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Biomedical subjects

D S Smith

Publications and source records attributed to D S Smith.

At least 235 records · Page 13Linked to original sources
PubMed1986

Correlation of mononuclear phagocyte assay results and in vivo haemolytic rate in subjects with a positive direct antiglobulin test.

A mononuclear phagocyte assay has been used to measure the in vitro interaction of normal donor monocytes with the red cells from subjects with a positive direct antiglobulin test (DAT). The relationship between the in vivo haemolytic rate in these subjects and the results obtained in the assay, expressed as the number of red cells associated with 100 monocytes (ARC value), has been examined. From the results of assays in which normal donor monocytes were incubated with normal (DAT negative) donor red cells it was calculated that ARC values of greater than 2 could be considered significantly elevated. Assays performed on 24 patients with a positive DAT and warm autoimmune haemolytic anaemia resulted in a mean ARC value of 42 (range 1-212). Assay results for two of the patients in this group, however, were not significantly elevated from normal. The red cells from three patients with a negative DAT who were suspected of having autoimmune haemolytic anaemia showed no association with normal donor monocytes in the assay. The mean ARC value obtained for 14 non-haemolysing subjects with a positive DAT was 7 (range 1-47). Assay results for only 10 of the 14 subjects in this non-haemolysing group fell within the normal range. The correlation of assay results and in vivo haemolysis was strengthened when the assays were performed with autologous monocytes. A possible explanation for the unexpectedly low ARC values obtained in some cases of autoimmune haemolytic anaemia is discussed.

Anemia, Hemolytic, Autoimmune↗
PubMed1986

Immune haemolysis in a renal transplant recipient due to antibodies with anti-c specificity.

A 55-year-old man received a cadaver kidney from a donor whose serum contained red cell antibodies with anti-c specificity. Atypical antibodies were shown to be absent from the recipient's red cells and serum at the time of transplant. Blood was not transfused during surgery. Two weeks after the transplant, the recipient developed a positive direct antiglobulin test due to antibodies with anti-c specificity. Immune haemolysis was diagnosed in the patient 3 weeks after transplant. The possible mechanisms involved in antibody formation in the recipient are discussed.

Antibody Specificity↗
PubMed1986

Reduced survival of isotope-labelled Rh(D)-negative donor red cells in a patient with anti-LWab.

The serum of an 85-year-old Caucasian male with no history of blood transfusion contained an IgG3 antibody with anti-LWab specificity. The antibody failed to react with dithiothreitol-treated red cells, and there was a marked reduction in titre of the antibody with pronase-treated cells, findings consistent with an antibody having this specificity. High association values were obtained in a mononuclear phagocyte assay when LW-positive red cells, sensitised in vitro with the patient's serum antibody, were incubated with peripheral blood monocytes from the patient. In vivo red cell survival studies demonstrated that 99mTc-labelled rhesus-negative (rr), LW-positive red cells had 53% survival at 1 h. The IgG subclass of the antibody, mononuclear phagocyte assay results and in vivo survival studies predicted a significant reduction in the posttransfusion survival of therapeutic volumes of rhesus-negative (rr), LW-positive red cells.

Aged↗
PubMed1986

Phosphorus magnetic resonance spectroscopy studies of the role of mitochondria in the disease process.

The incisive detection of bioenergetic insufficiency in an organ of known workload by P MRS is noninvasive and nondestructive, and in some cases the portion of the organ involved can be determined, particularly if both PCr and ATP are depleted. The fractional loss of ATP and hence the relative volumes of viable and "metabolically dead" tissue are thereby evaluated. In addition, the value of P MRS in following a therapy complements its value in diagnosis as this has been demonstrated in cases followed over 6 months to three years. The fact that deficiencies of the enzymes and substrates of oxidative metabolism can be detected by P MRS affords a global overview of energy metabolism that can be a key to rapid diagnosis. The distinction of the enzyme and/or substrate deficiency, while not directly indicated by steady state P MRS, can be identified by use of the "Crossover Theorem" and its impact upon blood and tissue levels of substrates (including oxygen). In the case of neonatal systemic hypoxia, there is no doubt about which of the equations applies, and similarly in metabolic disease, a glutaric acid urea is a direct consequence of the crossover response of metabolism and signifies that an enzyme deficiency may be involved. Furthermore, the clinical danger of a high Pi/PCr value is clarified by our observations, both from the animal models and from the theory, the high clues; i.e. 2 and over, suggest work stresses near the capability of oxidative metabolism and imminent failure of the negative feedback afforded by metabolic regulation, particularly ADP control of oxidative metabolism. This control is lost because of the fall of phosphocreatine to the point where creatine kinase is no longer in equilibrium, leading to the loss of ATP and its conversion to large amounts of ADP and its breakdown products. ATP then stimulates glycolysis and results in a massive lactic acidosis. At the same time, the low thermodynamic capability of glycolytic metabolism is unable to prevent irreversible ion disequilibration, water movements, edema, and eventually rupture of the cell membrane. The pathway of resynthesis of ATP is then tortuous, particularly as AMP is deaminated and adenosine is converted eventually to hypoxanthine. Thus, NMR reports that metabolic control is operating in the region where homeostasis of biochemical parameters is feasible. It further reports regions where the metabolic control is susceptible to failure and most aggressive clinical care is required.

Adenosine Triphosphate↗
PubMed1986

Single-reagent polarisation fluoroimmunoassay for the cocaine metabolite, benzoylecgonine, in urine.

A polarisation fluoroimmunoassay is described for the detection in urine of benzoylecgonine, the major metabolite of cocaine. The method uses a single reagent comprising sheep anti-benzoylecgonine serum pre-mixed with a fluorescein-labelled benzoylecgonine derivative as tracer. Under the assay conditions the antiserum has equal cross-reactivity with cocaine and the metabolite. The test is performed by the addition of 10 microL of urine to an aliquot of the single reagent, incubation for a few minutes and measurement of fluorescence polarisation. The assay has a positive/negative cut-off level of 1 mg/L benzoylecgonine and results compare favourably with the EMIT-d.a.u.TM (Syva) system.

Antibody Specificity↗
PubMed1986

Comparison of surgical and anesthetic complications in neurosurgical patients experiencing venous air embolism in the sitting position.

Because venous air embolism (VAE) has been considered to be a major deterrent to use of the sitting position, records of 255 patients undergoing neurosurgery in the sitting position from 1975 to 1982 were reviewed to determine the nature of morbidity and mortality in relation to the surgical procedure as well as to the occurrence of VAE. Complications were classified as surgical or anesthetic during joint review by a neurosurgeon and two neuroanesthesiologists. Outcome was classified on the basis of postoperative hospital course and discharge examination. The incidence of VAE was 30%. Although there was a variety of perioperative complications in patients with and without VAE, most of the complications were related to the operative procedure, not the sitting position or VAE. The episodes of VAE did not seem to be significant factors in the perioperative morbidity and mortality in our series of patients operated upon in the sitting position. Two case reports are discussed in detail.

Aged↗
PubMed1986

Direct homogeneous phosphoroimmunoassay for carbamazepine in serum.

In this "phosphoroimmunoassay," a phosphorescent label is used: erythrosin (tetraiodofluorescein). Its long-lived phosphorescence was detected after pulsed excitation in a time-resolved luminescence spectrometer. To achieve convenient open-atmosphere phosphorimetry in liquid solution at room temperature, we used sodium sulfite as an "in situ" chemical deoxygenator, to eliminate oxygen quenching of the excited triplet state. Time-resolved detection allows for complete rejection of short-lived background signals, including those from fluorescent or light-scattering components of biological fluids that can interfere in fluoroimmunoassays. We chose the antiepileptic drug carbamazepine (CBZ) and its active metabolite CBZ-10, 11-epoxide (CBZE) to demonstrate the development and validation of nonseparation assays based on quenching the phosphorescence of erythrosin-labeled drug upon binding to antibody. These two compounds cross reacted equally with the antiserum used; hence, we measured the activity of both in patients' sera. Alternatively, simple pre-treatment of the sample with acid destroys CBZE immunoreactivity and enables specific assay of CBZ.

Carbamazepine↗
PubMed1986

Effects of flavonoids on the metabolism of xenobiotics.

Flavonoids represent a large class of naturally occurring plant constituents that are consumed in substantial amounts by experimental animals and by human beings. The ability of flavonoids to activate or inhibit the principal enzyme system involved in the metabolism of lipophilic xenobiotics, including drugs, carcinogens, insecticides and other environmental pollutants, or to induce the synthesis of this enzyme system may have significant pharmacological and toxicological importance. The significant body of literature which illustrates that flavonoids can modulate the tumorigenic activity of polycyclic hydrocarbons and other chemical carcinogens has been reviewed recently (Slaga, Di Giovanni 1984; Wiebel 1980), but further elucidation of mechanisms of action are needed. Possible effects of flavonoids on the metabolism of lipophilic normal body constituents such as steroids and bile acids should be considered, and additional research is needed to determine the extent to which dietary flavonoids can influence the in vivo metabolism of xenobiotics.

Animals↗
PubMed1985

A sensitive and specific assay for plasminogen activators.

A simple, sensitive and specific assay for plasminogen activators is described. The assay utilizes fluorescein-labeled fibrinogen or fibrin at low concentrations, and enables simultaneous evaluation of the plasminogen and fibrin dependence of the reaction, that is, discrimination of tissue-type and urokinase-type plasminogen activators, and non-specific proteolysis. Addition of antisera verify identification of the activator species. The assay reagent contains plasminogen and fluorescein-labeled fibrinogen, to which is added the specimen and then then thrombin, either at the initiation or the termination of the reaction. Supernatant fluorescence is proportional to plasminogen activator concentration. With a four-hour incubation, 1 milliunit (14 pg) of tissue (melanoma) plasminogen activator (TPA) or 2 milliunit (36 pg) of urokinase (UK) may be detected.

Animals↗
PubMed1985

Aspiration during induction of anaesthesia in patients with colon interposition.

The risk of aspiration during induction of anaesthesia in patients with oesophageal disease is not well defined, and controversy exists with respect to patients who have undergone pharyngeal-gastric colon interposition. Excellent gastrooesophageal competence has been documented in many of these patients, and propulsive peristalsis has been demonstrated in interposed colonic segments, suggesting that aspiration risk is low. This report, however, describes recent anaesthetic experiences in two patients with colon interpositions and shows that these patients may have markedly redundant interposed segments that retain food or other particulate residue and, thus, present a significant risk of particulate aspiration. Awake intubation may be the best approach to avoid aspiration in these patients.

Adult↗
PubMed1985

Two-dimensional polyacrylamide gel analysis of changes in protein phosphorylation during maturation of Xenopus oocytes.

A three- to five-fold increase in non-cAMP-dependent protein phosphorylation has previously been found to occur in progesterone-treated oocytes shortly before germinal vesicle breakdown (GVBD) or immediately following maturation-promoting factor (MPF) injection. Analysis of phosphoprotein from 32Pi-labeled oocytes by both equilibrium and nonequilibrium two-dimensional gel electrophoresis revealed a large number of qualitative changes in phosphoproteins at GVBD, including both phosphorylation and dephosphorylation events. Time-course studies demonstrated that some of the new phosphoproteins appeared as early as 0.36 GVBD50, and all changes were stable at least through GVBD. The pattern of new phosphoproteins at GVBD was similar in oocytes microinjected with a partially purified preparation of MPF. A number of the new phosphoproteins were heat stable, which may facilitate their purification and characterization. These results support the hypothesis that key regulatory events during oocyte maturation are controlled by protein phosphorylation.

Animals↗
PubMed1985

Some properties of the action potentials conducted in the spines of the sea urchin Diadema antillarum.

Brief (2-5 msec) electrical pulses applied to the primary spines of the sea urchin Diadema antillarum elicit graded action potentials (ap's). These ap's can be attributed to the electrical activity of a set of 14-21 bundles of neurites, each comprising 1000 processes near the spine base and tapering towards the spine tip. The shape of the ap's varies from a simple diphasic deflection to a complex waveform with 6 or more components. Peak-to-peak amplitude is less than 1mV. The ap's are conducted at a uniform speed of ca. 27 cm/sec. The ap's are not affected by tetrodotoxin (1 microgram/ml) and continue to be produced in Na-free artificial sea water (ASW). The amplitude of the ap's is greatly reduced or totally abolished in Ca-free ASW. However, some electrical activity may continue in the absence of external Ca, due to release of Ca2+ ions from the calcium carbonate crystals of the spine shaft. Replacing the Ca content of ASW by barium ions causes an irreversible blockade of the ap's. Spines equilibrated with ASW containing Sr2+ ions instead of Ca2+ produce ap's of increased amplitude (up to X 2). The ap's are blocked by La3+, Co2+, Cd2+ (2-5 mM) and by the organic Ca channel blocker Bepridil (2 mM). We conclude that the spinal ap's are due to the summation of Ca spikes produced by the activation of Ca channels which are blocked by barium and have a high affinity for, or permeability to Sr vs Ca.

Action Potentials↗
PubMed1985

Nerves in the spine of a sea urchin: a neglected division of the echinoderm nervous system.

Electrical stimulation of the primary spines (greater than 10 cm long) of the tropical sea urchin Diadema antillarum elicits graded compound action potentials that are conducted at a constant speed of approximately equal to 27 cm/sec. Ion substitution experiments suggest that these are due to the summation of calcium spikes. Structural studies have revealed the presence of up to 21 regularly disposed nerves within the spine shaft, each nerve bundle including greater than 1000 neurites in the basal region, narrowing to slender groups of processes near the spine tip. The neurites in each nerve range in diameter from less than 0.1- approximately equal to 2 micron. Most appear to be distal processes of presumed sensory perikarya situated at the level of the tissue cone surrounding the spine base, or more proximally, although some neurites may arise from perikarya near the spine tip. These nerve tracts are thought to correspond to the nerve fibers described by Hamann [(1887) Jena Z. Naturwiss. 21, 114-176] almost a century ago in spines of Centrostephanus longispinus and, thus, to represent a long-neglected region of the echinoid nervous system.

Action Potentials↗
PubMed1985

Influence of sufentanil on cerebral metabolism and circulation in the rat.

The authors examined the effects of large intravenous doses of sufentanil (5-160 micrograms/kg) on cerebral blood flow (CBF) and cerebral metabolic rate for oxygen (CMRO2) in rats. CBF and CMRO2 were measured by a modified Kety-Schmidt technique using 133Xenon washout. Progressive decreases in CBF and CMRO2 occurred in animals receiving sufentanil. The maximum decrease was 53% and 40% for CBF and CMRO2 respectively, at a dose of 80 micrograms/kg. The values for CBF and CMRO2 in this group were 105 +/- 10 ml X 100 g-1 X min-1 (mean +/- SEM) and 6.5 +/- 0.5 ml X 100 g-1 X min-1, respectively, compared with 226 +/- 28 ml X 100 g-1 X min-1 and 10.9 +/- 1 ml X 100 g-1 X min-1 in the control group, which received N2O 70% in oxygen. Larger doses of sufentanil did not cause further significant changes in CBF and CMRO2. Sharp waves appeared on the electroencephalogram (EEG) of all the animals following sufentanil injection, and some animals had EEG changes develop consistent with seizure activity. This seizure-like activity appeared to consist of a single episode of short duration in the groups receiving 5, 10, and 20 micrograms/kg sufentanil. The incidence and frequency of seizure activity increased in the groups receiving higher doses of sufentanil, although the duration of seizures was still short. The results of this study indicate that sufentanil causes a significant decrease in CBF and CMRO2 similar to that previously reported for fentanyl, and high doses of sufentanil may cause frequent seizure-like patterns appearing on EEG.

Anesthetics↗
PubMed1985

Dual-label fluoroimmunoassay for simultaneous determination of primidone and phenobarbital.

A dual-label magnetizable solid-phase fluoroimmunoassay for direct determination of serum levels of primidone and its main metabolite, phenobarbital, in a single tube was developed and optimized. Fluorescein isothiocyanate was used to label phenobarbital and a rhodamine 101 derivative (XRITC) to label primidone; these could be independently quantitated with no fluorimetric "cross-talk." The dual-label assay employs mixed immunochemical reagents but is otherwise similar in performance to conventional, single-drug, magnetizable solid-phase fluoroimmunoassays. The ability to measure simultaneously two related analytes, such as a drug and its metabolite, represents a useful extension of immunoassay. This was illustrated in the present work by assay of sera from patients on primidone therapy. Dual-label assay results correlated well with those by a conventional enzymoimmunoassay (for primidone) and by a polarization fluoroimmunoassay (for phenobarbital).

Fluorescent Antibody Technique↗
PubMed1985

Effects of fentanyl on local cerebral blood flow in the rat.

Fentanyl reduces the cortical cerebral blood flow and metabolic rate for oxygen in rats, though seizure activity occurs in some animals at high doses. However, the effects of fentanyl on blood flow and metabolism in subcortical structures have not been clearly delineated. The present study examines the effects of intravenous fentanyl (100 or 400 micrograms . kg-1) on local cerebral blood flow (1-CBF) in paralyzed, mechanically ventilated rats. Rats ventilated with 70% N2O in 30% O2 served as controls. Local CBF was measured using 14C-iodoantipyrine and autoradiography. Blood pressure, PaO2, PaCO2, pH, and temperature were comparable in all groups. The EEG showed slow wave activity in most animals given 100 micrograms . kg-1 fentanyl while seizure activity occurred in all animals given 400 micrograms . kg-1 fentanyl. With 100 micrograms . kg-1 fentanyl, CBF tended to be depressed in all cortical and subcortical areas, except the peri-aqueductal gray; and with 400 micrograms . kg-1 fentanyl, 1-CBF tended to be elevated (compared to 100 micrograms . kg-1 fentanyl) in most areas of the brain. The limbic system structures, however, were most affected by 400 micrograms . kg-1 fentanyl with statistically significant increases (compared to the 100 micrograms . kg-1 group) in 1-CBF of 86% and 67% respectively in the amygdala and septal nucleus. These results confirm that moderately high doses of fentanyl which cause slow wave activity on the EEG also depress 1-CBF in rats; moreover, doses of fentanyl that produce seizure activity produce increases in 1-CBF in most cerebral structures with greatest effects on limbic system 1-CBF.

Animals↗