Biomedical subjects

K W Ashwell

Publications and source records attributed to K W Ashwell.

At least 19 recordsLinked to original sources

PubMed2001

Fluororuby as a marker for detection of acute axonal injury in rat spinal cord.

Axonal damage is a common pathological consequence of spinal cord injury. Previous studies have detected axonal injury with silver stains for degeneration or immunohistochemistry for alterations in components such as beta-amyloid precursor protein, neurofilament or ubiquitin. Fluororuby has recently been introduced as a neuronal tracer in studies of spinal cord injury and regeneration. Our study was carried out to determine whether Fluororuby can be used to identify injured axons and monitor the time course of axonal damage. Adult rats underwent needle puncture injury to the white matter in the midline and lateral spinal cord at T11. At the same time, 0.05 microl of Fluororuby was injected into the cord at the same sites. After survival times ranging from 6 h to 3 weeks, spinal cords were cut into longitudinal frozen sections and examined with confocal microscopy. Fluororuby was found to label key features of axonal injury including axonal swelling, retraction balls and disrupted axons. Damaged axons close to the injury site were consistently labeled within 6 h, with indications of swollen and disconnected axons spreading further from the site during the first week. Fewer injured axons were labeled after 1 week survival, but the marker revealed longer distances of degenerating axons both distal and rostral to the injury site. Our findings indicate that Fluororuby is a quick, sensitive, reliable and technically simple fluorescent marker for early stages of acute axonal injury and degeneration.

Acute Disease↗

PubMed2001

Organisation and maturation of the human thalamus as revealed by CD15.

The distribution of the CD15 antigen (CD15, 3-fucosyl-N-acetyl-lactosamine, Lewis x) has been studied immunohistochemically in the fetal human thalamus. Its changing patterns could be related to three successive, but overlapping, periods primarily due to its association with radial glial cells, neuropil, and neural cell bodies, respectively. From 9 weeks of gestation (wg), a subset of CD15-positive radial glial cells distinguished the neuroepithelium of the ventral thalamus, a characteristic also seen in the developing mouse. Distal processes of the radial glial cells converged at the root of the forebrain choroid tenia, which was also CD15 positive. From 13 wg until approximately 20 wg, CD15-positive neuropil labeling marked the differentiation areas of prospective nuclei within the dorsal thalamus and progressively outlined their territories in a time sequence, which appeared specific for each nucleus. CD15 labeling of differentiating nuclei of the ventral, medial, anterior, and intralaminar thalamic divisions showed a transient topographic relationship with restricted areas of the ventricular wall. After 26 wg, CD15 immunoreactivity was observed in subpopulations of glial cells and neurons. Transient CD15 immunoreactivity was also found in delimited compartments within the subventricular region. The time of CD15 expression, its location, and cellular association suggest that CD15 is involved in segmentation of diencephalon, in the specification of differentiating nuclear areas and initial processes regarding the formation of intercellular contacts and cellular maturation.

Biomarkers↗

PubMed2001

Development of the cyto- and chemoarchitectural organization of the rat nucleus of the solitary tract.

The nucleus of the solitary tract (NST) is the major visceral sensory nucleus in the brainstem. The development of the rat nucleus of the solitary tract was followed during late prenatal and early postnatal life in order to determine when subnuclear organization and chemoarchitectural features develop. In Nissl-stained sections, the nucleus of the solitary tract becomes visible as a distinct cluster of cells by about E17. Between E17 and E19, a profound change in the Nissl-stained appearance of the nucleus occurred, so that by E19 all the subnuclei were discernible. Acetylcholinesterase activity in the developing NST showed an early period of rapid differentiation (E15 to E17), while by E19 the basic adult pattern of distribution of this enzyme had already been achieved. The subnuclei of the NST began to show clear differential staining for nicotinamide adenine dinucleotide phosphate diaphorase at about the same time as reactivity for that enzyme first appeared (E19). With respect to calbindin- and calretinin-immunoreactive neurons within the nucleus, many of the chemoarchitectural features associated with these two markers were obvious even by late fetal life. For example, in the central subnucleus, a strongly labelled, dense population of calbindin-immunoreactive neurons was present from E17; while in calretinin-immunoreacted material, this subnucleus was prominent because of its immunonegativity also from E17. Nevertheless, the total number of calbindin- and calretinin-immunoreactive neurons in the NST did not peak until late postnatal life. Tyrosine hydroxylase immunoreactive neurons were visible from E15, began differentiation by E17 and were distributed in a similar pattern to the adult from E19. Substance P immunoreactivity in the NST was also very similar to the adult pattern by E19. Many of these immunochemical and histochemical markers indicate a similar pattern of development, i.e. a rapid period of differentiation until E19, by which time a relatively stable adult-like pattern has been attained. The present findings indicate that many of the cyto- and chemoarchitectural features of this nucleus are present well before birth, by which time the nucleus must serve vitally important functions such as relaying information for control of respiration and the circulation.

Acetylcholinesterase↗

PubMed2001

The development of cranial nerve and visceral afferents to the nucleus of the solitary tract in the rat.

We have used carbocyanine dye tracing techniques to examine the distribution of afferents from the facial, trigeminal and vagal nerves to the nucleus of the solitary tract (NST) in the developing rat (E13 to P13). Crystals of DiI (1, 1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate) were placed (unilaterally) into the facial or trigeminal ganglia, or into the cervical vagus nerve, and the sections examined with a laser scanning confocal microscope. Inputs from some peripheral structures (tongue, aortic arch, right atrium and lung) to the NST were also analyzed to provide information on the distribution of organ-specific afferents. No afferents were labeled following DiI placement in the above sites at E13. At E14, a few axons from the geniculate ganglion of the facial nerve were present in the NST anlage, but these were restricted to the area adjacent to the solitary tract. These axons began to invade the medial NST at E15. By E17, facial afferent axons had become widespread throughout rostral NST and from E19 the distribution of DiI labeling displayed a morphologically mature pattern. DiI-labeled afferent axons from the trigeminal nerve first emerged into the NST anlage at E14, initially coursing medially to penetrate the ventricular zone. Between E15 and E17, axonal density increased markedly but after E17 became progressively confined to the lateral NST. Axons from the vagus nerve first appeared in the caudal NST as early as E14 and coursed directly into the proliferative zone of the alar plate at all rostrocaudal levels by E15. From E19 through postnatal life, the distribution of vagal afferent axons was essentially stable with particularly dense label in the caudal NST. Cranial nerve afferents to the NST appear to be distributed to appropriate sites from the beginning of ingrowth, with the exception of trigeminal afferents, where some small initial exuberance was found. The terminal fields derived from selected peripheral organs such as lung, right atrium, aortic arch and tongue were also predominantly distributed to appropriate subnuclei from the beginning of ingrowth into the NST, although organ-specific afferent fields appeared to develop dense arbors somewhat later than did individual cranial nerves. Electron microscopy was used to examine regional synapse development in the rat NST. There was some delay between the ingrowth of afferents to the NST (E15) and the first appearance of synaptic thickenings. The earliest synapses were simple (usually) symmetrical membrane thickenings (from E17) and vesicles did not appear until E19. High synaptic density within the C subnucleus appeared during early postnatal life. Synaptic glomeruli, which are a characteristic feature of afferent input to the adult NST, had not developed by birth, indicating that the pre- and perinatal function of the NST must be mediated through simpler, single, axodendritic inputs to NST neurons.

Animals↗

PubMed2001

Expression of apoptosis-related proteins and structural features of cell death in explanted aortocoronary saphenous vein bypass grafts.

This study aimed to investigate the features of cell death occurring in aortocoronary saphenous vein bypass grafts. Human aortocoronary saphenous vein bypass grafts with angiographic luminal stenosis of > 75% were explanted from 14 patients at redo coronary artery bypass grafting. Proteins associated with apoptotic pathways were identified immunohistochemically using antibodies to Bcl-2, Fas, BAX, p53 and CPP32. Cells undergoing DNA fragmentation were identified by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL). DNA synthesis was investigated using the antibody to proliferating cell nuclear antigen (PCNA). Ultrastructural features of cell death were examined by electron microscopy. Anti-apoptotic (Bcl-2) and pro-apoptotic (Bax, p53, CPP32 and Fas) proteins were expressed throughout the graft wall, but marked differences in the characteristics of cell death were noted between atherosclerotic and non-atherosclerotic areas of the intima. In atherosclerotic areas, pro-apoptotic proteins were widely expressed, but ultrastructural analysis failed to identify cells showing typical features of apoptosis. In these areas, necrotic cells were frequently observed, with negative correlation of Bcl-2 expression with TUNEL. Pro-apoptotic proteins showed no correlation with TUNEL. In contrast, in non-atherosclerotic areas of vein grafts, the expression of both anti-apoptotic (Bcl-2) and pro-apoptotic proteins (p53, Bax and CPP32) correlated with TUNEL. In atherosclerotic areas, non-atherosclerotic intimal areas, and in the underlying media, the numbers of TUNEL+ cells correlated with PCNA positivity. Ultrastructurally, apoptotic bodies and features of necrosis were observed in non-atherosclerotic areas of grafts. The present observations indicate that in atherosclerotic areas, cell death occurs mainly by necrosis, while in non-atherosclerotic areas, cell death occurs by both necrosis and apoptosis. An imbalance between DNA fragmentation and DNA synthesis may contribute to graft instability and failure.

Aged↗

PubMed2000

The distribution of the neurokinin B receptor in the human and rat hypothalamus.

The neurokinin B receptor (NK3) is an element of the hypothalamic neuronal circuitry regulating blood pressure in rats. The present study used immunohistochemistry to reveal the distribution of NK3 in the human hypothalamus. The strongest NK3-like immunoreactivity in the human hypothalamus was found in neurons of the paraventricular nucleus, specifically in the parvicellular and posterior paraventricular subnuclei. Another prominent population of NK3-positive cells in the human hypothalamus was found in the perifornical nucleus. The present study also showed two previously unreported populations of NK3-positive neurons in the rat periventricular nucleus and medial magnocellular paraventricular subnucleus. It is concluded that there is a large degree of similarity in the distribution of NK3 in the human and rat hypothalamus.

Adult↗

PubMed2000

Organization of the human paraventricular hypothalamic nucleus.

The cyto- and chemoarchitecture of the human paraventricular hypothalamic nucleus (Pa) was studied with the aid of three-dimensional computer reconstruction. The adult human Pa is a vertically elongated structure that abuts the wall of the third ventricle (3V) medially and is indented dorsolaterally by the descending fornix. Chemoarchitecture revealed the following five subnuclei in the human Pa. The most prominent of these is the magnocellular subnucleus (PaM) occupying the ventrolateral quadrant of the Pa and comprised of a concentration of large arginin-vasopressin (AVP)- and acetylcholinesterase (AChE)-positive cells, and small calbindin (Cb)-positive neurons. Rostrally, the PaM is succeeded by the small anterior parvicellular subnucleus (PaAP), which contains small AChE-, AVP- and tyrosin hydroxylase (TH)-positive cells. Dorsal to the PaM is found the dorsal subnucleus (PaD), containing large spindle-shaped TH-, oxytocin (OXY)-, and AChE-positive cells, as well as a population of small Cb-positive neurons. Abutting the wall of the 3V and medial to PaM and PaD is the parvicellular subnucleus (PaP). The PaP contains small cells immunoreactive for corticotropin-releasing factor (CRF), neuromedin K receptor (NK3), and nonphosphorylated neurofilament protein (SMI32). The posterior subnucleus (PaPo) is situated posterior to the descending column of the fornix; it replaces all above-mentioned subdivisions caudally, and is a chemoarchitectonic amalgam that includes dispersed large AChE-, OXY-, AVP- and TH-positive cells, as well as small NK3-, CRF-, SMI32- and Cb-immunoreactive neurons. The present findings suggest that the human PaM and PaD are homologues to the magnocellular subnuclei of the rat Pa, whereas the human PaP and PaPo correspond to the rat medial parvicellular and posterior subnuclei, respectively.

Acetylcholinesterase↗

PubMed2000

Advances in secondary spinal cord injury: role of apoptosis.

The outcome of spinal cord injury depends on the extent of secondary damage produced by a series of cellular and molecular events initiated by the primary trauma. This article reviews the evidence that secondary spinal cord injury involves the apoptotic as well as necrotic death of neurons and glial cells. Also discussed are the major factors that can contribute to cell death, such as glutamatergic excitotoxicity, free radical damage, cytokines, and inflammation. The development of innovative therapeutic strategies to reduce secondary spinal cord injury depends on an increased understanding of secondary injury mechanisms at the molecular and biochemical level. Such therapeutic interventions may include the use of antiapoptotic drugs, free radical scavengers, and anti-inflammatory agents. These could be targeted to block key reactions on cellular and molecular injury cascades, thus reducing secondary tissue damage, minimizing side effects, and improving functional recovery.

Animals↗

PubMed2000

Development of the rat phrenic nucleus and its connections with brainstem respiratory nuclei.

The development of phrenic motoneurons and descending bulbospinal projections to the cervical spinal cord have been examined in prenatal and early postnatal rats with the aid of the carbocyanine dyes DiI and DiA. Phrenic motoneurons could be identified by retrograde labelling as early as E13, while aggregation of phrenic motoneurons into a column and the formation of dendritic bundles became apparent from E16. The initial phrenic motoneuron dendritic bundles were oriented in the dorsolateral and ventromedial directions, while ventrolaterally directed bundles entering the marginal zone appeared by E16, and rostrocaudal bundles were clearly visible by E21. The column of phrenic motoneurons extended rostrocaudally from C2 to C6 at E13 and E14, but this became confined to the C3-5 segments by E21. Two-way tracing of connections between putative brainstem respiratory centres and cervical spinal cord with the carbocyanine dyes, DiI and DiA, indicated that brainstem bulbospinal neurons in the position of the adult ventral respiratory group (VRG) and medial parabrachial (MPB) nuclei appeared to project to the cervical cord white matter as early as E15 and may contribute axons to the grey matter of the cervical cord as early as E17 These findings are consistent with electrophysiological studies of respiratory function development in the fetal rat, which found relatively regular rhythmic phrenic discharge by E20 to 21. In summary, our findings indicate that the structural differentiation of phrenic motoneurons is well-advanced prior to birth and that the descending pathways involved in the control of respiratory function are in place several days before birth.

Animals↗

PubMed2000

Electron-microscopic detection of apoptotic and necrotic cell death in non-atherosclerotic areas of stenotic aortocoronary saphenous vein bypass grafts.

Aortocoronary saphenous vein bypass grafts undergo structural alterations within the arterialized vein, resulting in graft stenosis and failure. Areas of the acellular intima contribute to fissuring, cracking and ulceration, while areas of the media become highly vascular but thinned. This study aimed to examine the ultrastructural features of cell death, including apoptosis and necrosis, in non-atherosclerotic areas of the stenotic aortocoronary saphenous vein bypass grafts. Thirteen stenotic vein grafts were obtained at redo coronary artery bypass grafting. The ultrastructural features of cell death were analysed by electron microscopy. Typical features of necrosis, including focal areas of cytoplasmic oedema, plasmalemmal destruction and nuclear condensation with cytoplasmic organelle destruction, were observed throughout the intima and media. Features of apoptosis, including the presence of apoptotic bodies, were also identified in the hyperplastic intima and its adjacent media. Our observations suggest that both apoptosis and necrosis occur in non-atherosclerotic areas of stenotic aortocoronary saphenous vein bypass grafts.

Aged↗

PubMed1999

Transient CD15 expression reflects stages of differentiation and maturation in the human subcortical central auditory pathway.

The expression of the terminal saccharide determinant CD15 (3[a1-3]-fucosyl-N-acetyl-lactosamine) was evaluated in the central auditory system of the human developing brain by using monoclonal antibodies against this epitope. CD15 immunoreactivity was first observed in the ventral cochlear nucleus at 10 weeks of gestation, whereas the dorsal cochlear nucleus became positive from 13 weeks of gestation. In both nuclei, the intensity of immunoreactivity increased until 16 weeks of gestation and lasted until 25 weeks of gestation. In the inferior colliculi, CD15 was poorly expressed in the central nucleus from 13 to 23 weeks of gestation and later with moderate levels until birth. Within the medial geniculate nucleus, a biphasic pattern of expression was observed with peaks around 14-17 and 21-24 weeks of gestation. Heterogeneous expression in the medial geniculate nucleus, which was associated either with neurons or the neuropil, allowed distinction of subnuclei. In many of the auditory pathway structures (e.g., ventral cochlear nucleus and central nucleus of the inferior colliculus), a heterogeneous pattern of CD15 expression in the form of repeating parallel bands, possibly related to tonotopic organization, became transiently apparent around 23 weeks of gestation, whereas in the magnocellular part of the medial geniculate nucleus, a striking modular or compartmental arrangement of immunoreactive structures (which could also be associated with tonotopic organization) was also noted at about 23 weeks of gestation. We propose that the initiation of CD15 expression in each nucleus heralds the appearance of functional contacts and that high levels of neuropil labeling are related to the formation of nonstabilized synaptic contacts. Thus, transient CD15 expression in the central auditory system is possibly correlated with phases of functional plasticity in this pathway.

Aging↗

PubMed1999

Development of the rat phrenic nerve and the terminal distribution of phrenic afferents in the cervical cord.

The development of the right phrenic nerve and the distribution of phrenic nerve afferents to the spinal cord have been examined with the aid of electron microscopy and carbocyanine dye retrograde diffusion along the phrenic nerve, respectively. The formation of fascicles in the right phrenic nerve commenced at E15, while Schwann cells penetrated the nerve from E17 and myelination began at P0. The total number of axons in the right phrenic nerve decreased from E15 (943, 965 in two animals) to E19 (539, 582), remained steady until P0 (564, 594) before rising to almost adult values by P7 (689, 934). The postnatal rise in number of axons appears to be due to a large influx of unmyelinated axons. Carbocyanine dye tracing revealed that at E13, neurons in dorsal root ganglia C(2) to C(6) contributed peripheral processes to the phrenic nerve. Phrenic afferents arrived in the spinal cord by E13 and penetrated the dorsal horn at E14. Three terminal fields for phrenic afferents became apparent by E17. These were:(1) in the central parts of laminae I to V, (2) medially in laminae V to VII or adjacent area X near the central canal, (3) in laminae VIII and IX, around the differentiating phrenic motoneurons. Around the time of birth, some phrenic afferents in the second group were distributed across the midline and could be seen to approach the ventromedial dendritic bundle of phrenic motoneurons on the contralateral side, but these were no longer seen by P4. Just before birth (E21), afferents in the third group divided into two further subsets, supplying the dorsolateral and ventromedial groups of phrenic motoneuron dendritic bundles, respectively. Our findings strongly suggest that phrenic afferent differentiation is largely complete by birth.

Afferent Pathways↗

PubMed1999

Spatiotemporal expression gradients of the carbohydrate antigen (CD15) (Lewis X) during development of the human basal ganglia.

The developmental expression pattern of the carbohydrate epitope CD15 (Lewis X, Le X) (alpha1-->3-fucosyl-N-acetyl-lactosamine) has been immunocytochemically evaluated in paraffin sections within the human basal ganglia from 10 weeks gestation to three years after birth. At 11 weeks of gestation, CD15 (Le X) positive radial glial cells were located in the anterior and dorsal parts of the lateral ganglionic eminence. Their processes ran from the subventricular zone radially in a highly ordered fashion to the dorsolateral margin of the caudate nucleus and further to the lateral rim of the putamen. At 12 weeks of gestation, strands of CD15 (Le X) material continued to the pial surface, forming a continuous CD15 (Le X) positive borderline separating the accumbens nucleus and olfactory tubercle from the piriform cortex. At 13 weeks of gestation the dorsal putamen was completely CD15 (Le X) immunoreactive along its perimeter and CD15 (Le X) patches, consisting of fine granular material, appeared at the dorsolateral margin of the putamen at this age; while the first CD15 (Le X) patches in the caudate nucleus were observed four weeks later. The matrix compartment of the caudate and dorsal putamen became gradually stained by granular CD15 (Le X) positive material into which CD15 (Le X) immunoreactive somata were embedded. The striking contrast in staining between patch and matrix compartments disappeared shortly after birth. The ventral striatum did not become immunoreactive until the last few weeks before birth. After the formation of CD15 (Le X) positive patches in the striatum (from 12 weeks of gestation), delicate CD15 (Le X) fibres, often accumulated in bundles and related to the striatal patches, became apparent coursing towards the external pallidal lamina and the globus pallidus. Immunoreactivity in the globus pallidus itself was transient, emerging from 16 weeks of gestation, reaching a peak at 21 weeks of gestation and disappearing by birth. Both processes, i.e. the occurrence of CD15 (Le X) striatopallidal fibres and the emerging immunoreactivity in their pallidal target, may be interrelated, so that ingrowing CD15 (Le X) positive axons from the striatum provoke CD15 (Le X) expression in the external and internal pallidum. The variable patterns and intensities of CD15 (Le X) expression are possibly related to periods of maturation of the striatum and the establishment of functional interactions within the basal ganglia. Differential staining of patch and matrix in the developing neostriatum suggests that a distinct phase of cellular adhesion or dishesion mediated by the CD15 (Le X) epitope occurs during establishment of the patch and matrix regions.

Aging↗

PubMed1999

Involvement of dendritic cells in long-term aortocoronary saphenous vein bypass graft failure.

Antigen-presenting dendritic cells are present in atherosclerotic lesions in human arterial intima, but have not been investigated in atherosclerotic and hyperplastic stenotic lesions that affect vein grafts used as arterial conduits. This study was undertaken to examine whether dendritic cells are present in aortocoronary artery saphenous vein bypass grafts affected by high-grade atheromatous stenosis. Stenotic saphenous vein coronary artery bypass grafts (angiographic luminal stenosis > 75%) were harvested from 10 patients (nine male, one female), aged 4271 years (mean 56.5) at re-do operation. The mean time interval from bypass surgery to the excision of stenotic grafts was 11.5 years (range 2-21). The specimens were fixed in 10% buffered formalin, embedded in paraffin blocks and the sections stained with antibodies to S-100 (to identify dendritic cells), CD3 (T cells), CD68 (macrophages), von Willebrand factor (endothelial cells) and alpha-smooth muscle actin (smooth muscle cells) using avidin-biotin complex immunoperoxidase technique. Normal veins were obtained during saphenous vein femoro-popliteal grafting. The stenotic venous grafts showed histological features typical of extensive arterialization, intimal hyperplasia, atherosclerotic plaque-like lesions, calcification and thrombosis. In areas of intimal hyperplasia, S-10O-positive cells were distributed irregularly among smooth muscle cells. S-100-positive dendritic cells were seen most frequently within atherosclerotic plaque-like lesions where they co-localized with CD3+ cells and CD68+ cells. S-100-positive dendritic cells were also seen accumulating within calcific foci. No S-100-positve cells were found in normal, ungrafted saphenous veins. We conclude that dendritic cells are present in aortocoronary saphenous vein bypass grafts affected by high grade stenosis. Dendritic cells are probably involved in immune mechanisms of atherogenesis through their interactions with T cells and macrophages. The accumulation of dendritic cells within calcific foci suggests their contribution to the calcification of stenotic venous grafts.

Adult↗

PubMed1999

Dendritic cells in venous pathologies.

Dendritic cells are potent antigen-presenting cells responsible for the activation of T-lymphocytes in various immune responses. Their role in the initiation of immune reactions in allergies, autoimmune diseases, tumors, transplantation, and, more recently, in atherosclerosis has been well established, but their involvement in venous pathologies has not been previously investigated. The aim of this study was to determine whether dendritic cells are present in veins affected by varicosity and thrombophlebitis. Three groups of veins obtained at operation were studied: (1) varicose veins of the great saphenous vein from patients who were undergoing vein stripping for primary varicosity; (2) segments of the great saphenous vein from patients with varicosity complicated by thrombophlebitis; and (3) great saphenous veins without varicosity or thrombophlebitis from patients who were undergoing femoropopliteal bypass grafting. The specimens were fixed in 10% neutral buffered formalin and embedded in paraffin, and the sections were stained with antibodies to S-100 (to identify dendritic cells), CD3 (T-lymphocytes), CD68 (macrophages), von Willebrand factor (endothelial cells), alpha-smooth muscle actin (smooth muscle cells), and CD15 (mast cells) by use of avidin-biotin complex (ABC) immunoperoxidase technique. Immunohistochemical examination showed that no S-100-positive dendritic cells were present in normal saphenous veins. In contrast, S-100-positive cells with dendritic cell morphology were detected in the intima and media of veins with varicosity and thrombophlebitis, where they represented a minor cell population. S-100-positive dendritic cells were located between smooth muscle cells as well as around areas of neovascularization where they colocalized with T-lymphocytes. The present work suggests that dendritic cells might be involved in pathological processes in veins affected by varicosity and thrombophlebitis. The authors speculate that dendritic cells may be involved in the inflammatory mechanisms in these veins through their interaction with T-lymphocytes.

Adult↗

PubMed1999

Structural features of cell death in atherosclerotic lesions affecting long-term aortocoronary saphenous vein bypass grafts.

Aortocoronary saphenous vein bypass grafts fail because of structural pathologies (thrombosis, intimal hyperplasia and atherosclerosis) within the 'arterialized' vein leading to graft stenosis. This study examined structural characteristics of atherosclerotic alterations in long-term aortocoronary artery saphenous vein bypass grafts with particular attention to the features of cell death in atherosclerotic lesions. Stenotic vein grafts were obtained from 10 patients at redo coronary artery bypass grafting operations. All the grafts were affected by histological abnormalities, with eight out of ten grafts showing evidence of atherosclerotic alterations in the intimal hyperplastic layer. Areas containing foam cells were examined by electron microscopy. Cells with cytoplasmic lipid accumulations were characterized by varying degrees of chromatin condensation, fragmentation or dispersion, by focal areas of oedema and vacuolisation of their cytoplasm, and by plasmalemmal destruction. Some lipid-filled cells exhibiting signs of destruction contained myofilaments and basal membrane fragments, allowing them to be identified as smooth muscle cells. Macrophage foam cells were found to have undergone similar destruction. No cells showing nuclear degeneration were observed to have intact cytoplasmic organelles. Neither were apoptotic bodies identified, but necrotic remnants were frequently seen. The results suggest that cell death in atherosclerotic lesions affecting aortocoronary artery saphenous vein bypass grafts occurs through oncosis rather than by apoptosis.

Adult↗

PubMed1998

Bcl-x and Bcl-2 immunoreactivity in postnatal mouse barrel fields.

BcL-xL and Bcl-2 proteins were identified by paraffin section immunohistochemistry in the neuropil core of the barrelettes of the caudalis spinal trigeminal nucleus 6 h after birth. They were subsequently identified at progressively more rostral levels of the trigeminal pathway, peaking in barreloid neuropil cores in the ventral posterior thalamic nucleus at postnatal day (P)4.5, and in cortical barrel cores at P7. Labelling was confined to the cores of barrel-like structures surrounded by immunonegative shells and became progressively less distinct at all levels from P8. These protein products, which are usually considered to control the onset of apoptosis, may serve other functions in the axon terminal fields of the trigeminal pathway.

Aging↗

PubMed1998

Prenatal development of the vestibular ganglion and vestibulocerebellar fibres in the rat.

We have used carbocyanine dye tracing techniques in conjunction with photoconversion and electronmicroscopy to examine the prenatal development of the central and peripheral processes of those vestibular ganglion cells projecting to the cerebellum. Developmental changes in the number of vestibular ganglion cells were assessed in paraffin-embedded material by nucleolar counting. In agreement with the results of parvalbumin staining, afferents to the cerebellum from the vestibular ganglion pursued a superficial course during early fetal life (E13 to E15). From E16 to E19, this superficial position was progressively lost and vestibulocerebellar fibres were seen to be directed towards the ventricular surface (prospective posterior/inferior vermis). The change in the course of vestibular afferents to the cerebellum coincided with a profound reduction in the number of ganglion cells which could be retrogradely 1a-belled from the cerebellar anlage (mean+/-SD: E16-2040+/-1130; E19-510+/-440). During that same period the total number of vestibular ganglion cells rose to peak at a mean of 9200 at E19, although there was a subsequent decline to an average of 4660 at P0. This population size was maintained through to adult life (4600). We also examined the development of connections between the vestibular ganglion and the vestibular apparatus. Peripheral processes of vestibular ganglion cells invaded the macula utricle and saccule and cristae of the semicircular canals from E13. We found that the peripheral vestibular ganglion cell processes themselves did not show any significant morphological changes from E16 to E21, but the sensory epithelium itself adopts a mature pseudostratified appearance by E21. This suggests that the loss of vestibular ganglion cells from E19 to birth is not related to major morphological changes in the peripheral axons, at least as revealed by carbocyanine dye labelling of these from the cerebellum, but may be associated with differentiation of the sensory epithelium to the mature pseudostratified form. Electronmicroscopy of photoconverted vestibulocerebellar fibres showed that at E14 these afferents were grouped in tight bundles of up to 20 axons. No particular association with the superficially placed external granular layer cells was found at that age. By E16 photoconverted vestibulocerebellar axons were no longer as tightly bundled and could be seen coursing more ventrally through the cerebellar anlage. The findings indicate that vestibulocerebellar fibres are not likely to physically facilitate external granular layer migration, since they do not attain a particularly close structural association with those cells. The observed developmental changes in the number of vestibular ganglion cells projecting to the cerebellum and the total number of vestibular ganglion cells suggests that changes in the course of vestibulocerebellar fibres are associated at first with retraction of cerebellar afferents, and subsequently with developmental cell death in the ganglion.

Afferent Pathways↗