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V Simmons

Publications and source records attributed to V Simmons.

16 recordsLinked to original sources
PubMed2004

Molecular dynamics study of the surface tension of a binary immiscible fluid.

The planar interface between two liquids having two degrees of affinity to mix has been studied by molecular dynamics simulations. The surface tension is calculated from the normal, PN, and transverse, PT, components of the pressure tensor P for a wide range of temperatures. An unusual increase in surface tension with increasing temperature is attributed to a pressure induced void transfer mechanism that is justified by basic thermodynamic arguments. This effect is diminished on the addition of a modest attractive potential between the two species, and there is a turnover point at higher temperatures beyond which the surface tension decreases with increasing temperature. An order parameter is identified as the gradient of the mole fraction distribution through the interfacial region. An additional effect is the dramatic inversion of the kinetic and potential contributions to the PN profile as the temperature is varied. It is found that a commonly used approximation for P, the Irving-Kirkwood 1 or IK1 method, results in a relatively modest unphysical variability in PN that weakly violates the condition of local mechanical stability. However, this artifact does not prevent the IK1 method from producing an interfacial tension which is nearly identical to that derived from the complete IK formula with no additional approximations.

Journal Article↗
PubMed1999

Homicide by paraquat poisoning.

We report on two cases of homicide by paraquat poisoning. Both cases occurred in children and the common clinical presentations were gastrointestinal ulceration and acute respiratory distress, with pneumomediastinitis. Bullous emphysema was a common autopsy finding. Physicians and pathologists should be aware of these findings, for they are almost diagnostic of acute paraquat poisoning.

Autopsy↗
PubMed1999

Forensic analysis of acute fatal poisonings in the southern districts of Trinidad.

A prospective autopsy study was undertaken at General Hospital in San Fernando, Trinidad, to analyze deaths that occurred from poisoning during 1996 and 1997. During that period 105 deaths occurred from acute poisoning. The major poisons used were: paraquat (80 cases), organophosphate/carbamate insecticides (10 cases), and anti-psychotic drugs (6 cases). Much less frequently, battery acid, ETHREL[Ethephon; (2-chloroethyl)phosphonic acid], phenols, ethanol, kerosene and flavine were the agents of choice. Suicide accounted for 99 (94.29%) deaths. Of these, 44.44% occurred in the 10-29 y-age-group. Ingestion of paraquat seems almost always fatal, since the large volumes ingested make treatment universally ineffective. Aspiration pneumonitis (100% of cases), and pneumothorax with pneumomediastinum (18.75% of cases), were remarkable autopsy findings in those dying from paraquat poisoning, while asphyxia due to respiratory paralysis was the mode of death from pesticide ingestion. Efforts to prevent suicide by poisoning may be more useful than treatment protocols.

Adolescent↗
PubMed1996

Alterations in tretinoin pharmacokinetics following administration of liposomal all-trans retinoic acid.

We administered liposome-encapsulated all-trans retinoic acid (L-ATRA) to 48 patients with refractory hematologic malignancies using an every-other-day schedule for 28 days and doses of 15 to 175 mg/m2. In 19 patients, pharmacology studies were conducted after the first (day 1) and seventh (day 15) doses. In contrast to the decline in tretinoin concentration seen within 3 to 4 days of administration of daily oral ATRA, there were no differences between the area under the curve (AUC) of tretinoin concentration versus time on day 1 and day 15 (P = .98, Wilcoxon signed-rank test). Peak day 1 concentrations after 15 mg/m2 were higher than those reported after 45 mg/m2 oral ATRA. Six patients with relapsed acute promyelocytic leukemia (APL) were treated. Three, each in first relapse and at least year from the last exposure to oral ATRA, achieved a complete response (CR). Disease recurred in two (one at 3 months despite maintenance L-ATRA and similarity in tretinoin AUC on days 1 and 85, and the other at 5 months, 2 months after discontinuation of L-ATRA) and the third was transplanted 1 month into CR. The three nonresponders were in at least a second relapse and failed to respond to oral ATRA before or immediately after receiving L-ATRA. Severe toxicity developed in three of eight patients treated at 175 mg/m2 (joint pains in two, skin in one). The maximum tolerated dose (MTD) was determined to be 140 mg/m2, at which dose grade 2 toxicity (primarily headache and skin) occurred in eight of eight patients, but grade 3 to 4 toxicity in none. Compared with oral ATRA, L-ATRA apparently results in greater exposure to tretinoin and for a longer time.

Drug Carriers↗
PubMed1996

Effectiveness of water exercise on postural mobility in the well elderly: an experimental study on balance enhancement.

BACKGROUND: The fear of falling may cause elderly people to limit their movement. As movement errors are known to facilitate the acquisition of motor skills, the elderly may inadvertently cause the loss of postural skills by constraining their movements, and hence avoid potential movement errors. It was hypothesized that by having elderly individuals exercise in a risk-free environment-water was utilized in this experiment-their postural capabilities would improve. METHODS: Four groups of elderly subjects (80 +/- 5.8 years old) were placed into four groups: Water Exercisers; Land Exercisers; Water Sitters; and Land Sitters. Each group met twice per week for 45 minutes for 5 weeks of simple exercises or socializing in the designated medium. The distance each individual could reach (Functional Reach, FR) was measured at the end of each week. RESULTS: Initially, each group was at risk (FR < 10 inches) for falling Statistical testing showed that the Water Exercisers (WE) increased their FR almost every week; the Land Exercisers (LE) increased only during the first week; and the Water Sitters (WS) and Land Sitters (LS) did not increase at all. The FRs after 5 weeks were 13.4 +/- 1.6 (WE), 11.3 +/- 1.5 (LE), 9.6 +/- 1.3 (WS), and 9.3 +/- 0.71 (LS) inches for each group, respectively. CONCLUSIONS: The data showed that the postural capabilities in these elderly people, as measured by the FR, were enhanced by the production of movement errors that was facilitated in a water environment (in the case of the Water groups) or the initiation of a novel exercise program (Land Exercisers). Alternative explanations, and implication of these results, are discussed.

Accidental Falls↗
PubMed1995

A new porous surface modification technology for peritoneal dialysis catheters as an exit-site cuff to reduce exit-site infections.

Catheter exit-site infection continues to be a more common morbid event in patients undergoing peritoneal dialysis. Previous attempts to place a biointegration material at the next site have failed to reduce infection rates. This study reports the use of an innovative microporous silicone material placed as a cuff around the catheter at the exit site. The porous material has a pore-sized distribution that stimulates and facilitates capillary ingrowth into the pores. This capillary ingrowth prevents scar tissue formation, increases blood supply, and theoretically improves the immunological competence of the tissue at the vulnerable exit site. Twenty-five test catheters (12 using standard exit-site creation and 13 using the Moncrief-Popovich implantation technique) were implanted in a canine model. The exit-site infection rate in a canine model without the microporous material was 100% at 2 months. The corresponding results with the microporous material was 40% at 2 months. The majority of the test catheters showed progressive drying and healing at the exit site. Sixty percent of the catheters healed quickly and remained infection-free. Biointegration of the microporous material at the exit-site was demonstrated. Several exit site infections with the test catheters treated only with local therapy (without systemic or topical antibiotics) demonstrated progressive healing and secondary adequate biointegration. Because of these encouraging results, human studies were initiated, with the first human implant occurring in August, 1994. A 10-patient project is planned for the next year.

Animals↗
PubMed1991

Suicide by poisoning.

An epidemiological evaluation was conducted on 270 patients who died at the General Hospital, Port-of-Spain after presenting with deliberate self-poisoning between January, 1986 and June, 1990. The cause of death was confirmed by autopsy and toxicological analysis. Epidemiological variables of age, sex, race, precipitating factors and types of poison used were assessed. It was found that the male to female ratio was 2.7:1. East Indians accounted for 54.4%, Africans 42.0%, people of mixed ethnic origin 3% and Caucasians 0.6%. The majority of cases (52.6%) were seen in the age group 11-34 years. "Lovers' quarrels" (35.4% of cases), psychiatric illness (27.8% of cases) and family disputes (27% of cases) were reported as the most frequent precipitating events in suicide. East Indians predominated in those suicides precipitated by "lovers' quarrels" and family disputes, accounting for 63.2% and 58.9% of these cases, respectively; while for those suicides in which psychiatric illnesses were the main precipitating event. Africans were represented by 53.3% and East Indians 45.3%. Depression was the most common psychiatric illness diagnosed. Paraquat was the most popular poison used in 63.7% of the suicidal cases, and other agrochemicals were used in 20% of cases.

Adolescent↗
PubMed1990

Effects of prenatal ethanol and long-chain n-3 fatty acid supplementation on development in mice. 2. Fatty acid composition of brain membrane phospholipids.

Pregnant mice were fed equivalent daily amounts of a liquid diet containing 25% (kcal) ethanol, or with maltose dextrin substituted isocalorically for ethanol. The diet also contained 20% oil; this was either of two mixtures, one comprised of predominantly n-6 (18:2n-6) fatty acids, and the other containing an equivalent amount of n-6, but supplemented with a source of long chain n-3 (20:5n-3, 22:6n-3) fatty acids. An additional control group was fed lab chow ad libitum. The treatment was implemented from day 7 to 17 of gestation, whereafter all groups were fed lab chow. Birth occurred on day 19, and the fatty acid composition of the brain membrane phospholipids was determined in the pups 3 days after birth (day 22 postconception) and again, 10 days later (day 32 postconception). On day 22 the polyunsaturated fatty acid (PUFA) composition of the brain phospholipids reflected dietary availability, with the n-3/n-6 ratio higher in the n-3 groups; this was decreased by ethanol in the phosphatidylcholine (PC) fraction. The dietary effect was still apparent on day 32; again ethanol reduced this in both the PC and phosphatidylethanolamine (PE) fractions. The n-3 oil, but not ethanol, increased the 20:3n-6/20:4n-6 ratio, indicative of an inhibition of the activity of delta-5 desaturase. With respect to the 22:C compounds, the n-3 oil decreased the levels of 22:5n-6, while increasing those of 22:6n-3, but generally the sum of these two fatty acids remained unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Fatty acid changes in liver choline and ethanolamine glycerophospholipids in aspirin-treated rats fed linoleate, gamma-linolenate and fish oil.

The effects of dietary linoleic acid, gamma-linolenic acid and marine fatty acids on the development of aspirin-induced gastric hemorrhage and the distribution of liver glycerophospholipid fatty acids in fat-deficient growing rats were studied. Aspirin (100 mg/day)-treated and nontreated rats were fed for 7 days, a mixed diet of 2.5% safflower oil and 7.5% hydrogenated coconut oil (SFO/HCO) or 7.5% fish oil (SFO/FO), or 2.5% gamma-linolenate concentrate and 7.5% fish oil (GLA/FO). Gastric hemorrhage was induced in animals by aspirin treatment to various extents. It was not affected by FO feeding, but was significantly alleviated by GLA feeding. Aspirin treatment reduced the proportions of 20:4n-6 in liver phosphatidylcholine. FO feeding (in SFO/FO and GLA/FO rats) further reduced the 20:4n-6 level and replaced it by n-3 fatty acids. GLA feeding, on the other hand, elevated the proportion of 20:4n-6. As a result, the reduction of 20:4n-6 by fish oil feeding, was less significant in GLA/FO rats than in SFO/FO rats. The degree of gastric hemorrhage appeared to relate negatively to the levels of 20:4n-6 in liver phosphatidylcholine, and to the sum of 20:4n-6 and 20:5n-3 when FO was included in the diet. It is suggested that long-chain polyunsaturated fatty acids (20:4n-6 and 20:5n-3) per se in addition to being precursors of prostaglandins, may also affect the development of gastric hemorrhage, possibly by modulating the permeability of cell membranes in the gastric mucosa.

Animals↗
PubMedDate not supplied

Lipid peroxidation in human breast cancer cells in response to gamma-linolenic acid and iron.

Lipid peroxidation in human breast cancer (ZR-75-1) cells and cancer cell killing were confirmed by using ultraviolet (UV)-spectrophotometry and mass spectrometry (MS). ZR-75-1 cells and human normal fibroblast CCD-41-SK (41Sk) cells were cultured with gamma-linolenic acid (GLA) and ferrous iron Fe (II) combinations. Formation of lipid peroxide and cytotoxic effect were highest in ZR-75-1 cells treated with GLA + Fe (II), though 41Sk cells showed little evidence of either lipid peroxidation or cytotoxity. These results indicate a cancer-cell-specific lipid peroxidation mechanism in association with the selective cancer cell killing effect in response to GLA.

Antineoplastic Agents↗
PubMedDate not supplied

Mechanism of lipid peroxidation in cancer cells in response to gamma-linolenic acid (GLA) analyzed by GC-MS(I): Conjugated dienes with peroxyl (or hydroperoxyl) groups and cell-killing effects.

We have investigated the nature of lipid peroxidation occurring in association with cancer-killing produced by gamma-linolenic acid (GLA) and iron (Fe) in cultured human breast cancer cells (ZR-75-1: ZR). UV-spectrophotometry, high performance liquid chromatography (HPLC) and gas chromatography (GC) or gas chromatography-mass spectrometry (GC-MS) have been used to analyze lipid peroxides and their derivatives. Formation of conjugated dienes (CD), the conversion of triphenylphosphine (TPP) to its oxide (TPPO), and the simultaneous production of hydroxy polyunsaturated fatty acids (PUFA-OHs) from these corresponding PUFAs hydroperoxides (PUFA-OOHs) were analyzed in the total lipid extract of ZR cells and of normal human skin fibroblasts (CCD-41Sk:Sk). Fe enhanced the formation of both the CD and TPPO and increased the percentage of dead cells, while vitamin E inhibited these effects. Neither of these events was observed at any significant level in Sk cells. Identity of PUFA-OHs was confirmed by determining the regional positions of the hydroxyl group by GC-MS analysis of hydrogenated methyl ester tert-butyldimethylsilyl ether alcohol derivatives (Me-H2-PUFA-O-TBDMS). The regional isomers identified were 15-, 12- and 8-OH 20 carbon and 13-OH 18 carbon fatty acid derivatives. These results suggest that the increased formation of conjugated dienes and/or hydroperoxyl (or peroxyl) groups in PUFA molecules is relevant to the cancer cell-killing effect of GLA+Fe.

Breast Neoplasms↗