Regrowth Potential Research Articles

Use of Low Temperature to Improve Storage ofin vitroBroccoli Seedlings Under Various Light Qualities

ABSTRACT Broccoli (Brassica oleracea L. Botrytis Group ‘Green Duke’) seeds were germinated in vitro photoautotrophically (without sugar in medium) or photomixotrophically (with sugar in medium) for 3 weeks at 23 ° C and 150 μmol · m−2 · s−1 photosynthetic photon flux (PPF). Vessels were then stored at 1 ± 0.35°C under 1.6 ± 0.20,4.1 ± 0.35, or 8.6 ± 0.50 μmol · m−2 · s−1 constant PPF each of white (400–800 nm), red (600–700 nm), or blue (400–500 nm) light. Concentrations of CO2 inside the vessels were monitored until equilibrium was reached. Light compensation point was reached at $2.0 μmol · m−2 · s−1 for photoautotrophic seedlings and at $4.0 μmol · m−2 · s−1 for photomixotrophic seedlings. Therefore, in the long-term storage experiment, seedlings were stored for 4, 8, or 12 weeks at 1 ± 0.35°C in darkness or under 3 μmol · m−2 · s−1 constant PPF (average light compensation point) of white, red, or blue light. Variable to maximal chlorophyll fluorescence (Fv/Fm) of leaves decreased as storage time increased, regardless of media composition. Illumination during storage was necessary to maintain dry weight and regrowth potentials of in vitro seedlings. All photo-autotrophic seedlings stored in darkness were of poor quality and died when transferred to the greenhouse. Seventy-five percent of dark-stored photomixotrophic seedlings survived storage for 12 weeks but declined in appearance, dry weight, total soluble sugars (TSS), and chlorophyll fluorescence. Red light during storage increased seedling dry weight, TSS, and regrowth potential. Supplying 2% sucrose in the culture medium increased dry weight and maintained overall seedling quality during irradiated storage.

The role of indigenous microorganisms in suppression of salmonella regrowth in composted biosolids

Composting is commonly used as an effective means of stabilizing wastewater biosolids and reducing pathogens to very low concentrations. However, it has been shown that under certain conditions Salmonella can regrow in previously composted biosolids. Growth of seeded Salmonella typhimurium in composted biosolids ranging from two weeks to two years maturity was monitored. Results from sterile and non-sterile composted biosolids were compared. Seeded S. typhimurium colonized rapidly in sterilized biosolids reaching a maximum population density of more than 10 8 g −1. Growth of seeded S. typhimurium was suppressed in non-sterilized compost with a maximum population density of less than 10 3 g −1. There was a significant decline in the growth rate of seeded Salmonella in sterilized compost when the compost was stored, suggesting that bio-available nutrients declined with storage. However, in non-sterilized compost this was not the case. This suggests that the indigenous microflora play a significant role in suppression of Salmonella regrowth in composted biosolids. There was a strong negative correlation (−0.85) between the Salmonella inactivation rate and the maturity of compost in non-sterilized compost. The Salmonella inactivation rate was seven times higher in biosolids composting for two weeks as compared to compost stored for two years. This suggests that the antagonistic effect of indigenous microorganisms towards Salmonella declined with compost storage. It was concluded that all composted biosolids had a Salmonella regrowth potential. However, the indigenous microflora significantly reduced this regrowth potential. Long-term storage of compost is not recommended as this may increase the pathogen regrowth potential.

Bacterial Dynamics in the drinking water distribution system of Brussels

Water samples and pipe coupons were collected from the Brussels's drinking water distribution system (DS). A treated surface water and various groundwaters feed this DS. Parameters related to bacterial regrowth have been measured on these samples: temperature, concentrations of free residual chlorine, concentration of biodegradable dissolved organic carbon (BDOC), abundance of suspended bacteria, densities of fixed bacteria and levels of bacterial activity. Results showed that groundwaters were less susceptible to favor bacterial regrowth in the DS pipes. Treated surface water and mixed waters had the highest potential of bacterial regrowth in the DS dead ends. Results also showed that the potential regrowth induced by the distribution of a treated surface water could be reduced if: (1) the BDOC levels were below 0.25 mg C/l at the outlet of the surface water treatment plant; (2) a significant free chlorine residual was present within the whole DS. Second-stage biological filtration using granular activated carbon is now under construction at the surface water treatment plant feeding a part of this DS. This treatment implementation should reduce BDOC levels and chlorine demand of the treated surface water and will further reduce the slight regrowth phenomena observed in this DS.

Media Composition and Light Affect Storability and Poststorage Recovery of Micropropagated Hosta Plantlets

Hosta (Hosta tokudama Makeawa `Newberry Gold') plantlets were micropropagated photoautotrophically (without sucrose in medium) or photomixotrophically (with 2% sucrose in medium) for 3 weeks at 23 °C under 80 μmol·m-2·s-1 photosynthetic photon flux (PPF) prior to long-term storage. Plantlets were stored for 4, 8, or 12 weeks at 5, 10, or 22 °C in darkness or under white (400-800 nm), blue (400-500 nm), or red (600-700 nm) light at or near light compensation points. Illumination during storage was necessary to maintain dry weight and regrowth potentials of plantlets in vitro, but light quality had no effect on these parameters. All photoautotrophic plantlets stored in darkness were of poor quality at the time of removal from storage and died when transferred to the greenhouse. Dark-stored photomixotrophic plantlets survived storage for 12 weeks at 5 °C, but declined in appearance (visual quality) as the storage duration increased. Decline in visual quality was greater when plantlets were stored at 10 and 22 °C. Leaf dry weight of illuminated plantlets increased and percentage of leaf yellowing decreased as storage temperature increased. Recovery of illuminated plantlets from photomixotrophic storage was best when plantlets were stored at 22 °C. These plantlets were characterized by increased visual quality (color and form) and increased dry weight compared with those in other treatments. After 60 days in the greenhouse, the dry weight of these plantlets was similar for 4-, 8-, and 12-week storage durations, indicating flexibility in storage time if specific light and temperature provisions are met.

Removal of assimilable organic carbon and biodegradable dissolved organic carbon by reverse osmosis and nanofiltration membranes

The main objective of this study was to evaluate the effectiveness of reverse osmosis (RO) and nanofiltration (NF), under various solution chemistries, on bacterial regrowth potential as quantified by assimilable organic carbon (AOC) and biodegradable dissolved organic carbon (BDOC). The bench-scale experiments, using tap groundwater spiked with acetate as organic carbon, revealed that AOC removals by RO/NF membranes were strongly dependent on charge repulsion. AOC removals were greater at conditions of low ionic strength and low hardness, and were slightly higher at high pH values. BDOC removals by NF membrane also increased with decreasing hardness and ionic strength, and increasing pH. However, the RO membrane showed less dependence on feed solution chemistry for BDOC removal, suggesting that BDOC removal was determined by the combined effect of both size exclusion and charge repulsion. The bench-scale observations were compared to a full-scale drinking water treatment plant that used nanofiltration as a primary treatment process. From full-scale operation, it was observed that nanofiltration was a very effective means to reduce BDOC, but conversely, did not reject the bulk of raw water AOC. The high BDOC rejection by NF membranes at full scale can be explained by size exclusion, since a significant fraction of BDOC in raw surficial ground water consists of compounds, such as humic and fulvic acids, which are larger than the pores of NF membranes. The insignificant AOC rejection observed in the full-scale system was probably due to the low pH, high hardness, and high ionic strength (TDS) of the raw groundwater combined with acid addition during pretreatment. These solution environments repress the electrostatic interaction between charged organic compounds and membranes, allowing passage of small molecular weight compounds and thus reducing AOC rejection.

Mowing Effects on the Growth of Zoysia japonica Steud ‘Wild Type5 Under Low Maintenance

Abstract Zoysiagrass is known for its slow rate of growth and for its ability to form a low growing turf with infrequent mowing. The objective of this study was to investigate the effects of mowing height on the regrowth potential, turf density, and morphology of Zoysia japonica £wild type'. Treatments included an unmowed control, and biweekly mowing at 5.1, 3.8, 2.5, and 1.3 cm. Shoot regrowth after mowing was greater for grass in plots mowed at 2.5 cm and higher than for grass mowed at 1.3 cm through the growing season. Lower mowing heights changed the morphology of the grass by reducing the leaf size, sheath length and also reduced the SiCb content of tissue. Turf density was improved by increased growth of rhizomes and stolons at the 5.1, 3.8, and 2.5 cm height. Shoot and root weight were increased by the 5,1 and 3.8 cm height as compared to the lower mowing heights and the unmowed plot. This research indicates thai Zoysia japonica ‘wild type’ should be mowed at 3.8 cm or higher for best performance u...

Effects of UV irradiation on organic matter

Many paired t‐tests showed—at a 95 percent confidence level—no evidence that UV treatment increased BDOC or AOC.The effects of low‐pressure mercury‐vapor ultraviolet (UV) irradiation at 254 nm on the biological regrowth potential of two surface water and two groundwater sources are reported. Because of possible effects of the pending Ground Water Rule, UV disinfection is being studied as an alternative to chlorination. Water samples to be tested were separated into hydrophilic and hydrophobic fractions. The concentration of biodegradable dissolved organic carbon (BDOC) was measured in nonfractionated and fractionated water samples collected before and after UV treatment at a dosage of 130 mW·s/cm2. Two methods were compared in these analyses: a 30‐day BDOC and a 5‐day assimilable organic carbon (AOC) test. Many paired t‐tests showed (at a 95 percent confidence level) no evidence that UV treatment increased BDOC or AOC. Because results differed in water from different sources, utilities considering UV treatment should evaluate the potential for biological regrowth in their own distribution systems.

The Pseudomonas group as an indicator of potential regrowth in water distribution systems.

The regrowth of micro-organisms in the water distribution system is assisted by the presence of biodegradable organic matter (BDOC). The low concentration of available organic carbon in this type of water favours the growth of bacteria belonging to the Pseudomonadaceae family, as this group can grow better at low concentrations of substrate than other bacteria also present in the distribution system. Although the genus Aeromonas has already been adopted as an indicator of this potential regrowth, members of the Pseudomonadaceae have not yet been proposed as indicators of potential bacterial regrowth in the water distribution system. The results are presented of a year-long study of the Barcelona distribution system in which the presence of Pseudomonas and Aeromonas was analysed and the validity of these micro-organisms as indicators of potential regrowth in the distribution system was assessed. It seems that, at least in the drinking waters of the Barcelona area, Pseudomonas is a better indicator of potential bacterial regrowth than Aeromonas.

Treatment of Groundwater Containing Methane - Combination of the Processing Stages Desorption and Filtration

Methane is produced under anaerobic conditions by metabolic processes in microbes and can occur in waters of the types anoxic-anaerobic (RG 1/2) and anaerobic-reduced (RG 2). If the concentration of methane lies below 0.2 mg/L, then no special treatment processes are required apart from dosing of oxygen and rapid sand filtration, which are performed to remove iron, manganese, and ammonium. The research results show that a higher concentration of methane must be specially treated. From the point of view of stable deferrisation, oxidation of up to 2 mg/L is tolerable in rapid sand filtration. However, an unusual increase in regrowth potential was observed. For this reason, the oxidation of methane should be reduced to 0.5 mg/L until further experiments yield results on the microbiological stability of treated water. Rapid sand filters for nitrification and demanganisation should have a maximum methane loading of 0.2 mg/L. The experiments show that nitrification first occurs at a methane concentration below 0.1 mg/L. During the working in of demanganisation, the inlet water should be free of methane. Therefore desorption is often required. If there is less than 1 mg/L to be degassed, then desorption can be achieved with overpressure in the oxidiser without any change in the carbonate-bicarbonate equilibrium. With other systems, such as packed columns, wetted-wall columns, or percolators, carbon dioxide is removed simultaneously. By means of the coefficients of similarity found, it was shown that methane and carbon dioxide desorb in different proportions depending on the system, and that the discharge of carbon dioxide can be reduced through a decrease in the air/water ratio. Aufbereitung methanhaltiger Grundwässer – Kombination der Verfahrensschritte Desorption und Filtration Methan wird unter anaeroben Bedingungen durch mikrobielle Stoffwechselprozesse gebildet und kann in Wässern der Typen anoxisch-anaerob (RG 1/2) und anaerob-reduziert (RG 2) vorkommen. Liegt die Methankonzentration unter 0.2 mg/L, so sind neben der Sauerstoffdosierung und der Schnellfiltration über Quarzsand, die zur Entfernung von Eisen, Mangan und Ammonium durchgeführt werden, keine speziellen Aufbereitungsschritte notwendig. Die Versuchsergebnisse zeigen, dass eine höhere Methankonzentration besonders berücksichtigt werden muss. Unter dem Gesichtspunkt einer stabilen Enteisenung sind bis zu 2 mg/L Methanoxidation in Schnellfiltern tolerierbar. Allerdings wurde eine erhebliche Zunahme des Wiederverkeimungspotentials beobachtet. Daher sollte die Methanoxidation auf 0.5 mg/L beschränkt werden, bis weitere Untersuchungsergebnisse zur Auswirkung auf die mikrobiologische Stabilität des aufbereiteten Wassers vorliegen. Schnellfilter zur Nitrifikation und Entmanganung sollten mit maximal 0.2 mg/L Methan belastet werden. Die Untersuchungen zeigen, dass die Nitrifikation erst bei einer Methankonzentration unter 0.1 mg/L einsetzt. Während der Einarbeitung der Entmanganung sollte das Zulaufwasser methanfrei sein. Bei vielen Wässern ist daher eine Desorption notwendig. Sind weniger als 1 mg/L Methan zu entfernen, so kann die Desorption ohne Veränderung des Kalk-Kohlensäure-Gleichgewichts bei Überdruck im Oxidator erfolgen. Bei den anderen Anlagen wie Füllkörperkolonne, Rieselfilm oder Riesler wird gleichzeitig Kohlendioxid entfernt. Anhand der ermittelten Ähnlichkeitskoeffizienten konnte gezeigt werden, dass Methan und Kohlendioxid je nach Anlage in unterschiedlichem Verhältnis desorbieren und dass durch eine Verringerung des Luft/Wasser-Verhältnisses der Austrag an Kohlendioxid beschränkt werden kann.

Regrowth of White Clover after Chilling: Assimilate Partitioning and Vegetative Storage Proteins

ABSTRACTUnder temperate climates, grassland species are subjected to overwintering which may significantly influence their early spring growth capacity. In white clover (Trifolium repens L.), it is known that overwintering capacity can differ among cultivars. Ability of this forage legume to recover from winter damage will, therefore, have a great influence on its persistence in grass–clover associations. Experiments were undertaken with two different white clover cultivars (Huia and AberHerald). Leaf appearance rate, dry matter distribution, 14C assimilate partitioning, and vegetative storage protein accumulation were determined in plants subjected to a 4‐wk chilling period (5/0°C, day/night) and subsequent warmer temperatures (15/10°C), and compared with control plants (20/15°C). Chilling treatment decreased leaf appearance rate, with AberHerald producing more leaves than Huia. This can be considered as a major aspect of cold adaptation strategy because leaf appearance rate controlled carbon acquisition. Low temperature increased dry matter partitioning to below‐ground tissues. AberHerald allocated more assimilates to stolons than Huia. Accumulation of a 17.3‐kDa protein, believed to act as a vegetative storage protein, also increased after the chilling treatment. Regrowth was characterized by rapid mobilization of the 17.3‐kDa protein in stolons and by preferential carbon allocation to stolon apices. AberHerald showed a higher regrowth potential than Huia in view of its morphological and physiological characters which include carbon acquisition and assimilate partitioning patterns, favoring shoot regrowth and acquisition of stolon reserves.

Selection of Salmonella typhimurium as an indicator for pathogen regrowth potential in composted biosolids.

In order to select a suitable indicator for monitoring the pathogen regrowth potential of composted biosolids, the growth kinetics of selected bacteria were investigated. Growth parameters of six serovars of Salmonella and three strains of Escherichia coli in sterilized compost were compared. Seeded Salmonella and E. coli grew rapidly, reaching population densities of more than 10(8) g-1 after 30 h of incubation. The specific growth rates of Salmonella serovars and E. coli strains were similar and varied from 0.49 to 0.55 h-1. The specific growth rate of the Salm. Typhimurium isolates was significantly higher than the other bacterial strains. It was concluded that an antibiotic-resistant strain of Salm. Typhimurium can be used as an indicator for a pathogen regrowth potential test.

Regrowth potential of coliforms after UV disinfection of municipal wastewater

Photoreactivation of fecal coliforms and subsequent regrowth was investigated in effluents of wastewater treatment plants using ultraviolet light as the disinfectant. Shielding of bacteria ingested in Daphnia sp in the plant outfalls was shown to be a major contributor to increased fecal coliform, E. coli, fecal streptococci and enterococci after fragmentation of the Daphnia sp due to normal dieoff. Representative fecal coliform colonies that comprised the regrowth population were identified to species with E. coli, a small fraction of the total fecal coliform population.

Grazing response groups among understorey plants in arid rangelands

Abstract.We analysed attributes of the understorey flora in different plant communities along two grazing gradients in arid Australian rangelands. We aimed to determine if there were patterns among species in response to grazing, and easily recognizable ‘indicator response types’ for monitoring grazing‐induced change in community composition. Measurements were stratified by vegetation patch type, in woody groves and open patches. Trait selection and analyses followed a hierarchical approach which searched for patterns within major plant life forms. Patch type exerted a dominant influence on both life forms and species attributes, but interacted with grazing. Grazing was associated with loss in differentiation of species composition between patch types, rather than loss in numbers of species overall. Heavy grazing was variously associated with small size, prostrate habit, low meristems, small leaves, coated leaves, high regrowth potential, plasticity in response to grazing, and high fecundity; and light grazing with opposing attributes. Many attributes tended to vary independently of each other and grazing‐related attribute syndromes were recognisable only among grasses. This could be because the environmental filters acting on the communities have given rise to many different species with different natural attribute combinations, few of which are closely associated with grazing resistance. For grassy communities ‘large, erect tussocks branching above‐ground’ and ‘small, sprawling basal tussocks’ may have potential as response types indicative of light and heavy grazing respectively, but no response types could be identified for herbaceous communities.

Advanced Wastewater Disinfection Technologies: State of the Art and Perspectives

Chlorination/dechlorination and advanced disinfection processes (UV irradiation, ozonation, membrane filtration) have been reviewed in terms of their efficiency, regrowth potential, design parameters, experimental set-up, scale-up and industrial experiences. Existing results show the great influence of water quality, in particular of suspended matter concentration and organic content. The efficiency and reliability of these processes are evaluated for different reuse applications. The critical analysis of the literature data and experimental results highlights UV irradiation as an effective and competitive advanced disinfection process. Ozonation is a viable solution in case of higher requirements for water quality including virus and protozoa removal. Ultrafiltration is a highly efficient process producing an excellent quality and totally disinfected effluent, particularly recommended for groundwater recharge and potable wastewater reuse. The choice between these advanced disinfection technologies depends on wastewater quality, existing standards, specific reuse applications and wastewater treatment work capacity.

Influence of NF on distribution system biostability

In a 12‐month study, nanofiltration achieved high percentages of BDOC removal but was less effective in reducing AOC concentrations.When biodegradable organic matter is not removed during water treatment, bacteria may proliferate in the distribution system. This bacterial growth can deteriorate water quality, accelerate pipe corrosion, and potentially increase the incidence of bacteriological diseases. This project's main objective was to collect and analyze full‐scale system data on long‐term results of nanofiltration (NF) with respect to its effect on bacterial regrowth potential as quantified by assimilable organic carbon (AOC) and biodegradable dissolved organic carbon (BDOC). One of the major observations over the sampling period was that NF had a strong effect on the BDOC concentration of the treated water. In contrast, NF did not reject the major fraction of AOC, which leaves NF's effect on biostability open to question.

Postoperative residual tumor growth of meningioma can be predicted by MIB-1 immunohistochemistry

Meningiomas are benign tumors that can be cured by surgical removal. However, tumors located deeply within or close to vital structures cannot be removed completely and require repeated surgery. This study was designed to clarify whether immunohistochemical study using MIB-1 monoclonal antibody is useful for determining the rate of regrowth for this tumor. Tumor volume doubling time (Td) was measured by using computed tomography or magnetic resonance imaging neuroimages during 29 different follow-up periods after surgery. MIB-1 monoclonal antibody was used to stain Ki-67 proliferating cell antigen in surgical specimens, and the MIB-1 staining index (SI) was determined independently of neuroimaging analysis. These two values and other clinical parameters were analyzed statistically. The Td values varied from 19-6830 days (median, 350 days); the Td values were <365 days in 15 cases, 365-730 days in 8 cases, and >730 days in 6 cases. There was no significant correlation between age and Td value, but all 6 patients whose Td values were >2 years were age >50. There was a strong inverse correlation between log(Td) and MIB-1 SI (P < 0.001). In three cases, more than three surgical procedures were performed for tumor recurrence. The MIB-1 values did not increase at the time of the first recurrence but increased at later recurrences. The calculated Td values also were not shortened until the second recurrence. Using the MIB-1 SI makes it possible to predict the regrowth potential of a tumor after initial surgery.

PROSTATE GLAND GROWTH DURING DEVELOPMENT IS STIMULATED IN BOTH MALE AND FEMALE RAT FETUSES BY INTRAUTERINE PROXIMITY TO FEMALE FETUSES

In rodents, steroid hormones are transported between adjacent fetuses, and male or female fetuses that develop in utero between female fetuses (2F males or 2F females) have higher serum levels of estradiol and lower serum levels of testosterone relative to siblings of the same sex that develop between two male fetuses (2M males or 2M females). The present study was prompted by the prior unexpected finding that as adults, 2F male mice have an enlarged prostate, and increased numbers of prostatic androgen receptors relative to 2M males. We examined prostate development in both male and female rat fetuses from different intrauterine positions using computer-assisted, 3-dimensional reconstruction of the urogenital complex. In males, this included the prostate, seminal vesicles and utricle (a remnant of the Müllerian ducts), while in females it included development of prostatic glandular buds. The mean cross-sectional area of developing prostatic epithelial buds, utricle and seminal vesicles was significantly increased in 2F male relative to 2M male fetuses. In female fetuses, prostatic bud development was significantly more likely to occur in 2F (67%) than in 2M (29%) animals. These findings suggest that the transport of a small supplement of estrogen from adjacent female fetuses enhances androgen-dependent accessory organ development. We also found that mRNAs encoding receptors for both estrogen and androgen were located in the mesenchyme of the developing male prostate. The localization of estrogen and androgen receptor mRNA in this region further suggests that the mesenchymal induction of prostatic epithelial growth involves both hormones. The cranial dorsolateral prostatic buds exhibited the greatest enlargement in 2F males. This region of the developing prostate in rats is comparable (that is the embryonic homologue) to the region exhibiting benign prostatic hyperplasia (BPH) during aging in men. We propose that the potential for pathological regrowth of the prostate during aging is imprinted by estradiol during fetal development.

Fall cutting management affects yield and persistence of alfalfa in Atlantic Canada

The existing recommendation to avoid harvesting alfalfa during a critical fall rest period, based on calendar dates, is under review in Canada and adjacent areas of the United States. The effect on yield and persistence of four fall cutting management treatments (based on cumulative growing degree-days between harvests) was investigated for two cultivars of alfalfa (Medicago sativa L. 'Apica' and 'Oneida VR') at five sites in Atlantic Canada. The average seasonal DM yield for the five sites in the first production year was 1.6 to 2.3 t ha−1 greater with an additional harvest as compared with the two-harvest system (Truro, Nappan, Fredericton, and Charlottetown) and the one-harvest system in St. John's. Seasonal DM yield benefits were reduced over time; by the third production year, there was no increase in seasonal DM yield with an additional harvest. The seasonal DM yield increased with increasing the interval between the final harvest and the previous one. Taking an additional harvest resulted in higher winter plant mortality between the first and second production years in Truro and Nappan, and the third and fourth production years in St. John's. At the other two sites (Charlottetown and Fredericton), and for the first three production years in St. John's, winter plant mortality was unchanged with an additional harvest but regrowth potential in the following year was reduced. At the two sites that experienced a severe winter (Nappan and Truro), the cultivar Oneida VR was more adversely affected by the additional harvest than Apica. Our results indicate that in Atlantic Canada, taking an additional harvest increases the risk of winterkill. If an additional harvest is to be taken, increasing the interval between the final harvest and the previous one to at least 500 growing degree-days will decrease the risk of winterkill and might have a positive effect on next year's regrowth. Key words: Medicago sativa L., alfalfa, yield, persistence, harvest management, cultivar

Advanced wastewater disinfection technologies: State of the art and perspectives

Chlorination/dechlorination and advanced disinfection processes (UV irradiation, ozonation, membrane filtration) have been reviewed in terms of their efficiency, regrowth potential, design parameters, experimental set-up, scale-up and industrial experiences. Existing results show the great influence of water quality, in particular of suspended matter concentration and organic content.The efficiency and reliability of these processes are evaluated for different reuse applications. The critical analysis of the literature data and experimental results highlights UV irradiation as an effective and competitive advanced disinfection process. Ozonation is a viable solution in case of higher requirements for water quality including virus and protozoa removal. Ultrafiltration is a highly efficient process producing an excellent quality and totally disinfected effluent, particularly recommended for groundwater recharge and potable wastewater reuse. The choice between these advanced disinfection technologies depends on wastewater quality, existing standards, specific reuse applications and wastewater treatment work capacity.

神経薬理・シリーズ教育講座 ４．ほ乳動物中枢神経伝導路の再生

Contrary to the current concept of abortive regeneration of mammalian central axons, marked and functionally active regeneration of the mammalian CNS pathway has been found to occur. In addition, the concept seems to be now widely accepted that the axonal environment is non-permissive for regeneration because of inhibitory activity derived from oligodendrocytes and CNS myelin, and that therefore, those procedures that render the environment permissive for regeneration are essential, e.g., graft of peripheral nerves, Schwann cells or olfactory ensheathing cells, and application of antibody for neurite growth inhibitors with or without neurotrophic factor. However, this idea is not true. These procedures led to sparse, dispersed and largely aberrant regeneration. By contrast, in our experiment using a young rat, a very sharp cut of the pyramidal tract at the level of the medulla produced edema-free lesions without subse-quent formation of either cysts or scars, and eventuated marked regeneration, very close to normal in the amount, extension, path, formation of a compact bundle, and termination. This manner of marked regeneration was also observed in the cerebellifugal projection, auditory pathway, vestibulospinal tract, and dorsal column axons. Thus, we conclude that whether or not axonal regeneration occurs depends on local condition of lesion rather than the global CNS axonal environment.Even in adult animals, embryonic brain tissue grafts introduced into the lesion site, which presumably contain axonal guidance cues by excising homotopic embryonal structure, induce marked and functionally active regeneration. The graft contains comprehensive axonal guidance cues, although the detailed mechanism of axonal guidance have yet to be elucidated sufficiently. The best treatment for brain and spinal cord injury is obviously to reconstruct the damaged neural connections. The enormous potential for regrowth and self-organization arouse a great hope for therapeutic breakthoughs in the near future.