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Biomedical subjects

J T Smith

Publications and source records attributed to J T Smith.

At least 37 records · Page 2Linked to original sources
PubMed2001

A critical review of measures to reduce radioactive doses from drinking water and consumption of freshwater foodstuffs.

Following a radioactive fallout event, there are a number of possible intervention measures to reduce radioactive doses to the public via the surface water pathway. We have critically reviewed the options available to decision-makers in the event of radioactive contamination of surface waters. We believe that the most effective and viable measures to reduce radioactivity in drinking water are those which operate at the water treatment and distribution stage. Intervention measures to reduce concentrations of radioactivity in rivers and reservoirs are expected to be much less viable and efficient at reducing doses via the drinking water pathway. Bans on consumption of freshwater fish can be effective, but there are few viable measures to reduce radioactivity in fish prior to the preparation stage. Lake liming and biomanipulation have been found to be ineffective for radiocaesium, although the addition of potassium to lakewaters appears promising in some situations. Lake liming may be effective in reducing radiostrontium in fish, though this has not, to our knowledge, been tested. De-boning fish contaminated by strontium is probably the most effective food preparation measure, but salting and freezing can also reduce radiocaesium concentrations in fish. The provision of accurate information to the public is highlighted as a key element of countermeasure implementation.

Animals↗
PubMed2000

Determination of radionuclide exchangeability in freshwater systems.

Two freshwater sediments were spiked with 57Co, 85Sr and 134Cs and left for adsorption times ranging from 1 day to over 60 days. Following adsorption, the 'exchangeable' pool of each radionuclide was measured using ammonium acetate extractions and a sequential leach procedure (Tessier et al., 1979), and the results were compared. Exchangeability was found to depend upon the sediment, radionuclide, sorption time and the identity of extracting agent. All three radionuclides showed a shift with increasing adsorption time from regular exchange sites to sites which are sterically hindered, but a fixation within the sediment was only observed for 57Co and 134Cs, with similar ammonium acetate extraction yields for both radionuclides. Misleading results were obtained during the sequential leach procedure due to redistribution and, therefore, the inclusion of a NH4+ leach after the MgCl2 extraction step was suggested. A mathematical model of element speciation was fairly successful at defining the 'exchangeable' fraction, suggesting that the chemically- and mathematically-defined fractions were similar.

Adsorption↗
PubMed2000

A comparison of the effects of patient-controlled analgesia with intravenous opioids versus Epidural analgesia on recovery after surgery for idiopathic scoliosis.

STUDY DESIGN: Epidural infusion was compared with standard patient-controlled analgesia (PCA) in 50 patients after surgical correction of adolescent idiopathic scoliosis with respect to certain postoperative parameters. OBJECTIVES: To compare postoperative parameters after posterior spinal instrumentation and fusion (PSIF) and to determine whether epidural infusion prolongs hospital stay or increases the risk of complications. SUMMARY OF BACKGROUND DATA: Patient-controlled analgesia and epidural infusion are both safe and effective in controlling postoperative pain after PSIF. One criticism of epidural infusion has been longer hospital stays. No study was found in the literature in which PCA was compared with epidural infusion. METHODS: The records of 50 consecutive patients who had undergone PSIF were reviewed. The epidural group consisted of 30 patients and the PCA group 20. Age, weight, degree of curve, and levels fused were evenly matched. Postoperative parameters including the day that each patient tolerated a full diet, day of independent ambulation, length of hospital stay, and pain control were compared. RESULTS: Pain control was comparable in each group. The epidural group tolerated a full diet earlier and on average were discharged 0.5 days sooner than the PCA group. Both differences are statistically significant. No significant complications were reported in either group. CONCLUSIONS: Epidural infusion of opioids with bupivacaine is safe and effective for controlling postoperative pain after PSIF without an increased complication rate when compared with PCA. In the current study, patients tolerated a full diet and were discharged from the hospital an average of 0.5 days earlier than PCA-treated patients.

Adolescent↗
PubMed2000

A prospective evaluation of the timing of postoperative radiotherapy for preventing heterotopic ossification following traumatic acetabular fractures.

PURPOSE: Preoperative and immediate postoperative irradiation of traumatic acetabular fractures (TAF), although known to reduce heterotopic ossification (HO), can cause significant organizational and logistic difficulties. We sought to determine an acceptable time interval between surgery and radiation without compromising control, as well as to update our large experience and to further validate our treatment philosophy. METHODS AND MATERIALS: Beginning in June 1995, we began a prospective study, irradiating 152 patients on postoperative days 1, 2, or 3. There were also 17 patients delayed further secondary to medical difficulties. RESULTS: All patients treated since June 1995 received 700 cGy/1 fx. Fifty-eight patients received radiation within 24 hours of surgery, 41 within 2 days, 53 within 3 days, 13 within 4 days, and 4 were delayed further. Delaying irradiation for up to 4 days postoperatively caused no statistical increase in HO (p = 0.625). Of 263 patients in our retrospective cohort, HO occurred in 5.3% of patients who received irradiation versus 60% of patients who did not. CONCLUSION: In our prospective study, we noted no perceptible increase in HO with up to a 3-day interval between surgery and radiotherapy. This allows a more structured treatment schedule and allows the patient more time to heal and recover. Updated results from our overall series continue to demonstrate that adjuvant radiation decreases the incidence and severity of HO after TAF.

Acetabulum↗
PubMed2000

Exercise induces isoform-specific increase in 5'AMP-activated protein kinase activity in human skeletal muscle.

The 5'AMP-activated protein kinase (AMPK) is stimulated by contractile activity in rat skeletal muscle. AMPK has emerged as an important signaling intermediary in the regulation of cell metabolism being linked to exercise-induced changes in muscle glucose and fatty acid metabolism. In the present study, we determined the effects of exercise on isoform-specific AMPK activity (alpha1 and alpha2) in human skeletal muscle. Needle biopsies of vastus lateralis muscle were obtained from seven healthy subjects at rest, after 20 and 60 min of cycle ergometer exercise at 70% of VO(2)max, and 30 min following the 60 min exercise bout. In comparison to the resting state, AMPK alpha2 activity significantly increased at 20 and 60 min of exercise, and remained at a higher level with 30 min of recovery. AMPK alpha1 activity tended to slightly decrease with 20 min of exercise at 70%VO(2)max; however, the change was not statistically significant. AMPK alpha1 activities were at basal levels at 60 min of exercise and 30 min of recovery. On a separate day, the same subjects exercised for 20 min at 50% of VO(2)max. Exercise at this intensity did not change alpha2 activity, and similar to exercise at 70% of VO(2)max, there was no significant change in alpha1 activity. In conclusion, exercise at a higher intensity for only 20 min leads to increases in AMPK alpha2 activity but not alpha1 activity. These results suggest that the alpha2-containing AMPK complex, rather than alpha1, may be involved in the metabolic responses to exercise in human skeletal muscle.

Adenosine Triphosphate↗
PubMed2000

An enantiomeric assay for the flavonoids medicarpin and vestitone using capillary electrophoresis.

An enantiomeric assay for the flavonoids vestitone and medicarpin from transgenic plant extracts was developed using capillary electrophoresis. It was found that no single cyclodextrin proved capable of resolving the enantiomers of both medicarpin and vestitone. Instead, hydroxypropyl-beta-cyclodextrin provided the best selectivity for the vestitones while hydroxypropyl-gamma-cyclodextrin was best for the medicarpins. The addition of organic modifiers improved the resolution of both enantiomers. Acetonitrile proved best for the vestitones and only methanol improved the resolution of the medicarpins. An optimization study of mixed hydroxypropyl-beta-cyclodextrin and hydroxypropyl-gamma-cyclodextrin containing electrolytes revealed that the separation of the medicarpin enantiomers was intolerant to the presence of hydroxypropyl-beta-cyclodextrin. Our optimized running electrolyte was composed of 2 mM hydroxypropyl-beta-cyclodextrin, 20 mM hydroxypropyl-gamma-cyclodextrin, and 25 mM borate at pH 10.0 with 10% v/v methanol. This system provided a resolution of 1.47 and 1.80 for the medicarpin and vestitone enantiomers, respectively. This analysis was completed in 12 min. This separation provided a rapid screen to determine the enantiomeric purity of key flavonoids biosynthesized by transgenic legumes.

2-Hydroxypropyl-beta-cyclodextrin↗
PubMed2000

Increased fetal glucocorticoid exposure delays puberty onset in postnatal life.

The fetal environment is now recognized as a key determinant of the adult phenotype, being linked to development of diseases, including hypertension, as well as the timing of puberty. Such links may be related, in part, to the level of fetal exposure to maternal glucocorticoids in utero, which is normally regulated by placental expression of the enzyme 11beta-hydroxysteroid dehydrogenase (11beta-HSD). The present study examined whether manipulation of fetal glucocorticoid exposure, either directly or indirectly via 11beta-HSD inhibition, influences the subsequent timing of puberty. Administration of dexamethasone acetate at low (LDEX, 0.25 microg/ml drinking water) or high doses (HDEX, 1 microg/ml) or carbenoxolone (CBX, 2 x 10 mg/day, sc; an inhibitor of 11beta-HSD) to pregnant rats from day 13 to term (day 23) reduced offspring birthweight (LDEX: 9%; HDEX: 27%; CBX: 8%) and resulted in a subsequent delay in the onset of puberty in females (control: 41.4 +/- 0.5; LDEX: 44.8 +/- 0.7; HDEX: 48.5 +/- 0.4; CBX: 43.6 +/- 0.5 days). Importantly, the effects of CBX were not observed in the absence of maternal adrenals, indicating that they were mediated by increased fetal exposure to endogenous maternal glucocorticoids. In contrast, maternal treatment with metyrapone (MET; an inhibitor of glucocorticoid synthesis; 500 microg/ml drinking water from day 13) increased birthweight by 5% and advanced puberty onset in male offspring (control: 48.8 +/- 1.0; MET: 45.7 +/- 0.8 days). Changes in the timing of puberty onset were not attributable to changes in either bodyweight at puberty or peripubertal plasma leptin concentrations. Peripubertal plasma LH was also unaffected in animals with delayed puberty but was elevated in male offspring of MET-treated mothers. Collectively, these results demonstrate that fetal glucocorticoid exposure is an important determinant of the timing of puberty onset in postnatal life, and that this effect is operable within the normal physiological range of glucocorticoid concentrations.

Aging↗
PubMed2000

Children in group homes: family dynamics, adolescent suicide attempts and drug use.

Three hundred children age 10-20 living in group homes for children were assessed for behaviors related to alcohol and other drug consumption, suicide attempts, frequency of punishment, attention from parents, conflicts with parents, and other family dynamics. Children who used substances were significantly more likely to have attempted suicide more frequently. Children who had attempted suicide were more likely to perceive that they had not received enough parental attention, to have had more conflicts with parents, and to have run away from home. This seminal article indicates inter-related prevalences of family factors, suicide and substance abuse issues and suggests the need for strong institutional and agency policy development for this understudied "at risk" population.

Adolescent↗
PubMed1999

Adjusting selectivity in micellar electrokinetic capillary chromatography with 1,2-hexanediol.

In this report, we introduce a new micelle modifier useful to alter selectivity in micellar electrokinetic capillary chromatography (MECC). 1,2-Hexanediol acts as a class I organic modifier in that its effects are on the sodium dodecyl sulfate (SDS) micellar rather than the surrounding aqueous phase. This characteristic allows 1,2-hexanediol to improve resolution when applied at concentrations as low as 20 mM (0.25% v/v) by altering the selectivity observed with SDS alone. The effects of 1,2-hexanediol on the critical micelle concentration of SDS, electroosmotic flow, electrophoretic mobility of the SDS micelle, and reproducibility are presented. 1,2-Hexanediol had little impact on the migration time window at concentrations below 100 mM. Changes in selectivity induced by 1,2-hexanediol for a large set of model compounds are presented. Analytes capable of forming hydrogen bonds tend to decrease their interactions with the micellar phase while nonhydrogen bonding analytes increase their interactions. The usefulness of 1,2-hexanediol was demonstrated by examining its effects on the separation of dansylated amino acids. Eighteen of twenty amino acids could be separated with a resolution greater than 1.6 within 1600 s using a combination of 1,2-hexanediol and isopropanol.

Chromatography, Micellar Electrokinetic Capillary↗
PubMed1999

Explorations of alkyl polyols as "class I" organic modifiers to adjust selectivity in micellar electrokinetic capillary chromatography.

In this study, we investigated a novel series of micelle modifiers useful to alter selectivity in micellar electrokinetic capillary chromatography (MEKC). These modifiers were alkyl polyalcohols, including 1-octanol, 1,2-octanediol, 1,2,3-octanetriol, 1,2-hexanediol, and 1,2-butanediol, which act as class I organic modifiers in that their effects are on the sodium dodecyl sulfate (SDS) micelle rather than the surrounding aqueous phase. This characteristic allows the alkyl polyols to effect resolution when applied at concentrations as low as 20 mM (0.25% v/v) by altering the selectivity observed with SDS without a modifier. The effects of the alkyl polyols on the critical micelle concentration of SDS, electroosmotic flow, and electrophoretic mobility of the SDS micelle are presented. These modifiers had little impact on the migration time window at the concentrations explored. Changes in selectivity induced by the alkyl polyols for a large set of model compounds are presented. Trends indicate that solutes capable of forming hydrogen bonds tend to decrease their interactions with the micellar phase while nonhydrogen bonding solutes increase their interactions upon addition of the modifiers. The solvation parameter model was used to characterize the induced changes in selectivity. This model suggests that even though the modifiers are structurally similar, each produced a unique set of system constants. It was also demonstrated that the addition of alkyl polyols improved the correlation between the partition coefficients of SDS and water to 1-octanol and water. The usefulness of the alkyl polyols was demonstrated by examining their effects on the separation of 11 priority phenols.

1-Octanol↗
PubMed1999

Recent advancements in amino acid analysis using capillary electrophoresis.

Recent advances in the analysis of amino acids using capillary electrophoresis are addressed. This area of research continues to receive increased attention as is evident from the 62 references reviewed. This review discusses current detection strategies including UV absorbance, laser-induced fluorescence, electrochemical, and others. Separation methodologies for both derivatized and underivatized amino acids are reviewed. Both direct and indirect enantiomeric resolution of amino acids are addressed. Applications utilizing capillary electrophoresis for the analysis of amino acids are discussed. This review covers literature published in 1997 and 1998.

Amino Acids↗
PubMed1998

A comparison of manual versus computer-assisted radiographic measurement. Intraobserver measurement variability for Cobb angles.

STUDY DESIGN: A comparison between computer-assisted measurement using digitized radiographs, which has the potential to reduce error, and manual measurement using standard radiographs. OBJECTIVE: To assess measurement variability for the Cobb method on digital radiographs and compare it with that of manual measurements on standard radiographs. BACKGROUND DATA: Studies of the Cobb method have demonstrated multiple sources of error leading to significant intraobserver measurement variability. Estimates for the 95% confidence interval for intraobserver variability range from 2.8 degrees to 10 degrees. METHODS: Twenty-four scoliosis radiographs were measured by six examiners. Two measurement sets were done manually ("manual set"), and two measurement sets were done on digitized images using a computer mouse ("computer set"). RESULTS: For the manual set, the 95% confidence interval for intraobserver variability was 3.3 degrees (range, 2.5-4.5 degrees). For the computer set, the value was 2.6 degrees (range, 2.3-3.3 degrees). This difference in 95% confidence intervals between the manual and computer sets was statistically significant (P < 0.001). CONCLUSIONS: The results of this study demonstrate that intraobserver variability for manual and computer Cobb angle measurements yield a 95% confidence interval of approximately 3 degrees, with the computer having a slightly lower variability. The computer technique removes sources of intrinsic error, e.g., the variability introduced by using different manual protractors, the inaccuracy of standard protractors, and the use of wide-diameter radiographic markers. Identical digital images can be shared electronically between centers, without having to duplicate and mail films. Multicenter studies in which different examiners will be measuring Cobb angles may consider using the computer as a measuring device to reduce intrinsic measurement errors.

Arthrography↗
PubMed1998

Use of a satellite-derived land cover map to estimate transport of radiocaesium to surface waters.

During the weeks to months after the deposition of radioactive fallout, the initial concentration of radioactivity in rivers and lakes declines as a result of flushing and removal to bottom sediments. In the long-term, however, radioactivity in the water body can remain at significant levels as a result of secondary contamination processes. In particular, it is known that soils contaminated by long-lived radionuclides such as 137Cs and 90Sr provide a significant source to surface waters over a period of years after fallout. Using The Land Cover Map of Great Britain, a satellite-derived land cover map as a surrogate indicator of soil type, we have related catchment land cover type to long-term 137Cs activity concentrations in 27 lakes in Cumbria, UK. The study has shown that satellite-derived maps could be used to indicate areas vulnerable to high long-term 137Cs transport to surface waters in the event of a nuclear accident. In these Cumbrian lakes, it appears that residual 137Cs levels are determined by transfers of 137Cs from contaminated catchments rather than within-lake processes. Only three of the cover types, open shrub moor, bog and dense shrub moor, as identified by the satellite, are needed to explain over 90% of the variation in long-term 137Cs activity concentrations in the lakes, and these have been shown to correlate spatially with occurrence of organic soils.

Cesium Radioisotopes↗
PubMed1998

Trauma patients with multiple extremity injuries: resource utilization and long-term outcome in relation to injury severity scores.

BACKGROUND: Trauma patients with multiple extremity injuries (MEI) make heavy demands on hospital resources and face long-term difficulties in rehabilitation, yet the literature contains little about their treatment as a distinct group. METHODS: In this study, a cohort of 54 patients with MEI, all treated at a Level I trauma center, was compared with a trauma control (TC) group that had major injuries not focused at the extremities (but excluding patients with neurologic sequelae of head or spinal cord injuries). Demographic features, primary measures reflecting utilization of hospital resources, return-to-employment and productivity data, and health-related quality of life scores (Medical Outcomes Study 36-Item Short Form Health Survey [SF-36]) were compared. RESULTS: Although mean Injury Severity Scores (ISS) for the MEI and TC groups were almost identical (16.2 and 17.4, respectively), the patients with MEI had a mean hospital stay almost twice as long (25 vs. 13 days) and had double the resource intensity weight compared with the TC group. After discharge, the trend of the MEI group was to greater long-term disability, based on SF-36 scores, and lower "return to productivity" figures. The ISS did not predict the greater demands on resources made by the MEI group relative to our TC group. Main injury severity scores for the extremities were more predictive than the ISS for length of hospital stay and the SF-36 concepts at the 2-year follow-up evaluation. CONCLUSION: The study emphasizes the need for injury scoring systems that better predict the needs of patients with MEI and that will serve as a basis for equitable funding of trauma centers.

Adolescent↗
PubMed1998

Postoperative epidural analgesia for pediatric spine surgery.

The safety of epidural infusion for postoperative analgesia in pediatric spine surgery continues to be established. A continuous epidural infusion of morphine sulfate and bupivacaine was used for postoperative analgesia in 12 pediatric patients undergoing spinal surgery. The epidural was placed intraoperatively by the operating surgeon, while continuous infusion was managed postoperatively by a pediatric anesthesiology pain service team. In addition to the continuous infusion, 2 of the 12 also were provided on-demand patient-controlled boluses via epidural catheter for breakthrough pain. Patients experienced analgesia as documented by a comprehensive pain scale form. No catheters failed, while side effects were minimal and easily managed. These results provide confirmation of the safety and efficacy of continuous epidural infusion for postoperative analgesia following pediatric spine surgery and evidence that patient-controlled epidural analgesia is an option.

Adolescent↗
PubMed1997

Developments in amino acid analysis using capillary electrophoresis.

The current status in the analysis of amino acids using capillary electrophoresis is addressed. This area of biological analysis has received increased attention with more than 200 articles being published in the last five years. This review discusses pre-, post-, and on-column derivatization techniques used to tag amino acids providing a detectable moiety. Several separation methodologies which provided resolution for large sets of amino acids are presented. An overview of advances in the enantiomeric resolution methodologies for amino acids is given. Both direct and indirect enantiomeric separation schemes are summarized. Recent advances in detection strategies for both derivatized and underivatized amino acids are presented. Applications utilizing amino acid analysis by capillary electrophoresis are described. This review covers articles published between 1991 and 1996.

Amino Acids↗