Process of ammonia removal from anaerobic digestion and associated ammonium sulphate production: Pilot plant demonstration

A process for the continuous extraction of ammonia from anaerobic digesters is proposed. In this process, a portion of the sludge treated in the digesters is continuously withdrawn and transferred to a thin film evaporator (TFE) unit, where the ammonia is stripped through a biogas stream. The ammonia-rich biogas is treated with a sulfuric acid/water solution in a reactive absorption unit, with production of ammonium sulphate. The chemistry of a CH₄/CO₂/NH₃ gas phase in thermodynamic equilibrium with a liquid sulfuric acid/water solution is investigated theoretically, with focus on the simultaneous absorption of CO₂ and NH₃ into the liquid phase. Pilot plant experimental data confirm the theoretical results. Further pilot plant experimental results obtained during on-off cycles of the stripping equipment demonstrate that, when the TFE unit is off, ammonia concentration in the digestate rises quickly, while, when the stripping equipment is turned on again, ammonia concentration drops down. On average, during the 180 days of pilot plant experimentation, 4.1 g N-NH₄ per kg of sludge fed to the digester, i.e. 19.3 g N-NH₄ per kg of total solids (TS) fed to the digester, are stripped from digestate and recovered as ammonium sulphate, demonstrating the feasibility of the proposed concept.

Deoxygenation of waste cooking oil and non-edible oil for the production of liquid hydrocarbon biofuels

Deoxygenation of waste cooking vegetable oil and Jatropha curcas oil under nitrogen atmosphere was performed in batch and semi-batch experiments using CaO and treated hydrotalcite (MG70) as catalysts at 400 °C. In batch conditions a single liquid fraction (with yields greater than 80 wt.%) was produced containing a high proportion of hydrocarbons (83%). In semi-batch conditions two liquid fractions (separated by a distillation step) were obtained: a light fraction and an intermediate fraction containing amounts of hydrocarbons between 72-80% and 85-88% respectively. In order to assess the possible use of the liquid products as alternative fuels a complete chemical characterization and measurement of their properties were carried out.

ANGIOTENSIN II INCREASES TISSUE-SPECIFIC INHIBITOR OF METALLOPROTEINASE-2 EXPRESSION IN RAT AORTIC SMOOTH MUSCLE CELLS IN VIVO: EVIDENCE OF A PRESSURE-INDEPENDENT EFFECT

1. Angiotensin (Ang) II plays a major role in vascular remodelling. Matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs) are involved in the tissue remodelling processes. The aim of the present study was to investigate whether AngII modulates TIMP-2 expression in rat aortic smooth muscle cells in vivo. 2. Angiotensin II (200 ng/kg per min, s.c.) or AngII + losartan (10 mg/kg per day, s.c.) or normal saline was administered continuously by osmotic minipumps to Sprague-Dawley rats for 1 week. In addition, the effect of endogenous AngII on TIMP-2 expression was evaluated in renovascular hypertensive rats (two kidney, one clip (2K1C) and one kidney, one clip (1K1C) models). Control rats (sham 2K1C and sham 1K1C rats) underwent sham-clipping of the left renal artery. At the end of the treatment, plasma renin activity was measured by radioimmunoassay, aortic TIMP-2 mRNA expression was evaluated by real-time polymerase chain reaction and/or northern blotting and protein expression was evaluated by immunohistochemistry. Systolic blood pressure (SBP) was measured twice a week by the tail-cuff method. 3. Exogenous AngII administration produced the expected increase in SBP (P = 0.02) compared with the control saline-treated group. The increase in SBP was abolished in AngII + losartan-treated rats. Administration of AngII caused a significant increase in TIMP-2 expression (P = 0.01) in rat aortic smooth muscle cells that was abolished in AngII + losartan-treated rats. In renovascular hypertensive rats, SBP was higher (P < 0.0001) in 2K1C and 1K1C rats compared with the corresponding sham-operated rats. Plasma renin activity was higher (P < 0.01) in 2K1C rats compared with the other groups. The expression of TIMP-2 was significantly (P < 0.05) increased only in 2K1C rats. 4. Our in vivo data demonstrate that exogenous and endogenous AngII increases TIMP-2 expression in rat aortic smooth muscle cells. This effect is not dependent on the AngII-induced increase in blood pressure and is mediated by angiotensin AT1 receptors.

Adsorption of trimethoxysilane and of 3-mercaptopropyltrimethoxysilane on silica and on silicon wafers from vapor phase: an IR study

The interaction of trimethoxysilane (TMS) and of 3-mercaptopropyltrimethoxysilane (MPTMS) with silica and silicon wafers has been studied by the mean of transmission FTIR spectroscopy. TMS vapor adsorption on silica's silanols results in the formation of Si-O-Si bonds at room temperature, mainly through the elimination of one methanol molecule per TMS molecule. Similarly, MPTMS vapor reacts with the surface through "hydroxolysis" of one of Si-O-CH3 bonds, and most of the molecules have their SH group free. The same species is formed over the silicon wafer surface. On the other side, deposition of liquid MPTMS over silicon surface leads to the detection of spectral features characterizing a condensed layer.

Assessment of selective homing and contribution to vessel formation of cryopreserved peripherally injected bone marrow mononuclear cells following experimental myocardial damage

In view of a potential clinical use we aimed this study to assess the selective homing to the injured myocardium and the definitive fate of peripherally injected labeled and previously cryopreserved Bone Marrow Mononuclear cells (BMMNCs). The myocardial damage (cryoinjury) was produced in 59 rats (45 treated, 14 controls). From 51 donor rats 4.4 x 10(9) BMMNCs were isolated and cryopreserved (slow-cooling protocols); the number of CD34+ and the viability of pooled cells was assessed by flow-cytometry analysis before and after cryopreservation and simulated delivery through a 23G needle. Seven days after injury, BMMNCs were thawed, labeled with PKH26 dye and peripherally injected (20 x 10(6) cells in 500 microl) in recipient rats. Two weeks after experimental injury, the heart, lungs, liver, kidneys, spleen and thymus were harvested to track transplanted cells. Except a small amount in the spleen, PKH26+ cells were found only in the infarcted myocardium of the treated animals. Typical vascular structures CD34+ were found in the infarcted areas of all animals; treated rats showed a significantly higher number of these structures if compared with untreated. Morphological ultra-structural examination of infarcted areas confirmed in treated rats the presence of early-stage PKH26+ vascular structures derived from injected BMMNCs. The estimated mean CD34+ cells loss due to the cryopreservation procedure and to the system of delivery was 0.24% and 0.1%, respectively, confirming the feasibility of the procedure. This study supports the possible therapeutic use of cryopreserved peripherally injecetd BMMNCs as a source of CD34+ independent vascular structures following myocardial damage.

Angiotensin II modulates calponin gene expression in rat vascular smooth muscle cells in vivo

OBJECTIVES

It has been shown that angiotensin II (Ang II) induces the expression of calponin, a 34 kD actin-binding protein, in vascular smooth muscle cells in vitro. The aim of this study was to investigate whether Ang II can modulate calponin gene expression in rat aorta in vivo.

DESIGN

Aortic calponin gene expression was studied after chronic exogenous Ang II administration and in Goldblatt hypertension.

METHODS

To investigate the effect of Ang II administration, Sprague Dawley rats were treated for 6 days with a continuous infusion of Ang II (200 ng/kg per min) or saline by osmotic minipumps. The effect of endogenous Ang II on aortic calponin mRNA expression was studied in Goldblatt hypertensive rats with (2K1C model), or without (1K1C model) activation of the renin-angiotensin system. In particular, calponin gene expression in 2K1C rats was studied both at 1 week (2K1C-HR, high renin) and 4 weeks after the onset of hypertension, when plasma renin activity (PRA) was returned to normal values (2K1C-NR, normal renin). Systolic blood pressure (SBP) was measured twice a week. At the end of the experimental period, PRA was measured by radioimmunoassay, and aortic calponin gene expression was measured by Northern hybridization.

RESULTS

SBP was significantly higher (P < 0.01), whereas PRA was suppressed (P < 0.01), in Ang II versus saline-treated rats. Northern hybridization showed that the aortic calponin gene expression significantly increased (2.5-fold) in Ang II-treated rats (P = 0.01). In Goldblatt hypertensive rats, SBP was significantly higher in 2K1C-HR (P < 0.01), 2K1C-NR (P < 0.01) and 1K1C (P < 0.01) rats compared with the corresponding sham-treated rats. Activation of the renin-angiotensin system was present only in 2K1C-HR rats (P < 0.01), and Northern analysis showed that aortic calponin mRNA expression was significantly increased (2.2-fold) in this group of rats only (P < 0.01).

CONCLUSIONS

Our data demonstrate that both exogenous and endogenous Ang II increase calponin gene expression in aortic smooth muscle cells, independently of the hemodynamic effect of Ang II.

Behavioural stress blunts the creatinine clearance increase induced by a protein load in healthy subjects

BACKGROUND

The aim of this study was to investigate how behavioural states related to different levels of stress affected the increments of glomerular filtration rate induced by an acute protein load.

METHODS

Thirteen healthy subjects were enrolled. Each subject was studied from 9:00 h to 15:00 h on two consecutive days. In random order, after a protein meal (1.2 g/kg b.w. of protein), each subject was required to remain in a relaxing, sitting position (resting period, R), or to solve graphical and mathematical problems (behavioural stress period, S). Mean blood pressure (MBP) and heart rate (HR) were monitored by an ambulatory blood pressure device. Urine samples collected in each period were used to measure glomerular filtration rate (GFR, creatinine clearance) and urinary sodium excretion (UNa+V).

RESULTS

Significant decreases in MBP and HR were observed during the resting period after the protein load, which significantly increased GFR. There was also a large increase of UNa+V. During S, the GFR changes were no longer seen whereas the increse of UNa+V was maintained. HR and MBP did not change compared to the prestimulus period.

CONCLUSIONS

We conclude that in healthy subjects behavioural stress can blunt the increase in GFR that follows a protein load, presumably by neuro-humoral activated mechanisms. In our experimental conditions, behavioural stress did not affect UNa+V.

Role of the renal nerves in the control of renin synthesis during different sodium intakes in the rat

OBJECTIVE

The aim of this study was to evaluate the role of the renal nerves in the regulation of renin synthesis in normotensive rats at different sodium balance.

METHODS

Forty-eight male Sprague-Dawley rats were divided in six experimental groups, combining three diets at different NaCl content (normal 0.4%, low 0.04% or high 4.0%), and the surgical, bilateral renal denervation or the sham procedure. After 7 days of dietary treatment, all rats were sacrificed and plasma renin activity (PRA) was measured. Renin messenger RNA (mRNA) levels in the renal cortex were determined by semiquantitative polymerase chain reaction.

RESULTS

PRA was higher in animals fed the low sodium diet compared with those at standard diet, while it was lower in animals fed the high sodium diet. Renal denervation decreased PRA in normal and low sodium groups, while it did not alter the PRA values in the high sodium group. Renin gene expression significantly increased in rats fed with the low sodium diet compared with the standard diet group, and significantly decreased in rats fed the high sodium diet Renal denervation significantly reduced renin mRNA levels in rats receiving the low sodium diet, but did not produce any significant change in normal or high-sodium groups.

CONCLUSION

The activation of renin gene expression during sodium depletion in rats is dependent on the presence of the renal nerves, while the suppression of renin gene expression during a sodium load seems to be due to the macula densa mechanism alone.

Short-term analysis of the relationship between blood pressure and urinary sodium excretion in normotensive subjects

The aim of this study was to investigate whether, in the short term, physiological blood pressure changes are coupled with changes in urinary sodium excretion in normotensive subjects, maintained at fixed sodium intake and under controlled postural and behavioural conditions. Twelve normotensive subjects were recruited. For each subject, seven urine samples were collected at fixed time intervals during an overall 26 h period: late afternoon (16.00-20.00 hours), evening (20.00-24.00 hours), night (24.00-06.00 hours), quiet wakefulness (06.00-09.00 hours), morning (09.00-12.00 hours), post-prandial (12.00-15.00 hours) and afternoon (15.00-18.00 hours). Blood pressure was monitored by an ambulatory blood pressure device during the whole 26 h period. Each urine sample was used to measure urinary sodium excretion and glomerular filtration rate (creatinine clearance). Blood pressure, heart rate, urinary sodium excretion and glomerular filtration rate recorded in the daytime were higher than those measured during the night-time. A significant positive correlation between mean blood pressure and urinary sodium excretion was found during the night, over the whole 26 h period, and during two subperiods of the daytime: quiet wakefulness and the post-prandial period. The coefficient of the pressure-natriuresis curve was significantly decreased by postural changes. We conclude that, in normotensive subjects, blood pressure and urinary sodium excretion are coupled in the short term. The assumption of an upright posture can mask this relationship, presumably by activating neurohumoral factors.

Effects of adenosine receptor agonists on renal function in anaesthetized rats

OBJECTIVES

To investigate the effects of the interaction between adenosine receptors and renal nerves on urinary sodium excretion and glomerular filtration rate.

METHODS AND DESIGN

The effects on water and sodium excretion and glomerular filtration rate of A1 [2-chloro-N6-cyclopentyl-adenosine (CCPA)] and A2 [2-hesinyl-5'-N-ethyl-carboxamido-adenosine (2HE-NECA)] adenosine agonists were studied in anaesthetized rats with one kidney surgically denervated. Arterial blood pressure, heart rate and rate of urine flow from each kidney were continuously recorded; inulin clearance was used as an index of glomerular filtration rate. The experiments were performed with three groups of rats, into which, after a control period of 20 min, CCPA, 2HE-NECA or vehicle was infused for two subsequent 20 min periods.

RESULT

During infusion of CCPA, the slight decrease in arterial pressure was associated with a transient decrease in glomerular filtration rate and marked long-lasting decreases in heart rate, water and sodium excretion and fractional sodium excretion. The response of the innervated kidney was similar to the response of the denervated kidney. Infusion of 2HE-NECA caused decreases in arterial pressure, glomerular filtration rate and excretion of water and sodium associated with an increase in heart rate. The reduction of water and sodium excretion from the innervated kidney was larger than that from the denervated kidney.

CONCLUSIONS

Activation both of A1 and of A2 receptor causes a reduction in urinary water and sodium excretion. The renal response to activation of A2 receptors is enhanced by the presence of renal nerves, whereas the response to activation of A1 receptors is not influenced by renal nerves.

Effects of erythropoietin administration on blood pressure and urinary albumin excretion in rats

The effects of recombinant human erythropoietin (rHuEPO) administration on blood pressure and urinary albumin excretion were studied in normotensive Wistar-Kyoto rats (WKY), in spontaneously hypertensive rats (SHR), and in SHR rats treated with an angiotensin converting enzyme inhibitor (SHR-ACEi). Rats were housed in metabolic cages and treated with rHuEPO (150 U/kg body weight [bw] three times a week) for 6 weeks. Control animals received the vehicle only (0.25 mL of physiological saline). An angiotensin converting enzyme inhibitor was administered in the drinking water for 6 weeks (spirapril 5 mg/kg bw). Systolic blood pressure (SBP), and 24 h urinary albumin excretion (UAE) were measured once a week. No significant differences in SBP were observed between rHuEPO and vehicle-treated normotensive animals at the end of the treatment (171.9 +/- 4.9 v 172.1 +/- 5.6 mm Hg, respectively). After 6 weeks, SBP was significantly higher in SHR and SHR-ACEi groups treated with rHuEPO than in control groups (239.8 +/- 7.3 and 243.0 +/- 7.3 mm Hg v 218.1 +/- 6.0 and 187.9 +/- 4.6 mm Hg, respectively); UAE was significantly higher in groups treated with rHuEPO than in control groups (WKY: 265.9 +/- 19.5 v 127.0 +/- 12.3 microg/100 g bw, SHR: 1668.4 +/- 564.6 v 234.8 +/- 22.9 microg/100 g bw, and SHR-ACEi: 1522.7 +/- 448.3 v 143.0 +/- 18.9 microg/100 g bw, respectively). We concluded that erythropoietin treatment causes an increase in arterial pressure in SHR only, and an increase in UAE in both normotensive and hypertensive rats. The albuminuric effect was not entirely dependent on increased blood pressure. The treatment with an angiotensin converting enzyme inhibitor did not modify either the proteinuric or the pressor effects.

Characterization of Silica-Containing Aluminum Hydroxide and Oxide Aerogels

Pure and silica-containing Al hydroxide aerogels were prepared by the supercritical drying method. The samples were later calcined, giving rise to alumina and Si-Al mixed oxides. The materials were characterized from the points of view of their bulk and surface structures. The Si-free material before calcination is well-crystallized boehmite that converts to gamma-alumina by calcination. The silica-containing hydroxides are composed of boehmite layers with silicates in the interlayer region. The resulting mixed oxides present silica essentially in the bulk. The surface structure of alumina seems poorly sensitive to silica addition. Surface silanol groups appear only for SiO2 more than 4%. No Bronsted acidity appears. Silica addition allows mixed oxides with higher surface areas to be obtained.

Effects of adenosine-receptor agonists on renin release in anaesthetized rats

OBJECTIVE

To investigate the effects of the interaction between adenosine receptors and renal nerves on renin release.

MATERIALS AND METHODS

The effects on renin secretion of A1 (2-chloro-N6-cyclopentiladenosine) and A2 (2-hexynil-5'-N-ethyl-carboxamido-adenosine) adenosine-receptor agonists were studied in two groups of anaesthetized rats, each with one kidney surgically denervated. Arterial blood pressure and the renal blood flow of innervated and denervated kidneys were continuously recorded. Cannulae were inserted into both renal veins through femoral veins. After 1h of rest, A1 and A2 agonists were intravenously infused for 30 min in the two groups of rats. Plasma renin activity was measured by radioimmunoassay in blood samples drawn simultaneously from both renal veins and the femoral artery before and after the drug infusion.

RESULTS

Infusions of A1 and A2 agonists produced comparable hypotensive effects. During A1 agonist administration, the heart rate decreased significantly, but it did not change after A2 agonist treatment. Renal blood flow was reduced by administration of the A1 agonist in both kidneys, while A2 agonist administration significantly reduced the renal blood flow of the innervated kidney only. The veno-arterial difference in plasma renin activity decreased after the A1 agonist infusion in both kidneys, but after the A2 agonist infusion it increased significantly in the innervated kidney only.

CONCLUSIONS

Renal nerves do not influence the inhibition of renin release mediated by A1 adenosine receptors. In vivo, A2-receptor agonist administration can stimulate renin release only in the presence of intact renal nerves.