Mechanisms of the ATP potentiation of hyposmotic taurine release in Swiss 3T3 fibroblasts

Reducing osmolarity by 35% increased ³H-taurine efflux from Swiss 3T3 fibroblasts from 0.5% to a peak of 5.7%. The presence of ATP (10–100 µM; EC₅₀ 1.5 µM) increased taurine efflux up to 10%, and decreased the set point for hyposmotically stimulated taurine release (HTR). ATP potentiation was mimicked by UTP, reduced by addition of suramin and pyridoxal phosphate-6-azophenyl-2,4-disulphonic acid (PPADS) and unaffected by ADP, ,-methylene-ATP (,-ATP) or 2-methylthio-ATP (Me-ATP), suggesting its mediation by purinergic P2Y₂ and P2Y₄ metabotropic receptors. Under isosmotic conditions ATP increased the cytosolic [Ca²⁺] ([Ca²⁺]_i) markedly, but did not increase taurine release. HTR was independent of external Ca²⁺ but was reduced (by 56–59%) by BAPTA-AM, thapsigargin-induced depletion of intracellular Ca²⁺ stores, or phospholipase C (PLC) inhibition. Blockade of calmodulin (CaM) or calmodulin kinase II (CaMKII) reduced HTR by 54% and 76%, respectively. The ATP-mediated potentiation was prevented fully by all these treatments. HTR was reduced by 30–50% by blockers of protein tyrosine kinases (AG18), phosphoinositide 3-kinase (PI3K) (wortmannin), p21rho (toxin B), p21rho-kinase (Y27632) and the stress-activated kinase p38 (PD169316). ATP-mediated potentiation was reduced similarly by these blockers. Simultaneous inhibition of PI3K and CaMKII abolished HTR. Altogether, these results suggest a modulatory effect of ATP, probably exerted by a potentiation of the Ca²⁺-dependent fraction of HTR. This fraction has as signalling elements a PLC-dependent [Ca²⁺]_i increase, resulting from Ca²⁺ released from thapsigargin-sensitive internal stores, followed by activation of CaM/CaMKII reactions. The Ca²⁺/ATP effect operates only when the Ca²⁺-independent, tyrosine kinase-mediated pathway is already activated. Suggested elements of cross-talk between the two pathways are PLC, PI3K and CaMKII.     

Effects of depressive symptoms and mental health quality of life on use of highly active antiretroviral therapy among HIV-seropositive women

This study examines the effects of depressive symptoms and mental health quality of life on utilization of highly active antiretroviral therapy (HAART) among HIV-seropositive women. Data were collected biannually from 1996 through 1998 in a prospective cohort study. Women reported use of antiretroviral therapy, health and mental health status, demographics, and social and behavioral factors; CD4 count and viral load also were assessed. Random effects regression models estimated the longitudinal effects of depressive symptoms and mental health quality of life on the probability of HAART utilization, controlling for clinical indicators (CD4 count, viral load, symptom presence), demographics (race, age, education), behavioral factors (drug/alcohol use, clinical trials participation), service features (insurance status, mental health service utilization), and study site. High levels of depressive symptoms and poor mental health quality of life were found, and they significantly reduced the probability of HAART utilization. Receiving mental health services significantly increased the probability of utilizing HAART. HIV-seropositive women characterized as being in poor mental health were less likely to use HAART, whereas those receiving treatment of mental health difficulties were more likely to use HAART. These findings suggest that efforts to enhance women's access to psychological treatment may increase their use of the latest HIV therapies.     

Hyposmolarity-activated fluxes of taurine in astrocytes are mediated by diffusion

In order to obtain information about the mechanism responsible for swelling associated taurine release in astrocytes, the kinetics of taurine uptake in cultured astrocytes from mouse cerebral cortex was studied under isosmotic and hyposmotic (50% osmolarity) conditions. It was found that the V_max for the high affinity component of taurine uptake was unaffected by exposure of the astrocytes to hyposmotic conditions and that the K_m value was somewhat increased. Contrary to V_max, the non-saturable component of the uptake was greatly increased (2.5-fold) after exposure of the cells to hyposmotic media leading to cell swelling. In addition to the kinetic characterization of taurine uptake the actual intracellular taurine content after incubation (15 min) in isosmotic or hyposmotic media with different taurine concentrations (0–100 mM) under Na⁺-free conditions was determined. At taurine concentrations < 30 mM corresponding to the intracellular content in cells not exposed to taurine, exposure to hyposmotic media led to a decrease in the intracellular taurine content. At higher external taurine concentrations (> 30 mM) the intracellular taurine contents were dramatically increased after exposure to hyposmotic conditions. The increase in intracellular taurine seen under hyposmotic conditions at 100 mM external taurine could be significantly reduced by 100 μM DIDS (4,4′-diisothiocyanatostilbene-2,2′-disulfonate). Altogether these results suggest that a diffusional process rather than the high affinity taurine carrier is involved in the swelling induced increase in astrocytic taurine influx and efflux.     

Preoperative infection prophylaxis with 1 % polyvidon-iodine solution based on the example of conjunctival staphylococci

Background: Most germs causing postoperative endophthalmitis derive from the conjunctival bacterial normal flora. Postoperative endophthalmitis is often induced by staphylococcal germs. The application of polyvidone-iodine solution to the conjunctiva is one possibility to reduce potential endophthalmitis-causing bacteria. The aim of this study was to evaluate the effectiveness of 1 % polyvidone-iodine solution concerning the reduction of colonization with staphylococci in the course of intraocular surgery. This is to evaluate the effectiveness of 1 % polyvidone-iodine solution concerning coagulase-negative and positive staphylococci.     

Properties of soluble and particulate cysteine sulfinate decarboxylase of the adult and the developing rat brain.

Some properties of cysteine sulfinate decarboxylase (CSD) activity were studied in the pellet and supernatant of a 18,000 X g centrifugation of isotonic sucrose rat brain homogenates. About 50% of the enzyme activity was found associated to the particulate fraction and 16% of the activity remained particle bound after hypo-osmotic shock of the 18,000 X g pellet. The activity of the 18,000 X g supernatant showed a lower dependence on exogenous pyridoxal phosphate (PLP) than the activity in the particulate fraction. The CSD activity of these fractions also differed in optimal pH and in apparent kinetic constants. The enzyme associated to particles showed the highest Vmax and the lowest Km. The activity and kinetic characteristics of CSD were studied during brain postnatal development. In the newborn brain only a small amount of the enzyme activity was found associated to the 18,000 X g pellet. CSD in brain homogenates of immature rats was less dependent on free PLP and showed a higher Km and a lower Vmax as compared with the enzyme in the adult brain. Between birth and adulthood the enzyme activity increased more than 10-fold in the particulate fraction and 2-fold in the soluble fraction. It is concluded that the differences observed in CSD activity between newborn and adult brain are due to an increase of the particulate form of the enzyme during postnatal development.     

The clinical value of laryngeal electromyography in laryngeal immobility

Although laryngeal electromyography (LEMG) is commonly performed, there are no data confirming its efficacy. We evaluated 40 patients with a laryngoscopic diagnosis of unilateral vocal-fold immobility who underwent LEMG of the thyroarytenoid (TA) and cricothyroid (CT) muscle, with the immobile side of each muscle being compared to the normal side. The immobile side compared to the normal side showed more fibrillation potentials and positive sharp waves for the TA (p = 0.04), longer MUAP duration for the TA (p = 0.04) and CT (p = 0.01), more polyphasic potentials for the TA (p = 0.002), and more frequent decreased recruitment for the TA (p < 0.01) and CT (p = 0.008). Specificity and positive predictive value were around 90%. Sensitivity, negative predictive value and accuracy were around 50%. These results suggest that altered LEMG findings are reliable and they can be used to determine the innervation status of an immobile muscle. Conversely, when the LEMG is normal, the results should be reviewed.     

Healthcare use by varied highly active antiretroviral therapy (HAART) strata: HAART use, discontinuation, and naivety

OBJECTIVES: Prior reports have found a temporal association between the introduction of highly active antiretroviral therapy (HAART) and population rates of health service use among persons living with HIV. Our objective was to explore further the effect of HAART by comparing healthcare use among persons who use HAART and persons who discontinue HAART to that among HAART-naive and HIV-negative persons. METHODS: Longitudinal analyses of 1485 women with and at-risk for HIV who contributed data to the Women's Interagency HIV Study between April 1997 and March 2000. RESULTS: Compared with HAART-naive women, those using HAART had a higher probability of more than three primary care visits per 6 months [odds ratio (OR), 1.38; 95% confidence interval (CI), 1.16-1.65), a lower probability of more than one emergency room visit per 6 months (OR, 0.75; CI, 0.59-0.95), and a lower probability of more than one hospitalization per 6 months (OR, 0.67; CI, 0.51-0.88). Compared with HAART-naive women, women who had discontinued HAART had a higher frequency of primary care visits (OR, 1.57; CI, 1.26-1.97) but did not demonstrate a significant change in emergency room or hospital use. Modeling of a standardized population HIV-positive women without AIDS indicated hospitalization and emergency room use among HAART users was equivalent to that among HIV-negative women. CONCLUSIONS: HIV-positive HAART users (without AIDS) exhibited emergency room and hospitalization use patterns equivalent to those of HIV-negative women. Furthermore, the discontinuation of HAART was associated with a loss of the reduction in hospital use that was achieved with HAART.     

Role of D1-like receptors in amphetamine-induced behavioral sensitization: a study using D1A receptor knockout mice

RATIONALE: The role played by D(1)-like receptors in amphetamine-induced behavioral sensitization has been examined using both the D(1)-like receptor antagonist, SCH 23390, and the D(1A) receptor knockout mouse (i.e. D(1A)-deficient mice). Studies using these two approaches have provided conflicting evidence about the importance of D(1)-like receptors for amphetamine-induced behavioral sensitization. OBJECTIVE: The purpose of the present study was to determine: (a) whether D(1A)-deficient mice exhibit amphetamine-induced locomotor sensitization after 3 and 17 drug abstinence days, and (b) whether SCH 23390, which binds to both D(1A) and D(1B) receptor subtypes, blocks development of amphetamine sensitization in wild-type and D(1A)-deficient mice. METHODS: In the first experiment, adult wild-type and D(1A)-deficient mice were injected with amphetamine (0, 1, 2, 4, or 8 mg/kg, IP) for 7 consecutive days. In the second experiment, wild-type and D(1A)-deficient mice were pretreated with SCH 23390 (0, 0.15, or 0.5 mg/kg, IP) 30 min prior to being injected with amphetamine (0 or 8 mg/kg, IP). After each daily amphetamine injection, mice were placed in activity chambers where distance traveled (i.e. horizontal locomotor activity) was measured for 60 min. On the test days, which occurred after 3 or 17 drug abstinence days, mice were injected with 1 mg/kg amphetamine and locomotion was measured for 120 min. RESULTS: Both wild-type and D(1A)-deficient mice exhibited amphetamine-induced locomotor sensitization. Pretreatment with 0.5 mg/kg SCH 23390 blocked the development of locomotor sensitization in wild-type mice, but did not alter the sensitized responding of D(1A)-deficient mice. CONCLUSIONS: It appears that D(1)-like receptors are necessary for the development of amphetamine sensitization in wild-type mice, while neither the D(1A) nor D(1B) receptor subtypes are necessary for the amphetamine-induced locomotor sensitization of D(1A)-deficient mice. A possible explanation for these conflicting results is that D(1A)-deficient mice may have a compensatory mechanism (not involving D(1B) receptors) that allows them to exhibit amphetamine-induced behavioral sensitization in the absence of the D(1A) receptor.