Tau Protein Modulates Perineuronal Extracellular Matrix Expression in the TauP301L-acan Mouse Model

Tau mutations promote the formation of tau oligomers and filaments, which are neuropathological signs of several tau-associated dementias. Types of neurons in the CNS are spared of tau pathology and are surrounded by a specialized form of extracellular matrix; called perineuronal nets (PNs). Aggrecan, the major PN proteoglycans, is suggested to mediate PNs neuroprotective function by forming an external shield preventing the internalization of misfolded tau. We recently demonstrated a correlation between aggrecan amount and the expression and phosphorylation of tau in a TauP310L-acan mouse model, generated by crossbreeding heterozygous aggrecan mice with a significant reduction of aggrecan and homozygous TauP301L mice. Neurodegenerative processes have been associated with changes of PN structure and protein signature. In this study, we hypothesized that the structure and protein expression of PNs in this TauP310L-acan mouse is regulated by tau. Immunohistochemical and biochemical analyses demonstrate that protein levels of PN components differ between TauP301L^HET-acan^WT and TauP301L^HET-acan^HET mice, accompanied by changes in the expression of protein phosphatase 2 A. In addition, tau can modulate PN components such as brevican. Co-immunoprecipitation experiments revealed a physical connection between PN components and tau. These data demonstrate a complex, mutual interrelation of tau and the proteoglycans of the PN.

Finding the best clearing approach - Towards 3D wide-scale multimodal imaging of aged human brain tissue

The accessibility of new wide-scale multimodal imaging techniques led to numerous clearing techniques emerging over the last decade. However, clearing mesoscopic-sized blocks of aged human brain tissue remains an extremely challenging task. Homogenizing refractive indices and reducing light absorption and scattering are the foundation of tissue clearing. Due to its dense and highly myelinated nature, especially in white matter, the human brain poses particular challenges to clearing techniques. Here, we present a comparative study of seven tissue clearing approaches and their impact on aged human brain tissue blocks (> 5 mm). The goal was to identify the most practical and efficient method in regards to macroscopic transparency, brief clearing time, compatibility with immunohistochemical processing and wide-scale multimodal microscopic imaging. We successfully cleared 26 × 26 × 5 mm³-sized human brain samples with two hydrophilic and two hydrophobic clearing techniques. Optical properties as well as light and antibody penetration depths highly vary between these methods. In addition to finding the best clearing approach, we compared three microscopic imaging setups (the Zeiss Laser Scanning Microscope (LSM) 880 , the Miltenyi Biotec Ultramicroscope ll (UM ll) and the 3i Marianas LightSheet microscope) regarding optimal imaging of large-scale tissue samples. We demonstrate that combining the CLARITY technique (Clear Lipid-exchanged Acrylamide-hybridized Rigid Imaging compatible Tissue hYdrogel) with the Zeiss LSM 880 and combining the iDISCO technique (immunolabeling-enabled three-dimensional imaging of solvent-cleared organs) with the Miltenyi Biotec UM ll are the most practical and efficient approaches to sufficiently clear aged human brain tissue and generate 3D microscopic images. Our results point out challenges that arise from seven clearing and three imaging techniques applied to non-standardized tissue samples such as aged human brain tissue.

Aggrecan modulates the expression and phosphorylation of tau in a novel bigenic TauP301L - Acan mouse model

Selected types of neurons in the central nervous system are associated with a specialized form of extracellular matrix. These so-called perineuronal nets (PNs) are supramolecular structures surrounding neuronal somata, proximal dendrites and axon initial segments. PNs are involved in the regulation of plasticity and synaptic physiology. In addition, PNs were proposed to carry neuroprotective functions as PN-ensheathed neurons are mostly spared of tau pathology in brains of Alzheimer patients. Recently, the neuroprotective action of PNs was confirmed experimentally, demonstrating (i) that mainly aggrecan mediates the neuroprotective function of PNs and (ii) that aggrecan seems to generate an external shielding preventing the internalization of pathological forms of tau. In the present study, we aimed at extending these findings and hypothesized that aggrecan further provides an intracellular protection by preventing mutation-triggered formation of pathological forms of tau. We used crossbreds of TauP301L mice and heterozygous aggrecan mice which are characterized by spontaneous deletion of the aggrecan allele. We analysed the extent of tau pathology in dependence of aggrecan protein amount by applying immunohistochemistry, Western blotting and ELISA. The results clearly indicate that aggrecan has no significant impact on tau aggregation in the brainstem of our mouse model. Still, reduced aggrecan levels were accompanied by increased levels of tau protein and reduced number of Tau-1-positive neurons, which indicate an increase in phosphorylation of tau. In conclusion, these data demonstrate a correlation between aggrecan and P301L mutation-triggered tau expression and phosphorylation in our bigenic mouse model.

Neurocan Contributes to Perineuronal Net Development

Perineuronal nets (PNs) are matrix molecule assemblies surrounding neuronal somata, dendrites and axon initial segments in a lattice-like appearance. PN molecules are involved in many structural and physiological processes during development and in adulthood, suggesting a crucial role in normal brain function. Neurocan, as one of the main PN proteoglycans, is suggested to control important developmental processes of neuronal tissue. This statement relies on thorough and excellent experimental work mainly conducted in reduced systems, such as cell cultures. However, previous data collected in neurocan-deficient mice do not seem to support neurocan's role in development since brain development in general and the formation of PNs especially in the hippocampus were reported to be undisturbed in neurocan-deficient mice. Here, we aim to re-address the role of neurocan in developmental processes by investigating the influence of neurocan on PN formation in the medial nucleus of the trapezoid body, a PN-enriched nucleus in the auditory brainstem, using neurocan-deficient mice. Immunohistochemical and biochemical analyses demonstrate that neurocan controls the regulation of PN development by influencing mRNA and protein quantity of various PN molecules. Resulting alterations in PN fine structure are critical for PN function as estimated by reduced amount of GAD65/67 and prolongation of synaptic transmission delay of calyx of Held synapses. Thus, neurocan contributes to proper PN formation and synapse physiology in the MNTB.

Structure variations within RSi2 and R2Si3 silicides. Part II. Structure driving factors

To gain an overview of the various structure reports on RSi₂ and R₂TSi₃ compounds (R is a member of the Sc group, an alkaline earth, lanthanide or actinide metal, T is a transition metal), compositions, lattice parameters a and c, ratios c/a, formula units per unit cell, and structure types are summarized in extensive tables and the variations of these properties when varying the R or T elements are analyzed. Following the structural systematization given in Part I, Part II focuses on revealing the driving factors for certain structure types, in particular, the electronic structure. Here, concepts of different complexity are presented, including molecular orbital theory, the principle of hard and soft acids and bases, and a Bader analysis based on Density Functional Theory calculations for representatives of the reported structure types. The potential Si/T ordering in different structures is discussed. Additionally, the influences from intrinsic and extrinsic properties (e.g. elemental size and electronics as well as lattice parameters and structure type) are investigated on each other using correlation plots. Thermal treatment is identified as an important factor for the ordering of Si/T atoms.

Structure variations within RSi2 and R2TSi3 silicides. Part I. Structure overview

Here, structural parameters of various structure reports on RSi2 and R2TSi3 compounds [where R is an alkaline earth metal, a rare earth metal (i.e. an element of the Sc group or a lathanide), or an actinide and T is a transition metal] are summarized. The parameters comprising composition, lattice parameters a and c, ratio c/a, formula unit per unit cell and structure type are tabulated. The relationships between the underlying structure types are presented within a group-subgroup scheme (Bärnighausen diagram). Additionally, unexpectedly missing compounds within the R2TSi3 compounds were examined with density functional theory and compounds that are promising candidates for synthesis are listed. Furthermore, a correlation was detected between the orthorhombic AlB2-like lattices of, for example, Ca2AgSi3 and the divalence of R and the monovalence of T. Finally, a potential tetragonal structure with ordered Si/T sites is proposed.

Topographic map refinement and synaptic strengthening of a sound localization circuit require spontaneous peripheral activity

KEY POINTS

Loss of the calcium sensor otoferlin disrupts neurotransmission from inner hair cells. Central auditory nuclei are functionally denervated in otoferlin knockout mice (Otof KOs) via gene ablation confined to the periphery. We employed juvenile and young adult Otof KO mice (postnatal days (P)10-12 and P27-49) as a model for lacking spontaneous activity and deafness, respectively. We studied the impact of peripheral activity on synaptic refinement in the sound localization circuit from the medial nucleus of the trapezoid body (MNTB) to the lateral superior olive (LSO). MNTB in vivo recordings demonstrated drastically reduced spontaneous spiking and deafness in Otof KOs. Juvenile KOs showed impaired synapse elimination and strengthening, manifested by broader MNTB-LSO inputs, imprecise MNTB-LSO topography and weaker MNTB-LSO fibres. The impairments persisted into young adulthood. Further functional refinement after hearing onset was undetected in young adult wild-types. Collectively, activity deprivation confined to peripheral protein loss impairs functional MNTB-LSO refinement during a critical prehearing period.

ABSTRACT

Circuit refinement is critical for the developing sound localization pathways in the auditory brainstem. In prehearing mice (hearing onset around postnatal day (P)12), spontaneous activity propagates from the periphery to central auditory nuclei. At the glycinergic projection from the medial nucleus of the trapezoid body (MNTB) to the lateral superior olive (LSO) of neonatal mice, super-numerous MNTB fibres innervate a given LSO neuron. Between P4 and P9, MNTB fibres are functionally eliminated, whereas the remaining fibres are strengthened. Little is known about MNTB-LSO circuit refinement after P20. Moreover, MNTB-LSO refinement upon activity deprivation confined to the periphery is largely unexplored. This leaves a considerable knowledge gap, as deprivation often occurs in patients with congenital deafness, e.g. upon mutations in the otoferlin gene (OTOF). Here, we analysed juvenile (P10-12) and young adult (P27-49) otoferlin knockout (Otof KO) mice with respect to MNTB-LSO refinement. MNTB in vivo recordings revealed drastically reduced spontaneous activity and deafness in knockouts (KOs), confirming deprivation. As RNA sequencing revealed Otof absence in the MNTB and LSO of wild-types, Otof loss in KOs is specific to the periphery. Functional denervation impaired MNTB-LSO synapse elimination and strengthening, which was assessed by glutamate uncaging and electrical stimulation. Impaired elimination led to imprecise MNTB-LSO topography. Impaired strengthening was associated with lower quantal content per MNTB fibre. In young adult KOs, the MNTB-LSO circuit remained unrefined. Further functional refinement after P12 appeared absent in wild-types. Collectively, we provide novel insights into functional MNTB-LSO circuit maturation governed by a cochlea-specific protein. The central malfunctions in Otof KOs may have implications for patients with sensorineuronal hearing loss.

Neuronal Activity in the Hibernating Brain

Hibernation is a natural phenomenon in many species which helps them to survive under extreme ambient conditions, such as cold temperatures and reduced availability of food in the winter months. It is characterized by a dramatic and regulated drop of body temperature, which in some cases can be near 0°C. Additionally, neural control of hibernation is maintained over all phases of a hibernation bout, including entrance into, during and arousal from torpor, despite a marked decrease in overall neural activity in torpor. In the present review, we provide an overview on what we know about neuronal activity in the hibernating brain focusing on cold-induced adaptations. We discuss pioneer and more recent in vitro and in vivo electrophysiological data and molecular analyses of activity markers which strikingly contributed to our understanding of the brain's sensitivity to dramatic changes in temperature across the hibernation cycle. Neuronal activity is markedly reduced with decreasing body temperature, and many neurons may fire infrequently in torpor at low brain temperatures. Still, there is convincing evidence that specific regions maintain their ability to generate action potentials in deep torpor, at least in response to adequate stimuli. Those regions include the peripheral system and primary central regions. However, further experiments on neuronal activity are needed to more precisely determine temperature effects on neuronal activity in specific cell types and specific brain nuclei.

Synaptic coupling of inner ear sensory cells is controlled by brevican-based extracellular matrix baskets resembling perineuronal nets

Background

Perineuronal nets (PNNs) are specialized aggregations of extracellular matrix (ECM) molecules surrounding specific neurons in the central nervous system (CNS). PNNs are supposed to control synaptic transmission and are frequently associated with neurons firing at high rates, including principal neurons of auditory brainstem nuclei. The origin of high-frequency activity of auditory brainstem neurons is the indefatigable sound-driven transmitter release of inner hair cells (IHCs) in the cochlea.

Results

Here, we show that synaptic poles of IHCs are ensheathed by basket-like ECM complexes formed by the same molecules that constitute PNNs of neurons in the CNS, including brevican, aggreccan, neurocan, hyaluronan, and proteoglycan link proteins 1 and 4 and tenascin-R. Genetic deletion of brevican, one of the main components, resulted in a massive degradation of ECM baskets at IHCs, a significant impairment in spatial coupling of pre- and postsynaptic elements and mild impairment of hearing.

Conclusions

These ECM baskets potentially contribute to control of synaptic transmission at IHCs and might be functionally related to PNNs of neurons in the CNS.

Electronic supplementary material

The online version of this article (10.1186/s12915-018-0566-8) contains supplementary material, which is available to authorized users.

Neuroanatomical characterization of perineuronal net components in the human cochlear nucleus and superior olivary complex

The human auditory brainstem, especially the cochlear nucleus (CN) and the superior olivary complex (SOC) are characterized by a high density of neurons associated with perineuronal nets (PNs). PNs build a specific form of extracellular matrix surrounding the neuronal somata, proximal dendrites and axon initial segments. They restrict synaptic plasticity and control high-frequency synaptic activity, a prominent characteristic of neurons of the auditory brainstem. The distribution of PNs within the auditory brainstem has been investigated in a number of mammalian species. However, much less is known regarding PNs in the human auditory brainstem. The present study aimed at the immunohistochemical identification of PNs in the cochlear nucleus (CN) and superior olivary complex (SOC) in the human brainstem. We focused on the complex nature and molecular variability of PNs in the CN and SOC by using specific antibodies against the main PN components (aggrecan, brevican, neurocan and hyaluronan and proteoglycan link protein 1). Virtually all subnuclei within the ventral CN and SOC were found to be associated with PNs. Direct comparison between gerbil and human yielded similar fine structure of PNs and confirmed the typical tight interdigitation of PNs with synaptic terminals in both species. Noticeably, an elaborate combination of immunohistochemical labelings clearly supports the still debated existence of the medial nucleus of trapezoid body (MNTB) in the human brain. In conclusion, the present study demonstrates that PNs form a prominent extracellular structure on CN and SOC neurons in the human brain, potentially stabilizing synaptic contacts, which is in agreement with many other mammalian species.

The extracellular matrix molecule brevican is an integral component of the machinery mediating fast synaptic transmission at the calyx of Held

KEY POINTS

The proteoglycan brevican is a major component of the extracellular matrix of perineuronal nets and is highly enriched in the perisynaptic space suggesting a role for synaptic transmission. We have introduced the calyx of Held in the auditory brainstem as a model system to study the impact of brevican on dynamics and reliability of synaptic transmission. In vivo extracellular single-unit recordings at the calyx of Held in brevican-deficient mice yielded a significant increase in the action potential (AP) transmission delay and a prolongation of pre- and postsynaptic APs. The changes in dynamics of signal transmission were accompanied by the reduction of presynaptic vGlut1 and ultrastructural changes in the perisynaptic space. These data show that brevican is an important mediator of fast synaptic transmission at the calyx of Held.

ABSTRACT

The extracellular matrix is an integral part of the neural tissue. Its most conspicuous manifestation in the brain are the perineuronal nets (PNs) which surround somata and proximal dendrites of distinct neuron types. The chondroitin sulfate proteoglycan brevican is a major component of PNs. In contrast to other PN-comprising proteoglycans (e.g. aggrecan and neurocan), brevican is mainly expressed in the perisynaptic space closely associated with both the pre- and postsynaptic membrane. This specific localization prompted the hypothesis that brevican might play a role in synaptic transmission. In the present study we specifically investigated the role of brevican in synaptic transmission at a central synapse, the calyx of Held in the medial nucleus of the trapezoid body, by the use of in vivo electrophysiology, immunohistochemistry, biochemistry and electron microscopy. In vivo extracellular single-unit recordings were acquired in brevican-deficient mice and the dynamics and reliability of synaptic transmission were compared to wild-type littermates. In knockout mice, the speed of pre-to-postsynaptic action potential (AP) transmission was reduced and the duration of the respective pre- and postsynaptic APs increased. The reliability of signal transmission, however, was not affected by the lack of brevican. The changes in dynamics of signal transmission were accompanied by the reduction of (i) presynaptic vGlut1 and (ii) the size of subsynaptic cavities. The present results suggest an essential role of brevican for the functionality of high-speed synaptic transmission at the calyx of Held.

The precise temporal pattern of prehearing spontaneous activity is necessary for tonotopic map refinement

Patterned spontaneous activity is a hallmark of developing sensory systems. In the auditory system, rhythmic bursts of spontaneous activity are generated in cochlear hair cells and propagated along central auditory pathways. The role of these activity patterns in the development of central auditory circuits has remained speculative. Here we demonstrate that blocking efferent cholinergic neurotransmission to developing hair cells in mice that lack the α9 subunit of nicotinic acetylcholine receptors (α9 KO mice) altered the temporal fine structure of spontaneous activity without changing activity levels. KO mice showed a severe impairment in the functional and structural sharpening of an inhibitory tonotopic map, as evidenced by deficits in synaptic strengthening and silencing of connections and an absence in axonal pruning. These results provide evidence that the precise temporal pattern of spontaneous activity before hearing onset is crucial for the establishment of precise tonotopy, the major organizing principle of central auditory pathways.

Unique features of extracellular matrix in the mouse medial nucleus of trapezoid body--implications for physiological functions

The medial nucleus of the trapezoid body (MNTB) is a vital structure of sound localization circuits in the auditory brainstem. Each principal cell of MNTB is contacted by a very large presynaptic glutamatergic terminal, the calyx of Held. The MNTB principal cells themselves are surrounded by extracellular matrix components forming prominent perineuronal nets (PNs). Throughout the CNS, PNs, which form lattice-like structures around the somata and proximal dendrites, are associated with distinct types of neurons. PNs are highly enriched in hyaluronan and chondroitin sulfate proteoglycans therefore providing a charged surface structure surrounding the cell body and proximal neurites of these neurons. The localization and composition of PNs have lead investigators to a number of hypotheses about their functions including: creating a specific extracellular ionic milieu around these neurons, stabilizing synapses, and influencing the outgrowth of axons. However, presently the precise functions of PNs are still quite unclear primarily due to the lack of an ideal experimental model system that is highly enriched in PNs and in which the synaptic transmission properties can be precisely measured. The MNTB principal cells could offer such a model, since they have been extensively characterized electrophysiologically. However, extracellular matrix (ECM) in these neurons has not yet been precisely detailed. The present study gives a detailed examination of the ECM organization and structural differences in PNs of the mouse MNTB. The different PN components and their distribution pattern are scrutinized throughout the MNTB. The data are complemented by electron microscopic investigations of the unique ultrastructural localization of PN-components and their interrelation with distinct pre- and postsynaptic MNTB cell structures. Therefore, we believe this work identifies the MNTB as an ideal system for studying PN function.

Multidimensional characterization and differentiation of neurons in the anteroventral cochlear nucleus

Multiple parallel auditory pathways ascend from the cochlear nucleus. It is generally accepted that the origin of these pathways are distinct groups of neurons differing in their anatomical and physiological properties. In extracellular in vivo recordings these neurons are typically classified on the basis of their peri-stimulus time histogram. In the present study we reconsider the question of classification of neurons in the anteroventral cochlear nucleus (AVCN) by taking a wider range of response properties into account. The study aims at a better understanding of the AVCN's functional organization and its significance as the source of different ascending auditory pathways. The analyses were based on 223 neurons recorded in the AVCN of the Mongolian gerbil. The range of analysed parameters encompassed spontaneous activity, frequency coding, sound level coding, as well as temporal coding. In order to categorize the unit sample without any presumptions as to the relevance of certain response parameters, hierarchical cluster analysis and additional principal component analysis were employed which both allow a classification on the basis of a multitude of parameters simultaneously. Even with the presently considered wider range of parameters, high number of neurons and more advanced analytical methods, no clear boundaries emerged which would separate the neurons based on their physiology. At the current resolution of the analysis, we therefore conclude that the AVCN units more likely constitute a multi-dimensional continuum with different physiological characteristics manifested at different poles. However, more complex stimuli could be useful to uncover physiological differences in future studies.

[Ulcus terebrans. Therapy options and their limits]

Basal cell carcinoma (BCC) is the most common tumor in humans and is defined as a slow-growing, locally invasive, epithelial skin tumor which rarely metastasizes. The first line treatment is surgical excision with histologic examination of the tumor margins, but numerous alternative therapies are available. A 75-year old patient with the most destructive form of BCC, ulcus terebrans, involving the scalp and invading the frontal bone. We discuss the problems and therapeutic limitations for this unusual BCC variant.

Upregulation of epidermal surface molecule expression in primary and ultraviolet-induced lesions of lupus erythematosus tumidus

BACKGROUND

Lupus erythematosus tumidus (LET), a photosensitive skin disorder with characteristic clinical and histological features, has not been generally accepted as a subset of cutaneous lupus erythematosus (CLE).

OBJECTIVES

To analyse the expression of epidermal surface molecules in skin biopsy specimens from patients with LET and to relate the results to other variants of CLE, such as discoid lupus erythematosus (DLE) and subacute CLE (SCLE).

METHODS

In total, 45 patients with different subtypes of CLE were included in the study, and cryostat sections from primary and ultraviolet (UV) A- and UVB-induced skin lesions were investigated using immunohistochemical methods.

RESULTS

In contrast to healthy controls, skin lesions of LET showed upregulation of intercellular adhesion molecule-1 (ICAM-1) and histocompatibility class II molecules (HLA-DR), with an expression pattern resembling that seen in DLE and SCLE. Furthermore, staining with a monoclonal antibody against 27E10, a distinct marker for cell activation and differentiation, revealed intense focal or band-like labelling of all epidermal layers independent of the type of lesion.

CONCLUSIONS

Expression of epidermal surface molecules such as ICAM-1, HLA-DR and 27E10 is equally upregulated in primary and UV-induced lesions of patients with LET, DLE and SCLE. These results support our recent clinical findings that LET represents a distinct subset of CLE with a similar immunopathomechanism rather than a different disease.

Phototesting in lupus erythematosus: a 15-year experience

It has long been observed that sun exposure can induce or exacerbate skin lesions in patients with certain forms of lupus erythematosus. Despite the frequency of photosensitivity in these patients, the mechanism by which ultraviolet radiation alters the pathogenic course of this disease remains poorly understood. After development of standardized test methods, our group demonstrated in 1986 that skin lesions in patients with lupus erythematosus can be experimentally reproduced by UVA and UVB irradiation. In the following years, phototesting has received much attention as a valid model to study photosensitivity of different forms of lupus erythematosus and the pathogenetic mechanism of this disease. Further investigations have also made it possible to find genetic and immunologic factors associated with photosensitivity and have helped to identify the pathophysiologic steps involved in the induction of such skin lesions. We present phototesting results and clinical correlations of more than 400 patients with different forms of lupus erythematosus and discuss the recent advances in provocative phototesting.

Phototesting in Lupus Erythematosus Tumidus—Review of 60 Patients¶

Photosensitivity is an important characteristic feature of several forms of lupus erythematosus (LE), and induction of skin lesions by UV-A and UV-B irradiation has been proved to be an optimal model for evaluating light sensitivity in patients with this disease. Because lupus erythematosus tumidus (LET) has rarely been documented in the literature and is often difficult to differentiate from other photodermatoses such as polymorphous light eruption, we performed photoprovocation tests in 60 patients with LET according to a standardized protocol. Areas of uninvolved skin on the upper back were irradiated with single doses of UV-A (100 J/cm2) and/or UV-B (1.5 minimal erythema dose) daily for three consecutive days. Interestingly, patients with LET are more photosensitive than those with subacute cutaneous lupus erythematosus, and in our study experimental phototesting revealed characteristic skin lesions in 43 patients (72%). Because of the latency period in developing positive phototest reactions, it might be difficult for these patients to link sun exposure with their skin lesions. Furthermore, our data revealed a positive correlation of antinuclear antibodies and positive provocative phototest reactions in these patients as seen for other forms of LE. In conclusion, the high incidence of positive phototest reactions in correlation with the clinical findings, history of photosensitivity and antinuclear antibodies enable the classification of LET as the most photosensitive type of LE.

[Posterolateral retroperitoneal approach and exclusion technique in therapy of infrarenal aortic aneurysm: initial experiences]

Although the infrarenal aorta is a retroperitoneal structure, the surgical access has been transperitoneal especially when dealing with infrarenal aneurysms. After the opening of the sack a tube-or bifurcated graft is implanted. With the posterolateral retroperitoneal (RP) approach described by G.M. Williams in 1980 access to the aorta can be gained without opening the peritoneal cavity. With the non resective exclusion technique the intraoperative blood loss is minimized. This method is routinely used in Albany N.Y. for the treatment of infrarenal aneurysms. We describe here our first experiences with 44 RP excluded aortic aneurysms. Despite the small number of cases we can confirm the advantages described in the larger series of Sicard et al. and Leather and Shah: the RP approach and the exclusion technique can be routinely used for infrarenal aneurysms. It is associated with a smoother and shorter postoperative period (8 to 10 days).

Intracranial microembolic signals in 500 patients with potential cardiac or carotid embolic source and in normal controls

BACKGROUND AND PURPOSE

We undertook this study to evaluate the prevalence and clinical correlations of Doppler microembolic signals (MES) in stroke-prone patients.

METHODS

Patients with potential cardiac (n = 300) or carotid (n = 100) embolic source and control subjects (n = 100) were monitored with transcranial Doppler sonography for MES. Transthoracic (n = 192) and/or transesophageal (n = 134) echocardiography and carotid studies (continuous-wave Doppler, n = 181; color-coded duplex, n = 47) were performed in all patients with potential native cardioembolic source. Carotid disease was evaluated by means of continuous-wave Doppler (n = 87), color-coded duplex (n = 70), or intra-arterial angiography (n = 24) in patients with potential carotid embolic source.

RESULTS

Overall MES prevalence was 23% in patients with potential native cardioembolic source (infective endocarditis [n = 7] 43%, left ventricular aneurysm [n = 38] 34%, intracardiac thrombus [n = 23] 26%, dilative cardiomyopathy [n = 39] 26%, nonvalvular atrial fibrillation [n = 24] 21%, valvular disease [n = 80] 15%), 55% in patients with prosthetic cardiac valves (mechanical [n = 77] 58%, porcine [n = 7] 43%, homografts [n = 5] 20%), 28% in patients with carotid disease (symptomatic [n = 46] 52%, asymptomatic [n = 54] 7%; P < .01), and 5% in control subjects. No relationship between MES counts and patients' age, sex, or actual medication was noted. The sensitivity and specificity of MES detection in identifying patients with potential embolic sources were 31% and 95%, respectively.

CONCLUSIONS

Our study confirmed the reported clinical significance of MES in patients with carotid disease and the high specificity of this technique. The demonstrated low sensitivity of MES detection could be due to short monitoring duration or application of antihemostatic treatment. Prospective large-scale studies are needed to determine the definitive value of MES detection as a diagnostic method in patients with potential cardioembolic source.

Minimal effects of nitric oxide on spatial blood flow heterogeneity of the dog heart

Eleven Beagle dogs were studied to elucidate the possible role of L-arginine-derived nitric oxide on local blood flow distribution in left and right ventricular myocardium. Local blood flow was determined in 256 samples from the left and 64 samples from the right ventricle per heart using the tracer microsphere technique (mean sample mass 319 +/- 131 mg). Nitric oxide production was effectively inhibited by intravenous infusion of 20 mg/kg nitro-L-arginine methylester (L-NAME) as evidenced by a shift of the dose/response curve for the effect of intracoronary administration of bradykinin (0.004-4.0 nmol/min) on coronary blood flow. L-NAME enhanced left and right ventricular systolic pressures from 132 +/- 18 to 155 +/- 15 mm Hg and from 26 +/- 3 to 29 +/- 3 mm Hg respectively (both P = 0.043). Mean left ventricular blood flow was 1.14 +/- 0.38 before and 0.99 +/- 0.28 ml min-1 g-1 after L-NAME (P = 0.068), while right ventricular blood flow fell from 0.72 +/- 0.28 to 0.53 +/- 0.20 ml min-1 g-1 (P = 0.043). Coronary conductance of left and right ventricular myocardium fell by 31 and 43% respectively (both P = 0.043). The coefficient of variation of left ventricular blood flow was 0.26 +/- 0.07 before and 0.29 +/- 0.07 after L-NAME (P = 0.068), that of right ventricular blood flow was 0.27 before and after L-NAME. Skewness (0.51) and kurtosis (4.23) of left ventricular blood flow distribution were unchanged after L-NAME, while in the right ventricle skewness decreased from 0.54 to 0.09 (P = 0.043) and kurtosis (3.68) tended to decrease after L-NAME (P = 0.080). The fractal dimension (D = 1.20-1.27) and the corresponding nearest-neighbor correlation coefficient (rn = 0.37-0.53) of left and right ventricular myocardium remained unchanged after infusion of L-NAME. From these results it is concluded that firstly, local nitric oxide release does not explain the higher perfusion of physiological high flow samples and secondly, that spatial myocardial blood flow coordination is not dependent on nitric oxide.

[Dermatitis bullosa striata pratensis caused by Dictamnus albus L. (burning bush)]

We report two patients with bullous phototoxic contact dermatitis caused by Dictamnus albus L. (gas plant) which belongs to the Rutaceae family. In both cases long lasting postinflammatory hyper-pigmentations were observed as a result of the phototoxic contact dermatitis. The phototoxic components of Dictamnus albus L. are the furocoumarins 5-methoxypsoralen (bergapten) and 8-methoxypsoralen, and the alkaloid dictamnin whose phototoxic properties were recently discovered. Even though reactions to the gas plant have been infrequently reported, it is becoming more popular with gardenus and should be considered in the differential diagnosis of phototoxic contact dermatitis.

Spatial heterogeneity of blood flow in the dog heart. I. Glucose uptake, free adenosine and oxidative/glycolytic enzyme activity

The spatial heterogeneity of myocardial perfusion and metabolism was studied in 11 anaesthetized dogs under resting conditions. In each heart local myocardial blood flow was assessed using the tracer microsphere technique in 256 samples (mean mass: 83.1 mg) taken from the left anterior ventricular wall. In the same samples, the following biochemical parameters were determined: accumulation of [3H]-deoxyglucose (a measure of glucose uptake), free cytosolic adenosine (S-adenosylhomocysteine accumulation technique, a measure of tissue oxygenation and a possible mediator of blood flow regulation), and the specific activities of oxidative (citrate synthase, cytochrome-c-oxidase) and glycolytic (hexokinase, phosphoglycerate kinase) enzymes. Capillary density and mitochondrial and myofibril volume densities were determined by morphometry. Myocardial perfusion in each sample (average 0.77 ml min-1 g-1) varied between 0.1 and 2.5 times the mean (coefficient of variation 0.30+/-0.02). [3H]-deoxyglucose was deposited locally in proportion to perfusion. Samples showing low flow (<0.2 ml min-1 g-1) did not exhibit increased levels of cytosolic adenosine. The specific activities of the oxidative and glycolytic enzymes, however, were uniformly distributed between low and high flow areas. Furthermore, capillary density and mitochondrial and myofibril densities were similar in high and low flow regions. The results show firstly that local glucose metabolism in the heart occurs in proportion to local blood flow, suggesting that high flow regions have a higher than average metabolic rate. Secondly, regions of low flow are not compromized by critical oxygenation and most likely have a lower than average oxygen demand and finally, the homogeneous distribution of oxidative and glycolytic enzymes, as well as the homogeneous myocardial ultrastructure, suggest that areas with high and low blood flow under resting conditions may increase their metabolic rate to similar levels when required.

Spatial heterogeneity of blood flow in the dog heart. II. Temporal stability in response to adrenergic stimulation

The effects of adrenergic stimulation on local myocardial blood flow in the left ventricle were studied in 13 anaesthetized Beagle dogs using the tracer microsphere technique. Adrenergic stimulation was induced by intravenous infusion of orciprenaline (1-2 microg kg-1 min-1) over 15 min or by electrical stimulation of the left ansa subclavia (10 Hz, 1 ms, 4-8 V) over 5 min. Local myocardial blood flow was analysed in 256 samples with an average (+/-SD) mass of 318+/-49 mg from the left ventricular myocardium using a standardized dissection procedure. Orciprenaline increased the average myocardial blood flow from 0.85+/-0.18 to 1.73+/-0.27 ml min-1 g-1, while oxygen consumption and the pressure-rate product increased by 129 and 119% respectively. The coefficients of variation of local myocardial blood flow, a measure of spatial blood flow heterogeneity, were 0.21 and 0.18 under control and orciprenaline respectively. Except for a slight transmural gradient (endomyocardium/epimyocardium flow ratio 1.19) myocardial blood flow did not exhibit significant spatial gradients. Stimulation with orciprenaline increased the average blood flow in all regions of the left ventricle by comparable extents. However, local blood flow during orciprenaline was significantly lower in samples from regions which had a lower blood flow under resting control conditions. A significant positive relationship was obtained between local myocardial blood flow under resting conditions and orciprenaline (r=0.45+/-0.18). Moreover, after recovery from orciprenaline stimulation (i.e. 40-112 min after the end of orciprenaline infusion) local myocardial blood flow exhibited a high degree of correlation with local flow before orciprenaline (r=0.71+/-0.08). Comparable results were obtained with electrical stimulation of the left ansa subclavia. For the comparison stimulation vs. control, the correlation coefficient of local blood flow was 0.52+/-0.04 and for recovery vs. control 0.77+/-0.06. From these results it is concluded firstly that local myocardial blood flow under resting conditions is an important determinant of local flow during adrenergic stimulation. Secondly, the anatomical region does not have any predictive value for the blood flow change during adrenergic stimulation and finally, the close relationship between local blood flow before and after cardiac stimulation indicates that the spatial blood flow heterogeneity is temporally stable over hours.

[Effect of arginine-dependent nitric oxide synthesis on regional perfusion of the eye in the anesthesized dog]

The changes of the retinal and uveal perfusion after inhibition of the arginine-dependent nitric oxide (NO) synthesis by systemic administration of NG-nitro-L-arginine methyl ester (L-NAME; 20 mg/kg bw i.v.) were studied in four anesthetized dogs using the tracer microsphere technique. The regional perfusion rates (ml.min-1.g-1) under steady-state control conditions were: retina 0.13 +/- 0.05, choroid 8.26 +/- 1.85, iris 0.24 +/- 0.05 and ciliary body 1.11 +/- 0.26. Infusion of L-NAME over 10 min reduced the perfusion of the retina on the average by 23% (P > 0.05). The perfusion of choroid, iris and ciliary body fell by 54 +/- 8%, 58 +/- 7% and 53 +/- 8%, respectively (P < or = 0.05 for all). In five additional experiments the local activity of NO-producing enzymes (NO synthases) was determined by measuring the production rate of citrullin in tissue extracts of the different eye regions. Total NO synthase activities (pmol citrullin.min-1.g-1) were: retina 31.0 +/- 5.5, choroid 3.1 +/- 2.8, iris 7.1 +/- 2.1 and ciliary body 1.3 +/- 1.3. Differences of the total NO synthase activities of retina, iris and cilary body were statistically significant (P < or = 0.02). The results show that the uvea perfusion is largely influenced by the steady-state production of NO. The homogeneous flow reduction in the uvea after inhibition of NO synthase is contrasted by the heterogeneous NO synthase activities of the different uvea regions.(ABSTRACT TRUNCATED AT 250 WORDS)

L-arginine-derived nitric oxide: a major determinant of uveal blood flow

The effect of inhibition of the L-arginine-nitric oxide pathway on regional ocular blood flow was studied in anaesthetized Beagle dogs. Under control conditions (mean arterial blood pressure 105 +/- 6 mmHg) trapping of 11 and 15-microns-diameter tracer microspheres revealed the following regional blood flows (ml min-1 g-1): retina 0.065 +/- 0.016, choroid 5.72 +/- 0.32, ciliary body 0.77 +/- 0.11, iris 0.18 +/- 0.04. After i.v. infusion of nitro-L-arginine methylester (20 mg kg-1), a potent inhibitor of nitric oxide production from L-arginine, mean arterial blood pressure increased from 105 +/- 6 mmHg by 19% to a new steady-state level of 125 +/- 7 mmHg. This increase of arterial blood pressure extended over 3 hr and was reversible after i.v. infusion of L-arginine (100 mg kg-1 over 10 min). Despite the increase in blood pressure following infusion of nitro-L-arginine methylester blood flow of choroid, ciliary body, and iris were significantly decreased by 40, 40 and 48%, respectively. Retinal blood flow did not change significantly (-12%). These results suggest that the L-arginine-nitric oxide pathway is of major importance for the adjustment of uveal blood flow under resting physiological conditions.

Role of nitric oxide in local blood flow control in the anaesthetized dog

Intravenous infusion of NG-nitro-L-arginine methyl ester (L-NAME), a potent inhibitor of nitric oxide (NO) formation from L-arginine, provokes marked rises in arterial blood pressure by increasing peripheral resistance. In order to further evaluate the contribution of basal NO-formation to control of organ blood flow, regional blood flow distribution within the myocardium, kidney and brain areas was assessed using the tracer-microsphere technique in anaesthetized dogs. After L-NAME (20 mg kg-1 i.v.) kidney perfusion was homogeneously reduced by 55% in the entire cortex and the outer medulla. Within the left ventricular myocardium regional blood flow significantly decreased only in subepicardial layers (-12%), whereas within the entire right ventricle regional blood flow was reduced by 19-24%. A close inverse relationship was found between all changes in regional myocardial blood flows observed after L-NAME and the respective control values. No significant changes in regional blood flow in different areas of the brain were detectable after L-NAME. It is concluded that the contribution of basal NO formation varies greatly between different organs and exhibits significant regional differences within the heart. It is possible that local metabolic mechanisms may compensate functionally for the inhibition of NO synthesis.

Neuropeptides within the nucleus tractus solitarii modulate the central cardiovascular control process

Local administration of small amounts of vasopressin, angiotensin or endothelin into the nucleus tractus solitarii elicits similar decreases in blood pressure and heart rate. These central effects oppose the peripheral action of these hormones on the cardiovascular system. The baroreceptor-heart-reflex, however, is influenced differentially: vasopressin and angiotensin II enhances the sensitivity of the reflex but angiotensin III impairs it. In this way the cardiovascular system may be adjusted to different demands including those related to electrolyte and fluid homeostasis.

Cardiovascular effects of vasopressin micro-injections into the nucleus tractus solitarii in normotensive and hypertensive rats

In anesthetized, normotensive Wistar rats, Wistar-Kyoto rats (WKY) and spontaneously hypertensive rats (SHR), 100 pg [Arg8]-vasopressin was micro-injected bilaterally into the nucleus tractus solitarii (NTS). Blood pressure and the interbeat heart interval were measured. In both Wistar rats and WKY the interbeat interval was prolonged and blood pressure was decreased, while in SHR only the interbeat interval was prolonged. Thus, within a very low dose range, the influence of [Arg8]-vasopressin within the NTS on mechanisms of cardiovascular regulation seems to differ between normotensive rats and SHR.

[Treatment of progressive axial deformities in children by surgical measures of the growth plate]

Report of the results of 4 surgically treated epiphyseal injuries with progressing deformities in the lower extremities (3 injuries type V, 1 epiphyseal fracture type IV according to Salter and Harris). Our Surgical procedure consisted in a resection of the posttraumatic transphyseal bony bridge with a following interposition of a silastic block to prevent again transphyseal blocking. The indications for such a surgical procedure is explained possibilities leading to failures are discussed. The results of our experimental studies being the basis for such operations are reported.

Entry of quinidine into cerebrospinal fluid

Some of the unwanted effects of quinidine commonly occurring in clinical practice involve the central nervous system. We therefore assessed the rate and extent of quinidine passage into cerebrospinal fluid (CSF) in humans and dogs. In eight human subjects receiving oral quinidine therapy, lumbar CSF quinidine concentrations averaged 16% of unbound serum concentrations (range: 4% to 37%). The findings were confirmed when simultaneous serum (total and unbound) and CSF quinidine concentrations were followed for up to 8 hours after a single intravenous dose of quinidine in anesthetized dogs. Quinidine appeared promptly in CSF of all animals, but CSF concentrations averaged only 37% to 46% of unbound serum levels. The in vitro octanol:water partition coefficient for quinidine at physiologic pH was greater than 100, indicating that unbound quinidine should readily traverse the blood-brain barrier. Thus, passage of quinidine into CSF appears not to be governed by passive diffusion alone. Quinidine may participate in an active transport system such as that which removes certain other basic substances from CSF.

[Results of treatment of leg paraspasm cases following longitudinal frontal myelotomy]

Follow-up examinations of 14 patients on whom longitudinal frontal myelotomy had been performed because of extreme leg spasms, showed consistently good results as far as spasm removal was concerned. Effective rehabilitation is possible only if the basic condition is stationary, if the operation is made at an early stage and followed by a comprehensive rehabilitation programme. For patients with an advancing condition the operation can alleviate the subjective discomfort felt, and it can make care easier.