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S Powell

Publications and source records attributed to S Powell.

At least 55 records · Page 3Linked to original sources
PubMed1997

Evidence for altered cell-mediated immunity in postmastectomy lymphoedema.

Patients with chronic lymphoedema are prone to develop chronic infections and various tumours in the lymphoedematous limb, suggesting that regional immune surveillance is impaired. To test the hypothesis that cutaneous cell-mediated immunity is impaired, 35 women with postmastectomy lymphoedema were investigated using dinitrochlorobenzene to test the afferent and efferent loops of the allergic contact immune response. The results support the role of lymphatics as an important component of the immune response to allergens by the demonstration of impairment of both the afferent and efferent loops of the allergic contact dermatitis reaction, and confirm that there is suppression of immune competence in a lymphoedematous limb.

Adult↗
PubMed1996

Equivalence of fast flush and square wave testing of blood pressure monitoring systems.

BACKGROUND: The accurate recording of intraarterial pressure depends upon an appropriate dynamic response of the monitoring system. Generation of a square wave (SW) at the catheter tip is the engineering and in vitro laboratory gold standard. Fast flush (FF) testing is the clinical test of choice. Results from these two test methods have been assumed equal but have not been empirically confirmed. METHODS: We studied three different 5.1 cm catheter sizes (16 G, 18 G, 20 G Becton Dickinson, Sandy, UT) attached to three different lengths of arterial pressure tubing (36 in, 91.4 cm; 72 in, 182.9 cm; 108 in, 274.3 cm). An arterial recording system was assembled in the standard fashion by attaching a catheter to arterial pressure tubing, which was attached to a transducer (TXX-R, Ohmeda, formerly Viggo-Spectramed, Oxnard, CA) whose signal was recorded by a strip chart recorder (Gould 2400, Rolling Meadows, IL). The system was attached to a pressurized saline flush. The catheter tip was inserted into one port of a pressure generator. With the other port of the pressure generator open to atmosphere, FF tests were performed by activating the flush device of the transducer. Subsequent step response signals from the FF tests were then recorded from which natural frequency (fn) and damping coefficient (zeta) were calculated. Next, square waves were generated by closing the port that was open to atmosphere and attaching a signal generator to a pressure generator. Square waves so generated were recorded as described above and natural frequency and damping coefficients calculated. These procedures were repeated after 0.05 cc of air was introduced in the transducer and repeated again in a system containing a damping device (R.O.S.E., Resonant OverShoot Eliminator, Viggo-Spectramed, Oxnard, CA). RESULTS: There was no significant difference between fn and zeta as calculated from the step response generated from the FF test versus fn and zeta as calculated from the square wave (SW) test in systems without air. However, in systems containing air, fn by FF testing was always less than fn by SW testing for all catheter sizes and extension tubing lengths (p < 0.05). Damping was also always greater by FF testing than by SW testing in systems with air for all catheter sizes and extension tubing lengths (p < 0.05). The R.O.S.E device created marked qualitative differences, although exact fn and zeta could not be quantified. CONCLUSIONS: For the characterization of dynamic response of invasive blood pressure monitoring systems, the FF test and SW test yield identical results. However, under certain conditions-air, R.O.S.E device-dynamic response as measured by FF testing was not equivalent to dynamic response as measured by the gold standard-the SW test. Specifically, small amounts of air in fluid-filled invasive blood pressure monitoring systems cause a slightly worse dynamic response as measured by FF testing versus the laboratory gold standard-the SW test.

Blood Pressure Monitors↗
PubMed1995

Selected pediatric viral infections.

Viral infections of the central nervous system in infants and children are uncommon but potentially serious illnesses. Common causes have included the enteroviruses (particularly polioviruses and coxsackieviruses), herpes viruses (type 1 and type 2 herpes simplex, varicella, and cytomegalovirus), arboviruses, rubella, mumps, measles (including subacute sclerosing panencephalitis), and human immunodeficiency virus. Several of these viruses, such as cytomegalovirus, herpes simplex, and vertically transmitted human immunodeficiency virus, may cause congenital infections. Others are acquired later in childhood. In recent years, immunization programs have significantly reduced the occurrence of some of these diseases. A brief survey of the clinical and pathological manifestations of these illnesses will be discussed along with current incidence data.

Central Nervous System Infections↗
PubMed1995

Mitochondrial deoxyribonucleic acid deletions in oocytes and reproductive aging in women.

OBJECTIVE: To determine whether oocytes from women harbor deletions in mitochondrial DNA (mtDNA) and whether deleted mtDNA is more common in oocytes from older women than oocytes from younger women. DESIGN: A polymerase chain reaction (PCR)-based strategy, which depends on deletions approximating otherwise widely separated primers to demonstrate mtDNA deletions in individual oocytes, was used. SETTING: Yale In Vitro Fertilization Clinic and Laboratory at Yale University School of Medicine. MAIN OUTCOME MEASURES: Primers flanked a region of the mitochondrial genome in which long direct repeated sequence predispose to deletions. The primers identified the 0.5-kb "common" deletion. Deleted mtDNA was represented by a 0.5-kb band when primers separated by 5 kb were used. Control reactions used primers that amplify mtDNA outside the deletion hotspot. Positive controls included brain and/or muscle from aged individuals, and negative controls included fetal tissue and DNA-free blanks. Nested primers confirmed the specificity of the deleted product. RESULTS: Unfertilized oocytes, muscle, and brain tissue contained PCR products consistent with deleted mtDNA. Fetal tissue lacked the mtDNA deletion product. Deleted mtDNA was detected in single oocytes. Oocytes from older women were more likely to contain deleted mtDNA than oocytes from younger women. CONCLUSION: Deleted mtDNA in unfertilized oocytes may serve as a marker of oocyte senescence.

Adult↗
PubMed1994

6-Methyluracil excretion in 2-methylacetoacetyl-CoA thiolase deficiency and in two children with an unexplained recurrent ketoacidaemia.

6-Methyluracil (6MU) has been identified in urine collected during acute illness in two children with beta-ketothiolase deficiency (approximately 1 mmol/L) and in two children with recurrent infection-related ketoacidaemia of unknown aetiology (levels of 6.3 and 7.1 mmol/mmol creatinine). Significant amounts of 6MU were not detected in children with fasting ketosis in whom a metabolic disorder was excluded (normal levels less than 25 mumol/mmol creatinine). We propose that the production of 6MU may be related to the accumulation of acetoacetyl-CoA and thus be a marker for disorders where this occurs.

Acetyl-CoA C-Acetyltransferase↗
PubMed1994

Metabolic disease and sudden, unexpected death in infancy.

The prevalence of metabolic disease in infants dying suddenly and unexpectedly is controversial. Most studies have centered on major pediatric institutes with appropriate facilities to study inherited metabolic disease. No studies have been reported from nonacademic centers. We have prospectively studied urine and blood organic and fatty acids from 58 consecutive infant deaths over a 1-year period in nonteaching hospital medical examiners' offices in the state of Illinois for evidence of metabolic disease. One infant was found to have medium-chain acyl-CoA dehydrogenase (MCAD) deficiency, homozygous for the common A985G mutation. One had probable non-A985G MCAD deficiency based on the identification of cis-4-decenoic acid in blood and one had ethylmalonic-adipic aciduria. Thus, we found evidence that inherited metabolic defects are related to unexpected infant death in this population. These disorders are present in a significant minority of infants who probably would have been given the diagnosis of sudden infant death syndrome if they had not undergone metabolic evaluation. We recommend that all infants who have died suddenly and unexpectedly be regarded as high-risk candidates for metabolic disease and that all such deaths be appropriately investigated as part of the routine autopsy procedure.

Acyl-CoA Dehydrogenase↗
PubMed1994

Isolation and characterization of neurokinin A receptor cDNAs from guinea-pig lung and rabbit pulmonary artery.

cDNA clones for NK-2 receptors (NK-2R) were isolated from guinea-pig lung (GPl) and rabbit pulmonary artery (Rpa) using a polymerase chain reaction based methodology. The GPl NK-2R consists of 402 amino acids and encodes a protein with a relative molecular mass of 45,097. The Rpa NK-2R consists of 384 amino acids and encodes a protein with a relative molecular mass of 43,169. The GPl and Rpa NK-2Rs share significant amino acid sequence homology amongst themselves (90.1%), as well as with human, bovine, hamster and rat NK-2 receptors. The two receptors were stably transfected into mouse erythroleukemia cells, high-speed membranes were prepared from induced cells and their pharmacological properties examined utilizing [3H]-NKA in a receptor-binding assay. [3H]NKA bound to both NK-2Rs with high affinity (KD = 2-7 nM) and saturable (Bmax = 633-9000 fmol/mg protein) manner which was inhibited by GTP analogs. Competition experiments with agonists demonstrated identical order of potency in both NK-2Rs; NKA > [Nle10]NKA(4-10) > [beta-Ala8]NKA(4-10) > > Substance P > > > Senktide. Similarly, an identical profile for both receptors was observed with selective NK-2 antagonists: SR48,968 > MEN10,376 > > R396. The rank order of antagonist affinity is consistent with that in cloned human NK-2R and the observations of NK-2 receptor pharmacology in native human, guinea pig and rabbit tissues.

Amino Acid Sequence↗
PubMed1994

Tiglylglycine excreted in urine in disorders of isoleucine metabolism and the respiratory chain measured by stable isotope dilution GC-MS.

Tiglyglycine (TG), an intermediate product of the catabolism of isoleucine, is increased in the urine of patients with beta-ketothiolase deficiency or with disorders of propionate metabolism. It is also implicated as a useful diagnostic marker in disorders of the respiratory chain. We present a method for the synthesis of TG and tiglyl[13C, 15N]glycine and the development of a stable isotope dilution mass spectrometric assay for TG. We compare data from controls with that from subjects with beta-ketothiolase deficiency and propionyl-CoA carboxylase deficiency, and with six patients with enzyme-confirmed disorders of the respiratory chain. TG was increased in the urine from all of the patient groups. The increased TG excretion did not persist in one patient with a respiratory chain defect, which suggests that, in some patients, multiple sample analysis may be necessary to identify a respiratory chain defect. This is the first urinary compound to be implicated as a potential marker of disorders of the respiratory chain.

Acetyl-CoA C-Acyltransferase↗
PubMed1994

The risk of repeating low birth weight and the role of prenatal care.

OBJECTIVE: To estimate the influence of adequacy of prenatal care and other known risk factors on the risk of repeating low birth weight (LBW) (less than 2500 g). METHODS: This was a retrospective cohort study of women having two births in Washington state during 1984-1990, as recorded using linked birth certificate records. Logistic regression was used to control for maternal age, marital status, smoking, miscarriage, inter-pregnancy interval, and prenatal care. RESULTS: Compared to the reference group of women with normal-weight first births (at least 2500 g), women with LBW first births, either preterm or small for gestational age (SGA), were significantly more likely to have an LBW second birth. The estimated relative risk of repeating LBW in general was 7.0 (95% confidence interval 4.8-10.1). Smoking during the second pregnancy was a significant effect modifier. The risk estimates were not significantly affected by any of the other variables entered into the models, including adequate prenatal care. CONCLUSIONS: Prior delivery of a preterm or SGA LBW infant was the strongest predictor of LBW delivery in a subsequent pregnancy. Adequate prenatal care during the second pregnancy did not provide statistically significant protection against the risk of repeat LBW. The tendency for women to have repeat LBW deliveries despite adequate prenatal care indicates a need for a better understanding of the underlying pathophysiology of preterm and SGA delivery.

Adult↗
PubMed1994

Heparin-induced thrombocytopenia.

Heparin-induced thrombocytopenia (HIT) is a rare complication of heparin with significant morbidity and mortality. In this study, a retrospective review of all patients referred to the platelet study lab at East Carolina University who tested positive for heparin-induced platelet aggregation was performed. From May 1988 through March 1991, 40 patients with clinically suspected HIT were referred for platelet aggregation studies. Ten patients tested positive for in-vitro platelet aggregation in the presence of heparin. The clinical characteristics of these patients are reviewed. Results show a preponderance of surgical patients with 8/10 patients having undergone a primary major surgical procedure. Six of the eight surgical patients underwent a major vascular or cardiac procedure. The mortality rate for patients with heparin-induced in-vitro platelet aggregation was 30 per cent. Major thromboembolic morbidity was substantial (80%) with 5/10 patients requiring an extremity amputation. The estimated incidence of HIT in surgical patients in this series was 0.3 per cent. HIT is an unusual complication of heparin therapy with devastating morbidity and mortality. Patients undergoing a major vascular or cardiac procedure appear to be at increased risk. Increased awareness of the syndrome and careful monitoring of platelet counts in patients at high risk may reduce the morbidity and mortality.

Aged↗
PubMed1994

Isolation and pharmacological characterization of a hamster urinary bladder neurokinin A receptor cDNA.

Functional cDNA clones for hamster neurokinin-2 receptor (NK-2R) were isolated from hamster urinary bladder using a polymerase chain reaction-based methodology. The hamster NK-2R consists of 384 amino acids with a relative molecular weight of 43,418. Hamster NK-2R shares significant amino acid sequence homology with other tachykinin receptors, particularly with rat, bovine, and human NK-2R (94.3, 84.4, and 86.5%, respectively). To examine the pharmacology of cloned hamster NK-2R, we transfected mouse erythroleukemia cells with this receptor, prepared high speed membranes, and studied the receptor properties utilizing the ligand [4,5-3H-Leu9]NKA in a receptor-binding assay. For pharmacological comparison, we also transfected the human NK-2R into mouse erythroleukemia cells. [3H]NKA bound to hamster NK-2R receptor in a protein-dependent, high affinity (Kd1 = 4.14 +/- 0.31 nM), saturable (Bmax1 = 679 +/- 26 fmol/mg of protein), and highly specific manner (89 +/- 2%). A smaller population (10% density) of lower affinity receptors (Kd2 = 150 +/- 92 nM), was also observed in competition experiments. [3H]NKA bound to the human receptor with significantly higher affinity and overall greater receptor density (Kd1 = 0.37 +/- 0.11 nM, Bmax1 = 234 +/- 175 fmol/mg of protein; Kd2 = 9.0 +/- 2 nM, Bmax2 = 1989 + 990 fmol/mg of protein). [3H]NKA binding to both hamster and human receptors was enhanced greatly by divalent cations, whereas GTP analogs weakly inhibited binding to hamster receptor, but potently inhibited binding to the human receptor. Competition experiments with agonists demonstrated binding to high and low affinity states of NK-2 receptors, with identical order of potency in hamster or human NK-2R; NKA > [Nle10]NKA(4-10) > [beta-Ala8]NKA(4-10) >> substance P >>> Senktide. However, remarkable differences were observed in studies with selective NK-2 antagonists (hamster, SR48,968 > L659,877 > R396 >> MEN10,376 versus human, SR48,968 > MEN10,376 > L659,877 > R396). The rank order of antagonist affinity is consistent with the observations of NK-2 receptor pharmacology in the native tissues.

Amino Acid Sequence↗
PubMed1993

Ataxia telangiectasia: an investigation of the repair defect in the cell line AT5BIVA by plasmid reconstitution.

The ataxia telangiectasia cell line, AT5BIVA, exhibited low repair fidelity measured by the reconstitution of transfected linear plasmid. This assay involves transfecting a linear plasmid containing two selectable marker genes: one gene (neo) is undamaged and marks transfection and the other gene (gpt) is cleaved to test functional repair. The proportion of transfected cells which have a functionally intact gpt gene gives a measure of repair fidelity. Southern analysis of individual transfected clones showed that integrated plasmids in AT5BIVA had a high frequency of sequence rearrangement. Blunt or staggered-ended termini of a linear plasmid did not determine the type of misrepair. A variety of sizes of deletions and sequence insertions were found at and around the cleavage site. Loss of intact sequence occurred similarly following transfection by linear or circular plasmid (misrepair or rearrangement error). This suggests that the action of excess exonuclease activity upon, or lack of protection of, exposed DNA termini is not the sole mechanism of misrepair. Erroneous rearrangement of circular plasmid could involve any location along the plasmid. Rearrangement of transfected circular plasmid occurred in multiple copies of the same abnormal size, suggesting that error-prone recombination rather than degradation of presumed nicked circular plasmid was the underlying mechanism. It is hypothesized that misrepair in ataxia-telangiectasia arises by error-prone recombination.

Ataxia Telangiectasia↗
PubMed1993

Pharmacological characterization of cloned human NK-2 (neurokinin A) receptor expressed in a baculovirus/Sf-21 insect cell system.

Using the novel ligand [4,5-3H-Leu9]neurokinin A ([4,5-3H-Leu9] NKA) in a receptor binding assay, we characterized the pharmacology of a cloned neurokinin NK-2 receptor from human lung (hNK-2R), expressed in baculovirus-infected Sf-21 insect cells. Functional hNK-2R cDNA clones were isolated from human lung using a polymerase chain reaction-based methodology. hNK-2R was cloned into pAcYM1, a vector designed to couple expression to the polyhedrin promoter, and the recombinant baculovirus was isolated and used to infect Sf-21 insect cells. hNK-2R expression levels were monitored by Northern blots and 125-I-NKA binding assays. Isolates demonstrating the highest specific binding of 125-I-NKA were grown and membrane preparations from high-speed centrifugations were prepared from both hNK-2R-expressing and wild-type virus-infected cells. [3H]NKA bound in a protein-dependent, saturable (Bmax = 820 +/- 167 fmol/mg of protein), and highly specific (88 +/- 5%) manner to hNK-2R, but not to membranes from cells infected with wild-type virus (14 +/- 8%, 7 +/- 10 fmol/mg of protein). [3H]NKA binding was rapid (k1 = 0.085 nM-1 x min-1) and reversible (t1/2 = 4-5 min). Equilibrium binding experiments demonstrated binding to a mixture of receptors in high and low affinity states (Kd1 = 2.28 +/- 0.26 nM and Kd2 = 266 +/- 91 nM). Binding to hNK-2R was greatly enhanced (400%-600%) by Ca2+ and Mg2+ (EC50 values of 30 microM and 140 microM, respectively), whereas guanosine-5'-O-(3'-thio)triphosphate and guanosine-5'-(beta, gamma-imido)diphosphate were inhibitory. Competition experiments with agonists also demonstrated binding to high and low affinity states, with the following order of potency: NKA > [Nle10]NKA(4-10) > [beta-Ala8]NKA(4-10) >> substance P; Senktide and the NK-1 antagonist CP96,345 (10 microM) did not inhibit binding. Inhibition of binding by selective NK-2 antagonists was consistent with a single affinity state and demonstrated the following order of affinity: SR48,968 >> MEN10,376 > L659,877 > R396. These data suggest that infection of Sf-21 cells with baculovirus expression vector harboring the cDNA of hNK-2R resulted in expression of high affinity, G protein-coupled hNK-2R, with pharmacological selectivity compatible with the NK-2A receptor subtype.

Animals↗
PubMed1992

Chemodectoma of the head and neck: results of treatment in 84 patients.

Eighty-four patients with chemodectoma of the head and neck presented to the Royal Marsden Hospital between 1949 and 1985. For tumors arising at the skull base (glomus jugulare and glomus tympanicum) 46 were treated with radiotherapy alone resulting in an actuarial local control rate of 73% at 25 years; 13 were treated with surgery plus radiotherapy with no recurrences during a median follow-up of 9 years; 4 had surgery alone but all recurred by 7 years. For tumors of the soft tissues of the neck (carotid body and glomus vagale) 13 were treated with surgery alone with an actuarial control rate of 54% at 15 years; 4 were treated with radiotherapy which resulted in local control at 1, 2, 8 and 11 years; and one patient who received both surgery and radiotherapy remained controlled at 1 year. Although comparison between radiotherapy and surgery in terms of tumor control is not simple, the case is argued for more frequent use of radiotherapy at all sites. This case is strengthened by minimal morbidity from radiotherapy in doses which appear effective: in the range of 45-50 Gy in 25 daily fractions over 5 weeks.

Adult↗
PubMed1992

Antibody to hepatitis C virus in selected groups of a Canadian urban population.

In an anonymous survey, 433 sera from Canadian individuals of selected categories were tested for the presence of antibody to hepatitis C virus (HCV) using a recombinant antigen-based immunoassay. About 50% of intravenous drug abusers (IVDA), 10% of transfusion recipients and an overall average of 7.9% of male homosexuals were reactive for antibody to HCV. Individuals with jaundice and negative hepatitis B virus (HBV) serology were not reactive for antibody to HCV compared with 26.7% of those with positive HBV serology. Similarly 58% of male Federal prisoners with positive HBV serology were also HCV-antibody reactive compared with 15% of those with negative HBV serology. A prevalence of 1.2% was recorded for individuals not in any of the above groups. Of 433 sera, 92 were reactive and the discrimination in absorbance values between reactive and not reactive samples was good except for 13 sera, eight of which gave values considerably higher than the average negative value and five which were just above the positive threshold.

Alberta↗