Low HCO3 Research Articles

Abnormal Duodenal [HCO3 −] Following Secretin Stimulation Develops Sooner Than Endocrine Insufficiency in Minimal Change Chronic Pancreatitis

Direct pancreatic function tests (PFTs) are often used to diagnose chronic pancreatitis (CP). We aimed to determine the temporal relationship between an abnormal PFT result, cross-sectional imaging, and clinical symptoms. All patients referred for endoscopic ultrasound (EUS) and PFT for suspected CP at our medical center from 2008 to 2010 were included. Each subject underwent EUS and PFT on the same day using secretin stimulation. Seventeen patients had duodenal HCO3 values of less than 80 mEq/L and were labeled as abnormal; the 25 other patients had at least 1 duodenal HCO3 values of 80 mEq/L or greater. Patients with abnormal PFTs had more parenchymal (2.0 vs 0.92, P = 0.012), ductal (1.18 vs 0.6, P = 0.036), and total features (3.18 vs 1.52, P = 0.009) than those with normal PFTs on EUS examination. There was no difference in regard to the frequency of abnormal CT scans (25% vs 15%, P = 0.139), diarrhea (67% vs 60%, P = 0.463), fat-soluble vitamin deficiency (33% vs 26%, P = 0.315), or diabetes (10% vs 4%, P = 0.066). Patients with equivocal imaging and abnormally low duodenal HCO3 have more EUS features of CP than do patients with normal duodenal HCO3 values, suggesting that low duodenal HCO3 values are among the first measurable abnormalities in CP.

The Physiology of Bicarbonate Transporters in Mammalian Reproduction1

HCO(3)(-) plays critically important roles during virtually the entire process of reproduction in mammals, including spermatogenesis, sperm capacitation, fertilization, and development of early stage embryos. Therefore, the acid-base balance in the male and female reproductive tracts must be finely modulated. The fluid milieu in the epididymis is acidic, containing very low concentration of HCO(3)(-). In this acidic low HCO(3)(-) environment, mature sperm are rendered quiescent in the epididymis. In contrast, the luminal fluid in the female uterus and oviduct is alkaline, with very high concentration of HCO(3)(-) that is essential for sperm to fulfill fertilization. HCO(3)(-) transporter of solute carrier 4 (SLC4) and SLC26 families represent the major carriers for HCO(3)(-) transport across the plasma membrane. These transporters play critical roles in intracellular pH regulation and transepithelial HCO(3)(-) transport. The physiological roles of these transporters in mammalian reproduction are of fundamental interest to investigators. Here we review recent progress in understanding the expression of HCO(3)(-) transporters in reproductive tract tissues as well as the physiological roles of these transporters in mammalian reproduction.

Effect of attached bacteria of carbonic anhydrase on the growth of <i>Microcystis aeruginosa</i>

为研究生长环境中微生物对铜绿微囊藻碳代谢的影响,本文分析太湖典型微囊藻水华样品附生菌中产碳酸酐酶(CA)细菌的比例,结果显示CA菌占11.6%;从微囊藻群体中分离获得了一株高胞外CA附生菌P201,通过ITS基因鉴定,该菌为一株荧光假单胞菌(Pseudomonas fluorescence).并研究了该菌在不同浓度HCO₃^-条件下对铜绿微囊藻生长的影响,结果表明无论是高HCO₃^-浓度还是低HCO₃^-浓度环境中,加入该菌对铜绿微囊藻的生长均有促进作用,说明产CA酶附生菌对铜绿微囊藻的生长有一定的促进作用.;To study the effect of attached bacteria on the carbon metabolism of M. aeruginosa, the percentage of carbonic anhydrase(CA) produced bacteria in total attached bacteria was analyzed. The result showed that the ratio of CA produced bacteria is 11.6% in a typical cyanobacterial bloom from Lake Taihu. An attached bacterium strain P201, which produced large amount of extracellular carbonic anhydrase, was isolated from M. aeruginosa assemblage. It was identified as a strain of Pseudomonas fluorescence by its ITS molecular characteristic. Effects of P201 on the growth of M. aeruginosa in different HCO₃^- concentrations were investigated. The results showed that no matter in the higher or the lower HCO₃^- culture medium, P201 could promote the growth of M. aeruginosa, which suggested that CA produced attached bacteria could enhance the growth of M. aeruginosa by regulating the ambient carbon environment.

Usefulness of pulmonary function tests and blood gases in acute neuromuscular respiratory failure

Define the usefulness of pulmonary function tests (PFT) and arterial blood gases (ABG) in patients admitted to the ICU with acute neuromuscular respiratory failure (NMRF). We reviewed 76 patients admitted to an ICU at Mayo Clinic (Rochester) between 2003 and 2009 with acute NMRF defined as need for mechanical ventilation (MV) because of primary impairment of the peripheral nervous system. Poor functional outcome was defined as a modified Rankin score >3. Median age was 65years. The most frequent diagnosis was myasthenia gravis (25 patients); 54% of patients had no known neuromuscular diagnosis before admission, and 11% had no specific diagnosis at discharge. Median MV time was 16days; 14% of patients died during hospitalization, and 63% were severely disabled at discharge. Maximal expiratory pressure ≤30cm H(2) O and maximal inspiratory pressure (MIP) worse than -28cm H2 O before MV were associated with need for invasive MV for longer than 7days (P=0.02). Indicators of chronic respiratory acidosis (low pH, high pCO2 , and high HCO3 ) before MV were associated with in-hospital death and poor functional outcome, but mostly in patients with progressive, untreatable neuromuscular diagnoses. In patients with primary acute NMRF, bedside PFT and ABG before MV can be used to predict evolution and outcome. Lower MIP and MEP portend prolonged MV and are more useful than forced vital capacity. Presentation with chronic respiratory acidosis is associated with high risk of in-hospital mortality and severe disability, especially in patients without treatable diagnoses.

Effects of Acetate‐Free Citrate‐Containing Dialysate on Metabolic Acidosis, Anemia, and Malnutrition in Hemodialysis Patients

Previously, dialysate contained small amounts of acetate as an alkaline buffer. Recently, acetate-free dialysate (A[-]D) has been available. We evaluated the clinical effect of A(-)D over acetate-containing dialysate (A(+)D) on acid-base balance, anemia, and nutritional status in maintenance hemodialysis (MHD) patients. Twenty-nine patients on MHD were treated with A(+)D for 4 months (first A(+)D), switched to A(-)D for 4 months, and returned to A(+)D for the next 4-month period (second A(+)D). Metabolic acidosis: Serum bicarbonate (HCO3(-) ) levels did not change in patients with normal HCO3(-) levels (≥20 mEq/L) throughout the study. Meanwhile, in patients with initially low HCO3(-) levels, it was significantly increased during the A(-)D period only. Anemia: In patients with target hemoglobin (Hb) ≥10 g/dL, Hb levels were maintained during the study period, even if the dose of erythropoiesis-stimulating agents (ESAs) decreased. In patients with low Hb levels, it was significantly increased in the A(-)D period without increasing ESA or iron doses. Nutritional Condition: In patients with normal albumin levels (≥3.8 g/dL), albumin did not change throughout the study period. However, in patients with lower albumin levels, it was significantly increased during the A(-)D period. These improvements in metabolic acidosis, anemia, and nutrition in the A(-)D period completely dissipated during the second A(+)D period. Hemodialysis (HD) with A(-)D may improve a patient's clinical status with intractable metabolic acidosis, hyporesponsiveness to ESA, and malnutrition that were not normalized in HD with A(+)D.

Mechanism of glutathione depletion during simulated ischemia-reperfusion of H9c2 cardiac myocytes

It has been reported that myocardial glutathione content is decreased during ischemia-reperfusion, but the mechanism of glutathione depletion has remained unclear. The present study tested whether osmotic stress is involved in the glutathione depletion during ischemia. Six hours of hypoxic acidosis with either high CO2 tension or low HCO3− concentration, which simulates the ischemic condition, resulted in a significant decrease of glutathione content and the glutathione depletion was prevented by hyperosmolarity. High-CO2 acidosis alone without hypoxia induced a similar degree of glutathione depletion. Intracellular pH was lowered by high-CO2 acidosis to 6.41 ± 0.03 in 15 min. Meanwhile, the cell size gradually increased and reached ∼110% in 10 min and the increased cell size was maintained for at least 30 min, which was also prevented by hyperosmolarity. Subsequent experiments observed the effects of simulated reperfusion on the glutathione content. Measured in 1 h after the hypoxic acidotic reperfusion, the glutathione content was further decreased compared to the level at the end of ischemia, which was not suppressed by increasing the osmolarity of reperfusion solution. The degree of glutathione depletion during hypoxic reperfusion with normal pH was similar to the hypoxic acidotic reperfusion group. On the other hand, normoxic reperfusion was not accompanied by further depletion of glutathione content. Based on these results, it was concluded that ischemia induces the glutathione depletion via osmotic stress, which results from intracellular acidification, and the glutathione content is further decreased during reperfusion through a mechanism other than oxygen toxicity.

Renal tubular acidosis in renal transplantation recipients

Aim: We aimed to investigate the prevalence, type, and possible risk factors of renal tubular acidosis (RTA) in Turkish patients with renal transplantation. Patients and method: The study included 66 adult renal transplantation recipients. We recorded the parameters of venous blood gas analysis including serum pH value, serum bicarbonate (HCO3) concentration, presence of metabolic acidosis, which was defined as low HCO3 (<22 mEq/L), and serum pH value (<7.35) together, and base excess and urine pH at the last follow-up. Creatinine clearance was determined from 24-hour collected urine samples. RTA was defined to be metabolic acidosis with normal serum anion gap and positive urine anion gap. Results: Mean age of 66 patients was 37.0 ± 10.4 years; 48 of 66 patients were male. RTA was found in 14 (21.2%) patients. Considering for differential diagnosis of RTA, 4 patients had type 2 RTA and 10 had type 1 RTA. On the contrary, type 4 RTA was observed in no patients. Creatinine clearance was meaningfully lower in acidosis group than in those of the nonacidosis group (55.16 ± 23.27 vs. 71.06 ± 28.14 mL/min; p = 0.028). HCO3 was correlated with hemoglobin level (r = 0.423, p = 0.001) and creatinine clearance (r = 0.262, p = 0.034). It was inversely correlated with cyclosporine A (CsA) level (r = −0.499, p = 0.035). Conclusion: RTA is a common complication after kidney transplantation. It is related with low creatinine clearance, low hemoglobin level, and high CsA level. Particularly, the value of creatinine clearance is lower and the possibility of RTA is higher.

Environmental isotopic and hydrochemical characteristics of groundwater systems in Daying and Qicun geothermal fields, Xinzhou Basin, Shanxi, China

AbstractThe conceptual hydrogeological model of the low to medium temperature Daying and Qicun geothermal fields has been proposed, based on hydrochemical characteristics and isotopic compositions. The two geothermal fields are located in the Xinzhou basin of Shanxi, China and exhibit similarities in their broad‐scale flow patterns. Geothermal water is derived from the regional groundwater flow system of the basin and is characterized by Cl·SO4‐Na type. Thermal water is hydrochemically distinct from cold groundwater having higher total dissolved solids (TDS) (&gt;0·8 g/l) and Sr contents, but relatively low Ca, Mg and HCO3 contents. Most shallow groundwater belongs to local flow systems which are subject to evaporation and mixing with irrigation returns. The groundwater residence times estimated by tritium and 14C activities indicate that deep non‐thermal groundwater (130–160 m) in the Daying region range from modern (post‐1950s) in the piedmont area to more than 9·4 ka BP (Before Present) in the downriver area and imply that this water belong to an intermediate flow system. Thermal water in the two geothermal fields contains no detectable active 14C, indicating long residence times (&gt;50 ka), consistent with this water being part of a large regional flow system. The mean recharge elevation estimated by using the obtained relationship Altitude (m) = − 23·8 × δ2H (‰ ) − 121·3, is 1980 and 1880 m for the Daying and Qicun geothermal fields, respectively. The annual infiltration rates in the Daying and Qicun geothermal fields can be estimated to be 9029 × 103 and 4107 × 103 m3/a, respectively. The variable 86Sr/87Sr values in the thermal and non‐thermal groundwater in the two fields reflect different lithologies encountered along the flow path(s) and possibly different extents of water‐rock interaction. Based on the analysis of groundwater flow systems in the two geothermal fields, hydrogeochemical inverse modelling was performed to indicate the possible water‐rock interaction processes that occur under different scenarios. Copyright © 2010 John Wiley &amp; Sons, Ltd.

Environment-dependent phenotypic variation among natural populations of Arabidopsis thaliana in the northern Tianshan Mountains.

Aims Little research has been done on natural environmental factors that impact phenotypic characters of Arabidopsis thaliana populations in their natural habitat. Our objective was to determine the distribution patterns of phenotypic characters and the relationship of phenotypic characters and environmental factors of A. thaliana populations. Methods From May to June 2009, we studied ten populations in the northern Tianshan Mountains. We placed 10 m × 10 m quadrats at each population plot, each comprised of about 400 smaller (0.5 m × 0.5 m) quadrats, and investigated the distributional patterns of populations and nine environmental factors. Twenty A. thaliana plants were selected, and ten phenotypic characteristics (branch number, plant height, plant biomass, root biomass, single fruit weight, fruit number per plant, fruits weight per plant, fruit length, fruit dehiscence force, fruit weight per plant/total weight) were measured. Variance, principal component and regression analyses were used. Important findings All phenotypic characteristics except branch number showed significant differences among populations, which indicated that there is strongly plasticity in the nine characters. The results of the analysis of variance and coefficients of variance indicated that fruit length and fruit dehiscence force have little variation within and among populations. Phenotypic characters varied little among different mountains, altitudes, latitudes and longitudes. The results indicated that A. thaliana populations mainly distributed on sandy soils that contained lower HCO3 - , pH values and higher soil organic carbon (SOC). The distribution frequencies of A. thaliana within populations are very low, ranging from 1.56% to 10.69%, with spatial autocorrelation distances being 15.4 to 46.7 cm and variable. Ten populations were all highly clumped in their distribution (p < 0.01), which was significantly correlated with the fruit dehiscence force, while the fruit dehiscence force increased as environmental stress in- creased. Results suggested that the growth and distribution of A. thaliana in the northern Tianshan Mountains are

NKCC1 and AE3 Appear to Accumulate Chloride in Embryonic Motoneurons

During early development, gamma-aminobutyric acid (GABA) depolarizes and excites neurons, contrary to its typical function in the mature nervous system. As a result, developing networks are hyperexcitable and experience a spontaneous network activity that is important for several aspects of development. GABA is depolarizing because chloride is accumulated beyond its passive distribution in these developing cells. Identifying all of the transporters that accumulate chloride in immature neurons has been elusive and it is unknown whether chloride levels are different at synaptic and extrasynaptic locations. We have therefore assessed intracellular chloride levels specifically at synaptic locations in embryonic motoneurons by measuring the GABAergic reversal potential (EGABA) for GABAA miniature postsynaptic currents. When whole cell patch solutions contained 17-52 mM chloride, we found that synaptic EGABA was around -30 mV. Because of the low HCO3- permeability of the GABAA receptor, this value of EGABA corresponds to approximately 50 mM intracellular chloride. It is likely that synaptic chloride is maintained at levels higher than the patch solution by chloride accumulators. We show that the Na+-K+-2Cl- cotransporter, NKCC1, is clearly involved in the accumulation of chloride in motoneurons because blocking this transporter hyperpolarized EGABA and reduced nerve potentials evoked by local application of a GABAA agonist. However, chloride accumulation following NKCC1 block was still clearly present. We find physiological evidence of chloride accumulation that is dependent on HCO3- and sensitive to an anion exchanger blocker. These results suggest that the anion exchanger, AE3, is also likely to contribute to chloride accumulation in embryonic motoneurons.

A Multi‐Transition HCN and HCO+Study of 12 Nearby Active Galaxies: Active Galactic Nucleus versus Starburst Environments

Recent studies have indicated that the HCN-to-CO(J = 1–0) and HCO+-to-HCN(J = 1–0) ratios are significantly different between galaxies with AGN (active galactic nucleus) and SB (starburst) signatures. In order to study the molecular gas properties in active galaxies and search for differences between AGN and SB environments, we observed the HCN(J = 1–0), (J = 2–1), (J = 3–2), HCO+(J = 1–0), and HCO+(J = 3–2) emission with the IRAM 30 m in the center of 12 nearby active galaxies which either exhibit nuclear SB and/or AGN signatures. Consistent with previous results, we find a significant difference of the HCN(J = 2–1)-to-HCN(J = 1–0), HCN(J = 3–2)-to-HCN(J = 1–0), HCO+(J = 3–2)-to-HCO+(J = 1–0), and HCO+-to-HCN intensity ratios between the sources dominated by an AGN and those with an additional or pure central SB: the HCN, HCO+, and HCO+-to-HCN intensity ratios tend to be higher in the galaxies of our sample with a central SB as opposed to the pure AGN cases, which show rather low intensity ratios. Based on an LVG analysis of these data, i.e., assuming purely collisional excitation, the (average) molecular gas densities in the SB-dominated sources of our sample seem to be systematically higher than in the AGN sources. The LVG analysis seems to further support systematically higher HCN and/or lower HCO+ abundances as well as similar or higher gas temperatures in AGNs compared to the SB sources of our sample. In addition, we find that the HCN-to-CO ratios decrease with increasing rotational number J for the AGNs while they stay mostly constant for the SB sources.

亜熱帯島嶼西表島における河川水の水質形成と酸性降下物による影響

River water quality formation on Iriomote Island of the Ryukyus was studied to understand the environment of an isolated subtropical island. The concentrations of the major ions in the water of five rivers and pH of each precipitation were measured for one year in 2005. The water quality was mainly classified into the alkali noncarbonate-type by mixing solutes of two different origins, i.e., sea salt and salt resulting from chemical weathering. In the five rivers, HCO3- concentrations ranged from 8 to 34 mg/l, and the Urauchi River, whose catchment area was the widest of the rivers on the island and was covered with siliceous sandstone, was characterized by a very low HCO3- concentration as a result of the chemical weathering of noncarbonate minerals. The average pH of the precipitation on this island was 4.7 except for the time of typhoons, and the river water chemistry reflected acid deposition. The total concentration of dissolved cations due to the chemical weathering of rocks (nss-cations) was equivalent to the sum of HCO3- and nss-SO42- concentrations, suggesting that acid deposition contributes to 10 - 20 % of the total chemical weathering. A further increase in the input level of acidic substances transported from long distances may negatively influence the quality of terrestrial water.

Effects of monensin and yeast supplementation on blood acid-base balance in finishing feedlot steers fed a high-grain, high-protein diet

AbstractThe aim of this study was to evaluate the effects of two dietary supplements (monensin and a live yeast culture) on acid-base balance in steers maintained in a commercial feedlot system, considering effects over the finishing productive cycle. Steers (no. =42) were allotted randomly to one of the three study groups: (1) control group (no supplementation, C), (2) monensin supplementation (MON), and (3) live Saccharomyces cerevisiae strain 47 supplementation (SACC). Venous blood samples were collected for the measurement of acid-base parameters and l-lactate. Production parameters were also used as a complementary tool for understanding the internal changes associated with supplementation. During the finishing period, MON steers tended to gain more efficiently than C and SACC steers. In the C group, the finishing-period diet caused a progressive decline in blood bases, in line with the high-grain diet consumption. In contrast, supplemented animals did not show this trend, although lower HCO3− and base excess values were registered in SACC steers than in MON, indicating that ionophore supplementation is less effective for reducing blood base consumption than yeast supplementation. In our study, the lack of the expected response to yeast supplementation may be attributable to the high crude protein content of the ration, a common feature of commercial feedlot industries.

Coupling Modes and Stoichiometry of Cl−/HCO3− Exchange by slc26a3 and slc26a6

The SLC26 transporters are a family of mostly luminal Cl− and HCO3 − transporters. The transport mechanism and the Cl−/HCO3 − stoichiometry are not known for any member of the family. To address these questions, we simultaneously measured the HCO3 − and Cl− fluxes and the current or membrane potential of slc26a3 and slc26a6 expressed in Xenopus laevis oocytes and the current of the transporters expressed in human embryonic kidney 293 cells. slc26a3 mediates a coupled 2Cl−/1HCO3 − exchanger. The membrane potential modulated the apparent affinity for extracellular Cl− of Cl−/HCO3 − exchange by slc26a3. Interestingly, the replacement of Cl− with NO3 − or SCN− uncoupled the transport, with large NO3 − and SCN− currents and low HCO3 − transport. An apparent uncoupled current was also developed during the incubation of slc26a3-expressing oocytes in HCO3 −-buffered Cl−-free media. These findings were used to develop a turnover cycle for Cl− and HCO3 − transport by slc26a3. Cl− and HCO3 − flux measurements revealed that slc26a6 mediates a 1Cl−/2HCO3 − exchange. Accordingly, holding the membrane potential at 40 and −100 mV accelerated and inhibited, respectively, Cl−-mediated HCO3 − influx, and holding the membrane potential at −100 mV increased HCO3 −-mediated Cl− influx. These findings indicate that slc26a6 functions as a coupled 1Cl−/2HCO3 − exchanger. The significance of isoform-specific Cl− and HCO3 − transport stoichiometry by slc26a3 and slc26a6 is discussed in the context of diseases of epithelial Cl− absorption and HCO3 − secretion.

Preparation of SBF with different [formula omitted] content and its influence on the composition of biomimetic apatites

The bioactivity of bone and dental implant materials is usually tested in vitro using simulated body fluid (SBF). The composition of common SBF differs from that of blood plasma in that it has a higher Cl − and a lower HCO 3 - concentration, which affects the composition of in vitro formed bone-like apatite. Five different SBFs with a composition of 142 Na +, 5 K +, 2.5 Ca 2+, 1 Mg 2+, 1 SO 4 2 - , 1 HPO 4 2 - , and 136 ( Cl - + HCO 3 - ) mmol/l were prepared with HCO 3 - concentrations ranging from 5 to 27 mmol/l. The SBF solutions were prepared by mixing stable concentrated solutions, which increase the reproducibility of in vitro tests due to negligible changes of pH during preparation. The high stability of thus prepared SBF enables the evaluation of hydroxyapatite formation on the surface of bioactive materials without the negative effect of spontaneous precipitation. Furthermore, the use of concentrated solutions offers a facile way to prepare SBF with different ionic contents and thus modify the composition of Ca–P layers precipitated on the surface of the bioactive materials exposed to the SBF solutions. The SBF solutions were shown to be supersaturated with respect to slightly carbonated apatite. The Fourier transform infrared (FT-IR), Raman and X-ray analyses of the precipitated layers indicate that the HCO 3 - content in SBF influences the composition and structure of the calcium phosphates obtained. It can be supposed that as long as the HCO 3 - concentration in the testing solutions is lower than 20 mmol/l, only B-type HCA precipitates. At higher HCO 3 - concentrations, it can be assumed that A-type HCA forms as well considering FT-IR, Raman and X-ray measurements.

Predictive factors of low HCO3– levels in peritoneal dialysis patients

Metabolic acidosis is a major metabolic abnormality in end-stage renal disease (ESRD) and alkali is provided with dialysis treatment to patients on chronic peritoneal dialysis (CPD) to keep their acid-base balance within normal serum HCO3- levels. We examined the levels of venous serum HCO3- in 163 patients on CPD and the predictive factors for HCO3- levels low enough to indicate metabolic acidosis. The mean value for HCO3- was 26+/-2.4 mmol/l and for anion gap was 13.1+/-3.1 mEq/l. A serum bicarbonate concentration of less than 24 mmol/l, compatible with metabolic acidosis, was observed in 13.5% of the patients. In a multivariate analysis HCO3- levels were directly correlated with older age and use of CaCO3- as phosphate binders, and inversely associated with serum potassium, the use of sevelamer and low lactate dialysis solutions. Higher serum urea levels, the use of low lactate solutions and sevelamer instead of CaCO3 were significantly predictive factors for HCO3- levels < 24 mmol/l. Venous HCO3- and anion gap values were within the normal ranges in stable CPD patients. In 13.5% of them, however, chronic metabolic acidosis was observed based on venous HCO3- levels < 24 mmol/l. Dietary protein intake, the use of sevelamer and low (35 mmol/l) concentration of lactate in dialysis solutions are important predictive factors for chronic metabolic acidosis in these patients.

Comparative study of apatite formation on CaSiO3 ceramics in simulated body fluids with different carbonate concentrations

Apatite formation on CaSiO3 ceramics was investigated using two different simulated body fluids (SBF) proposed by Kokubo (1990) and Tas (2000) and three sample/SBF (S/S) ratios (1.0, 2.5 and 8.3 mg/ml) at 36.5 degrees C for 1-25 days. The CaSiO3 ceramic was prepared by firing coprecipitated gel with Ca/Si = 0.91 at 1400 degrees C. The bulk density was 2.14 g/cm3 and the relative density about 76%. The two SBF solutions contain different concentrations of HCO3- and Cl- ions, the concentrations of which are closer to human blood plasma in the Tas SBF formulation than in the Kokubo formulation. The pH values in the former solution are also more realistic. The CaSiO3 ceramics show apatite formation in SBF (Kokubo) after soaking for only 1 day at all S/S ratios whereas different phases were formed at each S/S ratio in SBF (Tas). The crystalline phases formed were mainly apatite at S/S = 1.0 mg/ml, carbonate-type apatite at 2.5 mg/ml and calcite at 8.3 mg/ml. At higher S/S ratios the increase in the Ca concentration became higher while the P concentration became lower in the reacted SBF. These changes in SBF concentrations and increasing pH occurred at higher S/S ratios, producing more favorable conditions in the SBF for the formation of carbonate bearing phases, finally leading to the formation of calcite instead of apatite in the higher HCO3- ion concentration SBF (Tas). Apatite is, however, formed in the lower HCO3- ion concentration SBF (Kokubo) even though the Ca and P concentrations change in a similar manner to SBF (Tas).

Increased endothelin activity mediates augmented distal nephron acidification induced by dietary protein.

The hypothesis that increased dietary protein augments distal nephron acidification and does so through an endothelin (ET-1)-dependent mechanism was tested. Munich-Wistar rats that ate minimum electrolyte diets of 50% (HiPro) and 20% (CON) casein-provided protein, the latter comparable to standard diet, were compared. HiPro versus CON had higher distal nephron net HCO(3) reabsorption by in vivo microperfusion (37.8 +/- 3.2 versus 16.6 +/- 1.5 pmol/mm per min; P < 0.001) as a result of higher H(+) secretion (41.3 +/- 4.0 versus 23.0 +/- 2.1 pmol/mm per min; P < 0.002) and lower HCO(3) secretion (-3.5 +/- 0.4 versus -6.4 +/- 0.8 pmol/mm per min; P < 0.001). Perfusion with H(+) inhibitors support that increased H(+) secretion was mediated by augmented Na(+)/H(+) exchange and H(+)-ATPase activity without augmented H(+),K(+)-ATPase activity. HiPro versus CON had higher levels of urine ET-1 excretion, renal cortical ET-1 addition to microdialysate in vivo, and renal cortical ET-1 mRNA, consistent with increased renal ET-1 production. Oral bosentan, an ET A/B receptor antagonist, decreased distal nephron net HCO(3) reabsorption (22.4 +/- 1.9 versus 37.8 +/- 3.2 pmol/mm per min; P < 0.001) as a result of lower H(+) secretion (28.4 +/- 2.4 versus 41.3 +/- 4.0 pmol/mm per min; P < 0.016) and higher HCO(3) secretion (-6.0 +/- 0.7 versus -3.5 +/- 0.4 pmol/mm per min; P < 0.006). The H(+) inhibitors had no additional effect in HiPro ingesting bosentan, supporting that ET mediated the increased distal nephron Na(+)/H(+) exchange and H(+)-ATPase activity in HiPro. Increased dietary protein augments distal nephron acidification that is mediated through an ET-sensitive increase in Na(+)/H(+) exchange and H(+)-ATPase activity.

Distinctive functional features in prokaryotic and eukaryotic Cu,Zn superoxide dismutases.

Bacterial and eukaryotic Cu,Zn superoxide dismutases show remarkable differences in the active site region and in their quaternary structure organization. We report here a functional comparison between four Cu,Zn superoxide dismutases from Gram-negative bacteria and the eukaryotic bovine enzyme. Our data indicate that bacterial dimeric variants are characterized by catalytic rates higher than that of the bovine enzyme, probably due to the solvent accessibility of their active site. Prokaryotic Cu,Zn superoxide dismutases also show higher resistance to hydrogen peroxide inactivation and lower HCO3- -dependent peroxidative activity. Moreover, unlike the eukaryotic enzyme, all bacterial variants are susceptible to inactivation by chelating agents and show variable sensitivity to proteolytic attack, with the E. coli monomeric enzyme showing higher rates of inactivation by EDTA and proteinase K. We suggest that differences between individual bacterial variants could be due to the influence of modifications at the dimer interface on the enzyme conformational flexibility.

Early predictors of outcome in trauma patients

IN ORDER TO identify early clinical and laboratory predictors of outcome in trauma patients, we reviewed prospectively collected data from patients admitted to the Ryder Trauma Center at the University of Miami. There was a high incidence of early coagulation defects among trauma victims, as indicated by prolonged prothrombin and partial thromboplastin times, and such abnormalities were found to predict mortality independently of other risk factors. Other significant, independent predictors of both early and late death included advanced age and low values for Glasgow Coma Scale, low systolic blood pressure, hematocrit, and HCO3 levels. In addition, massive blood transfusion within the first 24 hours postinjury not only increased the risk of mortality, but also led to a greater probability of developing deep vein thrombosis (DVT). These observations suggest that the use of an effective hemostatic agent to reduce coagulopathy and blood loss may decrease the unfavorable influence of these variables on outcome, leading to a decline in mortality rates among trauma patients.