Lower Po Research Articles

Antibody-induced anemia in fetal sheep: model for hemolytic disease of the fetus and newborn.

Our purpose was to produce a condition analogous to alloimmune hemolytic disease of the fetus and newborn by infusing antierythrocyte antibodies in fetal sheep. Antierythrocyte antibodies were infused intravascularly into late-gestation ovine fetuses over a 10-day period. Fetal blood was sampled daily for complete blood cell counts, blood gases, iron, erythropoietin (EPO), and electrolyte concentrations. Red cell mass (RCM) and blood volume were determined every other day using indicator dilution techniques. Results were compared with eight similarly aged control animals. Statistical analysis included Student t test, three-factor analysis of variance, and least squares regression. The hematocrit in seven fetal sheep receiving antibody infusion declined significantly by 10.3 +/- 1.7%, whereas it increased in control animals 2.3 +/- 0.6% (P <.001). RCM was reduced by 18.9 +/- 3.2% over the 10-day protocol while increasing 34.1 +/- 4.2% in control animals, representing more than a 50% difference in RCM (P <.001). Fetal EPO was significantly increased with lower hematocrit and lower PO(2) (P <.001). As fetal hematocrit declined below 25%, lactate and reticulocytes also increased (P <.001). Plasma iron concentration was not significantly altered (P =.47). The chronically catheterized fetal sheep is a viable model for studying immunologically induced fetal anemia as hematocrit can be titrated and the fall in RCM and hematocrit are associated with fetal hypoxia and elevated EPO as occurs in the anemic human fetus. Furthermore, there appears to be a threshold degree of anemia required to elicit responses as the fetal EPO, PO(2), and lactate appeared unresponsive until hematocrit fell below 25%.

Materials for temperature independent resistive oxygen sensors for combustion exhaust gas control

Acceptor and donor doped SrTi 1− x Fe x O 3− δ materials for novel temperature independent resistive oxygen sensors for lean-burn engine exhaust gases were prepared and characterized by X-ray diffraction. Their electrical resistance, R, was investigated in the oxygen partial pressure range from 10 −4 to 1 bar between 700°C and 1000°C. Doped and undoped samples with x=0.3 obey an R∝ pO 2 −1/5 power law. Undoped samples show negligible temperature dependence in a small oxygen partial pressure ( pO 2) range between 10 −2 and 3×10 −2 bar. Acceptor (Ga) doping shifts the pO 2 range of negligible temperature dependence to lower pO 2, whereas donor (La) doping results in a right-hand shift to higher pO 2. Combined acceptor and donor doping leads to an extended pO 2 range of negligible temperature dependence. At pO 2=10 −1 bar the temperature coefficient of resistance (TCR) of this material composition is always below 250 ppm/K in the complete investigated temperature range. At about 725°C and 975°C TCR=0 can be found.

Supraventricular arrhythmia following lung resection for non-small cell lung cancer and its treatment with amiodarone.

From January 1998 to February 1999, 160 patients undergoing lung resection for non-small cell lung cancer were studied to define factors that increase the risk of postoperative supraventricular arrhythmia (SA) and to assess the effectiveness of amiodarone as an antiarrhythmic drug. All patients were monitored intraoperatively and postoperatively up to day 3. Onset of SA was documented with ECG. Amiodarone was administered to those who developed SA with a loading dose of 5 mg/kg in 30 min and a maintenance dose of 15 mg/kg in 24 h. Mean age was 64 years (range 27-83 years). There were nine wedge resections, six segmentectomies, 127 lobectomies and 18 pneumonectomies. Twenty-two patients (13%) had SA, all of which were atrial fibrillations. The incidence of supraventricular arrhythmia with pneumonectomy and lobectomy was 33 and 12%, respectively (P=0.02). None of the patients who had a minor resection developed SA. The peak incidence of onset of SA occurred on postoperative day 2 and lasted from 1 to 12 days (average 3.4 days). Sinus rhythm was achieved with amiodarone in 20 patients (90.9%) with no side effects. Two patients received electrical cardioversion because hemodynamically unstable. Mean preoperative pO(2) and pCO(2) were lower in patients with SA: pO(2) 80.8 vs. 85 mmHg (P=0.04); pCO(2) 35.5 vs. 38 mmHg (P=0.01). Patients with concomitant cardiopulmonary diseases presented an odds ratio for postoperative arrhythmia of 12.4 (confidence interval 4. 5-34.1) (P<0.0001). Concomitant cardiopulmonary diseases, lower pO(2), pCO(2) and extent of surgery increase the risk of postoperative SA after lung resection for non-small cell lung cancer. Cardiac monitoring in patients at risk is recommended. Amiodarone was both safe and effective in establishing and maintaining sinus rhythm.

Effects of waterborne nitrite onphase I–II biotransformation in channel catfish( Ictalurus punctatus)

The effects of waterborne nitrite (3 mg/l NO 2) on channel catfish were studied to evaluate changes in hematological parameters and phase I–II biotransformation in liver slices. Nitrite-exposed fish had significantly higher methemoglobin, blood and liver nitrite, and significantly lower pO 2 than control fish. Total phase I-mediated metabolism of 7-ethoxycoumarin (EC) was not altered in nitrite-exposed fish compared with control fish (291±43 and 312±20 pmol/mg/h, respectively). However, phase II glucuronosyltransferase-mediated metabolism of 7-hydroxycoumarin (HC), both as a phase I metabolite of EC and as a parent substrate, was elevated in nitrite-exposed fish (204±17 and 1007±103 pmol/mg/h, respectively) as compared to control fish (149±14 and 735±87 pmol/mg/h) ( P<0.05). Sulfotransferase-mediated metabolism of HC (as a metabolite of EC and as a parent substrate) was not notably altered in nitrite-exposed fish (95±16 and 617±33 pmol/mg protein/h, respectively) as compared with control fish (118±24 and 575±55 pmol/mg/h, respectively). These studies indicate that in vivo nitrite exposure and associated changes in hematological parameters do not appear to affect hepatic phase I EC biotransformation in channel catfish. However, subtle but significant changes in phase II glucuronidation, but not sulfation activity, were observed. The mechanism of these alterations is unclear. However, the data suggest that environmentally realistic concentrations of nitrite may affect the dynamics of conjugative metabolism in exposed fish.

Physiologically significant effects of pH and oxygen tension on granulopoiesis

Objective Granulocyte differentiation in the bone marrow (BM) takes place in regions with lower pH and O 2 tension (pO 2) than those in the BM sinuses. This suggests that granulopoiesis will be enhanced at subvascular pH and pO 2. Materials and Methods The effects of pH and pO 2 on granulocyte proliferation, differentiation, and granulocyte colony-stimulating factor receptor (G-CSFR) expression were evaluated using mobilized peripheral blood CD34 + cells directed down the granulocytic pathway with stem cell factor, interleukin 3, interleukin 6, and G-CSF. Results Cell expansion was enhanced at subvascular pH, with twice as many total cells and CD15 bright/CD11b + late neutrophil precursors (myelocytes, metamyelocytes, bands) produced at pH 7.07 to 7.21 as was produced at pH 7.38. Low pH accelerated the rate of differentiation concomitant with this increase in proliferation. Also, total, CD15 bright/CD11b − (promyelocytes, early myelocytes), and CD15 bright/CD11b + cell expansion was enhanced at lower pO 2, with twice as many of each cell type produced at 5% O 2 as at 20% O 2. The effects of low pH and low pO 2 were additive, such that generation of total, CD15 bright/CD11b − , and CD15 bright/CD11b + cells was 3.5-, 2.4-, and 4.0-fold greater at pH 7.21 and 5% O 2 than at the standard hematopoietic culture conditions of pH 7.38 and 20% O 2. Low pH resulted in faster upregulation of G-CSFR surface expression, whereas pO 2 had no effect on G-CSFR expression. Conclusion These data provide compelling evidence that pH and pO 2 gradients within the BM play significant roles in regulating hematopoiesis. More rapid granulocytic cell proliferation and differentiation at low pH may be explained in part by more rapid G-CSFR expression. The ability to alter cell development by manipulating pH and pO 2 has important implications for optimizing ex vivo production of neutrophil precursors.

Preparation and characterisation of monoclinic hydroxyapatite and its precipitated carbonate apatite intermediate

Five 100 g batches of a carbonate apatite (the intermediate) were produced by heating an aqueous slurry of CaCO 3 and CaHPO 4 with an overall Ca/P mole ratio of 5/3 with vigorous stirring. Each intermediate produced by boiling off water was heated in vacuum at 1100°C to remove carbonate, then steamed at 900°C to ensure complete hydroxylation. Comparison of calculated and observed X-ray diffraction patterns showed final products containing 50–100 wt% monoclinic hydroxyapatite (remainder hexagonal). Rietveld refinements in P6 3/m gave structures similar to several hydroxyapatite standards, including NIST SRM 2910, although there was no evidence from X-ray diffraction that the latter was in the monoclinic form. Refinements from standards and final products were slightly different from published single crystal data for Holly Springs hydroxyapatite. This is attributed to known impurities in mineral hydroxyapatite and indicates that parameters from the Rietveld refinements are closer to the true values for pure hydroxyapatite. Rietveld refinements for intermediates showed small, but significant differences from the final product, the largest being in O1 x, O2 x and O(H) z. All P–O bond lengths were shorter than in the final product, resulting in a 3.2% lower PO 4 tetrahedron volume. The occupancies of P and Ca(2) were reduced. These differences are attributed to partial replacement of PO 4 3− by CO 3 2− ions.

Automated Peritoneal Dialysis in Asia

The socioeconomic statuses of Asian countries are diverse, and government reimbursement policies for renal replacement programs vary greatly from one country to another. Both factors affect not only the availability of treatment, but also the choice of dialysis modality. A close correlation is demonstrated between the dialysis treatment rate for end-stage renal disease (ESRD) and the gross domestic product (GDP) per capita income. A biphasic relationship with the GDP per capita income and the peritoneal dialysis (PD) utilization rate is observed, in that the countries with the highest and lowest treatment rates tend to have lower PD utilization rates, whereas countries with modest treatment rates tend to have higher PD utilization rates. In contrast, countries with high continuous ambulatory peritoneal dialysis (CAPD) utilization rates have the lowest automated peritoneal dialysis (APD) utilization rates. The low APD utilization rates are due to fact that, in most instances, patients themselves must purchase the APD machine, and the machines are relatively more expensive in Asian Pacific countries. Continuous cycling peritoneal dialysis (CCPD) is most frequently practiced. Generally, convenience for employment is the main indication for the utilization of APD. Other important indications are the convenience of treatment in young or elderly uremic patients. Contrary to the practice in CAPD treatment, detailed documentation of dialysis adequacy and nutritional status is not routinely done in patients undergoing APD treatment in most Asian Pacific countries. In conclusion, APD is an underdeveloped treatment modality in the renal replacement programs of Asian Pacific countries. The low utilization of APD is clearly influenced by non medical factors including government reimbursement policy and the cost of PD machines.

Human Factors, Extreme Events and Floods in the Lower Po Plain (Northern Italy) in the 16th Century

Abstract Researches on climatic variations in the 16th century have stressed the exceptionality of extreme events, such as large and frequent floods, which are used as indicators of increased rainfall. The case of the lower Po basin, where lack of instrumental data renders the concept of exceptionality complex and relative, shows that this is not necessarily valid. There, various human factors determined a high environmental vulnerability. Since the lower Po Plain was a 'man-made' environment, past extreme events must be evaluated in strict relation with the territory's character. Thus the increase in floods constitutes a 'weak' indicator for an increase in rainfall.

New U–Pb zircon ages and the duration and division of Devonian time

Newly determined U–Pb zircon ages of volcanic ashes closely tied to biostratigraphic zones are used to revise the Devonian time-scale. They are: (1) 417.6±1.0 Ma for an ash within the conodont zone of Icriodus woschmidti/ I. w. hesperius (early Lochkovian); (2) 408.3±1.9 Ma for an ash of early Emsian age correlated with the conodont zones of Po. dehiscens–Lower Po. inversus; (3) 391.4±1.8 Ma for an ash within the Po. c. costatus Zone and probably within the upper half of the zone (Eifelian); and (4) 381.1±1.3 Ma for an ash within the range of the Frasnian conodont Palmatolepis punctata ( Pa. punctata Zone to Upper Pa. hassi Zone). U–Pb zircon ages for two rhyolites bracketing a palyniferous bed of the pusillites– lepidophyta spore zone, are dated at 363.8±2.2 Ma and 363.4±1.8 Ma, respectively, suggesting an age of ∼363 Ma for a level within the late Famennian Pa. g. expansa Zone. These data, together with other published zircon ages, suggest that the base and top of the Devonian lie close to 418 Ma and 362 Ma, respectively, thus lengthening the period by ∼20% over current estimates. We suggest that the duration of the Middle Devonian (Eifelian and Givetian) is rather brief, perhaps no longer than 11.5 Myr (394 Ma–382.5 Ma), and that the Emsian and Famennian are the longest stages in the period with estimated durations of ∼15.5 Myr and 14.5 Myr, respectively.

Human herpesvirus 8 seroprevalence in blood donors and lymphoma patients from different regions of Italy.

Independent epidemiologic studieshave shown a strong association be-tween Kaposi’s sarcoma (KS) and infec-tion with human herpesvirus 8 (HHV-8or KSHV). HHV-8 genomic sequenceshave been found in all forms (1–5)andall histologic stages (6) of KS, with viralDNA being localized to tumor endothe-lial cells and spindle cells (7,8). Detec-tion of HHV-8 DNA sequences in theperipheral blood of patients who are se-ropositive for human immunodeficiencyvirus 1 (HIV) is a strong predictor ofprogression to KS (9,10). The vast ma-jority of patients with KS have antibod-ies against HHV-8(11–14), with sero-conversion before clinical disease (15).HHV-8 infection is apparently not com-mon in the general population of theU.K. and the United States, but it iscommon in groups at high risk for KS(11–14).In addition, HHV-8 seropreva-lence is higher in HIV-positive homo-sexual men than in HIV-positive pa-tients with hemophilia (13), just asacquired immunodeficiency syndrome(AIDS)-related KS occurs far morecommonly in homosexual men than inpatients with hemophilia. HHV-8 infec-tion is common in the general popula-tion of Uganda, which has a high inci-dence of endemic KS (11,13,14).The classic form of KS affectsmainly elderly men in Mediterraneanand Eastern Europe (16). If HHV-8 isthe major etiologic agent in KS, a higherprevalence of antibodies against HHV-8would be expected in regions with anelevated incidence of KS. KS is preva-lent in Italy, especially in the South,Sardinia, and the lower Po valley(Northern Italy) (16–18). From 1976through 1984, before the era of AIDS,elevated incidence rates of KS werefound in nine Italian cancer registries;these incidence rates were twofold tothreefold higher than those in the UnitedStates and Sweden and 10-fold higherthan those in the U.K. (17–20) (Fig. 1,A, and data not shown).We investigated the prevalence of an-tibodies against the HHV-8 latentnuclear antigen (LNA-1) by use of animmunofluorescence assay (13) in 747blood donors from different regions ofItaly. Since HHV-8 is also associatedwith primary effusion lymphoma (21)and multicentric Castleman’s disease(22), we additionally investigated the se-roprevalence of this lymphotropic her-pesvirus in 163 lymphoma patientsfrom the same Italian regions; 78 ofthese patients had Hodgkin’s disease,and 85 had non-Hodgkin’s lymphomas(64 of B-cell origin and 21 of T-cell ori-gin). The immunofluorescence assay isthe most sensitive and specific assaycurrently available to detect HHV-8 in-fection (23). Sera were tested in ablinded manner at a dilution of 1:100,and 38 positive sera were also titrated to

Effect of oxygen availability on nitrogen fixation by two Lotus species under flooded conditions

the low pO 2 treatment in both species. Immunogold labelling showed that the MAC265 antigen was localThe pasture legumes Lotus uliginosus (Schk.) and ized primarily within intercellular spaces within nodule Lotus corniculatus (L.), known to differ in their toler- cortices from both Lotus species. A marked decrease ance to flooding, were inoculated with Rhizobium loti in deposition of the MAC265 antigen within the cortiand flooded for 60 d while subjected to two levels of ces of L. uliginosus nodules grown in the lower pO 2 . dissolved pO 2 : 0.241 and 0.094 mmol ml’-1. L. ulig- is discussed in terms of the relative abilities of the inosus showed significantly greater growth (shoot and two Lotus spp. to maintain an O

Transport of Carbon and Nitrogen to the Northern Adriatic Sea by the Po River

Concentrations of dissolved and particulate organic carbon (DOC, POC) and particulated nitrogen (PN) were measured in samples taken monthly for a year at two stations in the lower Po River and on four separate occasions in the mixing zone. From the results, the influence of suspended matter concentrations on POC and PN contents in the solid phase, and of flow variations on POC and PN contents in the water phase were evaluated. The behaviour of organic matter in the mixing zone was conservative in low to medium solid transport conditions, but had a strong negative deviation with respect to the dilution line during high solid transport, presumably due to both settling of particulate matter in the prodelta region and bacterial utilization of organic matter. Organic carbon was preferentially transported in the solid phase, in the lower Po, compared to world rivers in temperate zones. The loads of total organic carbon and nitrogen were estimated as 25·5×104and 15·5×104tonnes year−1respectively, making this river the most important contributor of organic matter and nutrients to the Mediterranean. These high loads together with lesser inputs from other Italian rivers flowing in to the northern Adriatic exert a significant impact on the productivity and trophic dynamics of this basin.

Oxygen tension in human tumours measured with polarographic needle electrodes and its relationship to vascular density, necrosis and hypoxia

Background and purpose: The use of polarographic needle electrodes for measurement of oxygen tension (pO 2) in tumours requires documentation of the validity of the method. In the present work the pO 2 values measured polarographically with the Eppendorf pO 2 histograph in human tumours were compared with the histological appearance of the tumour tissue, i.e. vascular density, fraction of necrosis and fraction of hypoxic tissue, to investigate whether the measurements reflected the expected pO 2. Materials and methods: The pO 2 was measured in cervix tumours in patients and in human melanoma xenografted tumours in athymic mice. Vascular density was determined in the cervix tumours by histological analysis of biopsies from the pO 2 measurement tracks. Fraction of necrosis and fraction of hypoxic tissue, i.e. tissue binding the hypoxia marker pimonidazole, were determined in the melanomas by analysis of histological sections from the tumour planes in which the pO 2 measurements were performed. Results: The pO 2 distributions showed large intratumour heterogeneity. In cervix tumours, tumour regions with vascular density (vascular length per unit tissue volume) in the range of 47–77 mm/mm 3 showed higher pO 2 than tumour regions with vascular density in the range of 20–47 mm/mm 3, which in turn showed higher pO 2 than tumour regions with vascular density in the range of 0–20 mm/mm 3. In melanomas, tumour regions in which necrosis and hypoxia constituted more than 50% of the tissue showed lower pO 2 than other tumour regions. Conclusions: The pO 2 measured in the tumours was consistent with the histological appearance of the tissue in which the measurements were performed, suggesting that reliable pO 2 distributions of tumours can be obtained with polarographic needle electrodes.

Interconverting gating modes of a nonselective cation channel from the tapeworm Echinococcus granulosus reconstituted on planar lipid bilayers.

A 107-pS (symmetrical 150 mM KCl), nonselective cation channel was reconstituted from a microsomal membrane fraction of the larval stage of the tapeworm Echinococcus granulosus. Most of the time, it displayed a high open probability (>>0.95) irrespective of either the applied voltage, Ca2+, Ba2+, or tetraethylammonium concentration. Nevertheless, in contrast with this "leaklike" behavior, less frequently this "all-the-time-open" channel reversibly entered two different kinetic modes. One of them was characterized by lower Po values and some voltage sensitivity (V(1/2) congruent with 129 mV, and an equilibrium constant for channel closing changing e-fold per 63-mV change) the kinetic analysis revealing that it resulted from the appearance of voltage-sensitivity in the mean closed times and a sixfold increase in the equilibrium constant for channel closing at 0 mV. The other mode was characterized by a very fast open-close activity leading to poorly resolved current levels and a Po around 0.6-0.7 which, occasionally and in a voltage-sensitive manner, entered a long-lived nonconducting state. However, the rare nature of these mode-shifting transitions precluded a more detailed analysis of their kinetics. The conductive properties of the channel were not affected by these switches. Model gating alone does not seem to ensure any physiological role of this channel and, instead, some other channel changes must occur if this phenomenon were to be of regulatory importance in vivo. Thus, mode-shifting might constitute an alternative target for channel activity modulation also in tapeworms.

Effectiveness of Border Irrigation: A Case Study

A method for the evaluation of adequacy, distribution and application efficiencies of border irrigation is proposed. A mathematical model for the simulation of surface runoff and infiltration is applied in order to analyse the waterings carried out according to traditional practice in the lower Po valley and according to systematic, full and deficit irrigation, on plots cropped with clover ley and spring maize. In the application of the model, it is assumed that the water stored in the root zone may be identified with the readily available water. The computations make it possible to analyse the traditional parameters and to find their optimal values for a selected adequacy, i.e. for a selected percentage of the length-of-run adequately irrigated. The model shows that the traditional practice causes an over-irrigation and that significant water savings of nearly 11% may be made in comparison with the experimental values.

Delta F508-CFTR channels: kinetics, activation by forskolin, and potentiation by xanthines.

Trafficking, activation, and kinetics of delta F508-cystic fibrosis transmembrane conductance regulator (CFTR) and CFTR were compared in stably transduced C127I mouse mammary epithelial cells. Western blots detected a small amount of fully glycosylated delta F508-CFTR Efflux of 125I was stimulated by forskolin with the same mean effective concentration (EC50; approximately 0.5 microM) for CFTR and delta F508-CFTR cells, but the maximum response was reduced more than fivefold and its latency increased approximately threefold in delta F508-CFTR cells. In delta F508-CFTR cells, 3-isobutyl-1-methylxanthine (IBMX; EC50 = 1.45 microM) and 8-cyclopentyl-1,3-dipropylxanthine (CPX; EC50 = 58 microM) increased the peak forskolin-stimulated efflux rate approximately 2.5-fold and decreased the time to peak. A sevenfold increase in intracellular adenosine 3',5'-cyclic monophosphate (cAMP) levels accompanied potentiation of forskolin-induced 125I efflux by IBMX but not by CPX. Elevation of intracellular cAMP increased linear voltage-independent whole cell currents 30-fold in CFTR and 4-fold in delta F508-CFTR cells; the response rate in delta F508-CFTR cells was much slower. Single-channel currents were detected in 57 of 68 cell-attached patches from forskolin-prestimulated CFTR cells vs. 6 of 35 patches in delta F508-CFTR cells. Mean number of active channels per patch was 4.1 for CFTR [open probability (Po) = 0.34] and 0.2 for delta F508-CFTR (Po = 0.11). The lower Po of delta F508-CFTR resulted from an approximately threefold longer mean interburst interval. We estimate that forskolin-stimulated chloride conductance of delta F508-CFTR C127I cells is < 5% of CFTR cells. CPX is approximately 25-fold more potent than IBMX in potentiating delta F508-CFTR and may operate by a mechanism other than elevation of cAMP.

The Po: Centuries of river training

The Po river drains the largest morphological unit of the Italian territory. River training works started in the lower Po during the Roman Age and developed upstream, first as discontinuous systems, then connected to form two uninterrupted belts, which have reduced the overflow frequency but also the storage capacity of the river flood bed. The outcome is an increasing value of the flood peak with given probability in the lower Po, which is the reach with the higher flooding risk. On the other hand, the upstream catchment, in which the river is provided with partial embankments, recently experienced a flooding event and require some form of protection. A risk mitigation policy should perceive and take into account all the components of the river system and their connections. In this perspective the development of traditional structural protection along the Po river has reached a critical stage; a further expansion of the existing levee system increases the down-stream risk. From the viewpoint of non structural protection, the river morphology and the past experience suggest that, based on rainfall and discharge monitoring, early warnings of flood hazards can be provided to communities that could be affected by such occurrences. Finally, to reduce the flooding risk in the lower Po a reduction of the flood discharge entering this reach is needed. This can be obtained by diverting the higher part of the flood from the river immediately upstream of the lower Po, allowing the inundation and the temporary storage of the diverted water on pre-designed large agricultural areas. Implementing such a policy will require a reliable system of flood warning and, above all, a sound regulatory authority.

Reduced PO 2 alters the behavior of Fura-2 and Indo-1 in bovine pulmonary artery endothelial cells

Calcium-sensitive fluorophores are used to estimate cytosolic free Ca 2+ in many cell types under various conditions. We tested the effect of reduced PO 2 on the behavior of Fura-2 and Indo-1 in cultured bovine pulmonary artery endothelial cells. Reduced PO 2 (PO 2 25–35 mmHg) caused a significant upward shift of in vivo calibration curves for both fluorophores. The in vivo emission spectrum of Fura-2 indicated that the effect was principally due to attenuated emission at the Ca 2+-unbound 380 nm wavelength, with no shift in position of the emission maxima for either Ca 2+-bound or unbound forms of the fluorophore. Reduced PO 2 did not directly alter the behavior of the dyes, as no shift of in vitro calibration curves was seen. Neither decreased photobleaching nor altered autofluorescence accounted for the shift. We investigated several potential indirect effects, including cellular acidification, reduced viscosity, inhibition of oxidative energy production and reductive stress. In contrast to lowered PO 2, acidification in vitro produced a leftward but not an upward shift. Estimation of intracellular pH with SNAFL-calcein under reduced PO 2 showed no apparent acidification in these cells, further strengthening the argument that altered intracellular pH was not causing the shift. Others have shown that decreases in viscosity in vitro may shift the calibration curve for Fura-2 upward, similar to our finding with reduced PO 2. However, for Indo-1 we found that decreased viscosity in vitro attenuated fluorescence emission at the Ca 2+-bound 405 nm wavelength, thus producing the opposite effect on fluorescence ratio and indicating that reduced PO 2 was not acting through changes in cellular microviscosity. Because reduced PO 2 could be acting through either reduced energy production or redox, we tested the effects of the metabolic inhibitor rotenone (100 nM), and the reducing agent glutathione (50 mM), on the calibration curves. Neither intervention changed Fura-2 fluorescence in vivo, suggesting that these mechanisms were not responsible for the shift in in vivo calibration under reduced PO 2. We conclude that in pulmonary artery endothelial cells, reduced PO 2 alters the behavior of Ca 2+-sensitive fluorophores through an unidentified, indirect mechanism, and recommend that investigators utilizing this technique to study oxygen-dependent effects employ PO 2-specific in vivo calibration curves to avoid errors in interpretation.

Soluble and particulate metals in the Po River: Factors affecting concentrations and partitioning

Fourteen metals (Ca, Mg, Al, Fe, Mn, Ba, As, Cd, Co, Cr, Cu, Ni, Pb and Zn) were monitored over a 2-year period in the waters of the lower Po River. Concentrations in the dissolved and particulate phases were measured, thus constructing a large database on metal variability. The influence of flow and solid transport on dissolved, particulate and total metal concentrations is discussed. In addition to flow rate and solid content, biological processes seem to be one of the main factors affecting concentrations in the dissolved phase, while the inorganic components of solids seem to control metal concentration in suspended matter. Data on partitioning of metals between the dissolved and particulate phases are presented, together with related information on the affinity sequence of metals for the particulate phase, and the influence of solid load on the modes of metal transport.

Effects of oxygen pressure on phase evolution and microstructural development in silver-clad (Bi,Pb)2Sr2Ca2Cu3O10+δ composite conductors

Abstract The kinetics of phase evolution and the development of microstructure in silver-clad composite conductors containing a Bi-Pb-Sr-Ca-Cu-O powder with a nominal stoichiometry of Bi 1.7 Pb 0.4 Sr 2 Ca 2 -Cu 3 O 10+δ were studied as a function of oxygen partial pressure ( pO 2 ), temperature, powder stoichiometry, and powder pre-treatment. The optimum temperature for growth kinetics of the Bi-2223 phase increased as the oxygen partial pressure was increased from 0.02 to 0.21 atm. The width of the phase stability region was largest for pO 2 = 0.075 atm and smallest for pO 2 = 0.21 atm. It was found that for a 25-h heat treatment, the reaction kinetics were the fastest in 0.075 atm of oxygen at temperatures between 825° and 830°C. The secondary phase particles (observed by scanning electron microscopy) were smaller for lower pO 2 (0.02 and 0.075 atm) than for higher pO 2 (0.13 and 0.21 atm).