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J A Jensen

Publications and source records attributed to J A Jensen.

At least 19 recordsLinked to original sources
PubMed1999

Quantitation of urinary metabolites of a tobacco-specific lung carcinogen after smoking cessation.

We quantified urinary levels of two metabolites of the tobacco-specific lung carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) in people who had stopped smoking: 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) and its O-glucuronide, 4-[(methylnitrosamino)-1-(3-pyridyl)but-1-yl]-beta-O-D-glucosiduronic acid (NNAL-Gluc). Twenty-seven people completed the study. Thirteen used the nicotine patch starting at the quit date, whereas the others used no patch. Two 24-h urine samples were collected on 2 consecutive days before smoking cessation; blood was also obtained. Beginning at their quit date, subjects provided 24-h urine samples on days 7, 21, 42, 70, 98, and 126, and some subjects also provided samples at later times. The urine was analyzed for NNAL, NNAL-Gluc, nicotine plus nicotine-N-glucuronide, and cotinine plus cotinine-N-glucuronide. Some blood samples were also analyzed for NNAL. The decline of urinary NNAL and NNAL-Gluc after smoking cessation was much slower than expected. This was clearly demonstrated by comparison with cotinine and nicotine levels in urine. One week after smoking cessation, 34.5% of baseline NNAL plus NNAL-Gluc was detected in urine, whereas the corresponding values for cotinine and nicotine were 1.1 and 0.5%, respectively. Even 6 weeks after cessation, 7.6% of the original levels of NNAL plus NNAL-Gluc remained. In some subjects, NNAL plus NNAL-Gluc were detected 281 days after cessation. The distribution half-life for NNAL and NNAL-Gluc was 3-4 days, whereas the elimination half-life was 40-45 days. Total body clearance of NNAL was estimated to be 61.4 +/- 35.4 ml/min, and volume of distribution in the beta-phase was estimated to be 3800 +/- 2100 liters, indicating substantial distribution into the tissues. Parallel studies in rats treated chronically or acutely with NNK in the drinking water support the conclusion that NNAL has a large volume of distribution. There was no effect of the nicotine patch on levels of NNAL plus NNAL-Gluc, indicating that NNK is not formed endogenously from nicotine. The results of this study demonstrate that NNAL and NNAL-Gluc are slowly cleared from the body after smoking cessation, indicating the presence of a high-affinity compartment where NNK, NNAL, and/or NNAL-Gluc are retained or sequestered and slowly released.

Adult↗
PubMed1997

Wound tissue oxygen tension predicts the risk of wound infection in surgical patients.

OBJECTIVE: To test the hypothesis that subcutaneous wound oxygen tension (PsqO2) has a predictive relation to the development of wound infection in surgical patients. DESIGN: A noninterventional, prospective study. SETTING: A university department of surgery. PATIENTS: One hundred thirty operative general surgical patients at notable risk of infection as predicted by an anticipated Study on the Effect of Nosocomial Infection Control (SENIC) score of 1 or greater. OUTCOME MEASURES: PsqO2 was measured perioperatively. Its relation to the subsequent incidence of surgical wound infection was then determined and compared with the SENIC score as a criterion standard. RESULTS: Although the SENIC score and PsqO2 are inversely correlated, PsqO2 is the stronger predictor of infection. Low PsqO2 identified patients at risk and concentrated them in a cohort that was about half the size of that identified by the SENIC score. CONCLUSIONS: Subcutaneous perfusion and oxygenation are important components of immunity to wound infections. The SENIC score identifies systemic physiological variables that are important to the development of wound infection. Nevertheless, PsqO2 is the more powerful predictor of wound infection. Moreover, PsqO2 can be manipulated by available clinical means, and thus may direct interventions to prevent infection.

Adult↗
PubMed1996

Cytologic features of clear cell carcinoma of the urethra and urinary bladder.

Clear cell carcinoma (CCL) arising in the lower urinary tract is unusual and we report the cytohistologic findings of three cases retrieved from our files. All patients presented with bleeding, and the tumors were localized in either the urethra or bladder base. Filter and cytocentrifuge preparations of the urine were studied and all cases displayed numerous scattered aggregates or single tumor cells in an inflammatory background. The enlarged cells had abundant clear, wispy cytoplasm with discrete vacuolation. Hobnail and signet ring cells were apparent. The nuclei had granular to vesicular chromatin with prominent often multiple nucleoli. The tumors were histologically distinctive and typically had a tubulocystic configuration with varying proportions of papillary and diffuse patterns. One patient has died of metastatic cancer and two are presently free of tumor. The cytohistologic features of this cancer are characteristic and from our review we conclude that this lesion can be diagnosed by cytologic means.

Adenocarcinoma, Clear Cell↗
PubMed1996

Breast conservation therapy after augmentation mammaplasty: is it appropriate?

Breast conservation therapy, consisting of lumpectomy, axillary node dissection, whole-breast irradiation, and a boost to the tumor bed, is an increasingly popular option for the treatment of breast cancer. Among patients with stage I and stage II disease, breast conservation therapy yields survival rates equivalent to those for mastectomy. The cosmetic results of radiotherapy are usually good, and this approach preserves an intact, sensate breast. Most studies on breast conservation therapy, however, have been performed in nonaugmented patients. Relatively little has been published regarding breast conservation therapy in the presence of silicone implants. Between 1981 and 1994, we treated 33 augmented patients with breast conservation therapy. Among 26 individuals for whom complete follow-up data were available, 17 (65 percent) developed significant capsular contracture on the irradiated side. Thus far 8 patients with radiation-induced contracture have undergone corrective surgery. In our experience, augmented breast cancer patients treated with breast conservation therapy have less satisfactory cosmetic results than nonaugmented women. In addition, mammographic follow-up, critical for identifying local recurrence, may be impaired by the presence of an implant and capsular contracture. On the basis of these considerations, breast conservation therapy may be less than optimal in augmented cancer patients unless explantation is performed before treatment.

Adult↗
PubMed1995

Pulmonary lymphoma in cardiac transplant patients treated with OKT3 for rejection: diagnosis by fine-needle aspiration.

At Hines VA Hospital, three out of 38 cardiac transplant patients, who were 9, 10, and 14 mo post-surgery and treated with immunosuppressive drugs, including OKT3 prophylaxis for acute rejection, developed a solitary pulmonary nodule. Fine-needle aspiration biopsy of the nodules in these three patients revealed a hypercellular, monotonous population of large lymphoid cells. These abnormal cells were isolated, with small aggregates occasionally seen. The nuclear membranes were irregular, the chromatin was finely granular, nucleoli were prominent, and mitotic figures were frequently noted. The cells were immunoreactive to leukocyte common antigen and B-lymphocyte. Lambda light chain immunoglobulin was positive in one case, kappa in the second case, and neither light chains in the third patient. By electron microscopy in one case, the cells were large immature lymphoid cells with immunoblastic features. Subsequent tissue studies, complemented by frozen section immunostaining, flow cytometry, and phenotyping, reaffirmed the diagnosis of malignant lymphoma. It appears that OKT3 therapy increases several fold the risk of lymphoma's developing in cardiac transplant patients. Preliminary published reports have also recommended close surveillance of patients receiving OKT3 for early indications of lymphoproliferative disorder and a reevaluation of the risk vs. benefit for the prophylatic use of OKT3.

Adult↗
PubMed1995

Extended skin island delay of the unipedicle TRAM flap: experience in 35 patients.

A technique to surgically delay a single-pedicle TRAM flap is described. This extended skin island delay essentially divides the unipedicle TRAM flap into two stages separated by 1 week. Experience with this flap in 35 patients is reported. On the basis of this experience, we believe that the extended skin island delayed TRAM flap should be considered a safe and reliable alternative to double muscle pedicle and free tissue transfer in high-risk patients.

Abdominal Muscles↗
PubMed1995

The fate of breast implants: a critical analysis of complications and outcomes.

Complications and outcomes were monitored following the implantation of 1655 breast implants over a 15-year period. Smooth, polyurethane, and textured implants were used in a variety of clinical settings. The time course of capsular contracture was analyzed by the Kaplan-Meier method. Regardless of implant type or indication for surgery, the probability of contracture increased with time. Polyurethane-covered implants were associated with a significant reduction in the risk of contracture for at least 7 years following implantation. Smooth and textured silicone implants had contracture rates similar to each other, and the particular type of surface texturing (Biocel versus Siltex) was of no consequence. Contracture was more common following breast reconstruction and implant replacement than after augmentation mammaplasty and was not affected by filler material or implant size. Implant position did not alter the risk of contracture after augmentation; tissue expansion did not affect the risk of contracture after breast reconstruction. Infections were unusual but most common after reconstruction and unrelated to surface texture or filler material. Skin wrinkling was more frequent with saline implants and in the presence of surface texturing. Implant rupture was rare, with an incidence of 1 per 760 implant-years. Implant-associated connective-tissue disease was noted in only one individual, an incidence of 1 per 3801 implant-years.

Breast Implants↗
PubMed1994

Artifacts in blood velocity estimation using ultrasound and cross-correlation.

Estimation of blood velocities using ultrasound and time-domain cross-correlation is investigated. The measurement principle is introduced, and the basic properties of the cross-correlation function are discussed. Expressions for the variance of the estimates of the peak location are given, showing the influence of integration time, transducer bandwidth and signal-to-noise ratio. It is also shown that the technique can be implemented using only the sign of the signals. A simple simulation program is used in order to study the exact influence from the different parameters. Using the program, it is shown that any velocity can result from the estimation with a certain probability regardless of the true velocity, when the signal-to-noise ratio is low. This is due to the non-linear estimation technique employed and shows that estimation variance yields little information for this estimator. Graphs are given for the probability of correct estimation, when the different parameters are varied.

Blood Flow Velocity↗
PubMed1994

Nonparametric estimation of ultrasound pulses.

An algorithm for nonparametric estimation of 1-D ultrasound pulses in echo sequences from human tissues is derived. The technique is a variation of the homomorphic filtering technique using the real cepstrum, and the underlying basis of the method is explained. The algorithm exploits a priori knowledge about the structure of rf line echo data and can employ a number of adjacent rf lines from an image. The prime application of the algorithm is to yield a pulse suitable for deconvolution algorithms. This will enable these algorithms to properly take into account the frequency dependence of the attenuation and its variation within a patient and among patients. It is also possible to use the estimated pulse for attenuation estimation, and the consistency of the assumptions underlying the proposed technique is demonstrated by its ability to recover low variance attenuation estimates in the normal liver from in vivo pulse-echo data. Estimates are given for eight different patients.

Adult↗
PubMed1994

Two-dimensional random arrays for real time volumetric imaging.

Two-dimensional arrays are necessary for a variety of ultrasonic imaging techniques, including elevation focusing, 2-D phase aberration correction, and real time volumetric imaging. In order to reduce system cost and complexity, sparse 2-D arrays have been considered with element geometries selected ad hoc, by algorithm, or by random process. Two random sparse array geometries and a sparse array with a Mills cross receive pattern were simulated and compared to a fully sampled aperture with the same overall dimensions. The sparse arrays were designed to the constraints of the Duke University real time volumetric imaging system, which employs a wide transmit beam and receive mode parallel processing to increase image frame rate. Depth-of-field comparisons were made from simulated on-axis and off-axis beamplots at ranges from 30 to 160 mm for both coaxial and offset transmit and receive beams. A random array with Gaussian distribution of transmitters and uniform distribution of receivers was found to have better resolution and depth-of-field than both a Mills cross array and a random array with uniform distribution of both transmit and receive elements. The Gaussian random array was constructed and experimental system response measurements were made at several ranges. Comparisons of B-scan images of a tissue mimicking phantom show improvement in resolution and depth-of-field consistent with simulation results.

Ultrasonography↗
PubMed1994

Estimation of in vivo pulses in medical ultrasound.

An algorithm for the estimation of one-dimensional in-vivo ultrasound pulses is derived. The routine estimates a set of ARMA parameters describing the pulse and uses data from a number of adjacent rf lines. Using multiple lines results in a decrease in variance on the estimated parameters and significantly reduces the risk of terminating the algorithm at a local minimum. Examples from use on synthetic data confirms the reduction in variance and increased chance of successful minimization termination. Simulations are also reported indicating the relation between the one-dimensional pulse and the three-dimensional, attenuated ultrasoud field for a concave transducer. Pulses are estimated from in-vivo liver data showing good resemblance to a pulse measured as the response from a planar reflector and then properly attenuated. The main application for the algorithm is to function as a preprocessing stage for deconvolution algorithms using parametric pulses.

Ultrasonography↗
PubMed1993

Range/velocity limitations for time-domain blood velocity estimation.

The traditional range/velocity limitation for blood velocity estimation systems using ultrasound is elucidated. It is stated that the equation is a property of the estimator used, not the actual physical measurement situation, as higher velocities can be estimated by the time domain cross-correlation approach. It is demonstrated that the time domain technique under certain measurement conditions will yield unsatisfactory results, when trying to estimate high velocities. Various methods to avoid these artifacts using temporal and spatial clustering techniques are suggested. The improvement in probability of correct detection is derived, and several examples of simulations are shown.

Artifacts↗
PubMed1993

A software program for exchanging MR data.

In an MR multicenter project, data exchange is a problem because most MR scanners do not use the same data format or have data export facilities. In the COMAC-BME Concerted Action on Tissue Characterization by MRS and MRI, a subgroup of seven MR centers had a need for data exchange in the form of digital MR images of the human brain. Because there was no common data format, software package was developed for data exchange. This article describes the basic features of the developed software. The software package was written in the language of C and was successfully tested on an IBM-6150 UNIX workstation. The software is currently being tested on the following series of UNIX workstations: SUN SPARC, IBM RS6000, and HP 9000/700.

Animals↗
PubMed1993

Knowledge, concern, and satisfaction among augmentation mammaplasty patients.

Eighty-five patients with augmentation mammaplasty were surveyed. Patients were polled about knowledge of risks, level of concern, awareness of media publicity, incidence of complications, and degree of satisfaction with breast implants. Sixty-one percent of the patients were satisfied or very satisfied with implants, whereas 32% were somewhat or very unsatisfied. Level of satisfaction was not related to knowledge of risks, but did correlate with having experienced side effects or complications. Virtually all patients were aware of recent media publicity about implants, and 90% of women perceived the publicity to be negative. Seventy-five percent of the patients expressed concern about implant safety. Even after exposure to negative publicity, however, < 10% of those surveyed regret having had the surgery and only 6% indicated they would like their implants removed. Overall, patients with augmentation mammaplasty perceive the benefits of implants greatly outweigh the risks.

Adult↗