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Biomedical subjects

J A Davis

Publications and source records attributed to J A Davis.

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

Immunoglobulin genes expressed by B-lymphocytes infiltrating cervical carcinomas show evidence of antigen-driven selection.

Lymphocyte infiltration is often present in cervical cancer lesions, possibly reflecting an ongoing (but ineffective) immune response to the tumour. B-lymphocytes are the predominant lymphocyte infiltrate in pre-malignant cervical lesions, where they are thought to comprise the host immune response to active human papillomavirus (HPV) infection. Although B cells are less frequently detected in cervical tumours, a high proportion of terminally differentiated plasma cells expressing tumour-specific immunoglobulin (Ig) remain. The antigen specificity and functional significance of the antibody response to cervical tumours is unknown. As part of a study to characterise the antibodies expressed by the tumour-infiltrating B cells (TIL-B) in cervical tumours using antibody phage display, we examined expressed Ig gene sequences to determine if there was molecular evidence of a selective response to antigenic changes in the transformed epithelial cells. We found that biased variable region gene usage by the B cells and the rate of somatic hypermutation in the rearranged Ig heavy chain variable regions (VH) both indicated antigenic selection of the B cells. We also found evidence of affinity maturation, as indicated by the detection of antibodies of the IgG1, IgG2 and IgA isotypes, and possible clonal selection of the Ig receptors. These data support the notion that B-lymphocytes and plasma cells infiltrating cervical carcinomas are the result of an antigen-induced response to HPV infection or transformation.

Antigen Presentation↗
PubMed2001

Nutritional status classification in the Department of Veterans Affairs.

The Department of Veterans Affairs (VA) Nutrition Status Classification scheme uses clinical data that are routinely collected on admission or shortly thereafter for quick inpatient nutrition screening. In this scheme, patients are assigned to 1 of 4 classification levels according to 7 individual indicators. The indicators include nutrition history, unintentional weight loss as a percent of usual body weight, percent of ideal body weight, diet, diagnosis, albumin, and total lymphocyte count. After ratings (1 to 4) are assigned to each of the 7 indicators, overall nutritional status for each patient is determined by an algorithm. The VA classification system includes many of the same criteria used in other nutritional status classifications. Where it differs is in the greater emphasis on the use of objective criteria and in the rigorous evaluation of reliability and validity that went into its development. Because of these extra measures, the VA classification can be used for prioritizing workload, as well as for determining staff requirements and for comparing workload and productivity across health care facilities. So that others might benefit from using this system, this article provides information on how the classification scheme was developed and explains how it is used.

Algorithms↗
PubMed2001

The gastrointestinal transit profile of 14C-labelled poly(acrylic acids): an in vivo study.

The gastrointestinal distribution profiles for three 14C-labelled poly(acrylic acid)s of different average molecular weights and degrees of cross-linking have been established using the rat model. Despite initial differences in transit times and retention characteristics, these structural features were found to be of little influence to the overall gastrointestinal transit of the materials under consideration. No evidence for the systemic absorption of any of the polymers could be identified.

Acrylic Resins↗
PubMed2001

Major coronary artery anomalies in a pediatric population: incidence and clinical importance.

OBJECTIVES: We sought to prospectively determine the incidence and clinical significance of major coronary artery anomalies in asymptomatic children using transthoracic two-dimensional echocardiography. BACKGROUND: Anomalous origins of the left main coronary artery (ALMCA) from the right sinus of Valsalva or anomalous origins the right coronary artery (ARCA) from the left sinus are rarely diagnosed in children and can cause sudden death, especially in young athletes. Because most patients are asymptomatic, the diagnosis is often made post mortem. No study to date has prospectively identified anomalous coronary arteries in asymptomatic children in the general population. METHODS: After serendipitously identifying an index case with ALMCA, we examined proximal coronary artery anatomy in children with otherwise anatomically normal hearts who were referred for echocardiography. In those diagnosed with ALMCA or ARCA, we performed further tests. RESULTS: Within a three-year period, echocardiograms were obtained in 2,388 children and adolescents. Four children (0.17%) were identified with anomalous origin of their coronary arteries, and angiograms, exercise perfusion studies and/or stress tests were then performed. One ARCA patient had decreased perfusion in the right coronary artery (RCA) perfusion area and showed ventricular ectopy on electrocardiogram (ECG) at rest that diminished but did not resolve with exercise. A second patient with ALMCA had atrial tachycardia immediately after exercise, with inferior and lateral ischemic changes on ECG and frequent junctional and/or ventricular premature complexes both at rest and recovery. CONCLUSIONS: This study demonstrates that although anomalous origins of coronary arteries are rare in asymptomatic children, the prevalence is greater than that found in other prospective studies. Ischemia can occur with both ALMCA and ARCA even though patients remain asymptomatic. Because of the high risk of sudden cardiac death, aggressive surgical management and close follow-up are necessary.

Adolescent↗
PubMed2001

Surgical technique for installing an eight-channel neuroprosthesis for standing.

A standardized surgical procedure to implant an eight-channel functional neuromuscular stimulation system in the lower extremities for standing, exercise, and transfers for individuals with spinal cord injury has been developed. The implanted components include: (1) one eight-channel receiver-stimulator, (2) epimysial electrodes, (3) intramuscular electrodes, and (4) inline connectors. The development process included identifying the target muscle set for electrode placement and the corresponding surgical approaches, determining the stages of the surgical procedure, and assessing the effectiveness and stability of the implanted neuroprosthesis. The bilateral muscle set consists of the vastus lateralis, the gluteus maximus, the semimembranosus, and the erector spinae. Surgical approaches to the nerve entry points were developed through a series of cadaveric studies and intraoperative tests. Electrode placement is related to bony landmarks and based on standard orthopaedic approaches. The components of the neuroprosthesis are installed in one surgical session, with three stages. This procedure has been applied successfully in seven individuals, resulting in strong, isolated stimulated contractions adequate to raise and lower the body, maintain standing with a walker, and perform pivot transfers. The standardized surgical procedure is repeatable and teachable and will be used in upcoming multicenter clinical trials of the implanted neuroprosthesis.

Adult↗
PubMed2001

Retrospective comparison of rat recovery weights using inhalation and injectable anaesthetics, nutritional and fluid supplementation for right unilateral neurosurgical lesioning.

Current veterinary standards of biomedical research support include refinements in animal models that are targeted at enhancing humane care and decreasing inter-animal variability. This ultimately results in fewer numbers of animals being used and reduction in animal experimentation through mitigation of waste as well as faster research results. 6-hydroxydopamine-lesioning of the substantia nigra using a stereotactic frame device is a common procedure and is routinely performed under pentobarbital anaesthesia with monitoring by 8 h workforces. Our programme supports the humane care and use of several protocols involving the unilateral stereotactic-lesioning of rats for the purposes of creating research models of Parkinsonianism. Such procedures are commonly performed as unilateral in order to minimize aphagia and other untoward effects of the lesion. Generally, this procedure is considered minor because it involves a small incision, a cranial burrhole, and penetration of the dura. Inflammation and/or irritation of the ear canal can occur secondarily to the earbar placement procedure. Human patients undergoing similar procedures typically complain of headaches from loss of intracranial pressure; which is a transient outcome. Despite the perception of minor insult, we provided aggressive periprocedural care, and our veterinary staff documented weight loss that was often greater than 15% body weight during the first 3 days. The goal of this study was to evaluate refinements to improve this outcome. For humane concerns, and because of the need to begin experimental testing one week following surgery, a goal in the recent past has been to enhance outcome for researchers and animals by refining postoperative support modalities as well as by seeking the best anaesthetic regimen to shorten postoperative deviations from baseline. Analysis of three groups of rat patients lesioned by the same investigative group over the course of refinements made in our programme indicate that an early return of homeostasis was achieved by the use of inhalation anaesthetics as replacements for barbiturates in these models. Comparison with pentobarbital recipients also indicated that homeostasis is achieved earlier when barbiturates are utilized with fluid therapy and analgesics immediately after operative procedures rather than the next morning.

Anesthetics, Inhalation↗
PubMed2000

A controlled NO-releasing compound: synthesis, molecular structure, spectroscopy, electrochemistry, and chemical reactivity of R,R,S,S-trans-[RuCl(NO)(cyclam)]2+(1,4,8,11-tetraazacyclotetradecane).

The synthesis of trans-[RuCl(NO)(cyclam)]2+ (cyclam = 1,4,8,11-tetraazacyclotetradecane) can be accomplished by either the addition of cyclam to K2[RuCl5NO] or by the addition of NO to trans-[RuCl(CF3SO3)(cyclam)](CF3-SO3). Crystals of trans-[RuCl(NO)(cyclam)](ClO4)2 form in the monoclinic space group P2(1)/c, with unit cell parameters of a = 7.66500(2) A, b = 24.7244(1) A, c = 16.2871(2) A, beta = 95.2550(10) degrees, and Z = 4. One of the two independent molecules in the unit cell lies disordered on a center of symmetry. For the ion in the general position, the Ru-N and N-O bond distances and the [Ru-N-O]3+ bond angle are 1.747(4) A, 1.128(5) A, 178.0(4) degrees, respectively. In both ions, cyclam adopts the (R,R,S,S) configuration, which is also consistent with 2D COSY 1H NMR studies in aqueous solution. Reduction (E degree = -0.1 V) results in the rapid loss of Cl- by first-order kinetics with k = 1.5 s-1 and the slower loss of NO (k = 6.10 x 10(-4) s-1, delta H++ = 15.3 kcal mol-1, delta S++ = -21.8 cal mol-1 K-1). The slow release of NO following reduction causes trans-[RuCl(NO)(cyclam)]2+ to be a promising controlled-release NO prodrug for vasodilation and other purposes. Unlike the related complex trans-[Ru(NO)(NH3)4(P(OEt)3)](PF6)2, trans-[RuCl(NO)(cyclam)]Cl2 is inactive in modulating evoked potentials recorded from mice hippocampal slices probably because of the slower dissociation of NO following reduction.

Animals↗
PubMed2000

Effects of single dose, postinduction dexamethasone on recovery after cardiac surgery.

BACKGROUND: Corticosteroids have been recommended to facilitate rapid recovery after cardiac surgery. We previously reported that dexamethasone given after induction of anesthesia decreases the incidence of postoperative shivering. We performed a post hoc analysis of the data obtained during that study, focusing on secondary outcomes. METHODS: A total of 235 adult patients undergoing elective coronary or valvular heart surgery were randomized to receive dexamethasone 0.6 mg/kg or placebo after induction of anesthesia. Patients who had pharmacologically treated diabetes mellitus, had hypersensitivity to dexamethasone, or were receiving treatment with corticosteroids were excluded. RESULTS: We found that, compared with placebo, patients receiving dexamethasone were more likely to remain tracheally intubated for 6 hours or less (26.4% vs 10.0%, p = 0.020) and had a lower incidence of early postoperative fever (20.2% vs 36.8%, p = 0.009) and new-onset atrial fibrillation during the first 3 days postoperatively (18.9% vs 32.3%, p = 0.027). However, we could not demonstrate a statistical difference in the intensive care unit or hospital length of stay, or in overall morbidity and mortality. The dexamethasone-treated patients were also more likely to have a higher blood glucose on admission to the intensive care unit (186 mg/dL vs 143 mg/dL, p = 0.012). CONCLUSIONS: Dexamethasone facilitates early tracheal extubation and is associated with a lower incidence of early postoperative fever and new-onset atrial fibrillation. Apart from a treatable decreased glucose tolerance, dexamethasone treatment was not shown to affect morbidity or mortality significantly.

Anesthesia↗
PubMed2000

Urea production is increased in neonatal piglets infused with alanine at 25, 50, and 75% of resting energy needs .

To study the ability of neonatal piglets to metabolize a nitrogen load and excrete it as urea, 12 newborn piglets, 6 small (0.99 +/- 0. 16 kg; expt. 1) and 6 large (1.86 +/- 0.16 kg; expt. 2), were infused intravenously with alanine (n = 8; 4 large, 4 small; treatment) or glucose (n = 4; 2 large, 2 small; control) at equal ATP equivalents, supplying 25-75% of the resting energy requirements of the piglet over 18 h. To adjust for differences in the baseline urinary urea nitrogen excretion, blood urea nitrogen (BUN) and estimated urea production between groups, the absolute changes from baseline to maximum value for piglets infused with alanine, and from baseline to the 24-h value for piglets infused with glucose were evaluated statistically. There were no differences (0.1 < P < 0.3) in the absolute changes from baseline to maximum values of urinary urea nitrogen, BUN or estimated urea production between small [18.6 +/- 3.8 mg N/(h. kg(0.75)); 19.1 +/- 2.2 mmol N/L; 2.7 +/- 1.2 mmol N/(h. kg(0.75)), respectively] and large [23.6 +/- 7.6 mg N/(h. kg(0. 75)); 21.6 +/- 3.3 mmol N/L; 3.7 +/- 1.5 mmol N/(h. kg(0.75)), respectively] piglets infused with alanine. Differences in the changes from baseline were detected between alanine and glucose (P = 0.001) infusions. Small piglets required more time (P < 0.005) for BUN to maximize after initiation of the alanine infusion, suggesting that small piglets require more time to process a nitrogen load. Infusion of alanine resulted in at least a threefold increase from baseline in the rate of calculated urea production, suggesting that neonatal piglets, small or large, have reserve capacity to metabolize nitrogen and excrete it as urea.

Alanine↗
PubMed2000

Comparison of total body urea production potential with total body carbamoyl phosphate synthetase (CPS-1) activity in newborn piglets infused with alanine at 50% of resting energy expenditure for 36 hours.

The calculated rate of urea production [U(p); mmol urea/(h. kg(0. 75))], based on urinary urea-N (UUN) excretion and changes in total body urea-N, was compared with the calculated total body V(max) of carbamoyl phosphate synthetase (CPS-1) of 24 neonatal piglets from four treatments as follows: 6 h baseline control (n = 8), 18 h of alanine intravenously (IV) at 50% of resting energy expenditure (REE; n = 4), 36 h of alanine IV at 50% of REE (n = 6), or 36 h of glucose IV at 50% of REE (n = 6). The following significant increases from baseline were seen in piglets infused with alanine for 36 h: 1) UUN excretion [10.6 +/- 5.9 mg N/(h. kg(0.75)) to 53.2 +/- 11.1]; 2) BUN concentrations (9.1 +/- 3.0 mmol urea N/L to 51.2 +/- 7.0); 3) calculated urea production [0.34 +/- 0.21 mmol urea/(h. kg(0.75)) to 2.39 +/- 0.53]; and 4) CPS-1 V(max) [2.0 +/- 0.81 mmol citrulline/(h. kg (0.75)) to 4.4 +/- 1.5], (P < 0.05). With the exception of CPS-1 activity, significant decreases from baseline were seen in these values in piglets infused with glucose for 36 h (P < 0.05). Comparison of calculated urea production with calculated total body CPS-1 V(max) at baseline, 18 or 36 h after the start of infusion of alanine or glucose revealed a positive relationship (slope = 0.263; P < 0.002). At all enzyme activities, infusion of alanine resulted in a significant increase in the rate of urea production compared with controls (P < 0.001). Total body CPS-1 activity varied from 1.8 to 5.8 times that of urea production, suggesting that CPS-1 did not limit urea production.

Alanine↗
PubMed2000

Localization of chromophore absorption signals in TEM with an improved prism-mirror-prism filter.

A corrected prism-mirror-prism electron energy filter with curved entrance and exit faces was designed and incorporated into a Zeiss EM902 transmission electron microscope. The installation of the new filter required little modification to the existing microscope geometry and electronics. The filter had an energy resolution of 1.1 eV over the full image plane (acceptance half angle 10 mradian). The improved energy resolution was applied in studies of the low electron energy loss region that includes molecular orbital excitations or chromophore energy absorptions. Chromophore signal behaviour under electron irradiation was characterized using embedded crystals of hematin and of the dye mercury orange. Images of these crystals confirmed the expected decrease in signal intensity on shifting the selected energy loss from the region of molecular orbital excitations (less than approximately 5 eV) to higher energy losses. Electron irradiation-induced fading of the chromophore signal from hematin and mercury orange yielded similar 1/e dose values of 1.1 x 10(5) e(-) nm(-2) and 1.4 x 10(5) e(-) nm(-2) respectively. In a cellular context, chromophore signals were obtained from energy-filtered images of RIF-1 cell sections containing the photosensitizer chlorin e6 and from sections of BS-C-1 cells with cytoskeletal labelling via FITC-conjugated antibodies. The respective signals were extracted using a dose-dependent method or a shift in selected energy. Chromophore signal distributions were in agreement with fluorescence light microscopic images, but provided detail at higher spatial resolution.

Animals↗
PubMed2000

Determinants of patient satisfaction in postmastectomy breast reconstruction.

In today's increasingly competitive health care marketplace, consumer satisfaction has become an important measure of quality. Furthermore, measures of satisfaction with treatment inteerventions are influential factors in determining patients' and payers' choices of health care. This study sought to evaluate satisfaction with postmastectomy breast reconstruction and to assess the effects of procedure type and timing on patient satisfaction. As part of the Michigan Breast Reconstruction Outcome Study, patients undergoing first-time mastectomy reconstruction were prospectively evaluated, including cohorts of women choosing expander/implant, pedicle TRFAM flap, and free TRAM flap procedures. Preoperatively and 1 year postoperatively, participants completed a questionnaire that collected a variety of health status information. The postoperative questionnaire had an additional seven items assessing both general satisfaction with reconstruction (five items) and aesthetic satisfaction (two items) as separate subscales. Patients were asked to respond to each item using a five-point Likert scale. Item responses ranged from 1, indicating high satisfaction, to 5, reflecting low satisfaction. In the data analysis, only patients responding with a 1 or 2 for all of the items within a subscale were classified as "satisfied" for the subscale. To assess the effects of procedure type (implant, pedicle TRAM flap, and free TRAM flap) and timing (immediate versus delayed) on satisfaction and to control for possible confounding effects from other independent variables, multiple logistic regression was employed. In our analysis, odds ratios and associated 95 percent confidence intervals were calculated for each independent variable in the regression. Statistical significance was designated at the p < or = 0.05 level. A total of 212 patients were followed during the period of 1994 to 1997, including 141 immediate and 71 delayed reconstructions. The study population consisted of 49 expander/implant, 102 pedicle TRAM flap, and 61 free TRAM flap reconstruction patients. The analysis showed a significant association between procedure type and patient satisfaction. TRAM flap patients (both free and pedicle) appeared to have significantly greater general and aesthetic satisfaction compared with expander/implant patients (p = 0.03 and 0.001, respectively). Furthermore, pedicle TRAM flap patients were more aesthetically satisfied than those with free TRAM flaps (p = 0.072). The other independent variables of age and procedure timing did not appear to significantly affect either general or aesthetic satisfaction. However, preoperative physical activity was positively correlated with general satisfaction at the p = 0.034 level. The choice of procedure seems to have a significant effect on both aesthetic and general patient satisfaction with breast reconstruction. In this study, autogenous tissue reconstructions produced higher levels of patient aesthetic and general satisfaction compared with implant techniques. Pedicle and free TRAM flap patients do not seem to differ significantly in general satisfaction. However, women receiving pedicle TRAM flaps reported greater aesthetic satisfaction compared with patients undergoing free TRAM flaps. Furthermore, patient age and procedure timing may not have an effect on patient satisfaction with breast reconstruction.

Adult↗
PubMed2000

Prospective analysis of psychosocial outcomes in breast reconstruction: one-year postoperative results from the Michigan Breast Reconstruction Outcome Study.

In the past decade, changing attitudes toward breast reconstruction among both patients and providers have led a growing number of women to seek breast reconstruction after mastectomy. Although investigators have documented the psychological, social, emotional, and functional benefits of breast reconstruction, little research has evaluated the effects of procedure choice on these outcomes. The current study prospectively evaluated and compared psychosocial outcomes for three common options for mastectomy reconstruction: tissue expander/implant, pedicle TRAM, and free TRAM techniques. In a prospective cohort design, patients undergoing postmastectomy reconstruction for the first time with expander/implant, pedicle TRAM, or free TRAM procedures were recruited from 12 centers and 23 plastic surgeons in the United States and Canada. Before reconstruction and at 1 year after reconstruction, patients were evaluated by a battery of questionnaires consisting of both generic and condition-specific surveys. Outcomes assessed included emotional well-being, vitality, general mental health, social functioning, functional well-being, social well-being, and body image. Baseline (preoperative) scores and the change in scores (the difference between postoperative and preoperative scores) were compared across procedure types using t tests and analysis of covariance. Preoperative and 1-year postoperative surveys were obtained from 273 patients. Procedure type was reported in 250 patients, of whom 56 received implant reconstructions, 128 pedicle TRAM flaps, and 66 free TRAM flaps. A total of 161 immediate and 89 delayed reconstructions were performed. Among women receiving immediate reconstruction, significant improvements were observed in all psychosocial variables except body image. However, no significant effects of procedure type on these changes over time existed. Similarly, delayed reconstruction patients had significant increases in emotional well-being, vitality, general mental health, functional well-being, and body image. Although the choice of reconstructive technique did not significantly impact most of these outcomes, significant differences existed among procedure types for three psychosocial subscales. Patients undergoing delayed expander/implant reconstructions reported greater improvements in vitality and social well-being relative to women receiving delayed TRAM procedures. By contrast, delayed TRAM patients noted significantly greater gains in body image compared with women choosing delayed expander-implant reconstruction. The authors conclude that both immediate and delayed breast reconstructions provide substantial psychosocial benefits for mastectomy patients. Although the choice of reconstructive procedure does not seem to significantly affect improvements in psychosocial status with immediate reconstruction, our data suggest that procedure type does have a significant effect on gains in vitality and body image for women undergoing delayed reconstruction.

Adaptation, Psychological↗
PubMed2000

Vibrational angioplasty and hydrophilic guidewires in the treatment of chronic total coronary occlusions.

PURPOSE: To study the efficacy and safety of vibrational angioplasty versus hydrophilic guidewires for recanalizing chronic total occlusions (CTOs) of the coronary arteries. METHODS: In a retrospective study, 99 patients with old (>3 months) CTOs resistant to conventional techniques were treated either with vibrational angioplasty (group A, n = 72) or 0.014-inch hydrophilic guidewires (group B, n = 27). The selection of the technique (vibrational angioplasty or hydrophylic guidewires) was dependent only upon device availability. A variety of guidewires were employed in conjunction with vibrational angioplasty. RESULTS: The crossing success rates in groups A and B were 86.1% (62/72) and 55.5% (15/27) (p < 0.05), with final procedural success rates of 75% (54/72) and 44.4% (12/27) (p < 0.01), respectively. The main reasons for failure were inability to cross the lesion with a guidewire (10/18 in group A and 12/15 in group B) and large dissections resulting in vessel closure (2/18 in group A and 2/15 in group B). Three major complications were seen, 2 in group A and 1 in group B. Three vessel perforations were reported in group A. Both techniques needed prolonged fluoroscopy times. CONCLUSIONS: Vibrational angioplasty was more successful in treating CTOs compared to hydrophilic guidewires and had similar complication rates (most without clinical sequelae).

Adult↗