Abnormalities of the hypothenar muscles have been described by many authors with a focus on their structural aspects, but there is not enough data about the possible functions they could induce. In our study, we try to elucidate the functions of this accessory muscle. We did not name the variant muscle as it has various functions, each similar to that of individual hypothenar muscles.

The cellular origin of the b-wave in the electroretinogram -- a developmental approach.

Retinal ganglion cells and retinotectal synapses of chick embryos can be activated by electrical stimulation at early stages of development (Rager, '76a,b), whereas light evoked responses occur only towards the end of the incubation period. Thus, photoreceptors seem to be the last cells to mature in the chain of elements necessary to enable transmission of visual information to tectal neurons. In the present study the development of light evoked activity in the retina was investigated and compared with the structural maturation of retinal cells. This ontogenetic approach offers a solution to the problem of the cellular origin of the b-wave called in question by recent records of the potassioretinogram (KRG). Lammellar structures in the developing outer segments of photoreceptors can first be observed on incubation day 17. Late on the same day a corneal electroretinogram (ERG) and a visual evoked response on the optic tectum (VER) can be recorded. The response properties of the developing b-wave and VER were tested using various stimulus parameters. From the latencies of the b-wave and of the VER it is concluded that the b-wave is not generated directly by the activity of neurons involved in intraretinal signal transmission. Thus it is necessary to consider secondary processes triggered by neuronal activity such as depolarization of glial cells. In the chick retina, Müller cells are virtually the only glial cells. They fulfill all structural requirements necessary to explain the current which spreads through the retina during the b-wave. Electronmicroscopic analysis reveals that Müller cells undergo drastic changes during the early phase of b-wave development (incubation day 18). In particular, the number of microtubules per unit volume and the surface area of Müller cell processes in the outer plexiform layer increase considerably. It is, therefore, suggested that the b-wave originates in the depolarization of Müller cells secondary to synaptic activity in the outer plexiform layer.i

Postnatal development of area 17 callosal connections in Tupaia.

The goal of the present study was to investigate the pattern of maturation of callosal projecting neurons in a well-studied mammalian visual system with unique structural and functional properties. Studies of the distribution pattern of interhemispheric connections in the adult tree shrew primary visual cortex reveal not only a high concentration of labeled neurons along the area 17/18 border, as in standard experimental animals such as the cat and monkey, but also numerous callosal projecting neurons in the adjacent dorsal part of area 17, which largely corresponds to the binocular visual field (Kretz and Rager, Exp. Brain Res. 82:271, '90). Callosal projections were anatomically traced in 11 tree shrews (Tupaia belangeri) at various ages between postnatal day 7 (7, 9, 10, 13, 15, 17, 19, and 26 days old) and adulthood (107 days old). In each animal, four injections of wheat germ agglutinin conjugated to horseradish peroxidase were made in a standard configuration into the striate cortex of one hemisphere. In young tree shrews only 7 and 9 days old, heavily labeled terminal axon structures could be seen in the white matter and in layer VI of the opposite hemisphere. Only a few labeled neurons, however, were detected in layer III. The small number of labeled neurons indicated that early in postnatal development, only a few callosal axons had invaded the upper cortical layers. By 10 days of age, the number of supragranular neurons was increasing and the maximal value was counted in a 13-day-old tree shrew. A sharp decline in the number of labeled supragranular neurons was noticed--about 94% in our case--between days 13 and 15. In animals more than 15 days old, the distribution pattern and the density of the neurons looked like the pattern seen in the adult Tupaia brain. The labeled cells were mostly concentrated in layers II and III. The majority of neurons resembled typical pyramidal cells. However, some of the neurons in sublayer IIIc had elongated cell bodies oriented parallel to the laminar boundaries. In contrast to the supragranular cells found in all stages investigated, small populations of labeled cells in layer VI were observed in 9- to 17-day-old tree shrews only. In young postnatal animals 7 to 13 days old, a peculiar cell type was labeled on the ipsilateral side. In coronal sections these cell bodies formed a continuous band that extended from the ventricular wall to the subcortical white matter. These cells might belong to a population of cells still in migration.

Classes of neurons in relation to the laminar organization of the lateral geniculate nucleus in the tree shrew, Tupaia belangeri.

We used the rapid Golgi and horseradish peroxidase (HRP) techniques to study the dendritic spread of relay neurons in functionally distinct laminae of the tree shrew dorsal lateral geniculate nucleus (LGNd). On the basis of their dendritic spread in relation to laminar and interlaminar zones, we describe three classes of relay neurons. Unilaminar neurons with multipolar radiate, bitufted, and intermediate types of dendrites. Dendrites of these neurons are confined to one lamina only, but also can have some of their segments in adjacent interlaminar zones. Multilaminar neurons with multipolar radiate, bitufted, and intermediate types of dendrites. Independent of the site of their cell bodies in a laminar or interlaminar zone, these neurons spread their dendrites over two or more laminae. Interlaminar neurons whose cell bodies and dendrites are confined to a single interlaminar zone. Unilaminar neurons are found in all the laminae. In the medial three laminae, they are more of the radiate type, whereas in laminae 4 and 5 their dendrites tend to be more of a tufted nature. Lamina 6 shows a preponderance of the elongated bitufted type. Multilaminar neurons, although less common as compared to the unilaminar, are also observed in all the laminae. Some neurons have their dendrites confined to an interlaminar zone. By retrograde transport of HRP injected into the visual cortex, we have shown that these neurons are, in fact, relay neurons. In addition to relay neurons, there are small interneurons with "axoniform" dendrites and an unmyelinated axon whose arborization is confined within the limits of the neuron's dendritic spread. Neurons of this type are not labeled with HRP injected into the visual cortex. We conclude that although each lamina is functionally specialized by input from ipsilateral or contralateral retina and by segregation of neurons responding to on or off stimuli, some multilaminar neurons can be found in each lamina. Thus, laminar as well as interlaminar zones contain a class of neurons that could provide a cross-talk between the functionally specialized laminae. Most relay neurons in all the laminae, however, confine their dendrites to their home lamina. Thus, the dendritic architecture of relay neurons allows for processing of information both within channels and between channels.

Expression of axonin-1 in developing amacrine cells in the chick retina.

This study focused on the temporal and spatial pattern of expression of the cell adhesion molecule axonin-1 in amacrine cells and the identification of these cells in the developing chick retina. We analyzed 5-20-day-old chick embryos. The antigen was localized and visualized by the indirect immunogold and the immunofluorescence technique. Colocalization studies with antibodies against tyrosine hydroxylase, acetylcholinesterase, choline acetyltransferase, parvalbumin, calbindin, and calretinin served to characterize these cells further and to explore whether they have other properties in common. Axonin-1 was expressed in amacrine cells from E8 onward in the inner nuclear, in the inner plexiform, and in the ganglion cell layer. Their maturation showed a gradient similar to that found for amacrinogenesis. Expression was closely correlated with the period when the cells develop and shape their processes. The interneurons were classified with reference to Cajal, and most of the morphological types described by him were found. In addition, some cells were considered as axon-bearing amacrine cells. However, the total number of labeled cells was rather small. At least two morphologically different types terminated in each of the inner plexiform sublayers. Narrow- and wide-field arbors indicated the existence of a diversified network. The colocalization studies revealed that the neurotransmitters and neuropeptides overlapped partially with axonin-1 expression. This indicated that axonin-1-immunoreactive amacrine cells were also functionally diverse.

Synaptogenesis in the primary visual cortex of the tree shrew (Tupaia belangeri).

The primary visual cortex of the tree shrew is characterized by the lack of ocular dominance columns. The two eyes are represented in sublayers of laminae 3 and 4. In an earlier study using the transneuronal transport we observed that the geniculate afferents from the two eyes do not initially overlap and then segregate into their appropriate sublaminae. The final distribution pattern can already be observed during the early postnatal period. Since segregation and elimination of afferent terminal branches do not seem to take place, we wanted to investigate whether or not an overproduction of synapses can be observed as in several other animals. We examined layers 3B, 3C, 4A, and 4B, which receive afferents from the retina via the lateral geniculate nucleus, from P5 to maturity by using the electron microscope. The brain tissue was excised in the region where the central vision is represented in adult animals. Then we determined the density of synapses per 100 microns 2 neuropil for each of the four sublayers at the ages P5, P15, P19, P23, P31, and P42 and in the adult animal (AD). In determining the neuropil we measured the size of two additional compartments, i.e., the compartments consisting of perikarya and of blood vessels. At a higher resolution we determined the fraction of Gray type I and type II synapses in each sublamina and in each developmental stage. The size of the neuropil increases from 57% at P5 to 81% in AD whereas the compartment of perikarya decreases from 42% to 15% and the compartment of blood vessels increases from 1.3% to 3.9%. The synaptic density starts with very low values (3.5/100 microns 2) at P5. Then it increases rapidly and attains a maximal rate of increase during the period of eyelid opening. After this period the increase is slowed down and approaches the adult value (12.5/100 microns 2) slowly. An overproduction of synapses could not be observed. The percentage of type I and type II synapses also changes during this period. The fraction of type I synapses amounts to 73% at P5 and increases to 92% in AD. The increase in density of type I synapses is continuous and does not show any sign of overproduction. The density of type II synapses rapidly reaches it final value and then remains constant. Possibly there is a slight overproduction during the period of eyelid opening.(ABSTRACT TRUNCATED AT 400 WORDS)

Expression of presynaptic proteins is closely correlated with the chronotopic pattern of axons in the retinotectal system of the chick.

Newly synthesized presynaptic integral membrane proteins in neurons are transported in precursor vesicles from the site of protein biosynthesis in the cell body by fast axonal flow to the presynaptic terminal. We followed the path that presynaptic proteins travel on the way to their central targets of the highly ordered primary visual pathway of the chick and analyzed the developmental changes in the expression of synaptic vesicle protein 2 (SV2), synaptotagmin, and syntaxin. Immunofluorescences revealed that: (1) the onset of protein expression in the retinal ganglion cells occurs in a central to peripheral developmental pattern from embryonic day 4 (E4) onward; (2) the proteins were found first in the inner and later in the outer plexiform layer of the retina; and (3) they were redistributed from the photoreceptor inner segments and cell bodies to the terminals in the outer plexiform layer. From E4 onward, immunopositive axons for SV2, synaptotagmin, and syntaxin were found in the optic nerve, disappearing after E9 for SV2 and synaptotagmin. The optic tract was stained for SV2 and synaptotagmin between E7 and E12, for syntaxin until the posthatching period. Finally, immunoreactivities for the investigated proteins were present at the surface of the tectum from E8 onward, when first retinal axons arrived there. The present study revealed that SV2 and synaptotagmin, but not syntaxin, are, expressed in a transient wave that follows the advancement of optic axons and the proteins towards the optic tectum.

Central retinal area is not the site where ganglion cells are generated first.

The development of retinal ganglion cells (RGC) was studied in the chick from stage 18 to adulthood. Our main objectives were to identify the retinal site where the first RGCs differentiate, to locate this site relative to the optically defined central retinal area, and to map the spatial arrangement of the RGC field at different stages in development. The eyes of the experimental animals were fixed and serially sectioned. The borders of RGC fields were determined from the presence of either ganglion cell perikarya or ganglion cell axons. In seven cases between stages 21 and 26, the borders of the RGC fields were confirmed electron microscopically. The serial sections together with the RGC fields were then reconstructed in three dimensions. The reconstructed retinae were projected onto a plane by using the radially equidistant polar azimuthal projection. First, RGCs appear dorsal to the apex of the optic fissure. Ganglion cell development then initially spreads out symmetrically with respect to the optic fissure. However, from stage 29 on, the nasal half of the retina expands much more than the temporal half. This asymmetrical growth entails that the optic fissure is eventually located in the temporal half of the retina in the mature animal. The RGC fields of the embryonic stages were superimposed on the retina of a visually active animal according to their real size and position. It turned out that the central retinal area was at least 2 mm away from the site where the first RGCs were generated. It is not before stage 28 that the prospective central retinal area is included into the expanding ganglion cell field. The fact that RGCs at the central retinal area are generated 2.5 days later than first RGCs near the apex of the optic fissure has important implications for the formation of the retinotectal projection.

Laminar organization of ON and OFF regions and ocular dominance in the striate cortex of the tree shrew (Tupaia belangeri).

The organization of ON and OFF responses and ocular dominance in the striate cortex of the tree shrew was electrophysiologically investigated by using flashed, stationary visual stimuli presented monocularly to either the ipsilateral or contralateral eye. We measured cortical multi-unit activity at 25-micron intervals with glass-insulated platinum-plated tungsten microelectrodes. Penetrations were made perpendicular to the cortical layers and the responses were quantitatively analyzed in layers IIIc to V. In sublayers IIIb, IIIc, and upper V, phasic responses of approximately equal magnitude occurred to both light ON and light OFF (ON-OFF regions). In layer IV, tonic as well as phasic responses were often evoked by the flashed spot of light. In sublayer IVa stronger responses occurred to light ON than to light OFF (ON region) while in sublayer IVb stronger responses occurred to light OFF than to light ON (OFF region). In an ON region, the increased neural activity that occurred at light ON was often accompanied by a decrease in activity below baseline level at light OFF. A similar decrease often occurred in an OFF region at light ON. Recordings from the region of the cell-sparse cleft in layer IV were characterized by ON-OFF responses, signalling a transition zone between sublayers IVa and IVb. In addition, the responses to stimulation of the ipsilateral eye typically were very weak in the cleft region. In the other regions examined, the multi-unit activity generally was driven binocularly with slightly greater responses being elicited by the contralateral eye. We conclude that the ON-center and OFF-center afferent pathways that are organized at the retinal level remain generally segregated in the tree shrew through the first synapse in the striate cortex. In addition, our recordings confirm that a horizontal organization of ocular dominance occurs in layer IV of the striate cortex in tree shrews.

Expression of the axonal cell adhesion molecules axonin-1 and Ng-CAM during the development of the chick retinotectal system.

Cell surface glycoproteins expressed on growth cones and axons during brain development have been postulated to be involved in the cell-cell interactions that guide axons into their target area. Nevertheless, an unequivocal description of the mechanism by which such molecules exert control over the pathway of a growing axon has not been done. As a crucial requirement in support of a relevant involvement of an axonal surface molecule in growth cone guidance, this molecule should be expressed in the growth cone. The developing retinotectal system provides an excellent opportunity to test whether a particular neuronal surface molecule fulfills the requirement of the spatiotemporal coincidence between its appearance and the emergence of growth cones because its setup follows the rule of chronotopy, i.e., the position of axons in a certain site is determined by the time of their arrival. We have analyzed axonin-1 and the neuron-glia cell adhesion molecule (Ng-CAM), two axonal surface molecules that promote neurite growth in vitro, for their expression in the retina and in the retinotectal system of the chick throughout its development. At stage 18, both axonin-like (A-LI) and Ng-CAM-like immunoreactivity (Ng-CAM-LI) are clearly present in the area where first retinal ganglion cells (RGCs) are generated. The immunoreactivity spreads synchronously with the formation of RGCs over the developing retina. From stage 32 on, the inner plexiform layer is also stained according to its temporospatial gradient of maturation. In later stages, the outer plexiform layer and the inner segments of photoreceptors also show immunoreactivity. The development of A-LI and Ng-CAM-LI along the optic nerve, chiasm, optic tract, and in the superficial layers of the optic tectum follows the chronotopic pattern of axons, as was found by earlier morphological investigations. Older axons loose their A-LI. This allows to localize the position of newly formed axons. The fact that A-LI and Ng-CAM-LI parallel the formation and maturation of axons suggests that axonin-1 and Ng-CAM may play an important role in the organization of the retinotectal system.

Developmental expression of dynamin in the chick retinotectal system.

Dynamin I, a GTPase involved in the endocytic cycle of synaptic vesicle membranes, is believed to support axonal outgrowth and/or synaptogenesis. To explore the temporal and spatial patterns of dynamin I distribution in neuronal morphogenesis, we compared the developmental expression of dynamin with the expression of presynaptic membrane proteins such as SV2, synaptotagmin, and syntaxin in the chick primary visual pathway. Western blots of retina and tectum revealed a steady increase of synaptotagmin and syntaxin from embryonic Day 7 (E7) to E11, whereas for the same time frame no detectable increase of dynamin was found. Later stages showed increasing amounts of all tested proteins until the first postnatal week. Immunofluorescence revealed that SV2, synaptotagmin, and syntaxin are present in retinal ganglion cell axons from E4 on. In later stages, the staining pattern in the retina and along the visual pathway paralleled the formation and maturation of axons. In contrast, dynamin is not detectable by immunofluorescence in the developing retina and optic tectum before synapse formation. Our data indicate that, in contrast to the early expression of synaptotagmin, SV2, and syntaxin during axonal growth, dynamin is upregulated after synapse formation, suggesting its function predominantly during and after synaptogenesis but not in axonogenesis.(J Histochem Cytochem 47:1297-1306, 1999)

ON and OFF regions in layer IV of striate cortex.

In vertical penetrations through the striate cortex in the tree shrew (Tupaia belangeri), we found regions where neural activity was evoked predominantly by light ON. These were followed by regions where responses were evoked predominantly by light OFF. Histological reconstructions indicated that the ON regions were correlated with layer IVa and the OFF regions were correlated with layer IVb. Local application of cobalt chloride produced a transient cessation of visually evoked activity, suggesting that the electrodes sampled cortical activity rather than lateral geniculate nucleus afferents. These data demonstrate that separate ON and OFF regions are present in the tree shrew striate cortex and suggest that spatially separate, parallel ON and OFF afferent channels extend, in this species, at least through the first synapse in the striate cortex.

The course of later generated axons in the developing optic nerve of the chick embryo. A morphometric electron microscopic study.

The topographic position of growth cones (GCs) shows the course of ingrowing axons within the optic nerve and allows to draw conclusions with respect to the fiber order in this pathway. Therefore, the topographic distribution and frequency of GCs as well as the proximal and distal axon shaft segments were studied within cross-sections of the distal, middle, and prechiasmatic part of the nerve of 3-8-day-old embryos using electron microscopy. The ingrowth of GCs was not confined to a particular region. Initially, GCs were found near the ventral periphery. With increasing age, simultaneous ingrowth occurred within an area that expanded dorsally. In parallel, GCs also occurred in dorsal regions and eventually in the dorsal periphery. GCs intermingled everywhere with more mature axon profiles. However, youngest profiles predominated ventrally, oldest dorsally. Hence, maturity increased from ventral to dorsal. This indicated that the time of arrival of axons and the topographic position in the cross-section correlated significantly. It is concluded that axons are chronotopically organized, but in a probabilistic sense. The predominant ingrowth of axons in the ventral part may be associated largely with the first wave of neurogenesis of retinal ganglion cells. The ingrowth in dorsal regions of the cross section may be related to later generated axons that enter the nerve following older axons of the same retinal sector as well as axons of neighboring ganglion cells which continue to leave the mitotic cycle while the front of neurogenesis has spread into the periphery.

Differential expression of the mRNAs of the axonal glycoproteins axonin-1 and NgCAM in the developing chick retina.

Cell adhesion molecules expressed on the axonal membrane have been thought to be involved in the guidance of axons to their target area. In the chick, axonin-1 and NgCAM have been shown to promote, through reciprocal interactions, neurite outgrowth in vitro. We have recently shown that chick retinal ganglion cells (RGC) express both proteins as early as the axonal elongation begins. Their expression continues throughout the development of the retinotectal system synchronously with the chronotopic spread of axons. To further investigate the spatiotemporal distribution of axonin-1 and NgCAM in the retina, we have analysed the expression of their mRNAs in the present study. From stage 36 (E10) until hatching photoreceptors express axonin-1 but not NgCAM. In the inner nuclear layer groups of amacrine cells were strongly labelled with both probes but they seemed to belong to different subgroups. These patterns of expression might indicate a differential influence of the two proteins on the development of the local neural circuits of the retina.

Transformations of the retinal topography along the visual pathway of the chicken.

It is still unclear how the retinotectal map of the chick is formed during development. In particular, it is not yet known whether or not the organization of fibres plays a role in the formation of this map. In order to contribute to the solution of this problem, we analysed the representation of the retinal topography at closely spaced intervals along the fibre pathway. We injected HRP into various sites of the tectal surface and traced the labelled fibre bundles back to the retina. The retinal topography was reconstructed at ten different levels, i.e. in the retina, the optic nerve head, the middle of the optic nerve, the chiasm (three levels), the optic tract (three levels), and the optic tectum. We obtained the following results: (1) The labelled fibre bundles as well as the fields of labelled retinal ganglion cells were always well delimited and coherent. (2) The reconstructions show that transformations of the retinal topography occur in the fibre pathway. The first and most important transformation is found in the optic nerve head where the retinal image is mirrored across an axis extending from dorsotemporal to ventronasal retina. In addition, the retinal representation is split in its temporal periphery. Thus, central and centrotemporal fibres are no longer in the centre of the image but close to the dorsal border of the nerve. Peripheral fibres are found along the medial, ventral and lateral circumference of the nerve. In the optic tract a second transformation occurs. The retinal topography is rotated clockwise by about 90 degrees and flattened to a band. The flattening is accompanied by a segregation of fibre bundles so that eventually central and centrotemporal retinal fibres are located centrally, ventral fibres dorsally and dorsal retinal fibres ventrally in the tract. By these two transformations an organization of fibres is produced in the optic tract which can be projected onto the tectal surface without major changes given that dorsal and ventral fibres remain in their relative positions, and that deep lying fibres project to the rostral and central tectum, superficial fibres to the caudal tectum. The transformations which we have observed follow specific rules and thus maintain order in the pathway although retinotopy is lost. In conjunction with our earlier studies on the development of the retinotectal system we conclude that fibres are laid down in a chronotopic order. The transformations take place under particular structural constraints.(ABSTRACT TRUNCATED AT 400 WORDS)

Extracellular matrix and development of lamination in the dorsal lateral geniculate nucleus in the tree shrew (Tupaia belangeri).

In the tree shrew (Tupaia belangeri), the cytoarchitectonic lamination of the lateral geniculate nucleus cannot be detected at birth; it only appears during the early postnatal period. However, a laminated pattern was revealed with rapid Golgi staining and retinal afferents were segregated into the appropriate laminae well before cytoarchitectonic lamination could be seen. Both observations indicate that the extracellular matrix may play a role in the separation of lateral geniculate nucleus cells into laminae. In the present study, the organization of the extracellular matrix was investigated during development using immunohistochemical and in situ hybridization techniques. For immunohistochemistry, peanut agglutinin (PNA) lectin and antibodies against tenascin (TN) were chosen, while for in situ hybridization, mTN riboprobes were used, simultaneously, with antibodies against Vimentin (Vim) and microtubule associated protein (MAP-2). The results showed that the pattern of PNA-binding glycoproteins and that of tenascin were relatively similar, although tenascin appeared later and disappeared earlier. The first interlaminar spaces to be detected were those between layers innervated by opposite eyes. The TN specific mRNA was detected in the lateral geniculate nucleus at P0, but was no longer visible at P7. By comparing TN mRNA and Vim or MAP-2 stainings a correspondence could be observed. The extracellular matrix lamination therefore seems to precede cytoarchitectonic lamination, suggesting that the extracellular matrix may play a role in the development of laminated structures. The TN-producing cells seem to be developing astrocytes and neurons.

[Infrapopliteal angioplasty: a forgotten region?]. / Infrapopliteale Angioplastie--die vergessene Region?

Although percutaneous transluminal angioplasty (PTA) has become established as an endovascular technique--in the more strict sense as a balloon dilatation but being increasingly supplemented by stent implantations--for many vascular regions, reports on infrapopliteal angioplasties are rather scarce. With the development of hydrophilically coated guide wires, improved catheter materials, and dedicated balloon catheters for infrapopliteal use, dilatation treatments distal of the popliteal artery are now standard procedures. Major advances in peri-interventional drug management have also made their contribution. The initial technical and clinical results obtained are excellent. For the majority of the patients, the main concern is for limb salvage. In this context, infrapopliteal PTA also achieves satisfactory results. However, the long-term results must still be considered as unsatisfactory since recurrences are frequent and require repeat interventions. Therefore new therapeutic strategies are required that can reduce re-stenoses especially in this peripheral vascular segment.