Stalagmite-like pre-retinal deposits in the optical coherence tomography of two vitrectomy patients with panuveitis.

Two patients with panuveitis are presented in whom, after undergoing a vitrectomy, the optical coherence tomography (OCT) revealed some unusual pre-retinal hyper-reflective deposits with the shape of stalagmites, distributed in a multifocal and perivascular pattern. Case 1: 51-year-old male with panuveitis in the right eye. After diagnostic-therapeutic vitrectomy, OCT showed pre-retinal stalagmite-like deposits. There was no clear aetiology, and the deposits persisted over the time. Case 2: 76-year-old woman with panuveitis in the right eye. After a surgery for cataract-vitrectomy and epiretinal membrane peeling, OCT revealed pre-retinal stalagmite-like deposits. The analysis reported elevated Toxoplasma IgG titres. Clarithromycin and corticosteroid were prescribed, resulting in the disappearance of pre-retinal deposits. The stalagmite-like deposits are not a very common tomographic sign of a posterior uveitis process, but they seem to correlate with inflammatory activity. There does not seem to be a clear mechanism or a particular aetiology.

Stalagmite-like pre-retinal deposits in the optical coherence tomography of two vitrectomy patients with panuveitis. / Depósitos prerretinianos tipo estalagmita en la tomografía de coherencia óptica de dos pacientes vitrectomizados con panuveítis.

Two patients with panuveitis are presented in whom, after undergoing a vitrectomy, the optical coherence tomography (OCT) revealed some unusual pre-retinal hyper-reflective deposits with the shape of stalagmites, distributed in a multifocal and perivascular pattern. Case 1: 51-year-old male with panuveitis in the right eye. After diagnostic-therapeutic vitrectomy, OCT showed pre-retinal stalagmite-like deposits. There was no clear aetiology, and the deposits persisted over the time. Case 2: 76-year-old woman with panuveitis in the right eye. After a surgery for cataract-vitrectomy and epiretinal membrane peeling, OCT revealed pre-retinal stalagmite-like deposits. The analysis reported elevated Toxoplasma IgG titres. Clarithromycin and corticosteroid were prescribed, resulting in the disappearance of pre-retinal deposits. The stalagmite-like deposits are not a very common tomographic sign of a posterior uveitis process, but they seem to correlate with inflammatory activity. There does not seem to be a clear mechanism or a particular aetiology.

Implication of cyclin-dependent kinase 5 in the neuroprotective properties of lithium.

Although numerous studies have demonstrated a neuroprotective and anti-apoptotic role of lithium in neuronal cell cultures, the precise mechanism by which this occurs, remains to be elucidated. In this study, we evaluated the lithium-mediated neuroprotection against colchicine-induced apoptosis in cultured cerebellar granule neurons. Previously, it has been demonstrated that colchicine mediates apoptosis in cerebellar granule neurons through cytoskeletal alteration and activation of an intrinsic pro-apoptotic pathway. Recently we also demonstrated a potential role of cyclin-dependent kinase 5 (cdk5) in this pathway. Here we report that colchicine induces dephosphorylation in Ser-9 and phosphorylation in Tyr-216, and thus activation, of glycogen synthase kinase-3beta in cerebellar granule neurons, and that this modification is inhibited by the presence of 5 mM lithium. However, the selective glycogen synthase kinase-3beta inhibitors SB-415286 and SB-216763 were unable to prevent colchicine-induced apoptosis in these cells, suggesting that the anti-apoptotic activity of lithium is not mediated by glycogen synthase kinase-3beta under these conditions. On the other hand, 5 mM lithium prevented the colchicine-induced increase in cdk5 expression and breakdown of cdk5/p35 to cdk5/p25. In addition, we show that up-regulation of cdk5/p25 is unrelated to inhibition of the activity of myocyte enhancer factor 2, a pro-survival transcription factor. These data suggest a previously undescribed neuroprotective mechanism of lithium associated with the modulation of cdk5/p35 or cdk5/p25 expression.

Differential effects of "Advanced glycation endproducts" and beta-amyloid peptide on glucose utilization and ATP levels in the neuronal cell line SH-SY5Y.

Beta-amyloid peptide (Abeta) and "Advanced glycation endproducts" (AGEs) are components of the senile plaques in Alzheimer's disease patients. It has been proposed that both AGEs and Abeta exert many of their effects, which include the upregulation of pro-inflammatory cytokines, through RAGE ("receptor for advanced glycation endproducts"). To investigate whether Abeta and AGEs cause similar or identical effects on cell survival and energy metabolism, we have compared the effects of a model-AGE and Abeta on cell viability, ATP level, glucose consumption and lactate production in the neuroblastoma cell line SH-SY5Y. The results show that AGEs and Abeta increase glucose consumption and decrease ATP levels in a dose dependent manner. Furthermore, both compounds decrease mitochondrial activity measured by the MTT assay. However, only AGEs decrease the number of cells and significantly increase lactate production. These data indicate that both AGEs and Abeta can cause differential disturbances in neuronal metabolism, which may contribute to the pathophysiological findings in Alzheimer's disease. However, their signalling pathways are apparently quite distinct, a fact which should stimulate a more detailed investigation in this field, e.g. for the purpose of a rational design of potential "neuroprotective" RAGE antagonists.

Early biochemical and histological alterations in rat corticoencephalic cell cultures following metabolic damage and treatment with modulators of mitochondrial ATP-sensitive potassium channels.

The present study was aimed at characterizing alterations of the nucleotide content and morphological state of rat corticoencephalic cell cultures subjected to metabolic damage and treatment with modulators of mitochondrial ATP-dependent potassium channels (mitoK(ATP)). In a first series of experiments, in vitro ischemic changes of the contents of purine and pyrimidine nucleoside diphosphates and triphosphates were measured by high performance liquid chromatography (HPLC) and the corresponding histological alterations were determined by celestine blue/acid fuchsin staining. As an ischemic stimulus, incubation with a glucose-free medium saturated with argon was used. Ischemia decreased the levels of adenosine, guanine and uridine triphosphate (ATP, GTP, UTP) and increased the levels of the respective dinucleotides ADP and UDP, whereas the GDP content was not changed. Both 5-hydroxydecanoate (5-HD) and diazoxide failed to alter the contents of nucleoside diphosphates and triphosphates, when applied under normoxic conditions. 5-HD (30 microM) prevented the ischemia-induced changes of nucleotide and nucleoside levels. Diazoxide (300 microM), either alone or in combination with 5-hydroxydecanoate (30 microM) was ineffective. Pyruvate (5 mM) partially reversed the effects of ischemia or ischemia plus 2-deoxyglucose (20mM) in the incubation medium. Diazoxide (300 microM) and 5-HD (30 microM) had no effect in the presence of pyruvate (5mM) and 2-deoxyglucose (20mM). Staining the cells with celestine blue/acid fuchsin in order to classify them as intact, reversibly or profoundly injured, revealed a protective effect of 5-HD. When compared with 5-HD, diazoxide, pyruvate and 2-deoxyglucose had similar but less pronounced effects. In conclusion, these results suggest a protective role of 5-hydroxydecanoate on early corticoencephalic nucleotide and cell viability alterations during ischemia.

Neuroprotection by ATP-dependent potassium channels in rat neocortical brain slices during hypoxia.

Morphological changes induced by 30 min of hypoxia (incubation in medium saturated with 95% N2-5% CO2 instead of the normal 95% O2-5% CO2) were investigated in neurons (layers II/III of the parietal cortex) of rat neocortical brain slices. The cells were identified as intact, reversibly or irreversibly injured. As expected, hypoxia decreased the number of intact cells and increased the number of irreversibly injured cells. Pretreatment of slices with diazoxide (300 microM), an agonist of ATP-dependent potassium (KATP) channels completely prevented the morphological damage induced by hypoxia, whereas tolbutamide (300 microM), an antagonist of KATP channels, was ineffective when given alone. However, tolbutamide (300 microM) co-applied with diazoxide (300 microM), partly reversed the neuroprotective effect of this agonist during hypoxia. In conclusion, KATP channels appear to be present on neocortical neurons and their opening counteracts hypoxia-induced cell injury.

Changes by short-term hypoxia in the membrane properties of pyramidal cells and the levels of purine and pyrimidine nucleotides in slices of rat neocortex; effects of agonists and antagonists of ATP-dependent potassium channels.

In a first series of experiments, intracellular recordings were made from pyramidal cells in layers II-III of the rat primary somatosensory cortex. Superfusion of the brain slice preparations with hypoxic medium (replacement of 95%O2-5%CO2 with 95%N2-5%CO2) for up to 30 min led to a time-dependent depolarization (HD) without a major change in input resistance. Short periods of hypoxia (5 min) induced reproducible depolarizations which were concentration-dependently depressed by an agonist of ATP-dependent potassium (K(ATP)) channels, diazoxide (3-300 microM). The effect of 30 but not 300 microM diazoxide was reversed by washout. Tolbutamide (300 microM), an antagonist of K(ATP) channels, did not alter the HD when given alone. It did, however, abolish the inhibitory effect of diazoxide (30 microM) on the HD. Neither diazoxide (3-300 microM) nor tolbutamide (300 microM) influenced the membrane potential or the apparent input resistance of the neocortical pyramidal cells. Current-voltage (I-V) curves constructed at a membrane potential of -90 mV by injecting both de- and hyperpolarizing current pulses were not altered by diazoxide (30 microM) or tolbutamide (300 microM). Moreover, normoxic and hypoxic I-V curves did not cross each other, excluding a reversal of the HD at any membrane potential between -130 and -50 mV. The hypoxia-induced change of the I-V relation was the same both in the absence and presence of tolbutamide (300 microM). In a second series of experiments, nucleoside di- and triphosphates separated with anion exchange HPLC were measured in the neocortical slices. After 5 min of hypoxia, levels of nucleoside triphosphates declined by 29% (GTP), 34% (ATP), 44% (UTP) and 58% (CTP). By contrast, the levels of nucleoside diphosphates either did not change (UDP) or increased by 13% (GDP) and 40% (ADP). In slices subjected to 30 min of hypoxia the triphosphate levels continued to decrease, while the levels of GDP and ADP returned to control values. The tri- to diphosphate ratios progressively declined for ATP/ADP and GTP/GDP, but not for UTP/UDP when the duration of hypoxia was increased from 5 to 30 min. Hence, the rapid fall in the ratios of nucleoside tri- to diphosphates without the induction of a potassium current failed to indicate an allosteric regulation of a plasmalemmal K(ATP) channel by purine and pyrimidine nucleotides. Diazoxide had no effect on neocortical pyramidal neurons and was effective only in combination with a hypoxic stimulus; it is suggested that both plasmalemmal and mitochondrial K(ATP) channels are involved under these conditions. The hypoxic depolarization may be due to blockade of K+,Na+-ATPase by limitation of energy supplying substrate.