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Biomedical subjects

D L Gilbert

Publications and source records attributed to D L Gilbert.

82 records · Page 5Linked to original sources
PubMed1969

Effect of divalent cations on potassium conductance of squid axons: determination of surface charge.

Potassium conductance-voltage curves have been determined for a squid axon in high external potassium solution for a wide range of divalent cation concentrations. A decrease in divalent ion concentration shifts the conductance-voltage curve along the voltage axis in the direction of more hyperpolarized voltages by as much as 9 mv for an e-fold change in concentration. When the divalent ion concentration is less than about 5 mM, a further decrease does not cause a significant shift of the conductance-voltage curve. These results can be explained by assuming that on the outer surface of the membrane there is a negative fixed charge which can bind calcium ions, and that the axon is sensitive to the resulting double-layer potential. From our data, the best value for charge density was found to be one electronic charge per 120 square angstroms, and a lower limit to be one electronic charge per 280 square angstroms.

Animals↗
PubMed1966

Slow changes of potassium permeability in the squid giant axon.

A slow potassium inactivation i.e. decrease of conductance when the inside of the membrane is made more positive with respect to the outside, has been observed for the squid axon. The conductance-potential curve is sigmoid shaped, and the ratio between maximum and minimum potassium conductance is at least 3. The time constant for the change of potassium conductance with potential is independent of the concentration of potassium in the external solution, but dependent upon potential and temperature. At 9 degrees C and at the normal sea water resting potential, the time constant is 11 sec. For lower temperature or more depolarizing potentials, the time constant is greater. The inactivation can be described by modifying the Hodgkin-Huxley equation for potassium current, using one additional parameter. The modified equation is similar in form to the Hodgkin-Huxley equation for sodium current, suggesting that the mechanism for the passive transport of potassium through the axon membrane is similar to that for sodium.

Animals↗
PubMedDate not supplied

Compatibility of gemcitabine hydrochloride with 107 selected drugs during simulated Y-site injection.

OBJECTIVE: To evaluate the physical compatibility of gemcitabine hydrochloride (Gemzar-Eli Lilly and Company) with 107 selected drugs. DESIGN: Controlled experimental trial. SETTING: Laboratory. INTERVENTIONS: Samples of 5 mL gemcitabine (as the hydrochloride salt) 10 mg/mL in 0.9% sodium chloride injection were mixed with 5 mL samples of the selected drugs diluted in 0.9% sodium chloride injection or, if necessary to avoid incompatibilities with the diluent, 5% dextrose injection. MAIN OUTCOME MEASURES: Visual examinations of the samples were performed in normal fluorescent light with the unaided eye and using a Tyndall beam (high-intensity monodirectional light) to enhance visualization of small particles and low-level haze. The turbidity of each sample was measured as well. In selected samples, electronic particle content assessment was performed. All of the samples were assessed initially and at 1 and 4 hours. RESULTS: Most of the drugs were physically compatible with gemcitabine hydrochloride during the 4-hour observation period. However, 15 drug combinations had incompatibilities that included color change, increase in haze or turbidity, particulate formation, and gross precipitation: acyclovir sodium, amphotericin B, cefoperazone sodium, cefotaxime sodium, furosemide, ganciclovir sodium, imipenem-cilastatin sodium, irinotecan, methotrexate sodium, methylprednisolone sodium succinate, mezlocillin disodium, mitomycin, piperacillin sodium, piperacillin sodium/tazobactam sodium, and prochlorperazine edisylate. CONCLUSION: Gemcitabine hydrochloride 10 mg/mL admixed in a compatible infusion solution is physically compatible for 4 hours at room temperature with 92 of 107 tested drugs. Simultaneous Y-site administration of gemcitabine hydrochloride with the 15 drugs resulting in incompatibilities should be avoided.

Antimetabolites, Antineoplastic↗
PubMedDate not supplied

Compatibility of medications with 3-in-1 parenteral nutrition admixtures.

BACKGROUND: The absence of drug compatibility information with 3-in-1 parenteral nutrition admixtures has been problematic. The purpose of this project was to evaluate the physical compatibility of 106 selected drugs during simulated Y-site injection into nine different 3-in-1 parenteral nutrition admixture formulations. METHODS: Four-milliliter samples of each of the representative 3-in-1 parenteral nutrition admixture formulations were combined in a 1:1 ratio with 4-mL samples of each of 106 drugs, including supportive care drugs, anti-infectives, and antineoplastic drugs. Six replicate samples of each combination were prepared. Two samples were evaluated initially after mixing, two more after 1 hour, and the last two after 4 hours at 23 degrees C. At each test interval, the samples were subjected to centrifugation, causing the fat to rise to the top. The top fat layer and most of the aqueous phase were removed, and the remaining liquid was diluted with about 7 mL of particle-free, high-performance liquid chromatography-grade water to facilitate observation of any particulates that might have formed. Visual examinations were performed in normal diffuse fluorescent laboratory light and under high-intensity, monodirectional light. RESULTS: Most of the drugs tested were physically compatible with the 3-in-1 parenteral nutrition admixtures for 4 hours at 23 degrees C. However, 23 drugs exhibited various incompatibilities with one or more of the parenteral nutrition admixtures. Six drugs resulted in the formation of precipitate with some or all of the admixtures. Seventeen drugs caused disruption of the emulsion, usually with oiling out. CONCLUSIONS: Most of the test drugs were physically compatible with the nine representative 3-in-1 parenteral nutrition admixtures. However, the 23 drugs that resulted in incompatibilities should not be administered simultaneously with the incompatible parenteral nutrition admixtures via a Y injection site.

Amikacin↗
PubMedDate not supplied

Compatibility screening of linezolid injection during simulated Y-site administration with other drugs and infusion solutions.

OBJECTIVE: To evaluate the physical compatibility of linezolid injection (Zyvox-Pharmacia) during simulated Y-site administration with 8 infusion solutions and 110 selected other drugs. DESIGN: Controlled experimental trial. SETTING: Laboratory. INTERVENTIONS: Five-milliliter samples of linezolid injection 2 mg/mL were mixed with 5 mL samples of the selected infusion solutions and the selected other drugs diluted in 5% dextrose injection, or, if necessary to avoid incompatibility with the diluent, 0.9% sodium chloride injection. MAIN OUTCOME MEASURES: Visual examinations of the samples were performed in normal fluorescent light with the unaided eye and using a Tyndall beam (high-intensity monodirectional light source) to enhance visualization of small particles and low-level haze. The turbidity of each sample was measured, and for samples that did not exhibit visible precipitation, the particle content was measured, as well. All of the samples were assessed initially and at 1 and 4 hours. RESULTS: All of the infusion solutions and most of the test drugs were physically compatible with linezolid injection during the 4-hour observation period. Physical incompatibilities resulted when linezolid injection was combined with five of the drugs: amphotericin B, chlorpromazine hydrochloride, diazepam, pentamidine isethionate, and phenytoin sodium. Precipitation, turbidity formation, and/or unacceptable changes in measured haze levels were observed. CONCLUSION: Linezolid 2 mg/mL was physically compatible for 4 hours at room temperature with all 8 infusion solutions tested and 105 of the drugs tested. Simultaneous Y-site administration of linezolid injection with the five drugs resulting in physical incompatibilities should be avoided.

Acetamides↗