NH2-truncated human tau induces deregulated mitophagy in neurons by aberrant recruitment of Parkin and UCHL-1: implications in Alzheimer's disease

Disarrangement in functions and quality control of mitochondria at synapses are early events in Alzheimer's disease (AD) pathobiology. We reported that a 20-22 kDa NH2-tau fragment mapping between 26 and 230 amino acids of the longest human tau isoform (aka NH2htau): (i) is detectable in cellular and animal AD models, as well in synaptic mitochondria and cerebrospinal fluids (CSF) from human AD subjects; (ii) is neurotoxic in primary hippocampal neurons; (iii) compromises the mitochondrial biology both directly, by inhibiting the ANT-1-dependent ADP/ATP exchange, and indirectly, by impairing their selective autophagic clearance (mitophagy). Here, we show that the extensive Parkin-dependent turnover of mitochondria occurring in NH2htau-expressing post-mitotic neurons plays a pro-death role and that UCHL-1, the cytosolic Ubiquitin-C-terminal hydrolase L1 which directs the physiological remodeling of synapses by controlling ubiquitin homeostasis, critically contributes to mitochondrial and synaptic failure in this in vitro AD model. Pharmacological or genetic suppression of improper mitophagy, either by inhibition of mitochondrial targeting to autophagosomes or by shRNA-mediated silencing of Parkin or UCHL-1 gene expression, restores synaptic and mitochondrial content providing partial but significant protection against the NH2htau-induced neuronal death. Moreover, in mitochondria from human AD synapses, the endogenous NH2htau is stably associated with Parkin and with UCHL-1. Taken together, our studies show a causative link between the excessive mitochondrial turnover and the NH2htau-induced in vitro neuronal death, suggesting that pathogenetic tau truncation may contribute to synaptic deterioration in AD by aberrant recruitment of Parkin and UCHL-1 to mitochondria making them more prone to detrimental autophagic clearance.

Controlling the activation of the Bv8/prokineticin system reduces neuroinflammation and abolishes thermal and tactile hyperalgesia in neuropathic animals

BACKGROUND AND PURPOSE

Chemokines are involved in neuroinflammation and contribute to chronic pain processing. The new chemokine prokineticin 2 (PROK2) and its receptors (PKR1 and PKR2 ) have a role in inflammatory pain and immunomodulation. In the present study, we investigated the involvement of PROK2 and its receptors in neuropathic pain.

EXPERIMENTAL APPROACH

Effects of single, intrathecal, perineural and s.c. injections of the PKR antagonist PC1, or of 1 week s.c. treatment, on thermal hyperalgesia and tactile allodynia was evaluated in mice with chronic constriction of the sciatic nerve (CCI). Expression and localization of PROK2 and of its receptors at peripheral and central level was evaluated 10 days after CCI, following treatment for 1 week with saline or PC1. IL-1β and IL-10 levels, along with glia activation, were evaluated.

KEY RESULTS

Subcutaneous, intrathecal and perineural PC1 acutely abolished the CCI-induced hyperalgesia and allodynia. At 10 days after CCI, PROK2 and its receptor PKR2 were up-regulated in nociceptors, in Schwann cells and in activated astrocytes of the spinal cord. Therapeutic treatment with PC1 (s.c., 1 week) alleviated established thermal hyperalgesia and allodynia, reduced the injury-induced overexpression of PROK2, significantly blunted nerve injury-induced microgliosis and astrocyte activation in the spinal cord and restored the physiological levels of proinflammatory and anti-inflammatory cytokines in periphery and in spinal cord.

CONCLUSION AND IMPLICATIONS

The prokineticin system contributes to pain modulation via neuron-glia interaction. Sustained inhibition of the prokineticin system, at peripheral or central levels, blocked both pain symptoms and some events underlying disease progression.

AD-linked, toxic NH2 human tau affects the quality control of mitochondria in neurons

Functional as well as structural alterations in mitochondria size, shape and distribution are precipitating, early events in progression of Alzheimer's Disease (AD). We reported that a 20-22kDa NH2-tau fragment (aka NH2htau), mapping between 26 and 230 amino acids of the longest human tau isoform, is detected in cellular and animal AD models and is neurotoxic in hippocampal neurons. The NH2htau -but not the physiological full-length protein- interacts with Aβ at human AD synapses and cooperates with it in inhibiting the mitochondrial ANT-1-dependent ADP/ATP exchange. Here we show that the NH2htau also adversely affects the interplay between the mitochondria dynamics and their selective autophagic clearance. Fragmentation and perinuclear mislocalization of mitochondria with smaller size and density are early found in dying NH2htau-expressing neurons. The specific effect of NH2htau on quality control of mitochondria is accompanied by (i) net reduction in their mass in correlation with a general Parkin-mediated remodeling of membrane proteome; (ii) their extensive association with LC3 and LAMP1 autophagic markers; (iii) bioenergetic deficits and (iv) in vitro synaptic pathology. These results suggest that NH2htau can compromise the mitochondrial biology thereby contributing to AD synaptic deficits not only by ANT-1 inactivation but also, indirectly, by impairing the quality control mechanism of these organelles.

ProNGF\NGF imbalance triggers learning and memory deficits, neurodegeneration and spontaneous epileptic-like discharges in transgenic mice

ProNGF, the precursor of mature nerve growth factor (NGF), is the most abundant form of NGF in the brain. ProNGF and mature NGF differ significantly in their receptor interaction properties and in their bioactivity. ProNGF increases markedly in the cortex of Alzheimer's disease (AD) brains and proNGF\NGF imbalance has been postulated to play a role in neurodegeneration. However, a direct proof for a causal link between increased proNGF and AD neurodegeneration is lacking. In order to evaluate the consequences of increased levels of proNGF in the postnatal brain, transgenic mice expressing a furin cleavage-resistant form of proNGF, under the control of the neuron-specific mouse Thy1.2 promoter, were derived and characterized. Different transgenic lines displayed a phenotypic gradient of neurodegenerative severity features. We focused the analysis on the two lines TgproNGF#3 and TgproNGF#72, which shared learning and memory impairments in behavioral tests, cholinergic deficit and increased Aβ-peptide immunoreactivity. In addition, TgproNGF#3 mice developed Aβ oligomer immunoreactivity, as well as late diffuse astrocytosis. Both TgproNGF lines also display electrophysiological alterations related to spontaneous epileptic-like events. The results provide direct evidence that alterations in the proNGF/NGF balance in the adult brain can be an upstream driver of neurodegeneration, contributing to a circular loop linking alterations of proNGF/NGF equilibrium to excitatory/inhibitory synaptic imbalance and amyloid precursor protein (APP) dysmetabolism.

Electroacupuncture counteracts the development of thermal hyperalgesia and the alteration of nerve growth factor and sensory neuromodulators induced by streptozotocin in adult rats

AIMS/HYPOTHESIS

Diabetes is considered the leading cause of neuropathies in developed countries. Dysfunction of nerve growth factor (NGF) production and/or utilisation may lead to the establishment of diabetic neuropathies. Electroacupuncture has been proved effective in the treatment of human neuropathic pain as well as in modulating NGF production/activity. We aimed at using electroacupuncture to correct the development of thermal hyperalgesia and the tissue alteration of NGF and sensory neuromodulators in a rat model of type 1 diabetes.

METHODS

Adult rats were injected with streptozotocin to induce diabetes and subsequently treated with low-frequency electroacupuncture for 3 weeks. Variation in thermal sensitivity was studied during the experimental course. Hindpaw skin and spinal cord protein content of NGF, NGF receptor tyrosine kinase A (TrkA), substance P (SP), transient receptor potential vanilloid 1 (TRPV1) receptor and glutamic acid decarboxylase-67 (GAD-67) were measured after electroacupuncture treatments. The skin and spinal cord cellular distribution of TrkA was analysed to explore NGF signalling.

RESULTS

Early after streptozotocin treatment, thermal hyperalgesia developed that was corrected by electroacupuncture. The parallel increases in NGF and TrkA in the spinal cord were counteracted by electroacupuncture. Streptozotocin also induced variation in skin/spinal TrkA phosphorylation, increases in skin SP and spinal TRPV1 and a decrease in spinal GAD-67. These changes were counteracted by electroacupuncture.

CONCLUSIONS/INTERPRETATION

Our results point to the potential of electroacupuncture as a supportive therapy for the treatment of diabetic neuropathies. The efficacy of electroacupuncture might depend on its actions on spinal/peripheral NGF synthesis/utilisation and normalisation of the levels of several sensory neuromodulators.

Endogenous Aβ causes cell death via early tau hyperphosphorylation

Alzheimer's disease (AD) is characterized by Aβ overproduction and tau hyperphosphorylation. We report that an early, transient and site-specific AD-like tau hyperphosphorylation at Ser262 and Thr231 epitopes is temporally and causally related with an activation of the endogenous amyloidogenic pathway that we previously reported in hippocampal neurons undergoing cell death upon NGF withdrawal [Matrone, C., Ciotti, M.T., Mercanti, D., Marolda, R., Calissano, P., 2008b. NGF and BDNF signaling control amyloidogenic route and Ab production in hippocampal neurons. Proc. Natl. Acad. Sci. 105, 13138-13143]. Such tau hyperphosphorylation, as well as apoptotic death, is (i) blocked by 4G8 and 6E10 Aβ antibodies or by specific β and/or γ-secretases inhibitors; (ii) temporally precedes tau cleavage mediated by a delayed (6-12h after NGF withdrawal) activation of caspase-3 and calpain-I; (iii) under control of Akt-GSK3β-mediated signaling. Finally, we show that such site-specific tau hyperphosphorylation causes tau detachment from microtubules and an impairment of mitochondrial trafficking. These results depict, for the first time, a rapid interplay between endogenous Aβ and tau post-translational modifications which act co-ordinately to compromise neuronal functions in the same neuronal system, under physiological conditions as seen in AD brain.

SP protects cerebellar granule cells against beta-amyloid-induced apoptosis by down-regulation and reduced activity of Kv4 potassium channels

The tachykinin endecapeptide substance P (SP) has been demonstrated to exert a functional role in neurodegenerative disorders, including Alzheimer's disease (AD). Aim of the present study was to evaluate the SP neuroprotective potential against apoptosis induced by the neurotoxic beta-amyloid peptide (A beta) in cultured rat cerebellar granule cells (CGCs). We found that SP protects CGCs against both A beta(25-35)- and A beta(1-42)-induced apoptotic CGCs death as revealed by live/dead cell assay, Hoechst staining and caspase(s)-induced PARP-1 cleavage, through an Akt-dependent mechanism. Since in CGCs the fast inactivating or A-type K(+) current (I(KA)) was potentiated by A beta treatment through up-regulation of Kv4 subunits, we investigated whether I(KA) and the related potassium channel subunits could be involved in the SP anti-apoptotic activity. Patch-clamp experiments showed that the A beta-induced increase of I(KA) current amplitude was reversed by SP treatment. In addition, as revealed by Western blot analysis and immunofluorescence studies, SP prevented the up-regulation of Kv4.2 and Kv4.3 channel subunits expression. These results indicate that SP plays a role in the regulation of voltage-gated potassium channels in A beta-mediated neuronal death and may represent a new approach in the understanding and treatment of AD.

Minocycline attenuates microglial activation but fails to mitigate degeneration in inferior olive and pontine nuclei after focal cerebellar lesion

Degenerative changes in areas remote from the primary lesion site have been linked to the clinical outcome of focal brain damage, and inflammatory mechanisms have been considered to play a key role in the pathogenesis of these remote cell death phenomena. Minocycline is a tetracycline derivative, therapeutically effective in various experimental models of central nervous system (CNS) injuries that include inflammatory and apoptotic mechanisms, although recent findings have yielded mixed results. In this study, we investigated the effectiveness of minocycline treatment in reducing remote cell death. Glial activation and neuronal loss in precerebellar stations following cerebellar lesion were investigated using immunohistochemistry and Western blot techniques. Our results show that minocycline was effective in reducing microglial activations in axotomized precerebellar nuclei, but failed to mitigate either astrocytic response or neuronal loss. This finding supports the role of minocycline in modulating inflammatory response after CNS lesion and suggests its ineffectiveness in influencing degenerative phenomena in areas remote from the primary lesion site.

Remote cell death in the cerebellar system

Functional impairment after focal CNS lesion is highly dependent on damage that occurs in regions that are remote but functionally connected to the primary lesion site. This pattern is particularly evident in the cerebellar system, in which functional interactions between the cerebellar cortex, deep cerebellar nuclei, and precerebellar stations are of paramount importance. Diffuse degeneration after development of a focal CNS lesion has been associated with poor outcomes in several pathologies, such as stroke, multiple sclerosis, and brain trauma. A greater understanding of the mechanisms that underlie the spread of death signals from focal lesions, however, can aid in identifying a neuroprotective approach for CNS pathologies. To this end, studies on degenerative mechanisms in the inferior olive and pontine nuclei after focal cerebellar damage have been a valuable asset in which pharmacological approaches have been tested. In this review, we focus on mechanisms of remote cell death in cerebellar circuits, analyzing the neuroprotective effects of inflammation-modulating drugs in particular.

Methylprednisolone treatment delays remote cell death after focal brain lesion

Glucocorticoids have a prominent role in the treatment of CNS injuries. However, the cellular consequences of glucocorticoid treatment on remote degenerative responses after focal brain lesions have been poorly investigated. Here we examine the effectiveness of a high dose (50 mg/kg) of methylprednisolone sodium succinate (MPSS) in reducing neuronal loss, glial response and glial-derived inflammatory mediators in inferior olive and pontine nuclei after lesion of the contralateral cerebellar hemisphere using immunohistochemistry and Western blot techniques. Quantitative analysis demonstrated that MPSS treatment significantly improved the survival of neurons in remote precerebellar stations. This survival was accompanied by reduction in the postlesional activation of microglia, astrocytes and interleukin-1 beta (IL-1beta). Cell death resumed after suspension of MPSS treatment and this delayed wave of cell loss was paralleled by reactivation of the inflammatory markers analyzed. The present study confirms the importance of inflammatory events in inducing remote cell death and that this type of degeneration can be delayed by MPSS treatment. Furthermore, the sustained effect of MPSS treatment, up to 28 days postlesion, and the reactivation of the degenerative phenomena after its suspension, support the hypothesis that glucocorticoid treatment, although capable of delaying cell death mechanisms, is not effective in blocking the cascade of remote degenerative events started by the primary lesion.

Do ATP and NO interact in the CNS?

Enzymatically derived NO and extracellular ATP are receiving greater attention due to their role as messengers in the CNS during different physiological and pathological processes. Ionotropic (P2XR) and metabotropic (P2YR) purinergic receptors mediate ATP effects and are present throughout the body. Particularly P2XR are crucial for brain plasticity mechanisms, and are involved in the pathogenesis of different CNS illnesses. NO does not have a specific receptor and its actions are directly dependent on the production on demand by different nitric oxide synthase isoforms. NO synthesizing enzymes are present virtually in all tissues, and NO influences multifarious physiological and pathological functions. Interestingly, various are the tissue and organs modulated by both ATP and NO, such as the immune, brain and vascular systems. Moreover, direct interactions between purinergic and nitrergic mechanisms outside the CNS are well documented, with several studies also indicating that ATP and NO do participate to the same CNS functions. In the past few years, further experimental evidence supported the physiological and pathological relevance of ATP and NO direct interactions in the CNS. The aim of the present review is to provide an account of the available information on the interplay between purinergic and nitrergic systems, focussing on the CNS. The already established relevance of ATP and NO in different pathological processes would predict that the knowledge of ATP/NO cross-talk mechanisms would support pharmacological approaches toward the development of novel ATP/NO combined pharmacological agents.

Partial resistance of ataxin-2-containing olivary and pontine neurons to axotomy-induced degeneration

Spinocerebellar ataxia type 2 (SCA2) is caused by the expansion of a polyglutamine tract in ataxin-2, the SCA2 gene product. In spite of the identification of the genetic defect and the coded protein, the function of wild-type ataxin-2 has not been clarified. In order to identify the possible resistance of ataxin-2-containing neurons to degeneration, we investigated in this study the distribution and the characteristics of cell reaction to axotomy in ataxin-2-positive olivary and pontine neurons in a model of cerebellar damage represented by hemicerebellectomy. We also performed double immunofluorescence studies of ataxin-2 and purinergic receptors to characterize ataxin-2-positive surviving neurons. The present data demonstrated that after axotomy olivary and pontine ataxin-2-expressing neurons survived longer than the ataxin-2-negative cell population. Cell counting performed in the different olivary subdivisions failed to reveal any topographical prevalence in the distribution of ataxin-2-positive neurons. Therefore, the relative resistance to axotomy appears to be an intrinsic property of the ataxin-2 cell population. In addition, the capacity to modify the pattern of purinergic receptor expression in response to damage was present in only one subset of ataxin-2-positive surviving neurons. These data suggest that ataxin-2 is involved in resistance to degeneration phenomena which may be lost after mutation.

Axotomy dependent purinergic and nitrergic co-expression

Different lines of evidence indicate that ATP and nitric oxide (NO) play key roles in mediating neuronal responses after cell damage. Purinergic and nitrergic interactions have been proposed in non neural tissues physiological functions and, in different experimental models of brain injury, both purinergic and nitrergic activations have been reported. The present study was planned to ascertain possible relations of these two systems after brain damage. Variations in the expression of the nitric oxide synthase neuronal isoform (nNOS) enzyme, and of two subunits of purinergic ionotrophic receptors (P2X) namely P2X(1) and P2X(2) in precerebellar stations after cerebellar lesion in rats were analyzed and compared. After the lesion nNOS positive cells presented a clear increment followed by a decrement. Conversely, nNOS negative cells presented a rapid decrement in the first postlesional weeks that continued less pronounced afterward. Postlesional nNOS activation was related with time course of P2X(1) and P2X(2) activations. The capacity of the same cells to express both nNOS and P2X markers was investigated immunocytochemically. Confocal microscopy of double immunofluorescence showed a high percentage of co-localization among P2X(1)/nNOS, P2X(2)/nNOS and P2X(1)/P2X(2) in olivary and pontine neurons. In addition, NeuN/P2X(1) and NeuN/P2X(2) double immunofluorescence showed P2X(1) expressed only in neurons while P2X(2) expressed by both neurons and glia. Present data demonstrate that after cerebellar lesion nitrergic and purinergic systems are activated with similar time courses in precerebellar stations. Further, time differences in the relation between nNOS expression and cell survival suggest a multifarious role of NO in mediating cell reaction to axotomy. The tight cellular co-localization and temporal co-activation of purinergic and nitrergic markers indicate possible interactions between these two systems also in the CNS.

Up-regulation of P2X2, P2X4 receptor and ischemic cell death: prevention by P2 antagonists

In the present work we examined the involvement of selected P2X receptors for extracellular ATP in the onset of neuronal cell death caused by glucose/oxygen deprivation. The in vitro studies of organotypic cultures from hippocampus evidenced that P2X2 and P2X4 were up-regulated by glucose/oxygen deprivation. Moreover, we showed that ischemic conditions induced specific neuronal loss not only in hippocampal, but also in cortical and striatal organotypic cultures and the P2 receptor antagonists basilen blue and suramin prevented these detrimental effects. In the in vivo experiments we confirmed the induction of P2X receptors in the hippocampus of gerbils subjected to bilateral common carotid occlusion. In particular, P2X2 and P2X4 proteins became significantly up-regulated, although to different extent and in different cellular phenotypes. The induction was confined to the pyramidal cell layer of the CA1 subfield and to the transition zone of the CA2 subfield and it was coincident with the area of neuronal damage. P2X2 was expressed in neuronal cell bodies and fibers in the CA1 pyramidal cell layer and in the strata oriens and radiatum. Intense P2X4 immunofluorescence was localized to microglia cells. Our results indicate a direct involvement of P2X receptors in the mechanisms sustaining cell death evoked by metabolism impairment and suggest the use of selected P2 antagonists as effective neuroprotecting agents.

Cerebellar lesion up-regulates P2X1 and P2X2 purinergic receptors in precerebellar nuclei

ATP released in the extracellular space by neuronal injury can influence neighboring neurons via activation of purinergic receptors. In vitro data suggest the involvement of ATP and purinergic receptors as trophic agents in different biological events such as neuritogenesis and cell survival. Recently, in vivo studies have demonstrated modifications in the glial expression of ionotropic purinergic receptors after CNS lesions. In the present study, we investigated the effects of CNS lesion on the neuronal expression of P2X(1) and P2X(2) receptor subunits by immunohistochemistry and western blotting techniques. In the precerebellar structures of normal animals the expression of P2X(1) and P2X(2) was lower than previously reported. P2X(1) immunostaining was confined only to fibers, while P2X(2) immunostaining demonstrated a neuronal expression. After unilateral cerebellar lesion (hemicerebellectomy) axotomized precerebellar neurons underwent marked cell loss; however, some precerebellar neurons did not degenerate. Seven to 35 days after hemicerebellectomy, a transient, time-dependent, marked increase in the number of immunopositive P2X(1) and P2X(2) neurons was observed in the precerebellar nuclei of the experimental side. An even distribution of immunopositive neurons was present in almost all precerebellar nuclei examined, except for the inferior olive. In this latter structure, differences in the distribution of immunopositive neurons were evident among the subnuclei. Up-regulation of immunoreactivity over relatively long time periods, distribution selectivity and absence of degenerating morphological features in immunopositive neurons suggest that purinergic receptors may have a role in mediating the survival of neuronal responses to axotomy. The present findings are the first report in the CNS of P2X(1) and P2X(2) receptor subunit involvement in neuronal reaction to axotomy. They provide in vivo evidence of a correlation between purinergic receptor subunit up-regulation and survival of injured neurons.

Degranulation of mast cells in the rat thalamus

Brain mast cells are selectively concentrated in the thalamus of many mammalian species. We here describe by light and electron microscopy in the normal thalamus of adult rats the features of mast cell degranulation, which indicate an active release of the mediators stored in their intracellular granules. The state of activity of thalamic mast cells in basal conditions was found to range from the release of a few granules to a massive degranulation, and the latter process was much less frequent than a partial degranulation. Mast cells were subdivided in three categories (fully granulated, partially or massively degranulated) on the basis of their cytoplasmic features revealed by acidic toluidine blue staining; the fully granulated cells were found to represent only 23 % of thalamic mast cells. This strategy of evaluation could be of help in the comparison of the functional correlates of mast cells in different conditions and experimental paradigms. However, we also demonstrated with image analysis a continuum of the variation of staining intensity of granulated and degranulating mast cells, without a sharp subdivision into different categories. Therefore our results reveal that the vast majority of mast cells are active in the thalamus in basal conditions, and that image analysis can provide an objective index of the activity of these cells.

A stability test of liposome preparations using steady-state fluorescent measurements

The stability of liposome preparations under the action of the nonionic detergent Triton X-100 was measured using the fluorescent molecular probe octadecylrhodamine B (R18). The probe inserted in the lipid bilayer shows a self-quenched fluorescence and the degree of quenching depends both on the probe concentration and the phase state of the lipid membrane. The addition of detergent to the liposomes produces a steep decrease in self-quenching caused by dilution of the probe in the bilayer. The curves of steady-state fluorescence intensity show an abrupt change in slope that corresponds to the point at which liposomes break down into lipid-detergent mixed entities that are different from the earlier liposome-monodisperse population. The lytic process was followed in parallel by dynamic light scattering (DLS), and the analysis of the DLS results agree with the interpretation of the fluorescence measurements. The probe R18 therefore is a useful marker to test the stability of liposome preparations. The advantages of the present method are discussed by comparison with other techniques.

[Thromboembolic risk factors in atrial flutter. Transesophageal echocardiographic study]

BACKGROUND

The thromboembolic risk of atrial flutter (AFL) is not well defined. On the other hand, in atrial fibrillation (AF), the echocardiographic demonstration of thrombus or spontaneous echo contrast in the left atria or its appendage, a lower flow velocity in the left atrial appendage, and its reduced mobility, are well known risk factors of thromboembolism.

AIM

To study the incidence of these echocardiographic risk factors in patients with AFL.

MATERIAL AND METHODS

We prospectively studied 50 consecutive patients with AFL comparing them with two groups of patients with a well known increased risk of thromboembolism: 54 patients with AF and 24 patients with sinus rhythm and severe mitral stenosis (RSEMS). The group of patients with AFL was also compared with a control group of 27 patients with sinus rhythm and no increased risk of thromboembolism. In each group, we studied the presence of thrombi and spontaneous echo contrast in the left atria and left atrial appendage, emptying velocity (Vel A), filling flow (Vel B) and motility of the left atrial appendage and left atrial dimensions.

RESULTS

When compared with control patients, AFL subjects had a higher incidence of spontaneous echo contrast in the left atria and left atrial appendage (11 and 42% respectively, p < 0.05); slower flow velocity in the left atrial appendage (Vel A 69.25 +/- 25 and 41 +/- 19 cm/s respectively, Vel B 55 +/- 16 and 46 +/- 20 cm/s respectively, p < 0.05); lower atrial appendage wall motility (4 and 84% respectively, p < 0.001) and a larger left atrium (40 +/- 10 and 45 +/- 0.6 mm respectively, p < 0.05). Patients with AFL had a lower incidence of echocardiographic abnormalities than subjects with AF or RSEMS. Thrombi were found in 2 patients with AFL, 12 patients with AF, 4 patients with RSEMS and in no control patient.

CONCLUSIONS

In AFL, there are echocardiographic markers of increased thromboembolic risk in comparison with a control group. Nevertheless, the incidence of these factors is lower than in patients with AF or with RSEMS.

Selective nicotinamide adenine dinucleotide phosphate-diaphorase histochemical labeling of Müller radial processes and photoreceptors in the earliest stages of retinal development in the tadpole

To investigate potential sources of nitric oxide production in the early stages of retinal development we used, in the tadpole, nicotinamide adenine dinucleotide phosphate-diaphorase histochemistry that was reported to reveal nitric oxide synthase isoforms in the retina. In the first stages of optic vesicle differentiation, prior to optic cup invagination, histochemical positivity was detected in the radial processes of Müller cells, that provide a scaffold for migrating retinal neuroblasts, and was soon followed by intense staining of photoreceptors. These events preceded retinal laminar patterning and the appearance of histochemical positivity in other retinal cell populations. The findings indicate that nitric oxide synthase is expressed during early retinogenesis at selective sites, which are implicated in the guidance of migrating cells and in phototransduction.

Degranulation, density, and distribution of mast cells in the rat thalamus: a light and electron microscopic study in basal conditions and after intracerebroventricular administration of nerve growth factor

In the adult rat brain mast cells reside selectively in the thalamus. We investigated thalamic mast cells stained by acidic toluidine blue or pinacyanol, and with histamine immunocytochemistry, focusing on their state of activity revealed by degranulation. Mast cells exhibited perivascular prevalence and high quantitative variability, between cases and in different sections, with no asymmetry or topographical selectivity in thalamic nuclei. Pinacyanol, alone or with erythrosine, stained mast cells with higher sensitivity than toluidine blue. However, toluidine blue was highly predictive of pinacyanol staining and provided the best resolution of mast cell cytoplasmic features. Histamine immunocytochemistry labeled 61% of pinacyanol-stained mast cells. Intensely toluidine blue-stained granulated cells, as well as cells exhibiting different degrees of degranulation that paralleled lighter staining, were observed. The response of thalamic mast cells to intracerebroventricular administration of nerve growth factor (NGF) and control cytochrome-c injections was evaluated after 2, 24, and 72 hours. No obvious changes in mast cell number or distribution were found after treatment, but massive degranulation was frequently observed after NGF administration. Significant decrease of staining intensity of mast cells, supporting enhanced degranulation, was documented in NGF-treated animals by quantitative image analysis. Ultrastructural features of mast cell degranulation, with granule coalescence and matrix dissolution, were detected in untreated and NGF-treated cases. The findings point out that mast cells are active in the thalamus in basal conditions and that NGF has the potential to elicit long-lasting degranulation of thalamic mast cells in vivo, exerting a direct effect and/or priming these cells to react to endogenous stimuli.

[Coronary angioplasty and stent placement through the radial artery. Report of a case]

Coronary angiography and percutaneous treatment of stenotic lesions have expanded in the last few years, due to availability of better diagnostic equipment. The femoral technique applied to this aims has prevailed, considering its efficacy, safety and wide acceptance. Since the beginning of this decade, an alternative access has been developed, in relation to miniaturization of the required elements to perform coronary diagnostic and therapeutic procedures. This new radial artery access is supported by multiple reports from many centers around the world that are increasingly using the technique. With this access it is possible to perform all the regular procedures done regularly through the femoral route. This case report illustrates a coronary angiography study through the radial access, followed by a stent implantation, through the same route.

Nociceptive stimulation induces glutamate receptor down-regulation in the trigeminal nucleus

The dorsal horn of the subnucleus caudalis of the spinal trigeminal nucleus is a relay of oro-facial pain transmission; increase in subnucleus caudalis neuronal activity in response to tissue injury affects the level of chemical mediators participating in nociceptive processing. We investigated, by means of immunocytochemistry, the expression of N-methyl-D-aspartate and alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) glutamate receptor subunits in this nucleus in a model of inflammation. Rats injected with formalin in the whisker pad were compared with saline-injected control rats. One and two days after formalin injection, the immunostaining of cell bodies and neuropil of the AMPA receptor subunits GluR1 and GluR2/3 was markedly decreased in the ipsilateral superficial laminae of the subnucleus caudalis compared to the contralateral side. Side differences were not evident in the saline-treated animals. The down-regulation of AMPA GluR1 and GluR2/3 was no longer detectable in the subnucleus caudalis three days after formalin injection. No side difference was detected in the N-methyl-D-aspartate receptor subunit NR2A/B immunoreactivity of the subnucleus caudalis at any time-point in the formalin-injected animals. The modulation of AMPA receptor may be related to the decrease of hyperalgesia evident 1 h after formalin injection, in spite of the increasing perioral inflammation evident later on and characteristic of the formalin model. The present findings point out a selective down-regulation of AMPA receptor subunits in the transduction of trigeminal pain. These data also support the involvement of glutamate receptor subunits in the processing of trigeminal inflammation induced by noxious chemical stimulation.

Heart rate variability in severe aortic stenosis

BACKGROUND AND AIM OF THE STUDY

Autonomic dysfunction may be a risk factor for the generation of arrhythmias and sudden death in patients with severe aortic stenosis; thus, patients with this condition were studied to assess cardiac autonomic function.

METHODS

Twelve patients (five males, seven females; mean age 63 +/- 13 years) with severe symptomatic aortic stenosis before and after aortic valve replacement, were compared with a control group matched by age and sex. In the study group, mean fractional shortening was 36.5 +/- 5% and maximal aortic gradient 94.7 +/- 12 mmHg, assessed echocardiographically. Autonomic dysfunction was evaluated by following heart rate variability in both time and frequency domains. Spectral analysis was assessed at very low frequency (VLF: 0.017-0.05 Hz), low frequency (LF: 0.05-0.15 Hz) and high frequency (HF: 0.15-0.50 Hz). Heart rate variability was analyzed during three intervals, between 6:00-8:00 am (morning), 14:00-16:00 (afternoon) and 02:00-04:00 (night), and re-evaluated at 8-10 months after aortic valve replacement.

RESULTS

Compared with controls, patients with aortic stenosis presented a significantly lower heart rate variability in the morning and afternoon, analyzed either by time or frequency domain: 50 +/- 22 versus 132 +/- 52 ms (p < 0.05); VLF 5.0 +/- 1.5 versus 7.9 +/- 1.4 ln (ms)2 (p < 0.05); LF 4.9 +/- 1.7 versus 7.5 +/- 1.8 ln (ms)2 (p < 0.05); HF 5.3 +/- 1.4 versus 7.5 +/- 1.8 ln (ms)2 (p < 0.05). Results at night showed a similar tendency, but were not statistically significantly different. At 8-10 months after aortic valve replacement, heart rate variability was increased significantly during the morning, from 50 +/- 22 to 79.5 +/- 22 ms (p < 0.05); VLF from 5.0 +/- 1.5 to 6.7 +/- 0.8 ln (ms)2 (p < 0.05); LF from 4.9 +/- 1.7 to 6.2 +/- 1.3 ln (ms)2 (p < 0.05). HF values tended to increase, though not significantly so. During the remainder of the day there was also a non-statistically significant increment in all values of heart rate variability.

CONCLUSIONS

The study results suggest that patients with severe symptomatic aortic stenosis present with autonomic dysfunction that tends to normalize within the first year of valve replacement.

[Unstable angina: invasive or conservative management?]

Acute coronary syndromes without ST segment elevation (Non-Q-Infarction and unstable angina) share a common pathophysiology, have no indication of thrombolysis, and should not routinely be catheterized on an emergency basis on admission. They should be put in bed rest, given anti-ischemic medications, aspirin and heparin. The small group of patients that do not stabilize with this medical regimen, should be catheterized, in order to have revascularization if they have the appropriate anatomy. There is nowadays a great controversy in the best management strategy for the larger group of patients that becomes stable after medical treatment installation. The invasive strategy proposes early, routine coronary angiography, and revascularization when anatomy is appropriate. The conservative strategy proposes continued medical treatment with invasive management only indicated by development of spontaneous or inducible ischemia. These two alternative strategies have been tested recently in large, prospective, randomized clinical trials: there is not a definitive answer, but the provisional guideline is that both are reasonably safe and effective.

[Variability of the heart rate: its physiopathological basis and its use as prognostic index after acute myocardial infarction]

The analysis of heart rate variability studies the normal oscillatory changes of the cardiac cycle. These changes are periodical or incidental and are controlled by humoral, sympathetic and parasympathetic stimuli. Frequency domain and time domain are the methods most used to assess heart rate variability. Time domain analyses variations of cardiac cycle using the standard deviation of RR intervals in 24 hours (SDRR) and the percentage of difference between adjacent normal RR intervals of more than 50 ms (pNN50). Frequency domain, converts beat to beat fluctuation of heart rate into different components of frequency by a fast Fourier transformation. They are classified, according to their magnitude, in high frequency (> 0.15 Hz), low frequency (0.04-0.15 Hz), very low frequency (0.003-0.04 Hz) and extremely low frequency (< 0.003 Hz). The high frequency fluctuations are predominantly related to parasympathetic activity whereas the low frequency fluctuations are related to sympathetic and parasympathetic activity. The physiology of very low and extremely low frequency fluctuations remains unclear. Many reports have shown that a decrease in heart rate variability after myocardial infarction may independently identify patients at risk for sudden death. However, the physiopathologic basis of these findings is not yet elucidated.

[Primary coronary angioplasty as a choice treatment in the 1st 6 hours following acute myocardial infarction]

Primary coronary angioplasty as treatment of acute myocardial infarction preserves more myocardium and has a lower mortality than thrombolysis. Aiming to assess the feasibility of its use in Chile, we studied 64 patients aged 59 +/- 2 years old, 27 with an anterior wall and 37 with an infero-lateral wall acute myocardial infarction of 118 +/- 62 min of evolution. Coronary angiography, performed 98 +/- 47 min after diagnosis, showed non significant disease in one, one vessel disease in 26 (40%), two vessel disease in 17 (27%) and three vessel disease in 20 (31%) patients. Responsible arteries for infarction were the anterior descending in 26 (40%), circumflex in 9 (14%), right in 27 (42%), a saphenous bridge in one and left main disease in one patient. In one patient with an obstruction over 50% and in two patients with left main disease, angioplasty was not attempted. The procedure was successful (defined as a residual lesion of less than 50%) in 56 of 61 patients (92%) and failed in four. One patient was re-perfused with intracoronary streptokinase. The delay in reperfusion was lower during working than non-working hours (89 +/- 48 vs 113 +/- 39 min). Four patients (6%) died during hospitalization, two had a reinfarction, two had a new vessel occlusion and three had a spontaneous ischemia. Eleven patients were operated during hospitalization and in two this was an emergency procedure. After 1993, mortality was lower (one of 55 patients) than before (three of nine). It is concluded that early coronary angioplasty in acute myocardial infarction is feasible in Chile, with a high degree of success.

[Adult pulmonary stenosis: percutaneous balloon valvuloplasty]

The results of balloon valvuloplasty as treatment for pulmonary stenosis in 8 adults (6 male) whose ages ranged from 17 to 58 years are presented. Three patients had been subjected to cardiac surgery 32, 40 and 10 years before. The procedure was performed through the right femoral vein using one or two balloons with a diameter of not less than 20 mm, without complications and excellent tolerance. The pulmonary gradient and the right ventricular pressure were reduced in 7 patients from 81.4 +/- 26.9 to 26.6 +/- 11.3 and from 99.3 +/- 25.5 to 47.7 +/- 13.6 mm Hg respectively (p < 0.0005). During follow up, 6 of the patients have remained in functional capacity I and in two, Doppler ultrasound examination showed a further reduction in valvular gradient. These results are in accordance with other reports and confirm that this technique is the treatment of choice for adult pulmonary stenosis.

Neuronal IFN-gamma in tuberomammillary neurones

Neuronal interferon-gamma (N-IFN-gamma), recently isolated from the nervous system, has a molecular weight distinct from that of lymphocyte-derived IFN-gamma, but crossreacts immunologically and shares certain bioactivities with this cytokine. In the rat brain N-IFN-gamma-immunoreactive perikarya were concentrated in the hypothalamic tuberomammillary nuclei; some immunostained neurones were also detected in the dorsal pontine tegmentum. Immunopositive nerve fibres were profusely distributed through the periventricular hypothalamus and midline thalamus. Scattered fibres occurred diffusely through the brain, ramified in the subpial layer and also surrounded intrathecal vessels. A dense concentration of puncta was detected in the suprachiasmatic nuclei and in the molecular layer of the hippocampal dentate gyrus. A role of N-IFN-gamma in immunological reactions and in modulation of selective brain functions is suggested.

[Percutaneous mitral valvuloplasty in 2 pregnant women]

In women with a significative mitral stenosis that become pregnant, medical treatment has limitations and surgical treatment is associated with maternal and fetal mortality. We report two pregnant women in whom a mitral valvuloplasty was performed in weeks 30 and 32 of pregnancy, using the single balloon Inoue technique. The indication for the procedure was the persistence of functional capacity IV heart failure in spite of hospital bed rest and the use of diuretics and beta-blockers. Basal mitral valvular area was 0.6 and 0.9 cm2 and improved to 1.7 and 1.8 cm2 after the procedure; six months later, the areas were 1.5 and 1.7 respectively. The procedure was well tolerated and was performed with abdominal and pelvic shielding. No complications occurred, which allowed hospital discharge in functional capacity I; they were readmitted for delivery, giving birth to two healthy girls. It is concluded that mitral valvuloplasty in safe and effective in pregnant women with mitral stenosis refractory to usual medical treatment.

[Percutaneous mitral valvuloplasty with the Inoue balloon. Report of a case]

Percutaneous mitral commissurotomy has recently been proposed as an alternative to surgery in mitral stenosis. The clinical and hemodynamic results are equivalent to those of surgical treatment. A new technique proposed by Inoue, using a single rubber balloon, with a low incidence of complications, can be performed in a shorter procedure time than the former double balloon technique. A 36 year-old woman with severe mitral stenosis, NYHA FC III, was treated percutaneously using a single rubber balloon designed by Inoue. Her mitral valve area increased from 0.83 to 1.96 cm2, her mean gradient decreased from 15 to 5.8 mmHg and the cardiac output increased from 4.14 to 5.3 l/min. Total procedure time was 2 h and the radioscopic time was 15 min. The follow-up at the fourth month showed persistence of the mitral valve area (2 cm2 at doppler measurement) and the patient was asymptomatic (NYHA FC I). A description of the technique is presented.

Suicidal behavior in Italy: data, trends and guidelines for a suicide intervention/prevention policy

Even though in Italy, as in the majority of Mediterranean countries, the increase in suicide rates is not among the highest in Europe, between 1969 and 1989 it showed a sharp upswing (+43% among males and +31% among females). In terms of geographical differences, the regions with the highest suicide rate are the northern ones (up to twice the national average). The age groups with the highest suicide risk are those over 74 years (in 1989 the rate among males over 65 was the highest of all: 31.3 per 100,000). The differences in the between-sexes distribution show that among females over 65 years old the suicide rate rose by 70% between 1974 and 1989, versus 77% for males of the same age. The preliminary epidemiological results of one of two Italian centers are presented. These centers are collaborating with the WHO/EURO Multicenter Study on Parasuicide; parasuicide rates are higher for females than for males (55.9 per 100,000, as against 38.1 for males), while the age group at highest risk is seen to be young women (15-24 years), with a specific rate of 115.6.

[Percutaneous valvuloplasty: a decade of continuous progress]

Percutaneous balloon valvuloplasty is an interventional procedure designed to treat valve stenosis. The indications, techniques and results depend on the valve being opened. It is currently the treatment of choice for pulmonary valve stenosis. It is an excellent alternative to surgery for mitral stenosis in patients with mobile valves and little abnormality of the subvalvular apparatus. In aortic stenosis it constitutes a gratifying palliative procedure in older patients at high surgical risk. Longer observation is needed to better appreciate the results and indications of balloon valvuloplasty.

[Incidence of myocarditis in patients with dilated cardiomyopathy]

We performed right ventricular endomyocardial biopsies in 23 patients with dilated cardiomyopathy aged 45 +/- 14 years. All patients had congestive heart failure of unknown etiology dating up to one year before the procedure (57% less than 3 months). NYHA functional class was II in 5, III in 12 and IV in 6 patients. All patients had evidence of systolic dysfunction and a dilated left ventricle (LV diastolic dimension 68 +/- 11 and systolic dimension 55 +/- 11). Definite evidence of myocarditis, based on findings of inflammatory infiltrate and cellular damage, was found in 6 patients (26%), borderline myocarditis in 9 and abnormalities consistent with dilated cardiomyopathy in 8. The incidence of myocarditis here reported is lower than previously figures based on findings of more than 5 lymphocytes per high power field. In this series, clinical and functional aspects of heart failure did not differ in patients with or without evidence of myocarditis.

[Cardiopulmonary resuscitation]

Cardiopulmonary resuscitation has been used for over 25 years. Recent developments related to a better understanding of the physiology of external massage and to the effect of drugs such as calcium and bicarbonate during cardiac arrest have improved the results of cardiopulmonary resuscitation.

[Percutaneous aortic valvuloplasty: immediate results in calcified aortic stenosis]

Symptomatic calcific aortic stenosis in elderly patients has a poor prognosis and a relatively high surgical risk. Percutaneous aortic valvuloplasty is a new therapeutic procedure that may be applied in this group of patients. We report immediate results obtained with this technique in a cooperative study of 3 hospitals. In 16 of 19 patients we were able to locate a balloon catheter across the aortic valve following a femoral artery puncture. Mean age was 72 years and almost all patients were considered high surgical risk. Peak aortic gradient fell from 89 + 33 to 47 + 21 mmHg while valve area rose from 0.43 + 0.14 to 0.66 + 0.27 cm2; cardiac output remained unchanged. In 5 patients, an aortic valve area above 0.7 cm2 was obtained. Four patients needed blood transfusion, one developed pericardial tamponade and other recovered uneventfully from ventricular fibrillation. One patient died hours after the procedure in a low output state probably related to aortic insufficiency. We feel that aortic valvuloplasty is indicated in patients with severe calcific aortic stenosis and high surgical risk. Moderate improvement can be obtained with risks commensurate with the severity of the illness.

[Association of coronary disease and valve diseases: implications for coronariography indication]

We studied 111 patients with valvular heart disease in order to detect associated coronary artery disease (CAD). Fifty had aortic valve disease, 47 mitral lesions and 14 mitro-aortic disease. Coronary angiography was performed in all subjects above 50 years of age and in 13 younger subjects with angina, atypical chest pain, prior myocardial infarction or unexplained left ventricular disfunction. Eight subjects (7.2%) had significant CAD: 1 with triple, 2 with double and 5 with single vessel disease. CAD was diagnosed in 11.5% of 26 patients with angina, in 6% of 17 patients with atypical chest pain and in 6% of 68 patients without pain. CAD was present in males only above age 55. We conclude that in our population, with low incidence of CAD, the association of this disease and valvular heart disease is unusual. Coronary arteriography would be unnecessary in these patients except in the presence of marked risk factors or other clinical findings suggesting CAD, like angina or prior myocardial infarction.

[Myocardial perfusion during exercise and rest in coronary patients. Evaluation with a thallium 201 analog (isonitrile-technetium 99 m)]

Isonitrile-technetium, a Thallium 201 analog, was used for myocardial perfusion imaging in 12 patients with known coronary heart disease. 10-40 mCu of the isotope were injected at maximal effort during a Bruce stress test. Imaging was performed using 3 projections immediately after exercise and 24 hr later, using a gamma camera attached to a computer. Myocardial necrosis was detected with a sensitivity of 89% and specificity of 63%. Corresponding figures for stress induced ischemia were 89% and 100%. Accurate localization of ischemia or necrosis was obtained in 70% of all cases, improving to 100% in cases of total artery occlusion. These results, similar to those reported in the literature, encourage the use of Tc labeled isonitrile for myocardial perfusion imaging whenever Thallium 201 is difficult to obtain.