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Biomedical subjects

L Harrison

Publications and source records attributed to L Harrison.

At least 73 records · Page 4Linked to original sources
PubMed1997

Introduction--the validity of self-reported drug use: improving the accuracy of survey estimates.

Measuring levels and patterns of illicit drug use, their correlates, and related behaviors requires the use of self-report methods. However, the validity of self-reported data on sensitive and highly stigmatized behaviors such as drug use has been questioned. The goal of this monograph is to review current and cutting-edge research on the validity of self-reported drug use and to describe methodological advances designed to reduce total error in estimates of drug use and quantify sources of nonsampling error. This monograph reviews a number of studies that use some presumably more accurate measure of drug use to validate self-reported use. In addition, evolving methods to improve a wide variety of procedures used in survey designs are explored, including computer-assisted interviewing, predictors of response propensity, measurement error models, and improved prevalence estimation techniques. Experimental manipulations of various survey conditions and situational factors also show promise in improving the validity of drug prevalence estimates in self-report surveys.

Computers↗
PubMed1997

The validity of self-reported drug use in survey research: an overview and critique of research methods.

Since illicit drug use is by definition illegal, the tasks of measuring incidence and prevalence and charting the course of the epidemic have fallen to survey researchers over the past 30 years. Although survey methods have obvious advantages over indirect measures such as arrests, seizures, and treatment admissions, they are frequently criticized because the rely on valid self-reporting of sensitive and highly stigmatized behavior. Validation studies conducted before the mid-1980s involving known samples of drug users or urinalysis techniques suggested that drug use was fairly accurately reported in self-report surveys. However, more recent validation studies conducted with criminal justice and former treatment clients using improved urinalysis techniques and hair analyses demonstrate that self-report methods miss a lot of recent drug use. A review of the research literature suggests that neither self-reports nor bioassays are wholly accurate, and both have inherent problems. However, because self-report measures are necessary to understand the complexity of causal and correlational attributes of drug abuse, it is necessary to determine what can be done to improve valid self-reporting. This chapter examines the research literature on validation studies to provide an overview of what is known about the accuracy of self-reported drug use.

Health Surveys↗
PubMed1997

Co-activation of the hamstrings and quadriceps during the lunge exercise.

The anterior lunge exercise is a closed chain kinetic exercise that has been developed to improve the function of the lower limb and to strengthen the hamstrings and quadriceps, simultaneously. In this study, a three-dimensional biomechanical analysis of this exercise was conducted in order to understand the mechanics of this rehabilitation activity. Experimental conditions were recorded using an active optoelectronic kinematic data capture system (OPTOTRAK), two force plates (AMTI) and electromyography (EMG). Data were collected from healthy male subjects while performing several lunges. When the distance between the toe of the rear leg and the heel of the front leg (lunging distance) was maximum, a large net flexion moment was predicted in the front leg in the extented position. This moment was reversed to a large net extension moment in the flexed position. A large increase in the net extension moment in the rear leg was also predicted as the front knee was bent from 5 degrees to 90 degrees of flexion. These data suggest that quadriceps and hamstring muscles co-contraction occur during a maximum lunge in the front leg when it is in the flexed position.

Biomechanical Phenomena↗
PubMed1997

Knee kinematics in-vivo of kneeling in deep flexion examined by bi-planar radiographs.

Squatting and kneeling are important daily activities for Middle and Far East cultures that require positioning the knee in deep flexion. In these activities, the limb becomes fully flexed with a knee flexion angle reaching between 150 and 160 degrees and the heel reaching the posterior surface of the upper thigh. Existing knee prostheses do not allow a full return to normal activities for this large population since they are limited to achieving knee flexion of about 120 degrees. Also, there is very limited information on knee kinematics and/or forces in the range beyond 120 degrees. The purpose of this study is to describe the kinematics of normal knees in-vivo, assessed in deep flexion, using bi-planar radiographs. A-P and lateral views were obtained from 5 healthy subjects during three sequential positions of kneeling. In the 1st position, the subject knelt with the knees fully flexed (deep flexion between 150 degrees and 160 degrees) and torso upright. In the 2nd position, the subject bowed forward to an intermediate position (about 120 degrees of knee flexion). In the 3rd position, the subject bowed further until his/her head touched the floor, supporting the upper torso with hands and attaining a knee flexion of about 90 degrees. The results show that past 135 degrees of knee flexion, the patella was found to clear the femoral groove and was in contact only with the condyles. The results also show that the classical femoral "roll back" does not appear to occur in deep flexion. It seems that the lateral femoral condyle rolls over the postero medial aspect of the lateral tibial plateau while contact of the medial femoral condyle occurs more anteriorly, but still in the posterior aspect of the medial tibial plateau. This asymmetric rolling motion implies an element of internal tibial rotation. Furthermore, the tibia was found to articulate with the femur at the most proximal points of the condyles in deep flexion. These data on the kinematics and contact characteristics of the tibio-femoral joint must be considered in any approach to design for a Deep Flexion Knee Implant.

Biomechanical Phenomena↗
PubMed1996

Low risk of perioperative infection without prophylactic antibiotics for transperineal prostate brachytherapy.

PURPOSE: To determine the incidence of postimplant infection in patients who are not given prophylactic antibiotics (ATBs). METHODS AND MATERIALS: One hundred thirty-one patients had computerized tomography (CT)-planned transperineal 125I implantation of the prostate from 1988 through 1995. One hundred fourteen of the patients did not receive prophylactic ATBs, 19 of whom required postimplant Foley catheter drainage for 1 day or more for acute urinary retention. RESULTS: The incidence of postimplant febrile episodes within 2 weeks of surgery among the patients who had not received prophylactic ATBs was 2 of 114 (2%). One of the two patients who developed postimplantation febrile episodes was treated successfully with ATBs as an outpatient. The second patient, who had a history of chronic lymphocytic leukemia (CLL) and immune suppression, developed E. coli sepsis and required intravenous antibiotics. Of 17 patients who received prophylactic ATBs, none had a postoperative febrile episode. CONCLUSION: We continue to refrain from routinely prescribing prophylactic ATBs unless there is some compelling circumstance including rheumatic heart disease, prosthetic devices, immune compromise, or a previous history of prostatitis.

Aged↗
PubMed1996

Reliability of the international normalized ratio for monitoring the induction phase of warfarin: comparison with the prothrombin time ratio.

The International Normalized Ratio (INR) was introduced to reduce the variability of prothrombin time (PT) reporting. One potential problem with the use of the INR is the assumption that its reliability is reduced when it is used to monitor patients during the induction phase of treatment. This shortcoming arises because the model used to establish the INR system is based on the use of pooled plasma from patients stabilized on warfarin for at least 6 weeks. Because the prolongation of the PT by warfarin during the induction phase mainly reflects reduction in factor VII levels (whereas the prolongation of the PT after 6 weeks of stabilization reflects reductions in factors X, II, and VII), there exists a potential for loss of accuracy of the INR during warfarin induction. To overcome this potential problem, it has been suggested that the PT ratio should be used to report results during the induction phase of treatment and that the INR system should be reserved for reporting results after the patient has been stabilized. This approach is confusing to the clinician. In addition, the validity of this approach has never been demonstrated in a clinical study. To address this issue, we studied 43 patients for the first 5 days after they started warfarin therapy. We measured the PT in the same plasma samples from each patient with five different commercial thromboplastins. The variance in the PT ratios among the five thromboplastins was compared with the variance obtained with the INR values derived from the PT ratios when using the international sensitivity indexes provided by the manufacturer. Our results indicate that, even during the induction phase, there is less variance with the INR system than with the PT ratio system.

Anticoagulants↗
PubMed1996

Regulated expression of APE apurinic endonuclease mRNA during wound healing in porcine epidermis.

Abasic (AP) sites in DNA are cytotoxic and mutagenic and their repair is initiated by AP endonucleases. The major AP endonuclease of mammalian cells is encoded by the APE gene. Ape protein has also been proposed to modulate the activity of some transcription factors independently of its AP endonuclease activity. We investigated whether APE expression is coordinated with cell division, which could diminish mutagenesis. The level of APE mRNA was followed during wound healing in porcine epidermis, in which surgical wounding prompts rapid cell proliferation followed by a differentiation program to regenerate normal skin. In situ hybridization with a probe from human APE cDNA revealed strongly decreased expression in rapidly proliferating migrating cells during the first 1-3 days following wounding, succeeded by sharply increased APE expression that exceeded the pre-wounding levels by days 9-17. These changes were not observed in the surrounding undamaged tissue. In contrast to the foregoing in vivo results, APE expression in cultured primary human fibroblasts (IMR90) or myeloid leukemia cells (K562) was not coordinated with cell division. This biphasic APE expression during wound healing could relate to transcription factor regulation or it could allow unhindered DNA synthesis or prepare the developing epidermis to handle DNA damage. However, if transient under-expression of APE-encoded repair enzyme does occur, it might render regenerating skin especially vulnerable to mutagenesis during the cell proliferation phase.

Animals↗
PubMed1996

Validation of catheter semiquantitative culture technique for nonstaphylococcal organisms.

The catheter semiquantitative culture roll tip technique has been validated as a discriminator between non-catheter-related bacteremias and catheter-related bacteremias (CRBs) caused by Staphylococcus species. However, this technique has not been specifically validated when used for the evaluation of catheters infected with organisms other than staphylococci. We reviewed catheters that had been submitted for semiquantitative roll tip culture as well as hospital records to determine clinical correlates of infection. Local infection and CRB were defined by standard criteria. Catheter-related sepsis (CRS) was defined as fever, leukocytosis, or hypotension which resolved with catheter removal, without another source of infection. For 195 catheters from 93 patients, gram-negative rods and enterococci were present on 36, fungi were on 25, Corynebacterium species were on 5, Bacillus species were on 3, Staphylococcus species were on 79, and 41 demonstrated no growth. Of 21 episodes of CRB or CRS due to nonstaphylococcal organisms, only 1 (questionable) episode was due to a catheter with < 15 CFU (P < 0.05). Eleven of these 21 episodes of CRB or CRS were due to gram-negative rods and enterococci, of which only the questionable episode was due to a catheter with < 15 CFU. Nine of these 21 episodes of CRB or CRS were due to fungi, none of which were associated with a catheter with < 15 CFU. The data for Staphylococcus species recapitulated published data (none of 21 CRB or CRS episodes were associated with catheters with < 15 CFU) and validated this retrospective technique. The data presented in this study validate the use of the semiquantitative culture technique for the evaluation of catheter-related infections caused by organisms other than staphylococci.

Bacteremia↗
PubMed1996

Tumor control and morbidity following transperineal iodine 125 implantation for stage T1/T2 prostatic carcinoma.

PURPOSE: To quantify disease progression and morbidity following computer tomography (CT)-based transperineal iodine 125 prostate implantation. METHODS: Ninety-two patients with clinical stage T1 or T2, Gleason score 2 to 7/10, prostatic carcinoma had outpatient, CT-based transperineal 125I prostate implantation and were monitored for 1 to 7 years (median, 3). The prescribed minimum radiation dose was 140 to 160 Gy. Lymph node dissection and postimplantation prostatic biopsies were not routinely performed. RESULTS: In 46% of patients, radiation-related urinary symptoms were substantial enough at 1 month following implantation to require medication. Radiation-related urinary symptoms gradually resolved. Two years after implantation, 14% of patients had persistent urinary symptoms of Radiation Therapy Oncology Group (RTOG) > or = grade 2. Eight percent of patients underwent a transurethral resection of the prostate (TURP) within 2 years of implantation. Five patients developed radiation-induced rectal ulcerations. Of 56 patients who were sexually potent preimplantation, 86% retained potency at 3 years. Twenty-five patients had biochemical disease progression. The overall actuarial freedom from biochemical failure rate at 4 years following implantation was 63%. In Cox proportional hazards multivariate analysis, the strongest predictor of failure was prostate-specific antigen (PSA) level less than or greater than 10 ng/mL (P = .005), followed by Gleason score (2 to 4 v 5 to 7, P = .08) and stage (T1 v T2, P = .09). CONCLUSION: The 5-year biochemical freedom-from-progression rates following transperineal 125I implantation are comparable with those achieved with prostatectomy. The morbidity has decreased with increased physician experience.

Aged↗
PubMed1996

Effects of gentle human touch on preterm infants: pilot study results.

A pilot study was conducted to evaluate the effects of gentle human touch (GHT) provided for 15 minutes a day to preterm infants from day 7 to day 12 of life. The study suggested that GHT has no adverse effects on the oxygen saturation or heart rate levels of small preterm infants and that GHT has a soothing effect as evidenced by decreased levels of active sleep, motor activity, and behavioral distress. These results can provide NICU nurses with a basis for guiding parents in their early interactions with preterm infants in the NICU.

Female↗
PubMed1995

Dosimetry guidelines to minimize urethral and rectal morbidity following transperineal I-125 prostate brachytherapy.

PURPOSE: To establish dosimetry guidelines to minimize urethral and rectal morbidity following permanent I-125 prostatic brachytherapy. METHODS AND MATERIALS: Dosimetric parameters were correlated with long-term morbidity for 65 patients following transperineal I-125 implantation for Stage T1/T2 prostatic carcinoma. The prescribed minimum prostatic dose was 150 Gy. The median total activity used was 48 mCi (range: 32-77 mCi). Patients were followed for 1-5 years (median follow-up: 2 years). Postimplant computerized tomography (CT)-based dosimetry was performed for 45 patients. Morbidity was evaluated using a modification of the RTOG grading system, with a scale of grade 0-5. RESULTS: The incidence of grades 2 and 3 urinary morbidity was associated with the maximum central urethral dose (p = 0.03), and with the length of urethra that received greater than 400 Gy (p = 0.07). Patients with larger prostates had more long-term urinary morbidity (p = 0.06). Rectal bleeding (RTOG grade 1) or ulceration (RTOG grade 2) was associated with irradiation of the rectal wall to doses in excess of 100 Gy (p = 0.02). There was no relationship between the matched peripheral dose (MPD), mCi/source or total mCi implanted and long-term morbidity. CONCLUSIONS: Postimplant, CT-based dosimetry can predict which patients are at higher risk of radiation-related morbidity. More simplistic parameters including the MPD, total activity implanted, or mCi/source, had no relationship with morbidity. To decrease the risk of long-term morbidity, an effort should be made to keep the central urethral dose below 400 Gy, and the rectal surface dose below 100 Gy.

Brachytherapy↗
PubMed1995

Characterization of the promoter region of the human apurinic endonuclease gene (APE).

Apurinic/apyrimidinic (AP) sites are mutagenic and block DNA synthesis in vitro. Repair of AP sites is initiated by AP endonucleases that cleave just 5' to the damage. We linked a 4.1-kilobase pair HindIII DNA fragment from the region upstream of the human AP endonuclease gene (APE) to the chloramphenicol acetyltransferase (CAT) gene. Deletions generated constructs containing 1.9 kilobase pairs to 50 base pairs (bp) of the APE upstream region. Transient transfection studies in HeLa cells established that the basal APE promoter is contained within a 500-bp fragment. The major transcriptional start site in HeLa, hepatoma (HepG2), and myeloid leukemic (K562) cells was mapped to a cluster of sites approximately 130 bp downstream of a putative "CCAAT box," approximately 130 bp 5' of the first splice junction in APE. Deletion of 5' sequences to within 10 bp of the CCAAT box reduced the CAT activity by only about half, and removal of the CCAAT box region left a residual promotor activity approximately 9%. Deletion to 31 bp upstream of the transcriptional start site abolished APE promoter activity. DNA sequence analysis revealed potential transcription factor recognition sites in the APE promoter. Gel mobility-shift assays showed that both human upstream factor and Sp1 can bind their respective sites in the APE promoter. However, DNase I footprinting using HeLa nuclear extract showed that the binding of Sp1 and upstream factor is blocked by the binding of other proteins to the nearby CCAAT box region.

Animals↗
PubMed1994

Short-term freedom from disease progression after I-125 prostate implantation.

PURPOSE: To evaluate short-term clinical and chemical disease progression following computed tomography (CT)-based transperineal I-125 prostate implantation. METHODS AND MATERIALS: Sixty-two patients with clinical Stage T1 or T2 prostatic carcinoma had outpatient, CT-based transperineal I-125 prostate implantation and have been followed for 6-55 months (median: 19 months). Fifty-six patients had an elevated prostate specific antigen (PSA) before implantation (> 4.0 ng/mL). Twenty patients had well-differentiated tumors, 39 were moderately differentiated, 2 were poorly differentiated, and 1 was indeterminate. A total of 32-73 mCi I-125 was implanted (median: 47 mCi). The prescribed minimum prostatic dose was 140-160 Gy, and the actual matched peripheral dose ranged from 109-258 Gy (median: 160 Gy). Lymph node dissection or postimplantation prostatic biopsies were not routinely performed. RESULTS: Of 54 patients with an elevated PSA prior to implantation and no prior hormonal treatment, 96% returned to normal within 24 months of treatment. In 85% of patients, the PSA fell below 2.0 ng/mL and in 74% of patients, the PSA value fell to below 1.0 ng/mL. Seven patients had disease progression, one of whom has an isolated, rising PSA. The actuarial rate of chemical (rising PSA) or clinical failure at 3 years following implantation was 17%. Of 38 patients who were sexually potent prior to implantation, 81% remained potent at 3 years. Five patients developed radiation-induced rectal ulcerations, 11-22 months following implantation. Three patients required a transurethral resection of the prostate for postimplant urinary symptoms. CONCLUSIONS: The short-term clinical and chemical freedom-from-progression rates following I-125 implantation are comparable to that achieved with prostatectomy, with high preservation of sexual potency and moderate morbidity.

Aged↗
PubMed1994

Fluoroscopic visualization of the prostatic urethra to guide transperineal prostate implantation.

PURPOSE: To describe a novel way to assure proper needle positioning within the prostate during transperineal implantation, using the urethra as the primary radiographic landmark. METHODS AND MATERIALS: Preoperative computerized tomography (CT) images through the prostate are used to plan optimal transperineal needle-seed placement. When performing the procedure, a Foley catheter, with radio-opaque wire is used to visualize the prostatic urethra fluoroscopically in anterior-posterior and lateral projections. Proper needle placement is determined by their position relative to the urethra. RESULTS: Sixty patients have been implanted with this method at Memorial Sloan-Kettering Cancer Center from 1990-1992. CONCLUSION: The method described here is an improvement over previously described CT-based techniques. It could be used to supplement or replace ultrasound imaging.

Brachytherapy↗