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Biomedical subjects

I R Tebbett

Publications and source records attributed to I R Tebbett.

At least 37 records · Page 2Linked to original sources
PubMed1994

Hemodynamic and cerebral blood flow effects of cocaine, cocaethylene and benzoylecgonine in conscious and anesthetized fetal lambs.

We studied hemodynamic responses to cocaine and two metabolites, cocaethylene (CE) and benzoylecgonine (BE), in five conscious ewes and fetuses, which were chronically instrumented to measure maternal and fetal aortic pressures, uterine artery blood flow (Qutr) and fetal common carotid artery blood flow (Qcar) to estimate cerebral blood flow. Conscious ewes of 121 to 128 days' (mean, 124 days) gestation received 1.0 mg/kg i.v. of cocaine (n = 12 doses), CE (n = 14) or BE (n = 12) and responses were compared to seven additional ewes and fetuses at 115 to 127 days' (mean, 122 days) gestation each given one 1.0 mg/kg i.v. of cocaine dose while anesthetized with halothane. In conscious ewes, cocaine, CE and BE all caused maternal and fetal hypertension. Qutr decreased 31% after cocaine, increased 37% after CE and was unaffected by BE. Cocaine induced fetal hypoxemia; fetal arterial blood gas tensions were unaffected by CE or BE. Fetal Qcar was reduced 51% at peak effect by cocaine (57 +/- 8 to 28 +/- 6 ml/min) and 46% by CE (65 +/- 7 to 33 +/- 6 ml/min), and was unaffected by BE because of variable subject response, although all three drugs increased calculated fetal cerebral vascular resistance. The cocaine-induced changes were attenuated or abolished in anesthetized sheep. Fetal/maternal peak serum concentrations were 100% for CE and only 2% for BE; amniotic fluid concentrations of CE were 10-fold higher than both fetal and maternal serum concentrations. Cocaine and cocaine metabolites have important effects on maternal and fetal hemodynamics and fetal cerebral blood flow which, for CE and BE, are not dependent on decreased uterine blood flow or fetal hypoxemia.

Amniotic Fluid↗
PubMed1994

Fetoplacental growth and placental protein synthesis in rats after chronic maternal cocaine administration.

This study evaluated the effects of chronic exposure to cocaine during pregnancy on the morphology and function of the placenta. Pregnant rats received either 45 or 60 mg/kg of cocaine hydrochloride by i.p. injection as a divided daily dose on days 8 to 18 of gestation. The maternal weight gain decreased by 20% to 24% (P < .05) in the two cocaine treatment groups, whereas the placental weight was not significantly altered. Fetal growth showed a dose-related decrease in the 45- and 60-mg/kg cocaine treatment groups; fetal body weights and length were significantly decreased by 5% to 10%. The plasma levels of cocaine were 0.79 and 1.09 micrograms/ml in the 45- and 60-mg treatment dose groups, respectively; the level in the fetal plasma was 3-fold higher in the latter group. Placental tissue explants were cultured in the presence of [35S]-methionine to investigate whether cocaine exposure altered placental protein synthesis. Secreted proteins were analyzed by polyacrylamide gel electrophoresis followed by fluorography or by western blotting and immunostaining with antibodies to placental prolactin-like proteins-B and -C and growth hormone-related protein-1. The data showed that there were no quantitative or qualitative changes in placental peptide hormone secretion as a result of the cocaine treatment. These data indicate that chronic cocaine exposure in the pregnant rat is associated with fetal growth retardation in the absence of alterations in placental morphology or secretory protein synthesis.

Amino Acid Sequence↗
PubMed1993

High-performance liquid chromatographic determination of morphine and its metabolites in plasma using diode-array detection.

An isocratic high-performance liquid chromatographic method has been developed for the determination of morphine, codeine, normorphine, morphine 3-glucuronide and morphine 6-glucuronide in plasma using a diol column and diode-array detection. Samples were extracted using solid-phase extraction with recoveries in excess of 90%. The limit of determination was 1 ng/ml for morphine, codeine and morphine 3-glucuronide, and 10 ng/ml for normorphine and morphine 6-glucuronide. Inter- and intra-day precision were better than 10%.

Chromatography, High Pressure Liquid↗
PubMed1993

Risk of intracranial hemorrhage and other adverse outcomes after cocaine exposure in a cohort of 323 very low birth weight infants.

We conducted a prospective cohort study of 323 consecutively born very low birth weight infants (< or = 1499 gm) to determine any association between prenatal cocaine exposure and (1) intracranial ultrasonographic abnormalities and (2) other adverse perinatal outcomes. The infants were assigned to either a cocaine-exposed group (n = 86) or a cocaine-nonexposed group (n = 146) on the basis of combined detection methods for prenatal maternal cocaine abuse including maternal history, maternal and infant urine immunoassay (Emit), and meconium analysis (high-performance liquid chromatography and gas chromatography-mass spectrometry). Ninety-one infants were not assigned because of early death before complete testing (n = 80) or missed tests (n = 11). The detected incidence of cocaine exposure in the assigned population was 37% (86/232). Meconium testing with high-performance liquid chromatography and gas chromatography-mass spectrometry was the sole means of detection in 30% (26/86) of cases. The cocaine-nonexposed infants did not differ from the cocaine-exposed infants in the incidence of intraventricular hemorrhage (36% vs 35%), grades III and IV intraventricular hemorrhage (14% vs 14%), or periventricular leukomalacia (4% vs 2%). Adverse outcomes increased by cocaine exposure were abruptio placentae (8% vs 18%; p = 0.046), surgical ligation of a patent ductus arteriosus (1% vs 7%; p = 0.02), and seizures (5% vs 17%; p = 0.004). We conclude that prenatal cocaine exposure does not increase the incidence or severity of intracranial hemorrhage or periventricular leukomalacia but does increase the risk of abruptio placentae, surgical ligation of a patent ductus arteriosus and seizures in very low birth weight infants.

Abruptio Placentae↗
PubMed1992

Analysis of meconium for cocaine in neonates.

A solid-phase extraction method was developed for the extraction of first-day meconium samples from premature infants of cocaine-dependent mothers. Extracts were analysed by high-performance liquid chromatography and gas chromatography-mass spectrometry for cocaine and its metabolites. Control stools showed no drug. Meconium from cocaine-dependent mothers showed cocaine in the range 0.1-0.78 micrograms/g. Benzoylecgonine, ecgonine and ecognine methyl ester were not present in the samples, which suggests that the metabolism of cocaine in the premature neonate is limited.

Chromatography, High Pressure Liquid↗
PubMed1992

Direct analysis for cocaine in urine by high-performance liquid chromatography (HPLC) using a column-switching technique.

The analysis of urine for the presence of drugs generally requires that the drug be first extracted from relatively large concentrations of endogenous compounds. By replacing the injection loop with a loop incorporating a cyano precolumn, urine can be injected directly onto the high-performance liquid chromatograph. Interfering compounds are washed off of the precolumn, with the valve in the load position. When the valve is then switched to inject, the mobile phase elutes the cocaine from the precolumn onto the analytical column. A preliminary identification of cocaine and benzoylecgonine can be made using this technique, which requires 100 microL of sample and has a detection limit of 10 ng/mL.

Chromatography, High Pressure Liquid↗
PubMed1991

High-performance liquid chromatographic determination of morphine, morphine-3-glucuronide, morphine-6-glucuronide and codeine in biological samples using multi-wavelength forward optical detection.

An isocratic high-performance liquid chromatographic method has been developed for the determination of morphine, morphine-3-glucuronide, morphine-6-glucuronide and codeine in plasma, urine and cerebrospinal fluid. The use of an efficient solid-phase extraction procedure together with a forward optical scanning detector allows a detection limit of 500 pg/ml. The method was evaluated by examination of biological samples taken from newborn infants following the intravenous administration of morphine sulfate.

Chromatography, High Pressure Liquid↗
PubMed1991

A rapid method for the determination of cocaine in brain tissue.

A rapid procedure is described for the extraction and analysis of brain samples for cocaine and benzoylecgonine. Human brain tissue was sectioned at autopsy, and samples were subjected to a lipase digestion, subsequent to solid-phase extraction. The distribution of cocaine and benzoylecgonine throughout different regions of the brain was determined by high-performance liquid chromatography.

Brain Chemistry↗
PubMed1988

A rapid method for the extraction of cocaine and benzoylecgonine from body fluids.

A method has been developed for the rapid extraction of cocaine and benzoylecgonine from post-mortem blood and urine samples. Solid phase columns containing C8 packing material gave clean, emulsion free extracts from body fluids. The total time for each extraction was approx. 10 min and the system has the capacity for the simultaneous extraction of up to 10 samples. Urine can be extracted directly, blood samples were sonicated before extraction to allow for their easy passage through the columns. The method gave excellent recoveries of cocaine (98-100%) from spiked samples at concentrations of between 50 ng/ml and 10 micrograms/ml. Analysis of the extracts was by high performance liquid chromatography (HPLC).

Chromatography, High Pressure Liquid↗
PubMed1984

Mushroom toxins of the genus Cortinarius.

3 major components of the toxic fungus Cortinarius speciosissimus have been isolated and their structures determined as cyclic polypeptides. 2 of these compounds have been shown in laboratory animals to cause nephrotoxicity characteristic of Cortinarius mushroom poisoning.

Amino Acid Sequence↗