Biomedical subjects

J Sweet

Publications and source records attributed to J Sweet.

At least 19 recordsLinked to original sources

PubMed2004

Entanglement between a photon and a quantum well.

The lack of translational invariance perpendicular to the plane of a single quantum well causes equal probability for spontaneous emission to the left or right. Combining one emission path from the left and one from the right into a common detector leads to interference fringes for fundamentally indistinguishable paths corresponding to geometries where the same in-plane momentum is transferred to the quantum well. For all other paths, no interference is observed because of the entanglement between the photon and extended Bloch states of the many-body system. In multiple-quantum-well structures the interference can be controlled via the spacing between the wells.

Journal Article↗

PubMed2002

A unique renal lesion in common variable immunodeficiency.

This article reports the case of a 33-year-old woman with common variable immunodeficiency (CVI) who developed renal failure 17 years after diagnosis and initiation of treatment with monthly IVIG. A renal biopsy revealed mesangial and paramesangial immune complex deposition and interstitial granulomatous infiltration. Renal function improved with oral corticosteroids, but did not return to normal. Decreasing the dose of IVIG had no effect on renal function. Immune dysfunction can be associated with both granulomatous disease and immune complex glomerulonephritis, or the latter may be related to chronic infection or immunoglobulin use. This is the first report of concomitant glomerular-tubulointerstitial lesions in this immunodeficiency syndrome. Renal function should be closely followed in patients with CVI.

Adult↗

PubMed2001

V89L polymorphism of type-2, 5-alpha reductase enzyme gene predicts prostate cancer presence and progression.

OBJECTIVES: The valine (V) to leucine (L) polymorphism of the SRD5A2 gene is associated with 5-alpha reductase-2 activity; patients with the V allele have high activity and patients with the L allele have low activity. We examined whether this polymorphism predicts the presence of prostate cancer in 320 men without cancer who underwent biopsy and cancer progression in 318 men who underwent radical prostatectomy. METHODS: The effect of the SRD5A2 gene in predicting the presence of prostate cancer was examined using logistic regression analysis, controlling for established risk factors. The effect of the SRD5A2 gene in predicting prostate cancer progression was examined using a nested, matched, case-control design. Most of the participants were white. RESULTS: Of the 320 men, 158 (49.4%) were found on biopsy to have prostate cancer. The overall distribution of the V/V, V/L, and L/L genotypes was 47.5%, 42.5%, and 10.0%, respectively. The adjusted odds ratio for having prostate cancer for patients with at least one V allele was 2.53 compared with patients with the L/L genotype (P = 0.03). Of the 318 patients with cancer, 80 had biochemically detected recurrence and 238 had no evidence of recurrence. The odds ratio for progression for patients with at least one V allele was 3.32 (95% confidence interval 1.67 to 6.62, P = 0.0006) compared with patients with the L/L genotype. CONCLUSIONS: Men who have the V allele of the SRD5A2 gene have a twofold increase in the risk of prostate cancer development and an additional twofold increase in the risk of progression compared with men with the L/L genotype.

Aged↗

PubMed2001

Development of a radiofrequency based thermal therapy technique in an in vivo porcine model for the treatment of small renal masses.

PURPOSE: Incidentally detected small renal tumors appear to grow slowly and be localized to the kidney. Minimally invasive therapies are being investigated as alternatives to standard surgical techniques. Radiofrequency ablation has been reported for the treatment of small renal cell carcinomas. We developed a radiofrequency technique and established its efficacy and safety in a large animal model. METHODS AND METHODS: A total of 22 lesions were created in normal kidneys of 7 pigs. Radiofrequency energy was administered during open exposure of the kidneys or percutaneously under ultrasound guidance. Lesion development was monitored with gray-scale and power Doppler ultrasound. To avoid heating surrounding tissues new hydro-dissection and gas-dissection techniques were developed. Lesion sizes and characteristics were assessed by ultrasound and pathological examination. RESULTS: No complications were observed due to probe insertion and removal. Perirenal structures were thermally damaged before the development and application of the dissection techniques. Lesion size was accurately predicted by gray-scale ultrasound on day 7. Loss of perfusion in the ablated volume was confirmed by power Doppler ultrasound. Lesions were wedge-shaped, presumably due to the effects of heating on segmental blood flow distribution. Pathological examination revealed changes consistent with thermal injury and ischemic type infarction. CONCLUSIONS: Radiofrequency thermal therapy is an effective and efficient method for ablating normal renal tissue in the pig. It may be applied percutaneously under ultrasound guidance with minimal complications provided that vital adjacent structures are protected from thermal damage. Further studies are required in humans before adopting this technique as definitive treatment for small renal cell carcinoma.

Animals↗

PubMed2000

Standard off-cord lung oblique fields do not include the entire mediastinum: a computed tomography simulator study.

The routinely recommended target volume for off-cord lung oblique fields in the treatment of postoperative bronchogenic carcinoma includes the entire mediastinum, as defined by coverage of the contralateral mainstem bronchus and subcarinal space. However, this may be difficult to accomplish with the field angles of 20 degrees to 40 degrees, recommended in the recently completed Intergroup Trial (Radiation Therapy Oncology Group 91-05). This project was undertaken to define the oblique angle necessary to encompass the entire mediastinum as determined by computerized tomography simulator verification. Axial computerized tomography simulation images of 25 patients with non-small-cell lung cancer were used in this study. Ten patients had prior lobectomy or pneumonectomy as part of their management. The contralateral mainstem bronchus, subcarinal space (SS), and the spinal cord were each contoured as separate volumes. The length of the contralateral mainstem bronchus was defined as extending from the carina to the bifurcation of the lobar bronchi. The subcarinal space was defined as a triangular space (in a coronal plane) with the carina at the apex, the mainstem bronchi superiorly, and a horizontal line 5 cm below the carina as the base of the triangle. The minimal angle to encompass the contralateral mainstem bronchus and subcarinal space, and to exclude the spinal cord was determined for each patient. The contoured volumes did not have additional margin added. The position of the carina was scored as "midline" if located in the midsagittal plane, or "off-midline" if deviated to either side from midline. Midline deviation was determined at the level of the carina to evaluate possible anatomical distortion relating to the tumor or prior surgery, and its effect on the minimal angle was assessed. The median minimal angle measured was 45 degrees (range: 28-65 degrees) for the entire group, and in 64% of those evaluated, this oblique angle was significantly greater than the 40 degrees recommended in Radiation Therapy Oncology Group guidelines (p = 0.017). In patients without midline deviation (n = 17), the median minimal angle was 45 degrees (range: 28-60 degrees), and in patients with midline deviation (n = 8), it was determined to be 44 degrees (range: 27-65 degrees), with no statistical difference noted between the two groups (p = NS). Although midline deviation was present in 4 of 10 patients previously resected, the above relationship remained unchanged. Based on computerized tomography simulation verification, off-cord oblique field angles of 20 degrees to 40 degrees do not adequately cover the entire mediastinum in most patients. To adequately encompass the entire mediastinum as defined in the Intergroup Trial (Radiation Therapy Oncology Group 91-05) with off-cord oblique fields, treatment angles greater than 40 degrees are necessary. Whether the potential increase in lung volume exposed to radiation from these larger angles results in a poorer therapeutic ratio requires further investigation.

Adult↗

PubMed2000

A comparative analysis of sextant and an extended 11-core multisite directed biopsy strategy.

PURPOSE: The 3 tumor locations unsampled by conventional sextant biopsies that have been identified on composite 3-dimensional reconstruction of 180 radical prostatectomy specimens are the anterior transition zone, midline peripheral zone and inferior portions of the anterior horn in the peripheral zone. We evaluated an 11-core multisite directed biopsy scheme incorporating these alternate areas and conventional sextant biopsies in 362 patients from 2 institutions. MATERIALS AND METHODS: Patients without a prior diagnosis of cancer underwent ultrasound guided 11-core biopsies which included conventional sextant and 3 alternate sites. All specimens were separated for specific location identification. Biopsy was performed in 183 patients at MD Anderson Cancer Center (group 1) and in 179 at Toronto General Hospital (group 2). All group 2 and 54% of group 1 patients (98 of 183) had a prior biopsy negative for cancer. RESULTS: Median prostate specific antigen was higher in group 2 than in group 1 patients (11.5 versus 9.5 ng./ml., p = 0.016). Overall a 33% increase (36 of 110 patients) in cancer detection was observed when biopsy technique included the alternate areas (p = 0.0021). The anterior horn was the most frequently positive biopsy site followed by the transition zone and midline sites. The 11-core technique had significantly better cancer detection rates when digital rectal examination and transrectal ultrasound were normal, and in men with serum prostate specific antigen between 4.1 and 10 ng./ml. CONCLUSIONS: Biopsies of the alternate sites suggested by our simulation studies are feasible and reproducible. This new strategy significantly enhanced (p = 0.0075) prostate cancer detection compared to conventional sextant biopsies in men undergoing a repeat procedure.

Adult↗

PubMed2000

Significance of the CAG repeat polymorphism of the androgen receptor gene in prostate cancer progression.

PURPOSE: The CAG repeat polymorphism of the androgen receptor gene has been associated with an increased prostate cancer risk, and the repeat length correlated with cancer stage and grade at presentation. Men with an allele length of </= 18 CAG repeats have a 2-fold increase in risk for high-stage or high-grade prostate cancer, compared with patients with a longer CAG repeat. We examined the significance of the CAG repeat polymorphism of the androgen receptor gene for predicting prostate cancer progression among 318 patients treated by radical prostatectomy for clinically localized prostate cancer between 1987 and 1994. MATERIALS AND METHODS: Leukocyte DNA was collected and genotyping of the CAG repeat polymorphism was performed using a PCR-based direct sequencing method. Risk ratios were calculated for developing biochemical recurrence for patients associated with an allele length of </= 18 CAG repeats, compared with patients with an allele length of >18 CAG repeats, controlling for grade, stage and serum PSA level at diagnosis using Cox proportional hazard modeling. RESULTS: Overall, the CAG repeat allele was not predictive of recurrence; tumor grade, stage and PSA level at diagnosis were the only predictors of recurrence in a multivariate analysis. However, for patients at low risk for recurrence (Gleason score 2 to 6, stage pT2, and PSA </= 10 ng./ml.), the relative risk of recurrence associated with an allele of </= 18 CAG repeats was 8.07 (95% C.I., 2.02 to 32.2, p = 0.004), compared with patients with an allele length of >18 CAG repeats. In contrast, for patients at high risk of recurrence (Gleason score >/= 7, stage pT3/4, or PSA >10 ng./ml.), the relative risk associated with the </= 18 CAG repeat allele was 0.72 (95% C.I., 0.33 to 1.57, p = 0.41), compared with patients with the >18 CAG repeat allele. CONCLUSIONS: The length of the CAG repeat polymorphism of the androgen receptor gene may be important for prostate cancer recurrence among patients who are otherwise at low risk for recurrence after radical prostatectomy. These findings have potential implications for patient selection for adjuvant treatment, and for the development of novel treatments.

Alleles↗

PubMed1999

Radiation exposure to children during coil occlusion of the patent ductus arteriosus.

The risks of excessive exposure to ionizing radiation are well described and measures are routinely taken to limit such exposure to both patient and personnel in the catheterization laboratory. Coll occlusion of the patent ductus arteriosus (PDA) as well as other more complex pediatric interventions has raised concern regarding radiation exposure, particularly as minimally invasive surgical techniques are being developed which lack such exposure risk. In eight consecutive patients, aged 0.7-7 years (median, 2.3 years), coil occlusion of a PDA was performed and surface entrance radiation dose determined by thermoluminescent dosimetry (TD). Total cumulative doses (PA + lateral dose) were also calculated for each patient. Entrance and cumulative dose was likewise measured in 12 patients undergoing standard diagnostic catheterization (DC) and in 5 consecutive patients undergoing pulmonary balloon valvuloplasty (PBV). The groups were comparable in age, weight, and body surface area (BSA). Total cumulative dose in the PDA patients was 97 +/- 25 mGy (mean +/- SE). There was no significant difference between the three groups in entrance dose absorbed at each location or in total cumulative dose. The mean total fluoroscopy time in the PDA occlusion group was significantly less than that of the PBV group (10.1 +/- 1.81 min vs. 19.3 +/- 2.29 min, P < 0.05) but was comparable to the DC group (13.2 +/- 1.5 min, P = NS). When the subjects were analyzed collectively, no correlation between fluoroscopy time and measured entrance dose was observed. The strongest correlates of total cumulative dose were patient weight (r = 0.67, P < 0.001) and BSA (r = 0.62, P = 0.001). Patients undergoing coil occlusion of a PDA are not exposed to increased radiation entrance dose compared to those undergoing standard DC and PBV. Furthermore, surface entrance radiation dose as determined by TD varies according to patient size for a given fluoroscopy time.

Body Height↗

PubMed1999

P300 scalp amplitude distribution as an index of deception in a simulated cognitive deficit model.

Truth-telling (Truth) and simulated malingering (Malinger) groups were tested in a matching-to-sample procedure in which each sample three-digit number was followed by a series of nine test numbers, only one of which matched the sample. P300 was recorded during test-number presentation. Group analyses revealed differences between the P300s of the groups in unscaled amplitude, but not latency, in response to match and mismatch stimuli. P300 amplitudes at Fz, Cz, and Pz were scaled to remove possible confounding effects of amplitude in tests of the interactions of site with other variables. Significant interactions of both stimulus-type (match vs. mismatch) and group (Truth vs. Malinger) with site were obtained. Within the Malinger group, a significant interaction was obtained (scaled data) between site and response type (honest vs. dishonest). These interactions suggest that deceptive and honest responding are associated with different neurogenerator sets or different sets of P300-overlapping components. In within-individual analyses, 100% of the Truth participants and 87% of the Malinger participants were found to have larger P300 responses at Pz to match stimuli than to mismatch stimuli on the basis of intra-individual bootstrap tests. This represents an improvement in comparison with our related, previous report on a matching-to-sample test using only one test stimulus per sample.

Adolescent↗

PubMed1999

GM gene flow.

Explore the source record for details and available documents.

Agriculture↗

PubMed1999

A comparison of bitemark injuries between fatal wolf and domestic dog attacks.

Bitemark patterns in adult human victims following a fatal wolf pack attack and a domestic dog pack attack are compared. Both victims exhibited a concentration of wounds to the extremities, left and right torso, but not to the groin or internal organs. The neck and face of the domestic dog attack victim were primary sites of attack while the feral wolf pack victim was spared damage to the neck, but had facial tissue destroyed postmortem. Most punctures were found on the ventral aspect of the domestic victim and dorsal aspect of the feral victim. It is speculated that most wounds were attributable to dominant animals of both packs and in both victims and this suggests a co-ordination of activity between. Differences in bitemark patterns may well have been caused in part by differences in genetics, training, breeding, socialization and impetus of attack between wolves and dogs. Distinct differences in bitemark patterns were found in these two human victims of a wolf and domestic dog attacks.

Adult↗

PubMed1998

P300 correlates of simulated malingered amnesia in a matching-to-sample task: topographic analyses of deception versus truthtelling responses.

Two experiments using a P300-enhanced Forced Choice Procedure (P3FCP) investigated simulated amnesia in a matching-to-sample task. In Experiment 1, successful manipulation of subjects towards different behavioral hit rates (75-80% vs. 85-90%) did not adversely affect the diagnostic sensitivity of match-mismatch Pz-P300 amplitude analyses, allowing detection of 69% of simulators. P300 amplitudes of simulators (Malinger group) were as large as those of truth-tellers (truth group, a control), indicating no dual task-related (Malingering) reduction across different behavioral hit rates. Experiment 2 found no main effect of oddball type, match vs. mismatch, on P300 (P3) amplitude with a mismatch-rare variant of the P3FCP. This study also revealed larger Pz-P3s in the Malingering (vs. Truth-telling) condition. Subsequent topographic analyses suggested different Truth and Malinger scaled P3 amplitude topographies in both these sets of P3FCP data and in those from a previous autobiographical memory paradigm. Further analysis yielded preliminary evidence for a common deception-related P3 amplitude topography across different paradigms/conditions.

Adult↗

PubMed1996

The Internet: an essential tool for college health networking.

With the advent of the Internet, college health professionals have available to them a new setting in which to network. The Internet provides opportunities for immediate communication with a large and diverse community of colleagues. Through both the Student Health Service (SHS) Discussion Group and numerous health-related databases, the Internet serves as a powerful research tool for program development and improvement. Answers to queries about practice options, solutions for local problems, and support of innovative policies can be received almost instantaneously from college health professionals from across the United States and Canada. In this article, the authors summarize the history and current use of the SHS Discussion Group, provide a brief overview of Internet basics, and identify more advanced uses of the Internet by college health professionals.

Computer Communication Networks↗

PubMed1996

The effect of co-administration of zolpidem with fluoxetine: pharmacokinetics and pharmacodynamics.

Since early treatment of depression with Selective Serotonin Reuptake Inhibitor (SSRI) can be associated with insomnia, daytime antidepressive therapy with SSRI is often combined with nighttime administration of a hypnotic. This study attempted to evaluate the pharmacokinetic and pharmacodynamic interactions between zolpidem 10 mg, a short-acting hypnotic, and fluoxetine 20 mg, an SSRI. Twenty-seven healthy male volunteers (mean age 23.5 years, range 20 - 29) received zolpidem and fluoxetine in the following open design: zolpidem on night 1, a morning dose of fluoxetine daily from day 2 through day 18 and zolpidem on night 18. Using HPLC, plasma levels of zolpidem, fluoxetine, and norfluoxetine were determined throughout night 1 for zolpidem, night 18 for zolpidem, fluoxetine, and norfluoxetine on days 16 and 17 for fluoxetine and norfluoxetine. Morning psychomotor tests were performed on days 1, 2, 18, and 19. Statistical analysis of data consisted of repeated measures of ANOVA. There was no significant difference in AUC, C(max), and T1/2 of zolpidem plasma concentrations between night 1 (zolpidem) and night 18 (zolpidem and fluoxetine). There was a significantly higher zolpidem plasma level at 0.5 hours after dosing together with a significantly shorter T(max) on night 18 compared to night 1. There was no significant difference in C(min) of plasma fluoxetine and norfluoxetine levels between day 16 and 17 of fluoxetine dosing, and there was no difference in T(max) between day 17 (fluoxetine) and day 18 (fluoxetine and zolpidem). There was a 3 - 4% increase in AUC and C(max) of fluoxetine and norfluoxetine plasma concentrations in the presence of zolpidem. There was no difference in the next morning performance tests after nighttime treatment of zolpidem alone after 17 consecutive days of fluoxetine treatment, or after zolpidem in the presence of steady-state plasma concentrations of fluoxetine. Both zolpidem and fluoxetine were well tolerated alone or in combination. It is concluded that the onset of action of zolpidem may possibly be shortened in the presence of fluoxetine, but no other significant pharmacokinetic or pharmacodynamic interactions occurred between zolpidem and fluoxetine.

Adult↗

PubMed1995

Detecting simulated amnesia with event-related brain potentials.

Two experiments were done in which groups of normal college undergraduate subjects were instructed to simulate autobiographical amnesia related to head injury. The subjects were tested for autobiographical knowledge with pencil-and-paper recall and recognition tasks, and on another day, with recognition tasks in which event-related potentials were recorded in response to the same autobiographical items, this time presented on a display screen. In the first study, three Event-Related Potential (ERP) block types were utilized: 1) a block in which the subject's birthdate was an oddball with p = 0.11 and other dates (not relevant to the subject) had p = 0.89, 2) a block in which phone numbers were used as stimuli, and 3) a block in which (mothers' maiden) names were used as stimuli. Only birthdate blocks were used in the second study. A P300 ERP was seen in response to rare, personally relevant items. In both studies, the main effect of stimulus type (personally relevant versus not personally relevant) on P300 amplitude was significant (p < 0.0001) and there was no main effect of block type in the first study. Under a sophisticated malingering instruction set, about 15% of the items were correctly recalled and about 50% were correctly recognized by simulators in pencil-and-paper tests. Under a naive malingering instruction set, most simulating subjects failed to recall and recognize autobiographical items. In the first study, an arbitrarily but a priori derived discrimination criterion based on a subject's average P300 amplitude afforded 92% correct discrimination of simulating individual subjects for birthdates and phone numbers. The value was 77% for mothers' maiden names. The same criterion applied to the single birthdate block in the second study yielded 93% correct discrimination. The results suggest the P300 may be useful in detection of malingered amnesia.

Amnesia↗

PubMed1995

Potential underdosing with the use of electron beam therapy in patients with cervical adenopathy and advanced head and neck cancer.

To define the adequacy of electron beam therapy in the treatment of N1-N3 head and neck cancer, 24 patients with primary head and neck cancers and N1-N3 cervical adenopathy received primary radiation therapy with or without chemotherapy for definitive control of their disease. All patients underwent computerized tomography (CT) to assist in the design of treatment to the posterior neck with electron beams after photon therapy to the level of spinal cord tolerance. Treatment with electrons to the posterior neck in patients with N1 disease was adequate in 92% (11/12) of patients. However, in patients with N2 and N3 disease, electron beam treatment failed, because of spinal cord tolerance problems, to cover the disease adequately in 92% (11/12). It is concluded that CT should be employed routinely in patients with N1-N3 neck disease to determine the proper electron energy prescription. For some patients, electron beam may not be appropriate, making it necessary to use individual planning to treat adequately the neck disease and avoid the spinal cord.

Electrons↗

PubMed1994

Potential underdosing with the use of electron-beam therapy in patients with cervical adenopathy and advanced head and neck cancer.

To define the adequacy of electron-beam therapy in the treatment of N1-N3 head and neck cancer, 24 patients with primary head and neck cancers and N1-N3 cervical adenopathy received primary radiation therapy with or without chemotherapy for definitive control of their disease. All patients underwent computerized tomography (CT) to assist in the design of treatment to the posterior neck with electron beams after photon therapy to the level of spinal cord tolerance. Treatment with electrons to the posterior neck in patients with N1 disease was adequate in 92% (11/12) of patients. However, in patients with N2/N3 disease, electron beam failed, because of spinal-cord tolerance problems, to adequately cover disease in 92% (11/12). It is concluded that CT should be routinely employed in patients with N1-N3 neck disease to determine the proper electron-energy prescription. For some patients, electron beam may not be appropriate, making it necessary to use individual planning to treat adequately the neck disease and avoid the spinal cord.

Electrons↗

PubMed1992

Purification and characterization of Epstein-Barr virus gp340/220 produced by a bovine papillomavirus virus expression vector system.

Our initial results with a bovine papilloma virus (BPV) vector expression system indicated that we could produce significant amounts of Epstein-Barr virus (EBV) gp340/220 in the supernatant of a mouse fibroblast cell line. We have now extended these findings to show that the truncated version of gp340/220, where the membrane anchor sequence is deleted, is produced even after extended passage of the cells, at a level of approximately 1 mg/4 x 10(8) cells. A simple purification protocol using Sephacryl S300HR and gelatin agarose gives a product which is greater than 90% pure. This product is recognized by anti-gp340 monoclonal antibodies from five different epitope groups and induces antibody that recognizes the authentic gp340/220 and neutralizes EBV in vitro. The purified gp340/220 can be used in ELISA and stimulates the proliferation of T-cell clones specific for gp340/220. These characteristics, together with the fact that BPV-transformed lines have been utilized for the production of pharmaceuticals for use in humans, suggest that this gp340/220 is suitable as a source of antigen for vaccination to prevent EBV infection and related diseases.

Animals↗