Comparative life cycle assessment study on environmental impact of oil production from micro-algae and terrestrial oilseed crops.

In this study the LCA methodology is applied in order to satisfy two goals: i) to evaluate the hot spots in site-specific production chain of biodiesel from terrestrial and micro-algae feedstock; ii) to compare quantitatively, utilizing primary data, the impacts of the first generation in respect to the third generation bio-fuels. Results show that micro-algae are neither competitive yet with traditional oil crops nor with fossil fuel. The use of renewable technologies as photovoltaics and biogas self production might increase the competitiveness of micro-algae oil. Further investigations are however necessary to optimize their production chain and to increase the added value of co-products.

Thermal desorption of polychlorobiphenyls from contaminated soils and their hydrodechlorination using Pd- and Rh-supported catalysts.

This paper reports about a combined technology for soil remediation from PCBs using the thermal desorption technique coupled with the catalytic hydrogenation of recovered PCBs. The reactor is a bench scale rotating desorption furnace through which nitrogen is flushed and used as carrier gas of desorbed PCBs. The latter are condensed into an hexane or hexane-acetone (1:1 v/v) solution that is then hydrogenated using phosphate-supported Pd or Rh as catalyst. The analysis of the treated soil, under variable operative conditions (temperature and desorption time), shows that the total (99.8%) decontamination from PCBs occurs. The recovery yield of the desorbed PCBs is better than 75% and the subsequent hydrogenation reaches 63% of the collected PCBs in 5h or 100% in 12h.

On the heterogeneous structure of thermally cured bis-GMA/TEGDMA resins.

In this paper we report on the morphogenesis of dental resins formed by a thermally initiated radical cross-linking copolymerization of model dental resins. These systems were considered reasonable model simplifications of the actual resins used in commercial filling composites, veneers, etc. Effect of bis-GMA content varying from 0 to 100% on the degree of conversion and morphology of the cured resin was investigated. Dynamic scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), dynamic mechanical thermal analysis (DMTA) and high temperature solvent extraction experiments were performed in order to determine the nature and location of unreacted unsaturations in relation to bis-GMA concentration. The interval of cure temperatures, ranging from 23 to 250 degrees C, may seem irrelevant from the clinical point of view but is instrumental for an understanding of the processes involved. Single glass transition temperature (Tg) found in DMTA experiments showed that the copolymerization process between bis-GMA and TEGDMA is random in nature, however, the overall cure reaction is inhomogeneous and this inhomogeneity is increasing with increasing bis-GMA molar fraction. Heterogeneous character of the cure was reflected into the network morphogenesis characterized by microgellation preceded by cyclization and, following connection of microgels. These cure kinetics resulted in a heterogeneous morphology of the cured resin. Moreover, it was shown that the cure kinetics controls to a great extent the degree of conversion of the reactive vinylidene C=C bonds in a fully cured resin. A decrease in bis-GMA concentration in the resin mixture led to a higher degree of conversion, however, even a neat TEGDMA homopolymer did not exhibit C=C conversion greater than 65-70% under the cure conditions used. Leaching out tests, consisting of an extraction of unreacted monomer from a finely ground cured resin in boiling cyclohexanone at 160 degrees C over a period of 5 d, revealed total weight loss of the order of 3.2-5.6 wt % regardless of the total conversion. No uncured monomer was detected in the extract solution using FTIR spectroscopy, however, the method used is not sensitive to the presence of oligomers. It was concluded that the remaining unreacted double bonds are the inevitable result of the diffusion controlled heterogeneous cure reaction. The low rate of diffusion in the resin beyond its gel point is controlled by high monomer rigidity, low mobility and radius of gyration of the monomers. The unreacted C=C bonds exist in the form of pendant, side groups chemically attached to the network. In addition, a hypothesis has been proposed that for concentrations of rigid bis-GMA monomers above 50 wt %, preferably only one methacrylate group of its molecule has reacted on the time span of the experiment performed and has been incorporated in the cured network. Hence, a substantial part of unsaturation exists in the solid polymer in the form of pendant groups formed by mechanically ineffective bis-GMA monomers. The results are in good qualitative agreement with computer simulations based on the kinetic gelation model.

A novel F box protein, NFB42, is highly enriched in neurons and induces growth arrest.

NFB42 (neural F Box 42 kDa) is a novel gene product that is highly enriched in the nervous system. Its predicted protein contains an F box, a motif recently shown to couple cell cycle regulation to the proteasome pathway (Bai, C., Sen, P., Hofmann, K., Ma, L., Goebl, M., Harper, J. W., and Elledge, S. (1996) Cell 86, 263-274). NFB42 mRNA and protein are expressed in all major areas of the adult rat brain but are not detected in non-neural tissues. NFB42 protein is localized primarily to the cytoplasm of neurons and does not appear to be present in glia. The presence of an F box in NFB42 suggests that it may be involved in cell cycle regulation; however, its expression in postmitotic neurons indicates that it is not involved in regulating typical cell cycle events. In an initial attempt to characterize the function of this protein, NFB42 was transfected into N1E-115 neuroblastoma and Chinese hamster ovary cells. The expression of full-length NFB42, but not an F box deletion mutant, inhibits proliferation in both cell lines. Additional experiments demonstrate that NFB42 interacts with Skp1p, a component of the proteasome pathway, and deletion of the F box also inhibits this interaction. Overall, the expression pattern of NFB42, along with the presence of an F box domain and the ability to inhibit growth, suggests that it may play a role in maintaining neurons in a postmitotic state.

Genes induced in programmed cell death of neuronal PC12 cells and developing sympathetic neurons in vivo.

To identify primary response genes induced during early stages of neuronal programmed cell death (PCD), we screened by differential hybridization a subtracted cDNA library prepared from neuronal PC12 cells deprived of NGF for 6 hr in the presence of cycloheximide. Eight induced cDNA sequences were identified and designated message up-regulated during death (mud)-1-8. To determine which cloned sequences might be involved in neuronal PCD in vivo, expression of mud genes was analyzed in developing rat superior cervical ganglia (SCG) undergoing programmed cell death, using a combination of reverse Southern, reverse transcription polymerase chain reaction (RT-PCR), and in situ hybridization. Five sequences (mud-1, -3, -5/8, -6, and -7) are induced in SCG undergoing cell death in vivo, and induction of at least three of these (mud-3, -6, and -7) occurs in neurons. Partial sequence analysis reveals that mud-1 corresponds to annexin VI; mud-3 corresponds to rat PC3, mouse TIS21; mud-4 appears to be the rat homolog of human TAFII70; mud-5 and -8 are >85% identical members of the rodent gene family of B2-transcribed repeats; and mud-6 appears to be the rat homolog of human Ring 3 and Drosophila female sterile homeotic (fsh). Mud-2 and mud-7 encode novel sequences. These new candidate genes provide markers for early stages of neuronal PCD, are potentially involved in the cell death process, and serve to expand our view of cell death control in the developing nervous system.

Unemployment in inner-city renal transplant recipients: predictive and sociodemographic factors.

Studies of dialysis patients report unemployment rates of 60% to 75%; however, it is generally believed that following transplantation, improvement in well-being and removal of time constraints imposed by the dialytic regimen afford improvement in employment status. We studied 58 stable renal transplant recipient attending an outpatient transplant clinic by questionnaire, administered anonymously. Only 25 (43%) of the patients were currently employed. Employed and unemployed patients did not differ when compared for age, gender, race, cause of renal disease, type of transplant or prior dialysis, time on dialysis or time since transplantation, years of education, or prestige score or classification ("blue collar" v "white collar") of prior job. In the employed group, 24 (96%) patients had worked before developing kidney disease compared with 23 (70%) patients in the unemployed group (P < 0.05). While on dialysis, 19 (79%) of the employed patients continued working compared with 10 (30%) of the unemployed patients (P < 0.005). Major reasons for discontinuing work after starting dialysis for both groups were subjective illness (feeling too sick, 51%), followed by interference of the dialysis regimen with time necessary for work (32%). Only 15% of the previously employed patients did not work after transplantation because of feeling too sick. By multiple logistic regression, the strongest predictors of employment posttransplant were being more than 1 year posttransplant (odds ratio, 2.35; 95% confidence interval, 1.01 to 5.5) and having been employed before transplantation (odds ratio, 3.79; 95% confidence interval, 1.60 to 9.02). Over half of the unemployed patients (20 [61%]) expressed interest in job training. Eighty percent to 90% of patients in both groups were insured by Medicare, with the second greatest number insured by Medicaid. Of the 15 unemployed patients insured by Medicaid, 67% reported that their decision not to work was related to fear of losing Medicaid benefits because they could not afford medications without it. Despite no difference in actual type of insurance carried, 17 (51%) of the unemployed patients believed their health insurance coverage was inadequate compared with four (12%) of the employed patients (P = 0.005, chi-squared test). Unemployment remains a significant problem for our population of inner-city renal transplant recipients. Attention to job retention or retraining during the early renal disease and dialysis therapy period may promote better rehabilitation following transplantation. However, for this population, with limited employment opportunities, removal of disincentives to work, including loss of Insurance and Inability to pay for medications, will be necessary before we can provide optimal rehabilitation for renal transplant recipients from all social strata.

Extent of conversion and its effect on the mechanical performance of Bis-GMA/PEGDMA-based resins and their composites with continuous glass fibres.

The reaction mechanism of bisphenol A bis(2-hydroxy propyl) methacrylate (Bis-GMA) and polyethylene glycol dimethacrylate (PEGDMA) was characterized by differential scanning calorimetry (DSC) and infrared (IR) spectroscopy. Composites of S2-glass fibres with different formulations of Bis-GMA/PEGDMA were fabricated by filament winding. The mechanical properties of neat resins and composites were investigated by dynamic mechanical thermal analysis (DMTA) and a three-point-bending flexural test.

Transosseous reconstruction of temporalis muscle for pterional craniotomy: technical note.

Temporalis muscle asymmetry is a bothersome complication of pterional craniotomy, resulting from atrophy, malposition, and unreliable fixation. The authors describe a simple, quick, and inexpensive technique to achieve firm, anatomic reapproximation of the temporalis muscle to its bone attachment.

Continuous fiber reinforced composite materials as alternatives for metal alloys used for dental appliances.

Two types of uniaxially oriented long S2-glass fiber reinforced composites were prepared for use in various dental appliances. Matrix polymers were polycarbonate (PC) and bisphenol A bis (2-hydroxy-propyl) methacrylate (Bis-GMA) based copolymers. Flexural tests were conducted on the composites using a procedure which simulates clinical usages. To evaluate the adhesion between the composites and the adhesive, the single-lap shear test was conducted. Mechanical properties of the small cross-sectional composite strips were superior to those used previously in clinical studies.

Death in the balance.

Two major hypotheses concerning programmed cell death are that it is the end result of a gene expression pathway and that it is the cellular response to conflicting growth control signals. These ideas are examined, and their potential applicant to neuronal cell death during development is discussed. Since most mammalian genes involved in cell death have other functions, it is possible that a novel set of death genes does not exist in mammals. Instead, the genes identified may serve to link an initial stimulus to die with the cellular events that actually cause death, primarily by providing regulatory signals that direct the decision. The idea of cell death as a response to conflicting growth regulatory signals, initially derived from studies on cycling, non-neuronal cells, is applied to proliferating neuronal precursors and postmitotic neurons. How neuronal death during development might be the outcome of conflicting signals, and how retinoblastoma protein might negotiate "death by conflict" in different populations of neurons is discussed.

Localization of tissue plasminogen activator mRNA in the developing rat cerebellum and effects of inhibiting tissue plasminogen activator on granule cell migration.

Tissue plasminogen activator (tPA) mRNA was localized in the developing cerebellum and the potential role of tPA in migration of cerebellar granule cells was investigated. Proteolytic assays and Northern blots showed little variation in levels of tPA proteolytic activity or tPA mRNA expression in the developing cerebellum. The distribution of cerebellar tPA mRNA at different ages was visualized by in situ hybridization histochemistry. At postnatal day 7 (P7), most labeled cells were in the internal granule layer or developing white matter, and very few if any premigratory granule cells contained tPA mRNA. Although the molecular layer contained labeled cells at all ages, cell counts indicated that a greater percentage of cells in the molecular layer contained tPA mRNA during adulthood than during the period of granule cell migration. The most striking change in tPA mRNA expression was in Purkinje neurons, most of which began to express tPA mRNA between P7 and P14. The potential role of tPA in granule cell migration was investigated by performing migration assays in cerebellar slice explants in the presence or absence of protease inhibitors. The presence of inhibitors did not affect the distance that granule cells migrated. Data in the present study do not support a role for tPA in granule neuron migration; however, they do indicate that tPA is both spatially and temporally regulated during cerebellar development. Possible functions of tPA in the cerebellum are discussed.

PC12 cells overexpressing tissue plasminogen activator regenerate neurites to a greater extent and migrate faster than control cells in complex extracellular matrix.

PC12 cells were stably transfected with expression vectors containing rat tissue plasminogen activator (tPA) under control of either a cytomegalovirus or rous sarcoma virus promoter. Cell lines were characterized using protease assays, ELISAs, immunoblots, northern blots, and Southern blots. Control PC12 cells or cells containing vectors alone released about 1 pg tPA/cell/24 h, whereas cells stably transfected with a tPA cDNA released 2-5 pg tPA/cell/24 h. A strong correlation existed between the amount of tPA released and the ability of cells to degrade extracellular matrix. Experiments with protease inhibitors and antibodies against tPA and plasminogen indicated that degradation of matrix involved tPA-generated plasmin and that the amount of matrix degraded was dependent on the amount of tPA released. Cells expressing high levels of tPA migrated on a three-dimensional matrix about twice as fast as control cells and regenerated neurites within three-dimensional gels of Matrigel to a greater extent than control cells. Antibodies that inhibited tPA and plasminogen decreased migration and neurite regeneration, indicating that tPA was involved in both events, PC12 cells overexpressing tPA should provide a useful model system for investigating neural functions of tPA including its role in migration and regeneration.

Localization of tissue plasminogen activator mRNA in adult rat brain.

The distribution of tissue plasminogen activator (tPA) messenger RNA in rat brain was studied using in situ hybridization with 35S UTP-labeled RNA probes derived from a full-length tPA cDNA. Sense strand controls produced low, even backgrounds, with small elevations in the hippocampus. Full-length antisense probes produced strong signals over cerebral ventricular ependyma (including ependyma of the subcommissural organ), meninges, blood vessels, and Purkinje cell layer of the cerebellum, as well as strong signals over scattered cells throughout the brain. Some of these scattered labeled cells were large with lightly stained nuclei, while others were small with darkly stained nuclei. The large labeled cells, which were probably neurons, constituted 6% and 8% of cells in the brain stem and neocortex, respectively, and 100% of Purkinje cells. The small cells, which were present in all areas of the brain, constituted 3-11% of cells in individual brain areas.

Neuronal cell death: searching for the smoking gun.

During the past year,several model systems have been developed to identify cellular and biochemical events involved in neuronal cell death, to investigate the role of bcl-2 in cell survival, and to characterize the relationship between cell death and the cell cycle.

Probing the function of Drosophila melanogaster accessory glands by directed cell ablation.

The female Drosophila melanogaster fly undergoes behavioral changes after mating, including an increase in egg laying and an avoidance of remating. Accessory-gland products elicit these changes transiently when introduced into unmated female flies. We report here the generation and phenotype of flies that lack functional accessory-gland main cells as a consequence of genetically directed delivery of diphtheria toxin subunit A to those cells. Only main-cell secretions are essential for the short-term inhibition to remating; no other products of the genital tract can replace their function. Long-term inhibition to remating depends only on the storage of sperm in the female. Both sperm and main-cell secretions have roles in the increase of egg laying by the mated female. In addition to full-strength diphtheria toxin, we used low-activity toxins to kill only those cells that express toxin at high levels. These transgenic strains that express diphtheria toxins of different strengths in accessory-gland main cells will be useful in further defining the role of these cells.

A system for characterizing cellular and molecular events in programmed neuronal cell death.

A model system has been established in which PC12 cells are converted to neuronal-like cells that undergo transcription-dependent cell death following removal of NGF. Nineteen sublines of PC12 cells were tested to establish parameters for making cells dependent on NGF for survival. In most sublines, a relatively small percentage of cells become dependent on NGF for survival, and following removal of NGF, most of the cells begin proliferating in serum-containing medium. In several sublines, however, a significant percentage of cells die following removal of NGF. One of these sublines, PC6-3, can be grown under conditions in which 90% of the cells undergo transcription-dependent cell death following removal of NGF in either serum-free or serum-containing medium. Fourteen hours after removing NGF, 50% of the cells are committed to die, while initial morphological signs of cell death as determined by time-lapse videomicroscopy occur 2-6 hr later and include loss of neurites followed by a 1-3 hr period of active membrane "blebbing" and protrusions. Cell death can be blocked by the RNA synthesis inhibitor actinomycin D, the protein synthesis inhibitor cycloheximide, KCl, basic fibroblast growth factor, or dibutryl-cAMP, but not by epidermal growth factor, leupeptin, or the endonuclease inhibitor aurintricarboxylic acid (ATA). Removal of NGF activates an endonuclease that causes nucleosomal laddering of the DNA; however, endonuclease activity does not appear to be required for cell death. In agreement with previous studies (Batistatou and Greene, 1991; Rukenstein et al., 1991) demonstrating that naive PC12 cells undergo transcription-independent cell death when shifted into serum-free medium in the absence of growth factors, all cell lines tested except for one die when cultured in RPMI medium lacking growth factors. DNA fragmentation is a prominent feature of transcription-independent cell death, and death can be blocked with NGF, ATA, and dibutryl-cAMP but not with actinomycin D or KCl. The PC12 model system described here should be useful for identifying cell death genes and for characterizing cellular and molecular events in programmed neuronal cell death.