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Biomedical subjects

W S Koski

Publications and source records attributed to W S Koski.

16 recordsLinked to original sources

The rate of sulfur hexafluoride escape from a plastic syringe.

Sulfur hexafluoride (SF6) gas is widely used for internal tamponade during retinal reattachment surgery and is commonly injected into the eye from a 10-mL plastic syringe. The rate of diffusion of SF6 out of a plastic syringe has not bee studied. We measured the percentage of SF6 gas in a 10-mL plastic syringe by gas chromatography, confirmed by infrared spectrometry. Measurements were obtained immediately after aspiration, and at 30 s and 10, 15, 60, 90, and 120 minutes, and 18 hours. A marked decrease in SF6 concentration, from 97% at 30 s to 76% at 60 minutes and 2% at 18 hours, was noted. The results were highly reproducible. Sulfur hexafluoride gas should be injected into the patient's eye as soon as possible after aspiration from the tank to ensure accurate concentrations.

Chromatography, Gas

Quantum chemical and other theoretical studies of carcinogens, their metabolic activation and attack on DNA constituents.

We have carried out a variety of different types of studies on carcinogens: ab-initio quantum chemical, including generation of electrostatic molecular potential contour (EMPC) maps and graph theoretical generation of polycyclic aromatic hydrocarbon (PAH) structures and characterization of the "carcinogenic" bay regions. Polycyclic aromatic hydrocarbon (PAH) carcinogens are activated metabolically from precarcinogen (PAH's) through proximate carcinogens (PAH epoxides and dihydrodiols) to ultimate carcinogens (PAH dihydrodiolepoxides) which then attack DNA constituents. We carried out ab-initio MODPOT/VRDDO/MERGE calculations on a variety of these molecules using our own ab-initio programs which incorporate as options a number of desirable options for ab-initio calculation on large molecules. From these electronic wave functions, we generated electrostatic molecular potential contour (EMPC) maps around these molecules. These EMPC maps indicated predictively the positions at which epoxides would form and the propensity and geometrical preference to form dihydrodiols and dihydrodiolepoxides. We performed spin and symmetry analyses for attack of O adding across C = C bonds or inserting in C-H or N-H bonds. We also carried out ab-initio calculations for attack of ultimate carcinogens on DNA constituents. Using graph theory we generated all possible structures for any arbitrary numbers of aromatic rings and also set up a graph theoretical characterization of the "carcinogenic" bay region. Most recently, we have incorporated this into a computer program for global prediction of toxicity.

Biotransformation

Burnout.

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Burnout, Professional

Correlation between the growth inhibitory effects, partition coefficients and teratogenic effects of lipophilic acids.

The inhibition of cell duplication by many lipophilic acids was measured in Bacillus subtilis and in the following mammalian cell lines, the human epithelial-type cell lines HeLa, strain R and strain L-132, the human fibroblast cell line VA-13, and the rat glial cell line C. The results were correlated to the partition coefficient and the distribution coefficient (= apparent partition coefficient at pH 7.2) of the compounds, using octanol/water partition coefficients and pKa values either from the literature or measured for this work. For B. subtilis, the logarithm of the inhibitory potency of most compounds increases linearly with the logarithm of the partition coefficient. Exceptional high potencies were observed for compounds that can efficiently delocalize the charge of the negative ion over the whole molecule. Most compounds inhibit tissue cultures at least as potently as they inhibit B. subtilis. But some compounds are significantly more potent in tissue cultures than would have been expected from the B. subtilis data; such compounds (analgesics/antipyretics, anti-inflammatory compounds, butyrate, norepinephrine) presumably inhibits mammalian cells by specific reactions with certain cell components. However, most compounds inhibit the different cell lines to a similar degree, indicating no cellular specificity; exceptions to this rule are chlorambucil, chlortetracycline and dexamethasone. Many of the lipophilic acids that are potent inhibitors of mammalian cell replication are also teratogenic. Exceptional compounds may not reach the embryo. We propose that a number of other lipophilic acids that are potenta inhibitors and to which humans are frequently exposed should be tested for their teratogenic effect.

Animals

Narcotic and narcotic antagonist pKa's and partition coefficients and their significance in clinical practice.

The pKa's, partition coefficients and drug distribution coefficients (apparent partition coefficients) have been investigated for a number of narcotics and where possible for their congener narcotic antagonist. These studies were carried out by a novel microelectrometric titration technique as a function of temperature and pH. This method enables one to determine not only the dissociation constants to deconvolute overlapping pKa's, but also to determine the solubilities and oil-water distribution of these various drugs. The drug distribution coefficients displayed marked sensitivity to pH at values which span the range of attainable human physiological pH values. This has significant pharmacological implications for proper choice and scaling of drug dosages under various clinical situations among which are cited hyperventilation under a general anesthetic while concomitantly under a narcotic analgesic, obstetetrical analgesia, and medical and anti-abuse usage of narcotic antagonists. The partition coefficients and drug distribution coefficients were noticeably different at 20degreesC (where such measurements are customarily made) from those at 37degreesC (body temperature). Furthermore, various drugs exhibit very non-equivalent increases in drug distribution coefficients with increasing temperature, ranging from 21% for naltrexone. This non-regularity indicates that it will not be valid to extrapolate by any constant factor the measurements made at lower temperatures. Even the true partition coefficients increase with temperature from 20degrees to 37degreesC.

Chemical Phenomena

Microelectrometric titration measurement of the pKa's and partition and drug distribution coefficients of narcotics and narcotic antagonists and their pH and temperature dependence.

The pKa's, partition coefficients, and drug distribution coefficients (apparent partition coefficients) have been investigated for a number of narcotics and, where possible, for their congener narcotic antagonists. These studies were carried out by a microelectrometric titration technique as a function of temperature and pH. This method enables one to determine not only the dissociation constants to deconvolute overlapping pKa's, but also to determine the solubilities of oil-water distribution of these various drugs. The drug distribution coefficients displayed marked sensitivity to pH at values which span the range of attainable human physiological pH values. This has significant pharmacological implications for proper choice and scaling of drug dosages under various clinical situations. The partition coefficients and drug distribution coefficients were noticeably different at 20 degrees (where such measurements are customarily made) than at 37 degrees (body temperature). Furthermore, various drugs exhibit very nonequivalent increases in drug distribution coefficients with increasing temperature, ranginf from 21% for morephine to 200% for naltrexone. This nonregularity indicates that it will not be valid to extrapolate by any constant factor the measurements made at lower temperatures. Even the true partition coefficients increase with temperature from 20 degrees to 37 degrees. There is more of a difference in the drug distribution coefficients for naloxone and naltrexone than might have been expected from the similarities in their structures with naltrexone being significantly less lipophilic than naloxone. This would imply that this would lead to naloxone having a more rapid onset for antagonist activity and likewise a shorter duration of action than naltrexone.

Electrochemistry

Theoretic significance of pH dependence of narcotics and narcotic antagonists in clinical anesthesia.

Determination of the effect of pH and temperature on pKa partition, and drug distribution coefficients in a series of common narcotics and their antagonists has shown that within the range of blood pH (7.1 to 7.7) encountered in the practice of anesthesiology, marked differences of distribution of the drugs between a model lipid (octanol) and water can occur. When these data are considered in the light of clinical experience with narcotics used in patients undergoing or recovering from surgical procedures, a correlation between the depth and duration of narcosis or the efficacy of narcotic antidotes and ventilatory status is seen. This correlation can be explained in part if the influence of blood pH on the probable CNS/blood distribution of a given drug is taken into consideration. Support is given to this proposal by representative studies in the literature. The very different drug distribution coefficients of two closely related narcotic antagonists, naloxone and naltrexone, correctly predicted the faster onset and shorter duration of the former, which was confirmed by reported clinical observations.

Anesthesia