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PubMed1998

Effect of sodium metabisulfite on hydrogen peroxide production in light-exposed pediatric parenteral amino acid solutions.

The effect of sodium metabisulfite (MBS) on hydrogen peroxide (HP) production in model and commercial amino acid solutions exposed to phototherapy light was studied. Model and commercial pediatric amino acid solutions were prepared such that the amino acid concentration was 1%. MBS concentration, riboflavin concentration, and duration of exposure to phototherapy light were varied to determine the effect on HP production. Control solutions were kept in the dark. HP production was assayed in the model amino acid solutions by using potassium iodide in the presence of ammonium molybdate. In all experiments, HP production was measured at 360 nm in the presence and absence of catalase. In light-exposed solutions, HP production increased linearly for several hours and reached a plateau by eight hours. A mean maximum of 940 microM was produced (data pooled for all solutions). No detectable HP was generated in the solutions kept in the dark. After two hours of light exposure, it was necessary to add at least 10 times more MBS than is typically found in commercial total parenteral nutrient solutions to scavenge all the HP produced. An average of up to 940 microM of HP was produced in model and commercial pediatric parenteral 1% amino acid solutions in the presence of phototherapy light and clinically relevant concentrations of riboflavin and MBS. Light exposure decreased the antioxidant effect of MBS.

Amino Acids↗
PubMed1998

Storage of extemporaneously prepared ophthalmic antimicrobial solutions.

The feasibility of long-term storage of commonly used ophthalmic antimicrobial solutions was studied. Solutions of tobramycin 15 mg/mL (as the sulfate salt), cefazolin 33 mg/mL (as the sodium salt), and vancomycin 50 mg/mL (as the hydrochloride salt), each in artificial tears, were prepared with aseptic technique. Ten 15-mL portions of each solution were prepared; five of each were stored at 4 degrees C and the other five at 25 degrees C. Samples of each portion were tested before storage and 7, 14, 21, and 28 days after preparation for osmolality, pH, and antimicrobial activity. For the tobramycin solution there were no differences in osmolality or the zone of inhibition associated with temperature or time. The pH dropped between days 0 and 7 at both temperatures. For the cefazolin solution there were no differences in osmolality associated with temperature or time. The pH was higher in portions stored at 25 degrees C than at 4 degrees C and increased over time in portions stored at either temperature. The zone of inhibition was larger for portions stored at 4 degrees C than at 25 degrees C but did not change over time. For the vancomycin solution there were no differences in osmolality associated with temperature or time. The pH did not differ between portions stored at 4 and 25 degrees C but dropped sharply at both temperatures between days 0 and 7. The zone of inhibition did not differ with temperature or time. The tobramycin solution could be stored for 28 days at room temperature and the cefazolin solution for 28 days under refrigeration. The pH of the vancomycin solution changed too quickly for storage to be recommended.

Anti-Bacterial Agents↗
PubMed1994

Measuring carbon dioxide tension in saline and alternative solutions: quantification of bias and precision in two blood gas analyzers.

OBJECTIVE: To quantify the precision and bias for two standard blood gas analyzers when measuring PCO2 in five different test solutions (blood, normal saline, human albumin solution, succinylated gelatin 4%, and Hartmann's solution). DESIGN: A comparative laboratory study of two blood gas analyzers measuring known PCO2 in test solutions prepared with a thin film tonometer. MEASUREMENTS: The PCO2 was determined simultaneously in both blood gas analyzers. The precision and bias for both machines were calculated from the measured PCO2. RESULTS: Analyzer 1 showed a negative bias of between 66.4% and 39.2% when measuring PCO2 in saline. Under the same conditions, analyzer 2 showed a negative bias of between 17.7% and 17.9% for PCO2 in the mid- and high ranges of PCO2, but a positive bias in the low range. Both machines measured PCO2 with satisfactory bias and precision in blood. The use of succinylated gelatin 4% as a test solution improved the bias and precision of both machines. CONCLUSIONS: Because of the large bias and precision, neither of these machines is suitable for measuring PCO2 in saline solution. The use of succinylated gelatin 4% as a test solution improves the bias and precision of both machines and we favor this solution for nasogastric tonometry. Even with succinylated gelatin 4%, there is a large negative bias with analyzer 1 and our preference is to use analyzer 2. We recommend that other workers review critically the performance of blood gas electrode systems when measuring PCO2 in saline solution. Because of varying performance of "standard" machines, we also recommend that each institution determine its own reference range for intramucosal pH.

Blood Gas Analysis↗
PubMed1996

Gastric tonometry: precision and reliability are improved by a phosphate buffered solution.

OBJECTIVE: To compare a phosphate buffered solution with normal saline as tonometric fluid in intramucosal PCO2 measurement in humans. DESIGN: Prospective, unblinded comparison. SETTING: Postsurgical critical care unit of a university hospital. PATIENTS: Six septic patients. INTERVENTIONS: Two tonometric probes were positioned in the gastric lumen in each patient. One tube was used for conventional tonometry (saline-filled balloon), while phosphate buffered solution was instilled into the second tube. MEASUREMENTS AND MAIN RESULTS: PCO2 was determined with three blood gas analyzers (ABL 2 [Radiometer, Copenhagen, Denmark], Corning 288 [Ciba Corning Diagnostics GmbH, Neuss, Germany], and StatProfile 9 Plus [Nova Biomedical, Waltham, MA]). Eight parallel PCO2 measurements per patient were evaluated, yielding a total of 48 measurements with each tonometric solution. Intrainstrumental comparison of the PCO2 determinations demonstrated an increase of 12.3 +/- 9.9% for ABL 2, 3.10 +/- 12.9% for Ciba Corning 288, and 101.2 +/- 31.5% for StatProfile 9 Plus with the phosphate buffered solution. The PCO2 values were decreased by the following amounts when the three instruments were compared, using the saline method: 14.2 +/- 8.2% (Ciba Corning 288 vs. ABL 2); 40.7 +/- 9.9% (StatProfile 9 Plus vs. ABL 2); and 30.9 +/- 9.35% (StatProfile 9 Plus vs. Ciba Corning 288). The difference in PCO2 determination, resulting from the different instrument designs, were significant between the three blood gas analyzers (p<.001). In addition, the variance of the intramucosal PCO2 values was significant between blood gas analyzers (p<.001) with normal saline as tonometric solution, but not with phosphate buffered solution. The coefficients of determination between PCO2 values in saline and phosphate buffered solution were r2=.85 for ABL 2, r2=.81 for Ciba Corning 288, and r2=.74 for StatProfile 9 Plus. When all 48 PCO2 values were analyzed, the interinstrumental coefficients of determination within a method for saline (and for phosphate buffered solution in parenthesis) were:r2=.83 (.92) between ABL 2 and Ciba Corning 288, r2=.72 (.92) between ABL 2 and StatProfile 9 Plus, and r2=.81 (.98) between Ciba Corning 288 and StatProfile 9 Plus. CONCLUSIONS: A considerable instrumental bias in PCO2 analysis is observed when saline is used as tonometric fluid in gastric tonometry, thus preventing a reliable determination of intramucosal pH. The present in vivo data show that the accuracy and reliability of intramucosal pH measurement can be improved by the use of phosphate buffered solution as tonometric fluid.

Adult↗
PubMed1997

Effects of crystalloid solutions on circulating lactate concentrations: Part 1. Implications for the proper handling of blood specimens obtained from critically ill patients.

OBJECTIVES: a) To test the hypothesis that circulating lactate concentrations are the same in simultaneously collected arterial and central venous blood specimens; b) to test the hypothesis that even small amounts of crystalloid solutions, which are inadequately "cleared" from these indwelling arterial and venous catheters, can lead to clinically important and misleading changes in the measured lactate values. DESIGN: A prospective, multiexperiment study. SETTING: A critical care research laboratory and a 20-bed intensive care unit (ICU). PATIENTS: Three hundred fifty-five patients. INTERVENTIONS: Blood samples were collected. MEASUREMENTS AND MAIN RESULTS: Experiment 1: Simultaneously collected arterial and central venous blood specimens were obtained on 148 occasions from 48 medical ICU patients receiving no lactated Ringer's solution (RL). Arterial and central venous lactate values were nearly identical in these patients. The correlation between the arterial and central venous lactate concentrations was excellent (r2 = .85; p < .0001) and the agreement between the arterial and central venous lactate concentrations was also excellent (bias and precision = 0.04 mmol/L and +/- 0.38 mmol/L, respectively). Experiment 2: Arterial and mixed venous blood samples were obtained from 100 percutaneous transluminal coronary angioplasty (PTCA) and 75 cardiac surgical patients immediately before the performance of these cardiac procedures. We found the central venous lactate concentrations to be higher than arterial lactate values in the cardiac surgical group, and there was a very poor correlation (r2 = .07) between arterial and central venous lactate values in the cardiac surgical group. The correlation between central venous and arterial lactate concentrations in the PTCA patients was excellent (r2 = .84) and similar to the findings of experiment 1. Since the cardiac surgical patients received RL and the PTCA patients received no RL, we speculated that the intravenous infusion of RL in the cardiac surgical group accounted for these discordant findings. To test this speculation, we performed experiments 3 and 4. Experiment 3: In a large bench study, blood specimens were divided into multiple 1-mL aliquot portions, to which 0.01, 0.05, 0.10, 0.50, or 1.0 mL of various crystalloid solutions, containing or not containing RL, were added. In a volume-dependent and linear manner, solutions containing RL increased the circulating lactate concentration from 10% to > 400% of the baseline lactate value. In a volume-dependent and linear fashion, the non-RL crystalloid solutions decreased the lactate concentration by 0 to 66% of the baseline nondiluted lactate concentration. Experiment 4: In 30 different cardiac surgical patients, we simultaneously obtained central venous and arterial blood specimens. Patients this time received no RL, and catheter lines were adequately cleared (removal > 5 mL) of crystalloid solutions. We found a correlation (r2 = .82; p < .0001) that was virtually identical to the findings of experiment 1 and to the findings in the PTCA group of experiment 2. CONCLUSIONS: a) Arterial and central venous lactate concentrations are similar in hemodynamically stable critically ill patients, b) Even small amounts of RL-containing solutions in catheters used for blood sampling may cause false increases in the circulating lactate concentration. c) Even small amounts of non-RL crystalloid solutions in catheters used for blood sampling may falsely decrease circulating lactate values. d) When blood specimens are drawn from indwelling catheters, all crystalloid solutions must be cleared from the line.

Blood Specimen Collection↗
PubMed1992

Effects of rigid gas permeable contact lens solutions on the human corneal epithelium.

In this investigation, the effects of three rigid gas permeable (RGP) contact lens wetting and soaking solutions, Boston Advance Conditioning Solution, Boston Conditioning Solution, and Allergan Wet-N-Soak Plus, were tested on the human corneal epithelium. Thirty subjects participated in three experimental sessions, during which one eye received three drops of one of these RGP solutions, while the other eye served as a control. After 10 and 30 min, corneal staining was graded in 5 areas and the eyes were photographed for a digitized analysis of staining. Our results indicate that corneas exposed to Boston Advance Conditioning Solution demonstrated significantly more fluorescein staining than control eyes at both 10 and 30 min by both methods of analysis, whereas corneas treated with the other two solutions were not significantly different from controls. The increased corneal staining noted with Boston Advance Conditioning Solution may be caused by the presence and concentration of the preservative, 0.0015% polyaminopropyl biguanide. An unforeseen result of this experiment was the relatively large number of subjects exposed to Boston Conditioning Solution and Allergan Wet-N-Soak Plus who had more corneal staining in the control eye. This may suggest that the two RGP solutions served as a barrier to fluorescein, protecting the epithelial cells from staining.

Adolescent↗
PubMed2002

Storage solution containing fructose-1,6-bisphosphate inhibits the excess activation of Kupffer cells in cold liver preservation.

BACKGROUND: In liver transplantation, the activation of Kupffer cells at the time of cold preservation and reperfusion is considered to play an important role. In the present study, the usefulness of cold storage solution containing fructose-1,6-bisphosphate (FBP) was compared with University of Wisconsin (UW) solution in the function of Kupffer cells. METHODS: Kupffer cells were separated from rat liver stored at 4 degrees C in each storage solution. Four kinds of storage solutions were used: UW, simplified UW without FBP (0-FBP), and solutions with 10 or 20 mM FBP (10-FBP, 20-FBP). Lipopolysaccharide (LPS) labeled by fluorescein was loaded after 12 or 24 hr of cold preservation in each solution. The rates of cells uptaking LPS as phagocytic ability were measured using flow cytometry. Tumor necrosis factor-alpha, cytokine-induced neutrophil chemoattractant, and nitric oxide (NO) were measured in the supernatant. RESULTS: Tumor necrosis factor-alpha values in the 20-FBP group were significantly lower than those in the UW group. Cytokine-induced neutrophil chemoattractant values at 60 min after loading LPS were significantly lower in the 20-FBP group than in the UW group. NO values at 24 hr after loading LPS were significantly lower in the 20-FBP group compared with the UW group. The 20-FBP group was highest in the rates of cells uptaking LPS after 24-hr cold preservation. CONCLUSIONS: The storage solution containing FBP controlled the secretion of cytokines and NO from Kupffer cells and maintained phagocytic ability. This solution was considered to be more useful than UW solution for Kupffer cell protection.

Adenosine↗
PubMed2003

Isovolume hypertonic solutes (sodium chloride or mannitol) in the treatment of refractory posttraumatic intracranial hypertension: 2 mL/kg 7.5% saline is more effective than 2 mL/kg 20% mannitol.

OBJECTIVE: To evaluate the clinical benefit of increasing the osmotic load of the hypertonic solution administered for the treatment of refractory intracranial hypertension episodes in patients with severe head injury. DESIGN: Prospective, randomized study. SETTINGS: A trauma center in a university hospital. PATIENTS: Twenty consecutive patients with head trauma and persistent coma who required infusions of an osmotic agent to treat episodes of intracranial hypertension resistant to well-conducted standard modes of therapy were studied. Intracranial hypertension was considered refractory when it persisted despite deep sedation, optimal hemodynamic status, and, in some patients, drainage of cerebral spinal fluid. INTERVENTIONS: Patients were randomly assigned to receive isovolume infusions of either 7.5% hypertonic saline solution (2400 mOsm/kg/H(2)O) or 20% mannitol (1160 mOsm/kg/H(2)O). The patients were given 2 mL/kg (body weight) of either solution, i.e., 361 +/- 13 mOsm of saline or 175 +/- 12 mOsm of mannitol per injection. MEASUREMENTS AND MAIN RESULTS: The main variables studied were the number and the duration of episodes of intracranial hypertension per day during the study period, which was stopped after the last episode of intracranial hypertension was recorded from intracranial pressure monitoring or after the allocated treatment failure. Patients in the HHS group were monitored for 7 +/- 5 days and those in the mannitol group for 7 +/- 6 days (not significant). The rate of failure for each treatment was also evaluated. Failure was defined as the persistence of intracranial hypertension despite two successive infusions of the same osmotic agent. The mean number of osmotic solute infusions was 3.7 +/- 5.3 in the mannitol group and 3.3 +/- 4.1 in the hypertonic saline solution group (not significant). The mean number (6.9 +/- 5.6 vs. 13.3 +/- 14.6 episodes) of intracranial hypertension episodes per day and the daily duration (67 +/- 85 vs. 131 +/- 123 min) of intracranial hypertension episodes were significantly lower in the hypertonic saline solution group (p <.01). The rate of clinical failure was also significantly lower in the hypertonic saline solution group: 1 of 10 patients vs. 7 of 10 patients (p <.01). CONCLUSION: In this study, when a hypertonic solute was required for the treatment of refractory intracranial hypertension episodes in patients with severe head trauma, increasing the osmotic load by giving 2 mL/kg (body weight) of 7.5% saline (361 +/- 13 mOsm) was more effective than giving 2 mL/kg (body weight) of 20% mannitol (175 +/- 12 mOsm). Within the limitations of the present study, these data suggest that giving 2 mL/kg hypertonic saline solution (approximately 480 mOsm/70 kg body weight) is an effective and safe initial treatment for intracranial hypertension episodes in head-trauma patients when osmotherapy is indicated.

Adult↗
PubMed2003

Comparative antimicrobial activity of no-rub multipurpose lens care solutions in the presence of organic soil.

PURPOSE: This study reports the effect of organic soil on the antimicrobial activity of four commercially available multipurpose contact lens care solutions used in no-rub regimens as determined by a modified International Organization for Standardization 14729 (ophthalmic optics-contact lens care products-microbiological requirements for products and regimens for hygienic management of contact lenses) Stand Alone Test procedure. METHODS: Testing was performed with organic soil consisting of a mixture of heat-killed yeast cells and heat-inactivated bovine serum or these components added separately. The organic soil was mixed with the challenge microorganisms before addition to the solution, added to the solution after addition of the challenge microorganisms, or added to the solution before addition of the challenge microorganisms. A final concentration of 0.4% v/v organic soil and 1 x 105 to 1 x 106 cfu/mL challenge microorganisms was realized in all test cases. RESULTS: The antimicrobial activity of no-rub multipurpose lens care solutions was reduced in the presence of added organic soil. The extent of reduction varied with the type of organic soil, the method of addition of the organic soil to the solution, the challenge organism, and the solution tested. CONCLUSION: The type of organic soil used and the method of addition of organic soil to the lens care solution may affect antimicrobial activity as determined by the primary criteria of the International Organization for Standardization Stand Alone Test procedure. The overall reduction in antimicrobial activity depends on the solution and organism.

Bacteria↗
PubMedDate not supplied

Bound solute dialysis.

We used the thermodynamic principles governing bound solute dialysis, commonly referred to as "albumin dialysis" or "sorbent dialysis" and practiced clinically with the Molecular Adsorbent Recirculating System (MARS) and Biologic-DT approaches, respectively, to develop a comprehensive understanding of the process. Dimensionless parameters emerging from the thermodynamic analysis that govern bound solute dialysis are as follows: (1) lambda, the binding power of the solute binding moiety; (2) kappa, the dialyzer mass transfer/blood flow rate ratio; (3) alpha, the dialysate/blood flow rate ratio; (4) beta, the dialysate/blood binding moiety concentration ratio, and (5) psi, the solute/binding moiety concentration ratio in the blood. Results from a mathematical model of countercurrent bound solute dialysis for phi = 0.9 indicate that for a given binding moiety (fixed lambda), the most important parameter for achieving high removal rates is the dialyzer mass transfer ratio for free (unbound) solute. The results also show solute removal approaching an asymptote with increasing beta that is dependent on kappa and independent of alpha. More importantly, results indicate that once a dialysis membrane is chosen, solute removal is virtually independent of blood flow rate, dialysate flow rate, and amount of binding moiety in the dialysate, provided the amount is greater than approximately 90% of that required to reach the asymptote. Experimental observations over a range of blood flow rates (100-400 ml/ minute), dialysate flow rates (50-400 ml/minute), and dialysate/blood albumin concentration ratios (beta = 0-0.3) corroborate the model predictions and indicate that < 4 g/L albumin in the dialysate solution is required for effective bound solute dialysis. The experimental results also show evidence of enhanced mass transfer once the dialysis membrane pore structure surface saturates with albumin.

Albumins↗
PubMedDate not supplied

Loss of catheter locking solution caused by fluid density.

The avoidance of clotting in catheter lumina between treatments usually entails locking with an anticoagulant solution such as heparin. In a previous work, it was shown that approximately 20% of locking solution flows from the catheter during instillation of the lock equal in volume to the lumen volume. Furthermore, the locking solution may spill into the blood stream under the influence of gravity. This work investigates the influence of density and viscosity of the locking solution on the volume and speed of locking solution loss from the catheter lumen. A large fraction of the catheter locking solution spills under the influence of gravity if the locking solution's density is higher than the fluid it spills to (blood). Locking solution lost is replaced by blood. Viscosity delays this process, but at 90 minutes after injection, the loss is completed even when highly viscous lock solutions are used. Slow administration of the lock has negligible influence upon the dynamics of the loss.

Anticoagulants↗
PubMedDate not supplied

Slow continuous ultrafiltration with bound solute dialysis.

Bound solute dialysis (BSD), often referred to as "albumin dialysis" (practiced clinically as the molecular adsorbents recirculating system, MARS, or single-pass albumin dialysis, SPAD) or "sorbent dialysis" (practiced clinically as the charcoal-based Biologic-DT), is based upon the thermodynamic principle that the driving force for solute mass transfer across a dialysis membrane is the difference in free solute concentration across the membrane. The clinically relevant practice of slow continuous ultrafiltration (SCUF) for maintenance of patients with liver failure is analyzed in conjunction with BSD. The primary dimensionless operating parameters that describe SCUF-BSD include (1) beta, the dialysate/blood binder concentration ratio; (2) kappa, the dialyzer mass transfer/blood flow rate ratio; (3) alpha, the dialysate/blood flow rate ratio; and, (4) gamma, the ultrafiltration/blood flow rate ratio. Results from mathematical modeling of solute removal during a single pass through a dialyzer and solute removal from a one-compartment model indicate that solute removal is remarkably insensitive to gamma. Solute removal approaches an asymptote (improvement in theoretical clearance over that obtainable with no binder in the dialysate) with increasing beta that is dependent on kappa and independent of alpha. The amount of binder required to approach the asymptote decreases with increasing solute-binder equilibrium constant, i.e., more strongly bound solutes require less binder in the dialysate. The results of experimental observations over a range of blood flow rates, 100 to 180 mL/min, dialysate flow rates, 600 to 2150 mL/h, ultrafiltration rates, 0 to 220 mL/h, and dialysate/blood albumin concentration ratios, beta = 0.01 to 0.04, were independently predicted remarkably well by the one-compartment model (with no adjustable parameters) based on BSD principles.

Albumins↗
PubMed2004

Molecular size as the main determinant of solute maximum flux across the skin.

One of the most important determinants of dermatological and systemic penetration after topical application is the delivery or flux of solutes into or through the skin. The maximum dose of solute able to be delivered over a given period of time and area of application is defined by its maximum flux (J(max), mol per cm(2) per h) from a given vehicle. In this work, J(max) values from aqueous solution across human skin were acquired or estimated from experimental data and correlated with solute physicochemical properties. Whereas epidermal permeability coefficients (k(p)) are optimally correlated to solute octanol-water partition coefficient (K(ow)) and molecular weight (MW) was found to be the dominant determinant of J(max) for this literature data set: log J(max)=-3.90-0.0190MW (n=87, r(2)=0.847, p<0.001). Estimated solubility in octanol (S(oc)) was also a determinant, but improvement in the regression by the addition of log S(oc) was small (r(2) increased to 0.856). Addition of other physicochemical parameters to MW by forward stepwise regression only marginally improved the regression with a melting point (Mpt) term (r(2)=0.879) and then hydrogen bonding acceptor capability (H(a)) (r(2)=0.917) is significant. Validation of the equation above was carried with a number of other data sets: an aqueous vehicle with full- and split-thickness skin (r(2)=0.784, n=56), some pure solutes (r(2)=0.537, n=34), an aqueous vehicle with ionizable solutes (r(2)=0.282, n=54) and solutes from a propylene glycol vehicle (r(2)=0.484, n=36). An analysis of the entire database gave the equation log J(max)=-4.52-0.0141MW (n=278, r(2)=0.688, p<0.001), with inclusion of Mpt and H(a) increasing r(2) to 0.760 (n=269). Separate analysis of full- and split-thickness skin data confirmed that the dermal resistance term had only a marginal effect on overall J(max). Application of the latter model to an in vivo situation where the dermal capillary bed is slightly below the epidermal-dermal junction revealed that the dermal resistance term was unnecessary for in vivo predictions for most solutes.

Biological Transport↗
PubMedDate not supplied

The contractile response of smooth muscle to immersion in hypertonic solutions.

1. Strips of bovine tracheal muscle and rabbit aorta produced sustained contractions on perfusion with Krebs solution made twice normal strength by addition of sucrose. The contractures were relaxed on return to normal Krebs solution. 2. Similar contractures were produced by tracheal muscle strips in Krebs solutions made twice normal strength by addition of galactose, glucose or NaCl whereas urea caused only a transient contraction. 3. In twice normal strength Krebs solution (sucrose added) the basal tension of rat portal vein and guinea-pig taenia coli was increased. Spontaneous mechanical activity was maintained, but the frequency of contractions was reduced. 4. The hypertonic contracture of bovine trachea in twice normal strength Krebs solution (sucrose added) was reduced by 15% by omission of Ca from the bathing fluid (0.1 mmol/l EGTA added). Severe Ca depletion, by prolonged washing in Ca-free Krebs with 12.5 mmol/l EGTA and Carbachol added, resulted in a 77% reduction in the hypertonic contracture. 5. In twice normal Krebs solution (sucrose added), the hypertonic contracture was partially relaxed by isoprenaline (4 x 10(-6) mol/l); the contractile response to carbachol was reduced; the contractile response to high-K Krebs solution was maintained. 6. Atropine (5 x 10(-7) mol/l) abolished the contractile response to carbachol, but had no effect on the hypertonic contracture. 7. It is suggested that the contraction of bovine tracheal strips in hypertonic solutions is mainly due to activation of the contractile myofilaments rather than simple cell shrinkage. Hypertonic solutions may also interfere with some steps in the excitation-contraction coupling sequence.

Animals↗
PubMed2004

Ameliorating small bowel injury using a cavitary two-layer preservation method with perfluorocarbon and a nutrient-rich solution.

The aim of this study was to improve small bowel (SB) quality during cold storage by combining two proven preservation strategies involving perfluorocarbon (PFC) and a novel luminal amino acid-rich solution. Rodent SB was flushed vascularly with UW solution and flushed luminally as follows: Group 1 (control)--no luminal flush, stored in UW; Group 2--luminal UW solution, stored in PFC; Group 3--luminal amino-acid (AA) solution, stored in PFC; and Group 4--luminal AA solution, stored in AA solution. Energetics, histology and mucosal function/electrophysiology were assessed over 24 h at 4 degrees C. ATP was consistently greater in Groups 2-4 than in the Control Group. Groups 3 and 4 exhibited significantly greater ATP, ATP/ADP ratios and energy charge levels after 12-h storage than in the other Groups. Histologic injury was generally lower in the AA-treated tissues (Groups 3 and 4); after 24 h, only minor epithelial clefting (Park's median grade 2) was present in Group 4; and consistent transmural infarction (grade 8) was evident in Groups 1 and 2. Combined treatment with luminal amino acid solution and oxygenated storage solution (PFC or AA solution) significantly improves energetics and mucosal function. This strategy may have implications for successful SB preservation in the clinic.

Adenosine Diphosphate↗
PubMed1997

Calibration of Mg(2+)-selective macroelectrodes down to 1 mumol l-1 in intracellular and Ca(2+)-containing extracellular solutions.

Using Mg(2+)-selective macroelectrodes based on the neutral carriers ETH 7025 and ETH 5506, methods were developed to determine accurately the apparent binding constant (Kapp) and purity, and hence the ionized magnesium concentration ([Mg2+]), in Ca(2+)-free, Mg2+ buffer solutions manufactured with either CDTA (trans-1,2-diaminocyclohexane-N,N,N',N'-tetraacetic acid monohydrate) or EDTA. In nominally Ca(2+)-free solutions, calibration of the macroelectrodes was possible down to 1 mumol l-1 in both intracellular (ETH 7025)- and extracellular (ETH 5506)-like physiological solutions. The measured [Mg2+] in the buffer solutions overlapped with the [Mg2+] set by dilution alone, suggesting that the method was reliable. These buffer solutions could then be used to manufacture standard Mg2+ solution containing known [Mg2+] at a set calcium concentration. Ca2+ sensitivity limits the use of ETH 7025 and, for extracellular measurements in Ca(2+)-containing solutions, Mg(2+)-selective macroelectrodes manufactured with ETH 5506 were the electrodes of choice. In 0.5-0.9 mmol l-1 Ca+, measurement of [Mg2+] was possible down to 10 mumol l-1. At [Mg2+] greater than 0.25 mmol l-1 there was no interference from Ca2+ (0.5-1.5 mmol l-1). With CDTA and/or EDTA buffer solutions there was a wide variation between the calculated values for the [Mg2+] and the measured [Mg2+] (the calculated values differed by a factor of up to 4.5 and 3, respectively). At present, measurement of the Kapp and ligand purity in the appropriate solution at the desired pH and temperature would seem to be the best strategy to adopt rather than attempting to calculate the constant. Since no recognized international standard exists for [Mg2+] at the micromolar level, values in the literature for Kd, etc. in this range can only be regarded as approximate.

Buffers↗
PubMed1991

Sodium-hydrogen exchange in guinea-pig ventricular muscle during exposure to hyperosmolar solutions.

1. The effect on intracellular pH (pHi) and intracellular Na+ activity (aNai) of exposure to hyperosmolar solutions was investigated in guinea-pig ventricular muscle using ion-sensitive microelectrodes. 2. Exposure of tissue to solution made hyperosmolar by the addition of 100 mM-sucrose produced an intracellular alkalinization of 0.10 pH units and hyperpolarization of the membrane potential. 3. When extracellular Na+ was reduced to 15 mM by substitution of NaCl with choline chloride, exposure to hyperosmolar solutions caused a decrease in pHi. Identical experiments using LiCl as the sodium substitute resulted in an increase in pHi of a magnitude similar to that seen at physiological Na+ levels. 4. In the presence of 50 microM-5-(N,N-dimethyl)amiloride (DMA), an inhibitor of Na(+)-H+ exchange, pHi decreased upon exposure to hyperosmolar solution. 5. The recovery of pHi from an intracellular acidosis (induced by brief exposure to NH4Cl) was enhanced in hyperosmolar solution when compared to recovery in isosmolar solution. This enhancement was observed even when aNai was markedly elevated (greater than 25 mM) by inhibition of the Na(+)-K+ pump. 6. There was an increase in aNai during exposure to hyperosmolar solutions. When the Na(+)-K+ pump was inhibited with dihydro-ouabain a component of this increase in aNai was sensitive to DMA. 7. We conclude that exposure of cardiac tissue to hyperosmolar solutions results in an intracellular alkalosis due to activation of the sarcolemmal Na(+)-H+ exchanger. Such changes should be considered when exposure to hyperosmolar solutions is used in the study of excitation-contraction coupling and cardiac muscle mechanics.

Acidosis↗
PubMed1996

Use of radionuclide imaging to determine gastric emptying of carbohydrate solutions during exercise.

OBJECTIVE: To investigate the repeatability of continual assessment of the gastric emptying rates of carbohydrate solutions in exercising subjects using 99mtechnetium labelling. METHODS: Gastric emptying of a 5% glucose solution and an iso-osmotic maltodextrin solution was measured using 3 MBq of 99mtechnetium labelled diethylene triamine penta-acetic acid (DTPA) and continuous gamma camera imaging in five male subjects. The subjects performed four 1 h trials at 70% VO2 peak on a cycle ergometer. After 15 min, 200 ml of a radiolabelled solution of glucose or maltodextrin were ingested in a blind crossover protocol. The two solutions were each ingested on separate occasions (trial 1 and trial 2) to establish repeatability. RESULTS: Statistical analysis showed no differences between trial 1 and trial 2 for both solutions. There were no significant differences for the emptying rates between the two test solutions. CONCLUSIONS: Posterior imaging using a computer linked gamma camera following the ingestion of 99mtechnetium labelled DTPA mixed with carbohydrate solutions provides a repeatable method of assessing gastric emptying characteristics in exercising subjects. This technique showed no significant differences between the emptying rates of a single dose of iso-osmotic glucose or maltodextrin solution.

Adult↗