Nanospheres based on PLGA/amphiphilic cyclodextrin assemblies as potential enhancers of Methylene Blue neuroprotective effect

Nanospheres of amphiphilic cyclodextrin and PLGA entrapping Methylene Blue are proposed as potential enhancers of drug neuroprotective effect on neuroblastoma cells.

Assessing silver nanoparticles behaviour in artificial seawater by mean of AF4 and spICP-MS

The use of nanotechnology-based products is constantly increasing and there are concerns about the fate and effect on the aquatic environment of antimicrobial products such as silver nanoparticles. By combining different characterization techniques (asymmetric flow field-flow fractionation, single particle ICP-MS, UV-Vis) we show that it is possible to assess in detail the agglomeration process of silver nanoparticles in artificial seawater. In particular we show that the presence of alginate or humic acid differentially affects the kinetic of the agglomeration process. This study provides an experimental methodology for the in-depth analysis of the fate and behaviour of silver nanoparticles in the aquatic environment.

Urinary excretion of arsenic following rice consumption

Patterns of arsenic excretion were followed in a cohort (n = 6) eating a defined rice diet, 300 g per day d.wt. where arsenic speciation was characterized in cooked rice, following a period of abstinence from rice, and other high arsenic containing foods. A control group who did not consume rice were also monitored. The rice consumed in the study contained inorganic arsenic and dimethylarsinic acid (DMA) at a ratio of 1:1, yet the urine speciation was dominated by DMA (90%). At steady state (rice consumption/urinary excretion) ∼40% of rice derived arsenic was excreted via urine. By monitoring of each urine pass throughout the day it was observed that there was considerable variation (up to 13-fold) for an individual's total arsenic urine content, and that there was a time dependent variation in urinary total arsenic content. This calls into question the robustness of routinely used first pass/spot check urine sampling for arsenic analysis.

Expression of vesicle-associated membrane-protein-associated protein B cleavage products in peripheral blood leukocytes and cerebrospinal fluid of patients with sporadic amyotrophic lateral sclerosis

BACKGROUND AND PURPOSE

Vesicle-associated membrane-protein-associated protein B (VAPB) is an endoplasmic reticulum (ER) resident protein participating in ER function, vesicle trafficking, calcium homeostasis and lipid transport. Its N-terminal domain, named MSP, is cleaved and secreted, serving as an extracellular ligand. VAPB mutations are linked to autosomal-dominant motor neuron diseases, including amyotrophic lateral sclerosis (ALS) type 8. An altered VAPB function is also suspected in sporadic ALS (SALS).

METHODS

The expression pattern of VAPB cleavage and secreted products in the peripheral blood leukocytes (PBL) and cerebrospinal fluid (CSF) of SALS patients and neurological controls was assessed. PBL from healthy controls were also analyzed. Assays were carried out through western blotting, using an anti-VAPB (N-terminal) antibody.

RESULTS

Two VAPB fragments containing the MSP domain (17 kDa and 14 kDa molecular sizes) were identified in PBL of SALS and controls, with no significant differences amongst groups. In CSF, only the 14 kDa VAPB MSP fragment was expressed and a corresponding VAPA fragment was not detected. The CSF VAPB fragment was absent in 58.7% of SALS patients, of whom 79.2% were bulbar onset (P = 0.001, bulbar versus spinal).

CONCLUSIONS

The absence of the CSF VAPB MSP fragment from most bulbar-onset SALS patients suggests a specific alteration of brain-derived VAPB cleavage and secretion in this group of patients, and hints at a role of VAPB in the pathophysiology of this motor neuron disease.

Fractional anisotropy distributions in 2- to 6-year-old children with autism

BACKGROUND

Increasing evidence suggests that autism is a disorder of distributed neural networks that may exhibit abnormal developmental trajectories. Characterisation of white matter early in the developmental course of the disorder is critical to understanding these aberrant trajectories.

METHODS

A cross-sectional study of 2- to 6-year-old children with autism was conducted using diffusion tensor imaging combined with a novel statistical approach employing fractional anisotropy distributions. Fifty-eight children aged 18-79 months were imaged: 33 were diagnosed with autism, 8 with general developmental delay, and 17 were typically developing. Fractional anisotropy values within global white matter, cortical lobes and the cerebellum were measured and transformed to random F distributions for each subject. Each distribution of values for a region was summarised by estimating δ, the estimated mean and standard deviation of the approximating F for each distribution.

RESULTS

The estimated δ parameter, , was significantly decreased in individuals with autism compared to the combined control group. This was true in all cortical lobes, as well as in the cerebellum, but differences were most robust in the temporal lobe. Predicted developmental trajectories of across the age range in the sample showed patterns that partially distinguished the groups. Exploratory analyses suggested that the variability, rather than the central tendency, component of was the driving force behind these results.

CONCLUSIONS

While preliminary, our results suggest white matter in young children with autism may be abnormally homogeneous, which may reflect poorly organised or differentiated pathways, particularly in the temporal lobe, which is important for social and emotional cognition.

Inefficiency of renin-angiotensin inhibitors in preventing atrial fibrillation in patients with a normal heart

AIM

Recent scientific evidence has emphasized the possible role of inhibitors of the renin-angiotensin system in preventing arrhythmic relapses in patients with paroxysmal or persistent atrial fibrillation and co-existing left ventricular hypertrophy or left ventricular dysfunction.

METHODS

In order to verify the effects of these drugs on patients with a normal heart, we collected a series of 187 patients admitted to our division of cardiology for paroxysmal or persistent atrial fibrillation. All patients underwent cardioversion (with antiarrhythmic drugs and/or by electrical cardioversion) and were discharged in sinus rhythm. Episodes of recurrent arrhythmia were recorded during a mean follow-up period was 2 years. Patients were subdivided into 2 groups according to therapy: group 1 comprised patients receiving renin-angiotensin system inhibitors, group 2 comprised those not receiving therapy with these agents. All 91 patients in group 1 and 76 of those in group 2 had hypertension. Among the 91 patients in the group 1, 55 were treated with angiotensin-converting enzyme (ACE) inhibitors and 36 with angiotensin receptor blockers. There were no statistically significant differences in cardiovascular risk factors or antiarrhythmic drug use between the 2 groups.

RESULTS

In group 1, 83% of patients experienced <2 recurrences of atrial fibrillation during the follow-up period, while 17% had >2 episodes. In group 2, 86% of patients experienced <2 relapses during the follow-up period, while the remaining 14% had >2 relapses. There was no statistically significant difference between the 2 groups (P=0.85). A subgroup analysis showed that treatment with angiotensin receptor blockers, beta-blockers, diuretics, and calcium-channel blockers brought no advantage in sinus rhythm maintenance.

CONCLUSION

In our sample of hypertensive patients with a healthy heart, treatment with ACE inhibitors showed no statistically significant advantage in the prevention of atrial fibrillation relapses.

17beta-estradiol synthesis in the adult male rat retina

17beta-Estradiol (E2) exerts neurotrophic and neuroprotective effects in the retina as well as in other CNS structures, independently of sex. Retinal effects, however, have not been supported by evidence on local synthesis, and whether CNS 17beta-estradiol is formed in a neurosteroidogenic pathway starting from cholesterol conversion into pregnenolone is a question still left unanswered. In the adult male rat retina, we have previously showed localization and activity of the P450 side chain cleavage (P450scc) enzyme, which is involved in pregnenolone synthesis. Here, we demonstrate both the mRNA and protein expression of 3beta-hydroxysteroid dehydrogenase (3beta-HSD), P450aromatase and also of P450scc, but only the protein expression of P450 17alpha-hydroxylase/lyase (P450c17). Using radiolabeled pregnenolone and testosterone as precursors, in the isolated and intact retina of adult male rats, E2 is produced in a large amount by each precursor within 1-4h, suggesting a highly active metabolic pathway towards its formation. The immunolocalization pattern shows enzymes and estrogen receptor subtypes (ERalpha, ERbeta) scattered in the retina with different intensities throughout the layers. The results point to the adult male rat retina as a neurosteroidogenic structure where E2 synthesis via a progesterone pathway and the presence of estrogen receptors provide important clues for understanding the neurotrophic and neuroprotective effects of the steroid hormone.

Stomata open at night in pole-sized and mature ponderosa pine: implications for O3 exposure metrics

Ponderosa pine (Pinus ponderosa Dougl. ex Laws.) is widely distributed in the western USA. We report the lack of stomatal closure at night in early summer for ponderosa pine at two of three sites investigated. Trees at a third site with lower nitrogen dioxide and nitric acid exposure, but greater drought stress, had slightly open stomata at night in early summer but closed stomata at night for the rest of the summer. The three sites had similar background ozone exposure during the summer of measurement (2001). Nighttime stomatal conductance (gs) ranged from one tenth to one fifth that of maximum daytime values. In general, pole-sized trees (< 40 years old) had greater nighttime gs than mature trees (> 250 years old). In late summer, nighttime gs was low (< 3.0 mmol H2O m(-2) s(-1)) for both tree size classes at all sites. Measurable nighttime gs has also been reported in other conifers, but the values we observed were higher. In June, nighttime ozone (O3) uptake accounted for 9, 5 and 3% of the total daily O3 uptake of pole-sized trees from west to east across the San Bernardino Mountains. In late summer, O3 uptake at night was < 2% of diel uptake at all sites. Nocturnal O3 uptake may contribute to greater oxidant injury development, especially in pole-sized trees in early summer.

Neurosteroids in the Retina

Steroids may have a powerful role in neuronal degeneration. Recent research has revealed that steroids may influence the onset and progression of some retinal disorders as well as neurodegenerative diseases and, as in brain, they accumulate in the retina via a local synthesis (neurosteroids) and metabolism of blood-circulating steroid hormones. Their crucial role as neurodegenerative and neuroprotective agents has been also upheld in a retinal excitotoxic paradigm. These findings are reviewed especially from the emerging perspective that after an insult local changes in steroidogenic responses and consequent neurosteroid availability might turn out to be offensive or defensive cellular adaptations for the potentiation or prevention of neuronal death.

A caspase-3-dependent pathway is predominantly activated by the excitotoxin pregnenolone sulfate and requires early and late cytochrome c release and cell-specific caspase-2 activation in the retinal cell death

This study investigates the implication of mitochondria- and caspase-dependent pathways in the death of retinal neurones exposed to the neurosteroid pregnenolone sulfate (PS) shown to evoke apoptosis and contribute to amplification and propagation of excitotoxicity. After a brief PS challenge of intact retinas, caspase-3 and caspase-2 activation and cytochrome c release occur early and independent of changes in the oxidative state measured by superoxide dismutase activity. The temporal and spatial relationship of these events suggests that a caspase-3-dependent pathway is activated in response to cytochrome c release and requires caspase-2 activation and a late cytochrome c release in specific cellular subsets of retinal layers. The protection by caspase inhibitors indicates a predominant role of the pathway in PS-induced retinal apoptosis, although a limited use of caspase inhibitors is upheld on a conceivable shift from apoptosis toward necrosis. Conversely, 3alpha-hydroxy-5beta-pregnan-20-one sulfate and 17beta-oestradiol provide complete prevention of PS-induced retinal death.

Identification of an antigen related to the sea urchin RNA-binding protein LP54 in mammalian central nervous system

LP54 is an RNA-binding protein involved in localization of maternal messengers in sea urchin egg and embryos. Using a polyclonal antibody directed against Paracentrotus lividus LP54 we detected a 66-kDa cross-reacting antigen in undifferentiated and differentiated SH-SY5Y human neuroblastoma cells. After treatment of undifferentiated cells with detergent, the 66-kDa antigen was found to be enriched in the cytoskeletal fraction. By Western blot the expression of this antigen was also analyzed in regions of the CNS and in tissues of the adult rat and its exclusive presence in the hippocampus and thalamus was revealed. The immunoreactivity with P. lividus antibody against LP54 in hippocampal lysate was also confirmed throughout anti-LP54 immunoaffinity column and competition experiments. The results indicates that a related protein to the sea urchin LP54 is evolutionary conserved in mammalian CNS.

Pathways of dehydroepiandrosterone formation in rat brain glia

In peripheral steroidogenic tissues, dehydroepiandrosterone (D) is formed from pregnenolone (P) by the microsomal cytochrome P450c17 enzyme. Although some steroidogenic P450s have been found in brain tissue, no enzyme has been shown to possess P450c17 activity. We recently demonstrated the presence of an alternative, Fe(2+)-dependent pathway responsible for D formation from alternative precursors in rat glioma cells. We and others could not find P450c17 mRNA and protein in rat brain, but demonstrate herein the presence of Fe(2+)-dependent alternative pathway for D formation in rat brain cortex microsomes. Using primary cultures of differentiating rat glial cells, we observed that P450c17 mRNA and protein were present in O-2A oligodendrocyte precursors and mature oligodendrocytes. In the presence of P, O-2A and mature oligodendrocytes formed D. Addition of Fe(2+) together with submaximal concentrations of P increased D formation by these cells. Treatment of oligodendrocytes with the P450c17 inhibitor SU 10603 in the presence or absence of P failed to inhibit D production. These data suggest that D formation in oligodendrocytes occurs independently of the P450c17 protein present in the cells. In isolated type I astrocytes we did not find neither P450c17 mRNA nor protein. These cells responded to Fe(2+) by producing D and addition of P together with Fe(2+) further increased D synthesis. SU 10603 failed to inhibit D formation by astrocytes. Taken together these results suggest that in differentiating rat brain oligodendrocytes and astrocytes D is formed via a P450c17-independent and oxidative stress-dependent alternative pathway.

Pregnenolone sulfate, a naturally occurring excitotoxin involved in delayed retinal cell death

The present study was designed to investigate the neurosteroid pregnenolone sulfate (PS), known for its ability to modulate NMDA receptors and interfere with acute excitotoxicity, in delayed retinal cell death. Three hours after exposure of the isolated and intact retina to a 30-min PS pulse, DNA fragmentation as assessed by genomic DNA gel electrophoresis and a modified in situ terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling (TUNEL) method appeared concurrently with an increase in superoxide dismutase (SOD) activity and thiobarbituric acid-reactive substances (TBARS) levels. At 7 h, the increased amount of DNA laddering was accompanied by a higher number of TUNEL-positive cells in the inner nuclear and ganglion cell layers. Necrotic signs were characterized by DNA smear migration, lactate dehydrogenase (LDH) release, and damage mainly in the inner nuclear layer. PS-induced delayed cell death was markedly reduced by the NMDA receptor antagonists 4-(3-phosphonopropyl)-2-piperazinecarboxylic acid and 3alpha-hydroxy-5beta-pregnan-20-one sulfate but completely blocked after concomitant addition of the non-NMDA receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione. Steroids with antioxidant properties (progesterone, dehydroepiandrosterone and its sulfate ester, and 17beta-estradiol) differently prevented PS-induced delayed cell death. Cycloheximide treatment protected against DNA fragmentation and LDH release but failed to prevent the rise in SOD activity and TBARS level. We conclude that a brief PS pulse causes delayed cell death in a slowly evolving apoptotic fashion characterized by a cycloheximide-sensitive death program downstream of reactive oxygen species generation and lipid peroxidation, turning into secondary necrosis in a retinal cell subset.

Human neuroblastoma SH-SY5Y cell line: neurosteroid-producing cell line relying on cytoskeletal organization

Pregnenolone, the precursor of all steroids, is synthesized by CNS structures. The synthesis requires an obligatory step involving cholesterol transport to mitochondrial cytochrome P450-cholesterol side chain cleavage (cytP450scc), although the underlying mechanism(s) are still mostly unknown. We used the human neuroblastoma SH-SY5Y cell line to investigate cytP450scc expression and activity and to establish a role of cytoskeleton in pregnenolone synthesis. Immunocytochemical and biochemical approaches revealed that undifferentiated as well as differentiated cells either by retinoic acid (RA) or phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA), possess cytP450scc and rapidly synthesize pregnenolone in the presence of a NADPH-generating system. The newly neurosteroid formation by SH-SY5Y cells was increased by 22R-hydroxycholesterol and blocked by the cytP450scc inhibitor, aminoglutethimide. When trilostane was used to inhibit 3beta-hydroxysteroid dehydrogenase catalyzing pregnenolone conversion into progesterone, a higher pregnenolone accumulation occurred in TPA-differentiated cells than in RA-differentiated ones. Although SU 10603, a blocker of 17alpha-hydroxylase/c17,20-lyase enzyme involved in DHEA formation from pregnenolone, gave rise to an elevated neurosteroid content only in RA-differentiated cells. No difference in pregnenolone levels was found in undifferentiated cells treated with each inhibitor. Thus, differentiation seems to promote pregnenolone-metabolizing enzyme activities that may vary upon phenotypic changes induced by RA or TPA. Treatments of differentiated cells with the microtubule-depolymerizing drug colchicine and the actin microfilament-altering agent cytochalasin D decreased pregnenolone synthesis without affecting cell viability or cytP450scc amount. Addition of the cell-permeant cholesterol analogue 22R-hydroxycholesterol known to elude cholesterol transport systems induced pregnenolone synthesis, however, indicating that perturbations in cytoskeleton likely affect endogenous cholesterol transport. The relevance of this finding may rest on the observed involvement of cytoskeletal organization in such events as neuronal plasticity, cognitive function and also neurodegenerative disorders in which neurosteroids have been shown to have a part.

Dopamine D2 receptors in the nucleus accumbens are important for social attachment in female prairie voles (Microtus ochrogaster)

The prairie vole (Microtus ochrogaster), a monogamous rodent that forms long-lasting pair bonds, has proven useful for the neurobiological study of social attachment. In the laboratory, pair bonds can be assessed by testing for a partner preference, a choice test in which pair-bonded voles regularly prefer their partner to a conspecific stranger. Studies reported here investigate the role of dopamine D2-like receptors (i.e., D2, D3, and D4 receptors) in the nucleus accumbens (NAcc) for the formation of a partner preference in female voles. Mating facilitated partner preference formation and associated with an approximately 50% increase in extracellular dopamine in the NAcc. Microinjection of the D2 antagonist eticlopride into the NAcc (but not the prelimbic cortex) blocked the formation of a partner preference in mating voles, whereas the D2 agonist quinpirole facilitated formation of a partner preference in the absence of mating. Taken together, these results suggest that D2-like receptors in the NAcc are important for the mediation of social attachments in female voles.

Pathways of neurosteroid biosynthesis in cell lines from human brain: regulation of dehydroepiandrosterone formation by oxidative stress and beta-amyloid peptide

Neurosteroids in rodents can originate from peripheral tissues or be locally synthesized in specific brain areas. There is, as yet, no information about the synthesis and regulation of neurosteroids in human brain. We examined the ability of human brain cells to synthesize steroids from a radiolabeled precursor and the mRNA and protein expression of key components of peripheral steroidogenic machinery. Oligodendrocytes are the source of pregnenolone in human brain. Human astrocytes do not synthesize radiolabeled pregnenolone, nor do human neurons. There is potential for all three cell types to metabolize pregnenolone to other neurosteroids, including dehydroepiandrosterone. mRNA and protein for cytochrome P450 17alpha-hydroxylase were found in all cell types, although no activity could be demonstrated. We examined the ability of the cells to make dehydroepiandrosterone via an alternative pathway induced by treatment with Fe2+. Oligodendrocytes and astrocytes make dehydroepiandrosterone via this pathway, but neurons do not. In searching for a natural regulator of dehydroepiandrosterone formation, we observed that treating oligodendrocytes with beta-amyloid, which increases reactive oxygen species, also increased dehydroepiandrosterone formation. These effects of beta-amyloid were blocked by vitamin E. These results indicate that human brain makes steroids in a cell-specific manner and suggest that dehydroepiandrosterone synthesis can be regulated by intracellular free radicals.

Dopamine D2 receptors in the nucleus accumbens are important for social attachment in female prairie voles (Microtus ochrogaster)

The prairie vole (Microtus ochrogaster), a monogamous rodent that forms long-lasting pair bonds, has proven useful for the neurobiological study of social attachment. In the laboratory, pair bonds can be assessed by testing for a partner preference, a choice test in which pair-bonded voles regularly prefer their partner to a conspecific stranger. Studies reported here investigate the role of dopamine D2-like receptors (i.e., D2, D3, and D4 receptors) in the nucleus accumbens (NAcc) for the formation of a partner preference in female voles. Mating facilitated partner preference formation and associated with an approximately 50% increase in extracellular dopamine in the NAcc. Microinjection of the D2 antagonist eticlopride into the NAcc (but not the prelimbic cortex) blocked the formation of a partner preference in mating voles, whereas the D2 agonist quinpirole facilitated formation of a partner preference in the absence of mating. Taken together, these results suggest that D2-like receptors in the NAcc are important for the mediation of social attachments in female voles.

Dopamine D2 receptor-mediated regulation of partner preferences in female prairie voles (Microtus ochrogaster): a mechanism for pair bonding?

This study examined the role of dopamine (DA) in partner preference (PP) formation in female prairie voles (Microtus ochrogaster). The nonspecific DA antagonist haloperidol blocked mating-induced PP, whereas the nonspecific DA agonist apomorphine induced PP without mating. The D2 antagonist eticlopride, but not the D1 antagonist SCH23390, blocked PP, whereas the D2 agonist quinpirole, but not the D1 agonist SKF38393, induced PP without mating. Injections of eticlopride before or immediately after mating, but not 24 hr after mating, impaired PP, indicating that DA's effects were not due to an interference with mating or sensory recognition. Finally, intracerebroventricular injections of eticlopride diminished PP. Together, these data suggest that mating-induced PP requires activation of D2 receptors and that social experience may activate dopaminergic pathways, with enduring effects on behavior.

Dopamine D2 receptor-mediated regulation of partner preferences in female prairie voles (Microtus ochrogaster): a mechanism for pair bonding?

This study examined the role of dopamine (DA) in partner preference (PP) formation in female prairie voles (Microtus ochrogaster). The nonspecific DA antagonist haloperidol blocked mating-induced PP, whereas the nonspecific DA agonist apomorphine induced PP without mating. The D2 antagonist eticlopride, but not the D1 antagonist SCH23390, blocked PP, whereas the D2 agonist quinpirole, but not the D1 agonist SKF38393, induced PP without mating. Injections of eticlopride before or immediately after mating, but not 24 hr after mating, impaired PP, indicating that DA's effects were not due to an interference with mating or sensory recognition. Finally, intracerebroventricular injections of eticlopride diminished PP. Together, these data suggest that mating-induced PP requires activation of D2 receptors and that social experience may activate dopaminergic pathways, with enduring effects on behavior.

Pregnenolone sulfate modulates NMDA receptors, inducing and potentiating acute excitotoxicity in isolated retina

Pregnenolone sulfate (PS) acts as a positive allosteric modulator of N-methyl-D-aspartate (NMDA) receptor-mediated responses. In the retina, we previously observed that the synthesis of pregnenolone and PS increases after stimulation of NMDA receptors and blockade of the synthesis reduces retinal cell death. This study was carried out to explore in the isolated and intact retina the possible role of PS in NMDA-induced excitotoxicity. Lactate dehydrogenase (LDH) measurements and morphological analysis revealed that a 90-min exogenous application of PS at 0.1-500 microM concentrations potentiated NMDA-induced cell death and at 50-500 microM concentrations caused cytotoxicity. After 45 min, either NMDA or PS caused no significant LDH release; but their co-application resulted in a high degree of toxicity. In addition, we found that a mild NMDA insult developed into serious damage when even low PS concentrations (0.1-10 microM) were used. Toxicity-inducing and -potentiating effects were specific to PS modulatory action on NMDA receptors, in that they were blocked by 4-(3-phosphonopropyl)2-piperazinecarboxylic acid (CPP) and MK-801 but not by 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), and neither dehydroepiandrosterone sulfate nor pregnenolone caused LDH release. Prevention of degenerative signs was seen in retinae pretreated with 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS), a Cl- channel blocker, thus indicating a Na+/Cl--dependent acute mode of excitotoxic cell death responsible for PS toxicity. The positive interaction between the neurosteroid and NMDA receptors was further proved by a PS dose-dependent increase in NMDA-induced stimulation of [3H] MK-801 binding to retinal membranes. The results suggest a crucial role of PS in retinal vulnerability and propose the toxicity-potentiating effects as an important key in linking NMDA-induced endogenous synthesis to acute excitotoxicity.

Induction of neurosteroid synthesis by NMDA receptors in isolated rat retina: a potential early event in excitotoxicity

Here we investigated the possible regulation of neurosteroidogenesis by N-methyl-D-aspartic acid (NMDA) receptor activation and addressed the hypothesis that neurosteroid synthesis may be involved in acute excitotoxicity. In the isolated retina, exposure to NMDA modified pregnenolone and pregnenolone sulphate formation. This effect was dose and time dependent, the synthesis being increased by relatively moderate NMDA doses (1-100 microM) within 30 min exposure and reduced to its control value by 60 min or by raising drug concentrations. NMDA-stimulated neurosteroid synthesis was blocked by (+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclo-hepten-5,10-imine hydrogen maleate (MK-801) and 3(2-carboxypiperazine-4-yl)propyl-1-phosphonic acid (CPP), depended on extracellular calcium and reproduced by glutamate. Lactate dehydrogenase (LDH) release and morphological analysis revealed that retinal cell viability was not significantly affected after 30 min exposure to 50 microM NMDA, but severe cell damage occurred by 60 min. When the GABAA (gamma-aminobutyric acid) receptor agonist muscimol (1-1000 microM), known to activate retinal neurosteroidogenesis, was added together with NMDA, no additional increase in neurosteroid synthesis was observed, and NMDA-induced LDH release remained unchanged. However, exposure to a high concentration of muscimol alone (500 microM) provoked a similar degree of toxicity to NMDA. By contrast, bicuculline abolished the increase in neurosteroidogenesis and LDH release. Similarly, pretreatment with R (+)-p-aminoglutethimide (AMG), an inhibitor of cholesterol side-chain cleavage cytochrome P450, attenuated acute retinal cell damage. The inhibitory nature of AMG on NMDA-stimulated neurosteroidogenesis was confirmed in the observation that drug treatment reduced pregnenolone content and did not affect the bindings of [3H] MK-801 and [3H] muscimol. The results demonstrate that NMDA receptors regulate neurosteroidogenesis through a transneuronal mechanism, which implies GABAA receptor activation. The early NMDA-mediated stimulation of neurosteroid synthesis seems to play a critical role in acute excitotoxicity; consequently, its inhibition is likely to delay neuronal cell death.

Detection of P450c17-independent pathways for dehydroepiandrosterone (DHEA) biosynthesis in brain glial tumor cells

Dehydroepiandrosterone (D) is biosynthesized in the brain by a pathway different from that existing in the adrenal cortex. C6 rat glioma tumor cells in culture biosynthesize both pregnenolone (P) and D. They possess the mRNA, protein, and side-chain cleavage activity of P450scc. On the other hand, P450c17 was not detected. Adding FeSO4 to C6 cells increased the synthesis of both P and D. Even in the presence of aminoglutethimide, an inhibitor of P450scc, FeSO4 increased the synthesis of both steroids, indicating that the Fe2+-sensitive process does not involve P450scc. Likewise, the FeSO4-induced formation of D was not blocked by the P450c17 inhibitor, SU-10603. These results suggest that the FeSO4-induced synthesis of D as well as of P in C6 cells may be due to the fragmentation of in situ-formed tertiary hydroperoxides. It is likely, however, that the effect of the Fe2+ is not limited to this one reaction. When exogenous P was added to C6 microsomes, along with FeSO4, the amount of D formed was greater than control values, indicating that Fe2+ facilitated the conversion of P to D. Unlike the constituents that are converted by Fe2+ to P, the precursor of D in C6 cells is not soluble in a 1:1 mixture of ether and ethylacetate. Treatment of C6 cells with KI, NaBH4, or HIO4 resulted in an increase in D synthesis. From this it seems clear that a precursor of the D produced in C6 cells is a steroid where both C-17 and C-20 are oxygenated.

Peripheral benzodiazepine receptor in cholesterol transport and steroidogenesis

Steroidogenesis begins with the metabolism of cholesterol to pregnenolone by the inner mitochondrial membrane cytochrome P450 side-chain cleavage (P450scc) enzyme. The rate of steroid formation, however, depends on the rate of cholesterol transport from intracellular stores to the inner mitochondrial membrane and loading of P450scc with cholesterol. In previous in vitro studies, we demonstrated that a key element in the regulation of cholesterol transport is the mitochondrial peripheral-type benzodiazepine receptor (PBR). We also showed that the polypeptide diazepam binding inhibitor (DBI), an endogenous PBR ligand, stimulates cholesterol transport and promotes loading of cholesterol to P450scc in vitro, and that its presence is vital for hCG-induced steroidogenesis by Leydig cells. Based on these data and the observations that i) the mitochondrial PBR binding and topography are regulated by hormones; ii) the 18-kDa PBR protein is functionally coupled to the mitochondrial contact site voltage-dependent anion channel protein; iii) the 18-kDa PBR protein is a channel for cholesterol, as shown by molecular modeling and in vitro reconstitution studies; iv) targeted disruption of the PBR gene in steroidogenic cells dramatically reduces the ability of the cells to transport cholesterol in the mitochondria and produce steroids; v) endocrine disruptors, with known anisteroidogenic effect, inhibit PBR ligand binding; and vi) in vivo reduction of adrenal PBR expression results in reduced circulating glucocorticoid levels, we conclude that PBR is an indispensable element of the steroidogenic machinery.

Multiple use of disposable (tubing) set of HomeChoice automated peritoneal dialysis (APD) system in PD patients

Our objective was to evaluate the multiple use of the tubing set of the HomeChoice automated peritoneal dialysis (PD) system in PD patients. The study was designed to reuse the tubing set of the HomeChoice automated PD system for two to seven treatments, each of 16-24 hours duration, in end-stage renal disease (ESRD) patients, and to continue to use the same set if the patient was disconnected for any reason. In a tertiary-referral university hospital, 17 ESRD patients on PD, admitted to a university hospital from January, 1995 to September, 1995, were studied. The patients were disconnected and connected in between or during PD treatments. Five-liter bags were used. All the fluid was either set initially or added as clinically indicated. One hundred and thirty-eight PD treatments were performed with the HomeChoice automated PD system, using 30 disposable (tubing) sets. Sixty-three disconnections were made for ambulation, transfer to other units, surgery, physical therapy, radiological investigations, and special procedures in between and during PD treatments. No episode of peritonitis occurred. The multiple use resulted in a 78% reduction in tubing sets and drain-line extension sets used, thereby reducing the disposable supplies and creating a substantial saving in nursing time. The multiple use of tubing sets of the HomeChoice automated PD system was safe and economical in patients undergoing automated PD in a hospital setting.

Correlations between plasminogen activator inhibitor-1 and peritoneal transport in pediatric CCPD patients

OBJECTIVE

Plasminogen activator inhibitor-1 (PAI-1) is an important regulator of plasminogen activators and has been shown to be involved in the accumulation of extracellular matrix (ECM) in various tissues. Since peritoneal ECM is a resistance site for peritoneal transport, the production and release of PAI-1 in the peritoneum may affect the peritoneal transport of water and small solutes.

DESIGN

The linear correlations between the dialysate PAI-1 levels and the variables of peritoneal transport during peritoneal equilibration tests (PET) were examined.

SETTING

A tertiary university hospital.

PATIENTS

Six stable pediatric patients (age 10.8 +/- 4 years) undergoing continuous cycler-assisted peritoneal dialysis were included.

INTERVENTIONS

None.

RESULTS

All data are mean +/- SD. There was a positive correlation between the infused volume and the net ultrafiltration (UF, 198 +/- 127 mL, r = 0.82, p < 0.05). The dialysate PAI-1 levels increased during the dwell time (2.44 +/- 2.23 ng/mL or 2.46 +/- 1.72 micrograms at 4 hours vs 0.04 +/- 0.1 ng/mL or 0.04 +/- 0.09 micrograms at 0 hour, p < 0.05). The saturation indices (dialysate/plasma ratio) of PAI-1 and albumin at 4 hours were 1.05 +/- 1.21 and 0.028 +/- 0.004, respectively. The changes from 0 hour dwell to 4 hour dwell in the dialysate PAI-1 concentration (PAI4-0, 2.4 +/- 2.2 ng/mL) or amount corrected to body surface area (APAI4-0/BSA, 2.61 +/- 2.11 micrograms/m2) negatively correlated with UF or UF/body surface area and positively correlated with the number of episodes of peritonitis. There was no correlation between PAI4-0,APAI4-0/BSA, or plasma PAI-1 concentration and the mass transfer coefficient and clearance of either urea or creatinine.

CONCLUSIONS

The elevated PAI-1 level during the PET was likely from the local production and release of PAI-1. It had an inverse relationship with the amount of ultrafiltration. Repeated inflammation of the peritoneum was associated with an increased production and release of PAI-1 into the peritoneum.

gamma-Aminobutyric acid type A/benzodiazepine receptors regulate rat retina neurosteroidogenesis

It has been previously shown that retinal ganglion cells have the ability to synthesize steroids including neuroactive steroids such as pregnenolone sulfate. Since ganglion cells possess GABAA/benzodiazepine (BZ) receptors and neurosteroids modulate retinal GABAA receptor function, we investigated the role of these receptors in isolated rat retina neurosteroidogenesis. Ligands for central-type BZ receptors stimulated retinal pregnenolone synthesis. Clonazepam was the most potent ligand examined acting at nanomolar concentrations. Moreover, the effective steroidogenesis stimulatory dose (ED50) for these ligands and the Ki to inhibit [3H]flunitrazepam binding showed a coefficient of correlation of r = 0.87, suggesting the involvement of the central-type BZ receptors in this event. Ro 5-4864, which preferentially binds to peripheral-type BZ receptors, was less efficacious and potent whereas PK 11195 did not affect the basal pregnenolone formation and did not antagonize the Ro 5-4864 stimulated steroid synthesis. The GABAergic agonist muscimol, stimulated neurosteroid synthesis and this effect was reversed by the GABAergic antagonists bicuculline and picrotoxinin. In addition, these antagonists decreased basal pregnenolone formation, suggesting a tonic GABAergic control of the steroidogenic pathway, and reduced clonazepam-stimulated steroidogenesis. These results, together with the reported ability of neurosteroids to modulate GABAA receptor function, suggest a novel regulatory mechanism to control the inhibitory transmission.

Neurosteroidogenesis in rat retinas

Neurosteroids (steroids synthesized in the CNS) function by modulating neurotransmission. To establish an experimental model for investigation of neurosteroid synthesis and regulation, independent of blood-borne steroids, we examined the steroidogenic activity of isolated rat retinas. We identified progesterone, pregnenolone, dehydroepiandrosterone, desoxycorticosterone, 3 alpha,5 alpha-tetrahydrodesoxycorticosterone, 3 alpha-hydroxy-5 alpha-dihydroprogesterone, 17-hydroxyprogesterone, and 17-hydroxypregnenolone together with their esterified forms. As pregnenolone is the precursor of all steroids, its formation was studied in detail as an index of a steroid-synthesizing tissue. Pregnenolone was identified further by gas chromatography coupled to mass spectrometry, and its in vitro synthesis was inhibited by lovastatin, an inhibitor of mevalonolactone and cholesterol biosynthesis. We then examined pregnenolone synthesis in the presence of mevalonolactone as a precursor of sterol formation together with lovastatin, which reduces endogenous mevalonolactone synthesis, as well as with inhibitors of pregnenolone metabolism. The incorporation of mevalonolactone into pregnenolone and its sulfate ester was time- and concentration-dependent and blocked by aminoglutethimide, a competitive inhibitor of cytochrome P450 side-chain cleavage (P450scc) enzyme. Immunocytochemical studies with a specific antibody to P450scc revealed a primary localization of the enzyme at the retinal ganglion cell layer. A less pronounced immunostaining was also seen at cells of the inner nuclear layer. Compounds known to stimulate cyclic AMP content also stimulated pregnenolone formation by rat retinas. These results demonstrate that rat retinas synthesize steroids and, for the first time, they reveal the steroidogenic ability of neuronal cells. We propose rat retinas as an in vitro model system to study neurosteroidogenesis in the CNS.

[Changes in the lipid profiles of hyperlipemic patients treated with binifibrate]

Forty six, after six weeks of low fat diet (step 1) hyperlipidemic patients, age 20 to 65 years, both sexes, have been studied to recognize the effectiveness of three months drug treatment with Binifibrate (600 mg T.I.D.). Total cholesterol, triglycerides, LDL-cholesterol (cLDL), HDL-cholesterol (cHDL), apoprotein A, apoprotein B and other routinal biochemical parameters were controlled at 0, 30 and 60 days of treatment. A significative total cholesterol, cLDL and apo B lowering plus a significative cHDL and apo A increase was registered. Results reflect a beneficial effect of Binifibrate on lipoprotein metabolism and in such wise, locate this drug as an interesting one for hyperlipidemic situations treatment.

Multiple use of cycler set in cycler peritoneal dialysis

STUDY OBJECTIVE

To evaluate the multiple use of cycler set with universal connector set.

DESIGN

The study was designed to reuse the cycler set for two to three treatments, each of 16-24 hours using Pac-X or Pac-Xtra cycler and to continue to use the same set if the patient was disconnected for any reason.

SETTING

Tertiary-referral university hospital.

PATIENTS AND METHODS

204 ESRD patients on peritoneal dialysis (PD) admitted to University Hospital from January 1989 to July 1991 were studied. The patients were disconnected and reconnected in between or during PD treatments. Five-liter dialysate bags were used. All the fluid was either set initially or added as clinically indicated.

RESULTS

2491 cycler PD treatments were performed with Pac-X and Pac-Xtra cyclers using 940 cycler tubing sets. 1624 disconnections were made in between and 336 were made for radiological investigations, special procedure, physical therapy and surgery during PD treatments. No episode of peritonitis or mechanical failure occurred. The multiple use resulted in 62% reduction in cycler sets thereby reducing the disposable supplies and a substantial saving in the nursing time.

CONCLUSIONS

The multiple use of cycler set with universal connector and manifold set was safe and economical in the patients undergoing cycler PD in the hospital setting.