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Biomedical subjects

M Allen

Publications and source records attributed to M Allen.

At least 235 records · Page 13Linked to original sources
PubMed1987

The effects of salbutamol on pulmonary function in cyclists exposed to ozone: a pilot study.

In order to determine the effects of an inhaled bronchodilator on the acute effects of ozone exposure on competitive cyclists, three subjects exercised on a stationary cycle ergometer for one hour in 0.34 +/- 0.02 ppm ozone, 29.8 +/- 0.3 degrees C. and 36.5 +/- 0.5% relative humidity under three experimental conditions. The initial test involved no pre-medication and served as a control. Using a double blind protocol the subjects were either given a placebo or salbutamol (200 micrograms via aerosol) prior to the second and third exposures. Pre- and post-exercise pulmonary function tests demonstrated a reduction in forced vital capacity (FVC) and forced expiratory volume in one second (FEV1), however, the magnitude of this reduction was not changed by the administration of salbutamol. These data suggest that pre-treatment with salbutamol is ineffective in reducing or eliminating pulmonary discomfort or respiratory dysfunction.

Adult↗
PubMed1986

The demonstration of B-cell, T-cell and myeloid antigens in paraffin sections.

The monoclonal antibodies MB1 and MT1, which detect B cells and T cells respectively, have been applied to human lymphoid tissues. The distribution of staining within paraffin sections was compared with that observed using frozen sections and was found to be identical. The antibodies were then applied to paraffin sections of 19 B-cell lymphomas and 10 T-cell lesions in which full immunophenotyping had been performed. The B lymphomas all consisted of a large majority of MB1 positive cells with a variable infiltrate of small MT1 positive lymphocytes. The T cell lesions consisted of MT1 positive cells with few MB1 positive cells except in residual B cell areas of lymph nodes. In paraffin sections from cases of Hodgkin's disease anti-Leu M1 identified Reed-Sternberg cells and their variants and MB1 and MT1 showed a similar distribution of B cells and T cells to that demonstrated in previous studies using frozen sections. The results show that MB1 and MT1 are useful markers for B and T cells in routinely fixed paraffin embedded tissue. In conjunction with anti-Leu M1 they provide a valuable panel of antisera for the examination of lymph nodes and other biopsies when frozen tissue is not available.

Antibodies, Monoclonal↗
PubMed1986

Rubella-associated arthritis. I. Comparative study of joint manifestations associated with natural rubella infection and RA 27/3 rubella immunisation.

Joint manifestations observed during the course of a prospective RA 27/3 rubella immunisation trial were compared with those observed during an intercurrent wild rubella epidemic in an outlying community. Among 44 rubella haemagglutination inhibition (HAI) negative females ranging in age from 17 to 33 years who received rubella vaccine, six (13.6%) developed acute polyarticular arthritis within two to four weeks postvaccine and two (4.5%) had continuing or recurrent arthropathy lasting longer than 18 months. In contrast, among 23 females ranging in age from 11 to 39 years undergoing wild rubella infection, 12 (52.2%) developed acute polyarticular arthritis and seven (30.4%) had recurrent arthropathy 18 months postinfection. Among 23 males ranging in age from 13 to 54 years undergoing wild rubella infection, only two (8.7%) developed acute arthritis and both individuals had continuing joint manifestations 18 months postinfection. Wild rubella infection in adult populations is associated with a higher incidence, increased severity, and more prolonged duration of joint manifestations than is seen after RA 27/3 rubella immunisation.

Adolescent↗
PubMed1985

Daily patterns of serotonin uptake in platelets from psychiatric patients and control volunteers.

Serotonin (5-HT) uptake into platelets from psychiatric patients and controls was measured in the morning and afternoon. Uptake varied with time of day in both groups studied, resulting in four recognizable patterns. Two patterns occurred in the majority of controls. In contrast, uptake patterns in the psychiatric patients were more variable, with each of the four patterns clearly represented. However, except for the fact that uptake was significantly decreased throughout the day in depressed patients, the patterns were not otherwise linked statistically to clinical condition. In any event, the greater variability of daily 5-HT uptake patterns in patients suggests that psychiatric disorders linked presumably to central nervous system (CNS) dysfunction are in some way reflected by labile platelet 5-HT pharmacokinetics.

Adolescent↗
PubMed1985

A possible increase in the incidence of congenital heart defects among the offspring of affected parents.

The incidence of congenital heart disease in the children of 219 probands was determined. Each of these probands had one of four selected defects: atrial septal defect, coarctation of the aorta, aortic valve stenosis or complex dextrocardia. Of their children, 8.8% had substantial congenital cardiac defects. This is a much higher incidence than that reported in most comparable studies. The difference is highly significant statistically and therefore is likely to be genuine. The cause of the high recurrence is probably environmental.

Adolescent↗
PubMed1985

Morphine kinetics and kidney transplantation: morphine removal is influenced by renal ischemia.

Morphine plasma concentrations were determined in six patients receiving kidney transplants from living-related donors, and nine patients receiving kidney transplants from cadavers. The total cold ischemic time was about 2 hr for kidneys from living-related donors and 14 hr for those from cadavers. After an intravenous bolus dose of morphine, plasma morphine concentrations decreased to a plateau that lasted for several hours; morphine elimination resumed when the transplanted kidney began to clear creatinine. The duration of the total cold ischemic time was significantly related to both the duration of the plateau in morphine concentration (P = 0.008) and the first postoperative day creatinine clearance (P = 0.021). Morphine elimination half-life after the plateau was related to first postoperative day creatinine clearance (P less than 0.001). It was concluded that morphine elimination depended upon intact renal function.

Adult↗
PubMed1985

The effect of tryptophan modification on the structure and function of a sea snake neurotoxin.

A neurotoxin has been isolated from the venom of the sea snake Lapemis hardwickii. This neurotoxin contains only one tryptophan residue which was chemically modified with two different reagents, 2-hydroxy-5-nitrobenzyl bromide and N-bromosuccinimide. Following modification, the neurotoxin almost completely lost its acetylcholine receptor-binding activity. To examine the effect tryptophan modification had on the conformation of the neurotoxin, circular dichroic and Raman spectra were taken of the modified neurotoxin and compared with those of the native toxin. The overall conformation of the modified neurotoxin was very similar to the native conformation. The Raman data also indicated some side chain conformations in the modified toxin were very similar to those of the native toxin. These data suggest that the tryptophan in sea snake venom short chain neurotoxins may have a direct role in the acetylcholine receptor binding process as well as a role in stabilizing the neurotoxin's active site in the proper conformation for optimum binding.

2-Hydroxy-5-nitrobenzyl Bromide↗
PubMed1984

The mechanism of degradation of cyclo(-Asn-Phe-Phe-D-Trp-Lys-Thr-Phe-Gaba-) and the relative stabilities of this and other octapeptide somatostatin analogues in rat intestinal juice.

The mechanism of degradation of the somatostatin analogue cyclo(-Asn-Phe-4-[3H]-Phe-D-Trp-Lys-Thr-Phe-Gaba-) in rat intestinal juice in vitro has been studied by isolation and identification of cleavage products. The analogue is much more stable than somatostatin but is nevertheless degraded in minutes in dilute intestinal juice. There is a single primary cleavage site at Lys-Thr and the linear peptide thus formed is subsequently rapidly degraded to smaller peptides. Analogues with a modified lysine are markedly stabilised relative to the octapeptide analogue.

Amino Acid Sequence↗
PubMed1984

Reduced permeation of 14C-sucrose, 3H-mannitol and 3H-inulin across blood-brain barrier in nephrectomized rats.

Experiments were carried out to determine if changes in the concentration-time profile of a blood-borne radiotracer such as 14C-sucrose would spuriously alter measurements of its permeation across the blood-brain barrier (permeability-area product, PA) based on a 2-compartment (plasma/brain) simple diffusion model. Anesthetized rats which were bilaterally nephrectomized and given a standard intravenous bolus injection of 14C-sucrose, 3H-mannitol or 3H-inulin exhibited an elevated plasma tracer concentration compared to control animals. However, tracer concentration measured in brain parenchyma after 30 min was not proportionally elevated, and PA calculated from the ratio, parenchymal tracer concentration: plasma concentration-time integral, was significantly reduced below control values. In control rats, distortion and elevation of the plasma 14C-sucrose profile by continuous intravenous infusion did not result in lowered PA values. This suggested that the lowering of PA by nephrectomy reflected reduced cerebrovascular permeability or area or other cerebral influence rather than a deficiency in the 2-compartment model for PA measurement.

Animals↗
PubMed1984

Aneurysmal degeneration of Blalock-Taussig shunts: identification and surgical treatment options.

Many Blalock-Taussig shunts (subclavian to pulmonary artery anastomoses) have been created and a significant number are still being done. Two cases of aneurysmal degeneration of a Blalock-Taussig shunt and their management are described. Development of this rare complication may be related to large shunt flow and long duration. Large, symptomatic or enlarging aneurysms should be repaired and smaller ones studied by serial computed axial tomography. A simple and safe approach to correct this lesion is division and oversewing of the proximal subclavian artery through an anterior approach, assuming adequate pulmonary blood flow is already present or can be established concomitantly.

Adult↗
PubMed1984

Spinal fluid kinetics of morphine and heroin.

Nine patients undergoing cardiopulmonary bypass surgery were given either 2 mg diamorphine or 2.5 mg morphine by intrathecal injection. Spinal fluid (sf) samples were collected over 25 min and drug concentrations measured by HPLC. Concentrations in sf were about 4000 times as great as after 1 mg/kg IV morphine. The kinetic properties of morphine and heroin in sf differed; diamorphine was removed from sf much more rapidly than morphine. Lipophilic opiates may be safer for intrathecal use because of the shorter life of substantial drug concentrations in the mobile sf phase.

Chromatography, High Pressure Liquid↗
PubMed1984

Morphine kinetics during and after renal transplantation.

Plasma concentrations after intravenous morphine were measured by a specific radioimmunoassay method in patients undergoing renal transplantation and in control subjects. In both transplant patients and controls, plasma morphine fell in the first 10 min, but there was no significant further fall in the transplant patients until between 3 and 5 hr, when there was an abrupt reversion to the same elimination t1/2 as the controls. This coincided with recovery of renal function after the period of cold ischemia. In the transplant patients the AUC over 24 hr was higher and the plasma clearance was lower than in controls. The role of the kidney in morphine elimination is discussed.

Adult↗
PubMed1984

Photochemistry of the atmosphere of Titan: comparison between model and observations.

The photochemistry of simple molecules containing carbon, hydrogen, nitrogen, and oxygen atoms in the atmosphere of Titan has been investigated using updated chemical schemes and our own estimates of a number of key rate coefficients. Proper exospheric boundary conditions, vertical transport, and condensation processes at the tropopause have been incorporated into the model. It is argued that he composition, climatology, and evolution of Titan's atmosphere are controlled by five major processes: (a) photolysis and photosensitized dissociation of CH4; (b) conversion of H to H2 and escape of hydrogen; (c) synthesis of higher hydrocarbons; (d) coupling between nitrogen and hydrocarbons; (e) coupling between oxygen and hydrocarbons. Starting with N2, CH4, and H2O, and invoking interactions with ultraviolet sunlight, energetic electrons, and cosmic rays, the model satisfactorily accounts for the concentrations of minor species observed by the Voyager IRIS and UVS instruments. Photochemistry is responsible for converting the simpler atmospheric species into more complex organic compounds, which are subsequently condensed at the tropopause and deposited on the surface. Titan might have lost 5.6 x 10(4), 1.8 x 10(3), and 4.0 g cm-2, or the equivalent of 8, 0.25, and 5 x 10(-4) bars of CH4, N2, and CO, respectively, over geologic time. Implications of abiotic organic synthesis on Titan for the origin of life on Earth are briefly discussed.

Atmosphere↗
PubMed1984

Effect of sulfhydryl group modification on the neurotoxic action of a sea snake toxin.

Pelamis toxin alpha is a major neurotoxin isolated from the venom of Pelamis platurus (yellow-bellied sea snake). The effect of sulfhydryl group modification by NN'-1,4-phenylenedimaleimide on the neurotoxic action of Pelamis toxin alpha has been investigated. The cross-linked toxin having a molecular weight of 11 000 was formed without significant structural changes in the toxin. Lethality tests on the modified toxin indicated that it retained considerable toxicity, although its potency was weaker than that of the native toxin. Binding studies with the acetylcholine receptor isolated from the electroplax of Torpedo californica indicated that the modified toxin binds to the receptor but less effectively than the native toxin. These results suggest that the decreases in toxicity and binding to the receptor are due to a decrease in accessibility of cross-linked neurotoxin to the receptor. This leads us to the conclusion that the region of the neurotoxin containing the sulfhydryl group is not essential for its biological activity. Analysis of the structure and function relationships of the modified toxin suggests that the neurotoxin-acetylcholine receptor interaction requires the proper orientation of the neurotoxin molecule.

Animals↗
PubMed1984

Plasma morphine concentrations and analgesic effects of lumbar extradural morphine and heroin.

Patients undergoing lumbar laminectomy were given extradural narcotic, either 5 mg morphine sulphate or 5.5 mg heroin (diamorphine hydrochloride); the extradural catheter had been positioned adjacent to the dura under direct vision. Plasma morphine concentrations measured by specific radioimmunoassay showed that peak concentrations occurred significantly earlier with heroin (4.7 +/- 0.6 min, mean +/- SEM) than with morphine (7.6 +/- 0.9 min) and that peak concentrations were significantly higher after heroin 5-10 min after extradural injection. The fraction of extradural heroin crossing the dura was estimated to be 55% of the fraction of morphine crossing the dura. Postoperative fentanyl requirements using demand analgesia were the same with extradural morphine as with extradural heroin (mean, 6.6 micrograms/hr). Clinically significant slowing of respiratory rate occurred only after extradural heroin (three patients).

Adult↗