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Biomedical subjects

E A Gordon

Publications and source records attributed to E A Gordon.

At least 19 recordsLinked to original sources
PubMed2001

Paraneoplastic syndromes associated with lung cancer: a unique case of concomitant subacute cerebellar degeneration and Lambert-Eaton myasthenic syndrome.

IMPLICATIONS: We report an unusual case in which a patient with paraneoplastic subacute cerebellar degeneration (a brain disorder resulting from antibody production by a tumor located outside the skull) developed Lambert-Eaton Myasthenic Syndrome (antibody-mediated skeletal muscle weakness) that was not apparent until she underwent surgery. Failure to recognize this disease process can cause life-threatening respiratory distress.

Aged↗
PubMed2000

Effects of particulate and soluble cadmium species on biochemical and functional parameters in cultured murine macrophages.

Cultured murine macrophages (RAW 264.7) were used to evaluate the temporal relationships between cytotoxicity, phagocytosis, tumor necrosis factor-alpha (TNF-alpha), and nitric oxide (NO) production, and alterations in expression of stress proteins after exposure to cadmium oxide (CdO) or cadmium chloride (CdCl(2)), particulate and soluble forms of cadmium, respectively. Macrophages were exposed in vitro to CdO (25 or 50 microg) or CdCl(2) (30 or 40 microM) for 2 to 72 h. Cytotoxicity was not evident until 18 h when exposed to 30 microM CdCl(2) or 25 microg CdO, but occurred as early as 12 h after exposure to 40 microM CdCl(2) or 50 microg CdO. Relative to untreated controls, phagocytic activity decreased progressively from 2 to 24 h after exposure to both forms of cadmium. TNF-alpha levels increased to 2- to 3-fold after 4 h and remained elevated until 24 h after exposure to 25 and 50 microg CdO and 30 microM CdCl(2), but decreased by 18-24 h at 40 microM CdCl(2). CdCl(2) or CdO alone did not induce NO; however, both cadmium species reduced lipopolysaccharide (LPS)-stimulated NO production in a dose-dependent manner. Enhanced de novo synthesis of 70- and 90-kD heat shock, or stress, proteins was observed 2 to 8 h after exposure to both CdCl(2) and CdO; however, synthesis of these proteins returned to control levels by 24 h. Stress protein synthesis was enhanced by CdCl(2) or CdO prior to cytotoxicity, but coincided with a decrease in phagocytic capacity and an increase in TNF-a levels. The data suggest that cultured macrophages respond similarly in vitro to a particulate form and a soluble form of cadmium in a cell type that plays a pivotal role in inflammatory and immune responses.

Animals↗
PubMed2000

Electrostimulators for acupuncture: safety issues.

Three representative electrostimulators were evaluated to determine whether they meet the manufacturers' labeled nominal output parameters and how the measured parameters compare with a safety standard written for implanted peripheral nerve stimulators. The pulsed outputs (pulse width, frequency, and voltage) of three devices were measured with an oscilloscope across a 500-ohm resistance, meant to simulate subdermal tissue stimulated during electroacupuncture. For each device, at least two measured parameters were not within 25% of the manufacturer's claimed values. The measured values were compared with the American National Standard ANSI/AAMI NS15 safety standard for implantable peripheral nerve stimulators. Although for two stimulators the pulse voltage at maximum intensity was above that specified by the standard, short-term clinical use may still be safe because the standard was written for long-term stimulation. Similarly, the net unbalanced DC current, which could lead to tissue damage, electrolysis, and electrolytic degradation of the acupuncture needle, was within the limits of the standard at 30 pulses per second, but not at higher frequencies. The primary conclusions are (1) that the outputs of electrostimulators must be calibrated and (2) that practitioners must be adequately trained to use these electrostimulators safely.

Electric Stimulation↗
PubMed2000

The antihypertensive effects of the Jamaican Cho-Cho (Sechium edule).

The experiments reported in this study constitute a preliminary investigation into the possible hypotensive effect of the Jamaican Cho-Cho (Sechium edule). Experiments were conducted in a random and blind fashion on two sub species of Sechium edule. Both the pulp and the peel were examined for hypotensive activity. Water-soluble extracts were prepared from these components of the fruit and injected into anaesthetised rats. Various cardiovascular parameters were measured including heart rate, mean arterial pressure (MAP) and several ECG intervals. We report that all extracts tested produced a fall in blood pressure with little change in ECG intervals. Extract B produced the least change in heart rate with a fall in MAP of approximately 23 mmHg. Changes in heart rate with all extracts appeared to be minimal as an ED25 value could only be determined for extract A, and ED10 values could not be evaluated for extracts C and D. The mechanism(s) by which these extracts produce their hypotensive effects could not be determined in these preliminary experiments. However, it appears not to involve direct effects on cardiac tissue. This conclusion is based on the finding that it took a minimum of 10 to 15 seconds for the hypotensive action to manifest post bolus. Future experiments will be aimed at delineating the mechanism(s) involved in decreasing MAP.

Algorithms↗
PubMed1998

Instability of ventilatory control in patients with obstructive sleep apnea.

Because of the oscillatory pattern of upper airway resistance and breathing during sleep in patients with obstructive sleep apnea (OSA), we hypothesized that OSA patients have an underlying instability of ventilatory drive to inspiratory muscles. To assess the stability of ventilatory drive in OSA patients and controls, we used the pseudorandom binary stimulation (PRBS) test and examined the closed- and open-loop responses to hyperoxic hypercapnia. The closed-loop response is produced by interactions of dynamic gain in controller, plant, and ventilatory feedback. The open-loop response reflects controller dynamic gain or frequency-dependent chemosensitivity. As compared with 16 nonapneic, nonobese control subjects, a group of nine obese OSA patients had a higher peak response and a more rapid and irregular recovery phase of the closed-loop CO2 response in the PRBS test. The two groups had similar open-loop responses in the PRBS test, suggesting that central dynamic CO2 chemosensitivity was not abnormal in OSA. We conclude that the differences between OSA patients and controls in the closed-loop response in the PRBS test are not due to differences in dynamic controller gain, but are related to differences in dynamic plant gain and/or negative ventilatory feedback. In addition to OSA, obesity may affect these variables and may have been responsible for our findings.

Adult↗
PubMed1997

Serotonin-induced cortisol release in CPAP-treated obstructive sleep apnea patients.

Previously, we demonstrated elevated cortisol production/release in response to the administration of the serotonin precursor, L-5-hydroxytryptophan (L-5-HTP) in untreated patients with obstructive sleep apnea (OSA). We hypothesized that if this elevated cortisol response to L-5-HTP was related to OSA, this finding would not be present in OSA patients treated with nasal continuous positive airway pressure (nCPAP). Eleven OSA patients treated for at least 1 month with nCPAP were studied. On two different days, we measured blood cortisol level every 15 min for 4 h following the ingestion of L-5-HTP, 0.4 mg/kg, or placebo, both given with carbidopa, a peripheral tryptophan decarboxylase inhibitor, used to prevent peripheral L-5-HTP metabolism before brain absorption. For a given subject, the cortisol response was calculated as the difference between the area under the curve of the L-5-HTP and placebo responses. In the nCPAP-treated OSA patients, this net cortisol response, 577 +/- 240 min.micrograms/dL, was less than the value found in the previously studied untreated OSA group, 1,198 +/- 227 min.micrograms/dL (p < 0.05) and not different from the previously studied nonapneic control group, 469 +/- 154 min.micrograms/dL. From these results, we speculate that nCPAP treatment reverses the elevated cortisol response to serotonergic stimulation seen in untreated OSA patients.

5-Hydroxytryptophan↗
PubMed1996

The K+ channel inward rectifier subunits form a channel similar to neuronal G protein-gated K+ channel.

G protein-activated inwardly rectifying K+ channel subunits GIRK1 (Kir 3.1), GIRK2 (Kir 3.2), and CIR (Kir 3.4) were expressed individually or in combination in Xenopus oocytes and CHO cells. GIRK1 coexpressed with CIR or GIRK2, produced currents up to 10-fold larger than any of the subunits expressed alone. No such clear synergistic effects were observed upon coexpression of CIR/GIRK2 under the same conditions. Coexpression of G protein beta gamma (G beta 1 gamma 2) increased the current through GIRK1/GIRK2 and GIRK2 channels. G beta gamma subunits purified from bovine brain, increased channel activity 50-1000-fold in patches from cells expressing GIRK1/GIRK2 or GIRK2 alone. The single GIRK1/GIRK2 channels resembled previously described neuronal G protein-gated K+ channels. In contrast, single GIRK2 channels were short-lived and unlike any previously described neuronal K+ channel. We propose that some neuronal G protein-activated inward rectifier K+ channels may be formed by a GIRK1/GIRK2 heteromultimer and that G beta gamma activation may involve both subunits.

Animals↗
PubMed1995

The G-protein-gated atrial K+ channel IKACh is a heteromultimer of two inwardly rectifying K(+)-channel proteins.

Heart rate is slowed in part by acetylcholine-dependent activation of a cardiac potassium (K+) channel, IKACh. Activated muscarinic receptors stimulate IKACh via the G-protein beta gamma-subunits. It has been assumed that the inwardly rectifying K(+)-channel gene, GIRK1, alone encodes IKACh. It is now shown that IKACh is a heteromultimer of two distinct inwardly rectifying K(+)-channel subunits, GIRK1 and a newly cloned member of the family, CIR.

Amino Acid Sequence↗
PubMed1995

Abnormal serotonergic stimulation of cortisol production in obstructive sleep apnea.

Because serotonin (5-HT) precursor or reuptake inhibitors improve obstructive sleep apnea (OSA), we hypothesized that brain serotonergic activity may be decreased in OSA. To test this hypothesis, we measured the cortisol response to the ingestion of L-5-hydroxytryptophan (L-5-HTP), a 5-HT precursor that is decarboxylated to 5-HT in the brain. Either L-5-HTP or an identical-looking placebo was administered at 0800, and blood was obtained over the following 4 h for serum cortisol determination. A placebo-controlled ACTH stimulation test was performed to evaluate adrenal function. We found that a group of 11 OSA patients had significantly higher cortisol production after L-5-HTP administration compared with a group of 11 control nonapneic subjects. The pretest cortisol levels and ACTH stimulation test results were not different between the two groups. We conclude that the cortisol response to L-5-HTP was elevated in the OSA patients studied, most likely as a result of increased hypophyseal 5-HT activity. We speculate that the 5-HT postsynaptic receptors that induce corticotropin releasing factor production and release are upregulated, or supersensitized, as a result of a brain 5-HT-deficient state that exists during sleep in OSA. We anticipate that medullary serotonergic neurons that affect ventilation would be altered similarly.

5-Hydroxytryptophan↗
PubMed1994

Molecular characterization of a swelling-induced chloride conductance regulatory protein, pICln.

Cells maintain control of their volume by the passage of KCl and water across their membranes, but the regulatory proteins are unknown. Expression in Xenopus oocytes of a novel protein, pICln, activated a chloride conductance. We have cloned analogs of pICln from rat heart and Xenopus ovary. pICln was identified as an abundant soluble cytosolic protein (approximately 40 kd) that does not immunolocalize with the plasma membrane. pICln was found in epithelial and cardiac cells, brain, and Xenopus oocytes, forming complexes with soluble actin and other cytosolic proteins. Monoclonal antibodies recognizing pICln blocked activation of a native hypotonicity-induced chloride conductance (ICl.swell) in Xenopus oocytes, suggesting that pICln may link actin-bound cytoskeletal elements to an unidentified volume-sensitive chloride channel. The high degree of sequence conservation and widespread expression of pICln suggest that it is an important element in cellular volume regulation.

Actins↗
PubMed1992

Disposition and pharmacology of propofol glucuronide administered intravenously to animals.

1. Propofol glucuronide (PG) is the major human metabolite of the i.v. anaesthetic propofol, 2,6-diisopropylphenol. 2. Bolus i.v. doses of 14C-PG (1 mg/kg) to rat and dog were eliminated in urine (40 and 66% respectively) and faeces (48 and 19%); 25 and 48% of the dose were excreted unchanged in urine. 3. In dog, PG was distributed from plasma (t 1/2 4 min) into a volume equivalent to extracellular water and eliminated with t 1/2 80 min. Total body clearance was 1.8 ml/min per kg, and renal clearance about 20% GFR. In rat, plasma 14C concentrations were about one-tenth those in dog, thus PG levels were not quantified. 4. Propofol was not detected in the plasma showing that PG is hydrolytically stable. Enterohepatic circulation of PG occurred in rat and to a lesser extent in dog. Metabolites, mainly side-chain hydroxylation products, were evident in both species from 4 h after dosing. 5. Bolus i.v. doses of PG (200 mg/kg) showed no hypnotic activity in mice.

Animals↗
PubMed1991

Species differences in blood profiles, metabolism and excretion of 14C-propofol after intravenous dosing to rat, dog and rabbit.

1. Bolus i.v. doses of 14C-propofol (7-10 mg/kg) to rat, dog and rabbit, or an infusion dose (0.47 mg/kg per min for 6 h) to dog were eliminated primarily in urine (60-95% dose); faecal elimination (13-31%) occurred for rat and dog, but was minimal (less than 2%) for rabbit. 2. After bolus administration, blood 14C concentrations were maximal (8-30 micrograms equiv./ml) at 2-15 min; these declined rapidly during the 0-2 h period and thereafter more slowly. Propofol concentrations were maximal (4-16 micrograms/ml) at 2 min and the profiles were best fitted by a tri-exponential (rat and dog) or bi-exponential (rabbit) equation. Duration of sleep ranged from 5 to 8 min. 3. Infusion of 14C-propofol in dog gave a blood 14C concentration of 117 micrograms equiv./ml at the end of the 6 h infusion period; this declined at a similar rate to that after the bolus dose. Propofol concentration on termination of infusion was 13 micrograms/ml; thereafter, propofol concentrations declined less rapidly than after the bolus dose. Waking occurred about 44 min post-infusion. 4. Propofol was cleared by conjugation of the parent molecule or its quinol metabolite; hydroxylation of an isopropyl group also occurred in rat and rabbit. Biliary excretion leading to enterohepatic recirculation, and in turn increased sulphate conjugation, occurred in rat and dog, but not rabbit, resulting in a marked interspecies variation in drug clearance and metabolite profiles.

Animals↗
PubMed1991

Distribution in female rats of an anaesthetic intravenous dose of 14C-propofol.

1. Bolus i.v. doses of 14C-propofol (9 mg/kg) were administered to female rats for measurement of tissue levels of total 14C and propofol from 2 min to 24 h post-dose; whole-body autoradiography was studied at 6 min, 2 h and 24 h post-dose, and also involved 15-day pregnant rats. 2. The blood propofol concentration-time profile was fitted by a tri-exponential function corresponding to a three-compartment open model. Data show rapid distribution during the mixing period into highly perfused tissues and muscle, comprising the central compartment, and slower uptake into less well-perfused skin and adipose tissues comprising the deeper compartments. 3. The initial decline in blood propofol concentration was associated with redistribution (t1/2 4 min), the second decline (15-240 min post-dose) was associated with metabolism (t1/2 33 min) and the third decline reflected slow depletion of drug from deep tissue compartments (t1/2 6.4 h). 4. Blood and brain propofol concentrations on waking (at 7 min post-dose) were 4 micrograms/ml and 9 micrograms/g respectively; the model shows that, at this time, 30% of the dose was lost from the central compartment by redistribution and a similar amount by metabolism. 5. Tissue profiles of total 14C and propofol diverged for highly perfused tissues (other than brain) because of slow clearance of metabolites, accentuated by enterohepatic recirculation.

Adipose Tissue↗
PubMed1990

Centrally truncated neuropeptide Y analog acts as an agonist for Y1 receptors on SK-N-MC cells.

The similarity of neuropeptide Y (NPY) to pancreatic polypeptide (PP), whose X-ray crystallographic structure is known, has allowed computer-assisted molecular modelling of NPY and predictions of its three-dimensional structure. Utilizing these techniques, Krstenansky et al. (Proc. Natl. Acad. Sci. U.S.A., 86 (1989) 4377-4381) reported that a centrally truncated analog of porcine NPY, [D-Cys7-Aoc8-17-Cys20]pNPY, which was designed to maintain the tertiary structure of the native molecule, bound to sites on membranes from mouse brain with even higher affinity than native NPY. As brain membranes may represent a heterogeneous mixture of receptor subtypes, we decided to characterize the activity of this analog on a defined cell line. SK-N-MC cells are a human epithelioma cell line with high-affinity receptors of the Y1 subtype which are coupled to inhibition of adenylate cyclase. (D-Cys7-Aoc8-17-Cys20]pNPY bound to receptors on SK-N-MC cells, but in contrast to membranes from mouse brain, with a lower affinity than pNPY. Furthermore, [D-Cys7-Aoc8-17-Cys20]pNPY was able to inhibit isoproterenol-stimulated cAMP production in these cells. Therefore, it appears that the central amino acids deleted from this analog are not involved in NPY binding, and biological activity can be maintained by conservation of the tertiary structure of NPY around the binding surface.

Animals↗
PubMed1990

Characterization of functional neuropeptide Y receptors in a human neuroblastoma cell line.

We identified receptors for neuropeptide Y (NPY) on an established human neuroblastoma cell line, SK-N-MC, which are functionally coupled to adenylate cyclase through the inhibitory guanine nucleotide-binding protein of adenylate cyclase, Gi. Intact SK-N-MC cells bound radiolabeled NPY with a KD of 2 nM and contained approximately 83,000 receptors/cell. Unlabeled porcine and human NPY and structurally related porcine peptide YY (PYY) competed with labeled NPY for binding to the receptors. NPY inhibited cyclic AMP accumulation in SK-N-MC cells stimulated by isoproterenol, dopamine, vasoactive intestinal peptide, cholera toxin, and forskolin. NPY inhibited isoproterenol-stimulated cyclic AMP production in a dose-dependent manner, with half-maximal inhibition at 0.5 nM NPY. Porcine and human NPY and porcine PYY gave similar dose-response curves. NPY also inhibited basal and isoproterenol-stimulated adenylate cyclase activity in disrupted cells. Pertussis toxin treatment of the cells completely blocked the ability of NPY to inhibit cyclic AMP production and adenylate cyclase activity. The toxin catalyzed the ADP-ribosylation of a 41-kDa protein in SK-N-MC cells that corresponds to Gi. The receptors on SK-N-MC cells appeared to be specific for NPY, as other neurotransmitter drugs, such as alpha-adrenergic, dopaminergic, muscarinic, and serotonergic antagonists, did not compete for either NPY binding or NPY inhibition of adenylate cyclase. Thus, SK-N-MC cells may be a useful model for investigating NPY receptors and NPY-mediated signal transduction.

Adenosine Diphosphate Ribose↗
PubMed1988

Disposition in male volunteers of a subanaesthetic intravenous dose of an oil in water emulsion of 14C-propofol.

1. An intravenous dose of 14C-propofol (0.47 mg/kg) administered to six male volunteers was rapidly eliminated with 88% recovered in the urine in 5 days and less than 2% in faeces. 2. The dose was cleared by metabolism with less than 0.3% excreted unchanged. The major metabolites were the glucuronic acid conjugate of propofol and the glucuronic acid and sulphate conjugates of its hydroxylated derivative, 2,6-diisopropyl-1,4-quinol. Propofol glucuronide accounted for about 53% of the urinary radioactivity and was the major metabolite in plasma from 30 min post dose. 3. The blood concentration of propofol declined in a biphasic manner from a maximum mean value of 0.44 microgram/ml, 2 min after injection. The half-lives of the first and second exponential phases, mean values 5 min and 97 min respectively, varied widely among subjects. A proportion of the dose was cleared slowly, probably due to slow release from less well perfused tissues. Propofol accounted for 94% of the total blood radioactivity at 2 min but only about 6% from 3 to 8 h post dose. 4. Propofol has a volume of distribution equivalent to about 3 to 4 times body weight, and a mean total body clearance of 2.2 1/min.

Adult↗
PubMed1986

Thrombin receptor occupancy initiates cell proliferation in the presence of phorbol myristic acetate.

A combination of DIP-thrombin and either PMA (50 ng/ml) or dioctanoyl glycerol stimulates DNA synthesis in serum free cultures of NIL hamster cells similar to that previously reported for the combinatory effect of DIP-thrombin and gamma-thrombin. Thus, PMA or dioctanoyl glycerol appears to generate signals normally stimulated by gamma-thrombin interaction with cells. This stimulation was not observed when cells were treated with DIP-thrombin and 4-beta-phorbol or 4-alpha-phorbol 12,13-didecanoate. Therefore, it appears that this effect is mediated through activation of protein kinase C and that this activation plays an important role in thrombin mitogenesis.

Animals↗