Ex vivo and in vitro testis and ovary explants: utility for identifying steroid biosynthesis inhibitors and comparison to a Tier I screening battery

Retinal ganglion cell (RGC) axons in lizards (reptiles) were found to regenerate after optic nerve injury. To determine whether regeneration occurs because the visual pathway has growth-supporting glia cells or whether RGC axons regrow despite the presence of neurite growth-inhibitory components, the substrate properties of lizard optic nerve myelin and of oligodendrocytes were analyzed in vitro, using rat dorsal root ganglion (DRG) neurons. In addition, the response of lizard RGC axons upon contact with rat and reptilian oligodendrocytes or with myelin proteins from the mammalian central nervous system (CNS) was monitored. Lizard optic nerve myelin inhibited extension of rat DRG neurites, and lizard oligodendrocytes elicited DRG growth cone collapse. Both effects were partially reversed by antibody IN-1 against mammalian 35/250 kD neurite growth inhibitors, and IN-1 stained myelinated fiber tracts in the lizard CNS. However, lizard RGC growth cones grew freely across oligodendrocytes from the rat and the reptilian CNS. Mammalian CNS myelin proteins reconstituted into liposomes and added to elongating lizard RGC axons caused at most a transient collapse reaction. Growth cones always recovered within an hour and regrew. Thus, lizard CNS myelin and oligodendrocytes possess nonpermissive substrate properties for DRG neurons--like corresponding structures and cells in the mammalian CNS, including mammalian-like neurite growth inhibitors. Lizard RGC axons, however, appear to be far less sensitive to these inhibitory substrate components and therefore may be able to regenerate through the visual pathway despite the presence of myelin and oligodendrocytes that block growth of DRG neurites.     

Linking service climate and customer perceptions of service quality: test of a causal model

A set of foundation issues that support employee work and service quality is conceptualized as a necessary but not sufficient cause of a climate for service, which in turn is proposed to be reflected in customer experiences. Climate for service rests on the foundation issues, but in addition it requires policies and practices that focus attention directly on service quality. Data were collected at multiple points in time from employees and customers of 134 branches of a bank and analyzed via structural equation modeling. Results indicated that the model in which the foundation issues yielded a climate for service, and climate for service in turn led to customer perceptions of service quality, fit the data well. However, subsequent cross-lagged analyses revealed the presence of a reciprocal effect for climate and customer perceptions. Implications of these results for theory and research are offered.     

Stability of fumonisins in thermally processed corn products

Little is known about the stability of fumonisins in corn-based foods during heating. This study investigated the effects of canning, baking, and roasting (dry heating) processes on the stability of fumonisins in artificially contaminated and naturally contaminated corn-based foods. All samples were analyzed for fumonisin levels by both a commercial enzyme-linked immunosorbent assay (ELISA) and a high-performance liquid chromatographic (HPLC) method. Canned whole-kernel corn showed a significant (P < or = 0.05) decrease in fumonisins by both ELISA (15%) and HPLC (11%) analyses. Canned cream-style corn and baked corn bread showed significant (P < or = 0.05) decreases in fumonisin levels at an average rate of 9% and 48%, respectively, as analyzed by ELISA. Corn-muffin mix artificially contaminated with 5 micrograms of fumonisin B1 (FB1) per g and naturally contaminated corn-muffin mix showed no significant (P < or = 0.05) losses of fumonisins upon baking. Roasting cornmeal samples artificially contaminated with 5 micrograms of FB1 per g and naturally contaminated cornmeal samples at 218 degrees C for 15 min resulted in almost complete loss of fumonisins.     

Effect of propranolol and nifedipine on maximal electroshock-induced seizures in mice: individually and in combination

To clarify the influence of the head-up position on cerebral oxygen metabolism during laparoscopy with CO2 insufflation in 12 patients who underwent laparoscopic cholecystectomy, changes in the concentrations of cerebral oxyhemoglobin (HbO2), deoxyhemoglobin (Hb), total hemoglobin (total Hb) and oxidized cytochrome aa3 (Cyt aa3) were measured by use of near-infrared laser spectroscopy. Anesthesia was maintained with nitrous oxide (66%), oxygen, and sevoflurane. Pneumoperitoneum was maintained at an intraabdominal pressure of 10-12 mm Hg by use of CO2. Minute ventilation was adjusted to maintain end-tidal CO2 tension (P(ET)CO2) between 35 and 40 mm Hg during the procedure. Patients were moved from supine to the head-up (20 degree) position before intraabdominal manipulation. The concentration of HbO2 decreased significantly when patients were moved to the head-up position and 30 min thereafter. It remained significantly low after they were returned to the supine position and at the end of surgery. The concentration of Hb was unchanged during the study. Therefore, the concentration of total Hb decreased significantly when patients were moved to the head-up position, as well as 30 min thereafter. It remained significantly low after they were returned to the supine position and at the end of surgery. The concentration of Cyt aa3, however, did not change significantly during the study. These results suggest that the head-up position during laparoscopic cholecystectomy decreases cerebral HbO2 and total Hb.     

Regulation of Sos activity by intramolecular interactions

The guanine nucleotide exchange factor Sos mediates the coupling of receptor tyrosine kinases to Ras activation. To investigate the mechanisms that control Sos activity, we have analyzed the contribution of various domains to its catalytic activity. Using human Sos1 (hSos1) truncation mutants, we show that Sos proteins lacking either the amino or the carboxyl terminus domain, or both, display a guanine nucleotide exchange activity that is significantly higher compared with that of the full-length protein. These results demonstrate that both the amino and the carboxyl terminus domains of Sos are involved in the negative regulation of its catalytic activity. Furthermore, in vitro Ras binding experiments suggest that the amino and carboxyl terminus domains exert negative allosteric control on the interaction of the Sos catalytic domain with Ras. The guanine nucleotide exchange activity of hSos1 was not augmented by growth factor stimulation, indicating that Sos activity is constitutively maintained in a downregulated state. Deletion of both the amino and the carboxyl terminus domains was sufficient to activate the transforming potential of Sos. These findings suggest a novel negative regulatory role for the amino terminus domain of Sos and indicate a cooperation between the amino and the carboxyl terminus domains in the regulation of Sos activity.     

Cellular constituent and intercellular adhesion in Schistosoma mansoni granuloma: an ultrastructural study

The present work deals with the structural analysis of Schistosoma mansoni granuloma and the visualization of cellular interaction at an ultrastuctural level in the acute (8 weeks) and chronic (20 weeks) stages of infection, for more detailed understanding of pathophysiology of the disease. Although, S. mansoni granuloma is mediated by T-lymphocytes, yet in this work the macrophage cells and not the lymphocytes represented the main cell type in cellular and fibrocellular granulomas. The cellular and fibrocellular granulomas detected in the acute stage of infection elicited no difference in cellular constituent to those of the chronic stage respectively. Macrophage cells and fibrocytes were the only cell type detected in fibrotic granuloma. The monocytes may be considered the first cell reaching the site of the trapped egg as they formed the first row of cells around the egg. The cellular infiltrate forming the granuloma: monocytes, macrophages, lymphocytes, eosinophils, fibroblasts and plasma cells revealed direct contact or adherence between them and even between the individual cell type, through extending protrusion from the cell membrane of adjacent cells. They constituted an integrated network which encircled the egg. Similar adhesion between inflammatory cells in the blood vessels and between the inflammatory cells and the endothelial cells were displayed. These points of intercellular adhesion appeared as if, not only used for functional communication between the cells, but also for cellular deplacement either in the extracellular matrix or in the blood stream until extravasation. In conclusion, S. mansoni granuloma is a highly organized cellular lesion, in which cell to cell communication occurs through direct cell contact.     

Optimal coupling and feasibility of a solar-powered year-round ejector air conditioner

An ejector refrigeration system that uses a conventional refrigerant (R-114) is introduced as a possible mechanism for providing solar-based air-conditioning. Optimal coupling conditions between the collectors' energy output and energy requirements of the cooling system, are investigated. Operation at such optimal conditions assures maximized overall efficiency. Procedures leading to the evaluation of the performance of a real system are disclosed. Design curves for such a system with R-114 as refrigerant are provided. A multi-ejectors arrangement that provides an efficient adjustment for variations of ambient conditions, is described. Year-round air-conditioning is facilitated by rerouting the refrigerant flow through a heating mode of the system. Calculations are carried out for illustrative configurations in which relatively low condensing temperature (water reservoirs, cooling towers, or moderate climate) can be maintained.     

Study of the non-steady state electrogenic transport of sodium ions by Na+,K(+)-ATPase by the capacitance measurement method

The goal of work was to investigate the electrogenic transport of Na ions by Na+,K(+)-ATPase in membrane fragments absorbed on a planar bilayer lipid membrane. The photorelease of ATP from an inactive precursor, caged ATP, induced a transient current and changes in the net system capacitance measured during the application of an alternating voltage. The increments of capacitance (delta c) decreased with the increase in the frequency of the applied voltage. The characteristic frequency F0 of the steepest slope of the curve significantly decreased in solutions with high ionic strength (either NaCl or choline chloride), in which Na+ transport is decelerated. The value of delta c correlated with the total charge delta q transported across the membrane. The capacitance increments decreased when the Na+ concentration in solution decreased. At a concentration below 2 mM the increment became negative. The increase in membrane capacitance can be attributed to the charge relaxation process inside the protein, as discovered in the cells by other methods. The characteristic frequency F0 depends on the time constants of charge redistribution. The nonlinear dependences of delta c on delta q were explained by a voltage bias across the membrane fragments resulting from pumping. The potentials corresponding to the maximum capacitance change were similar to the midpoint potentials of the equilibrium charge distribution and depended on the Na+ concentrations in solution. The model enabled also the determination of the total capacitance of the active region of a lipid membrane with the adsorbed protein containing membrane fragments.     

Breast disease: dynamic spiral MR imaging

The cochleo- and tonotopic organization of the second auditory area (AII) was investigated in cats anaesthetized with pentobarbital using a combination of macro- and microelectrode recording technique. The results obtained following electrical stimulation of the neural fibres innervating different regions of the organ of Corti indicate the existence of two complete representations of the cochlea in area AII: one in the dorsocaudal portion, the other in its ventrorostral portion. These two cortical representations of the cochlea differ in size and spatial orientation. The dorsocaudal projection area extends over a distance of 2.6-3.2 mm from the basal to the apical focus and is arc-shaped. The spatial orientation of cochlea representation within the dorsocaudal region of AII is similar to that described in AI, in that stimulation of the cochlea base results in maximal responses in the more rostral portion of AII and stimulation of the apex evokes cortical responses more caudally. The ventrorostral region within AII is smaller (1.4-2.5 mm length), and has the opposite cochleotopic orientation (base and apex stimulation represented caudally and rostrally, respectively). In both AII zones, there was a proportionally greater cortical representation of basilar membrane than of middle and apical portions. Although two distinct zones with the overall cochleotopic pattern described above were noted in all cats, their precise size and location considerably varied in different animals. Using microelectrode recordings, a cortical tonotopic organization can be observed that was consistent with and expanded on the earlier cochleotopic data. Within the dorsocaudal region of AII, neurons with higher best frequency responses were located in more rostral regions, while those with lower best frequencies were located caudally. An orderly progression of best frequency responses was noted as serial recordings carried out along the full extent of the representation. Neurons within the ventrorostral region of AII also displayed an orderly progression of best frequencies, but in the opposite direction, with higher best frequencies noted more caudally and lower best frequencies more rostrally.