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Biomedical subjects

D Thomas

Publications and source records attributed to D Thomas.

At least 361 records · Page 20Linked to original sources

Los Angeles study of residential magnetic fields and childhood brain tumors.

A measurement study of residential magnetic fields and brain tumors in children that was added onto an ongoing case-control interview study in Los Angeles County, California, include 298 children under age 20 years with a primary brain tumor diagnosed from 1984 to 1991 and 298 control children identified by random digit dialing. Magnetic fields were determined for all Los Angeles homes where these 596 children lived from conception to diagnosis (1,131 homes) by mapping and coding the wiring configurations outside the home and by taking a series of exterior spot and profile measurements. In addition, for a subset of subjects (35%; 211 homes) 24-hour measurements were taken in the child's room and one other room. Although measured fields are consistently highest in the highest of the five wire code categories, fields in homes in this category are much lower in Los Angeles than in Denver, where the code originated. Brain tumor risk appears not to relate to measured fields inside (p for trend for child's room = 0.98) or outside (p for trend for front wall = 0.82) the home. An apparent increase in risk among children living at diagnosis in homes with underground wiring appears to be an artifact introduced by using current controls for historical cases because this apparent excess risk disappeared in an analysis restricted to the later years of the study when cases and controls were accrued concurrently. Our study does not show an overall association of pediatric brain tumors with measured fields, with "very high" wiring configurations, or with any of several other potential sources of exposure, such as use of various electrical appliances, but the prevalence of high fields (> 2 mG) and very high fields (> 3 mG) in Los Angeles homes was too low to detect a moderate effect of the magnitude reported in other studies.

Adolescent↗

Application of combined mass spectrometry and partial amino acid sequence to the identification of gel-separated proteins.

The combined use of peptide mass information with amino acid sequence information derived by chemical sequencing or mass spectrometry (MS)-based approaches provides a powerful means of protein identification. We have used a two-part strategy to identify proteins from nerve growth factor (NGF)-stimulated rat adrenal pheochromocytoma cell line PC-12 cell lysates that associate with the adaptor protein Shc (Shc homologous and collagen protein). Initial experiments with metabolically radiolabeled cell extracts separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) revealed a number of proteins that coimmunoprecipitated with anti-Shc antibody compared with control (unstimulated) cell extracts. The experiment was scaled up and cell lysate from NGF-stimulated PC-12 cells was applied to a glutathione-S-transferase (GST)-Shc affinity column, eluted, separated by SDS-PAGE and blotted to Immobilon-CD. The blotted proteins were proteolytically digested in situ, and the masses obtained from the extracted peptides were used in a peptide-mass search program in an attempt to identify the protein. Even if a strong candidate was found using this search, an additional step was performed to confirm the identification. The mixtures were fractionated by reversed-phase high-performance liquid chromatography (RP-HPLC) and subjected to chemical sequencing to obtain (partial) sequence information, or post-source decay (PSD-) matrix-assisted laser-desorption ionization (MALDI)-MS to obtain sequence-specific fragment ions. This data was used in a peptide-sequence tag search to confirm the identity of the proteins. This combined approach allowed identification of four proteins of M(r) 43,000 to 200,000. In one case the identified protein clearly did not correspond to the radiolabeled band, but to a protein contaminant from the column. The advantages and pitfalls of the approach are discussed.

Actinin↗

Captopril does not acutely modulate plasma endothelin-1 concentration in human congestive heart failure.

Congestive heart failure (CHF) is a syndrome characterized by increased levels of angiotensin II (Ang II) and endothelin-1 (ET-1). In vitro, Ang II stimulates ET-1 release. The purpose of the study was to assess the effect of a single dose of an angiotensin-converting enzyme inhibitor (ACEI) captopril versus placebo on plasma endothelin concentration in human congestive heart failure. Captopril (25 mg, given orally) was compared with placebo in a group of 20 patients with systolic dysfunction in a double-blind randomized study. Plasma irET concentration was significantly increased in CHF patients compared with normal subjects (5.59 pg/ml +/- 0.35 vs. 3.58 pg/ml +/- 0.99, p < 0.0002). Despite the decrease in systolic blood pressure and the increase in plasma renin activity, suggesting a significant blockade of the renin-angiotensin system, no difference in plasma irET-1 was observed between captopril and placebo. Our results suggest that captopril does not acutely influence irET-1 plasma concentration in human CHF. These data do not support the hypothesis that the acute vasodilator effect of a single dose of 25 mg of captopril given daily orally involves modulation of the increased plasma concentration of endothelin observed in CHF.

Adult↗

The validation of a 7-locus multiplex STR test for use in forensic casework. (II), Artefacts, casework studies and success rates.

PCR-based DNA typing of biological evidence is now widely used in forensic analyses due to the obvious advantages of enhanced sensitivity, the ability to distinguish discrete alleles and efficacy with degraded samples. A multiplex short tandem repeat (STR) system has been previously developed which successfully co-amplifies six STR loci HUMTH01, D21S11, D18S51, D8S1179, HUMVWF31/A and HUMFIBRA (FGA) in conjunction with the X-Y homologous gene Amelogenin. This is known as the second generation multiplex system (SGM). Detection of the PCR products is undertaken on ABD 373A or 377 automated sequencers using denaturing polyacrylamide gels coupled with fluorescent-based technology. We have evaluated this system for routine forensic use and demonstrated that the technique is robust and reproducible under conditions consistent with those encountered in a forensic environment. A total of 132 stains from simulated and actual casework were analysed, together with relevant control areas and reference samples. The success rate was high with 76% of stains giving full profiles; we were also able to successfully detect and interpret mixtures. No mistyping was observed. A detailed examination of each of these profiles has assisted in the development of guidelines for casework interpretation. Although artefacts, stutter peaks and undenatured DNA were occasionally observed, these did not interfere with the accuracy of interpretation. In addition 38 samples, previously examined using the quadruplex system, were analysed with the SGM to enable a direct comparison to be made between the systems. The performance of the system with poor quality samples demonstrated its use as a rapid and powerful technique for individual identification.

Adult↗

Ultrastructural study of acquisition and retention of potato leafroll luteovirus in the alimentary canal of its aphid vector, Myzus persicae Sulz.

The chronology of PLRV acquisition and retention by Myzus persicae was investigated using electron microscopy. Examination demonstrated a rapid translocation of the virus through the intestine into the haemocoel. Indeed, viral particles could be observed in the intestinal epithelial cells, then in the haemocoel, 4 and 8 h, respectively, after their arrival in the lumen of the alimentary canal. However, the virus accumulated in the intestinal epithelial cells. In these cells, the first viral particles were seen enclosed in isometric or tubular isolated vesicles; a few hours later, they were present in tubular aggregated vesicles and also in lysosomes or multivesicular bodies. After a 40 h acquisition period, all studied intestinal epithelial cells exhibited high numbers of viral particles which were consistently distributed throughout these cell structures. When aphids were removed from viral source, viral particles were detected in intestinal lumen for a further three days and in intestinal epithelial cells for a total of eight days. Virus content in these cells began to decrease from the second day. Areas with tubular aggregated vesicles were maintained for seven days following aphid removal from viral source, but progressively became smaller and fewer. The accumulation and the persistence of PLRV in the intestine are discussed.

Animals↗

Tat-mediated protein delivery can facilitate MHC class I presentation of antigens.

We have previously shown that the tat protein of HIV-1 can be used as a carrier to promote the intracellular delivery of heterologous proteins. Here we have tested if the tat-delivery technology can be used to direct MHC class I presentation of native protein, using ovalbumin (OVA) as a model system. We show that a tat-ovalbumin conjugate (tatOVA) can be delivered into cells and that subsequent processing and presentation occurs, resulting in effective and specific killing of these target cells by an OVA specific cytotoxic T-lymphocyte (CTL) line. Comparison with the E.G7 line that expresses the OVA gene indicates that tat-mediated delivery is as efficient as endogenous expression in this system. Tat-mediated antigenic protein delivery may be useful both as a research technique and, potentially, as a therapeutic or prophylactic vaccine.

Amino Acid Sequence↗

Hemoglobin, horseradish peroxidase, and heme-bovine serum albumin as biocatalyst for the oxidation of dibenzothiophene.

Hemoglobin, horseradish peroxidase, and bovine serum albumin incubated heme-catalyzed the oxidation of dibenzothiophene into sulfoxide in the presence of hydrogen peroxide. This reaction was carried out in an aqueous buffer containing 25% of water-miscible organic solvents. The observation of this transient state of hemoproteins during sulfoxidation showed heme degradation. None of the compounds usually involved in a classical peroxidative activity mechanism were detected. Furthermore, this activity did not appear to be based on a Fenton-type reaction. The highest degrees of sulfoxidation were obtained with hemoglobin. Under the best conditions of reaction, 100% of dibenzothiophene were converted into dibenzothiophene sulfoxide by hemoglobin. Heat-denatured hemoproteins did keep their sulfoxidation activity. With hemoglobin, a kcat of 0.22 min-1 was determined. Nearly the same values were obtained with heat-denatured hemoglobin and bovine serum albumin-adsorbed heme. With horseradish peroxidase, only 4% of conversion was attained. This percentage could be slightly increased by using a less pure peroxidase or heat-denatured peroxidase.

Catalysis↗

Haemodynamic and ventilatory changes during laparoscopic cholecystectomy in elderly ASA III patients.

PURPOSE: To evaluate the haemodynamic and respiratory changes during laparoscopic cholecystectomy in elderly ASA III patients. METHODS: This clinical descriptive study included 16 patients aged > 75 yr. Anaesthesia was induced with fentanyl and etomidate and maintained with N2O in O2 (50%), fentanyl and isoflurane as needed. Inspired minute volume was kept constant during anaesthesia. Cardiovascular monitoring included a radial artery catheter and a pulmonary artery catheter for measurement of CO, RVEF and SvO2, and calculation of right ventricular end diastolic volume indexed (RVEDVI). Haemodynamic variables, arterial and venous blood gas analyses were collected before and 10 min after anaesthetic induction, 15, 30 and 60 min after insufflation (IAP = 12 mmHg) followed by a 10 degrees head-up tilt, and after exsufflation. RESULTS: The mean age was 81 +/- 4 yr. The main cardiovascular depression was recorded after anaesthetic induction. Peritoneal insufflation resulted in improvement of cardiovascular function with increases in cardiac index (+19%), heart rate (+21%), MAP (+ 19%) and SvO2 (+8%), (P < 0.05) which may be the result of a sympathetic stimulation. No change in preload (RVEDVI) and SVR was recorded. Cardiac index was unchanged during pneumoperitoneum. Laparoscopy was associated with an increase in PaCO2 15 min after CO2 insufflation (from 33.9 to 38.3 mmHg, P < 0.05) and a further elevation after 60 min (44.4 mmHg) without any sign of extra peritoneal diffusion. There was no change in the intra-pulmonary shunt and the Pa-ETCO2 gradient remained stable (mean 7.2 mmHg). CONCLUSION: We conclude that gradual abdominal insufflation to 12 mmHg followed by a limited 10 degrees head-up tilt is associated with cardiovascular stability in elderly ASA III patients.

Aged↗

Effect of pronuclear DNA microinjection on the development of porcine ova in utero.

The objective of this study was to assess the effect of various aspects of pronuclear DNA microinjection on the early development of porcine ova in utero. Estrus was synchronized and superovulation was achieved in sexually mature gilts by the administration of allyl trenbolone, PMSG and hCG. Donor gilts were bred at 12 and 24 h after the onset of estrus. Ova were recovered between 60 and 62 h after the administration of hCG. One-cell ova that exhibited pronuclei after centrifugation were randomly allocated in equal numbers from each donor across one of two pairs of treatments: micro-DNA (ova were injected with two gene constructs that code for the human complement regulatory proteins decay accelerating factor and membrane cofactor protein) and control (ova were centrifuged only) or micro-buffer (ova were injected with buffer only) and pierced (a pipette was inserted into one pronucleus). Ova were transferred by treatment pairs to recipients. Treatments were segregated by oviduct. Ova were recovered after 120 h in utero, fixed and stained with 1% orcein. The proportion of ova that possessed > or = 80 nuclei, the mean number of nuclei present and proportion of ova that formed blastocysts were all significantly (P<0.05) greater for control and pierced ova than for micro-DNA and micro-buffer ova. No difference in these parameters was observed between micro-DNA and micro-buffer ova. These results demonstrate that pronuclear microinjection of a buffer alone can adversely affect the early development of porcine ova in utero.

Journal Article↗

Quality of health care, survival and health outcomes in Ghana.

This paper analyzes the effect of quality and accessibility of health services and other public infrastructure on the health of children in Ghana. We focus on child survival, child height and weight using data from the Ghana Living Standards Survey. The results suggest an important role for public health policy in eliminating the rural-urban disparities in health status and particularly in improving the health status of rural children and reducing their mortality rates. Increased availability of birth services and other related child programs, as well as Improved water and sanitation infrastructure would have an immediate payoff.

Anthropometry↗

Is delayed surgery really better for congenital diaphragmatic hernia?: a prospective randomized clinical trial.

Delayed surgery has become widely accepted in the management of congenital diaphragmatic hernia after comparing outcomes only with historical retrospective controls. It was the aim of this study to compare early and delayed hernia repair in a randomized prospective clinical trial. Fifty-four infants were randomized to receive either early repair (within 4 hours of admission) or delayed repair (more than 24 hours after birth). The survival rate was higher for the delayed group (57% v 46%), but the difference was not significant (difference: -11; 95% confidence limits: -37.5, 15.5). There were no significant differences between the two groups with respect to length of hospital stay, ventilator dependency, or survival time. Recorded preoperative risk factors were similar for the two groups. Eight infants in the delayed repair group died without having undergone surgery. The optimum time for surgery still needs clarification.

Blood Gas Analysis↗

Depletion of glutathione from brain cells in hyponatremia.

In response to hyponatremia, brain cells extrude electrolytes and organic osmolytes, thereby minimizing brain edema. We demonstrate that rat brain is depleted of the antioxidant glutathione in response to hyponatremia and that osmotically-induced loss of glutathione makes neuronal cells more susceptible to oxidative injury. Total glutathione content of brain tissue decreased from 6.80 +/- 0.14 mumol/g dry wt in normonatremic controls to 5.00 +/- 0.31 mumol/g dry wt after 72 hours of hyponatremia. Following slow correction of hyponatremia, brain glutathione content returned to control values (6.77 +/- 0.34 mumol/g dry wt). Brain content of taurine, a beta-amino acid with antioxidant properties, similarly decreased in hyponatremia (29.6 +/- 0.9 to 17.1 +/- 1.2 mumol/g dry wt), then increased with slow correction (24.8 +/- 1.3 mumol/g dry wt). Although taurine served as an osmolyte in rat heart, liver and brain, osmotically-induced changes in glutathione content were found only in brain. We also studied osmotically-induced changes in glutathione and taurine content in C6 glioma and SK-N-SH neuroblastoma cells. In both cell lines, adaptive decreases in glutathione and taurine content were found in response to lowering medium sodium concentration from 140 mM to 100 mM. The cell content of these solutes increased after returning to media containing 140 mM sodium. Following exposure of both cell lines to hypoosmolar media, there was no increase in media content of glutathione. This suggest that osmotic depletion of glutathione is not due to cellular efflux of intact glutathione. We questioned if osmotic depletion of glutathione and taurine renders brain cells more susceptible to oxidative stress. Incubation of SK-N-SH cells with 1.0 mM H2O2 for four hours induced greater cytolytic injury in cells adapted to hypoosmolar media than in isoosmolar controls. Hypoosmolar C6 glioma cells were not significantly more sensitive to cytolytic injury from H2O2 than were cells grown in isosmolar media. We conclude that hypoosmolality induces glutathione depletion in rat brain in vivo and in cultured brain cells in vitro. Osmotic depletion of this antioxidant renders SK-N-SH neuronal cells more susceptible to oxidative injury.

Animals↗

Effects of differing pedalling speeds on the power-duration relationship of high intensity cycle ergometry.

The aim of this experiment was to investigate the effects of differing pedalling speeds on the power-duration relationship during high intensity cycle ergometry with pedal cadences of 50 (low), 90 (intermediate) and 110 (high) r.min-1. This hyperbolic power-duration relationship can be described as: (P - phiPA).t = W', where P = power output, t = time to exhaustion, and phiPA and W' are constants. Eight volunteer male subjects, aged 24 +/- 2.6 yr, with no competitive cycling training took part in this study and each undertook thirteen tests on a Lode BV Excalibur Sport V1.52 cycle ergometer over an eight week period. The first exercise bout was a 30 W.min-1 incremental cycle at 50 r.min-1 to volitional fatigue. This allowed the identification of a range of power outputs that would be used to construct and examine the power-duration relationships for each subject at 50, 90 and 110 r.min-1. At both 50 and 90 r.min-1, power outputs of 30 W above and below and 60 W above the highest work rate, as well as the maximum work rate achieved during the incremental exercise test were chosen, while at 110 r.min-1, the power outputs chosen were 25 W above and below as well as 50 W above the highest work rate achieved during the incremental exercise test and also the maximum work rate achieved during the incremental exercise test were chosen. These four work rates for each pedalling frequency were chosen because they would have exercise times to exhaustion in the range of 1-10 minutes. Each exercise bout was preceded by four minutes of unloaded cycling and then the work rate was adjusted quickly to the desired load setting by the previously programmed computerised ergometer. The results of this work indicate that for the group of subjects studied, pedalling a cycle ergometer at 50 r.min-1 allows subjects to pedal for a significantly greater time than when pedalling at either 90 or 110 r.min-1. phiPA at 50 r.min-1 was significantly greater than when pedalling at either 90 (F(1,21) = 7.47, p < 0.01) or 110 r.min-1 (F(1,21) = 10.83, p < 0.0005). There was no significant (p > 0.22) difference between phiPA at 90 and 110 r.min-1, F(1,21) = 1.36. W' however, was not significantly different when the data for 50 r.min-1, 90 r.min-1 and 110 r.min-1 were compared (F50 r.min-1 (1,21) = 0.95; p > 0.41; F90 r.min-1(1,21) = 0.79, p > 0.53; F110 r.min-1 (1,21) = 0.78, p > 0.53). Our hypothesis, that endurance performance was reduced when recreational cyclists pedal at a high cadence when compared to a low cadence was correct. Maximum sustainable power output during cycle ergometry was higher at 50 r.min-1 than at either 90 or 110 r.min-1. At the intermediate cadence endurance was better than at the high but worse than at the low cadence. In conclusion, during endurance cycling, recreaional cyclists should pedal at lower rather than higher cadences.

Adult↗

A comparison of direct, indirect, and fiberoptic laryngoscopy to evaluate vocal cord paralysis after thyroid surgery.

After thyroidectomy, the anesthesiologist usually performs a laryngoscopy to detect laryngeal edema and nerve palsies. The goal of this study was to compare three different methods of laryngeal examination after tracheal extubation of the patients. For that purpose, between 1990 and 1995, a prospective series of 1608 patients operated for thyroidectomy has been studied. The series was divided into 4 groups. In group I (n = 200), four anesthesiologists have evaluated the efficiency of the immediate postextubation direct laryngoscopy. In group II (n = 100), one anesthesiologist has compared the direct, indirect, and flexible laryngoscopies in every patient in a fixed and timed fashion. In group III (n = 100), the four examiners have evaluated the flexible laryngoscopy at a different timing so as to eliminate the possible temporal relationship of the ease of visualization in group II. In group IV (n = 1208), the four examiners have evaluated flexible laryngoscopy, on a large scale, at any time during the 1-h stay in the recovery room. Special attention was directed to the patients with known cardiovascular diseases. Direct and indirect laryngoscopies were only effective in 76 and 73%, respectively, of the patients, whereas flexible laryngoscopy was effective in 99.6% of them. Flexible laryngoscopy was easy to perform in 96.5% of the patients versus 65 and 55% with direct and indirect laryngoscopies. Finally, variations in monitored cardiovascular parameters were significantly lower with flexible and indirect laryngoscopies than with direct laryngoscopy. These mild variations induced by flexible laryngoscopy were well tolerated by patients with known cardiovascular diseases. Flexible laryngoscopy is the best method for an immediate laryngoscopic examination after thyroidectomy.

Fiber Optic Technology↗

IBIS version 3: an OSF/Motif-based interface for IBIS--integrated biological imaging system.

IBIS is a set of computer programs dedicated to the processing of electron micrographs, mainly for structural analysis of biological macromolecules. We present IBIS version 3, a UNIX/OSF/Motif 1.2-based package which carries out and provides visual display of the many operations essential to image analysis. To ensure portability, the software is written in FORTRAN 77 for computing mathematical functions and in C for display routines. A description of the IBIS OSF/Motif interface is given with the new functions added to the original version. IBIS v.3 is available free of charge to other laboratories on the internet via anonymous ftp (URL: ftp://ftp.univ-rennes1.fr/pub/ incoming/IBIS.tar.Z).

Computer Communication Networks↗

Delayed forced air warming prevents hypothermia during abdominal aortic surgery.

We have evaluated the efficacy of the delayed forced air warming during abdominal aortic surgery in 18 patients. Patients were allocated randomly to one of two groups: the control group (n = 9) received no intraoperative warming device; the Bair-Hugger group (n = 9) had active skin surface warming with an upper body cover. The device was activated when core temperature decreased to less than 36 degrees C. The reduction in core temperature was 0.6 degrees C during the first hour after induction and 0.4 degrees C during the second hour in both groups. In the control group, core temperature continued to decrease until the end of surgery, whereas in the Bair-Hugger group, the reduction in core temperature stopped after 1 h of warming, and then rewarming began. At the end of surgery, core temperature in the Bair-Hugger group was similar to core temperature before induction, and was higher than core temperature in the control group (P < 0.003).

Adult↗

Variations in R-plasmid DNA concentrations of Escherichia coli during starvation in sewage and brackish waters.

Cell culturability and plasmid stability in Escherichia coli containing plasmids RP1, R388 and pUB824 were studied in raw and treated wastewater, and in brackish water. The E. coli strain survived well in the three samples of water employed. Moreover, the three plasmids were maintained under all conditions studied. Interestingly, plasmid DNA concentration of individual plasmids followed the same evolution as the culturable bacteria in the corresponding selective medium when the bacteria grew in raw or treated wastewater. In contrast, in brackish water, the stress due to the oligotrophic and salinity conditions of the medium produced an initial paradoxical increase in plasmid DNA concentration, followed by a decrease in the number of culturable bacteria in the corresponding selective medium. Maintenance of RP1 (56 kbp) and R388 (33 kbp) was markedly influenced by nutritive conditions, which caused a segregation of the plasmids from cells. The results of the present study suggest that variations in plasmid DNA concentrations in an aquatic environment depend on the quality of the water and also on the molecular weight of the plasmid considered.

DNA, Bacterial↗

In vitro and in vivo profile of SB 206553, a potent 5-HT2C/5-HT2B receptor antagonist with anxiolytic-like properties.

1. SB 206553 (5-methyl-1-(3-pyridylcarbamoyl)-1,2,3,5-tetrahydropyrrolo[2 ,3-f]indole) displays a high affinity (pK1 7.9) for the cloned human 5-HT2C receptor expressed in HEK 293 cells and the 5-HT2B receptor (pA2 8.9) as measured in the rat stomach fundus preparation. SB 206553 has low affinity for cloned human 5-HT2A receptors expressed in HEK 293 cells (pK1 5.8) and (pK1 < 6) for a wide variety of other neurotransmitter receptors. 2. SB 206553 appears to be a surmountable antagonist of 5-HT-stimulated phosphoinositide hydrolysis in HEK 293 cells expressing the human 5-HT2C receptor (pKB 9.0). 3. The compound potently (ID50 5.5 mg kg-1, p.o., 0.27 mg kg-1, i.v.) inhibited the hypolocomotor response to m-chlorophenylpiperazine (mCPP), a putative model of 5-HT2C/5-HT2B receptor function in vivo. 4. At similar doses (2-20 mg kg-1, p.o.) SB 206553 increased total interaction scores in a rat social interaction test and increased punished responding in a rat Geller-Seifter conflict test. These effects are consistent with the possession of anxiolytic properties. 5. SB 206553 also increased suppressed responding in a marmoset conflict model of anxiety at somewhat higher doses (15 and 20 mg kg-1, p.o.) but also reduced unsuppressed responding. 6. These results suggest that SB 206553 is a potent mixed 5-HT2C/5-HT2B receptor antagonist with selectivity over the 5-HT2A and all other sites studied and possesses anxiolytic-like properties.

Animals↗