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Biomedical subjects

A Bennett

Publications and source records attributed to A Bennett.

At least 73 records · Page 4Linked to original sources
PubMed1994

Spinal anaesthesia for caesarean section: comparison of infusions of phenylephrine and ephedrine.

Maternal cardiovascular changes and neonatal acid-base status were assessed in 29 healthy women undergoing elective lower segment Caesarean section under spinal anaesthesia. The patients were allocated randomly to one of three groups to receive an i.v. infusion of one of the following: ephedrine 1 mg min-1 (group E1: n = 10), ephedrine 2 mg min-1 (group E2: n = 9), or phenylephrine 10 micrograms min-1 (group P: n = 10). Invasive arterial pressure was monitored continuously and if hypotension occurred (defined as a 20% decrease from baseline, taken after i.v. preload administration), bolus doses of either ephedrine (6 mg in groups E1 and E2) or phenylephrine (20 micrograms in group P) were given. Only four patients became hypotensive in group E2, compared with eight patients in group E1 and nine patients in group P. The total time that the patients remained hypotensive was greatest in group P (P < 0.005), less in group E1 and least in group E2. Neonatal Apgar scores and acid-base profiles were similar in all three groups. In this study, an infusion of phenylephrine 10 micrograms min-1 with bolus doses of 20 micrograms was shown to be significantly less effective in maintaining systolic arterial pressure within 20% limits of baseline compared with an infusion of ephedrine 1 or 2 mg min-1 with bolus doses of 6 mg.

Adult↗
PubMed1994

Comparison of invasive and non-invasive measurement of continuous arterial pressure using the Finapres in patients undergoing spinal anaesthesia for lower segment caesarean section.

We have compared arterial pressures measured by an indwelling radial cannula with those obtained non-invasively by the Finapres 2000 (Ohmeda) during spinal anaesthesia for lower segment Caesarean section. The digital outputs of both pressures were recorded using a computerized system. We studied 20 patients, yielding a total of 18,772 data points after elimination of data recorded during arterial flushing and erroneous results from each source. The data analysis demonstrated a normal distribution for differences between the two methods of measurement, and the correlations between invasive and Finapres readings for systolic, diastolic and mean pressures were 0.78, 0.72 and 0.79, respectively, indicating an overall poor reflection of intra-arterial pressure by the Finapres under these circumstances. Some patients and some periods of readings reflected a high degree of precision and little bias. However, unexplained large differences in pressure and trends of change that were out of phase over time occurred frequently. We conclude that the Finapres cannot be recommended as a monitor of arterial pressure in this group of patients in whom sudden hypotension may be a threat to maternal or fetal outcome.

Anesthesia, Obstetrical↗
PubMed1994

Effect of lignocaine on eicosanoid synthesis by pieces of human gastric mucosa.

Lignocaine can affect prostaglandin synthesis in various tissues, and it has anti-inflammatory activity. No studies have been made previously on human isolated gut tissues. When concentrations of 5, 50 and 250 micrograms mL-1 lignocaine were incubated with human gastric mucosa/submucosa at 37 degrees C for 30 min, only the highest concentration reduced the levels of prostaglandin E, thromboxane B2 and 6-keto-PGF1 alpha in the incubates, and leukotriene C4/D4 was unaffected. Therapeutically relevant amounts of lignocaine given parenterally would therefore seem unlikely to alter gastric mucosal prostanoids, but high doses can be given orally because of extensive first-pass metabolism in the liver.

6-Ketoprostaglandin F1 alpha↗
PubMed1994

IS WALKING COSTLY FOR ANURANS? THE ENERGETIC COST OF WALKING IN THE NORTHERN TOAD BUFO BOREAS HALOPHILUS

Locomotor mode and the maximal capacity for aerobic metabolism are thought to be co-adapted in anuran amphibians. Species that rely heavily on walking often have high capacities for aerobic metabolism relative to species that rely primarily on saltation. We tested the hypothesis of co-adaptation of gait and aerobic metabolism by investigating the locomotor energetics of Bufo boreas halophilus, a toad that walks, but does not hop. Rates of oxygen consumption during locomotion were measured in an enclosed variable-speed treadmill. The steady-state rate of oxygen consumption (V(dot)O2ss) increased linearly within a range of sustainable speeds [V(dot)O2ss (ml O2 g-1 h-1) = 0.93 x speed (km h-1) + 0.28]. The minimum cost of transport, Cmin (the slope of this relationship), varied significantly among individual toads. When expressed in units of oxygen consumed per distance travelled (ml O2 km-1), Cmin scaled isometrically with body mass: Cmin = 0.69mass1.07. Consequently, mass-specific Cmin (ml O2 g-1 km-1) was uncorrelated with body mass. Variation in Cmin was also unrelated to experimental temperature. Mass-specific Cmin estimates were similar to previous allometric predictions for terrestrial animals of similar size, which contrasts with previous findings for another toad species. Maximum rates of oxygen consumption measured in closed, rotating respirometers were significantly higher than the maximum rates achieved on the treadmill, but lower than those measured previously in other Bufo species. Our results indicate that walking is not necessarily a costly gait for toads and that high maximum rates of oxygen consumption are not associated with reliance on walking within the genus Bufo.

Journal Article↗
PubMed1993

Intrathecal injection of lysine acetylsalicylic acid in the rat: a neurotoxicological study.

Lysine acetylsalicylic acid has been reported to induce analgesic effects in humans after intrathecal (i.t.) injection. Before conducting further studies in humans with this drug, it is important to evaluate potential toxicological effects on the spinal cord in animals. In the present study the effects of chronic intrathecal administration of provocative doses of lysine acetylsalicylic acid (L-ASA) on the rat spinal cord were evaluated using light and electron microscopy and a quantitative morphometric method. We also investigated the effects of single doses of the drug on the spinal cord blood flow (SCBF) using the laser-Doppler flowmetry technique. No histopathological changes or differences in number or density of neuronal cells could be seen after chronic administration of L-ASA as compared to controls. The SCBF decreased immediately after i.t. injection of a large dose (4 mg) of L-ASA and returned to predrug levels within 10 min. At the end of the experiment metabolic acidosis was detected, indicating a systemic effect of acetylsalicylic acid. It is concluded that no neurotoxic effects on the spinal cord were seen after chronic i.t. injection of L-ASA. From a neurotoxicological point of view, our findings do not contraindicate the spinal use of L-ASA in humans.

Analgesics↗
PubMed1993

Acemetacin and indomethacin: differential inhibition of constitutive and inducible cyclo-oxygenases in human gastric mucosa and leucocytes.

Cyclo-oxygenase, a key enzyme in prostaglandin production, is mainly in the constitutive form (COX-1) in gastric mucosa, whereas leucocytes have an inducible enzyme (COX-2). We report that indomethacin and its glycolic acid ester acemetacin have quantitatively different effects on prostanoid synthesis in these tissues. Human gastric mucosa (fresh operation specimens, cut finely and washed), and 1-1.5 x 10(6) human blood leucocytes stimulated with lipopolysaccharide (5 micrograms/ml), were incubated with acemetacin or indomethacin (0.1, 1, 10, 100 micrograms/ml). Eicosanoids in the medium were measured by radioimmunoassay (RIA). In leucocytes, acemetacin and indomethacin were more potent cyclo-oxygenase inhibitors than in the gastric mucosa, and both reduced the PGE levels to similar extents (70-98% and 72-100% respectively, n = 5). LTB4 was reduced only at 100 micrograms/ml of either drug. In gastric mucosal incubates, acemetacin was less potent than indomethacin in causing a concentration-related inhibition of PGE accumulation (19-74% vs 34-84%; n = 6, p < 0.05). Acemetacin was also less potent than indomethacin in reducing gastric 6-keto-PGF1 alpha and TXB2 (by 11-79% vs 45-72%, and 0-80% vs 29-80% respectively, p < 0.05). The finding that acemetacin is equipotent to indomethacin on leucocyte cyclo-oxygenase (inducible enzyme, COX-2) but less active on the gastric mucosa (COX-1) is consistent with an effective analgesic and anti-inflammatory activity of acemetacin coupled with better gastric tolerance than that to indomethacin.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1993

The use of modulated energy carried on a high frequency wave for the relief of intractable pain.

Ten volunteer patients with chronic neck/shoulder or back pain had been taking analgesics, and using conventional transcutaneous electrical nerve stimulation (TENS) with no significant pain relief. On entry to the trial, they were requested to stop taking their analgesics for two days prior to the study and for two days after starting to use the Liss Bipolar Body Stimulator for 20 min 3-5 times daily. Resumption of medication was then allowed. The stimulator (15,000 Hz carrier wave with a double modulation of 15 and 500 Hz) was connected to two adhesive electrodes placed so that the current field encompassed the trigger points, and used at a current that was just threshold for perception (1-4 mA). A visual analogue pain score was recorded before the study, and each evening of the month's study. The pain showed an overall highly significant rapid reduction of approximately 62% (p < 0.001), and all but two of the patients received substantial benefit throughout the study. We conclude that the Liss Bipolar Body Stimulator usually causes a substantial reduction of pain even in patients not helped by conventional TENS devices.

Back Pain↗
PubMed1992

Methotrexate alters the fatty acid composition of NC adenocarcinoma cells in culture.

The effects of methotrexate and indomethacin alone and in combination have been examined on the fatty acid (FA) composition of total cellular lipids in cultured NC adenocarcinoma cells. These studies show that methotrexate can alter the lipid content of cancer cells. Methotrexate 16 ng/ml incubated with NC cells for 2 days increased the content of various FAs. When used alone, indomethacin 1 microgram/ml or methotrexate 8 ng/ml had no significant effect, but in combination caused FA increases, usually to about the same extent as with the higher concentration of methotrexate alone. No FA changes were seen up to 3 h with these drug concentrations or with methotrexate up to 10 micrograms/ml alone or with INDO 1 microgram/ml. These effects may explain previous findings that indomethacin potentiates methotrexate, an interaction which may be important in cancer therapy.

Animals↗
PubMed1992

Changes in tissue fatty acid composition in murine malignancy and following anticancer therapy.

We studied the mouse NC tumour, a subcutaneously transplanted adenocarcinoma originally of mammary origin. Measurements per g tissue were made of 17 fatty acids (FAs), the combined amounts of n-3, n-6, saturated, unsaturated, and total FAs, and of various FA ratios in the tumour, mammary tissue, spleen, liver and plasma. Compared with mammary tissue from normal mice, tumours of vehicle-treated controls had less of seven of the FAs and more of two FAs. Mice bearing the NC tumour often had changed (usually decreased) amounts of FAs in the 'normal' spleen, liver and plasma, but not in mammary tissue. Treatment with methotrexate (MTX) was studied alone and with indomethacin which can potentiate MTX cytotoxicity. Indomethacin 1.25 mg kg-1 (INDO) increased the amounts of 3/17 tumours FAs and the unsaturated FAs, but reduced 9/17 FAs, the saturated and the unsaturated FAs in 'normal' mammary tissue, and usually had no effect on the FAs of other tissues. MTX 2 or 4 mg kg-1 (MTX 2 or 4 mg) +/- INDO in general partly restored (increased) the amounts of tumour FAs, and reduced the saturated/unsaturated FA ratio. In the 'normal' spleen and plasma also, but not in the liver, MTX 2 mg generally somewhat restored the FA composition. However, as in the liver, the spleen 20:4 and 22:6 (which form prostaglandins and lipid peroxides) did not increase in the presence of INDO. With MTX 4 mg, some of the plasma and liver FAs decreased, in contrast to the tumour. There was generally no evidence of MTX potentiation by INDO. These results are discussed in relation to carcinogenesis, cachexia, and the response to treatment.

Animals↗
PubMed1992

A pharmacokinetic study of sulphasalazine and two new formulations of mesalazine.

We have examined the pharmacokinetics of enteric coated sulphasalazine compared with two new formulations of mesalazine. These consisted of microgranules of mesalazine coated with Eudragit S in a concentration of either 20 or 25% dry lacquer substance; these in turn were enclosed in capsules coated with Eudragit L. In-vitro dissolution studies of coated microgranules showed that drug release was pH dependent. Studies in 7 normal volunteers showed median peak concentrations of 5-amino-salicylic acid and N-acetyl-5-amino-salicylic acid occurred at about 6 hours with both microgranular preparations, compared with sulphasalazine at 15 h. The microgranule formulation coated with 20% Eudragit S gave serum levels and overall systemic absorption similar to values with sulphasalazine. This new formulation may be of value for delivering mesalazine and other therapeutic agents to the colon.

Adult↗
PubMed1992

Effects of cupric chloride and tamrabhasma, a traditional Indian preparation of copper, on eicosanoid production by human gastric and colonic mucosa.

Tamrabhasma is a traditional copper oxide-containing Indian preparation which has anti-ulcer activity. We have studied the effect of tamrabhasma and CuCl2.2H2O on prostaglandin formation by human gastric and colonic mucosa and submucosa, as prostaglandins have mucosal protective activity, and their release may contribute to the anti-ulcer effect. With the gastric mucosa, tamrabhasma 10 micrograms mL-1, but not 0.1 or 1 microgram mL-1, increased prostaglandin E (PGE) concentration by 38% (P < 0.05), with little or no effect on 6-keto-PGF1 alpha, thromboxane B2 or the leukotriene (LT) LTC4/LTD4. CuCl2.2H2O (10 micrograms mL-1) increased 6-keto-PGF1 alpha by 46% (P < 0.05), but 0.1, 1, 50 and 250 micrograms mL-1 did not significantly affect any of the prostanoids, and only the highest concentration reduced the amount of LTC4/LTD4. In the colon mucosa, tamrabhasma (0.1-10 micrograms mL-1) or CuCl2.2H2O (10-50 micrograms mL-1) increased all the prostanoids and this effect was greater than in the gastric mucosa but there was no significant change in LTC4/LTD4. CuCl2.2H2O showed a bell-shaped concentration-effect curve, with no significant effect at lower and higher amounts. Indomethacin (0.1-10 micrograms mL-1) caused a concentration-dependent reduction in the prostanoid amounts. The effect of tamrabhasma was probably not only due to the presence of Cu2+, as tamrabhasma was more effective than CuCl2.2H2O alone; in addition the solubility of CuO is very low. Increased prostanoid levels might explain, at least partly, the gastric mucosal protection by tamrabhasma. The results in the colon, however, raise the possibility that tamrabhasma should be examined for the treatment of inflammatory bowel disease.

Anti-Ulcer Agents↗
PubMed1992

PAF formation by human gastrointestinal mucosa/submucosa in-vitro: release by ricinoleic acid, and inhibition by 5-aminosalicylic acid.

Human isolated gastrointestinal mucosa/submucosa incubated with ricinoleic acid (12.5-100 micrograms mL-1) or the calcium ionophore A23187 (10 micrograms mL-1) released platelet-activating factor (PAF) as determined by a scintillation proximity assay after extraction and purification. 5-Aminosalicylic acid (25-100 micrograms mL-1) inhibited PAF release by ricinoleic acid in a concentration-dependent manner, and 50 micrograms mL-1 reduced the effect of A23187. We suggest that PAF may play a role in the laxation and mucosal damage by ricinoleic acid released from castor oil.

Aminosalicylic Acids↗
PubMed1992

The effects of various peptides on human isolated gut muscle.

The effects of eleven peptides of gastrointestinal origin have been studied on the contraction, relaxation and spontaneous activity of circular and longitudinal muscle strips from different regions of the human gastrointestinal tract. The effects varied with the peptides and sometimes with the region and muscle layer. There was either contraction, no effect, or relaxation and/or inhibition of an acetylcholine-induced contraction. Responses to some peptides are consistent with the possibility that they may contribute directly to the control of motility: galanin, neurotensin and substance P might be involved in contraction, and vasoactive intestinal peptide, peptide histidine isoleucine and peptide histidine methionine might be inhibitory transmitters.

Acetylcholine↗
PubMed1991

Loading-related increases in prostaglandin production in cores of adult canine cancellous bone in vitro: a role for prostacyclin in adaptive bone remodeling?

Cyclic mechanical loading sufficient to engender strains of physiologic magnitude applied to recently excised canine cancellous bone cores in vitro increased the release of prostaglandin E (PGE) and prostacyclin (PGI2, measured as its breakdown product 6-keto-PGF1 alpha), during a 15 minute loading period in which PG levels were measured in perfusing medium at 5 minute intervals. Peak production occurred in the 0-5 minute sample. Mean levels preload compared to during load were PGE, 2.66 and 3.67 ng/ml (p less than 0.002); and 6-keto-PGF1 alpha, 543 and 868 pg/ml (p less than 0.007). The elevated levels then declined to preload levels during the loading period. However, the 5-10 minute but not the 10-15 minute samples still contained levels greater than preload values. A second 15 minute period of load, 1 h following the end of the first, produced smaller increases in the levels of release that were statistically significant only for the first 0-5 minute sample during load (preload compared to load mean values, PGE, 1.09-1.66 ng/ml, p less than 0.02; 6-keto-PGF1 alpha, 401-558 pg/ml, p less than 0.04). Immunolocalization revealed PGE and 6-keto-PGF1 alpha in lining cells and 6-keto-PGF1 alpha but not PGE in osteocytes. Addition to the medium of 1 microM PGE2, approximating the concentration produced by loading, had no significant effect on the specific activity of the extractable RNA fraction labeled with [3H]uridine, whereas 1 microM PGI2 produced an increase similar to that seen previously with loading.(ABSTRACT TRUNCATED AT 250 WORDS)

6-Ketoprostaglandin F1 alpha↗