Enhancing biological stability of disinfectant-free drinking water by reducing high molecular weight organic compounds with ultrafiltration posttreatment.

The production of biologically stable drinking water is challenging in conventional surface water treatment plants. However, attainment of biological stability is essential to avoid regrowth in disinfectant-free distribution systems. A novel application of ultrafiltration as a posttreatment step to enhance biological stability of drinking water produced in an existing conventional surface water treatment plant was investigated. The conventional full-scale plant comprised coagulation/sedimentation/filtration, UV-disinfection, biological activated carbon filtration and chlorine dioxide post-disinfection. The produced water exhibited substantial regrowth of Aeromonads, invertebrates and colony counts in the distribution network. Recent literature attributes this phenomenon to the specific presence of slowly biodegradable, high molecular weight (MW) biopolymeric organic compounds. Hence, the aim of this study is to enhance the biological stability of conventionally treated surface water by reducing the concentration of high-MW organic compounds. For this purpose, biological active carbon filtrate was subjected to ultrafiltration with membrane pore sizes of 10 kDa, 150 kDa and 0.12 µm respectively, operating in parallel. The UF performance was evaluated in terms of the achieved reduction in particulate and high-MW organic carbon (PHMOC); the biopolymer fraction in Liquid Chromatography-Organic Carbon Detection; biomass (cells, ATP); Assimilable Organic Carbon (AOC) by the AOC-P17/NOX method for easily biodegradable, low-MW compounds and by the AOC-A3 method for slowly biodegradable, high-MW compounds; and overall microbial growth potential (MGP) as assessed by Biomass Production Potential (BPP) and Bacterial Growth Potential (BGP) bio-assays. Results showed increasing removal of high-MW organic carbon with decreasing UF pore size, i.e., 30%, 60% and 70% removal was observed for the 0.12 µm, 150 kDa and 10 kDa membranes, respectively. Biomass and particulates retention was more than 95% for all UF membranes. AOC-A3, BPP and BGP were substantially reduced by 90%, 70% and 50%, respectively. These respective reductions were similar for all three UF membranes despite their difference in pore size. Easily biodegradable organic compounds (as AOC-P17/NOX) were not reduced by any of the membranes, which was in accordance with expectations considering the low MW of the compounds involved. Based on the obtained results, growth potential appears to be largely attributable to high-MW organic compounds which are retained by a 0.12 µm UF membrane. Furthermore, the quality of all three UF permeates was equal to or better than in reference cases (literature data) which exhibit little regrowth in their disinfectant-free distribution networks. The results demonstrate that ultrafiltration posttreatment in conventional surface water treatment plants is a potentially promising approach to enhance the biological stability of drinking water.

Membrane-based pretreatment to mitigate variations in desalination plants.

The main source of potable water in high water-stress areas is commonly produced in brackish and seawater desalination plants. Owing to the presence of high concentration of suspended solids, organic matter and colloidal particles in raw water, pretreatment processes are needed for a stable operation of desalination plants. A submerged membrane ultrafiltration pilot plant has been operated as pretreatment of complex brackish surface water to study the filtration performance. The results show the membrane performance, chemical reagent requirements, water quality and cleaning procedures efficiency of an ultrafiltration pilot plant used as pretreatment for a reverse osmosis system. Alternative chemical cleaning procedures have been satisfactorily implemented, which maximize permeability recovery and allow a stable operation.

Differential effects of ceramide on cell viability and extracellular matrix remodeling in keratinocytes and fibroblasts.

Ceramides are used in skin care and treatment of dermatological diseases. Cell viability and extracellular matrix (ECM) remodeling are important parameters in skin health. Skin photoaging, from exposure to ultraviolet radiation, is associated with epidermal hyperplasia and dermal ECM atrophy caused by alterations in expression of matrixmetalloproteinases (MMPs), elastin and transforming growth factor-beta (TGF-beta). The purpose of this study was to determine the effects of c2-ceramide (ceramide) on the cell viability and expression of TGF-beta, MMP-1 and elastin in cultured keratinocytes and fibroblasts. Ceramide inhibited keratinocyte cell viability by apoptosis and stimulated expression of elastin, MMP-1 and TGF-beta, suggesting improved epidermal functioning by a TGF-beta mechanism. Conversely, ceramide stimulated fibroblast cell growth at the lower concentrations and inhibited the expression of MMP-1, elastin and TGF-beta, which indicates a predominantly beneficial effect in the prevention of photoaging-associated dermal alterationby TGF-beta and non-TGF-beta mechanisms. The regulation of MMP-1 expression by ceramide was transcriptionally mediated and via the activator protein-1 sequence in both keratinocytes and fibroblasts. The study delineates the specific, though differential, beneficial effects of ceramide in the prevention of epidermal hyperplasia and dermal ECM remodeling, associated with photoaging.

Molecular and serological characterization of HLA-B71 in association with different class I haplotypes or in different ethnic groups.

The HLA-B70 antigen is among the most common antigens present in African Americans; however, monospecific serologic reagents defining B70 and its subtypes, B71 and B72, are rare. We have recently reported the molecular characterization of a B71 allele (B*1510) from an African American individual carrying the haplotype HLA-A30, Cw3, B71(w6). In order to better define the degree of polymorphism of molecules carrying the B71 serological specificity in the human population, we have used serology, cDNA sequencing, and PCR/SSOP typing to characterize B71 alleles from additional individuals from different ethnic populations and carrying different class I haplotypes. All carried either B*1510 or B*1518 alleles. Other HLA-B alleles isolated from these individuals (B*5001, B*4901, B*3501, B*3701) were identical to previously reported sequences except for a novel B41 allele (B*4102) identified in one Hispanic individual. This allele has concurrently been identified by Rufer and colleagues in Caucasian individuals. The B*4102 allele differs from B*4101 at codons 95 (Leu/Trp) and 97 (Ser/Arg). In addition, the B*4102 allele differs from B*4101 by two silent substitutions at codons 94 (ACC/ACT) and 99 (TAC/TAT). Since the polymorphic sequence present in B*4102 is also present in other HLA-B alleles (e.g.., B*2707, B*4002, B*0702), it may represent a gene conversion cassette. The allelic diversity at the class I loci and the scarcity of monospecific alloantisera support the importance of the application of molecular based methods to identify HLA class I alleles in matching unrelated donor/recipient pairs for bone marrow transplantation.

Molecular characterization of HLA-B71 from an African American individual.

We have sequenced a cDNA clone encoding an HLA-B71 (B70) allele from an African American individual. Serologic definition of B70 allelic products is very difficult due to extensive cross-reactivity of the alloantisera with B35, B15, and B5 antigens. The new sequence most closely resembles the sequence of B*1503, differing only by three amino acids at positions 63, 67, and 116. The B71 sequence differs from alleles of the B15 antigenic group (serologically defined as B62) by 7-8 amino acids and from members of the B35 family by 10 to 12 amino acids. B71 may represent an evolutionary intermediate, sharing elements common to both B35 and B15 allelic groups.

[Cell-mediated lympholysis in kidney transplantation]. / Linfolisis mediada por células en el transplante renal.

Kidney transplant survival has been increased with the use of cyclosporine (CyA) and antilymphocyte globulin (ALG), in spite of which both significant morbidity and mortality persist. On the other hand, immunosuppression is mostly based on the state of renal function and not on the monitoring of immunologic parameters. Therefore, it is important to apply immunological techniques for early diagnosis of over-immunosuppression and eventually to stop maintenance immunosuppression completely. Seventeen kidney transplant recipients (3 from cadavers and 14 living related) were studied. They were initially treated with either 3-5 mg/kg/d CyA, ALG and 0.5 mg/kg/d prednisolone (current treatment) or with 2 mg/kg/d azathioprine and 1 mg/kg/d prednisolone (conventional treatment). Cell-mediated lympholysis (CML) was performed between receptor and, alternatively, specific donor and third unrelated control. CML figures were higher with conventional treatment (14.73 +/- 1.69) than with current treatment (3.14 +/- 0.8) (Table 2). CML responses between receptors and third unrelated donors increased significantly with conventional therapy to 77.67 +/- 8.17, a value not different from that encountered between unrelated controls (72.7 +/- 3.9). The CML responses with the current therapy increased significantly to 34.25 +/- 2.54 but remained lower than that observed in the other group. The data suggest that the use of GAL and CyA leads to a nonspecific decrease of the immune response. It remains to determine whether or not the pattern evolves later to a donor specific hypo-response, as observed in the present study with the group with conventional treatment, confirming previous results.

Linfolisis mediada por células en el transplante renal. / [Cell-mediated lympholysis in kidney transplantation]

Kidney transplant survival has been increased with the use of cyclosporine (CyA) and antilymphocyte globulin (ALG), in spite of which both significant morbidity and mortality persist. On the other hand, immunosuppression is mostly based on the state of renal function and not on the monitoring of immunologic parameters. Therefore, it is important to apply immunological techniques for early diagnosis of over-immunosuppression and eventually to stop maintenance immunosuppression completely. Seventeen kidney transplant recipients (3 from cadavers and 14 living related) were studied. They were initially treated with either 3-5 mg/kg/d CyA, ALG and 0.5 mg/kg/d prednisolone (current treatment) or with 2 mg/kg/d azathioprine and 1 mg/kg/d prednisolone (conventional treatment). Cell-mediated lympholysis (CML) was performed between receptor and, alternatively, specific donor and third unrelated control. CML figures were higher with conventional treatment (14.73 +/- 1.69) than with current treatment (3.14 +/- 0.8) (Table 2). CML responses between receptors and third unrelated donors increased significantly with conventional therapy to 77.67 +/- 8.17, a value not different from that encountered between unrelated controls (72.7 +/- 3.9). The CML responses with the current therapy increased significantly to 34.25 +/- 2.54 but remained lower than that observed in the other group. The data suggest that the use of GAL and CyA leads to a nonspecific decrease of the immune response. It remains to determine whether or not the pattern evolves later to a donor specific hypo-response, as observed in the present study with the group with conventional treatment, confirming previous results.