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PubMed2002

Survival of Listeria monocytogenes in commercial food-processing equipment cleaning solutions and subsequent sensitivity to sanitizers and heat.

AIMS: To determine the ability of Listeria monocytogenes to survive exposure to commercial food-processing equipment cleaning solutions and subsequent treatment with sanitizers or heat. METHODS AND RESULTS: Cells of five strains of L. monocytogenes were suspended in 1% solutions of eight commercial cleaners (pH 7.1-12.5) or in water (control) and incubated at 4 degrees C for 30 min or 48 h before populations were determined by plating on tryptose phosphate agar. After exposure of cells to cleaning solutions for 30 min, populations of the most resistant strain of L. monocytogenes were reduced by < or = 1.63 log10 cfu ml(-1). In only three highly alkaline cleaning solutions (pH 11.6-12.4) were populations reduced significantly (P < or = 0.05) compared with reductions in water. After 48 h, populations were significantly higher in one cleaning solution (pH 10.4) than in water, while populations in six of the other seven cleaning solutions were reduced by > or = 4.72 log10 cfu ml(-1). Cells exposed to cleaning solutions for 30 min became sensitive to 4.0 or 6.0 mg l(-1) free chlorine and to 50 or 100 mg l(-1) benzalkonium chloride and cetylpyridinium chloride, common components of quaternary ammonium sanitizers. Cells exposed to four of the five test cleaners had D56 degrees C values less than or equal to those of the control cells. CONCLUSIONS: Listeria monocytogenes tolerates exposure to a high concentration of alkaline cleaning solutions but consequently becomes sensitized to sanitizers. SIGNIFICANCE AND IMPACT OF THE STUDY: The elimination of L. monocytogenes surviving exposure to alkaline cleaning solutions widely used for food-processing equipment is essential and the appropriate use of sanitizers for subsequent application to equipment is important in achieving this goal.

Anti-Infective Agents, Local↗
PubMed2001

Intrinsic versus extrinsic stabilization of enzymes: the interaction of solutes and temperature on A4-lactate dehydrogenase orthologs from warm-adapted and cold-adapted marine fishes.

We examined the effects of temperature and stabilizing solutes on A4-lactate dehydrogenase (A4-LDH) from warm- and cold-adapted fishes, to determine how extrinsic stabilizers affect orthologs with different intrinsic stabilities. Conformational changes during substrate binding are rate-limiting for A4-LDH, thus stabilization due to intrinsic or extrinsic factors leads to decreased activity. A4-LDH from a warm-temperate goby (Gillichthys mirabilis), which has lower values for kcat and the Michaelis constant for pyruvate ( K m PYR), was intrinsically more stable than the orthologs of the cold-adapted Antarctic notothenioids Parachaenichthys charcoti and Chionodraco rastrospinosus, as shown by a higher apparent transition ('melting') temperature (Tm(APP)). We used four solutes, glycerol, sucrose, trimethylamine-N-oxide and poly(ethylene glycol) 8000, which stabilize proteins through different modes of preferential exclusion, to study temperature-solute interactions of the three orthologs. Changes in Tm(APP) were similar for all orthologs in each solute tested, but the catalytic rate of G. mirabilis A4-LDH was decreased most by solutes and increased most by temperature. In contrast, the K m PYR values of the Antarctic orthologs were more affected than that of the goby by both solutes and temperature. We conclude that (a) preferential exclusion of solutes functions within the native state of A4-LDH to favor conformational microstates with minimal surface area; (b) the varied effects of the different solutes on the kinetic properties are due to the interaction between this nonspecific stabilization and the differing intrinsic stabilities of the orthologs; (c) the catalytic rates of A4-LDH orthologs are equally affected by stabilizing solutes, if measurements are made at physiologically appropriate temperatures; and (d) global stability and localized flexibility of these A4-LDH orthologs may evolve independently.

Animals↗
PubMed2003

Effects of intraperitoneal 4% icodextrin solution on the healing of bowel anastomoses and laparotomy incisions in rabbits.

OBJECTIVE: Peri-operative lavage and postoperative instillation of a 4% icodextrin solution reduces de novo formation and reformation of peritoneal adhesions following abdominal surgery. This experimental study evaluated the effects of 4% icodextrin treatment on the healing of bowel anastomoses and laparotomy incisions. MATERIALS AND METHODS: Female New Zealand White rabbits (weight 2.21-2.77 kg) were randomised by ascending weight to one of 3 surgical treatments, each with 2 termination points (6 groups of 8 animals). The treatments were anastomotic bowel surgery alone or with lavage and postoperative instillation of either 4% icodextrin solution or Lactated Ringer's Solution (LRS). The solutions were coded A and B by the supplier, so that the study personnel were blinded to their identity. After the abdomen was opened, 30 ml of solution A or B was instilled and removed by aspiration prior to surgery. The ascending colon was then transected 5 cm aboral to the ileocaecal junction and the ends anastomosed. During surgery, 5 ml of the solution was applied 4 times at the surgical site, and a further 30 ml was administered and aspirated as a postoperative lavage. Just prior to closure of the abdominal wall, 50 ml of the solution was administered as a postoperative instillate. Duplicate treatment groups were terminated 7 and 21 days after surgery and the anastomotic sites inspected for adhesion and/or abscess formation. In 6 animals per group, an 8-12 cm length of colon including the anastomotic site was removed for measurement of bursting pressure, and a section of the abdominal wall including the incision line was tested for breaking strength. The other 2 animals per group provided tissue for histological analysis of wound healing at the bowel and incision sites. RESULTS: There was no significant difference between the 3 treatment groups for any parameter (P > 0.05). Compared with the surgical control at either day 7 or 21 after surgery, the administration of solutions A or B did not affect the formation of abscesses or adhesions, the bursting strength of the bowel, or the tear strength of the abdominal wall incision. Histological assessment of the quality of wound healing showed no differences between treatment groups in inflammatory cell infiltration, fibroblast density, blood vessel formation or collagen maturity. CONCLUSIONS: The use of a 4% icodextrin solution for peri-operative lavage and postoperative instillation in a rabbit model of bowel anastomotic healing did not result in any difference from either LRS treated or untreated surgical controls.

Anastomosis, Surgical↗
PubMed2002

[Visual documentation of the stability of intravenous solutions of omeprazole (Losec) and pantoprazole (Pantoloc)].

Patients with complications of peptic ulcers, high grade reflux oesophagitis, or Zollinger Ellison syndrome need a sufficient permanent acid suppression. In appropriate indications they receive proton pump inhibitors (PPI) intravenously or via perfusion over a longer period, if an oral application is not possible. PPIs are prodrugs, which should be converted into the active principle in the acidic canaliculus at pH 1 of the parietal cell. Otherwise they would be activated prematurely. Immediate chemical degradation causes discolouration. Aim of the study was to compare pH stabilities of the intravenous formulations of Omeprazole (different solutions for infusion and injection) and Pantoprazole (one solution for injection and infusion). The solutions prepared accordingly to the official instructions, were exposed to four different light conditions. Both manufacturers (AstraZeneca Osterreich GmbH, Byk Osterreich Pharma Ges.m.b.H.) state reference solutions for acceptable discolouration. Those were prepared according to the European Pharmacopeia. Discolouration of solutions were evaluated as criterion for stability of the PPI prodrugs. If change of colour is at least of the extent of the corresponding reference solution, further use is no longer permitted. Optical alterations under different light conditions were compared and documented photographically with standardized illumination. Intensity and spectral composition of light as well as temperature had only minor influence on discolouration as measure of degradation of the prodrugs. Both formulations for injection fulfill the specifications for pH stability within the stated time frames mentioned in the summaries of product characteristics (SPC). Comparing both products, after a short period (1 hour) Omeprazole injectable formulation showed a substantial optical discolouration. After 6 hours these changes were more intense than the reference solution BG5 allows. Pantoprazole showed optical alteration to a notable later time point. After 24 hours discolouration reached the reference colour B6. Injectable formulation of Pantoprazole is about three times more stable than that of Omeprazole. Infusion solution of Omeprazole shows no optical alteration within the stated time frame due to high dilution and pH value. Assuming that 100 ml of the infusion solution contains 40 mg Omeprazole. It takes 5 hours for the volume to be infused at a dose regimen of 8 mg/h. Therefor 5 x 100 ml/24 h are needed.

2-Pyridinylmethylsulfinylbenzimidazoles↗
PubMed2005

Transient cavities and the excess chemical potentials of hard-spheroid solutes in dipolar hard-sphere solvents.

Monte Carlo computer simulations are used to study transient cavities and the solvation of hard-spheroid solutes in dipolar hard-sphere solvents. The probability distribution of spheroidal cavities in the solvent is shown to be well described by a Gaussian function, and the variations of fit parameters with cavity elongation and solvent properties are analyzed. The excess chemical potentials of hard-spheroid solutes with aspect ratios x in the range of 15< or =x< or =5, and with volumes between 1 and 20 times that of a solvent molecule, are presented. It is shown that for a given molecular volume and solvent dipole moment (or temperature) a spherical solute has the lowest excess chemical potential and hence the highest solubility, while a prolate solute with aspect ratio x should be more soluble than an oblate solute with aspect ratio 1x. For a given solute molecule, the excess chemical potential increases with increasing temperature; this same trend can be observed in hydrophobic solvation. A scaled-particle theory based on the solvent equation of state and a fitted solute-solvent interfacial tension shows excellent agreement with the simulation results over the whole range of solute elongations and volumes considered. An information-theoretic model based on the solvent density and radial distribution function is less successful, being accurate only for small solute volumes and low solvent densities.

Journal Article↗
PubMed2005

Solvent phase behavior and the interaction of uniform and patterned solutes.

Isotropic and anisotropic hypernetted-chain (HNC) integral equation theories are used to obtain the interaction of solutes both near and far from the solvent liquid-vapor coexistence. Spherically symmetrical and chemically patterned (patched) solutes are considered, and the influences of particle and patch sizes are investigated. Solvophilic and solvophobic solutes (or patches) are examined. Near coexistence, in the solvophobic case drying-like behavior occurs for solutes (patches) of sufficient size. This gives rise to relatively long ranged attractive forces that are strongly orientation dependent for the patched solute particles. We also report grand canonical Monte Carlo results for a pair of spherically symmetric solutes. This demonstrates that the anisotropic HNC theory gives qualitatively correct solvent structure in the vicinity of the solutes. Comparison with previous simulations also shows that the solute-solute potentials of mean force given by the anisotropic theory are more accurate (particularly at small separations) than those obtained using the isotropic method.

Journal Article↗
PubMed2003

Wound irrigation in children: saline solution or tap water?

STUDY OBJECTIVE: Irrigation, a critical component of wound management, is commonly performed with sterile normal saline solution. The purpose of this study was to compare the infection rates of wounds irrigated with normal saline solution versus those of wounds irrigated with running tap water. METHODS: A prospective trial was conducted in an urban pediatric emergency department. Tap water pressure and flow rates were measured, and cultures were obtained before the study and at 5 months after study initiation. Patients 1 to 17 years of age presenting to the pediatric ED with a simple laceration were eligible. Exclusion criteria included immunocompromise, complicated lacerations, or current use of or need for antibiotics. Patients were allocated to the running tap water group or the standard normal saline solution irrigation group. Wounds were closed in standard fashion. Patients returned to the pediatric ED in 48 to 72 hours for evaluation. RESULTS: Two hundred seventy-one patients were enrolled in the normal saline solution group and 259 in the tap water group. Tap water and normal saline solution pressures and flow rates differed. The groups did not differ in terms of patient demographic characteristics or wound characteristics. However, more wounds were located on the hand in the tap water group (21.3%; 95% confidence interval [CI] 16.3% to 27.1%) compared with those in the normal saline solution group (9.2%; 95% CI 5.9% to 13.4%). The wound infection rates were similar in the 2 groups (normal saline solution group: 2.8% [95% CI 1.1% to 5.7%] versus running tap water group: 2.9% [95% CI 1.2% to 5.9%]). CONCLUSION: There were no clinically important differences in infection rates between wounds irrigated with tap water or normal saline solution. Tap water might be an effective alternative to normal saline solution for wound irrigation in children.

Adolescent↗
PubMed2002

A comparison of vaginally administered misoprostol with extra-amniotic saline solution infusion for cervical ripening and labor induction.

OBJECTIVE: The purpose of this study was to compare intravaginal misoprostol with extra-amniotic saline solution infusion with concomitant oxytocin for cervical ripening and labor induction in viable pregnancies. STUDY DESIGN: Two hundred women with indications for labor induction and unfavorable cervices were assigned randomly to vaginal misoprostol or extra-amniotic saline solution infusion. Twenty-five micrograms of misoprostol was administered every 4 hours up to six doses, followed by intravenous oxytocin administration. Patients who had received extra-amniotic saline solution infusion also received intravenous oxytocin along with a maximum 12-hour saline solution infusion through Foley catheters that were placed above the internal cervical os. RESULTS: One hundred women were randomly assigned to misoprostol, and 100 women were assigned randomly to extra-amniotic saline solution infusion. The average interval from start of induction to vaginal delivery was longer in the misoprostol group (1323.3 +/- 700.3 minutes) than in the extra-amniotic saline solution infusion group (970.4 +/- 502.7 minutes; P =.006, log transformed data). Abnormal fetal heart rate tracings were found in 30% of the patients who received misoprostol and in 19% of the patients who received extra-amniotic saline solution infusion (relative risk, 1.6; 95% CI, 1.0-2.4; P =.05). There was more tachysystole in the misoprostol group (8%) than in the extra-amniotic saline solution infusion group (1%; P =.02). There were no differences in the routes of deliveries or neonatal outcomes between groups. CONCLUSION: Extra-amniotic saline solution infusion with oxytocin administration appears more effective and is associated with fewer maternal complications than misoprostol for cervical ripening and labor induction.

Catheterization↗
PubMed1974

Solute flux coupling in a homopore membrane.

Our previous studies on solute drag on frog skin and synthetic heteropore membranes have been extended to a synthetic homopore membrane. The 150-A radius pores of this membrane are formed by irradiation and etching of polycarbonate films. The membrane is 6-microm thick and it has 6 x 10(8) pores cm(-2). In this study, sucrose has been used as the driver solute with bulk flow blocked by hydrostatic pressure. As before on heteroporous membranes, the transmembrane asymmetry of tracer solute is dependent on the concentration of the driver solute. Tracer sucrose shows no solute drag while maltotriose shows appreciable solute drag at 1.5 M sucrose. With tracer inulin and dextran, solute drag is detectable at 0.5 M sucrose. These results are in keeping with the previous findings on heteropore membranes. Transmembrane solute drag is the result of kinetic and frictional interaction of the driver and tracer solutes as the driver flows down its concentration gradient. The magnitude of the tracer flux asymmetry is also dependent on the size of the transmembrane pores.

Carbon Radioisotopes↗
PubMed2004

Stability and compatibility of reconstituted ertapenem with commonly used i.v. infusion and coinfusion solutions.

PURPOSE: The stability of ertapenem sodium in various commonly used i.v. infusion solutions and its compatibility with coinfusion solutions was studied. METHODS: Ertapenem was reconstituted with sterile water for injection and then diluted with various commercial i.v. infusion solutions to concentrations of 10 and 20 mg/mL. The solutions were stored in flexible polyvinyl chloride containers at 4 and 25 degrees C and in sterile glass vials at -20 degrees C. The drug's stability at 4 degrees C was monitored daily for up to 10 days, at 25 degrees C at appropriate hourly intervals for up to 30 hours, and at -20 degrees C. The daily for up to 14 days. Compatibility with the coinfusion solutions was monitored for up to eight hours at room temperature. Stability assays were conducted until the ertapenem concentration decreased by 10% or the corresponding degradation products exceeded the approved specifications. Ertapenem concentrations were determined by a stability-indicating high-performance liquid chromatography assay. RESULTS: Ertapenem was more stable in solutions stored at 4 degrees C versus 25 degrees C. Samples frozen at -20 degrees C showed extreme variability. Ertapenem 10 mg/mL was stable for a longer time than at the 20-mg/mL concentration. Ertapenem demonstrated the greatest stability in 0.9% and 0.225% sodium chloride solutions. CONCLUSION: Ertapenem sodium injection 10 and 20 mg/mL are relatively stable in sodium chloride injections and Ringer's solution when stored at 25 and 4 degrees C, but are unstable in mannitol and dextrose solutions. The drug can be coinfused with hetastarch, heparin sodium, and potassium chloride over several hours.

Chromatography, High Pressure Liquid↗
PubMed2001

The effects of balanced versus saline-based hetastarch and crystalloid solutions on acid-base and electrolyte status and gastric mucosal perfusion in elderly surgical patients.

UNLABELLED: The IV administration of sodium chloride solutions may produce a metabolic acidosis and gastrointestinal dysfunction. We designed this trial to determine whether, in elderly surgical patients, crystalloid and colloid solutions with a more physiologically balanced electrolyte formulation, such as Hartmann's solution and Hextend, can provide a superior metabolic environment and improved indices of organ perfusion when compared with saline-based fluids. Forty-seven elderly patients undergoing major surgery were randomly allocated to one of two study groups. Patients in the Balanced Fluid group received an intraoperative fluid regimen that consisted of Hartmann's solution and 6% hetastarch in balanced electrolyte and glucose injection (Hextend). Patients in the Saline group were given 0.9% sodium chloride solution and 6% hetastarch in 0.9% sodium chloride solution (Hespan). Biochemical indices and acid-base balance were determined. Gastric tonometry was used as a reflection of splanchnic perfusion. Postoperative chloride levels demonstrated a larger increase in the Saline group than the Balanced Fluid group (9.8 vs 3.3 mmol/L, P = 0.0001). Postoperative standard base excess showed a larger decline in the Saline group than the Balanced Fluid group (-5.5 vs -0.9 mmol/L, P = 0.0001). Two-thirds of patients in the Saline group, but none in the Balanced Fluid group, developed postoperative hyperchloremic metabolic acidosis (P = 0.0001). Gastric tonometry indicated a larger increase in the CO2 gap during surgery in the Saline group compared with the Balanced Fluid group (1.7 vs 0.9 kPa, P = 0.0394). In this study, the use of balanced crystalloid and colloid solutions in elderly surgical patients prevented the development of hyperchloremic metabolic acidosis and resulted in improved gastric mucosal perfusion when compared with saline-based solutions. IMPLICATIONS: This prospective, randomized, blinded trial showed that, in elderly surgical patients, the use of balanced IV solutions can prevent the development of hyperchloremic metabolic acidosis and provide better gastric mucosal perfusion compared with saline-based fluids.

Acid-Base Equilibrium↗
PubMed1997

Hextend (hetastarch solution) decreases multiple organ injury and xanthine oxidase release after hepatoenteric ischemia-reperfusion in rabbits.

OBJECTIVE: We hypothesized that multiple organ injury and concentrations of xanthine oxidase (an oxidant-generating enzyme released after hepatoenteric ischemia) would be decreased by the administration of a bolus of a colloid solution at reperfusion. DESIGN: Randomized, masked, controlled animal study. SETTING: University-based animal research facility. SUBJECTS: Fifty-four New Zealand white male rabbits, weighing 2 to 3 kg. INTERVENTIONS: Anesthetized rabbits were assigned to either the hepatoenteric ischemia-reperfusion group (n = 27) or the sham-operated group (n = 27). Hepatoenteric ischemia was maintained for 40 mins with a balloon catheter in the thoracic aorta, followed by 3 hrs of reperfusion. Each group was randomly administered a bolus of one of three fluids at the beginning of reperfusion: Hextend (hetastarch solution); 5% human albumin; or lactated Ringer's solution. The investigators were masked as to the identity of the fluid administered. MEASUREMENTS AND MAIN RESULTS: Multiple organ injury was assessed by the release of lactate dehydrogenase activity into the plasma and by indices of gastric and pulmonary injury. Circulating lactate dehydrogenase activity was significantly greater (p < .001) in animals receiving lactated Ringer's solution than in rabbits receiving either colloid solution. Gastric injury (tissue edema, Histologic injury Score) was significantly decreased (p < .01) by administration of both colloid solutions. Lung injury (bronchoalveolar lavage lactate dehydrogenase activity) was significantly decreased (p < .05) by the hetastarch solution administration. The hetastarch solution administration resulted in 50% less xanthine oxidase activity release during reperfusion compared with albumin or lactated Ringer's solution administration (p < .001). CONCLUSION: We conclude that multiple organ injury and xanthine oxidase release after hepatoenteric ischemia-reperfusion are decreased by colloid administration.

Animals↗
PubMed1999

Establishing oral preference for quinine, phencyclidine and caffeine solutions in rats.

Rats were given fixed-time, 1-min food-pellet delivery sessions, for 3 h every day, which resulted in over drinking (schedule-induced polydipsia). In previous research, groups of animals came to prefer solutions of cocaine or lidocaine to concurrently presented water, if the drugs were first offered in a glucose/saccharin vehicle, which was then gradually eliminated, so that the choice became a drug solution in water vehicle versus water. In the present experiment, the same procedure produced a preference for 0.025 mg/ml quinine solution to water, indicating that a bitter solution that was not a topical anesthetic agent could come to be preferred. After establishing preference for quinine solution, it was possible to gradually remove quinine while increasing phencyclidine (PCP) concentration to produce preference for 0.075 mg/ml PCP solution, and similarly to produce subsequent preference for 0.1 mg/ml caffeine solution, although not for all animals. For additional groups, drinking either 0.15 mg/ml PCP or 0.1 mg/ml caffeine, while gradually reducing the glucose/saccharin vehicle to water vehicle was a less successful procedure for establishing the respective drug preferences. The latter result suggests that first instituting a preference for quinine solution to water facilitated the later establishment of preferences for PCP and caffeine solutions.

Animals↗
PubMed2001

Two procedures establishing preference for oral cocaine and lidocaine solutions which do not use an associative history with a reinforcer.

Groups of rats were exposed to daily, 3-h, fixed-time 1-min food-pellet delivery sessions, a procedure that produces overdrinking (schedule-induced polydipsia, SIP). Previous research demonstrated that rats drinking a drug or non-drug solution come to prefer that solution to water if the solution had (a) a past association with either a highly acceptable vehicle (e.g. glucose/saccharin), or (b) allowed rats to eschew drinking an unacceptable solution under SIP conditions. The present experiments show that under the solution-avoidance procedure, preference for a concurrent, alternative solution (0.19 mg/ml lidocaine or 0.24 mg/ml cocaine) occurred when a concentrated quinine solution alternative was either abruptly removed or faded. A concentrated cocaine solution, however, was minimally effective in producing a preference for 0.19 mg/ml lidocaine to water when cocaine concentration was faded. Flavor/nutrient-conditioning (conditioned reinforcement) and solution-eschewing (avoidance) procedures may throw light on the kinds of historical situations that determine the genesis of stable preferences for drugs and other substances.

Animals↗
PubMed2005

In vitro evaluation of the cytotoxic effects of acid solutions used as canal irrigants.

Solutions of EDTA and citric acid have been used as canal irrigants. These substances must be compatible with apical periodontal tissue. The aim of this study was to evaluate comparatively the cytotoxicity of a 17% EDTA solution and that of three solutions with different concentrations of citric acid (10, 15, and 25%) on cultured fibroblasts. The solutions were diluted to 0.1% and 0.5% in culture medium and then applied to NIH 3T3 cells. After 0, 6, 12, and 24 h (short-term assay; viability) and 1, 3, 5, and 7 days (long-term assay; survival), the cells were counted. The data were compared by ANOVA. In the short-term experiments, all solutions presented a percentage of cell viability similar to that of control cells, except for the 17% EDTA solution diluted to 0.5%. After the long-term assay, all groups presented a continuous and progressive cell growth except for the 17% EDTA solution and for the 25% citric acid solution at a 0.5% dilution. The citric acid solution did not impair cell growth and viability, proving to be noncytotoxic in vitro.

3T3 Cells↗
PubMed1998

Root growth and oxygen relations at low water potentials. Impact Of oxygen availability in polyethylene glycol solutions

Polyethylene glycol (PEG), which is often used to impose low water potentials (psiw) in solution culture, decreases O2 movement by increasing solution viscosity. We investigated whether this property causes O2 deficiency that affects the elongation or metabolism of maize (Zea mays L.) primary roots. Seedlings grown in vigorously aerated PEG solutions at ambient solution O2 partial pressure (pO2) had decreased steady-state root elongation rates, increased root-tip alanine concentrations, and decreased root-tip proline concentrations relative to seedlings grown in PEG solutions of above-ambient pO2 (alanine and proline accumulation are responses to hypoxia and low psiw, respectively). Measurements of root pO2 were made using an O2 microsensor to ensure that increased solution pO2 did not increase root pO2 above physiological levels. In oxygenated PEG solutions that gave maximal root elongation rates, root pO2 was similar to or less than (depending on depth in the tissue) pO2 of roots growing in vermiculite at the same psiw. Even without PEG, high solution pO2 was necessary to raise root pO2 to the levels found in vermiculite-grown roots. Vermiculite was used for comparison because it has large air spaces that allow free movement of O2 to the root surface. The results show that supplemental oxygenation is required to avoid hypoxia in PEG solutions. Also, the data suggest that the O2 demand of the root elongation zone may be greater at low relative to high psiw, compounding the effect of PEG on O2 supply. Under O2-sufficient conditions root elongation was substantially less sensitive to the low psiw imposed by PEG than that imposed by dry vermiculite.

Journal Article↗
PubMed1976

Floral activity in solutions of deoxyribonucleic Acid extracted from tobacco stems.

For Nicotiana tabacum cv. Wis. 38 plants, the capabilities of solutions containing DNA, extracted from either homogenates of stems in a floral state or nuclei of stems in a vegetative state, to effect flowering of vegetative plants have been studied. Previous work indicates that the DNA from homogenates of stems in a floral state is mainly nuclear. If DNA solutions are supplied to axillary buds of vegetative plants and if the axillary buds are defoliated every 4th day for 12 days, the buds supplied a solution of DNA from stems in a floral state initiate flowers under noninductive conditions, and the buds supplied a solution of DNA from stems in a vegetative state remain vegetative. Heating and rapidly cooling a solution of DNA from stems in a floral state enhances its floral activity. Heating and cooling a DNA solution also results in novel flowers showing up in many treated plants. Novel flowers are more striking in the offspring than in the parents. The capabilities of heated-cooled DNA solution to initiate flowers in noninductive conditions and to cause novel flowers are eliminated completely by treating (before heating and cooling) the DNA solution with deoxyribonuclease. Heated-cooled solutions of DNA extracted from nuclei of either vegetative stems or vegetative leaves contain no floral activity.

Journal Article↗
PubMed1995

Selective minimum-norm solution of the biomagnetic inverse problem.

A new multidipole estimation method which gives a sparse solution of the biomagnetic inverse problem is proposed. This solution is extracted from the basic feasible solutions of linearly independent data equations. These feasible solutions are obtained by selecting exactly as many dipole-moments as the number of magnetic sensors. By changing the selection, we search for the minimum-norm vector of selected moments. As a result, a practically sparse solution is obtained; computer-simulated solutions for Lp-norm (p = 2, 1, 0.5, 0.2) have a small number of significant moments around the real source-dipoles. In particular, the solution for L1-norm is equivalent to the minimum-L1-norm solution of the original inverse problem. This solution can be uniquely computed by using Linear Programming.

Animals↗