Testing the effect of selectors in the control of bulking and foaming in full scale activated-sludge plants.

Selectors were operated at four full-scale activated sludge plants to control bulking and foaming problems due to filamentous microorganisms. Selector effectiveness was not related to reduction of biodegradable organic matter in the contact zone, but was related to soluble COD levels in selector effluent. Significant reductions in the numbers of filamentous m icroorganisms were reported.

Spatial distribution of microorganisms and measurements of oxygen uptake rate and ammonia uptake rate activity in a drinking water biofilter.

The biofilm characteristics (population dynamics and biofilm composition) in a biological filter for the removal of iron, manganese and ammonium were studied in a drinking water treatment plant. The objective was to examine the spatial distribution and biological composition of active biomass that grows in a biological filter and to verify the effect of the backwashing on the quantity of fixed biomass and on the density and activity of the biological population. Heterotrophic microorganisms activity was higher in the upper layer of the filter. Nitrifying microorganisms colonized the biofilter in a stratified manner and their activity was higher in the second layer of the filter. A total of 14 species of ciliated protozoa and 7 species of filamentous microorganisms were found in the biofilters. Ciliates were concentrated in the filterbed layer in which the heterotrophic activity was higher. The grazing activity of ciliates on heterotrophic bacteria reduced the competition pressure on nitrifying microorganisms, supporting their growth and thus raising the ammonium removal efficiency. In general, filamentous microorganisms appeared to be indifferent to operating changes in the plant such as backwashing and filtering cycles. Crenothrix was the prevalent filamentous microorganism in terms of both frequency and abundance; it was found prevalently in the first layer where the oxidisation of iron and manganese occurred.

Evaluation of dialysis access care by means of process quality indicators.

Improvement of dialysis access management depends on technical skill but also on effective choice, construction, monitoring and revision of the access. Surgical procedure is only one step of a complex course, beginning with the referral of patients to nephrologists. Using two process quality indicators, we describe the evolution of access management at our centre, where access surgery and access-related activities are performed by nephrologist. The first process indicator is based on the prevalence of temporary access at first dialysis (TA1st) in end stage renal disease ESRD patients, the second one measures the prevalence of permanent central venous catheters (%CVC) in dialysis population. TA1st increased to 27.1% in 1999, more than twofold compared to the previous year. There was also an increase in %CVC from 20.6 to 26.3%. Native access remained the most utilised, well above 70% of dialysis patients. Our process monitoring suggests a rapid worsening of late referral, as indicated by the increasing use of temporary catheters at the beginning of chronic dialysis. Increasing surgical activity and diagnostic procedures were only partly effective in containing the rise in CVC. Venous sparing, early referral, Continuous Quality Improvement and a multiprofessional access-team co-ordinated by a nephrologist could be the key-elements in facing the never-ending-story of dialysis vascular access.

Contrast-enhanced sonography in early kidney graft dysfunction.

OBJECTIVES: The aim of this study was a comparison of contrast-enhanced sonography (CEUS) and power Doppler ultrasound (US) findings in renal grafts within 30 days posttransplantation. METHODS: A total of 39 kidney recipients underwent CEUS (SonoVue bolus injection) and US examinations at 5 (T0), 15 (T1), and 30 (T2) days after grafting. The results were correlated with clinical findings and functional evolution. Fourteen patients displayed early acute kidney dysfunction: 10 had acute tubular necrosis (acute tubular necrosis [ATN] group); four acute rejection episodes (ARE group); 25 with normal evolution (as control, C group). Renal biopsies were performed to obtain a diagnosis in the four ATN cases and in all ARE patients. Creatinine and estimated glomerular filtration rate were used as kidney function parameters. CEUS analysis was performed both on cortical and medullary regions while US resistivity indexes (RI) were obtained on main, infrarenal, and arcuate arteries. From an analysis of CEUS time-intensity curves, we computed peak enhancement (PEAK), time to peak (TTP), mean transit time (MTT), regional blood flow (RBF) and volume (RBV), and cortical to medullary ratio of these indies (RATIO). RESULTS: An increased RI was present in the ATN and ARE groups as well as a reduced PEAK and RBF. RATIO-RBV and RATIO-MTT were lower than C among ATN cases, while TTP was higher compared to C in ARE. No statistical difference was evidence for RI between ATN and ARE groups. MTT (T0) was significantly related to creatinine at follow-up (T2). CONCLUSIONS: US and CEUS identified grafts with early dysfunction, but only some CEUS-derived parameters distinguished ATN from ARE, adding prognostic information.

Formation of reiterated simian virus 40 DNA.

We have described studies on the biological fate of a minicircular DNA molecule that is a specific, complex deletion mutant of SV40. When the minicircular DNA alone was used to infect monkey cells, its replication was not detected. However, after infection with the minicircles and SV40 DNA together, incorporation of (3H)thymidine into both species of viral DNA was demonstrated. This finding suggests that circular, duplex viral DNA segments, much smaller than SV40 DNA, are able to be replicated in vivo. Furthermore, 26% of the (3H)thymidine-labeled, superhelical DNA sedimented more rapidly than SV40 DNA I (21S) in neutral sucrose gradients (22S-32S). A similar amount of this rapidly sedimenting DNA was also detected when intact DAR DNA containing the triplication mutant was tested. Cleavage of the purified, rapidly sedimenting DNA with R.EcoRI produced 10.4S segments (one-third the size of unit-length SV40) in addition to full-length linears (14.5S) and a new cleavage product (16.7S). Cleavage of the 21S DNA I molecules also produced 10.4S DNA. These results indicate that the minicircular molecules are amplified in vivo, yielding not only the original triplication mutant but also a heterogeneous population of oligomers in which the 10.4S segment has been reiterated as many as 6 to 9 times. Our studies support the model proposed by Khoury et al. (1974) for the generation of the original DAR triplication mutant. In our experiments, cells were infected with a minicircular DNA molecule formed in vitro, which then served as a precursor in vivo in the formation of trimers and higher oligomers, as predicted by the proposed model. The DAR triplication mutant first appeared after the third passage in primary monkey kidney cells and rapidly became the predominant species in later passages (Fareed et al. 1974)...

[High frequency oscillatory ventilation (HFOV) in the newborn. Study of 10 cases]. / Ventilazione meccanica ad alta frequenza oscillatoria (HFOV) nel neonato. Studio di dieci casi.

OBJECTIVE: To evaluate clinical effectiveness of high frequency oscillatory ventilation (HFOV) with a high-volume strategy in severe neonatal respiratory failure from different causes. PATIENTS AND METHODS: Infants with respiratory failure with oxygenation index (O.I.) > 10, independently from weight, gestation age, kind of respiratory disease, previous treatment with conventional mechanical ventilation (IPPV). Patients were treated with respirator Sensormedics 3100 A. Values of O.I. were recorded at start of HFOV and after 1/2, 6 and 24 hours. Also blood gases, arterial blood pressure and vital data were monitored. If HFOV failed infants were allowed to be shifted to IPPV. RESULTS: 10 infants were selected whose gestation age was comprised between 25-38 weeks and birth weight between 640-2620 grams. Mean value of O.I. at the beginning of HFOV was 31.5 +/- 25.1. In all cases but one O.I. decreased rapidly after HFOV and improvement was significant after 6 hours (10.7 +/- 6.3; p < 0.003) still improving after 24 hours (9.5 +/- 5; p < 0.002). The neonate that did not respond to HFOV had severe congenital valvular aortic stenosis and weighted 930 grams. Four infants died: 3 after response of respiratory failure to HFOV and 1 for cardiopathy. Side-effects were: i) edema in all infants that was treated with furosemide, and ii) transient decrease of sistemic blood pressure after start of HFOV in 6 infants that was treated easily with low-dosage dopamine infusion. No significant increase of the rate of complicating disease was observed in survived patients. CONCLUSION: HFOV with high-volume strategy was able to improve rapidly and significantly O.I. in severe neonatal respiratory failure without increasing complications in survivors. Edema was present in all infants and this might depend on the relatively tardy use of HFOV that required higher mean airway pressures. A more precocious intervention has to be considered in clinical practice.

Structure of a defective simian virus 40 genome bearing an operator from bacteriophage lambda.

We examined further the physical structure of the simian virus 40 (SV40) and bacteriophage lambda DNA sequences in an SV40-lambda hybrid that had been propagated in monkey kidney cells. The SV40 vector portion of the hybrid, which was a small fragment isolated from a reiteration mutant of SV40, contained the site for initiation of SV40 DNA replication. Electron microscope heteroduplex and restriction endonuclease analyses revealed a tandem duplication of the SV40 vector segment linked to a 2,300-base pair portion (lambda map units 71 to 76) of the lambda immunity region. The defective hybrid genome thus harbors two origins for SV40 DNA replication in addition to the leftward operator and the N gene of lambda.

Construction and propagation of a defective simian virus 40 genome bearing an operator from bacteriophage lambda.

A 2400 base pair DNA segment containing the leftward operator (OL) of phage lambda was covalently joined in vitro to a fragment of simian virus 40 (SV40) DNA harboring the SV40 replication origin. The recombinant molecule was propagated in the presence of helper wild-type SV40 DNA in monkey kidney cells and partially cloned by an infectious center procedure. After propagation in monkey cells and purification, the hybrid DNA could be distinguished from wild-type SV40 DNA by its shortened length (about 80% that of SV40), specific hybridization to denatured lambda DNA immobilized on filters, specific affinity for lambda repressor, and preservation of a large part (about 2300 base pairs) of the lambda immunity region as determined by restriction nuclease cleavage patterns and electron microscopic heteroduplex analysis. These results indicate that defective SV40 replicons can serve as vectors for propagating foreign DNA in mammalian cells.

Propagation of a segment of bacteriophage lamda-DNA in monkey cells after covalent linkage to a defective simian virus 40 genome.

A 520 base pair DNA segment was excised from the bacteriophage lamda-genome by cleavage with the bacterial restriction endonuclease, endo R. Hindll. This segment was covalently joined in vitro to an 880 base pair simian virus 40 (SV40) DNA segment which contains the initation site for SV40 DNA replication. The latter segment was derived from the genome of a defective reiteration mutant of SV40 also by endo R. Hindlll cleavage. When the recombinant molecule, together with wild-type SV40 DNA as helper, was introduced into monkey cells by DNA infection, replication of the lamda-DNA sequences was observed, and hybrid genomes were encapsidated into progeny SV40 virions. The structure of the lamda-DNA segment after serial passage in monkey cells was examined by use of restriction endonucleases and electron microscopic heteroduplex analysis.

Effects of the GABAergic agent sodium valproate on the arginine vasopressin responses to hypertonic stimulation and upright posture in man.

In order to evaluate the possible influence of GABAergic neurotransmission on the arginine vasopressin (AVP) response to osmotic and pressure volumetric stimuli, the GABAergic drug sodium valproate was administered by mouth (200 or 400 mg 16 h, 8 h and just before tests) to eight normal men before osmotic (i.v. infusion of 0.51 , NaCl for 2 h) and orthostatic (standing upright and maintaining an orthostatic position for 20 min) tests. In both experimental conditions, the AVP rise was significantly lower in the presence than in absence of sodium valproate. The maximum AVP responses in the control orthostatic and osmotic tests were respectively 2.3 and 2.5 times higher than basal levels. When 600 mg sodium valproate was given, the maximum AVP rise in response to hypovolaemic and osmotic stimuli were respectively 1.75 and 2.1 times higher than basal value. Similar results were obtained giving 1.2 g sodium valproate. These results suggest that in man a GABAergic pathway is involved in the AVP responses to hypovolaemic and hyperosmotic stimuli.