Neutralisation of SARS-CoV-2 by anatomical embalming solutions

Teaching and learning anatomy by using human cadaveric specimens has been a foundation of medical and biomedical teaching for hundreds of years. Therefore, the majority of institutions that teach topographical anatomy rely on body donation programmes to provide specimens for both undergraduate and postgraduate teaching of gross anatomy. The COVID‐19 pandemic has posed an unprecedented challenge to anatomy teaching because of the suspension of donor acceptance at most institutions. This was largely due to concerns about the potential transmissibility of the SARS‐CoV‐2 virus and the absence of data about the ability of embalming solutions to neutralise the virus. Twenty embalming solutions commonly used in institutions in the United Kingdom and Ireland were tested for their ability to neutralise SARS‐CoV‐2, using an established cytotoxicity assay. All embalming solutions tested neutralised SARS‐CoV‐2, with the majority of solutions being effective at high‐working dilutions. These results suggest that successful embalming with the tested solutions can neutralise the SARS‐CoV‐2 virus, thereby facilitating the safe resumption of body donation programmes and cadaveric anatomy teaching.

Proof-of-concept prototype drill-guide for use in medial patello-femoral ligament (MPFL) reconstruction surgery

For surgical reconstruction of the medial patello-femoral ligament (MPFL) a variety of techniques are used for fixation of the graft to the medial border of the patella. The bone bridge or V-shaped tunnel technique utilises two tunnels drilled from the medial aspect of the patella that converge centrally creating a tunnel through which the graft is threaded. This technique has advantages: it avoids hardware (bone anchors) and their associated complications, creates a broad attachment of the ligament approximating normal anatomy and the tunnel does not breach the lateral cortex of the patella reducing the risk of patella fracture. In current practice the bony tunnels are created using freehand techniques. These rely on estimation of the patella centre by the surgeon and is subject to wide variation. Additionally this technique can be inefficient, inaccurate and time consuming. To address these disadvantages a new drill-guide device was developed. A prototype drill-guide was constructed using CAD and 3D printing methods. The device was designed to allow the surgeon to accurately and efficiently drill the required v-shaped bone tunnel. To assess the efficacy of the prototype drill guide, an experiment designed to assess a group of ten surgeons with an average of 4.2 years experience performing the task of creating a v-shaped bone tunnel using a free-hand technique and the drill-guide. To determine the accuracy of the tunnel placement, the angle between drill holes, distance from centre of the patella and the amount of over-drill were measured. Procedure duration was also compared. The results revealed that the prototype drill-guide created a more accurate bone bridge than the traditional free hand method. The root mean square error for the distance from centre was 0.50 mm vs 2.12 mm and the angle between tunnels was 2.6O vs 15.9O for the prototype and traditional methods respectively. There was a mean of 8.9 mm over-drill with the traditional method, which was negated when using the guide. Surgeons using the guide were approximately 25% faster than using the traditional free-hand technique. The prototype drill-guide improved the accuracy, reduced the variability, and reduced procedure duration compared to the traditional free-hand technique.

A morphometric analysis of the suitability of the transverse cervical artery as a recipient artery in head and neck free flap microvascular reconstruction

PURPOSE

Gold standard recipient arteries in head and neck free flap microvascular reconstruction are currently branches of the external carotid. However, these arteries can be compromised by neck dissection or radiotherapy, resulting in 'vessel-depleted neck' and 'frozen neck' respectively. In such cases, the transverse cervical artery (TCA) may be a suitable recipient artery.

METHODS

The origin, course and diameter of the TCA were determined in 46 sides of neck from 23 cadavers. The distances from the origin of the TCA to the angle of the mandible, floor of the mouth and mandibular symphysis were measured to determine the pedicle length required for free flap anastomosis.

RESULTS

The TCA was present bilaterally in all subjects investigated and its course across the posterior triangle of the neck was constant between individuals. The mean distances from the origin of the TCA to the angle of mandible, floor of mouth and mandibular symphysis were 10.0, 9.2 and 12.6 cm, respectively. There were no significant differences in these distances between the left and right sides of the neck (p > 0.05 for all comparisons). The distances from the TCA origin to the angle of the mandible and floor of the mouth were significantly longer in males than in females (p = 0.004) and correlated directly with the greater height of males compared to females (p = 0.0004). The mean diameter of the TCA measured 2 cm from its origin was 2.2 mm.

CONCLUSION

The TCA is a suitable and reliable recipient artery for free flap microvascular reconstruction, when branches of the external carotid artery are unavailable.

The role of anatomy demonstrators: A surgical trainees' perspective

Core Surgical Trainees (CST) in the London (UK) Postgraduate School of Surgery receive clinical anatomy teaching in their first year of training, and, in their second year, give 30 sessions of anatomy teaching to medical and other students. This study set out to investigate the role of demonstrators from the perspective of the trainees. A focus group was convened to ascertain trainees' perspectives on demonstrating anatomy and to identify problems and improvement strategies to optimize their ability to enhance students' learning. A questionnaire was formulated and all second-year CST (n = 186-from two cohorts) in the London Postgraduate School of Surgery were invited. A total of 109 out of 186 trainees completed the questionnaire. A high percentage (98%) of trainees that completed the questionnaire responded that demonstrating was an invaluable part of their training. Sixty-two per cent responded that anatomy teaching they received in their first year of core surgical training helped them in their teaching role and 80% responded that it helped them prepare for surgical training. The study also revealed the need for improved communication between trainees and the London Postgraduate School of Surgery/Medical Schools/National Health Service Trusts to address issues such as trainees' perceived difficulty in fulfilling their teaching session requirement. The stakeholders have acknowledged and addressed the outcomes to improve the experience for both surgical trainees and students. The results indicate that anatomy demonstrating delivers important benefits to early surgical trainees, in addition to those received by the students that they teach. Clin. Anat. 31:409-416, 2018. © 2017 Wiley Periodicals, Inc.

The Anatomical Society core regional anatomy syllabus for undergraduate medicine

The Anatomical Society's core syllabus for anatomy (2003 and later refined in 2007) set out a series of learning outcomes that an individual medical student should achieve on graduation. The core syllabus, with 182 learning outcomes grouped in body regions, referenced in the General Medical Council's Teaching Tomorrow's Doctors, was open to criticism on the grounds that the learning outcomes were generated by a relatively small group of anatomists, albeit some of whom were clinically qualified. We have therefore used a modified Delphi technique to seek a wider consensus. A Delphi panel was constructed involving 'experts' (n = 39). The revised core syllabus of 156 learning outcomes presented here is applicable to all medical programmes and may be used by curriculum planners, teachers and students alike in addressing the perennial question: 'What do I need to know ?'

GFAP immunoreactivity within the rat nucleus ambiguus after laryngeal nerve injury

Changes that occur in astroglial populations of the nucleus ambiguus after recurrent (RLN) or superior (SLN) laryngeal nerve injury have hitherto not been fully characterised. In the present study, rat RLN and SLN were lesioned. After 3, 7, 14, 28 or 56 days of survival, the nucleus ambiguus was investigated by means of glial fibrillary acidic protein (GFAP) immunofluorescence or a combination of GFAP immunofluorescence and the application of retrograde tracers. GFAP immunoreactivity was significantly increased 3 days after RLN resection and it remained significantly elevated until after 28 days post injury (dpi). By 56 dpi it had returned to basal levels. In contrast, following RLN transection with repair, GFAP immunoreactivity was significantly elevated at 7 dpi and remained significantly elevated until 14 dpi. It had returned to basal levels by 28 dpi. Topographical analysis of the distribution of GFAP immunoreactivity revealed that after RLN injury, GFAP immunoreactivity was increased beyond the area of the nucleus ambiguus within which RLN motor neuron somata were located. GFAP immunoreactivity was also observed in the vicinity of neuronal somata that project into the uninjured SLN. Similarly, lesion of the SLN resulted in increased GFAP immunoreactivity around the neuronal somata projecting into it and also in the vicinity of the motor neuron somata projecting into the RLN. The increase in GFAP immunoreactivity outside of the region containing the motor neurons projecting into the injured nerve, may reflect the onset of a regenerative process attempting to compensate for impairment of one of the laryngeal nerves and may occur because of the dual innervation of the posterior cricoarytenoid muscle. This dual innervation of a very specialised muscle could provide a useful model system for studying the molecular mechanisms underlying axonal regeneration process and the results of the current study could provide the basis for studies into functional regeneration following laryngeal nerve injury, with subsequent application to humans.

The role of fear in one-trial passive avoidance learning in Japanese quail chicks genetically selected for long or short duration of the tonic immobility reaction

Emotional arousal has been shown to affect learning in mammals, but little is known about the relationship between fear and learning in birds. In order to investigate this relationship, the learning abilities of Japanese quail chicks from lines that have been divergently selected for high or low levels of underlying fearfulness, as measured by the duration of tonic immobility behaviour, were compared. Day-old chicks from both lines were trained in a one-trial passive avoidance task. In this task, young chicks spontaneously peck at a small, visually conspicuous bead. If the bead has been coated with a gustatory aversant, the chicks learn in a single trial not to peck a similar, uncoated bead upon subsequent presentation. Significantly more chicks of the low fear line pecked the training bead compared to those of the high fear line. However, 2 h later, chicks of both lines trained on a methyl anthranilate-coated bead showed similar avoidance of the test bead. Therefore, although fear affected performance during training, it did not appear to directly affect memory formation in this task.

The anti-dopaminergic agent, haloperidol, antagonises the feminising effect of neonatal serotonin on sexually dimorphic hypothalamic nuclei and tyrosine hydroxylase immunoreactive neurones

There is a transient fall in hypothalamic serotonin (5-hydroxytryptamine; 5-HT) activity in the second week post partum in male but not female rats. When this fall is masked by administration of the 5-HT(2) agonist (-) 2,5-dimethoxy-4-iodophenyl]-2-aminopropane hydrochloride [(-)DOI], over days 8-16 post partum, males are feminised in adulthood. To investigate whether the effect of 5-HT is mediated by dopamine and whether testosterone exerts its masculinising effect by reducing 5-HT and dopamine activity, male pups were treated with (-)DOI alone or together with the dopamine antagonist, haloperidol, over days 8-16 post partum, whereas females were treated with testosterone propionate on day 2 post partum. In adulthood, the volumes of the anteroventral periventricular nucleus (AVPV), sexually dimorphic nucleus of the preoptic area (SDN-POA) and arcuate nucleus (ARC) were determined, together with the number of tyrosine hydroxylase-immunoreactive (TH-ir) cells and fibres within them. The concentrations of 5-HT, dopamine and their metabolites were also measured. (-)DOI treatment increased the volume of the AVPV, decreased that of the SDN-POA and increased the number of TH-ir cells in the AVPV. These feminising effects were antagonised by concurrent haloperidol treatment. Neonatal testosterone propionate masculinised the volumes of the female AVPV and SDN-POA and reduced the number of TH-ir cells in the AVPV. Dopamine and 5-HT turnover in the AVPV was greater in female compared to male rats and neonatal testosterone propionate reduced dopamine concentration in the female AVPV. Neonatal (-)DOI had no effect on dopamine and 5-HT activity in the AVPV but increased both in the ARC. The findings that TH-ir neurone number and dopamine activity are greater in the female AVPV; the feminising effect of 5-HT is prevented by a haloperidol; and the masculinising effect of testosterone propionate is accompanied by a decrease in TH-ir neurone number and dopamine concentration in the female AVPV, suggest that dopamine is involved in hypothalamic sexual differentiation and may mediate the effect of 5-HT.

The transverse acetabular ligament may be used to align the acetabular cup in total hip arthroplasty

Accurate positioning of the acetabular component in total hip arthroplasty is essential to minimise the risk of dislocation and preserve the range of movement of the hip. It also affects polyethylene wear and the rate of osteolysis. Although there are many tools available to the surgeon to aid placement of the acetabular component, errors still occur, especially in version. We conducted a study of 14 cadaveric hips to investigate whether the transverse acetabular ligament can be used to align implanted cups with the correct degree of anteversion. Radiographic measurement revealed that all of the implanted cups were found to lie within the 'safe zone' for anteversion, when aligned with the ligament.

Caecal ligation and puncture in the rat mimics the pathophysiological changes in human sepsis and causes multi-organ dysfunction

Sepsis is a major clinical challenge that is associated with encephalopathy and multi-organ dysfunction. Current therapeutic interventions are relatively ineffective and the development of novel treatments is hampered by the lack of a well-characterised animal model. Therefore, the behavioural, metabolic, physiological and histological changes resulting from 'through and through' caecal ligation and puncture (CLP) in the rat were investigated to determine its suitability as an animal model of human sepsis. CLP resulted in bacteraemia, characterised by the presence of multiple enteric species within 18-20 h. Locomotor activity was reduced within 4 h of CLP and this reduction increased with time. Pyrexia was evident 4-5 h after CLP and was followed by hypothermia beginning 17 h after intervention. CLP resulted in reduced white blood cell and platelet counts and an increased neutrophil: lymphocyte ratio within 18-20 h. It also resulted in decreased blood glucose, but not lactate levels. CLP caused histopathological changes in the cerebral cortex, liver, lungs and vascular system indicative of multi-organ dysfunction. Therefore, CLP in the rat mimics the cardinal clinical features of human sepsis and the subsequent development of multi-organ dysfunction. It appears to be the best available animal model currently available, in which to investigate the underlying pathophysiology of sepsis and identify therapeutic targets.

The control of sexual differentiation of the reproductive system and brain

This review summarizes current knowledge of the genetic and hormonal control of sexual differentiation of the reproductive system, brain and brain function. While the chromosomal regulation of sexual differentiation has been understood for over 60 years, the genes involved and their actions on the reproductive system and brain are still under investigation. In 1990, the predicted testicular determining factor was shown to be theSRYgene. However, this discovery has not been followed up by elucidation of the actions of SRY, which may either stimulate a cascade of downstream genes, or inhibit a suppressor gene. The number of other genes known to be involved in sexual differentiation is increasing and the way in which they may interact is discussed. The hormonal control of sexual differentiation is well-established in rodents, in which prenatal androgens masculinize the reproductive tract and perinatal oestradiol (derived from testosterone) masculinizes the brain. In humans, genetic mutations have revealed that it is probably prenatal testosterone that masculinizes both the reproductive system and the brain. Sexual differentiation of brain structures and the way in which steroids induce this differentiation, is an active research area. The multiplicity of steroid actions, which may be specific to individual cell types, demonstrates how a single hormonal regulator, e.g. oestradiol, can exert different and even opposite actions at different sites. This complexity is enhanced by the involvement of neurotransmitters as mediators of steroid hormone actions. In view of current environmental concerns, a brief summary of the effects of endocrine disruptors on sexual differentiation is presented.

High-resolution MRI in evaluation of the surgical anatomy of the esophagus and posterior mediastinum

OBJECTIVE

The purpose of this study was to use high-resolution MRI to evaluate the surgical anatomy of the posterior mediastinum, in particular the esophagus and its relation to the surrounding structures. The aim was to familiarize radiologists with the appearance of structures considered important in planning surgical resection of the esophagus.

MATERIALS AND METHODS

The thoraces of two cadavers were imaged with a 1.5-T magnet using a high-resolution T2-weighted sequence. Axial cadaveric sections of the posterior mediastinum were cut with a band saw at levels determined from the MR images, and histologic whole-mount sections of the esophagus and surrounding tissue were prepared from the cadaveric sections. The appearance of structures identified on the MR images was compared with the findings on corresponding gross anatomic and histologic whole-mount sections.

RESULTS

The MR images depicted the esophagus and structures in close anatomic relation: the pleural reflections and pericardium. The technique enabled visualization of structures to our knowledge not previously described on cross-sectional imaging: the individual layers of the esophageal wall, the thoracic duct, a connective tissue layer attaching the esophagus to the anterior wall of the aorta, and a fascial plane passing between layers of the right and left parietal pleura posterior to the esophagus.

CONCLUSION

High-resolution MRI of the posterior mediastinum provides detailed anatomic information, delineating structures not visible on other forms of cross-sectional imaging. It can provide important information for planning surgical intervention.

Neonatal 5HT activity antagonizes the masculinizing effect of testosterone on the luteinizing hormone release response to gonadal steroids and on brain structures in rats

Hypothalamic 5HT concentrations are transiently lower in male compared to female Wistar rats in the second week post partum (pp) and our previous findings have shown that pharmacologically potentiating 5HT activity over this period feminizes certain aspects of sexually differentiated behaviours in adult males and androgenized females. In order to investigate whether neonatal testosterone and 5HT interact to influence physiological and morphological brain sexual differences, females, androgenized females and males were treated with the 5HT2 agonist (-) [2,5 dimethoxy-4-iodophenyl]-2-amino propane HCl [(-) DOI], over days 8-16 pp. In androgenized females (250 microg testosterone proprionate, day 2 pp) (-) DOI prevented the delay in vaginal opening, but did not prevent the androgen-induced constant oestrus in females treated with 100 microg TP, day 2 pp. (-) DOI overcame the neonatal androgen effect in suppressing the positive feedback of ovarian steroids in a few males and androgenized females. (-) DOI had a feminizing effect on the volume of the anteroventral periventricular nucleus (normally smaller in males), by significantly increasing its volume in male and androgenized females. It also had a significant antagonistic effect on the testosterone-induced increase in the volume of the sexually dimorphic nucleus of the preoptic area in males and androgenized females. These findings support the view that raised 5HT activity in the second week of life antagonizes the masculinizing effect of neonatal testosterone.

Hyperphosphorylated tau and paired helical filament-like structures in the brains of mice carrying mutant amyloid precursor protein and mutant presenilin-1 transgenes

Senile plaques composed mainly of beta-amyloid (Abeta) and neurofibrillary tangles principally composed of hyperphosphorylated tau are the major pathological features of Alzheimer's disease (AD). Despite the fact that increased expression of amyloid precursor protein (APP) and presenilin-1 (PS1) transgenes in mice lead to increased Abeta deposition in plaquelike structures in the brain, little is known about the nature and distribution of tau in these mice. Therefore the relationship between Abeta and hyperphosphorylated tau was investigated in mice carrying mutant APP and mutant PS1 transgenes using both light (LM) and electron microscopy (EM) with immunocytochemistry. LM immunocytochemistry revealed cerebral Abeta deposits to be present from 8 weeks of age, whereas hyperphosphorylated tau was not detected until 24 weeks of age, when it appeared as punctate deposits in close association with the Abeta deposits in the cortex and hippocampus. However, dystrophic neurites were not as heavily immunolabeled as they are in AD brain. EM revealed that aggregations of straight filaments (10-12 nm wide) were present in some cellular processes at the periphery of Abeta plaques in 8-month-old APP/PS1 mice. In one such mouse, single filaments and paired filaments showing a helical configuration (50-55 nm half-period, 25 nm max. width) were present in a dark, atrophic hippocampal neuron. Immunogold labeling of APP/PS1 mouse brain revealed hyperphosphorylated tau epitopes in some dystrophic neurites from 24 weeks of age that were similar to those present in AD. These results suggest that hyperphosphorylated tau appears in APP/PS1 mouse brain after the onset of Abeta deposition and although it is associated with Abeta deposits, its distribution is not identical to that in AD.

Increased aquaporin 1 water channel expression in human brain tumours

Aquaporin 1 is a water channel protein. There was little aquaporin 1 immunoreactivity in normal brain parenchyma. In astrocytomas, aquaporin 1 was expressed in microvessel endothelia and neoplastic astrocytes. In metastatic carcinomas, aquaporin 1 was present in microvessel endothelia and reactive astrocytes. Aquaporin 1 may participate in the formation of brain tumour oedema.

Blood-brain barrier breakdown in septic encephalopathy and brain tumours

Septic encephalopathy is associated with breakdown of the blood-brain barrier and cerebral oedema. These features are also common properties of brain tumours. Perimicrovessel oedema, disruption of associated astrocyte end feet and neuronal injury occur in a porcine model of acute septic encephalopathy. The adrenergic system has been implicated in the inflammatory response to sepsis and may play a role in controlling blood-brain barrier permeability, since the beta2-adrenoceptor agonist dopexamine inhibits perimicrovessel oedema formation whereas the alpha1-adrenoceptor agonist methoxamine provokes it. Electron microscopy revealed tight junction opening in high-grade astrocytoma microvessels. Expression of the tight junction protein occludin is reduced in these microvessels and this reduction is inversely correlated with the degree of cerebral oedema. Normal astrocytes secrete factors that induce barrier properties in endothelial cells, whereas high-grade astrocytomas secrete vascular endothelial growth factor, which stimulates angiogenesis, down regulates occludin and increases endothelial cell permeability. The water channel protein aquaporin-4 is normally expressed in astrocyte foot processes around cerebral microvessels. Its expression is massively up-regulated in high-grade astrocytoma and around metastatic adenocarcinoma. There is a significant correlation between aquaporin-4 expression and the degree of cerebral oedema, but it is not clear whether increased aquaporin-4 expression enhances oedema formation or clearance. These results suggest that the pathophysiology of brain oedema is multifactorial, but that there may be common processes operating regardless of the aetiology.

The intrinsic neuronal organisation of the nucleus of the basal optic root in the domestic chicken; a light and electron microscopic study using anterograde tracers and postembedding GABA-immunostaining

The intrinsic neuronal organisation in the nucleus of the basal optic root of chickens was investigated. The divergent connections with various areas and the functional complexity of the nucleus require a complex intrinsic structural arrangement. Therefore, an analysis of Golgi impregnated material, ultrastructure, GABA-immunocytochemistry and biotinylated dextran-amine anterograde tracer analysis of the nucleus was carried out. In the Golgi analysis, a characteristic dendritic ramification pattern of two types of putative projection neurons was observed. These neurons form dendritic nests with their overlapping dendritic terminal sections, that develop synaptic fields with the optic fibre terminals. These synaptic fields were confirmed by electron microscopy. GABA-immunopositive terminals synapse with distinct loci of the dendritic trees of projection neurons; they may therefore play an important role in the inhibitory-modulatory system of the nucleus of the basal optic root. The GABA-immunopositive terminals derive from small and/or elongated local circuit neurons which receive retinal afferents, and from myelinated fibres afferents to the nucleus of unknown origin.

Aquaporin-4 expression is increased in oedematous human brain tumours

Aquaporin-4 (AQP4) is a highly conserved water channel protein. In rats, AQP4 is expressed in astrocyte foot processes and is important in brain water homeostasis. AQP4 expression has not been investigated in non-neoplastic human brain or oedematous brain tumours, where water homeostasis is disrupted. Therefore, immunohistochemistry was used to study AQP4 expression in non-neoplastic and neoplastic human brain and blood-brain barrier permeability was assessed using contrast enhanced computed tomograms. AQP4 was present around microvessels in five specimens of non-neoplastic brain and five low grade (Daumas-Duport I or II) astrocytomas. AQP4 was massively upregulated in four and absent in one high grade (Daumas-Duport III or IV) astrocytoma. Massive upregulation of AQP4 was also found in reactive astrocytes in five metastatic adenocarcinomas. There was significant (p<0.0001) correlation between blood-brain barrier opening and upregulated AQP4 expression. Increased AQP4 expression in high grade astrocytomas and adenocarcinomas may facilitate the flow of oedema fluid.

Striato-amygdaloid transition area lesions reduce the duration of tonic immobility in the lizard Podarcis hispanica

Neuroanatomical data suggest that the lizard striato-amygdaloid transition area is homologous with the mammalian central amygdala. In order to investigate possible functional similarities, tonic immobility was induced in adult lizards and its duration recorded. Each lizard was then randomly assigned to one of three treatments: (1) bilateral striato-amygdaloid transition area lesions, (2) bilateral dorsal cortex lesions or (3) untreated controls. Three days after trial 1, each lizard was subjected to a second trial and the tonic immobility duration recorded. The mean tonic immobility duration in lizards with striato-amygdaloid transition area lesions was significantly shorter (80.5%; p < 0.0033) in trial 2 than in trial 1. There were no inter-trial differences within dorsal cortex-lesioned lizards or untreated controls. There was a significant treatment effect on tonic immobility duration in trial 2 (p < 0.0001). The mean tonic immobility duration of lizards with striato-amygdaloid transition area lesions was significantly shorter than that of dorsal cortex-lesioned lizards (72.2%; p < 0.01) or untreated controls (78.2%; p < 0.01). There was no significant difference in mean tonic immobility duration between dorsal cortex-lesioned lizards and untreated controls. Tonic immobility is considered to be an anti-predator behaviour that reflects the underlying state of fear. Therefore, the reduced tonic immobility duration in lizards with striato-amygdaloid transition area lesions reflects a reduction of fear. These results provide the first data to indicate a functional similarity between the lizard striato-amygdaloid transition area and the mammalian central amygdala.

The ramification and connections of retinal fibres in layer 7 of the domestic chick optic tectum: a golgi impregnation, anterograde tracer and GABA-immunogold study

Layer 7 is one of the retinorecipient layers of the avian optic tectum. However, little information is available about the neuronal organization of this layer and its implications for visual function. Golgi impregnation was used to investigate the retinal input to and the neuronal architecture of layer 7 of the chick optic tectum, which forms a narrow band between the two cell-dense layers 6 and 8. Anterograde tracers were also used to investigate the afferent and efferent connections of layer 7, in both the light and the electron microscope, together with GABA immunogold labelling. Three types of radial neuron were defined according to the origin and course of their axons. The perikarya of these neurons were situated in tectal layers 10-11. The principal dendrites of these radial neurons ascended to the tectal surface and gave rise to dendritic side-branches in layer 7. These dendritic side-branches received asymmetric synapses from the terminations of retinal fibre arborisations. Type 2 radial neurons, whose axons arose from the deep pole of the perikaryon or occasionally from a basal dendrite, were shown to project to the nucleus isthmi pars magnocellularis, which has previously been demonstrated to be GABAergic and to project to glomerulus-like complexes in tectal layers 4-5. In these layers, the dendritic branches of layer 13 neurons that project to the nucleus rotundus have previously been shown to receive retinal fibre input. Therefore, the retinal input to layer 7 may be able to modulate the transmission of information to the visual thalamus, by way of a feed-back loop to layers 4-5 of the tectum involving the nucleus isthmi pars magnocellularis.

Occludin expression in microvessels of neoplastic and non-neoplastic human brain

The tight junction protein occludin 'glues' normal, adjacent brain microvessel endothelial cells together. Malignant brain tumours cause cerebral oedema because they have leaky endothelial tight junctions, which allow plasma fluid to enter the brain from the microvessel lumen. In order to identify molecular abnormalities in tumour endothelial tight junctions, we investigated occludin expression in microvessels from adult human non-neoplastic brain tissue using immunohistochemistry and immunoblotting. The proportions of microvessels immunolabelling for occludin were >2/3 in 5/5 non-neoplastic brain tissue samples, >1/3 in 5/5 low grade (Daumas-Duport I or II) astrocytomas and <1/3 in 5/5 high grade (III or IV) astrocytomas and 6/6 metastatic adenocarcinomas. Six non-neoplastic brain tissue immunoblots gave a 55-kDa occludin band, three low-grade astrocytomas gave 55-kDa and 60-kDa bands, 13 high-grade astrocytomas gave 60-kDa or no band and four adenocarcinomas did not give an occludin band. Expression of 55-kDa occludin inversely correlated with the presence of contrast enhancement on computed tomograms (P < 0.001). Electron microscopy showed open endothelial tight junctions in 0/2 non-neoplastic human brain specimens and 2/2 high-grade astrocytomas. We suggest that loss of 55-kDa occludin expression in human brain tumours may contribute to endothelial tight junction opening. Characterizing the molecular pathology of brain endothelial tight junctions may facilitate the design of novel drugs against cerebral oedema.

Neurodegenerative changes associated with beta-amyloid deposition in the brains of mice carrying mutant amyloid precursor protein and mutant presenilin-1 transgenes

Mutations of amyloid precursor protein (APP) and presenilin-1 (PS1) lead to an increase in beta-amyloid (Abeta) production. Despite the fact that a number of transgenic mice develop cerebral Abeta plaques, few have been subjected to ultrastructural investigation and the sequence of events leading to Abeta plaque formation is unclear. We therefore investigated the doubly transgenic (mutant APP(K670N,M671L)-mutant PS1(M146L)) mouse, which develops Abeta deposits much earlier than singly transgenic littermates. Widespread Abeta plaques with or without a distinct core were found in gray matter. Abeta plaques were also present in white matter. Astrocytosis was greater around gray matter plaques than around white matter plaques. In some plaques, Abeta cores were associated with cell profiles containing prominent endoplasmic reticulum and a homogeneous cytoplasm that appeared to be neuronal. The morphology and location of other profiles indicated them to be microglia or oligodendrocytes. Some Abeta fibrils appeared to lie within these profiles, but they may have been simply surrounded by the cell profile since the profile membrane was not always visible. Dark atrophic neurons, whose morphology suggested that they were apoptotic, were present around gray matter plaques. Cerebrovascular Abeta deposition was also observed in the brains of APP/PS1 transgenic mice. Thus, the amyloid deposition and neuropathology observed in APP/PS1 mouse brain are similar to those in Alzheimer's disease and they appear to develop earlier and become more severe than in the other transgenic models currently available.

Enlargement of the fornix in early-onset schizophrenia: a quantitative MRI study

Abnormalities of temporal lobe structure and frontal lobe function occur in schizophrenia. There have been few studies of young people with schizophrenia and little is known about temporo-frontal connectivity in the disease. Therefore, the cross-sectional area of the body of the fornix was measured on MR images from 17 young people with schizophrenia, nine with other serious psychiatric illnesses and eight without illness. The mean age of each group was 16-17 years. The mean cross-sectional fornix area in subjects with schizophrenia was significantly larger than that in subjects without illness ( approximately 40%) and psychiatric controls ( approximately 26%). There was no such significant difference between subjects without illness and psychiatric controls. The nature of the larger fornix in early-onset schizophrenia, whether it persists and whether it occurs in schizophrenia presenting in adulthood, remain to be elucidated.

Emerging molecular mechanisms of brain tumour oedema

A common property of brain tumours is their ability to cause oedema in the surrounding brain. Oedema forms as a result of a leaky blood-tumour barrier and persists when the brain fails to clear the excess fluid. It is a significant source of morbidity and mortality. The principal anatomical component of the blood-brain barrier is the endothelial tight junction which opens in glioma microvessels. Multiple tight junction proteins have recently been identified, such as occludin, claudin, ZO-1, ZO-2 and ZO-3. We propose a model to explain tight junction opening in gliomas based on vascular endothelial growth factor secretion and loss of tight junction inducing factor production by tumour cells. The level of expression of the water channel aquaporin-4 in peritumoural astrocytes may determine the rate of oedema fluid clearance. The identification of the molecular mechanisms of brain tumour oedema may allow the design of novel anti-oedema medications.

Conditional immortalization of freshly isolated human mammary fibroblasts and endothelial cells

Reports differ as to whether reconstitution of telomerase activity alone is sufficient for immortalization of different types of human somatic cells or whether additional activities encoded by other "immortalizing" genes are also required. Here we show that ectopic expression of either the catalytic subunit of human telomerase (hTERT) or a temperature-sensitive mutant (U19tsA58) of simian virus 40 large-tumor antigen alone was not sufficient for immortalization of freshly isolated normal adult human mammary fibroblasts and endothelial cells. However, a combination of both genes resulted in the efficient generation of immortal cell lines irrespective of the order in which they were introduced or whether they were introduced early or late in the normal proliferative lifespan of the cultures. The order and timing of transduction, however, did influence genomic stability. Karyotype analysis indicated that introduction of both transgenes at early passage, with hTERT first, yielded diploid cell lines. Temperature-shift experiments revealed that maintenance of the immortalized state depended on continued expression of functional U19tsA58 large-tumor antigen, with hTERT alone unable to maintain growth at nonpermissive temperatures for U19tsA58 large-tumor antigen. Such conditional diploid lines may provide a useful resource for both cell engineering and for studies on immortalization and in vitro transformation.

Comparison of methyl anthranilate and denatonium benzoate as aversants for learning in chicks

Methyl anthranilate (MeA) has been widely used as a taste aversant for domestic chicks in the one-trial passive avoidance learning (PAL) task. However, MeA has a strong smell that may be aversive to chicks. Therefore, odourless denatonium benzoate (DB) has been suggested as an alternative taste aversant in PAL. The present study was designed to compare the efficacy of MeA and DB as aversants in the one-trial PAL task. In this task, young chicks peck a visually conspicuous bead coated with a taste aversant and in a single trial learn to avoid a similar, but uncoated bead at subsequent presentation. In Experiment 1, chicks were trained using a silver-coloured bead coated with 100% MeA, 0.5% DB or distilled water. After 3 h, MeA-trained, but not DB-trained chicks, exhibited significantly higher avoidance of the test bead than water-trained chicks. In Experiment 2, three pre-training presentations of an uncoated red bead preceded training with the silver bead. MeA-trained chicks showed significantly higher avoidance of the test bead than water-trained chicks. The numbers of water- and DB-trained chicks that avoided pecking the test bead were low and not significantly different from each other. However, DB-trained chicks exhibited significantly longer latencies to peck the test bead than water-trained chicks, indicating that they had retained some memory of the task. Thus, 0.5% DB is a weaker aversant than MeA and it does not induce high levels of learning in the one-trial PAL task. However, DB may prove useful for investigating weakly reinforced learning.

Pathophysiology of septic encephalopathy: a review

OBJECTIVES

Encephalopathy is a common complication of sepsis. This review describes the different pathologic mechanisms that may be involved in its etiology.

DATA SOURCES

The studies described here were derived from the database PubMed (http:¿¿www.nlm.nih.gov) and from references identified in the bibliographies of pertinent articles and books. The citations are largely confined to English language articles between 1966 and 1998. Older publications were used if they were of historical significance.

STUDY SELECTION

All investigations in which any aspect of septic encephalopathy was reported were included. This selection encompasses clinical, animal, and in vitro cell culture work.

DATA EXTRACTION

The literature cited was published in peer-reviewed clinical or basic science journals or in books.

DATA SYNTHESIS

Contradictions between the results of published studies are discussed.

CONCLUSIONS

The most immediate and serious complication of septic encephalopathy is impaired consciousness, for which the patient may require ventilation. The etiology of septic encephalopathy involves reduced cerebral blood flow and oxygen extraction by the brain, cerebral edema, and disruption of the blood-brain barrier that may arise from the action of inflammatory mediators on the cerebrovascular endothelium, abnormal neurotransmitter composition of the reticular activating system, impaired astrocyte function, and neuronal degeneration. Currently, there is no treatment.

Distribution of CGRP-like immunoreactivity in the chick and quail brain

Calcitonin gene-related peptide (CGRP)-containing neurones have been implicated in the transmission of visceral sensory information to the cortex and in the control of arterial blood pressure in mammals. However, little is known about its function in other vertebrates. As a first step toward investigating the function of CGRP in birds, its distribution was studied in the domestic chick and quail brain by means of immunocytochemistry, by using antibodies against rat CGRP. The distribution of CGRP immunoreactivity in the chick and quail central nervous system was found to be similar. CGRP-immunoreactive (CGRPi) perikarya were not present in the telencephalon. In the diencephalon, CGRPi perikarya were present mainly in the shell of the thalamic nucleus ovoidalis, the nucleus semilunaris paraovoidalis, the nucleus dorsolateralis posterior thalami, and in the hypothalamic nucleus of the ansa lenticularis. In the brainstem, CGRPi perikarya were present in the nucleus mesencephalicus nervi trigemini, the nucleus tegmenti ventralis, the locus coeruleus, the nucleus linearis caudalis and in the parabrachial region. In addition CGRPi perikarya were found in the motor nuclei of the III, IV, V, VI, VII, IX, X, and XII cranial nerves. The telencephalon contained CGRPi fibres within the paleostriatal complex (mainly in the ventral paleostriatum), parts of the neostriatum and ventral hyperstriatum, parts of the archistriatum, and the septum. In the diencephalon, the densest plexus of CGRPi fibres was observed in the dorsal reticular thalamus. A less dense CGRPi innervation was present in some dorsal thalamic nuclei and in the medial and periventricular hypothalamus. The pretectum and midbrain tegmentum also contained CGRPi fibres, whereas the optic tectum was virtually devoid of immunolabelling. Scattered CGRPi fibres were observed in the central grey and neighbouring pontine areas. Some of the sensory fibres of the trigeminal, vagal, glossopharyngeal, and spinal nerves were also CGRPi. The results of comparative studies indicate that the presence of CGRP in some thalamo-telencephalic projections is a primitive feature of the forebrain of amniotes. Therefore, the brain areas giving rise to and receiving such a projection in different vertebrates, are likely to be homologous.

Synaptic deficit in the temporal cortex of partial trisomy 16 (Ts65Dn) mice

Down syndrome results from triplication of human chromosome 21. The distal end of mouse chromosome 16 shares a large region of genetic homology with the Down syndrome 'critical region' of human chromosome 21. Therefore, a partially trisomic mouse (Ts65Dn) that possesses a triplication of the distal region of chromosome 16 has been developed as a putative model for Down syndrome. Ts65Dn mice display learning and memory deficits. However, despite the importance of preserved synaptic integrity for learning and memory, the ultrastructure of neural connectivity has not yet been studied in Ts65Dn mice. Therefore, the density and apposition zone length of synapses in the temporal cortex of aged Ts65Dn mice (n=4) were compared with those in diploid controls (n=4), using quantitative electron microscopy. There were significantly less (30%) asymmetric synapses in the temporal cortex of Ts65Dn mice than in controls (t=-5.067; p=0.023). However, there was no significant difference between the mean density of symmetric synapses in Ts65Dn mice and control mice. In addition, the mean synaptic apposition lengths of both asymmetric (15%; t=9.812, p<0.0001) and symmetric (11%; t=5. 582; p<0.0001) synapses were significantly larger in Ts65Dn mice than in controls. These results suggest that excitatory synapses are preferentially affected in Ts65Dn mice and that there is an attempt to compensate for the deficit of asymmetric synapses by increasing the contact zone area of existing synapses. The results may also reveal the morphological basis for the learning and memory deficits observed in Ts65Dn mice and have a bearing on the cognitive deficits in Down syndrome in old age.

A golgi and a combined Golgi/GABA immunogold study of local circuit neurons in the homing pigeon hippocampus

Three types of local circuit neurons have recently been reported in the homing pigeon hippocampus. The principal type appears to be constituted by the medium-sized angular or ovoid local circuit neurons that occur in all layers of the hippocampus. The current Golgi study has revealed that these neurons can be classified according to their axonal arborisation extension: (1) in all directions, (2) principally medio-laterally, or (3) dorso-ventrally. The local circuit neurons with dorso-ventral axon arborisation are present only in the subpyramidal layer. Serial sections of a Golgi-impregnated medium-sized, multiangular local circuit neuron in the pyramidal layer and a small, ovoid neuron in the suprapyramidal layer were investigated in the electron microscope. Some of these sections were processed for GABA immunogold cytochemistry. The soma and large dendrites of both neurons displayed GABA immunogold labelling. On the soma of medium-sized local circuit neuron there were numerous terminals; on the soma of the small one relatively fewer terminals were observed. The terminals contained round and/or flat synaptic vesicles. The long axonal branches of the neurons exhibited varicosities containing flattened or pleomorphic vesicles. Axo-dendritic, axo-somatic and a few axo-axonic synapses were observed. The large dense axon arborisation field of medium-sized local circuit neurons is properly situated to modulate intrinsic hippocampal activity and that of the small local circuit neurons is well situated to modulate the hippocampal input in the suprapyramidal layer.

A comparative Golgi study of chicken (Gallus domesticus) and homing pigeon (Columba livia) hippocampus

Neurons and fibres in the chick and homing pigeon hippocampus were described following Golgi impregnation. Two principal classes of neurons were distinguished: projection neurons with distant projecting axons and spiny dendrites, and local circuit neurons. In the homing pigeon and chicken hippocampus there are three types of projection neurons: pyramidal, pyramidal-like and multipolar. The pyramidal and pyramidal-like neurons are only found in the central 'pyramidal' layer of the hippocampus whereas multipolar neurons are present in the suprapyramidal, pyramidal and infrapyramidal layers. The axon of projection neurons typically emits several varicose collaterals from the initial section. Most of these collaterals extend along the infrapyramidal layer of the hippocampus, while others ascend to the pyramidal and suprapyramidal layers where they branch. The number of impregnated axon collaterals was higher in the homing pigeon than in the chick hippocampus. A variety of multi-angular/ovoid local circuit neurons ranging from small to large size are found in the homing pigeon and chick hippocampus. Their axons develop local arborization of varicose branches, the extent of which varies with the type of local circuit neurons. The density of GABA immunopositive local circuit neurons was found to be greater in the homing pigeon than in the chick. The profuse arborization of projection neuron axon collaterals and the higher density of GABA-immunopositive local circuit neurons in the homing pigeon hippocampus may underlie the differences in hippocampal function between the homing pigeon and chick, and this complex local connectivity may contribute to the ability of spatial orientation and memory.

CD7 expression distinguishes subsets of CD4(+) T cells with distinct functional properties and ability to support replication of HIV-1

Enrichment of a subset of CD4(+)CD45R0(+)CD7(-) T cells has been observed in HIV-infected individuals. We have investigated the ability of CD7(+) and CD7(-) T cells to support replication of HIV and show that virus replicates preferentially in CD7(+) cells. Several possible mechanisms that may underlie such differences in susceptibility to HIV were studied. Our data demonstrate that mitogen stimulation induces poor expression of CD25 and IL-2 in CD7(-) compared with CD7(+) cells. We also show that uninfected CD7(-) cells are more resistant to mitogen-induced apoptosis than CD7(+) cells. Our data support the view that the CD7(-) subset is inherently resistant to HIV replication and that this is due in part to reduced CD25 expression and IL-2 production.

beta-Amyloid immunoreactivity in astrocytes in Alzheimer's disease brain biopsies: an electron microscope study

The deposition of amyloid beta (A beta) protein plays a central role in the neuropathology of Alzheimer's disease (AD) and it constitutes the core of classical senile plaques. However, little is known about its intracellular distribution. An immunogold electron microscope study was therefore carried out on biopsies of brain tissue from patients with AD using a monoclonal antibody raised against residues 8 to 17 of the A beta protein. Specific A beta immunogold labeling was observed over extracellular amyloid fibrils associated with senile plaques. In addition, widespread intracellular A beta immunolabeling was observed adjacent to granular structures (30-40 nm in diameter) within membrane-bound processes. Pretreatment of some sections with amylase or omission of lead citrate staining from others strongly suggests that the electron-dense granular structures associated with A beta immunoreactivity are glycogen. Some of the A beta-immunolabeled processes contained gliofilaments and immunolabeling of alternate sections for glial fibrillary acidic protein confirmed that the A beta-immunolabeled processes were astrocytic. A beta immunolabeling was not observed over neuronal or microglial processes. Whether the presence of A beta protein in astrocytes is the result of synthetic or degradation processes requires further investigation.

Faecal peritonitis causes oedema and neuronal injury in pig cerebral cortex

Encephalopathy is a common complication of sepsis. However, little is known about the morphological changes that occur in the brain during sepsis. Faecal peritonitis was induced in pigs that were killed 8 h later and frontal cortex samples were taken immediately after death. The tissue was investigated using light and electron microscopy and compared with frontal cortex samples taken from sham-operated controls. Septic pigs had 49.5% more perimicrovessel oedema than sham pigs. However, the tight junctions between cerebral microvessel endothelial cells appeared morphologically intact in both septic and sham pigs. Sepsis also resulted in neuronal injury, disruption of astrocytic end-feet and swollen, rounded erythrocytes. These morphological changes may be sufficient to underlie the clinical features seen in septic encephalopathy.

In vitro testing of calcium channel blockers and cytotoxic chemotherapy in B-cell low-grade non-Hodgkin's lymphoma

The flux of calcium forms an important intracellular messenger system. The bcl-2 oncoprotein is thought to make cells resistant to a variety of insults, including cytotoxic drugs, by the suppression of apoptosis, which appears to involve the repartitioning of intracellular calcium. Three drugs that affect calcium pathways and may influence this repartitioning, i.e. dantrolene, azumolene (a water-soluble dantrolene analogue) and nimodipine, were studied in cell culture, using both a transformed follicle centre lymphoma cell line and primary culture of lymphoma cells in vitro in a manner that resulted in a growth pattern closely resembling that of the malignancy in vivo. Dantrolene and azumolene were potent inducers of cell death in both systems reducing the viable cell count by 70-90% in comparison with normal controls. Nimodipine, in comparison, appeared to have no significant effect. These results obtained in an in vitro setting suggest that further evaluation of dantrolene and azumolene for the treatment of low-grade non-Hodgkin's lymphoma is warranted.

Efferent connections of the domestic chick archistriatum: a phaseolus lectin anterograde tracing study

The archistriatum of the domestic chick has been implicated in both fear behaviour and learning. However, relatively little is known about its organisation. The efferent connections of discrete anatomical regions of the chick archistriatum were therefore investigated by iontophoresis of the anterograde tracer Phaseolus vulgaris leucoagglutinin into its anterior, dorsal intermediate, ventral intermediate, medial, and posterior parts. The results of this study suggest that the chick archistriatum can be divided into two basic divisions according to whether they project to the following limbic structures: the hippocampal formation, septal areas, lobus parolfactorius, nucleus accumbens, ventral paleostriatum, and dorsomedial thalamus. The limbic archistriatum includes the posterior archistriatum and extends rostrally through the ventral intermediate archistriatum into the anterior archistriatum. The non-limbic archistriatum comprises the dorsal intermediate and medial archistriatum and largely gives rise to specific sensory, somatosensory, and motor telencephalofugal efferents. There may not be distinct borders between these two divisions of the chick archistriatum.

Paired helical filament morphology varies with intracellular location in Alzheimer's disease brain

Paired helical filaments (PHFs) are one of the hallmark pathologies of Alzheimer's disease (AD). PHFs occur in three intracellular locations, although hitherto, it was not known whether all PHFs are structurally homogeneous. Parietal cortex biopsies were taken from five patients with a clinical and histopathological diagnosis of AD and processed for electron microscopy. Photomicrographs were then taken of PHFs in neurofibrillary tangles (NFTs), neuropil threads (NTs) and neuritic plaque (NP) neurites and their dimensions measured. The mean half period, maximum and minimum widths of PHFs in NFTs were significantly smaller than those in NTs or NP neurites. The mean half period and maximum width of PHFs in NTs were similar to those in NP neurites. These results reveal the presence of two distinct PHF populations and investigation of their relationship may shed light on the pathogenesis of AD.

The effect of archistriatal lesions on 'open field' and fear/avoidance behaviour in the domestic chick

The chick archistriatum has been implicated in avoidance learning and filial imprinting. However, its role in these learning paradigms may be due to the inhibition of normal avoidance responses, since the avian archistriatum has been shown to play a role in fear/avoidance behaviour. The involvement of the archistriatum in the expression of unlearned fear/avoidance behaviour was therefore investigated in two day-old chicks. Chicks were exposed individually to a novel 'open field' for 5 min. Behaviour was recorded on videotape for analysis. In a separate but concurrent experiment, bilateral archistriatal lesions, sham archistriatal lesions or lateral cerebral lesions were made in day-old chicks which were then exposed to the 'open field' arena. At the end of each exposure a novel object was dropped near the chick. Chicks with archistriatal lesions generally displayed greater movement, more pecking behaviour and spent more time near the centre of the 'open field' than other chicks. There were no differences between the treatment groups in latencies to move or begin peeping. The behaviour of untreated chicks in the 'open field' was similar to that of sham-lesioned chicks and there was no effect of hatch on behaviour. Upon exposure to a novel object, indices of fear and avoidance were not changed in lesioned chicks. These results demonstrate that in the young chick, the archistriatum may be involved in the response to mild or intermediate levels of environment or isolation-related stress, but does not appear to be important for overt fear responses or avoidance of novel objects. Taken together with the results of previous work, the data suggests that the archistriatum may be directly involved in avoidance learning and imprinting.

Induction of CD80 expression in low-grade B cell lymphoma--a potential immunotherapeutic target

The CD80 antigen (B7) is expressed on activated B lymphocytes. It is thought to be important in eliciting a T cell response via its ligands CD28 and CTLA-4 when antigen is presented in the presence of the MHC-1 peptide. Low-grade B cell lymphomas analysed by flow cytometry express CD80 very poorly. However, when grown in vitro using the IL-4/anti-CD40 stromal cell culture system, following depletion of T and IgD-bearing cells, a monoclonal B cell expansion occurs. Cells harvested at days 10-13 express the antigen strongly, regardless of the histological subtype of lymphoma. Further investigation of CD80-mediated immune functions may be possible using this system as a basis for testing immunotherapy.

Myelinated axon number in the optic nerve is unaffected by Alzheimer's disease

AIMS/BACKGROUND

Visual symptoms are a common but not invariable feature of Alzheimer's disease (AD) and such symptoms appear to become more pronounced as the severity of the dementia increases. Pathology in both the pregeniculate and cortical parts of the visual system has been suggested to underlie the visual deficits in AD. In order to investigate the former possibility, the effect of AD on the optic nerve was investigated.

METHODS

Intraorbital segments of optic nerve were taken at autopsy from nine patients with AD and seven patients with no history of psychiatric or neurological disease and no abnormal neuropathology. All patients had functional vision before death and appeared free of retinal, optic nerve, or microvascular disease. The optic nerves were processed into resin, semi-thin sections cut perpendicular to the long axis of each optic nerve, and stained with paraphenylenediamine. The sections were then investigated using an image analysis system and standard morphometric techniques.

RESULTS

There was no significant difference in the mean cross sectional neural area of AD compared with control optic nerves. Neither were there any significant differences between myelinated axon surface density, total axon number, or mean cross sectional axon area in AD compared with control optic nerves.

CONCLUSION

These results indicate that optic nerve degeneration is not a feature of AD and suggest that the visual deficits in the disease result from cortical dysfunction. This view is supported by the fact that visuospatial dysfunction appears to be the most common visual problem in AD.

Termination pattern of medial hyperstriatum ventrale efferents in the archistriatum of the domestic chick

The chick archistriatum receives afferents from the intermediate part of the medial hyperstriatum ventrale (IMHV) and projects to the lobus parolfactorius (LPO). There is functional evidence to suggest that the IMHV and the LPO are connected, but there is no anatomical evidence for a direct connection between the two structures. The aim of the current study was to characterize the termination pattern of medial hyperstriatal afferents within the archistriatum to determine whether the archistriatum may act as a relay between the IMHV and LPO. Following iontophoresis of Phaseolus vulgaris leucoagglutinin into the medial hyperstriatum ventrale (including the IMHV) of 1-week-old domestic chicks, anterogradely labelled fibers were observed to descend through the medial neostriatum and paleostriatum to enter the archistriatum. These medial hyperstriatum ventrale afferents arborised profusely to give varicose axon branches within all except the anterior part of the archistriatum. However, the greatest density was present in the ventral part of the intermediate archistriatum. Electron microscope examination of Phaseolus lectin immunocytochemistry and Golgi impregnation revealed that medial hyperstriatum ventrale axons formed multiple asymmetric synapses with dendritic spines (head and neck regions) on the terminal and preterminal dendritic segments of densely spiny archistriatal projection neurons. Medial hyperstriatum ventrale afferents were not observed to contact calbindin immunoreactive, presumptive "local circuit" neurons, within the archistriatum, despite a spatial overlap in their distribution. These results suggest that the archistriatum may be capable of mediating the transfer of information from the IMHV to the LPO.

Immunolabelling of hippocampal microvessel glucose transporter protein is reduced in Alzheimer's disease

Changes in cerebral microvessel ultrastructure have been reported to occur in Alzheimer's disease (AD). In order to investigate whether these changes are associated with compromised blood-brain transport mechanisms, hippocampal formation sections from AD and age-matched normal brains were immunolabelled with an antibody to the GLUT-1 glucose transporter protein. GLUT-1 immunolabelling of microvessel endothelium was significantly reduced in the AD compared to normal hippocampal formation. Thus, AD is associated with a reduction in cerebral microvessel endothelium glucose transporter content, which may result in decreased glucose availability to the brain.

Archistriatal lesions impair the acquisition of filial preferences during imprinting in the domestic chick

The avian archistriatum has been demonstrated to play a role in agonistic behaviours and avoidance learning. However, the extent of its role in learning is unknown. The involvement of the archistriatum in the learning process of filial imprinting was therefore investigated in day-old chicks. Bilateral archistriatal lesions, lateral cerebral area lesions or sham archistriatal penetrations were made in dark-reared, day-old chicks, which were subsequently exposed to either a rotating red box or blue cylinder for 2 x 1 h training sessions. Three hours later, the approach of chicks to their training object and to the other, novel object was measured. Chicks with archistriatal lesions ran a similar distance towards each stimulus and therefore failed to display a preference for their training object. However, chicks with sham archistriatal penetrations or lateral cerebral area lesions exhibited a significant preference for the object they had been trained upon. These results demonstrate that the archistriatum is essential for the expression of an imprinted preference. All chicks approached their training object significantly more on their second compared to their first training exposure, suggesting that some aspects of imprinting behaviour remain intact in chicks with archistriatal lesions. Taken together with the results of previous work, the current data suggest that the archistriatum may be involved in retention of significant aspects of the imprinting experience, or in motivation to approach imprinting objects.

The effects of archistriatal lesions on one-trial passive avoidance learning in the chick

The avian archistriatum, part of which may be homologous with the mammalian amygdala, has been implicated in fear and avoidance behaviour. There is also evidence to suggest its involvement in learning. One-trial passive avoidance learning (PAL) has been used extensively to study memory formation in the chick. Young chicks will peck spontaneously at a small, visually conspicuous bead. If the bead has been coated with an aversive substance, the chicks show a disgust response and learn in a single trial not to peck a similar bead on subsequent presentation. Successful acquisition of this one-trial PAL task involves the formation of a learned association between the bead and a noxious taste, followed by the expression of an avoidance response. In view of the possible involvement of the archistriatum in avoidance and learning behaviour, its role in one-trial PAL was investigated by ablation. Bilateral electrolytic lesions of the entire archistriatum prevented the acquisition of the one-trial PAL task. Neither bilateral lesions of the lateral cerebral area nor sham operation affected learning. The impairment of one-trial PAL caused by archistriatal lesions was not due to effects on the visual or motor components of pecking behaviour. The archistriatum could therefore be directly involved in memory formation. It could also be involved in the organization of avoidance behaviour associated with the task, or it could form part of a circuit linking two other forebrain regions previously implicated in one-trial PAL, the intermediate part of the medial hyperstriatum ventrale and the lobus parolfactorius.

A Phaseolus lectin anterograde tracing study of the tectorotundal projections in the domestic chick

The projection from the chick optic tectum to the nucleus rotundus was investigated by iontophoresis of the anterograde tracer Phaseolus vulgaris lectin (PHA-L) into the optic tectum and by Golgi impregnation. PHA-L labelled fibres were observed within the ipsilateral nucleus rotundus and to course through the supraoptic decussation to the contralateral nucleus rotundus. They appeared similar to fibres evident in Golgi impregnated material. Before reaching the nucleus rotundus, PHA-L labelled fibres gave off short terminal branches in the caudoventral thalamic nucleus. Within the ipsilateral nucleus rotundus, the labelled fibres formed an extensive fibre net with a dense core and a less dense periphery. PHA-L labelled fibres in the contralateral nucleus rotundus exhibited a qualitatively similar but sparser distribution. There appeared to be a topographic representation of the optic tectum within the nucleus rotundus. Electron microscopy revealed that PHA-L labelled tectal fibres established asymmetric synapses with principal neurons in the nucleus rotundus.

Axonal loss from the olfactory tracts in Alzheimer's disease

Senile dementia of the Alzheimer type has been shown to be associated with impaired olfactory function early in the course of the disease. Neuropathology in the olfactory system is also a feature of Alzheimer's disease (AD) and it has been suggested that the disease may be caused by a pathogen entering the brain via olfactory pathways. To investigate this hypothesis, the effect of AD on the olfactory tract was investigated. There was a 40% decrease in the cross-sectional area of the olfactory tract and a 52% loss of myelinated axons from the tract in AD. These results, together with those of previous studies suggest that peripheral regions of the olfactory system, i.e., the olfactory bulb and primary sensory olfactory neurons are less affected by the pathology of AD than more central parts, i.e., cortical regions, the anterior olfactory nuclei, and olfactory tract. This less severe pathology at the periphery argues against a pathogen entering the brain via the peripheral olfactory apparatus and suggests a central pathogenesis which spreads centrifugally along olfactory pathways.

The effect of the neurotoxin DSP4 on the development of a predisposition in the domestic chick

Under certain conditions, dark-reared chicks preferentially approach objects resembling conspecifics. In the current study we investigated the effect of the catecholaminergic neurotoxin DSP4 on this predisposition. After hatching, chicks received an intraperitoneal injection of either DSP4 or vehicle (controls). The chicks were individually placed in running wheels for 2 x 1 hr, 24 hr before testing. The chicks were maintained in darkness until given a preference test, which involved the simultaneous presentation of an illuminated red box and a stuffed fowl at 36, 48, 60, 66, or 72 hr after hatching. The approach of each chick toward the two objects was recorded over 5 min and a preference score calculated. Control chicks placed in the running wheels at 24 and 36 hr posthatch and tested 24 hr later showed a significant preference for the fowl compared to the red box. In contrast, DSP4-treated chicks did not show such a preference at corresponding ages, but did express a greater preference for the fowl when placed in the running wheels at 42 and 48 hr posthatch and tested 24 hr later. These results suggest that experience of the running wheel or of associated factors, e.g., handling, must occur during a restricted period of time to influence the emergence of the predisposition to approach the stuffed fowl. DSP4 treatment delays the onset of this period.