Continuous glucose monitoring in the free-moving rat

The aim of this work was to set up an experimental model of glycemic fluctuations for assessing in the conscious freely moving rat, the performance of a continuous glucose-monitoring system, using a pocket-calculator-size electronic control unit and a miniaturized subcutaneous glucose sensor. The well-known triphasic glycemic pattern following streptozotocin injection (initial peak and secondary hypoglycemia preceding the establishment of permanent hyperglycemia) was used as a way to obtain spontaneous changes in blood glucose level over a wide concentration range. This report demonstrates that streptozotocin injection produced highly reproducible changes in the current generated by the sensor: an initial peak and a secondary nadir, during which blood sampling provided the evidence of hyperglycemia associated with immunoreactive hypoinsulinemia, and of hypoglycemia associated with hyperinsulinemia, respectively. This reproducible experimental model should be valuable for the assessment of a continuous glucose-monitoring system.     

Numerical methods for ultraparabolic equations

We analyze semidiscrete and fully discrete finite element approximations to the solution of an initial boundary value problem for a model ultraparabolic equation.     

Delayed neuropsychologic sequelae after carbon monoxide poisoning: prevention by treatment with hyperbaric oxygen

STUDY OBJECTIVE: Carbon monoxide (CO) poisoning is a major clinical problem. The risk of morbidity and the most effective treatment have not been clearly established. We measured the incidence of delayed neurologic sequelae (DNS) in a group of patients acutely poisoned with CO and tested the null hypothesis that the incidence would not be affected by treatment with hyperbaric oxygen (HBO). DESIGN: We conducted a prospective, randomized study in patients with mild to moderate CO poisoning who presented within 6 hours. Patients had no history of loss of consciousness or cardiac instability. INTERVENTIONS: The incidence of DNS was compared between groups treated with ambient pressure 100% oxygen or HBO (2.8 ATA for 30 minutes followed by 2.0 ATA oxygen for 90 minutes). DNS were defined as development of new symptoms after oxygen treatment plus deterioration on one or more subtests of a standardized neuropsychologic screening battery. RESULTS: In 7 of 30 patients (23%), DNS developed after treatment with ambient-pressure oxygen, whereas no sequelae developed in 30 patients after HBO treatment (P < .05). DNS occurred 6 +/- 1 (mean +/- SE) days after poisoning and persisted 41 +/- 8 days. At follow-up 4 weeks after poisoning, patients who had been treated with ambient pressure oxygen and had not sustained DNS exhibited a worse mean score on one subtest, Trail Making, compared with the group treated with HBO and with a control group matched according to age and education level. There were no differences in scores between the control group and the hyperbaric oxygen group. CONCLUSION: DNS after CO poisoning cannot be predicted on the basis of a patient's clinical history or CO level. HBO treatment decreased the incidence of DNS after CO poisoning.     

Cytotoxic effects of Aroclor 1254 on ultrastructure and biochemical parameters in cultured foetal rat hepatocytes

The cytotoxicity of a commercial PCB mixture, Aroclor 1254, was assessed on cultured foetal rat hepatocytes. Under control conditions, dexamethasone stimulates immature hepatocytes to differentiate into both hepatocytes and biliary epithelial cells. Consequently, foetal rat hepatocytes maintain, in vitro, a liver-like organization with spaces corresponding to the lumen of biliary canalicules, many mitochondria, and a well-developed rough endoplasmic reticulum (RER). This in vivo-like organization of cultured rat hepatocytes remains unchanged in medium supplemented with Aroclor 1254 at concentrations below 25 microM. In the 25-125 microM concentration range, however, PCBs severely alter some cellular organelles, notably causing important development of the RER and the appearance of cytoplasmic lacunae containing laminated concentric membrane arrays. In addition, the number of lipid droplets increases, the glycogen islets disappear, and dramatic local alterations of the mitochondrial cristae occur. In exposed and unexposed cells, the following biochemical parameters were measured: the DNA content, protein synthesis, lipid peroxidation, and urea formation. The results show that Aroclor 1254 at concentrations exceeding 25 microM (but not at lower concentrations) causes irreversible damage to cultured hepatocytes. The observed ultrastructural modifications are in good agreement with several in vivo studies on rat liver. Thus, isolated foetal rat hepatocytes have considerable potential as an alternative to whole animals for use in (eco)toxicological studies.     

A study of the metal sulfide-sulfur dioxide reaction in aqueous media by reaction pressure characterization and ultraviolet spectrophotometry

The metal sulfide-sulfur dioxide reaction has been characterized for seven different sulfide ores by using the changes in sulfur dioxide pressure during the reaction and by ultraviolet spectrophotometric analysis of the reaction products. The UV analysis, which showed that thiosulfuric acid is a major product of the metal sulfide-sulfur dioxide reaction, was used to monitor the r rate of formation of thiosulfuric acid during the reaction. Results from a series of base-line experiments using ferrous sulfide showed a high correlation between the rate of change of sulfur dioxide pressure, the rate of appearance of ferrous ion, and the rate of formation of thiosulfuric acid. These results were compared with those obtained in similar experiments with six naturally-occurring sulfide ores. Finally, the UV method was employed to monitor the kinetics of the decomposition of thiosulfuric acid into elemental sulfur. Using these results, in conjunction with the mechanisms previously developed for the Wackenroder reaction and the acid decomposition of thiosulfate, a mechanism is proposed for the acid oxidative dissolution of sulfide ores which accounts for the formation of elemental sulfur.     

An error estimate for theH −1 Galerkin method for a parabolic problem with non-smooth initial data

A non-smooth data error estimate with respect to theL ₂ norm is shown for a semidiscrete Galerkin-Petrov method for a parabolic problem in one space dimension. If the trial and test spaces consist of piecewise polynomials of degreer−1 inC ^k anr+1 inC ^k+2 , respectively, with test functions satisfying boundary conditions, then the error norm is bounded byCh ^r t ^−r/2 fort positive, whereh is the maximum mesh size.     

Isolation of a GPD gene from Debaryomyces hansenii encoding a glycerol 3-phosphate dehydrogenase (NAD+)

A gene homologous to GPD1, coding for glycerol-3-phosphate dehydrogenase (sn-glycerol 3-phosphate: NAD(+) oxidoreductase, EC 1.1.1.8), has been isolated from the halophilic yeast Debaryomyces hansenii by complementation of a Saccharomyces cerevisiae gpd1 Delta mutant. DNA sequencing of the complementing genomic clone indicated the existence of an open reading frame encoding a protein with 369 amino acids. Comparative analysis of the deduced amino acid sequence showed high similarity to homologous genes described for other eukaryotic GPD enzymes. The sequence has been submitted to the GenBank database under Accession No. AY333427.     

Influence of ion energy on damage induced by Au-ion implantation in silicon carbide single crystals

This article reports on the influence of the ion energy on the damage induced by Au-ion implantation in silicon carbide single crystals. 6H-SiC samples were implanted with Au ions at room temperature at two different energies: 4 and 20 MeV. Both Rutherford Backscattering spectrometry in channelling geometry (RBS/C) and Raman spectroscopy were used to probe the ion implantation-induced damage. Results show that the accumulated damage increases with the fluence up to the amorphization state. RBS/C data indicate that 4-MeV implantation induces more damage than 20-MeV implantation at a given fluence. This effect is attributed to nuclear collisions since the amount of damage is identical at 4 or 20 MeV when the fluence is rescaled in dpa. Surprisingly, Raman data detect more damage for 20-MeV implantation than for 4-MeV implantation at low fluence (below 10¹³ cm⁻²) where point defects are likely formed.